Unexpected Hydroxyspirolactone Formation upon Baeyer-Villiger Oxidation of a trans-α-decalone (trans-octahydronaphthalen-1(2H)-one) and X-ray structure of the product

trans-4,4,10-Trimethyl-9-decalone ( = trans-5,5,8a-trimethyl-octahydronaphthalen-1(2H)-one; 1 ), when treated with trifluoroperacetic acid, gave the unexpected hydroxyspirolactone 7-hydroxy-7,11,11-trimethyl-1-oxaspiro[5.5]undecan-2-one ( 6 ), in which the two new O-atoms were introduced in a 1,2-trans relationship. The structure of this compound was conclusively proven by X-ray crystallography. The process involves the intermediacy of 7-membered lactone 2 , the expected Baeyer-Villiger product, which could also be successfully prepared under controlled conditions at 0° in a buffered medium containing Na₂HPO₄.     

Dynamical calculation of the mass fragmentation in the collision238U-238U

The fragmentation of the nuclear system²³⁸U-²³⁸U is studied by treating the fragmentation coordinate quantum mechanically. The time dependent Schrödinger equation, the Hamiltonian of which is calculated from the microscopic asymmetric two center shell model, is solved by the finite difference method.In order to study the fragmentation mechanism, model calculations have been carried out, by assuming the collective fragmentation potential as an oscillator potential which is adjusted to the realistic potential. Effects arising from the dynamical treatment of the fragmentation coordinate are found to be important in the collision of²³⁸U on²³⁸U. The dependence of the fragmentation on the incident energy is discussed.     

Azametalla-closo-dodecaboranes

The azaborate K₂[nido-NB₁₀H₁₁] is gained from nido-NB₁₀H₁₃ and K[BHEt₃] in a 1:2 ratio. The anion [NB₁₀H₁₁]^2?, which is isoelectronic with [C₂B₉H₁₁]^2?, reacts with [{η⁶-(C₆R₆) · RuCl₂}₂] (R = H, Me), [{η⁵-(C₅Me₅)RhCl₂}₂], or [Ni(PPh₃)₂Cl₂] to give the azametalla-closo-dodecaboranes MNB₁₀H₁₁ with M = (C₆Me₆)Ru ( 2 ), (C₆H₆)Ru ( 3 ), (C₅Me₅)Rh ( 4 ), and (Ph₃P)₂Ni ( 5 ), respectively. The azametallaborane K[Co(NB₁₀H₁₁)₂] ( 6 ), which contains a sandwich-type coordinated Co atom, is formed from K₂[NB₁₀H₁₁] and CoCl₂. The structure of 2 · CH₂Cl₂ was determined by X-ray diffraction. The products 2 – 6 can be derived from the icosahedral anion [B₁₂H₁₂]^2? on replacing a BH^2? moiety by the isoelectronic nitrene NH and a BH moiety by the isolobal metal-complex fragment M. The N atom is six-coordinated in the cluster skeletons 2 – 6 .     

Noise reduction in pulse-code-modulated images by optical regenerative repeaters

Digital signal transmission in electronic communication links provides the possibility of periodic reshaping of the electronic pulses by so-called regenerative repeaters, thereby keeping the signal above the noise level. This concept of noise minimization is applied to the optical transmission of pulse-coded images. Optical elements are described which correspond to the regenerative repeaters used in electronic transmission systems. They are based on holographic as well as incoherent methods. Examples illustrating the basic idea are provided.     

Half-life of the h9/2 shell-model intruder-state isomer Au

The half-life of the $\text{9}\text{2}{}^{\mathrm{?}}$ shell-model intruder-state isomer in ¹⁸⁷Au has been measured by employing a technique in which each incoming event is tagged with a digital representation of time by means of a real-time clock. With this method we obtain a 2.3 ± 0.1 sec half-life for the $\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{→}\text{d}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ E3 isomeric transition resulting in a retardation of 50 relative to the Weisskopf single-particle estimate.     

On the correlation of nuclear track effects with basic track parameters

The formation of nuclear tracks in polymers in acompagnied by radiochemical, structural, electronic and optical changes that show up macroscopically above specific threshold values. The correlation of these effects with both the average transferred electronic energy density _e and with _eS_e (S_e = electronic stopping power) is examined in this work. Scaling with _eS_e yields in general better results: The consequence for the choice of the corresponding track model is discussed.