Ultrafast all-optical modulation of infrared radiation viametal-semiconductor waveguide structures

We present a novel optical-optical semiconductor switching technique for application to infrared laser beam modulation and ultrashort infrared laser pulse switching. This method relies on the ultrafast optical excitation, with femtosecond above-bandgap laser radiation, of an air-filled metal-clad semiconductor waveguide. Guided electromagnetic wave analysis combined with time-varying dielectric properties of the semiconductor layer are used to investigate the ultrafast switching speed of the structure. The device is capable of modulation at various infrared wavelengths. In particular, we investigate intensity modulation of the quasi-TE₁₀ mode for 10.6-μm laser radiation. At an electron-hole photoinjection density of ~1.8×10¹⁸ cm^-3, an extinction ratio of 83 dB is demonstrated. This ratio is significantly higher than that exhibited by current optical-optical semiconductor switches. Potential applications to all-optical Mach-Zehnder metal-clad semiconductor modulators and self-limiting switches are also discussed     

Modelling mass transfer phenomena and quantification of ventilation performance in a full scale installation

This paper outlines development of a low order model that can be used for control purposes and quantification of ventilation performance in ventilated systems. First informative pollutant transport data is generated using numerical simulations. Later on, identification procedures are followed to build a low order transfer function model from the CFD generated input–output data. The obtained results demonstrate that first order model can sufficiently describe the dominant mass transfer dynamics in the ventilated air space. Afterwards classical mass balance equation is used to explain the objectively formulated model in a meaningful manner. The developed model is compact in structure and accurate in nature making it an ideal input for model based controller algorithm development. Furthermore its model parameter is found to be an inverse of the local mean age of air. Therefore the model can also be used to assess ventilation performance.     

Immunological characterization, lipid dependence, and subcellular localization of CTP:phosphoethanolamine cytidylyltransferase purified from rat liver. Comparison with CTP:phosphocholine cytidylyltransferase

CTP:phosphoethanolamine cytidylyltransferase (ET) (ethanolamine-phosphate cytidylyltransferase, EC 2.7.7.14), which is generally considered as the rate-regulatory enzyme of phosphatidylethanolamine synthesis via the CDP-ethanolamine pathway, was purified to homogeneity from a rat liver postmicrosomal supernatant. A polyclonal antibody was raised against the enzyme in rabbits and subsequently purified by affinity chromatography. The affinity-purified antibody recognized one single immunoreactive 49.6-kDa protein band on SDS-polyacrylamide gel. The enzyme showed an isoelectric point at a pH of 6.5 and was sensitive to various sulfhydryl reagents. Cross-reactivity experiments of ET and CTP:phosphocholine cytidylyltransferase (CT) (choline-phosphate cytidylyltransferase, EC 2.7.7.15) with their corresponding antibodies showed that these enzymes were immunologically distinct. In contrast with the well known lipid dependence of CT, the activities of both purified and cytosolic ETs were not affected by the presence of various phospholipid preparations. Differential centrifugation studies as well as release experiments with digitonin-permeabilized hepatocytes demonstrated that ET, unlike CT, is not associated with cellular organelles. However, amino acid analysis of ET revealed a high content of hydrophobic amino acids, suggesting a possible association of this enzyme with some kind of cellular structure in the hepatocyte.     

Power losses in steel pipe delivering very large currents

This paper presents a finite difference time domain solution for the electromagnetic fields in ferromagnetic conducting steel pipes of the type used to deliver large currents for in situ heating of heavy oil reservoirs and for in situ environmental decontamination. A method is described whereby a single measured hysteresis loop can be used to deduce the family of hysteresis loops that governs the variable magnetic behavior throughout the pipe wall. Hysteresis and eddy current losses are calculated, and it is shown that hysteresis effects greatly alter the eddy current distribution and can more than triple the total power losses in the steel pipe when compared to the power losses that would be present if hysteresis effects are ignored and magnetic permeability is assumed constant     

Modeling and molecular dynamics of glutamine transaminase K/cysteine conjugate beta-lyase

The homodimeric, pyridoxal 5'-phosphate (PLP)-dependent enzyme glutamine transaminase K/cysteine conjugate beta-lyase (GTK/beta-lyase) has been implicated in the bioactivation of chemopreventive compounds. This paper describes the first homology model of rat renal GTK/beta-lyase and its active site residues, deduced from molecular dynamics (MD) simulations of the binding mode of 13 structurally diverse cysteine S-conjugates and amino acids after Amber-parametrization of PLP. Comparison with Thermus thermophilus aspartate aminotransferase (tAAT) and Trypanosoma cruzi tyrosine aminotransferase (tTAT), used as templates for modeling GTK/beta-lyase, showed that the PLP-binding site of GTK/beta-lyase is highly conserved. Binding of the ligand alpha-carboxylate-group occurred via the conserved residues Arg(432) and Asn(219), and Asn(50) and Gly(70). Two pockets accommodated the various ligand side chains. A small pocket, located directly above PLP, was of a highly hydrophobic and aromatic character. A larger pocket, formed partly by the substrate access channel, was more hydrophilic and notably involved the salt bridge partners Glu(54) and Arg(99*) (* denotes the other subunit). Ligand-binding residues included Leu(51), Phe(71), Tyr(135), Phe(373) and Phe(312*), and pi-stacking interactions were often observed. Tyr(135) and Asn(50) were prominent in hydrogen bonding with the sulfur-atom of cysteine S-conjugates.The observed binding mode of the ligands corresponded well with their experimentally determined inhibitory potency toward GTK/beta-lyase. The current homology model thus provides a starting point for further validation of the role of active site residues in ligand-binding by means of mutagenesis studies. Ultimately, insight in the binding of ligands to GTK/beta-lyase may result in the rational design of new ligands and selective inhibitors.     

ESCA-Untersuchungen an geätzten polytetrafluoräthylen-folien

In order to glue poly tetrafluoroethylene-films the surface of the polymer has to be etched. The etching is achieved by elemental sodium in liquid ammonia. The nature of the etched surface was investigated by means of ESCA (elektron spectroscopy for chemical analysis). No nitrogen, no sodium and most remarkably no fluorine was found. The surface contains only carbon and oxygen both of only one chemical sort. Contact with bromine or oxygen desactivates the etching. The desactivation is done by molecular oxygen only, not by oxygen compounds like water or methanol.     

Immunization with human papillomavirus type 16 (HPV16) oncoprotein-loaded dendritic cells as well as protein in adjuvant induces MHC class I-restricted protection to HPV16-induced tumor cells

Human papillomavirus (HPV) E6 and E7 oncoproteins are attractive targets for T-cell-based immunotherapy of cervical cancer. In this study, we demonstrate that dendritic cells (DCs) pulsed with HPV16 E7 protein are not only recognized in vitro by E7-specific CTLs but also elicit E7-specific CTL responses in vivo, associated with protection against a challenge with syngeneic HPV16-induced tumor cells. Vaccination with soluble E7 protein in incomplete Freund's adjuvant likewise induces E7-specific CTL responses associated with tumor protection. The presence of HPV16 E7-specific CTLs in vivo and the observation that depletion of CD8+ cells completely abolishes tumor protection demonstrate that CTLs are the major effector cells in mediating antitumor activity. The in vivo involvement of DCs in the activation of protective CTLs is suggested by the surface display of E7 peptide-loaded MHC class I molecules on these cells after E7 protein immunization. These data show that HPV16 E7 protein-pulsed DCs, as well as the administration of E7 protein antigen in adjuvant, can effectively stimulate tumor-specific MHC class I-restricted CD8+ T-cell-mediated protective immunity to HPV16-induced cancers.     

Testosterone and 5alpha-androstan-17beta-ol-3-one (DHT) levels in man

In order to test the hypothesis that plasma 17beta-hydroxy-5alpha-androstan-3-one (DHT) levels might represent a parameter of androgenicity independent of testosterone (T) levels, the T/DHT ratio was determined at low and high T levels in both sexes. High T levels in males were obtained either by stimulation of endogenous T secretion, but im injection of either short or long-acting T esters and finally by oral administration of 200 mg of crystalline testosterone. In females high T levels were obtained either by im injection of long-acting T esters or by oral administration of 200 mg of T. It was observed that the T/DHT ratio was not a function of sex but a function of T levels, whether T had an endogenous or a exogenous origin. When, as in patients with porto-caval shunt or cirrhosis of the liver, the liver was bypassed, oral administration of T resulted in relatively higher DHT levels than expected from T levels: this suggests an extra-hepatic origin of plasma DHT and/or a decreased hepatic metabolism of DHT. In a patient with the testicular feminization syndrome the T/dht ratios both under basal conditions and after im injection of T propionate were similar to those observed in normal subjects.     

Schweißen von Feinkornstählen und deren Eignung für Offshore‐Windenergieanlagen

Welding of fine grain structural steels and there suitability for offshore wind power plants. The investigations show that the high requirements on the mechanical values of a welded joint can be fulfilled by economical process versions of submerged arc welding. The submerged arc tandem twin welding process is predestined for the production of WPP (wind power plant) because of the high value of melting rate and the small expenditure of equipment. The used filler metal is suitable for the production of welded joints with mechanical values which fulfil safely the requirements. Steel grades produced by the TMCP becoming more and more popular for the producers of wind power generator tower because of there better processing and working properties. In comparison with normalized steel grades the TMCP steel grades have e.g. a lower carbon equivalent and higher toughness properties. With increasing clarity of the standards and of the working direction of the European offshore wind power industry further challenges will be appear for the producers of steel, wind power plants and welding equipment. A close cooperation between al partners is inalienable in that case.     

Effects of Low-dose Electron Beam Irradiation on Respiration, Microbiology, Texture, Color, and Sensory Characteristics of Fresh-cut Cantaloupe Stored in Modified-atmosphere Packages

Fresh‐cut cantaloupe was placed in modified‐atmosphere packages (4% oxygen, 10% carbon dioxide) and irradiated at 0 (control), 0.5, and 1.0 kGy. Irradiated samples had a lower and more stable rate of respiration than non‐irradiated samples over about 20 d. Total plate counts were higher (P < 0.05) in non‐irradiated control samples through day 11 (Trial 1) and for all dates tested (Trial 2). Color and texture remained stable for the duration of each study as measured by instruments and trained sensory panels. Sensory evaluation rated the 1.0‐kGy sample highest in “sweetness” and “cantaloupe flavor intensity” and lowest in “off‐flavor” after 17 (±3) d of storage. Low‐dose electron beam irradiation of fresh‐cut cantaloupe with modified‐atmosphere packaging offers promise as a method of extending shelf life.