Cooper pairs without 'glue' in high-TcT_c superconductors

We address the origin of the Cooper pairs in high-$T_c$ cuprates and the unique nature of the superconducting (SC) condensate. Itinerant holes in an antiferromagnetic background form pairs spontaneously, without any `glue', defining a new quantum object the `pairon'. In the incoherent pseudogap phase, above $T_c$ or within the vortex core, the pairon binding energies are distributed statistically, forming a `Cooper-pair glass'. Contrary to conventional SC, it is the mutual pair-pair interaction that is responsable for the condensation. We give a natural explanation for the {\it ergodic rigidity} of the excitation gap, being uniquely determined by the carrier concentration $p$ and $J$. The phase diagram can be understood, without spin fluctuations, in terms of a single energy scale $\sim J$, the exchange energy at the metal-insulator transition

Healthcare providers\u27 experience of chronic grief in a pediatric subacute facility

The purpose of this study was: (1) to evaluate the level of grief experienced by healthcare providers in a pediatric subacute facility, (2) to compare the levels of grief between different groups of healthcare providers (Certified Nurses\u27 Aides, Licensed Nurses, and Respiratory Care Practitioners), and (3) to describe the personality/demographic factors that influence a healthcare provider\u27s ability to cope effectively with compound grief

Statistics of the cuprate pairon states on a square lattice

In this paper the fundamental parameters of high-$T_c$ superconductivity are shown to be connected to the statistics of pairons (hole pairs in their antiferromagnetic environment) on a square lattice. In particular, we study the density fluctuations and the distribution of the area surrounding each pairon on the scale of the antiferromagnetic correlation length $\xi_{AF}$, for the complete range of hole concentration. We show that the key parameters of the phase diagram, the $T_c$ dome, and the pseudogap temperature $T^*$, emerge from the statistical properties of the pairon disordered state. In this approach, the superconducting and the pseudogap states appear as inseparable phenomena. The condensation energy, which fixes the critical temperature, is directly proportional to the {\it correlation energy} between pairons and {\it not} to the energy gap, contrary to conventional superconductors. When the correlation energy between pairons is suppressed by fluctuations, either thermally, by disorder, or in the vortex core, the pseudogap state of disordered pairons is obtained. We attribute the unique features of cuprate superconductivity to this order-disorder transition in real space, which clearly differs from the BCS mechanism. Our predictions are in quantitative agreement with low-temperature tunneling and photoemission spectroscopy experiments.Comment: 12 pages, 11 figure

Counseling Athletes Who Use Performance-Enhancing Drugs: A New Conceptual Framework Linked to Clinical Practice

Doping, the use of performance-enhancing drugs by athletes, is a major concern that the media have publicized prominently. Sport governing bodies currently use two primary methods to dissuade athletes from doping: punishment and didactic education. Neither of these approaches has eradicated doping from competitive athletics because the practice appears to be increasing. Including clinical interventions in systemic campaigns that address this problem would be efficacious. The current article provides a conceptual framework that addresses doping from a psychologist’s perspective and then operationalizes this framework, all the while identifying the unique environment in which athletes function. Practical interventions for working with clients who dope are identified, as are possible future research paths that could benefit work with this population

New insights into the effects on blood pressure of diets low in salt and high in fruits and vegetables and low-fat dairy products

Results from the recent Dietary Approaches to Stop Hypertension (DASH)-Sodium trial provide the latest evidence concerning the effects of dietary patterns and sodium intake on blood pressure. Participants ate either the DASH diet (high in fruits, vegetables and low-fat dairy products, and reduced in saturated and total fat) or a typical US diet. Within each diet arm, participants ate higher, intermediate, and lower sodium levels, each for 30 days. The results indicated lower blood pressure with lower sodium intake for both diet groups. Although some critics would argue otherwise, these findings provide important new evidence for the value of the DASH diet and sodium reduction in controlling blood pressure

How 'pairons' are revealed in the electronic specific heat of cuprates

Understanding the thermodynamic properties of high-$T_c$ cuprate superconductors is a key step to establish a satisfactory theory of these materials. The electronic specific heat is highly unconventional, distinctly non-BCS, with remarkable doping-dependent features extending well beyond $T_c$. The pairon concept, bound holes in their local antiferromagnetic environment, has successfully described the tunneling and photoemission spectra. In this article, we show that the model explains the distinctive features of the entropy and specific heat throughout the temperature-doping phase diagram. Their interpretation connects unambiguously the pseudogap, existing up to $T^*$, to the superconducting state below $T_c$. In the underdoped case, the specific heat is dominated by pairon excitations, following Bose statistics, while with increasing doping, both bosonic excitations and fermionic quasiparticles coexist

Selective effects of fatty acids upon cell growth and metabolic regulation

Positional isomers ofcis‐methyleneoctadecanoic acid differed greatly in their efficiency for growth of an unsaturated fatty acid auxotroph ofEscherichia coli upon glucose as a carbon source. The 8, 9, and 11 isomers were more efficient in producing cells (60–70 cells/fmole) than the others (0–7 cells/fmole), although all isomers were found esterified to a similar extent into cellular lipid. WithSaccharomyces cerevisiae mutants, all isomers between 6 and 12 supported some growth of the eukaryotic cells, and the 7 and 9 isomers were slightly more efficient than the 8‐isomer. WhenE. coli were grown with glycerol, all isomers from 5 to 14 supported growth, and those with the substituent near the center of the acyl chain had the greatest efficiency (70 cells/fmole). With the glycerol medium, the pattern of efficiencies for the variouscis‐methylene acyl chains resembled the broad selectivity reported earlier for thecis‐ethylenic isomers in glucose medium, which agreed closely with predictions based upon the physical property of their phospholipid derivatives. Thus, metabolism of glycerol appeared to allow the cyclopropane acyl chains to support cell functions to the limits expected for bulk phase chain‐chain fluidity considerations. This broad specificity was also obtained when cells were grown on glucose with cyclic AMP added to the culture. Therefore, the selective inadequacies of the 5, 6, 7, 10, 12 and 13 isomers in supporting cell growth on glucose may occur through an interaction modified by cAMP and dependent upon reduced cellular levels of cyclic AMP. The highly selective pattern of efficiency of thecis‐methylene acids forE. coli growth on glucose resembles that with the acetylenic acids, but was shifted one carbon atom toward the methyl terminus. This observed selectivity pattern seems due to interactions of the individual acyl chains with cellular protein(s) rather than to chain‐chain interactions in a bulk phase. The ability of certain positional isomers to support cell function equally well in both nutrient conditions suggests that the role of those acyl chain isomers may be independent of metabolite flux or cyclic nucleotide contents of the cell, whereas the actions of other isomeric fatty acids seem closely related to the metabolic status of the cell. A highly selective role for different fatty acids in modulating cellular function seems possible on the basis of the current evidence.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141577/1/lipd0878.pd