Electron transport across a quantum wire in the presence of electron leakage to a substrate

We investigate electron transport through a mono-atomic wire which is tunnel coupled to two electrodes and also to the underlying substrate. The setup is modeled by a tight-binding Hamiltonian and can be realized with a scanning tunnel microscope (STM). The transmission of the wire is obtained from the corresponding Green's function. If the wire is scanned by the contacting STM tip, the conductance as a function of the tip position exhibits oscillations which may change significantly upon increasing the number of wire atoms. Our numerical studies reveal that the conductance depends strongly on whether or not the substrate electrons are localized. As a further ubiquitous feature, we observe the formation of charge oscillations.Comment: 7 pages, 7 figure

The Autoimmune Manifestations in Patients with Genetic Defects in the B Cell Development and Differentiation Stages

Purpose: Primary B cell defects manifesting as predominantly antibody deficiencies result from variable inborn errors of the B cell lineage and their development, including impairments in early bone marrow development, class switch recombination (CSR), or terminal B cell differentiation. In this study, we aimed to investigate autoimmunity in monogenic patients with B cell development and differentiation defects. Methods: Patients with known genetic defects in the B cell development and differentiation were recruited from the Iranian inborn errors of immunity registry. Results: A total of 393 patients with a known genetic defect in the B cell development and differentiation (257 males; 65.4%) with a median age of 12 (6-20) years were enrolled in this study. After categorizing patients, 109 patients had intrinsic B cell defects. More than half of the patients had defects in one of the ATM (85 patients), BTK (76 patients), LRBA (34 patients), and DOCK8 (33 patients) genes. Fifteen patients (3.8%) showed autoimmune complications as their first manifestation. During the course of the disease, autoimmunity was reported in 81 (20.6%) patients at a median age of 4 (2-7) years, among which 65 patients had mixed intrinsic and extrinsic and 16 had intrinsic B cell defects. The comparison between patients with the mentioned four main gene defects showed that the patient group with LRBA defect had a significantly higher frequency of autoimmunity compared to those with other gene defects. Based on the B cell defect stage, 13% of patients with early B cell defect, 17% of patients with CSR defect, and 40% of patients who had terminal B cell defect presented at least one type of autoimmunity. Conclusion: Our results demonstrated that gene mutations involved in human B cell terminal stage development mainly LRBA gene defect have the highest association with autoimmunity

Search for annual and diurnal rate modulations in the LUX experiment

Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth’s motion in the halo. Observation of such features can provide generic evidence for detection of dark matter interactions. This paper reports a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of 2.3±0.2  cpd/keVee/tonne, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to 26  keVee. Between 2 and 6  keVee, this analysis demonstrates the most sensitive annual modulation search up to date, with 9.2σ tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above 0.2  cpd/keVee/tonne amplitude between 2 and 6  keVee.Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth's motion in the halo. Observation of such features can provide generic evidence for detection of dark matter interactions. This paper reports a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of 2.3$\pm$0.2~cpd/keV$_{\text{ee}}$/tonne, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to 26~keV$_{\text{ee}}$. Between 2 and 6~keV$_{\text{ee}}$, this analysis demonstrates the most sensitive annual modulation search up to date, with 9.2$\sigma$ tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above 0.2~cpd/keV$_{\text{ee}}$/tonne amplitude between 2 and 6~keV$_{\text{ee}}$

HIV prevention cascades for injection and sexual risk behaviors among HIV-negative people who inject drug in Iran

Background: The HIV prevention cascade complements the HIV treatment cascade and helps evaluate the access to and use of harm reduction programs among HIV-negative individuals at risk for HIV, including people who inject drugs (PWID). This study aimed to estimate the HIV prevention cascades among PWID in Iran. Methods: Using data from the 2014 national bio-behavioral surveillance survey, 2,391 PWID were recruited from 31 harm reduction facilities and through outreach efforts across 10 major cities. PWID aged �18 years who reported drug injection in the past year were interviewed, and information regarding their demographic characteristics, sexual and drug injection practices, and access to services were gathered. PWID were also tested for HIV infection. We examined the prevention cascade framework among HIV-negative PWID. Results: The majority of PWID were male (97.6) and more than half aged � 35 years old (55.5). Overall, 2,092 (92.5 95% CI: 90.8, 93.9) were HIV-negative; 93% of whom knew illicit drug injection could increase the risk of HIV transmission, 54% had access to free-of-charge sterile needles and syringes, 51% used sterile needles and syringes in their last injection practice, and 33% used sterile needles and syringes in all injection practices in the past month. Also, 87.8% (95% CI: 85.1, 90.0) of HIV-negative PWID had sex with any partner in the past year; 88% of whom knew using condoms could reduce the risk of HIV transmission, 35% had access to free-of-charge condoms, 32% used condoms in their last sexual practice, and 18% used condoms in all of their sexual practices in the past month. Conclusion: The majority of HIV-negative PWID in Iran were at risk for HIV acquisition through unsafe drug injection or sexual practices. Harm reduction programs should improve access to free sterile needles, syringes, and condoms for PWID. © 2020 Elsevier B.V

Chromatographic separation of radioactive noble gases from xenon

The Large Underground Xenon (LUX) experiment operates at the Sanford Underground Research Facility to detect nuclear recoils from the hypothetical Weakly Interacting Massive Particles (WIMPs) on a liquid xenon target. Liquid xenon typically contains trace amounts of the noble radioactive isotopes 85Kr and 39Ar that are not removed by the in situ gas purification system. The decays of these isotopes at concentrations typical of research-grade xenon would be a dominant background for a WIMP search experiment. To remove these impurities from the liquid xenon, a chromatographic separation system based on adsorption on activated charcoal was built. 400 kg of xenon was processed, reducing the average concentration of krypton from 130 ppb to 3.5 ppt as measured by a cold-trap assisted mass spectroscopy system. A 50 kg batch spiked to 0.001 g/g of krypton was processed twice and reduced to an upper limit of 0.2 ppt