University of Coimbra

About: University of Coimbra is a education organization based out in Coimbra, Portugal. It is known for research contribution in the topics: Population & Context (language use). The organization has 14318 authors who have published 43067 publications receiving 994733 citations. The organization is also known as: UC & Universidade dos Estudos Gerais.

Effect of electron lone-pairs on nuclear spin–spin coupling constants

Abstract: The nature and types of lone-pair effects on nuclear spin coupling constants are reviewed in the context of a localized bond description of molecular electronic structure. Emphasis is placed on the importance of residual delocalization involving the otherwise lone-pair orbital, in terms of which the effect of an X lone-pair, when compared with an isoelectronic YH or XH+ group or with an XR group, and its orientational dependence can be interpreted. One-, two- and three-bond coupling constants are considered and the importance of lone-pair effects for configurational and conformational information is stressed and illustrated. They also serve for a better understanding of substituent inductive effects on coupling constants. A large collection of illustrative examples are presented, with particular attention paid to couplings involving H, C, N, F and P nuclei, organized in a systematic manner into nine categories. The signs of the lone-pair effects on the reduced coupling constants are found to be independent of the actual nuclei under study in the same category. This is taken as an indication that the electron lone-pairs mainly affect the Fermi contact contribution to the coupling and, accordingly, an interpretation is given in terms of simple sum-over-states models. In addition, symmetry-based relationships are established involving the sign of lone-pair effects in coupling constants between nuclei which are a different number of bonds apart.

A literature review of manufacturing performance measures and measurement in an organizational context: a framework and direction for future research

Abstract: Competitive pressures in the global manufacturing environment are forcing manufacturing organizations to re‐engineer in order to become more competitive in the marketplace. Toward that end, management of these organizations is paying closer attention to the changing nature of manufacturing performance, and the systems, processes and measures used in its evaluation. Examines the literature concerned with issues related to the different facets of manufacturing organizational performance. Reviews and classifies articles published in relevant journals between 1988 and 2000. Based on this extensive literature review, identifies and discusses several issues relevant to both practice and theory of manufacturing performance measurement. Concludes by presenting a conceptual framework outlining the evolution of manufacturing performance measures and measurement in an organizational context.

Lipid-based nanoparticles for siRNA delivery in cancer therapy: paradigms and challenges.

Abstract: RNA interference (RNAi) is a specific gene-silencing mechanism that can be mediated by the delivery of chemical synthesized small-interfering RNA (siRNA). RNAi might constitute a novel therapeutic approach for cancer treatment because researchers can easily design siRNA molecules to inhibit, specifically and potently, the expression of any protein involved in tumor initiation and progression.Despite all the potential of siRNA as a novel class of drugs, the limited cellular uptake, low biological stability, and unfavorable pharmacokinetics of siRNAs have limited their application in the clinic. Indeed, blood nucleases easily degrade naked siRNAs, and the kidneys rapidly eliminate these molecules. Furthermore, at the level of target cells, the negative charge and hydrophilicity of siRNAs strongly impair their cellular internalization. Therefore, the translation of siRNA to the clinical setting is highly dependent on the development of an appropriate delivery system, able to ameliorate siRNA pharmacokinetic ...