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71.
Hugh Rieley Daniel J. Colby Darren P. McMurray Stuart M. Reeman 《Surface science》1997,390(1-3):243-249
The effects of physisorption and two-dimensional ordering on the photochemistry of N2O4 were investigated. Ordered monolayers were prepared by adsorption of NO2 at 100 K on a water-ice surface. Irradiation with a continuous light source in the wavelength region 300–400 nm or with pulsed laser radiation at 355 nm resulted in exclusive desorption of NO2. This desorption was induced by electronic absorption directly in the adsorbate via a transition corresponding to the (
)1B2u←(
)1Ag transition in N2O4, as in the gas phase. However, the subsequent dynamics in the excited state were markedly different from the gas-phase counterpart. Time-of-flight mass spectrometry of NO2 photodesorbed at 355 nm revealed a most probable fragment translational energy of ca. 17 meV; and the angular distribution of the nascent NO2 was peaked sharply in a direction around 10° from the normal. It is apparent that, despite the weak interaction with the substrate, significant energy transfer occurs in the ordered physisorbed monolayer to yield nascent NO2 with very low translational energy and a constrained angle of escape which is consistent with a high degree of adsorbate order and alignment. 相似文献
72.
Hugh Thomas 《Algebra Universalis》2005,53(4):481-489
We provide a direct proof that a finite graded lattice with a maximal chain of left modular elements is supersolvable. This result was first established via a detour through EL-labellings in [MT] by combining results of McNamara [Mc] and Liu [Li]. As part of our proof, we show that the maximum graded quotient of the free product of a chain and a single-element lattice is finite and distributive.Received May 24, 2004; accepted in final form October 12, 2004. 相似文献
73.
Conclusion Might there be a chance of proving in a simple way thatx/π(x) is asymptotic to an increasing function, thus getting another proof of PNT? This is probably wishful thinking. However,
there is a natural candidate for the increasing function. LetL(x) be the upper convex hull of the full graph ofxπ(x) (precise definition to follow). The piecewise linear functionL(x) is increasing becausex/π(x) → ∞ asx → ∞. Moreover, using PNT, we can give a proof thatL(x) is indeed asymptotic tox/π(x). But the point of our work in this article is that for someone who wishes to understand why the growth of primes is governed
by natural logarithms, a reasonable approach is to convince oneself via computation that the convex hull just mentioned satisfies
the hypothesis of our theorem, and then use the relatively simple proof to show that this hypothesis rigorously implies the
prime number theorem. 相似文献
74.
Hugh Felkin Peter W. Lednor Jean-Michael Normant Robin A.J. Smith 《Journal of organometallic chemistry》1978,157(4):C64-C66
Fe(cot)2 (cot = cyclooctatetraene) reacts with certain phosphines and phosphites to give Fe(cot)L3 compounds in good yield. Reaction of Fe(cot)2 with Ph2PCH2CH2PPh2 under N2 gives a complex containing coordinated dinitrogen, which is converted into Fe(cot)(Ph2PCH2CH2PPh2)(CO) on reaction with CO or formate esters. 相似文献
75.
76.
Hugh Y. Yee 《Microchemical Journal》1978,23(4):497-504
Five methods of acid digestion of amniotic fluid phospholipids for inorganic phosphate release were evaluated at a temperature of 225 °C and a heating time of 30 min. The methods used the following digestants: (A (perchloric acid), B (perchloric acid containing molybdate), C (sulfuric acid, 30% hydrogen peroxide, 5% urea), D (sulfuric-perchloric acids), and E (sulfuric-perchloric acids with vanadium pentoxide). After digestion and dilution with water, a hydrogen ion concentration of about 2.5 mol/ liter was obtained that permitted the use of stannous chloride-hydrazine sulfate as the reducing agent for phosphate color development. Recoveries of the different amniotic fluid phospholipids and aqueous phosphate standards were quantitative for all methods. A comparative study with amniotic fluids showed similar results for all methods. Since all methods were found to be equivalent under the specified conditions described, the choice was dependent upon the user's preference. 相似文献
77.
W. Hugh Woodin 《Archive for Mathematical Logic》1996,35(5-6):371-383
We prove that if where is an -sequence of ordinals then the GCH holds.
Received January 1, 1993 相似文献
78.
R. Alan Aitken Ian Gosney Hugh Farries Michael H. Palmer Isobel Simpson J.I.G. Cadogan Edward J. Tinley 《Tetrahedron》1985,41(7):1329-1346
The reactivity of a series of bicyclic olefins with nitrenes is profoundly influenced by the nature of remote functional groups. There is a marked lack of reactivity for reactions with carboethoxynitrene as compared to phthalimidonitrene which is distinctly nucleophilic in character. An explanation for the reluctance to form aziridines is offered in terms of orbital interactions between the distant groups and the olefinic bond, making the latter remarkably electron deficient as evidenced by UV-photoelectron spectrosoopy. Because of the complexity of the spectra, identification of the Ip associated with the reactive π-centre was made by recourse to ab initio configuration interaction calculations for key members of the series. 相似文献
79.
80.