Synthesis of α, ω-dichloro polyindene and poly(isobutylene-b-indene-b-isobutylene) employing Kennedy's inifer technique

Summary Kennedy's inifer technique has been modified and used for the preparation of ,-dichloro polyindene (PInCl₂). This telechelic has subsequently been used as initiator for the cationic isobutylene polymerization in conjunction with AlEt₂-Cl coinitiator. The resulting materials have been characterized by fractionation and GPC investigations.     

Zum Angriff von Aluminiumschmelzen auf niedriglegierten Stahl

Attack of molten aluminum on low alloy steel The present paper demonstrates the iron uptake by an initially ironfree hot dip aluminizing aluminum melt during the reaction with a low alloy steel (13 CrMo 44) between 700 and 800°C. The kinetic law governing iron accumulation in the melt is determined and correlated with the microscopically investigates phenomena at the phase boundary solid/melt. It is shown that an aluminum melt in contact with iron or steel not only takes up iron up to saturation but also removes from the solid additional iron, transforming it into the Θ-phase. The content of this phase in the iron saturated melt gradually increases during the process.     

On the influence of grain morphology on creep deformation and damage mechanisms in directionally solidified and oxide dispersion strengthened superalloys

Directionally solidified (DS) and oxide dispersion strengthened (ODS) superalloys like CM 247 LC and MA 760 exhibit elongated macrograins. In uniaxial creep tests, the creep strength of such alloys in the direction of the longitudinal grains is higher than that of an equiaxed grain structure, because significantly less grain boundary (GB) segments are perpendicular to the axis of the applied stress. The present study investigates how creep in the longitudinal direction of these alloys is influenced (1) by deviations of individual grain orientations from the optimum growth direction during casting (CM 247 LC) and (2) by the spatial distribution of the small transverse GB segments (MA 760) for a given grain aspect ratio. In the case of creep ductile CM 247 LC, it was shown that if there is a large fraction of grains that are oriented for single slip, this results in higher creep rates and lower rupture times than if there is only a small fraction of such grains. The study of the influence of grain morphology on creep damage accumulation in the creep-brittle and notch-sensitive ODS alloy MA 760 showed that large scatter in creep rupture lives is related to (1) the stochastic nature of creep damage accumulation on transverse GB segments and (2) the spatial distribution of transverse GB segments. It is the combination of these two factors that results in increased scatter in rupture lives as compared to equiaxed fine grain structures. This article is based on a presentation made at the “High Temperature Fracture Mechanisms in Advanced Materials” symposium as part of the 1994 Fall meeting of TMS, October 2-6, 1994, in Rosemont, Illinois, under the auspices of the ASM/SMD Flow and Fracture Committee.     

Induction effects for heterochromatic brightness matching, heterochromatic flicker photometry, and minimally distinct border: implications for the neural mechanisms underlying induction

Brightness induction refers to the finding that the apparent brightness of a stimulus changes when surrounded by a black versus a white stimulus. In the current study, we investigated the effects of black/white surrounding stimuli on settings made between red and green stimuli on three different tasks: heterochromatic brightness matching (HBM), heterochromatic flicker photometry (HFP), and minimally distinct border (MDB). For HBM, subjects varied the relative luminance between the red and green stimuli so that the brightness of the two colors appeared equal. For the two other tasks, matches were made based on minimizing red/green flicker (HFP) or the saliency of a red/green border (MDB). For all three tasks, the presence of black/white surrounding stimuli significantly altered red/green settings, demonstrating the existence of induction effects. These results are discussed in terms of which underlying color pathways (L+ M versus L-M) may contribute to induction effects for the different tasks.     

Simultaneous Detection and Differentiation of Campylobacter jejuni, C. coli, and C. lari in Chickens Using a Multiplex Real-Time PCR Assay

A multiplex real-time PCR (qPCR) assay was developed for simultaneous detection and differentiation of the three most important Campylobacter species in chickens. Three novel sets of PCR primers and TaqMan probes were designed to amplify the unique DNA sequences within the hipO, cdtA, and pepT genes which are specific to Campylobacter jejuni, Campylobacter coli, and Campylobacter lari, respectively. To avoid competition in the multiple target amplifications, the concentrations of primers and probes were optimized. By using the optimized qPCR conditions together with a minor-groove binding probe of pepT, amplification efficiency greater than 92% and detection sensitivity of 38 genome copies/reaction have been achieved for all three targets. The assay was highly specific for C. jejuni, C. coli, and C. lari with testing of 33 Campylobacter strains and 20 non-Campylobacter strains. In chicken samples spiked with known quantities of Campylobacter cells, the assay was able to detect 1 CFU/g after a 24-h enrichment. Application of the assay in food was further evaluated using 21 fresh chicken samples obtained from local supermarkets. The results revealed that, after a 24-h or 48-h enrichment, 14 samples (66.7%) were positive for C. jejuni, five samples (23.8%) were positive for C. coli, and none of the samples was contaminated by C. lari. Taken together, the multiplex qPCR assay combined with an enrichment step is a sensitive, species-specific, and non-labor-intensive method suitable for rapid detection of C. jejuni, C. coli, and C. lari in chicken samples.     

Spatial prices,search behavior and location

This paper presents a model that links spatial prices with search behavior and location. Consumers are assumed to search for a product at the lowest overall costs where suppliers are spatially distributed. The expected result of this “shopping decision” is linked with a longer term “quantity decision” relating the customer’s location via bid prices for land with the expected costs of buying the product. We demonstrate various characteristics of this model via numerical simulations.     

Separation of trace level hafnium from tungsten: a step toward solving an astronomical puzzle

182Hf (T(1/2) = 9 x 10(6) y) is believed to be formed by pure r-process during a supernova explosion, and therefore, the search for minute traces of 182Hf in the earth's crust is of great interest. Only accelerator mass spectrometry (AMS) is well suited for detecting such low levels of 182Hf. But any attempt to measure 182Hf by AMS must ensure that the sample is free from its naturally occurring stable isobar 182W. A simple method for separation of tungsten and hafnium has been developed using radiometric simulation followed by checking the decontamination of tungsten from Hf in a synthetic sample by AMS. The separation studies were performed by a liquid-liquid extraction technique using tri-n-octylamine (TOA) as the organic reagent. It has been found that a very high separation factor (1.6 x 10(6)) can be achieved when 0.3 M TOA diluted in cyclohexane is used as the organic phase and 6 M HCl (in the presence of small amount of H2O2) is used as the aqueous phase.