Lipasekatalysierte Triglyceridumesterung in einem lösungsmittelfreien Prozeß II: Verfahrenstechnische Parameter des kontinuierlichen Prozesses

Lipase-Catalyzed Interesterification of Triglycerides in a Solvent-Free Process II: Engineering Parameters for the Application of a Continuous Process Fixed bed reactors are promising reactor systems for the continuous interesterification of fats and oils with immobilized lipases in a solvent-free process. Engineering parameters which are necessary for the design of the bioreactor were studied. The kinetics of the interesterification in the continuous process are influenced by the washing out of water from the biocatalyst by the substrate. External mass transfer effects can be neglected, internal mass transfer reduces the reaction rate. The pressure drop across the catalyst bed is acceptable at temperatures higher than 60°C. The results show that the continuous interesterification in a solvent-free process can be performed.     

The capacity of visual working memory for features and conjunctions

Short-term memory storage can be divided into separate subsystems for verbal information and visual information, and recent studies have begun to delineate the neural substrates of these working-memory systems. Although the verbal storage system has been well characterized, the storage capacity of visual working memory has not yet been established for simple, suprathreshold features or for conjunctions of features. Here we demonstrate that it is possible to retain information about only four colours or orientations in visual working memory at one time. However, it is also possible to retain both the colour and the orientation of four objects, indicating that visual working memory stores integrated objects rather than individual features. Indeed, objects defined by a conjunction of four features can be retained in working memory just as well as single-feature objects, allowing sixteen individual features to be retained when distributed across four objects. Thus, the capacity of visual working memory must be understood in terms of integrated objects rather than individual features, which places significant constraints on cognitive and neurobiological models of the temporary storage of visual information.     

Unifying Agent Systems

Whilst there has been an explosion of interest multi-agent systems, there are still many problems that may have a potentially deleterious impact on the progress of the area. These problems have arisen primarily through the lack of a common structure and language for understanding multi-agent systems, and with which to organise and pursue research in this area. In response to this, previous work has been concerned with developing a computational formal framework for agency and autonomy which, we argue, provides an environment in which to develop, evaluate, and compare systems and theories of multi-agent systems. In this paper we go some way towards justifying these claims by reviewing the framework and showing what we can achieve within it by developing models of agent dimensions, categorising key inter-agent relationships and by applying it to evaluate existing multi-agent systems in a coherent computational model. We outline the benefits of specifying each of the systems within the framework and consider how it allows us to unify different systems and approaches in general.     

Impaired control of visual attention in schizophrenia.

To investigate attentional impairment in schizophrenia, the authors examined the performance of 22 patients with schizophrenia and 16 healthy control subjects in 4 visual search tasks that varied in perceptual requirements and in the need for precise attentional control. The rate of search was slowed in the patients in all tasks. However, the degree of slowing was largest in tasks requiring precise attentional control and smallest in tasks that were perceptually difficult but required less attentional control. This pattern of results indicates that the primary impairment of attention in schizophrenia lies in the control of attention and not in the selection processes that operate once attention has been directed to an object. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of attention in feature detection and conjunction discrimination: an electrophysiological analysis

An electrophysiological probe technique was used to ascertain whether the same attentional mechanisms are employed for both the detection of simple visual features and the discrimination of conjunctions of features. Visual search arrays containing 14 grey items and 2 colored items were presented; one color was designated relevant for each trial block. Subjects were required to report the presence or absence of the relevant color (feature detection condition) or the shape of the relevantly-colored item (conjunction discrimination condition). Shortly after the onset of the search array, a task-irrelevant probe stimulus was flashed at the location of the relevant or irrelevant color and the event-related potential (ERP) produced by this stimulus was used to assess sensory processing at the probed location. Probes presented at the location of the relevant color were found to elicit enhanced ERP components and probes presented on the opposite side of the display from the relevant color elicited suppressed components. These effects were observed in both the detection and discrimination conditions, indicating that spatially restricted attentional processes are used for both the detection of simple features and the discrimination of conjunctions. However, one ERP component (the PI wave) exhibited these effects in the discrimination condition but not in the detection condition, indicating that conjunction discrimination utilizes additional attentional processes beyond those required for feature detection.     

High frequency GaAs switched capacitor filter implemented with GaAs insulated gate FET switches

A switched capacitor filter implemented with 5 mu m GaAs IGFET switches and GaAs MESFET operational amplifiers is presented. The circuit is clocked at 25 MHz. By scaling to 1 mu m IGFETs, a switching speed of about 625 MHz should be attainable. Use of GaAs IGFET switches is shown to greatly reduce power consumption and complexity of the circuit. The low frequency switching instability of the GaAs IGFET is shown to be of no consequence in this application.<>     

Correlated In Situ Low‐Frequency Noise and Impedance Spectroscopy Reveal Recombination Dynamics in Organic Solar Cells Using Fullerene and Non‐Fullerene Acceptors

Non‐fullerene acceptors based on perylenediimides (PDIs) have garnered significant interest as an alternative to fullerene acceptors in organic photovoltaics (OPVs), but their charge transport phenomena are not well understood, especially in bulk heterojunctions (BHJs). Here, charge transport and current fluctuations are investigated by performing correlated low‐frequency noise and impedance spectroscopy measurements on two BHJ OPV systems, one employing a fullerene acceptor and the other employing a dimeric PDI acceptor. In the dark, these measurements reveal that PDI‐based OPVs have a greater degree of recombination in comparison to fullerene‐based OPVs. Furthermore, for the first time in organic solar cells, 1/f noise data are fit to the Kleinpenning model to reveal underlying current fluctuations in different transport regimes. Under illumination, 1/f noise increases by approximately four orders of magnitude for the fullerene‐based OPVs and three orders of magnitude for the PDI‐based OPVs. An inverse correlation is also observed between noise spectral density and power conversion efficiency. Overall, these results show that low‐frequency noise spectroscopy is an effective in situ diagnostic tool to assess charge transport in emerging photovoltaic materials, thereby providing quantitative guidance for the design of next‐generation solar cell materials and technologies.