12,698 research outputs found
Relativistic many-body calculations of the Stark-induced amplitude of the 6P1/2 -7P1/2 transition in thallium
Stark-induced amplitudes for the 6P1/2 - 7P1/2 transition in Tl I are
calculated using the relativistic SD approximation in which single and double
excitations of Dirac-Hartree-Fock levels are summed to all orders in
perturbation theory. Our SD values alpha S = 368 a0 3 and beta S= 298 a 0 3 are
in good agreement with the measurements alpha S=377(8) a 0 3$ and beta S =
313(8) a 0 3 by D. DeMille, D. Budker, and E. D. Commins [Phys. Rev. A 50, 4657
(1994)]. Calculations of the Stark shifts in the 6P1/2 - 7P1/2 and 6P1/2 -
7S1/2 transitions are also carried out. The Stark shifts predicted by our
calculations agree with the most accurate measured values within the
experimental uncertainties for both transitions
Unusual features of pomoviral RNA movement
This work is partially supported by the Scottish Governmentâs Rural and Environment Science and Analytical Services (RESAS) DivisionPotato mop-top pomovirus (PMTV) is one of a few viruses that can move systemically in plants in the absence of the capsid protein (CP). Pomoviruses encode the triple gene block genetic module of movement proteins (TGB 1, 2, and 3) and recent research suggests that PMTV RNA is transported either as ribonucleoprotein (RNP) complexes containing TGB1 or encapsidated in virions containing TGB1. Furthermore, there are different requirements for local or systemic (long-distance) movement. Research suggests that nucleolar passage of TGB1 may be important for the long-distance movement of both RNP and virions. Moreover, and uniquely, the long-distance movement of the CP-encoding RNA requires expression of both major and minor CP subunits and is inhibited when only the major CP sub unit is expressed. This paper reviews pomovirus research and presents a current model for RNA movement.Publisher PDFPeer reviewe
The Ubiquity of the Rapid Neutron-Capture Process
To better characterize the abundance patterns produced by the r-process, we
have derived new abundances or upper limits for the heavy elements zinc (Zn),
yttrium (Y), lanthanum (La), europium (Eu), and lead (Pb). Our sample of 161
metal-poor stars includes new measurements from 88 high resolution and high
signal-to-noise spectra obtained with the Tull Spectrograph on the 2.7m Smith
Telescope at McDonald Observatory, and other abundances are adopted from the
literature. We use models of the s-process in AGB stars to characterize the
high Pb/Eu ratios produced in the s-process at low metallicity, and our new
observations then allow us to identify a sample of stars with no detectable
s-process material. In these stars, we find no significant increase in the
Pb/Eu ratios with increasing metallicity. This suggests that s-process material
was not widely dispersed until the overall Galactic metallicity grew
considerably, perhaps even as high as [Fe/H]=-1.4. We identify a dispersion of
at least 0.5 dex in [La/Eu] in metal-poor stars with [Eu/Fe]<+0.6 attributable
to the r-process, suggesting that there is no unique "pure" r-process elemental
ratio among pairs of rare earth elements. We confirm earlier detections of an
anti-correlation between Y/Eu and Eu/Fe bookended by stars strongly enriched in
the r-process (e.g., CS 22892-052) and those with deficiencies of the heavy
elements (e.g., HD 122563). We can reproduce the range of Y/Eu ratios using
simulations of high-entropy neutrino winds of core-collapse supernovae that
include charged-particle and neutron-capture components of r-process
nucleosynthesis. The heavy element abundance patterns in most metal-poor stars
do not resemble that of CS 22892-052, but the presence of heavy elements such
as Ba in nearly all metal-poor stars without s-process enrichment suggests that
the r-process is a common phenomenon.Comment: Accepted for publication in the Astrophysical Journal. 25 pages, 13
figure
Facility-based delivery in the context of Zimbabwe's HIV epidemic--missed opportunities for improving engagement with care: a community-based serosurvey.
BackgroundIn developing countries, facility-based delivery is recommended for maternal and neonatal health, and for prevention of mother-to-child HIV transmission (PMTCT). However, little is known about whether or not learning one's HIV status affects one's decision to deliver in a health facility. We examined this association in Zimbabwe.MethodsWe analyzed data from a 2012 cross-sectional community-based serosurvey conducted to evaluate Zimbabwe's accelerated national PMTCT program. Eligible women (â„16 years old and mothers of infants born 9-18 months before the survey) were randomly sampled from the catchment areas of 157 health facilities in five of ten provinces. Participants were interviewed about where they delivered and provided blood samples for HIV testing.ResultsOverall 8796 (77 %) mothers reported facility-based delivery; uptake varied by community (30-100%). The likelihood of facility-based delivery was not associated with maternal HIV status. Women who self-reported being HIV-positive before delivery were as likely to deliver in a health facility as women who were HIV-negative, irrespective of when they learned their status - before (adjusted prevalence ratio (PRa)â=â1.04, 95% confidence interval (CI)â=â1.00-1.09) or during pregnancy (PRaâ=â1.05, 95% CIâ=â1.01-1.09). Mothers who had not accessed antenatal care or tested for HIV were most likely to deliver outside a health facility (69%). Overall, however 77% of home deliveries occurred among women who had accessed antenatal care and were HIV-tested.ConclusionsUptake of facility-based delivery was similar among HIV-infected and HIV-uninfected mothers, which was somewhat unexpected given the substantial technical and financial investment aimed at retaining HIV-positive women in care in Zimbabwe
Near-UV Observations of CS29497-030: New Constraints on Neutron-Capture Nucleosynthesis Processes
Employing spectra obtained with the new Keck I HIRES near-UV sensitive
detector, we have performed a comprehensive chemical composition analysis of
the binary blue metal-poor star CS29497-030. Abundances for 29 elements and
upper limits for an additional seven have been derived, concentrating on
elements largely produced via neutron-capture nucleosynthesis. Included in our
analysis are the two elements that define the termination point of the slow
neutron-capture process, lead and bismuth. We determine an extremely high value
of [Pb/Fe] = +3.65 +/- 0.07 (sigma = 0.13) from three features, supporting the
single-feature result obtained in previous studies. We also detect Bi for the
first time in a metal-poor star. Our derived Bi/Pb ratio is in accord with
those predicted from the most recent FRANEC calculations of the slow
neutron-capture process in low-mass AGB stars. We find that the neutron-capture
elemental abundances of CS29497-030 are best explained by an AGB model that
also includes very significant amounts of pre-enrichment of rapid
neutron-capture process material in the protostellar cloud out of which the
CS29497-030 binary system formed. Thus, CS29497-030 is both an ``r+s'' and
``extrinsic AGB'' star. Furthermore, we find that the mass of the AGB model can
be further constrained by the abundance of the light odd-element [Na/Fe] which
is sensitive to the neutron excess.Comment: 7 pages = 4 + 2 colour encapsulated postscript figures + 1 table; to
appear in ApJ Letters; additional jpeg figure available at
ftp://www.astro.caltech.edu/users/iii/cs2949703
Editorial: Thymic Epithelial Cells: New Insights Into the Essential Driving Force of T-Cell Differentiation
M.B. is supported by the Intramural Research Program of the NIH. I.O. is supported by grant from the MEXT-JSPS 17K08884 and Takeda Science Foundation. The laboratory of N.L.A. is supported by a starting grant from the European Research Council (ERC) under the project 637843 and by FEDER - Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 - Operacional Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by Portuguese funds through FCT - Fundação para a CiĂȘncia e a Tecnologia/MinistĂ©rio da CiĂȘncia, Tecnologia e Ensino Superior in the framework of the project POCI-01-0145-FEDER-029129 (PTDC/MED-IMU/29129/2017) and PTDC/ MED-IMU/1416/2020
Regulating Scotland's social landlords: localised resistance to technologies of performance management
Influenced by Foucault's later work on governmentality, this paper explores the regulation of social landlords as a 'technology of performance' concerned with governing the conduct of dispersed welfare agencies and the professionals within them. This is a mode of power that is both voluntary and coercive; it seeks to realise its ambitions not through direct acts of intervention, but by promoting the responsible self-governance of autonomous subjects. Through an analysis of the regulatory framework for social landlords in Scotland, this paper highlights the creation of a performance culture that seeks to mobilise housing organisations to reconcile their local management systems and service provision to external standards, whilst simultaneously wielding punitive interventions for non-compliance. However, housing professionals are not passive in all of this, and indeed, actively challenged and resisted these top-down attempts to govern them at arm's-length
Rival bishops, rival cathedrals : the election of Cormac, archdeacon of Sodor, as bishop in 1331
Peer reviewedPublisher PD
Evidence of Multiple r-Process Sites in the Early Galaxy: New Observations of CS 22892-052
First results are reported of a new abundance study of neutron-capture
elements in the ultra-metal-poor (UMP; [Fe/H] = -3.1) halo field giant star CS
22892-052. Using new high resolution, high signal-to-noise spectra, abundances
of more than 30 neutron-capture elements (Z>30) have been determined. Six
elements in the 40<Z<56 domain (Nb, Ru, Rh, Pd, Ag and Cd) have been detected
for the first time in a UMP star. Abundances are also derived for three of the
heaviest stable elements (Os, Ir, and Pb). A second transition of thorium,
Th{4086}, confirms the abundance deduced from the standard Th{4019} line, and
an upper limit to the abundance of uranium is established from the absence of
the U{3859} line. As found in previous studies, the abundances of the heavier
(Z>=56) stable neutron-capture elements in CS 22892-052 match well the scaled
solar system r-process abundance distribution. From the observed Th abundance,
an average age of ~= 16 +/- 4 Gyr is derived for cs22892-052, consistent with
the lower age limit of ~= 11 Gyr derived from the upper limit on the U
abundance. The concordance of scaled solar r-process and CS 22892-052
abundances breaks down for the lighter neutron-capture elements, supporting
previous suggestions that different r-process production sites are responsible
for lighter and heavier neutron-capture elements.Comment: To be published in the Astrophysical Journal Letter
New Results on e+e- Line Emission in U+Ta Collisions
We present new results obtained from a series of follow-up e+e- coincidence
measurements in heavy-ion collisions, utilizing an improved experimental set-up
at the double-Orange beta-spectrometer of GSI. The collision system U+Ta was
reinvestigated in three independent runs at beam energies in the range
(6.0-6.4)xA MeV and different target thicknesses, with the objective to
reproduce a narrow sum-energy e+e- line at ~635 keV observed previously in this
collision system. At improved statistical accuracy, the line could not be found
in these new data. For the ''fission'' scenario, an upper limit (1 sigma) on
its production probability per collision of 1.3x10^{-8} can be set which has to
be compared to the previously reported value of [4.9 +- 0.8 (stat.) +- 1.0
(syst)]x10^{-7}. In the light of the new results, a reanalysis of the old data
shows that the continuous part of the spectrum at the line position is
significantly higher than previously assumed, thus reducing the production
probability of the line by a factor of two and its statistical significance to
< 3.4sigma.Comment: 15 pages, standard LaTeX with 3 included PS figures; Submitted to
Physics Letters
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