461 research outputs found
Health impact of exposure to arsenic-contaminated drinking water in Vietnam
The public health situation of the population of Hanam Province in Vietnam is of great concern, as it is exposed daily to arsenic-contaminated drinking water. Optimising arsenic (As) removal efficiency of current sand filters at household level or switching to cleaner or As-free water sources is crucial to prevent or reduce community health risks
Condensation of Hard Spheres Under Gravity: Exact Results in One Dimension
We present exact results for the density profile of the one dimensional array
of N hard spheres of diameter D and mass m under gravity g. For a strictly one
dimensional system, the liquid-solid transition occurs at zero temperature,
because the close-pakced density, , is one. However, if we relax this
condition slightly such that , we find a series of critical
temperatures T_c^i=mgD(N+1-i)/\mu_o with \mu_o=const, at which the i-th
particle undergoes the liquid-solid transition. The functional form of the
onset temperature, T_c^1=mgDN/\mu_o, is consistent with the previous result
[Physica A 271, 192 (1999)] obtained by the Enskog equation. We also show that
the increase in the center of mass is linear in T before the transition, but it
becomes quadratic in T after the transition because of the formation of solid
near the bottom
Boron-carbon coatings: structure, morphology and mechanical properties
Boron-doped carbon coatings have been produced by a method combining the deposition of a pulsed carbon plasma coating and a boron flow formed as a result of the evaporation of a boron target by pulsed YAG: Nd3+ laser irradiation. Phase, chemical composition, structure, and mechanical properties of composite boron-carbon coatings have been determined. Changes in the coatings’ roughness depending on the boron concentration have been established using atomic force microscopy. It has been shown that the grain size is on the rise with increasing boron concentration. Raman spectroscopy has revealed that at a boron concentration of 43.2 at. %. There is a sharp increase in the ID/IG ratio, which indicates the carbon component’s graphitization. Low ID/IG ratios are observed in the coating at low boron concentrations (no more than 17.4 at. %), suggesting a high content of carbon atoms with sp3 bond hybridization. The coating studies, carried out by X-ray photoelectron microscopy, showed that boron could be in a free state or in the form of carbide or oxide depending on the concentration in the coating. In this case, with an increase in boron concentration, there is a decrease in the concentration of carbon atoms in the state with sp3 bond hybridization, accompanied by an increase in the number of B-C bonds and a reduction in the boron concentration not associated with carbon and oxygen. These coating and chemical composition features determine the boron concentration’s established non-monotonic nature on their microhardness, elastic and mechanical properties
Liquid-Solid Transition of Hard Spheres Under Gravity
We investigate the liquid-solid transition of two dimensional hard spheres in
the presence of gravity. We determine the transition temperature and the
fraction of particles in the solid regime as a function of temperature via
Even-Driven molecular dynamics simulations and compare them with the
theoretical predictions. We then examine the configurational statistics of a
vibrating bed from the view point of the liquid-solid transition by explicitly
determining the transition temperature and the effective temperature, T, of the
bed, and present a relation between T and the vibration strength.Comment: 14 total pages, 4 figure
Resting spontaneous baroreflex sensitivity and cardiac autonomic control in anabolic androgenic steroid users
OBJECTIVES: Misuse of anabolic androgenic steroids in athletes is a strategy used to enhance strength and skeletal muscle hypertrophy. However, its abuse leads to an imbalance in muscle sympathetic nerve activity, increased vascular resistance, and increased blood pressure. However, the mechanisms underlying these alterations are still unknown. Therefore, we tested whether anabolic androgenic steroids could impair resting baroreflex sensitivity and cardiac sympathovagal control. In addition, we evaluate pulse wave velocity to ascertain the arterial stiffness of large vessels. METHODS: Fourteen male anabolic androgenic steroid users and 12 nonusers were studied. Heart rate, blood pressure, and respiratory rate were recorded. Baroreflex sensitivity was estimated by the sequence method, and cardiac autonomic control by analysis of the R-R interval. Pulse wave velocity was measured using a noninvasive automatic device. RESULTS: Mean spontaneous baroreflex sensitivity, baroreflex sensitivity to activation of the baroreceptors, and baroreflex sensitivity to deactivation of the baroreceptors were significantly lower in users than in nonusers. In the spectral analysis of heart rate variability, high frequency activity was lower, while low frequency activity was higher in users than in nonusers. Moreover, the sympathovagal balance was higher in users. Users showed higher pulse wave velocity than nonusers showing arterial stiffness of large vessels. Single linear regression analysis showed significant correlations between mean blood pressure and baroreflex sensitivity and pulse wave velocity. CONCLUSIONS: Our results provide evidence for lower baroreflex sensitivity and sympathovagal imbalance in anabolic androgenic steroid users. Moreover, anabolic androgenic steroid users showed arterial stiffness. Together, these alterations might be the mechanisms triggering the increased blood pressure in this population
Synthesis of novel derivatives of murrayafoline A and their inhibitory effect on LPS-stimulated production of pro-inflammatory cytokines in bone marrow-derived dendritic cells
Cu(I)-catalyzed Huisgen–Meldal–Sharpless type dipolar ‘click’ reactions between azido-tetrathiafulvalene derivatives and ethynylferrocene yield the first examples of ferrocenyl-1,2,3-triazolyl-tetrathiafulvalene assemblies (4a, 4b). The electrochemical behavior of 4a and 4b, which integrate two distinctive redox probes, has been investigated, and their binding ability for various transition-metal cations has been studied by cyclic voltammetry. The contribution of the triazolyl ring in the guest binding process is illustrated by the specific electrochemical recognition of Zn2+ by receptor 4b
Heavy Quarks and Heavy Quarkonia as Tests of Thermalization
We present here a brief summary of new results on heavy quarks and heavy
quarkonia from the PHENIX experiment as presented at the "Quark Gluon Plasma
Thermalization" Workshop in Vienna, Austria in August 2005, directly following
the International Quark Matter Conference in Hungary.Comment: 8 pages, 5 figures, Quark Gluon Plasma Thermalization Workshop
(Vienna August 2005) Proceeding
Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV
PHENIX has measured the centrality dependence of charged hadron p_T spectra
from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T
decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction
of the contribution from hard scattering to high p_T hadron production. For
central collisions the yield at high p_T is shown to be suppressed compared to
binary nucleon-nucleon collision scaling of p+p data. This suppression is
monotonically increasing with centrality, but most of the change occurs below
30% centrality, i.e. for collisions with less than about 140 participating
nucleons. The observed p_T and centrality dependence is consistent with the
particle production predicted by models including hard scattering and
subsequent energy loss of the scattered partons in the dense matter created in
the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to
Phys. Lett. B. Revised to address referee concerns. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm
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Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV
The momentum distribution of electrons from semi-leptonic decays of charm and
bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is
measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC)
over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of
electrons from bottom to that from charm is presented. The ratio is determined
using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It
is found that the yield of electrons from bottom becomes significant above 4
GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative
quantum chromodynamics (pQCD) calculation agrees with the data within the
theoretical and experimental uncertainties. The extracted total bottom
production cross section at this energy is \sigma_{b\b^bar}= 3.2
^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
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
Single Electrons from Heavy Flavor Decays in p+p Collisions at sqrt(s) = 200 GeV
The invariant differential cross section for inclusive electron production in
p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment
at the Relativistic Heavy Ion Collider over the transverse momentum range $0.4
<= p_T <= 5.0 GeV/c at midrapidity (eta <= 0.35). The contribution to the
inclusive electron spectrum from semileptonic decays of hadrons carrying heavy
flavor, i.e. charm quarks or, at high p_T, bottom quarks, is determined via
three independent methods. The resulting electron spectrum from heavy flavor
decays is compared to recent leading and next-to-leading order perturbative QCD
calculations. The total cross section of charm quark-antiquark pair production
is determined as sigma_(c c^bar) = 0.92 +/- 0.15 (stat.) +- 0.54 (sys.) mb.Comment: 329 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
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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