Robust Superlubricity of Gold–Graphite Heterointerfaces

Noncommensurate 2D interfaces hold great promise toward low friction and nanoelectromechanical applications. For identical constituents, the crystals interlock at specific rotational configurations leading to high barriers for slide. In contrast, nonidentical constituents comprising different lattice parameters should enable robust superlubricity for all rotational configurations. This is however not the case for gold–graphite interfaces, as both theory and experiments show scaling behavior of the sliding force as a function of the interface contact area. By simulating the sliding force for gold–graphite interfaces, this work shows that the origin for high force barriers at special angular configurations is a result of commensurability between the moiré structure and the contact geometry. Consequently, this paper suggests new geometries that can potentially overcome such commensurability effects to enable robust superlubricity.     

Academic in-group bias in the top five economics journals

Scientometrics - This paper studies academic in-group bias in the top five economics journals. We examine citation counts for articles published in these journals during the years 2006–2015,...     

Negotiation as a form of persuasion: Arguments in first offers.

In this article we examined aspects of negotiation within a persuasion framework. Specifically, we investigated how the provision of arguments that justified the first offer in a negotiation affected the behavior of the parties, namely, how it influenced counteroffers and settlement prices. In a series of 4 experiments and 2 pilot studies, we demonstrated that when the generation of counterarguments was easy, negotiators who did not add arguments to their first offers achieved superior results compared with negotiators who used arguments to justify their first offer. We hypothesized and provided evidence that adding arguments to a first offer was likely to cause the responding party to search for counterarguments, and this, in turn, led him or her to present counteroffers that were further away from the first offer. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Tracking the Interplay between Bound Peptide and the Lid Domain of DnaK,Using Molecular Dynamics

Hsp70 chaperones consist of two functional domains: the 44 kDa Nucleotide Binding Domain (NBD), that binds and hydrolyses ATP, and the 26 kDa Substrate Binding Domain (SBD), which binds unfolded proteins and reactivates them, utilizing energy obtained from nucleotide hydrolysis. The structure of the SBD of the bacterial Hsp70, DnaK, consists of two sub-domains: A β-sandwich part containing the hydrophobic cavity to which the hepta-peptide NRLLLTG (NR) is bound, and a segment made of 5 α-helices, called the “lid” that caps the top of the β-sandwich domain. In the present study we used the Escherichia coli Hsp70, DnaK, as a model for Hsp70 proteins, focusing on its SBD domain, examining the changes in the lid conformation. We deliberately decoupled the NBD from the SBD, limiting the study to the structure of the SBD section, with an emphasis on the interaction between the charges of the peptide with the residues located in the lid. Molecular dynamics simulations of the complex revealed significant mobility within the lid structure; as the structure was released from the forces operating during the crystallization process, the two terminal helices established a contact with the positive charge at the tip of the peptide. This contact is manifested only in the presence of electrostatic attraction. The observed internal motions within the lid provide a molecular role for the function of this sub-domain during the reaction cycle of Hsp 70 chaperones.     

Hydrothermal degradation of adsorbed sulfur mustard on activated carbon

Thermal and hydrothermal degradations of adsorbed sulfur mustard (HD) on activated carbon particles from a chemical protective over-garment were studied. Carbon loaded with 5 wt.% HD was heated in a closed reactor at temperatures up to 160 °C for 0.5–6 h and analyzed by solid-state ¹³C MAS NMR. On dry carbon at room temperature, HD was stable for months. On a thoroughly pre-wetted carbon, adsorbed HD partially degraded to thiodiglycol (TDG) and TDG-sulfoxide (TDG-SO) within 2–3 months. Heating dry HD-loaded carbon to 160 °C caused partial degradation within 4 h to 1,4-thioxane, along with 1,4-dithiane and vinyl sulfides. Complete degradation within 2.5 h to the same products occurred upon hydrothermal treatment of the HD-loaded carbon, using a water/carbon ratio of 0.3:1. With higher water/carbon ratios of 0.6:1–5:1 at temperatures of 120 °C and above, adsorbed HD hydrolyzed rapidly within 0.5 h. The latter reaction led to the formation of TDG concurrent with either thioxane (at 160 °C) or TDG-SO and TDG-dimer (at 120 °C). The mechanisms of the observed degradation processes are discussed.     

Fast GL(n)-Invariant Framework for Tensors Regularization

We propose a novel framework for regularization of symmetric positive-definite (SPD) tensors (e.g., diffusion tensors). This framework is based on a local differential geometric approach. The manifold of symmetric positive-definite (SPD) matrices, P _n , is parameterized via the Iwasawa coordinate system. In this framework distances on P _n are measured in terms of a natural GL(n)-invariant metric. Via the mathematical concept of fiber bundles, we describe the tensor-valued image as a section where the metric over the section is induced by the metric over P _n . Then, a functional over the sections accompanied by a suitable data fitting term is defined. The variation of this functional with respect to the Iwasawa coordinates leads to a set of \frac12n(n+1)\frac{1}{2}n(n+1) coupled equations of motion. By means of the gradient descent method, these equations of motion define a Beltrami flow over P _n . It turns out that the local coordinate approach via the Iwasawa coordinate system results in very simple numerics that leads to fast convergence of the algorithm. Regularization results as well as results of fibers tractography for DTI are presented.     

Ferromagnetic shape memory flapper

A new method for propulsion using a Ni₂MnGa ferromagnetic shape memory flapper is introduced. We optically examine the magnetic field induced strain of pure shear by means of a state of the art generator that provides alternating magnetic fields of 7000 Oe at frequencies of up to 100 Hz. Preliminary measurements show local shear deformation of about 5%, which open new frontiers in propulsion mechanisms.     

Ocular parameters as an objective tool for the assessment of truck drivers fatigue

Ocular parameters are influenced by sleep derivation and the use of chemical substances which are two major causes for traffic accidents. We assessed the use of these parameters as an objective screening tool for a driver's fitness for duty. Pupillary diameter, pupil reaction to light and saccadic velocity were measured in 29 army truck drivers every morning for two months and compared to baseline measurements taken while the subjects were alert. An index which expressed the difference between study and baseline measurements was calculated, and drivers with significant deviation from baseline were disqualified and interviewed. Non-disqualified drivers served as controls. Twenty-nine percent of disqualified drivers reported sleeping less than the minimum of 7 h required by army regulations compared with 8% of control drivers (p = 0.01). Disqualified drivers had worse sleep quality the night before the test (Groningen Sleep Quality Scale, p = 0.03) and incurred more accidents per driving day during their service (0.023 vs. 0.015 accidents/day, p = 0.03). Two disqualified drivers admitted to using alcohol or sleeping pills. Thus, these ocular parameters may serve as a screening tool for drivers that are at high risk for driving. Drivers who were disqualified even once, tend to be involved in more motor vehicle accidents than their peers.