I sketch the rich life and multifaceted work of Philip Morrison (1915–2005), from his early life in Pittsburgh, Pennsylvania,
and higher education at the Carnegie Institute of Technology and the University of California at Berkeley, to his contributions
to the Manhattan Project, his research at Cornell University and the Massachusetts Institute of Technology after the war,
his subsequent political activity on behalf of nuclear disarmament, his role in the search for extraterrestrial intelligence,
and his enormous influence as an educator, public speaker, and writer.
A.P. French is Professor of Physics, Emeritus, at the Massachusetts Institute of Technology. 相似文献
A new model for the decomposition of triethylgallium on GaAs(100), with kinetic parameters derived from the results of surface science experiments, is presented. Deficiencies of early models are corrected by including surface coverage and site blocking effects, and lateral interactions between absorbed DEG species are included. The model successfully predicts variations in the rate of CBE growth of GaAs with substrate temperature, and addresses effects induced by variations in arsenic overpressure. This dependence of growth rate on the arsenic flux is modelled by computing the steady state concentrations of absorbed arsenic as a function of temperature and As2 and TEG flux. Excess arsenic is shown to inhibit GaAs growth by blocking sites for TEG absorption. 相似文献
RODOS is a Real-time On-line DecisiOn Support system intended for use throughout a nuclear emergency, extending into the longer term. In this paper we concentrate on the early phases in which decisions on sheltering and evacuation have to be taken quickly and under many pressures. RODOS is designed to assist off-site emergency management by formulating and structuring the evaluation of possible combinations of countermeasures. Because there can be very many such combinations to be evaluated, an expert system has been developed to eliminate those that do not satisfy certain constraints depending on factors such as the wind direction and evacuation practicalities. The system uses the ILOG solver constraint satisfaction package and its high-level programming library to reduce the number of strategies to a manageable fraction. This allows a later careful evaluation of the remaining alternatives. 相似文献
A laboratory system has been designed, constructed, and validated that reduces the complexity, time required, and data variability associated with catalytic microreactors that require post reaction steps prior to product analysis. In this work, a Varian (Walnut Creek, CA, USA) 3600 GC (gas chromatography) system coupled with a Saturn quadrupole ion trap mass spectrometer was used to perform mass spectral analysis in real-time catalytic cracking reactions. As this was an integrated reactor/analyzer, the GC column was exposed to temperatures beyond the degradation point of the column, and so selective ion storage RF waveform was used to remove the siloxane masses from the spectra. This produced lower detection limits and full scan data for identification. Mass/charge segmentation of the mass spectrometer allowed the complete product identification for electron impact spectra. Hexane was reacted over H-ZSM-5 catalyst for instrument validation. This produced a series of alkanes, alkenes, and aromatics with distributions consistent with that reported for the cracking of hexane. 相似文献
A series of tripodal imidazole frameworks (TIFs) are reported based on a tripodal, cavity-containing tris(imidazole) derivative. In the case of [Co(3)Cl(6)(1)(2)]·n(solvent) (TIF-1) which possesses a doubly interpenetrated framework structure, the material exhibits rigid, permanent porosity and selectively absorbs CO(2). The non-interpenetrated [Co(1)(2)(H(2)O)(2)]Cl(2)·4H(2)O (TIF-2) also absorbs gases and vapours fully reversibly exhibiting a reversible phase change in the process and considerable conditioning and hysteresis. The very highly hydrated [Co(1)(2)]Cl(2)·22H(2)O (TIF-3) irreversibly dehydrates to the layered structure [Co(1)(2)]Cl(2)·H(2)O (TIF-4). A nickel analogue [Ni(1)(2)]Cl(2)·22H(2)O (TIF-5) closely related to TIF-3 is also reported along with two isostructural, non-porous materials [MCl(2)(1)] (M = Mn, TIF-6; M = Cd, TIF-7) based on d(5) and d(10) Mn(II) and Cd(II). Some of the materials may be prepared by mechanochemical as well as solution based methods. We liken TIF-1 to a gas cylinder, TIF-2 to a sponge and TIF-3 to a fragile soda can that is crushed on emptying to give TIF-4. 相似文献
Experimental results showed that the crosslink density of polymeric stocks may be calculated from values of the gel content based on the reactive portion of the stocks, that is, exclusive of plasticizers and fillers. Where entanglements may be neglected, the crosslink density is directly proportional to functions of the gel and sol contents. Four such functions were found. Three of these were theoretically derived relations in the literature and these were modified to provide equations connecting crosslink density and the weight fraction of gel Wg and connecting extent of reaction and Wg for condensation polymers.
Although followed up to moderate degrees of cure, the Flory relation was shown not to be in proper form. A fourth but simpler relation, based on an empirical correlation, was found between crosslink density and gel content, namely, that the crosslink density was directly proportional to the square of the gel fraction divided by the first power of the sol fraction. The constant of proportionality was 0.0065 meq/g for three-functional networks. When placed in terms of extent of reaction, this equation was found to yield nearly the same gel content relative to extent of reaction as that of Charlesby and there was a smaller coefficient of variation of experimentally determined proportionality constants. 相似文献