Quantum transport of disordered Weyl semimetals at the nodal point

Weyl semimetals are paradigmatic topological gapless phases in three dimensions. We here address the effect of disorder on charge transport in Weyl semimetals. For a single Weyl node with energy at the degeneracy point and without interactions, theory predicts the existence of a critical disorder strength beyond which the density of states takes on a nonzero value. Predictions for the conductivity are divergent, however. In this work, we present a numerical study of transport properties for a disordered Weyl cone at zero energy. For weak disorder our results are consistent with a renormalization group flow towards an attractive pseudoballistic fixed point with zero conductivity and a scale-independent conductance; for stronger disorder diffusive behavior is reached. We identify the Fano factor as a signature that discriminates between these two regimes

Time-frequency analysis of ship wave patterns in shallow water: modelling and experiments

A spectrogram of a ship wake is a heat map that visualises the time-dependent frequency spectrum of surface height measurements taken at a single point as the ship travels by. Spectrograms are easy to compute and, if properly interpreted, have the potential to provide crucial information about various properties of the ship in question. Here we use geometrical arguments and analysis of an idealised mathematical model to identify features of spectrograms, concentrating on the effects of a finite-depth channel. Our results depend heavily on whether the flow regime is subcritical or supercritical. To support our theoretical predictions, we compare with data taken from experiments we conducted in a model test basin using a variety of realistic ship hulls. Finally, we note that vessels with a high aspect ratio appear to produce spectrogram data that contains periodic patterns. We can reproduce this behaviour in our mathematical model by using a so-called two-point wavemaker. These results highlight the role of wave interference effects in spectrograms of ship wakes.Comment: 14 pages, 7 figure

Visualization of steps and surface reconstructions in Helium Ion Microscopy with atomic precision

Helium Ion Microscopy is known for its surface sensitivity and high lateral resolution. Here, we present results of a Helium Ion Microscopy based investigation of a surface confined alloy of Ag on Pt(111). Based on a change of the work function of 25\,meV across the atomically flat terraces we can distinguish Pt rich from Pt poor areas and visualize the single atomic layer high steps between the terraces. Furthermore, dechanneling contrast has been utilized to measure the periodicity of the hcp/fcc pattern formed in the 2--3 layers thick Ag/Pt alloy film. A periodicity of 6.65\,nm along the $\langle\overline{11}2\rangle$ surface direction has been measured. In terms of crystallography a hcp domain is obtained through a lateral displacement of a part of the outermost layer by $1/\sqrt{3}$ of a nearest neighbour spacing along $\langle\overline{11}2\rangle$. This periodicity is measured with atomic precision: coincidence between the Ag and the Pt lattices is observed for 23 Ag atoms on 24 Pt atoms. The findings are perfectly in line with results obtained with Low Energy Electron Microscopy and Phase Contrast Atomic Force Microscopy.Comment: 15 pages, 7 figure

On the iterated Crank-Nicolson for hyperbolic and parabolic equations in numerical relativity

The iterated Crank-Nicolson is a predictor-corrector algorithm commonly used in numerical relativity for the solution of both hyperbolic and parabolic partial differential equations. We here extend the recent work on the stability of this scheme for hyperbolic equations by investigating the properties when the average between the predicted and corrected values is made with unequal weights and when the scheme is applied to a parabolic equation. We also propose a variant of the scheme in which the coefficients in the averages are swapped between two corrections leading to systematically larger amplification factors and to a smaller numerical dispersion.Comment: 7 pages, 3 figure

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity.

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes

Heat shock factor 1 regulates lifespan as distinct from disease onset in prion disease

Prion diseases are fatal, transmissible, neurodegenerative diseases caused by the misfolding of the prion protein (PrP). At present, the molecular pathways underlying prion-mediated neurotoxicity are largely unknown. We hypothesized that the transcriptional regulator of the stress response, heat shock factor 1 (HSF1), would play an important role in prion disease. Uninoculated HSF1 knockout (KO) mice used in our study do not show signs of neurodegeneration as assessed by survival, motor performance, or histopathology. When inoculated with Rocky Mountain Laboratory (RML) prions HSF1 KO mice had a dramatically shortened lifespan, succumbing to disease ≈20% faster than controls. Surprisingly, both the onset of home-cage behavioral symptoms and pathological alterations occurred at a similar time in HSF1 KO and control mice. The accumulation of proteinase K (PK)-resistant PrP also occurred with similar kinetics and prion infectivity accrued at an equal or slower rate. Thus, HSF1 provides an important protective function that is specifically manifest after the onset of behavioral symptoms of prion disease

A Comparison of Data Sources for Motor Vehicle Crash Characteristic Accuracy

Objective: To determine the accuracy of police reports (PRs), ambulance reports (ARs), and emergency department records (EDRs) in describing motor vehicle crash (MVC) characteristics when compared with an investigation performed by an experienced crash investigator trained in impact biomechanics. Methods: This was a cross-sectional, observational study. Ninety-one patients transported by ambulance to a university emergency department (ED) directly from the scene of an MVC from August 1997 to April 1998 were enrolled. Potential patients were identified from the ED log and consent was obtained to investigate the crash vehicle. Data describing MVC characteristics were abstracted from the PR, AR, and medical record. Variables of interest included restraint use (RU), air bag deployment (AD), and type of impact (TI). Agreements between the variables and the independent crash investigation were compared using kappa. Interrater reliability was determined using kappa by comparing a random sample of 20 abstracted reports for each data source with the originally abstracted data. Results: Agreement using kappa between the crash investigation and each data source was 0.588 (95% CI = 0.508 to 0.667) for the PR, 0.330 (95% CI = 0.252 to 0.407) for the AR, and 0.492 (95% CI = 0.413 to 0.572) for the EDR. Variable agreement was 0.239 (95% CI = 0.164 to 0.314) for RU, 0.350 (95% CI = 0.268 to 0.432) for AD, and 0.631 (95%= 0.563 to 0.698) for TI. Interrater reliability was excellent (kappa > 0.8) for all data sources. Conclusions: The strength of the agreement between the independent crash investigation and the data sources that were measured by kappa was fair to moderate, indicating inaccuracies. This presents ramifications for researchers and necessitates consideration of the validity and accuracy of crash characteristics contained in these data sources.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75653/1/j.1553-2712.2000.tb02067.x.pd

KINEMATIC ANALYSIS OF ELITE JAVELIN THROWERS

Research on various aspects of the throwing motion has indicated it to be a very complex movement (Atwater, 1979). Certain kinematic parameters appear t o be common determinants of successful performance regardless of the nature of the throwing task. Under ideal conditions (i.e., ignoring air resistance and the type of implement being thrown) the path, and hence distance thrown, is determined by the angle, height and velocity of release. Such an ideal analysis needs some modification for situations in which aerodynamics are considered. Since the release phase of the javelin throw encompasses these common throwing components as well as obvious aerodynamic influences, quantification of release characteristics which establish the initial conditions of f light is important