Valency and Transitivity in Contact: An Overview

Negative (vs positive) intergroup contact may have a disproportionately large impact on intergroup relations because of valencesalience effects, whereby negative contact causes higher category salience . One correlational and three experimental studies in three conflict areas (Northern Ireland, Arizona's border area, and Cyprus; Ns = 405, 83, 76, and 91) tested the moderation of these valence-salience effects by individuals' histories of outgroup contact. Consistent with a perceived fit principle valence-salience effects of face-to-face, television-mediated, and imagined contact held among individuals with negative or limited histories of outgroup contact; these effects were significantly reduced or nonsignificant among individuals with positive or extensive past outgroup contact. These moderation effects suggest that positive and diverse intergroup contact in the past buffers against the harmful effects of negative contact experiences in the present, thus limiting the potential for negative spiralling of intergroup relations.

Psychological Science, 2006

Surface Innovations, 2019

The contact angle is one of the most sensitive experimental values describing a junction between three phases, being influenced by the composition and properties of contacting media as well as the structure and composition of interfaces involved. The origins and importance of the contact angle in analysis of three-phase systems date back to the famous works on cohesion and adhesion of fluids published by Thomas Young in 1805 and later by Athanase Dupré in 1869. Since then, the contact angle has remained one of the most important values measured experimentally during characterization of solids and their wetting characteristics. Such measurements, however, involve solid surfaces that deviate from the idealized ones used in thermodynamic and mechanical modeling of three-phase junctions by Young, Dupré and others, and there is typically more than one value of contact angle measured on such surfaces. As a result, the attention of scientists and researchers in the past two centuries has b...

Chemical Reviews, 1999

Since 1998, he has been head of the Department of Chemical Physics at the J. Heyrovský Institute. He has been a fellow of the Learned Society of the Czech Republic since 1998. Dr. Hobza has authored or coauthored about 180 papers and two books. These studies dealt mainly with molecular interactions and their role in physical chemistry and biodisciplines.

Collection of Czechoslovak Chemical Communications, 2006

Physical Review Letters, 2007

The transition from tunneling to metallic contact between two surfaces does not always involve a jump, but can be smooth. We have observed that the configuration and material composition of the electrodes before contact largely determine the presence or absence of a jump. Moreover, when jumps are found preferential values of conductance have been identified. Through a combination of experiments, molecular dynamics, and first-principles transport calculations these conductance values are identified with atomic contacts of either monomers, dimers, or double-bond contacts.

Wiley Interdisciplinary Reviews: Computational Molecular Science, 2014

The Hellmann-Feynman theorem assures us that the forces felt by the nuclei in a molecule or complex are purely classically electrostatic. Nevertheless, it is often claimed (incorrectly) that electrostatic considerations are not sufficient to explain non-covalent interactions. Such assertions arise largely from neglecting the polarisation that is inherently part of the electrostatic interaction, and must be taken into account. Accordingly, we now outline the requirements for a correct electrostatic treatment and discuss the difference between physical observables and quantities that arise from mathematical models. Polarisation and donor-acceptor charge transfer are shown to be equivalent for weak interactions. However, polarisation is a physical observable while charge transfer, in this context, is mathematical modelling. We also discuss some popular schemes for analysing non-covalent interactions.

2021

In this fascina� ng collec� on of essays, an interna� onal group of scholars explores the sonic consequences of transcultural contact in the early modern period. They examine how cultural confi gura� ons of sound impacted communica� on, comprehension, and the categorisa� on of people. Addressing ques� ons of iden� ty, diff erence, sound, and subjec� vity in global early modernity, these authors share the convic� on that the body itself is the most in� mate of contact zones, and that the culturally con� ngent systems by which sounds made sense could be foreign to early modern listeners and to present day scholars.

Journal of Computational Chemistry, 2015

The recent r-hole concept emphasizes the contribution of electrostatic attraction to noncovalent bonds, and implies that the electrostatic force has an angular dependency. Here a set of clusters, which includes hydrogen bonding, halogen bonding, chalcogen bonding, and pnicogen bonding systems, is investigated to probe the magnitude of covalency and its contribution to the directionality in noncovalent bonding. The study is based on the block-localized wavefunction (BLW) method that decomposes the binding energy into the steric and the charge transfer (CT) (hyperconjugation) contributions. One unique feature of the BLW method is its capability to derive optimal geometries with only steric effect taken into account, while excluding the CT interaction. The results reveal that the overall steric energy exhibits angular dependency notably in halogen bonding, chalcogen bonding, and pnico-gen bonding systems. Turning on the CT interactions further shortens the intermolecular distances. This bond shortening enhances the Pauli repulsion, which in turn offsets the electrostatic attraction, such that in the final sum, the contribution of the steric effect to bonding is diminished, leaving the CT to dominate the binding energy. In several other systems particularly hydrogen bonding systems, the steric effect nevertheless still plays the major role whereas the CT interaction is minor. However, in all cases, the CT exhibits strong directionality, suggesting that the linearity or near linearity of noncovalent bonds is largely governed by the charge-transfer interaction whose magnitude determines the covalency in noncovalent bonds.