Diffraction dissociation of nuclei in 450 GeV/c proton-nucleus collisions

Diffractive dissociation of nuclei (Be, Al, W) in collisions with 450 GeV/c protons,pApX, has been measured with the HELIOS spectrometer at the CERN Super Proton synchrotron. The dependence of the single-diffraction cross-section on the nuclear massA can be parametrized as _SD mb×A ^0.35±0.02, showing the peripheral nature of the process. The differential cross-section d_SD=(3.8±0.3)mb ×A ^0.35±0.02, is exponential with the slope parameter, increasing from 6.2±0.4 (GeV/c)^–2 for beryllium to 7.9±0.5 (GeV/c)^–2 for tungsten. The slope parameter also increases with increasing massM _X of the diffractively produced state. The rapidity, multiplicity, and transverse-momentum distributions of the particles of the diffractively produced stateX show a longitudinal phase-space population and are remarkably insensitive to the nuclear mass. This, together with theA ^1/3 dependence of _SD, suggests that the dominant process of nuclear diffractive excitation is the dissociation of single nucleons.Deceased     

Kaon interferometry in heavy-ion collisions at the CERN SPS

K⁺K⁺ and K^–K^– correlations from S+Pb collisions at 200 GeV/c per nucleon and K⁺K⁺ correlations from p+Pb collisions at 450 GeV/c per nucleon, are presented as measured by the focusing spectrometer of the NA44 experiment at CERN. Multidimensional fits are performed in order to characterize the kaon-emission volume, which is found to be smaller than the pion-emission volume.     

Study of vector mesons in dimuon production in a large kinematic region in p-W and S-W interactions at 200 GeV/c/nucleon

Results are presented on and production in p–W and S–W interactions at 200 GeV/c/nucleon measured via the dimuon decay in a large kinematic region. The data are normalized to the charged particle multiplicity in the same rapidity interval. They have been collected using the HELIOS/3 muon spectrometer at the CERN SPS. The ratio , where is the relevant resonance branching fraction, increases between proton and sulphur projectiles, and is somewhat enhanced going from peripheral to central S–W interactions. This results from an increase in the number of produced 's per charged particle. The ratio is measured in different intervals of p and rapidity. It is not clearly dependent on p, but is larger at higher rapidities. production, likewise normalized to charged multiplicity, is significantly lower in S–W compared to p–W interactions. Received: 27 October 1997 / Revised version: 5 March 1998 / Published online: 13 July 1998     

Classification of exactly solvable potential problems

A differential equation with a known solution is transformed by changing both its dependent and independent variables, and the resulting nonlinear differential equation is then compared with the Schrödinger equation. The method is demonstrated using the confluent hypergeometric differential equation and the solutions to hydrogen, SHO and l=0 Morse potential problems are obtained.     

Solutions of the Schrödinger equation for Dirac delta decorated linear potential

We have studied bound states of the Schrödinger equation for a linear potential together with any finite number (P) of Dirac delta functions. Forx<-0, the potential is given as

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where 0<f; 0<x ₁<x ₂<...<x _P , theσ _i are arbitrary real numbers, and the potential is infinite forx<0.

     

Physics and engineering of peptide supramolecular nanostructures

The emerging "bottom-up" nanotechnology reveals a new field of bioinspired nanomaterials composed of chemically synthesized biomolecules. They are formed from elementary constituents in supramolecular structures by the use of a developed nature self-assembly mechanism. The focus of this perspective paper is on intrinsic fundamental physical properties of bioinspired peptide nanostructures and their small building units linked by weak noncovalent bonds. The observed exceptional optical properties indicate a phenomenon of quantum confinement in these supramolecular structures, which originates from nanoscale size of their elementary building blocks. The dimensionality of the confinement gives insight into intrinsic packing of peptide supramolecular nanomaterials. QC regions, revealed in bioinspired nanostructures, were found by us in amyloid fibrils formed from insulin protein. We describe ferroelectric and related properties found at the nanoscale based on original crystalline asymmetry of the nanoscale building blocks, packing these structures. In this context, we reveal a classic solid state physics phenomenon such as reconstructive phase transition observed in bioorganic peptide nanotubes. This irreversible phase transformation leads to drastic reshaping of their quantum structure from quantum dots to quantum wells, which is followed by variation of their space group symmetry from asymmetric to symmetric. We show that the supramolecular origin of these bioinspired nanomaterials provides them a unique chance to be disassembled into elementary building block peptide nanodots of 1-2 nm size possessing unique electronic, optical and ferroelectric properties. These multifunctional nanounits could lead to a new future step in nanotechnology and nanoscale advanced devices in the fields of nanophotonics, nanobiomedicine, nanobiopiezotronics, etc.     

Fast determination of ochratoxin A in serum by liquid chromatography: comparison with enzymic spectrofluorimetric method.

A rapid high-performance liquid chromatographic method for the determination of low concentrations of ochratoxin A in serum is described. The extraction procedure was simple and short, and liquid chromatographic analysis was carried out isocratically on a reversed-phase C18 column, with methanol-water-acetic acid (30:70:1) as mobile phase and fluorescence detection (excitation at 336 nm, emission at 465 nm). The examined concentration range, 5-50 ng/ml ochratoxin, the recovery method was 87-94%, compared with 62-67% for the enzymic spectrofluorimetric method. The high-performance liquid chromatographic method was faster because the extraction procedure was shorter, and more sensitive so that small sample volumes could be used.