971 research outputs found
Reflective Ghost Imaging through Turbulence
Recent work has indicated that ghost imaging may have applications in
standoff sensing. However, most theoretical work has addressed
transmission-based ghost imaging. To be a viable remote-sensing system, the
ghost imager needs to image rough-surfaced targets in reflection through long,
turbulent optical paths. We develop, within a Gaussian-state framework,
expressions for the spatial resolution, image contrast, and signal-to-noise
ratio of such a system. We consider rough-surfaced targets that create fully
developed speckle in their returns, and Kolmogorov-spectrum turbulence that is
uniformly distributed along all propagation paths. We address both classical
and nonclassical optical sources, as well as a computational ghost imager.Comment: 13 pages, 3 figure
Effects of Differential Rotation on the Maximum Mass of Neutron Stars
The merger of binary neutron stars is likely to lead to differentially
rotating remnants. In this paper we numerically construct models of
differentially rotating neutron stars in general relativity and determine their
maximum allowed mass. We model the stars adopting a polytropic equation of
state and tabulate maximum allowed masses as a function of differential
rotation and stiffness of the equation of state. We also provide a crude
argument that yields a qualitative estimate of the effect of stiffness and
differential rotation on the maximum allowed mass.Comment: 6 pages, to appear in Ap
Method of Scrapping Steel Structures
A method of breaking up a structure for the recovery of steel as scrap. The structure has steel plates forming a compartment secured to framing in the compartment. The method includes at least partially filling the compartment with a substantially incompressible substance and placing explosive in the substance in the compartment. The explosive is sufficient and adapted on detonation thereof to pressurize the compartment to the extent of causing separation of the plates from the framing. The method further includes detonating the explosive
Global oceanic microseism sources as seen by seismic arrays and predicted by wave action models.
International audienceWe analyze global microseism excitation patterns between July 2000 and June 2001. Seismological observations are compared with modeling results to isolate robust activity features of relevant source processes. First, we use observations of microseism source locations estimated by Landès et al. (2010) based on array processing of ambient noise correlations. Second, we construct synthetic activity patterns by coupling sea state estimates derived from wave action models to the excitation theory for microseisms. The overall spatiotemporal evolution of both estimates is characterized by a seasonal character that is associated with strong activity during winter months. The distribution of landmass causes seasonal changes on the Northern Hemisphere (NH) to exceed the variability on the Southern Hemisphere (SH). Our systematic comparison of the two estimates reveals significant microseism excitation along coastlines and in the open ocean. Since coastal reflections are not accounted for in the modeling approach, the consistent mismatch between near-coastal observations and predictions suggests that relevant microseism energy arriving at the networks is generated in these areas. Simultaneously, systematic coincidence away from coastlines verifies the open ocean generation hypothesis. These conclusions are universal and robust with respect to the seismic network locations on the NH. The spatially homogeneous resolution of our synthetics provides a valuable resource for the assessment of the global microseism weather. Similar to previously identified hot spot areas in the North Atlantic, the modeled distributions hypothesize regions of strong localized activity on the SH, which are only partially confirmed by the analyzed data sets
Attributing Learned Concepts in Neural Networks to Training Data
By now there is substantial evidence that deep learning models learn certain
human-interpretable features as part of their internal representations of data.
As having the right (or wrong) concepts is critical to trustworthy machine
learning systems, it is natural to ask which inputs from the model's original
training set were most important for learning a concept at a given layer. To
answer this, we combine data attribution methods with methods for probing the
concepts learned by a model. Training network and probe ensembles for two
concept datasets on a range of network layers, we use the recently developed
TRAK method for large-scale data attribution. We find some evidence for
convergence, where removing the 10,000 top attributing images for a concept and
retraining the model does not change the location of the concept in the network
nor the probing sparsity of the concept. This suggests that rather than being
highly dependent on a few specific examples, the features that inform the
development of a concept are spread in a more diffuse manner across its
exemplars, implying robustness in concept formation
Calciphylaxis following kidney transplantation: a case report
Introduction: Calciphylaxis occurring after kidney transplantation is rare and rarely reported. It results in chronic non-healing wounds and is associated with a poor prognosis and is often fatal. We present a case of proximal lower limb calciphylaxis that occurred early after kidney transplantation. The patient had no classic associated risk factors. He had previously had a total parathyroidectomy but had normal serum calcium-phosphate product and parathyroid hormone levels. The clinical outcome of this case was favorable and highlights some fundamental issues relating to management.
Case prsentation: A 70-year-old British Caucasian man with end-stage renal failure secondary to IgA nephropathy presented six months post kidney transplantation with cutaneous calciphylaxis lesions involving the medial aspect of the thigh bilaterally.
Conclusion: To the best of our knowledge, this is the first reported case of rapid onset cutaneous calciphylaxis occurring soon after kidney transplantation that was associated with a favorable outcome. Cutaneous calciphylaxis lesions should be promptly managed with meticulous wound care, antimicrobial therapy and the correction of calcium-phosphate product where indicated
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