230 research outputs found
Inequalities for Light Nuclei in the Wigner Symmetry Limit
Using effective field theory we derive inequalities for light nuclei in the
Wigner symmetry limit. This is the limit where isospin and spin degrees of
freedom can be interchanged. We prove that the energy of any three-nucleon
state is bounded below by the average energy of the lowest two-nucleon and
four-nucleon states. We show how this is modified by lowest-order terms
breaking Wigner symmetry and prove general energy convexity results for SU(N).
We also discuss the inclusion of Wigner-symmetric three and four-nucleon force
terms.Comment: 10 page
On the Quark Mass Dependence of Two Nucleon Observables
We study the implications of lattice QCD determinations of the S-wave
nucleon-nucleon scattering lengths at unphysical light quark masses. It is
found that with the help of nuclear effective field theory (NEFT), not only the
quark mass dependence of the effective range parameters, but also the leading
quark mass dependence of all the low energy deuteron matrix elements can be
obtained. The quark mass dependence of deuteron charge radius, magnetic moment,
polarizability and the deuteron photodisintegration cross section are shown
based on the NPLQCD lattice calculation of the scattering lengths at 354 MeV
pion mass and the NEFT power counting scheme of Beane, Kaplan and Vuorinen.
Further improvement can be obtained by performing the lattice calculation at
smaller quark masses. Our result can be used to constrain the time variation of
isoscalar combination of u and d quark mass m_q, to help the anthropic
principle study to find the m_q range which allows the existence of life, and
to provide a weak test of the multiverse conjecture.Comment: 18 pages, 5 figure
Photoluminescence Study of Hydrothermally Grown ZnO Nanostructures
In this work, the hydrothermally grown ZnO nanostructures were successfully prepared using the aqueous solution of zinc nitride dehydrate (Zn(NO3)2). The effect of solution molarity on the optical and structural properties of ZnO nanostructures were studied by temperature dependent photoluminescence (PL) measurements. The intensity ratio of the ultraviolet emission to the visible emission is calculated. It is found that the calculated results are also dependent on the solution molarity and consistent with the crystal quality of ZnO nanostructures
Mutations in the Salmonella enterica serovar Choleraesuis cAMP-receptor protein gene lead to functional defects in the SPI-1 Type III secretion system
Salmonella enterica serovar Choleraesuis (Salmonella Choleraesuis) causes a lethal systemic infection (salmonellosis) in swine. Live attenuated Salmonella Choleraesuis vaccines are effective in preventing the disease, and isolates of Salmonella Choleraesuis with mutations in the cAMP-receptor protein (CRP) gene (Salmonella Choleraesuis ∆crp) are the most widely used, although the basis of the attenuation remains unclear. The objective of this study was to determine if the attenuated phenotype of Salmonella Choleraesuis ∆crp was due to alterations in susceptibility to gastrointestinal factors such as pH and bile salts, ability to colonize or invade the intestine, or cytotoxicity for macrophages. Compared with the parental strain, the survival rate of Salmonella Choleraesuis ∆crp at low pH or in the presence of bile salts was higher, while the ability of the mutant to invade intestinal epithelia was significantly decreased. In examining the role of CRP on the secretory function of the Salmonella pathogenicity island 1 (SPI-1) encoded type III secretion system (T3SS), it was shown that Salmonella Choleraesuis ∆crp was unable to secrete the SPI-1 T3SS effector proteins, SopB and SipB, which play a role in Salmonella intestinal invasiveness and macrophage cytotoxicity, respectively. In addition, caspase-1 dependent cytotoxicity for macrophages was significantly reduced in Salmonella Choleraesuis ∆crp. Collectively, this study demonstrates that the CRP affects the secretory function of SPI-1 T3SS and the resulting ability to invade the host intestinal epithelium, which is a critical element in the pathogenesis of Salmonella Choleraesuis
A Holographic Model For Hall Viscosity
We have modified the holographic model of Saremi and Son by using a charged
black brane, instead of a neutral one, such that when the bulk pseudo scalar
potential is made of quadratic and quartic terms, parity can still be broken
spontaneously in the boundary theory. In our model, the 3+1 dimensional bulk
has a pseudo scalar coupled to the gravitational Chern-Simons term in the anti
de Sitter charged black brane back ground. Parity could be broken spontaneously
in the bulk by the pseudo scalar hairy solution and give rise to non-zero Hall
viscosity at the boundary theory.Comment: 15 pages, 4 figure
Elastic and Inelastic Neutrino-Deuteron Scattering in Effective Field Theory
The differential cross-sections for elastic and inelastic neutrino-deuteron
scattering are calculated analytically using nucleon-nucleon effective field
theory. For elastic scattering, the deuteron axial form factor and the deuteron
strange magnetic moment form factor are computed to next-to-leading order,
including two-body currents. For inelastic scattering, two neutral current
processes nu+d->nu+n+p, nubar+d->nubar+n+p and one charged current process
nubar+d->(e^+)+n+n are computed to next-to-leading order. These depend on an
isovector axial two-body matrix element whose value is yet to be fixed by
experiment. Potential model calculations by Kubodera et al. and Ying et al. are
reproduced for different values of the two-body matrix element. This implies
that the differences between the two potential model calculations lie in their
treatment of short distance physics. The charged current to neutral current
nubar-d cross-section ratio is confirmed to be insensitive to short distance
physics, and the same ratio is obtained by potential models and the calculation
presented here, within 5%, for incident incident neutrino energies up to 20
MeV. The two-body matrix element could be fixed using the parity violating
process epol+d->e+n+p.Comment: 29 pages, 11 figures; An error in the charged current cross section
has been corrected. Figures and discussion have been modified accordingl
KCNN2 polymorphisms and cardiac tachyarrhythmias
Potassium calcium-activated channel subfamily N member 2 (KCNN2) encodes an integral membrane protein that forms small-conductance calcium-activated potassium (SK) channels. Recent studies in animal models show that SK channels are important in atrial and ventricular repolarization and arrhythmogenesis. However, the importance of SK channels in human arrhythmia remains unclear. The purpose of the present study was to test the association between genetic polymorphism of the SK2 channel and the occurrence of cardiac tachyarrhythmias in humans. We enrolled 327 Han Chinese, including 72 with clinically significant ventricular tachyarrhythmias (VTa) who had a history of aborted sudden cardiac death (SCD) or unexplained syncope, 98 with a history of atrial fibrillation (AF), and 144 normal controls. We genotyped 12 representative tag single nucleotide polymorphisms (SNPs) across a 141-kb genetic region containing the KCNN2 gene; these captured the full haplotype information. The rs13184658 and rs10076582 variants of KCNN2 were associated with VTa in both the additive and dominant models (odds ratio [OR] 2.89, 95% confidence interval [CI] = 1.505-5.545, P = 0.001; and OR 2.55, 95% CI = 1.428-4.566, P = 0.002, respectively). After adjustment for potential risk factors, the association remained significant. The population attributable risks of these 2 variants of VTa were 17.3% and 10.6%, respectively. One variant (rs13184658) showed weak but significant association with AF in a dominant model (OR 1.91, CI = 1.025-3.570], P = 0.042). There was a significant association between the KCNN2 variants and clinically significant VTa. These findings suggest an association between KCNN2 and VTa; it also appears that KCNN2 variants may be adjunctive markers for risk stratification in patients susceptible to SCD
Neutrino-Deuteron Scattering in Effective Field Theory at Next-to-Next-to Leading Order
We study the four channels associated with neutrino-deuteron breakup
reactions at next-to-next to leading order in effective field theory. We find
that the total cross-section is indeed converging for neutrino energies up to
20 MeV, and thus our calculations can provide constraints on theoretical
uncertainties for the Sudbury Neutrino Observatory. We stress the importance of
a direct experimental measurement to high precision in at least one channel, in
order to fix an axial two-body counterterm.Comment: 32 pages, 14 figures (eps
Leukocyte Cell-Derived Chemotaxin 2 Retards Non-Small Cell Lung Cancer Progression Through Antagonizing MET and EGFR Activities
Background/Aims: Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) therapy is a clinical option for non-small cell lung cancer (NSCLC) harboring activating EGFR mutations or for cancer with wild-type (WT) EGFR when chemotherapy has failed. MET receptor activation or MET gene amplification was reported to be a major mechanism of acquired resistance to EGFR-TKI therapy in NSCLC cells. Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine that was shown to suppress metastasis of hepatocellular carcinoma via inhibiting MET activity. Until now, the biological function responsible for LECT2’s action in human NSCLC remains unclear. Methods: LECT2-knockout (KO) mice and NOD/SCID/IL2rgnull (NSG) mice were respectively used to investigate the effects of LECT2 on the tumorigenicity and metastasis of murine (Lewis lung carcinoma, LLC) and human (HCC827) lung cancer cells. The effect of LECT2 on in vitro cell proliferation was evaluated, using MTS and colony formation assays. The effect of LECT2 on cell motility was evaluated using transwell migration and invasion assays. An enzyme-linked immunosorbent assay was performed to detect secreted LECT2 in plasma and media. Co-immunoprecipitation and Western blot assays were used to investigate the underlying mechanisms of LECT2 in NSCLC cells. Results: Compared to WT mice, mice with LECT2 deletion exhibited enhanced growth and metastasis of LLC cells, and survival times decreased in LLC-implanted mice. Overexpression of LECT2 in orthotopic human HCC827 xenografts in NSG mice resulted in significant inhibition of tumor growth and metastasis. In vitro, overexpression of LECT2 or treatment with a recombinant LECT2 protein impaired the colony-forming ability and motility of NSCLC cells (HCC827 and PC9) harboring high levels of activated EGFR and MET. Mechanistic investigations found that LECT2 bound to MET and EGFR to antagonize their activation and further suppress their common downstream pathways: phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase. Conclusion: EGFR-MET signaling is critical for aggressive behaviors of NSCLC and is recognized as a therapeutic target for NSCLC especially for patients with acquired resistance to EGFR-TKI therapy. Our findings demonstrate, for the first time, that LECT2 functions as a suppressor of the progression of NSCLC by targeting EGFR-MET signaling
Holographic Superconductors
A holographic model of superconductors based on the action proposed by
Benini, Herzog, and Yarom [arXiv:1006.0731] is studied. This model has a
charged spin two field in an AdS black hole spacetime. Working in the probe
limit, the normalizable solution of the spin two field in the bulk gives rise
to a superconducting order parameter at the boundary of the AdS. We
calculate the fermion spectral function in this\ superconducting background and
confirm the existence of fermi arcs for non-vanishing Majorana couplings. By
changing the relative strength of the and condensations, the
position and the size of the fermi arcs are changed. When , the
spectrum becomes isotropic and the spectral function is s-wave like. By
changing the fermion mass, the fermi momentum is changed. We also calculate the
conductivity for these holographic superconductors where time reversal
symmetry has been broken spontaneously. A non-vanishing Hall conductivity is
obtained even without an external magnetic field.Comment: 24 pages,17 figures, Add more discussions on hall conductivity, two
new figures, Matched with published versio
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