1,863 research outputs found
Genetic heterogeneity of hepatitis E virus in Darfur, Sudan, and neighboring Chad.
The within-outbreak diversity of hepatitis E virus (HEV) was studied during the outbreak of hepatitis E that occurred in Sudan in 2004. Specimens were collected from internally displaced persons living in a Sudanese refugee camp and two camps implanted in Chad. A comparison of the sequences in the ORF2 region of 23 Sudanese isolates and five HEV samples from the two Chadian camps displayed a high similarity (>99.7%) to strains belonging to Genotype 1. But four isolates collected in one of the Chadian camps were close to Genotype 2. Circulation of divergent strains argues for possible multiple sources of infection
Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor
Surface characterizations of an organophosphorus (OP) gas detector based on
chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET)
were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and
correlated with changes in the current-voltage characteristics of the devices.
KPFM measurements on FETs allow (i) to investigate the contact potential
difference (CPD) distribution of the polarized device as function of the gate
voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis
associated to the presence of mobile ions on the surface. The CPD measured by
KPFM on the silicon nanoribbon was corrected due to side capacitance effects in
order to determine the real quantitative surface potential. Comparison with
macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out.
These two approaches were quantitatively consistent. An important increase of
the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor
grafting, corresponding to a decrease of the work function, and a weaker
variation after exposure to OP (between - 14 mV and - 61 mV) was measured.
Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The
OP molecules were essentially localized on the Si-NR confirming effectiveness
and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and
succeeded in the detection of low vapor concentrations (40 ppm).Comment: Paper and supporting information, J. Phys. Chem. C, 201
Prevalence study of yaws in the Democratic Republic of Congo using the lot quality assurance sampling method.
BACKGROUND: Until the 1970s the prevalence of non-venereal trepanomatosis, including yaws, was greatly reduced after worldwide mass treatment. In 2005, cases were again reported in the Democratic Republic of the Congo. We carried out a survey to estimate the village-level prevalence of yaws in the region of Equator in the north of the country in order to define appropriate strategies to effectively treat the affected population. METHODOLOGY/PRINCIPAL FINDINGS: We designed a community-based survey using the Lot Quality Assurance Sampling method to classify the prevalence of active yaws in 14 groups of villages (lots). The classification into high, moderate, or low yaws prevalence corresponded to World Health Organization prevalence thresholds for identifying appropriate operational treatment strategies. Active yaws cases were defined by suggestive clinical signs and positive rapid plasma reagin and Treponema pallidum hemagglutination serological tests. The overall prevalence in the study area was 4.7% (95% confidence interval: 3.4-6.0). Two of 14 lots had high prevalence (>10%), three moderate prevalence (5-10%) and nine low prevalence (<5%.). CONCLUSIONS/SIGNIFICANCE: Although yaws is no longer a World Health Organization priority disease, the presence of yaws in a region where it was supposed to be eradicated demonstrates the importance of continued surveillance and control efforts. Yaws should remain a public health priority in countries where previously it was known to be endemic. The integration of sensitive surveillance systems together with free access to effective treatment is recommended. As a consequence of our study results, more than 16,000 people received free treatment against yaws
L\'evy flights of photons in hot atomic vapours
Properties of random and fluctuating systems are often studied through the
use of Gaussian distributions. However, in a number of situations, rare events
have drastic consequences, which can not be explained by Gaussian statistics.
Considerable efforts have thus been devoted to the study of non Gaussian
fluctuations such as L\'evy statistics, generalizing the standard description
of random walks. Unfortunately only macroscopic signatures, obtained by
averaging over many random steps, are usually observed in physical systems. We
present experimental results investigating the elementary process of anomalous
diffusion of photons in hot atomic vapours. We measure the step size
distribution of the random walk and show that it follows a power law
characteristic of L\'evy flights.Comment: This final version is identical to the one published in Nature
Physic
Shear viscosity of hot scalar field theory in the real-time formalism
Within the closed time path formalism a general nonperturbative expression is
derived which resums through the Bethe-Salpter equation all leading order
contributions to the shear viscosity in hot scalar field theory. Using a
previously derived generalized fluctuation-dissipation theorem for nonlinear
response functions in the real-time formalism, it is shown that the
Bethe-Salpeter equation decouples in the so-called (r,a) basis. The general
result is applied to scalar field theory with pure lambda*phi**4 and mixed
g*phi**3+lambda*phi**4 interactions. In both cases our calculation confirms the
leading order expression for the shear viscosity previously obtained in the
imaginary time formalism.Comment: Expanded introduction and conclusions. Several references and a
footnote added. Fig.5 and its discussion in the text modified to avoid double
counting. Signs in Eqs. (45) and (53) correcte
A new regime of anomalous penetration of relativistically strong laser radiation into an overdense plasma
It is shown that penetration of relativistically intense laser light into an
overdense plasma, accessible by self-induced transparency, occurs over a finite
length only. The penetration length depends crucially on the overdense plasma
parameter and increases with increasing incident intensity after exceeding the
threshold for self-induced transparency. Exact analytical solutions describing
the plasma-field distributions are presented.Comment: 6 pages, 2 figures in 2 separate eps files; submitted to JETP Letter
High mortality associated with an outbreak of hepatitis E among displaced persons in Darfur, Sudan
BACKGROUND: Hepatitis E virus (HEV) causes acute onset of jaundice and a high case-fatality ratio in pregnant women. We provide a clinical description of hospitalized case patients and assess the specific impact on pregnant women during a large epidemic of HEV infection in a displaced population in Mornay camp (78,800 inhabitants), western Darfur, Sudan. METHODS: We reviewed hospital records. A sample of 20 clinical cases underwent laboratory confirmation. These patients were tested for immunoglobulin G (IgG) and immunoglobulin M (IgM) antibody to HEV (serum) and for amplification of the HEV genome (serum and stool). We performed a cross-sectional survey in the community to determine the attack rate and case-fatality ratio in pregnant women. RESULTS: Over 6 months, 253 HEV cases were recorded at the hospital, of which 61 (24.1%) were in pregnant women. A total of 72 cases (39.1% of those for whom clinical records were available) had a diagnosis of hepatic encephalopathy. Of the 45 who died (case-fatality ratio, 17.8%), 19 were pregnant women (specific case-fatality ratio, 31.1%). Acute hepatitis E was confirmed in 95% (19/20) of cases sampled; 18 case-patients were positive for IgG (optical density ratio > or =3), for IgM (optical density ratio >2 ), or for both, whereas 1 was negative for IgG and IgM but positive for HEV RNA in serum. The survey identified 220 jaundiced women among the 1133 pregnant women recorded over 3 months (attack rate, 19.4%). A total of 18 deaths were recorded among these jaundiced pregnant women (specific case-fatality ratio, 8.2%). CONCLUSIONS: This large epidemic of HEV infection illustrates the dramatic impact of this disease on pregnant women. Timely interventions and a vaccine are urgently needed to prevent mortality in this special group
Cardiac and arterial interactions in end-stage renal disease
Cardiac and arterial interactions in end-stage renal disease. Although cardiac hypertrophy is a frequent complication of end-stage renal disease (ESRD), relatively little is known about large arterial geometry and function in vivo in these patients, and the relationship between arterial changes and cardiac hypertrophy is unknown. Common carotid artery (CCA) intima-media thickness and internal diameter and left ventricular geometry and function were determined by ultrasound imaging in 70 uncomplicated ESRD patients and in 50 age-, sex-, and blood pressure-matched controls. Arterial distensibility and compliance were determined from simultaneously recorded CCA diameter and stroke changes in diameter and CCA pressure waveforms, obtained by applanation tonometry, and also by the measurement of carotid-femoral pulse wave velocity. Compared with control subjects, ESRD patients had greater left ventricular diameter (P < 0.01), wall thicknesses and mass (P < 0.001), increased CCA diameter (6.25 ± 0.87 vs. 5.55 ± 0.65 mm; P < 0.001), larger CCA intima-media thickness (777 ± 115 vs. 678 ± 105 µ m; P < 0.001) and intima-media cross-sectional area (17.5 ± 4.5 vs. 13.4 ± 3.3mm2; P < 0.001). In uremic patients, arterial hypertrophy was associated with decreased CCA distensibility (17.8 ± 8.8 vs. 24.0 ± 12.7kPa−1 · 10−3; P < 0.001) and compliance (5.15 ± 2 vs. 6.0 ± 2.5m2 · kPa−1 · 10−7; P < 0.05), accelerated carotid-femoral pulse wave velocity (1055 ± 290 vs. 957 ± 180 cm/seconds; P < 0.001), early return and increased effect of arterial wave reflections (20.5 ± 15.4 vs. 9.2 ± 18.4%; P < 0.001). The latter phenomenons were responsible for increased pulsatile pressure load in CCA (58.3 ± 21 vs. 48 ± 17mm Hg; P < 0.01) and were associated with a decreased subendocardial viability index (157 ± 31 vs. 173 ± 30%; P < 0.001). The CCA diameter was correlated with the left ventricular diameter (P < 0.01), and a significant correlations existed between CCA wall thickness or CCA intima-media cross-sectional area and left ventricular wall thicknesses and/or left ventricular mass (P < 0.01). In multivariate analysis, these relationships were independent regarding age, sex, blood pressure and body surface area. The present study documents parallel cardiac and vascular adaptation in ESRD, and demonstrates the potential contribution of structural and functional large artery alterations to the pathogenesis of left ventricular hypertrophy and functional alterations
Conductance switching at the nanoscale of diarylethene derivatives self-assembled monolayers on LaSrMnO
We report on the phosphonic acid route for the grafting of functional
molecules, optical switch (dithienylethene diphosphonic acid, DDA), on
La0.7Sr0.3MnO3 (LSMO). Compact self-assembled monolayers (SAMs) of DDA are
formed on LSMO as studied by topographic atomic force microscopy (AFM),
ellipsometry, water contact angle and X-ray photoemission spectroscopy (XPS).
The conducting AFM measurements show that the electrical conductance of
LSMO/DDA is about 3 decades below that of the bare LSMO substrate. Moreover,
the presence of the DDA SAM suppresses the known conductance switching of the
LSMO substrate that is induced by mechanical and/or bias constraints during
C-AFM measurements. A partial light-induced conductance switching between the
open and closed forms of the DDA is observed for the LSMO/DDA/C-AFM tip
molecular junctions (closed/open conductance ratio of about 8). We show that,
in the case of long-time exposition to UV light, this feature can be masked by
a non-reversible decrease (a factor of about 15) of the conductance of the LSMO
electrode.Comment: Full paper with supporting informatio
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