Interaction between explosive and analyte layers in explosive matrix-assisted plasma desorption mass spectrometry

An HMX/insulin two-layer system was chosen as a model for further investigation of the matrix properties of explosive materials for protein analytes in plasma desorption mass spectrometry. The dependencies of the molecular ion yield and average charge state as a function of the analyte thickness were studied. An increase in the charge state of multiply protonated molecular species was confirmed as the major matrix effect, with the average charge state z at the smallest thickness studied being higher than in matrix-assisted laser desorption/ionization and closer to the value obtained in electrospray ionization under standard acidic conditions. Observed charge state distributions are significantly narrower than the corresponding Poisson distributions, which suggests that the protonation of insulin is limited in plasma desorption by the number of basic sites in the molecule, similar to electrospray ionization. Both the curve displaying total molecular ion yield and the one showing the total charge (proton) yield as a function of the insulin thickness have maxima at a thickness different from an insulin monolayer. These observations diminish the significance of a matrix/analyte interface mechanism for the explosive matrix assistance. Instead, a mechanism related to the chemical energy release during conversion of the explosive after the ion impact is proposed. As additional mechanisms, enhanced protonation of the analyte through collisions with products of the explosive decay is considered, as well as electron scavenging by other products, which leads to a higher survival probability of positively charged protein molecular ions. Copyright 1999 John Wiley & Sons, Ltd.     

Research Progress of Ferrite Materials for Photoelectrochemical Water Splitting

Photoelectrochemical(PEC)water splitting is an effective strategy to convert solar energy into clean and renewable hydrogen energy.In order to carry out effective PEC conversion,researchers have conducted a lot of exploration and developed a variety of semiconductors suitable for PEC water splitting.Among them,metal oxides stand out due to their higher stability.Compared with traditional oxide semiconductors,ferrite-based photoelectrodes have the advantages of low cost,small band gap,and good stability.Interestingly,due to the unique characteristics of ferrite,most of them have various tunable features,which will be more conducive to the development of efficient PEC electrode.However,this complex metal oxide is also troubled by severe charge recombination and low carrier transport efficiency,resulting in lower conversion efficiency compared to theoretical value.Based on this,this article reviews the structure,preparation methods,characteristics and modification strategies of various common ferrites.In addition,we analyzed the future research direction of ferrite for PEC water splitting,and looked forward to the development of more efficient catalysts.     

Deciphering the Biophysical Effects of Oxidizing Sulfur-Containing Amino Acids in Interferon-beta-1a using MS and HDX-MS

Introduction of a chemical change to one or more amino acids in a protein’s polypeptide chain can result in various effects on its higher-order structure (HOS) and biophysical behavior (or properties). These effects range from no detectable change to significant structural or conformational alteration that can greatly affect the protein’s biophysical properties and its resulting biological function. The ability to reliably detect the absence or presence of such changes is essential to understanding the structure–function relationship in a protein and in the successful commercial development of protein-based drugs (biopharmaceuticals). In this paper, we focus our attention on the latter by specifically elucidating the impact of oxidation on the HOS, structural dynamics, and biophysical properties of interferon beta-1a (IFNβ-1a). Oxidation is a common biochemical modification that occurs in many biopharmaceuticals, specifically in two naturally-occurring sulfur-containing amino acids, methionine and cysteine. To carry out this work, we used combinations of hydrogen peroxide and pH to differentially oxidize IFNβ-1a (to focus on only methionine oxidation versus methionine and cysteine oxidation). We then employed several analytical and biophysical techniques to acquire information about the differential impact of these two oxidation scenarios on IFNβ-1a. In particular, the use of MS-based techniques, especially HDX-MS, play a dominant role in revealing the differential effects.

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Adaptive artificial boundary condition for the two-level Schrödinger equation with conical crossings

In this paper, we present an adaptive approach to design the artificial boundary conditions for the two-level Schrödinger equation with conical crossings on the unbounded domain. We use the windowed Fourier transform to obtain the local wave number information in the vicinity of artificial boundaries, and adopt the operator splitting method to obtain an adaptive local artificial boundary condition. Then reduce the original problem into an initial boundary value problem on the bounded computational domain, which can be solved by the finite difference method. By this numerical method, we observe the surface hopping phenomena of the two-level Schrödinger equation with conical crossings. Several numerical examples are provided to show the accuracy and convergence of the proposed method.     

Demogenetic study of three populations within a region with strong founder effects

OBJECTIVES: The population of the Saguenay-Lac-St-Jean (SLSJ) region (Quebec, Canada) is known to have a relatively high prevalence of certain hereditary disorders, which can be explained by the consequences of founder effects. This study aims at providing new insights on the origins and subregional stratification of these founder effects. METHODS: The genealogies of 300 individuals were reconstructed and analyzed using the BALSAC population register. RESULTS: Inbreeding and kinship levels are higher in Lower Saguenay than in Upper Saguenay and Lac-St-Jean. The population of Lower Saguenay also distinguishes itself because of a fewer number of distinct ancestors. CONCLUSION: Beyond the genetic features that characterize the whole region, SLSJ also displays intraregional variability. Thus it is important to take into account the settlement patterns and the demographic history of this population for a better appraisal of its contemporary genetic structure.     

Experimental, Theoretical and Biological Activity Study on the Acyl-Substituted Benzo-18-crown-6, Dibenzo-18-crown-6 and Dibenzo-24-crown-8

Hexadecanoyl, dihexadecanoyl, dioctadecaneoyl, di-10-undecenoyl, and dicis-9-octadecenoyl derivatives of benzo[18]crown-6, dibenzo[18]crown-6 and dibenzo[24]-8 were synthesized by the condensation of carboxylic acids (palmitic, stearic, oleic and undecenoic acid) with benzo and dibenzo crown ethers in the presence of zinc chloride. The extraction equilibrium constants of such macrocyclic ethers with long side chains were estimated using chloroform/water and dichloromethane/water membranes transfer of Na-PAR (4-(2-pyridylazo)-resorcinol mono sodium monohydrate) with UV–Vis spectroscopy. It was found that they were in the range of 10.88–11.71 in dichloromethane and 8.04–11.77 in chloroform. These results actually show that the Na+ binding effect of macrocyclic ethers depends on the type and the length of side chains. The geometrical properties of the molecules were studied employing semi-empirical calculations by simulated annealing technique. The frontier molecular orbital energies and dipole moments were also examined. The biological activity results showed that the synthesized crown ethers have no activity against the studied microorganisms.     

A boundary element method for Signorini problems in three dimensions

Summary In this paper, a Signorini problem in three dimensions is reduced to a variational inequality on the boundary, and a boundary element method is described for the numerical approximation of its solution; an optimal error estimate is also given.This work is supported in part by the National Natural Science Foundation of China, and by the Royal Society of London     

Numerical solution to a linearized KdV equation on unbounded domain

Exact absorbing boundary conditions for a linearized KdV equation are derived in this paper. Applying these boundary conditions at artificial boundary points yields an initial‐boundary value problem defined only on a finite interval. A dual‐Petrov‐Galerkin scheme is proposed for numerical approximation. Fast evaluation method is developed to deal with convolutions involved in the exact absorbing boundary conditions. In the end, some numerical tests are presented to demonstrate the effectiveness and efficiency of the proposed method.© 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2008     

FEATURES OF BIOECONOMICS MODELS FOR THE OPTIMAL MANAGEMENT OF A FISHERY EXPLOITED BY TWO DIFFERENT FLEETS

ABSTRACT. After the extension of the Exclusive Economic Zone, in 1977, to 200 miles, most fish stocks came under jurisdiction of the adjacent coastal states. This development opened prospects of effective management of the open sea fisheries. Coastal states have the right to plan out the operation of so-called by Clarke and Munro “distant water fishing nations” from their Exclusive Economic Zone. Under some arrangements, a foreign fleet is allowed to harvest the resource in the Exclusive Economic Zone area. Clarke and Munro, in [1987] and [1991], focus on the issue of optimum terms and conditions of access and, in doing so, built a multiobjective model. The main goal of the present work is the development of a more general model including more variables and parameters related to the presence of a domestic fleet as well as a distant water fishing nation. The main difficulty resides in sharing the harvesting between the two fleets. The study responds to the realistic problemof coastal states who own enough resource stocks to allow harvesting by several kinds of fleets. Two optimal scenarios are developed, in each of them a solution is given.