A Berry-Esseen type bound in kernel density estimation for strong mixing censored samples

In this paper, we discuss the estimation of a density function based on censored data by the kernel smoothing method when the survival and the censoring times form a stationary α-mixing sequence. A Berry-Esseen type bound is derived for the kernel density estimator at a fixed point x. For practical purposes, a randomly weighted estimator of the density function is also constructed and investigated.     

Nonparametric estimation of a conditional distribution from length-biased data

In this paper we consider the problem of estimating a conditional distribution function in a nonparametric way, when the response variable is nonnegative, and the observational procedure is length-biased. We propose a proper adaptation of the estimate to right-censoring provoked by limitation in following-up. Large sample analysis of the introduced estimator is given, including rates of convergence, limiting distribution, and efficiency results. We show that the length-bias model results in less variance in estimation, when compared to methods based on observed truncation times. Practical performance of the proposed estimator is explored through simulations. Application to unemployment data analysis is provided.     

Chitosan magnetic microspheres for technological applications: Preparation and characterization

One of the major applications of chitosan and its many derivatives are based on its ability to bind strongly heavy and toxic metal ions. In this study chitosan magnetic microspheres have been synthesized. Acetic acid (1%w/v) solution was used as solvent for the chitosan polymer solution (2%w/v) where magnetite nanoparticles were suspended in order to obtain a stable ferrofluid. Glutaraldehyde was used as cross-linker. The magnetic characteristic of these materials allows an easy removal after use if is necessary. The morphological characterization of the microspheres shows that they can be produced in the size range 800–1100 μm.The adsorption of Cu(II) onto chitosan–magnetite nanoparticles was studied in batch system. A second-order kinetic model was used to fit the kinetic data, leading to an equilibrium adsorption capacity of 19 mg Cu/g chitosan.     

Enzymatic metabolism of ergosterol by cytochrome p450scc to biologically active 17alpha,24-dihydroxyergosterol

We demonstrate the metabolism of ergosterol by cytochrome P450scc in either a reconstituted system or isolated adrenal mitochondria. The major reaction product was identified as 17alpha,24-dihydroxyergosterol. Purified P450scc also generated hydroxyergosterol as a minor product, which is probably an intermediate in the synthesis of 17alpha,24-dihydroxyergosterol. In contrast to cholesterol and 7-dehydrocholesterol, cleavage of the ergosterol side chain was not observed. NMR analysis clearly located one hydroxyl group to C24, with evidence that the second hydroxyl group is at C17. 17alpha,24-Dihydroxyergosterol inhibited cell proliferation of HaCaT keratinocytes and melanoma cells. Thus, in comparison with cholesterol and 7-dehydrocholesterol, the 24-methyl group and the C22-C23 double bond of ergosterol prevent side chain cleavage by P450scc and change the enzyme's hydroxylase activity from C22 and C20, to C24 and C17, generating bioactive product.     

An efficient preparation of stereospecific β-hydroxy nitriles

The cyanide-ring opening of thionocarbonates with NaCN in DMF and TBACN in THF is described. This reaction occurred regioselectively to afford β-hydroxy nitrile with preserved stereochemistry of the hydroxy group in high yield.     

Organometalloidal derivatives of the transition metals : XXX. Mass spectrometry of transition metal substituted disilanes

Mass spectral fragmentation of a series of transition metal substituted disilanes, LMSiMe₂SiMe₂ML, LM = (η⁵-C₅H₅)Fe(CO)₂- (Fp), (η⁵-C₅H₅)Fe(η⁵-C₅H₄)- (Fc), RFe(CO)₂(η⁵-C₅H₄), are reported. They exhibit significant distinctions depending on the nature of LM. Direct cleavage of the Si---Si bond occurs in the order Fc å Fp å RFe(CO)₂(η⁵-C₅H₄) owing to the capacity of the LM fragment to stabilize positive charge. For complexes containing a direct Fe---Si bond, i.e. Fp-SiMe₂SiMe₂ML, disilene complexed ions are observed, and those complexes containing both an Fp group and a (η⁵-C₅H₄-SiMe₂SiMe₂) group exhibit significant formation of (C₅H₄=Si=SiMe₂) complexed ions. Little disproportionation is observed for any of the complexes studied, in contrast to organodisilanes.     

Globalizations of partial actions on nonunital rings

In this note we prove a criteria for the existence of a globalization for a given partial action of a group on an -unital ring. If the globalization exists, it is unique in a natural sense. This extends the globalization theorem from Dokuchaev and Exel, 2005, obtained in the context of rings with

     

Density and refractive index in mixtures of ionic liquids and organic solvents: Correlations and predictions

Correlations between volumetric properties and refractive index of binary mixtures of room temperature ionic liquids (RTILs) and organic solvents were examined. To this end, the density and refractive index for a set of these systems were measured at atmospheric pressure at 298.15 K throughout the composition range. These data were used to calculate excess volumes and refractive index deviations by using expressions firmly based on the physical significance of each quantity, fact that allowed the expected relations between the two quantities to be confirmed. Based on these results, the molar refraction and free or void volume of the mixtures are calculated with a view to estimating the relative contribution of both quantities to the excess molar volume. Once molar refraction was confirmed to exhibit a near-ideal behaviour in all mixtures, a method for predicting the density and refractive index of RTIL + organic solvent mixtures was developed; the results show that this procedure can be a highly useful alternative to the usually complex experimental methods available for the thermophysical characterization of these systems.     

Stable numerical solution of the Cauchy problem for the Laplace equation in irregular annular regions

This article is mainly concerned with the numerical study of the Cauchy problem for the Laplace equation in a bounded annular region. To solve this ill‐posed problem, we follow a variational approach based on its reformulation as a boundary control problem, for which the cost function incorporates a penalized term with the input data. The cost function is minimized by a conjugate gradient method in combination with a finite element discretization. In the case where the input data is noisy, some preliminary error estimates, show that the penalization parameter may be chosen like the inverse of the level of noise. Numerical solutions in simple and complex domains show that this methodology produces stable and accurate solutions.© 2017 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 33: 1799–1822, 2017