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: 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: The structure of the inner core region (L-glycero-D-mannoheptose/2-keto-3-deoxy-D-mannooctulosonic acid region) of lipopolysaccharides from Salmonella minnesota rough mutants was investigated. Using conventional methods (neutral sugar analysis, Smith degradation and methylation analysis) combined with gas chromatography/mass spectrometry (GC/MS) of higher oligosaccharides (up to tetrasaccharide), the linkages of the core sugars of lipopolysaccharides from S. minnesota rough mutants, strains R4 (Rd2P-), R7 (Rd1P-) and R5 (RcP-) were determined as: with R representing H in R4, L-glycero-D-mannoheptopyranosyl in R7, and D-glucopyranosyl-(1→3)-L-glycero-D-mannoheptopyranosyl in R5, respectively. In addition, it is shown that heterogeneity within the neutral sugar part of these lipopolysaccharides is low.

Notes: The Community Bureau of Reference has organized a collaborative interlaboratory project to improve the analytical protocol for some specific chlorobiphenyls (CBs) within the European Community (EC). A series of test procedures were prescribed to optimize the gas chromatographic conditions for splitless and on-column injection, which substantially improved the quality of data. Important parameters included the initial column and injector temperatures and the choice of the polarity of the stationary phase. In a study with cleaned eel-fat extracts, coefficients of variation for reproducibility CV(R) ranging from 11 to 24% at the 0.04-0.3 mg/kg level per CB congener were obtained. No significant difference could be found between splitless- and on-column injection.

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: Die Halogenide sind entweder mit K2PrCl5 (orthorhombisch, Pnma, Z = 4, hexagonal gebündelte Ketten kantenverknüpfter Polyeder [PrCl7]) order mit Cs2DyCl5 (orthorhombisch, Pbnm, Z = 4, hexagonal gebündelte Ketten cis-eckenverknüpfter Oktaeder [DyCl6]) isotyp, sie können in Strukturfeld-Diagrammen voneinander abgegrenzt werden. Die Thermische Ausdehnung wird für Cs2SLuCl5 und Rb2PrX5 (X = Cl, Br, I) röntgenographisch verfolgt.

Notes: Feinteiliges NaOH kann im Temperaturgefälle von 523 nach 473 K aus NH3 bei 6 kbar Druck innerhalb von 10 d in Form glasklarer, leicht auffächernder Kristallplättchen erhalten werden, Unter vergleichbaren Bedingungen führt auch die Protolyse von KNH2 bzw. RbNH2 mit K(H2O)OH und Rb(H2O)OH bei Temperaturen 〈423 bzw. 〈365 K zu plättchen- und quaderförmigen Kristallen von KOH bzw. RbOH. Die Kristallzüchtung erfolgte für das jeweilige Hydroxid im Existenzbereich der bei Raumtemperatur stabilen Modifikation.Durch Röntgenbeugung an Einkristallen wurden die Atomanordnungen in den drei Verbindungen neu bestimmt. Bei NaOH gelang es, auch die Lagen der H-Atome aus Messungen bei 294 und 147 K zu ermitteln; die Struktur war aus Röntgendaten bezüglich der Na- und O-Anordnung bereits bekannt. Es handelt sich um den TlI-Typ. Die OH--Ionen bilden bei quadratisch pyramidaler Koordination durch Na+-Ionen lineare Na—O—H-Anordnungen mit dem Na+-Ion an der Spitze. Dadurch treten H-Doppelschichten auf, die die leichte Spaltbarkeit der Kristalle senkrecht zur Richtung [010] erklären.Für KOH und RbOH, die isotyp kristallisieren, ergibt sich für die schweren Teilchen eine monoklin verzerrte NaCl-Anordnung. Die Molekülanionen führen bei Raumtemperatur noch Librationen aus. Daher konnte auch im Falle des KOH das H-Atom nicht lokalisiert werden.

Notes: The synthesis of styrene-acrylonitrile copolymers by seeded emulsion copolymerization on polybutadiene has been studied. The influence of the emulsifier concentration and of the size of the supporting area on the formation of new particles is demonstrated. Kinetic studies and particles size measurements indicate the development of the reaction after the formation of new particles.