ALBERT

Notes: One of the basic prerequisites for rational and high quality production of plastic parts is a tool layout tailored to the production process. To date, both design and construction have generally been based on values acquired by experience. This first, necessitates highly qualified personnel and second, involves what is frequently time consuming and costly finishing work. Experience acquired so far with computer-aided layout of injection molds shows that even a designer with little experience reaches the target more quickly and more reliably. At the same time he is able to draw on the results of intricate calculation and simulation methods which he was unable to apply in the past for reasons of time alone. This paper thus sets out the possibilities currently open and the experience available for computer-aided mold layout. The chief point of focus here is a system for the layout of injection molds. Working on from this system, however, the potentials for computer application are presented for blow mold- and foaming mold-design. After finding the mold principle, mold layout essentially divides up into two major areas, namely dimensioning calculations (CAE) and compilation of production documents (CAD). In dimensioning, the different functional elements of the mold are calculated. The aids that have been developed and the potentials of computer-aided dimensioning are presented with examples from the fields of rheological, thermal, and mechanical mold layout. Computer-aided rheological layout divides up into two steps. The first gives information on qualitative filling behavior (filling picture, flow paths) and the second provides quantitative results (pressures, shear stresses, temperatures). Computer-aided thermal layout similarly divides up into part steps. These are a rough overall energy balance, a rough layout of the tempering system, a segmented layout, and a homogeneity check, which involves simulating the temperature conditions in the mold by means of difference methods. When it comes to mechanical layout of the mold, programs are available for deformation calculations on basic cases and these will frequently be sufficient. For more complex cases of loading and deformation, a finite element program is used. Graphic data processing units can be used to supply extra facilities - first, to provide an aid for the simulation programs in dimensioning and second, to rationalize the compilation of the production documents. An illustration of a CAD workplace is given, incorporating the necessary computer configuration and peripherals. Compiling production documents is essentially a problem of variant design. The variants in this case are the individual components of the mold and a number of standardized accessories that can be called up as “standardized components.” The mold cavity, however, always has to be a free design. All programs are dialogue driven and are in a standardized manner so that even designers with no data processing experience can use the computer as an aid. The CAD/CAE system presented duly fulfils all these requirements. It allows the designer, at a single computer work station, to carry out both simulation and dimensioning calculations, to obtain information on material data, and to compile production documents on the basis of variant and free design. This provides the designer with a readily manageable aid and makes a considerable contribution towards improving the design result. Finally, the capacity of different computer concepts and the CAE/CAD/CAM systems on the market are discussed. For the future it will be possible to establish a computer-aided link between the different areas of design, from development of the molded part, via mold design and production, through setting the processing parameters of the injection molding machine.

Notes: Summary The plasma levels and excretion of tritium-labeled iloprost in healthy elderly male and female volunteers have been measured after i.v. infusion of 2 ng·kg−1·min−1 for 4 h and oral administration of 0.1 and 0.48 μg/kg. During infusion, a steady-state of labeled compounds in the plasma was not achieved. Total radioactivity declined from a mean of 408 pg equiv/ml in three phases, with half-lives of 24 min, 1.7 h and 5.0 h, respectively. A steady-state of unchanged iloprost was reached rapidly with a peak of 81 pg/ml. Plasma levels declined biphasically with half-lives of 6 min and 31 min. Total clearance was 24 ml· min−1·kg−1. Maximum concentrations of labeled substances after oral administration were 307 and 1,051 pg equiv/ml after 29 and 39 min respectively. The peak of unchanged iloprost (116 pg/ml) was observed 7.5 min after an oral dose of 0.48 μg/kg. Bioavailability was 16%. Iloprost was totally metabolized and the metabolities were mainly excreted in urine. The main biotransformation products in plasma and urine were tentatively identified by cochromatography as dinor-and tetranoriloprost and their glucuronides. ADP-induced platelet aggregation was reduce by 60% during the i.v. infusion and 15 min after oral administration of 0.48 μg/kg. Heart rate and blood pressure were virtually unaffected. Common side-effects were facial flush, headache and nausea.

Notes: Summary We have studied the pharmacokinetics of theophylline and enprofylline in patients with liver cirrhosis, patients with chronic renal failure, and healthy subjects, and have assessed the predictive value of routine tests of liver function and renal function (creatinine clearance) for theophylline and enprofylline total body clearances. Theophylline clearance was significantly decreased in the patients with liver cirrhosis compared with both the patients with renal failure and the healthy subjects (the mean values in the three groups were 24, 47, and 46 ml·h−1·kg−1 respectively. Enprofylline clearance was significantly decreased in the patients with chronic renal failure, compared with both the patients with liver cirrhosis and the healthy subjects (the values in the three groups were 64, 250, and 289 ml·h−1·kg−1 respectively. There was a strong correlation between creatinine clearance and enprofylline clearance, while there was only a poor correlation between the liver function tests and theophylline clearance. It appears that in various clinical situations enprofylline elimination can be predicted more precisely than theophylline elimination, which may make the drug safer in clinical practice.

Notes: Summary The pharmacokinetics and effects on blood pressure and heart rate of nisoldipine were studied in 8 patients with cirrhosis and in 8 age-matched healthy controls. On separate occasions each subject received nisoldipine by i.v. infusion (0.37 mg in 40 min) and as a tablet (5 mg for patients and 20 mg for control subjects). After i.v. nisoldipine, the elimination half-life was 9.7 h in control subjects and 16.6 h in the cirrhotics. The volume of distribution was 4.1 l/kg and 6.4 l/kg and the total systemic clearance was 847 ml/min and 494 ml/min, respectively. On oral nisoldipine, systemic availability was fourfold higher in patients with cirrhosis: 14.7% versus 3.7%. After i.v. administration of nisoldipine there was a brief decrease in systolic and diastolic blood pressure in both groups, whereas the heart rate increased. After 4 h a second effect peak appeared in the control subjects. After oral nisoldipine similar effect-time profiles were found, but effects lasted longer than after i.v. administration. Comparison of the maximal total plasma concentration of nisoldipine and the maximal effect in the two groups revealed that sensitivity to nisoldipine was not different in patients with cirrhosis. A reduction in the dose of nisoldipine is recommended when cirrhotics require oral nisoldipine in therapeutic practice.

Notes: Summary Plasma levels of the prostacyclin analogue, iloprost, were measured by antibody/GC/MS in healthy male volunteers given 1 and 3 ng/kg per min i.v. for 45 min, and 1 µg/kg p.o. Following i.v. infusion, the steady-state plasma levels of iloprost were strictly dose-dependent (46±8 pg/ml and 135±24 pg/ml). The disposition was biphasic with half-lives of 3–4 min and 0.5 h. After oral administration, absorption of the drug was extremely rapid, the maximum plasma level of 251±32 pg/ml being achieved after 10±6 min. The bioavailability was 16±4%. Platelet aggregation induced by 2 µM ADP was reduced by 53% and 68% at the end of the two different infusions, and by 68% 15 min after p.o. administration. The ex-vivo inhibition of platelet aggregation by iloprost was not affected by preceding drug treatment. The cAMP content of platelets was increased by a factor of 2.5 at the end of the infusions and to a lesser extent 15 min after oral dosing. A slight increase in heart rate occurred during the infusion and within 30 min after oral administration; blood pressure was virtually unaffected. Except for transient side-effects (facial flush and headache) no adverse reactions were observed.

Notes: Thermo-oxidative ageing processes were investigated in films (100 μm thick) made from isotactic polypropylene with different antioxidant concentrations between 0% and 0.1% using isothermal long-term differential thermal analysis (ILDTA). The end of the oven life of polypropylene coincided with the loss of mechanical properties which was confirmed by tensile tests at temperatures far below the crystallite melting range. Already prior to the beginning of autocatalytic decomposition, ILDTA experiments permits conclusions to be drawn on the thermal history of the specimens and statements made regarding the end of thermo-oxidative stability of the polymer, which is accompanied by a deterioration in the mechanical properties.In consequence of the correlation between oxidation time and antioxidant concentration the local antioxidant concentration in sheets or films can be measured by ILDTA. Thus, investigating the diffusion of an antioxidant in polypropylene using ILDTA is possible.

Notes: Recently, it was suggested that parallel β-sheets have a significant dipole moment, in contrast to antiparallel sheets. Ab initio molecular-orbital (MO) calculations on parallel and antiparallel β-strands of tetra(Gly) show that they have very similar charge distributions. Interaction energies between two and three strands of tetra(Gly), obtained using the direct reaction field Hamiltonian, show that a particular choice of point charges is probably not crucial for calculating interactions within β-sheets, but that it might be for calculating interactions between these sheets and other parts of a protein, in particular, α-helices. The point-charge representation of our MO-SCF results will probably reduce the hazard of introducing artefacts in electrostatic calculations of protein conformational energies, provided the short-range interactions are treated in a more realistic way, i.e., such that intra- and interchain induction effects are included.

Notes: Nach dem Pulverpackverfahren werden Diffusionsschutzschichten auf den Stahl 13 CrMo 44 (Werkstoff Nr. 1.7335) aufgebracht. Ihr Aufbau wird durch Aluminiumkonzentration in der Probenoberfläche, Schichtdicke und Oberflächenbeschaffenheit beschrieben. Es wird berichtet, wie diese Kenngrößen von Pulverzusammensetzung, Beschichtungstemperatur und Beschichtungszeit abhängen. In 16wöchigen Auslagerungen pulveraluminierter Proben bei 608 °C unter Schutzgas erfolgt nur eine geringe Abnahme der Aluminiumkonzentration in der Probenoberfläche und keine Schichtverbreiterung. Im Verlauf der Auslagerung bildet sich zunehmend eine neue Phase der Zusammensetzung Fe3Al in der Interdiffusionszone aus.

Notes: Using idealised assumptions, the stress condition in the semi infinite body of the Hertzian contact region can be calculated for various geometries as a function of the surface pressure (normal force), the friction (tangential force at the surface) and the residual stresses in the material.Equivalent stresses can be formed from the coordinate stresses using various stress hypotheses (distortion energy hypothesis, shear stress hypothesis and alternating shear stress hypothesis).The effects of friction, residual stresses and contact geometry on the location and magnitude of the equivalent stresses appearing in the material have been investigated, the stress hypotheses being evaluated in terms of the extent to which they take account of these effects in an appropriate form.These investigations show clearly that the distortion energy hypothesis is the best representation of the extent of material stress in the case of dynamically loaded rolling elements. The shear stress hypothesis can be considered as a good approximation whereas the alternating shear stress hypothesis is only capable of providing useful conclusions to a limited extent.

Notes: Zum Schutz vor Schwingungsverschleißschäden wurden Flachproben der Legierung Ti-6Al-4V mit metallischen Schutzschichten versehen. Dazu wurden die Proben mit Cu, Cr, V, Ti und durch einen Al/Cu-Verbund beschichtet. Die beschichteten Proben wurden dann in einer Reibkufenapparatur geprüft.Es zeigte sich, daß alle Beschichtungen außer dem Al/Cu-Verbund zu erheblichen Steigerungen der Probenlebensdauer bzw. -festigkeit führten.Wie rasterelektronenmikroskopische Untersuchungen ergaben, gelingt durch die Beschichtungen eine Trennung von Grundwerkstoff und Oberflächenfunktion, wodurch die Wirksamkeit der Beschichtungen von eher geringer Verschleißfestigkeit erklärbar wird.