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     

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.     

Synthesis of telechelic monodispersed diols

Summary The synthesis of telechelic monodispersed diols produced from the radical telomerization of an excess of undecylenol with commercialy available , -dithiols HSC₂H₄XC₂H₄SH (X=0, S or CH₂) initiated by peroxides is presented. In each case, the diols were obtained selectively and quantitatively and they were characterized by both ¹H and ¹³C NMR. Their physical characteristics (Tg, T_m and decomposition temperatures) were determined. Such compounds are thermally more stable than polydispersed telechelic commercially available diols.     

A Flavanone and Two Phenolic Acids from Chrysanthemum morifolium with Phytotoxic and Insect Growth Regulating Activity

Leaves of Chrysanthemum morifolium cv. Ramat were extracted sequentially with hexane, ethyl acetate, and methanol. The methanol fraction, when incorporated into artificial diet was found to reduce the growth of cabbage looper (Trichoplusia ni Hubner) larvae at concentrations between 500 and 5000 ppm of diet. Fractionation of the methanol extract on a Sephadex column yielded five fractions, three of which reduced the weight of larvae relative to the control. One fraction was analyzed using high performance liquid chromatography (HPLC) and found to contain three main constituents. These compounds were purified using a combination of gel permeation chromatography on Sephadex LH20 and HPLC, and analyzed by 1H and 13CNMR as well as undergoing chemical and physical analyses. The compounds were identified as: 1, chlorogenic acid (5-O-caffeoylquinic acid); 2, 3,5-O-dicaffeoylquinic acid; and 3, 3', 4',5-trihydroxyflavanone7-O-glucuronide (eriodictyol7-O-glucuronide). At concentrations between 100 to 1000 ppm these compounds reduced both growth and photosynthesis of Lemna gibba L. with the order of efficacy being: flavanone > chlorogenic acid > 3,5-O-dicaffeoylquinic acid. Furthermore, when incorporated separately into artificial diet these compounds, at 10 to 1000 ppm, enhanced or reduced growth of the cabbage looper (Trichoplusia ni) and gypsy moth (Lymantria dispar L.).     

Kinetics of the selective catalytic reduction of NO by NH3 on a Cu-faujasite catalyst

The kinetics of the selective catalytic reduction (SCR) of NO by NH₃ in the presence of O₂ has been studied on a 5.5% Cu-faujasite (Cu-FAU) catalyst. Cu-FAU was composed of cationic and oxocationic Cu species. The SCR was studied in a gas phase-flowing reactor operating at atmospheric pressure. The reaction conditions explored were: 458<T_R<513 K, 2503 (ppm) < 4000, 12 (%) < 4. The kinetic orders were 0.8–1 with respect to NO, 0.5–1 with respect to O₂, and essentially 0 with respect to NH₃. Based on these kinetic partial orders of reactions and elementary chemistry, a wide variety of mechanisms were explored, and different rate laws were derived. The best fit between the measured and calculated rates for the SCR of NO by NH₃ was obtained with a rate law derived from a redox Mars and van Krevelen mechanism. The catalytic cycle is described by a sequence of three reactions: (i) Cu^I is oxidized by O₂ to “Cu^II-oxo”, (ii) “Cu^II-oxo” reacts with NO to yield “Cu^II-N_xO_y”, and (iii) finally “Cu^II-N_xO_y” is reduced by NH₃ to give N₂, H₂O, and the regeneration of Cu^I (closing of the catalytic cycle). The rate constants of the three steps have been determined at 458, 483, and 513 K. It is shown that Cu^I or “Cu^II-oxo” species constitute the rate-determining active center.