Towards Diastereomeric Pure Salts with Antisolvent Methods

Chiral molecules, especially enantiomers and diastereomers of purity > 99 %, present a significant market share within the chemical, pharmaceutical, and flavor industries. Antisolvent precipitations, both batch and semicontinuous operations to serve the current trends in flow chemistry were demonstrated to be environmentally benign and efficient tools in achieving high optical purities. Although salts are known to be insoluble in supercritical CO₂, instabilities of the nascent salts were detected and applied for increasing efficiency. Diastereomeric excess values of the crystalline products exceeded 99 % in maximum of three consecutive steps both by repeated resolution with half molar equivalent of the amine to the acid and by direct recrystallization of the salts.     

The complexity of economic equilibria for house allocation markets

We prove NP-completeness of deciding the existence of an economic equilibrium in so-called house allocation markets. House allocation markets are markets with indivisible goods in which every agent holds exactly one copy of some good.     

A technique for controlling the placement of the thin area in electrojetpolished tem foils of tungsten

Recently we have been making extensive use of TEM observations of grain boundaries in a research program concerned with the deformation behavior of tungsten bicrystals. A major problem in this research involved the preparation of thin foils which contained the grain boundary in the electron tranparent region, since standard cell type electrojetpolishing techniques do not allow adequate control of the placement of the thin area. Since the grain boundary comprises a very small percentage of a foil, good thin area placement control is critical to obtaining useful samples consistently. Masking techniques which use electrically insulating lacquers are not precise enough to guarantee the position of the thin area. However, we have found that one can use the dishing characteristic of the jetpolisher (i.e., the fact that the center of the foil thins faster than the perimeter) in conjunction with the masking technique to predict the position of the thin area within a preferentially thinned region created by the masking procedure outlined below. This is the essence of the procedure outlined below.     

A Unified Approach to Submicron DC MOS Transistor Modeling for Low-Voltage ICs

A unified single-equation approach for the MOS transistordrain current modeling for energy-efficient submicron MOS circuitsis presented. Instead of three sets of separate equations forthe triode, saturation, and weak inversion regions, only a continuousexpression which is valid to describe the behavior of drain currentand the derivatives in all operation regions can be realizedby using a combination of hyperbola, sigmoid, and interpolationmethods. The model expression can predict accurate results forthe current, output conductance, and transconductance with continuousand smooth characteristics. The simulation results agree wellwith experimental data.     

Thyroxine,Triiodothyronine, Reverse-Triiodothyronine,and Other Physiological Characteristics of Periparturient Cows Fed Restricted Energy

Eighty-six cows were assigned to two equal groups with group A fed according to National Research Council recommendations for total digestible nutrients for the 8 wk before parturition and group B was fed 21% higher energy in the first 6 wk and 15% higher in the last 2 preparturient wk. Thyroxine in blood serum decreased in both groups 14 days before and on the day of delivery. It was significantly lower in group A. Findings were similar with triiodothyronine. Blood serum concentrations of reverse-triiodothyronine of group A was significantly higher in group A on day 28 and 14 than group B before delivery. Energy intake had little influence on the serum concentrations of other constituents (albumin, total protein, immunoglobulin G, total and free cholesterol, nonesterified fatty acids). Restricted energy intake that does not alter thyrotropin-thyrotropin-releasing hormone secretion results in higher rate of production of reverse-triiodothyronine and in decreased serum concentration of triiodothyronine. Slight changes of energy balance might be indicated readily by reverse-triiodothyronine concentration in blood serum.     

Stoichiometric dye-binding procedure for the determination of the reactive lysine content of soya bean protein

A new analytical method has been developed for the determination of the reactive lysine content of soya bean protein. The method is based on the reaction of the free basic groups of the protein with 1-phenylazo-2 naphthol-6,8 disulphonic acid. With regard to the stoichiometry of the procedure, it has been proved, contrary to earlier reports, that the basic amino acids, histidine, arginine and lysine, each combine with one mole of the dye. After acylation with propionic anhydride lysine alone loses its dye reactivity. The usefulness of the proposed method has been demonstrated by the determination of the reactive lysine content of several untreated, heat-treated and acid-treated soya bean samples. The results show that heat damage of about 5% in reactive lysine content can be measured in 1·5 h with good reproducibility.     

Corticofugal regulation of auditory sensitivity in the bat inferior colliculus

Risk factors for severe acute asthma involve the patient, the environment and the society in general. In addition, there are strong interrelationships between these factors. Personal characteristics linked to acute severe asthma include age (teenagers), denial leading to poor compliance, depression with atypical symptoms in children, and some medical features of asthma associated with increased severity. Environmental factors include airborne allergens, infections, irritants such as air pollutants and passive smoking. Life events have not been extensively studied but are likely to play a predominant role. The social setting, particularly the health care system, acts as an interface between the patient and the environment. Most all asthma deaths are avoidable and related to dysfunctions in the health care system.     

Modeling study of migration-driven lateral instability in autocatalytic systems

The lateral stability of reaction fronts in simple autocatalytic models with the components carrying various charges is investigated when the system is exposed to an inhomogeneous electric field parallel to the direction of propagation. The enhanced migrational flux of the reactant destabilizes the planar front giving rise to a cellular structure because the electric field strength is greater on the reactant side of the reaction front. The onset of instability depends not only on the charge difference between the reactant and the autocatalyst but also on the variation of specific conductance in the course of the reaction, which results in a difference in electric field strength on the opposite sides of the reaction front.