Hadronic Parity Violation in Few-Nucleon Systems

The weak interaction between quarks induces a parity-violating component in the interactions between nucleons, which is typically suppressed by a factor of \({\approx 10^{-7}}\) compared to the dominant parity-conserving part. Because of the short range of the weak interactions, it provides a unique probe of the strong dynamics that confine quarks into nucleons. An experimental program to map out this weak component of the nuclear force is underway at a number of facilities, including the Spallation Neutron Source at Oak Ridge National Laboratory. The corresponding observables are related to few-nucleon processes at very low energies, at which pionless effective field theory provides a reliable and model-independent theoretical approach to hadronic parity violation. Results in two- and three-nucleon systems, the role of parity-violating three-nucleon forces, and possible extensions to other few-nucleon systems are discussed.     

Synthesis of Binol-based diphosphinites bearing chiral phospholane units and their application in asymmetric catalysis

New diphosphinite ligands based on atropoisomeric diol backbones and (R,R)-2,5-dimethylphospholane moieties have been prepared and fully characterised. For each ligand structure, both diastereomers have been synthesised. These ligands are available through a straightforward procedure in good yields. The solid state structures of two diastereomeric ligands are reported. These ligands have been applied to Rh-catalysed asymmetric hydrogenations and hydroformylations of CC bonds as well as in Ir-catalysed asymmetric hydrogenations of CN bonds. Turnover frequencies in the range of 10,000 h^?1 and enantioselectivities of up to 98% ee have been achieved. The different chirality elements within the ligands led to marked cooperative effect in catalysis. Interestingly, there is no general privileged diastereomeric structure but rather a matched diastereomer for each application.     

Ion beam smoothing of indium-containing III-V compound semiconductors

2 has been used for smoothing of rough InAs, InP, and InSb surfaces, prepared by argon ion beam etching (IBE). The evolution of the surface roughness and morphology has been studied by atomic force microscopy (AFM) as a function of the N₂ RIBE process parameters (ion beam energy, ion beam angle of incidence, and ion dose). A drastic improvement of the surface roughness has been observed for ion beam angles near normal incidence and larger than 70° with increasing ion doses. By using this technique, the initial root-mean-square (rms) roughness of, e.g., InSb of about 40 nm could be decreased to about 1 nm. Received: 20 March 1998/Accepted: 24 March 1998     

Infrared free air application: the area of photodiodes beyond the silicon window

The use of wavelength division multiplexing in free air applications requires the use of selective receivers for wavelengths beyond the absorption range of silicon, i.e. for wavelengths greater than 1100 nm. The detector materials and semiconductor filters used there are cost-intensive, therefore the area size of the receiver diode is a significant factor from the economic point of view. The introduction of the diode efficiency η provides an evaluation criterion for determining a reasonable size of the sensitive area.     

Mass spectrometric in-situ determination of NO2 in gas mixtures by resonance enhanced multiphoton ionisation

One- and two-colour photoionisation spectra for NO₂ have been investigated using a time of flight mass spectrometer as detector to find the most efficient REMPI process for analytical applications. Two different inlet systems have been employed: a pulsed supersonic jet expansion stage and a flow reactor. Selective and sensitive mass spectrometric determinations of free NO₂ have been possible even in the presence of high concentrations of organic nitrates, HNO₃ and other NO₂ precursors. Employing two-colour (1+1′+1) excitation using a concentration of HNO₃≤5·10¹⁴ molecules/cm³ a detection limit of 5·10¹¹ molecules/cm³ has been found for NO₂ whereas in the absence of HNO₃ a detection limit of 5·10¹⁰ molecules/cm³ is reported.     

Eine neue Konstruktion von Durchflu?sensoren mit tubul?ren ionenselektiven Carrier-PVC-Membranen und Zement-Festableitung

Summary Ion-selective sensors with tubular carrier-PVC membranes and a further developed solid-state cement contact are described. As a component of a sensor's flow channel and an interposed segment, each membrane is absolutely tight diffusion-welded between two PVC tube interfaces. Multiple measuring systems including these oxygen-independent, sturdy, maintenance-free sensors with stable measuring properties have already stood the tests under clinical conditions in the electrochemically-controlled hemodialysis.     

Quantum logics with the existence property

Aquantum logic (-orthocomplete orthomodular poset L with a convex, unital, and separating set of states) is said to have theexistence property if the expectation functionals onlin() associated with the bounded observables of L form a vector space. Classical quantum logics as well as the Hilbert space logics of traditional quantum mechanics have this property. We show that, if a quantum logic satisfies certain conditions in addition to having property E, then the number of its blocks (maximal classical subsystems) must either be one (classical logics) or uncountable (as in Hilbert space logics).Part of this work was done while the author was a visitor at the Department of Mathematics and Computer Science of the University of Denver, Denver, Colorado.     

Normal functional and spaces of weights

It is shown that the cone of positive normal functionals on a hypergraphA may be substantially larger than the cone of positive weights onA. For a semiclassical hypergraphA the two cones coincide if and only if the number of edges ofA of cardinality 2 is finite. This disproves an earlier statement of T. A. Cook.