Computer modelling of intrinsic defects and migration processes in KY3F10

Abstract

The computer modelling technique was used in the present work to study the intrinsic defects and the migration processes in KY₃F₁₀. The main intrinsic disorder was found to be F Frenkel pairs but at higher temperatures it is possible that KF pseudo-Schottky defects could also be present in the material. The ionic conduction process is mainly due to the fluorine ions migrating via both vacancy and interstitialcy mechanisms.     

Use of rotofor preparative isoelectrofocusing cell in protein purification procedure

The Rotofor cell is a preparative isoelectric focusing (IEF) apparatus, in which IEF is performed entirely in free solution. Electrofocusing in Rotofor cell has been described as well-suited for use at any stage of a purification scheme. However, it has some important limitations in resolving complex mixtures of proteins. This paper describes the advantages and disadvantages of using the Rotofor cell in purification protocols.     

Λ0 polarization in ultrarelativistic nucleus-nucleus collisions

We study the polarization of Λ⁰’s produced in ultrarelativistic heavy-ion collisions. We argue that when the density of participants in the reaction is below the critical value for the production of a Quark-Gluon Plasma (QGP), recombination processes dominate the Λ⁰ production cross section and hence, Λ⁰’s are polarized. However, when the density of participants is above the critical value for QGP formation, coalescence processes dominate Λ⁰ production, giving rise to a reduction in the Λ⁰ polarization. For densities below the critical density for QGP production, we describe Λ⁰ polarization in terms of the DeGrand-Miettinen model and correct for the effects introduced by multiple scattering of the produced Λ⁰ within the nuclear environment.     

The photocurrent response of human cones is fast and monophasic

Background  

The precise form of the light response of human cone photoreceptors in vivo has not been established with certainty. To investigate the response shape we compare the predictions of a recent model of transduction in primate cone photoreceptors with measurements extracted from human cones using the paired-flash electroretinogram method. As a check, we also compare the predictions with previous single-cell measurements of ground squirrel cone responses.     

Simultaneous Determination of Hydroquinone and Catechol by Differential Alternative Pulses Voltammetry

The second order voltammetric technique of high resolution, Differential Alternative Pulses Voltammetry (DAPV), was applied for the simultaneous determination of hydroquinone (HQ) and catechol (CC) on bare spectroscopic graphite electrode. Well resolved anodic and cathodic peaks situated on both sides of the zero line were obtained, while the differential pulse voltammograms were overlapped. The linear concentration range for HQ and CC quantification by DAPV was extended up to 20 μmol L⁻¹ for both the isomers. The sensitivity of the determination was found to be 6.00 μA L μmol⁻¹ and 3.61 μA L μmol⁻¹, while the limit of detection reached was 0.2 μmol L⁻¹ and 0.5 μmol L⁻¹ for HQ and CC, respectively. No interference was observed from the commonly coexisting organic species such as resorcinol, phenol and p‐benzoquinone. The great resolution power of DAPV permitted obtaining excellent results without any electrode modification and any mathematical data processing.     

The ionic liquid 1-hexadecyl-3-methylimidazolium bromide as novel extracting system for polycyclic aromatic hydrocarbons contained in sediments using focused microwave-assisted extraction

A method to extract PAHs from sediments is carried out using aqueous solutions containing aggregates of the ionic liquid (IL) 1-hexadecyl-3-methylimidazolium bromide (HDMIm-Br) as the extracting medium. Focused microwave-assisted extraction has been used to accelerate the extraction step, followed by HPLC with fluorescence detection without clean-up steps to remove the IL prior to injection. The method has been applied to certified reference sediment BCR-535 and marine sediments from Tenerife (Canary Islands) with successful results. The optimized method gave average absolute recoveries of 91.1% for six of the seven PAHs studied, with relative standard deviations lower than 10.4%. The overall method is characterized for presenting low extraction times (6min), low amounts of the sediment (0.1g), low amounts of IL (45mM), and low volumes of aqueous extractant solution (9mL). The use of small amounts of both IL and aqueous extractant solution allows the method to be considered environmental-friendly.     

Micelle-mediated extractions using nonionic surfactant mixtures and HPLC-UV to determine endocrine-disrupting phenols in seawaters

An environmentally friendly method to extract endocrine-disrupting phenols (EDPs) from seawaters was realized using nonionic surfactant mixtures and micelle-mediated extractions. The preconcentration step was achieved directly in the seawater matrix, and was followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection without any clean-up steps to remove the surfactant mixture prior to injection. Various nonionic surfactant mixtures were used, and polyoxyethylene-10-laurylether (POLE) with polyoxyethylene-4-laurylether (Brij 30) was found to be the best to work with. Method optimization involved maximizing the preconcentration factor using the studied mixtures. The proposed method gave extraction recoveries ranging from 83.3 to 114.4% for an EDP spiking level of 46.7 μg L⁻¹, and from 63.4 to 112.4% for a spiking level of 4.7 μg L⁻¹ for EDPs studied in real seawater matrices, with relative standard deviations of <12.1%. The detection limits of the method varied from 0.18 μg L⁻¹ for bisphenol A (BPA) to 1.17 μg L⁻¹ for 4-cumylphenol (4-CP). The method was applied to seawaters from the Canary Islands with successful results. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The Histogram and Boxplot for the Display of Lifetime Data

Abstract

The importance of histograms and boxplots as exploratory data analysis (EDA) tools has been well established. Yet, adopting them for lifetime data is not straightforward. The first problem, particularly in histograms, is how to deal with censored observations. The second problem is that the underlying distribution of lifetime data is often highly positively skewed. Therefore, in the classical boxplot, large observations can be wrongly diagnosed as outliers. This article extends the definition of the histogram to accommodate for right-censored observations. We apply the “redistribution to the right” method so that the weight of each uncensored observation is actually the jump of the Kaplan—Meier estimation at this point. We also propose modified boxplots to resolve both problems of right censoring and skewness. In our procedure, the fences differ from those of the classical boxplot. Simulation results are presented for an evaluation of our procedure and an example is presented for illustration.     

Bases normales d'entiers et unités modulaires

LetK be an imaginary quadratic field with discriminantd _K <−4,d _K ≡2, 3 mod 4, andp a prime number,p≡1 mod 8,p split inK; let Ω _p be the ring class field overK with conductorp andK(p) the ray class field overK with conductorp. An explicit normal basis is constructed for the ring of integers of the unique quadratic extension of Ω _p contained inK(p) over the ring of integers of Ω _p . This uses certain classical modular units considered by Deuring and Hecke.