Confinement from a scalar-gluon coupling in gauge theory

A model is introduced with a massive scalar coupling to the Yang-Mills term in four-dimensional gauge theory. It is shown that the resulting potential of colour sources consists of a short distance Coulomb interaction and a confining part dominating at large distances. Far away from the source the scalar vanishes while the potential diverges linearly. Up to an -dependent factor of order 1 the tension parameter in the model is gmf, where m denotes the mass of the scalar and f is a coupling scale entering the scalar-gluon coupling. Received: 18 May 1998 / Published online: 26 August 1998     

Functionalization of Biodegradable Polyester for Tissue Engineering Applications

Summary: Chemical modification of polymer surface may potentially be used to create smart materials that can guide cellular adhesion, proliferation and maintenance of specific expression of molecules. The microbial polyester poly (3-hydroxybutyrate) (PHB) has been attracted attention as promising material for applications in tissue engineering. In this work, a wet-chemical method, base ethylenediamine aminolysis, was performed to improve the adhesion of chondrocytes isolated from human articular cartilage to PHB films. The effects of chemical treatment on PHB films was evaluated by following changes in morphology and surface chemical composition using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. While the effect on cells morphology was studied by scanning electron microscopy (SEM). The treatment with ethylenediamine did not change significantly the morphology of the structures of PHB films surface. However, the roughness of the aminolyzed films was slightly higher. The introduction of nitrogen-containing groups was confirmed by XPS. In vitro experiments indicated that the surface modification did not have toxic effects in cells, since they could adhere and proliferate on modified PHB films. It was observed that long-time treatment improved ability of PHB films to support cell growth, which could be accounted to physicochemical and topological effects.     

The influence of signal parameters on the sound source localization ability of a harbor porpoise (Phocoena phocoena)

It is unclear how well harbor porpoises can locate sound sources, and thus can locate acoustic alarms on gillnets. Therefore the ability of a porpoise to determine the location of a sound source was determined. The animal was trained to indicate the active one of 16 transducers in a 16-m-diam circle around a central listening station. The duration and received level of the narrowband frequency-modulated signals (center frequencies 16, 64 and 100 kHz) were varied. The animal's localization performance increased when the signal duration increased from 600 to 1000 ms. The lower the received sound pressure level (SPL) of the signal, the harder the animal found it to localize the sound source. When pulse duration was long enough (approximately 1 s) and the received SPLs of the sounds were high (34-50 dB above basic hearing thresholds or 3-15 dB above the theoretical masked detection threshold in the ambient noise condition of the present study), the animal could locate sounds of the three frequencies almost equally well. The porpoise was able to locate sound sources up to 124 degrees to its left or right more easily than sounds from behind it.     

Double-resonant second harmonic generation from surface coverages of nile-blue A

Second harmonic emission from a dye covered quartz surface has been observed in total internal reflection. Coverages with the dye nile-blue A yielded an increase in second harmonic output by several orders of magnitude as compared to coverages with rhodamine 6G. In the latter case only the harmonic light is at resonance with the S₀–S₂ transition of the adsorbed dye molecules, whereas for nile-blue A both, the fundamental and the harmonic frequency, are at resonance with the respective singlet transitions.     

Synthesis,structural characterization and in vitro antitumour properties of triorganoantimony(V) disalicylates: Crystal and molecular structures of [5-Y-2-(ho)-C6H3COO]2SbMe3 (YH,Me, MeO)

Triorganoantimony(V) salicylates, [5-Y-2-(HO)-C₆H₃COO]₂SbR₃ (R=Me, Ph; Y=H, Me, MeO), were obtained by reacting R₃SbCl₂ with the appropriate sodium salt. The compounds have been characterized by IR, MS, ¹H and ¹³C NMR spectroscopy. The molecular structure of the three substituted trimethylantimony(V) disalicylates has been determined by X-ray diffraction. The salicylate ligands are mono-coordinated to antimony through an oxygen atom of each carboxylate, leading to a trigonal bipyramidal geometry, with the antimony-methyl groups in equatorial positions and the oxygen atoms in axial positions. The trimethylantimony compounds tested in vitro against a series of human tumour cell lines were found to be inactive.     

Irreducible tensor analysis of sum- and difference-frequency generation in partially oriented samples

The macroscopic non-liner optical susceptibility _X⁽²⁾ for a system of partially oriented molecules is written as the ensemble average of molecular hyperpolarizability tensors β. The orientational distribution of these molecules is described by a probability function expanded in Wigner matrices. For a rotationally invariant system _X⁽²⁾ has seven non-vanishing components, and a method is outlined to determine these by sum- or difference-frequency mixing experiments. The method could be applied to electrically poled samples, adsorbates liquid crystals and membranes to determine several components of the molecular hyperpolarizability tensor, or to extract information about the orientational distribution.     

Experimental study of vibrational and pure rotational coherent anti-stokes Raman scattering (CARS) in molecular hydrogen

Using a specially designed excimer-laser-pumped dye laser of adjustable bandwidth high-lying pure rotational transitions of both, ortho-and para-hydrogen have been identified by coherent anti-Stokes Raman scattering (CARS). As an interesting application H₂-based CARS-thermometry is discussed.     

The gas temperature in and the gas expulsion from a graphite furnace used for atomic absorption spectrometry

A simplified model for heat transfer based on thermal conduction is used to calculate the radial gas temperature distribution inside a semi-enclosed, commercial graphite tube furnace used for atomic absorption spectrometry. In the absence of a forced convective flow of a purge gas, the gas temperature inside the graphite furnace during its heating is lower than the wall temperature. After the wall temperature has attained a steady-state value, the gas temperature approaches the wall temperature and the radial temperature gradient in the gas decreases. The difference between the wall temperature and the gas temperature depends on the temperature program used, the thermal properties of the purge gas, and the atomizer geometry. The residence time of relatively volatile analyte elements is largely controlled by expulsion when wall atomization at high heating rates and high atomization temperatures are used. Analytical sensitivities are often enhanced by vaporizing the analyte into a gas having an approximately constant temperature.