Is the PAMELA Positron Excess Winos?

Recently the PAMELA satellite-based experiment reported an excess of galactic positrons that could be a signal of annihilating dark matter. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties associated with their propagation. It is not unreasonable to take this well-motivated candidate seriously, at present, in part because it can be tested in several ways soon. The forthcoming PAMELA data on higher energy positrons and the FGST (formerly GLAST) data, should provide important clues as to whether this scenario is correct. If correct, the wino interpretation implies a cosmological history in which the dark matter does not originate in thermal equilibrium.Comment: 7 pages, 4 figue

Effects of Insulin Sensitivity Modulators on the Mitochondrial Fate of Oxygen in Skeletal Muscle

Increasingly, reactive oxygen species (ROS) are implicated in the development of insulin resistance. To test the hypothesis that modulators of insulin sensitivity (i.e., metformin, ovarian sex steroids and exercise training) affect the fate of oxygen in skeletal muscle, mitochondrial H₂O₂ emission (mE[subscript]H2O2) and respiratory O₂ flux (JO₂) were measured in saponin-permeabilized myofibers from rodents and women. Concommitant with improved glucose tolerance, complex I-linked mE[subscript]H2O2, but not JO₂, was reduced in metformin-treated obese rats to rates near or below those in the lean animals. Ex vivo dose-response experiments revealed that metformin inhibits complex I-linked mE[subscript]H2O2 at a concentration ~2 orders of magnitude lower than that required to inhibit JO₂. To determine if estradiol or progesterone directly affect mitochondrial function, saponin-permeabilized vastus lateralis myofibers biopsied from women in the menstrual cycle follicular phase were incubated breifly in luteal phase serum concentrations of estradiol, progesterone, or both. While progesterone alone inhibited respiration, the effect was absent in the presence of estradiol. Progesterone, alone or in combination with estradiol increased complex I-linked mE[subscript]H2O2. Complex I-linked mE[subscript]H2O2 measured in permeabilized myofibers from insulin sensitive and resistant women correlated significantly with serum progesterone in these subjects. Moreover, mE[subscript]H2O2 was more than 80% greater in the insulin resistant women. Regular exercise is known to improve insulin sensitivity. To determine the effects of exercise training on mitochondrial function, mE[subscript]H2O2 and JO₂ were measured in saponin-permeabilized vastus lateralis myofibers from lean (BMI 30) women before (Pre) and after (Post) 8 weeks of exercise training (8WT = stationary cycling, 1 h/d, 5 d/w at heart rate corresponding to 70-75% VO₂). Interestingly, while Pre-Post there were no changes in JO₂ supported by multiple substrates or calculated ratios of respiratory control, there was a reduction in the potential for complex I-linked mE[subscript]H2O2 following training in the lean women. Altogether, the results of this project support the notion that modulators of insulin sensitivity may do so through their ability to affect complex I-linked mE[subscript]H2O2, but not necessarily JO₂ in skeletal muscle.  Ph.D

Flow-process controls on grain type distribution in an experimental turbidity current deposit: Implications for detrital signal preservation and microplastic distribution in submarine fans

Deep-water depositional systems are the ultimate sink for vast quantities of terrigenous sediment, organic carbon and anthropogenic pollutants, forming valuable archives of environmental change. Our understanding of the distribution of these particles and the preservation of environmental signals, in deep-water systems is limited due to the inaccessibility of modern systems, and the incomplete nature of ancient systems. Here, the deposit of a physically modelled turbidity current was sampled (n = 49) to determine how grain size and grain type vary spatially. The turbidity current had a sediment concentration of 17%. The sediment consisted of, by weight, 65% quartz sand (2.65 g/cm3), 17.5% silt (2.65 g/cm3), 7.5% clay (2.60 g/cm3) and 5% each of sand-grade garnet (3.90 g/cm3) and microplastic fragments (1.50 g/cm3). The grain size and composition of each sample was determined using laser diffraction and density separation, respectively. The results show that: (a) bulk grain size coarsened axially downstream on the basin floor challenging the notion that basin floor deposits fine radially from an apex upon becoming unconfined; (b) no sample composition matched the input composition of the flow, indicating that allogenic signals can be autogenically shredded and spatially variable in sediment gravity flow deposits; and (c) microplastic fragments were concentrated in levee and lateral basin floor fringe positions; however, microplastic concentrations in these positions were lower than input, suggesting microplastics bypassed the sampled positions. These findings have implications for: (a) the development of ‘finger-like’ geometries and facies distributions observed in modern and ancient systems; (b) interpreting environmental signals in the stratigraphic record; and (c) predicting the distribution of microplastics on the sea floor. © 2021 The Authors. The Depositional Record published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologist

Forecasts for the Attainment of Major Research Milestones in Parkinson's Disease.

BACKGROUND: Projections about when research milestones will be attained are often of interest to patients and can help inform decisions about research funding and health system planning. OBJECTIVE: To collect aggregated expert forecasts on the attainment of 11 major research milestones in Parkinson's disease (PD). METHODS: Experts were asked to provide predictions about the attainment of 11 milestones in PD research in an online survey. PD experts were identified from: 1) The Michael J. Fox Foundation for Parkinson's Research data base, 2) doctors specializing in PD at top ranked neurology centers in the US and Canada, and 3) corresponding authors of articles on PD in top medical journals. Judgments were aggregated using coherence weighting. We tested the relationship between demographic variables and individual judgments using a linear regression. RESULTS: 249 PD experts completed the survey. In the aggregate, experts believed that new treatments like gene therapy for monogenic PD, immunotherapy and cell therapy had 56.1%, 59.7%, and 66.6% probability, respectively of progressing in the clinical approval process within the next 10 years. Milestones involving existing management approaches, like the approval of a deep brain stimulation device or a body worn sensor had 78.4% and 82.2% probability of occurring within the next 10 years. Demographic factors were unable to explain deviations from the aggregate forecast (R2 = 0.029). CONCLUSIONS: Aggregated expert opinion suggests that milestones for the advancement of new treatment options for PD are still many years away. However, other improvements in PD diagnosis and management are believed to be near at hand

Comparison of Patient and Expert Perceptions of the Attainment of Research Milestones in Parkinson's Disease.

BACKGROUND: Commentators suggest that patients have unrealistic expectations about the pace of research advances and that such expectations interfere with patient decision-making. OBJECTIVE: The objective of this study was to compare expert expectations about the timing of research milestone attainment with those of patients who follow Parkinson's disease (PD) research. METHODS: Patients with PD and experts were asked to provide forecasts about 11 milestones in PD research in an online survey. PD experts were identified from a Michael J. Fox Foundation database, highly ranked neurology centers in the United States and Canada, and corresponding authors of articles on PD in top medical journals. Patients with PD were recruited through the Michael J. Fox Foundation. We tested whether patient forecasts differed on average from expert forecasts. We also tested whether differences between patient forecasts and the average expert forecasts were associated with any demographic factors. RESULTS: A total of 256 patients and 249 PD experts completed the survey. For 9 of the 11 milestones, patients' forecasts were on average higher than those of experts. Only exercise therapy met our 10% difference threshold for practical significance. Education was the only demographic that predicted patient deviations from expert forecasts on milestone forecasts. Patients offered significantly higher forecasts than experts that the clinical trials used in milestone queries would report positive primary outcomes. CONCLUSIONS: Differences between patient and expert expectations about research milestones were generally minor, suggesting that there is little cause for concern that patients who follow PD research are unduly swayed by inaccurate representations of research advancement in the media or elsewhere. © 2020 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society

Universal Quantum Computation using Exchange Interactions and Teleportation of Single-Qubit Operations

We show how to construct a universal set of quantum logic gates using control over exchange interactions and single- and two-spin measurements only. Single-spin unitary operations are teleported instead of being executed directly, thus eliminating a major difficulty in the construction of several of the most promising proposals for solid-state quantum computation, such as spin-coupled quantum dots, donor-atom nuclear spins in silicon, and electrons on helium. Contrary to previous proposals dealing with this difficulty, our scheme requires no encoding redundancy. We also discuss an application to superconducting phase qubits.Comment: 4.5 pages, including 2 figure

A quantum phase gate implementation for trapped ions in thermal motion

We propose a novel scheme to implement a quantum controlled phase gate for trapped ions in thermal motion with one standing wave laser pulse. Instead of applying the rotating wave approximation this scheme makes use of the counter-rotating terms of operators. We also demonstrate that the same scheme can be used to generate maximally entangled states of $N$ trapped ions by a single laser pulse