Breakdown of the compound-nucleus model in the fusion-evaporation process for110Pd+110Pd

The fusion of the massive systems¹¹⁰Pd+¹⁰⁴Ru and¹¹⁰Pd+¹¹⁰Pd was uniquely identified by observing the a decay of the evaporation residues. The observed distribution of the fusion cross section on the different evaporation-residue channels is in clear contradiction to calculations based on the compound-nucleus model. As a possible explanation the precompound evaporation of a particles is proposed.     

Spectral Asymptotics for Higher-Order Ordinary Differential Equations

This paper gives one-term componentwise asymptotics for theM and spectral matrices of a self-adjoint realisation of aneven-order ordinary differential expression. The underlyinginterval is assumed to have at least one regular endpoint, andthe boundary conditions are supposed to be separated. Furthermore,the weight function and the reciprocal of the highest-ordercoefficient are supposed to be of regular variation at the regularendpoint, in the sense of Bingham, Goldie and Teugels. 1991Mathematics Subject Classification: 34B24, 34E05.     

Solid neon moderated electrostatic or magnetic positron beam

A high intensity variable energy positron beam has been constructed at Brookhaven National Laboratory (BNL). Positrons from a 97 mCi²²Na source are moderated by a thin layer of solid neon. A magnetic guiding system delivered up to 5×10⁶ e⁺/sec to an experiment. Currently, tests are under way to facilitate the operation with the magnetic guiding system or—for other experimental sites—with an electrostatic beam transport. The electrostatic lenses are fabricated from μ-metal. No compensation of the earth's magnetic field is required. Several experiments can utilize the beam on a time-sharing basis. In the near future, the source will be replaced by⁶⁴Cu, which has a much higher activity. Beam intensities up to 10⁹ e⁺/sec are expected.     

Low-energy fission investigated in reactions of 750 AMeV238U-ions with Pb and Be targets

Charge distributions of fragments from low energy nuclear fission are investigated in reactions of highly fissile²³⁸U projectiles at relativistic energies (750 A·MeV) with a heavy (Pb) and a light (Be) target. The fully stripped fission fragments are separated by the Fragment Separator (FRS). Their high kinetic energies in the laboratory system allow the identification of all atomic numbers by using Multiple-Sampling Ionization Chambers (MUSIC). The elemental distributions of fragments observed at larger magnetic rigidities than the²³⁸U projectiles show asymmetric break-up and odd-even effects. They indicate a low energy fission process, induced mainly by dissociation in the electro-magnetic field for the U/Pb-system, or by peripheral nuclear interactions for the U/Be-system.     

Normal modes of vibrations in CuBr

Phonon dispersion curves of CuBr have been measured at room temperature in the [001], [110] and [111] directions using inelastic neutron scattering. The results are interpreted in terms of a rigid ion model. Estimations are given for elastic constants.     

Improvement of a Stereoselective Biocatalytic Synthesis by Substrate and Enzyme Engineering: 2‐Hydroxy‐(4′‐oxocyclohexyl)acetonitrile as the Model

Even if biocatalysis is finding increasing application, it still has to gain widespread use in synthetic chemistry. Reasons for this are limitations that enzymes have with regard to substrate range, reaction scope, and insufficient selectivity with unnatural compounds. These shortcomings can be challenged by enzyme and/or substrate engineering, which are employed to alter substrate specificity and enhance the enzyme selectivity toward unnatural substrates. Herein, these two approaches are coupled to improve the hydroxynitrile lyase catalyzed synthesis of 2‐hydroxy‐(4′‐oxocyclohexyl)acetonitrile ( 4 ). The ketone functionality is masked as an enol ether, and the oxynitrilase of Hevea brasiliensis is engineered towards this masked substrate to give the product with a high optical purity and to drastically lower the amount of enzyme needed.     

Adaptive wavelet algorithms for elliptic PDE's on product domains

With standard isotropic approximation by (piecewise) polynomials of fixed order in a domain , the convergence rate in terms of the number of degrees of freedom is inversely proportional to the space dimension . This so-called curse of dimensionality can be circumvented by applying sparse tensor product approximation, when certain high order mixed derivatives of the approximated function happen to be bounded in . It was shown by Nitsche (2006) that this regularity constraint can be dramatically reduced by considering best -term approximation from tensor product wavelet bases. When the function is the solution of some well-posed operator equation, dimension independent approximation rates can be practically realized in linear complexity by adaptive wavelet algorithms, assuming that the infinite stiffness matrix of the operator with respect to such a basis is highly compressible. Applying piecewise smooth wavelets, we verify this compressibility for general, non-separable elliptic PDEs in tensor domains. Applications of the general theory developed include adaptive Galerkin discretizations of multiple scale homogenization problems and of anisotropic equations which are robust, i.e., independent of the scale parameters, resp. of the size of the anisotropy.