Preparation of Photodegradable Oligomers Containing Metal–Metal Bonds Using ADMET

ADMET was evaluated as a method for preparing organometallic polymers with metal–metal bonds in the main chain. The Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized, and the X-ray crystal structure is reported. The molecule did not undergo ADMET polymerization with Grubbs’ or Schrock’s catalysts. In a control experiment to test if the Ph₂P(CH₂)₆CH=CH₂ ligand was interfering with the ADMET reaction, the phosphine was reacted with Grubbs’ 2nd generation catalyst. The dimerized metathesis product Ph₂P(CH₂)₆CH=CH(CH₂)₆PPh₂ was obtained with no observed degradation or deactivation of the catalyst. To test the inherent ADMET reactivity of the Ph₂P(CH₂)₆CH=CH₂ ligand when it is bonded to a metal center, the mononuclear cis-Mo(CO)₄(Ph₂P(CH₂)₆CH=CH₂)₂ complex was synthesized and polymerized using Grubbs’ 2nd generation catalyst. These control experiments suggest that the inability of Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize is not due to electronic effects pertaining to the C=C unit of the Ph₂P(CH₂)₆CH=CH₂ ligand. Accordingly, steric effects are implicated in the inability of the Cp₂Mo₂CO₄(Ph₂P(CH₂)₆CH=CH₂)₂ to polymerize by ADMET.     

Mid-ventricular obstruction: a variant of obstructive cardiomyopathy

In two patients with clinical and catheterization findings of hypertrophic obstructive cardiomyopathy, the level of intraventricular obstruction was found to be in the mid-ventricular area rather than at the junction of the inflow and outflow tracts. One patient died suddenly shortly after unsuccessful outflow tract myectomy. In vivo recognition of this probably rare variant form of obstructive cardiomyopathy rests mainly on the angiograhic appearance of the left ventricle and on the recording of pressures in multiple sites of the left ventricular cavity. Surgical relief of the obstruction in these patients is not likely to be obtained by a transaortic left ventricular outflow myectomy but may require either papillary muscle resection by the transatrial or transventricular approach or mid-ventricular septectomy, or both.     

Mitral valve malformation of Ebstein type in absence of corrected transposition

Coffee and its most important constituent, caffeine, may not only stimulate the function of many organs but also increase the metabolism in the body. These effects require a higher energy production which is mainly obtained from striated muscles by glycogenolysis and from fat tissue by lipolysis. Sutherland and Butcher were able to demonstrate that these degradation processes are primarily caused by an increase of cyclic 3,5-AMP. - In this connection caffeine and other methylxanthines are of special interest because these compounds also increase the intracellular amount of cyclic 3,5-AMP. This effect may be caused by an inhibition of phosphodiesterase, a release of catecholamines with resulting stimulation of adenylcyclase or by competitive inhibition of adenosine. At the present time it cannot be said which of these mechanisms primarily is involved in the in vivo effects of caffeine and other methylxanthines.     

Nonaqueous chromatography of biopolymers by means of their poly(ethylene glycol)-mediated solubilization in alcohols

Freeze-drying of aqueous solutions of biopolymers and excess poly(ethylene glycol)s leads to formation of hydrophobic complex. Complexation with PEG increases solubility of low molecular weight DNA, RNA, and several proteins in neat ethanol and methanol. Solubilized nucleic acids can be fractionated, and proteins separated by nonaqueous reversed phase HPLC. © 1995 John Wiley & Sons, Inc.     

Antiferromagnetic Inverse Spinel Oxide LiCoVO4 with Spin-Polarized Channels for Water Oxidation

Exploring highly efficient catalysts for the oxygen evolution reaction (OER) is essential for water electrolysis. Cost-effective transition-metal oxides with reasonable activity are raising attention. Recently, OER reactants' and products' differing spin configurations have been thought to cause slow reaction kinetics. Catalysts with magnetically polarized channels could selectively remove electrons with opposite magnetic moment and conserve overall spin during OER, enhancing triplet state oxygen molecule evolution. Herein, antiferromagnetic inverse spinel oxide LiCoVO₄ is found to contain d⁷ Co²⁺ ions that can be stabilized under active octahedral sites, possessing high spin states S = 3/2 (t_2g⁵e_g²). With high spin configuration, each Co²⁺ ion has an ideal magnetic moment of 3 µ_B, allowing the edge-shared Co²⁺ octahedra in spinel to be magnetically polarized. Density functional theory simulation results show that the layered antiferromagnetic LiCoVO₄ studied contains magnetically polarized channels. The average magnetic moment (µ_ave) per transition-metal atom in the spin conduction channel is around 2.66 µ_B. Such channels are able to enhance the selective removal of spin-oriented electrons from the reactants during the OER, which facilitates the accumulation of appropriate magnetic moments for triplet oxygen molecule evolution. In addition, the LiCoVO₄ reported has been identified as an oxide catalyst with excellent OER activity.     

Imprecise Reliability of General Structures

This paper discusses the important aspects of the reliability of systems with an imprecise general model of the structure function. It is assumed that the information about reliability behavior of components is restricted by the mean levels of component performance. In this case the classical reliability theory cannot provide a way for analyzing the reliability of systems. The theory of imprecise probabilities may be a basis in developing a general reliability theory which allows us to solve such problems. The basic tool for computing new reliability measures is the natural extension which can be regarded as a linear optimization problem. However, the linear programming computations will become impracticable when the number of components in the system is large. Therefore, the main aim of this paper is to obtain explicit expressions for computing the system reliability measures. We analyze the reliability of general structures and typical systems. The numerical examples illustrate the usefulness of the presented approach to reliability analyzing.