99 research outputs found
Nucleon isovector structure functions in (2+1)-flavor QCD with domain wall fermions
We report on numerical lattice QCD calculations of some of the low moments of
the nucleon structure functions. The calculations are carried out with gauge
configurations generated by the RBC and UKQCD collaborations with (2+1)-flavors
of dynamical domain wall fermions and the Iwasaki gauge action (). The inverse lattice spacing is GeV, and two spatial
volumes of ((2.7{\rm fm})^3) and ((1.8 {\rm fm})^3) are used. The up and down
quark masses are varied so the pion mass lies between 0.33 and 0.67 GeV while
the strange mass is about 12 % heavier than the physical one. The structure
function moments we present include fully non-perturbatively renormalized
iso-vector quark momentum fraction, (_{u-d}), helicity fraction, (< x
>_{\Delta u - \Delta d}), and transversity, (_{\delta u - \delta d}), as
well as an unrenormalized twist-3 coefficient, (d_1). The ratio of the momentum
to helicity fractions, (_{u-d}/_{\Delta u - \Delta d}), does not show
dependence on the light quark mass and agrees well with the value obtained from
experiment. Their respective absolute values, fully renormalized, show
interesting trends toward their respective experimental values at the lightest
quark mass. A prediction for the transversity, (0.7 _{\delta u -\delta
d} < 1.1), in the (\bar{\rm MS}) scheme at 2 GeV is obtained. The twist-3
coefficient, (d_1), though yet to be renormalized, supports the perturbative
Wandzura-Wilczek relation.Comment: 14 pages, 22 figures
Charm as a domain wall fermion in quenched lattice QCD
We report a study describing the charm quark by a domain-wall fermion (DWF)
in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge
ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of
GeV. We calculate masses of heavy-light (charmed) and
heavy-heavy (charmonium) mesons with spin-parity and ,
leptonic decay constants of the charmed pseudoscalar mesons ( and ),
and the - mixing parameter. The charm quark mass is found to be
GeV. The mass splittings in
charmed-meson parity partners and are
degenerate within statistical errors, in accord with experiment, and they
satisfy a relation , also consistent with
experiment. A C-odd axial vector charmonium state, \chi_{c1}m_{h_{c}} = 3533(11)_{\rm stat.}\chi_{c1}) mass. However, in this regard, we emphasize
significant discrepancies in the calculation of hyperfine splittings on the
lattice. The leptonic decay constants of and mesons are found to be
MeV and
,
where the first error is statistical, the second a systematic due to chiral
extrapolation and the third error combination of other known systematics. The
- mixing bag parameter, which enters the
transition amplitude, is found to be .Comment: 49 pages, 15 figure
Continuum Limit of from 2+1 Flavor Domain Wall QCD
We determine the neutral kaon mixing matrix element in the continuum
limit with 2+1 flavors of domain wall fermions, using the Iwasaki gauge action
at two different lattice spacings. These lattice fermions have near exact
chiral symmetry and therefore avoid artificial lattice operator mixing.
We introduce a significant improvement to the conventional NPR method in
which the bare matrix elements are renormalized non-perturbatively in the
RI-MOM scheme and are then converted into the MSbar scheme using continuum
perturbation theory. In addition to RI-MOM, we introduce and implement four
non-exceptional intermediate momentum schemes that suppress infrared
non-perturbative uncertainties in the renormalization procedure. We compute the
conversion factors relating the matrix elements in this family of RI-SMOM
schemes and MSbar at one-loop order. Comparison of the results obtained using
these different intermediate schemes allows for a more reliable estimate of the
unknown higher-order contributions and hence for a correspondingly more robust
estimate of the systematic error. We also apply a recently proposed approach in
which twisted boundary conditions are used to control the Symanzik expansion
for off-shell vertex functions leading to a better control of the
renormalization in the continuum limit.
We control chiral extrapolation errors by considering both the NLO SU(2)
chiral effective theory, and an analytic mass expansion. We obtain
B_K^{\msbar}(3 GeV) = 0.529(5)_{stat}(15)_\chi(2)_{FV}(11)_{NPR}. This
corresponds to . Adding
all sources of error in quadrature we obtain , with an overall combined error of 3.6%.Comment: 65 page
A Lattice Study of the Nucleon Excited States with Domain Wall Fermions
We present results of our numerical calculation of the mass spectrum for
isospin one-half and spin one-half non-strange baryons, i.e. the ground and
excited states of the nucleon, in quenched lattice QCD. We use a new lattice
discretization scheme for fermions, domain wall fermions, which possess almost
exact chiral symmetry at non-zero lattice spacing. We make a systematic
investigation of the negative-parity spectrum by using two distinct
interpolating operators at on a
lattice. The mass estimates extracted from the two operators are consistent
with each other. The observed large mass splitting between this state,
, and the positive-parity ground state, the nucleon N(939), is well
reproduced by our calculations. We have also calculated the mass of the first
positive-parity excited state and found that it is heavier than the
negative-parity excited state for the quark masses studied.Comment: 46 pages, REVTeX, 11 figures included, revised version accepted for
publication in Phys. Rev.
Deconfinement transition and string tensions in SU(4) Yang-Mills Theory
We present results from numerical lattice calculations of SU(4) Yang-Mills
theory. This work has two goals: to determine the order of the finite
temperature deconfinement transition on an lattice and to study the
string tensions between static charges in the irreducible representations of
SU(4). Motivated by Pisarski and Tytgat's argument that a second-order
SU() deconfinement transition would explain some features of the SU(3)
and QCD transitions, we confirm older results on a coarser, , lattice.
We see a clear two-phase coexistence signal, characteristic of a first-order
transition, at on a lattice, on which we also
compute a latent heat of . Computing
Polyakov loop correlation functions we calculate the string tension at finite
temperature in the confined phase between fundamental charges, ,
between diquark charges, , and between adjoint charges . We
find that , and our result for the adjoint string
tension is consistent with string breaking.Comment: 10 pages with included figures. For version 2: New calculation and
discussion of latent heat added; 2 new figures and 1 new table. Typo in
abstract corrected for v3. To appear in Physical Review
The G-Protein β3 subunit 825 TT genotype is associated with epigastric pain syndrome-like dyspepsia
<p>Abstract</p> <p>Background</p> <p>Although familial clustering of functional dyspepsia (FD) has been reported, the role of genetics in the susceptibility to FD is still not well understood. Several reports indicate an association between FD and G-protein β3 (GNB3) subunit gene polymorphism (C825T); however, these studies had small sample sizes and the findings are inconclusive. In the present study we clarified the association between GNB3 gene polymorphism and dyspepsia in a large population of Japanese subjects who visited a hospital for annual health check-up.</p> <p>Methods</p> <p>Subjects with significant upper gastrointestinal findings were excluded. Subjects with dyspeptic symptoms were divided into either a postprandial distress syndrome (PDS) group or an epigastric pain syndrome (EPS) group according to the Rome III criteria. The presence of the GNB3 C825T polymorphism was then evaluated and logistic regression analysis was used to test all variables.</p> <p>Results</p> <p>The GNB3 genotype distribution in subjects without dyspepsia was 191 CC (25.1%), 368 TC (48.4%), and 202 TT (26.5%) and 17 CC (25.0%), 29 TC (42.6%), and 22 TT (32.4%) in subjects with dyspepsia. No significant correlation was found between the GNB3 825TT genotype and dyspepsia. However, the TT genotype was significantly associated with subjects with EPS-like symptoms (odds ratio (OR) = 2.00, 95% confidence interval (CI); 1.07-3.76) compared to the CT/CC genotype adjusted for gender and age. No significant correlation was found between GNB3 polymorphism and PDS-like symptoms (OR = 0.68, 95% CI; 0.31-1.51). With the exclusion of subjects with both EPS- and PDS-like symptoms, only the TT genotype was significantly associated with EPS-like symptoms (OR = 2.73, 95% CI; 1.23-5.91).</p> <p>Conclusion</p> <p>The homozygous GNB3 825T allele influences the susceptibility to EPS-like dyspepsia.</p
An interspecific linkage map of SSR and intronic polymorphism markers in tomato
Despite the collection and availability of abundant tomato genome sequences, PCR-based markers adapted to large scale analysis have not been developed in tomato species. Therefore, using public genome sequence data in tomato, we developed three types of DNA markers: expressed sequence tag (EST)-derived simple sequence repeat (SSR) markers (TES markers), genome-derived SSR markers (TGS markers) and EST-derived intronic polymorphism markers (TEI markers). A total of 2,047 TES, 3,510 TGS and 674 TEI markers were established and used in the polymorphic analysis of a cultivated tomato (Solanum lycopersicum) ‘LA925’ and its wild relative Solanum pennellii ‘LA716’, parents of the Tomato-EXPEN 2000 mapping population. The polymorphic ratios between parents revealed by the TES, TGS and TEI markers were 37.3, 22.6 and 80.0%, respectively. Those showing polymorphisms were used to genotype the Tomato-EXPEN 2000 mapping population, and a high-density genetic linkage map composed of 1,433 new and 683 existing marker loci was constructed on 12 chromosomes, covering 1,503.1 cM. In the present map, 48% of the mapped TGS loci were located within heterochromatic regions, while 18 and 21% of TES and TEI loci, respectively, were located in heterochromatin. The large number of SSR and SNP markers developed in this study provide easily handling genomic tools for molecular breeding in tomato. Information on the DNA markers developed in this study is available at http://www.kazusa.or.jp/tomato/
Magnetic tunnel junctions with metastable bcc Co3Mn electrodes
We studied magnetic tunnel junctions (MTJs) with a MgO(001) barrier and metastable bcc Co3Mn(001) disordered alloy electrodes. A tunnel magnetoresistance (TMR) ratio was approximately 200{250% observed at room temperature.We successfully observed the TMR ratio greater than 600% at 10 K which was higher than the past reported value of MgO-based MTJs with ultrathin bcc Co(001) electrodes. However our experimental value was still much lower than the past theoretical prediction in bcc Co/MgO/Co(001) MTJs. We discuss some differences in the bulk band structure affecting the TMR effect for bcc Co and bcc Co3Mn
Comparative molecular biological analysis of membrane transport genes in organisms
Comparative analyses of membrane transport genes revealed many differences in the features of transport homeostasis in eight diverse organisms, ranging from bacteria to animals and plants. In bacteria, membrane-transport systems depend mainly on single genes encoding proteins involved in an ATP-dependent pump and secondary transport proteins that use H+ as a co-transport molecule. Animals are especially divergent in their channel genes, and plants have larger numbers of P-type ATPase and secondary active transporters than do other organisms. The secondary transporter genes have diverged evolutionarily in both animals and plants for different co-transporter molecules. Animals use Na+ ions for the formation of concentration gradients across plasma membranes, dependent on secondary active transporters and on membrane voltages that in turn are dependent on ion transport regulation systems. Plants use H+ ions pooled in vacuoles and the apoplast to transport various substances; these proton gradients are also dependent on secondary active transporters. We also compared the numbers of membrane transporter genes in Arabidopsis and rice. Although many transporter genes are similar in these plants, Arabidopsis has a more diverse array of genes for multi-efflux transport and for response to stress signals, and rice has more secondary transporter genes for carbohydrate and nutrient transport
Redox Modulation at Work: Natural Phytoprotective Polysulfanes From Alliums Based on Redox-Active Sulfur
Purpose of review: This article provides a brief overview of natural phytoprotective products of allium with a special focus on the therapeutic potential of diallyl polysulfanes from garlic, their molecular targets and their fate in the living organisms. A comprehensive overview of antimicrobial and anticancer properties of published literature is presented for the reader to understand the effective concentrations of polysulfanes and their sensitivity towards different human pathogenic microbes, fungi, and cancer cell lines. Recent findings: The article finds polysulfanes potentials as new generation novel antibiotics and chemo preventive agent. The effective dose rates of polysulfanes for antimicrobial properties are in the range of 0.5–40 mg/L and for anticancer 20–100 μM. The molecular targets for these redox modulators are mainly cellular thiols as well as inhibition and/or activation of certain cellular proteins in cancer cell lines. Summary: Antimicrobial and anticancer activities of polysulfanes published in the literature indicate that with further development, they could be promising candidates for cancer prevention due to their selectivity towards abnormal cells
- …