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991.
The effect of cycling the external conditions on the timber quality and drying time during seasoning has been studied for red beech (Nothofagus fusca), a difficult-to-dry New Zealand hardwood, inalaboratorybatchdryer. Intermittent drying at anair temperature of 45°C and a wet-bulb depression of 10°C takes longer to yield a given moisture content than continuous drying under the same conditions, but produces timber without honeycomb or severe case-hardening as observed in continuous drying. The experiments also indicate that the timber can tolerate a higher air temperature (55°C) in intermittent drying at the same wet-bulb depression with less case-hardening and without showing honeycomb compared with continuous drying at 45°C, having a similar total drying time. Intermittent drying at a slightly higher dry-bulb temperature (60°C) and a much higher wet-bulb depression (18°C) gives a similar degree of case-hardening to that found in samples dried continuously at a dry-bulb temperature of 45°C. 相似文献
992.
993.
Computers with analytical capabilities have proven their worth in sophisticated gaging applications, but they can intimidate operators. Dedicated keyboards with a logical button-to-button function connection present the user with multiple options. They can be cumbersome and often require adaptation for different parameters or program options. Standard P.C. keyboards do provide more programming flexibility but keys are not easily related to function. This paper discusses the development of a touch screen and related software functions as a dedicated keyboard which presents a very limited number of operating options at any one time. Using simple color graphic icons or “windows”, the described software guides the operator through the measurement process via a logical series of questions and menu operations. The program presents only specific questions or options that are relevant to the current measurement, which provides for a more friendly interface between operator and instrument. 相似文献
994.
It has been known for some time that crystal-field matrix elements (i.e., matrix elements of sums over spherical harmonics involving the coordinates of the individual electrons) are often unexpectedly proportional to one another in the f shell. To see whether similar relations hold for more complicated operators than those provided by the crystal field, we examined the matrix elements of the three-electron scalar operators ti for all configurations fN, as calculated by W. T. Carnall on the basis of the computer program of Hannah Crosswhite. These operators are widely used to take configuration interaction into account, and we found a surprising number of proportionalities that go beyond what would be expected on a straightforward application of the Wigner-Eckart theorem, as applied to the irreducible representations of the classic groups SO(7), G2 and SO(3) used by Racah in defining the f-electron states. A listing of such relations is provided. 相似文献
995.
We have studied theoretically and experimentally the fluorescence enhancement in fluoroborate glasses, doped with the ion Eu3+, containing small silver particles. The model developed shows that the gain coefficient has quenching and enhancement regions. The absorption peak of the metallic particles occurs at 425 nm, which is not in resonance with the 5L6 level of the ion Eu3+. For this reason it is not possible to make a complete comparison between theoretical and experimental results, but the structure of the absorption spectra allows us to check some crucial aspects of the problem, such as energy transfer, enhancement of the local field and the high absorption by the particle system. Results of electronic microscopy have revealed non-uniformity of the particle distribution with average radii of approximately 20 Å and 35 Å and a measured localized mean filling factor of 0.02. 相似文献
996.
Fast pitting corrosion in a steel/water system as a result of unusual stabilization of anodes Corrosion damage as a result of fast pitting was observed in industrial equipment made of unalloyed steel. The rate of formation and the manifestation of the pits are similar to pitting corrosion of stainless steels. Estimation of the kinetics of the localized corrosion in terms of differential aeration cells led to a model which indicates the stabilization of small anodic regions. The stabilization was caused by precipitation of the products of reaction between ferrous ions and polymeric silicate. The high rate of pitting also suggests that the oxygen entering the system during service periods involving the exposure of the system to air has enhanced the corrosion. These ideas could be substantiated by experiments, which also revealed particularly the effect of the concentration of NaCl. Anodic passivation by the addition of Na2CO3 or perhaps inhibition may be considered as candidate protective measures. 相似文献
997.
Despite differences in the structures of aldoses and ascorbic acid, ASA, the non-enzymic browning of the latter involves intermediates similar to those found in Maillard browning. The kinetics of the sulphite-inhibited browning of ASA suggest that, under anaerobic conditions, the rate of reaction of sulphite species, S(IV), is of first order with respect to S(IV). The possibility that S(IV) could catalyse the hydrolysis of the lactone ring of ASA is considered by reference to D-glucono-delta-lactone. Evidence is presented to suggest that, under aerobic conditions, autoxidation of ASA leads to the oxidation of S(IV). The composition of melanoidins from ASA-glycine mixtures is compared with that from arabinose-glycine; the former contain 2 x 5 times more ASA-derived residues per glycine molecule than arabinose-derived residues per glycine molecule in the latter. The implications of these findings to the mechanism of ASA browning are discussed. 相似文献
998.
A Stammati C Zanetti L Pizzoferrato E Quattrucci G B Tranquilli 《Food Additives & Contaminants》1992,9(5):551-560
The food preservatives, sulphur dioxide and its salts, are known to present some toxic, mutagenic and antinutritional effects; in fact they interact with a number of nutrients, e.g. some vitamins, notably thiamine (Th) and folic acid (FA). The effect of different concentrations of sodium bisulphite in cell culture media has been studied in vitro on a human cell line, HEp-2, deriving from a carcinoma of the larynx. Moreover, the sulphites have been tested with different levels of Th and FA with the aim of elucidating how much the cellular response depended on either the anti-nutritional effect or the toxicity of sulphites. Cell growth has been taken as an index of cytotoxicity and measured both as total protein content and as colony-forming ability. With no Th and FA in the culture medium, a clear decrease of cell growth was observed either with or without addition of sodium bisulphite. A dose-dependent reduction of protein content was detected in cells treated with 10, 50, 100, 200, 250 or 500 microM sodium bisulphite. Moreover, when the cells were treated with 10 or 100 microM of this compound, the colony-forming ability was reduced both in number and colony size. As far as the interaction of the two vitamins with sodium bisulphite is concerned, when these nutrients were present in the medium at 0.5, 1.0, 1.5, 2.0 or 2.5 mg/l, a similar growth profile, determined from their concentration, was observed in treated and control cells, the growth levels being affected by the sodium bisulphite contents. At higher levels of Th and FA, the growth index was still increasing only in treated cells, this phenomenon being particularly evident in cultures treated with 200 microM sodium bisulphite. The colony-forming ability was reduced in controls but still increased in treated cells at the highest concentration of vitamins. 相似文献
999.
A Veldman G J Borggreve E J Mulders D van de Lagemaat 《Food Additives & Contaminants》1992,9(6):647-655
The mycotoxin contamination of feed components used by the Dutch cooperative feed industry was surveyed to estimate the risk for animal production losses. Of 89 randomly and 6 selectively taken samples of raw materials harvested in 1988 and 1989 27% were contaminated with ochratoxin A (OCHRA), 31% with zearalenone (ZEA) and 20% with deoxynivalenol (DON). The mean content (microgram/kg) of all positive randomly taken samples was 18 (OCHRA), 62 (ZEA) and 630 (DON). The highest level (microgram/kg) for all samples was 120 (OCHRA) in barley, 3100 (ZEA) in corn cob mix and 1900 (DON) in maizegluten feed. The results of this survey show that feed components are often contaminated with mycotoxins. However, the contamination level could only sporadically cause production losses in animal husbandry. 相似文献
1000.
We have localized gene MSS51 on chromosome XII of Saccharomyces cerevisiae between the RDN1 and CDC42 loci. 'Head to head' with MSS51 is another gene, QRI5, the function of which is unknown. However, the proximity of these genes, the structure of the intergenic region and the presence of an ABF1 binding site right in the middle of this region suggest that the MSS51 and QRI5 expressions are submitted to a common regulatory process. 相似文献