Transient Zitterbewegung of charge carriers in graphene and carbon nanotubes

Observable effects due to trembling motion (Zitterbewegung, ZB) of charge carriers in bilayer graphene, monolayer graphene and carbon nanotubes are calculated. It is shown that, when the charge carriers are prepared in the form of gaussian wave packets, the ZB has a transient character with the decay time of femtoseconds in graphene and picoseconds in nanotubes. Analytical results for bilayer graphene allow us to investigate phenomena which accompany the trembling motion. In particular, it is shown that the transient character of ZB in graphene is due to the fact that wave subpackets related to positive and negative electron energies move in opposite directions, so their overlap diminishes with time. This behavior is analogous to that of the wave packets representing relativistic electrons in a vacuum.Comment: 7 pages, 3 figures, augmented versio

High Turnover Rates for Hydrogen Sulfide Allow for Rapid Regulation of Its Tissue Concentrations

Abstract Aims: Hydrogen sulfide (H2S) is a signaling molecule, which influences many physiological processes. While H2S is produced and degraded in many cell types, the kinetics of its turnover in different tissues has not been reported. In this study, we have assessed the rates of H2S production in murine liver, kidney, and brain homogenates at pH 7.4, 37°C, and at physiologically relevant cysteine concentrations. We have also studied the kinetics of H2S clearance by liver, kidney, and brain homogenates under aerobic and anaerobic conditions. Results: We find that the rate of H2S production by these tissue homogenates is considerably higher than background rates observed in the absence of exogenous substrates. An exponential decay of H2S with time is observed and, as expected, is significantly faster under aerobic conditions. The half-life for H2S under aerobic conditions is 2.0, 2.8, and 10.0?min with liver, kidney, and brain homogenate, respectively. Western-blot analysis of the sulfur dioxygenase, ETHE1, involved in H2S catabolism, demonstrates higher steady-state protein levels in liver and kidney versus brain. Innovation: By combining experimental and simulation approaches, we demonstrate high rates of tissue H2S turnover and provide estimates of steady-state H2S levels. Conclusion: Our study reveals that tissues maintain a high metabolic flux of sulfur through H2S, providing a rationale for how H2S levels can be rapidly regulated. Antioxid. Redox Signal. 17, 22?31.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98481/1/ars%2E2011%2E4310.pd

The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples

Non-locality of energy separating transformations for Dirac electrons in a magnetic field

We investigate a non-locality of Moss-Okninski transformation (MOT) used to separate positive and negative energy states in the 3+1 Dirac equation for relativistic electrons in the presence of a magnetic field. Properties of functional kernels generated by the MOT are analyzed and kernel non-localities are characterized by calculating their second moments parallel and perpendicular to the magnetic field. Transformed functions are described and investigated by computing their variances. It is shown that the non-locality of the energy-separating transformation in the direction parallel to the magnetic field is characterized by the Compton wavelength $\lambda_c=\hbar/mc$. In the plane transverse to magnetic field the non-locality depends both on magnetic radius $L=(\hbar/eB)^{1/2}$ and $\lambda_c$. The non-locality of MO transformation for the 2+1 Dirac equation is also considered.Comment: 11 pages 3 figure

Atomic Scale Structure and Chemical Composition across Order-Disorder Interfaces

Through a combination of aberration-corrected high-resolution scanning transmission electron microscopy and three-dimensional atom probe tomography, the true atomic-scale structure and change in chemical composition across the complex order-disorder interface in a metallic alloy has been determined. The study reveals the presence of two interfacial widths, one corresponding to an order-disorder transition, and the other to the compositional transition across the interface, raising fundamental questions regarding the definition of the interfacial width in such systems

Self-driving Multimodal Studies at User Facilities

Multimodal characterization is commonly required for understanding materials. User facilities possess the infrastructure to perform these measurements, albeit in serial over days to months. In this paper, we describe a unified multimodal measurement of a single sample library at distant instruments, driven by a concert of distributed agents that use analysis from each modality to inform the direction of the other in real time. Powered by the Bluesky project at the National Synchrotron Light Source II, this experiment is a world's first for beamline science, and provides a blueprint for future approaches to multimodal and multifidelity experiments at user facilities.Comment: 36th Conference on Neural Information Processing Systems (NeurIPS 2022). AI4Mat Worksho

Block bond-order potential as a convergent moments-based method

The theory of a novel bond-order potential, which is based on the block Lanczos algorithm, is presented within an orthogonal tight-binding representation. The block scheme handles automatically the very different character of sigma and pi bonds by introducing block elements, which produces rapid convergence of the energies and forces within insulators, semiconductors, metals, and molecules. The method gives the first convergent results for vacancies in semiconductors using a moments-based method with a low number of moments. Our use of the Lanczos basis simplifies the calculations of the band energy and forces, which allows the application of the method to the molecular dynamics simulations of large systems. As an illustration of this convergent O(N) method we apply the block bond-order potential to the large scale simulation of the deformation of a carbon nanotube.Comment: revtex, 43 pages, 11 figures, submitted to Phys. Rev.

A pilot study evaluating GSK1070806 inhibition of interleukin-18 in renal transplant delayed graft function.

INTRODUCTION: Delayed graft function (DGF) following renal transplantation is a manifestation of acute kidney injury (AKI) leading to poor long-term outcome. Current treatments have limited effectiveness in preventing DGF. Interleukin-18 (IL18), a biomarker of AKI, induces interferon-γ expression and immune activation. GSK1070806, an anti-IL18 monoclonal antibody, neutralizes activated (mature) IL18 released from damaged cells following inflammasome activation. This phase IIa, single-arm trial assessed the effect of a single dose of GSK1070806 on DGF occurrence post donation after circulatory death (DCD) kidney transplantation. METHODS: The 3 mg/kg intravenous dose was selected based on prior studies and physiologically based pharmacokinetic (PBPK) modeling, indicating the high likelihood of a rapid and high level of IL18 target engagement when administered prior to kidney allograft reperfusion. Utilization of a Bayesian sequential design with a background standard-of-care DGF rate of 50% based on literature, and confirmed via extensive registry data analyses, enabled a statistical efficacy assessment with a minimal sample size. The primary endpoint was DGF frequency, defined as dialysis requirement ≤7 days post transplantation (except for hyperkalemia). Secondary endpoints included safety, pharmacokinetics and pharmacodynamic biomarkers. RESULTS: GSK1070806 administration was associated with IL18-GSK1070806 complex detection and increased total serum IL18 levels due to IL18 half-life prolongation induced by GSK1070806 binding. Interferon-γ-induced chemokine levels declined or remained unchanged in most patients. Although the study was concluded prior to the Bayesian-defined stopping point, 4/7 enrolled patients (57%) had DGF, exceeding the 50% standard-of-care rate, and an additional two patients, although not reaching the protocol-defined DGF definition, demonstrated poor graft function. Six of seven patients experienced serious adverse events (SAEs), including two treatment-related SAEs. CONCLUSION: Overall, using a Bayesian design and extensive PBPK dose modeling with only a small sample size, it was deemed unlikely that GSK1070806 would be efficacious in preventing DGF in the enrolled DCD transplant population. TRIAL REGISTRATION: NCT02723786