Development of a multifunctional coating system for laser-induced material transport

The aim of our research is to develop a novel surface coating for the use in laser microdissection and laser pressure catapulting (LMPC). LMPC is a contact- and contamination-free technique to separate histologic material and living cells for further proteomic and genomic analysis. Several physico-chemical functions must be included within the optimum coating system designed for this purpose, like optical absorption at the laser wavelength, combined with optical transparency in the visible region, a control of the laser ablation process, mechanical stability and biocompability for the adhesion of the histologic material.To achieve the optimum system the combination of several layers is required. The optical absorbance to capture the radiation energy from a frequency-tripled Nd:YAG laser (λ = 355 nm) is reached by a thin layer of zinc oxide (ZnO), deposited by hollow cathode gas flow sputtering. The laser ablation process is controlled by a polyelectrolyte multilayer, consisting of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS). The evaporation of chemisorbed water from the film is used to promote the catapulting process. For the mechanically stable, laser-dissectible layer organic coatings, like photoresists or lacquers, are suitable. Silica-containing polyacrylate nanocomposites were employed for this purpose.The investigation of the coating system included LMPC experiments with varying compositions of the layer system. The best results were obtained using a system consisting of ZnO, a polyelectrolyte multilayer deposited from 0.1 M Na₂SO₄ containing polymer solutions, and a 1.5-μm thick layer of the polyacrylate nanocomposite.To check the quality of the developed system, experiments with the commonly used poly(ethylene naphthalate) (PEN) foil were performed simultaneously. In addition to the determination of the parameters required for LMPC, quantitative real-time Polymerase Chain Reaction (rt-PCR) of the dissected material verified the benefit of the new system.     

The modified outflow funnel — A device to assess the flow characteristics of powders

Flow regulators are added to solid pharmaceutical formulations to improve the flow properties of powder mixtures. During the blending process the glidants adsorb successively at the surface of the host particles and thus lead to a reduction of attractive forces. A large variety of flow additives based on silicon dioxide is commercially available, but not all glidants are just as well suited for each technological problem or each cohesive bulk powder. To assess the improvement of the flowability parameters caused by a glidant a classification system and an adequate measuring device is needed. We would like to present a new measuring device to evaluate the flow enhancing potency of glidants. The modified outflow funnel features a stirrer that acts in the region of bulk arches obstructing the outflow process of a cohesive powder. By destruction of the bulk arches powder outflow is enabled and the time needed for emanation can be measured as a parameter of the flow properties. In addition other measuring parameters like the force needed to destroy the bulk arches are capable to evaluate the flowability of the powder mixture. Binary powder mixtures consisting of corn starch and flow regulator were blended in a Turbula® mixer for a defined period of time. The flow regulators were represented by fumed silica and a selection of various types of SIPERNAT^® precipitated silica provided by Evonik Degussa GmbH, Hanau, Germany. Flowability parameters of the mixtures were characterized with a modified outflow funnel, Hausner Ratio and a shear tester.     

Irradiation-Assisted Stress-Corrosion Cracking of Nitinol During eBeam Sterilization

Medical device fractures during gamma and electron beam (eBeam) sterilization have been reported. Two common factors in these device fractures were a constraining force and the presence of fluorinated ethylene propylene (FEP). This study investigated the effects of eBeam sterilization on constrained light-oxide nitinol wires in FEP. The goal was to recreate these fractures and determine their root cause. Superelastic nitinol wires were placed inside FEP tubes and constrained with nominal outer fiber strains of 10, 15, and 20%. These samples were then subjected to a range of eBeam sterilization doses up to 400 kGy and compared with unconstrained wires also subjected to sterilization. Fractures were observed at doses of >100 kGy. Analysis of the fracture surfaces indicated that the samples failed due to irradiation-assisted stress-corrosion cracking (IASCC). This same effect was also observed to occur with PTFE at 400 kGy. These results suggest that nitinol is susceptible to IASCC when in the presence of a constraining stress, fluorinated polymers, and irradiation.     

Me-DLC films as material for highly sensitive temperature compensated strain gauges

In technical applications strain gauges are widely used. Apart from conventional polymer foil based strain gauges that are glued to the work piece surface, sputtered strain gauges are already commercially used in special applications. Those sputter strain gauges are typically made of NiCr alloy and the sensor layer is as sensitive to strain as the ones used in the glued strain gauges with a gauge factor of 2, but neglecting problems of creeping and swelling of the involved polymer materials. Diamond-like carbon (DLC) films offer significantly higher strain sensitivity, but usually they are also very sensitive to temperature effects. Using metal doped diamond-like carbon (Me-DLC), higher strain sensitivity than conventional metal based systems, in combination with thermal compensation, is possible. The influence of different process parameters on the gauge factor and temperature coefficient of resistance (TCR) of DLC and Me-DLC films produced in industrial sputtering systems was investigated. Gauge factors up to 13 in combination with a high negative TCR in the range of a few thousand ppm/K were reached with sputtered DLC films. The substrate bias voltage in particular showed a strong influence on the resulting gauge factor of the films. For Me-DLC films different deposition methods (dc and rf sputtering) and various doping metals (Ag, Ni, Ti, and W) were investigated. Using dc sputtering of the Me-DLC films only Ni-DLC showed gauge factors slightly higher than 2. Furthermore, only for Ni-DLC zero crossing of the TCR was observed by variation of the metal content. Using rf excitation especially Ni-DLC films showed gauge factors exceeding values of 15 in combination with a TCR close to zero.     

Site selectivity in praseodymium- and bismuth-substituted gadolinium gallium garnet epilayers

Praseodymium- and bismuth-substituted gadolinium gallium garnet (GGG) layers have been prepared by liquid phase epitaxy on (111)- and (110)-orientated GGG substrates. By an investigation of linear dichroism of Pr³⁺-transitions, the supercooling dependence of dodecahedral site selectivity in Pr-substituted GGG can be shown to differ considerably for (110)- and (111)-epitaxial layers: An increase of site selectivity with supercooling is found in (111) layers while it is constant in (110) layers. The long wavelength ¹S₀ → ³P₁-transition of the Bi³⁺ ion has been utilized to detect site selectivity in (110)- orientated Bi-substituted GGG layers.     

Dissolution of iron garnet LPE layers in acidic solutions containing reducing agents

The dissolution rates of liquid phase epitaxial iron garnet layers in acidic solvents are increased by up to two orders of magnitude in the presence of suitable reducing agents. Experiments with differently orientated layers and with single crystal spheres reveal a change in the anisotropy of dissolution rates.     

Dimensions of psychotherapy in private practice.

Categorical approaches to psychotherapy on 4 bipolar dimensions are presented, including emotional intensity, location of problem, location of therapy, and location of responsibility. By means of a questionnaire, 142 psychotherapists in private practice were surveyed regarding types of patients treated, techniques utilized, clinical specialty areas, and self-ratings on the 4 dimensions. Of the 142 Ss, 41% were psychologists; 32% were marriage, family, and child counselors; 14% were psychiatrists; 9% were social workers; and 4% were psychological assistants or other specialists. Therapists whose theoretical orientation suggested conceptual clarity produced more discriminating responses on the dimensions, whereas therapists with conflicting orientations made less discriminating responses. Practitioners appeared to differ most along those dimensions over which they had practical control. (1 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Glucosuria of pregnancy: frequency of diabetes mellitus and renal glucosuria (author's transl)

From 1974 to 1979 352 pregnant women were referred to our diabetic outpatient clinic because of glycosuria during pregnancy. In 118 women (34%) oral glucose tolerance tests revealed a pathologic glucose tolerance. In 234 pregnant women (66%) a "renal glycosuria of pregnancy" was found to be the cause for the observed glycosuria. A pathologic glucose tolerance was relatively more frequent in the 3rd trimenon, whereas renal glycosuria was observed to be more frequent in the second trimenon.     

A rapid and velocity-independent damage localization approach for ultrasonic structural health monitoring

This paper presents a novel damage localization approach for active ultrasonic structural health monitoring. The formalism considers triplets of two actuators and one sensor in a spatially distributed transducer network. Depending on time-of-flight measurements that are automatically conducted on differential signals, the defect position in isotropic and quasi-isotropic plates is located very rapidly without the wave velocity information. This is particularly beneficial when the wave speed cannot be obtained because of an unknown stacking sequence of the laminate. Results are shown for different point-like defects on isotropic and quasi-isotropic structures for which the processing time is less than 1 s on a standard computer.