Investigations of the properties of blockpolymerized and injection-moulded PLLA

The blockpolymerization and injection-moulding procedure are two main techniques used to produce PLLA for medical devices. Until now there has been no comparison of the well known data of blockpolymerized material and data of injection-moulded material. Test rods (2×3×25 mm) were made from block polymerized balls by the injection-moulding procedure. The rods were incubated in tris-buffer-saline for different periods (0, 2, 4, 6, and 8 weeks) at a pH of 7.4 and a temperature of 37°C. The test methods we used were the three-point-bending, the fatigue behaviour and the calculation of the decrease of molecular weight. Both materials under investigation are chemically similar but show very different mechanical properties, in particular the injection moulded material has a very decreased behaviour and a very low loss of molecular weight. Blockpolymerized PLLA rods show a very fast lost bending strength and after 6 weeks a low resistance against cyclic loads in the fatigue behaviour test. Injection moulded PLLA will be used in future for internal fixation of fractures.     

Signaling Induced by Chronic Viral Hepatitis: Dependence and Consequences

Chronic viral hepatitis is a main cause of liver disease and hepatocellular carcinoma. There are striking similarities in the pathological impact of hepatitis B, C, and D, although these diseases are caused by very different viruses. Paired with the conventional study of protein–host interactions, the rapid technological development of -omics and bioinformatics has allowed highlighting the important role of signaling networks in viral pathogenesis. In this review, we provide an integrated look on the three major viruses associated with chronic viral hepatitis in patients, summarizing similarities and differences in virus-induced cellular signaling relevant to the viral life cycles and liver disease progression.     

Influence of the Internal Crystallizer Geometry and the Operational Conditions on the Solid Product Quality

From an industrial point of view, control of precipitated particles′ quality turns out to be crucial. Experiments carried out in a pilot-scale baffled stirred tank with and without draft tube of two different diameters under different process conditions show a great influence of internal geometry and feed point locations on crystal size distribution and morphology of precipitated particles. Several results in contradiction with those expected by intuition show that much more work is needed to elucidate the interaction between mixing and precipitation phenomena in stirred tanks. In this context, the paper provides a frame of reference and some rules of thumb useful to industrial manufacturers for controlling the product quality.     

Electrical issues associated with sea-water immersed windings in electrical generators for wave- and tidal current-driven power generation

For the majority of proposed wave- and tidal current-driven power generation applications, the electrical generators are submerged in sea water, frequently at many metres of depth. The environment places significant stress on the rotating or translating seals between the driven shaft and the electrical generator leading to reduced reliability and lifetime. A potential solution is to eliminate the seal, thereby flooding the generator and allowing sea water to circulate around the shaft, windings and rotor of the machine. The impact of immersing the windings of the machine in sea water is assessed here. Specifically, the impact that the insulation has on the leakage capacitance as well as the consequent impact the leakage capacitance has on current and voltage oscillations in the switching converter used to excite the winding is assessed. Thermal tests are conducted to assess the impact of the insulation on the thermal conductance of the coil?insulation system. Experimental evidence is provided.     

Effect of Sonication on the Thermotropic Behavior of DODAB Vesicles Studied by Fluorescence Probe Solubilization

The effect of sonication on fluorescence probe solubilization in cationic vesicles of dioctadecyldimethylammonium bromide (DODAB) was investigated by steady-state fluorescence of pyrene (Py), trans-diphenylpolyenes—diphenylbutadiene (DPB), diphenylhexatriene (DPH), and their corresponding 4,4′-dialkyl derivatives 4B4A and 4H4A fluorescence probes. The data indicate that sonication affects the bilayer polarity, the melting temperature (T _m), and the cooperativity of the melting process due to changes in vesicle morphology. The effect of temperature on the fluorescence intensity and yielding Φ_f and anisotropy <r> shows that the ionizable probes 4B4A and 4H4A are solubilized close to the vesicle interfaces, whereas the non-ionizable DPH and DPB are deeper in the bilayers. Py solubilization indicates that sonicated vesicles exhibit less densely packed bilayers.     

Quantitative analysis of protein far UV circular dichroism spectra by neural networks

A new method based on neural network theory is presented toanalyze and quantify the information content of far UV circulardichroism spectra. Using a backpropagation network model witha single hidden layer between input and output, it was possibleto deduce five different secondary structure fractions (helix,parallel and antiparallel ß-sheet, ß-turnand random coil) with satisfactory correlations between calculatedand measured secondary structure data. We demonstrate that foreach wavelength interval a specific network is suitable. Theremaining discrepancy between the secondary structure data fromneural network prediction and crystallography may be attributedto errors in the determination of protein concentration andrandom noise in the CD signal, as indicated by simulations.     

Improved Osteointegration of Ti-6Al-4V-implants of Different Surface Texture by the Use of Bone Morphogenetic Protein-3 （BMP-3）

Half of altogether 60 cylindrical implant devices made of titanium-aluminum-vanadium alloy （ Ti-6Al-4V） were plusna-sprayed with a hydroxyapatite-couting and the other half had a corundum blasted porous surface. 15 implants of each group of the titanium test buplants were coated with 230 μg porcine, high-purified BMP- 3-precipitute per implant. In each case a BMP- 3-couted and an uncoated control-device were implanted into the femoral part of the putellofemoral joint of the right and left leg of 30 adult giant rabbits. Histomorphological and histomorphometrical we found in both groups with BMP- 3-coated test devices an improved osteointegrution. Stutistical evaluation using the t-test for matched samples showed 5 weeks after surgery a significant higher volume of tony formed bone of the BMP- 3-coated corundum- blasted or hydroxyapathe- coated Ti- 6Al- 4 V test devices compared to the non-couted controls of the same t）pe （p 〈 0.01, t-test for matched samples）. In both implant groups with BMP-couting a synergetic effect was verifiable although the bone ongrowth in the hydroxyaputite coated implants was more extensive than in the corundum blasted implants. Light microscopy demonstrated osteointegrution without connective tissue membrane around the surface of the implants. Our results indicate that composite metal implants,as used in endoprosthetics and implantology , are suitable carriers for BMP- 3 and im proved fixation of the implants can be achieved. The hydroxyapatite surface is superior to the corundum-blasted surface with regards to the observed parameters because of its pronounced bioactivity and its osteoconductive characteristics.     

Erfahrungen mit On-Line- und Off-Line-TE-Messungen von Generatoren

Ohne Zusammenfassung Kurzfassung des Beitrags für die CIGRé-Konferenz 1998.     

Monocondylar fractures of the femur. Therapeutic strategy and clinical outcome]

Two groups of 3 120-160-kg Holstein steers were fed a diet high in carbohydrate and low in long fiber and either with or without added sodium sulfate. Prior to and during the course of feeding the experimental diet, the concentrations of rumen hydrogen sulfide gas and rumen fluid sulfide were determined by a simple sulfide detector tube method and by sulfide-selective electrode, respectively. Other measurements included rumen fluid pH, blood creatine kinase, and blood sulfhemoglobin. Two of the 3 steers fed the high-sulfate diet developed signs and lesions of polioencephalomalacia. Clinical signs included episodic ataxia and blunted or absent menace reaction. Increased ruminal H2S gas concentrations occurred in all 3 steers consuming the diet with added sulfate. The onset of clinical signs coincided with the onset of elevated H2S concentrations. These increases were 40-60 times the values measured in the steers consuming the diet without added sulfate. In contrast, increases in rumen fluid sulfide concentrations usually rose to 4 times that of control steers. The steers fed an identical diet but without added sulfate exhibited no signs or lesions of polioencephalomalacia and no elevations of sulfide in rumen gas or fluid. All steers had a modest decrease in rumen fluid pH associated with the transition to the concentrate diet. No significant changes were observed in any of the blood measurements of any of the steers. An additional pair of steers was fed the experimental diet with or without added sulfate to compare the ruminal H2S gas concentrations estimated by H2S detector tubes with those estimated by a different method of analysis utilizing charcoal trapping of H2S, conversion to sulfate, and measurement of the sulfate. Both methods yielded comparable estimates of H2S concentration. Overall, these data indicate that changes in rumen gas cap H2S concentrations are larger than changes in rumen fluid sulfide concentration and the estimation of rumen gas cap H2S concentration may be a practical approach to detecting pathologic increases in ruminal H2S gas. This simple, rapid, minimally invasive method should be useful for estimating the H2S content of ruminal gas under field conditions.