1,922 research outputs found
Early Stage Cavitation Erosion within Ceramics: An Experimental Investigation
Six ceramic material types were considered within an experimental investigation to identify the erosion damages mechanisms resulting from cavitation exposure. These materials were a Y-TZP type of zirconia, different commercially available silicon nitrides, a high purity
alumina and an hardened high nitrogen stainless steel. An ultrasonic transducer was utilised to produce cavitation conditions and the configuration was “static specimen method” using a 5mm diameter probe, 20kHz and 50μm of amplitude. The exposure times were periods from
15 seconds to 2 hours. Experimental methods employed to characterise wear mechanisms were light microscopy,
scanning light interferometry, scanning electronic microscopy. It was found that the zirconia and silicon nitrides demonstrated evidence of local pseudoplastic
deformation or depression prior to more pronounced erosion damages by fracture. Zirconia showed evidence of delayed surface changes when the sample is at rest stored in air
possibly by spontaneous phase transformation after the completion of the erosion tests. Alumina showed evidence of brittle surface fracture and negligible or no pseudo-plastic deformation. All wear mechanisms are discussed and the materials are ranked in terms of cavitation resistance performance
Current distribution in a parallel configuration superconducting strip-line detector
Superconducting detectors based on parallel microscopic strip-lines are promising candidates for single molecule detection in time-of-flight mass spectrometry. The device physics of this configuration is complex. In this letter, we employ nano-optical techniques to study the variation of current density, count rate, and pulse amplitude transversely across the parallel strip device. Using the phenomenological London theory, we are able to correlate our results to a non-uniform current distribution between the strips, governed by the London magnetic penetration depth. This fresh perspective convincingly explains anomalous behaviour in large area parallel superconducting strip-line detectors reported in previous studies
Investigations of afterpulsing and detection efficiency recovery in superconducting nanowire single-photon detectors
We report on the observation of a non-uniform dark count rate in
Superconducting Nanowire Single Photon Detectors (SNSPDs), specifically
focusing on an afterpulsing effect present when the SNSPD is operated at a high
bias current regime. The afterpulsing exists for real detection events
(triggered by input photons) as well as for dark counts (no laser input). In
our standard set-up, the afterpulsing is most likely to occur at around 180 ns
following a detection event, for both real counts and dark counts. We
characterize the afterpulsing behavior and speculate that it is not due to the
SNSPD itself but rather the amplifiers used to boost the electrical output
signal from the SNSPD. We show that the afterpulsing indeed disappears when we
use a different amplifier with a better low frequency response. We also examine
the short-lived enhancement of detection efficiency during the recovery of the
SNSPD due to temporary perturbation of the bias and grounding conditions
Expression of PEG11 and PEG11AS transcripts in normal and callipyge sheep
BACKGROUND: The callipyge mutation is located within an imprinted gene cluster on ovine chromosome 18. The callipyge trait exhibits polar overdominant inheritance due to the fact that only heterozygotes inheriting a mutant paternal allele (paternal heterozygotes) have a phenotype of muscle hypertrophy, reduced fat and a more compact skeleton. The mutation is a single A to G transition in an intergenic region that results in the increased expression of several genes within the imprinted cluster without changing their parent-of-origin allele-specific expression. RESULTS: There was a significant effect of genotype (p < 0.0001) on the transcript abundance of DLK1, PEG11, and MEG8 in the muscles of lambs with the callipyge allele. DLK1 and PEG11 transcript levels were elevated in the hypertrophied muscles of paternal heterozygous animals relative to animals of the other three genotypes. The PEG11 locus produces a single 6.5 kb transcript and two smaller antisense strand transcripts, referred to as PEG11AS, in skeletal muscle. PEG11AS transcripts were detectable over a 5.5 kb region beginning 1.2 kb upstream of the PEG11 start codon and spanning the entire open reading frame. Analysis of PEG11 expression by quantitative PCR shows a 200-fold induction in the hypertrophied muscles of paternal heterozygous animals and a 13-fold induction in homozygous callipyge animals. PEG11 transcripts were 14-fold more abundant than PEG11AS transcripts in the gluteus medius of paternal heterozygous animals. PEG11AS transcripts were expressed at higher levels than PEG11 transcripts in the gluteus medius of animals of the other three genotypes. CONCLUSIONS: The effect of the callipyge mutation has been to alter the expression of DLK1, GTL2, PEG11 and MEG8 in the hypertrophied skeletal muscles. Transcript abundance of DLK1 and PEG11 was highest in paternal heterozygous animals and exhibited polar overdominant gene expression patterns; therefore, both genes are candidates for causing skeletal muscle hypertrophy. There was unique relationship of PEG11 and PEG11AS transcript abundance in the paternal heterozygous animals that suggests a RNA interference mechanism may have a role in PEG11 gene regulation and polar overdominance in callipyge sheep
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REFORM: Rotor Estimation From Object Resampling and Matching
Abstract: In this paper we tackle the problem of correspondence and rotor estimation between models composed of geometric primitives of different types. We frame this problem as searching for the rotor that takes a query model to a reference model. The situations that we consider are those in which our query model: contains additional primitives not present in the reference; is missing primitives that are present in the reference. We will also look at cases in which there are a large number of primitives per model. These are all common issues facing any SLAM-type (simultaneous localisation and mapping) systems. To overcome these problems we introduce an inter-object rotor magnitude-based matching function and a subsampled iterative rotor estimation and matching algorithm. We title the finished algorithm: Rotor Estimation From Object Resampling and Matching—REFORM. REFORM builds on ideas from the RANSAC (RAndom SAmple Consensus) [7] and ICP (Iterative Closest Point) [3, 11] algorithms and extends these to multivector correspondence. It is easily parallelisable and designed for good convergence performance with models of real objects
Towards Hybrid Classical-Quantum Computation Structures in Wirelessly-Networked Systems
With unprecedented increases in traffic load in today's wireless networks,
design challenges shift from the wireless network itself to the computational
support behind the wireless network. In this vein, there is new interest in
quantum-compute approaches because of their potential to substantially speed up
processing, and so improve network throughput. However, quantum hardware that
actually exists today is much more susceptible to computational errors than
silicon-based hardware, due to the physical phenomena of decoherence and noise.
This paper explores the boundary between the two types of
computation---classical-quantum hybrid processing for optimization problems in
wireless systems---envisioning how wireless can simultaneously leverage the
benefit of both approaches. We explore the feasibility of a hybrid system with
a real hardware prototype using one of the most advanced experimentally
available techniques today, reverse quantum annealing. Preliminary results on a
low-latency, large MIMO system envisioned in the 5G New Radio roadmap are
encouraging, showing approximately 2--10X better performance in terms of
processing time than prior published results.Comment: HotNets 2020: Nineteenth ACM Workshop on Hot Topics in Networks
(https://doi.org/10.1145/3422604.3425924
Characterization of fiber-generated entangled photon pairs with superconducting single-photon detectors
We demonstrate the suitability of fiber-generated entangled photon pairs for practical quantum communications in the telecom band by measuring their properties with superconducting single-photon detectors that produce negligible dark counts. The photon pairs are created in approximately 5-ps duration windows at 50 MHz rate while the detectors are operated in ungated free running mode. We obtain a coincidence to accidental-coincidence ratio >80 with raw photon-counting data, i.e., without making any post-measurement corrections. Using a previously demonstrated counter-propagating scheme we also produce polarizationentangled photon pairs at 50-MHz rate, which in coincidence detection directly yield two-photon interference with a fringe visibility >98%
Quantum-accelerated constraint programming
Constraint programming (CP) is a paradigm used to model and solve constraint
satisfaction and combinatorial optimization problems. In CP, problems are
modeled with constraints that describe acceptable solutions and solved with
backtracking tree search augmented with logical inference. In this paper, we
show how quantum algorithms can accelerate CP, at both the levels of inference
and search. Leveraging existing quantum algorithms, we introduce a
quantum-accelerated filtering algorithm for the global
constraint and discuss its applicability to a broader family of global
constraints with similar structure. We propose frameworks for the integration
of quantum filtering algorithms within both classical and quantum backtracking
search schemes, including a novel hybrid classical-quantum backtracking search
method. This work suggests that CP is a promising candidate application for
early fault-tolerant quantum computers and beyond.Comment: published in Quantu
SMARCB1/INI1 germline mutations contribute to 10% of sporadic schwannomatosis
<p>Abstract</p> <p>Background</p> <p>Schwannomatosis is a disease characterized by multiple non-vestibular schwannomas. Although biallelic <it>NF2 </it>mutations are found in schwannomas, no germ line event is detected in schwannomatosis patients. In contrast, germline mutations of the <it>SMARCB1 </it>(<it>INI1</it>) tumor suppressor gene were described in familial and sporadic schwannomatosis patients.</p> <p>Methods</p> <p>To delineate the <it>SMARCB1 </it>gene contribution, the nine coding exons were sequenced in a series of 56 patients affected with a variable number of non-vestibular schwannomas.</p> <p>Results</p> <p>Nine variants scattered along the sequence of <it>SMARCB1 </it>were identified. Five of them were classified as deleterious. All five patients carrying a <it>SMARCB1 </it>mutation had more multiple schwannomas, corresponding to 10.2% of patients with schwannomatosis. They were also diagnosed before 35 years of age.</p> <p>Conclusions</p> <p>These results suggest that patients with schwannomas have a significant probability of carrying a <it>SMARCB1 </it>mutation. Combined with data available from other studies, they confirm the clinical indications for genetic screening of the <it>SMARCB1 </it>gene.</p
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