The carcinogenic effect of 5-bromodeoxyuridine and its amplification by x-rays in rats

5-bromodeoxyuridine (BUdR) injected to rats in the neonatal period is shown to produce a pronounced carcinogenic effect which brings about the appearance of various benign and malignant tumours. Exposure of females to X-ray total-body irradiation (1.5 Gy) was followed by intensification of the carcinogenic effect of BUdR. Assuming that this pyrimidine analog reacts solely with DNA substituting thymidine during DNA synthesis and induces point mutations due to tautomerization, the data obtained demonstrate the possibility of tumour induction by a selective DNA perturbation.     

Experimental study on optically band-limited 40-Gb/s RZ signals with optically time-division demultiplexing receiver

The impact of optical filtering on 40-Gb/s return-to-zero (RZ) signals was experimentally investigated with an optically time-division multiplexing (OTDM) receiver. Through the evaluation of the signal performance by changing the interpulse-phase conditions of the symmetrically band-limited 40-Gb/s signals, we have confirmed that similar performance was obtained regardless of the interpulse-phase condition, owing to the pulse-reshaping capability of an OTDM receiver. A performance comparison was also conducted between symmetrically and asymmetrically filtered 40-Gb/s RZ signals. It was found that the symmetrically filtered signal was more tolerant for the dispersion-compensation error, while the asymmetrically filtered signal was more tolerant for fiber nonlinearity with optical filters that have a 3-dB bandwidth of 45 GHz.     

Stabilization of a Linear Object by Frequency-Modulated Pulsed Signals

A control system consisting of an unstable continuous linear part and a pulse-frequency modulator in the feedback circuit is studied. Conditions for the boundedness of the solutions of the system under any initial data are determined.     

Practice characteristics that lead to 21st century learning outcomes

Abstract The key research question for this study was to ask whether or not innovative teaching practices would lead to the development of learning outcomes essential for preparing the younger generation for the challenges of life in the knowledge society of the 21st century, and if so, how are the pedagogical features related to the different learning outcomes. Preliminary analyses of the case study data collected from the SITES M2 Study in Hong Kong reveal that where the development of more significant learning gains were observed, the cases possess characteristics additional to the criteria defined in the Study for selection of innovation. More importantly, it was found that the impact of the pedagogical practices was not determined simply by the aggregation of characteristics of the practices per se , nor on the technologies used, but on whether 'empowerment' permeates the curriculum goal and process. Further, this paper claims that these affective and socio-cognitive learning outcomes are more important as preparation for lifelong learning in the 21st century than 'knowledge management competencies'.     

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��Consulting the relevant documents at home and abroad,the author finisheid the derivation of quations about critical flow quantity,critical flow rate,contrast flow quantity,contrast flow rate which are necessary to the continuous water withdrawal through the flow string with different diameters and the rational flow string formula that should be selected when the contrust parameter1.The author also works out the solving programme for TI-59 computer and designs and draws up the nomograrn of mathematical mode.The evident economical results have been obtained from practice of optimizing the flow string for water withdrawal in gas production in Southern Sichuan and from studying the gas-water two-phase flow characteristics through vertical pipe.     

Fivefold symmetry in real and reciprocal spaces

Tetrahedrally close-packed structures with juxtaposed pentagonal antiprisms, such as the μ, C14 Laves and the newly found C phases, were studied by means of HREM and SAD. It was found that each bright spot in the structural image corresponds to an antiprism. Differently oriented domains of these phases intergrow frequently with a fairly good match at the interphase boundary. All diffraction patterns of these phases show a fivefold distribution of spot-pairs, and it is shown that this fivefold symmetry comes from the pentagons and spot-pairs from two pentagonal prisms superposed in antisymmetrical positions.     

Change in physicomechanical properties of steel D1604AT15 during fatigue at different loading frequencies

Results are presented in a statistical arrangement for studying the effect of loading frequency on the fatigue life in bending of plates with a stress concentrator. The nature of change in microhardness, electrical conductivity, dislocation density, and block dimensions during fatigue at frequencies of 2.8, 8.8, and 18 kHz has been demonstrated. It has been established that in spite of some qualitative difference the main indicators of fatigue at these frequencies are retained.S. M. Kirov Belorussian Technology Institute, Minsk. Translated from Problemy Prochnosti, No. 10, pp. 31–34, October, 1989.