Spatial Effects of Interaction of a Shock with a Lateral Low-Density Gas Channel

Three-dimensional interaction of a shock with lateral low-density gas channel of round, elliptic or rectangular cross-section is numerically studied using Euler’s equations. The structure of formed shock wave precursor is described in detail. Internal shear layer instabilities in three-dimensional flow are shown to develop faster than in axisymmetric case. Moderate amplification of high-pressure jet cumulation effect is noted for elliptic and rectangular channel cases. Dependence of precursor growth rate on cross-section shape is studied. It is found that stretching of cross-section shape significantly increases the duration of linear precursor growth phase.     

Identification of zinc phosphide in a falsely labeled rodenticide bait

"Kela" is a commercial rodenticide bait commonly used in Israel, made of wheat grains, which, according to its label, contains chlorophacinone. This product was involved in the death case of a man in which the victim's female companion was accused of assisting in this suicide and was subsequently convicted. Analysis of the wheat grains revealed zinc phosphide, whose use is restricted to authorized exterminators only, instead of chlorophacinone. Zinc phosphide was identified using microscopic examination, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray powder diffraction (XRD).     

Spatial aspects of interspecific competition

The aggregation-mediated conjugation system of Bacillus thuringiensis subsp. israelensis, encoded by the 200-kb plasmid pXO16, is highly potent in transferring itself and efficient in mobilizing other nonconjugative plasmids. The present study reveals some salient features of this conjugation system. Our observations can be summarized as follows: (i) The conjugative transfer takes about 3(1/2) to 4 min. For a 200-kb plasmid this corresponds to about 1 kb per second. (ii) The ability to transfer the plasmid seems to be evenly distributed among the donors. (iii) Functionally, the mating complex was found to consist of one donor and one recipient cell, even though aggregates comprising thousands of interconnected cells are formed. (iv) Having donated the plasmid, the donor needs a "period of recovery" of about 10 min before it can redonate the plasmid. (v) Secondary transfer, i.e., transfer from newly formed transconjugants, is delayed about 40 min. This maturation time exceeds the generation time, and it may indicate that to display donor activity, a surface protein (the aggregation substance) has to be uniformly incorporated into the cell wall. Lastly, we found that when the experiments were sufficiently short and when the recipient cells were in excess compared with the donors, the process of conjugation could be reasonably described by a kinetic model analogous to the Michaelis-Menten model for enzyme catalysis. This allowed us to estimate (vi) the maximal conjugation rate to be about 0.05 transconjugant per donor per minute, and (vii) the Km value, i.e., the concentration of recipient that results in half of the maximal conjugation rate, to be about 4 x 10(6) recipients/ml.     

On the development of software support for solving problems of optimal design of power boilers

Power boilers are complicated technical objects consisting of a large number of interconnected components. Main problems of creating mathematical models and software support for optimal design of power boiler units are analyzed, approaches to the solution of them are described, and distinctive features of their software implementation are considered. Results of testing software are considered.     

Amperometric biosensor for formic acid in air

The possibility of developing a simple, inexpensive and specific personal passive “real-time” air sampler incorporating a biosensor for formic acid was investigated. The sensor is based on the enzymatic reaction between formic acid and formate dehydrogenase (FDH) with nicotinamide adenine dinucleotide (NAD⁺) as a co-factor and Meldola's blue as mediator. An effective way to immobilise the enzyme, co-factor and Meldola's blue on screen-printed, disposable, electrodes was found to be in a mixture of glycerol and phosphate buffer covered with a gas-permeable membrane. Steady-state current was reached after 4–15 min and the limit of detection was calculated to be below 1 mg/m³. However, the response decreased by 50% after storage at −15°C for 1 day.     

User assisted separation of reflections from a single image using a sparsity prior

When we take a picture through transparent glass the image we obtain is often a linear superposition of two images: the image of the scene beyond the glass plus the image of the scene reflected by the glass. Decomposing the single input image into two images is a massively ill-posed problem: in the absence of additional knowledge about the scene being viewed there are an infinite number of valid decompositions. In this paper we focus on an easier problem: user assisted separation in which the user interactively labels a small number of gradients as belonging to one of the layers. Even given labels on part of the gradients, the problem is still ill-posed and additional prior knowledge is needed. Following recent results on the statistics of natural images we use a sparsity prior over derivative filters. This sparsity prior is optimized using the terative reweighted least squares (IRLS) approach. Our results show that using a prior derived from the statistics of natural images gives a far superior performance compared to a Gaussian prior and it enables good separations from a modest number of labeled gradients.     

Combinatorial scheme for management of life cycle: Example for concrete macrotechnology

The paper describes a combinatorial scheme for the analysis and synthesis of product life cycle on the basis of a typical compressed structure: design of materials and manufacturing process. In addition, the following problems are studied: system refinement, series-parallel production process, and multistage design (design of product trajectories). Hierarchical combinatorial morphological approach is proposed. The solving process is based on ordinal expert knowledge. The following phases are examined: design of a basic system morphology, generation of local design alternatives, knowledge acquisition as ordinal estimates for local design alternatives and their compatibility, and synthesis of the best compositions.A realistic numerical example for concrete-macrotechnology (composing of concrete from constituents and selection of manufacturing alternatives) illustrates the approach.     

Gröbner bases with respect to several orderings and multivariable dimension polynomials

Let D=K[X]$D=K\left[X\right]$ be a ring of Ore polynomials over a field K$K$ and let a partition of the set of indeterminates into p$p$ disjoint subsets be fixed. Considering D$D$ as a filtered ring with the natural p$p$-dimensional filtration, we introduce a special type of reduction in a free D$D$-module and develop the corresponding Gröbner basis technique (in particular, we obtain a generalization of the Buchberger Algorithm). Using such a modification of the Gröbner basis method, we prove the existence of a Hilbert-type dimension polynomial in p$p$ variables associated with a finitely generated filtered D$D$-module, give a method of computation and describe invariants of such a polynomial. The results obtained are applied in differential algebra where the classical theorems on differential dimension polynomials are generalized to the case of differential structures with several basic sets of derivation operators.     

A liquid level sensor using the absorption of guided acoustic waves

This liquid level sensor consists of a vertically movable 10-cm-long hollow cylinder with an impedance matching conic section suspended at one end of a few-meters-long magnetorestrictive wire. The wire is automatically wound up or unwound such that the cylindrical sensor element at the bottom of the wire is immersed by just a small and measurable distance into the liquid whose level is sought. Acoustic waves are launched in the wire by a pulse of current in a coil and are transmitted to the hollow cylinder through the cylindrical horn. The carrier frequency of the wave trains and the thickness of the tube are chosen so that the elastic waves strongly leak into the liquid when the hollow cylinder is immersed. The level is then determined by measuring the time-of-flight of the echo reflected at the junction between the wire and the horn, followed by taking into account a small correction term computed from the attenuation of the end echo.