Controlled growth of SnO(2) hierarchical nanostructures by a multistep thermal vapor deposition process

Branched and sub-branched SnO(2) hierarchical architectures in which numerous aligned nanowires grew on the surface of nanobelt substrates have been obtained by a multistep thermal vapor deposition route. Branch size and morphology can be controlled by adjusting the temperature and duration of growth. The same approach was used to grow branched ZnO-SnO(2) heterojunction nanostructures. In addition, the third level of SnO(2) nanostructures was obtained by repeating the vapor deposition growth process. This technique provides a general, facile, and convenient approach for preparing even more complex nanoarchitectures, and should open up new opportunities for both fundamental research and applications, such as nanobelt-based three-dimensional nanodevices.     

Novel method for measurement of glutathione kinetics in neonates using liquid chromatography coupled to isotope ratio mass spectrometry

A novel analytical method using liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS) was developed for measuring the fractional synthesis rate (FSR) of glutathione (GSH) in neonates after infusion of [1-(13)C]-glycine as a tracer. After transformation of GSH into GSSG, its dimeric form, the intra-erythrocytic concentration and (13)C-isotopic enrichment of GSH were determined using 200 microL of blood. The results showed that, using LC/IRMS, the concentration (range of micromol/mL) was reliably measured using norvaline as internal standard with precision better than 0.1 micromol/mL. In addition, the (13)C-isotopic enrichment measured in the same run gave reliable values with excellent precision (with standard deviation (sd) lower than 0.3 per thousand) and accuracy (measured between 0 and 2 Atom % Excess (APE)). The inter-assay repeatability of delta(13)C of norvaline used as internal standard with in vivo samples was assessed at -26.07 +/- 0.28 per thousand with coefficient of variance (CV) at 1.1%. The FSR calculated either with GSH or GSSG showed similar results with slightly higher values for GSSG (41.6 +/- 4.7 and 46.5 +/- 4.4, respectively). The slightly lower FSR of GSH is probably due to interfering compounds in the biological matrix. Successfully used in a clinical study, this rapid and reliable method opens up a variety of kinetic studies with relatively low administration of tracer infusates, reducing the total cost of the study design. The small volume of blood needed enables studies even in extremely small subjects, such as premature infants, as reported in this study.     

A policy iteration algorithm for fixed point problems with nonexpansive operators

The aim of this paper is to solve the fixed point problems:

On the degree of iterates of automorphisms¶of the affine plane

For a polynomial automorphism f of ?² _ℂ, we set τ = deg f ²)/(deg f). We prove that τ≤ 1 if and only if f is triangularizable. In this situation, we show (by using a deep result from number theory known as the theorem of Skolem–Mahler–Lech) that the sequence (deg f ⁿ ) _{n ∈ℕ} is periodic for large n. In the opposite case, we prove that τ is an integer (τ≥ 2) and that the sequence (deg f ⁿ ) _{n ∈ℕ} is a geometric progression of ratio τ. In particular, if f is any automorphism, we obtain the rationality of the formal series . Received: 1 December 1997     

Reactivity between CuxV2O5 and AgyV2O5 bronzes studied by spark plasma sintering

A method based on the analysis of reaction layers that form in Cu_xV₂O₅–Ag_yV₂O₅ interdiffusion couples annealed by spark plasma sintering to quickly explore the Cu–Ag–V₂O₅ ternary system at high pressure is presented. Through use of microanalysis profiling, the phases occurring in this system have been obtained much faster than by conventional techniques of solid-state chemistry. Microdiffraction profiling has also been used to properly identify the Cu_0.5Ag_0.5V₂O₅ phase in the reaction layer between CuV₂O₅ and Ag_0.8V₂O₅. The stability domains of the phases have been approximately determined and interpreted. In most cases, reaction kinetics occurs quickly, as expected by the high diffusion coefficient of Cu and Ag in V₂O₅. Though the experiments have been carried out under high pressure (75 MPa), the same phases are obtained than with sealed quartz tubes experiments.     

A simple method to significantly increase filaments’ length and?ionization density

A simple method to produce longer filaments with higher ionization density in air by controlling the diameter of an aperture in the laser beam path is studied via an analysis of the backscattered N₂ fluorescence collected by LIDAR. Significant increase in the fluorescence signal (approximately by a factor of five depending on the conditions) and an increased filament length was observed at an optimum diameter. 3D + time stochastic numerical simulations have shown that the optimum aperture size corresponds to the case of multiple filament ‘squeezing’ around the propagation axis forming the regularized elongated structure with higher overall amount of plasma. The optimum range of aperture sizes is the same for the initial transverse perturbation scale variation at least within a factor of three.     

Incorporating glycidyl methacrylate into block copolymers using poly(methacrylate‐ran‐styrene) macroinitiators synthesized by nitroxide‐mediated polymerization

Methyl methacrylate/styrene (MMA/S), ethyl methacrylate/styrene (EMA/S) and butyl methacrylate/styrene (BMA/S) feeds (>90 mol % methacrylate) were copolymerized in 50 wt % p‐xylene at 90 °C with 10 mol % of additional SG1‐free nitroxide mediator relative to unimolecular initiator (BlocBuilder^®) to yield methacrylate rich copolymers with polydispersities _w/ _n = 1.23–1.46. k_pK values (k_p = propagation rate constant, K = equilibrium constant) for MMA/S copolymerizations were comparable with previous literature, whereas EMA/S and BMA/S copolymerizations were characterized by slightly higher k_pK's. Chain extensions with styrene at 110 °C initiated by the methacrylate‐rich macroinitiators (number average molecular weight _n = 12.9–33.5 kg mol^?1) resulted in slightly broader molecular weight distributions with _w/ _n = 1.24–1.86 and were often bimodal. Chain extensions with glycidyl methacrylate/styrene/methacrylate (GMA/S/XMA where XMA = MMA, EMA or BMA) mixtures at 90 °C using the same macroinitiators resulted frequently in bimodal molecular weight distributions with many inactive macroinitiators and higher _w/ _n = 2.01–2.48. P(XMA/S) macroinitiators ( _n = 4.9–8.9 kg mol^?1), polymerized to low conversion and purified to remove “dead” chains, initiated chain extensions with GMA/MMA/S and GMA/EMA/S giving products with _w/ _n ～ 1.5 and much fewer unreacted macroinitiators (<5%), whereas the GMA/BMA/S chain extension was characterized by slightly more unreacted macroinitiators (～20%). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2574–2588, 2009     

Criteria to define the standard deviation for proficiency assessment for the determination of essential trace elements in serum: comparison of Z-scores based on the Horwitz function or on biological variability

A critical issue in the organisation of Proficiency Testing/External Quality Assessment Schemes is the definition of the criteria against which the performance of individual laboratories should be evaluated. Organisers of EQAS in Occupational and Environmental Laboratory Medicine (http://www.occupational-environmental-laboratory.com) collaborate to define common acceptable levels of performance. The aim of this study was to compare the Horwitz function to the Fraser’s approach. Sets of results obtained from the distribution of test materials in the Network schemes (for the measurands: copper, selenium or zinc in serum) were used to calculate Z-scores according to both approaches. Quality specifications derived from both approaches were also compared to the standard deviations obtained. Except for selenium, Horwitz criteria suggests a more stringent evaluation than Fraser criteria, the latter being very stringent as regard the participant analytical variability.     

Oxidation and chlorination reactions of perfluoroketene-N,S-acetals

The paper presents the results of the investigation of oxidation and chlorination reactions of perfluoroketene-N,S-acetals. Oxidation reactions of perfluoroketene-N,S-acetals proved to be dependent on the nature of oxidizing agent and led to the formation of corresponding sulfone in the case of m-chloroperbenzoic acid or amides of α-H-perfluoroalkane carboxylic acids in the case of tert-butyl hydroperoxide or hydrogen peroxide. Reaction of 1-tert-butylsulfanyl-2,3,3,4,4,4-hexafluoro-1-[N-methyl,N-((S)-α-methylbenzyl)amino]-but-1-ene with sulfuryl chloride demonstrated the chlorination of perfluoroketene-N,S-acetals as a new approach in the synthesis of chiral α-chloro perfluoroalkane carboxylic acid amides.     

Valid inequalities for MIPs and group polyhedra from approximate liftings

In this paper, we present an approximate lifting scheme to derive valid inequalities for general mixed integer programs and for the group problem. This scheme uses superadditive functions as the building block of integer and continuous lifting procedures. It yields a simple derivation of new and known families of cuts that correspond to extreme inequalities for group problems. This new approximate lifting approach is constructive and potentially efficient in computation. J.-P. P. Richard was supported by NSF grant DMI-348611.