Magnetism of Superconducting UPt3

The phase diagram of superconducting $U\!Pt_{3}$ in pressure-temperature plane, together with the neutron scattering data is studied within a two component superconducting order parameter scenario. In order to give a qualitative explanation to the experimental data a set of two linearly independent antiferromagnetic moments which emerge appropriately at the temperature \mbox{$T_{N}\sim 10\cdot T_{c}$} and \mbox{$T_{m}\sim T_{c}$} and couple to superconductivity is proposed. Several constraints on the fourth order coefficients in the Ginzburg-Landau free energy are obtained.Comment: 17 pages, figures available on request to [email protected]

Uric acid enhances longevity and endurance and protects the brain against ischemia

Among mammals, there is a positive correlation between serum uric acid (UA) levels and life span. Humans have high levels of UA because they lack a functional urate oxidase (UOX) enzyme that is present in shorter lived mammals. Here, we show that male and female mice with UOX haploinsufficiency exhibit an age-related elevation of UA levels, and that the life span of female but not male UOX+/− mice is significantly increased compared to wild-type mice. Serum UA levels are elevated in response to treadmill exercise in UOX+/− mice, but not wild-type mice, and the endurance of the UOX+/− mice is significantly greater than wild-type mice. UOX+/− mice exhibit elevated levels of brain-derived neurotrophic factor, reduced brain damage and improved functional outcome in a model of focal ischemic stroke. Levels of oxidative protein nitration and lipid peroxidation are reduced in muscle and brain tissues of UOX+/− mice under conditions of metabolic and oxidative stress (running in the case of muscle and ischemia in the case of the brain), consistent with prior evidence that UA can scavenge peroxynitrite and hydroxyl radical. Our findings reveal roles for UA in life span determination, endurance and adaptive responses to brain injury, and suggest novel approaches for protecting cells against injury and for optimizing physical performance.España, Ministerio de Educación, Cultura y Deporte EX2009–091

Ice Model Calibration using Semi-continuous Spatial Data

Rapid changes in Earth’s cryosphere caused by human activity can lead to significant environmental impacts. Computer models provide a useful tool for understanding the behavior and projecting the future of Arctic and Antarctic ice sheets. However, these models are typically subject to large parametric uncertainties due to poorly constrained model input parameters that govern the behavior of simulated ice sheets. Computer model calibration provides a formal statistical framework to infer parameters using observational data, and to quantify the uncertainty in projections due to the uncertainty in these parameters. Calibration of ice sheet models is often challenging because the relevant model output and observational data take the form of semi-continuous spatial data, with a point mass at zero and a right-skewed continuous distribution for positive values. Current calibration approaches cannot handle such data. Here we introduce a hierarchical latent variable model that handles binary spatial patterns and positive continuous spatial patterns as separate components. To overcome challenges due to high-dimensionality we use likelihood-based generalized principal component analysis to impose low-dimensional structures on the latent variables for spatial dependence. We apply our methodology to calibrate a physical model for the Antarctic ice sheet and demonstrate that we can overcome the aforementioned modeling and computational challenges. As a result of our calibration, we obtain improved future ice-volume change projections

Weak anisotropic impurity scattering in unconventional superconductors

The effect of weak anisotropic (momentum-dependent) impurity scattering in unconventional superconductors has been investigated. It is shown that the anisotropic scattering can lead either to a small reduction or a small enhancement of the isotropic pair-breaking effect. The influence of the anisotropy of the scattering potential becomes significant for the order parameters with large Fermi surface average values. In that case an unexpected enhancement (up to 10%) of the critical temperature over the critical temperature in the absence of impurities is predicted for a small impurity concentration.Comment: 12 pages, RevTeX, 3 PostScript figure

Predicting Radiated Emissions from an Electrical Drive System

A Measurement-Based SPICE Model is Proposed to Predict Radiated Emissions from an Electrical Drive System over a Frequency Range from 20-300 MHz. the Model Combines a Model for the Radiated Emissions from the Cabling and Housings with a Model for Coupling Inside the Electrical Motor. the Electromagnetic Properties of the Cabling and Housings Were Captured with Measured S-Parameters. the Coupling Mechanisms Inside the Electrical Machine Were Represented using a Circuit- Element based Model. the Intent is to Provide Insight into How Coupling Mechanisms and Placement of Structures in the Motor Affect Radiated Emissions from the Drive System, and to Give the Designer an Opportunity to Evaluate the Impact of Changes to the Motor Design. the Model Was Able to Predict Radiated Emissions within Several Decibels of the Measurement over the Frequency Range of Interest, to Provide Insight into Strategies for Fixing Emissions Issues, and to Provide Estimates for the Reduction in Emissions that Could Be Expected from Each Fix

Influence of Conformal Coatings on the Emc Performance of a Printed Circuit Board

Conformal coatings are often applied to printed circuit boards to protect the board and its components from environmental factors like moisture, chemicals, and vibration. The impact of a conformal coating on crosstalk and radiated emissions was studied in the following paper. Two coating materials were characterized in terms of their permittivity and permeability. The impact of the conformal coating was evaluated based on the crosstalk between microstrip traces, the radiated emissions from a switch-mode power supply (SMPS), and on coupling from an EMI filter to nearby components. The coatings increased crosstalk between microstrip traces by up to 5 ~ 6 dB, and increased radiated emissions from the SMPS by up to 8 dB. While the coating did not affect the performance of the EMI filter, a 5.5 dB increase in coupling was observed from the filter to nearby components. These effects should be considered if pre-compliance testing is performed before the coatings are applied

The aggregation of cytochrome C may be linked to its flexibility during refolding

Large-scale expression of biopharmaceutical proteins in cellular hosts results in production of large insoluble mass aggregates. In order to generate functional product, these aggregates require further processing through refolding with denaturant, a process in itself that can result in aggregation. Using a model folding protein, cytochrome C, we show how an increase in final denaturant concentration decreases the propensity of the protein to aggregate during refolding. Using polarised fluorescence anisotropy, we show how reduced levels of aggregation can be achieved by increasing the period of time the protein remains flexible during refolding, mediated through dilution ratios. This highlights the relationship between the flexibility of a protein and its propensity to aggregate. We attribute this behaviour to the preferential urea-residue interaction, over self-association between molecules