MNDO study of reaction paths: Diboration of acetylene

The reaction of B₂H₄ with acetylene has been studied by the MNDO method. It is shown that the reaction is exothermic and proceeds in two steps. The first step is the formation of a three-center mv2/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-complex and this is the rate-determining step of the reaction. The second step is the rearrangement of the mv2/xxlarge960.gif" alt="pgr" align="BASELINE" BORDER="0">-complex to the product and this step requires a very small amount of activation energy. The activation barrier for the diboration reaction is 12.8 kcal/mol.The proposed mechanism is significantly different from those proposed earlier and explains all experimental data relating to this reaction.     

Exo-H- andendo-H-η4-pentamethylcyclopentadiene complexes of platinum

A mixture ofendo-H andexo-H isomers (1a and1b) of the (mv/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">⁴-C₅Me₅H)PtCl₂ complex was prepared by the reaction of K₂PtCl₄ with C₅Me₅H in MeOH. The mixture of isomers reacts with CpTl in the presence of TiBF₄ to give a novel complex, [(mv/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">⁴-C₅Me₅H)Pt(mv/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">⁵-C₅H₅)]⁺BF₄ ^–, as a mixture ofendo-H- andexo-H-isomers (2a and2b). The data of¹H and¹³C NMR spectroscopy of the resulting complexes are discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 514–517, March, 1994.     

Brown–Peterson Cohomology from Morava K ‐Theory, II

We improve on some results with Ravenel and Yagita in a paper by the same name. In particular, we generalize when injectivity, surjectivity, and exactness of Morava Kmv4617p20l486435/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">theory implies the same for Brown–Peterson cohomology. A type of flatness is no longer assumed, but instead it is a consequence of weaker assumptions. The main application is an easier proof that QS2k+1 has this flatness property. In addition, we show that if elements in the Brown–Peterson cohomology generate all of the Morava Kmv4617p20l486435/xxlarge8208.gif" alt="dash" align="MIDDLE" BORDER="0">theories, then they also generate the Brown–Peterson cohomology and it is Landweber flat.     

Asymptotic Expansions for the Congestion Period for the M/M/∞ Queue

We consider the M/M/mv37676n77818831/xxlarge8734.gif" alt="infin" align="MIDDLE" BORDER="0"> queue with arrival rate mv37676n77818831/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0">, service rate mv37676n77818831/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0"> and traffic intensity mv37676n77818831/xxlarge961.gif" alt="rgr" align="MIDDLE" BORDER="0">=mv37676n77818831/xxlarge955.gif" alt="lambda" align="BASELINE" BORDER="0">/mv37676n77818831/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">. We analyze the first passage distribution of the time the number of customers N(t) reaches the level c, starting from N(0)=m>c. If m=c+1 we refer to this time period as the congestion period above the level c. We give detailed asymptotic expansions for the distribution of this first passage time for mv37676n77818831/xxlarge961.gif" alt="rgr" align="MIDDLE" BORDER="0">mv37676n77818831/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0">mv37676n77818831/xxlarge8734.gif" alt="infin" align="MIDDLE" BORDER="0">, various ranges of m and c, and several different time scales. Numerical studies back up the asymptotic results.     

Synthesis of some polycyclic noncondensed pyrimidine structures

Methods for the synthesis of compounds containing two or more pyrimidine rings linked through aliphatic chains with different numbers of carbon atoms are described.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 335–340, February, 1995     

E–mv coupling of vibrational overtone in organic conductors: Relationship to optical nonlinearities and ferroelectricity

A strong electron–phonon coupling effect, referred to as electron–molecular vibration (e–mv) coupling, induces characteristic vibronic signals in the vibrational spectra of organic conductors. This paper discusses a new spectroscopic signal induced by the e–mv coupling effect, and the physical implications of its emergence. This vibronic signal, attributable to an overtone of a molecular vibration, appears with an anti-resonance form in the infrared spectrum of some mixed-valency complexes when the compounds undergo a charge-ordering transition. Based on the results of cluster model calculations, the activation of the overtone signal is interpreted as an indication of the generation of anharmonicity in the electronic potential. This analysis suggests that the series of the complexes should possess potential nonlinear optical abilities, though these compounds have long been viewed as electric conductors having the opposite characteristics of dielectrics that show nonlinear optical properties.     

Convergence Theorems for ℓ<Subscript><Emphasis Type="Italic">p</Emphasis></Subscript>-Norm Minimizers with Respect to <Emphasis Type="Italic">p</Emphasis>

Let C be a fixed compact convex subset of mv38012414/10957_2005_Article_2090_TeX2GIFIEq1.gif" alt="$${\mathbb R}_{++}^{n}$$" align="middle" border="0"> and let x_p be the unique minimal mv38012414/xxlarge8467.gif" alt="ell" align="BASELINE" BORDER="0">_p-norm element in C for any mv38012414/10957_2005_Article_2090_TeX2GIFIEq2.gif" alt="$$p: \ 1 . In this paper, we study the convergence of x_p as pmv38012414/xxlarge8594.gif" alt="rarr" align="BASELINE" BORDER="0"> mv38012414/xxlarge8734.gif" alt="infin" align="MIDDLE" BORDER="0"> or mv38012414/10957_2005_Article_2090_TeX2GIFIEq3.gif" alt="$$p\searrow 1$$" align="middle" border="0"> , respectively. We characterize also the limit point as the minimal element of C with respect to the lexical minimax order relation or the lexical minitotal order relation, respectively.Communicated by D. G. LuenbergerThe author thanks Professor H. Komiya for valuable advice and an anonymous referee for kind comments.     

ESR study of μ-allyl Co(II) complexes in Ziegler type catalytic systems

ESR study of the interaction between the components of the catalytic system Co(acac)₂- PBu₃-LiBu in the presence of butadiene revealed the formation of stable paramagnetic cobalt complexes containing a PBu₃ ligand and butadiene molecules. Complexes (mv503x2522u74132/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">³-R)₂CoPBu₃ (where R is allyl, crotyl, benzyl) have been synthesized by ordinary methodsin situ, in order to identify the structures of the complexes. ESR parameters and geometry of the central core have been determined. The influence of the nature of phosphine ligands on the parameters of the ESR spectra has been studied. The general regularities in the ESR spectra of (mv503x2522u74132/xxlarge951.gif" alt="eegr" align="MIDDLE" BORDER="0">³-R)2CoPBu₃ and the complexes formed in the catalytic system have been revealed.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 152–155, January, 1994.     

The calcination of limestone — Studies on the past, the presence and the future of a crucial industrial process

The calcination of limestone is one of the oldest technical processes and it is still of actual interest. Very early calcitic mortars from Turkey have been investigated and compared with materials of other early civilisations i.e. with Egyptian mortars containing gypsum as well as medieval dolomite-based mortars from alpine regions. Contemporary calcination procedures, in particular the cement production, range among the most important global industrial processes causing non neglectable environmental problems. Sustainable, solar energy assisted calcination technologies and the conversion of product CO₂ into useful commodities are discussed.The authors like to thank Prof. K. von Salis Perch-Nielson, Institute of Geology, ETH Zürich, for assistance in sedimentological investigations.