2,826 research outputs found

    Electron-beam-sustained discharge revisited - light emission from combined electron beam and microwave excited argon at atmospheric pressure

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    A novel kind of electron beam sustained discharge is presented in which a 12keV electron beam is combined with a 2.45GHz microwave power to excite argon gas at atmospheric pressure in a continuous mode of operation. Optical emission spectroscopy is performed over a wide wavelength range from the vacuum ultraviolet (VUV) to the near infrared (NIR). Several effects which modify the emission spectra compared to sole electron beam excitation are observed and interpreted by the changing plasma parameters such as electron density, electron temperature and gas temperature.Comment: 10 pages, 9 figure

    Special issue: deformation monitoring

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    Selective Activation of Alternative MYC Core Promoters by Wnt-Responsive Enhancers.

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    In Metazoans, transcription of most genes is driven by the use of multiple alternative promoters. Although the precise regulation of alternative promoters is important for proper gene expression, the mechanisms that mediates their differential utilization remains unclear. Here, we investigate how the two alternative promoters (P1, P2) that drive MYC expression are regulated. We find that P1 and P2 can be differentially regulated across cell-types and that their selective usage is largely mediated by distal regulatory sequences. Moreover, we show that in colon carcinoma cells, Wnt-responsive enhancers preferentially upregulate transcription from the P1 promoter using reporter assays and in the context of the endogenous Wnt induction. In addition, multiple enhancer deletions using CRISPR/Cas9 corroborate the regulatory specificity of P1. Finally, we show that preferential activation between Wnt-responsive enhancers and the P1 promoter is influenced by the distinct core promoter elements that are present in the MYC promoters. Taken together, our results provide new insight into how enhancers can specifically target alternative promoters and suggest that formation of these selective interactions could allow more precise combinatorial regulation of transcription initiation

    Learning Redundant Motor Tasks With and Without Overlapping Dimensions: Facilitation and Interference Effects

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    Prior learning of a motor skill creates motor memories that can facilitate or interfere with learning of new, but related, motor skills. One hypothesis of motor learning posits that for a sensorimotor task with redundant degrees of freedom, the nervous system learns the geometric structure of the task and improves performance by selectively operating within that task space. We tested this hypothesis by examining if transfer of learning between two tasks depends on shared dimensionality between their respective task spaces. Human participants wore a data glove and learned to manipulate a computer cursor by moving their fingers. Separate groups of participants learned two tasks: a prior task that was unique to each group and a criterion task that was common to all groups. We manipulated the mapping between finger motions and cursor positions in the prior task to define task spaces that either shared or did not share the task space dimensions (x-y axes) of the criterion task. We found that if the prior task shared task dimensions with the criterion task, there was an initial facilitation in criterion task performance. However, if the prior task did not share task dimensions with the criterion task, there was prolonged interference in learning the criterion task due to participants finding inefficient task solutions. These results show that the nervous system learns the task space through practice, and that the degree of shared task space dimensionality influences the extent to which prior experience transfers to subsequent learning of related motor skills

    Attentional threat biases and their role in anxiety: A neurophysiological perspective

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    One of the most important function of selective attention is the efficient and accurate detection and identification of cues associated with threat. However, in pathological anxiety, this attentional mechanism seems to be dysfunctional, which leads to an exaggeration of threat processing and significant functional impairment. This attentional threat bias (ATB) has been proposed as a key mechanism in the etiology and maintenance of anxiety disorders. Recently, evidence has accumulated that the behavioral assessment of ATB by means of reaction times is compromised by conceptual and methodological problems. In this review paper we argue that a brain-based assessment of ATB, which includes different mechanistic aspects of biased attention, may provide neuromechanistic knowledge regarding the etiology and maintenance of anxiety, and potentially start identifying different targets for effective treatment. We summarize examples for such an approach, highlighting the strengths of electrophysiological measurements, which include the sensitivity to time dynamics, specificity to specific neurocomputational mechanisms, and the continuous/dimensional nature of the resulting variables. These desirable properties are a prerequisite for developing trans-diagnostic biomarkers of attentional bias, and hence may inform individually tailored treatment approaches
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