146 research outputs found
One-line γ ray spectroscopic investigation of the 180Hg(T 1/2 = 3 s) decay chain
With the rebuilt ISOLDE 2 facility we have investigated on-line the 18080Hg decay products. The decay half-lives, the energies and intensities of the main γ lines of both 180Hg(T 1/2 = 3.0 ± 0.3 s) and 18079Au(T1/2 = 8.1 ± 0.3 s) , and a tentative decay scheme of 18078Pt are given
The pd <--> pi+ t reaction around the Delta resonance
The pd pi+ t process has been calculated in the energy region around the
Delta-resonance with elementary production/absorption mechanisms involving one
and two nucleons. The isobar degrees of freedom have been explicitly included
in the two-nucleon mechanism via pi-- and rho-exchange diagrams. No free
parameters have been employed in the analysis since all the parameters have
been fixed in previous studies on the simpler pp pi+ d process. The
treatment of the few-nucleon dynamics entailed a Faddeev-based calculation of
the reaction, with continuum calculations for the initial p-d state and
accurate solutions of the three-nucleon bound-state equation. The integral
cross-section was found to be quite sensitive to the NN interaction employed
while the angular dependence showed less sensitivity. Approximately a 4% effect
was found for the one-body mechanism, for the three-nucleon dynamics in the p-d
channel, and for the inclusion of a large, possibly converged, number of
three-body partial states, indicating that these different aspects are of
comparable importance in the calculation of the spin-averaged observables.Comment: 40 Pages, RevTex, plus 5 PostScript figure
COMPLIS experiments : COllaboration for spectroscopy Measurements using a Pulsed Laser Ion Source
Laser spectroscopy measurements have been carried out on very neutron-deficient isotopes of Au, Pt and Ir, produced as daughter elements from a Hg ISOLDE beam. For these transitional region nuclides, the hyperfine structure (HFS) and isotope shift (IS) were measured by Resonance Ionization Spectroscopy (RIS). Magnetic moments μ, spectroscopic quadrupole moments Qs and changes of the nuclear mean square charge radius δ〈rc 2〉along isotopic series have been extracted. For some results, a detailed comparison with theoretical predictions is presented. (Springer
Fecal Indicators in Sand, Sand Contact, and Risk of Enteric Illness Among Beachgoers
Beach sand can harbor fecal indicator organisms and pathogens, but enteric illness risk associated with sand contact remains unclear
Water quality, weather and environmental factors associated with fecal indicator organism density in beach sand at two recreational marine beaches
Recent studies showing an association between fecal indicator organisms (FIOs) in sand and gastrointestinal (GI) illness among beachgoers with sand contact have important public health implications because of the large numbers of people who recreate at beaches and engage in sand contact activities. Yet, factors that influence fecal pollution in beach sand remain unclear. During the 2007 National Epidemiological and Environmental Assessment of Recreational (NEEAR) Water Study, sand samples were collected at three locations (60 m apart) on weekend days (Sat, Sun) and holidays between June and September at two marine beaches — Fairhope Beach, AL and Goddard Beach, RI — with nearby publicly-owned treatment works (POTWs) outfalls. F+ coliphage, enterococci, Bacteroidales, fecal Bacteroides spp., and Clostridium spp. were measured in sand using culture and qPCR-based calibrator-cell equivalent methods. Water samples were also collected on the same days, times and transects as the 144 sand samples and were assayed using the same FIO measurements. Weather and environmental data were collected at the time of sample collection. Mean FIO concentrations in sand varied over time, but not space. Enterococci CFU and CCE densities in sand were not correlated, although other FIOs in sand were. The strongest correlation between FIO density in sand and water was fecal Bacteroides CCE, followed by enterococci CFU, Clostridium spp. CCE, and Bacteroidales CCE. Overall, the factors associated with FIO concentrations in sand were related to the sand–water interface (i.e., sand-wetting) and included daily average densities of FIOs in water, rainfall, and wave height. Targeted monitoring that focuses on daily trends of sand FIO variability, combined with information about specific water quality, weather, and environmental factors may inform beach monitoring and management decisions to reduce microbial burdens in beach sand
Comparing the Health Effects of Ambient Particulate Matter Estimated Using Ground-Based versus Remote Sensing Exposure Estimates
BACKGROUND: Remote sensing (RS) is increasingly used for
exposure assessment in epidemiological and burden of disease
studies, including those investigating whether chronic exposure
to ambient fine particulate matter (PM2.5) is associated with
mortality. OBJECTIVES: To compare relative risk estimates of
mortality from diseases of the circulatory system for PM2.5
modeled from RS with that for PM2.5 modeled using ground-level
information. METHODS: We geocoded the baseline residence of
668,629 American Cancer Society Cancer Prevention Study II
(CPS-II) cohort participants followed from 1982 to 2004 and
assigned PM2.5 levels to all participants using seven different
exposure models. Most of the exposure models were averaged for
the years 2002-2004, while one RS estimate was for a longer,
contemporaneous period. We used Cox proportional hazards
regression to estimate relative risks (RR) for the association
of PM2.5 with circulatory mortality and ischemic heart disease.
RESULTS: Estimates of mortality risk differed among exposure
models. The smallest relative risk was observed for the RS
estimates that excluded ground-based monitors for circulatory
deaths (RR = 1.02 (95% confidence interval (CI): 1.00-1.04 per
10 microg/m3 increment in PM2.5). The largest relative risk was
observed for the land use regression model that included traffic
information (RR = 1.14, 95% CI: 1.11-1.17 per 10 microg/m3
increment in PM2.5). CONCLUSIONS: We found significant
associations between PM2.5 and mortality in every model;
however, relative risks estimated from exposure models using
ground-based information were generally larger than those
estimated with RS alone
Congestion in a macroscopic model of self-driven particles modeling gregariousness
International audienceWe analyze a macroscopic model with a maximal density constraint which describes short range repulsion in biological systems. This system aims at modeling finite-size particles which cannot overlap and repel each other when they are too close. The parts of the fluid where the maximal density is reached behave like incompressible fluids while lower density regions are compressible. This paper investigates the transition between the compressible and incompressible regions. To capture this transition, we study a one-dimensional Riemann problem and introduce a perturbation problem which regularizes the compressible-incompressible transition. Specific difficulties related to the non-conservativity of the problem are discussed
DNA Methylation Analysis of Chromosome 21 Gene Promoters at Single Base Pair and Single Allele Resolution
Differential DNA methylation is an essential epigenetic signal for gene regulation, development, and disease processes. We mapped DNA methylation patterns of 190 gene promoter regions on chromosome 21 using bisulfite conversion and subclone sequencing in five human cell types. A total of 28,626 subclones were sequenced at high accuracy using (long-read) Sanger sequencing resulting in the measurement of the DNA methylation state of 580427 CpG sites. Our results show that average DNA methylation levels are distributed bimodally with enrichment of highly methylated and unmethylated sequences, both for amplicons and individual subclones, which represent single alleles from individual cells. Within CpG-rich sequences, DNA methylation was found to be anti-correlated with CpG dinucleotide density and GC content, and methylated CpGs are more likely to be flanked by AT-rich sequences. We observed over-representation of CpG sites in distances of 9, 18, and 27 bps in highly methylated amplicons. However, DNA sequence alone is not sufficient to predict an amplicon's DNA methylation status, since 43% of all amplicons are differentially methylated between the cell types studied here. DNA methylation in promoter regions is strongly correlated with the absence of gene expression and low levels of activating epigenetic marks like H3K4 methylation and H3K9 and K14 acetylation. Utilizing the single base pair and single allele resolution of our data, we found that i) amplicons from different parts of a CpG island frequently differ in their DNA methylation level, ii) methylation levels of individual cells in one tissue are very similar, and iii) methylation patterns follow a relaxed site-specific distribution. Furthermore, iv) we identified three cases of allele-specific DNA methylation on chromosome 21. Our data shed new light on the nature of methylation patterns in human cells, the sequence dependence of DNA methylation, and its function as epigenetic signal in gene regulation. Further, we illustrate genotype–epigenotype interactions by showing novel examples of allele-specific methylation
Pion Absorption Cross Section for ^2H and ^3He in the Delta-Isobar Region: A Phenomenological Connection
The absorption of \pi^+ on ^3He in the -region is evaluated with
exact inclusion of the final state interaction among the three emerging
protons. The absorption is described by a vertex and a
transition t-matrix which are calculated from a phenomenological
model for NN and \pi d reactions. In a calculation where the initial pion
scattering effects are neglected, the predicted peaks of the pion absorption
cross sections for ^2H and ^3He lie too high in energy in relation to the data.
The effect of the final state three-nucleon interaction turns out to be too
small for changing the magnitude and shifting the peak position of the total
absorption cross section for ^3He. We demonstrate that the adjustment of the
peak position for the deuteron cross section by small modifications of the
-parameters, automatically leads to the correct peak position in ^3He.Comment: 12 pages, REVTeX, 10 PostScript figures, submitted to Phys. Rev.
The Role of Geography in Human Adaptation
Various observations argue for a role of adaptation in recent human evolution, including results from genome-wide studies and analyses of selection signals at candidate genes. Here, we use genome-wide SNP data from the HapMap and CEPH-Human Genome Diversity Panel samples to study the geographic distributions of putatively selected alleles at a range of geographic scales. We find that the average allele frequency divergence is highly predictive of the most extreme FST values across the whole genome. On a broad scale, the geographic distribution of putatively selected alleles almost invariably conforms to population clusters identified using randomly chosen genetic markers. Given this structure, there are surprisingly few fixed or nearly fixed differences between human populations. Among the nearly fixed differences that do exist, nearly all are due to fixation events that occurred outside of Africa, and most appear in East Asia. These patterns suggest that selection is often weak enough that neutral processes—especially population history, migration, and drift—exert powerful influences over the fate and geographic distribution of selected alleles
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