Photo induced hydrogen evolution from water in the presence of EDTA and a supported catalyst

A flow reaction system was developed to study the steady state kinetics of hydrogen evolution in the presence of Ru(bipy)²⁺, MV⁺², EDTA and a heterogeneous supported catalyst. Under the conditions used, steady state rates similar to those previously reported with colloidal Pt particles were attained. Furthermore, over much of the range of concentrations used, the reaction was zero order and it did not exhibit an Arrhenius behavior. Examination of the various rate determining steps involved led us to conclude that surface processes such as the recombination and desorption of hydrogen from the Pt surface might be rate determining.     

Early child-care selection: variation by geographic location, maternal characteristics, and family structure

More than half of all U.S. infants and toddlers spend at least 20 hr per week in the care of a nonparent adult. This article uses survival analysis to identify which families are most likely to place their child in care and the ages when these choices are made, using data from a national probability sample of 2,614 households. Median age at first placement is 33 months, but age varies by geographic region, mother's employment status during pregnancy, mother's education level, and family structure (1 vs. 2 parents, mother's age at 1st birth, and number of siblings). Controlling for these effects, differences by race and ethnicity are small. Implications for studies of child-care selection and evaluations of early childhood programs are discussed.     

Comparative studies of O,O-dialkyl-O-chloromethylchloroformimino phosphates: interaction with neuropathy target esterase and acetylcholinesterase

Acetylcholinesterase (AChE) and neuropathy target esterase (neurotoxic esterase, NTE) are two major target enzymes for organophosphorus (OP) esters. The relative potency of an OP ester to react with AChE or with NTE in vitro correlates with its relative potency in vivo to cause acute toxicity (death) or organopohosphate-induced delayed neurotoxicity (OPIDN). On this basis extrapolation from in vitro to in vivo data now seems justifiable to predict risk of OPIDN. The kinetics of NTE and AChE inhibition by experimental pesticides of the general formula (RO)2P(O)ON=CClCH2Cl, where R = methyl, ethyl, isopropyl, propyl, isobutyl, butyl, pentyl, has been studied. Compounds with short R (methyl, ethyl) were shown to be far more potent inhibitors of AChE than NTE. Both anti-NTE activity, selectivity for NTE and, correspondingly, the propensity of compounds to cause OPIDN rise with increasing their hydrophobicity. A high value of ki(NTE)/ki(AChE) for R = pentyl suggests that this compound would have the potential to cause OPIDN at doses lower than the LD50. A quantitative structure-activity relationships (QSAR) analysis indicated that NTE and AChE have different structural and electronic requirements for their respective OP inhibitors.     

Reading epilepsy: report of five new cases and further considerations on the pathophysiology

Liposomes, microscopic lipid vesicles consisting of concentric phospholipid bilayers enclosing discrete aqueous spaces, have been investigated extensively as carries for drugs in attempts to achieve selective deposition and/or reduced toxicity. Liposomes radiolabeled with gamma emitters (67Ga, 111In and 99mTc) have been used for imaging purposes. Liposomes as formulated in the past, are rapidly taken up by cells of the mononuclear phagocyte system, primarily those located in liver and spleen. However, it has been shown during the last two decades that the in vivo behavior of liposomes can be modulated by modifying their formulation. The size and the lipid composition have a major influence on the blood clearance rate, hepatic uptake and splenic uptake of liposomes. The development of long circulating liposomes, in particular coating of the bilayer with polyethyleneglycol (PEG) resulted in liposomes that oppose recognition by the MPS, thus displaying even longer circulatory half-lives. By carefully adjusting the liposomal formulation, the in vivo characteristics of liposomes can be tailored such that they become suitable vehicles for imaging various pathological processes in vivo. Liposomes have been proposed for tumor imaging, for infection imaging and as blood pool markers. Here, the factors that determine the in vivo behavior of liposomes and the current status of liposome-based radiopharmaceuticals are reviewed.     

Antibodies against transforming growth factor-beta 1 suppress intimal hyperplasia in a rat model

Intimal hyperplasia is induced by therapeutic vascular interventions and often results in clinically important narrowing of the vascular lumen. Examination of the role of TGF-beta 1 in a rat carotid artery injury model confirmed the presence of a previously reported increase in TGF-beta 1 mRNA in the media of injured arteries. Administration of neutralizing anti- TGF-beta 1 antibodies significantly (P < 0.05) reduced the size of the intimal lesions that developed after carotid balloon injury. A control antibody had no effect. The intimal/medial area ratio was also reduced in the anti-TGF-beta 1 group relative to controls (P < 0.01). Immunohistochemical staining showed that two TGF-beta 1-induced extracellular matrix components, EDA + fibronectin and versican, were greatly increased in the untreated neointimal lesions, but were almost completely absent from the lesions of the anti-TGF-beta 1-treated animals. We conclude that TGF-beta 1 is causally involved in the development of intimal hyperplasia, and that anti-TGF-beta 1 agents may be useful in achieving at least partial control of this condition.     

Spontaneous regression of familial glioma of the optic nerve in a boy with suspected neurofibromatosis 1 (Recklinghausen''s disease)

A boy with a large intracranial glioma of the optic tract and probable neurofibromatosis of the first type was observed for 8 years since the age of 7 years. A series of MR scans was made over this period. A notable decrease of the tumor size was seen on its signals on the MR scans. This was paralleled by an improvement of the vision acuity, color field, and visual field on the involved eye. Patient's grandmother had an intracranial glioma of the optic nerve with a slight but stable decrease of the visual functions. The tumor shape in the grandmother and grandchild is remarkably similar. This finding in the grandmother and stability of her vision decreased from childhood permit us to propose that the tumor did not develop and even regressed with time.     

High-temperature properties of the Bi-Sr-Ca-Cu-O system: Simultaneous occurrence of melting, oxygen desorption, and a metal-insulator transition

We have investigated the temperature dependence of the electrical transport and the thermogravimetric properties, from -200°C to +1000, of the Bi-Sr-Ca-Cu-O high-temperature superconductor. We conclude that this system has a cooperative, simultaneous-melting/oxygen desorption/metal-insulator transition that occurs near 900°C. We speculate on its nature and on its relationship to phenomena found in other high-T _c superconductors.     

Corrosion and wear properties of multipurpose coatings deposited by ion-beam-assisted deposition

Electrochemical measurements and wear tests were performed on aluminium and aluminium alloy coatings containing magnesium for uniform and local pitting corrosion protection of low carbon steel substrates. Final hard chromium nitride and aluminium nitride layers were deposited at the surface of the protective films in order to lower friction and wear. The results show that wear and corrosion protection can be improved by use of bifunctional multilayers. The coatings for multipurpose application were generated by ion-beam-assisted deposition. The defined intrinsic film stress controlled by the ion-to-atom arrival ratio influences the corrosion properties. Increasing the ion-to-atom ratios usually improves the corrosion resistance.     

Transient studies on methane oxidative coupling over alkali-metal promoted titanate catalysts

A transient method to study the role of the different oxygen species involved in oxidative coupling of methane is discussed. The method is applied to two new active catalysts for this process, which are based on alkali metal loaded titanates of lanthanum and nickel and also to a lithium/titania catalyst used in previous works. The results show that the participation of lattice oxygen in the formation of C2 products depends on the Li loading and the type of titanate used.