Liquid-phase degradation of poly(vinyl chloride)

The main kinetic regularities of the thermal and thermal-oxidative degradation of poly(vinyl chloride) (PVC) in the liquid phase have been analyzed in comparison with the solid-phase degradation of PVC. The thermal (in an N₂ atmosphere) degradation of PVC in the form of dilute solutions is characterized by a number of essential distinctions, the primary peculiarity consisting of a lower dehydrochlorination rate due to the retarded reaction of the formation of bond polyconjugated systems. The same is observed for the thermal degradation of PVC plasticized with di- and polyesters. On the contrary, in an oxygen-containing atmosphere the solvents promote PVC decomposition. Accelerated PVC degradation under such conditions is due to the solvent oxidation that causes the appearance, within the system, of products activating the PVC macromolecular decomposition. The intensified degradation processes are accounted for, in the first place, by an increased reaction rate of the statistical (by the random law) detachment of HCl from normal macromolecular units. In general, the kinetics of the thermal-oxidative liquid-phase degradation of PVC is determined by the partial pressure of oxygen in the reaction zone, by the quantity of the solvent introduced into the polymer, as well as by the oxidative stability of the solvent. It has been shown that an effective stabilization of PVC in the liquid phase, particularly in the systems highly plasticized with esters, can be achieved through stabilizing the solvent, first of all, rather than the polymer, against oxidative decomposition. In this case the PVC dehydrochlorination rate decreases sharply and may reach an essentially lower value than under similar conditions of the solid-phase thermal degradation of PVC. PVC stabilization with respect to the reaction of HCl elimination achieved through the solvent stabilization against thermal-oxidative decomposition has been called the effect of “echo-stabilization” of PVC.     

Terminal residues of hog pancreatic amylase

We have considered a differential diagnosis of clinical hyperkalemia. The clinical signs and symptoms of patients with hyperkalemia are manifold and can involve many organ systems. The nonoliguric chronic renal failure patient with hyporeninemia and hypoaldosteronemia may have as one of his principal problems recurrent hyperkalemia. Treatment of this condition includes well-known modalities such as administration of calcium salts, NaHCO3, removal of potassium with resin or dialysis as well as placement of a transvenous pacemaker in anticipation of bradyarrhythmias or asystole.     

Hartnup disease. Clinical, pathological, and biochemical observations

Hartnup disease is a rare genetic disorder of amino acid transport associated with variable and intermittent clinical abnormalities. A family is described in which three siblings had an intermittently progressive neurological disease and two of the affected siblings had the Hartnup-pattern aminoaciduria. Neuropathological examination of one case showed severe diffuse atrophy, generalized neuronal loss in the cortex, and Purkinje cell loss in the cerebellum. In vivo and in vitro studies of intestinal amino acid transport in the surviving sibling indicated a partial defect in the transport of several neutral amino acids (tryptophan, alanine, serine, and methionine) with normal transport of other neutral amino acids (threonine, phenylalanine, histidine, tyrosine, and isoleucine). Transport of glycine, proline, hydroxyproline, and the basic amino acids appeared normal.     

Continuous dynamic monitoring of pressure and flow patterns during assisted ventilation

On curettage, done in a 39 year old patient because of metorrhagia, a peanut-sized nodule was scraped away from the endometrium. Histologically it consisted of a jumble of irregularly shaped portions of normal appearing embryonal cartilage, of tortuous thick-walled vessels, of twisted bundles of nerves of ducts of respiratory and intestinal epithelium, and of sheets of hornifying skin. The haphazard disarray of tissues supported the notion that the lesion was not a remnant of a malformed embryo. Step-sections through the lesion revealed no traces of placental villi or decidua in the surrounding endometrium. The following were considered as possible origins of the teratoma: 1. displaced germinal cells, 2. retention of pluripotent müllerian epithelium, 3. overaged or blighted ovum. The latter seems most compatible with the histological findings.     

Strain differences among chickens in tonic immobility: evidence for an emotionality component

Substantial strain differences in tonic immobility were found between different breeds of chickens. Crossbreeding between strains showing different immobility durations yielded hybrids that exhibited intermediate reactions. For purpose of relating the strain differences in tonic immobility to more conventional measures of emotionality, data were collected on open-field activity, defecation, and adrenal weight. Overall, the results implicated strain-specific differences in emotionality as being the basis for the observed differences in immobility. Latency to defecate in an open field, however, was highly correlated with latency to ambulate. It was argued that defecation, rather than being an absolute measure of fear or emotionality, may in fact be an intermediate response to gradual fear reduction.