86 research outputs found
Radiative corrections to deep-inelastic scattering. Case of tensor polarized deuteron
The model-independent radiative corrections to deep-inelastic scattering of
unpolarized electron beam off the tensor polarized deuteron target have been
considered. The contribution to the radiative corrections due to the
hard-photon emission from the elastic electron-deuteron scattering (the
so-called elastic radiative tail) is also investigated. The calculation is
based on the covariant parametrization of the deuteron quadrupole polarization
tensor. The numerical estimates of the radiative corrections to the
polarization observables have been done for the kinematical conditions of the
current experiment at HERAComment: 21 pages, 5 figure
Radiative corrections to polarization observables in elastic electron-deuteron scattering in leptonic variables
The model--independent QED radiative corrections to polarization observables
in elastic scattering of unpolarized and longitudinally--polarized electron
beam by the deuteron target have been calculated in leptonic variables. The
experimental setup when the deuteron target is arbitrarily polarized is
considered and the procedure for applying derived results to the vector or
tensor polarization of the recoil deuteron is discussed. The basis of the
calculations consists of the account for all essential Feynman diagrams which
results in the form of the Drell-Yan representation for the cross-section and
use of the covariant parametrization of the deuteron polarization state. The
numerical estimates of the radiative corrections are given for the case when
event selection allows the undetected particles (photons and electron-positron
pairs) and the restriction on the lost invariant mass is used.Comment: 43 pages,3 figures. To be published in ZhTEF. revised 14.02.2012.
arXiv admin note: text overlap with arXiv:nucl-ex/0002003 by other author
Radiative Corrections to Polarized Inelastic Scattering in Coincidence
The coplete analysis of the model-independent leading radiative corrections
to cross-section and polarization observables in semi-inclusive deep-inelastic
electron-nucleus scattering with detection of a proton and scattered electron
in coincidence has been performed. The basis of the calculations consists of
the Drell-Yan like representation in electrodynamics for both spin-independent
and spin-dependent parts of the cross-section in terms of the electron
structure functions. The applications to the polarization transfer effect from
longitudinally polarized electron beam to detected proton as well as to
scattering by the polarized target are considered.Comment: 18p, to be published in JET
Step-Wise Computational Synthesis of Fullerene C60 derivatives. 1.Fluorinated Fullerenes C60F2k
The reactions of fullerene C60 with atomic fluorine have been studied by
unrestricted broken spin-symmetry Hartree-Fock (UBS HF) approach implemented in
semiempirical codes based on AM1 technique. The calculations were focused on a
sequential addition of fluorine atom to the fullerene cage following indication
of the cage atom highest chemical susceptibility that is calculated at each
step. The effectively-non-paired-electron concept of the fullerene atoms
chemical susceptibility lays the foundation of the suggested computational
synthesis. The obtained results are analyzed from energetic, symmetry, and the
composition abundance viewpoints. A good fitting of the data to experimental
findings proves a creative role of the suggested synthesis methodology.Comment: 33 pages, 11 figures, 2 tables, 2 chart
Tagged-photon events in polarized DIS process
Deep-inelastic events for the scattering of the longitudinally polarized
electron by polarized proton with tagged collinear photon radiated from
initial-state electron are considered. The corresponding cross-section is
derived in the Born approximation. The model-independent radiative corrections
to the Born cross-section are also calculated. Obtained result is applied to
the case of elastic scattering.Comment: 14 pages, 2 figures, submitted to JET
Precise method for the determination of the neutron electric form factor based on a relativistic analysis of the process $d(e,e'n)p
We generalize the recoil polarization method for the determination of the
proton form factor to the case of the disintegration of vector polarized
deuterons by longitudinally polarized electrons, . We
suggest to measure for this reaction, in the kinematics of quasi-elastic
-scattering, the ratio of the asymmetries induced by the
- and -components of the deuteron vector polarization. In the framework
of the relativistic impulse approximation the ratio is sensitive to
in a wide interval of momentum transfer squared, whereas it depends
weakly on the details of the -interaction and on the choice of the deuteron
wave function. Moreover, in the range 1.5 GeV, the ratio
shows a smooth dependence on , making the analysis simpler.Comment: 7 pages, 4 figs, 1 tabl
The relativistic impulse approximation for the exclusive electrodisintegration of the deuteron
The electrodisintegration of the deuteron in the frame of the Bethe-Salpeter
approach with a separable kernel of the nucleon-nucleon interaction is
considered. This conception keeps the covariance of a description of the
process. A comparison of relativistic and nonrelativistic calculations is
presented. The factorization of the cross section of the reaction in the
impulse approximation is obtained by analytical calculations. It is shown that
the photon-neutron interaction plays an important role.Comment: 31 pages, 14 figures, 1 tabl
Open Babel: An open chemical toolbox
Background: A frequent problem in computational modeling is the interconversion of chemical structures between different formats. While standard interchange formats exist (for example, Chemical Markup Language) and de facto standards have arisen (for example, SMILES format), the need to interconvert formats is a continuing problem due to the multitude of different application areas for chemistry data, differences in the data stored by different formats (0D versus 3D, for example), and competition between software along with a lack of vendorneutral formats. Results: We discuss, for the first time, Open Babel, an open-source chemical toolbox that speaks the many languages of chemical data. Open Babel version 2.3 interconverts over 110 formats. The need to represent such a wide variety of chemical and molecular data requires a library that implements a wide range of cheminformatics algorithms, from partial charge assignment and aromaticity detection, to bond order perception and canonicalization. We detail the implementation of Open Babel, describe key advances in the 2.3 release, and outline a variety of uses both in terms of software products and scientific research, including applications far beyond simple format interconversion. Conclusions: Open Babel presents a solution to the proliferation of multiple chemical file formats. In addition, it provides a variety of useful utilities from conformer searching and 2D depiction, to filtering, batch conversion, and substructure and similarity searching. For developers, it can be used as a programming library to handle chemical data in areas such as organic chemistry, drug design, materials science, and computational chemistry. It is freely available under an open-source license fro
Human Iron−Sulfur Cluster Assembly, Cellular Iron Homeostasis, and Diseaseâ€
ABSTRACT: Iron-sulfur (Fe-S) proteins contain prosthetic groups consisting of two or more iron atoms bridged by sulfur ligands, which facilitate multiple functions, including redox activity, enzymatic function, and maintenance of structural integrity. More than 20 proteins are involved in the biosynthesis of iron-sulfur clusters in eukaryotes. Defective Fe-S cluster synthesis not only affects activities of many iron-sulfur enzymes, such as aconitase and succinate dehydrogenase, but also alters the regulation of cellular iron homeostasis, causing both mitochondrial iron overload and cytosolic iron deficiency. In this work, we review human Fe-S cluster biogenesis and human diseases that are caused by defective Fe-S cluster biogenesis. Fe-S cluster biogenesis takes place essentially in every tissue of humans, and products of human disease genes, including frataxin, GLRX5, ISCU, and ABCB7, have important roles in the process. However, the human diseases, Friedreich ataxia, glutaredoxin 5-deficient sideroblastic anemia, ISCU myopathy, and ABCB7 sideroblastic anemia/ataxia syndrome, affect specific tissues, while sparing others. Here we discuss the phenotypes caused by mutations in these different disease genes, and we compare the underlying pathophysiology and discuss the possible explanations for tissue-specific pathology in these diseases caused by defective Fe-S cluster biogenesis. HUMAN CELLULAR IRON HOMEOSTASI
Lentivirus-meditated frataxin gene delivery reverses genome instability in Friedreich ataxia patient and mouse model fibroblasts
Friedreich ataxia (FRDA) is a progressive neurodegenerative disease caused by deficiency of frataxin protein, with the primary sites of pathology being the large sensory neurons of the dorsal root ganglia and the cerebellum. FRDA is also often accompanied by severe cardiomyopathy and diabetes mellitus. Frataxin is important in mitochondrial iron–sulfur cluster (ISC) biogenesis and low-frataxin expression is due to a GAA repeat expansion in intron 1 of the FXN gene. FRDA cells are genomically unstable, with increased levels of reactive oxygen species and sensitivity to oxidative stress. Here we report the identification of elevated levels of DNA double strand breaks (DSBs) in FRDA patient and YG8sR FRDA mouse model fibroblasts compared to normal fibroblasts. Using lentivirus FXN gene delivery to FRDA patient and YG8sR cells, we obtained long-term overexpression of FXN mRNA and frataxin protein levels with reduced DSB levels towards normal. Furthermore, γ-irradiation of FRDA patient and YG8sR cells revealed impaired DSB repair that was recovered on FXN gene transfer. This suggests that frataxin may be involved in DSB repair, either directly by an unknown mechanism, or indirectly via ISC biogenesis for DNA repair enzymes, which may be essential for the prevention of neurodegeneration.Ataxia UK, FARA Australasia and FARA US
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