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Sample records for large collapse sinkhole

  1. Distinct Element modeling of geophysical signatures during sinkhole collapse

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    Al-Halbouni, Djamil; Holohan, Eoghan P.; Taheri, Abbas; Dahm, Torsten

    2017-04-01

    A sinkhole forms due to the collapse of rocks or soil near the Earth's surface into an underground cavity. Such cavities represent large secondary pore spaces derived by dissolution and subrosion in the underground. By changing the stress field in the surrounding material, the growth of cavities can lead to a positive feedback, in which expansion and mechanical instability in the surrounding material increases or generates new secondary pore space (e.g. by fracturing), which in turn increases the cavity size, etc. A sinkhole forms due to the eventual subsidence or collapse of the overburden that becomes destabilized and fails all the way to the Earth's surface. Both natural processes like (sub)surface water movement and earthquakes, and human activities, such as mining, construction and groundwater extraction, intensify such feedbacks. The development of models for the mechanical interaction of a growing cavity and fracturing of its surrounding material, thus capturing related precursory geophysical signatures, has been limited, however. Here we report on the advances of a general, simplified approach to simulating cavity growth and sinkhole formation by using 2D Distinct Element Modeling (DEM) PFC5.0 software and thereby constraining pre-, syn- and post-collapse geophysical and geodetic signatures. This physically realistic approach allows for spontaneous cavity development and dislocation of rock mass to be simulated by bonded particle formulation of DEM. First, we present calibration and validation of our model. Surface subsidence above an instantaneously excavated circular cavity is tracked and compared with an incrementally increasing dissolution zone both for purely elastic and non-elastic material.This validation is important for the optimal choice of model dimensions and particles size with respect to simulation time. Second, a cavity growth approach is presented and compared to a well-documented case study, the deliberately intensified sinkhole collapse at

  2. Investigation of a large collapse sinkhole affecting a multi-storey building by means of geophysics and the trenching technique (Zaragoza city, NE Spain)

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    Gutiérrez, F.; Galve, J. P.; Lucha, P.; Bonachea, J.; Jordá, L.; Jordá, R.

    2009-09-01

    An active sinkhole around 100 m long has been investigated in the city of Zaragoza (NE Spain). Subsidence activity on this depression, including the sudden occurrence of a collapse sinkhole 5 m across, led to the abandonment of a factory in the 1990s. At the present time, a building with 100 flats and shallow pad foundations partially built on the sinkhole, is affected by rapid differential settlement. The development of the sinkhole results from the karstification of the halite- and glauberite- bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium, more than 30 m thick. GPR and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure. The application of the trenching technique and geochronological methods (AMS and OSL dating) has allowed us to infer objective and practical data on the sinkhole including (1) Limits of the subsidence structure, (2) subsidence mechanisms, (3) cumulative subsidence (>408 cm), (4) subsidence rates on specific failure planes (>1.8 cm/year), (5) episodic displacement regime of some fault planes. The available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement. This work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas.

  3. Results of Integrated Investigation of Collapse Sinkhole in Sarkayevo Village

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    O. N. Kovin

    2014-03-01

    Full Text Available The integrated investigations of karstic collapse sinkhole were conducted at the area of Sarkayevo village. The obtained hydrogeologic data show the local concentration of underground water flow at the investigated site, and high sulfate ion content in the water samples that suggests that a sinkhole is karstic in nature. Geophysical investigations allowed determining basic parameters of the site geological structure, to reveal the depth distribution of the disturbed ground in vicinity of the sinkhole, and delineate zones of different soil compaction. The recommendations for detail site study, aimed to the mitigation of further karst development hazards, are presented.

  4. Subsidence and collapse sinkholes in soluble rock: a numerical perspective

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    Kaufmann, Georg; Romanov, Douchko; Hiller, Thomas

    2016-04-01

    Soluble rocks such as limestone, gypsum, anhydrite, and salt are prone to subsidence and the sudden creation of collapse sinkholes. The reason for this behaviour stems from the solubility of the rock: Water percolating through fissures and bedding partings can remove material from the rock walls and thus increase the permeability of the host rock by orders of magnitudes. This process occurs on time scales of 1,000-100,000 years, resulting in enlarged fractures, voids and cavities, which then carry flow efficiently through the rock. The enlargement of sub-surface voids to the meter-size within such short times creates mechanical conditions prone to collapse. The collapse initiates at depth, but then propagates to the surface. By means of numerical modelling, we discuss the long-term evolution of secondary porosity in gypsum rocks, resulting in zones of sub-surface voids, which then become mechanically unstable and collapse. We study two real-world case scenarios, in which we can relate field observations to our numerical model: (i) A dam-site scenario, where flow around the dam caused widespread dissolution of gypsum and subsequent subsidence of the dam and a nearby highway. (ii) A natural collapse sinkhole forming as a result of freshwater inflow into a shallow anhydrite formation with rapid evolution of voids in the sub-surface.

  5. Basic processes and factors determining the evolution of collapse sinkholes: a sensitivity study

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    Romanov, Douchko; Kaufmann, Georg

    2017-04-01

    Collapse sinkholes appear as closed depressions at the surface. The origin of these karst features is related to the continuous dissolution of the soluble rock caused by a focussed sub-surface flow. Water flowing along a preferential pathway through fissures and fractures within the phreatic part of a karst aquifer is able to dissolve the rock (limestone, gypsum, anhydrite). With time, the dissolved void volume increases and part of the ceiling above the stream can become unstable, collapses, and accumulates as debris in the flow path. The debris partially blocks the flow and thus activates new pathways. Because of the low compaction of the debris (high hydraulic conductivity), the flow and the dissolution rates within this crushed zone remain high. This allows a relatively fast dissolutional and erosional removal of the crushed material and the development of new empty voids. The void volume expands upwards towards the surface until a collapse sinkhole is formed. The collapse sinkholes exhibit a large variety of shapes (cylindrical, cone-, bowl-shaped), depths (from few to few hundred meters) and diameters (meters up to hundreds of meters). Two major processes are responsible for this diversity: a) the karst evolution of the aquifer - responsible for the dissolutional and erosional removal of material; b) the mechanical evolution of the host rock and the existence of structural features, faults for example, which determine the stability and the magnitude of the subsequent collapses. In this work we demonstrate the influence of the host rock type, the hydrological and geological boundary conditions, the chemical composition of the flowing water, and the geometry and the scale of the crushed zone, on the location and the evolution of the growing sinkhole. We demonstrate the ability of the karst evolution models to explain, at least qualitatively, the growth and the morphology of the collapse sinkholes and to roughly predict their shape and location. Implementing

  6. Into the Abyss: The Case of the Collapsing Sinkhole.

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    Ozsvath, David L.

    2000-01-01

    Presents a case study to teach about the relationship between sinkhole development and groundwater levels in Orlando, Florida. Discusses the relationship between groundwater levels and sinkhole formation in a karst terrane. Includes discussion questions. (YDS)

  7. Evaluating susceptibility of karst dolines (sinkholes) for collapse in Sango, Tennessee, USA.

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    Siska, Peter P; Goovaerts, Pierre; Hung, I-K

    2016-08-01

    Dolines or sinkholes are earth depressions that develop in soluble rocks complexes such as limestone, dolomite, gypsum, anhydrite, and halite; dolines appear in a variety of shapes from nearly circular to complex structures with highly curved perimeters. The occurrence of dolines in the studied karst area is not random; they are the results of geomorphic, hydrologic, and chemical processes that have caused partial subsidence, even the total collapse of the land surface when voids and caves are present in the bedrock and the regolith arch overbridging these voids is unstable. In the study area, the majority of collapses occur in the regolith (bedrock cover) that bridges voids in the bedrock. Because these collapsing dolines may result in property damage and even cause the loss of lives, there is a need to develop methods for evaluating karst hazards. These methods can then be used by planners and practitioners for urban and economic development, especially in regions with a growing population. The purpose of this project is threefold: 1) to develop a karst feature database, 2) to investigate critical indicators associated with doline collapse, and 3) to develop a doline susceptibility model for potential doline collapse based on external morphometric data. The study has revealed the presence of short range spatial dependence in the distribution of the dolines' morphometric parameters such as circularity, the geographic orientation of the main doline axes, and the length-to-width doline ratios; therefore, geostatistics can be used to spatially evaluate the susceptibility of the karst area for doline collapse. The partial susceptibility estimates were combined into a final probability map enabling the identification of areas where, until now, undetected dolines may cause significant hazards.

  8. Genetic variety of sinkholes and their reconaissance and classification for the derivation of hazards and to forecast of collapses

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    Mucke, D.

    2012-04-01

    Genetic variety of sinkholes and their reconnaissance and classification for the derivation of hazards and to forecast of collapses Dieter Mucke GEOMONTAN Gesellschaft für Geologie und Bergbau mbH&Co.KG, Muldentalstrasse 56, 09603 Rothenfurth, Saxony/Germany The term "sinkhole" covers a lot of depressions on the earth's surface, caused by very different geological processes and anthropogenic activities. The speed of the origin of the depressions is different and leads to different hazards. The forecast look for hazards and the introduction of preventive measures gets safer if type and cause of the depressions are known of. First aim of the lecture is the classification of sinkholes in different types. Geogenic depressions develope in karst landscapes as well as in plain areas of detrital sediments on soluble rocks. The depressions are in karst landscapes localized directly in the soluble rocks like limestone or sulphate rocks (anhydrite, gypsum). It results there for solution dolines and collapse dolines in these rocks themselves.. In other cases the soluble rocks often are in large depth under overlaying claystones, siltstones, sandstones or clays, silts, sands. A cave deeply is formed under the earth's surface and when a roof failure happens, the overburden sinks after. A depression of caldera shape with abrupt slopes suddenly forms in the non-karst rock at the surface. Such erdfall-collapses in Triassic claystones develop flatter walls in the course of the time. In German such depressions are called "Erdfall" to distinguish them of dolines. Because in English the term "earth fall" has an other meaning, I will further call such depressions "erdfall-collaps". The solution of limestones and sulphate rocks results with the formation of caves and following emergence of collapse dolines and erdfall-collapses. The underground dissolution (subrosion) of rock salt is as opposed to without formation of caves. It leads to a slow lowering of the earth's surface in flat

  9. Development of IoT-based Urban Sinkhole and Road Collapse Monitoring System

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    Jung, B.; Bang, E.; Lee, H. J.; Jeong, S. W.; Ryu, D.; Kim, S. W.; Kim, B. K.; Yum, B. W.; Lee, I. H.

    2015-12-01

    The consortium of Korean government-funded research institutes is developing IoT- (Internet of things) based underground safety monitoring and alerting system to manage risks arisen from land subsidence and road collapses in metropolitan areas in South Korea. The system consists of four major functional units: subsurface monitoring sensors sending data directly through the internet, centralized servers capable of collecting and processing big data, computational modules providing physical and statistical models for predicting high-risk areas, and geologic information service platforms visualizing underground safety maps for the public. The target urban area will be regionally covered by multi-sensors monitoring soil and groundwater conditions, and by high resolution satellite InSAR images filtering vertical land movements in a centimeter scale. Integrity of buried water supply and sewer lines are also monitored for the possibility of underground cavity formation. Once high-risk area is predicted, more tangible surveying methods such as ground penetrating radar (GPR) and resistivity survey can be applied for locating the cavities. Additionally, laboratory and field experiments are performed to understand overall road collapsing mechanism from the initial cavity creation to its progressive development depending on soil types, degree of compaction, and groundwater condition. Acquired results will update existing fully-coupled hydromechanical models for more accurate prediction of the collapsing-vulnerable area. Preliminary laboratory experiments show that the upward propagation of subsurface cavity is closely related to the soil properties, such as sand-clay ratios and moisture contents, and groundwater dynamics.

  10. Sinkhole occurrence in consequence of heavy rainstorms

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    Parise, Mario; Pisano, Luca; Vennari, Carmela

    2016-04-01

    ) affected the lower sector of a karst depression. Their shape is predominantly circular, but the dimensions are assorted. Some of the landforms are just subdued, and appear to be less developed. Morphometry and shape of the observed sinkholes allow to attribute them to the typology of collapse or cover-collapse sinkholes. Additional sinkholes were triggered in a rural area in the northern part of Monte Sant'Angelo. These are five sinkholes linked to natural cavities, that were activated during the September 2014 storm, and subsequently were enlarged. In the area, terra rossa deposits cover limestone rocks. The largest sinkhole is 25.2 m deep and 12 m wide. From its base, speleological explorations documented a series of pits, going down at least until a depth of -130 m below the ground surface, thus testifying the direct link with the subsurface system of groundwater circulation. The sinkholes occurred in the Gargano area are natural events quite common in karst areas (Waltham et al., 2005; Ford & Williams, 2007; Parise, 2008, 2015b; Gutierrez et al., 2008, 2014; Parise et al., 2015), as a result of intense and/or prolonged rainfall events that increase the superficial and underground outflow. The speed of outflow of large quantities of water may be able to remove unconsolidated soil, creating new ways of underground water circulation, and as a consequence the material on the surface could collapse in the underlying cavities (Parise et al., 2015b). Documenting these phenomena, especially in relation to intense rainstorms, is of great importance, since in the great majority of cases they go unreported, especially where (as is the Gargano case) the karst lands are thickly covered by forests, or develop in mostly rural areas. The collection of direct data from the observed sinkholes allowed us, further, to update the chronological catalogue of sinkholes in Italy, managed by CNR-IRPI since several years (Parise & Vennari, 2013) within the framework of research projects on karst

  11. Florida Sinkholes and Grout Injection Stabilization

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    Charles Hunt Griffith II

    2014-09-01

    Full Text Available Florida has a major problem when it comes to sinkholes. These sinkholes can become very hazardous to people, homes, and to the landscape as a whole. Florida sits on a carbonate platform which is highly indicative of sinkholes. There are three main types of sinkholes which occur in Florida: dissolution, cover subsidence, and cover collapse. I will compare these types of sinkholes to the underlying formation beneath Florida to see if there is a connection between the types of sinkholes that occur. I will also create a 3D model of grout injection stabilization and calculate its volume to compare to the actual volume placed under the house. This information will help inform and bring attention to the problem in Florida and in turn, may help alleviate the problem if we can understand what causes these sinkholes. The 3D model may help engineering companies become more efficient in predicting the projected amount of volume to stabilize a house that may be in danger.

  12. The Extreme Results of Climate Changes in Turkey: Sinkholes

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    Onursal Denli, G.; Denli, H. H.

    2016-12-01

    During the past few years a strange phenomenon has been increasingly observed all over the world. Residents of various places around the world have been taken aback to find sinkholes suddenly come up in their locality - sometimes involving fatalities. A sinkhole is a depression or hole in the ground caused by some form of collapse of the surface layer. The ground caves in all of a sudden, creating large holes in the ground and sometimes devouring whole buildings. Geologists have offered various theories for the natural causes of sinkholes such as the type of soil / rock giving way to rainwater and underground water. Other natural causes submitted by experts include heavy rainfall, global warming, underground gas explosions, etc. They can also occur from the over-pumping and extraction of groundwater and subsurface fluids. In Turkey, especially mid and south-east Anatolian regions have very arid soils. There is not sufficient rain and irrigation in these regions. Despite of using 75% of the fresh water for agriculture, old methods of irrigation causes wastefulness of water. Planless and randomly used water causes difficulties in agriculture. These regions are known as granary in the country. Because of drought, farmers use underground water with draw well unconsciously. At the result of underground water movement and withdrawal of water to surface, depression and very huge holes are occurred in the ground with tremendous noise. During the last two years dozens of sinkholes occurred in these regions in Turkey. Most of them are in the rural area, the others are also in center of the cities. Various sizes of holes scare the people living in these regions. In this study, sinkholes, which are occurred in different dimensions in central Anatolia region in the last years, are observed and the causes of these formations are examined. According to the reasons, suggestions to avoid these formations will be given respectively.

  13. Integrating geomorphological mapping, InSAR, GPR and trenching for the identification and investigation of buried sinkholes in the mantled evaporite karst of the Ebro Valley (NE Spain)

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    Gutiérrez, Francisco; Galve, Jorge Pedro; Lucha, Pedro; Bonachea, Jaime; Castañeda, Carmen

    2010-05-01

    The first and most important step in sinkhole hazard analysis is the construction of a cartographic sinkhole inventory. The effectiveness of the mitigation measures and the reliability of the susceptibility and hazard maps will depend on the completeness and accuracy of the sinkhole inventories on which they are based. Sinkhole data bases preferably should include information on the following aspects: (1) Precise location of the sinkholes edges. (2) Morphometric parameters. (3) Geomorphological and hydrological context. (4) Genetic type; that is subsidence mechanisms and material affected by subsidence. (5) Chronology; this information is essential to calculate probability of occurrence values. (6) Active or inactive character. (7) Kinematical regime (gradual, episodic or mixed). (8) Current and/or long-term subsidence rates. (9) Evolution of the subsidence and its relationship with causal factors. Sinkholes are generally mapped using conventional geomorphological methods like aerial photographs, topographic maps and field surveys. However, the usefulness of these methods may be limited in areas where the geomorphic expression of sinkholes has been obliterated by natural processes or anthropogenic fill. Additionally, gaining data on some of the practical aspects indicated above requires the application of other techniques. In this contribution we present the main findings learnt through the construction of a sinkhole inventory in a terrace of the Ebro River valley (NE Spain). The study area covers around 27.5 ha and is located west of Zaragoza city. The bedrock consists of subhorizontal evaporites including gypsum, halite and glauberite. The terrace is situated at 7-10 m above the channel and the alluvium, 10-30 m thick, is composed of unconsolidated gravels and subordinate fines. Previous studies carried out in this sector of the valley reveal that: (1) Three main types of sinkholes may be differentiated: cover collapse, cover and bedrock collapse, and cover and

  14. Sinkholes in the salt-bearing evaporite karst of the Ebro River valley upstream of Zaragoza city (NE Spain): Geomorphological mapping and analysis as a basis for risk management

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    Galve, J. P.; Gutiérrez, F.; Lucha, P.; Bonachea, J.; Remondo, J.; Cendrero, A.; Gutiérrez, M.; Gimeno, M. J.; Pardo, G.; Sánchez, J. A.

    2009-07-01

    A detailed sinkhole map has been produced in a stretch of the Ebro Valley (40.8 km 2) including the western sector of Zaragoza city (NE Spain). During the last few decades, around 70% of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands. The interstratal karstification of salts (halite and glauberite) and a WNW-ESE-trending joint set have played a major control in the development of sinkholes. Three morphometric types of sinkholes have been differentiated, each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of Zaragoza city; sagging of bedrock and cover, collapse of bedrock and cover, and collapse of cover material related to the downward migration of particles through dissolutional conduits. Each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors, spatio-temporal distribution and kinematics, and consequently the proposed differentiation may have a practical utility. The vast majority of the subsidence damage identified in the area occurs within the boundaries of pre-existing sinkholes identifiable in old aerial photographs and topographical maps. This fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area, of the order of hundreds of thousands of euros per year.

  15. Morphometric analysis of sinkholes in a karst coastal area

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    Basso, A.; Bruno, E.; Parise, M.; Pepe, M.

    2012-04-01

    Salento, the southern portion of Apulia region (SE Italy) is a narrow and elongated peninsula in carbonate rocks, with prevailing low coastlines, locally interrupted by high rock cliffs. The long stretches of low coasts are marked by typical karst landforms consisting of collapse sinkholes. These are locally designated with the dialectal term "spunnulate" (deriving from the verb "spunnare", which means to break, to sink; PARISE et al., 2003). As observed in many other karst coastal settings worldwide (FORTH et al., 1999), development of sinkholes may be particularly severe along the coast, where both natural and anthropogenic processes contribute to accelerate the dissolution of carbonate rocks and subsidence processes, influencing the coastline evolution. Following a previous study, where the main features of sinkholes at Torre Castiglione (Taranto province) were investigated and described, and a preliminary susceptibility map produced (BRUNO et al., 2008), in the present paper we perform a detailed morphometric analysis on the sample of identified sinkholes. The main morphometric parameters generally used for sinkhole characterization have been considered in this study: shape of the sinkhole, azimuth and length of major and minimum axes, depth, elongation ratio, distance from the shorelines. Each of them is described, both as individual parameter and in conjunction with the others, in the attempt to identify the main factors controlling development of sinkholes in the area, and their evolution as well. As regards this latter aspect, beside simple morphometry of the sample of sinkholes at Torre Castiglione, we also focused our attention on the likely relationships existing between distribution and shape of the sinkholes and the tectonic discontinuities. The role played by discontinuities in controlling both distribution and evolution of sinkholes has been pointed out by several authors (WHITE & WHITE, 1987; DENIZMAN, 2003; FLOREA, 2005). To investigate the matter

  16. Single-station seismic noise measures, microgravity, and 3D electrical tomographies to assess the sinkhole susceptibility: the "Il Piano" area (Elba Island - Italy) case study

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    Pazzi, Veronica; Di Filippo, Michele; Di Nezza, Maria; Carlà, Tommaso; Bardi, Federica; Marini, Federico; Fontanelli, Katia; Intrieri, Emanuele; Fanti, Riccardo

    2017-04-01

    Sudden subsurface collapse, cavities, and surface depressions, regardless of shape and origin, as well as doline are currently indicate by means of the term "sinkhole". This phenomenon can be classified according to a large variety of different schemes, depending on the dominant formation processes (soluble rocks karstic processes, acidic groundwater circulation, anthropogenic caves, bedrock poor geomechanical properties), and on the geological scenario behind the development of the phenomenon. Considering that generally sinkholes are densely clustered in "sinkhole prone areas", detection, forecasting, early warning, and effective monitoring are key aspects in sinkhole susceptibility assessment and risk mitigation. Nevertheless, techniques developed specifically for sinkhole detection, forecasting and monitoring are missing, probably because of a general lack of sinkhole risk awareness, and an intrinsic difficulties involved in detecting precursory sinkhole deformations before collapse. In this framework, integration of different indirect/non-invasive geophysical methods is the best practice approach. In this paper we present the results of an integrated geophysical survey at "Il Piano" (Elba Island - Italy), where at least nine sinkholes occurred between 2008 and 2014. 120 single-station seismic noise measures, 17 3D electrical tomographies (min area 140.3 m2, max area 10,188.9 m2; min electrode spacing 2 m, max electrode spacing 5 m), 964 measurement of microgravity spaced in a grid of 6 m to 8 m were carried out at the study area. The most likely origin for these sinkholes was considered related to sediment net erosion from the alluvium, caused by downward water circulation between aquifers. Therefore, the goals of the study were: i) obtaining a suitable geological and hydrogeological model of the area; ii) detecting possible cavities which could evolve in sinkholes, and finally iii) assess the sinkhole susceptibility of the area. Among the results of the

  17. The role of flooding in the occurrence of sinkholes in mantled karst setting, Orléans area (France)

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    Noury, Gildas; Perrin, Jerome; Luu, Li-Hua; Philippe, Pierre

    2017-04-01

    The Loire River basin is regularly impacted by sinkholes because of its specific geological context constituted of karstic limestone overlain by soft materials. Intense rainfall and associated flooding that occurred in this area in May and June 2016 triggered the collapse of tens of sinkholes. At least 20 houses, one high-traffic road, one levee of the Loire River and one highway were directly threatened. This event highlights not only the vulnerability of the area, especially in the case of a disastrous flood of the Loire River, but also an unexpected kinetic of the process. Two different types of sinkholes occurred in flooded areas: on the plateau, spectacular drop out of former natural caves is suspected; in the Loire valley, flooding is supposed to have accelerated the suffosion of alluvium by a factor of 10 000 to 20 000. This feedback bring new insights on the process dynamics that is currently being analysed in more details using an innovative internal erosion numerical modeling approach, based on Discrete Element - DEM and Lattice Boltzmann methods - LBM. A better understanding of the sinkhole formation is crucial for adequate risk management, especially in the case of a large flooding event.

  18. Sinkhole formation and subsidence along the Dead Sea coast, Israel

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    Yechieli, Yoseph; Abelson, Meir; Baer, Gideon

    2016-05-01

    More than 4,000 sinkholes have formed since the 1980s within a 60-km-long and 1-km-wide strip along the western coast of the Dead Sea (DS) in Israel. Their formation rate accelerated in recent years to >400 sinkholes per year. They cluster mostly in specific sites up to 1,000 m long and 200 m wide, which align parallel to the general direction of the fault systems associated with the DS Rift. The abrupt appearance of the sinkholes reflects changes to the groundwater regime around the shrinking DS. The eastward retreat of the shoreline and the lake-level drop (1 m/year in recent years) cause an eastward and downward migration of the fresh/saline groundwater interface. Consequently, a subsurface salt layer, which was previously enveloped by saline groundwater, is gradually being invaded and submerged by relatively fresh groundwater, and cavities form due to the rapid dissolution of the salt. Collapse of the overlying sediments into these cavities results in sinkholes at the surface. An association between sinkhole sites and land subsidence is revealed by interferometric synthetic aperture radar (InSAR) measurements. On a broad scale (hundreds of meters), subsidence occurs due to compaction of fine-grained sediments as groundwater levels decline along the retreating DS shoreline. At smaller scales (tens of meters), subsidence appears above subsurface cavities in association with the sinkholes, serving in many cases as sinkhole precursors, a few weeks to more than a year before their actual appearance at the surface. This paper overviews the processes of sinkhole formation and their relation to land subsidence.

  19. Evidence of spring formation and subrosion-induced sinkhole development at Ghor Al-Haditha, Jordan, from repeated close-range photogrammetry

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    Al-Halbouni, Djamil; Eoghan, P. Holohan; Leila, Saberi; Hussam, Alrshdan; Thomas, Walter; Ali, Sawarieh; Torsten, Dahm

    2016-04-01

    The widespread development of sinkholes and land subsidence poses a major geological hazard to infrastructure, local population, agriculture and industry in the Dead Sea area. For assessment of the key physical factors in this development, repeated photogrammetric and field surveys at Ghor Al-Haditha in Jordan have been undertaken. Recent results provide evidence for subrosion based on strong periodic water flows, as the basic underlying physical process of such land subsidence phenomena. From combined Helikite- and Quatrocopter-based photogrammetric surveys, high resolution Digital Surface Models from October 2014 and October 2015 are compared. Change detection reveals: (1) active subsidence in a hundred metre-scale depression zone, (2) a highly-dynamic spring and canyon system connected with recent sinkhole collapses and (3) the rapid formation of new sinkholes both in alluvium and mud cover sediments. The formation of new sinkholes has been documented locally by means of aerial and field observations during a storm with strong rainfall. A new artesian spring formed in the former Dead Sea bed (mud-flat) at this event. The alluvial sediment load of the stream, a periodic location change of the spring and a connected uphill sinkhole cluster formation provide strong evidence for subrosion of weak material with subsequent underground void collapse. Additionally a documented lake and its' subsequent drainage forming a new canyon reveals the local penetration of the aquiclude behavior of the mud-flat in the major depression area, which can be explained by an under-saturated groundwater flow at a strong hydrostatic gradient. Furthermore an enlargement of the investigated area in the 2015 survey indicates a continuation of subsidence and sinkhole activity towards the North. It reveals several points of emanation of water streams in the mud-flat beneath the alluvial cover and vegetation as an indicator of relatively fresh groundwater inflow. This repeated photogrammetry

  20. Urban areas of Carbonia (Sardinia, Italy): anthropogenic and natural sinkhole

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    Mureddu, A.; Corda, A. S.

    2012-04-01

    This work aims to contribute to knowledge on the phenomena of sinkholes in the urban area of Carbonia, primed mostly as a result of mining in underground coal Sulcis, as well as natural causes, in the hills and valleys structurated on the bedrock of Cambrian area, in the localities of Cannas and Serbariu. During the exploitation of the coal deposits, (so called Lignitifero), mines of the Sulcis Area, in over a century of mining, have produced large underground excavations, which were extracted more than 50 million tons of coal and large quantities of tailings. On older crops of mineral minings centers of Serbariu, Cortoghiana and Bacu Abis, the mining operations reached the depth of 300 meters from the surface of the country, over 100 meters below sea level. In the late of 1960, following the closure of the mines, were manifested in the temporal effects of the disruptions caused by the collapse of underground voids, affecting a much wider area of the below mining cultivations. The first signs of instability are occurred with the sudden opening of large potholes and structural damage to buildings up area of Bacu Abis, in neighboring areas to the Mine of Serbariu, intended for production facilities ("Su Landiri Durci"), and along certain streets service. In the case of mine "Serbariu" located on the outskirts of the urban west Carbonia, exploited in the period between 1940 and 1964, the cultivation of the layers of coal left in place, at short depth from the surface level, consisting of empty mines, with more than 5 km of galleries. So, have been found important effects of instability of the soil in urban areas and in the recently built road infrastructure linking lots of settlements. The area affected by mining operations has an area of over 4 square kilometers, is covered in part by the built environment and road infrastructure of regional and state level. In the mining center, now converted to craft and commercial area, have continued various undergrounds mining

  1. Human-induced hydrological changes and sinkholes in the gypsum karst of Lesina Marina area (Foggia Province, Italy)

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    Fidelibus, M. D.; Gutierrez, F.; Spilotro, G.

    2009-04-01

    The Lesina Lagoon is located in the East-West-trending northern cost of Gargano (southern Italy). The lagoon is fed by springs draining the northern side of the Gargano Mesozoic carbonate aquifer and is connected with the sea by three channels, including the 2.2 km long Acquarotta Canal with a N-S orientation. The sea-side mouth of this canal was frequently clogged by sand accumulation. In 1927, the path of the northern section of this canal was changed to improve the water exchange between the lagoon and the Adriatic Sea for environmental and fish-farming purposes. The new portion of the canal, 8.5 m wide and 1.5 m deep, was excavated in evaporite bedrock and in a small outcrop of igneous rocks situated in the coast that inhibits sand accumulation. The Acquarotta Canal conveys water in both directions depending on the relative water levels of the lagoon and the sea. Initially the reach of the canal dug in gypsum was lined with concrete, which was replaced in 1993 by gabions for scenery improvement. The northern reach of the canal is dug in Upper Triassic gypsiferous sediments of the Burano Anhydrite Formation. The evaporite bedrock is mantled by unconsolidated deposits a few meters thick, largely made up of loose sand. The exposures found in the banks of the canal and in some sinkholes reveal that the gypsum has a high density of dissolutional conduits and cavities. Locally, it also shows open fractures and brecciated structure (crackle, mosaic and chaotic packbreccias) caused by dissolution-induced collapse processes. These voids, either of solutional or mechanical origin, are partially filled with detrital sediments derived from the mantling deposits. These features seem to correspond to a paleokarst, probably developed at several depths controlled by different and much lower sea level stands during the Quaternary. The construction Acquarotta Canal has caused significant changes in the local hydrology. According to the piezometric series recorded at several

  2. A genetic classification of sinkholes illustrated from evaporite paleokarst exposures in Spain

    Science.gov (United States)

    Gutiérrez, Francisco; Guerrero, Jesús; Lucha, Pedro

    2008-01-01

    This contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four Spanish Tertiary basins. Bedrock strata are subhorizontal evaporites, and in three of the basins they include halite and glauberite in the subsurface. Our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications; a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed. With the exception of solution dolines, it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements (cover, bedrock or caprock) and the main type of process involved (collapse, suffosion or sagging). Sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one (e.g. bedrock sagging and collapse sinkhole). The mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material, such as upward stoping of cavities by roof failure, development of well-defined failure planes and rock brecciation. Suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling. Sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock. The paleokarsts we analysed suggest that the sagging mechanism (not included in previous genetic classifications) plays an important role in the generation of sinkholes in evaporites. Moreover, collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst, primarily due to the greater solubility of the

  3. Inception horizon concept as a basis for sinkhole hazard mapping

    Science.gov (United States)

    Vouillamoz, J.; Jeannin, P.-Y.; Kopp, L.; Chantry, R.

    2012-04-01

    The office for natural hazards of the Vaud canton (Switzerland) is interested for a pragmatic approach to map sinkhole hazard in karst areas. A team was created by merging resources from a geoengineering company (CSD) and a karst specialist (SISKA). Large areas in Vaud territory are limestone karst in which the collapse hazard is essentially related to the collapse of soft-rocks covering underground cavities, rather than the collapse of limestone roofs or underground chambers. This statement is probably not valid for cases in gypsum and salt. Thus, for limestone areas, zones of highest danger are voids covered by a thin layer of soft-sediments. The spatial distributions of void and cover-thickness should therefore be used for the hazard assessment. VOID ASSESSMENT Inception features (IF) are millimetre to decimetre thick planes (mainly bedding but also fractures) showing a mineralogical, a granulometrical or a physical contrast with the surrounding formation that make them especially susceptible to karst development (FILIPPONI ET AL., 2009). The analysis of more than 1500 km of cave passage showed that karst conduits are mainly developed along such discrete layers within a limestone series. The so-called Karst-ALEA method (FILIPPONI ET AL., 2011) is based on this concept and aims at assessing the probability of karst conduit occurrences in the drilling of a tunnel. This approach requires as entries the identification of inception features (IF), the recognition of paleo-water-table (PWT), and their respective spatial distribution in a 3D geological model. We suggest the Karst-ALEA method to be adjusted in order to assess the void distribution in subsurface as a basis for sinkhole hazard mapping. Inception features (horizons or fractures) and paleo-water-tables (PWT) have to be first identified using visible caves and dolines. These features should then be introduced into a 3D geological model. Intersections of HI and PWT located close to landsurface are areas with a

  4. A geomechanical model of a sinkhole formation

    Science.gov (United States)

    Danchiv, Alexandru; Zamfirescu, Florian; Mocuta, Marius; Popa, Iulian; Zlibut, Alexandru; Huggenberger, Peter; Zechner, Eric; Dresmann, Horst; Scheidler, Stefan; Wiesmeier, Stefan

    2016-04-01

    On December 2010 a sinkhole was suddenly formed close to the eastern flank of Ocna-Mures salt dome. Soon after the collapse the sinkhole was filled with brine forming a salt lake called Plus Lake. The total volume of sinkhole of about 100000 m3 remained constant since February 2011. The Ocna Mures salt dome is situated on the western border of the Transylvanian basin (Romania) and has been exploited for a long time. The ceilings of some shallow mine chambers are now collapsed and filled with brine. Along the eastern flank of the salt dome there is a disturbed zone due to diapirism. Its presence is suggested by the strong fragmentation of rock in the boreholes drilled along the salt-sterile contact, as it resulted from the low values of RQD index. The sinkhole is probably due to a pressure increase along the diapir flank. The causes of this sudden increase of pressure are not well known. Most probably it is due to the damage of the tubing of a flank borehole as mentioned in a technical report of the exploiting company. The injected fresh water expelled through the breaches of the damaged borehole and, due to the high pressure flushed up the crushed material of the disturbed zone. In order to better understand the setting up of the Plus Lake joint research efforts were performed by teams from Bucharest and Basel Universities since 2013. For the geomechanical approach a numerical model was performed using the Flac 7.0 code. In a first stage the creep behavior of salt was analyzed considering a Norton creep law. It resulted that after 100 years the salt reached equilibrium, the creep could be neglected and in a first approximation mechanical equilibrium could be analyzed considering only an elasto-plastic behavior of both the salt and the sterile. For both the salt and the surrounding sedimentary rocks the Mohr-Coulomb criterion was considered. The properties of sterile rocks were estimated following the GSI system. Due to poor rock quality the strength parameters have

  5. The effect of the depth and groundwater on the formation of sinkholes or ground subsidence associated with abandoned room and pillar lignite mines under static and dynamic conditions

    Science.gov (United States)

    Aydan, Ö.; Ito, T.

    2015-11-01

    It is well known that some sinkholes or subsidence take place from time to time in the areas where abandoned room and pillar type mines exist. The author has been involved with the stability of abandoned mines beneath urbanized residential areas in Tokai region and there is a great concern about the stability of these abandoned mines during large earthquakes as well as in the long term. The 2003 Miyagi Hokubu and 2011 Great East Japan earthquakes caused great damage to abandoned mines and resulted in many collapses. The author presents the effect of the depth and groundwater on the formation of sinkholes or ground subsidence associated with abandoned room and pillar lignite mines under static and dynamic conditions and discusses the implications on the areas above abandoned lignite mines in this paper.

  6. Study of the factors affecting the karst volume assessment in the Dead Sea sinkhole problem using microgravity field analysis and 3-D modeling

    Directory of Open Access Journals (Sweden)

    L. V. Eppelbaum

    2008-11-01

    Full Text Available Thousands of sinkholes have appeared in the Dead Sea (DS coastal area in Israel and Jordan during two last decades. The sinkhole development is recently associated with the buried evaporation karst at the depth of 25–50 m from earth's surface caused by the drop of the DS level at the rate of 0.8–1.0 m/yr. Drop in the Dead Sea level has changed hydrogeological conditions in the subsurface and caused surface to collapse. The pre-existing cavern was detected using microgravity mapping in the Nahal Hever South site where seven sinkholes of 1–2 m diameter had been opened. About 5000 gravity stations were observed in the area of 200×200 m2 by the use of Scintrex CG-3M AutoGrav gravimeter. Besides the conventional set of corrections applied in microgravity investigations, a correction for a strong gravity horizontal gradient (DS Transform Zone negative gravity anomaly influence was inserted. As a result, residual gravity anomaly of –(0.08÷0.14 mGal was revealed. The gravity field analysis was supported by resistivity measurements. We applied the Emigma 7.8 gravity software to create the 3-D physical-geological models of the sinkholes development area. The modeling was confirmed by application of the GSFC program developed especially for 3-D combined gravity-magnetic modeling in complicated environments. Computed numerous gravity models verified an effective applicability of the microgravity technology for detection of karst cavities and estimation of their physical-geological parameters. A volume of the karst was approximately estimated as 35 000 m3. The visual analysis of large sinkhole clusters have been forming at the microgravity anomaly site, confirmed the results of microgravity mapping and 3-D modeling.

  7. Legal aspects of sinkhole development and flooding in karst terranes: 1. Review and synthesis

    Science.gov (United States)

    Quinlan, James F.

    1986-03-01

    Structures built within the area of influence of a sinkhole can be affected by collapse, subsidence, or flooding. Unanticipated property losses may be involved, and litigation commonly ensues. Insurance compensation for damages that result from sinkhole collapse or subsidence in a karst terrane are covered by statute only in Florida and by voluntary agreement of companies operating in Tennessee Liability or insurance compensation for damages resulting from sinkhole flooding is not specifically covered by any state or federal statute. Regulations of the National Flood Insurance Program have been interpreted to allow coverage by this program for homes affected by sinkhole flooding in Bowling Green, Kentucky In the present article, case law, legal concepts of groundwater and surface water, liability, and law review articles relevant to sinkhole litigation are summarized The rationales of plaintiffs and defendants are reviewed Liability for damages have been based on allegations of negligence, breach of various water law doctrines, trespass, nuisance, loss of support, breach of contract, and implied warranty of habitability Defenses against these allegations have been based on the merits of each of them and on caveat emptor Several alternative rationales for claiming liability for losses incurred because of sinkhole development or flooding are proposed and discussed. The little-known Henderson v Wade Sand and Gravel is highly recommended as an alternative leading case that clearly and justifiably gives protection to adjacent landowners, and ties liability for damages caused by groundwater pumpage to nuisance law and related interference with property rights. Several little-known litigated cases of sinkhole development in response to groundwater pumpage will be summarized in a second article at a later date. Concepts of liability are evolving It can be expected that the professional geologist or engineer will have an increasing number of claims made against him or her

  8. Investigating a damaging buried sinkhole cluster in an urban area (Zaragoza city, NE Spain) integrating multiple techniques: Geomorphological surveys, DInSAR, DEMs, GPR, ERT, and trenching

    Science.gov (United States)

    Carbonel, Domingo; Rodríguez-Tribaldos, Verónica; Gutiérrez, Francisco; Galve, Jorge Pedro; Guerrero, Jesús; Zarroca, Mario; Roqué, Carles; Linares, Rogelio; McCalpin, James P.; Acosta, Enrique

    2015-01-01

    This contribution analyses a complex sinkhole cluster buried by urban elements in the mantled evaporite karst of Zaragoza city, NE Spain, where active subsidence has caused significant economic losses (~ 0.3 million Euro). The investigation, conducted after the development of the area, has involved the application of multiple surface and subsurface techniques. A detailed map of modern surface deformation indicates two active coalescing sinkholes, whereas the interpretation of old aerial photographs reveals the presence of two additional dormant sinkholes beneath human structures that might reactivate in the near future. DInSAR (Differential Interferometry Synthetic Aperture Radar) displacement data have limited spatial coverage mainly due to high subsidence rates and surface changes (re-pavement), and the Electrical Resistivity Tomography (ERT) and trenching investigations were severely restricted by the presence of urban elements. Nonetheless, the three techniques consistently indicate that the area affected by subsidence is larger than that defined by surface deformation features. The performance of the Ground Penetrating Radar (GPR) technique was adversely affected by the presence of highly conductive and massive anthropogenic deposits, but some profiles reveal that subsidence in the central sector of one of the sinkholes is mainly accommodated by sagging. The stratigraphic and structural relationships observed in a trench dug across the topographic margin of one of the sinkholes may be alternatively interpreted by three collapse events of around 0.6 m that occurred after 290 yr BP, or by progressive fault displacement combined with episodic anthropogenic excavation and fill. Average subsidence rates of > 6.6 mm/yr and 40 mm/yr have been calculated using stratigraphic markers dated by the radiocarbon method and historical information, respectively. This case study illustrates the need of conducting thorough investigations in sinkhole areas during the pre

  9. Early sinkhole detection using a drone-based thermal camera and image processing

    Science.gov (United States)

    Lee, Eun Ju; Shin, Sang Young; Ko, Byoung Chul; Chang, Chunho

    2016-09-01

    Accurate advance detection of the sinkholes that are occurring more frequently now is an important way of preventing human fatalities and property damage. Unlike naturally occurring sinkholes, human-induced ones in urban areas are typically due to groundwater disturbances and leaks of water and sewage caused by large-scale construction. Although many sinkhole detection methods have been developed, it is still difficult to predict sinkholes that occur in depth areas. In addition, conventional methods are inappropriate for scanning a large area because of their high cost. Therefore, this paper uses a drone combined with a thermal far-infrared (FIR) camera to detect potential sinkholes over a large area based on computer vision and pattern classification techniques. To make a standard dataset, we dug eight holes of depths 0.5-2 m in increments of 0.5 m and with a maximum width of 1 m. We filmed these using the drone-based FIR camera at a height of 50 m. We first detect candidate regions by analysing cold spots in the thermal images based on the fact that a sinkhole typically has a lower thermal energy than its background. Then, these regions are classified into sinkhole and non-sinkhole classes using a pattern classifier. In this study, we ensemble the classification results based on a light convolutional neural network (CNN) and those based on a Boosted Random Forest (BRF) with handcrafted features. We apply the proposed ensemble method successfully to sinkhole data for various sizes and depths in different environments, and prove that the CNN ensemble and the BRF one with handcrafted features are better at detecting sinkholes than other classifiers or standalone CNN.

  10. Long-term evolution of Wink sinkholes in West Texas observed by high-resolution satellite imagery

    Science.gov (United States)

    Kim, J. W.; Lu, Z.

    2016-12-01

    Sinkhole is ground depression and/or collapse over the subsurface cavity in the karst terrain underlain by the carbonates, evaporites, and other soluble soils and rocks. The geohazards have been considered as a "hidden threat" to human life, infrastructures, and properties. The Delaware Basin of West Texas in the southwest part of the Permian Basin contains one of the greatest accumulations of evaporites in the United States. Sinkholes in West Texas have been developed by the dissolution of the subsurface evaporite deposits that come in contact with groundwater. Two Wink sinkholes in Wink, Texas, were developed in 1980 and 2002, respectively. However, monitoring the sinkholes in no man's lands has been challenging due to the lack of availability of high-resolution and temporally dense acquisitions. We employ aerial photography and radar satellite imagery to measure the long-term deformation from early 2000 and characterize the inherent hydrogeology that is closely related to sinkhole collapse and subsidence. Furthermore, data on oil/gas production and water injection into the subsurface as well as ground water level are analyzed to study their effects on the concurrent unstable ground surface in Wink sinkholes. Our study will provide invaluable information to understand the mechanism of sinkhole development and mitigate the catastrophic outcomes of the geohazards.

  11. Current Sinkhole Boundaries in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This dataset is a polygon coverage of the sinkhole boundaries as determined by using LiDAR data. The polygons relate to the point coverage using the KPolyID field in...

  12. Definition of a Sinkhole hazard methodology in the Pontina Plain (Latium Region, Central Italy)

    Science.gov (United States)

    Teoli, Pamela; Mazza, Roberto; Capelli, Giuseppe

    2010-05-01

    The work presented here is the continuation of " Sinkhole Project of Latium Region" (2002), carried out by Researchers of the Laboratory of Applied Geology and Hydrogeology of the Department of Geological Sciences of the University "Roma Tre", Rome (Italy), through which were found, in different plain of the whole Region, Sinkhole prone areas, using a methodology based on the superimposition of thematic layers corresponding to geological and anthropogenic breaking factors. In the last years several specific investigations have been conducted by Researchers of the Laboratory in the Pontina Plain, that is located in the south west of the Latium Region, concerning the geological-stratigraphic setting, the sketch of flow in the aquifers located in the Pontine depression, the chemiphysical groundwater characheteristics, the density of wells, the amount of well pumping and piezometric changes. This required the implementation of several piezometric and chemiphysical surveys, the collection and validation of a large number of stratigraphic and geophysical data. All data in the archive have been computerized and the maps vectorized. This makes it possible today to address the analysis with Geographical Information Systems and to start numerical flow simulations, regarding both the heavily drained deep confined aquifer, and the areas subject to the presence of an important water exchange between the recharge area in the Lepini Mountains (carbonatic ridge) and terrigenous aquifers of the plain. Among the main causes that trigger the catastrophic collapses there are, in fact, all the phenomena that cause the mass density reduction through erosion, leaching, dissolution. All these agents are associated with water circulation: flow, velocity, CO2 saturation rate, carbonates saturation rate. The spread in the Pontina plain of deep and high pumping wells, wrongly built without the correct way of progress, and without the realization of cemented portions properly located, can lead

  13. Rapid declines of large mammal populations after the collapse of the Soviet Union.

    Science.gov (United States)

    Bragina, Eugenia V; Ives, A R; Pidgeon, A M; Kuemmerle, T; Baskin, L M; Gubar, Y P; Piquer-Rodríguez, M; Keuler, N S; Petrosyan, V G; Radeloff, V C

    2015-06-01

    Anecdotal evidence suggests that socioeconomic shocks strongly affect wildlife populations, but quantitative evidence is sparse. The collapse of socialism in Russia in 1991 caused a major socioeconomic shock, including a sharp increase in poverty. We analyzed population trends of 8 large mammals in Russia from 1981 to 2010 (i.e., before and after the collapse). We hypothesized that the collapse would first cause population declines, primarily due to overexploitation, and then population increases due to adaptation of wildlife to new environments following the collapse. The long-term Database of the Russian Federal Agency of Game Mammal Monitoring, consisting of up to 50,000 transects that are monitored annually, provided an exceptional data set for investigating these population trends. Three species showed strong declines in population growth rates in the decade following the collapse, while grey wolf (Canis lupus) increased by more than 150%. After 2000 some trends reversed. For example, roe deer (Capreolus spp.) abundance in 2010 was the highest of any period in our study. Likely reasons for the population declines in the 1990s include poaching and the erosion of wildlife protection enforcement. The rapid increase of the grey wolf populations is likely due to the cessation of governmental population control. In general, the widespread declines in wildlife populations after the collapse of the Soviet Union highlight the magnitude of the effects that socioeconomic shocks can have on wildlife populations and the possible need for special conservation efforts during such times. © 2015 Society for Conservation Biology.

  14. Large-scale Sector Collapses in the Evolution of Santa Maria Island, Azores

    Science.gov (United States)

    Marques, F. O.; Sibrant, A.; Hildenbrand, A.; Costa, A. C.

    2013-12-01

    Oceanic volcanic islands typically evolve through large-scale short-term events, either constructing or destructing the volcanic edifice. This tug of war between construction and catastrophic destruction should be recorded within a volcanic island, but old collapse events are sometimes hard to recognize because a number of processes modify the associated structures; therefore, recognition of the testimony of such events onshore, without recourse to offshore high-resolution bathymetry, is challenging and comprises our main objective. Additionally, no large-scale catastrophic sector collapses have ever been reported in the Azores, which makes Santa Maria Island a particularly interesting target. In Santa Maria, lava flows of the two main sub-aerial volcanic complexes dip gently to the west, they are separated by a volcano-sedimentary complex lying on an unconformity dipping gently to the east, and the ages decrease to the east. From this geometry and geochronology, we infer that: (1) more than half of the early shield volcano is missing (absence of all eastern flank, summit and part of the western flank), which we interpret as a large-scale sector collapse whose scar is in part the east-dipping unconformity covered with sediments ca. 4.2 Ma old; (2) the scar was filled by a younger shield volcano that grew very rapidly (ca. 4.0-3.6 Ma); (3) a second large-scale sector collapse followed, which again spared only part of the western flank of the younger shield volcano; (4) new volcanism made of dykes and volcanic cones aligned with the arcuate collapse scar indicate that the slide may have occurred ca. 3.6 Ma ago. We conclude that Santa Maria records onshore evidence of two large-scale sector collapses.

  15. Bubbles, Bubbles, Tremors & Trouble: The Bayou Corne Sinkhole

    Science.gov (United States)

    Nunn, J. A.

    2013-12-01

    In May 2012, thermogenic methane bubbles were first observed in Bayou Corne in Assumption Parish, Louisiana. As of July 2013, ninety one bubbling sites have been identified. Gas was also found in the top of the Mississippi River Alluvial Aquifer (MRAA) about 125 ft below the surface. Vent wells drilled into the MRAA have flared more 16 million SCF of gas. Trace amounts of hydrogen sulfide also have been detected. Bayou Corne flows above the Napoleonville salt dome which has been an active area for oil and gas exploration since the 1920s. The dome is also a site of dissolution salt mining which has produced large caverns with diameters of up to 300 ft and heights of 2000 ft. Some caverns are used for storage of natural gas. Microseismic activity was confirmed by an Earthscope seismic station in White Castle, LA in July 2012. An array of microseismic stations set up in the area recorded more than 60 microseismic events in late July and early August, 2012. These microseismic events were located on the western side of the dome. Estimated focal depths are just above the top of salt. In August 2012, a sinkhole developed overnight just to the northwest of a plugged and abandoned brine filled cavern (see figure below). The sinkhole continues to grow in area to more than 20 acres and has consumed a pipeline right of way. The sinkhole is more than 750 ft deep at its center. Microseismic activity was reduced for several months following the formation of the sinkhole. Microseismic events have reoccurred episodically since then with periods of frequent events preceding slumping of material into the sinkhole or a 'burp' where fluid levels in the sinkhole drop and then rebound followed by a decrease in microseismic activity. Some gas and/or oil may appear at the surface of the sinkhole following a 'burp'. Very long period events also have been observed which are believed to be related to subsurface fluid movement. A relief well drilled into the abandoned brine cavern found that

  16. Urbanisation of Suweimeh area, Jordan, versus sinkholes and landslides proliferation

    Science.gov (United States)

    Closson, Damien; Abou Karaki, Najib

    2013-04-01

    The Dead Sea is a terminal lake whose level lowers each year of about one meter per year since more than one decade. This is caused mainly by the diversion of surface waters from its watershed. Currently, 1/10 of the Jordan River still reaches the salt lake. The rapid lowering of the lake level does not allow all the surrounding groundwater tables to adjust their level to that of the Dead Sea. This imbalance causes an always faster migration of a part of the groundwater causing underground erosion leading to the formation of sinkholes along the coast, especially where discontinuities, such as faults, are present. The first collapses occurred in the years 1980-90. From the 2000s, in Jordan, they have proliferated to the point of causing serious damages to the facilities of the Arab Potash Company, the agricultural area of Ghor Al Haditha, and more recently the touristic region of Suweimeh. Aware of the problem and the need for gradual rising of the lake level, the Jordanian authorities attended from 2009 to 2011 to the feasibility study of the Red Sea - Dead Sea conduit. Currently, on the one hand, the growing environmental imbalance, and, on the other hand, the desires to develop economic activities along the coast, imply that more goods will be exposed to damages. For example, the area of Wadi Mujib Bridge was rebuilt completely in the late 2000s. It is the same for the 12 km of the dam 18 of an evaporation pond Arab Potash Company. The Numeira Salt Factory was completely destroyed in Ghor Al Haditha and was relocated to Safi. In August 2012, during touristic period, a landslide destroyed half of the Holiday Inn front beach, Suweimeh area ... End of December 2012, a team lead by Prof. Najib Abou Karaki warned the Arab Potash Company of the presence of a circular depression 250 m in diameter within the evaporation pond SP-0A. Although the dike of this saltpan is closely monitored, the exact location and shape of this large sinkhole were not known to the security

  17. SH-wave reflection seismic and VSP as tools for the investigation of sinkhole areas in Germany

    Science.gov (United States)

    Wadas, Sonja; Tschache, Saskia; Polom, Ulrich; Buness, Hermann; Krawczyk, Charlotte M.

    2017-04-01

    Sinkholes can lead to damage of buildings and infrastructure and they can cause life-threatening situations, if they occur in urban areas. The process behind this phenomenon is called subrosion. Subrosion is the underground leaching of soluble rocks, e.g. anhydrite and gypsum, due to the contact with ground- and meteoric water. Depending on the leached material, and especially the dissolution rate, different kinds of subrosion structures evolve in the subsurface. The two end members are collapse and depression structures. For a better understanding of the subrosion processes a detailed characterization of the resulting structures is necessary. In Germany sinkholes are a problem in many areas. In northern Germany salt and in central and southern Germany sulfate and carbonate deposits are affected by subrosion. The study areas described here are located in Thuringia in central Germany and the underground is characterized by soluble Permian deposits. The occurrence of 20 to 50 sinkholes is reported per year. Two regions, Bad Frankenhausen and Schmalkalden, are investigated, showing a leaning church tower and a sinkhole of 30 m diameter and 20 m depth, respectively. In Bad Frankenhausen four P-wave and 16 SH-wave reflection seismic profiles were carried out, supplemented by three zero-offset VSPs. In Schmalkalden five SH-wave reflection seismic profiles and one zero-offset VSP were acquired. The 2-D seismic sections, in particular the SH-wave profiles, showed known and unknown near-surface faults in the vicinity of sinkholes and depressions. For imaging the near-surface ( 2,5, probably indicating unstable areas due to subrosion. We conclude, that SH-wave reflection seismic offer an important tool for the imaging and characterization of near-surface subrosion structures and the identification of unstable zones, especially in combination with P-wave reflection seismic and zero-offset VSP with P- and S-waves. Presumably there is a connection between the presence of large

  18. Point of collapse and continuation methods for large ac/dc systems

    Energy Technology Data Exchange (ETDEWEB)

    Canizares, C.A. (Escuela Politecnica Nacional, Quito (Ecuador)); Alvarado, F.L. (Univ. of Wisconsin, Madison, WI (United States))

    1993-02-01

    This paper describes the implementation of both Point of Collapse (PoC) methods and continuation methods for the computation of voltage collapse points (saddle-node bifurcations) in large ac/dc systems. A comparison of the performance of these methods is presented for real systems of up to 2,158 buses. The paper discusses computational details of the implementation of the PoC and continuation methods, and the unique challenges encountered due to the presence of high voltage direct current (HVDC) transmission, area interchange power control regulating transformers, and voltage and reactive power limits. The characteristics of a robust PoC power flow program are presented, and its application to detection and solution of voltage stability problems is demonstrated.

  19. Potential of sinkhole precursor detection through interferometric SAR

    CSIR Research Space (South Africa)

    Theron, Andre

    2016-08-01

    Full Text Available detection through interferometric SAR Theron, A.1, 2, Engelbrecht, J.1 and Kemp, J.2 1 Remote Sensing Research Unit, CSIR Meraka Institute, ATheron1@csir.co.za 2 Department of Geography and Environmental Sciences, Stellenbosch University...]. However, the location and timing of sinkholes is typically unpredictable. The in situ monitoring of large areas for small scale subsidence is therefore not feasible. Satellite remote sensing, specifically Synthetic aperture radar (SAR), is a unique...

  20. Collapse calderas

    Science.gov (United States)

    Aguirre-Diaz, G. J.; Marti, J.

    2007-05-01

    A collapse caldera is a volcanic explosive structure that forms during the collapse of crustal blocks on top of a shallow magma chamber. During this collapse, a large volume of magma is evacuated, first explosively, in the form of pyroclastic fallouts and pyroclastic flows, and then effusively, as lava domes or flows after collapse. The result is a catastrophic explosive volcanic collapse that forms a depression that could end with different shapes, circular, oval, rectangular, or irregular. Three main types of collapse calderas can be defined, 1) summit caldera, 2) classic caldera, and 3) graben caldera. Summit calderas are those formed at the top of large volcanoes and are related to relatively small-volume pyroclastic products that include plinian fallouts and ignimbrites, such as Crater Lake, Las Cañadas, and Somma-Vesuvio. Classic calderas are semi-circular to irregular-shaped large structures, several km in diameter that are related to relatively large-volume pyroclastic products including pumice fallouts and widespread ignimbrites, such as Long-Valley, Campi Flegrei, and Los Humeros. Graben calderas are explosive volcano-tectonic collapse structures from which large-volume, ignimbrite-forming eruptions occurred through several vents along the graben walls and the intra-graben block faults causing the collapse of the graben or of a sector of the graben. The main products of graben calderas are surge-deposits and large-volume widespread ignimbrite sheets. Pumice fallouts are practically absent. Examples include the Sierra Madre Occidental in Mexico, La Pacana (Andes), Catalan Pyrenees, and perhaps Scafell (United Kingdom). Any of the three caldera types mentioned above could have collapsed in three different ways, 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

  1. Using lidar data to analyse sinkhole characteristics relevant for understory vegetation under forest cover-case study of a high karst area in the dinaric mountains.

    Science.gov (United States)

    Kobal, Milan; Bertoncelj, Irena; Pirotti, Francesco; Dakskobler, Igor; Kutnar, Lado

    2015-01-01

    In this article, we investigate the potential for detection and characterization of sinkholes under dense forest cover by using airborne laser scanning data. Laser pulse returns from the ground provide important data for the estimation of digital elevation model (DEM), which can be used for further processing. The main objectives of this study were to map and determine the geomorphometric characteristics of a large number of sinkholes and to investigate the correlations between geomorphology and vegetation in areas with such characteristics. The selected study area has very low anthropogenic influences and is particularly suitable for studying undisturbed karst sinkholes. The information extracted from this study regarding the shapes and depths of sinkholes show significant directionality for both orientation of sinkholes and their distribution over the area. Furthermore, significant differences in vegetation diversity and composition occur inside and outside the sinkholes, which indicates their presence has important ecological impacts.

  2. Using lidar data to analyse sinkhole characteristics relevant for understory vegetation under forest cover-case study of a high karst area in the dinaric mountains.

    Directory of Open Access Journals (Sweden)

    Milan Kobal

    Full Text Available In this article, we investigate the potential for detection and characterization of sinkholes under dense forest cover by using airborne laser scanning data. Laser pulse returns from the ground provide important data for the estimation of digital elevation model (DEM, which can be used for further processing. The main objectives of this study were to map and determine the geomorphometric characteristics of a large number of sinkholes and to investigate the correlations between geomorphology and vegetation in areas with such characteristics. The selected study area has very low anthropogenic influences and is particularly suitable for studying undisturbed karst sinkholes. The information extracted from this study regarding the shapes and depths of sinkholes show significant directionality for both orientation of sinkholes and their distribution over the area. Furthermore, significant differences in vegetation diversity and composition occur inside and outside the sinkholes, which indicates their presence has important ecological impacts.

  3. Natural and induced sinkholes of the Obruk Plateau and Karapınar-Hotamış Plain, Turkey

    Science.gov (United States)

    Doğan, Uğur; Yılmaz, Mutlu

    2011-01-01

    The number of sinkholes (locally known as obruks) has increased rapidly in recent years near Karapınar, located in the semi-arid Konya Closed Basin in Central Anatolia. Nineteen sinkholes have formed in the last 33 years (1977-2009) as a result of the collapse of cavity roofs in the Neogene lacustrine limestone in the Obruk Plateau and beneath Quaternary lake sediments in the Karapınar-Hotamış Plain. Of these, 13 have formed within the past 4 years (2006-2009). The Obruk Plateau takes its name from the presence of several hundred paleo-sinkholes which formed as a result of natural processes during the Quaternary period. More recently, human activity has induced the formation of new sinkholes, which presents a hazard to life and property. Changing agricultural patterns have led to the opening of thousands of deep wells in recent years, and increased water pumping currently exceeds the sustainable yield of the aquifer. Thus the formation of sinkholes has been triggered by a combination of natural and human causes. The groundwater level has dropped almost 24 m in the vicinity of Karapınar during the last 26 years (1983-2008). Approximately 8 m of this drop occurred within the 4 years prior to the study (2005-2008). Legally-binding precautions must be taken to prevent further water table decline, in order to decrease sinkhole formation within the basin in the years to come.

  4. A study of sinkhole hazard at area of locked colliery

    Energy Technology Data Exchange (ETDEWEB)

    Kotyrba, A. [Central Mining Institute, Gwarkow (Poland)

    2005-07-01

    Transformations of polish industry began the process of mine closures. Among various mines being in process of abandoning, there are a large number of collieries, which exploited coal since 17. century. The depth of mining openings ranged from some to hundreds meters. The height of primary mining openings ranged from 1 to 9 m. Mining operations have left in geological basement large number of cavities, which still create a hazard to the surface stability. Post mining deformations of the surface can take continuous and discontinuous forms. The last ones are the topic of paper. Although those deformations can take various forms, they are commonly called as sinkholes. In paper, the sinkholes hazard has been analyzed in a scale of selected one mine area, in regard to various parameters. The selected 'Siemianowice' mine is located in northern part of the Upper Silesian Coal Basin. A database containing full set of sinkholes, recorded within area of mine in a period of 50 years, has been tested in geomechanical and statistical approaches. (author)

  5. The Sinkholes at "Piano dell'Acqua

    Science.gov (United States)

    Iovine, G. G. R.; Parise, M.; Caloiero, T.; Lanza, G.; Suriano, S.

    2012-04-01

    Five sinkholes have recently been identified in the territory of San Basile (Northern Calabria, Southern Italy), in locality "Piano dell'Acqua". The sinkholes are located in a hilly setting, where the main landform is represented by a slight valley draining toward the east. The sinkholes are limited in size, with maximum diameter of 10 m, and maximum depth of 2.5 m. Two of them are elongated, whilst the remaining three are circular. The area where the sinkholes develop is characterized by Pliocene conglomerate and sand, likely dislocated by tectonic lines. The sinkholes were initially examined by means of multi-temporal aerial photos, and the outcomes from this analysis were checked in the field through geological, structural and geomorphological surveys. At the same time, an historical analysis was started in order to collect and critically evaluate the existing information and testimonies about age of occurrence of the phenomena. At this aim, several interviews with local inhabitants were performed, and a number of archives scrutinized. As a result, the study allowed to hypothesize that two sinkholes developed during the winter 2000-2001, with likely rapid formation. Two other cases probably originated during the 70's, as also suggested by the age of the vegetation hosted within the sinkholes. The last sinkhole, eventually, opened sometime between February 2001 and November 2007. According to the collected testimonies, a further phase of sinkhole development might have occurred in the first half of the past Century, but no field evidence of this older phase has been found so far. Analysis of the seismic catalogues showed that no earthquake can be identified as possible trigger of any of the sinkholes at Piano dell'Acqua. Therefore, the origin of the studied phenomena should be related to sub-cutaneous erosion, within an area that is rich in groundwater (as also shown by the site name, meaning "Water Plain"). Local changes in the water table, both related to

  6. 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.

  7. Detecting Sinkhole Attacks in Wireless Sensor Network using Hop Count

    Directory of Open Access Journals (Sweden)

    Md. Ibrahim Abdullah

    2015-02-01

    Full Text Available Nowadays, Wireless Sensor Networks (WSNs are widely used in many areas, especially in environment applications, military applications, queue tracking, etc. WSNs are vulnerable to different types of security attacks due to various constraints such as broadcasted nature of transmission medium, deployment in open or hostile environment where they are not physically protected, less memory, and limited battery power. So, security system is the crucial requirements of these networks. One of the most notably routing attacks is the sinkhole attack where an adversary captures or insert nodes in the sensor field that advertise high quality routes to the base station. In this paper, a mechanism is proposed against sinkhole attacks which detect malicious nodes using hop counting. The main advantage of the proposed technique is that, a node can detects malicious nodes only collaborating with the neighbor nodes without requiring any negotiation with the base station. Simulation result shows that, the proposed technique successfully detects the sinkhole nodes for large sensor field.

  8. Could the collapse of a massive speleothem be the record of a large paleoearthquake?

    Science.gov (United States)

    Valentini, Alessandro; Pace, Bruno; Vasta, Marcello; Ferranti, Luigi; Colella, Abner; Vassallo, Maurizio

    2016-04-01

    Earthquake forecast and seismic hazard models are generally based on historical and instrumental seismicity. However, in regions characterized by moderate strain rates and by strong earthquakes with recurrence longer than the time span covered by historical catalogues, different approaches are desirable to provide an independent test of seismologically-based models. We used non-conventional methods, such as the so-called "Fragile Geological Features", and in particular cave speleothems, for assessing and improving existing paleoseismological databases and seismic hazard models. In this work we present a detailed study of a massive speleothem found collapsed in the Cola Cave (Abruzzo region, Central Apennines, Italy) that could be considered the record of a large paleoearthquake. Radiometric dating and geotechnical measurements are carried out to characterize the collapse time and the mechanical properties of speleothem. We performed theoretical and numerical modelling in order to estimate the values of the horizontal ground acceleration required to failure the speleothems. In particular we used a finite element method (FEM), with the SAP200 software, starting from the detailed geometry of the speleothem and its mechanical properties. We used several individual seismogenic source geometries and four different ground motion prediction equations to calculate the possible response spectra. We carried out also a seismic noise survey to understand and quantify any ground motion amplification phenomenon. The results suggest two faults located in the Fucino area as the most probable causative sources of the cave speleothem collapses, recorded ~4-5 ka ago, with a Mw=6.8 ± 0.2. Our approach contributes to assess the existence of past earthquakes integrating the classical paleoseismological trenches techniques, and to attribute the retrieved event to geometrically-defined individual seismogenic sources, which represents a key contribution to improve fault-based seismic

  9. Detection of Sinkhole Activity in Central Florida with High Spatial-Resolution InSAR Time Series Observations

    Science.gov (United States)

    Oliver-Cabrera, T.; Wdowinski, S.; Kruse, S.

    2016-12-01

    Central Florida's thick carbonate deposits and hydrological conditions make the area prone to sinkhole development. Sinkhole collapse is a major geologic hazard, threatening human life and causing substantial damage to property. Detecting sinkhole deformation before a collapse is a difficult task, due to small and typically unnoticeable surface changes. Most techniques used to map sinkholes, such as ground penetrating radar, require ground contact and are practical for localized (typically 2D, tens to hundreds of meters) surveys but not for broad study areas. In this study we use Persistent Scatterer (PS) time series analysis of Interferometric Synthetic Aperture Radar (InSAR), which is a very useful technique for detecting localized deformation while covering vast areas. We acquired SAR images over four locations in central Florida in order to detect possible pre-collapse or slow subsidence surface movements. The data used in this study were acquired by TerraSAR-X and COSMO-SkyMed satellites with pixel resolutions ranging between 25cm and 2m. To date, we have obtained four datasets, each of 25-30 acquisitions, covering a period of roughly one year over a total of roughly 2200 km2. We also installed two corner reflectors over a subsiding sinkhole located in an open vegetated area, to provide strong scattering and improve coherence over that particular location. We generate PS time series for each of the four datasets. Preliminary results show localized deformation at several houses and commercial buildings in several locations. Deforming areas vary in size from approximately 10mx20m of a single house to 60mx60m for a commercial building. On site ground penetrating radar surveys will be performed in these areas to verify their relationship to possible sinkhole activities. Our results also confirm that the corner reflectors improved PS detection over low coherence areas.

  10. Anthropogenic sinkholes in the town of Naples

    Science.gov (United States)

    Vennari, Carmela; Parise, Mario

    2016-04-01

    The importance of sinkhole as a natural hazard is often underrated when compared with landslides, floods, volcanic eruptions and earthquakes in Italy. Sinkholes are rarely included in risk analysis despite their frequent occurrence in several parts of Italy, especially in karst lands or in those sectors of the country where artificial cavities have been realized underground by man for different purposes. Among the most affected Italian regions, Campania (southern Italy) stands out for several reasons, with particular regard to the town of Naples, highly affected by anthropogenic sinkholes. These latter have caused serious damage to society, and above all to people in terms of deaths, missing persons, and injured people, due to the high urbanization of the city, developed above a complex and extensive network of cavities, excavated during the 2000 years of history of the town. Among the different typologies of artificial cavities, it is worth mentioning the high number of ancient quarry used to extract the building materials for the town construction. The Institute of Research for the Hydrological Protection (IRPI) of the National Research Council of Italy (CNR) has been working in the last years at populating a specific chronological database on sinkholes in the whole Italian country. On the base of the collected data, Naples appears to have been affected by not less than 250 events from the beginning of the century to nowadays. The IRPI database includes only sinkholes for which a temporal reference on their time of occurrence is known. Particular attention was given on this information, since the catalogue idea is to make a starting point for a complete sinkhole hazard analysis. At this aim, knowledge of the time of occurrence is mandatory. Day, month and year of the event are known for about 70% of sinkholes that took place in Naples, but the hour of occurrence is known for just 6% of the data. Information about site of occurrence are, on the other hand, highly

  11. Geomorphological analysis of sinkhole and landslide hazard in a karst area of the Venetian Prealps- Italy

    Science.gov (United States)

    Tiberi, Valentina

    2010-05-01

    In the pedemountain area of the Asiago Plateau (Venetian Prealps - NE Italy) sinkholes and landslides represent in many cases a complex response to karst processes. Field survey showed that both soil and bedrock are involved, mainly represented by colluvial-alluvial sediments and carbonate rocks. Preliminary observations also reveal the key role of piping and cave-collapse phenomena and the importance of human remedial measures. Within study area, these processes cause damage mainly to agricultural and pasture activities and expose peoples and farm animals to very high hazards. This work provides preliminary results of geomorphological analysis carried out to define sinkhole and landslide hazard and his connections with karst processes. During first phases of the research program, an inventory of interesting phenomena has been elaborated employing GIS technologies. The database has been constantly revised and enriched with new field measurements and thematic maps (i.e. geomorphological, geo-structural, hydrogeological, caves development maps). Specifically, field survey focused on the morphodynamic definition of instability elements allowing to recognize a wide range of morphotypes (mainly with regard to sinkholes) and polygenic morphologies (i.e. mixed sinkholes-landslides configurations). Geomorphological analysis also revealed specific evolutionary trends of instability processes; they could be useful employed to program more effective mitigation strategies.

  12. Anthropogenic sinkholes susceptibility and underground caves density of Naples (Southern Italy)

    Science.gov (United States)

    Ciotoli, Giancarlo; Guarino, Paolo Maria; Nisio, Stefania

    2016-04-01

    A study of historical anthropogenic sinkholes, the underground caves and related susceptibility in the municipality of Naples is presented. The goals of the research is to construct an inventory of historical sinkholes (events from 1960 to 2015), to identify and analyze their predisposing and triggering factors, and to evaluate the related susceptibility. A fairly complete assessment of historical events occurred up to December 2015 has been carried out. The analysis related to the last sinkholes phenomena is presented, especially regarding those caused by the collapse of subterranean lapillus quarries. The genetic mechanisms of the surveyed sinkholes appear sufficiently clear; the knowledge of how the predisposing factors vary within the study area is adequate as far as the sewage system is considered, whereas it is still defective as concerns the role of the cavity network. The obtained susceptibility map could be a useful contribution to further detailed zoning maps in a densely urbanized area, such as the city of Naples. In addition to the need of further increasing the knowledge on the subsoil of the Neapolitan area, a key issue remains the use of temporal information on historical events for the purposes of hazard evaluation; further studies in this regard are still in progress.

  13. Detection of sinkholes using 2D electrical resistivity imaging

    CSIR Research Space (South Africa)

    Van Schoor, Abraham M

    2002-07-01

    Full Text Available Sinkholes in dolomitic areas are notoriously difficult geophysical targets, and selecting an appropriate geophysical solution is not straightforward. Electrical resistivity imaging or tomography (RESTOM) is well suited to mapping sinkholes because...

  14. Natural versus human control on subsurface salt dissolution and development of thousands of sinkholes along the Dead Sea coast

    Science.gov (United States)

    Abelson, Meir; Yechieli, Yoseph; Baer, Gidon; Lapid, Gil; Behar, Nicole; Calvo, Ran; Rosensaft, Marcelo

    2017-06-01

    One of the most hazardous results of the human-induced Dead Sea (DS) shrinkage is the formation of more than 6000 sinkholes over the last 25 years. The DS shrinkage caused eastward retreat of underground brine replaced by fresh groundwater, which in turn dissolved a subsurface salt layer, to generate cavities and collapse sinkholes. The areal growth rate of sinkhole clusters is considered the most pertinent proxy for sinkholes development. Analysis of light detection and ranging, digital elevation models, and interferometric synthetic aperture radar allows translation of the areal growth rate to a salt dissolution rate of the salt layer, revealing two peaks in the history of the salt dissolution rate. These peaks cannot be attributed to the decline of the DS level. Instead, we show that they are related to long-term variations of precipitation in the groundwater source region, the Judea Mountains, and the delayed response of the aquifer system between the mountains and the DS rift. This response is documented by groundwater levels and salinity variations. We thus conclude that while the DS level decline is the major trigger for sinkholes formation, the rainfall variations more than 30 km to the west dominate their evolution rate. The influence of increasing rainfall in the Judea Mountains reaches the DS at a typical time lag of 4 years, and the resulting increase in the salt dissolution rate lags by a total time of 5-6 years.

  15. Role of large flank-collapse events on magma evolution of volcanoes. Insights from the Lesser Antilles Arc

    Science.gov (United States)

    Boudon, Georges; Villemant, Benoît; Friant, Anne Le; Paterne, Martine; Cortijo, Elsa

    2013-08-01

    Flank-collapse events are now recognized as common processes of destruction of volcanoes. They may occur several times on a volcanic edifice pulling out varying volumes of material from km3 to thousands of km3. In the Lesser Antilles Arc, a large number of flank-collapse events were identified. Here, we show that some of the largest events are correlated to significant variations in erupted magma compositions and eruptive styles. On Montagne Pelée (Martinique), magma production rate has been sustained during several thousand years following a 32 ka old flank-collapse event. Basic and dense magmas were emitted through open-vent eruptions that generated abundant scoria flows while significantly more acidic magmas were produced before the flank collapse. The rapid building of a new cone increased the load on magma bodies at depth and the density threshold. Magma production rate decreased and composition of the erupted products changed to more acidic compared to the preceding period of activity. These low density magma generated plinian and dome-forming eruptions up to the Present. In contrast at Soufrière Volcanic Centre of St. Lucia and at Pitons du Carbet in Martinique, the flank-collapses have an opposite effect: in both cases, the acidic magmas erupted immediately after the flank-collapses. These magmas are highly porphyritic (up to 60% phenocrysts) and much more viscous than the magmas erupted before the flank-collapses. They have been generally emplaced as voluminous and uptight lava domes (called “the Pitons”). Such magmas could not ascent without a significant decrease of the threshold effect produced by the volcanic edifice loading before the flank-collapse.

  16. Hollow nanoshell formation and collapse in binary solid solutions with large range of solubility

    Energy Technology Data Exchange (ETDEWEB)

    Gusak, A M; Zaporozhets, T V, E-mail: gusak@cdu.edu.u, E-mail: tvz@phys.cdu.edu.u [Cherkasy National University, 81, Boulevard Shevchenko, Cherkasy, 18031 (Ukraine)

    2009-10-14

    The formation of a solid solution hollow nanoshell from core-shell structure and collapse of this nanoshell into a compact particle is modelled by a phenomenological scheme and by Monte Carlo simulation. The cross-over between formation and collapse, and the criteria of nanoshell formation are analysed.

  17. Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate (Mandrillus leucophaeus).

    Science.gov (United States)

    Ting, Nelson; Astaras, Christos; Hearn, Gail; Honarvar, Shaya; Corush, Joel; Burrell, Andrew S; Phillips, Naomi; Morgan, Bethan J; Gadsby, Elizabeth L; Raaum, Ryan; Roos, Christian

    2012-03-01

    It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkey's geographic range is Lake Barombi Mbo, which has a well-documented palynological record of environmental change that dates to the Late Pleistocene. We used a Bayesian coalescent-based framework to analyze 2,076 base pairs of mitochondrial DNA across wild drill populations to infer past changes in female effective population size since the Late Pleistocene. Our results suggest that the drill underwent a nearly 15-fold demographic collapse in female effective population size that was most prominent during the Mid Holocene (approximately 3-5 Ka). This time period coincides with a period of increased dryness and seasonality across Africa and a dramatic reduction in forest coverage at Lake Barombi Mbo. We believe that these changes in climate and forest coverage were the driving forces behind the drill population decline. Furthermore, the warm temperatures and increased aridity of the Mid Holocene are potentially analogous to current and future conditions faced by many tropical rainforest communities. In order to prevent future declines in population size in rainforest-adapted species such as the drill, large tracts of forest should be protected to both preserve habitat and prevent forest loss through aridification.

  18. The sinkhole of Schmalkalden, Germany - Imaging of near-surface subrosion structures and faults

    Science.gov (United States)

    Wadas, Sonja H.; Tschache, Saskia; Polom, Ulrich; Krawczyk, Charlotte M.

    2017-04-01

    In November 2010 a sinkhole of 30 m diameter and 20 m depth opened in a residential area in the village Schmalkalden, Germany, which fortunately led to damage of buildings and property only. The collapse was caused by leaching of soluble rocks in the subsurface, called subrosion. For an improved understanding of the processes leading to subrosion and sinkhole development a detailed characterization of the subsurface structures and elastic parameters is required. We used shear wave reflection seismic, which has proven to be a suitable method for high-resolution imaging of the near-surface. The village Schmalkalden is located in southern Thuringia in Germany. Since the Upper Cretaceous the area is dominated by fault tectonics, fractures and joints, which increase the rock permeability. The circulating groundwater leaches the Permian saline deposits in the subsurface and forms upward migrating cavities, which can develop into sinkholes, if the overburden collapses. In the direct vicinity of the backfilled sinkhole, five 2-D shear wave reflection seismic profiles with total length of ca. 900 m and a zero-offset VSP down to 150 m depth were acquired. For the surface profiles a 120-channel landstreamer attached with horizontal geophones and an electrodynamic micro-vibrator, exciting horizontally polarized shear waves, were used. For the VSP survey an oriented borehole probe equipped with a 3C-geophone and electrodynamic and hydraulic vibrators, exciting compression- and shear waves, were utilized. The seismic sections show high-resolution images from the surface to ca. 100 m depth. They display heterogeneous structures as indicated by strong vertical and lateral variations of the reflectors. In the near-surface, depressions are visible and zones of low seismic velocities < 180 m/s show increased attenuation of the seismic wave field. These are probably the result of the fractured underground, due to fault tectonics and the ongoing subrosion. The unstable zones are

  19. Regional sinkhole susceptibility maps: The Latium Region case (central Italy)

    Science.gov (United States)

    La Vigna, F.; Teoli, P.; Mazza, R.; Leoni, G.; Capelli, G.

    2012-04-01

    Several and frequent studies were internationally presented about landslide susceptibility, meanwhile in literature is missing a broad diffusion of studies regarding sinkhole susceptibility. That's why sinkhole recurrence depends on several geological conditions related to specific geological and hydrogeological context (sinkhole prone area) that vary case by case. Notwithstanding this regionalization problem of sinkhole recurrence, in the central Appenine sedimentary basins (Italy) a certain number of geological, geomorphologic and hydrogeological conditions (sinkhole predisposing issues) can be considered in common between the surveyed sinkholes. Eventually this could be compared with similar geological conditions and sinkhole occurrence in the rest of Italy or in other countries. In this case study is presented a probabilistic approach regarding the Latium Region deriving from the comparison between the regional sinkhole inventory realized during a precedent project and the dataset of the new Hydrogeological Map of Latium Region (scale 1:100.000). Indexed elements, chosen because associated to the majority of sinkhole phenomena, are: outcropping lithologies, water table depth, main faults (even if buried), hydrothermal springs, land use and the epicentres of recent earthquakes. These indexed elements were weighted and combined in a matrix which preliminary result is the sinkhole susceptibility map of Latium Region. When definitively validated, this approach could be suitable for local authorities to planning more targeted studies in major hazard areas.

  20. The current status of mapping karst areas and availability of public sinkhole-risk resources in karst terrains of the United States

    Science.gov (United States)

    Kuniansky, Eve L.; Weary, David J.; Kaufmann, James E.

    2016-01-01

    Subsidence from sinkhole collapse is a common occurrence in areas underlain by water-soluble rocks such as carbonate and evaporite rocks, typical of karst terrain. Almost all 50 States within the United States (excluding Delaware and Rhode Island) have karst areas, with sinkhole damage highest in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. A conservative estimate of losses to all types of ground subsidence was $125 million per year in 1997. This estimate may now be low, as review of cost reports from the last 15 years indicates that the cost of karst collapses in the United States averages more than $300 million per year. Knowing when a catastrophic event will occur is not possible; however, understanding where such occurrences are likely is possible. The US Geological Survey has developed and maintains national-scale maps of karst areas and areas prone to sinkhole formation. Several States provide additional resources for their citizens; Alabama, Colorado, Florida, Indiana, Iowa, Kentucky, Minnesota, Missouri, Ohio, and Pennsylvania maintain databases of sinkholes or karst features, with Florida, Kentucky, Missouri, and Ohio providing sinkhole reporting mechanisms for the public.

  1. The current status of mapping karst areas and availability of public sinkhole-risk resources in karst terrains of the United States

    Science.gov (United States)

    Kuniansky, Eve L.; Weary, David J.; Kaufmann, James E.

    2016-05-01

    Subsidence from sinkhole collapse is a common occurrence in areas underlain by water-soluble rocks such as carbonate and evaporite rocks, typical of karst terrain. Almost all 50 States within the United States (excluding Delaware and Rhode Island) have karst areas, with sinkhole damage highest in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. A conservative estimate of losses to all types of ground subsidence was 125 million per year in 1997. This estimate may now be low, as review of cost reports from the last 15 years indicates that the cost of karst collapses in the United States averages more than 300 million per year. Knowing when a catastrophic event will occur is not possible; however, understanding where such occurrences are likely is possible. The US Geological Survey has developed and maintains national-scale maps of karst areas and areas prone to sinkhole formation. Several States provide additional resources for their citizens; Alabama, Colorado, Florida, Indiana, Iowa, Kentucky, Minnesota, Missouri, Ohio, and Pennsylvania maintain databases of sinkholes or karst features, with Florida, Kentucky, Missouri, and Ohio providing sinkhole reporting mechanisms for the public.

  2. Collapsible Photovoltaic Module for a Large-Scale Solar Power Plant

    DEFF Research Database (Denmark)

    2014-01-01

    An elongate photovoltaic (PV) module for use in a solar energy conversion plant for the production of electricity from incident light, the PV-module comprising a top portion with a support panel (G) carrying on a front side a plurality of electrically connected PV cells (D), and a transparent...... protective layer (A) sealed to the support panel (G) so as to encapsulate the PV-cells (D) between the support panel (G) and the protective layer (A), wherein prior to installation of the PV-module at the deployment site a collapsible portion of the PV-module is configured to be collapsible in a longitudinal...... direction by folding and/or rolling, wherein the collapsible portion includes at least the top portion, wherein the PV-module further comprises one or more integrated ballast chambers (I) in a bottom portion of the PV-module arranged on a rear side of the support panel (G), wherein said integrated ballast...

  3. Sinkholes Due to Groundwater Withdrawal in Tazerbo Wellfield, SE Libya.

    Science.gov (United States)

    Alfarrah, Nawal; Berhane, Gebremedhin; Hweesh, Abdelrahim; Walraevens, Kristine

    2017-07-01

    The desert of eastern Libya forms one of the most arid regions of the Sahara. The Great Man-Made River Project (GMRP) was established. It transports millions of cubic meters of water a day from desert wellfields to the coastal cities, where over 80% of the population lives. The Tazerbo Wellfield is one of the wellfields designed within the GMRP, delivering water to the eastern coast of Libya through an underground pipe network. Tazerbo Wellfield consists of 108 production wells; each well was designed to pump 100 L/s. The planned total groundwater withdrawal from all wells is 1 million m(3) /d. The deep sandstone aquifer (Nubian sandstone) is covered by a thick mudstone-siltstone aquitard and is being heavily pumped. The aquifer and fine-grained sediments of the aquitard may be compacted resulting in land subsidence as a result of high exploitation. Local sinkholes have developed in the area of Tazerbo since the start of the pumping from the wellfield in 2004. These sinkholes have been caused mainly by lowering of the piezometric heads due to the withdrawal of groundwater. In this study, a hydrogeological investigation is presented about the effect of large groundwater pumping from the Nubian sandstone aquifer in Tazerbo Wellfield, SE Libya, based on physical parameters for 108 production wells and 23 observation wells. © 2017, National Ground Water Association.

  4. Relationships between sinkholes areal distribution and main tectonic alignments in Abruzzo (Central Italy)

    Science.gov (United States)

    Ferrini, G.; Moretti, A.; De Rose, C.; Stagnini, E.,; Serafini, M.

    2012-04-01

    Intermountain basins, developed at the back side of the Apennines overturning front, are the most evident morphological expressions of extensional tectonics in Central Italy and can be recognized in many different sections of the chain. L'Aquila basin and the adjoining Subequana valley are part of a single NW-SE elongated depression (about 60 km long) which began to develop about in the early Quaternary in response to the identification of various regional extensional tectonic alignments and the consequent starting of the basin subsidence. This impressive morphological element is characterized by the presence of several large funnel-shaped features (locally named Fosse = trench) which affect mainly the Meso-Cenozoic carbonatic bedrock but also the Neogenic clastic sedimentary filling of the valley. Some of these last elements are often occupied by ponds or significant artesian water resurgences like the Sinizzo Lake where, during L'Aquila earthquake of April 6th 2009, the shores collapsed and strong microseismic activity, deep rumbles and flow rate changes were reported for the following months. The Fosse mapped in the L'Aquila basin have widths in the order of hundreds of meters, a considerable difference of elevation respect the rims and present a general morphology very close to that of the classic dissolution karst sinkholes. Their evolution/localization is strictly related to the active fault systems which controls also the main tracts of the relief; the low volume of residual sedimentary deposits within the depression, not comparable with the total volume of rock removed, indicates that surface karst dissolution phenomena are absent or secondary. The elevations of the floor of many Fosse are higher respect the actual flood plain depending on their age; in fact relict circular forms, recognizable at upper altitude on the relief slope, confirm that the phenomenon has been active for a considerable period of time. About the genesis of this features, even if at

  5. Scale-free distribution of Dead Sea sinkholes--observations and modeling

    CERN Document Server

    Yizhaq, Hezi; Raz, Eli; Ashkenazy, Yosef

    2016-01-01

    There are currently more than 5500 sinkholes along the Dead Sea in Israel. These were formed due to dissolution of subsurface salt layers as a result of the replacement of hypersaline groundwater by fresh brackish groundwater. This process was associated with a sharp decline in the Dead Sea level, currently more than one meter per year, resulting in a lower water table that has allowed the intrusion of fresher brackish water. We studied the distribution of the sinkholes sizes and found that it is scale-free with a power-law exponent close to 2. We constructed a stochastic cellular automata model to understand the observed scale-free behavior and the growth of the sinkholes area in time. The model consists of a lower salt layer and an upper soil layer in which cavities that develop in the lower layer lead to collapses in the upper layer. The model reproduces the observed power-law distribution without entailing the threshold behavior commonly associated with criticality.

  6. Large-scale flank collapse events during the activity of Montagne Pelée, Martinique, Lesser Antilles

    Science.gov (United States)

    Le Friant, Anne; Boudon, Georges; Deplus, Christine; Villemant, Benoã®T.

    2003-01-01

    A horseshoe-shaped structure already identified on the southwestern flank of Montagne Pelée (Martinique, Lesser Antilles arc) was previously interpreted as resulting of a flank collapse event, but no debris avalanche deposits were observed at the time. New offshore high-resolution bathymetry and geophysical data (Aguadomar cruise; December 1998 to January 1999; R/V L'Atalante) lead us to identify three debris avalanche deposits on the submarine western flank of Montagne Pelée extending down to the Grenada Basin. They display morphological fronts and hummocky morphology on bathymetric data, speckled pattern on backscatter data and hyperbolic facies on 3.5 kHz and seismic profiles. New on-land geological studies lead us to identify two other horseshoe-shaped structures on the same flank of the volcano. The three submarine deposits have been traced back to the structures identified on land, which confirms the occurrence of repeated flank collapse events during the evolution of Montagne Pelée. The ages of the last two events are estimated at ˜9 ka and ˜25 ka on the basis of 14C and 238U/230Th dates. Every flank collapse produced debris avalanches which flowed down to the Caribbean Sea. We propose that the repeated instabilities are due to the large asymmetry of the island with western aerial and submarine slopes steeper than the eastern slopes. The asymmetry results from progressive loading by accumulation of volcanic products on the western slopes of the volcano and development of long-term gravitational instabilities. Meteoric and hydrothermal fluid circulation on the floor of the second flank collapse structure also creates a weakened hydrothermalized area, which favors the recurrence of flank collapses.

  7. Improved collapse resistance of large diameter pipe for deepwater applications using a new impander technology

    Energy Technology Data Exchange (ETDEWEB)

    Reichel, Thilo; Pavlyk, Vitaliy; Beissel, Jochem [Eisenbau Kramer GmbH, Kreutztal-Kredenbach, (Germany); Kyriakides, Stelias; Jang, Wen-Yea [The University of Texas at Austin, Austin, TX, (United States)

    2010-07-01

    The UOE and JCO processes are usually used to design pipes larger than 16 inches. The reduced collapse pressures are caused by the cold forming process used during these processes. This paper investigated a new manufacturing process in which longitudinally welded pipe formed by the JCO process is finished by controlled compression using a new cold sizing press called the Impander. Various rings have been evaluated to measure the dimensional and mechanical properties performed by this new compression process. Dimensional measurements were measured using calipers, micrometers and later a custom scanning system. The results showed that the compression improved the circularity of the pipe. The mechanical properties were measured by bending residual stress tests and a custom numerical model BEPTICO was used for evaluating the collapse pressure. It is found that this new process reduces the residual stresses of the pipe and improves its straightness.

  8. Sinkholes, subsidence and subrosion on the eastern shore of the Dead Sea as revealed by a close-range photogrammetric survey

    Science.gov (United States)

    Al-Halbouni, Djamil; Holohan, Eoghan P.; Saberi, Leila; Alrshdan, Hussam; Sawarieh, Ali; Closson, Damien; Walter, Thomas R.; Dahm, Torsten

    2017-05-01

    Ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide. The rapid development of such phenomena around the Dead Sea in the last four decades poses a major geological hazard to the local population, agriculture and industry. Nonetheless many aspects of this hazard are still incompletely described and understood, especially on the eastern Dead Sea shore. In this work, we present a first low altitude (tectonic faults. The estimated minimum volume loss of this subsided zone is 1.83 ṡ 106 m3 with an average subsidence rate of 0.21 m yr-1 over the last 25 years. Sinkholes in the surveyed area are localized mainly within this depression. The sinkholes are commonly elliptically shaped (mean eccentricity 1.31) and clustered (nearest neighbor ratio 0.69). Their morphologies and orientations depend on the type of sediment they form in: in mud, sinkholes have a low depth to diameter ratio (0.14) and a long-axis azimuth of NNE-NE. In alluvium, sinkholes have a higher ratio (0.4) and are orientated NNW-N. From field work, we identify actively evolving artesian springs and channelized, sediment-laden groundwater flows that appear locally in the main depression. Consequently, subrosion, i.e. subsurface mechanical erosion, is identified as a key physical process, in addition to dissolution, behind the subsidence and sinkhole hazard. Furthermore, satellite image analysis links the development of the sinuous depression and sinkhole formation at Ghor Al-Haditha to preferential groundwater flow paths along ancient and current wadi riverbeds.

  9. Long-term (17 Ma) turbidite record of the timing and frequency of large flank collapses of the Canary Islands

    Science.gov (United States)

    Hunt, J. E.; Talling, P. J.; Clare, M. A.; Jarvis, I.; Wynn, R. B.

    2014-08-01

    turbidites on the Madeira Abyssal Plain provide a record of large-volume volcanic island flank collapses from the Canary Islands. This long-term record spans 17 Ma, and comprises 125 volcaniclastic beds. Determining the timing, provenance and volumes of these turbidites provides key information about the occurrence of mass wasting from the Canary Islands, especially the western islands of Tenerife, La Palma and El Hierro. These turbidite records demonstrate that landslides often coincide with protracted periods of volcanic edifice growth, suggesting that loading of the volcanic edifices may be a key preconditioning factor for landslide triggers. Furthermore, the last large-volume failures from Tenerife coincide with explosive volcanism at the end of eruptive cycles. Many large-volume Canary Island landslides also occurred during periods of warmer and wetter climates associated with sea-level rise and subsequent highstand. However, these turbidites are not serially dependent and any association with climate or sea level change is not statistically significant.

  10. Rome: sinkhole events and network of underground cavities (Italy)

    Science.gov (United States)

    Nisio, Stefania; Ciotoli, Giancarlo

    2016-04-01

    The anthropogenic sinkholes in the city of Rome are closely linked to the network of underground cavities produced by human activities in more than two thousand years of history. Over the past fifteen years the increased frequency of intense rainfall events, favors sinkhole formation. The risk assessment induced by anthropogenic sinkhole is really difficult. However, a susceptibility of the territory to sinkholes can be more easily determined as the probability that an event may occur in a given space, with unique geological-morphological characteristics, and in an infinite time. A sinkhole susceptibility map of the Rome territory, up to the ring road, has been constructed by using Geographically Weighted Regression technique and geostatistics. The spatial regression model includes the analysis of more than 2700 anthropogenic sinkholes (recorded from 1875 to 2015), as well as geological, morphological, hydrological and predisposing anthropogenic characteristics of the study area. The numerous available data (underground cavities, the ancient entrances to the quarry, bunkers, etc.) facilitate the creation of a series of maps. The density map of the cavity, updated to 2015, showed that more than 20 km2 of the Roman territory are affected by underground cavities. The census of sinkholes (over 2700) shows that over 30 km2 has been affected by sinkholes. The final susceptibility map highlights that inside the Ring Road about 40 km2 of the territory (about 11%) have a very high probability of triggering a sinkhole event. The susceptibility map was also compared with the data of ground subsidence (InSAR) to obtain a predictive model.

  11. A GIS analysis of the relationship between sinkholes, dry-well complaints and groundwater pumping for frost-freeze protection of winter strawberry production in Florida.

    Directory of Open Access Journals (Sweden)

    Mark D Aurit

    Full Text Available Florida is riddled with sinkholes due to its karst topography. Sometimes these sinkholes can cause extensive damage to infrastructure and homes. It has been suggested that agricultural practices, such as sprinkler irrigation methods used to protect crops, can increase the development of sinkholes, particularly when temperatures drop below freezing, causing groundwater levels to drop quickly during groundwater pumping. In the strawberry growing region, Dover/Plant City, Florida, the effects have caused water shortages resulting in dry-wells and ground subsidence through the development of sinkholes that can be costly to maintain and repair. In this study, we look at how frost-freeze events have affected West Central Florida over the past 25 years with detailed comparisons made between two cold-years (with severe frost-freeze events and a warm year (no frost-freeze events. We analyzed the spatial and temporal correlation between strawberry farming freeze protection practices and the development of sinkholes/dry well complaints, and assessed the economic impact of such events from a water management perspective by evaluating the cost of repairing and drilling new wells and how these compared with using alternative crop-protection methods. We found that the spatial distribution of sinkholes was non-random during both frost-freeze events. A strong correlation between sinkhole occurrence and water extraction and minimum temperatures was found. Furthermore as temperatures fall below 41°F and water levels decrease by more than 20 ft, the number of sinkholes increase greatly (N >10. At this time alternative protection methods such as freeze-cloth are cost prohibitive in comparison to repairing dry wells. In conclusion, the findings from this study are applicable in other agricultural areas and can be used to develop comprehensive water management plans in areas where the abstraction of large quantities of water occur.

  12. Dust Destruction in Fast Shocks of Core-Collapse Supernova Remnants in the Large Magellanic Cloud

    CERN Document Server

    Williams, B J; Reynolds, S P; Blair, W P; Ghavamian, P; Hendrick, S P; Long, K S; Points, S; Raymond, J C; Sankrit, R; Smith, R C; Winkler, P F; Williams, Brian J.

    2006-01-01

    We report observations with the MIPS instrument aboard the {\\it Spitzer Space Telescope} (SST) of four supernova remnants (SNRs) believed to be the result of core-collapse SNe: N132D (0525-69.6), N49B (0525-66.0), N23 (0506-68.0), and 0453-68.5. All four of these SNRs were detected in whole at 24 $\\mu$m and in part at 70 $\\mu$m. Comparisons with {\\it Chandra} broadband X-ray images show an association of infrared (IR) emission with the blast wave. We attribute the observed IR emission to dust that has been collisionally heated by electrons and ions in the hot, X-ray emitting plasma, with grain size distributions appropriate for the LMC and the destruction of small grains via sputtering by ions. As with our earlier analysis of Type Ia SNRs, models can reproduce observed 70/24 $\\mu$m ratios only if effects from sputtering are included, destroying small grains. We calculate the mass of dust swept up by the blast wave in these remnants, and we derive a dust-to-gas mass ratio of several times less than the often a...

  13. Current and Historic Sinkhole and Depression locations in Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — This dataset is all of the sinkholes and depressions that originated from the SSURGO spot data, and has been updated using LiDAR and historic photography to capture...

  14. Hydrogeology - SINKHOLE_INVENTORY_IN_KY_2011: Sinkhole inventory for southern Indiana and northern Kentucky (Indiana Geological Survey, Point Shapefile)

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This point shapefile was created to display in a geographic information system (GIS) mapped and modeled (indirectly mapped) sinkhole locations in southern Indiana...

  15. Genetic signatures of a demographic collapse in a large-bodied forest dwelling primate (Mandrillus leucophaeus)

    OpenAIRE

    Ting, Nelson; Astaras, Christos; Hearn, Gail; Honarvar, Shaya; Corush, Joel; Burrell, Andrew S; Phillips, Naomi; Morgan, Bethan J; Gadsby, Elizabeth L; Raaum, Ryan; Roos, Christian

    2012-01-01

    It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkey's geographic range is Lake Barombi Mbo, which has a well-documented palyno...

  16. Continuum viscoplastic simulation of a granular column collapse on large slopes: μ(I) rheology and lateral wall effects

    Science.gov (United States)

    Martin, N.; Ionescu, I. R.; Mangeney, A.; Bouchut, F.; Farin, M.

    2017-01-01

    We simulate here dry granular flows resulting from the collapse of granular columns on an inclined channel (up to 22°) and compare precisely the results with laboratory experiments. Incompressibility is assumed despite the dilatancy observed in the experiments (up to 10%). The 2-D model is based on the so-called μ (I ) rheology that induces a Drucker-Prager yield stress and a variable viscosity. A nonlinear Coulomb friction term, representing the friction on the lateral walls of the channel, is added to the model. We demonstrate that this term is crucial to accurately reproduce granular collapses on slopes ≳10°, whereas it remains of little effect on the horizontal slope. Quantitative comparison between the experimental and numerical changes with time of the thickness profiles and front velocity makes it possible to strongly constrain the rheology. In particular, we show that the use of a variable or a constant viscosity does not change significantly the results provided that these viscosities are of the same order. However, only a fine tuning of the constant viscosity (η =1 Pa s) makes it possible to predict the slow propagation phase observed experimentally at large slopes. Finally, we observed that small-scale instabilities develop when refining the mesh (also called ill-posed behavior, characterized in the work of Barker et al. ["Well-posed and ill-posed behaviour of the μ (I ) -rheology for granular flow," J. Fluid Mech. 779, 794-818 (2015)] and in the present work) associated with the mechanical model. The velocity field becomes stratified and the bands of high velocity gradient appear. These model instabilities are not avoided by using variable viscosity models such as the μ (I ) rheology. However we show that the velocity range, the static-flowing transition, and the thickness profiles are almost not affected by them.

  17. A large-scale dynamo and magnetoturbulence in rapidly rotating core-collapse supernovae.

    Science.gov (United States)

    Mösta, Philipp; Ott, Christian D; Radice, David; Roberts, Luke F; Schnetter, Erik; Haas, Roland

    2015-12-17

    Magnetohydrodynamic turbulence is important in many high-energy astrophysical systems, where instabilities can amplify the local magnetic field over very short timescales. Specifically, the magnetorotational instability and dynamo action have been suggested as a mechanism for the growth of magnetar-strength magnetic fields (of 10(15) gauss and above) and for powering the explosion of a rotating massive star. Such stars are candidate progenitors of type Ic-bl hypernovae, which make up all supernovae that are connected to long γ-ray bursts. The magnetorotational instability has been studied with local high-resolution shearing-box simulations in three dimensions, and with global two-dimensional simulations, but it is not known whether turbulence driven by this instability can result in the creation of a large-scale, ordered and dynamically relevant field. Here we report results from global, three-dimensional, general-relativistic magnetohydrodynamic turbulence simulations. We show that hydromagnetic turbulence in rapidly rotating protoneutron stars produces an inverse cascade of energy. We find a large-scale, ordered toroidal field that is consistent with the formation of bipolar magnetorotationally driven outflows. Our results demonstrate that rapidly rotating massive stars are plausible progenitors for both type Ic-bl supernovae and long γ-ray bursts, and provide a viable mechanism for the formation of magnetars. Moreover, our findings suggest that rapidly rotating massive stars might lie behind potentially magnetar-powered superluminous supernovae.

  18. A large scale dynamo and magnetoturbulence in rapidly rotating core-collapse supernovae

    CERN Document Server

    Mösta, Philipp; Radice, David; Roberts, Luke F; Schnetter, Erik; Haas, Roland

    2015-01-01

    Magnetohydrodynamic (MHD) turbulence is of key importance in many high-energy astrophysical systems, including black-hole accretion disks, protoplanetary disks, neutron stars, and stellar interiors. MHD instabilities can amplify local magnetic field strength over very short time scales, but it is an open question whether this can result in the creation of a large scale ordered and dynamically relevant field. Specifically, the magnetorotational instability (MRI) has been suggested as a mechanism to grow magnetar-strength magnetic field ($\\gtrsim 10^{15}\\, \\mathrm{G}$) and magnetorotationally power the explosion of a rotating massive star. Such stars are progenitor candidates for type Ic-bl hypernova explosions that involve relativistic outflows and make up all supernovae connected to long gamma-ray bursts (GRBs). We have carried out global 3D general-relativistic magnetohydrodynamic (GRMHD) turbulence simulations that resolve the fastest growing mode (FGM) of the MRI. We show that MRI-driven MHD turbulence in ...

  19. Detection of sinkhole precursors through SAR interferometry: radar and geological considerations

    CSIR Research Space (South Africa)

    Theron, Andre

    2017-06-01

    Full Text Available Sinkholes are an unpredictable geohazard that endanger life and property in dolomitic terrains. Sinkholes are a significant threat in Gauteng, South Africa’s most populated and urbanized province. Small-scale surface subsidence is frequently present...

  20. Sinkholes and caves related to evaporite dissolution in a stratigraphically and structurally complex setting, Fluvia Valley, eastern Spanish Pyrenees. Geological, geomorphological and environmental implications

    Science.gov (United States)

    Gutiérrez, Francisco; Fabregat, Ivan; Roqué, Carles; Carbonel, Domingo; Guerrero, Jesús; García-Hermoso, Fernando; Zarroca, Mario; Linares, Rogelio

    2016-08-01

    Evaporite karst and sinkhole development is analysed in a geologically complex area of NE Spain, including four evaporite units with different characteristics and affected by compressional and extensional tectonic structures. The exposed paleosinkholes, including remarkable Early Pleistocene paleontological sites, provide valuable information on the subsidence mechanisms and reveal the significant role played by interstratal karstification in the area. These gravitational deformation structures, including hectometre-scale bending folds and oversteepened normal faults, strongly suggest that the present-day compressional regime inferred in previous studies may be largely based on the analysis of non-tectonic structures. Two gypsum caves ca. 1 km long show that passages with restricted cross-sectional area may produce large breccia pipes and sinkholes thanks to the removal of breakdown boulders by high-competence episodic floods. Moreover, the upward progression of cave ceilings by paragenesis and condensation dissolution contributes to increase the probability of sinkhole occurrence. An inventory of 135 sinkholes together with their geological and geomorphological context has been developed. This data base has been used to infer several properties of the sinkholes with practical implications: a magnitude and frequency scaling relationship, spatial distribution patterns, dominant controlling factors and risk implications.

  1. A large-signal model for CMUT arrays with arbitrary membrane geometry operating in non-collapsed mode.

    Science.gov (United States)

    Satir, Sarp; Zahorian, Jaime; Degertekin, F Levent

    2013-11-01

    A large-signal, transient model has been developed to predict the output characteristics of a CMUT array operated in the non-collapse mode. The model is based on separation of the nonlinear electrostatic voltage-to-force relation and the linear acoustic array response. For modeling of linear acoustic radiation and crosstalk effects, the boundary element method is used. The stiffness matrix in the vibroacoustics calculations is obtained using static finite element analysis of a single membrane which can have arbitrary geometry and boundary conditions. A lumped modeling approach is used to reduce the order of the system for modeling the transient nonlinear electrostatic actuation. To accurately capture the dynamics of the non-uniform electrostatic force distribution over the CMUT electrode during large deflections, the membrane electrode is divided into patches shaped to match higher order membrane modes, each introducing a variable to the system model. This reduced order nonlinear lumped model is solved in the time domain using commercial software. The model has two linear blocks to calculate the displacement profile of the electrode patches and the output pressure for a given force distribution over the array. The force-to-array-displacement block uses the linear acoustic model, and the Rayleigh integral is evaluated to calculate the pressure at any field point. Using the model, the time-domain transmitted pressure can be simulated for different large drive signal configurations. The acoustic model is verified by comparison to harmonic FEA in vacuum and fluid for high- and low-aspect-ratio membranes as well as mass-loaded membranes. The overall software model is verified by comparison to transient 3-D finite element analysis and experimental results for different large drive signals, and an example for a phased array simulation is given.

  2. Study on vertical permeability regularity and collapsibility of a large thickness loess foundation by in-situ testing

    Directory of Open Access Journals (Sweden)

    Kong Yang

    2016-01-01

    Full Text Available In many regions in China there is a wide distribution of dead-weight collapsible loess that experience frequent disasters resulting in enormous losses to national property. Loess collapsibility is the leading cause of disasters in loess areas. Many international scholars are working collaboratively to avoid property losses and human casualties caused by the collapsible loess. Loess collapsibility is closely related to the vertical permeability regularity, so the vertical permeability regularity should be the first critical factor taken into account in studying loess collapsibility. In Lanzhou city, the in-situ soaking test is carried out on an unsaturated natural loess foundation with a thickness of 36.5m, the test pit diameter is 40m, TDR moisture probes are embedded, and the test lasts 282 days. During the test, the vertical migration of water is observed and the temporal and spatial variations of volumetric water content are considered. In the detailed research of the vertical permeability regularity, the relation between permeability regularity and collapsibility are discussed. For shallow layer soil, soil volumetric water content reaches saturation at wetting front, the water flows downward due to gravity and the infiltration rate is larger. For deep layer soil, the moisture will increase because of the upper soil permeability and its own suction, but, due to soil compression caused by the occurrence of the upper soil collapsibility, the infiltration rate is significantly reduced. The temporal and spatial variations of water volumetric content can be used to determine whether a loess collapsible deformation has occurred. The limit permeability depth in this test is 25m, and the limit permeability depth can also be served as the collapsibility evaluation depth of the unsaturated natural Malan loess foundation.

  3. Automated delineation of karst sinkholes from LiDAR-derived digital elevation models

    Science.gov (United States)

    Wu, Qiusheng; Deng, Chengbin; Chen, Zuoqi

    2016-08-01

    Sinkhole mapping is critical for understanding hydrological processes and mitigating geological hazards in karst landscapes. Current methods for identifying sinkholes are primarily based on visual interpretation of low-resolution topographic maps and aerial photographs with subsequent field verification, which is labor-intensive and time-consuming. The increasing availability of high-resolution LiDAR-derived digital elevation data allows for an entirely new level of detailed delineation and analyses of small-scale geomorphologic features and landscape structures at fine scales. In this paper, we present a localized contour tree method for automated extraction of sinkholes in karst landscapes. One significant advantage of our automated approach for sinkhole extraction is that it may reduce inconsistencies and alleviate repeatability concerns associated with visual interpretation methods. In addition, the proposed method has contributed to improving the sinkhole inventory in several ways: (1) detection of non-inventoried sinkholes; (2) identification of previously inventoried sinkholes that have been filled; (3) delineation of sinkhole boundaries; and (4) characterization of sinkhole morphometric properties. We applied the method to Fillmore County in southeastern Minnesota, USA, and identified three times as many sinkholes as the existing database for the same area. The results suggest that previous visual interpretation method might significantly underestimate the number of potential sinkholes in the region. Our method holds great potential for creating and updating sinkhole inventory databases at a regional scale in a timely manner.

  4. Study on Sinkhole Attacks in Wireless Ad hoc Networks

    Directory of Open Access Journals (Sweden)

    GAGANDEEP

    2012-06-01

    Full Text Available Wireless ad hoc network is a collection of wireless mobile nodes that dynamically self-organize in arbitrary and temporary network topologies. As compared to conventional network, wireless ad hocnetwork are more vulnerable to the security attacks. The nature and structure of wireless ad hoc network makes it very attractive to attackers, because there is no fixed infrastructure and administrativeapproach in it. “Sinkhole attack” is one of the severe attacks in this type of network; this makes trustable nodes to malicious nodes that result in loss of secure information. This paper focuses on sinkhole attacks on routing protocols such as DSR, AODV. To overcome the problems occur due to sinkhole we discuss about Security-aware routing (SAR which helps to reduce the impact of such attack.

  5. Improved Dead Sea sinkhole site characterization at Ghor Al Haditha, Jordan, based on repeated shear wave reflection seismic profiling

    Science.gov (United States)

    Polom, Ulrich; Alrshdan, Hussam; Al-Halbouni, Djamil; Sawarieh, Ali; Dahm, Torsten; Krawczyk, CharLotte M.

    2016-04-01

    In October 2014 a high-resolution shallow shear wave reflection seismic survey was carried out at the Dead Sea sinkhole site Ghor Al Haditha, Jordan. It extended a survey undertaken in 2013, also in order to gather time-lapse profiles. In the framework of the DEad SEa Research Venue (DESERVE), a virtual institute of the Helmholtz Association and international partners, this investigation is part of a cross-disciplinary and cooperative international project of the Helmholtz Centers KIT, GFZ, and UFZ. At the investigation site, characterized by alluvial fan deposits, ongoing subsidence and sinkhole processes in the subsurface create massive reshaping of farming areas, including the destruction of housings, industrial sites, and infrastructure. The sinkhole hazard at the Dead Sea is significant, since similar processes are observed at several coastal segments of the Dead Sea. The new survey (in total 2.1 profile km) was targeted to improve the knowledge about the subsurface structures and to confine the results of the initial survey (1.8 km profile km), with respect to the presence or non-presence of a massive salt layer proposed at nearly 40 m depth. This salt layer is the central part of a widely established process hypothesis to generate shallow cavities by salt subrosion, which subsequently collapse to sinkholes at the surface. Results of the initial survey carried out in 2013 highlighted a new process hypothesis of subsurface mass transport by Dead Sea mud mobilization enclosed in the alluvial fan, so that an extended survey was undertaken in 2014. This, indeed, confirmed that there are no reflection seismic signal responses that would be expected to occur in the presence of a massive salt layer. Since evaluation of both hypothesis by new drilling could not be carried out due to safety reasons and permissions, it remained unclear which hypothesis is valid for the investigation site. However, we combined the 2013 and 2014 reflection seismic profiles and the

  6. Causes and consequences of the sinkhole at El Trébol of Quito, Ecuador - implications for economic damage and risk assessment

    Science.gov (United States)

    Toulkeridis, Theofilos; Rodríguez, Fabián; Arias Jiménez, Nelson; Simón Baile, Débora; Salazar Martínez, Rodolfo; Addison, Aaron; Carreón Freyre, Dora; Mato, Fernando; Díaz Perez, Carmen

    2016-09-01

    The so-called El Trébol is a critical road interchange in Quito connecting the north and south regions of the city. In addition, it connects Quito with the highly populated Los Chillos Valley, one of the most traveled zones in the Ecuadorian capital. El Trébol was constructed in the late 1960s in order to resolve the traffic jams of the capital city and for that purpose the Machángara River was rerouted through an underground concrete box tunnel. In March 2008, the tunnel contained a high amount of discarded furniture that had been impacting the top portion of the tunnel, compromising the structural integrity. On 31 March 2008 after a heavy rainfall a sinkhole of great proportions formed in the Trébol traffic hub. In the first few minutes, the sinkhole reached an initial diameter of 30 m. The collapse continued to grow in the following days until the final dimensions of 120 m in diameter and some 40 m of depth, revealing the Machángara River at the base of the sinkhole.A state of emergency was declared. The cause of the sinkhole was a result of the lack of monitoring of the older subterranean infrastructure where trash had accumulated and damaged the concrete tunnel that channelized the Machángara River until it was worn away for a length of some 20 m, leaving behind the sinkhole and the fear of recurrence in populated areas.With the intent to understand the causes and consequences of this sinkhole event, rainfall data are shown together with hydrogeological characteristics and a view back to the recent history of sinkhole lineation or arrangement of the city of Quito. The economic impact is also emphasized, where the direct costs of the damage and the reconstruction are presented and compared to indirect costs associated with this socio-natural disaster. These analyses suggest that the costs of indirect financial damage, like time loss or delay, and subsequent higher expenses for different types of vehicles, are equivalent to many times the costs of the

  7. Tephra deposits associated with a large lava dome collapse, Soufrière Hills Volcano, Montserrat, 12 15 July 2003

    Science.gov (United States)

    Edmonds, Marie; Herd, Richard A.; Strutt, Michael H.

    2006-05-01

    The 12-13 July 2003 dome collapse at Soufrière Hills Volcano, Montserrat, was the largest event of its kind during the eruption thus far (1995-2005), involving the removal of 210 million m 3 of the lava dome complex over 18 h. Less than 2% of the total volume of material involved in the dome collapse was deposited on land. A pyroclastic density current deposit alongshore and inland from the Tar River Fan was generated from a single blast originating at the shoreline. The blast was caused by the interaction of pyroclastic flows with seawater. We propose that at the peak of the lava dome collapse, a sharp increase in the volume flux of pyroclastic flows caused substantial displacement of seawater from the shoreline, followed by inrush of seawater when the flux decreased a few minutes later. The tsunami allowed penetration of seawater into the main body of the pyroclastic flow at the shoreline, which led to explosive fragmentation of pyroclastic blocks. Tephra fall deposits accumulated at a high rate on Montserrat, causing extensive damage to vegetation and buildings. Their stratigraphy recorded fallout from high co-pyroclastic flow clouds, from a vulcanian explosion cloud at the peak in collapse rate (caused by the fragmentation of degassed lava dome) and from four vulcanian explosion clouds after the dome collapse (caused by fragmentation of bubbly magma in the conduit). The total tephra fall volume is estimated at 10-20 million m 3.

  8. Spatial analysis of geologic and hydrologic features relating to sinkhole occurrence in Jefferson County, West Virginia

    Science.gov (United States)

    Doctor, Daniel H.; Doctor, Katarina Z.

    2012-01-01

    In this study the influence of geologic features related to sinkhole susceptibility was analyzed and the results were mapped for the region of Jefferson County, West Virginia. A model of sinkhole density was constructed using Geographically Weighted Regression (GWR) that estimated the relations among discrete geologic or hydrologic features and sinkhole density at each sinkhole location. Nine conditioning factors on sinkhole occurrence were considered as independent variables: distance to faults, fold axes, fracture traces oriented along bedrock strike, fracture traces oriented across bedrock strike, ponds, streams, springs, quarries, and interpolated depth to groundwater. GWR model parameter estimates for each variable were evaluated for significance, and the results were mapped. The results provide visual insight into the influence of these variables on localized sinkhole density, and can be used to provide an objective means of weighting conditioning factors in models of sinkhole susceptibility or hazard risk.

  9. Actual extension of sinkholes: Considerations about geophysical, geomorphological, and field inspection techniques in urban planning projects in the Ebro basin (NE Spain)

    Science.gov (United States)

    Pueyo Anchuela, Ó.; Pocoví Juan, A.; Casas-Sainz, A. M.; Ansón-López, D.; Gil-Garbi, H.

    2013-05-01

    Aerial photographs, historical cartographies, and field inspection are useful tools in urban planning design on mantled karst because they permit a wide time interval to be analyzed. In the case of Zaragoza city, several works have confirmed the interest of these approaches in configuring the urban planning code and therefore represent a promising technique. Nevertheless, some caveats should be taken into account when using this kind of information. A detailed analysis is presented comparing (in a case study from the surroundings of Zaragoza) geomorphological, historical analysis, and field inspection with geophysical data. Field inspection in a noncultivated area permits the constraint of the presence of karst indicators below the geomorphological resolution of aerial photographs and shows results consistent with geophysical surveys. The studied case shows an inner zone coinciding with the sinkhole mapped from aerial photographs that correlates with changes in the position of the substratum and changes in thickness of alluvial sediments. The integrated analysis permits us to define an external subsidence ring around the geomorphological sinkhole whose surface is twice the size of the inner zone. This outer ring is indicated by geometrical changes in GPR profiles, increases of thickness of the conductive shallower unit toward the collapse, and small collapses on marginal cracks. These results support the higher extension of karst hazards linked to sinkholes with respect to their geomorphological expression and the needed detailed analysis to constrain the real sinkhole size or the use of security radii surrounding this surficial evidence when geomorphological data is used for the hazard analyses or the urban planning at karstic zones.

  10. Combining Geological and Geophysical Surveys with Cave Explorations for the Assessment of the Sinkhole Susceptibility in Coastal Areas

    Science.gov (United States)

    Margiotta, Stefano; Negri, Sergio; Pagliara, Antonio; Parise, Mario; Quarta, Tatiana A. M.

    2013-04-01

    the required resolution and depth of penetration, but also because major pitfalls may arise in such geologically complex areas, from the speculative interpretation of geophysical anomalies as geological features. Data integration from different geophysical methods is essential to remove these interpretation ambiguities, caused by large near-surface gradients and heterogeneities in the soil properties, as well as by water table. In the case of Torre Castiglione, we illustrate here an investigation procedure consisting in the sequential application and integrated interpretation of several geophysical methods (Electrical Resistivity Tomography and Seismic Reflection measurements) for locating sinkholes and for the characterization of the subsoil. Geophysical surveys allowed us to obtain a detailed geological model in the study area, cross-checked by the outcomes of several boreholes, and to detect the presence of underground voids, that are characterized by low resistivity values (<100 ohm*m) and a seismic velocity of about 1500 m/s.

  11. Analysis of the damage caused by natural and anthropogenic sinkholes in Italy, on the basis of a nation-wide chronological catalogue

    Science.gov (United States)

    Vennari, Carmela; Guzzetti, Fausto; Marchesini, Ivan; Parise, Mario; Salvati, Paola

    2013-04-01

    where alluvial sediments are present; they definitely have a lower impact on the built-up environment, mostly affecting rural areas. Trigger of the sinkholes can be due to rainfall or seismic events, or to man-made works (realization and/or maintenance of pipelines, quarrying activities, etc.). Further, other important features of sinkholes are shown in the catalogue, covering morphometric characters (width and depth), lithologies involved, and occurrence as first collapse or as a re-activation of a former sinkhole. The regions with the highest number of documented sinkholes are: Campania (246), Sicily (117), Latium (107) and Apulia (88). Only two Italian regions (Molise and Valle d'Aosta) so far are not present in the catalogue with any documented sinkhole. Sinkholes have repeatedly caused in Italy heavy damage to the society. Water supply systems, sewer systems, roads and other communication routes were often damaged; in addition, damage and/or collapse of buildings, with the deriving casualties, had also to be registered in several circumstances. In the time span covered by the catalogue, casualties (which include deaths, missing persons, and injured people) are reported in 3.5 % of the events, whilst damage are documented in 32.6 % of the cases. The numbers above are underestimated, because most of the sources typically provide generic information, that often simply refer to the occurrence of an unspecified number of deaths and injured people (especially as regards the oldest reports). This, together with the ancient date of many events, is at the origin of the difficulty in precisely quantifying the intensity of the sinkholes, in terms of their effects on the society. Most of the damage was registered in central-southern Italy, and in particular in the aforementioned regions. This is partly due to the geological setting of these territories, and to availability of specific studies on sinkholes carried out in these regions (especially in the towns of Palermo, Naples

  12. Monitoring of sinkholes and subsidence affecting the Jordanian coast of the Dead Sea through Synthetic Aperture Radar data and last generation Sentinel-1 data

    Science.gov (United States)

    Tessari, Giulia; Riccardi, Paolo; Lecci, Daniele; Pasquali, Paolo; Floris, Mario

    2017-04-01

    Since the mid-1980s the coast of the Dead Sea is affected by sinkholes occurring over and around the emerged mud and salt flats. Strong subsidence and landslides also affect some segments of the coast. Nowadays, several thousands of sinkholes attest that the degradation of the Dead Sea coast is worsening. Furthermore, soil deformations are interesting the main streets running along both the Israeli and Jordanian sides of the Dead Sea. These hazards are due to the dramatic dropping of the Dead Sea level, characterized by an increasing rate from about 60 cm/yr in the 1970s up to 1 m/yr in the 2000s, which provokes a lowering of the fresh-saline groundwater interface, replacing the hypersaline groundwater with fresh water and causing a consequent erosion of the subsurface salt layers. Subsidence, sinkholes, river erosion and landslides damage bridges, roads, dikes, houses, factories worsening this ongoing disaster. One of the most emblematic effects is the catastrophic collapse of a 12-km newly constructed dyke, located on the Lisan Peninsula (Jordan), occurred in 2000. Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques and Advanced stacking DInSAR techniques (A-DInSAR) were applied to investigate sinkholes and subsidence affecting the Jordanian coast of the Dead Sea. The use of SAR data already proof to be efficient on the risk management of the area, allowing to identify a vulnerable portion of an Israeli highway, averting a possible collapse. Deformation analysis has been focused on the Ghor Al Haditha area and Lisan peninsula, located in the South-Eastern part of the lake coast. The availability of a huge database of SAR data, since the beginning of the 90s, allowed to observe the evolution of the displacements which are damaging this area. Furthermore, last generation Sentinel-1 data, acquired by the ESA mission, were processed to obtain information about the recent evolution of the subsidence and sinkholes affecting the study area, from

  13. Collapse of axion stars

    Science.gov (United States)

    Eby, Joshua; Leembruggen, Madelyn; Suranyi, Peter; Wijewardhana, L. C. R.

    2016-12-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.

  14. Collapse of axion stars

    Energy Technology Data Exchange (ETDEWEB)

    Eby, Joshua [Department of Physics, University of Cincinnati,2600 Clifton Ave, Cincinnati, OH, 45221 (United States); Fermi National Accelerator Laboratory,P.O. Box 500, Batavia, IL, 60510 (United States); Leembruggen, Madelyn; Suranyi, Peter; Wijewardhana, L.C.R. [Department of Physics, University of Cincinnati,2600 Clifton Ave, Cincinnati, OH, 45221 (United States)

    2016-12-15

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. In the last moments of collapse, the binding energy of the axion star grows rapidly, and we provide evidence that a large amount of its energy is lost through rapid emission of relativistic axions.

  15. Finite-Element Modeling of the Vredefort Impact Structure with Implications for the Collapse and Modification Stage of Large Crater Formation

    Science.gov (United States)

    Turtle, E. P.; Melosh, H. J.

    1996-03-01

    While the morphology of large impact craters has been studied in some detail, the processes which generate structures such as central peaks, peak rings, and multiple external rings are still poorly understood. We are using finite-element modeling to investigate the collapse and relaxation phase of impact crater formation with the specific intention of determining the mechanisms necessary to reproduce the subsurface structure observed at Vredefort in South Africa. We have incorporated the rheologic parameters for a simplified stratigraphy into a mesh which has been modified to reflect the displacements that occur during the crater excavation phase. The modeling of the subsequent relaxation of this transient crater has generated up-turning of layers at stratigraphic boundaries similar to that observed at Vredefort. In addition, the stresses produced are consistent with the collapse of the transient crater wall in the formation of a complex crater.

  16. Composition, geometry, and emplacement dynamics of a large volcanic island landslide offshore Martinique: From volcano flank-collapse to seafloor sediment failure?

    Science.gov (United States)

    Brunet, Morgane; Le Friant, Anne; Boudon, Georges; Lafuerza, Sara; Talling, Peter; Hornbach, Matthew; Ishizuka, Osamu; Lebas, Elodie; Guyard, Hervé

    2016-03-01

    Landslides are common features in the vicinity of volcanic islands. In this contribution, we investigate landslides emplacement and dynamics around the volcanic island of Martinique based on the first scientific drilling of such deposits. The evolution of the active Montagne Pelée volcano on this island has been marked by three major flank-collapses that removed much of the western flank of the volcano. Subaerial collapse volumes vary from 2 to 25 km3 and debris avalanches flowed into the Grenada Basin. High-resolution seismic data (AGUADOMAR-1999, CARAVAL-2002, and GWADASEIS-2009) is combined with new drill cores that penetrate up to 430 m through the three submarine landslide deposits previously associated to the aerial flank-collapses (Site U1399, Site U1400, Site U1401, IODP Expedition 340, Joides Resolution, March-April 2012). This combined geophysical and core data provide an improved understanding of landslide processes offshore a volcanic island. The integrated analysis shows a large submarine landslide deposit, without debris avalanche deposits coming from the volcano, comprising up to 300 km3 of remobilized seafloor sediment that extends for 70 km away from the coast and covers an area of 2100 km2. Our new data suggest that the aerial debris avalanche deposit enter the sea but stop at the base of submarine flank. We propose a new model dealing with seafloor sediment failures and landslide propagation mechanisms, triggered by volcanic flank-collapse events affecting Montagne Pelée volcano. Newly recognized landslide deposits occur deeper in the stratigraphy, suggesting the recurrence of large-scale mass-wasting processes offshore the island and thus, the necessity to better assess the associated tsunami hazards in the region.

  17. Collapsed Lung

    Science.gov (United States)

    A collapsed lung happens when air enters the pleural space, the area between the lung and the chest wall. If it is a ... is called pneumothorax. If only part of the lung is affected, it is called atelectasis. Causes of ...

  18. Modeling karst spring hydrograph recession based on head drop at sinkholes

    Science.gov (United States)

    Li, Guangquan; Goldscheider, Nico; Field, Malcolm S.

    2016-11-01

    Spring discharge often responds to rainfall with a rapid increase followed by a slower recession, and the mode of recession is often exponential-like. We propose a new model of the response of spring discharge to rainfall based on the square law for turbulent conduit flow. The new non-exponential model is compared against the exponential model under specific constraints. A hydrograph of St. Marks River in Florida is used to illustrate that when the change in "sinkhole head" (defined as the hydraulic head at the upstream end of the karst conduit connected to the spring) is relatively small, the solution of the new model is close to that of the exponential model, which extends the validity and application of the exponential solution. When the change in sinkhole head is very large, the solutions from the two models clearly differ from each other. Limitations of the non-exponential model are analyzed by simulation of a hydrograph observed downstream of Wakulla Springs. It is concluded that both solutions are applicable when spring response is smaller than or comparable to the base flow, but are nonphysical when the response is much larger than the base discharge.

  19. Plant distribution-altitude and landform relationships in karstic sinkholes of Mediterranean region of Turkey.

    Science.gov (United States)

    Ozkan, Kürsad; Gulsoy, Serkan; Mert, Ahmet; Ozturk, Munir; Muys, Bart

    2010-01-01

    The purpose of this study was to investigate the relationships between the plant distribution and the altitude-shape-size characteristics of sinkholes, and the landform characteristics inside sinkholes in the Mediterranean region of Turkey. Block kriging, Factor analysis, Cluster Analysis and Detrended Correspondence Analysis were performed. The sinkhole type and altitudinal zone were found to be the significant factors affecting the plant distribution. However, the sinkhole type was more important than the altitudinal zone. Hence, the sinkholes were first subdivided into groups according to types and then the groups were divided into subgroups according to the altitudinal zones. Consequently, 4 groups were defined; A-type sinkholes [1400-1550 m (A1), 1550-1700 m (A2)] and B-type sinkholes [1400-1550 (B1), 1550-1700 m (B2)]. The B-type was wider vertically and shorter horizontally than A-type sinkholes. Significant differences were found between the plant distribution and slope position inside the sinkholes. Plant distribution in the lower slopes was different from that in the flats and ridges in the B1 sub-type of B-type. Plant distribution in B2 subtype was different among the slope positions (ridge, middle slope, lower slope, and flat). Although distribution of plants is different in different parts (ridges, upper slope, middle slope, lower slope and basal flats) of A sinkhole, the differences between the parts of intermediate slope position are not significant. A high plant variability along short distances in the sinkholes was observed in the study area. That is why the site of sinkholes have a big potential for the distribution of many species. Hence, the area must be separated as strictly protected zone.

  20. 3D numerical modeling of an anthropogenic sinkhole in the Marsala area of western Sicily

    Science.gov (United States)

    Bonamini, Marco; Di Maggio, Cipriano; Lollino, Piernicola; Madonia, Giuliana; Parise, Mario; Vattano, Marco

    2013-04-01

    The Marsala area (western Sicily) is characterized by the presence of a Lower Pleistocene (Calabrian) calcarenite succession (Marsala Calcarenite Fm). It can be divided into three lithofacies that show the regressive evolution of the depositional system: a) coarse to fine yellow bio- and lithoclastic calcarenites, b) sands, and c) gray sandy clays. At least 80 m-thick, this succession gently dips (5-10°) towards the south and the south-west. Locally, the Marsala Calcarenite may be covered by Middle and Upper Pleistocene marine terraced deposits. The town of Marsala presents several historical quarries for the extraction of this building material. Many of them were excavated underground, at depth ranging from a few meters to about 25 m, and are arranged in one or two levels, following the galleries and pillars excavation technique. With time, the underground quarries have been progressively abandoned due to the high costs of extraction, as well as to the dangers and difficulties encountered in working underground. Since the 1960's the quarries, as a matter of fact, have been affected by several instability processes for the decay of the physical and mechanical properties of the calcarenite rock mass and the interaction with the groundwater. Such instability processes are represented by collapses and deformations of vaults and pillars. These phenomena often propagate upward reaching the topographic surface and forming sinkholes which may likely affect and severely damage the built-up areas above. In particular, two case studies of sinkholes related to different underground quarries have been already described by the Authors in a previous contribution at EGU 2012, also integrated by a two-dimensional numerical study. The aim of the present work is to develop a three-dimensional numerical analysis aimed at describing the most significant processes and factors responsible of the instability processes, as well as to investigate the three-dimensional features of the same

  1. Collapse of Axion Stars

    CERN Document Server

    Eby, Joshua; Suranyi, Peter; Wijewardhana, L C R

    2016-01-01

    Axion stars, gravitationally bound states of low-energy axion particles, have a maximum mass allowed by gravitational stability. Weakly bound states obtaining this maximum mass have sufficiently large radii such that they are dilute, and as a result, they are well described by a leading-order expansion of the axion potential. Heavier states are susceptible to gravitational collapse. Inclusion of higher-order interactions, present in the full potential, can give qualitatively different results in the analysis of collapsing heavy states, as compared to the leading-order expansion. In this work, we find that collapsing axion stars are stabilized by repulsive interactions present in the full potential, providing evidence that such objects do not form black holes. These dense configurations, which are the endpoints of collapse, have extremely high binding energy, and as a result, decay through number changing $3\\,a\\rightarrow a$ interactions with an extremely short lifetime.

  2. Hydrogeology - SINKHOLE_DENSITY_KM2_IN_KY_2011: Density of sinkholes per square kilometer in southern Indiana and Kentucky, Derived from the 2011 Sinkhole Inventory (Indiana Geological Survey, 30-Meter TIFF Image)

    Data.gov (United States)

    NSGIC State | GIS Inventory — This raster file was created to display in a geographic information systems (GIS) the density in square kilometers of mapped and modeled (indirectly mapped) sinkhole...

  3. Collapsing Containers.

    Science.gov (United States)

    Brown, Justina L.; Battino, Rubin

    1994-01-01

    Describes variations on atmospheric pressure demonstrations and some systematic studies. Demonstrations use steam, generated either externally or internally to the container, to sweep out residual air. Preferred vessels collapsed slowly. Demonstrations use plastic milk jugs set in layers of aluminum foil, pop bottles immersed in 4-L beakers…

  4. Alba Patera Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This image of the Alba Patera region has both lava tube collapse pits (running generally east/west) and subsidence related collapse within structural grabens. Image information: IR instrument. Latitude 26.9, Longitude 256.5 East (103.5 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  5. Lava Tube Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in the southern hemisphere of Mars. They are likely lava tube collapse pits related to flows from Hadriaca Patera. Image information: VIS instrument. Latitude -36.8, Longitude 89.6 East (270.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D

  6. Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions.

    Science.gov (United States)

    Schoonover, Jon E; Crim, Jackie F; Williard, Karl W J; Groninger, John W; Zaczek, James J; Pattumma, Klairoong

    2015-09-01

    Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.

  7. Utilizing NASA Earth Observations to Monitor Sinkhole Development and Identify Risk Areas in Dougherty County, Georgia

    Science.gov (United States)

    Cahalan, M. D.; Berry, K.; Amin, M.; Xu, W.; Hu, T.; Milewski, A.

    2015-12-01

    Located in southwest Georgia, Dougherty County has a growing populace in an agricultural region that relies heavily on groundwater resources. Partly due to escalated groundwater extraction, this area has experienced an increase in sinkhole development over the last decade. Sinkholes pose a threat to infrastructure development, groundwater pollution, and land use operations. The NASA DEVELOP Georgia Disasters and Water Resources team partnered with the City of Albany and Dougherty County Planning and Development Services (PDS) and the Southwest Georgia Water Resources Task Force (SGWRTF) to assess past sinkhole development and identify areas susceptible to future sinkhole formation. Sinkhole mapping was completed utilizing a time-series of elevation data (1999 - 2011) from NASA's SRTM and ASTER missions, as well as European Remote-Sensing (ERS-1 and 2) satellite-derived elevation data. The sinkhole inventory maps and spatial statistical techniques (i.e., geographically-weighted regression) were employed to quantify the factors most influential in sinkhole development. With those results, the susceptibility of every area within Dougherty County to future sinkhole formation was identified. The results of this applied science project will enable the PDS and SGWRTF to make informed decisions on current and future land use, safe infrastructure development, and sustainable water resource management.

  8. Caldera types and collapse styles

    Science.gov (United States)

    Aguirre-Diaz, G. J.

    2008-12-01

    Three main types of collapse calderas can be defined, 1) summit caldera, 2) classic caldera, and 3) graben caldera. Summit calderas are those formed at the top of large volcanoes and are related to relatively small- volume pyroclastic products that include plinian fallouts and ignimbrites, such as Crater Lake, Las Cañadas, and Somma-Vesuvio. Classic calderas are semi-circular to irregular-shaped large structures, several km in diameter that are related to relatively large-volume pyroclastic products including pumice fallouts and widespread ignimbrites, such as Long-Valley, Campi Flegrei, and Los Humeros. Graben calderas are explosive volcano-tectonic collapse structures from which large-volume, ignimbrite-forming eruptions occurred through several vents along the graben walls and the intra-graben block faults causing the collapse of the graben or of a sector of the graben. The main products of graben calderas are surge-deposits and large-volume widespread ignimbrite sheets. Pumice fallouts are practically absent. Examples include the Sierra Madre Occidental in Mexico, La Pacana (Andes), Catalan Pyrenees, and perhaps Scafell (United Kingdom). Any of the three caldera types mentioned above could have collapsed at least in three different ways, 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.

  9. Collapsed City

    DEFF Research Database (Denmark)

    Allen, Nacho Ruiz

    2015-01-01

    Currently, when the socio-economic circumstances seem to announce another change of cultural paradigm for the 21st century, the interest in the urban fact seems to have been renewed in architecture. However, this is no longer focused on models of growth and efficiency, as happened in the 70s....... Nowadays the situation is quite different. The enthusiasm for the economic growth which had characterized late capitalism and much of the postmodern cultural production has disappeared, and has given place to some global unease on a possible system collapse. Once the economy does not grow, but threatens...... with its imminent breakdown, the architectural interests have shifted to urban environments like Tokyo, Detroit, Lagos or Rio de Janeiro; places that demonstrate, somehow, an urban culture of collapse....

  10. Ascraeus Mons Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found on the flank of Ascraeus Mons. The pits and channels are all related to lava tube formation and emptying. Image information: IR instrument. Latitude 8, Longitude 253.9 East (106.1 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal

  11. Sulci Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. This is the Noctis Labyrinthus region of Mars. These collapse pits are forming along structural fractures that are allowing the release of volatiles from the subsurface. This is believed to be the way that chaos terrain forms on Mars. This area represents the early stage of chaos formation. Image information: VIS instrument. Latitude -12.6, Longitude 264 East (96 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project

  12. Tharsis Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found within the extensive lava flows of the Tharsis region. They are related to lava tubes, likely coming from Ascraeus Mons. Image information: VIS instrument. Latitude 22.8, Longitude 266.8 East (93.2 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington

  13. Tractus Catena Collapse Pits

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found in graben located in Tractus Catena. These features are related to subsidence after magma chamber evacuation of Alba Patera. Image information: VIS instrument. Latitude 35.8, Longitude 241.7 East (118.3 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science

  14. The expected collapse of a large dam Saddam Dam in Iraq; Un grand barrage a haut risque Saddam Dam en Irak

    Energy Technology Data Exchange (ETDEWEB)

    Mesny, M. [Conseil general du genie rural, des eaux et des forets, 75 - Paris (France)

    2004-07-01

    The Saddam dam is a very large dam in Iraq on the Tigris River, 80 kilometres upstream from the city of Mosul. It is a fill dam with a clayey silt core. The height of the dam is 120 meters and the capacity of the reservoir is 11 billions m3. But this dam has been built on foundations of gypsum that is a rock soluble in water. The impounding of the reservoir in 1986 has shown that, in spite of the grout curtain, substantial seepage has occurred (up to 1.4 m{sup 3}/s), as well as the dissolution of minerals from foundations (up to 80 tons per day). The substantial increase in permeability and seepage through the dam foundations results in a severe concern about the stability of the dam. The program of injection has been stopped in 1991, due to the circumstances. So there is a real risk that this dam would collapse through a quickly developing leak in the dike, resulting in the devastation of the rich agricultural valley of the Tigris River and in potential human losses at Mosul. A 10 to 20-meter high submersion wave would reach this town 3 to 4 hours after the collapse of the dam. An international action is urgently required to check the conditions of the dam and to propose remedial solutions, which may be a 120-meter deep concrete wall down to the calcareous floor existing below the soluble layers of the foundations. (author)

  15. On the Flow and Fluidization of Granular Materials: Applications to Large Lunar Craters, Cliff Collapses and Asteroid Shapes

    Science.gov (United States)

    Holsapple, K. A.

    2011-03-01

    About flows of granular materials and assumptions about fluidization mechanisms to explain large flat craters and landslide run outs. No such mechanisms are needed, the reasons and examples are given.

  16. Study of DSR and AODV under Sinkhole Attack and Its Proposed Prevention Technique

    Directory of Open Access Journals (Sweden)

    Winnie Main

    2014-03-01

    Full Text Available Mobile Ad-hoc Networks (MANET are wireless mobile nodes that communicate without any predefined infrastructure. This allows MANETs to be easily setup in geographical and terrestrial constraints. To achieve this kind of communication MANET routing protocols play an important role. Two routing protocols, DSR and AODV are studied in detail. This basic trait of a MANET makes its routing protocols very vulnerable to security attacks. One such attack is the ‘Sinkhole’ attack which lures packets towards the sinkhole node. A malicious Sinkhole node severely degrades the network once the attack is in progress. This paper describes two of the popular MANET routing protocols, DSR and AODV and the sinkhole attack on these protocols. Prior research carried out to prevent the sinkhole attack is analyzed. Multiple procedures are documented to prevent and mitigate the problem of Sinkhole in MANETs. The proposed solution relies on tackling the sequence number discontinuity to contain Sinkhole attacks. A prevention technique is proposed that relies on the fact that the sequence number discontinuity if tackled can go a long way in containing Sinkhole attacks.

  17. Impact Crater Collapse

    Science.gov (United States)

    Melosh, H. J.; Ivanov, B. A.

    The detailed morphology of impact craters is now believed to be mainly caused by the collapse of a geometrically simple, bowl-shaped "transient crater." The transient crater forms immediately after the impact. In small craters, those less than approximately 15 km diameter on the Moon, the steepest part of the rim collapses into the crater bowl to produce a lens of broken rock in an otherwise unmodified transient crater. Such craters are called "simple" and have a depth-to-diameter ratio near 1:5. Large craters collapse more spectacularly, giving rise to central peaks, wall terraces, and internal rings in still larger craters. These are called "complex" craters. The transition between simple and complex craters depends on 1/g, suggesting that the collapse occurs when a strength threshold is exceeded. The apparent strength, however, is very low: only a few bars, and with little or no internal friction. This behavior requires a mechanism for temporary strength degradation in the rocks surrounding the impact site. Several models for this process, including acoustic fluidization and shock weakening, have been considered by recent investigations. Acoustic fluidization, in particular, appears to produce results in good agreement with observations, although better understanding is still needed.

  18. Large-scale range collapse of Hawaiian forest birds under climate change and the need 21st century conservation options

    Science.gov (United States)

    Fortini, Lucas; Vorsino, Adam E.; Amidon, Fred A.; Paxton, Eben; Jacobi, James D.

    2015-01-01

    Hawaiian forest birds serve as an ideal group to explore the extent of climate change impacts on at-risk species. Avian malaria constrains many remaining Hawaiian forest bird species to high elevations where temperatures are too cool for malaria's life cycle and its principal mosquito vector. The impact of climate change on Hawaiian forest birds has been a recent focus of Hawaiian conservation biology, and has centered on the links between climate and avian malaria. To elucidate the differential impacts of projected climate shifts on species with known varying niches, disease resistance and tolerance, we use a comprehensive database of species sightings, regional climate projections and ensemble distribution models to project distribution shifts for all Hawaiian forest bird species. We illustrate that, under a likely scenario of continued disease-driven distribution limitation, all 10 species with highly reliable models (mostly narrow-ranged, single-island endemics) are expected to lose >50% of their range by 2100. Of those, three are expected to lose all range and three others are expected to lose >90% of their range. Projected range loss was smaller for several of the more widespread species; however improved data and models are necessary to refine future projections. Like other at-risk species, Hawaiian forest birds have specific habitat requirements that limit the possibility of range expansion for most species, as projected expansion is frequently in areas where forest habitat is presently not available (such as recent lava flows). Given the large projected range losses for all species, protecting high elevation forest alone is not an adequate long-term strategy for many species under climate change. We describe the types of additional conservation actions practitioners will likely need to consider, while providing results to help with such considerations.

  19. Analysis of Paleokarst Sinkholes in the Arkoma Basin using 3-D Seismic

    Science.gov (United States)

    Kumbalek, Michael

    Paleokarst features are important to understand, both with regards to research geologists and to the petroleum industry. In terms of geology, understanding paleokarst features can yield more information about the depositional and surface environments of past times, and how diagenetic alteration affected the environment during the formation of karst features. In the petroleum industry, paleokarst features can have positive or negative consequence resulting in a potential reservoir with enhanced porosity due to the paleokarst features, or as a geo-hazard to prepare for or avoid when drilling. Inspired by issues faced when drilling in the Ft. Worth basin, this study utilizes multiple 3-D seismic surveys and subsurface well control to map paleokarsts within the Viola Limestone in the Arkoma Basin. Calculated seismic attribute volumes used to identify paleokarst sinkholes within the Viola Group include coherency and curvature attributes. ImageJ software was used to aid in counting and measuring paleokarst sinkholes identified using seismic mapping, coherency, and curvature attribute volumes. In addition to mapping, a cumulative distribution plot was produced from the diameters of the seismically mapped paleokarst sinkholes, allowing for an estimate to be made as to what the total amount of paleokarst sinkholes are within the study area. The methods detailed in this study proved to be effective in mapping and analyzing paleokarst sinkholes within the Viola Group. The paleokarst sinkholes mapped were determined to have been formed on the outer edge of the Southern Oklahoma aulacogen, as a result of the Sylvan/Viola unconformity. In addition to this, it has been determined that these paleokarst sinkholes are linked in formation to visually similar paleokarst sinkholes located in the Ellenburger Group in the Fort Worth Basin.

  20. Geotechnical analysis and 4D GPR measurements for the assessment of the risk of sinkholes occurring in a Polish mining area

    Energy Technology Data Exchange (ETDEWEB)

    Marcak, H.; Golebiowski, T.; Tomecka-Suchon, S. [AGH University of Science and Technology, Krakow (Poland). Dept. of Geophysics

    2008-08-15

    The study presented in this paper concerns georadar investigations at a selected former coal mining site in Upper Silesia (Poland) where the risk of sinkhole appearance is high. The results of 3D GPR surveys obtained in three measurement sessions in December 1997, October 2006 and March 2007 were interpreted. The 4D interpretation, i.e., a time-space analysis, allowed for the identification of loose zones in the ground and fractured zones of the rock mass, which might be a source of sinkhole creation. After the first measurement session, on the basis of the GPR survey results, a dangerous, fractured zone in the ground was localized. This zone was confirmed by a borehole. Between the second and third session, a large sinkhole appeared on site, as predicted on the basis of georadar investigations. The geomechanical analyses presented in this paper explain the development of the fractured zones over the earlier mining excavations. Such zones accumulate water and high contrasts of dielectrical permittivity appear, allowing the use of the GPR method for the location of these zones.

  1. Drying Induced Hydrophobic Polymer Collapse

    OpenAIRE

    ten Wolde, Pieter Rein; Chandler, David

    2002-01-01

    We have used computer simulation to study the collapse of a hydrophobic chain in water. We find that the mechanism of collapse is much like that of a first-order phase transition. The evaporation of water in the vicinity of the polymer provides the driving force for collapse, and the rate limiting step is the nucleation of a sufficiently large vapor bubble. The study is made possible through the application of transition path sampling and a coarse-grained treatment of liquid water. Relevance ...

  2. Far-Field Tsunami Impact in the North Atlantic Basin from Large Scale Flank Collapses of the Cumbre Vieja Volcano, La Palma

    Science.gov (United States)

    Tehranirad, Babak; Harris, Jeffrey C.; Grilli, Annette R.; Grilli, Stephan T.; Abadie, Stéphane; Kirby, James T.; Shi, Fengyan

    2015-12-01

    In their pioneering work, Ward and Day suggested that a large scale flank collapse of the Cumbre Vieja Volcano (CVV) on La Palma (Canary Islands) could trigger a mega-tsunami throughout the North Atlantic Ocean basin, causing major coastal impact in the far-field. While more recent studies indicate that near-field waves from such a collapse would be more moderate than originally predicted by Ward and Day [Løvholt et al. (J Geophy Res 113:C09026, 2008); Abadie et al. (J Geophy Res 117:C05030, 2012)], these would still be formidable and devastate the Canary Island, while causing major impact in the far-field at many locations along the western European, African, and the US east coasts. Abadie et al. (J Geophy Res 117:C05030, 2012) simulated tsunami generation and near-field tsunami impact from a few CVV subaerial slide scenarios, with volumes ranging from 20 to 450 km^3; the latter representing the most extreme scenario proposed by Ward and Day. They modeled tsunami generation, i.e., the tsunami source, using THETIS, a 3D Navier-Stokes (NS) multi-fluid VOF model, in which slide material was considered as a nearly inviscid heavy fluid. Near-field tsunami impact was then simulated for each source using FUNWAVE-TVD, a dispersive and fully nonlinear long wave Boussinesq model [ Shi et al. (Ocean Modell 43-44:36-51, 2012); Kirby et al. (Ocean Modeling, 62:39-55, 2013)]. Here, using FUNWAVE-TVD for a series of nested grids of increasingly fine resolution, we model and analyze far-field tsunami impact from two of Abadie et al.'s extreme CVV flank collapse scenarios: (i) that deemed the most "credible worst case scenario" based on a slope stability analysis, with a 80 km^3 volume; and (ii) the most extreme scenario, similar to Ward and Day's, with a 450 km^3 volume. Simulations are performed using a one-way coupling scheme in between two given levels of nested grids. Based on the simulation results, the overall tsunami impact is first assessed in terms of maximum surface

  3. Ongoing Deformation of Sinkholes in Wink, Texas, Observed by Time-Series Sentinel-1A SAR Interferometry (Preliminary Results

    Directory of Open Access Journals (Sweden)

    Jin-Woo Kim

    2016-04-01

    Full Text Available Spatiotemporal deformation of existing sinkholes and the surrounding region in Wink, TX are probed using time-series interferometric synthetic aperture radar (InSAR methods with radar images acquired from the Sentinel-1A satellite launched in April 2014. The two-dimensional deformation maps, calculated using InSAR observations from ascending and descending tracks, reveal that much of the observed deformation is vertical. Our results indicate that the sinkholes are still influenced by ground depression, implying that the sinkholes continue to expand. Particularly, a region 1 km northeast of sinkhole #2 is sinking at a rate of up to 13 cm/year, and its aerial extent has been enlarged in the past eight years when compared with a previous survey. Furthermore, there is a high correlation between groundwater level and surficial subsidence during the summer months, representing the complicated characteristics of sinkhole deformation under the influence of successive roof failures in underlying cavities. We also modeled the sinkhole deformation in a homogenous elastic half-space with two dislocation sources, and the ground depression above cavities could be numerically analyzed. Measurements of ongoing deformation in sinkholes and assessments of the stability of the land surface at sinkhole-prone locations in near real-time, are essential for mitigating the threat posed to people and property by the materialization of sinkholes.

  4. Collapsing granular suspensions

    OpenAIRE

    Kadau, D.; Andrade Jr, J. S.; Herrmann, H. J.

    2009-01-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for...

  5. Integrated geological and geophisycal methods for the evaluation of the ceiling collapse hazard of the Poesia Cave in the Salento peninsula (southern Italy)

    Science.gov (United States)

    Delle Rose, M.; Leucci, G.; Quarta, G.

    2012-04-01

    According to the Protection Civil Department database, Apulia is the fourth region in Italy affected by sinkholes, due to collapse of natural or man-made cavities. The southern part of the region (the Salento peninsula) had hosted in the last twenty years at least fifteen events of sinkholes, the greatest part of which occurred inside "soft" carbonate rocks (calcarenites). The most catastrophic sinkhole, due to the presence of underground quarries, occurred at Gallipoli on 29 March 2007, when a collapse created a 12 x 18 m sinkhole which involved two 3 floors buildings. and 140 people were evacuated. In these cases, the usual approach of investigation of the area consist of geological survey supported by geophysical prospecting aimed to evaluate the real size of sinkhole crater and to predict its development over the time. In spite of the importance on the civil protection, the prediction of the sinkhole events is currently an hard issue, especially if they are related to caves of cultural interest as the case at hand, where are summarised questions of safety of people and cultural heritage. The "Poesia Piccola" cave, located at the Salento area of the Puglia region (southern Italy), has such features and it is the case study of this paper. The cave is an outstanding example of hypogean archaeological site morphologically in evolution and potentially dangerous for humans. It belongs to a karst system formed by dome-shaped caves, minor cavities and galleries. The system, named "Grotte della Poesia", is joined to the ground through vertical and horizontal entrances, respectively placed on a coastal plateau and along the contiguous cliff. This paper provides a new methodological approach on the evaluation of sinkhole hazard in such "soft" carbonate rocks combing geological, geophysical and mine engineering complementary methods, such as: geological analysis of outcrops and boreholes, aerophotogrammetric interpretation of aerial photos, electrical resistivity

  6. Natural and human-induced sinkhole hazards in Saudi Arabia: distribution, investigation, causes and impacts

    Science.gov (United States)

    Youssef, Ahmed M.; Al-Harbi, Hasan M.; Gutiérrez, Francisco; Zabramwi, Yasser A.; Bulkhi, Ali B.; Zahrani, Saeed A.; Bahamil, Alaa M.; Zahrani, Ahmed J.; Otaibi, Zaam A.; El-Haddad, Bosy A.

    2016-05-01

    Approximately 60 % of the 2,150,000 km2 area of Saudi Arabia is underlain by soluble sediments (carbonate and evaporite rock formations, salt diapirs, sabkha deposits). Despite its hyper-arid climate, a wide variety of recent sinkholes have been reported in numerous areas, involving significant property losses. Human activities, most notably groundwater extraction, have induced unstable conditions on pre-existing cavities. This work provides an overview of the sinkhole hazard in Saudi Arabia, a scarcely explored topic. It identifies the main karst formations and the distribution of the most problematic sinkhole areas, illustrated through several case studies covering the wide spectrum of subsidence mechanisms. Some of the main investigation methods are presented through selected examples, including remote sensing, trenching and geophysics. Based on the available data, the main causal factors are identified and further actions that should be undertaken to better assess and manage the risk are discussed.

  7. The Hydrochemical Evolution of Water-Filled Sinkholes at Bitter Lake NWR, Roswell, NM

    Science.gov (United States)

    Premo, E.; Crossey, L. J.

    2013-12-01

    Bitter Lake National Wildlife Refuge in Roswell, NM houses one of the most ecologically significant wetlands in the US-SW including approximately 52 water-filled sinkholes each supporting a unique biological assemblage, including several endangered and endemic species (e.g., Pecos pupfish and Noel's amphipod, respectively). Forming in the karst landscape adjacent to the Pecos River where the regional dual-aquifer system discharges through a network of springs and seeps, these sinkholes are recharged by saline groundwater that is subject to anthropogenic withdrawals for irrigation and hydrocarbon production and chemically altered by a complex series of evaporation-precipitation reactions after discharge. This study investigates the hydrochemical differences among these sinkholes while considering the evolutionary processes affecting water column structure, geochemical mixing and ecological sustainability. Two major sampling suites, pre- and post-irrigation, yielded waters from 1.0m increments along the water columns of 10 representative sinkholes. Samples were analyzed for major ions, stable isotopes [δ18O, δD ], and dissolved gases; PHREEQc was used to model mineral saturation and speciation. An in-situ mineral precipitation experiment provided growth rate and mineral morphological (SEM) data. Source water is chemically similar to shallow springs found at the Refuge (Sago Spring). Sinkholes exhibit bimodal water column structure (well-mixed or stratified) organized in response to water density (with ~1.035 g/cm3 forming the modal transition threshold). By measuring the density, TDS or conductivity at sinkhole surface it is possible to predict modality of water column structure. Sinkhole waters - regardless of depth or season - fall along a common isotopic evaporation trajectory (δ D = 3.387*δ18O - 19.38), and adopt a Na-Cl chemical endmember facies. Driven primarily by physical sinkhole geometry (e.g., depth and surface area), sinkhole water follows a

  8. Edifice growth and collapse of the Pliocene Mt. Kenya: Evidence of large scale debris avalanches on a high altitude glaciated volcano

    NARCIS (Netherlands)

    Schoorl, J.M.; Veldkamp, A.; Claessens, L.F.G.; Gorp, van W.; Wijbrans, J.R.

    2014-01-01

    The cyclic growth and destruction of the Late Cenozoic Stratovolcano Mt. Kenya have been reconstructed for its southeastern segment. At least three major debris avalanche deposits have been reconstructed and dated. The oldest deposits indicate an edifice collapse around 4.9 Ma (40Ar/39Ar), followed

  9. Edifice growth and collapse of the Pliocene Mt. Kenya : Evidence of large scale debris avalanches on a high altitude glaciated volcano

    NARCIS (Netherlands)

    Schoorl, J. M.; Veldkamp, A.; Claessens, L.; van Gorp, W.; Wijbrans, J. R.

    2014-01-01

    The cyclic growth and destruction of the Late Cenozoic Stratovolcano Mt. Kenya have been reconstructed for its southeastern segment. At least three major debris avalanche deposits have been reconstructed and dated. The oldest deposits indicate an edifice collapse around 4.9 Ma (Ar-40/Ar-39), followe

  10. 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.

  11. Collapsing granular suspensions.

    Science.gov (United States)

    Kadau, D; Andrade, J S; Herrmann, H J

    2009-11-01

    A 2D contact dynamics model is proposed as a microscopic description of a collapsing suspension/soil to capture the essential physical processes underlying the dynamics of generation and collapse of the system. Our physical model is compared with real data obtained from in situ measurements performed with a natural collapsing/suspension soil. We show that the shear strength behavior of our collapsing suspension/soil model is very similar to the behavior of this collapsing suspension soil, for both the unperturbed and the perturbed phases of the material.

  12. Direct Push supported geotechnical and hydrogeological characterisation of an active sinkhole area

    Science.gov (United States)

    Tippelt, Thomas; Vienken, Thomas; Kirsch, Reinhard; Dietrich, Peter; Werban, Ulrike

    2017-04-01

    Sinkholes represent a natural geologic hazard in areas where soluble layers are present in the subsurface. A detailed knowledge of the composition of the subsurface and its hydrogeological and geotechnical properties is essential for the understanding of sinkhole formation and propagation. This serves as base for risk evaluation and the development of an early warning system. However, site models often depend on data from drillings and surface geophysical surveys that in many cases cannot resolve the spatial distribution of relevant hydrogeological and geotechnical parameters sufficiently. Therefore, an active sinkhole area in Münsterdorf, Northern Germany, was investigated in detail using Direct Push technology, a minimally invasive sounding method. The obtained vertical high-resolution profiles of geotechnical and hydrogeological characteristics, in combination with Direct Push based sampling and surface geophysical measurements lead to a strong improvement of the geologic site model. The conceptual site model regarding sinkhole formation and propagation will then be tested based on the gathered data and, if necessary, adapted accordingly.

  13. 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

  14. Hierarchical Cluster Assembly in Globally Collapsing Clouds

    CERN Document Server

    Vazquez-Semadeni, Enrique; Colin, Pedro

    2016-01-01

    We discuss the mechanism of cluster formation in a numerical simulation of a molecular cloud (MC) undergoing global hierarchical collapse (GHC). The global nature of the collapse implies that the SFR increases over time. The hierarchical nature of the collapse consists of small-scale collapses within larger-scale ones. The large-scale collapses culminate a few Myr later than the small-scale ones and consist of filamentary flows that accrete onto massive central clumps. The small-scale collapses form clumps that are embedded in the filaments and falling onto the large-scale collapse centers. The stars formed in the early, small-scale collapses share the infall motion of their parent clumps. Thus, the filaments feed both gaseous and stellar material to the massive central clump. This leads to the presence of a few older stars in a region where new protostars are forming, and also to a self-similar structure, in which each unit is composed of smaller-scale sub-units that approach each other and may merge. Becaus...

  15. Environmental consequences of the Retsof Salt Mine roof collapse

    Science.gov (United States)

    Yager, Richard M.

    2013-01-01

    In 1994, the largest salt mine in North America, which had been in operation for more than 100 years, catastrophically flooded when the mine ceiling collapsed. In addition to causing the loss of the mine and the mineral resources it provided, this event formed sinkholes, caused widespread subsidence to land, caused structures to crack and subside, and changed stream flow and erosion patterns. Subsequent flooding of the mine drained overlying aquifers, changed the groundwater salinity distribution (rendering domestic wells unusable), and allowed locally present natural gas to enter dwellings through water wells. Investigations including exploratory drilling, hydrologic and water-quality monitoring, geologic and geophysical studies, and numerical simulation of groundwater flow, salinity, and subsidence have been effective tools in understanding the environmental consequences of the mine collapse and informing decisions about management of those consequences for the future. Salt mines are generally dry, but are susceptible to leaks and can become flooded if groundwater from overlying aquifers or surface water finds a way downward into the mined cavity through hundreds of feet of rock. With its potential to flood the entire mine cavity, groundwater is a constant source of concern for mine operators. The problem is compounded by the viscous nature of salt and the fact that salt mines commonly lie beneath water-bearing aquifers. Salt (for example halite or potash) deforms and “creeps” into the mined openings over time spans that range from years to centuries. This movement of salt can destabilize the overlying rock layers and lead to their eventual sagging and collapse, creating permeable pathways for leakage of water and depressions or openings at land surface, such as sinkholes. Salt is also highly soluble in water; therefore, whenever water begins to flow into a salt mine, the channels through which it flows increase in diameter as the surrounding salt dissolves

  16. Spatial analysis for susceptibility of second-time karst sinkholes: A case study of Jili Village in Guangxi, China

    Science.gov (United States)

    Zhou, Guoqing; Yan, Hongbo; Chen, Kunhua; Zhang, Rongting

    2016-04-01

    After a big karst sinkhole happened in Jili Village of Guangxi, China, the local government was eager to quantitatively analyze and map susceptible areas of the potential second-time karst sinkholes in order to make timely decisions whether the residents living in the first-time sinkhole areas should move. For this reason, karst sinkholes susceptibility geospatial analysis is investigated using multivariate spatial data, logistic regression model (LRM) and Geographical Information System (GIS). Ten major karst sinkholes related factors, including (1) formation lithology, (2) soil structure, (3) profile curvature, (4) groundwater depth, (5) fluctuation of groundwater level, (6) percolation rate of soil, (7) degree of karst development, (8) distance from fault, (9) distance from the traffic route, and (10) overburden thickness were selected, and then each of factors was classified and quantitated with the three or four levels. The LRM was applied to evaluate which factor makes significant contributions to sinkhole. The results demonstrated that formation lithology, soil structure, profile curvature, groundwater depth, ground water level, percolation rate of soil, and degree of karst development, the distance from fault, and overburden thickness are positive, while one factor, the distance from traffic routes is negative, which is deleted from LRM model. The susceptibility of the potential sinkholes in the study area is estimated and mapped using the solved impact factors. The susceptible degrees of the study area are classified into five levels, very high, high, moderate, low, and ignore susceptibility. It has been found that that both very high and high susceptibility areas are along Datou Hill and the foothills of the study area. This finding is verified by field observations. With the investigations conducted in this paper, it can be concluded that the susceptibility maps produced in this paper are reliable and accurate, and useful as a reference for local

  17. Geophysical analysis of the recent sinkhole trend at Ghor-Haditha (Dead Sea, Jordan)

    Science.gov (United States)

    Camerlynck, Christian; Bodet, Ludovic; Galibert, Pierre-Yves; Boucher, Marie; Al-Zoubi, Abdallah

    2013-04-01

    For essentially the last 30 year the water level of the Dead Sea has highly dropped. One of the major associated facts is sinkhole occurrences along the shoreline both in Jordan and Israel. As the principal invoked mechanism, many studies have concluded that sinkhole formation results from the dissolution of a previously immersed salt layer, progressively in contact with fresh to brackish water. In Jordan, the triggering of this phenomenon could also be the result of particular tectonic settings, associated with the Jordan-Dead Sea transform fault system. At Ghor Haditha (south-est Jordan), the consequences have been dramatic for farmers with the shrinking of temporary available lands and industry with the closing of at least one factory. The shallow material in this area is heterogeneous and composed of intercalated sand and clay layers of alluvial-colluvial origin, over a salty substratum, whose precise depth and thickness are yet partially hypothesized. Between 2005 and 2008, a multi-method high-resolution geophysical survey was performed, approximately over a 1 km2 area at Ghor Haditha, associating mainly electromagnetic soundings, magnetic resonance soundings (MRS), and seismic profiling, ground-penetrating radar and electrical resistivity tomography. At the same time, this specific area was the location of a dramatic evolution of sinkhole occurences, regularly followed by geodetic measurements. Over the 3 years period, about 120 TEM (Transient ElectroMagnetic) soundings allow to map precisely the depth of the conductive layers below the resistive overburden. Two conductive layer are then revealed, the latter showing the lowest resistivity below 1 Ohm.m corresponding to the saline substratum. Several MRS (3 in 2005, repeated in 2007 and 12 additional soundings) show an east-west hydraulic gradient towards the Dead. However, the main sinkhole trend coincides with both: - a clear low transmissivity axis determined from MRS measurements; - the western side of a

  18. Wetting dynamics of a collapsing fluid hole

    Science.gov (United States)

    Bostwick, J. B.; Dijksman, J. A.; Shearer, M.

    2017-01-01

    The collapse dynamics of an axisymmetric fluid cavity that wets the bottom of a rotating bucket bound by vertical sidewalls are studied. Lubrication theory is applied to the governing field equations for the thin film to yield an evolution equation that captures the effect of capillary, gravitational, and centrifugal forces on this converging flow. The focus is on the quasistatic spreading regime, whereby contact-line motion is governed by a constitutive law relating the contact-angle to the contact-line speed. Surface tension forces dominate the collapse dynamics for small holes with the collapse time appearing as a power law whose exponent compares favorably to experiments in the literature. Gravity accelerates the collapse process. Volume dependence is predicted and compared with experiment. Centrifugal forces slow the collapse process and lead to complex dynamics characterized by stalled spreading behavior that separates the large and small hole asymptotic regimes.

  19. Use of 2D Multi Electrodes Resistivity Imagining for Sinkholes Hazard Assessment along the Eastern Part of the Dead Sea, Jordan

    Directory of Open Access Journals (Sweden)

    Abdallah S.   Al-Zoubi

    2007-01-01

    Full Text Available Sinkholes and subsidence are natural phenomena can be occurred in shallow geology sediments at different regions in the world. Sinkholes assessment is one of the most difficult near subsurface investigations. Geophysical prospecting is appropriate method to determine environmental and geotechnical problems. 2D multi electrodes resistivity imagining with Wenner-Schulmberge array was conducted within active sinkholes area. The objective of the survey is to detect features combined with sinkhole formation like zone of weakness, cavities and fractures. Soil in the study area contains alluvial, conglomerate and silty clay which represent good target for resistivity survey. The interpretation of resistivity data along the profiles show different model of the resistivity variation in active sinkhole zones compared with inactive zones in the study area. The deformation in the layer continuity and the direct contact between high resistive and low resistive layers can appear only in the subsidence area or active sinkhole zones.

  20. Gravitational Collapse End States

    OpenAIRE

    Joshi, Pankaj S.

    2004-01-01

    Recent developments on the final state of a gravitationally collapsing massive matter cloud are summarized and reviewed here. After a brief background on the problem, we point out how the black hole and naked singularity end states arise naturally in spherical collapse. We see that it is the geometry of trapped surfaces that governs this phenomena.

  1. Collapsing floating-point operations

    OpenAIRE

    Defour, David

    2004-01-01

    This paper addresses the issue of collapsing dependent floating-point operations. The presentation focuses on studying the dataflow graph of benchmark involving a large number of floating-point instructions. In particular, it focuses on the relevance of new floating-point operators performing two dependent operations which are similar to "fused multiply and add". Finally, this paper examines the implementation cost and critical path reduction from this strategy.

  2. Engineering geologic conditions at the sinkhole entrance to Logan Cave, Benton County, Arkansas

    Science.gov (United States)

    Schulz, William H.; McKenna, Jonathan P.

    2004-01-01

    Logan Cave, located in Benton County, Arkansas, is inhabited by several endangered and threatened species. The cave and surrounding area was designated a National Wildlife Refuge under the control of the U.S. Fish and Wildlife Service (USFWS) in 1989. Cave researchers access the cave through a steep-sided sinkhole entrance, which also is one of the two access points used by endangered bats. There is evidence of instability of one of the entrance slopes that has raised concerns that the entrance could close if slope failure was to occur. At the request of USFWS, we performed an engineering geologic investigation of the sinkhole to evaluate stability of this slope, which is comprised of soil, and other mechanisms of sediment transport into the cave entrance. The investigation included engineering geologic mapping, sampling and laboratory testing of subsurface geologic materials, and slope-stability analysis. We found that the sinkhole slope that extends into the entrance of the cave is comprised of sandy and gravelly soil to the depths explored (6.4 meters). This soil likely was deposited as alluvium within a previous, larger sinkhole. Based on properties of the alluvium, geometry of the slope, and results of finite-element slope-stability analyses, we conclude that the slope is marginally stable. Future failures of the slope probably would be relatively thin and small, thus several would be required to completely close the cave entrance. However, sediment is accumulating within the cave entrance due to foot traffic of those accessing the cave, surface-water erosion and transport, and shallow slope failures from the other sinkhole slopes. We conclude that the entrance will be closed by sediment in the future, similar to another entrance that we identified that completely closed in the past. Several measures could be taken to reduce the potential for closure of the cave entrance, including periodic sediment removal, installation of materials that reduce erosion by

  3. DR21 Main: A Collapsing Cloud

    OpenAIRE

    Kirby, Larry

    2008-01-01

    The molecular cloud, DR21 Main, is an example of a large-scale gravitational collapse about an axis near the plane of the sky where the collapse is free of major disturbances due to rotation or other effects. Using flux maps, polarimetric maps, and measurements of the field inclination by comparing the line widths of ion and neutral species, we estimate the temperature, mass, magnetic field, and the turbulent kinetic, mean magnetic, and gravitational potential energies, and present a 3D model...

  4. Progressive collapse and methods of prevention

    OpenAIRE

    Vasilieva, Anastasia

    2013-01-01

    The purpose of the study was to describe the process of progressive collapse and to find more methods and approaches to design the structure for preventing from this kind of failure. And the last aim was to find Russian norms and standards and make calculations on progressive collapse of the trade center, according to them. In this way the work was commissioned by Finnmap Consulting Oy. The thesis should be interesting to design engineers working with designing the large-span structures o...

  5. Cosmogenesis and Collapse

    CERN Document Server

    Pearle, Philip

    2010-01-01

    Some possible benefits of dynamical collapse for a quantum theory of cosmogenesis are discussed. These are a possible long wait before creation begins, creation of energy and space, and choice of a particular universe out of a superposition.

  6. Application of Geophysical Techniques for 3D Geohazard Mapping to Delineate Cavities and Potential Sinkholes in the Northern Part of Kuala Lumpur, Malaysia

    Directory of Open Access Journals (Sweden)

    Zeinab Bakhshipour

    2013-01-01

    Full Text Available This work describes the application of the electrical resistivity (ER method to delineating subsurface structures and cavities in Kuala Lumpur Limestone within the Batu Cave area of Selangor Darul Ehsan, Malaysia. In all, 17 ER profiles were measured by using a Wenner electrode configuration with 2 m spacing. The field survey was accompanied by laboratory work, which involves taking resistivity measurements of rock, soil, and water samples taken from the field to obtain the formation factor. The relationship between resistivity and the formation factor and porosity for all the samples was established. The porosity values were plotted and contoured. A 2-dimensional and 3-dimensional representation of the subsurface topography of the area was prepared through use of commercial computer software. The results show the presence of cavities and sinkholes in some parts of the study area. This work could help engineers and environmental managers by providing the information necessary to produce a sustainable management plan in order to prevent catastrophic collapses of structures and other related geohazard problems.

  7. Signatures of star formation by cold collapse

    CERN Document Server

    Kuznetsova, Aleksandra; Ballesteros-Paredes, Javier

    2015-01-01

    Sub-virial gravitational collapse is one mechanism by which star clusters may form. Here we investigate whether this mechanism can be inferred from observations of young clusters. To address this question, we have computed SPH simulations of the initial formation and evolution of a dynamically young star cluster through cold (sub-virial) collapse, starting with an ellipsoidal, turbulently seeded distribution of gas, and forming sink particles representing (proto)stars. While the initial density distributions of the clouds do not have large initial mass concentrations, gravitational focusing due to the global morphology leads to cluster formation. We use the resulting structures to extract observable morphological and kinematic signatures for the case of sub-virial collapse. We find that the signatures of the initial conditions can be erased rapidly as the gas and stars collapse, suggesting that kinematic observations need to be made either early in cluster formation and/or at larger scales, away from the grow...

  8. 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.

  9. Ground-Truthing Seismic Refraction Tomography for Sinkhole Detection in Florida

    Science.gov (United States)

    Hiltunen, D. R.; Hudyma, N.; Quigley, T. P.; Samakur, C.

    2007-12-01

    In order to provide effective return of storm water runoff to the subsurface aquifer, the Florida Department of Transportation (FDOT) constructs detention basins adjacent to its transportation facilities. These basins serve as a collection point for runoff within a local drainage area, and the overburden soil above the aquifer provides a natural filter for contaminants in the surface runoff water. However, the geologic setting for many of these basins in Florida is karst, limestone bedrock at shallow depth, and the concentration of water flow in these basins leads to frequent development of sinkholes. These sinkholes are an environmental hazard, as they provide a direct, open conduit for contaminant-laden runoff water to return to the aquifer rather than percolate through the overburden soil. Consequently, FDOT is keenly interested in all aspects of sinkholes, including factors leading to formation, methods of early detection, and effective methods for rapid repair. Recently, FDOT has engaged in a research effort to evaluate the capabilities of a wide range of geophysical investigation tools with regard to detection of sinkhole-prone areas within sites being considered for construction of detention ponds. The geophysical techniques evaluated have included ground penetrating radar (GPR), multi- electrode electrical resistivity (MER), seismic MASW, and seismic refraction tomography. In addition to geophysical testing at the research sites, extensive traditional geotechnical site characterization has been conducted, including boring and sampling of soil and rock, standard penetration tests (SPT), and cone penetration tests (CPT). The proposed paper will evaluate the capabilities of seismic refraction tomography. Comparisons between refraction tomograms and borehole logs, SPT soundings, and CPT soundings suggest that the refraction method can map the laterally-variable top of bedrock surface typical of karst terrane. During a recent ground proving exercise at the

  10. Part A: Geochemistry of Soil Samples from 50 Solution-Collapse Features on the Coconino Plateau, Northern Arizona

    Science.gov (United States)

    Van Gosen, Bradley S.; Wenrich, Karen J.

    1991-01-01

    Soil sampling surveys were conducted during 1984-1986 across 50 solution-collapse features exposed on the Coconino Plateau of northern Arizona in order to determine whether soil geochemistry can be used to distinguish mineralized breccia pipes from unmineralized collapse features. The 50 sampled features represent the variety of collapse features that crop out on plateau surfaces in northwestern Arizonaoodeeplyorooted solution-collapse breccia pipes, near-surface gypsum collapses, and sinkholes. Of the 50 features that were sampled in this study, 3 are confirmed breccia pipes that contain significant uranium and base-metal minerals, I is believed to be a sinkhole with no economic potential, and 4 are stratabound copper deposits whose possible relationship to breccia pipes is yet to be determined. The remaining collapse features are suspected to overlie breccia pipes, although some of these may represent near surface gypsum collapse features. However, no exploratory drilling results or breccia exposures exist to indicate their underlying structure. The low cost and ease of soil sampling suggested that this technique be evaluated for breccia pipe exploration. This report provides the locations and geochemical results for the soil sampling surveys and brief descriptions of the 50 collapse features. The analytical results of almost 2,000 soil samples are provided in tabular hardcopy and dBase III Plus diskcopy format. The analytical data is provided in digital format to allow the reader to choose their own methods for evaluating the effectiveness of soil sampling over known and suspected breccia pipes. A pilot survey conducted over 17 collapse features in 1984 suggested that soil sampling might be useful in distinguishing mineralized breccia pipes from other circular features. Followup detailed surveys in 1985 and 1986 used a radial sampling pattern at each of 50 sites; at least one third of the samples were collected from areas outside of the collapse feature to

  11. Part D: Geochemistry of Soil Samples from 50 Solution-Collapse Features on the Coconino Plateau, Northern Arizona

    Science.gov (United States)

    Van Gosen, Bradley S.; Wenrich, Karen J.

    1991-01-01

    Soil sampling surveys were conducted during 1984-1986 across 50 solution-collapse features exposed on the Coconino Plateau of northern Arizona in order to determine whether soil geochemistry can be used to distinguish mineralized breccia pipes from unmineralized collapse features. The 50 sampled features represent the variety of collapse features that crop out on plateau surfaces in northwestern Arizonaoodeeplyorooted solution-collapse breccia pipes, near-surface gypsum collapses, and sinkholes. Of the 50 features that were sampled in this study, 3 are confirmed breccia pipes that contain significant uranium and base-metal minerals, I is believed to be a sinkhole with no economic potential, and 4 are stratabound copper deposits whose possible relationship to breccia pipes is yet to be determined. The remaining collapse features are suspected to overlie breccia pipes, although some of these may represent near surface gypsum collapse features. However, no exploratory drilling results or breccia exposures exist to indicate their underlying structure. The low cost and ease of soil sampling suggested that this technique be evaluated for breccia pipe exploration. This report provides the locations and geochemical results for the soil sampling surveys and brief descriptions of the 50 collapse features. The analytical results of almost 2,000 soil samples are provided in tabular hardcopy and dBase III Plus diskcopy format. The analytical data is provided in digital format to allow the reader to choose their own methods for evaluating the effectiveness of soil sampling over known and suspected breccia pipes. A pilot survey conducted over 17 collapse features in 1984 suggested that soil sampling might be useful in distinguishing mineralized breccia pipes from other circular features. Followup detailed surveys in 1985 and 1986 used a radial sampling pattern at each of 50 sites; at least one third of the samples were collected from areas outside of the collapse feature to

  12. Overview of the geophysical studies in the Dead Sea coastal area related to evaporite karst and recent sinkhole development

    Directory of Open Access Journals (Sweden)

    Mikhail G. Ezersky

    2017-05-01

    Full Text Available Since the early 80s, a progressively increasing number of sinkholes appeared along the Dead Sea coastal line. It has been found that their appearance is strongly correlating with the lowering of the Dead Sea level taking place with the rate of approximately 1 m/yr. Location of areas affected by sinkhole development corresponds to location of the salt formation deposited during the latest Pleistocene, when the Lake Lisan receded to later become the Dead Sea. Water flowing to the Dead Sea from adjacent and underlying aquifers dissolves salt and creates caverns that cause ground subsidence and consequent formation of sinkholes. Before subsidence, these caverns are not visible on the surface but can be investigated with surface geophysical methods. For that, we applied Surface Nuclear Magnetic Resonance (SNMR, Transient Electromagnetic (TEM Seismic refraction and reflection, Multichannel Analysis of Surface waves (MASW, microgravity and magnetic surveys and their combinations. Our geophysical results allowed us to locate the salt formation and to detect caverns in salt thus contributing to better understanding sinkhole development mechanisms. Comparison of sinkhole appearance along the western DS shore derived from the recent database (2017 shows that predictions made on the base of geophysical data (2005-2008 are now confirmed thus demonstrating efficiency of our study. In this paper, we briefly present a summary of up to date knowledge of the geology and hydrogeology of Dead Sea basin, of the physical properties of the salt rock and the most popular models explaining mechanisms of sinkhole development. We also share our experience gained during geophysical studies carried out in the framework of national and international research projects in this area for the last 20 years.

  13. Geophysical Identification of Filled Sinkholes and Buried Fractures in Glaciated Karst

    Science.gov (United States)

    Carpenter, P. J.

    2006-05-01

    Karst aquifers are highly susceptible to contamination, with numerous points of entry for contaminants through recharge features such as sinkholes, swallow holes and soil pipes. These recharge features may be filled or obscured at the surface, requiring the use of geophysical techniques or remote sensing for their identification. This problem is particularly acute in recently glaciated terrain, where surface topography is often unrelated to underlying active karst features, as illustrated by three Illinois examples in this study. Approximately 10 km south of Rockford, IL, a network-type cave of interconnected solutionally-enlarged fractures extends over an area of approximately 1 ha, beneath a low Ordovician dolomite ridge covered with approximately 5 m of glacial till and outwash. Ground-penetrating radar (GPR) profiles along the ridge top, utilizing 50 and 100 MHz antennas, showed strong diffractions over unsaturated caves and karst conduits. A trough-like feature approximately 20 m wide and 3 m deep was also identified in GPR profiles approximately 20 m west of the mapped cave passages. It probably represents an elongate filled sinkhole, similar to those observed along the wall of a quarry less than 1 km west of the cave. GPR profiles and two-dimensional electrical resistivity imaging identified clay-filled sinkholes 2-3 m wide and about 3 m deep in Bourbonnais, IL, 100 km south of Chicago, where 1 to 4 meters of loess and till overlie karstic Silurian dolomite. Penetrometer surveys revealed deeply weathered bedrock zones containing vertical clay-filled caves beneath the filled sinkholes. Surface water infiltration estimates are being made for these features, utilizing the geophysically-derived geometries, along with hydraulic conductivity and gradient data. EM conductivity profiles were combined with resistivity soundings at landfill in southern Illinois near St. Louis, where approximately 5 m of till overlies karstic limestone. Linear high conductivity

  14. Growth cone collapse assay.

    Science.gov (United States)

    Cook, Geoffrey M W; Jareonsettasin, Prem; Keynes, Roger J

    2014-01-01

    The growth cone collapse assay has proved invaluable in detecting and purifying axonal repellents. Glycoproteins/proteins present in detergent extracts of biological tissues are incorporated into liposomes, added to growth cones in culture and changes in morphology are then assessed. Alternatively purified or recombinant molecules in aqueous solution may be added directly to the cultures. In both cases after a defined period of time (up to 1 h), the cultures are fixed and then assessed by inverted phase contrast microscopy for the percentage of growth cones showing a collapsed profile with loss of flattened morphology, filopodia, and lamellipodia.

  15. On bore collapse

    Science.gov (United States)

    Yeh, Harry H.; Ghazali, A.

    1988-06-01

    Using the laser-induced fluorescent method, the transition process from bore to runup mode, i.e., "bore collapse," is investigated experimentally. The observed process appears to be different from both previous analytical and numerical predictions. The results indicate that momentum exchange takes place between the incident bore and the quiescent water body along the shoreline. Turbulence generated in a bore nearshore is highly three-dimensional and sporadic. Very close to the shore, turbulence is advected with the bore front, and consequently, the bore collapse process involves strong turbulent action onto the dry beach bed.

  16. Use of Raman Spectroscopy and Delta Volume Growth from Void Collapse to Assess Overwrap Stress Gradients Compromising the Reliability of Large Kevlar/Epoxy COPVs

    Science.gov (United States)

    Kezirian, Michael T.; Phoenix, S. Leigh; Eldridge, Jeffrey I.

    2009-01-01

    Composite Overwrapped Pressure Vessels (COPVs) are frequently used for storing pressurized gases aboard spacecraft and aircraft when weight saving is desirable compared to all-metal versions. Failure mechanisms in fibrous COPVs and variability in lifetime can be very different from their metallic counterparts; in the former, catastrophic stress-rupture can occur with virtually no warning, whereas in latter, a leak before burst design philosophy can be implemented. Qualification and certification typically requires only one burst test on a production sample (possibly after several pressure cycles) and the vessel need only meet a design burst strength (the maximum operating pressure divided by a knockdown factor). Typically there is no requirement to assess variability in burst strength or lifetime, much less determine production and materials processing parameters important to control of such variability. Characterizing such variability and its source is crucial to models for calculating required reliability over a given lifetime (e.g. R = 0.9999 for 15 years). In this paper we present a case study of how lack of control of certain process parameters in COPV manufacturing can result in variations among vessels and between production runs that can greatly increase uncertainty and reduce reliability. The vessels considered are 40-inch ( NASA Glenn Research center, Cleveland, OH, 44135 29,500 in3 ) spherical COPVs with a 0.74 in. thick Kevlar49/epoxy overwrap and with a titanium liner of which 34 were originally produced. Two burst tests were eventually performed that unexpectedly differed by almost 5%, and were 10% lower than anticipated from burst tests on 26-inch sister vessels similar in every detail. A major observation from measurements made during proof testing (autofrettage) of the 40-inch vessels was that permanent volume growth from liner yielding varied by a factor of more than two (150 in3 to 360 in3 ), which suggests large differences in the residual

  17. Collapsible Geostrut Structure

    Science.gov (United States)

    Robertson, Glen A.

    1994-01-01

    Portable truss structure collapsible into smaller volume for storage and transportation. At new site, reerected quickly, without need to reassemble parts. Structure could be tent, dome, tunnel, or platform. Key element in structure joint, called "geostrut joint," includes internal cable. Structure is network of struts attached to geostrut joints. Pulling cables taut in all joints makes structure rigid. Releasing cables relaxes structure.

  18. Scapholunate advanced collapse.

    Science.gov (United States)

    Pomeranz, Stephen J; Salazar, Peter

    2015-01-01

    This case study reviews the pathophysiology of scapholunate advanced collapse (SLAC), which is the most common etiology of degenerative arthritis in the wrist. The scapholunate ligament serves a critical role in stability of the carpus. Disruption of the scapholunate ligament, its sequela, and the magnetic resonance imaging evaluation are discussed, with review of the defining features of this disease and its progression.

  19. Dancing building prevents collapse

    NARCIS (Netherlands)

    Visscher, R.

    2007-01-01

    In future, anybody caught inside a building during an earthquake need no longer fear the roof collapsing on them. Thanks to the use of composite materials, all the building will do is dance along, riding the waves of the earthquake. At least, according to Professor Ir. Adriaan Beukers of the

  20. Dancing building prevents collapse

    NARCIS (Netherlands)

    Visscher, R.

    2007-01-01

    In future, anybody caught inside a building during an earthquake need no longer fear the roof collapsing on them. Thanks to the use of composite materials, all the building will do is dance along, riding the waves of the earthquake. At least, according to Professor Ir. Adriaan Beukers of the Aerospa

  1. Modeling Core Collapse Supernovae

    Science.gov (United States)

    Mezzacappa, Anthony

    2017-01-01

    Core collapse supernovae, or the death throes of massive stars, are general relativistic, neutrino-magneto-hydrodynamic events. The core collapse supernova mechanism is still not in hand, though key components have been illuminated, and the potential for multiple mechanisms for different progenitors exists. Core collapse supernovae are the single most important source of elements in the Universe, and serve other critical roles in galactic chemical and thermal evolution, the birth of neutron stars, pulsars, and stellar mass black holes, the production of a subclass of gamma-ray bursts, and as potential cosmic laboratories for fundamental nuclear and particle physics. Given this, the so called ``supernova problem'' is one of the most important unsolved problems in astrophysics. It has been fifty years since the first numerical simulations of core collapse supernovae were performed. Progress in the past decade, and especially within the past five years, has been exponential, yet much work remains. Spherically symmetric simulations over nearly four decades laid the foundation for this progress. Two-dimensional modeling that assumes axial symmetry is maturing. And three-dimensional modeling, while in its infancy, has begun in earnest. I will present some of the recent work from the ``Oak Ridge'' group, and will discuss this work in the context of the broader work by other researchers in the field. I will then point to future requirements and challenges. Connections with other experimental, observational, and theoretical efforts will be discussed, as well.

  2. Road Collapse in Magnum

    NARCIS (Netherlands)

    Wilschut, A.N.; van Zwol, Roelof; Flokstra, Jan; Brasa, Niek; Quak, Wilko

    1998-01-01

    This paper describes the implementation of a triangulation based collapse algorithm in the general-purpose object oriented DBMS Magnum. The contribution of the paper is twofold. First, we show that true integration of complex spatial functionality in a DBMS can be achieved. Second, we worked out a c

  3. Dancing building prevents collapse

    NARCIS (Netherlands)

    Visscher, R.

    2007-01-01

    In future, anybody caught inside a building during an earthquake need no longer fear the roof collapsing on them. Thanks to the use of composite materials, all the building will do is dance along, riding the waves of the earthquake. At least, according to Professor Ir. Adriaan Beukers of the Aerospa

  4. Arsia Mons Collapse Pits in IR

    Science.gov (United States)

    2004-01-01

    [figure removed for brevity, see original site] We will be looking at collapse pits for the next two weeks. Collapse pits on Mars are formed in several ways. In volcanic areas, channelized lava flows can form roofs which insulate the flowing lava. These features are termed lava tubes on Earth and are common features in basaltic flows. After the lava has drained, parts of the roof of the tube will collapse under its own weight. These collapse pits will only be as deep as the bottom of the original lava tube. Another type of collapse feature associated with volcanic areas arises when very large eruptions completely evacuate the magma chamber beneath the volcano. The weight of the volcano will cause the entire edifice to subside into the void space below it. Structural features including fractures and graben will form during the subsidence. Many times collapse pits will form within the graben. In addition to volcanic collapse pits, Mars has many collapse pits formed when volatiles (such as subsurface ice) are released from the surface layers. As the volatiles leave, the weight of the surrounding rock causes collapse pits to form. These collapse pits are found on the flank of Arsia Mons and are related to lava tube collapse. Image information: IR instrument. Latitude -8.8, Longitude 240.4 East (119.6 West). 100 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was

  5. Large-Scale Range Collapse of Hawaiian Forest Birds under Climate Change and the Need for 21st Century Conservation Options [corrected].

    Science.gov (United States)

    Fortini, Lucas B; Vorsino, Adam E; Amidon, Fred A; Paxton, Eben H; Jacobi, James D

    2015-01-01

    Hawaiian forest birds serve as an ideal group to explore the extent of climate change impacts on at-risk species. Avian malaria constrains many remaining Hawaiian forest bird species to high elevations where temperatures are too cool for malaria's life cycle and its principal mosquito vector. The impact of climate change on Hawaiian forest birds has been a recent focus of Hawaiian conservation biology, and has centered on the links between climate and avian malaria. To elucidate the differential impacts of projected climate shifts on species with known varying niches, disease resistance and tolerance, we use a comprehensive database of species sightings, regional climate projections and ensemble distribution models to project distribution shifts for all Hawaiian forest bird species. We illustrate that, under a likely scenario of continued disease-driven distribution limitation, all 10 species with highly reliable models (mostly narrow-ranged, single-island endemics) are expected to lose >50% of their range by 2100. Of those, three are expected to lose all range and three others are expected to lose >90% of their range. Projected range loss was smaller for several of the more widespread species; however improved data and models are necessary to refine future projections. Like other at-risk species, Hawaiian forest birds have specific habitat requirements that limit the possibility of range expansion for most species, as projected expansion is frequently in areas where forest habitat is presently not available (such as recent lava flows). Given the large projected range losses for all species, protecting high elevation forest alone is not an adequate long-term strategy for many species under climate change. We describe the types of additional conservation actions practitioners will likely need to consider, while providing results to help with such considerations.

  6. Large-Scale Range Collapse of Hawaiian Forest Birds under Climate Change and the Need for 21st Century Conservation Options [corrected].

    Directory of Open Access Journals (Sweden)

    Lucas B Fortini

    Full Text Available Hawaiian forest birds serve as an ideal group to explore the extent of climate change impacts on at-risk species. Avian malaria constrains many remaining Hawaiian forest bird species to high elevations where temperatures are too cool for malaria's life cycle and its principal mosquito vector. The impact of climate change on Hawaiian forest birds has been a recent focus of Hawaiian conservation biology, and has centered on the links between climate and avian malaria. To elucidate the differential impacts of projected climate shifts on species with known varying niches, disease resistance and tolerance, we use a comprehensive database of species sightings, regional climate projections and ensemble distribution models to project distribution shifts for all Hawaiian forest bird species. We illustrate that, under a likely scenario of continued disease-driven distribution limitation, all 10 species with highly reliable models (mostly narrow-ranged, single-island endemics are expected to lose >50% of their range by 2100. Of those, three are expected to lose all range and three others are expected to lose >90% of their range. Projected range loss was smaller for several of the more widespread species; however improved data and models are necessary to refine future projections. Like other at-risk species, Hawaiian forest birds have specific habitat requirements that limit the possibility of range expansion for most species, as projected expansion is frequently in areas where forest habitat is presently not available (such as recent lava flows. Given the large projected range losses for all species, protecting high elevation forest alone is not an adequate long-term strategy for many species under climate change. We describe the types of additional conservation actions practitioners will likely need to consider, while providing results to help with such considerations.

  7. Shell instability of a collapsing dense core

    CERN Document Server

    Ntormousi, Evangelia

    2014-01-01

    Understanding the formation of binary and multiple stellar systems largely comes down to studying the circumstances for the fragmentation of a condensing core during the first stages of the collapse. However, the probability of fragmentation and the number of fragments seem to be determined to a large degree by the initial conditions. In this work we study the fate of the linear perturbations of a homogeneous gas sphere both analytically and numerically. In particular, we investigate the stability of the well-known homologous solution that describes the collapse of a uniform spherical cloud. The difficulty of the mathematical singularity in the perturbation equations is surpassed here by explicitly introducing a weak shock next to the sonic point. In parallel, we perform adaptive mesh refinement (AMR) numerical simulations of the linear stages of the collapse and compared the growth rates obtained by each method. With this combination of analytical and numerical tools, we explore the behavior of both spherica...

  8. Collapse in the Endurance Athlete

    Institute of Scientific and Technical Information of China (English)

    Robert Sallis

    2005-01-01

    @@ KEY POINTS · Most cases of collapse are benign in nature and occur after an athlete crosses the finish line or stops exercising. Athletes who collapse before finishing are more likely to have a serious condition.

  9. Rigid collapsible dish structure

    Science.gov (United States)

    Palmer, William B. (Inventor); Giebler, Martin M. (Inventor)

    1982-01-01

    A collapsible dish structure composed of a plurality of rows of rigid radial petal assemblies concentric with the axis of the dish. The petal assemblies consist of a center petal and two side petals, the center petal hinged on an axis tangent to a circle concentric with the axis of the dish and the side petals hinged to the center petal at their mating edge. The center petal is foldable inwardly and the side petals rotate about their hinges such that the collapsed dish structure occupies a much smaller volume than the deployed dish. Means of controlling the shape of the dish to compensate for differential expansion of the deployed dish are also provided.

  10. On the Wavefunction Collapse

    Directory of Open Access Journals (Sweden)

    Ovidiu Cristinel Stoica

    2016-01-01

    Full Text Available Wavefunction collapse is usually seen as a discontinuous violation of the unitary evolution of a quantum system, caused by the observation. Moreover, the collapse appears to be nonlocal in a sense which seems at odds with general relativity. In this article the possibility that the wavefunction evolves continuously and hopefully unitarily during the measurement process is analyzed. It is argued that such a solution has to be formulated using a time symmetric replacement of the initial value problem in quantum mechanics. Major difficulties in apparent conflict with unitary evolution are identified, but eventually its possibility is not completely ruled out. This interpretation is in a weakened sense both local and realistic, without contradicting Bell's theorem. Moreover, if it is true, it makes general relativity consistent with quantum mechanics in the semiclassical framework.Quanta 2016; 5: 19–33.

  11. Shock induced cavity collapse

    Science.gov (United States)

    Skidmore, Jonathan; Doyle, Hugo; Tully, Brett; Betney, Matthew; Foster, Peta; Ringrose, Tim; Ramasamy, Rohan; Parkin, James; Edwards, Tom; Hawker, Nicholas

    2016-10-01

    Results from the experimental investigation of cavity collapse driven by a strong planar shock (>6km/s) are presented. Data from high speed framing cameras, laser backlit diagnostics and time-resolved pyromety are used to validate the results of hydrodynamic front-tracking simulations. As a code validation exercise, a 2-stage light gas gun was used to accelerate a 1g Polycarbonate projectile to velocities exceeding 6km/s; impact with a PMMA target containing a gas filled void results in the formation of a strong shockwave with pressures exceeding 1Mbar. The subsequent phenomena associated with the collapse of the void and excitation of the inert gas fill are recorded and compared to simulated data. Variation of the mass density and atomic number of the gas fill is used to alter the plasma parameters furthering the extent of the code validation.

  12. Self-Collapse Lithography.

    Science.gov (United States)

    Zhao, Chuanzhen; Xu, Xiaobin; Yang, Qing; Man, Tianxing; Jonas, Steven J; Schwartz, Jeffrey J; Andrews, Anne M; Weiss, Paul S

    2017-08-09

    We report a facile, high-throughput soft lithography process that utilizes nanoscale channels formed naturally at the edges of microscale relief features on soft, elastomeric stamps. Upon contact with self-assembled monolayer (SAM) functionalized substrates, the roof of the stamp collapses, resulting in the selective removal of SAM molecules via a chemical lift-off process. With this technique, which we call self-collapse lithography (SCL), sub-30 nm patterns were achieved readily using masters with microscale features prepared by conventional photolithography. The feature sizes of the chemical patterns can be varied continuously from ∼2 μm to below 30 nm by decreasing stamp relief heights from 1 μm to 50 nm. Likewise, for fixed relief heights, reducing the stamp Young's modulus from ∼2.0 to ∼0.8 MPa resulted in shrinking the features of resulting patterns from ∼400 to ∼100 nm. The self-collapse mechanism was studied using finite element simulation methods to model the competition between adhesion and restoring stresses during patterning. These results correlate well with the experimental data and reveal the relationship between the line widths, channel heights, and Young's moduli of the stamps. In addition, SCL was applied to pattern two-dimensional arrays of circles and squares. These chemical patterns served as resists during etching processes to transfer patterns to the underlying materials (e.g., gold nanostructures). This work provides new insights into the natural propensity of elastomeric stamps to self-collapse and demonstrates a means of exploiting this behavior to achieve patterning via nanoscale chemical lift-off lithography.

  13. Inhomogeneous electromagnetic gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Stein-Schabes, J.A.

    1985-04-15

    The collapse of an inhomogeneous dust cloud in the presence of an electromagnetic field is investigated in detail. The possibility of a naked singularity arising is studied using some known solutions for a spherical charged inhomogeneous dust cloud. It is found that locally naked singularities may develop when the arbitrary functions in the solution are chosen in a special way, but that a global naked singularity will not form. Also the role of the electromagnetic pressure is discussed.

  14. Collapse, environment, and society.

    Science.gov (United States)

    Butzer, Karl W

    2012-03-06

    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.

  15. Colony Collapse Disorder: A descriptive studey

    Science.gov (United States)

    Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We ...

  16. Black Hole Formation in Fuzzy Sphere Collapse

    CERN Document Server

    Iizuka, Norihiro; Roy, Shubho; Sarkar, Debajyoti

    2013-01-01

    We study the collapse of a fuzzy sphere, that is a spherical membrane built out of D0-branes, in the BFSS model. At weak coupling, as the sphere shrinks, open strings are produced. If the initial radius is large then open string production is not important and the sphere behaves classically. At intermediate initial radius the back-reaction from open string production is important but the fuzzy sphere retains its identity. At small initial radius the sphere collapses to form a black hole. The crossover between the later two regimes is smooth and occurs at the correspondence point of Horowitz and Polchinski.

  17. Application of geoelectrical methods in the DS sinkhole problem, Israel and Jordan

    Science.gov (United States)

    Levi, E.; Abueladas, A.-R.; Al-Zoubi, A.; Akkawi, E.; Ezersky, M.

    2012-04-01

    We consider a new approach to use the geoelectric methods for studying the both uppermost part of section and salt layer conditions in the sinkhole development sites. The Electric Resistivity Tomography (ERT) is used here to detect shallow deformations in subsurface sediments. Resistivity prospecting yields information about both lateral and vertical distribution of resistivity through the geological section and can therefore be used in both qualitative and quantitative ways for the identification of structure and features at shallow depths. As it follows from the modified Archie's Law, resistivity of the unsaturated sediments is determined by their porosity. The higher the porosity, the higher is the resistivity. It will also depend on volume of the electrolyte in pores and resistivity of the fluid . Note that after mechanical models available the higher porosity in sinkhole development sites is caused by the void presence at depth. 2D and 3D mapping was carried out in the Mineral Beach area in Israel and in the Ghor Al-Haditha site in Jordan. ERT method shown high resistivity anomaly of some thousands Ohm-m located along the salt edge. The Transient Electromagnetic Method (TEM) also referred to as the Time Domain Electromagnetic Method (TDEM) is sensitive to the bulk resistivity (conductivity) of the studied medium, especially in the low-resistivity range. Transient Electromagnetic (TEM) method in its FAST modification was used for studying the salt layer conditions (salt porosity, depth of the salt top and thickness of the salt layer) and distribution of bulk resistivity in vicinity of the salt border (to resolve the problem of water salinity). The methodology includes numerous measurements through the sinkhole development areas. Earlier the TEM method was used extensively worldwide for locating the fresh-saline water interface in coastal areas and for estimating groundwater salinity. In our study we have mapped salt layer geometrical parameters (e.g. depth to

  18. Fishing amplifies forage fish population collapses.

    Science.gov (United States)

    Essington, Timothy E; Moriarty, Pamela E; Froehlich, Halley E; Hodgson, Emma E; Koehn, Laura E; Oken, Kiva L; Siple, Margaret C; Stawitz, Christine C

    2015-05-26

    Forage fish support the largest fisheries in the world but also play key roles in marine food webs by transferring energy from plankton to upper trophic-level predators, such as large fish, seabirds, and marine mammals. Fishing can, thereby, have far reaching consequences on marine food webs unless safeguards are in place to avoid depleting forage fish to dangerously low levels, where dependent predators are most vulnerable. However, disentangling the contributions of fishing vs. natural processes on population dynamics has been difficult because of the sensitivity of these stocks to environmental conditions. Here, we overcome this difficulty by collating population time series for forage fish populations that account for nearly two-thirds of global catch of forage fish to identify the fingerprint of fisheries on their population dynamics. Forage fish population collapses shared a set of common and unique characteristics: high fishing pressure for several years before collapse, a sharp drop in natural population productivity, and a lagged response to reduce fishing pressure. Lagged response to natural productivity declines can sharply amplify the magnitude of naturally occurring population fluctuations. Finally, we show that the magnitude and frequency of collapses are greater than expected from natural productivity characteristics and therefore, likely attributed to fishing. The durations of collapses, however, were not different from those expected based on natural productivity shifts. A risk-based management scheme that reduces fishing when populations become scarce would protect forage fish and their predators from collapse with little effect on long-term average catches.

  19. 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.

  20. 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.

  1. Sinkhole Attack detection and prevention in MANET & Improving the performance of AODV Protocol

    Directory of Open Access Journals (Sweden)

    Rajeshwar L. Balla

    2013-07-01

    Full Text Available MANET is one of self configuring fastest emerging wireless technology. MANET is multi-hop wireless network of autonomous mobile nodes with no preset infrastructure where each node can move in any direction as well play a role of router. Dynamic nature of this network makes routing protocols to play a prominent role in setting up efficient route among pair of nodes. Therefore many proactive, reactive & hybrid routing protocols have been proposed, among which one of well known is AODV due to its high performance gain. Cooperative nature of nodes exposes MANET to various kinds of passive & active attacks. Sinkhole is one of severe kind of attack which attempts to attract most of network traffic towards it & degrade the performance of network. this paper, shows performance metrics as throughput, PDR, End to end delay & Packet loss. Simulation is carried out using widely used simulator NS2.

  2. 3D geostatistical modelling for identifying sinkhole disaster potential zones around the Verkhnekamskoye potash deposit (Russia)

    Science.gov (United States)

    Royer, J. J.; Litaudon, J.; Filippov, L. O.; Lyubimova, T.; Maximovich, N.

    2017-07-01

    This work results from a cooperative scientific program between the Perm State University (Russia) and the University of Lorraine (France). Its objectives are to integrate modern 3D geomodeling in order to improve sustainable mining extraction, especially for predicting and avoiding the formation of sinkholes disaster potential zones. Systematic exploration drill holes performed in the Verkhnekamskoye potash deposit (Perm region, Russia) have been used to build a comprehensive 3D model for better understanding the spatial repartition of the ore quality (geometallurgy). A precise modelling of the mineralized layers allows an estimation of the in-situ ore reserves after interpolating by kriging the potassium (K) and magnesium (Mg) contents at the node of a regular centred grid (over a million cells). Total resources in potassium vary according to the cut-off between 4.7Gt @ 16.1 % K2O; 0.32 % MgCl2 for a cut-off grade at 13.1% K2O and 2.06 Gt @ 18.2 % K2O; 0.32 % MgCl2 at a cut-off of 16.5% K2O. Most of reserves are located in the KPI, KPII and KPIII layers, the KPI being the richest, and KPIII the largest in terms of tonnage. A systematic study of the curvature calculated along the roof of the mineralized layers points out the location of potential main faults which play a major role in the formation of sinkhole during exploitation. A risk map is then derived from this attribute.

  3. Collapse of modern carbonate platform margins

    Energy Technology Data Exchange (ETDEWEB)

    Mullins, H.T.; Hine, A.C.; Gardulski, A.

    1985-01-01

    Modern carbonate platform margins in the Florida-Bahama region have been viewed as depositional or constructional features. However, recent studies have shown that carbonate escarpments, such as the Blake-Bahama and West Florida Escarpments, are erosional in origin where the platform margins have a scalloped or horse-shoe shape. Seismic reflection data from one of these crescentic features along the west Florida platform margin indicate that it originated by large scale gravity collapse (slump). This collapse structure extends for at least 120 km along the margin and has removed about 350 m of strata as young as early Neogene. Although at least three generations of slope failure are recognized, catastrophic collapse appears to have occurred in the mid-Miocene. Gravitational instability due to high rates of sediment accumulation may have been the triggering mechanism. These data suggest that submarine slumping is an important process in the retreat of limestone escarpments and in the generation of carbonate megabreccia debris flows. Scalloped platform margins occur on satellite images of northern Exuma Sound and Columbus Basin in the Bahamas. The authors suggest that large-scale submarine slumping can cause elongation of structurally controlled intraplatform basins (Exuma South), and produce anomalous horse-shoe shaped basins (Columbus Basin) by mega-collapse processes.

  4. Inadequate stakeholder management and its effect on a coherent sinkhole risk management strategy: The case of the Merafong Local Municipality, South Africa

    Directory of Open Access Journals (Sweden)

    Tshepo Moshodi

    2016-03-01

    Full Text Available The Merafong Local Municipality (MLM has historically suffered financial and human losses because of the presence of dolomite and the consequent formation of sinkholes. There is a great need for the MLM to address the risk posed by sinkholes to ensure the continued safety of communities. However, as the risk is so pervasive, the MLM needs to coordinate their risk reduction strategies with a wide array of stakeholders in the municipality. Efficient stakeholder management is thus crucial if the sinkhole risk is to be addressed appropriately. This article reviews the current status of stakeholder management in the MLM as it pertains to the formulation of a holistic sinkhole risk reduction strategy. Findings indicate that there are serious deficiencies in the MLM’s stakeholder management relating to key risk management processes such as community involvement in risk management structures, disaster risk assessment, training and awareness, and early warning and response. Improved stakeholder management could be characterised by the following factors: improved two-way communication between the municipality and community stakeholders, fostering a relationship based upon trust and equality amongst stakeholders, participation by a wide array of stakeholder groups affected by the sinkhole risk and a mutual commitment by all stakeholders to address the risk. These factors could contribute to enhancing current and future sinkhole risk reduction strategies.

  5. A three-dimensional back-analysis of the collapse of an underground cavity in soft rocks

    Science.gov (United States)

    Fazio, Nunzio Luciano; Lollino, Piernicola; Perrotti, Michele; Parise, Mario; Bonamini, Marco; Di Maggio, Cipriano; Madonia, Giuliana; Vattano, Marco

    2016-04-01

    Anthropogenic sinkholes have recently occurred in built-up areas of Sicily (southern Italy) and are generally associated with the presence of ancient underground quarries for the extraction of soft calcarenite rock, used as building material. These quarries were poorly excavated and then were abandoned in the following decades; urban expansion has recently enlarged to involve the areas affected by presence of the cavities, so that the likely collapse of the underground systems poses serious risks to people, buildings and infrastructures. The present work focuses on the case of the town of Marsala, where in 2003 a sinkhole opened at the outskirts of town, near peri-urban buildings. Field surveys, structural analysis of the joint networks in the rock mass and numerical modeling were carried out in order to investigate the most significant factors responsible of the instability processes of the underground quarry. In particular, a geotechnical three-dimensional model has been defined based on in-situ measurements and surveys. The FEM analyses have been performed with the code Plaxis-3D, by using initially the Mohr-Coulomb elasto-plastic model and then assessing the influence of the joint systems on the rock-mass stability with a jointed rock anisotropic model. Discrete planar bands have been also used to simulate the effect of specific joints, as an alternative to the jointed rock model. The results are in good agreement with the failure mechanism generated during the 2003 sinkhole event, and confirm that reliable analyses of these problems requires 3-D sophisticated tools.

  6. Disproportionate Collapse in Building Structures.

    OpenAIRE

    JANSSENS, VICTORIA MARIA; O'DWYER, DERMOT WILLIAM

    2010-01-01

    PUBLISHED Cork, Ireland The failure of the Ronan Point apartment tower focused interest in disproportionate collapse, and prompted the ?Fifth Amendment? to the UK Building Regulations which was introduced in 1970. From this point on structures were required to exhibit a minimum level of robustness to resist progressive collapse. These rules have remained relatively unchanged for over 40 years. This paper presents a review of the concepts relating to structural collapse, and the robustne...

  7. Cylindrical Collapse and Gravitational Waves

    CERN Document Server

    Herrera, L

    2005-01-01

    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.

  8. On collapsibilities of Yule's measure

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    impson's paradox reminds people that the statistical inference in a low-dimensional space probably distorts the reality in a high one seriously.To study the paradox with respect to Yule's measure,this paper discusses simple collapsibility,strong collapsibility and consecutive collapsibility,and presents necessary and sufficient conditions of them.In fact,these conditions are of great importance for observational and experimental designs,eliminating confounding bias,categorizing discrete variables and so on.

  9. Holocene environmental change of the northern Caribbean inferred from the sediments of a flooded sinkhole, Cayo Coco, Cuba

    Science.gov (United States)

    Peros, M. C.; Agosta G'meiner, A. M.; Collins, S.

    2016-12-01

    We present new data on the Holocene environments of the northern Caribbean inferred from the sediments of a flooded sinkhole (Cenote Jennifer) on the island of Cayo Coco in north-central Cuba. Cenote Jennifer is located several meters above sea level and has an average depth of 13 meters. Water chemistry measurements indicate that the water in the sinkhole is highly stratified with a halocline at about 8 meters depth and an anoxic base. A series of sediment cores collected at the center of the sinkhole were analyzed for fossil pollen, microcharcoal, dinoflagellate cysts, elemental geochemistry (by high-resolution XRF core-scanning), and grain size and were dated by Pb-210 and AMS radiocarbon techniques (using well-preserved macrofossils of leaves, bark, and twigs). The results show that sediments first began to accumulate in Cenote Jennifer approximately 9000 years ago and continued until the present. The elemental geochemistry results record increases in elements such as Br, Cl, Ni, and Cu during the 8.2 kyr event which may reflect enhanced deep-ocean upwelling at this time. The fossil pollen data record a succession in vegetation that included cattail marsh, thorny coastal scrubland, dry evergreen forest, and secondary forest communities over the course of the Holocene. Changes in vegetation were driven mostly by relative sea level rise in the early Holocene but climate change was more important by the middle to late Holocene. Hundreds of mm- to cm-scale laminations are also present in the core, many of which represent past hurricane strikes. The microcharcoal and pollen evidence also suggests that prehistoric humans may have settled the area and practiced agriculture as early as 2800 cal yr BP. The findings from Cenote Jennifer highlight the utility of flooded sinkholes as paleoenvironmental archives in tropical kart regions and provide important new data on the hydroclimatology of the northern Caribbean.

  10. Sinkhole susceptibility in carbonate rocks of the Apulian karst (southern Italy)

    Science.gov (United States)

    Di Santo, Antonio; Fazio, Nunzio L.; Fiore, Antonio; Lollino, Piernicola; Luisi, Michele; Miccoli, Maria N.; Pagliarulo, Rosa; Parise, Mario; Perrotti, Michele; Pisano, Luca; Spalluto, Luigi; Vennari, Carmela; Vessia, Giovanna

    2016-04-01

    Apulia region, the foreland of the southern Italian Apennines, is made up of a 6-7 km-thick succession of Mesozoic shallow-water limestones and dolostones, locally covered by thin and discontinuous Tertiary and Quaternary carbonate and clastic deposits. Due to their long subaerial exposure, the Mesozoic carbonate bedrock recorded the development in the subsurface of a dense network of karst cavities, mostly controlled by tectonic discontinuities. As a result, a strong susceptibility to natural sinkholes has to be recorded in Apulia. In addition, the possibility of occurrence of other problems related to the high number of man-made cavities has to be added in the region. A great variety of different typologies of artificial cavities (mostly excavated in the Plio-Pleistocene soft calcarenites) is actually present, including underground quarries, worship sites, oil mills, civilian settlements, etc. Overall, 2200 natural and 1200 artificial cavities, respectively, have been so far surveyed in Apulia. Following the urban development in the last century in Apulia, many of these cavities lie nowadays below densely populated neighborhoods, roads or communication routes. These conditions are at the origin of the main geomorphological hazard for the human society in Apulia, which requires a careful evaluation, aimed at protecting and safeguarding the human life, and at providing the necessary information for a correct land use planning and management. The importance of the sinkhole hazard is further testified by the worrying increase in the number of events during the last 5-6 years. In response to these situations, joint research activities were started by the Institute of Research for Hydrological Protection of the National Research Council (CNR-IRPI) and the Basin Authority of Apulia, aimed at several goals, that include (but are not limited to) the collection of information on natural and anthropogenic sinkholes in Apulia, the implementation of numerical analyses for

  11. The collapsed football pla yer

    African Journals Online (AJOL)

    There are several reasons why football players collapse or appear to have collapsed on ... minor, resulting in mild concussion (brain injury), but ... after being struck by lightning. The match ... does occur, it attracts a great deal of media attention ...

  12. Environmental dependence in the ellipsoidal collapse model

    CERN Document Server

    Desjacques, Vincent

    2007-01-01

    N-body simulations have demonstrated a correlation between the properties of haloes and their environment. In this paper, we assess whether the ellipsoidal collapse model can produce a similar dependence. First, we explore the statistical correlation that originates from Gaussian initial conditions. We derive analytic expressions for a number of joint statistics of the shear tensor and estimate the sensitivity of the local characteristics of the shear to the global geometry of the large scale environment. Next, we concentrate on the dynamical aspect of the environmental dependence using a simplified model that takes into account the interaction between a collapsing halo and its environment. We find that the tidal force exerted by the surrounding mass distribution causes haloes embedded in overdense regions to virialize earlier. An effective density threshold whose shape depends on the large scale density provides a good description of this environmental effect. We show that, using this approach, a correlation...

  13. Caldera rim collapse: A hidden volcanic hazard

    OpenAIRE

    Merle, Olivier; Michon, Laurent; Bachèlery, Patrick

    2008-01-01

    International audience; Following the emblematic flank collapse of Mount St Helens in 1981, numerous models of flank sliding have been proposed. These models have allowed to largely improve the understanding of mechanisms involved in such landslides, which represent a tremendous risk for populations living around volcanoes. In this article, a new mode of landslide formation, related to buried calderas, is described. The model emphasizes the paramount importance of the hidden ring fault that, ...

  14. Simulations of protostellar collapse using multigroup radiation hydrodynamics. II. The second collapse

    CERN Document Server

    Vaytet, N; Audit, E; Commercon, B; Masson, J; Ferguson, J; Delahaye, F

    2013-01-01

    Star formation begins with the gravitational collapse of a dense core inside a molecular cloud. As the collapse progresses, the centre of the core begins to heat up as it becomes optically thick. The temperature and density in the centre eventually reach high enough values where fusion reactions can ignite; the protostar is born. This sequence of events entail many physical processes, of which radiative transfer is of paramount importance. Many simulations of protostellar collapse make use of a grey treatment of radiative transfer coupled to the hydrodynamics. However, interstellar gas and dust opacities present large variations as a function of frequency. In this paper, we follow-up on a previous paper on the collapse and formation of Larson's first core using multigroup radiation hydrodynamics (Paper I) by extending the calculations to the second phase of the collapse and the formation of Larson's second core. We have made the use of a non-ideal gas equation of state as well as an extensive set of spectral ...

  15. Influence of stratigraphic factors on the failure mechanisms of sinkholes related to man-made underground caves at Cutrofiano (South-Eastern Italy)

    Science.gov (United States)

    Lollino, Piernicola; Margiotta, Stefano; Parise, Mario

    2013-04-01

    strata, dipping toward the SW, and to lateral variations in the geological succession. Thus, at least two different geological settings may be recognized: the first is typical of those areas closest to the town, where the calcarenite rock mass is at low depth, and appears to be covered by very thin deposits; in such a situation, the underground quarries develop at depths ranging from 7 to 10 meters below the ground surface. The second setting, which typically characterizes the sectors a few kilometres farther south, shows, on the other hand, the presence of thick cover of the clay-sandy intervals, and has the galleries of underground quarries located at depth variable from 15 to 45 m. Starting from these different situations, two-dimensional numerical analyses have been developed by using the finite element method to investigate the stress-strain evolution of the rock mass surrounding the galleries due to long-term degradation of the rock properties induced by weathering and water infiltration. The results obtained from the numerical simulations point out a quite different behaviour between the two geological settings, since the presence of the significant clay layer overlying the calcarenite substratum affects the geometry of the subsidence cone, and, consequently, the real extent of the likely sinkholes at the surface. These outcomes are of great importance to highlight the need to use detailed, site-specific, data in order to perform numerical modelling, and warn about the common habit of extending a small number of borehole data, tens of hundreds of meters apart, over large areas. Especially when carried out to define vulnerability and/or risk of specific elements at risk, the researches should be performed having available on-site data, or, alternatively, the end users should be properly warned in the use of the outcomes from the study.

  16. Analytical and numerical method assessing the risk of sinkholes formation in mining areas

    Institute of Scientific and Technical Information of China (English)

    Piotr Strzalkowski; Krzysztof Tomiczek⇑

    2015-01-01

    Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had been formed as a result of mining operations in the deeper strata. Taking into account the impact of lower coal seams mining on shallow excavations and based on the example of a region that had been intensely exploited, this paper proposes a methodology for analysing the stability of shallow mine voids in the rock mass. Deformations in the excavation region were calculated by using FLAC2D computer pro-gram and assigning the Coulomb–Mohr model to the rock mass. Based on the numerical analysis, this paper evaluated the stability of the void in the event of a roof support fall. The results indicate the like-lihood of void formation. Based on the Budryk–Knothe theory, the deformations of rock mass and sand-stone strata in the roof of the void, which had been caused by mining exploitation in consecutive years, were calculated. The results of numerical calculations and analyses were compared with the limit defor-mations values of sandstone in tension. It is concluded that the exploitations cause the void to break down. The proposed method can forecast the discontinuous deformations threats in the areas that have undergone shallow undermining exploitation and the areas of underground urban.

  17. Water and dissolved gas geochemistry of the monomictic Paterno sinkhole (central Italy

    Directory of Open Access Journals (Sweden)

    Matteo Nocentini

    2012-07-01

    Full Text Available This paper describes the chemical and isotope features of water and dissolved gases from lake Paterno (max. depth 54 m, a sinkhole located in the NE sector of the S. Vittorino plain (Rieti, Central Italy, where evidences of past and present hydrothermal activity exists. In winter (February 2011 lake Paterno waters were almost completely mixed, whereas in summer time (July 2011 thermal and chemical stratifications established. During the stratification period, water and dissolved gas chemistry along the vertical water column were mainly controlled by biological processes, such as methanogenesis, sulfate-reduction, calcite precipitation, denitrification, and NH4 and H2 production. Reducing conditions at the interface between the bottom sediments and the anoxic waters are responsible for the relatively high concentrations of dissolved iron (Fe and manganese (Mn, likely present in their reduced oxidation state. Minerogenic and biogenic products were recognized at the lake bottom even during the winter sampling. At relatively shallow depth the distribution of CH4 and CO2 was controlled by methanotrophic bacteria and photosynthesis, respectively. The carbon isotope signature of CO2 indicates a significant contribution of deep-originated inorganic CO2 that is related to the hydrothermal system feeding the CO2-rich mineralized springs discharging in the surrounding areas of lake Paterno. The seasonal lake stratification likely controls the vertical and horizontal distribution of fish populations in the different periods of the year.

  18. 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.

  19. Geophysical observations at cavity collapse

    OpenAIRE

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

    2010-01-01

    International audience; 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 ...

  20. Vibrational Collapse of Hexapod Packings

    Science.gov (United States)

    Zhao, Yuchen; Ding, Jingqiu; Barés, Jonathan; Dierichs, Karola; Behringer, Robert

    2016-11-01

    Columns made of convex noncohesive grains like sand collapse after being released from a confining container. However, structures built from concave grains can be stable without external support. Previous research show that the stability of the columns depends on column diameter and height, by observing column stability after carefully lifting their confinement tubes. Thinner and taller columns collapse with higher probability. While the column stability weakly depends on packing density, it strongly depends on inter-particle friction. Experiments that cause the column to collapse also reveal similar trends, as more effort (such as heavier loading or shearing) is required to destabilize columns that are intrinsically more stable. In the current experiments, we invesitage the effect of vibration on destructing a column. Short columns collapse following the relaxation dynamics of disorder systems, which coincides with similar experiments on staple packings. However, tall columns collapse faster at the beginning, in addition to the relaxation process coming after. Using high-speed imaging, we analyze column collapse data from different column geometries. Ongoing work is focusing on characterizing the stability of hexapod packings to vibration. We thanks NSF-DMR-1206351 and the William M. Keck Foundation.

  1. The impact of droughts and climate change on sinkhole occurrence. A case study from the evaporite karst of the Fluvia Valley, NE Spain.

    Science.gov (United States)

    Linares, Rogelio; Roqué, Carles; Gutiérrez, Francisco; Zarroca, Mario; Carbonel, Domingo; Bach, Joan; Fabregat, Ivan

    2017-02-01

    This work introduces the concept that sinkhole frequency in some karst settings increases during drought periods. This conception is tested in a sector of the Fluvia River valley in NE Spain, where subsidence phenomena is related to the karstification of folded Eocene evaporite formations. In the discharge areas, the evaporites behave as confined aquifers affected by hypogene karstification caused by aggressive artesian flows coming form an underlying carbonate aquifer. A sinkhole inventory with chronological data has been constructed, revealing temporal clusters. Those clusters show a good correlation with drought periods, as revealed by precipitation, river discharge and piezometric data. This temporal association is particularly obvious for the last and current drought starting in 1998, which is the most intense of the record period (1940-present). Climatic projections based on recent studies foresee an intensification of the droughts in this sector of NE Spain, which could be accompanied by the enhancement of the sinkhole hazard and the associated risks.

  2. Effect of confinement on the collapsing mechanism of a flexible polymer chain.

    Science.gov (United States)

    Das, Siddhartha; Chakraborty, Suman

    2010-11-07

    In this paper, Brownian dynamics simulation (BDS) studies are executed to demonstrate the distinctive influences of the extent of confinement on the collapsing mechanism and kinetics of a flexible hydrophobic polymer chain in a poor solvent. The collapsing behavior is quantified by the time of collapse, which below a critical dimension of the confinement (h(c)), encounters a drastic reduction with a further strengthening in the degree of confinement. For dimensions greater than this critical one, the collapse occurs through the well-known hydrodynamic interaction (HI) controlled multiple-globule-mediated mechanisms. However, for channel dimensions less than this critical one, the collapse mechanism is drastically altered. Under such circumstances, the collapse gets predominantly controlled by the confinement effects (with negligible contribution of the HIs) and occurs via the formation of a single central globule. This central globule rapidly engulfs the noncondensed polymer segments, and in the process largely hastens up the collapsing event. Under such circumstances, the collapse time is found to decrease linearly with decrements in the channel height. On the contrary, for channel heights greater than h(c), the multiple-globule-mediated collapse is characterized by a collapse time that shows an exponential dependence on the channel height, rapidly attaining a state in which the confinement effect becomes inconsequential and HIs dictate the entire collapsing behavior. We further propose detailed arguments based on physical reasoning as well as free energy estimations to conclusively support the qualitative and quantitative nature of influences of the confinement on the polymer collapse.

  3. Study of film boiling collapse behavior during vapor explosion

    Energy Technology Data Exchange (ETDEWEB)

    Yagi, Masahiro; Yamano, Norihiro; Sugimoto, Jun [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; 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.)

  4. Connectivity among sinkholes and complex networks: The case of Ring of Cenotes in northwest Yucatan, Mexico

    Science.gov (United States)

    Gomez-Nicolas, Mariana; Rebolledo-Vieyra, Mario; Huerta-Quintanilla, Rodrigo; Canto-Lugo, Efrain

    2014-05-01

    A 180-km-diameter semicircular alignment of abundant karst sinkholes (locally known as cenotes) in northwestern Yucatán, México, coincides approximately with a concentric ring of the buried Chicxulub structure, a circular feature manifested in Cretaceous and older rocks, that has been identified as the product of the impact of a meteorite. The secondary permeability generated by the fracturing and faulting of the sedimentary sequence in the Chicxulub impact, has favored the karstification process and hence the development of genuine underground rivers that carry water from the continent to the sea. The study of the structure and morphology of the crater has allowed researchers to understand the key role of the crater in the Yucatán hydrogeology. It is generally accepted that the Ring of Cenotes, produced by the gravitational deformation of the Tertiary sedimentary sequence within the crater, controls the groundwater in northern Yucatán. However, today there is not solid evidence about the connectivity among cenotes, which is important because if established, public policies could be designed to manage sanitary infrastructure, septic control, regulation of agricultural and industrial activities and the protection of water that has not been compromised by anthropogenic pollution. All these directly affect more than half a million people whose main source of drinking water lies in the aquifer. In this contribution we investigated a set of 16 cenotes located in the vicinity of a gravimetric anomaly of Chicxulub crater ring, using complex networks to model the interconnectivity among them. Data from a geoelectrical tomography survey, collected with SuperSting R1/IP equipment, with multi-electrodes (72 electrodes), in a dipole-dipole configuration was used as input of our model. Since the total number of cenotes on the ring structure amounts to about 2000, the application of graph theoretic algorithms and Monte Carlo simulation to efficiently investigate network

  5. Hydrogeochemical processes controlling water and dissolved gas chemistry at the Accesa sinkhole (southern Tuscany, central Italy

    Directory of Open Access Journals (Sweden)

    Franco Tassi

    2014-05-01

    Full Text Available The 38.5 m deep Lake Accesa is a sinkhole located in southern Tuscany (Italy that shows a peculiar water composition, being characterized by relatively high total dissolved solids (TDS values (2 g L-1 and a Ca(Mg-SO4 geochemical facies. The presence of significant amounts of extra-atmospheric gases (CO2 and CH4, which increase their concentrations with depth, is also recognized. These chemical features, mimicking those commonly shown by volcanic lakes fed by hydrothermal-magmatic reservoirs, are consistent with those of mineral springs emerging in the study area whose chemistry is produced by the interaction of meteoric-derived waters with Mesozoic carbonates and Triassic evaporites. Although the lake has a pronounced thermocline, water chemistry does not show significant changes along the vertical profile. Lake water balance calculations demonstrate that Lake Accesa has >90% of its water supply from sublacustrine springs whose subterranean pathways are controlled by the local structural assessment that likely determined the sinking event, the resulting funnel-shape being then filled by the Accesa waters. Such a huge water inflow from the lake bottom (~9·106 m3 yr-1 feeds the lake effluent (Bruna River and promotes the formation of water currents, which are able to prevent the establishment of a vertical density gradient. Consequently, a continuous mixing along the whole vertical water column is established. Changes of the drainage system by the deep-originated waters in the nearby former mining district have strongly affected the outflow rates of the local mineral springs; thus, future intervention associated with the ongoing remediation activities should carefully be evaluated to preserve the peculiar chemical features of Lake Accesa.

  6. Formation of satellites from cold collapse

    Science.gov (United States)

    Benhaiem, David; Sylos Labini, Francesco

    2017-02-01

    We study the collapse of an isolated, initially cold, irregular (but almost spherical) and slightly inhomogeneous cloud of self-gravitating particles.The cloud is driven towards a virialized quasi-equilibrium state by a fast relaxation mechanism, occurring in a typical time τc, whose signature is a large change in the particle energy distribution. Post-collapse particles are divided into two main species: bound and free, the latter being ejected from the system. Because of the initial system's anisotropy, the time varying gravitational field breaks spherical symmetry so that the ejected mass can carry away angular momentum and the bound system can gain a non-zero angular momentum. In addition, while strongly bound particles form a compact core, weakly bound ones may form, in a time scale of the order of τc, several satellite sub-structures. These satellites have a finite lifetime that can be longer than τc and generally form a flattened distribution. Their origin and their abundance are related to the amplitude and nature ofinitial density fluctuations and to the initial cloud deviations from spherical symmetry, which are both amplified during the collapse phase. Satellites show a time dependent virial ratio that can be different from the equilibrium value b ≈ -1: although they are bound to the main virialized object, they are not necessarily virially relaxed.

  7. Properties of Neutron Star Critical Collapses

    Science.gov (United States)

    Wan, Mew-Bing

    2010-01-01

    Critical phenomena in gravitational collapse opened a new mathematical vista into the theory of general relativity and may ultimately entail fundamental physical implication in observations. However, at present, the dynamics of critical phenomena in gravitational collapse scenarios are still largely unknown. My thesis seeks to understand the properties of the threshold in the solution space of the Einstein field equations between the black hole and neutron star phases, understand the properties of the neutron star critical solution and clarify the implication of these results on realistic astrophysical scenarios. We develop a new set of neutron star-like initial data to establish the universality of the neutron star critical solution and analyze the structure of neutron star and neutron star-like critical collapses via the study of the phase spaces. We also study the different time scales involved in the neutron star critical solution and analyze the properties of the critical index via comparisons between neutron star and neutron star-like initial data. Finally, we explore the boundary of the attraction basin of the neutron star critical solution and its transition to a known set of non-critical fixed points.

  8. Late Holocene stable carbon and nitrogen isotopic variation of bulk organic matter deposited in Blackwood Sinkhole, Abaco, The Bahamas

    Science.gov (United States)

    Tamalavage, A.; van Hengstum, P. J.; Louchouarn, P.; Fall, P. L.; Donnelly, J. P.

    2015-12-01

    In the modern climate of the Bahamas, a latitudinal precipitation gradient only allows Pine (Pinus caribaea var. bahamensis) dominated forests to exist on the more mesic (humid) northern islands (Abaco, Andros, New Providence, Grand Bahamas). Previous research suggests that the northern Bahamas underwent dramatic environmental changes in the late Holocene (e.g., waves of human arrival, shifts in terrestrial vegetation and animal extinctions). However, disentangling the timing and relative forcing (climatic vs. anthropogenic) of these changes has proven challenging without high-resolution terrestrial climate records. Recently, a late Holocene decadal to multi-decadal laminated sedimentary record was recovered from Blackwood Sinkhole, on Abaco Island. The bottom of the sinkhole is characterized by anoxic, saline groundwater, while the upper, brackish meteoric lens provides a habitat to fish, algae and other organisms. Here, we present δ13Corg and δ15Norg values of bulk organic matter (OM) taken every cm of the 110 cm core to help elucidate changes in the chemical composition of the source of OM reaching the anoxic sediments of the sinkhole. δ13Corg values change at 812 Cal yrs BP (2s: 931-681 Cal yrs BP, 31.7 cm depth) from -30.5 ± 1.6‰ in the lower 80 cm of the core to -27.6 ± 1.2‰ in the upper 30 cm. There is a synchronous change from more enriched δ15N values, 3.7 ± 1.1‰, in the lower portion of the core, to lower δ15N values (1.9 ± .5‰), in the upper portion of the core. A pollen-based reconstruction of terrestrial vegetation from the same core indicates that these isotopic shifts are concomitant with a shift from a dominance of Arecaceae (Palms) and tropical dry hardwoods below 30 cm, to Pinus and Conocarpus predominance above 30 cm. These results indicate that the source of sedimentary OM deposited into the sinkhole changed coherently with regional landscape change. Biomarker analyses will be used to further identify the role of autochthonous

  9. 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.

  10. Dissipative Collapse of a Spherical Cluster of Gas Clouds

    CERN Document Server

    Indulekha, K; Ramadurai, S

    2000-01-01

    We investigate the dissipative collapse of a spherical cluster of gas clouds with an isotropic velocity distribution. The time scale for collapse to one tenth radius is studied as a function of the collision time in the system. The scalar virial equation is used to investigate the evolution of the size of the cluster. This is supplemented with an evolution equation for the random kinetic energy. The above system is numerically solved and the results analyzed. For small values of the collision time we find that the time scale for collapse is proportional to the collision time as expected. However for large values of the dissipation the collapse time shows a nonlinear dependence on the collision time.

  11. Seismic Progressive Collapse: Qualitative Point of View

    Directory of Open Access Journals (Sweden)

    H. Wibowo

    2009-01-01

    Full Text Available Progressive collapse is a catastrophic structural phenomenon that can occur because of human-made and natural hazards. In progressive collapse mechanism, a single local failure may cause a significant deformation which then may lead to collapse of a structure. The current practices in progressive collapse analysis and design method generally focus on preventing progressive collapse due to abnormal gravity and blast loads. Progressive collapse behaviour of structures due to earthquake loads has not received as much attention. This paper presents a brief overview of the current state-of-knowledge, insights, and issues related to progressive collapse behaviour of structures caused by earthquake loading.

  12. Gravitational collapse and naked singularities

    Indian Academy of Sciences (India)

    Tomohiro Harada

    2004-10-01

    Gravitational collapse is one of the most striking phenomena in gravitational physics. The cosmic censorship conjecture has provided strong motivation for research in this field. In the absence of a general proof for censorship, many examples have been proposed, in which naked singularity is the outcome of gravitational collapse. Recent developments have revealed that there are examples of naked singularity formation in the collapse of physically reasonable matter fields, although the stability of these examples is still uncertain. We propose the concept of `effective naked singularities', which will be quite helpful because general relativity has limitation in its application at the high-energy end. The appearance of naked singularities is not detestable but can open a window for the new physics of strongly curved space-times.

  13. Black hole collapse and democratic models

    Science.gov (United States)

    Jansen, Aron; Magán, Javier M.

    2016-11-01

    We study the evolution of black hole entropy and temperature in collapse scenarios in asymptotically anti-de Sitter spacetime, finding three generic lessons. First, entropy evolution is extensive. Second, at large times, entropy and temperature ring with twice the frequency of the lowest quasinormal mode. Third, the entropy oscillations saturate black hole area theorems in general relativity. The first two features are characteristic of entanglement dynamics in "democratic" models. Solely based on general relativity and the Bekenstein-Hawking entropy formula, our results point to democratic models as microscopic theories of black holes. The third feature can be taken as a prediction for microscopic models of black hole physics.

  14. 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.

  15. Ekpyrotic collapse with multiple fields

    CERN Document Server

    Koyama, K; Koyama, Kazuya; Wands, David

    2007-01-01

    A scale invariant spectrum of isocurvature perturbations is generated during collapse in the scaling solution in models where two or more fields have steep negative exponential potentials. The scale invariance of the spectrum is realised by a tachyonic instability in the isocurvature field. We show that this instability is due to the fact that the scaling solution is a saddle point in the phase space. The late time attractor is identified with a single field dominated ekpyrotic collapse in which a steep blue spectrum for isocurvature perturbations is found. Although quantum fluctuations do not necessarily to disrupt the classical solution, an additional preceding stage is required to establish classical homogeneity.

  16. On the number density of `direct collapse' black hole seeds

    Science.gov (United States)

    Habouzit, Mélanie; Volonteri, Marta; Latif, Muhammad; Dubois, Yohan; Peirani, Sébastien

    2016-11-01

    Supermassive black holes (BHs) reside in the centre of most local galaxies, but they also power active galactic nuclei and quasars, detected up to z = 7. These quasars put constraints on early BH growth and the mass of BH seeds. The scenario of `direct collapse' is appealing as it leads to the formation of large mass BH seeds, 104-106 M⊙, which eases explaining how quasars at z = 6-7 are powered by BHs with masses >109 M⊙. Direct collapse, however, appears to be rare, as the conditions required by the scenario are that gas is metal-free, the presence of a strong photodissociating Lyman-Werner flux, and large inflows of gas at the centre of the halo, sustained for 10-100 Myr. We performed several cosmological hydrodynamical simulations that cover a large range of box sizes and resolutions, thus allowing us to understand the impact of several physical processes on the distribution of direct collapse BHs. We identify haloes where direct collapse can happen, and derive the number density of BHs. We also investigate the discrepancies between hydrodynamical simulations, direct or post-processed, and semi-analytical studies. Under optimistic assumptions, we find that for direct collapse to account for BHs in normal galaxies, the critical Lyman-Werner flux required for direct collapse must be about two orders of magnitude lower than predicted by 3D simulations that include detailed chemical models. However, when supernova feedback is relatively weak, enough direct collapse BHs to explain z = 6-7 quasars can be obtained for Lyman-Werner fluxes about one order of magnitude lower than found in 3D simulations.

  17. Modelling study of challenges in sinkhole detection with shear wave reflection seismics

    Science.gov (United States)

    Burschil, Thomas; Krawczyk, CharLotte M.

    2016-04-01

    conjugated fracture system shadows the cavity with crossing cracks, but in a tensile fracture zone the shear wave travels parallel to the cracks and reflects at the cavity. For P-wave propagation the fracture zone has no fundamental influence on the cavity reflection. We reveal that a fracture zone can hamper transmission of shear waves and shadow a cavity, and that seismic pathways are crucial for shear wave propagation through a fracture zone. Schneider-Löbens, C., Wuttke, M.W., Backers, T. & Krawczyk, C.M. (2015). Numerical modeling approach of sinkhole propagation using the eXtended FEM code 'roxol'. Geophysical Research Abstracts, Vol. 17, EGU2015-12230-2.

  18. Critical behavior of collapsing surfaces

    DEFF Research Database (Denmark)

    Olsen, Kasper; Sourdis, C.

    2009-01-01

    We consider the mean curvature evolution of rotationally symmetric surfaces. Using numerical methods, we detect critical behavior at the threshold of singularity formation resembling that of gravitational collapse. In particular, the mean curvature simulation of a one-parameter family of initial...

  19. Simulations of protostellar collapse using multigroup radiation hydrodynamics. I. The first collapse

    CERN Document Server

    Vaytet, Neil; Chabrier, Gilles; Commercon, Benoit; Masson, Jacques

    2012-01-01

    Radiative transfer plays a major role in the process of star formation. Many simulations of gravitational collapse of a cold gas cloud followed by the formation of a protostellar core use a grey treatment of radiative transfer coupled to the hydrodynamics. However, dust opacities which dominate extinction show large variations as a function of frequency. In this paper, we used frequency-dependent radiative transfer to investigate the influence of the opacity variations on the properties of Larson's first core. We used a multigroup M1 moment model in a 1D radiation hydrodynamics code to simulate the spherically symmetric collapse of a 1 solar mass cloud core. Monochromatic dust opacities for five different temperature ranges were used to compute Planck and Rosseland means inside each frequency group. The results are very consistent with previous studies and only small differences were observed between the grey and multigroup simulations. For a same central density, the multigroup simulations tend to produce fi...

  20. Hierarchical star cluster assembly in globally collapsing molecular clouds

    Science.gov (United States)

    Vázquez-Semadeni, Enrique; González-Samaniego, Alejandro; Colín, Pedro

    2017-05-01

    We discuss the mechanism of cluster formation in a numerical simulation of a molecular cloud (MC) undergoing global hierarchical collapse, focusing on how the gas motions in the parent cloud control the assembly of the cluster. The global collapse implies that the star formation rate (SFR) increases over time. The collapse is hierarchical because it consists of small-scale collapses within larger scale ones. The latter culminate a few Myr later than the first small-scale ones and consist of filamentary flows that accrete on to massive central clumps. The small-scale collapses consist of clumps that are embedded in the filaments and falling on to the large-scale collapse centres. The stars formed in the early, small-scale collapses share the infall motion of their parent clumps, so that the filaments feed both gas and stars to the massive central clump. This process leads to the presence of a few older stars in a region where new protostars are forming, and also to a self-similar structure, in which each unit is composed of smaller scale subunits that approach each other and may merge. Because the older stars formed in the filaments share the infall motion of the gas on to the central clump, they tend to have larger velocities and to be distributed over larger areas than the younger stars formed in the central clump. Finally, interpreting the initial mass function (IMF) simply as a probability distribution implies that massive stars only form once the local SFR is large enough to sample the IMF up to high masses. In combination with the increase of the SFR, this implies that massive stars tend to appear late in the evolution of the MC, and only in the central massive clumps. We discuss the correspondence of these features with observed properties of young stellar clusters, finding very good qualitative agreement.

  1. Hierarchical gravitational fragmentation. I. Collapsing cores within collapsing clouds

    CERN Document Server

    Romero, Raúl Naranjo; Loughnane, Robert M

    2015-01-01

    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 $r^-2$ 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 t...

  2. Construction Techniques for the Treatment of the Collapse of Bored Holes for Large-Diameter Foundation Piles%大直径基桩坍孔处理施工技术

    Institute of Scientific and Technical Information of China (English)

    尤春颖

    2011-01-01

    新月铁路分离式立交桥21-1基桩紧邻电气化铁路,振动较大且砂土层较厚,在试桩过程中发生坍孔。分析工程具体情况,决定采用预制钢筋混凝土沉井护壁处理。介绍了沉井的设计、加工与下沉,大直径冲击钻成孔过程及相应的质量控制措施,处理后的基桩质量良好。可为类似工程处理提供有益借鉴。%Owing to the fact that the No. 21-1 foundation pile of the Xinyue Railway Separate Overpass is near an electrified railway, where the vibration is very strong and the sand layer is thick, the wall of the bored hole collapsed in the course of test-boring

  3. Computational Models of Stellar Collapse and Core-Collapse Supernovae

    CERN Document Server

    Ott, C D; Burrows, A; Livne, E; O'Connor, E; Löffler, F

    2009-01-01

    Core-collapse supernovae are among Nature's most energetic events. They mark the end of massive star evolution and pollute the interstellar medium with the life-enabling ashes of thermonuclear burning. Despite their importance for the evolution of galaxies and life in the universe, the details of the core-collapse supernova explosion mechanism remain in the dark and pose a daunting computational challenge. We outline the multi-dimensional, multi-scale, and multi-physics nature of the core-collapse supernova problem and discuss computational strategies and requirements for its solution. Specifically, we highlight the axisymmetric (2D) radiation-MHD code VULCAN/2D and present results obtained from the first full-2D angle-dependent neutrino radiation-hydrodynamics simulations of the post-core-bounce supernova evolution. We then go on to discuss the new code Zelmani which is based on the open-source HPC Cactus framework and provides a scalable AMR approach for 3D fully general-relativistic modeling of stellar col...

  4. How fast is protein hydrophobic collapse?

    OpenAIRE

    Sadqi, Mourad; Lapidus, Lisa J.; Muñoz, Victor

    2003-01-01

    One of the most recurring questions in protein folding refers to the interplay between formation of secondary structure and hydrophobic collapse. In contrast with secondary structure, it is hard to isolate hydrophobic collapse from other folding events. We have directly measured the dynamics of protein hydrophobic collapse in the absence of competing processes. Collapse was triggered with laser-induced temperature jumps in the acid-denatured form of a simple protein and monitored by fluoresce...

  5. On collapsibilities of Yule's measure

    Institute of Scientific and Technical Information of China (English)

    GUO; Jianhua

    2001-01-01

    [1]Simpson,E.H.,The interpretation of interaction in contingency tables,J.R.Statist.Soc.B,1951,13:238-241.[2]Bishop,Y.M.M.,Effects of collapsing multidimensional contingency tables,Biometrics,1971,27:545-562.[3]Whittemore,A.S.,Collapsibility of multidimensional contingency tables,J.R.Statist.Soc.B,1978,40:328-340.[4]Good,I.J.,Mittal,Y.,The amalgamation and geometry of two-by-two contingency tables,Ann.Statist.,1987,15:694-711.[5]Gail,M.H.,Adjusting for covariates that have the same distribution in exposed and unexposed cohorts,Modern Statistical Methods in Chronic Disease Epidemiology (eds.Moolgavkar,S.H.,Prentice,R.L.),New York:Wiley,1986,3-18.[6]Wermuth,N.,Parametric collapsibility and the lack of moderating effects in contingency tables with a dichotomous response variable,J.R.Statist.Soc.B,1987,49:353-364.[7]Wermuth,N.,Moderating effects of subgroups in linear models,Biometrika,1989,76:81-92.[8]Ducharme,G.R.,Lepage,Y.,Testing collapsibility in contingency tables,J.R.Statist.Soc.B,1986,48:197-205.[9]Geng Zhi,Collapsibility of relative risk in contingency tables with a response variable,J.R.Statist.Soc.B,1992,54:585-593.[10]Guo Jianhua,Geng Zhi,Collapsibility of logistic regression coefficients,J.R.Statist.Soc.B,1995,57:263-267.[11]Rosenbaum,P.,Rubin,D.B.,The central role of the propensity score in observational studies for causal effects,Biometrika,1983,70:41-55.[12]Greenland,S.,Robins,J.M.,Pearl,J.,Confounding and collapsibility in causal inference,Statist.Sci.,1999,14:29-46.[13]Freedman,D.,From association to causation:some remarks on the history of statistics,Statist.Sci.,1999,14:243-258.[14]Geng,Z.,Guo,J.H.,Lau,T.S.et al.,Confounding,consistency and collapsibility for causal effects in epidemiologic studies,To appear in Statist.Sinica,2001.[15]Yule,G.U.,Notes on the theory of association of attributes in statistics,Biometrika,1903,2:121-134.[16]Lancaster,H.O.,The Chi-squared Distribution

  6. Spreadsheets and the Financial Collapse

    CERN Document Server

    Croll, Grenville J

    2009-01-01

    We briefly review the well-known risks, weaknesses and limitations of spreadsheets and then introduce some more. We review and slightly extend our previous work on the importance and criticality of spreadsheets in the City of London, introducing the notions of ubiquity, centrality, legality and contagion. We identify the sector of the financial market that we believed in 2005 to be highly dependant on the use of spreadsheets and relate this to its recent catastrophic financial performance. We outline the role of spreadsheets in the collapse of the Jamaican banking system in the late 1990's and then review the UK financial regulator's knowledge of the risks of spreadsheets in the contemporary financial system. We summarise the available evidence and suggest that there is a link between the use of spreadsheets and the recent collapse of the global financial system. We provide governments and regulating authorities with some simple recommendations to reduce the risks of continued overdependence on unreliable spr...

  7. Preventing State Collapse in Syria

    Science.gov (United States)

    2017-01-01

    region.4 The longer the war goes on, the higher the probability of state collapse, fragmentation, endemic terrorism, and continued refugee flows. The...fighting extremism, sectarianism, and non-interference in the internal affairs of Syria, a political solution, respect for minority rights , human rights ...Even the Muslim Brotherhood had de-emphasized sectarian loyalties in favor of human rights and rule of law.56 A tradition of centralized governance

  8. Temperature evolution during dissipative collapse

    Indian Academy of Sciences (India)

    S D Maharaj; G Govender; M Govender

    2011-09-01

    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 particular model are obtained within the framework of causal thermodynamics. The overall temperature evolution is enhanced by contributions from the temperature gradient induced by perturbations as well as relaxational effects within the stellar core.

  9. Bubble-induced cave collapse.

    Directory of Open Access Journals (Sweden)

    Lakshika Girihagama

    Full Text Available Conventional wisdom among cave divers is that submerged caves in aquifers, such as in Florida or the Yucatan, are unstable due to their ever-growing size from limestone dissolution in water. Cave divers occasionally noted partial cave collapses occurring while they were in the cave, attributing this to their unintentional (and frowned upon physical contact with the cave walls or the aforementioned "natural" instability of the cave. Here, we suggest that these cave collapses do not necessarily result from cave instability or contacts with walls, but rather from divers bubbles rising to the ceiling and reducing the buoyancy acting on isolated ceiling rocks. Using familiar theories for the strength of flat and arched (un-cracked beams, we first show that the flat ceiling of a submerged limestone cave can have a horizontal expanse of 63 meters. This is much broader than that of most submerged Florida caves (~ 10 m. Similarly, we show that an arched cave roof can have a still larger expanse of 240 meters, again implying that Florida caves are structurally stable. Using familiar bubble dynamics, fluid dynamics of bubble-induced flows, and accustomed diving practices, we show that a group of 1-3 divers submerged below a loosely connected ceiling rock will quickly trigger it to fall causing a "collapse". We then present a set of qualitative laboratory experiments illustrating such a collapse in a circular laboratory cave (i.e., a cave with a circular cross section, with concave and convex ceilings. In these experiments, a metal ball represented the rock (attached to the cave ceiling with a magnet, and the bubbles were produced using a syringe located at the cave floor.

  10. Understanding Core-Collapse Supernovae

    CERN Document Server

    Burrows, A

    2004-01-01

    I summarize, in the form of an extended abstract, the ongoing efforts at the University of Arizona (and in collaboration) to understand core-collapse supernovae theoretically. Included are short discussions of 1D (SESAME) and 2D (VULCAN/2D) codes and results, as well as discussions of the possible role of rotation. Highlighted are recent developments in multi-dimensional radiation hydrodynamics and the essential physics of the neutrino-driven mechanism.

  11. Colony collapse disorder in Europe.

    Science.gov (United States)

    Dainat, Benjamin; Vanengelsdorp, Dennis; Neumann, Peter

    2012-02-01

    Colony collapse disorder (CCD) is a condition of honey bees, which has contributed in part to the recent major losses of honey bee colonies in the USA. Here we report the first CCD case from outside of the USA. We suggest that more standardization is needed for the case definition to diagnose CCD and to compare data on a global scale. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  12. Atomic Structure and Energy Distribution of Collapsed Carbon Nanotubes of Different Chiralities

    Directory of Open Access Journals (Sweden)

    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.

  13. Parametric nonlinear lumped element model for circular CMUTs in collapsed mode.

    Science.gov (United States)

    Aydoğdu, Elif; Ozgurluk, Alper; Atalar, Abdullah; Köymen, Hayrettin

    2014-01-01

    We present a parametric equivalent circuit model for a circular CMUT in collapsed mode. First, we calculate the collapsed membrane deflection, utilizing the exact electrical force distribution in the analytical formulation of membrane deflection. Then we develop a lumped element model of collapsed membrane operation. The radiation impedance for collapsed mode is also included in the model. The model is merged with the uncollapsed mode model to obtain a simulation tool that handles all CMUT behavior, in transmit or receive. Large- and small-signal operation of a single CMUT can be fully simulated for any excitation regime. The results are in good agreement with FEM simulations.

  14. Anthropological analysis of the Second World War skeletal remains from three karst sinkholes located in southern Croatia.

    Science.gov (United States)

    Jerković, Ivan; Bašić, Željana; Bečić, Kristijan; Jambrešić, Gordana; Grujić, Ivan; Alujević, Antonio; Kružić, Ivana

    2016-11-01

    Although in the cases of war crimes the main effort goes to the identification of victims, it is crucial to consider the execution event as a whole. Thus, the goal of the research was to determine the trauma type and probable cause of death on skeletal remains of civilians executed by partisans from WWS found in the three karst sinkholes and to explain the context in which the injuries occurred. We determined biological profiles, pathological conditions, traumas, and assessed their lethality. Nineteen skeletons were found, 68.4% had, at least, one perimortem trauma, classified as lethal/lethal if untreated in 69.2% cases. The type of execution and administered violence showed to be age and health dependent: elderly and diseased were executed with the intention to kill, by the gunshot facing victims, whilst the more violent behavior expressed towards younger and healthy individuals was indicated by the higher frequency of blunt force trauma.

  15. Characterization Criteria of Karst Collapse Hazard on Groundwater Fluctuations in Qingyun Village, Guigang, Guangxi, China%岩溶塌陷灾害的水动力条件危险性评价指标——以广西贵港青云村为例

    Institute of Scientific and Technical Information of China (English)

    蒋小珍; 雷明堂; 管振德

    2012-01-01

    Sinkhole collapse is the main geohazard for Qingyun village, Guigang, Guangxi Autonomous Region, China. It is necessary to study the characterization criteria of Karst collapse hazard. So the water levels of residential and community wells were monitored. By comparison with real-time monitoring of groundwater level in a reference ar-ea with no sinkhole collapsing event, a characterization process was developed to assess sinkhole hazards in the Qingyun village area. Characterization criteria include 2 factors: daily water level fluctuations of Karst aquifer, recov-ery of water level in Karst aquifer, and maximum declining rate of water level in Karst aquifer. This characterization process could be used to assess impact of construction work on ground water, and to obtain its impact level, to judge the possibility of Karst collapse hazard and prevent the development of soil voids and human-induced sinkholes in ac-tive Karst areas.%针对广西贵港覃塘镇青云村岩溶塌陷问题,开展该区岩溶塌陷水动力条件的危险性评价指标研究工作.通过实时、高分辨率的自动化监测设备对该区的岩溶地下水进行了监测.结果表明,岩溶地下水的变化是该地区岩溶塌陷发生的主要诱发因素.通过对比抽水活动强烈,无岩溶塌陷事件发生地区的地下水动态监测资料,综合分析提炼出岩溶塌陷水动力条件危险性评价指标,即:岩溶水日波动最大幅度及水位恢复时间、岩溶水位瞬时最大下降速度.该指标可应用于评价工程活动对地下水的影响,实时获取工程活动对地下水的影响程度,判断岩溶塌陷的可能性,反过来也可指导工程活动,减少灾害的发生及损失.

  16. Landslides, floods and sinkholes in a karst environment: the 1-6 September 2014 Gargano event, southern Italy

    Science.gov (United States)

    Martinotti, Maria Elena; Pisano, Luca; Marchesini, Ivan; Rossi, Mauro; Peruccacci, Silvia; Brunetti, Maria Teresa; Melillo, Massimo; Amoruso, Giuseppe; Loiacono, Pierluigi; Vennari, Carmela; Vessia, Giovanna; Trabace, Maria; Parise, Mario; Guzzetti, Fausto

    2017-03-01

    In karst environments, heavy rainfall is known to cause multiple geohydrological hazards, including inundations, flash floods, landslides and sinkholes. We studied a period of intense rainfall from 1 to 6 September 2014 in the Gargano Promontory, a karst area in Puglia, southern Italy. In the period, a sequence of torrential rainfall events caused severe damage and claimed two fatalities. The amount and accuracy of the geographical and temporal information varied for the different hazards. The temporal information was most accurate for the inundation caused by a major river, less accurate for flash floods caused by minor torrents and even less accurate for landslides. For sinkholes, only generic information on the period of occurrence of the failures was available. Our analysis revealed that in the promontory, rainfall-driven hazards occurred in response to extreme meteorological conditions and that the karst landscape responded to the torrential rainfall with a threshold behaviour. We exploited the rainfall and the landslide information to design the new ensemble-non-exceedance probability (E-NEP) algorithm for the quantitative evaluation of the possible occurrence of rainfall-induced landslides and of related geohydrological hazards. The ensemble of the metrics produced by the E-NEP algorithm provided better diagnostics than the single metrics often used for landslide forecasting, including rainfall duration, cumulated rainfall and rainfall intensity. We expect that the E-NEP algorithm will be useful for landslide early warning in karst areas and in other similar environments. We acknowledge that further tests are needed to evaluate the algorithm in different meteorological, geological and physiographical settings.

  17. Sudden Trust Collapse in Networked Societies

    CERN Document Server

    Batista, João da Gama; Challet, Damien

    2014-01-01

    Trust is a collective, self-fulfilling phenomenon that suggests analogies with phase transitions. We introduce a stylized model for the build-up and collapse of trust in networks, which generically displays a first order transition. The basic assumption of our model is that whereas trust begets trust, panic also begets panic, in the sense that a small decrease in trust may be amplified and ultimately lead to a sudden and catastrophic drop of trust. We show, using both numerical simulations and mean-field analytic arguments, that there are extended regions of the parameter space where two equilibrium states coexist: a well-connected network where confidence is high, and a poorly connected network where confidence is low. In these coexistence regions, spontaneous jumps from the well-connected state to the poorly connected state can occur, corresponding to a sudden collapse of trust that is not caused by any major external catastrophe. In large systems, spontaneous crises are replaced by history dependence: whet...

  18. Null fluid collapse in brane world models

    Science.gov (United States)

    Harko, Tiberiu; Lake, Matthew J.

    2014-03-01

    The brane world description of our Universe entails a large extra dimension and a fundamental scale of gravity that may be lower than the Planck scale by several orders of magnitude. An interesting consequence of this scenario occurs in the nature of spherically symmetric vacuum solutions to the brane gravitational field equations, which often have properties quite distinct from the standard black hole solutions of general relativity. In this paper, the spherically symmetric collapse on the brane world of four types of null fluid, governed by the barotropic, polytropic, strange quark "bag" model and Hagedorn equations of state, is investigated. In each case, we solve the approximate gravitational field equations, obtained in the high-density limit, determine the equation which governs the formation of apparent horizons and investigate the conditions for the formation of naked singularities. Though, naively, one would expect the increased effective energy density on the brane to favor the formation of black holes over naked singularities, we find that, for the types of fluid considered, this is not the case. However, the black hole solutions differ substantially from their general-relativistic counterparts and brane world corrections often play a role analogous to charge in general relativity. As an astrophysical application of this work, the possibility that energy emission from a Hagedorn fluid collapsing to form a naked singularity may be a source of GRBs in the brane world is also considered.

  19. Collapse Mechanisms Of Masonry Structures

    Science.gov (United States)

    Zuccaro, G.; Rauci, M.

    2008-07-01

    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

  20. Firn air depletion as a precursor of Antarctic ice-shelf collapse

    NARCIS (Netherlands)

    Kuipers Munneke, P.; Ligtenberg, S.R.M.; van den Broeke, M.R.; Vaughan, D.G.

    2014-01-01

    Since the 1970s, the sudden, rapid collapse of 20% of ice shelves on the Antarctic Peninsula has led to large-scale thinning and acceleration of its tributary glaciers. The leading hypothesis for the collapse of most of these ice shelves is the process of hydrofracturing, whereby a water-filled crev

  1. Gravitational collapse of colloidal gels: Origins of the tipping point

    Science.gov (United States)

    Zia, Roseanna; Padmanabhan, Poornima

    2016-11-01

    Reversible colloidal gels are soft viscoelastic solids in which durable but reversible bonds permit on-demand transition from solidlike to liquidlike behavior; these O(kT) bonds also lead to ongoing coarsening and age stiffening, making their rheology inherently time dependent. To wit, such gels may remain stable for an extended time, but then suddenly collapse, sedimenting to the bottom of the container (or creaming to the top) and eliminating any intended functionality of the material. Although this phenomenon has been studied extensively in the experimental literature, the microscopic mechanism underlying the collapse is not well understood. Effects of gel age, interparticle attraction strength, and wall effects all have been shown to affect collapse behavior, but the microstructural transformations underlying the 'tipping point' remain murky. To study this behavior, we conduct large-scale dynamic simulation to model the structural and rheological evolution of colloidal gels subjected to various gravitational stresses, examining the detailed micromechanics in three temporal regimes: slow sedimentation prior to collapse; the tipping point leading to the onset of rapid collapse; and the subsequent compaction of the material as it approaches its final bed height. Acknowledgment for funding and support from the Office of Naval Research; the National Science Foundation; and NSF XSEDE.

  2. SIGNATURES OF STAR CLUSTER FORMATION BY COLD COLLAPSE

    Energy Technology Data Exchange (ETDEWEB)

    Kuznetsova, Aleksandra; Hartmann, Lee [Department of Astronomy, University of Michigan, 1085 S. University Ave., Ann Arbor, MI 48109 (United States); Ballesteros-Paredes, Javier, E-mail: kuza@umich.edu [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apdo. Postal 72-3 (Xangari), Morelia, Michocán 58089, México (Mexico)

    2015-12-10

    Subvirial gravitational collapse is one mechanism by which star clusters may form. Here we investigate whether this mechanism can be inferred from observations of young clusters. To address this question, we have computed smoothed particle hydrodynamics simulations of the initial formation and evolution of a dynamically young star cluster through cold (subvirial) collapse, starting with an ellipsoidal, turbulently seeded distribution of gas, and forming sink particles representing (proto)stars. While the initial density distributions of the clouds do not have large initial mass concentrations, gravitational focusing due to the global morphology leads to cluster formation. We use the resulting structures to extract observable morphological and kinematic signatures for the case of subvirial collapse. We find that the signatures of the initial conditions can be erased rapidly as the gas and stars collapse, suggesting that kinematic observations need to be made early in cluster formation and/or at larger scales, away from the growing cluster core. Our results emphasize that a dynamically young system is inherently evolving on short timescales, so that it can be highly misleading to use current-epoch conditions to study aspects such as star formation rates as a function of local density. Our simulations serve as a starting point for further studies of collapse including other factors such as magnetic fields and stellar feedback.

  3. Tunneling into Microstate Geometries: Quantum Effects Stop Gravitational Collapse

    CERN Document Server

    Bena, Iosif; Puhm, Andrea; Vercnocke, Bert

    2015-01-01

    Collapsing shells form horizons, and when the curvature is small classical general relativity is believed to describe this process arbitrarily well. On the other hand, quantum information theory based (fuzzball/firewall) arguments suggest the existence of some structure at the black hole horizon. This structure can only form if classical general relativity stops being the correct description of the collapsing shell before it reaches the horizon size. We present strong evidence that classical general relativity can indeed break down prematurely, by explicitly computing the quantum tunneling amplitude of a collapsing shell of branes into smooth horizonless microstate geometries. We show that the amplitude for tunneling into microstate geometries with a large number of topologically non-trivial cycles is parametrically larger than exp(-S), which indicates that the shell can tunnel into a horizonless configuration long before the horizon has any chance to form. We also use this technology to investigate the tunne...

  4. Gravitation collapse of spherical symmetry with non-uniform density

    Institute of Scientific and Technical Information of China (English)

    GU Chao-hao

    2006-01-01

    A star with sufficiently large mass will collapse in its senectitude because of gravitation.Many researchers have tried to describe this collapse process.Investigations have been conducted in the case that the star has spherical symmetry and the initial density is uniform.In this article,the case that the initial density is not uniform will be considered.When the density function is high in the center and decreasing with the radius,the collapse process will be described,and in this case,the singularity will only come out in the center because of collision.If the density is not monotonic and there is a crust with high density around the star,it is proved that the non-central collision singularity may come out either in the Schwarzschild sphere or outside of it,i.e.,the naked singularize may come out.

  5. Gravitational collapse of thin shells of dust in Shape Dynamics

    CERN Document Server

    Gomes, Henrique; Mercati, Flavio; Napoletano, Andrea

    2015-01-01

    Shape dynamics is a theory of gravity whose physical configuration space is composed of spatial conformal equivalence classes of 3-dimensional geometries. This physical configuration space is not a priori related to the one given by 4-dimensional space-time geometries, familiar to general relativists. Although one can largely match dynamical solutions arising in each theory, this is not always the case. One expects such differences in collapse situations that lead to the formation of black holes. In this paper we study spherical collapse of thin-shells of pressureless dust as a fully back-reacting dynamical system, in a context related to both shape dynamics and general relativity in ADM form in Constant Mean Curvature (CMC) gauge -- the particular time slicing where any correspondence between ADM and shape dynamics is manifest. To better accommodate the relational setting of shape dynamics, we also begin a study of collapse of two such shells in a compact Universe.

  6. Collapsing shells, critical phenomena and black hole formation

    CERN Document Server

    Cardoso, Vitor

    2016-01-01

    We study the gravitational collapse of two thin shells of matter, in asymptotically flat spacetime or constrained to move within a spherical box. We show that this simple two-body system has surprisingly rich dynamics, which includes prompt collapse to a black hole, perpetually oscillating solutions or black hole formation at arbitrarily large times. Collapse is induced by shell crossing and the black hole mass depends sensitively on the number of shell crossings. At certain critical points, the black hole mass exhibits critical behavior, determined by the change in parity (even or odd) of the number of crossings, with or without mass-gap during the transition. Some of the features we observe are reminiscent of confined scalars undergoing "turbulent" dynamics.

  7. Quantum dust collapse in 2 +1 dimension

    Science.gov (United States)

    Sarkar, Souvik; Vaz, Cenalo; Wijewardhana, L. C. R.

    2016-02-01

    In this paper we will examine the consequence of a canonical theory of quantum dust collapse in 2 +1 dimensions. The solution of the Wheeler-DeWitt equation describing the collapse indicates that collapsing shells outside the apparent horizon are accompanied by outgoing shells within the apparent horizon during their collapse phase and stop collapsing once they reach the apparent horizon. Taking this picture of quantum collapse seriously, we determine a static solution with energy density corresponding to a dust ball whose collapse has terminated at the apparent horizon. We show that the boundary radius of the ball is larger than the Banados-Teitelboim-Zanelli radius confirming that no event horizon is formed. The ball is sustained by radial pressure which we determine and which we attribute to the Unruh radiation within it.

  8. Design of Pneumatic Collapsible Steering

    Directory of Open Access Journals (Sweden)

    Anish Nair

    2013-08-01

    Full Text Available The steering wheel is the important cause of fatal injury for drivers in frontal collision. When frontal collision occurs, due to the kinetic energy of driver or occupant body, it moves forward against steering wheel and wind shield. Actually in a frontal collision forces will be first transmitted through driver’s feet which act as fulcrum so the body will rotate about it. For the taller driver steering works as fulcrum. Driver head & chest hit the steering or windshield which may cause severe injury or death. Considering the injury potential of steering wheel we are presenting a new idea Pneumatic Collapsible Steering Column (PCS.

  9. Spherically symmetric scalar field collapse

    Indian Academy of Sciences (India)

    Koyel Ganguly; Narayan Banerjee

    2013-03-01

    It is shown that a scalar field, minimally coupled to gravity, may have collapsing modes even when the energy condition is violated, that is, for ( + 3) < 0. This result may be useful in the investigation of the possible clustering of dark energy. All the examples dealt with have apparent horizons formed before the formation of singularity. The singularities formed are shell focussing in nature. The density of the scalar field distribution is seen to diverge at singularity. The Ricci scalar also diverges at the singularity. The interior spherically symmetric metric is matched with exterior Vaidya metric at the hypersurface and the appropriate junction conditions are obtained.

  10. Thermodynamics of a collapsed object

    Energy Technology Data Exchange (ETDEWEB)

    Chaubey, N. (Inst. of Science and Techn., Sultanpur (India). Technological Faculty); De Sabbata, V. (Bologna Univ. (Italy). Ist. di Fisica)

    1981-06-20

    Here is presented a thermodynamic study in the Reissner-Nordstroem blackhole which leads to a beautiful conclusion that the product of surface gravities of the outer horizon and the inner horizon of the blackhole is equal to the inverse square of charge distribution over it. If one considers a more general collapsed object wherein rotation is also considered, a similar inference is that the product of surface gravities of the inner and the outer horizon is equal to the inverse of the sum of squares of the charge distribution and angular momentum per unit mass of the rotation.

  11. Non-linear cosmological collapse of quintessence

    CERN Document Server

    Rekier, Jeremy; Cordero-Carrion, Isabel

    2015-01-01

    We present a study of the fully relativistic spherical collapse in presence of quintessence using on Numerical Relativity, following the method proposed by the authors in a previous article [arXiv:1409.3476]. We ascertain the validity of the method by studying the evolution of a spherically symmetric quintessence inhomogeneity on a de Sitter background and we find that it has an impact on the local expansion around the centre of coordinates. We then proceed to compare the results of our method to those of the more largely adopted top-hat model. We find that quintessence inhomogeneities do build up under the effect that matter inhomogeneities have on the local space-time yet remain very small due to the presence of momentum transfer from the over-dense to the background regions. We expect that these might have an even more important role in modified theories of gravitation.

  12. Electron acceleration by magnetic collapse during decoupling

    Science.gov (United States)

    Bennet, Euan D.; Potts, Hugh E.; Teodoro, Luis F. A.; Diver, Declan A.

    2014-12-01

    This paper identifies the non-equilibrium evolution of magnetic field structures at the onset of large-scale recombination of an inhomogeneously ionized plasma. The context for this is the Universe during the epoch of recombination. The electromagnetic treatment of this phase transition can produce energetic electrons scattered throughout the Universe, localized near the edges of magnetic domains. This is confirmed by a numerical simulation in which a magnetic domain is modelled as a uniform field region produced by a thin surrounding current sheet. Conduction currents sustaining the magnetic structure are removed as the charges comprising them combine into neutrals. The induced electric field accompanying the magnetic collapse is able to accelerate ambient stationary electrons (that is, electrons not participating in the current sheet) to energies of up to order 10keV. This is consistent with theoretical predictions. The localized electron acceleration leads to local imbalances of charge which has implications for charge separation in the early Universe.

  13. Null fluid collapse in brane world models

    CERN Document Server

    Harko, Tiberiu

    2013-01-01

    The brane world description of our universe entails a large extra dimension and a fundamental scale of gravity that may be lower than the Planck scale by several orders of magnitude. An interesting consequence of this scenario occurs in the nature of spherically-symmetric vacuum solutions to the brane gravitational field equations, which often have properties quite distinct from the standard black hole solutions of general relativity. In this paper, the spherically-symmetric collapse on the brane world of four types of null fluid, governed by the barotropic, polytropic, strange quark "bag" model and Hagedorn equations of state, is investigated. In each case, we solve the approximate gravitational field equations, obtained in the high density limit, determine the equation which governs the formation of apparent horizons and investigate the conditions for the formation of naked singularities. Though, naively, one would expect the increased effective energy density on the brane to favor the formation of black ho...

  14. Gravitational collapse of the OMC-1 region

    Science.gov (United States)

    Hacar, A.; Alves, J.; Tafalla, M.; Goicoechea, J. R.

    2017-06-01

    We have investigated the global dynamical state of the integral shaped filament in the Orion A cloud using new N2H+ (1-0) large-scale, IRAM 30 m observations. Our analysis of its internal gas dynamics reveals the presence of accelerated motions towards the Orion Nebula Cluster, showing a characteristic blue-shifted profile centred at the position of the OMC-1 South region. The properties of these observed gas motions (profile, extension, and magnitude) are consistent with the expected accelerations for the gravitational collapse of the OMC-1 region and explain both the physical and kinematic structure of this cloud. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  15. Silo Collapse under Granular Discharge

    Science.gov (United States)

    Gutiérrez, G.; Colonnello, C.; Boltenhagen, P.; Darias, J. R.; Peralta-Fabi, R.; Brau, F.; Clément, E.

    2015-01-01

    We investigate, at a laboratory scale, the collapse of cylindrical shells of radius R and thickness t induced by a granular discharge. We measure the critical filling height for which the structure fails upon discharge. We observe that the silos sustain filling heights significantly above an estimation obtained by coupling standard shell-buckling and granular stress distribution theories. Two effects contribute to stabilize the structure: (i) below the critical filling height, a dynamical stabilization due to granular wall friction prevents the localized shell-buckling modes to grow irreversibly; (ii) above the critical filling height, collapse occurs before the downward sliding motion of the whole granular column sets in, such that only a partial friction mobilization is at play. However, we notice also that the critical filling height is reduced as the grain size d increases. The importance of grain size contribution is controlled by the ratio d /√{R t }. We rationalize these antagonist effects with a novel fluid-structure theory both accounting for the actual status of granular friction at the wall and the inherent shell imperfections mediated by the grains. This theory yields new scaling predictions which are compared with the experimental results.

  16. Partially saturated granular column collapse

    Science.gov (United States)

    Turnbull, Barbara; Johnson, Chris

    2017-04-01

    Debris flows are gravity-driven sub-aerial mass movements containing water, sediments, soil and rocks. These elements lead to characteristics common to dry granular media (e.g. levee formation) and viscous gravity currents (viscous fingering and surge instabilities). The importance of pore fluid in these flows is widely recognised, but there is significant debate over the mechanisms of build up and dissipation of pore fluid pressure within debris flows, and the resultant effect this has on dilation and mobility of the grains. Here we specifically consider the effects of the liquid surface in the flow. We start with a simple experiment constituting a classical axisymmetric granular column collapse, but with fluid filling the column up to a depth comparable to the depth of grains. Thus, as the column collapses, capillary forces may be generated between the grains that prevent dilation. We explore a parameter space to uncover the effects of fluid viscosity, particle size, column size, aspect ratio, grain shape, saturation level, initial packing fraction and significantly, the effects of fine sediments in suspension which can alter the capillary interaction between wetted macroscopic grains. This work presents an initial scaling analysis and attempts to relate the findings to current debris flow modelling approaches.

  17. On the dynamics of dust during protostellar collapse

    Science.gov (United States)

    Bate, Matthew R.; Lorén-Aguilar, Pablo

    2017-02-01

    The dynamics of dust and gas can be quite different from each other when the dust is poorly coupled to the gas. In protoplanetary discs, it is well known that this decoupling of the dust and gas can lead to diverse spatial structures and dust-to-gas ratios. In this paper, we study the dynamics of dust and gas during the earlier phase of protostellar collapse, before a protoplanetary disc is formed. We find that for dust grains with sizes ≲ 10 μm, the dust is well coupled during the collapse of a rotating, pre-stellar core and there is little variation of the dust-to-gas ratio during the collapse. However, if larger grains are present, they may have trajectories that are very different from the gas during the collapse, leading to mid-plane settling and/or oscillations of the dust grains through the mid-plane. This may produce variations in the dust-to-gas ratio and very different distributions of large and small dust grains at the very earliest stages of star formation, if large grains are present in pre-stellar cores.

  18. On the dynamics of dust during protostellar collapse

    CERN Document Server

    Bate, Matthew R

    2016-01-01

    The dynamics of dust and gas can be quite different from each other when the dust is poorly coupled to the gas. In protoplanetary discs, it is well known that this decoupling of the dust and gas can lead to diverse spatial structures and dust-to-gas ratios. In this paper, we study the dynamics of dust and gas during the earlier phase of protostellar collapse, before a protoplanetary disc is formed. We find that for dust grains with sizes < 10 micron, the dust is well coupled during the collapse of a rotating, pre-stellar core and there is little variation of the dust-to-gas ratio during the collapse. However, if larger grains are present, they may have trajectories that are very different from the gas during the collapse, leading to mid-plane settling and/or oscillations of the dust grains through the mid-plane. This may produce variations in the dust-to-gas ratio and very different distributions of large and small dust grains at the very earliest stages of star formation, if large grains are present in pr...

  19. Time symmetry in wave-function collapse

    Science.gov (United States)

    Bedingham, D. J.; Maroney, O. J. E.

    2017-04-01

    The notion of a physical collapse of the wave function is embodied in dynamical collapse models. These involve a modification of the unitary evolution of the wave function so as to give a dynamical account of collapse. The resulting dynamics is at first sight time asymmetric for the simple reason that the wave function depends on those collapse events in the past but not those in the future. Here we show that dynamical wave-function collapse models admit a general description that has no built-in direction of time. Given some simple constraints, we show that there exist empirically equivalent pictures of collapsing wave functions in both time directions, each satisfying the same dynamical rules. A preferred direction is singled out only by the asymmetric initial and final time constraints on the state of the universe.

  20. Radiation driven collapse of protein crystals.

    Science.gov (United States)

    Boutet, Sébastien; Robinson, Ian K

    2006-01-01

    During coherent X-ray diffraction measurements on crystals of ferritin at room temperature using monochromatic undulator radiation from the Advanced Photon Source, a sudden lattice contraction was observed following a characteristic latent period and ultimately leading to the collapse of the crystal. The progression of this collapse is analysed using a two-state Hendricks-Teller model. It reveals that 55% of the layers collapse by 1.6% before the crystal completely stops diffracting.

  1. Collapse of three on a sphere

    Energy Technology Data Exchange (ETDEWEB)

    Kidambi, R.; Newton, P.K. [Southern California Univ., Los Angeles (United States). Dept. of Aerospace Engineering, Center for Applied Mathematical Sciences

    1999-12-01

    The self-similar collapse of three vortices moving on the surface of a sphere of radius R is analysed and compared with known results of critical literature. Formulas for the collapsing trajectories are derived and compared with the planar formulas. The Hamiltonian system is derived governing the vortex motion. In this projected plane, the solutions are not self-similar. In the last section, the collapse process is studied using tri-linear coordinates, which reduces the system to a planar one.

  2. Self-similar scalar field collapse

    Science.gov (United States)

    Banerjee, Narayan; Chakrabarti, Soumya

    2017-01-01

    A spherically symmetric collapsing scalar field model is discussed with a dissipative fluid which includes a heat flux. This vastly general matter distribution is analyzed at the expense of a high degree of symmetry in the space-time, that of conformal flatness and self-similarity. Indeed collapsing models terminating into a curvature singularity can be obtained. The formation of black holes or the occurrence of naked singularities depends on the initial collapsing profiles.

  3. Spreading and collapse of big basaltic volcanoes

    Science.gov (United States)

    Puglisi, Giuseppe; Bonforte, Alessandro; Guglielmino, Francesco; Peltier, Aline; Poland, Michael

    2016-04-01

    Among the different types of volcanoes, basaltic ones usually form the most voluminous edifices. Because volcanoes are growing on a pre-existing landscape, the geologic and structural framework of the basement (and earlier volcanic landforms) influences the stress regime, seismicity, and volcanic activity. Conversely, the masses of these volcanoes introduce a morphological anomaly that affects neighboring areas. Growth of a volcano disturbs the tectonic framework of the region, clamps and unclamps existing faults (some of which may be reactivated by the new stress field), and deforms the substratum. A volcano's weight on its basement can trigger edifice spreading and collapse that can affect populated areas even at significant distance. Volcano instability can also be driven by slow tectonic deformation and magmatic intrusion. The manifestations of instability span a range of temporal and spatial scales, ranging from slow creep on individual faults to large earthquakes affecting a broad area. In the frame of MED-SVU project, our work aims to investigate the relation between basement setting and volcanic activity and stability at three Supersite volcanoes: Etna (Sicily, Italy), Kilauea (Island of Hawaii, USA) and Piton de la Fournaise (La Reunion Island, France). These volcanoes host frequent eruptive activity (effusive and explosive) and share common features indicating lateral spreading and collapse, yet they are characterized by different morphologies, dimensions, and tectonic frameworks. For instance, the basaltic ocean island volcanoes of Kilauea and Piton de la Fournaise are near the active ends of long hotspot chains while Mt. Etna has developed at junction along a convergent margin between the African and Eurasian plates and a passive margin separating the oceanic Ionian crust from the African continental crust. Magma supply and plate velocity also differ in the three settings, as to the sizes of the edifices and the extents of their rift zones. These

  4. Catastrophic volcanic collapse: relation to hydrothermal processes.

    Science.gov (United States)

    López, D L; Williams, S N

    1993-06-18

    Catastrophic volcanic collapse, without precursory magmatic activity, is characteristic of many volcanic disasters. The extent and locations of hydrothermal discharges at Nevado del Ruiz volcano, Colombia, suggest that at many volcanoes collapse may result from the interactions between hydrothermal fluids and the volcanic edifice. Rock dissolution and hydrothermal mineral alteration, combined with physical triggers such as earth-quakes, can produce volcanic collapse. Hot spring water compositions, residence times, and flow paths through faults were used to model potential collapse at Ruiz. Caldera dimensions, deposits, and alteration mineral volumes are consistent with parameters observed at other volcanoes.

  5. Collapse of granular media subjected to wetting

    Directory of Open Access Journals (Sweden)

    El Korchi Fatima Zahra

    2017-01-01

    Full Text Available This paper focuses on the collapse of granular materials subjected to wetting action. For soils, the collapse potential depends on several parameters such as liquid limit, matric suction, compactness, initial water content and the amount of fine particles. The effect of grain size, which plays a key role in the rearrangement of grains, remains little studied and poorly understood. To investigate the capillary origin of the collapse phenomenon, we present an experimental study on macroscopic and local scales. Our results show the effect of grain size and water content on collapse.

  6. Collapse Analysis of Timber Structures

    DEFF Research Database (Denmark)

    Kirkegaard, Poul Henning; Sørensen, John Dalsgaard

    2008-01-01

    A probabilistic based collapse analysis has been performed for a glulam frame structure supporting the roof over the main court in a Norwegian sports centre. The robustness analysis is based on the framework for robustness analysis introduced in the Danish Code of Practice for the Safety...... of Structures and a probabilistic modelling of the timber material proposed in the Probabilistic Model Code (PMC) of the Joint Committee on Structural Safety (JCSS). Due to the framework in the Danish Code the timber structure has to be evaluated with respect to the following criteria where at least one shall...... be fulfilled: a) demonstrating that those parts of the structure essential for the safety only have little sensitivity with respect to unintentional loads and defects, or b) demonstrating a load case with „removal of a limited part of the structure‟ in order to document that an extensive failure...

  7. Gravitational Collapse in Gravity's Rainbow

    CERN Document Server

    Ali, Ahmed Farag; Majumder, Barun; Mistry, Ravi

    2015-01-01

    In this paper, we will analyze the gravitational collapse in the framework of gravity's rainbow. We will demonstrate that the position of the horizon for a particle inside the black hole depends on the energy of that particle. It will also be observe that the position of the horizon for a particle falling radially into the black hole also depends on its energy. Thus, it is possible for a particle coming from outside to interact with a particle inside the black, and take some information outside the black hole. This is because for both these particles the position of horizon is different. So, even though the particle from inside the black hole is in its own horizon, it is not in the horizon of the particle coming from outside. Thus, we will demonstrate that in gravity's rainbow information can get out of a black hole.

  8. Critical perspectives on historical collapse.

    Science.gov (United States)

    Butzer, Karl W; Endfield, Georgina H

    2012-03-06

    Historical collapse of ancient states or civilizations has raised new awareness about its possible relevance to current issues of sustainability, in the context of global change. This Special Feature examines 12 case studies of societies under stress, of which seven suffered severe transformation. Outcomes were complex and unpredictable. Five others overcame breakdown through environmental, political, or socio-cultural resilience, which deserves as much attention as the identification of stressors. Response to environmental crises of the last millennium varied greatly according to place and time but drew from traditional knowledge to evaluate new information or experiment with increasing flexibility, even if modernization or intensification were decentralized and protracted. Longer-term diachronic experience offers insight into how societies have dealt with acute stress, a more instructive perspective for the future than is offered by apocalyptic scenarios.

  9. Higgs portals to pulsar collapse

    CERN Document Server

    Bramante, Joseph

    2015-01-01

    Pulsars apparently missing from the galactic center could have been destroyed by asymmetric fermionic dark matter ($m_X = 1-100$ GeV) coupled to a light scalar ($m_{\\phi}= 5-20$ MeV), which mixes with the Higgs boson. We point out that this pulsar-collapsing dark sector can resolve the core-cusp problem and will either be excluded or discovered by upcoming direct detection experiments. Another implication is a maximum pulsar age curve that increases with distance from the galactic center, with a normalization that depends on the couplings and masses of dark sector particles. In addition, we use old pulsars outside the galactic center to place bounds on asymmetric Higgs portal models.

  10. Three-dimensional analysis of a developing sinkhole using GPR and dynamic cone penetrometer (DCP) testing

    Science.gov (United States)

    Brook, Martin; Gaines, Andrew; Nobes, David

    2016-04-01

    Ground penetrating radar (GPR) imaging is one of the most promising non-destructive and non-invasive methods that have offered new opportunities for mapping shallow subsurface disturbances in urbanized and industrialized zones. However, difficulties often arise in choosing the optimum antenna frequency to image subsurface features. While high frequency antennas may provide lots of detail, lower frequency antennas may provide information on larger-scale features that provide more site context. In this study, we performed GPR surveys to investigate a zone of subtle surface subsidence and pavement cracking on reclaimed land at a quayside. A 3-stage approach was used, and included: (1) a 250 MHz antenna survey to delineate the spatial extent of the area of interest; (2) a 500 MHz antenna survey to yield greater detail; and (3) direct verification of some of the key features using dynamic cone penetrometer (DCP) testing to "ground-truth" anomalies. This staged approach proved successful in imaging the sub-grade, and minor voids within approximately 2 m depth. Moreover, the quality of the data can be further improved by using GPR-Slice software in conjunction with DCP data to develop a 3D ground model. Through this approach, a combination of GPR survey and direct testing, we demonstrate the efficiency and quality of this method in mapping shallow subsidence features. An interpretation of the process-origin of the collapse feature is also proposed.

  11. 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.

  12. Collapse dynamics of a fluid hole in a rotating thin film

    CERN Document Server

    Bostwick, Joshua

    2015-01-01

    We study the collapse dynamics of an axisymmetric fluid cavity that wets the bottom of a rotating bucket bound by vertical sidewalls. Lubrication theory is applied to the governing field equations for the thin film to yield an evolution equation that captures the effect of capillary, gravitational and centrifugal forces on this converging flow. We focus on the quasi-static spreading regime, whereby contact-line motion is governed by a constitutive law relating the contact-angle to the contact-line speed. We report the collapse time, as it depends upon the initial hole size, showing that gravity accelerates the collapse process. Surface tension forces dominate the collapse dynamics for small holes leading to a universal power law whose exponent compares favorably to experiments reported in the literature. Centrifugal forces slow the collapse process and lead to complex dynamics characterized by stalled spreading behavior that separates the large and small hole asymptotic regimes.

  13. Measuring the Angular Momentum Distribution in Core-Collapse Supernova Progenitors with Gravitational Waves

    CERN Document Server

    Abdikamalov, Ernazar; DeMaio, Alexandra M; Ott, Christian D

    2013-01-01

    The late collapse, core bounce, and the early postbounce phase of rotating core collapse leads to a characteristic gravitational wave (GW) signal. The precise shape of the signal is governed by the interplay of gravity, rotation, nuclear equation of state (EOS), and electron capture during collapse. We explore the dependence of the signal on total angular momentum and its distribution in the progenitor core by means of a large set of axisymmetric general-relativistic core collapse simulations in which we vary the initial angular momentum distribution in the core. Our simulations include a microphysical finite-temperature EOS, an approximate electron capture treatment during collapse, and a neutrino leakage scheme for the postbounce evolution. We find that the precise distribution of angular momentum is relevant only for very rapidly rotating cores with T/|W|>~8% at bounce. We construct a numerical template bank from our baseline set of simulations, and carry out additional simulations to generate trial wavefo...

  14. Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow.

    Science.gov (United States)

    Gudmundsson, Magnús T; Jónsdóttir, Kristín; Hooper, Andrew; Holohan, Eoghan P; Halldórsson, Sæmundur A; Ófeigsson, Benedikt G; Cesca, Simone; Vogfjörd, Kristín S; Sigmundsson, Freysteinn; Högnadóttir, Thórdís; Einarsson, Páll; Sigmarsson, Olgeir; Jarosch, Alexander H; Jónasson, Kristján; Magnússon, Eyjólfur; Hreinsdóttir, Sigrún; Bagnardi, Marco; Parks, Michelle M; Hjörleifsdóttir, Vala; Pálsson, Finnur; Walter, Thomas R; Schöpfer, Martin P J; Heimann, Sebastian; Reynolds, Hannah I; Dumont, Stéphanie; Bali, Eniko; Gudfinnsson, Gudmundur H; Dahm, Torsten; Roberts, Matthew J; Hensch, Martin; Belart, Joaquín M C; Spaans, Karsten; Jakobsson, Sigurdur; Gudmundsson, Gunnar B; Fridriksdóttir, Hildur M; Drouin, Vincent; Dürig, Tobias; Aðalgeirsdóttir, Guðfinna; Riishuus, Morten S; Pedersen, Gro B M; van Boeckel, Tayo; Oddsson, Björn; Pfeffer, Melissa A; Barsotti, Sara; Bergsson, Baldur; Donovan, Amy; Burton, Mike R; Aiuppa, Alessandro

    2016-07-15

    Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption. We use multiparameter geophysical and geochemical data to show that the 110-square-kilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, near-exponential decline of both collapse rate and the intensity of the 180-day-long eruption.

  15. A multidisciplinary approach to the investigation of a collapsed building.

    Science.gov (United States)

    Pomara, Cristoforo; Turillazzi, Emanuela; Neri, Margherita; Bello, Stefania C; Di Donato, Sabina; Riezzo, Irene; D'Errico, Stefano; Fiore, Carmela; Zizzo, Giulio; Karch, Steven B; Fineschi, Vittorio

    2010-09-01

    Investigating the collapse of a building poses multiple and complex forensic challenges. Large numbers of specialized personnel and equipment are required, as are the combined technical skills of many different kinds of forensic investigators. Forensic pathology teams are integral to these efforts. This report describes the investigation that occurred after a building collapsed in southern Italian location. Several families were still living in small, and abandoned building built in the early 20th century. The buildings were located over cellars 3 meters underground, known locally as "the caves." Eight people were found dead under the debris of one of the collapsed houses and 6 were brought out alive. A team of forensic pathologists and engineers was appointed to investigate the causes of death and of the collapse, respectively. A complete autopsy was performed in every case, along with radiologic assessment and toxicological analysis. Autopsy findings were coded using the Abbreviated Injury Scale and the New Injury Severity Score. Systems for victim identification, arrangements for human remains, management of dead bodies, evaluation of the different patterns of injuries and, finally, detailed identification of the cause of death all played an important role.

  16. Unveiling the High Energy Obscured Universe: Hunting Collapsed Objects Physics

    Science.gov (United States)

    Ubertini, P.; Bazzano, A.; Cocchi, M.; Natalucci, L.; Bassani, L.; Caroli, E.; Stephen, J. B.; Caraveo, P.; Mereghetti, S.; Villa, G.

    2005-01-01

    A large part of energy from space is coming from collapsing stars (SN, Hypernovae) and collapsed stars (black holes, neutron stars and white dwarfs). The peak of their energy release is in the hard-X and gamma-ray wavelengths where photons are insensitive to absorption and can travel from the edge the Universe or the central core of the Galaxy without loosing the primordial information of energy, time signature and polarization. The most efficient process to produce energetic photons is gravitational accretion of matter from a "normal" star onto a collapsed companion (LGxMcollxdMacc/dtx( 1Rdisc)-dMacc/dt x c2), exceeding by far the nuclear reaction capability to generate high energy quanta. Thus our natural laboratory for "in situ" investigations are collapsed objects in which matter and radiation co-exist in extreme conditions of temperature and density due to gravitationally bent geometry and magnetic fields. This is a unique opportunity to study the physics of accretion flows in stellar mass and super-massive Black Holes (SMBHs), plasmoids generated in relativistic jets in galactic microQSOs and AGNs, ionised plasma interacting at the touching point of weakly magnetized NS surface, GRB/Supernovae connection, and the mysterious origins of "dark" GRB and X-ray flash.

  17. Progenitors of the Accretion-Induced Collapse of White Dwarfs

    CERN Document Server

    Kwiatkowski, Damian

    2015-01-01

    Recent calculations of accretion-induced collapse of an oxygen-neon-magnesium white dwarf into a neutron star [Piro & Thompson 2014] allow for a potentially detectable transient electromagnetic signal. Motivated by these results, I present theoretical rates and physical properties of binary stars that can produce accretion-induced collapse. The rates are presented for various types of host galaxies (e.g. old ellipticals versus spirals) and are differentiated by the donor star type (e.g. large giant star versus compact helium-rich donor). Results presented in this thesis may help to guide near-future electromagnetic transient search campaigns to find likely candidates for accretion-induced collapse events. My predictions are based on binary evolution calculations that include the most recent updates on mass accretion and secular mass growth of white dwarfs. I find that the most likely systems that undergo accretion-induced collapse consist of an ONeMg white dwarf with a Hertzsprung gap star or a red giant ...

  18. Simulating the Entropic Collapse of Coarse-Grained Chromosomes

    Science.gov (United States)

    Shendruk, Tyler N.; Bertrand, Martin; de Haan, Hendrick W.; Harden, James L.; Slater, Gary W.

    2015-02-01

    Depletion forces play a role in the compaction and de-compation of chromosomal material in simple cells but it remains debatable whether they are sufficient to account for chromosomal collapse. We present coarse-grained molecular dynamics simulations, which reveal that depletion-induced attraction is sufficient to cause the collapse of a flexible chain of large structural monomers immersed in a bath of smaller depletants. These simulations use an explicit coarse-grained computational model that treats both the supercoiled DNA structural monomers and the smaller protein crowding agents as combinatorial, truncated Lennard-Jones spheres. By presenting a simple theoretical model, we quantitatively cast the action of depletants on supercoiled bacterial DNA as an effective solvent quality. The rapid collapse of the simulated flexible chromosome at the predicted volume fraction of depletants is a continous phase transition. Additional physical effects to such simple chromosome models, such as enthalpic interactions between structural monomers or chain rigidity, are required if the collapse is to be a first-order phase transition.

  19. The Collapse of Differentially Rotating Supermassive Stars: Conformally Flat Simulations

    CERN Document Server

    Saijo, M

    2004-01-01

    We investigate the gravitational collapse of rapidly rotating relativistic supermassive stars by means of a 3+1 hydrodynamical simulations in conformally flat spacetime of general relativity. We study the evolution of differentially rotating supermassive stars of $q \\equiv J/M^{2} \\sim 1$ ($J$ is the angular momentum and $M$ is the gravitational mass of the star) from the onset of radial instability at $R/M \\sim 65$ ($R$ is the circumferential radius of the star) to the point where the conformally flat approximation breaks down. We find that the collapse of the star of $q \\gtrsim 1$, a radially unstable differentially rotating star form a black hole of $q \\lesssim 1$. The main reason to prevent formation of a black hole of $q \\gtrsim 1$ is that quite a large amount of angular momentum stays at the surface. We also find that most of the mass density collapses coherently to form a supermassive black hole with no appreciable disk nor bar. In the absence of nonaxisymmetric deformation, the collapse of differentia...

  20. Black hole free energy during charged collapse: a numerical study

    CERN Document Server

    Beauchesne, Hugues

    2012-01-01

    We perform a numerical investigation of the thermodynamics during the collapse of a charged (complex) scalar field to a Reissner-Nordstr\\"om (RN) black hole in isotropic coordinates. Numerical work on gravitational collapse in isotropic coordinates has recently shown that the negative of the total Lagrangian approaches the Helmholtz free energy F= E-TS of a Schwarzschild black hole at late times of the collapse (where E is the black hole mass, T the temperature and S the entropy). The relevant thermodynamic potential for the RN black hole is the Gibbs free energy G=E-TS-$\\Phi_H$ Q where Q is the charge and $\\Phi_H$ the electrostatic potential at the outer horizon. In charged collapse, there is a large outgoing matter wave which prevents the exterior from settling quickly to a static state. However, the interior region is not affected significantly by the wave. We find numerically that the interior contribution to the Gibbs free energy is entirely gravitational and accumulates in a thin shell just inside the h...

  1. 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....

  2. Critical gravitational collapse with angular momentum

    CERN Document Server

    Gundlach, Carsten

    2016-01-01

    We derive a theoretical model of mass and angular momentum scaling in type-II critical collapse with rotation. We focus on the case where the critical solution has precisely one, spherically symmetric, unstable mode. We demonstrate excellent agreement with numerical results for critical collapse of a rotating radiation fluid, which falls into this case.

  3. 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...

  4. Contagious cooperation, temptation and ecosystem collapse

    NARCIS (Netherlands)

    Richter, A.P.; Soest, van D.; 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 end

  5. Collapse dynamics of bubble raft under compression

    Science.gov (United States)

    Kuo, Chin-Chang; Kachan, Devin; Levine, Alexander; Dennin, Michael; Department of Physics; Astronomy, University of California, Irvine Collaboration; Department of Physics; Astronomy, University of California, Los Angeles Collaboration

    2015-03-01

    We report on the collapse of bubble rafts under compression in a closed rectangular geometry. A bubble raft is a single layer of bubbles at the air-water interface. A collapse event occurs when bubbles submerge beneath the neighboring bubbles under applied compression causing the structure of the bubble raft to go from single-layer to multi-layer. We studied the collapse dynamics as a function of compression velocity. At higher compression velocity we observe a more uniform distribution of collapse events, whereas at lower compression velocities, the collapse events accumulate at the system boundaries. We will present results that compare the distribution of collapse probability in the experiments to simulations based on a one-dimensional Ising model with elastic coupling between spin elements. Both the experimental system and simulations are excellent models for collapse in a number of complex systems. By comparing the two systems, we can tune the simulation to better understand the role of the Ising and elastic couplings in determining the collapse dynamics. We acknowledge DMR-1309402.

  6. Collapsing cavities in reactive and nonreactive media

    Science.gov (United States)

    Bourne, Neil K.; Field, John E.

    1991-04-01

    This paper presents results of a high-speed photographic study of cavities collapsed asymmetrically by shocks of strengths in the range 0.26 GPa to 3.5 GPa. Two-dimensional collapses of cavity configurations punched into a 12% by weight gelatine in water sheet, and an ammonium nitrate/sodium nitrate (AN/SN) emulsion explosive were photographed using schlieren optics. The single cavity collapses were characterized by the velocity of the liquid jet formed by the upstream wall as it was accelerated by the shock and by the time taken for the cavity to collapse. The shock pressure did not qualitatively affect the collapse behaviour but jet velocities were found to exceed incident shock velocities at higher pressures. The more violent collapses induced light emission from the compressed gas in the cavity. When an array of cavities collapsed, a wave, characterized by the particle velocity in the medium, the cavity diameter and the inter-cavity spacing, was found to run through the array. When such an array was created within an emulsion explosive, ignition of the reactive matrix occurred ahead of the collapse wave when the incident shock was strong.

  7. 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....

  8. On Mine Too Large Collapse Treatment and Preventive Measures of Roof Column%浅谈煤矿过大陷落柱冒顶处理及预防措施

    Institute of Scientific and Technical Information of China (English)

    鄢德恒

    2015-01-01

    The roof falling caused casualties, production and damage to equipment, is one of the five major disasters in coal mine production. In the roof accident in China coal mine, the roof fall accidents in heading face a larger proportion of. Taking Shanxi Jizhong 9102 mine belt along the groove excavation construction had subsided column as an example, in the accident, the emergence of a large area roof fall, lead to the normal construction, greatly influences the safety production of the coal mine working face. Through the analysis of the roof fall accident, put forward to control and the corresponding treatment methods, in order to ensure the safety of the working face.%顶板冒落造成的人员伤亡、停产和设备损坏等事故,是煤矿生产的五大灾害之一。在我国煤矿的顶板事故中,掘进工作面冒顶事故占有较大的比例。以山西冀中某矿9102胶带顺槽掘进施工过陷落柱为例,在该事故中,出现大面积冒顶,导致无法正常施工,极大地影响了该矿工作面的安全生产。通过分析该冒顶事故,提出了相应的控制和处理方法,以确保工作面安全。

  9. 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...... 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....... 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...

  10. Four Tails Problems for Dynamical Collapse Theories

    CERN Document Server

    McQueen, Kelvin J

    2015-01-01

    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 di...

  11. Continuous Observations and the Wave Function Collapse

    CERN Document Server

    Marchewka, A

    2011-01-01

    We propose to modify the collapse axiom of quantum measurement theory by replacing the instantaneous with a continuous collapse of the wave function in finite time $\\tau$. We apply it to coordinate measurement of a free quantum particle that is initially confined to a domain $D\\subset\\rR^d$ and is observed continuously by illuminating $\\rR^d-D$. The continuous collapse axiom (CCA) defines the post-measurement wave function (PMWF)in $D$ after a negative measurement as the solution of Schr\\"odinger's equation at time $\\tau$ with instantaneously collapsed initial condition and homogeneous Dirichlet condition on the boundary of $D$. The CCA applies to all cases that exhibit the Zeno effect. It rids quantum mechanics of the unphysical artifacts caused by instantaneous collapse and introduces no new artifacts.

  12. Collapse in Self-gravitating Turbulent Fluids

    CERN Document Server

    Murray, Daniel W; Pittman, John

    2015-01-01

    We perform simulations of star formation in self-gravitating turbulently driven gas. We find that star formation is not a self-similar process; two length scales enter, the radius of the rotationally supported disk $r_d$, and the radius $r_*$ of the sphere of influence of the nascent star, where the enclosed gas mass exceeds the stellar mass. The character of the flow changes at these two scales. We do not see any examples of inside-out collapse. Rather, the accretion of mass starts at large scales where we see large infall velocities $|u_r(r)| \\approx (1/3) v_{ff} \\sim (1/3)\\sqrt{GM(r)/r}\\gtrsim c_s$ out to $r \\sim 1 \\, \\rm{pc}$ hundreds of thousands of years before a star forms. The density evolves to a fixed attractor, $\\rho(r,t ) \\rightarrow \\rho(r)$, for $r_dr_d$ and rotational support becomes important for $r

  13. Non-linear dark matter collapse under diffusion

    CERN Document Server

    Velten, Hermano E S

    2014-01-01

    Diffusion is one of the physical processes allowed for describing the large scale dark matter dynamics. At the same time, it can be seen as a possible mechanism behind the interacting cosmologies. We study the non-linear spherical "top-hat" collapse of dark matter which undergoes velocity diffusion into a solvent dark energy field. We show constraints on the maximum magnitude allowed for the dark matter diffusion. Our results reinforce previous analysis concerning the linear perturbation theory.

  14. On the number density of "direct collapse" black hole seeds

    CERN Document Server

    Habouzit, Melanie; Latif, Muhammad; Dubois, Yohan; Peirani, Sebastien

    2016-01-01

    Supermassive black holes (BHs) of millions solar masses and above reside in the center of most local galaxies, but they also power active galactic nuclei and quasars, detected up to z=7. This observational evidence puts strong constraints on the BH growth and the mass of the first BH seeds. The scenario of "direct collapse" is very appealing as it leads to the formation of large mass BH seeds in the range 10^4-10^6 Msun, which eases explaining how quasars at z=6-7 are powered by BHs with masses >10^9 Msun. Direct collapse, however, appears to be rare, as the conditions required by the scenario are that gas is metal-free, the presence of a strong photo-dissociating Lyman-Werner flux, and large inflows of gas at the center of the halo, sustained for 10-100 Myr. We performed several cosmological hydrodynamical simulations that cover a large range of box sizes and resolutions, thus allowing us to understand the impact of several physical processes on the distribution of direct collapse BHs. We identify halos wher...

  15. Numerical modelling of collapsing volcanic edifices

    Science.gov (United States)

    Costa, Ana; Marques, Fernando; Kaus, Boris

    2017-04-01

    The flanks of Oceanic Volcanic Edifice's (OVEs) can occasionally become unstable. If that occurs, they can deform in two different modes: either slowly along localization failure zones (slumps) or catastrophically as debris avalanches. Yet the physics of this process is incompletely understood, and the role of factors such as the OVE's strength (viscosity, cohesion, friction angle), dimensions, geometry, and existence of weak layers remain to be addressed. Here we perform numerical simulations to study the interplay between viscous and plastic deformation on the gravitational collapse of an OVE (diffuse deformation vs. localization of failure along discrete structures). We focus on the contribution of the edifice's strength parameters for the mode of deformation, as well as on the type of basement. Tests were performed for a large OVE (7.5 km high, 200 km long) and either purely viscous (overall volcano edifice viscosities between 1019-1023 Pa.s), or viscoplastic rheology (within a range of cohesion and friction angle values). Results show that (a) for a strong basement (no slip basal boundary condition), the deformation pattern suggests wide/diffuse "listric" deformation within the volcanic edifice, without the development of discrete plastic failure zones; (b) for a weak basement (free slip basal boundary condition), rapid collapse of the edifice through the propagation of plastic failure structures within the edifice occurs. Tests for a smaller OVE (4.5 km by 30 km) show that failure localization along large-scale listric structures occurs more readily for different combinations of cohesion and friction angles. In these tests, high cohesion values combined with small friction angles lead to focusing of deformation along a narrower band. Tests with a weak layer underlying part of the volcanic edifice base show deformation focused along discrete structures mainly dipping towards the distal sector of the volcano. These tests for a small OVE constitute a promising

  16. Scapholunate advanced collapse wrist salvage.

    Science.gov (United States)

    Ashmead, D; Watson, H K; Damon, C; Herber, S; Paly, W

    1994-09-01

    Patients with scapholunate advanced collapse (SLAC) wrist do not have to undergo total wrist arthrodesis; the SLAC pattern spares the radiolunate articulation, providing a basis for salvage. We report the results of 100 cases in which a technique comprised of scaphoid excision and limited wrist arthrodesis was used. The average followup period of 44 months revealed excellent functional status and a high rate of patient satisfaction. The majority of employed patients were able to return to their original jobs, and many chose to resume wrist-related recreational activities. Pain relief was good to excellent in most cases. Extension/flexion averaged 72 degrees (53% of a normal opposite wrist), radioulnar deviation 37 degrees (59%), and grip strength 80% of the opposite side. X-ray films revealed only two instances of radiolunate destruction, both in conjunction with ulnar translation of the carpus. The other 98 patients demonstrated a well-preserved radiolunate joint regardless of followup interval. Complications were few. Nonunion occurred in three cases. A dorsal impingement of the capitate and radius (12%) was felt to be technique-related and avoidable by careful capitolunate alignment.

  17. Motion of three vortices near collapse

    Science.gov (United States)

    Leoncini, X.; Kuznetsov, L.; Zaslavsky, G. M.

    2000-08-01

    A system of three point vortices in an unbounded plane has a special family of self-similarly contracting or expanding solutions: during the motion, the vortex triangle remains similar to the original one, while its area decreases (grows) at a constant rate. A contracting configuration brings three vortices to a single point in a finite time; this phenomenon known as vortex collapse is of principal importance for many-vortex systems. Dynamics of close-to-collapse vortex configurations depends on the way the collapse conditions are violated. Using an effective potential representation, a detailed quantitative analysis of all the different types of near-collapse dynamics is performed when two of the vortices are identical. We discuss time and length scales, emerging in the problem, and their behavior as the initial vortex triangle is approaching an exact collapse configuration. Different types of critical behaviors, such as logarithmic or power-law divergences are exhibited, which emphasize the importance of the way the collapse is approached. Period asymptotics for all singular cases are presented as functions of the initial vortice's configurations. Special features of passive particle mixing by near-collapse flows are illustrated numerically.

  18. Estimating the Topography Before Volcanic Sector Collapses Using Tsunami Survey Data and Numerical Simulations

    Science.gov (United States)

    Yamanaka, Yusuke; Tanioka, Yuichiro

    2017-08-01

    Large sector collapses and landslides have the potential to cause significant disasters. Estimating the topography and conditions, such as volume, before the collapse is thus important for analyzing the behavior of moving collapsed material and hazard risks. This study considers three historical volcanic sector collapses in Japan that caused tsunamis: the collapses of the Komagatake Volcano in 1640, Oshima-Oshima Island in 1741, and Unzen-Mayuyama Volcano in 1792. Numerical simulations of the tsunamis generated by each event were first carried out based on assumed collapse scenarios. The primary objective of this study is to present conditions related to the topography before the events based on inverse models of the topography from those results and tsunami survey data. The Oshima-Oshima Tsunami, which is the subject of many previous studies, was first simulated to validate the model accuracy and evaluate how run-up heights changed during the simulation as the topographic conditions changed. The run-up height was especially sensitive to the collapsed volume and frictional acceleration affecting the collapsed material; however, the observed run-up heights could be reproduced with high accuracy using proper conditions of frictional acceleration for the scenarios, even if they were not exact. A minimum requirement for the collapsed volume to generate the observed run-up height was introduced and quantitatively evaluated using the results of numerical tsunami simulations. The minimum volumes of the collapses of the Komagatake and Unzen-Mayuyama volcanoes were estimated to be approximately 1.2 and 0.3 km3, respectively.

  19. Biological effects of stellar collapse neutrinos

    CERN Document Server

    Collar, J I

    1996-01-01

    Massive stars in their final stages of collapse radiate most of their binding energy in the form of MeV neutrinos. The recoil atoms that they produce in elastic scattering off nuclei in organic tissue create a radiation damage which is highly effective in the production of irreparable DNA harm, leading to cellular mutation, neoplasia and oncogenesis. Using a conventional model of the galaxy and of the collapse mechanism, the periodicity of nearby stellar collapses and the radiation dose are calculated. The possible contribution of this process to the paleontological record of mass extinctions is examined.

  20. Core-Collapse supernovae and its progenitors

    CERN Document Server

    Bose, Subhash; Misra, Kuntal

    2016-01-01

    Massive stars unable to sustain gravitational collapse, at the end of nuclear burning stage, turns out into core-collapse supernovae, leaving behind compact objects like neutron stars or black holes. The progenitor properties like mass and metallicity primarily governs the explosion parameters and type of compact remnant. In this contribution we summarize observational study of three Core Collapse type IIP SNe 2012aw, 2013ab and 2013ej, which are rigorously observed from ARIES and other Indian observatories and discuss their progenitor and explosion properties.

  1. How fast is the wave function collapse?

    CERN Document Server

    Ignatiev, A Yu

    2012-01-01

    Using complex quantum Hamilton-Jacobi formulation, a new kind of non-linear equations is proposed that have almost classical structure and extend the Schroedinger equation to describe the collapse of the wave function as a finite-time process. Experimental bounds on the collapse time are reported (of order 0.1 ms to 0.1 ps) and its convenient dimensionless measure is introduced. This parameter helps to identify the areas where sensitive probes of the possible collapse dynamics can be done. Examples are experiments with Bose-Einstein condensates, ultracold neutrons or ultrafast optics.

  2. Matter and gravitons in the gravitational collapse

    CERN Document Server

    Casadio, Roberto; Giusti, Andrea

    2016-01-01

    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 the 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 supports a scenario in which the gravitational collapse of regular baryonic matter produces a corpuscular black hole without singularity.

  3. On the quantum corrected gravitational collapse

    Energy Technology Data Exchange (ETDEWEB)

    Torres, Ramón, E-mail: ramon.torres-herrera@upc.edu; Fayos, Francesc, E-mail: f.fayos@upc.edu

    2015-07-30

    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.

  4. 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.

  5. Collapse transition of a hydrophobic self-avoiding random walk in a coarse-grained model solvent.

    Science.gov (United States)

    Gaudreault, Mathieu; Viñals, Jorge

    2009-08-01

    In order to study solvation effects on protein folding, we analyze the collapse transition of a self-avoiding random walk composed of hydrophobic segments that is embedded in a lattice model of a solvent. As expected, hydrophobic interactions lead to an attractive potential of mean force among chain segments. As a consequence, the random walk in solvent undergoes a collapse transition at a higher temperature than in its absence. Chain collapse is accompanied by the formation of a region depleted of solvent around the chain. In our simulation, the depleted region at collapse is as large as our computational domain.

  6. Collapse transition of a hydrophobic self-avoiding random walk in a coarse-grained model solvent

    Science.gov (United States)

    Gaudreault, Mathieu; Viñals, Jorge

    2009-08-01

    In order to study solvation effects on protein folding, we analyze the collapse transition of a self-avoiding random walk composed of hydrophobic segments that is embedded in a lattice model of a solvent. As expected, hydrophobic interactions lead to an attractive potential of mean force among chain segments. As a consequence, the random walk in solvent undergoes a collapse transition at a higher temperature than in its absence. Chain collapse is accompanied by the formation of a region depleted of solvent around the chain. In our simulation, the depleted region at collapse is as large as our computational domain.

  7. Collapse and recovery of marine fishes.

    Science.gov (United States)

    Hutchings, J A

    2000-08-24

    Overexploitation and subsequent collapse of marine fishes has focused attention on the ability of affected populations to recover to former abundance levels and on the degree to which their persistence is threatened by extinction. Although potential for recovery has been assessed indirectly, actual changes in population size following long-term declines have not been examined empirically. Here I show that there is very little evidence for rapid recovery from prolonged declines, in contrast to the perception that marine fishes are highly resilient to large population reductions. With the possible exception of herring and related species that mature early in life and are fished with highly selective equipment, my analysis of 90 stocks reveals that many gadids (for example, cod, haddock) and other non-clupeids (for example, flatfishes) have experienced little, if any, recovery as much as 15 years after 45-99% reductions in reproductive biomass. Although the effects of overfishing on single species may generally be reversible, the actual time required for recovery appears to be considerable. To exempt marine fishes from existing criteria used to assign extinction risk would be inconsistent with precautionary approaches to fisheries management and the conservation of marine biodiversity.

  8. Collapse in self-gravitating turbulent fluids

    Science.gov (United States)

    Murray, Daniel W.; Chang, Philip; Murray, Norman W.; Pittman, John

    2017-02-01

    Motivated by the non-linear star formation efficiency found in recent numerical simulations by a number of workers, we perform high-resolution adaptive mesh refinement simulations of star formation in self-gravitating turbulently driven gas. As we follow the collapse of this gas, we find that the character of the flow changes at two radii, the disc radius rd and the radius r*, where the enclosed gas mass exceeds the stellar mass. Accretion starts at large scales and works inwards. In line with recent analytical work, we find that the density evolves to a fixed attractor, ρ(r, t) → ρ(r), for rd structure on to a sporadically gravitationally unstable disc and from thence on to the star. In the bulk of the simulation box, we find that the random motions vT ∼ rp with p ∼ 0.5 are in agreement with Larson's size-linewidth relation. In the vicinity of massive star-forming regions, we find p ∼ 0.2-0.3, as seen in observations. For r < r*, vT increases inwards, with p = -1/2. Finally, we find that the total stellar mass M*(t) ∼ t2 is in line with previous numerical and analytic work that suggests a non-linear rate of star formation.

  9. Tulsa oklahoma oktoberfest tent collapse report.

    Science.gov (United States)

    Deal, Kelly E; Synovitz, Carolyn K; Goodloe, Jeffrey M; King, Brandi; Stewart, Charles E

    2012-01-01

    Background. On October 17, 2007, a severe weather event collapsed two large tents and several smaller tents causing 23 injuries requiring evacuation to emergency departments in Tulsa, OK. Methods. This paper is a retrospective analysis of the regional health system's response to this event. Data from the Tulsa Fire Department, The Emergency Medical Services Authority (EMSA), receiving hospitals and coordinating services were reviewed and analyzed. EMS patient care reports were reviewed and analyzed using triage designators assigned in the field, injury severity scores, and critical mortality. Results. EMT's and paramedics from Tulsa Fire Department and EMSA provided care at the scene under unified incident command. Of the 23 patients transported by EMS, four were hospitalized, one with critical spinal injury and one with critical head injury. One patient is still in ongoing rehabilitation. Discussion. Analysis of the 2007 Tulsa Oktoberfest mass casualty incident revealed rapid police/fire/EMS response despite challenges of operations at dark under severe weather conditions and the need to treat a significant number of injured victims. There were no fatalities. Of the patients transported by EMS, a minority sustained critical injuries, with most sustaining injuries amenable to discharge after emergency department care.

  10. Collapse of superhydrophobicity on nanopillared surfaces

    Science.gov (United States)

    Amabili, Matteo; Giacomello, Alberto; Meloni, Simone; Casciola, Carlo Massimo

    2017-03-01

    The mechanism of the collapse of the superhydrophobic state is elucidated for submerged nanoscale textures forming a three-dimensional interconnected vapor domain. This key issue for the design of nanotextures poses significant simulation challenges as it is characterized by diverse time and length scales. State-of-the-art atomistic rare events simulations are applied for overcoming the long time scales connected with the large free energy barriers. In such interconnected surface cavities wetting starts with the formation of a liquid finger between two pillars. This break of symmetry induces a more gentle bend in the rest of the liquid-vapor interface, which triggers the wetting of the neighboring pillars. This collective mechanism, involving the wetting of several pillars at the same time, could not be captured by previous atomistic simulations using surface models comprising a small number of pillars (often just one). Atomistic results are interpreted in terms of a sharp-interface continuum model which suggests that line tension, condensation, and other nanoscale phenomena play a minor role in the simulated conditions.

  11. Tulsa Oklahoma Oktoberfest Tent Collapse Report

    Directory of Open Access Journals (Sweden)

    Kelly E. Deal

    2012-01-01

    Full Text Available Background. On October 17, 2007, a severe weather event collapsed two large tents and several smaller tents causing 23 injuries requiring evacuation to emergency departments in Tulsa, OK. Methods. This paper is a retrospective analysis of the regional health system’s response to this event. Data from the Tulsa Fire Department, The Emergency Medical Services Authority (EMSA, receiving hospitals and coordinating services were reviewed and analyzed. EMS patient care reports were reviewed and analyzed using triage designators assigned in the field, injury severity scores, and critical mortality. Results. EMT's and paramedics from Tulsa Fire Department and EMSA provided care at the scene under unified incident command. Of the 23 patients transported by EMS, four were hospitalized, one with critical spinal injury and one with critical head injury. One patient is still in ongoing rehabilitation. Discussion. Analysis of the 2007 Tulsa Oktoberfest mass casualty incident revealed rapid police/fire/EMS response despite challenges of operations at dark under severe weather conditions and the need to treat a significant number of injured victims. There were no fatalities. Of the patients transported by EMS, a minority sustained critical injuries, with most sustaining injuries amenable to discharge after emergency department care.

  12. Colony collapse disorder: a descriptive study.

    Science.gov (United States)

    Vanengelsdorp, Dennis; Evans, Jay D; Saegerman, Claude; Mullin, Chris; Haubruge, Eric; Nguyen, Bach Kim; Frazier, Maryann; Frazier, Jim; Cox-Foster, Diana; Chen, Yanping; Underwood, Robyn; Tarpy, David R; Pettis, Jeffery S

    2009-08-03

    Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L.) colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD) because the main trait was a rapid loss of adult worker bees. We initiated a descriptive epizootiological study in order to better characterize CCD and compare risk factor exposure between populations afflicted by and not afflicted by CCD. Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels), no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor) were higher in control colonies than CCD-affected colonies. This is the first comprehensive survey of CCD-affected bee populations that suggests CCD involves an interaction between pathogens and other stress factors. We present evidence that this condition is contagious or the result of exposure to a common risk factor. Potentially important areas for future hypothesis-driven research, including the possible legacy effect of mite parasitism and the role of honey bee resistance to pesticides, are highlighted.

  13. Colony collapse disorder: a descriptive study.

    Directory of Open Access Journals (Sweden)

    Dennis Vanengelsdorp

    Full Text Available BACKGROUND: Over the last two winters, there have been large-scale, unexplained losses of managed honey bee (Apis mellifera L. colonies in the United States. In the absence of a known cause, this syndrome was named Colony Collapse Disorder (CCD because the main trait was a rapid loss of adult worker bees. We initiated a descriptive epizootiological study in order to better characterize CCD and compare risk factor exposure between populations afflicted by and not afflicted by CCD. METHODS AND PRINCIPAL FINDINGS: Of 61 quantified variables (including adult bee physiology, pathogen loads, and pesticide levels, no single measure emerged as a most-likely cause of CCD. Bees in CCD colonies had higher pathogen loads and were co-infected with a greater number of pathogens than control populations, suggesting either an increased exposure to pathogens or a reduced resistance of bees toward pathogens. Levels of the synthetic acaricide coumaphos (used by beekeepers to control the parasitic mite Varroa destructor were higher in control colonies than CCD-affected colonies. CONCLUSIONS/SIGNIFICANCE: This is the first comprehensive survey of CCD-affected bee populations that suggests CCD involves an interaction between pathogens and other stress factors. We present evidence that this condition is contagious or the result of exposure to a common risk factor. Potentially important areas for future hypothesis-driven research, including the possible legacy effect of mite parasitism and the role of honey bee resistance to pesticides, are highlighted.

  14. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron's submerged sinkholes.

    Science.gov (United States)

    Biddanda, Bopaiah A; McMillan, Adam C; Long, Stephen A; Snider, Michael J; Weinke, Anthony D

    2015-01-01

    We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen, and high-sulfur conditions in Lake Huron's submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100-10,000 μm long filaments, composed of cells ∼10 μm wide and ∼3 μm tall) revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ∼50 μm min(-1) or ∼15 body lengths min(-1) at 10°C to ∼215 μm min(-1) or ∼70 body lengths min(-1) at 35°C - rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis toward pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield - suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3-4 diurnal cycles - likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth's early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing photosynthesis while favoring

  15. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron’s submerged sinkholes

    Directory of Open Access Journals (Sweden)

    Bopaiah A Biddanda

    2015-09-01

    Full Text Available We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen and high-sulfur conditions in Lake Huron’s submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100-10,000 µm long filaments, composed of cells ~10 µm wide and ~3 µm tall revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ~50 µm minute-1 or ~15 body lengths minute-1 at 10°C to ~215 µm minute-1 or ~70 body lengths minute-1 at 35°C – rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis towards pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield – suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3-4 diurnal cycles – likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth’s early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing

  16. Atmospheric heat redistribution and collapse on tidally locked rocky planets

    CERN Document Server

    Wordsworth, Robin

    2014-01-01

    Atmospheric collapse is likely to be of fundamental importance to tidally locked rocky exoplanets but remains understudied. Here, general results on the heat transport and stability of tidally locked terrestrial-type atmospheres are reported. First, the problem is modeled with an idealized 3D general circulation model (GCM) with gray gas radiative transfer. It is shown that over a wide range of parameters the atmospheric boundary layer, rather than the large-scale circulation, is the key to understanding the planetary energy balance. Through a scaling analysis of the interhemispheric energy transfer, theoretical expressions for the day-night temperature difference and surface wind speed are created that reproduce the GCM results without tuning. Next, the GCM is used with correlated-k radiative transfer to study heat transport for two real gases (CO2 and CO). For CO2, empirical formulae for the collapse pressure as a function of planetary mass and stellar flux are produced, and critical pressures for atmospher...

  17. Catastrophic ice lake collapse in Aram Chaos, Mars

    CERN Document Server

    Roda, Manuel; Zegers, Tanja E; Oosthoek, Jelmer H P

    2014-01-01

    Hesperian chaotic terrains have been recognized as the source of outflow channels formed by catastrophic outflows. Four main scenarios have been proposed for the formation of chaotic terrains that involve different amounts of water and single or multiple outflow events. Here, we test these scenarios with morphological and structural analyses of imagery and elevation data for Aram Chaos in conjunction with numerical modeling of the morphological evolution of the catastrophic carving of the outflow valley. The morphological and geological analyses of Aram Chaos suggest large-scale collapse and subsidence (1500 m) of the entire area, which is consistent with a massive expulsion of liquid water from the subsurface in one single event. The combined observations suggest a complex process starting with the outflow of water from two small channels, followed by continuous groundwater sapping and headward erosion and ending with a catastrophic lake rim collapse and carving of the Aram Valley, which is synchronous with ...

  18. Signatures of hydrophobic collapse in extended proteins captured with force spectroscopy

    OpenAIRE

    2007-01-01

    We unfold and extend single proteins at a high force and then linearly relax the force to probe their collapse mechanisms. We observe a large variability in the extent of their recoil. Although chain entropy makes a small contribution, we show that the observed variability results from hydrophobic interactions with randomly varying magnitude from protein to protein. This collapse mechanism is common to highly extended proteins, including nonfolding elastomeric proteins like PEVK from titin. O...

  19. Three magnetic reversals recorded in an 80-m organic-rich core from a sinkhole east of Tampa, FL

    Energy Technology Data Exchange (ETDEWEB)

    McCartan, L.; Rubin, M. (Geological Survey, Reston, VA (United States)); Liddicoat, J.C. (Barnard Coll, New York, NY (United States)); Bond, P.A.; Osmond, J.K. (Florida State Univ., Tallahassee, FL (United States))

    1994-03-01

    Preliminary analysis of a continuous 80-m core from a phosphate mines at Bartow, Fla., indicates as many as three magnetically reversed and five normal sections and five upward-fining depositional sequences. The paleomagnetic data are based on analysis of 16 samples; 100 additional samples have been taken for more detailed analysis. The authors estimate the maximum age to be 1.1--2.6 Ma. The core is composed of massive to faintly laminated beds of black to dark-brown, organic-rich, fine quartz sand and silt, kaolinitic and organic clay, and peat, Only the top meter is within the 40 Ka range of [sup 14]C; a sample at 8.5 m yielded an age estimate close to 350,000 years, the limit of the open-system U/Th dating technique. Rates of deposition are 2--7.5 cm/1,000 years, which is much slower than rates in late Quaternary lakes elsewhere in Florida. There is no clear relation between the magnetic stratigraphy and the depositional stratigraphy. The authors assume that most of the sand was derived from dissolved limestone around the sinkhole, but some of the sand as well as the silt and clay may be windborne. Textural variations may be coincident with differences in rainfall, and this concept will be investigated through pollen analysis of approximately 800 samples. The one sample examined so far is from the bottom of the core, and it has an equivocal biostratigraphic age. The high grass pollen content indicates a drier climate than at present; it is from a long interval of peat with sand, which is typically windborne in dry climates.

  20. Gravitational collapse with decaying vacuum energy

    Indian Academy of Sciences (India)

    A Beesham

    2011-09-01

    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.

  1. Collapsible truss structure is automatically expandable

    Science.gov (United States)

    1965-01-01

    Coil springs wound with maximum initial tension in a three-truss, closed loop structure form a collapsible truss structure. The truss automatically expands and provides excellent rigidity and close dimensional tolerance when expanded.

  2. Climate and the Collapse of Maya Civilization

    National Research Council Canada - National Science Library

    Gerald H. Haug; Detlef Günther; Larry C. Peterson; Daniel M. Sigman; Konrad A. Hughen; Beat Aeschlimann

    2003-01-01

    .... A seasonally resolved record of titanium shows that the collapse of Maya civilization in the Terminal Classic Period occurred during an extended regional dry period, punctuated by more intense...

  3. Hawking radiation from a collapsing quantum shell

    Science.gov (United States)

    Pullin, Jorge; Eyheralde, Rodrigo; Gambini, Rodolfo

    2017-01-01

    We study Hawking radiation from a collapsing shell with uncertainty in its position and momentum. We see there are deviations from the usual spectrum early on in the evolution, tending asymptotically to the usual spectrum plus small corrections.

  4. Loop quantum dynamics of the gravitational collapse

    CERN Document Server

    Tavakoli, Yaser; Dapor, Andrea

    2013-01-01

    We consider a quantum description for a spherically symmetric gravitational collapse of a massless scalar field. The effective scenario from loop quantum gravity is applied to a homogeneous interior spacetime. Classical singularity that arises at the final stage of our collapsing system, is resolved and replaced by a quantum bounce. Our main purpose is to investigate the evolution of trapped surfaces during the collapse in semiclassical regime. We show that, in this regime, there exists a threshold scale bellow which no horizon can form as collapse evolves towards the bounce. By employing the matching conditions at the boundary shell, quantum effects are carried out to the exterior region, leading to an improved Vaidya geometry. In addition, the effective mass loss emerging in this model predicts an outward energy flux from the interior quantum geometry regime.

  5. 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.

  6. Calculation of reactivity changes due to bubble collapse. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, T.J.; Petrie, L.M.

    1977-01-01

    Calculations based on Behrens' method indicate that a substantial increase in reactivity may accompany the collapse of a large number of small bubbles in an LMFBR core. More sophisticated transport approaches to this problem have encountered several difficulties: the large number of bubbles requires many mesh points; the desired effect can easily be masked by the movement of fuel to regions of greater (or lesser) importance; the reactivity is desired for a random distribution of spherical bubbles. This paper describes a transport approach to this problem which avoids the above difficulties by using the ''sub-group'' or ''probability table'' method.

  7. Precursory singularities in spherical gravitational collapse

    Science.gov (United States)

    Lake, Kayll

    1992-05-01

    General conditions are developed for the formation of naked precursory ('shell-focusing') singularities in spherical gravitational collapse. These singularities owe their nakedness to the fact that the gravitational potential fails to be single valued prior to the onset of a true gravitational singularity. It is argued that they do not violate the spirit of cosmic censorship. Rather, they may well be an essentially generic feature of relativistic gravitational collapse.

  8. Nonlinear Progressive Collapse Analysis Including Distributed Plasticity

    OpenAIRE

    Mohamed Osama Ahmed; Imam Zubair Syed; Khattab Rania

    2016-01-01

    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, develop...

  9. Cardiovascular collapse with attempted pericardial drain withdrawal

    Directory of Open Access Journals (Sweden)

    Molly B Kraus

    2016-01-01

    Full Text Available Cardiac tamponade is a rare but serious emergency condition in the pediatric population. As treatment, a pericardial drain is often placed to evacuate the fluid. We present a case of a 4-year-old girl with cardiac tamponade secondary to renal failure. After the tamponade resolved, she suffered cardiovascular collapse upon attempted drain withdrawal. This case highlights an unusual cause for cardiovascular collapse, which occurred on blind removal of a pericardial drain.

  10. Cardiovascular collapse with attempted pericardial drain withdrawal

    OpenAIRE

    Molly B Kraus; Spitznagel, Rachel A; Kugler, Jane A

    2016-01-01

    Cardiac tamponade is a rare but serious emergency condition in the pediatric population. As treatment, a pericardial drain is often placed to evacuate the fluid. We present a case of a 4-year-old girl with cardiac tamponade secondary to renal failure. After the tamponade resolved, she suffered cardiovascular collapse upon attempted drain withdrawal. This case highlights an unusual cause for cardiovascular collapse, which occurred on blind removal of a pericardial drain.

  11. Scalar field collapse with an exponential potential

    Science.gov (United States)

    Chakrabarti, Soumya

    2017-02-01

    An analogue of the Oppenheimer-Synder collapsing model is treated analytically, where the matter source is a scalar field with an exponential potential. An exact solution is derived followed by matching to a suitable exterior geometry, and an analysis of the visibility of the singularity. In some situations, the collapse indeed leads to a finite time curvature singularity, which is always hidden from the exterior by an apparent horizon.

  12. The universe remembers no wavefunction collapse

    OpenAIRE

    Stoica, Ovidiu Cristinel

    2016-01-01

    Two thought experiments are analyzed, revealing that the quantum state of the universe does not contain definitive evidence of the wavefunction collapse. The first thought experiment shows that unitary quantum evolution alone can account for the outcomes of any combination of quantum experiments. This is in contradiction with the standard view on quantum measurement, which appeals to the wavefunction collapse, but it is in full agreement with the special state proposal (L.S. Schulman in Phys ...

  13. Study on the stress path dependency of collapse behavior of Gorgan loess implementing unsaturated oedometer devices

    Directory of Open Access Journals (Sweden)

    Haeri S. Mohsen

    2016-01-01

    Full Text Available Collapsible soils such as loess are particular types of problematic soils, whose collapse potential have caused severe damages to the buildings and structures. Loess is susceptible to large and sudden volume reduction upon wetting in constant normal stress or upon increasing normal stress in constant water content or a combination of these two stress paths. In this research both of these collapse induced paths: wetting and stress paths are investigated on undisturbed specimens of a Loess to observe the effect of various parameters on the collapse behavior of the tested soil., Seven controlled matric suction unsaturated oedometer tests have been conducted on undisturbed specimens taken from loessial soil of Gorgan, a city in Golestan province in Iran to study the collapse mechanisms of this type of soils. Two identical sets of unsaturated oedometer apparatuses designed and developed at Sharif University of Technology, with the capability of controlling matric suction have been utilized. In these tests, the matric suction, vertical net stress, volumetric water content, and vertical deformation of the samples have been controlled and recorded. Tests have been performed under two separate stress paths: constant matric suction with varying vertical net stress (loading and unloading and constant vertical net stress with varying matric suction (wetting and drying. Obtained results show the high collapse potential of the tested soil and significant effects of stress path, matric suction, and vertical net stress on the collapse behavior of the tested soil.

  14. Can agricultural groundwater economies collapse? An inquiry into the pathways of four groundwater economies under threat

    Science.gov (United States)

    Petit, Olivier; Kuper, Marcel; López-Gunn, Elena; Rinaudo, Jean-Daniel; Daoudi, Ali; Lejars, Caroline

    2017-09-01

    The aim of this paper is to investigate the notion of collapse of agricultural groundwater economies using the adaptive-cycle analytical framework. This framework was applied to four case studies in southern Europe and North Africa to question and discuss the dynamics of agricultural groundwater economies. In two case studies (Saiss in Morocco and Clain basin in France), the imminent physical or socio-economic collapse was a major concern for stakeholders and the early signs of collapse led to re-organization of the groundwater economy. In the other two cases (Biskra in Algeria and Almeria in Spain), collapse was either not yet a concern or had been temporarily resolved through increased efficiency and access to additional water resources. This comparative analysis shows the importance of taking the early signs of collapse into account. These signs can be either related to resource depletion or to environmental and socio-economic impacts. Beyond these four case studies, the large number of groundwater economies under threat in (semi-)arid areas should present a warning regarding their possible collapse. Collapse can have severe and irreversible consequences in some cases, but it can also mean new opportunities and changes.

  15. Buckling and unstable collapse of seamless pipes and tubes

    Energy Technology Data Exchange (ETDEWEB)

    Jakani, S.; Van den Abeele, F. [ArcelorMittal Global RnD Ghent, Zelzate, (Belgium); Bar, J. [ArcelorMittal Tubular Products Ostrava, Ostrava, (Czech Republic)

    2010-07-01

    Off-shore pipelines and high pressure casings are subject to buckling and unstable collapse. This paper investigated the unstable collapse of seamless pipes under compressive loading. Collapse pressure tests for high collapse casing grades L80HC and P110HC were carried out by enclosing end-capped specimens in a pressure vessel, and applying hydrostatic pressure. Analytical calculations were performed to predict the critical collapse pressure for pipes with different values of diameter to wall thickness. Four regimes were identified and studied: yielding collapse, plastic collapse, transition range and elastic collapse. Simplified design equations were produced for each regime to estimate the collapse pressure more efficiently. The influence of initial geometric imperfections and material properties was studied with the aim of developing a modified design equation for collapse able to predict the critical collapse pressure of dented seamless pipes. Experimental tests showed that the pipes complied with API standards and the modified equation was validated.

  16. 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.

  17. Scapholunate advanced collapse and scaphoid nonunion advanced collapse arthritis--update on evaluation and treatment.

    Science.gov (United States)

    Strauch, Robert J

    2011-04-01

    Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse are common patterns of wrist arthritis. Scaphoid nonunion advanced collapse is caused by trauma, whereas SLAC wrist may also result from chronic pseudogout and can appear bilaterally without a clear history of injury. Surgical treatment for SLAC wrist includes 4-corner arthrodesis, capitolunate arthrodesis, complete wrist arthrodesis, proximal row carpectomy (PRC), denervation, and radial styloidectomy. Scaphoid nonunion advanced collapse wrist has the additional surgical option of excision of the distal ununited scaphoid fragment. Controversy persists over the relative merits of PRC versus 4-corner arthrodesis and whether PRC may be performed in the setting of capitate arthritis.

  18. Specificity of the initial collapse in the folding of the cold shock protein.

    Science.gov (United States)

    Magg, Christine; Kubelka, Jan; Holtermann, Georg; Haas, Elisha; Schmid, Franz X

    2006-07-28

    The two-state folding reaction of the cold shock protein from Bacillus caldolyticus (Bc-Csp) is preceded by a rapid chain collapse. A fast shortening of intra-protein distances was revealed by Förster resonance energy transfer (FRET) measurements with protein variants that carried individual pairs of donor and acceptor chromophores at various positions along the polypeptide chain. Here we investigated the specificity of this rapid compaction. Energy transfer experiments that probed the stretching of strand beta2 and the close approach between the strands beta1 and beta2 revealed that the beta1-beta2 hairpin is barely formed in the collapsed form, although it is native-like in the folding transition state of Bc-Csp. The time course of the collapse could not be resolved by pressure or temperature jump experiments, indicating that the collapsed and extended forms are not separated by an energy barrier. The co-solute (NH4)2SO4 stabilizes both native Bc-Csp and the collapsed form, which suggests that the large hydrated SO4(2-) ions are excluded from the surface of the collapsed form in a similar fashion as they are excluded from folded Bc-Csp. Ethylene glycol increases the stability of proteins because it is excluded preferentially from the backbone, which is accessible in the unfolded state. The collapsed form of Bc-Csp resembles the unfolded form in its interaction with ethylene glycol, suggesting that in the collapsed form the backbone is still accessible to water and small molecules. Our results thus rule out that the collapsed form is a folding intermediate with native-like chain topology. It is better described as a mixture of compact conformations that belong to the unfolded state ensemble. However, some of its structural elements are reminiscent of the native protein.

  19. Compressible air flow through a collapsing liquid cavity

    CERN Document Server

    Gordillo, Stephan Gekle \\and José Manuel

    2010-01-01

    We present a multiscale approach to simulate the impact of a solid object on a liquid surface: upon impact a thin liquid sheet is thrown upwards all around the rim of the impactor while in its wake a large surface cavity forms. Under the influence of hydrostatic pressure the cavity immediately starts to collapse and eventually closes in a single point from which a thin, needle-like jet is ejected. Existing numerical treatments of liquid impact either consider the surrounding air as an incompressible fluid or neglect air effects altogether. In contrast, our approach couples a boundary-integral method for the liquid with a Roe scheme for the gas domain and is thus able to handle the fully \\emph{compressible} gas stream that is pushed out of the collapsing impact cavity. Taking into account air compressibility is crucial, since, as we show in this work, the impact crater collapses so violently that the air flow through the cavity neck attains supersonic velocities already at cavity diameters larger than 1 mm. Ou...

  20. Growth, collapse, and self-organized criticality in complex networks

    Science.gov (United States)

    Wang, Yafeng; Fan, Huawei; Lin, Weijie; Lai, Ying-Cheng; Wang, Xingang

    2016-04-01

    Network growth is ubiquitous in nature (e.g., biological networks) and technological systems (e.g., modern infrastructures). To understand how certain dynamical behaviors can or cannot persist as the underlying network grows is a problem of increasing importance in complex dynamical systems as well as sustainability science and engineering. We address the question of whether a complex network of nonlinear oscillators can maintain its synchronization stability as it expands. We find that a large scale avalanche over the entire network can be triggered in the sense that the individual nodal dynamics diverges from the synchronous state in a cascading manner within a relatively short time period. In particular, after an initial stage of linear growth, the network typically evolves into a critical state where the addition of a single new node can cause a group of nodes to lose synchronization, leading to synchronization collapse for the entire network. A statistical analysis reveals that the collapse size is approximately algebraically distributed, indicating the emergence of self-organized criticality. We demonstrate the generality of the phenomenon of synchronization collapse using a variety of complex network models, and uncover the underlying dynamical mechanism through an eigenvector analysis.

  1. Jeans Collapse of a System of Electron Emitting Dust Particles

    Science.gov (United States)

    Delzanno, G. L.; Lapenta, G.

    2004-05-01

    The collapse of a molecular cloud to form a planetary system is a classic process in astrophysics. The length scale of the collapsed system and the rate of its formation is described in the simplest model by the Jeans instability. When the model is complicated by additional processes, the rate and scale of the Jeans instability is modified [1]. We focus on the processes involved with the charging of the dust in the initial cloud. The presence of charge of the same sign on the dust particles inhibits the process of collapse. Yet, the process of charging is expected to be operational. We propose a mechanism that can explain this apparent contradiction. In a recent work [2], we have shown that in presence of electron emission from the dust the interaction potential of a dust particle becomes similar to the Lennard-Jones (LJ) potential. The important consequence of this discovery is that emitting dust particles with LJ like potential can actually attract each other even though they all share the same sign of charge. Here, we present a series of simulations conducted with a new code designed to study a large system of weakly coupled dust particles, interacting with a LJ like potential. [1] P. K. Shukla, Dust plasma interaction in space, Nova Science Publ., 2002. [2] G.L. Delzanno, G. Lapenta, M. Rosenberg, Phys. Rev. Lett., to appear.

  2. Growth, collapse, and self-organized criticality in complex networks

    Science.gov (United States)

    Wang, Yafeng; Fan, Huawei; Lin, Weijie; Lai, Ying-Cheng; Wang, Xingang

    2016-01-01

    Network growth is ubiquitous in nature (e.g., biological networks) and technological systems (e.g., modern infrastructures). To understand how certain dynamical behaviors can or cannot persist as the underlying network grows is a problem of increasing importance in complex dynamical systems as well as sustainability science and engineering. We address the question of whether a complex network of nonlinear oscillators can maintain its synchronization stability as it expands. We find that a large scale avalanche over the entire network can be triggered in the sense that the individual nodal dynamics diverges from the synchronous state in a cascading manner within a relatively short time period. In particular, after an initial stage of linear growth, the network typically evolves into a critical state where the addition of a single new node can cause a group of nodes to lose synchronization, leading to synchronization collapse for the entire network. A statistical analysis reveals that the collapse size is approximately algebraically distributed, indicating the emergence of self-organized criticality. We demonstrate the generality of the phenomenon of synchronization collapse using a variety of complex network models, and uncover the underlying dynamical mechanism through an eigenvector analysis. PMID:27079515

  3. Surgical repair of traumatically induced collapsing trachea in an ostrich.

    Science.gov (United States)

    McClure, S R; Taylor, T S; Johnson, J H; Heisterkamp, K B; Sanders, E A

    1995-08-15

    A region of tracheal collapse was identified by endoscopy after surgical repair of a traumatic injury to the neck in an ostrich. During periods of excitation, the ostrich would become dyspneic and collapse. A tracheal split-ring prosthesis was placed surgically to support the collapsing trachea. This technique, which is frequently used in dogs, is applicable for use in birds with collapsing trachea.

  4. An equivalent circuit model for transmitting capacitive micromachined ultrasonic transducers in collapse mode.

    Science.gov (United States)

    Olcum, Selim; Yamaner, F Yalcin; Bozkurt, Ayhan; Köymen, Hayrettin; Atalar, Abdullah

    2011-07-01

    The collapse mode of operation of capacitive micromachined ultrasonic transducers (CMUTs) was shown to be a very effective way to achieve high output pressures. However, no accurate analytical or equivalent circuit model exists for understanding the mechanics and limits of the collapse mode. In this work, we develop an equivalent nonlinear electrical circuit that can accurately simulate the mechanical behavior of a CMUT with given dimensions and mechanical parameters under any large or small signal electrical excitation, including the collapse mode. The static and dynamic deflections of a plate predicted from the model are compared with finite element simulations. The equivalent circuit model can estimate the static deflection and transient behavior of a CMUT plate to within 5% accuracy. The circuit model is in good agreement with experimental results of pulse excitation applied to fabricated CMUTs. The model is suitable as a powerful design and optimization tool for collapsed and uncollapsed CMUTs.

  5. Truthing the stretch: Non-perturbative cosmological realizations with multiscale spherical collapse

    CERN Document Server

    Neyrinck, Mark C

    2015-01-01

    Here we present a simple, parameter-free, non-perturbative algorithm that gives low-redshift cosmological particle realizations accurate to few-Megaparsec scales, called muscle (MUltiscale Spherical ColLapse Evolution). It has virtually the same cost as producing N-body-simulation initial conditions, since it works with the 'stretch' parameter {\\psi}, the Lagrangian divergence of the displacement field. It promises to be useful in quickly producing mock catalogs, and to simplify computationally intensive reconstructions of galaxy surveys. muscle applies a spherical-collapse prescription on multiple Gaussian-smoothed scales. It achieves higher accuracy than perturbative schemes (Zel'dovich and 2LPT), and, by including the void-in-cloud process (voids in large-scale collapsing regions), solves problems with a single-scale spherical-collapse scheme. Additionally, we show the behavior of {\\psi} for different morphologies (voids, walls, filaments, and haloes). A Python code to produce these realizations is availab...

  6. 关于黄土湿陷性评价和剩余湿陷量的新认识%New recognition of collapsibility evaluation and remnant collapse of loess

    Institute of Scientific and Technical Information of China (English)

    姚志华; 黄雪峰; 陈正汉; 方祥位; 苗强强; 张江水

    2014-01-01

    Based on summarized results of several large-scale soaking tests, some new recognition about methodology of collapsibility evaluation and reasonable limit of remnant collapse are proposed to modify difference between computed collapse under overburden pressure and measured value, and to decrease the collapsible loess treatment depth. When acquiring the computed collapse under overburden pressure, a depth correction factoris suggested to make computed collapse under overburden pressure and the computed collapse of laboratory tests approximate measured collapse of in-situ tests;and it will decrease remnant collapse of collapsible loess in deeper position in some degree. When obtaining computed collapse, a scheme amplifying coefficient threshold of collapsibility (0.015) is presented, the method combined with depth correction factorcan reach the expected goal to enlarge the computed collapse and decrease remnant collapse of deeper collapsible loess. The conception“critical collapsibility depth”of dead weight collapse loess with heavy section is proposed;the critical collapsibility depth is set as 20-25 m temporarily according to some test data. In combination with the method of depth correction factor and amplifying coefficient threshold of collapsibility, the conception of critical collapsibility depth can decrease effectively remnant collapse of collapsible loess. The research results will be of interest for similar projects in the area of dead weight collapse loess and be useful to revise“standard for building construction in collapsible loess regions”.%在总结诸多大型浸水现场试验成果的基础上,提出了一些关于湿陷性评价方法和剩余湿陷量合理控制等问题的新认识,目的是为了修正自重湿陷性黄土场地的自重湿陷量计算值与其实测值之间的差异,并减小地基处理深度。在获取自重湿陷量的计算值时,引进了一个深度修正系数,使自重湿陷量和湿陷

  7. Early Archaean crustal collapse structures and sedimentary basin dynamics

    Science.gov (United States)

    Nijman, W.; de Vries, S. T.

    2003-04-01

    Observations in the Lower Archaean (>3.3 Ga) of the Pilbara and Kaapvaal Cratons point to a direct genetic relationship between the thickness and facies distribution of volcano-sedimentary basin fills and non-linear patterns of extensional faults in early Earth. The basin fills consist of mafic volcanic products, largely pillow basalts, with distinct phases of intermediate to felsic volcanism and concentration of silica, either primary or secondary, in sediments deposited near base-level. The extensional structures are listric growth-faults, arranged in superposed arrays, that migrated upwards with the growth of the Early Archaean stratigraphical column. The faults linked intermittently occurring shallow-level felsic intrusions via porphyry pipes, veins and hydrothermal circulations with the surficial sedimentary basin fill of cherty sediments, concurrent mineralisation and alteration products. The non-linear pattern of the fault systems is recorded by their restored facing directions over large areas and corresponds best with over 100 km-wide (semi)circular crustal collapse structures. Crustal collapse, and therefore basin formation, did not represent a reaction to compression and crustal thickening. It also had no relationship with the present-day distribution of granitoid domes and greenstone belts. Collapse followed crustal uplift recorded by shallowing of the basin fill from a general subaqueous level of deposition of pillow basalts towards zero water level for the sediments and low-relief emersion. Maxima of extension coincide with the appearance of intermediate or felsic volcanic rocks in the overall mafic environment. The geodynamical setting is most appropriately explained by crustal delamination and related plume activity. Although individual features may be compared to Phanerozoic and Recent geological phenomena, like calderas, for the collapse structures as a whole such younger counterparts cannot be found. Rather they have their equivalents in collapse

  8. Blue straggler formation at core collapse

    CERN Document Server

    Banerjee, Sambaran

    2016-01-01

    Among the most striking feature of blue straggler stars (BSS) is the presence of multiple sequences of BSSs in the colour-magnitude diagrams (CMDs) of several globular clusters. It is often envisaged that such a multiple BSS sequence would arise due a recent core collapse of the host cluster, triggering a number of stellar collisions and binary mass transfers simultaneously over a brief episode of time. Here we examine this scenario using direct N-body computations of moderately massive star clusters (of order 10^4 Msun ). As a preliminary attempt, these models are initiated with approx. 8-10 Gyr old stellar population and King profiles of high concentrations, being "tuned" to undergo core collapse quickly. BSSs are indeed found to form in a "burst" at the onset of the core collapse and several of such BS-bursts occur during the post-core-collapse phase. In those models that include a few percent primordial binaries, both collisional and binary BSSs form after the onset of the (near) core-collapse. However, t...

  9. Collapsibility and Wettability of Hydrothermally Treated Wood

    Directory of Open Access Journals (Sweden)

    Ghane Mirzaee

    2012-06-01

    Full Text Available Study on collapsibility of oriental beech (Fagus orientalis and paulownia (Paulownia fortune woods due to their hydrothermal modification as well as the wettability and the water absorption were the main concerns of this research work. Out of these species, blocks of sizes 50×6×6cm were prepared and treated at temperatures of 130 and 150°C with a holding time of 30min in a stainless steel reactor containing the water. Oven dried weights and dimensions of the blocks were measured before and after the hydrothermal treatment to determine the density, collapsibility and mass loss due to applied treatment. Furthermore, small blocks of the treated wood were prepared and soaked in water for 1000-hr to determine their water absorption. The wettability of the woods were also measured to determine the water repellency. Results revealed that any raise of treatment temperature up to 150°C increases the density and the collapsibility. Treated wood collapsed in all directions; however, tangential collapse was much worse than the other directions. The contact angle was increased by rise of the treatment temperature. Hydrothermal treatment has reduced water absorption and increased the hydrophobicity of the woods.

  10. Stellar core collapse. I - Infall epoch

    Science.gov (United States)

    van Riper, K. A.; Lattimer, J. M.

    1981-10-01

    Simulations of the collapse of the central iron core of a 15-solar-mass spherically symmetric star are reported. In this paper the infall epoch, between the onset of collapse and core bounce, is considered. The models use the recent equation of state of Lamb, Lattimer, Pethick, and Ravenhall and general-relativistic hydrodynamics. The electron capture rates on nuclei proceed rapidly for densities less than 10 to the 11th g/cu cm, but are suppressed at higher densities where the neutron number of the nucleus, N, exceeds 40 (Fuller, Fowler, and Newman). Neutrino transport is treated by a leakage scheme. The effects of changes in the neutrino trapping density and of qualitative changes in the electron capture reactions on the evolution are explored. Greater lepton loss during collapse leads to larger pressure deficits, more rapid collapse, and smaller inner homologous cores. The entropy change during the infall is small, the absolute value of delta s being less than 0.8. The mass of inner core is given, to about 20%, by the formula of Goldreich and Weber. Because the collapsing core is far from equilibrium, the effects of general relativity are small.

  11. Anterior septal deviation and contralateral alar collapse.

    Science.gov (United States)

    Schalek, P; Hahn, A

    2011-01-01

    Septal deviation is often found in conjunction with other pathological conditions that adversely affect nasal patency. Anterior septal deviation, together with contralateral alar collapse, is a relatively rare type of anatomical and functional incompetence. In our experience, it can often be resolved with septoplasty, without the necessity of surgery involving the external valve. The aim of this paper was to verify this hypothesis prospectively. Twelve patients with anterior septal deviation and simultaneous alar collapse on the opposite side were prospectively enrolled in the study. Subjective assessment of nasal patency was made on post-operative day 1, and again 6 months after surgery, using a subjective evaluation of nasal breathing. The width of the nostril (alar-columellar distance) on the side with the alar collapse was measured during inspiration pre-operatively, 1 day after surgery and again 6 months after surgery. Immediately after surgery, all patients reported improved or excellent nasal breathing on the side of the original septal deviation. On the collapsed side, one patient reported no change in condition. With the exception of one patient, all measurements showed some degree of improvement in the extension of the alar-columellar distance. The average benefit 6 months after surgery was an improvement of 4.54 mm. In our group of patients (anterior septal deviation and simultaneous contralateral alar collapse and no obvious structural changes of the alar cartilage) we found septoplasty to be entirely suitable and we recommend it as the treatment of choice in such cases.

  12. Motion of Three Vortices near Collapse

    CERN Document Server

    Leoncini, X; Zaslavsky, G M

    2000-01-01

    A system of three point vortices in an unbounded plane has a special family of self-similarly contracting or expanding solutions: during the motion, vortex triangle remains similar to the original one, while its area decreases (grows) at a constant rate. A contracting configuration brings three vortices to a single point in a finite time; this phenomenon is known as vortex collapse and is of principal importance for many-vortex systems. The self-similar motion (contracting or expanding) is not generic, it arises when vortex strengths and initial positions satisfy two special collapse conditions. Dynamics of close-to-collapse vortex configurations depends on the way the collapse conditions are violated. We show, that when two of the vortices are identical, it is possible to reduce a three-vortex system to a problem of motion of a particle in an effective potential, defined by initial conditions. Using the effective potential representation, a detailed quantitative analysis of different types of near-collapse d...

  13. Seismic Characteristics and Generations of Sinkholes in the Liuhua Carbonate Platform,Pearl River Mouth Basin%珠江口盆地流花碳酸盐台地灰岩坑的地震反射特征及成因探讨

    Institute of Scientific and Technical Information of China (English)

    陈端新; 吴时国; 施和生; 赵淑娟

    2012-01-01

    , and depressions of mudstone stopping at T10 unconformity, Dongsha Movement is considered to be the key factor leading to the occurrence of sinkholes. Concretely, basal magmatic activities might provide acidic hydrothermal fluid to dissolve the carbonate rock. NWW oriented faults produced by Dongsha Movement served as pathways for fluid flow and rooms for fluid exchange. At the end of Late Miocene, exposure caused by Dongsha Movement accelerated the dissolution rate of carbonate rocks. With continuous corrosion, the dissolved cavern became larger and larger until the carbonate strata over the cavern couldn't hold the upper loading, and then carbonate strata collapsed and the sinkhole formed.

  14. Inversion Build-Up and Cold-Air Outflow in a Small Alpine Sinkhole

    Science.gov (United States)

    Lehner, Manuela; Whiteman, C. David; Dorninger, Manfred

    2017-06-01

    Semi-idealized model simulations are made of the nocturnal cold-air pool development in the approximately 1-km wide and 100-200-m deep Grünloch basin, Austria. The simulations show qualitatively good agreement with vertical temperature and wind profiles and surface measurements collected during a meteorological field expedition. A two-layer stable atmosphere forms in the basin, with a very strong inversion in the lowest part, below the approximate height of the lowest gap in the surrounding orography. The upper part of the stable layer is less strongly stratified and extends to the approximate height of the second-lowest gap. The basin atmosphere cools most strongly during the first few hours of the night, after which temperatures decrease only slowly. An outflow of air forms through the lowest gap in the surrounding orography. The outflow connects with a weak inflow of air through a gap on the opposite sidewall, forming a vertically and horizontally confined jet over the basin. Basin cooling shows strong sensitivity to surface-layer characteristics, highlighting the large impact of variations in vegetation and soil cover on cold-air pool development, as well as the importance of surface-layer parametrization in numerical simulations of cold-air-pool development.

  15. 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.

  16. Gravitational collapse of generalised Vaidya spacetime

    CERN Document Server

    Mkenyeleye, Maombi D; Maharaj, Sunil D

    2014-01-01

    We study the gravitational collapse of a generalised Vaidya spacetime in the context of the Cosmic Censorship hypothesis. We develop a general mathematical framework to study the conditions on the mass function so that future directed non-spacelike geodesics can terminate at the singularity in the past. Thus our result generalises earlier works on gravitational collapse of the combinations of Type-I and Type-II matter fields. Our analysis shows transparently that there exist classes of generalised Vaidya mass functions for which the collapse terminates with a locally naked central singularity. We calculate the strength of the these singularities to show that they are strong curvature singularities and there can be no extension of spacetime through them.

  17. Effect of Rotation in Cloud Core Collapse

    Science.gov (United States)

    Tsuribe, T.

    The collapse of rotating clouds is investigated.At first, isothermal collapse of an initially uniform-density, uniform-rotating, molecular cloud core with pressure and self-gravity is investigated to determine the conditions under which a cloud is unstable to fragmentation. A semianalytic model for the collapse of rotating spheroids is developed with the method of characteristics for inwardly propagating rarefaction waves. Three-dimensional self-gravitating hydrodynamical calculations are performed for the initially uniform-density rigid-rotating sphere. Both investigations show that the criterion for fragmentation is modified from the one in the literature if the property of the non-homologous collapse is taken into account. It is shown that the central flatness, that is, the axial ratio of the isodensity contour in the central region, is a good indicator for the fate of the cloud. We derive the criterion for the fragmentation considering the evolution of the flatness of the central core. If the central flatness becomes greater than the critical value ˜ 4π, a collapsing cloud with moderate perturbations is unstable for fragmentation, while if the central flatness stays smaller than the critical value, it does not fragment at least before adiabatic core formation. Warm clouds (α0 ≳ 0.5) are not expected to fragment before adiabatic core formation almost independent of the initial rotation (β0) and the properties of the initial perturbation. The effect of the initial density central concentration is also investigated. If it exists, distortion or flattening of a cloud core is suppressed even if α0 ≲ 0.5 in small rotation cases due to stronger nonhomologous property of the collapse. We conclude that the binary fragmentation is difficult during isothermal stage if a core collapse had started from near spherical configurations with moderate thermal energy or small rotation. We suggest that the close binary fragmentation may be possible in the nonisothermal

  18. Relativistic Axions from Collapsing Bose Stars

    Science.gov (United States)

    Levkov, D. G.; Panin, A. G.; Tkachev, I. I.

    2017-01-01

    The substructures of light bosonic (axionlike) dark matter may condense into compact Bose stars. We study the collapse of critical-mass stars caused by attractive self-interaction of the axionlike particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (called "wave collapse" in condensed matter physics) forces the particles to fall into the star center. Second, interactions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.

  19. Plastic collapse load of corroded steel plates

    Indian Academy of Sciences (India)

    Rahbar Ranji Ahmad

    2012-06-01

    Corrosion is one of the detrimental phenomena which reduces strength of structures. It is common practice to assume a uniform thickness reduction for general corrosion. Since the actual corroded plate has rough surfaces, to estimate the remaining strength of corroded structures, typically a much higher level of accuracy is required. 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 by using computer code ANSYS was employed to determine plastic collapse load. By comparing the results with uniform thickness assumption, a reduction factor was proposed. It is found that by uniform thickness assumption, plastic collapse load of corroded plates are overestimated.

  20. Gravitational collapse: The story so far

    Indian Academy of Sciences (India)

    Pankaj S Joshi

    2000-10-01

    An outstanding problem in gravitation theory and relativistic astrophysics today is to understand the final outcome of an endless gravitational collapse. Such a continual collapse would take place when stars more massive than few times the mass of the sun collapse under their own gravity on exhausting their nuclear fuel. According to the general theory of relativity, this results either in a black hole, or a naked singularity – which can communicate with far away observers in the universe. While black holes are (almost) being detected and are increasingly used to model high energy astrophysical phenomena, naked singularities have turned into a topic of active discussion, aimed at understanding their structure and implications. Recent developments here are reviewed, indicating future directions.

  1. Relativistic axions from collapsing Bose stars

    CERN Document Server

    Levkov, D G; Tkachev, I I

    2016-01-01

    The substructures of light bosonic (axion-like) dark matter may condense into compact Bose stars. We study collapses of the critical-mass stars caused by attractive self-interaction of the axion-like particles and find that these processes proceed in an unexpected universal way. First, nonlinear self-similar evolution (similar to "wave collapse" in plasma physics) forces the particles to fall into the star center. Second, collisions in the dense center create an outgoing stream of mildly relativistic particles which carries away an essential part of the star mass. The collapse stops when the star remnant is no longer able to support the self-similar infall feeding the collisions. We shortly discuss possible astrophysical and cosmological implications of these phenomena.

  2. Core-Collapse Supernovae: Reflections and Directions

    CERN Document Server

    Janka, H -Thomas; Huedepohl, Lorenz; Marek, Andreas; Mueller, Bernhard; Obergaulinger, Martin

    2012-01-01

    Core-collapse supernovae are among the most fascinating phenomena in astrophysics and provide a formidable challenge for theoretical investigation. They mark the spectacular end of the lives of massive stars and, in an explosive eruption, release as much energy as the sun produces during its whole life. A better understanding of the astrophysical role of supernovae as birth sites of neutron stars, black holes, and heavy chemical elements, and more reliable predictions of the observable signals from stellar death events are tightly linked to the solution of the long-standing puzzle how collapsing stars achieve to explode. In this article our current knowledge of the processes that contribute to the success of the explosion mechanism are concisely reviewed. After a short overview of the sequence of stages of stellar core-collapse events, the general properties of the progenitor-dependent neutrino emission will be briefly described. Applying sophisticated neutrino transport in axisymmetric (2D) simulations with ...

  3. Collapse of biodiversity in fractured metacommunities

    Science.gov (United States)

    Fisher, Charles; Mehta, Pankaj

    2014-03-01

    The increasing threat to global biodiversity from climate change, habitat destruction, and other anthropogenic factors motivates the search for features that increase the resistance of ecological communities to destructive disturbances. Recently, Gibson et al (Science 2013) observed that the damming of the Khlong Saeng river in Thailand caused a rapid collapse of biodiversity in the remaining tropical forests. Using a theoretical model that maps the distribution of coexisting species in an ecological community to a disordered system of Ising spins, we show that fracturing a metacommunity by inhibiting species dispersal leads to a collapse in biodiversity in the constituent local communities. The biodiversity collapse can be modeled as a diffusion on a rough energy landscape, and the resulting estimate for the rate of extinction highlights the role of species functional diversity in maintaining biodiversity following a disturbance.

  4. Air flow in a collapsing cavity

    CERN Document Server

    Peters, Ivo R; Lohse, Detlef; van der Meer, Devaraj

    2013-01-01

    We experimentally study the airflow in a collapsing cavity created by the impact of a circular disk on a water surface. We measure the air velocity in the collapsing neck in two ways: Directly, by means of employing particle image velocimetry of smoke injected into the cavity and indirectly, by determining the time rate of change of the volume of the cavity at pinch-off and deducing the air flow in the neck under the assumption that the air is incompressible. We compare our experiments to boundary integral simulations and show that close to the moment of pinch-off, compressibility of the air starts to play a crucial role in the behavior of the cavity. Finally, we measure how the air flow rate at pinch-off depends on the Froude number and explain the observed dependence using a theoretical model of the cavity collapse.

  5. Inflationary gravitational waves in collapse scheme models

    Directory of Open Access Journals (Sweden)

    Mauro Mariani

    2016-01-01

    Full Text Available 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.

  6. CAUSES AND COUNTERMEASURES FOR CHAOHU LAKESHORE COLLAPSE

    Institute of Scientific and Technical Information of China (English)

    GAO Chao; WANG Xin-yuan; YANG Ze-dong; LU Ying-cheng; HE Hui

    2005-01-01

    By interpreting the remote sensing data of aerial photos and satellite images in different time, combining with field investigation, landform and water level observation, collecting data of weather, hydrology in Chaohu Lake, Anhui Province from 1957 to 2003, the reasons for collapse of Chaohu lakeshore were analyzed. The results are as follows: 1) The collapse of the Chaohu lakeshore is controlled macroscopically by two sets of north-east and the north-west faults, and the degree of collapse is determined microcosmically by lithology. 2) The constant change of water level, resulting from precipitation, wind speed and its direction, is one of the main reasons for intermittence collapse. 3) The soil and water loss or mud and sand filling up, resulting from artificial factors, such as inconsequence control of Chaohu sluice or irrational agricultural and industrial activities, etc., can uplift the lake's bed and drive water level up. The high water level also results in the collapse. Judging from the above mentioned reasons for the collapse, we have proposed some countermeasures: 1) Putting the lakeshore slope protection project such as stone and cement mortar into practice, and upstream slope should be 1:2.5 or 1:3, some parts of them should be 1:4, if they were not stable. The back slope, which is from Gui Mountain to Zhongmiao Temple, should be 1:1.5-1:3.2) Constructing a greenbelt for the lakeshore, planting some vegetation such as osier, bulrush and poplar, to resist waves between the high and the low water level. 3) Controlling Chaohu Lake water level scientifically. Corrosion of lakeshore that contains gravel clay and ferruginous-manganese concretionary structures, can decrease at low water level. 4) Renovating Chaohu Lake drainage area, strengthening the administration and supervision, breaking regionalism and establishing special administration organization.

  7. Source Analysis of the Crandall Canyon, Utah, Mine Collapse

    Science.gov (United States)

    Dreger, Douglas S.; Ford, Sean R.; Walter, William R.

    2008-07-01

    Analysis of seismograms from a magnitude 3.9 seismic event on 6 August 2007 in central Utah reveals an anomalous radiation pattern that is contrary to that expected for a tectonic earthquake and which is dominated by an implosive component. The results show that the seismic event is best modeled as a shallow underground collapse. Interestingly, large transverse surface waves require a smaller additional noncollapse source component that represents either faulting in the rocks above the mine workings or deformation of the medium surrounding the mine.

  8. Core-Collapse Supernovae: Modeling between Pragmatism and Perfectionism

    CERN Document Server

    Janka, H T; Kitaura Joyanes, F S; Marek, A; Rampp, M

    2004-01-01

    We briefly summarize recent efforts in Garching for modeling stellar core collapse and post-bounce evolution in one and two dimensions. The transport of neutrinos of all flavors is treated by iteratively solving the coupled system of frequency-dependent moment equations together with a model Boltzmann equation which provides the closure. A variety of progenitor stars, different nuclear equations of state, stellar rotation, and global asymmetries due to large-mode hydrodynamic instabilities have been investigated to ascertain the road to finally successful, convectively supported neutrino-driven explosions.

  9. Newtonian Collapse of Scalar Field Dark Matter

    CERN Document Server

    Guzman, F S

    2003-01-01

    In this letter, we develop a Newtonian approach to the collapse of galaxy fluctuations of scalar field dark matter under initial conditions inferred from simple assumptions. The full relativistic system, the so called Einstein-Klein-Gordon, is reduced to the Schr\\"odinger-Newton one in the weak field limit. The scaling symmetries of the SN equations are exploited to track the non-linear collapse of single scalar matter fluctuations. The results can be applied to both real and complex scalar fields.

  10. Gravitational blueshift from a collapsing object

    Directory of Open Access Journals (Sweden)

    Lingyao Kong

    2015-02-01

    Full Text Available We discuss a counterintuitive phenomenon of classical general relativity, in which a significant fraction of the radiation emitted by a collapsing object and detected by a distant observer may be blueshifted rather than redshifted. The key-point is that when the radiation propagates inside the collapsing body, it is blueshifted, and this time interval may be sufficiently long for the effect to be larger than the later redshift due to the propagation in the vacuum exterior, from the surface of the body to the distant observer. Unfortunately, the phenomenon can unlikely have direct observational implications, but it is interesting by itself as a pure relativistic effect.

  11. Gravitational blueshift from a collapsing object

    Energy Technology Data Exchange (ETDEWEB)

    Kong, Lingyao; Malafarina, Daniele; Bambi, Cosimo, E-mail: bambi@fudan.edu.cn

    2015-02-04

    We discuss a counterintuitive phenomenon of classical general relativity, in which a significant fraction of the radiation emitted by a collapsing object and detected by a distant observer may be blueshifted rather than redshifted. The key-point is that when the radiation propagates inside the collapsing body, it is blueshifted, and this time interval may be sufficiently long for the effect to be larger than the later redshift due to the propagation in the vacuum exterior, from the surface of the body to the distant observer. Unfortunately, the phenomenon can unlikely have direct observational implications, but it is interesting by itself as a pure relativistic effect.

  12. Stability of Reflection Symmetric Collapsing Structures

    CERN Document Server

    Sharif, M

    2015-01-01

    In this paper, we explore instability regions of non-static axial reflection symmetric spacetime with anisotropic source in the interior. We impose linear perturbation on the Einstein field equations and dynamical equations to establish the collapse equation. The effects of different physical factors like energy density and anisotropic stresses on the instability regions are studied under Newtonian and post-Newtonian limits. We conclude that stiffness parameter has a significant role in this analysis while the reflection terms increase instability ranges of non-static axial collapse.

  13. Sonographic Analysis of the Collapsed Gall Bladder

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sang Suk; Choi, Jae Young; Choi, Seok Jin; Eun, Chung Ki [Pusan Paik Hospital, College of Medicine Inje University, Busan (Korea, Republic of); Nam, Kyung Jin; Lee, Jeong Mi [Donga University Collge of Medicine, Busan (Korea, Republic of)

    1996-06-15

    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

  14. Role of evaporation in gravitational collapse

    CERN Document Server

    Baccetti, Valentina; Terno, Daniel R

    2016-01-01

    We study collapse of evaporating thin dust shells using two families of metrics to describe the {exterior geometry: the outgoing Vaidya metric and the retarded Schwarzschild metric. Both allow incorporation of Page's evaporation law (the latter in terms of the time at infinity), resulting in a modified equation} of motion for the shell. In these scenarios we find in each case that the collapse is accelerated due to evaporation, but the Schwarzschild radius is not crossed. Instead the shell is always at a certain sub-Planckian distance from this would-be horizon that depends only on the mass and evaporation rate.

  15. Glacier surge after ice shelf collapse.

    Science.gov (United States)

    De Angelis, Hernán; Skvarca, Pedro

    2003-03-07

    The possibility that the West Antarctic Ice Sheet will collapse as a consequence of ice shelf disintegration has been debated for many years. This matter is of concern because such an event would imply a sudden increase in sea level. Evidence is presented here showing drastic dynamic perturbations on former tributary glaciers that fed sections of the Larsen Ice Shelf on the Antarctic Peninsula before its collapse in 1995. Satellite images and airborne surveys allowed unambiguous identification of active surging phases of Boydell, Sjögren, Edgeworth, Bombardier, and Drygalski glaciers. This discovery calls for a reconsideration of former hypotheses about the stabilizing role of ice shelves.

  16. Atomic Collapse in Graphene: Lost of Unitarity

    CERN Document Server

    Valenzuela, David; Loewe, Marcelo; Raya, Alfredo

    2016-01-01

    We explore the problem of atomic collapse in graphene by monopole impurities, both electric and magnetic, within the context of supersymmetric quantum mechanics. For electric impurities, upon factorizing the radial Dirac Hamiltonian and identifying the supercharges, existence of a critical charge that makes the ground state {\\em fall-into-the-center} translates into lost of unitarity for the corresponding Hamiltonian. For the problem of magnetic monopole impurities, preservation of unitarity for all values of the parameters of the corresponding potential translates into the absence of atomic collapse in this case.

  17. Volcano collapse promoted by hydrothermal alteration and edifice shape, Mount Rainier, Washington

    Science.gov (United States)

    Reid, M.E.; Sisson, T.W.; Brien, D.L.

    2001-01-01

    Catastrophic collapses of steep volcano flanks threaten many populated regions, and understanding factors that promote collapse could save lives and property. Large collapses of hydrothermally altered parts of Mount Rainier have generated far-traveled debris flows; future flows would threaten densely populated parts of the Puget Sound region. We evaluate edifice collapse hazards at Mount Rainier using a new three-dimensional slope stability method incorporating detailed geologic mapping and subsurface geophysical imaging to determine distributions of strong (fresh) and weak (altered) rock. Quantitative three-dimensional slope stability calculations reveal that sizeable flank collapse (>0.1 km3) is promoted by voluminous, weak, hydrothermally altered rock situated high on steep slopes. These conditions exist only on Mount Rainier's upper west slope, consistent with the Holocene debris-flow history. Widespread alteration on lower flanks or concealed in regions of gentle slope high on the edifice does not greatly facilitate collapse. Our quantitative stability assessment method can also provide useful hazard predictions using reconnaissance geologic information and is a potentially rapid and inexpensive new tool for aiding volcano hazard assessments.

  18. Carbon loss and chemical changes from permafrost collapse in the northern Tibetan Plateau

    Science.gov (United States)

    Mu, Cuicui; Zhang, Tingjun; Zhang, Xiankai; Li, Lili; Guo, Hong; Zhao, Qian; Cao, Lin; Wu, Qingbai; Cheng, Guodong

    2016-07-01

    Permafrost collapse, known as thermokarst, can alter soil properties and carbon emissions. However, little is known regarding the effects of permafrost collapse in upland landscapes on the biogeochemical processes that affect carbon balance. In this study, we measured soil carbon and physiochemical properties at a large thermokarst feature on a hillslope in the northeastern Tibetan Plateau. We categorized surfaces into three different microrelief patches based on type and extent of collapse (control, drape, and exposed areas). Permafrost collapse resulted in substantial decreases of surface soil carbon and nitrogen stocks, with losses of 29.6 ± 4.2% and 28.9 ± 3.1% for carbon and nitrogen, respectively, in the 0-10 cm soil layer. Laboratory incubation experiments indicated that control soil had significantly higher CO2 production rates than that of drapes. The results from Fourier transform infrared spectroscopy analysis showed that exposed soils accumulated some organic matter due to their low position within the feature, which was accompanied by substantial changes in the chemical structure and characteristics of the soil carbon. Exposed soils had higher hydrocarbon and lignin/phenol backbone content than in control and drape soils in the 0-10 cm layer. This study demonstrates that permafrost collapse can cause abundant carbon and nitrogen loss, potentially from mineralization, leaching, photodegradation, and lateral displacement. These results demonstrate that permafrost collapse redistributes the soil organic matter, changes its chemical characteristics, and leads to losses of organic carbon due to the greenhouse gas emission.

  19. Volcano collapse promoted by hydrothermal alteration and edifice shape, Mount Rainier, Washington

    Science.gov (United States)

    Reid, Mark E.; Sisson, Thomas W.; Brien, Dianne L.

    2001-09-01

    Catastrophic collapses of steep volcano flanks threaten many populated regions, and understanding factors that promote collapse could save lives and property. Large collapses of hydrothermally altered parts of Mount Rainier have generated far-traveled debris flows; future flows would threaten densely populated parts of the Puget Sound region. We evaluate edifice collapse hazards at Mount Rainier using a new three-dimensional slope stability method incorporating detailed geologic mapping and subsurface geophysical imaging to determine distributions of strong (fresh) and weak (altered) rock. Quantitative three-dimensional slope stability calculations reveal that sizeable flank collapse (>0.1 km3) is promoted by voluminous, weak, hydrothermally altered rock situated high on steep slopes. These conditions exist only on Mount Rainier's upper west slope, consistent with the Holocene debris-flow history. Widespread alteration on lower flanks or concealed in regions of gentle slope high on the edifice does not greatly facilitate collapse. Our quantitative stability assessment method can also provide useful hazard predictions using reconnaissance geologic information and is a potentially rapid and inexpensive new tool for aiding volcano hazard assessments.

  20. Critical Phenomena in Gravitational Collapse

    Directory of Open Access Journals (Sweden)

    Martín-García José M.

    2007-12-01

    Full Text Available As first discovered by Choptuik, the black hole threshold in the space of initial data for general relativity shows both surprising structure and surprising simplicity. Universality, power-law scaling of the black hole mass, and scale echoing have given rise to the term “critical phenomena”. They are explained by the existence of exact solutions which are attractors within the black hole threshold, that is, attractors of codimension one in phase space, and which are typically self-similar. Critical phenomena give a natural route from smooth initial data to arbitrarily large curvatures visible from infinity, and are therefore likely to be relevant for cosmic censorship, quantum gravity, astrophysics, and our general understanding of the dynamics of general relativity.

  1. Galactic Collapse of Scalar Field Dark Matter

    CERN Document Server

    Alcubierre, M; Matos, T; Núñez, D; Urena-Lopez, L A; Wiederhold, P; Alcubierre, Miguel; Matos, Tonatiuh; Nunez, Dario; Wiederhold, Petra

    2002-01-01

    We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies.

  2. Galactic Collapse of Scalar Field Dark Matter

    OpenAIRE

    2001-01-01

    We present a scenario for galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for galactic formation, which is in agreement with cosmological observations and phenomenological studies in galaxies.

  3. Collapsible structure for an antenna reflector

    Science.gov (United States)

    Trubert, M. R. (Inventor)

    1973-01-01

    A collapsible support for an antenna reflector for use in supporting spacecraft antennas is described. The support has a regid base and a number of struts which are pivoted at the base. The deployment of the struts and their final configuration for supporting the antenna are illustrated.

  4. Higher Dimensional Radiation Collapse and Cosmic Censorship

    CERN Document Server

    Ghosh, S G

    2000-01-01

    We study the occurrence of naked singularities in the spherically symmetric collapse of radiation shells in a higher dimensional spacetime. The necessary conditions for the formation of a naked singularity or a black hole are obtained. The naked singularities are found to be strong in the Tipler's sense and thus violating cosmic censorship conjecture.

  5. Tetanus with multiple wedge vertebral collapses

    African Journals Online (AJOL)

    owner

    2012-07-06

    Jul 6, 2012 ... plication of paediatric tetanus and the associated ... of back pains-11 days, inability to open her mouth- 9 days, ... multiple vertebral collapses and the management chal- ... symptoms made the parents take her to a prayer house where the .... overlying the affected vertebrae, low-grade fever, chills,. Multiple.

  6. Collapse of a Bose gas: Kinetic approach

    Indian Academy of Sciences (India)

    Shyamal Biswas

    2012-08-01

    We have analytically explored the temperature dependence of critical number of particales for the collapse of a harmonically trapped attractively interacting Bose gas below the condensation point by introducing a kinetic approach within the Hartee-Fock approximation. The temperature dependence obtained by this easy approach is consistant with that obtained from the scaling theory.

  7. 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.

  8. The heterogeneity of world trade collapses

    NARCIS (Netherlands)

    P.A.G. van Bergeijk (Peter)

    2015-01-01

    textabstractThis paper analyses drivers of imports during the major world trade collapses of the Great Depression (1930s; 34 countries) and the Great Recession (1930s; 173 countries). The analysis deals with the first year of these episodes and develops a small empirical model that shows a significa

  9. Drops: The collapse of capillary jets

    Science.gov (United States)

    Cordoba, Antonio; Cordoba, Diego; Fefferman, Charles; Fontelos, Marco A.

    2002-01-01

    The appearance of fluid filaments during the evolution of a viscous fluid jet is a commonly observed phenomenon. It is shown here that the break-up of such a jet subject to capillary forces is impossible through the collapse of a uniform filament. PMID:12172005

  10. Collapsing spherical null shells in general relativity

    Directory of Open Access Journals (Sweden)

    S Khakshournia

    2011-03-01

    Full Text Available In this work, the gravitational collapse of a spherically symmetric null shell with the flat interior and a charged Vaidya exterior spacetimes is studied. There is no gravitational impulsive wave present on the null hypersurface which is shear-free and contracting. It follows that there is a critical radius at which the shell bounces and starts expanding.

  11. Supermassive black holes formed by direct collapse of inflationary perturbations

    CERN Document Server

    Nakama, Tomohiro; Yokoyama, Jun'ichi

    2016-01-01

    We propose a mechanism of producing a new type of primordial perturbations which collapse to primordial black holes whose mass can be as large as necessary for them to grow to the supermassive black holes observed at high redshifts, without contradicting COBE/FIRAS upper limits on cosmic microwave background (CMB) spectral distortions. In our model, the observable Universe consists of two kinds of many small patches which experienced different expansion histories during inflation. Large amplitudes of primordial perturbations enough to form primordial black holes are realized on patches that experienced more Hubble expansion than the others. By making these patches the minor component, the rarity of supermassive black holes can be explained. On the other hand, most regions of the Universe experienced the standard history and hence have only standard almost scale-invariant adiabatic perturbations confirmed by observations of CMB or large-scale structures of the universe. Thus our mechanism can evade the constra...

  12. Experiences Acquired by a Building Collapse

    Directory of Open Access Journals (Sweden)

    Murat Durusu

    2012-04-01

    Full Text Available In this study, it has been purposed to share practice of event-scene administration, search and rescue and evacuation of injured and acquired experiences carried out throughout a building collapse. After an explosion at Diyarbakir Kurdoglu housings at 11 December 2006 about 08:20AM, five flats of an apartment that has five floors-ten flats were collapsed. Local military hospital ambulances, city ambulances, and fire-fighting vehicles arrived to event-place 10 minutes later. It has been found out that there were 13 people inside, 6 of which were children. Army rescue team arrived event-place about 01:30PM, then all non-professional persons has been sent away from region. Eight dead including five children, and five injured including one child have been taken out. Two people from close area have been also injured mildly due to the explosion. It has been found out that accident caused by boiler tank exploding. Sixth of total eight injured had only superficial wounds. Other two injured have been followed because of head trauma at first one and hepatic contusion and rib fracture at the other one. No complication observed after follow-up. Building collapses can create disaster potential according to the number of people inside and facilities of nearby region of the place accident taken place. The evaluation of the direction of building collapse during search and rescue operation would enhance possibility to reach more living in shorter time. Building collapses which can be considered as a miniature of big disaster potentials like earthquakes can be appraised as an important practical training and experience source on event-place administration, search and rescue operations and injured evacuation. We believe that share of the analysis and acquired experiences of this kind of studies would contribute interfering big disaster potentials. [TAF Prev Med Bull 2012; 11(2.000: 241-244

  13. Preliminary Seismological Report on the 6 August 2007 Crandall Canyon Mine Collapse in Utah

    Science.gov (United States)

    Pechmann, J. C.; Arabasz, W. J.; Pankow, K. L.; Burlacu, R.; McCarter, M. K.

    2007-12-01

    A large and tragic collapse occurred in the Crandall Canyon coal mine in east-central Utah on 6 Aug 2007, causing the loss of six miners and generating national attention. This collapse was accompanied by a local magnitude (ML) 3.9 seismic event having an origin time of 2:48 am MDT (8:48 UTC) and a location near the collapse. Two lines of evidence indicate that most of the seismic wave energy of this event was generated by the mine collapse rather than an earthquake: (1) the observation that all of the P-wave first motion directions are down and (2) the results of a moment tensor inversion by Ford et al. (2007; http://seismo.berkeley.edu/seismo/Homepage.html). The Crandall Canyon mine is in an area of Utah where there is abundant mining-induced seismicity, including events with both collapse and shear-slip sources. Prior to the 6 Aug collapse, and within a 3 km radius of it, there were 28 seismic events during 2007 that were large enough to be detected and located as part of the routine processing of University of Utah regional seismic network data: 8 in the 2.5-week period prior to the collapse (ML ≤ 1.9) and 15 during an earlier period of activity in late February and early March (ML ≤ 1.8). The 6 Aug collapse was followed by 37 locatable seismic events of ML ≤ 2.2 before the end of August. One of these "aftershocks" (ML 1.6) occurred in conjunction with the violent burst of coal from the mine walls on 17 Aug (UTC) that killed three rescuers. The aftershocks have an exponential frequency-magnitude distribution with a lower ratio between the frequencies of smaller- and larger-magnitude events (lower b-value) than for the prior events in the area. Aftershock rates generally decreased with time through August but there was a noteworthy 5.8-day hiatus in activity that began 37 hours after the collapse. The University of Utah deployed a 5-station temporary network near the mine beginning on 8 Aug. Data from these stations are being used to help develop travel

  14. Parametric initial conditions for core-collapse supernova simulations

    Science.gov (United States)

    Suwa, Yudai; Müller, Ewald

    2016-08-01

    We investigate a method to construct parametrized progenitor models for core-collapse supernova simulations. Different from all modern core-collapse supernova studies, which rely on progenitor models from stellar evolution calculations, we follow the methodology of Baron & Cooperstein to construct initial models. Choosing parametrized spatial distributions of entropy and electron fraction as a function of mass coordinate and solving the equation of hydrostatic equilibrium, we obtain the initial density structures of our progenitor models. First, we calculate structures with parameters fitting broadly the evolutionary model s11.2 of Woosley et al. (2002). We then demonstrate the reliability of our method by performing general relativistic hydrodynamic simulations in spherical symmetry with the isotropic diffusion source approximation to solve the neutrino transport. Our comprehensive parameter study shows that initial models with a small central entropy (≲0.4 kB nucleon-1) can explode even in spherically symmetric simulations. Models with a large entropy (≳6 kB nucleon-1) in the Si/O layer have a rather large explosion energy (˜4 × 1050 erg) at the end of the simulations, which is still rapidly increasing.

  15. Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist arthritis.

    Science.gov (United States)

    Shah, Chirag M; Stern, Peter J

    2013-03-01

    Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) are the two most common patterns of posttraumatic wrist arthritis. This review discusses the etiology and clinical evaluation, as well as up-to-date treatment options, for both of these conditions. Classic as well as newer innovative techniques are discussed with clinical outcomes in order to provide an evidence-based review of the world's literature on SLAC/SNAC wrist.

  16. Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist arthritis

    OpenAIRE

    Shah, Chirag M.; Stern, Peter J.

    2013-01-01

    Scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) are the two most common patterns of posttraumatic wrist arthritis. This review discusses the etiology and clinical evaluation, as well as up-to-date treatment options, for both of these conditions. Classic as well as newer innovative techniques are discussed with clinical outcomes in order to provide an evidence-based review of the world’s literature on SLAC/SNAC wrist.

  17. Gravitational and electric energies in collapse of spherically thin capacitor

    CERN Document Server

    Ruffini, Remo

    2013-01-01

    In our previous article (PHYSICAL REVIEW D 86, 084004 (2012)), we present a study of strong oscillating electric fields and electron-positron pair-production in gravitational collapse of a neutral stellar core at or over nuclear densities. In order to understand the back-reaction of such electric energy building and radiating on collapse, we adopt a simplified model describing the collapse of a spherically thin capacitor to give an analytical description how gravitational energy is converted to both kinetic and electric energies in collapse. It is shown that (i) averaged kinetic and electric energies are the same order, about an half of gravitational energy of spherically thin capacitor in collapse; (ii) caused by radiating and rebuilding electric energy, gravitational collapse undergoes a sequence of "on and off" hopping steps in the microscopic Compton scale. Although such a collapse process is still continuous in terms of macroscopic scales, it is slowed down as kinetic energy is reduced and collapsing tim...

  18. A discrete model of energy-conserved wavefunction collapse

    CERN Document Server

    Gao, Shan

    2013-01-01

    Energy nonconservation is a serious problem of dynamical collapse theories. In this paper, we propose a discrete model of energy-conserved wavefunction collapse. It is shown that the model is consistent with existing experiments and our macroscopic experience.

  19. Observations on cyanobacterial population collapse in eutrophic lake water

    NARCIS (Netherlands)

    Gons, H.J.; Ebert, J.; Hoogveld, H.L.; Van den Hove, L.; Pel, R.; Takkenberg, W.; Woldringh, C.J.

    2002-01-01

    In two laboratory-scale enclosures of water from the shallow, eutrophic Lake Loosdrecht (the Netherlands), the predominating filamentous cyanobacteria grew vigorously for 2 weeks, but then their populations simultaneously collapsed, whereas coccoid cyanobacteria and algae persisted . The collapse co

  20. Modeling of surface cleaning by cavitation bubble dynamics and collapse.

    Science.gov (United States)

    Chahine, Georges L; Kapahi, Anil; Choi, Jin-Keun; Hsiao, Chao-Tsung

    2016-03-01

    Surface cleaning using cavitation bubble dynamics is investigated numerically through modeling of bubble dynamics, dirt particle motion, and fluid material interaction. Three fluid dynamics models; a potential flow model, a viscous model, and a compressible model, are used to describe the flow field generated by the bubble all showing the strong effects bubble explosive growth and collapse have on a dirt particle and on a layer of material to remove. Bubble deformation and reentrant jet formation are seen to be responsible for generating concentrated pressures, shear, and lift forces on the dirt particle and high impulsive loads on a layer of material to remove. Bubble explosive growth is also an important mechanism for removal of dirt particles, since strong suction forces in addition to shear are generated around the explosively growing bubble and can exert strong forces lifting the particles from the surface to clean and sucking them toward the bubble. To model material failure and removal, a finite element structure code is used and enables simulation of full fluid-structure interaction and investigation of the effects of various parameters. High impulsive pressures are generated during bubble collapse due to the impact of the bubble reentrant jet on the material surface and the subsequent collapse of the resulting toroidal bubble. Pits and material removal develop on the material surface when the impulsive pressure is large enough to result in high equivalent stresses exceeding the material yield stress or its ultimate strain. Cleaning depends on parameters such as the relative size between the bubble at its maximum volume and the particle size, the bubble standoff distance from the particle and from the material wall, and the excitation pressure field driving the bubble dynamics. These effects are discussed in this contribution.

  1. GIS-Based Evaluation of Danger in Karst Collapse

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, feasibility and advantage of GIS technology are discussed to make a quantitative evaluation of karst collapses, a fast and precise evaluation method for developing interface between the karst collapse and GIS-based evaluation model is used to predict major natural geological disasters. A complete procedure of fuzzy-hierarchical GIS-based evaluation of karst collapses is illustrated with the karst collapses in western urban area of Guilin, China.

  2. 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...

  3. 26 CFR 1.341-1 - Collapsible corporations; in general.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 4 2010-04-01 2010-04-01 false Collapsible corporations; in general. 1.341-1... TAX (CONTINUED) INCOME TAXES Collapsible Corporations; Foreign Personal Holding Companies § 1.341-1 Collapsible corporations; in general. Subject to the limitations contained in § 1.341-4 and the...

  4. Collapse and Revival in Holographic Quenches

    CERN Document Server

    da Silva, Emilia; Mas, Javier; Serantes, Alexandre

    2014-01-01

    We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.

  5. Energy balance in the WTC collapse

    Science.gov (United States)

    Zhu, Kaiqi; Xu, Kang; Ansourian, Peter; Tahmasebinia, Faham; Alonso-Marroquin, Fernando

    2016-08-01

    The main aim of this report is to provide an analysis of Twin Towers of the New York City's World Trade Centre collapsed after attacked by two jet aircrafts. The approach mainly focused on the effect of temperature on mechanical properties of the building, by modelling heat energy in the south tower. Energy balance during the collapse between the energy inputs by aircraft petrol and the transient heat to the towers was conducted. Both the overall structure between 80 to 83 stories and individual elements was modelled. The main elements contributed to the heat transition includes external and internal columns. Heat applied in 2D and 3D models for single elements was through convection and conduction. Analysis of transient heat was done using Strand7.

  6. What prevents gravitational collapse in string theory?

    CERN Document Server

    Mathur, Samir D

    2016-01-01

    It is conventionally believed that if a ball of matter of mass $M$ has a radius close to $2GM$ then it must collapse to a black hole. But string theory microstates (fuzzballs) have no horizon or singularity, and they do {\\it not} collapse. We consider two simple examples from classical gravity to illustrate how this violation of our intuition happens. In each case the `matter' arises from an extra compact dimension, but the topology of this extra dimension is not trivial. The pressure and density of this matter diverge at various points, but this is only an artifact of dimensional reduction; thus we bypass results like Buchadahl's theorem. Such microstates give the entropy of black holes, so these topologically nontrivial constructions dominate the state space of quantum gravity.

  7. Singularities in gravitational collapse with radial pressure

    CERN Document Server

    Gonçalves, S M C V; Goncalves, Sergio M. C. V.; Jhingan, Sanjay

    2001-01-01

    We analyze spherical dust collapse with non-vanishing radial pressure, $\\Pi$, and vanishing tangential stresses. Considering a barotropic equation of state, $\\Pi=\\gamma\\rho$, we obtain an analytical solution in closed form---which is exact for $\\gamma=-1,0$, and approximate otherwise---near the center of symmetry (where the curvature singularity forms). We study the formation, visibility, and curvature strength of singularities in the resulting spacetime. We find that visible, Tipler strong singularities can develop from generic initial data. Radial pressure alters the spectrum of possible endstates for collapse, increasing the parameter space region that contains no visible singularities, but cannot by itself prevent the formation of visible singularities for sufficiently low values of the energy density. Known results from pressureless dust are recovered in the $\\gamma=0$ limit.

  8. Transport processes in anisotropic gravitational collapse

    CERN Document Server

    Martínez, J

    1996-01-01

    In this paper we introduce a new method to study the influence of thermal conduction and viscous processes in anisotropic gravitational collapse. To this end we employ the HJR method to solve the Einstein equations. The Maxwell-Cattaneo type transport equations are used to find the temperature and bulk and shear viscous pressures. Under some conditions Maxwell-Cattaneo transport equations comply with relativistic causality. Thus, it is advisable to use them instead of Eckart transport equations. In the inner layers of the star the temperature ceases to be sensitive to the boundary condition. This behavior, which can be explained in terms of the Eddington approximation, allows us to find the thickness of the neutrinosphere. The dynamics of collapsing dense stars is deeply influenced by the neutrino emission/absorption processes. These cool the star and drive it to a new equilibrium state. Therefore, the calculation of transport coefficients is based on these processes.

  9. Collapse and revival in holographic quenches

    Science.gov (United States)

    da Silva, Emilia; Lopez, Esperanza; Mas, Javier; Serantes, Alexandre

    2015-04-01

    We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.

  10. Critical collapse of rotating radiation fluids

    CERN Document Server

    Baumgarte, Thomas W

    2016-01-01

    We present results from the first fully relativistic simulations of the critical collapse of rotating radiation fluids. We observe critical scaling both in subcritical evolutions, in which case the fluid disperses to infinity and leaves behind flat space, and in supercritical evolutions that lead to the formation of black holes. We measure the mass and angular momentum of these black holes, and find that both show critical scaling with critical exponents that are consistent with perturbative results. The critical exponents are universal; they are not affected by angular momentum, and are independent of the direction in which the critical curve, which separates subcritical from supercritical evolutions in our two-dimensional parameter space, is crossed. In particular, these findings suggest that the angular momentum decreases more rapidly than the square of the mass, so that, as criticality is approached, the collapse leads to the formation of a non-spinning black hole. We also demonstrate excellent agreement ...

  11. Cosmic no hair for collapsing universes

    Energy Technology Data Exchange (ETDEWEB)

    Lidsey, James E [Astronomy Unit, School of Mathematical Sciences Queen Mary, University of London, Mile End Road, London E1 4NS (United Kingdom)

    2006-05-21

    It is shown that all contracting, spatially homogeneous, orthogonal Bianchi cosmologies that are sourced by an ultra-stiff fluid with an arbitrary and, in general, varying equation of state asymptote to the spatially flat and isotropic universe in the neighbourhood of the big crunch singularity. This result is employed to investigate the asymptotic dynamics of a collapsing Bianchi type IX universe sourced by a scalar field rolling down a steep, negative exponential potential. A toroidally compactified version of M*-theory that leads to such a potential is discussed and it is shown that the isotropic attractor solution for a collapsing Bianchi type IX universe is supersymmetric when interpreted in an 11-dimensional context.

  12. Spherical collapse for unified dark matter models

    CERN Document Server

    Caramês, Thiago R P; Velten, Hermano E S

    2014-01-01

    We study the non-linear spherical "top hat" collapse for Chaplygin and viscous unified cosmologies. The term unified refers to models where dark energy and dark matter are replaced by one single component. For the generalized Chaplygin gas (GCG) we extend previous results of [R. A. A. Fernandes {\\it et al}. Physical Review D 85, 083501 (2012)]. We discuss the differences at non-linear level between the GCG with $\\alpha=0$ and the $\\Lambda$CDM model. We show that both are indeed different. The bulk viscous model which differs from the GCG due to the existence of non-adiabatic perturbations is also studied. In this case, the clustering process is in general suppressed and the viable parameter space of the viscous model that accelerates the background expansion does not lead to collapsed structures. This result challenges the viability of unified viscous models.

  13. Scapholunate advanced collapse: a pictorial review

    OpenAIRE

    Tischler, Brian T.; Diaz, Luis E.; Murakami, Akira M.; Roemer, Frank W.; Goud, Ajay R.; Arndt, William F.; Guermazi, Ali

    2014-01-01

    Abstract Scapholunate advanced collapse (SLAC) is the most common cause of osteoarthritis involving the wrist. Along with clinical investigation, radiological studies play a vital role in the diagnosis of SLAC wrist. Given that the osteoarthritic changes that are seen with SLAC occur in a predictable progressive pattern, it is important to understand the pathological evolution of SLAC to be able to recognise the associated progressive imaging findings seen with this disease process. Focusing ...

  14. Simulated cytoskeletal collapse via tau degradation.

    Directory of Open Access Journals (Sweden)

    Austin Sendek

    Full Text Available We present a coarse-grained two dimensional mechanical model for the microtubule-tau bundles in neuronal axons in which we remove taus, as can happen in various neurodegenerative conditions such as Alzheimers disease, tauopathies, and chronic traumatic encephalopathy. Our simplified model includes (i taus modeled as entropic springs between microtubules, (ii removal of taus from the bundles due to phosphorylation, and (iii a possible depletion force between microtubules due to these dissociated phosphorylated taus. We equilibrate upon tau removal using steepest descent relaxation. In the absence of the depletion force, the transverse rigidity to radial compression of the bundles falls to zero at about 60% tau occupancy, in agreement with standard percolation theory results. However, with the attractive depletion force, spring removal leads to a first order collapse of the bundles over a wide range of tau occupancies for physiologically realizable conditions. While our simplest calculations assume a constant concentration of microtubule intercalants to mediate the depletion force, including a dependence that is linear in the detached taus yields the same collapse. Applying percolation theory to removal of taus at microtubule tips, which are likely to be the protective sites against dynamic instability, we argue that the microtubule instability can only obtain at low tau occupancy, from 0.06-0.30 depending upon the tau coordination at the microtubule tips. Hence, the collapse we discover is likely to be more robust over a wide range of tau occupancies than the dynamic instability. We suggest in vitro tests of our predicted collapse.

  15. Collapse of Langmuir solitons in inhomogeneous plasmas

    CERN Document Server

    Chen, Y A; Nishida, Y; Cheng, C Z

    2016-01-01

    Propagation of Langmuir solitons in inhomogeneous plasmas is investigated numerically. Through numerical simulation solving Zakharov equations, the solitons are accelerated toward the low density side. As a consequence, isolated cavities moving at ion sound velocities are emitted. When the acceleration is further increased, solitons collapse and the cavities separate into two lumps released at ion sound velocities. The threshold is estimated by an analogy between the soliton and a particle overcoming the self-generated potential well.

  16. Gravitational collapse of barotropic spherical fluids

    CERN Document Server

    Giambo, R; Magli, G; Piccione, P; Giambo', Roberto; Giannoni, Fabio; Magli, Giulio; Piccione, Paolo

    2003-01-01

    The gravitational collapse of spherical, barotropic perfect fluids is analyzed here. For the first time, the final state of these systems is characterized without resorting to simplifying assumptions - such as self-similarity - using a new approach based on non-linear o.d.e. techniques. Formation of naked singularities is shown to occur for solutions such that the mass function is sufficiently regular in a neighborhood of the spacetime singularity.

  17. Physics of collapses in toroidal helical plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Kimitaka [National Inst. for Fusion Science, Toki, Gifu (Japan); Itoh, Sanae; Fukuyama, Atsushi; Yagi, Masatoshi

    1998-12-31

    Theoretical model for the collapse events in toroidal helical plasmas with magnetic hill is presented. There exists a turbulent-turbulent transition at a critical pressure gradient, leading to a sudden increase of the anomalous transport. When the magnetic shear is low, the nonlinear excitation of the global mode is possible. This model explains an abrupt growth of the perturbations, i.e., the trigger phenomena. Achievable limit of the plasma beta value is discussed. (author)

  18. Collapse and bounce of null fluids

    OpenAIRE

    Creelman, Bradley; Booth, Ivan

    2016-01-01

    Exact solutions describing the spherical collapse of null fluids can contain regions which violate the energy conditions. Physically the violations occur when the infalling matter continues to move inwards even when non-gravitational repulsive forces become stronger than gravity. In 1991 Ori proposed a resolution for these violations: spacetime surgery should be used to replace the energy condition violating region with an outgoing solution. The matter bounces. We revisit and implement this p...

  19. Galactic collapse of scalar field dark matter

    Energy Technology Data Exchange (ETDEWEB)

    Alcubierre, Miguel [Max-Planck-Institut fuer Gravitationsphysik, Am Muehlenberg 1, D-14476 Golm (Germany); Guzman, F Siddhartha [Max-Planck-Institut fuer Gravitationsphysik, Am Muehlenberg 1, D-14476 Golm (Germany); Matos, Tonatiuh [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, AP 14-740, 07000 Mexico, DF (Mexico); Nunez, Dario [Centre for Gravitational Physics and Geometry, Penn State University, University Park, PA 16802 (United States); Urena-Lopez, L Arturo [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, AP 14-740, 07000 Mexico, DF (Mexico); Wiederhold, Petra [Departamento de Control Automatico, Centro de Investigacion y de Estudios Avanzados del IPN, AP 14-740, 07000 Mexico, DF (Mexico)

    2002-10-07

    We present a scenario for core galaxy formation based on the hypothesis of scalar field dark matter. We interpret galaxy formation through the collapse of a scalar field fluctuation. We find that a cosh potential for the self-interaction of the scalar field provides a reasonable scenario for the formation of a galactic core plus a remnant halo, which is in agreement with cosmological observations and phenomenological studies in galaxies.

  20. Closed String Tachyon: Inflation and Cosmological Collapse

    CERN Document Server

    Escamilla-Rivera, Celia; Loaiza-Brito, Oscar; Obregon, Octavio

    2011-01-01

    By compactifying a critical bosonic string theory on an internal non-flat space with a constant volume, we study the role played by the closed string tachyon in the cosmology of the effective four-dimensional space-time. The effective tachyon potential consists on a negative constant related to the internal curvature space and a polynomial with only quadratic and quartic terms of the tachyon field. Based on it, we present a solution for the tachyon field and the scale factor, which describes an accelerated universe which expands to a maximum value before collapsing. At early times, the closed string tachyon potential behaves as a cosmological constant driving the Universe to an expansion. The value of the cosmological constant is determined by the curvature of the internal space which also fixes the value of the vacuum energy. As time evolves, inflation is present in our models, and it finishes long before the collapsing. At late times, we show that the collapse of the Universe starts as soon as the tachyon f...

  1. Chameleonic equivalence postulate and wave function collapse

    CERN Document Server

    Zanzi, Andrea

    2014-01-01

    A chameleonic solution to the cosmological constant problem and the non-equivalence of different conformal frames at the quantum level have been recently suggested [Phys. Rev. D82 (2010) 044006]. In this article we further discuss the theoretical grounds of that model and we are led to a chameleonic equivalence postulate (CEP). Whenever a theory satisfies our CEP (and some other additional conditions), a density-dependence of the mass of matter fields is naturally present. Let us summarize the main results of this paper. 1) The CEP can be considered the microscopic counterpart of the Einstein's Equivalence Principle and, hence, a chameleonic description of quantum gravity is obtained: in our model, (quantum) gravitation is equivalent to a conformal anomaly. 2) To illustrate one of the possible applications of the CEP, we point out a connection between chameleon fields and quantum-mechanical wave function collapse. The collapse is induced by the chameleonic nature of the theory. We discuss the collapse for a S...

  2. Quantum Mechanical Effects in Gravitational Collapse

    CERN Document Server

    Greenwood, Eric

    2010-01-01

    In this thesis we investigate quantum mechanical effects to various aspects of gravitational collapse. These quantum mechanical effects are implemented in the context of the Functional Schr\\"odinger formalism. The Functional Schr\\"odinger formalism allows us to investigate the time-dependent evolutions of the quantum mechanical effects, which is beyond the scope of the usual methods used to investigate the quantum mechanical corrections of gravitational collapse. Utilizing the time-dependent nature of the Functional Schr\\"odinger formalism, we study the quantization of a spherically symmetric domain wall from the view point of an asymptotic and infalling observer, in the absence of radiation. To build a more realistic picture, we then study the time-dependent nature of the induced radiation during the collapse using a semi-classical approach. Using the domain wall and the induced radiation, we then study the time-dependent evolution of the entropy of the domain wall. Finally we make some remarks about the pos...

  3. Essential ingredients in core-collapse supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Hix, W. Raphael [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Lentz, Eric J.; Chertkow, M. Austin; Harris, J. Austin [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Endeve, Eirik [Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6008 (United States); Baird, Mark [Reactor and Nuclear Systems Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6003 (United States); Messer, O. E. Bronson [Physics Division, Oak Ridge National Laboratory, Oak Ridge TN 37831-6354 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Center for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge TN 37831-6008 (United States); Mezzacappa, Anthony [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996-1200 (United States); Joint Institute for Computational Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6173 (United States); Bruenn, Stephen [Department of Physics, Florida Atlantic University, 777 W Glades Road, Boca Raton, FL 33431-0991 (United States); Blondin, John [Department of Physics, North Carolina State University, Raleigh, NC 27695-8202 (United States)

    2014-04-15

    Carrying 10{sup 44} joules of kinetic energy and a rich mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up our solar system and ourselves. Signaling the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae combine physics over a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale) down to femtometer-scale nuclear reactions. We will discuss our emerging understanding of the convectively-unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have recently 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 the births of neutron stars and the supernovae that result. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  4. Essential ingredients in core-collapse supernovae

    Directory of Open Access Journals (Sweden)

    W. Raphael Hix

    2014-03-01

    Full Text Available Carrying 1044 joules of kinetic energy and a rich mix of newly synthesized atomic nuclei, core-collapse supernovae are the preeminent foundries of the nuclear species which make up our solar system and ourselves. Signaling the inevitable death of a massive star, and the birth of a neutron star or black hole, core-collapse supernovae combine physics over a wide range in spatial scales, from kilometer-sized hydrodynamic motions (eventually growing to gigameter scale down to femtometer-scale nuclear reactions. We will discuss our emerging understanding of the convectively-unstable, neutrino-driven explosion mechanism, based on increasingly realistic neutrino radiation hydrodynamic simulations that include progressively better nuclear and particle physics. Multi-dimensional models with spectral neutrino transport from several research groups, which slowly develop successful explosions for a range of progenitors, have recently 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 the births of neutron stars and the supernovae that result. Recent progress on both the macroscopic and microscopic effects that affect core-collapse supernovae are discussed.

  5. 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.

  6. Matter and gravitons in the gravitational collapse

    Science.gov (United States)

    Casadio, Roberto; Giugno, Andrea; Giusti, Andrea

    2016-12-01

    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.

  7. Seepage characteristics of collapse column fillings

    Institute of Scientific and Technical Information of China (English)

    Zhang Boyang; Bai Haibo; Zhang Kai

    2016-01-01

    With concealment and hysteresis, water-inrush from Karst collapse column has become an important security hazard of lower group coal mining in North China. Based on the MTS815.02 seepage test system, we analyzed the impact of consolidation pressure, initial moisture content and confining pressure on the permeability of fillings in order to study the seepage characteristics of collapse column fillings. The results show that:(1) The permeability of collapse column fillings is of the order of 10?16–10?15 magni-tude and decreases with an increase in consolidation pressure and decrease in initial moisture content. (2) The essence of filling seepage law change is the change in porosity, and a power function relationship exists between the permeability ratio and porosity ratio. (3) With increasing confining pressure, the per-meability of fillings decreases. However, under low confining pressure (1.2–4 MPa), the change of confin-ing pressure has no obvious influence on the permeability.

  8. Cosmic-ray ionisation in collapsing clouds

    CERN Document Server

    Padovani, Marco; Galli, Daniele

    2013-01-01

    Cosmic rays (CR) play an important role in dense molecular cores, affecting their thermal and dynamical evolution and initiating the chemistry. Several studies have shown that the formation of protostellar discs in collapsing clouds is severely hampered by the braking torque exerted by the entrained magnetic field on the infalling gas, as long as the field remains frozen to the gas. We examine the possibility that the concentration and twisting of the field lines in the inner region of collapse can produce a significant reduction of the ionisation fraction. To check whether the CR ionisation rate (CRir) can fall below the critical value required to maintain good coupling, we first study the propagation of CRs in a model of a static magnetised cloud varying the relative strength of the toroidal/poloidal components and the mass-to-flux ratio. We then follow the path of CRs using realistic magnetic field configurations generated by numerical simulations of a rotating collapsing core. We find that an increment of...

  9. Production of complex bio-molecules in collapsing interstellar cloud

    Science.gov (United States)

    Acharyya, Kinsuk; Chakrabarti, S. K.; Chakrabarti, S.; Das, Ankan

    We present step by step production of biologically important complex molecules in the interstellar medium. We considered grains of different size distributions. We then solve the Master equation for small grains and Rate equation for grains of larger size to obtain the abundance of molecular hydrogen on grains and their desorption to gaseous phase. We then studied the molecular hydrogen formation in a collapsing molecular cloud. Activation barrier energies for desorption of H and H2 and hopping rate for H are taken from recent experimental results. We found that the production of molecular hydrogen is very much dependent on the cloud temperature since molecular hydrogen formation on grains are very much temperature sensitive. For clouds with grain temperature more than 25 K it is difficult to produce significant amount molecular hydrogen during the life time of molecular cloud. In a collapsing cloud only in a small temperature range adequate formation of H2 is possible and in the rest of the collapsing phase molecular hydrogen formation is very small. We also use the Monte-Carlo simulation to form H2 on grains and compute recombination efficiency and its dependence on the number of grain sites. We then continue to compute the production rate of more complex molecules by including a large number (422) of chemical species in a reaction network, and using updated reaction rates. The cloud models have been chosen to be stationary as well as non-stationary. In the later cases we do hydrodynamic simulations and couple the result with chemical evolution. We constructed a model study the possibility of glycine formation in the interstellar medium keeping in mind that present debate of detection of glycine in molecular clouds. We choose two gas phase pathways to form glycine formation: first one is through ion molecule reactions between protonated amino-alcohols and formic acid and in a second process we consider reaction between protonated hydroxyl-amine and acetic acid to

  10. The dynamics of collapsing cores and star formation

    CERN Document Server

    Keto, Eric; Rawlings, Jonathan

    2014-01-01

    Low-mass stars are generally understood to form by the gravitational collapse of the dense molecular clouds known as starless cores. Continuum observations have not been able to distinguish among the several different hypotheses that describe the collapse because the predicted density distributions are the almost the same, as they are for all spherical self-gravitating clouds. However, the predicted contraction velocities are different enough that the models can be discriminated by comparing the velocities at large and small radii. This can be done by observing at least two different molecular line transitions that are excited at different densities. For example, the spectral lines of the H2O (110 - 101) and C18O (1-0) have critical densities for collisional de-excitation that differ by 5 orders of magnitude. We compare observations of these lines from the contracting starless core L1544 against the spectra predicted for several different hypothetical models of contraction including the Larson-Penston flow, t...

  11. 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}.

  12. Enhanced direct collapse due to Lyman {\\alpha} feedback

    CERN Document Server

    Johnson, Jarrett L

    2016-01-01

    We assess the impact of trapped Lyman {\\alpha} cooling radiation on the formation of direct collapse black holes (DCBHs). We apply a one-zone chemical and thermal evolution model, accounting for the photodetachment of H$^-$ ions, precursors to the key coolant H$_{\\rm 2}$, by Lyman {\\alpha} photons produced during the collapse of a cloud of primordial gas in an atomic cooling halo at high redshift. We find that photodetachment of H$^-$ by trapped Lyman {\\alpha} photons can lower the level of the H$_{\\rm 2}$-dissociating background radiation field required for DCBH formation substantially, dropping the critical flux by up to an order of magnitude. This translates into a large increase in the expected number density of DCBHs in the early Universe, and implies that DCBHs may be the seeds for the BHs residing in the centers of a significant fraction of galaxies today. We find that detachment of H$^-$ by Lyman {\\alpha} has the strongest impact on the critical flux for the relatively high background radiation temper...

  13. Volcano collapse along the Aleutian Ridge (western Aleutian Arc

    Directory of Open Access Journals (Sweden)

    C. Montanaro

    2011-03-01

    Full Text Available The Aleutian Ridge, in the western part of the Aleutian Arc, consists of a chain of volcanic islands perched atop the crest of a submarine ridge with most of the active Quaternary stratocones or caldera-like volcanoes being located on the northern margins of the Aleutian Islands. Integrated analysis of marine and terrestrial data resulted in the identification and characterization of 17 extensive submarine debris avalanche deposits from 11 volcanoes. Two morphological types of deposits are recognizable, elongate and lobate, with primary controls on the size and distribution of the volcanic debris being the volume and nature of material involved, proportion of fine grained material, depth of emplacement and the paleo-bathymetry. Volume calculations show the amount of material deposited in debris avalanches is as much as three times larger than the amount of material initially involved in the collapse, suggesting the incorporation of large amounts of submarine material during transport. The orientation of the collapse events is influenced by regional fault systems underling the volcanoes. The western Aleutian Arc has a significant tsunamigenic potential and communities within the Aleutian Islands and surrounding areas of the North Pacific as well as shipping and fishing fleets that cross the North Pacific may be at risk during future eruptions in this area.

  14. Black Hole Collapse in the 1/c Expansion

    CERN Document Server

    Anous, Tarek; Rovai, Antonin; Sonner, Julian

    2016-01-01

    We present a first-principles CFT calculation corresponding to the spherical collapse of a shell of matter in three dimensional quantum gravity. In field theory terms, we describe the equilibration process, from early times to thermalization, of a CFT following a sudden injection of energy at time t=0. By formulating a continuum version of Zamolodchikov's monodromy method to calculate conformal blocks at large central charge c, we give a framework to compute a general class of probe observables in the collapse state, incorporating the full backreaction of matter fields on the dual geometry. This is illustrated by calculating a scalar field two-point function at time-like separation and the time-dependent entanglement entropy of an interval, both showing thermalization at late times. The results are in perfect agreement with previous gravity calculations in the AdS$_3$-Vaidya geometry. Information loss appears in the CFT as an explicit violation of unitarity in the 1/c expansion, restored by nonperturbative co...

  15. C₆₀/collapsed carbon nanotube hybrids: a variant of peapods.

    Science.gov (United States)

    Barzegar, Hamid Reza; Gracia-Espino, Eduardo; Yan, Aiming; Ojeda-Aristizabal, Claudia; Dunn, Gabriel; Wågberg, Thomas; Zettl, Alex

    2015-02-11

    We examine a variant of so-called carbon nanotube peapods by packing C60 molecules inside the open edge ducts of collapsed carbon nanotubes. C60 insertion is accomplished through a facile single-step solution-based process. Theoretical modeling is used to evaluate favorable low-energy structural configurations. Overfilling of the collapsed tubes allows infiltration of C60 over the full cross-section of the tubes and consequent partial or complete reinflation, yielding few-wall, large diameter cylindrical nanotubes packed with crystalline C60 solid cores.

  16. Detecting collapsed buildings from image data for estimation of disaster debris

    Science.gov (United States)

    Yoshinari, N.; Yamamoto, M.; Tonegawa, R.; Oyanagi, Y.; Ohuchi, A.

    2017-04-01

    In the event of a massive earthquake, it is difficult to assess the situation in affected areas because access to these areas is usually blocked off. Tsunamis, in particular, create a large amount of debris and block many access paths. It is necessary to estimate the amount of disaster debris as early as possible in order to begin restoration in affected areas. This data helps to determine the required amount of temporary storage and arrange proper transportation. We propose a system that detects collapsed buildings after a disaster by using three aerial photographs. We verify the accuracy of the proposed method and discuss how detecting collapsed buildings aids in estimating total disaster debris.

  17. Spatiotemporal collapse in a nonlinear waveguide with a randomly fluctuating refractive index.

    Science.gov (United States)

    Gaididei, Y B; Christiansen, P L

    1998-07-15

    Analytical results, based on the virial theorem and the Furutsu-Novikov theorem, of the spatiotemporal evolution of a pulse in a nonlinear waveguide with a randomly fluctuating refractive index are presented. For initial conditions in which total collapse occurs in a homogeneous waveguide, random fluctuations postpone the collapse. Sufficiently large-amplitude and short-wavelength fluctuations can cause an initially localized pulse to spread instead of contracting. We show that the disorder can be applied to induce a high degree of controllability of the spatiotemporal extent of the pulses in the nonlinear waveguide.

  18. Complex behavior of internal collapse due to self-generated radial electric field

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, Taro; Tokuda, Shinji; Kishimoto, Yasuaki; Takizuka, Tomonori [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment; Naitou, Hiroshi [Department of Electical and Electronic Engineering, Yamaguchi University, Ube, Yamaguchi (Japan)

    2000-07-01

    The density gradient effect is taken into account in the gyro-kinetic nonlinear simulation of the kinetic m=1 internal kink mode to clarify the nonlinear behavior of the internal collapse. Even when the density gradient is not so large enough to change the process of the full reconnection, the later process is changed considerably due to the self-generated radial electric field. The nonlinear growth of the 0/0 mode after the internal collapse violates the symmetrical flow of the parallel current, restricting the secondary reconnection. (author)

  19. Observation of Weak Collapse in a Bose-Einstein Condensate

    CERN Document Server

    Eigen, Christoph; Suleymanzade, Aziza; Navon, Nir; Hadzibabic, Zoran; Smith, Robert P

    2016-01-01

    We study the collapse of an attractive atomic Bose-Einstein condensate prepared in the uniform potential an optical-box trap. We characterise the critical point for collapse and the collapse dynamics, observing universal behaviour in agreement with theoretical expectations. Most importantly, we observe a clear experimental signature of the counterintuitive weak collapse, namely that making the system more unstable can result in a smaller particle loss. We experimentally determine the scaling laws that govern the weak-collapse atom loss, providing a benchmark for the general theories of nonlinear wave phenomena.

  20. 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.

  1. Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum

    Science.gov (United States)

    Mead, A. J.

    2016-09-01

    I examine differences in non-linear structure formation between cosmological models that share a z = 0 linear power spectrum in both shape and amplitude, but that differ via their growth history. N-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power spectrum predictions for dark energy models for k ≤ 5 hMpc-1 by using the halo model as a correction to accurate ΛCDM simulations. In the appendix I provide some fitting functions for the linear-collapse threshold (δc) and virialized overdensity (Δv) that are valid for a wide range of dark energy models. I also make my spherical-collapse code available at https://github.com/alexander-mead/collapse.

  2. 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.

  3. Spherical collapse, formation hysteresis and the deeply non-linear cosmological power spectrum

    Science.gov (United States)

    Mead, A. J.

    2017-01-01

    I examine differences in non-linear structure formation between cosmological models that share a z = 0 linear power spectrum in both shape and amplitude, but that differ via their growth history. N-body simulations of these models display an approximately identical large-scale-structure skeleton, but reveal deeply non-linear differences in the demographics and properties of haloes. I investigate to what extent the spherical-collapse model can help in understanding these differences, in both real and redshift space. I discuss how this is difficult to do if one attempts to identify haloes directly, because in that case one is subject to the vagaries of halo-finding algorithms. However, I demonstrate that the halo model of structure formation provides an accurate non-linear response in the power spectrum, but only if results from spherical collapse that include formation hysteresis are properly incorporated. I comment on how this fact can be used to provide per cent level accurate matter power-spectrum predictions for dark energy models for k ≤ 5 h Mpc-1 by using the halo model as a correction to accurate ΛCDM simulations. In the Appendix, I provide some fitting functions for the linear-collapse threshold (δc) and virialized overdensity (Δv) that are valid for a wide range of dark energy models. I also make my spherical-collapse code available at https://github.com/alexander-mead/collapse.

  4. Boundary condition of grounding lines prior to collapse, Larsen-B Ice Shelf, Antarctica.

    Science.gov (United States)

    Rebesco, M; Domack, E; Zgur, F; Lavoie, C; Leventer, A; Brachfeld, S; Willmott, V; Halverson, G; Truffer, M; Scambos, T; Smith, J; Pettit, E

    2014-09-12

    Grounding zones, where ice sheets transition between resting on bedrock to full floatation, help regulate ice flow. Exposure of the sea floor by the 2002 Larsen-B Ice Shelf collapse allowed detailed morphologic mapping and sampling of the embayment sea floor. Marine geophysical data collected in 2006 reveal a large, arcuate, complex grounding zone sediment system at the front of Crane Fjord. Radiocarbon-constrained chronologies from marine sediment cores indicate loss of ice contact with the bed at this site about 12,000 years ago. Previous studies and morphologic mapping of the fjord suggest that the Crane Glacier grounding zone was well within the fjord before 2002 and did not retreat further until after the ice shelf collapse. This implies that the 2002 Larsen-B Ice Shelf collapse likely was a response to surface warming rather than to grounding zone instability, strengthening the idea that surface processes controlled the disintegration of the Larsen Ice Shelf.

  5. Anisotropic electron-beam damage and the collapse of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Crespi, V.H.; Chopra, N.G.; Cohen, M.L.; Zettl, A.; Louie, S.G. [Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)]|[Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

    1996-08-01

    Irradiation of multiwalled carbon nanotubes with the 800-keV electron beam of a transmission electron microscope induces anisotropic collapse of the nanotube. Tight-binding molecular-dynamics simulations of tube response following momentum transfer from large-angle electron-nuclear collisions reveal a strongly anisotropic threshold for atomic displacement. The theoretical displacement threshold for an impulse perpendicular to the local tangent plane of a single-walled tube is roughly half the damage threshold for impulses within the tangent plane. The electron beam preferentially damages the front and back of the nanotube, producing the observed anisotropic collapse perpendicular to the direction of the beam. The attraction of opposite faces of the inner wall then accelerates the collapse. {copyright} {ital 1996 The American Physical Society.}

  6. Glacier Acceleration and Thinning after Ice Shelf Collapse in the Larsen B Embayment, Antarctica

    Science.gov (United States)

    Scambos, T. A.; Bohlander, J. A.; Shuman, C. A.; Skvarca, P.

    2004-01-01

    Ice velocities derived from five Landsat 7 images acquired between January 2000 and February 2003 show a two- to six-fold increase in centerline speed of four glaciers flowing into the now-collapsed section of the Larsen B Ice Shelf. Satellite laser altimetry from ICEsat indicates the surface of Hektoria Glacier lowered by up to 38 +/- 6 m a six-month period beginning one year after the break-up in March 2002. Smaller elevation losses are observed for Crane and Jorum glaciers over a later 5-month period. Two glaciers south of the collapse area, Flask and Leppard, show little change in speed or elevation. Seasonal variations in speed preceding the large post-collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics.

  7. Stellar electron capture rates on neutron-rich nuclei and their impact on core-collapse

    CERN Document Server

    Raduta, Ad R; Oertel, M

    2016-01-01

    During the late stages of gravitational core-collapse of massive stars, extreme isospin asymmetries are reached within the core. Due to the lack of microscopic calculations of electron capture (EC) rates for all relevant nuclei, in general simple analytic parameterizations are employed. We study here several extensions of these parameterizations, allowing for a temperature, electron density and isospin dependence as well as for odd-even effects. The latter extra degrees of freedom considerably improve the agreement with large scale microscopic rate calculations. We find, in particular, that the isospin dependence leads to a significant reduction of the global EC rates during core collapse with respect to fiducial results, where rates optimized on calculations of stable $fp$-shell nuclei are used. Our results indicate that systematic microscopic calculations and experimental measurements in the $N\\approx 50$ neutron rich region are desirable for realistic simulations of the core-collapse.

  8. Signatures of hydrophobic collapse in extended proteins captured with force spectroscopy

    Science.gov (United States)

    Walther, Kirstin A.; Gräter, Frauke; Dougan, Lorna; Badilla, Carmen L.; Berne, Bruce J.; Fernandez, Julio M.

    2007-01-01

    We unfold and extend single proteins at a high force and then linearly relax the force to probe their collapse mechanisms. We observe a large variability in the extent of their recoil. Although chain entropy makes a small contribution, we show that the observed variability results from hydrophobic interactions with randomly varying magnitude from protein to protein. This collapse mechanism is common to highly extended proteins, including nonfolding elastomeric proteins like PEVK from titin. Our observations explain the puzzling differences between the folding behavior of highly extended proteins, from those folding after chemical or thermal denaturation. Probing the collapse of highly extended proteins with force spectroscopy allows separation of the different driving forces in protein folding. PMID:17470816

  9. A-Collapsibility of Distribution Dependence and Quantile Regression Coefficients

    CERN Document Server

    Meerschaert, Mark M

    2010-01-01

    The Yule-Simpson paradox notes that an association between random variables can be reversed when averaged over a background variable. Cox and Wermuth (2003) introduced the concept of distribution dependence between two random variables X and Y , and developed two dependence conditions, each of which guarantees that reversal cannot occur. Ma, Xie and Geng (2006) studied the collapsibility of distribution dependence over a background variable W, under a rather strong homogeneity condition. Collapsibility ensures the association remains the same for conditional and marginal models, so that Yule-Simpson reversal cannot occur. In this paper, we investigate a more general condition for avoiding e?ect reversal: A-collapsibility. The conditions of Cox and Wermuth imply A-collapsibility, without assuming homogeneity. In fact, we show that, when W is a binary variable, collapsibility is equivalent to A-collapsibility plus homogeneity, and A-collapsibility is equivalent to the conditions of Cox and Wermuth. Recently, Co...

  10. Quantum dust collapse in 2+1 dimensions

    CERN Document Server

    Sarkar, Souvik; Wijewardhana, L C R

    2016-01-01

    In this paper we will examine the consequence of a canonical theory of quantum dust collapse in 2+1 dimensions. The solution of the WDW equation describing the collapse indicates that collapsing shells outside the apparent horizon are accompanied by outgoing shells within the apparent horizon during their collapse phase and stop collapsing once they reach the apparent horizon. Taking this picture of quantum collapse seriously, we determine a static solution with energy density corresponding to a dust ball whose collapse has terminated at the apparent horizon. We show that the boundary radius of the ball is larger than the BTZ radius confirming that no event horizon is formed. The ball is sustained by radial pressure which we determine and which we attribute to the Unruh radiation within it.

  11. Assessing inflow rates in atomic cooling haloes: implications for direct collapse black holes

    Science.gov (United States)

    Latif, M. A.; Volonteri, M.

    2015-09-01

    Supermassive black holes are not only common in the present-day galaxies, but billion solar masses black holes also powered z ≥ 6 quasars. One efficient way to form such black holes is the collapse of a massive primordial gas cloud into a so-called direct collapse black hole. The main requirement for this scenario is the presence of large accretion rates of ≥ 0.1 M⊙ yr- 1 to form a supermassive star. It is not yet clear how and under what conditions such accretion rates can be obtained. The prime aim of this work is to determine the mass accretion rates under non-isothermal collapse conditions. We perform high-resolution cosmological simulations for three primordial haloes of a few times 107 M⊙ illuminated by an external UV flux, J21 = 100-1000. We find that a rotationally supported structure of about parsec size is assembled, with an aspect ratio between 0.25 and 1 depending upon the thermodynamical properties. Rotational support, however, does not halt collapse, and mass inflow rates of ˜ 0.1 M⊙ yr- 1 can be obtained in the presence of even a moderate UV background flux of strength J21 ≥ 100. To assess whether such large accretion rates can be maintained over longer time-scales, we employed sink particles, confirming the persistence of accretion rates of ˜ 0.1 M⊙ yr- 1. We propose that complete isothermal collapse and molecular hydrogen suppression may not always be necessary to form supermassive stars, precursors of black hole seeds. Sufficiently high inflow rates can be obtained for UV flux J21 = 500-1000, at least for some cases. This value brings the estimate of the abundance of direct collapse black hole seeds closer to that high-redshift quasars.

  12. Transient 3D numerical simulations of column collapse and pyroclastic density current scenarios at Vesuvius

    Science.gov (United States)

    Esposti Ongaro, T.; Neri, A.; Menconi, G.; de'Michieli Vitturi, M.; Marianelli, P.; Cavazzoni, C.; Erbacci, G.; Baxter, P. J.

    2008-12-01

    Numerical simulations of column collapse and pyroclastic density current (PDC) scenarios at Vesuvius were carried out using a transient 3D flow model based on multiphase transport laws. The model describes the dynamics of the collapse as well as the effects of the 3D topography of the volcano on PDC propagation. Source conditions refer to a medium-scale sub-Plinian event and consider a pressure-balanced jet. Simulation results provide new insights into the complex dynamics of these phenomena. In particular: 1) column collapse can be characterized by different regimes, from incipient collapse to partial or nearly total collapse, thus confirming the possibility of a transitional field of behaviour of the column characterized by the contemporaneous and/or intermittent occurrence of ash fallout and PDCs; 2) the collapse regime can be characterized by its fraction of eruptive mass reaching the ground and generating PDCs; 3) within the range of the investigated source conditions, the propagation and hazard potential of PDCs appear to be directly correlated with the flow-rate of the mass collapsing to the ground, rather than to the collapse height of the column (this finding is in contrast with predictions based on the energy-line concept, which simply correlates the PDC runout and kinetic energy with the collapse height of the column); 4) first-order values of hazard variables associated with PDCs (i.e., dynamic pressure, temperature, airborne ash concentration) can be derived from simulation results, thereby providing initial estimates for the quantification of damage scenarios; 5) for scenarios assuming a location of the central vent coinciding with that of the present Gran Cono, Mount Somma significantly influences the propagation of PDCs, largely reducing their propagation in the northern sector, and diverting mass toward the west and southeast, accentuating runouts and hazard variables for these sectors; 6) the 2D modelling approximation can force an artificial

  13. Thermal and Chemical Evolution of Collapsing Filaments

    Energy Technology Data Exchange (ETDEWEB)

    Gray, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scannapieco, Evan [Arizona State Univ., Mesa, AZ (United States). School of Earth and Space Exploration

    2013-01-15

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z ≈ 0.1Z filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10-3Z filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253, but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  14. Thermal and Chemical Evolution of Collapsing Filaments

    Energy Technology Data Exchange (ETDEWEB)

    Gray, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scannapieco, Evan [Arizona State Univ., Mesa, AZ (United States). School of Earth and Space Exploration

    2013-01-15

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z ≈ 0.1Z filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10-3Z filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253 but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  15. Scalar field collapse with negative cosmological constant

    CERN Document Server

    Baier, R; Stricker, S A

    2014-01-01

    The formation of black holes or naked singularities is studied in a model in which a homogeneous time-dependent scalar field with an exponential potential couples to four dimensional gravity with negative cosmological constant. An analytic solution is derived and its consequences are discussed. The model depends only on one free parameter which determines the equation of state and decides the fate of the spacetime. Depending on the value of this parameter the collapse ends in a black hole or a naked singularity. The latter case violates the cosmic censorship conjecture.

  16. Conditional Probabilities and Collapse in Quantum Measurements

    Science.gov (United States)

    Laura, Roberto; Vanni, Leonardo

    2008-09-01

    We show that including both the system and the apparatus in the quantum description of the measurement process, and using the concept of conditional probabilities, it is possible to deduce the statistical operator of the system after a measurement with a given result, which gives the probability distribution for all possible consecutive measurements on the system. This statistical operator, representing the state of the system after the first measurement, is in general not the same that would be obtained using the postulate of collapse.

  17. A Riccati equation in radiative stellar collapse

    CERN Document Server

    Rajah, S S

    2008-01-01

    We model the behaviour of a relativistic spherically symmetric shearing fluid undergoing gravitational collapse with heat flux. It is demonstrated that the governing equation for the gravitational behaviour is a Riccati equation. We show that the Riccati equation admits two classes of new solutions in closed form. We regain particular models, obtained in previous investigations, as special cases. A significant feature of our solutions is the general spatial dependence in the metric functions which allows for a wider study of the physical features of the model, such as the behaviour of the causal temperature in inhomogeneous spacetimes.

  18. Ideal-Chain Collapse in Biopolymers

    CERN Document Server

    Neumann, R M

    2000-01-01

    A conceptual difficulty in the Hooke's-law description of ideal Gaussian polymer-chain elasticity is sometimes apparent in analyses of experimental data or in physical models designed to simulate the behavior of biopolymers. The problem, the tendency of a chain to collapse in the absence of external forces, is examined in the following examples: DNA-stretching experiments, gel electrophoresis, and protein folding. We demonstrate that the application of a statistical-mechanically derived repulsive force, acting between the chain ends, whose magnitude is proportional to the absolute temperature and inversely proportional to the scalar end separation removes this difficulty.

  19. Inelastic collapse of a randomly forced particle

    OpenAIRE

    1998-01-01

    We consider a randomly forced particle moving in a finite region, which rebounds inelastically with coefficient of restitution r on collision with the boundaries. We show that there is a transition at a critical value of r, r_c\\equiv e^{-\\pi/\\sqrt{3}}, above which the dynamics is ergodic but beneath which the particle undergoes inelastic collapse, coming to rest after an infinite number of collisions in a finite time. The value of r_c is argued to be independent of the size of the region or t...

  20. Qualitative analysis of collapsing isotropic fluid spacetimes

    CERN Document Server

    Giambò, Roberto

    2013-01-01

    The structure of the Einstein field equations describing the gravitational collapse of spherically symmetric isotropic fluids is analyzed here for general equations of state. A suitable system of coordinates is constructed which allows us, under a hypothesis of Taylor-expandability with respect to one of the coordinates, to approach the problem of the nature of the final state without knowing explicitely the metric. The method is applied to investigate the singularities of linear barotropic perfect fluids solutions and to a family of accelerating fluids.

  1. Electromagnetic wave collapse in a radiation background.

    Science.gov (United States)

    Marklund, Mattias; Brodin, Gert; Stenflo, Lennart

    2003-10-17

    The nonlinear interaction, due to quantum electrodynamical (QED) effects between an electromagnetic pulse and a radiation background, is investigated by combining the methods of radiation hydrodynamics with the QED theory for photon-photon scattering. For the case of a single coherent electromagnetic pulse, we obtain a Zakharov-like system, where the radiation pressure of the pulse acts as a driver of acoustic waves in the photon gas. For a sufficiently intense pulse and/or background energy density, there is focusing and the subsequent collapse of the pulse. The relevance of our results for various astrophysical applications are discussed.

  2. Collapsing glomerulopathy in systemic lupus erythematosus.

    Science.gov (United States)

    Abadeer, Kerolos; Alsaad, Ali A; Geiger, Xochiquetzal J; Porter, Ivan E

    2017-02-27

    Collapsing glomerulopathy (CG) is a rare disease that can be associated with multiple other disorders. It usually leads to poor prognosis with a high percentage of patients progressing to end-stage renal disease. In this article, we illustrate a clinical case of CG associated with systemic lupus erythematosus that had a prompt response to mycophenolate and prednisone. The condition started after sudden cessation of the already established mycophenolate treatment regimen. The patient then presented with acute kidney injury due to kidney biopsy-proven CG. In that circumstance, we hypothesised that mycophenolate may play a role in prevention and development of CG.

  3. (Extreme) Core-collapse Supernova Simulations

    Science.gov (United States)

    Mösta, Philipp

    2017-01-01

    In this talk I will present recent progress on modeling core-collapse supernovae with massively parallel simulations on the largest supercomputers available. I will discuss the unique challenges in both input physics and computational modeling that come with a problem involving all four fundamental forces and relativistic effects and will highlight recent breakthroughs overcoming these challenges in full 3D simulations. I will pay particular attention to how these simulations can be used to reveal the engines driving some of the most extreme explosions and conclude by discussing what remains to be done in simulation work to maximize what we can learn from current and future time-domain astronomy transient surveys.

  4. Protostellar collapse and fragmentation using an MHD GADGET

    CERN Document Server

    Bürzle, Florian; Stasyszyn, Federico; Greif, Thomas; Dolag, Klaus; Klessen, Ralf S; Nielaba, Peter

    2010-01-01

    Although the influence of magnetic fields is regarded as vital in the star formation process, only a few magnetohydrodynamics (MHD) simulations have been performed on this subject within the smoothed particle hydrodynamics (SPH) method. This is largely due to the unsatisfactory treatment of non-vanishing divergence of the magnetic field. Recently smoothed particle magnetohydrodynamics (SPMHD) simulations based on Euler potentials have proven to be successful in treating MHD collapse and fragmentation problems, however these methods are known to have some intrinsical difficulties. We have performed SPMHD simulations based on a traditional approach evolving the magnetic field itself using the induction equation. To account for the numerical divergence, we have chosen an approach that subtracts the effects of numerical divergence from the force equation, and additionally we employ artificial magnetic dissipation as a regularization scheme. We apply this realization of SPMHD to a widely known setup, a variation o...

  5. Origin of calderas: discriminating between collapses and explosions

    Directory of Open Access Journals (Sweden)

    Izumi Yokoyama

    2017-01-01

    Full Text Available Origins of calderas may differ according to their subsurface structure that may be characterized by high or low density deposits that may be observed as high or low gravity anomalies, respectively. In the Introduction, the pioneering work of Fouqué[1879] on Santorini caldera is referred to in relation to definition of calderas. First, our discussion is focused on four calderas that were seen forming during the period from 1815 (the Tambora eruption to 1991 (the Pinatubo eruption. Coincidently, these four calderas are all low-gravity-anomaly type. Their formation processes and subsurface structure are summarized by the existing data analyzed by various authors. These results are confirmed by results of drillings at some other calderas. Then, caldera formation of both types is discussed: High-gravity-anomaly-type calderas are expected to originate from subsidence of high-density ejecta into the summit magma reservoir. On the calderas of this type, the genetic eruptions believed to be accompanied by subsidences were not actually observed, and consequently three examples are mentioned only briefly. The low-gravity-anomaly-type calderas are discussed from standpoint of both the models of collapses and explosions. It is also emphasized that dynamic pressure ofexplosions is an important factor in the caldera formation, not only volume of the ejecta. To confirm the possibility that volcanic ejecta and edifices collapse into magma reservoirs, we discuss stress propagation from a depleted reservoir upward towards the Earth surface. Formation mechanisms of large calderas of this type are speculated; large calderas measuring about 20 km across may develop by successive merging of component calderas over a long period of times. A Kamchatka caldera under enlargement during the Holocene period is interpreted by successive merging of five component calderas.

  6. Protostellar collapse of magneto-turbulent cloud cores: shape during collapse and outflow formation

    CERN Document Server

    Matsumoto, Tomoaki

    2010-01-01

    We investigate protostellar collapse of molecular cloud cores by numerical simulations, taking into account turbulence and magnetic fields. By using the adaptive mesh refinement technique, the collapse is followed over a wide dynamic range from the scale of a turbulent cloud core to that of the first core. The cloud core is lumpy in the low density region owing to the turbulence, while it has a smooth density distribution in the dense region produced by the collapse. The shape of the dense region depends mainly on the mass of the cloud core; a massive cloud core tends to be prolate while a less massive cloud core tends to be oblate. In both cases, anisotropy of the dense region increases during the isothermal collapse. The minor axis of the dense region is always oriented parallel to the local magnetic field. All the models eventually yield spherical first cores supported mainly by the thermal pressure. Most of turbulent cloud cores exhibit protostellar outflows around the first cores. These outflows are clas...

  7. Core Collapse Supernova Models For Nucleosynthesis

    Science.gov (United States)

    Casanova, Jordi; Frohlich, C.; Perego, A.; Hempel, M.

    2014-01-01

    Type II supernova explosions are the product of the collapse of massive stars (M > 8-10 Msun), which explode with a kinetic energy release of 1e51 erg. While sophisticated multi-dimensional models can reveal details of the explosion mechanism (role of convection, fluid instabilities, etc.), they are computationally too expensive for nucleosynthesis studies. However, precise nucleosynthesis predictions are needed to understand the supernova contribution to the heavy elements and the abundances observed in metal-poor stars. We have modeled the core collapse, bounce and subsequent explosion of massive stars assuming spherical symmetry with the code Agile-IDSA (Liebendoerfer et al. 2009) combined with a novel method to artificially trigger the explosion (PUSH). The code also includes the Hempel EOS, which uses a modern non-NSE to cover the entire nucleosynthesis duration. In our simulations, based on the neutrino-delayed explosion mechanism, the explosion sets in by depositing a small amount of additional energy (from mu and tau neutrinos) to revive the stalled shock. Our results show that the code Agile-IDSA combined with PUSH is very robust and can successfully reproduce an explosion with a more reliable treatment of the crucial quantities involved in nucleosynthesis (i.e., the electron fraction). Here, we present a detailed isotopic abundance study for a wide variety of progenitors, as well as an analysis of the explosion properties, such as the explosion energies, remnant masses or compactness of the progenitor models.

  8. Holographic probes of collapsing black holes

    CERN Document Server

    Hubeny, Veronika E

    2013-01-01

    We continue the programme of exploring the means of holographically decoding the geometry of spacetime inside a black hole using the gauge/gravity correspondence. To this end, we study the behaviour of certain extremal surfaces (focusing on those relevant for equal-time correlators and entanglement entropy in the dual CFT) in a dynamically evolving asymptotically AdS spacetime, specifically examining how deep such probes reach. To highlight the novel effects of putting the system far out of equilibrium and at finite volume, we consider spherically symmetric Vaidya-AdS, describing black hole formation by gravitational collapse of a null shell, which provides a convenient toy model of a quantum quench in the field theory. Extremal surfaces anchored on the boundary exhibit rather rich behaviour, whose features depend on dimension of both the spacetime and the surface, as well as on the anchoring region. The main common feature is that they reach inside the horizon even in the post-collapse part of the geometry. ...

  9. Perspectives on Core-Collapse Supernova Theory

    CERN Document Server

    Burrows, Adam

    2012-01-01

    Core-collapse theory brings together many facets of high-energy and nuclear astrophysics and the numerical arts to present theorists with one of the most important, yet frustrating, astronomical questions: "What is the mechanism of core-collapse supernova explosions?" A review of all the physics and the fifty-year history involved would soon bury the reader in minutiae that could easily obscure the essential elements of the phenomenon, as we understand it today. Moreover, much remains to be discovered and explained, and a complicated review of an unresolved subject in flux could grow stale fast. Therefore, in this paper I describe what I think are various important facts and perspectives that may have escaped the attention of those interested in this puzzle. Furthermore, I attempt to describe the modern theory's physical underpinnings and briefly summarize the current state of play. In the process, I identify a few myths (as I see them) that have crept into modern discourse. However, there is much more to do ...

  10. Caldera collapse and the generation of waves

    Science.gov (United States)

    Gray, J. P.; Monaghan, J. J.

    2003-02-01

    The aim of this paper is to begin a study of the waves produced by the collapse of a caldera connected to the sea. An example is the bronze age collapse of the caldera of Santorini (Thera), which is thought to have involved an area of approximately 70 km2 subsiding to a depth close to the present 390 m. In this paper, we concentrate on the purely mechanical aspects of the flow and adopt a simple geometry that replicates some of the features of the pre-bronze age caldera of Santorini. By combining laboratory experiments with computer simulations, we have been able to determine the amplitude of the waves for a wide range of cavity parameters. For cavities with a width comparable to the depth of water entering the cavity, we have determined a scaling relation for the amplitude in terms of the geometry of the system. In the case of wider cavities, the flow begins like a breaking dam flow; it then becomes similar to a classical bore before breaking up into waves. The computer simulations agree well with experiment and will allow us to simulate more complicated geometries.

  11. Gravitational Collapse, Negative World and Complex Holism

    CERN Document Server

    Sengupta, A

    2010-01-01

    Building on the engine-pump paradigm of ChaNoXity, this paper argues that complex holism - as the competitive homeostasis of dispersion and concentration - is the operating mode of Nature. Specifically, we show that the negative world \\mathfrak{W} is a gravitationally collapsed black hole that was formed at big-bang time t=0 as the pair (W,\\mathfrak{W}), with W a real world, and gravity the unique expression of the maximal multifunctional nonlinearity of the negative world \\mathfrak{W} in the functional reality of W. The temperature of a gravitationally collapsed system does enjoy the relationship T\\propto1/r with its radius, but the entropy follows the usual volumetric alignment with microstates, reducing to the surface approximation only at small r. It is not clear if quantum non-locality is merely a linear manifestation of complex holism, with the interaction of quantum gates in quantum entanglements resulting in distinctive features from the self-evolved structures of complex holism remaining an open ques...

  12. Online fuzzy voltage collapse risk quantification

    Energy Technology Data Exchange (ETDEWEB)

    Berizzi, A.; Bovo, C.; Delfanti, M.; Merlo, M. [Politecnico di Milano, 20133 Milano (Italy); Cirio, D. [CESI Ricerca (Italy); Pozzi, M. [CESI (Italy)

    2009-05-15

    Many voltage stability indicators have been proposed in the past for the voltage collapse assessment. Almost all of them are determined through quite complex analytical tools; therefore, it is difficult for system operators to give them a physical meaning. In order to perform a simple and reliable evaluation of the security margins, it is necessary to make a synthesis of the information given by the various indices. The present work proposes an Artificial Intelligence-based tool for the evaluation of the voltage security. In particular, a Fuzzy Inference Engine is developed and optimized by two different approaches (Neural Networks and Genetic Algorithms). Starting from the state estimation, a given set of mathematical indices is computed to represent a snapshot of the current electric system operating point. The numerical values are then translated into a set of symbolic and linguistic quantities that are manipulated through a set of logical connectives and Inference Methods provided by the mathematical logic. As a result, the Fuzzy Logic gives a MW measure of the distance from the collapse limit, a metric usually appreciated by system operators. The Fuzzy System has been built and optimized by using, as a test system, a detailed model of the EHV Italian transmission network connected to an equivalent of the UCTE network (about 1700 buses). (author)

  13. Critical Collapse of Rotating Radiation Fluids.

    Science.gov (United States)

    Baumgarte, Thomas W; Gundlach, Carsten

    2016-06-03

    We present results from the first fully relativistic simulations of the critical collapse of rotating radiation fluids. We observe critical scaling both in subcritical evolutions-in which case the fluid disperses to infinity and leaves behind flat space-and in supercritical evolutions, which lead to the formation of black holes. We measure the mass and angular momentum of these black holes, and find that both show critical scaling with critical exponents that are consistent with perturbative results. The critical exponents are universal: they are not affected by angular momentum, and are independent of the direction in which the critical curve, which separates subcritical from supercritical evolutions in our two-dimensional parameter space, is crossed. In particular, these findings suggest that the angular momentum decreases more rapidly than the square of the mass, so that, as criticality is approached, the collapse leads to the formation of a nonspinning black hole. We also demonstrate excellent agreement of our numerical data with new closed-form extensions of power-law scalings that describe the mass and angular momentum of rotating black holes formed close to criticality.

  14. Phase II modification of the Water Availability Tool for Environmental Resources (WATER) for Kentucky: The sinkhole-drainage process, point-and-click basin delineation, and results of karst test-basin simulations

    Science.gov (United States)

    Taylor, Charles J.; Williamson, Tanja N.; Newson, Jeremy K.; Ulery, Randy L.; Nelson, Hugh L.; Cinotto, Peter J.

    2012-01-01

    This report describes Phase II modifications made to the Water Availability Tool for Environmental Resources (WATER), which applies the process-based TOPMODEL approach to simulate or predict stream discharge in surface basins in the Commonwealth of Kentucky. The previous (Phase I) version of WATER did not provide a means of identifying sinkhole catchments or accounting for the effects of karst (internal) drainage in a TOPMODEL-simulated basin. In the Phase II version of WATER, sinkhole catchments are automatically identified and delineated as internally drained subbasins, and a modified TOPMODEL approach (called the sinkhole drainage process, or SDP-TOPMODEL) is applied that calculates mean daily discharges for the basin based on summed area-weighted contributions from sinkhole drain-age (SD) areas and non-karstic topographically drained (TD) areas. Results obtained using the SDP-TOPMODEL approach were evaluated for 12 karst test basins located in each of the major karst terrains in Kentucky. Visual comparison of simulated hydrographs and flow-duration curves, along with statistical measures applied to the simulated discharge data (bias, correlation, root mean square error, and Nash-Sutcliffe efficiency coefficients), indicate that the SDPOPMODEL approach provides acceptably accurate estimates of discharge for most flow conditions and typically provides more accurate simulation of stream discharge in karstic basins compared to the standard TOPMODEL approach. Additional programming modifications made to the Phase II version of WATER included implementation of a point-and-click graphical user interface (GUI), which fully automates the delineation of simulation-basin boundaries and improves the speed of input-data processing. The Phase II version of WATER enables the user to select a pour point anywhere on a stream reach of interest, and the program will automatically delineate all upstream areas that contribute drainage to that point. This capability enables

  15. The characteristic black hole mass resulting from direct collapse in the early Universe

    Science.gov (United States)

    Latif, M. A.; Schleicher, D. R. G.; Schmidt, W.; Niemeyer, J. C.

    2013-12-01

    Black holes of a billion solar masses are observed in the infant Universe a few hundred million years after the big bang. The direct collapse of protogalactic gas clouds in primordial haloes with Tvir ≥ 104 K provides the most promising way to assemble massive black holes. In this study, we aim to determine the characteristic mass scale of seed black holes and the time evolution of the accretion rates resulting from the direct collapse model. We explore the formation of supermassive black holes via cosmological large eddy simulations (LES) by employing sink particles and following their evolution for 20 000 yr after the formation of the first sink. As the resulting protostars were shown to have cool atmospheres in the presence of strong accretion, we assume here that UV feedback is negligible during this calculation. We confirm this result in a comparison run without sinks. Our findings show that black hole seeds with characteristic mass of 105 M⊙ are formed in the presence of strong Lyman-Werner flux which leads to an isothermal collapse. The characteristic mass is about two times higher in LES compared to the implicit large eddy simulations. The accretion rates increase with time and reach a maximum value of 10 M⊙ yr-1 after 104 yr. Our results show that the direct collapse model is clearly feasible as it provides the expected mass of the seed black holes.

  16. Collapse and rebound of a gas-filled spherical bubble immersed in a diagnostic ultrasonic field.

    Science.gov (United States)

    Aymé-Bellegarda, E J

    1990-08-01

    This work is concerned with the influence of the finite-amplitude distortion of a driving diagnostic ultrasonic field on the collapse and rebound of a gas-filled spherical microbubble, present in the exposed compressible liquid. Such an analysis is especially important since one of the mechanisms for cavitation damage comes from the very large gas pressures generated at bubble collapse and in the subsequent pressure wave formed by bubble rebound. Gilmore's model [F.R. Gilmore, "The growth or collapse of a spherical bubble in a viscous compressible liquid," Hydrodynamics Lab. Rep. No. 26-4, California Institute of Technology, Pasadena, CA (1952)] for bubble dynamics is used to obtain the motion of the bubble interface when subjected to a pulsed diagnostic ultrasonic field of large amplitude. Knowledge of the bubble motion allows one to derive the pressure distribution around the bubble. Numerical results over a range of initial bubble sizes, acoustic pressures, and frequencies relevant to medical use show that the strength of the pressure spikes radiated by the rebounding bubble depends upon (i) the acoustic frequency (f), (ii) the initial bubble size (R0), and (iii) the magnitude of the pressure amplitude of the fundamental (PF) in a Fourier series description of the distorted pulse. As the pressure spikes propagate outward from the bubble wall, their strength is attenuated as the reciprocal of the distance from the center of collapse.

  17. Aerogeophysical measurements of collapse-prone hydrothermally altered zones at Mount Rainier volcano.

    Science.gov (United States)

    Finn, C A; Sisson, T W; Deszcz-Pan, M

    2001-02-01

    Hydrothermally altered rocks can weaken volcanoes, increasing the potential for catastrophic sector collapses that can lead to destructive debris flows. Evaluating the hazards associated with such alteration is difficult because alteration has been mapped on few active volcanoes and the distribution and severity of subsurface alteration is largely unknown on any active volcano. At Mount Rainier volcano (Washington, USA), collapses of hydrothermally altered edifice flanks have generated numerous extensive debris flows and future collapses could threaten areas that are now densely populated. Preliminary geological mapping and remote-sensing data indicated that exposed alteration is contained in a dyke-controlled belt trending east-west that passes through the volcano's summit. But here we present helicopter-borne electromagnetic and magnetic data, combined with detailed geological mapping, to show that appreciable thicknesses of mostly buried hydrothermally altered rock lie mainly in the upper west flank of Mount Rainier. We identify this as the likely source for future large debris flows. But as negligible amounts of highly altered rock lie in the volcano's core, this might impede collapse retrogression and so limit the volumes and inundation areas of future debris flows. Our results demonstrate that high-resolution geophysical and geological observations can yield unprecedented views of the three-dimensional distribution of altered rock.

  18. The suppression of direct collapse black hole formation by soft X-ray irradiation

    Science.gov (United States)

    Inayoshi, Kohei; Tanaka, Takamitsu L.

    2015-07-01

    The origin of supermassive black holes (SMBHs) in galactic nuclei is one of the major unsolved problems in astrophysics. One hypothesis is that they grew from ≳ 105 M⊙ black holes that formed in the `direct collapse' of massive gas clouds that have low concentrations of both metals and molecular hydrogen (H2). Such clouds could form in the early (z ≳ 10) Universe if pre-galactic gas is irradiated by H2-photodissociating, far-ultraviolet (FUV) light from a nearby star-forming galaxy. In this work, we re-examine the critical FUV flux Jcrit that is required to keep H2 photodissociated and lead to direct collapse. We submit that the same galaxies that putatively supply the extraordinary FUV fluxes required for direct collapse should also produce copious amounts of soft X-rays, which work to offset H2 photodissociation by increasing the ionization fraction and promoting H2 formation. Accounting for this effect increases the value of Jcrit by a factor of at least 3-10, depending on the brightness temperature of FUV radiation. This enhancement of Jcrit suppresses the abundance of potential direct collapse sites at z > 10 by several orders of magnitude. Recent studies - without accounting for the soft X-rays from the FUV source galaxies - had already arrived at large values of Jcrit that implied that direct collapse may occur too rarely to account for the observed abundance of high-redshift quasars. Our results suggest that Jcrit should be even higher than previously estimated, and pose an additional challenge for the direct collapse scenario via strong FUV radiation to explain the high-redshift quasar population.

  19. Finite-element modeling of magma chamber-host rock interactions prior to caldera collapse

    Science.gov (United States)

    Kabele, Petr; Žák, Jiří; Somr, Michael

    2017-06-01

    Gravity-driven failure of shallow magma chamber roofs and formation of collapse calderas are commonly accompanied by ejection of large volumes of pyroclastic material to the Earth's atmosphere and thus represent severe volcanic hazards. In this respect, numerical analysis has proven as a key tool in understanding the mechanical conditions of caldera collapse. The main objective of this paper is to find a suitable approach to finite-element simulation of roof fracturing and caldera collapse during inflation and subsequent deflation of shallow magma chambers. Such a model should capture the dominant mechanical phenomena, for example, interaction of the host rock with magma and progressive deformation of the chamber roof. To this end, a comparative study, which involves various representations of magma (inviscid fluid, nearly incompressible elastic, or plastic solid) and constitutive models of the host rock (fracture and plasticity), was carried out. In particular, the quasi-brittle fracture model of host rock reproduced well the formation of tension-induced radial and circumferential fractures during magma injection into the chamber (inflation stage), especially at shallow crustal levels. Conversely, the Mohr-Coulomb shear criterion has shown to be more appropriate for greater depths. Subsequent magma withdrawal from the chamber (deflation stage) results in further damage or even collapse of the chamber roof. While most of the previous studies of caldera collapse rely on the elastic stress analysis, the proposed approach advances modeling of the process by incorporating non-linear failure phenomena and nearly incompressible behaviour of magma. This leads to a perhaps more realistic representation of the fracture processes preceding roof collapse and caldera formation.

  20. Simulation of weak and strong Langmuir collapse regimes

    Energy Technology Data Exchange (ETDEWEB)

    Hadzievski, L.R.; Skoric, M.M. [Vinca Inst. of Nuclear Sciences, Belgrade (Yugoslavia); 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)

  1. The final outcome of dissipative collapse in the presence of

    Indian Academy of Sciences (India)

    S Thirukkanesh; S Moopanar; M Govender

    2012-08-01

    We investigate the role played by the cosmological constant during gravitational collapse of a radiating star with vanishing Weyl stresses in the interior. We highlight the role played by the cosmological constant during the latter stages of collapse. The evolution of the temperature of the collapsing body is studied by employing causal heat transport equation. We show that the inclusion of the cosmological constant enhances the temperature within the stellar core.

  2. MATHEMATICAL ANALYSIS OF THE COLLAPSE IN BOSE-EINSTEIN CONDENSATE

    Institute of Scientific and Technical Information of China (English)

    Li Xiaoguang; Zhang Jian; Wu Yonghong

    2009-01-01

    In this article, the authors consider the collapse solutions of Cauchy problem for the nonlinear Schrodinger equation iψt +1/2Δψ-1/2ω2|x|2ψ+ |ψ|2+|ψ|2ψ=0, x∈R2, which models the Bose-Einstein condensate with attractive interactions. The authors establish the lower bound of collapse rate as t→T. Furthermore, the L2-concentration property of the radially symmetric collapse solutions is obtained.

  3. Lessons Learned from Collapse of Zumrut Building under Gravity Loads

    OpenAIRE

    Balkaya, Can

    2017-01-01

    The 11-story reinforcedconcrete Zumrut Building in Konya, Turkey collapsed on February 2, 2004.Ninety-two people died. This study was conducted to determine the mechanism ofthe collapse and identify lessons learned to avoid future disasters. Usingstructural drawings, material samples, and soil information obtained from thesite, reasons for the collapse were investigated. A three-dimensional (3-D)structural model and analyses were performed using ETABSV8.11, and variouspossible critical cases ...

  4. Caldera collapse at near-ridge seamounts: an experimental investigation

    Science.gov (United States)

    Coumans, Jason P.; Stix, John

    2016-10-01

    Collapse calderas are sub-circular volcanic depressions caused by subsidence of the magma reservoir roof during an eruption. Scaled physical models of caldera collapse using flat topography have been instrumental in investigating the spatial and temporal development of calderas, in particular, two distinctive sets of concentric ring faults, one reverse and one normal. More recent analog studies have investigated the effect of non-flat topography which alters the principle stress trajectories and resulting collapse structure. This work provides the basis for investigating how naturally scaled topographic loads may affect caldera collapse in relation to shallow magma reservoirs. The objective of this study is to understand how a near-ridge seamount affects caldera collapse from both a central and offset position as the seamount migrates above the magma reservoir as a result of plate motion. We utilize scaled analog models of caldera collapse in conjunction with three-dimensional (3D) laser scanning and digital particle image velocimetry (DPIV) to investigate caldera collapse dynamics at near-ridge seamounts. Experiments using a seamount cone positioned centrally above the magma reservoir result in (1) increased subsidence along the interior outward-dipping faults and (2) a preference to more symmetric collapse patterns as indicated by the subsidence profile and structure of the caldera relative to experiments with an offset cone. When the cone is offset, the collapse is asymmetric and trapdoor in nature, with the center of greatest subsidence displaced away from the region of largest topographic load. For these latter experiments, subsidence is focused where the roof is thinnest along an initial reverse fault, followed by a transition to an antithetic graben structure. The asymmetric collapse in the experiments results in a caldera with a tilted profile. Offset calderas at near-ridge seamounts are tilted towards the ridge axis, suggesting that they may have collapsed

  5. Inherently unstable networks collapse to a critical point.

    Science.gov (United States)

    Sheinman, M; Sharma, A; Alvarado, J; Koenderink, G H; MacKintosh, F C

    2015-07-01

    Nonequilibrium systems that are driven or drive themselves towards a critical point have been studied for almost three decades. Here we present a minimalist example of such a system, motivated by experiments on collapsing active elastic networks. Our model of an unstable elastic network exhibits a collapse towards a critical point from any macroscopically connected initial configuration. Taking into account steric interactions within the network, the model qualitatively and quantitatively reproduces results of the experiments on collapsing active gels.

  6. Sonoluminescence and the probability of isothermal bubble collapse

    Institute of Scientific and Technical Information of China (English)

    ThomasVPrevenslik

    1997-01-01

    Computations of air bubble collapse dynamics usually neglect thermal conduction.but recent computations show about a 3-fold reduction in bubble gas temperature if thermal conduction is included.However,an isothermal collapse at ambient temperature is even more likely because the air molecuses collide with and stick to the bubble walls during bubble expansion and are not available for compression heating during collapse.The probability of isothermal collapse is shown to depend on the mean free path of the air molecules moving through the H2O vapor molecules within the bullbe during bubble expansion and is sensitive to the lowering of ambinet temperature to the freezing point.

  7. Atomistic modeling of shock-induced void collapse in copper

    Energy Technology Data Exchange (ETDEWEB)

    Davila, L P; Erhart, P; Bringa, E M; Meyers, M A; Lubarda, V A; Schneider, M S; Becker, R; Kumar, M

    2005-03-09

    Nonequilibrium molecular dynamics (MD) simulations show that shock-induced void collapse in copper occurs by emission of shear loops. These loops carry away the vacancies which comprise the void. The growth of the loops continues even after they collide and form sessile junctions, creating a hardened region around the collapsing void. The scenario seen in our simulations differs from current models that assume that prismatic loop emission is responsible for void collapse. We propose a new dislocation-based model that gives excellent agreement with the stress threshold found in the MD simulations for void collapse as a function of void radius.

  8. 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.

  9. Experimental bounds on collapse models from gravitational wave detectors

    Science.gov (United States)

    Carlesso, Matteo; Bassi, Angelo; Falferi, Paolo; Vinante, Andrea

    2016-12-01

    Wave function collapse models postulate a fundamental breakdown of the quantum superposition principle at the macroscale. Therefore, experimental tests of collapse models are also fundamental tests of quantum mechanics. Here, we compute the upper bounds on the collapse parameters, which can be inferred by the gravitational wave detectors LIGO, LISA Pathfinder, and AURIGA. We consider the most widely used collapse model, the continuous spontaneous localization (CSL) model. We show that these experiments exclude a huge portion of the CSL parameter space, the strongest bound being set by the recently launched space mission LISA Pathfinder. We also rule out a proposal for quantum-gravity-induced decoherence.

  10. Interacting dark energy collapse with matter components separation

    CERN Document Server

    Delliou, Morgan Le

    2012-01-01

    We use the spherical collapse model of structure formation to investigate the separation in the collapse of uncoupled matter (including dark matter and baryons) and coupled dark matter in an interacting dark energy scenario. Following the usual assumption of a single radius of collapse for all species, we show that we only need to evolve the uncoupled matter sector to obtain the evolution for all matter components. This gives us more information on the collapse with a simplified set of evolution equations compared with the usual approaches. We then apply these results to five quintessence potentials and show how we can discriminate between different quintessence models.

  11. Interacting dark energy collapse with matter components separation

    Energy Technology Data Exchange (ETDEWEB)

    Delliou, M. Le [Departamento de Física Matemática, Instituto de Física, Universidade de São Paulo, CP 66.318 — 05314-970, São Paulo, SP (Brazil); Barreiro, T., E-mail: delliou@cii.fc.ul.pt, E-mail: tmbarreiro@ulusofona.pt [Departamento de Matemática da FFMCC, Universidade Lusófona de Humanidades e Tecnologias, Campo Grande, 376 — 1749-024 Lisboa (Portugal)

    2013-02-01

    We use the spherical collapse model of structure formation to investigate the separation in the collapse of uncoupled matter (essentially baryons) and coupled dark matter in an interacting dark energy scenario. Following the usual assumption of a single radius of collapse for all species, we show that we only need to evolve the uncoupled matter sector to obtain the evolution for all matter components. This gives us more information on the collapse with a simplified set of evolution equations compared with the usual approaches. We then apply these results to four quintessence potentials and show how we can discriminate between different quintessence models.

  12. Interpretation of collapsed terrain on Mars

    Science.gov (United States)

    Ewa Zalewska, Natalia; Skocki, Krzysztof

    2016-10-01

    On the images from HiRISE camera within volcanoes and circumpolar areas there are depressions that can be explained in two ways, either by melting subsurface layer of ice or by cooling of lava which forms branch intrusion and flank craters underneath. On many pictures from Mars similar cavities are found on the slopes of Martian craters on Arsia Mons , Pavonis Mons on northern hemisphere and Alba Patera on southern hemisphere. Such cavities can be compared to a Hawaiian type volcanoes. At the top of Mauna Loa linearly arranged craters can be seen, strikingly similar to those on Arsia Mons . Basing on map ice content measured by Odyssey GRS apparatus, in this place of the volcanic cone, quite small ice content can be observed that varies in the range of 2-4% hydrogen abundance. It is therefore difficult to explain these collapses by unfreezing of subsurface ice. In an infrared spectrum of these areas there are no bands of water in the CRISM spectra, although it does not say that the water in the form of ice couldn't have been there before. In the central part of Chryse, there are series of chains depressions caused most likely by the collapse of land. These forms have been associated with an open pingo type system additionally with assisted topography of the area or tectonics and internal cracks in the rocks. These are noticed on the slopes of craters or wherever the area decline. Then flowing subsurface water or brine coming from the ice layer could while freezing accumulate and create a longitudinal hill that collapsed due to seasonal thawing forming gullies or canyons . At the end of these gullies remaining trace of the leak can be seen, as if there was a crack in the ground and liquid flew out on the surface. Cryosubsurface processes on Mars can support the hypothesis of geochemical origin of water, which separates from the magma, and its primary source comes from the protoplanetary disk. The water separated from the magma migrates up to the surface and if the

  13. Abrupt climatic changes as triggering mechanisms of massive volcanic collapses: examples from Mexico (Invited)

    Science.gov (United States)

    Capra, L.

    2010-12-01

    Climate changes have been considered to be a triggering mechanism for large magmatic eruptions. However they can also trigger volcanic collapses, phenomena that cause the destruction of the entire sector of a volcano, including its summit. During the past 30 ka, major volcanic collapses occurred just after main glacial peaks that ended with a rapid deglaciation. Glacial debuttressing, load discharge and fluid circulation coupled with the post-glacial increase of humidity and heavy rains can activate the failure of unstable edifices. Looking at the synchronicity of the maximum glaciations during the late Pleistocene and Holocene in the northern and southern hemispheres it is evident that several volcanic collapses are absent during a glacial climax, but start immediately after it during a period of rapid retreat. Several examples can be detected around the world and Mexico is not an exception. The 28 ka Nevado de Toluca volcanic collapse occurred during an intraglacial stage, under humid conditions as evidenced by paleoclimatic studies on lacustrine sediments of the area. The debris avalanche deposit associated to this event clearly shows evidence of a large amount of water into the mass previous to the failure that enhanced its mobility. It also contains peculiar, plastically deformed, m-sized fragment of lacustrine sediments eroded from glacial berms. The 17 ka BP collapse of the Colima Volcano corresponds to the initial stage of glacial retreat in Mexico after the Last Glacial Maximum (22-17.5ka). Also in this case the depositional sequence reflects high humidity conditions with voluminous debris flow containing a large amount logs left by pine trees. The occurrence of cohesive debris flows originating from the failure of a volcanic edifice can also reflect the climatic conditions, indicating important hydrothermal alteration and fluid circulation from ice-melting at an ice-capped volcano, as observed for example at the Pico de Orizaba volcano for the Tetelzingo

  14. Supermassive black holes formed by direct collapse of inflationary perturbations

    Science.gov (United States)

    Nakama, Tomohiro; Suyama, Teruaki; Yokoyama, Jun'ichi

    2016-11-01

    We propose a mechanism of producing a new type of primordial perturbations that collapse to primordial black holes, whose mass can be as large as necessary for them to grow to the supermassive black holes observed at high redshifts, without contradicting Cosmic Background Explorer/Far Infrared Absolute Spectrophotometer (COBE/FIRAS) upper limits on cosmic microwave background (CMB) spectral distortions. In our model, the observable Universe consists of two kinds of many small patches which experienced different expansion histories during inflation. Primordial perturbations large enough to form primordial black holes are realized on patches that experienced more Hubble expansion than the others. By making these patches the minor component, the rarity of supermassive black holes can be explained. On the other hand, most regions of the Universe experienced the standard history and, hence, only have standard almost-scale-invariant adiabatic perturbations confirmed by observations of CMB or large-scale structures of the Universe. Thus, our mechanism can evade the constraint from the nondetection of the CMB distortion set by the COBE/FIRAS measurement. Our model predicts the existence of supermassive black holes even at redshifts much higher than those observed. Hence, our model can be tested by future observations peeking into the higher-redshift Universe.

  15. Angular momentum in cluster Spherical Collapse Model

    CERN Document Server

    Cupani, Guido; Mardirossian, Fabio

    2011-01-01

    Our new formulation of the Spherical Collapse Model (SCM-L) takes into account the presence of angular momentum associated with the motion of galaxy groups infalling towards the centre of galaxy clusters. The angular momentum is responsible for an additional term in the dynamical equation which is useful to describe the evolution of the clusters in the non-equilibrium region which is investigated in the present paper. Our SCM-L can be used to predict the profiles of several strategic dynamical quantities as the radial and tangential velocities of member galaxies, and the total cluster mass. A good understanding of the non-equilibrium region is important since it is the natural scenario where to study the infall in galaxy clusters and the accretion phenomena present in these objects. Our results corroborate previous estimates and are in very good agreement with the analysis of recent observations and of simulated clusters.

  16. A Pseudospectral Method for Gravitational Wave Collapse

    CERN Document Server

    Hilditch, David; Bruegmann, Bernd

    2015-01-01

    We present a new pseudospectral code, bamps, for numerical relativity written with the evolution of collapsing gravitational waves in mind. We employ the first order generalized harmonic gauge formulation. The relevant theory is reviewed and the numerical method is critically examined and specialized for the task at hand. In particular we investigate formulation parameters, gauge and constraint preserving boundary conditions well-suited to non-vanishing gauge source functions. Different types of axisymmetric twist-free moment of time symmetry gravitational wave initial data are discussed. A treatment of the axisymmetric apparent horizon condition is presented with careful attention to regularity on axis. Our apparent horizon finder is then evaluated in a number of test cases. Moving on to evolutions, we investigate modifications to the generalized harmonic gauge constraint damping scheme to improve conservation in the strong field regime. We demonstrate strong-scaling of our pseudospectral penalty code. We em...

  17. The Radiative Tail of Realistic Gravitational Collapse

    CERN Document Server

    Hod, S

    2000-01-01

    An astrophysically realistic model of wave dynamics in black-hole spacetimes must involve a {\\it non}-spherical background geometry with {\\it angular momentum}. We consider the evolution of {\\it gravitational} (and electromagnetic) perturbations in {\\it rotating} Kerr spacetimes. We show that a rotating Kerr black hole becomes ``bald'' {\\it slower} than the corresponding spherically-symmetric Schwarzschild black hole. Moreover, our results {\\it turn over} the traditional belief (which has been widely accepted during the last three decades) that the late-time tail of gravitational collapse is universal. In particular, we show that different fields have {\\it different} decaying rates. Our results are also of importance both to the study of the no-hair conjecture and the mass-inflation scenario (stability of Cauchy horizons).

  18. Inhomogeneities from quantum collapse scheme without inflation

    Directory of Open Access Journals (Sweden)

    Gabriel R. Bengochea

    2015-04-01

    Full Text Available In this work, we consider the problem of the emergence of seeds of cosmic structure in the framework of the non-inflationary model proposed by Hollands and Wald. In particular, we consider a modification to that proposal designed to account for breaking the symmetries of the initial quantum state, leading to the generation of the primordial inhomogeneities. This new ingredient is described in terms of a spontaneous reduction of the wave function. We investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities, and which are the dominant deviations that arise in the model as a consequence of the introduction of the collapse of the quantum state into that scenario.

  19. Wetting dynamics of a collapsing fluid hole

    Science.gov (United States)

    Bostwick, Joshua; Dijksman, Joshua; Shearer, Michael

    2016-11-01

    An axisymmetric fluid cavity at the bottom of a rotating bucket bound by vertical sidewalls is studied, as it is filled in by the wetting fluid. Lubrication theory is applied to reduce the governing equations to a single evolution equation for the film thickness. In the quasi-static regime the contact-line motion is governed by a constitutive law relating the effective contact angle to the contact-line speed. The dependence of the collapse time on the initial hole size is calculated. For small holes, surface tension dominates the dynamics, leading to a universal power law that compares favorably to experiments in the literature. Further verification of the model is obtained through comparison of volume dependence with experimental results.

  20. Inhomogeneities from quantum collapse scheme without inflation

    Energy Technology Data Exchange (ETDEWEB)

    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); Cañate, Pedro, E-mail: pedro.canate@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico); Sudarsky, Daniel, E-mail: sudarsky@nucleares.unam.mx [Instituto de Ciencias Nucleares, UNAM, México D.F. 04510, México (Mexico)

    2015-04-09

    In this work, we consider the problem of the emergence of seeds of cosmic structure in the framework of the non-inflationary model proposed by Hollands and Wald. In particular, we consider a modification to that proposal designed to account for breaking the symmetries of the initial quantum state, leading to the generation of the primordial inhomogeneities. This new ingredient is described in terms of a spontaneous reduction of the wave function. We investigate under which conditions one can recover an essentially scale free spectrum of primordial inhomogeneities, and which are the dominant deviations that arise in the model as a consequence of the introduction of the collapse of the quantum state into that scenario.