5,725 research outputs found
Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores
We study the origin of large abundances of complex organic molecules in the
Galactic center (GC). We carried out a systematic study of the complex organic
molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward
40 GC molecular clouds. Using the LTE approximation, we derived the physical
properties of GC molecular clouds and the abundances of the complex
molecules.The CH3OH abundance between clouds varies by nearly two orders of
magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex
organic molecules relative to that of CH3OH is basically independent of the
CH3OH abundance, with variations of only a factor 4-8. The abundances of
complex organic molecules in the GC are compared with those measured in hot
cores and hot corinos, in which these complex molecules are also abundant. We
find that both the abundance and the abundance ratios of the complex molecules
relative to CH3OH in hot cores are similar to those found in the GC clouds.
However, hot corinos show different abundance ratios than observed in hot cores
and in GC clouds. The rather constant abundance of all the complex molecules
relative to CH3OH suggests that all complex molecules are ejected from grain
mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s
are required to explain the high abundances in gas phase of complex organic
molecules in the GC molecular clouds. The rather uniform abundance ratios in
the GC clouds and in Galactic hot cores indicate a similar average composition
of grain mantles in both kinds of regions. The Sickle and the Thermal Radio
Arches, affected by UV radiation, show different relative abundances in the
complex organic molecules due to the differentially photodissociation of these
molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx,
natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in
A&A 2006. version 2. relocated figures and tables. Language editor
suggestions. added reference
Evidence of defect-induced ferromagnetism in ZnFeO thin films
X-ray absorption near-edge and grazing incidence X-ray fluorescence
spectroscopy are employed to investigate the electronic structure of
ZnFeO thin films. The spectroscopy techniques are used to determine
the non-equilibrium cation site occupancy as a function of depth and oxygen
pressure during deposition and its effects on the magnetic properties. It is
found that low deposition pressures below 10 mbar cause iron
superoccupation of tetrahedral sites without Zn inversion, resulting in
an ordered magnetic phase with high room temperature magnetic moment.Comment: Accepted for publication in Phys. Rev.
Pilates Mat and body composition of postmenopausal women
El objetivo de este trabajo es cuantificar, mediante Absorciometría Dual
Fotónica de Rayos- X (DXA), las modificaciones de la composición corporal que
la práctica de Pilates Mat produce en mujeres posmenopaúsicas de vida
sedentaria. Tras un programa de ejercicios de 9 meses de duración a razón de
2 sesiones por semana de 60 minutos cada una, se observó un aumento
significativo del compartimento muscular a nivel de tronco (p=0,028), abdomen
(p=0,010) y brazos (p=0,042), así como una disminución significativa de la grasa
de las piernas (p=0,000). La densidad mineral ósea de la columna lumbar (L2,
L3 y L4) también aumentó de forma significativa. Los resultados sugieren que la
práctica de Pilates Mat en mujeres posmenopaúsicas mejora su composición
corporalThe aim of this study was to quantify the changes in body composition after Mat
Pilates practice in postmenopausal sedentary women using Dual X-ray Photon
Absorptiometry (DXA). After a 9-month exercise program consisting of 2
sessions per week of 60 minutes each, a significant increase was observed in
the muscle mass of the trunk (p = 0.028), abdomen (p = 0.010) and arms (p =
0.042). A significant decrease was observed in the leg fat mass (p = 0.000).
Bone mineral density of the lumbar spine (L2, L3 and L4) also increased
significantly. The results suggest that the practice of Mat Pilates in
postmenopausal women improves their body compositio
Modeling Plain Vacuum Drying by Considering a Dynamic Capillary Pressure
A coupled drying model for wood is proposed by introducing a dynamic capillary pressure. The pressures of non-wetting phase, the wetting phase, and the capillary pressure at equilibrium has been considered as non-static; this approach includes a two-scale
model. According to numerical results, liquid, water vapor and air dynamics in the chamber have strong interactions with re-homogenization in the surface, controlled by capillary
forces. The results at 60–100 bar and 70 °C are discussed. The phenomenological one-dimensional drying model is solved by using the COMSOL’s coefficient form and a global equation format. A good description of drying kinetics, moisture redistribution, and mass fluxes is obtained. A comprehensible transition at the fiber saturation point is well simulated
XAS study of the local environment of impurities in doped TiO2 thin films
In this work we present an X-ray Absorption Spectroscopy characterization of
the local environment of the impurity in room temperature ferromagnetic anatase
TiO2 thin films doped with Co, Ni, Cu, or Zn, deposited on LaAlO3 substrate by
Pulsed Laser Deposition. It was found that there is a considerable amount of
impurity atoms substituting Ti in TiO2 anatase, although the presence of metal
transition monoxide clusters can not be discarded. From our results we infer
that the observed room temperature ferromagnetism of the samples could be
assigned to the metal transition atoms replacing Ti in TiO2 anatase.Comment: 4 pages, 3 figures, 1 table, Physica B (in press
A semi-analytical perspective on massive galaxies at
The most massive and luminous galaxies in the Universe serve as powerful
probes to study the formation of structure, the assembly of mass, and
cosmology. However, their detailed formation and evolution is still barely
understood. Here we extract a sample of massive mock galaxies from the
semi-analytical model of galaxy formation (SAM) GALACTICUS from the
MultiDark-Galaxies, by replicating the CMASS photometric selection from the
SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). The comparison of the
GALACTICUS CMASS-mock with BOSS-CMASS data allows us to explore different
aspects of the massive galaxy population at , including the
galaxy-halo connection and the galaxy clustering. We find good agreement
between our modelled galaxies and observations regarding the galaxy-halo
connection, but our CMASS-mock over-estimates the clustering amplitude of the
2-point correlation function, due to a smaller number density compared to BOSS,
a lack of blue objects, and a small intrinsic scatter in stellar mass at fixed
halo mass of dex. To alleviate this problem, we construct an alternative
mock catalogue mimicking the CMASS colour-magnitude distribution by randomly
down-sampling the SAM catalogue. This CMASS-mock reproduces the clustering of
CMASS galaxies within 1 and shows some environmental dependency of star
formation properties that could be connected to the quenching of star formation
and the assembly bias.Comment: 15 pages, 10 figures, 2 tables, submitted to MNRA
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