Einfluß des Aluminiums auf die Ausscheidung des Kohlenstoffs im α-Eisen

Untersuchung des Einflusses von Aluminium auf die Abschreck- und Verformungsalterung des Kohlenstoffs an sechs Eisen-Kohlenstoff-Aluminium-Legierungen mit 0,007 bis 0,019% C, ≦ 0,01% Si, ≦ 0,05% Un, ≦ 0,003% P, ≦ 0,005% S, ≦ 0,001% N und 0,003 bis 4,0% Al. Ermittlung des Einflusses von Aluminium auf die Aktivierungsenergie der Kohlenstoffdiffusion und auf die Versetzungsstruktur nach einer Kaltumformung.     

Quantum-Confinement-Enhanced Thermoelectric Properties in Modulation-Doped GaAs–AlGaAs Core–Shell Nanowires

Nanowires (NWs) hold great potential in advanced thermoelectrics due to their reduced dimensions and low-dimensional electronic character. However, unfavorable links between electrical and thermal conductivity in state-of-the-art unpassivated NWs have, so far, prevented the full exploitation of their distinct advantages. A promising model system for a surface-passivated one-dimensional (1D)-quantum confined NW thermoelectric is developed that enables simultaneously the observation of enhanced thermopower via quantum oscillations in the thermoelectric transport and a strong reduction in thermal conductivity induced by the core–shell heterostructure. High-mobility modulation-doped GaAs/AlGaAs core–shell NWs with thin (sub-40 nm) GaAs NW core channel are employed, where the electrical and thermoelectric transport is characterized on the same exact 1D-channel. 1D-sub-band transport at low temperature is verified by a discrete stepwise increase in the conductance, which coincided with strong oscillations in the corresponding Seebeck voltage that decay with increasing sub-band number. Peak Seebeck coefficients as high as ≈65–85 µV K⁻¹ are observed for the lowest sub-bands, resulting in equivalent thermopower of S²σ ≈ 60 µW m⁻¹ K⁻² and S²G ≈ 0.06 pW K⁻² within a single sub-band. Remarkably, these core–shell NW heterostructures also exhibit thermal conductivities as low as ≈3 W m⁻¹ K⁻¹, about one order of magnitude lower than state-of-the-art unpassivated GaAs NWs.     

Analytical modeling and dimensionless characteristics of open wet clutches in consideration of gravity

Forschung im Ingenieurwesen - Wet clutches are widely used in power transmission, but lack of the fact of an energy loss in open state condition. The flow conditions in the fluid flow of an open...     

„Personalisierte Medizin“ in der Onkologie: Ärztliche Einschätzungen der aktuellen Entwicklung in der Krankenversorgung

Definition of the ProblemPublic discussions about “personalised medicine” indicate that this approach is associated with high expectations regarding its contribution to clinical practice. However, little is known about physicians’ perspectives on “personalised medicine”. This qualitative interview study aims to provide insight into physicians’ perceptions and views regarding clinical practice. Arguments/ResultsPhysicians in this sample view “personalised medicine” as a progress within medicine, but do not see a major departure from long-standing practices. As a major problem, physicians identified handling the amount of molecular and genetic information and integrating this information into the diagnosis and treatment. ConclusionTaking the results into account, one may ask whether “personalised medicine” is not the opposite of what its name connotes—a more patient-centred medicine. The strategies for handling the large amount of information raise novel challenges which are in contrast to the ideas of patient-centred medicine.     

An augmented weighted Tchebycheff method with adaptively chosen parameters for discrete bicriteria optimization problems

The augmented weighted Tchebycheff norm was introduced in the context of multicriteria optimization by Steuer and Choo [21] in order to avoid the generation of weakly nondominated points. It augments a weighted _l∞-norm$l_{\infty }\mathrm{-}\mathrm{norm}$ with an l₁-term, multiplied by a “small” parameter ρ>0$\rho >0$. However, the appropriate selection of the parameter ρ$\rho$ remained an open question: A too small value of ρ$\rho$ may cause numerical difficulties, while a too large value of ρ$\rho$ may lead to the oversight of some nondominated points.     

Optimal scheduling of peer-to-peer file dissemination

Peer-to-peer (P2P) overlay networks such as BitTorrent and Avalanche are increasingly used for disseminating potentially large files from a server to many end users via the Internet. The key idea is to divide the file into many equally-sized parts and then let users download each part (or, for network coding based systems such as Avalanche, linear combinations of the parts) either from the server or from another user who has already downloaded it. However, their performance evaluation has typically been limited to comparing one system relative to another and has typically been realized by means of simulation and measurements. By contrast, we provide an analytic performance analysis that is based on a new uplink-sharing version of the well-known broadcasting problem. Assuming equal upload capacities, we show that the minimal time to disseminate the file is the same as for the simultaneous send/receive version of the broadcasting problem. For general upload capacities, we provide a mixed integer linear program (MILP) solution and a complementary fluid limit solution. We thus provide a lower bound which can be used as a performance benchmark for any P2P file dissemination system. We also investigate the performance of a decentralized strategy, providing evidence that the performance of necessarily decentralized P2P file dissemination systems should be close to this bound and, therefore, that it is useful in practice. Research of G. Weiss is supported in part by Israel Science Foundation Grants 249/02 and 454/05. Collaboration of the authors was supported in part by European Network of Excellence Euro-NGI.     

Spatial compatibility effects with tool use

OBJECTIVE: We explored constraints in responding to spatially variable stimuli when hand movements are transformed into inverse movements of a tool. BACKGROUND: Generally, the spatial compatibility between stimuli and responses is a powerful determinant of performance. However, many tasks require the use of simple tools such as first-class levers that transform hand movements into inverted movements of a tool. What types of compatibility effects arise with such tools? METHOD: Participants moved the tip of a pointer to the left or right according to the color of a stimulus. The pointer was manipulated either directly, so that a hand movement caused a pointer movement in the corresponding direction, or indirectly, so that the hand moved the pointer in the opposite direction. RESULTS: Responding was faster when the location of stimulus and the movement direction of the tool corresponded than when they did not correspond, independent of the movement direction of the hand. This occurred when stimulus location was task relevant (Experiment 1) as well as when it was task irrelevant (Experiment 2). Furthermore, responding was delayed when the hand and the relevant end of the tool moved in noncorresponding rather than corresponding directions. CONCLUSION: These results point to two distinct compatibility effects in tool use: one that relates to the transformation of stimuli into goals and one that relates to the transformation of goals into movements. APPLICATION: Potential applications of this research include the prediction and possibly manipulation of unwanted "fulcrum effects" in laparoscopic surgery and other first-class lever movements.     

Response surface study of the performance of lean NOx storage catalysts as a function of reaction conditions and catalyst composition

NO_x storage and reduction (NSR) catalysts containing Pt, Ba and Fe were studied as a function of reaction conditions and catalyst composition using response surface methodology combined with high-throughput experimentation. The concentrations of the reactant gases and the reactor temperature were varied to probe their effect on catalyst performance, as quantified by lean NO_x storage and N₂O production. An empirical model relating the catalyst performance to five reaction condition variables and three metal weight loading variables has also been developed. It was found that the temperature and the concentrations of the reducing agents, i.e. carbon monoxide and ethylene, had the strongest effect on the lean NO_x storage. It was also found that the Pt and Ba weight loadings had a much greater effect than Fe weight loadings on the performance of NSR catalysts. This model provides insight about the factors controlling the NO_x conversion by NSR catalysts and also predicts the optimum catalyst composition for given reaction conditions and vice versa. As an additional study, the relationship between sulfur poisoning, nitrous oxide production, and exotherm generation was also explored.