Aligned Immobilization of Proteins Using AC Electric Fields

Protein molecules are aligned and immobilized from solution by AC electric fields. In a single‐step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X‐ray crystal data.     

Influence of different trocar tips on abdominal wall penetration during laparoscopy

Most trocars currently used to place a cannula through the abdominal wall have a conical or pyramidal tip. Because the risk of inadvertent injury along with removal of the cannula is probably related to (a) the force needed to traverse the abdominal wall, (b) the force needed to remove the trocar, and (c) the defect in the abdominal wall, the optimum configuration of the penetrating tip should be determined. The entry force needed to perforate the abdominal wall, the removal force necessary to remove the trocar, and the defect in the abdominal wall were measured in a porcine model under standardized conditions (general anesthesia, 12 mmHg pneumoperitoneum). Nineteen trocars (six disposable, seven reusable, six custom-made) have been tested. They were divided into six groups according to the shape of the tip (conical, pyramidal, or a combination). The entry force (F = 25.6, p < 0.0001) and the removal force (F = 5.1, p < 0.01) were related to the shape of the tip. Conical tips needed a higher force than purely pyramidal tips. The abdominal defect was also different between groups (F = 6.5, p < 0. 001). The trocar with a pyramidal shape caused a greater defect than conical tips. The defect in the abdominal wall was inversely related to the entry force (r = -0.55, p < 0.001) and to the removal force (r = -0.57, p < 0.001). There is not an optimum configuration of a simple push-through trocar with a low entry force and a high removal force. Some kind of a conical tip is recommended for insertion of trocars under direct view.     

Verschiedenes

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Methodische Untersuchungen über die Möglichkeit der Drehwuchsfeststellung in verschiedenen Alterszonen von Laubhölzern

European Journal of Wood and Wood Products - Methodische Untersuchungen über die Möglichkeit der Drehwnchsfeststellung an verschiedenen Stanmeseiten und in verschiedenen Alterszonen an...     

Proton-implanted shallow-ridge quantum-cascade laser

We demonstrate a shallow-ridge quantum-cascade laser (QCL) with performance comparable or better than that of deep-ridge QCLs fabricated from the same wafer. The shallow-ridge QCL emits at /spl ap/4 /spl mu/m with a 4.6-4.8 kA/cm/sup 2/ threshold current density at room temperature which is similar to the deep-ridge QCL. At the same time the shallow-ridge QCL shows a better temperature stability, T/sub 0/=160 K, than the deep-ridge QCL, with T/sub 0/=120 K. The increase in the characteristic temperature of the shallow-ridge laser compared to the deep-ridge laser results from the improved heat dissipation out of the laser ridge through the lateral heat flow. Lateral spreading of the injection current-usually a drawback of shallow-ridge lasers-is suppressed by proton implantation into the strain-compensated InGaAs-AlAs active region layers on either side of the ridge. In contrast to the case of In/sub 0.53/Ga/sub 0.47/As layers and of In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As heterostructures lattice matched to InP, the proton implantation of strain-compensated In/sub 0.73/Ga/sub 0.27/As-AlAs heterostructure on InP creates deep (180 meV) carrier traps, resulting in this material being electrically insulating even at room temperature.     

Professor Fred E. Dickinson 65 Jahre

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Suppression of cross-track vibrations using a self-sensing micro-actuator in hard disk drives

In this study we utilize the self-sensing capabilities of piezoelectric micro-actuators in hard disk drives (HDD) to actively suppress in-plane resonance modes of the suspension in an HDD. The self-sensing circuit is based on a tunable capacitance bridge that decouples the control signal from the sensing signal in the micro-actuator. A hybrid modeling technique based on a realization algorithm and least-squares optimization for continuous-time systems is used to model the single-input dual-output system. An analog controller was computed using standard $H_{\infty}$ -controller design tools and reduced in order using model reduction routines. Experimental implementation using analog filter design shows the effectiveness of the proposed method in reducing the main sway modes of the suspension.