Electric pulse heating device for the analysis of solid/solid phase transformations.

Ohmic pulse heating is applied to investigate diffusion and interface controlled solid-state phase transformations. The developed device uses extensive solid-state electronics providing a high current, low voltage approach that overcomes the limitations of existing setups, most notably the use of sample geometries that allow for the reliable measurement of local temperatures and their assignment to microstructures. Power for heating is supplied by a capacitor array with adjustable voltage, and the process is controlled by microcontrollers and a solid-state relay, which allows for controlled pulses that are adjustable in microseconds. Electric currents of up to 22 kA at 90 V can be realized by the setup. Electric data are monitored and collected during the experiments, and temperature data are captured using a high-resolution infrared camera at high frame rates (1200 fps). The capabilities of the setup are demonstrated by rapid heating (106 K/s) and subsequent cooling of a brass sample. Two distinct areas of the sample are analyzed in detail, showing similar heating, but different cooling curves with rates of 104 and 102 K/s. Local microstructure analysis shows that different phase transformation mechanisms were dominant, and thus, the setup fulfills its purpose.

Custom-made wrist prothesis (UNI-2™) in a patient with giant cell tumor of the distal radius: 10-year follow-up.

Wrist endoprosthesis is still an exceptional indication compared to the prosthesis of large joints, especially when a rescue surgery procedure of the wrist is no longer possible and the complete wrist arthrodesis is to be considered the ultima ratio. However, a suspended function in the wrist is accompanied by a significant restriction in the patient`s daily life. Using the fourth-generation endoprosthesis, the situation regarding long-term results for the hand has already improved. This means that a durability of more than 6 years is no longer a rarity. Defect situations in joints, in particular those which occur after tumor, still pose a greater challenge. If autologous reconstructions cannot be performed, custom-made prostheses can be considered as very rare indications for joint reconstruction. While these have been used for years on large joints such as shoulder, elbow, knee and hip, they have only been described on the hand in particular cases. We report the 10-year follow-up of implantation of a custom-made wrist prothesis (UNI-2™, KMI, Germany) in a 36-year-old patient with tumorous destruction of the distal radius by a giant cell tumor.

[Revision surgery after total wrist arthroplasty]. / Revisionen nach Implantation von Totalendoprothesen am Handgelenk.

BACKGROUND: Wrist arthroplasty is still an exceptional indication in the field of hand surgery. In recent years, it has become increasingly accepted as an alternative to wrist arthrodesis as the ultima ratio for panarthrosis or similar destruction of the wrist. In particular, the patient's desire for functional integrity also plays an important role. COMPLICATIONS: While there were often complications with earlier prosthesis designs of the older generations and only a short survival rate could be achieved, this has improved, if the indication of the so-called fourth generation prostheses is done properly. Survival rates of over 10 years are no longer uncommon, even without revision operations. Currently, the indication for hemiarthroplasty has been increasing, particularly in the case of post-traumatic destruction. Those who are seriously interested in endoprosthesis should also be able to treat the associated complications. The present article is intended to provide an overview of common or potential complications in the context of wrist arthroplasty and to demonstrate possible solutions by presenting case studies. The basics of primary implantation are, therefore, not discussed. Reference is made to further literature.

[Lie detection and mind reading: is there a use for fMRI?: A critical survey and reflection]. / MRT als Lügendetektor und Gedankenleser?: Kritische Bestandsaufnahme und Reflexion.

Great efforts have been made in recent years to use functional magnetic resonance imaging (fMRI) in the context of lie detection. In the present paper the pros and cons of such an approach are analyzed and critically discussed.Both epistemological and methodical considerations have shown that all attempts to derive mental states from fMRI findings ("reverse inference") are not valid. Consequently, fMRI scans cannot reveal a person's thoughts and whether (s)he is lying or telling the truth.

Phase contrast in Simultaneous Topography and Recognition imaging.

The operation of a force microscope in Simultaneous Topography and Recognition (TREC) imaging mode is analyzed by means of numerical simulations. Both topography and recognition signals are analyzed by using a worm-like chain force as the specific interaction between the functionalized tip probe and the sample. The special feedback mechanism in this mode is shown to couple the phase signal to the presence of molecular recognition interactions even in absence of dissipation.

Tissue reactions to polyethylene implants with different surface topography.

This study investigates the importance of implant surface topography on soft tissue response. The tissue response in the rat abdominal wall to discs of low density polyethylene with smooth to coarse surfaces was evaluated after one, six or 12 weeks. Capsule thickness and immunohistochemical quantification of monocytes-macrophages were used as measures. The macrophage specific antibody ED1 was used for identification of newly recruited macrophages and the ED2 antibody for the mature tissue macrophages. The smoother surfaces gave a thicker capsule than the rougher surfaces, and at one week also larger total numbers of cells and ED1 positive macrophages at interface. The capsule thickness increased over time for the smooth and intermediate surface topographies. In contrast, the cell numbers generally decreased over time. In conclusion, a coarse surface elicited lesser tissue reaction compared with a smooth surface.

Tissue response to commercial silicone and polyurethane elastomers after different sterilization procedures.

Two different commercial polymeric materials, a silicone and a polyurethane (PUR), were studied with regard to correlations between the chemical and physical compositions of the polymer surfaces and the biological response on implantation. Test specimens of the materials were manufactured according to standard procedures. The specimens were implanted in rats for 10 and 90 days. Before implantation the polymers were sterilized in three different ways, namely, beta irradiation, ethylene oxide sterilization and steam sterilization. The polymers were characterized before and after the implantation with respect to the chemical composition and the morphology of the surfaces. After implantation the biological response was evaluated by counting numbers of macrophages, giant cells, fibroblasts and other cells present at the surfaces. The thickness of the fibrous capsule surrounding the test specimens was measured at the thickest and thinnest parts. PUR surfaces showed signs of degradation already after sterilization and after 10 to 90 days of implantation, pits and cracks appeared, especially in the ethylene oxide sterilized samples. However, differences in the biological responses were small and independent of the sterilization method. After 10 days of implantation the capsule thickness and the amounts of cell material adhering at the surfaces were different, and it appears that the silicone rubber induces more tissue response than PUR. The differences in the early tissue response evened out after 90 days implantation time and a steady state situation evolved, which was similar for the silicone and the polyurethane.

Protein adsorption of poly(ether urethane) surfaces modified by amphiphilic and hydrophilic polymers.

A commercial biomedical poly(ether urethane), Pellethane 2363-80AE, was surface modified through the use of amphiphilic polymeric additives, and through surface grafting with poly(ethylene glycol), PEG. Two different amphiphilic polymers, Polymer C and Pluronic PE9400, were used as additives. Polymer C, a segmented polyurethane, was prepared from PEG1500, 4,4'-diphenylmethane diisocyanate and a C16-C18 monoglyceride chain extender. Pluronic PE9400 is a propylene oxide-ethylene oxide tri-block co-polymer obtained from BASF. Adsorption of human albumin and fibrinogen to the modified surfaces was studied by means of radiolabelled proteins. By contact angle measurements and X-ray photoelectron spectra the amphiphilic polymers were shown to accumulate at the polyurethane surfaces. Adsorption of fibrinogen, in particular, was significantly reduced by the amphiphilic additives to levels similar to those obtained for Pellethane surfaces grafted with PEG 20,000. In vitro clotting times for citrate-buffered blood in contact with the amphiphilic surfaces increased as compared with the unmodified ones.

Adhesion of staphylococci to chemically modified and native polymers, and the influence of preadsorbed fibronectin, vitronectin and fibrinogen.

A commercially available poly(ether urethane), polyethylene, and modifications of these polymers have been compared with respect to adsorption of fibronectin, fibrinogen and vitronectin. The adhesion of staphylococcal strains (characterized for ability to bind immobilized proteins, cell surface hydrophobicity and charge) was studied by bioluminescence with and without preadsorption of proteins to the surfaces. The least amount of proteins and the fewest bacteria adhered to the amphiphilic surfaces. When polymers were preincubated with plasma or albumin, lower numbers of bacteria adhered, except to Pellethane grafted with PEG 20,000, to which coagulase-negative staphylococci adhered to a higher extent.

Cryptolepis sanguinolenta: antimuscarinic properties of cryptolepine and the alkaloid fraction at M1, M2 and M3 receptors.

From an ethanol extract of the roots of Cryptolepis sanguinolenia the alkaloid fraction and its main constituent cryptolepine were isolated by partitioning at pH 11 and column chromatography using silica gel and chloroform/methanol as eluent. Cryptolepine was identified mainly by EI-MS and 1H/13C-NMR spectroscopy. Cryptolepine (3-30 microM) and the alkaloid fraction of Cryptolepis sanguinolenta (3-10 micrograms/ml) antagonized muscarinic effects at M1 receptors in rabbit vas deferens, M2 receptors in guinea-pig atria, and M3 receptors in guinea-pig ileum. The experiments, using N-methylatropine as reference drug, showed a significant antimuscarinic activity for both cryptolepine and the alkaloid fraction, but no appreciable receptor subtype selectivity (pA2 = 5.00-5.73). Cryptolepine was determined as the antimuscarinic principle of Cryptolepis sanguinolenta. At higher concentrations both materials displayed negative inotropic effects.

Influence of repeated washings with soap and synthetic detergents on pH and resident flora of the skin of forehead and forearm. Results of a cross-over trial in health probationers.

Ten healthy individuals washed their forehead and forearm twice a day over consecutive periods of four weeks with soap and synthetic detergents or vice versa (cross-over design). In general the pH values were higher during the period when soap was applied (the mean pH differed by 0.3 units, p less than 0.01). As a rule the counts of coagulase-negative staphylococci were not much altered. The number of propionibacteria, however, was markedly higher when soap was used (p = 0.02 and 0.01 resp.). At the forehead there was a clear correlation between bacterial counts and skin pH both with propionibacteria (0.56, p less than 0.001) and staphylococci (0.51, p less than 0.001). At the forearm only the former proved true (0.24, p less than 0.05). Thus the skin pH seems to be open to long-standing changes according to the preferred washing habits which may also be of major influence on the composition of the cutaneous bacterial flora.