Molecular structure,morphology, and antioxidant consumption in medium density polyethylene pipes in hot-water applications

Changes in polymer structure and antioxidant concentration have been systematically studied as functions of temperature, hoop stress, exposure time, and location in pipe wall on pressure tested pipes of medium density polyethylene. The pressure tests have been performed with water as the internal medium and air as the external medium at temperatures in the range 80 to 105°. Infrared spectroscopy shows that oxidation is initiated at the inner wall surface just prior to the onset of the so-called stage III fracture. X-ray diffraction and size exclusion chromatography show that oxidation involves only the amorphous phase and results in a significant molar mass reduction. The near-inner-wall material exhibits a 10% reduction in mass average molar mass before the onset of stage III fracture and thereafter a more dramatic decrease. Oxidation induction time measurements by differential scanning calorimetry show that the antioxidant concentration is almost twice as high in the center of the wall as in the near-inner-wall and outer-wall material of the unexposed pipe, that the loss of antioxidant is anomalously rapid at the beginning of the high temperature exposure, and that the antioxidant concentration profile gradually becomes more skewed towards the outer wall on prolonged exposure. The data presented in this paper are used in a parallel paper for modeling purposes.     

Female sex is associated with increased mortality and morbidity early, but not late, after coronary artery bypass grafting

OBJECTIVE: To describe mortality and morbidity during a period of 2 years after coronary artery bypass grafting in relation to gender. DESIGN: Prospective follow-up study. SETTING: Two regional cardiothoracic centres which performed all the coronary artery bypass operations in western Sweden at the time. SUBJECTS: A total of 2129 (1727 (81%) men and 402 (19%) women) consecutive patients undergoing coronary artery bypass surgery between June 1988 and June 1991 without concomitant procedures. RESULTS: Females were older and more frequently had a history of hypertension, diabetes mellitus, congestive heart failure, renal dysfunction and obesity. In a multivariate analysis, taking account of age, history of cardiovascular diseases and renal dysfunction, female sex appeared as a significant independent predictor of mortality during the 30 days after coronary artery bypass grafting (P < 0.05), but not thereafter. Various postoperative complications including neurological deficit, hydro- and pneumo-thorax, perioperative myocardial damage and the need for assist devices and prolonged reperfusion were more common in females than males. CONCLUSION: Females run an increased risk of early death and the development of postoperative complications after coronary artery bypass surgery as compared with males. Late mortality does not appear to be influenced by gender and the long-term benefit of the coronary artery bypass graft operation is similar in men and women.     

Preparation, characterization and stability tests of selectively absorbing oxides on stainless steel

Selectively absorbing surfaces have been prepared on ferritic stainless steel by thermal oxidation and four different wet chemical methods: sodium dichromate, Ebonol, chemical coloured and chemical coloured followed by cathodic hardening. The solar optical parameters were determined by spectral reflectance measurements and a_sol values obtained were around 0.90 and e₃₇₃ values in the interval 0.10–0.15. The surface oxides have been analyzed by x-ray diffraction, ESCA and AES. The Ebonol treatment resulted in Fe₃O₄ while the other methods produced surfaces mainly consisting of chromium oxide with some content of iron oxide. The selective surfaces have been exposed to accelerated and natural aging. Optical and surface analysis did not reveal any degradation of the samples. The surfaces oxidized by sodium dichromate and in particular the thermally oxidized surfaces exhibited excellent temperature stability. In low temperature applications the chemically coloured surface is superior owing to its better solar selectivity.     

The cost-benefit balance of coronary artery bypass grafting: need for hospitalization during the two years before and the two years after

To derive and compare the need for hospitalization during 2 years prior to coronary artery bypass grafting (CABG) and 2 years after, all the patients from western Sweden in whom CABG without simultaneous valve surgery was performed between June 1988 and June 1991 were evaluated. Hospitalization prior to and after surgery was derived via questionnaires sent to the patients and via data from their hospital medical record forms. In all, 2099 patients were studied. The mean total number of days in hospital was 16 during the 2 years before and 24 including surgery and postoperative complications during the 2 years after the operation (p < 0.001). When the days for operation and postoperative complications were excluded, the mean number of days after operation was 7 (p < 0.001). Hospitalization due to myocardial infarction, angina pectoris, percutaneous transluminal coronary angioplasty and other investigations for heart disease were significantly reduced after CABG. On the other hand, hospitalization due to chest pain with causes other than ischemic heart disease, congestive heart failure, arrhythmias, and reoperation was more frequent during the 2 years after surgery. The total number of days in hospital was higher during the 2 years after CABG than during the 2 years before, despite the fact that hospitalization due to ischemic events was significantly reduced after the operation.     

The absence of stereoselective P-glycoprotein-mediated transport of R/S-verapamil across the rat jejunum

We have studied the potential stereoselective transport and metabolism of R/S-verapamil in rat jejunum, in-situ. A regional single-pass perfusion of the rat jejunum was performed on 24 rats in six separate groups. The effective permeability (Peff) was assessed for three different concentrations of verapamil, 4, 40 and 400 mg L(-1). The Peff of each enantiomer was also determined at 400 mg L(-1) when chlorpromazine (10 mM) was added to the perfusion solution. Two other groups of rats received R/S-verapamil as an intravenous infusion and the intestinal secretion and metabolism were studied by simultaneously perfusing the jejunum with a control or with chlorpromazine (10 mM) added. The concentrations in the outlet perfusate of each enantiomer of verapamil and norverapamil were assayed with HPLC. R/S-Verapamil is a high permeability drug in the proximal rat small intestine throughout the luminal concentration range studied and complete intestinal absorption was expected. There was an increase of Peff from 0.42 x 10(-4) cm s(-1) to 0.80 x 10(-4) cm s(-1) (P < 0.05) at concentrations from 4 to 400 mg L(-1), respectively. The observed concentration-dependent jejunal Peff and fraction absorbed (P < 0.05) of R/S-verapamil is consistent with the saturation of an efflux mechanism. When chlorpromazine (a P-glycoprotein inhibitor/substrate) was added the jejunal Peff increased to 1.47 x 10(-4) cm s(-1). There was no difference between the Peff of the two enantiomers in any of these experiments. The efflux of R/S-norverapamil into the rat jejunum was high after intravenous administration of R/S-verapamil, suggesting extensive metabolism in the enterocyte. In conclusion, both R/S-verapamil enantiomers are P-glycoprotein substrates, but there is no stereoselective transport of R/S-verapamil in the rat jejunum. The results also suggests that R/S-norverapamil is formed inside the enterocytes.     

Thermal and mechanical characterization of cellulose acetate phthalate films for pharmaceutical tablet coating: effect of humidity during measurements

Films from a polymer used in pharmaceutical coating (cellulose acetate phthalate) were analyzed by thermomechanical techniques including dynamic mechanical thermal analysis (DMTA) and tensile tests. Emphasis was placed on relative humidity (RH) at the measurement site (as opposed to storage or conditioning RH). The films were plasticized with either triethyl citrate or diethyl phthalate. The results show that the films respond rapidly to changes in the environmental humidity. This in turn influences the data obtained from DMTA and tensile testing; thus, good control of the humidity is essential. Absorption isotherms have been obtained for the two types of films, and the results were interpreted in terms of the equilibrium moisture content which is determined by the polar nature of the plasticizer. This factor must be considered when formulating a film composition because moisture can, apart from its influence on mechanical properties, also speed the chemical degradation processes. When the stability of a film composition during storage is studied, the actual measurements on the films should preferably be done at 0% RH, irrespective of the storage RH. At 0% RH, the mechanical testing results will reflect the chemical stability correctly, without interference from plasticizing effect of absorbed water. A functionality test for films has been suggested: DMTA under isothermal conditions using either step or continuous humidity scans. Isothermal dynamic humidity scans on the DMTA were performed for the first time, and the utility of these measurements is discussed.     

Development of young children's prosocial moral judgment: A longitudinal follow-up.

34 4–5 yr old children whose prosocial moral judgment had been assessed in preschool were reinterviewed 18 mo later. At the follow-up, Ss used significantly more needs-oriented and approval-oriented reasoning and less hedonistic reasoning than earlier. High religious participation at the time of the follow-up was positively related to the use of needs-oriented reasoning and negatively related to hedonistic reasoning. (3 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

ON THE INTEGRAL EVALUATION OF TUBULAR REACTOR DATA

An explicit method for evaluating the kinetics of data obtained in an integral tubular reactor has been developed. The method is demonstrated for n:th order irreversible reactions by using experimental data. The reaction order is obtained from the slope and the rate constant is calculated from the intercept in a straight line plot