2,162 research outputs found
Sensitivity Study of Four Land Surface Schemes in the WRF Model
The Weather Research and Forecasting (WRF) model version 3.0 developed by the National Center for Atmospheric Research (NCAR) includes three land surface schemes: the simple soil thermal diffusion (STD) scheme, the Noah scheme, and the Rapid Update Cycle (RUC) scheme. We have recently coupled the sophisticated NCAR Community Land Model version 3 (CLM3) into WRF to better characterize land surface processes. Among these four land surface schemes, the STD scheme is the simplest in both structure and process physics. The Noah and RUC schemes are at the intermediate level of complexity. CLM3 includes the most sophisticated snow, soil, and vegetation physics among these land surface schemes. WRF simulations with all four land surface schemes over the western United States (WUS) were carried out for the 1 October 1995 through 30 September 1996. The results show that land surface processes strongly affect temperature simulations over the (WUS). As compared to observations, WRF-CLM3 with the highest complexity level significantly improves temperature simulations, except for the wintertime maximum temperature. Precipitation is dramatically overestimated by WRF with all four land surface schemes over the (WUS) analyzed in this study and does not show a close relationship with land surface processes
Correlative analysis of structure and chemistry of LixFePO4 platelets using 4D-STEM and X-ray ptychography
Lithium iron phosphate (LixFePO4), a cathode material used in rechargeable
Li-ion batteries, phase separates upon de/lithiation under equilibrium. The
interfacial structure and chemistry within these cathode materials affects
Li-ion transport, and therefore battery performance. Correlative imaging of
LixFePO4 was performed using four-dimensional scanning transmission electron
microscopy (4D-STEM), scanning transmission X-ray microscopy (STXM), and X-ray
ptychography in order to analyze the local structure and chemistry of the same
particle set. Over 50,000 diffraction patterns from 10 particles provided
measurements of both structure and chemistry at a nanoscale spatial resolution
(16.6-49.5 nm) over wide (several micron) fields-of-view with statistical
robustness.LixFePO4 particles at varying stages of delithiation were measured
to examine the evolution of structure and chemistry as a function of
delithiation. In lithiated and delithiated particles, local variations were
observed in the degree of lithiation even while local lattice structures
remained comparatively constant, and calculation of linear coefficients of
chemical expansion suggest pinning of the lattice structures in these
populations. Partially delithiated particles displayed broadly core-shell-like
structures, however, with highly variable behavior both locally and per
individual particle that exhibited distinctive intermediate regions at the
interface between phases, and pockets within the lithiated core that correspond
to FePO4 in structure and chemistry.The results provide insight into the
LixFePO4 system, subtleties in the scope and applicability of Vegards law
(linear lattice parameter-composition behavior) under local versus global
measurements, and demonstrate a powerful new combination of experimental and
analytical modalities for bridging the crucial gap between local and
statistical characterization.Comment: 17 pages, 4 figure
Doping evolution of the phonon density of states and electron-lattice interaction in NdCeCuO
We use inelastic neutron scattering to study the evolution of the generalized
phonon density of states (GDOS) of the -type high- superconductor
NdCeCuO (NCCO), from the half-filled Mott-insulator
() to the K superconductor (). Upon doping the CuO
planes in NdCuO (NCO) with electrons by Ce substitution, the
most significant change in the GDOS is the softening of the highest phonon
branches associated with the Cu-O bond stretching and out-of-plane oxygen
vibration modes. However, the softening occurs within the first few percent of
Ce-doping and is not related to the electron doping induced
nonsuperconducting-superconducting transition (NST) at . These
results suggest that the electron-lattice coupling in the -type high-
superconductors is different from that in the -type materials.Comment: 4 pages and 3 figure
Homologous and heterologous re-challenge with Salmonella Typhi and Salmonella Paratyphi A in a randomised controlled human infection model
Enteric fever is a systemic infection caused by Salmonella Typhi or Paratyphi A. In many endemic areas, these serovars co-circulate and can cause multiple infection-episodes in childhood. Prior exposure is thought to confer partial, but incomplete, protection against subsequent attacks of enteric fever. Empirical data to support this hypothesis are limited, and there are few studies describing the occurrence of heterologous-protection between these closely related serovars. We performed a challenge-re-challenge study using a controlled human infection model (CHIM) to investigate the extent of infection-derived immunity to Salmonella Typhi or Paratyphi A infection. We recruited healthy volunteers into two groups: naïve volunteers with no prior exposure to Salmonella Typhi/Paratyphi A and volunteers previously-exposed to Salmonella Typhi or Paratyphi A in earlier CHIM studies. Within each group, participants were randomised 1:1 to oral challenge with either Salmonella Typhi (104 CFU) or Paratyphi A (103 CFU). The primary objective was to compare the attack rate between naïve and previously challenged individuals, defined as the proportion of participants per group meeting the diagnostic criteria of temperature of ≥38°C persisting for ≥12 hours and/or S. Typhi/Paratyphi bacteraemia up to day 14 post challenge. The attack-rate in participants who underwent homologous re-challenge with Salmonella Typhi was reduced compared with challenged naïve controls, although this reduction was not statistically significant (12/27[44%] vs. 12/19[63%]; Relative risk 0.70; 95% CI 0.41–1.21; p = 0.24). Homologous re-challenge with Salmonella Paratyphi A also resulted in a lower attack-rate than was seen in challenged naïve controls (3/12[25%] vs. 10/18[56%]; RR0.45; 95% CI 0.16–1.30; p = 0.14). Evidence of protection was supported by a post hoc analysis in which previous exposure was associated with an approximately 36% and 57% reduced risk of typhoid or paratyphoid disease respectively on re-challenge. Individuals who did not develop enteric fever on primary exposure were significantly more likely to be protected on re-challenge, compared with individuals who developed disease on primary exposure. Heterologous re-challenge with Salmonella Typhi or Salmonella Paratyphi A was not associated with a reduced attack rate following challenge. Within the context of the model, prior exposure was not associated with reduced disease severity, altered microbiological profile or boosting of humoral immune responses. We conclude that prior Salmonella Typhi and Paratyphi A exposure may confer partial but incomplete protection against subsequent infection, but with a comparable clinical and microbiological phenotype. There is no demonstrable cross-protection between these serovars, consistent with the co-circulation of Salmonella Typhi and Paratyphi A. Collectively, these data are consistent with surveillance and modelling studies that indicate multiple infections can occur in high transmission settings, supporting the need for vaccines to reduce the burden of disease in childhood and achieve disease control.
Trial registration NCT02192008; clinicaltrials.gov
The 700 ks Chandra Spiderweb Field II: Evidence for inverse-Compton and thermal diffuse emission in the Spiderweb galaxy
We present the X-ray imaging and spectral analysis of the diffuse emission
around the Spiderweb galaxy at z=2.16 and of its nuclear emission, based on a
deep (700 ks) Chandra observation. We characterize the nuclear emission and
computed the contamination in the surrounding regions due to the wings of the
instrument PSF. Then, we quantified the extended emission within 12". We find
that the Spiderweb galaxy hosts a mildly absorbed quasar, with modest yet
significant variability on a timescale of ~1 year. We find that the emission in
the jet regions is well described by a power law with Gamma~2-2.5, and it is
consistent with IC upscattering of the CMB photons by the relativistic
electrons. We also find a roughly symmetric, diffuse emission within a radius
of ~100 kpc. This emission is consistent with thermal bremsstrahlung from a hot
ICM with a temperature of kT=2.0_{-0.4}^{+0.7} keV, and a metallicity of
Z<1.6Z_sun. The average electron density within 100 kpc is
n_e=(1.51+-0.24+-0.14)E-2 cm^{-3}, corresponding to an upper limit for the
total ICM mass of <=(1.76+-0.30+-0.17)E+12 M_sun (where error bars are 1 sigma
statistical and systematic, respectively). If we apply hydrostatic equilibrium
to the ICM, we measure a total gravitational mass M(<100
kpc)=(1.5^{+0.5}_{-0.3})E+13 M_sun and, extrapolating at larger radii, we
estimate a total mass M_{500}=(3.2^{+1.1}_{-0.6})E+13 M_sun within a radius of
r_{500}=(220+-30) kpc. We conclude that the Spiderweb protocluster shows
significant diffuse emission within a radius of 12 arcsec, whose major
contribution is provided by IC scattering associated with the radio jets.
Outside the jet regions, we also identified thermal emission within a radius of
~100 kpc, revealing the presence of hot, diffuse baryons that may represent the
embryonic virialized halo of the forming cluster.Comment: 19 pages, 16 figures, accepted in Astronomy & Astrophysic
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Public Health-Related Impacts of Climate Change in California
In June 2005 Governor Arnold Schwarzenegger issued Executive Order S-3-05 that set greenhouse gas emission reduction targets for California, and directed the Secretary of the California Environmental Protection Agency to report to the governor and the State legislature by January 2006 and biannually thereafter on the impacts to California of global warming, including impacts to water supply, public health, agriculture, the coastline, and forestry, and to prepare and report on mitigation and adaptation plans to combat these impacts. This report is a part of the report to the governor and legislature, and focuses on public health impacts that have been associated with climate change. Considerable evidence suggests that average ambient temperature is increasing worldwide, that temperatures will continue to increase into the future, and that global warming will result in changes to many aspects of climate, including temperature, humidity, and precipitation (McMichael and Githeko, 2001). It is expected that California will experience changes in both temperature and precipitation under current trends. Many of the changes in climate projected for California could have ramifications for public health (McMichael and Githeko, 2001), and this document summarizes the impacts judged most likely to occur in California, based on a review of available peer-reviewed scientific literature and new modeling and statistical analyses. The impacts identified as most significant to public health in California include mortality and morbidity related to temperature, air pollution, vector and water-borne diseases, and wildfires. There is considerable complexity underlying the health of a population with many contributing factors including biological, ecological, social, political, and geographical. In addition, the relationship between climate change and changes in public health is difficult to predict for the most part, although more detailed information is available on temperature-related mortality and air pollution effects than the other endpoints discussed in this document. Consequently, these two topics are discussed in greater detail. Where possible, estimates of the magnitude and significance of these impacts are also discussed, along with possible adaptations that could reduce climate-related health impacts. In the context of this review, weather refers to meteorological conditions at a specific place and time over a relatively short time frame, such as up to a year or two. Climate, on the other hand, refers to the same meteorological conditions, but over a longer time frame, such as decades or centuries
Anomalous Transport Phenomena in Fermi Liquids with Strong Magnetic Fluctuations
In many strongly correlated electron systems, remarkable violation of the
relaxation time approximation (RTA) is observed. The most famous example would
be high-Tc superconductors (HTSCs), and similar anomalous transport phenomena
have been observed in metals near their antiferromagnetic (AF) quantum critical
point (QCP). Here, we develop a transport theory involving resistivity and Hall
coefficient on the basis of the microscopic Fermi liquid theory, by considering
the current vertex correction (CVC). In nearly AF Fermi liquids, the CVC
accounts for the significant enhancements in the Hall coefficient,
magnetoresistance, thermoelectric power, and Nernst coefficient in nearly AF
metals. According to the numerical study, aspects of anomalous transport
phenomena in HTSC are explained in a unified way by considering the CVC,
without introducing any fitting parameters; this strongly supports the idea
that HTSCs are Fermi liquids with strong AF fluctuations. In addition, the
striking \omega-dependence of the AC Hall coefficient and the remarkable
effects of impurities on the transport coefficients in HTSCs appear to fit
naturally into the present theory. The present theory also explains very
similar anomalous transport phenomena occurring in CeCoIn5 and CeRhIn5, which
is a heavy-fermion system near the AF QCP, and in the organic superconductor
\kappa-(BEDT-TTF).Comment: 100 pages, Rep. Prog. Phys. 71, 026501 (2008
Measurement of high-p_T Single Electrons from Heavy-Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The momentum distribution of electrons from decays of heavy flavor (charm and
beauty) for midrapidity |y| < 0.35 in p+p collisions at sqrt(s) = 200 GeV has
been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider
(RHIC) over the transverse momentum range 0.3 < p_T < 9 GeV/c. Two independent
methods have been used to determine the heavy flavor yields, and the results
are in good agreement with each other. A fixed-order-plus-next-to-leading-log
pQCD calculation agrees with the data within the theoretical and experimental
uncertainties, with the data/theory ratio of 1.72 +/- 0.02^stat +/- 0.19^sys
for 0.3 < p_T < 9 GeV/c. The total charm production cross section at this
energy has also been deduced to be sigma_(c c^bar) = 567 +/- 57^stat +/-
224^sys micro barns.Comment: 375 authors from 57 institutions, 6 pages, 3 figures. Submitted to
Physical Review Letters. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
Transverse momentum and centrality dependence of dihadron correlations in Au+Au collisions at sqrt(s_NN)=200 GeV: Jet-quenching and the response of partonic matter
Azimuthal angle \Delta\phi correlations are presented for charged hadrons
from dijets for 0.4 < p_T < 10 GeV/c in Au+Au collisions at sqrt(s_NN) = 200
GeV. With increasing p_T, the away-side distribution evolves from a broad to a
concave shape, then to a convex shape. Comparisons to p+p data suggest that the
away-side can be divided into a partially suppressed "head" region centered at
Delta\phi ~ \pi, and an enhanced "shoulder" region centered at Delta\phi ~ \pi
+/- 1.1. The p_T spectrum for the "head" region softens toward central
collisions, consistent with the onset of jet quenching. The spectral slope for
the "shoulder" region is independent of centrality and trigger p_T, which
offers constraints on energy transport mechanisms and suggests that the
"shoulder" region contains the medium response to energetic jets.Comment: 420 authors from 58 institutions, 6 pages, 4 figures. Submitted to
Physical Review Letters. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
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