Emissivity of Lanthanum Hexaboride Thermionic Electron Gun Cathode

The emissivity of the thermionic electron gun cathode material lanthanum hexaboride (LaB \(_6\) ) at an operating temperature of 1622 K has been measured for wavelengths from 550 nm to 2400 nm. The emissivity is calculated from scanning monochromator spectral measurements calibrated with a tungsten lamp and the published emissivity of 0.82 at 1600 K for LaB \(_6\) at 650 nm. The results show a higher emissivity at shorter wavelengths (up to 0.86 at 729 nm) and a lower emissivity in the near-IR to mid-IR (down to 0.41 at 2146 nm). These measurements were motivated by the need to make fast, accurate optical measurements of the temperature of the LaB \(_6\) cathode in our thermionic microwave gun, and to select the wavelength most readily absorbed by the cathode for manipulation of its surface temperature as a means of counteracting back-bombardment heating.     

Spermatogenic and sperm quality differences in an experimental model of metabolic syndrome and hypogonadal hypogonadism

The synergistic effect of the co-morbidities that comprise metabolic syndrome (MetS) is increasingly being recognised as an important contributor in the pathology of a broad spectrum of seemingly disparate conditions. However, in terms of male reproductive function, beyond erectile dysfunction, little is known about the influence of this cohort (collectively or separately) on spermatogenesis and sperm quality. The aims of this study were to assess the reproductive tract of a MetS animal model for detrimental changes, to determine whether a group of compounds (advanced glycation end products and their receptor) known to cause cell dysfunction and DNA damage was present and assess whether hypogonadotropic hypogonadism was the main contributing factor for the changes seen. Animals fed a high-fat diet were found to have significantly increased cholesterol, triglycerides, blood glucose, mean arterial pressure and visceral fat levels. Although serum testosterone was decreased, no changes were seen in either testicular or epididymal histology. Immunolocalisation of N(ε)-carboxymethyl-lysine and the receptor for advanced glycation end products was found in the testes, epididymides and sperm of the two treated groups of animals; however, ELISA did not show any difference in protein levels. Similarly, assessment of sperm nuclear DNA (nDNA) fragmentation by acridine orange test did not find significant differences in nDNA integrity. We conclude that the minimal effect on spermatogenesis and sperm quality seen in our model is probably due to the moderate increase of blood glucose rather than the hypogonadism.     

DFT study of trichloroethene reaction with permanganate in aqueous solution

The mechanism of the environmentally important reaction between permanganate anion and trichloroethene (TCE) has been studied theoretically using modern DFT functional. It has been shown that IEFPCM/M05-2X/aug-cc-pVDZ theory level yields activation parameters and carbon isotopic fractionation factor in excellent agreement with the experimental data. Obtained results indicate that this reaction proceeds via the 3+2 mechanism with a very early transition state, in which the new C-O bonds are formed only in about 20%. An alternative, stepwise mechanism that involves initial formation of a single new C-O bond and a C-Mn bond, followed by rearrangement to the permanganate-TCE adduct, has been found to be more energetically demanding and in disagreement with the experimental isotopic fractionation.     

In vitro synthesis of biogenic amines by Brochothrix thermosphacta isolates from meat and meat products and the influence of other microorganisms

Twenty Brochothrix thermosphacta strains tested for biogenic amines (BAs) production, formed histamine (6.6-16.2 mg/kg) and tyramine (18.7-35.4 mg/kg) but neither putrescine nor cadaverine. Six of the twenty strains were also investigated in respect of their influence on the synthesis of BAs by Escherichia coli, Pseudomonas sp., Proteus mirabilis and Lactobacillus sakei. In pure culture Escherichia coli produced all of the studied amines (histamine, tyramine, putrescine and cadaverine) with a total concentration of 167.7 mg/kg, P. mirabilis produced a total of 56.7 mg/kg histamine, tyramine and cadaverine, while Lactobacillus sakei and Pseudomonas sp. produced histamine and tyramine, totaling 37.9 and 35.2 mg/kg respectively. All B. thermosphacta promoted cadaverine production by Escherichia coli which increased by 12-68%, and some of them contributed to the appearance of this amine among the metabolites of Pseudomonas. The presence of B. thermosphacta decreased the potential ability of P. mirabilis to produce BAs.     

Modeling the conductance and DNA blockade of solid-state nanopores

We present measurements and theoretical modeling of the ionic conductance G of solid-state nanopores with 5-100 nm diameters, with and without DNA inserted into the pore. First, we show that it is essential to include access resistance to describe the conductance, in particular for larger pore diameters. We then present an exact solution for G of an hourglass-shaped pore, which agrees very well with our measurements without any adjustable parameters, and which is an improvement over the cylindrical approximation. Subsequently we discuss the conductance blockade ΔG due to the insertion of a DNA molecule into the pore, which we study experimentally as a function of pore diameter. We find that ΔG decreases with pore diameter, contrary to the predictions of earlier models that forecasted a constant ΔG. We compare three models for ΔG, all of which provide good agreement with our experimental data.     

Tight and uniform layer of covalently bound aminoethylophenyl groups perpendicular to gold surface for attachment of biomolecules

Strongly adhered layers of the compound with the primary amino group directed toward the solution were obtained at the gold surface by chronoamperometric electroreduction of 4-aminoethylobenzenodiazonium salt (AEBD) in acetonitrile solution at appropriately selected potential. The used techniques (EQCM, AFM, EIS, PM, IRRAS) showed that the nature and thickness of formed aminoethylophenyl layer strongly depend on the potential applied to the electrode. Electroreduction of AEBD salt at a potential more negative than -0.6 V (vs Ag/AgCl) leads to about monolayer on the gold surface. Additionally, such a layer was very tight and uniform. The electrochemical measurements indicate that the efficient and precise attachment of biomolecules to the aminoethylophenyl layer is only possible when this layer is formed at appropriate potential. This was shown for ss- and dsDNA.     

On the computation of design derivatives for Huber–Mises plasticity with non‐linear hardening

This paper concerns design sensitivity analysis (DSA) for an elasto–plastic material, with material parameters depending on, or serving as, design variables. The considered constitutive model is Huber–Mises deviatoric plasticity with non‐linear isotropic/kinematic hardening, one which is applicable to metals. The standard radial return algorithm for linear hardening is generalized to account for non‐linear hardening functions. Two generalizations are presented; in both the non‐linearity is treated iteratively, but the iteration loop contains either a scalar equation or a group of tensorial equations. It is proven that the second formulation, which is the one used in some parallel codes, can be equivalently brought to a scalar form, more suitable for design differentiation. The design derivatives of both the algorithms are given explicitly, enabling thus calculation of the ‘explicit’ design derivative of stresses entering the global sensitivity equation. The paper addresses several issues related to the implementation and testing of the DSA module; among them the concept of verification tests, both outside and inside a FE code, as well as the data handling implied by the algorithm. The numerical tests, which are used for verification of the DSA module, are described. They shed light on (a) the accuracy of the design derivatives, by comparison with finite difference computations and (b) the effect of the finite element formulation on the design derivatives for an isochoric plastic flow. Copyright © 2003 John Wiley & Sons, Ltd.     

Structural and immunochemical studies on the O-specific polysaccharide of Proteus penneri strain 15

On the basis of sugar analysis and 1H- and 13C-NMR spectroscopy, it was shown that the O-specific polysaccharide of Proteus penneri strain 15 has a trisaccharide repeating unit, including an acetal-linked pyruvic acid residue, and is structurally identical to the capsular polysaccharide of Proteus vulgaris strain ATCC 49990. Serological studies supported this conclusion and demonstrated the presence in the homological antiserum of both anti-core and anti-O chain antibodies reacting with a lipopolysaccharide (LPS) epitope containing N-acetylglucosamine and galactose residues.