We describe the development of Lewis's ideas concerning the chemical bond and in particular the concept of the electron pair bond and the octet rule. We show that the concept of the electron pair bond has endured to the present day and is now understood to be a consequence of the Pauli principle. In contrast the octet rule is now regarded as much less important than was originally generally bel...

While the knowledge creation benefits of archaeology are widely understood, there is less awareness or assessment other potential benefits. These can be associated with wellbeing and health, including mental health. significant given that a creative outdoor activity to enhance social bond through collaborative working. Using data from NEARCH survey 2015, this paper seeks encourage wider partici...

Novel C2-symmetric diiminosphosphoranes and diketimines are useful ligands for Pd-and Cu-catalyzed C±C bond forming reactions, Angermund's molecular modeling based on accessible molecular surface serving as a guide in predicting catalyst activity. The ®rst highly enantioselective diphosphites as ligands in Rh-catalyzed hydrogenation are also described, the selectivity principle being based on i...

The mathematical representation of chemical bonds in molecules is discussed. The molecule is viewed as a system of weakly interacting chemical bonds. The intrabond problems and the averaged electrostatic interbond interactions are handled at the . zeroth order, while the small interbond delocalization and dispersion effects are taken into account on the basis of the perturbation theory. A speci...

A third polymorph of the title compound, C(16)H(14)N(4), has been obtained. The mol-ecule adopts a non-planar conformation with an E configuration at the two partially double exo C N bonds of the 2-pyridyl-amine units. Like in the triclinic form [Bensemann et al. (2002 ▶). New J. Chem.26, 448-456], the recognition process between 2-pyridyl-amine units takes place through formation of a cyclic R...

This paper presents a new method for smoothing haptic interaction with molecular force calculations that uses Lennard-Jones forcefield. The gradient of the forcefield is used unaltered when the distance between two atoms is greater than the sum of their van der Waals radii. However, when they are smaller, a hard-surface wall implemented using a spring model is used to repel two atoms. This elim...

The dinuclear title compound, [Pb(2)(C(6)H(8)O(4))(NO(3))(2)(C(19)H(13)N(5))(2)], lies with the mid-point of the butyl chain of the bridging adipate unit on a center of inversion. The Pb(II) ion is covalently bonded to the nitrate anion and is bonded to a carboxyl-ate group of the adipate unit by another covalent bond. The N-heterocycle functions in a chelating tridentate mode. The metal atom e...

Biological catalysis frequently causes changes in noncovalent bonding. By building on Pauling's assertion that any long-lived, chemically distinct interaction is a chemical bond, this article redefines enzyme catalysis as the facilitated making and/or breaking of chemical bonds, not just of covalent bonds. It is also argued that nearly every ATPase or GTPase is misnamed as a hydrolase and actua...

The aim of this study was to compare the bond strengths of three self-etching materials during one year of storage. Clearfil SE Bond (SE), Clearfil Protect Bond (PB), and Clearfil Tri-S Bond (TS) were used for bonding to dentin and enamel according to manufacturer's instructions. Microshear bond strength values were measured after 24 hours, six months, and one year. Two-way ANOVA showed that th...

BACKGROUND During the first weeks of hospitalization, premature babies and their parents encounter difficulties in establishing early bonds and interactions. Only a few studies have explored what caregivers can do to meet parents' needs in relation to these interactions and help optimize them. This study sought to explore parents' perception of these first interactions and to identify the actio...