Polymer derived ceramic materials from Si,B and MoSiB filler-loaded perhydropolysilazane precursor for oxidation protection

Silica-based coating systems were developed using polymer derived ceramics (PDCs) technology. Ceramic composites on the base of a SiO₂ and SiNO matrix and homogeneously distributed Mo₅SiB₂, SiB₆, Si and B fillers were manufactured. The coating systems have low porosity and provide a high oxidation resistance up to 100 h at 800 °C and 1100 °C in air. The influence of temperature and atmosphere of pyrolysis on the polymer precursor, the volume fraction of filler materials on the chemical composition of compacts as well as their high-temperature oxidation protection was investigated.     

Effect of complexation of oxidised corn starch with mineral elements on physicochemical properties

The objective of this study was to determine the effect of complexation of oxidised starch with mineral elements on its physicochemical properties. Corn starch was oxidised with sodium hypochlorite and, afterwards, modified with ions of potassium, magnesium and iron. Thus, native and modified starches were analysed for: contents of mineral elements, colour parameters (L*a*b*), water binding capacity and solubility in water at temperature of 60 and 80 °C. Thermodynamic characteristics of gelatinisation by DSC, molecular weight distribution by GPC, intrinsic viscosity and pasting properties by RVA were studied. The efficiency of incorporation of metal ions into oxidised corn starch was about 30%, 20% and 20% for potassium, magnesium and iron ions, respectively. The complexation with potassium ions caused the greatest changes in the molecular weight distribution and the intrinsic viscosity of starches and viscosity of starch pastes. Only modification of starch with iron ions affected the colour parameters of the starch. Incorporation of metal ions into starch resulted also in changes in its water binding capacity and solubility in water.     

Impact of adhesive ingredients on adhesion between rubber and brass-plated steel wire in tire

Proficiency on underlying mechanism of rubber-metal adhesion has been increased significantly in the last few decades. Researchers have investigated the effect of various ingredients, such as hexamethoxymethyl melamine, resorcinol, cobalt stearate, and silica, on rubber-metal interface. The role of each ingredient on rubber-metal interfacial adhesion is still a subject of scrutiny. In this article, a typical belt skim compound of truck radial tire is selected and the effect of each adhesive ingredient on adhesion strength is explored. Out of these ingredients, the effect of cobalt stearate is found noteworthy. It has improved adhesion strength by 12% (without aging) and by 11% (humid-aged), respectively, over control compound. For detailed understanding of the effect of cobalt stearate on adhesion, scanning electron microscopy and energy dispersive spectroscopy are utilized to ascertain the rubber coverage and distribution of elements. X-ray photoelectron spectroscopy results helped us to understand the impact of Cu_XS layer depth on rubber-metal adhesion. The depth profile of the Cu_XS layer was found to be one of the dominant factors of rubber-metal adhesion retention. Thus, this study has made an attempt to find the impact of different adhesive ingredients on the formation of Cu_XS layer depth at rubber-metal interface and establish a correlation with adhesion strength simultaneously.     

Performance of PKI-based security mechanisms in mobile ad hoc networks

Security for ad hoc network environments has received a lot of attention as of today. Previous work has mainly been focussing on secure routing, fairness issues, and malicious node detection. However, the issue of introducing and conserving trust relationships has received considerably less attention. In this article, we present a scalable method for the use of public key certificates and their revocation in mobile ad hoc networks (MANETs). With the LKN-ad hoc security framework (LKN-ASF) a certificate management protocol has been introduced, bringing PKI technology to MANETs. In addition a performance analysis of two different revocation approaches for MANETs will be presented.     

Purification of the cardiac sarcoplasmic reticulum membrane protein phospholamban from recombinant Escherichia coli

Phospholamban (PLN) was expressed in Escherichia coli as a protein fusion with glutathione S-transferase (GST). GST-PLN was mostly present in the insoluble protein fraction and accounted for approximately 50% of total insoluble protein. Attempts to suppress inclusion body formation or to use GST as an affinity-purification tag failed. A successful purification method is based on preparative SDS/PAGE and electrodialysis. From 1 g cells we typically purified 13.5 mg fusion protein with a PLN content of 2.8 mg. We genetically inserted an enterokinase (EK) protease site just in front of the PLN sequence and demonstrated the proteolytical liberation of PLN from the carrier protein. The approach described represents a substantial advancement in PLN expression and purification.     

Does {charm} need depth? Similarity and levels-of-processing effects in cued recall.

Eich (1985) recently presented a distributed memory model in which the pattern of results used to support the levels-of-processing view of Craik and Lockhart (1972) was modeled by different degrees of similarity between the encoding context and the to-be-recalled item. We report two experiments in which both phonemic and semantic similarity were varied between pairs of words and incidental acquisition (rhyme vs. category judgments) was varied across the same pairs of items. In both experiments the manipulation of the acquisition task produced a difference in cued-recall performance for positive and negative rhyme and category judgments. Recall was better following a category encoding decision than following a rhyme decision. This difference was independent of the effects of similarity, which demonstrated that Eich's (1985) assumptions regarding the effects of similarity are not sufficient to account for the differences resulting from the manner in which subjects encode information. An alternative method of modeling the levels-of-processing effect within the framework of distributed memory models is proposed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An artificial neural network approach on parametric optimization of laser micro-machining of die-steel

In the present research, laser micro machining (LMM) of tungsten-molybdenum general purpose high speed steel (Rex M2) has been studied. Selection of optimum machining parameter combinations for obtaining higher depth of groove and smaller height of recast layer is a challenging task in LMM due to the presence of a large number of process variables. There is no perfect combination of parameters which can simultaneously result in both the highest depth of groove and lowest height of recast layer. This paper presents an attempt to develop a strategy for predicting the optimum machining parameter setting for the generation of the maximum depth of groove with minimum height of recast layer. A feed forward back-propagation neural network has been developed to model the machining process. The model, after proper training, is capable of predicting the response parameters as a function of four different control parameters. Experimental results demonstrate that the machining model is suitable and the optimization strategy satisfies practical requirements. The developed model has been found to be quite unique, powerful and flexible.     

Context-gated knowledge partitioning in categorization.

According to the knowledge partitioning framework, people sometimes master complex tasks by creating multiple independent parcels of partial knowledge. Research has shown that knowledge parcels may contain mutually contradictory information, and that each parcel may be used without regard to knowledge that is demonstrably present in other parcels. This article reports 4 experiments that investigated knowledge partitioning in categorization. When component boundaries of a complex categorization were identified by a context cue, a significant proportion of participants learned partial and independent categorization strategies that were chosen on the basis of context. For those participants, a strategy used in one context was unaffected by knowledge demonstrably present in other contexts, suggesting that knowledge partitioning in categorization can be complete. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Polarization control in a vertical cavity surface emitting laser submitted to optical feedback

We study experimentally and theoretically two polarization effects in a vertical cavity surface emitting laser submitted to optical feedback. In a first experiment, we obtain flips between two linearly polarized laser modes up to a frequency of 50 MHz using an external cavity with a polarizer. In a second experiment, polarization self modulation is demonstrated up to a frequency of 2.6 GHz, using a quarter wave plate instead. Numerical calculations, based on a four levels model for the active medium, show a good agreement with the experiments.     

Potency comparison of peptidomimetic inhibitors against HIV-1 and HIV-2 proteinases: design of equipotent lead compounds

The results of investigation of haptoglobin (Hp) types in 596 donor blood samples in some towns of Ukraine (Dnepropetrovsk, Kharkov, Odessa, Kiev, Uzhgorod, Zhitomir) are presented. Three normal Hp types (Hp1-1, Hp2-1 and Hp2-2) have been found. The reliable interpopulation differences in the Hp types frequency were not found. On the whole the Hp types frequency in the type Hp1-1 comprised 12.7%. In the type Hp2-1-48.1% and in the type Hp2-2-36.5%. The frequency of the gene Hp1 is 0.38. The frequency of the Hp types and of the gene Hpl in Ukraine is similar to that in population of Eastern Europe and European Part of Russia.