Preparatory processes in the task-switching paradigm: Evidence from the use of probability cues.

The purpose of the investigations was to dissociate processes of task preparation from task execution in the task-switching paradigm. The basic assumption was that task repetitions have 2 advantages over task shifts: an activation advantage as a result of the execution of the same task type in the pretrial, and an expectation advantage, because participants, in general, implicitly expect a repetition. In Experiments 1-3, the authors explicitly manipulated expectancies by presenting cues that announced a shift and/or a repetition with probabilities of 1.00, .75, .50, or .25. Increasing latencies with decreasing probability for shifts and repetitions show that the expectation advantage can be equalized by preparation. However, the activation advantage represented by constant shift costs between tasks of the same probability is not penetrable by preparation. In Experiments 4 and 5, the authors found evidence that preparation involves activation of the expected task and inhibition of distracting tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prospects for the use of high-Tc superconductors in fusion magnets and options for their test in SULTAN

In the last few years, the critical current densities of long commercially available REBa₂Cu₃O_7?x (RE-123, where RE represents Y or a rare earth element) coated conductors have reached values of 250 A/cm-width at 77 K and zero applied field. Even higher values of 600 A/cm-w (77 K, B = 0) have been demonstrated in shorter lengths. The attractive features of the use of these high-T_c superconductors (HTS) are operation temperatures above 20 K and/or magnetic fields higher than those envisaged for the ITER TF coils. Possible operation conditions for HTS fusion magnets have been studied taking into consideration the possible further improvements of RE-123 coated conductors. Investigations of stability and quench behavior indicate that stability is not a problem, whereas quench detection and protection need attention. Because of the high currents necessary for fusion magnets, many tapes need to be assembled into a transposed conductor. The qualification of HTS conductors for fusion magnets would require their test at magnetic fields of 11 T and currents well above 10 kA. The possibilities to test straight HTS conductor samples in SULTAN have been considered. For a test at 4.5 K, only the development of a low resistance joint between the HTS conductor under test and the NbTi transformer of SULTAN would be necessary. Tests up to 20 K would require that the HTS sample is connected with the NbTi transformer by a conduction-cooled HTS bus bar of large thermal resistance similar to the HTS module of a current lead. HTS conductor tests at temperatures around 50 K would be possible with modified cryogenics.     

WI – Call for Papers,Heft 5/2009, Internet der Dienste

Ohne Zusammenfassung     

Tensile Testing of Nitinol Tubes and Wires with Higher Strain Rates

During tensile testing of superelastic Nitinol material, the specimen temperature increases as result of the exothermic Austenite-to-Martensite phase transformation. The increase in specimen temperature has great influence on the stress-strain response—in particular, upper and lower plateau values—and limits the strain rate of the tensile test, so that for larger specimen dimension, the strain rate has to be reduced. A special setup of the tensile testing equipment has been developed using a fan to improve the heat exchange between the specimen and the ambiance to allow much higher strain rates as well as even gradient of the upper and lower plateau. It could be shown that the strain rate of the first loading and unloading cycle could be two to four times higher as recommended in ASTM F 2516-07 without any negative impact on the determined values. The needed time for tensile testing of Nitinol products could be reduced considerably. The improved heat exchange gives a better comparability and reproducibility of the tensile test data.     

Adaptive Modulation and Multiple Access for the OFDM Transmission Technique

For the transmission of flexible andhigh data rates in future mobile communicationsystems, the multicarrier transmission technique(Orthogonal Frequency Division Multiplexing, OFDM) canbe regarded as a possible alternative tosingle-carrier transmission that is used in today'ssystems. One of the advantages of OFDM is theflexibility concerning modulation and multiple accesstechniques. Since in OFDM the total bandwidth isdivided into a large number of subcarriers, it can beflexibly shared among all the users. In addition, themodulation scheme can be individually chosen for eachsubcarrier, thus granting the possibility of anadaptation to the radio channel characteristics. Inthis paper, the combination of two different multipleaccess schemes, OFDM-FDMA and OFDM-TDMA, and anappropriate adaptive modulation technique isconsidered for the downlink of a communication system.Different degrees of adaptivity are analysed andcompared to show the benefit of an ``intelligent'multiple access and modulation strategy. For thegiven parameters and assumptions, OFDM-TDMA withadaptive modulation yields an improvement of 6 dB insignal-to-noise ratio (SNR) at a bit error rate (BER)of 10^-2. When OFDM-FDMA with adaptive subcarrierallocation is applied, the SNR gain amounts to 12.5 dB(BER of 10^-2).     

Scheduling and staffing multiple projects with a multi-skilled workforce

We consider the problem of simultaneously scheduling IT-projects and assigning multi-skilled internal and external human resources with resource-specific efficiencies to the project work. The objective is to minimize labor costs. The problem is modeled as a mixed-integer linear program (MIP) with a tight LP-bound. The performance of the model w.r.t. solution gap and computation time is assessed and managerial insight is given concerning different problem parameters such as the time window size of projects, the number of skills of human resources, and the workload. Furthermore, we show the benefit of applying the MIP compared to simple heuristics used in practice in terms of obtaining feasible and low-cost solutions. Finally, we provide insight into the benefit of applying the MIP in case of central compared to decentral planning.     

Binding of external ligands onto an engineered virus capsid

The development of novel delivery systems for therapeutic substancesincludes targeting of the carriers to a specific site or tissuewithin the body of the recipient. This can be accomplished byappropriate receptor-binding domains and requires linking ofthese domains to the carrier. We have used recombinantly expressedpolyomavirus-like particles as a model system and inserted thesequence of a WW domain into different surface loops of theviral capsid protein VP1. In one variant, the WW domain maintainedits highly selective binding properties of proline-rich ligandsand showed an increased affinity but also an accelerated association/dissociationequilibrium compared to the isolated WW domain, thus allowinga short-term coupling of external ligands onto the surface ofthe virus-like particles.     

Ein neues integrales Verfahren zur Quantifizierung der Grundwasserimmission, Teil II: Numerische L?sung und Anwendung in Eppelheim

Im ersten Beitrag zu diesem Thema ( Teutsch et al. 2000) wurde ein neues Erkundungsverfahren zur Quantifiziuerng der Schadstoffbelastung in Grundwasser an Deponien und Altlasten vorgestellt, das eine Bestimmung der Schadstoffbelastung im natürlichen Str?mungsfeld mit einer hohen Erkundungssicherheit erm?glicht. In diesem zweiten Beitrag wird der erstmalige praktische Einsatz des Verfahrens an einem Feldstandort vorgestellt. Dabei stand die erweiterte, differentielle Immissionsmessung im Vordergrund, die zus?tzlich zur Bestimmung von Gesamt-Schadstofffrachten und mittleren Konzentrationen auch Angaben zur r?umlichen Konzentrationsverteilung entlang definierter Kontrollquerschnitte senkrecht zur Str?mungsrichtung erm?glicht. Neben der allgemeinen Erprobung der Mess- und Auswerteans?tze sollte mit den Messungen insbesondere gezeigt werden, dass das neue Verfahren auch bei geringen Grundwasserschadstoffkonzentrationen einsetzbar ist. Ferner sollte die erreichbare r?umliche Aufl?sung der Konzentrationsverteilung im Abstrom demonstriert werden.