Morphological and physical property effects for solvent cast films of poly-2, 5(6) benzimidazole

A polybenzimidazole having the structural repeat unit and designated AB-PBI was formed into films by casting or precipitating from dilute solutions. Selected films were swollen in a plasticizing medium arid drawn about 2X. All films were dried in a vacuum oven to aid in the removal of residual solvent and moisture. Wide angle X-ray scattering (WAXS) was used to show the type of ordering found in this material and to indicate the extent of molecular orientation. Neither a glass transition nor a crystalline melting point has been observed for this polymer, A Perkin-Elmer DSC was used to scan the temperature range from ?150 to H-400°C in search of secondary transitions. The rheovibron proved more sensitive and a transition was located in the vicinity of ?60°C. An activation energy-was determined. The morphology of this polymer is subject to speculation. The ability of the chain to adopt a linear conformation leads to the possibility of a liquid-crystalline nature in solution. A model based on the data in hand is suggested. Stress-strain data was used to compare the mechanical properties of films prepared by several methods as well as to demonstrate the effect of orientation on strength.     

The laws of similitude and crack propagation

The mechanics of cracking follow the laws of similitude in an odd sense. As a result, crack load-external displacement-crack extension data are not usually non-dimensionalized. It follows that a new “group” should be used (analogous to the Reynolds, Froude or Cauchy numbers) when scaling ship ice-breaking resistance from tests of models in ice-towing-tanks.     

Measuring oxygen permeabilities of polymer films by a new singlet oxygen technique

A new sensitive method is described for measuring the permeation and diffusion of oxygen through polymer films. For these measurements an ethyl cellulose film containing 9,10-dimethylanthracene (DMA) and erythrosin may be either tightly sealed between two pieces of sample film in a simple cell or sealed in a pouch made from the test material, and is used to absorb oxygen which has passed through the polymer film sample from the air. On illumination this oxygen is converted by the erythrosin to singlet oxygen which then reacts with the DMA. After an initial scavenging period, the rate of permeation of oxygen under the atmospheric pressure gradient across the film is monitored by determining the rate of disappearance of DMA spectrophotometrically.     

Group composition using interpersonal skills: An analogue study on the effects of members' interpersonal skills on peer ratings and group cohesiveness.

Analyzed characteristics of groups in which all members were rated previously as performing at either high or low levels of interpersonal skills during a behavioral assessment procedure. Ss were 138 undergraduates. Group members evaluated each other's interpersonal behavior and their group's cohesiveness after a 2-hr leaderless session. Members of highly skilled groups were seen as more empathically understanding, more honest and open, more accepting, and as discussing more personally meaningful topics. Highly skilled groups were seen as more cohesive. It is suggested that a behavioral approach to group composition has a powerful effect on group members' perceptions of each other and of their group experience. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A virial coefficient analysis of helium adsorption isotherms

A model in which the atoms in the second layer of a monolayer-plus helium film are assumed to form a quasi-two-dimensional gas is used to analyze the isotherm data of Goellner, Daunt, and Lerner for helium on Grafoil. The parameters in the model are determined by a least-squares fit of the model isotherm to the data. These parameters include the second and third virial coefficients of the quasi-two-dimensional gas and the binding energy of the second-layer atoms to the first layer. The empirical values are compared to recent theoretical predictions for the two-dimensional helium gas. The agreement and discrepancies between theoretical and empirical values are discussed. The conclusion is that the second layer (at low densities) can be described as an imperfect two-dimensional gas with perhaps some modification of the interatomic potential due to substrate effects.     

Effect of protein-induced calciuria on calcium metabolism and bone status in adult rats

45Ca-labeled adult male rats were fed diets high in protein to determine long-term effects on calcium metabolism and bone status. Factors influencing renal excretion of calcium were examined for their involvement in protein-induced hypercalciuria. Control rats were fed a 6% casein diet. Test diets contained 6% casein plus 24% protein as lactalbumin, beef, casein, soy, egg white or gelatin. All diets were equal in Mg, P, and Ca. Collections made during the 20-week feeding regimen indicated a transient but marked calciuria (greater than or equal to 200% of control) occurring at or prior to days 56-59 by rats fed the lactalbumin, egg white, gelatin (P less than or equal to 0.001) and 30% casein (P less than or equal 0.01) diets. Soy and beef diets were not calciuric. At days 56-59, rats fed lactalbumin, 30% casein, soy and egg white exhibited significantly depressed urinary specific activity of calcium (P less than or equal to 0.001), and all rats fed test diets produced higher fecal endogenous calcium, suggesting an increased absorption. No compositional differences indicative of bone resorption were present in the femur or mandibles of any rat fed test protein, dismissing bone as the source of calciuria. End-products of protein metabolism known to chelate calcium or compete with its renal reabsorption were significantly correlated with urinary calcium; these included sulfate, oxalate and sodium.     

Primary lithiasis of the bile ducts

An analysis is made of 24 cases of primitive lithiasis of the biliary tracts, viz; 10 of diffuse intrahepatic lithiasis, 9 of intrahepatic lithiasis localized in one of the ducts; and 5 of extrahepatic lithiasis. The most common cause were stenosis (14 cases) generally of idiopathic or congenital nature, followed by those of iatrogenic or tumoral origin. There were also cases of isolated or diffuse anomalus dilatation of the biliary ducts. A lithogenetic bile as well as infectious processes are rather considered secondary factors. The diagnosis of the real nature of the condiction was usually established in the postoperative period, this being an explanation why repeated surgery was so common (75%). There was a high postoperative mortality in the diffuse forms owing to severe manifestations of biliary sepsis perpetuated by the stones. Depending upon the individual cases the following procedures are proposed: 1) Biliodigestive anastomosis 2) Sphinteropapilloplasty 3) Dilatation and calibration of the stenosis 4) Postoperative instrumental extraction of calculi. The last-named procedure was carried out in 58% of the cases and result in an improvement in the serious prognosis. Primitive lithiasis should always be borne in mind when undertaking surgery of the biliary tracts in order to avoid additional surgery.     

Bulling among yearling feedlot steers

The effect of ingestion of 250 ml X-ray contrast medium on resting gastrooesophageal sphincter pressure was studied in 10 normal human subjects. Twenty minutes after initiated intake of the contrast medium, a significant fall in sphincter pressure was recorded. In the light of studies on the neurogenic and hormonal regulation of the sphincter pressure it is attempted to account for this effect, and it is concluded that it must be a manifestation of a reflectory relaxation of the sphincter region. From a clinical point of view the consequence must be a demand for standardized conditions with regard to composition and pH of the contrast medium, time schedule and degree of abdominal compression in those cases in which radiological evaluation of the resistance against reflux is called for.     

Biomedical instrumentation in the Soviet Union

A modified technique for vaso-vasostomy is described with the aim to achieve better results in operative recanalization and restoration of fertility after vasectomy. Vaso-vasostomy is a success when the man is able to produce fertile semen. Criteria for a fertile semen are mentioned. Fertile semen was obtained in all 5 patients treated by this modified technique.