A note on the genericity of simultaneous stabilizability and pole assignability

In this paper we study the genericity of simultaneous stabilizability, simultaneous strong stabilizability, and simultaneous pole assignability, in linear multivariable systems. The main results of the paper had been previously established by Ghosh and Byrnes using state-space methods. In contrast, the proofs in the present paper are based on input-output arguments, and are much simpler to follow, especially in the case of simultaneous and simultaneous strong stabilizability. Moreover, the input-output methods used here suggest computationally reliable algorithms for solving these two types of problems. In addition to the main results, we also prove some lemmas on generic greatest common divisors which are of independent interest.This work was supported in part by the Natural Sciences and Engineering Research Council of Canada under Grant Number A-1240.This work was supported in part by The Army Research Office under Grant Number BAAG29-84-K-0005.This work was partially supported by the Department of Electronics, Government of India.     

Definition of the Geometric Area of a Microelectrode Tip by Plasma Etching of Parylene

The geometric area of the tip of an intracortical stimulation electrode can be defined by combining photoresist masking with oxygen plasma etching of Parylene.1 The method was tested with both capacitor and iridium oxide electrodes and caused no significant degradation of the electrical properties of the electrode.     

Suxamethonium-induced porcine malignant hyperthermia

Metabolic, haemodynamic and neuroendocrine responses to suxamethonium (SCh) were measured in five normal swine and five swine susceptible to malignant hyperthermia (MH), to compare the responses with those previously reported for halothane. Following SCh, the onset of MH was sooner and more abrupt than following halothane. The maximal changes in aerobic metabolism and body temperature sere similar, while the changes in lactate, potassium, hydrogen ion and catecholamine concentrations were smaller than those observed following halothane. These results are discussed in terms of the action of chemical depolarizing drugs such as suxamethonium and acetylcholine. The propagated muscle action potentials produce an increase in the free intracellular calcium concentration which may be self-regenerative, but which may become uncontrollable because of the peculiarities of MH that effect the calcium pump or storage areas.     

Substrate inhibition of beta-lactamases, a method for predicting enzymatic stability of cephalosporins

Selected cephalosporins, including cefamandole, cephaloridine, cephaloglycin, and cefoxitin, were examined for their ability to inhibit the enzymatic activity of and act as substrates for beta-lactamases produced by Enterobacter cloacae and Staphylococcus aureus. Enzyme inhibition was determined by Michaelis-Menten kinetic measurements and by a spot plate assay using a chromogenic substrate (Glaxo compound 87/312). These two methods provide comparable estimates of kinetic parameters. Inhibition of beta-lactamase, as measured by these two methods, was generally found to correlate with resistance to hydrolysis and is proposed as a preliminary method of assessing susceptibility of cephalosporins to beta-lactamase hydrolysis. Four 7-alphaOCH(3), 7-alphaH cephalosporin analogue pairs were also examined. The presence of the 7-alphaOCH(3) substituent invariably resulted in reduced susceptibility to enzymatic hydrolysis, regardless of the other C7 substituent. The 7-alphaOCH(3) compounds were also better inhibitors than were their 7-alphaH analogues, with the exception that 7-alphaOCH(3) compounds having C7 adipic acid substituents were less inhibitory to the S. aureus enzyme than were the corresponding 7-alphaH analogues. Response of these two enzymes to 7-alphaOCH(3) and 7-alphaH cephalosporins suggests that beta-lactamase hydrolysis of these compounds involves attack at the alpha side of the betalactam ring.     

Specific inhibition of hepatic fatty acid synthesis exerted by dietary linoleate and linolenate in essential fatty acid adequate rats

Dietary linoleate and linolenate were investigated for their ability to specifically inhibit liver and adipose tissue lipogenesis in meal-fed (access to food 900-1,200 hr), essential fatty acid (EFA) adequate rats. Supplementing a high carbohydrate diet containing 2.5% safflower oil with 3% palmitate 16:0, oleate 18:1, or linoleate 18:2 did not affect in vivo liver or adipose tissue fatty acid synthesis. However, 18:2 addition to the basal diet did result in a significant (P less than 0.05) decline of liver fatty acid synthetase (FAS) and glucose-6-phosphate dehydrogenase (G6PD) activities. When the safflower oil content of the basal diet was reduced to 1%, the addition of 3% 18:2 or linolenate 18:3 significantly (P less than 0.05) depressed hepatic FAS, G6PD, and in vivo fatty acid synthesis by 50%. Addition of 18:1 caused no depression in hepatic FAS activity but did result in a significant (P less than 0.05) decline in liver G6PD activity and fatty acid synthesis which was intermediate between basal and basal +18:2- or +18:3-fed animals. Adipose tissue rates of lipogenesis were completely unaffected by dietary fatty acid supplementation. Similarly, the addition of 3 or 5% 18:3 to a basal diet for only one meal resulted in no change in lipogenesis relative to that in animals fed the basal diet. The data indicate that, like rats fed EFA-deficient diets, dietary 18:2 and 18:3 exert a specific capacity to depress rat liver FAS and G6PD activities and rate of fatty acid synthesis.     

The wider uses of conjoint psychotherapy

Aged (12- to 14-month-old) C57BL oestrous mice exhibited significantly lower (P less than 0-001) ovarian delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) concentration, specific activity and total content than young (3-month-old) oestrous mice, suggesting a decrease in the potential of the older animals to produce ovarian delta 4-3-oxosteroids. Mice in both age groups maintaining pregnancy to 10 or 18 days post coitum (p.c.) had similar values for activity of ovarian 3 beta-HSD. In the aged females in which foetal resorption had occurred, the majority of foetuses had been resorbed by 10 days p.c. However, ovarian 3 beta-HSD activity in these animals was not significantly different from that of young or aged mice maintaining pregnancy. By day 18, however, ovarian dehydrogenase activity in aged females failing to maintain pregnancy had decreased significantly. It is suggested that foetal death in aged mice is not the result of a deficiency in ovarian 3 beta-HSD, but rather may initiate luteal regression and consequently a decline in 3 beta-HSD.     

Intersubject variation of warfarin binding to protein in serum of normal subjects

The protein binding of warfarin was determined in the serum of 18 normal adult subjects (8 males and 10 females). A statistically significant negative correlation between free fraction of warfarin and albumin concentration was found. The free fraction of warfarin in the serum of women was significantly larger than that in the serum of men, apparently due to the lower albumin concentration in the serum of women.