1,522 research outputs found
A bolometric measurement of the antineutrino mass
High statistics calorimetric measurements of the beta spectrum of 187Re are
being performed with arrays of silver perrhenate crystals operated at low
temperature. After a modification of the experimental set-up, which allowed to
substantially reduce the background of spurious counts and therefore to
increase the sensitivity on the electron antineutrino mass, a new measurement
with 10 silver perrhenate microbolometers is running since July 2002. The
crystals have masses between 250 and 350 micrograms and their average FWHM
energy resolution, constantly monitored by means of fluorescence X-rays, is of
28.3 eV at the beta end-point. The Kurie plot collected during 4485 hours x mg
effective running time has an end-point energy of 2466.1 +/- 0.8{stat} +/- 1.5
{syst} eV, while the half lifetime of the decay is found to be 43.2 +/-
0.2{stat} +/- 0.1{syst} Gy. These values are the most precise obtained so far
for 187Re. From the fit of the Kurie plot we can deduce a value for the squared
electron antineutrino mass m(nu)^2 of 147 +/- 237{stat} +/- 90{syst} eV^2. The
corresponding 90% C.L. upper limit for m(nu) is 21.7 eV.Comment: 3 pages, 3 figures. Submitted to Phys. Rev. Let
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Identification and quantification of major faba bean seed proteins
Faba bean (Vicia faba L.) holds great importance for human and animal nutrition for its high protein content. However, better understanding of its seed protein composition is required in order to develop cultivars that meet market demands for plant proteins with specific quality attributes. In this study, we screened 35 diverse Vicia faba genotypes by employing the one-dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis (1D SDS-PAGE) method, and 35 major protein bands obtained from three genotypes with contrasting seed protein profiles were further analyzed by mass spectrometry (MS). Twenty-five of these protein bands (MW range: ∼ 9–107 kDa) had significant (p ≤ 0.05) matches to polypeptides in protein databases. MS analysis showed that most of the analyzed protein bands contained more than one protein type and, in total, over 100 proteins were identified. These included major seed storage proteins such as legumin, vicilin, and convicilin, as well as other protein classes like lipoxygenase, heat shock proteins, sucrose-binding proteins, albumin, and defensin. Furthermore, seed protein extracts were separated by size-exclusion high-performance liquid chromatography (SE-HPLC), and percentages of the major protein classes were determined. On average, legumin and vicilin/convicilin accounted for 50 and 27% of the total protein extract, respectively. However, the proportions of these proteins varied considerably among genotypes, with the ratio of legumin:vicilin/convicilin ranging from 1:1 to 1:3. In addition, there was a significant (p < 0.01) negative correlation between the contents of these major fractions (r = −0.83). This study significantly extends the number of identified Vicia faba seed proteins and reveals new qualitative and quantitative variation in seed protein composition, filling a significant gap in the literature. Moreover, the germplasm and screening methods presented here are expected to contribute in selecting varieties with improved protein content and quality
Enhancement of the electric dipole moment of the electron in BaF molecule
We report results of ab initio calculation of the spin-rotational Hamiltonian
parameters including P- and P,T-odd terms for the BaF molecule. The ground
state wave function of BaF molecule is found with the help of the Relativistic
Effective Core Potential method followed by the restoration of molecular
four-component spinors in the core region of barium in the framework of a
non-variational procedure. Core polarization effects are included with the help
of the atomic Many Body Perturbation Theory for Barium atom. For the hyperfine
constants the accuracy of this method is about 5-10%.Comment: 8 pages, REVTEX, report at II International Symposium on Symmetries
in Subatomic Physics, Seattle 199
First-Principles Studies of Hydrogenated Si(111)--77
The relaxed geometries and electronic properties of the hydrogenated phases
of the Si(111)-77 surface are studied using first-principles molecular
dynamics. A monohydride phase, with one H per dangling bond adsorbed on the
bare surface is found to be energetically favorable. Another phase where 43
hydrogens saturate the dangling bonds created by the removal of the adatoms
from the clean surface is found to be nearly equivalent energetically.
Experimental STM and differential reflectance characteristics of the
hydrogenated surfaces agree well with the calculated features.Comment: REVTEX manuscript with 3 postscript figures, all included in uu file.
Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.htm
Optogalvanic Spectroscopy of Metastable States in Yb^{+}
The metastable ^{2}F_{7/2} and ^{2}D_{3/2} states of Yb^{+} are of interest
for applications in metrology and quantum information and also act as dark
states in laser cooling. These metastable states are commonly repumped to the
ground state via the 638.6 nm ^{2}F_{7/2} -- ^{1}D[5/2]_{5/2} and 935.2 nm
^{2}D_{3/2} -- ^{3}D[3/2]_{1/2} transitions. We have performed optogalvanic
spectroscopy of these transitions in Yb^{+} ions generated in a discharge. We
measure the pressure broadening coefficient for the 638.6 nm transition to be
70 \pm 10 MHz mbar^{-1}. We place an upper bound of 375 MHz/nucleon on the
638.6 nm isotope splitting and show that our observations are consistent with
theory for the hyperfine splitting. Our measurements of the 935.2 nm transition
extend those made by Sugiyama et al, showing well-resolved isotope and
hyperfine splitting. We obtain high signal to noise, sufficient for laser
stabilisation applications.Comment: 8 pages, 5 figure
Plasmon single- and multi-quantum excitation in free metal clusters as seen by photoelectron spectroscopy.
Plasmons are investigated in free nanoscale Na, Mg, and K metal clusters using synchrotron radiation-based x-ray photoelectron spectroscopy. The core levels for which the response from bulk and surface atoms can be resolved are probed over an extended binding energy range to include the plasmon loss features. In all species the features due to fundamental plasmons are identified, and in Na and K also those due to either the first order plasmon overtones or sequential plasmon excitation are observed. These features are discussed in view of earlier results for planar macroscopic samples and free clusters of the same materials
Calculation of T_ odd effects in $"" sup 205_TIF including electron correlation
A method and codes for two-step correlation calculation of heavy-atom
molecules have been developed, employing the generalized relativistic effective
core potential and relativistic coupled cluster (RCC) methods at the first
step, followed by nonvariational one-center restoration of proper
four-component spinors in the heavy cores. Electron correlation is included for
the first time in an ab initio calculation of the interaction of the permanent
P,T-odd proton electric dipole moment with the internal electromagnetic field
in a molecule. The calculation is performed for the ground state of TlF at the
experimental equilibrium, R_e=2.0844 A, and at R=2.1 A, with spin-orbit and
correlation effects included by RCC. Calculated results with single cluster
amplitudes only are in good agreement (3% and 1%) with recent
Dirac-Hartree-Fock (DHF) values of the magnetic parameter M; the larger
differences occurring between present and DHF volume parameter (X) values, as
well as between the two DHF calculations, are explained. Inclusion of electron
correlation by GRECP/RCC with single and double excitations has a major effect
on the P,T-odd parameters, decreasing M by 17% and X by 22%.Comment: 5 pages, REVTeX4 style Accepted for publication in Phys.Rev.Letter
A new limit on the permanent electric dipole moment of ^{199}Hg
We present the first results of a new search for a permanent electric dipole
moment of the ^{199}Hg atom using a UV laser. Our measurements give d(Hg)= -
(1.06 +/- 0.49 +/- 0.40) 10^{-28} e cm. We interpret the result as an upper
limit |d(Hg)| < 2.1 10^{-28} e cm (95% C.L.), which sets new constraints on
theta_{QCD}, chromo-EDMs of the quarks, and CP violation in Supersymmetric
models.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let
The usefulness of rapid diagnostic tests in the new context of low malaria transmission in zanzibar.
BACKGROUND\ud
\ud
We assessed if histidine-rich-protein-2 (HRP2) based rapid diagnostic test (RDT) remains an efficient tool for Plasmodium falciparum case detection among fever patients in Zanzibar and if primary health care workers continue to adhere to RDT results in the new epidemiological context of low malaria transmission. Further, we evaluated the performance of RDT within the newly adopted integrated management of childhood illness (IMCI) algorithm in Zanzibar.\ud
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METHODS AND FINDINGS\ud
\ud
We enrolled 3890 patients aged ≥2 months with uncomplicated febrile illness in this health facility based observational study conducted in 12 primary health care facilities in Zanzibar, between May-July 2010. One patient had an inconclusive RDT result. Overall 121/3889 (3.1%) patients were RDT positive. The highest RDT positivity rate, 32/528 (6.1%), was found in children aged 5-14 years. RDT sensitivity and specificity against PCR was 76.5% (95% CI 69.0-83.9%) and 99.9% (95% CI 99.7-100%), and against blood smear microscopy 78.6% (95% CI 70.8-85.1%) and 99.7% (95% CI 99.6-99.9%), respectively. All RDT positive, but only 3/3768 RDT negative patients received anti-malarial treatment. Adherence to RDT results was thus 3887/3889 (99.9%). RDT performed well in the IMCI algorithm with equally high adherence among children <5 years as compared with other age groups.\ud
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CONCLUSIONS\ud
\ud
The sensitivity of HRP-2 based RDT in the hands of health care workers compared with both PCR and microscopy for P. falciparum case detection was relatively low, whereas adherence to test results with anti-malarial treatment was excellent. Moreover, the results provide evidence that RDT can be reliably integrated in IMCI as a tool for improved childhood fever management. However, the relatively low RDT sensitivity highlights the need for improved quality control of RDT use in primary health care facilities, but also for more sensitive point-of-care malaria diagnostic tools in the new epidemiological context of low malaria transmission in Zanzibar.\ud
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TRIAL REGISTRATION\ud
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ClinicalTrials.gov NCT01002066
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