Evolution of hydrogen chloride from the surface of PVC wire-insulation

Long-term dark ageing in the temperature range 35 to 91°C, has shown that hydrogen chloride is released in small but measurable quantities from the surface of fully-stabilized PVC wire-insulating compounds. The rate of release is temperature- and time-dependent. For the particular formulations studied, there is an inverse dependence on the half-power of neutralizer content. Risks to electrical circuit components associated with PVC insulation in enclosed equipment are assessed and shown to be negligible for most normal operating conditions.     

Theoretically-based algorithms for robustly tracking intersection curves of deforming surfaces

This paper applies singularity theory of mappings of surfaces to 3-space and the generic transitions occurring in their deformations to develop algorithms for continuously and robustly tracking the intersection curves of two deforming parametric spline surfaces, when the deformation is represented as a family of generalized offset surfaces. The set of intersection curves of two deforming surfaces over all time is formulated as an implicit 2-manifold I in an augmented (by time domain) parametric space R⁵. Hyperplanes corresponding to some fixed time instants may touchI at some isolated transition points, which delineate transition events, i.e. the topological changes to the intersection curves. These transition points are the 0-dimensional solution to a rational system of five constraints in five variables, and can be computed efficiently and robustly with a rational constraint solver using subdivision and hyper-tangent bounding cones. The actual transition events are computed by contouring the local osculating paraboloids. Away from any transition points, the intersection curves do not change topology and evolve according to a simple evolution vector field that is constructed in the Euclidean space in which the surfaces are embedded.     

Management functions of clinical psychologists: A further assessment.

Surveyed 336 clinical psychologists to assess the extent and nature of their involvement in management functions. Findings indicate that 225 Ss (67%) claimed management as one of their major professional roles, occupying an average of 33% of their work time. These proportions varied little across diverse work settings or age groups. Most Ss reported that they felt inadequately prepared for their management roles. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Evaluation of acid and enzyme hydrolytic methods for the determination of edible aroid starch content

The starch content of four edible aroid (Araceae) cultivars was determined using acid and enzyme methods of hydrolysis. Hydrolysates were analysed using ferricyanide reduction, glucose oxidase and high performance liquid chromatography methods. Differences in starch values were obtained between the method of sugar analysis used when acid hydrolysis of samples was employed. The results obtained using enzyme hydrolysis, however, showed no significant differences between the methods of sugar analysis used. The results of these experiments indicate that, to obtain accurate starch values for edible aroids using the least expensive options, it is recommended that acid hydrolysis and the glucose oxidase-peroxidase glucose-specific assay methods or enzyme hydrolysis and ferricyanide sugar analysis be used. Starch degradation of ungelatinised samples by enzymic hydrolysis was very limited and showed considerable cultivar variation.     

Mechanische Hochtemperatureigenschaften von flugaschebasierten Geopolymerbetonen

Mechanical properties of fly ash‐based geopolymer concretes at high temperature At present, concretes based on alkali‐activated binders, so‐called geopolymer concretes, are investigated intensively in the building materials industry and by the research community as environmentally friendly alternative to Portland cement‐based concretes. These inorganic binders, which are based on industrial by‐products such as fly ash and ground granulated blast furnace slag, exhibit high resistance against corrosive acids and salts, if properly designed. The mechanical properties of fly ash‐based geopolymer concretes at high temperatures are subject of systematic investigations at the Bundesanstalt für Materialforschung und ‐prüfung (BAM) to create a basis for the structural design of fire exposed concrete members based on alkali‐activated binders. The concrete specimens, produced with quartz aggregates or lightweight aggregates and heated to a maximum temperature of 750 °C, exhibited a decrease of compressive strength up to temperatures of ca. 300 °C, attributed to formation of microcracks caused by dehydration. At higher temperatures the compressive strength of the investigated geopolymer concretes recovered partly, due to sintering processes starting from ca. 500 °C. Because of this beneficial property when compared to conventional concretes, geopolymer concretes can potentially be applied in infrastructure facilities where fire resistance is critical. From the results of the thermomechanical tests stress‐strain relationships are derived that can be used for the structural design of members made from geopolymer concretes.     

Identification of phenolic compounds in edible aroids

The objective of these experiments was to study the phenolic compounds present in the cormels of the edible aroids, Colocasia spp and Xanthosoma spp. This investigation shows the existence of a range of phenolic compounds which includes gallic acid, chlorogenic acid, ( + )-catechin, ( ? )-epicatechin and ( ? )-epigallocatechin and the possible presence of proanthocyanidins and jlavonols. Aqueous acetone extracts were examined by thin layer chromatography and high performance liquid chromatography for their phenolic constituents.     

Wideband propagation measurements of short range millimetric radiochannels

There is an increasing emphasis to extend the services available on fixed telecommunication networks to the mobile user. One area of the RACE 1043 project examined the possibility of universal mobile services within future integrated broadband communications networks. Essential to the feasibility of such a scheme is an understanding of the wideband characteristics of the radio channel. The article describes the results of a wideband channel sounding programme conducted at 39 and 60 GHz, together with a channel-modelling exercise based on these measurements, aimed at producing a statistical model of the wideband millimetric channel     

A Revised Identical Elements Model of Arithmetic Fact Representation.

The identical elements model of arithmetic fact representation (T. C. Rickard, A. F. Healy, & L. E. Bourne, 1994) states that, for each triplet of numbers (e.g., 4, 7, 28) that are related by complementary multiplication and division problems, there are 3 independent fact representations in memory: (4, 7, x)→ 28; (28 / 7) 3 4; and (28 / 4) 3 7. In this article, the author reviews the evidence for this model, considers alternative accounts, and proposes a simple and empirically motivated revision to the model that (a) accommodates conflicting results, (b) provides a novel account of the ties effect, and (c) makes new and nonintuitive predictions for the factoring operation (e.g., factoring of 28 into 4 and 7). The author reports 3 experiments designed to test these predictions and discusses implications for arithmetic instruction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The hydrolysis of xylan by Cellulomonas preparations

Thin layer chromatography was demonstrated as an effective technique for observing the time course of hydrolysis of a substituted xylan (arabinoxylan) by crude preparations of Cellulomonas. The chromatograms revealed a sequential pattern of appearance of xylooligomers and arabinoxylooligomers, with early appearance of relatively large oligomers and subsequent accumulation of xylobiose and (to a lesser extent) xylose and arabinose. The pattern indicated that the dominant enzymic activity towards arabinoxylan is that of an endoxylanase.     

Sulfuric acid pressure leaching of nickeliferous limonites

This laboratory study examines the sulfuric acid pressure leaching characteristics of nickeliferous limonite samples from South New Caledonia. The effect of temperature (225°C to 300°C), acid-to-ore ratio (0.21 to 0.30), pct solids (10 to 45), particle size (-20 to -270 mesh), and agitation (50 to 600 rpm) on nickel extraction and selectivity are discussed. For overall improvement of the leach response, leaching is best conducted at temperatures higher than 250°C and at solids less than 33 pct. Variation of goethite, hematite, and basic aluminum sulfate content of the leach residue was determined semiquantitatively as a function of leaching time. Sulfate content of the residue rises sharply during the first several minutes of leaching, then falls, and finally equilibrates at five to six percent. This change in sulfate analysis can be explained by assuming a series of consecutive iron and aluminum hydrolysis reactions.