591 research outputs found
Geminin deficiency enhances survival in a murine medulloblastoma model by inducing apoptosis of preneoplastic granule neuron precursors
Vascular uptake of rehydration fluids in hypohydrated men at rest and exercise
The purpose of this study was to formulate and to evaluate rehydration drinks, which would restore total body water and plasma volume (PV), for astronauts to consume before and during extravehicular activity, a few hours before reentry, and immediately after landing. In the first experiment (rest, sitting), five healthy men (23-41 yr), previously dehydrated for 24 hr., drank six (1a, 2, 4, 5, 6, 7) fluid formulations (one each at weekly intervals) and then sat for 70 min. Pre-test PV were measured with Evans blue dye and changes in PV were calculated with the hematocrit-hemoglobin transformation equation. This rest experiment simulated hypohydrated astronauts preparing for reentry. The second experiment (exercise, supine) followed the same protocol except four healthy men (30-46 yr) worked for 70 min. in the supine position on a cycle ergometer at a mean load of 71+/-1 percent of their peak aerobic work capacity. This exercise experiment simulated conditions for astronauts with reduced total body water engaging in extravehicular activity
The N Enrichment and Supernova Ejection of the Runaway Microquasar LS 5039
We present an investigation of new optical and ultraviolet spectra of the
mass donor star in the massive X-ray binary LS 5039. The optical band spectral
line strengths indicate that the atmosphere is N-rich and C-poor, and we
classify the stellar spectrum as type ON6.5 V((f)). The N-strong and C-weak
pattern is also found in the stellar wind P Cygni lines of N V 1240 and C IV
1550. We suggest that the N-enrichment may result from internal mixing if the
O-star was born as a rapid rotator, or the O-star may have accreted N-rich gas
prior to a common-envelope interaction with the progenitor of the supernova. We
re-evaluated the orbital elements to find an orbital period of P=4.4267 +/-
0.0010 d. We compared the spectral line profiles with new non-LTE,
line-blanketed model spectra, from which we derive an effective temperature
T_eff = 37.5 +/- 1.7 kK, gravity log g = 4.0 +/- 0.1, and projected rotational
velocity V sin i = 140 +/- 8 km/s. We fit the UV, optical, and IR flux
distribution using a model spectrum and extinction law with parameters E(B-V)=
1.28 +/- 0.02 and R= 3.18 +/- 0.07. We confirm the co-variability of the
observed X-ray flux and stellar wind mass loss rate derived from the H-alpha
profile, which supports the wind accretion scenario for the X-ray production in
LS 5039. Wind accretion models indicate that the compact companion has a mass
M_X/M_sun = 1.4 +/- 0.4, consistent with its identification as a neutron star.
The observed eccentricity and runaway velocity of the binary can only be
reconciled if the neutron star received a modest kick velocity due to a slight
asymmetry in the supernova explosion (during which >5 solar masses was
ejected).Comment: 38 pages, 9 figures; 2004, ApJ, 600, Jan. 10 issue, in press
Discussion revised thanks to comments from P. Podsiadlowsk
Comprehensive functional characterization of murine infantile Batten disease including Parkinson-like behavior and dopaminergic markers
Infantile neuronal ceroid lipofuscinosis (INCL, Infantile Batten disease) is a neurodegenerative lysosomal storage disease caused by a deficiency in palmitoyl protein thioesterase-1 (PPT1). The PPT1-deficient mouse (Cln1−/−) is a useful phenocopy of human INCL. Cln1−/− mice display retinal dysfunction, seizures, motor deficits, and die at ~8 months of age. However, little is known about the cognitive and behavioral functions of Cln1−/− mice during disease progression. In the present study, younger (~1–2 months of age) Cln1−/− mice showed minor deficits in motor/sensorimotor functions while older (~5–6 months of age) Cln1−/− mice exhibited more severe impairments, including decreased locomotor activity, inferior cued water maze performance, decreased running wheel ability, and altered auditory cue conditioning. Unexpectedly, certain cognitive functions such as some learning and memory capabilities seemed intact in older Cln1−/− mice. Younger and older Cln1−/− mice presented with walking initiation defects, gait abnormalities, and slowed movements, which are analogous to some symptoms reported in INCL and parkinsonism. However, there was no evidence of alterations in dopaminergic markers in Cln1−/− mice. Results from this study demonstrate quantifiable changes in behavioral functions during progression of murine INCL and suggest that Parkinson-like motor/sensorimotor deficits in Cln1−/− mice are not mediated by dopamine deficiency
Cool bottom processes on the thermally-pulsing AGB and the isotopic composition of circumstellar dust grains
(Abridged) We examine the effects of cool bottom processing (CBP) on several
isotopic ratios in the convective envelope during the TP-AGB phase of evolution
in a 1.5 M_sun initial-mass star of solar initial composition. We use a
parametric model which treats extra mixing by introducing mass flow between the
convective envelope and the underlying radiative zone. The parameters of this
model are the mass circulation rate (Mdot) and the maximum temperature (T_P)
experienced by the circulating material. The effects of nuclear reactions in
the flowing matter were calculated using a set of structures of the radiative
zone selected from a complete stellar evolution calculation. The compositions
of the flowing material were obtained and the resulting changes in the envelope
determined. Abundant ^26Al was produced by CBP for log T_P > 7.65. While
^26Al/^27Al depends on T_P, the isotopic ratios in CNO elements depend
dominantly on the circulation rate. The correspondence is shown between models
of CBP as parameterized by a diffusion formalism within the stellar evolution
model and those using the mass-flow formalism employed here. The isotopic
ratios are compared with the data on circumstellar dust grains. It is found
that the ratios ^{18}O/^{16}O, ^{17}O/^{16}O, and ^26Al/^27Al observed for
oxide grains formed at C/O < 1 are reasonably well-understood. However, the
^15N/^14N, ^12C/^13C, and ^26Al/^27Al in carbide grains (C/O > 1) require many
stellar sources with ^14N/^15N at least a factor of 4 below solar. The rare
grains with ^12C/^13C < 10 cannot be produced by any red-giant or AGB source.Comment: 35 pages, plus 18 included figures. Scheduled for January 10, 2003
issue of Ap
TB160: The Horse Flies and Deer Flies of Maine (Diptera, Tabanidae)
The distribution of Maine Tabanidae is of special interest because of the number of species with more southern ranges which reach their northeastern limit in Maine. A few northern species reach their southern limit in the state. This paper includes all of the species known or likely to be found in Maine with specific localities by county for the more unusual species and for species not found throughout the state.https://digitalcommons.library.umaine.edu/aes_techbulletin/1036/thumbnail.jp
Effect of Finite Mass on Primordial Nucleosynthesis
We have calculated the small effect of finite nucleon mass on the
weak-interaction rates that interconvert protons and neutrons in the early
Universe. We have modified the standard code for primordial nucleosynthesis to
include these corrections and find a small, systematic increase in the 4He
yield, , depending slightly on the
baryon-to-photon ratio. The fractional changes in the abundances of the other
light elements are a few percent or less for interesting values of the
baryon-to-photon ratio.Comment: 15 pages, 8 figures, uses psfig.st
Effect of Neutrino Heating on Primordial Nucleosynthesis
We have modified the standard code for primordial nucleosynthesis to include
the effect of the slight heating of neutrinos by annihilations. There
is a small, systematic change in the He yield, , which is insensitive to the value of the baryon-to-photon ratio
for 10^{-10}\la \eta \la 10^{-9}. We also find that the
baryon-to-photon ratio decreases by about 0.5\% less than the canonical factor
of 4/11 because some of the entropy in pairs is transferred to
neutrinos. These results are in accord with recent analytical estimates.Comment: 14 pages/4 Figs (upon request
Garden varieties: how attractive are recommended garden plants to butterflies?
One way the public can engage in insect conservation is through wildlife gardening, including the growing of insect-friendly flowers as sources of nectar. However, plant varieties differ in the types of insects they attract. To determine which garden plants attracted which butterflies, we counted butterflies nectaring on 11 varieties of summer-flowering garden plants in a rural garden in East Sussex, UK. These plants were all from a list of 100 varieties considered attractive to British butterflies, and included the five varieties specifically listed by the UK charity Butterfly Conservation as best for summer nectar. A total of 2659 flower visits from 14 butterfly and one moth species were observed. We performed a principal components analysis which showed contrasting patterns between the species attracted to Origanum vulgare and Buddleia davidii. The “butterfly bush” Buddleia attracted many nymphalines, such as the peacock, Inachis io, but very few satyrines such as the gatekeeper, Pyronia tithonus, which mostly visited Origanum. Eupatorium cannibinum had the highest Simpson’s Diversity score of 0.75, while Buddleia and Origanum were lower, scoring 0.66 and 0.50 respectively. No one plant was good at attracting all observed butterfly species, as each attracted only a subset of the butterfly community. We conclude that to create a butterfly-friendly garden, a variety of plant species are required as nectar sources for butterflies. Furthermore, garden plant recommendations can probably benefit from being more precise as to the species of butterfly they attract
Particle Physics Approach to Dark Matter
We review the main proposals of particle physics for the composition of the
cold dark matter in the universe. Strong axion contribution to cold dark matter
is not favored if the Peccei-Quinn field emerges with non-zero value at the end
of inflation and the inflationary scale is superheavy since, under these
circumstances, it leads to unacceptably large isocurvature perturbations. The
lightest neutralino is the most popular candidate constituent of cold dark
matter. Its relic abundance in the constrained minimal supersymmetric standard
model can be reduced to acceptable values by pole annihilation of neutralinos
or neutralino-stau coannihilation. Axinos can also contribute to cold dark
matter provided that the reheat temperature is adequately low. Gravitinos can
constitute the cold dark matter only in limited regions of the parameter space.
We present a supersymmetric grand unified model leading to violation of Yukawa
unification and, thus, allowing an acceptable b-quark mass within the
constrained minimal supersymmetric standard model with mu>0. The model
possesses a wide range of parameters consistent with the data on the cold dark
matter abundance as well as other phenomenological constraints. Also, it leads
to a new version of shifted hybrid inflation.Comment: 32 pages including 6 figures, uses svmult.cls, some clarifications
added, lectures given at the Third Aegean Summer School "The Invisible
Universe: Dark Matter and Dark Energy", 26 September-1 October 2005, Karfas,
Island of Chios, Greece (to appear in the proceedings
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