Search

REBa$_{2}$Cu$_{3}$O$_{7}$−x (REBCO, RE = rare earth) compounds with different single RE elements were grown via TFA-MOD (metal-organic deposition of trifluoroacetates) to clarify their T$_{c}$ values when grown by the same preparation method and their processing windows; here: the crystallisation temperatures at a constant process gas composition (pO$_{2}$, pH$_{2}$O). We focussed on the lanthanides (Ln) Nd, Sm, Gd, Dy, Ho, Er and Yb as substituents for Y in the REBCO phase and investigated their growth behaviour in terms of resulting physical (inductive T$_{c}$ and J$_{c}$(77 K)) and structural properties (determined by XRD, SEM, TEM). All phases were grown as pristine films on LaAlO$_{3}$ and SrTiOx$_{3}$ and compared to their respective nanocomposites with 12 mol% BaHfO$_{3}$ for in-field pinning enhancement. With regard to T$_{c}$ and J$_{c}$(77 K), the optima of both values shift towards higher growth temperatures for increasing and decreasing RE ion size with respect to yttrium. Highest T$_{c}$ values achieved so far do not show a trend that can solely be related to the RE ionic size. On the contrary, T$_{c,90}$ values of the LnBCO compounds from Sm to Er range between 94.0 and 95.3 K and are, therefore, significantly larger than the highest values of the average-size non-lanthanide, Y, with T$_{c,90}$ = 91.5 K. J$_{c,sf}$ values at 77 K seem to plateau between 5 and 6 MA cm$^{-2}$ from Sm to Er and are again clearly above the maximum values we ever achieved for Y with 4.2 MA cm$^{-2}$. REBCO phase formations of the very small Yb and large Nd turned out to be more difficult and require further adjustment of growth parameters. All REBCO phases investigated here show distinct dependences of T$_{c}$ on the lattice parameter c.

An interactive quantitative temporal model of glucose intake, absorption and utilization in humans has been assembled using the Center for Research and Education in Aging Language (CREAL). CREAL is a language that can be used to describe biological systems from a macro to a molecular scale. This model displays the concentration of glucose throughout the gastrointestinal (GI) tract in relation to time. The rate of absorption of glucose through the intestinal walls and subsequent modulation of insulin and glucagon secretion rates can be graphed in relation to time as well as the utilization and depletion of glucose by the various organ systems. The model can also be utilized as part of a more comprehensive system that can simulate the intake, absorption and utilization of other compounds, such as lipids, proteins, minerals and carbohydrates. The quantitative results from these large scale simulations can be used to validate results from higher resolution simulations such as those that take place at the cellular scale.

Advanced ceramic composite materials that exhibit high strength and toughness with good thermal shock resistance are needed for emerging high-temperature engineering applications. A recently developed in situ reinforced barium aluminosilicate glass-ceramic shows promise of meeting many of the requirements for these types of applications with the added benefit of low-cost fabrication through densification by pressureless sintering. The material is toughened through in situ growth of rodlike {beta}-Si{sub 3}N{sub 4} grains resulting from the {alpha}-{beta} silicon nitride phase transformation. Microstructural development and material properties for temperatures up to 1,400 C are discussed. When compared to monolithic barium aluminosilicate, barium aluminosilicate reinforced with 70% by volume of Si{sub 3}N{sub 4} shows a significant increase in flexural strength (from 80 to 565 MPa) and fracture toughness (from 1.8 to 5.74 MPa {center_dot} m{sup 1/2}) with a high resistance to thermal shock.

The use of barium aluminosilicate (BAS) for transient liquid-phase sintering of Si 3 N 4 is being explored as a low-cost processing route which can provide improved properties. The effect of processing conditions on sinterability, crystalline structure and microstructure was examined. It was demonstrated that Si 3 N 4 could be pressureless sintered to high densities with BAS but that high volumes of BAS are required and hexacelsian preferentially forms as the intergranular phase. Even though hexacelsian is structurally unstable when acting alone, when present in a BAS-Si 3 N 4 composite, the in situ reinforcement provided by Si 3 N 4 serves to stabilize the composite sufficiently to permit its use in severe thermal environments.

During sintering of Si{sub 3}N{sub 4}, oxide based additives are added as sintering aids. These oxides form a liquid phase at elevated temperature which aids the {alpha} to {beta} transformation in Si{sub 3}N{sub 4} ultimately resulting in a uniform distribution of randomly oriented {beta}-Si{sub 3}N{sub 4}. It has been reported that the {alpha} to {beta} transformation in Si{sub 3}N{sub 4} is a reconstructive transformation of secondary coordination. This type of transformation requires breaking bonds, so a liquid phase is often needed to enable the transformation to occur. In addition, as this is a solution-diffusion-precipitation type of transformation, the kinetics of the transformation will depend on the sintering time, sintering temperature and amount of liquid phase present in the composites. The intent of this work was to evaluate the role of BAS content and temperature of sintering on the kinetics of the {alpha} to {beta} transformation in Si{sub 3}N{sub 4}.

A language that can describe biological systems from a macro to a molecular scale can play an important role in better understanding the mechanisms that drive the aging process and other biological processes. The Center for Research and Education in Aging Language (CREAL), was developed to allow biologists and Artificial Intelligence (AI) systems to augment a Knowledge Base (KB) that can be used as a data source by a massively paralleled simulation engine to describe complex systems. CREAL uses Java Script Object Notation (JSON) as its template to create nodes of information that can interact with other nodes within the simulation. The language can describe systems of transportation and location as well as properties, actions, and conditions of biological components and processes. A simulation using a KB with CREAL nodes can reveal many relationships between processes when using Dijkstra's shortest path algorithm, and with the aid of tools such as Hidden Markov Models (HMM) could suggest possible linkages...

The results obtained in the development of binders for coating materials and adhesives using dicyclopentadiene (DCPD) or DCPD secondary products are presented. Resin formation was undertaken via polycondensation and free-radical polymerisation in particular. The investigations were highly application-oriented and were aimed at industrial use. DCPD was incorporated via addition and polymerisation mechanisms. The resulting alkyd resins, polyesters and styrene/acrylate copolymers were tested in a large number of paint formulations and in special adhesives. It was found that the binders prepared using dihydrodicyclopentadienyl maleate (DHCM) exhibited particularly advantageous properties. In combination with other resins, they are suitable for air-drying and oven-drying coating materials, and after appropriate modification, water-thinnable resins may be obtained. Oxidatively crosslinking acrylate copolymers can be obtained via the corresponding maleate ester. The use of DCPD/styrene oligomers in alkyd resin synthesis gave binders with a high solids content and good drying times. The description and discussion of the results indicate a number of further practical uses for DCPD, the opportunity for industrial realisation in conventional resin plants being particularly notable.

Mechanical properties of two different purity MoSi2 intermetallic matrices reinforced with 20 vol percent silicon carbide platelets were investigated. The mechanical properties are found to increase significantly (up to 98 percent higher flexure strength) through the addition of silicon carbide platelets. The ultimate properties achieved at elevated temperature were influenced by intergranular phases formed during fabrication, while those achieved at room temperature were influenced by residual porosity. The brittle-to-ductile transition common to MoSi2 underwent a shift in transition temperature with a related change in the fracture surface morphology. At room temperature the best properties measured were for a composition using 99.95 percent pure MoSi2 (flexure strength of 297 MPa, fracture toughness of 7.50 MPa sq rt of m, and pin shear strength of 54.4 MPa). At elevated temperature the best properties measured were for a composition using 99.5 percent pure MoSi2 (flexure strength of 340 MPa at 1093 C). 7 refs.

Both life-long caloric restriction (CR) and the suppression of insulin-like growth factor-1 (IGF-1) signaling reliably extend the mammalian lifespan. The neuroendocrine system, regulated by the hypothalamus, remains the most convincing site of action for both these modes of life extension. Yet, determining whether CR actions are mediated by the modulation of neuroendocrine IGF-1 signaling remains unclear. Of the hypothalamic nuclei that express the IGF-1 receptor (IGF-1R), the cells of the supraoptic nucleus (SON) display some of the most robust IGF-1R expression. Taking IGF-1R immunoreactivity as an index of sensitivity to IGF-1, we counted IGF-1R immunoreactive and non-immunoreactive cells in the SON of young-ad-libitum fed (young-Al, 6 weeks), old-ad-libitum fed (Old-Al, 22 months), and old-calorie-restricted (Old-CR, 22 months) female B6D2F1 mice. An automated imaging microscopy system (AIMS) was used to generate cell counts for each section of supraoptic hypothalamus. Results show that while the total number of cells in the SON of ad-libitum fed mice does not change significantly with aging, a significant reduction in IGF-1R immunoreactive cells does occur in ad-libitum fed mice with aging. In contrast to this, calorie restricted mice show both a decline in the total number of cells and IGF-1R immunoreactive cells in the SON with age, but with the decrease in the latter being notably attenuated when compared to the degree of loss seen in ad-libitum fed mice. Thus, while CR induces greater loss in the total number of cells in the SON with age, it reduces the degree of age-dependent loss seen in IGF-1R expressing cells. As a result, when compared to Old-AL mice, the SON of Old-CR mice displays a greater proportion of IGF-1R cells and thus possibly enhanced IGF-1 sensitivity with aging.

The effects of electrophoretically pure murine interferon (Mu-IFN-alpha beta) on the T suppressor pathway and on the T effector cell of delayed hypersensitivity (TDH) were investigated in BALB/c mice, in a 2,4-dinitrofluorobenzene (DNFB) contact-sensitivity model. Various T cell subpopulations, suppressor T cells of the afferent (Ts-aff) and efferent (Ts-eff) types, an auxiliary Ts (Ts-aux), as well as TDH were induced, and their function was assessed in transfer experiments. The results were as follows. At a dose of 5 X 10(3) U, IFN was shown to inhibit the Ts-aff response, when given to the donor animal shortly after induction of the Ts-aff subpopulation or when injected into the recipient 2 hr after spleen cell transfer. Pretreatment in vitro with IFN of the splenic cells to be transferred also abolished the Ts-aff response. Similar amounts of IFN were able to inhibit the generation of Ts-eff in the donor animals, whereas 10-fold-higher amounts were needed in vivo or in vitro to block the functional expression of Ts-eff in the recipient animal. Intravenous injection of IFN into recipients of Ts-eff on day 0 and 1 after sensitization inhibited the expression of the Ts-eff transferred 1 day before ear challenge. This suggests that the Ts-aux response required for the TDH suppression by Ts-eff is blocked by IFN. Secretion of a suppressor factor by Ts in vitro was not blocked by IFN. Treatment of the donor of suppressor factor-secreting Ts with IFN, however, blocked the induction of this Ts. The TDH were not sensitive to IFN even at amounts approximately 100 times higher than those used for the Ts inhibition in vivo as well as in vitro. These results demonstrate that low amounts of IFN may selectively block the suppressor pathway, because induction of these regulatory T cell subsets appears to be particularly sensitive to IFN. The exact mechanism of the IFN-mediated inhibition of Ts is not yet clear. The data suggest an important regulatory function of IFN in delayed-type hypersensitivity (DTH) reactions.

About two dozen lubricating fluids were tested for use on electrical contacts on card edge or pin-and-socket connectors. The lubricants selected for screening represented a cross section of thewide variety of natural and synthetic materials available on the market. Among them were polyphenyl ethers, natural and synthetic hydrocarbons, several types of esters, polygiycols, some fluorinated materials, a few silicones, and some proprietary formulations. Lubricants were evaluated on the basis of volatility and their ability to prevent fretting corrosion on tin-to-solder contacts. Limited tests were also done on their spreading characteristics, their thermal degradation properties, and their effect on contact resistance. The objective of the work was to develop guidelines in the selection of contact lubricants for field testing. The lubricants were ranked on the basis of weight loss from thin deposits of the samples on solder foil coupons at 65°C. Fretting experiments were done by forcibly moving a printed circuit card finger between a pair of spring contacts cut from actual cards and connectors. The time required for contact resistance to increase from a few milliohms to 2 \Omeg was determined as a function of the amount of lubricant present.

We describe the wear process which occurs when a P.C. card with copper/nickel/solder metallization is inserted into an edge card connector that has a contacting pin with a spherical gold alloy dot and a normal force of about 300 gms. The presence of a lubricant delayed the successive wear processes and reduced the amount of solder displaced during a single pass by minimizing the cold welding of solder to the gold dot. Fretting corrosion experiments were made using a simple test jig which permits the use of actual production cards and connector parts. The fretting test fixture provides a way of comparing and evaluating actual connector designs, as well as a means of comparing the effectiveness of various lubricant formulations.

Fur den von HARINGTON synthetisierten (±)-β-Hydroxy-glutaminsaure-athylester wird die erythro-Konfiguration bewiesen. Der daraus gewonnene (±)-3-Hydroxy-prolin-athylester ist dementsprechend ein trans-Derivat.

Certain glass compositions in common use as gap spacers in ferrite recording head sliders have been shown to interact with air at 75% R.H. The reaction proceeds at 20°C and the corrosion products appear within a few days. The products vary from shape-less lumps to long single-crystal whiskers. In the presence of 300 ppb each of SO 2 and NO 2 the products are more voluminous. While the products are more prominent at the interface between glass and ferrite, they also appear on polished bulk glass specimens in total absence of a ferrite. The effect has been traced to the diffusion of lead, barium or lanthanum to the glass-air surface where the ions react with the atmosphere. An interaction between glass and ferrite was observed to occur during glass bonding. This interaction was indicated by the appearance of prominant grain boundaries in the ferrite at the ferrite/glass interface. Transgranular grain etching was also found. It is believed that interdiffusion of glass and ferrite components occurs and that this contributes to the mobility of the metal ions in the glass.

The corrosion resistance of cobalt alloy magnetic recording media was studied using both electrochemical and accelerated business environment corrosion testing. The electrochemical test was found to correlate reasonably well with the environmental test. Examination of various cobalt alloy discs, after exposure to the environmental test, showed similar corrosion product sizes, the presence of sulfur and oxygen in the corrosion products and different corrosion morphologies. A carbon overcoat served to improve a disc's corrosion resistance by inhibiting the lateral growth of corrosion products across the disc surface. Generally, Co-Cr media are the most corrosion resistant, followed by Co-Ni and Co-P, in decreasing order.

The deterioration of performance caused by aging was examined in 3,469 swimmers divided into 9 age groups and 4 styles of swimming. Comparisons using cross and longitudinal sections show that older swimmers become progressively slower, and the reduction of speed in all styles of swimming follows a quadratic trend. The losses of efficiency increase with age group, being by far the most in back-stroke and the least in crawl swimming. The combined longitudinal and cross sectional comparisons confirm this result, but not without any exception, for very often no statistically significant differences could be recognized between adjacent age groups. The interindividual comparison shows that it is also possible to maintain or even improve the efficiency over 10 to 12 years, even in the fifth or sixth decade of age, if the intensity and volume of training can be increased. The curve comprising reductions in the later stages of life may additionally be caused by the smaller number of persons per group and the deficient homogeneity within these groups. In addition to this, the tendency towards higher losses in older age groups is not significant, if only the best competitors of each age group are compared.

A method is described for the quantitative determination of the polymeric light stabiliser Chimassorb 944 in polypropylene. The polymer matrix is dissolved in hot decalin and precipitated by cooling. Extracting Chimassorb 944 from the suspension with diluted sulphuric acid effects a separation from other interfering additives. Chimassorb 944 is then quantitatively determined by UV spectroscopy. Depending on the solvent for dissolving and precipitating of the polypropylene matrix, different degrees of coprecipitation are found. By Soxhlet extraction during 16 h with chloroform, Chimassorb 944 is only slightly extracted. This is an advantage in view of its technical application.