explanation blue bibcodes open ADS page with paths to full text
Author name code: vazquez
ADS astronomy entries on 2022-09-14
author:"Vazquez, Manolo"
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Title: Ka-Band Monopulse Antenna Pointing Calibration Using Wideband
Radio Sources
Authors: Buu, C.; Calvo, J.; Cheng, T. -H.; Vazquez, M.
2010IPNPR.182A...1B Altcode:
A new method of performing a system end-to-end monopulse antenna
calibration using widely available wideband astronomical radio
sources is presented as an alternative to the current method of
using a spacecraft signal. Current monopulse calibration requires a
spacecraft carrier signal to measure amplitude and phase differences
in the monopulse feed and low-noise amplifiers (LNAs). The alternative
method presented here will allow the ground station to perform monopulse
calibrations during maintenance periods instead of spacecraft track
time, and provide an end-to-end system check-out capability without
requiring a spacecraft signal. In this article, we give an overview of
the current calibration approach, describe a new method for calibrating
with radio sources, and present results from field testing of this
new method.
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Title: Studies of CSS/GPS sources with the Deep Space Network antennas
in Madrid
Authors: Garcia-Miro, C.; Moll, E.; Vazquez, M.; Kuiper, T. B. H.
2009AN....330..137G Altcode:
This contribution summarizes the antennas and receivers available at
the Madrid Deep Space Communication Complex (MDSCC) and outlines the
type of observations that can be performed to contribute to the study
of the CSS/GPS sources. The last section provides guidelines on how
to observe with the DSN antennas, and in particular at MDSCC.
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Title: Identifying the Rotation Rate and the Presence of Dynamic
Weather on Extrasolar Earth-like Planets from Photometric Observations
Authors: Pallé, E.; Ford, Eric B.; Seager, S.; Montañés-Rodríguez,
P.; Vazquez, M.
2008ApJ...676.1319P Altcode: 2008arXiv0802.1836P
With the recent discoveries of hundreds of extrasolar planets, the
search for planets like Earth and life in the universe is quickly
gaining momentum. In the future, large space observatories could
directly detect the light scattered from rocky planets, but they
would not be able to spatially resolve a planet's surface. Using
reflectance models and real cloud data from satellite observations,
here we show that, despite Earth's dynamic weather patterns, the light
scattered by the Earth to a hypothetical distant observer as a function
of time contains sufficient information to accurately measure Earth's
rotation period. This is because ocean currents and continents result
in relatively stable averaged global cloud patterns. The accuracy
of these measurements will vary with the viewing geometry and other
observational constraints. If the rotation period can be measured with
accuracy, data spanning several months could be coherently combined
to obtain spectroscopic information about individual regions of the
planetary surface. Moreover, deviations from a periodic signal can be
used to infer the presence of relatively short-lived structures in its
atmosphere (i.e., clouds). This could provide a useful technique for
recognizing exoplanets that have active weather systems, changing on
a timescale comparable to their rotation. Such variability is likely
to be related to the atmospheric temperature and pressure being near
a phase transition and could support the possibility of liquid water
on the planet's surface.
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Title: Cloudiness and Apparent Rotation Rate of Earth-like Planets
Authors: Pallé, E.; Montañś-Rodríguez, P.; Vazquez, M.; Ford,
E. B.; Seager, S.
2008ASPC..398..399P Altcode:
If we were to observe the light reflected from an extrasolar planet,
the portion of the planet reflecting starlight toward us would change
due to rotation and orbital motion. Reflected light will come from
the planet's surface, but also from the clouds and atmosphere. It is
possible that these two planetary components have different rotation
speeds, and the presence of clouds might result in so much variability
that complicates efforts to determine its rotational period. Here
we show how the differential rotation of the atmosphere/clouds is
detectable even on Earth for certain observing geometries.
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Title: New Antenna Calibration Techniques in the Deep Space Network
Authors: Rochblatt, D.; Richter, P.; Withington, P.; Vazquez, M.;
Calvo, J.
2007IPNPR.169A...1R Altcode:
This work describes the development of new automated antenna
calibration instrumentation for the Deep Space Network (DSN). The
purpose of the antenna calibration instrumentation is to provide
reliable tools for the assessment, calibration, and improvement of
the performance of the large number of antenna systems in the DSN,
with special emphasis on Ka-band (32-GHz) performance of the 34-m
beam-waveguide (BWG) antennas. The work describes the analysis that
was done to characterize the various mechanisms that contribute to
noise in the measurements. The results from the analysis led to design
and development of a research and development calibration system that
utilized the on-the-fly-mapping technique and was deployed at the DSN
complex in Goldstone, California. Early results for calibration of
the DSN ground antennas and the Cassini onboard radar as a radiometer
are presented and agree well with analytical predictions. The system
was further used in conjunction with a new fourth-order pointing
model to achieve a record blind-pointing performance of the 34-m BWG
antennas. The article concludes with a description of the design and
implementation of an automated antenna calibration system based on
these principles for the DSN: the Antenna Calibration and Measurement
Equipment (ACME).
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Title: Human Exploration of Phobos and Deimos: Radioprotection Issues
Authors: Vazquez, M. E.
2007epd..conf...40V Altcode:
No abstract at ADS
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Title: Solar Rotation in the 17th century
Authors: Casas, R.; Vaquero, J. M.; Vazquez, M.
2006SoPh..234..379C Altcode:
Sunspot drawings made by Galileo Galilei in 1612 are used to derive
the law of differential rotation at that time. The main interest of
the work is during the time of observations, just at the beginning of
telescopic observations and some decades before the Maunder Minimum
(1645 - 1715), a period where the sunspots almost disappeared from
the solar surface. For this purpose we have carried out careful
corrections of the different sources of errors derived from the
observing technique. By comparing with other results of the same
century, a significant difference is only detected by comparing with
data corresponding to the deep Maunder Minimum (Paris Observatory
drawings). The characteristics of the solar differential rotation,
and extrapolating the behavior of solar activity, did not differ before
or after the Maunder Minimum. We also include an analysis of hitherto
ignored sunspot drawings by N. Bion made in October and November 1672.
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Title: Neurotoxicity of human neural cells induced by space radiation:
in vitro risk assessment and countermeasure
Authors: Guida, P.; Vazquez, M.; Kim, A.
2006cosp...36..669G Altcode: 2006cosp.meet..669G
As the duration of space missions increases the potential for
neurological damage to astronauts resulting from exposure to radiation
also increases To explore the cytotoxic effects of low and high LET
radiation on cells of the central nervous system we utilized a model
in vitro system consisting of a human neuronal progenitor cell line NT2
and its terminally differentiated derivative hNT neurons We found that
exposure to numerous forms of ionizing radiation induced cell detachment
necrosis and apoptosis in time dose and LET dependent manners From the
slopes of the dose-response curves we calculated RBE values for each
form of heavy ion radiation A sequential field of 1 GeV n protons and
iron ions induced apoptosis to a greater extent than either ion alone
and the time between hits was also an important determining factor
In addition cycling neuronal progenitor cells underwent a dramatic G2
phase specific cell cycle delay within 6 hours following exposure to
either low or high LET radiation The molecular effects of HZE radiation
were also investigated with an emphasis on the cell stress response
protein p53 Heavy ion radiation induced expression of p53 in a time
and dose dependent manner in both neuronal progenitor and mature
neuronal cells Furthermore several post-translational modifications
to the p53 protein were detected 2 hours after exposure to gamma rays
Experiments incorporating pifithrin- alpha a small molecule inhibitor
of p53 suggest that induction of both apoptosis and the cell cycle
delay in human NT2 cells is
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Title: Mice heterozygous for the ATM gene are more sensitive to both
X-ray and heavy ion exposure than are wildtypes
Authors: Worgul, B. V.; Smilenov, L.; Brenner, D. J.; Vazquez, M.;
Hall, E. J.
2005AdSpR..35..254W Altcode:
Previous studies have shown that the eyes of ATM heterozygous
mice exposed to low-LET radiation (X-rays) are significantly more
susceptible to the development of cataracts than are those of wildtype
mice. The findings, as well as others, run counter to the assumption
underpinning current radiation safety guidelines, that individuals
are all equally sensitive to the biological effects of radiation. A
question, highly relevant to human space activities is whether or not,
in similar fashion there may exist a genetic predisposition to high-LET
radiation damage. Mice haplodeficient for the ATM gene and wildtypes
were exposed to 325 mGy of 1 GeV/amu <SUP>56</SUP>Fe ions at the AGS
facility of Brookhaven National Laboratory. The fluence was equivalent
to 1 ion per lens epithelial cell nuclear area. Controls consisted of
irradiated wildtype as well as unirradiated wildtype and heterozygous
mice. Prevalence analyses for stage 0.5-3.0 cataracts indicated that
not only cataract onset but also progression were accelerated in the
mice haplo-deficient for the ATM gene. The data show that heterozygosity
for the ATM gene predisposes the eye to the cataractogenic influence of
heavy ions and suggest that ATM heterozygotes in the human population
may also be radiosensitive. This may have to be considered in the
selection of individuals who will be exposed to both HZE particles and
low-LET radiation as they may be predisposed to increased late normal
tissue damage.
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Title: Effects of Low Dose Particle Radiation to Mouse Neonatal
Neurons in Culture
Authors: Nojima, K.; Vazquez, M. E.; Okayasu, R.; Nagaoka, S.
2004cosp...35.2542N Altcode: 2004cosp.meet.2542N
To investigate effects of low dose heavy particle radiation to CNS
system, we adopted mouse neonatal brain cells in culture being exposed
to heavy ions by HIMAC at NIRS and NSRL at BNL. The applied dose
varied from 0.05Gy up to 2.0Gy. The subsequent biological effectswere
evaluated by an induction of apoptosis and neuron survival focusing
on the dependencies of the animal strains, SCID, B6, B6C3F1, C3H,
used for brain cell culture, SCID was the most sensitive and C3H the
least sensitive to particle radiation as evaluated by 10% apoptotic
criterion. The LET dependency was compared with using SCID and B6 cells
exposing to different ions (H, C, Ne, Si, Ar, and Fe). Although no
detectable LET dependency was observed in the high LET (55 -200 keV/μ
m) and low dose (<0.5 Gy) regions. The survivability profiles of the
neurons were different in the mouse strains and ions. In this repot,
a result of memory and learning function to adult mice after whole-body
and brainlocal irradiation at carbon ion and iron ion.
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Title: The ALTEA/ALTEINO projects: studying functional effects of
microgravity and cosmic radiation
Authors: Narici, L.; Belli, F.; Bidoli, V.; Casolino, M.; De Pascale,
M. P.; Di Fino, L.; Furano, G.; Modena, I.; Morselli, A.; Picozza,
P.; Reali, E.; Rinaldi, A.; Ruggieri, D.; Sparvoli, R.; Zaconte, V.;
Sannita, W. G.; Carozzo, S.; Licoccia, S.; Romagnoli, P.; Traversa, E.;
Cotronei, V.; Vazquez, M.; Miller, J.; Salnitskii, V. P.; Shevchenko,
O. I.; Petrov, V. P.; Trukhanov, K. A.; Galper, A.; Khodarovich,
A.; Korotkov, M. G.; Popov, A.; Vavilov, N.; Avdeev, S.; Boezio,
M.; Bonvicini, W.; Vacchi, A.; Zampa, N.; Mazzenga, G.; Ricci, M.;
Spillantini, P.; Castellini, G.; Vittori, R.; Carlson, P.; Fuglesang,
C.; Schardt, D.
2004AdSpR..33.1352N Altcode:
The ALTEA project investigates the risks of functional brain damage
induced by particle radiation in space. A modular facility (the ALTEA
facility) is being implemented and will be operated in the International
Space Station (ISS) to record electrophysiological and behavioral
descriptors of brain function and to monitor their time dynamics and
correlation with particles and space environment. The focus of the
program will be on abnormal visual perceptions (often reported as "light
flashes" by astronauts) and the impact on retinal and brain visual
structures of particle in microgravity conditions. The facility will
be made available to the international scientific community for human
neurophysiological, electrophysiological and psychophysics experiments,
studies on particle fluxes, and dosimetry. A precursor of ALTEA
(the `Alteino' project) helps set the experimental baseline for the
ALTEA experiments, while providing novel information on the radiation
environment onboard the ISS and on the brain electrophysiology of the
astronauts during orbital flights. Alteino was flown to the ISS on the
Soyuz TM34 as part of mission Marco Polo. Controlled ground experiments
using mice and accelerator beams complete the experimental strategy of
ALTEA. We present here the status of progress of the ALTEA project and
preliminary results of the Alteino study on brain dynamics, particle
fluxes and abnormal visual perceptions.
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Title: Animal imaging studies of potential brain damage
Authors: Gatley, S. J.; Vazquez, M. E.; Rice, O.
2004cosp...35.3060G Altcode: 2004cosp.meet.3060G
To date, animal studies have not been able to predict the likelihood
of problems in human neurological health due to HZE particle exposure
during space missions outside the Earth's magnetosphere. In ongoing
studies in mice, we have demonstrated that cocaine stimulated
locomotor activity is reduced by a moderate dose (120 cGy) of 1 GeV
<SUP>56</SUP>Fe particles. We postulate that imaging experiments in
animals may provide more sensitive and earlier indicators of damage
due to HZE particles than behavioral tests. Since the small size of
the mouse brain is not well suited to the spatial resolution offered by
microPET, we are now repeating some of our studies in a rat model. We
anticipate that this will enable us to identify imaging correlates of
behavioral endpoints. A specific hypothesis of our studies is that
changes in the metabolic rate for glucose in striatum of animals
will be correlated with alterations in locomotor activity. We will
also evaluate whether the neuroprotective drug L-deprenyl reduces
the effect of radiation on locomotor activity. In addition, we will
conduct microPET studies of brain monoamine oxidase A and monoamine
oxidase B in rats before and at various times after irradiation with
HZE particles. The hypothesis is that monoamine oxidase A, which
is located in nerve terminals, will be unchanged or decreased after
irradiation, while monoamine oxidase B, which is located in glial cells,
will be increased after irradiation. Neurochemical effects that could
be measured using PET could in principle be applied in astronauts,
in terms of detecting and monitoring subtle neurological damage that
might have occurred during long space missions. More speculative
uses of PET are in screening candidates for prolonged space missions
(for example, for adequate reserve in critical brain circuits) and in
optimizing medications to treat impairments after missions.
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Title: Effects of heavy ions on visual function and electrophysiology
of rodents: the ALTEA-MICE project
Authors: Sannita, W. G.; Acquaviva, M.; Ball, S. L.; Belli, F.; Bisti,
S.; Bidoli, V.; Carozzo, S.; Casolino, M.; Cucinotta, F.; De Pascale,
M. P.; Di Fino, L.; Di Marco, S.; Maccarone, R.; Martello, C.; Miller,
J.; Narici, L.; Peachey, N. S.; Picozza, P.; Rinaldi, A.; Ruggieri,
D.; Saturno, M.; Schardt, D.; Vazquez, M.
2004AdSpR..33.1347S Altcode:
ALTEA-MICE will supplement the ALTEA project on astronauts and provide
information on the functional visual impairment possibly induced
by heavy ions during prolonged operations in microgravity. Goals of
ALTEA-MICE are: (1) to investigate the effects of heavy ions on the
visual system of normal and mutant mice with retinal defects; (2)
to define reliable experimental conditions for space research; and
(3) to develop animal models to study the physiological consequences
of space travels on humans. Remotely controlled mouse setup, applied
electrophysiological recording methods, remote particle monitoring,
and experimental procedures were developed and tested. The project
has proved feasible under laboratory-controlled conditions comparable
in important aspects to those of astronauts' exposure to particle
in space. Experiments are performed at the Brookhaven National
Laboratories [BNL] (Upton, NY, USA) and the Gesellschaft für
Schwerionenforschung mbH [GSI]/Biophysik (Darmstadt, FRG) to identify
possible electrophysiological changes and/or activation of protective
mechanisms in response to pulsed radiation. Offline data analyses are
in progress and observations are still anecdotal. Electrophysiological
changes after pulsed radiation are within the limits of spontaneous
variability under anesthesia, with only indirect evidence of possible
retinal/cortical responses. Immunostaining showed changes (e.g increased
expression of FGF2 protein in the outer nuclear layer) suggesting a
retinal stress reaction to high-energy particles of potential relevance
in space.
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Title: Mice heterozygous for the ATM gene are more sensitive to
heavy ions exposure than are wildtypes
Authors: Worgul, B.; Smilenov, L.; Brenner, D.; Vazquez, M.; Hall, E.
2004cosp...35.4027W Altcode: 2004cosp.meet.4027W
Previous studies have shown that the eyes of atm heterozygous mice
exposed to Low LET radiation (X-rays) are more susceptible to the
development of cataracts than are those of wildtype mice. The findings,
as well as others, run counter to the assumption underpinning current
radiation safety guidelines, that individuals are all equally sensitive
to the biological effects of radiation. A question, highly relevant
to human space activities is whether or not, in similar fashion there
may exist a genetic predisposition to High LET radiation damage. Again
the lens and, its primary radiopathy, cataract, were used to assay for
the effects of ATM deficiency in a late-responding tissue. Together
with those of wildtypes, the eyes of AT heterozygous knockout mice
were exposed to 325 mGy of 1 GEV/amu <SUP>56</SUP>Fe ions at the AGS
facility of Brookhaven National Laboratory. The fluence was equivalent
to 1 ion per nuclear area. As was the case in the earlier X-ray studies
all irradiations were done on the 28th day after birth. Controls
consisted of wildtype irradiated as well as unirradiated wildtype
and heterozygotes. Ten mice from each group were examined weekly by
conventional slitlamp biomicroscopy for a total of 35 weeks. The time
required for prevalence to reach 50% (T<SUB>50</SUB>) as an endpoint for
each stage indicated that not only cataract onset but also progression
were accelerated in the mice haplo-deficient for the atm gene. For
example the T<SUB>50</SUB> for definitive cataract onset (stage 1) in
the atm heterozygotes was 10 weeks whereas 17 weeks were required for
the wildtypes. Similarly at the conclusion of the experiment (35 weeks),
40% of the lenses of allele-deficient mice had progressed to stage 3
(near fully opaque and obviously visually debilitating), while only one
lens (5%) from the wildtype irradiated eyes achieved that stage. The
data show that heterozygosity for the atm gene predisposes the eye
to the cataractogenic influence of heavy ions and suggest that AT
heterozygotes in the human population may also be radiosensitive. This
may have to be considered in the selection of individuals who will
be exposed to both HZE particles and Low-LET radiation as they may be
predisposed to increased late normal tissue damage. Supported by NASA
Grant NAG 9-1148 and Research to Prevent Blindness, Inc.
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Title: Effect of 1 GeV/n Fe particles on cocaine-stimulated locomotor
activity
Authors: Vazquez, M.; Bruneus, M.; Gatley, J.; Russell, S.; Billups, A.
2004cosp...35.3082V Altcode: 2004cosp.meet.3082V
Space travel beyond the Earth's protective magnetic field (for
example, to Mars) will involve exposure of astronauts to irradiation
by high-energy nuclei such as 56Fe (HZE radiation), which are a
component of galactic cosmic rays. These particles have high linear
energy transfer (LET) and are expected to irreversibly damage cells
they traverse. Our working hypothesis is that long-term behavioral
alterations are induced after exposure of the brain to 1 GeV/n iron
particles with fluences of 1 to 8 particles/cell targets. Previous
studies support this notion but are not definitive, especially with
regard to long-term effects. Using the Alternating Gradient Synchrotron
(AGS) we expose C57 mice to 1 GeV/n 56Fe radiation (head only) at
doses of 0, 15, 30, 60, 120 and 240 cGy. There were originally 19
mice per group. The ability of cocaine to increase locomotor activity
in 16 of these animals in response to an intraperitoneal injection
of cocaine has been measured so far at 1, 4, 8, 12, 16, 20, 24 and
28 weeks. Cocaine-stimulated locomotor activity was chosen in part
because it is a behavioral assay with which we have considerable
experience. More importantly, the ability to respond to cocaine is
a complex behavior involving many neurotransmitter systems and brain
circuits. Therefore, the probability of alteration of this behavior
by HZE particles was considered high. However, the central circuit is
the nigrostriatal dopamine system, in which dopamine is released in
striatum from nerve terminals whose cell bodies are located in the
substantia nigra. Cocaine activates behavior by blocking dopamine
transporters on striatal nerve terminals and therefore elevating the
concentration of dopamine in the synapse. Dopamine activates receptors
on striatal GABAergic cells that project via other brain regions to the
thalamus. Activation of the motor cortex by glutamatergic projections
from the thalamus leads ultimately to increased locomotion. The
experimental paradigm involves placing mice in a plexiglass box
fitted with arrays of photocells. A mouse placed in the box exhibits
exploratory behavior that diminishes to a low level over the course of
about 20 min. Iron particle irradiation caused dose related reductions
in locomotor activity stimulated by cocaine, as evidenced by the group
data presented here. The impairments after HZE radiation appeared to be
persistent. Irradiation using a 137Co source also led to alterations in
cocaine-stimulated locomotion at early times, but, unlike the situation
for HZE radiation, these disappeared at later times. These studies were
very recently terminated and data analysis is not yet complete. For
example, spontaneous activity was also monitored, and it is possible
that comparison of stimulated and spontaneous locomotion for each animal
may expose larger changes. Most of the mice were sacrificed and their
brains stored for histology and neurochemistry. Ex vivo determination
of dopamine transporter status in striata of some of the mice indicated
no large decrease in this marker of pre-synaptic dopamine terminals,
supporting an earlier pilot study in rats.
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Title: Cellular and molecular effects of high-LET radiation on human
neural stem cells and neurons
Authors: Vazquez, M.; Guida, P.; Green, L.; Chang, P.; Otto, S.
2004cosp...35.3061V Altcode: 2004cosp.meet.3061V
Because successful operations in space depend in part on the performance
capabilities of astronauts, radiation-induced neurological damage could
jeopardize the successful completion of mission requirements, as well
as have long-term consequences on the health of astronauts. As such,
understanding the nature of this risk may be vital to the effective
performance of astronauts during future missions in space. This paper
describes the neural cell responses to conventional and charged
particles radiation in cell culture systems. One of the goals
is to characterize radiation-induced neural cell damage pathways;
especially those related to apoptosis induction and its modification
by pharmacological manipulation. Our laboratory utilizes the method
of flow cytometry to measure the induction of apoptosis and necrosis
in cells. Neural stem cells (NT2) were exposed to the different ions;
we measured a dose-dependent induction of apoptosis. NT2 cells were
exposed to graded doses of 1 and 5 GeV/n Fe, 0.29 GeV/n C, 1 GeV/n
Ti, and 0.6 GeV/n Si ions and samples were taken at 48 hours after
exposure. The percentage of apoptotic cells in culture was measured
by FITC-Annexin V by flow cytometry. Similar data obtained from
NT2 cells exposed to 255 MeV/n protons and 137Cs are included for
comparison. Preliminary RBE calculations demonstrated that iron
ions are more effective in inducing apoptosis. Exposure of cells
to ionizing radiation produces changes in the expression of many
genes as cells react to this insult. At present, the identities
of the molecular changes that occur in response to HZE radiation
remain largely unknown. In an effort to reveal this information, we
screened an array (Superarray) of p53-related genes with RNA purified
from NT2 cells mock irradiated or exposed to 50 cGy of 1 GeV/n iron
ions. Preliminary results indicated that the expression of numerous
critical genes was altered 3 hours after HZE radiation exposure. By
performing Western blot analysis on NT2 cells exposed to 5 GeV/n iron
ions, we demonstrated a time and dose dependent increase in p53 protein
levels. This induction occurred as early as 6 hours post-irradiation,
and was detectable with a dose as low as 10 cGy. Meanwhile, the levels
of the structural protein actin did not change in these cell samples,
assuring accurate protein quantization and equal loading from sample
to sample. We have also shown a time and dose dependent increase in p53
protein levels in terminally differentiated human neuronal (hNT) cells
exposed to 1 GeV/n iron ions. Using a more detailed protocol of early
harvesting times, we determined that p53 accumulated in these neuronal
cells within 8 hours after irradiation. Our laboratory's demonstration
that HZE radiation exposure results in a dose dependent induction of
p53 protein, concomitant with our finding of a dose dependent induction
of apoptosis in the neural stem (NT2) cells, strongly implies that
p53 plays a major role in this HZE radiation-induced apoptosis response.
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Title: Detection of microlesions induced by heavy ions using liposomes
filled with fluorescent dye
Authors: Koniarek, J. P.; Thomas, J. L.; Vazquez, M.
2004AdSpR..34.1373K Altcode:
In cells irradiation by heavy ions has been hypothesized to produce
microlesions, regions of local damage. In cell membranes this damage is
thought to manifest itself in the form of holes. The primary evidence
for microlesions comes from morphological studies of cell membranes,
but this evidence is still controversial, especially since holes
also have been observed in membranes of normal, nonirradiated,
cells. However, it is possible that damage not associated with
histologically discernable disruptions may still occur. In order to
resolve this issue, we developed a system for detecting microlesions
based on liposomes filled with fluorescent dye. We hypothesized that
if microlesions form in these liposomes as the result of irradiation,
then the entrapped dye will leak out into the surrounding medium
in a measurable way. Polypropylene vials containing suspensions of
vesicles composed of either dipalmitoyl phosphatidylcholine, or a
combination of egg phosphatidylcholine and cholesterol were irradiated
at the Brookhaven National Laboratory using <SUP>56</SUP>Fe ions at
1 GeV/amu. In several cases we obtained a significant loss of the
entrapped dye above the background level. Our results suggest that
holes may form in liposomes as the result of heavy ion irradiation,
and that these holes are large enough to allow leakage of cell internal
contents that are at least as large as a 1 nm diameter calcein molecule.
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Title: Transmediterranean flights,in the edge of two centuries.
Authors: Cosentino, O.; Caballero, F.; Ibba, R.; Gerardi, G.; Cecchini,
G.; Fernandez Abad, A.; Vazquez, M.
2002cosp...34E.378C Altcode: 2002cosp.meetE.378C
Transmediterranean flights program goal is to perform stratospheric
balloons flights carrying scientific/technological payloads at 40 Km
altitude and approximate 38°N latitude.ASI and INTA continued the
early ASI-CNES-INTA program with several stratospheric flights since
1993.The network comprises three stations located at Trapani-Milo
(Italy),Palma de Mallorca and El Arenosillo(Spain). Nine successful
transmediterranean crossings were performed in this program stage. Four
new transmediterranean flights are scheduled for summer 2002 .These
include astronomical,biological and technological experiments
.Beside , three local flights will be performed at Trapani-Milo next
summer. Technical tracking that encompasses telemetry,telecommand and
localization uses allocated UHF band,in the old classical and the new
Mini Telemetry configurations. Flight qualification of a S-band TM/TC
equipment was realised ,using local flights, in 1997 and 1998.In summer
2002,a S band flight will be realised over the Mediterranean with the
UHF telemetry as a backup. A summary of system requirements , that
would assure state-of-the-art open stratospheric balloons flights is
presented . When flying over the Iberian Peninsula , the time of land
overflight diminishes , in direct relationship , with the balloon
drift toward the South.A latitude control , applied in our case ,
should enhance the flight feasibility. Trajectory predictions,must
incorporate radiosoundings of more places,to take into account
several possibilities of descent.Also El Arenosillo soundings ,usually
three days a week,should be increased ,in order to validate the new
atmospheric models. Beside altitude control handled mainly by the
ballast , in the future "boomerang" flights of a transmediterranean
scale,opening/closing of the valves will be used. Active floating
system,comb ined with waterproof electronic and experiment boxes and
a minimal time of arrival to the gondola , become critical points
in case of an unplanned overwater descent for recovery.With regard
to power storage subsystems Ni-H2,NiMH and Li-ion batteries,should
be embarked onboard new flights to gain experiences,acting in this
way,as in others,as a technological testbed of industry designs. Thermal
control subsystems,should withstand the cycle sunrise-sunset-sunrise,if
the usual 1 day flights are to be extended 10 hours , under the
"boomerang" principle.In summer 2002 , a High Performance Gondola
experiment will carry an azimuthal stabilization system using GPS
phase variation.Parachutes employed were either in- dividual or a
bunch of three,in the ASI-CNES-INTA program stage. A payload precision
descent,involving GPS to aim at a preselected descent point,will help
to reduce the risk index over land zones.
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Title: Effects of high-LET radiation on neural cells in culture:
apoptosis induction, cell toxicity and gene expression
Authors: Vazquez, M.; Otto, S.; Estevez, L.; Rios, D.; Pena, L.;
Anderson, C.
2002cosp...34E2299V Altcode: 2002cosp.meetE2299V
Despite the fact that some in vivo studies suggest that chronic low-dose
exposure to HZE particles might produce effects similar to aging and
neurodegeneration, the basic mechanisms of HZE particle neurotoxicity
remain to be elucidated. The goal of these experiments is to establish
neural cellular models to evaluate the capacity of low- and high-LET
radiation, to induce cell damage and apoptosis. In the present study
we measured apoptosis, cell toxicity and gene expression induced by
low fluences-doses of heavy ions, protons and photons using neuronal
precursor cells (NT2, STRATAGENE) and post-mitotic neurons as models
for adult neural cell system. Using heavy ions accelerated at AGS
(BNL) and HIMAC (Chiba, Japan), and protons (Loma Linda) we study the
neurotoxic effects of a variety of heavy particles (1 and 0.6 GeV/n Fe,
580 MeV/n Si, 290 MeV/n C, 550 MeV/n Ar; LET ranging from 13 to148
keV/μm), and 255 MeV/n protons. Apoptosis Induction: We measured
the induction of apoptosis by flow cytometry using a FACSCalibur
to detect the expression of Annexin V, as an early marker in the
apoptotic pathway, in NT-2 cells. The ApoAlert Annexin V assay is
based on the observation that soon after initiating apoptosis, most
cell types translocate phosphatidylserine (PS) from the inner face of
the plasma membrane to the cell surface. Once on the cell surface, PS
can be easily detected by staining with a FITC conjugate of Annexin V,
a protein that has a strong natural affinity for PS. Externalization of
PS occurs earlier than the nuclear changes associated with apoptosis, so
the ApoAlert Assay detects apoptotic cells significantly earlier than do
DNA-based assays. Exposing NT-2 cells to Fe ions and protons induced a
strong dose- and time-dependent induction of apoptosis with the peak of
apoptosis appearing at 72 hours post-irradiation. It was determined that
Fe ion exposure were more effective to induce apoptosis in comparison to
protons and gamma rays, suggesting an high RBE values for apoptosis in
exposed NT2 cells at 72 hr post-irradiation. Cell Toxicity: Cell damage
at different time points after exposure to charge particle radiation was
determined by using the Live/Dead Viability/Cytotoxicity Kit on attached
cells from 4 well plates. The LIVE/DEAD Kit provides a two-color
fluorescence-based cell viability assay that allows the simultaneous
determination of live and dead cells. Results obtained from BNL-7
indicated a dose- and time dependent increase of cell damage. Doses
as low as 0.1 Gy were able to induce a significant increase of cell
damage in comparison to controls. Colorimetric (XTT) assays and the
evaluation of the number of attached and floating cells confirmed
this trend. Gene Expression: Conventional western blot techniques were
employed to monitor p53 and WAF-p21 gene expression. A subset of NT2
cell samples were lysed at different time points for the determination
of p53 and WAFp21 expression using monoclonal antibodies against human
p53 and p21. In BNL-7 we observed that p53 is over-expressed as a
function of dose of particle exposure and time post-exposure. Doses as
low as 0.25 Gy were able to up- regulate p53 and as early as 24 hours
post-exposure. Doses of 0.75 Gy were able to up-regulate p53 as early as
12 hours post-exposure. Similar results were obtained when NT-2 cells
were exposed to gamma or proton exposures, although higher doses were
required to obtain similar degree of expression. These results appear
to confirm that p53 gene is involved in the stress pathway induced by
low- and high- LET radiation exposures. Up to this point we were not
able to confirm changes in the expression of WAFp21 after radiation
exposure in NT2 cells.
---------------------------------------------------------
Title: Behavioral effects of heavy ions and protons and potential
countermeasure agents
Authors: Vazquez, M.; Gatley, J.; Bruneus, M.; Koslosky, S.;
Billups, A.
2002cosp...34E2300V Altcode: 2002cosp.meetE2300V
Space travel beyond the Earth's protective magnetic field (for
example, to Mars) will involve exposure of astronauts to irradiation
by high-energy nuclei such as 56 Fe, which are a component of galactic
cosmic rays. These particles have high linear energy transfer (LET)
and are expected to irreversibly damage cells they traverse. Exposure
to HZE radiation may therefore cause progressive deterioration
of brain function, adding to other inescapable damage involved in
normal aging. We propose a study of the hypothesis that long-term
behavioral alterations are induced after exposure of the brain to 1
GeV/n iron and silicon particles with fluences of 1 to 8 particles/cell
targets. Previous studies support this notion but are not definitive,
especially with regard to long-term effects. Our principal goal is to
examine the neurological effects of high-LET radiation on C57BL/6 mice
using a series of behavioral tests to unveil the temporal expression of
altered behaviors in the radiation response, as well as the means, which
can modulate these responses. The studies planned in this project are
designed to: 1) Characterize the behavioral consequences after exposure
to low-fluences of heavy ions and protons on C57BL/6 mice. The main
behavioral endpoints to be used in these studies are locomotor activity
to evaluate the integrity of striatal dopaminergic pathways, and
spatial reference memory to probe hippocampal cholinergic pathways. 2)
Characterize the neurochemical and structural changes induced by heavy
ions and protons. 3) To develop countermeasures to protect neural cell
populations exposed to low fluences of heavy ions and protons. The
project will test methods to protect injured neural cells based on
their molecular and cellular mechanisms that may regulate neural cell
survival in the central nervous system. Among the methods that will
be studied is the direct administration of neuroprotective molecules
as well as the modulation of apoptotic pathways by pharmacological
manipulation. The effects of 3 different neuro/radioprotectors (GM1,
melatonin and PTF-) on the levels of radiation induced neurochemical
and structural damage will be compared with the level of behavioral
alterations to determine a cause/effect relationship
---------------------------------------------------------
Title: Earthshine: A Proposal To Build An Automatic System For
Observing Terrestrial Albedo.
Authors: Thejll, P.; Ulla, A.; Hanslmeier, A.; Chou, D. -Y.; Goode,
P.; Vazquez, M.; Belmonte, J. A.
2002EGSGA..27.4058T Altcode:
Terrestrial albedo data are important for climate model studies
because of the impor- tance albedo has on the net radiation budget
of the Earth. Direct measurements of the albedo are not common, and
there is no dataset with global coverage that offers an alternative
to data from satellite measurements. The satellite data, however, are
often from weather satellites that were not specifically designed to
guarantee long-term sen- sitivity stability in the imaging data, and
thus in the albedo data that can be derived from these. Therefore,
absolute calibration of terrestrial satellite albedo data is not
possible. <P />The Earth reflects light onto the Moon proportional to
the albedo, and it is possible to measure from the Earth the so called
'earthshine' on the Moon, so accurately that a cost-effective system
for mean-terrestrial albedo monitoring can be built on the basis of
small robotic telescopes. We present a system for observation and
data-handling, that could provide data for albedo studies. The system
is intrinsically stable and would be able to produce data of long-term
stability so that questions related to the drift in satellite data
could be investigated in the future.
---------------------------------------------------------
Title: Fluorescein dye filled vesicles as models for detection
of microlesions
Authors: Koniarek, J.; Thomas, J.; Vazquez, M.
2002cosp...34E2659K Altcode: 2002cosp.meetE2659K
The primary evidence for microlesions in cell membranes caused by heavy
ions is from morphological studies. This evidence, however, could not be
corroborated. That said, it is possible to envision functional damage
not associated with histologically discernable disruption. In order to
resolve this issue experimental evidence is needed using a model that
can produce reliable and unequivocal results. We developed a model
system for detecting microlesions based on cell membrane mimics made
of spherical vesicles 0.1 μm in diameter formed by molecules prepared
from phosphatidylcholine and cholesterol. These vesicles contain the
fluorescent dye calcein. We hypothesize that if microlesions form in
these vesicles then upon irradiation the fluorescent dye will leak out
into the surrounding medium in a measurable way. Vials containing these
vesicles were irradiated at the Brookhaven National Laboratory. In
one instance irradiation by 1 GeV 56Fe ions produced a significant
loss of the entrapped fluorescent dye, 15 % above the background
level. However, a replicate irradiation produced no leakage above the
background level. Despite these initial inconclusive results we believe
that the dye-filled vesicle model still has potential to clarify the
microlesion hypothesis. However additional experiments are needed to
validate this model in view of the contradictory results obtained in
our initial experiments.
---------------------------------------------------------
Title: Cosmic Ray Hits in the Central Nervous System at Solar Maximum
Authors: Curtis, S. B.; Vazquez, M. E.; Wilson, J. W.; Atwell, W.;
Kim, M. -H. Y.
2000AdSpR..25.2035C Altcode:
It has been suggested that a manned mission to Mars be launched at
solar maximum rather than at solar minimum to minimize the radiation
exposure to galactic cosmic rays. It is true that the number of hits
from highly ionizing particles to critical regions in the brain will
be less at solar maximum, and it is of interest to estimate how much
less. We present here calculations for several sites within the brain
from iron ions (z = 26) and from particles with charge, z, greater than
or equal to 15. The same shielding configurations and sites in the brain
used in an earlier paper for solar minimum are employed so that direct
comparison of results between the two solar activity conditions can be
made. A simple pressure-vessel wall and an equipment room onboard a
spacecraft are chosen as shielding examples. In the equipment room,
typical results for the thalamus are that the probability of any
particles with z greater than or equal to 15 and from 2.3 percent to 1.3
percent for iron ions. The extra shielding provided in the equipment
room makes little difference in these numbers. We conclude that this
decrease in hit frequency (less than a factor of two) does not provide
a compelling reason to avoid solar minimum for a manned mission to
Mars. This conclusion could be revised, however, if a very small number
of hits is found to cause critical malfunction within the brain
---------------------------------------------------------
Title: Long-Term Observations of Solar Active Regions at the VNT
Authors: Bonet, J. A.; Casas, R.; Giammanco, C.; Martinez Pillet,
V.; Vazquez
2000ESASP.463..635B Altcode: 2000sctc.proc..635B
No abstract at ADS
---------------------------------------------------------
Title: In Vitro Neurotoxic Effects of 1 GeV/n Iron Particles Assessed
in Retinal Explants
Authors: Vazquez, M. E.; Kirk, E.
2000AdSpR..25.2041V Altcode:
The heavy ion component of the cosmic radiation remains problematic
to the assessment of risk in manned space flight. The biological
effectiveness of HZE particles has yet to be established, particularly
with regard to nervous tissue. Using heavy ions accelerated at the AGS
of Brookhaven National Laboratory, we study the neurotoxic effects
of iron particles. We exposed retinal explants, taken from chick
embryos, to determine the dose response relationships for neurite
outgrowth. Morphometric techniques were used to evaluate the in vitro
effects of 1 GeV/a iron particles (LET 148 keV/μm). Iron particles
produced a dose-dependent reduction of neurite outgrowth with a maximal
effect achieved with a dose of 100 cGy. Doses as low as 10-50 cGy were
able to induce reductions of the neurite outgrowth as compared to
the control group. Neurite generation is a more sensitive parameter
than neurite elongation, suggesting different mechanism of radiation
damage in our model. These results showed that low doses/fluences of
iron particles could impair the retinal ganglion cells' capacity to
generate neurites indicating the highly neurotoxic capability of this
heavy charged particle
---------------------------------------------------------
Title: Neurobiological problems in long-term deep space flights
Authors: Vazquez, M. E.
1998AdSpR..22..171V Altcode:
Future missions in space may involve long-term travel beyond the
magnetic field of the Earth, subjecting astronauts to radiation
hazards posed by solar flares and galactic cosmic rays, altered
gravitation fields and physiological stress. Thus, it is critical to
determine if there will be any reversible or irreversible, detrimental
neurological effects from this prolonged exposure to space. A question
of particular importance focuses on the long-term effects of the space
environment on the central nervous system (CNS) neuroplasticity, with
the potential acute and/or delayed effects that such perturbations
might entail. Although the short-term effects of microgravity on
neural control were studied on previous low earth orbit missions,
the late consequences of stress in space, microgravity and space
radiation have not been addressed sufficiently at the molecular,
cellular and tissue levels. The possibility that space flight factors
can interact influencing the neuroplastic response in the CNS looms
critical issue not only to understand the ontogeny of the CNS and
its functional integrity, but also, ultimately the performance of
astronauts in extended space forays. The purpose of this paper is to
review the neurobiological modifications that occur in the CNS exposed
to the space environment, and its potential consequences for extended
deep space flight.
---------------------------------------------------------
Title: Cosmic ray hit frequencies in critical sites in the central
nervous system
Authors: Curtis, S. B.; Vazquez, M. E.; Wilson, J. W.; Atwell, W.;
Kim, M.; Capala, J.
1998AdSpR..22..197C Altcode:
One outstanding question to be addressed in assessing the risk of
exposure to space travelers from galactic cosmic rays (GCR) outside the
geomagnetosphere is to ascertain the effects of single heavy-ion hits
on cells in critical regions of the central nervous system (CNS). As
a first step toward this end, it is important to determine how many
“hits” might be received by a neural cell in several critical
CNS areas during an extended mission outside the confines of the
earth's magnetic field. Critical sites in the CNS: the macula, and
an interior brain point (typical of the genu, thalamus, hippocampus
and nucleus basalis of Meynert) were chosen for the calculation of
hit frequencies from galactic cosmic rays for a mission to Mars during
solar minimum (i.e., at maximum cosmic-ray intensity). The shielding at
a given position inside the body was obtained using the Computerized
Anatomical Man (CAM) model, and a radiation transport code which
includes nuclear fragmentation was used to calculate yearly fluences
at the point of interest. Since the final Mars spacecraft shielding
configuration has not yet been determined, we considered the minimum
amount of aluminum required for pressure vessel-wall requirements
in the living quarters of a spacecraft, and a typical duty area as
a pressure vessel plus necessary equipment. The conclusions are: (1)
variation of the position of the “target site” within the head plays
only a small role in varying hit frequencies; (2) the average number
of hits depends linearly on the cross section of the critical portion
of the cell assumed in the calculation; (3) for a three-year mission
to Mars at solar minimum (i.e., assuming the 1977 spectrum of galactic
cosmic rays), 2% or 13% of the “critical sites” of cells in the CNS
would be directly hit at least once by iron ions, depending on whether
60 mum^2 or 471 mum^2 is assumed as the critical cross sectional area;
and (4) roughly 6 million out of some 43 million hippocampal cells and
55 thousand out of 1.8 million thalamus cell nuclei would be directly
hit by iron ions at least once on such a mission for space travelers
inside a simple pressure vessel. Also, roughly 20 million out of 43
million hippocampal cells and 230 thousand out of 1.8 million thalamus
cell nuclei would be directly hit by one or more particles with z >=
15 on such a mission.
---------------------------------------------------------
Title: Preface
Authors: Vazquez, M. E.
1998AdSpR..22..169V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The IAC's Near Infrared Camera
Authors: Collados, M.; Joven, E.; Fuentes, F. J.; Diaz, J. J.;
Gonzalez Escalera, V.; Bonet, J. A.; Vazquez, M.
1997ASPC..118..361C Altcode: 1997fasp.conf..361C
Here we report the main characteristics of the recently acquired near
infrared camera. It is based on a 256x256 HgCdTe Nicmos-3 array,
sensitive from 1 mu m to 2.5mu m. The pixel size is 40mu mx40mu
m, adequate for the spatial and spectral scales at the different
telescopes operating at the observatories of La Palma and Tenerife. The
cooling system operates with LN2 with a hold time larger than 20
hours. The camera will be used for photometric, spectroscopic and
spectropolarimetric observations.
---------------------------------------------------------
Title: 1st Advances in Solar Physics Euroconference: Advances in
the Physics of Sunspots
Authors: Schmieder, B.; del Toro Iniesta, J. C.; Vazquez, M.
1997ASPC..118.....S Altcode: 1997fasp.conf.....S
No abstract at ADS
---------------------------------------------------------
Title: Spatial changes of the oscillatory pattern in sunspot penumbrae
at the photospheric level.
Authors: Marco, E.; Aballe Villero, M. A.; Vazquez, M.; Garcia de La
Rosa, J. I.
1996A&A...309..284M Altcode:
We analyze time sequences of photospheric spectral lines in the penumbra
of two sunspots. Two spectral lines sensitive to velocity fluctuations
at two different heights in the atmosphere (Ti I 8396.9A and Fe II
7224.5A) are used. The observations were taken using the Gregory-Coude
Telescope (GCT) at the Observatorio del Teide (Tenerife). Velocity
fluctuations were determined by measuring the shifts of the line
cores. The oscillatory power was calculated at three frequency bands:
low frequency (1.5-2.5mHz), and five (2.8-3.8mHz) and three minute
bands (5.1-6.1mHz). The main results are: -For the first time penumbral
oscillations are clearly detected in the deep layers of the photosphere
(Fe II line). -Significant variations are found between the inner,
medium and outer parts of the penumbra. Based on a geometrical model for
the average inclination of the magnetic field lines and assuming that
these are co-spatial with the filaments, we conclude that for the lower
photospheric layers (Fe II line) the velocity perturbations, at the
inner and middle penumbra, are aligned with magnetic field lines. This
is clearly not the case for the outer penumbra. However, the Ti line,
formed in the upper layers, exhibits a more irregular behaviour. Hence,
the oscillatory behaviour of the penumbral upper layers does not seem
to be related to the filamentary topology visible in the continuum.
---------------------------------------------------------
Title: Numerical modelling of spectral line asymmetries in
photospheric structures. II. Plage regions.
Authors: Marquez, I.; Bonet, J. A.; Vazquez, M.
1996A&A...306..305M Altcode:
A numerical code has been developed for modelling the asymmetries in
three spectral lines (K I 7699, Fe I 5576 and Fe I 5635A) formed at
different photospheric heights and observed in plage regions near the
solar disk center. The aim of this work was to reproduce the absolute
line bisectors obtained from low resolution observations. The mere
insertion of a flux tube in a model of quiet granulation, without
mutual interaction, has proved insufficient to explain many of
the observational results. Therefore, several models of abnormal
granulation close to the tube, representing the influence of the
magnetic field, are considered. The code consists of two computation
modules, one representing a model of the unperturbed photosphere,
and the other including a flux tube inserted in a model of altered
granulation; various combinations of both computation modules allow
different values of the magnetic filling factor to be simulated. The
influence of other physical parameters and observational aspects
on the bisector is also discussed, e.g. waves, microturbulence,
defective time or spatial averages, etc. The proposed model reproduces
the observed variation in the shape and in the absolute shift of the
bisector when the filling factor increases. Likewise, the computed
spatial distribution of intensity in the continuum fits many of the
photometric results reported in the literature for plage regions.
---------------------------------------------------------
Title: Numerical modelling of spectral line asymmetries in
photospheric structures. I. Quiet Sun.
Authors: Marquez, I.; Bonet, J. A.; Vazquez, M.; Woehl, H.
1996A&A...305..316M Altcode:
Modelling of asymmetries in spectral lines with different formation
heights (K I 7699, Fe I 5576 and Fe I 5635A), observed in the quiet Sun
at the disk center, has been performed with the aim of reproducing the
absolute line bisectors obtained from low resolution observations. The
influence of a number of physical and observational factors on the
bisector shape and line shifts, acting together or separately, is
discussed, e.g. mesogranular flows, waves, microturbulence, defective
temporal and spatial averages, etc. The simulations are based on the
VAL-C model (Vernazza et al. 1981) representing the mean photosphere,
and the granular model by Nelson (1978). Following evidence in the
literature, the best match to the observed absolute mean bisectors
is obtained by including in the numerical code a gravity wave and
a strengthening of the microturbulence in the lower layers of the
intergranule.
---------------------------------------------------------
Title: Book-Review : New Windows to the Universe vol. 1 and 2
Authors: Sanchez, R.; Vazquez, M.; Andrews, A. D.
1996IrAJ...23Q.127S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Optic systems with spherical, cylindrical, and toric surfaces
Authors: Barcala, J.; Vazquez, M. C.; Garcia, A.
1995ApOpt..34.4900B Altcode:
A simple analytical method for tracing rays in an optical system that is
made up of spherical, cylindrical, and toric surfaces with an arbitrary
rotation of its meridian plane with respect to the reference system
is described. An analytical procedure is also given for obtaining
the spot diagram on an arbitrarily oriented section, as well as for
relating the diagram obtained for the plane of this section as a plane
z = 0. Finally, as an application of this procedure, several graphic
representations of the spot diagrams in the planes perpendicular or
nonperpendicular to the axis are presented.
---------------------------------------------------------
Title: Photometry of sunspot pores from partial eclipse observations.
Authors: Bonet, J. A.; Sobotka, M.; Vazquez, M.
1995A&A...296..241B Altcode:
White-light images, centered at λ6708A, were obtained at the Swedish
Solar Telescope, La Palma, on occasion of the 1994 May 10 partial solar
eclipse. From the recorded information, 5 frames showing several pores
together with the moon's limb were selected for detailed photometric
analysis. The observed intensity profile of the moon's limb projected
against the solar disk was used to derive, from each frame, the
Point Spread Function of the atmosphere + instrument to restore the
images. The characteristics of the obtained PSFs -low noise and precise
determination of the wings far away from the core- enabled us to avoid
arbitrary assumptions about analytical approximations. The FWHM of these
functions was typically 0.47". Several bright features were identified
in one of the pores. After determining the photometric parameters of
these fine umbral structures their link with the population of the
bright features in the umbra of evolved spots is discussed in the
framework of the dependence of sunspot properties on the spot size.
---------------------------------------------------------
Title: Observed differences between large and small sunspots.
Authors: Collados, M.; Martinez Pillet, V.; Ruiz Cobo, B.; del Toro
Iniesta, J. C.; Vazquez, M.
1994A&A...291..622C Altcode:
We confirm recent results about the differences in temperature
and magnetic field strength between the umbra of large and small
sunspots. Five Stokes I- and V-spectra from the darkest cores of
three different umbrae have been analysed with the inversion code
of the radiative transfer equation by Ruiz Cobo & del Toro
Iniesta (1992). The run with depth of temperature, magnetic field
(strength and inclination) and velocity along the line of sight are
obtained. The larger sunspots turn out to be cooler and possesing
a larger magnetic field strength, practically throughout the whole
atmosphere. Neither significant gradients of the line-of-sight velocity,
nor of the magnetic field inclination, are detected in any of the
spots analysed. Two model atmospheres are given corresponding to hot
(small) and cool (large) sunspots. The models are, to a large extent,
free from effects of penumbral/photospheric stray-light because it is
nearly absent in the large spots and because in the small one, where
it is important for the Stokes I-profile, only Stokes V is considered
to obtain the model atmosphere. These are the first umbral models in
the literature for which a simultaneous determination of the magnetic
field and thermodynamic stratifications is presented. The implications
of these stratifications for the energy transport in sunspot umbrae
are discussed.
---------------------------------------------------------
Title: Neuritogenesis: A model for space radiation effects on the
central nervous system
Authors: Vazquez, M. E.; Broglio, T. M.; Worgul, B. V.; Benton, E. V.
1994AdSpR..14j.467V Altcode: 1994AdSpR..14..467V
Pivotal to the astronauts' functional integrity and survival during long
space flights are the strategies to deal with space radiations. The
majority of the cellular studies in this area emphasize simple
endpoints such as growth related events which, although useful to
understand the nature of primary cell injury, have poor predictive
value for extrapolation to more complex tissues such as the central
nervous system (CNS). In order to assess the radiation damage on neural
cell populations, we developed an in vitro model in which neuronal
differentiation, neurite extension, and synaptogenesis occur under
controlled conditions. The model exploits chick embryo neural explants
to study the effects of radiations on neuritogenesis. In addition,
neurobiological problems associated with long-term space flights
are discussed.
---------------------------------------------------------
Title: Variations of properties of the quiet photosphere along the
equator and the central meridian: Spectroscopic results
Authors: Rodriguez Hidalgo, I.; Collados, M.; Vazquez, M.
1994A&A...283..263R Altcode:
Spectra of four lines (CI5380.3 A, MnI 5394.7 A, FeI 5930.2 A and
SiI 5948.5 A) have been obtained in the quiet photosphere, at regular
intervals along the polar axis and the equator. The spatially averaged
spectra have been analyzed, studying the center-to-limb variation (CLV)
and possible changes with the heliographic latitude of the residual
intensity (RI), equivalent width (EW), full width at half line minimum
(FWHM), and bisector of the line profiles. The aim of this spectroscopic
study is to complete the photometric work carried out and recently
published by the authors (Rodriguez Hildago et al. 1992, hereafter Paper
I). It allows us to test some conclusions of Paper I and to extend our
analysis to higher photospheric layers. Firstly the general behavior
of the CLV is shown and discussed. From the comparison betwen the CLV
along the North-South and East-West diameters, it is observed that the
Cl line, formed very deep in the photosphere, broadens and shows raised
minima with latitude, not showing variations in its EW, except at very
high latitudes. The other three lines, which inform about the physical
conditions in the middle photosphere, become deeper and stronger, and
the FeI one seems broader, with latitude. The observational results
are discussed in terms of physical scenarios based on changes in the
velocity fields present in the photosphere (mainly of the granulation),
possible spatial anisotropies in the distribution of network bright
points (which would be related to differences in the mean temperature
gradient) and the latitudinal variation of the granulation contrast
found in Paper I.
---------------------------------------------------------
Title: Spatially highly resolved time series of solar granulation
spectra.
Authors: Hanslmeier, A.; Bonet, J. A.; Vazquez, M.
1994AGAb...10..114H Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The distribution of sunspot decay rates.
Authors: Martinez Pillet, V.; Moreno-Insertis, F.; Vazquez, M.
1993A&A...274..521M Altcode:
The distribution of sunspot decay rates is studied using the Greenwich
Photoheliographic Results (GPR) for a total of approximately hundred
years between 1874 and 1976. <P />The decay rates are seen to be
lognormally distributed. The discrepancies between the decay rates
given in the past by different authors are shown to originate as
a consequence of this asymmetric distribution. It is pointed out
that the extended tails shown by the lognormal distributions are
associated to spots decaying much faster than suggested by Bumba's
(1963) work. A cycle by cycle analysis of the lognormal distributions
associated with each sunspot group type and for single spots is
presented. The differences between the nine solar cycles involved are
studied. <P />As a remarkable property of the decay process, we show
that it happens at a nearly constant total to umbral area ratio. This
property holds for decaying spots which are still large enough to
show a penumbra. <P />We have studied the suitability of a decay law
with the instantaneous decay rate proportional to the length of the
spot boundary. This law predicts a parabolic decay pattern with some
specific characteristics. No definite conclusion in favour of this
law is reached, but it is suggested that a linear decay is as weakly
supported by the GPR data as a peripheral one. On the other hand, weak
non-linearities are seen in the decay of isolated spots with a clear
tendency to produce a convex pattern in the area vs. time diagram. The
implication is that sunspot decay is braked as time proceeds.
---------------------------------------------------------
Title: The continuum intensity-magnetic field relation in sunspot
umbrae
Authors: Martinez Pillet, V.; Vazquez, M.
1993A&A...270..494M Altcode:
We describe the work carried out to obtain observational evidence
of a local relation between the temperature and the magnetic field in
different regions of several sunspots. Information about the temperature
is extracted from the continuum intensity. The magnetic field is
deduced by using the Stokes V profile of lines with different excitation
potentials. A scaling relation between Stokes V and continuum intensity
is used to estimate the stray-light contamination. The observed local
relation between continuum intensity and magnetic field can be adapted
to the equations describing magnetostatic horizontal force balance. The
commonly accepted value for the Wilson depression suggests that the
tension forces are as important as the magnetic pressure in defining
horizontal equilibrium. The local relation observed holds for spatial
scales larger than 1 arcsec. Evidence of unresolved hot magnetic regions
inside the umbra is presented. Our study provides clues pointing to a
dependence of continuum intensity with sunspot area. Small spots are
seen to be brighter than big ones.
---------------------------------------------------------
Title: High Resolution Observations of Umbral Fine Structure
Authors: Sobotka, M.; Bonet, J. A.; Vazquez, M.
1993ASPC...46...20S Altcode: 1993mvfs.conf...20S; 1993IAUCo.141...20S
No abstract at ADS
---------------------------------------------------------
Title: The Continuum Intensity Magnetic Field Relation in Sunspot
Umbrae
Authors: Martinez Pillet, V.; Vazquez, M.
1993ASPC...46...60M Altcode: 1993mvfs.conf...60M; 1993IAUCo.141...60M
No abstract at ADS
---------------------------------------------------------
Title: The Distribution of Sunspot Decay Rates
Authors: Martinez Pillet, V.; Moreno-Insertis, F.; Vazquez, M.
1993ASPC...46...67M Altcode: 1993mvfs.conf...67M; 1993IAUCo.141...67M
No abstract at ADS
---------------------------------------------------------
Title: On the correlation of power in sunspot umbral oscillations
with continuum brightness
Authors: Aballe Villero, M. A.; Marco, E.; Vazquez, M.; Garcia de La
Rosa, J. I.
1993A&A...267..275A Altcode:
We analyze time sequences of spectral lines formed at the photospheric
level in order to study the correlation of umbral oscillations with
continuum brightness and the influence of the fine structure and
evolutionary stage of sunspots. The observations were taken using
the Gregory-Coude Telescope (GCT) at the Observatorio del Teide
(Tenerife). Power integrated in two frequency bands, 5 minutes (2.5-4.5
mHz) and 3 minutes (5-7 mHz), are used as parameters for this study. Our
study yields the following results. A clear correlation exists between
the power at the 3 minute band and the umbral brightness in dark
cores. The light bridges do not follow this behavior. No correlation
is apparent between the 5 minute power and the brightness. The same
is obtained after normalization to the power in the adjacent light
bridges. There is no correlation between the umbral oscillations
of different umbral dark cores. The center-to-limb variation of the
power (both bands) seems to support the interpretation of the umbral
oscillations as slow body modes. Finally, we discuss the physical
context of the observations.
---------------------------------------------------------
Title: Centre-to-limb variation of solar granulation along the
equator and the central meridian
Authors: Rodriguez Hidalgo, I.; Collados, M.; Vazquez, M.
1992A&A...264..661R Altcode:
The paper analyzes white-light images of solar granulation taken
outside active regions, at regular intervals along the polar axis
and the equator, in order to study its center-to-limb variation
and possible changes with the solar latitude. The 2D spatial
power spectra of the brightness distribution are calculated and
corrected for the distortions produced by the atmosphere and the
telescope. One-dimensional integrated spectra are obtained for each
position, with the geometrical foreshortening effect taken into
account. A lower contrast, a smaller mean wavenumber, and a steeper
center-to-limb variation of the contrast are found in the central
meridian as compared to the equator. Sources of error are discussed,
and different scenarios are presented in order to interpret these
observational facts. Intensity fluctuations were detected until the
extreme limb, with a spatial scale of about 10 arcsec.
---------------------------------------------------------
Title: Book-Review - Solar Observations - Techniques and
Interpretation - First Canary Islands Winter School of Astrophysics
Authors: Sanchez, F.; Collados, M.; Vazquez, M.; Staude, J.
1992AN....313Q.302S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectroscopic determination of intensities of umbral bright
features and adjacent background
Authors: Sobotka, M.; Bonet, J. A.; Vazquez, M.
1992A&A...260..437S Altcode:
Profiles of the Na I D doublet in three bright features (clusters
of umbral dots), located in a relatively dark umbra, were analyzed
by means of the 'local two-component modeling' to obtain the 'true'
continuum intensities and temperatures of the bright features and
their dark surroundings (background). The intensities of two central
and one peripheral bright feature were 0.31 (background 0.11), 0.33
(0.13), and 0.40 (0.17), respectively. For the ratio of the object and
background intensity (assumed to be constant, but unknown until now)
the value of 2.6 +/- 0.2 was obtained.
---------------------------------------------------------
Title: On the relation between the intensities of bright features
and the local background in sunspot umbrae
Authors: Sobotka, M.; Bonet, J. A.; Vazquez, M.
1992A&A...257..757S Altcode:
A photometric study of umbral bright features (umbral dots, clusters
of umbral dots, bright grains of light bridges) in sunspots is
presented. It is based on white-light images taken with a CCD video
camera driven by an automatic image selection system. A direct linear
relation between the observed brightness of the features and that
of the surrounding background areas has been found. To eliminate the
influence of the seeing on this result, the radiative fluxes, which
are much less sensitive to the image degradation, have been examined
and an analogous relation has been found. Finally, a possible physical
explanation is suggested.
---------------------------------------------------------
Title: Book-Review - Solar Observations - Techniques and
Interpretations
Authors: Sanchez, F.; Collados, M.; Vazquez, M.
1992Sci...255.1757S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Estimating the Degradation of Brightness Power Spectra of
Solar Granulation from Images Outside the Disk Centre
Authors: Rodriguez Hidalgo, I.; Collados, M.; Vazquez, M.
1992A&A...254..371R Altcode:
A method is presented to estimate the influence of the atmospheric
turbulence and the telescope on the mean power spectra of the
granulation brightness distribution at positions outside the disk
centre, derived using the determination of Fried's parameter. <P />The
procedure is based on the differential degradation suffered by the
directions perpendicular and parallel to the solar limb; the former one
is more affected because it contains more power at high frequencies,
due to the geometrical foreshortening effect. A certain spectral ratio
is defined, which can be evaluated after the observed power spectra
and can be described directly by a Korff's function for a given value
of the Fried parameter r<SUB>0</SUB>. The best fit of the measured
attenuation to the theoretical one is calculated, allowing to obtain
the adequate Modulation Transfer Function to reconstruct the original
power spectra. A test has been performed by evaluating the mentioned
ratio after restored spectra showing that these present the required
elongation up to a resolution of about 0".4.
---------------------------------------------------------
Title: Solar observations : techniques and interpretation
Authors: Sanchez, F.; Collados, M.; Vazquez, M.
1992soti.book.....S Altcode:
This book includes four chapters devoted to techniques and
interpretation of solar observations. The chapter on high spatial
resolution techniques considers basic concepts, single frame analysis,
interferometry techniques, and other methods. The magnetic field
measurements chapter discusses a prototype polarimeter, physical
components of polarimeters, radiative transfer for polarized radiation,
transfer equations for the Stokes parameters in a magnetized atmosphere,
and magnetic field measurements in unresolved structures and in
prominences. The chapter on solar postfocus instrumentation gives
particular attention on the locations of postfocus instrumentation,
postfocus imaging, spectrometers, detectors for spectrometers, and
special instruments at spectrometer foci. The chapter on the dynamics
of the solar atmosphere focuses on the features of the solar structure,
diagnostic methods for velocity measurements, rotation and convection,
motions in magnetic flux tubes and spots, and velocity fields in
prominences and filaments.
---------------------------------------------------------
Title: Book-Review - New Windows to the Universe
Authors: Sanchez, F.; Vazquez, M.
1991Sci...254.1667S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Observations
Authors: Sánchez, F.; Collados, M.; Vazquez, M.
1991soob.book.....S Altcode:
This book is a collection of papers by four internationally known
speakers who explore some key areas in solar physics. O. von der Lühe
discusses new techniques that are being developed for observing the sun
at high spatial resolution and which have played a key role in most
of the recent discoveries about the Sun. Egidio Landi Degl'Innocenti
describes the magnetic field that dominates much of the structure we
see and many of the active phenomena on the Sun. An understanding of
how to measure the field is important. New solar telescopes in Europe
and the United States have led the way in the present revolution
in the understanding of the sun and important new breakthroughs are
expected from LEST. In particular, the post-focus instrumentation has
been crucial, and this is detailed by Hubertus Wohl; finally Pierre
Mein writes about the solar atmosphere, which is now known to be a
dynamic atmosphere with many puzzling features.
---------------------------------------------------------
Title: Asymmetries and shifts of the solar K I 7699 A line and
possible evidence for gravity waves in the quiet photosphere
Authors: Bonet, J. A.; Marquez, I.; Vazquez, M.; Woehl, H.
1991A&A...244..492B Altcode:
A computing code has been developed to simulate the center-to-limb
variation (CLV) of the bisector's shape, and absolute wavelength
shift of the core in strong photospheric lines. Observational results
concerning these aspects are also reported for the K I 7699 line. In
the numerical simulation, granulation is represented, as a first
approximation, by means of the granular model by Nelson (1978). It
appears that granulation alone does not reproduce the observations and
thus some modification has to be implemented in the dynamical model
employed. A good match to the observed CLV of the wavelength shift
of the line core is achieved by adding two 8-min period gravity waves
with horizontal wavelength of the granular scale, the only difference
between them being the sign of their horizontal wavenumber. Changes
in the phase difference between the oscillating parameters have a
decisive influence on the result.
---------------------------------------------------------
Title: Book-Review - New Windows to the Universe - 11TH European
Regional Astronomy Meeting - V.1&2
Authors: Sanchez, F.; Vazquez, M.
1991JBAA..101..128S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar Research at the I.A.C.
Authors: Vazquez, M.
1991ApL&C..28..113V Altcode: 1991ApL....28..113V
No abstract at ADS
---------------------------------------------------------
Title: Circular Polarization of the CA II H and K Lines in Solar
Quiet and Active Regions
Authors: Martinez Pillet, V.; Garcia Lopez, R. J.; del Toro Iniesta,
J. C.; Rebolo, R.; Vazquez, M.; Beckman, J. E.; Char, S.
1990ApJ...361L..81M Altcode:
A representative set of profiles is presented for the Ca II H resonace
line in Stokes V and I, for the quiet sun, plages, sunspot umbrae,
and a flare, as well as one example of the Ca II K line in a sunspot
penumbra. The degree of polarization is highest in the spots and zero
in the quiet sun, within error limits. The V profile asymmetries are,
however, highest in the flare. The spectra of the Ca II K line are
used to obtain a linear relation between V(lambda) and -dI/d(lambda)
and a value for B(parallel) of 820 + or - 40 G using the weak-field
approximation.
---------------------------------------------------------
Title: New windows to the universe
Authors: Sanchez, F.; Vazquez, M.
1990Ap&SS.171.....S Altcode:
Topics discussed in this issue include active galaxies and
cosmology, interstellar and intergalactic medium, and astronomical
instrumentation. Papers are presented on modeling rich clusters of
galaxies, optical variability of NGC 7469 in 1967-1987, the structure
of the broad line region in Fairall 9, the resolution of the compact
core of quasars and active galaxies with the gravitational lens effect,
and galaxy formation in pancake models. Consideration is also given
to molecular clouds around outflow sources, modeling OH in regions of
star formation, density studies of giant extragalactic H II regions,
observations of the star formation region NGC 7129, and interstellar
medium parameters derived from low-frequency variability. Other
papers are on recent developments of IR array cameras in France, an
automated astrographic plates measuring process, a low-resolution
spectrophotometer for measuring the integrated color of galaxies,
the HUS solar flare and cosmic gamma-ray burst detector aboard the
Ulysses spacecraft, and the Grecos operating system of the GCT.
---------------------------------------------------------
Title: Decay rates of sunspot groups from 1874 to 1976
Authors: Martinez Pillet, V.; Moreno-Insertis, F.; Vazquez, M.
1990Ap&SS.170....3M Altcode:
The global behaviour and fine structure of the distribution of sunspot
decay rates from activity cycle 13 to 20 are presented. It is shown
that the distribution of this parameter is lognormal. Statistically
significantly lower values of decay rates are found in cycles 13,
14, and 18 for isolated spots. The complex groups had no appreciable
changes.
---------------------------------------------------------
Title: Fried's Parameter Derived from Observations of Granulation
Outside the Disk Centre
Authors: Rodriguez Hidalgo, I.; Collados, M.; Vazquez, M.
1990Ap&SS.170..155R Altcode:
A new method has recently been developed to obtain the Fried's parameter
from observations of granulation outsude the disk centre, based on
the different degradation suffered by the images on the directions
parallel and perpendicular to the solar limb, due to the geometrical
foreshortening. This procedure has been applied to CCD images obtained
at the Swedish Solar Tower of the Observatorio del Roque de los
Muchachos, with satisfactory results which are presented and discussed.
---------------------------------------------------------
Title: On the Continuum Intensity Magnetic Field Relation Along the
Decay Phase of Sunspots
Authors: Martinez Pillet, V.; Vazquez, M.
1990Ap&SS.170...75M Altcode:
We present continuum intensity-magnetic field distributions for a
decaying sunspot. It is shown that a very simple model accounts for
the observed correlation. The Wilson depression is determined.
---------------------------------------------------------
Title: Oscillatory Behaviour in Sunspot Umbrae
Authors: Aballe Villero, M. A.; Garcia de La Rosa, J. I.; Vazquez,
M.; Marco, E.
1990Ap&SS.170..121A Altcode:
Using a set of series of spectra of high spectral resoltion
corresponding to the same umbra on several days, we have studied the
oscillations related to evolution of the two main dark cores of it. We
have detected differences in the behaviour of each core and an evolution
in the power spectra not related with the external appearance of the
spot. A quite constant value of the ratio of power at five minutes
over three minutes has been found.
---------------------------------------------------------
Title: New windows to the universe; Proceedings of the Eleventh
European Regional Astronomy Meeting, Universidad de la Laguna, Spain,
July 3-8, 1989. Part II
Authors: Sanchez, F.; Vazquez, M.
1990Ap&SS.170.....S Altcode: 1990Ap&SS.170...91S
Recent observational and theoretical investigations of the sun and
sunlike stars and of galactic structure and evolution are discussed in
reviews and reports. Topics addressed include sunspot-group decay rates
for 1874-1976, photometry and spectroscopy of solar granulation along
the polar axis and equator, the quiescent radio emission of RS CVn
binaries, and two-dimensional high-resolution spectroscopy of quiet
regions on the sun. Consideration is given to spherical harmonics
and Taylor harmonics in the kinematics of the solar neighborhood,
radio observations of early-type galaxies with dust lanes, mean-field
escapers in nonequilibrium systems, long-slit spectroscopy of the
nuclear zone of NGC 253, the early nucleosynthesis of O and Fe,
the structure and dynamics of two-dimensional oval configurations,
and stochasticity in galactic models.
---------------------------------------------------------
Title: Photometry and Spectroscopy of the Solar Granulation Along
the Polar Axis and Equator
Authors: Rodriguez Hidalgo, I.; Collados, M.; Vazquez, M.
1990Ap&SS.170...23R Altcode:
From high-resolution CCD images of granulation obtained at the Swedish
Solar Tower of the Observatorio del Roque de los Muchachos at different
positions on the solar disk, mean bi-dimensional spatial power spectra
have been obtained at each position and restored following the method
proposed by Rodríguez Hidalgoet al. (1990). The variation with latitude
of the power spectrum, of the granular brightness contrast and of the
mean wave number of the power spectrum are presented. The analysis
is completed with spectroscopic observations obtained at the Gregory
Coudé Telescope of the Observatorio del Teide. The centre-to-limb
and latitudinal variation of the bisectors, residual intensities and
equivalent widths are shown for several photometric lines.
---------------------------------------------------------
Title: New windows to the universe. Vol.1, Vol.2
Authors: Sanchez, F.; Vazquez, M.
1990Ap&SS.169.....S Altcode:
Papers are presented on stellar structure and evolution. Particular
attention is given to the deep CCD photometry of stars in the globular
cluster M3; dynamical instability in accreting white dwarfs; the
IR photometry of open clusters; stellar mass loss in late B-type
supergiants; and multicolor photopolarimetry of magnetic catalysmic
variables. Consideration is also given to white dwarfs with magnetic
field and differential rotation, phase shifts between colors in
pulsating stars, axion decay in a strong magnetic field and radio fluxes
from magnetic white dwarfs, and line transfer in supernovae envelopes.
---------------------------------------------------------
Title: Preface
Authors: Sanchez, F.; Vazquez, M.
1990Ap&SS.169D...9S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Stray-light measurements at the Observatorio del Teide
Authors: Martinez Pillet, V.; Ruiz Cobo, B.; Vazquez, M.
1990SoPh..125..211M Altcode:
A new procedure to separate the instrumental and atmospheric components
of stray light is presented. It is based on the dependence of the
aureole's atmospheric component on the air mass and is applied to
measurements taken with the Vacuum Newton Telescope (VNT) at the
Observatorio del Teide (Tenerife). The resulting instrumental part
is independent of the air mass. The variation of both components
with wavelength is also studied. The instrumental component shows no
dependence on wavelength, in contrast to the atmospheric one which is
greater in the blue than in the red. It is concluded that observations
with air masses larger than two will probably be strongly affected by
stray light.
---------------------------------------------------------
Title: Comparison of heliographic sunspot coordinates observed with
seven different solar telescopes.
Authors: von Alvensleben, A.; Casas, R.; Csepura, G.; Lustig, G.;
Otruba, W.; Schroll, A.; Vazquez, M.; Wittmann, A. D.; Wöhl, H.
1990AGAb....5...43V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: New windows to the universe. Volumes I, II. Invited review
papers and general lectures.
Authors: Sanchez, F.; Vazquez, M.
1990nwtu.book.....S Altcode:
Contents: Vol. I: The Sun and solar-like stars. Stellar structure and
evolution. Astronomical instrumentation. General lectures. Vol. II:
Structure and evolution of galaxies. Active galaxies and
cosmology. Interstellar and intergalactic medium.
---------------------------------------------------------
Title: New Windows to the Universe, Set, XIth European Meeting of
the International Astronomical Union
Authors: Sanchez, F.; Vazquez, M.
1990nwus.book.....S Altcode: 1990nwus....2.....S
No abstract at ADS
---------------------------------------------------------
Title: Book-Review - the Role of Finescale Magnetic Fields on the
Structure of the Solar Atmosphere
Authors: Schroter, E. H.; Vazquez, M.; Wyller, A. A.; Wiedemann, E.
1989AN....310..318S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A statistical study of the decay phase of sunspot groups from
1874 to 1939
Authors: Moreno-Insertis, F.; Vazquez, M.
1988A&A...205..289M Altcode:
A statistical study of the decay of sunspots and sunspot groups is
carried out using data contained in the Greenwich Photoheliographic
Results. The period studied spans more than six decades, namely from
1874 to 1939. The adequacy of exponential, quadratic and linear
decay laws to the area decay data is considered. The dependence,
or otherwise, of the mean area decay rate for each single spot, D,
on its maximum area, A<SUB>0</SUB>, is studied; no relationship of the
form D(A<SUB>0</SUB>) can be ascertained. In fact, when plotted on a
D vs. A<SUB>0</SUB> diagram, the couples (A<SUB>0</SUB>, D) cluster
in two pencils issuing from the origin of coordinates. These two
clusters can be seen to correspond with the families of the recurrent
and non-recurrent spot groups. The adequacy of a quadratic law to
the decay data is considered. A most probable parabolic decay law is
obtained; this law corresponds to the case in which the decay rate
is proportional to the spot perimeter. Finally, the variation of the
decay rates in successive activity cycles is also discussed.
---------------------------------------------------------
Title: Book-Review - the Role of Finescale Magnetic Fields on the
Structure of the Solar Atmosphere
Authors: Schroter, E. H.; Vazquez, M.; Wyller, A. A.
1988S&T....76R.264S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Temporal and center-to-limb variations of the K I 769.9 NM
line profiles in quiet and active solar regions
Authors: Bonet, J. A.; Marquez, I.; Vazquez, M.; Woehl, H.
1988A&A...198..322B Altcode:
The temporal and spatial behaviour of the K I 769.9 nm solar line are
investigated using several series of high spectral resolution low-noise
photoelectric scans obtained at Kitt Peak National Observatory in
quiet and active (plages and sunspots) regions. Corrections due
to the instrumental profile were applied to yield the best line
shape. A systematic center-to-limb investigation of the behaviour
of the line shape was performed in quiet regions. Power and phase
spectra of the main parameters defining the line shape have also
been determined. Within several umbrae at different cos θ positions,
an inverse C-shape or even an "S"-shape of the bisectors was found.
---------------------------------------------------------
Title: Photometry of sunspot penumbrae
Authors: Collados, M.; del Toro Iniesta, J. C.; Vazquez, M.
1988A&A...195..315C Altcode:
The authors present the results of a statistical analysis of the
penumbra of sunspots. The intensity distribution, and several
parameters derived from it, is analysed at different heliocentric
angles and positions on the spot. It has revealed, on the one hand,
that a two-component model is compatible with the observations and
that both components lie at the same height, and on the other, that
the penumbral asymmetry found by Collados et al. (1987) is confirmed
under a photometrical point of view, the western penumbra being slightly
shorter than the eastern one.
---------------------------------------------------------
Title: On the Age Dependence of the Asymmetry of Penumbrae of Sunspots
Authors: Collados, M.; del Toro Iniesta, J. C.; Vazquez, M.; Woehl, H.
1988SoPh..117..199C Altcode:
The age dependence of the recently described asymmetry of penumbrae
of large stable sunspots was analyzed. Young sunspots showed shorter
eastern penumbrae, which differed by a maximum of ± 10 % from their
mean width. For older sunspots the western penumbrae became smaller
than the mean penumbra reaching differences of 20 % for spots of two
months age.
---------------------------------------------------------
Title: Coordination of Astronomical Observations at the Canary
1049.01-ISLANDS
Authors: Sanchez, F.; Vazquez, M.
1988copa.conf..181S Altcode:
The Instituto de Astrofisica de Canarias has two observatories on the
Canary Islands; Roque de los Muchachos Observatory on La Palma and Teide
Observatory, on Tenerife. In this contribution the authors explain the
guidelines for the allocation of this observing time and mention some
of the future plans for remote observing and control of the telescopes.
---------------------------------------------------------
Title: A Statistical Study of the Geometrical Wilson Effect
Authors: Collados, M.; del Toro Iniesta, J. C.; Vazquez, M.
1987SoPh..112..281C Altcode:
An analysis has been carried out of the centre-to-limb variation of the
apparent sizes of the umbra, penumbra and whole spot. It has revealed
that the umbral size decreases with height. We have interpreted this
result in terms of the penumbral geometrical height scale. A value
of 230 km, which is larger than that of the photosphere or the umbra,
explains the observed decrease. An intrinsic asymmetry in the penumbra
of old sunspots has also been found, the western penumbra being slightly
shorter that the rest of the penumbra. This explains why the inverse
Wilson effect is present, preferentially, in the western hemisphere,
as found in previous investigations. A comparison with other works is
also made.
---------------------------------------------------------
Title: A new determination of the solar granulation contrast
Authors: Collados, M.; Vazquez, M.
1987A&A...180..223C Altcode:
The contrast of the photospheric granulation in the centre of the
disk at a wavelength of 500 nm has been determined by means of
photographs taken during the solar eclipse of May 30<SUP>th</SUP>
1984. After restoration, values of 17.3% and 20.4%, using the sum of
two lorentzians to define the instrumental profile, and of 11.7% and
14.3%, using the sum of two gaussians, have been obtained. This suggests
that the results are quite sensitive to the particular choice which is
made of the analytical approximation to the point spread function. The
corrected power spectrum does not show significant differences to those
of previous works. A comparison between the method for correcting the
image degradation which the authors propose with those used by other
investigators is also made.
---------------------------------------------------------
Title: Variation of the granulation with the solar latitude.
Authors: Collados, M.; Rodriguez Hidalgo, I.; Vazquez, M.
1987PAICz..66...41C Altcode: 1987eram....1...41C
Preliminary results of a search for the variation of the
solar granulation properties with the heliographic latitude are
presented. Within errors, no changes are found in the power spectra
and sizes between N-S and E-W scans.
---------------------------------------------------------
Title: Granulation Deformation Near and in Sunspot Regions
Authors: Collados, M.; Marco, E.; del Toro, J. C.; Vazquez, M.
1986SoPh..105...17C Altcode:
High-resolution white-light pictures are analyzed to study the
differences between the granular size near sunspot penumbrae and in
light-bridges presenting granular structure and that of the quiet
photosphere. No difference is found between the mean granular diameter
in light-bridges and the quiet photosphere. The dispersion found in the
results corresponding to different zones around the sunspots indicates
that the size of the granulation may vary from place to place near the
sunspots, its mean value not differing significantly from that of the
quiet photosphere. A possible systematic bias in the selection of the
granules by Macris (1979) is found.
---------------------------------------------------------
Title: Differential rotation of sunspot groups in the period from
1874 through 1976 and changes of the rotation velocity within the
solar cycle
Authors: Balthasar, H.; Vazquez, M.; Woehl, H.
1986A&A...155...87B Altcode:
An effort is made to determine the differential rotation of the sun
on the basis of the complete sample (1874-1976) of the Greenwich
Photoheliographic Results. In order to improve the representation
of differential rotation, a modified fit formula whose constant
lies at 15 deg latitude (where sunspots nearly always occur) is
introduced. Rotation is noted to strongly depend on sunspot type,
with C-groups exhibiting high velocities and H- and J-spots the lowest
ones. The new fit formula indicates that the highest velocity is found
around the minima; at the beginning of an activity maximum, there
is a secondary velocity maximum. The lowest velocities lie between
the activity maximum and minimum. The braking of recurrent sunspots
is confirmed.
---------------------------------------------------------
Title: Observations of the Birth and Fine Structure of Sunspot
Penumbrae
Authors: Collados, M.; Garcia de La Rosa, J. I.; Moreno-Insertis,
F.; Vazquez, M.
1985LNP...233..133C Altcode: 1985hrsp.proc..133C
High resolution white-light pictures of sunspot penumbrae are
presented. These include pictures showing details of their filamentary
structure and some instances of the birth of a penumbra. The
observations are discussed in the framework of current penumbra
theories.
---------------------------------------------------------
Title: Photometry of Light-Bridges in Sunspots
Authors: Collados, M.; Marco, E.; Vazquez, M.
1985LNP...233..299C Altcode: 1985hrsp.proc..299C
The decay of a sunspot region was studied using high resolution
white-light pictures. The photometric and geometric parameters of a
light-bridge showing granular structure were determined. No difference
is found comparing it with the quiet photosphere.
---------------------------------------------------------
Title: The response of the line KI 7699 to the solar oscillations
Authors: Marmolino, C.; Roberti, G.; Severino, G.; Vazquez, M.;
Woehl, H.
1984ESASP.220..191M Altcode: 1984ESPM....4..191M
The time behavior of the KI 7699 line profile in presence of
acoustic-gravity waves with periods of 300, 180, and 30 sec was
studied. The response of the line to the waves depends strongly on
the period and is not linear for the 30 sec wave. The height increase
of the amplitude in the longer period waves explains the observed
anticorrelation between line asymmetry and line core shift. The time
averaged profile for the 30 sec wave has a red shifted line core. This
could account for the lowest part of the C shaped solar bisectors.
---------------------------------------------------------
Title: New information about solar rotation
Authors: Woehl, H.; Balthasar, H.; Koch, A.; Kueveler, G.; Roca-Cortes,
T.; Schmidt, W.; Vazquez, M.
1984S&W....23...73W Altcode:
It is pointed out that the phenomenon of solar rotation is known
since the introduction of the telescope into astronomy by Galilei in
1610. Regular measurements concerning the positions of sunspots were
conducted with the aid of photographic plates at the Royal Greenwich
Observatory during the time from 1874 to 1976. The obtained data
provide an excellent basis for statistical analysis. Information
obtained as a result of such analyses is discussed. Attention is given
to the determination of the Wilson depression, details regarding
solar differential rotation, plans for an evaluation of data with
the aid of a computer, the rotation of the solar plasma, a comparison
of sunspots and plasma, the theory of differential rotation, and new
information concerning solar rotation partly obtained with the aid of
solar telescopes in a Spanish observatory on the island of Tenerife.
---------------------------------------------------------
Title: The Age Decay of Stellar Magnetic Activity in MS Field Solar
Type Stars
Authors: Cabestany, J.; Vazquez, M.
1983Ap&SS..97..151C Altcode:
The age decay of two indicators of the stellar magnetic activity (λ
2800 Mg ii emission flux and λ 10830 He i equivalent width) have been
studied for field solar-type stars. The Li abundance has been used,
in most of the cases, as a stellar age indicator. A calibrated decay
law for Mg ii has been determined and compared with a similar one,
recently published, for the Ca ii K emission. The greater scatter in
the He i results is atributed to the different rotation rates.
---------------------------------------------------------
Title: Space and time variations of KI 7699 solar line profile
Authors: Roca-Cortes, T.; Vazquez, M.; Woehl, H.
1983SoPh...88....1R Altcode:
The temporal and spatial behaviour of the KI7699 line profile is
investigated. In particular we have measured the asymmetries of the line
profile at several residual intensities using the bisector method. We
find, in the bisector of the mean line profile, similar shapes as those
obtained before for different positions on the solar disk. However the
strong variations of the bisector found with time and geometry of input
aperture, warns us against the use of the mean or integrated profiles
(either in time or space). Moreover, we find an anticorrelation between
the asymmetry in the line profile at different residual intensities
and the shift, found as the distance to a terrestrial line, for any
position observed on the solar disk. No limb effect for this line is
found, within errors.
---------------------------------------------------------
Title: Erratum - Differential Rotation and Meridional Motions of
Sunspots from 1874 TO 1902
Authors: Arevalo, M. J.; Gomez, R.; Vazquez, M.; Balthasar, H.;
Wohl, H.
1983A&A...117..170A Altcode:
No abstract at ADS
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Title: Introduction to the theory of stellar atmospheres
Authors: Vazquez, M.
1983STIN...8331559V Altcode:
The fundamental equations of continuity and transport, the Eddington
approximation, the excitation, ionization and absorption processes,
the formation of spectral lines, and the models of stellar atmospheres
are described. Convection in the stellar atmosphere is discussed
including the Schwarzschild criterium, the computation of velocity
fields, and the characteristics of chromospheres and coronas.
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Title: Differential rotation and meridional motions of sunspots from
1874 to 1902
Authors: Arevalo, M. J.; Gomez, R.; Vazquez, M.; Balthasar, H.;
Woehl, H.
1982A&A...111..266A Altcode:
Position data of sunspot groups from the period 1874-1902 are used to
investigate the differential rotation of the Sun and the meridional
motions of the sunspots. The equatorial velocity is higher than in
the period 1940-1968 investigated by Balthasar and Wöhl (1980), while
differences between the northern and southern hemispheres are less. For
cycle 12 we find meridional motions towards north while in cycle 13 the
motions are directed towards south like in the period 1940-1968. Our
other results are comparable to those of Balthasar and Wöhl (1980)
for the period 1940-1968.
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Title: On the Width Distribution of Penumbral Filaments in Sunspots
Authors: Bonet, J. A.; Ponz, J. D.; Vazquez, M.
1982SoPh...77...69B Altcode:
The mean width and distribution of penumbral filaments of a sunspot have
been estimated, using white light photographs obtained with a vacuum,
Newtonian type, telescope. Three areas corresponding to the penumbra
of a sunspot have been analysed. Data were collected during the solar
eclipse of June 1973. The photometric profiles of the Moon limb over the
photosphere have been analysed to obtain useful information on both,
atmospheric and instrumental perturbation on each exposure. The mean
value of the width of penumbral filaments is 0.37 arc sec.
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Title: A model for constructing artificial integrated spectral lines
and their Fourier transform properties relevant to the search for
differential rotation of stars
Authors: Garcia-Alegre, M. C.; Vazquez, M.; Woehl, H.
1982A&A...106..261G Altcode:
A model is given for constructing artificial integrated spectral lines
which allows the inclusion of all effects relevant to the synthesis
of these lines by numerical methods. Among the effects included are
noise, limb darkening, the centre-to-limb variation of the shapes and
wavelength positions of the spectral line profiles, different laws
of the differential rotation and a tilting of the rotating star. <P
/>Fourier transformation of the artificial integrated spectral lines
is applied to decide whether the different effects may influence the
possibility of detecting stellar differential rotation by the method
of Gray (1977).
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Title: IUE MG II doublet observations in F and G main sequence stars.
Authors: Garcia-Alegre, M. C.; Ponz, J. D.; Vazquez, M.
1981A&A....96...17G Altcode:
Mg II resonance lines at 2800 A were studied in the spectra of F
and G main sequence stars, observed with the IUE satellite in high
resolution mode. Correlation with other chromospheric indicators were
investigated and a search was conducted for the best candidates to
continue further studies of differential rotation. An attempt has been
made to see whether there is a unique relation between the logarithm
of the Mg II k emission line width and the absolute visual magnitude,
independent of luminosity and emission strengths, as derived for the
Ca II K emission line.
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Title: Large-Scale Solar Motions as Determined by Doppler Shift
Measurements Using a Linear Photodiode Array
Authors: Perez Garde, M.; Vazquez, M.; Schwan, H.; Woehl, H.
1981A&A....93...67P Altcode: 1981MiABB..96...67P
Doppler shifts of the solar Fe line 630.15 nm relative to the
terrestrial O2 line 630.2 nm were determined at many positions on
the solar disk to investigate the rotation of the solar plasma and
locate large-scale plasma motions. The spectrum was measured by a
self-scanning linear photodiode array with 128 diodes; and average
rotation velocity of (2.881 plus or minus 0.027) microrad/s was found at
the solar equator in September 1978, and large-scale velocity pattern
occurred between plus 40 and minus 30 deg in latitude with a period
of 45 deg in longitude during Sept. 6 to 13, 1978.
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Title: An Umbral Brightening Associated with a Two-Ribbon Flare
Authors: Vazquez, M.; Herrera, F.
1979SoPh...64..329V Altcode:
We report an unusual case of a two-ribbon flare associated with an
umbral brightening in a magnetically unipolar region.
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Title: An attempt to compare the differential rotation of the
Ca<SUP>+</SUP>-network with that of the photospheric plasma.
Authors: Schroeter, E. H.; Woehl, H.; Soltau, D.; Vazquez, M.
1978SoPh...60..181S Altcode:
In this third paper of a series we report on results obtained
from almost simultaneous observations of the differential
rotation of the Ca<SUP>+</SUP>-chromosphere and the photospheric
plasma. The observations (tracings of Ca<SUP>+</SUP>-mottles,
Doppler-shift-measurements in a photospheric line) were performed
at the Locarno station during two extended periods in 1976. Both
data sets were used to search for a large scale circulation
pattern. A regular long-lived pattern could not be detected, but a
single cell with radial outflow (∼40 ms<SUP>-1</SUP>) extending
over more than 50° in longitude has been found. Statistically
significant temporal changes of the differential rotation law of the
Ca<SUP>+</SUP>-chromosphere correlated with changes of meridional
motions and differences in the rotation of the two hemispheres
were observed. The data of 1976 show no significant difference in
the equatorial velocity of the Ca<SUP>+</SUP>-chromosphere and the
photosphere. A comparison of temporal variations of the rotation
velocity of the Ca<SUP>+</SUP>-mottles and the photospheric plasma
yielded no significant correlation. Finally, we correlated the
measurements of the photospheric rotation performed within the
equatorial belts at Locarno with those obtained at Mt. Wilson by a
different method during the same periods. The Locarno data show small
temporal variations (±50 m<SUP>-1</SUP>s) with no correlation between
the two hemispheres, while from the Mt. Wilson data larger variations
(±100 m s<SUP>-1</SUP>) with a very high correlation between the two
hemispheres have been found. A comparison of both sets of data yielded
no correlation at all demonstrating the need for further coordinated
observations and a drastic increase of internal accuracy.
---------------------------------------------------------
Title: Flamenco Sounding Rocket
Authors: Simon, J.; Mateo, A.; Vazquez, M.
1976ESASP.115..541S Altcode: 1976epsr.conf..541S
No abstract at ADS
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Title: Differential Rotation and the Spot Zones
Authors: Deubner, F. -L.; Vazquez, M.
1975SoPh...43...87D Altcode:
A minimum of angular velocity is not found at the equator as suggested
by Gilman, but at a latitude of 6° in both hemispheres.
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Title: Aspectos magneticos de la evolucion de las manchas solares.
Authors: Casanovas, J.; Vazquez, M.; Bonet, J. A.
1974UrBar..59...79C Altcode:
The spectroscopic determinations of the solar magnetic fields are based
on the Zeeman effect observed in relation to a number of absorption
lines of the solar spectrum. It is attempted to deduce indirectly
certain characteristics of the magnetic field in a sunspot, giving
attention to morphological aspects and the magnetic polarities. The
results of the investigation are illustrated with the aid of a number
of pictures.
---------------------------------------------------------
Title: A Morphological Study of the Light-Bridges in Sunspots
Authors: Vazquez, M.
1973SoPh...31..377V Altcode:
This study is based on photographs taken during the period March 1971
to June 1972. Various morphological features observed are described and
their possible role in sunspot evolution discussed. It is pointed out
that a light-bridge looks like the re-establishment of photospheric-like
conditions.
