XRD Investigations of the Phosphorus Effect on the Oxidation of TiAl Alloys by High-Resolution Methods

Recently it has been found that very small amounts (a few 100 ppm) of Padded to -titanium aluminide can significantly alter the oxidationbehavior between 973 and 1273 K. The mechanism responsible for this changeis, however, still not clear. In the present study, phosphorus wasincorporated into the surface of TiAl (containing 50 at.% Al) by ionimplantation and oxidation tests were carried out at 1173 K inair. Improvement of oxidation resistance is only temporary up to 100 hr forphosphorus-implanted TiAl. After 100 hr, the oxidation rate increases andbreakaway oxidation follows. XRD and EPMA showed that the breakawayoxidation is connected with massive nitride formation. Two different modelsare proposed which can explain the effect of phosphorus additions on theoxidation kinetics of TiAl during the protective stage within the first100 hr. The breakaway effect can be explained by penetration of air to themetal–oxide interface zone because of microcrack formation in theoxide scale, which was experimentally proved by acoustic-emission analysis.     

Characterization of the human gonadotropin-releasing hormone receptor heterologously produced using the baculovirus/insect cell and the Semliki Forest virus systems

1. Two eukaryotic viral systems, the baculovirus/insect cell and the Semliki Forest virus systems, were tested for heterologous expression of human gonadotropin-releasing hormone receptor (GnRHR) cDNA. 2. An unmodified as well as a c-myc epitope-tagged human GnRH receptor was produced in two insect cell lines (Spodoptera frugiperda, Trichoplusia ni) after infection with the respective recombinant baculoviruses. In both insect cell lines, the receptor was identified by immunoblot analysis as a triplet of bands between 35 and 40 kDa. After deglycosylation of the receptor the molecular mass decreased to 35 kDa. The GnRH receptor was localized in membrane compartments within the infected insect cells. However, only in membranes of infected Trichoplusia ni insect cells could approximately 2000 receptors per cell be detected. 3. Production of the GnRH receptor in BHK cells using the Semliki Forest virus system resulted in approximately 50,000 receptors per cell. A maximal yield of 0.42 pmol/mg membrane protein was obtained 24 hr after electroporation of BHK cells with in vitro synthesized RNA. Binding of the antagonist [125I]Cetrorelix was saturable with a KD of 1.3 nM. The receptor produced in the BHK cells was further characterized by ligand displacement studies. The rank order of agonist and antagonist affinities was Cetrorelix > Triptorelin > Antide > GnRH.     

Hydroxyl Group Separation Distances in Anti-Freeze Compounds and Their Effects on Ice Nucleation

Since the discovery of biological antifreeze glycoproteins (AFGPs), which can inhibit ice nucleation, there has been considerable interest in understanding their mechanisms and mimicking them in synthetic polymers. In this study, we used molecular dynamics simulations of modified polyvinyl alcohol (PVA) compounds to show that the hydroxyl (OH) group distance is a key factor in whether certain compounds promote or inhibit ice nucleation. A hydroxyl distance smaller than ~2.8 Å but greater than ~7.1 Å in modified PVA (MPVA) compounds was associated with the promotion of ice nucleation, while a hydroxyl group separation distance of approximately ~5.0 Å was correlated with a delay in ice nucleation, owing to changes in the energy of the system. Thus, these results may help explain some of the mechanisms of current known anti-freeze compounds and may have implications for designing new anti-freeze compounds in the future.     

靴套的创新开发--QualiFlex靴套

对比了QualiFlex Q型,QualiFlex QX型、QualiFlex QV型三种聚胺酯材料靴套的性能,从而说明独特的QualiFlex靴套性能,使纸幅横幅水分的均匀性得到改善,纸幅出压榨干度得以维持恒定.     

Expression and initial characterization of a soluble glycine binding domain of the N-methyl-D-aspartate receptor NR1 subunit

Glycine is an essential co-agonist of the excitatory N-methyl-D-aspartate (NMDA) receptor, a subtype of the ionotropic glutamate receptor family. The glycine binding site of this hetero-oligomeric ion channel protein is formed by two distinct extracellular regions, S1 and S2, of the NR1 subunit, whereas the homologous domains of the NR2 subunit mediate glutamate binding. Here, segments S1 and S2 of the NR1 polypeptide were fused via a linker peptide followed by N- and C-terminally tagging with Flag and His6 epitopes, respectively. Infection of High Five insect cells with a recombinant baculovirus containing this glycine binding site construct resulted in efficient secretion of a soluble fusion protein of about 53 kDa. After affinity purification to near-homogeneity, the fusion protein bound the competitive glycine site antagonist [3H]MDL105,519 with high affinity (Kd = 5.22 +/- 0. 13 nM) similar to that determined with rat brain membrane fractions. This high affinity binding could be competed by the glycine site antagonist 7-chlorokynurenic acid as well as the agonists glycine and D-serine but not by L-glutamate. This indicates that the S1 and S2 domains of the NR1 subunit are sufficient for the formation of a glycine binding site that displays pharmacological properties similar to those of the NMDA receptor in vivo.     

Characterization of gonadotropin-releasing hormone analogs based on a sensitive cellular luciferase reporter gene assay

Blood samples and questionnaire background data were collected from 96 children (age 2-14 years) living in urban, suburban, or rural areas with varying traffic intensity and industrial lead pollution in Uruguay. Spot samples of tap water were collected from the homes of 44 children, and samples of top soil were taken from seven areas. Samples of air-borne dust were collected in central and suburban Montevideo. Blood lead concentrations (B-Pb) in children ranged between 47 and 191 (mean 96) micrograms/L and exceeded in 36% of the children 100 micrograms/L, the intervention level adopted by the United States Centers for Disease Control. Lead in tap water ranged from 0.2 to 230 (mean 15) micrograms/L and exceeded in 39% of the samples the maximum level recommended by WHO, 10 micrograms/L. Lead pipes were used in parts of the water supply systems. Lead in air varied between different locations from 0.15 to 1.7 micrograms/m3, highest in the very center of Montevideo. The median soil lead ranged from 6 to 2100 micrograms/g and was highest in industrially polluted areas. At multiple regression analysis, B-Pb was significantly associated only with age (P = 0.032) and traffic intensity at school (P = 0.045). No significant impact on B-Pb of lead in water or soil could be established.     

Evolution of central pattern generators for bipedal walking in areal-time physics environment

We describe an evolutionary approach to the control problem of bipedal walking. Using a full rigid-body simulation of a biped, it was possible to evolve recurrent neural networks that controlled stable straight-line walking on a planar surface. No proprioceptive information was necessary in order to achieve this task. Furthermore, simple sensory input to locate a sound source was integrated to achieve directional walking. To our knowledge, this is the first work that demonstrates the application of evolutionary optimization to 3D physically simulated biped locomotion     

Solubilization and purification of the human ETB endothelin receptor produced by high-level fermentation in Pichia pastoris

In the present report, the successful solubilization and purification of the ETB receptor heterologously produced in the methylotrophic yeast P. pastoris is described for the first time. In comparison to the baculovirus system where successful production, solubilization and purification have already been reported, handling and up-scaling of recombinant P. pastoris cells was much easier and less time consuming. Recombinant P. pastoris clones producing two different ETB receptor constructs were grown in a fermenter to a density of about 360 g/l. After induction with methanol, a production level of maximally 45 pmol/mg was obtained, a value which is in the range of that reported for baculovirus-infected insect cells. A method for the large-scale preparation of membranes was established. Solubilization of the recombinant ETB receptor was achieved with the detergent n-dodecyl-/beta-D-maltopyranoside. The stability of the solubilized and ligand-bound receptor was examined in detail. Subsequently, two purification methods for two different receptor constructs were tested and a large-scale procedure for isolation of recombinant receptor was established. In general, the purification methods described herein will be adaptable to other G protein-coupled receptors heterologously produced in heterologous expression systems including P. pastoris.     

Three-dimensional SU-8 sub-micrometer structuring by electron beam lithography

We demonstrate electron beam lithography on the negative tone electron resist SU-8 to fabricate self-supporting three-dimensional structures in sub-micrometer range. Applying SU-8 thin films spin cast on glass substrates and forming layers of 1 μm thickness, the structuring is performed in a two step process. First, the SU-8 film is exposed for supporting structures down to the substrate, a second exposure step with accordingly modified parameters leads to elevated structures. Applications as microscale shadow masks for evaporation based deposition processes and microfluidics are discussed.