398 research outputs found

    New Landscapes and New Eyes: The Role of Virtual World Design for Supply Chain Education

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    With the common availability of advanced educational technology, we are able to increase the emphasis on the design of learning experiences and benefit from the given flexibility and variety of opportunities to create learning spaces. As instructional design models become more commonplace we examine their role vis-à-vis with the fidelity of the experience while learning. High-fidelity experiences are known to be valuable in learning as they provide authenticity in learning and motivation; yet, high fidelity comes at the cost of greater investment. In this paper, we outline our experiments with two setups of differing levels of fidelity: using Second Life and the consumer-focused Oculus Rift Head-Mounted Display (HMD). We show qualitatively interpreted comments and user responses to demonstrate importance of the level of fidelity, uncover important elements, and relate back the fidelity to the learning experience. High-fidelity experiences can be supported by software and hardware that are now readily available but present the seductive opportunity to greatly improve participant engagement in the virtual environments presented

    On-chip phase-shift induced control of supercontinuum generation in a dual-core Si3N4 waveguide

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    We investigate on-chip spectral control of supercontinuum generation, taking advantage of the additional spatial degree of freedom in strongly-coupled dual-core waveguides. Using numerical integration of the multi-mode generalized nonlinear Schrödinger equation, we show that, with proper waveguide cross-section design, selective excitation of supermodes can vary the dispersion to its extremes, i.e., all-normal or anomalous dispersion can be selected via phase shifting in a Mach-Zehnder input circuit. The resulting control allows to provide vastly different supercontinuum spectra with the same waveguide circuit

    The effect of practical experience on perceptions of assessment authenticity, study approach and learning outcome

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    Does authentic assessment or the perception of it affect how students study and learn? Does practical experience affect how assessment authenticity is perceived? And does practical experience influence how an authentic assessment affects student learning? Mixed methods design yielded insight into the answers to these questions. This article presents the results of a study on the relationships between authenticity perceptions of different cohorts of students, who differed in the amount of practical experience, their study approach and their perceived degree of professional skill development. The results showed some salient differences in how freshman- and senior-student groups perceive the same authentic assessment and how this assessment influences their learning. These results suggest possible guidelines for developing and using authentic assessments during a curriculum in which learning and working are intertwined. (c) 2007 Elsevier Ltd. All rights reserved

    Some Secrets of Fluorescent Proteins: Distinct Bleaching in Various Mounting Fluids and Photoactivation of cyan fluorescent proteins at YFP-Excitation

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    Background
The use of spectrally distinct variants of green fluorescent protein (GFP) such as cyan or yellow mutants (CFP and YFP, respectively) is very common in all different fields of life sciences, e.g. for marking specific proteins or cells or to determine protein interactions. In the latter case, the quantum physical phenomenon of fluorescence resonance energy transfer (FRET) is exploited by specific microscopy techniques to visualize proximity of proteins.

Methodology/Principal Findings
When we applied a commonly used FRET microscopy technique - the increase in donor (CFP)-fluorescence after bleaching of acceptor fluorophores (YFP), we obtained good signals in live cells, but very weak signals for the same samples after fixation and mounting in commercial microscopy mounting fluids. This observation could be traced back to much faster bleaching of CFP in these mounting media. Strikingly, the opposite effect of the mounting fluid was observed for YFP and also for other proteins such as Cerulean, TFP or Venus. The changes in photostability of CFP and YFP were not caused by the fixation but directly dependent on the mounting fluid. Furthermore we made the interesting observation that the CFP-fluorescence intensity increases by about 10 - 15% after illumination at the YFP-excitation wavelength – a phenomenon, which was also observed for Cerulean. This photoactivation of cyan fluorescent proteins at the YFP-excitation can cause false-positive signals in the FRET-microscopy technique that is based on bleaching of a yellow FRET acceptor.

Conclusions/Significance
Our results show that photostability of fluorescent proteins differs significantly for various media and that CFP bleaches significantly faster in commercial mounting fluids, while the opposite is observed for YFP and some other proteins. Moreover, we show that the FRET microscopy technique that is based on bleaching of the YFP is prone to artifacts due to photoactivation of cyan fluorescent proteins under these conditions

    Formation and quenching mechanisms of the electron beam pumped (XeRb)+ ionic excimer in different buffer gases

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    The ionic excimer molecule XeRb+ is formed in an electron beam excited gas mixture of Xe, Rb, and a buffer gas. The formation and quenching mechanisms of ionic excimers are investigated by measuring the XeRb+fluorescence as a function of the gas composition and gas pressure. The formation of XeRb+ is achieved by a three‐body association reaction between Xe+, Rb, and a buffer gas atom. For the buffer gases He, Ne, or Ar the values of the important formationrate constants are determined from the observed fluorescence signal decay

    A Protein-Interaction Array Inside a Living Cell

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    Protein-interaction arrays were generated in living cells by the interaction of bait-presenting artificial receptor constructs (bait-PARCs) with micrometer-scaled antibody surface patterns (see figure). This method was applied to simultaneously monitor the interaction kinetics of a prey protein with two distinct bait proteins in individual living cells

    Supercritical CO<sub>2</sub> extraction of <i>Nannochloropsis</i> sp.: a lipidomic study on the influence of pretreatment on yield and composition

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    Algal lipids have gained wide interest in various applications ranging from biofuels to nutraceuticals. Given their complex nature composed of different lipid classes, a deep knowledge between extraction conditions and lipid characteristics is essential. In this paper, we investigated the influence of different pretreatments on lipid extraction with supercritical CO2 by a lipidomic approach. Pretreatment was found to double the total extraction yield, thereby reaching 23.1 wt.% comparable to the 26.9 wt.% obtained with chloroform/methanol. An increase in acylglycerides was concurrently observed, together with a nearly doubling of free fatty acids indicative of partial hydrolysis. Moreover, an alteration in the distribution of glyco- and phospholipids was noted, especially promoting digalactosyldiglycerides and phosphatidylcholine as compared to monogalactosyldiglycerides and phosphatidylglycerol. At optimized conditions, supercritical CO2 extraction provided a lipid extract richer in neutral lipids and poorer in phospholipids as compared to chloroform/methanol, though with a very similar fatty acid distribution within each lipid class
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