Upper limit for DD production in pp interactions at C.M. energy of 55 GeV

From a search for e^±μ^± production at the CERN ISR an upper limit of 0.92 μb (95% confidence limit) has been inferred for σ·B_e·B_μ for the reaction $\text{p}\text{+}\text{p}\text{→}\text{D}\text{+}\text{D}\text{+}\text{X}\text{at}\text{√s}\text{of}\text{55}\text{GeV}$.     

The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

A BMAP|G|1-analysis based on convolution calculus

Stochastic models of high-speed communication systems typically require the analysis of special Markov additive processes, known thus far as “batch Markovian arrival processes” (BMAPs). In most cases, the solution of nonlinear matrix equations of the form or is necessary, leading, in general, to severe numerical problems. Several efficient algorithms for that purpose have been reported in the literature. In this contribution, we present a new approach (the BMAP|G| 1-analysis), which is based on a convolution calculus for matrix sequences. The main results are the unified representation of Poisson, compound Poisson, and batch Markovian arrival processes by so-called convolutional exponential distributions, and the computation of the fundamental-period matrix G via so-called semi-convolutions. The resulting algorithms, in general, cannot outperform known algorithms as, for instance, those exploiting Horner schemes as proposed by D. M. Lucantoni and other authors, or the highly efficient cyclic reduction algorithm of D. Bini and B. Meini; nevertheless, they allow the direct computation of step matrices such as the “arrival matrices” A_n with and the component matrices G_n summing to G. Further, there is some hope that the proposed framework may lead to a unification of the theory in the sense that queues with arrival and/or service processes that are characterized by convolutional exponential distributions may possess formally similar properties, as known from the scalar case. Proceedings of the Seminar on Stability Problems for Stochastic Models. Hajdúszoboszló. Hungary, 1997. Part II.     

Extractionsapparate

Ohne Zusammenfassung     

Eine kettenförmige η5-Cp*Bi-Verbindung mit 11fach koordiniertem Bismut

A Chain-like η⁵-Cp*Bi Compound with Bismuth elevenfold coordinated The reaction of (Cp*Al)₄ with BiI₃ in toluene at room temperature affords red crystals of the new compound (η⁵-CpAl)(η⁵-Cp*Bi)(μ-AlI₄)(AlI₄)₂ · 2 C₇H₈. The solid state structure exhibits a chain-like arrangement of Cp*Bi units that are bridged by tetraiodoaluminate ions. These structural features are compared with some arene complexes of the heavy group 14 elements (tin, lead).     

Brewster-angled chirped mirrors for broadband pulse compression without dispersion oscillations

We use Brewster-angled chirped mirrors for dispersion compensation of a noncollinear optical parametric amplifier. This novel mirror design virtually eliminates spurious surface reflections and resultant dispersion ripple. The absence of compression artifacts is demonstrated by the generation of clean 5.6 fs pulses, with what is believed to be an unprecedented low ripple-induced satellite content for a nonadaptive scheme. In addition, the 270 THz spectral coverage allows generation of widely tunable visible pulses of 8 to 15 fs duration.