Extravascular lung water index: a new method to determine dry weight in chronic hemodialysis patients

To assess the dry weight of chronic hemodialysis (HD) patients, the extravascular lung water index (ELWI) as a volume parameter was investigated to identify fluid overload. Forty-two patients (30 males, 12 females) with a mean age of 55.7+/-13.0 years who were clinically not overhydrated were connected to the PiCCO system before starting HD treatment. We determined ELWI (normal range 3-7 mL/kg) and the following parameters: global end-diastolic volume index (GEDI, normal range 680-800 mL/m(2)) and intrathoracic blood volume index (ITBI, normal range 850-1000 mL/m(2)) before and after HD to assess the volume status. Brain natriuretic peptide (BNP), aldosterone, and renin as vasoactive hormones were measured at the beginning and at the end of HD treatment as well. In 28 of the 42 patients (67%), elevated values of ELWI were found, indicating interstitial volume overload. There were significant correlations between ELWI and cardiac function index (p=0.003; Pearson's coefficient -0.451), global ejection fraction (p=0.012; Pearson's coefficient -0.389), ITBI (p=0.004; Pearson's coefficient 0.437), and GEDI (p=0.004; Pearson's coefficient 0.437). No significant relations among ELWI and mean arterial pressure (MAP), BNP, aldosterone, and renin were found. In conclusion, the use of ELWI is safe in chronic HD patients and identifies fluid-overloaded patients, who show no obvious signs of hypervolemia. The determination of ELWI is an excellent method to quantify the exact volume in chronic HD patients.     

Experimental Modelling using Low Melting Point Metallic Melts: Relevance for Metallurgical Engineering

This paper describes model experiments with liquid metals of low melting point as an important tool to investigate the flow structure and related transport processes in melt flows being relevant for metallurgical applications. Three examples have been selected to demonstrate the benefit of such experiments, namely the electromagnetic stirring of a metallic melt in a pool, the directional solidification of Al‐Si alloys under the influence of an electromagnetically driven flow and the behaviour of a liquid metal bubble plume if a vertically travelling field is applied. Results of flow measurements are presented and the relevance for metallurgical processes is discussed.     

Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor

A combination of a Hartmann-Shack sensor and a standard far-field measurement on one single detector is proposed. The technique is fast and operates without movable parts, thus permitting a compact design. It is not only suited for characterization of the wave-front distribution but may also be considered for determination of the important parameters of beam width, beam divergence, and beam propagation ratio M2 of partially coherent laser beams. First results indicate that a fairly thorough beam characterization, including spatial coherence, propagation characteristics, and beam quality, can be achieved with this method.     

A new spatiotemporal regularization approach for reconstruction of cardiac transmembrane potential patterns

The single-beat reconstruction of electrical cardiac sources from body-surface electrocardiogram data might become an important issue for clinical application. The feasibility and field of application of noninvasive imaging methods strongly depend on development of stable algorithms for solving the underlying ill-posed inverse problems. We propose a novel spatiotemporal regularization approach for the reconstruction of surface transmembrane potential (TMP) patterns. Regularization is achieved by imposing linearly formulated constraints on the solution in the spatial as well as in the temporal domain. In the spatial domain an operator similar to the surface Laplacian, weighted by a regularization parameter, is used. In the temporal domain monotonic nondecreasing behavior of the potential is presumed. This is formulated as side condition without the need of any regularization parameter. Compared to presuming template functions, the weaker temporal constraint widens the field of application because it enables the reconstruction of TMP patterns with ischemic and infarcted regions. Following the line of Tikhonov regularization, but considering all time points simultaneously, we obtain a linearly constrained sparse large-scale convex optimization problem solved by a fast interior point optimizer. We demonstrate the performance with simulations by comparing reconstructed TMP patterns with the underlying reference patterns.     

Ultrathin SiO(2) layers on Si(111): preparation, interface gap states and the influence of passivation

An essential prerequisite for the successful application of Si/SiO(2) nanostructures in photovoltaics is the realization of well-defined and abrupt interfaces with low densities of interface gap states. Here, a complete in situ process from preparation and hydrogen passivation to interface gap state analysis by near-UV photoelectron spectroscopy without breaking ultrahigh vacuum (UHV) conditions is introduced. It is demonstrated that by RF plasma oxidation of Si(111) substrates with thermalized neutral oxygen atoms, ultrathin SiO(2) layers can be realized with compositionally and structurally abrupt Si/SiO(2) interfaces and a minimal amount of intermediate oxidation states bridging the transition from Si to SiO(2). Plasma oxidized samples have significantly lower interface gap states than samples oxidized by thermal oxidation at 850?°C. Interface gap state densities were further reduced by in situ hydrogen plasma passivation with nearly thermalized H atoms. The resulting reduction of interface recombination velocity and the increase of effective majority and minority carrier lifetimes are revealed by constant photocurrent measurements and quasi-steady-state photoconductance, respectively.     

Videokeratoscope for accurate and detailed measurement of the cornea surface

A videokeratoscope based on the imaging of a gridlike pattern is introduced. Unlike conventional videokeratoscopes that rely on Placido disks, the new measurement principle allows an exact reconstruction of the surface and the display of fine details. The experimental instrument was tested on precision glass spheres; the maximum error of the height data was less than 3 microm. The sensitivity and the potential to resolve fine details were demonstrated with irregular surfaces of specially prepared contact lenses. Structures with height deviations of 0.1 microm are well identifiable. The eyes of 18 individuals were investigated, and fine structures were found on these cornea surfaces. Conventional videokeratoscopes do not resolve such detail.     

Production of Strong Steel‐Aluminum Composites by Formation of Intermetallic Phases in Compound Forging

In times of increasing energy costs automotive light weight construction is gaining more importance. The production of hybrid compounds by forging is a promising method to successfully manufacture functional parts by applying resource‐saving process steps. However, in compound forging of steel‐aluminum parts shrinking gaps may form because of the different thermal expansion coefficients. To avoid these unwanted gaps, it is necessary to achieve a firmly bonded joint e.g. by intermetallic phases. This paper deals with the investigation of the influences of different sample preparations, process parameters and true strains on the formation of intermetallic phases. Thus, the optimum production parameters for compound forging of steel‐aluminum parts will be determined.