Optimization of nutrient-induced germination of Bacillus sporothermodurans spores using response surface methodology

Spores of Bacillus sporothermodurans are known to be contaminant of dairy products and to be extremely heat-resistant. The induction of endospore germination before a heat treatment could be an efficient method to inactivate these bacteria and ensure milk stability. In this study, the nutrient-induced germination of B. sporothermodurans LTIS27 spores was studied. Testing the effect of 23 nutrient elements to trigger an important germination rate of B. sporothermodurans spores, only d-glucose, l-alanine, and inosine were considered as strong independent germinants. Both inosine and l-alanine play major roles as co-germinants with several other amino acids. A central composite experimental design with three factors (l-alanine, d-glucose, and temperature) using response surface methodology was used to optimize the nutrient-induced germination. The optimal rate of nutrient-induced germination (100%) of B. sporothermodurans spores was obtained after incubation of spore for 60 min at 35 °C in presence of 9 and 60 mM of d-glucose and l-alanine, respectively. The results in this study can help to predict the effect of environmental factors and nutrients on spore germination, which will be beneficial for screening of B. sporothermodurans in milk after induction their germination. Moreover, the chosen method of optimization of the nutrient-induced germination was efficient in finding the optimum values of three factors.     

Design of a compact size tag antenna based on split ring resonator for UHF RFID application

In this article, a new design of miniaturized split‐ring resonator antenna using a meander line technique with a simple impedance matching method applicable to UHF‐RFID tags is presented. The new approach is based on the integration of a meander line into the radiating element of SRR to reduce the electrical tag size and a theoretical demonstration to calculate the conjugate impedance matching and directly attach the antenna with the chip. The new SRR antenna, which is printed on the flexible substrate Arlon CuClad 250LX, is designed using Alien Higgs 3 RFID ASIC whose input impedance is 25‐j190. The prototype antenna has a low‐cost compact size (18.28 mm × 18.28 mm) with a read range higher than 4 m within the RFID UHF band and with a roughly 4.2‐m peak range at 915 MHz. As a proof of behavior, a tag prototype is fabricated and measured to operate at a UHF RFID band. Based on some works' results, an optimized design is obtained with a 48% size reduction compared with the classic split ring resonator antenna and with a good impedance matching the antenna with RFID ASIC without the need for any external matching network.     

Polymorphisme du dioxotriplomb (II) tetraoxosulfate (VI) Pb3O2(SO4) a basse temperature. II - Etude structurale de la phase ferroelastique gamma-Pb3O2 (SO4) par diffraction neutronique sur poudres a 2 et 45K

Full-profile neutron powder diffraction structure refinements of dioxotrilead(II)tetraoxosulfate(VI) at 2 and 45K reveal that both the alpha- and the gamma-Pb₃O₂ (SO₄) polymorphs have to be refined simultaneously at these temperatures. Accordingly, the paraelastic alpha phase is trapped in the ferroelastic gamma phase, yielding thus mixtures of both compounds in a nearly 1:1 molar ratio. Both structures are essentially similar. The slight variations of the lead-oxygen distances in the infinite edge-sharing tetrahedral (Pb₃ O₂)n double-chains force the sulfate group to adopt nearly C3v and C2v site symmetries respectively in the alpha and gamma phases. The present work is a good example of the behaviour of the DBW3.2 program (1) when mixtures of very similar structures are refined simultaneously (high correlation between some structural parameters).     

Decentralized Networked Control System Design Using Takagi-Sugeno (TS) Fuzzy Approach

This paper proposes a new method for control of continuous large-scale systems where the measures and control functions are distributed on calculating members which can be shared with other applications and connected to digital network communications.At first, the nonlinear large-scale system is described by a Takagi-Sugeno(TS) fuzzy model. After that, by using a fuzzy LyapunovKrasovskii functional, sufficient conditions of asymptotic stability of the behavior of the decentralized networked control system(DNCS),are developed in terms of linear matrix inequalities(LMIs). Finally, to illustrate the proposed approach, a numerical example and simulation results are presented.     

Structure cristalline de la phase haute temperature de PbSO4.2PbO A 973K

Full profile X-ray powder diffraction structure refinements have been performed on the two polymorphs of the PbSO₄.2PbO phase. Both structures can be described as infinite double-chains of edge-sharing OPb₄ tetrahedra linked by the sulfate groups and running parallel to the (010) direction for the low temperature phase, and parallel to the (001) direction for the high temperature one. The mechanism of the phase transition may be described as a rotation of the sulfate group about one of its pseudo-ternary axis. The space group adopted for the refinement of the structure of the high temperature phase is Cmcm.     

The crystal structures of PbO.PbXO4 (X = S,Cr, Mo) at 5K by neutron powder profile refinement

The structures of PbO.PbXO₄ monobasic lead oxide- lead sulphate, chromate and molybdate have been determined at 5K by neutron powder profile refinement. They are all isostructural with Lanarkite (the sulphate), being based on the red PbO structure with PbO₂^2? and its lone pair electrons replaced by XO₄^2?. A similar mechanism apparently produces the di-basic and tetra-basic oxides nPbO.PbXO₄. These materials are of relevence to solid state reactions in lead — acid battery electrodes.     

Production of titanium-containing metal-ceramic composites based on boron carbide in the nanocrystalline state

ABSTRACT

The results of the study of the production technology, phase composition, structure and physico-mechanical properties of metal-ceramic materials based on boron carbide and their components are presented. Boron carbide was obtained by direct synthesis from chemical elements using amorphous boron and carbon black. By mechanical dispersion, solid reagents were converted into an ultrafine state. Using a chemical method, nanoscale (70–80?nm) boron carbide was synthesised from suspension solutions of amorphous boron and liquid hydrocarbons. Boron carbide-based metal-ceramic composite powder B₄C–(Co–Ni–Ti) was obtained by mechanical dispersion of the constituent components. Based on results of studying of the temperature-dependence of wetting angle of boron carbide with Co–Ni–Ti metallic alloy, the compacting modes of metal-ceramic composite powders by plasma-spark sintering and hot pressing have been developed. The influence of the component content of the binder metal (alloy) on some physico-mechanical properties (linear expansion coefficient, hardness, and bending strength) of hardmetal-ceramic materials based on boron carbide was studied. It was found that the optimum content of the metal component in the composite is ～ 25?wt-%. In the temperature range 300–600°C, the materials obtained are characterised by stable dimensional factors, since in this temperature range the thermal conductivity coefficient does not depend much on temperature. At room temperature, their bending strength is about 1?GPa. A new method of chemical synthesis of nanocrystalline ceramic compositions of boron carbide and titanium diboride using suspension solutions for the preparation of powders and their spark plasma sintering was also developed to obtain a compacted material of composition B₄C+30?wt-%TiB₂, which has a high hardness of 95 HRA (with maximum microhardness 45.6?GPa) and sufficient strength (with a bending strength of 834?MPa).     

Fabrication of Bulk Targets of MgB2 with Stoichiometric and Nonstoichiometric Contents

Powder of magnesium diboride was obtained by solid phase reaction of mixture of magnesium （〉 99% pure） and amorphous boron （〉 99% pure） powders at 650-900 ℃ temperatures in inert atmosphere. During synthesis process main attention was paid. to removing oxide layer of surfaces of powder particles by organic solvents in Glovebox, where concentration of oxygen and water steam is less than 5 ppm. Homogenization and activation of powders were conducted in a planetary nano-mill by WC balls in an inert area. Pressing of the obtained powders was conducted in an argon atmosphere. MgB2 nonstoichiometric powders contained excess boron and magnesium, Magnesium hydride was used as source of excess boron, which is fragile compound and easy to grind in nano-mill. It decomposites with metallic magnesium and hydrogen up to 280 ℃ temperature. Commercial magnesium diboride powder （Aldrich, 〉 99%） was used for fabrication of MgB2 bulk targets. Powders systems of MgB2-Mg, MgB2-MgH2, MgB2-B homogenized by nano-mill in Glove box was used for fabrication of composites with nonstoichiometric contents. The targets were cylinders with diameters of 27-52 mm and height of 5-15 mm. Consolidation of pressed powdery composites was conducted in argon atmosphere. Synthesis of MgB2 from mixture of magnesium and amorphous boron powders and simultaneous consolidation were conducted by hot pressing （HP） method. Phase content of the obtained targets were established by XRD method after dry polishing. Superconducting characteristic of the obtained samples were measured by vibrational magnetometer. The superconducting transition with an onset at 39 K was observed in a good agreement with the results of the other groups obtained on samples prepared by conventional techniques. The phase exists near the nominal composition without a significant homogeneity range.     

Hybrid rectenna and monolithic integrated zero-bias microwave rectifier

In this study, we have developed a hybrid sensitive rectenna (rectifier + antenna) system at 2.45 GHz. To achieve this system, we have first optimized and validated a zero-bias microwave sensitive rectifier using commercial Schottky diodes. We have then optimized and achieved a 2/spl times/2 patch antenna array, which is associated to the microwave rectifier in order to validate the rectenna system, where an RF-dc conversion efficiency of 56% has been observed experimentally. In order to minimize the rectenna dimensions, we have conducted a study using the OMMIC ED02AH 0.20-/spl mu/m GaAs pseudomorphic high electron-mobility transistor process to develop and achieve a monolithic rectifier at 2.45 GHz with RF-dc conversion efficiency of 65%.