In situ measurement of free radical formation during the thermal decomposition of grape seed oil using “spin trapping” and electron paramagnetic resonance spectroscopy

The generation of free radical intermediates as a result of the oxidative degradation of lipid molecules during the heating of grape seed oil has been established by a combination of “spin trapping” and electron paramagnetic resonance spectroscopy. The effects of temperature on the rates of formation and decomposition of the adduct with the spin trapN-t-butyl-α-phenylnitrone (PBN) have been investigated over the temperature range 105–180°C. The results show that PBN can be used for studies of free radical processes in oils in situ in the spectrometer cavity at temperatures up to 180°C.     

Time-of-day effects in maximal anaerobic leg exercise

The pathogenesis of AIDS is a complex and prolonged process that is affected by a variety of cofactors, including the abuse of both intravenous and smoked (crack) cocaine. The exact mechanisms by which cocaine facilitates this disease are yet to be proven, but likely include a combination of increased risk due to cocaine-related social behaviours, a wide-ranging capacity for cocaine to suppress the immune system, and an effect of cocaine on the infectivity and replication of HIV. While sometimes contradictory, both human and animal studies document that cocaine alters the function of natural killer (NK) cells, T cells, neutrophils and macrophages, and alters the ability of these cells to secrete immunoregulatory cytokines. In addition to these effects on the immune system, cocaine also enhances the infectivity and/or replication of HIV when tested using human cells in vitro.     

Synthesis of phosphonated styrenic copolymers and their chemical modifications

We report, for the first time, the synthesis of a phosphonated styrenic monomer dimethyl vinylbenzyl phosphonate (VBP) according to the methods described in the literature for its equivalent diethyl vinylbenzyl phosphonate, and also the monodealkylation of this monomer (VBP) to the monosalt in a neutral medium and to the corresponding monoacid via a sulfonic resin. Various statistical copolymers and statistical block copolymers of styrene and VBP were prepared with different molar percentages of these comonomers. The dealkylation of statistical copolymers was carried out in the same way as for VBP. The phosphonated statistical copolymers, prepared, were characterized by various analytical methods which show good agreement with their structures. © 2002 Society of Chemical Industry     

Modification of alkenyl chain profile in plasmalogens of rat heart mitochondria by dietary trielaidin

Effects of dietary trielaidin upon the alkenyl chain profile of plasmalogens were studied using heart mitochondria of rats fed a semi-purified diet containing 10% of fat supplement in which elaidic acid accounted for 69% of total fatty acids. Alkyl substituted dioxane (ASD) derivatives of the alkenyl groups of plasmalogens were prepared and analyzed by silver nitrate TLC and by GLC on different phases (BDS and OV-275). After two months of feeding the experimental diet, 40% of the ASD contained atrans-octadecenyl chain, suggesting that dietary elaidic acid was reduced in vivo to the corresponding alcohol and incorporated into plasmalogens. There was a simultaneous decrease in the percentage of ASD containing saturated chains, but the percentage of ASD substituted withcis-octadecenyl chains was not significantly affected. These observations suggested that elaidic acid may compete with saturated fatty acids, but not withcis-octadecenoic acids during the plasmalogen biosynthesis. Feeding trielaidin did not seem to have any significant influence on the relative proportions of plasmalogens, which accounted for 11–12%, on a phosphorus basis, of total heart mitochondria phospholipids.     

Detection of Heat-Resistant Proteases Produced by Psychrotrophs in Refrigerated Milk

Proteases from four species of Pseudomonas were added to pasteurized milk at .18, 1.8, and 18 units of protease activity per milliliter followed by incubation at 5 C for 18 days. During this period milks were analyzed every 2 days for proteolysis by methods of Hull, ninhydrin, and absorption at 280 nm. Sensory analysis was done twice weekly for 18 days. There were no significant differences noted for protease activity when ninhydrin and absorption at 280 nm were used; however, only 18 units protease/ml were detected by the Hull test. Sensory evaluation correlated with the Hull test data. When 50 and 500 cells/ml were added to milk, a curvilinear increase in proteolysis was noted by 11 and 13 days, respectively, for three of the four Pseudomonas species as detected by the Hull method. Heat inactivation of the proteases at 62.8°C for 30 min was 0 to 73.1% and 10 to 36% as measured by the Hull and agar diffusion methods, respectively.     

Elaboration and characterization of magnesium-substituted La5Ni19 hydride forming alloys as active materials for negative electrode in Ni-MH battery

The crystallographic structure as well as the thermodynamic and electrochemical properties of the hydrogen absorbing compounds La₅Ni₁₉ and La₄MgNi₁₉ have been determined. X-ray diffraction and microprobe analysis have shown the presence of a single hexagonal (P6₃/mmc) phase for the Mg-free binary compound whereas only one composition but two different crystallographic structures, hexagonal (P6₃/mmc) and rhombohedral (R-3m), are observed for La₄MgNi₁₉. Each phase can be described as the stacking along the c-axis of n[A₂B₄]/m[AB₅] sub-units with n = 1 and m = 3 and A = La, Mg; B = Ni. Depending on the stacking sequence, either the hexagonal or the rhombohedral phase is obtained. Thermodynamic properties toward hydrogen uptake (capacity and equilibrium pressure) and electrochemical properties (cycling behavior) in alkaline medium have been measured and are compared for these compounds with and without magnesium. It is observed that the Mg-free compound exhibits a much lower reversible hydrogen capacity than the Mg-containing one. However, despite larger capacity, this latter compound remains to be optimized in term of cycle life.     

Eyepiece focus and vergence/accommodation conflict: Implications for night‐vision devices

Abstract— Aviation increasingly conducts night operations using night‐vision devices. However, design of some aspects may limit performance. As pointed out by Kotulak, vergence/accommodation mismatch in NVDs, usually due to eyepiece focus misadjustments, is sometimes a source of visual acuity (VA) decrement. The increased separation between sensors, existing in some binocular helmetmounted displays, was also identified to be potentially responsible for decreased VA at short distances. Based upon knowledge pertaining to vergence and accommodation, a study was performed to better understand the problem of dissociation accommodation/convergence. Different conditions of interocular separation and viewing distances were used. Twelve subjects participated and were asked to resolve Landolt C charts using night‐vision goggles. The results show that, with the eyepiece focus fixed at 10 m, the decrease in VA is roughly proportional to the interocular separation, when looking at short distances. A fixed eyepiece focus at 4 m considerably reduces the conflict and results in improved VA. An additional experiment was conducted to investigate the effect of fixing the objective lenses focus at infinity. With this setting, the decrease in VA at a short distance was such that effects of the mismatch accommodation/convergence are no longer apparent regardless of the interocular separation.     

Syntheses and characterizations of new copolymers of vinylidene cyanide with para substituted α acetoxystyrenes

Summary Vinylidene cyanide has been copolymerized in solution by radical reaction with equal initial mole fraction of para substituted acetoxystyrenes. The copolymers have been characterized by means of DSC, TGA and GPC. These products are stable up to 220° and have no visible glass transition temperature. The microstructure of these new copolymers has been studied by ¹³CNMR; they have an alternating structure and monomers units are arranged in head-to-tail placements.