High-pressure freezing causes structural alterations in phospholipid model membranes

The influence of high-pressure freezing (HPF) on the lipid arrangement in phospholipid model membranes has been investigated. Liposomes consisting of pure dipalmitoylphosphatidylcholine (DPPC) and of DPPC mixed with a branched-chain phosphocholine (1,2-di(4-dodecyl-palmitoyl)-sn-glycero-3-phosphocholine) have been analysed by freeze-fracture electron microscopy. The liposomes were frozen either by plunging into liquid propane or by HPF. The characteristic macroripple-phase of the two-component liposome system is drastically changed in its morphology when frozen under high-pressure conditions. The influence of ethanol which acts as pressure transfer medium was ruled out by control experiments. In contrast, no high-pressure alterations of the pure DPPC bilayer membrane have been observed. We assume that the modification of the binary system is due to a pressure-induced relaxation of a stressed and unstable lipid molecule packing configuration. HPF was performed with a newly designed sample holder for using sandwiched copper platelets with the high-pressure freezing machine Balzers HPM010. The sandwich construction turned out to be superior to the original holder system with regard to freeze-fracturing of fluid samples. By inserting a spacer between the supports samples with a thickness of 20–100 μm can be high-pressure frozen. The sandwich holder is provided with a thermocouple to monitor cooling rates and allows exact sample temperature control. Despite a two-fold mass reduction compared to the original holder no HPF cooling rate improvement has been achieved (4000 °C s⁻¹). We conclude that the cooling process in high-pressure freezing is determined mainly by cryogen velocity.     

Analysis of the reorganization of poly(ethylen terephthalate) in the melting range by temperature-modulated calorimetry

Although melting of flexible macromolecules in an irreversible process, it was demonstrated recently with temperature-modulated calorimetry (TMC) that some of the overall melting may be reversible within a fraction of a kelvin. This was taken as evidence for incompletely melted molecules with a remaining molecular nucleus. The reversing heat capacity that characterizes this effect was observed to decrease with time. It is shown by new TMC experiments that this time effect is not induced by the temperature modulation, but is due to an inherent annealing process. It is also proven that it is not dependent on the type of calorimeter. Received: 7 November 1997/Revised version: 19 December 1997/Accepted: 19 December 1997     

Testosterone induces Ca2+ influx via non-genomic surface receptors in activated T cells

MalK is the ATP-hydrolyzing subunit of the binding protein-dependent ATP-binding-cassette (ABC) transport system for maltose from Salmonella typhimurium. In a recent hypothesis, Glu64 and Glu94 of MalK were proposed as candidates for 'catalytic carboxylate', common to ATP- and GTP-hydrolyzing proteins [Yoshida and Amano (1995) FEBS Lett. 359, 1-5]. Substitution of both residues and, additionally, Glu74 by either glutamine or glycine and valine, respectively, had no deleterious effect on maltose transport. Thus, our data disprove the above notion.     

A New Hybrid Fault-Tolerant Architecture for Digital CMOS Circuits and Systems

This paper presents a new hybrid fault-tolerant architecture for robustness improvement of digital CMOS circuits and systems. It targets all kinds of errors in combinational part of logic circuits and thus, can be combined with advanced SEU protection techniques for sequential elements while reducing the power consumption. The proposed architecture combines different types of redundancies: information redundancy for error detection, temporal redundancy for soft error correction and hardware redundancy for hard error correction. Moreover, it uses a pseudo-dynamic comparator for SET and timing errors detection. Besides, the proposed method also aims to reduce power consumption of fault-tolerant architectures while keeping a comparable area overhead compared to existing solutions. Results on the largest ISCAS’85 and ITC’99 benchmark circuits show that our approach has an area cost of about 3 % to 6 % with a power consumption saving of about 33 % compared to TMR architectures.     

Festigkeitsberechnung von Ventilfedern

Zusammenfassung Für neuzeitliche Motoren und Einspritzpumpen sind die Federn zu hochwertigen Maschinenteilen entwickelt worden, für deren Berechnung besonders zuverl?ssige Unterlagen zu fordern sind. Mit einer Sonderprüfmaschine wurde das Verhalten derartiger Federn untersucht, woraus sich Dauerfestigkeitsbilder für die praktische Anwendung ableiten lassen.     

Oxidative Cyclization-Induced Activation of a Phosphoinositide 3-Kinase Inhibitor for Enhanced Selectivity of Cancer Chemotherapeutics

In this work, we designed a prodrug that reacts with cellular oxidative equivalents leading to ether cleavage and cyclization to release an active phosphatidylinositol 3-kinase (PI3K) inhibitor. We show that the compound reduces affinity for PI3KA relative to the PI3K inhibitor, is slow to intercellularly oxidize, and is resistant to liver microsomes. We observed modest activity in untreated acute myeloid leukemia cells and 14-fold selectivity relative to non-cancerous cells. The cellular activity of the compound can be modulated by the addition of antioxidants or oxidants, indicating the compound activity is sensitive to cellular reactive oxygen species (ROS) state. Co-treatment with cytosine arabinoside or doxorubicin was used to activate the compound inside cells. We observed strong synergistic activity specifically in acute myeloid leukemia (AML) cancer cells with an increase in selective anticancer activity of up to 90-fold. Thus, these new self-cyclizing compounds can be used to increase the selectivity of anticancer agents.     

Spin Hall effect devices

The spin Hall effect is a relativistic spin-orbit coupling phenomenon that can be used to electrically generate or detect spin currents in non-magnetic systems. Here we review the experimental results that, since the first experimental observation of the spin Hall effect less than 10 years ago, have established the basic physical understanding of the phenomenon, and the role that several of the spin Hall devices have had in the demonstration of spintronic functionalities and physical phenomena. We have attempted to organize the experiments in a chronological order, while simultaneously dividing the Review into sections on semiconductor or metal spin Hall devices, and on optical or electrical spin Hall experiments. The spin Hall device studies are placed in a broader context of the field of spin injection, manipulation, and detection in non-magnetic conductors.     

Link travel time prediction for decentralized route guidancearchitectures

A critical problem in decentralized route guidance is to communicate anticipated congestion to individual drivers in such a way that the routes chosen are likely to be consistent with the forecast. We propose a prediction technique for decentralized route guidance architectures to identify time-dependent link travel times which when communicated to drivers leads to time-dependent fastest paths consistent with this forecast. The fixed-point property of the forecast is assured by an iterative process of traffic simulations followed by dynamic route determinations until the routes and hence the resulting dynamic link times become stable. The resulting routes yield an inherently accurate forecast of congestion as well as being user-optimal by construction. A back-dating process is utilized to insure the discovery of a stable routing after a finite and usually small number of iterations, An empirical case study based on the roadway network in Troy, MI is included