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Proper Choice (proper + choice)
Selected AbstractsStereoselective Aldol Reactions Catalyzed by Acyclic Amino Acids in Aqueous MicellesHELVETICA CHIMICA ACTA, Issue 1 2007Dong-Sheng Deng Abstract The catalytic properties of all proteinogenic, acyclic amino acids for direct aldol reaction in H2O, assisted by various surfactants, were investigated. The basic and neutral amino acids were shown to be efficient catalysts, giving rise to good-to-excellent yields of adducts (up to 95%), with moderate-to-good diastereoselectivities (up to 86%), L -arginine being the most-effective catalyst. The syn/anti diastereoisomer ratio could be readily tuned by proper choice of the amino acid used. Also, the range of substrates that underwent the reaction was extended to less-reactive aldehydes carrying electron-donating Br substituents. [source] Polymeric Nanohairs: Stooped Nanohairs: Geometry-Controllable, Unidirectional, Reversible, and Robust Gecko-like Dry Adhesive (Adv. Mater.ADVANCED MATERIALS, Issue 22 200922/2009) Kahp Suh, Hong Lee, and co-workers present on p. 2276 a simple, yet robust method for fabricating an array of stooped "nanohairs" by applying a proper choice of materials and post e-beam exposure, even for an aspect ratio of 10. The stooped nanohairs possess the unidirectional feature of frictional adhesion with a remarkably high adhesion force (,11 N cm,2). [source] Stooped Nanohairs: Geometry-Controllable, Unidirectional, Reversible, and Robust Gecko-like Dry AdhesiveADVANCED MATERIALS, Issue 22 2009Tae-il Kim A simple yet robust method to fabricate an array of stooped nanohairs is presented, with a proper choice of material and post e-beam exposure even for an aspect ratio of 10. The stooped nanohairs have the unidirectional feature of frictional adhesion with a remarkably high adhesion force (,11,N cm,2). [source] Unusual low-intensity regime in laser-induced molecular photodissociationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2009R. Lefebvre Abstract Previous investigations of laser-induced photodissociation of a diatomic molecule (Atabek et al., Phys Rev A 2006, 74, 063412 and Atabek and Lefebvre, Phys Rev A 2008, 78, 043419) have shown that some of the Floquet eigenstates have the property that at some critical intensities their width is vanishing. These intensities are wavelength dependent. We exploit further this property by showing that by a proper choice of the wavelength, the critical intensity for a Floquet state originating from a given field-free vibrational state can be made vanishingly small. In such a case, the rate increases with intensity in an abnormally slow way. The wavelengths, which are required to reach this regime, can be derived accurately from the semiclassical criterion to obtain a zero-width resonance. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Asymmetric Carbonyl Reductions with Microbial KetoreductasesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2008Menno Abstract The biocatalytic reduction of ,-keto esters and some aromatic ketones in the presence of a variety of ketoreductases from different microbial origins was investigated. The prochiral selectivity was generally high and both product enantiomers could be obtained by a proper choice of enzyme. Aromatic ketones reacted slower than the esters but the prochiral selectivity was often high. The organic cosolvent tolerance of these enzymes was rather variable but useful activity could be maintained in a number of cases. Reduction of the oxidized cofactors NAD and NADP, employing 2-propanol as a sacrificial reductant, was catalyzed by the ketoreductases from Rhodococcus erythropolis and Lactobacillus kefir, respectively. [source] New Approach to Biphasic Waveforms for Internal Defibrillation:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000Fully Discharging Capacitors Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 ,F) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 ,F, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 ± 2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of ,40 ,F had the same E50 (6.7 ± 1.7 J to 7.3 ± 3.9 J) as the single-capacitor truncated waveform (7.3 ± 3.7 J), whereas waveforms with phase-2 capacitors of ,60 ,F had an extremely high E50 (14.5 ± 10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of ,60 ,F additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344 ± 65 V to 407 ± 50 V vs 339 ± 83 V). Conclusion: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors. [source] Specific recommendations for PROs and HRQoL assessment in allergic rhinitis and/or asthma: a GA2LEN taskforce position paperALLERGY, Issue 8 2010F. Braido To cite this article: Braido F, Bousquet PJ, Brzoza Z, Canonica GW, Compalati E, Fiocchi A, Fokkens W, Gerth van Wijk R, La Grutta S, Lombardi C, Maurer M, Pinto AM, Ridolo E, Senna GE, Terreehorst I, Todo Bom A, Bousquet J, Zuberbier T, Baiardini I. Specific recommendations for PROs and HRQoL assessment in allergic rhinitis and/or asthma: a GA2LEN taskforce position paper. Allergy 2010; 65: 959,968. Abstract The GA2LEN taskforce on Patient-Reported Outcomes (PROs) and Health-Related Quality of Life (HRQoL) published in 2009 a position paper concerning PROS and HRQoL assessment in clinical trials on allergy. Because of the specificity of this topic in asthma and rhinitis, specific recommendations are needed. The aim of this position paper is to define PROs and their meaning in asthma and rhinitis research, explore the available tools to provide criteria for a proper choice, identify patient-related factor which could influence PROs assessment, define specific recommendations for assessment, analysis and results spreading, underline the unexplored areas and unmet needs. PROs assessment is gaining increasing importance, and it must be performed with a rigorous methodological procedure and using validated tools. This approach enables to better understand patient-related factors influencing clinical trials and real-life management outcomes, identify patients subgroups that can benefit from specific treatment and management plan and tailor treatment to address PROs (not only physician-defined targets) to improve asthma and rhinitis management. [source] Entanglement swapping in presence of dephasingPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2009J. Dajka Abstract Entanglement which originates from a pair of non-interacting qubits by means of entanglement swapping is discussed when dephasing mechanisms are present. Then, the exact reduced dynamics can be evaluated for two pairs of independent qubits which each are coupled to their own bosonic environment. Each of two pairs of qubits is initially maximally entangled. The conditions for the entanglement survival at asymptotic long times in terms of environment spectral properties are elaborated. It is shown that these conditions hold true also for the inter,pair entanglement stemming. Entanglement swapping can effectively been controlled by a proper choice of initial state of the finite environment (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Two-dimensional electrons occupying multiple valleys in AlAsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2006M. Shayegan Abstract Two-dimensional electrons in AlAs quantum wells occupy multiple conduction-band minima at the X-points of the Brillouin zone. These valleys have large effective mass and g -factor compared to the standard GaAs electrons, and are also highly anisotropic. With proper choice of well width and by applying symmetry-breaking strain in the plane, one can control the occupation of different valleys thus rendering a system with tuneable effective mass, g -factor, Fermi contour anisotropy, and valley degeneracy. Here we review some of the rich physics that this system has allowed us to explore. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Intraply and interply hybrid composites based on E-glass and poly(vinyl alcohol) woven fabrics: tensile and impact propertiesPOLYMER INTERNATIONAL, Issue 9 2004Prof Alessandro Pegoretti Abstract E-glass and poly(vinyl alcohol) (PVA) fibres were used to produce both homogeneous and hybrid composites with an orthophthalic unsatured polyester resin. Results are presented regarding the tensile and impact behaviour of both intraply and interply hybrid composites, with particular regard to the effects of the plies stacking sequence and the loading direction. With a proper choice of composition and stacking sequence, E-glass/PVA hybrid composites were proved to achieve a property profile superior to those of homogeneous E-glass laminates in terms of specific properties. In particular, hybridization with PVA fibres resulted in improving the specific impact energy of E-glass laminates. Resistance to impact crack propagation was higher for intraply with respect to interply hybrid composites, as evidenced by their ductility index values. Copyright © 2004 Society of Chemical Industry [source] Ovum Pick-up in Sheep: a Comparison between Different Aspiration Devices for Optimal Oocyte RetrievalREPRODUCTION IN DOMESTIC ANIMALS, Issue 2 2006C Rodríguez Contents In vivo ovum pick-up (OPU) in sheep may be improved with a proper choice of aspiration elements (needle and tubing) and aspiration vacuum pressure. In the present study, two experiments were carried out. In Expt 1, visible follicles in ovaries of slaughtered ewes (treated separately according to their diameters: small <3 mm, medium 3,5 mm and large >5 mm) were aspirated using different combinations of the three studied factors such as aspiration flow rate (10, 20, 30, 40 and 50 ml water/min), needle gauge (18 and 20 G) and tubing inner diameter (1, 2 or 3 mm internal diameter). In Expt 2, a study with two 18 G needles of different lengths (18 G: 82 mm; 18 GL: 600 mm) was carried out, using ovaries obtained post-mortem, and performing in vivo laparoscopic follicular aspiration on ewes. We considered good quality oocytes as those with both complete compact cumulus and a homogeneous cytoplasm. Recovery rate, proportion of good quality oocytes (good quality oocytes/100 oocytes recovered) and overall efficiency (good quality oocytes/100 follicles aspirated) were noted. In Expt 1, aspiration flow rate affect remarkable proportion of good quality oocytes (69.5%, 50.5%, 44.8%, 36.5% and 28.3% for flows from 10 to 50 ml/min respectively, p < 0.05). Needle gauge did not affect aspiration device efficiency. Thin and intermediate tubings were more effective (overall efficiency rates: 34.9%, 32.3% and 28.1% for 1, 2 and 3 mm respectively, p < 0.05). Follicle size did not affect recovery rate, but proportion of good quality oocytes was higher for large (77.9%) and medium (64.4%) follicles (p < 0.05). Finally, some combinations of the aspiration device showed greater effectiveness. In Expt 2, needle length did not influence recovery rate, but good quality oocytes rate was significantly modified both post-mortem and in vivo (good quality rate for 18 G vs 18 GL needles: 69.5% vs 47.7% and 58.1% vs 25.4%, post-mortem and in vivo respectively, p < 0.05). We conclude that low-aspiration flow rates (10 and 20 ml/min) with thin or intermediate tubings (1 and 2 mm), and any short needle (18 G or 20 G) are the most adequate aspiration factors for OPU in sheep. [source] Applying a Thermodynamic Model to the Non-Stoichiometric Precipitation of Barium SulfateCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2003L. Vicum Abstract Thermodynamic models for aqueous Ba2+ -SO42, -Na+ -Cl, -solutions are compared in their accuracy to predict ion activities in saturated and supersaturated solutions. The Pitzer and the Bromley model are employed, taking into account ion pair formation of barium sulfate. Such models are then used to describe particle nucleation and growth, and finally they are imbedded in a mechanistic mixing-precipitation model for a single feed semibatch process. The effect of the key operating parameters on the mean particle size is analyzed through simulations. The results are compared with previous experimental data, thus highlighting the significance of a proper choice of the thermodynamic model. [source] Effect of Polarity and Structural Design on Molecular Photorefractive Properties of Heteroaromatic-Based Push,Pull DyesCHEMISTRY - A EUROPEAN JOURNAL, Issue 27 2006Graziano Archetti Dr. Abstract A combined experimental (optical and electro-optical absorption measurements) and computational (ab initio RHF and DFT) approach has been used to investigate the molecular low- and high- Tg photorefractive (PR) performances of neutral and zwitterionic heteroaromatic dipolar chromophores in terms of structural and solvent-polarity effects. We have found that the nature of the building units (donor, acceptor, and spacer) and the polarity of the surrounding medium strongly affect all the relevant ground-state and nonlinear optical properties involved in the PR activity, that is, the dipole moment, the polarizability anisotropy, and first hyperpolarizability of the electronic ground-state. The variation of these properties is in turn transferred to molecular low- and high- Tg PR figures of merit. It is shown that PR molecular performance not only relies on a proper choice of structural components but varies by orders of magnitude as a function of the medium polarity, and this suggests that a combination of molecular design and host-matrix engineering is required for optimized performances of PR materials. [source] | ||||||||||||||||