57 research outputs found
Fast Neural Representations for Direct Volume Rendering
Despite the potential of neural scene representations to effectively compress
3D scalar fields at high reconstruction quality, the computational complexity
of the training and data reconstruction step using scene representation
networks limits their use in practical applications. In this paper, we analyze
whether scene representation networks can be modified to reduce these
limitations and whether such architectures can also be used for temporal
reconstruction tasks. We propose a novel design of scene representation
networks using GPU tensor cores to integrate the reconstruction seamlessly into
on-chip raytracing kernels, and compare the quality and performance of this
network to alternative network- and non-network-based compression schemes. The
results indicate competitive quality of our design at high compression rates,
and significantly faster decoding times and lower memory consumption during
data reconstruction. We investigate how density gradients can be computed using
the network and show an extension where density, gradient and curvature are
predicted jointly. As an alternative to spatial super-resolution approaches for
time-varying fields, we propose a solution that builds upon latent-space
interpolation to enable random access reconstruction at arbitrary granularity.
We summarize our findings in the form of an assessment of the strengths and
limitations of scene representation networks \changed{for compression domain
volume rendering, and outline future research directions
Efficient wide-field radio interferometry response
Radio interferometers do not measure the sky brightness distribution directly
but rather a modified Fourier transform of it. Imaging algorithms, thus, need a
computational representation of the linear measurement operator and its
adjoint, irrespective of the specific chosen imaging algorithm. In this paper,
we present a C++ implementation of the radio interferometric measurement
operator for wide-field measurements which is based on "improved -stacking".
It can provide high accuracy (down to ), is based on a new
gridding kernel which allows smaller kernel support for given accuracy,
dynamically chooses kernel, kernel support and oversampling factor for maximum
performance, uses piece-wise polynomial approximation for cheap evaluations of
the gridding kernel, treats the visibilities in cache-friendly order, uses
explicit vectorisation if available and comes with a parallelisation scheme
which scales well also in the adjoint direction (which is a problem for many
previous implementations). The implementation has a small memory footprint in
the sense that temporary internal data structures are much smaller than the
respective input and output data, allowing in-memory processing of data sets
which needed to be read from disk or distributed across several compute nodes
before.Comment: 13 pages, 8 figure
Bayesian radio interferometric imaging with direction-dependent calibration
Context: Radio interferometers measure frequency components of the sky
brightness, modulated by the gains of the individual radio antennas. Due to
atmospheric turbulence and variations in the operational conditions of the
antennas these gains fluctuate. Thereby the gains do not only depend on time
but also on the spatial direction on the sky. To recover high quality radio
maps an accurate reconstruction of the direction and time-dependent individual
antenna gains is required. Aims: This paper aims to improve the reconstruction
of radio images, by introducing a novel joint imaging and calibration algorithm
including direction-dependent antenna gains. Methods: Building on the
\texttt{resolve} framework, we designed a Bayesian imaging and calibration
algorithm utilizing the image domain gridding method for numerically efficient
application of direction-dependent antenna gains. Furthermore by approximating
the posterior probability distribution with variational inference, our
algorithm can provide reliable uncertainty maps. Results: We demonstrate the
ability of the algorithm to recover high resolution high dynamic range radio
maps from VLA data of the radio galaxy Cygnus A. We compare the quality of the
recovered images with previous work relying on classically calibrated data.
Furthermore we compare with a compressed sensing algorithm also incorporating
direction-dependent gains. Conclusions: Including direction-dependent effects
in the calibration model significantly improves the dynamic range of the
reconstructed images compared to reconstructions from classically calibrated
data. Compared to the compressed sensing reconstruction, the resulting sky
images have a higher resolution and show fewer artifacts. For utilizing the
full potential of radio interferometric data, it is essential to consider the
direction dependence of the antenna gains.Comment: 13 pages, 9 figure
The myocardium and its fibrous matrix working in concert as a spatially netted mesh: a critical review of the purported tertiary structure of the ventricular mass
With the increasing interest now paid to volume reduction surgery, in which the cardiac surgeon is required to resect the ventricular myocardium to an extent unenvisaged in the previous century, it is imperative that we develop as precise knowledge as is possible of the basic structure of the ventricular myocardial mass and its functional correlates. This is the most important in the light of the adoption by some cardiac surgeons of an unvalidated model which hypothesises that the entire myocardial mass can be unravelled to produce one continuous band. It is our opinion that this model, and the phylogenetic and functional correlates derived from it, is incompatible with current concepts of cardiac structure and cardiodynamics. Furthermore, the proponents of the continuous myocardial band have made no effort to demonstrate perceived deficiencies with current concepts, nor have they performed any histological studies to validate their model. Clinical results using modifications of radius reduction surgery based on the concept of the continuous myocardial band show that the procedure essentially becomes ineffective. As we show in this review, if we understand the situation correctly, it was the erstwhile intention of the promoters of the continuous band to elucidate the basic mechanism of diastolic ventricular dilation. Their attempts, however, are doomed to failure, as is any attempt to conceptualise the myocardial mass on the basis of a tertiary structure, because of the underlying three-dimensional netting of the myocardial aggregates and the supporting fibrous tissue to form the myocardial syncytium. Thus, the ventricular myocardium is arranged in the form of a modified blood vessel rather than a skeletal muscle. If an analogy is required with skeletal muscle, then the ventricular myocardium possesses the freedom of motion, and the ability for shaping and conformational self-controlling that is better seen in the tongue. It is part of this ability that contributes to the rapid end-systolic ventricular dilation. Histologic investigations reveal that the fibrous content of the three-dimensional mesh is relatively inhomogeneous through the ventricular walls, particularly when the myocardium is diseased. The regional capacity to control systolic mural thickening, therefore, varies throughout the walls of the ventricular components. The existence of the spatially netted structure of the ventricular mass, therefore, must invalidate any attempt to conceptualise the ventricular myocardium as a tertiary arrangement of individual myocardial bands or tract
Calciumâdependent protein kinase 5 links calcium signaling with Nâhydroxyâlâpipecolic acidâ and SARD1âdependent immune memory in systemic acquired resistance
Systemic acquired resistance (SAR) prepares infected plants for faster and stronger defense activation upon subsequent attacks. SAR requires an information relay from primary infection to distal tissue and the initiation and maintenance of a selfâmaintaining phytohormone salicylic acid (SA)âdefense loop.
In spatial and temporal resolution, we show that calciumâdependent protein kinase CPK5 contributes to immunity and SAR. In local basal resistance, CPK5 functions upstream of SA synthesis, perception, and signaling. In systemic tissue, CPK5 signaling leads to accumulation of SARâinducing metabolite NâhydroxyâLâpipecolic acid (NHP) and SAR marker genes, including Systemic Acquired Resistance Deficient 1 (SARD1)
Plants of increased CPK5, but not CPK6, signaling display an âenhanced SARâ phenotype towards a secondary bacterial infection. In the sard1â1 background, CPK5âmediated basal resistance is still mounted, but NHP concentration is reduced and enhanced SAR is lost.
The biochemical analysis estimated CPK5 half maximal kinase activity for calcium, K50 [Ca2+], to be c. 100 nM, close to the cytoplasmic resting level. This low threshold uniquely qualifies CPK5 to decode subtle changes in calcium, a prerequisite to signal relay and onset and maintenance of priming at later time points in distal tissue. Our data explain why CPK5 functions as a hub in basal and systemic plant immunity
Joy leads to overconfidence, and a simple countermeasure
Overconfidence has been identified as a source of suboptimal decision making in many real-life domains, with often far-reaching consequences. This study identifies a mechanism that can cause overconfidence and demonstrates a simple, effective countermeasure in an incentive-compatible experimental study. We observed that joy induced overconfidence if the reason for joy (an unexpected gift) was u
EffektivitÀt des Kooperativen Lernens im Sportunterricht
Gröben B. EffektivitĂ€t des Kooperativen Lernens im Sportunterricht. In: Westermann P, Berntzen D, eds. Kooperation in Schule und Unterricht. MĂŒnster: ZFL-Verlag; 2010: 103-114
Measuring the magnetic field of a low frequency LC-circuit with phyphox
In high school, LC(R)-circuits are an integral component of physics education. We propose a new setup for exploring those circuits utilizing the magnetic field sensor of a smartphone in combination with the application phyphox, which reads and displays sensor input. Coils with high inductance and low resistance generate low frequency oscillations which can be visualized without any measuring devices other than a smartphone. The results are very satisfactory, because the resolution of the graph is high and the theoretical values match principal features of the measurements. Also, the setup can be achieved with low-cost components.publishe
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