154 research outputs found
A proposal of a UCN experiment to check an earthquake waves model
Elastic waves with transverse polarization inside incidence plane can create
longitudinal surface wave (LSW) after reflection from a free surface. At a
critical incidence angle this LSW accumulates energy density, which can be
orders of magnitude higher than energy density of the incident transverse wave.
A specially arranged vessel for storage of ultracold neutrons (UCN) can be used
to verify this effect.Comment: 8 pages 3 figures added a paragraph on vibrations along surface at
critical angl
Molecular Diagnostics of Histoplasmosis
Histoplasmosis is a systemic fungal disease that occurs worldwide. The highest incidence of the disease is reported on the American continent. It also occurs in China, India, South-Eastern Asia, Africa, Australia and Europe. Clinical syndromes of histoplasmosis are not specific and in most cases immunocompetent individuals are asymptomatic or present mild influenza-like disease. Immunocompromised patients especially individuals with AIDS, can develop a severe and fatal disease due to fungal dissemination to many organs. Etiological agent of histoplasmosis is the dimorphic fungus Histoplasma capsulatum, which inhabits the soils contaminated with bird or bat droppings. Three biological varieties are considered for this fungus: H. capsulatum var. capsulatum, H. capsulatum var. duboissii and H. capsulatum var. farciminosum. Genetic differences are observed among H. capsulatum strains from diverse regions of the world. The main molecular methodologies for genetic typing of fungi are based on DNA fingerprinting. They have been an important instrument to identify possible sources of infection in outbreaks of histoplasmosis. Genetic profiles of H. capsulatum, isolated from bats and humans, helped to understand the distribution of the disease in certain endemic regions. The con-ventional diagnosis of histoplasmosis is performed by means of cultural and microscopic examination of samples from the respiratory tract and biologic fluids. However, these techniques yield positive results in only 50 % of cases. In the last two decades, approaches for the detecting of H. capsulatum in clinical samples, using different molecular targets, based on PCR assay have been developed. Their use can shorten the time span of analysis for diagnosis confirmation. Molecular methods have high specificity and sensitivity and reduce the risk of infection for the laboratory personnel. In this study we reviewed the recently published data on the use of main molecular methods for diagnosis of histoplasmosis
Wide band-gap tuning Cu2ZnSn1-xGexS4 single crystals: Optical and vibrational properties
The linear optical properties of Cu2ZnSn1-xGe x S4 high quality single crystals with a wide range of Ge contents (x=0.1, 0.3, 0.5, 0.7, 0.9 and 1) have been investigated in the ultraviolet and near infrared range using spectroscopic ellipsometry measurements. From the analysis of the complex dielectric function spectra it has been found that the bandgap E 0 increases continuously from 1.49eV to 2.25eV with the Ge content. Furthermore, the evolution of the interband transitions E 1A and E 1B has been also determined. Raman scattering using three different excitation wavelengths and its analysis have been performed to confirm the absence of secondary phases in the samples, and to distinguish between stannite, wurtzite, wurzstannite and kesterite structures. Additionally, the analysis of the high resolution Raman spectra obtained in samples with different [Ge]/([Ge]+[Sn]) ratios allows describing a bimodal behavior of the dominant A modes. The understanding of the incorporation of Ge into the Cu2ZnSnS4 lattice is fundamental in order to develop efficient bandgap engineering of these compounds towards the fabrication of kesterite based solar cells with enhanced performanceThis work was supported by the Marie Curie-ITN project (KESTCELL, GA: 316488), Marie Curie-IRSES project (PVICOKEST, GA: 269167), AMALIE (TEC2012-38901-C02-01) and SUNBEAM (ENE2013-49136-C4-3-R) project funded by the Spanish Ministry of Economy and Competitiveness. RC acknowledges financial support from Spanish MINECO within the RamĂłn y Cajal program (RYC-2011-08521
Spectroscopic ellipsometry study of Cu2ZnSnS4 bulk poly-crystals
The linear optical properties of Cu2ZnSnS4 bulk poly-crystals have been investigated using spectroscopic ellipsometry in the range of 1.2-4.6 eV at room temperature. The characteristic features identified in the optical spectra are explained by using the Adachi analytical model for the interband transitions at the corresponding critical points in the Brillouin zone. The experimental data have been modeled over the entire spectral range taking into account the lowest E0 transition near the fundamental absorption edge and E1A and E1B higher energy interband transitions. In addition, the spectral dependences of the refractive index, extinction coefficient, absorption coefficient, and normal-incidence reflectivity values have been accurately determined and are provided since they are essential data for the design of Cu2ZnSnS4 based optoelectronic devicesThe research leading to the presented results was partially
supported by the European Project INFINITE-CELL (Ref.
H2020-MSCA-RISE-2017-777968, 2017–2021, www.infinitecell.eu)
and the Spanish MINECO Projects “WINCOST”
(ENE2016-80788-C5-2-R) and PHOTOMANA (TEC2015-
69916-C2-1-R). The authors from the Institute of Applied
Physics appreciate the financial support from STCU 6224 and
from the Institutional Project No. CSSDT 15.817.02.04
First observation of a narrow charm-strange meson DsJ(2632) -> Ds eta and D0 K+
We report the first observation of a charm-strange meson DsJ(2632) at a mass
of 2632.6+/-1.6 MeV/c^2 in data from SELEX, the charm hadro-production
experiment E781 at Fermilab. This state is seen in two decay modes, Ds eta and
D0 K+. In the Ds eta decay mode we observe an excess of 49.3 events with a
significance of 7.2sigma at a mass of 2635.9+/-2.9 MeV/c^2. There is a
corresponding peak of 14 events with a significance of 5.3sigma at 2631.5+/-1.9
MeV/c^2 in the decay mode D0 K+. The decay width of this state is <17 MeV/c^2
at 90% confidence level. The relative branching ratio Gamma(D0K+)/Gamma(Dseta)
is 0.16+/-0.06. The mechanism which keeps this state narrow is unclear. Its
decay pattern is also unusual, being dominated by the Ds eta decay mode.Comment: 5 pages, 3 included eps figures. v2 as accepted for publication by
PR
First Observation of the Doubly Charmed Baryon Xi_cc^+
We observe a signal for the doubly charmed baryon Xi_cc^+ in the charged
decay mode Xi_cc^+ --> Lambda_c^+ K- pi+ in data from SELEX, the charm
hadro-production experiment at Fermilab. We observe an excess of 15.9 events
over an expected background of 6.1 +/- 0.5 events, a statistical significance
of 6.3sigma. The observed mass of this state is (3519 +/- 1) MeV/c^2. The
Gaussian mass width of this state is 3MeV/c^2, consistent with resolution; its
lifetime is less than 33fsec at 90% confidence.Comment: 5 pages, 3 figures, accepted for publication in Physical Review
Letter
Wide band-gap tuning Cu2ZnSn1-xGexS4 single crystals: optical and vibrational properties
The linear optical properties of Cu2ZnSn1-xGexS4 high quality single crystals with a wide range of Ge contents (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1) have been investigated in the ultraviolet and near infrared range using spectroscopic ellipsometry measurements. From the analysis of the complex dielectric function spectra it has been found that the bandgap E0 increases continuously from 1.49 eV to 2.25 eV with the Ge content. Furthermore, the evolution of the interband transitions E1A and E1B has been also determined. Raman scattering using three different excitation wavelengths and its analysis have been performed to confirm the absence of secondary phases in the samples, and to distinguish between stannite, wurtzite, wurzstannite and kesterite structures. Additionally, the analysis of the high resolution Raman spectra obtained in samples with different [Ge]/([Ge]+[Sn]) ratios allows describing a bimodal behavior of the dominant A modes. The understanding of the incorporation of Ge into the Cu2ZnSnS4 lattice is fundamental in order to develop efficient bandgap engineering of these compounds towards the fabrication of kesterite based solar cells with enhanced performanc
First Measurement of pi e -> pi e gamma Pion Virtual Compton Scattering
Pion Virtual Compton Scattering (VCS) via the reaction pi e --> pi e gamma
was observed in the Fermilab E781 SELEX experiment. SELEX used a 600 GeV/c pi-
beam incident on target atomic electrons, detecting the incident pi- and the
final state pi-, electron and gamma. Theoretical predictions based on chiral
perturbation theory are incorporated into a Monte Carlo simulation of the
experiment and are compared to the data. The number of reconstructed events (9)
and their distribution with respect to the kinematic variables (for the
kinematic region studied) are in reasonable accord with the predictions. The
corresponding pi- VCS experimental cross section is sigma=38.8+-13 nb, in
agreement with the theoretical expectation sigma=34.7 nb.Comment: 10 pages, 12 figures, 4 tables, 25 references, SELEX home page is
http://fn781a.fnal.gov/, revised July 21, 2002 in response to journal referee
Comment
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