115 research outputs found
Frustration of the isotropic-columnar phase transition of colloidal hard platelets by a transient cubatic phase
Using simulations and theory, we show that the cubatic phase is metastable
for three model hard platelets. The locally favored structures of perpendicular
particle stacks in the fluid prevent the formation of the columnar phase
through geometric frustration resulting in vitrification. Also, we find a
direct link between structure and dynamic heterogeneities in the cooperative
rotation of particle stacks, which is crucial for the devitrification process.
Finally, we show that the life time of the glassy cubatic phase can be tuned by
surprisingly small differences in particle shape.Comment: Submitted to Phys. Rev. Let
Формування стратегії фінансування зобов’язань при здійсненні комерційними банками інвестиційної діяльності
Проведено аналіз мікро- і макроекономічних аспектів інвестиційної діяльності комерційних банків. Досліджені проблеми формування ефективної інвестиційної політики банків. У статті наведена постановка задачі узгодження фінансових потоків при різних обмеженнях
High Intratumoral Stromal Content Defines Reactive Breast Cancer as a Low-risk Breast Cancer Subtype
The current study evaluated associative effects of breast cancer cells with the tumor microenvironment and its influence on tumor behavior
Tracing Carbon Sources through Aquatic and Terrestrial Food Webs Using Amino Acid Stable Isotope Fingerprinting
Tracing the origin of nutrients is a fundamental goal of food web research but methodological issues associated with current research techniques such as using stable isotope ratios of bulk tissue can lead to confounding results. We investigated whether naturally occurring delta C-13 patterns among amino acids (delta C-13(AA)) could distinguish between multiple aquatic and terrestrial primary production sources. We found that delta C-13(AA) patterns in contrast to bulk delta C-13 values distinguished between carbon derived from algae, seagrass, terrestrial plants, bacteria and fungi. Furthermore, we showed for two aquatic producers that their delta C-13(AA) patterns were largely unaffected by different environmental conditions despite substantial shifts in bulk delta C-13 values. The potential of assessing the major carbon sources at the base of the food web was demonstrated for freshwater, pelagic, and estuarine consumers; consumer delta C-13 patterns of essential amino acids largely matched those of the dominant primary producers in each system. Since amino acids make up about half of organismal carbon, source diagnostic isotope fingerprints can be used as a new complementary approach to overcome some of the limitations of variable source bulk isotope values commonly encountered in estuarine areas and other complex environments with mixed aquatic and terrestrial inputs
A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope
Globular clusters with their large populations of millisecond pulsars (MSPs)
are believed to be potential emitters of high-energy gamma-ray emission. Our
goal is to constrain the millisecond pulsar populations in globular clusters
from analysis of gamma-ray observations. We use 546 days of continuous
sky-survey observations obtained with the Large Area Telescope aboard the Fermi
Gamma-ray Space Telescope to study the gamma-ray emission towards 13 globular
clusters. Steady point-like high-energy gamma-ray emission has been
significantly detected towards 8 globular clusters. Five of them (47 Tucanae,
Omega Cen, NGC 6388, Terzan 5, and M 28) show hard spectral power indices and clear evidence for an exponential cut-off in the range
1.0-2.6 GeV, which is the characteristic signature of magnetospheric emission
from MSPs. Three of them (M 62, NGC 6440 and NGC 6652) also show hard spectral
indices , however the presence of an exponential cut-off
can not be unambiguously established. Three of them (Omega Cen, NGC 6388, NGC
6652) have no known radio or X-ray MSPs yet still exhibit MSP spectral
properties. From the observed gamma-ray luminosities, we estimate the total
number of MSPs that is expected to be present in these globular clusters. We
show that our estimates of the MSP population correlate with the stellar
encounter rate and we estimate 2600-4700 MSPs in Galactic globular clusters,
commensurate with previous estimates. The observation of high-energy gamma-ray
emission from a globular cluster thus provides a reliable independent method to
assess their millisecond pulsar populations that can be used to make
constraints on the original neutron star X-ray binary population, essential for
understanding the importance of binary systems in slowing the inevitable core
collapse of globular clusters.Comment: Accepted for publication in A&A. Corresponding authors: J.
Kn\"odlseder, N. Webb, B. Pancraz
Fermi Large Area Telescope Constraints on the Gamma-ray Opacity of the Universe
The Extragalactic Background Light (EBL) includes photons with wavelengths
from ultraviolet to infrared, which are effective at attenuating gamma rays
with energy above ~10 GeV during propagation from sources at cosmological
distances. This results in a redshift- and energy-dependent attenuation of the
gamma-ray flux of extragalactic sources such as blazars and Gamma-Ray Bursts
(GRBs). The Large Area Telescope onboard Fermi detects a sample of gamma-ray
blazars with redshift up to z~3, and GRBs with redshift up to z~4.3. Using
photons above 10 GeV collected by Fermi over more than one year of observations
for these sources, we investigate the effect of gamma-ray flux attenuation by
the EBL. We place upper limits on the gamma-ray opacity of the Universe at
various energies and redshifts, and compare this with predictions from
well-known EBL models. We find that an EBL intensity in the optical-ultraviolet
wavelengths as great as predicted by the "baseline" model of Stecker et al.
(2006) can be ruled out with high confidence.Comment: 42 pages, 12 figures, accepted version (24 Aug.2010) for publication
in ApJ; Contact authors: A. Bouvier, A. Chen, S. Raino, S. Razzaque, A.
Reimer, L.C. Reye
Obesity prevention in child care: A review of U.S. state regulations
<p>ABSTRACT</p> <p>Objective</p> <p>To describe and contrast individual state nutrition and physical activity regulations related to childhood obesity for child care centers and family child care homes in the United States.</p> <p>Methods</p> <p>We conducted a review of regulations for child care facilities for all 50 states and the District of Columbia. We examined state regulations and recorded key nutrition and physical activity items that may contribute to childhood obesity. Items included in this review were: 1) Water is freely available; 2) Sugar-sweetened beverages are limited; 3) Foods of low nutritional value are limited; 4) Children are not forced to eat; 5) Food is not used as a reward; 6) Support is provided for breastfeeding and provision of breast milk; 7) Screen time is limited; and 8) Physical activity is required daily.</p> <p>Results</p> <p>Considerable variation exists among state nutrition and physical activity regulations related to obesity. Tennessee had six of the eight regulations for child care centers, and Delaware, Georgia, Indiana, and Nevada had five of the eight regulations. Conversely, the District of Columbia, Idaho, Nebraska and Washington had none of the eight regulations. For family child care homes, Georgia and Nevada had five of the eight regulations; Arizona, Mississippi, North Carolina, Oregon, Tennessee, Texas, Vermont, and West Virginia had four of the eight regulations. California, the District of Columbia, Idaho, Iowa, Kansas, and Nebraska did not have any of the regulations related to obesity for family child care homes.</p> <p>Conclusion</p> <p>Many states lack specific nutrition and physical activity regulations related to childhood obesity for child care facilities. If widely implemented, enhancing state regulations could help address the obesity epidemic in young children in the United States.</p
The home environment and childhood obesity in low-income households: indirect effects via sleep duration and screen time
Background
Childhood obesity disproportionally affects children from low-income households. With the aim of informing interventions, this study examined pathways through which the physical and social home environment may promote childhood overweight/obesity in low-income households.
Methods
Data on health behaviors and the home environment were collected at home visits in low-income, urban households with either only normal weight (n = 48) or predominantly overweight/obese (n = 55) children aged 6–13 years. Research staff conducted comprehensive, in-person audits of the foods, media, and sports equipment in each household. Anthropometric measurements were collected, and children’s physical activity was assessed through accelerometry. Caregivers and children jointly reported on child sleep duration, screen time, and dietary intake of foods previously implicated in childhood obesity risk. Path analysis was used to test direct and indirect associations between the home environment and child weight status via the health behaviors assessed.
Results
Sleep duration was the only health behavior associated with child weight status (OR = 0.45, 95% CI: 0.27, 0.77), with normal weight children sleeping 33.3 minutes/day longer on average than overweight/obese children. The best-fitting path model explained 26% of variance in child weight status, and included paths linking chaos in the home environment, lower caregiver screen time monitoring, inconsistent implementation of bedtime routines, and the presence of a television in children’s bedrooms to childhood overweight/obesity through effects on screen time and sleep duration.
Conclusions
This study adds to the existing literature by identifying aspects of the home environment that influence childhood weight status via indirect effects on screen time and sleep duration in children from low-income households. Pediatric weight management interventions for low-income households may be improved by targeting aspects of the physical and social home environment associated with sleep
Genome-Wide Association Study Using Extreme Truncate Selection Identifies Novel Genes Affecting Bone Mineral Density and Fracture Risk
Osteoporotic fracture is a major cause of morbidity and mortality worldwide. Low
bone mineral density (BMD) is a major predisposing factor to fracture and is
known to be highly heritable. Site-, gender-, and age-specific genetic effects
on BMD are thought to be significant, but have largely not been considered in
the design of genome-wide association studies (GWAS) of BMD to date. We report
here a GWAS using a novel study design focusing on women of a specific age
(postmenopausal women, age 55–85 years), with either extreme high or low
hip BMD (age- and gender-adjusted BMD z-scores of +1.5 to +4.0,
n = 1055, or −4.0 to −1.5,
n = 900), with replication in cohorts of women drawn from
the general population (n = 20,898). The study replicates
21 of 26 known BMD–associated genes. Additionally, we report suggestive
association of a further six new genetic associations in or around the genes
CLCN7, GALNT3, IBSP, LTBP3, RSPO3, and
SOX4, with replication in two independent datasets. A novel
mouse model with a loss-of-function mutation in GALNT3 is also
reported, which has high bone mass, supporting the involvement of this gene in
BMD determination. In addition to identifying further genes associated with BMD,
this study confirms the efficiency of extreme-truncate selection designs for
quantitative trait association studies
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