Retrieval-induced forgetting in a category recognition task.

Prior work on retrieval-induced forgetting showed that retrieving a subset of formerly studied items can impair item recognition of related, nonretrieved material. Here it was investigated whether retrieval practice can also impair the items' recognition as a member of a studied category. Subjects studied preexperimentally unrelated words that were categorized by their font colors, then practiced retrieving a subset of the words using a word stem completion task. Finally, an episodic category recognition test based on confidence ratings was applied. Receiver operating characteristic analysis of the data demonstrated a reliable impairment in subjects' recognition of the nonretrieved items' category relative to control items. The result indicates that retrieval-induced forgetting is not restricted to item recognition but generalizes to category recognition tasks. Inhibitory as well as noninhibitory explanations of the finding are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Enabling interoperability for LMS educational services

Nowadays, e-learning is undergoing a standardization process. In this paper, an overview of e-learning standardization state of the art is provided and the relationship between Learning Management System (LMS) functionalities and current e-learning standards is presented. Some lacks are found and the importance of defining new standards to cover several LMS aspects is justified. This work describes new e-service specifications for LMS final user application functionalities in order to cover such lacks. In addition, a web-based authoring tool has been implemented according to these new specifications, generating XML files. In this way, interoperability between different new LMS aspects is enabled.     

Einfluß von Legierungselementen auf die Verschlackung von basischen feuerfesten Stoffen in Lichtbogenöfen

Untersuchung des Verschleißverhaltens von drei verschiedenen basischen feuerfesten Steinsorten durch Ermittlung der chemischen Zusammensetzung, durch Röntgenbeugung, Auflichtmikroskopie und Elektronenstrahlmikroanalyse. Versuche unter Betriebsbedingungen in einem 20-t-Lichtbogenofen mit Edelstahlprogramm. Probenahme nach dem ?statischen? und ?dynamischen? Modell. Verhalten wesentlicher Legierungselemente auf den Verschleiß.     

Precipitation polymerization of acrylic acid: Kinetics,viscosity and heat transfer

The free-radical precipitation polymerization of acrylic acid in toluene was studied in an isothermal reaction calorimeter. The polymerization shows an autocatalytic behaviour of the rate of polymerization typical for precipitation polymerizations. The rate of polymerization with respect to conversion can be modeled by taking the volume fraction of the precipitated polymer into consideration. The viscosity of the reaction mixture increases with increasing volume fraction of precipitated polymer. The viscosity runs through a maximum at high conversion. The final viscosity decrease is probably due to shear stress caused aggregation phenomena of the polymer particles. A model is discussed which can describe the increase and decrease of viscosity of the system. By means of reaction calorimetry it is possible to determine the reaction-sided heat transfer coefficient during polymerization. The comparison of the experimentally determined temperature course of the reaction mixture and the temperature course calculated with a coupled model of the polymerization and the calorimeter shows that the heat-transfer characteristic changes instantaneously during a small conversion interval at the very beginning of the polymerization.     

Laser Bonding of Glass to Silicon Using Polymer for Microsystems Packaging

Laser joining is a promising technique for wafer-level bonding. It avoids subjecting the complete microelectromechanical system (MEMS) package to a high temperature and/or the high electric field associated with conventional wafer-level bonding processes, using the laser to provide only localized heating. We demonstrate that a benzocyclobutene (BCB) polymer, used as an intermediate bonding layer in the packaging of MEMS devices, can be satisfactorily cured by using laser heating with a substantial reduction of curing time compared with an oven-based process. A glass-on-silicon (Si) cavity bonded with a BCB ring can be produced in a few seconds at a typical laser intensity of 1 W/mm² resulting in a local temperature of ~300degC. Hermeticity and bond strength tests show that such cavities have similar or better performance than cavities sealed by commercial substrate bonders. The influence of exposure time, laser power, and applied pressure on the degree of cure, bond strength, and hermeticity is investigated. The concept of using a large area uniform laser beam together with a simple mirror mask is tested, demonstrating that such a mask is capable of protecting the center of the cavity from the laser beam; however, to prevent lateral heating via conduction through the Si, a high-conductivity heat sink is required to be in good thermal contact with the rear of the Si.     

Control aspects of a tracked magnetic levitation high speed test vehicle

The paper deals with the control system of the high speed test vehicle KOMET. The control hardware configuration consisting of digital computer, interface, sensors, magnet drivers and magnets is described. Control system synthesis is performed based on the state space approach and the classical approach of the z-transform. It leads to various control concepts, which are evaluated with regard to their responses to guideway irregularities, external forces and their sensitivity to plant parameter variations. The measurements used to reconstruct the state vector are magnet gaps, vehicle accelerations and/or magnet currents. To be efficient, the magnets have to be operated on small magnet gaps. This demands a fast system response to external disturbances and guideway inputs. This in turn may lead to the excitation of the elastic modes of the system. The higher order modes of vehicle and guideway are therefore included in the control synthesis. The speed range of the KOMET extends to 400 km/hr. Results from high speed testing are evaluated with regard to system responses, power requirements, and loss in magnetic force due to eddycurrents.     

Efficient DNA sticker algorithms for NP-complete graph problems

Adleman's successful solution of a seven-vertex instance of the NP-complete Hamiltonian directed path problem by a DNA algorithm initiated the field of biomolecular computing. We provide DNA algorithms based on the sticker model to compute all k-cliques, independent k-sets, Hamiltonian paths, and Steiner trees with respect to a given edge or vertex set. The algorithms determine not merely the existence of a solution but yield all solutions (if any). For an undirected graph with n vertices and m edges, the running time of the algorithms is linear in n+m. For this, the sticker algorithms make use of small combinatorial input libraries instead of commonly used large libraries. The described algorithms are entirely theoretical in nature. They may become very useful in practice, when further advances in biotechnology lead to an efficient implementation of the sticker model.