196,622 research outputs found
Noise removal at the rod synapse of mammalian retina
No full textMammalian rods respond to single photons with a hyperpolarization of about 1 mV which is accompanied by continuous noise. Since the mammalian rod bipolar cell collects signals from 20–100 rods, the noise from the converging rods would overwhelm the single-photon signal from one rod at scotopic intensities (starlight) if the bipolar cell summed signals linearly (Baylor et al., 1984). However, it is known that at scotopic intensities the retina preserves single-photon responses (Barlow et al., 1971; Mastronarde, 1983). To explore noise summation in the rod bipolar pathway, we simulated an array of rods synaptically connected to a rod bipolar cell using a compartmental model. The performance of the circuit was evaluated with a discriminator measuring errors in photon detection as false positives and false negatives, which were compared to physiologically and psychophysically measured error rates. When only one rod was connected to the rod bipolar, a Poisson rate of 80 vesicles0s was necessary for reliable transmission of the single-photon signal. When 25 rods converged through a linear synapse the noise caused an unacceptably high false positive rate, even when either dark continuous noise or synaptic noise where completely removed. We propose that a threshold nonlinearity is provided by the mGluR6 receptor in the rod bipolar dendrite (Shiells & Falk, 1994) to yield a synapse with a noise removing mechanism. With the threshold nonlinearity the synapse removed most of the noise. These results suggest that a threshold provided by the mGluR6 receptor in the rod bipolar cell is necessary for proper functioning of the retina at scotopic intensities and that the metabotropic domains in the rod bipolar are distinct. Such a nonlinear threshold could also reduce synaptic noise for cortical circuits in which sparse signals converge. <br/
The optimal synapse for sparse, binary signals in the rod pathway:Neural Computation
No full textThe sparsity of photons at very low light levels necessitates a nonlinear synaptic transfer function between the rod photoreceptors and the rod-bipolar cells. We examine different ways to characterize the performance of the pathway: the error rate, two variants of the mutual information, and the signal-to-noise ratio. Simulation of the pathway shows that these approaches yield substantially different performance at very low light levels and that maximizing the signal-to-noise ratio yields the best performance when judged from simulated images. The results are compared to recent data.</p
Internal Cooling of the Piston Rod in Non-Lubricated Piston Compressors
No full textIn non-lubricated piston compressors the wear of the piston rod packing rings is still a problem that needs to be considered. Due to the demands of high gas pressure and leak-tight sealing the frictional heat of the rings is causing high temperatures in the area of the piston rod packing. High temperatures are – among other factors – one reason for an increase of wear and thus for a lifetime reduction of the packing. To increase this lifetime – and so to increase the time between two technical services – the idea of an internal cooling of the piston rod with a phase changing medium was created. To investigate this new cooling method for non-lubricated piston compressors a research project between the EFRC R&D Working Group (European Forum for Reciprocating Compressors) and the Technical University of Dresden was initiated. Within this project a test bench with a full scale balanced opposed process gas compressor was set up and measurements shall be taken. The measured values will be used for a validation of a thermal simulation model based on the software ANSYS. Also a model test rig is investigated which allows the investigation of temperature along a hollow piston rod in a moving system
Modelling Rod-like Flexible Biological Tissues for Medical Training
No full textThis paper outlines a framework for the modelling of slender rod-like biological tissue structures in both global and local scales. Volumetric discretization of a rod-like structure is expensive in computation and therefore
is not ideal for applications where real-time performance is essential. In our approach, the Cosserat rod model is introduced to capture the global shape changes, which models the structure as a one-dimensional entity, while the
local deformation is handled separately. In this way a good balance in accuracy and efficiency is achieved. These advantages make our method appropriate for
the modelling of soft tissues for medical training applications
Intent to Speed: Cyclical Production, Topicality and the 1950s Hot Rod Movie
No full textThis essay tracks the emergence, consolidation and dissolution of the short cycle of hot rod movies that was exhibited from 1956 to 1958. The aim is to explore this cycle’s connection to topical issues and show how filmmakers used timely subjects. The essay examines the media frenzy that whirled around the subculture of hot rodding and the sensationalist marketing strategies used to promote the films, which are linked to exhibition in drive-in theatres. There is an extraordinary mismatch between the thrills promised by the sales pitch for the films and the pedestrian action of the films themselves. While showing intent to speed, few examples of the cycle actually delivered on the promise to thrill. Finally, questions of turnover and the speed of production are considered. What draws these areas of interest together is a series of enquiries about what made hot rods and hot rod culture useful to film producers and audiences
riddling-rod/riddle-rod /wriggle-rod
No full textriddle n_FENCES_ bough fence ranch fence picket fence pailing fences riddling-rod/riddle-rod /wriggle-rod paling fences/pailing fences rod fence stake fence three-longer fence rock wall stone wall wall fence slab fence wing fence hawk fenceUsed I and SupNot usedThis is entered under "riddle n" because "riddle-rod" is one of the types of fences liste
mm-Wave DRW Antenna Phase Centre Determination
No full textThis document presents an approach to the phase centre determination of a dielectric rod waveguide (DRW) antenna by means of measurements obtained with a planar measuring system at millimeter wave lengths. Phase centre determination by the least squares fit technique is described in this document for different DRW antennas (silicon and sapphire). Results at different operating frequencies are offered
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Light raw data and codebook
No full textContains Issues 1-10 of The Light and a codebook to allow the replication and adaptation of the approach taken in:
Dacombe, R., Souter, N., & Westerlund, L. (2021). Research note: Understanding offline Covid-19 conspiracy theories: A content analysis of The Light “truthpaper”. Harvard Kennedy School (HKS) Misinformation Review. https://doi.org/10.37016/mr-2020-8
A note on the diffraction by a semi-Infinite thick half plane, and a semi-infinite cylindrical rod with an absorbent end face
No full textThe known solutions for:
(i) A plane wave incident on two rigid semi-infinite parallel plane distance 2b apart, (ii) The radiation of an arbitrary mode from two parallel rigid semi-infinite plates 2b apart,
are used to construct the solution of the problem of the diffraction of a plane wave by a semi-infinite thick half plane (thickness 2b), whose sides are rigid and whose end face is absorbent. The method used is simple superposition of the solutions (i) and (ii). The problem solved has applications in noise barrier design. Analogously by using the known solutions for the diffraction of a plane wave by, and the radiation of an arbitrary mode from, a rigid hollow cylindrical semi-infinite duct, the solution for the diffraction of a plane wave by a thick semi-infinite rigid rod with an absorbent end face can be obtained
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