Differential expression and distribution of focal adhesion and cell adhesion molecules in rat hepatocyte differentiation

The present study has examined the distribution of axons of differing sizes in the optic pathway of the ground squirrel. Axon diameters were measured from electron micrographs at various locations across sections of the optic nerve and tract, and total distributions and numbers were estimated. In both the nerve and tract, roughly 1.2 million optic axons were present. The population of optic axons had a unimodal size distribution, peaking at 0.9 microm in diameter and having an extended tail toward larger diameters. Local axon diameter distributions in the optic tract indicated distinct (though partially overlapping) axon diameter classes, including one of fine sizes peaking at 0.8-0.9 microm, a second of medium sizes peaking around 1.7-1.8 microm, and a third composed of the larger fibers with diameters up to 4.8 microm. The fine-caliber axons were found at all locations in the tract, and were the only axons present immediately adjacent to the pia, while the medium- and coarse-caliber axons were found at deeper locations. Curiously, the larger axons were found primarily in the medial parts of the tract, where axons from the dorsal retina normally course. A similarly restricted distribution of the larger axons was observed in the dorsotemporal parts of the optic nerve, suggesting that this difference in the tract may relate to an asymmetric distribution of ganglion cells on the retina giving rise to these axons. Measurements of axonal size taken within the optic fiber layer in dorsal and ventral parts of the retina confirmed this asymmetry, consistent with previous demonstrations of soma size differences in the dorsal versus ventral retina. The partial segregation of axons by size in the optic tract of the ground squirrel then reflects both the asymmetric distribution of retinal ganglion cell classes and the chronotopic reordering of optic axons that occurs within the chiasmatic region.     

Berechnung der Stillstandserwärmung explosionsgeschützter Asynchronmotoren mittels dreidimensionaler Finite-Elemente-Methode und Zeitschrittrechnung

Übersicht Zur Berechnung der Temperatureverteilung im Rotor einer Asynchronmaschine mit Käfigläufer wird die dreidimensionale Finite-Elemente-Methode mit Zeitschrittverfahren verwendet. Die örtliche Diskretisierung erfolgt über Dreiecksprismen. Die Verlustverteilung wird über eine zweidimensionale Wirbelstromberechnung mittels Finiter-Elemente-Methode für Stab und Ring bestimmt. Die Eisensättigung wird dabei berücksichtigt. Die Theorie wird durch Messungen an einem handelsüblichen Motor mit unterschiedlichen Kurzschlußringen bestätigt. Anhand experimenteller und numerischer Parameterstudien werden konstruktive Richtlinien für eine optimale Form und Lage der Kurzschlußringe entwickelt.

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Calculation of the temperature field at standstill of explosion-protected induction motors by three-dimensional finite element time-stepping method

Contents A three-dimensional finite element time-stepping method is presented for calculation of the temperature field in the rotor of a cage induction machine. For the discretisation of the region triangular prisms are used. Losses and eddy currents are determined by separated calculations using the two-dimensional finite element method for bar and end-ring. The variable permeability is taken into account. Comparisons between calculations and measurements are given for a machine with different end-rings. Rules for an optimal form and position of the end-rings are given from experimental and numerical studies.

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Übersicht der wichtigsten Formelzeichen A magnetisches Vektorpotential - B magnetische Flußdichte - E elektrische Feldstärke - H magnetische Feldstärke - J Stromdichte - _e elektrisches Potential - , Übertemperatur, Celsiustemperatur - I _St ,I _R Stabstrom, Ringstrom - U Spannung - c _p spezifische Wärmekapazität - q Wärmequellendichte - Wärmeübergangszahl - elektrischer Leitwert - Wärmeleitfähigkeit - Permeabilität - _m Dichte - a,b,c,d,e Koeffizienten des Gleichungssystems - f _i Formfunktionen der FE-Berechnung - t zeitliche Schrittweite - D Dreiecksfläche der Finiten Elemente - V Prismenvolumen der Elemente - b _R Breite des Kurzschlußringes - h _R Höhe des Kurzschlußringes - S Außenrandfläche - S Fläche allgemein - k _r Widerstandserhöhungsfaktor - t Zeit - Eindringtiefe der Felder - f, Frequenz, Kreisfrequenz - x,y,z Kartesische Koordinaten - ₂ Rotorpositionswinkel     

Electronic Synthesis of the Avian Retina

An electronic model, based upon reported physiological and anatomical findings and capable of replicating the optical-to-electrical transformations performed by the avian retina has been constructed.     

The yeast telomere length counting machinery is sensitive to sequences at the telomere-nontelomere junction

Saccharomyces cerevisiae telomeres consist of a continuous 325 +/- 75-bp tract of the heterogeneous repeat TG1-3 which contains irregularly spaced, high-affinity sites for the protein Rap1p. Yeast cells monitor or count the number of telomeric Rap1p molecules in a negative feedback mechanism which modulates telomere length. To investigate the mechanism by which Rap1p molecules are counted, the continuous telomeric TG1-3 sequences were divided into internal TG1-3 sequences and a terminal tract separated by nontelomeric spacers of different lengths. While all of the internal sequences were counted as part of the terminal tract across a 38-bp spacer, a 138-bp disruption completely prevented the internal TG1-3 sequences from being considered part of the telomere and defined the terminal tract as a discrete entity separate from the subtelomeric sequences. We also used regularly spaced arrays of six Rap1p sites internal to the terminal TG1-3 repeats to show that each Rap1p molecule was counted as about 19 bp of TG1-3 in vivo and that cells could count Rap1p molecules with different spacings between tandem sites. As previous in vitro experiments had shown that telomeric Rap1p sites occur about once every 18 bp, all Rap1p molecules at the junction of telomeric and nontelomeric chromatin (the telomere-nontelomere junction) must participate in telomere length measurement. The conserved arrangement of these six Rap1p molecules at the telomere-nontelomere junction in independent transformants also caused the elongated TG1-3 tracts to be maintained at nearly identical lengths, showing that sequences at the telomere-nontelomere junction had an effect on length regulation. These results can be explained by a model in which telomeres beyond a threshold length form a folded structure that links the chromosome terminus to the telomere-nontelomere junction and prevents telomere elongation.     

Optical Rotations of Open-Chain Allenes Revisited

A semiempirical theory for the calculation of optical rotations of allenes in the transparent region is presented. The significance of the suggested model is demonstrated by comparison between calculated and observed rotations of 75 open-chain allenes with various chemically relevant (carbon and hetero-) substituents. The physical interpretation of the model reveals that the substituent effect on the optical rotation is exerted via the substituent's polarity (field effect through space) and its polarizability.     

Submicron silicon bipolar master-slave D-type flip-flop for use as 8.1 Gbit/s decision circuit and 11.2 Gbit/s demultiplexer

The authors have designed and implemented a submicron silicon bipolar master-slave D-type flip-flop integrated circuit which can be used either as a decision circuit or a demultiplexer, operating at data rates as high as 8.1 and 11.2 Gbit/s, respectively. The circuit was fabricated using a 0.6 mu m, nonpolysilicon emitter technology, occupying an area of 0.8 mm*0.9 mm, and dissipating 410 mW of power.<>     

Beziehungen zwischen herstellung,struktur und mechanischen eigenschaften bei elastmodifizierten,schlagzähen styrolpolymeren

Rubber-modified polystyrenes of different impact resistance were prepared by varying the polymerization conditions. The samples were thoroughly studied with regard to their morphology and toughness. Based on structural investigations performed by transmission electron microscopy characteristic features of the rubber particles have been established and six standard structures have been defined. Micromechanical processes were studied with emphasis to craze formation as the main toughness-generating mechanism by investigating thin samples in a high-voltage (1000 kV) electron microscope as they were stretched mechanically. A qualitative as well as quantitative relationship has been obtained between size distribution of rubber particles and toughness owing to a quantitative evaluation of the stretching behaviour of the samples.