Crystallinity and lateral crystallite size of different UHMW PE materials

Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70–75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15–25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.     

7.5 Gb/s monolithically integrated clock recovery circuit using PLLand 0.3-μm gate length quantum well HEMT's

A monolithically integrated clock recovery (CR) circuit making use of the phase-locked loop (PLL) circuit technique and enhancement/depletion AlGaAs/GaAs quantum well-high electron mobility transistors (QW-HEMT's) with gate lengths of 0.3 μm has been realized. A novel preprocessing circuit was used. In the PLL a fully-balanced varactorless VCO was applied. The VCO has a center oscillating frequency of about 7.7 GHz and a tuning range greater than 500 MHz. A satisfactory clock signal has been obtained at a bit rate of about 7.5 Gb/s. The power consumption is less than 200 mW at a supply voltage of -5 V     

Design aspects of MOS-controlled thyristor elements: technology,simulation, and experimental results

2.5-kV thyristor devices have been fabricated with integrated MOS controlled n⁺-emitter shorts and a bipolar turn-on gate using a p-channel DMOS technology. Square-cell geometries with pitch variations ranging from 15 to 30 μm were implemented in one- and two-dimensional arrays with up to 20000 units. The impact of the cell pitch on the turn-off performance and the on-state voltage was studied for arrays with constant cathode area as well as for single-cell structures. By realizing MOS components with submicrometer channel lengths, scaled single cells are shown to turn off with current densities of several kiloamperes per square centimeter at a gate bias of 5 V. In the case of multi-cell ensembles, turn-off performance is limited due to inhomogeneous current distribution. Critical process parameters as well as the device behavior were optimized through multidimensional numerical simulation     

One-step synthesis of functional Co nanoparticles for surface-initiated polymerization

Much effort is conducted to construct artificial objects that are capable of converting chemical or electromagnetic energy into a specific, predetermined motion on the nanoscale. We present results on the synthesis of core–shell nanoparticles capable to be set in rotation by the application of electromagnetic fields. The nanorotors implied in the study are based on the cobalt nanospheres decorated with a stabilizing brush shell composed of poly(?-caprolactone) that is attached by surface-initiated polymerization. The functional cores used as macroinitiators can be fabricated alternatively by a two-step or a one-step process.     

Einsatz moderner Informationstechnik im militärischen Bereich: Für den Verteidiger notwendig und verantwortbar

Zusammenfassung Nach Pädagogen, Ärzten etc. haben sich nun auch Informatiker für den Frieden organisiert. So sehr sich der Verfasser mit den Zielen von Friedensinitiativen identifizieren kann, so sieht er doch die Gefahr, daß diese Bemühungen insgesamt eher destabilisierend und damit kontraproduktiv wirken. Bevor im folgenden Beitrag dieser Gedankengang weiter ausgeführt wird, soll zunächst versucht werden, die Bereiche darzustellen, in denen bislang und in absehbarer Zukunft Rechensysteme in modern ausgerüsteten Streitkräften eingesetzt werden, wobei besonders auf die Situation in Mitteleuropa und speziell auf die Bundeswehr eingegangen wird. Es wird aufgezeigt, daß gerade der Verteidiger auf moderne Führungs- und Aufklärungssysteme angewiesen ist, insbesondere in der kritischen Anfangsphase eines Konflikts, und daß die Vertreter alternativer Verteidigungsstrukturen, die den Schwerpunkt auf defensiv ausgerüstete Verbände mit struktureller Nichtangriffsfähigkeit legen, wie auch offizielle Programme der NATO zur Verbesserung der konventionellen Verteidigungsfähigkeit auf moderne Technologie setzen. In diesem Zusammenhang wird ein Forschungsprojekt vorgestellt, das zum Ziel hat, die Wirksamkeit derartiger reaktiver, rüstungskontrollfreundlicher Verteidigungs- und Bewaffnungsstrukturen sowie moderner Technologie im Gefecht der verbundenen Waffen zu untersuchen. Entsprechend der Themenstellung dieses Sonderheftes soll schließlich auch auf moralisch-ethische Aspekte des Einsatzes moderner Informationstechnik für die Verteidigungsplanung eingegangen werden. Dies geschieht in der Form von Thesen, um die Aussagen als persönliche Meinung des Verfassers besonders zu kennzeichnen.     

From the history of electrocardiography

The basis of electrocardiography was established in the innovative years between 1850 and 1930. Men like Waller, DuBois-Reymond, and Einthoven were the innovators of what we today recognize as modern electrocardiography. Others, like Lewis and Bedford, introduced analysis of cardiac arrhythmias, of the S-T segment and the QRS complex. The article gives an overview of this innovative period and its instrumentation.