4,315 research outputs found
On how to Mitigate the Packet Reordering Issue in the Explicit Load Balancing Scheme
科研費報告書収録論文(課題番号:17500030/研究代表者:加藤寧/インターネットと高親和性を有する次世代低軌道衛星ネットワークに関する基盤研究
ELB: An Explicit Load Balancing Routing Protocol for Multi-Hop NGEO Satellite Constellations
科研費報告書収録論文(課題番号:17500030/研究代表者:加藤寧/インターネットと高親和性を有する次世代低軌道衛星ネットワークに関する基盤研究
Metallic liquid hydrogen and likely Al2O3 metallic glass
Dynamic compression has been used to synthesize liquid metallic hydrogen at
140 GPa (1.4 million bar) and experimental data and theory predict Al2O3 might
be a metallic glass at ~300 GPa. The mechanism of metallization in both cases
is probably a Mott-like transition. The strength of sapphire causes shock
dissipation to be split differently in the strong solid and soft fluid. Once
the 4.5-eV H-H and Al-O bonds are broken at sufficiently high pressures in
liquid H2 and in sapphire (single-crystal Al2O3), electrons are delocalized,
which leads to formation of energy bands in fluid H and probably in amorphous
Al2O3. The high strength of sapphire causes shock dissipation to be absorbed
primarily in entropy up to ~400 GPa, which also causes the 300-K isotherm and
Hugoniot to be virtually coincident in this pressure range. Above ~400 GPa
shock dissipation must go primarily into temperature, which is observed
experimentally as a rapid increase in shock pressure above ~400 GPa. The
metallization of glassy Al2O3, if verified, is expected to be general in strong
oxide insulators. Implications for Super Earths are discussed.Comment: 8 pages, 5 figures, 14th Liquid and Amorphous Metals Conference, Rome
201
Absorption of Scintillation Light in a 100 Liquid Xenon Ray Detector and Expected Detector Performance
An 800L liquid xenon scintillation ray detector is being developed
for the MEG experiment which will search for decay
at the Paul Scherrer Institut. Absorption of scintillation light of xenon by
impurities might possibly limit the performance of such a detector. We used a
100L prototype with an active volume of 372x372x496 mm to study the
scintillation light absorption. We have developed a method to evaluate the
light absorption, separately from elastic scattering of light, by measuring
cosmic rays and sources. By using a suitable purification technique,
an absorption length longer than 100 cm has been achieved. The effects of the
light absorption on the energy resolution are estimated by Monte Carlo
simulation.Comment: 18 pages, 10 figures (eps). Submitted to Nucl. Instr. and Meth.
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Volumetric laser endomicroscopy and its application to Barrett's esophagus: results from a 1,000 patient registry.
Volumetric laser endomicroscopy (VLE) uses optical coherence tomography (OCT) for real-time, microscopic cross-sectional imaging. A US-based multi-center registry was constructed to prospectively collect data on patients undergoing upper endoscopy during which a VLE scan was performed. The objective of this registry was to determine usage patterns of VLE in clinical practice and to estimate quantitative and qualitative performance metrics as they are applied to Barrett's esophagus (BE) management. All procedures utilized the NvisionVLE Imaging System (NinePoint Medical, Bedford, MA) which was used by investigators to identify the tissue types present, along with focal areas of concern. Following the VLE procedure, investigators were asked to answer six key questions regarding how VLE impacted each case. Statistical analyses including neoplasia diagnostic yield improvement using VLE was performed. One thousand patients were enrolled across 18 US trial sites from August 2014 through April 2016. In patients with previously diagnosed or suspected BE (894/1000), investigators used VLE and identified areas of concern not seen on white light endoscopy (WLE) in 59% of the procedures. VLE imaging also guided tissue acquisition and treatment in 71% and 54% of procedures, respectively. VLE as an adjunct modality improved the neoplasia diagnostic yield by 55% beyond the standard of care practice. In patients with no prior history of therapy, and without visual findings from other technologies, VLE-guided tissue acquisition increased neoplasia detection over random biopsies by 700%. Registry investigators reported that VLE improved the BE management process when used as an adjunct tissue acquisition and treatment guidance tool. The ability of VLE to image large segments of the esophagus with microscopic cross-sectional detail may provide additional benefits including higher yield biopsies and more efficient tissue acquisition. Clinicaltrials.gov NCT02215291
Entropy-Dominated Dissipation in Sapphire Shock-Compressed up to 400 GPa (4 Mbar)
Sapphire (single-crystal Al2O3) is a representative Earth material and is
used as a window and/or anvil in shock experiments. Pressure, for example, at
the core-mantle boundary is about 130 gigapascals (GPa). Defects induced by
100-GPa shock waves cause sapphire to become opaque, which precludes measuring
temperature with thermal radiance. We have measured wave profiles of sapphire
crystals with several crystallographic orientations at shock pressures of 16,
23, and 86 GPa. At 23 GPa plastic-shock rise times are generally quite long
(~100 ns) and their values depend sensitively on the direction of shock
propagation in the crystal lattice. The long rise times are probably caused by
the high strength of inter-atomic interactions in the ordered three-dimensional
sapphire lattice. Our wave profiles and recent theoretical and laser-driven
experimental results imply that sapphire disorders without significant shock
heating up to about 400 GPa, above which Al2O3 is amorphous and must heat. This
picture suggests that the characteristic shape of shock compression curves of
many Earth materials at 100 GPa pressures is caused by a combination of entropy
and temperature.Comment: 12 pages, 4 figure
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Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology
We developed a micromotor based miniature catheter with an outer diameter of 3.2 mm for ultrahigh speed endoscopic swept source optical coherence tomography (OCT) using a vertical cavity surface-emitting laser (VCSEL) at a 1 MHz axial scan rate. The micromotor can rotate a micro-prism at several hundred frames per second with less than 5 V drive voltage to provide fast and stable scanning, which is not sensitive to the bending of the catheter. The side-viewing probe can be pulled back to acquire a three-dimensional (3D) data set covering a large area on the specimen. The VCSEL provides a high axial scan rate to support dense sampling under high frame rate operation. Using a high speed data acquisition system, in vivo 3D-OCT imaging in the rabbit GI tract and ex vivo imaging of a human colon specimen with 8 μm axial resolution, 8 μm lateral resolution and 1.2 mm depth range in tissue at a frame rate of 400 fps was demonstrated
Characterization of buried glands before and after radiofrequency ablation by using 3-dimensional optical coherence tomography (with videos)
Background
Radiofrequency ablation (RFA) is an endoscopic technique used to eradicate Barrett's esophagus (BE). However, such ablation can commonly lead to neosquamous epithelium overlying residual BE glands not visible by conventional endoscopy and may evade detection on random biopsy samples.
Objective
To demonstrate the capability of endoscopic 3-dimensional optical coherence tomography (3D-OCT) for the identification and characterization of buried glands before and after RFA therapy.
Design
Cross-sectional study.
Setting
Single teaching hospital.
Patients
Twenty-six male and 1 female white patients with BE undergoing RFA treatment.
Interventions
3D-OCT was performed at the gastroesophageal junction in 18 patients before attaining complete eradication of intestinal metaplasia (pre–CE-IM group) and in 16 patients after CE-IM (post–CE-IM group).
Main Outcome Measurements
Prevalence, size, and location of buried glands relative to the squamocolumnar junction.
Results
3D-OCT provided an approximately 30 to 60 times larger field of view compared with jumbo and standard biopsy and sufficient imaging depth for detecting buried glands. Based on 3D-OCT results, buried glands were found in 72% of patients (13/18) in the pre–CE-IM group and 63% of patients (10/16) in the post–CE-IM group. The number (mean [standard deviation]) of buried glands per patient in the post–CE-IM group (7.1 [9.3]) was significantly lower compared with the pre–CE-IM group (34.4 [44.6]; P = .02). The buried gland size (P = .69) and distribution (P = .54) were not significantly different before and after CE-IM.
Limitations
A single-center, cross-sectional study comparing patients at different time points in treatment. Lack of 1-to-1 coregistered histology for all OCT data sets obtained in vivo.
Conclusion
Buried glands were frequently detected with 3D-OCT near the gastroesophageal junction before and after radiofrequency ablation.National Institutes of Health (U.S.) (Grant R01-CA75289-15)National Institutes of Health (U.S.) (Grant R44CA101067-06)National Institutes of Health (U.S.) (Grant R01-HL095717-03)National Institutes of Health (U.S.) (Grant R01-NS057476-05)National Institutes of Health (U.S.) (Grant K99-EB010071-01A1)United States. Air Force Office of Scientific Research (Contract FA9550-10-1-0063)United States. Air Force Office of Scientific Research. Medical Free Electron Laser Program (Contract FA9550-10-1-0551)Center for Integration of Medicine and Innovative Technolog
Structural markers observed with endoscopic 3-dimensional optical coherence tomography correlating with Barrett's esophagus radiofrequency ablation treatment response
Background
Radiofrequency ablation (RFA) is effective for treating Barrett's esophagus (BE) but often involves multiple endoscopy sessions over several months to achieve complete response.
Objective
Identify structural markers that correlate with treatment response by using 3-dimensional (3-D) optical coherence tomography (OCT; 3-D OCT).
Design
Cross-sectional.
Setting
Single teaching hospital.
Patients
Thirty-three patients, 32 male and 1 female, with short-segment (<3 cm) BE undergoing RFA treatment.
Intervention
Patients were treated with focal RFA, and 3-D OCT was performed at the gastroesophageal junction before and immediately after the RFA treatment. Patients were re-examined with standard endoscopy 6 to 8 weeks later and had biopsies to rule out BE if not visibly evident.
Main Outcome Measurements
The thickness of BE epithelium before RFA and the presence of residual gland-like structures immediately after RFA were determined by using 3-D OCT. The presence of BE at follow-up was assessed endoscopically.
Results
BE mucosa was significantly thinner in patients who achieved complete eradication of intestinal metaplasia than in patients who did not achieve complete eradication of intestinal metaplasia at follow-up (257 ± 60 μm vs 403 ± 86 μm; P < .0001). A threshold thickness of 333 μm derived from receiver operating characteristic curves corresponded to a 92.3% sensitivity, 85% specificity, and 87.9% accuracy in predicting the presence of BE at follow-up. The presence of OCT-visible glands immediately after RFA also correlated with the presence of residual BE at follow-up (83.3% sensitivity, 95% specificity, 90.6% accuracy).
Limitations
Single center, cross-sectional study in which only patients with short-segment BE were examined.
Conclusion
Three-dimensional OCT assessment of BE thickness and residual glands during RFA sessions correlated with treatment response. Three-dimensional OCT may predict responses to RFA or aid in making real-time RFA retreatment decisions in the future.Center for Integration of Medicine and Innovative Technology (Medical Engineering Fellowship)United States. Dept. of Veterans Affairs. Boston Healthcare SystemNational Institutes of Health (U.S.) (Grant R01-CA75289-15)National Institutes of Health (U.S.) (Grant R44CA101067-06)National Institutes of Health (U.S.) (Grant K99-EB010071-01A1)United States. Air Force Office of Scientific Research (Grant FA9550-10-1-0063)United States. Air Force Office of Scientific Research. Medical Free Electron Laser Program (Grant FA9550-10-1-0551
Tests of model of color reconnection and a search for glueballs using gluon jets with a rapidity gap
Gluon jets with a mean energy of 22 GeV and purity of 95% are selected from
hadronic Z0 decay events produced in e+e- annihilations. A subsample of these
jets is identified which exhibits a large gap in the rapidity distribution of
particles within the jet. After imposing the requirement of a rapidity gap, the
gluon jet purity is 86%. These jets are observed to demonstrate a high degree
of sensitivity to the presence of color reconnection, i.e. higher order QCD
processes affecting the underlying color structure. We use our data to test
three QCD models which include a simulation of color reconnection: one in the
Ariadne Monte Carlo, one in the Herwig Monte Carlo, and the other by Rathsman
in the Pythia Monte Carlo. We find the Rathsman and Ariadne color reconnection
models can describe our gluon jet measurements only if very large values are
used for the cutoff parameters which serve to terminate the parton showers, and
that the description of inclusive Z0 data is significantly degraded in this
case. We conclude that color reconnection as implemented by these two models is
disfavored. The signal from the Herwig color reconnection model is less clear
and we do not obtain a definite conclusion concerning this model. In a separate
study, we follow recent theoretical suggestions and search for glueball-like
objects in the leading part of the gluon jets. No clear evidence is observed
for these objects.Comment: 42 pages, 18 figure
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