Phase interaction in composite materials Zr-Mo,W

Conclusions Composite materials based on the thermodynamically unstable systems Zr-Mo and Zr-W have satisfactory kinetic stability of the structure up to 1373°K. At higher temperatures there occurs intense interaction between fibers and matrix entailingthe formation of solid solutions and intermetallic phases. The course of the diffusion processes in the investigated CM is determined by the history of their components, and this makes it possible to a certain extent to control these processes by corresponding preliminary thermomechanical treatment of the components.Translated from Poroshkovaya Metallurgiya, No. 12(300), pp. 40–44, December, 1987.     

Crack growth resistance of a gray cast iron

Gray cast iron exhibits a discontinuous crack growth process. No definite crack front is observed but fracture is induced by the progression and extension of a damaged zone whose extremities remain ill-defined. It was demonstrated, in an earlier study, that the crack resistance of a grey cast iron is therefore strongly dependent on the length of the cracked zone. In order to otbain a meaningful toughness value, i.e. a measurement of the resistance to crack propagation, it is necessary to use a specimen configuration in which the size and position of the damaged zone remain unaffected by the crack propagation. Such measurements have been made on a continuously cooled gray cast iron by using DCB specimens with circular side grooves. After the fracture had initially progressed to a relatively large extent, the loading points were moved forward and a new loading sequence was applied. Crack resistance was measured during successive loading sequences, applied after displacement of the loading points. Compliance measurements were used to evaluate the crack increase and an equivalent R-curve was drawn for each loading sequence. Except for the initial sequence the successive R-curves remained fairly identical. Moreover, a constant R-value was observed for a relatively large range of crack extensions. This demonstrates that stationary fracture conditions have been obtained. From these results it may be concluded that by using this particular procedure applied to a DCB specimen, a resistance to fracture propagation has been measured which is independent of the size of the cracked zone and which is representative of the microstructure.     

Individual differences in extended practice functions and solution strategies for basic addition facts.

Practice on addition basic facts and changes in solution strategies were examined in 3rd- and 4th-grade students, practicing over 3 months. Response latencies decreased, indicating positive practice effects. Each of 3 student groups demonstrated different solution–strategy mixtures. Different mixtures led to different practice effects, indexed by shifts to more efficient counting strategies and more direct retrieval. Expectations about effects of practice and instructional strategies for optimizing practice must be sensitive to a child's actual strategy pattern. Most students had decreasing latency practice functions. However, quantitative functions fit to the practice session data indicated a high proportion of cases where the latency pattern over sessions was nonmonotonic. Trends over a small number of practice sessions may be inadequate for decisions about the utility of further practice, because such data may poorly represent long-term, cumulative effects on modifying strategy usage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cytochemical characteristics of blast cells forming autologous rosettes in acute lymphoblastic leukemia in children

An increased content of cytochemically heterogeneous A-RFC (responses to acid phosphatase and acid nonspecific esterase) in peripheral blood of children with T-ALL in comparison with non-T, non-B-ALL has been established. No correlation between A-RFC content and T-cells bearing FcG- and FcM-receptors has been revealed. It is supposed that A-RFC is a heterogeneous group of T-cells differing in the stage of maturity.     

A new technique for on-line and off-line high speed computation

A novel technique for both online and offline computation is presented. With this technique, a reconstruction analysis in elementary particle physics, otherwise prohibitively long, has been accomplished. It will be used online in an upcoming Fermilab experiment to reconstruct more than 100000 events per second and to trigger on the basis of that information. The technique delivers 40 gigaoperations per second, has a bandwidth on the order of gigabytes per second, and has a modest cost. An overview of the program, details of the system, and performance measurements are presented     

Examination of the iron, copper and zinc contents in the daily menu of teen-agers

The Fe, Cu- and Zn contents of the daily menu of teen-agers were examined over two years with 124 samples taken. The samples were homogenized, subsequently dried at 104 degrees C finally incinerated at 480 degrees C. The ash was dissolved by heating with 3 N HCl. Determination of the three micro-elements was carried out by atomic absorption spectrophotometry. It was found that the daily intake of the micro-elements investigated is much below the value proposed by FAO/WHO, however, somewhat higher than the calculated Hungarian data. According to measurements, the average daily micro-element intake is 10.77 +/- 4.42 mg for iron; 1.23 +/- 0.65 mg for copper and 9.44 +/- 2.39 mg for zinc. With enumeration of iron, copper and zinc sources, dietary recommendations are given in order to increase the average values.     

Ionoluminescence decay measured with single ions

A new ion beam analysis-based, single ion technique called the time to first photon has been developed to measure the decay of the luminescence signal of phosphors. Such measurements are currently needed to study luminescence decay mechanisms following high-density excitations and to identify strongly luminescent phosphor coatings with short lifetimes for ion photon emission microscopy (IPEM). The samples for this technique consist of thin phosphor layers placed or coated on the surface of PIN diodes. Single ions from an accelerator strike this sample and simultaneously create ion beam induced luminescence (IBIL) from the phosphor that is measured by a single-photon-detector, and an ion beam induced charge collection (IBICC) signal in the PIN diode. In this case, the IBICC signal provides the start pulse and the IBIL signal the stop pulse to a time to amplitude converter. It is straightforward to show that this approach also measures a signal proportional to activity versus time with an accuracy of 5% as long as the number of detected photons per ion is less than 0.1, which usually requires the use of absorbers for the IBIL detector or electronic discrimination for the IBIL signals. Details of the new analysis are given together with examples of luminescence decay measurements of several ceramic phosphors being considered to coat IPEM samples. IPEM is currently being developed at Sandia National Laboratory (SNL), the University of North Texas in Denton, and the Universities and INFN of Padova and Torino.     

The effect of penicillin on fatty acid synthesis and excretion inStreptococcus mutans BHT

Treatment of exponentially growing cultures ofStreptococcus mutans BHT with growth-inhibitory concentrations (0.2 μg/ml) of benzylpenicillin stimulates the incorporation of [2-¹⁴C] acetate into lipids excreted by the cells by as much as 69-fold, but does not change the amount of¹⁴C incorporated into intracellular lipids. At this concentration of penicillin cellular lysis does not occur. The radioactive label is incorporated exclusively into the fatty acid moieties of the glycerolipids. The increase in the radioactive content of the extracellular lipids reflects an actual net increase in the total fatty acid content as determined by a chemical assay. During a 4-hr incubation in the presence of penicillin, the extracellular fatty acid ester concentration (per mg cell dry weight) increases 1.5 fold, even though there is no growth or cellular lysis. No change is observed in the intracellular fatty acid ester content. An indication of the relative rate of fatty acid synthesis was most readily obtained by placingS. mutans BHT in a buffer containing¹⁴C-acetate. Under these nongrowing conditions free fatty acids are the only lipids labeled, a factor which simplifies the assay. The addition of glycerol to the buffer causes all of the nonesterified fatty acids to be incorporated into glycerolipid. The cells excrete much of the lipid whether glycerol is present or not. Addition of penicillin to the nongrowth supporting buffer system does not stimulate the incorporation of [¹⁴C]-acetate into fatty acids. However, if cells are exposed to penicillin in a growth-supporting medium and then are transferred to the nongrowing buffer system containing no penicillin, the previously exposed cells retain the ability to incorporate [¹⁴C]-acetate into fatty acid at a higher rate than untreated cells over a prolonged period of time. The stimulation of [¹⁴C]-acetate into fatty acids in this system parallels but is not dependent on the stimulation by penicillin of the incorporation of [¹⁴C]-glycerol into glycerolipid and lipoteichoic acid synthesis previously demonstrated by our laboratory. The material of this paper is part of a thesis to be submitted by J.L.B. in partial fulfillment of the requirements for the Ph.D. degree from the Department of Biochemistry, Temple University.     

Tunable multifunction logic modules based on parametric representation of functions of k-valued logic over quasifields

We propose a new class of tunable logic modules that realize functions of k-valued logic. These modules are characterized by homogeneous structure and linear dependence of the number of tunable inputs on the number of input variables.Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 24–29, July–August, 1991.