High Temperature Superconductivity: the explanation

Soon after the discovery of the first high temperature superconductor by Georg Bednorz and Alex Mueller in 1986 the late Sir Nevill Mott answering his own question "Is there an explanation?" [Nature v 327 (1987) 185] expressed a view that the Bose-Einstein condensation (BEC) of small bipolarons, predicted by us in 1981, could be the one. Several authors then contemplated BEC of real space tightly bound pairs, but with a purely electronic mechanism of pairing rather than with the electron-phonon interaction (EPI). However, a number of other researchers criticized the bipolaron (or any real-space pairing) scenario as incompatible with some angle-resolved photoemission spectra (ARPES), with experimentally determined effective masses of carriers and unconventional symmetry of the superconducting order parameter in cuprates. Since then the controversial issue of whether the electron-phonon interaction (EPI) is crucial for high-temperature superconductivity or weak and inessential has been one of the most challenging problems of contemporary condensed matter physics. Here I outline some developments in the bipolaron theory suggesting that the true origin of high-temperature superconductivity is found in a proper combination of strong electron-electron correlations with a significant finite-range (Froehlich) EPI, and that the theory is fully compatible with the key experiments.Comment: 8 pages, 2 figures, invited comment to Physica Script

Healthcare providers’ perceptions of socioeconomically disadvantaged patients with chronic pain: A qualitative investigation

Socioeconomically disadvantaged individuals are at-risk for chronic pain and disparate care. In this qualitative study, we explored providers’ experiences with socioeconomically disadvantaged patients, with a particular focus on providers’: (1) perceptions of socioeconomically disadvantaged patients’ barriers to pain care, (2) attitudes towards this patient population, and (3) chronic pain decisions for these patients. Individual interviews were conducted with twenty-four healthcare providers. Providers discussed several patient-level access barriers, such as not having health insurance, financial constraints, and scheduling difficulties. Providers believed socioeconomically disadvantaged patients were at-risk to misuse prescription opioids and were less comfortable prescribing opioids to these patients. This investigation found that providers perceived numerous patient-level barriers to pain care, expressed suspicion towards these patients, and considered patients’ socioeconomic status when making pain management decisions. Future investigations should examine the extent to which providers’ attitudes influence their actual pain management decisions and lead to treatment disparities for this patient population

Impact of Race and Sex on Pain Management by Medical Trainees: A Mixed Methods Pilot Study of Decision Making and Awareness of Influence

Objective Previous research suggests female and black patients receive less optimal treatment for their chronic pain compared with male and white patients. Provider-related factors are hypothesized to contribute to unequal treatment, but these factors have not been examined extensively. This mixed methods investigation examined the influence of patients' demographic characteristics on providers' treatment decisions and providers' awareness of these influences on their treatment decisions. Methods Twenty medical trainees made treatment decisions (opioid, antidepressant, physical therapy) for 16 virtual patients with chronic low back pain; patient sex and race were manipulated across patients. Participants then indicated from a provided list the factors that influenced their treatment decisions, including patient demographics. Finally, individual interviews were conducted to discuss the role of patient demographics on providers' clinical decisions. Results Individual regression analyses indicated that 30% of participants were reliably influenced by patient sex and 15% by patient race when making their decisions (P < 0.05 or P < 0.10). Group analyses indicated that white patients received higher antidepressant recommendations, on average, than black patients (P < 0.05). Half of the medical trainees demonstrated awareness of the influence of demographic characteristics on their decision making. Participants, regardless of whether they were influenced by patients' demographics, discussed themes related to patient sex and race; however, participants' discussion of patient demographics in the interviews did not always align with their online study results. Conclusions These findings suggest there is a considerable variability in the extent to which medical trainees are influenced by patient demographics and their awareness of these decision making influences

C-axis Optical Sum Rule in Josephson Coupled Vortex State

Observed violations of the $c$-axis optical sum rule can give important information on deviations from in-plane Fermi liquid behavior and on the nature of interlayer coupling between adjacent copper oxide planes. Application of a magnetic field perpendicular to these planes is another way to probe in-plane dynamics. We find that the optical sum rule is considerably modified in the presence of the $c$-axis magnetic field. Interlayer correlation of pancake vortices is involved in the sum rule modification; however, details of the vortex distribution in the plane are less important.Comment: one figure. To be published in PRB (Sep. 20001

Emergence of hyperons in failed supernovae: trigger of the black hole formation

We investigate the emergence of strange baryons in the dynamical collapse of a non-rotating massive star to a black hole by the neutrino-radiation hydrodynamical simulations in general relativity. By following the dynamical formation and collapse of nascent proto-neutron star from the gravitational collapse of a 40Msun star adopting a new hyperonic EOS table, we show that the hyperons do not appear at the core bounce but populate quickly at ~0.5-0.7 s after the bounce to trigger the re-collapse to a black hole. They start to show up off center owing to high temperatures and later prevail at center when the central density becomes high enough. The neutrino emission from the accreting proto-neutron star with the hyperonic EOS stops much earlier than the corresponding case with a nucleonic EOS while the average energies and luminosities are quite similar between them. These features of neutrino signal are a potential probe of the emergence of new degrees of freedom inside the black hole forming collapse.Comment: 11 pages, 3 figures, accepted for publication in ApJ

Shovels and Swords: How realistic and fantastical themes affect children's word learning

Cataloged from PDF version of article.Research has shown that storybooks and play sessions help preschool children learn vocabulary, thereby benefiting their language and school readiness skills. But the kind of content that leads to optimal vocabulary learning – realistic or fantastical – remains largely unexplored. We investigate this issue as part of a large-scale study of vocabulary learning in low-income classrooms. Preschoolers (N = 154) learned 20 new words over the course of a two-week intervention. These words were taught using either realistic (e.g., farms) or fantastical (e.g., dragons) storybooks and toys. Children learned the new words in both conditions, and their comprehension knowledge did not differ across conditions. However, children who engaged in stories and play with a fantastical theme showed significantly greater gains in their production knowledge. Reasons for and implications of this result are discussed

Non equilibrium effects in fragmentation

We study, using molecular dynamics techniques, how boundary conditions affect the process of fragmentation of finite, highly excited, Lennard-Jones systems. We analyze the behavior of the caloric curves (CC), the associated thermal response functions (TRF) and cluster mass distributions for constrained and unconstrained hot drops. It is shown that the resulting CC's for the constrained case differ from the one in the unconstrained case, mainly in the presence of a ``vapor branch''. This branch is absent in the free expanding case even at high energies . This effect is traced to the role played by the collective expansion motion. On the other hand, we found that the recently proposed characteristic features of a first order phase transition taking place in a finite isolated system, i.e. abnormally large kinetic energy fluctuations and a negative branch in the TRF, are present for the constrained (dilute) as well the unconstrained case. The microscopic origin of this behavior is also analyzed.Comment: 21 pages, 11 figure

Large Magnetoresistance Ratio in Ferromagnetic Single-Electron Transistors in the Strong Tunneling Regime

We study transport through a ferromagnetic single-electron transistor. The resistance is represented as a path integral, so that systems where the tunnel resistances are smaller than the quantum resistance can be investigated. Beyond the low order sequential tunneling and co-tunneling regimes, a large magnetoresistance ratio at sufficiently low temperatures is found. In the opposite limit, when the thermal energy is larger than the charging energy, the magnetoresistance ratio is only slightly enhanced.Comment: updated versio

Spin-Wave Theory of the Spiral Phase of the t-J Model

A graded H.P,realization of the SU(2|1) algebra is proposed.A spin-wave theory with a condition that the sublattice magnetization is zero is discussed.The long-range spiral phase is investigated.The spin-spin correlator is calculated.Comment: 17 page

Associations between immigrant status and pharmacological treatments for diabetes in U.S. adults

Objectives: Although treatment disparities in diabetes have been documented along racial/ethnic lines, it is unclear if immigrant groups in the United States experience similar treatment disparities. Our objective was to determine whether immigrant status is associated with differences in pharmacological treatment of diabetes in a nationally representative sample of adults with diabetes. We were specifically interested in differences in treatment with oral hypoglycemic agents (OHA) and insulin. Method: Respondents were 2,260 adults from National Health and Nutritional Examination Survey (NHANES) 2003–2012 with a self-reported diabetes diagnosis. Immigrant status was indicated by birth within (U.S.-born) or outside (foreign-born) the 50 U.S. States or Washington, DC. Multinomial logistic regression analyses examined associations between immigrant status and (a) treatment with OHAs only and (b) treatment with insulin only or insulin and OHA combination therapy, using no treatment as the reference group. Results: Adjusting for demographics, diabetes severity and duration, cardiovascular disease (CVD), and CVD risk factors, being foreign-born versus U.S.-born was not associated with treatment with OHAs only (odds ratio [OR] = 1.59; 95% confidence interval [CI] [0.97, 2.60]). However, being foreign-born was associated with decreased odds (OR = 0.53; 95% CI [0.28, 0.99]) of treatment with insulin. Conclusions: Pharmacological treatment of diabetes differs along immigrant status lines. To understand these findings, studies capturing the processes underlying treatment differences in diabetes among immigrants are needed. Findings raise the possibility that integrating information about a patient’s immigrant status, in addition to racial/ethnic identity, may be an important component of culturally sensitive diabetes care