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Selected AbstractsResolution of neutron three-axis spectrometers using acceptance diagramsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2002L. D. Cussen Two-dimensional `acceptance diagrams' are used to discuss the transmission function and the resolution of neutron three-axis spectrometers. The discussion is simplified by assuming rectangular rather than the usual Gaussian transmission profiles for the beam elements, i.e. collimators and crystal mosaic spreads, but the results can be applied to the Gaussian profile approximation. The formalism clearly shows the effects of beam elements on the instrument transmission to the detector. Suitable choices of beam elements are determined to match the transmission functions of the primary and secondary spectrometers and hence optimize measurements. The effect of sample mosaic is addressed. The `focusing angle' for inelastic scattering is determined and discussed. [source] On the solution of the nonlinear Korteweg,de Vries equation by the homotopy perturbation methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2009Ahmet Yildirim Abstract In this paper, the homotopy perturbation method is used to implement the nonlinear Korteweg,de Vries equation. The analytical solution of the equation is calculated in the form of a convergent power series with easily computable components. A suitable choice of an initial solution can lead to the needed exact solution by a few iterations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Product Selectivity Control in the Heteroannulation of o -(1-Alkynyl)benzamidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1 2010Gabriele Bianchi Abstract The selective synthesis of (Z)- or (E)-3-aryl/vinyl/alkylidene-isoindolones, and 2-benzopyran derivatives from o -(1-alkynyl)benzamides by means of a suitable choice of bases or silver catalysis is described. [source] Interlaboratory validation of oxidation-index measurement methods for UHMWPE after long-term shelf agingJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2002S. M. Kurtz Abstract An international oxidation index standard would greatly benefit the orthopedic community by providing a universal scale for reporting oxidation data of ultra-high molecular weight polyethylene (UHMWPE). We investigated whether severe oxidation associated with long-term shelf aging affects the repeatability and reproducibility of area-based oxidation index measurement techniques based on normalization with the use of 1370- or 2022-cm,1 infrared (IR) absorption reference peaks. Because an oxidation index is expected to be independent of sample thickness, subsurface oxidation was examined with the use of both 100- and 200-,m-thick sections from tibial components (compression-molded GUR 1120, gamma irradiated in air) that were shelf aged for up to 11.5 years. Eight institutions in the United States and Europe participated in the present study, which was administered in accordance with ASTM E691. On average, the 100-,m-thick samples were associated with significantly greater interlaboratory relative standard uncertainty (40.3%) when compared with the 200-,m samples (21.8%, p = 0.002). In contrast, the intralaboratory relative standard uncertainty was not significantly affected by the sample thickness (p = 0.21). The oxidation index method did not significantly influence either the interlaboratory or intralaboratory relative standard uncertainty (p = 0.32 or 0.75, respectively). Our interlaboratory data suggest that with the suitable choice of specimen thickness (e.g., 200 ,m) and either of the two optimal oxidation index methods, interlaboratory reproducibility of the most heavily oxidized regions in long-term shelf-aged components can be quantified with a relative standard uncertainty of 21% or less. Therefore, both the 1370-cm,1 and the 2022-cm,1 reference peaks appear equally suitable for use in defining a standard method for calculating an oxidation index for UHMWPE. © 2001 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 15,23, 2002 [source] Bayesian calibration of computer modelsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 3 2001Marc C. Kennedy We consider prediction and uncertainty analysis for systems which are approximated using complex mathematical models. Such models, implemented as computer codes, are often generic in the sense that by a suitable choice of some of the model's input parameters the code can be used to predict the behaviour of the system in a variety of specific applications. However, in any specific application the values of necessary parameters may be unknown. In this case, physical observations of the system in the specific context are used to learn about the unknown parameters. The process of fitting the model to the observed data by adjusting the parameters is known as calibration. Calibration is typically effected by ad hoc fitting, and after calibration the model is used, with the fitted input values, to predict the future behaviour of the system. We present a Bayesian calibration technique which improves on this traditional approach in two respects. First, the predictions allow for all sources of uncertainty, including the remaining uncertainty over the fitted parameters. Second, they attempt to correct for any inadequacy of the model which is revealed by a discrepancy between the observed data and the model predictions from even the best-fitting parameter values. The method is illustrated by using data from a nuclear radiation release at Tomsk, and from a more complex simulated nuclear accident exercise. [source] Clinical trial: lansoprazole 15 or 30 mg once daily vs. placebo for treatment of frequent nighttime heartburn in self-treating subjectsALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 5 2009D. A. PEURA Summary Background, Frequent nighttime heartburn is common. Lansoprazole 15 mg is indicated for treatment of heartburn and other gastro-oesophageal reflux disease-related symptoms. Aim, To evaluate the efficacy and safety of lansoprazole in self-treating subjects with frequent nocturnal heartburn. Methods, A total of 864 subjects with heartburn on ,2 days/week over the past month were randomized to double-blind treatment with lansoprazole 15 or 30 mg or placebo each morning. Endpoints were percentage of nighttimes without heartburn (primary), percentage of 24-h days without heartburn and percentage of subjects without heartburn on day 1. Results, Mean percentage of nighttimes without heartburn was significantly greater with lansoprazole 15 mg (61.3%) or lansoprazole 30 mg (61.7%) vs. placebo (47.8%) over 14 days (P < 0.0001 vs. placebo for both doses). Percentage of 24-h days without heartburn and percentage of subjects without heartburn on day 1 were significantly greater with lansoprazole 15 or 30 mg vs. placebo. Conclusions, Both lansoprazole 15 and 30 mg were highly effective and well tolerated in reducing symptoms in subjects with frequent nighttime heartburn. The benefit of therapy on 24-h heartburn and nighttime heartburn on day 1 of treatment was also evident. Lansoprazole 15 mg is a suitable choice for management of frequent nighttime heartburn. [source] Robust Automatic Bandwidth for Long MemoryJOURNAL OF TIME SERIES ANALYSIS, Issue 3 2001Marc Henry The choice of bandwidth, or number of harmonic frequencies, is crucial to semiparametric estimation of long memory in a covariance stationary time series as it determines the rate of convergence of the estimate, and a suitable choice can insure robustness to some non-standard error specifications, such as (possibly long-memory) conditional heteroscedasticity. This paper considers mean squared error minimizing bandwidths proposed in the literature for the local Whittle, the averaged periodogram and the log periodogram estimates of long memory. Robustness of these optimal bandwidth formulae to conditional heteroscedasticity of general form in the errors is considered. Feasible approximations to the optimal bandwidths are assessed in an extensive Monte Carlo study that provides a good basis for comparison of the above-mentioned estimates with automatic bandwidth selection. [source] Wide variation in effectiveness of laboratory disinfectants against bacteriophagesLETTERS IN APPLIED MICROBIOLOGY, Issue 6 2008D.E. Halfhide Abstract Aims:, The purpose of this study was to identify an effective disinfectant for the inactivation of the bacteriophages (phages) being used in our laboratory, as published studies on phage inactivation are far from unanimous in their conclusions. Methods and Results:, The phages studied were three closely related strains of Myoviridae and three strains of Siphoviridae. Three disinfectants which are used commonly in microbiology laboratories were evaluated: Virkon (1%), ethanol (75%) and sodium hypochlorite (2500 ppm available chlorine). The most effective of these was Virkon, which inactivated all six phages rapidly. Ethanol was effective against the Myoviridae but had little effect on the Siphoviridae. Sodium hypochlorite was the least effective of the disinfectants evaluated. Conclusions:, The findings of this study demonstrate a wide diversity in the effectiveness of disinfectants tested for inactivation of phages. Significance and Impact of the Study:, Of the disinfectants tested Virkon is the most suitable choice for those unable to carry out disinfection validation studies, or where a broad spectrum disinfectant against phages is required. All of the phages in this study showed resilience to inactivation by sodium hypochlorite, and therefore this disinfectant is an unwise choice for use against phage without first assessing its effectiveness. [source] Probing cosmology and galaxy cluster structure with the Sunyaev,Zel'dovich decrement versus X-ray temperature scaling relationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009Cien Shang ABSTRACT Scaling relations among galaxy cluster observables, which will become available in large future samples of galaxy clusters, could be used to constrain not only cluster structure, but also cosmology. We study the utility of this approach, employing a physically motivated parametric model to describe cluster structure and applying it to the expected relation between the Sunyaev,Zel'dovich decrement (S,) and the emission-weighted X-ray temperature (Tew). The slope and normalization of the entropy profile, the concentration of the dark matter potential, the pressure at the virial radius and the level of non-thermal pressure support as well as the mass and redshift dependence of these quantities are described by free parameters. With a suitable choice of fiducial parameter values, the cluster model satisfies several existing observational constraints. We employ a Fisher matrix approach to estimate the joint errors on cosmological and cluster structure parameters from a measurement of S, versus Tew in a future survey. We find that different cosmological parameters affect the scaling relation differently: predominantly through the baryon fraction (,m and ,b), the virial overdensity (w0 and wa for low- z clusters) and the angular diameter distance (w0 and wa for high- z clusters; ,DE and h). We find that the cosmology constraints from the scaling relation are comparable to those expected from the number counts (dN/dz) of the same clusters. The scaling-relation approach is relatively insensitive to selection effects and it offers a valuable consistency check; combining the information from the scaling relation and dN/dz is also useful to break parameter degeneracies and help disentangle cluster physics from cosmology. Our work suggests that scaling relations should be a useful component in extracting cosmological information from large future cluster surveys. [source] Scaling and correlation analysis of galactic imagesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2001P. Frick Different scaling and autocorrelation characteristics and their application to astronomical images are discussed: the structure function, the autocorrelation function, Fourier spectra and wavelet spectra. The choice of the mathematical tool is of great importance for the scaling analysis of images. The structure function, for example, cannot resolve scales that are close to the dominating large-scale structures, and can lead to the wrong interpretation that a continuous range of scales with a power law exists. The traditional Fourier technique, applied to real data, gives very spiky spectra, in which the separation of real maxima and high harmonics can be difficult. We recommend as the optimal tool the wavelet spectrum with a suitable choice of the analysing wavelet. We introduce the wavelet cross-correlation function, which enables us to study the correlation between images as a function of scale. The cross-correlation coefficient strongly depends on the scale. The classical cross-correlation coefficient can be misleading if a bright, extended central region or an extended disc exists in the galactic images. An analysis of the scaling and cross-correlation characteristics of nine optical and radio maps of the nearby spiral galaxy NGC 6946 is presented. The wavelet spectra allow us to separate structures on different scales like spiral arms and diffuse extended emission. Only the images of thermal radio emission and H, emission give indications of three-dimensional Kolmogorov-type turbulence on the smallest resolved scales . The cross-correlations between the images of NGC 6946 show strong similarities between the images of total radio emission, red light and mid-infrared dust emission on all scales. The best correlation is found between total radio emission and dust emission. Thermal radio continuum and H, emission are best correlated on a scale of about , the typical width of a spiral arm. On a similar scale, the images of polarized radio and H, emission are anticorrelated, a fact that remains undetected with classical cross-correlation analysis. [source] Synthesis, characterization and application of poly[(1-vinyl-2-pyrrolidone)- co -(2-hydroxyethyl methacrylate)] as controlled-release polymeric system for 2,4-dichlorophenoxyacetic chloride using an ultrafiltration techniquePOLYMER INTERNATIONAL, Issue 7 2008Guadalupe del C Pizarro Abstract BACKGROUND: Polymers supporting chemicals used in agriculture have recently been developed to overcome the serious environmental problems of conventional agrochemicals. The success of these formulations is based on a suitable choice of polymer support. Degradable polymeric hydrogels are of particular interest. The gradual release of the bioactive agent can be achieved by hydrolytic or enzymatic cleavage of the linking bond. RESULTS: In this context, poly[(1-vinyl-2-pyrrolidone)- co -(2-hydroxyethyl methacrylate)] [poly(NVP- co -HEMA)] has been used as a bioactive carrier reagent. Herein, we report a controlled-release system with the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) using an ultrafiltration system. Hydrolysis was studied by testing the release at various pH values. A high release with poly(NVP- co -HEMA),2,4-D was observed at pH = 7 and 10 after two days (Z = 2). The release percentage of copolymer,herbicide increased at pH = 10. It showed release values between 79.0 and 94.5%. Poly(NVP- co -HEMA),herbicide can release a bioactive compound in aqueous solution at pH = 3, 7 and 10. CONCLUSION: Based on the results of homogeneous hydrolysis, it is argued that the herbicide release rate depends on the pH of the reaction environment. This functional polymer could be employed as a biodegradable material for applications in agrichemical release. Copyright © 2008 Society of Chemical Industry [source] Fitting Semiparametric Additive Hazards Models using Standard Statistical SoftwareBIOMETRICAL JOURNAL, Issue 5 2007Douglas E. Schaubel Abstract The Cox proportional hazards model has become the standard in biomedical studies, particularly for settings in which the estimation covariate effects (as opposed to prediction) is the primary objective. In spite of the obvious flexibility of this approach and its wide applicability, the model is not usually chosen for its fit to the data, but by convention and for reasons of convenience. It is quite possible that the covariates add to, rather than multiply the baseline hazard, making an additive hazards model a more suitable choice. Typically, proportionality is assumed, with the potential for additive covariate effects not evaluated or even seriously considered. Contributing to this phenomenon is the fact that many popular software packages (e.g., SAS, S-PLUS/R) have standard procedures to fit the Cox model (e.g., proc phreg, coxph), but as of yet no analogous procedures to fit its additive analog, the Lin and Ying (1994) semiparametric additive hazards model. In this article, we establish the connections between the Lin and Ying (1994) model and both Cox and least squares regression. We demonstrate how SAS's phreg and reg procedures may be used to fit the additive hazards model, after some straightforward data manipulations. We then apply the additive hazards model to examine the relationship between Model for End-stage Liver Disease (MELD) score and mortality among patients wait-listed for liver transplantation. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Role of valproate across the ages.ACTA NEUROLOGICA SCANDINAVICA, Issue 2006Treatment of epilepsy in adults A workshop was held in Göteborg in June 2005 to discuss the place of valproate in treating adult epilepsies. Consensus positions were developed on the epilepsy types for which the drug is most suitable and the use of valproate in women of child-bearing age, in men and in patients with psychiatric comorbidity. Valproate was considered to be effective across a broad variety of epilepsy syndromes and seizure types and should be considered a suitable choice for first-line monotherapy of juvenile myoclonic epilepsy and other idiopathic generalized epilepsies. The use of valproate by women of child-bearing age is associated with potential harm to the foetus. A conservative approach to treatment is recommended in these patients whereby alternative antiepileptic drugs should be proposed to women planning pregnancies wherever satisfactory seizure control can be thereby maintained. In cases where valproate is used during pregnancy, either because the pregnancy was unplanned or because alternative treatment options of equivalent efficacy are unavailable, appropriate counselling, precautionary measures and monitoring should be provided. The evidence for an impact of valproate on male reproductive health is equivocal and considerations of male fertility should not be taken into account in deciding whether to prescribe valproate to men. Valproate can be proposed safely to patients with comorbid psychiatric disease or underlying psychiatric vulnerability. [source] Theoretical Simulation of Vibrational Sum-Frequency Generation Spectra from Density Functional Theory: Application to p -Nitrothiophenol and 2,4-DinitroanilineCHEMPHYSCHEM, Issue 12 2009Julien Guthmuller Dr. Abstract The molecular orientation of adsorbed molecules forming self-assembled monolayers can be determined by combining vibrational sum-frequency generation (SFG) measurements with quantum chemical calculations. Herein, we present a theoretical methodology used to simulate the SFG spectra for different combinations of polarizations. These simulations are based on calculations of the IR vectors and Raman tensors, which are obtained from density functional theory computations. The dependency of the SFG vibrational signature with respect to the molecular orientation is presented for the molecules p -nitrothiophenol and 2,4-dinitroaniline. It is found that a suitable choice of basis set as well as of exchange-correlation (XC) functional is mandatory to correctly simulate the SFG intensities and consequently provide an accurate estimation of the adsorbed molecule orientation. Comparison with experimental data shows that calculations performed at the B3LYP/6-311++G(d,p) level of approximation provide good agreement with experimental frequencies, and with IR and Raman intensities. In particular, it is demonstrated that polarization and diffuse functions are compulsory for reproducing the IR and Raman spectra, and consequently vibrational SFG spectra, of systems such as p -nitrothiophenol. Moreover, the investigated XC functionals reveal their influence on the relative intensities, which show rather systematic variations with the amount of Hartree,Fock exchange. Finally, further aspects of the modeling are revealed by considering the frequency dependence of the Raman tensors. [source] Linking biological and artificial olfaction: biomimetic quartz crystal microbalance odor sensorsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2009Bartosz Wyszynski Non-member Abstract Biological olfaction is a powerful system enabling acquisition and processing of various chemical information from environment. Vast significance of the sense of smell is reflected in attempts to create instrumental techniques mimicking the biological system,artificial/machine olfaction. Following the biological systems, the artificial olfaction relies on arrays of gas sensors with broad specificities to odorants. Arguably, among available gas-sensing technologies, the most suitable choices for artificial olfaction are acoustic wave sensors, including quartz crystal microbalance (QCM) gas/odor sensors. The short review herein presents basic information on organization and principles of biological and artificial olfaction systems as well as several methods for fabrication of biomimetic or bioinspired (QCM) sensors for artificial olfaction. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Alternately linearized implicit iteration methods for the minimal nonnegative solutions of the nonsymmetric algebraic Riccati equationsNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 8 2006Zhong-Zhi Bai Abstract For the non-symmetric algebraic Riccati equations, we establish a class of alternately linearized implicit (ALI) iteration methods for computing its minimal non-negative solutions by technical combination of alternate splitting and successive approximating of the algebraic Riccati operators. These methods include one iteration parameter, and suitable choices of this parameter may result in fast convergent iteration methods. Under suitable conditions, we prove the monotone convergence and estimate the asymptotic convergence factor of the ALI iteration matrix sequences. Numerical experiments show that the ALI iteration methods are feasible and effective, and can outperform the Newton iteration method and the fixed-point iteration methods. Besides, we further generalize the known fixed-point iterations, obtaining an extensive class of relaxed splitting iteration methods for solving the non-symmetric algebraic Riccati equations. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||