Simulated precipitation diurnal cycles over East Asia using different CAPE-based convective closure schemes in WRF model

Science.gov (United States)

Yang, Ben; Zhou, Yang; Zhang, Yaocun; Huang, Anning; Qian, Yun; Zhang, Lujun

2018-03-01

Closure assumption in convection parameterization is critical for reasonably modeling the precipitation diurnal variation in climate models. This study evaluates the precipitation diurnal cycles over East Asia during the summer of 2008 simulated with three convective available potential energy (CAPE) based closure assumptions, i.e. CAPE-relaxing (CR), quasi-equilibrium (QE), and free-troposphere QE (FTQE) and investigates the impacts of planetary boundary layer (PBL) mixing, advection, and radiation on the simulation by using the weather research and forecasting model. The sensitivity of precipitation diurnal cycle to PBL vertical resolution is also examined. Results show that the precipitation diurnal cycles simulated with different closures all exhibit large biases over land and the simulation with FTQE closure agrees best with observation. In the simulation with QE closure, the intensified PBL mixing after sunrise is responsible for the late-morning peak of convective precipitation, while in the simulation with FTQE closure, convective precipitation is mainly controlled by advection cooling. The relative contributions of different processes to precipitation formation are functions of rainfall intensity. In the simulation with CR closure, the dynamical equilibrium in the free troposphere still can be reached, implying the complex cause-effect relationship between atmospheric motion and convection. For simulations in which total CAPE is consumed for the closures, daytime precipitation decreases with increased PBL resolution because thinner model layer produces lower convection starting layer, leading to stronger downdraft cooling and CAPE consumption. The sensitivity of the diurnal peak time of precipitation to closure assumption can also be modulated by changes in PBL vertical resolution. The results of this study help us better understand the impacts of various processes on the precipitation diurnal cycle simulation.

Comparative analysis of ear-hole closure identifies epimorphic regeneration as a discrete trait in mammals

Science.gov (United States)

Gawriluk, Thomas R.; Simkin, Jennifer; Thompson, Katherine L.; Biswas, Shishir K.; Clare-Salzler, Zak; Kimani, John M.; Kiama, Stephen G.; Smith, Jeramiah J.; Ezenwa, Vanessa O.; Seifert, Ashley W.

2016-01-01

Why mammals have poor regenerative ability has remained a long-standing question in biology. In regenerating vertebrates, injury can induce a process known as epimorphic regeneration to replace damaged structures. Using a 4-mm ear punch assay across multiple mammalian species, here we show that several Acomys spp. (spiny mice) and Oryctolagus cuniculus completely regenerate tissue, whereas other rodents including MRL/MpJ ‘healer' mice heal similar injuries by scarring. We demonstrate ear-hole closure is independent of ear size, and closure rate can be modelled with a cubic function. Cellular and genetic analyses reveal that injury induces blastema formation in Acomys cahirinus. Despite cell cycle re-entry in Mus musculus and A. cahirinus, efficient cell cycle progression and proliferation only occurs in spiny mice. Together, our data unite blastema-mediated regeneration in spiny mice with regeneration in other vertebrates such as salamanders, newts and zebrafish, where all healthy adults regenerate in response to injury. PMID:27109826

Simulation of magnetic holes formation in the magnetosheath

Science.gov (United States)

Ahmadi, Narges; Germaschewski, Kai; Raeder, Joachim

2017-12-01

Magnetic holes have been frequently observed in the Earth's magnetosheath and are believed to be the consequence of the nonlinear evolution of the mirror instability. Mirror mode perturbations mainly form as magnetic holes in regions where the plasma is marginally mirror stable with respect to the linear instability criterion. We present an expanding box particle-in-cell simulation to mimic the changing conditions in the magnetosheath as the plasma is convected through it that produces mirror mode magnetic holes. We show that in the initial nonlinear evolution, where the plasma conditions are mirror unstable, the magnetic peaks are dominant, while later, as the plasma relaxes toward marginal stability, the fluctuations evolve into deep magnetic holes. While the averaged plasma parameters in the simulation remain close to the mirror instability threshold, the local plasma in the magnetic holes is highly unstable to mirror instability and locally mirror stable in the magnetic peaks.

Epiretinal proliferation in lamellar macular holes and full-thickness macular holes: clinical and surgical findings.

Science.gov (United States)

Lai, Tso-Ting; Chen, San-Ni; Yang, Chung-May

2016-04-01

To report the clinical findings and surgical outcomes of lamellar macular holes (LMH) with or without lamellar hole-associated epiretinal proliferation (LHEP), and those of full-thickness macular holes (FTMH) presenting with LHEP. From 2009 to 2013, consecutive cases of surgically treated LMH, and all FTMH cases with LHEP were reviewed, given a follow-up time over 1 year. In the LMH group (43 cases), those with LHEP (19 cases) had significantly thinner bases and larger openings than those without (24 cases). The rate of disrupted IS/OS line was higher in the LHEP subgroup preoperatively (68.4 % vs 37.5 %), but similar between subgroups postoperatively (36.8 % and 33.3 %). The preoperative and postoperative visual acuity showed no significant difference between two subgroups. In the FTMH group (13 cases), the average hole size was 219.2 ± 92.1 μm. Permanent or transient spontaneous hole closure was noted in 69.2 % of cases. An intact IS-OS line was found in only 23 % of cases at the final follow-up. In the LMH group, LHEP was associated with a more severe defect but didn't affect surgical outcomes. In the FTMH group, spontaneous hole closure was frequently noted. Despite small holes, disruption of IS-OS line was common after hole closure.

Video studies of passage by Anopheles gambiae mosquitoes through holes in a simulated bed net: effects of hole size, hole orientation and net environment.

Science.gov (United States)

Sutcliffe, James; Colborn, Kathryn L

2015-05-13

Holes in netting provide potential routes for mosquitoes to enter ITNs. Despite this, there is little information on how mosquitoes respond to holes in bed nets and how their responses are affected by hole size, shape and orientation or by ambient conditions around the net. Female Anopheles gambiae (G3) were recorded in a simulated bed net consisting of two sizes of untreated netting-covered behavioural arenas placed above and beside (to simulate the bed net roof and sides respectively) the experimenter who was a source of host cues from 'inside' the net. A round hole of 9 mm or 13 mm diameter was cut into the centre of the netting of each arena. Videos of unfed female mosquitoes in arenas were analysed for time spent flying, walking and standing still and for exit through the hole. The effects of the experimenter on temperature and relative humidity around the simulated net were also measured. Mosquitoes were significantly more active in overhead arenas than in arenas to the side. Hole passage was significantly more likely in smaller arenas than larger ones and for larger holes than smaller ones. In arenas to the side, hole passage rate through small holes was about 50% less likely than what could be explained by area alone. Passage rate through holes in overhead arenas was consistent with hole area. Temperature in arenas did not strongly reflect the experimenter's presence in the simulated net. Relative humidity and absolute humidity in overhead arenas, but not in arenas to the side, were immediately affected by experimenter presence. Higher levels of activity in overhead arenas than in arenas to the side were likely due to the rising heat and humidity plume from the experimenter. Lower than expected passage rates through smaller vertically oriented holes may have been be due to an edge effect that does not apply to horizontally oriented holes. Results suggest that current methods of assessing the importance of physical damage to ITNs may not accurately reflect

Numerical calculation of backfilling of scour holes

DEFF Research Database (Denmark)

Sumer, B. Mutlu; Baykal, Cüneyt; Fuhrman, David R.

2014-01-01

A fully-coupled hydrodynamic and morphologic CFD model is presented for simulating backfilling processes around structures. The hydrodynamic model is based on Reynolds-averaged Navier-Stokes equations, coupled with two-equation k-ω turbulence closure. The sediment transport model consists of sepa...... of structures: piles, and pipelines. Initial scour holes are generated by the same model. The numerical results appear to be in accord with the existing experimental information....

Long-term Follow-up and Outcomes in Traumatic Macular Holes.

Science.gov (United States)

Miller, John B; Yonekawa, Yoshihiro; Eliott, Dean; Kim, Ivana K; Kim, Leo A; Loewenstein, John I; Sobrin, Lucia; Young, Lucy H; Mukai, Shizuo; Vavvas, Demetrios G

2015-12-01

To review presenting characteristics, clinical course, and long-term visual and anatomic outcomes of patients with traumatic macular holes at a tertiary referral center. Retrospective case series. Twenty-eight consecutive patients with traumatic macular holes at a single tertiary referral center were reviewed. In addition to visual acuities and treatments throughout the clinical course, specific dimensions of the macular hole, including diameters, height, configuration, shape, and the presence of a cuff of fluid, were examined using spectral-domain optical coherence tomography (OCT). Twenty-eight patients were identified with a mean initial visual acuity (VA) of logMAR 1.3 (20/400) and a mean follow-up of 2.2 years. Eleven holes (39.3%) closed spontaneously in median 5.7 weeks. Eleven underwent vitrectomy with a median time to intervention of 35.1 weeks. Median time to surgery for the 5 eyes with successful hole closure was 11.0 weeks vs 56.3 weeks for the 6 eyes that failed to close (P = .02). VA improved in closed holes (P holes that did not close (P = .22). There was no relation between initial OCT dimensions and final hole closure status, although there was a trend, which did not reach statistical significance, toward small dimensions for those that closed spontaneously. A fairly high spontaneous closure rate was observed, with a trend toward smaller OCT dimensions. We found no relationship between hole closure and the OCT characteristics of the hole. Surgical intervention was less successful at hole closure when elected after 3 months. Copyright © 2015 Elsevier Inc. All rights reserved.

Numerical Relativity Simulations for Black Hole Merger Astrophysics

Science.gov (United States)

Baker, John G.

2010-01-01

Massive black hole mergers are perhaps the most energetic astronomical events, establishing their importance as gravitational wave sources for LISA, and also possibly leading to observable influences on their local environments. Advances in numerical relativity over the last five years have fueled the development of a rich physical understanding of general relativity's predictions for these events. Z will overview the understanding of these event emerging from numerical simulation studies. These simulations elucidate the pre-merger dynamics of the black hole binaries, the consequent gravitational waveform signatures ' and the resulting state, including its kick velocity, for the final black hole produced by the merger. Scenarios are now being considered for observing each of these aspects of the merger, involving both gravitational-wave and electromagnetic astronomy.

Satellite hole formation during dewetting: experiment and simulation

International Nuclear Information System (INIS)

Neto, Chiara; Jacobs, Karin; Seemann, Ralf; Blossey, Ralf; Becker, Juergen; Gruen, Guenther

2003-01-01

The dewetting of thin polymer films on solid substrates has been studied extensively in recent years. These films can decay either by nucleation events or by spinodal dewetting, essentially only depending on the interface potential describing the short- and long-range intermolecular interactions between the interfaces and the initial film thickness. Here, we describe experiments and simulations concerned with the decay of polystyrene thin films. The rupture of the film occurs by the formation of a correlated pattern of holes ('satellite holes') along the liquid rims accumulating at the channel borders. The development of this complex film rupture process, which is neither simply spinodal nor nucleation dewetting, can be mimicked precisely by making use of a novel simulation code based on a rigorous mathematical treatment of the thin film equation and on the knowledge of the effective interface potential of the system. The conditions that determine the appearance and the position of the satellite holes around pre-existing holes are discussed

Simulations of black holes in compactified spacetimes

Energy Technology Data Exchange (ETDEWEB)

Zilhao, Miguel; Herdeiro, Carlos [Centro de Fisica do Porto, Departamento de Fisica e Astronomia, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto (Portugal); Cardoso, Vitor; Nerozzi, Andrea; Sperhake, Ulrich; Witek, Helvi [Centro Multidisciplinar de Astrofisica, Deptartamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Gualtieri, Leonardo, E-mail: mzilhao@fc.up.pt [Dipartimento di Fisica, Universita di Roma ' Sapienza' and Sezione INFN Roma1, P.A. Moro 5, 00185, Roma (Italy)

2011-09-22

From the gauge/gravity duality to braneworld scenarios, black holes in compactified spacetimes play an important role in fundamental physics. Our current understanding of black hole solutions and their dynamics in such spacetimes is rather poor because analytical tools are capable of handling a limited class of idealized scenarios, only. Breakthroughs in numerical relativity in recent years, however, have opened up the study of such spacetimes to a computational treatment which facilitates accurate studies of a wider class of configurations. We here report on recent efforts of our group to perform numerical simulations of black holes in cylindrical spacetimes.

The effects of school closures on influenza outbreaks and pandemics: systematic review of simulation studies.

Science.gov (United States)

Jackson, Charlotte; Mangtani, Punam; Hawker, Jeremy; Olowokure, Babatunde; Vynnycky, Emilia

2014-01-01

School closure is a potential intervention during an influenza pandemic and has been investigated in many modelling studies. To systematically review the effects of school closure on influenza outbreaks as predicted by simulation studies. We searched Medline and Embase for relevant modelling studies published by the end of October 2012, and handsearched key journals. We summarised the predicted effects of school closure on the peak and cumulative attack rates and the duration of the epidemic. We investigated how these predictions depended on the basic reproduction number, the timing and duration of closure and the assumed effects of school closures on contact patterns. School closures were usually predicted to be most effective if they caused large reductions in contact, if transmissibility was low (e.g. a basic reproduction number 90% reductions or even increases under certain assumptions). This partly reflected differences in model assumptions, such as those regarding population contact patterns. Simulation studies suggest that school closure can be a useful control measure during an influenza pandemic, particularly for reducing peak demand on health services. However, it is difficult to accurately quantify the likely benefits. Further studies of the effects of reactive school closures on contact patterns are needed to improve the accuracy of model predictions.

Many-particle and many-hole states in neutron-rich Ne isotopes related to broken N=20 shell closure

International Nuclear Information System (INIS)

Kimura, Masaaki; Horiuchi, Hisashi

2004-01-01

The low-lying level structures of 26 Ne, 28 Ne and 30 Ne which are related to the breaking of the N=20 shell closure have been studied in the framework of the deformed-basis anti-symmetrized molecular dynamics plus generator coordinate method using the Gogny D1S force. The properties of the many-particle and many-hole states are studied as well as that of the ground band. We predict that the negative-parity states, in which neutrons are promoted into the pf-orbit from the sd orbit, have a small excitation energy in the cases of 28 Ne and 30 Ne. We regard this to be a typical phenomena accompanying the breaking of the N=20 shell closure. It is also found that the neutron 4p4h structure of 30 Ne appears at low excitation energy, which contains α + 16 O correlations. (author)

Simulated production of a black hole in ATLAS

CERN Multimedia

2007-01-01

This track is an example of simulated data modelled for the ATLAS detector on the Large Hadron Collider (LHC) at CERN, which will begin taking data in 2008. These tracks would be produced if a miniature black hole was created in the proton-proton collision. Such a small black hole would decay instantly to various particles via a process known as Hawking radiation.

Does Internal Limiting Membrane Peeling in Macular Hole Surgery Improve Reading Vision?

Directory of Open Access Journals (Sweden)

Das Taraprasad

2003-01-01

Full Text Available Purpose: To document the effect of internal limiting membrane (ILM peeling in macular hole closure and reading vision. Method: Fifty-four patients with idiopathic and traumatic macular hole underwent standard vitreous surgery and received either ILM peeling (n= 25 or no ILM peeling (n= 29. The hole closure, and Snellen acuity (distant and near were recorded 12 weeks after surgery and statistically analysed. Results: The macular hole closure rate was 96% (24 of 25 and 72.4% (21 of 29 with and without ILM peeling respectively (P = 0.028. Distant vision improvement of two or more lines was recorded in 64% (16 of 25 and 51.7% (15 of 29 eyes (P = 0.417 with and without ILM peeling respectively. Near vision improvement of two or more lines was seen in 68% (17 of 25 and 41.2% (12 of 29 eyes (P = 0.048 with and without ILM peeling respectively. Conclusion: ILM peeling in macular hole surgery improves the macular hole closure rate and reading vision.

Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model

Energy Technology Data Exchange (ETDEWEB)

Yamagishi, Osamu, E-mail: yamagisi@nifs.ac.jp; Sugama, Hideo [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

2016-03-15

Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.

Fluid simulation of tokamak ion temperature gradient turbulence with zonal flow closure model

Science.gov (United States)

Yamagishi, Osamu; Sugama, Hideo

2016-03-01

Nonlinear fluid simulation of turbulence driven by ion temperature gradient modes in the tokamak fluxtube configuration is performed by combining two different closure models. One model is a gyrofluid model by Beer and Hammett [Phys. Plasmas 3, 4046 (1996)], and the other is a closure model to reproduce the kinetic zonal flow response [Sugama et al., Phys. Plasmas 14, 022502 (2007)]. By including the zonal flow closure, generation of zonal flows, significant reduction in energy transport, reproduction of the gyrokinetic transport level, and nonlinear upshift on the critical value of gradient scale length are observed.

Satellite hole formation during dewetting: experiment and simulation

CERN Document Server

Neto, C; Seemann, R; Blossey, R; Becker, J; Grün, G

2003-01-01

The dewetting of thin polymer films on solid substrates has been studied extensively in recent years. These films can decay either by nucleation events or by spinodal dewetting, essentially only depending on the interface potential describing the short- and long-range intermolecular interactions between the interfaces and the initial film thickness. Here, we describe experiments and simulations concerned with the decay of polystyrene thin films. The rupture of the film occurs by the formation of a correlated pattern of holes ('satellite holes') along the liquid rims accumulating at the channel borders. The development of this complex film rupture process, which is neither simply spinodal nor nucleation dewetting, can be mimicked precisely by making use of a novel simulation code based on a rigorous mathematical treatment of the thin film equation and on the knowledge of the effective interface potential of the system. The conditions that determine the appearance and the position of the satellite holes around ...

Expanding the catalog of binary black-hole simulations: aligned-spin configurations

Science.gov (United States)

Chu, Tony; Pfeiffer, Harald; Scheel, Mark; Szilagyi, Bela; SXS Collaboration

2015-04-01

A major goal of numerical relativity is to model the inspiral and merger of binary black holes through sufficiently accurate and long simulations, to enable the successful detection of gravitational waves. However, covering the full parameter space of binary configurations is a computationally daunting task. The SXS Collaboration has made important progress in this direction recently, with a catalog of 174 publicly available binary black-hole simulations [black-holes.org/waveforms]. Nevertheless, the parameter-space coverage remains sparse, even for non-precessing binaries. In this talk, I will describe an addition to the SXS catalog to improve its coverage, consisting of 95 new simulations of aligned-spin binaries with moderate mass ratios and dimensionless spins as high as 0.9. Some applications of these new simulations will also be mentioned.

Monte Carlo simulation for thermal assisted reversal process of micro-magnetic torus ring with bistable closure domain structure

Energy Technology Data Exchange (ETDEWEB)

Terashima, Kenichi; Suzuki, Kenji; Yamaguchi, Katsuhiko, E-mail: yama@sss.fukushima-u.ac.jp

2016-04-01

Monte Carlo simulations were performed for temperature dependences of closure domain parameter for a magnetic micro-torus ring cluster under magnetic field on limited temperature regions. Simulation results show that magnetic field on tiny limited temperature region can reverse magnetic closure domain structures when the magnetic field is applied at a threshold temperature corresponding to intensity of applied magnetic field. This is one of thermally assisted switching phenomena through a self-organization process. The results show the way to find non-wasteful pairs between intensity of magnetic field and temperature region for reversing closure domain structure by temperature dependence of the fluctuation of closure domain parameter. Monte Carlo method for this simulation is very valuable to optimize the design of thermally assisted switching devices.

Flow simulation in piping system dead legs using second moment, closure and k-epsilon model

International Nuclear Information System (INIS)

Deutsch, E.; Mechitoua, N.; Mattei, J.D.

1996-01-01

This paper deals with an industrial application of second moment closure turbulence model in in numerical simulation of 3D turbulent flows in piping system dead legs. Calculations performed with the 3D ESTET code are presented which contrast the performance of k-epsilon eddy viscosity model and second moment closure turbulence models. Coarse (100 000), medium (400 000) and fine (1 500 000) meshes were used. The second moment closure performs significantly better than eddy viscosity model and predicts with a good agreement the vortex penetration in dead legs provided to use sufficiently refined meshes. The results point out the necessity to be able to perform calculations using fine mesh before introducing refined physical models such as second moment closure turbulence model in a numerical code. This study illustrates the ability of second moment closure turbulence model to simulate 3D turbulent industrial flows. Reynolds stress model computation does not require special care, the calculation is carried on as simply as the k-ξ one. The CPU time needed is less that twice the CPU time needed using k-ξ model. (authors)

What is a black hole

International Nuclear Information System (INIS)

Tipler, F.J.

1979-01-01

A definition of a black hole is proposed that should work in any stably causal space-time. This is that a black hole is the closure of the smaller future set that contains all noncosmological trapped surfaces and which has its boundary generated by null geodesic segments that are boundary generators of TIPs. This allows precise definitions of cosmic censorship and white holes. (UK)

Numerical simulation of responses for cased-hole density logging

International Nuclear Information System (INIS)

Wu, Wensheng; Fu, Yaping; Niu, Wei

2013-01-01

Stabilizing or stimulating oil production in old oil fields requires density logging in cased holes where open-hole logging data are either missing or of bad quality. However, measured values from cased-hole density logging are more severely influenced by factors such as fluid, casing, cement sheath and the outer diameter of the open-hole well compared with those from open-hole logging. To correctly apply the cased-hole formation density logging data, one must eliminate these influences on the measured values and study the characteristics of how the cased-hole density logging instrument responds to these factors. In this paper, a Monte Carlo numerical simulation technique was used to calculate the responses of the far detector of a cased-hole density logging instrument to in-hole fluid, casing wall thickness, cement sheath density and the formation and thus to obtain influence rules and response coefficients. The obtained response of the detector is a function of in-hole liquid, casing wall thickness, the casing's outer diameter, cement sheath density, open-hole well diameter and formation density. The ratio of the counting rate of the detector in the calibration well to that in the measurement well was used to get a fairly simple detector response equation and the coefficients in the equation are easy to acquire. These provide a new way of calculating cased-hole density through forward modelling methods. (paper)

Segmented slant hole collimator for stationary cardiac SPECT: Monte Carlo simulations.

Science.gov (United States)

Mao, Yanfei; Yu, Zhicong; Zeng, Gengsheng L

2015-09-01

This work is a preliminary study of a stationary cardiac SPECT system. The goal of this research is to propose a stationary cardiac SPECT system using segmented slant-hole collimators and to perform computer simulations to test the feasibility. Compared to the rotational SPECT, a stationary system has a benefit of acquiring temporally consistent projections. The most challenging issue in building a stationary system is to provide sufficient projection view-angles. A GATE (GEANT4 application for tomographic emission) Monte Carlo model was developed to simulate a two-detector stationary cardiac SPECT that uses segmented slant-hole collimators. Each detector contains seven segmented slant-hole sections that slant to a common volume at the rotation center. Consequently, 14 view-angles over 180° were acquired without any gantry rotation. The NCAT phantom was used for data generation and a tailored maximum-likelihood expectation-maximization algorithm was used for image reconstruction. Effects of limited number of view-angles and data truncation were carefully evaluated in the paper. Simulation results indicated that the proposed segmented slant-hole stationary cardiac SPECT system is able to acquire sufficient data for cardiac imaging without a loss of image quality, even when the uptakes in the liver and kidneys are high. Seven views are acquired simultaneously at each detector, leading to 5-fold sensitivity gain over the conventional dual-head system at the same total acquisition time, which in turn increases the signal-to-noise ratio by 19%. The segmented slant-hole SPECT system also showed a good performance in lesion detection. In our prototype system, a short hole-length was used to reduce the dead zone between neighboring collimator segments. The measured sensitivity gain is about 17-fold over the conventional dual-head system. The gate Monte Carlo simulations confirm the feasibility of the proposed stationary cardiac SPECT system with segmented slant-hole

Segmented slant hole collimator for stationary cardiac SPECT: Monte Carlo simulations

Energy Technology Data Exchange (ETDEWEB)

Mao, Yanfei, E-mail: ymao@ucair.med.utah.edu [Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108 and Department of Bioengineering, University of Utah, Salt Lake City, Utah 84112 (United States); Yu, Zhicong [Department of Radiology, Mayo Clinic, Rochester, Minnesota 55905 (United States); Zeng, Gengsheng L. [Department of Radiology, Utah Center for Advanced Imaging Research (UCAIR), University of Utah, Salt Lake City, Utah 84108 and Department of Engineering, Weber State University, Ogden, Utah 84408 (United States)

2015-09-15

Purpose: This work is a preliminary study of a stationary cardiac SPECT system. The goal of this research is to propose a stationary cardiac SPECT system using segmented slant-hole collimators and to perform computer simulations to test the feasibility. Compared to the rotational SPECT, a stationary system has a benefit of acquiring temporally consistent projections. The most challenging issue in building a stationary system is to provide sufficient projection view-angles. Methods: A GATE (GEANT4 application for tomographic emission) Monte Carlo model was developed to simulate a two-detector stationary cardiac SPECT that uses segmented slant-hole collimators. Each detector contains seven segmented slant-hole sections that slant to a common volume at the rotation center. Consequently, 14 view-angles over 180° were acquired without any gantry rotation. The NCAT phantom was used for data generation and a tailored maximum-likelihood expectation-maximization algorithm was used for image reconstruction. Effects of limited number of view-angles and data truncation were carefully evaluated in the paper. Results: Simulation results indicated that the proposed segmented slant-hole stationary cardiac SPECT system is able to acquire sufficient data for cardiac imaging without a loss of image quality, even when the uptakes in the liver and kidneys are high. Seven views are acquired simultaneously at each detector, leading to 5-fold sensitivity gain over the conventional dual-head system at the same total acquisition time, which in turn increases the signal-to-noise ratio by 19%. The segmented slant-hole SPECT system also showed a good performance in lesion detection. In our prototype system, a short hole-length was used to reduce the dead zone between neighboring collimator segments. The measured sensitivity gain is about 17-fold over the conventional dual-head system. Conclusions: The GATE Monte Carlo simulations confirm the feasibility of the proposed stationary cardiac

Artificial Leaks in Container Closure Integrity Testing: Nonlinear Finite Element Simulation of Aperture Size Originated by a Copper Wire Sandwiched between the Stopper and the Glass Vial.

Science.gov (United States)

Nieto, Alejandra; Roehl, Holger; Brown, Helen; Adler, Michael; Chalus, Pascal; Mahler, Hanns-Christian

2016-01-01

Container closure integrity (CCI) testing is required by different regulatory authorities in order to provide assurance of tightness of the container closure system against possible contamination, for example, by microorganisms. Microbial ingress CCI testing is performed by incubation of the container closure system with microorganisms under specified testing conditions. Physical CCI uses surrogate endpoints, such as coloration by dye solution ingress or gas flow (helium leakage testing). In order to correlate microbial CCI and physical CCI test methods and to evaluate the methods' capability to detect a given leak, artificial leaks are being introduced into the container closure system in a variety of different ways. In our study, artificial leaks were generated using inserted copper wires between the glass vial opening and rubber stopper. However, the insertion of copper wires introduces leaks of unknown size and shape. With nonlinear finite element simulations, the aperture size between the rubber stopper and the glass vial was calculated, depending on wire diameter and capping force. The dependency of the aperture size on the copper wire diameter was quadratic. With the data obtained, we were able to calculate the leak size and model leak shape. Our results suggest that the size as well as the shape of the artificial leaks should be taken into account when evaluating critical leak sizes, as flow rate does not, independently, correlate to hole size. Capping force also affected leak size. An increase in the capping force from 30 to 70 N resulted in a reduction of the aperture (leak size) by approximately 50% for all wire diameters. From 30 to 50 N, the reduction was approximately 33%. Container closure integrity (CCI) testing is required by different regulatory authorities in order to provide assurance of tightness of the container closure system against contamination, for example, by microorganisms. Microbial ingress CCI testing is performed by incubation of the

The use of an impedance antenna for hole closure detection. Phase II: Detailed antenna design, electronics and software development

International Nuclear Information System (INIS)

Murray, C.N.; Fortescue, T.R.

1991-01-01

C.C.R. Euratom Ispra are currently involved in studies on the possibility of storing radioactive wastes in deep ocean sediment beds. The proposal involves sealing the wastes into torpedo shaped penetrators, which can then be dropped into the ocean over areas where the bottom is suitable. The weight and shape of the penetrators is such that they achieve high terminal velocities (30-50m/s), and in consequence, bury themselves to a considerable depth in suitable clay sediments. Fundamental to the concept is a requirement that the hole made by the entry of the penetrator shall close up again above it, and form an effective seal. This is because it is inevitable that over a period of several hundred years, the containers will become corroded, and when this happens, there must be no possibility of any radioactive species migrating, or being transported to the surface of the sediment. The Hole Closure Problem is thus fundamental to such studies

The use of an impedance antenna for hole closure detection. Phase I: Definition of measurement problems and antenna type

International Nuclear Information System (INIS)

Murray, C.N.; Fortescue, T.R.

1991-01-01

C.C.R. Euratom Ispra are currently involved in studies on the possibility of storing radioactive wastes in deep ocean sediment beds. The proposal involves sealing the wastes into torpedo shaped penetrators, which can then be dropped into the ocean over areas where the bottom is suitable. The weight and shape of the penetrators is such that they achieve high terminal velocities (30-50m/s), and in consequence, bury themselves to a considerable depth in suitable clay sediments. Fundamental to the concept is a requirement that the hole made by the entry of the penetrator shall close up again above it, and form an effective seal. This is because it is inevitable that over a period of several hundred years, the containers will become corroded, and when this happens, there must be no possibility of any radioactive species migrating, or being transported to the surface of the sediment. The Hole Closure Problem is thus fundamental to such studies

Quantum simulations of small electron-hole complexes

International Nuclear Information System (INIS)

Lee, M.A.; Kalia, R.K.; Vashishta, P.D.

1984-09-01

The Green's Function Monte Carlo method is applied to the calculation of the binding energies of electron-hole complexes in semiconductors. The quantum simulation method allows the unambiguous determination of the ground state energy and the effects of band anisotropy on the binding energy. 22 refs., 1 fig

Disk Emission from Magnetohydrodynamic Simulations of Spinning Black Holes

Science.gov (United States)

Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

2016-01-01

We present the results of a new series of global, three-dimensional, relativistic magnetohydrodynamic (MHD) simulations of thin accretion disks around spinning black holes. The disks have aspect ratios of H/R approx. 0.05 and spin parameters of a/M = 0, 0.5, 0.9, and 0.99. Using the ray-tracing code Pandurata, we generate broadband thermal spectra and polarization signatures from the MHD simulations. We find that the simulated spectra can be well fit with a simple, universal emissivity profile that better reproduces the behavior of the emission from the inner disk, compared to traditional analyses carried out using a Novikov-Thorne thin disk model. Finally, we show how spectropolarization observations can be used to convincingly break the spin-inclination degeneracy well known to the continuum-fitting method of measuring black hole spin.

Efficacy of autologous platelets in macular hole surgery.

Science.gov (United States)

Konstantinidis, Aristeidis; Hero, Mark; Nanos, Panagiotis; Panos, Georgios D

2013-01-01

The introduction of optical coherence tomography has allowed accurate measurement of the size of macular holes. A retrospective consecutive review was performed of 21 patients undergoing macular hole repair with vitrectomy, gas tamponade, and autologous platelet injection and we assessed the effect of macular hole parameters on anatomic and functional outcomes. We looked at the demographic features, final visual outcome, and anatomical closure. Twenty-one patients were included in the study. They underwent routine vitrectomy with gas tamponade (C3F8) and injection of autologous platelets. All patients were advised to maintain a facedown posture for 2 weeks. Anatomical closure was confirmed in all cases and 20 out of 21 of patients had improved postoperative visual acuity by two or more lines. In our series, the macular hole dimensions did not have much effect on the final results. The use of autologous platelets and strict facedown posture seems to be the deciding factor in good anatomical and visual outcome irrespective of macular hole dimensions.

Internal limiting membrane flap transposition for surgical repair of macular holes in primary surgery and in persistent macular holes.

Science.gov (United States)

Leisser, Christoph; Hirnschall, Nino; Döller, Birgit; Varsits, Ralph; Ullrich, Marlies; Kefer, Katharina; Findl, Oliver

2018-03-01

Classical or temporal internal limiting membrane (ILM) flap transposition with air or gas tamponade are current trends with the potential to improve surgical results, especially in cases with large macular holes. A prospective case series included patients with idiopathic macular holes or persistent macular holes after 23-G pars plana vitrectomy (PPV) and ILM peeling with gas tamponade. In all patients, 23-G PPV and ILM peeling with ILM flap transposition with gas tamponade and postoperative face-down position was performed. In 7 of 9 eyes, temporal ILM flap transposition combined with pedicle ILM flap could be successfully performed and macular holes were closed in all eyes after surgery. The remaining 2 eyes were converted to pedicle ILM flap transposition with macular hole closure after surgery. Three eyes were scheduled as pedicle ILM flap transposition due to previous ILM peeling. In 2 of these eyes, the macular hole could be closed with pedicle ILM flap transposition. In 3 eyes, free ILM flap transposition was performed and in 2 of these eyes macular hole could be closed after surgery, whereas in 1 eye a second surgery, performed as pedicle ILM flap transposition, was performed and led to successful macular hole closure. Use of ILM flaps in surgical repair of macular hole surgery is a new option of treatment with excellent results independent of the diameter of macular holes. For patients with persistent macular holes, pedicle ILM flap transposition or free ILM flap transposition are surgical options.

Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network

Science.gov (United States)

Yin, Haodong; Han, Baoming; Li, Dewei; Wu, Jianjun; Sun, Huijun

2016-01-01

A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1) A basic passenger behavior optimization model is mathematically constructed based on 0–1 integer programming to describe passengers’ responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2) An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1), the impact of the closure can be somewhat mitigated. PMID:27935963

Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network.

Directory of Open Access Journals (Sweden)

Haodong Yin

Full Text Available A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1 A basic passenger behavior optimization model is mathematically constructed based on 0-1 integer programming to describe passengers' responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2 An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1, the impact of the closure can be somewhat mitigated.

Modeling and Simulating Passenger Behavior for a Station Closure in a Rail Transit Network.

Science.gov (United States)

Yin, Haodong; Han, Baoming; Li, Dewei; Wu, Jianjun; Sun, Huijun

2016-01-01

A station closure is an abnormal operational situation in which the entrances or exits of a rail transit station have to be closed for some time due to an unexpected incident. A novel approach is developed to estimate the impacts of the alternative station closure scenarios on both passenger behavioral choices at the individual level and passenger demand at the disaggregate level in a rail transit network. Therefore, the contributions of this study are two-fold: (1) A basic passenger behavior optimization model is mathematically constructed based on 0-1 integer programming to describe passengers' responses to alternative origin station closure scenarios and destination station closure scenarios; this model also considers the availability of multi-mode transportation and the uncertain duration of the station closure; (2) An integrated solution algorithm based on the passenger simulation is developed to solve the proposed model and to estimate the effects of a station closure on passenger demand in a rail transit network. Furthermore, 13 groups of numerical experiments based on the Beijing rail transit network are performed as case studies with 2,074,267 records of smart card data. The comparisons of the model outputs and the manual survey show that the accuracy of our proposed behavior optimization model is approximately 80%. The results also show that our model can be used to capture the passenger behavior and to quantitatively estimate the effects of alternative closure scenarios on passenger flow demand for the rail transit network. Moreover, the closure duration and its overestimation greatly influence the individual behavioral choices of the affected passengers and the passenger demand. Furthermore, if the rail transit operator can more accurately estimate the closure duration (namely, as g approaches 1), the impact of the closure can be somewhat mitigated.

Tracing the Origin of Black Hole Accretion Through Numerical Hydrodynamic Simulations

Science.gov (United States)

Spicer, Sandy; Somerville, Rachel; Choi, Ena; Brennan, Ryan

2018-01-01

It is now widely accepted that supermassive black holes co-evolve with galaxies, and may play an important role in galaxy evolution. However, the origin of the gas that fuels black hole accretion, and the resulting observable radiation, is not well understood or quantified. We use high-resolution "zoom-in" cosmological numerical hydrodynamic simulations including modeling of black hole accretion and feedback to trace the inflow and outflow of gas within galaxies from the early formation period up to present day. We track gas particles that black holes interact with over time to trace the origin of the gas that feeds supermassive black holes. These gas particles can come from satellite galaxies, cosmological accretion, or be a result of stellar evolution. We aim to track the origin of the gas particles that accrete onto the central black hole as a function of halo mass and cosmic time. Answering these questions will help us understand the connection between galaxy and black hole evolution.

Quarter elliptical crack growth using three dimensional finite element method and crack closure technique

Energy Technology Data Exchange (ETDEWEB)

Gozin, Mohammad-Hosein; Aghaie-Khafri, Mehrdad [K. N. Toosi University of Technology, Tehran (Korea, Republic of)

2014-06-15

Shape evolution of a quarter-elliptical crack emanating from a hole is studied. Three dimensional elastic-plastic finite element analysis of the fatigue crack closure was considered and the stress intensity factor was calculated based on the duplicated elastic model at each crack tip node. The crack front node was advanced proportional to the imposed effective stress intensity factor. Remeshing was applied at each step of the crack growth and solution mapping algorithm was considered. Crack growth retardation at free surfaces was successfully observed. A MATLAB-ABAQUS interference code was developed for the first time to perform crack growth on the basis of crack closure. Simulation results indicated that crack shape is sensitive to the remeshing strategy. Predictions based on the proposed models were in good agreement with Carlson's experiments results.

Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation

Science.gov (United States)

Ahmadi, N.; Wilder, F. D.; Usanova, M.; Ergun, R.; Argall, M. R.; Goodrich, K.; Eriksson, S.; Germaschewski, K.; Torbert, R. B.; Lindqvist, P. A.; Le Contel, O.; Khotyaintsev, Y. V.; Strangeway, R. J.; Schwartz, S. J.; Giles, B. L.; Burch, J.

2017-12-01

The Magnetospheric Multiscale (MMS) mission observed electron whistler waves at the center and at the gradients of magnetic holes on the dayside magnetosheath. The magnetic holes are nonlinear mirror structures which are anti-correlated with particle density. We used expanding box Particle-in-cell simulations and produced the mirror instability magnetic holes. We show that the electron whistler waves can be generated at the gradients and the center of magnetic holes in our simulations which is in agreement with MMS observations. At the nonlinear regime of mirror instability, the proton and electron temperature anisotropy are anti-correlated with the magnetic hole. The plasma is unstable to electron whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are dominant, electron temperature anisotropy develops at the edges of the magnetic holes and electrons become isotropic at the magnetic field minimum. We investigate the possible mechanism for enhancing the electron temperature anisotropy and analyze the electron pitch angle distributions and electron distribution functions in our simulations and compare it with MMS observations.

Analysis and simulation of BGK electron holes

Directory of Open Access Journals (Sweden)

L. Muschietti

1999-01-01

Full Text Available Recent observations from satellites crossing regions of magnetic-field-aligned electron streams reveal solitary potential structures that move at speeds much greater than the ion acoustic/thermal velocity. The structures appear as positive potential pulses rapidly drifting along the magnetic field, and are electrostatic in their rest frame. We interpret them as BGK electron holes supported by a drifting population of trapped electrons. Using Laplace transforms, we analyse the behavior of one phase-space electron hole. The resulting potential shapes and electron distribution functions are self-consistent and compatible with the field and particle data associated with the observed pulses. In particular, the spatial width increases with increasing amplitude. The stability of the analytic solution is tested by means of a two-dimensional particle-in-cell simulation code with open boundaries. We consider a strongly magnetized parameter regime in which the bounce frequency of the trapped electrons is much less than their gyrofrequency. Our investigation includes the influence of the ions, which in the frame of the hole appear as an incident beam, and impinge on the BGK potential with considerable energy. The nonlinear structure is remarkably resilient

Successful closure of treatment-naïve, flat edge (Type II, full-thickness macular hole using inverted internal limiting membrane flap technique

Directory of Open Access Journals (Sweden)

Hussain N

2016-10-01

Full Text Available Nazimul Hussain,1 Anjli Hussain2 1Department of Ophthalmology, Al Zahra Hospital, 2Al Zahra Medical Center, Dubai, United Arab Emirates Objective: The objective of this study was to present the outcome of the internal limiting membrane (ILM peeling flap technique for a treatment-naïve, flat edge (Type II, full-thickness macular hole (MH. Methods: A 52-year-old man presented with complaints of decreased vision and seeing black spot. He was diagnosed to have a flat edge, full-thickness MH, which was confirmed by optical coherence tomography (OCT. He underwent 23G vitrectomy with brilliant blue G-assisted inverted ILM peeling with an inverted flap over the hole followed by fluid gas exchange. Results: Postoperative follow-up until 3 months showed successful closure of the MH, which was confirmed by OCT. The best-corrected visual acuity improved from baseline 6/60 to 6/12 at the final follow-up. Conclusion: Using the inverted ILM flap technique, a treatment-naïve, flat edge (Type II, full thickness MH achieved successful anatomical and functional outcomes. Keywords: macular hole, inverted ILM, optical coherence tomography

A Dancing Black Hole

Science.gov (United States)

Shoemaker, Deirdre; Smith, Kenneth; Schnetter, Erik; Fiske, David; Laguna, Pablo; Pullin, Jorge

2002-04-01

Recently, stationary black holes have been successfully simulated for up to times of approximately 600-1000M, where M is the mass of the black hole. Considering that the expected burst of gravitational radiation from a binary black hole merger would last approximately 200-500M, black hole codes are approaching the point where simulations of mergers may be feasible. We will present two types of simulations of single black holes obtained with a code based on the Baumgarte-Shapiro-Shibata-Nakamura formulation of the Einstein evolution equations. One type of simulations addresses the stability properties of stationary black hole evolutions. The second type of simulations demonstrates the ability of our code to move a black hole through the computational domain. This is accomplished by shifting the stationary black hole solution to a coordinate system in which the location of the black hole is time dependent.

Verification of Heat and Mass Transfer Closures in Industrial Scale Packed Bed Reactor Simulations

Directory of Open Access Journals (Sweden)

Arpit Singhal

2018-03-01

Full Text Available Particle-resolved direct numerical simulation (PR-DNS is known to provide an accurate detailed insight into the local flow phenomena in static particle arrays. Most PR-DNS studies in literature do not account for reactions taking place inside the porous particles. In this study, PR-DNS is performed for catalytic reactions inside the particles using the multifluid approach where all heat and mass transfer phenomena are directly resolved both inside and outside the particles. These simulation results are then used to verify existing 1D model closures from literature over a number of different reaction parameters including different reaction orders, multiple reactions and reactants, interacting reactions, and reactions involving gas volume generation/consumption inside the particle. Results clearly showed that several modifications to existing 1D model closures are required to reproduce PR-DNS results. The resulting enhanced 1D model was then used to accurately simulate steam methane reforming, which includes all of the aforementioned reaction complexities. The effect of multiple reactants was found to be the most influential in this case.

Cierre espontáneo de agujero macular idiopático:: seguimiento por tomografía de coherencia óptica y microperimetría MP1 Spontaneous closure of the idiopathic macular hole.: Follow-up of this case by optical coherence tomography and microperimetry MP1

Directory of Open Access Journals (Sweden)

Julio César Molina Martín

2010-12-01

Full Text Available Se presenta un caso de cierre espontáneo de agujero macular idiopático seguido por tomografía de coherencia óptica y microperimetría MP1 antes y después del cierre. El cierre espontáneo de un estadio 4 no ocurre con frecuencia, sin embargo, puede aparecer fundamentalmente en pacientes con diámetro superior del agujero menor a 150 micras. La tomografía de coherencia óptica y la microperimetría constituyen herramientas útiles en el diagnóstico, pronóstico y seguimiento de esta entidad.The case of spontaneous closure of a stage 4 idiopathic macular hole at followed up by Optical Coherence Tomography and microperimetry MP1 before and after the closure was presented. The spontaneous closure of a stage 4 macular hole is rare but it can occur in patients with hole upper diameters less than 150 µm. The OCT and the microperimetry MP1 are very useful tools in the diagnosis, prognosis and follow-up of this maculopathy.

Simulated Leaching (Migration) Study for a Model Container-Closure System Applicable to Parenteral and Ophthalmic Drug Products.

Science.gov (United States)

Jenke, Dennis; Egert, Thomas; Hendricker, Alan; Castner, James; Feinberg, Tom; Houston, Christopher; Hunt, Desmond G; Lynch, Michael; Nicholas, Kumudini; Norwood, Daniel L; Paskiet, Diane; Ruberto, Michael; Smith, Edward J; Holcomb, Frank; Markovic, Ingrid

2017-01-01

A simulating leaching (migration) study was performed on a model container-closure system relevant to parenteral and ophthalmic drug products. This container-closure system consisted of a linear low-density polyethylene bottle (primary container), a polypropylene cap and an elastomeric cap liner (closure), an adhesive label (labeling), and a foil overpouch (secondary container). The bottles were filled with simulating solvents (aqueous salt/acid mixture at pH 2.5, aqueous buffer at pH 9.5, and 1/1 v/v isopropanol/water), a label was affixed to the filled and capped bottles, the filled bottles were placed into the foil overpouch, and the filled and pouched units were stored either upright or inverted for up to 6 months at 40 °C. After storage, the leaching solutions were tested for leached substances using multiple complementary analytical techniques to address volatile, semi-volatile, and non-volatile organic and inorganic extractables as potential leachables.The leaching data generated supported several conclusions, including that (1) the extractables (leachables) profile revealed by a simulating leaching study can qualitatively be correlated with compositional information for materials of construction, (2) the chemical nature of both the extracting medium and the individual extractables (leachables) can markedly affect the resulting profile, and (3) while direct contact between a drug product and a system's material of construction may exacerbate the leaching of substances from that material by the drug product, direct contact is not a prerequisite for migration and leaching to occur. LAY ABSTRACT: The migration of container-related extractables from a model pharmaceutical container-closure system and into simulated drug product solutions was studied, focusing on circumstances relevant to parenteral and ophthalmic drug products. The model system was constructed specifically to address the migration of extractables from labels applied to the outside of the

Closure Report for Corrective Action Unit 145: Wells and Storage Holes, Nevada Test Site, Nevada

International Nuclear Information System (INIS)

2008-01-01

The purpose of this Closure Report is to provide a summary of the completed closure activities, to document waste disposal, and to present information confirming that the remediation goals were met. The closure alternatives consisted of closure in place with administrative controls for one CAS, and no further action with implementation of best management practices (BMPs) for the remaining five CASs

Influence of heat flow on drift closure during Climax granite spent-fuel test: measurements and calculations

International Nuclear Information System (INIS)

Butkovich, T.R.; Yow, J.L. Jr.; Montan, D.N.

1982-01-01

Measurements of drift closure caused by the thermal load have been made routinely during the Spent Fuel Test in Climax granite since about six weeks after emplacement of the fuel. Horizontal and vertical closure was measured with a manually operated tape extensometer at various locations along the lengths of the drifts. Average closures ranged from 0 to 0.6 mm, horizontal and vertical, out to about 2.2 years since the start of the test. At the same time, displacements from the thermal loads were measured with rod extensometers emplaced to measure relative displacements between hole collars and anchor points in holes drilled from two parallel heater drifts. These data are compared with thermo-elastic finite element calculations which utilized measured properties of the Climax granite. The calculations show that more than half of the closures occur between fuel installation and the first closure measurement. The comparisons show that the results track each other, in that where closure followed by dilation is measured, the calculations also show this effect. The agreement is excellent, considering the averaged measured closures remain within 30% of the total calculated drift closures and the extremely small magnitude of the relative displacements (0.5 mm), measured or calculated

Efficacy of autologous platelets in macular hole surgery

Directory of Open Access Journals (Sweden)

Konstantinidis A

2013-04-01

Full Text Available Aristeidis Konstantinidis,1,2 Mark Hero,2 Panagiotis Nanos,1 Georgios D Panos1,3 1Department of Ophthalmology, University Hospital of Alexandroupolis, Alexandroupolis, Greece; 2Opthalmology Department, University Hospital Coventry and Warwickshire, Coventry, UK; 3Department of Ophthalmology, University Hospitals of Geneva, Geneva, Switzerland Abstract: The introduction of optical coherence tomography has allowed accurate measurement of the size of macular holes. A retrospective consecutive review was performed of 21 patients undergoing macular hole repair with vitrectomy, gas tamponade, and autologous platelet injection and we assessed the effect of macular hole parameters on anatomic and functional outcomes. We looked at the demographic features, final visual outcome, and anatomical closure. Twenty-one patients were included in the study. They underwent routine vitrectomy with gas tamponade (C3F8 and injection of autologous platelets. All patients were advised to maintain a facedown posture for 2 weeks. Anatomical closure was confirmed in all cases and 20 out of 21 of patients had improved postoperative visual acuity by two or more lines. In our series, the macular hole dimensions did not have much effect on the final results. The use of autologous platelets and strict facedown posture seems to be the deciding factor in good anatomical and visual outcome irrespective of macular hole dimensions. Keywords: macular hole, platelets, vitrectomy

Simulation of hole mobility in two-dimensional systems

International Nuclear Information System (INIS)

Donetti, Luca; Gamiz, Francisco; Rodriguez, Noel

2009-01-01

We develop a fully self-consistent solver for the six-band k . p Schrödinger and Poisson equations to compute the valence-band structure of Si and Ge devices with arbitrary substrate orientation and uniaxial or biaxial strain. This allows us to compute the potential, charge distribution and subband energy dispersion relation for hole inversion layers in different devices and, using a simplex Monte Carlo simulator, to evaluate the low-field mobility. New procedures have been developed to calculate the scattering rates. The results obtained in the case of a (0 0 1) Si MOSFET device are compared with experimental mobility curves and a very good agreement is found. Then, hole mobility curves for different structures and crystallographic orientations both with strained and unstrained materials are evaluated

Gravitational waveforms for neutron star binaries from binary black hole simulations

Science.gov (United States)

Barkett, Kevin; Scheel, Mark; Haas, Roland; Ott, Christian; Bernuzzi, Sebastiano; Brown, Duncan; Szilagyi, Bela; Kaplan, Jeffrey; Lippuner, Jonas; Muhlberger, Curran; Foucart, Francois; Duez, Matthew

2016-03-01

Gravitational waves from binary neutron star (BNS) and black-hole/neutron star (BHNS) inspirals are primary sources for detection by the Advanced Laser Interferometer Gravitational-Wave Observatory. The tidal forces acting on the neutron stars induce changes in the phase evolution of the gravitational waveform, and these changes can be used to constrain the nuclear equation of state. Current methods of generating BNS and BHNS waveforms rely on either computationally challenging full 3D hydrodynamical simulations or approximate analytic solutions. We introduce a new method for computing inspiral waveforms for BNS/BHNS systems by adding the post-Newtonian (PN) tidal effects to full numerical simulations of binary black holes (BBHs), effectively replacing the non-tidal terms in the PN expansion with BBH results. Comparing a waveform generated with this method against a full hydrodynamical simulation of a BNS inspiral yields a phase difference of < 1 radian over ~ 15 orbits. The numerical phase accuracy required of BNS simulations to measure the accuracy of the method we present here is estimated as a function of the tidal deformability parameter λ.

Ocriplasmin for treatment of stage 2 macular holes: early clinical results.

Science.gov (United States)

Miller, John B; Kim, Leo A; Wu, David M; Vavvas, Demetrios G; Eliott, Dean; Husain, Deeba

2014-01-01

To review clinical and structural outcomes of ocriplasmin for treatment of stage 2 macular holes. A retrospective review of the first patients with stage 2 macular holes to be treated with ocriplasmin at Massachusetts Eye and Ear Infirmary. All patients were imaged with spectral-domain optical coherence tomography (SD-OCT). Eight patients with stage 2 macular holes received a single injection of 125 μg of ocriplasmin. One patient (12.5%) demonstrated macular hole closure. The posterior hyaloid separated from the macula in six eyes (75%). All seven holes that remained open showed enlargement in hole diameters (narrowest, apical, and basal) at 1 week and 1 month. All seven were successfully closed with surgery. Ellipsoid zone disruptions were observed by OCT in four eyes (50%) and persisted throughout follow-up (more than 6 months on average). In early clinical results, the authors found a lower macular hole closure rate with ocriplasmin than previously reported. Enlargement was observed in all holes that failed to close with ocriplasmin. The authors found ellipsoid zone disruptions that persisted through 6 months of follow-up after ocriplasmin injection. Further work is needed to investigate the cause for these ellipsoid zone changes. Copyright 2014, SLACK Incorporated.

CLOSING MACULAR HOLES WITH "MACULAR PLUG" WITHOUT GAS TAMPONADE AND POSTOPERATIVE POSTURING.

Science.gov (United States)

Chakrabarti, Meena; Benjamin, Preethi; Chakrabarti, Keya; Chakrabarti, Arup

2017-03-01

To investigate the surgical results of macular hole surgery without gas tamponade or postoperative posturing in patients with Stage 3 and Stage 4 macular holes with ≥500 μm mean base diameter. Retrospective interventional case series. Twenty-six patients with Stage 3 and Stage 4 macular holes. Twenty-six eyes of 26 patients with Stage 3 and Stage 4 macular holes and a mean base diameter of 892.8 ± 349 μm underwent pars plana 23-gauge vitrectomy with broad internal limiting membrane peel (ILM peel), inverted ILM flap repositioning (ILMR), and use of autologous gluconated blood clumps as a macular plug to close the macular hole. No fluid-air exchange, endotamponade, or postoperative posturing was used. The subjects were followed up for 12 months. The anatomical outcome of the procedure was evaluated by fundus examination and optical coherence tomography. Spectral domain optical coherence tomography was used to study the restoration of the outer retinal layer integrity in the postoperative period. The preoperative and postoperative best-corrected visual acuities in logMAR units were compared to evaluate functional outcome. Macular hole closure and best-corrected visual acuity before and after surgery. Twenty-six patients with mean age 62.8 ± 7.3 years, preoperative median best-corrected visual acuity 6/60 (1.0 logMAR units), and a mean base diameter of 892.8 ± 349 μm underwent surgery to close macular holes without gas tamponade or postoperative posturing. Twenty patients (76.9%) were phakic. Twenty eyes (76.92%) had Stage 3 macular holes and 6 eyes (23.10%) had Stage 4 macular holes. After a single surgery, hole closure was achieved in 100% of eyes. The median best-corrected visual acuity improved from 6/60 (1.0 logMAR units) to 6/18 (0.50 logMAR units) (P hole closure with statically significant functional improvement for large Stage 3 and Stage 4 macular holes.

Study on the Growth of Holes in Cold Spraying via Numerical Simulation and Experimental Methods

Directory of Open Access Journals (Sweden)

Guosheng Huang

2016-12-01

Full Text Available Cold spraying is a promising method for rapid prototyping due to its high deposition efficiency and high-quality bonding characteristic. However, many researchers have noticed that holes cannot be replenished and will grow larger and larger once formed, which will significantly decrease the deposition efficiency. No work has yet been done on this problem. In this paper, a computational simulation method was used to investigate the origins of these holes and the reasons for their growth. A thick copper coating was deposited around the pre-drilled, micro-size holes using a cold spraying method on copper substrate to verify the simulation results. The results indicate that the deposition efficiency inside the hole decreases as the hole become deeper and narrower. The repellant force between the particles perpendicular to the impaction direction will lead to porosity if the particles are too close. There is a much lower flattening ratio for successive particles if they are too close at the same location, because the momentum energy contributes to the former particle’s deformation. There is a high probability that the above two phenomena, resulting from high powder-feeding rate, will form the original hole, which will grow larger and larger once it is formed. It is very important to control the powder feeding rate, but the upper limit is yet to be determined by further simulation and experimental investigation.

Simulating school closure policies for cost effective pandemic decision making

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Araz Ozgur M

2012-06-01

Full Text Available Abstract Background Around the globe, school closures were used sporadically to mitigate the 2009 H1N1 influenza pandemic. However, such closures can detrimentally impact economic and social life. Methods Here, we couple a decision analytic approach with a mathematical model of influenza transmission to estimate the impact of school closures in terms of epidemiological and cost effectiveness. Our method assumes that the transmissibility and the severity of the disease are uncertain, and evaluates several closure and reopening strategies that cover a range of thresholds in school-aged prevalence (SAP and closure durations. Results Assuming a willingness to pay per quality adjusted life-year (QALY threshold equal to the US per capita GDP ($46,000, we found that the cost effectiveness of these strategies is highly dependent on the severity and on a willingness to pay per QALY. For severe pandemics, the preferred strategy couples the earliest closure trigger (0.5% SAP with the longest duration closure (24 weeks considered. For milder pandemics, the preferred strategies also involve the earliest closure trigger, but are shorter duration (12 weeks for low transmission rates and variable length for high transmission rates. Conclusions These findings highlight the importance of obtaining early estimates of pandemic severity and provide guidance to public health decision-makers for effectively tailoring school closures strategies in response to a newly emergent influenza pandemic.

Dynamic hole closure behind a deep ocean sediment penetrator

International Nuclear Information System (INIS)

Dzwilewski, P.T.; Karnes, C.H.

1982-01-01

A freefall or boosted penetrator is one concept being considered to dispose of nuclear waste in the deep ocean seabed. For this technique to be acceptable, the sediment must be an effective barrier to the migration of radioactive nuclides, which means that the hole behind the advancing penetrator must close. One mechanism which can cause the hole to close immediately behind the penetrator is the reduction in water pressure in the wake as water tries to follow the penetrator into the sediment. An approximate solution to this complex problem is presented which analyzes the deformation of the sediment with a nonlinear, large displacement and strain, Lagrangian finite-difference computer code (STEALTH). The water was treated by Bernoulli's Principle for flow in a pipe resulting in a pressure boundary condition applied to the sediment surface along the path after passage of the penetrator. Two one-dimensional and eight two-dimensional calculations were performed with various penetrator velocities (15, 30, and 60 m/s) and sediment shear strengths. In two of the calculations, the dynamic pressure reduction was neglected to see if geostatic stresses alone would close the hole. The results of this study showed that geostatic stresses alone would not close the hole but the dynamic pressure reduction would. The largest uncertainty in the analysis was the pressure conditions in the water behind the penetrator in which frictionless, steady-state flow, in a uniform diameter pipe was assumed. A more sophisticated and realistic pressure condition has been formulated and will be implemented in the computer code in the near future

SIMULATIONS OF RECOILING MASSIVE BLACK HOLES IN THE VIA LACTEA HALO

International Nuclear Information System (INIS)

Guedes, J.; Madau, P.; Diemand, J.; Kuhlen, M.; Zemp, M.

2009-01-01

The coalescence of a massive black hole (MBH) binary leads to the gravitational-wave recoil of the system and its ejection from the galaxy core. We have carried out N-body simulations of the motion of a M BH = 3.7 x 10 6 M sun MBH remnant in the 'Via Lactea I' simulation, a Milky Way-sized dark matter halo. The black hole receives a recoil velocity of V kick = 80, 120, 200, 300, and 400 km s -1 at redshift 1.5, and its orbit is followed for over 1 Gyr within a 'live' host halo, subject only to gravity and dynamical friction against the dark matter background. We show that, owing to asphericities in the dark matter potential, the orbit of the MBH is highly nonradial, resulting in a significantly increased decay timescale compared to a spherical halo. The simulations are used to construct a semi-analytic model of the motion of the MBH in a time-varying triaxial Navarro-Frenk-White dark matter halo plus a spherical stellar bulge, where the dynamical friction force is calculated directly from the velocity dispersion tensor. Such a model should offer a realistic picture of the dynamics of kicked MBHs in situations where gas drag, friction by disk stars, and the flattening of the central cusp by the returning black hole are all negligible effects. We find that MBHs ejected with initial recoil velocities V kick ∼> 500 km s -1 do not return to the host center within a Hubble time. In a Milky Way-sized galaxy, a recoiling hole carrying a gaseous disk of initial mass ∼M BH may shine as a quasar for a substantial fraction of its 'wandering' phase. The long decay timescales of kicked MBHs predicted by this study may thus be favorable to the detection of off-nuclear quasar activity.

Autologous transplantation of the internal limiting membrane for refractory macular holes.

Science.gov (United States)

Morizane, Yuki; Shiraga, Fumio; Kimura, Shuhei; Hosokawa, Mio; Shiode, Yusuke; Kawata, Tetsuhiro; Hosogi, Mika; Shirakata, Yukari; Okanouchi, Toshio

2014-04-01

To determine the effectiveness of autologous transplantation of the internal limiting membrane (ILM) for refractory macular holes. Prospective, interventional case series. Ten eyes of 10 consecutive patients who underwent autologous transplantation of the ILM for the treatment of refractory macular holes were studied. The primary diseases in these patients were large idiopathic macular holes that had existed for more than 1 year (4 eyes), a traumatic macular hole (1 eye), myopic foveoschisis (2 eyes), foveoschisis resulting from pit-macular syndrome (2 eyes), and proliferative diabetic retinopathy (1 eye). Apart from the 5 eyes with idiopathic or traumatic macular holes, macular holes developed in the other 5 eyes after initial vitrectomies with ILM removal. In all eyes, regular macular hole surgery failed to achieve closure. The main outcome measures used in this study were macular hole closure and best-corrected visual acuity (BCVA). Macular holes were closed successfully in 9 eyes (90%) after autologous transplantation of the ILM. The postoperative BCVAs were significantly better than the preoperative BCVAs (P = .007, paired t test). Postoperative BCVAs improved by more than 0.2 logarithm of the minimal angle of resolution units in 8 eyes (80%) and were unchanged in 2 eyes (20%). Although this is a pilot study, the results suggest that autologous transplantation of the ILM may contribute to improved anatomic and visual outcomes in the treatment of refractory macular holes and may warrant further investigation. Copyright © 2014 Elsevier Inc. All rights reserved.

Some Recent Developments in Turbulence Closure Modeling

Science.gov (United States)

Durbin, Paul A.

2018-01-01

Turbulence closure models are central to a good deal of applied computational fluid dynamical analysis. Closure modeling endures as a productive area of research. This review covers recent developments in elliptic relaxation and elliptic blending models, unified rotation and curvature corrections, transition prediction, hybrid simulation, and data-driven methods. The focus is on closure models in which transport equations are solved for scalar variables, such as the turbulent kinetic energy, a timescale, or a measure of anisotropy. Algebraic constitutive representations are reviewed for their role in relating scalar closures to the Reynolds stress tensor. Seamless and nonzonal methods, which invoke a single closure model, are reviewed, especially detached eddy simulation (DES) and adaptive DES. Other topics surveyed include data-driven modeling and intermittency and laminar fluctuation models for transition prediction. The review concludes with an outlook.

Music from the heavens - gravitational waves from supermassive black hole mergers in the EAGLE simulations

Science.gov (United States)

Salcido, Jaime; Bower, Richard G.; Theuns, Tom; McAlpine, Stuart; Schaller, Matthieu; Crain, Robert A.; Schaye, Joop; Regan, John

2016-11-01

We estimate the expected event rate of gravitational wave signals from mergers of supermassive black holes that could be resolved by a space-based interferometer, such as the Evolved Laser Interferometer Space Antenna (eLISA), utilizing the reference cosmological hydrodynamical simulation from the EAGLE suite. These simulations assume a Lambda cold dark matter cosmogony with state-of-the-art subgrid models for radiative cooling, star formation, stellar mass loss, and feedback from stars and accreting black holes. They have been shown to reproduce the observed galaxy population with unprecedented fidelity. We combine the merger rates of supermassive black holes in EAGLE with the latest phenomenological waveform models to calculate the gravitational waves signals from the intrinsic parameters of the merging black holes. The EAGLE models predict ˜2 detections per year by a gravitational wave detector such as eLISA. We find that these signals are largely dominated by mergers between seed mass black holes merging at redshifts between z ˜ 2 and z ˜ 1. In order to investigate the dependence on the assumed black hole seed mass, we introduce an additional model with a black hole seed mass an order of magnitude smaller than in our reference model. We also consider a variation of the reference model where a prescription for the expected delays in the black hole merger time-scale has been included after their host galaxies merge. We find that the merger rate is similar in all models, but that the initial black hole seed mass could be distinguished through their detected gravitational waveforms. Hence, the characteristic gravitational wave signals detected by eLISA will provide profound insight into the origin of supermassive black holes and the initial mass distribution of black hole seeds.

Black holes

OpenAIRE

Brügmann, B.; Ghez, A. M.; Greiner, J.

2001-01-01

Recent progress in black hole research is illustrated by three examples. We discuss the observational challenges that were met to show that a supermassive black hole exists at the center of our galaxy. Stellar-size black holes have been studied in x-ray binaries and microquasars. Finally, numerical simulations have become possible for the merger of black hole binaries.

Numerical simulation on reasonable hole-sealing depth of boreholes for gas extraction

Science.gov (United States)

Zhao, Dan; Pan, Jingtao

2018-04-01

To overcome the low efficiency of extracting gas in coal reservoirs with a low gas permeability, some boreholes were drilled for gas extraction in No. 2 coal reservoir of Wangjialing Coalmine in Shanxi Province, China and reasonably sealed. Aiming at shortfalls such as rapid attenuation of volume for extracted gas as well as low gas permeability when using boreholes in the No. 2 coal reservoir, the traditional COMSOL MultiphysicsMT Earth Science Module was used to couple the three governing equations (Darcy-Brinkman-Navier-Stokes) for fluids. On this basis, numerical simulation on the seepage law along the directions of roadways and boreholes was carried out. The simulation results indicated that when the hole-sealing length was within the width range of fractures in roadways, the negative pressure not only led the gas in surrounding rock masses to flow to the boreholes, but also made the air flow in roadways to permeate into coal walls. As a result, gas and air flows both entered into the boreholes through the loosening zone containing fractures, resulting in seepage of air in roadway to the boreholes. The seepage velocity along the roadway direction under condition with a hole-sealing length of 12 m was obviously slower than that when the hole-sealing length was 8 m. While, the method by simply increasing the length of the hole-sealing section for boreholes failed to effectively stop the air flow in roadways from permeating into the coal wall and then entering the boreholes. Moreover, the increase in the hole-sealing length brought about much more difficulties to the hole-sealing construction. So, the method is not operable in practical condition of the coal mine. Therefore, it is necessary to improve the traditional hole-sealing technology based on foamed macromolecular materials which are mainly made of polyurethane (PU) and use the fluid wall-type hole-sealing technology based on solid-liquid coupling. Then, the effects of gas extraction before and after using

Numerical simulation on reasonable hole-sealing depth of boreholes for gas extraction

Directory of Open Access Journals (Sweden)

Dan Zhao

2018-04-01

Full Text Available To overcome the low efficiency of extracting gas in coal reservoirs with a low gas permeability, some boreholes were drilled for gas extraction in No. 2 coal reservoir of Wangjialing Coalmine in Shanxi Province, China and reasonably sealed. Aiming at shortfalls such as rapid attenuation of volume for extracted gas as well as low gas permeability when using boreholes in the No. 2 coal reservoir, the traditional COMSOL MultiphysicsMT Earth Science Module was used to couple the three governing equations (Darcy-Brinkman–Navier-Stokes for fluids. On this basis, numerical simulation on the seepage law along the directions of roadways and boreholes was carried out. The simulation results indicated that when the hole-sealing length was within the width range of fractures in roadways, the negative pressure not only led the gas in surrounding rock masses to flow to the boreholes, but also made the air flow in roadways to permeate into coal walls. As a result, gas and air flows both entered into the boreholes through the loosening zone containing fractures, resulting in seepage of air in roadway to the boreholes. The seepage velocity along the roadway direction under condition with a hole-sealing length of 12 m was obviously slower than that when the hole-sealing length was 8 m. While, the method by simply increasing the length of the hole-sealing section for boreholes failed to effectively stop the air flow in roadways from permeating into the coal wall and then entering the boreholes. Moreover, the increase in the hole-sealing length brought about much more difficulties to the hole-sealing construction. So, the method is not operable in practical condition of the coal mine. Therefore, it is necessary to improve the traditional hole-sealing technology based on foamed macromolecular materials which are mainly made of polyurethane (PU and use the fluid wall-type hole-sealing technology based on solid-liquid coupling. Then, the effects of gas extraction

Molecular origin of differences in hole and electron mobility in amorphous Alq3--a multiscale simulation study.

Science.gov (United States)

Fuchs, Andreas; Steinbrecher, Thomas; Mommer, Mario S; Nagata, Yuki; Elstner, Marcus; Lennartz, Christian

2012-03-28

In order to determine the molecular origin of the difference in electron and hole mobilities of amorphous thin films of Alq(3) (meridional Alq(3) (tris(8-hydroxyquinoline) aluminium)) we performed multiscale simulations covering quantum mechanics, molecular mechanics and lattice models. The study includes realistic disordered morphologies, polarized site energies to describe diagonal disorder, quantum chemically calculated transfer integrals for the off-diagonal disorder, inner sphere reorganization energies and an approximative scheme for outer sphere reorganization energies. Intermolecular transfer rates were calculated via Marcus-theory and mobilities were simulated via kinetic Monte Carlo simulations and by a Master Equation approach. The difference in electron and hole mobility originates from the different localization of charge density in the radical anion (more delocalized) compared to the radical cation (more confined). This results in higher diagonal disorder for holes and less favourable overlap properties for the hole transfer integrals leading to an overall higher electron mobility.

Closure simulation of the MSIV of Unit 1 of the Laguna Verde nuclear power plant using the Simulate 3K code

International Nuclear Information System (INIS)

Alegria A, A.

2015-09-01

In this paper the simulation of closure transient of all main steam isolation valves (MSIV) was performed with the Simulate-3K (S-3K) code for the Unit 1 of the Laguna Verde nuclear power plant (NPP-LV), which operates to thermal power of 2317 MWt, corresponding to the cycle 15 of operation. The set points for the performance of systems correspond to those set out in transient analysis: 3 seconds for the closure of all MSIV; the start of Scram when 121% of the neutron flux is reached, respect from baseline before the transient; the opening by peer of safety relief valves (SRV) in relief mode when the set point of the pressure is reached, the shoot of the feedwater flow seconds after the start of closing of the MSIV and the shoot of the recirculation water pumps when the pressure is reached in the dome of 1048 psig. The simulation time was of 57 seconds, with the top 50 to reach the steady state, from which the closure of all MSIV starts. In this paper the behavior of the pressure in the dome are analyzed, thermal power, neutron flux, the collapsed water level, the flow at the entrance of core, the steam flow coming out of vessel and the flow through of the SRV; the fuel temperature, the minimal critical power ratio, the readings in the instrumentation systems and reactivities. Instrumentation systems were implemented to analyze the neutron flux, these consist of 96 local power range monitors (LPRM) located in different radial and axial positions of the core and 4 channels of average power range monitors, which grouped at 24 LPRM each one. LPRM response to the change of neutron flux in the center of the core, at different axial positions is also shown. Finally, the results show that the safety limit MCPR is not exceeded. (Author)

Magnetohydrodynamic Simulations of Black Hole Accretion

Science.gov (United States)

Avara, Mark J.

Black holes embody one of the few, simple, solutions to the Einstein field equations that describe our modern understanding of gravitation. In isolation they are small, dark, and elusive. However, when a gas cloud or star wanders too close, they light up our universe in a way no other cosmic object can. The processes of magnetohydrodynamics which describe the accretion inflow and outflows of plasma around black holes are highly coupled and nonlinear and so require numerical experiments for elucidation. These processes are at the heart of astrophysics since black holes, once they somehow reach super-massive status, influence the evolution of the largest structures in the universe. It has been my goal, with the body of work comprising this thesis, to explore the ways in which the influence of black holes on their surroundings differs from the predictions of standard accretion models. I have especially focused on how magnetization of the greater black hole environment can impact accretion systems.

Occupancy estimation and the closure assumption

Science.gov (United States)

Rota, Christopher T.; Fletcher, Robert J.; Dorazio, Robert M.; Betts, Matthew G.

2009-01-01

1. Recent advances in occupancy estimation that adjust for imperfect detection have provided substantial improvements over traditional approaches and are receiving considerable use in applied ecology. To estimate and adjust for detectability, occupancy modelling requires multiple surveys at a site and requires the assumption of 'closure' between surveys, i.e. no changes in occupancy between surveys. Violations of this assumption could bias parameter estimates; however, little work has assessed model sensitivity to violations of this assumption or how commonly such violations occur in nature. 2. We apply a modelling procedure that can test for closure to two avian point-count data sets in Montana and New Hampshire, USA, that exemplify time-scales at which closure is often assumed. These data sets illustrate different sampling designs that allow testing for closure but are currently rarely employed in field investigations. Using a simulation study, we then evaluate the sensitivity of parameter estimates to changes in site occupancy and evaluate a power analysis developed for sampling designs that is aimed at limiting the likelihood of closure. 3. Application of our approach to point-count data indicates that habitats may frequently be open to changes in site occupancy at time-scales typical of many occupancy investigations, with 71% and 100% of species investigated in Montana and New Hampshire respectively, showing violation of closure across time periods of 3 weeks and 8 days respectively. 4. Simulations suggest that models assuming closure are sensitive to changes in occupancy. Power analyses further suggest that the modelling procedure we apply can effectively test for closure. 5. Synthesis and applications. Our demonstration that sites may be open to changes in site occupancy over time-scales typical of many occupancy investigations, combined with the sensitivity of models to violations of the closure assumption, highlights the importance of properly addressing

Physical modeling and numerical simulation of V-die forging ingot with central void

DEFF Research Database (Denmark)

Christiansen, Peter; Hattel, Jesper Henri; Bay, Niels

2014-01-01

Numerical simulation and physical modeling performed on small-scale ingots made from pure lead, having a hole drilled through their centerline to mimic porosity, are utilized to characterize the deformation mechanics of a single open die forging compression stage and to identify the influence...... of the lower V-die angle on porosity closure and forging load requirements of large cast ingots. Results show that a lower V-die angle of 120 provides the best closure of centerline porosity without demanding the highest forging loads or developing unreasonably asymmetric shapes that may create difficulties...... in multi-stage open die forging procedures....

LOW-FREQUENCY OSCILLATIONS IN GLOBAL SIMULATIONS OF BLACK HOLE ACCRETION

International Nuclear Information System (INIS)

O'Neill, Sean M.; Reynolds, Christopher S.; Coleman Miller, M.; Sorathia, Kareem A.

2011-01-01

We have identified the presence of large-scale, low-frequency dynamo cycles in a long-duration, global, magnetohydrodynamic (MHD) simulation of black hole accretion. Such cycles have previously been seen in local shearing box simulations, but we discuss their evolution over 1500 inner disk orbits of a global π/4 disk wedge spanning two orders of magnitude in radius and seven scale heights in elevation above/below the disk midplane. The observed cycles manifest themselves as oscillations in azimuthal magnetic field occupying a region that extends into a low-density corona several scale heights above the disk. The cycle frequencies are 10-20 times lower than the local orbital frequency, making them potentially interesting sources of low-frequency variability when scaled to real astrophysical systems. Furthermore, power spectra derived from the full time series reveal that the cycles manifest themselves at discrete, narrowband frequencies that often share power across broad radial ranges. We explore possible connections between these simulated cycles and observed low-frequency quasi-periodic oscillations (LFQPOs) in galactic black hole binary systems, finding that dynamo cycles have the appropriate frequencies and are located in a spatial region associated with X-ray emission in real systems. Derived observational proxies, however, fail to feature peaks with rms amplitudes comparable to LFQPO observations, suggesting that further theoretical work and more sophisticated simulations will be required to form a complete theory of dynamo-driven LFQPOs. Nonetheless, this work clearly illustrates that global MHD dynamos exhibit quasi-periodic behavior on timescales much longer than those derived from test particle considerations.

Value of internal limiting membrane peeling in surgery for idiopathic macular hole and the correlation between function and retinal morphology

DEFF Research Database (Denmark)

Christensen, Ulrik Correll

2009-01-01

conducted a randomized clinical trial including 78 pseudophakic patients with idiopathic macular hole stages 2 and 3. Patients were randomly assigned to macular hole surgery consisting of (i) vitrectomy alone without instrumental retinal surface contact (non-peeling), (ii) vitrectomy plus 0.05% isotonic ICG...... rate than surgery without ILM peeling (95% versus 45%). The overall functional results confirm that surgery for macular hole generally leads to favourable visual results, with two-thirds of eyes regaining reading vision (>or=20/40). Macular hole surgery can be considered a safe procedure with a low...... incidence of sight-threatening adverse events; the retinal detachment rate was 2.2%. Visual outcomes in eyes with primary hole closure were not significantly different between the intervention groups; however, for the stage 2 subgroup with primary macular hole closure, there was a trend towards a better...

Development of an arid site closure plan

International Nuclear Information System (INIS)

Nyhan, J.W.; Barnes, F.J.

1987-01-01

This document describes the development of a prototype plan for the effective closure and stabilization of an arid low-level waste disposal site. This plan will provide demonstrated closure techniques for a trench in a disposal site at Los Alamos. The accuracy of modeling soil water storage by two hydrologic models, CREAMS and HELP, was tested by comparing simulation results with field measurements of soil moisture in eight experimental landfill cover systems having a range of well-defined soil profiles and vegetative covers. Regression analysis showed that CREAMS generally represented soil moisture more accurately than HELP simulations. Precautions for determining parameter values for model input and for interpreting simulation results are discussed. A specific example is presented showing how the field-validated hydrologic models can be used to develop a final prototype closure plan. 15 refs., 13 figs., 3 tabs

Modeling Supermassive Black Holes in Cosmological Simulations

Science.gov (United States)

Tremmel, Michael

My thesis work has focused on improving the implementation of supermassive black hole (SMBH) physics in cosmological hydrodynamic simulations. SMBHs are ubiquitous in mas- sive galaxies, as well as bulge-less galaxies and dwarfs, and are thought to be a critical component to massive galaxy evolution. Still, much is unknown about how SMBHs form, grow, and affect their host galaxies. Cosmological simulations are an invaluable tool for un- derstanding the formation of galaxies, self-consistently tracking their evolution with realistic merger and gas accretion histories. SMBHs are often modeled in these simulations (generally as a necessity to produce realistic massive galaxies), but their implementations are commonly simplified in ways that can limit what can be learned. Current and future observations are opening new windows into the lifecycle of SMBHs and their host galaxies, but require more detailed, physically motivated simulations. Within the novel framework I have developed, SMBHs 1) are seeded at early times without a priori assumptions of galaxy occupation, 2) grow in a way that accounts for the angular momentum of gas, and 3) experience realistic orbital evolution. I show how this model, properly tuned with a novel parameter optimiza- tion technique, results in realistic galaxies and SMBHs. Utilizing the unique ability of these simulations to capture the dynamical evolution of SMBHs, I present the first self-consistent prediction for the formation timescales of close SMBH pairs, precursors to SMBH binaries and merger events potentially detected by future gravitational wave experiments.

Study on the Gap Flow Simulation in EDM Small Hole Machining with Ti Alloy

Directory of Open Access Journals (Sweden)

Shengfang Zhang

2017-01-01

Full Text Available In electrical discharge machining (EDM process, the debris removed from electrode material strongly affects the machining efficiency and accuracy, especially for the deep small hole machining process. In case of Ti alloy, the debris movement and removal process in gap flow between electrodes for small hole EDM process is studied in this paper. Based on the solid-liquid two-phase flow equation, the mathematical model on the gap flow field with flushing and self-adaptive disturbation is developed. In our 3D simulation process, the count of debris increases with number of EDM discharge cycles, and the disturbation generated by the movement of self-adaptive tool in the gap flow is considered. The methods of smoothing and remeshing are also applied in the modeling process to enable a movable tool. Under different depth, flushing velocity, and tool diameter, the distribution of velocity field, pressure field of gap flow, and debris movement are analyzed. The statistical study of debris distribution under different machining conditions is also carried out. Finally, a series of experiments are conducted on a self-made machine to verify the 3D simulation model. The experiment results show the burn mark at hole bottom and the tapered wall, which corresponds well with the simulating conclusion.

Macular morphology and visual acuity after macular hole surgery with or without internal limiting membrane peeling

DEFF Research Database (Denmark)

Christensen, U.C.; Kroyer, K.; Sander, B.

2010-01-01

Aim: To examine postoperative macular morphology and visual outcome after 12 months in relation to internal limiting membrane (ILM) peeling versus no peeling, indocyanine green (ICG) staining and re-operation in eyes that achieved macular hole closure after surgery. Methods: Seventy-four eyes...... with closed stage 2 or 3 macular holes were recruited from a randomised clinical trial comparing: (1) vitrectomy without ILM peeling; (2) vitrectomy with 0.05% isotonic ICG-assisted ILM peeling; and (3) vitrectomy with 0.15% trypan blue-assisted ILM peeling. Contrast-enhanced Stratus optical coherence...... between subgroups. Conclusions: Poor vision after 12 months despite macular hole closure was associated with attenuation and disruption of the foveolar photoreceptor matrix. The extent of attenuation and disruption was independent of peeling and staining....

The impact of rural hospital closures on equity of commuting time for haemodialysis patients: simulation analysis using the capacity-distance model.

Science.gov (United States)

Matsumoto, Masatoshi; Ogawa, Takahiko; Kashima, Saori; Takeuchi, Keisuke

2012-07-23

Frequent and long-term commuting is a requirement for dialysis patients. Accessibility thus affects their quality of lives. In this paper, a new model for accessibility measurement is proposed in which both geographic distance and facility capacity are taken into account. Simulation of closure of rural facilities and that of capacity transfer between urban and rural facilities are conducted to evaluate the impacts of these phenomena on equity of accessibility among dialysis patients. Post code information as of August 2011 of all the 7,374 patients certified by municipalities of Hiroshima prefecture as having first or third grade renal disability were collected. Information on post code and the maximum number of outpatients (capacity) of all the 98 dialysis facilities were also collected. Using geographic information systems, patient commuting times were calculated in two models: one that takes into account road distance (distance model), and the other that takes into account both the road distance and facility capacity (capacity-distance model). Simulations of closures of rural and urban facilities were then conducted. The median commuting time among rural patients was more than twice as long as that among urban patients (15 versus 7 minutes, psimulation, when five rural public facilitiess were closed, Gini coefficient of commuting times among the patients increased by 16%, indicating a substantial worsening of equity, and the number of patients with commuting times longer than 90 minutes increased by 72 times. In contrast, closure of four urban public facilities with similar capacities did not affect these values. Closures of dialysis facilities in rural areas have a substantially larger impact on equity of commuting times among dialysis patients than closures of urban facilities. The accessibility simulations using the capacity-distance model will provide an analytic framework upon which rational resource distribution policies might be planned.

Simulation optimization of filament parameters for uniform depositions of diamond films on surfaces of ultra-large circular holes

Energy Technology Data Exchange (ETDEWEB)

Wang, Xinchang, E-mail: wangxinchangz@163.com; Shen, Xiaotian; Sun, Fanghong; Shen, Bin

2016-12-01

Highlights: • A verified simulation model using a novel filament arrangement is constructed. • Influences of filament parameters are clarified. • A coefficient between simulated and experimental results is proposed. • Orthogonal simulations are adopted to optimize filament parameters. • A general filament arrangement suitable for different conditions is determined. - Abstract: Chemical vapor deposition (CVD) diamond films have been widely applied as protective coatings on varieties of anti-frictional and wear-resistant components, owing to their excellent mechanical and tribological properties close to the natural diamond. In applications of some components, the inner hole surface will serve as the working surface that suffers severe frictional or erosive wear. It is difficult to realize uniform depositions of diamond films on surfaces of inner holes, especially ultra-large inner holes. Adopting a SiC compact die with an aperture of 80 mm as an example, a novel filament arrangement with a certain number of filaments evenly distributed on a circle is designed, and specific effects of filament parameters, including the filament number, arrangement direction, filament temperature, filament diameter, circumradius and the downward translation, on the substrate temperature distribution are studied by computational fluid dynamics (CFD) simulations based on the finite volume method (FVM), adopting a modified computational model well consistent with the actual deposition environment. Corresponding temperature measurement experiments are also conducted to verify the rationality of the computational model. From the aspect of depositing uniform boron-doped micro-crystalline, undoped micro-crystalline and undoped fine-grained composite diamond (BDM-UMC-UFGCD) film on such the inner hole surface, filament parameters as mentioned above are accurately optimized and compensated by orthogonal simulations. Moreover, deposition experiments adopting compensated optimized

Reducing orbital eccentricity in binary black hole simulations

International Nuclear Information System (INIS)

Pfeiffer, Harald P; Brown, Duncan A; Kidder, Lawrence E; Lindblom, Lee; Lovelace, Geoffrey; Scheel, Mark A

2007-01-01

Binary black hole simulations starting from quasi-circular (i.e., zero radial velocity) initial data have orbits with small but nonzero orbital eccentricities. In this paper, the quasi-equilibrium initial-data method is extended to allow nonzero radial velocities to be specified in binary black hole initial data. New low-eccentricity initial data are obtained by adjusting the orbital frequency and radial velocities to minimize the orbital eccentricity, and the resulting (∼5 orbit) evolutions are compared with those of quasi-circular initial data. Evolutions of the quasi-circular data clearly show eccentric orbits, with eccentricity that decays over time. The precise decay rate depends on the definition of eccentricity; if defined in terms of variations in the orbital frequency, the decay rate agrees well with the prediction of Peters (1964 Phys. Rev. 136 1224-32). The gravitational waveforms, which contain ∼8 cycles in the dominant l = m = 2 mode, are largely unaffected by the eccentricity of the quasi-circular initial data. The overlap between the dominant mode in the quasi-circular evolution and the same mode in the low-eccentricity evolution is about 0.99

Simulation of hole-mobility in doped relaxed and strained Ge layers

Science.gov (United States)

Watling, Jeremy R.; Riddet, Craig; Chan, Morgan Kah H.; Asenov, Asen

2010-11-01

As silicon based metal-oxide-semiconductor field-effect transistors (MOSFETs) are reaching the limits of their performance with scaling, alternative channel materials are being considered to maintain performance in future complementary metal-oxide semiconductor technology generations. Thus there is renewed interest in employing Ge as a channel material in p-MOSFETs, due to the significant improvement in hole mobility as compared to Si. Here we employ full-band Monte Carlo to study hole transport properties in Ge. We present mobility and velocity-field characteristics for different transport directions in p-doped relaxed and strained Ge layers. The simulations are based on a method for over-coming the potentially large dynamic range of scattering rates, which results from the long-range nature of the unscreened Coulombic interaction. Our model for ionized impurity scattering includes the affects of dynamic Lindhard screening, coupled with phase-shift, and multi-ion corrections along with plasmon scattering. We show that all these effects play a role in determining the hole carrier transport in doped Ge layers and cannot be neglected.

Reconnection-driven Magnetohydrodynamic Turbulence in a Simulated Coronal-hole Jet

Energy Technology Data Exchange (ETDEWEB)

Uritsky, Vadim M.; Roberts, Merrill A. [Catholic University of America, 620 Michigan Avenue NE, Washington, DC 20064 (United States); DeVore, C. Richard; Karpen, Judith T., E-mail: vadim.uritsky@nasa.gov [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2017-03-10

Extreme-ultraviolet and X-ray jets occur frequently in magnetically open coronal holes on the Sun, especially at high solar latitudes. Some of these jets are observed by white-light coronagraphs as they propagate through the outer corona toward the inner heliosphere, and it has been proposed that they give rise to microstreams and torsional Alfvén waves detected in situ in the solar wind. To predict and understand the signatures of coronal-hole jets, we have performed a detailed statistical analysis of such a jet simulated by an adaptively refined magnetohydrodynamics model. The results confirm the generation and persistence of three-dimensional, reconnection-driven magnetic turbulence in the simulation. We calculate the spatial correlations of magnetic fluctuations within the jet and find that they agree best with the Müller–Biskamp scaling model including intermittent current sheets of various sizes coupled via hydrodynamic turbulent cascade. The anisotropy of the magnetic fluctuations and the spatial orientation of the current sheets are consistent with an ensemble of nonlinear Alfvén waves. These properties also reflect the overall collimated jet structure imposed by the geometry of the reconnecting magnetic field. A comparison with Ulysses observations shows that turbulence in the jet wake is in quantitative agreement with that in the fast solar wind.

New methods to benchmark simulations of accreting black holes systems against observations

Science.gov (United States)

Markoff, Sera; Chatterjee, Koushik; Liska, Matthew; Tchekhovskoy, Alexander; Hesp, Casper; Ceccobello, Chiara; Russell, Thomas

2017-08-01

The field of black hole accretion has been significantly advanced by the use of complex ideal general relativistic magnetohydrodynamics (GRMHD) codes, now capable of simulating scales from the event horizon out to ~10^5 gravitational radii at high resolution. The challenge remains how to test these simulations against data, because the self-consistent treatment of radiation is still in its early days, and is complicated by dependence on non-ideal/microphysical processes not yet included in the codes. On the other extreme, a variety of phenomenological models (disk, corona, jet, wind) can well-describe spectra or variability signatures in a particular waveband, although often not both. To bring these two methodologies together, we need robust observational “benchmarks” that can be identified and studied in simulations. I will focus on one example of such a benchmark, from recent observational campaigns on black holes across the mass scale: the jet break. I will describe new work attempting to understand what drives this feature by searching for regions that share similar trends in terms of dependence on accretion power or magnetisation. Such methods can allow early tests of simulation assumptions and help pinpoint which regions will dominate the light production, well before full radiative processes are incorporated, and will help guide the interpretation of, e.g. Event Horizon Telescope data.

The impact of rural hospital closures on equity of commuting time for haemodialysis patients: simulation analysis using the capacity-distance model

Directory of Open Access Journals (Sweden)

Matsumoto Masatoshi

2012-07-01

Full Text Available Abstract Background Frequent and long-term commuting is a requirement for dialysis patients. Accessibility thus affects their quality of lives. In this paper, a new model for accessibility measurement is proposed in which both geographic distance and facility capacity are taken into account. Simulation of closure of rural facilities and that of capacity transfer between urban and rural facilities are conducted to evaluate the impacts of these phenomena on equity of accessibility among dialysis patients. Methods Post code information as of August 2011 of all the 7,374 patients certified by municipalities of Hiroshima prefecture as having first or third grade renal disability were collected. Information on post code and the maximum number of outpatients (capacity of all the 98 dialysis facilities were also collected. Using geographic information systems, patient commuting times were calculated in two models: one that takes into account road distance (distance model, and the other that takes into account both the road distance and facility capacity (capacity-distance model. Simulations of closures of rural and urban facilities were then conducted. Results The median commuting time among rural patients was more than twice as long as that among urban patients (15 versus 7 minutes, p  Conclusions Closures of dialysis facilities in rural areas have a substantially larger impact on equity of commuting times among dialysis patients than closures of urban facilities. The accessibility simulations using thecapacity-distance model will provide an analytic framework upon which rational resource distribution policies might be planned.

Numerical Simulation and Optimization of Hole Spacing for Cement Grouting in Rocks

Directory of Open Access Journals (Sweden)

Ping Fu

2013-01-01

Full Text Available The fine fissures of V-diabase were the main stratigraphic that affected the effectiveness of foundation grout curtain in Dagang Mountain Hydropower Station. Thus, specialized in situ grouting tests were conducted to determine reasonable hole spacing and other parameters. Considering time variation of the rheological parameters of grout, variation of grouting pressure gradient, and evolution law of the fracture opening, numerical simulations were performed on the diffusion process of cement grouting in the fissures of the rock mass. The distribution of permeability after grouting was obtained on the basis of analysis results, and the grouting hole spacing was discussed based on the reliability analysis. A probability of optimization along with a finer optimization precision as 0.1 m could be adopted when compared with the accuracy of 0.5 m that is commonly used. The results could provide a useful reference for choosing reasonable grouting hole spacing in similar projects.

Value of internal limiting membrane peeling in surgery for idiopathic macular hole stage 2 and 3: a randomised clinical trial

DEFF Research Database (Denmark)

Christensen, U C; Krøyer, K; Sander, B

2009-01-01

AIM: To determine the effect of internal limiting membrane (ILM) peeling on anatomical and functional success rates in stage 2 and 3 idiopathic macular hole surgery (MHS). METHODS: Randomised clinical trial of stage 2 and 3 idiopathic macular hole without visible epiretinal fibrosis and with less...... than 1 year's duration of symptoms. Eyes were randomised to (1) vitrectomy alone without retinal surface manipulation, (2) vitrectomy plus 0.05% isotonic Indocyanine Green (ICG)-assisted ILM peeling or (3) vitrectomy plus 0.15% Trypan Blue (TB)-assisted ILM peeling. Main outcomes were hole closure...... after 3 and 12 months and best-corrected visual acuity after 12 months. RESULTS: 78 eyes were enrolled. Primary closure rates were significantly higher with ILM peeling than without peeling for both stage 2 holes (ICG peeling 100%, non-peeling 55%, p = 0.014) and for stage 3 holes (ICG peeling 91%, TB...

PIMS (Positioning In Macular hole Surgery) trial - a multicentre interventional comparative randomised controlled clinical trial comparing face-down positioning, with an inactive face-forward position on the outcome of surgery for large macular holes: study protocol for a randomised controlled trial.

Science.gov (United States)

Pasu, Saruban; Bunce, Catey; Hooper, Richard; Thomson, Ann; Bainbridge, James

2015-11-17

Idiopathic macular holes are an important cause of blindness. They have an annual incidence of 8 per 100,000 individuals, and prevalence of 0.2 to 3.3 per 1000 individuals with visual impairment. The condition occurs more frequently in adults aged 75 years or older. Macular holes can be repaired by surgery in which the causative tractional forces in the eye are released and a temporary bubble of gas is injected. To promote successful hole closure individuals may be advised to maintain a face-down position for up to 10 days following surgery. The aim of this study is to determine whether advice to position face-down improves the surgical success rate of closure of large (>400 μm) macular holes, and thereby reduces the need for further surgery. This will be a multicentre interventional, comparative randomised controlled clinical trial comparing face-down positioning with face-forward positioning. At the conclusion of standardised surgery across all sites, participants still eligible for inclusion will be allocated randomly 1:1 to 1 of the 2 treatment arms stratified by site, using random permuted blocks of size 4 or 6 in equal proportions. We will recruit 192 participants having surgery for large macular holes (>400 μm); 96 in each of the 2 arms of the study. The primary objective is to determine the impact of face-down positioning on the likelihood of closure of large (≥400 μm) full-thickness macular holes following surgery. This will be the first multicentre randomised control trial to investigate the value of face-down positioning following macular hole standardised surgery. UK CRN: 17966 (date of registration 26 November 2014).

SURGICAL OUTCOMES AFTER INVERTED INTERNAL LIMITING MEMBRANE FLAP VERSUS CONVENTIONAL PEELING FOR VERY LARGE MACULAR HOLES.

Science.gov (United States)

Narayanan, Raja; Singh, Sumit R; Taylor, Stanford; Berrocal, Maria H; Chhablani, Jay; Tyagi, Mudit; Ohno-Matsui, Kyoko; Pappuru, Rajeev R; Apte, Rajendra S

2018-04-23

To evaluate the anatomical and visual outcomes of inverted flap technique of peeling of internal limiting membrane (ILM) versus standard peeling of ILM for macular holes of basal diameter more than 800 μm. Patients with very large idiopathic macular holes more than 800 μm in basal diameter (ranging from 243 μm to 840 μm in minimum diameter) were retrospectively included in the study. In Group A, 18 eyes of 18 patients underwent ILM peeling using the inverted flap technique. In Group B, 18 eyes of 18 patients underwent conventional ILM peeling. The primary endpoint was the rate of hole closure at 6 months after surgery. The secondary outcome measure was the change in best-corrected visual acuity at 6 months after surgery. There were no significant differences in ocular characteristics of the study groups at baseline except for the age distribution. Mean macular hole diameter was 1,162.8 ± 206.0 μm and 1,229.6 ± 228.1 μm in Group A and Group B, respectively. The hole closure rate was 88.9% (16/18) in Group A and 77.8% (14/18) in Group B (P = 0.66). The mean gain in best-corrected visual acuity was higher in Group A than in Group B (P = 0.12) at 6 months, but this was not statistically significant. There were no severe ocular adverse events in either group. In this multicenter series, inverted ILM flap technique did not lead to significantly higher anatomical closure rates than conventional ILM peeling in large macular holes more than 800 μm in diameter.

Numerical simulation of residual stresses at holes near edges and corners in tempered glass: A parametric study

DEFF Research Database (Denmark)

Pourmoghaddam, Navid; Nielsen, Jens Henrik; Schneider, Jens

2016-01-01

This work presents 3D results of the thermal tempering simulation by the Finite Element Method in order to calculate the residual stresses in the area of the holes near edges and corners of a tem-pered glass plate. A viscoelastic material behavior of the glass is considered for the tempering...... process. The structural relaxation is taken into account using Narayanaswamy’s model. The motiva-tion for this work is to study the effect of the reduction of the hole and edge minimum distances, which are defined according to EN 12150-1. It is the objective of the paper to demonstrate and elucidate...... the influence of the hole and edge distances on the minimal residual compressive stress-es at holes after the tempering process. The residual stresses in the area of the holes are calculat-ed varying the following parameters: the hole diameter, the plate thickness and the interaction between holes and edges...

RELAP-7 Closure Correlations

Energy Technology Data Exchange (ETDEWEB)

Zou, Ling [Idaho National Lab. (INL), Idaho Falls, ID (United States); Berry, R. A. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Martineau, R. C. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Andrs, D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Zhang, H. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hansel, J. E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Sharpe, J. P. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Johns, Russell C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-04-01

The RELAP-7 code is the next generation nuclear reactor system safety analysis code being developed at the Idaho National Laboratory (INL). The code is based on the INL’s modern scientific software development framework, MOOSE (Multi-Physics Object Oriented Simulation Environment). The overall design goal of RELAP-7 is to take advantage of the previous thirty years of advancements in computer architecture, software design, numerical integration methods, and physical models. The end result will be a reactor systems analysis capability that retains and improves upon RELAP5’s and TRACE’s capabilities and extends their analysis capabilities for all reactor system simulation scenarios. The RELAP-7 code utilizes the well-posed 7-equation two-phase flow model for compressible two-phase flow. Closure models used in the TRACE code has been reviewed and selected to reflect the progress made during the past decades and provide a basis for the colure correlations implemented in the RELAP-7 code. This document provides a summary on the closure correlations that are currently implemented in the RELAP-7 code. The closure correlations include sub-grid models that describe interactions between the fluids and the flow channel, and interactions between the two phases.

X-Ray Spectra from MHD Simulations of Accreting Black Holes

Science.gov (United States)

Schnittman, Jeremy D.; Krolik, Julian H.; Noble, Scott C.

2012-01-01

We present the results of a new global radiation transport code coupled to a general relativistic magneto-hydrodynamic simulation of an accreting, nonrotating black hole. For the first time, we are able to explain from first principles in a self-consistent way the X-ray spectra observed from stellar-mass black holes, including a thermal peak, Compton reflection hump, power-law tail, and broad iron line. Varying only the mass accretion rate, we are able to reproduce the low/hard, steep power-law, and thermal-dominant states seen in most galactic black hole sources. The temperature in the corona is T(sub e) 10 keV in a boundary layer near the disk and rises smoothly to T(sub e) greater than or approximately 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to approximately equal to 6M as the accretion rate decreases, we find that the shape of the Fe Ka line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.

Macular hole formation, progression, and surgical repair: case series of serial optical coherence tomography and time lapse morphing video study

Science.gov (United States)

2010-01-01

Background To use a new medium to dynamically visualize serial optical coherence tomography (OCT) scans in order to illustrate and elucidate the pathogenesis of idiopathic macular hole formation, progression, and surgical closure. Case Presentations Two patients at the onset of symptoms with early stage macular holes and one patient following repair were followed with serial OCTs. Images centered at the fovea and at the same orientation were digitally exported and morphed into an Audiovisual Interleaving (avi) movie format. Morphing videos from serial OCTs allowed the OCTs to be viewed dynamically. The videos supported anterior-posterior vitreofoveal traction as the initial event in macular hole formation. Progression of the macular hole occurred with increased cystic thickening of the fovea without evidence of further vitreofoveal traction. During cyst formation, the macular hole enlarged as the edges of the hole became elevated from the retinal pigment epithelium (RPE) with an increase in subretinal fluid. Surgical repair of a macular hole revealed initial closure of the macular hole with subsequent reabsorption of the sub-retinal fluid and restoration of the foveal contour. Conclusions Morphing videos from serial OCTs are a useful tool and helped illustrate and support anterior-posterior vitreofoveal traction with subsequent retinal hydration as the pathogenesis of idiopathic macular holes. PMID:20849638

Frictional effects between Overton sand and a simulated casing for a bore hole

International Nuclear Information System (INIS)

Dong, R.G.

1975-01-01

A series of tests were run to simulate the frictional effects between Overton sand and the casing for a bore hole for an underground nuclear test. The objective was to find a description for this frictional interaction which can be applied to an analysis of stemming materials under field conditions

THREE-DIMENSIONAL SIMULATIONS OF VERTICAL MAGNETIC FLUX IN THE IMMEDIATE VICINITY OF BLACK HOLES

International Nuclear Information System (INIS)

Punsly, Brian; Igumenshchev, Igor V.; Hirose, Shigenobu

2009-01-01

This article reports on three-dimensional MHD simulations of non-rotating and rapidly rotating black holes and the adjacent black hole accretion disk magnetospheres. A particular emphasis is placed on the vertical magnetic flux that is advected inward from large radii and threads the equatorial plane near the event horizon. In both cases of non-rotating and rotating black holes, the existence of a significant vertical magnetic field in this region is like a switch that creates powerful jets. There are many similarities in the vertical flux dynamics in these two cases in spite of the tremendous enhancement of azimuthal twisting of the field lines and enhancement of the jet power because of an 'ergospheric disk' in the Kerr metric. A three-dimensional approach is essential because two-dimensional axisymmetric flows are incapable of revealing the nature of the vertical flux near a black hole. Poloidal field lines from the ergospheric accretion region have been visualized in three dimensions and much of the article is devoted to a formal classification of the different manifestations of the vertical flux in the Kerr case.

[Functional and Anatomic Outcomes of Primary and Secondary Internal Limiting Membrane Transplantation in Large and Persistent Macular Holes].

Science.gov (United States)

Hess, Jelka A; Michels, Stephan; Becker, Matthias D

2017-11-20

Background The gold standard therapy for full-thickness macular holes (FTMH) is vitrectomy (PPV) with peeling of the internal limiting membrane (ILM), gas tamponade of the vitreous cavity and postoperative face-down positioning. Nevertheless, eyes with large macular holes (> 400 µm) and surgical failures remain difficult to manage. Recently, ILM transplantation (ILM-TX) techniques were developed with acceptable results, advocating different mechanisms of hole closure: in such a setting, the ILM could serve as a scaffold for neuronal tissue in the pedicle ILM flap technique or the ILM could induce a contraction of the FTMH rims through shrinking of a folded ILM plug. Patients/Material and Methods This retrospective study evaluates the functional and anatomic outcomes following ILM-TX for large FTMH and failed FMTH surgery. Large holes (group 1) were treated by the pedicle flap and the plug technique. Persistent holes following vitrectomy and ILM peeling (group 2) were treated with the plug technique. All ILM-TX were performed under perfluorocarbon liquid (PFCL) with a subsequent silicone oil tamponade. Results In group 1 (6 eyes), three eyes had a free ILM graft and three eyes underwent a pedunculated ILM-TX. The mean best corrected visual acuity (BCVA, LogMar) before primary ILM-TX was 1.18 ± 0.54 with a mean initial hole size of 681 ± 106 µm and a photoreceptor defect (PRD) of 1829 ± 474 µm. Five of six eyes showed a postoperative anatomical macular hole closure (83%). The mean BCVA after a mean follow-up of 9.3 ± 5.1 months was 0.83 ± 0.31 after a free ILM graft and 0.95 ± 0.79 after a pedunculated ILM flap. The PRD reduced to 1781 ± 713 µm after a free ILM graft and 1148 ± 378 µm after a pedunculated ILM flap. In group 2 (7 eyes), all patients had failed initial macular hole surgery closure. Prior to free ILM-TX BCVA was 1.05 ± 0.41, the hole size was 433 ± 183 µm and PRD was 2012 ± 718�

General Relativistic Simulations of Magnetized Plasmas Around Merging Supermassive Black Holes

Science.gov (United States)

Giacomazzo, Bruno; Baker, John G.; Miller, M. Coleman; Reynolds, Christopher S.; van Meter, James R.

2012-01-01

Coalescing supermassive black hole binaries are produced by the mergers of galaxies and are the most powerful sources of gravitational waves accessible to space-based gravitational observatories. Some such mergers may occur in the presence of matter and magnetic fields and hence generate an electromagnetic counterpart. In this paper we present the first general relativistic simulations of magnetized plasma around merging supermassive black holes using the general relativistic magnetohydrodynamic code Whisky. By considering different magnetic field strengths, going from non-magnetically dominated to magnetically dominated regimes, we explore how magnetic fields affect the dynamics of the plasma and the possible emission of electromagnetic signals. In particular we observe, total amplification of the magnetic field of approx 2 orders of magnitude which is driven by the accretion onto the binary and that leads to stronger electromagnetic signals than in the force-free regime where such amplifications are not possible.

Optimal management of idiopathic macular holes.

Science.gov (United States)

Madi, Haifa A; Masri, Ibrahim; Steel, David H

2016-01-01

This review evaluates the current surgical options for the management of idiopathic macular holes (IMHs), including vitrectomy, ocriplasmin (OCP), and expansile gas use, and discusses key background information to inform the choice of treatment. An evidence-based approach to selecting the best treatment option for the individual patient based on IMH characteristics and patient-specific factors is suggested. For holes without vitreomacular attachment (VMA), vitrectomy is the only option with three key surgical variables: whether to peel the inner limiting membrane (ILM), the type of tamponade agent to be used, and the requirement for postoperative face-down posturing. There is a general consensus that ILM peeling improves primary anatomical hole closure rate; however, in small holes (holes, but large (>400 µm) and chronic holes (>1-year history) are usually treated with long-acting gas and posturing. Several studies on posturing and gas choice were carried out in combination with ILM peeling, which may also influence the gas and posturing requirement. Combined phacovitrectomy appears to offer more rapid visual recovery without affecting the long-term outcomes of vitrectomy for IMH. OCP is licensed for use in patients with small- or medium-sized holes and VMA. A greater success rate in using OCP has been reported in smaller holes, but further predictive factors for its success are needed to refine its use. It is important to counsel patients realistically regarding the rates of success with intravitreal OCP and its potential complications. Expansile gas can be considered as a further option in small holes with VMA; however, larger studies are required to provide guidance on its use.

Simulation of perovskite solar cells with inorganic hole transporting materials

DEFF Research Database (Denmark)

Wang, Yan; Xia, Zhonggao; Liu, Yiming

2015-01-01

Device modeling organolead halide perovskite solar cells with planar architecture based on inorganic hole transporting materials (HTMs) were performed. A thorough understanding of the role of the inorganic HTMs and the effect of band offset between HTM/absorber layers is indispensable for further...... improvement in power conversion efficiency (PCE). Here, we investigated the effect of band offset between inorganic HTM/absorber layers. The solar cell simulation program adopted in this work is named wxAMPS, an updated version of the AMPS tool (Analysis of Microelectronic and Photonic Structure)....

Efficacy of vitrectomy with triamcinolone assistance versus internal limiting membrane peeling for highly myopic macular hole retinal detachment.

Science.gov (United States)

Wei, Yong; Wang, Ningli; Zu, Zhongqiao; Bi, Chuncao; Wang, Huaizhou; Chen, Fenghua; Yang, Xingguang

2013-06-01

To compare the outcomes of pars plana vitrectomy (PPV) with or without the adjuvant surgical procedures: triamcinolone acetonide (TA) assistance and/or internal limiting membrane (ILM) peeling for the treatment of highly myopic macular hole retinal detachment (MHRD). Case-control study. Pars plana vitrectomy combined with 2 kinds of adjuvant surgical procedures were used on 96 highly myopic eyes with MHRD. These eyes were assigned to 4 groups randomly: Group 1, non-TA-assisted PPV and without ILM peeling; Group 2, non-TA-assisted PPV with ILM peeling; Group 3, TA-assisted PPV and without ILM peeling; Group 4, TA-assisted PPV with ILM peeling. Anatomical reattachment of the retina, macular hole closure, and best-corrected visual acuity were measured. The rates of both retinal reattachment and macular hole closure were higher in Group 2 (84.0 and 44.0%) and Group 3 (80.8 and 46.2%) than Group 1 (73.9 and 17.4%); however, there were no differences between Group 2 and Group 3 (P > 0.05). The rates of macular hole closure were extremely low in Group 1 and also in eyes with extreme long axial lengths (≥29.0 mm), "severe" chorioretinal atrophy, and posterior staphyloma. Pars plana vitrectomy with either TA assistance or ILM peeling was effective for the treatment of highly myopic MHRD. If you peel the ILM, adding TA does not affect closure rates; and if TA is used to visualize the vitreous, ILM peeling may not be necessary in MHRD. There was a lower anatomical success rate in MHRD with extreme long axial lengths, severe chorioretinal atrophy, and posterior staphyloma.

BHDD: Primordial black hole binaries code

Science.gov (United States)

Kavanagh, Bradley J.; Gaggero, Daniele; Bertone, Gianfranco

2018-06-01

BHDD (BlackHolesDarkDress) simulates primordial black hole (PBH) binaries that are clothed in dark matter (DM) halos. The software uses N-body simulations and analytical estimates to follow the evolution of PBH binaries formed in the early Universe.

Evaluation of the Momentum Closure Schemes in MPAS-Ocean

Science.gov (United States)

Zhao, Shimei; Liu, Yudi; Liu, Wei

2018-04-01

In order to compare and evaluate the performances of the Laplacian viscosity closure, the biharmonic viscosity closure, and the Leith closure momentum schemes in the MPAS-Ocean model, a variety of physical quantities, such as the relative reference potential energy (RPE) change, the RPE time change rate (RPETCR), the grid Reynolds number, the root mean square (RMS) of kinetic energy, and the spectra of kinetic energy and enstrophy, are calculated on the basis of results of a 3D baroclinic periodic channel. Results indicate that: 1) The RPETCR demonstrates a saturation phenomenon in baroclinic eddy tests. The critical grid Reynolds number corresponding to RPETCR saturation differs between the three closures: the largest value is in the biharmonic viscosity closure, followed by that in the Laplacian viscosity closure, and that in the Leith closure is the smallest. 2) All three closures can effectively suppress spurious dianeutral mixing by reducing the grid Reynolds number under sub-saturation conditions of the RPETCR, but they can also damage certain physical processes. Generally, the damage to the rotation process is greater than that to the advection process. 3) The dissipation in the biharmonic viscosity closure is strongly dependent on scales. Most dissipation concentrates on small scales, and the energy of small-scale eddies is often transferred to large-scale kinetic energy. The viscous dissipation in the Laplacian viscosity closure is the strongest on various scales, followed by that in the Leith closure. Note that part of the small-scale kinetic energy is also transferred to large-scale kinetic energy in the Leith closure. 4) The characteristic length scale L and the dimensionless parameter D in the Leith closure are inherently coupled. The RPETCR is inversely proportional to the product of D and L. When the product of D and L is constant, both the simulated RPETCR and the inhibition of spurious dianeutral mixing are the same in all tests using the Leith

Autonomic Closure for Turbulent Flows Using Approximate Bayesian Computation

Science.gov (United States)

Doronina, Olga; Christopher, Jason; Hamlington, Peter; Dahm, Werner

2017-11-01

Autonomic closure is a new technique for achieving fully adaptive and physically accurate closure of coarse-grained turbulent flow governing equations, such as those solved in large eddy simulations (LES). Although autonomic closure has been shown in recent a priori tests to more accurately represent unclosed terms than do dynamic versions of traditional LES models, the computational cost of the approach makes it challenging to implement for simulations of practical turbulent flows at realistically high Reynolds numbers. The optimization step used in the approach introduces large matrices that must be inverted and is highly memory intensive. In order to reduce memory requirements, here we propose to use approximate Bayesian computation (ABC) in place of the optimization step, thereby yielding a computationally-efficient implementation of autonomic closure that trades memory-intensive for processor-intensive computations. The latter challenge can be overcome as co-processors such as general purpose graphical processing units become increasingly available on current generation petascale and exascale supercomputers. In this work, we outline the formulation of ABC-enabled autonomic closure and present initial results demonstrating the accuracy and computational cost of the approach.

2003 Initial Assessments of Closure for the C Tank Farm Field Investigation Report (FIR):Numerical Simulations

International Nuclear Information System (INIS)

Zhang, Z F.; Freedman, Vicky L.; White, Mark D.

2003-01-01

In support of CH2M HILL Hanford Group, Inc.'s (CHG) preparation of a Field Investigative Report (FIR) for the closure of the Hanford Site Single-Shell Tank (SST) Waste Management Area (WMA) tank farms, a set of numerical simulations of flow and solute transport was executed to predict the performance of surface barriers for reducing long-term risks from potential groundwater contamination at the C Farm WMA. This report documents the simulation of 14 cases (and two verification cases) involving two-dimensional cross sections through the C Farm WMA tanks C-103 - C-112. Utilizing a unit release scenario at Tank C-112, four different types of leaks were simulated. These simulations assessed the impact of leakage during retrieval, past leaks, and tank residual wastes and tank ancillary equipment following closure activities. . Two transported solutes were considered: uranium-238 (U-238) and technetium-99 (Tc-99). To evaluate the impact of sorption to the subsurface materials, six different retardation coefficients were simulated for U-238. Overall, simulations results for the C Farm WMA showed that only a small fraction of the U-238 with retardation factors greater than 0.6 migrated from the vadose zone in all of the cases. For the conservative solute, Tc-99, results showed that the simulations investigating leakages during retrieval demonstrated the highest WMA peak concentrations and the earliest arrival times due to the high infiltration rate before the use of surface barriers and the addition of water into the system. Simulations investigating past leaks showed similar peaks and arrival times as the retrieval leak cases. Several different release rates were used to investigate contaminant transport from residual tank wastes. All showed similar peak concentrations and arrival times, except for the lowest initial release rate, which was 1,000 times slower than the highest release rate. Past leaks were also investigated with different release rate models, including

Computer simulation of the formation of Langmuir solitons and holes in a cylindrical magnetized plasma column

International Nuclear Information System (INIS)

Turikov, V.A.

1978-06-01

Nonlinear plasma oscillations in a cylindrical plasma resulting from a short localized external excitation are examined by means of a particle-in-cell simulation scheme. Computer calculations are performed for describing the experimental results obtained in a single-ended Q-machine plasma in a cylindrical waveguide. It is assumed that there is a strong magnetic field in the direction of the column axis. When the amplitude of the excitation potential is close to the kinetic energy of electrons having a phase velocity of the electron plasma wave, the formation is observed of solitons and holes in phase space. After formation, the solitons and holes move with constant velocities. The velocities of solitons are close to the wave-phase velocity, while holes move with smaller velocities. When the external potential amplitude is increased, there is a tendency that the number of holes grows. The potential amplitude of the self-consistent field in the soliton region damps in time with increasing soliton width. The potential profile of the hole does not change after its formation. (Auth.)

When Supermassive Black Holes Wander

Science.gov (United States)

Kohler, Susanna

2018-05-01

Are supermassive black holes found only at the centers of galaxies? Definitely not, according to a new study in fact, galaxies like the Milky Way may harbor several such monsters wandering through their midst.Collecting Black Holes Through MergersIts generally believed that galaxies are built up hierarchically, growing in size through repeated mergers over time. Each galaxy in a major merger likely hosts a supermassive black hole a black hole of millions to billions of times the mass of the Sun at its center. When a pair of galaxies merges, their supermassive black holes will often sink to the center of the merger via a process known as dynamical friction. There the supermassive black holes themselves will eventually merge in a burst of gravitational waves.Spatial distribution and velocities of wandering supermassive black holes in three of the authors simulated galaxies, shown in edge-on (left) and face-on (right) views of the galaxy disks. Click for a closer look. [Tremmel et al. 2018]But if a galaxy the size of the Milky Way was built through a history of many major galactic mergers, are we sure that all its accumulated supermassive black holes eventually merged at the galactic center? A new study suggests that some of these giants might have escaped such a fate and they now wander unseen on wide orbits through their galaxies.Black Holes in an Evolving UniverseLed by Michael Tremmel (Yale Center for Astronomy Astrophysics), a team of scientists has used data from a large-scale cosmological simulation, Romulus25, to explore the possibility of wandering supermassive black holes. The Romulus simulations are uniquely suited to track the formation and subsequent orbital motion of supermassive black holes as galactic halos are built up through mergers over the history of the universe.From these simulations, Tremmel and collaborators find an end total of 316 supermassive black holes residing within the bounds of 26 Milky-Way-mass halos. Of these, roughly a third are

Low-scale gravity black holes at LHC

CERN Document Server

Regos, E; Gamsizkan, H; Trocsanyi, Z

2009-01-01

We search for extra dimensions by looking for black holes at LHC. Theoretical investigations provide the basis for the collider experiments. We use black hole generators to simulate the experimental signatures (colour, charge, spectrum of emitted particles, missing transverse energy) of black holes at LHC in models with TeV scale quantum gravity, rotation, fermion splitting, brane tension and Hawking radiation. We implement the extra-dimensional simulations at the CMS data analysis and test further beyond standard models of black holes too.

GPU-accelerated simulations of isolated black holes

Science.gov (United States)

Lewis, Adam G. M.; Pfeiffer, Harald P.

2018-05-01

We present a port of the numerical relativity code SpEC which is capable of running on NVIDIA GPUs. Since this code must be maintained in parallel with SpEC itself, a primary design consideration is to perform as few explicit code changes as possible. We therefore rely on a hierarchy of automated porting strategies. At the highest level we use TLoops, a C++ library of our design, to automatically emit CUDA code equivalent to tensorial expressions written into C++ source using a syntax similar to analytic calculation. Next, we trace out and cache explicit matrix representations of the numerous linear transformations in the SpEC code, which allows these to be performed on the GPU using pre-existing matrix-multiplication libraries. We port the few remaining important modules by hand. In this paper we detail the specifics of our port, and present benchmarks of it simulating isolated black hole spacetimes on several generations of NVIDIA GPU.

Defining Higher-Order Turbulent Moment Closures with an Artificial Neural Network and Random Forest

Science.gov (United States)

McGibbon, J.; Bretherton, C. S.

2017-12-01

Unresolved turbulent advection and clouds must be parameterized in atmospheric models. Modern higher-order closure schemes depend on analytic moment closure assumptions that diagnose higher-order moments in terms of lower-order ones. These are then tested against Large-Eddy Simulation (LES) higher-order moment relations. However, these relations may not be neatly analytic in nature. Rather than rely on an analytic higher-order moment closure, can we use machine learning on LES data itself to define a higher-order moment closure?We assess the ability of a deep artificial neural network (NN) and random forest (RF) to perform this task using a set of observationally-based LES runs from the MAGIC field campaign. By training on a subset of 12 simulations and testing on remaining simulations, we avoid over-fitting the training data.Performance of the NN and RF will be assessed and compared to the Analytic Double Gaussian 1 (ADG1) closure assumed by Cloudy Layers Unified By Binormals (CLUBB), a higher-order turbulence closure currently used in the Community Atmosphere Model (CAM). We will show that the RF outperforms the NN and the ADG1 closure for the MAGIC cases within this diagnostic framework. Progress and challenges in using a diagnostic machine learning closure within a prognostic cloud and turbulence parameterization will also be discussed.

Closure behavior of spherical void in slab during hot rolling process

Science.gov (United States)

Cheng, Rong; Zhang, Jiongming; Wang, Bo

2018-04-01

The mechanical properties of steels are heavily deteriorated by voids. The influence of voids on the product quality should be eliminated through rolling processes. The study on the void closure during hot rolling processes is necessary. In present work, the closure behavior of voids at the center of a slab at 800 °C during hot rolling processes has been simulated with a 3D finite element model. The shape of the void and the plastic strain distribution of the slab are obtained by this model. The void decreases along the slab thickness direction and spreads along the rolling direction but hardly changes along the strip width direction. The relationship between closure behavior of voids and the plastic strain at the center of the slab is analyzed. The effects of rolling reduction, slab thickness and roller diameter on the closure behavior of voids are discussed. The larger reduction, thinner slab and larger roller diameter all improve the closure of voids during hot rolling processes. Experimental results of the closure behavior of a void in the slab during hot rolling process mostly agree with the simulation results..

Vitrectomy with internal limiting membrane peeling for macular hole in high myopia eyes

Directory of Open Access Journals (Sweden)

Chun-Mei Deng

2015-08-01

Full Text Available AIM: To compare the clinical effects between pars plana vitrectomy(PPVand PPV with internal limiting membrane peeling(ILMPfor macular hole in high myopia eyes. METHODS:The clinical data of 33 high myopia with macular hole patients(36 eyeswith or without retinal detachment caused by macular hole were retrospectively analyzed. The patients were divided into two groups according to different operation methods: 15 eyes in groupⅠhad undergone PPV; 21 eyes in groupⅡhad undergone PPV with ILMPP peeling. According to different conditions of patients,different auxiliary methods were accepted, such as silicone oil tamponade, C3F8 tamponade, photocoagulation, condensation, etc. The follow-up period was 3～12mo. Best corrected visual acuity(BCVA, macular hole closure rate and retinal reattachment rate were continuous checked after operation. Then we evaluated the outcome in the two groups by statistical analysis.RESULTS: The postoperative mean BCVA increased by 0.167 in group Ⅰand 0.456 in group Ⅱ than preoperative, the difference was significant(t=2.46,6.753; P=0.027,0.000. And the difference of BCVA improvement was significant between those two groups(t=-2.943, P=0.006. The macular hole closed in 7 eyes(46.67%in group Ⅰ,and 18 eyes(85.71%in group Ⅱ; The difference was significant between those two groups(χ2=6.287,P=0.025.Retinal reattachment was found in 11 eyes(91.67%in group Ⅰ and 19 eyes(94.73%in group Ⅱ. The difference was not significant between the two groups(χ2=0.856, P=0.418. CONCLUSION: PPV with ILMPP peeling for macular hole in high myopia eyes can obviously improve closure of macular hole and postoperative visual acuity. But the difference of retinal reattachment rate was not significant between peeling and unpeeling of ILMP.

Heat Transfer and Friction Studies in a Tilted and Rib-Roughened Trailing-Edge Cooling Cavity with and without the Trailing-Edge Cooling Holes

Directory of Open Access Journals (Sweden)

M. E. Taslim

2014-01-01

Full Text Available Local and average heat transfer coefficients and friction factors were measured in a test section simulating the trailing-edge cooling cavity of a turbine airfoil. The test rig with a trapezoidal cross-sectional area was rib-roughened on two opposite sides of the trapezoid (airfoil pressure and suction sides with tapered ribs to conform to the cooling cavity shape and had a 22-degree tilt in the flow direction upstream of the ribs that affected the heat transfer coefficients on the two rib-roughened surfaces. The radial cooling flow traveled from the airfoil root to the tip while exiting through 22 cooling holes along the airfoil trailing-edge. Two rib geometries, with and without the presence of the trailing-edge cooling holes, were examined. The numerical model contained the entire trailing-edge channel, ribs, and trailing-edge cooling holes to simulate exactly the tested geometry. A pressure-correction based, multiblock, multigrid, unstructured/adaptive commercial software was used in this investigation. Realizable k-ε turbulence model in conjunction with enhanced wall treatment approach for the near wall regions was used for turbulence closure. The applied thermal boundary conditions to the CFD models matched the test boundary conditions. Comparisons are made between the experimental and numerical results.

Obturation and holding back device for a leakproof closure plug for a steam generator tube

International Nuclear Information System (INIS)

Lenoble, R.

1991-01-01

This leak proof closure plug has a bolt with at least a transversal aperture perpendicular to its axis. In the aperture is jammed a bracking piece. When screwing the bolt in the expander, the extremity part of the bracking piece is jammed in the tapped hole of the expander [fr

Top-down and Bottom-up aerosol-cloud-closure: towards understanding sources of unvertainty in deriving cloud radiative flux

Science.gov (United States)

Sanchez, K.; Roberts, G.; Calmer, R.; Nicoll, K.; Hashimshoni, E.; Rosenfeld, D.; Ovadnevaite, J.; Preissler, J.; Ceburnis, D.; O'Dowd, C. D. D.; Russell, L. M.

2017-12-01

Top-down and bottom-up aerosol-cloud shortwave radiative flux closures were conducted at the Mace Head atmospheric research station in Galway, Ireland in August 2015. Instrument platforms include ground-based, unmanned aerial vehicles (UAV), and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1D microphysical aerosol-cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction, or a 5-hole probe for 3D wind vectors. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in-situ cloud extinction measurements from UAVs to quantify closure in terms of cloud shortwave radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud shortwave radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top shortwave radiative flux (δRF) by between 25 W m-2 and 60 W m-2. After accounting for entrainment, satellite-derived cloud droplet number concentrations (CDNC) were within 30% of simulated CDNC. In cases with a well-mixed boundary layer, δRF is no greater than 20 W m-2 after accounting for cloud-top entrainment, and up to 50 W m-2 when entrainment is not taken into account. In cases with a decoupled boundary layer, cloud microphysical properties are inconsistent with ground-based aerosol measurements, as expected, and δRF is as high as 88 W m-2, even high (> 30 W m-2) after

Numeric simulations of en-masse space closure with sliding mechanics.

Science.gov (United States)

Kojima, Yukio; Fukui, Hisao

2010-12-01

En-masse sliding mechanics have been typically used for space closure. Because of friction created at the bracket-wire interface, the force system during tooth movement has not been clarified. Long-term tooth movements in en-masse sliding mechanics were simulated with the finite element method. Tipping of the anterior teeth occurred immediately after application of retraction forces. The force system then changed so that the teeth moved almost bodily, and friction occurred at the bracket-wire interface. Net force transferred to the anterior teeth was approximately one fourth of the applied force. The amount of the mesial force acting on the posterior teeth was the same as that acting on the anterior teeth. Irrespective of the amount of friction, the ratio of movement distances between the posterior and anterior teeth was almost the same. By increasing the applied force or decreasing the frictional coefficient, the teeth moved rapidly, but the tipping angle of the anterior teeth increased because of the elastic deflection of the archwire. Finite element simulation clarified the tooth movement and the force system in en-masse sliding mechanics. Long-term tooth movement could not be predicted from the initial force system. The friction was not detrimental to the anchorage. Increasing the applied force or decreasing the friction for rapid tooth movement might result in tipping of the teeth. Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Flow and transport simulation of Madeira River using three depth-averaged two-equation turbulence closure models

Directory of Open Access Journals (Sweden)

Li-ren Yu

2012-03-01

Full Text Available This paper describes a numerical simulation in the Amazon water system, aiming to develop a quasi-three-dimensional numerical tool for refined modeling of turbulent flow and passive transport of mass in natural waters. Three depth-averaged two-equation turbulence closure models, k˜−ε˜,k˜−w˜, and k˜−ω˜ , were used to close the non-simplified quasi-three dimensional hydrodynamic fundamental governing equations. The discretized equations were solved with the advanced multi-grid iterative method using non-orthogonal body-fitted coarse and fine grids with collocated variable arrangement. Except for steady flow computation, the processes of contaminant inpouring and plume development at the beginning of discharge, caused by a side-discharge of a tributary, have also been numerically investigated. The three depth-averaged two-equation closure models are all suitable for modeling strong mixing turbulence. The newly established turbulence models such as the k˜−ω˜ model, with a higher order of magnitude of the turbulence parameter, provide a possibility for improving computational precision.

Study on Gap Flow Field Simulation in Small Hole Machining of Ultrasonic Assisted EDM

Science.gov (United States)

Liu, Yu; Chang, Hao; Zhang, Wenchao; Ma, Fujian; Sha, Zhihua; Zhang, Shengfang

2017-12-01

When machining a small hole with high aspect ratio in EDM, it is hard for the flushing liquid entering the bottom gap and the debris could hardly be removed, which results in the accumulation of debris and affects the machining efficiency and machining accuracy. The assisted ultrasonic vibration can improve the removal of debris in the gap. Based on dynamics simulation software Fluent, a 3D model of debris movement in the gap flow field of EDM small hole machining assisted with side flushing and ultrasonic vibration is established in this paper. When depth to ratio is 3, the laws of different amplitudes and frequencies on debris distribution and removal are quantitatively analysed. The research results show that periodic ultrasonic vibration can promote the movement of debris, which is beneficial to the removal of debris in the machining gap. Compared to traditional small hole machining in EDM, the debris in the machining gap is greatly reduced, which ensures the stability of machining process and improves the machining efficiency.

Numerical simulation of binary black hole and neutron star mergers

Energy Technology Data Exchange (ETDEWEB)

Kastaun, W.; Rezzolla, L. [Albert Einstein Institut, Potsdam-Golm (Germany)

2016-11-01

One of the last predictions of general relativity that still awaits direct observational confirmation is the existence of gravitational waves. Those fluctuations of the geometry of space and time are expected to travel with the speed of light and are emitted by any accelerating mass. Only the most violent events in the universe, such as mergers of two black holes or neutron stars, produce gravitational waves strong enough to be measured. Even those waves are extremely weak when arriving at Earth, and their detection is a formidable technological challenge. In recent years sufficiently sensitive detectors became operational, such as GEO600, Virgo, and LIGO. They are expected to observe around 40 events per year. To interpret the observational data, theoretical modeling of the sources is a necessity, and requires numerical simulations of the equations of general relativity and relativistic hydrodynamics. Such computations can only be carried out on large scale supercomputers, given that many scenarios need to be simulated, each of which typically occupies hundreds of CPU cores for a week. Our main goal is to predict the gravitational wave signal from the merger of two compact objects. Comparison with future observations will provide important insights into the fundamental forces of nature in regimes that are impossible to recreate in laboratory experiments. The waveforms from binary black hole mergers would allow one to test the correctness of general relativity in previously inaccessible regimes. The signal from binary neutron star mergers will provide input for nuclear physics, because the signal depends strongly on the unknown properties of matter at the ultra high densities inside neutron stars, which cannot be observed in any other astrophysical scenario. Besides mergers, we also want to improve the theoretical models of close encounters between black holes. A gravitational wave detector with even higher sensitivity, the Einstein Telescope, is already in the

Non-destructive vacuum decay method for pre-filled syringe closure integrity testing compared with dye ingress testing and high-voltage leak detection.

Science.gov (United States)

Simonetti, Andrea; Amari, Filippo

2015-01-01

In reaction to the limitations of the traditional sterility test methods, in 2008, the U.S. Food and Drug Administration issued the guidance "Container and Closure System Integrity Testing in Lieu of Sterility Testing as a Component of the Stability Protocol for Sterile Products" encouraging sterile drug manufacturers to use properly validated physical methods, apart from conventional microbial challenge testing, to confirm container closure integrity as part of the stability protocol. The case study presented in this article investigated the capability of four container closure integrity testing methods to detect simulated defects of different sizes and types on glass syringes, prefilled both with drug product intended for parenteral administration and sterile water. The drug product was a flu vaccine (Agrippal, Novartis Vaccines, Siena, Italy). Vacuum decay, pharmacopoeial dye ingress test, Novartis specific dye ingress test, and high-voltage leak detection were, in succession, the methods involved in the comparative studies. The case study execution was preceded by the preparation of two independent sets of reference prefilled syringes, classified, respectively, as examples of conforming to closure integrity requirements (negative controls) and as defective (positive controls). Positive controls were, in turn, split in six groups, three of with holes laser-drilled through the prefilled syringe glass barrel, while the other three with capillary tubes embedded in the prefilled syringe plunger. These reference populations were then investigated by means of validated equipment used for container closure integrity testing of prefilled syringe commercial production; data were collected and analyzed to determine the detection rate and the percentage of false results. Results showed that the vacuum decay method had the highest performance in terms of detection sensitivity and also ensured the best reliability and repeatability of measurements. An innovative technical

Facility Closure Report for Tunnel U16a, Area 16, Nevada Test Site, Nevada

International Nuclear Information System (INIS)

2009-01-01

U16a is not listed in the Federal Facility Agreement and Consent Order. The closure of U16a was sponsored by the Defense Threat Reduction Agency (DTRA) and performed with the cooperation of the U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office and the Nevada Division of Environmental Protection. This report documents closure of this site as identified in the DTRA Fiscal Year 2008 Statement of Work, Task 6.3. Closure activities included: (1) Removing and disposing of a shack and its contents; (2) Disposing of debris from within the shack and in the vicinity of the tunnel entrance; (3) Verifying that the tunnel is empty; (4) Welding screened covers over tunnel vent holes to limit access and allow ventilation; and (5) Constructing a full-tunnel cross-section fibercrete bulkhead to prevent access to the tunnel Field activities were conducted from July to August 2008.

Numerical analysis of drilling hole work-hardening effects in hole-drilling residual stress measurement

Science.gov (United States)

Li, H.; Liu, Y. H.

2008-11-01

The hole-drilling strain gage method is an effective semi-destructive technique for determining residual stresses in the component. As a mechanical technique, a work-hardening layer will be formed on the surface of the hole after drilling, and affect the strain relaxation. By increasing Young's modulus of the material near the hole, the work-hardening layer is simplified as a heterogeneous annulus. As an example, two finite rectangular plates submitted to different initial stresses are treated, and the relieved strains are measured by finite element simulation. The accuracy of the measurement is estimated by comparing the simulated residual stresses with the given initial ones. The results are shown for various hardness of work-hardening layer. The influence of the relative position of the gages compared with the thickness of the work-hardening layer, and the effect of the ratio of hole diameter to work-hardening layer thickness are analyzed as well.

Comparison of different moment-closure approximations for stochastic chemical kinetics

Energy Technology Data Exchange (ETDEWEB)

Schnoerr, David [School of Biological Sciences, University of Edinburgh, Edinburgh (United Kingdom); School of Informatics, University of Edinburgh, Edinburgh (United Kingdom); Sanguinetti, Guido [School of Informatics, University of Edinburgh, Edinburgh (United Kingdom); Grima, Ramon [School of Biological Sciences, University of Edinburgh, Edinburgh (United Kingdom)

2015-11-14

In recent years, moment-closure approximations (MAs) of the chemical master equation have become a popular method for the study of stochastic effects in chemical reaction systems. Several different MA methods have been proposed and applied in the literature, but it remains unclear how they perform with respect to each other. In this paper, we study the normal, Poisson, log-normal, and central-moment-neglect MAs by applying them to understand the stochastic properties of chemical systems whose deterministic rate equations show the properties of bistability, ultrasensitivity, and oscillatory behaviour. Our results suggest that the normal MA is favourable over the other studied MAs. In particular, we found that (i) the size of the region of parameter space where a closure gives physically meaningful results, e.g., positive mean and variance, is considerably larger for the normal closure than for the other three closures, (ii) the accuracy of the predictions of the four closures (relative to simulations using the stochastic simulation algorithm) is comparable in those regions of parameter space where all closures give physically meaningful results, and (iii) the Poisson and log-normal MAs are not uniquely defined for systems involving conservation laws in molecule numbers. We also describe the new software package MOCA which enables the automated numerical analysis of various MA methods in a graphical user interface and which was used to perform the comparative analysis presented in this paper. MOCA allows the user to develop novel closure methods and can treat polynomial, non-polynomial, as well as time-dependent propensity functions, thus being applicable to virtually any chemical reaction system.

Top-down and bottom-up aerosol-cloud closure: towards understanding sources of uncertainty in deriving cloud shortwave radiative flux

Science.gov (United States)

Sanchez, Kevin J.; Roberts, Gregory C.; Calmer, Radiance; Nicoll, Keri; Hashimshoni, Eyal; Rosenfeld, Daniel; Ovadnevaite, Jurgita; Preissler, Jana; Ceburnis, Darius; O'Dowd, Colin; Russell, Lynn M.

2017-08-01

Top-down and bottom-up aerosol-cloud shortwave radiative flux closures were conducted at the Mace Head Atmospheric Research Station in Galway, Ireland, in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) European collaborative project, with the goal of understanding key processes affecting aerosol-cloud shortwave radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based unmanned aerial vehicles (UAVs)1 and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN) concentration were used to initiate a 1-D microphysical aerosol-cloud parcel model (ACPM). UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction or a five-hole probe for 3-D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in situ cloud extinction measurements from UAVs to quantify closure in terms of cloud shortwave radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud shortwave radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top shortwave radiative flux (δRF) by between 25 and 60 W m-2. After accounting for entrainment

Dancing with Black Holes

Science.gov (United States)

Aarseth, S. J.

2008-05-01

We describe efforts over the last six years to implement regularization methods suitable for studying one or more interacting black holes by direct N-body simulations. Three different methods have been adapted to large-N systems: (i) Time-Transformed Leapfrog, (ii) Wheel-Spoke, and (iii) Algorithmic Regularization. These methods have been tried out with some success on GRAPE-type computers. Special emphasis has also been devoted to including post-Newtonian terms, with application to moderately massive black holes in stellar clusters. Some examples of simulations leading to coalescence by gravitational radiation will be presented to illustrate the practical usefulness of such methods.

Numerical simulation of the hole-flanging process for steel-polymer sandwich sheets

Science.gov (United States)

Griesel, Dominic; Keller, Marco C.; Groche, Peter

2018-05-01

In light of increasing demand for lightweight structures, hybrid materials are frequently used in load-optimized parts. Sandwich structures like metal-polymer sandwich sheets provide equal bending stiffness as their monolithic counterparts at a drastically reduced weight. In addition, sandwich sheets have noise-damping properties, thus they are well-suited for a large variety of parts, e.g. façade and car body panels, but also load-carrying components. However, due to the creep tendency and low heat resistance of the polymer cores, conventional joining technologies are only applicable to a limited degree. Through hole-flanging it is possible to create branches in sandwich sheets to be used as reinforced joints. While it is state of the art for monolithic materials, hole-flanging of sandwich sheets has not been investigated yet. In order to simulate this process for different material combinations and tool geometries, an axisymmetric model has been developed in the FE software Abaqus/CAE. In the present paper, various modeling strategies for steel-polymer sandwich sheets are examined, including volume elements, shell elements and combinations thereof. Different methods for joining the distinct layers in the FE model are discussed. By comparison with CT scans and optical 3D measurements of experimentally produced hole-flanges, the feasibility of the presented models is evaluated. Although a good agreement of the numerical and experimental results has been achieved, it becomes clear that the classical forming limit diagram (FLD) does not adequately predict failure of the steel skins.

Innovative real CSF leak simulation model for rhinology training: human cadaveric design.

Science.gov (United States)

AlQahtani, Abdulaziz A; Albathi, Abeer A; Alhammad, Othman M; Alrabie, Abdulkarim S

2018-04-01

To study the feasibility of designing a human cadaveric simulation model of real CSF leak for rhinology training. The laboratory investigation took place at the surgical academic center of Prince Sultan Military Medical City between 2016 and 2017. Five heads of human cadaveric specimens were cannulated into the intradural space through two frontal bone holes. Fluorescein-dyed fluid was injected intracranialy, then endoscopic endonasal iatrogenic skull base defect was created with observation of fluid leak, followed by skull base reconstruction. The outcome measures included subjective assessment of integrity of the design, the ability of creating real CSF leak in multiple site of skull base and the possibility of watertight closure by various surgical techniques. The fluid filled the intradural space in all specimens without spontaneous leak from skull base or extra sinus areas. Successfully, we demonstrated fluid leak from all areas after iatrogenic defect in the cribriform plate, fovea ethmoidalis, planum sphenoidale sellar and clival regions. Watertight closure was achieved in all defects using different reconstruction techniques (overly, underlay and gasket seal closure). The design is simulating the real patient with CSF leak. It has potential in the learning process of acquiring and maintaining the surgical skills of skull base reconstruction before direct involvement of the patient. This model needs further evaluation and competence measurement as training tools in rhinology training.

Robust identification and localization of intramedullary nail holes for distal locking using CBCT: a simulation study.

Science.gov (United States)

Kamarianakis, Z; Buliev, I; Pallikarakis, N

2011-05-01

Closed intramedullary nailing is a common technique for treatment of femur and tibia fractures. The most challenging step in this procedure is the precise placement of the lateral screws that stabilize the fragmented bone. The present work concerns the development and the evaluation of a method to accurately identify in the 3D space the axes of the nail hole canals. A limited number of projection images are acquired around the leg with the help of a C-arm. On two of them, the locking hole entries are interactively selected and a rough localization of the hole axes is performed. Perpendicularly to one of them, cone-beam computed tomography (CBCT) reconstructions are produced. The accurate identification and localization of the hole axes are done by an identification of the centers of the nail holes on the tomograms and a further 3D linear regression through principal component analysis (PCA). Various feature-based approaches (RANSAC, least-square fitting, Hough transform) have been compared for best matching the contours and the centers of the holes on the tomograms. The robustness of the suggested method was investigated using simulations. Programming is done in Matlab and C++. Results obtained on synthetic data confirm very good localization accuracy - mean translational error of 0.14 mm (std=0.08 mm) and mean angular error of 0.84° (std=0.35°) at no radiation excess. Successful localization can be further used to guide a surgeon or a robot for correct drilling the bone along the nail openings. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Optimal Ge/SiGe nanofin geometries for hole mobility enhancement: Technology limit from atomic simulations

Science.gov (United States)

Vedula, Ravi Pramod; Mehrotra, Saumitra; Kubis, Tillmann; Povolotskyi, Michael; Klimeck, Gerhard; Strachan, Alejandro

2015-05-01

We use first principles simulations to engineer Ge nanofins for maximum hole mobility by controlling strain tri-axially through nano-patterning. Large-scale molecular dynamics predict fully relaxed, atomic structures for experimentally achievable nanofins, and orthogonal tight binding is used to obtain the corresponding electronic structure. Hole transport properties are then obtained via a linearized Boltzmann formalism. This approach explicitly accounts for free surfaces and associated strain relaxation as well as strain gradients which are critical for quantitative predictions in nanoscale structures. We show that the transverse strain relaxation resulting from the reduction in the aspect ratio of the fins leads to a significant enhancement in phonon limited hole mobility (7× over unstrained, bulk Ge, and 3.5× over biaxially strained Ge). Maximum enhancement is achieved by reducing the width to be approximately 1.5 times the height and further reduction in width does not result in additional gains. These results indicate significant room for improvement over current-generation Ge nanofins, provide geometrical guidelines to design optimized geometries and insight into the physics behind the significant mobility enhancement.

Optimal Ge/SiGe nanofin geometries for hole mobility enhancement: Technology limit from atomic simulations

International Nuclear Information System (INIS)

Vedula, Ravi Pramod; Mehrotra, Saumitra; Kubis, Tillmann; Povolotskyi, Michael; Klimeck, Gerhard; Strachan, Alejandro

2015-01-01

We use first principles simulations to engineer Ge nanofins for maximum hole mobility by controlling strain tri-axially through nano-patterning. Large-scale molecular dynamics predict fully relaxed, atomic structures for experimentally achievable nanofins, and orthogonal tight binding is used to obtain the corresponding electronic structure. Hole transport properties are then obtained via a linearized Boltzmann formalism. This approach explicitly accounts for free surfaces and associated strain relaxation as well as strain gradients which are critical for quantitative predictions in nanoscale structures. We show that the transverse strain relaxation resulting from the reduction in the aspect ratio of the fins leads to a significant enhancement in phonon limited hole mobility (7× over unstrained, bulk Ge, and 3.5× over biaxially strained Ge). Maximum enhancement is achieved by reducing the width to be approximately 1.5 times the height and further reduction in width does not result in additional gains. These results indicate significant room for improvement over current-generation Ge nanofins, provide geometrical guidelines to design optimized geometries and insight into the physics behind the significant mobility enhancement

Optimal Ge/SiGe nanofin geometries for hole mobility enhancement: Technology limit from atomic simulations

Energy Technology Data Exchange (ETDEWEB)

Vedula, Ravi Pramod; Mehrotra, Saumitra; Kubis, Tillmann; Povolotskyi, Michael; Klimeck, Gerhard [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Strachan, Alejandro, E-mail: strachan@purdue.edu [School of Materials Engineering and Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907 (United States)

2015-05-07

We use first principles simulations to engineer Ge nanofins for maximum hole mobility by controlling strain tri-axially through nano-patterning. Large-scale molecular dynamics predict fully relaxed, atomic structures for experimentally achievable nanofins, and orthogonal tight binding is used to obtain the corresponding electronic structure. Hole transport properties are then obtained via a linearized Boltzmann formalism. This approach explicitly accounts for free surfaces and associated strain relaxation as well as strain gradients which are critical for quantitative predictions in nanoscale structures. We show that the transverse strain relaxation resulting from the reduction in the aspect ratio of the fins leads to a significant enhancement in phonon limited hole mobility (7× over unstrained, bulk Ge, and 3.5× over biaxially strained Ge). Maximum enhancement is achieved by reducing the width to be approximately 1.5 times the height and further reduction in width does not result in additional gains. These results indicate significant room for improvement over current-generation Ge nanofins, provide geometrical guidelines to design optimized geometries and insight into the physics behind the significant mobility enhancement.

Non-Markovian closure models for large eddy simulations using the Mori-Zwanzig formalism

Science.gov (United States)

Parish, Eric J.; Duraisamy, Karthik

2017-01-01

This work uses the Mori-Zwanzig (M-Z) formalism, a concept originating from nonequilibrium statistical mechanics, as a basis for the development of coarse-grained models of turbulence. The mechanics of the generalized Langevin equation (GLE) are considered, and insight gained from the orthogonal dynamics equation is used as a starting point for model development. A class of subgrid models is considered which represent nonlocal behavior via a finite memory approximation [Stinis, arXiv:1211.4285 (2012)], the length of which is determined using a heuristic that is related to the spectral radius of the Jacobian of the resolved variables. The resulting models are intimately tied to the underlying numerical resolution and are capable of approximating non-Markovian effects. Numerical experiments on the Burgers equation demonstrate that the M-Z-based models can accurately predict the temporal evolution of the total kinetic energy and the total dissipation rate at varying mesh resolutions. The trajectory of each resolved mode in phase space is accurately predicted for cases where the coarse graining is moderate. Large eddy simulations (LESs) of homogeneous isotropic turbulence and the Taylor-Green Vortex show that the M-Z-based models are able to provide excellent predictions, accurately capturing the subgrid contribution to energy transfer. Last, LESs of fully developed channel flow demonstrate the applicability of M-Z-based models to nondecaying problems. It is notable that the form of the closure is not imposed by the modeler, but is rather derived from the mathematics of the coarse graining, highlighting the potential of M-Z-based techniques to define LES closures.

Vitrectomy with internal limiting membrane peeling versus inverted internal limiting membrane flap technique for macular hole-induced retinal detachment: a systematic review of literature and meta-analysis.

Science.gov (United States)

Yuan, Jing; Zhang, Ling-Lin; Lu, Yu-Jie; Han, Meng-Yao; Yu, Ai-Hua; Cai, Xiao-Jun

2017-11-28

To evaluate the effects on vitrectomy with internal limiting membrane (ILM) peeling versus vitrectomy with inverted internal limiting membrane flap technique for macular hole-induced retinal detachment (MHRD). Pubmed, Cochrane Library, and Embase were systematically searched for studies that compared ILM peeling with inverted ILM flap technique for macular hole-induced retinal detachment. The primary outcomes are the rate of retinal reattachment and the rate of macular hole closure 6 months later after initial surgery, the secondary outcome is the postoperative best-corrected visual acuity (BCVA) 6 months later after initial surgery. Four studies that included 98 eyes were selected. All the included studies were retrospective comparative studies. The preoperative best-corrected visual acuity was equal between ILM peeling and inverted ILM flap technique groups. It was indicated that the rate of retinal reattachment (odds ratio (OR) = 0.14, 95% confidence interval (CI):0.03 to 0.69; P = 0.02) and macular hole closure (OR = 0.06, 95% CI:0.02 to 0.19; P peeling. However, there was no statistically significant difference in postoperative best-corrected visual acuity (mean difference (MD) 0.18 logarithm of the minimum angle of resolution; 95% CI -0.06 to 0.43 ; P = 0.14) between the two surgery groups. Compared with ILM peeling, vitrectomy with inverted ILM flap technique resulted significantly higher of the rate of retinal reattachment and macular hole closure, but seemed does not improve postoperative best-corrected visual acuity.

Closure requirements

International Nuclear Information System (INIS)

Hutchinson, I.P.G.; Ellison, R.D.

1992-01-01

Closure of a waste management unit can be either permanent or temporary. Permanent closure may be due to: economic factors which make it uneconomical to mine the remaining minerals; depletion of mineral resources; physical site constraints that preclude further mining and beneficiation; environmental, regulatory or other requirements that make it uneconomical to continue to develop the resources. Temporary closure can occur for a period of several months to several years, and may be caused by factors such as: periods of high rainfall or snowfall which prevent mining and waste disposal; economic circumstances which temporarily make it uneconomical to mine the target mineral; labor problems requiring a cessation of operations for a period of time; construction activities that are required to upgrade project components such as the process facilities and waste management units; and mine or process plant failures that require extensive repairs. Permanent closure of a mine waste management unit involves the provision of durable surface containment features to protect the waters of the State in the long-term. Temporary closure may involve activities that range from ongoing maintenance of the existing facilities to the installation of several permanent closure features in order to reduce ongoing maintenance. This paper deals with the permanent closure features

Simulation of Residual Stresses at Holes in Tempered Glass

DEFF Research Database (Denmark)

Nielsen, Jens Henrik; Olesen, John Forbes; Poulsen, Peter Noe

2010-01-01

This work presents a full 3D numerical study of the residual stresses in tempered (toughened) glass near holes using Narayanaswamy’s model for the tempering process. It is the objective of the paper to elucidate the influence on the minimal residual compressive stresses at holes from variations in...

Optimal management of idiopathic macular holes

Directory of Open Access Journals (Sweden)

Madi HA

2016-01-01

Full Text Available Haifa A Madi,1,* Ibrahim Masri,1,* David H Steel1,2 1Sunderland Eye Infirmary, Sunderland, 2Institute of Genetic Medicine, Newcastle University, International Centre for Life, Newcastle, UK *These authors contributed equally to this work Abstract: This review evaluates the current surgical options for the management of idiopathic macular holes (IMHs, including vitrectomy, ocriplasmin (OCP, and expansile gas use, and discusses key background information to inform the choice of treatment. An evidence-based approach to selecting the best treatment option for the individual patient based on IMH characteristics and patient-specific factors is suggested. For holes without vitreomacular attachment (VMA, vitrectomy is the only option with three key surgical variables: whether to peel the inner limiting membrane (ILM, the type of tamponade agent to be used, and the requirement for postoperative face-down posturing. There is a general consensus that ILM peeling improves primary anatomical hole closure rate; however, in small holes (<250 µm, it is uncertain whether peeling is always required. It has been increasingly recognized that long-acting gas and face-down positioning are not always necessary in patients with small- and medium-sized holes, but large (>400 µm and chronic holes (>1-year history are usually treated with long-acting gas and posturing. Several studies on posturing and gas choice were carried out in combination with ILM peeling, which may also influence the gas and posturing requirement. Combined phacovitrectomy appears to offer more rapid visual recovery without affecting the long-term outcomes of vitrectomy for IMH. OCP is licensed for use in patients with small- or medium-sized holes and VMA. A greater success rate in using OCP has been reported in smaller holes, but further predictive factors for its success are needed to refine its use. It is important to counsel patients realistically regarding the rates of success with

Clinical and cost-effectiveness of internal limiting membrane peeling for patients with idiopathic full thickness macular hole. Protocol for a Randomised Controlled Trial: FILMS (Full-thickness macular hole and Internal Limiting Membrane peeling Study

Directory of Open Access Journals (Sweden)

Cook Jonathan

2008-11-01

Full Text Available Abstract Background A full-thickness macular hole (FTMH is a common retinal condition associated with impaired vision. Randomised controlled trials (RCTs have demonstrated that surgery, by means of pars plana vitrectomy and post-operative intraocular tamponade with gas, is effective for stage 2, 3 and 4 FTMH. Internal limiting membrane (ILM peeling has been introduced as an additional surgical manoeuvre to increase the success of the surgery; i.e. increase rates of hole closure and visual improvement. However, little robust evidence exists supporting the superiority of ILM peeling compared with no-peeling techniques. The purpose of FILMS (Full-thickness macular hole and Internal Limiting Membrane peeling Study is to determine whether ILM peeling improves the visual function, the anatomical closure of FTMH, and the quality of life of patients affected by this disorder, and the cost-effectiveness of the surgery. Methods/Design Patients with stage 2–3 idiopathic FTMH of less or equal than 18 months duration (based on symptoms reported by the participant and with a visual acuity ≤ 20/40 in the study eye will be enrolled in this FILMS from eight sites across the UK and Ireland. Participants will be randomised to receive combined cataract surgery (phacoemulsification and intraocular lens implantation and pars plana vitrectomy with postoperative intraocular tamponade with gas, with or without ILM peeling. The primary outcome is distance visual acuity at 6 months. Secondary outcomes include distance visual acuity at 3 and 24 months, near visual acuity at 3, 6, and 24 months, contrast sensitivity at 6 months, reading speed at 6 months, anatomical closure of the macular hole at each time point (1, 3, 6, and 24 months, health related quality of life (HRQOL at six months, costs to the health service and the participant, incremental costs per quality adjusted life year (QALY and adverse events. Discussion FILMS will provide high quality evidence on the

A critical assessment of flux and source term closures in shallow water models with porosity for urban flood simulations

Science.gov (United States)

Guinot, Vincent

2017-11-01

The validity of flux and source term formulae used in shallow water models with porosity for urban flood simulations is assessed by solving the two-dimensional shallow water equations over computational domains representing periodic building layouts. The models under assessment are the Single Porosity (SP), the Integral Porosity (IP) and the Dual Integral Porosity (DIP) models. 9 different geometries are considered. 18 two-dimensional initial value problems and 6 two-dimensional boundary value problems are defined. This results in a set of 96 fine grid simulations. Analysing the simulation results leads to the following conclusions: (i) the DIP flux and source term models outperform those of the SP and IP models when the Riemann problem is aligned with the main street directions, (ii) all models give erroneous flux closures when is the Riemann problem is not aligned with one of the main street directions or when the main street directions are not orthogonal, (iii) the solution of the Riemann problem is self-similar in space-time when the street directions are orthogonal and the Riemann problem is aligned with one of them, (iv) a momentum balance confirms the existence of the transient momentum dissipation model presented in the DIP model, (v) none of the source term models presented so far in the literature allows all flow configurations to be accounted for(vi) future laboratory experiments aiming at the validation of flux and source term closures should focus on the high-resolution, two-dimensional monitoring of both water depth and flow velocity fields.

Black-Hole Binaries, Gravitational Waves, and Numerical Relativity

Science.gov (United States)

Kelly, Bernard J.; Centrella, Joan; Baker, John G.; Kelly, Bernard J.; vanMeter, James R.

2010-01-01

Understanding the predictions of general relativity for the dynamical interactions of two black holes has been a long-standing unsolved problem in theoretical physics. Black-hole mergers are monumental astrophysical events ' releasing tremendous amounts of energy in the form of gravitational radiation ' and are key sources for both ground- and spacebased gravitational wave detectors. The black-hole merger dynamics and the resulting gravitational waveforms can only he calculated through numerical simulations of Einstein's equations of general relativity. For many years, numerical relativists attempting to model these mergers encountered a host of problems, causing their codes to crash after just a fraction of a binary orbit cnuld be simulated. Recently ' however, a series of dramatic advances in numerical relativity has ' for the first time, allowed stable / robust black hole merger simulations. We chronicle this remarkable progress in the rapidly maturing field of numerical relativity, and the new understanding of black-hole binary dynamics that is emerging. We also discuss important applications of these fundamental physics results to astrophysics, to gravitationalwave astronomy, and in other areas.

Flip-flopping binary black holes.

Science.gov (United States)

Lousto, Carlos O; Healy, James

2015-04-10

We study binary spinning black holes to display the long term individual spin dynamics. We perform a full numerical simulation starting at an initial proper separation of d≈25M between equal mass holes and evolve them down to merger for nearly 48 orbits, 3 precession cycles, and half of a flip-flop cycle. The simulation lasts for t=20 000M and displays a total change in the orientation of the spin of one of the black holes from an initial alignment with the orbital angular momentum to a complete antialignment after half of a flip-flop cycle. We compare this evolution with an integration of the 3.5 post-Newtonian equations of motion and spin evolution to show that this process continuously flip flops the spin during the lifetime of the binary until merger. We also provide lower order analytic expressions for the maximum flip-flop angle and frequency. We discuss the effects this dynamics may have on spin growth in accreting binaries and on the observational consequences for galactic and supermassive binary black holes.

Black holes escaping from domain walls

International Nuclear Information System (INIS)

Flachi, Antonino; Sasaki, Misao; Pujolas, Oriol; Tanaka, Takahiro

2006-01-01

Previous studies concerning the interaction of branes and black holes suggested that a small black hole intersecting a brane may escape via a mechanism of reconnection. Here we consider this problem by studying the interaction of a small black hole and a domain wall composed of a scalar field and simulate the evolution of this system when the black hole acquires an initial recoil velocity. We test and confirm previous results, however, unlike the cases previously studied, in the more general set-up considered here, we are able to follow the evolution of the system also during the separation, and completely illustrate how the escape of the black hole takes place

Numerical simulation of evolution of electron-hole avalanches and streamers in silicon in a uniform electric field

International Nuclear Information System (INIS)

Kyuregyan, A. S.

2010-01-01

Numerical simulation of origination and evolution of streamers in Si is performed for the first time. It is assumed that an external electric field E 0 is constant and uniform, the avalanche and streamer are axially symmetric, and background electrons and holes are absent. The calculations have been performed in the context of the diffusion-drift approximation with impact and tunneling ionization, Auger recombination, and electron-hole scattering taken into account. The most realistic values of the ionization and recombination rates, diffusion coefficients, and drift mobilities of electrons and holes have been used. It is shown that the features of evolution of avalanches and streamers are generally consistent with the result obtained previously for a hypothetic semiconductor with equal kinetic coefficients for electrons and holes. Asymmetry of these coefficients (mostly, the impact-ionization coefficients) manifests itself only at the initial stage of evolution. However, with time, two exponentially self-similar streamers are formed, differing only in the sign of charge of fronts and directions of their propagation. Empirical dependences of the main parameters of streamers on E 0 in the range of 0.34-0.75 MV/cm have been derived for this most important stage of evolution.

The dynamics of electron and ion holes in a collisionless plasma

Directory of Open Access Journals (Sweden)

B. Eliasson

2005-01-01

Full Text Available We present a review of recent analytical and numerical studies of the dynamics of electron and ion holes in a collisionless plasma. The new results are based on the class of analytic solutions which were found by Schamel more than three decades ago, and which here work as initial conditions to numerical simulations of the dynamics of ion and electron holes and their interaction with radiation and the background plasma. Our analytic and numerical studies reveal that ion holes in an electron-ion plasma can trap Langmuir waves, due the local electron density depletion associated with the negative ion hole potential. Since the scale-length of the ion holes are on a relatively small Debye scale, the trapped Langmuir waves are Landau damped. We also find that colliding ion holes accelerate electron streams by the negative ion hole potentials, and that these streams of electrons excite Langmuir waves due to a streaming instability. In our Vlasov simulation of two colliding ion holes, the holes survive the collision and after the collision, the electron distribution becomes flat-topped between the two ion holes due to the ion hole potentials which work as potential barriers for low-energy electrons. Our study of the dynamics between electron holes and the ion background reveals that standing electron holes can be accelerated by the self-created ion cavity owing to the positive electron hole potential. Vlasov simulations show that electron holes are repelled by ion density minima and attracted by ion density maxima. We also present an extension of Schamel's theory to relativistically hot plasmas, where the relativistic mass increase of the accelerated electrons have a dramatic effect on the electron hole, with an increase in the electron hole potential and in the width of the electron hole. A study of the interaction between electromagnetic waves with relativistic electron holes shows that electromagnetic waves can be both linearly and nonlinearly

Large-eddy simulation of stable atmospheric boundary layers to develop better turbulence closures for climate and weather models

Science.gov (United States)

Bou-Zeid, Elie; Huang, Jing; Golaz, Jean-Christophe

2011-11-01

A disconnect remains between our improved physical understanding of boundary layers stabilized by buoyancy and how we parameterize them in coarse atmospheric models. Most operational climate models require excessive turbulence mixing in such conditions to prevent decoupling of the atmospheric component from the land component, but the performance of such a model is unlikely to be satisfactory under weakly and moderately stable conditions. Using Large-eddy simulation, we revisit some of the basic challenges in parameterizing stable atmospheric boundary layers: eddy-viscosity closure is found to be more reliable due to an improved alignment of vertical Reynolds stresses and mean strains under stable conditions, but the dependence of the magnitude of the eddy viscosity on stability is not well represented by several models tested here. Thus, we propose a new closure that reproduces the different stability regimes better. Subsequently, tests of this model in the GFDL's single-column model (SCM) are found to yield good agreement with LES results in idealized steady-stability cases, as well as in cases with gradual and sharp changes of stability with time.

Plasma electron hole kinematics. I. Momentum conservation

Energy Technology Data Exchange (ETDEWEB)

Hutchinson, I. H.; Zhou, C. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2016-08-15

We analyse the kinematic properties of a plasma electron hole: a non-linear self-sustained localized positive electric potential perturbation, trapping electrons, which behaves as a coherent entity. When a hole accelerates or grows in depth, ion and electron plasma momentum is changed both within the hole and outside, by an energization process we call jetting. We present a comprehensive analytic calculation of the momentum changes of an isolated general one-dimensional hole. The conservation of the total momentum gives the hole's kinematics, determining its velocity evolution. Our results explain many features of the behavior of hole speed observed in numerical simulations, including self-acceleration at formation, and hole pushing and trapping by ion streams.

INTERNAL LIMITING MEMBRANE PEELING IN MACULAR HOLE SURGERY; WHY, WHEN, AND HOW?

Science.gov (United States)

Chatziralli, Irini P; Theodossiadis, Panagiotis G; Steel, David H W

2018-05-01

To review the current rationale for internal limiting membrane (ILM) peeling in macular hole (MH) surgery and to discuss the evidence base behind why, when, and how surgeons peel the ILM. Review of the current literature. Pars plana vitrectomy is an effective treatment for idiopathic MH, and peeling of the ILM has been shown to improve closure rates and to prevent postoperative reopening. However, some authors argue against ILM peeling because it results in a number of changes in retinal structure and function and may not be necessary in all cases. Furthermore, the extent of ILM peeling optimally performed and the most favorable techniques to remove the ILM are uncertain. Several technique variations including ILM flaps, ILM scraping, and foveal sparing ILM peeling have been described as alternatives to conventional peeling in specific clinical scenarios. Internal limiting membrane peeling improves MH closure rates but can have several consequences on retinal structure and function. Adjuvants to aid peeling, instrumentation, technique, and experience may all alter the outcome. Hole size and other variables are important in assessing the requirement for peeling and potentially its extent. A variety of evolving alternatives to conventional peeling may improve outcomes and need further study.

Electron holes observed in the Moon Plasma Wake

Science.gov (United States)

Hutchinson, I. H.; Malaspina, D.; Zhou, C.

2017-10-01

Electrostatic instabilities are predicted in the magnetized wake of plasma flowing past a non-magnetic absorbing object such as a probe or the moon. Analysis of the data from the Artemis satellites, now orbiting the moon at distances ten moon radii and less, shows very clear evidence of fast-moving isolated solitary potential structures causing bipolar electric field excursions as they pass the satellite's probes. These structures have all the hallmarks of electron holes: BGK solitons typically a few Debye-lengths in size, self-sustaining by a deficit of phase-space density on trapped orbits. Electron holes are now observed to be widespread in space plasmas. They have been observed in PIC simulations of the moon wake to be the non-linear consequence of the predicted electron instabilities. Simulations document hole prevalence, speed, length, and depth; and theory can explain many of these features from kinetic analysis. The solar wind wake is certainly the cause of the overwhelming majority of the holes observed by Artemis, because we observe almost all holes to be in or very near to the wake. We compare theory and simulation of the hole generation, lifetime, and transport mechanisms with observations. Work partially supported by NASA Grant NNX16AG82G.

A summary of methods for approximating salt creep and disposal room closure in numerical models of multiphase flow

Energy Technology Data Exchange (ETDEWEB)

Freeze, G.A.; Larson, K.W. [INTERA, Inc., Albuquerque, NM (United States); Davies, P.B. [Sandia National Labs., Albuquerque, NM (United States)

1995-10-01

Eight alternative methods for approximating salt creep and disposal room closure in a multiphase flow model of the Waste Isolation Pilot Plant (WIPP) were implemented and evaluated: Three fixed-room geometries three porosity functions and two fluid-phase-salt methods. The pressure-time-porosity line interpolation method is the method used in current WIPP Performance Assessment calculations. The room closure approximation methods were calibrated against a series of room closure simulations performed using a creep closure code, SANCHO. The fixed-room geometries did not incorporate a direct coupling between room void volume and room pressure. The two porosity function methods that utilized moles of gas as an independent parameter for closure coupling. The capillary backstress method was unable to accurately simulate conditions of re-closure of the room. Two methods were found to be accurate enough to approximate the effects of room closure; the boundary backstress method and pressure-time-porosity line interpolation. The boundary backstress method is a more reliable indicator of system behavior due to a theoretical basis for modeling salt deformation as a viscous process. It is a complex method and a detailed calibration process is required. The pressure lines method is thought to be less reliable because the results were skewed towards SANCHO results in simulations where the sequence of gas generation was significantly different from the SANCHO gas-generation rate histories used for closure calibration. This limitation in the pressure lines method is most pronounced at higher gas-generation rates and is relatively insignificant at lower gas-generation rates. Due to its relative simplicity, the pressure lines method is easier to implement in multiphase flow codes and simulations have a shorter execution time.

A summary of methods for approximating salt creep and disposal room closure in numerical models of multiphase flow

International Nuclear Information System (INIS)

Freeze, G.A.; Larson, K.W.; Davies, P.B.

1995-10-01

Eight alternative methods for approximating salt creep and disposal room closure in a multiphase flow model of the Waste Isolation Pilot Plant (WIPP) were implemented and evaluated: Three fixed-room geometries three porosity functions and two fluid-phase-salt methods. The pressure-time-porosity line interpolation method is the method used in current WIPP Performance Assessment calculations. The room closure approximation methods were calibrated against a series of room closure simulations performed using a creep closure code, SANCHO. The fixed-room geometries did not incorporate a direct coupling between room void volume and room pressure. The two porosity function methods that utilized moles of gas as an independent parameter for closure coupling. The capillary backstress method was unable to accurately simulate conditions of re-closure of the room. Two methods were found to be accurate enough to approximate the effects of room closure; the boundary backstress method and pressure-time-porosity line interpolation. The boundary backstress method is a more reliable indicator of system behavior due to a theoretical basis for modeling salt deformation as a viscous process. It is a complex method and a detailed calibration process is required. The pressure lines method is thought to be less reliable because the results were skewed towards SANCHO results in simulations where the sequence of gas generation was significantly different from the SANCHO gas-generation rate histories used for closure calibration. This limitation in the pressure lines method is most pronounced at higher gas-generation rates and is relatively insignificant at lower gas-generation rates. Due to its relative simplicity, the pressure lines method is easier to implement in multiphase flow codes and simulations have a shorter execution time

Potential application of CuSbS2 as the hole transport material in perovskite solar cell: A simulation study

Science.gov (United States)

Teimouri, R.; Mohammadpour, R.

2018-06-01

CH3 NH3 PbI3 (MAPbI3) thin film solar cells, which are reported at laboratory efficiency scale of nearly 22%, are the subject of much attention by energy researchers due to their low cost buildup, acceptable efficiency, high absorption coefficient and diffusion length. The main purpose of this research is to simulate the structure of thin film perovskite solar cells through numerical simulation of SCAPS based on the empirical data for different hole transport layers. After simulating the initial structure of FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD solar cell, the hole transport layer Spiro-OMeTAD thickness was optimized on a small scale using modeling. The researchers also sought to reduce the amount of this material and the cost of construction. Ultimately, an optimum thickness of 140 nm was obtained for this cell with efficiency of 22.88%. The effect of employing alternative inorganic hole transport layer was investigated as a substitute for Spiro-OMeTAD; Copper antimony sulphide (CuSbS2) was selected due to abundant and available material and high open circuit voltage of about 988 mV. Thickness variations were also performed on a MAPbI3/CuSbS2 solar cell. Finally, It has obtained that perovskite solar cell with 120 nm-thick of CuSbS2 has 23.14% conversion efficiency with acceptable VOC and JSC values.

Top-down and bottom-up aerosol–cloud closure: towards understanding sources of uncertainty in deriving cloud shortwave radiative flux

Directory of Open Access Journals (Sweden)

K. J. Sanchez

2017-08-01

Full Text Available Top-down and bottom-up aerosol–cloud shortwave radiative flux closures were conducted at the Mace Head Atmospheric Research Station in Galway, Ireland, in August 2015. This study is part of the BACCHUS (Impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding European collaborative project, with the goal of understanding key processes affecting aerosol–cloud shortwave radiative flux closures to improve future climate predictions and develop sustainable policies for Europe. Instrument platforms include ground-based unmanned aerial vehicles (UAVs1 and satellite measurements of aerosols, clouds and meteorological variables. The ground-based and airborne measurements of aerosol size distributions and cloud condensation nuclei (CCN concentration were used to initiate a 1-D microphysical aerosol–cloud parcel model (ACPM. UAVs were equipped for a specific science mission, with an optical particle counter for aerosol distribution profiles, a cloud sensor to measure cloud extinction or a five-hole probe for 3-D wind vectors. UAV cloud measurements are rare and have only become possible in recent years through the miniaturization of instrumentation. These are the first UAV measurements at Mace Head. ACPM simulations are compared to in situ cloud extinction measurements from UAVs to quantify closure in terms of cloud shortwave radiative flux. Two out of seven cases exhibit sub-adiabatic vertical temperature profiles within the cloud, which suggests that entrainment processes affect cloud microphysical properties and lead to an overestimate of simulated cloud shortwave radiative flux. Including an entrainment parameterization and explicitly calculating the entrainment fraction in the ACPM simulations both improved cloud-top radiative closure. Entrainment reduced the difference between simulated and observation-derived cloud-top shortwave radiative flux (δRF by between 25 and 60 W m−2. After

Accretion Disks Around Binary Black Holes of Unequal Mass: GRMHD Simulations Near Decoupling

Science.gov (United States)

Gold, Roman; Paschalidis, Vasileios; Etienne, Zachariah B.; Shapiro, Stuart L.; Pfeiffer, Harald, P.

2013-01-01

We report on simulations in general relativity of magnetized disks onto black hole binaries. We vary the binary mass ratio from 1:1 to 1:10 and evolve the systems when they orbit near the binary disk decoupling radius. We compare (surface) density profiles, accretion rates (relative to a single, non-spinning black hole), variability, effective alpha-stress levels and luminosities as functions of the mass ratio. We treat the disks in two limiting regimes: rapid radiative cooling and no radiative cooling. The magnetic field lines clearly reveal jets emerging from both black hole horizons and merging into one common jet at large distances. The magnetic fields give rise to much stronger shock heating than the pure hydrodynamic flows, completely alter the disk structure, and boost accretion rates and luminosities. Accretion streams near the horizons are among the densest structures; in fact, the 1:10 no-cooling evolution results in a refilling of the cavity. The typical effective temperature in the bulk of the disk is approx. 10(exp5) (M / 10(exp 8)M solar mass (exp -1/4(L/L(sub edd) (exp 1/4K) yielding characteristic thermal frequencies approx. 10 (exp 15) (M /10(exp 8)M solar mass) (exp -1/4(L/L (sub edd) (1+z) (exp -1)Hz. These systems are thus promising targets for many extragalactic optical surveys, such as LSST, WFIRST, and PanSTARRS.

Sealing behavior of Container Closure Systems under Frozen Storage Conditions: Nonlinear Finite Element Simulation of Serum Rubber Stoppers.

Science.gov (United States)

Nieto, Alejandra; Roehl, Holger

2018-03-15

There has been a growing interest in recent years in the assessment of suitable vial/stopper combinations for storage and shipment of frozen drug products. Considering that the glass transition temperature (Tg) of butyl rubber stoppers used in Container Closure Systems (CCS) is between -55°C to -65°C, a storage or shipment temperature of a frozen product below the Tg of the rubber stopper, may require special attention, since below the Tg the rubber becomes more plastic-like and loses its elastic (sealing) characteristics. Thus they risk maintaining Container Closure Integrity (CCI). Given that the rubber regains its elastic properties and reseals after rewarming to ambient temperature, leaks during frozen temperature storage and transportation are transient and the CCI methods used at room temperature conditions are unable to confirm CCI in the frozen state. Hence, several experimental methods have been developed in recent years in order to evaluate CCI at low temperatures. Finite Element (FE) simulations were applied in order to investigate the sealing behaviour of rubber stoppers for the drug product CCS under frozen storage conditions. FE analysis can help reducing the experimental design space and thus number of measurements needed, as they can be used as an ad-on to experimental testing. Several scenarios have been simulated including the effect of thermal history, rubber type, storage time, worst case CCS geometric tolerances and capping pressure. The results of these calculations have been validated with experimental data derived from laboratory experiments (CCI at low temperatures), and a concept for tightness has been developed. It has been concluded that FE simulations have the potential to become a powerful predictive tool towards a better understanding of the influence of cold storage on the rubber sealing properties (and hence on CCI) when dealing with frozen drug products. Copyright © 2018, Parenteral Drug Association.

Terahertz-dependent identification of simulated hole shapes in oil-gas reservoirs

Science.gov (United States)

Bao, Ri-Ma; Zhan, Hong-Lei; Miao, Xin-Yang; Zhao, Kun; Feng, Cheng-Jing; Dong, Chen; Li, Yi-Zhang; Xiao, Li-Zhi

2016-10-01

Detecting holes in oil-gas reservoirs is vital to the evaluation of reservoir potential. The main objective of this study is to demonstrate the feasibility of identifying general micro-hole shapes, including triangular, circular, and square shapes, in oil-gas reservoirs by adopting terahertz time-domain spectroscopy (THz-TDS). We evaluate the THz absorption responses of punched silicon (Si) wafers having micro-holes with sizes of 20 μm-500 μm. Principal component analysis (PCA) is used to establish a model between THz absorbance and hole shapes. The positions of samples in three-dimensional spaces for three principal components are used to determine the differences among diverse hole shapes and the homogeneity of similar shapes. In addition, a new Si wafer with the unknown hole shapes, including triangular, circular, and square, can be qualitatively identified by combining THz-TDS and PCA. Therefore, the combination of THz-TDS with mathematical statistical methods can serve as an effective approach to the rapid identification of micro-hole shapes in oil-gas reservoirs. Project supported by the National Natural Science Foundation of China (Grant No. 61405259), the National Basic Research Program of China (Grant No. 2014CB744302), and the Specially Founded Program on National Key Scientific Instruments and Equipment Development, China (Grant No. 2012YQ140005).

Reversal of Flux Closure States in Cobalt Nanoparticle Rings With Coaxial Magnetic Pulses

DEFF Research Database (Denmark)

Kasama, T; Dunin-Borkowski, Rafal E.; Scheinfein, MR

2008-01-01

Bistable flux closure (FC) states in Co nanoparticle rings can be switched reversibly by applying a coaxial magnetic field (H-z). The FC switching phenomena can be reproduced by micromagnetics simulations, which also reveal novel magnetic states at intermediate applied field strengths.......Bistable flux closure (FC) states in Co nanoparticle rings can be switched reversibly by applying a coaxial magnetic field (H-z). The FC switching phenomena can be reproduced by micromagnetics simulations, which also reveal novel magnetic states at intermediate applied field strengths....

The Seepage Simulation of Single Hole and Composite Gas Drainage Based on LB Method

Science.gov (United States)

Chen, Yanhao; Zhong, Qiu; Gong, Zhenzhao

2018-01-01

Gas drainage is the most effective method to prevent and solve coal mine gas power disasters. It is very important to study the seepage flow law of gas in fissure coal gas. The LB method is a simplified computational model based on micro-scale, especially for the study of seepage problem. Based on fracture seepage mathematical model on the basis of single coal gas drainage, using the LB method during coal gas drainage of gas flow numerical simulation, this paper maps the single-hole drainage gas, symmetric slot and asymmetric slot, the different width of the slot combined drainage area gas flow under working condition of gas cloud of gas pressure, flow path diagram and flow velocity vector diagram, and analyses the influence on gas seepage field under various working conditions, and also discusses effective drainage method of the center hole slot on both sides, and preliminary exploration that is related to the combination of gas drainage has been carried on as well.

Black hole accretion: the quasar powerhouse

International Nuclear Information System (INIS)

Anon.

1983-01-01

A program is described which calculates the effects of material falling into the curved space-time surrounding a rotation black hole. The authors have developed a two-dimensional, general-relativistic hydrodynamics code to simulate fluid flow in the gravitational field of a rotating black hole. Such calculations represent models that have been proposed for the energy sources of both quasars and jets from radiogalaxies. In each case, the black hole that powers the quasar or jet would have a mass of about 100 million times the mass of the sun. The black hole would be located in the center of a galaxy whose total mass is 1000 time greater than the black hole mass. (SC)

Macular hole-associated retinal detachment in Best vitelliform dystrophy: Series of two cases and literature review

Science.gov (United States)

Tewari, Ruchir; Kumar, Vinod; Ravani, Raghav; Dubey, Devashish; Chandra, Parijat; Kumar, Atul

2018-01-01

Two eyes of 2 patients with macular hole-associated retinal detachment in clinically diagnosed vitelliruptive stage of Best vitelliform dystrophy were surgically managed by 25-gauge sutureless pars plana vitrectomy, internal limiting membrane (ILM) peeling with inverted ILM flap, and short-acting (SF6) gas tamponade. The patients were assessed with respect to best-corrected visual acuity, color fundus photographs, shortwave fundus autofluorescence, and swept source optical coherence tomography. Surgical intervention led to Type 1 closure of macular hole, resolution of retinal detachment, and improvement in vision in both patients. PMID:29676326

Macular hole-associated retinal detachment in Best vitelliform dystrophy: Series of two cases and literature review

Directory of Open Access Journals (Sweden)

Ruchir Tewari

2018-01-01

Full Text Available Two eyes of 2 patients with macular hole-associated retinal detachment in clinically diagnosed vitelliruptive stage of Best vitelliform dystrophy were surgically managed by 25-gauge sutureless pars plana vitrectomy, internal limiting membrane (ILM peeling with inverted ILM flap, and short-acting (SF6 gas tamponade. The patients were assessed with respect to best-corrected visual acuity, color fundus photographs, shortwave fundus autofluorescence, and swept source optical coherence tomography. Surgical intervention led to Type 1 closure of macular hole, resolution of retinal detachment, and improvement in vision in both patients.

Interaction between Electron Holes in a Strongly Magnetized Plasma

DEFF Research Database (Denmark)

Lynov, Jens-Peter; Michelsen, Poul; Pécseli, Hans

1980-01-01

The interaction between electron holes in a strongly magnetized, plasma-filled waveguide is investigated by means of computer simulation. Two holes may or may not coalesce, depending on their amplitudes and velocities. The interaction between holes and Trivelpiece-Gould solitons is demonstrated...

Semiclassical Approach to Black Hole Evaporation

OpenAIRE

Lowe, David A.

1992-01-01

Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two dimensional black hole models. The first is the original CGHS model, the second is another two dimensional dilaton-gravity model, but with properties much closer to physics in the real, four dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are fou...

Merging Black Holes

Science.gov (United States)

Centrella, Joan

2012-01-01

The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as future. space-based detectors. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. For many years, numerical codes designed to simulate black hole mergers were plagued by a host of instabilities. However, recent breakthroughs have conquered these instabilities and opened up this field dramatically. This talk will focus on.the resulting 'gold rush' of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, testing general relativity, and astrophysics

Single night postoperative prone posturing in idiopathic macular hole surgery.

LENUS (Irish Health Repository)

2012-02-01

Purpose. To evaluate the role of postoperative prone posturing for a single night in the outcome of trans pars plana vitrectomy (TPPV) with internal limiting membrane (ILM) peel and 20% perfluoroethane (C2F6) internal tamponade for idiopathic macular hole. Methods. This prospective trial enrolled 14 eyes in 14 consecutive patients with idiopathic macular hole. All eyes underwent TPPV with vision blue assisted ILM peeling with and without phacoemulsification and intraocular lens (IOL) for macular hole. Intraocular gas tamponade (20% C2F6) was used in all cases with postoperative face-down posturing overnight and without specific posturing afterwards. LogMAR visual acuity, appearance by slit-lamp biomicroscopy, and ocular coherence tomography (OCT) scans were compared preoperatively and postoperatively to assess outcome. Results. Among 14 eyes recruited, all eyes were phakic; 50% of patients underwent concurrent phacoemulsification with IOL. The macular holes were categorized preoperatively by OCT appearance, 4 (28.57%) were stage 2, 7 (50%) were stage 3, and 3 (21.43%) were stage 4. Mean macular hole size was 0.35 disk diameters. Symptoms of macular hole had been present for an average of 6.5 months. All holes (100%) were closed 3 and 6 months postoperatively. Mean visual acuity (logMAR) was improved to 0.61 at 3 months and was stable at 6 months after the surgery. None of the eyes had worse vision postoperatively. Conclusions. Vitrectomy with ILM peeling and 20% C2F6 gas with a brief postoperative 1 night prone posturing regimen is a reasonable approach to achieve anatomic closure in idiopathic macular hole. Concurrent cataract extraction did not alter outcomes and was not associated with any additional complications.

Probing the Magnetic Field Structure in Sgr A* on Black Hole Horizon Scales with Polarized Radiative Transfer Simulations

Energy Technology Data Exchange (ETDEWEB)

Gold, Roman; McKinney, Jonathan C. [Department of Physics and Joint Space-Science Institute, University of Maryland, College Park, MD 20742 (United States); Johnson, Michael D.; Doeleman, Sheperd S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2017-03-10

Magnetic fields are believed to drive accretion and relativistic jets in black hole accretion systems, but the magnetic field structure that controls these phenomena remains uncertain. We perform general relativistic (GR) polarized radiative transfer of time-dependent three-dimensional GR magnetohydrodynamical simulations to model thermal synchrotron emission from the Galactic Center source Sagittarius A* (Sgr A*). We compare our results to new polarimetry measurements by the Event Horizon Telescope (EHT) and show how polarization in the visibility (Fourier) domain distinguishes and constrains accretion flow models with different magnetic field structures. These include models with small-scale fields in disks driven by the magnetorotational instability as well as models with large-scale ordered fields in magnetically arrested disks. We also consider different electron temperature and jet mass-loading prescriptions that control the brightness of the disk, funnel-wall jet, and Blandford–Znajek-driven funnel jet. Our comparisons between the simulations and observations favor models with ordered magnetic fields near the black hole event horizon in Sgr A*, though both disk- and jet-dominated emission can satisfactorily explain most of the current EHT data. We also discuss how the black hole shadow can be filled-in by jet emission or mimicked by the absence of funnel jet emission. We show that stronger model constraints should be possible with upcoming circular polarization and higher frequency (349 GHz) measurements.

Simulating the X-ray luminosity of Be X-ray binaries: the case for black holes versus neutron stars

Science.gov (United States)

Brown, R. O.; Ho, W. C. G.; Coe, M. J.; Okazaki, A. T.

2018-04-01

There are over 100 Be stars that are known to have neutron star companions but only one such system with a black hole. Previous theoretical work suggests this is not due to their formation but due to differences in X-ray luminosity. It has also been proposed that the truncation of the Be star's circumstellar disc is dependent on the mass of the compact object. Hence, Be star discs in black hole binaries are smaller. Since accretion onto the compact object from the Be star's disc is what powers the X-ray luminosity, a smaller disc in black hole systems leads to a lower luminosity. In this paper, simulations are performed with a range of eccentricities and compact object mass. The disc's size and density are shown to be dependent on both quantities. Mass capture and, in turn, X-ray luminosity are heavily dependent on the size and density of the disc. Be/black hole binaries are expected to be up to ˜10 times fainter than Be/neutron star binaries when both systems have the same eccentricity and can be 100 times fainter when comparing systems with different eccentricity.

INDUCTION OF MACULAR DETACHMENT FOR THE TREATMENT OF PERSISTENT OR RECURRENT IDIOPATHIC MACULAR HOLES.

Science.gov (United States)

Szigiato, Andrei-Alexandru; Gilani, Fatimah; Walsh, Mark K; Mandelcorn, Efrem D; Muni, Rajeev H

2016-09-01

To analyze the efficacy of induced macular detachment for the treatment of persistent or recurrent idiopathic macular holes after treatment with one or more standard pars plana vitrectomies (PPVs) with internal limiting membrane peeling. This study is a retrospective consecutive case series of 10 patients who underwent a PPV with subretinal balanced salt solution injection from 2011 to 2014 to treat persistent or recurrent idiopathic macular holes. All patients had previously undergone PPV with internal limiting membrane peeling. Visual acuity, ocular examination findings, and optical coherence tomographic images were reviewed preoperatively and postoperatively to assess the anatomical and visual outcomes of this procedure. Nine of the 10 patients who underwent the procedure had closure of their macular holes postoperatively (90%) and remained closed 6 months postoperatively. Most patients reported a subjective visual improvement. A mean objective visual improvement of 16 letters (Early Treatment Diabetic Retinopathy Study, 0.324 logMAR) was seen between preoperative and 6-month postoperative assessments of all patients (pre = 1.490, post = 1.166; P = 0.022). Subgroup analysis of patients with successful closure revealed 20 letters of improvement (0.398 logMAR) in visual acuity (pre = 1.491, post = 1.093; P = 0.004). There were no intraoperative or postoperative complications. In eyes with persistent or recurrent idiopathic macular holes after standard PPV with internal limiting membrane peeling, repeat PPV with subretinal balanced salt solution injection to create a macular detachment may be a viable surgical treatment option. Our results show improved anatomical and visual outcomes postoperatively that compare favorably to other case series describing various surgical treatments for these challenging cases.

Road Closures

Data.gov (United States)

Montgomery County of Maryland — This is an up to date map of current road closures in Montgomery County.This dataset is updated every few minutes from the Department of Transportation road closure...

Self-testing security sensor for monitoring closure of vault doors and the like

International Nuclear Information System (INIS)

Cawthorne, D.C.

1997-01-01

A self-testing device is provided for a monitoring system for monitoring whether a closure member such as a door or window is closed. The monitoring system includes a switch unit mounted on the frame of the closure member being monitored and including magnetically biased switches connected in one or more electrical monitoring circuits, and a door magnet unit mounted on the closure member being monitored. The door magnet includes one or more permanent magnets that produce a magnetic field which, when the closure member is closed, cause said switches to assume a first state. When the closure member is opened, the switches switch to a second, alarm state. The self-testing device is electrically controllable from a remote location and produces a canceling or diverting magnetic field which simulates the effect of movement of the closure member from the closed position thereof without any actual movement of the member. 5 figs

Hamiltonian closures in fluid models for plasmas

Science.gov (United States)

Tassi, Emanuele

2017-11-01

This article reviews recent activity on the Hamiltonian formulation of fluid models for plasmas in the non-dissipative limit, with emphasis on the relations between the fluid closures adopted for the different models and the Hamiltonian structures. The review focuses on results obtained during the last decade, but a few classical results are also described, in order to illustrate connections with the most recent developments. With the hope of making the review accessible not only to specialists in the field, an introduction to the mathematical tools applied in the Hamiltonian formalism for continuum models is provided. Subsequently, we review the Hamiltonian formulation of models based on the magnetohydrodynamics description, including those based on the adiabatic and double adiabatic closure. It is shown how Dirac's theory of constrained Hamiltonian systems can be applied to impose the incompressibility closure on a magnetohydrodynamic model and how an extended version of barotropic magnetohydrodynamics, accounting for two-fluid effects, is amenable to a Hamiltonian formulation. Hamiltonian reduced fluid models, valid in the presence of a strong magnetic field, are also reviewed. In particular, reduced magnetohydrodynamics and models assuming cold ions and different closures for the electron fluid are discussed. Hamiltonian models relaxing the cold-ion assumption are then introduced. These include models where finite Larmor radius effects are added by means of the gyromap technique, and gyrofluid models. Numerical simulations of Hamiltonian reduced fluid models investigating the phenomenon of magnetic reconnection are illustrated. The last part of the review concerns recent results based on the derivation of closures preserving a Hamiltonian structure, based on the Hamiltonian structure of parent kinetic models. Identification of such closures for fluid models derived from kinetic systems based on the Vlasov and drift-kinetic equations are presented, and

Star clusters containing massive, central black holes: evolution calculations

International Nuclear Information System (INIS)

Marchant, A.B.

1980-01-01

This dissertation presents a detailed, two-dimensional simulations of star cluster evolution. A Monte-Carlo method is adapted to simulate the development with time of isolated star clusters. Clusters which evolve on relaxation timescales with and without central black holes are treated. The method is flexible and rugged, rather than highly accurate. It treats the boundary conditions of stellar evaporation and tidal disruption by a central black hole in a precise, stochastic fashion. Dynamical cloning and renormalization and the use of a time-step adjustment algorithm enhance the feasibility of the method which simulates systems with wide ranges of intrinsic length and time scales. First, the method is applied to follow the development and core collapse of an initial Plummer-model cluster without a central black hole. Agreement of these results for early times with the results of previous authors serves as a verification of this method. Three calculations of cluster re-expansion, each beginning with the insertion of a black hole at the center of a highly collapsed cluster core is presented. Each case is characterized by a different value of initial black hole mass or black hole accretion efficiency for the consumption of debris from disrupted stars. It is found that for the special cases examined here substantial, but not catastrophic, growth of the central black hole may accompany core re-expansion. Also, the observability of the evolutionary phases associated with core collapse and re-expansion, constraints on x-ray sources which could be associated with growing black holes, and the observable signature of the cusp of stars surrounding a central black hole are discussed

Interferometric Imaging Directly with Closure Phases and Closure Amplitudes

Science.gov (United States)

Chael, Andrew A.; Johnson, Michael D.; Bouman, Katherine L.; Blackburn, Lindy L.; Akiyama, Kazunori; Narayan, Ramesh

2018-04-01

Interferometric imaging now achieves angular resolutions as fine as ∼10 μas, probing scales that are inaccessible to single telescopes. Traditional synthesis imaging methods require calibrated visibilities; however, interferometric calibration is challenging, especially at high frequencies. Nevertheless, most studies present only a single image of their data after a process of “self-calibration,” an iterative procedure where the initial image and calibration assumptions can significantly influence the final image. We present a method for efficient interferometric imaging directly using only closure amplitudes and closure phases, which are immune to station-based calibration errors. Closure-only imaging provides results that are as noncommittal as possible and allows for reconstructing an image independently from separate amplitude and phase self-calibration. While closure-only imaging eliminates some image information (e.g., the total image flux density and the image centroid), this information can be recovered through a small number of additional constraints. We demonstrate that closure-only imaging can produce high-fidelity results, even for sparse arrays such as the Event Horizon Telescope, and that the resulting images are independent of the level of systematic amplitude error. We apply closure imaging to VLBA and ALMA data and show that it is capable of matching or exceeding the performance of traditional self-calibration and CLEAN for these data sets.

Featured Image: Making a Rapidly Rotating Black Hole

Science.gov (United States)

Kohler, Susanna

2017-10-01

These stills from a simulation show the evolution (from left to right and top to bottom) of a high-mass X-ray binary over 1.1 days, starting after the star on the right fails to explode as a supernova and then collapses into a black hole. Many high-mass X-ray binaries like the well-known Cygnus X-1, the first source widely accepted to be a black hole host rapidly spinning black holes. Despite our observations of these systems, however, were still not sure how these objects end up with such high rotation speeds. Using simulations like that shown above, a team of scientists led by Aldo Batta (UC Santa Cruz) has demonstrated how a failed supernova explosion can result in such a rapidly spinning black hole. The authors work shows that in a binary where one star attempts to explode as a supernova and fails it doesnt succeed in unbinding the star the large amount of fallback material can interact with the companion star and then accrete onto the black hole, spinning it up in the process. You can read more about the authors simulations and conclusions in the paper below.CitationAldo Batta et al 2017 ApJL 846 L15. doi:10.3847/2041-8213/aa8506

Development and validation of a laparoscopic hysterectomy cuff closure simulation model for surgical training.

Science.gov (United States)

Tunitsky-Bitton, Elena; Propst, Katie; Muffly, Tyler

2016-03-01

The number of robotically assisted hysterectomies is increasing, and therefore, the opportunities for trainees to become competent in performing traditional laparoscopic hysterectomy are decreasing. Simulation-based training is ideal for filling this gap in training. The objective of the study was to design a surgical model for training in laparoscopic vaginal cuff closure and to present evidence of its validity and reliability as an assessment and training tool. Participants included gynecology staff and trainees at 2 tertiary care centers. Experienced surgeons were also recruited at the combined International Urogynecologic Association and American Urogynecologic Society scientific meeting. Participants included 19 experts and 21 trainees. All participants were recorded using the laparoscopic hysterectomy cuff closure simulation model. The model was constructed using the an advanced uterine manipulation system with a sacrocolopexy tip/vaginal stent, a vaginal cuff constructed from neoprene material and lined with a swimsuit material (nylon and spandex) secured to the vaginal stent with a plastic cable tie. The uterine manipulation system was attached to the fundamentals of laparoscopic surgery laparoscopic training box trainer using a metal bracket. Performance was evaluated using the Global Operative Assessment of Laparoscopic Skills scale. In addition, needle handling, knot tying, and incorporation of epithelial edge were also evaluated. The Student t test was used to compare the scores and the operating times between the groups. Intrarater reliability between the scores by the 2 masked experts was measured using the interclass correlation coefficient. Total and annual experience with laparoscopic suturing and specifically vaginal cuff closure varied greatly among the participants. For the construct validity, the participants in the expert group received significantly higher scores in each of the domains of the Global Operative Assessment of Laparoscopic Skills

Visualizing, Approximating, and Understanding Black-Hole Binaries

Science.gov (United States)

Nichols, David A.

Numerical-relativity simulations of black-hole binaries and advancements in gravitational-wave detectors now make it possible to learn more about the collisions of compact astrophysical bodies. To be able to infer more about the dynamical behavior of these objects requires a fuller analysis of the connection between the dynamics of pairs of black holes and their emitted gravitational waves. The chapters of this thesis describe three approaches to learn more about the relationship between the dynamics of black-hole binaries and their gravitational waves: modeling momentum flow in binaries with the Landau-Lifshitz formalism, approximating binary dynamics near the time of merger with post-Newtonian and black-hole-perturbation theories, and visualizing spacetime curvature with tidal tendexes and frame-drag vortexes. In Chapters 2--4, my collaborators and I present a method to quantify the flow of momentum in black-hole binaries using the Landau-Lifshitz formalism. Chapter 2 reviews an intuitive version of the formalism in the first-post-Newtonian approximation that bears a strong resemblance to Maxwell's theory of electromagnetism. Chapter 3 applies this approximation to relate the simultaneous bobbing motion of rotating black holes in the superkick configuration---equal-mass black holes with their spins anti-aligned and in the orbital plane---to the flow of momentum in the spacetime, prior to the black holes' merger. Chapter 4 then uses the Landau-Lifshitz formalism to explain the dynamics of a head-on merger of spinning black holes, whose spins are anti-aligned and transverse to the infalling motion. Before they merge, the black holes move with a large, transverse, velocity, which we can explain using the post-Newtonian approximation; as the holes merge and form a single black hole, we can use the Landau-Lifshitz formalism without any approximations to connect the slowing of the final black hole to its absorbing momentum density during the merger. In Chapters 5

Extraordinary mid-infrared transmission of subwavelength holes in gold films

KAUST Repository

Yue, Weisheng

2014-04-01

Gold (Au) nanoholes are fabricated with electron-beam lithography and used for the investigation of extraordinary transmission in mid-infrared regime. Transmission properties of the nanoholes are studied as the dependence on hole-size. Transmittance spectra are characterized by Fourier transform infrared spectroscopy (FTIR) and enhanced transmittance through the subwavelength holes is observed. The transmission spectra exhibit well-defined maximum and minimum of which the position are determined by the lattice of the hole array. The hole-size primarily influence the transmission intensity and bandwidth of the resonance peak. With an increase of hole-size, while keep lattice constant fixed, the intensity of the resonance peak and the bandwidth increases, which are due to the localized surface plasmons. Numerical simulation for the transmission through the subwavelength holes is performed and the simulated results agree with the experimental observations. Copyright © 2014 American Scientific Publishers.

Extraordinary mid-infrared transmission of subwavelength holes in gold films

KAUST Repository

Yue, Weisheng; Wang, Zhihong; Yang, Yang; Chen, Longqing; Syed, Ahad A.; Wang, Xianbin

2014-01-01

Gold (Au) nanoholes are fabricated with electron-beam lithography and used for the investigation of extraordinary transmission in mid-infrared regime. Transmission properties of the nanoholes are studied as the dependence on hole-size. Transmittance spectra are characterized by Fourier transform infrared spectroscopy (FTIR) and enhanced transmittance through the subwavelength holes is observed. The transmission spectra exhibit well-defined maximum and minimum of which the position are determined by the lattice of the hole array. The hole-size primarily influence the transmission intensity and bandwidth of the resonance peak. With an increase of hole-size, while keep lattice constant fixed, the intensity of the resonance peak and the bandwidth increases, which are due to the localized surface plasmons. Numerical simulation for the transmission through the subwavelength holes is performed and the simulated results agree with the experimental observations. Copyright © 2014 American Scientific Publishers.

Reinvestigation of moving punctured black holes with a new code

International Nuclear Information System (INIS)

Cao Zhoujian; Yo Hweijang; Yu Juiping

2008-01-01

We report on our code, in which the moving puncture method is applied and an adaptive/fixed mesh refinement is implemented, and on its preliminary performance on black hole simulations. Based on the Baumgarte-Sharpiro-Shibata-Nakamura (BSSN) formulation, up-to-date gauge conditions and the modifications of the formulation are also implemented and tested. In this work, we present our primary results about the simulation of a single static black hole, of a moving single black hole, and of the head-on collision of a binary black hole system. For the static punctured black hole simulations, different modifications of the BSSN formulation are applied. It is demonstrated that both the currently used sets of modifications lead to a stable evolution. For cases of a moving punctured black hole with or without spin, we search for viable gauge conditions and study the effect of spin on the black hole evolution. Our results confirm previous results obtained by other research groups. In addition, we find a new gauge condition, which has not yet been adopted by any other researchers, which can also give stable and accurate black hole evolution calculations. We examine the performance of the code for the head-on collision of a binary black hole system, and the agreement of the gravitational waveform it produces with that obtained in other works. In order to understand qualitatively the influence of matter on the binary black hole collisions, we also investigate the same head-on collision scenarios but perturbed by a scalar field. The numerical simulations performed with this code not only give stable and accurate results that are consistent with the works by other numerical relativity groups, but also lead to the discovery of a new viable gauge condition, as well as clarify some ambiguities in the modification of the BSSN formulation. These results demonstrate that this code is reliable and ready to be used in the study of more realistic astrophysical scenarios and of numerical

Numerical Relativity, Black Hole Mergers, and Gravitational Waves: Part II

Science.gov (United States)

Centrella, Joan

2012-01-01

This series of 3 lectures will present recent developments in numerical relativity, and their applications to simulating black hole mergers and computing the resulting gravitational waveforms. In this second lecture, we focus on simulations of black hole binary mergers. We hig hlight the instabilities that plagued the codes for many years, the r ecent breakthroughs that led to the first accurate simulations, and the current state of the art.

Understanding the fate of merging supermassive black holes

International Nuclear Information System (INIS)

Campanelli, Manuela

2005-01-01

Understanding the fate of merging supermassive black holes in galactic mergers, and the gravitational wave emission from this process, are important LISA science goals. To this end, we present results from numerical relativity simulations of binary black hole mergers using the so-called Lazarus approach to model gravitational radiation from these events. In particular, we focus here on some recent calculations of the final spin and recoil velocity of the remnant hole formed at the end of a binary black hole merger process, which may constrain the growth history of massive black holes at the core of galaxies and globular clusters

The theory of optical black hole lasers

Energy Technology Data Exchange (ETDEWEB)

Gaona-Reyes, José L., E-mail: jgaona@fis.cinvestav.mx; Bermudez, David, E-mail: dbermudez@fis.cinvestav.mx

2017-05-15

The event horizon of black holes and white holes can be achieved in the context of analogue gravity. It was proven for a sonic case that if these two horizons are close to each other their dynamics resemble a laser, a black hole laser, where the analogue of Hawking radiation is trapped and amplified. Optical analogues are also very successful and a similar system can be achieved there. In this work we develop the theory of optical black hole lasers and prove that the amplification is also possible. Then, we study the optical system by determining the forward propagation of modes, obtaining an approximation for the phase difference which governs the amplification, and performing numerical simulations of the pulse propagation of our system. - Highlights: • We develop the conditions to obtain the kinematics of the optical black hole laser. • We prove the amplification of Hawking radiation for the optical case. • We derive the forward propagation of modes and check the result of the backward case. • A model is proposed to calculate the phase difference and the amplification rate. • We perform numerical simulations of a pulse between two solitons forming a cavity.

Closure simulation of the MSIV of Unit 1 of the Laguna Verde nuclear power plant using the Simulate 3K code; Simulacion del cierre de las MSIV de la Unidad 1 de la central nuclear Laguna Verde empleando el codigo Simulate-3K

Energy Technology Data Exchange (ETDEWEB)

Alegria A, A., E-mail: aalegria@cnsns.gob.mx [Comision Nacional de Seguridad Nuclear y Salvaguardias, Dr. Barragan 779, Col. Narvarte, 03020 Ciudad de Mexico (Mexico)

2015-09-15

In this paper the simulation of closure transient of all main steam isolation valves (MSIV) was performed with the Simulate-3K (S-3K) code for the Unit 1 of the Laguna Verde nuclear power plant (NPP-LV), which operates to thermal power of 2317 MWt, corresponding to the cycle 15 of operation. The set points for the performance of systems correspond to those set out in transient analysis: 3 seconds for the closure of all MSIV; the start of Scram when 121% of the neutron flux is reached, respect from baseline before the transient; the opening by peer of safety relief valves (SRV) in relief mode when the set point of the pressure is reached, the shoot of the feedwater flow seconds after the start of closing of the MSIV and the shoot of the recirculation water pumps when the pressure is reached in the dome of 1048 psig. The simulation time was of 57 seconds, with the top 50 to reach the steady state, from which the closure of all MSIV starts. In this paper the behavior of the pressure in the dome are analyzed, thermal power, neutron flux, the collapsed water level, the flow at the entrance of core, the steam flow coming out of vessel and the flow through of the SRV; the fuel temperature, the minimal critical power ratio, the readings in the instrumentation systems and reactivities. Instrumentation systems were implemented to analyze the neutron flux, these consist of 96 local power range monitors (LPRM) located in different radial and axial positions of the core and 4 channels of average power range monitors, which grouped at 24 LPRM each one. LPRM response to the change of neutron flux in the center of the core, at different axial positions is also shown. Finally, the results show that the safety limit MCPR is not exceeded. (Author)

When Black Holes Collide

Science.gov (United States)

Baker, John

2010-01-01

Among the fascinating phenomena predicted by General Relativity, Einstein's theory of gravity, black holes and gravitational waves, are particularly important in astronomy. Though once viewed as a mathematical oddity, black holes are now recognized as the central engines of many of astronomy's most energetic cataclysms. Gravitational waves, though weakly interacting with ordinary matter, may be observed with new gravitational wave telescopes, opening a new window to the universe. These observations promise a direct view of the strong gravitational dynamics involving dense, often dark objects, such as black holes. The most powerful of these events may be merger of two colliding black holes. Though dark, these mergers may briefly release more energy that all the stars in the visible universe, in gravitational waves. General relativity makes precise predictions for the gravitational-wave signatures of these events, predictions which we can now calculate with the aid of supercomputer simulations. These results provide a foundation for interpreting expect observations in the emerging field of gravitational wave astronomy.

ATLAS: Black hole production and decay

CERN Multimedia

2004-01-01

This track is an example of simulated data modelled for the ATLAS detector on the Large Hadron Collider (LHC) at CERN, which will begin taking data in 2008. These tracks would be produced if a miniature black hole was produced in the proton-proton collision. Such a small black hole would decay instantly to various particles via a process known as Hawking radiation.

RECURRENT MACULAR HOLES IN THE ERA OF SMALL-GAUGE VITRECTOMY: A Review of Incidence, Risk Factors, and Outcomes.

Science.gov (United States)

Abbey, Ashkan M; Van Laere, Lily; Shah, Ankoor R; Hassan, Tarek S

2017-05-01

To evaluate the preoperative features, intraoperative management, and postoperative outcomes of recurrent macular holes that developed after initial successful repair with small-gauge vitrectomy techniques. We retrospectively reviewed 392 eyes with idiopathic macular holes successfully treated with small-gauge vitrectomy. Thirteen of these eyes underwent reoperation after macular hole reopening. We assessed patient demographics, visual acuity, postoperative anatomical success, potential precipitating clinical factors of hole reopening, and details of the surgical repairs of these eyes. Macular hole reopening occurred in 13 (3.3%) of 392 eyes in a mean of 28 months (range, 1-120 months) after initial repair. All 13 recurrent holes closed after a second vitrectomy, but 4 (31%) holes reopened again and had vitrectomy. Of these, 2 reopened a third time. Ultimately, 11 (85%) holes were closed at the most recent follow-up. The mean best-corrected visual acuity was 20/81 before initial repair, 20/148 after the first reopening, 20/115 after repair of the first reopening, and 20/55 after repair of >1 reopening. Ten of 13 (77%) patients had, or later developed, macular holes in the other eye during follow-up. Reoperation successfully achieved hole closure and ultimate visual improvement in most eyes with recurrent macular holes. Most patients with recurrent holes previously had, or later developed, full-thickness macular holes in the other eye.

Tracking black holes in numerical relativity

International Nuclear Information System (INIS)

Caveny, Scott A.; Anderson, Matthew; Matzner, Richard A.

2003-01-01

This work addresses the problem of generically tracking black hole event horizons in computational simulation of black hole interactions. Solutions of the hyperbolic eikonal equation, solved on a curved spacetime manifold containing black hole sources, are employed in development of a robust tracking method capable of continuously monitoring arbitrary changes of topology in the event horizon as well as arbitrary numbers of gravitational sources. The method makes use of continuous families of level set viscosity solutions of the eikonal equation with identification of the black hole event horizon obtained by the signature feature of discontinuity formation in the eikonal's solution. The method is employed in the analysis of the event horizon for the asymmetric merger in a binary black hole system. In this first such three dimensional analysis, we establish both qualitative and quantitative evidence for our method and its application to the asymmetric problem. We focus attention on (1) the topology of the throat connecting the holes following merger, (2) the time of merger, and (3) continuing to account for the surface of section areas of the black hole sources

Closure The Definitive Guide

CERN Document Server

Bolin, Michael

2010-01-01

If you're ready to use Closure to build rich web applications with JavaScript, this hands-on guide has precisely what you need to learn this suite of tools in depth. Closure makes it easy for experienced JavaScript developers to write and maintain large and complex codebases -- as Google has demonstrated by using Closure with Gmail, Google Docs, and Google Maps. Author and Closure contributor Michael Bolin has included numerous code examples and best practices, as well as valuable information not available publicly until now. You'll learn all about Closure's Library, Compiler, Templates, tes

Multivariate moment closure techniques for stochastic kinetic models

International Nuclear Information System (INIS)

Lakatos, Eszter; Ale, Angelique; Kirk, Paul D. W.; Stumpf, Michael P. H.

2015-01-01

Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs

Multivariate moment closure techniques for stochastic kinetic models

Energy Technology Data Exchange (ETDEWEB)

Lakatos, Eszter, E-mail: e.lakatos13@imperial.ac.uk; Ale, Angelique; Kirk, Paul D. W.; Stumpf, Michael P. H., E-mail: m.stumpf@imperial.ac.uk [Department of Life Sciences, Centre for Integrative Systems Biology and Bioinformatics, Imperial College London, London SW7 2AZ (United Kingdom)

2015-09-07

Stochastic effects dominate many chemical and biochemical processes. Their analysis, however, can be computationally prohibitively expensive and a range of approximation schemes have been proposed to lighten the computational burden. These, notably the increasingly popular linear noise approximation and the more general moment expansion methods, perform well for many dynamical regimes, especially linear systems. At higher levels of nonlinearity, it comes to an interplay between the nonlinearities and the stochastic dynamics, which is much harder to capture correctly by such approximations to the true stochastic processes. Moment-closure approaches promise to address this problem by capturing higher-order terms of the temporally evolving probability distribution. Here, we develop a set of multivariate moment-closures that allows us to describe the stochastic dynamics of nonlinear systems. Multivariate closure captures the way that correlations between different molecular species, induced by the reaction dynamics, interact with stochastic effects. We use multivariate Gaussian, gamma, and lognormal closure and illustrate their use in the context of two models that have proved challenging to the previous attempts at approximating stochastic dynamics: oscillations in p53 and Hes1. In addition, we consider a larger system, Erk-mediated mitogen-activated protein kinases signalling, where conventional stochastic simulation approaches incur unacceptably high computational costs.

Reynolds Stress Closure for Inertial Frames and Rotating Frames

Science.gov (United States)

Petty, Charles; Benard, Andre

2017-11-01

In a rotating frame-of-reference, the Coriolis acceleration and the mean vorticity field have a profound impact on the redistribution of kinetic energy among the three components of the fluctuating velocity. Consequently, the normalized Reynolds (NR) stress is not objective. Furthermore, because the Reynolds stress is defined as an ensemble average of a product of fluctuating velocity vector fields, its eigenvalues must be non-negative for all turbulent flows. These fundamental properties (realizability and non-objectivity) of the NR-stress cannot be compromised in computational fluid dynamic (CFD) simulations of turbulent flows in either inertial frames or in rotating frames. The recently developed universal realizable anisotropic prestress (URAPS) closure for the NR-stress depends explicitly on the local mean velocity gradient and the Coriolis operator. The URAPS-closure is a significant paradigm shift from turbulent closure models that assume that dyadic-valued operators associated with turbulent fluctuations are objective.

[Long-term outcome of vitrectomy combined with internal limiting membrane peeling for idiopathic macular holes].

Science.gov (United States)

Yamamoto, Kaori; Hori, Sadao

2011-01-01

To elucidate the long-term outcome of internal limiting membrane (ILM) peeling on visual function during vitrectomy for idiopathic macular holes using scanning laser ophthalmoscope (SLO) microperimetry. Prospective uncontrolled study. We studied 31 eyes (29 patients) with idiopathic macular holes. All patients underwent vitrectomy with ILM peeling. The SLO microperimetry was performed preoperatively, and once a year for 3 years postoperatively to detect scotomas in and around the macular holes, and both within and in close vicinity to the areas of ILM peeling. Closure of macular holes after one surgery was confirmed in all cases except for 2 with second surgery. The visual acuity by logarithmic minimum angle of resolution (logMAR) averaged 0.71 +/- 0.36 before surgery, 0.23 +/- 0.31 one year, 0.14 +/- 0.27 two years and 0.12 +/- 0.26 three years after surgery. There was significant improvement up to 2 years after the surgery. All scotomas detected before surgery in the holes, and 77.4% of those detected around the holes decreased gradually. No scotomas were detected in or around the area of ILM peeling either before or after surgery. ILM peeling in vitrectomy for idiopathic macular holes successfully improved visual acuity and did not influence retinal sensitivity in and around the area of ILM peeling. The scotomas detected in and around the holes before surgery gradually reduced or disappeared.

Black holes go supersonic

Energy Technology Data Exchange (ETDEWEB)

Leonhardt, Ulf [School of Physics and Astronomy, University of St. Andrews (United Kingdom)

2001-02-01

In modern physics, the unification of gravity and quantum mechanics remains a mystery. Gravity rules the macroscopic world of planets, stars and galaxies, while quantum mechanics governs the micro-cosmos of atoms, light quanta and elementary particles. However, cosmologists believe that these two disparate worlds may meet at the edges of black holes. Now Luis Garay, James Anglin, Ignacio Cirac and Peter Zoller at the University of Innsbruck in Austria have proposed a realistic way to make an artificial 'sonic' black hole in a tabletop experiment (L J Garay et al. 2000 Phys. Rev. Lett. 85 4643). In the February issue of Physics World, Ulf Leonhardt of the School of Physics and Astronomy, University of St. Andrews, UK, explains how the simulated black holes work. (U.K.)

Simulation of polarization-dependent film with subwavelength nano-hole array

Science.gov (United States)

Yu, Yue; Wei, Dong; Long, Huabao; Xin, Zhaowei; Zhang, Xinyu; Wang, Haiwei; Xie, Changsheng

2018-02-01

When lightwave passes through a metal thin film with a periodic subwavelength hole arrays structure, its transmittance is significantly improved in the partial band compared to other wavelength. Changing the size of the hole, the period or metal material, will make the transmission curve different. Here, we add a layer of dielectric material on the surface of the metal film, such as liquid crystal(LC), by controlling voltage on LC to change the refractive index of this layer, then we can change the transmission curve, and achieve using voltage to move the transmission curve. When there is need for polarization, the holes can be made of a rectangle whose length and width are different or other shapes, for different polarization state of the light, and the film will display different transmission characteristics.

Impact of Different Standard Type A7A Drum Closure-Ring Practices on Gasket Contraction and Bolt Closure Distance– 15621

Energy Technology Data Exchange (ETDEWEB)

Ketusky, Edward [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Blanton, Paul [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Bobbitt, John H. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

2015-03-11

The Department of Energy, the Savannah River National Laboratory, several manufacturers of specification drums, and the United States Department of Transportation (DOT) are collaborating in the development of a guidance document for DOE contractors and vendors who wish to qualify containers to DOT 7A Type A requirements. Currently, the effort is focused on DOT 7A Type A 208-liter (55-gallons) drums with a standard 12-gauge bolted closure ring. The U.S. requirements, contained in Title 49, Part 178.350 “Specification 7A; general packaging, Type A specifies a competent authority review of the packaging is not required for the transport of (Class 7) radioactive material containing less than Type A quantities of radioactive material. For Type AF drums, a 4 ft. regulatory free drop must be performed, such that the drum “suffers maximum damage.” Although the actual orientation is not defined by the specification, recent studies suggest that maximum damage would result from a shallow angle top impact, where kinetic energy is transferred to the lid, ultimately causing heavy damage to the lid, or even worse, causing the lid to come off. Since each vendor develops closure recommendations/procedures for the drums they manufacture, key parameters applied to drums during closing vary based on vendor. As part of the initial phase of the collaboration, the impact of the closure variants on the ability of the drum to suffer maximum damage is investigated. Specifically, closure testing is performed varying: 1) the amount of torque applied to the closure ring bolt; and, 2) stress relief protocol, including: a) weight of hammer; and, b) orientation that the hammer hits the closure ring. After closure, the amount of drum lid gasket contraction and the distance that the closure bolt moves through the closure ring is measured.

Formation of black hole and emission of gravitational waves.

Science.gov (United States)

Nakamura, Takashi

2006-12-01

Numerical simulations were performed for the formation process of rotating black holes. It is suggested that Kerr black holes are formed for wide ranges of initial parameters. The nature of gravitational waves from a test particle falling into a Kerr black hole as well as the development of 3D numerical relativity for the coalescing binary neutron stars are discussed.

RIP Input Tables From WAPDEG for LA Design Selection: Continuous Post-Closure Ventilation Design- Open Loop

International Nuclear Information System (INIS)

K.G. Mon; P.K. Mast; R. Howard; J.H. Lee

1999-01-01

The purpose of this calculation is to document (1) the Waste Package Degradation (WAPDEG) version 3.09 (CRWMS M and O 1998b). Software Routine Report for WAPDEG (Version 3.09) simulations used to analyze waste package degradation and failure under the repository exposure conditions characterized by the open loop option of the post-closure ventilation design and, (2) post-processing of these results into tables of waste package degradation time histories suitable for use as input into the Integrated Probabilistic Simulator for Environmental Systems version 5.19.0 1 (RIP) computer program (Golder Associates 1998). Specifically, the WAPDEG simulations discussed in this calculation correspond to waste package emplacement conditions (repository environment and design) defined in the Total System Performance Assessment-Viability Assessment (TSPA-VA), with the exception that the open loop option of the post-closure ventilation License Application Design Selection (LADS) Design Alternative (Design Alternative 3b) was analyzed. The open loop post-closure ventilation design alternative, under which airways to the surface remain open after repository closure, could result in substantial cooling and drying of the potential repository. In open loop post-closure ventilation, expanded air heated by waste decay would move up an exhaust shaft, pulling denser, cooler air into the repository through intake shafts. The exchange of air with the atmosphere could remove more heat and moisture. As a result of the enhanced ventilation relative to the TSPA-VA base-case design, different temperature and relative humidity time histories at the waste package surface are calculated (input to the WAPDEG simulations), and consequently different waste package failure histories (as calculated by WAPDEG) result

Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

Science.gov (United States)

Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

2016-11-01

A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

Positive Catch & Economic Benefits of Periodic Octopus Fishery Closures: Do Effective, Narrowly Targeted Actions 'Catalyze' Broader Management?

Science.gov (United States)

Oliver, Thomas A; Oleson, Kirsten L L; Ratsimbazafy, Hajanaina; Raberinary, Daniel; Benbow, Sophie; Harris, Alasdair

2015-01-01

Eight years of octopus fishery records from southwest Madagascar reveal significant positive impacts from 36 periodic closures on: (a) fishery catches and (b) village fishery income, such that (c) economic benefits from increased landings outweigh costs of foregone catch. Closures covered ~20% of a village's fished area and lasted 2-7 months. Octopus landings and catch per unit effort (CPUE) significantly increased in the 30 days following a closure's reopening, relative to the 30 days before a closure (landings: +718%, poctopus fishery income doubled in the 30 days after a closure, relative to 30 days before (+132%, p<0.001, n = 28). Control villages not implementing a closure showed no increase in income after "no ban" closures and modest increases after "ban" closures. Villages did not show a significant decline in income during closure events. Landings in closure sites generated more revenue than simulated landings assuming continued open-access fishing at that site (27/36 show positive net earnings; mean +$305/closure; mean +57.7% monthly). Benefits accrued faster than local fishers' time preferences during 17-27 of the 36 closures. High reported rates of illegal fishing during closures correlated with poor economic performance. We discuss the implications of our findings for broader co-management arrangements, particularly for catalyzing more comprehensive management.

Vlasov simulations of electron hole dynamics in inhomogeneous magnetic field

Science.gov (United States)

Kuzichev, Ilya; Vasko, Ivan; Agapitov, Oleksiy; Mozer, Forrest; Artemyev, Anton

2017-04-01

Electron holes (EHs) or phase space vortices are solitary electrostatic waves existing due to electrons trapped within EH electrostatic potential. Since the first direct observation [1], EHs have been widely observed in the Earth's magnetosphere: in reconnecting current sheets [2], injection fronts [3], auroral region [4], and many other space plasma systems. EHs have typical spatial scales up to tens of Debye lengths, electric field amplitudes up to hundreds of mV/m and propagate along magnetic field lines with velocities of about electron thermal velocity [5]. The role of EHs in energy dissipation and supporting of large-scale potential drops is under active investigation. The accurate interpretation of spacecraft observations requires understanding of EH evolution in inhomogeneous plasma. The critical role of plasma density gradients in EH evolution was demonstrated in [6] using PIC simulations. Interestingly, up to date no studies have addressed a role of magnetic field gradients in EH evolution. In this report, we use 1.5D gyrokinetic Vlasov code to demonstrate the critical role of magnetic field gradients in EH dynamics. We show that EHs propagating into stronger (weaker) magnetic field are decelerated (accelerated) with deceleration (acceleration) rate dependent on the magnetic field gradient. Remarkably, the reflection points of decelerating EHs are independent of the average magnetic field gradient in the system and depend only on the EH parameters. EHs are decelerated (accelerated) faster than would follow from the "quasi-particle" concept assuming that EH is decelerated (accelerated) entirely due to the mirror force acting on electrons trapped within EH. We demonstrate that EH propagation in inhomogeneous magnetic fields results in development of a net potential drop along an EH, which depends on the magnetic field gradient. The revealed features will be helpful for interpreting spacecraft observations and results of advanced particle simulations. In

Professional Closure Beyond State Authorization

Directory of Open Access Journals (Sweden)

Gitte Sommer Harrits

2014-03-01

Full Text Available For decades, the Weberian approach to the study of professions has been strong, emphasizing state authorization and market monopolies as constituting what is considered a profession. Originally, however, the Weberian conception of closure, or the ways in which a profession is constituted and made separate, was broader. This article suggests a revision of the closure concept, integrating insights from Pierre Bourdieu, and conceptualizing professional closure as the intersection of social, symbolic and legal closure. Based on this revision, this article demonstrates how to apply such a concept in empirical studies. This is done by exploring social, symbolic and legal closure across sixteen professional degree programs. The analyses show a tendency for some overlap between different forms of closure, with a somewhat divergent pattern for legal closure. Results support the argument that we need to study these processes as an intersection of different sources of closure, including capital, lifestyles and discourse

Reinvestigation into Closure Predictions of Room D at the Waste Isolation Pilot Plant

Energy Technology Data Exchange (ETDEWEB)

Reedlunn, Benjamin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-10-01

Room D was an in-situ, isothermal, underground experiment conducted at theWaste Isolation Pilot Plant between 1984 and 1991. The room was carefully instrumented to measure the horizontal and vertical closure immediately upon excavation and for several years thereafter. Early finite element simulations of salt creep around Room D under predicted the vertical closure by 4.5×, causing investigators to explore a series of changes to the way Room D was modeled. Discrepancies between simulations and measurements were resolved through a series of adjustments to model parameters, which were openly acknowledged in published reports. Interest in Room D has been rekindled recently by the U.S./German Joint Project III and Project WEIMOS, which seek to improve the predictions of rock salt constitutive models. Joint Project participants calibrate their models solely against laboratory tests, and benchmark the models against underground experiments, such as room D. This report describes updating legacy Room D simulations to today’s computational standards by rectifying several numerical issues. Subsequently, the constitutive model used in previous modeling is recalibrated two different ways against a suite of new laboratory creep experiments on salt extracted from the repository horizon of the Waste Isolation Pilot Plant. Simulations with the new, laboratory-based, calibrations under predict Room D vertical closure by 3.1×. A list of potential improvements is discussed.

Reinvestigation into Closure Predictions of Room D at the Waste Isolation Pilot Plant

Energy Technology Data Exchange (ETDEWEB)

Reedlunn, Benjamin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-09-27

Room D was an in-situ, isothermal, underground experiment conducted at the Waste Isolation Pilot Plant between 1984 and 1991. The room was carefully instrumented to measure the horizontal and vertical closure immediately upon excavation and for several years thereafter. Early finite element simulations of salt creep around Room D under-predicted the vertical closure by 4.5×, causing investigators to explore a series of changes to the way Room D was modeled. Discrepancies between simulations and measurements were resolved through a series of adjustments to model parameters, which were openly acknowledged in published reports. Interest in Room D has been rekindled recently by the U.S./German Joint Project III and Project WEIMOS, which seek to improve the predictions of rock salt constitutive models. Joint Project participants calibrate their models solely against laboratory tests, and benchmark the models against underground experiments, such as room D. This report describes updating legacy Room D simulations to today’s computational standards by rectifying several numerical issues. Subsequently, the constitutive model used in previous modeling is recalibrated two different ways against a suite of new laboratory creep experiments on salt extracted from the repository horizon of the Waste Isolation Pilot Plant. Simulations with the new, laboratory-based, calibrations under-predict Room D vertical closure by 3.1×. A list of potential improvements is discussed.

Decreased retinal sensitivity after internal limiting membrane peeling for macular hole surgery.

Science.gov (United States)

Tadayoni, Ramin; Svorenova, Ivana; Erginay, Ali; Gaudric, Alain; Massin, Pascale

2012-12-01

To compare the retinal sensitivity and frequency of microscotomas found by spectral domain optical coherence tomography (SD-OCT) combined with scanning laser ophthalmoscopy (SLO) microperimetry after idiopathic macular hole closure, in eyes that underwent internal limiting membrane (ILM) peeling and eyes that did not. This was a retrospective, non-randomised, comparative study. Combined SD-OCT and SLO microperimetry was performed in 16 consecutive eyes after closure of an idiopathic macular hole. A customised microperimetry pattern with 29 measurement points was used. The ILM was peeled in 8/16 eyes. The main outcome measure was mean retinal sensitivity. Mean retinal sensitivity (in dB) was lower after peeling: 9.80 ± 2.35 dB with peeling versus 13.19 ± 2.92 without (p=0.0209). Postoperative microscotomas were significantly more frequent after ILM peeling: 11.3 ± 6.6 points with retinal sensitivity below 10 dB in eyes that underwent peeling versus 2.9 ± 4.6 in those that did not (p=0.0093). These results suggest that ILM peeling may reduce retinal sensitivity, and significantly increase the incidence of microscotomas. Until a prospective trial confirming or not these results, it seems justified to avoid peeling the ILM when its potential benefit seems minor or unproved, and when peeling is carried out, to limit the surface peeled to the bare minimum.

Face-down positioning versus non-supine positioning in macular hole surgery

DEFF Research Database (Denmark)

Alberti, Mark; Dornonville de la Cour, Morten

2015-01-01

AIM: To evaluate the full thickness macular hole (FTMH) closure rate in patients positioning non-supine (NSP) compared with patients positioning face-down (FDP). METHODS: We retrospectively reviewed two FTMH case series-postoperative positioning was FDP and NSP, respectively. All eyes were...... group fully complied with the recommended positioning protocol. CONCLUSIONS: Results from consistent FTMH repair indicate similar anatomical success rates in FDP and NSP groups, suggesting that FDP is unnecessary. Objective monitoring of positioning would be beneficial in future FTMH studies to be able...

Tight closure and vanishing theorems

International Nuclear Information System (INIS)

Smith, K.E.

2001-01-01

Tight closure has become a thriving branch of commutative algebra since it was first introduced by Mel Hochster and Craig Huneke in 1986. Over the past few years, it has become increasingly clear that tight closure has deep connections with complex algebraic geometry as well, especially with those areas of algebraic geometry where vanishing theorems play a starring role. The purpose of these lectures is to introduce tight closure and to explain some of these connections with algebraic geometry. Tight closure is basically a technique for harnessing the power of the Frobenius map. The use of the Frobenius map to prove theorems about complex algebraic varieties is a familiar technique in algebraic geometry, so it should perhaps come as no surprise that tight closure is applicable to algebraic geometry. On the other hand, it seems that so far we are only seeing the tip of a large and very beautiful iceberg in terms of tight closure's interpretation and applications to algebraic geometry. Interestingly, although tight closure is a 'characteristic p' tool, many of the problems where tight closure has proved useful have also yielded to analytic (L2) techniques. Despite some striking parallels, there had been no specific result directly linking tight closure and L∼ techniques. Recently, however, the equivalence of an ideal central to the theory of tight closure was shown to be equivalent to a certain 'multiplier ideal' first defined using L2 methods. Presumably, deeper connections will continue to emerge. There are two main types of problems for which tight closure has been helpful: in identifying nice structure and in establishing uniform behavior. The original algebraic applications of tight closure include, for example, a quick proof of the Hochster-Roberts theorem on the Cohen-Macaulayness of rings of invariants, and also a refined version of the Brianqon-Skoda theorem on the uniform behaviour of integral closures of powers of ideals. More recent, geometric

40 CFR 264.228 - Closure and post-closure care.

Science.gov (United States)

2010-07-01

... remaining wastes to a bearing capacity sufficient to support final cover; and (iii) Cover the surface....112 must include both a plan for complying with paragraph (a)(1) of this section and a contingent plan... practicably removed at closure; and (ii) The owner or operator must prepare a contingent post-closure plan...

ULTRAMASSIVE BLACK HOLE COALESCENCE

International Nuclear Information System (INIS)

Khan, Fazeel Mahmood; Holley-Bockelmann, Kelly; Berczik, Peter

2015-01-01

Although supermassive black holes (SMBHs) correlate well with their host galaxies, there is an emerging view that outliers exist. Henize 2-10, NGC 4889, and NGC 1277 are examples of SMBHs at least an order of magnitude more massive than their host galaxy suggests. The dynamical effects of such ultramassive central black holes is unclear. Here, we perform direct N-body simulations of mergers of galactic nuclei where one black hole is ultramassive to study the evolution of the remnant and the black hole dynamics in this extreme regime. We find that the merger remnant is axisymmetric near the center, while near the large SMBH influence radius, the galaxy is triaxial. The SMBH separation shrinks rapidly due to dynamical friction, and quickly forms a binary black hole; if we scale our model to the most massive estimate for the NGC 1277 black hole, for example, the timescale for the SMBH separation to shrink from nearly a kiloparsec to less than a parsec is roughly 10 Myr. By the time the SMBHs form a hard binary, gravitational wave emission dominates, and the black holes coalesce in a mere few Myr. Curiously, these extremely massive binaries appear to nearly bypass the three-body scattering evolutionary phase. Our study suggests that in this extreme case, SMBH coalescence is governed by dynamical friction followed nearly directly by gravitational wave emission, resulting in a rapid and efficient SMBH coalescence timescale. We discuss the implications for gravitational wave event rates and hypervelocity star production

RCRA corrective action and closure

International Nuclear Information System (INIS)

1995-02-01

This information brief explains how RCRA corrective action and closure processes affect one another. It examines the similarities and differences between corrective action and closure, regulators' interests in RCRA facilities undergoing closure, and how the need to perform corrective action affects the closure of DOE's permitted facilities and interim status facilities

Sensitivity of GRETINA position resolution to hole mobility

Energy Technology Data Exchange (ETDEWEB)

Prasher, V.S. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Cromaz, M. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Merchan, E.; Chowdhury, P. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Crawford, H.L. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Lister, C.J. [Department of Physics, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Campbell, C.M.; Lee, I.Y.; Macchiavelli, A.O. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Radford, D.C. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Wiens, A. [Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

2017-02-21

The sensitivity of the position resolution of the gamma-ray tracking array GRETINA to the hole charge-carrier mobility parameter is investigated. The χ{sup 2} results from a fit of averaged signal (“superpulse”) data exhibit a shallow minimum for hole mobilities 15% lower than the currently adopted values. Calibration data on position resolution is analyzed, together with simulations that isolate the hole mobility dependence of signal decomposition from other effects such as electronics cross-talk. The results effectively exclude hole mobility as a dominant parameter for improving the position resolution for reconstruction of gamma-ray interaction points in GRETINA.

Post-operative analgesic requirement in non-closure and closure of peritoneum during open appendectomy

International Nuclear Information System (INIS)

Khan, A.W.; Maqsood, R.; Saleem, M.M.

2017-01-01

To compare the mean post-operative analgesic requirement in non-closure and closure of peritoneum during open appendectomy. Study Design: Randomized controlled trial. Place and Duration of Study: Department of General Surgery Combined Military Hospital Quetta, from 1st August 2014 to 30th April 2015. Material and Methods: A total of 60 patients were included in this study and were divided into two groups of 30 each. Patients in group A underwent open appendectomy with closure of peritoneum while patients in group B had non-closure of peritoneum during the same procedure. Post-operatively, pain severity was assessed on visual analogue scale (VAS) numeric pain distress scale. On presence of VAS numeric pain distress scale between 5 to 7, intramuscular (IM) diclofenac sodium was given and on score >7, intravascular (IV) tramadol was given. The final outcome was measured at day 0 and day 1. Results: Pain score and analgesic requirements were significantly less in non-closure group than closure group on day 0 and day 1, showing statistically significant difference between the two groups. Conclusion: Mean post-operative analgesic requirement is significantly less in non-closure group as compared to closure group during open appendectomy. (author)

Primary closure after carotid endarterectomy is not inferior to other closure techniques.

Science.gov (United States)

Avgerinos, Efthymios D; Chaer, Rabih A; Naddaf, Abdallah; El-Shazly, Omar M; Marone, Luke; Makaroun, Michel S

2016-09-01

Primary closure after carotid endarterectomy (CEA) has been much maligned as an inferior technique with worse outcomes than in patch closure. Our purpose was to compare perioperative and long-term results of different CEA closure techniques in a large institutional experience. A consecutive cohort of CEAs between January 1, 2000, and December 31, 2010, was retrospectively analyzed. Closure technique was used to divide patients into three groups: primary longitudinal arteriotomy closure (PRC), patch closure (PAC), and eversion closure (EVC). End points were perioperative events, long-term strokes, and restenosis ≥70%. Multivariate regression models were used to assess the effect of baseline predictors. There were 1737 CEA cases (bilateral, 143; mean age, 71.4 ± 9.3 years; 56.2% men; 35.3% symptomatic) performed during the study period with a mean clinical follow-up of 49.8 ± 36.4 months (range, 0-155 months). More men had primary closure, but other demographic and baseline symptoms were similar between groups. Half the patients had PAC, with the rest evenly distributed between PRC and EVC. The rate of nerve injury was 2.7%, the rate of reintervention for hematoma was 1.5%, and the length of hospital stay was 2.4 ± 3.0 days, with no significant differences among groups. The combined stroke and death rate was 2.5% overall and 3.9% and 1.7% in the symptomatic and asymptomatic cohort, respectively. Stroke and death rates were similar between groups: PRC, 11 (2.7%); PAC, 19 (2.2%); EVC, 13 (2.9%). Multivariate analysis showed baseline symptomatic disease (odds ratio, 2.4; P = .007) and heart failure (odds ratio, 3.1; P = .003) as predictors of perioperative stroke and death, but not the type of closure. Cox regression analysis demonstrated, among other risk factors, no statin use (hazard ratio, 2.1; P = .008) as a predictor of ipsilateral stroke and severe (glomerular filtration rate <30 mL/min/1.73 m(2)) renal insufficiency (hazard ratio, 2.6; P�

The birth of a supermassive black hole binary

Science.gov (United States)

Pfister, Hugo; Lupi, Alessandro; Capelo, Pedro R.; Volonteri, Marta; Bellovary, Jillian M.; Dotti, Massimo

2017-11-01

We study the dynamical evolution of supermassive black holes, in the late stage of galaxy mergers, from kpc to pc scales. In particular, we capture the formation of the binary, a necessary step before the final coalescence, and trace back the main processes causing the decay of the orbit. We use hydrodynamical simulations of galaxy mergers with different resolutions, from 20 pc down to 1 pc, in order to study the effects of the resolution on our results, remove numerical effects, and assess that resolving the influence radius of the orbiting black hole is a minimum condition to fully capture the formation of the binary. Our simulations include the relevant physical processes, namely star formation, supernova feedback, accretion on to the black holes and the ensuing feedback. We find that, in these mergers, dynamical friction from the smooth stellar component of the nucleus is the main process that drives black holes from kpc to pc scales. Gas does not play a crucial role and even clumps do not induce scattering or perturb the orbits. We compare the time needed for the formation of the binary to analytical predictions and suggest how to apply such analytical formalism to obtain estimates of binary formation times in lower resolution simulations.

Borehole closure in salt

International Nuclear Information System (INIS)

Fuenkajorn, K.; Daemen, J.J.K.

1988-12-01

Constitutive law parameters are determined from salt behavior characterization experiments. The results are applied to predict creep (time-dependent) closure of boreholes in salt specimens subjected to various loading configurations. Rheological models (linear and nonlinear viscoelastic and viscoplastic models), empirical models, and physical theory models have been formulated from the results of uniaxial creep tests, strain and stress rate controlled uniaxial tests, constant strain rate triaxial tests, cyclic loading tests, and seismic velocity measurements. Analytical solutions for a thick-walled cylinder subjected to internal and external pressures and for a circular hole in an infinite plate subjected to a biaxial or uniaxial stressfield have been derived from each of the linear viscoelastic models and from one of the empirical laws. The experimental results indicate that the salt samples behave as an elastic-viscoplastic material. The elastic behavior tends to be linear and time-independent. The plastic deformation is time-dependent. The stress increment to strain rate increment ratio gradually decreases as the stress level increases. The transient potential creep law seems to give the simplest satisfactory governing equation describing the viscoplastic behavior of salt during the transient phase. 204 refs., 27 figs., 29 tabs

Semiclassical approach to black hole evaporation

International Nuclear Information System (INIS)

Lowe, D.A.

1993-01-01

Black hole evaporation may lead to massive or massless remnants, or naked singularities. This paper investigates this process in the context of two quite different two-dimensional black hole models. The first is the original Callan-Giddings-Harvey-Strominger (CGHS) model, the second is another two-dimensional dilaton-gravity model, but with properties much closer to physics in the real, four-dimensional, world. Numerical simulations are performed of the formation and subsequent evaporation of black holes and the results are found to agree qualitatively with the exactly solved modified CGHS models, namely, that the semiclassical approximation breaks down just before a naked singularity appears

RIP Input Tables From WAPDEG for LA Design Selection: Continuous Pre-Closure Ventilation

International Nuclear Information System (INIS)

K.G. Mon

1999-01-01

The purpose of this calculation is to document the creation of .tables for input into Integrated Probabilistic Simulator for Environmental Systems (RIP) version 5.19.01 (Golder Associates 1998) from Waste Package Degradation (WAPDEG) version 3.09 (CRWMS M and O 1998b. ''Software Routine Report for WAPDEG'' (Version 3.09)) simulations. This calculation details the creation of the RIP input tables (representing waste package corrosion degradation over time) for the License Application Design Selection (LADS) analysis of the effects of continuous pre-closure ventilation. Ventilation during the operational phase of the repository could remove considerable water from the system, as well as reduce temperatures. Pre-closure ventilation is LADS Design Feature 7

Black hole information, unitarity, and nonlocality

OpenAIRE

Giddings, Steven B.

2006-01-01

The black hole information paradox apparently indicates the need for a fundamentally new ingredient in physics. The leading contender is nonlocality. Possible mechanisms for the nonlocality needed to restore unitarity to black hole evolution are investigated. Suggestions that such dynamics arises from ultra-planckian modes in Hawking's derivation are investigated and found not to be relevant, in a picture using smooth slices spanning the exterior and interior of the horizon. However, no simul...

Effect of diameter of the drill hole on torque of screw insertion and pushout strength for headless tapered compression screws in simulated fractures of the lateral condyle of the equine third metacarpal bone.

Science.gov (United States)

Carpenter, Ryan S; Galuppo, Larry D; Stover, Susan M

2006-05-01

To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model. 6 pairs of third metacarpal bones from horse cadavers. Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests. Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes. Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.

Effectiveness of Closure of Public Places with Time Delay in Disease Control

Directory of Open Access Journals (Sweden)

Wang Zhenggang

2008-06-01

Full Text Available A theoretical basis for the evaluation of the effciency of quarantine measure is developed in a SIR model with time delay. In this model, the effectiveness of the closure of public places such as schools in disease control, modeled as a high degree node in a social network, is evaluated by considering the effect of the time delay in the identification of the infected. In the context of the SIR model, the relation between the number of infectious individuals who are identified with time delay and then quarantined and those who are not identified and continue spreading the virus are investigated numerically. The social network for the simulation is modeled by a scale free network. Closure measures are applied to those infected nodes with high degrees. The effectiveness of the measure can be controlled by the present value of the critical degree KC: only those nodes with degree higher than KC will be quarantined. The cost CQ incurred for the closure measure is assumed to be proportional to the total links rendered inactive as a result of the measure, and generally decreases with KC, while the medical cost CQ incurred for virus spreading increases with KC. The total social cost (CM + CQ will have a minimum at a critical KC, which depends on the ratio of medical cost coeffcient αM and closure cost coeffcient αQ. Our simulation results demonstrate a mathematical procedure to evaluate the effciency of quarantine measure. Although the numerical work is based on a scale free network, the procedure can be readily generalized and applied to a more realistic social network to determine the proper closure measure in future epidemics.

Quantum gravity effects in black holes at the LHC

International Nuclear Information System (INIS)

Alberghi, G L; Casadio, R; Tronconi, A

2007-01-01

We study possible back-reaction and quantum gravity effects in the evaporation of black holes which could be produced at the LHC through a modification of the Hawking emission. The corrections are phenomenologically taken into account by employing a modified relation between the black hole mass and temperature. The usual assumption that black holes explode around 1 TeV is also released, and the evaporation process is extended to (possibly much) smaller final masses. We show that these effects could be observable for black holes produced with a relatively large mass and should therefore be taken into account when simulating micro-black hole events for the experiments planned at the LHC

Dynamics of Coronal Hole Boundaries

Energy Technology Data Exchange (ETDEWEB)

Higginson, A. K.; Zurbuchen, T. H. [Department of Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Antiochos, S. K.; DeVore, C. R. [Heliophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Wyper, P. F. [Universities Space Research Association, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

2017-03-10

Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposes that photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-hole boundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamic simulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model corona with a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used to approximate photospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer. The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open and closed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with some flux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs all along the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions that were not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the implications of our simulations for understanding the observed properties of the slow solar wind, with particular focus on the global-scale consequences of interchange reconnection.

Massive disc formation in the tidal disruption of a neutron star by a nearly extremal black hole

International Nuclear Information System (INIS)

Lovelace, Geoffrey; Kidder, Lawrence E; Duez, Matthew D; Foucart, Francois; Pfeiffer, Harald P; Scheel, Mark A; Szilágyi, Béla

2013-01-01

Black hole–neutron star (BHNS) binaries are important sources of gravitational waves for second-generation interferometers, and BHNS mergers are also a proposed engine for short, hard gamma-ray bursts. The behavior of both the spacetime (and thus the emitted gravitational waves) and the neutron-star matter in a BHNS merger depend strongly and nonlinearly on the black hole's spin. While there is a significant possibility that astrophysical black holes could have spins that are nearly extremal (i.e. near the theoretical maximum), to date fully relativistic simulations of BHNS binaries have included black-hole spins only up to S/M 2 = 0.9, which corresponds to the black hole having approximately half as much rotational energy as possible, given the black hole's mass. In this paper, we present a new simulation of a BHNS binary with a mass ratio q = 3 and black-hole spin S/M 2 = 0.97, the highest simulated to date. We find that the black hole's large spin leads to the most massive accretion disc and the largest tidal tail outflow of any fully relativistic BHNS simulations to date, even exceeding the results implied by extrapolating results from simulations with lower black-hole spin. The disc appears to be remarkably stable. We also find that the high black-hole spin persists until shortly before the time of merger; afterward, both merger and accretion spin down the black hole. (paper)

High-accuracy waveforms for binary black hole inspiral, merger, and ringdown

International Nuclear Information System (INIS)

Scheel, Mark A.; Boyle, Michael; Chu, Tony; Matthews, Keith D.; Pfeiffer, Harald P.; Kidder, Lawrence E.

2009-01-01

The first spectral numerical simulations of 16 orbits, merger, and ringdown of an equal-mass nonspinning binary black hole system are presented. Gravitational waveforms from these simulations have accumulated numerical phase errors through ringdown of f /M=0.951 62±0.000 02, and the final black hole spin is S f /M f 2 =0.686 46±0.000 04.

Massive Black Hole Mergers: Can we see what LISA will hear?

Science.gov (United States)

Centrella, Joan

2009-01-01

Coalescing massive black hole binaries are formed when galaxies merge. The final stages of this coalescence produce strong gravitational wave signals that can be detected by the space-borne LISA. When the black holes merge in the presence of gas and magnetic fields, various types of electromagnetic signals may also be produced. Modeling such electromagnetic counterparts requires evolving the behavior of both gas and fields in the strong-field regions around the black holes. We have taken a first step towards this problem by mapping the flow of pressureless matter in the dynamic, 3-D general relativistic spacetime around the merging black holes. We report on the results of these initial simulations and discuss their likely importance for future hydrodynamical simulations.

Ring closure in actin polymers

Energy Technology Data Exchange (ETDEWEB)

Sinha, Supurna, E-mail: supurna@rri.res.in [Raman Research Institute, Bangalore 560080 (India); Chattopadhyay, Sebanti [Doon University, Dehradun 248001 (India)

2017-03-18

We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers. - Highlights: • Ring closure of biopolymers. • Worm like chain model. • Predictions for experiments.

Role of plasticity-induced crack closure in fatigue crack growth

Directory of Open Access Journals (Sweden)

Jesús Toribio

2013-07-01

Full Text Available The premature contact of crack surfaces attributable to the near-tip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure (PICC, has long been focused as supposedly controlling factor of fatigue crack growth (FCG. Nevertheless, when the plane-strain near-tip constraint is approached, PICC lacks of straightforward evidence, so that its significance in FCG, and even the very existence, remain debatable. To add insights into this matter, large-deformation elastoplastic simulations of plane-strain crack under constant amplitude load cycling at different load ranges and ratios, as well as with an overload, have been performed. Modeling visualizes the Laird-Smith conceptual mechanism of FCG by plastic blunting and re-sharpening. Simulation reproduces the experimental trends of FCG concerning the roles of stress intensity factor range and overload, but PICC has never been detected. Near-tip deformation patterns discard the filling-in a crack with material stretched out of the crack plane in the wake behind the tip as supposed PICC origin. Despite the absence of closure, load-deformation curves appear bent, which raises doubts about the trustworthiness of closure assessment from the compliance variation. This demonstrates ambiguities of PICC as a supposedly intrinsic factor of FCG and, by implication, favors the stresses and strains in front of the crack tip as genuine fatigue drivers.

White holes and eternal black holes

International Nuclear Information System (INIS)

Hsu, Stephen D H

2012-01-01

We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi-thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal. (paper)

Merging Black Holes and Gravitational Waves

Science.gov (United States)

Centrella, Joan

2009-01-01

This talk will focus on simulations of binary black hole mergers and the gravitational wave signals they produce. Applications to gravitational wave detection with LISA, and electronagnetic counterparts, will be highlighted.

Tubular closure device

International Nuclear Information System (INIS)

Klahn, F.C.; Nolan, J.H.; Wills, C.

1982-01-01

This invention relates to a closure mechanism for closing openings such as the bore of a conduit and for releasably securing members within the bore. More particularly, this invention relates to a closure mechanism for tubular irradiation surveillance specimen assembly holders used in nuclear reactors

A nonlinear structural subgrid-scale closure for compressible MHD. I. Derivation and energy dissipation properties

Energy Technology Data Exchange (ETDEWEB)

Vlaykov, Dimitar G., E-mail: Dimitar.Vlaykov@ds.mpg.de [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Dynamik und Selbstorganisation, Am Faßberg 17, D-37077 Göttingen (Germany); Grete, Philipp [Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany); Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Schmidt, Wolfram [Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany); Schleicher, Dominik R. G. [Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160-C (Chile)

2016-06-15

Compressible magnetohydrodynamic (MHD) turbulence is ubiquitous in astrophysical phenomena ranging from the intergalactic to the stellar scales. In studying them, numerical simulations are nearly inescapable, due to the large degree of nonlinearity involved. However, the dynamical ranges of these phenomena are much larger than what is computationally accessible. In large eddy simulations (LESs), the resulting limited resolution effects are addressed explicitly by introducing to the equations of motion additional terms associated with the unresolved, subgrid-scale dynamics. This renders the system unclosed. We derive a set of nonlinear structural closures for the ideal MHD LES equations with particular emphasis on the effects of compressibility. The closures are based on a gradient expansion of the finite-resolution operator [W. K. Yeo (CUP, 1993)] and require no assumptions about the nature of the flow or magnetic field. Thus, the scope of their applicability ranges from the sub- to the hyper-sonic and -Alfvénic regimes. The closures support spectral energy cascades both up and down-scale, as well as direct transfer between kinetic and magnetic resolved and unresolved energy budgets. They implicitly take into account the local geometry, and in particular, the anisotropy of the flow. Their properties are a priori validated in Paper II [P. Grete et al., Phys. Plasmas 23, 062317 (2016)] against alternative closures available in the literature with respect to a wide range of simulation data of homogeneous and isotropic turbulence.

Elemental logging in the KTB Pilot Hole. Pt. 1

International Nuclear Information System (INIS)

Grau, J.A.; Schweitzer, J.S.; Draxler, J.K.; Gatto, H.; Lauterjung, J.

1993-01-01

Neutron-induced γ-ray spectrometry, of prompt capture and delayed activation, together with natural γ-ray measurements, provide a borehole elemental analysis to characterize rock matrix composition. Elemental concentrations from the prompt capture measurements are derived through the use of a closure model that was developed from data on rocks in a sedimentary environment. This set of spectrometers was used to log the 4000 m of the German Continental Deep Drilling Project (KTB) Pilot Hole. The model was tested, with a minor change, for suitability to the crystalline rock environment. Good overall agreement was found between the logging measurements and laboratory analyses performed on cuttings and cores. (Author)

A wavenumber-partitioning scheme for two-dimensional statistical closures

International Nuclear Information System (INIS)

Bowman, J.C.

1994-11-01

One of the principal advantages of statistical closure approximations for fluid turbulence is that they involve smoothly varying functions of wavenumber. This suggests the possibility of modeling a flow by following the evolution of only a few representative wavenumbers. This work presents two new techniques for the implementation of two-dimensional isotropic statistical closures that for the first time allows the inertial-range scalings of these approximation to be numerically demonstrated. A technique of wavenumber partitioning that conserves both energy and enstrophy is developed for two-dimensional statistical closures. Coupled with a new time-stepping scheme based on a variable integrating factor, this advance facilitates the computation of energy spectra over seven wavenumber decades, a task that will clearly remain outside the realm of conventional numerical simulations for the foreseeable future. Within the context of the test-field model, the method is used to demonstrate Kraichnan's logarithmically-corrected scaling for the enstrophy inertial range and to make a quantitative assessment of the effect of replacing the physical Laplacian viscosity with an enhanced hyperviscosity

Black Holes, the Brightest Objects in the Universe

Energy Technology Data Exchange (ETDEWEB)

McKinney, Jonathan (Stanford University)

2009-04-28

Black holes are everywhere in the Universe. They form when massive stars end their life in a simultaneous violent collapse and energetic explosion. Galaxies end up littered with small black holes, each roughly the mass of ten Suns. Nearly every galaxy center ends up with a single huge black hole, with the mass of a million to a billion Suns. During their lifetimes, black holes chew up their surroundings and spew out ultra-energetic beams of radiation and matter that are visible from across the Universe. In this lecture, I will discuss how black holes form, outline how we detect them, and show movies that illustrate how they work according to Einstein and state-of-the-art computer simulations. We will see that these blackest of all objects in the Universe actually shine the brightest.

A patient specific finite element simulation of intramedullary nailing to predict the displacement of the distal locking hole.

Science.gov (United States)

Mortazavi, Javad; Farahmand, Farzam; Behzadipour, Saeed; Yeganeh, Ali; Aghighi, Mohammad

2018-05-01

Distal locking is a challenging subtask of intramedullary nailing fracture fixation due to the nail deformation that makes the proximally mounted targeting systems ineffective. A patient specific finite element model was developed, based on the QCT data of a cadaveric femur, to predict the position of the distal hole of the nail postoperatively. The mechanical interactions of femur and nail (of two sizes) during nail insertion was simulated using ABAQUS in two steps of dynamic pushing and static equilibrium, for the intact and distally fractured bone. Experiments were also performed on the same specimen to validate the simulation results. A good agreement was found between the model predictions and the experimental observations. There was a three-point contact pattern between the nail and medullary canal, only on the proximal fragment of the fractured bone. The nail deflection was much larger in the sagittal plane and increased for the larger diameter nail, as well as for more distally fractured or intact femur. The altered position of the distal hole was predicted by the model with an acceptable error (mean: 0.95; max: 1.5 mm, in different tests) to be used as the compensatory information for fine tuning of proximally mounted targeting systems. Copyright © 2018 IPEM. Published by Elsevier Ltd. All rights reserved.

Black-hole production from ultrarelativistic collisions

International Nuclear Information System (INIS)

Rezzolla, Luciano; Takami, Kentaro

2013-01-01

Determining the conditions under which a black hole can be produced is a long-standing and fundamental problem in general relativity. We use numerical simulations of colliding self-gravitating fluid objects to study the conditions of black-hole formation when the objects are boosted to ultrarelativistic speeds. Expanding on the previous work, we show that the collision is characterized by a type-I critical behaviour, with a black hole being produced for masses above a critical value, M c , and a partially bound object for masses below the critical one. More importantly, we show for the first time that the critical mass varies with the initial effective Lorentz factor 〈γ〉 following a simple scaling of the type M c ∼ K〈γ〉 −1.0 , thus indicating that a black hole of infinitesimal mass is produced in the limit of a diverging Lorentz factor. Furthermore, because a scaling is present also in terms of the initial stellar compactness, we provide a condition for black-hole formation in the spirit of the hoop conjecture. (fast track communication)

Effectiveness of closure of public places with time delay in disease control.

Science.gov (United States)

Wang, Zhenggang; Szeto, Kwok Yip; Leung, Frederick Chi-Ching

2008-08-25

A theoretical basis for the evaluation of the effciency of quarantine measure is developed in a SIR model with time delay. In this model, the effectiveness of the closure of public places such as schools in disease control, modeled as a high degree node in a social network, is evaluated by considering the effect of the time delay in the identification of the infected. In the context of the SIR model, the relation between the number of infectious individuals who are identified with time delay and then quarantined and those who are not identified and continue spreading the virus are investigated numerically. The social network for the simulation is modeled by a scale free network. Closure measures are applied to those infected nodes with high degrees. The effectiveness of the measure can be controlled by the present value of the critical degree K(C): only those nodes with degree higher than K(C) will be quarantined. The cost C(Q) incurred for the closure measure is assumed to be proportional to the total links rendered inactive as a result of the measure, and generally decreases with K(C), while the medical cost C(Q) incurred for virus spreading increases with K(C). The total social cost (C(M) + C(Q)) will have a minimum at a critical K(*), which depends on the ratio of medical cost coeffcient alpha(M) and closure cost coeffcient alpha(Q). Our simulation results demonstrate a mathematical procedure to evaluate the effciency of quarantine measure. Although the numerical work is based on a scale free network, the procedure can be readily generalized and applied to a more realistic social network to determine the proper closure measure in future epidemics.

Minidisks in Binary Black Hole Accretion

Energy Technology Data Exchange (ETDEWEB)

Ryan, Geoffrey; MacFadyen, Andrew, E-mail: gsr257@nyu.edu [Center for Cosmology and Particle Physics, Physics Department, New York University, New York, NY 10003 (United States)

2017-02-01

Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole (“minidisks”), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov–Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.

Structure of highly asymmetric hard-sphere mixtures: an efficient closure of the Ornstein-Zernike equations.

Science.gov (United States)

Amokrane, S; Ayadim, A; Malherbe, J G

2005-11-01

A simple modification of the reference hypernetted chain (RHNC) closure of the multicomponent Ornstein-Zernike equations with bridge functions taken from Rosenfeld's hard-sphere bridge functional is proposed. Its main effect is to remedy the major limitation of the RHNC closure in the case of highly asymmetric mixtures--the wide domain of packing fractions in which it has no solution. The modified closure is also much faster, while being of similar complexity. This is achieved with a limited loss of accuracy, mainly for the contact value of the big sphere correlation functions. Comparison with simulation shows that inside the RHNC no-solution domain, it provides a good description of the structure, while being clearly superior to all the other closures used so far to study highly asymmetric mixtures. The generic nature of this closure and its good accuracy combined with a reduced no-solution domain open up the possibility to study the phase diagram of complex fluids beyond the hard-sphere model.

CIRSE Vascular Closure Device Registry

NARCIS (Netherlands)

Reekers, Jim A.; Müller-Hülsbeck, Stefan; Libicher, Martin; Atar, Eli; Trentmann, Jens; Goffette, Pierre; Borggrefe, Jan; Zeleňák, Kamil; Hooijboer, Pieter; Belli, Anna-Maria

2011-01-01

Vascular closure devices are routinely used after many vascular interventional radiology procedures. However, there have been no major multicenter studies to assess the safety and effectiveness of the routine use of closure devices in interventional radiology. The CIRSE registry of closure devices

A Dual Regime Reactive Transport Model for Simulation of High Level Waste Tank Closure Scenarios - 13375

International Nuclear Information System (INIS)

Sarkar, Sohini; Kosson, David S.; Brown, Kevin; Garrabrants, Andrew C.; Meeussen, Hans; Van der Sloot, Hans

2013-01-01

A numerical simulation framework is presented in this paper for estimating evolution of pH and release of major species from grout within high-level waste tanks after closure. This model was developed as part of the Cementitious Barriers Partnership. The reactive transport model consists of two parts - (1) transport of species, and (2) chemical reactions. The closure grout can be assumed to have varying extents of cracking and composition for performance assessment purposes. The partially or completely degraded grouted tank is idealized as a dual regime system comprising of a mobile region having solid materials with cracks and macro-pores, and an immobile/stagnant region having solid matrix with micropores. The transport profiles of the species are calculated by incorporating advection of species through the mobile region, diffusion of species through the immobile/stagnant region, and exchange of species between the mobile and immobile regions. A geochemical speciation code in conjunction with the pH dependent test data for a grout material is used to obtain a mineral set that best describes the trends in the test data of the major species. The dual regime reactive transport model predictions are compared with the release data from an up-flow column percolation test. The coupled model is then used to assess effects of crack state of the structure, rate and composition of the infiltrating water on the pH evolution at the grout-waste interface. The coupled reactive transport model developed in this work can be used as part of the performance assessment process for evaluating potential risks from leaching of a cracked tank containing elements of human health and environmental concern. (authors)

A Dual Regime Reactive Transport Model for Simulation of High Level Waste Tank Closure Scenarios - 13375

Energy Technology Data Exchange (ETDEWEB)

Sarkar, Sohini; Kosson, David S.; Brown, Kevin; Garrabrants, Andrew C. [Consortium for Risk Assessment with Stakeholder Participation - CRESP, Vanderbilt University, Nashville, TN (United States); Meeussen, Hans [Consortium for Risk Assessment with Stakeholder Participation - CRESP, Nuclear Research and Consultancy Group, Petten (Netherlands); Van der Sloot, Hans [Consortium for Risk Assessment with Stakeholder Participation - CRESP, Hans Van der Sloot Consultancy (Netherlands)

2013-07-01

A numerical simulation framework is presented in this paper for estimating evolution of pH and release of major species from grout within high-level waste tanks after closure. This model was developed as part of the Cementitious Barriers Partnership. The reactive transport model consists of two parts - (1) transport of species, and (2) chemical reactions. The closure grout can be assumed to have varying extents of cracking and composition for performance assessment purposes. The partially or completely degraded grouted tank is idealized as a dual regime system comprising of a mobile region having solid materials with cracks and macro-pores, and an immobile/stagnant region having solid matrix with micropores. The transport profiles of the species are calculated by incorporating advection of species through the mobile region, diffusion of species through the immobile/stagnant region, and exchange of species between the mobile and immobile regions. A geochemical speciation code in conjunction with the pH dependent test data for a grout material is used to obtain a mineral set that best describes the trends in the test data of the major species. The dual regime reactive transport model predictions are compared with the release data from an up-flow column percolation test. The coupled model is then used to assess effects of crack state of the structure, rate and composition of the infiltrating water on the pH evolution at the grout-waste interface. The coupled reactive transport model developed in this work can be used as part of the performance assessment process for evaluating potential risks from leaching of a cracked tank containing elements of human health and environmental concern. (authors)

The immediate environment of an astrophysical black hole

Science.gov (United States)

Contopoulos, I.

2018-01-01

In view of the upcoming observations with the Event Horizon Telescope (EHT), we present our thoughts on the immediate environment of an astrophysical black hole. We are concerned that two approximations used in general relativistic magnetohydrodynamic numerical simulations, namely numerical density floors implemented near the base of the black hole jet, and a magnetic field that comes from large distances, may mislead our interpretation of the observations. We predict that three physical processes will manifest themselves in EHT observations, namely dynamic pair formation just above the horizon, electromagnetic energy dissipation along the boundary of the black hole jet, and a region of weak magnetic field separating the black hole jet from the disc wind.

Extraordinary light transmission through opaque thin metal film with subwavelength holes blocked by metal disks.

Science.gov (United States)

Li, Wen-Di; Hu, Jonathan; Chou, Stephen Y

2011-10-10

We observed that when subwavelength-sized holes in an optically opaque metal film are completely covered by opaque metal disks larger than the holes, the light transmission through the holes is not reduced, but rather enhanced. Particularly we report (i) the observation of light transmission through the holes blocked by the metal disks up to 70% larger than the unblocked holes; (ii) the observation of tuning the light transmission by varying the coupling strength between the blocking disks and the hole array, or by changing the size of the disks and holes; (iii) the observation and simulation that the metal disk blocker can improve light coupling from free space to a subwavelength hole; and (iv) the simulation that shows the light transmission through subwavelength holes can be enhanced, even though the gap between the disk and the metal film is partially connected with a metal. We believe these finding should have broad and significant impacts and applications to optical systems in many fields.

Large eddy simulations of compressible magnetohydrodynamic turbulence

International Nuclear Information System (INIS)

Grete, Philipp

2016-01-01

Supersonic, magnetohydrodynamic (MHD) turbulence is thought to play an important role in many processes - especially in astrophysics, where detailed three-dimensional observations are scarce. Simulations can partially fill this gap and help to understand these processes. However, direct simulations with realistic parameters are often not feasible. Consequently, large eddy simulations (LES) have emerged as a viable alternative. In LES the overall complexity is reduced by simulating only large and intermediate scales directly. The smallest scales, usually referred to as subgrid-scales (SGS), are introduced to the simulation by means of an SGS model. Thus, the overall quality of an LES with respect to properly accounting for small-scale physics crucially depends on the quality of the SGS model. While there has been a lot of successful research on SGS models in the hydrodynamic regime for decades, SGS modeling in MHD is a rather recent topic, in particular, in the compressible regime. In this thesis, we derive and validate a new nonlinear MHD SGS model that explicitly takes compressibility effects into account. A filter is used to separate the large and intermediate scales, and it is thought to mimic finite resolution effects. In the derivation, we use a deconvolution approach on the filter kernel. With this approach, we are able to derive nonlinear closures for all SGS terms in MHD: the turbulent Reynolds and Maxwell stresses, and the turbulent electromotive force (EMF). We validate the new closures both a priori and a posteriori. In the a priori tests, we use high-resolution reference data of stationary, homogeneous, isotropic MHD turbulence to compare exact SGS quantities against predictions by the closures. The comparison includes, for example, correlations of turbulent fluxes, the average dissipative behavior, and alignment of SGS vectors such as the EMF. In order to quantify the performance of the new nonlinear closure, this comparison is conducted from the

Large eddy simulations of compressible magnetohydrodynamic turbulence

Science.gov (United States)

Grete, Philipp

2017-02-01

Supersonic, magnetohydrodynamic (MHD) turbulence is thought to play an important role in many processes - especially in astrophysics, where detailed three-dimensional observations are scarce. Simulations can partially fill this gap and help to understand these processes. However, direct simulations with realistic parameters are often not feasible. Consequently, large eddy simulations (LES) have emerged as a viable alternative. In LES the overall complexity is reduced by simulating only large and intermediate scales directly. The smallest scales, usually referred to as subgrid-scales (SGS), are introduced to the simulation by means of an SGS model. Thus, the overall quality of an LES with respect to properly accounting for small-scale physics crucially depends on the quality of the SGS model. While there has been a lot of successful research on SGS models in the hydrodynamic regime for decades, SGS modeling in MHD is a rather recent topic, in particular, in the compressible regime. In this thesis, we derive and validate a new nonlinear MHD SGS model that explicitly takes compressibility effects into account. A filter is used to separate the large and intermediate scales, and it is thought to mimic finite resolution effects. In the derivation, we use a deconvolution approach on the filter kernel. With this approach, we are able to derive nonlinear closures for all SGS terms in MHD: the turbulent Reynolds and Maxwell stresses, and the turbulent electromotive force (EMF). We validate the new closures both a priori and a posteriori. In the a priori tests, we use high-resolution reference data of stationary, homogeneous, isotropic MHD turbulence to compare exact SGS quantities against predictions by the closures. The comparison includes, for example, correlations of turbulent fluxes, the average dissipative behavior, and alignment of SGS vectors such as the EMF. In order to quantify the performance of the new nonlinear closure, this comparison is conducted from the

Evaluation of tomographic image quality of extended and conventional parallel hole collimators using maximum likelihood expectation maximization algorithm by Monte Carlo simulations.

Science.gov (United States)

Moslemi, Vahid; Ashoor, Mansour

2017-10-01

One of the major problems associated with parallel hole collimators (PCs) is the trade-off between their resolution and sensitivity. To solve this problem, a novel PC - namely, extended parallel hole collimator (EPC) - was proposed, in which particular trapezoidal denticles were increased upon septa on the side of the detector. In this study, an EPC was designed and its performance was compared with that of two PCs, PC35 and PC41, with a hole size of 1.5 mm and hole lengths of 35 and 41 mm, respectively. The Monte Carlo method was used to calculate the important parameters such as resolution, sensitivity, scattering, and penetration ratio. A Jaszczak phantom was also simulated to evaluate the resolution and contrast of tomographic images, which were produced by the EPC6, PC35, and PC41 using the Monte Carlo N-particle version 5 code, and tomographic images were reconstructed by using maximum likelihood expectation maximization algorithm. Sensitivity of the EPC6 was increased by 20.3% in comparison with that of the PC41 at the identical spatial resolution and full-width at tenth of maximum here. Moreover, the penetration and scattering ratio of the EPC6 was 1.2% less than that of the PC41. The simulated phantom images show that the EPC6 increases contrast-resolution and contrast-to-noise ratio compared with those of PC41 and PC35. When compared with PC41 and PC35, EPC6 improved trade-off between resolution and sensitivity, reduced penetrating and scattering ratios, and produced images with higher quality. EPC6 can be used to increase detectability of more details in nuclear medicine images.

Black-hole-regulated star formation in massive galaxies

Science.gov (United States)

Martín-Navarro, Ignacio; Brodie, Jean P.; Romanowsky, Aaron J.; Ruiz-Lara, Tomás; van de Ven, Glenn

2018-01-01

Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations fail to reproduce the number density and properties of massive galaxies in the local Universe. There is, however, no observational evidence of this strongly coupled coevolution between supermassive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we report that the star formation histories of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central supermassive black hole. Our results indicate that the black-hole mass scales with the gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes. The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and baryon cooling.

Black-hole-regulated star formation in massive galaxies.

Science.gov (United States)

Martín-Navarro, Ignacio; Brodie, Jean P; Romanowsky, Aaron J; Ruiz-Lara, Tomás; van de Ven, Glenn

2018-01-18

Supermassive black holes, with masses more than a million times that of the Sun, seem to inhabit the centres of all massive galaxies. Cosmologically motivated theories of galaxy formation require feedback from these supermassive black holes to regulate star formation. In the absence of such feedback, state-of-the-art numerical simulations fail to reproduce the number density and properties of massive galaxies in the local Universe. There is, however, no observational evidence of this strongly coupled coevolution between supermassive black holes and star formation, impeding our understanding of baryonic processes within galaxies. Here we report that the star formation histories of nearby massive galaxies, as measured from their integrated optical spectra, depend on the mass of the central supermassive black hole. Our results indicate that the black-hole mass scales with the gas cooling rate in the early Universe. The subsequent quenching of star formation takes place earlier and more efficiently in galaxies that host higher-mass central black holes. The observed relation between black-hole mass and star formation efficiency applies to all generations of stars formed throughout the life of a galaxy, revealing a continuous interplay between black-hole activity and baryon cooling.

Statistics of structural holes in the one-component classical plasma near freezing

International Nuclear Information System (INIS)

Cardenas, M.; Tosi, M.P.

1998-03-01

The correlations between structural holes in the fluid phase of the one-component classical plasma near its freezing point at coupling strength Γ=179 are studied by a statistical method using the Ornstein-Zernike relations for a partly quenched disordered system in combination with the hypernetted chain closure. The method involves inserting in the quenched structure of the plasma variable numbers of point-like charged particles, which on reaching equilibrium probe the holes in the matrix. When the probes carry the same charge as the plasma particles, the results may also be interpreted as describing the evolution of the correlations between annealed particles in a partly quenched disordered plasma upon varying the fraction of quenched particles at constant total density. Doubling the charge carried by the probes sharpens their correlations and improves the resolution that can be obtained in this method of structural analysis. (author)

Recommended management practices for operation and closure of shallow injection wells at DOE facilities

International Nuclear Information System (INIS)

1993-07-01

The Safe Drinking Water Act established the Underground Injection Control (UIC) program to ensure that underground injection of wastes does not endanger an underground source of drinking water. Under UIC regulations, an injection well is a hole in the ground, deeper than it is wide, that receives wastes or other fluid substances. Types of injection wells range from deep cased wells to shallow sumps, drywells, and drainfields. The report describes the five classes of UIC wells and summarizes relevant regulations for each class of wells and for the UIC program. The main focus of the report is Class IV and V shallow injection wells. Class IV wells are prohibited and should be closed when they are identified. Class V wells are generally authorized by rule, but EPA or a delegated state may require a permit for a Class V well. This report provides recommendations on sound operating and closure practices for shallow injection wells. In addition the report contains copies of several relevant EPA documents that provide additional information on well operation and closure. Another appendix contains information on the UIC programs in 21 states in which there are DOE facilities discharging to injection wells. The appendix includes the name of the responsible regulatory agency and contact person, a summary of differences between the state's regulations and Federal regulations, and any closure guidelines for Class IV and V wells

Surgical treatment and optical coherence tomographic evaluation for accidental laser-induced full-thickness macular holes.

Science.gov (United States)

Qi, Y; Wang, Y; You, Q; Tsai, F; Liu, W

2017-07-01

PurposeTo report OCT appearance and surgical outcomes of full-thickness macular holes (MHs) accidentally caused by laser devices.Patients and methodsThis retrospective case series included 11 eyes of 11 patients with laser-induced MHs treated by pars plana vitrectomy, internal limiting membrane (ILM) peeling, and gas or silicone oil tamponade. Evaluations included a full ophthalmic examination, macular spectral-domain optical coherence tomography (SD-OCT), and fundus photography. Main outcome measures is MH closure and final visual acuity; the secondary outcome was the changes of retinal pigment epithelium and photoreceptor layer evaluated by sequential post-operative SD-OCT images.ResultsFive patients were accidentally injured by a yttrium aluminum garnet (YAG) laser and six patients by handheld laser. MH diameters ranged from 272 to 815 μm (mean, 505.5±163.0 μm) preoperatively. Best-corrected visual acuity (BCVA) improved from a mean of 0.90 logMAR (range, counting finger-8/20) preoperatively to a mean of 0.34 logMAR (range, a counting finger-20/20) postoperatively (P=0.001, t=4.521). Seven of 11 patients (63.6%) achieved a BCVA better than 10/20. Ten patients had a subfoveal hyperreflectivity and four patients had a focal choroidal depression subfoveal preoperatively. At the last follow-up, all 11 eyes demonstrated the following: closure of the macular hole, variable degrees of disruption of external limiting membrane (ELM) and outer photoreceptor ellipsoid and interdigitation bands. In 10 eyes, the disruption was in the form of focal defects in the outer retina. After surgery, the subfoveal hyperreflectivity and focal choroidal depression remained.ConclusionAccidental laser-induced full-thickness macular holes can be successfully closed with surgery. Inadvertent retinal injury from laser devices, especially handheld laser injury has occurred with increasing frequency in recent years. However, there is a paucity of data regarding these types of injuries

Post-Newtonian Dynamical Modeling of Supermassive Black Holes in Galactic-scale Simulations

Energy Technology Data Exchange (ETDEWEB)

Rantala, Antti; Pihajoki, Pauli; Johansson, Peter H.; Lahén, Natalia; Sawala, Till [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a (Finland); Naab, Thorsten, E-mail: antti.rantala@helsinki.fi [Max-Planck-Insitut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748, Garching (Germany)

2017-05-01

We present KETJU, a new extension of the widely used smoothed particle hydrodynamics simulation code GADGET-3. The key feature of the code is the inclusion of algorithmically regularized regions around every supermassive black hole (SMBH). This allows for simultaneously following global galactic-scale dynamical and astrophysical processes, while solving the dynamics of SMBHs, SMBH binaries, and surrounding stellar systems at subparsec scales. The KETJU code includes post-Newtonian terms in the equations of motions of the SMBHs, which enables a new SMBH merger criterion based on the gravitational wave coalescence timescale, pushing the merger separation of SMBHs down to ∼0.005 pc. We test the performance of our code by comparison to NBODY7 and rVINE. We set up dynamically stable multicomponent merger progenitor galaxies to study the SMBH binary evolution during galaxy mergers. In our simulation sample the SMBH binaries do not suffer from the final-parsec problem, which we attribute to the nonspherical shape of the merger remnants. For bulge-only models, the hardening rate decreases with increasing resolution, whereas for models that in addition include massive dark matter halos, the SMBH binary hardening rate becomes practically independent of the mass resolution of the stellar bulge. The SMBHs coalesce on average 200 Myr after the formation of the SMBH binary. However, small differences in the initial SMBH binary eccentricities can result in large differences in the SMBH coalescence times. Finally, we discuss the future prospects of KETJU, which allows for a straightforward inclusion of gas physics in the simulations.

The current ability to test theories of gravity with black hole shadows

Science.gov (United States)

Mizuno, Yosuke; Younsi, Ziri; Fromm, Christian M.; Porth, Oliver; De Laurentis, Mariafelicia; Olivares, Hector; Falcke, Heino; Kramer, Michael; Rezzolla, Luciano

2018-04-01

Our Galactic Centre, Sagittarius A*, is believed to harbour a supermassive black hole, as suggested by observations tracking individual orbiting stars1,2. Upcoming submillimetre very-long baseline interferometry images of Sagittarius A* carried out by the Event Horizon Telescope collaboration (EHTC)3,4 are expected to provide critical evidence for the existence of this supermassive black hole5,6. We assess our present ability to use EHTC images to determine whether they correspond to a Kerr black hole as predicted by Einstein's theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform general-relativistic magnetohydrodynamical simulations and use general-relativistic radiative-transfer calculations to generate synthetic shadow images of a magnetized accretion flow onto a Kerr black hole. In addition, we perform these simulations and calculations for a dilaton black hole, which we take as a representative solution of an alternative theory of gravity. Adopting the very-long baseline interferometry configuration from the 2017 EHTC campaign, we find that it could be extremely difficult to distinguish between black holes from different theories of gravity, thus highlighting that great caution is needed when interpreting black hole images as tests of general relativity.

Observations on early and delayed colostomy closure.

Science.gov (United States)

Tade, A O; Salami, B A; Ayoade, B A

2011-06-01

Traditional treatment of a variety of colorectal pathologies had included a diverting colostomy that was closed eight or more weeks later during a readmission. The aim of this retrospective study was to determine the outcomes of early colostomy closure and delayed colostomy closure in patients with temporary colostomies following traumatic and non-traumatic colorectal pathologies. In this study early colostomy closure was the closure of a colostomy within three weeks of its construction, while delayed colostomy closure referred to closure after 3 weeks. Complete records of the 37 adult patients who had temporary colostomy constructed and closed between Jan. 1997 December 2003 for various colorectal pathologies were studied. Fourteen patients had early colostomy closure while 23 had delayed closure. In the early colostomy closure group there were 10 men and 4 women. The mean age of the patients was 28yr with a range of 18-65yr. Colostomies were closed 9-18 days after initial colostomy construction. There was no mortality. Morbidity rate 28.6% (4 out of 14). There were two faecal fistulas (14.3%). Twenty-three patients had delayed colostomy closure 8 weeks to 18 months after initial colostomy construction. These were patients unfit for early surgery after initial colostomy construction because of carcinoma, significant weight loss, or sepsis. There was no mortality. Morbidity rate was 26.1%. There were 3 faecal fistulas (13.2%). Outcomes following early colostomy closure and delayed closure were comparable. Patients fit for surgery should have early closure whilst patients who may have compromised health should have delayed closure.

Closure Report for Corrective Action Unit 547: Miscellaneous Contaminated Waste Sites, Nevada National Security Site, Nevada

Energy Technology Data Exchange (ETDEWEB)

NSTec Environmental Restoration

2012-07-17

This Closure Report (CR) presents information supporting closure of Corrective Action Unit (CAU) 547, Miscellaneous Contaminated Waste Sites, and provides documentation supporting the completed corrective actions and confirmation that closure objectives for CAU 547 were met. This CR complies with the requirements of the Federal Facility Agreement and Consent Order (FFACO) that was agreed to by the State of Nevada; the U.S. Department of Energy (DOE), Environmental Management; the U.S. Department of Defense; and DOE, Legacy Management (FFACO, 1996 as amended). CAU 547 consists of the following three Corrective Action Sites (CASs), located in Areas 2, 3, and 9 of the Nevada National Security Site: (1) CAS 02-37-02, Gas Sampling Assembly; (2) CAS 03-99-19, Gas Sampling Assembly; AND (3) CAS 09-99-06, Gas Sampling Assembly Closure activities began in August 2011 and were completed in June 2012. Activities were conducted according to the Corrective Action Decision Document/Corrective Action Plan (CADD/CAP) for CAU 547 (U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office [NNSA/NSO], 2011). The recommended corrective action for the three CASs in CAU 547 was closure in place with administrative controls. The following closure activities were performed: (1) Open holes were filled with concrete; (2) Steel casings were placed over vertical expansion joints and filled with cement; (3) Engineered soil covers were constructed over piping and exposed sections of the gas sampling system components; (4) Fencing, monuments, Jersey barriers, radiological postings, and use restriction (UR) warning signs were installed around the perimeters of the sites; (5) Housekeeping debris was picked up from around the sites and disposed; and (6) Radiological surveys were performed to confirm final radiological postings. UR documentation is included in Appendix D. The post-closure plan was presented in detail in the CADD/CAP for CAU 547 and is included as

Closure Report for Corrective Action Unit 547: Miscellaneous Contaminated Waste Sites, Nevada National Security Site, Nevada

International Nuclear Information System (INIS)

2012-01-01

This Closure Report (CR) presents information supporting closure of Corrective Action Unit (CAU) 547, Miscellaneous Contaminated Waste Sites, and provides documentation supporting the completed corrective actions and confirmation that closure objectives for CAU 547 were met. This CR complies with the requirements of the Federal Facility Agreement and Consent Order (FFACO) that was agreed to by the State of Nevada; the U.S. Department of Energy (DOE), Environmental Management; the U.S. Department of Defense; and DOE, Legacy Management (FFACO, 1996 as amended). CAU 547 consists of the following three Corrective Action Sites (CASs), located in Areas 2, 3, and 9 of the Nevada National Security Site: (1) CAS 02-37-02, Gas Sampling Assembly; (2) CAS 03-99-19, Gas Sampling Assembly; AND (3) CAS 09-99-06, Gas Sampling Assembly Closure activities began in August 2011 and were completed in June 2012. Activities were conducted according to the Corrective Action Decision Document/Corrective Action Plan (CADD/CAP) for CAU 547 (U.S. Department of Energy, National Nuclear Security Administration Nevada Site Office [NNSA/NSO], 2011). The recommended corrective action for the three CASs in CAU 547 was closure in place with administrative controls. The following closure activities were performed: (1) Open holes were filled with concrete; (2) Steel casings were placed over vertical expansion joints and filled with cement; (3) Engineered soil covers were constructed over piping and exposed sections of the gas sampling system components; (4) Fencing, monuments, Jersey barriers, radiological postings, and use restriction (UR) warning signs were installed around the perimeters of the sites; (5) Housekeeping debris was picked up from around the sites and disposed; and (6) Radiological surveys were performed to confirm final radiological postings. UR documentation is included in Appendix D. The post-closure plan was presented in detail in the CADD/CAP for CAU 547 and is included as

Outcomes of macular hole surgery in patients treated intraoperatively for retinal breaks and/or lattice degeneration.

Science.gov (United States)

Hwang, John; Escariao, Paulo; Iranmanesh, Reza; Tosi, Gian Marco; Chang, Stanley

2007-01-01

To assess the outcome of macular hole surgery in patients treated intraoperatively for retinal breaks and/or lattice degeneration. Retrospective review of patients who underwent macular hole surgery from September 1998 to August 2005. Outcomes in eyes that received intraoperative endolaser photocoagulation for retinal breaks and/or lattice degeneration were compared to outcomes in a case-matched control group without retinal breaks or lattice degeneration. A total of 235 consecutive macular hole surgery cases were reviewed. Twenty-four eyes from 24 patients received intraoperative endolaser photocoagulation for retinal breaks and/or lattice degeneration. Macular hole closure occurred in all case and control eyes without any incidence of postoperative retinal detachment. Best-corrected visual acuity improvement of at least three Snellen lines occurred in 100% of case eyes and 92% of control eyes. Outcomes of macular hole surgery in patients with retinal breaks and/or lattice degeneration are similar to outcomes in the overall population when these conditions are treated with intraoperative endolaser photocoagulation. Postoperative retinal detachment does not appear to be correlated with treated retinal tears and greater attention should focus on detecting and managing intraoperative breaks. In our hands, routine use panoramic viewing has replaced indirect ophthalmoscopy, by saving time, and reducing the risk of contamination.

Sternal exploration or closure

Science.gov (United States)

VAC - vacuum-assisted closure - sternal wound; Sternal dehiscence; Sternal infection ... in the wound to look for signs of infection Remove dead or infected ... use a VAC (vacuum-assisted closure) dressing. It is a negative ...

Reconstructing the massive black hole cosmic history through gravitational waves

International Nuclear Information System (INIS)

Sesana, Alberto; Gair, Jonathan; Berti, Emanuele; Volonteri, Marta

2011-01-01

The massive black holes we observe in galaxies today are the natural end-product of a complex evolutionary path, in which black holes seeded in proto-galaxies at high redshift grow through cosmic history via a sequence of mergers and accretion episodes. Electromagnetic observations probe a small subset of the population of massive black holes (namely, those that are active or those that are very close to us), but planned space-based gravitational wave observatories such as the Laser Interferometer Space Antenna (LISA) can measure the parameters of 'electromagnetically invisible' massive black holes out to high redshift. In this paper we introduce a Bayesian framework to analyze the information that can be gathered from a set of such measurements. Our goal is to connect a set of massive black hole binary merger observations to the underlying model of massive black hole formation. In other words, given a set of observed massive black hole coalescences, we assess what information can be extracted about the underlying massive black hole population model. For concreteness we consider ten specific models of massive black hole formation, chosen to probe four important (and largely unconstrained) aspects of the input physics used in structure formation simulations: seed formation, metallicity ''feedback'', accretion efficiency and accretion geometry. For the first time we allow for the possibility of 'model mixing', by drawing the observed population from some combination of the 'pure' models that have been simulated. A Bayesian analysis allows us to recover a posterior probability distribution for the ''mixing parameters'' that characterize the fractions of each model represented in the observed distribution. Our work shows that LISA has enormous potential to probe the underlying physics of structure formation.

Perturbation methods and closure approximations in nonlinear systems

International Nuclear Information System (INIS)

Dubin, D.H.E.

1984-01-01

In the first section of this thesis, Hamiltonian theories of guiding center and gyro-center motion are developed using modern symplectic methods and Lie transformations. Littlejohn's techniques, combined with the theory of resonant interaction and island overlap, are used to explore the problem of adiabatic invariance and onset of stochasticity. As an example, the breakdown of invariance due to resonance between drift motion and gyromotion in a tokamak is considered. A Hamiltonian is developed for motion in a straight magnetic field with electrostatic perturbations in the gyrokinetic ordering, from which nonlinear gyrokinetic equations are constructed which have the property of phase-space preservation, useful for computer simulation. Energy invariants are found and various limits of the equations are considered. In the second section, statistical closure theories are applied to simple dynamical systems. The logistic map is used as an example because of its universal properties and simple quadratic nonlinearity. The first closure considered is the direct interaction approximation of Kraichnan, which is found to fail when applied to the logistic map because it cannot approximate the bounded support of the map's equilibrium distribution. By imposing a periodically constraint on a Langevin form of the DIA a new stable closure is developed

Full closure strategic analysis.

Science.gov (United States)

2014-07-01

The full closure strategic analysis was conducted to create a decision process whereby full roadway : closures for construction and maintenance activities can be evaluated and approved or denied by CDOT : Traffic personnel. The study reviewed current...

Crack closure, a literature study

Science.gov (United States)

Holmgren, M.

1993-08-01

In this report crack closure is treated. The state of the art is reviewed. Different empirical formulas for determining the crack closure are compared with each other, and their benefits are discussed. Experimental techniques for determining the crack closure stress are discussed, and some results from fatigue tests are also reported. Experimental data from the literature are reported.

A Particular Appetite: Cosmological Hydrodynamic Simulations of Preferential Accretion in the Supermassive Black Holes of Milky Way Size Galaxies

Science.gov (United States)

Sanchez, Natalie; Bellovary, Jillian M.; Holley-Bockelmann, Kelly

2016-01-01

With the use of cosmological hydrodynamic simulations of Milky Way-type galaxies, we identify the preferential source of gas that is accreted by the supermassive black holes (SMBHs) they host. We examine simulations of two Milky Way analogs, each distinguished by a differing merger history. One galaxy is characterized by several major mergers and the other has a more quiescent history. By examining and comparing these two galaxies, which have a similar structure at z=0, we asses the importance of merger history on black hole accretion. This study is an extension of Bellovary et. al. 2013, which studied accretion onto SMBHs in massive, high redshift galaxies. Bellovary found that the fraction of gas accreted by the galaxy was proportional to that which was accreted by its SMBH. Contrary to Bellovary's previous results, we found that though the gas accreted by a quiescent galaxy will mirror the accretion of its central SMBH, a galaxy that is characterized by an active merger history will have a SMBH that preferentially accretes gas gained through mergers. We move forward by examining the angular momentum of the gas accreted by these Milky Way-type galaxies to better understand the mechanisms fueling their central SMBH.

West Valley Demonstration Project, Waste Management Area #3 -- Closure Alternative I

Energy Technology Data Exchange (ETDEWEB)

Marschke, Stephen F. [Environmental Measurements Laboratory (EML), New York, NY (United States)

2000-06-30

The Draft Environmental Impact Statement for the completion of the West Valley Demonstration Project and closure and/or long-term management of facilities at the Western New York Nuclear Service Center divided the site into Waste Management Areas (WMAs), and for each WMA, presented the impacts associated with five potential closure alternatives. This report focuses on WMA 3 (the High-Level Waste (HLW) Storage Area (Tanks 8D-1 and 8D-2), the Vitrification Facility and other facilities) and closure Alternative I (the complete removal of all structures, systems and components and the release of the area for unrestricted use), and reestimates the impacts associated with the complete removal of the HLW tanks, and surrounding facilities. A 32-step approach was developed for the complete removal of Tanks 8D-1 and 8D-2, the Supernatant Treatment System Support Building, and the Transfer Trench. First, a shielded Confinement Structure would be constructed to reduce the shine dose rate and to control radioactivity releases. Similarly, the tank heels would be stabilized to reduce potential radiation exposures. Next, the tank removal methodology would include: 1) excavation of the vault cover soil, 2) removal of the vault roof, 3) cutting off the tank’s top, 4) removal of the stabilized heel remaining inside the tank, 5) cutting up the tank’s walls and floor, 6) removal of the vault’s walls, the perlite blocks, and vault floor, and 7) radiation surveying and backfilling the resulting hole. After the tanks are removed, the Confinement Structure would be decontaminated and dismantled, and the site backfilled and landscaped. The impacts (including waste disposal quantities, emissions, work-effort, radiation exposures, injuries and fatalities, consumable materials used, and costs) were estimated based on this 32 step removal methodology, and added to the previously estimated impacts for closure of the other facilities within WMA 3 to obtain the total impacts from

CONSTRAINING THE STRUCTURE OF SAGITTARIUS A*'s ACCRETION FLOW WITH MILLIMETER VERY LONG BASELINE INTERFEROMETRY CLOSURE PHASES

Energy Technology Data Exchange (ETDEWEB)

Broderick, Avery E [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Fish, Vincent L; Doeleman, Sheperd S [Massachusetts Institute of Technology, Haystack Observatory, Route 40, Westford, MA 01886 (United States); Loeb, Abraham [Institute for Theory and Computation, Harvard University, Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2011-09-01

Millimeter wave very long baseline interferometry (mm-VLBI) provides access to the emission region surrounding Sagittarius A* (Sgr A*), the supermassive black hole at the center of the Milky Way, on sub-horizon scales. Recently, a closure phase of 0{sup 0} {+-} 40{sup 0} was reported on a triangle of Earth-sized baselines (SMT-CARMA-JCMT) representing a new constraint upon the structure and orientation of the emission region, independent from those provided by the previously measured 1.3 mm-VLBI visibility amplitudes alone. Here, we compare this to the closure phases associated with a class of physically motivated, radiatively inefficient accretion flow models and present predictions for future mm-VLBI experiments with the developing Event Horizon Telescope (EHT). We find that the accretion flow models are capable of producing a wide variety of closure phases on the SMT-CARMA-JCMT triangle and thus not all models are consistent with the recent observations. However, those models that reproduce the 1.3 mm-VLBI visibility amplitudes overwhelmingly have SMT-CARMA-JCMT closure phases between {+-}30{sup 0}, and are therefore broadly consistent with all current mm-VLBI observations. Improving station sensitivity by factors of a few, achievable by increases in bandwidth and phasing together multiple antennas at individual sites, should result in physically relevant additional constraints upon the model parameters and eliminate the current 180{sup 0} ambiguity on the source orientation. When additional stations are included, closure phases of order 45{sup 0}-90{sup 0} are typical. In all cases, the EHT will be able to measure these with sufficient precision to produce dramatic improvements in the constraints upon the spin of Sgr A*.

Positive Catch & Economic Benefits of Periodic Octopus Fishery Closures: Do Effective, Narrowly Targeted Actions ‘Catalyze’ Broader Management?

Science.gov (United States)

Oliver, Thomas A.; Oleson, Kirsten L. L.; Ratsimbazafy, Hajanaina; Raberinary, Daniel; Benbow, Sophie; Harris, Alasdair

2015-01-01

Overview Eight years of octopus fishery records from southwest Madagascar reveal significant positive impacts from 36 periodic closures on: (a) fishery catches and (b) village fishery income, such that (c) economic benefits from increased landings outweigh costs of foregone catch. Closures covered ~20% of a village’s fished area and lasted 2-7 months. Fishery Catches from Each Closed Site Octopus landings and catch per unit effort (CPUE) significantly increased in the 30 days following a closure’s reopening, relative to the 30 days before a closure (landings: +718%, poctopus fishery income doubled in the 30 days after a closure, relative to 30 days before (+132%, p<0.001, n = 28). Control villages not implementing a closure showed no increase in income after “no ban” closures and modest increases after “ban” closures. Villages did not show a significant decline in income during closure events. Net Economic Benefits from Each Closed Site Landings in closure sites generated more revenue than simulated landings assuming continued open-access fishing at that site (27/36 show positive net earnings; mean +$305/closure; mean +57.7% monthly). Benefits accrued faster than local fishers’ time preferences during 17-27 of the 36 closures. High reported rates of illegal fishing during closures correlated with poor economic performance. Broader Co-Management We discuss the implications of our findings for broader co-management arrangements, particularly for catalyzing more comprehensive management. PMID:26083862

Scalp Wound Closure with K wires: An alternative easier method to scalp wound closure.

Science.gov (United States)

Ramesh, S; Ajik, S

2012-12-01

Scalp defects and lacerations present a reconstructive challenge to plastic surgeons. Many methods have been described from the use of skin grafting to rotation flaps. Here we present a method of closure of a contaminated scalp wound with the use of Kirschner wires. In our case, closure of scalp laceration was made possible with the use of 1.4 Kirschner wires and cable tie/ zip tie fasteners. The duration to closure of wound was 10 days. In reconstructing the scalp defect, this method was found to adhere to principles of scalp reconstruction. There were no post operative complications found from the procedure. On initial application on the edge of the wound, tension applied caused the K wires to cut through the wound edge. On replacement of K wires 1cm away from wound edge the procedure was not plagued by any further complication. In conclusion we find scalp closure with Kirschner wires are a simple and effective method for scalp wound closure.

Revisit to Grad's Closure and Development of Physically Motivated Closure for Phenomenological High-Order Moment Model

International Nuclear Information System (INIS)

Myong, R. S.; Nagdewe, S. P.

2011-01-01

The Grad's closure for the high-order moment equation is revisited and, by extending his theory, a physically motivated closure is developed for the one-dimensional velocity shear gas flow. The closure is based on the physical argument of the relative importance of various terms appearing in the moment equation. Also, the closure is derived such that the resulting theory may be inclusive of the well established linear theory (Navier-Stokes-Fourier) as limiting case near local thermal equilibrium.

The Converging Inflow Spectrum Is an Intrinsic Signature for a Black Hole: Monte Carlo Simulations of Comptonization on Free-falling Electrons

Science.gov (United States)

Laurent, Philippe; Titarchuk, Lev

1999-01-01

An accreting black hole is, by definition, characterized by the drain. Namely, matter falls into a black hole much the same way as water disappears down a drain: matter goes in and nothing comes out. As this can only happen in a black hole, it provides a way to see ``a black hole,'' a unique observational signature of black holes. The accretion proceeds almost in a free-fall manner close to the black hole horizon, where the strong gravitational field dominates the pressure forces. In this paper we calculate (by using Monte Carlo simulations) the specific features of X-ray spectra formed as a result of upscattering of the soft (disk) photons in the converging inflow (CI) within about 3 Schwarzschild radii of the black hole. The full relativistic treatment has been implemented to reproduce these spectra. We show that spectra in the soft state of black hole systems (BHS) can be described as the sum of a thermal (disk) component and the convolution of some fraction of this component with the CI upscattering spread (Green's) function. The latter boosted photon component is seen as an extended power law at energies much higher than the characteristic energy of the soft photons. We demonstrate the stability of the power spectral index (α=1.8+/-0.1) over a wide range of the plasma temperature, 0-10 keV, and mass accretion rates (higher than 2 in Eddington units). We also demonstrate that the sharp high-energy cutoff occurs at energies of 200-400 keV, which are related to the average energy of electrons mec2 impinging on the event horizon. The spectrum is practically identical to the standard thermal Comptonization spectrum (Hua & Titarchuk) when the CI plasma temperature is getting of order of 50 keV (the typical ones for the hard state of BHS). In this case one can see the effect of the bulk motion only at high energies, where there is an excess in the CI spectrum with respect to the pure thermal one. Furthermore, we demonstrate that the change of spectral shapes from

Large eddy simulations of compressible magnetohydrodynamic turbulence

Energy Technology Data Exchange (ETDEWEB)

Grete, Philipp

2016-09-09

Supersonic, magnetohydrodynamic (MHD) turbulence is thought to play an important role in many processes - especially in astrophysics, where detailed three-dimensional observations are scarce. Simulations can partially fill this gap and help to understand these processes. However, direct simulations with realistic parameters are often not feasible. Consequently, large eddy simulations (LES) have emerged as a viable alternative. In LES the overall complexity is reduced by simulating only large and intermediate scales directly. The smallest scales, usually referred to as subgrid-scales (SGS), are introduced to the simulation by means of an SGS model. Thus, the overall quality of an LES with respect to properly accounting for small-scale physics crucially depends on the quality of the SGS model. While there has been a lot of successful research on SGS models in the hydrodynamic regime for decades, SGS modeling in MHD is a rather recent topic, in particular, in the compressible regime. In this thesis, we derive and validate a new nonlinear MHD SGS model that explicitly takes compressibility effects into account. A filter is used to separate the large and intermediate scales, and it is thought to mimic finite resolution effects. In the derivation, we use a deconvolution approach on the filter kernel. With this approach, we are able to derive nonlinear closures for all SGS terms in MHD: the turbulent Reynolds and Maxwell stresses, and the turbulent electromotive force (EMF). We validate the new closures both a priori and a posteriori. In the a priori tests, we use high-resolution reference data of stationary, homogeneous, isotropic MHD turbulence to compare exact SGS quantities against predictions by the closures. The comparison includes, for example, correlations of turbulent fluxes, the average dissipative behavior, and alignment of SGS vectors such as the EMF. In order to quantify the performance of the new nonlinear closure, this comparison is conducted from the

Evaluation of Two Energy Balance Closure Parametrizations

Science.gov (United States)

Eder, Fabian; De Roo, Frederik; Kohnert, Katrin; Desjardins, Raymond L.; Schmid, Hans Peter; Mauder, Matthias

2014-05-01

A general lack of energy balance closure indicates that tower-based eddy-covariance (EC) measurements underestimate turbulent heat fluxes, which calls for robust correction schemes. Two parametrization approaches that can be found in the literature were tested using data from the Canadian Twin Otter research aircraft and from tower-based measurements of the German Terrestrial Environmental Observatories (TERENO) programme. Our analysis shows that the approach of Huang et al. (Boundary-Layer Meteorol 127:273-292, 2008), based on large-eddy simulation, is not applicable to typical near-surface flux measurements because it was developed for heights above the surface layer and over homogeneous terrain. The biggest shortcoming of this parametrization is that the grid resolution of the model was too coarse so that the surface layer, where EC measurements are usually made, is not properly resolved. The empirical approach of Panin and Bernhofer (Izvestiya Atmos Oceanic Phys 44:701-716, 2008) considers landscape-level roughness heterogeneities that induce secondary circulations and at least gives a qualitative estimate of the energy balance closure. However, it does not consider any feature of landscape-scale heterogeneity other than surface roughness, such as surface temperature, surface moisture or topography. The failures of both approaches might indicate that the influence of mesoscale structures is not a sufficient explanation for the energy balance closure problem. However, our analysis of different wind-direction sectors shows that the upwind landscape-scale heterogeneity indeed influences the energy balance closure determined from tower flux data. We also analyzed the aircraft measurements with respect to the partitioning of the "missing energy" between sensible and latent heat fluxes and we could confirm the assumption of scalar similarity only for Bowen ratios 1.

High Fidelity BWR Fuel Simulations

Energy Technology Data Exchange (ETDEWEB)

Yoon, Su Jong [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-08-01

This report describes the Consortium for Advanced Simulation of Light Water Reactors (CASL) work conducted for completion of the Thermal Hydraulics Methods (THM) Level 3 milestone THM.CFD.P13.03: High Fidelity BWR Fuel Simulation. High fidelity computational fluid dynamics (CFD) simulation for Boiling Water Reactor (BWR) was conducted to investigate the applicability and robustness performance of BWR closures. As a preliminary study, a CFD model with simplified Ferrule spacer grid geometry of NUPEC BWR Full-size Fine-mesh Bundle Test (BFBT) benchmark has been implemented. Performance of multiphase segregated solver with baseline boiling closures has been evaluated. Although the mean values of void fraction and exit quality of CFD result for BFBT case 4101-61 agreed with experimental data, the local void distribution was not predicted accurately. The mesh quality was one of the critical factors to obtain converged result. The stability and robustness of the simulation was mainly affected by the mesh quality, combination of BWR closure models. In addition, the CFD modeling of fully-detailed spacer grid geometry with mixing vane is necessary for improving the accuracy of CFD simulation.

The cosmic evolution of massive black holes in the Horizon-AGN simulation

Science.gov (United States)

Volonteri, M.; Dubois, Y.; Pichon, C.; Devriendt, J.

2016-08-01

We analyse the demographics of black holes (BHs) in the large-volume cosmological hydrodynamical simulation Horizon-AGN. This simulation statistically models how much gas is accreted on to BHs, traces the energy deposited into their environment and, consequently, the back-reaction of the ambient medium on BH growth. The synthetic BHs reproduce a variety of observational constraints such as the redshift evolution of the BH mass density and the mass function. Strong self-regulation via AGN feedback, weak supernova feedback, and unresolved internal processes result in a tight BH-galaxy mass correlation. Starting at z ˜ 2, tidal stripping creates a small population of BHs over-massive with respect to the halo. The fraction of galaxies hosting a central BH or an AGN increases with stellar mass. The AGN fraction agrees better with multi-wavelength studies, than single-wavelength ones, unless obscuration is taken into account. The most massive haloes present BH multiplicity, with additional BHs gained by ongoing or past mergers. In some cases, both a central and an off-centre AGN shine concurrently, producing a dual AGN. This dual AGN population dwindles with decreasing redshift, as found in observations. Specific accretion rate and Eddington ratio distributions are in good agreement with observational estimates. The BH population is dominated in turn by fast, slow, and very slow accretors, with transitions occurring at z = 3 and z = 2, respectively.

Slowly balding black holes

International Nuclear Information System (INIS)

Lyutikov, Maxim; McKinney, Jonathan C.

2011-01-01

The 'no-hair' theorem, a key result in general relativity, states that an isolated black hole is defined by only three parameters: mass, angular momentum, and electric charge; this asymptotic state is reached on a light-crossing time scale. We find that the no-hair theorem is not formally applicable for black holes formed from the collapse of a rotating neutron star. Rotating neutron stars can self-produce particles via vacuum breakdown forming a highly conducting plasma magnetosphere such that magnetic field lines are effectively ''frozen in'' the star both before and during collapse. In the limit of no resistivity, this introduces a topological constraint which prohibits the magnetic field from sliding off the newly-formed event horizon. As a result, during collapse of a neutron star into a black hole, the latter conserves the number of magnetic flux tubes N B =eΦ ∞ /(πc(ℎ/2π)), where Φ ∞ ≅2π 2 B NS R NS 3 /(P NS c) is the initial magnetic flux through the hemispheres of the progenitor and out to infinity. We test this theoretical result via 3-dimensional general relativistic plasma simulations of rotating black holes that start with a neutron star dipole magnetic field with no currents initially present outside the event horizon. The black hole's magnetosphere subsequently relaxes to the split-monopole magnetic field geometry with self-generated currents outside the event horizon. The dissipation of the resulting equatorial current sheet leads to a slow loss of the anchored flux tubes, a process that balds the black hole on long resistive time scales rather than the short light-crossing time scales expected from the vacuum no-hair theorem.

BLACK HOLE-GALAXY CORRELATIONS WITHOUT SELF-REGULATION

International Nuclear Information System (INIS)

Anglés-Alcázar, Daniel; Özel, Feryal; Davé, Romeel

2013-01-01

Recent models of black hole growth in a cosmological context have forwarded a paradigm in which the growth is self-regulated by feedback from the black hole itself. Here we use cosmological zoom simulations of galaxy formation down to z = 2 to show that such strong self-regulation is required in the popular spherical Bondi accretion model, but that a plausible alternative model in which black hole growth is limited by galaxy-scale torques does not require self-regulation. Instead, this torque-limited accretion model yields black holes and galaxies evolving on average along the observed scaling relations by relying only on a fixed, 5% mass retention rate onto the black hole from the radius at which the accretion flow is fed. Feedback from the black hole may (and likely does) occur, but does not need to couple to galaxy-scale gas in order to regulate black hole growth. We show that this result is insensitive to variations in the initial black hole mass, stellar feedback, or other implementation details. The torque-limited model allows for high accretion rates at very early epochs (unlike the Bondi case), which if viable can help explain the rapid early growth of black holes, while by z ∼ 2 it yields Eddington factors of ∼1%-10%. This model also yields a less direct correspondence between major merger events and rapid phases of black hole growth. Instead, growth is more closely tied to cosmological disk feeding, which may help explain observational studies showing that, at least at z ∼> 1, active galaxies do not preferentially show merger signatures.

HEMI-TEMPORAL INTERNAL LIMITING MEMBRANE PEELING IS AS EFFECTIVE AND SAFE AS CONVENTIONAL FULL PEELING FOR MACULAR HOLE SURGERY.

Science.gov (United States)

Shiono, Akira; Kogo, Jiro; Sasaki, Hiroki; Yomoda, Ryo; Jujo, Tatsuya; Tokuda, Naoto; Kitaoka, Yasushi; Takagi, Hitoshi

2018-05-09

To investigate the efficacy of hemi-temporal internal limiting membrane (ILM) peeling for idiopathic macular hole. The medical records of patients with macular holes who had undergone vitrectomy with ILM peeling were studied. Forty-two eyes with macular hole were divided into 2 groups based on surgical procedure (hemi-temporal ILM peeling [hemi group]: 15 eyes; 360° ILM peeling [360° group]: 27 eyes). The closure rates and distances between the optic disc and the intersection of two retinal vessels most closely located nasally or temporally to the macular hole were compared. The primary closure rates were not significantly different between the two groups (hemi group: 93.3%; 360° group: 92.5%, P = 0.92). The temporal retinal vessels in the hemi group were displaced 120.5 ± 102.0 µm toward the optic disc at 1 week postoperatively, which did not differ significantly from the 360° group (136.1 ± 106.1 µm) (P = 0.107). However, the nasal retinal vessels in the hemi group were displaced by 42.4 ± 42.9 µm at 1 week postoperatively, which was significantly less than the 90.1 ± 77.3 µm displacement seen in the 360° group (P = 0.040). Hemi-temporal ILM peeling may be preferable to 360° ILM peeling because of less displacement of the retina and greater safety.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

Relativistic hydrodynamics in the presence of puncture black holes

International Nuclear Information System (INIS)

Faber, Joshua A.; Etienne, Zachariah B.; Shapiro, Stuart L.; Taniguchi, Keisuke; Baumgarte, Thomas W.

2007-01-01

Many of the recent numerical simulations of binary black holes in vacuum adopt the moving puncture approach. This successful approach avoids the need to impose numerical excision of the black hole interior and is easy to implement. Here we wish to explore how well the same approach can be applied to moving black hole punctures in the presence of relativistic hydrodynamic matter. First, we evolve single black hole punctures in vacuum to calibrate our Baumgarte-Shapiro-Shibata-Nakamura implementation and to confirm that the numerical solution for the exterior spacetime is invariant to any junk (i.e., constraint-violating) initial data employed in the black hole interior. Then we focus on relativistic Bondi accretion onto a moving puncture Schwarzschild black hole as a numerical test bed for our high-resolution shock-capturing relativistic hydrodynamics scheme. We find that the hydrodynamical equations can be evolved successfully in the interior without imposing numerical excision. These results help motivate the adoption of the moving puncture approach to treat the binary black hole-neutron star problem using conformal thin-sandwich initial data

Nevada Test Site closure program

International Nuclear Information System (INIS)

Shenk, D.P.

1994-08-01

This report is a summary of the history, design and development, procurement, fabrication, installation and operation of the closures used as containment devices on underground nuclear tests at the Nevada Test Site. It also addresses the closure program mothball and start-up procedures. The Closure Program Document Index and equipment inventories, included as appendices, serve as location directories for future document reference and equipment use

Evaluation of a novel trocar-site closure and comparison with a standard Carter-Thomason closure device.

Science.gov (United States)

del Junco, Michael; Okhunov, Zhamshid; Juncal, Samuel; Yoon, Renai; Landman, Jaime

2014-07-01

The aim of this study was to evaluate and compare a novel trocars-site closure device, the WECK EFx™ Endo Fascial Closure System (EFx) with the Carter-Thomason CloseSure System® (CT) for the closure of laparoscopic trocar site defects created by a 12-mm dilating trocar. We created standardized laparoscopic trocars-site abdominal wall defects in cadaver models using a standard 12-mm laparoscopic dilating trocar. Trocar defects were closed in a randomized fashion using one of the two closure systems. We recorded time and number of attempts needed for complete defect closure. In addition, we recorded the ability to maintain pneumoperitoneum, endoscopic visualization, safety, security, and facility based on the surgeon's subjective evaluations. We compared outcomes for the EFx and CT closure systems. We created 72 standardized laparoscopic trocars-site abdominal wall defects. The mean time needed for complete defect closure was 98.53 seconds (±28.9) for the EFx compared with 133.61 seconds (±54.61) for the CT (Psafety were 2.92 for EFx vs 2.19 for CT (Pvs 1.83 for EFx and CT, respectively (Pvs 2.33 for CT (P=0.022). No significant difference was observed between the EFx and the CT systems for endoscopic visualization (2.28 vs 2.50, P=0.080). In this in vitro cadaver trial, the EFx was superior in terms of time needed to complete defect closure, safety, and facility. CT was superior in terms of maintenance of pneumoperitoneum. Both systems were equal in the number of attempts needed to complete the defect closure and endoscopic visualization.

Performance of an Orifice Compensated Two-Lobe Hole-Entry Hybrid Journal Bearing

Directory of Open Access Journals (Sweden)

J. Sharana Basavaraja

2008-01-01

Full Text Available The work presented in this paper aims to study the performance of a two-lobe hole-entry hybrid journal bearing system compensated by orifice restrictors. The Reynolds equation governing the flow of lubricant in the clearance space between the journal and bearing together with the equation of flow through an orifice restrictor has been solved using FEM and Galerkin's method. The bearing performance characteristics results have been simulated for an orifice compensated nonrecessed two-lobe hole-entry hybrid journal bearing symmetric configuration for the various values of offset factor (, restrictor design parameter (2, and the value of external load (0. Further, a comparative study of the performance of a two-lobe hole-entry hybrid journal bearing system with a circular hole-entry symmetric hybrid journal bearing system has also been carried out so that a designer has a better flexibility in choosing a suitable bearing configuration. The simulated numerical results indicate that for the two-lobe symmetric hole-entry hybrid journal bearing system with an offset factor ( greater than one provides 30 to 50 percent larger values of direct stiffness and direct damping coefficients as compared to a circular symmetric hole-entry hybrid journal bearing system.

GPU based 3D feature profile simulation of high-aspect ratio contact hole etch process under fluorocarbon plasmas

Science.gov (United States)

Chun, Poo-Reum; Lee, Se-Ah; Yook, Yeong-Geun; Choi, Kwang-Sung; Cho, Deog-Geun; Yu, Dong-Hun; Chang, Won-Seok; Kwon, Deuk-Chul; Im, Yeon-Ho

2013-09-01

Although plasma etch profile simulation has been attracted much interest for developing reliable plasma etching, there still exist big gaps between current research status and predictable modeling due to the inherent complexity of plasma process. As an effort to address this issue, we present 3D feature profile simulation coupled with well-defined plasma-surface kinetic model for silicon dioxide etching process under fluorocarbon plasmas. To capture the realistic plasma surface reaction behaviors, a polymer layer based surface kinetic model was proposed to consider the simultaneous polymer deposition and oxide etching. Finally, the realistic plasma surface model was used for calculation of speed function for 3D topology simulation, which consists of multiple level set based moving algorithm, and ballistic transport module. In addition, the time consumable computations in the ballistic transport calculation were improved drastically by GPU based numerical computation, leading to the real time computation. Finally, we demonstrated that the surface kinetic model could be coupled successfully for 3D etch profile simulations in high-aspect ratio contact hole plasma etching.

Black Holes and Galactic Density Cusps II Spherically Symmetric Anisotropic Cusps

CERN Document Server

Henriksen, Richard N; Macmillan, Joseph D

2010-01-01

Aims. In this paper we study density cusps that may contain central black holes. The actual co-eval self-similar growth would not distinguish between the central object and the surroundings. Methods. To study the environment of a growing black hole we seek descriptions of steady 'cusps' that may contain a black hole and that retain at least a memory of self-similarity. We refer to the environment in brief as the 'bulge' and on smaller scales, the 'halo'. Results. We find simple descriptions of the simulations of collisionless matter by comparing predicted densities, velocity dispersions and distribution functions with the simulations. In some cases central point masses may be included by iteration. We emphasize that the co-eval self-similar growth allows an explanation of the black hole bulge mass correlation between approximately similar collisionless systems. Conclusions. We have derived our results from first principles assuming adiabatic self-similarity and either self-similar virialisation or normal stea...

Effect of strain rate on cavity closure during compression between flat platens using superplastic tin-lead alloy

International Nuclear Information System (INIS)

Zaid, A.I.O.; Al-Tamimi, M.M.

2011-01-01

Superplasticity is a feature of a material or alloy which allows the material to deform plastically to an extremely large strain at low values of stress under certain loading conditions of strain rate and temperature. Eutectic tin-lead alloy is a practical material for research investigations as it possesses a superplastic behavior at room temperature and low strain rate which makes it a useful tool in simulating the ordinary engineering materials at high strain rate and temperature. This alloy has been extensively used as a model material to simulate behavior of engineering materials at high strain rates and temperatures. In this paper, superplastic tin-lead alloy was used at room temperature to simulate the closure of cavities in steels at high temperatures in the hot region under dynamic loading (high strain rate) under the effect of compressive loads using flat platens (open dies). Hollow specimens having different values of bore diameter (D/sub b/) to outer diameter (D/sub out/), of the same height and volume were investigated under different values of height reduction percentages ranging from 20% to 80% , and the percentage of cavity closure at each reduction percentage was determined. It was found that the cavity closure percentage increases or decreases at slow rate for reduction percentage in height less than 40% and increases more rapidly for reduction percentages in height above this value. Furthermore, specimens having smaller values of ratio (D/sub b//D/sub out/) resulted in higher percentage of cavity closure than specimens having higher ratios at the same value of reduction in height percentage. Complete cavity closure has occurred in specimens having the ratios of 0.1 and 0.2 at 75% reduction in height. (author)

Eyelid closure at death

Directory of Open Access Journals (Sweden)

A D Macleod

2009-01-01

Full Text Available Aim: To observe the incidence of full or partial eyelid closure at death. Materials and Methods: The presence of ptosis was recorded in 100 consecutive hospice patient deaths. Results: Majority (63% of the patients died with their eyes fully closed, however, 37% had bilateral ptosis at death, with incomplete eye closure. In this study, central nervous system tumor involvement and/or acute hepatic encephalopathy appeared to be pre-mortem risk factors of bilateral ptosis at death. Conclusion: Organicity and not psychogenicity is, therefore, the likely etiology of failure of full eyelid closure at death.

Study on antioxidant experiment on forged steel tube sheet and tube hole for steam generator

International Nuclear Information System (INIS)

Zong Hai; Wang Detai; Ding Yang

2012-01-01

Antioxidant experiment on forged steel tube sheet and tube hole for steam generator was studied and the influence of different simulated heat treatments on the antioxidant performance of tube sheet and tube hole was made. The influence of different antioxidant methods on the size of tube hole was drawn. Furthermore, the change of size and weight of 18MnD5 forged steel tube sheet on the condition of different simulated heat treatments was also studied. The analytical results have proved reference information for the use of 18MnD5 material and for key processes of processing tube hole and wearing and expanding U-style tube. (authors)

Examining the microtexture evolution in a hole-edge punched into 780 MPa grade hot-rolled steel

Energy Technology Data Exchange (ETDEWEB)

Shin, J.H.; Kim, M.S. [Department of Printed Electronics Engineering, Sunchon National University, 315 Maegok, Sunchon, Jeonnam 540-950 (Korea, Republic of); Kim, S.I.; Seo, S.J. [POSCO Technical Research Laboratories, Gwangyang 545-090 (Korea, Republic of); Choi, S.-H., E-mail: shihoon@sunchon.ac.kr [Department of Printed Electronics Engineering, Sunchon National University, 315 Maegok, Sunchon, Jeonnam 540-950 (Korea, Republic of)

2016-08-15

The deformation behavior in the hole-edge of 780 MPa grade hot-rolled steel during the punching process was investigated via microstructure characterization and computational simulation. Microstructure characterization was conducted to observe the edges of punched holes through the thickness direction, and electron back-scattered diffraction (EBSD) was used to analyze the heterogeneity of the deformation. Finite element analysis (FEA) that could account for a ductile fracture criterion was conducted to simulate the deformation and fracture behaviors of 780 MPa grade hot-rolled steel during the punching process. Calculation of rotation rate fields at the edges of the punched holes during the punching process revealed that metastable orientations in Euler space were confined to specific orientation groups. Rotation-rate fields effectively explained the stability of the initial texture components in the hole-edge region during the punching process. A visco-plastic self-consistent (VPSC) polycrystal model was used to calculate the microtexture evolution in the hole-edge region during the punching process. FEA revealed that the heterogeneous effective strain was closely related to the heterogeneity of the Kernel average misorientation (KAM) distribution in the hole-edge region. A simulation of the deformation microtexture evolution in the hole-edge region using a VPSC model was in good agreement with the experimental results. - Highlights: •We analyzed the microstructure in a hole-edge punched in HR 780HB steel. •Rotation rate fields revealed the stability of the initial texture components. •Heterogeneous effective stain was closely related to the KAM distribution. •VPSC model successfully simulated the deformation microtexture evolution.

Closure and Sealing Design Calculation

International Nuclear Information System (INIS)

T. Lahnalampi; J. Case

2005-01-01

The purpose of the ''Closure and Sealing Design Calculation'' is to illustrate closure and sealing methods for sealing shafts, ramps, and identify boreholes that require sealing in order to limit the potential of water infiltration. In addition, this calculation will provide a description of the magma that can reduce the consequences of an igneous event intersecting the repository. This calculation will also include a listing of the project requirements related to closure and sealing. The scope of this calculation is to: summarize applicable project requirements and codes relating to backfilling nonemplacement openings, removal of uncommitted materials from the subsurface, installation of drip shields, and erecting monuments; compile an inventory of boreholes that are found in the area of the subsurface repository; describe the magma bulkhead feature and location; and include figures for the proposed shaft and ramp seals. The objective of this calculation is to: categorize the boreholes for sealing by depth and proximity to the subsurface repository; develop drawing figures which show the location and geometry for the magma bulkhead; include the shaft seal figures and a proposed construction sequence; and include the ramp seal figure and a proposed construction sequence. The intent of this closure and sealing calculation is to support the License Application by providing a description of the closure and sealing methods for the Safety Analysis Report. The closure and sealing calculation will also provide input for Post Closure Activities by describing the location of the magma bulkhead. This calculation is limited to describing the final configuration of the sealing and backfill systems for the underground area. The methods and procedures used to place the backfill and remove uncommitted materials (such as concrete) from the repository and detailed design of the magma bulkhead will be the subject of separate analyses or calculations. Post-closure monitoring will not

Scope and closures

CERN Document Server

Simpson, Kyle

2014-01-01

No matter how much experience you have with JavaScript, odds are you don’t fully understand the language. This concise yet in-depth guide takes you inside scope and closures, two core concepts you need to know to become a more efficient and effective JavaScript programmer. You’ll learn how and why they work, and how an understanding of closures can be a powerful part of your development skillset.

Galactic nuclei evolution with spinning black holes: method and implementation

Science.gov (United States)

Fiacconi, Davide; Sijacki, Debora; Pringle, J. E.

2018-04-01

Supermassive black holes at the centre of galactic nuclei mostly grow in mass through gas accretion over cosmic time. This process also modifies the angular momentum (or spin) of black holes, both in magnitude and in orientation. Despite being often neglected in galaxy formation simulations, spin plays a crucial role in modulating accretion power, driving jet feedback, and determining recoil velocity of coalescing black hole binaries. We present a new accretion model for the moving-mesh code AREPO that incorporates (i) mass accretion through a thin α-disc, and (ii) spin evolution through the Bardeen-Petterson effect. We use a diverse suite of idealised simulations to explore the physical connection between spin evolution and larger scale environment. We find that black holes with mass ≲ 107 M⊙ experience quick alignment with the accretion disc. This favours prolonged phases of spin-up, and the spin direction evolves according to the gas inflow on timescales as short as ≲ 100 Myr, which might explain the observed jet direction distribution in Seyfert galaxies. Heavier black holes (≳ 108 M⊙) are instead more sensitive to the local gas kinematic. Here we find a wider distribution in spin magnitudes: spin-ups are favoured if gas inflow maintains a preferential direction, and spin-downs occur for nearly isotropic infall, while the spin direction does not change much over short timescales ˜100 Myr. We therefore conclude that supermassive black holes with masses ≳ 5 × 108 M⊙ may be the ideal testbed to determine the main mode of black hole fuelling over cosmic time.

BLACK HOLE FORAGING: FEEDBACK DRIVES FEEDING

International Nuclear Information System (INIS)

Dehnen, Walter; King, Andrew

2013-01-01

We suggest a new picture of supermassive black hole (SMBH) growth in galaxy centers. Momentum-driven feedback from an accreting hole gives significant orbital energy, but little angular momentum to the surrounding gas. Once central accretion drops, the feedback weakens and swept-up gas falls back toward the SMBH on near-parabolic orbits. These intersect near the black hole with partially opposed specific angular momenta, causing further infall and ultimately the formation of a small-scale accretion disk. The feeding rates into the disk typically exceed Eddington by factors of a few, growing the hole on the Salpeter timescale and stimulating further feedback. Natural consequences of this picture include (1) the formation and maintenance of a roughly toroidal distribution of obscuring matter near the hole; (2) random orientations of successive accretion disk episodes; (3) the possibility of rapid SMBH growth; (4) tidal disruption of stars and close binaries formed from infalling gas, resulting in visible flares and ejection of hypervelocity stars; (5) super-solar abundances of the matter accreting on to the SMBH; and (6) a lower central dark-matter density, and hence annihilation signal, than adiabatic SMBH growth implies. We also suggest a simple subgrid recipe for implementing this process in numerical simulations

Development of hole inspection program using touch trigger probe on CNC machine tools

International Nuclear Information System (INIS)

Lee, Chan Ho; Lee, Eung Suk

2012-01-01

According to many customers' requests, optical measurement module (OMM) applications using automatic measuring devices to measure the machined part rapidly on a machine tool have increased steeply. Touch trigger probes are being used for job setup and feature inspection as automatic measuring devices, and this makes quality checking and machining compensation possible. Therefore, in this study, the use of touch trigger probes for accurate measurement of the machined part has been studied and a macro program for a hole measuring cycle has been developed. This hole is the most common feature to be measured, but conventional methods are still not free from measuring error. In addition, the eccentricity change of the least square circle was simulated according to the roundness error in a hole measurement. To evaluate the reliability of this study, the developed hole measuring program was executed to measure the hole plate on the machine and verify the roundness error in the eccentricity simulation result

Primordial Black Holes from First Principles (Overview)

Science.gov (United States)

Lam, Casey; Bloomfield, Jolyon; Moss, Zander; Russell, Megan; Face, Stephen; Guth, Alan

2017-01-01

Given a power spectrum from inflation, our goal is to calculate, from first principles, the number density and mass spectrum of primordial black holes that form in the early universe. Previously, these have been calculated using the Press- Schechter formalism and some demonstrably dubious rules of thumb regarding predictions of black hole collapse. Instead, we use Monte Carlo integration methods to sample field configurations from a power spectrum combined with numerical relativity simulations to obtain a more accurate picture of primordial black hole formation. We demonstrate how this can be applied for both Gaussian perturbations and the more interesting (for primordial black holes) theory of hybrid inflation. One of the tools that we employ is a variant of the BBKS formalism for computing the statistics of density peaks in the early universe. We discuss the issue of overcounting due to subpeaks that can arise from this approach (the ``cloud-in-cloud'' problem). MIT UROP Office- Paul E. Gray (1954) Endowed Fund.

Black holes as critical point of quantum phase transition.

Science.gov (United States)

Dvali, Gia; Gomez, Cesar

We reformulate the quantum black hole portrait in the language of modern condensed matter physics. We show that black holes can be understood as a graviton Bose-Einstein condensate at the critical point of a quantum phase transition, identical to what has been observed in systems of cold atoms. The Bogoliubov modes that become degenerate and nearly gapless at this point are the holographic quantum degrees of freedom responsible for the black hole entropy and the information storage. They have no (semi)classical counterparts and become inaccessible in this limit. These findings indicate a deep connection between the seemingly remote systems and suggest a new quantum foundation of holography. They also open an intriguing possibility of simulating black hole information processing in table-top labs.

Economic Evaluation of Individual School Closure Strategies: The Hong Kong 2009 H1N1 Pandemic.

Directory of Open Access Journals (Sweden)

Zoie Shui-Yee Wong

Full Text Available School closures as a means of containing the spread of disease have received considerable attention from the public health community. Although they have been implemented during previous pandemics, the epidemiological and economic effects of the closure of individual schools remain unclear.This study used data from the 2009 H1N1 pandemic in Hong Kong to develop a simulation model of an influenza pandemic with a localised population structure to provide scientific justifications for and economic evaluations of individual-level school closure strategies.The estimated cost of the study's baseline scenario was USD330 million. We found that the individual school closure strategies that involved all types of schools and those that used a lower threshold to trigger school closures had the best performance. The best scenario resulted in an 80% decrease in the number of cases (i.e., prevention of about 830,000 cases, and the cost per case prevented by this intervention was USD1,145; thus, the total cost was USD1.28 billion.This study predicts the effects of individual school closure strategies on the 2009 H1N1 pandemic in Hong Kong. Further research could determine optimal strategies that combine various system-wide and district-wide school closures with individual school triggers across types of schools. The effects of different closure triggers at different phases of a pandemic should also be examined.

Dynamical evolution of quasicircular binary black hole data

International Nuclear Information System (INIS)

Alcubierre, Miguel; Bruegmann, Bernd; Diener, Peter; Guzman, F. Siddhartha; Hawke, Ian; Hawley, Scott; Herrmann, Frank; Pollney, Denis; Thornburg, Jonathan; Koppitz, Michael; Seidel, Edward

2005-01-01

We study the fully nonlinear dynamical evolution of binary black hole data, whose orbital parameters are specified via the effective potential method for determining quasicircular orbits. The cases studied range from the Cook-Baumgarte innermost stable circular orbit (ISCO) to significantly beyond that separation. In all cases we find the black holes to coalesce (as determined by the appearance of a common apparent horizon) in less than half an orbital period. The results of the numerical simulations indicate that the initial holes are not actually in quasicircular orbits, but that they are in fact nearly plunging together. The dynamics of the final horizon are studied to determine physical parameters of the final black hole, such as its spin, mass, and oscillation frequency, revealing information about the inspiral process. We show that considerable resolution is required to extract accurate physical information from the final black hole formed in the merger process, and that the quasinormal modes of the final hole are strongly excited in the merger process. For the ISCO case, by comparing physical measurements of the final black hole formed to the initial data, we estimate that less than 3% of the total energy is radiated in the merger process

Detecting Boundary Nodes and Coverage Holes in Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Li-Hui Zhao

2016-01-01

Full Text Available The emergence of coverage holes in wireless sensor networks (WSNs means that some special events have broken out and the function of WSNs will be seriously influenced. Therefore, the issues of coverage holes have attracted considerable attention. In this paper, we focus on the identification of boundary nodes and coverage holes, which is crucially important to preventing the enlargement of coverage holes and ensuring the transmission of data. We define the problem of coverage holes and propose two novel algorithms to identify the coverage holes in WSNs. The first algorithm, Distributed Sector Cover Scanning (DSCS, can be used to identify the nodes on hole borders and the outer boundary of WSNs. The second scheme, Directional Walk (DW, can locate the coverage holes based on the boundary nodes identified with DSCS. We implement the algorithms in various scenarios and fully evaluate their performance. The simulation results show that the boundary nodes can be accurately detected by DSCS and the holes enclosed by the detected boundary nodes can be identified by DW. The comparisons confirm that the proposed algorithms outperform the existing ones.

100-D Ponds closure plan. Revision 1

International Nuclear Information System (INIS)

Petersen, S.W.

1997-09-01

The 100-D Ponds is a Treatment, Storage, and Disposal (TSD) unit on the Hanford Facility that received both dangerous and nonregulated waste. This Closure Plan (Rev. 1) for the 100-D Ponds TSD unit consists of a RCRA Part A Dangerous Waste Permit Application (Rev. 3), a RCRA Closure Plan, and supporting information contained in the appendices to the plan. The closure plan consists of eight chapters containing facility description, process information, waste characteristics, and groundwater monitoring data. There are also chapters containing the closure strategy and performance standards. The strategy for the closure of the 100-D Ponds TSD unit is clean closure. Appendices A and B of the closure plan demonstrate that soil and groundwater beneath 100-D Ponds are below cleanup limits. All dangerous wastes or dangerous waste constituents or residues associated with the operation of the ponds have been removed, therefore, human health and the environment are protected. Discharges to the 100-D Ponds, which are located in the 100-DR-1 operable unit, were discontinued in June 1994. Contaminated sediment was removed from the ponds in August 1996. Subsequent sampling and analysis demonstrated that there is no contamination remaining in the ponds, therefore, this closure plan is a demonstration of clean closure

Optimization and large scale computation of an entropy-based moment closure

Science.gov (United States)

Kristopher Garrett, C.; Hauck, Cory; Hill, Judith

2015-12-01

We present computational advances and results in the implementation of an entropy-based moment closure, MN, in the context of linear kinetic equations, with an emphasis on heterogeneous and large-scale computing platforms. Entropy-based closures are known in several cases to yield more accurate results than closures based on standard spectral approximations, such as PN, but the computational cost is generally much higher and often prohibitive. Several optimizations are introduced to improve the performance of entropy-based algorithms over previous implementations. These optimizations include the use of GPU acceleration and the exploitation of the mathematical properties of spherical harmonics, which are used as test functions in the moment formulation. To test the emerging high-performance computing paradigm of communication bound simulations, we present timing results at the largest computational scales currently available. These results show, in particular, load balancing issues in scaling the MN algorithm that do not appear for the PN algorithm. We also observe that in weak scaling tests, the ratio in time to solution of MN to PN decreases.

Closure for spent-fuel transport and storage containers

International Nuclear Information System (INIS)

Ahner, S.; Knackstedt, H.G.; Srostlik, P.

1980-01-01

The container has a transport closure and a shielding closure. This shielding closure consists of two pieces (double closure system), which can be fartened to one another like a bayonet fixing. A central motion of rotation is enough to open the closure. It can be done remote-controlled as well as manually. (DG) [de

Black holes

International Nuclear Information System (INIS)

Feast, M.W.

1981-01-01

This article deals with two questions, namely whether it is possible for black holes to exist, and if the answer is yes, whether we have found any yet. In deciding whether black holes can exist or not the central role in the shaping of our universe played by the forse of gravity is discussed, and in deciding whether we are likely to find black holes in the universe the author looks at the way stars evolve, as well as white dwarfs and neutron stars. He also discusses the problem how to detect a black hole, possible black holes, a southern black hole, massive black holes, as well as why black holes are studied

High-resolution Hydrodynamic Simulation of Tidal Detonation of a Helium White Dwarf by an Intermediate Mass Black Hole

Science.gov (United States)

Tanikawa, Ataru

2018-05-01

We demonstrate tidal detonation during a tidal disruption event (TDE) of a helium (He) white dwarf (WD) with 0.45 M ⊙ by an intermediate mass black hole using extremely high-resolution simulations. Tanikawa et al. have shown tidal detonation in results of previous studies from unphysical heating due to low-resolution simulations, and such unphysical heating occurs in three-dimensional (3D) smoothed particle hydrodynamics (SPH) simulations even with 10 million SPH particles. In order to avoid such unphysical heating, we perform 3D SPH simulations up to 300 million SPH particles, and 1D mesh simulations using flow structure in the 3D SPH simulations for 1D initial conditions. The 1D mesh simulations have higher resolutions than the 3D SPH simulations. We show that tidal detonation occurs and confirm that this result is perfectly converged with different space resolution in both 3D SPH and 1D mesh simulations. We find that detonation waves independently arise in leading parts of the WD, and yield large amounts of 56Ni. Although detonation waves are not generated in trailing parts of the WD, the trailing parts would receive detonation waves generated in the leading parts and would leave large amounts of Si group elements. Eventually, this He WD TDE would synthesize 56Ni of 0.30 M ⊙ and Si group elements of 0.08 M ⊙, and could be observed as a luminous thermonuclear transient comparable to SNe Ia.

Echocardiographic predictors of coil vs device closure in patients undergoing percutaneous patent ductus arteriosus closure.

Science.gov (United States)

Roushdy, Alaa; Abd El Razek, Yasmeen; Mamdouh Tawfik, Ahmed

2018-01-01

To determine anatomic and hemodynamic echocardiographic predictors for patent ductus arteriosus (PDA) device vs coil closure. Seventy-six patients who were referred for elective transcatheter PDA closure were enrolled in the study. All patients underwent full echocardiogram including measurement of the PDA pulmonary end diameter, color flow width and extent, peak and end-diastolic Doppler gradients across the duct, diastolic flow reversal, left atrial dimensions and volume, left ventricular sphericity index, and volumes. The study group was subdivided into 2 subgroups based on the mode of PDA closure whether by coil (n = 42) or device (n = 34). Using univariate analysis there was a highly significant difference between the 2 groups as regard the pulmonary end diameter measured in both the suprasternal and parasternal short-axis views as well as the color flow width and color flow extent (P closure group had statistically significant higher end-systolic and end-diastolic volumes indexed, left atrial volume, and diastolic flow reversal. Receiver operating characteristic curve analysis showed a pulmonary end diameter cutoff point from the suprasternal view > 2.5 mm and from parasternal short-axis view > 2.61 mm to have the highest balanced sensitivity and specificity to predict the likelihood for device closure (AUC 0.971 and 0.979 respectively). The pulmonary end diameter measured from the suprasternal view was the most independent predictor of device closure. The selection between PDA coil or device closure can be done on the basis of multiple anatomic and hemodynamic echocardiographic variables. © 2017 Wiley Periodicals, Inc.

Black Holes, Gravitational Waves, and LISA

Science.gov (United States)

Baker, John

2009-01-01

Binary black hole mergers are central to many key science objectives of the Laser Interferometer Space Antenna (LISA). For many systems the strongest part of the signal is only understood by numerical simulations. Gravitational wave emissions are understood by simulations of vacuum General Relativity (GR). I discuss numerical simulation results from the perspective of LISA's needs, with indications of work that remains to be done. Some exciting scientific opportunities associated with LISA observations would be greatly enhanced if prompt electromagnetic signature could be associated. I discuss simulations to explore this possibility. Numerical simulations are important now for clarifying LISA's science potential and planning the mission. We also consider how numerical simulations might be applied at the time of LISA's operation.

Initial-State Graviton Radiation in Quantum Black Hole Production

CERN Document Server

AUTHOR|(CDS)2262067

2017-01-01

Monte Carlo simulation of quantum black hole production in the ATLAS experiment that allows for graviton radiation in the initial state is discussed and studied. It is concluded that, using trapped surface calculations and graviton emission, a black hole signal would be significant for Planck scales up to 4.5 TeV given a proton-proton luminosity of 37 fb$^{-1}$ in the 13 TeV LHC configuration.

Comparison of Outcomes between Early Fascial Closure and Delayed Abdominal Closure in Patients with Open Abdomen: A Systematic Review and Meta-Analysis

Directory of Open Access Journals (Sweden)

Yu Chen

2014-01-01

Full Text Available Up to the present, the optimal time to close an open abdomen remains controversial. This study was designed to evaluate whether early fascial abdominal closure had advantages over delayed approach for open abdomen populations. Medline, Embase, and Cochrane Library were searched until April 2013. Search terms included “open abdomen,” “abdominal compartment syndrome,” “laparostomy,” “celiotomy,” “abdominal closure,” “primary,” “delayed,” “permanent,” “fascial closure,” and “definitive closure.” Open abdomen was defined as “fail to close abdominal fascia after a laparotomy.” Mortality, complications, and length of stay were compared between early and delayed fascial closure. In total, 3125 patients were included for final analysis, and 1942 (62% patients successfully achieved early fascial closure. Vacuum assisted fascial closure had no impact on pooled fascial closure rate. Compared with delayed abdominal closure, early fascial closure significantly reduced mortality (12.3% versus 24.8%, RR, 0.53, P<0.0001 and complication incidence (RR, 0.68, P<0.0001. The mean interval from open abdomen to definitive closure ranged from 2.2 to 14.6 days in early fascial closure groups, but from 32.5 to 300 days in delayed closure groups. This study confirmed clinical advantages of early fascial closure over delayed approach in treatment of patients with open abdomen.

Numerical simulations of heat transfer distribution of a two-pass square channel with V-rib turbulator and bleed holes

Science.gov (United States)

Kumar, Sourabh; Amano, R. S.; Lucci, Jose Martinez

2013-08-01

The blade tip region in gas turbine encounters high thermal loads due to temperature difference and hence efforts for high durability and safe operations are essential. Improved and robust methods of cooling are required to downgrade heat transfer rate to turbine blades. The blade tip regions, which are exposed to high gas flow, suffers high local thermal load which are due to external tip leakage. Jet impingement, pin cooling etc. are techniques used for cooling blades. A more usual way is to use serpentine passage with 180-degree turn. In this study, numerical simulation of heat transfer distribution of a two-pass square channel with rib turbulators and bleed holes were done. Periodical rib turbulators and bleed holes were used in the channel. The ribs arrangement were 60 degree V rib, 60 degree inverted V ribs, combination of 60 degree V rib at inlet and 60 inverted V rib at outlet section and combination of Inverted V at inlet and V rib at the outlet. The results were numerically computed using Fluent with Reynolds number of 12,500 and 28,500. Turbulence models used for computations were k-ω-SST and RSM. Temperature based and shear stress based techniques were used for heat transfer distribution prediction. The results for 60 degree V rib, 60 degree inverted V ribs were compared with the experimental results for validation of the results obtained. Detailed distribution shows distinctive peaks in heat transfer around bleed holes and rib turbulator. Comparisons of the overall performance of the models with different orientation of rib turbulator are presented. It is found that due to the combination of 60 degree inverted V rib in inlet and 60 V rib in outlet with bleed holes provides better heat treatment. It is suggested that the use of rib turbulator with bleed holes provides suitable for augmenting blade cooling to achieve an optimal balance between thermal and mechanical design requirements.

Tools for Closure Project and Contract Management: Development of the Rocky Flats Integrated Closure Project Baseline

International Nuclear Information System (INIS)

Gelles, C. M.; Sheppard, F. R.

2002-01-01

This paper details the development of the Rocky Flats Integrated Closure Project Baseline - an innovative project management effort undertaken to ensure proactive management of the Rocky Flats Closure Contract in support of the Department's goal for achieving the safe closure of the Rocky Flats Environmental Technology Site (RFETS) in December 2006. The accelerated closure of RFETS is one of the most prominent projects within the Department of Energy (DOE) Environmental Management program. As the first major former weapons plant to be remediated and closed, it is a first-of-kind effort requiring the resolution of multiple complex technical and institutional challenges. Most significantly, the closure of RFETS is dependent upon the shipment of all special nuclear material and wastes to other DOE sites. The Department is actively working to strengthen project management across programs, and there is increasing external interest in this progress. The development of the Rocky Flats Integrated Closure Project Baseline represents a groundbreaking and cooperative effort to formalize the management of such a complex project across multiple sites and organizations. It is original in both scope and process, however it provides a useful precedent for the other ongoing project management efforts within the Environmental Management program

Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Context

International Nuclear Information System (INIS)

Levine, Robyn Deborah; JILA, Boulder

2008-01-01

Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmological scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Lyα forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely

CD-SEM metrology of spike detection on sub-40 nm contact holes

Science.gov (United States)

Momonoi, Yoshinori; Osabe, Taro; Yamaguchi, Atsuko; Mclellan Martin, Erin; Koyanagi, Hajime; Colburn, Matthew E.; Torii, Kazuyoshi

2010-03-01

In this work, for the purpose of contact-hole process control, new metrics for contact-hole edge roughness (CER) are being proposed. The metrics are correlated to lithographic process variation which result in increased electric fields; a primary driver of time-dependent dielectric breakdown (TDDB). Electric field strength at the tip of spoke-shaped CER has been simulated; and new hole-feature metrics have been introduced. An algorithm for defining critical features like spoke angle, spoke length, etc has been defined. In addition, a method for identifying at-risk holes has been demonstrated. The number of spike holes can determine slight defocus conditions that are not detected though the conventional CER metrics. The newly proposed metrics can identify contact holes with a propensity for increased electric field concentration and are expected to improve contact-hole reliability in the sub-40-nm contact-hole process.

50 CFR 648.161 - Closures.

Science.gov (United States)

2010-10-01

... Bluefish Fishery § 648.161 Closures. (a) EEZ closure. NMFS shall close the EEZ to fishing for bluefish by... dealer permit holders that no commercial quota is available for landing bluefish in that state. ...

A meta-analysis of vitrectomy with or without internal limiting membrane peeling for macular hole retinal detachment in the highly myopic eyes.

Science.gov (United States)

Gao, Xinxiao; Guo, Jia; Meng, Xin; Wang, Jun; Peng, Xiaoyan; Ikuno, Yasushi

2016-06-13

To evaluate the anatomical and visual outcomes by par plana vitrectomy with or without internal limiting membrane (ILM) peeling in highly myopic eyes with macular hole retinal detachment (MHRD). MEDLINE (Ovid, PubMed) and EMBASE were used for data collection up to September 30, 2015. The parameters of anatomical success, macular hole closure and improved best corrected visual acuity (BCVA) at or beyond 6 months after operation were assessed as the primary outcome measurement. The meta-analysis was performed with the fixed-effects model. Seven comparative analyses involving a total of 373 patients were included in the present meta-analysis. Statistically the pooled data showed significant relative risk (RR) in terms of primary reattachment between ILM peeling and non-peeling groups (RR, 1.19; 95 % CI, 1.04 to 1.36; P = 0.012). An effect favoring ILM peeling with regard to macular hole closure was also detected (RR, 1.71; 95 % CI, 1.20 to 2.43; P = 0.003). However, no statistically significant difference was found in the improved BCVA (logarithm of the minimum angle of resolution) at 6 months or more (95 % CI, -0.31 to 0.44; P = 0.738). There is no proved benefit of postoperative visual improvement. However, the available evidences from this study suggested a superiority of ILM peeling over no peeling for myopic patients with MHRD.

σ-holes and π-holes: Similarities and differences.

Science.gov (United States)

Politzer, Peter; Murray, Jane S

2018-04-05

σ-Holes and π-holes are regions of molecules with electronic densities lower than their surroundings. There are often positive electrostatic potentials associated with them. Through these potentials, the molecule can interact attractively with negative sites, such as lone pairs, π electrons, and anions. Such noncovalent interactions, "σ-hole bonding" and "π-hole bonding," are increasingly recognized as being important in a number of different areas. In this article, we discuss and compare the natures and characteristics of σ-holes and π-holes, and factors that influence the strengths and locations of the resulting electrostatic potentials. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

[Comparative study of the effects of sterilized air and perfluoropropane gas tamponades on recovery after idiopathic full-thickness macular hole surgery].

Science.gov (United States)

He, F; Zheng, L; Dong, F T

2017-05-11

Objective: To compare the effects of sterilized air and perfluoropropane (C(3)F(8)) tamponades on recovery after vitrectomy for the treatment of idiopathic full-thickness macular hole (IFTMH). Methods: Case control study. Seventy-three eyes of 69 consecutive cases underwent vitrectomy with air (53 eyes) or 10% C(3)F(8) gas (20 eyes) tamponade. Surgical outcomes were retrospectively analyzed between the two groups, including logarithm of the minimal angle of resolution (logMAR) and optical coherence tomography findings like the size of the macular hole and the photoreceptor layer defect. Results: Preoperatively, the mean best corrected visual acuity (BCVA) was (0.10±0.49), the mean hole diameter was (777.9±320.7) μm, and the mean diameter of the photoreceptor layer defect was (1 709.3±516.0) μm in the sterilized air group, while in the C(3)F(8) group, the mean BCVA was (0.07±0.50), the mean hole diameter was (853.9±355.0) μm, and the mean defect diameter was (1 480.5±429.9) μm. The primary closure rate was 90.6% in the sterilized air group and 95.0% in the C(3)F(8) group. One month after surgery, the mean BCVA was (0.17±0.41), and the mean diameter of the photoreceptor layer defect was (820.5±598.0) μm in the sterilized air group, while in the C(3)F(8) group, the mean BCVA was 0.12±0.49, and the mean defect diameter was (762.5±658.0) μm. There was no statistically significant difference in the closure rate (χ(2)=0.019), BCVA ( t =-1.689), hole diameter ( t =0.837) and diameter of the photoreceptor layer defect ( t =0.338) between the two groups( P >0.05). Conclusions: Vitrectomy with sterilized air tamponade is safe and effective for the treatment of IFTMH and even cases with relatively large diameters. (Chin J Ophthalmol, 2017, 53: 327 - 331) .

Hole transport in c-plane InGaN-based green laser diodes

Energy Technology Data Exchange (ETDEWEB)

Cheng, Yang; Liu, Jianping, E-mail: jpliu2010@sinano.ac.cn; Tian, Aiqin; Zhang, Feng; Feng, Meixin; Hu, Weiwei; Zhang, Shuming; Ikeda, Masao; Li, Deyao; Zhang, Liqun; Yang, Hui [Key Lab of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences (CAS), Suzhou 215123 (China); School of Nano Technology and Nano Bionics, University of Science and Technology of China, Suzhou 215123 (China)

2016-08-29

Hole transport in c-plane InGaN-based green laser diodes (LDs) has been investigated by both simulations and experiments. It is found that holes can overflow from the green double quantum wells (DQWs) at high current density, which reduces carrier injection efficiency of c-plane InGaN-based green LDs. A heavily silicon-doped layer right below the green DQWs can effectively suppress hole overflow from the green DQWs.

Laboratory Observation of Electron Phase-Space Holes during Magnetic Reconnection

International Nuclear Information System (INIS)

Fox, W.; Porkolab, M.; Egedal, J.; Katz, N.; Le, A.

2008-01-01

We report the observation of large-amplitude, nonlinear electrostatic structures, identified as electron phase-space holes, during magnetic reconnection experiments on the Versatile Toroidal Facility at MIT. The holes are positive electric potential spikes, observed on high-bandwidth (∼2 GHz) Langmuir probes. Investigations with multiple probes establish that the holes travel at or above the electron thermal speed and have a three-dimensional, approximately spherical shape, with a scale size ∼2 mm. This corresponds to a few electron gyroradii, or many tens of Debye lengths, which is large compared to holes considered in simulations and observed by satellites, whose length scale is typically only a few Debye lengths. Finally, a statistical study over many discharges confirms that the holes appear in conjunction with the large inductive electric fields and the creation of energetic electrons associated with the magnetic energy release

Comparison of fasciotomy wound closures using traditional dressing changes and the vacuum-assisted closure device.

Science.gov (United States)

Zannis, John; Angobaldo, Jeff; Marks, Malcolm; DeFranzo, Anthony; David, Lisa; Molnar, Joseph; Argenta, Louis

2009-04-01

Fasciotomy wounds can be a major contributor to length of stay for patients as well as a difficult reconstructive challenge. Once the compartment pressure has been relieved and stabilized, the wound should be closed as quickly and early as possible to avoid later complications. Skin grafting can lead to morbidity and scarring at both the donor and fasciotomy site. Primary closure results in a more functional and esthetic outcome with less morbidity for the patient, but can often be difficult to achieve secondary to edema, skin retraction, and skin edge necrosis. Our objective was to examine fasciotomy wound outcomes, including time to definitive closure, comparing traditional wet-to-dry dressings, and the vacuum-assisted closure (VAC) device. This retrospective chart review included a consecutive series of patients over a 10-year period. This series included 458 patients who underwent 804 fasciotomies. Of these fasciotomy wounds, 438 received exclusively VAC. dressings, 270 received only normal saline wet-to-dry dressings, and 96 were treated with a combination of both. Of the sample, 408 patients were treated with exclusively VAC therapy or wet-to-dry dressings and 50 patients were treated with a combination of both. In comparing all wounds, there was a statistically significant higher rate of primary closure using the VAC versus traditional wet-to-dry dressings (P lower extremities and P extremities). The time to primary closure of wounds was shorter in the VAC. group in comparison with the non-VAC group. This study has shown that the use of the VAC for fasciotomy wound closure results in a higher rate of primary closure versus traditional wet-to-dry dressings. In addition, the time to primary closure of wounds or time to skin grafting is shorter when the VAC was employed. The VAC used in the described settings decreases hospitalization time, allows for earlier rehabilitation, and ultimately leads to increased patient satisfaction.

Strain effect on the heat transport properties of bismuth telluride nanofilms with a hole

Science.gov (United States)

Fang, Te-Hua; Chang, Win-Jin; Wang, Kuan-Yu; Huang, Chao-Chun

2018-06-01

We investigated the mechanical behavior of bismuth telluride nanofilms with holes by using an equilibrium molecular dynamics (MD) approach. The holes had diameters of 20, 30, 40, and 50 Å. The thermal conductivity values of the nanofilms were calculated under different strains at different temperatures using a nonequilibrium MD simulation. The simulation revealed that the thermal conductivity of a bismuth telluride nanofilm with a hole decreases with an increase in hole diameter at different strains. For a film with a perfect structure at 300 K, a 48% reduction (from 0.33 to 0.17 W/m K) in the thermal conductivity was observed at a 7% tensile strain. In addition, the thermal conductivity increased by approximately 39% (from 0.33 to 0.46 W/m K) at a 7% compressive strain. A very low value (0.11 W/m K) of thermal conductivity is obtained for the nanofilm with a hole diameter of 50 Å at a 7% tensile strain at 300 K.

Spinal endoscopy combined with selective CT myelography for dural closure of the spinal dural defect with superficial siderosis: technical note.

Science.gov (United States)

Arishima, Hidetaka; Higashino, Yoshifumi; Yamada, Shinsuke; Akazawa, Ayumi; Arai, Hiroshi; Tsunetoshi, Kenzo; Matsuda, Ken; Kodera, Toshiaki; Kitai, Ryuhei; Awara, Kousuke; Kikuta, Ken-Ichiro

2018-01-01

The authors describe a new procedure to detect the tiny dural hole in patients with superficial siderosis (SS) and CSF leakage using a coronary angioscope system for spinal endoscopy and selective CT myelography using a spinal drainage tube. Under fluoroscopy, surgeons inserted the coronary angioscope into the spinal subarachnoid space, similar to the procedure of spinal drainage, and slowly advanced it to the cervical spine. The angioscope clearly showed the small dural hole and injured arachnoid membrane. One week later, the spinal drainage tube was inserted, and the tip of the drainage tube was located just below the level of the dural defect found by the spinal endoscopic examination. This selective CT myelography clarifies the location of the dural defect. During surgery, the small dural hole could be easily located, and it was securely sutured. It is sometimes difficult to detect the actual location of the small dural hole even with thin-slice MRI or dynamic CT myelography in patients with SS. The use of a coronary angioscope for the spinal endoscopy combined with selective CT myelography may provide an effective examination to assess dural closure of the spinal dural defect with SS in cases without obvious dural defects on conventional imaging.

Classical black holes: the nonlinear dynamics of curved spacetime.

Science.gov (United States)

Thorne, Kip S

2012-08-03

Numerical simulations have revealed two types of physical structures, made from curved spacetime, that are attached to black holes: tendexes, which stretch or squeeze anything they encounter, and vortexes, which twist adjacent inertial frames relative to each other. When black holes collide, their tendexes and vortexes interact and oscillate (a form of nonlinear dynamics of curved spacetime). These oscillations generate gravitational waves, which can give kicks up to 4000 kilometers per second to the merged black hole. The gravitational waves encode details of the spacetime dynamics and will soon be observed and studied by the Laser Interferometer Gravitational Wave Observatory and its international partners.

Large eddy simulation of bundle turbulent flows

International Nuclear Information System (INIS)

Hassan, Y.A.; Barsamian, H.R.

1995-01-01

Large eddy simulation may be defined as simulation of a turbulent flow in which the large scale motions are explicitly resolved while the small scale motions are modeled. This results into a system of equations that require closure models. The closure models relate the effects of the small scale motions onto the large scale motions. There have been several models developed, the most popular is the Smagorinsky eddy viscosity model. A new model has recently been introduced by Lee that modified the Smagorinsky model. Using both of the above mentioned closure models, two different geometric arrangements were used in the simulation of turbulent cross flow within rigid tube bundles. An inlined array simulations was performed for a deep bundle (10,816 nodes) as well as an inlet/outlet simulation (57,600 nodes). Comparisons were made to available experimental data. Flow visualization enabled the distinction of different characteristics within the flow such as jet switching effects in the wake of the bundle flow for the inlet/outlet simulation case, as well as within tube bundles. The results indicate that the large eddy simulation technique is capable of turbulence prediction and may be used as a viable engineering tool with the careful consideration of the subgrid scale model. (author)

Electron vortex magnetic holes: A nonlinear coherent plasma structure

Energy Technology Data Exchange (ETDEWEB)

Haynes, Christopher T., E-mail: c.t.haynes@qmul.ac.uk; Burgess, David; Sundberg, Torbjorn [School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom); Camporeale, Enrico [Multiscale Dynamics, Centrum Wiskunde and Informatica (CWI), Amsterdam (Netherlands)

2015-01-15

We report the properties of a novel type of sub-proton scale magnetic hole found in two dimensional particle-in-cell simulations of decaying turbulence with a guide field. The simulations were performed with a realistic value for ion to electron mass ratio. These structures, electron vortex magnetic holes (EVMHs), have circular cross-section. The magnetic field depression is associated with a diamagnetic azimuthal current provided by a population of trapped electrons in petal-like orbits. The trapped electron population provides a mean azimuthal velocity and since trapping preferentially selects high pitch angles, a perpendicular temperature anisotropy. The structures arise out of initial perturbations in the course of the turbulent evolution of the plasma, and are stable over at least 100 electron gyroperiods. We have verified the model for the EVMH by carrying out test particle and PIC simulations of isolated structures in a uniform plasma. It is found that (quasi-)stable structures can be formed provided that there is some initial perpendicular temperature anisotropy at the structure location. The properties of these structures (scale size, trapped population, etc.) are able to explain the observed properties of magnetic holes in the terrestrial plasma sheet. EVMHs may also contribute to turbulence properties, such as intermittency, at short scale lengths in other astrophysical plasmas.

Hanford Patrol Academy Demolition Sites Closure Plan

International Nuclear Information System (INIS)

1992-11-01

From 1975 to 1991 the Hanford Patrol Academy Demolition Sites (HPADS) were used for demolition events. These demolition events were a form of thermal treatment for spent or abandoned chemical waste. Because the HPADS will no longer be used for this thermal activity, the sites will be closed. Closure will be conducted pursuant to the requirements of the Washington State Department of Ecology (Ecology) Dangerous Waste Regulations, Washington Administrative Code (WAC) 173-303-610 and 40 CFR 270.1. Closure also will satisfy closure requirements of WAC 173-303-680 and for the thermal treatment closure requirements of 40 CFR 265.381. This closure plan presents a description of the HPADS, the history of the waste treated, and the approach that will be followed to close the HPADS. Because dangerous waste does not include the source, special nuclear, and by-product material components of mixed waste, radionuclides are not within the scope of WAC 173-303 or of this closure plan. The information on radionuclides is provided only for general knowledge where appropriate. Only dangerous constituents derived from HPADS operations will be addressed in this closure plan in accordance with WAC 173-303-610(2)(b)(i). The HPADS are actually two distinct soil closure areas within the Hanford Patrol Academy training area

A mapping closure for turbulent scalar mixing using a time-evolving reference field

Science.gov (United States)

Girimaji, Sharath S.

1992-01-01

A general mapping-closure approach for modeling scalar mixing in homogeneous turbulence is developed. This approach is different from the previous methods in that the reference field also evolves according to the same equations as the physical scalar field. The use of a time-evolving Gaussian reference field results in a model that is similar to the mapping closure model of Pope (1991), which is based on the methodology of Chen et al. (1989). Both models yield identical relationships between the scalar variance and higher-order moments, which are in good agreement with heat conduction simulation data and can be consistent with any type of epsilon(phi) evolution. The present methodology can be extended to any reference field whose behavior is known. The possibility of a beta-pdf reference field is explored. The shortcomings of the mapping closure methods are discussed, and the limit at which the mapping becomes invalid is identified.

Troughs on Martian Ice Sheets: Analysis of Their Closure and Mass Balance

Science.gov (United States)

Fountain, A.; Kargel, J.; Lewis, K.; MacAyeal, D.; Pfeffer, T.; Zwally, J.

2000-01-01

At the Copenhagen workshop on Martian polar processes, Ralf Greve commented that the flow regime surrounding scarps and troughs of the Martian polar ice sheets cannot be modeled using traditional "plan view" ice-sheet models. Such models are inadequate because they typically use reduced equations that embody certain simplifications applicable only to terrestrial ice sheets where the upper ice sheet surface is smooth. In response to this suggestion, we have constructed a 2-dimensional, time dependent "side view" (two spatial dimensions: one horizontal, one vertical) model of scarp closure that is designed to overcome the difficulties described by Greve. The purpose of the model is to evaluate the scales of stress variation and styles of flow closure so as to estimate errors that may be encountered by "plan view" models. We show that there may be avenues whereby the complications associated with scarp closure can be overcome in "plan view" models through appropriate parameterizations of 3-dimensional effects. Following this, we apply the flow model to simulate the evolution of a typical scarp on the North Polar Cap of Mars. Our simulations investigate: (a) the role of "radiation trapping" (see our companion abstract) in creating and maintaining "spiral-like" scarps on the ice sheet, (b) the consequences of different flowlaws and ice compositions on scarp evolution and, in particular, scarp age, and (c) the role of dust and debris in scarp evolution.

Lagrangian Modeling of Evaporating Sprays at Diesel Engine Conditions: Effects of Multi-Hole Injector Nozzles With JP-8 Surrogates

Science.gov (United States)

2014-05-01

Lagrangian Modeling of Evaporating Sprays at Diesel Engine Conditions: Effects of Multi-Hole Injector Nozzles With JP-8 Surrogates by L...efficiency. In this study, three-dimensional numerical simulations of single and two-hole injector nozzles under diesel conditions are conducted to...numerical simulations of single and two-hole injector nozzles under diesel conditions are conducted to study the spray behavior and the effect of

ASD Closure in Structural Heart Disease.

Science.gov (United States)

Wiktor, Dominik M; Carroll, John D

2018-04-17

While the safety and efficacy of percutaneous ASD closure has been established, new data have recently emerged regarding the negative impact of residual iatrogenic ASD (iASD) following left heart structural interventions. Additionally, new devices with potential advantages have recently been studied. We will review here the potential indications for closure of iASD along with new generation closure devices and potential late complications requiring long-term follow-up. With the expansion of left-heart structural interventions and large-bore transseptal access, there has been growing experience gained with management of residual iASD. Some recently published reports have implicated residual iASD after these procedures as a potential source of diminished clinical outcomes and mortality. Additionally, recent trials investigating new generation closure devices as well as expanding knowledge regarding late complications of percutaneous ASD closure have been published. While percutaneous ASD closure is no longer a novel approach to managing septal defects, there are several contemporary issues related to residual iASD following large-bore transseptal access and new generation devices which serve as an impetus for this review. Ongoing attention to potential late complications and decreasing their incidence with ongoing study is clearly needed.

32 CFR 989.25 - Base closure and realignment.

Science.gov (United States)

2010-07-01

... 32 National Defense 6 2010-07-01 2010-07-01 false Base closure and realignment. 989.25 Section 989... PROTECTION ENVIRONMENTAL IMPACT ANALYSIS PROCESS (EIAP) § 989.25 Base closure and realignment. Base closure or realignment may entail special requirements for environmental analysis. The permanent base closure...

Probing loop quantum gravity with evaporating black holes.

Science.gov (United States)

Barrau, A; Cailleteau, T; Cao, X; Diaz-Polo, J; Grain, J

2011-12-16

This Letter aims at showing that the observation of evaporating black holes should allow the usual Hawking behavior to be distinguished from loop quantum gravity (LQG) expectations. We present a full Monte Carlo simulation of the evaporation in LQG and statistical tests that discriminate between competing models. We conclude that contrarily to what was commonly thought, the discreteness of the area in LQG leads to characteristic features that qualify evaporating black holes as objects that could reveal quantum gravity footprints. © 2011 American Physical Society

SIMULATIONS OF VISCOUS ACCRETION FLOW AROUND BLACK HOLES IN A TWO-DIMENSIONAL CYLINDRICAL GEOMETRY

Energy Technology Data Exchange (ETDEWEB)

Lee, Seong-Jae; Hyung, Siek [School of Science Education (Astronomy), Chungbuk National University, Chungbuk 28644 (Korea, Republic of); Chattopadhyay, Indranil; Kumar, Rajiv [ARIES, Manora Peak, Nainital-263002, Uttarakhand (India); Ryu, Dongsu, E-mail: seong@chungbuk.ac.kr [Department of Physics, School of Natural Sciences UNIST, Ulsan 44919 (Korea, Republic of)

2016-11-01

We simulate shock-free and shocked viscous accretion flows onto a black hole in a two-dimensional cylindrical geometry, where initial conditions were chosen from analytical solutions. The simulation code used the Lagrangian total variation diminishing plus remap routine, which enabled us to attain high accuracy in capturing shocks and to handle the angular momentum distribution correctly. The inviscid shock-free accretion disk solution produced a thick disk structure, while the viscous shock-free solution attained a Bondi-like structure, but in either case, no jet activity nor any quasi-periodic oscillation (QPO)-like activity developed. The steady-state shocked solution in the inviscid as well as in the viscous regime matched theoretical predictions well. However, increasing viscosity renders the accretion shock unstable. Large-amplitude shock oscillation is accompanied by intermittent, transient inner multiple shocks. This oscillation of the inner part of the disk is interpreted as the source of QPO in hard X-rays observed in micro-quasars. Strong shock oscillation induces strong episodic jet emission. The jets also show the existence of shocks, which are produced as one shell hits the preceding one. The periodicities of the jets and shock oscillation are similar; the jets for the higher viscosity parameter appear to be stronger and faster.

Tomographic Structural Changes of Retinal Layers after Internal Limiting Membrane Peeling for Macular Hole Surgery.

Science.gov (United States)

Faria, Mun Yueh; Ferreira, Nuno P; Cristóvao, Diana M; Mano, Sofia; Sousa, David Cordeiro; Monteiro-Grillo, Manuel

2018-01-01

To highlight tomographic structural changes of retinal layers after internal limiting membrane (ILM) peeling in macular hole surgery. Nonrandomized prospective, interventional study in 38 eyes (34 patients) subjected to pars plana vitrectomy and ILM peeling for idiopathic macular hole. Retinal layers were assessed in nasal and temporal regions before and 6 months after surgery using spectral domain optical coherence tomography. Total retinal thickness increased in the nasal region and decreased in the temporal region. The retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) showed thinning on both nasal and temporal sides of the fovea. The thickness of the outer plexiform layer (OPL) increased. The outer nuclear layer (ONL) and outer retinal layers (ORL) increased in thickness after surgery in both nasal and temporal regions. ILM peeling is associated with important alterations in the inner retinal layer architecture, with thinning of the RNFL-GCL-IPL complex and thickening of OPL, ONL, and ORL. These structural alterations can help explain functional outcome and could give indications regarding the extent of ILM peeling, even though peeling seems important for higher rate of hole closure. © 2017 S. Karger AG, Basel.

Artificial black holes

CERN Document Server

Visser, Matt; Volovik, Grigory E

2009-01-01

Physicists are pondering on the possibility of simulating black holes in the laboratory by means of various "analog models". These analog models, typically based on condensed matter physics, can be used to help us understand general relativity (Einstein's gravity); conversely, abstract techniques developed in general relativity can sometimes be used to help us understand certain aspects of condensed matter physics. This book contains 13 chapters - written by experts in general relativity, particle physics, and condensed matter physics - that explore various aspects of this two-way traffic.

Patent ductus arteriosus closure using an Amplatzer™ ventricular septal defect closure device

Science.gov (United States)

Fernando, Rajeev; Koranne, Ketan; Loyalka, Pranav; Kar, Biswajit; Gregoric, Igor

2013-01-01

The ductus arteriosus originates from the persistence of the distal portion of the left sixth aortic arch. It connects the descending aorta (immediately distal to the left subclavian artery) to the roof of the main pulmonary artery, near the origin of the left pulmonary artery. Persistence of the duct beyond 48 h after birth is abnormal and results in patent ductus arteriosus (PDA). PDA is rare in adults because it is usually discovered and treated in childhood. Mechanical closure remains the definitive therapy because the patency of ductus arteriosus may lead to multiple complications, depending on the size and flow through the ductus. PDA closure is indicated in patients with symptoms and evidence of left heart enlargement, and in patients with elevated pulmonary pressures when reversal is possible. Transcatheter closure is the preferred technique in adults because it avoids sternotomy, reduces the length of hospital stay and is associated with fewer complications compared with surgery. First demonstrated in 1967, both the technique and the occluder devices used have since evolved. However, designing an ideal PDA occluder has been a challenge due to the variability in size, shape and orientation of PDAs. The present article describes a case involving a 35-year-old woman who presented to the Center for Advanced Heart Failure (Houston, USA) with congestive heart failure due to a large PDA, which was successfully occluded using an Amplatzer (St Jude Medical, USA) muscular ventricular septal defect closure device. The wider waist and dual-retention discs of these ventricular septal defect closure devices may be important factors to consider in the future development of devices for the occlusion of large PDAs. PMID:24294051

Nearly extremal apparent horizons in simulations of merging black holes

Science.gov (United States)

Lovelace, Geoffrey; Scheel, Mark; Owen, Robert; Giesler, Matthew; Katebi, Reza; Szilagyi, Bela; Chu, Tony; Demos, Nicholas; Hemberger, Daniel; Kidder, Lawrence; Pfeiffer, Harald; Afshari, Nousha; SXS Collaboration

2015-04-01

The spin S of a Kerr black hole is bounded by the surface area A of its apparent horizon: 8 πS A and e0 > 1 , but these surfaces are always surrounded by apparent horizons with 8 πS < A and e0 < 1 .

Decoding Mode-mixing in Black-hole Merger Ringdown

Science.gov (United States)

Kelly, Bernard J.; Baker, John G.

2013-01-01

Optimal extraction of information from gravitational-wave observations of binary black-hole coalescences requires detailed knowledge of the waveforms. Current approaches for representing waveform information are based on spin-weighted spherical harmonic decomposition. Higher-order harmonic modes carrying a few percent of the total power output near merger can supply information critical to determining intrinsic and extrinsic parameters of the binary. One obstacle to constructing a full multi-mode template of merger waveforms is the apparently complicated behavior of some of these modes; instead of settling down to a simple quasinormal frequency with decaying amplitude, some |m| = modes show periodic bumps characteristic of mode-mixing. We analyze the strongest of these modes the anomalous (3, 2) harmonic mode measured in a set of binary black-hole merger waveform simulations, and show that to leading order, they are due to a mismatch between the spherical harmonic basis used for extraction in 3D numerical relativity simulations, and the spheroidal harmonics adapted to the perturbation theory of Kerr black holes. Other causes of mode-mixing arising from gauge ambiguities and physical properties of the quasinormal ringdown modes are also considered and found to be small for the waveforms studied here.

Black hole astrophysics

International Nuclear Information System (INIS)

Blandford, R.D.; Thorne, K.S.

1979-01-01

Following an introductory section, the subject is discussed under the headings: on the character of research in black hole astrophysics; isolated holes produced by collapse of normal stars; black holes in binary systems; black holes in globular clusters; black holes in quasars and active galactic nuclei; primordial black holes; concluding remarks on the present state of research in black hole astrophysics. (U.K.)

Clinical and histological evaluation of large macular hole surgery using the inverted internal limiting membrane flap technique

Directory of Open Access Journals (Sweden)

Kase S

2016-12-01

Full Text Available Satoru Kase, Wataru Saito, Shohei Mori, Michiyuki Saito, Ryo Ando, Zhenyu Dong, Tomohiro Suzuki, Kousuke Noda, Susumu Ishida Department of Ophthalmology, Hokkaido University Graduate School of Medicine, Sapporo, Japan Purpose: The aims of this study were to analyze optical coherence tomography (OCT imaging of large macular holes (MHs treated with inverted internal limiting membrane (ILM flap technique and to perform a histological examination of an ILM-like membrane tissue obtained during vitrectomy.Patients and methods: This is a retrospective observational case study. Nine patients, comprising of five males and four females, showing large and myopic MHs, underwent pars plana vitrectomy (PPV with inverted ILM flap technique assisted by brilliant blue G (BBG staining. Ophthalmological findings including visual acuity and OCT were investigated based on medical records. Formalin-fixed paraffin-embedded tissue section of an ILM-like membrane was submitted for immunohistochemistry with glial fibrillary acidic protein (GFAP.Results: ILM was clearly stained with BBG in eight patients, whereas the ILM in one case revealed no staining with BBG during PPV. Visual acuities improved to >0.2 LogMAR in six patients. The complete closure of MH following PPV with inverted ILM technique was eventually achieved in all patients determined by OCT imaging (100%. Only one patient showed recovery of ellipsoid zone and interdigitation zone following the surgery. Elongation of outer nuclear layer was noted in three eyes. The ILM-like membrane not stained with BBG histologically revealed an amorphous structure admixed with GFAP-positive mononuclear cell infiltration.Conclusion: PPV with inverted ILM flap technique achieved 100% closure rates with favorable configuration at an initial surgery in large MHs. Our histopathological data also suggest that even BBG staining-negative membrane may be a useful material for autologous transplantation to the hole. Keywords

Vitrectomy with internal limiting membrane peeling vs no peeling for Macular Hole-induced Retinal Detachment (MHRD): a meta-analysis.

Science.gov (United States)

Su, Jing; Liu, Xinquan; Zheng, Lijun; Cui, Hongping

2015-06-20

we conducted our meta-analysis of published studies to assess existing evidence about the efficacy and safety of vitrectomy with ILM peeling vs. that of vitrectomy with no ILM peeling for Macular hole-induced retinal detachment. Databases, including Pubmed, Cochrane Library, Ovid, Web of Science, Wanfang and CNKI, were searched to identify studies comparing outcomes following vitrectomy with ILM peeling and that with no ILM peeling for macular hole-induced retinal detachment. The meta-analysis was performed by RevMan 5.1. Six comparative studies comprising 180 eyes were identified. It was indicated that the rate of retinal reattachment (Odds ratio (OR) = 3.03, 95 % Confidence interval (CI):1.35 to 6.78; P = 0.007) and macular hole closure (OR = 6.74, 95 % CI:3.26 to 13.93; P peeling than that in the group of vitrectomy with no ILM peeling. However, the improved BCVA (Weighted mean difference (WMD) = 0.14, 95 % CI: -0.20 to 0.47; P = 0.42) and the rate of postoperative complications were similar between the two groups. Vitrectomy with internal limiting membrane peeling is an efficient and safe procedure for macular hole-induced retinal detachment.

Vitrectomy with internal limiting membrane (ILM) peeling versus vitrectomy with no peeling for idiopathic full-thickness macular hole (FTMH).

Science.gov (United States)

Spiteri Cornish, Kurt; Lois, Noemi; Scott, Neil; Burr, Jennifer; Cook, Jonathan; Boachie, Charles; Tadayoni, Ramin; la Cour, Morten; Christensen, Ulrik; Kwok, Alvin

2013-06-05

(ASRS), Annual Meeting of the Retina Society, Congress of the Asia-Pacific Academy of Ophthalmology (APAO), European Association for Vision and Eye Research (EVER) Annual Congress, European Vitreoretinal Society (EVRS) Annual Meeting, Association for Research in Vision and Ophthalmology (ARVO) Meeting, International Vitreoretinal Meeting, and World Ophthalmology Congress. Only randomised controlled trials (RCTs) comparing ILM peeling with the no-peeling counterpart were included. Two review authors (KSC and NL) independently assessed the titles and abstracts of all RCTs identified by electronic and manual searches.We obtained Individual patient data (IPD) from three of the four identified eligible trials. The fourth identified RCT had only been published in abstract form and no IPD were available; we included data from this published abstract for one outcome (macular hole closure).The primary outcome was distance visual acuity at six months. Secondary outcomes included distance and near  visual acuity at three and 12 months postoperatively, near visual acuity at six months postoperatively, primary (after a single surgery) and final (following more than one surgery) macular hole closure, need for additional surgical interventions, vision-related quality of life and intraoperative and postoperative complications.We performed meta-analysis using standard techniques (the Mantel-Haenszel odds ratio (OR) for binary outcomes, mean difference (MD) for continuous outcomes) using a fixed-effect model. For two outcomes we also used the IPD to perform adjusted analyses using regression methods. We identified and included four RCTs; these were conducted in Denmark, France, Hong Kong and the United Kingdom/Republic of Ireland and randomised 47, 80, 49 and 141 participants respectively.There was no evidence of a difference in the primary outcome (distance visual acuity at six months), nor in distance visual acuity at 12 months between randomised groups. However, there was evidence

Above-cutoff impedance measurements of pumping holes for the Collider Liner

International Nuclear Information System (INIS)

Walling, L.; Barts, T.; Ruiz, E.; Turner, W.; Spayd, N.

1994-04-01

A holed liner was considered for the Superconducting Super Collider (SSC) Collider Ring because of vacuum problems caused by photon-induced desorption. The liner would serve to shield the cold surface of the beam tube from the synchrotron radiation and the holes (or slots) would allow distributed pumping by gas-absorption material that could be placed between the liner and the beam tube. The impedance of holes and slots in a liner were studied by means of simulations using both MAFIA and HFSS, analytical modelling, wire measurements and electron beam measurements

Massive Black Hole Mergers: Can We "See" what LISA will "Hear"?

Science.gov (United States)

Centrella, Joan

2010-01-01

The final merger of massive black holes produces strong gravitational radiation that can be detected by the space-borne LISA. If the black hole merger takes place in the presence of gas and magnetic fields, various types of electromagnetic signals may also be produced. Modeling such electromagnetic counterparts of the final merger requires evolving the behavior of both gas and fields in the strong-field regions around the black holes. We will review current efforts to simulate these systems, and discuss possibilities for observing the electromagnetic signals they produce.

Phacoemulsification with intraocular lens implantation in primary angle-closure suspect, primary angle-closure and primary angle-closure glaucoma with cataract

Directory of Open Access Journals (Sweden)

Kun Zeng

2013-08-01

Full Text Available AIM: To evaluate the features and clinical outcomes of cataract extraction by phacoemulsification with intraocular lens implantation in primary angle-closure suspect(PACS, primary angle-closure(PACand primary angle-closure glaucoma(PACGwith cataract.METHODS:Phacoemulsification with intraocular lens implantation was performed on 86 cases(86 eyesdiagnosed as PACS, PAC and PACG co-existing cataract from January to December 2012. All cases were followed up for 3 months to 1 year. Pre-operative and post-operative visual acuity, intraocular pressure(IOP, gonioscopy, ultrasound biomicroscopy(UBM, visual field and usage of anti-glaucomaous eye drops were recorded.RESULTS:Zonular dialysis existed in 19 eyes(22%. The post-operative visual acuity improved in 84 eyes(98%. The post-operative visual acuity was CONCLUSION: PACS, PAC and PACG co-existing zonular dialysis is common. Phacoemulsification with IOL implantation can reduce IOP, deepen anterior chamber and open angle.

40 CFR 264.178 - Closure.

Science.gov (United States)

2010-07-01

... Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Use and Management of Containers § 264.178 Closure. At closure, all hazardous waste and hazardous waste residues must be removed...

Closure report for N Reactor

International Nuclear Information System (INIS)

1994-01-01

This report has been prepared to satisfy Section 3156(b) of Public Law 101-189 (Reports in Connection with Permanent Closures of Department of Energy Defense Nuclear Facilities), which requires submittal of a Closure Report to Congress by the Secretary of Energy upon the permanent cessation of production operations at a US Department of Energy (DOE) defense nuclear facility (Watkins 1991). This closure report provides: (1) A complete survey of the environmental problems at the facility; (2) Budget quality data indicating the cost of environmental restoration and other remediation and cleanup efforts at the facility; (3) A proposed cleanup schedule

Closure report for N Reactor

Energy Technology Data Exchange (ETDEWEB)

1994-01-01

This report has been prepared to satisfy Section 3156(b) of Public Law 101-189 (Reports in Connection with Permanent Closures of Department of Energy Defense Nuclear Facilities), which requires submittal of a Closure Report to Congress by the Secretary of Energy upon the permanent cessation of production operations at a US Department of Energy (DOE) defense nuclear facility (Watkins 1991). This closure report provides: (1) A complete survey of the environmental problems at the facility; (2) Budget quality data indicating the cost of environmental restoration and other remediation and cleanup efforts at the facility; (3) A proposed cleanup schedule.

Black-hole spectroscopy: testing general relativity through gravitational-wave observations

Energy Technology Data Exchange (ETDEWEB)

Dreyer, Olaf [Perimeter Institute of Theoretical Physics, 35 King Street North, Waterloo, Ontario, N2J 2G9 (Canada); Kelly, Bernard [Center for Gravitational Wave Physics, Center for Gravitational Physics and Geometry and Department of Physics, 104 Davey Laboratory, University Park, PA 16802 (United States); Krishnan, Badri [Max Planck Institut fuer Gravitationsphysik, Am Muehlenberg 1, D-14476 Golm (Germany); Finn, Lee Samuel [Center for Gravitational Wave Physics, Center for Gravitational Physics and Geometry, Department of Physics and Department of Astronomy and Astrophysics, 104 Davey Laboratory, University Park, PA 16802 (United States); Garrison, David [University of Houston, Clear Lake, 2700 Bay Area Bvd, Room 3531-2, Houston, TX 77058 (United States); Lopez-Aleman, Ramon [Physical Sciences Department, University of Puerto Rico, Rio Piedras Campus, Rio Piedras, Puerto Rico 00931 (Puerto Rico)

2004-02-21

Assuming that general relativity is the correct theory of gravity in the strong-field limit, can gravitational-wave observations distinguish between black holes and other compact object sources? Alternatively, can gravitational-wave observations provide a test of one of the fundamental predictions of general relativity: the no-hair theorem? Here we describe a definitive test of the hypothesis that observations of damped, sinusoidal gravitational waves originate from a black hole or, alternatively, that nature respects the general relativistic no-hair theorem. For astrophysical black holes, which have a negligible charge-to-mass ratio, the black-hole quasi-normal mode spectrum is characterized entirely by the black-hole mass and angular momentum and is unique to black holes. In a different theory of gravity, or if the observed radiation arises from a different source (e.g., a neutron star, strange matter or boson star), the spectrum will be inconsistent with that predicted for general relativistic black holes. We give a statistical characterization of the consistency between the noisy observation and the theoretical predictions of general relativity and a demonstration, through simulation, of the effectiveness of the test for strong sources.

Black-hole spectroscopy: testing general relativity through gravitational-wave observations

International Nuclear Information System (INIS)

Dreyer, Olaf; Kelly, Bernard; Krishnan, Badri; Finn, Lee Samuel; Garrison, David; Lopez-Aleman, Ramon

2004-01-01

Assuming that general relativity is the correct theory of gravity in the strong-field limit, can gravitational-wave observations distinguish between black holes and other compact object sources? Alternatively, can gravitational-wave observations provide a test of one of the fundamental predictions of general relativity: the no-hair theorem? Here we describe a definitive test of the hypothesis that observations of damped, sinusoidal gravitational waves originate from a black hole or, alternatively, that nature respects the general relativistic no-hair theorem. For astrophysical black holes, which have a negligible charge-to-mass ratio, the black-hole quasi-normal mode spectrum is characterized entirely by the black-hole mass and angular momentum and is unique to black holes. In a different theory of gravity, or if the observed radiation arises from a different source (e.g., a neutron star, strange matter or boson star), the spectrum will be inconsistent with that predicted for general relativistic black holes. We give a statistical characterization of the consistency between the noisy observation and the theoretical predictions of general relativity and a demonstration, through simulation, of the effectiveness of the test for strong sources

SHORT-PULSE ELECTROMAGNETIC TRANSPONDER FOR HOLE-TO-HOLE USE.

Science.gov (United States)

Wright, David L.; Watts, Raymond D.; Bramsoe, Erik

1983-01-01

Hole-to-hole observations were made through nearly 20 m of granite using an electromagnetic transponder (an active reflector) in one borehole and a single-hole short-pulse radar in another. The transponder is inexpensive, operationally simple, and effective in extending the capability of a short-pulse borehole radar system to allow hole-to-hole operation without requiring timing cables. A detector in the transponder senses the arrival of each pulse from the radar. Each pulse detection triggers a kilovolt-amplitude pulse for retransmission. The transponder 'echo' may be stronger than that of a passive reflector by a factor of as much as 120 db. The result is an increase in range capability by a factor which depends on attenuation in the medium and hole-to-hole wavepath geometry.

Femoral Artery Stenosis Following Percutaneous Closure Using a Starclose Closure Device

International Nuclear Information System (INIS)

Bent, Clare Louise; Kyriakides, Constantinos; Matson, Matthew

2008-01-01

Starclose (Abbott Vascular Devices, Redwood City, CA) is a new arterial closure device that seals a femoral puncture site with an extravascular star-shaped nitinol clip. The clip projects small tines into the arterial wall which fold inward, causing the arterial wall to pucker, producing a purse-string-like seal closing the puncture site. The case history is that of a 76-year-old female patient who underwent day-case percutaneous diagnostic coronary angiography. A Starclose femoral artery closure device was used to achieve hemostasis with subsequent femoral artery stenosis.

Gravitational properties of monopole spacetimes near the black hole threshold

International Nuclear Information System (INIS)

Lue, Arthur; Weinberg, Erick J.

2000-01-01

Although nonsingular spacetimes and those containing black holes are qualitatively quite different, there are continuous families of configurations that connect the two. In this paper we use self-gravitating monopole solutions as tools for investigating the transition between these two types of spacetimes. We show how causally distinct regions emerge as the black hole limit is achieved, even though the measurements made by an external observer vary continuously. We find that near-critical solutions have a naturally defined entropy, despite the absence of a true horizon, and that this has a clear connection with the Hawking-Bekenstein entropy. We find that certain classes of near-critical solutions display naked black hole behavior, although they are not truly black holes at all. Finally, we present a numerical simulation illustrating how an incident pulse of matter can induce the dynamical collapse of a monopole into an extremal black hole. We discuss the implications of this process for the third law of black hole thermodynamics. (c) 2000 The American Physical Society

Black-hole universe: time evolution.

Science.gov (United States)

Yoo, Chul-Moon; Okawa, Hirotada; Nakao, Ken-ichi

2013-10-18

Time evolution of a black hole lattice toy model universe is simulated. The vacuum Einstein equations in a cubic box with a black hole at the origin are numerically solved with periodic boundary conditions on all pairs of faces opposite to each other. Defining effective scale factors by using the area of a surface and the length of an edge of the cubic box, we compare them with that in the Einstein-de Sitter universe. It is found that the behavior of the effective scale factors is well approximated by that in the Einstein-de Sitter universe. In our model, if the box size is sufficiently larger than the horizon radius, local inhomogeneities do not significantly affect the global expansion law of the Universe even though the inhomogeneity is extremely nonlinear.

9 CFR 318.301 - Containers and closures.

Science.gov (United States)

2010-01-01

... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Containers and closures. 318.301... Canning and Canned Products § 318.301 Containers and closures. (a) Examination and cleaning of empty containers. (1) Empty containers, closures, and flexible pouch roll stock shall be evaluated by the...

75 FR 29322 - Base Closure and Realignment

Science.gov (United States)

2010-05-25

... DEPARTMENT OF DEFENSE Office of the Secretary Base Closure and Realignment AGENCY: Office of...)(ii) of the Defense Base Closure and Realignment Act of 1990. It provides a partial list of military installations closing or realigning pursuant to the 2005 Base Closure and Realignment (BRAC) Report. It also...

Numerical Relativity, Black Hole Mergers, and Gravitational Waves: Part III

Science.gov (United States)

Centrella, Joan

2012-01-01

This series of 3 lectures will present recent developments in numerical relativity, and their applications to simulating black hole mergers and computing the resulting gravitational waveforms. In this third and final lecture, we present applications of the results of numerical relativity simulations to gravitational wave detection and astrophysics.

Era of Galaxy and Black Hole Growth Spurt Discovered

Science.gov (United States)

2005-04-01

Distant galaxies undergoing intense bursts of star formation have been shown by NASA's Chandra X-ray Observatory to be fertile growing grounds for the largest black holes in the Universe. Collisions between galaxies in the early Universe may be the ultimate cause for both the accelerated star formation and black hole growth. By combining the deepest X-ray image ever obtained with submillimeter and optical observations, an international team of scientists has found evidence that some extremely luminous adolescent galaxies and their central black holes underwent a phenomenal spurt of growth more than 10 billion years ago. This concurrent black hole and galaxy growth spurt is only seen in these galaxies and may have set the stage for the birth of quasars - distant galaxies that contain the largest and most active black holes in the Universe. Simulation of a Galaxy Collision Simulation of a Galaxy Collision "The extreme distances of these galaxies allow us to look back in time, and take a snapshot of how today's largest galaxies looked when they were producing most of their stars and growing black holes," said David Alexander of the University of Cambridge, UK, and lead author of a paper in the April 7, 2005 issue of Nature that describes this work. The galaxies studied by Alexander and his colleagues are known as submillimeter galaxies, so-called because they were originally identified by the James Clerk Maxwell submillimeter telescope (JCMT) on Mauna Kea in Hawaii. The submillimeter observations along with optical data from Keck indicate these galaxies had an unusually large amount of gas. The gas in each galaxy was forming into stars at a rate of about one per day, or 100 times the present rate in the Milky Way galaxy. The Chandra X-ray data show that the supermassive black holes in the galaxies were also growing at the same time. Chandra X-ray Image of CDFN Chandra X-ray Image of CDFN These galaxies are very faint and it is only with the deepest observations of the

Shaping Globular Clusters with Black Holes

Science.gov (United States)

Kohler, Susanna

2018-03-01

, single and binary star evolution, galactic tides, and multi-body encounters. From their grid of models with varying input parameters, the authors then determine which fit best to NGC 3201s final observational properties.Surface brightness profiles for all globular-cluster models at late times compared to observations of NGC 3201 (yellow circles). Blue lines represent models with few retained black holes; black lines represent models with many retained black holes. [Kremer et al. 2018]Retention MattersKremer and collaborators find that the models that best represent NGC 3201 all retain more than 200 black holes at the end of the simulation; models that lost too many black holes due to natal kicks did not match observations of NGC 3201 as well. The models with large numbers of retained black holes also harbored binaries just like the one recently detected in NGC 3201.Models that retain few black holes, on the other hand, may instead be good descriptions of so-called core-collapsed globular clusters observed in the Milky Way. The authors demonstrate that these clusters could contain black holes in binaries with stars known as blue stragglers, which may also be detectable with radial velocity techniques.Kremer and collaborators results suggest that globular clusters similar to NGC 3201 contain hundreds of invisible black holes waiting to be discovered, and they indicate some of the differences in cluster properties caused by hosting such a large population of black holes. We can hope that future observations and modeling will continue to illuminate the complicated relationship between globular clusters and the black holes that live in them.CitationKyle Kremer et al 2018 ApJL 855 L15. doi:10.3847/2041-8213/aab26c

Hole digging in ensembles of tunneling molecular magnets

Science.gov (United States)

Tupitsyn, I. S.; Stamp, P. C.; Prokof'ev, N. V.

2004-04-01

The nuclear spin-mediated quantum relaxation of ensembles of tunneling magnetic molecules causes a “hole” to appear in the distribution of internal fields in the system. The form of this hole and its time evolution, are studied using Monte Carlo simulations. It is shown that the line shape of the tunneling hole in a partially depolarized sample must have a Lorentzian line shape. The short-time half-width ξo in Fe8 crystals should be ˜E0, the half-width of the nuclear spin multiplet, but this result is not generally true. The Lorentzian hole line shape and the short-time √(t) relaxation in weakly polarized samples are both connected to a correlation time τde(ξ) for bias diffusion, whose inverse value also has a Lorentzian dependence on ξ.

Verification of Small Hole Theory for Application to Wire Chaffing Resulting in Shield Faults

Science.gov (United States)

Schuet, Stefan R.; Timucin, Dogan A.; Wheeler, Kevin R.

2011-01-01

Our work is focused upon developing methods for wire chafe fault detection through the use of reflectometry to assess shield integrity. When shielded electrical aircraft wiring first begins to chafe typically the resulting evidence is small hole(s) in the shielding. We are focused upon developing algorithms and the signal processing necessary to first detect these small holes prior to incurring damage to the inner conductors. Our approach has been to develop a first principles physics model combined with probabilistic inference, and to verify this model with laboratory experiments as well as through simulation. Previously we have presented the electromagnetic small-hole theory and how it might be applied to coaxial cable. In this presentation, we present our efforts to verify this theoretical approach with high-fidelity electromagnetic simulations (COMSOL). Laboratory observations are used to parameterize the computationally efficient theoretical model with probabilistic inference resulting in quantification of hole size and location. Our efforts in characterizing faults in coaxial cable are subsequently leading to fault detection in shielded twisted pair as well as analysis of intermittent faulty connectors using similar techniques.

An explicit harmonic code for black-hole evolution using excision

International Nuclear Information System (INIS)

Szilagyi, Bela; Pollney, Denis; Rezzolla, Luciano; Thornburg, Jonathan; Winicour, Jeffrey

2007-01-01

We describe an explicit in time, finite-difference code designed to simulate black holes by using the excision method. The code is based upon the harmonic formulation of the Einstein equations and incorporates several features regarding the well-posedness and numerical stability of the initial-boundary problem for the quasilinear wave equation. After a discussion of the equations solved and of the techniques employed, we present a series of testbeds carried out to validate the code. Such tests range from the evolution of isolated black holes to the head-on collision of two black holes and then to a binary black hole inspiral and merger. Besides assessing the accuracy of the code, the inspiral and merger test has revealed that the marginally trapped surfaces contained within the common apparent horizon of the merged black hole can touch and even intersect. This novel feature in the dynamics of the marginally trapped surfaces is unexpected but consistent with theorems on the properties of these surfaces

An explicit harmonic code for black-hole evolution using excision

Energy Technology Data Exchange (ETDEWEB)

Szilagyi, Bela [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Pollney, Denis [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Thornburg, Jonathan [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Winicour, Jeffrey [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany)

2007-06-21

We describe an explicit in time, finite-difference code designed to simulate black holes by using the excision method. The code is based upon the harmonic formulation of the Einstein equations and incorporates several features regarding the well-posedness and numerical stability of the initial-boundary problem for the quasilinear wave equation. After a discussion of the equations solved and of the techniques employed, we present a series of testbeds carried out to validate the code. Such tests range from the evolution of isolated black holes to the head-on collision of two black holes and then to a binary black hole inspiral and merger. Besides assessing the accuracy of the code, the inspiral and merger test has revealed that the marginally trapped surfaces contained within the common apparent horizon of the merged black hole can touch and even intersect. This novel feature in the dynamics of the marginally trapped surfaces is unexpected but consistent with theorems on the properties of these surfaces.

Closure Welding of Plutonium Bearing Storage Containers

International Nuclear Information System (INIS)

Cannell, G.R.

2002-01-01

A key element in the Department of Energy (DOE) strategy for the stabilization, packaging and storage of plutonium-bearing materials involves closure welding of DOE-STD-3013 Outer Containers (3013 container). The 3013 container provides the primary barrier and pressure boundary preventing release of plutonium-bearing materials to the environment. The final closure (closure weld) of the 3013 container must be leaktight, structurally sound and meet DOE STD 3013 specified criteria. This paper focuses on the development, qualification and demonstration of the welding process for the closure welding of Hanford PFP 3013 outer containers

Numerical Relativity, Black Hole Mergers, and Gravitational Waves: Part I

Science.gov (United States)

Centrella, Joan

2012-01-01

This series of 3 lectures will present recent developments in numerical relativity, and their applications to simulating black hole mergers and computing the resulting gravitational waveforms. In this first lecture, we introduce the basic ideas of numerical relativity, highlighting the challenges that arise in simulating gravitational wave sources on a computer.

Fuel channel closure and adapter

International Nuclear Information System (INIS)

Cashen, W.S.

1985-01-01

This invention provides a mechanical closure/actuating ram combination particularly suited for use in sealing the ends of the pressure tubes when a CANDU-type reactor is refueled. It provides a cluster that may be inserted into a fuel channel end fitting to provide at least partial closing off of a pressure tube while permitting the disengagement of the fueling machine and its withdrawal from the closure for other purposes. The invention also provides a ram/closure combination wherein the application of loading force to a deformable sealing disk is regulated by a massive load bar component forming part of the fueling machine and being therefore accessible for maintenance or replacement

Monte-Carlo simulations of geminate electron-hole pair dissociation in a molecular heterojunction: a two-step dissociation mechanism

International Nuclear Information System (INIS)

Offermans, Ton; Meskers, Stefan C.J.; Janssen, Rene A.J.

2005-01-01

The Monte-Carlo simulations are used to investigate the dissociation of a Coulomb correlated charge pair at an idealized interface between an electron accepting and an electron donating molecular material. In the simulations the materials are represented by cubic lattices of sites, with site the energies spread according to Gaussian distributions. The influence of temperature, applied external fields, and the width of the Gaussian densities of states distribution for both the electron and the hole transporting material are investigated. The results show that the dissociation of geminate charge pairs is assisted by disorder and the results can be understood in terms of a two-step model. In the first step, the slow carrier in the most disordered material jumps away from the interface. In the following, second step, the reduced Coulombic attraction allows the faster carrier in the less disordered material to escape from the interface by thermally activated hopping. When the rate for geminate recombination at the interface is very low ( -1 ) the simulations predict a high yield for carrier collection, as observed experimentally. Comparison of the simulated and experimentally observed temperature dependence of the collection efficiency indicates that at low temperature dissociation of the geminate charge pairs may be one of the factors limiting the device performance

Restaurant closures

CERN Document Server

Novae Restauration

2012-01-01

Christmas Restaurant closures Please note that the Restaurant 1 and Restaurant 3 will be closed from Friday, 21 December at 5 p.m. to Sunday, 6 January, inclusive. They will reopen on Monday, 7 January 2013.   Restaurant 2 closure for renovation To meet greater demand and to modernize its infrastructure, Restaurant 2 will be closed from Monday, 17 December. On Monday, 14 January 2013, Sophie Vuetaz’s team will welcome you to a renovated self-service area on the 1st floor. The selections on the ground floor will also be expanded to include pasta and pizza, as well as snacks to eat in or take away. To ensure a continuity of service, we suggest you take your break at Restaurant 1 or Restaurant 3 (Prévessin).

Influence of the hole geometry on the flow distribution in ventricular catheters for hydrocephalus.

Science.gov (United States)

Giménez, Ángel; Galarza, Marcelo; Pellicer, Olga; Valero, José; Amigó, José M

2016-07-15

Hydrocephalus is a medical condition consisting of an abnormal accumulation of cerebrospinal fluid within the brain. A catheter is inserted in one of the brain ventricles and then connected to an external valve to drain the excess of cerebrospinal fluid. The main drawback of this technique is that, over time, the ventricular catheter ends up getting blocked by the cells and macromolecules present in the cerebrospinal fluid. A crucial factor influencing this obstruction is a non-uniform flow pattern through the catheter, since it facilitates adhesion of suspended particles to the walls. In this paper we focus on the effects that tilted holes as well as conical holes have on the flow distribution and shear stress. We have carried out 3D computational simulations to study the effect of the hole geometry on the cerebrospinal fluid flow through ventricular catheters. All the simulations were done with the OpenFOAM® toolbox. In particular, three different groups of models were investigated by varying (i) the tilt angles of the holes, (ii) the inner and outer diameters of the holes, and (iii) the distances between the so-called hole segments. The replacement of cylindrical holes by conical holes was found to have a strong influence on the flow distribution and to lower slightly the shear stress. Tilted holes did not involve flow distribution changes when the hole segments are sufficiently separated, but the mean shear stress was certainly reduced. The authors present new results about the behavior of the fluid flow through ventricular catheters. These results complete earlier work on this topic by adding the influence of the hole geometry. The overall objective pursued by this research is to provide guidelines to improve existing commercially available ventricular catheters.

Anterior Segment Imaging Predicts Incident Gonioscopic Angle Closure.

Science.gov (United States)

Baskaran, Mani; Iyer, Jayant V; Narayanaswamy, Arun K; He, Yingke; Sakata, Lisandro M; Wu, Renyi; Liu, Dianna; Nongpiur, Monisha E; Friedman, David S; Aung, Tin

2015-12-01

To investigate the incidence of gonioscopic angle closure after 4 years in subjects with gonioscopically open angles but varying degrees of angle closure detected on anterior segment optical coherence tomography (AS OCT; Visante; Carl Zeiss Meditec, Dublin, CA) at baseline. Prospective, observational study. Three hundred forty-two subjects, mostly Chinese, 50 years of age or older, were recruited, of whom 65 were controls with open angles on gonioscopy and AS OCT at baseline, and 277 were cases with baseline open angles on gonioscopy but closed angles (1-4 quadrants) on AS OCT scans. All subjects underwent gonioscopy and AS OCT at baseline (horizontal and vertical single scans) and after 4 years. The examiner performing gonioscopy was masked to the baseline and AS OCT data. Angle closure in a quadrant was defined as nonvisibility of the posterior trabecular meshwork by gonioscopy and visible iridotrabecular contact beyond the scleral spur in AS OCT scans. Gonioscopic angle closure in 2 or 3 quadrants after 4 years. There were no statistically significant differences in age, ethnicity, or gender between cases and controls. None of the control subjects demonstrated gonioscopic angle closure after 4 years. Forty-eight of the 277 subjects (17.3%; 95% confidence interval [CI], 12.8-23; P < 0.0001) with at least 1 quadrant of angle closure on AS OCT at baseline demonstrated gonioscopic angle closure in 2 or more quadrants, whereas 28 subjects (10.1%; 95% CI, 6.7-14.6; P < 0.004) demonstrated gonioscopic angle closure in 3 or more quadrants after 4 years. Individuals with more quadrants of angle closure on baseline AS OCT scans had a greater likelihood of gonioscopic angle closure developing after 4 years (P < 0.0001, chi-square test for trend for both definitions of angle closure). Anterior segment OCT imaging at baseline predicts incident gonioscopic angle closure after 4 years among subjects who have gonioscopically open angles and iridotrabecular contact on AS OCT at

The doubling of stellar black hole nuclei

Science.gov (United States)

Kazandjian, Mher V.; Touma, J. R.

2013-04-01

It is strongly believed that Andromeda's double nucleus signals a disc of stars revolving around its central supermassive black hole on eccentric Keplerian orbits with nearly aligned apsides. A self-consistent stellar dynamical origin for such apparently long-lived alignment has so far been lacking, with indications that cluster self-gravity is capable of sustaining such lopsided configurations if and when stimulated by external perturbations. Here, we present results of N-body simulations which show unstable counter-rotating stellar clusters around supermassive black holes saturating into uniformly precessing lopsided nuclei. The double nucleus in our featured experiment decomposes naturally into a thick eccentric disc of apo-apse aligned stars which is embedded in a lighter triaxial cluster. The eccentric disc reproduces key features of Keplerian disc models of Andromeda's double nucleus; the triaxial cluster has a distinctive kinematic signature which is evident in Hubble Space Telescope observations of Andromeda's double nucleus, and has been difficult to reproduce with Keplerian discs alone. Our simulations demonstrate how the combination of an eccentric disc and a triaxial cluster arises naturally when a star cluster accreted over a preexisting and counter-rotating disc of stars drives disc and cluster into a mutually destabilizing dance. Such accretion events are inherent to standard galaxy formation scenarios. They are here shown to double stellar black hole nuclei as they feed them.

Chandra Data Reveal Rapidly Whirling Black Holes

Science.gov (United States)

2008-01-01

A new study using results from NASA's Chandra X-ray Observatory provides one of the best pieces of evidence yet that many supermassive black holes are spinning extremely rapidly. The whirling of these giant black holes drives powerful jets that pump huge amounts of energy into their environment and affects galaxy growth. A team of scientists compared leading theories of jets produced by rotating supermassive black holes with Chandra data. A sampling of nine giant galaxies that exhibit large disturbances in their gaseous atmospheres showed that the central black holes in these galaxies must be spinning at near their maximum rates. People Who Read This Also Read... NASA’s Swift Satellite Catches First Supernova in The Act of Exploding Black Holes Have Simple Feeding Habits Jet Power and Black Hole Assortment Revealed in New Chandra Image Erratic Black Hole Regulates Itself "We think these monster black holes are spinning close to the limit set by Einstein's theory of relativity, which means that they can drag material around them at close to the speed of light," said Rodrigo Nemmen, a visiting graduate student at Penn State University, and lead author of a paper on the new results presented at American Astronomical Society in Austin, Texas. The research reinforces other, less direct methods previously used which have indicated that some stellar and supermassive black holes are spinning rapidly. According to Einstein's theory, a rapidly spinning black hole makes space itself rotate. This effect, coupled with gas spiraling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic, high-speed jet. Computer simulations by other authors have suggested that black holes may acquire their rapid spins when galaxies merge, and through the accretion of gas from their surroundings. "Extremely fast spin might be very common for large

Randomized clinical trial of intestinal ostomy takedown comparing pursestring wound closure vs conventional closure to eliminate the risk of wound infection.

Science.gov (United States)

Camacho-Mauries, Daniel; Rodriguez-Díaz, José Luis; Salgado-Nesme, Noel; González, Quintín H; Vergara-Fernández, Omar

2013-02-01

The use of temporary stomas has been demonstrated to reduce septic complications, especially in high-risk anastomosis; therefore, it is necessary to reduce the number of complications secondary to ostomy takedowns, namely wound infection, anastomotic leaks, and intestinal obstruction. To compare the rates of superficial wound infection and patient satisfaction after pursestring closure of ostomy wound vs conventional linear closure. Patients undergoing colostomy or ileostomy closure between January 2010 and February 2011 were randomly assigned to linear closure (n = 30) or pursestring closure (n = 31) of their ostomy wound. Wound infection within 30 days of surgery was defined as the presence of purulent discharge, pain, erythema, warmth, or positive culture for bacteria. Patient satisfaction, healing time, difficulty managing the wound, and limitation of activities were analyzed with the Likert questionnaire. The infection rate for the control group was 36.6% (n = 11) vs 0% in the pursestring closure group (p ostomy wound closure (shorter healing time and improved patient satisfaction).

Neutrino constraints that transform black holes into grey holes

International Nuclear Information System (INIS)

Ruderfer, M.

1982-01-01

Existing black hole theory is found to be defective in its neglect of the physical properties of matter and radiation at superhigh densities. Nongravitational neutrino effects are shown to be physically relevant to the evolution of astronomical black holes and their equations of state. Gravitational collapse to supernovae combined with the Davis and Ray vacuum solution for neutrinos limit attainment of a singularity and require black holes to evolve into ''grey holes''. These allow a better justification than do black holes for explaining the unique existence of galactic masses. (Auth.)

A new view of a black hole event. ATLAS collision events

CERN Multimedia

ATLAS, Experiment

2014-01-01

In some theories, microscopic black holes may be produced in particle collisions that occur when very-high-energy cosmic rays hit particles in our atmosphere. These microscopic-black-holes would decay into ordinary particles in a tiny fraction of a second and would be very difficult to observe in our atmosphere. The ATLAS Experiment offers the exciting possibility to study them in the lab (if they exist). The simulated collision event shown is viewed along the beampipe. The event is one in which a microscopic-black-hole was produced in the collision of two protons (not shown). The microscopic-black-hole decayed immediately into many particles. The colors of the tracks show different types of particles emerging from the collision (at the center).

Patent ductus arteriosus closure using an Amplatzer(™) ventricular septal defect closure device.

Science.gov (United States)

Fernando, Rajeev; Koranne, Ketan; Loyalka, Pranav; Kar, Biswajit; Gregoric, Igor

2013-01-01

The ductus arteriosus originates from the persistence of the distal portion of the left sixth aortic arch. It connects the descending aorta (immediately distal to the left subclavian artery) to the roof of the main pulmonary artery, near the origin of the left pulmonary artery. Persistence of the duct beyond 48 h after birth is abnormal and results in patent ductus arteriosus (PDA). PDA is rare in adults because it is usually discovered and treated in childhood. Mechanical closure remains the definitive therapy because the patency of ductus arteriosus may lead to multiple complications, depending on the size and flow through the ductus. PDA closure is indicated in patients with symptoms and evidence of left heart enlargement, and in patients with elevated pulmonary pressures when reversal is possible. Transcatheter closure is the preferred technique in adults because it avoids sternotomy, reduces the length of hospital stay and is associated with fewer complications compared with surgery. First demonstrated in 1967, both the technique and the occluder devices used have since evolved. However, designing an ideal PDA occluder has been a challenge due to the variability in size, shape and orientation of PDAs. The present article describes a case involving a 35-year-old woman who presented to the Center for Advanced Heart Failure (Houston, USA) with congestive heart failure due to a large PDA, which was successfully occluded using an Amplatzer (St Jude Medical, USA) muscular ventricular septal defect closure device. The wider waist and dual-retention discs of these ventricular septal defect closure devices may be important factors to consider in the future development of devices for the occlusion of large PDAs.

Temporary Closure of the Open Abdomen: A Systematic Review on Delayed Primary Fascial Closure in Patients with an Open Abdomen

NARCIS (Netherlands)

Boele van Hensbroek, Pieter; Wind, Jan; Dijkgraaf, Marcel G. W.; Busch, Olivier R. C.; Goslings, J. Carel

2009-01-01

Background This study was designed to systematically review the literature to assess which temporary abdominal closure (TAC) technique is associated with the highest delayed primary fascial closure (FC) rate. In some cases of abdominal trauma or infection, edema or packing precludes fascial closure

Special closures for steel drum shipping containers

International Nuclear Information System (INIS)

Bonzon, L.L.; Otts, J.V.

1976-01-01

The objective of this program was to develop special lid closures for typical, steel drum, radioactive material shipping containers. Previous experience and testing had shown that the existing container was adequate to withstand the required environmental tests for certification, but that the lid and closure were just marginally effective. Specifically, the lid closure failed to consistently maintain a tight seal between the container and the lid after drop tests, thus causing the package contents to be vulnerable in the subsequent fire test. Recognizing the deficiency, the United States Energy Research and Development Administration requested the development of new closure(s) which would: (1) be as strong and resistant to a drop as the bottom of the container; (2) have minimal economic impact on the overall container cost; (3) maximize the use of existing container designs; (4) consider crush loads; and (5) result in less dependence on personnel and loading procedures. Several techniques were evaluated and found to be more effective than the standard closure mechanism. Of these, three new closure techniques were designed, fabricated, and proven to be structurally adequate to provide containment when a 454-kg drum was drop tested from 9.14-m onto an unyielding surface. The three designs were: (1) a 152-mm long lid extension or skirt welded to the standard drum lid, (2) a separate inner lid, with 152-mm long skirt and (3) C-clamps used at the container-lid interface. Based upon structural integrity, economic impact, and minimal design change, the lid extension is the recommended special closure

Preliminary prediction of inflow into the D-holes at the Stripa Mine

International Nuclear Information System (INIS)

Long, J.C.S.; Karasaki, K.; Davey, A.; Peterson, J.; Landsfeld, M.; Kemeny, J.; Martel, S.

1990-02-01

Lawrence Berkeley Laboratory (LBL) is contracted by the US Department of Energy to provide an auxiliary modeling effort for the Stripa Project. Within this effort, we are making calculations of inflow to the Simulated Drift Experiment (SDE), i.e. inflow to six parallel, closely spaced D-holes, using a preliminary set of data collected in five other holes, the N- and W-holes during Stages 1 and 2 of the Site Characterization and Validation (SCV) project. Our approach has been to focus on the fracture zones rather than the general set of ubiquitous fractures. Approximately 90% of all the water flowing in the rock is flowing in fracture zones which are neither uniformly conductive nor are they infinitely extensive. Our approach has been to adopt the fracture zone locations as they have been identified with geophysics. We use geologic sense and the original geophysical data to add one zone where significant water inflow has been observed that can not be explained with the other geophysical zones. This report covers LBL's preliminary prediction of flow into the D-holes. Care should be taken in interpreting the results given in this report. As explained below, the approach that LBL has designed for developing a fracture hydrology model requires cross-hole hydrologic data. Cross-hole tests are planned for Stage 3 but were unavailable in Stage 1. As such, we have inferred from available data what a cross-hole test might show and used this synthetic data to make a preliminary calculation of the inflow into the D-holes. Then using all the Stage 3 data we will calculate flow into the Validation Drift itself. The report mainly demonstrates the use of our methodology and the simulated results should be considered preliminary

Nonphotochemical Hole-Burning Studies of Energy Transfer Dynamics in Antenna Complexes of Photosynthetic Bacteria

International Nuclear Information System (INIS)

Satoshi Matsuzaki

2002-01-01

Burn wavelength (λ B )-dependent nonphotochemical hole spectra are reported for the lowest energy Q y -absorption band of the Fenna-Matthews-Olson (FMO) trimer complex from Prosthecochloris aestuarii. This band at 825 nm is contributed to by three states that stem from the lowest energy state of the subunit of the trimer. The spectra reveal unusually rich and quite sharp low energy satellite structure that consists of holes at 18, 24, 36, 48, 72, 120 and 165 cm -1 as measured relative to the resonant hole at λ B . The possibility that some of these holes are due to correlated downward energy transfer from the two higher energy states that contribute to the 825 nm band could be rejected. Thus, the FMO complex is yet another example of a photosynthetic complex for which structural heterogeneity results in distributions for the values of the energy gaps between Q y -states. The results of theoretical simulations of the hole spectra are consistent with the above holes being due to intermolecular phonons and low energy intramolecular vibrations of the bacteriochlorophyll a (BChl a) molecule. The 36 cm -1 and higher energy modes are most likely due to the intramolecular BChl a modes. The simulations lead to the determination of the Huang-Rhys (S) factor for all modes

Super massive black hole in galactic nuclei with tidal disruption of stars

International Nuclear Information System (INIS)

Zhong, Shiyan; Berczik, Peter; Spurzem, Rainer

2014-01-01

Tidal disruption of stars by super massive central black holes from dense star clusters is modeled by high-accuracy direct N-body simulation. The time evolution of the stellar tidal disruption rate, the effect of tidal disruption on the stellar density profile, and, for the first time, the detailed origin of tidally disrupted stars are carefully examined and compared with classic papers in the field. Up to 128k particles are used in simulation to model the star cluster around a super massive black hole, and we use the particle number and the tidal radius of the black hole as free parameters for a scaling analysis. The transition from full to empty loss-cone is analyzed in our data, and the tidal disruption rate scales with the particle number, N, in the expected way for both cases. For the first time in numerical simulations (under certain conditions) we can support the concept of a critical radius of Frank and Rees, which claims that most stars are tidally accreted on highly eccentric orbits originating from regions far outside the tidal radius. Due to the consumption of stars moving on radial orbits, a velocity anisotropy is found inside the cluster. Finally we estimate the real galactic center based on our simulation results and the scaling analysis.

Super Massive Black Hole in Galactic Nuclei with Tidal Disruption of Stars

Science.gov (United States)

Zhong, Shiyan; Berczik, Peter; Spurzem, Rainer

2014-09-01

Tidal disruption of stars by super massive central black holes from dense star clusters is modeled by high-accuracy direct N-body simulation. The time evolution of the stellar tidal disruption rate, the effect of tidal disruption on the stellar density profile, and, for the first time, the detailed origin of tidally disrupted stars are carefully examined and compared with classic papers in the field. Up to 128k particles are used in simulation to model the star cluster around a super massive black hole, and we use the particle number and the tidal radius of the black hole as free parameters for a scaling analysis. The transition from full to empty loss-cone is analyzed in our data, and the tidal disruption rate scales with the particle number, N, in the expected way for both cases. For the first time in numerical simulations (under certain conditions) we can support the concept of a critical radius of Frank & Rees, which claims that most stars are tidally accreted on highly eccentric orbits originating from regions far outside the tidal radius. Due to the consumption of stars moving on radial orbits, a velocity anisotropy is found inside the cluster. Finally we estimate the real galactic center based on our simulation results and the scaling analysis.

Analysis of Mining-induced Valley Closure Movements

Science.gov (United States)

Zhang, C.; Mitra, R.; Oh, J.; Hebblewhite, B.

2016-05-01

Valley closure movements have been observed for decades in Australia and overseas when underground mining occurred beneath or in close proximity to valleys and other forms of irregular topographies. Valley closure is defined as the inward movements of the valley sides towards the valley centreline. Due to the complexity of the local geology and the interplay between several geological, topographical and mining factors, the underlying mechanisms that actually cause this behaviour are not completely understood. A comprehensive programme of numerical modelling investigations has been carried out to further evaluate and quantify the influence of a number of these mining and geological factors and their inter-relationships. The factors investigated in this paper include longwall positional factors, horizontal stress, panel width, depth of cover and geological structures around the valley. It is found that mining in a series passing beneath the valley dramatically increases valley closure, and mining parallel to valley induces much more closure than other mining orientations. The redistribution of horizontal stress and influence of mining activity have also been recognised as important factors promoting valley closure, and the effect of geological structure around the valley is found to be relatively small. This paper provides further insight into both the valley closure mechanisms and how these mechanisms should be considered in valley closure prediction models.

Biomechanics Strategies for Space Closure in Deep Overbite

Directory of Open Access Journals (Sweden)

Harryanto Wijaya

2013-07-01

Full Text Available Space closure is an interesting aspect of orthodontic treatment related to principles of biomechanics. It should be tailored individually based on patient’s diagnosis and treatment plan. Understanding the space closure biomechanics basis leads to achieve the desired treatment objective. Overbite deepening and losing posterior anchorage are the two most common unwanted side effects in space closure. Conventionally, correction of overbite must be done before space closure resulted in longer treatment. Application of proper space closure biomechanics strategies is necessary to achieve the desired treatment outcome. This cases report aimed to show the space closure biomechanics strategies that effectively control the overbite as well as posterior anchorage in deep overbite patients without increasing treatment time. Two patients who presented with class II division 1 malocclusion were treated with fixed orthodontic appliance. The primary strategies included extraction space closure on segmented arch that employed two-step space closure, namely single canine retraction simultaneously with incisors intrusion followed by enmasse retraction of four incisors by using differential moment concept. These strategies successfully closed the space, corrected deep overbite and controlled posterior anchorage simultaneously so that the treatment time was shortened. Biomechanics strategies that utilized were effective to achieve the desired treatment outcome.

Magnetisable container closure and means for its removal

International Nuclear Information System (INIS)

Barrett, W.I.

1984-01-01

A container has a closed lower end and an open upper end, is made of a non-magnetic material such as aluminium, and has a peripheral groove spaced from the open end. A disc-like closure is of magnetic material such as ferritic steel, has a pair of spring jaws joined to the disc by a joining member such that when the disc of the closure is in position closing the open end of the container, the jaws engage in groove and hold the closure in position. To remove the closure, it is engaged by magnetic means mounted for example on a wall and having a step such that when the container is moved laterally away the closure is retained by the magnetic means aided by the step and thereby the closure becomes removed from the container. (author)

Is black-hole ringdown a memory of its progenitor?

Science.gov (United States)

Kamaretsos, Ioannis; Hannam, Mark; Sathyaprakash, B S

2012-10-05

We perform an extensive numerical study of coalescing black-hole binaries to understand the gravitational-wave spectrum of quasinormal modes excited in the merged black hole. Remarkably, we find that the masses and spins of the progenitor are clearly encoded in the mode spectrum of the ringdown signal. Some of the mode amplitudes carry the signature of the binary's mass ratio, while others depend critically on the spins. Simulations of precessing binaries suggest that our results carry over to generic systems. Using Bayesian inference, we demonstrate that it is possible to accurately measure the mass ratio and a proper combination of spins even when the binary is itself invisible to a detector. Using a mapping of the binary masses and spins to the final black-hole spin allows us to further extract the spin components of the progenitor. Our results could have tremendous implications for gravitational astronomy by facilitating novel tests of general relativity using merging black holes.

Primary black holes

International Nuclear Information System (INIS)

Novikov, I.; Polnarev, A.

1981-01-01

Proves are searched for of the formation of the so-called primary black holes at the very origin of the universe. The black holes would weigh less than 10 13 kg. The formation of a primary black hole is conditional on strong fluctuations of the gravitational field corresponding roughly to a half of the fluctuation maximally permissible by the general relativity theory. Only big fluctuations of the gravitational field can overcome the forces of the hot gas pressure and compress the originally expanding matter into a black hole. Low-mass black holes have a temperature exceeding that of the black holes formed from stars. A quantum process of particle formation, the so-called evaporation takes place in the strong gravitational field of a black hole. The lower the mass of the black hole, the shorter the evaporation time. The analyses of processes taking place during the evaporation of low-mass primary black holes show that only a very small proportion of the total mass of the matter in the universe could turn into primary black holes. (M.D.)

Urethrovaginal fistula closure.

Science.gov (United States)

Clifton, Marisa M; Goldman, Howard B

2017-01-01

In the developed world, urethrovaginal fistulas are most the likely the result of iatrogenic injury. These fistulas are quite rare. Proper surgical repair requires careful dissection and tension-free closure. The objective of this video is to demonstrate the identification and surgical correction of an urethrovaginal fistula. The case presented is of a 59-year-old woman with a history of pelvic organ prolapse and symptomatic stress urinary incontinence who underwent vaginal hysterectomy, anterior colporrhaphy, posterior colporrhaphy, and synthetic sling placement. Postoperatively, she developed a mesh extrusion and underwent sling excision. After removal of her synthetic sling, she began to experience continuous urinary incontinence. Physical examination and cystourethroscopy demonstrated an urethrovaginal fistula at the midurethra. Options were discussed and the patient wished to undergo transvaginal fistula repair. The urethrovaginal fistula was intubated with a Foley catheter. The fistula tract was isolated and removed. The urethra was then closed with multiple tension-free layers. This video demonstrates several techniques for identifying and subsequently repairing an urethrovaginal fistula. Additionally, it demonstrates the importance of tension-free closure. Urethrovaginal fistulas are rare. They should be repaired with careful dissection and tension-free closure.

Instability, Turbulence, and Enhanced Transport in Collisionless Black-Hole Accretion Flows

Science.gov (United States)

Kunz, Matthew

Many astrophysical plasmas are so hot and diffuse that the collisional mean free path is larger than the system size. Perhaps the best examples of such systems are lowluminosity accretion flows onto black holes such as Sgr A* at the center of our own Galaxy, or M87 in the Virgo cluster. To date, theoretical models of these accretion flows are based on magnetohydrodynamics (MHD), a collisional fluid theory, sometimes (but rarely) extended with non-MHD features such as anisotropic (i.e. magnetic-field-aligned) viscosity and thermal conduction. While these extensions have been recognized as crucial, they require ad hoc assumptions about the role of microscopic kinetic instabilities (namely, firehose and mirror) in regulating the transport properties. These assumptions strongly affect the outcome of the calculations, and yet they have never been tested using more fundamental (i.e. kinetic) models. This proposal outlines a comprehensive first-principles study of the plasma physics of collisionless accretion flows using both analytic and state-of-the-art numerical models. The latter will utilize a new hybrid-kinetic particle-in-cell code, Pegasus, developed by the PI and Co-I specifically to study this problem. A comprehensive kinetic study of the 3D saturation of the magnetorotational instability in a collisionless plasma will be performed, in order to understand the interplay between turbulence, transport, and Larmor-scale kinetic instabilities such as firehose and mirror. Whether such instabilities alter the macroscopic saturated state, for example by limiting the transport of angular momentum by anisotropic pressure, will be addressed. Using these results, an appropriate "fluid" closure will be developed that can capture the multi-scale effects of plasma kinetics on magnetorotational turbulence, for use by the astrophysics community in building evolutionary models of accretion disks. The PI has already successfully performed the first three-dimensional kinetic

Slim hole drilling and testing strategies

Science.gov (United States)

Nielson, Dennis L.; Garg, Sabodh K.; Goranson, Colin

2017-12-01

The financial and geologic advantages of drilling slim holes instead of large production wells in the early stages of geothermal reservoir assessment has been understood for many years. However, the practice has not been fully embraced by geothermal developers. We believe that the reason for this is that there is a poor understanding of testing and reservoir analysis that can be conducted in slim holes. In addition to reservoir engineering information, coring through the cap rock and into the reservoir provides important data for designing subsequent production well drilling and completion. Core drilling requires significantly less mud volume than conventional rotary drilling, and it is typically not necessary to cure lost circulation zones (LCZ). LCZs should be tested by either production or injection methods as they are encountered. The testing methodologies are similar to those conducted on large-diameter wells; although produced and/or injected fluid volumes are much less. Pressure, temperature and spinner (PTS) surveys in slim holes under static conditions can used to characterize temperature and pressure distribution in the geothermal reservoir. In many cases it is possible to discharge slim holes and obtain fluid samples to delineate the geochemical properties of the reservoir fluid. Also in the latter case, drawdown and buildup data obtained using a downhole pressure tool can be employed to determine formation transmissivity and well properties. Even if it proves difficult to discharge a slim hole, an injection test can be performed to obtain formation transmissivity. Given the discharge (or injection) data from a slimhole, discharge properties of a large-diameter well can be inferred using wellbore modeling. Finally, slim hole data (pressure, temperature, transmissivity, fluid properties) together with reservoir simulation can help predict the ability of the geothermal reservoir to sustain power production.

Risk and Performance Analyses Supporting Closure of WMA C at the Hanford Site in Southeast Washington

International Nuclear Information System (INIS)

Eberlein, Susan J.; Bergeron, Marcel P.; Kemp, Christopher J.; Hildebrand, R. Douglas; Aly, Alaa; Kozak, Matthew; Mehta, Sunil; Connelly, Michael

2013-01-01

The Office of River Protection under the U.S. Department of Energy (DOE) is pursuing closure of the Single-Shell Tank (SST) Waste Management Area (WMA) C as stipulated by the Hanford Federal Facility Agreement and Consent Order (HFFACO) under federal requirements and work tasks will be done under the State-approved closure plans and permits. An initial step in meeting the regulatory requirements is to develop a baseline risk assessment representing current conditions based on available characterization data and information collected at the WMA C location. The baseline risk assessment will be supporting a Resource Conservation and Recovery Act of 1976 (RCRA) Field Investigation (RFI)/Corrective Measures Study (CMS) for WMA closure and RCRA corrective action. Complying with the HFFACO conditions also involves developing a long-term closure Performance Assessment (PA) that evaluates human health and environmental impacts resulting from radionuclide inventories in residual wastes remaining in WMA C tanks and ancillary equipment. This PA is being developed to meet the requirements necessary for closure authorization under DOE Order 435.1 and Washington State Hazardous Waste Management Act. To meet the HFFACO conditions, the long-term closure risk analysis will include an evaluation of human health and environmental impacts from hazardous chemical inventories along with other performance Comprehensive Environmental Response, Compensation, and Liability Act Appropriate and Applicable Requirements (CERCLA ARARs) in residual wastes left in WMA C facilities after retrieval and removal. This closure risk analysis is needed to needed to comply with the requirements for permitted closure. Progress to date in developing a baseline risk assessment of WMA C has involved aspects of an evaluation of soil characterization and groundwater monitoring data collected as a part of the RFI/CMS and RCRA monitoring. Developing the long-term performance assessment aspects has involved the

Risk and Performance Analyses Supporting Closure of WMA C at the Hanford Site in Southeast Washington

Energy Technology Data Exchange (ETDEWEB)

Eberlein, Susan J.; Bergeron, Marcel P.; Kemp, Christopher J.

2013-11-11

The Office of River Protection under the U.S. Department of Energy (DOE) is pursuing closure of the Single-Shell Tank (SST) Waste Management Area (WMA) C as stipulated by the Hanford Federal Facility Agreement and Consent Order (HFFACO) under federal requirements and work tasks will be done under the State-approved closure plans and permits. An initial step in meeting the regulatory requirements is to develop a baseline risk assessment representing current conditions based on available characterization data and information collected at the WMA C location. The baseline risk assessment will be supporting a Resource Conservation and Recovery Act of 1976 (RCRA) Field Investigation (RFI)/Corrective Measures Study (CMS) for WMA closure and RCRA corrective action. Complying with the HFFACO conditions also involves developing a long-term closure Performance Assessment (PA) that evaluates human health and environmental impacts resulting from radionuclide inventories in residual wastes remaining in WMA C tanks and ancillary equipment. This PA is being developed to meet the requirements necessary for closure authorization under DOE Order 435.1 and Washington State Hazardous Waste Management Act. To meet the HFFACO conditions, the long-term closure risk analysis will include an evaluation of human health and environmental impacts from hazardous chemical inventories along with other performance Comprehensive Environmental Response, Compensation, and Liability Act Appropriate and Applicable Requirements (CERCLA ARARs) in residual wastes left in WMA C facilities after retrieval and removal. This closure risk analysis is needed to needed to comply with the requirements for permitted closure. Progress to date in developing a baseline risk assessment of WMA C has involved aspects of an evaluation of soil characterization and groundwater monitoring data collected as a part of the RFI/CMS and RCRA monitoring. Developing the long-term performance assessment aspects has involved the

The causal structure of dynamical charged black holes

International Nuclear Information System (INIS)

Hong, Sungwook E; Hwang, Dong-il; Stewart, Ewan D; Yeom, Dong-han

2010-01-01

We study the causal structure of dynamical charged black holes, with a sufficient number of massless fields, using numerical simulations. Neglecting Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature singularity due to mass inflation. When we include Hawking radiation, the inner horizon becomes space-like and is separated from the Cauchy horizon, which is parallel to the out-going null direction. Since a charged black hole must eventually transit to a neutral black hole, we studied the neutralization of the black hole and observed that the inner horizon evolves into a space-like singularity, generating a Cauchy horizon which is parallel to the in-going null direction. Since the mass function is finite around the inner horizon, the inner horizon is regular and penetrable in a general relativistic sense. However, since the curvature functions become trans-Planckian, we cannot say more about the region beyond the inner horizon, and it is natural to say that there is a 'physical' space-like singularity. However, if we assume an exponentially large number of massless scalar fields, our results can be extended beyond the inner horizon. In this case, strong cosmic censorship and black hole complementarity can be violated.

The causal structure of dynamical charged black holes

Energy Technology Data Exchange (ETDEWEB)

Hong, Sungwook E; Hwang, Dong-il; Stewart, Ewan D; Yeom, Dong-han, E-mail: eostm@muon.kaist.ac.k, E-mail: enotsae@gmail.co, E-mail: innocent@muon.kaist.ac.k [Department of Physics, KAIST, Daejeon 305-701 (Korea, Republic of)

2010-02-21

We study the causal structure of dynamical charged black holes, with a sufficient number of massless fields, using numerical simulations. Neglecting Hawking radiation, the inner horizon is a null Cauchy horizon and a curvature singularity due to mass inflation. When we include Hawking radiation, the inner horizon becomes space-like and is separated from the Cauchy horizon, which is parallel to the out-going null direction. Since a charged black hole must eventually transit to a neutral black hole, we studied the neutralization of the black hole and observed that the inner horizon evolves into a space-like singularity, generating a Cauchy horizon which is parallel to the in-going null direction. Since the mass function is finite around the inner horizon, the inner horizon is regular and penetrable in a general relativistic sense. However, since the curvature functions become trans-Planckian, we cannot say more about the region beyond the inner horizon, and it is natural to say that there is a 'physical' space-like singularity. However, if we assume an exponentially large number of massless scalar fields, our results can be extended beyond the inner horizon. In this case, strong cosmic censorship and black hole complementarity can be violated.

Phase transition for black holes with scalar hair and topological black holes

International Nuclear Information System (INIS)

Myung, Yun Soo

2008-01-01

We study phase transitions between black holes with scalar hair and topological black holes in asymptotically anti-de Sitter spacetimes. As the ground state solutions, we introduce the non-rotating BTZ black hole in three dimensions and topological black hole with hyperbolic horizon in four dimensions. For the temperature matching only, we show that the phase transition between black hole with scalar hair (Martinez-Troncoso-Zanelli black hole) and topological black hole is second-order by using differences between two free energies. However, we do not identify what order of the phase transition between scalar and non-rotating BTZ black holes occurs in three dimensions, although there exists a possible decay of scalar black hole to non-rotating BTZ black hole

Numerical simulation of temperature's sensitivity of chamfer hole's resistance on hydraulic step cylinder

International Nuclear Information System (INIS)

Jinhua, Wang; Hanliang, Bo; Wenxiang, Zheng; Jinnong, Yang

2003-01-01

The control rod drive is a very important device for controlling nuclear reactor startup, operation, shut down, and power change. The ability of the control rod drive to move safely and reliably directly relates to reactor safety. The Hydraulic Control Rod Drive System (HCRDS) is a new type of control rod drive system developed by the Institute of Nuclear Energy Technology (INET) of Tsinghua University for Nuclear Heating Reactors. The HCRDS, designed using the hydrodynamic principle, has many advantages, including having the structure complete in the vessel, no possible ejection accident, short drive line, simple movable parts structure and safe shutdown during accidents. The hydraulic step cylinder is the key part for the HCRDS. In the process of reactor startup, the variation of temperature could make the water's density and viscosity change, and the force from the water flow would change accordingly. These factors could influence the performance of the hydraulic step cylinder. In this paper, the temperature sensitivity of the chamfer hole's resistance in the hydraulic step cylinder was studied with the Computational Fluid Dynamics (CFD) program CFX5.5. The results were satisfactory: the discipline of variation of the chamfer hole's resistance with the outer tube's position was the same at different temperatures, the discrepancy of the chamfer hole's resistance was small for the same position at different temperatures, the chamfer hole's resistance decreased gradually with the increase of temperature, and the decrease extent was relatively small

Closure of shallow underground injection wells

International Nuclear Information System (INIS)

Veil, J.A.; Grunewald, B.

1993-01-01

Shallow injection wells have long been used for disposing liquid wastes. Some of these wells have received hazardous or radioactive wastes. According to US Environmental Protection Agency (EPA) regulations, Class IV wells are those injection wells through which hazardous or radioactive wastes are injected into or above an underground source of drinking water (USDW). These wells must be closed. Generally Class V wells are injection wells through which fluids that do not contain hazardous or radioactive wastes are injected into or above a USDW. Class V wells that are responsible for violations of drinking water regulations or that pose a threat to human health must also be closed. Although EPA regulations require closure of certain types of shallow injection wells, they do not provide specific details on the closure process. This paper describes the regulatory background, DOE requirements, and the steps in a shallow injection well closure process: Identification of wells needing closure; monitoring and disposal of accumulated substances; filling and sealing of wells; and remediation. In addition, the paper describes a major national EPA shallow injection well enforcement initiative, including closure plan guidance for wells used to dispose of wastes from service station operations

Reliability assessment of underground shaft closure

International Nuclear Information System (INIS)

Fossum, A.F.; Munson, D.E.

1994-01-01

The intent of the WIPP, being constructed in the bedded geologic salt deposits of Southeastern New Mexico, is to provide the technological basis for the safe disposal of radioactive Transuranic (TRU) wastes generated by the defense programs of the United States. In determining this technological basis, advanced reliability and structural analysis techniques are used to determine the probability of time-to-closure of a hypothetical underground shaft located in an argillaceous salt formation and filled with compacted crushed salt. Before being filled with crushed salt for sealing, the shaft provides access to an underground facility. Reliable closure of the shaft depends upon the sealing of the shaft through creep closure and recompaction of crushed backfill. Appropriate methods are demonstrated to calculate cumulative distribution functions of the closure based on laboratory determined random variable uncertainty in salt creep properties

Black Holes

OpenAIRE

Townsend, P. K.

1997-01-01

This paper is concerned with several not-quantum aspects of black holes, with emphasis on theoretical and mathematical issues related to numerical modeling of black hole space-times. Part of the material has a review character, but some new results or proposals are also presented. We review the experimental evidence for existence of black holes. We propose a definition of black hole region for any theory governed by a symmetric hyperbolic system of equations. Our definition reproduces the usu...

MINIMIZING THE MHD POTENTIAL ENERGY FOR THE CURRENT HOLE REGION IN TOKAMAKS

International Nuclear Information System (INIS)

CHU, M.S; PARKS, P.B

2004-01-01

The current hole region in the tokamak has been observed to arise naturally during the development of internal transport barriers. The magnetohydrodynamic (MHD) potential energy in the current hole region is shown to be determined completely in terms of the displacements at the edge of the current hole. For modes with finite toroidal mode number n ≠ 0, the minimized potential energy is the same as if the current hole region were a vacuum region. For modes with toroidal mode number n = 0, the displacement is a superposition of three types of independent displacements: a vertical displacement or displacements that compress only the plasma or the toroidal field uniformly. Thus for ideal MHD perturbations of plasma with a current hole, the plasma behaves as if it were bordered by an extra ''internal vacuum region''. The relevance of the present work to computer simulations of plasma with a current hole region is also discussed

Minimizing the magnetohydrodynamic potential energy for the current hole region in tokamaks

International Nuclear Information System (INIS)

Chu, M.S.; Parks, P.B.

2004-01-01

The current hole region in the tokamak has been observed to arise naturally during the development of internal transport barriers. The magnetohydrodynamic (MHD) potential energy in the current hole region is shown to be determined completely in terms of the displacements at the edge of the current hole. For modes with finite toroidal mode number n≠0, the minimized potential energy is the same as if the current hole region were a vacuum region. For modes with toroidal mode number n=0, the displacement is a superposition of three types of independent displacements: a vertical displacement or displacements that compress only the plasma, or the toroidal field uniformly. Thus for ideal MHD perturbations of plasma with a current hole, the plasma behaves as if it were bordered by an extra ''internal vacuum region.'' The relevance of the present work to computer simulations of plasma with a current hole region is also discussed

Electron holes in phase space: What they are and why they matter

Science.gov (United States)

Hutchinson, I. H.

2017-05-01

This is a tutorial and selective review explaining the fundamental concepts and some currently open questions concerning the plasma phenomenon of the electron hole. The widespread occurrence of electron holes in numerical simulations, space-craft observations, and laboratory experiments is illustrated. The elementary underlying theory is developed of a one-dimensional electron hole as a localized potential maximum, self-consistently sustained by a deficit of trapped electron phase-space density. The spatial extent of a hole is typically a few Debye lengths; what determines the minimum and maximum possible lengths is explained, addressing the key aspects of the as yet unsettled dispute between the integral and differential approaches to hole structure. In multiple dimensions, holes tend to form less readily; they generally require a magnetic field and distribution-function anisotropy. The mechanisms by which they break up are explained, noting that this transverse instability is not fully understood. Examples are given of plasma circumstances where holes play an important role, and of recent progress on understanding their holistic kinematics and self-acceleration.

Observations of electron vortex magnetic holes and related wave-particle interactions in the turbulent magnetosheath

Science.gov (United States)

Huang, S.; Sahraoui, F.; Yuan, Z.; He, J.; Zhao, J.; Du, J.; Le Contel, O.; Wang, X.; Deng, X.; Fu, H.; Zhou, M.; Shi, Q.; Breuillard, H.; Pang, Y.; Yu, X.; Wang, D.

2017-12-01

Magnetic hole is characterized by a magnetic depression, a density peak, a total electron temperature increase (with a parallel temperature decrease but a perpendicular temperature increase), and strong currents carried by the electrons. The current has a dip in the core region of the magnetic hole and a peak in the outer region of the magnetic hole. There is an enhancement in the perpendicular electron fluxes at 90° pitch angles inside the magnetic hole, implying that the electrons are trapped within it. The variations of the electron velocity components Vem and Ven suggest that an electron vortex is formed by trapping electrons inside the magnetic hole in the circular cross-section. These observations demonstrate the existence of a new type of coherent structures behaving as an electron vortex magnetic hole in turbulent space plasmas as predicted by recent kinetic simulations. We perform a statistically study using high time solution data from the MMS mission. The magnetic holes with short duration (i.e., < 0.5 s) have their cross section smaller than the ion gyro-radius. Superposed epoch analysis of all events reveals that an increase in the electron density and total temperature, significantly increase (resp. decrease) the electron perpendicular (resp. parallel) temperature, and an electron vortex inside the holes. Electron fluxes at 90° pitch angles with selective energies increase in the KSMHs, are trapped inside KSMHs and form the electron vortex due to their collective motion. All these features are consistent with the electron vortex magnetic holes obtained in 2D and 3D particle-in-cell simulations, indicating that the observed the magnetic holes seem to be best explained as electron vortex magnetic holes. It is furthermore shown that the magnetic holes are likely to heat and accelerate the electrons. We also investigate the coupling between whistler waves and electron vortex magnetic holes. These whistler waves can be locally generated inside electron

Fundamental solution of bond pricing in the Ho-Lee stochastic interest rate model under the invariant criteria

Directory of Open Access Journals (Sweden)

Burhaneddin İzgi

2017-03-01

under the invariant criteria. We obtain transformations between Ho-Lee model with the corresponding linear (1 + 1 partial differential equation and the first Lie canonical form which is identical to the classical heat equation. These transformations help us to generate the fundamental solution for the Ho-Lee model with respect to the fundamental solution of the classical heat equation sense. Moreover, as a financial application of the Ho-Lee model, we choose the drift term from power functions and perform simulations via Milstein method. Furthermore, we obtain important results for the parameter calibration of the corresponding drift term by using the simulation results.

Comparison of cost-effectiveness and postoperative outcome of device closure and open surgery closure techniques for treatment of patent ductus arteriosus

Directory of Open Access Journals (Sweden)

Alireza Ahmadi

2014-01-01

Full Text Available BACKGROUND: Various devices have been recently employed for percutaneous closure of the patent ductus arteriosus (PDA. Although the high effectiveness of device closure techniques has been clearly determined, a few studies have focused on the cost-effectiveness and also postoperative complications of these procedures in comparison with open surgery. The present study aimed to evaluate the clinical outcome and cost-effectiveness of PDA occlusion by Amplatzer and coil device in comparisong with open surgery. METHODS: In this cross-sectional study, a randomized sample of 201 patients aged 1 month to 16 years (105 patients with device closure and 96 patients with surgical closure was selected. The ratio of total pulmonary blood flow to total systemic blood flow, the Qp/Qs ratio, was measured using a pulmonary artery catheter. The cost analysis included direct medical care costs associated with device implantation and open surgery, as well as professional fees. All costs were calculated in Iranian Rials and then converted to US dollars. RESULTS: There was no statistical difference in mean Qp/Qs ratio before the procedure between the device closure group and the open surgery group (2.1 ± 0.7 versus 1.7 ± 0.6, P = 0.090. The mean measured costs were overall higher in the device closure group than in open closure group (948.87 ± 548.76 US$ versus 743.70 ± 696.91 US$, P < 0.001. This difference remained significant after adjustment for age and gender (Standardized Beta = 0.160, P = 0.031. PDA closure with the Amplatzer ductal occluder (1053.05 ± 525.73 US$ or with Nit-Occlud coils (PFM (912.73 ± 565.94 US$, P < 0.001 was more expensive than that via open surgery. However, the Cook detachable spring coils device closure (605.65 ± 194.62 US$, P = 0.650 had a non-significant cost difference with open surgery. No event was observed in the device closure group regarding in-hospital mortality or morbidity; however, in another group, 2 in-hospital deaths

Spontaneous hole-clump pair creation in weakly unstable plasmas

International Nuclear Information System (INIS)

Berk, H.L.; Breizman, B.N.; Petviashvili, N.V.

1997-03-01

A numerical simulation of a kinetic instability near threshold shows how a hole and clump spontaneously appear in the particle distribution function. The hole and clump support a pair of Bernstein, Greene, Kruskal (BGK) nonlinear waves that last much longer than the inverse linear damping rate while they are upshifting and downshifting in frequency. The frequency shifting allows a balance between the power nonlinearly extracted from the resonant particles and the power dissipated into the background plasma. These waves eventually decay due to phase space gradient smoothing caused by collisionality

Numerical approximation of the Boltzmann equation : moment closure

NARCIS (Netherlands)

Abdel Malik, M.R.A.; Brummelen, van E.H.

2012-01-01

This work applies the moment method onto a generic form of kinetic equations to simplify kinetic models of particle systems. This leads to the moment closure problem which is addressed using entropy-based moment closure techniques utilizing entropy minimization. The resulting moment closure system

WASTE PACKAGE OPERATIONS FY99 CLOSURE METHODS REPORT

Energy Technology Data Exchange (ETDEWEB)

M. C. Knapp

1999-09-23

The waste package (WP) closure weld development task is part of a larger engineering development program to develop waste package designs. The purpose of the larger waste package engineering development program is to develop nuclear waste package fabrication and closure methods that the Nuclear Regulatory Commission will find acceptable and will license for disposal of spent nuclear fuel (SNF), non-fuel components, and vitrified high-level waste within a Monitored Geologic Repository (MGR). Within the WP closure development program are several major development tasks, which, in turn, are divided into subtasks. The major tasks include: WP fabrication development, WP closure weld development, nondestructive examination (NDE) development, and remote in-service inspection development. The purpose of this report is to present the objectives, technical information, and work scope relating to the WP closure weld development.and NDE tasks and subtasks and to report results of the closure weld and NDE development programs for fiscal year 1999 (FY-99). The objective of the FY-99 WP closure weld development task was to develop requirements for closure weld surface and volumetric NDE performance demonstrations, investigate alternative NDE inspection techniques, and develop specifications for welding, NDE, and handling system integration. In addition, objectives included fabricating several flat plate mock-ups that could be used for NDE development, stress relief peening, corrosion testing, and residual stress testing.

WASTE PACKAGE OPERATIONS FY-99 CLOSURE METHODS REPORT

International Nuclear Information System (INIS)

M. C. Knapp

1999-01-01

The waste package (WP) closure weld development task is part of a larger engineering development program to develop waste package designs. The purpose of the larger waste package engineering development program is to develop nuclear waste package fabrication and closure methods that the Nuclear Regulatory Commission will find acceptable and will license for disposal of spent nuclear fuel (SNF), non-fuel components, and vitrified high-level waste within a Monitored Geologic Repository (MGR). Within the WP closure development program are several major development tasks, which, in turn, are divided into subtasks. The major tasks include: WP fabrication development, WP closure weld development, nondestructive examination (NDE) development, and remote in-service inspection development. The purpose of this report is to present the objectives, technical information, and work scope relating to the WP closure weld development.and NDE tasks and subtasks and to report results of the closure weld and NDE development programs for fiscal year 1999 (FY-99). The objective of the FY-99 WP closure weld development task was to develop requirements for closure weld surface and volumetric NDE performance demonstrations, investigate alternative NDE inspection techniques, and develop specifications for welding, NDE, and handling system integration. In addition, objectives included fabricating several flat plate mock-ups that could be used for NDE development, stress relief peening, corrosion testing, and residual stress testing

T-tube vs Primary Common Bile Duct Closure

Directory of Open Access Journals (Sweden)

M R Joshi

2010-09-01

Full Text Available INTRODUCTION: Closure of the common bile duct over T-tube after exploration is a widely practiced traditional method. However, its use may give rise to many complications. We do primary closure of common bile duct after exploration. Aim of the study is to see the efficacy and safety of the primary closure. METHODS: Study was carried out to compare the results of both the techniques from 2006 to 2009 in the cases proven to have common bile duct stone with or without the features of obstructive jaundice. Post operative hospital stay and morbidities related to both the groups were recorded and analyzed. RESULTS: There were total 71 cases included in the study. Thirty one in T-tube group and 40 in primary closure group. T-tube was removed in most of the cases after three weeks where as average time of drain removal in primary closure group is 5.79 +/-1.79 days. Incidence of retained stone was equal in each group. Major complication in T-tube group is biliary peritonitis in four patients at the time of T-tube removal whereas none of the patient from primary closure group suffered from such major complication. CONCLUSIONS: Primary closure after the common bile duct exploration is safe and it helps to avoid the morbidities related to T-tube. Keywords: Choledocholithiasis, Primary closure, retained stone, T-tube, Ureterorenoscope.

Modelling of Non-Premixed Turbulent Combustion of Hydrogen using Conditional Moment Closure Method

International Nuclear Information System (INIS)

Noor, M M; Hairuddin, A Aziz; Wandel, Andrew P; Yusaf, T F

2012-01-01

Most of the electricity generation and energy for transport is still generated by the conversion of chemical to mechanical energy by burning the fuels in the combustion chamber. Regulation for pollution and the demand for more fuel economy had driven worldwide researcher to focus on combustion efficiency. In order to reduce experimental cost, accurate modelling and simulation is very critical step. Taylor series expansion was utilised to reduce the error term for the discretization. FORTRAN code was used to execute the discretized partial differential equation. Hydrogen combustion was simulated using Conditional Moment Closure (CMC) model. Combustion of hydrogen with oxygen was successfully simulated and reported in this paper.

Characterizing the velocity of a wandering black hole and properties of the surrounding medium using convolutional neural networks

Science.gov (United States)

González, J. A.; Guzmán, F. S.

2018-03-01

We present a method for estimating the velocity of a wandering black hole and the equation of state for the gas around it based on a catalog of numerical simulations. The method uses machine-learning methods based on convolutional neural networks applied to the classification of images resulting from numerical simulations. Specifically we focus on the supersonic velocity regime and choose the direction of the black hole to be parallel to its spin. We build a catalog of 900 simulations by numerically solving Euler's equations onto the fixed space-time background of a black hole, for two parameters: the adiabatic index Γ with values in the range [1.1, 5 /3 ], and the asymptotic relative velocity of the black hole with respect to the surroundings v∞, with values within [0.2 ,0.8 ]c . For each simulation we produce a 2D image of the gas density once the process of accretion has approached a stationary regime. The results obtained show that the implemented convolutional neural networks are able to correctly classify the adiabatic index 87.78% of the time within an uncertainty of ±0.0284 , while the prediction of the velocity is correct 96.67% of the time within an uncertainty of ±0.03 c . We expect that this combination of a massive number of numerical simulations and machine-learning methods will help us analyze more complicated scenarios related to future high-resolution observations of black holes, like those from the Event Horizon Telescope.

Techniques for Abdominal Wall Closure after Damage Control Laparotomy: From Temporary Abdominal Closure to Early/Delayed Fascial Closure—A Review

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Qian Huang

2016-01-01

Full Text Available Open abdomen (OA has been an effective treatment for abdominal catastrophes in traumatic and general surgery. However, management of patients with OA remains a formidable task for surgeons. The central goal of OA is closure of fascial defect as early as is clinically feasible without precipitating abdominal compartment syndrome. Historically, techniques such as packing, mesh, and vacuum-assisted closure have been developed to assist temporary abdominal closure, and techniques such as components separation, mesh-mediated traction, bridging fascial defect with permanent synthetic mesh, or biologic mesh have also been attempted to achieve early primary fascial closure, either alone or in combined use. The objective of this review is to present the challenges of these techniques for OA with a goal of early primary fascial closure, when the patient’s physiological condition allows.

Uncertainty Quantification of Multi-Phase Closures

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Nadiga, Balasubramanya T. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baglietto, Emilio [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)

2017-10-27

In the ensemble-averaged dispersed phase formulation used for CFD of multiphase ows in nuclear reactor thermohydraulics, closures of interphase transfer of mass, momentum, and energy constitute, by far, the biggest source of error and uncertainty. Reliable estimators of this source of error and uncertainty are currently non-existent. Here, we report on how modern Validation and Uncertainty Quanti cation (VUQ) techniques can be leveraged to not only quantify such errors and uncertainties, but also to uncover (unintended) interactions between closures of di erent phenomena. As such this approach serves as a valuable aide in the research and development of multiphase closures. The joint modeling of lift, drag, wall lubrication, and turbulent dispersion|forces that lead to tranfer of momentum between the liquid and gas phases|is examined in the frame- work of validation of the adiabatic but turbulent experiments of Liu and Banko , 1993. An extensive calibration study is undertaken with a popular combination of closure relations and the popular k-ϵ turbulence model in a Bayesian framework. When a wide range of super cial liquid and gas velocities and void fractions is considered, it is found that this set of closures can be validated against the experimental data only by allowing large variations in the coe cients associated with the closures. We argue that such an extent of variation is a measure of uncertainty induced by the chosen set of closures. We also nd that while mean uid velocity and void fraction pro les are properly t, uctuating uid velocity may or may not be properly t. This aspect needs to be investigated further. The popular set of closures considered contains ad-hoc components and are undesirable from a predictive modeling point of view. Consequently, we next consider improvements that are being developed by the MIT group under CASL and which remove the ad-hoc elements. We use non-intrusive methodologies for sensitivity analysis and calibration (using

Factors affecting closure of a temporary stoma.

Science.gov (United States)

Taylor, Claire; Varma, Sarah

2012-01-01

The purpose of the study was to examine time to reversal of a temporary ostomy, reasons for delayed closure, and patient satisfaction with the scheduling of their closure and related hospital care. Cross-sectional, descriptive study. The target population comprised patients who underwent creation of a temporary ostomy and reversal surgery within one National Health System Hospital Trust in the United Kingdom. The population served by this Trust are ethnically and socioeconomically diverse, predominantly living in urban areas around Greater London. Sixty-one persons who met inclusion criteria were identified. A two-step analytical process was undertaken. First, a literature review examining incidence and causes of delayed stoma closure was undertaken. Second, a postal survey of all patients who had had their stoma closed in 2009 was conducted. Respondents were allowed 2 weeks to complete and return the questionnaire. The survey instrument was developed locally and subjected to content validation using ostomy patients, surgical and nursing colleagues. It consisted of 9 questions querying time from original surgery to closure, reasons for delaying closure surgery beyond 12 weeks, and satisfaction with care. Twenty-seven patients returned their questionnaires, indicating they consented to participate; a response rate of 44%. Half of the respondents (n = 14 [52%]) underwent closure surgery within 6 months of stoma formation; the remaining 48% waited more than 6 months (median: 6.5 months, range: 1.5-26 months). Thirteen patients (48%) reported a delay in receiving their stoma closure; the main reason cited was the need for a course of adjuvant postoperative chemotherapy. Three quarters of respondents (22 [74%]) were satisfied with the overall care they received. Findings from this study suggest that stoma closure may be associated with fewest complications if performed before 12 weeks.

Black Hole Mergers, Gravitational Waves, and Multi-Messenger Astronomy

Science.gov (United States)

Centrella, Joan M.

2010-01-01

The final merger of two black holes is expected to be the strongest source of gravitational waves for both ground-based detectors such as LIGO and VIRGO, as well as the space-based LISA. Since the merger takes place in the regime of strong dynamical gravity, computing the resulting gravitational waveforms requires solving the full Einstein equations of general relativity on a computer. Although numerical codes designed to simulate black hole mergers were plagued for many years by a host of instabilities, recent breakthroughs have conquered these problems and opened up this field dramatically. This talk will focus on the resulting gold rush of new results that is revealing the dynamics and waveforms of binary black hole mergers, and their applications in gravitational wave detection, astrophysics, and testing general relativity.