315 research outputs found
Noncommutative gravity coupled to fermions: second order expansion via Seiberg-Witten map
We use the Seiberg-Witten map (SW map) to expand noncommutative gravity
coupled to fermions in terms of ordinary commuting fields. The action is
invariant under general coordinate transformations and local Lorentz rotations,
and has the same degrees of freedom as the commutative gravity action. The
expansion is given up to second order in the noncommutativity parameter
{\theta}. A geometric reformulation and generalization of the SW map is
presented that applies to any abelian twist. Compatibility of the map with
hermiticity and charge conjugation conditions is proven. The action is shown to
be real and invariant under charge conjugation at all orders in {\theta}. This
implies the bosonic part of the action to be even in {\theta}, while the
fermionic part is even in {\theta} for Majorana fermions.Comment: 27 pages, LaTeX. Revised version with proof of charge conjugation
symmetry of the NC action and its parity under theta --> - theta (see new
sect. 2.6, sect. 6 and app. B). References added. arXiv admin note:
substantial text overlap with arXiv:0902.381
Experimental evaluation of impact ionization coefficients in Al xGa1-xN based avalanche photodiodes
The authors report on the metal-organic chemical vapor deposition growth, fabrication, and characterization of high performance solar-blind avalanche photodetectors and the experimental evaluation of the impact ionization coefficients that are obtained from the photomultiplication data. A Schottky barrier, suitable for back and front illuminations, is used to determine the impact ionization coefficients of electrons and holes in an AlGaN based avalanche photodiode. © 2006 American Institute of Physics
A Pilot Study to Determine Whether Disability and Disease Activity Are Different in African-American and Caucasian Patients with Rheumatoid Arthritis in
ABSTRACT. Objective. To compare the levels of disability and disease activity in African-Americans and Caucasians with rheumatoid arthritis (RA) in an academic medical center practice, and to determine whether the differences are independently associated with ethnicity. Methods. Data on socioeconomic, disease related, psychological, and behavioral variables were obtained from 100 outpatients (67 Caucasians, 33 African-Americans) with RA. Functional status was assessed with the Health Assessment Questionnaire (HAQ) and Disease Activity Score (DAS-28). Chi-square and Student t tests were used to test for differences between groups. Multiple regression analysis was used to determine whether ethnicity was associated with these differences independent of other factors known to influence disease outcome. Results. African-Americans and Caucasians did not differ with respect to age, sex, disease duration, rheumatoid factor positivity, and medication compliance. African-Americans had higher scores than Caucasians for HAQ (1.5 ± 0.8 vs 0.9 ± 0.7; p < 0.001) and DAS-28 (5.5 ± 1.3 vs 4.3 ± 1.4; p < 0.001). Regression models showed that ethnicity was not independently associated with the higher HAQ and DAS-28 scores when controlled for demographic, socioeconomic, psychological, and behavioral factors. Arthritis self-efficacy approaches significance in the regression model. Conclusion. HAQ disability and RA disease activity were higher in African-Americans than Caucasians in this sample from an academic medical center practice. However, ethnicity was not independently associated with these outcomes when socioeconomic and psychological factors were taken into account. Improvement in self-efficacy has the potential to improve outcome in AfricanAmericans with RA. (J Rheumatol 2005;32:602-8
A hybrid light source with integrated inorganic light-emitting diode and organic polymer distributed feedback grating
We report a compact light source that incorporates a semiconductor light-emitting diode, nanostructured distributed feedback (DFB) Bragg grating and spin-coated thin conjugated polymer film. With this hybrid structure, we transferred electrically generated 390 nm ultraviolet light to an organic polymer via optical pumping and out-couple green luminescence to air through a second-order DFB grating. We demonstrate the feasibility of electrically driven, hybrid, compact light-emitting devices and lasers in the visible range. © IOP Publishing Ltd
The maximally entangled symmetric state in terms of the geometric measure
The geometric measure of entanglement is investigated for permutation
symmetric pure states of multipartite qubit systems, in particular the question
of maximum entanglement. This is done with the help of the Majorana
representation, which maps an n qubit symmetric state to n points on the unit
sphere. It is shown how symmetries of the point distribution can be exploited
to simplify the calculation of entanglement and also help find the maximally
entangled symmetric state. Using a combination of analytical and numerical
results, the most entangled symmetric states for up to 12 qubits are explored
and discussed. The optimization problem on the sphere presented here is then
compared with two classical optimization problems on the S^2 sphere, namely
Toth's problem and Thomson's problem, and it is observed that, in general, they
are different problems.Comment: 18 pages, 15 figures, small corrections and additions to contents and
reference
InGaN/GaN based LEDs with electroluminescence in violet, blue, and green tuned by epitaxial growth temperature
[No abstract available
Energy utilization and growth performance of chickens fed novel wheat inbred lines selected for different pentosan levels with and without xylanase supplementation
Different F5 recombinant inbred lines
from the cross Yumai 34 × Ukrainka were grown in
replicated trials on a single site in one harvest year at
Rothamsted Research. A total of 10 samples from those
lines were harvested and used in a broiler experiment.
Twenty nutritionally complete meal-form diets that had
630 g/kg of wheat with different amounts of pentosan,
with and without exogenous xylanase supplementation,
were used to compare broiler growth performance and
determine apparent metabolizable energy corrected for
N retention (AMEn). We examined the relationship between the nutritive value of the wheat samples and their
chemical compositions and results of quality tests. The
amounts of total and water soluble pentosans in wheat
samples ranged from 36.7 to 48.0 g/kg DM, and 6.7 to
11.6 g/kg DM, respectively. The mean crude oil and
protein contents of the wheat samples were 10.5 and
143.9 g/kg DM, respectively. The average determined
value for the kinematic viscosity was 0.0018 mPa.s, and
2.1 mPa.s for the dynamic viscosity. The AMEn of the
wheat-based diets had a maximum range of 0.47 MJ/kg
DM within the ten wheat samples that were tested. Xylanase supplementation improved (P < 0.05) dietary
AMEn, dry matter, and fat digestibility coefficients.
There was a positive (P < 0.05) relationship between in
vitro kinematic viscosity of the wheat samples and the
total pentosan content. There was a negative relationship between the total pentosan content in the wheat
and broiler growth performance. An increase by 10 g of
pentosan per kg of wheat reduced (P < 0.001) daily feed
intake and weight gain by 2.9 g and 3.5 g, respectively.
The study shows that the feeding quality of wheat samples can be predicted by their total pentosan content.
Supplementary xylanase improved energy and nutrient
availability of all wheat samples that was independent
of differences in pentosan content
PtrWRKY19, a novel WRKY transcription factor, contributes to the regulation of pith secondary wall formation in Populus trichocarpa
WRKY proteins are one of the largest transcription factor families in higher plants and play diverse roles in various biological processes. Previous studies have shown that some WRKY members act as negative regulators of secondary cell wall formation in pith parenchyma cells. However, the regulatory mechanism of pith secondary wall formation in tree species remains largely unknown. In this study, PtrWRKY19 encoding a homolog of Arabidopsis WRKY12 was isolated from Populus trichocarpa. PtrWRKY19 was expressed in all tissues tested, with highest expression in stems, especially in pith. PtrWRKY19 was located in the nucleus and functioned as a transcriptional repressor. Ectopic expression of PtrWRKY19 in an atwrky12 mutant successfully rescued the phenotype in pith cell walls caused by the defect of AtWRKY12, suggesting that PtrWRKY19 had conserved functions for homologous AtWRKY12. Overexpression of PtrWRKY19 in poplar plants led to a significant increase in the number of pith parenchyma cells. qRT-PCR analysis showed that lignin biosynthesis-related genes were repressed in transgenic plants. In transcient reporter assays, PtrWRKY19 was identified to repress transcription from the PtoC4H2 promoter containing the conserved W-box elements. These results indicated that PtrWRKY19 may function as a negative regulator of pith secondary wall formation in poplar
Investigating Agrobacterium-Mediated Transformation of Verticillium albo-atrum on Plant Surfaces
Background: Agrobacterium tumefaciens has long been known to transform plant tissue in nature as part of its infection process. This natural mechanism has been utilised over the last few decades in laboratories world wide to genetically manipulate many species of plants. More recently this technology has been successfully applied to non-plant organisms in the laboratory, including fungi, where the plant wound hormone acetosyringone, an inducer of transformation, is supplied exogenously. In the natural environment it is possible that Agrobacterium and fungi may encounter each other at plant wound sites, where acetosyringone would be present, raising the possibility of natural gene transfer from bacterium to fungus. Methodology/Principal Findings: We investigate this hypothesis through the development of experiments designed to replicate such a situation at a plant wound site. A. tumefaciens harbouring the plasmid pCAMDsRed was co-cultivated with the common plant pathogenic fungus Verticillium albo-atrum on a range of wounded plant tissues. Fungal transformants were obtained from co-cultivation on a range of plant tissue types, demonstrating that plant tissue provides sufficient vir gene inducers to allow A. tumefaciens to transform fungi in planta. Conclusions/Significance: This work raises interesting questions about whether A. tumefaciens may be able to transform organisms other than plants in nature, or indeed should be considered during GM risk assessments, with furthe
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