Comment on Leptophobic Bosons and νN\nu N Neutral Current Scattering Data

The relevance of existing $\nu N$ deep inelastic scattering data to models containing a leptophobic neutral vector boson is discussed. It is shown that this neutral current data is in good agreement with the Standard Model and disfavors such a leptophobic boson.Comment: LaTeX, 3 pages, 1 embedded PS figure, available at http://cordelia.fnal.gov/~ksmcf/publications/moriond_comment.ps.gz . Presented at the XXXIieme Rencontres de Moriond, Electroweak Interactions and Unified Theorie

A Precision Measurement of Electroweak Parameters in Neutrino-Nucleon Scattering

The CCFR collaboration reports a precise measurement of electroweak parameters derived from the ratio of neutral-current to charged-current cross-sections in neutrino-nucleon scattering at the Fermilab Tevatron. This ratio of cross-sections measures the neutral current couplings to quarks, which implies a determination of sin^2 theta_W (on-shell) = 0.2236 +/- 0.0028(expt.) +/- 0.0030(model) for m_top=175 GeV, m_Higgs=150 GeV. This is equivalent to M_W=80.35+/-0.21 GeV. The good agreement of this measurement with Standard Model expectations implies the exclusion of additional neutrino-neutrino-quark-quark contact interactions at 95% confidence at a mass scale of 1-8 TeV, depending on the form of the contact interaction.Comment: formatted in revtex, 5 pages, 3 eps figures included via psfig, submitted to Physical Review Letter

Neutrino Scattering in a Magnetic Field

Motivated by the evidence for a finite neutrino mass we examine anew the interaction of neutrinos in a magnetic field. We present the rate for radiative scattering for both massless and massive neutrinos in the standard model and give the corresponding numerical estimates. We also consider the effects arising from a possible neutrino magnetic moment.Comment: 10 pages, 3 figures; Acknowledgements added 05.07.200

Antiretroviral drug resistance mutations in naïve and experienced patients in Shiraz, Iran, 2014

Resistance to antiretroviral agents is a significant concern in the clinical management of HIV-infected individuals, particularly in areas of the world where treatment options are limited. In this study, we aimed to identify HIV drug-resistance-associated mutations in 40 drug-naïve patients and 62 patients under antiretroviral therapy (ART) referred to the Shiraz HIV/AIDS Research Center – the first such data available for the south of Iran. HIV reverse transcriptase and protease genes were amplified and sequenced to determine subtypes and antiretroviral- resistance-associated mutations (RAMs). Subtype CRF35-AD recombinant was the most prevalent in all patients (98 of 102, 96 % ), followed by subtype A1, and subtype B (one each, 2 % ). Among the 40 ART-naïve patients, two mutations associated with nucleoside reverse transcriptase inhibitor (NRTI) resistance (two with Y115F and T215I) and three associated with non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance (two with G190S and Y181C, four with V179T) were found. Among ART-experienced patients, four mutations associated with resistance to NRTI, four with NNRTI, and five with protease inhibitors (PI) were found. Twenty patients with high levels of resistance were already on second-line therapy. We document for the first time in this region of Iran high levels of ART resistance to multiple drugs. Our findings call for more vigilant systematic ART resistance surveillance, increased resistance testing, careful management of patients with existing regimens, and strong advocacy for expansion of available drugs in Iran. © 2016, Springer-Verlag Wien

High mobility two-dimensional electron system on hydrogen-passivated silicon(111) surfaces

We have fabricated and characterized a field-effect transistor in which an electric field is applied through an encapsulated vacuum cavity and induces a two-dimensional electron system on a hydrogen-passivated Si(111) surface. This vacuum cavity preserves the ambient sensitive surface and is created via room temperature contact bonding of two Si substrates. Hall measurements are made on the H-Si(111) surface prepared in aqueous ammonium fluoride solution. We obtain electron densities up to $6.5 \times 10^{11}$ cm$^{-2}$ and peak mobilities of $\sim 8000$ cm$^{2}$/V s at 4.2 K.Comment: to appear in Applied Physics Letter

Implication of W-boson Charge Asymmetry Measurements in p-pbar Collisions for Models of Charge Symmetry Violations in Parton Distributions

A surprisingly large charge symmetry violation of the sea quarks in the nucleon has been proposed in a recent article by Boros et al. as an explanation of the discrepancy between neutrino (CCFR) and muon (NMC) nucleon structure function data at low x. We show that these models are ruled out by the published CDF W charge asymmetry measurements, which strongly constrain the ratio of d and u quark momentum distributions in the proton over the x range of 0.006 to 0.34. This constraint also limits the systematic error from possible charge symmetry violation in the determination of sin^2(theta) from nu-N scattering experiments.Comment: 4 pages, 2 figures, Submitted to Phys. Rev. Let

Integer quantum Hall effect on a six valley hydrogen-passivated silicon (111) surface

We report magneto-transport studies of a two-dimensional electron system formed in an inversion layer at the interface between a hydrogen-passivated Si(111) surface and vacuum. Measurements in the integer quantum Hall regime demonstrate the expected sixfold valley degeneracy for these surfaces is broken, resulting in an unequal occupation of the six valleys and anisotropy in the resistance. We hypothesize the misorientation of Si surface breaks the valley states into three unequally spaced pairs, but the observation of odd filling factors, is difficult to reconcile with non-interacting electron theory.Comment: 4 pages, 4 figures, to appear in Physical Review Letter