Ligand Substitution Dynamics

Substitution of a ligand in an inner sphere complex by an outside group is the most fundamental reaction in metal ion chemistr

Ligand Substitution Processes

From the preface: The subject of the mechanistic study of ligand substitution reactions is currently undergoing an exciting growth. New fast-reaction techniques have removed the upper limit on rates that can be measured, and extension to less familiar central metal atoms has begun in earnest. This might seem the wrong moment for review of the field. As yet, definitive treatment is possible only for those complexes involving monodentate ligands with cobalt(III) and platinurn(II). But, because information is so extensive for these systems, it is clear that they are functioning as models from which concepts and experiments are generated for application over the fast-growing range of the subject. We believe that this is an important moment to reopen debate on fundamentals so that concepts will be most felicitously formulated to aid growth of understanding. This monograph is centrally concerned with three aspects of those fundamentals. We have attempted to develop an approach to classification of ligand substitution reactions that is adapted to what seem to have emerged as the characteristic features of these reactions and is susceptible to operational tests. (We do recognize that any such scheme of ideas is necessarily obsolescent once it is formulated since new experiments will certainly follow immediately.) We have tried to evaluate the basis for making generalizations about ligand substitution processes and to formulate tests to show whether new reactions fall within familiar patterns. Finally, we have sought to base the models of ligand substitution processes in the language of molecular-orbital theory. We believe that MO theory is most useful, because it may be used to correlate rate data on complexes with the extensive information available from spectral and magnetic studies, yet differs from crystal-field theory in providing a natural place for consideration of the bonding electrons, which must be a principal determinant of reaction processes. To keep this essay within bounds, we assume familiarity with the elements of experimental kinetics, transition-state theory, and the simple molecular-orbital theory of complexes. Introductory physical chemistry, some familiarity with the study of reaction mechanisms, and mastery of one of the qualitative treatments of MO theory as applied to transition-metal complexes should provide sufficient background. Thus, we hope that this book will be useful to students, relatively early in their careers, who wish to explore this field. Our debts to very many workers will be obvious throughout. We want to record here our special personal debt to Professors Ralph G. Pearson and Fred Basolo and to Dr. Martin Tobe. We particularly thank Professor George S. Hammond for his interest and enthusiasm in this project. Professor Hammond carefully read and criticized the entire manuscript in the final drafts. We received many other valuable criticisms at various stages of this project from Professors R. D. Archer, F. Basolo, J. O. Edwards, J. Finholt, P. Haake, J. Halpern, A. Kropf, R. G. Pearson, S. I. Shupack, M. S. Silver, and C. Walling, and Dr. U. Belluco and Dr. L. Cattalini. We very much appreciate their help and probably should have followed their suggestions more closely. We warmly acknowledge expert assistance from Mrs. Madeline deFriesse, Miss Jan Denby, and Mrs. Diane Celeste in preparation of the manuscript. COOPER H. LANGFORD HARRY B. GRAY Amherst, Massachusetts New York, New York October 196

The Relationship Between Collectivism and Climate: A Review of the Literature

Collectivism is one of the well-researched dimensions of culture that pertains to an individual’s relationship to an in-group. Organisational climate, on the other hand, is predominantly defined as the shared perceptions of employees about their working environment. In spite of the long tradition of both constructs in the literature, the conceptual relationship between collectivism and climate has oftentimes been neglected. This paper explores this relationship by presenting (1) the conceptual overlap between culture and climate; (2) the congruence between collectivism and climate in terms of levels of conceptualisation and analysis; (3) the apparent influence of collectivism on organisational processes and practices that have been the domain of climate studies; and (4) the apparent influence of collectivism on climate outcomes. This paper also offers some recommendations to guide future studies including suggestions to have more empirical investigation to strongly establish the relationship between collectivism and climate, to investigate facets of climate simultaneously, to extend the link between climate and other work outcomes, to engage in multi-level research, and to explore how collectivism influences climate formation and change

Efficient Parallel Translating Embedding For Knowledge Graphs

Knowledge graph embedding aims to embed entities and relations of knowledge graphs into low-dimensional vector spaces. Translating embedding methods regard relations as the translation from head entities to tail entities, which achieve the state-of-the-art results among knowledge graph embedding methods. However, a major limitation of these methods is the time consuming training process, which may take several days or even weeks for large knowledge graphs, and result in great difficulty in practical applications. In this paper, we propose an efficient parallel framework for translating embedding methods, called ParTrans-X, which enables the methods to be paralleled without locks by utilizing the distinguished structures of knowledge graphs. Experiments on two datasets with three typical translating embedding methods, i.e., TransE [3], TransH [17], and a more efficient variant TransE- AdaGrad [10] validate that ParTrans-X can speed up the training process by more than an order of magnitude.Comment: WI 2017: 460-46

Rayleigh and depinning instabilities of forced liquid ridges on heterogeneous substrates

Depinning of two-dimensional liquid ridges and three-dimensional drops on an inclined substrate is studied within the lubrication approximation. The structures are pinned to wetting heterogeneities arising from variations of the strength of the short-range polar contribution to the disjoining pressure. The case of a periodic array of hydrophobic stripes transverse to the slope is studied in detail using a combination of direct numerical simulation and branch-following techniques. Under appropriate conditions the ridges may either depin and slide downslope as the slope is increased, or first breakup into drops via a transverse instability, prior to depinning. The different transition scenarios are examined together with the stability properties of the different possible states of the system.Comment: Physics synopsis link: http://physics.aps.org/synopsis-for/10.1103/PhysRevE.83.01630

4D Printing of origami structures for minimally invasive surgeries using functional scaffold

Origami structures have attracted attention in biomedical applications due to their ability to develop surgical tools that can be expanded from a minimal volume to a larger and functional device. On the other hand, four-dimensional (4D) printing is an emerging technology, which involves 3D printing of smart materials that can respond to external stimuli such as heat. This short communication introduces the proof of concept of merging origami and 4D printing technologies to develop minimally invasive delivery of functional biomedical scaffolds with high shape recovery. The shape-memory effect (SME) of the PLA filament and the origami designs were also assessed in terms of deformability and recovery rate. The results showed that herringbone tessellation origami structure combined with internal natural cancellous bone core satisfies the design requirement of foldable scaffolds. The substantial and consistent SME of the 4D printed herringbone tessellation origami, which exhibited 96% recovery compared to 61% for PLA filament, was the most significant discovery of this paper. The experiments demonstrated how the use of 4D printing in situ with origami structures could achieve reliable and repeatable results, therefore conclusively proving how 4D printing of origami structures can be applied to biomedical scaffolds