Preparation,Crystal Structures,and Thermal Studies of Alkaline Earth Nitrocarboxylates

The preparation, crystal structures, and thermal properties of [Ca(pyr)₂(4‐nba)₂]_n ( 1 ) (pyr = pyrazole; 4‐nba = 4‐nitrobenzoate) {[Ca(H₂O)₂(3‐npth)] · H₂O}_n ( 2 ) (3‐npth = 3‐nitrophthalate), [Mg(H₂O)₅(3‐npth)] · 2H₂O ( 3 ), and [Mg(H₂O)₄(2‐nba)₂] ( 4 ) (2‐nba = 2‐nitrobenzoate) are reported. The anhydrous Ca^II compound 1 and the diaqua Ca^II‐3‐nitrophthalate monohydrate 2 are one‐dimensional coordination polymers containing a hexacoordinate Ca^II ion located on a center of inversion in 1 and a heptacoordinated Ca^II ion in 2 . In 1 , the 4‐nitrobenzoate moiety acts as a μ₂‐bridging bidentate ligand, whereas the 3‐nitrophthalate anion exhibits a μ₃‐bridging pentadentate coordination mode in 2 . The hexacoordinate Mg^II‐containing compounds 3 and 4 do not contain a [Mg(H₂O)₆]²⁺ unit and the central Mg^II ion is coordinated to at least one monodentate carboxylate unit namely the monodentate 3‐npth molecule in 3 and two trans monodentate 2‐nba molecules in 4 . Hydrogen bonding between the lattice water molecules results in the formation of a water dimer in 3 . A comparative study of 17 alkaline earth nitrocarboxylates is described.     

Similarities and Differences between Crystal and Enzyme Environmental Effects on the Electron Density of Drug Molecules

The crystal interaction density is generally assumed to be a suitable measure of the polarization of a low-molecular weight ligand inside an enzyme, but this approximation has seldomly been tested and has never been quantified before. In this study, we compare the crystal interaction density and the interaction electrostatic potential for a model compound of loxistatin acid (E64c) with those inside cathepsin B, in solution, and in vacuum. We apply QM/MM calculations and experimental quantum crystallography to show that the crystal interaction density is indeed very similar to the enzyme interaction density. Less than 0.1 e are shifted between these two environments in total. However, this difference has non-negligible consequences for derived properties.     

Understanding Refractive Index Changes in Homologous Series of Unbranched Organic Compounds Based on Beer's Law

Changes of the refractive index for homologous series of hydrocarbons are usually plotted versus the density. While there is a clear linear dependence for alkanes and alkenes, the linearity deteriorates for homologous series with functional groups involving heteroatoms. The slope can even become negative, e. g., for carboxylic acids. For gaining a deeper understanding and to establish a more general correlation, we reinvestigate the corresponding theories starting with the Newton-Laplace, Gladstone-Dale and the Lorentz-Lorenz rules. We revisit the concept of molar refractivity pioneered by Landolt and Brühl and show that it is closely connected with a twin of Beer's law. We conclude that the refractive index of homologues series should better be plotted versus the molar concentration of the main UV-chromophore, the C−H bond, which actually causes the refractive index changes. This new approach is not limited to alkanes and alkenes but holds for homologous series with functional groups including heteroatoms.     

Eine Bemerkung zum Axiomensystem des Morgenstern/Thompson-Außenhandelsmodells

Zusammenfassung Es kann gezeigt werden, daß sich im Außenhandelsmodell vonMorgenstern/ Thompson gewisse Aussagen nicht unbedingt als Resultate aus dem vorgeschlagenen Axiomensystem ergeben. Werden diese Aussagen in das Axiomensystem aufgenommen, so bleibt das System unabhängig.

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Summary In the Open Expanding Economy Model ofMorgenstern/Thompson it can be shown that some of the statements do not follow from the axioms. Adding these statements to the given system of axioms the new system is still independent.

     

High-performance liquid chromatography-electrochemical detection of vecuronium and its metabolites in human plasma.

A high-performance liquid chromatographic assay coupled with electrochemical detection has been developed for the determination of vecuronium and its three putative deacetylated metabolites in human plasma. A novel solid-phase extraction procedure allowed good recovery of both vecuronium and its metabolites, together with ease and speed of execution. This method was sensitive, reproducible and accurate over the therapeutic range of concentrations of vecuronium and its metabolites, and was applied successfully to a study of the pharmacokinetics of vecuronium in anaesthetized patients.     

Decentered directional data

Directional data analysis usually assumes that the observations are recorded according to a coordinate system whose origin coincides with the center of their support. However, it may happen that the observer does not sit at this center and record the directions from another point. The object of this paper is to investigate the statistical behavior of such decentered directions. First we derive the family of distributions of these directions and produce statistical procedures that recover some information about the underlying process. An important special case is explored in details and compared with the Langevin model. Finally, an example is given where the introduced family of models makes physical sense and well fits the observations.This research was supported by the Natural Sciences and Engineering Research Council of Canada and by the FCAR and FRSQ funds of Québec.