5,542 research outputs found
Sex differences in variability across timescales in BALB/c mice.
BackgroundFemales are markedly underinvestigated in the biological and behavioral sciences due to the presumption that cyclic hormonal changes across the ovulatory cycle introduce excess variability to measures of interest in comparison to males. However, recent analyses indicate that male and female mice and rats exhibit comparable variability across numerous physiological and behavioral measures, even when the stage of the estrous cycle is not considered. Hormonal changes across the ovulatory cycle likely contribute cyclic, intra-individual variability in females, but the source(s) of male variability has, to our knowledge, not been investigated. It is unclear whether male variability, like that of females, is temporally structured and, therefore, quantifiable and predictable. Finally, whether males and females exhibit variability on similar time scales has not been explored.MethodsThese questions were addressed by collecting chronic, high temporal resolution locomotor activity (LA) and core body temperature (CBT) data from male and female BALB/c mice.ResultsContrary to expectation, males are more variable than females over the course of the day (diel variability) and exhibit higher intra-individual daily range than females in both LA and CBT. Between mice of a given sex, variability is comparable for LA but the inter-individual daily range in CBT is greater for males. To identify potential rhythmic processes contributing to these sex differences, we employed wavelet transformations across a range of periodicities (1-39 h).ConclusionsAlthough variability in circadian power is comparable between the sexes for both LA and CBT, infradian variability is greater in females and ultradian variability is greater in males. Thus, exclusion of female mice from studies because of estrous cycle variability may increase variance in investigations where only male measures are collected over a span of several hours and limit generalization of findings from males to females
Teaching Object-Oriented Programming Concepts Using Visual Basic .NET
This paper presents an object-oriented approach to Visual Basic .NET instruction to be delivered in a traditional academic semester for information system curricula. The paper first discusses some of the inherent problems with Visual Basic .NET instruction and then proposes an object-oriented approach. This approach includes a systematic set of programming projects to take students on a journey that traces the principles of the object-oriented, the event-driven, and the procedural paradigms into a coherent framework. The Unified Modeling Language Class Diagram notation is used to model an object-oriented system that is developed and enhanced throughout the duration of the course. Practical recommendations and programming exercises are provided and evaluated in the discussion. This course is intended to be at minimum a second programming course for information system students to satisfy IS 2002 guidelines
Hodge numbers for the cohomology of Calabi-Yau type local systems
We use Higgs cohomology to determine the Hodge numbers of the first
intersection cohomology group of a local system V arising from the third direct
image of a family of Calabi-Yau 3-folds over a smooth, quasi-projective curve.
We give applications to Rhode's families of Calabi-Yau 3-folds without MUM.Comment: Some signs corrected. This article draws heavily from arXiv:0911.027
Vacuum energy for the supersymmetric twisted D-brane in constant electromagnetic field
We calculate vacuum energy for twisted SUSY D-brane on toroidal background
with constant magnetic or constant electric field. Its behaviour for toroidal
D-brane (p=2) in constant electric field shows the presence of stable minimum
for twisted versions of the theory. That indicates such a background maybe
reasonable groundstate.Comment: LaTeX, 10 page
Leo V: A Companion of a Companion of the Milky Way Galaxy
We report the discovery of a new Milky Way dwarf spheroidal galaxy in the
constellation of Leo identified in data from the Sloan Digital Sky Survey. Leo
V lies at a distance of about 180 kpc, and is separated by about 3 degrees from
another recent discovery, Leo IV. We present follow-up imaging from the Isaac
Newton Telescope and spectroscopy from the Hectochelle fiber spectrograph at
the Multiple Mirror Telescope. Leo V's heliocentric velocity is 173.4 km/s,
which is offset by about 40 km/s from that of Leo IV. A simple interpretation
of the kinematic data is that both objects may lie on the same stream, though
the implied orbit is only modestly eccentric (e = 0.2)Comment: Submitted to ApJ (Letters
The Via Lactea INCITE Simulation: Galactic Dark Matter Substructure at High Resolution
It is a clear unique prediction of the cold dark matter paradigm of
cosmological structure formation that galaxies form hierarchically and are
embedded in massive, extended dark halos teeming with self-bound substructure
or "subhalos". The amount and spatial distribution of subhalos around their
host provide unique information and clues on the galaxy assembly process and
the nature of the dark matter. Here we present results from the Via Lactea
INCITE simulation, a one billion particle, one million cpu-hour simulation of
the formation and evolution of a Galactic dark matter halo and its substructure
population.Comment: 10 pages, Proceedings of the SciDAC 2008 conference, (Seattle, July
13-17, 2008
Investigation of the New Local Group Galaxy VV 124
We present the results of our stellar photometry and spectroscopy for the new
Local Group galaxy VV 124 (UGC 4879) obtained with the 6-m BTA telescope. The
presence of a few bright supergiants in the galaxy indicates that the current
star formation process is weak. The apparent distribution of stars with
different ages in VV 124 does not differ from the analogous distributions of
stars in irregular galaxies, but the ratio of the numbers of young and old
stars indicates that VV 124 belongs to the rare Irr/Sph type of galaxies. The
old stars (red giants) form the most extended structure, a thick disk with an
exponential decrease in the star number density to the edge. Definitely, the
young population unresolvable in images makes a great contribution to the
background emission from the central galactic regions. The presence of young
stars is also confirmed by the [O III] emission line visible in the spectra
that belongs to extensive diffuse galactic regions. The mean radial velocity of
several components (two bright supergiants, the unresolvable stellar
population, and the diffuse gas) is v_h = -70+/-15 km/s and the velocity with
which VV 124 falls into the Local Group is v_LG = -12+/-15 km/s. We confirm the
distance to the galaxy D = 1.1+/-0.1 Mpc and the metallicity of red giants
([Fe/H] = -1.37) found by Kopylov et al. (2008).VV 124 is located on the
periphery of the Local Group approximately at the same distance from M 31 and
our Galaxy and is isolated from other galaxies. The galaxy LeoA nearest to it
is 0.5 Mpc away.Comment: 10 pages, 8 figures. Accepted for publication in Astronomy Letters
(2010, Vol. 36, No. 5, pp. 309-318
Alcohol Schema Acquisition in Preschoolers: Differences Between Children of Alcoholics and Children of Nonalcoholics
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65209/1/j.1530-0277.1995.tb00982.x.pd
The discovery of two extremely low luminosity Milky Way globular clusters
We report the discovery of two extremely low luminosity globular clusters in
the Milky Way Halo. These objects were detected in the Sloan Digital Sky Survey
Data Release 5 and confirmed with deeper imaging at the Calar Alto Observatory.
The clusters, Koposov 1 and Koposov 2, are located at kpc and
appear to have old stellar populations and luminosities of only
mag. Their observed sizes of pc are well within the expected tidal
limit of 10 pc at that distance. Together with Palomar 1, AM 4 and
Whiting 1, these new clusters are the lowest luminosity globulars orbiting the
Milky Way, with Koposov 2 the most extreme. Koposov 1 appears to lie close to
distant branch of the Sagittarius stream. The half-mass relaxation times of
Koposov 1 and 2 are only and Myr respectively (2 orders of
magnitude shorter than the age of the stellar populations), so it would seem
that they have undergone drastic mass segregation. Since they do not appear to
be very concentrated, their evaporation timescales may be as low as . These discoveries show that the structural parameter space of
globular clusters in the Milky Way halo is not yet fully explored. They also
add, through their short remaining survival times, significant direct evidence
for a once much larger population of globular clusters.Comment: accepted for publication in ApJ, minor revision
HD 5388 b is a 69 M_Jup companion instead of a planet
We examined six exoplanet host stars with non-standard Hipparcos astrometric
solution, which may be indicative of unrecognised orbital motion. Using
Hipparcos intermediate astrometric data, we detected the astrometric orbit of
HD 5388 at a significance level of 99.4 % (2.7 sigma). HD 5388 is a
metal-deficient star and hosts a planet candidate with a minimum mass of 1.96
M_J discovered in 2010. We determined its orbit inclination to be i = 178.3
+0.4/-0.7 deg and the corresponding mass of its companion HD 5388 b to be M_2 =
69 +/- 20 M_J. The orbit is seen almost face-on and the companion mass lies at
the upper end of the brown-dwarf mass range. A mass lower than 13 M_J was
excluded at the 3-sigma level. The astrometric motions of the five other stars
had been investigated by other authors revealing two planetary companions, one
stellar companion, and two statistically insignificant orbits. We conclude that
HD 5388 b is not a planet but most likely a brown-dwarf companion. In addition,
we find that the inclinations of the stellar rotation axis and the companion's
orbital axis differ significantly.Comment: 5 pages, 4 figures, Accepted for publication in Astronomy and
Astrophysics Letter
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