Investigation of a catalytic zinc binding site in Escherichia coli L-threonine dehydrogenase by site-directed mutagenesis of cysteine-38

We studied block of the internal pore of the ROMK1 inward-rectifier K+ channel by Mg2+ and five quaternary ammoniums (tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetrabutylammonium, and tetrapentylammonium). The apparent affinity of these blockers varied as a function of membrane voltage. As a consequence, the channel conducted K+ current more efficiently in the inward than the outward direction; i.e., inward rectification. Although the size of some monovalent quaternary ammoniums is rather large, the zdelta values (which measure voltage dependence of their binding to the pore) were near unity in symmetric 100 mM K+. Furthermore, we observed that not only the apparent affinities of the blockers themselves, but also their dependence on membrane voltage (or zdelta), varied as a function of the concentration of extracellular K+. These results suggest that there is energetic coupling between the binding of blocking and permeating (K+) ions, and that the voltage dependence of channel blockade results, at least in part, from the movement of K+ ions in the electrical field. A further quantitative analysis of the results explains why the complex phenomenon of inward rectification depends on both membrane voltage and the equilibrium potential for K+.     

Prenatal diagnosis of beta-thalassemia. Detection of a single nucleotide mutation in DNA

We investigated a method employing synthetic oligonucleotides for the prenatal diagnosis of beta-thalassemia due to a single nucleotide mutation. The beta 0 thalassemia we tested is produced by a nonsense mutation and is commonly found in Sardinia and other parts of the Mediterranean. In this DNA lesion, the glutamine codon CAG at the beta 39 position is mutated to TAG, which results in a stop codon and premature termination of the beta-globin chain. We synthesized two oligonucleotides: one homologous to the normal beta A gene and the other to the beta 0 thalassemia gene at the beta 39 location. The oligonucleotides were labeled with 32P and used as hybridization probes for normal and thalassemic DNA. The beta A probe hybridized only to the normal DNA, and the beta-thalassemia probe only to thalassemic DNA, thus providing a technique for direct demonstration of the mutation. The method is sensitive enough to be applied directly to DNA that is isolated from uncultured cells obtained from only 20 ml of amniotic fluid as early as the 16th gestational week.     

Adaptive online quality control for injection‐molding by monitoring and controlling mold separation

This paper presents a unique method that makes use of a small signal (of the magnitude of microns) measured by a precision linear displacement transducer mounted on the outside of mold plates to monitor the momentary separation of the core and cavity plates. The maximum value of the separation is found to be highly correlated with part weight, one of the important quality indices. The whole profile of the mold separation (MS) is monitored and used in order to control the process adaptively and to keep the part quality consistent. Adaptive algorithms are developed to control the switchover point from filling to packing in terms of hydraulic pressure from shot to shot. Within a shot, the hydraulic pressure during the holding stage is manipulated to control the MS profile. The experimental results with different resins and mold geometries show that the variation of part weight is reduced significantly as compared to the conventional hydraulic pressure control. POLYM. ENG. SCI. 46:569–580, 2006. © 2006 Society of Plastics Engineers     

A novel electron‐transport material for organic light‐emitting devices

Abstract— A nanocrystalline electron‐transport material [ET68] was introduced into organic light‐emitting devices (OLEDs). By integrating a p‐doped transport system and phosphorescent emitters, a very bright and stable device could be obtained. Furthermore, 40% saving in power consumption can be achieved when the efficient pixels with ET68 were applied to AMOLEDs.     

Plasma transferred arc repair welding of the nickel-base superalloy IN-738LC

Plasma transferred arc welding (PTA) has been considered a promising process to restore worn areas of land-based gas turbine blades and vanes. The objective of this investigation was to study the effect of PTA welding on the repairing of IN-738LC superalloy components. Tensile tests were conducted on specimens welded with various combinations of parameters. Room temperature, 760 °C, and 980 °C were selected as tensile test temperatures. High-temperature phase transformed, during solidification, were identified by differential thermal analysis (DTA). The weld-pool shapes and microstructures of welded specimens prepared by various welding parameters were evaluated by optical metallography (OM), a scanning electron microscope (SEM) equipped with energy dispersive x-ray spectrometer (EDS), and microhardness testing. Results of this study showed that PTA welded specimens exhibited 96% nominal tensile strength of IN738LC base materials. Specimen failure was observed predominantly in the base materials instead of in the heat-affected zone (HAZ) for gas tungsten arc weld (GTAW) repair weldments. IN-738LC is considered susceptible to weld cracking during fusion welding; however, using a low-input heat repair welding process (PTA), cracking susceptibility could be minimized by the optimized welding parameters.     

On fully orientability of 2-degenerate graphs

Suppose that D is an acyclic orientation of the graph G. An arc of D is dependent if its reversal creates a directed cycle. Let d(D) denote the number of dependent arcs in D. Define dmin(G) (dmax(G)) to be the minimum (maximum) number of d(D) over all acyclic orientations D of G. We call G fully orientable if G has an acyclic orientation with exactly k dependent arcs for every k satisfying dmin(G)?k?dmax(G). We prove that every 2-degenerate graph is fully orientable and give interpretations to their dmin.     

Activation of an adenosine 3'',5''-cyclic monophosphate-dependent Cl- conductance in response to neurohormonal stimuli in mouse endometrial epithelial cells: the role of cystic fibrosis transmembrane conductance regulator

Nitrogen-fixing microbial populations in a Douglas fir forest on the western slope of the Oregon Cascade Mountain Range were analyzed. The complexity of the nifH gene pool (nifH is the marker gene which encodes nitrogenase reductase) was assessed by performing nested PCR with bulk DNA extracted from plant litter and soil. The restriction fragment length polymorphisms (RFLPs) of PCR products obtained from litter were reproducibly different than the RFLPs of PCR products obtained from the underlying soil. The characteristic differences were found during the entire sampling period between May and September. RFLP analyses of cloned nifH PCR products also revealed characteristic patterns for each sample type. Among 42 nifH clones obtained from a forest litter library nine different RFLP patterns were found, and among 64 nifH clones obtained from forest soil libraries 13 different patterns were found. Only two of the patterns were found in both the litter and the soil, indicating that there were major differences between the nitrogen-fixing microbial populations. A sequence analysis of clones representing the 20 distinct patterns revealed that 19 of the patterns had a proteobacterial origin. All of the nifH sequences obtained from the Douglas fir forest litter localized in a distinct phylogenetic cluster characterized by the nifH sequences of members of the genera Rhizobium, Sinorhizobium, and Azospirillum. The nifH sequences obtained from soil were found in two additional clusters, one characterized by sequences of members of the genera Bradyrhizobium, Azorhizobium, Herbaspirillum, and Thiobacillus and the other, represented by a single nifH clone, located between the gram-positive bacteria and the cyanobacteria. Our results revealed the distinctness of the nitrogen-fixing microbial populations in litter and soil in a Douglas fir forest; the differences may be related to special requirements for degradation and mineralization processes in the plant litter.     

Residual wall thickness of water‐powered projectile‐assisted injection molding pipes

Water‐powered projectile‐assisted injection molding (W‐PAIM) is an innovative molding process for the production of hollow shaped polymer parts. The W‐PAIM utilizes high pressure water as a power to drive a solid projectile to displace the molten polymer core to form the hollow space. The residual wall thickness (RWT) and its distribution are the important quality criteria. The experimental and numerical investigations were conducted. Experimental specimens showed that the RWT of a W‐PAIM pipe was much thinner than that of a water‐assisted injection molding pipe. The cross‐section size of the projectile defined the basic penetration section size. The software FLUENT was used to obtain the instantaneous distributions of the flow field, which revealed the forming mechanism of the RWT. The experiments indicated that the processing parameters, such as melt temperature, melt injection pressure, mold temperature, and water injection delay time had obvious effects on the RWT, while the water pressure had little effect on it. The RWT of curved pipes was thin at the inner concave side while thick at the outer convex side. The RWTs at the bend portion are influenced by the deflection angle and bending radius, which is due to the pressure difference between the two sides. POLYM. ENG. SCI., 59:295–303, 2019. © 2018 Society of Plastics Engineers