A statistical method to determine whether micro-organisms are randomly distributed in a food matrix,applied to coliforms and Escherichia coli O157 in minced beef

A method is presented to determine whether micro-organisms are distributed randomly or not in a batch of food. This is important information for quantitative microbiological risk assessment (QMRA). If micro-organisms are distributed randomly, this variation in numbers of micro-organisms between samples from a batch of food theoretically agrees with a Poisson distribution, with a fixed value for parameter λ. Other sources for variation (such as clustering of micro-organisms or experimental error) can lead to an increase of variation of the data, which can be described by a Poisson distribution with a Gamma distributed λ (Poisson(Gamma)). The Poisson and Poisson(Gamma) distributions were used to describe the effect of grinding on the variation of endogenous flora of coliforms and artificial, clustered contamination of Escherichia coli O157 in minced beef. In addition, the Poisson and Poisson(Gamma) distributions were compared to the Lognormal distribution. Coliforms were enumerated in 25 samples in the starting material and in the mince produced after grinding once, twice and three times. E. coli O157 was spiked into the starting material in 1 or 10 clusters, and enumerated in 25 samples after grinding once and twice. Coliforms were not randomly distributed in the starting material. Grinding resulted in random and non-random distributed coliforms and E. coli O157, respectively. Generally, the Lognormal and Poisson(Gamma) distribution fitted equally well to the data, but only the Poisson(Gamma) distribution is useful to determine whether micro-organisms are randomly distributed or not.     

Review on materials science and supercritical fluids

Some supercritical fluids are able to replace toxic industrial solvents. So, from an industrial point of view, supercritical fluids are widely used in many fields such as pharmacy, food industry and environment. From a scientific point of view, the main interest of supercritical fluids is connected to the possibility to adjust continuously the physicochemical properties of these reactive media, such as selectivity, solvation, solubility or reactivity. In this paper, we present recent work on processes using supercritical media for processing materials related to fine particle synthesis, porous materials synthesis, polymer synthesis and surface modifications.     

Motion of 〈1 0 0〉-tilt grain boundaries

The motion of planar symmetrical 〈1 0 0〉-tilt boundaries in high-purity aluminum was investigated in situ under the influence of an external mechanical stress field. It was observed that the motion of planar 〈1 0 0〉-tilt boundaries could be activated by an applied shear stress which acts perpendicular to the grain boundary plane. The motion of the grain boundaries is thermally activated so that we could derive the activation parameters for the motion from the in situ data of the mobility at different temperatures. A sharp transition between low angle grain boundaries and high angle grain boundaries was observed for the planar tilt boundaries at 8.6° which was apparent from a step change in the activation enthalpy for the stress induced grain boundary motion. The observed activation parameters for the stress-induced motion can be correlated to the activation parameters of self-diffusion for the motion of low angle boundaries and to the activation parameters of grain boundary diffusion for the motion of high angle grain boundaries. From these correlations, it seems obvious that the motion of planar low and high angle grain boundaries under the influence of a mechanical stress field can be attributed to the movement of the grain boundary dislocations which comprise the structure of the boundary.     

INSTANTANEOUS INDICATORS OF STRUCTURAL BEHAVIOUR BASED ON THE CONTINUOUS CAUCHY WAVELET ANALYSIS

In this contribution, four instantaneous indicators are proposed to characterize the non-linear behaviour of mechanical structures from their transient responses. These indicators are developed from the Cauchy wavelet analysis of the accelerometric responses of the structure. They are based on the notion of ridges and skeletons introduced for the wavelet processing of signals that are assumed to be defined as a sum of asymptotic amplitude and phase-modulated terms. The proposed indicators are then applied to the data collected at the University of Liège. Some preliminary results are given for the characterization of the non-linear behaviour of the beam.     

Extraction of cobalt(II) from an ammonium nitrate-containing leach liquor by an ammonium salt of di(2-ethylhexyl)phosphoric acid

A hydrometallurgical process that involves solvent extraction and selective precipitation has been used to selectively recover Co²⁺ from an aqueous filtrate containing mostly Co²⁺, NH₄⁺ and NO⁻₃ ions and trace amounts of Pt²⁺, Al³⁺ and Fe³⁺ ions. The effect of pH on the precipitation efficiencies of Al³⁺ and Fe³⁺ ions from the leach liquor was investigated. Solvent extraction exhibited good performance in terms of both Co²⁺ and Pt²⁺ ions extraction efficiency and phase separation when ammonium salt of di(2-ethylhexyl)phosphoric acid was used as an extractant in the presence of a tributylphosphate modifier. Cobalt was stripped from the organic phase with nitric acid to yield cobalt nitrate.     

Synthesis of nanocrystalline SnO2 powder by amorphous citrate route

Nanocrystalline SnO₂ has been synthesized by liquid mix technique using citric acid as the complexing agent. The tin oxide powder obtained at different calcination temperatures (773–1223 K) is characterized using powder X-ray diffraction (XRD), SEM, TEM, TG-DTG and UV spectroscopic techniques. The material obtained is nanocrystalline, having particle size in the range of 10–14 nm. The technique is cost-effective and yields the desired product at temperatures as low as 773 K.     

On the geometrical characteristics of chaotic dynamics,I

We introduce some geometrical structures in the phase space of a dynamical system, naturally defined by the system. We study some properties of these structures and discuss their use for the constructing new characteristics of chaotic dynamical behaviour.     

Effect of synthesis pressure on hydride phases in Mg–M systems (M=Mn,Y)

High-pressure synthesis of the hydrides in Mg–M (M=Mn, Y) systems and the influence of applied pressures during synthesis on present phases and their crystal structures have been studied. In Mg–Mn system, it was found that the crystal structure of Mg₃MnH_y changed from hexagonal structure (a=0.47107(4) nm and c=1.0297(1) nm) to monoclinic structure (a=0.8819(8) nm, b=0.4658(4) nm, c=0.4678(5) nm and β=105.6(1)°) in a pressure range of 3–3.5 GPa. This crystal structural change was reversible with respect to pressure. The Mg₃MnH_y synthesized under 5 GPa was stable up to around 620 K. From thermogravimetric and fusion extraction analyses, the hydrogen content was determined as Mg₃MnH_5.0–5.6. In Mg–Y system, the high-pressure hydride (MgY₂H_y) with yellowish color was synthesized at 1073 K for 2 h under 3 GPa or higher. This phase exhibited an FCC-type structure with a cell parameter of a=0.516 nm. Its hydrogen content was determined to be about 3.7 mass%, corresponding to a chemical formula of MgY₂H_7.8. The hydride was partially dehydrogenated at around 600 K, and the amount of hydrogen partially desorbed was 1.4 mass%. The FCC-type structure was stable even after the partial dehydrogenation.     

Disjunctive optimization,max-separable problems and extremal algebras

The paper was motivated by solution methods suggested in the literature for solving linear optimization problems over (max,+)- or (max,min)-algebras and certain class of so called max-separable optimization problems. General features of these optimization problems, which play a crucial role in the optimization methods were used to formulate a general class of optimization problems with disjunctive constraints and a max-separable objective function and suggest a solution procedure for solving such problems. Linear problems over (max,+)-algebras and the max-separable problems are contained in this general class of optimization problems as special cases.