Empirical model for the waveguiding properties of directly UV-written waveguides

We present an empirical model for the waveguiding properties of directly UV-written planar waveguides in silica-on-silicon. The waveguides are described by a rectangular core step-index profile, in which model parameters are found by comparison of the measured waveguide width and effective index with modal field calculations. The model is used as input for beam propagation method calculations to design UV-written optical components. Subsequent fabrication of such components showed a good agreement with the model predictions. Using the model will reduce the number of iterations and thereby the development time of new optical devices.     

Reconstructing Open Surfaces from Image Data

In this paper a method for fitting open surfaces to data obtained from images is presented using a level set representation of the surface. This is done by tracking a curve, representing the boundary, on the implicitly defined surface. This curve is given as the intersection of the level set describing the surface and an auxiliary level set. These two level sets are propagated using the same motion vector field. Special care has to be taken in order for the surfaces not to intersect at other places than at the desired boundary. Methods for accomplishing this are presented and a fast scheme for finding initial values is proposed. This method gives a piecewise linear approximation of the initial surface boundary using a partition of the convex hull of the recovered 3D data. With the approach described in this paper, open surfaces can be fitted to e.g. point clouds obtained using structure from motion techniques. This paper solves an important practical problem since in many cases the surfaces in the scene are open or can only be viewed from certain directions. Experiments on several data sets support the method.     

Procurement Bidding in First-Price and Second-Price,Sealed-Bid Auctions within the Common-Value Paradigm

Within the common-value paradigm, I examine the magnitude of the differencein expected outcome between first-price and second-price, sealed-bid auctions.I limit myself to two empirical specifications of bidders' signals: Weibulland normal distribution. The optimal bid functions and the expected procurer'scost under both auction formats are derived. Simultions are undertaken toanalyze the impact that random draws of signals have on the differences inoutcome from the two auction formats. Using estimates from structuralestimation in previous empirical work on first-price auction data, whereWeibull and normal distributions of signals have been applied, thehypothetical expected gain from switching from a first-price, sealed-bidauction to a second-price, sealed-bid auction mechanism is computed.     

Analysis of the motion of a flat jet in a direct strip casting feeding system

The motion and shape of a vertically falling flat rectangular jet of liquid metal issuing from an inclined plane is analysed numerically and analytically. The jet is affected by surface tension and gravity. The main interest in this problem originates from the technological application of the direct strip casting process, which is a novel process to cast steel strips in a thickness range from 2 to 15 mm with a minimum or no hot-rolling. In this process the liquid metal is fed onto a single endless horizontal belt that runs between two rollers. The bottom of the belt is cooled by water. One of the techniques to feed the liquid metal is down an inclined plane. Due to disturbances in the flow, for instance slag in the liquid metal, the jet issuing from the inclined plane may split into two or several jets. The large convergence of the individual jets causes an unfavourable non uniform distribution of the liquid metal over the belt. In the analysis of the present paper it is shown, using an expansion in the inverse Froude number, that the convergence of a single jet depends to zero order on the inverse square root of the Weber number We^?1/2 = (γl(ρw₀² h₀))^1/2. Small convergence of the jet is found for large Weber numbers, which can be accomplished with a large initial velocity w₀.     

Intraoperative monitoring with stimulus-evoked electromyography during placement of iliosacral screws. An initial clinical study

Cells of the innate immune system secrete cytokines early in immune responses that guide maturing T helper (Th) cells along appropriate lineages. This study investigates the role of cytokine networks, bridging the innate and acquired immune systems, in the pathogenesis of an organ specific autoimmune disease. Experimental allergic encephalomyelitis (EAE), a demyelinating disease of the central nervous system, is widely used as an animal model for multiple sclerosis. We demonstrate that interleukin (IL)-12 is essential for the generation of the autoreactive Th1 cells that induce EAE, both in the presence and absence of interferon gamma. The disease-promoting effects of IL-12 are antagonized by IL-10 produced by an antigen nonspecific CD4+ T cell which, in turn, is regulated by the endogenous production of IL-12. This unique immunoregulatory circuit appears to play a critical role in controlling Th cell differentiation and provides a mechanism by which microbial triggers of the innate immune system can modulate autoimmune disease.     

On the consistency of line-drawings, obtained by projections of piecewise planar objects

This paper deals with line-drawings, obtained from images of piecewise planar objects after edge detection. Such images are used, e.g., for navigation and recognition. In order to be a possible image of a three dimensional piecewise planar object, it has to obey some projective conditions. Criteria for a line-drawing to be correct is given in this paper, along with methods to find possible interpretations. In real life situations, due to digitization errors and noise, a line-drawing in general does not obey the geometric conditions imposed by the projective imaging process. Under various optimality conditions, algorithms are presented for the correction of such distorted line-drawings.This work has been done within the ESPRIT-BRA project VIVA.     

Quantification of aroma vapours sorbed in polyethene films using supercritical carbon dioxide

Extraction with supercritical carbon dioxide was used to quantity the amounts of seven different aroma vapours sorbed in polyethene films. The method was found to completely extract all aroma compounds from the films. The solution of aroma compounds in the polymer films decreased with increasing polymer density. Monoterpenes were always completely sorbed in the films, whereas aldehydes and ketones had a much lower affinity for the films. The sulphur-containing compound, thiophene, was difficult to analyse due to its adsorption on metal surfaces.     

Crystal chemistry of γ-(Zn, Me)3(PO4)2 solid solutions

A number of γ-(Zn,$\text{Me}$)₃(PO₄)₂ solid solutions with the “γ-Zn₃(PO₄)₂” structure have been prepared and equilibrated at about 1070 K ($\text{Me}\text{= Mg, Mn, Fe, Co, Ni, Cu, and Cd}$). Approximate homogeneity ranges are given. The monoclinic unit cell dimensions have been accurately determined from Guinier-Hägg photographs. The structure contains five- and six-coordinated cations. Correlations between homogeneity ranges, unit cell dimensions, cation radii and cation distributions are pointed out, and the phases are also compared with isotypic (Mg,$\text{Me}$₃(PO₄)₂ and (Co,$\text{Me}$)₃(PO₄)₂ solid solutions.     

An approach to genetic transformation in the Xiphophorine fish

The paper describes the clinical and morphological features of a congenital neurological disease affecting two in-bred litter-mate kittens. The principal neurological features were ataxia and dysmetria. In one of the kittens light microscopy revealed widespread vacuolation of white and grey matter of the brain and spinal cord. Electron microscopy revealved intra-myelinic vacuolation and some expansion of the extracellular space. Neuronal, axonal and glial changes were not seen, nor was there evidence of myelin breakdown. The entity is compared with congenital brain oedema of calves and spongy degeneration of the CNS in man.     

Coke formation during cracking of hydrocarbons. I. The effect of pre-sulphiding on coke formation on a nickel-chromium-iron alloy under steam cracking conditions

Studies have been carried out on the effect of pre-sulphiding a nickel-chromium-iron alloy on coke formation under steam cracking conditions. Pre-sulphiding has no great effect on the gaseous product spectrum as long as some sulphur is present, but the coking rate is dependent on the amount of sulphur pre-deposited. Small amounts of sulphur reduce the coke formation, but the coking rate increases with increasing amounts of pre-deposited sulphur. As the sulphur content increases still further, coke formation passes through a maximum. A tentative explanation of these observations is advanced in terms of the effect of metal sulphides on the established mechanism of coke formation. Initial sulphiding is suggested to increase grain boundary penetration by coke and to result in the accumulation of iron sulphide on the surface. Eventually this may act to seal off grain boundaries, thereby inhibiting further coke formation.