944 research outputs found
B-meson decay constants: a more complete picture from full lattice QCD
We extend the picture of -meson decay constants obtained in lattice QCD
beyond those of the , and to give the first full lattice QCD
results for the , and . We use improved NonRelativistic QCD
for the valence quark and the Highly Improved Staggered Quark (HISQ) action
for the lighter quarks on gluon field configurations that include the effect of
, and quarks in the sea with quark masses going down to
physical values. For the ratio of vector to pseudoscalar decay constants, we
find = 0.941(26), = 0.953(23) (both
less than 1.0) and = 0.988(27). Taking correlated
uncertainties into account we see clear indications that the ratio increases as
the mass of the lighter quark increases. We compare our results to those using
the HISQ formalism for all quarks and find good agreement both on decay
constant values when the heaviest quark is a and on the dependence on the
mass of the heaviest quark in the region of the . Finally, we give an
overview plot of decay constants for gold-plated mesons, the most complete
picture of these hadronic parameters to date.Comment: 20 pages, 9 figures. Minor updates to the discussion in several
places and some additional reference
An adaptive cross approximation (ACA) for the extended boundary element method (XBEM) in anisotropic materials
The extended boundary element method (XBEM) is a modification from the standard BEM, where enrichment functions are embedded into the BEM formulation. The results obtained with this method were seen to be accurate and stable, being especially useful for fracture problems. However, the method suffers from the presence of a linear system containing unsymmetric and fully populated matrices which needs to be solved in order to get the solution of the boundary problem. This can be computationally expensive for problems dealing with multiple cracks for instance. Adaptive cross approximation (ACA) is used to reduce the number of operations necessary to solve the linear system of equations for a fracture problem with an anisotropic material
Forest Trees in Human Modified Landscapes: Ecological and Genetic Drivers of Recruitment Failure in Dysoxylum malabaricum (Meliaceae)
Tropical agro-forest landscapes are global priority areas for biodiversity conservation. Little is known about the ability of these landscapes to sustain large late successional forest trees upon which much forest biodiversity depends. These landscapes are subject to fragmentation and additional habitat degradation which may limit tree recruitment and thus compromise numerous ecosystem services including carbon storage and timber production. Dysoxylum malabaricum is a large canopy tree species in the Meliaceae, a family including many important tropical timber trees. This species is found in
highly fragmented forest patches within a complex agro-forest landscape of the Western Ghats biodiversity hot spot, South India. In this paper we combined a molecular assessment of inbreeding with ecological and demographic data to explore the multiple threats to recruitment of this tree species. An evaluation of inbreeding, using eleven microsatellite loci in 297 nursery-reared seedlings collected form low and high density forest patches embedded in an agro-forest matrix, shows that
mating between related individuals in low density patches leads to reduced seedling performance. By quantifying habitat degradation and tree recruitment within these forest patches we show that increasing canopy openness and the increased abundance of pioneer tree species lead to a general decline in the suitability of forest patches for the recruitment of D. malabaricum. We conclude that elevated inbreeding due to reduced adult tree density coupled with increased degradation of forest patches, limit the recruitment of this rare late successional tree species. Management strategies which maintain canopy cover and enhance local densities of adult trees in agro-forest mosaics will be required to ensure D. malabaricum persists in these landscapes. Our study highlights the need for a holistic understanding of the incipient processes that threaten populations of many important and rare tropical tree species in human dominated agro-forest landscapes
Cross-talk compensation of hyperfine control in donor qubit architectures
We theoretically investigate cross-talk in hyperfine gate control of
donor-qubit quantum computer architectures, in particular the Kane proposal. By
numerically solving the Poisson and Schr\"{o}dinger equations for the gated
donor system, we calculate the change in hyperfine coupling and thus the error
in spin-rotation for the donor nuclear-electron spin system, as the gate-donor
distance is varied. We thus determine the effect of cross-talk - the
inadvertent effect on non-target neighbouring qubits - which occurs due to
closeness of the control gates (20-30nm). The use of compensation protocols is
investigated, whereby the extent of crosstalk is limited by the application of
compensation bias to a series of gates. In light of these factors the
architectural implications are then considered.Comment: 15 pages, 22 figures, submitted to Nanotechnolog
Isoniazid as a substrate and inhibitor of myeloperoxidase: Identification of amine adducts and the influence of superoxide dismutase on their formation
Neutrophils ingest Mycobacteria tuberculosis (Mtb) in the lungs of infected individuals. During
phagocytosis they use myeloperoxidase (MPO) to catalyze production of hypochlorous acid (HOCl), their
most potent antimicrobial agent. Isoniazid (INH),the foremost antibiotic in the treatment oftuberculosis,
is oxidized by MPO. It rapidly reduced compound I of MPO [k = (1.22 0.05) 106 M 1 s
1
] but reacted less
favorably with compound II [(9.8 0.6) 102 M 1 s
1
]. Oxidation of INH by MPO and hydrogen peroxide was
unaffected by chloride,the physiological substrate for compound I, and the enzyme was partially converted
to compound III. This indicates that INH is oxidized outside the classical peroxidation cycle. In combination
with superoxide dismutase (SOD), MPO oxidized INH without exogenous hydrogen peroxide. SOD must
favor reduction of oxygen by the INH radical to give superoxide and ultimately hydrogen peroxide. In both
oxidation systems, an adduct with methionine was formed and it was a major product with MPO and SOD.
We show that it is a conjugate of an acyldiimide with amines. INH substantially inhibited HOCl production
by MPO and neutrophils below pharmacological concentrations. The reversible inhibition is explained by
diversion of MPO to its ferrous and compound III forms during oxidation of INH. MPO, along with SOD
released by Mtb, will oxidize INH at sites of infection and their interactions are likely to limit the efficacy of
the drug, promote adverse drug reactions via formation of protein adducts, and impair a major bacterial
killing mechanism of neutrophils
Myeloperoxidase and oxidative stress in rheumatoid arthritis
Objective. To determine whether MPO contributes to oxidative stress and disease activity in RA and
whether it produces hypochlorous acid in SF.
Methods. Plasma and where possible SF were collected from 77 RA patients while 120 healthy controls
supplied plasma only. MPO and protein carbonyls were measured by ELISAs. 3-Chlorotyrosine in proteins
and allantoin in plasma were measured by mass spectrometry.
Results. Plasma MPO concentrations were significantly higher in patients with RA compared with
healthy controls [10.8 ng/ml, inter-quartile range (IQR): 7.214.2; P < 0.05], but there was no significant
difference in plasma MPO protein concentrations between RA patients with high disease activity
(HDA; DAS-28 >3.2) and those with low disease activity (LDA; DAS-28 43.2) (HDA 27.9 ng/ml,
20.234.1 vs LDA 22.1 ng/ml, 16.934.9; P > 0.05). There was a significant relationship between plasma
MPO and DAS-28 (r = 0.35; P = 0.005). Plasma protein carbonyls and allantoin were significantly higher in
patients with RA compared with the healthy controls. MPO protein was significantly higher in SF compared with plasma (median 624.0 ng/ml, IQR 258.42433.0 vs 30.2 ng/ml, IQR 25.150.9; P < 0.0001). The
MPO present in SF was mostly active. 3-Chlorotyrosine, a specific biomarker of hypochlorous acid, was
present in proteins from SF and related to the concentration of MPO (r = 0.69; P = 0.001). Protein carbonyls
in SF were associated with MPO protein concentration (r = 0.40; P = 0.019) and 3-chlorotyrosine (r = 0.66;
P = 0.003).
Conclusion. MPO is elevated in patients with RA and promotes oxidative stress through the production of
hypochlorous acid
Generation of photoionized plasmas in the laboratory of relevance to accretion-powered x-ray sources using keV line radiation
We describe laboratory experiments to generate x-ray photoionized plasmas of
relevance to accretion-powered x-ray sources such as neutron star binaries and
quasars, with significant improvements over previous work. We refer to a key
quantity, the photoionization parameter, defined as xi = 4{\pi}F/n_e where F is
the x-ray flux and n_e the electron density. This is usually meaningful in a
steady state context, but is commonly used, in the literature, as a figure of
merit for laboratory experiments that are, of necessity, time dependent. We
demonstrate that we can achieve values of xi >100 erg-cm s-1 using laser-plasma
x-ray sources, in the regime of interest for several astrophysical scenarios.
In particular, we show that our use of a keV line source, rather than the
quasi-blackbody radiation fields normally employed in such experiments, has
allowed generation of a ratio of inner-shell to outer-shell photoionization
expected from a blackbody source with ~keV spectral temperature. This is a key
factor in allowing experiments to be compared to the predictions of codes
employed to model astrophysical sources. We compare calculations from our
in-house plasma modelling code with those from Cloudy and find moderately good
agreement for the time evolution of both electron temperature and average
ionisation. However, a comparison of code predictions of a K-beta argon X-ray
spectrum with experimental data reveals that our Cloudy simulation
overestimates the intensities of more highly ionised argon species. This is not
totally surprising as the Cloudy model was generated for a single set of plasma
conditions, while the experimental data are spatially integrated.Comment: 20 pages, 9 figure
Fragmentation Genetics of Vateria indica: implications for management of forest genetic resources of an endemic dipterocarp
Tropical agro-forest landscapes are potentially valuable reserves of forest genetic resources for forestry and restoration of degraded forests. The Dipterocarpaceae is a dominant Southeast Asian family of tree species of global significance for the tropical timber industry. Very little information exists about how effective human modified landscapes are for conserving genetic diversity in dipterocarp species. This study provides a baseline for understanding how fragmented agro-forest landscapes in India sustain forest genetic resources in an endemic dipterocarp tree. We compare genetic diversity and fine-scale spatial genetic structure (FSGS) in the threatened tree species Vateria indica within an isolated and a continuous forest site in the Western Ghats, South India. We place these results in the context of dipterocarps from both the Seychelles and Borneo. Parentage analysis of 694 progeny using twelve nuclear microsatellite markers is applied to estimate pollen and seed dispersal. Using a nursery trial we evaluate effects of inbreeding on growth performance. Our results show that levels of FSGS, and gene dispersal are comparable between a small isolated and a large continuous site of V. indica. Realized long-distance pollen flow into the isolated patch appears to help maintaining genetic diversity. The nursery experiment suggests that selection favours outbred progeny. Individuals of V. indica in close proximity appear less related to each other than in another highly fragmented and endangered dipterocarp species from the Seychelles, but more related than in three dipterocarp species studied in continuous forest in Borneo. We discuss the wider implications of our findings in the context of conservation and restoration of dipterocarp forest genetic resources in fragmented populations
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