Direct Collapse to Supermassive Black Hole Seeds with Radiation Transfer: Cosmological Halos

Science.gov (United States)

Ardaneh, Kazem; Luo, Yang; Shlosman, Isaac; Nagamine, Kentaro; Wise, John H.; Begelman, Mitchell C.

2018-06-01

We have modeled direct collapse of a primordial gas within dark matter halos in the presence of radiative transfer, in high-resolution zoom-in simulations in a cosmological framework, down to the formation of the photosphere and the central object. Radiative transfer has been implemented in the flux-limited diffusion (FLD) approximation. Adiabatic models were run for comparison. We find that (a) the FLD flow forms an irregular central structure and does not exhibit fragmentation, contrary to adiabatic flow which forms a thick disk, driving a pair of spiral shocks, subject to Kelvin-Helmholtz shear instability forming fragments; (b) the growing central core in the FLD flow quickly reaches ˜10 M⊙ and a highly variable luminosity of 1038 - 1039 erg s-1, comparable to the Eddington luminosity. It experiences massive recurrent outflows driven by radiation force and thermal pressure gradients, which mix with the accretion flow and transfer the angular momentum outwards; and (c) the interplay between these processes and a massive accretion, results in photosphere at ˜10 AU. We conclude that in the FLD model (1) the central object exhibits dynamically insignificant rotation and slower than adiabatic temperature rise with density; (2) does not experience fragmentation leading to star formation, thus promoting the fast track formation of a supermassive black hole (SMBH) seed; (3) inclusion of radiation force leads to outflows, resulting in the mass accumulation within the central 10-3 pc, which is ˜100 times larger than characteristic scale of star formation. The inclusion of radiative transfer reveals complex early stages of formation and growth of the central structure in the direct collapse scenario of SMBH seed formation.

Cylindrical collapse and gravitational waves

Energy Technology Data Exchange (ETDEWEB)

Herrera, L [Escuela de FIsica, Faculdad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela (Venezuela); Santos, N O [Universite Pierre et Marie Curie, CNRS/FRE 2460 LERMA/ERGA, Tour 22-12, 4eme etage, BoIte 142, 4 place Jussieu, 75252 Paris Cedex 05 (France); Laboratorio Nacional de Computacao Cientifica, 25651-070 Petropolis RJ (Brazil); Centro Brasileiro de Pesquisas Fisicas, 22290-180 Rio de Janeiro RJ (Brazil)

2005-06-21

We study the matching conditions for a collapsing anisotropic cylindrical perfect fluid, and we show that its radial pressure is non-zero on the surface of the cylinder and proportional to the time-dependent part of the field produced by the collapsing fluid. This result resembles the one that arises for the radiation-though non-gravitational-in the spherically symmetric collapsing dissipative fluid, in the diffusion approximation.

The prediction and prevention of voltage collapse in the Finnish power system

Energy Technology Data Exchange (ETDEWEB)

Bastman, J; Lakervi, E [Tampere Univ. of Tech. (Finland); Hirvonen, R; Kuronen, P; Hagman, E [IVO Group (Finland)

1994-12-31

The Finnish power system is a part of the Nordic power system (NORDEL), which includes Finland, Sweden, Norway and the eastern part of Denmark. In NORDEL the transmission distances are long, which implies that the power transmission capacities are determined by stability criteria . The methods to prevent and predict the voltage collapse during severe disturbances are studied using advances simulation program. Results are presented. (author) 10 figs., 1 tab.

[The injection of acrylic bone cement prevents bone collapse in the intercalar bones lacking bony support: an experimental sheep semilunar bone model].

Science.gov (United States)

Unsal, Murat; Tetik, Cihangir; Erol, Bülent; Cabukoğlu, Cengiz

2003-01-01

In a sheep semilunar bone model, we investigated whether collapse in the intercalar bones lacking bony support could be prevented by the injection of acrylic bone cement. The study included 16 limbs of eight sheep. Preoperatively, anteroposterior and lateral views of the carpal joints in the fore limbs were obtained. The animals were divided into four groups. In group 1 (n=3) no surgical procedure was performed in the right semilunar bones, whereas the periosteum on the contralateral side was elevated (group 2; n=3). The first two groups were left as controls. In Group 3 (n=5) the left semilunar bones were filled with acrylic bone cement following decancellation of the bone, while the right semilunar bones were left decancellated (group 4; n=5). The sheep were monitored for three months. Radiographs of the carpal joints were obtained to evaluate collapse occurrence in the semilunar bones. Thereafter, the animals were sacrificed and the semilunar bones were excised for biomechanical and histological examinations. Osteonecrosis and cartilage damage were sought and resistance to compressive forces was investigated. Radiologically, the extent of collapse was statistically significant in the semilunar bones in group 4 (pbone cement was found to prevent collapse in group 3, with no significant difference being noted between preoperative and postoperative semilunar bone heights (p>0.05). Biomechanically, the least resistance to compressive forces was measured in group 4 (pbone cement prevents collapse in the semilunar bones, without inducing any cartilage damage or osteonecrosis.

The collapse of acoustic waves in dispersive media

International Nuclear Information System (INIS)

Kuznetsov, E.A.; Musher, S.L.; Shafarenko, A.V.

1983-01-01

The existence of the collapse of acoustic waves with a positive dispersion is demonstrated. A qualitative description of wave collapse, based on the analysis of invariants, is proposed. Through the use of a numerical simulation, it is established that, in the Kadomtsev-Petviashvili three-dimensional equation, collapse is accompanied by the formation of a weakly turbulent background by the wave radiation from the cavity

General relativistic collapse of rotating stars

International Nuclear Information System (INIS)

Nakamura, T.

1984-01-01

When a rotating star begins to collapse, the gravity becomes so strong that there appears a region from which even a photon cannot escape. After the distortion of space-time is radiated as gravitational waves, a Kerr black hole is formed finally. One of the main goals for numerical relativity is to simulate the collapse of a rotating star under realistic conditions. However, to know both the dynamics of matter and the propagation of gravitational radiation seems to be very difficult. Therefore, in this paper the problem is divided into 4 stages. They are: (1) The time evolution of pure gravitational waves is calculated in a 2-D code. (2) In this stage, the author tries to understand the dynamics of a collapsing, rotating star in 2D code. (3) Combining the techniques from stages 1, 2, the author tries to know both the dynamics of matter and the propagation of gravitational waves generated by the nonspherical motion of matter. (4) The author simulates the gravitational collapse of a rotating star to a black hole in 3D. 25 references, 12 figures, 1 table

Ionizing radiation and cancer prevention

International Nuclear Information System (INIS)

Hoel, D.G.

1995-01-01

Ionizing radiation long has been recognized as a cause of cancer. Among environmental cancer risks, radiation in unique in the variety of organs and tissues that it can affect. Numerous epidemiological studies with good dosimetry provide the basis for cancer risk estimation, including quantitative information derived from observed dose-response relationships. The amount of cancer attributable to ionizing radiation is difficult to estimate, but numbers such as 1 to 3% have been suggested. Some radiation-induced cancers attributable to ionizing radiation is difficult to estimate, but numbers such as 1 to 3% have been suggested. Some radiation-induced cancers attributable to naturally occurring exposures, such as cosmic and terrestrial radiation, are not preventable. The major natural radiation exposure, radon, can often be reduced, especially in the home, but not entirely eliminated. Medical use of radiation constitutes the other main category of exposure, radon, can often be reduced, especially in the home, but not entirely eliminated. Medical use of radiation constitutes the other main category of exposure; because of the importance of its benefits to one's health, the appropriate prevention strategy is to simply work to minimize exposures. 9 refs., 1 fig., 5 tabs

Current status of relativistic core collapse simulations

Energy Technology Data Exchange (ETDEWEB)

Font, Jose A [Departamento de Astronomia y Astrofisica, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot (Valencia) (Spain)

2007-05-15

With the first generation of ground-based gravitational wave laser interferometers already taking data, the availability of reliable waveform templates from astrophysical sources, which may help extract the signal from the anticipated noisy data, is urgently required. Gravitational stellar core collapse supernova has traditionally been considered among the most important astrophysical sources of potentially detectable gravitational radiation. Only very recently the first multidimensional simulations of relativistic rotational core collapse have been possible (albeit for models with simplified input physics), thanks to the use of conservative formulations of the hydrodynamics equations and advanced numerical methodology, as well as stable formulations of Einstein's equations. In this paper, the current status of relativistic core collapse simulations is discussed, with the emphasis given to the modelling of the collapse dynamics and to the computation of the gravitational radiation in the existing numerical approaches. Work employing the conformally-flat approximation (CFC) of the 3+1 Einstein's equations is reported, as well as extensions of this approximation (CFC+) and investigations within the framework of the so-called BSSN formulation of the 3+1 gravitational field equations (with no approximation for the spacetime dynamics). On the other hand, the incorporation of magnetic fields and the MHD equations in numerical codes to improve the realism of core collapse simulations in general relativity, is currently an emerging field where significant progress is bound to be soon achieved. The paper also contains a brief discussion of magneto-rotational simulations of core collapse, aiming at addressing the effects of magnetic fields on the collapse dynamics and on the gravitational waveforms.

Current status of relativistic core collapse simulations

International Nuclear Information System (INIS)

Font, Jose A

2007-01-01

With the first generation of ground-based gravitational wave laser interferometers already taking data, the availability of reliable waveform templates from astrophysical sources, which may help extract the signal from the anticipated noisy data, is urgently required. Gravitational stellar core collapse supernova has traditionally been considered among the most important astrophysical sources of potentially detectable gravitational radiation. Only very recently the first multidimensional simulations of relativistic rotational core collapse have been possible (albeit for models with simplified input physics), thanks to the use of conservative formulations of the hydrodynamics equations and advanced numerical methodology, as well as stable formulations of Einstein's equations. In this paper, the current status of relativistic core collapse simulations is discussed, with the emphasis given to the modelling of the collapse dynamics and to the computation of the gravitational radiation in the existing numerical approaches. Work employing the conformally-flat approximation (CFC) of the 3+1 Einstein's equations is reported, as well as extensions of this approximation (CFC+) and investigations within the framework of the so-called BSSN formulation of the 3+1 gravitational field equations (with no approximation for the spacetime dynamics). On the other hand, the incorporation of magnetic fields and the MHD equations in numerical codes to improve the realism of core collapse simulations in general relativity, is currently an emerging field where significant progress is bound to be soon achieved. The paper also contains a brief discussion of magneto-rotational simulations of core collapse, aiming at addressing the effects of magnetic fields on the collapse dynamics and on the gravitational waveforms

Debris prevention system, radiation system, and lithograpic apparatus

NARCIS (Netherlands)

2009-01-01

A debris prevention system is constructed and arranged to prevent debris that emanates from a radiation source from propagating with radiation from the radiation source into or within a lithographic apparatus. The debris prevention system includes an aperture that defines a maximum emission angle of

Treatment and prevention of acute radiation dermatitis

International Nuclear Information System (INIS)

Benomar, S.; Hassam, B.; Boutayeb, S.; Errihani, H.; Lalya, I.; El Gueddari, B.K.

2010-01-01

Acute radiation dermatitis is a common side-effect of radiotherapy which often necessitates interruption of the therapy. Currently, there is no general consensus about its prevention or about the treatment of choice. The goal of this work was to focus on optimal methods to prevent and manage acute skin reactions related to radiation therapy and to determine if there are specific topical or oral agents for the prevention of this acute skin reaction. The prevention and the early treatment are the two focus points of the management of the acute radiation dermatitis. (authors)

Creep collapse of TAPS fuel cladding

International Nuclear Information System (INIS)

Chaudhry, S.M.; Anand, A.K.

1975-01-01

Densification of UO 2 can cause axial gaps between fuel pelets and cladding in unsupported (internally) at these regions. An analysis is carried out regarding the possibility of creep collapse in these regions. The analysis is based on Timoshenko's theory of collapse. At various times during the residence of fuel in reactor following parameters are calculated : (1) inelastic collapse of perfectly circular tubes (2) plastic instability in oval tubes (3) effect of creep on ovality. Creep is considered to be a non-linear combination of the following : (a) thermal creep (b) intresenic creep (c) stress aided radiation enhanced (d) stress free growth (4) Critical pressure ratio. The results obtained are compared with G.E. predictions. The results do not predict collapse of TAPS fuel cladding for five year residence time. (author)

Radiation Protection Ordinance. Preventive Radiation Protection Act. 3. rev. and enlarged ed.

International Nuclear Information System (INIS)

Kramer, R.; Zerlett, G.

1990-01-01

This 3rd edition presents the official explanations of the legislative intent behind the Radiation Protection Ordinance of 1976 and the 2nd amending ordinance, and the commentaries which as usual refer to the legal aspects and the related medical, scientific, and technical aspects. As a consequence of the reactor accident at Chernobyl, the existing radiation protection law has been extended by the Act for Preventive Measures for Pretection of the Population Against the Hazards of Ionizing Radiation (Preventive Radiation Protection Act), establishing preventive legal provisions and measures, so that this new edition has likewise been extended by commentaries on the Protective Radiation Protection Act and an introduction to the new area of law. The material also includes the Act for Establishment of a Federal Office for Radiation Protection, of October 9, 1989, which amended the Atomic Energy Act and the Preventive Radiation Protection Act. The correction of the Radiation Protection Ordinance of October 16, 1989 (BGBl. I p. 1926) has been incorporated into the text of the amended version of the Radiation Protection Ordinance. Court decisions and literature referred to cover material published up to the first months of 1989. (orig.) [de

On the quantum corrected gravitational collapse

International Nuclear Information System (INIS)

Torres, Ramón; Fayos, Francesc

2015-01-01

Based on a previously found general class of quantum improved exact solutions composed of non-interacting (dust) particles, we model the gravitational collapse of stars. As the modeled star collapses a closed apparent 3-horizon is generated due to the consideration of quantum effects. The effect of the subsequent emission of Hawking radiation related to this horizon is taken into consideration. Our computations lead us to argue that a total evaporation could be reached. The inferred global picture of the spacetime corresponding to gravitational collapse is devoid of both event horizons and shell-focusing singularities. As a consequence, there is no information paradox and no need of firewalls

On the quantum corrected gravitational collapse

Directory of Open Access Journals (Sweden)

Ramón Torres

2015-07-01

Full Text Available Based on a previously found general class of quantum improved exact solutions composed of non-interacting (dust particles, we model the gravitational collapse of stars. As the modeled star collapses a closed apparent 3-horizon is generated due to the consideration of quantum effects. The effect of the subsequent emission of Hawking radiation related to this horizon is taken into consideration. Our computations lead us to argue that a total evaporation could be reached. The inferred global picture of the spacetime corresponding to gravitational collapse is devoid of both event horizons and shell-focusing singularities. As a consequence, there is no information paradox and no need of firewalls.

On the quantum corrected gravitational collapse

Science.gov (United States)

Torres, Ramón; Fayos, Francesc

2015-07-01

Based on a previously found general class of quantum improved exact solutions composed of non-interacting (dust) particles, we model the gravitational collapse of stars. As the modeled star collapses a closed apparent 3-horizon is generated due to the consideration of quantum effects. The effect of the subsequent emission of Hawking radiation related to this horizon is taken into consideration. Our computations lead us to argue that a total evaporation could be reached. The inferred global picture of the spacetime corresponding to gravitational collapse is devoid of both event horizons and shell-focusing singularities. As a consequence, there is no information paradox and no need of firewalls.

Precombination Cloud Collapse and Baryonic Dark Matter

Science.gov (United States)

Hogan, Craig J.

1993-01-01

A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

Collapsed Dark Matter Structures

Science.gov (United States)

Buckley, Matthew R.; DiFranzo, Anthony

2018-02-01

The distributions of dark matter and baryons in the Universe are known to be very different: The dark matter resides in extended halos, while a significant fraction of the baryons have radiated away much of their initial energy and fallen deep into the potential wells. This difference in morphology leads to the widely held conclusion that dark matter cannot cool and collapse on any scale. We revisit this assumption and show that a simple model where dark matter is charged under a "dark electromagnetism" can allow dark matter to form gravitationally collapsed objects with characteristic mass scales much smaller than that of a Milky-Way-type galaxy. Though the majority of the dark matter in spiral galaxies would remain in the halo, such a model opens the possibility that galaxies and their associated dark matter play host to a significant number of collapsed substructures. The observational signatures of such structures are not well explored but potentially interesting.

Collapsed Dark Matter Structures.

Science.gov (United States)

Buckley, Matthew R; DiFranzo, Anthony

2018-02-02

The distributions of dark matter and baryons in the Universe are known to be very different: The dark matter resides in extended halos, while a significant fraction of the baryons have radiated away much of their initial energy and fallen deep into the potential wells. This difference in morphology leads to the widely held conclusion that dark matter cannot cool and collapse on any scale. We revisit this assumption and show that a simple model where dark matter is charged under a "dark electromagnetism" can allow dark matter to form gravitationally collapsed objects with characteristic mass scales much smaller than that of a Milky-Way-type galaxy. Though the majority of the dark matter in spiral galaxies would remain in the halo, such a model opens the possibility that galaxies and their associated dark matter play host to a significant number of collapsed substructures. The observational signatures of such structures are not well explored but potentially interesting.

Non-adiabatic radiative collapse of a relativistic star under different ...

Indian Academy of Sciences (India)

ditions. The collapse of a star filled with a homogeneous perfect fluid is compared with that of a star filled with ... We have examined the collapse of a relativistic star with matter density and fluid pressure decreasing ..... are invoked to extract information about the change in the equation of state of the interior matter of a ...

Temperature evolution during dissipative collapse

Indian Academy of Sciences (India)

Abstract. We investigate the gravitational collapse of a radiating sphere evolving into a final static configuration described by the interior Schwarzschild solution. The temperature profiles of this par- ticular model are obtained within the framework of causal thermodynamics. The overall temperature evolution is enhanced by ...

Exploring the role of genome and structural ions in preventing viral capsid collapse during dehydration

Science.gov (United States)

Martín-González, Natalia; Guérin Darvas, Sofía M.; Durana, Aritz; Marti, Gerardo A.; Guérin, Diego M. A.; de Pablo, Pedro J.

2018-03-01

Even though viruses evolve mainly in liquid milieu, their horizontal transmission routes often include episodes of dry environment. Along their life cycle, some insect viruses, such as viruses from the Dicistroviridae family, withstand dehydrated conditions with presently unknown consequences to their structural stability. Here, we use atomic force microscopy to monitor the structural changes of viral particles of Triatoma virus (TrV) after desiccation. Our results demonstrate that TrV capsids preserve their genome inside, conserving their height after exposure to dehydrating conditions, which is in stark contrast with other viruses that expel their genome when desiccated. Moreover, empty capsids (without genome) resulted in collapsed particles after desiccation. We also explored the role of structural ions in the dehydration process of the virions (capsid containing genome) by chelating the accessible cations from the external solvent milieu. We observed that ion suppression helps to keep the virus height upon desiccation. Our results show that under drying conditions, the genome of TrV prevents the capsid from collapsing during dehydration, while the structural ions are responsible for promoting solvent exchange through the virion wall.

Radiation induced cancer: risk assessment and prevention

International Nuclear Information System (INIS)

Shore, R.E.

1984-01-01

A number of factors have to be considered in defining the cancer risk from ionizing radiation. These include the radiation sensitivity of the target tissue(s), the temporal pattern of risk, the shape of the dose-incidence curve, the effects of low dose rates, host susceptibility factors, and synergism with other environmental exposures. For the population as a whole the largest sources of radiation exposure are natural background radiation and medical/dental radiation. Radiation exposures in the medical field make up the largest volume of occupational exposures as well. Although new technologies offer opportunities to lower exposures, worker training, careful exposure monitoring with remedial feedback, and monitoring to prevent unnecessary radiodiagnostic procedures may be even more important means of reducing radiation exposure. Screening of irradiated populations can serve a useful preventive function, but only for those who have received very high doses

Gravitational collapse with decaying vacuum energy

Indian Academy of Sciences (India)

Abstract. The effect of dark energy on the end state of spherical radiation collapse is considered within the context of the cosmic censorship hypothesis. It is found that it is possible to have both black holes as well as naked singularities.

Lung lobe collapse: pathophysiology and radiologic significance

International Nuclear Information System (INIS)

Lord, P.F.; Gomez, J.A.

1985-01-01

The radiographic changes caused by collapse of lung lobes in pulmonary disease, pneumothorax, and pleural effusion depend on the lobar recoiling force and local pleural pressure. Differences in the tendency of normal lung lobes or regions to collapse depend on the relative surface-to-volume ratio, determined by shape and size of the region or lobe. This ratio affects the physiologic parameters of pulmonary interdependence, compliance, and collateral air flow. Pulmonary surfactant increases compliance, particularly at low volumes, maintains alveolar stability, and assists in maintaining capillary patency and preventing pulmonary edema. Its loss due to lung injury increases collapsing forces. In the presence of pneumothorax or pleural effusion, diseases that cause lobar collapse produce localized air or fluid entrapment that is a diagnostic sign of the presence of the underlying pulmonary disease

Magnetic tension and gravitational collapse

International Nuclear Information System (INIS)

Tsagas, Christos G

2006-01-01

The gravitational collapse of a magnetized medium is investigated by studying qualitatively the convergence of a timelike family of non-geodesic worldlines in the presence of a magnetic field. Focusing on the field's tension, we illustrate how the winding of the magnetic forcelines due to the fluid's rotation assists the collapse, while shear-like distortions in the distribution of the field's gradients resist contraction. We also show that the relativistic coupling between magnetism and geometry, together with the tension properties of the field, lead to a magneto-curvature stress that opposes the collapse. This tension stress grows stronger with increasing curvature distortion, which means that it could potentially dominate over the gravitational pull of the matter. If this happens, a converging family of non-geodesic worldlines can be prevented from focusing without violating the standard energy conditions

Predicting mining collapse: Superjerks and the appearance of record-breaking events in coal as collapse precursors

Science.gov (United States)

Jiang, Xiang; Liu, Hanlong; Main, Ian G.; Salje, Ekhard K. H.

2017-08-01

The quest for predictive indicators for the collapse of coal mines has led to a robust criterion from scale-model tests in the laboratory. Mechanical collapse under uniaxial stress forms avalanches with a power-law probability distribution function of radiated energy P ˜E-ɛ , with exponent ɛ =1.5 . Impending major collapse is preceded by a reduction of the energy exponent to the mean-field value ɛ =1.32 . Concurrently, the crackling noise increases in intensity and the waiting time between avalanches is reduced when the major collapse is approaching. These latter criteria were so-far deemed too unreliable for safety assessments in coal mines. We report a reassessment of previously collected extensive collapse data sets using "record-breaking analysis," based on the statistical appearance of "superjerks" within a smaller spectrum of collapse events. Superjerks are defined as avalanche signals with energies that surpass those of all previous events. The final major collapse is one such superjerk but other "near collapse" events equally qualify. In this way a very large data set of events is reduced to a sparse sequence of superjerks (21 in our coal sample). The main collapse can be anticipated from the sequence of energies and waiting times of superjerks, ignoring all weaker events. Superjerks are excellent indicators for the temporal evolution, and reveal clear nonstationarity of the crackling noise at constant loading rate, as well as self-similarity in the energy distribution of superjerks as a function of the number of events so far in the sequence Es j˜nδ with δ =1.79 . They are less robust in identifying the precise time of the final collapse, however, than the shift of the energy exponents in the whole data set which occurs only over a short time interval just before the major event. Nevertheless, they provide additional diagnostics that may increase the reliability of such forecasts.

Static axisymmetric discs and gravitational collapse

Energy Technology Data Exchange (ETDEWEB)

Chamorro, A.; Gregory, R.; Stewart, J.M.

1987-09-08

Regular static axisymmetric vacuum solutions of Einstein's field equations representing the exterior field of a finite thin disc are found. These are used to describe the slow collapse of a disc-like object. If no conditions are placed on the matter, a naked singularity is formed and the cosmic censorship hypothesis would be violated. Imposition of the weak energy condition, however, prevents slow collapse to a singularity and preserves the validity of this hypothesis. The validity of the hoop conjecture is also discussed.

Preventive Radiation Protection Act

International Nuclear Information System (INIS)

Roewer, H.

1988-01-01

The commentary is intended to contribute to protection of the population by a practice-oriented discussion and explanation of questions arising in connection with the Preventive Radiation Protection Act. Leaving aside discussions about abandonment of nuclear power, or criticism from any legal point of view, the commentary adopts the practical approach that accepts, and tries to help implementing, the act as it is. It is a guide for readers who are not experts in the law and gives a line of orientation by means of explanations and sometimes by citations from other acts (in footnotes). The commentary also presents the EURATOM Directive No. 3954/87 dated 22 December 1987, the EC Directive No. 3955/87 dated 22 December 1987, and the EC Directive No. 1983/88 dated 5 July 1988. A tabular survey shows the system of duties and competences defined by the Preventive Radiation Protection Act. (RST) [de

Steroid-associated hip joint collapse in bipedal emus.

Directory of Open Access Journals (Sweden)

Li-Zhen Zheng

Full Text Available In this study we established a bipedal animal model of steroid-associated hip joint collapse in emus for testing potential treatment protocols to be developed for prevention of steroid-associated joint collapse in preclinical settings. Five adult male emus were treated with a steroid-associated osteonecrosis (SAON induction protocol using combination of pulsed lipopolysaccharide (LPS and methylprednisolone (MPS. Additional three emus were used as normal control. Post-induction, emu gait was observed, magnetic resonance imaging (MRI was performed, and blood was collected for routine examination, including testing blood coagulation and lipid metabolism. Emus were sacrificed at week 24 post-induction, bilateral femora were collected for micro-computed tomography (micro-CT and histological analysis. Asymmetric limping gait and abnormal MRI signals were found in steroid-treated emus. SAON was found in all emus with a joint collapse incidence of 70%. The percentage of neutrophils (Neut % and parameters on lipid metabolism significantly increased after induction. Micro-CT revealed structure deterioration of subchondral trabecular bone. Histomorphometry showed larger fat cell fraction and size, thinning of subchondral plate and cartilage layer, smaller osteoblast perimeter percentage and less blood vessels distributed at collapsed region in SAON group as compared with the normal controls. Scanning electron microscope (SEM showed poor mineral matrix and more osteo-lacunae outline in the collapsed region in SAON group. The combination of pulsed LPS and MPS developed in the current study was safe and effective to induce SAON and deterioration of subchondral bone in bipedal emus with subsequent femoral head collapse, a typical clinical feature observed in patients under pulsed steroid treatment. In conclusion, bipedal emus could be used as an effective preclinical experimental model to evaluate potential treatment protocols to be developed for prevention of

Radiation physics

International Nuclear Information System (INIS)

Nam, Sang Hui

1991-02-01

This book deals with radiation physics, which introduces atomic theory and an atomic nucleus of materials, conception of an atom and materials, wave and particle, X ray generation and character, a radioactive element and change law, nature of radioactivity, neutron rays, fission, alpha collapse and beta collage and a neutrino collapse of artificial radioactivity such as collapse of artificial nucleus and artificial radioactivity and radiative capture, interaction with materials like interaction between a charged particle and materials and interaction among X-ray, r-ray and materials, radiation of quantity and unit and a charged particle accelerator.

Thermal conduction and gravitational collapse

International Nuclear Information System (INIS)

Herrera, L.; Jimenez, J.; Esculpi, M.

1987-01-01

A method used to study the evolution of radiating spheres, reported some years ago by Herrera, Jimenez, and Ruggeri, is extended to the case in which thermal conduction within the sphere is taken into account. By means of an explicit example it is shown that heat flow, if present, may play an important role, affecting the final outcome of collapse

Gravitational wave generation by stellar core collapse

International Nuclear Information System (INIS)

Moore, T.A.

1981-01-01

Stars which have masses greater than 5 to 8 solar masses are thought to undergo a stage of catastrophic core collapse and subsequent supernova explosion at the end of their lives. If the core is not spherically symmetric, the bounce which halts its collapse at transnuclear densities will generate a pulse of gravitational waves. This thesis presents a fully relativistic model of core collapse which treats deviations from spherical symmetry as small perturbations on a spherical background. This model may be used to predict qualitative and quantitative features of the gravitational radiation emitted by stellar cores with odd-parity, axisymmetric fluid perturbations, and represents a first step in the application of perturbative methods to more general asymmetries. The first chapter reviews the present consensus on the physics of core collapse and outlines the important features, assumptions, and limitations of the model. A series of model runs are presented and discussed. Finally, several proposals for future research are presented. Subsequent chapters explore in detail the mathematical features of the present model and its realization on the computer

The final outcome of dissipative collapse in the presence of

Indian Academy of Sciences (India)

in the gravitational collapse of conformally flat, radiating spheres. ... Comprehensive studies of static fluid spheres in the presence of a cosmological constant have led .... tions with isotropic pressures in the presence of heat flux and cosmological constant ..... radiation from the stellar surface reaches our observer at infinity.

Emergent horizon, Hawking radiation and chaos in the collapsed polymer model of a black hole

International Nuclear Information System (INIS)

Brustein, Ram; Medved, A.J.M.

2017-01-01

We have proposed that the interior of a macroscopic Schwarzschild black hole (BH) consists of highly excited, long, closed, interacting strings and, as such, can be modeled as a collapsed polymer. It was previously shown that the scaling relations of the collapsed-polymer model agree with those of the BH. The current paper further substantiates this proposal with an investigation into some of its dynamical consequences. In particular, we show that the model predicts, without relying on gravitational effects, an emergent horizon. We further show that the horizon fluctuates quantum mechanically as it should and that the strength of the fluctuations is inversely proportional to the BH entropy. It is then demonstrated that the emission of Hawking radiation is realized microscopically by the quantum-induced escape of small pieces of string, with the rate of escape and the energy per emitted piece both parametrically matching the Hawking temperature. We also show, using standard methods from statistical mechanics and chaos theory, how our model accounts for some other known properties of BHs. These include the accepted results for the scrambling time and the viscosity-to-entropy ratio, which in our model apply not only at the horizon but throughout the BH interior. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Emergent horizon, Hawking radiation and chaos in the collapsed polymer model of a black hole

Energy Technology Data Exchange (ETDEWEB)

Brustein, Ram [Department of Physics, Ben-Gurion University, Beer-Sheva (Israel); Medved, A.J.M. [Department of Physics and Electronics, Rhodes University, Grahamstown (South Africa); National Institute for Theoretical Physics (NITheP), Western Cape (South Africa)

2017-02-15

We have proposed that the interior of a macroscopic Schwarzschild black hole (BH) consists of highly excited, long, closed, interacting strings and, as such, can be modeled as a collapsed polymer. It was previously shown that the scaling relations of the collapsed-polymer model agree with those of the BH. The current paper further substantiates this proposal with an investigation into some of its dynamical consequences. In particular, we show that the model predicts, without relying on gravitational effects, an emergent horizon. We further show that the horizon fluctuates quantum mechanically as it should and that the strength of the fluctuations is inversely proportional to the BH entropy. It is then demonstrated that the emission of Hawking radiation is realized microscopically by the quantum-induced escape of small pieces of string, with the rate of escape and the energy per emitted piece both parametrically matching the Hawking temperature. We also show, using standard methods from statistical mechanics and chaos theory, how our model accounts for some other known properties of BHs. These include the accepted results for the scrambling time and the viscosity-to-entropy ratio, which in our model apply not only at the horizon but throughout the BH interior. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

A full general relativistic neutrino radiation-hydrodynamics simulation of a collapsing very massive star and the formation of a black hole

Science.gov (United States)

Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya; Thielemann, Friedrich-Karl

2018-06-01

We study the final fate of a very massive star by performing full general relativistic (GR), three-dimensional (3D) simulation with three-flavour multi-energy neutrino transport. Utilizing a 70 solar mass zero-metallicity progenitor, we self-consistently follow the radiation-hydrodynamics from the onset of gravitational core-collapse until the second collapse of the proto-neutron star (PNS), leading to black hole (BH) formation. Our results show that the BH formation occurs at a post-bounce time of Tpb ˜ 300 ms for the 70 M⊙ star. This is significantly earlier than those in the literature where lower mass progenitors were employed. At a few ˜10 ms before BH formation, we find that the stalled bounce shock is revived by intense neutrino heating from the very hot PNS, which is aided by violent convection behind the shock. In the context of 3D-GR core-collapse modelling with multi-energy neutrino transport, our numerical results present the first evidence to validate a fallback BH formation scenario of the 70 M⊙ star.

A full general relativistic neutrino radiation-hydrodynamics simulation of a collapsing very massive star and the formation of a black hole

Science.gov (United States)

Kuroda, Takami; Kotake, Kei; Takiwaki, Tomoya; Thielemann, Friedrich-Karl

2018-04-01

We study the final fate of a very massive star by performing full general relativistic (GR), three-dimensional (3D) simulation with three-flavor multi-energy neutrino transport. Utilizing a 70 solar mass zero metallicity progenitor, we self-consistently follow the radiation-hydrodynamics from the onset of gravitational core-collapse until the second collapse of the proto-neutron star (PNS), leading to black hole (BH) formation. Our results show that the BH formation occurs at a post-bounce time of Tpb ˜ 300 ms for the 70 M⊙ star. This is significantly earlier than those in the literature where lower mass progenitors were employed. At a few ˜10 ms before BH formation, we find that the stalled bounce shock is revived by intense neutrino heating from the very hot PNS, which is aided by violent convection behind the shock. In the context of 3D-GR core-collapse modeling with multi-energy neutrino transport, our numerical results present the first evidence to validate a fallback BH formation scenario of the 70M⊙ star.

Nonlinear analysis of collapse mechanism in superstructure vehicle

Science.gov (United States)

Nor, M. K. Mohd; Ho, C. S.; Ma'at, N.

2017-04-01

The EU directive 2001/85/EC is an official European text which describes the specifications for "single deck class II and III vehicles" required to be approved by the regulation UN/ECE no.66 (R66). To prevent the catastrophic consequences by occupant during an accident, the Malaysian government has reinforced the same regulation upon superstructure construction. This paper discusses collapse mechanism analysis of a superstructure vehicle using a Crash D nonlinear analysis computer program based on this regulation. The analysis starts by hand calculation to define the required energy absorption by the chosen structure. Simple calculations were then performed to define the weakest collapse mechanism after undesirable collapse modes are eliminated. There are few factors highlighted in this work to pass the regulation. Using the selected cross section, Crash D simulation showed a good result. Generally, the deformation is linearly correlates to the energy absorption for the structure with low stiffness. Failure of critical members such as vertical lower side wall must be avoided to sustain safety of the passenger compartment and prevent from severe and fatal injuries to the trapped occupant.

Prediction of Underground Cavity Roof Collapse using the Hoek–Brown Failure Criterion

DEFF Research Database (Denmark)

Suchowerska, A. M.; Merifield, R. S.; Carter, J. P.

2012-01-01

Preventing roof collapse in underground cavities is a challenge to geotechnical engineering. In this study, three independent methods have been used to evaluate the roof collapse of underground rectangular cavities for a range of geometries and rock properties. The rock mass strength has been des...

Current problems of prevention diagnosis and treatment of radiation sickness

International Nuclear Information System (INIS)

Gus'kova, A.K.

1986-01-01

Causes of increasing interest to the problems of prevention, diagnosis and treatment of radiation sickness are presented. On the basis of recent publications some new aspects as quantitative criteria in radiobiology, organization problems of medical aid at radiation incidents estimation of efficiency of preventive medicine and radiation sickness therapy, theoretical development of radiotherapy of different organs et al., are characterized

High Structural Stability of Textile Implants Prevents Pore Collapse and Preserves Effective Porosity at Strain

Directory of Open Access Journals (Sweden)

Uwe Klinge

2015-01-01

Full Text Available Reinforcement of tissues by use of textiles is encouraged by the reduced rate of recurrent tissue dehiscence but for the price of an inflammatory and fibrotic tissue reaction to the implant. The latter mainly is affected by the size of the pores, whereas only sufficiently large pores are effective in preventing a complete scar entrapment. Comparing two different sling implants (TVT and SIS, which are used for the treatment of urinary incontinence, we can demonstrate that the measurement of the effective porosity reveals considerable differences in the textile construction. Furthermore the changes of porosity after application of a tensile load can indicate a structural instability, favouring pore collapse at stress and questioning the use for purposes that are not “tension-free.”

Submandibular salivary gland transfer prevents radiation-induced xerostomia

International Nuclear Information System (INIS)

Jha, Naresh; Seikaly, Hadi; McGaw, Timothy; Coulter, Linda

2000-01-01

Background: Xerostomia is a significant morbidity of radiation therapy in the management of head and neck cancers. We hypothesized that the surgical transfer of one submandibular salivary gland to submental space, outside the proposed radiation field, prior to starting radiation treatment, would prevent xerostomia. Methods: We are conducting a prospective clinical trial where the submandibular gland is transferred as part of the surgical intervention. The patients are followed clinically, with salivary flow studies and University of Washington quality of life questionnaire. Results: We report early results of 16 patients who have undergone this procedure. Seven patients have finished and 2 patients are currently undergoing radiation treatment. In 2 patients, no postoperative radiation treatment was indicated. Two patients are waiting to start radiation treatment and 2 patients refused treatment after surgery. The surgical transfer was abandoned in 1 patient. All of the transferred salivary glands were positioned outside the proposed radiation fields and were functional. The patients did not complain of any xerostomia and developed only minimal oral mucositis. There were no surgical complications. Conclusions: Surgical transfer of a submandibular salivary gland to the submental space (outside the radiation field) preserves its function and prevents the development of radiation-induced xerostomia

Evaluating nuclear physics inputs in core-collapse supernova models

Science.gov (United States)

Lentz, E.; Hix, W. R.; Baird, M. L.; Messer, O. E. B.; Mezzacappa, A.

Core-collapse supernova models depend on the details of the nuclear and weak interaction physics inputs just as they depend on the details of the macroscopic physics (transport, hydrodynamics, etc.), numerical methods, and progenitors. We present preliminary results from our ongoing comparison studies of nuclear and weak interaction physics inputs to core collapse supernova models using the spherically-symmetric, general relativistic, neutrino radiation hydrodynamics code Agile-Boltztran. We focus on comparisons of the effects of the nuclear EoS and the effects of improving the opacities, particularly neutrino--nucleon interactions.

Preventive effects of Ancer 20 injection against radiation stomatitis

Energy Technology Data Exchange (ETDEWEB)

Watanabe, Naohiko; Nomura, Yasuya; Takano, Shinya (Showa Univ., Tokyo (Japan). School of Medicine) (and others)

1993-10-01

Ancer 20 was injected subcutaneously twice a day into 23 patients during the couse of radiation therapy for head and neck cancer, with the aim of preventing radiation stomatitis. Oral mucosa was assessed both subjectively and objectively, in addition to white blood cell counts. Objective findings of oral mucosa revealed grade I in 71%, grade II in 52%, grade III in 14%, and grade IV in 5%. The dose of irradiation needed to produce grade I in 50% was 22.8 Gy. Subjective findings revealed grade I in 67%, grade II in 33%, and grade III in 10%. Irradiation dose needed to produce grade I in 50% was 23.9 Gy. Mucosous damage was slight when the white blood cell count of 6,000/mm[sup 3] was maintained. According to the rate of leukopenia, this drug was effective in 86.4%. These findings showed that Ancer 20 injection is useful in maintaining white blood cell counts and in preventing radiation stomatitis associated with radiation therapy especially to the field of mucous membrane. There was inverse correlation between white blood cell counts and both the occurrence rate and degree of radiation stomatitis. It seemed necessary to maintain white blood cell counts to prevent radiation stomatitis. (N.K.).

Topical betamethasone for prevention of radiation dermatitis

Directory of Open Access Journals (Sweden)

Omidvari Shapour

2007-01-01

Full Text Available Background: Although acute radiation dermatitis (ARD is a common side-effect of radiotherapy (RT, currently there is no general consensus about its prevention or treatment of choice. Aims: The purpose of this study was to investigate whether prophylactic use of topical betamethasone 0.1% can prevent ARD caused by chest wall irradiation. Methods: Fifty-one patients who underwent modified radical mastectomy for breast cancer and were going to receive RT, were randomly assigned to receive topical betamethasone 0.1%, petrolatum or none during RT. The frequency and severity of ARD (measured using Radiation Therapy Oncology Group acute radiation morbidity scoring criteria were recorded at the end of each week during RT and two weeks after its completion. Clinical outcomes were analyzed by relevant statistical methods. Results: All patients developed some degree of ARD, the frequency and severity of which increased with time and reached the maximum at the end of the seventh week for all groups. Patients receiving betamethasone had less severe ARD than the other two groups throughout the course of the study, but this difference was significant only at the end of the third week (p =0.027. No significant difference was observed between the petrolatum and control arms. Conclusion: Prophylactic and ongoing use of topical betamethasone 0.1% during chest wall RT for breast cancer delays occurrence of ARD but does not prevent it. Petrolatum has no effect on the prevention of ARD in these patients.

Topical betamethasone for prevention of radiation dermatitis.

Science.gov (United States)

Omidvari, Shapour; Saboori, Hojjatollah; Mohammadianpanah, Mohammad; Mosalaei, Ahmad; Ahmadloo, Niloofar; Mosleh-Shirazi, Mohammad Amin; Jowkar, Farideh; Namaz, Soha

2007-01-01

Although acute radiation dermatitis (ARD) is a common side-effect of radiotherapy (RT), currently there is no general consensus about its prevention or treatment of choice. The purpose of this study was to investigate whether prophylactic use of topical betamethasone 0.1% can prevent ARD caused by chest wall irradiation. Fifty-one patients who underwent modified radical mastectomy for breast cancer and were going to receive RT, were randomly assigned to receive topical betamethasone 0.1%, petrolatum or none during RT. The frequency and severity of ARD (measured using Radiation Therapy Oncology Group acute radiation morbidity scoring criteria) were recorded at the end of each week during RT and two weeks after its completion. Clinical outcomes were analyzed by relevant statistical methods. All patients developed some degree of ARD, the frequency and severity of which increased with time and reached the maximum at the end of the seventh week for all groups. Patients receiving betamethasone had less severe ARD than the other two groups throughout the course of the study, but this difference was significant only at the end of the third week (p = 0.027). No significant difference was observed between the petrolatum and control arms. Prophylactic and ongoing use of topical betamethasone 0.1% during chest wall RT for breast cancer delays occurrence of ARD but does not prevent it. Petrolatum has no effect on the prevention of ARD in these patients.

CT of lobar collapse

International Nuclear Information System (INIS)

Suh, D. C.; Im, J. G.; Park, J. H.; Han, M. C.

1987-01-01

The computed tomographic (CT) findings of labor collapse are analysed in an attempt to evaluate the patterns of labor collapse and to get the helpful signs in differentiation between benign and malignant causes of collapse. 43 cases of labor collapse with or without endobronchial obstruction were reviewed. In 29 of 43 cases the collapses were caused by lung cancer. Benign causes of labor collapse included tuberculosis(10), broncholith(2), organizing pneumonia(1) and hamartoma(1). The helpful signs favoring malignant cause of the labor collapse were proximal bulging of the collapsed lobe, low density mass within the collapsed lung, and endobronchial lesion. Above described differential findings were especially applicable in cases of upper lobe collapse

Radiator scald burns: a preventable hazard.

Science.gov (United States)

Benmeir, P; Rosenberg, L; Sagi, A; Ben-Yakar, Y

1990-04-01

During the last 13 years 80 patients have been admitted to our department suffering from burns caused by a vehicle's radiator. Ten of them were deeply burned and had to be treated surgically. The preventive aspect of this injury is emphasized.

Multidimensional simulations of core-collapse supernovae with CHIMERA

Science.gov (United States)

Lentz, Eric J.; Bruenn, S. W.; Yakunin, K.; Endeve, E.; Blondin, J. M.; Harris, J. A.; Hix, W. R.; Marronetti, P.; Messer, O. B.; Mezzacappa, A.

2014-01-01

Core-collapse supernovae are driven by a multidimensional neutrino radiation hydrodynamic (RHD) engine, and full simulation requires at least axisymmetric (2D) and ultimately symmetry-free 3D RHD simulation. We present recent and ongoing work with our multidimensional RHD supernova code CHIMERA to understand the nature of the core-collapse explosion mechanism and its consequences. Recently completed simulations of 12-25 solar mass progenitors(Woosley & Heger 2007) in well resolved (0.7 degrees in latitude) 2D simulations exhibit robust explosions meeting the observationally expected explosion energy. We examine the role of hydrodynamic instabilities (standing accretion shock instability, neutrino driven convection, etc.) on the explosion dynamics and the development of the explosion energy. Ongoing 3D and 2D simulations examine the role that simulation resolution and the removal of the imposed axisymmetry have in the triggering and development of an explosion from stellar core collapse. Companion posters will explore the gravitational wave signals (Yakunin et al.) and nucleosynthesis (Harris et al.) of our simulations.

When the firm prevents the crash: Avoiding market collapse with partial control.

Science.gov (United States)

Levi, Asaf; Sabuco, Juan; A F Sanjuán, Miguel

2017-01-01

Market collapse is one of the most dramatic events in economics. Such a catastrophic event can emerge from the nonlinear interactions between the economic agents at the micro level of the economy. Transient chaos might be a good description of how a collapsing market behaves. In this work, we apply a new control method, the partial control method, with the goal of avoiding this disastrous event. Contrary to common control methods that try to influence the system from the outside, here the market is controlled from the bottom up by one of the most basic components of the market-the firm. This is the first time that the partial control method is applied on a strictly economical system in which we also introduce external disturbances. We show how the firm is capable of controlling the system avoiding the collapse by only adjusting the selling price of the product or the quantity of production in accordance to the market circumstances. Additionally, we demonstrate how a firm with a large market share is capable of influencing the demand achieving price stability across the retail and wholesale markets. Furthermore, we prove that the control applied in both cases is much smaller than the external disturbances.

Regulations on the prevention of ionizing radiation hazards

International Nuclear Information System (INIS)

1979-01-01

The regulations are defined under the labor safety and health law and the provisions of the order for enforcing the law. The enterpriser shall try to reduce to the minimum doses of ionizing radiation received by workers. Ionizing radiation hereunder includes such rays as deutron, proton, beta, electron, neutron, gamma and X-ray. The enterpriser engaged in radiation business shall indicate by marks the area whose radiation dose may exceed 30 mili-rem per week by exterior radiation or radioactive materials in the air. Doses of the workers regularly engaged in radiation business in the controlled area shall not surpass the accumulative dose calculated by the formula D = 5(N-18), when D means limit of accumulative dose (unit rem) and N number of the age of the worker concerned. Doses of the workers entering into the controlled area on business shall not go over 1.5 rem for a year. The maximum permissible dose is 12 rem for the urgent work. Measures for prevention from exterior radiation are designated, including irradiation tubes, filter plates, signals, shelters and alarms, etc. Independent regular inspection, record, measurement and others are particularly essential. Prevention of contamination, emergent measures, appointment of the head of X or gamma rays business, measurement of working environment, health examination and others are stipulated respectively. (Okada, K.)

Interventions for preventing and managing of skin lesions after radiation.

Directory of Open Access Journals (Sweden)

Eleni Bafe

2017-12-01

Full Text Available Introduction: Radiotherapy has a pivotal role in the fight against cancer. However 85% of patients, who undergo radiotherapy, will face moderate to severe skin reactions, for the treatment of which various local products, available in the market, are used. Aim: The aim of this systematic literature review was to investigate the prevention and treatment of these skin lesions induced by radiation. Methods: For this purpose 34 articles were collected concerning materials, approved by the FDA, for the prevention and treatment of skin damage due to radiation, preclinical factors tested in animal models, factors involved in the prevention and treatment of moist desquamation and unauthorized agents or with little information about them. Results: According to the study results, the moisturizing and hydrophilic creams, herbal preparations, gels based on hyaluronic acid, and Vitamin E, heparinoid creams and formulations based on oils appear to have a positive effect in preventing dermatitis as well as in providing symptom relief. Patches are suitable for the case of moist desquamation. Vasculotide, agent EUK-207, agent RTA 408, agent ALDH2 and the agent Celecoxib are still in the preclinical stage but may become future therapeutic targets. Conclusion: Skin reactions due to radiation remain a significant problem for patients undergoing radical treatment. However, thanks to the multitude of formulations available in the market and several clinical trials it is possible that early prevention and treatment for actinic dermatitis could be achieved. In conclusion, it is crucial that health professionals are aware of the formulations indicated and contraindicated in case of skin reactions induced by radiation and adjust the treatment for the prevention and management of skin reactions in patients receiving radiation therapy.

Prevention of ionizing radiation injuries

International Nuclear Information System (INIS)

Suzuki, Masashi

1976-01-01

In the first age (1895 - 1940), radiation injuries of skin (75% of death caused by RI injury) and chronic radiation injury of heamatopoietic organs (almost remains) appeared in radiologist and people engaged in RI treatment for medical use, and Ra poisoning appeared in workers who treated aluminous paint. As prevention of radiation injuries in this age, measurement of radiation dose, shelter effect and finding of injuries were studied, and internal radiation allowed level was determined. From 1942 to 1960, acute RI injuries due to exposure of large amount of RI by an accident and secondary leukemia appeared to workers of atomic-bomb industries and researcher of atomic energy. U and Pu poisoning accompanied with development of nuclear fuel industry appeared. This expanded industrial hygiene of this age together with epidemiological data of atomic-bomb exposed people. From 1960 onward, it is an age of industry for peaceful use of atomic energy, and manifestation of various kinds of delayed injuries, especially malignant tumor due to RI exposure, is recognized. Labourer has many opportunity to encounter dangerously with pollution and injuries by RI, and regional examination of RI enterprise and countermeasure to decrease exposure dose were mentioned as future theme from a viewpoint of exposure dose of nation. (Kanao, N.)

Non-adiabatic radiative collapse of a relativistic star under different

Indian Academy of Sciences (India)

The collapse of a star filled with a homogeneous perfect fluid is compared with that of a star filled with inhomogeneous imperfect fluid under anisotropic ... Department of Physics, P.D. Women's College, Jalpaiguri 735 101, India; Department of Mathematics, Sardar Patel University, Vallabh Vidyanagar 388 120, India ...

A novel animal model for hyperdynamic airway collapse.

Science.gov (United States)

Tsukada, Hisashi; O'Donnell, Carl R; Garland, Robert; Herth, Felix; Decamp, Malcolm; Ernst, Armin

2010-12-01

Tracheobronchomalacia (TBM) is increasingly recognized as a condition associated with significant pulmonary morbidity. However, treatment is invasive and complex, and because there is no appropriate animal model, novel diagnostic and treatment strategies are difficult to evaluate. We endeavored to develop a reliable airway model to simulate hyperdynamic airway collapse in humans. Seven 20-kg male sheep were enrolled in this study. Tracheomalacia was created by submucosal resection of > 50% of the circumference of 10 consecutive cervical tracheal cartilage rings through a midline cervical incision. A silicone stent was placed in the trachea to prevent airway collapse during recovery. Tracheal collapsibility was assessed at protocol-specific time points by bronchoscopy and multidetector CT imaging while temporarily removing the stent. Esophageal pressure and flow data were collected to assess flow limitation during spontaneous breathing. All animals tolerated the surgical procedure well and were stented without complications. One sheep died at 2 weeks because of respiratory failure related to stent migration. In all sheep, near-total forced inspiratory airway collapse was observed up to 3 months postprocedure. Esophageal manometry demonstrated flow limitation associated with large negative pleural pressure swings during rapid spontaneous inhalation. Hyperdynamic airway collapse can reliably be induced with this technique. It may serve as a model for evaluation of novel diagnostic and therapeutic strategies for TBM.

Car radiator burns: a prevention issue.

Science.gov (United States)

Rabbitts, Angela; Alden, Nicole E; Conlin, Tara; Yurt, Roger W

2004-01-01

Scald burns continue to be the major cause of injury to patients admitted to the burn center. Scald burns occurring from car radiator fluid comprise a significant subgroup. Although manufacturer warning labels have been placed on car radiators, these burns continue to occur. This retrospective review looks at all patients admitted to our burn center who suffered scald burns from car radiator fluid to assess the extent of this problem. During the study period, 86 patients were identified as having suffered scald burns as a result of contact with car radiator fluid. Seventy-one percent of the burn injuries occurred in the summer months. The areas most commonly burned were the head and upper extremities. Burn prevention efforts have improved greatly over the years; however, this study demonstrates that scald burns from car radiator fluid continue to cause physical, emotional, and financial devastation. The current radiator warning labels alone are not effective. The National Highway Traffic Safety Administration has proposed a new federal motor vehicle safety standard to aid in decreasing the number of scald burns from car radiators. The results of this study were submitted to the United States Department of Transportation for inclusion in a docket for federal legislation supporting these safety measures.

Shearfree cylindrical gravitational collapse

International Nuclear Information System (INIS)

Di Prisco, A.; Herrera, L.; MacCallum, M. A. H.; Santos, N. O.

2009-01-01

We consider diagonal cylindrically symmetric metrics, with an interior representing a general nonrotating fluid with anisotropic pressures. An exterior vacuum Einstein-Rosen spacetime is matched to this using Darmois matching conditions. We show that the matching conditions can be explicitly solved for the boundary values of metric components and their derivatives, either for the interior or exterior. Specializing to shearfree interiors, a static exterior can only be matched to a static interior, and the evolution in the nonstatic case is found to be given in general by an elliptic function of time. For a collapsing shearfree isotropic fluid, only a Robertson-Walker dust interior is possible, and we show that all such cases were included in Cocke's discussion. For these metrics, Nolan and Nolan have shown that the matching breaks down before collapse is complete, and Tod and Mena have shown that the spacetime is not asymptotically flat in the sense of Berger, Chrusciel, and Moncrief. The issues about energy that then arise are revisited, and it is shown that the exterior is not in an intrinsic gravitational or superenergy radiative state at the boundary.

Review of collapse triggering mechanism of collapsible soils due to wetting

Directory of Open Access Journals (Sweden)

Ping Li

2016-04-01

Full Text Available Loess soil deposits are widely distributed in arid and semi-arid regions and constitute about 10% of land area of the world. These soils typically have a loose honeycomb-type meta-stable structure that is susceptible to a large reduction in total volume or collapse upon wetting. Collapse characteristics contribute to various problems to infrastructures that are constructed on loess soils. For this reason, collapse triggering mechanism for loess soils has been of significant interest for researchers and practitioners all over the world. This paper aims at providing a state-of-the-art review on collapse mechanism with special reference to loess soil deposits. The collapse mechanism studies are summarized under three different categories, i.e. traditional approaches, microstructure approach, and soil mechanics-based approaches. The traditional and microstructure approaches for interpreting the collapse behavior are comprehensively summarized and critically reviewed based on the experimental results from the literature. The soil mechanics-based approaches proposed based on the experimental results of both compacted soils and natural loess soils are reviewed highlighting their strengths and limitations for estimating the collapse behavior. Simpler soil mechanics-based approaches with less parameters or parameters that are easy-to-determine from conventional tests are suggested for future research to better understand the collapse behavior of natural loess soils. Such studies would be more valuable for use in conventional geotechnical engineering practice applications.

Types of collapse calderas

Energy Technology Data Exchange (ETDEWEB)

Aguirre-Diaz, Gerardo J [Centro de Geociencias, Universidad Nacional Autonoma de Mexico, Campus Juriquilla, Queretaro, Qro., 76230 (Mexico)], E-mail: ger@geociencias.unam.mx

2008-10-01

Three main types of collapse calderas can be defined, 1) summit caldera: those formed at the top of large volcanoes, 2) classic caldera: semi-circular to irregular-shaped large structures, several km in diameter and related to relatively large-volume pyroclastic products, and 3) graben caldera: explosive volcano-tectonic collapse structures from which large-volume, ignimbrite-forming eruptions occurred through several fissural vents along the graben master faults and the intra-graben block faults. These in turn can collapse at least with three styles: 1) Piston: when the collapse occurs as a single crustal block; 2) Trap-door: when collapse occurs unevenly along one side while the opposite side remains with no collapse; 3) Piece-meal: when collapse occurs as broken pieces of the crust on top of the magma chamber.

Competition between global warming and an abrupt collapse of the AMOC in Earth's energy imbalance.

Science.gov (United States)

Drijfhout, Sybren

2015-10-06

A collapse of the Atlantic Meridional Overturning Circulation (AMOC) leads to global cooling through fast feedbacks that selectively amplify the response in the Northern Hemisphere (NH). How such cooling competes with global warming has long been a topic for speculation, but was never addressed using a climate model. Here it is shown that global cooling due to a collapsing AMOC obliterates global warming for a period of 15-20 years. Thereafter, the global mean temperature trend is reversed and becomes similar to a simulation without an AMOC collapse. The resulting surface warming hiatus lasts for 40-50 years. Global warming and AMOC-induced NH cooling are governed by similar feedbacks, giving rise to a global net radiative imbalance of similar sign, although the former is associated with surface warming, the latter with cooling. Their footprints in outgoing longwave and absorbed shortwave radiation are very distinct, making attribution possible.

Quantum vacuum effects on the final fate of a collapsing ball of dust

Energy Technology Data Exchange (ETDEWEB)

Arfaei, Hessamaddin [Department of Physics, Sharif University of Technology,P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); School of Particles and Accelerators, Institute for Research in Fundamental Sciences(IPM),P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Noorikuhani, Milad [Department of Physics, Sharif University of Technology,P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of)

2017-02-24

We consider the quantum vacuum effects of the massless scalar fields that are non-minimally coupled to the background geometry of a collapsing homogeneous ball of dust. It is shown that for a definite range of coupling constants, there are repulsive quantum vacuum effects, capable of stopping the collapse process inside the black hole and precluding the formation of singularity. The final fate of the collapse will be a black hole with no singularity, inside which the matter stays balanced. The density of the final static matter will be close to the Planck density. We show that the largest possible radius of the stable static ball inside a black hole with Schwarzschild mass M is given by ((1/(90π))(M/(m{sub p}))){sup (1/3)}ℓ{sub p}. If the black hole undergoes Hawking radiation, the final state will be an extremal quantum-corrected black hole, with zero temperature, with a remnant of matter inside. We show that the resolution of singularity is not disrupted under Hawking radiation.

Star formation: study of the collapse of pre-stellar dense cores

International Nuclear Information System (INIS)

Commercon, Benoit

2009-01-01

One of the priorities of contemporary astrophysics remains to understand the mechanisms which lead to star formation. In the dense cores where star formation occurs, temperature, pressure, etc... are such that it is impossible to reproduce them in the laboratory. Numerical calculations remain the only mean to study physical phenomena that are involved in the star formation process. The focus of this thesis has been on the numerical methods that are used in the star formation context to describe highly non-linear and multi-scale phenomena. In particular, I have concentrated my work on the first stages of the pre-stellar dense cores collapse. This work is divided in 4 linked part. In a first study, I use a 1D Lagrangian code in spherical symmetry (Audit et al. 2002) to compare three models that incorporate radiative transfer and matter-radiation interactions. This comparison was based on simple gravitational collapse calculations which lead to the first Larson core formation. It was found that the Flux Limited Diffusion model is appropriate for star formation calculations. I also took benefit from this first work to study the properties of the accretion shock on the first Larson core. We developed a semi-analytic model based on well-known assumptions, which reproduces the jump properties at the shock. The second study consisted in implementing the Flux Limited Diffusion model with the radiation-hydrodynamics equations in the RAMSES code (Teyssier 2002). After a first step of numerical tests that validate the scheme, we used RAMSES to perform the first multidimensional collapse calculations that combine magnetic field and radiative transfer effects at small scales with a high numerical resolution. Our results show that the radiative transfer has a significant impact on the fragmentation in the collapse of pre-stellar dense cores. I also present a comparison we made between the RAMSES code (Eulerian approach) and the SPH code DRAGON (Goodwin 2004, Lagrangian approach

The Evaluation of Melatonin Effect Against The Early Effect of Ionizing Radiation Induced Lung Injury

Directory of Open Access Journals (Sweden)

raziyeh tahamtan

2014-06-01

Results: the results indicated that radiation increases the collapse and fibrosis and cause the abundance of macrophage compared to control group (p<0.05. Oral administration of melatonin before radiation therapy significantly increased the lymphocyte and macrophage frequency (p<0.001 and decreased the RBC (p<0.05 frequency compared to the radiation group. Conclusion: According to the results, melatonin can prevent early damages in irradiated lungs. Free radicals cause cytotoxicity and melatonin can directly decrease the radiation induced cell damages by converting the free radicals to non- toxic compounds and also through the activation of the major antioxidant enzymes.

Multidimensional, multiphysics simulations of core-collapse supernovae

Energy Technology Data Exchange (ETDEWEB)

Messer, O E B [National Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6008 (United States); Bruenn, S W [Department of Physics, Florida Atlantic University, Boca Raton, FL 33431-0991 (United States); Blondin, J M [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States); Hix, W R; Mezzacappa, A [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6354 (United States)

2008-07-15

CHIMERA is a multi-dimensional radiation hydrodynamics code designed to study core-collapse supernovae. The code is made up of three essentially independent parts: a hydrodynamics module, a nuclear burning module, and a neutrino transport solver combined within an operator-split approach. We review the code's architecture and some recently improved implementations used in the code. We also briefly discuss preliminary results obtained with the code in three spatial dimensions.

Collapse arrest and soliton stabilization in nonlocal nonlinear media

DEFF Research Database (Denmark)

Bang, Ole; Krolikowski, Wieslaw; Wyller, John

2002-01-01

that nonlocality of the nonlinearity prevents collapse in, e.g., Bose-Einstein condensates and optical Kerr media in all physical dimensions. The nonlocal nonlinear response must be symmetric and have a positive definite Fourier spectrum, but can otherwise be of completely arbitrary shape and degree of nonlocality...

Entanglement entropy production in gravitational collapse: covariant regularization and solvable models

Science.gov (United States)

Bianchi, Eugenio; De Lorenzo, Tommaso; Smerlak, Matteo

2015-06-01

We study the dynamics of vacuum entanglement in the process of gravitational collapse and subsequent black hole evaporation. In the first part of the paper, we introduce a covariant regularization of entanglement entropy tailored to curved spacetimes; this regularization allows us to propose precise definitions for the concepts of black hole "exterior entropy" and "radiation entropy." For a Vaidya model of collapse we find results consistent with the standard thermodynamic properties of Hawking radiation. In the second part of the paper, we compute the vacuum entanglement entropy of various spherically-symmetric spacetimes of interest, including the nonsingular black hole model of Bardeen, Hayward, Frolov and Rovelli-Vidotto and the "black hole fireworks" model of Haggard-Rovelli. We discuss specifically the role of event and trapping horizons in connection with the behavior of the radiation entropy at future null infinity. We observe in particular that ( i) in the presence of an event horizon the radiation entropy diverges at the end of the evaporation process, ( ii) in models of nonsingular evaporation (with a trapped region but no event horizon) the generalized second law holds only at early times and is violated in the "purifying" phase, ( iii) at late times the radiation entropy can become negative (i.e. the radiation can be less correlated than the vacuum) before going back to zero leading to an up-down-up behavior for the Page curve of a unitarily evaporating black hole.

Entanglement entropy production in gravitational collapse: covariant regularization and solvable models

International Nuclear Information System (INIS)

Bianchi, Eugenio; Lorenzo, Tommaso De; Smerlak, Matteo

2015-01-01

We study the dynamics of vacuum entanglement in the process of gravitational collapse and subsequent black hole evaporation. In the first part of the paper, we introduce a covariant regularization of entanglement entropy tailored to curved spacetimes; this regularization allows us to propose precise definitions for the concepts of black hole “exterior entropy” and “radiation entropy.” For a Vaidya model of collapse we find results consistent with the standard thermodynamic properties of Hawking radiation. In the second part of the paper, we compute the vacuum entanglement entropy of various spherically-symmetric spacetimes of interest, including the nonsingular black hole model of Bardeen, Hayward, Frolov and Rovelli-Vidotto and the “black hole fireworks” model of Haggard-Rovelli. We discuss specifically the role of event and trapping horizons in connection with the behavior of the radiation entropy at future null infinity. We observe in particular that (i) in the presence of an event horizon the radiation entropy diverges at the end of the evaporation process, (ii) in models of nonsingular evaporation (with a trapped region but no event horizon) the generalized second law holds only at early times and is violated in the “purifying” phase, (iii) at late times the radiation entropy can become negative (i.e. the radiation can be less correlated than the vacuum) before going back to zero leading to an up-down-up behavior for the Page curve of a unitarily evaporating black hole.

Performance Evaluation of Moment Connections of Moment Resisting Frames Against Progressive Collapse

Directory of Open Access Journals (Sweden)

M. Mahmoudi

2017-02-01

Full Text Available When a primary structural element fails due to sudden load such as explosion, the building undergoes progressive collapse. The method for design of moment connections during progressive collapse is different to seismic design of moment connections. Because in this case, the axial force on the connections makes it behave differently. The purpose of this paper is to evaluate the performance of a variety of moment connections in preventing progressive collapse in steel moment frames. To achieve this goal, three prequalified moment connections (BSEEP, BFP and WUP-W were designed according seismic codes. These moment connections were analyzed numerically using ABAQUS software for progressive collapse. The results show that the BFP connection (bolted flange plate has capacity much more than other connections because of the use of plates at the junction of beam-column.

Quantum gravitational collapse: non-singularity and non-locality

International Nuclear Information System (INIS)

Greenwood, Eric; Stojkovic, Dejan

2008-01-01

We investigate gravitational collapse in the context of quantum mechanics. We take primary interest in the behavior of the collapse near the horizon and near the origin (classical singularity) from the point of view of an infalling observer. In the absence of radiation, quantum effects near the horizon do not change the classical conclusions for an infalling observer, meaning the horizon is not an obstacle for him. However, quantum effects are able to remove the classical singularity at the origin, since the wave function is non-singular at the origin. Also, near the classical singularity, some non-local effects become important. In the Schrodinger equation describing behavior near the origin, derivatives of the wave function at one point are related to the value of the wave function at some other distant point.

Recommendations for prevention of radiation accident in industrial gammagraphy

International Nuclear Information System (INIS)

Souza, L.S.; Silva, F.C.A. da

2017-01-01

Industrial Gammagraphy plays an important role in the quality control of various materials and components. It is classified by the International Atomic Energy Agency - IAEA as Category 2, due to its radiation risk caused by the use of high activity radioactive sources. This risk is based on the harmful consequences of human health, described in some accidents in the world, due to failures. In 2012, the 'Brazilian National Workshop on Accident Prevention in Industrial Gammagraphy' was carried out by DIAPI/CNEN, with the objective of disseminating knowledge about radiation accidents. At the time, the IRD/CNEN-RJ carried out a survey with the 75 participants using a form with 22 recommendations to prevent radiological accidents, in order to select the 10 most voted. A statistical study, using the 'Frequency Distribution' method, was performed to define 10 recommendations. The percentage and vote results were obtained by category of the participants and the 10 most important recommendations were defined to prevent radiation accidents. The recommendation that came in first place was 'Always use an individual monitor with alarm during all work'

Guanidinium can both Cause and Prevent the Hydrophobic Collapse of Biomacromolecules

Czech Academy of Sciences Publication Activity Database

Heyda, J.; Okur, H. I.; Hladílková, Jana; Rembert, K. B.; Hunn, W.; Yang, T.; Dzubiella, J.; Jungwirth, Pavel; Cremer, P. S.

2017-01-01

Roč. 139, č. 2 (2017), s. 863-870 ISSN 0002-7863 R&D Projects: GA ČR(CZ) GBP208/12/G016 Institutional support: RVO:61388963 Keywords : molecular dynamics * infrared spectroscopy * guanidinium thiocyanate * elastin * hydrophobic collapse Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 13.858, year: 2016 https://pubs.acs.org/doi/full/10.1021/jacs.6b11082

The spectral appearance of solar-type collapsing protostellar clouds

International Nuclear Information System (INIS)

Bertout, C.; Yorke, H.W.

1978-04-01

In this paper, we review the spectral properties of collapsing protostellar clouds, based on radiative transfer computations in hydrodynamic protostar models. In the first section, the basic results of protostar evolution computations in spherically symmetric and axially symmetry geometries, as they pertain to the appearance of protostars, are briefly reviewed. In the second section, we discuss the continuum appearance of spherically symmetric protostars with various masses. Also, we present recent results for the continuum appearance of an axially symmetric protostellar cloud. The third section deals with the line formation problem and describes preliminary results for a OH molecule in an axially symmetric collapsing cloud. Then we review recent theoretical and observational results obtained for the last evolutionary phase of protostars, known as the YY Orionis phase, when the stellar core first becomes visible in the optical range. Some of the new results and conclusions presented here can be summarized as follows: Rotating collapsing clouds are in general less luminous and cooler than corresponding non-rotating clouds - due to the longer evolutionary time scale. Nevertheless, high resolution studies (resolution [de

Gravitational Waves from Gravitational Collapse

Directory of Open Access Journals (Sweden)

Chris L. Fryer

2011-01-01

Full Text Available Gravitational-wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion-induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.

Gravitational waves from gravitational collapse

Energy Technology Data Exchange (ETDEWEB)

Fryer, Christopher L [Los Alamos National Laboratory; New, Kimberly C [Los Alamos National Laboratory

2008-01-01

Gravitational wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars.

Preventive treatment of combined radiation injuries

International Nuclear Information System (INIS)

Boudagov, R.; Uljanova, L.; Makarov, G.

1996-01-01

The risk of sepsis development increases when thermal burns and other trauma occur in combination with exposure to radiation. Only surgical correction of the life-threatening state recommends within 48 hours after irradiation. All other arrangements have to carry out when hemopoiesis recovery will complete. However exposed patients with combined injuries (CI) die during the first two or three weeks mainly due to sepsis. Therefore prophylaxis and preventive therapy of infectious complications are need early. Actual difficulties in choice of valid treatment procedure for acute radiation syndrome (ARS) exhibit additional aggravation under CI. The available facts prove decreasing early therapy efficiency for rather high dose exposure and wound trauma occurrence. The own results showed that bacterial polysaccharide pyrogenal, glycopin (synthetic analogue of muramil-dipeptide), thymus preparations (thymozin, thymotropin, thymogen), tuftsin, heterologic human and bovine immunoglobulins did not modify the low values of 30-day survival under CI (irradiation + thermal burn). Single injection of prodigiozan, zymozan and some other yeast polysaccharides in 1 hr after CI resulted at moderate increasing of survival. The main purpose of this study, which bases upon our understanding of CI pathogenesis, was search more effective means for preventive treatment of combined radiation injuries. Two groups of remedies were under study. The first group included so called 'biological response modifiers' (BRM). These agents may increase host defences to infection, macrophage's activity and hemopoietic growth factor's secretion. The second group included antibiotics that should be directed against the potential gram-negative as well as gram-positive pathogens and simultaneously be useful for selective decontamination of gastrointestinal tract. (author)

The dynamics of Affleck-Dine condensate collapse

International Nuclear Information System (INIS)

Enqvist, Kari; McDonald, John

2000-01-01

In the MSSM, cosmological scalar field condensates formed along flat directions of the scalar potential (Affleck-Dine condensates) are typically unstable with respect to formation of Q-balls, a type of non-topological soliton. We consider the dynamical evolution of the Affleck-Dine condensate in the MSSM. We discuss the creation and linear growth, in F- and D-term inflation models, of the quantum seed perturbations which in the non-linear regime catalyse the collapse of the condensate to non-topological soliton lumps. We study numerically the evolution of the collapsing condensate lumps and show that the solitons initially formed are not in general Q-balls, but Q-axitons, a pseudo-breather which can have very different properties from Q-balls of the same charge. We calculate the energy and charge radiated from a spherically symmetric condensate lump as it evolves into a Q-axiton. We also discuss the implications for baryogenesis and dark matter

Gravitational Waves from Gravitational Collapse.

Science.gov (United States)

Fryer, Chris L; New, Kimberly C B

2011-01-01

Gravitational-wave emission from stellar collapse has been studied for nearly four decades. Current state-of-the-art numerical investigations of collapse include those that use progenitors with more realistic angular momentum profiles, properly treat microphysics issues, account for general relativity, and examine non-axisymmetric effects in three dimensions. Such simulations predict that gravitational waves from various phenomena associated with gravitational collapse could be detectable with ground-based and space-based interferometric observatories. This review covers the entire range of stellar collapse sources of gravitational waves: from the accretion-induced collapse of a white dwarf through the collapse down to neutron stars or black holes of massive stars to the collapse of supermassive stars. Supplementary material is available for this article at 10.12942/lrr-2011-1.

Competition of neutrino and gravitational radiation in neutron star formation

International Nuclear Information System (INIS)

Kazanas, D.; Schramm, D.N.

1976-01-01

The possibility is explored that neutrino radiation, rather than gravitational radiation, may be the dominant way by which non-radial pulsations are damped out in a collapsing star. If this is so it implies that hopes of detecting gravity waves from supernovae explosions are very optimistic. Neutron stars and black holes are probably the collapsed central remnants of a supernovae explosion. These objects presumably originate from collapse of the cores of sufficiently massive stars, following the cessation of thermonuclear burning. Although there is at present no completely consistent detailed theory as to how collapse of the core and the subsequent supernova explosion take place, a general model exists for the final stages of stellar evolution and supernovae explosions. According to this model the electrons of a sufficiently massive stellar core, due to the high density and temperature, become absorbed by the protons through the reaction p + e - → n + v. Very large numbers of neutrinos, resulting from this and other thermal processes, such as pair annihilation, plasma decay, and Bremsstrahlung, are emitted, taking away most of the gravitational energy of the collapse. These neutrinos possibly drive ejection of the overlying stellar mantle, whilst the neutron-rich core collapses further to a condensed remnant. Gravitational radiation comes into play only at very late stages of the collapse. All of this implies that neutrino radiation might contribute to the decay of the non-radial oscillations of the collapsing core and the newly formed neutron star, possibly damping out these oscillations much faster than gravitational radiation. In order to obtain a more quantitative answer to the question the effects of neutrino radiation on the non-radial oscillations are examined. The implication is that neutrino radiation, by more rapid damping of the non-radial oscillations of a newly formed neutron star in a supernova explosion, would hinder gravitational radiation and

Neutrino-induced nucleosynthesis in core-collapse supernovae

International Nuclear Information System (INIS)

Hartmann, D.H.; Haxton, W.C.; Hoffman, R.D.; Woosley, S.E.; California Univ., Santa Cruz, CA

1990-01-01

Almost all of the 3·10 53 ergs liberated in a core collapse supernova is radiated as neutrinos by the cooling neutron star. The neutrinos can excite nuclei in the mantle of the star by their neutral and charged current reactions. The resulting spallation reactions are an important nuleosynthesis mechanism that may be responsible for the galactic abundances of 7 Li, 11 B, 19 F, 138 La, 180 Ta, and number of other nuclei. 10 refs., 1 fig., 1 tab

Salivary gland transfer to prevent radiation-induced xerostomia: a systematic review and meta-analysis.

Science.gov (United States)

Sood, Amit J; Fox, Nyssa F; O'Connell, Brendan P; Lovelace, Tiffany L; Nguyen, Shaun A; Sharma, Anand K; Hornig, Joshua D; Day, Terry A

2014-02-01

Salivary gland transfer (SGT) has the potential to prevent radiation-induced xerostomia. We attempt to analyze the efficacy of SGT in prevention of xerostomia and maintenance of salivary flow rates after radiation treatment (XRT). Systematic review and meta-analysis. Primary endpoint was efficacy of SGT in prevention of radiation-induced xerostomia. Secondary endpoint was change from baseline of unstimulated and stimulated salivary flow rates after XRT. Seven articles, accruing data from 12 institutions, met inclusion criteria. In a total of 177 patients at mean follow-up of 22.7months, SGT prevented radiation-induced xerostomia in 82.7% (95% CI, 76.6-87.7%) of patients. Twelve months after XRT, unstimulated and stimulated salivary flow rates rose to 88% and 76% of baseline values, respectively. In comparison to control subjects twelve months after XRT, SGT subjects' unstimulated (75% vs. 11%) and stimulated (86% vs. 8%) salivary flow rates were drastically higher in SGT patients. Salivary gland transfer appears to be highly effective in preventing the incidence of xerostomia in patients receiving definitive head and neck radiation therapy. Copyright © 2013 Elsevier Ltd. All rights reserved.

Explanation of the law on radiation injury prevention for mechanical engineers

International Nuclear Information System (INIS)

Fukuyama, Hiroyuki

1991-01-01

Generally to the facilities in which radioisotopes are treated, the Law on Radiation Injury Prevention is applied, but this law was revised in May, 1988, and enforced on April 1, 1989. As to the retroaction to existing facilities, the delay till March 31, 1991 is granted. In this report, by rearranging the system of contents so as to suit to mechanical engineers, the procedure of application and the standard for exhaust facilities and drainage facilities, which seem to be necessary matters, are described. In addition, the standard for facilities related to architecture which seems useful for design and construction if it is known as the basic matter and the standard for the control of the exposure of human bodies, surface contamination and measurement, related to the RI contamination in the air are referred to. The main points of revision in terms, unit and the law are shown. The Law on Radiation Injury Prevention is composed of the Law on Prevention of Radiation Injuries Due to Radioisotopes and Others, the enforcement ordinance, the enforcement regulation and the notice on determining the quantity of isotopes emitting radiation. (K.I.)

Law No. 31 for the year 2002 on the prevention of radiation

International Nuclear Information System (INIS)

2002-01-01

The Law No. 31 for the year 2002 on the prevention of radiation contains 19 rules. This law contains articles on several things, including: the supervisory authority may regulate and control the use of radioactive materials and the prevention of hazards through the development of border and national standards for all radiological exposures and the development of regulations and guidance and control of radioactive waste, and also includes the formation of a technical committee called the 'Commission on Radiation Protection' jurisdiction preparing plans for protection from radiation hazards in the State of Qatar and licensing of personal and institutional for this area. The law also contains the sanctions regime imposed by the State on violators in the area of radiation

Ear canal collapse prevalence and associated factors among users of a center of prevention and rehabilitation for disabilities

Directory of Open Access Journals (Sweden)

Elisana Costa Dourado

Full Text Available ABSTRACT Purpose: to investigate the prevalence of the ear canal collapse when using supra-aural earphones and to verify if this event is influenced by sex, age, color of the skin and prominent ear. Methods: the collapse was assessed by a visual inspection after the positioning of a detached cushion, pressured against the external ear. Results: a total of 436 individuals, aged 3 to 97 years, participated in the study. Ear canal collapse was observed in 11.4% of the subjects, being mostly bilateral (90.0%. The prevalence ranged from 6.3% to 36.6% across age groups. Males, aged 65 years or above and presence of prominent ear were independently identified as associated factors for the occurrence of ear canal collapse (p<0.05. Despite a higher prevalence for those self-identified as white skinned when compared to non-whites, the difference was not statistically significant. Conclusion: the ear canal collapse, when supra-aural earphones are used, is more likely to occur in men, in elderly people, and among those with prominent ears. The prevalence of the event in this population raises the necessity of a careful examination, previous to any evaluation using supra-aural earphones.

Anti-ceramide antibody prevents the radiation gastrointestinal syndrome in mice

Science.gov (United States)

Rotolo, Jimmy; Stancevic, Branka; Zhang, Jianjun; Hua, Guoqiang; Fuller, John; Yin, Xianglei; Haimovitz-Friedman, Adriana; Kim, Kisu; Qian, Ming; Cardó-Vila, Marina; Fuks, Zvi; Pasqualini, Renata; Arap, Wadih; Kolesnick, Richard

2012-01-01

Radiation gastrointestinal (GI) syndrome is a major lethal toxicity that may occur after a radiation/nuclear incident. Currently, there are no prophylactic countermeasures against radiation GI syndrome lethality for first responders, military personnel, or remediation workers entering a contaminated area. The pathophysiology of this syndrome requires depletion of stem cell clonogens (SCCs) within the crypts of Lieberkühn, which are a subset of cells necessary for postinjury regeneration of gut epithelium. Recent evidence indicates that SCC depletion is not exclusively a result of DNA damage but is critically coupled to ceramide-induced endothelial cell apoptosis within the mucosal microvascular network. Here we show that ceramide generated on the surface of endothelium coalesces to form ceramide-rich platforms that transmit an apoptotic signal. Moreover, we report the generation of 2A2, an anti-ceramide monoclonal antibody that binds to ceramide to prevent platform formation on the surface of irradiated endothelial cells of the murine GI tract. Consequently, we found that 2A2 protected against endothelial apoptosis in the small intestinal lamina propria and facilitated recovery of crypt SCCs, preventing the death of mice from radiation GI syndrome after high radiation doses. As such, we suggest that 2A2 represents a prototype of a new class of anti-ceramide therapeutics and an effective countermeasure against radiation GI syndrome mortality. PMID:22466649

NPP planning based on analysis of ground vibration caused by collapse of large-scale cooling towers

Energy Technology Data Exchange (ETDEWEB)

Lin, Feng; Ji, Hongkui [Department of Structural Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China); Gu, Xianglin, E-mail: gxl@tongji.edu.cn [Department of Structural Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China); Li, Yi [Department of Structural Engineering, Tongji University, No. 1239 Siping Road, Shanghai 200092 (China); Wang, Mingreng; Lin, Tao [East China Electric Power Design Institute Co., Ltd, No. 409 Wuning Road, Shanghai 200063 (China)

2015-12-15

Highlights: • New recommendations for NPP planning were addressed taking into account collapse-induced ground vibration. • Critical factors influencing the collapse-induced ground vibration were investigated. • Comprehensive approach was presented to describe the initiation and propagation of collapse-induced disaster. - Abstract: Ground vibration induced by collapse of large-scale cooling towers can detrimentally influence the safe operation of adjacent nuclear-related facilities. To prevent and mitigate these hazards, new planning methods for nuclear power plants (NPPs) were studied considering the influence of these hazards. First, a “cooling tower-soil” model was developed, verified, and used as a numerical means to investigate ground vibration. Afterwards, five critical factors influencing collapse-induced ground vibration were analyzed in-depth. These influencing factors included the height and weight of the towers, accidental loads, soil properties, overlying soil, and isolation trench. Finally, recommendations relating to the control and mitigation of collapse-induced ground vibration in NPP planning were proposed, which addressed five issues, i.e., appropriate spacing between a cooling tower and the nuclear island, control of collapse modes, sitting of a cooling tower and the nuclear island, application of vibration reduction techniques, and the influence of tower collapse on surroundings.

Spacetime Junctions and the Collapse to Black Holes in Higher Dimensions

Directory of Open Access Journals (Sweden)

Filipe C. Mena

2012-01-01

Full Text Available We review recent results about the modelling of gravitational collapse to black holes in higher dimensions. The models are constructed through the junction of two exact solutions of the Einstein field equations: an interior collapsing fluid solution and a vacuum exterior solution. The vacuum exterior solutions are either static or containing gravitational waves. We then review the global geometrical properties of the matched solutions which, besides black holes, may include the existence of naked singularities and wormholes. In the case of radiating exteriors, we show that the data at the boundary can be chosen to be, in some sense, arbitrarily close to the data for the Schwarzschild-Tangherlini solution.

The f electron collapse revisited

International Nuclear Information System (INIS)

Bennett, B.I.

1987-03-01

A reexamination of the collapse of 4f and 5f electrons in the lanthanide and actinide series is presented. The calculations show the well-known collapse of the f electron density at the thresholds of these series along with an f 2 collapse between thorium and protactinium. The collapse is sensitive to the choice of model for the exchange-correlation potential and the behavior of the potential at large radius

Concurrent Transient Activation of Wnt/{beta}-Catenin Pathway Prevents Radiation Damage to Salivary Glands

Energy Technology Data Exchange (ETDEWEB)

Hai Bo; Yang Zhenhua; Shangguan Lei; Zhao Yanqiu [Institute for Regenerative Medicine, Scott and White Hospital, Molecular and Cellular Medicine Department, Texas A and M Health Science Center, Temple, Texas (United States); Boyer, Arthur [Department of Radiology, Scott and White Hospital, Temple, Texas (United States); Liu, Fei, E-mail: fliu@medicine.tamhsc.edu [Institute for Regenerative Medicine, Scott and White Hospital, Molecular and Cellular Medicine Department, Texas A and M Health Science Center, Temple, Texas (United States)

2012-05-01

Purpose: Many head and neck cancer survivors treated with radiotherapy suffer from permanent impairment of their salivary gland function, for which few effective prevention or treatment options are available. This study explored the potential of transient activation of Wnt/{beta}-catenin signaling in preventing radiation damage to salivary glands in a preclinical model. Methods and Materials: Wnt reporter transgenic mice were exposed to 15 Gy single-dose radiation in the head and neck area to evaluate the effects of radiation on Wnt activity in salivary glands. Transient Wnt1 overexpression in basal epithelia was induced in inducible Wnt1 transgenic mice before together with, after, or without local radiation, and then saliva flow rate, histology, apoptosis, proliferation, stem cell activity, and mRNA expression were evaluated. Results: Radiation damage did not significantly affect activity of Wnt/{beta}-catenin pathway as physical damage did. Transient expression of Wnt1 in basal epithelia significantly activated the Wnt/{beta}-catenin pathway in submandibular glands of male mice but not in those of females. Concurrent transient activation of the Wnt pathway prevented chronic salivary gland dysfunction following radiation by suppressing apoptosis and preserving functional salivary stem/progenitor cells. In contrast, Wnt activation 3 days before or after irradiation did not show significant beneficial effects, mainly due to failure to inhibit acute apoptosis after radiation. Excessive Wnt activation before radiation failed to inhibit apoptosis, likely due to extensive induction of mitosis and up-regulation of proapoptosis gene PUMA while that after radiation might miss the critical treatment window. Conclusion: These results suggest that concurrent transient activation of the Wnt/{beta}-catenin pathway could prevent radiation-induced salivary gland dysfunction.

Concurrent Transient Activation of Wnt/β-Catenin Pathway Prevents Radiation Damage to Salivary Glands

International Nuclear Information System (INIS)

Hai Bo; Yang Zhenhua; Shangguan Lei; Zhao Yanqiu; Boyer, Arthur; Liu, Fei

2012-01-01

Purpose: Many head and neck cancer survivors treated with radiotherapy suffer from permanent impairment of their salivary gland function, for which few effective prevention or treatment options are available. This study explored the potential of transient activation of Wnt/β-catenin signaling in preventing radiation damage to salivary glands in a preclinical model. Methods and Materials: Wnt reporter transgenic mice were exposed to 15 Gy single-dose radiation in the head and neck area to evaluate the effects of radiation on Wnt activity in salivary glands. Transient Wnt1 overexpression in basal epithelia was induced in inducible Wnt1 transgenic mice before together with, after, or without local radiation, and then saliva flow rate, histology, apoptosis, proliferation, stem cell activity, and mRNA expression were evaluated. Results: Radiation damage did not significantly affect activity of Wnt/β-catenin pathway as physical damage did. Transient expression of Wnt1 in basal epithelia significantly activated the Wnt/β-catenin pathway in submandibular glands of male mice but not in those of females. Concurrent transient activation of the Wnt pathway prevented chronic salivary gland dysfunction following radiation by suppressing apoptosis and preserving functional salivary stem/progenitor cells. In contrast, Wnt activation 3 days before or after irradiation did not show significant beneficial effects, mainly due to failure to inhibit acute apoptosis after radiation. Excessive Wnt activation before radiation failed to inhibit apoptosis, likely due to extensive induction of mitosis and up-regulation of proapoptosis gene PUMA while that after radiation might miss the critical treatment window. Conclusion: These results suggest that concurrent transient activation of the Wnt/β-catenin pathway could prevent radiation-induced salivary gland dysfunction.

Collapse instability of solitons in the nonpolynomial Schroedinger equation with dipole-dipole interactions

International Nuclear Information System (INIS)

Gligoric, G; Hadzievski, Lj; Maluckov, A; Malomed, B A

2009-01-01

A model of the Bose-Einstein condensate (BEC) of dipolar atoms, confined in a combination of a cigar-shaped trap and optical lattice acting in the axial direction, is studied in the framework of the one-dimensional (1D) nonpolynomial Schroedinger equation (NPSE) with additional terms describing long-range dipole-dipole (DD) interactions. The NPSE makes it possible to describe the collapse of localized modes, which was experimentally observed in the self-attractive BEC confined in tight traps, in the framework of the 1D description. We study the influence of the DD interactions on the dynamics of bright solitons, especially concerning their collapse-induced instability. Both attractive and repulsive contact and DD interactions are considered. The results are summarized in the form of stability/collapse diagrams in a respective parametric space. In particular, it is shown that the attractive DD interactions may prevent the collapse instability in the condensate with attractive contact interactions.

Radiation safety supervisory system in Latvia and its role in prevention of unauthorised practices with radiation sources

International Nuclear Information System (INIS)

Eglajs, A.; Salmins, A.

2001-01-01

This report provides an overview of the practical and legal aspects of the use of radiation sources. The existing regulatory infrastructure is briefly analysed and proposed systems are described. The proposed interactions between the regulatory body and the advisory board are presented and some details about joint activities of different institutions concerning radiation safety are given. An implementation example of the supervisory system in combating illicit trafficking is analysed and the essential components in the prevention of illicit trafficking are assessed. Some findings of investigations are quoted regarding improvements in protection and prevention on the national and the international level. (author)

Numerical simulations of stellar collapse in scalar-tensor theories of gravity

International Nuclear Information System (INIS)

Gerosa, Davide; Sperhake, Ulrich; Ott, Christian D

2016-01-01

We present numerical-relativity simulations of spherically symmetric core collapse and compact-object formation in scalar-tensor theories of gravity. The additional scalar degree of freedom introduces a propagating monopole gravitational-wave mode. Detection of monopole scalar waves with current and future gravitational-wave experiments may constitute smoking gun evidence for strong-field modifications of general relativity. We collapse both polytropic and more realistic pre-supernova profiles using a high-resolution shock-capturing scheme and an approximate prescription for the nuclear equation of state. The most promising sources of scalar radiation are protoneutron stars collapsing to black holes. In case of a galactic core collapse event forming a black hole, Advanced LIGO may be able to place independent constraints on the parameters of the theory at a level comparable to current solar-system and binary-pulsar measurements. In the region of the parameter space admitting spontaneously scalarised stars, transition to configurations with prominent scalar hair before black-hole formation further enhances the emitted signal. Although a more realistic treatment of the microphysics is necessary to fully investigate the occurrence of spontaneous scalarisation of neutron star remnants, we speculate that formation of such objects could constrain the parameters of the theory beyond the current bounds obtained with solar-system and binary-pulsar experiments. (paper)

Geotechnical properties of Egyptian collapsible soils

Directory of Open Access Journals (Sweden)

Khaled E. Gaaver

2012-09-01

Full Text Available The risk of constructing structures on collapsible soils presents significant challenges to geotechnical engineers due to sudden reduction in volume upon wetting. Identifying collapsible soils when encountered in the field and taking the needed precautions should substantially reduce the risk of such problems usually reported in buildings and highways. Collapsible soils are those unsaturated soils that can withstand relatively high pressure without showing significant change in volume, however upon wetting; they are susceptible to a large and sudden reduction in volume. Collapsible soils cover significant areas around the world. In Egypt, collapsible soils were observed within the northern portion of the western desert including Borg El-Arab region, and around the city of Cairo in Six-of-October plateau, and Tenth-of-Ramadan city. Settlements associated with development on untreated collapsible soils usually lead to expensive repairs. One method for treating collapsible soils is to densify their structure by compaction. The ongoing study presents the effect of compaction on the geotechnical properties of the collapsible soils. Undisturbed block samples were recovered from test pits at four sites in Borg El-Arab district, located at about 20 km west of the city of Alexandria, Egypt. The samples were tested in both unsoaked and soaked conditions. Influence of water inundation on the geotechnical properties of collapsible soils was demonstrated. A comparative study between natural undisturbed and compacted samples of collapsible soils was performed. An attempt was made to relate the collapse potential to the initial moisture content. An empirical correlation between California Bearing Ratio of the compacted collapsible soils and liquid limit was adopted. The presented simple relationships should enable the geotechnical engineers to estimate the complex parameters of collapsible soils using simple laboratory tests with a reasonable accuracy.

Radiation Detection System for Prevention of Radiological and Nuclear Terrorism

International Nuclear Information System (INIS)

Kwak, Sung-Woo; Yoo, Ho-Sik; Jang, Sung-Sun; Kim, Jae-Kwang; Kim, Jung-Soo

2007-01-01

After the September 11 terrorist attack, the threat of a potential for a radiological or nuclear terrorist attack became more apparent. The threats relating to radiological or nuclear materials include a Radiological Dispersion Device (RDD), an Improved Nuclear Device (IND) or a State Nuclear Device (such as a Soviet manufactured suitcase nuclear weapon). For more effective countermeasures against the disaster, multilayer protection concept - prevention of smuggling of radioactive or nuclear material into our country through seaports or airports, detection and prevention of the threat materials in transit on a road, and prevention of their entry into a target building - is recommended. Due to different surrounding circumstances of where detection system is deployed, different types of radiation detection systems are required. There have been no studies on characteristics of detection equipment required under Korean specific conditions. This paper provides information on technical requirements of radiation detection system to achieve multi-layer countermeasures for the purpose of protecting the public and environment against radiological and nuclear terrorism

The law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1984-01-01

The law regulates uses, sales and disposal of radioisotopes, uses of radiation generating apparatuses, disposal of materials contaminated with radioisotopes, and so on, in accordance with the Atomic Energy Fundamental Act, for public safety. Covered are the following: permission for and notification of the uses and permission for businesses selling and disposing of radioisotopes, and approval of designs concerning radiation hazard prevention mechanisms, obligations of the users and business enterprises selling and disposing of radioisotopes, the licensed engineers of radiation, organs, etc. for confirmation of the mechanisms, punitive provisions, and so on. (Mori, K.)

Mechanisms of cascade collapse

International Nuclear Information System (INIS)

Diaz de la Rubia, T.; Smalinskas, K.; Averback, R.S.; Robertson, I.M.; Hseih, H.; Benedek, R.

1988-12-01

The spontaneous collapse of energetic displacement cascades in metals into vacancy dislocation loops has been investigated by molecular dynamics (MD) computer simulation and transmission electron microscopy (TEM). Simulations of 5 keV recoil events in Cu and Ni provide the following scenario of cascade collapse: atoms are ejected from the central region of the cascade by replacement collision sequences; the central region subsequently melts; vacancies are driven to the center of the cascade during resolidification where they may collapse into loops. Whether or not collapse occurs depends critically on the melting temperature of the metal and the energy density and total energy in the cascade. Results of TEM are presented in support of this mechanism. 14 refs., 4 figs., 1 tab

Radiation oxidative stress in cancer induction and prevention

International Nuclear Information System (INIS)

Meher, Prabodha Kumar; Mishra, Kaushala Prasad

2017-01-01

Exposure of cells to ionizing radiation causes generation of intracellular reactive oxygen species (ROS) which are implicated in the mechanism of carcinogenesis. Molecular steps involved in the transformation of normal cells to cancer cells have been enigmatic but generally believed to arise from aberration in cellular redox homeostasis. In normal cell function, a delicate balance is maintained between ROS generated in the metabolic process and level of endogenous antioxidant defense. ROS are known to regulate various cellular functions, such as cell division, signal transduction, and apoptosis. Cells experience oxidative stress when excess production of ROS occurs inside a cell upon exposure to external stress or agents. This redox imbalance affects the cellular functions due to DNA strand breaks, chromosomal aberrations, gene mutations, alteration in signal transduction, and inhibition of apoptosis leading to induction of cancer and other diseases. Radiation-induced ROS are involved in initiation and promotion of carcinogenesis. Therefore, detoxification of ROS by exogenous antioxidants including dietary polyphenols offers an important strategy for cancer prevention. Recent research results have shown that resistance of cancer stem cells to therapies is linked to low level of ROS. Interestingly, in vitro and in vivo experiments have reported that radiotherapy- and chemotherapy-induced ROS in cytosol sensitize the tumor cells to death, resulting in tumor growth retardation. This review is an attempt to delineate mechanisms of ROS in carcinogenesis and prevention by dietary compounds. Natural polyphenols and dietary antioxidants hold potential to prevent cancer. Interventions in ROS-mediated signal alteration, apoptosis activation, and modulation of epigenetic processes may offer effective cancer prevention strategy. (author)

Fundamentals of risk/benefit analysis in radiation uses in preventive medicine

International Nuclear Information System (INIS)

Stieve, F.E.

1977-01-01

The term 'risk' stems from the insurance branch. It serves to estimate the probability of making statements about future events on the basis of events which have taken place. Risk estimations are increasingly being made in medicine, especially for determining the advantages and dangers brought to the population by preventive measures. The international radiation protection commission has, for some time, been expressing the dangers of ionising radiation in terms of risk and using these terms as basis for the dose limit values it determined for the professional and general population. This paper deals with possibilities of determining risks in preventive medicine. For doing this, acceptable risk values must be determined and risks resulting from diseases, esp. from those which were not recognized in time, must be compared with those resulting from the application of ionising radiation. (orig.) [de

Radiation-related caries. Etiology and possible preventive strategies. What should the radiotherapist know?

International Nuclear Information System (INIS)

Schweyen, R.; Hey, J.; Fraenzel, W.; Vordermark, D.; Hildebrandt, G.; Kuhnt, T.

2012-01-01

After radiation treatment of head-and-neck cancer, the impairment of patient's quality of life still remains an issue. After completion of the treatment course, a substantial number of patients develop so-called radiation caries. In addition, almost 50% of all cases of infectious osteoradionecrosis (iORN) of the jaws are directly associated with radiation caries. This review addresses our current knowledge on the etiology and pathogenesis of radiation caries including possible preventive strategies. Materials and methods A PubMed search using the terms ''radiation caries'' (''radiation related caries'', ''radiation related damage to dentition'') and ''radiogenic caries'' (''postradiation caries'', ''dental complications and radiotherapy'') was performed. The analysis of its content focused on the etiology, the pathogenesis, and the available knowledge on prophylaxis as well as treatment of radiation caries. Results For this review, 60 publications were selected. As main causal factors for radiogenic caries, either indirect impairment, resulting from alterations in the oral environment (e.g., radiation-induced xerostomia) or direct radiation-induced damage in teeth hard tissues are discussed. Radiation caries remains a lifelong threat and, therefore, requires permanent prevention programs. Conclusion To enable optimal medical care of the patients during the time course of radiotherapy as well as afterwards, close interdisciplinary cooperation between radiotherapists, oral surgeons, otorhinolaryngologists, and dentists is absolutely essential. (orig.)

Pseudopotential multi-relaxation-time lattice Boltzmann model for cavitation bubble collapse with high density ratio

International Nuclear Information System (INIS)

Shan Ming-Lei; Zhu Chang-Ping; Yao Cheng; Yin Cheng; Jiang Xiao-Yan

2016-01-01

The dynamics of the cavitation bubble collapse is a fundamental issue for the bubble collapse application and prevention. In the present work, the modified forcing scheme for the pseudopotential multi-relaxation-time lattice Boltzmann model developed by Li Q et al. [Li Q, Luo K H and Li X J 2013 Phys. Rev. E 87 053301] is adopted to develop a cavitation bubble collapse model. In the respects of coexistence curves and Laplace law verification, the improved pseudopotential multi-relaxation-time lattice Boltzmann model is investigated. It is found that the thermodynamic consistency and surface tension are independent of kinematic viscosity. By homogeneous and heterogeneous cavitation simulation, the ability of the present model to describe the cavitation bubble development as well as the cavitation inception is verified. The bubble collapse between two parallel walls is simulated. The dynamic process of a collapsing bubble is consistent with the results from experiments and simulations by other numerical methods. It is demonstrated that the present pseudopotential multi-relaxation-time lattice Boltzmann model is applicable and efficient, and the lattice Boltzmann method is an alternative tool for collapsing bubble modeling. (paper)

A Model of Dust-like Spherically Symmetric Gravitational Collapse without Event Horizon Formation

Directory of Open Access Journals (Sweden)

Piñol M.

2015-10-01

Full Text Available Some dynamical aspects of gravitational collapse are explored in this paper. A time- dependent spherically symmetric metric is proposed and the corresponding Einstein field equations are derived. An ultrarelativistic dust-like stress-momentum tensor is considered to obtain analytical solutions of these equations, with the perfect fluid con- sisting of two purely radial fluxes — the inwards flux of collapsing matter and the outwards flux of thermally emitted radiation. Thermal emission is calculated by means of a simplistic but illustrative model of uninteracting collapsing shells. Our results show an asymptotic approach to a maximal space-time deformation without the formation of event horizons. The size of the body is slightly larger than the Schwarzschild radius during most of its lifetime, so that there is no contradiction with either observations or previous theorems on black holes. The relation of the latter with our results is scruti- nized in detail.

On radiative density limits in stellarators

International Nuclear Information System (INIS)

Wobig, H.

2001-01-01

Density limits in stellarators are caused mainly by enhanced impurity radiation leading to a collapse of the temperature. A simple model can be established, which computes the temperature in the plasma with a fixed heating profile and a temperature-dependent radiation profile. If the temperature-dependent radiation function has one or several extrema, multiple solutions of the transport equation exist and radiative collapse occurs when the high temperature branch merges with the unstable temperature branch. At this bifurcation point the temperature decreases to a stable low temperature solution. The bifurcation point is a function of the heating power and the plasma density. Thus a density limit can be defined as the point where bifurcation occurs. It is shown that bifurcation and sudden temperature collapse does not occur below a power threshold. Anomalous thermal conductivity and the details of the impurity radiation, which in the present model is assumed to be in corona equilibrium, determine the scaling of the density limit. A model of the anomalous transport is developed, which leads to Gyro-Bohm scaling of the confinement time. The density limit based on this transport model is close to experimental findings in Wendelstein 7-AS. (author)

On the role of the magnetic tension during the gravitational collapse of a magnetised fluid

International Nuclear Information System (INIS)

Tsagas, Christos G

2005-01-01

We investigate the physics of magnetised gravitational collapse by studying the behaviour of a timelike congruence of non-geodesic worldlines in the presence of a magnetic field. We show that the general relativistic coupling between magnetism and geometry, and the tension properties of the field, lead to magneto-curvature stresses that resist the collapse. When these tension stresses dominate, they can prevent an initially converging family of non-geodesic worldlines from focusing without violating the standard energy conditions

Multigroup models of the convective epoch in core collapse supernovae

International Nuclear Information System (INIS)

Swesty, F Douglas; Myra, Eric S

2005-01-01

Understanding the explosion mechanism of core collapse supernovae is a problem that has plagued nuclear astrophysicists since the first computational models of this phenomenon were carried out in the 1960s. Our current theories of this violent phenomenon center around multi-dimensional effects involving radiation-hydrodynamic flows of hot, dense matter and neutrinos. Modeling these multi-dimensional radiative flows presents a computational challenge that will continue to stress high-performance computing beyond the teraflops to the petaflop level. In this paper we describe a few of the scientific discoveries that we have made via terascale computational simulations of supernovae under the auspices of the SciDAC-funded Terascale Supernova Initiative

Spherical dust collapse in higher dimensions

International Nuclear Information System (INIS)

Goswami, Rituparno; Joshi, Pankaj S.

2004-01-01

We consider here whether it is possible to recover cosmic censorship when a transition is made to higher-dimensional spacetimes, by studying the spherically symmetric dust collapse in an arbitrary higher spacetime dimension. It is pointed out that if only black holes are to result as the end state of a continual gravitational collapse, several conditions must be imposed on the collapsing configuration, some of which may appear to be restrictive, and we need to study carefully if these can be suitably motivated physically in a realistic collapse scenario. It would appear, that, in a generic higher-dimensional dust collapse, both black holes and naked singularities would develop as end states as indicated by the results here. The mathematical approach developed here generalizes and unifies the earlier available results on higher-dimensional dust collapse as we point out. Further, the dependence of black hole or naked singularity end states as collapse outcomes on the nature of the initial data from which the collapse develops is brought out explicitly and in a transparent manner as we show here. Our method also allows us to consider here in some detail the genericity and stability aspects related to the occurrence of naked singularities in gravitational collapse

Spherical Collapse in Chameleon Models

CERN Document Server

Brax, Ph; Steer, D A

2010-01-01

We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse depends on the initial comoving size of the inhomogeneity.

Spherical collapse in chameleon models

Energy Technology Data Exchange (ETDEWEB)

Brax, Ph. [Institut de Physique Théorique, CEA, IPhT, CNRS, URA 2306, F-91191Gif/Yvette Cedex (France); Rosenfeld, R. [Instituto de Física Teórica, Universidade Estadual Paulista, Rua Dr. Bento T. Ferraz, 271, 01140-070, São Paulo (Brazil); Steer, D.A., E-mail: brax@spht.saclay.cea.fr, E-mail: rosenfel@ift.unesp.br, E-mail: daniele.steer@apc.univ-paris7.fr [APC, UMR 7164, CNRS, Université Paris 7, 10 rue Alice Domon et Léonie Duquet, 75205 Paris Cedex 13 (France)

2010-08-01

We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity.

Spherical collapse in chameleon models

International Nuclear Information System (INIS)

Brax, Ph.; Rosenfeld, R.; Steer, D.A.

2010-01-01

We study the gravitational collapse of an overdensity of nonrelativistic matter under the action of gravity and a chameleon scalar field. We show that the spherical collapse model is modified by the presence of a chameleon field. In particular, we find that even though the chameleon effects can be potentially large at small scales, for a large enough initial size of the inhomogeneity the collapsing region possesses a thin shell that shields the modification of gravity induced by the chameleon field, recovering the standard gravity results. We analyse the behaviour of a collapsing shell in a cosmological setting in the presence of a thin shell and find that, in contrast to the usual case, the critical density for collapse in principle depends on the initial comoving size of the inhomogeneity

Gravitational Collapse of Charged Matter in Einstein-DeSitter Universe

Science.gov (United States)

Avinash, K.; Krishnan, V.

1997-11-01

Gravitational collapse of charged matter in expanding universe is studied. We consider a quasi neutral electron-ion-massive grain plasma in which all the three species are expanding at the same rate i.e., ni ∝ 1/R^3 [ ni is the number density of the i^ th species and R is the scale factor ]. In Einstein-DeSitter universe the scale factor R goes as ~ t^2/3. The electrons and ions follow Boltzmann's relation. The stability of this equilibrium is studied on Jeans times scale. Depending on the ratio a = fracq d^2Gmd^2 the growth of gravitational collapse is further moderated from t^2/3 growth. For a=1, the instability is completely quenched. In curvature and radiation dominated universe, there is no additional effect due to finite charge of the matter.

Tracheal collapse in two cats

International Nuclear Information System (INIS)

Hendricks, J.C.; O'Brien, J.A.

1985-01-01

Two cats examined bronchoscopically to discover the cause of tracheal collapse were found to have tracheal obstruction cranial to the collapse. Cats with this unusual sign should be examined bronchoscopically to ascertain whether there is an obstruction, as the cause in these 2 cats was distinct from the diffuse airway abnormality that causes tracheal collapse in dogs

Electromagnetic radiation from strong Langmuir turbulence

International Nuclear Information System (INIS)

Akimoto, K.; Rowland, H.L.; Papadopoulos, K.

1988-01-01

A series of computer simulations is reported showing the generation of electromagnetic radiation by strong Langmuir turbulence. The simulations were carried out with a fully electromagnetic 2 1/2 -dimensional fluid code. The radiation process takes place in two stages that reflect the evolution of the electrostatic turbulence. During the first stage while the electrostatic turbulence is evolving from an initial linear wave packet into a planar soliton, the radiation is primarily at ω/sub e/. During the second stage when transverse instabilities lead to the collapse and dissipation of the solitons, 2ω/sub e/ and ω/sub e/ radiation are comparable, and 3ω/sub e/ is also present. The radiation power at ω = 2ω/sub e/ is in good agreement with theoretical predictions for electromagnetic emissions by collapsing solitons

On the stability of radiation-pressure-dominated cavities

Science.gov (United States)

Kuiper, R.; Klahr, H.; Beuther, H.; Henning, Th.

2012-01-01

Context. When massive stars exert a radiation pressure onto their environment that is higher than their gravitational attraction (super-Eddington condition), they launch a radiation-pressure-driven outflow, which creates cleared cavities. These cavities should prevent any further accretion onto the star from the direction of the bubble, although it has been claimed that a radiative Rayleigh-Taylor instability should lead to the collapse of the outflow cavity and foster the growth of massive stars. Aims: We investigate the stability of idealized radiation-pressure-dominated cavities, focusing on its dependence on the radiation transport approach used in numerical simulations for the stellar radiation feedback. Methods: We compare two different methods for stellar radiation feedback: gray flux-limited diffusion (FLD) and ray-tracing (RT). Both methods are implemented in our self-gravity radiation hydrodynamics simulations for various initial density structures of the collapsing clouds, eventually forming massive stars. We also derive simple analytical models to support our findings. Results: Both methods lead to the launch of a radiation-pressure-dominated outflow cavity. However, only the FLD cases lead to prominent instability in the cavity shell. The RT cases do not show such instability; once the outflow has started, it precedes continuously. The FLD cases display extended epochs of marginal Eddington equilibrium in the cavity shell, making them prone to the radiative Rayleigh-Taylor instability. In the RT cases, the radiation pressure exceeds gravity by 1-2 orders of magnitude. The radiative Rayleigh-Taylor instability is then consequently suppressed. It is a fundamental property of the gray FLD method to neglect the stellar radiation temperature at the location of absorption and thus to underestimate the opacity at the location of the cavity shell. Conclusions: Treating the stellar irradiation in the gray FLD approximation underestimates the radiative forces

The efficacy of sucralfate suspension in the prevention of oral mucositis due to radiation therapy

International Nuclear Information System (INIS)

Epstein, J.B.; Wong, F.L.W.

1994-01-01

The purpose of this study was to assess the value of sucralfate suspension in prevention of oral mucositis and for reduction of oral pain in patients who develop mucositis during radiation therapy. The study was a double-blind, placebo-controlled, randomized prospective trial of a sucralfate suspension in the prevention and management of oral mucositis during radiation therapy. Oral mucositis was assessed using a quantitative scale and symptoms were assessed using visual analogue scales. The statistical model was developed to detect a 40% reduction in mucositis. No statistically significant reduction in mucositis was seen. Early during radiation therapy less oral pain was reported in the sucralfate group, but as treatment progressed all patients experienced pain. Patients in the sucralfate group were prescribed topical and systemic analgesics later in the course of radiation therapy. Prophylactic oral rinsing with sucralfate did not prevent oral ulcerative mucositis. Sucralfate may reduce the experience of pain during radiation therapy. 32 refs., 3 tabs

The efficacy of sucralfate suspension in the prevention of oral mucositis due to radiation therapy

Energy Technology Data Exchange (ETDEWEB)

Epstein, J.B.; Wong, F.L.W. (British Columbia Cancer Agency, Vancouver (Canada))

1994-02-01

The purpose of this study was to assess the value of sucralfate suspension in prevention of oral mucositis and for reduction of oral pain in patients who develop mucositis during radiation therapy. The study was a double-blind, placebo-controlled, randomized prospective trial of a sucralfate suspension in the prevention and management of oral mucositis during radiation therapy. Oral mucositis was assessed using a quantitative scale and symptoms were assessed using visual analogue scales. The statistical model was developed to detect a 40% reduction in mucositis. No statistically significant reduction in mucositis was seen. Early during radiation therapy less oral pain was reported in the sucralfate group, but as treatment progressed all patients experienced pain. Patients in the sucralfate group were prescribed topical and systemic analgesics later in the course of radiation therapy. Prophylactic oral rinsing with sucralfate did not prevent oral ulcerative mucositis. Sucralfate may reduce the experience of pain during radiation therapy. 32 refs., 3 tabs.

Management of avascular necrosis of femoral head at pre-collapse stage

Directory of Open Access Journals (Sweden)

Sen Ramesh

2009-01-01

Full Text Available In osteonecrosis the success of interventions that forestall or prevent femoral head collapse and maintain hip function would represent a substantial achievement in the treatment of this disease. A review of recent literature regarding bisphosphonate, anticoagulant, and vasodilators and biophysical modalities have demonstrated efficacy in reducing pain and delaying disease progression in early stage osteonecrosis. Though it has been considered still insufficient, to support their routine use in the treatment or prevention of osteonecrosis of the hip. Core decompression with modification of technique is still one of the safest and most commonly employed procedures with evidence based success in the pre-collapse stage of AVN of femoral head. The additional use of bone morphogenic protein, and bone marrow stem cells may provide the opportunity to enhance the results of core decompression. At present, the use of large vascularised cortical grafts, the other surgical procedure with high success rate is still not common due to technical difficulty in surgery. Likewise osteotomies are also not getting common as arthroplasty is getting more acceptable, so is awaited without any intermediate big surgical interventions.

State-of-the-Art-Review of Collapsible Soils

Directory of Open Access Journals (Sweden)

A. A. AL-Rawas

2000-12-01

Full Text Available Collapsible soils are encountered in arid and semi-arid regions. Such soils cause potential construction problems due to their collapse upon wetting. The collapse phenomenon is primarily related to the open structure of the soil. Several soil collapse classifications based on parameters such as moisture content, dry density, Atterberg limits and clay content have been proposed in the literature as indicators of the soil collapse potential. Direct measurement of the magnitude of collapse, using laboratory and/or field tests, is essential once a soil showed indications of collapse potential. Treatment methods such as soil replacement, compaction control and chemical stabilization showed significant reduction in the settlement of collapsible soils. The design of foundations on collapsible soils depends on the depth of the soil, magnitude of collapse and economics of the design. Strip foundations are commonly used when collapsing soil extends to a shallow depth while piles and drilled piers are recommended in cases where the soil extends to several meters. This paper provides a comprehensive review of collapsible soils. These include the different types of collapsible soils, mechanisms of collapse, identification and classification methods, laboratory and field testing, treatment methods and guidelines for foundation design.

Collapse of large extra dimensions

International Nuclear Information System (INIS)

Geddes, James

2002-01-01

In models of spacetime that are the product of a four-dimensional spacetime with an 'extra' dimension, there is the possibility that the extra dimension will collapse to zero size, forming a singularity. We ask whether this collapse is likely to destroy the spacetime. We argue, by an appeal to the four-dimensional cosmic censorship conjecture, that--at least in the case when the extra dimension is homogeneous--such a collapse will lead to a singularity hidden within a black string. We also construct explicit initial data for a spacetime in which such a collapse is guaranteed to occur and show how the formation of a naked singularity is likely avoided

Long term prevention of disturbance induces the collapse of a dominant species without altering ecosystem function.

Science.gov (United States)

Yu, Qiang; Wu, Honghui; Wang, Zhengwen; Flynn, Dan F B; Yang, Hao; Lü, Fumei; Smith, Melinda; Han, Xingguo

2015-09-21

Limitation of disturbances, such as grazing and fire, is a key tool for nature reserve management and ecological restoration. While the role of these disturbances in shaping ecosystem structure and functioning has been intensively studied, less is known about the consequences of long-term prevention of grazing and fire. Based on a 31-year study, we show that relative biomass of the dominant grass, Leymus chinensis, of grasslands in northern China declined dramatically, but only after 21 years of exclusion of fire and grazing. However, aboveground net primary productivity (ANPP) did not decline accordingly due to compensatory responses of several subdominant grass species. The decline in dominance of L. chinensis was not related to gradually changing climate during the same period, whereas experimentally imposed litter removal (simulating fire), mowing (simulating grazing), fire and moderate grazing enhanced dominance of L. chinensis significantly. Thus, our findings show that disturbances can be critical to maintain the dominance of key grass species in semiarid grassland, but that the collapse of a dominant species does not necessarily result in significant change in ANPP if there are species in the community capable of compensating for loss of a dominant.

Collapse models with non-white noises

International Nuclear Information System (INIS)

Adler, Stephen L; Bassi, Angelo

2007-01-01

We set up a general formalism for models of spontaneous wavefunction collapse with dynamics represented by a stochastic differential equation driven by general Gaussian noises, not necessarily white in time. In particular, we show that the non-Schroedinger terms of the equation induce the collapse of the wavefunction to one of the common eigenstates of the collapsing operators, and that the collapse occurs with the correct quantum probabilities. We also develop a perturbation expansion of the solution of the equation with respect to the parameter which sets the strength of the collapse process; such an approximation allows one to compute the leading-order terms for the deviations of the predictions of collapse models with respect to those of standard quantum mechanics. This analysis shows that to leading order, the 'imaginary noise' trick can be used for non-white Gaussian noise

Upper limits on gravitational-wave bursts radiated from stellar-core collapses in our galaxy

International Nuclear Information System (INIS)

Ando, Masaki; Akutsu, Tomomi; Akutsu, Tomotada

2005-01-01

We present the results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. We used an excess-power filter to extract gravitational-wave candidates, and developed two methods to reduce fake events caused by non-stationary noises of the detector. These analysis methods were applied to real data from the TAMA300 interferometric gravitational wave detector. We compared the data-processed results with those of a Monte Carlo simulation with an assumed galactic-event distribution model and with burst waveforms expected from numerical simulations of stellar-core collapses, in order to interpret the event candidates from an astronomical viewpoint. We set an upper limit of 5.0 x 10 3 events s -1 on the burst gravitational-wave event rate in our galaxy with a confidence level of 90%

Radiation-induced dental caries, prevention and treatment - A systematic review.

Science.gov (United States)

Gupta, Nishtha; Pal, Manoj; Rawat, Sheh; Grewal, Mandeep S; Garg, Himani; Chauhan, Deepika; Ahlawat, Parveen; Tandon, Sarthak; Khurana, Ruparna; Pahuja, Anjali K; Mayank, Mayur; Devnani, Bharti

2015-01-01

Treatment of head and neck cancers (HNCs) involves radiotherapy. Patients undergoing radiotherapy for HNCs are prone to dental complications. Radiotherapy to the head and neck region causes xerostomia and salivary gland dysfunction which dramatically increases the risk of dental caries and its sequelae. Radiation therapy (RT) also affects the dental hard tissues increasing their susceptibility to demineralization following RT. Postradiation caries is a rapidly progressing and highly destructive type of dental caries. Radiation-related caries and other dental hard tissue changes can appear within the first 3 months following RT. Hence, every effort should be focused on prevention to manage patients with severe caries. This can be accomplished through good preoperative dental treatment, frequent dental evaluation and treatment after RT (with the exception of extractions), and consistent home care that includes self-applied fluoride. Restorative management of radiation caries can be challenging. The restorative dentist must consider the altered dental substrate and a hostile oral environment when selecting restorative materials. Radiation-induced changes in enamel and dentine may compromise bonding of adhesive materials. Consequently, glass ionomer cements have proved to be a better alternative to composite resins in irradiated patients. Counseling of patients before and after radiotherapy can be done to make them aware of the complications of radiotherapy and thus can help in preventing them.

High-resolution simulations of cylindrical void collapse in energetic materials: Effect of primary and secondary collapse on initiation thresholds

Science.gov (United States)

Rai, Nirmal Kumar; Schmidt, Martin J.; Udaykumar, H. S.

2017-04-01

Void collapse in energetic materials leads to hot spot formation and enhanced sensitivity. Much recent work has been directed towards simulation of collapse-generated reactive hot spots. The resolution of voids in calculations to date has varied as have the resulting predictions of hot spot intensity. Here we determine the required resolution for reliable cylindrical void collapse calculations leading to initiation of chemical reactions. High-resolution simulations of collapse provide new insights into the mechanism of hot spot generation. It is found that initiation can occur in two different modes depending on the loading intensity: Either the initiation occurs due to jet impact at the first collapse instant or it can occur at secondary lobes at the periphery of the collapsed void. A key observation is that secondary lobe collapse leads to large local temperatures that initiate reactions. This is due to a combination of a strong blast wave from the site of primary void collapse and strong colliding jets and vortical flows generated during the collapse of the secondary lobes. The secondary lobe collapse results in a significant lowering of the predicted threshold for ignition of the energetic material. The results suggest that mesoscale simulations of void fields may suffer from significant uncertainty in threshold predictions because unresolved calculations cannot capture the secondary lobe collapse phenomenon. The implications of this uncertainty for mesoscale simulations are discussed in this paper.

Intravascular radiation for restenosis prevention: could it be the holy grail?

International Nuclear Information System (INIS)

King, S.B.

1996-01-01

This brief editorial discusses the use of intravascular radiation in preventing restenosis after angioplasty in coronary interventions. Results in porcine coronary arteries and clinical applications are briefly reported. (UK)

Diagnosis, injury and prevention of internal radiation exposure

International Nuclear Information System (INIS)

Tatsuzaki, Hideo

2012-01-01

Radiation exposure is classified into three categories: external exposure, surface contamination, and internal exposure (also called internal contamination). Internal exposure is an exposure by the ionizing radiation emitted from radioactive materials taken into a human body. Uptake of radioactive materials can go through inhalation, ingestion, or wound contamination. Not like external exposure, alpha ray or beta ray, which has a limited penetration, is also important in internal exposure. Diagnosis of internal exposure is based on measurement and dose assessment in addition to the history taking. Two methods, direct measurement and/or bioassay (indirect measurement), are used for the measurement. These measurements provide information of radioactive materials in the body at the time of the measurement. The exposure dose to the body needs to be calculated in a process of dose assessment, based on the results of these measurements and history of intake, either acute intake or chronic intake. Another method, measurement of environmental samples or food stuff, is also used for dose assessment. For internal exposure, radiation dose to the body is expressed as committed effective dose or committed equivalent dose, which are accumulation of dose over a defined period. Radioactive materials taken into body are transferred among many body components depending on the type of radionuclide or chemicals etc. Some radioactive materials concentrate in a specific organ. Symptoms and signs depend on the distribution of the radioactive materials in the body. Monitoring the concentration in air or foods is conducted in order to control human activities and foods and consequently reduce the amount of intake to human bodies as a preventive measure. Prevention of internal exposure is also conducted by protective gears such as full face masks. Iodine prophylaxis could be used against radioactive iodine intake. Stable iodine, mostly potassium iodide, could be taken into the thyroid and

Stress evolution during caldera collapse

Science.gov (United States)

Holohan, E. P.; Schöpfer, M. P. J.; Walsh, J. J.

2015-07-01

The mechanics of caldera collapse are subject of long-running debate. Particular uncertainties concern how stresses around a magma reservoir relate to fracturing as the reservoir roof collapses, and how roof collapse in turn impacts upon the reservoir. We used two-dimensional Distinct Element Method models to characterise the evolution of stress around a depleting sub-surface magma body during gravity-driven collapse of its roof. These models illustrate how principal stress orientations rotate during progressive deformation so that roof fracturing transitions from initial reverse faulting to later normal faulting. They also reveal four end-member stress paths to fracture, each corresponding to a particular location within the roof. Analysis of these paths indicates that fractures associated with ultimate roof failure initiate in compression (i.e. as shear fractures). We also report on how mechanical and geometric conditions in the roof affect pre-failure unloading and post-failure reloading of the reservoir. In particular, the models show how residual friction within a failed roof could, without friction reduction mechanisms or fluid-derived counter-effects, inhibit a return to a lithostatically equilibrated pressure in the magma reservoir. Many of these findings should be transferable to other gravity-driven collapse processes, such as sinkhole formation, mine collapse and subsidence above hydrocarbon reservoirs.

Simulation of pulsed-ionizing-radiation-induced errors in CMOS memory circuits

International Nuclear Information System (INIS)

Massengill, L.W.

1987-01-01

Effects of transient ionizing radiation on complementary metal-oxide-semiconductor (CMOS) memory circuits was studied by computer simulation. Simulation results have uncovered the dominant mechanism leading to information loss (upset) in dense (CMOS) circuits: rail span collapse. This effect is the catastrophic reduction in the local power supply at a RAM cell location due to the conglomerate radiation-induced photocurrents from all other RAM cells flowing through the power-supply-interconnect distribution. Rail-span collapse leads to reduced RAM cell-noise margins and can predicate upset. Results show that rail-span collapse in the dominant pulsed radiation effect in many memory circuits, preempting local circuit responses to the radiation. Several techniques to model power-supply noise, such as that arising from rail span collapse, are presented in this work. These include an analytical model for design optimization against these effects, a hierarchical computer-analysis technique for efficient power bus noise simulation in arrayed circuits, such as memories, and a complete circuit-simulation tool for noise margin analysis of circuits with arbitrary topologies

Fire-induced collapses of steel structures

DEFF Research Database (Denmark)

Dondera, Alexandru; Giuliani, Luisa

Single-story steel buildings such as car parks and industrial halls are often characterised by stiff beams and flexible columns and may experience an outward (sway) collapse during a fire, endangering people and properties outside the building. It is therefore a current interest of the research...... to investigate the collapse behaviour of single-story steel frames and identify relevant structural characteristics that influence the collapse mode. In this paper, a parametric study on the collapse a steel beam-column assembly with beam hinged connection and fixed column support is carried out under...... on the beam. By means of those tables, a simple method for the assessment and the countermeasure of unsafe collapse mode of single-story steel buildings can be derived....

Granular Silo collapse: an experimental study

Science.gov (United States)

Clement, Eric; Gutierriez, Gustavo; Boltenhagen, Philippe; Lanuza, Jose

2008-03-01

We present an experimental work that develop some basic insight into the pre-buckling behavior and the buckling transition toward plastic collapse of a granular silo. We study different patterns of deformation generated on thin paper cylindrical shells during granular discharge. We study the collapse threshold for different bed height, flow rates and grain sizes. We compare the patterns that appear during the discharge of spherical beads, with those obtained in the axially compressed cylindrical shells. When the height of the granular column is close to the collapse threshold, we describe a ladder like pattern that rises around the cylinder surface in a spiral path of diamond shaped localizations, and develops into a plastic collapsing fold that grows around the collapsing silo.

Prevention of risks in relation with occupational exposure to ionizing radiation

International Nuclear Information System (INIS)

2005-01-01

After remind the base notions in the field of ionizing radiation, this file evaluates the situation on the natural and occupational exposures: modes, sources, and exposure level, risk for health. It presents the principles of prevention allowing in a professional area (out of nuclear industry) to reduce and control these exposures. Some practical cases illustrate the radiation protection approach. references are given: regulatory benchmarks, useful links, books to consult. (N.C.)

Quantum superposition of massive objects and collapse models

International Nuclear Information System (INIS)

Romero-Isart, Oriol

2011-01-01

We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.

Quantum superposition of massive objects and collapse models

Energy Technology Data Exchange (ETDEWEB)

Romero-Isart, Oriol [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching (Germany)

2011-11-15

We analyze the requirements to test some of the most paradigmatic collapse models with a protocol that prepares quantum superpositions of massive objects. This consists of coherently expanding the wave function of a ground-state-cooled mechanical resonator, performing a squared position measurement that acts as a double slit, and observing interference after further evolution. The analysis is performed in a general framework and takes into account only unavoidable sources of decoherence: blackbody radiation and scattering of environmental particles. We also discuss the limitations imposed by the experimental implementation of this protocol using cavity quantum optomechanics with levitating dielectric nanospheres.

Geophysical observations at cavity collapse

Science.gov (United States)

Jousset, Philippe; Bazargan-Sabet, Behrooz; Lebert, François; Bernardie, Séverine; Gourry, Jean-Christophe

2010-05-01

In Lorraine region (France) salt layers at about 200 meters depth are exploited by Solvay using solution mining methodology which consists in extracting the salt by dissolution, collapsing the cavern overburden during the exploitation phase and finally reclaiming the landscape by creating a water area. In this process, one of the main challenges for the exploiting company is to control the initial 120-m diameter collapse so as to minimize possible damages. In order to detect potential precursors and understand processes associated with such collapses, a wide series of monitoring techniques including micro seismics, broad-band seismology, hydro-acoustic, electromagnetism, gas probing, automatic leveling, continuous GPS, continuous gravity and borehole extensometry was set-up in the frame of an in-situ study carried out by the "Research Group for the Impact and Safety of Underground Works" (GISOS, France). Equipments were set-up well before the final collapse, giving a unique opportunity to analyze a great deal of information prior to and during the collapse process which has been successfully achieved on February the 13th, 2009 by controlling the cavity internal pressure. In this work, we present the results of data recorded by a network of 3 broadband seismometers, 2 accelerometers, 2 tilt-meters and a continuously gravity meter. We relate the variations of the brine pumping rate with the evolutions of the induced geophysical signals and finally we propose a first mechanical model for describing the controlled collapse. Beyond the studied case, extrapolation of the results obtained might contribute to the understanding of uncontrolled cavity collapses, such as pit-craters or calderas at volcanoes.

Velocity structure of protostellar envelopes: gravitational collapse and rotation

International Nuclear Information System (INIS)

Belloche, Arnaud

2002-01-01

Stars form from the gravitational collapse of pre-stellar condensations in molecular clouds. The major aim of this thesis is to compare the predictions of collapse models with observations of both very young (class 0) protostars and starless condensations in millimeter molecular lines. We wish to understand what determines the masses of forming stars and whether the initial conditions have an effect on the dynamical evolution of a condensation. Using a Monte-Carlo radiative transfer code, we analyze rotation and infall spectroscopic signatures to study the velocity structure of a sample of protostellar condensations. We show that the envelope of the class 0 protostar IRAM 04191 in the Taurus molecular cloud is undergoing both extended, subsonic infall and fast, differential rotation. We propose that the inner part of the envelope is a magnetically supercritical core in the process of decoupling from the ambient cloud still supported by the magnetic field. We suggest that the kinematical properties observed for IRAM 04191 are representative of the physical conditions characterizing isolated protostars shortly after point mass formation. On the other hand, a similar study for the pre-stellar condensations of the Rho Ophiuchi proto-cluster yields mass accretion rates that are an order of magnitude higher than in IRAM 04191. This suggests that individual protostellar collapse in clusters is induced by external disturbances. Moreover, we show that the condensations do not have time to orbit significantly through the proto-cluster gas before evolving into protostars and pre-main-sequence stars. This seems inconsistent with models which resort to dynamical interactions and competitive accretion to build up a mass spectrum comparable to the stellar initial mass function. We conclude that protostellar collapse is nearly spontaneous in regions of isolated star formation such as the Taurus cloud but probably strongly induced in proto-clusters. (author) [fr

Quantum Oscillations Can Prevent the Big Bang Singularity in an Einstein-Dirac Cosmology

Science.gov (United States)

Finster, Felix; Hainzl, Christian

2010-01-01

We consider a spatially homogeneous and isotropic system of Dirac particles coupled to classical gravity. The dust and radiation dominated closed Friedmann-Robertson-Walker space-times are recovered as limiting cases. We find a mechanism where quantum oscillations of the Dirac wave functions can prevent the formation of the big bang or big crunch singularity. Thus before the big crunch, the collapse of the universe is stopped by quantum effects and reversed to an expansion, so that the universe opens up entering a new era of classical behavior. Numerical examples of such space-times are given, and the dependence on various parameters is discussed. Generically, one has a collapse after a finite number of cycles. By fine-tuning the parameters we construct an example of a space-time which satisfies the dominant energy condition and is time-periodic, thus running through an infinite number of contraction and expansion cycles.

The regulations for enforcing the law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1978-01-01

These provisions are established on the basis of and to enforce the ''Law for the prevention of radiation hazards due to radioisotopes'' and the Enforcement Order for the ''Law concerning the prevention of radiation hazards due to radioisotopes''. The Regulation includes the definitions of terms, applications for the permission of the use of radioisotopes, standards on usage, obligation of measurement, persons in charge of radiation, etc. Terms are explained, such as persons engaging in radiation works, persons who enter at any time the control areas, radiation facilities, maximum permissible exposure dose, cumulative dose, maximum permissible cumulative dose, maximum permissible concentration in the air, maximum permissible concentration in water and maximum permissible surface density. The applications for permission in written forms are required for the use, sale and abandonment of radioisotopes. Radioisotopes or the apparatuses for generating radiation shall be used in the using facilities. The measurement of radiation dose rate, particle flux density and contamination due to radioisotopes shall be made with radiation-measuring instruments. At least one person shall be chosen as the chief radiation-handling person in each factory, establishment, selling office or abandoning establishment by a user, a trademan or a person engaged in abandonment of radioisotopes. The forms for the application for permission, etc. are attached. (Okada, K.)

Clinical effectiveness of Ancer 20 injection for prevention of radiation-induced oral mucositis

International Nuclear Information System (INIS)

Suzuki, Tsubura; Shimoyama, Tetsuo; Nasu, Daisuke; Kaneko, Takahiro; Horie, Norio

2000-01-01

Although radiotherapy is very useful for treatment of oral cancer, it can cause radiation-induced oral mucositis as a troublesome side effect. Ancer 20 injection is useful for enhancing macrophage function, and apart from its inductive effect on IL-3, it also enhances G-CSF production. Therefore, Ancer 20 injection might also prevent mucositis. This effect was tested by administering the drug to prevent oral mucositis during radiotherapy. Eleven patients (5 males and 6 females, aged 39 to 84 yr, mean 64.5 yr) with squamous cell carcinoma were examined. Radiation was applied externally with a linear accelerator up to a total dose of 20-70 Gy, mean 38.2 Gy. All patients received a small dose of cisplatin concomitantly. Ancer 20 injection 1 ml twice weekly was administered subcutaneously. There was almost no objective or subjective abnormality up to a dose of 30 Gy, and at doses higher than that, the symptoms were mild in comparison with general mucosal reactions. This showed that Ancer 20 injection is useful for prevention of radiation-induced oral mucositis during radiotherapy of oral cancer. (author)

Unifying Research on Social-Ecological Resilience and Collapse.

Science.gov (United States)

Cumming, Graeme S; Peterson, Garry D

2017-09-01

Ecosystems influence human societies, leading people to manage ecosystems for human benefit. Poor environmental management can lead to reduced ecological resilience and social-ecological collapse. We review research on resilience and collapse across different systems and propose a unifying social-ecological framework based on (i) a clear definition of system identity; (ii) the use of quantitative thresholds to define collapse; (iii) relating collapse processes to system structure; and (iv) explicit comparison of alternative hypotheses and models of collapse. Analysis of 17 representative cases identified 14 mechanisms, in five classes, that explain social-ecological collapse. System structure influences the kind of collapse a system may experience. Mechanistic theories of collapse that unite structure and process can make fundamental contributions to solving global environmental problems. Copyright © 2017. Published by Elsevier Ltd.

Investigation of the possible use of Arglabin, new antitumor medicine to prevent oncological diseases after radiation

International Nuclear Information System (INIS)

Shaikenov, T.; Karabalin, B.; Rakhimov, K.; Adekenov, S.

1996-01-01

Background: One of the heaviest effects of radiation exposure and its pollutants to the environment is a growth of oncologic diseases as a sequence of breakage of genetic body substance and transmission of Genetic load to the next generation. People of Kazakstan are anxious of the present situation with harmful effect of remaining radiation doses.Purpose of research: the examination of molecular mechanisms of action for a new drug 'Arglabin' was done with the purpose of preventing the malignant tumor occurrence for those people living on the territory of higher risk (in high radiation locations). Research work of the mechanisms of action for 'Arglabin' drug: - examination of the drug effectiveness to enzymes of prenylated proteins; - examination of the drug effectiveness on functioning the oncogene products; - examination of drug metabolism. Research work of the possibility for using 'Arglabin' to prevent oncology diseases includes: - establishment of experimental model of increased risk of oncologic disease on different groups of laboratory animals using the low-dosage radiation sphere; - examination of the drug effectiveness in oncology diseases prevention; - determination of mechanisms and the prevention's results on cancer

Collapse settlement in compacted soils

CSIR Research Space (South Africa)

Booth, AR

1977-01-01

Full Text Available Research into collapse settlement in compacted soils is described, with special reference to recent cases in Southern Africa where collapse settlement occurred in road embankments following wetting of the soil. The laboratory work described...

NEW EQUATIONS OF STATE IN SIMULATIONS OF CORE-COLLAPSE SUPERNOVAE

International Nuclear Information System (INIS)

Hempel, M.; Liebendörfer, M.; Fischer, T.; Schaffner-Bielich, J.

2012-01-01

We discuss three new equations of state (EOS) in core-collapse supernova simulations. The new EOS are based on the nuclear statistical equilibrium model of Hempel and Schaffner-Bielich (HS), which includes excluded volume effects and relativistic mean-field (RMF) interactions. We consider the RMF parameterizations TM1, TMA, and FSUgold. These EOS are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics and three-flavor Boltzmann neutrino transport. The results obtained for the new EOS are compared with the widely used EOS of H. Shen et al. and Lattimer and Swesty. The systematic comparison shows that the model description of inhomogeneous nuclear matter is as important as the parameterization of the nuclear interactions for the supernova dynamics and the neutrino signal. Furthermore, several new aspects of nuclear physics are investigated: the HS EOS contains distributions of nuclei, including nuclear shell effects. The appearance of light nuclei, e.g., deuterium and tritium, is also explored, which can become as abundant as alphas and free protons. In addition, we investigate the black hole formation in failed core-collapse supernovae, which is mainly determined by the high-density EOS. We find that temperature effects lead to a systematically faster collapse for the non-relativistic LS EOS in comparison with the RMF EOS. We deduce a new correlation for the time until black hole formation, which allows the determination of the maximum mass of proto-neutron stars, if the neutrino signal from such a failed supernova would be measured in the future. This would give a constraint for the nuclear EOS at finite entropy, complementary to observations of cold neutron stars.

INTERPLAY OF NEUTRINO OPACITIES IN CORE-COLLAPSE SUPERNOVA SIMULATIONS

Energy Technology Data Exchange (ETDEWEB)

Lentz, Eric J. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Mezzacappa, Anthony; Hix, W. Raphael [Physics Division, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6354 (United States); Messer, O. E. Bronson [National Center for Computational Sciences, Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831-6164 (United States); Bruenn, Stephen W., E-mail: elentz@utk.edu [Department of Physics, Florida Atlantic University, 777 Glades Road, Boca Raton, FL 33431-0991 (United States)

2012-11-20

We have conducted a series of numerical experiments using spherically symmetric, general relativistic, neutrino radiation hydrodynamics with the code Agile-BOLTZTRAN to examine the effects of modern neutrino opacities on the development of supernova simulations. We test the effects of opacities by removing opacities or by undoing opacity improvements for individual opacities and groups of opacities. We find that improvements to electron capture (EC) on nuclei, namely EC on an ensemble of nuclei using modern nuclear structure models rather than the simpler independent-particle approximation (IPA) for EC on a mean nucleus, plays the most important role during core collapse of all tested neutrino opacities. Low-energy neutrinos emitted by modern nuclear EC preferentially escape during collapse without the energy downscattering on electrons required to enhance neutrino escape and deleptonization for the models with IPA nuclear EC. During shock breakout the primary influence on the emergent neutrinos arises from non-isoenergetic scattering (NIS) on electrons. For the accretion phase, NIS on free nucleons and pair emission by e {sup +} e {sup -} annihilation have the largest impact on the neutrino emission and shock evolution. Other opacities evaluated, including nucleon-nucleon bremsstrahlung and especially neutrino-positron scattering, have little measurable impact on neutrino emission or shock dynamics. Modern treatments of nuclear EC, e {sup +} e {sup -}-annihilation pair emission, and NIS on electrons and free nucleons are critical elements of core-collapse simulations of all dimensionality.

The collapse of a molecular cloud core to stellar densities using radiation non-ideal magnetohydrodynamics

Science.gov (United States)

Wurster, James; Bate, Matthew R.; Price, Daniel J.

2018-04-01

We present results from radiation non-ideal magnetohydrodynamics (MHD) calculations that follow the collapse of rotating, magnetized, molecular cloud cores to stellar densities. These are the first such calculations to include all three non-ideal effects: ambipolar diffusion, Ohmic resistivity, and the Hall effect. We employ an ionization model in which cosmic ray ionization dominates at low temperatures and thermal ionization takes over at high temperatures. We explore the effects of varying the cosmic ray ionization rate from ζcr = 10-10 to 10-16 s-1. Models with ionization rates ≳10-12 s-1 produce results that are indistinguishable from ideal MHD. Decreasing the cosmic ray ionization rate extends the lifetime of the first hydrostatic core up to a factor of 2, but the lifetimes are still substantially shorter than those obtained without magnetic fields. Outflows from the first hydrostatic core phase are launched in all models, but the outflows become broader and slower as the ionization rate is reduced. The outflow morphology following stellar core formation is complex and strongly dependent on the cosmic ray ionization rate. Calculations with high ionization rates quickly produce a fast (≈14 km s-1) bipolar outflow that is distinct from the first core outflow, but with the lowest ionization rate, a slower (≈3-4 km s-1) conical outflow develops gradually and seamlessly merges into the first core outflow.

Collapse of stars as a possible source of closed and semiclosed universes

International Nuclear Information System (INIS)

Markov, M.A.

1990-01-01

This paper reports that in a full space-time Kruskal type diagram the trajectory of a free particle must start from a singularity or infinity and end in infinity or a singularity. If for some reason a black hole 'passes by' (does not reach) singularity in the process of collapse, e.g. the space is transformed into the De Sitter space, then its space-time map should or can be continued into the 'second' (R double-prime) space of a Kruskal type diagram forming a closed or semiclosed world and, perhaps, even a white hole in this space. Strictly speaking we are discussing the future fate of the black holes. If in the process of collapse a star is transformed into a black hole, its external Schwartzschild mass starts decreasing due to Hawking's radiation. On the other hand, our attention is drawn by the appearance under the Schwatzschild radius of new particles produced in the gravitational field of a collapsing star as it approaches the state of singularity. It is of importance to emphasize that the production of these particles cannot increase the star (black hole) mass registered by a Schwartzschild observer. In other words, the particle mass produced in the discussed process must be completely compensated by the arising gravitational mass defect. If Hawking's radiation is capable of completely nullifying the external mass of a black hole, the final (singular) phase of a star vanishing in our space must be a closed universe in its singular state with a density ρ → ∞ and an arbitrarily large but a probability value of the bare mass caused by particle production already under the Schwartzschild sphere

Spherically symmetric scalar field collapse

Indian Academy of Sciences (India)

2013-03-01

Mar 1, 2013 ... The very recent interest in scalar field collapse stems from a cosmological ... The objective of the present investigation is to explore the collapsing modes of a simple ..... The authors thank the BRNS (DAE) for financial support.

Dynamics of charged bulk viscous collapsing cylindrical source with heat flux

Energy Technology Data Exchange (ETDEWEB)

Shah, S.M.; Abbas, G. [The Islamia University of Bahawalpur, Department of Mathematics, Bahawalpur (Pakistan)

2017-04-15

In this paper, we have explored the effects of dissipation on the dynamics of charged bulk viscous collapsing cylindrical source which allows the out-flow of heat flux in the form of radiations. The Misner-Sharp formalism has been implemented to drive the dynamical equation in terms of proper time and radial derivatives. We have investigated the effects of charge and bulk viscosity on the dynamics of collapsing cylinder. To determine the effects of radial heat flux, we have formulated the heat transport equations in the context of Mueller-Israel-Stewart theory by assuming that thermodynamics viscous/heat coupling coefficients can be neglected within some approximations. In our discussion, we have introduced the viscosity by the standard (non-causal) thermodynamics approach. The dynamical equations have been coupled with the heat transport equation; the consequences of the resulting coupled heat equation have been analyzed in detail. (orig.)

Intraperitoneal administration of chitosan/DsiRNA nanoparticles targeting TNFα prevents radiation-induced fibrosis

International Nuclear Information System (INIS)

Nawroth, Isabel; Alsner, Jan; Behlke, Mark A.; Besenbacher, Flemming; Overgaard, Jens; Howard, Kenneth A.; Kjems, Jorgen

2010-01-01

Background and purpose: One of the most common and dose-limiting long-term adverse effects of radiation therapy is radiation-induced fibrosis (RIF), which is characterized by restricted tissue flexibility, reduced compliance or strictures, pain and in severe cases, ulceration and necrosis. Several strategies have been proposed to ameliorate RIF but presently no effective one is available. Recent studies have reported that tumor necrosis factor-α (TNFα) plays a role in fibrogenesis. Material and methods: Male CDF1 mice were radiated with a single dose of 45 Gy. Chitosan/DsiRNA nanoparticles targeting TNFα were intraperitoneal injected and late radiation-induced fibrosis (RIF) was assessed using a modification of the leg contracture model. Additionally, the effect of these nanoparticles on tumor growth and tumor control probability in the absence of radiation was examined in a C3H mammary carcinoma model. Results: We show in this work, that targeting TNFα in macrophages by intraperitoneal administration of chitosan/DsiRNA nanoparticles completely prevented radiation-induced fibrosis in CDF1 mice without revealing any cytotoxic side-effects after a long-term administration. Furthermore, such TNFα targeting was selective without any significant influence on tumor growth or irradiation-related tumor control probability. Conclusion: This nanoparticle-based RNAi approach represents a novel approach to prevent RIF with potential application to improve clinical radiation therapeutic strategies.

Progressive Collapse of High-Rise Buildings from Fire

Directory of Open Access Journals (Sweden)

Pershakov Valerii

2016-01-01

Full Text Available Considers ensuring the stability of structures of high-rise buildings against progressive collapse due to fire, proposed measures to ensure the stability of high-rise buildings due to progressive collapse. The analysis of large fires in high-rise buildings with progressive collapse and review of the literature on the issue of progressive collapse. The analysis of the Ukrainian normative documents on progressive collapse resistance.

Bose-Einstein condensate collapse and dynamical squeezing of vacuum fluctuations

International Nuclear Information System (INIS)

Calzetta, E.A.; Hu, B.L.

2003-01-01

We analyze the phenomena of condensate collapse, as described by Donley et al. [Nature 412, 295 (2001)] and N. Claussen [Ph. D thesis, University of Colorado, 2003 (unpublished)] by focusing on the behavior of excitations or fluctuations above the condensate, as driven by the dynamics of the condensate, rather than the dynamics of the condensate alone or the kinetics of the atoms. The dynamics of the condensate squeezes and amplifies the quantum excitations, mixing the positive and negative frequency components of their wave functions thereby creating particles that appear as bursts and jets. By analyzing the changing amplitude and particle content of these excitations, our simple physical picture explains well the overall features of the collapse phenomena and provides excellent quantitative fits with experimental data on several aspects, such as the scaling behavior of the collapse time and the number of particles in the jet. The prediction of the bursts at this level of approximation is less than satisfactory but may be improved by including the backreaction of the excitations on the condensate. The mechanism behind the dominant effect--parametric amplification of vacuum fluctuations and freezing of modes outside of horizon--is similar to that of cosmological particle creation and structure formation in a rapid quench (which is fundamentally different from Hawking radiation in black holes). This shows that Bose-Einstein condensate dynamics is a promising venue for doing 'laboratory cosmology'

Radiative collapse of a Bennett-relaxed z-pinch

International Nuclear Information System (INIS)

Turner, L.

1989-01-01

The global evolution of a z-pinch has been studied with the assumption of a relaxed state consisting of ions and electrons, each in a rigidly drifting isothermal Maxwellian distribution. This speculative approach has the pragmatic feature of possessing phenomenologically useful global parameters such as drift velocity and temperature that vary in accordance with global physical quantities such as energy and entropy. The plasma gains energy from a time-dependent electric field by means of Poynting's vector. Coulomb collisions between electrons and ions is calculated with a Fokker-Planck treatment analogous to that used by Dreicer to calculate runaways. For a variety of initial conditions and time-independent applied electric fields, the pinch evolution always culminates in a time-independent (attractor) state whose current is the Pease-Braginskii current and whose final radius is proportional to (line density)/sup 3/4//(electric field)/sup 1/2/. Before the final state is attained, the pinch may bounce toward and away from a highly collapsed state. For the case of a Bennett pinch, the classical limit of the resistivity is attained when the line density is much greater than 4πm/sub e//e 2 μ/sub o/; i.e., 3.55 /times/ 10 14 m/sup /minus/1/. 6 refs., 2 figs

Underdiagnosis of Vertebral Collapse on Routine Multidetector Computed Tomography Scan of the Abdomen

International Nuclear Information System (INIS)

Obaid, H.; Husamaldin, Z.; Bhatt, R.

2008-01-01

Background: Vertebral fractures are commonly associated with osteoporosis and have significant morbidity and mortality rates. Osteoporotic vertebral fractures are presently considered as a treatable and preventable condition, and early detection is vital for further management. The evaluation of vertebral compression on multidetector computed tomography (MDCT) scans of the abdomen has, to our knowledge, not been reported before. Purpose: To assess the prevalence of vertebral collapse on routine abdominal CT scans, and to evaluate the usefulness of the multiplanar reconstruction (MPR) capability of MDCT scans in accurately identifying vertebral abnormalities such as vertebral collapse, spondylolisthesis, and retrolisthesis. Material and Methods: A retrospective review of 307 MDCT scans of the abdomen was carried out at a university teaching hospital. Identifiable patient information was anonymized for data protection. All images were reviewed on a picture archiving and communications system (PACS) using sagittal MPR and bone window for the assessment of the vertebrae. Data were collected from the Computerized Radiology Information System (CRIS). Results: Vertebral collapse was seen in 42 (13.6%) of the 307 patients undergoing routine MDCT of the abdomen. Multilevel and single-level collapses were seen in 24 and 18 patients, respectively. Spondylolisthesis was identified in 5.5% (n=17), and retrolisthesis was seen in 0.6% (n=2). All patients with vertebral fracture were older than 50 years. Women were more commonly affected than men. Conclusion: A significant number of patients with vertebral collapse were diagnosed using MPR on MDCT routine scans of the abdomen

Comparison of two occurrence risk assessment methods for collapse gully erosion ——A case study in Guangdong province

Science.gov (United States)

Sun, K.; Cheng, D. B.; He, J. J.; Zhao, Y. L.

2018-02-01

Collapse gully erosion is a specific type of soil erosion in the red soil region of southern China, and early warning and prevention of the occurrence of collapse gully erosion is very important. Based on the idea of risk assessment, this research, taking Guangdong province as an example, adopt the information acquisition analysis and the logistic regression analysis, to discuss the feasibility for collapse gully erosion risk assessment in regional scale, and compare the applicability of the different risk assessment methods. The results show that in the Guangdong province, the risk degree of collapse gully erosion occurrence is high in northeastern and western area, and relatively low in southwestern and central part. The comparing analysis of the different risk assessment methods on collapse gully also indicated that the risk distribution patterns from the different methods were basically consistent. However, the accuracy of risk map from the information acquisition analysis method was slightly better than that from the logistic regression analysis method.

Dosimetric analysis of the alopecia preventing effect of hippocampus sparing whole brain radiation therapy

International Nuclear Information System (INIS)

Mahadevan, Anand; Sampson, Carrie; LaRosa, Salvatore; Floyd, Scott R.; Wong, Eric T.; Uhlmann, Erik J.; Sengupta, Soma; Kasper, Ekkehard M.

2015-01-01

Whole brain radiation therapy (WBRT) is widely used for the treatment of brain metastases. Cognitive decline and alopecia are recognized adverse effects of WBRT. Recently hippocampus sparing whole brain radiation therapy (HS-WBRT) has been shown to reduce the incidence of memory loss. In this study, we found that multi-field intensity modulated radiation therapy (IMRT), with strict constraints to the brain parenchyma and to the hippocampus, reduces follicular scalp dose and prevents alopecia. Suitable patients befitting the inclusion criteria of the RTOG 0933 trial received Hippocampus sparing whole brain radiation. On follow up, they were noticed to have full scalp hair preservation. 5 mm thickness of follicle bearing scalp in the radiation field was outlined in the planning CT scans. Conventional opposed lateral WBRT radiation fields were applied to these patient-specific image sets and planned with the same nominal dose of 30 Gy in 10 fractions. The mean and maximum dose to follicle bearing skin and Dose Volume Histogram (DVH) data were analyzed for conventional and HS-WBRT. Paired t-test was used to compare the means. All six patients had fully preserved scalp hair and remained clinically cognitively intact 1–3 months after HS-WBRT. Compared to conventional WBRT, in addition to the intended sparing of the Hippocampus, HS-WBRT delivered significantly lower mean dose (22.42 cGy vs. 16.33 cGy, p < 0.0001), V 24 (9 cc vs. 44 cc, p < 0.0000) and V 30 (9 cc vs. 0.096 cc, p = 0.0106) to follicle hair bearing scalp and prevented alopecia. There were no recurrences in the Hippocampus area. HS-WBRT, with an 11-field set up as described, while attempting to conserve hippocampus radiation and maintain radiation dose to brain inadvertently spares follicle-bearing scalp and prevents alopecia

The Jeans Condition and Collapsing Molecular Cloud Cores: Filaments or Binaries?

International Nuclear Information System (INIS)

Boss, Alan P.; Fisher, Robert T.; Klein, Richard I.; McKee, Christopher F.

2000-01-01

consistent results. However, the B and M barotropic result differs significantly from the B and M Eddington result at the same maximum density, demonstrating the importance of detailed radiative transfer effects. Finally, we confirm that even in the case of isothermal collapse, an initially uniform density sphere can collapse and fragment into a binary system, in agreement with the 1998 results of Truelove et al. Fragmentation of molecular cloud cores thus appears to remain as a likely explanation of the formation of binary stars, but the sensitivity of these calculations to the numerical resolution and to the thermodynamical treatment demonstrates the need for considerable caution in computing and interpreting three-dimensional protostellar collapse calculations. (c) (c) 2000. The American Astronomical Society

Single-dose radiation therapy for prevention of heterotopic ossification after total hip arthroplasty

International Nuclear Information System (INIS)

Healy, W.L.; Lo, T.C.; Covall, D.J.; Pfeifer, B.A.; Wasilewski, S.A.

1990-01-01

Single-dose radiation therapy was prospectively evaluated for its efficacy in prevention of heterotopic ossification in patients at high risk after total hip arthroplasty. Thirty-one patients (34 hips) were treated between 1981 and 1988. Risk factors for inclusion in the protocol included prior evidence of heterotopic ossification, ankylosing spondylitis, and diffuse idiopathic skeletal hyperostosis. Patients with hypertrophic osteoarthritis or traumatic arthritis with osteophytes were not included. Operations on 34 hips included 19 primary total and 11 revision total hip arthroplasties and 4 excisions of heterotopic ossification. All patients received radiotherapy to the hip after operation with a single dose of 700 centigray. Radiotherapy is recommended on the first postoperative day. After this single-dose radiation treatment, no patient had clinically significant heterotopic ossification. Recurrent disease developed in two hips (6%), as seen on radiography (grades 2 and 3). This series documents a 100% clinical success rate and a 94% radiographic success rate in preventing heterotopic ossification in patients at high risk after total hip arthroplasty. Single-dose radiotherapy is as effective as other radiation protocols in preventing heterotopic ossification after total hip arthroplasty. It is less expensive and easier to administer than multidose radiotherapy

Black hole formation in perfect fluid collapse

International Nuclear Information System (INIS)

Goswami, Rituparno; Joshi, Pankaj S

2004-01-01

We construct here a special class of perfect fluid collapse models which generalizes the homogeneous dust collapse solution in order to include nonzero pressures and inhomogeneities into evolution. It is shown that a black hole is necessarily generated as the end product of continued gravitational collapse, rather than a naked singularity. We examine the nature of the central singularity forming as a result of endless collapse and it is shown that no nonspacelike trajectories can escape from the central singularity. Our results provide some insights into how the dynamical collapse works and into the possible formulations of the cosmic censorship hypothesis, which is as yet a major unsolved problem in black hole physics

Gravitational collapse and the vacuum energy

International Nuclear Information System (INIS)

Campos, M

2014-01-01

To explain the accelerated expansion of the universe, models with interacting dark components (dark energy and dark matter) have been considered recently in the literature. Generally, the dark energy component is physically interpreted as the vacuum energy of the all fields that fill the universe. As the other side of the same coin, the influence of the vacuum energy on the gravitational collapse is of great interest. We study such collapse adopting different parameterizations for the evolution of the vacuum energy. We discuss the homogeneous collapsing star fluid, that interacts with a vacuum energy component, using the stiff matter case as example. We conclude this work with a discussion of the Cahill-McVittie mass for the collapsed object.

Simple Analytic Models of Gravitational Collapse

Energy Technology Data Exchange (ETDEWEB)

Adler, R.

2005-02-09

Most general relativity textbooks devote considerable space to the simplest example of a black hole containing a singularity, the Schwarzschild geometry. However only a few discuss the dynamical process of gravitational collapse, by which black holes and singularities form. We present here two types of analytic models for this process, which we believe are the simplest available; the first involves collapsing spherical shells of light, analyzed mainly in Eddington-Finkelstein coordinates; the second involves collapsing spheres filled with a perfect fluid, analyzed mainly in Painleve-Gullstrand coordinates. Our main goal is pedagogical simplicity and algebraic completeness, but we also present some results that we believe are new, such as the collapse of a light shell in Kruskal-Szekeres coordinates.

Multi-dimensional simulations of core-collapse supernova explosions with CHIMERA

Science.gov (United States)

Messer, O. E. B.; Harris, J. A.; Hix, W. R.; Lentz, E. J.; Bruenn, S. W.; Mezzacappa, A.

2018-04-01

Unraveling the core-collapse supernova (CCSN) mechanism is a problem that remains essentially unsolved despite more than four decades of effort. Spherically symmetric models with otherwise high physical fidelity generally fail to produce explosions, and it is widely accepted that CCSNe are inherently multi-dimensional. Progress in realistic modeling has occurred recently through the availability of petascale platforms and the increasing sophistication of supernova codes. We will discuss our most recent work on understanding neutrino-driven CCSN explosions employing multi-dimensional neutrino-radiation hydrodynamics simulations with the Chimera code. We discuss the inputs and resulting outputs from these simulations, the role of neutrino radiation transport, and the importance of multi-dimensional fluid flows in shaping the explosions. We also highlight the production of 48Ca in long-running Chimera simulations.

Effect of cepharanthin to prevent radiation induced xerostomia in head and neck cancer

International Nuclear Information System (INIS)

Imada, Hajime; Nomoto, Satoshi; Ohguri, Takayuki; Yahara, Katsuya; Kato, Fumio; Morioka, Tomoaki; Korogi Yukunori

2004-01-01

We retrospectively examined the effect of Cepharanthin to prevent radiation xerostomia in 37 cases of head and neck cancer. In the Cepharanthin group, the degree of xerostomia was milder than in the non-Cepharanthin group in spite of higher normal tissue complication probability (NTCP) and mean dose (MD) of parotid glands. In the non-Cepharanthin group, the degree of xerostomia was significantly correlated with NTCP and MD of parotid glands. MD of parotid glands and use of Cepharanthin were significantly related to more severe xerostomia by multivariate analysis with logistic regression. Cepharanthin may prevent radiation xerostomia after radiotherapy for head and neck cancer. (author)

On the Induced Gravitational Collapse

Directory of Open Access Journals (Sweden)

M. Becerra Laura

2018-01-01

Full Text Available The induced gravitational collapse (IGC paradigm has been applied to explain the long gamma ray burst (GRB associated with type Ic supernova, and recently the Xray flashes (XRFs. The progenitor is a binary systems of a carbon-oxygen core (CO and a neutron star (NS. The CO core collapses and undergoes a supernova explosion which triggers the hypercritical accretion onto the NS companion (up to 10-2 M⊙s-1. For the binary driven hypernova (BdHNe, the binary system is enough bound, the NS reach its critical mass, and collapse to a black hole (BH with a GRB emission characterized by an isotropic energy Eiso > 1052 erg. Otherwise, for binary systems with larger binary separations, the hypercritical accretion onto the NS is not sufficient to induced its gravitational collapse, a X-ray flash is produced with Eiso < 1052 erg. We’re going to focus in identify the binary parameters that limits the BdHNe systems with the XRFs systems.

Gravity induced wave function collapse

Science.gov (United States)

Gasbarri, G.; Toroš, M.; Donadi, S.; Bassi, A.

2017-11-01

Starting from an idea of S. L. Adler [in Quantum Nonlocality and Reality: 50 Years of Bell's Theorem, edited by M. Bell and S. Gao (Cambridge University Press, Cambridge, England 2016)], we develop a novel model of gravity induced spontaneous wave function collapse. The collapse is driven by complex stochastic fluctuations of the spacetime metric. After deriving the fundamental equations, we prove the collapse and amplification mechanism, the two most important features of a consistent collapse model. Under reasonable simplifying assumptions, we constrain the strength ξ of the complex metric fluctuations with available experimental data. We show that ξ ≥10-26 in order for the model to guarantee classicality of macro-objects, and at the same time ξ ≤10-20 in order not to contradict experimental evidence. As a comparison, in the recent discovery of gravitational waves in the frequency range 35 to 250 Hz, the (real) metric fluctuations reach a peak of ξ ˜10-21.

Nonlinear wave collapse and strong turbulence

International Nuclear Information System (INIS)

Robinson, P.A.

1997-01-01

The theory and applications of wave self-focusing, collapse, and strongly nonlinear wave turbulence are reviewed. In the last decade, the theory of these phenomena and experimental realizations have progressed rapidly. Various nonlinear wave systems are discussed, but the simplest case of collapse and strong turbulence of Langmuir waves in an unmagnetized plasma is primarily used in explaining the theory and illustrating the main ideas. First, an overview of the basic physics of linear waves and nonlinear wave-wave interactions is given from an introductory perspective. Wave-wave processes are then considered in more detail. Next, an introductory overview of the physics of wave collapse and strong turbulence is provided, followed by a more detailed theoretical treatment. Later sections cover numerical simulations of Langmuir collapse and strong turbulence and experimental applications to space, ionospheric, and laboratory plasmas, including laser-plasma and beam-plasma interactions. Generalizations to self-focusing, collapse, and strong turbulence of waves in other systems are also discussed, including nonlinear optics, solid-state systems, magnetized auroral and astrophysical plasmas, and deep-water waves. The review ends with a summary of the main ideas of wave collapse and strong-turbulence theory, a collection of open questions in the field, and a brief discussion of possible future research directions. copyright 1997 The American Physical Society

Constraints on cosmic strings due to black holes formed from collapsed cosmic string loops

International Nuclear Information System (INIS)

Caldwell, R.R.; Gates, E.

1993-05-01

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f, the fraction of cosmic string loops which collapse to form black holes, and μ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and μ is due to the energy density in 100MeV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict μ, and therefore limit the viability of the cosmic string large-scale structure scenario

Neutrinos and supernova collapse

International Nuclear Information System (INIS)

Colgate, S.A.; Petschek, A.G.

1980-01-01

The neutrino emission resulting from stellar collapse and supernova formation is reviewed. The electron capture and consequent neutronization of the collapsing stellar matter at the end of evolution determines both the initial adiabat of core collapse as well as the trapped lepton fraction. The initial lepton fraction, Y/sub l/ = .48 supplies the pressure for neutral support of the star at the Chandrasekhar limit. High trapping values, Y/sub l/ = .4, lead to soft core collapses; low values to harder collapses. The value of Y/sub l/ is presently in dispute. The neutrino emission from initial electron capture is relatively small. A strong core-bounce shock releases both electron neutrino as well as thermal muon and tau neutrinos. Subsequent neutrino emission and cooling can sometimes lead to an unstable buoyancy gradient in the core in which case unstable core overturn is expected. Calculations have already shown the importance of the largest possible eddy or equivalently the lowest mode of overturn. Present models of low lepton trapping ratio lead to high entropy creation by the reflected shock and the stabilization of the core matter against overturn. In such cases the exterior matter must cool below an entropy of approximately s/k approx. = 2 to become unstable. This may require too long a time approximately one second for neutrino cooling from a neutrinosphere at rho approx. = 2 x 10 12 g cm -3 . On the other hand, high values of Y/sub l/ such as .4 lead to softer bounces at lower density and values of the critical stabilizing entropy of 3 or higher. Under such circumstances, core overturn can still occur

Collapsing supra-massive magnetars: FRBs, the repeating FRB121102 and GRBs

Science.gov (United States)

Gupta, Patrick Das; Saini, Nidhi

2018-02-01

Fast Radio Bursts (FRBs) last for ˜ few milli-seconds and, hence, are likely to arise from the gravitational collapse of supra-massive, spinning neutron stars after they lose the centrifugal support (Falcke & Rezzolla 2014). In this paper, we provide arguments to show that the repeating burst, FRB 121102, can also be modeled in the collapse framework provided the supra-massive object implodes either into a Kerr black hole surrounded by highly magnetized plasma or into a strange quark star. Since the estimated rates of FRBs and SN Ib/c are comparable, we put forward a common progenitor scenario for FRBs and long GRBs in which only those compact remnants entail prompt γ -emission whose kick velocities are almost aligned or anti-aligned with the stellar spin axes. In such a scenario, emission of detectable gravitational radiation and, possibly, of neutrinos are expected to occur during the SN Ib/c explosion as well as, later, at the time of magnetar implosion.

Gravitational wave extraction in simulations of rotating stellar core collapse

International Nuclear Information System (INIS)

Reisswig, C.; Ott, C. D.; Sperhake, U.; Schnetter, E.

2011-01-01

We perform simulations of general relativistic rotating stellar core collapse and compute the gravitational waves (GWs) emitted in the core-bounce phase of three representative models via multiple techniques. The simplest technique, the quadrupole formula (QF), estimates the GW content in the spacetime from the mass-quadrupole tensor only. It is strictly valid only in the weak-field and slow-motion approximation. For the first time, we apply GW extraction methods in core collapse that are fully curvature based and valid for strongly radiating and highly relativistic sources. These techniques are not restricted to weak-field and slow-motion assumptions. We employ three extraction methods computing (i) the Newman-Penrose (NP) scalar Ψ 4 , (ii) Regge-Wheeler-Zerilli-Moncrief master functions, and (iii) Cauchy-characteristic extraction (CCE) allowing for the extraction of GWs at future null infinity, where the spacetime is asymptotically flat and the GW content is unambiguously defined. The latter technique is the only one not suffering from residual gauge and finite-radius effects. All curvature-based methods suffer from strong nonlinear drifts. We employ the fixed-frequency integration technique as a high-pass waveform filter. Using the CCE results as a benchmark, we find that finite-radius NP extraction yields results that agree nearly perfectly in phase, but differ in amplitude by ∼1%-7% at core bounce, depending on the model. Regge-Wheeler-Zerilli-Moncrief waveforms, while, in general, agreeing in phase, contain spurious high-frequency noise of comparable amplitudes to those of the relatively weak GWs emitted in core collapse. We also find remarkably good agreement of the waveforms obtained from the QF with those obtained from CCE. The results from QF agree very well in phase and systematically underpredict peak amplitudes by ∼5%-11%, which is comparable to the NP results and is certainly within the uncertainties associated with core collapse physics.

Interiors of Vaidya's radiating metric: Gravitational collapse

International Nuclear Information System (INIS)

Fayos, F.; Jaen, X.; Llanta, E.; Senovilla, J.M.M.

1992-01-01

Using the Darmois junction conditions, we give the necessary and sufficient conditions for the matching of a general spherically symmetric metric to a Vaidya radiating solution. We present also these conditions in terms of the physical quantities of the corresponding energy-momentum tensors. The physical interpretation of the results and their possible applications are studied, and we also perform a detailed analysis of previous work on the subject by other authors

Karst collapse in cities and mining areas, China

International Nuclear Information System (INIS)

Jian Chen

1988-01-01

Karst collapse is a dynamic geological phenomenon, in which the rock mass or deposits overlying the karstified zone subsides down along the karst cavity, resulting in a collapse pit or sinkhole. After discussing the typical examples of collapse emerging in the karst cities and mines in provinces and regions of South China, such as Guangdong, Guangxi, Hunan, Hubei, Zhejiang, Yunnan, Guizhou, and Jiangxi, it is considered that human activities of economy and production have become a major effect in causing karst collapse. Man-made collapses make 66.4 percent of the total, whereas natural ones 33.6 percent. Most of the collapses occurred to the area with soil overburden (96.7 percent), only a few in areas of bedrock overburden (3.3 percent). The karst collapses have a close relationship with the extent of karst development, the character and the thickness of overburden, and the dynamic condition of underground water. Collapse usually occurs in those parts of an area that are more intensely karstified, with soil thickness less than 5 m and a high amplitude of water table fluctuation. Many kinds of mechanical effects are caused by pumping or draining on the over-burden and destroying its equilibrium, leading to the collapse. These effects included the support loss and load-added effect, penetrating suffusion, gas explosion, water-hammer, suction pressure erosion, and liquefaction effects. The collapses are the result of varied comprehensive effects, particularly the support loss and load-added, and penetrating suffusion

The law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1977-01-01

Based on the gist of the Atomic Energy Basic Law (Law No. 186, 1955), this Law regulates the use, sale, disposal and other handling of radioactive isotopes, use of radiation-generating apparatuses, disposal and other handling of matters contaminated by radioactive isotopes, thereby aims at the prevention of radiation injuries and securing the safety of the public. The radioactive isotopes referred to in this Law are the isotopes emitting radiation such as phosphorus-32 and cobalt-60, their compounds, and those containing such isotopes and compounds. The radiation-generating apparatuses referred to in this Law are the apparatuses generating radiation by accelerating charged particles such as cyclotron and synchrotron. Those who want to use the radioactive isotopes and radiation-generating apparatuses must file applications and obtain approval of the Director of the Science and Technology Agency. Those who want to use sealed radioactive isotopes of the amount less than that stipulated by the Cabinet Order, those who want to sell and those who want to dispose of radioactive isotopes or matters contaiminated thereby as occupation should file notices and obtain approval of the Director of the Science and Technology Agency. Said Director should not approve such notices unless they meet the required specification, and when he approves such notices, he issues licenses. (Rikitake, Y.)

Behavior of wet precast beam column connections under progressive collapse scenario: an experimental study

Science.gov (United States)

Nimse, Rohit B.; Joshi, Digesh D.; Patel, Paresh V.

2014-12-01

Progressive collapse denotes a failure of a major portion of a structure that has been initiated by failure of a relatively small part of the structure such as failure of any vertical load carrying element (typically columns). Failure of large part of any structure will results into substantial loss of human lives and natural resources. Therefore, it is important to prevent progressive collapse which is also known as disproportionate collapse. Nowadays, there is an increasing trend toward construction of buildings using precast concrete. In precast concrete construction, all the components of structures are produced in controlled environment and they are being transported to the site. At site such individual components are connected appropriately. Connections are the most critical elements of any precast structure, because in past major collapse of precast structure took place because of connection failure. In this study, behavior of three different 1/3rd scaled wet precast beam column connections under progressive collapse scenario are studied and its performance is compared with monolithic connection. Precast connections are constructed by adopting different connection detailing at the junction by considering reinforced concrete corbel for two specimens and steel billet for one specimen. Performance of specimen is evaluated on the basis of ultimate load carrying capacity, maximum deflection and deflection measured along the span of the beam. From the results, it is observed that load carrying capacity and ductility of precast connections considered in this study are more than that of monolithic connections.

Neutrinos from gravitational collapse

International Nuclear Information System (INIS)

Mayle, R.; Wilson, J.R.; Schramm, D.N.

1986-05-01

Detailed calculations are made of the neutrino spectra emitted during gravitational collapse events (Type II supernovae). Those aspects of the neutrino signal which are relatively independent of the collapse model and those aspects which are sensitive to model details are discussed. The easier-to-detect high energy tail of the emitted neutrinos has been calculated using the Boltzmann equation which is compared with the result of the traditional multi-group flux limited diffusion calculations. 8 figs., 28 refs

Developing empirical collapse fragility functions for global building types

Science.gov (United States)

Jaiswal, K.; Wald, D.; D'Ayala, D.

2011-01-01

Building collapse is the dominant cause of casualties during earthquakes. In order to better predict human fatalities, the U.S. Geological Survey’s Prompt Assessment of Global Earthquakes for Response (PAGER) program requires collapse fragility functions for global building types. The collapse fragility is expressed as the probability of collapse at discrete levels of the input hazard defined in terms of macroseismic intensity. This article provides a simple procedure for quantifying collapse fragility using vulnerability criteria based on the European Macroseismic Scale (1998) for selected European building types. In addition, the collapse fragility functions are developed for global building types by fitting the beta distribution to the multiple experts’ estimates for the same building type (obtained from EERI’s World Housing Encyclopedia (WHE)-PAGER survey). Finally, using the collapse probability distributions at each shaking intensity level as a prior and field-based collapse-rate observations as likelihood, it is possible to update the collapse fragility functions for global building types using the Bayesian procedure.

Diversity loss with persistent human disturbance increases vulnerability to ecosystem collapse.

Science.gov (United States)

MacDougall, A S; McCann, K S; Gellner, G; Turkington, R

2013-02-07

Long-term and persistent human disturbances have simultaneously altered the stability and diversity of ecological systems, with disturbances directly reducing functional attributes such as invasion resistance, while eliminating the buffering effects of high species diversity. Theory predicts that this combination of environmental change and diversity loss increases the risk of abrupt and potentially irreversible ecosystem collapse, but long-term empirical evidence from natural systems is lacking. Here we demonstrate this relationship in a degraded but species-rich pyrogenic grassland in which the combined effects of fire suppression, invasion and trophic collapse have created a species-poor grassland that is highly productive, resilient to yearly climatic fluctuations, and resistant to invasion, but vulnerable to rapid collapse after the re-introduction of fire. We initially show how human disturbance has created a negative relationship between diversity and function, contrary to theoretical predictions. Fire prevention since the mid-nineteenth century is associated with the loss of plant species but it has stabilized high-yield annual production and invasion resistance, comparable to a managed high-yield low-diversity agricultural system. In managing for fire suppression, however, a hidden vulnerability to sudden environmental change emerges that is explained by the elimination of the buffering effects of high species diversity. With the re-introduction of fire, grasslands only persist in areas with remnant concentrations of native species, in which a range of rare and mostly functionally redundant plants proliferate after burning and prevent extensive invasion including a rapid conversion towards woodland. This research shows how biodiversity can be crucial for ecosystem stability despite appearing functionally insignificant beforehand, a relationship probably applicable to many ecosystems given the globally prevalent combination of intensive long-term land

FINDING THE FIRST COSMIC EXPLOSIONS. II. CORE-COLLAPSE SUPERNOVAE

International Nuclear Information System (INIS)

Whalen, Daniel J.; Joggerst, Candace C.; Fryer, Chris L.; Stiavelli, Massimo; Heger, Alexander; Holz, Daniel E.

2013-01-01

Understanding the properties of Population III (Pop III) stars is prerequisite to elucidating the nature of primeval galaxies, the chemical enrichment and reionization of the early intergalactic medium, and the origin of supermassive black holes. While the primordial initial mass function (IMF) remains unknown, recent evidence from numerical simulations and stellar archaeology suggests that some Pop III stars may have had lower masses than previously thought, 15-50 M ☉ in addition to 50-500 M ☉ . The detection of Pop III supernovae (SNe) by JWST, WFIRST, or the TMT could directly probe the primordial IMF for the first time. We present numerical simulations of 15-40 M ☉ Pop III core-collapse SNe performed with the Los Alamos radiation hydrodynamics code RAGE. We find that they will be visible in the earliest galaxies out to z ∼ 10-15, tracing their star formation rates and in some cases revealing their positions on the sky. Since the central engines of Pop III and solar-metallicity core-collapse SNe are quite similar, future detection of any Type II SNe by next-generation NIR instruments will in general be limited to this epoch.

Four tails problems for dynamical collapse theories

Science.gov (United States)

McQueen, Kelvin J.

2015-02-01

The primary quantum mechanical equation of motion entails that measurements typically do not have determinate outcomes, but result in superpositions of all possible outcomes. Dynamical collapse theories (e.g. GRW) supplement this equation with a stochastic Gaussian collapse function, intended to collapse the superposition of outcomes into one outcome. But the Gaussian collapses are imperfect in a way that leaves the superpositions intact. This is the tails problem. There are several ways of making this problem more precise. But many authors dismiss the problem without considering the more severe formulations. Here I distinguish four distinct tails problems. The first (bare tails problem) and second (structured tails problem) exist in the literature. I argue that while the first is a pseudo-problem, the second has not been adequately addressed. The third (multiverse tails problem) reformulates the second to account for recently discovered dynamical consequences of collapse. Finally the fourth (tails problem dilemma) shows that solving the third by replacing the Gaussian with a non-Gaussian collapse function introduces new conflict with relativity theory.

Radiating axisymmetric metric

International Nuclear Information System (INIS)

Patel, M.D.

1978-01-01

The Einstein's field equations for an enveloping radiating zone surrounding rotating axisymmetric collapsing source are studied. The solution has singularity along the axis of rotation. It is proved that on null hyper surface u = 0, the solution of the field equation for the radiating zone match with solution of axially symmetric vacuum field equations obtained by the author. Landau Lifshitz complex is used to obtain conserved total mass. (author)

Collapse of radiating fluid spheres and cosmic censorship

International Nuclear Information System (INIS)

Unruh, W.G.

1985-01-01

The radiating-fluid-sphere model studied by Lake and Hellaby is reanalyzed to show that flat spacetime is a valid C 1 extension to their model and thus it does not force a violation of strong cosmic censorship

Probability Assessment and Risk Management of Progressive Collapse in Strategic Buildings Facing Blast Loads

Directory of Open Access Journals (Sweden)

Gholamreza Abdollahzadeh

2016-12-01

Full Text Available Nowadays, as a result of increased terrorist and bomb attacks throughout the globe in the vicinity of strategic buildings, designing these structures against impact loads, particularly the blast-related ones, has been taken into more consideration. The current procedure for designing the structure against an explosion is a design against the local failure of the current elements in the first step and then, in the next step, against local damage as well as tactful thinking to prevent this damage from spreading to other parts of the structure. The present research investigates the impacts of explosives, derived from probable terror–stricken scenarios inside and outside a strategic four-story steel building with a special moment frame system. Then, the resistive capacity of the damaged building (due to blast has been evaluated against the progressive collapse, and finally, the rate of the collapse risk and the reliability of the structure have been obtained by presenting a probable method. Thus, the vulnerable parts inside and outside the building are identified and safety measures have been determined, so that in case of no safety or excessive collapse risk- access to dangerous parts of the building could be reinforced or limited. Results show that progressive collapse probability and reliability of the building are 57% and 43% respectively.

The collapse of interstellar gas clouds

International Nuclear Information System (INIS)

McNally, D.; Settle, J.J.

1980-01-01

The stability of spherically symmetric free-fall collapse to small radial perturbations is examined for non-uniform clouds. It is concluded that fragmentation of the central region of a collapsing gas cloud is possible if: (a) the density distribution is sufficiently smooth; and (b) the collapse is nearly free fall. Generally, perturbations enjoy only finite amplification during the collapse, and the amplification tends to decrease with increasing distance from the centre of the cloud. Unlimited amplification occurs only for uniform density clouds. Fragmentation is therefore unlikely to result from dynamical instability in the outer parts of a non-uniform cloud. Isothermal clouds are also briefly considered and, while it is argued that an earlier suggestion of their instability to fragmentation is unfounded, no general conclusion on the instability of such clouds could be drawn. (author)

Collapse of nonlinear Langmuir waves

International Nuclear Information System (INIS)

Malkin, V.M.

1986-01-01

The dispersion of sufficiently intensive Langmuir waves is determined by intrinsic (electron) nonlinearity. During Langmuir collapse the wave energy density required for the appearance of electron nonlinearity is attained, generally speaking, prior to the development of dissipative processes. Up to now, the effect of electron nonlinearity on the collapse dynamics and spectrum of strong Langmuir turbulence ( which may be very appreciable ) has not been studied extensively because of the difficulty of describing nonlinear Langmuir waves. In the present paper the positive determinacy of the electron nonlinear hamiltonian is proven, the increment of modulation instability of a nonlinear Langmuir wave cluster localized in a cavity is calculated, and the universal law of their collapse is found

Magnetized hypermassive neutron-star collapse: a central engine for short gamma-ray bursts.

Science.gov (United States)

Shibata, Masaru; Duez, Matthew D; Liu, Yuk Tung; Shapiro, Stuart L; Stephens, Branson C

2006-01-27

A hypermassive neutron star (HMNS) is a possible transient formed after the merger of a neutron-star binary. In the latest axisymmetric magnetohydrodynamic simulations in full general relativity, we find that a magnetized HMNS undergoes "delayed" collapse to a rotating black hole (BH) as a result of angular momentum transport via magnetic braking and the magnetorotational instability. The outcome is a BH surrounded by a massive, hot torus with a collimated magnetic field. The torus accretes onto the BH at a quasisteady accretion rate [FORMULA: SEE TEXT]; the lifetime of the torus is approximately 10 ms. The torus has a temperature [FORMULA: SEE TEXT], leading to copious ([FORMULA: SEE TEXT]) thermal radiation that could trigger a fireball. Therefore, the collapse of a HMNS is a promising scenario for generating short-duration gamma-ray bursts and an accompanying burst of gravitational waves and neutrinos.

Six collapses

International Nuclear Information System (INIS)

Miller, R.H.; Smith, B.F.

1979-01-01

The self-consistent dynamical development of six stellar systems, started from rotating spherical configurations, has been studied by means of a fully three-dimensional n-body integration. The six examples had different initial angular velocities and velocity dispersions. All settled down into prolate bars rotating about a short axis within two initial rotation periods. The bars are long-lived, robust, and stable. Bars are the natural form toward which rapidly rotating stellar dynamical systems develop, instead of the flattened axisymmetric disks that had been expected.The early stages of each collapse are reasonably well described by a theoretical model according to which a collapse passes through a sequence of rigidly rotating, uniform-density spheroids. The first significant departures from spheroidal form were axisymmetric in all cases. Rings formed in some examples, sheets in others, with transition cases between these extremes. Nonaxisymmetry forms developed from these intermediate stages

Numerical studies of rotational core collapse in axisymmetry using the conformally flat metric approach

International Nuclear Information System (INIS)

Dimmelmeier, H.; Font, J.A.; Mueller, E.

2001-01-01

The numerical simulation of hydrodynamic processes in general relativity is a highly complex problem. In order to reduce the complexity of the gravitational field equations, Wilson and coworkers have proposed an approximation scheme, where the 3-metric γ ij is chosen to be conformally flat. In this approximation the Einstein equations reduce to a set of 5 coupled elliptic equations. In this paper we present an axisymmetric general relativistic hydrodynamic code which utilizes this approach together with high-resolution shock-capturing schemes to solve the hydrodynamic equations. We report on tests and preliminary applications of the code to rotating neutron stars and supernova core collapse in axisymmetry. The code promises good applicability to handle a variety of relativistic astrophysical situations, and is prepared to provide information about gravitational radiation from rotating gravitational collapse. (author)

Dynamic Control of Collapse in a Vortex Airy Beam

Science.gov (United States)

Chen, Rui-Pin; Chew, Khian-Hooi; He, Sailing

2013-01-01

Here we study systematically the self-focusing dynamics and collapse of vortex Airy optical beams in a Kerr medium. The collapse is suppressed compared to a non-vortex Airy beam in a Kerr medium due to the existence of vortex fields. The locations of collapse depend sensitively on the initial power, vortex order, and modulation parameters. The collapse may occur in a position where the initial field is nearly zero, while no collapse appears in the region where the initial field is mainly distributed. Compared with a non-vortex Airy beam, the collapse of a vortex Airy beam can occur at a position away from the area of the initial field distribution. Our study shows the possibility of controlling and manipulating the collapse, especially the precise position of collapse, by purposely choosing appropriate initial power, vortex order or modulation parameters of a vortex Airy beam. PMID:23518858

Interventions to prevent skin cancer by reducing exposure to ultraviolet radiation: a systematic review.

Science.gov (United States)

Saraiya, Mona; Glanz, Karen; Briss, Peter A; Nichols, Phyllis; White, Cornelia; Das, Debjani; Smith, S Jay; Tannor, Bernice; Hutchinson, Angela B; Wilson, Katherine M; Gandhi, Nisha; Lee, Nancy C; Rimer, Barbara; Coates, Ralph C; Kerner, Jon F; Hiatt, Robert A; Buffler, Patricia; Rochester, Phyllis

2004-12-01

The relationship between skin cancer and ultraviolet radiation is well established. Behaviors such as seeking shade, avoiding sun exposure during peak hours of radiation, wearing protective clothing, or some combination of these behaviors can provide protection. Sunscreen use alone is not considered an adequate protection against ultraviolet radiation. This report presents the results of systematic reviews of effectiveness, applicability, other harms or benefits, economic evaluations, and barriers to use of selected interventions to prevent skin cancer by reducing exposure to ultraviolet radiation. The Task Force on Community Preventive Services found that education and policy approaches to increasing sun-protective behaviors were effective when implemented in primary schools and in recreational or tourism settings, but found insufficient evidence to determine effectiveness when implemented in other settings, such as child care centers, secondary schools and colleges, and occupational settings. They also found insufficient evidence to determine the effectiveness of interventions oriented to healthcare settings and providers, media campaigns alone, interventions oriented to parents or caregivers of children, and community-wide multicomponent interventions. The report also provides suggestions for areas for future research.

Sharper criteria for the wave collapse

DEFF Research Database (Denmark)

Kuznetsov, E.A.; Juul Rasmussen, J.; Rypdal, K.

1995-01-01

Sharper criteria for three-dimensional wave collapse described by the Nonlinear Schrodinger Equation (NLSE) are derived. The collapse threshold corresponds to the ground state soliton which is known to be unstable. Thus, for nonprefocusing distributions this represents the separatrix between...

Collapsing dynamics of attractive Bose-Einstein condensates

DEFF Research Database (Denmark)

Bergé, L.; Juul Rasmussen, J.

2002-01-01

The self-similar collapse of 3D and quasi-2D atom condensates with negative scattering length is examined. 3D condensates are shown to blow up following the scenario of weak collapse, for which 3-body recombination weakly dissipates the atoms. In contrast, 2D condensates undergo a strong collapse......, that absorbs a significant amount of particles. (C) 2002 Elsevier Science B.V. All rights reserved....

Experimental study of the preventional effects of drugs to lung radiation damage

Energy Technology Data Exchange (ETDEWEB)

Tomita, N [Kurume Univ., Fukuoka (Japan). School of Medicine

1977-01-01

The author experimented on effects of Cepharanthin (CR) and Urokinase (UK) on the lung of rabbits to which /sup 60/Co was irradiated by dividing a total dose of 10,000R into 500R a day. The rabbits irradiated were divided into 3 groups: a group administered ''CR'' (Group A), a group administered ''UK'' (Group B) and a control group (Group C). Body weight, leukocytes and chest x-ray findings were examined, and macroscopic and microscopic findings were discussed immediately and 3 months after irradiation. CR was effective in preventing the decrease of leukocytes and body weight. In the case of 5000R irradiation, an abnormal shadow was not recognized, but in the case of 10,000R irradiation, radiation pneumonitis began to appear immediately after the irradiation, and heart dilation and the shift of mediastinum on the side of irradiation were observed 3 months after that. In Group C, adhesion, hydropericardium and bleeding lesion were observed. In Groups A and B, the preventive effects were noted macroscopically. Group A seemed to show more significant results. In this group, the infiltration of the cells, and the appearance of foamy cells and eosinophyl cells which are characteristic of lung radiation disease were less observed than those in the other groups, and therefore, Group A showed more preventive effect upon inflammation than the other groups. In Group B, the thickness of the wall of the blood vessel tended to be improved 3 months after irradiation. Microthrombosis was not recognized, either. From these results, CR was effective in decreasing the infiltration of the cells, and UK was effective in decreasing the thickness of the wall of the blood vessel and in forming thromboses. Thus, these drugs should be used simultaneously because they had different reaction to the prevention of lung radiation disease.

Finite element analysis of the collapse and post-collapse behavior of steel pipes applications to the oil industry

CERN Document Server

Dvorkin, Eduardo N

2013-01-01

This book presents a detailed discussion of the models that were developed to simulate the collapse and post-collapse behavior of steel pipes. The finite element method offers to engineers the possibility of developing models to simulate the collapse behavior of casings inside oil wells and the collapse behavior of deepwater pipelines. However, if technological decisions are going to be reached from these model results, with implications for the economic success of industrial operations, for the occupational safety and health and for the environment, the engineering models need to be highly reliable. Using these models engineers can quantify the effect of manufacturing tolerances, wear, corrosion, etc. This book describes in great details the experimental programs that are developed to validate the numerical results.

Initial non-weight-bearing therapy is important for preventing vertebral body collapse in elderly patients with clinical vertebral fractures

Directory of Open Access Journals (Sweden)

Kishikawa Y

2012-04-01

group.Conclusion: These results suggest that initial non-weight-bearing therapy is important for preventing vertebral body collapse and for relieving pain among elderly patients with clinical vertebral fractures.Keywords: clinical vertebral fracture, non-weight-bearing, brace, osteoporosis

Collapse of Electrostatic Waves in Magnetoplasmas

DEFF Research Database (Denmark)

Shukla, P. K.; Yu, M. Y.; Juul Rasmussen, Jens

1984-01-01

The two-fluid model is employed to investigate the collapse of electrostatic waves in magnetized plasmas. It is found that nonlinear interaction of ion cyclotron, upper-, and lower-hybrid waves with adiabatic particle motion along the external magnetic field can cause wave-field collapse....

Revise of the law concerning prevention from radiation hazards due to radioisotopes, etc

International Nuclear Information System (INIS)

Sakamoto, Yoshiaki; Sendo, Muneaki

2004-01-01

The Law Concerning Prevention from Radiation Hazards due to Radioisotopes, etc. was revised in 2004. The regulation about disposal of RI waste was fixed at this revise of the law. Regulation of an application about the disposal of the RI waste was added to former radioactive waste control business. And regulation of confirmation of waste disposal by a regulation body was added. By this law revision, a necessary system for the RI waste disposal is ready. Furthermore, the Basic Safety Standard (BSS) and the following rationalization of related to regulation were introduced into the Law Concerning Prevention from Radiation Hazards due to Radioisotopes, etc. by this law revision. The regulation for a handling of radionuclides will be changed a lot due to the introduction of the BSS. (author)

Contagious cooperation, temptation, and ecosystem collapse

NARCIS (Netherlands)

Richter, A.; van Soest, D.P.; Grasman, J.

2013-01-01

Real world observations suggest that social norms of cooperation can be effective in overcoming social dilemmas such as the joint management of a common pool resource—but also that they can be subject to slow erosion and sudden collapse. We show that these patterns of erosion and collapse emerge

How summit calderas collapse on basaltic volcanoes: new insights from the April 2007 caldera collapse of Piton de la Fournaise volcano

Energy Technology Data Exchange (ETDEWEB)

Michon, Laurent; Catry, Thibault; Merle, Olivier [Laboratoire GeoSciences Reunion, Universite de la Reunion, Institut de Physique du Globe de Paris, CNRS, UMR 7154 - Geologie des Systemes Volcaniques, 15 avenue Rene Cassin, 97715 Saint Denis (France); Villeneuve, Nicolas [Institut de Recherche pour le Developpement, US 140, BP172, 97492 Sainte-Clotilde cedex (France)], E-mail: laurent.michon@univ-reunion.fr

2008-10-01

In April 2007, Piton de la Fournaise volcano experienced a caldera collapse during its largest historical eruption. We present here the resulting deformation and a synthesis of the seismicity recorded during recent caldera collapses. It allows us to propose a unifying mechanism that explains the pulsating collapse dynamics.

HIERARCHICAL GRAVITATIONAL FRAGMENTATION. I. COLLAPSING CORES WITHIN COLLAPSING CLOUDS

Energy Technology Data Exchange (ETDEWEB)

Naranjo-Romero, Raúl; Vázquez-Semadeni, Enrique; Loughnane, Robert M. [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 3-72, Morelia, Michoacán, 58089, México (Mexico)

2015-11-20

We investigate the Hierarchical Gravitational Fragmentation scenario through numerical simulations of the prestellar stages of the collapse of a marginally gravitationally unstable isothermal sphere immersed in a strongly gravitationally unstable, uniform background medium. The core developes a Bonnor–Ebert (BE)-like density profile, while at the time of singularity (the protostar) formation the envelope approaches a singular-isothermal-sphere (SIS)-like r{sup −2} density profile. However, these structures are never hydrostatic. In this case, the central flat region is characterized by an infall speed, while the envelope is characterized by a uniform speed. This implies that the hydrostatic SIS initial condition leading to Shu's classical inside-out solution is not expected to occur, and therefore neither should the inside-out solution. Instead, the solution collapses from the outside-in, naturally explaining the observation of extended infall velocities. The core, defined by the radius at which it merges with the background, has a time-variable mass, and evolves along the locus of the ensemble of observed prestellar cores in a plot of M/M{sub BE} versus M, where M is the core's mass and M{sub BE} is the critical BE mass, spanning the range from the “stable” to the “unstable” regimes, even though it is collapsing at all times. We conclude that the presence of an unstable background allows a core to evolve dynamically from the time when it first appears, even when it resembles a pressure-confined, stable BE-sphere. The core can be thought of as a ram-pressure confined BE-sphere, with an increasing mass due to the accretion from the unstable background.

Timescales of isotropic and anisotropic cluster collapse

Science.gov (United States)

Bartelmann, M.; Ehlers, J.; Schneider, P.

1993-12-01

From a simple estimate for the formation time of galaxy clusters, Richstone et al. have recently concluded that the evidence for non-virialized structures in a large fraction of observed clusters points towards a high value for the cosmological density parameter Omega0. This conclusion was based on a study of the spherical collapse of density perturbations, assumed to follow a Gaussian probability distribution. In this paper, we extend their treatment in several respects: first, we argue that the collapse does not start from a comoving motion of the perturbation, but that the continuity equation requires an initial velocity perturbation directly related to the density perturbation. This requirement modifies the initial condition for the evolution equation and has the effect that the collapse proceeds faster than in the case where the initial velocity perturbation is set to zero; the timescale is reduced by a factor of up to approximately equal 0.5. Our results thus strengthens the conclusion of Richstone et al. for a high Omega0. In addition, we study the collapse of density fluctuations in the frame of the Zel'dovich approximation, using as starting condition the analytically known probability distribution of the eigenvalues of the deformation tensor, which depends only on the (Gaussian) width of the perturbation spectrum. Finally, we consider the anisotropic collapse of density perturbations dynamically, again with initial conditions drawn from the probability distribution of the deformation tensor. We find that in both cases of anisotropic collapse, in the Zel'dovich approximation and in the dynamical calculations, the resulting distribution of collapse times agrees remarkably well with the results from spherical collapse. We discuss this agreement and conclude that it is mainly due to the properties of the probability distribution for the eigenvalues of the Zel'dovich deformation tensor. Hence, the conclusions of Richstone et al. on the value of Omega0 can be

Thermal duality and gravitational collapse

International Nuclear Information System (INIS)

Hewitt, Michael

2015-01-01

Thermal duality is a relationship between the behaviour of heterotic string models of the E(8)×E(8) or SO(32) types at inversely related temperatures, a variant of T duality in the Euclidean regime. This duality would have consequences for the nature of the Hagedorn transition in these string models. We propose that the vacuum admits a family of deformations in situations where there are closed surfaces of constant area but high radial acceleration (a string regularized version of a Penrose trapped surface), such as would be formed in situations of extreme gravitational collapse. This would allow a radical resolution of the firewall paradox by allowing quantum effects to significantly modify the spacetime geometry around a collapsed object. A string bremsstrahlung process would convert the kinetic energy of infalling matter in extreme gravitational collapse to form a region of the deformed vacuum, which would be equivalent to forming a high temperature string phase. A heuristic criterion for the conversion process is presented, relating Newtonian gravity to the string tension, suggesting an upper limit to the strength of the gravitational interaction. This conversion process might have observable consequences for charged particles falling into a rotating collapsed object by producing high energy particles via a variant of the Penrose process. (paper)

Hydrogen-Poor Core-Collapse Supernovae

Science.gov (United States)

Pian, Elena; Mazzali, Paolo A.

Hydrogen-poor core-collapse supernovae (SNe) signal the explosive death of stars more massive than the progenitors of hydrogen-rich core-collapse supernovae, i.e., approximately in the range 15-50 M⊙ in main sequence. Since hydrogen-poor core-collapse supernovae include those that accompany gamma-ray bursts (GRBs), which were all rigorously identified with type Ic supernovae, their explosion energies cover almost two decades. The light curves and spectra are consequently very heterogeneous and often bear the signature of an asymmetric, i.e., aspherical, explosion. Asphericity is best traced by early-time (within days of the explosion) optical spectropolarimetry and by late-epoch (more than ˜ 100 days after explosion) low-resolution spectroscopy. While the relationship between hydrogen-poor core-collapse supernovae to hydrogen-poor super-luminous supernovae is not understood, a known case of association between an ultra-long gamma-ray burst and a very luminous hydrogen-poor supernova may help unraveling the connection. This is tantalizingly pointing to a magnetar powering source for both phenomena, although this scenario is still highly speculative. Host galaxies of hydrogen-poor supernovae are always star forming; in those of completely stripped supernovae and gamma-ray burst supernovae, the spatial distribution of the explosions follows the blue/ultraviolet light, with a correlation that is more than linear.

Understanding Core-Collapse Supernovae

Science.gov (United States)

Hix, W. R.; Lentz, E. J.; Baird, M.; Messer, O. E. B.; Mezzacappa, A.; Lee, C.-T.; Bruenn, S. W.; Blondin, J. M.; Marronetti, P.

2010-03-01

Our understanding of core-collapse supernovae continues to improve as better microphysics is included in increasingly realistic neutrino-radiationhydrodynamic simulations. Recent multi-dimensional models with spectral neutrino transport, which slowly develop successful explosions for a range of progenitors between 12 and 25 solar mass, have motivated changes in our understanding of the neutrino reheating mechanism. In a similar fashion, improvements in nuclear physics, most notably explorations of weak interactions on nuclei and the nuclear equation of state, continue to refine our understanding of how supernovae explode. Recent progresses on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

Shock-induced nanobubble collapse and its applications

Science.gov (United States)

Vedadi, Mohammad Hossein

The shock-induced collapse of nanobubbles in water is investigated using molecular dynamics simulations based on a reactive force field. Monitoring the collapse of a cavitation nanobubble, we observe a focused nanojet at the onset of bubble shrinkage and a water hammer shock wave upon bubble collapse. The nanojet length scales linearly with the nanobubble radius, as observed in experiments on micron-to-millimeter size bubbles. The shock induces dramatic structural changes, including an ice-VII-like structural motif at a particle velocity of approximately 1 km/s. The incipient ice VII formation and the calculated Hugoniot curve are in good agreement with experimental results. Moreover, a substantial number of positive and negative ions appear when the nanojet hits the distal side of the nanobubble and the water hammer shock forms. Furthermore, two promising applications of shock-induced nanobubble collapse have been explored. Our simulations of poration in lipid bilayers due to shock-induced collapse of nanobubbles reveal penetration of nanojets into lipid bilayers. The nanojet impact generates shear flow of water on bilayer leaflets and pressure gradients across them, which transiently enhance the bilayer permeability by creating nanopores through which water molecules translocate across the bilayer. The effects of nanobubble size and temperature on the porosity of lipid bilayers are examined. Finally, the shock-induced collapse of CO2-filled nanobubbles in water is investigated. The energetic nanojet and high-pressure water hammer shock formed during and after collapse of the nanobubble trigger mechano-chemical H2O-CO2 reactions, some of which lead to splitting of water molecules. The dominant pathways through which splitting of water molecules occur are identified.

Pretreatment with ascorbic acid prevents lethal gastrointestinal syndrome in mice receiving a massive amount of radiation

International Nuclear Information System (INIS)

Yamamoto, Tetsuo; Kinoshita, Manabu; Shinomiya, Nariyoshi; Hiroi, Sadayuki; Sugasawa, Hidekazu; Majima, Takashi; Seki, Shuhji; Matsushita, Yoshitaro; Saitoh, Daizoh

2010-01-01

While bone marrow or stem cell transplantation can rescue bone marrow aplasia in patients accidentally exposed to a lethal radiation dose, radiation-induced irreversible gastrointestinal damage (GI syndrome) is fatal. We investigated the effects of ascorbic acid on radiation-induced GI syndrome in mice. Ascorbic acid (150 mg/kg/day) was orally administered to mice for 3 days, and then the mice underwent whole body irradiation (WBI). Bone marrow transplantation (BMT) 24 h after irradiation rescued mice receiving a WBI dose of less than 12 Gy. No mice receiving 14 Gy-WBI survived, because of radiation-induced GI syndrome, even if they received BMT. However, pretreatment with ascorbic acid significantly suppressed radiation-induced DNA damage in the crypt cells and prevented denudation of intestinal mucosa; therefore, ascorbic acid in combination with BMT rescued mice after 14 Gy-WBI. DNA microarray analysis demonstrated that irradiation up-regulated expressions of apoptosis-related genes in the small intestine, including those related to the caspase-9-mediated intrinsic pathway as well as the caspase-8-mediated extrinsic pathway, and down-regulated expressions of these genes in ascorbic acid-pretreated mice. Thus, pretreatment with ascorbic acid may effectively prevent radiation-induced GI syndrome. (author)

Collapse and stability of single- and multi-wall carbon nanotubes

International Nuclear Information System (INIS)

Xiao, J; Liu, B; Huang, Y; Zuo, J; Hwang, K-C; Yu, M-F

2007-01-01

The collapse and stability of carbon nanotubes (CNTs) have important implications for their synthesis and applications. While nanotube collapse has been observed experimentally, the conditions for the collapse, especially its dependence on tube structures, are not clear. We have studied the energetics of the collapse of single- and multi-wall CNTs via atomistic simulations. The collapse is governed by the number of walls and the radius of the inner-most wall. The collapsed structure is energetically favored about a certain diameter, which is 4.12, 4.96 and 5.76 nm for single-, double- and triple-wall CNTs, respectively. The CNT chirality also has a strong influence on the collapsed structure, leading to flat, warped and twisted CNTs, depending on the chiral angle

Mesoscopic states in graphene in magnetic field: collapse and revival of wave packets

International Nuclear Information System (INIS)

Demikhovskij, V.Ya.; Telezhnikov, A.V.; Frolova, E.V.; Kravets, N.A.

2013-01-01

The effects of wave packet collapse and revival in monolayer and bilayer graphene at an external perpendicular magnetic field are described. The evolution of electron wave packets, which are a superposition of the states with quantum numbers n around that of some Landau level n 0 was studied. The probability densities as well as average velocities of the packet center were calculated analytically and then visualized. The initial wave packet consisting only of positive energy decomposed into several subpackets at the moments t = (m/n)T R , where T R is the revival time and m, n are the mutually prime integers. Besides, it is shown that the behavior of a wave packet containing the states of both energy bands (with E n > 0 and E n < 0) is more complicated. Such packet splits into two parts, which rotate with a cyclotron frequency in the opposite directions, and then experience collapse and revival. The structure of multipole electromagnetic radiation of these packets is analyzed.

The order for enforcing the law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1977-01-01

The radioactive isotopes stipulated in Item 2, Article 2 of the Law Concerning Prevention from Radiation Hazards due to Radisotopes (hereinafter referred to as the Law) are the isotopes emitting radiation, their compounds, and those containing these isotopes or compounds. The radiation-generating apparatuses in Item 3, Article 2 of the Law are cyclotron, synchrotron, synchrocyclotron, linear accelerator, betatron, Van de Graaff accelerator, Cockcroft Walton accelerator, the apparatuses generating radiation by accelerating charged particles, which are designated by the Director of the Science and Technology Agency as necessary for preventing radiation injuries. Those who want to use, sell or dispose of radioactive isotopes should file applications for approval or notices with required documents. The approval should be obtained for each factory or place of business. The amount of completely sealed radioactive isotopes specified by the cabinet order stipulated in Item 1, Article 3-2 of the Law is 100 m curie per factory or place of business. Those who are going to change the approved items of the use, sale or disposal of radioactive isotopes should file applications. The amount of radioactive isotopes specified by the cabinet order stipulated in Item 5, Article 10 of the Law is 10 curies. Controlled areas, facilities for using, refilling, and storing isotopes, refilling and disposing wastes should meet the stipulated standards. (Rikitake, Y.)

The Role of Cerenkov Radiation in the Pressure Balance of Cool Core Clusters of Galaxies

Energy Technology Data Exchange (ETDEWEB)

Lieu, Richard [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States)

2017-03-20

Despite the substantial progress made recently in understanding the role of AGN feedback and associated non-thermal effects, the precise mechanism that prevents the core of some clusters of galaxies from collapsing catastrophically by radiative cooling remains unidentified. In this Letter, we demonstrate that the evolution of a cluster's cooling core, in terms of its density, temperature, and magnetic field strength, inevitably enables the plasma electrons there to quickly become Cerenkov loss dominated, with emission at the radio frequency of ≲350 Hz, and with a rate considerably exceeding free–free continuum and line emission. However, the same does not apply to the plasmas at the cluster's outskirts, which lacks such radiation. Owing to its low frequency, the radiation cannot escape, but because over the relevant scale size of a Cerenkov wavelength the energy of an electron in the gas cannot follow the Boltzmann distribution to the requisite precision to ensure reabsorption always occurs faster than stimulated emission, the emitting gas cools before it reheats. This leaves behind the radiation itself, trapped by the overlying reflective plasma, yet providing enough pressure to maintain quasi-hydrostatic equilibrium. The mass condensation then happens by Rayleigh–Taylor instability, at a rate determined by the outermost radius where Cerenkov radiation can occur. In this way, it is possible to estimate the rate at ≈2 M {sub ⊙} year{sup −1}, consistent with observational inference. Thus, the process appears to provide a natural solution to the longstanding problem of “cooling flow” in clusters; at least it offers another line of defense against cooling and collapse should gas heating by AGN feedback be inadequate in some clusters.

Nonlinear behavior of the radiative condensation instability

International Nuclear Information System (INIS)

McCarthy, D.; Drake, J.F.

1991-01-01

An investigation of the nonlinear behavior of the radiative condensation instability is presented in a simple one-dimensional magnetized plasma. It is shown that the radiative condensation is typically a nonlinear instability---the growth of the instability is stronger once the disturbance reaches finite amplitude. Moreover, classical parallel thermal conduction is insufficient by itself to saturate the instability. Radiative collapse continues until the temperature in the high density condensation falls sufficiently to reduce the radiation rate

Metric elasticity in a collapsing star: Gravitational radiation coupled to torsional motion

International Nuclear Information System (INIS)

Gerlach, U.H.; Scott, J.F.

1986-01-01

Torsional oscillatory matter motion as well as differential rotation couple via the linearized Einstein field equations to the gravitational degrees of freedom. For an arbitrary spherically symmetric background, such as that of a wildly pulsating or a catastrophically collapsing star, we exhibit (a) the strain tensor and (b) the corresponding stress-energy tensor. It is found that in the star there are two elasticity tensors. One expresses the familiar elasticity of matter, the other expresses the elasticity of the geometry. This metric elasticity is responsible for coupling the gravitational and matter degrees of freedom. The two coupled scalar wave equations for these degrees of freedom are exhibited. Also exhibited are their characteristics as well as the junction conditions for their solutions across any spherical surface of discontinuity

Collapse and revival in atom internal dynamics due to quantum translational motion

International Nuclear Information System (INIS)

Muradyan, A Zh; Muradyan, G A

2004-01-01

Interaction of a lossless two-level atom with a monochromatic (classical) field of radiation is considered, as the atom initially possesses a translational state with a number of equidistant and discrete momenta. It is shown that the Rabi oscillations in such an atom evolve as a sequence of collapses and revivals, if the coupling wave deeply saturates the optical transition. Between revivals, the populations undergo subrevivals. Approximate analytical formulae are obtained taking the initial momentum distribution in the form of two shifted Gaussians or a Besselian. A possible experimental realization of such revivals is discussed

The experimental study of the preventional effects of drugs to lung radiation damage

International Nuclear Information System (INIS)

Tomita, Naoaki

1977-01-01

The author experimented on effects of Cepharanthin (CR) and Urokinase (UK) on the lung of rabbits to which 60 Co was irradiated by dividing a total dose of 10,000R into 500R a day. The rabbits irradiated were divided into 3 groups: a group administered ''CR'' (Group A), a group administered ''UK'' (Group B) and a control group (Group C). Body weight, leukocytes and chest x-ray findings were examined, and macroscopic and microscopic findings were discussed immediately and 3 months after irradiation. CR was effective in preventing the decrease of leukocytes and body weight. In the case of 5000R irradiation, an abnormal shadow was not recognized, but in the case of 10,000R irradiation, radiation pneumonitis began to appear immediately after the irradiation, and heart dilation and the shift of mediastinum on the side of irradiation were observed 3 months after that. In Group C, adhesion, hydropericardium and bleeding lesion were observed. In Groups A and B, the preventive effects were noted macroscopically. Group A seemed to show more significant results. In this group, the infiltration of the cells, and the appearance of foamy cells and eosinophyl cells which are characteristic of lung radiation disease were less observed than those in the other groups, and therefore, Group A showed more preventive effect upon inflammation than the other groups. In Group B, the thickness of the wall of the blood vessel tended to be improved 3 months after irradiation. Microthrombosis was not recognized, either. From these results, CR was effective in decreasing the infiltration of the cells, and UK was effective in decreasing the thickness of the wall of the blood vessel and in forming thromboses. Thus, these drugs should be used simultaneously because they had different reaction to the prevention of lung radiation disease. (J.P.N.)

Field Experiment on Soaking Characteristics of Collapsible Loess

Directory of Open Access Journals (Sweden)

Zhichao Wang

2017-01-01

Full Text Available In collapsible loess area, migration of soil moisture often causes the temporal discontinuity and spatial nonuniformity of collapsibility, which leads to great damage for infrastructures. Therefore, the research on water infiltration is the key to solving the problem of collapsibility. The aim of this paper is to investigate the spatiotemporal evolution of infiltration characteristics of collapsible loess. A field soaking experiment was conducted on collapsible loess in western China, in which a soaking pool with diameter of 15 m was built. Time-Domain-Reflectometry (TDR system and soil sampling were employed to measure the water content within the depth of 12 m. Then the saturation isograms were drawn for visualization of the process of infiltration. Also, a pilot tunnel was excavated to investigate how the free face can affect the infiltration behaviors. The experimental results revealed the characteristics of infiltration in both horizontal and vertical directions. Moreover, the response of free face on infiltration behaviors was also found. These findings of research could provide the data for the infiltration laws of unsaturated loess and thereby provide the basis for integrated treatment of collapsible loess.

Correlated random walks induced by dynamical wavefunction collapse

Science.gov (United States)

Bedingham, Daniel

2015-03-01

Wavefunction collapse models modify Schrödinger's equation so that it describes the collapse of a superposition of macroscopically distinguishable states as a genuine physical process [PRA 42, 78 (1990)]. This provides a basis for the resolution of the quantum measurement problem. An additional generic consequence of the collapse mechanism is that it causes particles to exhibit a tiny random diffusive motion. Furthermore, the diffusions of two sufficiently nearby particles are positively correlated -- it is more likely that the particles diffuse in the same direction than would happen if they behaved independently [PRA 89, 032713 (2014)]. The use of this effect is proposed as an experimental test of wave function collapse models in which pairs of nanoparticles are simultaneously released from nearby traps and allowed a brief period of free fall. The random displacements of the particles are then measured. The experiment must be carried out at sufficiently low temperature and pressure for the collapse effects to dominate over the ambient environmental noise. It is argued that these constraints can be satisfied by current technologies for a large class of viable wavefunction collapse models. Work supported by the Templeton World Charity Foundation.

Cooperation, cheating, and collapse in biological populations

Science.gov (United States)

Gore, Jeff

2014-03-01

Natural populations can collapse suddenly in response to small changes in environmental conditions, and recovery from such a collapse can be difficult. We have used laboratory microbial ecosystems to directly measure theoretically proposed early warning signals of impending population collapse. Yeast cooperatively break down the sugar sucrose, meaning that below a critical size the population cannot sustain itself. We have demonstrated experimentally that changes in the fluctuations of the population size can serve as an early warning signal that the population is close to collapse. The cooperative nature of yeast growth on sucrose suggests that the population may be susceptible to ``cheater'' cells, which do not contribute to the public good and instead merely take advantage of the cooperative cells. We confirm this possibility experimentally and find that such social parasitism decreases the resilience of the population.

The onset of coherence collapse in DBR lasers

International Nuclear Information System (INIS)

Woodward, S.L.; Koch, T.L.; Koren, U.

1990-01-01

The authors investigate how the onset of coherence collapse depends on laser output power. The lasers were three-section multiquantum-well distributed-Bragg-reflector (MQW-DBR) lasers. The fraction of light reflected back into the lasing mode was varied, and the point at which the transition to coherence collapse occurred was measured. This feedback level varies approximately linearly with laser output power. For these lasers, when the output power is 1 mW, the transition to coherence collapse beings when the optical feedback into the lasing mode is below - 40 dBm; when the feedback power is - 35 dBm the laser line is completely collapsed

Homoclinic phenomena in the gravitational collapse

International Nuclear Information System (INIS)

Koiller, J.; Mello Neto, J.R.T. de; Soares, I.D.

1984-01-01

A class of Bianchi IX cosmological models is shown to have chaotic gravitational collapse, due to Poincare's homoclinic phenomena. Such models can be programmed so that for any given positive integer N (N=infinity included) the universe undergoes N non-periodic oscillations (each oscillation requiring a long time) before collapsing. For N=infinity the universe undergoes periodic oscillations. (Author) [pt

Non explosive collapse of white dwarfs

International Nuclear Information System (INIS)

Canal, R.; Schatzmann, E.

1976-01-01

We show that if a sufficiently cold carbon-oxygen white dwarf, close to the critical mass, accretes matter from a companion in a binary system, the time scale of collapse is long enough to allow neutronization before the onset of pycnonuclear reactions. This can possibly lead to the formation of X-ray sources by a non explosive collapse. (orig.) [de

The regulations for enforcing the law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1979-01-01

The regulations are wholly revised under the law concerning prevention from radiation hazards due to radioisotopes and the provisions of the order for enforcing the law. Basic concepts and terms are defined, such as: employee engaged in radiation work; person regularly entering into the controlled area; the maximum permissible exposure dose; accumulative dose; the maximum permissible accumulative dose; the maximum permissible concentration in the air; the maximum permissible concentration under water; the maximum permissible surface density. The application for permission of the uses shall be made according to the form attached and include as appendix following documents: copy of register of the applicant legal person; plane drawings of the works or the enterprise and their surroundings in reduced scales and with directions, centering on facilities in use, of storage and disposal, etc. The report of the uses shall list name and address of the user, object and method of the uses, and include as annex copy of register of the user legal person and papers explaining the expected date of beginning and the period of the uses, etc. Standards of the uses, refilling, storage, transport and disposal are in detail stipulated. Specified measures shall be taken for measurement, prevention of radiation hazards, finding out of persons injured by radiation and others. (Okada, K.)

Does tadalafil prevent erectile dysfunction in patients undergoing radiation therapy for prostate cancer?

NARCIS (Netherlands)

L. Incrocci (Luca)

2014-01-01

textabstractA recently published paper addressed the interesting topic of prevention of erectile dysfunction (ED) with tadalafil, a phosphodiesterase-type 5 inhibitor (PDE5i) in patients undergoing radiation therapy for localized prostate cancer. ^[1]Tadalafil 5 mg or placebo was

The Global and Local Climatic Response to the Collapse of the West Antarctic Ice Sheet

Science.gov (United States)

Huybers, K. M.; Singh, H.; Steiger, N. J.; Frierson, D. M.; Steig, E. J.; Bitz, C. M.

2014-12-01

Glaciologists have suggested that a relatively small external forcing may compromise the stability of the West Antarctic Ice Sheet (WAIS). Further, there is compelling physical evidence that the WAIS has collapsed in the past, at times when the mean global temperature was only a few degrees warmer than it is today. In addition to a rapid increase in global sea level, the collapse of the WAIS could also affect the global circulation of the atmosphere. Ice sheets are some of the largest topographic features on Earth, causing large regional anomalies in albedo and radiative balance. Our work uses idealized aquaplanet models in tandem with a fully coupled ocean/atmosphere/sea-ice model (CCSM4) to compare the atmospheric, radiative, and oceanic response to a complete loss of the WAIS. Initial findings indicate that the loss of the WAIS leads to a weakening and equator-ward shift of the zonal winds, a development of strong zonal asymmetries in the meridional wind, and a northward migration of the Intertropical Convergence Zone. We aim to characterize how the local and global climate is affected by the presence of the WAIS, and how changes in the distribution of Southern Hemisphere ice may be represented in the proxy record.

Radiation Safety and Culture of Prevention in the Use of Radioactive Materials in Industry. Criteria and Trends

International Nuclear Information System (INIS)

Truppa, W.A.

2011-01-01

As time goes by and experience is gained, modernization and technological development show the need to implement more complex programs and procedures to ensure a high level of compliance with radiation safety, particularly in those activities in which radioactive material is used in industry. A relevant aspect of present technology is the concern to introduce mechanisms to prevent radiological accidents or incidents, to ensure early detection of failures. This includes systems that either individually or as a whole, increase the level of responsibility of the different disciplines involved, so as to avoid a situation that could lead to loss of control of the facility or part of it. The prevention of an abnormal situation, overexposure of workers or unwanted risks, should be considered in the level of vulnerability of the facility, a concept drawn from international protection systems and which is applied directly in radiation safety. Preventive management, risk communication and proposals for change or improvement along with the detection of risks and training, constitute all the factors contained within prevention policies. Dose limitation, optimization and justification, old tools used for decades, could not be replaced by other modern concepts and criteria. ALARA culture (including performance indicators) should be considered. The atmosphere at work, working under pressure as well as other factors such as quality issues, ethics of prevention, etc. align with this idea of prevention and safety, besides changes in attitude, towards risk prevention (methods, reports, intervention guides, working instructions, and any other helpful tool), are followed by preventive, as well as predictive and corrective maintenance, applied to minimize the dose absorbed by workers. A clear policy of prevention is needed as well as an appropriate level of radiation safety which should be taken into account since the very beginning of the development of a given practice. All these

Radiation safety and culture of prevention in the use of radioactive materials in industry : criteria and trends

International Nuclear Information System (INIS)

Truppa, Walter Adrian

2008-01-01

As time goes by and experience is gained, modernization and technological development show the need to implement more complex programs and procedures to ensure a high level of compliance with radiation safety, particularly in those activities in which radioactive material is used in industry. A relevant aspect of present technology is the concern to introduce mechanisms to prevent radiological accidents or incidents, to ensure early detection of failures. This includes systems that either individually or as a whole, increase the level of responsibility of the different disciplines involved, so as to avoid a situation that could lead to loss of control of the facility or part of it. The prevention of an abnormal situation, overexposure of workers or unwanted risks, should be considered in the level of vulnerability of the facility, a concept drawn from international protection systems and which is applied directly in radiation safety. Preventive management, risk communication and proposals for change or improvement along with the detection of risks and training, constitute all the factors contained within prevention policies. Dose limitation, optimization and justification, old tools used for decades, could not be replaced by other modern concepts and criteria. ALARA culture (including performance indicators) should be considered. The atmosphere at work, working under pressure as well as other factors such as quality issues, ethics of prevention, etc. align with this idea of prevention and safety, besides changes in attitude, towards risk prevention (methods, reports, intervention guides, working instructions, and any other helpful tool), are followed by preventive, as well as predictive and corrective maintenance, applied to minimize the dose absorbed by workers. A clear policy of prevention is needed as well as an appropriate level of radiation safety which should be taken into account since the very beginning of the development of a given practice. All these

Experimental survey on percutaneous injection of calcium phosphate cement in preventing the articular surface collapsing secondary to avascular necrosis of femoral head

International Nuclear Information System (INIS)

Hou Changlong; Lv Weifu; Zhang Xuebin; Wang Weiyu; Zhang Xingming

2007-01-01

Objective: To study the technical way for animal model of ANFH with TAE (transcatheter arterial embolization)and to observe the image and pathologic changes of percutaneous injection with CPC (Calcium Phosphate Cement)in preventing the articular surface collapsing secondary to ANFH (avascular necrosis of femoral head)in pigs and its feasibility and safety. Methods: Branch arteries of the pig's left femoral head were embolized with woolly threads. Twenty pigs were randomly divided into A and B groups, and after about 1 month changes were assessed by imagings. Group A(n=8)was served as control of model contrast group, with only TAE and then surveyed the avascular necrosis features of femoral head by imaging together with pathologic and histologic examinations. Group B (n=12) was designated as percutaneous injection with CPC for interventional treatment group of ANFH at the stage Ficat II. Results: The animal models of ANFH in early stage were established by embolization of feeding arteries. In Group A, bone collapse occurred in 1.5 months after TAE, with imaging features of femoral head necrosis aggravated gradually. In group B, technical success of percutaneous injection with CPC was high and technical criteria included precise injection time, vigorous percutaneous fixing of bone, suitable proportion of CPC powder to liquid. CT scan of femoral head with injection CPC showed that it diffused well. Volume of bone trabecula (TBV)and percentage of bone lacuna (PBL)at unit area under microscopy were also inspected in two groups. TBV and PBL of two groups were compared in different special times and calculated especially for group B (P<0.05). Conclusion: The percutaneous injection of CPC to femoral head is a quite safe and effective palliative therapy for ANFH in early stage. (authors)

Non-Spherical Gravitational Collapse of Strange Quark Matter

Institute of Scientific and Technical Information of China (English)

Zade S S; Patil K D; Mulkalwar P N

2008-01-01

We study the non-spherical gravitational collapse of the strange quark null fluid.The interesting feature which emerges is that the non-spherical collapse of charged strange quark matter leads to a naked singularity whereas the gravitational collapse of neutral quark matter proceeds to form a black hole.We extend the earlier work of Harko and Cheng[Phys.Lett.A 266 (2000) 249]to the non-spherical case.

Cardiopulmonary Collapse during Labour

Directory of Open Access Journals (Sweden)

Vasilis Sitras

2010-01-01

Full Text Available Cardiopulmonary collapse during labour is a catastrophic event caused by various medical, surgical and obstetrical conditions. It is an emergency that threatens the life of the mother and her unborn child. We present a case of a pregnant woman who suffered from preeclampsia and underwent induction of labour. Severe lung edema occurred early in labour that caused cardiopulmonary collapse. Advanced heart-lung resuscitation was established immediately and continued until an emergency cesarean section was performed few minutes later. The outcome was favourable for both mother and child. We further discuss some aspects of the pathophysiology and appropriate treatment of cardiorespiratory arrest during labour, which involves the coordinated action of the obstetric, pediatric and surgical ward personnel.

Coherence versus incoherence: Collapse and revival in a simple quantum model

International Nuclear Information System (INIS)

Narozhny, N.B.; Sanchez-Mondragon, J.J.; Eberly, J.H.

1981-01-01

We describe the temporal behavior of the dynamic elements of an exactly soluble quantum model. The model consists of a single two-level atom or spin interacting with a single mode of the quantized radiation field in the dipole approximation, the mode being initially in an arbitrary coherent state of excitation. We give new long-time numerical and closed-form approximate analytic solutions for the expectation values of the atomic dipole moment and the difference in population of the two atomic levels in the rotating wave approximation. The atomic dipole-dipole correlation function is calculated. All of the results are obtained without semiclassical or decorrelation approximations. Unusual features found in the temporal behavior of this lossless model problem are ''collapse,'' i.e., episodic nonexponential damping of both the atomic inversion and dipole moment, and two kinds of ''revival'' or partial recorrelation, in the dynamic evolution, during which the initial state is nearly recovered. We give analytic formulas for the collapse function, for both of the revival times, and for the envelope of the revival maxima. Some remarks are made about the nature of irreversibility in this exactly soluble and loss-free model

The covariant entropy bound in gravitational collapse

International Nuclear Information System (INIS)

Gao, Sijie; Lemos, Jose P. S.

2004-01-01

We study the covariant entropy bound in the context of gravitational collapse. First, we discuss critically the heuristic arguments advanced by Bousso. Then we solve the problem through an exact model: a Tolman-Bondi dust shell collapsing into a Schwarzschild black hole. After the collapse, a new black hole with a larger mass is formed. The horizon, L, of the old black hole then terminates at the singularity. We show that the entropy crossing L does not exceed a quarter of the area of the old horizon. Therefore, the covariant entropy bound is satisfied in this process. (author)

Scalar field collapse in Gauss-Bonnet gravity

Science.gov (United States)

Banerjee, Narayan; Paul, Tanmoy

2018-02-01

We consider a "scalar-Einstein-Gauss-Bonnet" theory in four dimension, where the scalar field couples non-minimally with the Gauss-Bonnet (GB) term. This coupling with the scalar field ensures the non-topological character of the GB term. In this scenario, we examine the possibility for collapsing of the scalar field. Our result reveals that such a collapse is possible in the presence of Gauss-Bonnet gravity for suitable choices of parametric regions. The singularity formed as a result of the collapse is found to be a curvature singularity which is hidden from the exterior by an apparent horizon.

Self-similar Langmuir collapse at critical dimension

International Nuclear Information System (INIS)

Berge, L.; Dousseau, Ph.; Pelletier, G.; Pesme, D.

1991-01-01

Two spherically symmetric versions of a self-similar collapse are investigated within the framework of the Zakharov equations, namely, one relative to a vectorial electric field and the other corresponding to a scalar modeling of the Langmuir field. Singular solutions of both of them depend on a linear time contraction rate ξ(t) = V(t * -t), where t * and V = -ξ denote, respectively, the collapse time and the constant collapse velocity. It is shown that under certain conditions, only the scalar model admits self-similar solutions, varying regularly as a function of the control parameter V from the subsonic (V >1) regime. (author)

Prevention and treatment of the gastric symptoms of radiation sickness

International Nuclear Information System (INIS)

Dubois, A.; Fiala, N.; Boward, C.A.; Bogo, V.

1988-01-01

Currently available treatments for radiation-induced nausea and vomiting either are ineffective or reduce performance. The new antiemetic and gastrokinetic agent zacopride was tested in rhesus monkeys to assess its behavioral toxicity and its ability to inhibit radiation-induced emesis. Zacopride (intragastric, 0.3 mg/kg) or a placebo was given blindly and randomly in the basal state and 15 min before a whole-body 800 cGy 60Co gamma-radiation dose (except for the legs which were partially protected to permit survival of some bone marrow). We determined (1) gastric emptying rates; (2) the presence and frequency of retching and vomiting; and (3) the effect of zacopride on the performance of a visual discrimination task in nonirradiated subjects. No vomiting, retching, or decreased performance was observed after either placebo or zacopride in the control state. Following irradiation plus placebo, 70 emeses were observed in 5 of 6 monkeys, and 353 retches were observed in all 6 monkeys. In contrast, only 1 emesis was observed in 1 of 6 monkeys and 173 retches were seen in 4 of 6 monkeys after irradiation plus zacopride (P less than 0.01). Zacopride also significantly inhibited radiation-induced suppression of gastric emptying. When given after the first vomiting episode in a separate group of irradiated monkeys, zacopride completely prevented any subsequent vomiting. The present results demonstrate that intragastric administration of zacopride significantly inhibited radiation-induced retching, vomiting, and suppression of gastric emptying in rhesus monkeys and did not cause detectable behavioral side effects when given to nonradiated monkeys. This observation has important implications in the treatment of radiation sickness

Core-Collapse Supernovae, Neutrinos, and Gravitational Waves

Energy Technology Data Exchange (ETDEWEB)

Ott, C.D. [TAPIR, California Institute of Technology, Pasadena, California (United States); Kavli Institute for the Physics and Mathematics of the Universe, Kashiwa, Chiba (Japan); O' Connor, E.P. [Canadian Institute for Theoretical Astrophysics, Toronto, Ontario (Canada); Gossan, S.; Abdikamalov, E.; Gamma, U.C.T. [TAPIR, California Institute of Technology, Pasadena, California (United States); Drasco, S. [Grinnell College, Grinnell, Iowa (United States); TAPIR, California Institute of Technology, Pasadena, California (United States)

2013-02-15

Core-collapse supernovae are among the most energetic cosmic cataclysms. They are prodigious emitters of neutrinos and quite likely strong galactic sources of gravitational waves. Observation of both neutrinos and gravitational waves from the next galactic or near extragalactic core-collapse supernova will yield a wealth of information on the explosion mechanism, but also on the structure and angular momentum of the progenitor star, and on aspects of fundamental physics such as the equation of state of nuclear matter at high densities and low entropies. In this contribution to the proceedings of the Neutrino 2012 conference, we summarize recent progress made in the theoretical understanding and modeling of core-collapse supernovae. In this, our emphasis is on multi-dimensional processes involved in the explosion mechanism such as neutrino-driven convection and the standing accretion shock instability. As an example of how supernova neutrinos can be used to probe fundamental physics, we discuss how the rise time of the electron antineutrino flux observed in detectors can be used to probe the neutrino mass hierarchy. Finally, we lay out aspects of the neutrino and gravitational-wave signature of core-collapse supernovae and discuss the power of combined analysis of neutrino and gravitational wave data from the next galactic core-collapse supernova.

Core-Collapse Supernovae, Neutrinos, and Gravitational Waves

International Nuclear Information System (INIS)

Ott, C.D.; O'Connor, E.P.; Gossan, S.; Abdikamalov, E.; Gamma, U.C.T.; Drasco, S.

2013-01-01

Core-collapse supernovae are among the most energetic cosmic cataclysms. They are prodigious emitters of neutrinos and quite likely strong galactic sources of gravitational waves. Observation of both neutrinos and gravitational waves from the next galactic or near extragalactic core-collapse supernova will yield a wealth of information on the explosion mechanism, but also on the structure and angular momentum of the progenitor star, and on aspects of fundamental physics such as the equation of state of nuclear matter at high densities and low entropies. In this contribution to the proceedings of the Neutrino 2012 conference, we summarize recent progress made in the theoretical understanding and modeling of core-collapse supernovae. In this, our emphasis is on multi-dimensional processes involved in the explosion mechanism such as neutrino-driven convection and the standing accretion shock instability. As an example of how supernova neutrinos can be used to probe fundamental physics, we discuss how the rise time of the electron antineutrino flux observed in detectors can be used to probe the neutrino mass hierarchy. Finally, we lay out aspects of the neutrino and gravitational-wave signature of core-collapse supernovae and discuss the power of combined analysis of neutrino and gravitational wave data from the next galactic core-collapse supernova

GRAVITATIONAL WAVE SIGNATURES IN BLACK HOLE FORMING CORE COLLAPSE

Energy Technology Data Exchange (ETDEWEB)

Cerdá-Durán, Pablo; DeBrye, Nicolas; Aloy, Miguel A.; Font, José A.; Obergaulinger, Martin, E-mail: pablo.cerda@uv.es [Departamento de Astronomia y Astrofísica, Universidad de Valencia, c/Dr. Moliner 50, E-46100-Burjassot (Spain)

2013-12-20

We present general relativistic numerical simulations of collapsing stellar cores. Our initial model consists of a low metallicity rapidly-rotating progenitor which is evolved in axisymmetry with the latest version of our general relativistic code CoCoNuT, which allows for black hole formation and includes the effects of a microphysical equation of state (LS220) and a neutrino leakage scheme to account for radiative losses. The motivation of our study is to analyze in detail the emission of gravitational waves in the collapsar scenario of long gamma-ray bursts. Our simulations show that the phase during which the proto-neutron star (PNS) survives before ultimately collapsing to a black hole is particularly optimal for gravitational wave emission. The high-amplitude waves last for several seconds and show a remarkable quasi-periodicity associated with the violent PNS dynamics, namely during the episodes of convection and the subsequent nonlinear development of the standing-accretion shock instability (SASI). By analyzing the spectrogram of our simulations we are able to identify the frequencies associated with the presence of g-modes and with the SASI motions at the PNS surface. We note that the gravitational waves emitted reach large enough amplitudes to be detected with third-generation detectors such as the Einstein Telescope within a Virgo Cluster volume at rates ≲ 0.1 yr{sup –1}.

Collapse of the wave function models, ontology, origin, and implications

CERN Document Server

2018-01-01

This is the first single volume about the collapse theories of quantum mechanics, which is becoming a very active field of research in both physics and philosophy. In standard quantum mechanics, it is postulated that when the wave function of a quantum system is measured, it no longer follows the Schrödinger equation, but instantaneously and randomly collapses to one of the wave functions that correspond to definite measurement results. However, why and how a definite measurement result appears is unknown. A promising solution to this problem are collapse theories in which the collapse of the wave function is spontaneous and dynamical. Chapters written by distinguished physicists and philosophers of physics discuss the origin and implications of wave-function collapse, the controversies around collapse models and their ontologies, and new arguments for the reality of wave function collapse. This is an invaluable resource for students and researchers interested in the philosophy of physics and foundations of ...

Prevention of risks in relation with occupational exposure to ionizing radiation; Prevention des risques lies a l'exposition professionnelle aux rayonnements ionisants

Energy Technology Data Exchange (ETDEWEB)

NONE

2005-07-01

After remind the base notions in the field of ionizing radiation, this file evaluates the situation on the natural and occupational exposures: modes, sources, and exposure level, risk for health. It presents the principles of prevention allowing in a professional area (out of nuclear industry) to reduce and control these exposures. Some practical cases illustrate the radiation protection approach. references are given: regulatory benchmarks, useful links, books to consult. (N.C.)

Moduli destabilization via gravitational collapse

Energy Technology Data Exchange (ETDEWEB)

Hwang, Dong-il [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Pedro, Francisco G. [Deutsches Elektronen-Synchrotron DESY, Hamburg (Germany). Theory Group; Yeom, Dong-han [Sogang Univ., Seoul (Korea, Republic of). Center for Quantum Spacetime; Kyoto Univ. (Japan). Yukawa Inst. for Theoretical Physics

2013-06-15

We examine the interplay between gravitational collapse and moduli stability in the context of black hole formation. We perform numerical simulations of the collapse using the double null formalism and show that the very dense regions one expects to find in the process of black hole formation are able to destabilize the volume modulus. We establish that the effects of the destabilization will be visible to an observer at infinity, opening up a window to a region in spacetime where standard model's couplings and masses can differ significantly from their background values.

Extracting Information about the Initial State from the Black Hole Radiation.

Science.gov (United States)

Lochan, Kinjalk; Padmanabhan, T

2016-02-05

The crux of the black hole information paradox is related to the fact that the complete information about the initial state of a quantum field in a collapsing spacetime is not available to future asymptotic observers, belying the expectations from a unitary quantum theory. We study the imprints of the initial quantum state contained in a specific class of distortions of the black hole radiation and identify the classes of in states that can be partially or fully reconstructed from the information contained within. Even for the general in state, we can uncover some specific information. These results suggest that a classical collapse scenario ignores this richness of information in the resulting spectrum and a consistent quantum treatment of the entire collapse process might allow us to retrieve much more information from the spectrum of the final radiation.

Did mud contribute to freeway collapse?

Science.gov (United States)

Hough, Susan E.; Friberg, Paul A.; Busby, Robert; Field, Edward F.; Jacob, Klaus H.; Borcherdt, Roger D.

At least 41 people were killed October 17 when the upper tier of the Nimitz Freeway in Oakland, Calif., collapsed during the Ms = 7.1 Loma Prieta earthquake. Seismologists studying aftershocks concluded that soil conditions and resulting ground motion amplification were important in the failure of the structure and should be considered in the reconstruction of the highway.Structural design weaknesses in the two-tiered freeway, known as the Cypress structure, had been identified before the tragedy. The seismologists, from Lamont Doherty Geological Observatory in Palisades, N.Y., and the U.S. Geological Survey in Menlo Park, Calif., found that the collapsed section was built on fill over Bay mud. A southern section of the Cypress structure built on alluvium of Quaternary age did not collapse (see Figure 1).

Nucleosynthesis in Core-Collapse Supernovae

Science.gov (United States)

Stevenson, Taylor Shannon; Viktoria Ohstrom, Eva; Harris, James Austin; Hix, William R.

2018-01-01

The nucleosynthesis which occurs in core-collapse supernovae (CCSN) is one of the most important sources of elements in the universe. Elements from Oxygen through Iron come predominantly from supernovae, and contributions of heavier elements are also possible through processes like the weak r-process, the gamma process and the light element primary process. The composition of the ejecta depends on the mechanism of the explosion, thus simulations of high physical fidelity are needed to explore what elements and isotopes CCSN can contribute to Galactic Chemical Evolution. We will analyze the nucleosynthesis results from self-consistent CCSN simulations performed with CHIMERA, a multi-dimensional neutrino radiation-hydrodynamics code. Much of our understanding of CCSN nucleosynthesis comes from parameterized models, but unlike CHIMERA these fail to address essential physics, including turbulent flow/instability and neutrino-matter interaction. We will present nucleosynthesis predictions for the explosion of a 9.6 solar mass first generation star, relying both on results of the 160 species nuclear reaction network used in CHIMERA within this model and on post-processing with a more extensive network. The lowest mass iron core-collapse supernovae, like this model, are distinct from their more massive brethren, with their explosion mechanism and nucleosynthesis being more like electron capture supernovae resulting from Oxygen-Neon white dwarves. We will highlight the differences between the nucleosynthesis in this model and more massive supernovae. The inline 160 species network is a feature unique to CHIMERA, making this the most sophisticated model to date for a star of this type. We will discuss the need and mechanism to extrapolate the post-processing to times post-simulation and analyze the uncertainties this introduces for supernova nucleosynthesis. We will also compare the results from the inline 160 species network to the post-processing results to study further

mode of collapse of square single panel reinforced concrete space

African Journals Online (AJOL)

The models were loaded directly till collapse. The estimated and actual collapse loads of the five models were compared. The estimated collapse load for the slab was 35 kN/m2. Also, the numerical estimate of the collapse load for the beam was 10.2kN/m (with an equivalent slab load of 40.8kN/m2), while the shear capacity ...

Study of film boiling collapse behavior during vapor explosion

International Nuclear Information System (INIS)

Yagi, Masahiro; Yamano, Norihiro; Sugimoto, Jun; Abe, Yutaka; Adachi, Hiromichi; Kobayashi, Tomoyoshi.

1996-06-01

Possible large scale vapor explosions are safety concern in nuclear power plants during severe accident. In order to identify the occurrence of the vapor explosion and to estimate the magnitude of the induced pressure pulse, it is necessary to investigate the triggering condition for the vapor explosion. As a first step of this study, scooping analysis was conducted with a simulation code based on thermal detonation model. It was found that the pressure at the collapse of film boiling much affects the trigger condition of vapor explosion. Based on this analytical results, basic experiments were conducted to clarify the collapse conditions of film boiling on a high temperature solid ball surface. Film boiling condition was established by flooding water onto a high temperature stainless steel ball heated by a high frequency induction heater. After the film boiling was established, the pressure pulse generated by a shock tube was applied to collapse the steam film on the ball surface. As the experimental boundary conditions, materials and size of the balls, magnitude of pressure pulse and initial temperature of the carbon and stainless steel balls were varied. The transients of pressure and surface temperature were measured. It was found that the surface temperature on the balls sharply decreased when the pressure wave passed through the film on balls. Based on the surface temperature behavior, the film boiling collapse pattern was found to be categorized into several types. Especially, the pattern for stainless steel ball was categorized into three types; no collapse, collapse and reestablishment after collapse. It was thus clarified that the film boiling collapse behavior was identified by initial conditions and that the pressure required to collapse film boiling strongly depended on the initial surface temperature. The present results will provide a useful information for the analysis of vapor explosions based on the thermal detonation model. (J.P.N.)

Plastic collapse load of corroded steel plates

Indian Academy of Sciences (India)

Keywords. Corroded steel plate; plastic collapse; FEM; rough surface. ... The main aim of present work is to study plastic collapse load of corroded steel plates with irregular surfaces under tension. Non-linear finite element method ... Department of Ocean Engineering, AmirKabir University of Technology, 15914 Tehran, Iran ...

Constraining quantum collapse inflationary models with CMB data

Energy Technology Data Exchange (ETDEWEB)

Benetti, Micol; Alcaniz, Jailson S. [Departamento de Astronomia, Observatório Nacional, 20921-400, Rio de Janeiro, RJ (Brazil); Landau, Susana J., E-mail: micolbenetti@on.br, E-mail: slandau@df.uba.ar, E-mail: alcaniz@on.br [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, PabI, Buenos Aires 1428 (Argentina)

2016-12-01

The hypothesis of the self-induced collapse of the inflaton wave function was proposed as responsible for the emergence of inhomogeneity and anisotropy at all scales. This proposal was studied within an almost de Sitter space-time approximation for the background, which led to a perfect scale-invariant power spectrum, and also for a quasi-de Sitter background, which allows to distinguish departures from the standard approach due to the inclusion of the collapse hypothesis. In this work we perform a Bayesian model comparison for two different choices of the self-induced collapse in a full quasi-de Sitter expansion scenario. In particular, we analyze the possibility of detecting the imprint of these collapse schemes at low multipoles of the anisotropy temperature power spectrum of the Cosmic Microwave Background (CMB) using the most recent data provided by the Planck Collaboration. Our results show that one of the two collapse schemes analyzed provides the same Bayesian evidence of the minimal standard cosmological model ΛCDM, while the other scenario is weakly disfavoured with respect to the standard cosmology.

Ion confinement and radiation losses in the Advanced Toroidal Facility

International Nuclear Information System (INIS)

Isler, R.C.; Colchin, R.J.; Wade, M.R.; Lyon, J.F.; Fowler, R.H.; Rome, J.A.; Hiroe, S.; Baylor, L.R.; England, A.; Ma, C.H.; Rasmussen, D.A.; Ochando, M.; Paul, S.

1991-01-01

Collapses of stored energy are typically observed in low-density (anti n e ∼ 10 13 cm -3 ) extensively gettered ATF plasmas when the electron density rises to the ECH cutoff point, and the central heating is supplied only by neutral- beam-injection (NBI). However, the decline of stored energy can be avoided if the density is raised rapidly to about 5 x 10 13 cm -3 . Three mechanisms have been proposed to explain the collapses: (1) impurity radiation, (2) excitation of an electron instability driven by the neutral beams, or (3) poor coupling of the beam ions to the thermal plasmas. Detailed spectroscopic studies of plasma cleanliness as a function of the gettering procedure have shown that radiation is an unlikely candidate for initiating collapses, although it may become an important loss mechanism once the electron temperature has fallen to a low level. No specific electron instability has yet been identified with injection, but recent experimental and computational work indicates that losses by shinethrough and charge exchange strongly influence the evolution of low-density plasmas. This report discusses the beam particle losses, thermal ions, and the evolution of radiation profiles

Scalar field collapse in Gauss-Bonnet gravity

Energy Technology Data Exchange (ETDEWEB)

Banerjee, Narayan [Indian Institute of Science Education and Research Kolkata, Department of Physical Sciences, Nadia, West Bengal (India); Paul, Tanmoy [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

2018-02-15

We consider a ''scalar-Einstein-Gauss-Bonnet'' theory in four dimension, where the scalar field couples non-minimally with the Gauss-Bonnet (GB) term. This coupling with the scalar field ensures the non-topological character of the GB term. In this scenario, we examine the possibility for collapsing of the scalar field. Our result reveals that such a collapse is possible in the presence of Gauss-Bonnet gravity for suitable choices of parametric regions. The singularity formed as a result of the collapse is found to be a curvature singularity which is hidden from the exterior by an apparent horizon. (orig.)

Critical gravitational collapse with angular momentum. II. Soft equations of state

Science.gov (United States)

Gundlach, Carsten; Baumgarte, Thomas W.

2018-03-01

We study critical phenomena in the collapse of rotating ultrarelativistic perfect fluids, in which the pressure P is related to the total energy density ρ by P =κ ρ , where κ is a constant. We generalize earlier results for radiation fluids with κ =1 /3 to other values of κ , focusing on κ power-law scalings of the black-hole mass. We do see systematic effects in the black-hole angular momentum, but it is not clear yet if these are due to the predicted nontrivial scaling functions, or to nonlinear effects at sufficiently large initial angular momentum (which we do not account for in our theoretical model).

Static end-expiratory and dynamic forced expiratory tracheal collapse in COPD

International Nuclear Information System (INIS)

O'Donnell, C.R.; Bankier, A.A.; O'Donnell, D.H.; Loring, S.H.; Boiselle, P.M.

2014-01-01

Aim: To determine the range of tracheal collapse at end-expiration among chronic obstructive pulmonary disease (COPD) patients and to compare the extent of tracheal collapse between static end-expiratory and dynamic forced-expiratory multidetector-row computed tomography (MDCT). Materials and methods: After institutional review board approval and obtaining informed consent, 67 patients meeting the National Heart, Lung, and Blood Institute (NHLBI)/World Health Organization (WHO) Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria for COPD were sequentially imaged using a 64-detector-row CT machine at end-inspiration, during forced expiration, and at end-expiration. Standardized respiratory coaching and spirometric monitoring were employed. Mean percentage tracheal collapse at end-expiration and forced expiration were compared using correlation analysis, and the power of end-expiratory cross-sectional area to predict excessive forced-expiratory tracheal collapse was computed following construction of receiver operating characteristic (ROC) curves. Results: Mean percentage expiratory collapse among COPD patients was 17 ± 18% at end-expiration compared to 62 ± 16% during forced expiration. Over the observed range of end-expiratory tracheal collapse (approximately 10–50%), the positive predictive value of end-expiratory collapse to predict excessive (≥80%) forced expiratory tracheal collapse was <0.3. Conclusion: COPD patients demonstrate a wide range of end-expiratory tracheal collapse. The magnitude of static end-expiratory tracheal collapse does not predict excessive dynamic expiratory tracheal collapse

Simulation of weak and strong Langmuir collapse regimes

International Nuclear Information System (INIS)

Hadzievski, L.R.; Skoric, M.M.; Kono, M.; Sato, T.

1998-01-01

In order to check the validity of the self-similar solutions and the existence of weak and strong collapse regimes, direct two dimensional simulation of the time evolution of a Langmuir soliton instability is performed. Simulation is based on the Zakharov model of strong Langmuir turbulence in a weakly magnetized plasma accounting for the full ion dynamics. For parameters considered, agreement with self-similar dynamics of the weak collapse type is found with no evidence of the strong Langmuir collapse. (author)

The order for enforcing the law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1981-01-01

This rule is established under the provisions of the law on the prevention of radiation injuries by radioisotopes, and the former ordinance No. 14, 1958, is hereby totally amended. Radioisotopes under the law are the isotopes which emit radiation, and of which the concentration exceeds the levels defined by the Director General of the Science and Technology Agency, their compounds or the substances containing these compounds, excluding those defined in the atomic energy act and other particular laws. The apparatuses fitted with radioisotopes under the law are electron capture detectors for gas chromatography. The radiation emitting installations under the law are cyclotron, synchrotron, synchro-cyclotron, linear accelerator, betatron, Van de Graaff accelerator, Cockcroft-Walton's accelerator, etc. The permission of usage under the law shall be obtained for each works or enterprise. Persons who intend to get the permission shall file the application for them attaching the documents describing expected period of usage and other papers specified by the Director General. The total quantity of radioisotopes sealed tightly for each works or enterprise under the law shall be 100 milli-curie. The design of apparatus for the prevention of radiation injuries, the capacities of storage facilities regularly inspected, the period of regular inspection, the confirmation of transport and disposal and fees to be paid, etc. are defined, respectively. (Okada, K.)

A chip-level modeling approach for rail span collapse and survivability analyses

International Nuclear Information System (INIS)

Marvis, D.G.; Alexander, D.R.; Dinger, G.L.

1989-01-01

A general semiautomated analysis technique has been developed for analyzing rail span collapse and survivability of VLSI microcircuits in high ionizing dose rate radiation environments. Hierarchical macrocell modeling permits analyses at the chip level and interactive graphical postprocessing provides a rapid visualization of voltage, current and power distributions over an entire VLSIC. The technique is demonstrated for a 16k C MOS/SOI SRAM and a CMOS/SOS 8-bit multiplier. The authors also present an efficient method to treat memory arrays as well as a three-dimensional integration technique to compute sapphire photoconduction from the design layout

Collapse of Incoherent Light Beams in Inertial Bulk Kerr Media

DEFF Research Database (Denmark)

Bang, Ole; Edmundson, Darran; Królikowski, Wieslaw

1999-01-01

We use the coherent density function theory to show that partially coherent beams are unstable and may collapse in inertial bulk Kerr media. The threshold power for collapse, and its dependence on the degree of coherence, is found analytically and checked-numerically. The internal dynamics of the...... of the walk-off modes is illustrated for collapsing and diffracting partially coherent beams.......We use the coherent density function theory to show that partially coherent beams are unstable and may collapse in inertial bulk Kerr media. The threshold power for collapse, and its dependence on the degree of coherence, is found analytically and checked-numerically. The internal dynamics...

Gravitational collapse from smooth initial data with vanishing radial pressure

International Nuclear Information System (INIS)

Mahajan, Ashutosh; Goswami, Rituparno; Joshi, Pankaj S

2005-01-01

We study here the spherical gravitational collapse assuming initial data to be necessarily smooth, as motivated by requirements based on physical reasonableness. A tangential pressure model is constructed and analysed in order to understand the final fate of collapse explicitly in terms of the density and pressure parameters at the initial epoch from which the collapse develops. It is seen that both black holes and naked singularities are produced as collapse end states even when the initial data are smooth. We show that the outcome is decided entirely in terms of the initial data, as given by density, pressure and velocity profiles at the initial epoch, from which the collapse evolves

Identification and behavior of collapsible soils : [technical summary].

Science.gov (United States)

2011-01-01

Collapsible soils are susceptible to large volumetric strains when they become saturated. Numerous soil types : fall in the general category of collapsible soils, including : loess, a well-known aeolian deposit, present throughout : most of Indiana. ...

Electron capture and stellar collapse

International Nuclear Information System (INIS)

Chung, K.C.

1979-01-01

In order, to investigate the function of electron capture in the phenomenon of pre-supernovae gravitacional collapse, an hydrodynamic caculation was carried out, coupling capture, decay and nuclear reaction equation system. A star simplified model (homogeneous model) was adopted using fermi ideal gas approximation for tthe sea of free electrons and neutrons. The non simplified treatment from quasi-static evolution to collapse is presented. The capture and beta decay rates, as wellas neutron delayed emission, were calculated by beta decay crude theory, while the other reaction rates were determined by usual theories. The preliminary results are presented. (M.C.K.) [pt

The Experimental Study of Dynamics of Scaled Gas-Filled Bubble Collapse in Liquid

Science.gov (United States)

Pavlenko, Alexander

2011-06-01

The article provides results of analyzing special features of the single-bubble sonoluminescence, developing the special apparatus to investigate this phenomenon on a larger-scale basis. Certain very important effects of high energy density physics, i.e. liquid compressibility, shock-wave formation under the collapse of the gas cavity in liquid, shock-wave focusing in the gas-filled cavity, occurrence of hot dense plasma in the focusing area, and high-temperature radiation yield are observed in this phenomenon. Specificity of the process is conditioned by the ``ideal'' preparation and sphericity of the gas-and-liquid contact boundary what makes the collapse process efficient due to the reduced influence of hydrodynamic instabilities. Results of experimental investigations; results of developing the facilities, description of methods used to register parameters of facilities and the system under consideration; analytical estimates how gas-filled bubbles evolve in liquid with the regard for scale effects; results of preliminary 1-D gas dynamic calculations of the gas bubble evolution are presented. The work supported by ISTC Project #2116.

Collapse, environment, and society

Science.gov (United States)

2012-01-01

Historical collapse of ancient states poses intriguing social-ecological questions, as well as potential applications to global change and contemporary strategies for sustainability. Five Old World case studies are developed to identify interactive inputs, triggers, and feedbacks in devolution. Collapse is multicausal and rarely abrupt. Political simplification undermines traditional structures of authority to favor militarization, whereas disintegration is preconditioned or triggered by acute stress (insecurity, environmental or economic crises, famine), with breakdown accompanied or followed by demographic decline. Undue attention to stressors risks underestimating the intricate interplay of environmental, political, and sociocultural resilience in limiting the damages of collapse or in facilitating reconstruction. The conceptual model emphasizes resilience, as well as the historical roles of leaders, elites, and ideology. However, a historical model cannot simply be applied to contemporary problems of sustainability without adjustment for cumulative information and increasing possibilities for popular participation. Between the 14th and 18th centuries, Western Europe responded to environmental crises by innovation and intensification; such modernization was decentralized, protracted, flexible, and broadly based. Much of the current alarmist literature that claims to draw from historical experience is poorly focused, simplistic, and unhelpful. It fails to appreciate that resilience and readaptation depend on identified options, improved understanding, cultural solidarity, enlightened leadership, and opportunities for participation and fresh ideas. PMID:22371579

Collections of laws and ordinances concerning radiation injury prevention as of July 24, 1981

International Nuclear Information System (INIS)

Tsuruta, Takao

1981-01-01

There are laws, government and ministerial ordinances and notifications, each of them bears a definite role, and the contents of the legal regulation on a certain range of matter are determined by their close interrelation and mutual supplementation. Many laws and ordinances concerning atomic energy also form a legal system under such mutual relation. The Atomic Energy Act is positioned at its top, and the main part related to radiation injury prevention comprises a law, two ordinances, a regulation and a notification. Such relationship of individual laws and ordinances is mostly shown in lower rank laws and ordinances. In Chapter 1 of this book, the Atomic Energy Act and the government ordinance concerning the definition of nuclear fuel materials, nuclear raw materials, nuclear reactors and radiation are described. In Chapter 2, the law concerning prevention of radiation injuries due to radiactive isotopes and others, the ordinances and eight notifications closely related to them are collected. In Chapter 3, other related laws and ordinances are gathered. To understand the laws and ordinances synthetically and systematically, the provisions of different laws and ordinances, which are mutually related, are arranged together showing their relation. (Kako, I.)

Neutrino-pair emission from nuclear de-excitation in core-collapse supernova simulations

Science.gov (United States)

Fischer, T.; Langanke, K.; Martínez-Pinedo, G.

2013-12-01

We study the impact of neutrino-pair production from the de-excitation of highly excited heavy nuclei on core-collapse supernova simulations, following the evolution up to several 100 ms after core bounce. Our study is based on the agile-boltztransupernova code, which features general relativistic radiation hydrodynamics and accurate three-flavor Boltzmann neutrino transport in spherical symmetry. In our simulations the nuclear de-excitation process is described in two different ways. At first we follow the approach proposed by Fuller and Meyer [Astrophys. J.AJLEEY0004-637X10.1086/170317 376, 701 (1991)], which is based on strength functions derived in the framework of the nuclear Fermi-gas model of noninteracting nucleons. Second, we parametrize the allowed and forbidden strength distributions in accordance with measurements for selected nuclear ground states. We determine the de-excitation strength by applying the Brink hypothesis and detailed balance. For both approaches, we find that nuclear de-excitation has no effect on the supernova dynamics. However, we find that nuclear de-excitation is the leading source for the production of electron antineutrinos as well as heavy-lepton-flavor (anti)neutrinos during the collapse phase. At sufficiently high densities, the associated neutrino spectra are influenced by interactions with the surrounding matter, making proper simulations of neutrino transport important for the determination of the neutrino-energy loss rate. We find that, even including nuclear de-excitations, the energy loss during the collapse phase is overwhelmingly dominated by electron neutrinos produced by electron capture.

Newton force from wave function collapse: speculation and test

International Nuclear Information System (INIS)

Diósi, Lajos

2014-01-01

The Diosi-Penrose model of quantum-classical boundary postulates gravity-related spontaneous wave function collapse of massive degrees of freedom. The decoherence effects of the collapses are in principle detectable if not masked by the overwhelming environmental decoherence. But the DP (or any other, like GRW, CSL) spontaneous collapses are not detectable themselves, they are merely the redundant formalism of spontaneous decoherence. To let DP collapses become testable physics, recently we extended the DP model and proposed that DP collapses are responsible for the emergence of the Newton gravitational force between massive objects. We identified the collapse rate, possibly of the order of 1/ms, with the rate of emergence of the Newton force. A simple heuristic emergence (delay) time was added to the Newton law of gravity. This non-relativistic delay is in peaceful coexistence with Einstein's relativistic theory of gravitation, at least no experimental evidence has so far surfaced against it. We derive new predictions of such a 'lazy' Newton law that will enable decisive laboratory tests with available technologies. The simple equation of 'lazy' Newton law deserves theoretical and experimental studies in itself, independently of the underlying quantum foundational considerations.

Prediction of the wetting-induced collapse behaviour using the soil-water characteristic curve

Science.gov (United States)

Xie, Wan-Li; Li, Ping; Vanapalli, Sai K.; Wang, Jia-Ding

2018-01-01

Collapsible soils go through three distinct phases in response to matric suction decrease during wetting: pre-collapse phase, collapse phase and post-collapse phase. It is reasonable and conservative to consider a strain path that includes a pre-collapse phase in which constant volume is maintained and a collapse phase that extends to the final matric suction to be experienced by collapsible soils during wetting. Upon this assumption, a method is proposed for predicting the collapse behaviour due to wetting. To use the proposed method, two parameters, critical suction and collapse rate, are required. The former is the suction value below which significant collapse deformations take place in response to matric suction decease, and the later is the rate at which void ratio reduces with matric suction in the collapse phase. The value of critical suction can be estimated from the water-entry value taking account of both the microstructure characteristics and collapse mechanism of fine-grained collapsible soils; the wetting soil-water characteristic curve thus can be used as a tool. Five sets of data of wetting tests on both compacted and natural collapsible soils reported in the literature were used to validate the proposed method. The critical suction values were estimated from the water-entry value with parameter a that is suggested to vary between 0.10 and 0.25 for compacted soils and to be lower for natural collapsible soils. The results of a field permeation test in collapsible loess soils were also used to validate the proposed method. The relatively good agreement between the measured and estimated collapse deformations suggests that the proposed method can provide reasonable prediction of the collapse behaviour due to wetting.

Regular Bulk Solutions in Brane-Worlds with Inhomogeneous Dust and Generalized Dark Radiation

International Nuclear Information System (INIS)

Rocha, Roldão da; Kuerten, A. M.; Herrera-Aguilar, A.

2015-01-01

From the dynamics of a brane-world with matter fields present in the bulk, the bulk metric and the black string solution near the brane are generalized, when both the dynamics of inhomogeneous dust/generalized dark radiation on the brane-world and inhomogeneous dark radiation in the bulk as well are considered as exact dynamical collapse solutions. Based on the analysis on the inhomogeneous static exterior of a collapsing sphere of homogeneous dark radiation on the brane, the associated black string warped horizon is studied, as well as the 5D bulk metric near the brane. Moreover, the black string and the bulk are shown to be more regular upon time evolution, for suitable values for the dark radiation parameter in the model, by analyzing the soft physical singularities

Noncrossing timelike singularities of irrotational dust collapse

International Nuclear Information System (INIS)

Liang, E.P.T.

1979-01-01

Known naked singularities in spherical dust collapse are either due to shell-crossing or localized to the central world line. They will probably be destroyed by pressure gradients or blue-shift instabilities. To violate the cosmic censorship hypothesis in a more convincing and general context, collapse solutions with naked singularities that are at least nonshell-crossing and nonlocalized need to be constructed. Some results concerning the probable structure of a class of nonshellcrossing and nonlocalized timelike singularities are reviewed. The cylindrical dust model is considered but this model is not asymptotically flat. To make these noncrossing singularities viable counter examples to the cosmic censorship hypothesis, the occurrence of such singularities in asymptotically flat collapse needs to be demonstrated. (UK)

Collapse Scenarios of High-Rise Buildings Using Plastic Limit Analysis

Directory of Open Access Journals (Sweden)

G. Liu

2009-01-01

Full Text Available The Twin Towers of the World Trade Center (WTC in New York, USA collapsed on 11 September, 2001. The incident is regarded as the most severe disaster for high-rise buildings in history. Investigations into the collapse scenarios are still being conducted. Possible collapse scenarios assessed by local and international experts were reported. Another possible collapse scenario of the WTC based on two hypotheses was proposed in this paper, and the idea of plastic limit analysis was applied to evaluate the approximate limit load. According to the theory analysis and numerical calculations, a conclusion can be drawn that the large fires, aroused by the terrorist attack, play a significant role on the collapse of the WTC.

Collapse arresting in an inhomogeneous two-dimensional nonlinear Schrodinger model

DEFF Research Database (Denmark)

Schjødt-Eriksen, Jens; Gaididei, Yuri Borisovich; Christiansen, Peter Leth

2001-01-01

Collapse of (2 + 1)-dimensional beams in the inhomogeneous two-dimensional cubic nonlinear Schrodinger equation is analyzed numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams that in a homogeneous medium would collapse may...

Radiation Detection System for Prevention of Illicit Trafficking of Nuclear and Radioactive Materials

International Nuclear Information System (INIS)

Kwak, Sung Woo; Chang, Sung Soon; Yoo, Ho Sik

2010-01-01

Fixed radiation portal monitors (RPMs) deployed at border, seaport, airport and key traffic checkpoints have played an important role in preventing the illicit trafficking and transport of nuclear and radioactive materials. However, the RPM is usually large and heavy and can't easily be moved to different locations. These reasons motivate us to develop a mobile radiation detection system. The objective of this paper is to report our experience on developing the mobile radiation detection system for search and detection of nuclear and radioactive materials during road transport. Field tests to characterize the developed detection system were performed at various speeds and distances between the radioactive isotope (RI) transporting car and the measurement car. Results of measurements and detection limits of our system are described in this paper. The mobile radiation detection system developed should contribute to defending public's health and safety and the environment against nuclear and radiological terrorism by detecting nuclear or radioactive material hidden illegally in a vehicle

On the collapse of iron stellar cores

International Nuclear Information System (INIS)

Barkat, Z.; Rakavy, G.; Reiss, Y.; Wilson, J.R.

1975-01-01

The collapse of iron stellar cores is investigated to see whether the outward shock produced by the bounce at neutron star density is sufficient to burn appreciable amounts of the envelope around the iron core. Several models were tried, and in all cases no appreciable burn took place; hence no explosion results from the collapse of these models

The Collapse of the 'Celtic Tiger' Narrative

DEFF Research Database (Denmark)

Böss, Michael

2011-01-01

An account of the factors that led to the collapse of the 'Celtic Tiger' economy in 2008 and an explanation of the political effects and implications for Irish identity.......An account of the factors that led to the collapse of the 'Celtic Tiger' economy in 2008 and an explanation of the political effects and implications for Irish identity....

Sonographic Analysis of the Collapsed Gall Bladder

International Nuclear Information System (INIS)

Han, Sang Suk; Choi, Jae Young; Choi, Seok Jin; Eun, Chung Ki; Nam, Kyung Jin; Lee, Jeong Mi

1996-01-01

This study was done to find answers for further following questions in cases of the collapsed gallbladder (GB) : What is the probability of the presence of stone when stony echo is visible in GB area? What is the probability of the presence of stone when only acoustic shadow is visible from GB area? What are the associated GB pathologies except stone or cholecystitis in previously mentioned situations and is it possible to differentiate them? What are the underlying pathologies of GB collapse without stony echo or acoustic shadow and is it possible to differentiate them sonographic ally? What are the rate and causes of re-expansion of the collapsed GB on follow-up study? Prospective study was done in 157 cases of collapsed GB with no visible or nearly no visible bile filled lumen in recent 3 years. Sonographic analysis for GB lesions was done in 61 confirmed cases. Changing pattern of GB lumen on follow-up study and their underlying pathologies were analyzed in 28 cases. Initial sonographic examination was done with 3 or 3.5 MHz transducer. No other transducer was used in cases showing stony echo or acoustic shadow in GB area, but additional examination was done with 5 or 7-4 MHz transducer in cases without stony echo or acoustic shadow. Among 31 cases, which showed stony echo, stone was found in 30 cases and milk of calcium bile in one case. Stone was present in all of the 11 cases which showed only acoustic shadow from the collapsed GB without stony echo. GB cancer was accompanied in 2 cases among upper 42 cases, and its possibility could be suspected sonographic ally. Underlying pathologies of the 19cases without stony echo or acoustic shadow were as follows : GB stone (3), cholecystitis (6), GB cancer (1), bile plug syndrome (1), hepatitis (5), and ascites (3). And sonographic differentiation of the underlying causes for the collapse was possible in only 1 case of GB cancer. Among 28 cases of the follow-up study, 20 cases showed re-expansion of the GB lumen and

The phenomenon of radiative compression in dense magnetized plasmas

International Nuclear Information System (INIS)

Choi, Peter

1998-01-01

Full text: Localized regions of extremely high energy density have long been observed in dense magnetized plasma, created in different experiments, including vacuum spark, exploding wire, Z-pinch and plasma focus. The physical dimensions of these regions are typically tens to hundreds of microns with a characteristic temperature of few hundred eV upward. A theory of self-compression under enhanced cooling, when the radiation rate exceeds the joule heating rate, was first put forward by Shearer to explain the possible responsible mechanism. More recent work suggests that a radiative collapse formalism could indeed produce eaters of ultra-high density. In the paper the experimental evidences are examined, and the applicability limit of the radiative collapse picture is discussed, when the properties of the driving generator are considered. A new set of relations connecting the driver parameters and the limiting size of the compression is proposed

Collapse Mechanisms Of Masonry Structures

International Nuclear Information System (INIS)

Zuccaro, G.; Rauci, M.

2008-01-01

The paper outlines a possible approach to typology recognition, safety check analyses and/or damage measuring taking advantage by a multimedia tool (MEDEA), tracing a guided procedure useful for seismic safety check evaluation and post event macroseismic assessment. A list of the possible collapse mechanisms observed in the post event surveys on masonry structures and a complete abacus of the damages are provided in MEDEA. In this tool a possible combination between a set of damage typologies and each collapse mechanism is supplied in order to improve the homogeneity of the damages interpretation. On the other hand recent researches of one of the author have selected a number of possible typological vulnerability factors of masonry buildings, these are listed in the paper and combined with potential collapse mechanisms to be activated under seismic excitation. The procedure takes place from simple structural behavior models, derived from the Umbria-Marche earthquake observations, and tested after the San Giuliano di Puglia event; it provides the basis either for safety check analyses of the existing buildings or for post-event structural safety assessment and economic damage evaluation. In the paper taking advantage of MEDEA mechanisms analysis, mainly developed for the post event safety check surveyors training, a simple logic path is traced in order to approach the evaluation of the masonry building safety check. The procedure starts from the identification of the typological vulnerability factors to derive the potential collapse mechanisms and their collapse multipliers and finally addresses the simplest and cheapest strengthening techniques to reduce the original vulnerability. The procedure has been introduced in the Guide Lines of the Regione Campania for the professionals in charge of the safety check analyses and the buildings strengthening in application of the national mitigation campaign introduced by the Ordinance of the Central Government n. 3362

Oral lesions following radiation therapy and their preventive considerations

Directory of Open Access Journals (Sweden)

Ghavam M

2001-09-01

Full Text Available Oral cancers account for a relatively high percent of neoplasms in the elderly population. Treatment protocols often include anti-neoplastic pharmaco-therapeutics, irradiation of the head and neck region, and surgery. These treatments, specially radiation, have detrimental effects on oral hard and soft tissues. Salivary glands undergo a distinct and longterm dysfunction, which leads to decrease in salivary How. Xerostomia is a common clinical problem in these patients which contributes to dry mouth, mucosites, change in oral ecosystem and dental caries, followed by difficulties in speech, swallowing and use of dentures which cause malnutrition. This phenomenon has an irreversible weakening effect on the patient's health. To prevent this negative impact on oral health in this group of patients, definitive dental treatments prior to the initiation of medical therapies is imperative, and will decrease the morbidity rates. Today's dentistry benefits from improved methods and materials, which enable us to give these patients a better preventive dental treatment. Consultation between dentist and medical team would be the best way to help our sufferer patients.

Risk factor analysis for predicting vertebral body re-collapse after posterior instrumented fusion in thoracolumbar burst fracture.

Science.gov (United States)

Jang, Hae-Dong; Bang, Chungwon; Lee, Jae Chul; Soh, Jae-Wan; Choi, Sung-Woo; Cho, Hyeung-Kyu; Shin, Byung-Joon

2018-02-01

In the posterior instrumented fusion surgery for thoracolumbar (T-L) burst fracture, early postoperative re-collapse of well-reduced vertebral body fracture could induce critical complications such as correction loss, posttraumatic kyphosis, and metal failure, often leading to revision surgery. Furthermore, re-collapse is quite difficult to predict because of the variety of risk factors, and no widely accepted accurate prediction systems exist. Although load-sharing classification has been known to help to decide the need for additional anterior column support, this radiographic scoring system has several critical limitations. (1) To evaluate risk factors and predictors for postoperative re-collapse in T-L burst fractures. (2) Through the decision-making model, we aimed to predict re-collapse and prevent unnecessary additional anterior spinal surgery. Retrospective comparative study. Two-hundred and eight (104 men and 104 women) consecutive patients with T-L burst fracture who underwent posterior instrumented fusion were reviewed retrospectively. Burst fractures caused by high-energy trauma (fall from a height and motor vehicle accident) with a minimum 1-year follow-up were included. The average age at the time of surgery was 45.9 years (range, 15-79). With respect to the involved spinal level, 95 cases (45.6%) involved L1, 51 involved T12, 54 involved L2, and 8 involved T11. Mean fixation segments were 3.5 (range, 2-5). Pedicle screw instrumentation including fractured vertebra had been performed in 129 patients (62.3%). Clinical data using self-report measures (visual analog scale score), radiographic measurements (plain radiograph, computed tomography, and magnetic resonance image), and functional measures using the Oswestry Disability Index were evaluated. Body height loss of fractured vertebra, body wedge angle, and Cobb angle were measured in serial plain radiographs. We assigned patients to the re-collapse group if their body height loss progressed greater

Collapse above the world's largest potash mine (Ural, Russia.

Directory of Open Access Journals (Sweden)

Andrejchuk Vjacheslav

2002-01-01

Full Text Available This paper reports the results of the study of a huge collapse that occurred in June 1986 within the area of the 3rd Berezniki potash mine (the Verkhnekamsky potash deposit, Ural. Processes that took place between the first appearance of a water inflow through the mine roof and the eventual collapse are reconstructed in detail. The origin and development of a cavity that induced the collapse are revealed. Two factors played a major role in the formation of the collapse: the presence of a tectonic fold/rupture zone with in both the salt sequence and the overburden (the zone of crush and enhanced permeability, and the ductile pillars mining system.

Surface tension effects on the behavior of a cavity growing, collapsing, and rebounding near a rigid wall.

Science.gov (United States)

Zhang, Zhen-yu; Zhang, Hui-sheng

2004-11-01

Surface tension effects on the behavior of a pure vapor cavity or a cavity containing some noncondensible contents, which is growing, collapsing, and rebounding axisymmetrically near a rigid wall, are investigated numerically by the boundary integral method for different values of dimensionless stand-off parameter gamma, buoyancy parameter delta, and surface tension parameter beta. It is found that at the late stage of the collapse, if the resultant action of the Bjerknes force and the buoyancy force is not small, surface tension will not have significant effects on bubble behavior except that the bubble collapse time is shortened and the liquid jet becomes wider. If the resultant action of the two force is small enough, surface tension will have significant and in some cases substantial effects on bubble behavior, such as changing the direction of the liquid jet, making a new liquid jet appear, in some cases preventing the bubble from rebound before jet impact, and in other cases causing the bubble to rebound or even recollapse before jet impact. The mechanism of surface tension effects on the collapsing behavior of a cavity has been analyzed. The mechanisms of some complicated phenomena induced by surface tension effects are illustrated by analysis of the computed velocity fields and pressure contours of the liquid flow outside the bubble at different stages of the bubble evolution.

Inertial collapse of bubble pairs near a solid surface

Science.gov (United States)

Alahyari Beig, Shahaboddin; Johnsen, Eric

2017-11-01

Cavitation occurs in a variety of applications ranging from naval structures to biomedical ultrasound. One important consequence is structural damage to neighboring surfaces following repeated inertial collapse of vapor bubbles. Although the mechanical loading produced by the collapse of a single bubble has been widely investigated, less is known about the detailed dynamics of the collapse of multiple bubbles. In such a problem, the bubble-bubble interactions typically affect the dynamics, e.g., by increasing the non-sphericity of the bubbles and amplifying/hindering the collapse intensity depending on the flow parameters. Here, we quantify the effects of bubble-bubble interactions on the bubble dynamics, as well as the pressures/temperatures produced by the collapse of a pair of gas bubbles near a rigid surface. We perform high-resolution simulations of this problem by solving the three-dimensional compressible Navier-Stokes equations for gas/liquid flows. The results are used to investigate the non-spherical bubble dynamics and characterize the pressure and temperature fields based on the relevant parameters entering the problem: stand-off distance, geometrical configuration (angle, relative size, distance), collapse strength. This research was supported in part by ONR Grant N00014-12-1-0751 and NSF Grant CBET 1253157.

The Collapse of Ecosystem Engineer Populations

Directory of Open Access Journals (Sweden)

José F. Fontanari

2018-01-01

Full Text Available Humans are the ultimate ecosystem engineers who have profoundly transformed the world’s landscapes in order to enhance their survival. Somewhat paradoxically, however, sometimes the unforeseen effect of this ecosystem engineering is the very collapse of the population it intended to protect. Here we use a spatial version of a standard population dynamics model of ecosystem engineers to study the colonization of unexplored virgin territories by a small settlement of engineers. We find that during the expansion phase the population density reaches values much higher than those the environment can support in the equilibrium situation. When the colonization front reaches the boundary of the available space, the population density plunges sharply and attains its equilibrium value. The collapse takes place without warning and happens just after the population reaches its peak number. We conclude that overpopulation and the consequent collapse of an expanding population of ecosystem engineers is a natural consequence of the nonlinear feedback between the population and environment variables.

Can a collapse of global civilization be avoided?

OpenAIRE

Ehrlich, Paul R.; Ehrlich, Anne H.

2013-01-01

Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity.

Can a collapse of global civilization be avoided?

Science.gov (United States)

Ehrlich, Paul R; Ehrlich, Anne H

2013-03-07

Environmental problems have contributed to numerous collapses of civilizations in the past. Now, for the first time, a global collapse appears likely. Overpopulation, overconsumption by the rich and poor choices of technologies are major drivers; dramatic cultural change provides the main hope of averting calamity.

Nonlinear Progressive Collapse Analysis Including Distributed Plasticity

Directory of Open Access Journals (Sweden)

Mohamed Osama Ahmed

2016-01-01

Full Text Available This paper demonstrates the effect of incorporating distributed plasticity in nonlinear analytical models used to assess the potential for progressive collapse of steel framed regular building structures. Emphasis on this paper is on the deformation response under the notionally removed column, in a typical Alternate Path (AP method. The AP method employed in this paper is based on the provisions of the Unified Facilities Criteria – Design of Buildings to Resist Progressive Collapse, developed and updated by the U.S. Department of Defense [1]. The AP method is often used for to assess the potential for progressive collapse of building structures that fall under Occupancy Category III or IV. A case study steel building is used to examine the effect of incorporating distributed plasticity, where moment frames were used on perimeter as well as the interior of the three dimensional structural system. It is concluded that the use of moment resisting frames within the structural system will enhance resistance to progressive collapse through ductile deformation response and that it is conserative to ignore the effects of distributed plasticity in determining peak displacement response under the notionally removed column.

Radiation pressure in super star cluster formation

Science.gov (United States)

Tsang, Benny T.-H.; Milosavljević, Miloš

2018-05-01

The physics of star formation at its extreme, in the nuclei of the densest and the most massive star clusters in the universe—potential massive black hole nurseries—has for decades eluded scrutiny. Spectroscopy of these systems has been scarce, whereas theoretical arguments suggest that radiation pressure on dust grains somehow inhibits star formation. Here, we harness an accelerated Monte Carlo radiation transport scheme to report a radiation hydrodynamical simulation of super star cluster formation in turbulent clouds. We find that radiation pressure reduces the global star formation efficiency by 30-35%, and the star formation rate by 15-50%, both relative to a radiation-free control run. Overall, radiation pressure does not terminate the gas supply for star formation and the final stellar mass of the most massive cluster is ˜1.3 × 106 M⊙. The limited impact as compared to in idealized theoretical models is attributed to a radiation-matter anti-correlation in the supersonically turbulent, gravitationally collapsing medium. In isolated regions outside massive clusters, where the gas distribution is less disturbed, radiation pressure is more effective in limiting star formation. The resulting stellar density at the cluster core is ≥108 M⊙ pc-3, with stellar velocity dispersion ≳ 70 km s-1. We conclude that the super star cluster nucleus is propitious to the formation of very massive stars via dynamical core collapse and stellar merging. We speculate that the very massive star may avoid the claimed catastrophic mass loss by continuing to accrete dense gas condensing from a gravitationally-confined ionized phase.

Vapour and air bubble collapse analysis in viscous compressible water

Directory of Open Access Journals (Sweden)

Gil Bazanini

2001-01-01

Full Text Available Numerical simulations of the collapse of bubbles (or cavities are shown, using the finite difference method, taking into account the compressibility of the liquid, expected to occur in the final stages of the collapse process. Results are compared with experimental and theoretical data for incompressible liquids, to see the influence of the compressibility of the water in the bubble collapse. Pressure fields values are calculated in an area of 800 x 800 mm, for the case of one bubble under the hypothesis of spherical symmetry. Results are shown as radius versus time curves for the collapse (to compare collapse times, and pressure curves in the plane, for pressure fields. Such calculations are new because of their general point of view, since the existing works do not take into account the existence of vapour in the bubble, neither show the pressure fields seen here. It is also expected to see the influence of the compressibility of the water in the collapse time, and in the pressure field, when comparing pressure values.

Large-scale Instability during Gravitational Collapse with Neutrino Transport and a Core-Collapse Supernova

Science.gov (United States)

Aksenov, A. G.; Chechetkin, V. M.

2018-04-01

Most of the energy released in the gravitational collapse of the cores of massive stars is carried away by neutrinos. Neutrinos play a pivotal role in explaining core-collape supernovae. Currently, mathematical models of the gravitational collapse are based on multi-dimensional gas dynamics and thermonuclear reactions, while neutrino transport is considered in a simplified way. Multidimensional gas dynamics is used with neutrino transport in the flux-limited diffusion approximation to study the role of multi-dimensional effects. The possibility of large-scale convection is discussed, which is interesting both for explaining SN II and for setting up observations to register possible high-energy (≳10MeV) neutrinos from the supernova. A new multi-dimensional, multi-temperature gas dynamics method with neutrino transport is presented.

Inflationary gravitational waves in collapse scheme models

Energy Technology Data Exchange (ETDEWEB)

Mariani, Mauro, E-mail: mariani@carina.fcaglp.unlp.edu.ar [Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque S/N, 1900 La Plata (Argentina); Bengochea, Gabriel R., E-mail: gabriel@iafe.uba.ar [Instituto de Astronomía y Física del Espacio (IAFE), UBA-CONICET, CC 67, Suc. 28, 1428 Buenos Aires (Argentina); León, Gabriel, E-mail: gleon@df.uba.ar [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria – Pab. I, 1428 Buenos Aires (Argentina)

2016-01-10

The inflationary paradigm is an important cornerstone of the concordance cosmological model. However, standard inflation cannot fully address the transition from an early homogeneous and isotropic stage, to another one lacking such symmetries corresponding to our present universe. In previous works, a self-induced collapse of the wave function has been suggested as the missing ingredient of inflation. Most of the analysis regarding the collapse hypothesis has been solely focused on the characteristics of the spectrum associated to scalar perturbations, and within a semiclassical gravity framework. In this Letter, working in terms of a joint metric-matter quantization for inflation, we calculate, for the first time, the tensor power spectrum and the tensor-to-scalar ratio corresponding to the amplitude of primordial gravitational waves resulting from considering a generic self-induced collapse.

Self-Gravitating Stellar Collapse: Explicit Geodesics and Path Integration

Energy Technology Data Exchange (ETDEWEB)

Balakrishna, Jayashree [Department of Mathematics and Natural Sciences, College of Arts and Sciences, Harris-Stowe State University, St. Louis, MO (United States); Bondarescu, Ruxandra [Department of Physics, University of Zurich, Zurich (Switzerland); Moran, Christine C., E-mail: corbett@tapir.caltech.edu [TAPIR, Department of Theoretical Astrophysics, California Institute of Technology, Pasadena, CA (United States)

2016-11-25

We extend the work of Oppenheimer and Synder to model the gravitational collapse of a star to a black hole by including quantum mechanical effects. We first derive closed-form solutions for classical paths followed by a particle on the surface of the collapsing star in Schwarzschild and Kruskal coordinates for space-like, time-like, and light-like geodesics. We next present an application of these paths to model the collapse of ultra-light dark matter particles, which necessitates incorporating quantum effects. To do so we treat a particle on the surface of the star as a wavepacket and integrate over all possible paths taken by the particle. The waveform is computed in Schwarzschild coordinates and found to exhibit an ingoing and an outgoing component, where the former contains the probability of collapse, while the latter contains the probability that the star will disperse. These calculations pave the way for investigating the possibility of quantum collapse that does not lead to black hole formation as well as for exploring the nature of the wavefunction inside r = 2M.

Self-Gravitating Stellar Collapse: Explicit Geodesics and Path Integration

International Nuclear Information System (INIS)

Balakrishna, Jayashree; Bondarescu, Ruxandra; Moran, Christine C.

2016-01-01

We extend the work of Oppenheimer and Synder to model the gravitational collapse of a star to a black hole by including quantum mechanical effects. We first derive closed-form solutions for classical paths followed by a particle on the surface of the collapsing star in Schwarzschild and Kruskal coordinates for space-like, time-like, and light-like geodesics. We next present an application of these paths to model the collapse of ultra-light dark matter particles, which necessitates incorporating quantum effects. To do so we treat a particle on the surface of the star as a wavepacket and integrate over all possible paths taken by the particle. The waveform is computed in Schwarzschild coordinates and found to exhibit an ingoing and an outgoing component, where the former contains the probability of collapse, while the latter contains the probability that the star will disperse. These calculations pave the way for investigating the possibility of quantum collapse that does not lead to black hole formation as well as for exploring the nature of the wavefunction inside r = 2M.

Free Thyroid Transfer: A Novel Procedure to Prevent Radiation-induced Hypothyroidism

International Nuclear Information System (INIS)

Harris, Jeffrey; Almarzouki, Hani; Barber, Brittany; Scrimger, Rufus; Romney, Jacques; O'Connell, Daniel; Urken, Mark; Seikaly, Hadi

2016-01-01

Purpose: The incidence of hypothyroidism after radiation therapy for head and neck cancer (HNC) has been found to be ≤53%. Medical treatment of hypothyroidism can be costly and difficult to titrate. The aim of the present study was to assess the feasibility of free thyroid transfer as a strategy for the prevention of radiation-induced damage to the thyroid gland during radiation therapy for HNC. Methods and Materials: A prospective feasibility study was performed involving 10 patients with a new diagnosis of advanced HNC undergoing ablative surgery, radial forearm free-tissue transfer reconstruction, and postoperative adjuvant radiation therapy. During the neck dissection, hemithyroid dissection was completed with preservation of the thyroid arterial and venous supply for implantation into the donor forearm site. All patients underwent a diagnostic thyroid technetium scan 6 weeks and 12 months postoperatively to examine the functional integrity of the transferred thyroid tissue. Results: Free thyroid transfer was executed in 9 of the 10 recruited patients with advanced HNC. The postoperative technetium scans demonstrated strong uptake of technetium at the forearm donor site at 6 weeks and 12 months for all 9 of the transplanted patients. Conclusions: The thyroid gland can be transferred as a microvascular free transfer with maintenance of function. This technique could represent a novel strategy for maintenance of thyroid function after head and neck irradiation.

Free Thyroid Transfer: A Novel Procedure to Prevent Radiation-induced Hypothyroidism

Energy Technology Data Exchange (ETDEWEB)

Harris, Jeffrey [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Almarzouki, Hani [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Department of Otolaryngology-Head and Neck Surgery, King Abdulaziz University, Jeddah (Saudi Arabia); Barber, Brittany, E-mail: brittanybarber0@gmail.com [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Scrimger, Rufus [Division of Radiation Oncology, Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Romney, Jacques [Division of Endocrinology and Metabolism, Department of Medicine, University of Alberta, Edmonton, Alberta (Canada); O' Connell, Daniel [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada); Urken, Mark [Institute for Head and Neck and Thyroid Cancers, Icahn School of Medicine, Mount Sinai Hospital, New York, New York (United States); Seikaly, Hadi [Division of Otolaryngology-Head and Neck Surgery, Department of Surgery, University of Alberta, Edmonton, Alberta (Canada)

2016-09-01

Purpose: The incidence of hypothyroidism after radiation therapy for head and neck cancer (HNC) has been found to be ≤53%. Medical treatment of hypothyroidism can be costly and difficult to titrate. The aim of the present study was to assess the feasibility of free thyroid transfer as a strategy for the prevention of radiation-induced damage to the thyroid gland during radiation therapy for HNC. Methods and Materials: A prospective feasibility study was performed involving 10 patients with a new diagnosis of advanced HNC undergoing ablative surgery, radial forearm free-tissue transfer reconstruction, and postoperative adjuvant radiation therapy. During the neck dissection, hemithyroid dissection was completed with preservation of the thyroid arterial and venous supply for implantation into the donor forearm site. All patients underwent a diagnostic thyroid technetium scan 6 weeks and 12 months postoperatively to examine the functional integrity of the transferred thyroid tissue. Results: Free thyroid transfer was executed in 9 of the 10 recruited patients with advanced HNC. The postoperative technetium scans demonstrated strong uptake of technetium at the forearm donor site at 6 weeks and 12 months for all 9 of the transplanted patients. Conclusions: The thyroid gland can be transferred as a microvascular free transfer with maintenance of function. This technique could represent a novel strategy for maintenance of thyroid function after head and neck irradiation.

Enhanced desorption of cesium from collapsed interlayer regions in vermiculite by hydrothermal treatment with divalent cations

Energy Technology Data Exchange (ETDEWEB)

Yin, Xiangbiao, E-mail: yin.x.aa@m.titech.ac.jp [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Wang, Xinpeng [College of Resources and Metallurgy, Guangxi University, 100 Daxue East Road, Nanning 530004 (China); Wu, Hao; Ohnuki, Toshihiko; Takeshita, Kenji [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2017-03-15

Highlights: • Desorption of Cs{sup +} fixed in collapsed interlayer region of vermiculite was studied. • Monovalent cations readily induced interlayer collapse inhibiting Cs{sup +} desorption. • Larger hydrous ionic radii of divalent cations greatly prevented Cs{sup +} desorption. • Effect of divalent cation on Cs{sup +} desorption changes depending on thermal treatment. • ∼100% removal of saturated Cs{sup +} was achieved by hydrothermal treatment at 250 °C. - Abstract: Adsorption of cesium (Cs) on phyllosilicates has been intensively investigated because natural soils have strong ability of immobilizing Cs within clay minerals resulting in difficulty of decontamination. The objectives of present study are to clarify how Cs fixation on vermiculite is influenced by structure change caused by Cs sorption at different loading levels and how Cs desorption is affected by various replacing cations induced at different treating temperature. As a result, more than 80% of Cs was readily desorbed from vermiculite with loading amount of 2% saturated Cs (5.49 × 10{sup −3} mmol g{sup −1}) after four cycles of treatment of 0.01 M Mg{sup 2+}/Ca{sup 2+} at room temperature, but less than 20% of Cs was desorbed from saturated vermiculite. These distinct desorption patterns were attributed to inhibition of Cs desorption by interlayer collapse of vermiculite, especially at high Cs loadings. In contrast, elevated temperature significantly facilitated divalent cations to efficiently desorb Cs from collapsed regions. After five cycles of treatment at 250 °C with 0.01 M Mg{sup 2+}, ∼100% removal of saturated Cs was achieved. X-ray diffraction analysis results suggested that Cs desorption was completed through enhanced diffusion of Mg{sup 2+} cations into collapsed interlayer space under hydrothermal condition resulting in subsequent interlayer decollapse and readily release of Cs{sup +}.

Preventing radiation retinopathy with hyperfractionation

International Nuclear Information System (INIS)

Monroe, Alan T.; Bhandare, Niranjan; Morris, Christopher G.; Mendenhall, William M.

2005-01-01

Purpose: The purpose of this study was to determine factors associated with the development of radiation retinopathy in a large series of patients with head-and-neck cancer. In particular, we addressed whether the use of hyperfractionated radiation therapy was effective in reducing the risk of retinopathy. Methods and materials: One hundred eighty-six patients received a significant dose to the retina as part of curative radiotherapy. Primary sites included: nasopharynx, 46; paranasal sinus, 64; nasal cavity, 69; and palate, 7. Prescription doses varied depending on primary site and histology. Hyperfractionated (twice-daily) radiation was delivered to 42% of the patients in this study, typically at 1.10 to 1.20 Gy per fraction. The remainder were treated once-daily. Retinal doses were determined from computerized dosimetry plans when available. For all other patients, retinal doses were retrospectively calculated using reconstructed off-axis dosimetry taken from contours through the center of the globes. Retinal dose was defined as the minimum dose received by at least 25% of the globe. The median retinal dose was 56.85 Gy. Patients were followed for a median of 7.6 years. Results: Thirty-one eyes in 30 patients developed radiation retinopathy, resulting in monocular blindness in 25, bilateral blindness in 1, and decreased visual acuity in 4. The median time to the diagnosis of retinopathy was 2.6 years (range, 11 months to 5.3 years). The actuarial incidence of developing radiation retinopathy was 20% at both 5 and 10 years. The incidence of developing ipsilateral blindness due to retinopathy was 16% at 5 years and 17% at 10 years. Site-specific incidences varied considerably, with ethmoid sinus (9 of 25, 36%), nasal cavity (13 of 69, 19%), and maxillary sinus (6 of 35, 17%) being the most common sites associated with radiation retinopathy. Three of 72 patients (4%) receiving retinal doses less than 50 Gy developed retinopathy. Higher retinal doses resulted in a

Intracapsular implant rupture: MR findings of incomplete shell collapse.

Science.gov (United States)

Soo, M S; Kornguth, P J; Walsh, R; Elenberger, C; Georgiade, G S; DeLong, D; Spritzer, C E

1997-01-01

The objective of this study was to determine the frequency and significance of the MR findings of incomplete shell collapse for detecting implant rupture in a series of surgically removed breast prostheses. MR images of 86 breast implants in 44 patients were studied retrospectively and correlated with surgical findings at explantation. MR findings included (a) complete shell collapse (linguine sign), 21 implants; (b) incomplete shell collapse (subcapsular line sign, teardrop sign, and keyhole sign), 33 implants; (c) radial folds, 31 implants; and (d) normal, 1 implant. The subcapsular line sign was seen in 26 implants, the teardrop sign was seen in 27 implants, and the keyhole sign was seen in 23 implants. At surgery, 48 implants were found to be ruptured and 38 were intact. The MR findings of ruptured implants showed signs of incomplete collapse in 52% (n = 25), linguine sign in 44% (n = 21), and radial folds in 4% (n = 2). The linguine sign perfectly predicted implant rupture, but sensitivity was low. Findings of incomplete shell collapse improved sensitivity and negative predictive values, and the subcapsular line sign produced a significant incremental increase in predictive ability. MRI signs of incomplete shell collapse were more common than the linguine sign in ruptured implants and are significant contributors to the high sensitivity and negative predictive values of MRI for evaluating implant integrity.

Spherical top-hat collapse of a viscous unified dark fluid

Energy Technology Data Exchange (ETDEWEB)

Li, Wei [Bohai University, Department of Physics, Jinzhou (China); Dalian University of Technology, Institute of Theoretical Physics, Dalian (China); Xu, Lixin [Dalian University of Technology, Institute of Theoretical Physics, Dalian (China)

2014-05-15

In this paper, we test the spherical collapse of a viscous unified dark fluid (VUDF) which has constant adiabatic sound speed and show the nonlinear collapse for VUDF, baryons, and darkmatter, which are important in forming the large-scale structure of our Universe. By varying the values of the model parameters α and ζ{sub 0}, we discuss their effects on the nonlinear collapse of the VUDF model, and we compare its result to the ΛCDM model. The results of the analysis show that, within the spherical top-hat collapse framework, larger values of α and smaller values of ζ{sub 0} make the structure formation earlier and faster, and the other collapse curves are almost distinguished with the curve of ΛCDM model if the bulk viscosity coefficient ζ{sub 0} is less than 10{sup -3}. (orig.)

Endograft Collapse After Endovascular Treatment for Thoracic Aortic Disease

International Nuclear Information System (INIS)

Bandorski, Dirk; Brueck, Martin; Guenther, Hans-Ulrich; Manke, Christoph

2010-01-01

Endovascular treatment is an established therapy for thoracic aortic disease. Collapse of the endograft is a potentially fatal complication. We reviewed 16 patients with a thoracic endograft between 2001 and 2006. Medical records of the treated patients were studied. Data collected include age, gender, diagnosis, indication for endoluminal treatment, type of endograft, and time of follow up. All patients (n = 16; mean age, 61 years; range, 21-82 years) underwent computed tomography (CT) for location of the lesion and planning of the intervention. Time of follow-up with CT scan ranged from 1 to 61 months. Indications for endovascular treatment were degenerative aneurysm (n = 7; 44%), aortic dissection (n = 2; 12%), perforated aortic ulcer (n = 4; 25%), and traumatic aortic injury (n = 3; 19%). Three patients suffered from a collapse of the endograft (one patient distal, two patients proximal) between 3 and 8 days after endovascular treatment. These patients were younger (mean age, 37 ± 25 years vs. 67 ± 16 years; P 0.05]; distal, 45 ± 23.5% vs. 38 ± 21.7% [P > 0.05]). Proximal collapse was corrected by placing a bare stent. In conclusion, risk factors for stent-graft collapse are a small lumen of the aorta and a small radius of the aortic arch curvature (young patients), as well as oversizing, which is an important risk factor and is described for different types of endografts and protheses (Gore TAG and Cook Zenith). Dilatation of the collapsed stent-graft is not sufficient. Following therapy implantation of a second stent or surgery is necessary in patients with a proximal endograft collapse. Distal endograft collapse can possibly be treated conservatively under close follow-up.

Lung collapse among aquatic reptiles and amphibians during long-term diving.

Science.gov (United States)

Ultsch, Gordon R; Brainerd, Elizabeth L; Jackson, Donald C

2004-09-01

Numerous aquatic reptiles and amphibians that typically breathe both air and water can remain fully aerobic in normoxic (aerated) water by taking up oxygen from the water via extrapulmonary avenues. Nevertheless, if air access is available, these animals do breathe air, however infrequently. We suggest that such air breathing does not serve an immediate gas exchange function under these conditions, nor is it necessarily related to buoyancy requirements, but serves to keep lungs inflated that would otherwise collapse during prolonged submergence. We also suggest that lung deflation is routine in hibernating aquatic reptiles and amphibians in the northern portions of their ranges, where ice cover prevents surfacing for extended periods.

Shock waves from non-spherically collapsing cavitation bubbles

Science.gov (United States)

Supponen, Outi; Obreschkow, Danail; Farhat, Mohamed

2017-11-01

Combining simultaneous high-speed imaging and hydrophone measurements, we uncover details of the multiple shock wave emission from laser-induced cavitation bubbles collapsing in a non-spherical way. For strongly deformed bubbles collapsing near a free surface, we identify the distinct shock waves caused by the jet impact onto the opposite bubble wall and by the individual collapses of the remaining bubble segments. The energy carried by each of these shocks depends on the level of bubble deformation, quantified by the anisotropy parameter ζ, the dimensionless equivalent of the Kelvin impulse. For jetting bubbles, at ζ water hammer as ph = 0.45 (ρc2 Δp) 1 / 2ζ-1 .

Radiation safety and formation of public opinion

International Nuclear Information System (INIS)

Qurbanov, M.

2002-01-01

Full text: Team-administrative system of long years has been a reason of environmental pollution and health consequences and still does. This includes soil pollution with pesticides, ecological condition of micro and macro flora of the Caspian Sea, soil pollution with oil, deforestation and etc. Scientists and environmental NGOs have given some information to public and public opinion has already been formed on this issue. But public opinion is not necessarily formed on radiation - the most important and invisible problem. The reason of this is that radiation danger has been hidden as a closed theme from the public. After the soviet collapse this problem is also being revealed. Number of NGOs have held the seminar on this issue and given some information to public. The researches cover the following problems:To hold the public monitoring in the fields polluted with oil and separate it from the other fields by determining the fields polluted with radiation. To take measures in order to prevent public entrance to these fields; To inform about the usage of radiation based equipment in the industrial fields and to hold the regular monitoring; To advertise the differential signs of radiation sources in the city landfill and other polluted zones; To broaden the advocacy on ultraviolet rays and their influence to human health; To disseminate the brochures and advertisement papers on high technical radiation and their influence to human health; To analyze the radio environmental condition around the Gabala Radar Station; To advocate the possible radiation danger in using the x-ray and other medical equipment; Analyze the possible radon danger in shipping materials; To create the idea on possible transition of radioactive gases and elements from neighbor countries; Creation of idea on possible danger around the high voltage. The formation of public opinion on mentioned problem will depend on combining the scientists' and NGOs activities

Preventive radiation protection in Hamburg

International Nuclear Information System (INIS)

Boikat, U.; Lauer, R.; Plath, S.; Sachde, Z.G.

2001-01-01

Monitoring of environmental radioactivity as well as complex investigations for precautionary radiation protection are carried out in Hamburg by two radiation monitoring labs. The spectrum of their tasks is specified by the media to be investigated. The tasks are originating from the Federal Precautionary Radiation Protection Act and from local needs. Mostly since a lot of years all interesting materials are analysed for their radioactivity content, as a safe and precautionary radiation protection demands. Until today samples show the influence of global nuclear weapon fallout of the period until 1964. Partly they show the radioactivity of Caesium originating from the Chernobyl accident. Since ten years the radioactivity contents in the material investigated are decreasing. Mostly the activity reached levels as at the end of 1985. The basic food stuff investigated in Hamburg can be considered as to be uncontaminated by radioactivity. With the introduction of the Federal Precautionary Radiation Protection Act, a series of new investigation programs and investigation methods were developed. This allows a better preparedness for extraordinary situations of increased radioactivity in the environment as 12 years ago. Thus a precise assessment of situations of increased radioactivity levels can be given together with coordinated and solid information to the public concerning provisions and actions. (orig.) [de

Preventive effect of interferon-γ of Chinese genotype on radiation pulmonary fibrosis

International Nuclear Information System (INIS)

Sun Li; Song Liangwen; Liu Tao; Zhang Yong; Yin Jiye; Diao Ruiying

2006-01-01

Objective: To investigate the inhibitive effect of Interferon-γ (γ-IFN) of Chinese genotype on proliferation of human lung fibroblast (HLF) induced by radiation, and examine its possible mechanism and role in prevention and treatment of radiation pulmonary fibrosis. Methods: The proliferation of HLF was determined by MTT assay, the expression of γ-smooth muscle actin (αa-SMA) and the synthesis of collagen type IV by immunocytochemistry assays. Results: Chinese α-IFN was observed to inhibit, proportionally to irradiation dose, the proliferation of HLF induced by 60 Co γ-irradiation. The expression of γ-SMA was remarkable in cytoplasmic matrix after the irradiation, suggesting that irradiation could induce the transformation from fibroblast (FB) to myofibroblast (MFB). The expression of collagen IV was increased with irradiation. Compared with the irradiated group, the expression of collagen IV was lower when γ-IFN was administered before being irradiated. Conclusion: 60 Co γ irradiation can induce pulmonary fibrosis by promoting the proliferation of HLF, inducing the transformation from FB to MFB, and increasing the excreting of collagen type IV. γ-IFN can prevent pulmonary fibrosis by effectively inhibiting the abnormal proliferation of HLF and the excessive synthesis of collagen IV after irradiation. (authors)

A proposal for prevention of acute radiation hazard and social panic regarding orphan sources in Japan

Energy Technology Data Exchange (ETDEWEB)

Takahash, T. [Research Reactor Institute, Kyoto Univ., Osaka (Japan); Kai, M. [Oita Univ., of Nursing and Health Sciences, Oita (Japan); Yamazaki, K. [Chiyoda Technol Corporation, Tokyo (Japan); Gomi, K. [Japan Radioisotope Association, Tokyo (Japan); Nakazato, K. [School of Medicine, Keio univ., Tokyo (Japan); Iida, T. [Nagoya Univ., Nagoya (Japan)

2002-07-01

To respond to an increase of social problems concerning orphan sources in Japan, a working group was formed in the Japan Health Physics Society. In this working group, we investigated how to prevent acute radiation hazard or social panic regarding orphan sources in scrap metal and detection system for orphan sources brought into scrap yards before recycle. For detection system in a scrap yard we conducted an experiment on detectability of monitoring instrument using a radiation source mixed in scrap metal on a truck. The result showed that it was not easy to detect even a high-level source if it was shielded by scrap metal. We also estimated detection limits for radioactive materials in scrap metal by calculation that was validated with experimental data. We summarized present status about orphan sources in Japan and proposed a categorization of orphan sources according to dose rates to deal with unknown sources in a scrap yard. Our report includes some proposals to the government, industry and academic world for preventing acute radiation hazard and social panic.

A proposal for prevention of acute radiation hazard and social panic regarding orphan sources in Japan

International Nuclear Information System (INIS)

Takahash, T.; Kai, M.; Yamazaki, K.; Gomi, K.; Nakazato, K.; Iida, T.

2002-01-01

To respond to an increase of social problems concerning orphan sources in Japan, a working group was formed in the Japan Health Physics Society. In this working group, we investigated how to prevent acute radiation hazard or social panic regarding orphan sources in scrap metal and detection system for orphan sources brought into scrap yards before recycle. For detection system in a scrap yard we conducted an experiment on detectability of monitoring instrument using a radiation source mixed in scrap metal on a truck. The result showed that it was not easy to detect even a high-level source if it was shielded by scrap metal. We also estimated detection limits for radioactive materials in scrap metal by calculation that was validated with experimental data. We summarized present status about orphan sources in Japan and proposed a categorization of orphan sources according to dose rates to deal with unknown sources in a scrap yard. Our report includes some proposals to the government, industry and academic world for preventing acute radiation hazard and social panic

Fatal collapse due to autonomic dysreflexia during manual self-evacuation of bowel in a tetraplegic patient living alone: lessons to learn

Directory of Open Access Journals (Sweden)

Vaidyanathan S

2017-11-01

Full Text Available Subramanian Vaidyanathan,1 Bakul M Soni,1 Paul Mansour,2 Tun Oo1 1Regional Spinal Injuries Centre, 2Department of Histopathology, Southport and Formby District General Hospital, Town Lane, Southport, UK Background: To identify areas for improvement, the National Health Service in England mandates the review of case reports of patients who have died, which should be translated into improved care for other patients. Case report: A 49-year-old Caucasian man sustained C-7 tetraplegia in a motorcycle accident in 1992. In 2009, he developed seizures and collapsed in the lavatory on a number of occasions during manual self-evacuation of his bowel. A 24-hour electrocardiogram recording at that time showed sinus rhythm with a maximum heart rate of 97 and a minimum of 39 beats per minute; there were no significant arrhythmias that could have contributed to his episodes of collapse. In 2015, the patient again collapsed while performing manual evacuation of his bowel; on this occasion, he did not suffer a seizure. He was found unresponsive in the bathroom by his daughter, who contacted the emergency services. He recovered consciousness on arrival at the Accident and Emergency Department. A noncontrast computed tomography scan of his head revealed no acute intracranial pathology. In 2016, he suffered a fatal collapse in the lavatory, again while performing manual bowel evacuation. At autopsy, no other significant disease was found that might have caused death, and given the clinical history, the cause of death was recorded as autonomic dysreflexia. Conclusion: There were delays in 1 recognizing that his episodes of collapse in the lavatory were due to autonomic dysreflexia induced by manual bowel evacuation; 2 recommending the prior application of topical 2% lidocaine jelly to prevent or limit autonomic dysreflexia occurring during manual bowel evacuation; and 3 considering alternative bowel management such as stimulant laxatives, transanal irrigation, or

Langmuir field structures favored in wave collapse

International Nuclear Information System (INIS)

Robinson, P.A.; Wouters, M.J.; Broderick, N.G.

1996-01-01

Study of Langmuir collapse thresholds shows that they have little polarization dependence and that moving packets have the lowest thresholds in the undamped case. However, incorporation of damping into the density response inhibits collapse of packets moving at more than a small fraction of the sound speed. Investigation of energy transfer to packets localized in density wells emdash the nucleation process emdash shows that at most a few trapped states can exist and that energy transfer is most effective when there is a single barely-trapped state. Coupled with an argument that closely packed wave packets have lower collapse thresholds, this argument yields an estimate of the number density of localized nucleating states in a turbulent plasma. It also leads to a simple and direct semiquantitative estimate of the collapse threshold. All these results are in accord with previous numerical simulations incorporating ion-sound damping, which show a preponderance of slow-moving or stationary packets with little or no intrinsic polarization dependence of thresholds. Likewise, the number densities obtained are in good agreement with simulation values, and the simple estimate of the threshold is semiquantitatively correct. The extent of the agreement supports the nucleation scenario with close-packed nucleation sites in the turbulent state. copyright 1996 American Institute of Physics

Search for stellar gravitational collapses with the MACRO detector

CERN Document Server

Ambrosio, M; Baldini, A; Barbarino, G C; Barish, B C; Battistoni, G; Bellotti, R; Bemporad, C; Bernardini, P; Bilokon, H; Bloise, C; Bower, C; Brigida, M; Bussino, S; Cafagna, F; Campana, D; Carboni, M; Cecchini, S; Cei, F; Chiarella, V; Choudhary, B C; Coutu, S; Cozzi, M; De Cataldo, G; De Marzo, C; De Mitri, I; De Vincenzi, M; Dekhissi, H; Derkaoui, J; Di Credico, A; Favuzzi, C; Forti, C; Fusco, P; Giacomelli, G; Giannini, G; Giglietto, N; Giorgini, M; Grassi, M; Grillo, A; Gustavino, C; Habig, A; Hanson, K; Heinz, R; Iarocci, E; Katsavounidis, E; Katsavounidis, I; Kearns, E; Kim, H; Kyriazopoulou, S; Lamanna, E; Lane, C; Levin, D S; Lipari, P; Longley, N P; Longo, M J; Loparco, F; Maaroufi, F; Mancarella, G; Mandrioli, G; Margiotta, A; Marini, A; Martello, D; Marzari-Chiesa, A; Mazziotta, M N; Michael, D G; Monacelli, P; Montaruli, T; Monteno, M; Mufson, S; Musser, J; Nicolò, D; Nolty, R; Orth, C; Osteria, G; Palamara, O; Patera, V; Patrizii, L; Pazzi, R; Peck, C W; Perrone, L; Petrera, S; Popa, V; Raino, J A; Reynoldson, J; Ronga, F; Satriano, C; Scapparone, E; Scholberg, K; Sciubba, A; Sioli, M; Sirri, G; Sitta, M; Spinelli, P; Spinetti, M; Spurio, M; Steinberg, R; Stone, J L; Sulak, L R; Surdo, A; Tarle, G; Togo, V; Vakili, M; Walter, C W; Webb, R; 10.1140/epjc/s2004-01981-3

2004-01-01

We present the final results of the search for stellar gravitational collapses obtained by the MACRO experiment. The detector was active for a stellar collapse search for more than 11 years and it was sensitive to collapses occurring all over in our galaxy for 8.6 years. A real time system for a prompt recognition of neutrino bursts was developed and was operating on-line for almost the whole life of the experiment. No signal compatible with a neutrino burst from a galactic supernova was observed.

Is radiation superior to indomethacin to prevent heterotopic ossification in acetabular fractures?: a systematic review.

NARCIS (Netherlands)

Blokhuis, T.J.; Frolke, J.P.M.

2009-01-01

Heterotopic ossification is a well-known complication after fixation of an acetabular fracture. Indomethacin and radiation therapy are used as prophylaxis to prevent heterotopic ossification. It is unclear, however, whether either is superior, although this may relate to lack of power in individual

The regulations for enforcing the law concerning prevention from radiation hazards due to radioisotopes

International Nuclear Information System (INIS)

1977-01-01

Those who want to use, sell or dispose of radioactive isotopes as occupation should file applications for approval attached with the required documents. Those who want to change the approved items of use, sale or disposal of radioactive isotopes should file applications for approval. The number of documents for the application of approval are one original and four duplicates. The use, refilling, storage, transportation and disposal of radioactive isotopes should be carried out in accordance with the specified standards, respectively. Radiation dose rate, density of particle fluxes, and the state of contamination caused by radioactive isotopes should be measured in the specified places at the specified frequency, and the records of such measurements should be kept. Prevention of radiation injuries including the measures for finding those who suffer from radiation injuries and the measures for those who underwent or might undergo radiation injuries should be carried out in accordance with the respective specifications. (Rikitake, Y.)

Tracheal collapse diagnosed by multidetector computed tomography: evaluation of different image analysis methods

DEFF Research Database (Denmark)

Nygaard, Mette; Bendstrup, Elisabeth; Dahl, Ronald

2017-01-01

diseases when using an expiratory collapse of = 50% as a threshold. The four methods were comparable with highly significant Pearsons correlation coefficients (0.764-0.856). However, the four methods identified different patients with collapse of = 50 There was no correlation between symptoms...... and the degree of collapse. Conclusion: The different methods identify tracheal collapse in different patients. Hence, the diagnosis of excessive tracheal collapse can not rely solely on MDCT images. Generally, there is a poor correlation between symptoms and the degree of collapse in the different methods....... However, when using the maximal collapse, there is some correlation with symptoms. When in doubt regarding the diagnosis, further investigations, such as bronchoscopy, should be carried out....

Pentoxifylline and vitamin E for treatment or prevention of radiation-induced fibrosis in patients with breast cancer.

Science.gov (United States)

Kaidar-Person, Orit; Marks, Lawrence B; Jones, Ellen L

2018-04-23

Radiation therapy (RT) plays an important role in the management of breast cancer. Radiation-induced fibrosis is a side effect of radiation therapy and may occur in up to 13% of the cases in patients (Radiother Oncol, 2009;90:80), fortunately usually is modest/localized and not associated with marked symptoms. However, occasionally, fibrosis can be moderate-to-severe, and cause clinically-meaningful symptoms. The current review summarizes the use of pentoxifylline and vitamin E of treatment or prevention of radiation-induced fibrosis in breast cancer patients. Even though data are limited, this regimen may reduce RT-associated toxicity. © 2018 Wiley Periodicals, Inc.

The burning issues of motor vehicle radiator scald injuries revisited - a fresh review and changing prevention strategies.

Science.gov (United States)

Patel, J N; Tan, A; Frew, Q; Dziewulski, P

2016-12-31

A preventable subgroup of burn injuries is scalds sustained from motor vehicle radiators. This study was to determine changes in trends in epidemiology of such injuries and to discuss whether current and other prevention efforts proposed previously require reinforcement. We conducted a retrospective study (February 2007-August 2015) of all motor vehicle-related burn referrals to our regional burns service. 68 cases of motor vehicle radiator burns were identified. Male to female ratio was 65:3. Mean age was 35.1 (range = 9-71). Most cases occurred in the summer months (22/68 = 32.4%). 65 cases (95.6%) involved car radiators. 66% of injuries resulted from actively removing the pressure cap of an overheated radiator in the motor vehicle. Mean total burn surface area (%TBSA) was 2.1% (range = 0.5- 11%). The depths of burn injuries were mostly superficial partial thickness. Face, chest and upper limbs were the most common sites of injury. Mean healing time was 14.2 days (range = 4-60). Following the introduction of safety measures by vehicle manufacturers, motor vehicle radiator burns in this era are mostly minor injuries and can be potentially managed conservatively as an outpatient. This contrasts with findings from previous studies over a decade ago of larger, more significant injuries requiring admission and surgery. Whilst manufacturers have installed safety measures into the design of radiator caps, our findings suggest that re-educating the public to allow a period of cooling prior to opening caps should be reinforced.

Rotating collapse of stellar iron cores in general relativity

International Nuclear Information System (INIS)

Ott, C D; Dimmelmeier, H; Marek, A; Janka, H-T; Zink, B; Hawke, I; Schnetter, E

2007-01-01

We present results from the first 2 + 1 and 3 + 1 simulations of the collapse of rotating stellar iron cores in general relativity employing a finite-temperature equation of state and an approximate treatment of deleptonization during collapse. We compare full 3 + 1 and conformally-flat spacetime evolution methods and find that the conformally-flat treatment is sufficiently accurate for the core-collapse supernova problem. We focus on the gravitational wave (GW) emission from rotating collapse, core bounce and early postbounce phases. Our results indicate that the GW signature of these phases is much more generic than previously estimated. In addition, we track the growth of a nonaxisymmetric instability of dominant m = 1 character in two of our models that leads to prolonged narrow-band GW emission at ∼920-930 Hz over several tens of milliseconds

On the gravitational collapse of a gas cloud in the presence of bulk viscosity

International Nuclear Information System (INIS)

Carlevaro, Nakia; Montani, Giovanni

2005-01-01

We analyse the effects induced by the bulk (or second) viscosity on the dynamics associated with the extreme gravitational collapse. The aim of the work is to investigate whether the presence of viscous corrections to the evolution of a collapsing gas cloud influences the top-down fragmentation process. To this end, we generalize the approach presented by Hunter (1962 Astrophys. J. 136 594) to include in the dynamics of the (uniform and spherically symmetric) cloud the negative pressure contribution associated with the bulk viscosity phenomenology. Within the framework of a Newtonian approach (whose range of validity is outlined), we extend to the viscous case either the Lagrangian or the Eulerian motion of the system addressed in Hunter (1962 Astrophys. J. 136 594) and we treat the asymptotic evolution in correspondence with a viscosity coefficient of the form ζ = ζ 0 ρ 5/6 (ρ being the cloud density and ζ 0 = const). We show how the adiabatic-like behaviour of the gas (i.e. when the polytropic index γ takes values 4/3 < γ ≤ 5/3) is deeply influenced by viscous correction when its collapse reaches the extreme regime toward the singularity. In fact, for sufficiently large viscous contributions, density contrasts associated with a given scale of the fragmentation process acquire, asymptotically, a vanishing behaviour which prevents the formation of sub-structures. Since in the non-dissipative case density contrasts diverge (except for the purely adiabatic behaviour γ = 5/3 in which they remain constant), we can conclude that in the adiabatic-like collapse the top-down mechanism of structure formation is suppressed as soon as enough strong viscous effects are taken into account. Such a feature is not present in the isothermal-like (i.e. 1 ≤ γ < 4/3) collapse because the sub-structure formation is yet present and outlines the same behaviour as in the non-viscous case. We emphasize that in the adiabatic-like collapse the bulk viscosity is also responsible

Multi-temporal SAR interferometry reveals acceleration of bridge sinking before collapse

Science.gov (United States)

Sousa, J. J.; Bastos, L.

2013-03-01

On the night of 4 March 2001, at Entre-os-Rios (Northern Portugal), the Hintze Ribeiro centennial bridge collapsed killing 59 people traveling in a bus and three cars that were crossing the Douro River. According to the national authorities, the collapse was due to two decades of uncontrolled sand extraction which compromised the stability of the bridge's pillars, together with underestimating the warnings from divers and technicians. In this work we do not intend to corroborate or contradict the official version of the accident's causes, but only demonstrate the potential of Multi-Temporal Interferometric techniques for detection and monitoring of deformations in structures such as bridges, and consequently the usefulness of the derived information in some type of early warning system to help prevent new catastrophic events. Based on the analysis of 52 ERS-1/2 covering the period from May 1995 to the fatal occurrence, we were able to detect significant movements, reaching rates of 20 mm yr-1, in the section of the bridge that fell into the Douro River, which are obvious signs of the bridge's instability. These promising results demonstrate that with the new high-resolution synthetic aperture radar satellite scenes it is possible to develop interferometric based methodologies for structural health monitoring.

Origin of Hawking radiation

International Nuclear Information System (INIS)

Hajicek, P.

1987-01-01

In the first part of the paper, the possible influence that quantum corrections could have on the existence and position of an event horizon in a spherically symmetric collapse is studied. A counterexample is constructed proving that the small value of near the gravitational radius does not guarantee the formation of an event horizon. In an exactly solvable model of black-hole evaporation, the spacetime structure is manipulated in the Planck neighborhood of the singularity so that the event horizon is shifted arbitrarily to the future or removed completely. This change in the position of the event horizon has no observable consequences until the retarded time of the end of the black-hole evaporation is reached. However, even in the absence of the event horizon, the Hawking radiation survives. In the second part of the paper, its origin is studied. The old idea is adopted that it is coming from a neighborhood of the so-called ergosphere. The concept of the ergosphere is generalized to nonstationary, spherically symmetric spacetimes using the notion of Hawking quasilocal mass. The boundary of such an ergosphere is shown to coincide with the locus of apparent horizons. It seems, therefore, that the Hawking effect is associated with the apparent rather than the event horizon. An extrapolation of some properties of from a neighborhood of the Schwarzschild horizon to that of an apparent horizon forming in a collapse leads to the result that too much energy is radiated away already before the apparent horizon forms, similarly as in the Boulware scenario of gravitational collapse

Crystallite structure formation at the collapse pressure of fatty acid Langmuir films

International Nuclear Information System (INIS)

Valdes-Covarrubias, M A; Cadena-Nava, R D; Vasquez-MartInez, E; Valdez-Perez, D; Ruiz-GarcIa, J

2004-01-01

We report isotherm and atomic force microscopy studies of collapsed Langmuir monolayers of fatty acids. The Langmuir monolayers were overcompressed in the range 7-40 deg. C and transferred onto mica after the sharp pressure drop when the collapse pressure was reached. Collapsed material was observed by AFM, which revealed that the multilayers are indeed three-dimensional crystallites. We found that the shape of the crystallites depends on the collapse temperature, the phase from which the collapse occurs and/or the chain length. However, at higher temperatures the collapsed films no longer show a well defined crystallite formation, but rather a more heterogeneous melt-like pattern. We associated the crystallite formation with known bulk crystal phases of the fatty acids

Study on preventive effects of i.v. administration of flavin adenine dinucleotide (FAD) before irradiation on radiation stomatitis

International Nuclear Information System (INIS)

Nagai, Masao; Houzawa, Jiro; Hakamada, Masaru

1984-01-01

In order to compare the preventive effect on radiation stomatitis, flavin adenine dinucleotide (FAD) or vitamin C was administered intravenously until the blood level reached the maximum at the time of irradiation. Thirtyfive patients with cranial or cervical tumors were allocated into the group with FAD (15), the group with vitamin C (10), and the group with irradiation alone (10). The incidence of stomititis was significantly lower and the number of patients in whom the drug was withdrawn due to stomatitis was extremely smaller in the group with FAD than in the other groups. FAD administered before irradiation was considered very useful in preventing radiation stomatitis. (Namekawa, K.)

Collapse of thin wall tubes small initial ovality

International Nuclear Information System (INIS)

Moreno, A.

1977-01-01

In this work a simple model of creep collapse of tubes based on the bending theory of curved beams, is developed. The model is compared with more complex models. The main result of this work is the definition of a new model of creep collapse of tubes with a minimum of limitative hypothesis. (Author) 6 refs

Intense electromagnetic outbursts from collapsing hypermassive neutron stars

Science.gov (United States)

Lehner, Luis; Palenzuela, Carlos; Liebling, Steven L.; Thompson, Christopher; Hanna, Chad

2012-11-01

We study the gravitational collapse of a magnetized neutron star using a novel numerical approach able to capture both the dynamics of the star and the behavior of the surrounding plasma. In this approach, a fully general relativistic magnetohydrodynamics implementation models the collapse of the star and provides appropriate boundary conditions to a force-free model which describes the stellar exterior. We validate this strategy by comparing with known results for the rotating monopole and aligned rotator solutions and then apply it to study both rotating and nonrotating stellar collapse scenarios and contrast the behavior with what is obtained when employing the electrovacuum approximation outside the star. The nonrotating electrovacuum collapse is shown to agree qualitatively with a Newtonian model of the electromagnetic field outside a collapsing star. We illustrate and discuss a fundamental difference between the force-free and electrovacuum solutions, involving the appearance of large zones of electric-dominated field in the vacuum case. This provides a clear demonstration of how dissipative singularities appear generically in the nonlinear time evolution of force-free fluids. In both the rotating and nonrotating cases, our simulations indicate that the collapse induces a strong electromagnetic transient, which leaves behind an uncharged, unmagnetized Kerr black hole. In the case of submillisecond rotation, the magnetic field experiences strong winding, and the transient carries much more energy. This result has important implications for models of gamma-ray bursts. Even when the neutron star is surrounded by an accretion torus (as in binary merger and collapsar scenarios), a magnetosphere may emerge through a dynamo process operating in a surface shear layer. When this rapidly rotating magnetar collapses to a black hole, the electromagnetic energy released can compete with the later output in a Blandford-Znajek jet. Much less electromagnetic energy is

PREFACE: Collapse Calderas Workshop

Science.gov (United States)

Gottsmann, Jo; Aguirre-Diaz, Gerardo

2008-10-01

Caldera-formation is one of the most awe-inspiring and powerful displays of nature's force. Resultant deposits may cover vast areas and significantly alter the immediate topography. Post-collapse activity may include resurgence, unrest, intra-caldera volcanism and potentially the start of a new magmatic cycle, perhaps eventually leading to renewed collapse. Since volcanoes and their eruptions are the surface manifestation of magmatic processes, calderas provide key insights into the generation and evolution of large-volume silicic magma bodies in the Earth's crust. Despite their potentially ferocious nature, calderas play a crucial role in modern society's life. Collapse calderas host essential economic deposits and supply power for many via the exploitation of geothermal reservoirs, and thus receive considerable scientific, economic and industrial attention. Calderas also attract millions of visitors world-wide with their spectacular scenic displays. To build on the outcomes of the 2005 calderas workshop in Tenerife (Spain) and to assess the most recent advances on caldera research, a follow-up meeting was proposed to be held in Mexico in 2008. This abstract volume presents contributions to the 2nd Calderas Workshop held at Hotel Misión La Muralla, Querétaro, Mexico, 19-25 October 2008. The title of the workshop `Reconstructing the evolution of collapse calderas: Magma storage, mobilisation and eruption' set the theme for five days of presentations and discussions, both at the venue as well as during visits to the surrounding calderas of Amealco, Amazcala and Huichapan. The multi-disciplinary workshop was attended by more than 40 scientist from North, Central and South America, Europe, Australia and Asia. Contributions covered five thematic topics: geology, geochemistry/petrology, structural analysis/modelling, geophysics, and hazards. The workshop was generously supported by the International Association of Volcanology and the Chemistry of The Earth's Interior

FULLY GENERAL RELATIVISTIC SIMULATIONS OF CORE-COLLAPSE SUPERNOVAE WITH AN APPROXIMATE NEUTRINO TRANSPORT

Energy Technology Data Exchange (ETDEWEB)

Kuroda, Takami; Kotake, Kei [Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan); Takiwaki, Tomoya [Center for Computational Astrophysics, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)

2012-08-10

We present results from the first generation of multi-dimensional hydrodynamic core-collapse simulations in full general relativity (GR) that include an approximate treatment of neutrino transport. Using an M1 closure scheme with an analytic variable Eddington factor, we solve the energy-independent set of radiation energy and momentum based on the Thorne's momentum formalism. Our newly developed code is designed to evolve the Einstein field equation together with the GR radiation hydrodynamic equations. We follow the dynamics starting from the onset of gravitational core collapse of a 15 M{sub Sun} star, through bounce, up to about 100 ms postbounce in this study. By computing four models that differ according to 1D to 3D and by switching from special relativistic (SR) to GR hydrodynamics, we study how the spacial multi-dimensionality and GR would affect the dynamics in the early postbounce phase. Our 3D results support the anticipation in previous 1D results that the neutrino luminosity and average neutrino energy of any neutrino flavor in the postbounce phase increase when switching from SR to GR hydrodynamics. This is because the deeper gravitational well of GR produces more compact core structures, and thus hotter neutrino spheres at smaller radii. By analyzing the residency timescale to the neutrino-heating timescale in the gain region, we show that the criterion to initiate neutrino-driven explosions can be most easily satisfied in 3D models, irrespective of SR or GR hydrodynamics. Our results suggest that the combination of GR and 3D hydrodynamics provides the most favorable condition to drive a robust neutrino-driven explosion.

The 10 recommendations for prevention of radiation accidents in industrial gamma radiography

International Nuclear Information System (INIS)

Souza, Luana Silva de

2015-01-01

The Industrial Gamma Radiography, as part of Industrial Radiography, stands out as the most widespread and plays an important role in the quality control of different materials and devices. However, IAEA classifies industrial gamma radiography in the Category 2 as very dangerous due to the radiological risk caused by the use of high activity radioactive sources. In March, 2012, a Brazilian Workshop on Prevention of Industrial Gamma Radiography Accident was performed by DIAPI/CNEN with the objective of disseminating knowledge about radiological accidents with radioactive sources in this application. During this Workshop, IRD/CNEN conducted a survey with 75 participants using a form with 22 recommendations to prevent radiological accidents, aiming to select the most voted. This present work aims to perform a detailed statistical study to define the Top 10 Recommendations for industrial gamma radiography operator avoids radiological accidents and to prepare a brochure with these top 10 recommendations to be distributed to all industrial gamma radiography radiation workers. Data analysis was performed using the statistical method 'Frequency Distribution', among the 75 participants categorized as General, RPO, and Other Workers of the area. The results were obtained for each category, accounting for the total of 22 recommendations in its percentage and number of votes, and the top 10 recommendations were defined to prevent radiological accidents. The first place and most important recommendation is 'Always use a personal alarm monitor throughout the work'. One of the conclusions is that the brochure with the Top 10 Recommendations shows to be understandable and useful for dissemination and training of radiation workers to avoid radiological accidents in industrial gamma radiography. (author)

Study of creep collapse of tubes subject to external pressure at elevated temperature

International Nuclear Information System (INIS)

Takikawa, N.

1982-01-01

Intermediate heat exchanger (IHX) tubes of VHTR form the boundary between the primary and secondary coolants of the reactor. The tubes are subject to external pressures at a postulated secondary coolant depressurization accident, which might lead to creep collapse. Therefore, it is necessary to ensure the integrity against creep collapse by analysis. The objective of this work is to study a simplified analytical method for predicting collapse time of a curved tube subjected to an external pressure. The study is made based on the comparison of experimental collapse time of curved and straight tubes. Creep collapse tests were conducted under an elevated temperature and an external pressure. Test results showed that curved tubes had longer collapse time than straight tubes with the same cross sectional ovality. The simplified analytical method for a curved tube is proposed in this report, which is to compute collapse time of a straight tube with the same ovality. And in this method the computed time is considered as collapse time of the curved tube. The above test results show that this simplified method gives the conservative collapse time. And it is confirmed by additional IHX tube tests that the method is applicable to creep collapse analysis of IHX tubes

Structural elements of collapses in shallow water flows with horizontally nonuniform density

Energy Technology Data Exchange (ETDEWEB)

Goncharov, V. P., E-mail: v.goncharov@rambler.ru [Russian Academy of Sciences, Obukhov Institute of Atmospheric Physics (Russian Federation); Pavlov, V. I., E-mail: Vadim.Pavlov@univ-lille1.fr [Universite de Lille 1, UFR de Mathematiques Pures et Appliquees-LML UMR 8107 (France)

2013-10-15

The mechanisms and structural elements of instability whose evolution results in the occurrence of the collapse are studied in the scope of the rotating shallow water model with a horizontally nonuniform density. The diagram stability based on the integral collapse criterion is suggested to explain system behavior in the space of constants of motion. Analysis of the instability shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing drop-like fragment with the bottom contracts into a rotating segment. The other implies isotropic contraction of the area into a point.

State of enforcement of the law concerning prevention from radiation hazards due to radio-isotopes

International Nuclear Information System (INIS)

1977-01-01

In view of the recent advance of radiation utilization in many fields, the situation as of the end of fiscal 1976 under the law is described. The statistics on the number of enterprises concerning radioisotope usage, sales and waste-treatment are first given. Then, the measures taken by the Science and Technology Agency to improve radiation hazard prevention are explained, and cooperation with other governmental offices, efforts by the enterprises, steps taken for the enterprises of nondestructive testing, hospitals, universities, etc., and restudy on the law are described. (Mori, K.)

Biological prevention and/or treatment strategies for radiation myelopathy. Discussion of a new perspective

International Nuclear Information System (INIS)

Nieder, C.; Ataman, F.; Price, R.E.; Kian Ang, K.

1999-01-01

Background: Radiosensitivity of the spinal cord makes both curative first-line treatment of numerous malignancies and re-irradiation of recurrent or second tumors more difficult. This review discusses recent advances in basic research that alter the view on the pathogenesis of radiation myelopathy, possibly offering strategies for prevention and/or therapy. Results: Available data of developmental neurobiology and preclinical studies of demyelinating diseases revealed interesting insights into oligodendrocyte development, intercellular signaling pathways, and myelination processes. Current findings suggest that administration of cytokines could increase proliferation of oligodendrocyte progenitor cells, enhance their differentiation, upregulate synthesis of myelin constituents, and promote myelin regeneration in the adult central nervous system. Other compounds might also be able to modulate progression of pathogenic processes that eventually lead to radiation myelopathy. This offers several possible biological prevention and/or treatment strategies, which currently are being investigated in animal studies. Conclusions: Technical options as well as optimization of fractionation parameters should be given priority in the attempt to reduce iatrogenic neurotoxicity. However, rational biological strategies could offer a new perspective for many patients. (orig.) [de

Lipid peroxidation in radiation pneumonitis in mouse lung and its preventation

International Nuclear Information System (INIS)

Kodama, Akihisa; Tsujino, Kayoko; Kono, Michio

1998-01-01

Lipid peroxidation of the lung in irradiated C57BL6J mice was analyzed by gas chromatography. Among six major fatty acids in the mouse lung tissue, the amounts of two unsaturated fatty acids, arachidonic acid and DHA reduced one day after irradiation, and then recovered up to the level of in the control group four weeks after irradiation. In contrast, the amounts of stearic and palmitic acid did not change significantly. The mice fed with vitamin E-enriched food showed no significant changes of fatty acids which were compatible with pathophysiological findings 4 weeks after irradiation. Reduction of both arachidonic acid and DHA following lipid peroxidation in lung tissue, was assumed to play an important role in development of radiation pneumonitis. Vitamin E seems to enable to prevent or reduce the occurrence and progression of radiation pneumonitis, but as a radical scavenger, it may also weaken the anti-tumor growth effect of low linear energy transfer (LET) irradiation as photon. (author)

White noise from dark matter: 21 cm observations of early baryon collapse

International Nuclear Information System (INIS)

Zurek, Kathryn M.; Hogan, Craig J.

2007-01-01

In concordance cosmology, dark matter density perturbations generated by inflation lead to nonlinear, virialized minihalos, into which baryons collapse at redshift z∼20. We survey here novel baryon evolution produced by a modification of the power spectrum from white noise density perturbations at scales below k∼10h Mpc -1 (the smallest scales currently measured with the Lyman-α forest). Exotic dark matter dynamics, such as would arise from scalar dark matter with a late phase transition (similar to an axion, but with lower mass), or primordial black hole dark matter, create such an amplification of small scale power. The dark matter produced in such a phase transition collapses into minihalos, with a size given by the dark matter mass within the horizon at the phase transition. If the mass of the initial minihalos is larger than ∼10 -3 M · , the modified power spectrum is found to cause widespread baryon collapse earlier than standard ΛCDM, leading to earlier gas heating. It also results in higher spin temperature of the baryons in the 21 cm line relative to ΛCDM at redshifts z>20 if the mass of the minihalo is larger than 1M · . It is estimated that experiments probing 21 cm radiation at high redshift will contribute a significant constraint on dark matter models of this type for initial minihalos larger than ∼10M · . These experiments may also detect (or rule out) primordial black holes as the dark matter in the window 30M · H 3 M · still left open by strong microlensing experiments and other astrophysical constraints. Early experiments reaching to z≅15 will constrain minihalos down to ∼10 3 M ·

Flow-induced plastic collapse of stacked fuel plates

Energy Technology Data Exchange (ETDEWEB)

Davis, D C; Scarton, H A

1985-03-01

Flow-induced plastic collapse of stacked fuel plate assemblies was first noted in experimental reactors such as the ORNL High Flux Reactor Assembly and the Engineering Test Reactor (ETR). The ETR assembly is a stack of 19 thin flat rectangular fuel plates separated by narrow channels through which a coolant flows to remove the heat generated by fission of the fuel within the plates. The uranium alloyed plates have been noted to buckle laterally and plastically collapse at the system design coolant flow rate of 10.7 m/s, thus restricting the coolant flow through adjacent channels. A methodology and criterion are developed for predicting the plastic collapse of ETR fuel plates. The criterion is compared to some experimental results and the Miller critical velocity theory.

Collapse arresting in an inhomogeneous quintic nonlinear Schrodinger model

DEFF Research Database (Denmark)

Gaididei, Yuri Borisovich; Schjødt-Eriksen, Jens; Christiansen, Peter Leth

1999-01-01

Collapse of (1 + 1)-dimensional beams in the inhomogeneous one-dimensional quintic nonlinear Schrodinger equation is analyzed both numerically and analytically. It is shown that in the vicinity of a narrow attractive inhomogeneity, the collapse of beams in which the homogeneous medium would blow up...

The Seneca effect why growth is slow but collapse is rapid

CERN Document Server

Bardi, Ugo

2017-01-01

The essence of this book can be found in a line written by the ancient Roman Stoic Philosopher Lucius Annaeus Seneca: "Fortune is of sluggish growth, but ruin is rapid". This sentence summarizes the features of the phenomenon that we call "collapse," which is typically sudden and often unexpected, like the proverbial "house of cards." But why are such collapses so common, and what generates them? Several books have been published on the subject, including the well-known "Collapse" by Jared Diamond (2005), "The collapse of complex societies" by Joseph Tainter (1998) and "The Tipping Point," by Malcom Gladwell (2000). Why The Seneca Effect? This book is an ambitious attempt to pull these various strands together by describing collapse from a multi-disciplinary viewpoint. The reader will discover how collapse is a collective phenomenon that occurs in what we call today "complex systems," with a special emphasis on system dynamics and t he concept of "feedback." From this foundation, Bardi applies the...

Long gamma-ray bursts and core-collapse supernovae have different environments.

Science.gov (United States)

Fruchter, A S; Levan, A J; Strolger, L; Vreeswijk, P M; Thorsett, S E; Bersier, D; Burud, I; Castro Cerón, J M; Castro-Tirado, A J; Conselice, C; Dahlen, T; Ferguson, H C; Fynbo, J P U; Garnavich, P M; Gibbons, R A; Gorosabel, J; Gull, T R; Hjorth, J; Holland, S T; Kouveliotou, C; Levay, Z; Livio, M; Metzger, M R; Nugent, P E; Petro, L; Pian, E; Rhoads, J E; Riess, A G; Sahu, K C; Smette, A; Tanvir, N R; Wijers, R A M J; Woosley, S E

2006-05-25

When massive stars exhaust their fuel, they collapse and often produce the extraordinarily bright explosions known as core-collapse supernovae. On occasion, this stellar collapse also powers an even more brilliant relativistic explosion known as a long-duration gamma-ray burst. One would then expect that these long gamma-ray bursts and core-collapse supernovae should be found in similar galactic environments. Here we show that this expectation is wrong. We find that the gamma-ray bursts are far more concentrated in the very brightest regions of their host galaxies than are the core-collapse supernovae. Furthermore, the host galaxies of the long gamma-ray bursts are significantly fainter and more irregular than the hosts of the core-collapse supernovae. Together these results suggest that long-duration gamma-ray bursts are associated with the most extremely massive stars and may be restricted to galaxies of limited chemical evolution. Our results directly imply that long gamma-ray bursts are relatively rare in galaxies such as our own Milky Way.

Hamiltonian treatment of the gravitational collapse of thin shells

International Nuclear Information System (INIS)

Crisostomo, Juan; Olea, Rodrigo

2004-01-01

A Hamiltonian treatment of the gravitational collapse of thin shells is presented. The direct integration of the canonical constraints reproduces the standard shell dynamics for a number of known cases. The formalism is applied in detail to three-dimensional spacetime and the properties of the (2+1)-dimensional charged black hole collapse are further elucidated. The procedure is also extended to deal with rotating solutions in three dimensions. The general form of the equations providing the shell dynamics implies the stability of black holes, as they cannot be converted into naked singularities by any shell collapse process

Protostellar formation in rotation interstellar clouds. III. Nonaxisymmetric collapse

International Nuclear Information System (INIS)

Boss, A.P.

1980-01-01

A full three spatial-dimension gravitational hydrodynamics code has been used to follow the collapse of isothermal rotating clouds subjected to various nonaxialy symmetric perturbations (NAP). An initially axially symmetric cloud collapsed to form a ring which then fragmented into a binary protostellar system. A low thermal energy cloud with a large bar-shaped NAP collapsed and fragmented directly into a binary; higher thermal energy clouds damp out such NAPs while higher rotational rotational energy clouds produce binaries with wider separations. Fragmentation into single and binary systems has been seen. The tidal effects of other nearby protostellar clouds are shown to have an important effect upon the collapse and should not be neglected. The three-dimensional calculations indicate that isothermal interstellar clouds may fragment (with or without passing through a transitory ring phase) into protostellar objects while still in the isothermal regime. The fragments obtained have masses and specific spin angular momenta roughly a 10th that of the original cloud. Interstellar clouds and their fragments may pass through successive collapse phases with fragmentation and reduction of spin angular momentum (by conversion to orbital angular momentum and preferential accretion of low angular momentum matter) terminating in the formation of pre--main-sequence stars with the observed pre--main-sequence rotation rates

Research on Collapse Process of Cable-Stayed Bridges under Strong Seismic Excitations

Directory of Open Access Journals (Sweden)

Xuewei Wang

2017-01-01

Full Text Available In order to present the collapse process and failure mechanism of long-span cable-stayed bridges under strong seismic excitations, a rail-cum-road steel truss cable-stayed bridge was selected as engineering background, the collapse failure numerical model of the cable-stayed bridge was established based on the explicit dynamic finite element method (FEM, and the whole collapse process of the cable-stayed bridge was analyzed and studied with three different seismic waves acted in the horizontal longitudinal direction, respectively. It can be found from the numerical simulation analysis that the whole collapse failure process and failure modes of the cable-stayed bridge under three different seismic waves are similar. Furthermore, the piers and the main pylons are critical components contributing to the collapse of the cable-stayed bridge structure. However, the cables and the main girder are damaged owing to the failure of piers and main pylons during the whole structure collapse process, so the failure of cable and main girder components is not the main reason for the collapse of cable-stayed bridge. The analysis results can provide theoretical basis for collapse resistance design and the determination of critical damage components of long-span highway and railway cable-stayed bridges in the research of seismic vulnerability analysis.

OWN EXPERIENCE OF LASER THERAPY FOR THE PREVENTION AND TREATMENT OF EARLY AND LATE RADIATION-INDUCED SKIN INJURIES IN PATIENTS WITH BREAST CANCER AFTER SIMULTANEOUS RECONSTRUCTIVE PLASTIC SURGERY

Directory of Open Access Journals (Sweden)

S. I. Tkachev

2017-01-01

Full Text Available Low-energy laser radiation has a good anti-inflammatory and stimulating effect on the damaged tissues; therefore, it can be used for the prevention and treatment of both early and late radiation-induced skin injuries in patients receiving radiotherapy. So far, the effect of low-energy laser radiation in the prevention of radiation-induced skin damage remains poorly understood. This article presents a brief overview of the results obtained in the latest foreign studies as well as own experience of laser therapy for the prevention and treatment of both early and late radiation-induced skin injuries in patients with breast cancer after simultaneous reconstructive plastic surgery.

Forecasting giant, catastrophic slope collapse: lessons from Vajont, Northern Italy

Science.gov (United States)

Kilburn, Christopher R. J.; Petley, David N.

2003-08-01

Rapid, giant landslides, or sturzstroms, are among the most powerful natural hazards on Earth. They have minimum volumes of ˜10 6-10 7 m 3 and, normally preceded by prolonged intervals of accelerating creep, are produced by catastrophic and deep-seated slope collapse (loads ˜1-10 MPa). Conventional analyses attribute rapid collapse to unusual mechanisms, such as the vaporization of ground water during sliding. Here, catastrophic collapse is related to self-accelerating rock fracture, common in crustal rocks at loads ˜1-10 MPa and readily catalysed by circulating fluids. Fracturing produces an abrupt drop in resisting stress. Measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations. Fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure.

Weak-interaction processes in stars: applications to core-collapse supernovae

International Nuclear Information System (INIS)

Martinez-Pinedo, G.

2003-01-01

The role of weak-interaction processes in core collapse and neutrino nucleosynthesis is reviewed. Recent calculations of the electron capture rates for nuclei with mass numbers A=65-112 show that, contrarily to previous assumptions, during core collapse electron capture is dominated by captures on heavy nuclei. Astrophysical simulations demonstrate that these rates have an important impact on the collapse. Neutrinos emitted by the collapsing core can interact with the overlying shells of the star producing substantial nuclear transmutations. This process known as ν-process seems to be responsible for the production of 138 La by charged current neutrino interactions with 138 Ba. The ν-process is then sensitive to the spectra of different neutrino species and to neutrino oscillations. (orig.)

Origami-inspired, on-demand deployable and collapsible mechanical metamaterials with tunable stiffness

Science.gov (United States)

Zhai, Zirui; Wang, Yong; Jiang, Hanqing

2018-03-01

Origami has been employed to build deployable mechanical metamaterials through folding and unfolding along the crease lines. Deployable metamaterials are usually flexible, particularly along their deploying and collapsing directions, which unfortunately in many cases leads to an unstable deployed state, i.e., small perturbations may collapse the structure along the same deployment path. Here we create an origami-inspired mechanical metamaterial with on-demand deployability and selective collapsibility through energy analysis. This metamaterial has autonomous deployability from the collapsed state and can be selectively collapsed along two different paths, embodying low stiffness for one path and substantially high stiffness for another path. The created mechanical metamaterial yields load-bearing capability in the deployed direction while possessing great deployability and collapsibility. The principle in this work can be utilized to design and create versatile origami-inspired mechanical metamaterials that can find many applications.

Matter and gravitons in the gravitational collapse

Directory of Open Access Journals (Sweden)

Roberto Casadio

2016-12-01

Full Text Available We consider the effects of gravitons in the collapse of baryonic matter that forms a black hole. We first note that the effective number of (soft off-shell gravitons that account for the (negative Newtonian potential energy generated by the baryons is conserved and always in agreement with Bekenstein's area law of black holes. Moreover, their (positive interaction energy reproduces the expected post-Newtonian correction and becomes of the order of the total ADM mass of the system when the size of the collapsing object approaches its gravitational radius. This result supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without central singularity, in which both gravitons and baryons are marginally bound and form a Bose–Einstein condensate at the critical point. The Hawking emission of baryons and gravitons is then described by the quantum depletion of the condensate and we show the two energy fluxes are comparable, albeit negligibly small on astrophysical scales.

Matter and gravitons in the gravitational collapse

Energy Technology Data Exchange (ETDEWEB)

Casadio, Roberto, E-mail: casadio@bo.infn.it [Dipartimento di Fisica e Astronomia, Alma Mater Universià di Bologna, via Irnerio 46, 40126 Bologna (Italy); I.N.F.N., Sezione di Bologna, IS FLAG, viale B. Pichat 6/2, I-40127 Bologna (Italy); Giugno, Andrea, E-mail: A.Giugno@physik.uni-muenchen.de [Arnold Sommerfeld Center, Ludwig-Maximilians-Universität, Theresienstraße 37, 80333 München (Germany); Giusti, Andrea, E-mail: andrea.giusti@bo.infn.it [Dipartimento di Fisica e Astronomia, Alma Mater Universià di Bologna, via Irnerio 46, 40126 Bologna (Italy); I.N.F.N., Sezione di Bologna, IS FLAG, viale B. Pichat 6/2, I-40127 Bologna (Italy)

2016-12-10

We consider the effects of gravitons in the collapse of baryonic matter that forms a black hole. We first note that the effective number of (soft off-shell) gravitons that account for the (negative) Newtonian potential energy generated by the baryons is conserved and always in agreement with Bekenstein's area law of black holes. Moreover, their (positive) interaction energy reproduces the expected post-Newtonian correction and becomes of the order of the total ADM mass of the system when the size of the collapsing object approaches its gravitational radius. This result supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without central singularity, in which both gravitons and baryons are marginally bound and form a Bose–Einstein condensate at the critical point. The Hawking emission of baryons and gravitons is then described by the quantum depletion of the condensate and we show the two energy fluxes are comparable, albeit negligibly small on astrophysical scales.

Comment on 'Hawking radiation from fluctuating black holes'

NARCIS (Netherlands)

Khavkine, I.

2010-01-01

Takahashi and Soda (2010 Class. Quantum Grav. 27 175008) have recently considered the effect (at lowest non-trivial order) of dynamical, quantized gravitational fluctuations on the spectrum of scalar Hawking radiation from a collapsing Schwarzschild black hole. However, due to an unfortunate choice

The role of sucralfate oral suspension in prevention of radiation induced mucositis

Directory of Open Access Journals (Sweden)

Hamid Emami

2008-12-01

Full Text Available

• BACKGROUND: Mucositis is one of the most common complications of radiotherapy in head and neck cancers. The aim of this study was to evaluate sucralfate mouthwash in prevention of radiation induced mucositis.
• METHODS: A clinical randomized trial performed on 52 patients with head and neck cancers in Sayyed-Al-Shohada Hospital of Isfahan University of Medical Sciences. These patients randomly assigned in 2 groups of 26 patients. Placebo and sucralfate was used for control and experimental patients respectiv ly, from the beginning of radiotherapy. Patients were visited weekly until the end of treatment. Grade of the mucositis was evaluated according to WHO grading scale.
• RESULTS: Sucralfate significantly reduced the mean grade of mucositis in weeks one to four (with P-values of 0.02, 0.02, 0.001 and 0.004, respectively. Development of grade3 mucositis was also lower in sucralfate group (P-value = 0.0001. But, time interval between radiotherapy and appearance of mucositis was not statistically different in the two groups (P-value = 0.9
• CONCLUSIONS: This study indicated that using oral suspension of sucralfate reduced the grade of radiation-induced mucositis, but did not prevent or delay it.
• KEYWORDS: Mucositis, radiotherapy, sucralfate, head and neck cancers.

Use of trolamine to prevent and treat acute radiation dermatitis: a systematic review and meta-analysis

Directory of Open Access Journals (Sweden)

Amanda Gomes de Menêses

2018-05-01

Full Text Available ABSTRACT Objective: to evaluate the effects of trolamine in the prevention or treatment of radiation dermatitis. Method: systematic review and meta-analysis. Detailed individual search strategies for Cinahl, Cochrane Library Central, LILACS, PubMed, and Web of Science were developed in January 2016. A manual search was also performed to find additional references. A grey literature search was executed by using Google Scholar. Two researchers independently read the titles and abstracts from every cross-reference. The risk of bias of the included studies was analyzed by the Cochrane Collaboration Risk of Bias Tool. The quality of evidence and grading of strength of recommendations was assessed using Grades of Recommendation, Assessment, Development and Evaluation (GRADE. Results: seven controlled clinical trials were identified. The controls used were calendula, placebo, institutional preference / usual care, Aquaphor®, RadiaCare™, and Lipiderm™. The studies were pooled using frequency of events and risk ratio with 95% confidence intervals, in subgroups according to radiation dermatitis graduation. Conclusion: based on the studies included in this review, trolamine cannot be considered as a standardized product to prevent or treat radiation dermatitis in patients with breast and head and neck cancer.

The influence of collapse wall on self-excited oscillation pulsed jet nozzle performance

International Nuclear Information System (INIS)

Fang, Z L; Kang, Y; Yang, X F; Yuan, B; Li, D

2012-01-01

The self-excited oscillation pulsed jet (SOPJ) is widely used owing to its simple structure and good separation of pressure source and system. The structure of nozzle is one of the main factors that influence the performance of the SOPJ nozzle. Upper collapse wall and lower collapse wall is important to the formation and transmission of eddy in oscillation cavity. In this paper, the influence of collapse wall on SOPJ nozzle was analyzed by numerical simulation. The LES algorithm was used to simulate the flow of different combinations of collapse wall. The result showed that when both collapse walls are of the same type, the SOPJ nozzle will have a good performance; the influence of upper collapse wall is more obvious than lower one; model of two-semi-circle upper collapse wall is the first choice when we design SOPJ nozzle.

Probing spontaneous wave-function collapse with entangled levitating nanospheres

Science.gov (United States)

Zhang, Jing; Zhang, Tiancai; Li, Jie

2017-01-01

Wave-function collapse models are considered to be the modified theories of standard quantum mechanics at the macroscopic level. By introducing nonlinear stochastic terms in the Schrödinger equation, these models (different from standard quantum mechanics) predict that it is fundamentally impossible to prepare macroscopic systems in macroscopic superpositions. The validity of these models can only be examined by experiments, and hence efficient protocols for these kinds of experiments are greatly needed. Here we provide a protocol that is able to probe the postulated collapse effect by means of the entanglement of the center-of-mass motion of two nanospheres optically trapped in a Fabry-Pérot cavity. We show that the collapse noise results in a large reduction of the steady-state entanglement, and the entanglement, with and without the collapse effect, shows distinguishable scalings with certain system parameters, which can be used to determine unambiguously the effect of these models.

REVIEWS OF TOPICAL PROBLEMS Rotational explosion mechanism for collapsing supernovae and the two-stage neutrino signal from supernova 1987A in the Large Magellanic Cloud

Science.gov (United States)

Imshennik, Vladimir S.

2011-02-01

The two-stage (double) signal produced by the outburst of the close supernova (SN) in the Large Magellanic Cloud, which started on and involved two neutrino signals during the night of 23 February 1987 UT, is theoretically interpreted in terms of a scenario of rotationally exploding collapsing SNs, to whose class the outburst undoubtedly belongs. This scenario consists of a set of hydrodynamic and kinetic models in which key results are obtained by numerically solving non-one-dimensional and nonstationary problems. Of vital importance in this context is the inclusion of rotation effects, their role being particularly significant precisely in terms of the question of the transformation of the original collapse of the presupernova iron core to the explosion of the SN shell, with an energy release on a familiar scale of 1051 erg. The collapse in itself leads to the birth of neutron stars (black holes) emitting neutrino and gravitational radiation signals of gigantic intensity, whose total energy significantly (by a factor of hundreds) exceeds the above-cited SN burst energy. The proposed rotational scenario is described briefly by artificially dividing it into three (or four) characteristic stages. This division is dictated by the physical meaning of the chain of events a rotating iron core of a sufficiently massive (more than 10M) star triggers when it collapses. An attempt is made to quantitatively describe the properties of the associated neutrino and gravitational radiations. The review highlights the interpretation of the two-stage neutrino signal from SN 1987A, a problem which, given the present status of theoretical astrophysics, cannot, in the author's view, be solved without including rotation effects.

3-D collapse of rotating stars to Kerr black holes

International Nuclear Information System (INIS)

Baiotti, L; Hawke, I; Montero, P J; Loeffler, F L; Rezzolla, L; Stergioulas, N; Font, J A; Seidel, E

2005-01-01

We study gravitational collapse of uniformly rotating neutron stars to Kerr black holes, using a new three-dimensional, fully general relativistic hydrodynamics code, which uses high-resolution shock-capturing techniques and a conformal traceless formulation of the Einstein equations. We investigate the gravitational collapse by carefully studying not only the dynamics of the matter, but also that of the trapped surfaces, i.e. of both the apparent and event horizons formed during the collapse. The use of these surfaces, together with the dynamical horizon framework, allows for a precise measurement of the black-hole mass and spin. The ability to successfully perform these simulations for sufficiently long times relies on excising a region of the computational domain which includes the singularity and is within the apparent horizon. The dynamics of the collapsing matter is strongly influenced by the initial amount of angular momentum in the progenitor star and, for initial models with sufficiently high angular velocities, the collapse can lead to the formation of an unstable disc in differential rotation

FORMATION OF CARBON-ENHANCED METAL-POOR STARS IN THE PRESENCE OF FAR-ULTRAVIOLET RADIATION

Energy Technology Data Exchange (ETDEWEB)

Bovino, S.; Schleicher, D. R. G.; Latif, M. A. [Institut für Astrophysik Georg-August-Universität, Friedrich-Hund Platz 1, 37077 Göttingen (Germany); Grassi, T., E-mail: sbovino@astro.physik.uni-goettingen.de [Centre for Star and Planet Formation, Natural History Museum of Denmark, Øster Voldgade 5-7, 1350 Copenhagen (Denmark)

2014-08-01

Recent discoveries of carbon-enhanced metal-poor stars like SMSS J031300.36–670839.3 provide increasing observational insights into the formation conditions of the first second-generation stars in the universe, reflecting the chemical conditions after the first supernova explosion. Here, we present the first cosmological simulations with a detailed chemical network including primordial species as well as C, C{sup +}, O, O{sup +}, Si, Si{sup +}, and Si{sup 2+} following the formation of carbon-enhanced metal-poor stars. The presence of background UV flux delays the collapse from z = 21 to z = 15 and cool the gas down to the cosmic microwave background temperature for a metallicity of Z/Z {sub ☉} = 10{sup –3}. This can potentially lead to the formation of lower-mass stars. Overall, we find that the metals have a stronger effect on the collapse than the radiation, yielding a comparable thermal structure for large variations in the radiative background. We further find that radiative backgrounds are not able to delay the collapse for Z/Z {sub ☉} = 10{sup –2} or a carbon abundance as in SMSS J031300.36–670839.3.

Two-dimensional collapse calculations of cylindrical clouds

International Nuclear Information System (INIS)

Bastien, P.; Mitalas, R.

1979-01-01

A two-dimensional hydrodynamic computer code has been extensively modified and expanded to study the collapse of non-rotating interstellar clouds. The physics and the numerical methods involved are discussed. The results are presented and discussed in terms of the Jeans number. The critical Jeans number for collapse of non-rotating cylindrical clouds whose length is the same as their diameter is 1.00. No evidence for fragmentation has been found for these clouds, but fragmentation seems quite likely for more elongated cylindrical clouds. (author)

The collapsed football pla yer

African Journals Online (AJOL)

Football is the most popular sport in the world, played by over 265 ... FIFA Medical Officer and Honorary Part-time Lecturer, Wits Centre for Exercise Science and Sports Medicine, Johannesburg .... Management of a collapsed player does not.

Gravitational radiation and 3D numerical relativity

International Nuclear Information System (INIS)

Nakamura, T.

1986-01-01

Study of Numerical Relativity in Kyoto is reviewed. Main topics discussed are 2D rotating collapse, phase cancellation effects and perturbation calculation of the gravitational radiation from a particle falling into a black hole. New numerical results on 3D time evolution of pure gravitational waves are also presented

Localized microjetting in the collapse of surface macrocavities

Science.gov (United States)

Olney, K. L.; Chiu, P.-H.; Benson, D. J.; Higgins, A.; Serge, M.; Nesterenko, V. F.

2015-02-01

This paper focuses on the multiscale mechanism of collapse of hemicylindrical annular surface macrocavities in steel caused by high-strain, high-strain rate plastic flow of copper. Experiments and simulations revealed that a two-stage process is responsible for the observed microjetting phenomena: the formation of lateral copper microjets from the localized shear flow in copper at the interface during the filling of the cavity, and their subsequent collision at the apex of the macrocavity generating two additional horizontal microjets. The lengths of these microjets were an order of magnitude smaller than the cavity size but linearly scaled with the cavity radius. This process of microjet development is sensitive to the cavity geometry and is unlike the previously observed jetting phenomena in cavitation, impact crater collapse, or shock-induced cavity collapse.

A new open-source code for spherically symmetric stellar collapse to neutron stars and black holes

International Nuclear Information System (INIS)

O'Connor, Evan; Ott, Christian D

2010-01-01

We present the new open-source spherically symmetric general-relativistic (GR) hydrodynamics code GR1D. It is based on the Eulerian formulation of GR hydrodynamics (GRHD) put forth by Romero-Ibanez-Gourgoulhon and employs radial-gauge, polar-slicing coordinates in which the 3+1 equations simplify substantially. We discretize the GRHD equations with a finite-volume scheme, employing piecewise-parabolic reconstruction and an approximate Riemann solver. GR1D is intended for the simulation of stellar collapse to neutron stars and black holes and will also serve as a testbed for modeling technology to be incorporated in multi-D GR codes. Its GRHD part is coupled to various finite-temperature microphysical equations of state in tabulated form that we make available with GR1D. An approximate deleptonization scheme for the collapse phase and a neutrino-leakage/heating scheme for the postbounce epoch are included and described. We also derive the equations for effective rotation in 1D and implement them in GR1D. We present an array of standard test calculations and also show how simple analytic equations of state in combination with presupernova models from stellar evolutionary calculations can be used to study qualitative aspects of black hole formation in failing rotating core-collapse supernovae. In addition, we present a simulation with microphysical equations of state and neutrino leakage/heating of a failing core-collapse supernova and black hole formation in a presupernova model of a 40 M o-dot zero-age main-sequence star. We find good agreement on the time of black hole formation (within 20%) and last stable protoneutron star mass (within 10%) with predictions from simulations with full Boltzmann neutrino radiation hydrodynamics.

A new open-source code for spherically symmetric stellar collapse to neutron stars and black holes

Energy Technology Data Exchange (ETDEWEB)

O' Connor, Evan; Ott, Christian D, E-mail: evanoc@tapir.caltech.ed, E-mail: cott@tapir.caltech.ed [TAPIR, Mail Code 350-17, California Institute of Technology, Pasadena, CA 91125 (United States)

2010-06-07

We present the new open-source spherically symmetric general-relativistic (GR) hydrodynamics code GR1D. It is based on the Eulerian formulation of GR hydrodynamics (GRHD) put forth by Romero-Ibanez-Gourgoulhon and employs radial-gauge, polar-slicing coordinates in which the 3+1 equations simplify substantially. We discretize the GRHD equations with a finite-volume scheme, employing piecewise-parabolic reconstruction and an approximate Riemann solver. GR1D is intended for the simulation of stellar collapse to neutron stars and black holes and will also serve as a testbed for modeling technology to be incorporated in multi-D GR codes. Its GRHD part is coupled to various finite-temperature microphysical equations of state in tabulated form that we make available with GR1D. An approximate deleptonization scheme for the collapse phase and a neutrino-leakage/heating scheme for the postbounce epoch are included and described. We also derive the equations for effective rotation in 1D and implement them in GR1D. We present an array of standard test calculations and also show how simple analytic equations of state in combination with presupernova models from stellar evolutionary calculations can be used to study qualitative aspects of black hole formation in failing rotating core-collapse supernovae. In addition, we present a simulation with microphysical equations of state and neutrino leakage/heating of a failing core-collapse supernova and black hole formation in a presupernova model of a 40 M{sub o-dot} zero-age main-sequence star. We find good agreement on the time of black hole formation (within 20%) and last stable protoneutron star mass (within 10%) with predictions from simulations with full Boltzmann neutrino radiation hydrodynamics.

Hydromagnetic instabilities and magnetic field amplification in core collapse supernovae

Energy Technology Data Exchange (ETDEWEB)

Cerda-Duran, P; Obergaulinger, M; Mueller, E [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-st. 1, 85748 Garching (Germany); Aloy, M A; Font, J A, E-mail: cerda@mpa-garching.mpg.de [Departamento de Astronomia y Astrofisica, Universidad de Valencia, 46100 Burjassot, Valencia (Spain)

2011-09-22

Some of the most violent events in the universe, the gamma ray burst, could be related to the gravitational collapse of massive stellar cores. The recent association of long GRBs to some class of type Ic supernova seems to support this view. In such scenario fast rotation, strong magnetic fields and general relativistic effects are key ingredients. It is thus important to understand the mechanism that amplifies the magnetic field under that conditions. I present global simulations of the magneto-rotational collapse of stellar cores in general relativity and semi-global simulations of hydromagnetic instabilities under core collapse conditions. I discuss effect of the magneto-rotational instability and the magnetic field amplification during the collapse, the uncertainties in this process and the dynamical effects in the supernova explosion.

Modelling of cladding creep collapse

International Nuclear Information System (INIS)

Koundy, V.; Forgeron, T.; Hivroz, J.

1993-01-01

The effects of the initial ovality and pressure level on the collapse time of Zircaloy-4 tubing subjected to uniform external pressure were examined experimentally and analytically. Experiments were performed on end closed tubes with two metallurgical states: stress relieved and recrystallized. Numerical simulations were accomplished with a specific computer program based on an analytical approach and the calculated results were compared with the experimental ones. As a comparison, the finite element method is also partially examined in this analysis. Numerical collapse times are in good agreement with regard to experimental results in the case of stress relieved structure. They seem to be too conservative in the case of a recrystallized metallurgical state and the use of the anisotropic option ameliorates numerical results. Sensibility of numerical solutions to the formulation of primary creep laws are presented

Maximally Rotating Supermassive Stars at the Onset of Collapse: The Perturbative Effects of Gas Pressure, Magnetic Fields, Dark Matter and Dark Energy

Science.gov (United States)

Butler, Satya P.; Lima, Alicia R.; Baumgarte, Thomas W.; Shapiro, Stuart L.

2018-04-01

The discovery of quasars at increasingly large cosmological redshifts may favor "direct collapse" as the most promising evolutionary route to the formation of supermassive black holes. In this scenario, supermassive black holes form when their progenitors - supermassive stars - become unstable to gravitational collapse. For uniformly rotating stars supported by pure radiation pressure and spinning at the mass-shedding limit, the critical configuration at the onset of collapse is characterized by universal values of the dimensionless spin and radius parameters J/M2 and R/M, independent of mass M. We consider perturbative effects of gas pressure, magnetic fields, dark matter and dark energy on these parameters, and thereby determine the domain of validity of this universality. We obtain leading-order corrections for the critical parameters and establish their scaling with the relevant physical parameters. We compare two different approaches to approximate the effects of gas pressure, which plays the most important role, find identical results for the above dimensionless parameters, and also find good agreement with recent numerical results.

A novel topical protectant for the prevention of β-radiation induced moist desquamation

International Nuclear Information System (INIS)

Ma, L.; Wilcock, S.; Rezvani, M.; Hsia, C.

2003-01-01

Full text: Effective therapies for the prevention of radiation-induced skin burns that could be readily deployed under a nuclear accident or nuclear terrorism scenario are urgently needed. In this report we describe the efficacy of a novel radioprotectant (DMZ911) in a model of b-radiation induced moist desquamation (MD) in pig skin. DMZ911 is a nitroxide-based topical cream that effectively delivers the nitroxide into viable skin cells. Stable nitroxide compounds have been shown to be effective against both X-ray and ?-ray-induced damage in vivo and in vitro. A pig skin model of β-radiation-induced MD was employed in this study. Exposure to 30 Gy was used to induce skin lesions involving >80% moist desquamation in prescribed test sites on flank skin of female Large White pigs. DMZ911 or placebo was applied to various test sites 2 hours prior to radiation exposure. Lesions were scored based on the area of the test site containing 50% MD (severe) as determined by clinical assessment using blinded observers. Treatment with DMZ911 resulted in a 31% net reduction in MD when compared to placebo treated sites following an 8-week study period. This reduction was observed whether all sites or only those with severe MD were considered. Skin damage (as indicated by MD) from radiation exposure was significantly reduced by 31% (p = 0.05) following pretreatment with the novel topical radioprotectant DMZ911. This observation suggests that skin lesion development from radiation-induced oxidative damage cascades may be successfully inhibited by treatment with DMZ911. This topical therapeutic agent represents a novel treatment for nuclear radiation induced skin injury. DMZ911 may have unique applications in radiation oncology, cosmetic and therapeutic UV, laser, glycolic and dermabrasion procedures

Efficiency criterion for teleportation via channel matrix, measurement matrix and collapsed matrix

Directory of Open Access Journals (Sweden)

Xin-Wei Zha

Full Text Available In this paper, three kinds of coefficient matrixes (channel matrix, measurement matrix, collapsed matrix associated with the pure state for teleportation are presented, the general relation among channel matrix, measurement matrix and collapsed matrix is obtained. In addition, a criterion for judging whether a state can be teleported successfully is given, depending on the relation between the number of parameter of an unknown state and the rank of the collapsed matrix. Keywords: Channel matrix, Measurement matrix, Collapsed matrix, Teleportation

Cancer risks and prevention

International Nuclear Information System (INIS)

Vessey, M.P.; Gray, M.

1985-01-01

A series of essays in honour of Sir Richard Doll is presented. Chapters cover the preventability of cancer, geography, smoking, diet, occupation, radiation, infections and immune impairment, exogenous and endogenous hormones, other drugs, prevention through legislation and by education and cancer risks and prevention in the Third World. The chapter on radiation has been indexed separately. (UK)

Asymmetric explosion of core-collapse supernovae

International Nuclear Information System (INIS)

Kazeroni, Remi

2016-01-01

A core-collapse supernova represents the ultimate stage of the evolution of massive stars.The iron core contraction may be followed by a gigantic explosion which gives birth to a neutron star.The multidimensional dynamics of the innermost region, during the first hundreds milliseconds, plays a decisive role on the explosion success because hydrodynamical instabilities are able to break the spherical symmetry of the collapse. Large scale transverse motions generated by two instabilities, the neutrino-driven convection and the Standing Accretion Shock Instability (SASI),increase the heating efficiency up to the point of launching an asymmetric explosion and influencing the birth properties of the neutron star. In this thesis, hydrodynamical instabilities are studied using numerical simulations of simplified models. These models enable a wide exploration of the parameter space and a better physical understanding of the instabilities, generally inaccessible to realistic models.The non-linear regime of SASI is analysed to characterize the conditions under which a spiral mode prevails and to assess its ability to redistribute angular momentum radially.The influence of rotation on the shock dynamics is also addressed. For fast enough rotation rates, a corotation instability overlaps with SASI and greatly impacts the dynamics. The simulations enable to better constrain the effect of non-axisymmetric modes on the angular momentum budget of the iron core collapsing into a neutron star. SASI may under specific conditions spin up or down the pulsar born during the explosion. Finally, an idealised model of the heating region is studied to characterize the non-linear onset of convection by perturbations such as those produced by SASI or pre-collapse combustion inhomogeneities. The dimensionality issue is examined to stress the beneficial consequences of the three-dimensional dynamics on the onset of the explosion. (author) [fr

Can static regular black holes form from gravitational collapse?

International Nuclear Information System (INIS)

Zhang, Yiyang; Zhu, Yiwei; Modesto, Leonardo; Bambi, Cosimo

2015-01-01

Starting from the Oppenheimer-Snyder model, we know how in classical general relativity the gravitational collapse of matter forms a black hole with a central spacetime singularity. It is widely believed that the singularity must be removed by quantum-gravity effects. Some static quantum-inspired singularity-free black hole solutions have been proposed in the literature, but when one considers simple examples of gravitational collapse the classical singularity is replaced by a bounce, after which the collapsing matter expands for ever. We may expect three possible explanations: (i) the static regular black hole solutions are not physical, in the sense that they cannot be realized in Nature, (ii) the final product of the collapse is not unique, but it depends on the initial conditions, or (iii) boundary effects play an important role and our simple models miss important physics. In the latter case, after proper adjustment, the bouncing solution would approach the static one. We argue that the ''correct answer'' may be related to the appearance of a ghost state in de Sitter spacetimes with super Planckian mass. Our black holes have indeed a de Sitter core and the ghost would make these configurations unstable. Therefore we believe that these black hole static solutions represent the transient phase of a gravitational collapse but never survive as asymptotic states. (orig.)

Naked singularities in self-similar spherical gravitational collapse

International Nuclear Information System (INIS)

Ori, A.; Piran, T.

1987-01-01

We present general-relativistic solutions of self-similar spherical collapse of an adiabatic perfect fluid. We show that if the equation of state is soft enough (Γ-1<<1), a naked singularity forms. The singularity resembles the shell-focusing naked singularities that arise in dust collapse. This solution increases significantly the range of matter fields that should be ruled out in order that the cosmic-censorship hypothesis will hold

STELLAR TIDAL DISRUPTION EVENTS BY DIRECT-COLLAPSE BLACK HOLES

Energy Technology Data Exchange (ETDEWEB)

Kashiyama, Kazumi [Theoretical Astrophysics Center, Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720 (United States); Inayoshi, Kohei, E-mail: kashiyama@berkeley.edu, E-mail: inayoshi@astro.columbia.edu [Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States)

2016-07-20

We analyze the early growth stage of direct-collapse black holes (DCBHs) with ∼10{sup 5} M {sub ⊙}, which are formed by collapse of supermassive stars in atomic-cooling halos at z ≳ 10. A nuclear accretion disk around a newborn DCBH is gravitationally unstable and fragments into clumps with a few × 10 M {sub ⊙} at ∼0.01–0.1 pc from the center. Such clumps evolve into massive Population III stars with a few × 10–10{sup 2} M {sub ⊙} via successive gas accretion, and a nuclear star cluster is formed. Radiative and mechanical feedback from an inner slim disk and the star cluster will significantly reduce the gas accretion rate onto the DCBH within ∼10{sup 6} yr. Some of the nuclear stars can be scattered onto the loss cone orbits also within ≲10{sup 6} yr and tidally disrupted by the central DCBH. The jet luminosity powered by such tidal disruption events can be L {sub j} ≳ 10{sup 50} erg s{sup 1}. The prompt emission will be observed in X-ray bands with a peak duration of δt {sub obs} ∼ 10{sup 5–6}(1 + z ) s followed by a tail ∝ t {sub obs} {sup 5/3}, which can be detectable by Swift BAT and eROSITA even from z ∼ 20. Follow-up observations of the radio afterglows with, e.g., eVLA and the host halos with James Webb Space Telescope could probe the earliest active galactic nucleus feedback from DCBHs.

Bridge Collapse Revealed By Multi-Temporal SAR Interferometry

Science.gov (United States)

Sousa, Joaquim; Bastos, Luisa

2013-12-01

On the night of March 4, 2001, the Hintze Ribeiro centennial Bridge, made of steel and concrete, collapsed in Entre-os-Rios (Northern Portugal), killing 59 people, including those in a bus and three cars that were attempting to reach the other side of the Douro River. It still remains the most serious road accident in the Portuguese history. In this work we do not intend to corroborate or contradict the official version of the accident causes, but only demonstrate the potential of Multi-Temporal Interferometric (MTI-InSAR) techniques for detection and monitoring of deformations in structures such as bridges, helping to prevent new catastrophic events. Based on the analysis of 57 ERS-1/2 covering the period from December 1992 to the fatality occurrence, we were able to detect significant movements (up to 20 mm/yr) in the section of the bridge that fell in the Douro River, obvious signs of the bridge instability.

Collapse and equilibrium of rotating, adiabatic clouds

International Nuclear Information System (INIS)

Boss, A.P.

1980-01-01

A numerical hydrodynamics computer code has been used to follow the collapse and establishment of equilibrium of adiabatic gas clouds restricted to axial symmetry. The clouds are initially uniform in density and rotation, with adiabatic exponents γ=5/3 and 7/5. The numerical technique allows, for the first time, a direct comparison to be made between the dynamic collapse and approach to equilibrium of unconstrained clouds on the one hand, and the results for incompressible, uniformly rotating equilibrium clouds, and the equilibrium structures of differentially rotating polytropes, on the other hand

Collapse and revival of entanglement between qubits coupled to a spin coherent state

Science.gov (United States)

Bahari, Iskandar; Spiller, Timothy P.; Dooley, Shane; Hayes, Anthony; McCrossan, Francis

We extend the study of the Jayne-Cummings (JC) model involving a pair of identical two-level atoms (or qubits) interacting with a single mode quantized field. We investigate the effects of replacing the radiation field mode with a composite spin, comprising N qubits, or spin-1/2 particles. This model is relevant for physical implementations in superconducting circuit QED, ion trap and molecular systems. For the case of the composite spin prepared in a spin coherent state, we demonstrate the similarities of this set-up to the qubits-field model in terms of the time evolution, attractor states and in particular the collapse and revival of the entanglement between the two qubits. We extend our analysis by taking into account an effect due to qubit imperfections. We consider a difference (or “mismatch”) in the dipole interaction strengths of the two qubits, for both the field mode and composite spin cases. To address decoherence due to this mismatch, we then average over this coupling strength difference with distributions of varying width. We demonstrate in both the field mode and the composite spin scenarios that increasing the width of the “error” distribution increases suppression of the coherent dynamics of the coupled system, including the collapse and revival of the entanglement between the qubits.

Gravitational collapse and supernovae

International Nuclear Information System (INIS)

Lattimer, J.M.

1989-01-01

The collapse of the core of a massive star and the subsequent birth of a neutron star in a supernova explosion are discussed, and a model of the supernova mechanism is developed. The basic theory is then compared with the particular case of SN1987A, whose emitted neutrinos permitted the first direct test of the model. (author)

Collapse of thin wall tubes with small initial ovality

International Nuclear Information System (INIS)

Moreno, A.

1977-01-01

A simple model of creep collapse of tubes based on the bending theory of curved beams is developed. The model is compared with more complex models. The main result of this study is the definition of a new model of creep collapse of tubes with a minimum of limited hypothesis. (author) [es

Management and Prevention of Breast Cancer After Radiation to the Chest for Childhood, Adolescent, and Young Adulthood Malignancy.

Science.gov (United States)

Koo, Eva; Henderson, Michael A; Dwyer, Mary; Skandarajah, Anita R

2015-12-01

Women treated with chest irradiation for childhood, adolescent, and young adulthood (CAYA) malignancies, in particular Hodgkin's lymphoma, have an increased risk of developing second cancers of the breast (SCB). However, there are few uniform guidelines regarding surveillance and prevention for this high-risk group. A systematic search using PUBMED and OVID MEDLINE was performed. Publications listed under the terms "breast neoplasm", "neoplasm, radiation-induced", "therapeutic radiation-induced breast cancer", "screening", "surveillance", "prevention", and "prophylaxis" between January 1992 and January 2015 were assessed. A total of 138 publications were reviewed. Factors associated with increased SCB risk include young age at irradiation, prolong duration since irradiation (peak relative risk 13.87 at 15-19 years postradiation), and increased radiation dose and field. Early menopause reduces SCB risk. Annual screening mammography and breast MRI is recommended from age 25 or 8 years posttreatment for women treated with ≥20 Gy chest radiation before age 30 years. Compared with sporadic primary breast cancers (PBC), SCB more often are bilateral (6-34 %), managed with mastectomy (56-100 %), hormone receptor-negative (27-49 %), and high-grade (35 %). Women with SCB have a similar breast cancer event-free survival and breast cancer-specific survival compared to women with PBC. However, their overall survival is worse due to comorbid conditions. There is paucity of information regarding secondary prevention of SCB. Survivors of CAYA malignancy are at risk of many late effects, including iatrogenic breast cancer from chest irradiation. They are best managed in a multidisciplinary late-effects setting where tailored risk management can be provided.

Collapsing criteria for vapor film around solid spheres as a fundamental stage leading to vapor explosion

Energy Technology Data Exchange (ETDEWEB)

Freud, Roy [Nuclear Research Center - Negev, Beer-Sheva (Israel)], E-mail: freud@bgu.ac.il; Harari, Ronen [Nuclear Research Center - Negev, Beer-Sheva (Israel); Sher, Eran [Pearlstone Center for Aeronautical Studies, Department of Mechanical Engineering, Ben-Gurion University, Beer-Sheva (Israel)

2009-04-15

Following a partial fuel-melting accident, a Fuel-Coolant Interaction (FCI) can result with the fragmentation of the melt into tiny droplets. A vapor film is then formed between the melt fragments and the coolant, while preventing a contact between them. Triggering, propagation and expansion typically follow the premixing stage. In the triggering stage, vapor film collapse around one or several of the fragments occurs. This collapse can be the result of fragments cooling, a sort of mechanical force, or by any other means. When the vapor film collapses and the coolant re-establishes contact with the dry surface of the hot melt, it may lead to a very rapid and rather violent boiling. In the propagation stage the shock wave front leads to stripping of the films surrounding adjacent droplets which enhance the fragmentation and the process escalates. During this process a large quantity of liquid vaporizes and its expansion can result in destructive mechanical damage to the surrounding structures. This multiphase thermal detonation in which high pressure shock wave is formed is regarded as 'vapor explosion'. The film boiling and its possible collapse is a fundamental stage leading to vapor explosion. If the interaction of the melt and the coolant does not result in a film boiling, no explosion occurs. Many studies have been devoted to determine the minimum temperature and heat flux that is required to maintain a film boiling. The present experimental study examines the minimum temperature that is required to maintain a film boiling around metal spheres immersed into a liquid (subcooled distilled water) reservoir. In order to simulate fuel fragments that are small in dimension and has mirror-like surface, small spheres coated with anti-oxidation layer were used. The heat flux from the spheres was calculated from the sphere's temperature profiles and the sphere's properties. The vapor film collapse was associated with a sharp rise of the heat flux

Collapsing criteria for vapor film around solid spheres as a fundamental stage leading to vapor explosion

International Nuclear Information System (INIS)

Freud, Roy; Harari, Ronen; Sher, Eran

2009-01-01

Following a partial fuel-melting accident, a Fuel-Coolant Interaction (FCI) can result with the fragmentation of the melt into tiny droplets. A vapor film is then formed between the melt fragments and the coolant, while preventing a contact between them. Triggering, propagation and expansion typically follow the premixing stage. In the triggering stage, vapor film collapse around one or several of the fragments occurs. This collapse can be the result of fragments cooling, a sort of mechanical force, or by any other means. When the vapor film collapses and the coolant re-establishes contact with the dry surface of the hot melt, it may lead to a very rapid and rather violent boiling. In the propagation stage the shock wave front leads to stripping of the films surrounding adjacent droplets which enhance the fragmentation and the process escalates. During this process a large quantity of liquid vaporizes and its expansion can result in destructive mechanical damage to the surrounding structures. This multiphase thermal detonation in which high pressure shock wave is formed is regarded as 'vapor explosion'. The film boiling and its possible collapse is a fundamental stage leading to vapor explosion. If the interaction of the melt and the coolant does not result in a film boiling, no explosion occurs. Many studies have been devoted to determine the minimum temperature and heat flux that is required to maintain a film boiling. The present experimental study examines the minimum temperature that is required to maintain a film boiling around metal spheres immersed into a liquid (subcooled distilled water) reservoir. In order to simulate fuel fragments that are small in dimension and has mirror-like surface, small spheres coated with anti-oxidation layer were used. The heat flux from the spheres was calculated from the sphere's temperature profiles and the sphere's properties. The vapor film collapse was associated with a sharp rise of the heat flux during the cooling

Important Details in Performing and Interpreting the Scratch Collapse Test.

Science.gov (United States)

Kahn, Lorna C; Yee, Andrew; Mackinnon, Susan E

2018-02-01

The utility of the scratch collapse test has been demonstrated in examination of patients with carpal and cubital tunnel syndromes and long thoracic and peroneal nerve compressions. In the authors' clinic, this lesser known test plays a key role in peripheral nerve examination where localization of the nerve irritation or injury is not fully understood. Test utility and accuracy in patients with more challenging presentations likely correlate with tester understanding and experience. This article offers a clear outline of all stages of the test to improve interrater reliability. The nuances of test performance are described, including a description of situations where the scratch collapse test is deemed inappropriate. Four clinical scenarios where the scratch collapse test may be useful are included. Corresponding video content is provided to improve performance and interpretation of the scratch collapse test. Diagnostic, V.

Gravitational collapse of charged dust shell and maximal slicing condition

International Nuclear Information System (INIS)

Maeda, Keiichi

1980-01-01

The maximal slicing condition is a good time coordinate condition qualitatively when pursuing the gravitational collapse by the numerical calculation. The analytic solution of the gravitational collapse under the maximal slicing condition is given in the case of a spherical charged dust shell and the behavior of time slices with this coordinate condition is investigated. It is concluded that under the maximal slicing condition we can pursue the gravitational collapse until the radius of the shell decreases to about 0.7 x (the radius of the event horizon). (author)

Recoverable and Programmable Collapse from Folding Pressurized Origami Cellular Solids.

Science.gov (United States)

Li, S; Fang, H; Wang, K W

2016-09-09

We report a unique collapse mechanism by exploiting the negative stiffness observed in the folding of an origami solid, which consists of pressurized cells made by stacking origami sheets. Such a collapse mechanism is recoverable, since it only involves rigid folding of the origami sheets and it is programmable by pressure control and the custom design of the crease pattern. The collapse mechanism features many attractive characteristics for applications such as energy absorption. The reported results also suggest a new branch of origami study focused on its nonlinear mechanics associated with folding.

Three-dimensional simulations of void collapse in energetic materials

Science.gov (United States)

Rai, Nirmal Kumar; Udaykumar, H. S.

2018-03-01

The collapse of voids in porous energetic materials leads to hot-spot formation and reaction initiation. This work advances the current knowledge of the dynamics of void collapse and hot-spot formation using 3D reactive void collapse simulations in HMX. Four different void shapes, i.e., sphere, cylinder, plate, and ellipsoid, are studied. For all four shapes, collapse generates complex three-dimensional (3D) baroclinic vortical structures. The hot spots are collocated with regions of intense vorticity. The differences in the vortical structures for the different void shapes are shown to significantly impact the relative sensitivity of the voids. Voids of high surface area generate hot spots of greater intensity; intricate, highly contorted vortical structures lead to hot spots of corresponding tortuosity and therefore enhanced growth rates of reaction fronts. In addition, all 3D voids are shown to be more sensitive than their two-dimensional (2D) counterparts. The results provide physical insights into hot-spot formation and growth and point to the limitations of 2D analyses of hot-spot formation.

Defining Design Limits of a Portable Radiation Dispersion Prevention System

Energy Technology Data Exchange (ETDEWEB)

Kang Seong Woo; Yim, Man Sung [KAIST, Daejeon (Korea, Republic of)

2016-05-15

To the eyes of the general public, however, reducing the chance of such accident is not enough. A typical engineer views a risk as a combination of both consequences and likelihoods, whereas an ordinary person may only consider consequences. The implementations of better regulations, improved human operator actions, and installations of extra safety systems may reduce the chance of having uncontrolled accident practically to zero, yet the public still fears having nuclear reactors. One such barrier system is a portable suction-based radiation dispersion prevention system, called Integrated Portable Suction-Centrifugal Filtration System (IPS-CFS). To design such systems, detailed information about the radioactive source term at the release point to the environment must be available to draw design limits. The preliminary design limits of the IPS-CFS are presented in this paper. It may seem challenging to design a comprehensive radioactive dispersion system that can successfully prevent such extreme accident conditions, especially due to the releases from high pressure. However, as more technologies develop and more realistic source term analyses are performed, it may be possible to develop such a public relief technology. With the development of such technology that can effectively prevent the dispersion of the uncontrolled radioactive releases in case of another Fukushima-like accident, it will result in increased safety of the nuclear power plants for both the public and the workers and may contribute to the increase in the public acceptance of nuclear energy.

CORE-COLLAPSE SUPERNOVA EQUATIONS OF STATE BASED ON NEUTRON STAR OBSERVATIONS

International Nuclear Information System (INIS)

Steiner, A. W.; Hempel, M.; Fischer, T.

2013-01-01

Many of the currently available equations of state for core-collapse supernova simulations give large neutron star radii and do not provide large enough neutron star masses, both of which are inconsistent with some recent neutron star observations. In addition, one of the critical uncertainties in the nucleon-nucleon interaction, the nuclear symmetry energy, is not fully explored by the currently available equations of state. In this article, we construct two new equations of state which match recent neutron star observations and provide more flexibility in studying the dependence on nuclear matter properties. The equations of state are also provided in tabular form, covering a wide range in density, temperature, and asymmetry, suitable for astrophysical simulations. These new equations of state are implemented into our spherically symmetric core-collapse supernova model, which is based on general relativistic radiation hydrodynamics with three-flavor Boltzmann neutrino transport. The results are compared with commonly used equations of state in supernova simulations of 11.2 and 40 M ☉ progenitors. We consider only equations of state which are fitted to nuclear binding energies and other experimental and observational constraints. We find that central densities at bounce are weakly correlated with L and that there is a moderate influence of the symmetry energy on the evolution of the electron fraction. The new models also obey the previously observed correlation between the time to black hole formation and the maximum mass of an s = 4 neutron star

Cooperation, cheating, and collapse in microbial populations

Science.gov (United States)

Gore, Jeff

2012-02-01

Natural populations can suffer catastrophic collapse in response to small changes in environmental conditions, and recovery after such a collapse can be exceedingly difficult. We have used laboratory yeast populations to study proposed early warning signals of impending extinction. Yeast cooperatively breakdown the sugar sucrose, meaning that there is a minimum number of cells required to sustain the population. We have demonstrated experimentally that the fluctuations in the population size increase in magnitude and become slower as the population approaches collapse. The cooperative nature of yeast growth on sucrose suggests that the population may be susceptible to cheater cells, which do not contribute to the public good and instead merely take advantage of the cooperative cells. We have confirmed this possibility experimentally by using a cheater yeast strain that lacks the gene encoding the cooperative behavior [1]. However, recent results in the lab demonstrate that the presence of a bacterial competitor may drive cooperation within the yeast population.[4pt] [1] Gore et al, Nature 459, 253 -- 256 (2009)

Transport in the Sawtooth Collapse

International Nuclear Information System (INIS)

Wesson, J.A.; Alper, B.; Edwards, A.W.; Gill, R.D.

1997-01-01

The rapid temperature collapse in tokamak sawtooth oscillations having incomplete magnetic reconnection is generally thought to occur through ergodization of the magnetic field. An experiment in JET using injected nickel indicates that this explanation is improbable. copyright 1997 The American Physical Society

Collapse dynamics of ultrasound contrast agent microbubbles

Science.gov (United States)

King, Daniel Alan

Ultrasound contrast agents (UCAs) are micron-sized gas bubbles encapsulated with thin shells on the order of nanometers thick. The damping effects of these viscoelastic coatings are widely known to significantly alter the bubble dynamics for linear and low-amplitude behavior; however, their effects on strongly nonlinear and destruction responses are much less studied. This dissertation examines the behaviors of single collapsing shelled microbubbles using experimental and theoretical methods. The study of their dynamics is particularly relevant for emerging experimental uses of UCAs which seek to leverage localized mechanical forces to create or avoid specialized biomedical effects. The central component in this work is the study of postexcitation rebound and collapse, observed acoustically to identify shell rupture and transient inertial cavitation of single UCA microbubbles. This time-domain analysis of the acoustic response provides a unique method for characterization of UCA destruction dynamics. The research contains a systematic documentation of single bubble postexcitation collapse through experimental measurement with the double passive cavitation detection (PCD) system at frequencies ranging from 0.9 to 7.1 MHz and peak rarefactional pressure amplitudes (PRPA) ranging from 230 kPa to 6.37 MPa. The double PCD setup is shown to improve the quality of collected data over previous setups by allowing symmetric responses from a localized confocal region to be identified. Postexcitation signal percentages are shown to generally follow trends consistent with other similar cavitation metrics such as inertial cavitation, with greater destruction observed at both increased PRPA and lower frequency over the tested ranges. Two different types of commercially available UCAs are characterized and found to have very different collapse thresholds; lipid-shelled Definity exhibits greater postexcitation at lower PRPAs than albumin-shelled Optison. Furthermore, by altering

Cutting-edge issues of core-collapse supernova theory

International Nuclear Information System (INIS)

Kotake, Kei; Nakamura, Ko; Kuroda, Takami; Takiwaki, Tomoya

2014-01-01

Based on multi-dimensional neutrino-radiation hydrodynamic simulations, we report several cutting-edge issues about the long-veiled explosion mechanism of core-collapse supernovae (CCSNe). In this contribution, we pay particular attention to whether three-dimensional (3D) hydrodynamics and/or general relativity (GR) would or would not help the onset of explosions. By performing 3D simulations with spectral neutrino transport, we show that it is more difficult to obtain an explosion in 3D than in 2D. In addition, our results from the first generation of full general relativistic 3D simulations including approximate neutrino transport indicate that GR can foster the onset of neutrino-driven explosions. Based on our recent parametric studies using a light-bulb scheme, we discuss impacts of nuclear energy deposition behind the supernova shock and stellar rotation on the neutrino-driven mechanism, both of which have yet to be included in the self-consistent 3D supernova models. Finally we give an outlook with a summary of the most urgent tasks to extract the information about the explosion mechanisms from multi-messenger CCSN observables

Collapse models and perceptual processes

International Nuclear Information System (INIS)

Ghirardi, Gian Carlo; Romano, Raffaele

2014-01-01

Theories including a collapse mechanism have been presented various years ago. They are based on a modification of standard quantum mechanics in which nonlinear and stochastic terms are added to the evolution equation. Their principal merits derive from the fact that they are mathematically precise schemes accounting, on the basis of a unique universal dynamical principle, both for the quantum behavior of microscopic systems as well as for the reduction associated to measurement processes and for the classical behavior of macroscopic objects. Since such theories qualify themselves not as new interpretations but as modifications of the standard theory they can be, in principle, tested against quantum mechanics. Recently, various investigations identifying possible crucial test have been discussed. In spite of the extreme difficulty to perform such tests it seems that recent technological developments allow at least to put precise limits on the parameters characterizing the modifications of the evolution equation. Here we will simply mention some of the recent investigations in this direction, while we will mainly concentrate our attention to the way in which collapse theories account for definite perceptual process. The differences between the case of reductions induced by perceptions and those related to measurement procedures by means of standard macroscopic devices will be discussed. On this basis, we suggest a precise experimental test of collapse theories involving conscious observers. We make plausible, by discussing in detail a toy model, that the modified dynamics can give rise to quite small but systematic errors in the visual perceptual process.

Prevention of radiation induced xerostomia by surgical transfer of submandibular salivary gland into the submental space

International Nuclear Information System (INIS)

Jha, Naresh; Seikaly, Hadi; Harris, Jeff; Williams, David; Liu, Richard; McGaw, Timothy; Hofmann, Henry; Robinson, Don; Hanson, John; Barnaby, Pam

2003-01-01

Background and purpose: Xerostomia is a significant morbidity of radiation treatment in the management of head and neck cancers. We hypothesized that the surgical transfer of one submandibular salivary gland to the submental space, where it can be shielded from radiation treatment (XRT), would prevent xerostomia. Materials and methods: We conducted a prospective Phase II clinical trial and the patients were followed clinically with salivary flow studies and the University of Washington Quality of Life questionnaire. Results: We report the results on 76 evaluable patients. The salivary gland transfer was done in 60 patients. Nine patients (of 60) did not have postoperative XRT and in eight patients (of 60) the transferred gland was not shielded from XRT due to proximity of disease. The median follow up is 14 months. Of the 43 patients with the salivary gland transfer and post-operative XRT with protection of the transferred gland, 81% have none or minimal xerostomia, and 19% developed moderate to severe xerostomia. Three patients (6.9%) developed local recurrence, five patients (11.6%) developed distant metastases and five patients (11.6%) have died. There were no complications attributed to the surgical procedure. Conclusion: Surgical transfer of a submandibular salivary gland to the submental space preserves its function and prevents the development of radiation induced xerostomia

Non-singular Brans–Dicke collapse in deformed phase space

Energy Technology Data Exchange (ETDEWEB)

Rasouli, S.M.M., E-mail: mrasouli@ubi.pt [Departamento de Física, Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Centro de Matemática e Aplicações (CMA - UBI), Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Physics Group, Qazvin Branch, Islamic Azad University, Qazvin (Iran, Islamic Republic of); Ziaie, A.H., E-mail: ah_ziaie@sbu.ac.ir [Department of Physics, Shahid Beheshti University, G. C., Evin, 19839 Tehran (Iran, Islamic Republic of); Department of Physics, Shahid Bahonar University, PO Box 76175, Kerman (Iran, Islamic Republic of); Jalalzadeh, S., E-mail: shahram.jalalzadeh@unila.edu.br [Federal University of Latin-American Integration, Technological Park of Itaipu PO box 2123, Foz do Iguaçu-PR, 85867-670 (Brazil); Moniz, P.V., E-mail: pmoniz@ubi.pt [Departamento de Física, Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal); Centro de Matemática e Aplicações (CMA - UBI), Universidade da Beira Interior, Rua Marquês d’Avila e Bolama, 6200 Covilhã (Portugal)

2016-12-15

We study the collapse process of a homogeneous perfect fluid (in FLRW background) with a barotropic equation of state in Brans–Dicke (BD) theory in the presence of phase space deformation effects. Such a deformation is introduced as a particular type of non-commutativity between phase space coordinates. For the commutative case, it has been shown in the literature (Scheel, 1995), that the dust collapse in BD theory leads to the formation of a spacetime singularity which is covered by an event horizon. In comparison to general relativity (GR), the authors concluded that the final state of black holes in BD theory is identical to the GR case but differs from GR during the dynamical evolution of the collapse process. However, the presence of non-commutative effects influences the dynamics of the collapse scenario and consequently a non-singular evolution is developed in the sense that a bounce emerges at a minimum radius, after which an expanding phase begins. Such a behavior is observed for positive values of the BD coupling parameter. For large positive values of the BD coupling parameter, when non-commutative effects are present, the dynamics of collapse process differs from the GR case. Finally, we show that for negative values of the BD coupling parameter, the singularity is replaced by an oscillatory bounce occurring at a finite time, with the frequency of oscillation and amplitude being damped at late times.

Non-singular Brans–Dicke collapse in deformed phase space

International Nuclear Information System (INIS)

Rasouli, S.M.M.; Ziaie, A.H.; Jalalzadeh, S.; Moniz, P.V.

2016-01-01

We study the collapse process of a homogeneous perfect fluid (in FLRW background) with a barotropic equation of state in Brans–Dicke (BD) theory in the presence of phase space deformation effects. Such a deformation is introduced as a particular type of non-commutativity between phase space coordinates. For the commutative case, it has been shown in the literature (Scheel, 1995), that the dust collapse in BD theory leads to the formation of a spacetime singularity which is covered by an event horizon. In comparison to general relativity (GR), the authors concluded that the final state of black holes in BD theory is identical to the GR case but differs from GR during the dynamical evolution of the collapse process. However, the presence of non-commutative effects influences the dynamics of the collapse scenario and consequently a non-singular evolution is developed in the sense that a bounce emerges at a minimum radius, after which an expanding phase begins. Such a behavior is observed for positive values of the BD coupling parameter. For large positive values of the BD coupling parameter, when non-commutative effects are present, the dynamics of collapse process differs from the GR case. Finally, we show that for negative values of the BD coupling parameter, the singularity is replaced by an oscillatory bounce occurring at a finite time, with the frequency of oscillation and amplitude being damped at late times.

Dynamics of bubble collapse under vessel confinement in 2D hydrodynamic experiments

Science.gov (United States)

Shpuntova, Galina; Austin, Joanna

2013-11-01

One trauma mechanism in biomedical treatment techniques based on the application of cumulative pressure pulses generated either externally (as in shock-wave lithotripsy) or internally (by laser-induced plasma) is the collapse of voids. However, prediction of void-collapse driven tissue damage is a challenging problem, involving complex and dynamic thermomechanical processes in a heterogeneous material. We carry out a series of model experiments to investigate the hydrodynamic processes of voids collapsing under dynamic loading in configurations designed to model cavitation with vessel confinement. The baseline case of void collapse near a single interface is also examined. Thin sheets of tissue-surrogate polymer materials with varying acoustic impedance are used to create one or two parallel material interfaces near the void. Shadowgraph photography and two-color, single-frame particle image velocimetry quantify bubble collapse dynamics including jetting, interface dynamics and penetration, and the response of the surrounding material. Research supported by NSF Award #0954769, ``CAREER: Dynamics and damage of void collapse in biological materials under stress wave loading.''

Does Pressure Accentuate General Relativistic Gravitational Collapse and Formation of Trapped Surfaces?

Science.gov (United States)

Mitra, Abhas

2013-04-01

It is widely believed that though pressure resists gravitational collapse in Newtonian gravity, it aids the same in general relativity (GR) so that GR collapse should eventually be similar to the monotonous free fall case. But we show that, even in the context of radiationless adiabatic collapse of a perfect fluid, pressure tends to resist GR collapse in a manner which is more pronounced than the corresponding Newtonian case and formation of trapped surfaces is inhibited. In fact there are many works which show such collapse to rebound or become oscillatory implying a tug of war between attractive gravity and repulsive pressure gradient. Furthermore, for an imperfect fluid, the resistive effect of pressure could be significant due to likely dramatic increase of tangential pressure beyond the "photon sphere." Indeed, with inclusion of tangential pressure, in principle, there can be static objects with surface gravitational redshift z → ∞. Therefore, pressure can certainly oppose gravitational contraction in GR in a significant manner in contradiction to the idea of Roger Penrose that GR continued collapse must be unstoppable.

The role of fluid viscosity in an immersed granular collapse

Science.gov (United States)

Yang, Geng Chao; Kwok, Chung Yee; Sobral, Yuri Dumaresq

2017-06-01

Instabilities of immersed slopes and cliffs can lead to catastrophic events that involve a sudden release of huge soil mass. The scaled deposit height and runout distance are found to follow simple power laws when a granular column collapses on a horizontal plane. However, if the granular column is submerged in a fluid, the mobility of the granular collapse due to high inertia effects will be reduced by fluid-particle interactions. In this study, the effects of fluid viscosity on granular collapse is investigated qualitatively by adopting a numerical approach based on the coupled lattice Boltzmann method (LBM) and discrete element method (DEM). It is found that the granular collapse can be dramatically slowed down due to the presence of viscous fluids. For the considered granular configuration, when the fluid viscosity increases. the runout distance decreases and the final deposition shows a larger deposit angle.

The role of fluid viscosity in an immersed granular collapse

Directory of Open Access Journals (Sweden)

Yang Geng Chao

2017-01-01

Full Text Available Instabilities of immersed slopes and cliffs can lead to catastrophic events that involve a sudden release of huge soil mass. The scaled deposit height and runout distance are found to follow simple power laws when a granular column collapses on a horizontal plane. However, if the granular column is submerged in a fluid, the mobility of the granular collapse due to high inertia effects will be reduced by fluid-particle interactions. In this study, the effects of fluid viscosity on granular collapse is investigated qualitatively by adopting a numerical approach based on the coupled lattice Boltzmann method (LBM and discrete element method (DEM. It is found that the granular collapse can be dramatically slowed down due to the presence of viscous fluids. For the considered granular configuration, when the fluid viscosity increases. the runout distance decreases and the final deposition shows a larger deposit angle.

The burning issues of motor vehicle radiator scald injuries revisited – a fresh review and changing prevention strategies

Science.gov (United States)

Patel, J.N.; Tan, A.; Frew, Q.; Dziewulski, P.

2016-01-01

Summary A preventable subgroup of burn injuries is scalds sustained from motor vehicle radiators. This study was to determine changes in trends in epidemiology of such injuries and to discuss whether current and other prevention efforts proposed previously require reinforcement. We conducted a retrospective study (February 2007-August 2015) of all motor vehicle-related burn referrals to our regional burns service. 68 cases of motor vehicle radiator burns were identified. Male to female ratio was 65:3. Mean age was 35.1 (range = 9-71). Most cases occurred in the summer months (22/68 = 32.4%). 65 cases (95.6%) involved car radiators. 66% of injuries resulted from actively removing the pressure cap of an overheated radiator in the motor vehicle. Mean total burn surface area (%TBSA) was 2.1% (range = 0.5- 11%). The depths of burn injuries were mostly superficial partial thickness. Face, chest and upper limbs were the most common sites of injury. Mean healing time was 14.2 days (range = 4-60). Following the introduction of safety measures by vehicle manufacturers, motor vehicle radiator burns in this era are mostly minor injuries and can be potentially managed conservatively as an outpatient. This contrasts with findings from previous studies over a decade ago of larger, more significant injuries requiring admission and surgery. Whilst manufacturers have installed safety measures into the design of radiator caps, our findings suggest that re-educating the public to allow a period of cooling prior to opening caps should be reinforced. PMID:28289357

Weak Interaction processes in core-collapse supernova

International Nuclear Information System (INIS)

Martinez-Pinedo, Gabriel

2008-01-01

In this manuscript we review the role that weak interaction processes play in supernova. This includes electron captures and inelastic neutrino-nucleus scattering (INNS). Electron captures during the collapse occur mainly in heavy nuclei, however the proton contribution is responsible for the convergence of different models to a 'norm' stellar trajectory. Neutrino-nucleus cross sections at supernova neutrino energies can be determined from precise data on the magnetic dipole strength. The results agree well with large-scale shell-model calculations. When incorporated in core-collapse simulations INNS increases the neutrino opacities noticeably and strongly reduces the high-energy part of the supernova spectrum

Relativistic collapse using Regge calculus: Pt. 1

International Nuclear Information System (INIS)

Dubal, M.R.; Leicester Univ.

1989-01-01

Regge calculus is used to simulate the dynamical collapse of model stars. In this paper we describe the general methodology of including a perfect fluid in dynamical Regge calculus spacetimes. The Regge-Einstein equations for spherical collapse are obtained and are then specialised to mimic a particular continuum gauge. The equivalent continuum problem is also set up. This is to be solved using standard numerical techniques (i.e. the method of finite difference). A subsequent paper will consider the solution of the equations presented here and will use the continuum problem for comparison purposes in order to check the Regge calculus results. (author)

Growing quasi-modes in dynamics of supersonic collapse

International Nuclear Information System (INIS)

Malkin, V.M.; Khudik, V.N.

1989-01-01

The hypothesis of globally stable self-similar regimes existence for supersonic Langmuir collapse plays a significant role in the attempts to construct a theory of strong Langmuir turbulence. A possibility for destruction of the stable against infinitely small perturbations self-similar regime of supersonic collapse by growing quasi-modes is demonstrated via the numerical solution of Cauchi problem for Zakharov equations. The quantitative criterion for the destruction of self-similar regimes is formulated. 9 refs.; 5 figs

PTH prevents the adverse effects of focal radiation on bone architecture in young rats.

Science.gov (United States)

Chandra, Abhishek; Lan, Shenghui; Zhu, Ji; Lin, Tiao; Zhang, Xianrong; Siclari, Valerie A; Altman, Allison R; Cengel, Keith A; Liu, X Sherry; Qin, Ling

2013-08-01

Radiation therapy is a common treatment regimen for cancer patients. However, its adverse effects on the neighboring bone could lead to fractures with a great impact on quality of life. The underlying mechanism is still elusive and there is no preventive or curative solution for this bone loss. Parathyroid hormone (PTH) is a current therapy for osteoporosis that has potent anabolic effects on bone. In this study, we found that focal radiation from frequent scans of the right tibiae in 1-month-old rats by micro-computed tomography severely decreased trabecular bone mass and deteriorated bone structure. Interestingly, PTH daily injections remarkably improved trabecular bone in the radiated tibiae with increases in trabecular number, thickness, connectivity, structure model index and stiffness, and a decrease in trabecular separation. Histomorphometric analysis revealed that radiation mainly decreased the number of osteoblasts and impaired their mineralization activity but had little effects on osteoclasts. PTH reversed these adverse effects and greatly increased bone formation to a similar level in both radiated and non-radiated bones. Furthermore, PTH protects bone marrow mesenchymal stem cells from radiation-induced damage, including a decrease in number and an increase in adipogenic differentiation. While radiation generated the same amount of free radicals in the bone marrow of vehicle-treated and PTH-treated animals, the percentage of apoptotic bone marrow cells was significantly attenuated in the PTH group. Taken together, our data demonstrate a radioprotective effect of PTH on bone structure and bone marrow and shed new light on a possible clinical application of anabolic treatment in radiotherapy. Copyright © 2013 Elsevier Inc. All rights reserved.

Evidence supporting pre-radiation elimination of oral foci of infection in head and neck cancer patients to prevent oral sequelae. A systematic review.

Science.gov (United States)

Schuurhuis, Jennifer M; Stokman, Monique A; Witjes, Max J H; Dijkstra, Pieter U; Vissink, Arjan; Spijkervet, Frederik K L

2015-03-01

Pre-radiation dental screening of head-neck cancer patients aims to identify and eliminate oral foci of infection to prevent post-radiation oral problems. The evidence for the efficacy of dental screening is unclear. In this systematic review, we analyzed available evidence on the efficacy of pre-radiation elimination of oral foci of infection in preventing oral sequelae. A search was conducted (MEDLINE/EMBASE) for papers published up to May 2014. Papers on head-neck cancer patients subjected to pre-radiation dental screening, (chemo)radiation and oral follow-up were included. Of the 1770 identified papers, 20 studies fulfilled the inclusion criteria of which 17 were retrospective. A great heterogeneity in patient groups, dental screening techniques, definitions of oral foci of infection and techniques for eliminating foci was found. Most papers lacked essential details on how dental screening was performed and a clear definition of an oral focus of infection. The evidence for efficacy of elimination of oral foci of infection to prevent post-radiotherapy oral sequelae was inconclusive. Consequently, the efficacy of pre-radiation elimination of oral foci of infection remains unclear. No conclusions can be drawn about a definition of an oral focus of infection and whether pre-radiation elimination of these foci should be mandatory. We therefore suggest prospective studies with well-defined criteria for oral foci of infection, a clear description of which foci were eliminated and how, a detailed description of pre-radiation dental screening, clearly described patient and tumor characteristics, and a detailed dental history and dental status. Subsequently, oral problems that occur post-radiation should be systematically recorded. Copyright © 2014 Elsevier Ltd. All rights reserved.

Are the new resonances superexotic or collapsed han nambu states

International Nuclear Information System (INIS)

Lipkin, H.J.

1975-01-01

Possible descriptions of the psi states as unorthodox color octet states in the Han-Nambu model are discussed. Simple quark-antiquark configurations are unbound in the static colored gluon exchange model. More complicated states having indefinite numbers of quark-antiquark pairs, or ''collapsed configurations'' might be bound. Their radiative decays would be suppressed by the small overlap with conventional states. The unexplained spin dependence of both conventional and new meson spectra is pointed out. The rho-π mass difference is about half the rho-f splitting, while the B-f splitting is small. New particles have low-lying vectors and no trace of pseudo-scalars. A link between these spectra is suggested by the observation that precisely these features follow from adding a repulsive core to the colored gluon exchange potential in the color singlet spin triplet state which also reverses sign in the color octet states. (author)

Production Potential Of Nchanga Underground Mines Collapsed Blocks

Directory of Open Access Journals (Sweden)

Eugie Kabwe

2015-08-01

Full Text Available Abstract the main purpose of this study is to recommend modification to block caving at Nchanga ensure that it meets anticipated production levels and address the adverse ground conditions of the intensely fractured orebody. Excavations of current methods are driven close to the incompetent orebody. Determination of the appropriate method based on criteria of selection techniques together with the analysis of operating costs and safety. Reclamation of ore in the collapsed blocks entirely depended on maximizing revenue recovery of the mineral and safe working environment for equipment and personnel. On recommendation of a suitable method extent of the collapsed blocks was another aspect considered. The proposed methods of extraction were variants of block caving further shortlisted based on the extent of collapse. Economic appraisal of both the recommended and current mining methods employed included extraction recovery development reclamation costs revenue estimation and revenue raised from finished copper.

UV radiation and health: prevention in school; UV-Strahlung und Gesundheit: Praevention in der Schule

Energy Technology Data Exchange (ETDEWEB)

Gerber, B.U. [Bundesamt fuer Gesundheit (Switzerland)

2004-07-01

It is well known that children's skin and eyes are very sensitive to UV radiation, and that sunburn during childhood increases the risk of skin cancer later in life. Because of these facts and the easier influence to attitudes and behaviour at a young age, prevention in school becomes an important issue. There are difficulties and chances pointed out for prevention in schools. It is stated on the basis of a running prevention program for primary and secondary school in Switzerland how a concrete conversion can look. Teaching materials and worksheets for the different school stages form the principal item in this program. Described is the total concept, the method for the development of the materials as well as the experiences after three-year application. (orig.)

The effects of narrow-band middle infrared radiation in enhancing the antitumor activity of paclitaxel.

Science.gov (United States)

Tsai, Shang-Ru; Sheu, Bor-Ching; Huang, Pei-Shen; Lee, Si-Chen

2016-01-01

Paclitaxel is used as an adjuvant to enhance the effectiveness of ionization radiation therapy; however, high-energy radiation often damages the healthy cells surrounding cancer cells. Low-energy, middle-infrared radiation (MIR) has been shown to prevent tissue damage, and recent studies have begun combining MIR with paclitaxel. However, the cytotoxic effects of this treatment combination remain unclear, and the mechanism underlying its effects on HeLa cells has yet to be elucidated. This study investigated the effectiveness of treating HeLa human cervical cancer cells with a combination of paclitaxel for 48 h in conjunction with narrow-band MIR from 3.0 to 5.0 μm. This combined treatment significantly inhibited the growth of HeLa cells. Specifically, results from Annexin V-FITC/PI apoptosis detection and cell mitochondrial membrane potential analyses revealed an increase in apoptotic cell death and a collapse of mitochondrial membrane potential. One possible mechanism underlying cellular apoptosis is an increase in oxidative stress. These preliminary findings provide evidence to support the combination of narrow-band MIR with paclitaxel as an alternative approach in the treatment of human cervical cancer.

Earthquakes as collapse precursors at the Han-sur-Lesse Cave in the Belgian Ardennes

Science.gov (United States)

Camelbeeck, Thierry; Quinif, Yves; Verheyden, Sophie; Vanneste, Kris; Knuts, Elisabeth

2018-05-01

Collapse activation is an ongoing process in the evolution of karstic networks related to the weakening of cave vaults. Because collapses are infrequent, few have been directly observed, making it challenging to evaluate the role of external processes in their initiation and triggering. Here, we study the two most recent collapses in the Dôme chamber of the Han-sur-Lesse Cave (Belgian Ardenne) that occurred on or shortly after 3rd December 1828 and between the 13th and 14th of March 1984. Because of the low probability that the two earthquakes that generated the strongest ground motions in Han-sur-Lesse since 1800, on 23rd February 1828 (Mw = 5.1 in Central Belgium) and 8th November 1983 (Mw = 4.8 in Liège) occurred by coincidence less than one year before these collapses, we suggest that the collapses are related to these earthquakes. We argue that the earthquakes accelerated the cave vault instability, leading to the collapses by the action of other factors weakening the host rock. In particular, the 1828 collapse was likely triggered by a smaller Mw = 4.2 nearby earthquake. The 1984 collapse followed two months of heavy rainfall that would have increased water infiltration and pressure in the rock mass favoring destabilization of the cave ceiling. Lamina counting of a stalagmite growing on the 1828 debris dates the collapse at 1826 ± 9 CE, demonstrating the possibility of dating previous collapses with a few years of uncertainty. Furthermore, our study opens new perspectives for studying collapses and their chronology both in the Han-sur-Lesse Cave and in other karstic networks. We suggest that earthquake activity could play a stronger role than previously thought in initiating cave collapses.

Coexistence of collapse and stable spatiotemporal solitons in multimode fibers

Science.gov (United States)

Shtyrina, Olga V.; Fedoruk, Mikhail P.; Kivshar, Yuri S.; Turitsyn, Sergei K.

2018-01-01

We analyze spatiotemporal solitons in multimode optical fibers and demonstrate the existence of stable solitons, in a sharp contrast to earlier predictions of collapse of multidimensional solitons in three-dimensional media. We discuss the coexistence of blow-up solutions and collapse stabilization by a low-dimensional external potential in graded-index media, and also predict the existence of stable higher-order nonlinear waves such as dipole-mode spatiotemporal solitons. To support the main conclusions of our numerical studies we employ a variational approach and derive analytically the stability criterion for input powers for the collapse stabilization.

Bose-Einstein condensate collapse: A comparison between theory and experiment

International Nuclear Information System (INIS)

Savage, C.M.; Robins, N.P.; Hope, J.J.

2003-01-01

We solve the Gross-Pitaevskii equation numerically for the collapse induced by a switch from positive to negative scattering lengths. We compare our results with experiments performed with Bose-Einstein condensates of 85 Rb, in which the scattering length was controlled using a Feshbach resonance. Building on previous theoretical work we identify quantitative differences between the predictions of mean-field theory and the results of the experiments. In addition to the previously reported difference between the predicted and observed critical atom number for collapse, we also find that the predicted collapse times systematically exceed those observed experimentally

Collapse in a forced three-dimensional nonlinear Schrodinger equation

DEFF Research Database (Denmark)

Lushnikov, P.M.; Saffman, M.

2000-01-01

We derive sufficient conditions for the occurrence of collapse in a forced three-dimensional nonlinear Schrodinger equation without dissipation. Numerical studies continue the results to the case of finite dissipation.......We derive sufficient conditions for the occurrence of collapse in a forced three-dimensional nonlinear Schrodinger equation without dissipation. Numerical studies continue the results to the case of finite dissipation....

Study on preventive and therapeutic function of compound white peony root oral liquids in treating radiation-induced esophagitis

International Nuclear Information System (INIS)

Shen Li; Shan Baoen; Zhang Li; Li Wei; Gong Yanjun; Gao Haixiang

2007-01-01

Wistar rats were divided into seven groups: the normal group, the irradiated group, the preventive group treated with the normal dose of compound white peony root oral liquids (cWPROL) (immediately administered on the day after rats were irradiated), the preventive group treated with the high dose of cWPROL (immediately administered on the day after rats were irradiated), the group treated with normal dose of cWPROL (administered on the 7th day after rats were irradiated), the group treated with high dose of cWPROL (administered on the 7th day after rats were irradiated), the group treated with Western medicine administered from the seventh day after irradiation. The radiation esophagitis of rats was induced by single irradiation of 43 Gy gamma ray locally. Then the rats with radiation esophagitis were treated in different ways. The food weight, water volume intaked by the rats and its body weight change were observed; The rats were killed on the 14th day after irradiation and the leucocyte count and DIFF were analyzed and the esophageal pathological sections were made. The pathological change of rats' esophageal mucosa and ultrastructure change of cells were observed for different groups. The results showed all the cWPROL and Western medicine have therapeutic function of treating radiation-induced esophagitis of rats. The ultrastructure of cells of rats in the group treated with normal dose of cWPROL recovered. The food weight and water volume intaked by the rats had increased in the group infused with cWPROL compared with purely irradiated groups, especially in the preventive group treated with high dose of cWPROL. The weight of food, the WBC count, the lymphocyte differential count in the group which was treated with Western medicine decreased compared with the purely irradiated group. Lymphocyte differential count increased in the groups administered cWPROL compared with the purely irradiated group. The compound white peony root oral liquids serves the function

Spherical collapse model in time varying vacuum cosmologies

International Nuclear Information System (INIS)

Basilakos, Spyros; Plionis, Manolis; Sola, Joan

2010-01-01

We investigate the virialization of cosmic structures in the framework of flat Friedmann-Lemaitre-Robertson-Walker cosmological models, in which the vacuum energy density evolves with time. In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, 'turn around', and finally collapse. We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, Λ=Λ(H). A particularly well-motivated model of this type is the so-called quantum field vacuum, in which Λ(H) is a quadratic function, Λ(H)=n 0 +n 2 H 2 , with n 0 ≠0. This model was previously studied by our team using the latest high quality cosmological data to constrain its free parameters, as well as the predicted cluster formation rate. It turns out that the corresponding Hubble expansion history resembles that of the traditional ΛCDM cosmology. We use this Λ(t)CDM framework to illustrate the fact that the properties of the spherical collapse model (virial density, collapse factor, etc.) depend on the choice of the considered vacuum energy (homogeneous or clustered). In particular, if the distribution of the vacuum energy is clustered, then, under specific conditions, we can produce more concentrated structures with respect to the homogeneous vacuum energy case.

A Mathematical Model Development for the Lateral Collapse of Octagonal Tubes

Science.gov (United States)

Ghazali Kamardan, M.; Sufahani, Suliadi; Othman, M. Z. M.; Che-Him, Norziha; Khalid, Kamil; Roslan, Rozaini; Ali, Maselan; Zaidi, A. M. A.

2018-04-01

Many researches has been done on the lateral collapse of tube. However, the previous researches only focus on cylindrical and square tubes. Then a research has been done discovering the collapse behaviour of hexagonal tube and the mathematic model of the deformation behaviour had been developed [8]. The purpose of this research is to study the lateral collapse behaviour of symmetric octagonal tubes and hence to develop a mathematical model of the collapse behaviour of these tubes. For that, a predictive mathematical model was developed and a finite element analysis procedure was conducted for the lateral collapse behaviour of symmetric octagonal tubes. Lastly, the mathematical model was verified by using the finite element analysis simulation results. It was discovered that these tubes performed different deformation behaviour than the cylindrical tube. Symmetric octagonal tubes perform 2 phases of elastic - plastic deformation behaviour patterns. The mathematical model had managed to show the fundamental of the deformation behaviour of octagonal tubes. However, further studies need to be conducted in order to further improve on the proposed mathematical model.

Collapse and dispersal of a homogeneous spin fluid in Einstein-Cartan theory

Science.gov (United States)

Hashemi, M.; Jalalzadeh, S.; Ziaie, A. H.

2015-02-01

In the present work, we revisit the process of gravitational collapse of a spherically symmetric homogeneous dust fluid which is described by the Oppenheimer-Snyder (OS) model (Oppenheimer and Snyder in Phys Rev D 56:455, 1939). We show that such a scenario would not end in a spacetime singularity when the spin degrees of freedom of fermionic particles within the collapsing cloud are taken into account. To this purpose, we take the matter content of the stellar object as a homogeneous Weyssenhoff fluid. Employing the homogeneous and isotropic FLRW metric for the interior spacetime setup, it is shown that the spin of matter, in the context of a negative pressure, acts against the pull of gravity and decelerates the dynamical evolution of the collapse in its later stages. Our results show a picture of gravitational collapse in which the collapse process halts at a finite radius, whose value depends on the initial configuration. We thus show that the spacetime singularity that occurs in the OS model is replaced by a non-singular bounce beyond which the collapsing cloud re-expands to infinity. Depending on the model parameters, one can find a minimum value for the boundary of the collapsing cloud or correspondingly a threshold value for the mass content below which the horizon formation can be avoided. Our results are supported by a thorough numerical analysis.

Collapse and dispersal of a homogeneous spin fluid in Einstein-Cartan theory

International Nuclear Information System (INIS)

Hashemi, M.; Jalalzadeh, S.; Ziaie, A.H.

2015-01-01

In the present work, we revisit the process of gravitational collapse of a spherically symmetric homogeneous dust fluid which is described by the Oppenheimer-Snyder (OS) model (Oppenheimer and Snyder in Phys Rev D 56:455, 1939). We show that such a scenario would not end in a spacetime singularity when the spin degrees of freedom of fermionic particles within the collapsing cloud are taken into account. To this purpose, we take the matter content of the stellar object as a homogeneous Weyssenhoff fluid. Employing the homogeneous and isotropic FLRW metric for the interior spacetime setup, it is shown that the spin of matter, in the context of a negative pressure, acts against the pull of gravity and decelerates the dynamical evolution of the collapse in its later stages. Our results show a picture of gravitational collapse in which the collapse process halts at a finite radius, whose value depends on the initial configuration. We thus show that the spacetime singularity that occurs in the OS model is replaced by a non-singular bounce beyond which the collapsing cloud re-expands to infinity. Depending on the model parameters, one can find a minimum value for the boundary of the collapsing cloud or correspondingly a threshold value for the mass content below which the horizon formation can be avoided. Our results are supported by a thorough numerical analysis. (orig.)

Collapsing stellar cores and supernovae

Energy Technology Data Exchange (ETDEWEB)

Epstein, R J [Nordisk Inst. for Teoretisk Atomfysik, Copenhagen (Denmark); Noorgaard, H [Nordisk Inst. for Teoretisk Atomfysik, Copenhagen (Denmark); Chicago Univ., IL (USA). Enrico Fermi Inst.); Bond, J R [Niels Bohr Institutet, Copenhagen (Denmark); California Inst. of Tech., Pasadena (USA). W.K. Kellogg Radiation Lab.)

1979-05-01

The evolution of a stellar core is studied during its final quasi-hydrostatic contraction. The core structure and the (poorly known) properties of neutron rich matter are parametrized to include most plausible cases. It is found that the density-temperature trajectory of the material in the central part of the core (the core-center) is insensitive to nearly all reasonable parameter variations. The central density at the onset of the dynamic phase of the collapse (when the core-center begins to fall away from the rest of the star) and the fraction of the emitted neutrinos which are trapped in the collapsing core-center depend quite sensitively on the properties of neutron rich matter. We estimate that the amount of energy Ecm which is imparted to the core-mantle by the neutrinos which escape from the imploded core-center can span a large range of values. For plausible choices of nuclear and model parameters Ecm can be large enough to yield a supernova event.

The study of efficiency of endogenous and exogenous preventive methods of tooth enamel remineralisation by FTIR microscopy using synchrotron radiation

International Nuclear Information System (INIS)

Goloshchapov, D L; Kashkarov, V M; Seredin, P V; Ippolitov, Y A; Plotnikova, Y A; Bambery, K

2016-01-01

The efficiency carious preventive methods was detected with the use of equipment for IR-spectromicroscopy and high-intensive synchrotron radiation. The results of the experiment are indicative of the use of exogenous caries prevention alone (use of a toothpaste) being inadequate in saturating hard dental tissues by mineral groups and, thus, keeping teeth healthy, as this method is only short-lived. The use of endogenous methods (mineral tablets based on calcium glycerophosphate) in combination with exogenous prevention enhances prevention as part of remineralisation of dental tissues. (paper)

Radiation Mapping in Post-Disaster Environments Using an Autonomous Helicopter

OpenAIRE

Towler, Jerry; Krawiec, Bryan; Kochersberger, Kevin

2012-01-01

Recent events have highlighted the need for unmanned remote sensing in dangerous areas, particularly where structures have collapsed or explosions have occurred, to limit hazards to first responders and increase their efficiency in planning response operations. In the case of the Fukushima nuclear reactor explosion, an unmanned helicopter capable of obtaining overhead images, gathering radiation measurements, and mapping both the structural and radiation content of the environment would have ...

A study to determine the optimum romurtide regimen to prevent radiation-induced leukopenia

International Nuclear Information System (INIS)

Inoue, Toshihiko; Teshima, Teruki; Ohtani, Masatoshi

1994-01-01

To evaluate the best dose of romurtide to counter radiation-induced leukopenia, two romurtide regimens have been studied in 69 patients undergoing radiation therapy, said patients divided into two groups. Those assigned to Group A, consisting of 33 patients, received a daily subcutaneous injection of 200 μg of romurtide for 10 consecutive days, and those assigned to Group B, consisting of 36 patients, received the same injection dose of romurtide every other day. Three weeks after the start of this study, it was found that both the leukocyte count and neutrophil count were significantly higher in the Group B patients (p<0.05). These results suggest that leukopenia resulting from exposure to radiotherapy can be prevented from developing over a longer period by the every other day romurtide injection regimen, compared to the daily romurtide injection regimen. (author)

Is radiation-induced ovarian failure in rhesus monkeys preventable by luteinizing hormone-releasing hormone agonists?: Preliminary observations

International Nuclear Information System (INIS)

Ataya, K.; Pydyn, E.; Ramahi-Ataya

1995-01-01

With the advent of cancer therapy, increasing numbers of cancer patients are achieving long term survival. Impaired ovarian function after radiation therapy has been reported in several studies. Some investigators have suggested that luteinizing hormone-releasing hormone agonists (LHRHa) can prevent radiation-induced ovarian injury in rodents. Adult female rhesus monkeys were given either vehicle or Leuprolide acetate before, during, and after radiation. Radiation was given in a dose of 200 rads/day for a total of 4000 rads to the ovaries. Frequent serum samples were assayed for estradiol (E 2 ) and FSH. Ovariectomy was performed later. Ovaries were processed and serially sectioned. Follicle count and size distribution were determined. Shortly after radiation started, E 2 dropped to low levels, at which it remained, whereas serum FSH level, which was low before radiation, rose soon after starting radiation. In monkeys treated with a combination of LHRHa and radiation, FSH started rising soon after the LHRHa-loaded minipump was removed (after the end of radiation). Serum E 2 increased after the end of LHRHa treatment in the non-irradiated monkey, but not in the irradiated monkey. Follicle counts were not preserved in the LHRHa-treated monkeys that received radiation. The data demonstrated no protective effect of LHRHa treatment against radiation-induced ovarian injury in this rhesus monkey model. 58 refs., 2 figs., 1 tab

Wave function collapse implies divergence of average displacement

OpenAIRE

Marchewka, A.; Schuss, Z.

2005-01-01

We show that propagating a truncated discontinuous wave function by Schr\\"odinger's equation, as asserted by the collapse axiom, gives rise to non-existence of the average displacement of the particle on the line. It also implies that there is no Zeno effect. On the other hand, if the truncation is done so that the reduced wave function is continuous, the average coordinate is finite and there is a Zeno effect. Therefore the collapse axiom of measurement needs to be revised.

Mobile radiation monitoring of Delhi for the prevention of malicious acts during the Common Wealth Games (CWG-2010)

International Nuclear Information System (INIS)

Saindane, Shashank S.; Chatterjee, M.K.; Romal, Jis; Pradeepkumar, K.S.; Singh, B.R.

2012-01-01

Radioactive sources are widely used in industry, research, agriculture and medical applications. In spite of various measures adopted for ensuring the safety and security of these sources, similar to Mayapuri incident, many cases of lost, misplaced, stolen radioactive sources and inadvertent radiation exposure due to radiological emergencies are reported world over. In the aftermath of the attack on the World Trade Center 2001, malicious acts using radioactive material is considered as a threat for which prevention and preparedness for response are recommended by IAEA. Hence radiation monitoring of all related area prior to and during Major Public Events (MPEs) like Olympics, World cup football etc are implemented by many nations for prevention and preparedness to such radiological threats/emergencies. Department of Atomic Energy (DAE) through their Emergency Response Centres planned and executed detailed radiation monitoring programme for the Delhi Common Wealth Games (CWG 2010) which covered all CWG stadiums. Commonwealth village etc. In addition to DAE emergency response teams of 15 members in readiness, source recovery and shielding facilities, Portable Personnel Decontamination Unit (PPDU), Radiation monitors, Protective gears, Aerial Gamma Spectrometry System (AGSS for Aerial surveys) etc. were maintained at two DAE control rooms. This paper discusses the mobile radiation monitoring carried out on Delhi city roads with the help of various state-of-the-art monitoring systems to detect the presence or movement of any orphan sources. The mobile radiation monitoring was focused on main road networks connecting to stadiums, areas surrounding stadiums, airport and Games village. For this state-of-the-art systems like Portable Mobile Gamma Spectrometry System (PMGSS), Portable Radiation Scanner (PRS), Compact Radiation Monitoring System integrated with GPS, GSM based Radiation Monitoring System (GRaMS), Gammatracers, Selection and placement of different monitoring

Indicators of collapse in systems undergoing unsustainable growth.

Science.gov (United States)

Ridolfi, Luca; D'Odorico, Paolo; Laio, Francesco

2015-02-01

Unsustainable growth is typical of systems that rely on a finite pool of non-renewable resources that are tapped until they are depleted. The decrease in resource availability eventually leads these systems to a decline. Here we investigate the dynamics of systems that exhibit unsustainable growth and are prone to a collapse to an alternative ("degraded") state. For these systems the possible imminent occurrence of a collapse is difficult to avert because they keep growing as they approach the transition point. It is therefore important to identify some early warning signs that can be used to predict whether the system is approaching a critical and likely irreversible transition to an undesired and degraded state. This study evaluates whether existing theories of precursors of phase transitions based on the critical slowing down phenomenon are applicable as leading indicators of state shift in unsustainable growth dynamics. It is found that such indicators fail to serve as reliable early warning signs of the system's collapse.

Gravitational instability in a primordial collapsing gas cloud

International Nuclear Information System (INIS)

Lacey, C.G.

1989-01-01

This paper presents an analysis of the linear evolution of short-wavelength perturbations in a background fluid flow which is undergoing gravitational collapse on large scales. Local evolution equations for perturbations to an arbitrary flow are derived in the linear regime and the short-wavelength limit. Local perturbation behavior in an inhomogeneous flow is found to be the same as that in a homogeneous anisotropic flow having the same local velocity field. Background flows in which the scale factors vary as power laws in time are considered to illustrate the relative effects of self-gravity, pressure and kinematics of the background flow on the density perturbation evolution. Perturbation analyses are then presented for more realistic background flows arising from the evolution into the nonlinear regime of initially small density perturbations in an isotropically expanding cosmological model. For low-pressure, inhomogeneous collapses, kinematic effects tend to dominate over self-gravity in driving perturbation growth as the collapse proceeds. 28 references

On the possibility of a two-bang supernova collapse

International Nuclear Information System (INIS)

Berezinsky, V.S.; Castagnoli, C.; Dokuchaev, V.I.; Galeotti, P.

1988-01-01

The possibility of a two-bang stellar collapse originating SN 1987a, and having the characteristics of the events recorded in Mont Blanc and Kamiokande, is discussed here. According to the ''standard'' collapse models of nonrotating stars, which predict the formation of a neutrino-sphere with a nondegenerate neutrino gas inside the star, the Mont Blanc and kamiokande data for the first burst give a too large stellar mass. On the contrary, a degenerate neutrino gas with low temperature T ∼ 0.5 MeV, and chemical potential μ ∼ (12-15), predicts a relatively low total energy outflow W ν ∼ (2-6) x 10 54 erg, and a small number of expected interactions in Kamiokande. A possible scenario is suggested: a massive (M ∼ 20M o ) rotating star is fragmented into two pieces, one light and the other heavy, at the onset of the collapse.The massive component collapses to a black hole, and produces the first burst. Neutrinos are trapped inside the collapsing star because of elastic scattering in the outer core off heavy nuclei, with A ∼ 300. It is shown that neutrinos fill up the quantum states, producing a degenerate neutrino gas. The second burst is explained by coalescence of the light fragment (M ∼ (1-3)M o ) onto the massive black hole. The time delay between the two observed bursts (4.7h) is mostly connected with gravitational braking, when the light fragment falls down onto the black hole, with an accompanying emission of gravitational waves for times of order of hours

New strategies for the prevention of radiation injury. Possible implications for countering radiation hazards of long-term space travel

International Nuclear Information System (INIS)

Seed, T.; Kumar, S.; Whitnall, M.

2002-01-01

New strategies for the prevention of radiation injuries are currently being explored with the ultimate aim of developing globally radioprotective, nontoxic pharmacologics. The prophylactic treatments under review encompass such diverse pharmacologic classes as novel immunomodulators, nutritional antioxidants, and cytokines. An immunomodulator that shows promise is 5-androstenediol (AED), a well-tolerated, long-acting and rostene steroid with broad-spectrum radioprotective attributes that include not only protection against acute tissue injury, but also reduced susceptibility to infectious agents, as well as reduced rates of neoplastic transformation. Other potentially useful radioprotectants currently under study include the nutraceutical vitamin E and analogs, a chemically-engineered cytokine, interleukin-1β, and a sustained-release formulation of an aminothiol, amifostine. Results suggest that a new paradigm is evolving for the prophylaxes of radiation injuries, based on use of newly identified, nontoxic, broad-spectrum prophylactic agents whose protective action may be leveraged by subsequent postexposure use of cytokines with organ-specific reparative functions. (author)

New strategies for the prevention of radiation injury. Possible implications for countering radiation hazards of long-term space travel

Energy Technology Data Exchange (ETDEWEB)

Seed, T.; Kumar, S.; Whitnall, M. [Armed Forces Radiobiology Research Inst., Bethesda, MD (United States). Radiation Casualty Management] [and others

2002-12-01

New strategies for the prevention of radiation injuries are currently being explored with the ultimate aim of developing globally radioprotective, nontoxic pharmacologics. The prophylactic treatments under review encompass such diverse pharmacologic classes as novel immunomodulators, nutritional antioxidants, and cytokines. An immunomodulator that shows promise is 5-androstenediol (AED), a well-tolerated, long-acting and rostene steroid with broad-spectrum radioprotective attributes that include not only protection against acute tissue injury, but also reduced susceptibility to infectious agents, as well as reduced rates of neoplastic transformation. Other potentially useful radioprotectants currently under study include the nutraceutical vitamin E and analogs, a chemically-engineered cytokine, interleukin-1{beta}, and a sustained-release formulation of an aminothiol, amifostine. Results suggest that a new paradigm is evolving for the prophylaxes of radiation injuries, based on use of newly identified, nontoxic, broad-spectrum prophylactic agents whose protective action may be leveraged by subsequent postexposure use of cytokines with organ-specific reparative functions. (author)

a Statistical Texture Feature for Building Collapse Information Extraction of SAR Image

Science.gov (United States)

Li, L.; Yang, H.; Chen, Q.; Liu, X.

2018-04-01

Synthetic Aperture Radar (SAR) has become one of the most important ways to extract post-disaster collapsed building information, due to its extreme versatility and almost all-weather, day-and-night working capability, etc. In view of the fact that the inherent statistical distribution of speckle in SAR images is not used to extract collapsed building information, this paper proposed a novel texture feature of statistical models of SAR images to extract the collapsed buildings. In the proposed feature, the texture parameter of G0 distribution from SAR images is used to reflect the uniformity of the target to extract the collapsed building. This feature not only considers the statistical distribution of SAR images, providing more accurate description of the object texture, but also is applied to extract collapsed building information of single-, dual- or full-polarization SAR data. The RADARSAT-2 data of Yushu earthquake which acquired on April 21, 2010 is used to present and analyze the performance of the proposed method. In addition, the applicability of this feature to SAR data with different polarizations is also analysed, which provides decision support for the data selection of collapsed building information extraction.

De Novo Collapsing Glomerulopathy in a Renal Allograft Recipient

Directory of Open Access Journals (Sweden)

Kanodia K

2008-01-01

Full Text Available Collapsing glomerulopathy (CG, characterized histologically by segmental/global glomerular capillary collapse, podocyte hypertrophy and hypercellularity and tubulo-interstitial injury; is characterized clinically by massive proteinuria and rapid progressive renal failure. CG is known to recur in renal allograft and rarely de novo. We report de novo CG 3 years post-transplant in a patient who received renal allograft from haplo-identical type donor.

Collapse postulate for observables with continuous area

International Nuclear Information System (INIS)

Srinivas, M.D.

1979-03-01

In order to provide a mathematical framework for discussing the statistical correlations between the outcomes, when an arbitrary sequence of observables are measured, it is necessary to generalize the conventional von Neumann-Lueders collapse postulate to observables with a continuous spectrum. It is shown that the standard prescription in conventional quantum theory for the joint probabilities of compatible observables is sufficient to characterize, more or less completely, the appropriate ''generalized collapse postulate'' which associates with each observable a unique ''finitely additive expectation valued measure''. An interesting feature of the collapse associated with observables with continuous spectra, which again follows from the basic principles of conventional quantum theory, is that it must be formulated in terms of the so-called non-normal conditional expectations, which implies that the joint probabilities associated with successive observations of such observables are not in general σ-additive. The implications of this non-σ-additivity on the determination of expectation values, correlation functions etc., are also investigated. It is demonstrated that the basic prescriptions introduced in this paper constitute a natural completion of the framework of conventional quantum theory for discussing the statistics of an arbitrary sequence of observations

Collapse of experimental capsules under external pressure

International Nuclear Information System (INIS)

Simonen, F.A.; Shippell, R.J. Jr.

1980-01-01

Stress analyses and developmental tests of capsules fabricated from thick-walled tubing were performed for an external pressure design condition. In the design procedure no credit was taken for the expected margin in pressure between yielding of the capsule wall and catastrophic collapse or flattening. In tests of AISI-1018 low carbon steel capsules, a significant margin was seen between yield and collapse pressure. However, the experimental yield pressures were significantly below predictions, essentially eliminating the safety margin present in the conservative design approach. The differences between predictions and test results are attributed to deficiencies in the plasticity theories commonly in use for engineering stress analyses. The results of this study show that the von Mises yield condition does not accurately describe the yield behavior of the AISI-1018 steel tubing material for the triaxial stress conditions of interest. Finite element stress analyses successfully predicted the transition between uniform inward plastic deformation and ovalization that leads to catastrophic collapse. After adjustments to correct for the unexpected yield behavior of the tube material, the predicted pressure-deflection trends were found to follow the experimental data

Collapse postulate for observables with continuous spectra

International Nuclear Information System (INIS)

Srinivas, M.D.; Madras Univ.

1980-01-01

In order to provide a mathematical framework for discussing the statistical correlations between the outcomes, when an arbitrary sequence of observables are measured, it is necessary to generalize the conventional von Neumann-Lueders collapse postulate to observables with a continuous spectrum. It is shown that the standard prescription in conventional quantum theory for the joint probabilities of compatible observables is sufficient to characterize, more or less completely, the appropriate 'generalized collapse postulate' which associates with each observable a unique 'finitely additive expectation valued measure'. An interesting feature of the collapse associated with observables with continuous spectra, which again follows from the basic principles of conventional quantum theory, is that it must be formulated in terms of the so-called non-normal conditional expectations, which implies that the joint probabilities associated with successive observations of such observables are not in general sigma-additive. The implications of this non-sigma-additivity on the determination of expectation values, correlation functions etc., are also investigated. It is demonstrated that the basic prescriptions introduced in this paper constitute a natural completion of the framework of conventional quantum theory for discussing the statistics of an arbitrary sequence of observations. (orig.) 891 HJ/orig. 892 CKA

Atomic Structure and Energy Distribution of Collapsed Carbon Nanotubes of Different Chiralities

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Julia A. Baimova

2015-01-01

Full Text Available For carbon nanotubes of sufficiently large diameter at sufficiently low temperature, due to the action of the van der Waals forces, the ground state is a bilayer graphene with closed edges, the so-called collapsed configuration. Molecular dynamics simulation of collapsed carbon nanotubes is performed. The effect of length, diameter, and chirality of the nanotubes on their properties is investigated. It is shown that collapsed nanotubes after relaxation have rippled structure which is strongly dependent on the nanotube chirality. The structural properties are studied by calculating the radial distribution function and energy distribution along various regions in the collapsed carbon nanotubes.

Prevention of collapse of the contralateral half of the mandible after hemimandibulectomy: Our experience in a low-resource center

Directory of Open Access Journals (Sweden)

Charles E Anyanechi

2017-01-01

Full Text Available Background: The management of pathologic lesions of the mandible includes plans for the reconstruction of the resultant defect to give the patients optimal surgical reconstructive and prosthetic results. Objective: To evaluate the degree of deviation of the contralateral half of the mandible toward the surgical defect after hemimandibulectomy and intermaxillary fixation (IMF. Patients and Methods: This is a 9-year prospective single-blinded clinical study conducted at the Dental and Maxillofacial Surgery Clinic of our institution. Information obtained from the patients included age, gender, type of mandibular lesion, method of wound closure, duration of IMF, temporo-mandibular joint (TMJ symptom(s, and the deviation toward the surgical defect of the remnant contralateral half of the mandible, measured in centimeter at maximum mouth opening. Results: Ninety-six patients, unevenly distributed according to their duration of tolerance of IMF, were studied. The age of the patients ranged from 29 to 57 years with an overall mean age of 42.6 ± 5.1 years. There were 72 males and 24 females with a male-to-female ratio of 3:1 (P = 0.001. The lesions that were extirpated were all benign, and ameloblastoma was the most common tumor (P = 0.001. The shorter the duration of IMF, the greater the deviation of the mandibular mid-line toward the surgical defect (P = 0.001. Conclusion: This study shows that there is a deviation of mid-line of the residual mandible toward the surgical defect after hemimandibulectomy, even after its immobilization with IMF for 4–12 weeks. IMF is still useful in the prevention of mandibular collapse after hemimandibulectomy.

A new source of radiation in single-bubble sonoluminescence

Indian Academy of Sciences (India)

2017-03-28

Mar 28, 2017 ... two origins of light for SBSL at the time of collapse: radiation from the ..... [5] M Dan, J D N Cheeke and L Kondic, Ultrasonics 38, 566. (2000). [6] K Yasui ... [26] S C Brown, Basic data of plasma physics (AIP, New York,. 1994).

Improved Noninterferometric Test of Collapse Models Using Ultracold Cantilevers

Science.gov (United States)

Vinante, A.; Mezzena, R.; Falferi, P.; Carlesso, M.; Bassi, A.

2017-09-01

Spontaneous collapse models predict that a weak force noise acts on any mechanical system, as a consequence of the collapse of the wave function. Significant upper limits on the collapse rate have been recently inferred from precision mechanical experiments, such as ultracold cantilevers and the space mission LISA Pathfinder. Here, we report new results from an experiment based on a high-Q cantilever cooled to millikelvin temperatures, which is potentially able to improve the current bounds on the continuous spontaneous localization (CSL) model by 1 order of magnitude. High accuracy measurements of the cantilever thermal fluctuations reveal a nonthermal force noise of unknown origin. This excess noise is compatible with the CSL heating predicted by Adler. Several physical mechanisms able to explain the observed noise have been ruled out.

A Critique: Jared Diamond’s Collapse Put In Perspective

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Emma Gause

2014-09-01

Full Text Available Jared Diamond’s book 'Collapse' captivated readers with its tales of past great civilizations succumbing to dramatic cycles of decline, and among them are the ancient Maya. Diamond’s model of the Maya collapse has become quite popular since its publication, however numerous other divergent theories exist as well, which attempt to explain the phenomenon. Diamond, buoyed by the success of his book and his renown as an author, is the assumed authority, despite academic criticism. By comparing Diamond’s 'Collapse' with current research I hope to critique Diamond and thus elucidate the condition of the Maya decline concerning the roles of the environment, the regional variability of various sociopolitical dynamics, such as those that were played out in the Petexbatun region, and the extent of Post Classic continuation of Maya tradition.

Collapsed Lung: MedlinePlus Health Topic

Science.gov (United States)

... Spanish Pneumothorax - infants (Medical Encyclopedia) Also in Spanish Topic Image MedlinePlus Email Updates Get Collapsed Lung updates ... Lung surgery Pneumothorax - slideshow Pneumothorax - infants Related Health Topics Chest Injuries and Disorders Lung Diseases Pleural Disorders ...

Concept of assistance of the Federal Office for Radiation Protection with regard to prevention of serious cases of nuclear hazards

Energy Technology Data Exchange (ETDEWEB)

Becker, D.E. [Federal Office for Radiation Protection, Salzgitter (Germany)

2000-05-01

For the defence against the threats caused by radioactive substances, a general concept was elaborated under the overall control of the Federal Government. A number of competent organisations are involved in this, for example the Federal Office of Criminal Investigation, the Federal Armed Forces, and the Federal Office for Radiation Protection. In Germany, the 16 Federal States are responsible for the prevention of nuclear hazards. In the case of hazards caused by radioactive material, experts from the competent radiation protection authorities are consulted. For the prevention of serious cases of nuclear hazards (nuclear fuels, criticality, danger of dispersion), the Federal Office for Radiation Protection - a subordinate authority of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety responsible for radiation protection, nuclear safety, and waste management - was given order to elaborate a concept for assistance to those Federal States. The field of prevention of nuclear hazards ranges from combatting illegal trade with radioactive test sources up to the defence of nuclear fuels with the possibility to construct critical assemblies or the threatening by the distribution of airborne material which might enter the lungs. The latter are considered as serious cases of nuclear hazards. Since the expenditures for devices and personal to be trained would be inadequately high, the Federal Office for Radiation Protection (BfS) is prepared to support the Federal States if it becomes necessary. The concept includes a stand-by service, the search for radioactive material by helicopter or a ground team, analysis of the activity and the type of nuclides, risk assessment, and also measures to steam the risk. This concept will be presented. (author)

Concept of assistance of the Federal Office for Radiation Protection with regard to prevention of serious cases of nuclear hazards

International Nuclear Information System (INIS)

Becker, D.E.

2000-01-01

For the defence against the threats caused by radioactive substances, a general concept was elaborated under the overall control of the Federal Government. A number of competent organisations are involved in this, for example the Federal Office of Criminal Investigation, the Federal Armed Forces, and the Federal Office for Radiation Protection. In Germany, the 16 Federal States are responsible for the prevention of nuclear hazards. In the case of hazards caused by radioactive material, experts from the competent radiation protection authorities are consulted. For the prevention of serious cases of nuclear hazards (nuclear fuels, criticality, danger of dispersion), the Federal Office for Radiation Protection - a subordinate authority of the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety responsible for radiation protection, nuclear safety, and waste management - was given order to elaborate a concept for assistance to those Federal States. The field of prevention of nuclear hazards ranges from combatting illegal trade with radioactive test sources up to the defence of nuclear fuels with the possibility to construct critical assemblies or the threatening by the distribution of airborne material which might enter the lungs. The latter are considered as serious cases of nuclear hazards. Since the expenditures for devices and personal to be trained would be inadequately high, the Federal Office for Radiation Protection (BfS) is prepared to support the Federal States if it becomes necessary. The concept includes a stand-by service, the search for radioactive material by helicopter or a ground team, analysis of the activity and the type of nuclides, risk assessment, and also measures to steam the risk. This concept will be presented. (author)

Numerical Investigation of Progressive Collapse Resistance for Seismically Designed RC Buildings

OpenAIRE

Marchiş, Adrian G.; Ioani, Adrian M.

2014-01-01

In this paper the progressive collapse behavior of a reinforced concrete framed building located in different seismic areas from Romania is investigated. The six-storey structure is designed for low (ag = 0.08 g), moderate (ag = 0.16 g) and high (ag = 0.24 g) seismic zone. Based on the GSA (2003) criteria, a nonlinear static analysis is conducted first in order to estimate the progressive collapse resistance of the models. It was shown that all the structures will collapse when subjected to i...

Preventive effect of Chinese traditional medicine-Qing-Xue granula on radiation induced lung injury in mice

International Nuclear Information System (INIS)

Wang Xiaozhen; Ji Wei; Jiang Heng; Zhao Lujun; Yang Weizhi; Yang Yufei; Wang Luhua

2012-01-01

Objective: To evaluate whether oral administration of Chinese traditional medicine, Qing-Xue granula, can prevent mouse lung injury caused by thoracic radiation. Methods: 128 BalB/C mice were divided into 4 groups: control (C) group; radiation (R) group; radiation plus high dose Qing-Xue granula (H) group and radiation plus median dose Qing-Xue granula (M) group. The H and M groups were fed 0.64 g and 0.32 g of Qing-Xue granula dissolved in 0.5 ml saline once daily for two months,which were 4 and 2 times of human dosage, respectively. Whole thorax radiation of 12 Gy was delivered with a single ventral-dorsal field with 6 MV X-ray. Group C and group R received 21 days of 0.5 ml saline feeding. Mice were sacrificed at 1, 2, 4 or 6 months after radiation. Macrophage cell count of lung lavage fluid and hydroxyproline content of left lung were assayed, and the lung fibrosis was scored according to the Ashcroft's criteria. The plasma interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) concentration were assayed with ELISA method. The One-way ANOVA was used to test the significance of any differences between groups at each time point. Results: The macrophage cell number of lung lavage fluid was significantly lower in the 1 st month in group M than in group R (2:4, q =3.92, P 0.05). The hydroxyproline content of group H was significantly lower than group R in the 1 st and 6 th months (q =3.62, 3.54, all P nd , 4 th and 6 th months (q=3.38 -4.16, all P st month (q=3.53, P 0.05). The VEGF concentration was significantly higher in group R than group C since the 2 nd month (q =3.12 - 3.78, P nd and 6 th months (q =3.08 - 3.92, all P<0.05). Conclusions: Oral Chinese traditional medicine, Qing-Xue granula, could prevent radiation induced lung fibrosis in mice, especially at high dosage. The degree of elevation of VEGF in plasma was not parallel with that of lung fibrosis. (authors)

Collapse and Revival of an Atomic Beam Interacting with a Coherent State Light Field

International Nuclear Information System (INIS)

Ben, Li; Jing-Biao, Chen

2009-01-01

We report on the phenomena of the periodic spontaneous collapse and revival in the dynamics of an atomic beam interacting with a single-mode and coherent-state light field. Conventional collapse and revival by Eberly et al. [Phys. Rev. Lett. 44 (1980) 1323] are presented in the case of the evolution with time of the population inversion. Here, we study the evolution with coupling strength of population inversion. We define the collapse and revival coupling strengths as characteristic parameters to describe the above collapse and revival. Furthermore, we present the analytic formulas for the population inversion, the collapse and revival coupling strengths

Classical Collapse to Black Holes and Quantum Bounces: A Review

Directory of Open Access Journals (Sweden)

Daniele Malafarina

2017-05-01

Full Text Available In the last four decades, different programs have been carried out aiming at understanding the final fate of gravitational collapse of massive bodies once some prescriptions for the behaviour of gravity in the strong field regime are provided. The general picture arising from most of these scenarios is that the classical singularity at the end of collapse is replaced by a bounce. The most striking consequence of the bounce is that the black hole horizon may live for only a finite time. The possible implications for astrophysics are important since, if these models capture the essence of the collapse of a massive star, an observable signature of quantum gravity may be hiding in astrophysical phenomena. One intriguing idea that is implied by these models is the possible existence of exotic compact objects, of high density and finite size, that may not be covered by an horizon. The present article outlines the main features of these collapse models and some of the most relevant open problems. The aim is to provide a comprehensive (as much as possible overview of the current status of the field from the point of view of astrophysics. As a little extra, a new toy model for collapse leading to the formation of a quasi static compact object is presented.

Acupuncture for the prevention of radiation-induced xerostomia in patients with head and neck cancer

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Fabio do Prado Florence Braga

2011-04-01

Full Text Available The aim of this study was to evaluate the effectiveness of acupuncture in minimizing the severity of radiation-induced xerostomia in patients with head and neck cancer. A total of 24 consecutive patients receiving > 5000 cGy radiotherapy (RT involving the major salivary glands bilaterally were assigned to either the preventive acupuncture group (PA, n = 12, treated with acupuncture before and during RT, or the control group (CT, n = 12, treated with RT and not receiving acupuncture. After RT completion, clinical response was assessed in all patients by syalometry, measuring the resting (RSFR and stimulated (SSFR salivary flow rates, and by the visual analogue scale (VAS regarding dry mouth-related symptoms. Statistical analyses were performed with repeated-measures using a mixed-effect modeling procedure and analysis of variance. An alpha level of 0.05 was accepted for statistical significance. Although all patients exhibited some degree of impairment in salivary gland functioning after RT, significant differences were found between the groups. Patients in the PA group showed improved salivary flow rates (RSFR, SSFR; p < 0.001 and decreased xerostomia-related symptoms (VAS, p < 0.05 compared with patients in the CT group. Although PA treatment did not prevent the oral sequelae of RT completely, it significantly minimized the severity of radiation-induced xerostomia. The results suggest that acupuncture focused in a preventive approach can be a useful therapy in the management of patients with head and neck cancer undergoing RT.

A Plastic Design Method for RC Moment Frame Buildings against Progressive Collapse

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Hadi Faghihmaleki

2017-04-01

Full Text Available In this study, progressive collapse potential of generic 3-, 8- and 12-storey RC moment frame buildings designed based on IBC-2006 code was investigated by performing non-linear static and dynamic analyses. It was observed that the model structures had high potential for progressive collapse when the second floor column was suddenly removed. Then, the size of beams required to satisfy the failure criteria for progressive collapse was obtained by using the virtual work method; i.e., using the equilibrium of the external work done by gravity load due to loss of a column and the internal work done by plastic rotation of beams. According to the nonlinear dynamic analysis results, the model structures designed only for normal load turned out to have strong potential for progressive collapse whereas the structures designed by plastic design concept for progressive collapse satisfied the failure criterion recommended by the GSA code. 

Maternal Postpartum Role Collapse as a Theory of Postpartum Depression

Science.gov (United States)

Amankwaa, Linda Clark

2005-01-01

The purpose of this paper is to discuss the development of a theory of maternal postpartum role collapse. The influences of traditional role theory and symbolic interactionism are presented. The development of the maternal postpartum role collapse theory emerged from the study of postpartum depression among African-American women (Amankwaa, 2000).…

[Effect of Kou Yan Qing Ke Li on the prevention and treatment of radiation-induced oral mucositis in patients with nasopharyngeal carcinoma].

Science.gov (United States)

Yun, Gong; Li, Zhang; Zehui, Feng; Xudong, He

2016-02-01

The effect of Kou Yan Qing Ke Li on the prevention and treatment of radiation-induced oral mucositis was investigated in patients with nasopharyngeal carcinoma. Sixty patients with nasopharyngeal carcinoma to be treated with radiotherapy were randomized into two groups: the experimental and control groups. The experimental group (30 patients) was treated with Kou Yan Qing Ke Li during the full course of radiotherapy. The control group (30 patients) rinsed their mouths in the same way with mouth washes containing 0.9% sodium chloride injection, lidocaine, dexamethasone, vitamin B2 and B2 gargle liquid mixture, when grade 2 and above radiation-induced oral mucositis appeared in the process of radiation. Radiation-induced oral mucositis was assessed according to the radiation therapy oncology group criteria. The time of occurrence and degree of pain grade were compared between the two groups. The first onset of oral mucositis in the experimental group (12.40 d ± 2.74 d) was later than that in the control group (9.46 d ± 1.39 d) (t = 5.241, P Qing Ke Li could delay the time of occurrence of radiation-induced oral mucositis, reduce the severity of radiation stomatitis, alleviate the pain of patients, improve the clinical symptoms of patients, and effectively prevent and treat radiation-induced oral mucositis in patients with nasopharyngeal carcinoma.

Tetanus with multiple wedge vertebral collapses

African Journals Online (AJOL)

owner

2012-07-06

Jul 6, 2012 ... associated with traumatic injury, often a penetrating wound inflicted by dirty ... multiple vertebral collapses and the management chal- .... back pains and swelling as in our patient.9 There are usually no ... The cervical and.

An experimental study on the impact collapse characteristics of CF/Epoxy circular tubes

International Nuclear Information System (INIS)

Kim, Y.N.; Im, K.H.; Park, J.W.; Yang, I.Y.

2003-01-01

This study is to investigate the energy absorption characteristics of CF/Epoxy (Carbon-Fiber/Epoxy Resin) circular tubes in static and impact tests. The experimental results varied significantly as a function of interlaminar number, orientation angle of outer and trigger. When a CFRP composite tube is crushed, static/impact energy is consumed by friction between the loading plate and the splayed fronds of the tube, by fracture of the fibers, matrix and their interface, and the response is complex and depends on the interaction among the different mechanisms, such as transverse shearing, laminar bending and local buckling. The collapse mode depended upon orientation angle of outer of CFRP tubes and loading status(static/impact). Typical collapse modes of CFRP tubes are wedge collapse mode, splaying collapse mode and fragmentation collapse mode

Experimental study of collapsing properties of the compacted soil foundation of auto-road embankment

Directory of Open Access Journals (Sweden)

Yushkov Boris Semenovich

2014-06-01

Full Text Available The loess collapsing soils are practically ubiquitously distributed in the Perm region. They occupy about 30% of the region area. The mass construction of buildings and structures of different purposes is conducted there. Design and construction of auto-roads on the collapsing soils by ensuring their strength and normal operation is one of the most important and difficult problems of the modern construction. It is recommended to eliminate collapsing properties of soils within the entire collapsing strata with the use of deep compaction by rammers and presoaking of foundation soils, including that with deepwater explosions, chemical or thermal fixing. Multi-year practice of construction on the collapsing soils in the regions of our country showed that during erection of the various structures the removal of the powerful loess soil collapsibility is achieved with the help of methods described above, each of which is selected on the basis of the conditions and possibilities of application. This article describes the following tasks: 1. Study and generalization of the available experience of road construction on the loess soils; 2. Zoning and classification (typing of the loess strata; 3. Selection of the engineering-geological factors influencing the choice of method for compacting collapsing soils; 4. General provisions for road construction on the collapsing soils.