Potassium-N-Butyl Xanthate as a New Antioxidant for Natural Rubber

Potassium-n-butyl xanthate (PBX) has been synthesized and its role as an efficient antioxidant and accelerator has been verified by cure characteristics and aging studies, and compared with the performance of commercially available antioxidant phenyl-β-naphthylamine (PBN). A suitable mechanism for the role of potassium-n-butyl xanthate in stabilizing the rubber has been suggested.     

Influence of TiB2 content on microstructure and hardness of TiB2-B4C composite

In this study a composite ceramic powder mixture using fine powders of titanium diboride (TiB₂) and boron carbide (B₄C) was consolidated to theoretical density using the technique of plasma pressure compaction. Achieving rapid consolidation of the composite powder mixture is an essential requirement for achieving microstructural control and better mechanical properties in the consolidated end product. The variables chosen in making the composite samples was the titanium diboride (TiB₂) content. The microstructure and hardness of the ceramic composite sample made by consolidating various powder mixtures at a temperature of 1700 °C are compared. Microhardness measurements reveal a gradual increase in hardness with an increase in TiB₂ content in the starting powder mixture. The specific role of TiB₂ content in influencing microstructural development and hardness is presented and discussed.     

Creep life prediction of low-alloy steels based on the β-envelope method

The creep life of low-alloy steels has been analyzed based on the β-envelope method. A parameter that compensates both the stress and the time axes is proposed involving the coefficients of the creep strain-time relations.     

Optimal concentration of epinephrine for vasoconstriction in neck surgery

The addition of epinephrine to local anesthetics decreases bleeding, reduces systemic toxicity, and increases duration of action. However, epinephrine has significant side effects. Four concentrations of epinephrine were compared to determine the minimum concentration required for maximal vasoconstriction. Eighty-one subjects undergoing surgical procedures with general anesthesia were injected with 1% lidocaine containing varying concentrations of epinephrine. Blood flow measurements were then made at 1-minute intervals for 10 minutes using a laser Doppler flowmeter. There were no differences in blood flow reduction between epinephrine concentrations of 1:100,000, 1:200,000, and 1:400,000. However, epinephrine 1:800,000 provided significantly less vasoconstriction. We recommend using an epinephrine concentration of 1:200,000 or 1:400,000 to provide optimal initial hemostasis while minimizing potential side effects.     

Optical activity of a nucleotide-sensitive tryptophan in myosin subfragment 1 during ATP hydrolysis

Male rats of the Wistar strain were divided 4 groups, and give a liquid diet of control feed, bezafibrate (150 mg/kg), ethanol, and ethanol plus bezafibrate for 5 week. The effect of bezafibrate supplementation on rats fed ethanol was examined in terms of the fatty acid composition of the phospholipids in the erythrocyte membrane. In the phospholipids profiles of erythrocyte membranes, PI was significantly decreased. The decrease in PI caused by bezafibrate appeared to substantially affect the membrane and consequently lead to changes in the membrane anchor. In the fatty acid composition of the PC, C20: 4 was significantly decreased in the group receiving alcohol (p < 0.05) but increased in the groups receiving bezafibrate (p < 0.05). In the fatty acid composition of the PE, C16: 0 was significantly increased in the three groups when compared with the control, and C20: 4 was decreased in the alcohol group (p < 0.05). In the fatty acid of SM and PI, C20: 4 was decreased and C18: 0 increased in the alcohol group. In the PS, C14: 0 was increased in the alcohol group, and decreased in the alcohol plus bezafibrate group (p < 0.01). The levels of arachidonic acid in the total fatty acids that constituted the membrane phospholipids were decreased in the rats given ethanol (p < 0.05). However, arachidonic acid in the group of bezafibrate supplementation on rats fed ethanol were elevated in comparison with the alcohol group (p < 0.05). With decreasing arachidonic acid as a marker of alcohol tissue injury following chronic alcohol intake, the effects of bezafibrate supplementation appear to contribute to membrane fluidity by altering the biochemical flexibility of the membrane.     

Incorporating crossover interference into pedigree analysis using the chi 2 model

Crossover interference is now known to exist in humans but to date has been ignored in routine genetic mapping because of the computational burden involved. In a recent paper by Weeks et al. [Hum Hered 1993;43:86-97], interference was accounted for by the use of a variety of multilocus feasible map functions and a crossover model of Goldgar and Fain [Am J Hum Genet 1988;43:38-45]. In this paper, we present an alternative approach to incorporating crossover interference into multilocus likelihood computation, by modelling the underlying chiasma process directly using the chi 2 model, supplemented by an assumption of no chromatid interference. This procedure was applied to the same CEPH consortium chromosome 10 data set that was analyzed by Weeks et al. A fit to the data was achieved which was significantly better than that offered by the no-interference model, and comparable to the best of the alternatives considered by Weeks et al. We briefly discuss the relative merits of the different models for interference.     

The blending of competitive and regulatory strategies: a second opinion

A comparison of the 10 states that as of 30 June 1994 witnessed the highest and lowest percent of health maintenance organization market penetration, and the findings reported in the Dartmouth Atlas of Health Care in the United States, both illustrate dramatic differences among the various states in the distribution, utilization, and cost of hospital and other health services. This article thereafter focuses on the implications of these findings in the context of the states eventually blending competitive and regulatory strategies to constrain hospital expenditures-a conceptual framework that is consistent with Americans being advocates of pluralism when organizing and financing their health care system.     

Role of the divalent metal ion in the NAD:malic enzyme reaction: an ESEEM determination of the ground state conformation of malate in the E:Mn:malate complex

The conformation of L-malate bound at the active site of Ascaris suum malic enzyme has been investigated by electron spin echo envelope modulation spectroscopy. Dipolar interactions between Mn2+ bound to the enzyme active site and deuterium specifically placed at the 2-position, the 3R-position, and the 3S-position of L-malate were observed. The intensities of these interactions are related to the distance between each deuterium and Mn2+. Several models of possible Mn-malate complexes were constructed using molecular graphics techniques, and conformational searches were conducted to identify conformers of malate that meet the distance criteria defined by the spectroscopic measurements. These searches suggest that L-malate binds to the enzyme active site in the trans conformation, which would be expected to be the most stable conformer in solution, not in the gauche conformer, which would be more similar to the conformation required for oxidative decarboxylation of oxalacetate formed from L-malate at the active site of the enzyme.     

Freon inhalational abuse presenting with ventricular fibrillation

Inhalation of volatile halogenated hydrocarbons may produce life-threatening cardiac and neurological toxicity. A 15-year-old boy developed ventricular fibrillation immediately after intentional inhalation of a fluorinated hydrocarbon from an automobile air conditioner recharge unit. After the use of intravenous bretylium, a hemodynamically stable sinus tachycardia was restored. Aspiration pneumonitis and rhabdomyolysis complicated his hospital course before complete neurological recovery. The mechanism and treatment of cardiac arrhythmias after volatile fluorinated hydrocarbon inhalation are reviewed.     

IgG3 reactive rheumatoid factor in rheumatoid arthritis: etiologic and pathogenic considerations

Rheumatoid factor (RF) is a polyclonal autoantibody directed against the Fc portion of IgG. Although the role of RF in patients with rheumatoid arthritis (RA) is unclear, immune complexes that form between RF and IgG can activate the classical complement (C) pathway, leading to pathogenic outcomes involving inflammatory events and tissue damage. The specificity of serum RF and RF produced by rheumatoid synovial cells (RSC) is different. Serum RF has specificity for rabbit IgG and human IgG subclasses IgG1, 2, and 4, but binds poorly to IgG3. The affinity of serum RF for IgG Fc is low, having an association constant of 10(4)-10(5) M-1. RSC RF, however, has specificity for human IgG and high avidity for IgG3. Because of this greater specificity and avidity for IgG3, and because RSC RF may be pathogenically more important than serum RF, an important role for IgG3-reactive RF in RA may exist. Binding of RF to IgG may be dependent on the allotype and glycosylation of IgG. Infectious agents present in RA patients may directly or indirectly induce the production of certain RF. In this communication, we review and expand on several observations examining the role of IgG3-reactive RF in RA including: 1) binding differences between RF derived from RSC and serum; 2) glycosylation characteristics of IgG and its interaction with RF; 3) apparent allotype dependent binding of IgG3-reactive RF; and 4) possible relationship between infectious agents and the production of IgG3-reactive RF. Taken together, these observations suggest an important role for IgG3-reactive RF in better understanding the etiology and pathogenesis of RA.