Self-Charging of Quench Condensed Tritium Films

Self-charging of a solid tritium film (T₂) has been discovered by chance in a precision spectroscopy experiment on tritium decay as a shift of the endpoint energy by several eV. The effect was then investigated systematically as a function of film thickness and time by measuring the energy shift of monochromatic conversion electrons from ^{83 m} Kr evaporated onto T₂ films. The steady state is characterized by a practically constant, critical electric field strength E _c 62 MV/m (20 mV/monolayer) over the film, at which the residual positive charges attain sufficient mobility to penetrate the film towards the conducting substrate. This kind of breakthrough behaviour is analyzed in terms of a thermal hopping model, where a trapping potential of ₀175 k _BK is lowered in direction of the electric force by a factor of 3 in order to facilitate hopping at a film temperature of about 1.9 K.     

Reversible cardiopathy after accidental overdose of mitoxantrone

Corpora lutea from Sprague-Dawley rats that were orally administered 0.0 (control), 1.0, 10.0, and 100.0 mg/kg hexachlorobenzene (HCB) for 21 days were analyzed by electron microscopy. Granulosa lutein cells (GLC) from animals of the 10.0 mg group showed differences from the cells of animals that served as the controls. Golgi complexes and smooth endoplasmic reticulum appeared more conspicuous, possibly due to dilation resulting from hyperactivity. Free polysomes seemed more prominent in the cells of the 10.0 mg group. The GLC architecture from animals of the 1.0 and 100.0 mg groups was similar to that of the corresponding cells in the control group. Since smooth endoplasmic reticulum is involved in the synthesis of steroid hormones, and that free polysomes are engaged in synthesis of cytoplasmic proteins, it is suggested that HCB at a dose of 10.0 mg/kg given for 21 days may alter the synthetic activity of the GLC of the rat.     

Morphometric quantification of atherosclerotic plaques by computer-assisted image-analysis of histographs

A method is described for quantifying the amount of atherosclerotic plaque in collapsible blood vessels by a computer-assisted image analysis of cross-sectional contours traced under microscopic visualization. The digitized contours are processed using a computer program that transforms the irregular image of the collapsed vessel into an ideal geometry and then calculates in vivo linear and areal parameters, variables, and ratios. The analysis is based on conventional stereologic principles and utilizes relatively inexpensive and widely available equipment: microscope with drawing tube attachment, digitizing board, microcomputer, monitor, and printer or plotter. Some of the output data include the fraction of vessel lumen occluded by plaque, average thickness of plaque, the fraction of wall surface area covered by plaque, and the ratio of the vessel bore to vessel wall volumes. The error and precision of measuring lumen occlusion and plaque surface area are assessed.     

A novel model-based approach to optimization and control design of batch processes

Traditionally, many industrial batch processes have been operated according to rigid recipies, in spite of the fact that production would yield more profit or a better product if they were efficiently adapted to changes in quality and cost of the used and/or produced products, process and scheduling conditions, and so on. In this paper a approach, called the flexible recipe approach, is given, which transforms the common rather static recipes into recipes that can be easily improved and used for systematic and efficient production adaptation at the start of a batch and during the processing. To be able to use this approach in an industrial environment a practical implementation is made in the software package FRIS. A fermentation process chosen as an example shows the methods and gives an indication of the expected profit.     

Rectifying effect in boron nanowire devices

It has been found that Ni forms ohmic contacts and Ti forms Schottky-barrier contacts to boron nanowires (BNWs). Using two-step electron-beam lithography, Ni and Ti electrodes are subsequently attached onto the ends of a single BNW. As a result, a nanoscale rectifier is created using a BNW.     

Development of design charts for fixed-bed adsorption

A mathematical model of the dynamic behaviour of non-isothermal fixed-bed adsorbers has been developed which takes into account the various mass and heat transfer resistances. Comparison of experimental and simulated results confirms that the model can predict the adsorption and desorption breakthrough curves of an adiabatically operated column, using only equilibrium data and tortuosity factors obtained from single pellet experiments. A simplified model with a reduced number of parameters was derived by investigation of the dimensionless transfer parameters under industrial conditions. It becomes evident that the main transfer mechanisms are convective heat and mass transfer in the bulk flow and diffusion within the pores of the particle. Dimensionless effluent concentration is expresses in terms of dimensionless time, a transport parameter, a non-isothermal parameter, the adsorption equilibrium and the inlet and initial concentrations and temperatures in the simplified model. For a chosen system of adsorbate and adsorbent, design charts can be developed by computer simulation, to determine graphically the breakthrough time as a function of significant process parameters, i.e. the dimensionless transfer parameter and the feed concentration.     

Modeling the behavior of selenium in Pulverized-Coal Combustion systems

The behavior of Se during coal combustion is different from other trace metals because of the high degree of vaporization and high vapor pressures of the oxide (SeO₂) in coal flue gas. In a coal-fired boiler, these gaseous oxides are absorbed on the fly ash surface in the convective section by a chemical reaction. The composition of the fly ash (and of the parent coal) as well as the time-temperature history in the boiler therefore influences the formation of selenium compounds on the surface of the fly ash. A model was created for interactions between selenium and fly ash post-combustion. The reaction mechanism assumed that iron reacts with selenium at temperatures above 1200 °C and that calcium reacts with selenium at temperatures less than 800 °C. The model also included competing reactions of SO₂ with calcium and iron in the ash. Predicted selenium distributions in fly ash (concentration versus particle size) were compared against measurements from pilot-scale experiments for combustion of six coals, four bituminous and two low-rank coals. The model predicted the selenium distribution in the fly ash from the pilot-scale experiments reasonably well for six coals of different compositions.     

Mechanical and Electric Control of Photonic Modes in Random Dielectrics

Random dielectrics defines a class of non‐absorbing materials where the index of refraction is randomly arranged in space. Whenever the transport mean free path is sufficiently small, light can be confined in modes with very small volume. Random photonic modes have been investigated for their basic physical insights, such as Anderson localization, and recently several applications have been envisioned in the field of renewable energies, telecommunications, and quantum electrodynamics. An advantage for optoelectronics and quantum source integration offered by random systems is their high density of photonic modes, which span a large range of spectral resonances and spatial distributions, thus increasing the probability to match randomly distributed emitters. Conversely, the main disadvantage is the lack of deterministic engineering of one or more of the many random photonic modes achieved. This issue is solved by demonstrating the capability to electrically and mechanically control the random modes at telecom wavelengths in a 2D double membrane system. Very large and reversible mode tuning (up to 50 nm), both toward shorter or longer wavelength, is obtained for random modes with modal volumes of the order of few tens of (λ/n)³.