Two-level system with a thermally fluctuating transfer matrix element: Application to the problem of DNA charge transfer

Charge transfer along the base-pair stack in DNA is modeled in terms of thermally-assisted tunneling between adjacent base pairs. Central to our approach is the notion that tunneling between fluctuating pairs is rate-limited by the requirement of their optimal alignment. We focus on this aspect of the process by modeling two adjacent base pairs in terms of a classical damped oscillator subject to thermal fluctuations as described by a Fokker-Planck equation. We find that the process is characterized by two time scales, a result that is in accord with experimental findings.Comment: original file is revtex4, 10 pages, three eps figure

Pb0.4Bi1.6Sr2Ca1Cu2O8+xPb_{0.4}Bi_{1.6}Sr_{2}Ca_{1}Cu_{2}O_{8+x} and Oxygen Stoichiometry: Structure, Resistivity, Fermi Surface Topology and Normal State Properties

$Pb_{0.4}Bi_{1.6}Sr_2CaCu_2O_{8+x}$ ($Bi(Pb)-$2212) single crystal samples were studied using transmission electron microscopy (TEM), $ab-$plane ($\rho_{ab}$) and $c-$axis ($\rho_c$) resistivity, and high resolution angle-resolved ultraviolet photoemission spectroscopy (ARUPS). TEM reveals that the modulation in the $b-$axis for $Pb(0.4)-$doped $Bi(Pb)-$2212 is dominantly of $Pb-$type that is not sensitive to the oxygen content of the system, and the system clearly shows a structure of orthorhombic symmetry. Oxygen annealed samples exhibit a much lower $c-$axis resistivity and a resistivity minimum at $80-130$K. He-annealed samples exhibit a much higher $c-$axis resistivity and $d\rho_c/dT<0$ behavior below 300K. The Fermi surface (FS) of oxygen annealed $Bi(Pb)-$2212 mapped out by ARUPS has a pocket in the FS around the $\bar{M}$ point and exhibits orthorhombic symmetry. There are flat, parallel sections of the FS, about 60\% of the maximum possible along $k_x = k_y$, and about 30\% along $k_x = - k_y$. The wavevectors connecting the flat sections are about $0.72(\pi, \pi)$ along $k_x = k_y$, and about $0.80(\pi, \pi)$ along $k_x = - k_y$, rather than $(\pi,\pi)$. The symmetry of the near-Fermi-energy dispersing states in the normal state changes between oxygen-annealed and He-annealed samples.Comment: APS_REVTEX 3.0, 49 pages, including 11 figures, available upon request. Submitted to Phys. Rev. B

Perceptions of COVID-19 vaccines among healthcare assistants: A national survey

Background: Limited COVID-19 vaccination acceptance among healthcare assistants (HCAs) may adversely impact older adults, who are at increased risk for severe COVID-19 infections. Our study objective was to evaluate the perceptions of COVID-19 vaccine safety and efficacy in a sample of frontline HCAs, overall and by race and ethnicity. Methods: An online survey was conducted from December 2020 to January 2021 through national e-mail listserv and private Facebook page for the National Association of Health Care Assistants. Responses from 155 HCAs, including certified nursing assistants, home health aides, certified medical assistants, and certified medication technicians, were included. A 27-item survey asked questions about experiences and perceptions of COVID-19 vaccines, including how confident they were that COVID-19 vaccines are safe, effective, and adequately tested in people of color. Multivariable regression was used to identify associations with confidence in COVID-19 vaccines. Results: We analyzed data from 155 completed responses. Among respondents, 23.9% were black and 8.4% Latino/a. Most respondents worked in the nursing home setting (53.5%), followed by hospitals (12.9%), assisted living (11.6%), and home care (10.3%). Respondents expressed low levels of confidence in COVID-19 vaccines, with fewer than 40% expressing at least moderate confidence in safety (38.1%), effectiveness (31.0%), or adequate testing in people of color (27.1%). Non-white respondents reported lower levels of confidence in adequate testing of vaccines compared to white respondents. In bivariate and adjusted models, respondents who gave more favorable scores of organizational leadership at their workplace expressed greater confidence in COVID-19 vaccines. Conclusion: Frontline HCAs reported low confidence in COVID-19 vaccines. Stronger organizational leadership in the workplace appears to be an important factor in influencing HCA's willingness to be vaccinated. Action is needed to enhance COVID-19 vaccine uptake in this important population with employers playing an important role to build vaccine confidence and trust among employees. © 2021 The American Geriatrics Society

Ultrasound attenuation in gap-anisotropic systems

Transverse ultrasound attenuation provides a weakly-coupled probe of momentum current correlations in electronic systems. We develop a simple theory for the interpretation of transverse ultrasound attenuation coefficients in systems with nodal gap anisotropy. Applying this theory we show how ultrasound can delineate between extended-s and d-wave scenarios for the cuprate superconductors.Comment: Uuencode file: 4 pages (Revtex), 3 figures. Some references adde

The Primordial Inflation Explorer (PIXIE): A Nulling Polarimeter for Cosmic Microwave Background Observations

The Primordial Inflation Explorer (PIXIE) is an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. The instrument consists of a polarizing Michelson interferometer configured as a nulling polarimeter to measure the difference spectrum between orthogonal linear polarizations from two co-aligned beams. Either input can view the sky or a temperature-controlled absolute reference blackbody calibrator. PIXIE will map the absolute intensity and linear polarization (Stokes I, Q, and U parameters) over the full sky in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 um wavelength). Multi-moded optics provide background-limited sensitivity using only 4 detectors, while the highly symmetric design and multiple signal modulations provide robust rejection of potential systematic errors. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r < 10^{-3} at 5 standard deviations. The rich PIXIE data set will also constrain physical processes ranging from Big Bang cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy.Comment: 37 pages including 17 figures. Submitted to the Journal of Cosmology and Astroparticle Physic

Distinguishing d-wave from highly anisotropic s-wave superconductors

Systematic impurity doping in the Cu-O plane of the hole-doped cuprate superconductors may allow one to decide between unconvention al ("d-wave") and anisotropic conventional ("s-wave") states as possible candidates for the order parameter in these materials. We show that potential scattering of any strength always increases the gap minima of such s-wave states, leading to activated behavior in temperature with characteristic impurity concentration dependence in observable quantities such as the penetration depth. A magnetic component to the scattering may destroy the energy gap and give rise to conventional gapless behavior, or lead to a nonmonotonic dependence of the gap on impurity concentration. We discuss how experiments constrain this analysis.Comment: 5 page

The Hahn Quantum Variational Calculus

We introduce the Hahn quantum variational calculus. Necessary and sufficient optimality conditions for the basic, isoperimetric, and Hahn quantum Lagrange problems, are studied. We also show the validity of Leitmann's direct method for the Hahn quantum variational calculus, and give explicit solutions to some concrete problems. To illustrate the results, we provide several examples and discuss a quantum version of the well known Ramsey model of economics.Comment: Submitted: 3/March/2010; 4th revision: 9/June/2010; accepted: 18/June/2010; for publication in Journal of Optimization Theory and Application

Standardized Outcome Measurement for Patients With Coronary Artery Disease: Consensus From the International Consortium for Health Outcomes Measurement (ICHOM)

Coronary artery disease (CAD) outcomes consistently improve when they are routinely measured and provided back to physicians and hospitals. The International Consortium for Health Outcomes Measurement (ICHOM) established a Working Group to define a standard set of outcome measures and risk factors of CAD care. Members were drawn from 4 continents and 6 countries. Using a modified Delphi method, the Group defined who should be tracked, what should be measured, and when such measurements should be performed. Thirteen specific outcomes were chosen, including acute complications occurring within 30 days of acute myocardial infarction, coronary artery bypass grafting surgery, or percutaneous coronary intervention; and longitudinal outcomes for up to 5 years for patient‐reported health status (Seattle Angina Questionnaire [SAQ‐7], elements of Rose Dyspnea Score, and Patient Health Questionnaire [PHQ‐2]), cardiovascular hospital admissions, cardiovascular procedures, renal failure, and mortality. Baseline demographic, cardiovascular disease, and comorbidity information is included to improve the interpretability of comparisons

Perceived barriers and facilitators to participating in the North Carolina Healthy Food Small Retailer Program: a mixed-methods examination considering investment effectiveness

Objective: The North Carolina Legislature appropriated funds in 2016-2019 for the Healthy Food Small Retailer Program (HFSRP), providing small retailers located in food deserts with equipment to stock nutrient-dense foods and beverages. The study aimed to: (1) examine factors facilitating and constraining implementation of, and participation in, the HFSRP from the perspective of storeowners and (2) measure and evaluate the impact and effectiveness of investment in the HFSRP. Design: The current analysis uses both qualitative and quantitative assessments of storeowner perceptions and store outcomes, as well as two innovative measures of policy investment effectiveness. Qualitative semi-structured interviews and descriptive quantitative approaches, including monthly financial reports and activity forms, and end-of-programme evaluations were collected from participating HFSRP storeowners. Setting: Eight corner stores in North Carolina that participated in the two cohorts (2016-2018; 2017-2019) of the HFSRP. Participants: Owners of corner stores participating in the HFSRP. Results: All storeowners reported that the HFSRP benefitted their stores. In addition, the HFSRP had a positive impact on sales across each category of healthy food products. Storeowners reported that benefits would be enhanced with adjustments to programme administration and support. Specific suggestions included additional information regarding which healthy foods and beverages to stock; inventory management; handling of perishable produce; product display; modified reporting requirements and a more efficient process of delivering and maintaining equipment. Conclusions: All storeowners reported several benefits of the HFSRP and would recommend that other storeowners participate. The barriers and challenges they reported inform potential approaches to ensuring success and sustainability of the HFSRP and similar initiatives underway in other jurisdictions

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics