Failure mechanisms and reliability of the Al-chip-metallization during power cycling

Cet article étudie les mécanismes de rupture et la fiabilité de la couche de métallisation d'une puce électronique d'un nouveau module de puissance, remplaçant les fils de connexion par un clip en cuivre. A la fois des tests de cycles actifs de puissance et des simulations thermomécaniques par éléments finis ont été réalisés. Cette étude utilise les simulations numériques pour analyser en détail les déformations plastiques et la propagation de fissures dans la métallisation de la puce sous différents cycles actifs de puissance. Les modèles de durée de vie sont ensuite déduits en corrélant la durée de vie des modules obtenue par expérimentation avec les déformations plastiques et les critères de propagations de fissures calculés correspondants

Influence of material damage during the forming process on the vibration fatigue behaviour of a clinched connection.

This paper presents the results of an analysation of forming damage during the joining process on the fatigue failure behaviour of a clinched connection. The two joining partners out of aluminium, AlMg0.7Si on the punch side and AlMg3 on the die side, are clinched with a flat clinching system and the use of a preformed hole at the die side. By the use of two different geometry variants it could be shown, in fatigue Wöhler tests, that the fatigue failure behaviour is influenced by the material damage in the deformed material of the clinch. The material damage during the clinching process could be calculated with the help of FE-Simulations. So it was possible to show that more forming damage during the joining process causes less lifetime of the connection

Adjuvant Analgesics in Acute Pain - Evaluation of Efficacy.

PURPOSE OF THE REVIEW Acute postoperative pain impacts a significant number of patients and is associated with various complications, such as a higher occurrence of chronic postsurgical pain as well as increased morbidity and mortality. RECENT FINDINGS Opioids are often used to manage severe pain, but they come with serious adverse effects, such as sedation, respiratory depression, postoperative nausea and vomiting, and impaired bowel function. Therefore, most enhanced recovery after surgery protocols promote multimodal analgesia, which includes adjuvant analgesics, to provide optimal pain control. In this article, we aim to offer a comprehensive review of the contemporary literature on adjuvant analgesics in the management of acute pain, especially in the perioperative setting. Adjuvant analgesics have proven efficacy in treating postoperative pain and reducing need for opioids. While ketamine is an established option for opioid-dependent patients, magnesium and α2-agonists have, in addition to their analgetic effect, the potential to attenuate hemodynamic responses, which make them especially useful in painful laparoscopic procedures. Furthermore, α2-agonists and dexamethasone can extend the analgesic effect of regional anesthesia techniques. However, findings for lidocaine remain inconclusive

Probing the Drosophila retinal determination gene network in Tribolium (II): The Pax6 genes eyeless and twin of eyeless

AbstractThe Pax6 genes eyeless (ey) and twin of eyeless (toy) are upstream regulators in the retinal determination gene network (RDGN), which instructs the formation of the adult eye primordium in Drosophila. Most animals possess a singleton Pax6 ortholog, but the dependence of eye development on Pax6 is widely conserved. A rare exception is given by the larval eyes of Drosophila, which develop independently of ey and toy. To obtain insight into the origin of differential larval and adult eye regulation, we studied the function of toy and ey in the red flour beetle Tribolium castaneum. We find that single and combinatorial knockdown of toy and ey affect larval eye development strongly but adult eye development only mildly in this primitive hemimetabolous species. Compound eye-loss, however, was provoked when ey and toy were RNAi-silenced in combination with the early retinal gene dachshund (dac). We propose that these data reflect a role of Pax6 during regional specification in the developing head and that the subsequent maintenance and growth of the adult eye primordium is regulated partly by redundant and partly by specific functions of toy, ey and dac in Tribolium. The results from embryonic knockdown and comparative protein sequence analysis lead us further to conclude that Tribolium represents an ancestral state of redundant control by ey and toy

Functionality of the GAL4/UAS system in Tribolium requires the use of endogenous core promoters

<p>Abstract</p> <p>Background</p> <p>The red flour beetle <it>Tribolium castaneum </it>has developed into an insect model system second only to <it>Drosophila</it>. Moreover, as a coleopteran it represents the most species-rich metazoan taxon which also includes many pest species. The genetic toolbox for <it>Tribolium </it>research has expanded in the past years but spatio-temporally controlled misexpression of genes has not been possible so far.</p> <p>Results</p> <p>Here we report the establishment of the GAL4/UAS binary expression system in <it>Tribolium castaneum</it>. Both GAL4Δ and GAL4VP16 driven by the endogenous heat shock inducible promoter of the <it>Tribolium hsp68 </it>gene are efficient in activating reporter gene expression under the control of the Upstream Activating Sequence (UAS). UAS driven ubiquitous tGFP fluorescence was observed in embryos within four hours after activation while <it>in-situ </it>hybridization against tGFP revealed expression already after two hours. The response is quick in relation to the duration of embryonic development in <it>Tribolium </it>- 72 hours with segmentation being completed after 24 hours - which makes the study of early embryonic processes possible using this system. By comparing the efficiency of constructs based on <it>Tribolium, Drosophila</it>, and artificial core promoters, respectively, we find that the use of endogenous core promoters is essential for high-level expression of transgenic constructs.</p> <p>Conclusions</p> <p>With the established GAL4/UAS binary expression system, ectopic misexpression approaches are now feasible in <it>Tribolium</it>. Our results support the contention that high-level transgene expression usually requires endogenous regulatory sequences, including endogenous core promoters in <it>Tribolium </it>and probably also other model systems.</p

The Finite Mass Method in astrophysical hydrodynamics

Diese Arbeit befasst sich mit der Anwendbarkeit der Methode der Finiten Massen auf astrophysikalische Problemstellungen. Die Methode der Finiten Massen ist eine neu entwickelte Lagrangesche Teilchenmethode zur Beschreibung kompressibler Strömungen. In der Arbeit werden grundlegende Eigenschaften der Methode untersucht sowie die notwendigen Simulationstechniken bereitgestellt. In den durchgeführten Simulationen werden prinzipielle Eigenschaften von Akkretionsscheiben untersucht, wie etwa der Einfluß der turbulenten Viskosität auf die Scheibendynamik, der Einfluß großer, ausgedehnter Wirbel in protoplanetaren Scheiben auf den Drehimpulstransport sowie der Einfluß des Roche-Potentials auf die Entwicklung einer zweiarmigen Spiralstruktur in der Scheibe im Fall eines Binärsystems. Unter Berücksichtigung des Strahlungstransports in vertikaler Richtung in der Energiegleichung werden Akkretionsscheiben in Kataklysmischen Variablen untersucht. Die Simulationen liefern eine präzedierende Scheibe in dem Superhumpsystem AM CVn sowie eine detaillierte Beschreibung eines Scheibenausbruchs in der Zwergnova U Geminorum. Im Anhang wird eine Erweiterung der Methode der Finiten Massen vorgestellt, die eine Behandlung fester Ränder im laminaren und nicht-laminaren Fall erlauben.This work is concerned with the study of the Finite Mass Method and its application on astrophysical hydrodynamics. The Finite Mass Method is a newly developed Lagrangian particle method to solve problems in compressible fluid dynamics. We study the basic behaviour of the method and provide the necessary simulation techniques. In the simulations we study the basic properties of flows in accretion disks, the influence of the turbulent viscosity on the flow dynamic, the influence of large eddies on the angular momentum transport and the influence of the Roche potential on the development of a two armed spiral structure in the disk in the case of a binary system. We consider radiation transport in vertical direction to solve the energy equation and simulate accretion disks in cataclysmic variables. The simulations result in an eccentric, precession disk in the superhumpsystem AM CVn and in a detailed description of a disk outburst in the dwarf nova U Geminorum. In the appendix we present an enhancement of the method that provide the implementation of standard slip and no-slip boundary conditions

When to stop? - Towards universal instructional policies

The adaptivity of intelligent tutoring systems relies on the accuracy of the student model and the design of the instructional policy. Recently an instructional policy has been presented that is compatible with all common student models. In this work we present the next step towards a universal instructional policy. We introduce a new policy that is applicable to an even wider range of student models including DBNs modeling skill topologies and forgetting. We theoretically and empirically compare our policy to previous policies. Using synthetic and real world data sets we show that our policy can effectively handle wheel-spinning students as well as forgetting across a wide range of student models

The Finite Mass Method on Domains with Boundary

The nite mass method is a gridless Lagrangian method to simulate compressible ows that has been introduced in a recent paper of Gauger, Leinen, and Yserentant [SIAM J. Numer. Anal. 37, 2000]. It is based on a discretization of mass, not of space as with classical discretization schemes. Mass is subdivided into little mass packets of nite extension each of which is equipped with nitely many internal degrees of freedom. These mass packets move under the inuence of internal and external forces and the laws of thermodynamics and can change their shape to follow the motion of the uid. Only free ows in vacuum have been considered so far. In this article, a concept is presented to extend the method to ows in domains having boundaries. It maintains the second order accuracy of the basic method and can be implemented along the same lines

Influence of material damage during the forming process on the vibration fatigue behaviour of a clinched connection.

This paper presents the results of an analysation of forming damage during the joining process on the fatigue failure behaviour of a clinched connection. The two joining partners out of aluminium, AlMg0.7Si on the punch side and AlMg3 on the die side, are clinched with a flat clinching system and the use of a preformed hole at the die side. By the use of two different geometry variants it could be shown, in fatigue Wöhler tests, that the fatigue failure behaviour is influenced by the material damage in the deformed material of the clinch. The material damage during the clinching process could be calculated with the help of FE-Simulations. So it was possible to show that more forming damage during the joining process causes less lifetime of the connection