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An experimental thermal pulse combustor and a differential equation model of this device are shown to exhibit chaotic behavior under certain conditions. Chaos arises in the model by means of a progression of period-doubling bifurcations that occur when operating parameters such as combustor wall temperature or air/fuel flow are adjusted to push the system toward flameout. Bifurcation sequences have not yet been reproduced experimentally, but similarities are demonstrated between the dynamic features of pressure fluctuations in the model and experiment. Correlation dimension, Kolmogorov entropy, and projections of reconstructed attractors using chaotic time series analysis are demonstrated to be useful in classifying dynamical behavior of the experimental combustor and for comparison of test data to the model results. Ways to improve the model are suggested. (c) 1995 American Institute of Physics. 相似文献
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M. B. Alamin A. A. Mhapes A. M. Bejey A. Sadek R. H. Atweer K. Dubali Daw M. Saad 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(1):247-250
Since there is no database in Libya defining the intake of the individuals from different essential (minor and trace) and
toxic elements provided through food, drinking water and aerosol, a project has been proposed with the cooperation of IAEA
to determine the concentration of a number of elements such as Cs, Fe, Cr, Rb, Sc, Se, Co, Zn in the three mentioned sources.
Emphasis was placed on the use of nuclear and nuclear-related techniques. In this paper, the primary results are presented
for the concentration of minor and trace elements in some vegetables, spices and other foods which are widely used in the
Libyan meals. Instrumental neutron activation analysis utilizing a 10 MW water pool reactor and a γ-ray spectroscopy facility
was employed. For quality control, certified reference materials were analyzed simultaneosly with the samples which show good
agreements compared with the certified data. Emphasis was given to both elements iron and zinc for their importance. 相似文献
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Biosynthesis of Streptolidine Involved Two Unexpected Intermediates Produced by a Dihydroxylase and a Cyclase through Unusual Mechanisms
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Dr. Chin‐Yuan Chang Syue‐Yi Lyu Dr. Yu‐Chen Liu Ning‐Shian Hsu Dr. Chih‐Chung Wu Dr. Cheng‐Fong Tang Kuan‐Hung Lin Dr. Jin‐Yuan Ho Dr. Chang‐Jer Wu Dr. Ming‐Daw Tsai Dr. Tsung‐Lin Li 《Angewandte Chemie (International ed. in English)》2014,53(7):1943-1948
Streptothricin‐F (STT‐F), one of the early‐discovered antibiotics, consists of three components, a β‐lysine homopolymer, an aminosugar D ‐gulosamine, and an unusual bicyclic streptolidine. The biosynthesis of streptolidine is a long‐lasting but unresolved puzzle. Herein, a combination of genetic/biochemical/structural approaches was used to unravel this problem. The STT gene cluster was first sequenced from a Streptomyces variant BCRC 12163, wherein two gene products OrfP and OrfR were characterized in vitro to be a dihydroxylase and a cyclase, respectively. Thirteen high‐resolution crystal structures for both enzymes in different reaction intermediate states were snapshotted to help elucidate their catalytic mechanisms. OrfP catalyzes an FeII‐dependent double hydroxylation reaction converting L ‐Arg into (3R,4R)‐(OH)2‐L ‐Arg via (3S)‐OH‐L ‐Arg, while OrfR catalyzes an unusual PLP‐dependent elimination/addition reaction cyclizing (3R,4R)‐(OH)2‐L ‐Arg to the six‐membered (4R)‐OH‐capreomycidine. The biosynthetic mystery finally comes to light as the latter product was incorporation into STT‐F by a feeding experiment. 相似文献
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We give an unconditional proof of the André?COort conjecture for Hilbert modular surfaces asserting that an algebraic curve contained in such a surface and containing an infinite set of special points, is special. The proof relies on a combination of Galois-theoretic techniques and results from the theory of o-minimal structures. 相似文献
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We present calculations of the energy levels of anion vacancies near the (110) surface of GaInAs, GaInP and GaAlAs. The results suggest that the defect model of Schottky barrier formation with anion vacancy-like states being responsible for Fermi level pinning is consistent with the common anion rule as observed in GaInAs and GaInP and also with the exception to the rule presented by GaAlAs. 相似文献
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Amit Kumar Trevor Janes Subrata Chakraborty Prosenjit Daw Niklas vonWolff Raanan Carmieli Yael Diskin‐Posner David Milstein 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3411-3415
We report a C?C bond‐forming reaction between benzyl alcohols and alkynes in the presence of a catalytic amount of KOtBu to form α‐alkylated ketones in which the C=O group is located on the side derived from the alcohol. The reaction proceeds under thermal conditions (125 °C) and produces no waste, making the reaction highly atom efficient, environmentally benign, and sustainable. Based on our mechanistic investigations, we propose that the reaction proceeds through radical pathways. 相似文献
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Recent advancements in digital audio technology have made highly detailed analysis of the voice signal possible. Utilizing a digital audio tape recorder, 16-bit analog-digital converter, and a fast microcomputer with large memory, such an acoustic analysis was performed on five vowels using 13 normal subjects. This article presents results that indicate the normal voice contains significant amounts of very high-frequency energy above 10 kHz. The power of this high-frequency energy is affected by vocal tract shape, which varies significantly among different individuals. 相似文献
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