pinecone/core-2020-05-10-deduplication huggingface dataset:
Photometric Properties of Long-period Variables in the Large Magellanic Cloud

Approximately four thousand light curves of red variable stars in the LMC were selected from the 2.3-years duration MOA database by a period analysis using the Phase Dispersion Minimization method. Their optical features (amplitudes, periodicities, position in CMD) were investigated. Stars with large amplitues and high periodicities were distributed on the only one strip amongst multiple structure on the LMC period-luminosity relation. In the CMD, the five strips were located in the order of the period. The stars with characterized light curves were also discussed
Astrometry of circumstellar masers

The circumstellar masers around evolved stars offer an interesting possibility to measure stellar parameters through VLBI astrometry. In this paper the application of this technique is discussed, including the accuracy and the uncertainties of the method. The different maser species (OH, H_2O, SiO) have slightly different characteristics and applications. This paper does not concern astrometry of maser spots to study the kinematics of the envelope, but concentrates on attempting to measure the motion of the underlying star
Nonlinear Properties of the Semiregular Variable Stars

We demonstrate how, with a purely empirical analysis of the irregular lightcurve data, one can extract a great deal of information about the stellar pulsation mechanism. An application to R Sct thus shows that the irregular lightcurve is the result of the nonlinear interaction of two highly nonadiabatic pulsation modes, namely a linearly unstable, low frequency mode, and the second mode that, although linearly stable, gets entrained through a 2:1 resonance. In the parlance of nonlinear dynamics the pulsation is the result of a 4 dimensional chaotic dynamics
Spectral Indices of Stars at Super-solar Regime

We derived Lick narrow-band indices for 139 candidate super metal-rich stars of different luminosity class previously studied in Malagnini et al. (2000). Indices include Iron Fe50, Fe52, Fe53, and Magnesium Mgb and Mg2 features. By comparing observations with Kurucz' synthetic model atmospheres, no evidence is found for non-standard Mg vs. Fe relative abundance (i.e. [Mg/Fe]~ 0, on the average, for our sample). A comparison with the Worthey et al.(1994) and Buzzoni et al.(1992, 1994) fitting function predictions for [Fe/H] > 0 is performed and briefly discussed
Nishimori point in random-bond Ising and Potts models in 2D

We study the universality class of the fixed points of the 2D random bond
q-state Potts model by means of numerical transfer matrix methods. In
particular, we determine the critical exponents associated with the fixed point
on the Nishimori line. Precise measurements show that the universality class of
this fixed point is inconsistent with percolation on Potts clusters for q=2,
corresponding to the Ising model, and q=3Comment: 11 pages, 3 figures. Contribution to the proceedings of the NATO
  Advanced Research Workshop on Statistical Field Theories, Como 18-23 June
  200
Nonlinear Impurity Modes in Homogeneous and Periodic Media

We analyze the existence and stability of nonlinear localized waves described
by the Kronig-Penney model with a nonlinear impurity. We study the properties
of such waves in a homogeneous medium, and then analyze new effects introduced
by periodicity of the medium parameters. In particular, we demonstrate the
existence of a novel type of stable nonlinear band-gap localized states, and
also reveal an important physical mechanism of the oscillatory wave
instabilities associated with the band-gap wave resonances.Comment: 11 pages, 3 figures; To be published in: Proceedings of the NATO
  Advanced Research Workshop "Nonlinearity and Disorder: Theory and
  Applications" (Tashkent, 2-6 Oct, 2000) Editors: P.L. Christiansen and F.K.
  Abdullaev (Kluwer, 2001
Large-Scale Environmental Effects of the Cluster Distribution

Using the APM cluster distribution we find interesting alignment effects: (1) Cluster substructure is strongly correlated with the tendency of clusters to be aligned with their nearest neighbour and in general with the nearby clusters that belong to the same supercluster, (2) Clusters belonging in superclusters show a statistical significant tendency to be aligned with the major axis orientation of their parent supercluster. Furthermore we find that dynamically young clusters are more clustered than the overall cluster population. These are strong indications that cluster develop in a hierarchical fashion by merging along the large-scale filamentary superclusters within which they are embedded
Scale Dependence of Dark Energy Antigravity

We investigate the effects of negative pressure induced by dark energy (cosmological constant or quintessence) on the dynamics at various astrophysical scales. Negative pressure induces a repulsive term (antigravity) in Newton's law which dominates on large scales. Assuming a value of the cosmological constant consistent with the recent SnIa data we determine the critical scale $r_c$ beyond which antigravity dominates the dynamics ($r_c \sim 1Mpc $) and discuss some of the dynamical effects implied. We show that dynamically induced mass estimates on the scale of the Local Group and beyond are significantly modified due to negative pressure. We also briefly discuss possible dynamical tests (eg effects on local Hubble flow) that can be applied on relatively small scales (a few $Mpc$) to determine the density and equation of state of dark energy
Geometrical Aspects of Cosmic Magnetic Fields

We discuss how the vector nature of magnetic fields, and the geometrical
interpretation of gravity introduced by general relativity, lead to a special
coupling between magnetism and spacetime curvature. This magneto-geometrical
interaction effectively transfers the tension properties of the field into the
spacetime fabric, triggering a variety of effects with potentially far-reaching
implications.Comment: To appear in proceedings of the 2nd Hellenic Cosmology Workshop,
  Athens 2001 (Kluwer-ASSL series
Inflation in String Theory and how you can get out of it

Inflation is now a basic ingredient of the modern cosmology. After reviewing
the basic characteristics of inflation, we briefly discuss inflation in string
and brane theories, focusing on the problem of the exit from inflation in these
theories. We present a model, based on type-0 string theory, in which our
universe after the inflationary phase, passes smoothly to a flat
Robertson-Walker universe.Comment: 11 pages, 2 figures, Talk given at the 2nd Hellenic Cosmology
  Workshop, National Observatory of Athens (Penteli), 19-20 April 2001.
  References adde
Experimental testing of the blind ocean acoustic tomography concept

Acoustic focalization is a well known concept that aims at estimating source location
through the adjustment of multiple environmental parameters. This paper uses the same
concept for inverting water column sound speed in a blind fashion, where both source
location and source emitted waveform are not known at the receiver - that is Blind Ocean
Acoustic Tomography (BOAT). The results obtained with BOAT, using ship noise data
received on a vertical line array in a shallow water area off the coast of Portugal, show
that it is indeed possible to obtain reliable joint estimates of source location and water
column sound speed. During that process, it was shown that source range and depth,
and Bartlett power, where good indicators of the degree of focus of the model being
used.This work was supported by FCT, Portugal, under projects INTIMATE
(2/2.1/MAR/1698/95) and ATOMS (PDCTM/P/MAR/15296/1999). The authors
are also in debt to the crew of NRP D. Carlos I of IH, that made the sea trial successful
OPTICON: EC Optical Infrared Coordination Network for Astronomy

OPTICON, the ICN Optical Infrared Coordination Network for Astronomy, brings together for the first time the operators of all Europe's medium to large optical-infrared telescopes, the largest corresponding data archives, and several user representatives. The OPTICON partners work with their communities to identify those major challenges for the future development of European optical-infrared astronomy which require Europe-wide collaboration. OPTICON sponsors and coordinates developments towards these goals, involving the entire astronomical community through workshops and meetings targeted towards these agreed common goals of general importance
Dynamics of localization in a waveguide

This is a review of the dynamics of wave propagation through a disordered
N-mode waveguide in the localized regime. The basic quantities considered are
the Wigner-Smith and single-mode delay times, plus the time-dependent power
spectrum of a reflected pulse. The long-time dynamics is dominated by resonant
transmission over length scales much larger than the localization length. The
corresponding distribution of the Wigner-Smith delay times is the Laguerre
ensemble of random-matrix theory. In the power spectrum the resonances show up
as a 1/t^2 tail after N^2 scattering times. In the distribution of single-mode
delay times the resonances introduce a dynamic coherent backscattering effect,
that provides a way to distinguish localization from absorption.Comment: 18 pages including 8 figures; minor correction
Probing the Neutron Star Interior with Glitches

With the aim of constraining the structural properties of neutron stars and
the equation of state of dense matter, we study sudden spin-ups, glitches,
occurring in the Vela pulsar and in six other pulsars. We present evidence that
glitches represent a self-regulating instability for which the star prepares
over a waiting time. The angular momentum requirements of glitches in Vela
indicate that at least 1.4% of the star's moment of inertia drives these
events. If glitches originate in the liquid of the inner crust, Vela's
`radiation radius' $R_\infty$ must exceed ~12 km for a mass of 1.4 solar
masses. The isolated neutron star RX J18563-3754 is a promising candidate for a
definitive radius measurement, and offers to further our understanding of dense
matter and the origin of glitches.Comment: Invited talk at the Pacific Rim Conference on Stellar Astrophysics,
  Hong Kong, Aug. 1999. 9 pages, 5 figure
A New Parameter In Accretion Disk Model

Taking optically thin accretion flows as an example, we investigate the
dynamics and the emergent spectra of accretion flows with different outer
boundary conditions (OBCs) and find that OBC plays an important role in
accretion disk model. This is because the accretion equations describing the
behavior of accretion flows are a set of {\em differential} equations,
therefore, accretion is intrinsically an initial-value problem. We argue that
optically thick accretion flow should also show OBC-dependent behavior. The
result means that we should seriously consider the initial physical state of
the accretion flow such as its angular momentum and its temperature. An
application example to Sgr A$^*$ is presented.Comment: 6 pages, 4 figures, to appear in the Proceeding of "Pacific Rim
  Conference on Stellar Astrophysics", Aug. 1999, HongKong, Chin
On the inverse Compton scattering model of radio pulsars

Some characteristics of the inverse Compton scattering (ICS) model are
reviewed. At least the following properties of radio pulsars can be reproduced
in the model: core or central emission beam, one or two hollow emission cones,
different emission heights of these components, diverse pulse profiles at
various frequencies, linear and circular polarization features of core and
cones.Comment: 5 pages, no figures, LaTeX, a proceeding paper for Pacific Rim
  Conference on Stellar Astrophysics, Aug. 1999, HongKong, Chin
Can Mira Variables Tell us the Chemical Abundances in Stellar Systems?

A period-metallicity relation for oxygen-rich Miras derived from globular
clusters is applied to similar variables in the galactic Bulge. The metallicity
distribution in the Bulge thus obtained is in good agreement with that derived
from K giants. This suggests that the periods of Miras are useful indicators of
metallicity distributions, at least in old systems such as galactic bulges. For
systems such as the LMC the situation is not yet clear.Comment: 8 pages, 2 figures. Proceedings of Roma-Trieste Workshop on: The
  Chemical Evolution of the Milky Way. To be published by Kluwer; editors: F.
  Giovannelli & F. Matteucc
Compact High-Velocity Clouds at High Resolution

Six examples of the compact, isolated high-velocity clouds catalogued by
Braun & Burton (1999) and identified with a dynamically cold ensemble of
primitive objects falling towards the barycenter of the Local Group have been
imaged with the Westerbork Synthesis Radio Telescope; an additional ten have
been imaged with the Arecibo telescope. The imaging reveals a characteristic
core/halo morphology: one or several cores of cool, relatively
high-column-density material, are embedded in an extended halo of warmer,
lower-density material. Several of the cores show kinematic gradients
consistent with rotation; these CHVCs are evidently rotationally supported and
dark-matter dominated. The imaging data allows several independent estimates of
the distances to these objects, which lie in the range 0.3 to 1.0 Mpc. The CHVC
properties resemble what might be expected from very dark dwarf irregular
galaxies.Comment: 12 pages, 7 figures, to appear in "The Chemical Evolution of the
  Milky Way: Stars versus Clusters", eds. F. Matteuchi and F. Giovannelli,
  Kluwer Academic Publisher
Chemical yields from low- and intermediate-mass stars

We present new sets of chemical yields from low- and intermediate-mass stars
with 0.8 Msun <= M <= Mup ~ 5 Msun, and three choices of the metallicity,
Z=0.02, Z=0.008, and Z=0.004 (Marigo 2000, in preparation). These are then
compared with the yields calculated by other authors on the basis of different
model prescriptions, and basic observational constraints which should be
reproduced.Comment: 6 pages, 4 postscript figures, to appear in "The chemical evolution
  of the Milky Way: stars versus clusters", Proceedings of the Roma-Trieste
  Workshop, (Vulcano, September 1999), eds. F. Matteucci and F. Giovannell
Observational Constraints to the Evolution of Massive Stars

We consider some aspects of the evolution of massive stars which can only be
elucidated by means of "indirect" observations, i.e. measurements of the
effects of massive stars on their environments. We discuss in detail the early
evolution of massive stars formed in high metallicity regions as inferred from
studies of HII regions in external galaxies.Comment: 6 pages, 1 figure; Invited Paper presented at the Roma-Trieste
  Workshop 1999 "The Chemical Evolution of the Milky Way: Stars versus
  Clusters", Vulcano Island (ME, Italy), 20-24 September, 1999, eds. F.
  Giovannelli & F. Matteucci, Kluwer-Holland (in press
The Chemical Evolution of the Milky Way

The field of chemical evolution modeling of the Galaxy is experiencing in the
last years a phase of high activity and important achievements. There are,
however, several open questions which still need to be answered. In this review
I summarize what have been the most important achievements and what are some of
the most urgent questions to be answered.Comment: 10 pages including 3 figs, to appear in "The Chemical Evolution of
  the Milky Way. Stars vs Clusters", Proceedings of the Sept.1999 Vulcano
  Workshop, F.Giovannelli and F.Matteucci eds (Kluwer, Dordrecht) in pres
Reconstructing the Star Formation History of the Galaxy

The evolution of the star formation rate in the Galaxy is one of the key
ingredients quantifying the formation and determining the chemical and
luminosity evolution of galaxies. Many complementary methods exist to infer the
star formation history of the components of the Galaxy, from indirect methods
for analysis of low-precision data, to new exact analytic methods for analysis
of sufficiently high quality data. We summarise available general constraints
on star formation histories, showing that derived star formation rates are in
general comparable to those seen today. We then show how colour-magnitude
diagrams of volume- and absolute magnitude-limited samples of the solar
neighbourhood observed by Hipparcos may be analysed, using variational calculus
techniques, to reconstruct the local star formation history. The remarkable
accuracy of the data coupled to our maximum-likelihood variational method
allows objective quantification of the local star formation history with a time
resolution of ~ 50 Myr. Over the past 3Gyr, the solar neighbourhood star
formation rate has varied by a factor of ~ 4, with characteristic timescale
about 0.5Gyr, possibly triggered by interactions with spiral arms.Comment: 12 pages, Proc. of the Sept. 20-24, 1999 Vulcano Workshop ``The
  chemical evolution of the Milky Way: stars vs. clusters'', eds. F. Matteucci
  & F. Giovanell
Formation of Disk Galaxies: On the Angular Momentum Problem, the
  Tully-Fisher Relation and Magnetohydrodynamics

Two ways of possibly solving the angular momentum problem plaguing cold dark
matter (CDM) ab initio simulations of disk galaxy formation are discussed: 1)
Stellar feedback processes and 2) Warm dark matter (WDM) rather than CDM.
  In relation to the chemical evolution of disk galaxies our simulations
indicate that in case 1) the first generation of disk stars formed in disk
galaxies like the Milky Way should have an abundance about two dex below solar,
in fairly good agreement with the lowest observed abundance of the metal-weak
tail of the Galactic thick disk. For the second case no such statements can be
made without further assumptions about the star-formation history of the
galaxies.
  We find that the I-band Tully-Fisher relation can be matched by WDM disk
galaxy formation simulations provided (M/L_I) is about 0.8 for disk galaxies,
which Sommer-Larsen & Dolgov (1999) argue is a reasonable value.
  Finally it is discussed how the magnetic field strengths observed in galactic
disks can be obtained through disk galaxy formation, as an alternative to the
conventional dynamo hypothesis.Comment: 10 pages incl. 5 figures (Kluwer NATO format). Contribution to the
  Roma-Trieste Workshop 1999 "The Chemical Evolution of the Milky Way: Stars
  versus Clusters", Vulcano, September 20-24, 199
Planetary Nebulae as Probes of Stellar Evolution and Populations

Planetary Nebulae (PNe) have been used satisfactory to test the effects of
stellar evolution on the Galactic chemical environment. Moreover, a link exists
between nebular morphology and stellar populations and evolution. We present
the latest results on Galactic PN morphology, and an extension to a distance
unbiased and homogeneous sample of Large Magellanic Cloud PNe. We show that PNe
and their morphology may be successfully used as probes of stellar evolution
and populations.Comment: to appear in: Chemical Evolution of the Milky Way: stars versus
  clusters, ed. F. Giovannelli and F. Matteucci, Kluwer (2000), in pres
X-Ray and Radio Observations of Bright GeV Sources

We present X-ray and radio studies of sources which are brightabove 1 GeV (F_{>1GeV} > 4e-8 ph/cm^2/s. Only 11 out of ~30 of these gamma-ray sources have been identified with lower energy counterparts: 5 blazars and 6 pulsars. Three of these pulsars are surrounded by radio pulsar wind nebulae (PWN), two of which are also seen as bright, extended X-ray synchrotron nebulae. The ASCA X-ray telescope has observed 28 of the bright GeV sources, revealing an excess of F_{2-10keV} > 10e-12 ergs/cm^2/s sources within the {\it EGRET} error contours of the unidentified sources. Although several supernova remnants are positionally coincident with these sources, we find no X-ray evidence of high energy particle production in SNR shell shocks consistent with the GeV positions. We also present initial results from follow on radio imaging studies of several fields containing unidentified sources. We have discovered new X-ray/radio nebulae in three of these fields which are strong candidates for PWN. These sources, along with a similar nebula in CTA 1 and the PWN around PSR B1853+01 in W44, are all positionally coincident with variable EGRET sources. This suggests a class of variable gamma-ray sources associated with synchrotron emitting regions powered by the winds of young pulsars
Space Based Astronomy

This NASA educator guide tells the story of why it is important to observe celestial objects from outer space and how to study the entire electromagnetic spectrum. It features a set of hands-on activities and demonstrations which can be performed by teachers to reinforce the concept that Earth's atmosphere interferes with the passage of electromagnetic radiation and to investigate the properties and uses of radiation throughout the electromagnetic spectrum. Educational levels: Intermediate elementary, Middle school
Reaction kinetics of the thermal decomposition of cellulose and hemicellulose in biomass materials

Sugar cane bagasse, wheat straw, pine and cotton wood pyrolysis was studied by TGA in argon at heating rates of 5 and 20°C/min. The DTG ( dm/dt) peaks associated with the components of an untreated plant material are relatively wide and strongly overlap each other. A reduction in the amount of inorganic ions in the samples by simple water or dilute acid washing procedures resulted in sharper peaks with a better separation. The thermal decomposition of the major biomass components was described, more or less formally, by first order reactions and the DTG curves of the biomass samples were approximated by a linear combination of first order reactions. Good fits between the calculated and the experimental data and good reproducibility of the model parameters were achieved. The kinetic model applied here may serve as a starting point to build more complex models capable of describing the thermal behavior of plant materials during a thermal or thermochemical processing or burning. Theoretically, there is also a possibility to utilize this sort of calculation in the quantitative analysis of the cellulose and hemicellulose content of the lignocellulosic materials
Use of Vesicular - Arbuscular Mycorrhiza (VAM) as Biofertilizer for Horticultural Plants in Developing Countries

Mycorrhiza is the product of an association between a fungus and plant root. Vesicular-arbuscular mycorrhiza (VAM) is formed by the symbiotic association between certain phycomycetous fungi and angiosperm roots. The fungus colonizes the root cortex forming a mycelial network and characteristic vesicles (bladder-like structures) and arbuscules (branched finger-like hyphae). The mycelia are aseptate or septate ramifying intercellularly thus causing little damage to tissues. The arbuscules are the most characteristic structures, formed intracellularly and probably having an absorptive function. The vesicles are terminal swellings of hyphae formed inter and intracellularly having a storage function. There are six genera of fungi belonging to Endogonaceae which have been shown to form mycorrhizal associations: Glomus, Gigaspora, Acaulospora, Entrophospora Sclerocystis and Scutellospora. These are mainly identified by their characteristic spores and sporocarps which are formed mostly in the soil surrounding the roots and rarely inside the roots. The identification of VAM fungi directly from roots has been difficult. One of the striking features of VAM fungi is their very wide host range which includes angiosperm species belonging to almost all the families. Even the roots of some aquatic plants are colonized by VAM fungi