Isobaric thermal expansivities of polyethylenes with various crystallinities over the pressure range from 0.1 to 300 MPa and over the temperature range from 303 to 393 K

A pressure-controlled scanning calorimeter (PCSC) has been applied for measuring the isobaric volume thermal expansivities (α_p) of crystalline polymers as a function of pressure up to 300 MPa at various temperatures. The measurements have been performed for several well-defined polyethylenes with various degrees of crystallinity at 302.6, 333.0, 362.6, and 393.0 K. The results are reported as values of coefficients in a correlation equation, which facilitates the use of reported data over large ranges of temperature and pressure. The general pressure-temperature behavior of α_p for all polyethylenes under study is such that α_p increases with temperature and decreases with pressure. The increase with temperature is smaller at high pressures and the isotherms of α_p have a tendency to converge at high pressures; α_p decreases linearly with the crystallinity of the polyethylene over the whole range of pressure and temperature under investigation. From the linear approximation of experimental data for polyethylenes with various crystallinities the estimated α_p for both crystal and amorphous phases of polyethylenes have been determined as a function of pressure up to 300 MPa at 302.6, 333.0, and 362.5 K. The obtained results have been compared with available literature crystallographic data and with the values derived from the Pastine theoretical equation of state for both crystalline and amorphous phases. © 1996 John Wiley & Sons, Inc.     

HILITE—A tool to investigate interactions of matter and light

Detailed investigations of laser–ion interactions require well-defined ion targets and detection techniques for high-sensitivity measurements of reaction educts and products. To this end, we have designed and built the High-Intensity Laser-Ion Trap Experiment Penning trap setup, which features various ion-target preparation techniques including selection, cooling, compression, and positioning as well as destructive and non-destructive measurement techniques to determine the number of stored ions for all charge states individually and simultaneously. We have recently performed first commissioning experiments of ion deceleration and dynamic ion capture with highly charged ion bunches from an electron beam ion source. We have characterized our single-pass non-destructive ion counter in detail and were able to determine the ion velocity as well as the number of ions from the signals acquired.     

Completely J —positive linear systems of finite order

Completely J — positive linear systems of finite order are introduced as a generalization of completely symmetric linear systems. To any completely J — positive linear system of finite order there is associated a defining measure with respect to which the transfer function has a certain integral representation. It is proved that these systems are asymptotically stable. The observability and reachability operators obey a certain duality rule and the number of negative squares of the Hankel operator is estimated. The Hankel operator is bounded if and only if a certain measure associated with the defining measure is of Carleson type. We prove that a real symmetric operator valued function which is analytic outside the unit disk has a realization with a completely J — symmetric linear space which is reachable, observable and parbalanced. Uniqueness and spectral minimality of the completely J — symmetric realizations are discussed.     

Laser spectroscopy of the 1s HFS of H-like ions at a bunched beam in the storage ring ESR

The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in ²⁰⁷Pb⁸¹⁺. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics from an ion beam at relativistic velocities. This revised version was published online in July 2006 with corrections to the Cover Date.     

A semi-implicit monotone difference scheme for an initial-boundary value problem of a strongly degenerate parabolic equation modeling sedimentation-consolidation processes

We prove the convergence of a semi-implicit monotone finite difference scheme approximating an initial-boundary value problem for a spatially one-dimensional quasilinear strongly degenerate parabolic equation, which is supplied with two different inhomogeneous flux-type boundary conditions. This problem arises in the modeling of the sedimentation-consolidation process. We formulate the definition of entropy solution of the model in the sense of Kru kov and prove convergence of the scheme to the unique entropy solution of the problem, up to satisfaction of one of the boundary conditions.

     

Determination of enzyme activity inhibition by FTIR spectroscopy on the example of fructose bisphosphatase

A mid-infrared enzymatic assay for label-free monitoring of the enzymatic reaction of fructose-1,6-bisphosphatase with fructose 1,6-bisphosphate has been proposed. The whole procedure was done in an automated way operating in the stopped flow mode by incorporating a temperature-controlled flow cell in a sequential injection manifold. Fourier transform infrared difference spectra were evaluated for kinetic parameters, like the Michaelis–Menten constant (K _M) of the enzyme and V _max of the reaction. The obtained K _M of the reaction was 14 ± 3 g L⁻¹ (41 μM). Furthermore, inhibition by adenosine 5′-monophosphate (AMP) was evaluated, and the K _M^App value was determined to be 12 ± 2 g L⁻¹ (35 μM) for 7.5 and 15 μM AMP, respectively, with V _max decreasing from 0.1 ± 0.03 to 0.05 ± 0.01 g L⁻¹ min⁻¹. Therefore, AMP exerted a non-competitive inhibition.     

High resolution photofragment spectroscopy of the gas phase methyl iodide ion

Photodissociation spectra of the molecular ion CH₃I⁺ were obtained with a three stage quadrupole mass spectrometer. Starting from the \(\tilde X^2 E_{3/2} \) ground state, theà ² E _1/2 state was excited with a stilbene 3 cw dye laser. This state predissociates to CH ₊ ³ +I. Measuring the intensity of the CH ₊ ³ fragment ions as a function of the wavelength of the exciting laser, a spectrum showing vibrational and rotational structure was obtained. The vibrational structure was assigned to three progressions ofv ₃ and new vibrational frequencies were determined. From a computer simulation of the (0, 1, 10) band rotational constants were derived. In particular, their dependence on the vibrationv ₃ was studied.     

Survey of chemical residues and biological evaluation of photochemically pre-vulcanized surgical gloves

Abstract  

Latex allergies arise from the presence of latex proteins as well as noxious rubber additives (mainly accelerators and activators used in conventional sulfur-accelerated vulcanization processes) in medical devices (e.g., medical gloves, catheters) made from natural rubber latex. As a new approach the ultraviolet (UV) light-initiated pre-vulcanization of natural rubber latex makes efficient cross-linking feasible without using any toxic, mutagenic, or irritating chemicals. The cross-linking in the latex particles is accomplished via the thiol-ene addition reaction in the presence of a polyfunctional thiol and a photoinitiator. The new process is carried out in a falling film photoreactor on a pilot scale which provides a continuous irradiation of the latex emulsion. The UV technique is suitable for an easy up-scaling and represents the entrance into large-volume industrial production. The surgical gloves are then made by a conventional coagulant dipping process comprising good physical properties and high ageing stabilities. The aim of this study was to evaluate the biological properties and skin compatibility of UV-pre-cured gloves in skin sensitization, skin irritation studies, and cytotoxic tests. In addition the biologically available chemical residues in the gloves were characterized by UV–visible spectroscopy, elementary analyses, and high-performance liquid chromatography coupled with mass spectroscopy. The results of the studies revealed that UV-cross-linked surgical gloves exhibit good skin compatibility together with low cytotoxicity and residual chemical levels in the range of 60 and 120 μg/g_glove.