Coupling three-field formulation and meshless mixed Galerkin methods using radial basis functions

In this work, we solve the elliptic partial differential equation by coupling the meshless mixed Galerkin approximation using radial basis function with the three-field domain decomposition method. The formulation has been adopted to increase the efficiency of the numerical technique by decreasing the error and dealing with the ill conditioning of the linear system caused by the radial basis function. Convergence analysis of the coupled technique is treated and numerical results of some solved examples are given at the end of this paper.     

Bifurcation indicator based on meshless and asymptotic numerical methods for nonlinear poisson problems

We propose in this work new algorithms associating asymptotic numerical method and meshless discretization (MFS‐MPS: Method of fundamental solutions‐Method of particular solutions) to compute branch solutions of nonlinear Poisson problems. To detect singular points on these branches, geometrical indicator, Padé approximants, and analytical bifurcation indicator are proposed. Numerical applications show the robustness and the effectiveness of the proposed algorithms. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 978–993, 2014     

Sufficient Conditions for Converging Drift-Diffusion Discrete Systems. Application to The Finite Element Method

In this paper we generalize the abstract results of Mock and Marcowich [13, 12] for convergence of discrete Van Roosbroeck systems [12, 13, 17], to the case when the solutions are typically in W^1,4-ε and not in H². These conditions are verified on finite element discretizations. Error estimates are derived when the solution is unique. Due to the singularity at the flat angles, these estimates in the H¹ norm are only O(h^1/2). The techniques that are presented are broad and may be applied to other type of discretizations.     

Investigations on Hydrolytic Activities from Stachybotrys microspora and Their Use as an Alternative in Yeast DNA Extraction

Stachybotrys microspora is a filamentous fungus characterized by the secretion of multiple hydrolytic activities (cellulolytic and non-cellulolytic enzymes). The production of these biocatalysts was studied under submerged culture using glucose, cellulose, and wheat bran as carbon sources. Endoglucanases, pectinases, xylanases, β-glucanases, chitinases, and proteases were induced on cellulose-based medium and repressed on glucose in both strains with higher amounts produced by the mutant. β-glucosidases were roughly equally produced by both strains under glucose and cellulose conditions. The yield of chitinases, β-glucanases, and proteases produced by Stachybotrys strains was as much higher than the commercialized lysing enzyme called “zymolyase,” currently used in yeast DNA extraction. In this context, we showed that S. microspora hydrolases can be successfully applied in the extraction of yeast DNA.     

Crystal structure,electronic structure and electrical conductivity of the antimony selenide BaLaSb2Se6

BaLaSb₂S₆ and BaLaSb₂Se₆ were prepared by heating the elements in the stoichiometric ratio under exclusion of air at 850 °C. Both chalcogenides adopt the KThSb₆Se₆ structure type, crystallizing in the space group P2₁/c (Z = 4) with a = 4.324(3) Å, b = 14.7057(16) Å, c = 15.910(2) Å, β = 92.741(3)°, Z = 4 for the sulfide and a = 4.4173(3) Å, b = 15.333(1) Å, c = 16.816(1) Å, β = 92.545(2)°, Z = 4 for the selenide. The structure of BaLaSb₂Se₆ is composed of ribbons of distorted SbSe₆ octahedra and Se₂^2? pairs. Electronic structure calculations show that the selenide is a semiconductor, in accord with the electrical conductivity measurement.     

Two new titanium molybdenum arsenides: Ti2MoAs2 and Ti3MoAs3, ternary substitution variants of V3As2 and β-V4As3

The title compounds were prepared by arc-melting pre-annealed mixtures of Ti, Mo, and As. Both Ti₂MoAs₂ and Ti₃MoAs₃ adopt structures formed by the corresponding binary vanadium arsenides, V₃As₂ and β-V₄As₃. Ti₂MoAs₂ crystallizes in the tetragonal space group P4/m, with a=9.706(4) Å, c=3.451(2) Å, V=325.1(3) Å³ (Z=4), and Ti₃MoAs₃ in the monoclinic space group C2/m, with a=14.107(3) Å, b=3.5148(7) Å, c=9.522(2) Å, β=100.66(3)°, V=464.0(2) Å³ (Z=4). In both cases, the metal atoms form infinite chains of trans edge-condensed octahedra, and the As atoms are located in (capped) trigonal prismatic voids. While most metal atom sites exhibit mixed Ti/Mo occupancies, the Mo atoms prefer the sites with more metal atom and fewer As atom neighbors. Ti₂MoAs₂ and Ti₃MoAs₃ are metallic entropy-stabilized materials that decompose upon annealing at intermediate temperatures.     

Optimization of Bioethanol Production from Enzymatic Treatment of Argan Pulp Feedstock

Argan pulp is an abundant byproduct from the argan oil process. It was investigated to study the feasibility of second-generation bioethanol production using, for the first time, enzymatic hydrolysis pretreatment. Argan pulp was subjected to an industrial grinding process before enzymatic hydrolysis using Viscozyme L and Celluclast 1.5 L, followed by fermentation of the resulting sugar solution by Saccharomyces cerevisiae. The argan pulp, as a biomass rich on carbohydrates, presented high saccharification yields (up to 91% and 88%) and an optimal ethanol bioconversion of 44.82% and 47.16% using 30 FBGU/g and 30 U/g of Viscozyme L and Celluclast 1.5 L, respectively, at 10%_w/v of argan biomass.     

Structures and properties of the ternary thallium chalcogenides Tl2MQ3 (M = Zr, Hf; Q = S, Se)

We have synthesized new compounds of the formula Tl(2)MQ(3), with M = Zr and Hf and Q = S and Se, and studied their crystallographic features, electronic structures and electrical conductivity. These isostructural compounds crystallize in the monoclinic space group P2(1)/m (Z = 2), with unit cell parameters for the representative Tl(2)ZrS(3) of a = 7.9159(10) ?, b = 3.7651(5) ?, c = 10.275(2) ?, and β = 97.476(2)°. The Zr atoms of Tl(2)ZrS(3) are (distorted) octahedrally coordinated by the S atoms, with two such octahedra sharing edges along the c axis and forming infinite double chains running parallel to the b axis. Tl atoms separate these chains from one another along the a and c axes. The Tl atoms are also surrounded by S atoms in a distorted octahedral coordination. The structure may be viewed as alternating layers of Zr/Tl atoms and S atoms, and is therefore a distorted, ordered variant of the α-NaFeO(2) structure type. All atoms are in their standard oxidation states: Tl(+), Zr(4+), S(2-). The sulphide Tl(2)ZrS(3) has a calculated band gap of 1.15 eV, and the selenide Tl(2)HfSe(3) a gap of 0.57 eV. The electrical conductivity values of Tl(2)ZrS(3) and Tl(2)HfSe(3) at room temperature are 7.1 × 10(-6)Ω(-1) cm(-1) and 3.9 × 10(-3)Ω(-1) cm(-1), respectively.     

A shape optimization approach for a class of free boundary problems of Bernoulli type

We are interested in an optimal shape design formulation for a class of free boundary problems of Bernoulli type. We show the existence of the optimal solution of this problem by proving continuity of the solution of the state problem with respect to the domain. The main tools in establishing such a continuity are a result concerning uniform continuity of the trace operator with respect to the domain and a recent result on the uniform Poincaré inequality for variable domains.     

MA(delta)Sb(2-delta) (M = Zr, Hf; A = Si, Ge): a new series of ternary antimonides and not "beta-ZrSb2"

The ternary antimonides ZrSi(delta)Sb(2-delta), HfGe(delta)Sb(2-delta), and ZrGe(delta)Sb(2-delta) were prepared by annealing of the elements in stoichiometric ratios below 800 degrees C. ZrSi(delta)Sb(2-delta) was earlier erroneously described as the binary "beta-ZrSb(2)", which does not exist as such, because the incorporation of tetrel atoms is necessary for the formation of this structure. ZrSi(delta)Sb(2-delta) has a small yet significant phase width with at least 0.066(7) < or = delta < or = 0.115(3), whereas the Ge analogues exist with larger tetrel concentration, i.e., ZrGe(0.211(5))Sb(1.789) and HfGe(0.205(6))Sb(1.795). The whole series of title compounds crystallizes in the Co(2)Si type (space group Pnma), with lattice dimensions of, e.g., for ZrGe(0.211(5))Sb(1.789), a = 730.4(1) pm, b = 395.13(6) pm, c = 957.6(2) pm, V = 0.27635(7) nm(3), Z = 4. The anionic substructure comprises infinite ribbons formed by the atom sites Q1 and Sb2, with Q1 being mixed occupied by Si or Ge and Sb atoms. These ribbons exhibit Q1-Q1 single bonds and Q1-Sb2 "half" bonds. Assuming the validity of the 8 - N rule, one can assign seven valence-electrons to Sb2 but only five to Q1, which might explain the preference of the tetrel atoms for the latter site.