Improved Thermoelectric Performance of Higher Manganese Silicides with Ge Additions

Polycrystalline higher manganese silicides (HMS) with Ge additions were prepared by induction melting followed by hot-pressing. The phase structures and microstructure of the pellets were investigated, and their thermoelectric properties were measured from room temperature to 650°C. It was found that the solubility of Ge in HMS was limited to around 1.6%, beyond which an extra phase of Si _y Ge_1?y appeared. The electrical conductivity was continuously enhanced by Ge additions, while the Seebeck coefficient was slightly decreased. The thermal conductivity showed first a decreasing then an increasing relationship with increasing Ge additions. The HMS cells, mainly along the c-axis, were remarkably enlarged by the substitution of Ge, which probably resulted in the enhancement of phonon scattering due to an increased number of defects, reducing the phonon thermal conductivity. The dimensionless figure of merit of the optimized HMS polycrystals was improved by more than 30% compared with the pure HMS material.     

Vibration isolation using open or filled trenches

The problem of structural isolation from ground transmitted vibrations by open or infilled trenches under conditions of plane strain is numerically studied. The soil medium is assumed to be linear elastic or viscoelastic, homogeneous and isotropic. Horizontally propagating Rayleigh waves or waves generated by the motion of a rigid foundation or by surface blasting are considered in this work. The formulation and solution of the problem is accomplished by the boundary element method in the frequency domain for harmonic disturbances or in conjunction with Laplace transform for transient disturbances. The proposed method, which requires a discretisation of only the trench perimeter, the soil-foundation interface and some portion of the free soil surface on either side of the trench appears to be better than either finite element or finite difference techniques. Some parametric studies are also conducted to assess the importance of the various geometrical, material and dynamic input parameters and provide useful guidelines to the design engineer.     

Stochastic shape functions and stochastic strain–displacement matrix for a stochastic finite element stiffness matrix

Summary For conventional finite element problems, element geometry is adequate to determine shape functions. However, to account for secondary effects due to material randomness, conventional shape functions need to be modified according to the spatial fluctuation of constitutive variables in each Monte Carlo sample. This paper develops a method to compute stochastic shape functions based on local equilibrium criteria when each simulated sample complies with the same order of accuracy as designated for the associated deterministic problem. The resulting stochastic stiffness matrix is then calculated via the stochastic strain–displacement matrix based on those stochastic shape functions. In order to attain high accuracy, which is the characteristic of the boundary element method, rational polynomial shape functions are used in this paper. The proposed formulation is indispensable when secondary effects (due to nano size and time scale in modern technology, fiber randomness in composites, thermodynamic interactions in biological tissues, to name a few) demand a high accuracy finite element formulation. The elasto-plastic deformation that introduces concavity motivated the numerical example elaborated here. An example of a concave quadrilateral element with spatial randomness for the modulus of elasticity is illustrated. Since isoparametric shape functions for concave quadrilaterals do not exist, the Wachspress rational polynomial shape functions with irrational terms are used. The computer algebra environment Mathematica is employed here. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday     

Antioxidant activity of some leafy vegetables of India: A comparative study

Eleven edible leafy vegetables of India have been analysed for their free radical-scavenging activity in different systems of assay, e.g. DPPH radical-scavenging activity, superoxide radical-scavenging activity in riboflavin/light/NBT system, hydroxyl radical-scavenging activity, and inhibition of lipid peroxidation induced by FeSO₄ in egg yolk. Total antioxidant activity was measured, based on the reduction of Mo(VI) to Mo(V) by the extract and subsequent formation of green phosphate/Mo(V) complex at acid pH. The extracts were found to have different levels of antioxidant properties in the systems tested. Considering all the activities, it can be said that Ipomoea reptans has good activity amongst the eleven plant materials screened for their antioxidant properties. Lowest activity was found in Nyctanthes arbortristis. Many flavonoids and related polyphenols contribute significantly to the total antioxidant activity of many fruits and vegetables. However, there was no correlation between antioxidant activity and total phenol/flavonoid content.     

Equalization and interference cancellation in linear multiusersystems based on second-order statistics

Potential applications of blind channel identification and equalization in data communication systems have recently been explored. For multiuser systems that are irreducible and column-reduced, second-order statistical methods normally can identify channel dynamics up to a unitary mixing matrix. Additional user separation (equalization) can rely on higher order statistics and other prior information. In this paper, we investigate the equalizability of user signals and the cancellation of unwanted interfering signals based only on second-order output statistics. We show that a user channel can be equalized if it has the longest memory. Furthermore, interfering user signals can be cancelled under a more relaxed multiuser channel condition     

Field instrument for simultaneous large dynamic range measurement of atmospheric hydrogen sulfide, methanethiol, and sulfur dioxide

We describe a membrane-based collection/analysis system that differentially monitors H2S and CH3SH, and to which a conductometric SO2 analyzer using the same collector was coupled. A diffusion scrubber (DS) comprised of a Nafion tube collects H2S selectively while a porous polytetrafluoroethylene (pPTFE) DS collects both H2S and CH3SH. Both gases are measured via their ability to react with fluorescein mercuric acetate (FMA) which results in decreased fluorescence. The limited dynamic range of a negative signal procedure was overcome by using dual DS units comprised of short and long scrubbers, placed serially in the liquid flow line. Different DS designs and membrane materials were investigated. H2S, CH3SH, and SO2 from a biogenic point source were continuously measured, and the H2S/CH3SH data compared well with a standard procedure involving Tedlar bag collection, preconcentration and thermal desorption from a Tenax trap, and measurement by gas chromatography/flame photometric detection. Walkaround portability of the instrument and very large dynamic range measurement of H2S and SO2 were demonstrated around the Mt. Aso volcano.     

Enhancing gas phase Fischer-Tropsch synthesis catalyst design

This paper presents the results on the research in the development of a Fe-based catalyst with Co as a co-catalyst, and Ru and ZnO as promoters. The catalytic performance of these materials for FT synthesis was investigated in the gas phase employing a fixed bed reactor system. The Fe-Zn-K/γ-Al₂O₃ catalyst performance was used as the benchmark. The data show that by varying the process conditions (T, P, flow rate), it is possible to achieve a narrow distribution of the liquid products. The effect of co-catalysts and promoters such as K and Zn are also presented. The results from a series of Fe₄Co₁Zn_0.04 based catalysts for Fischer-Tropsch (FT) synthesis, in which the different amounts of Ru are incorporated showed that the addition of Ru suppressed the CH₄ formation at the cost of increasing the CO₂ selectivity. The newly designed catalysts showed significantly high activity towards CO conversion (>70%), along with low selectivity towards CO₂ (5-15%) and methane (ND - 3%). It is also shown that the support material plays a role in the selectivities obtained.     

ATP depletion blocks herpes simplex virus DNA packaging and capsid maturation

During herpes simplex virus (HSV) assembly, immature procapsids must expel their internal scaffold proteins, transform their outer shell to form mature polyhedrons, and become packaged with the viral double-stranded (ds) DNA genome. A large number of virally encoded proteins are required for successful completion of these events, but their molecular roles are poorly understood. By analogy with the dsDNA bacteriophage we reasoned that HSV DNA packaging might be an ATP-requiring process and tested this hypothesis by adding an ATP depletion cocktail to cells accumulating unpackaged procapsids due to the presence of a temperature-sensitive lesion in the HSV maturational protease UL26. Following return to permissive temperature, HSV capsids were found to be unable to package DNA, suggesting that this process is indeed ATP dependent. Surprisingly, however, the display of epitopes indicative of capsid maturation was also inhibited. We conclude that either formation of these epitopes directly requires ATP or capsid maturation is normally arrested by a proofreading mechanism until DNA packaging has been successfully completed.     

Locking-free compressible quadrilateral finite elements: Poisson’s ratio-dependent vector interpolants

In any high-quality viscoplastic calculation, the objectivity related to shape and constitutive parameter indifference is desirable, especially when a continuous deformation into concavity is tracked. In the physical x?y frame, quadratic displacement vectors—explicitly coupled via Poisson’s ratio—encompass bar and Euler–Bernoulli beam modes. Analytically, the unique set of shape functions yields nodal loads and the element stiffness matrix from its area and the first and second area moments. Closed-form Mathematica results exhibit full compliance with all requirements of Iron’s patch tests.     

Estimation of skin impedance models with experimental data and a proposed model for human skin impedance

The skin is a complex biological tissue whose impedance varies with frequency. The properties and structure of skin changes with the location on the body, age, geographical location and other factors. Considering these factors, skin impedance analysis is a sophisticated data analysis. However, despite all these variations, various researchers have always worked to develop an equivalent electrical model of the skin. The two most important categories of electrical models are RC‐based model and CPE‐based model which focus on the physiological stratification and biological properties of skin, respectively. In this work, experimental skin impedance data is acquired from ten sites on the body to find the fitting model. It is observed that a hybrid of fractional‐order CPE‐based model and higher‐order RC layered‐based model can provide the best fitting electrical model of skin. A new model is developed with this hybrid orders. Genetic algorithm is used for the extraction of parameter components. Least error of fitting has been observed for the proposed model as compared with the other models. This model can be used in correlating many skin problems and in the development of diagnostic tools. It will offer an additional supportive tool in‐vitro to the medical specialist.Inspec keywords: genetic algorithms, skin, data analysis, bioelectric phenomena, medical computing, electric impedance, patient diagnosisOther keywords: skin impedance models, human skin impedance, skin impedance analysis, data analysis, electrical models, RC‐based model, biological properties, experimental skin impedance data, fractional‐order CPE‐based model, skin problems, complex biological tissue, higher‐order RC layered‐based model, genetic algorithm, diagnostic tools