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1

New insights into the ground thermal regime of talus slopes with permafrost below the timberline  

Science.gov (United States)

In the central Alps permafrost can be expected above 2400 m a.s.l., at altitudes where mean annual air temperatures are below -1° C. However, isolated permafrost occurrences are present in north-exposed talus slopes, far below the timberline, where mean annual air temperatures are positive. Driving factors are assumed to be a low income of solar radiation, a thick organic layer with high insulation capacities as well as the thermally induced chimney effect (Wakonigg, 1996). Investigated are three talus slopes with permafrost in the Swiss Alps that differ with regard to elevation level, talus material, humus characteristics and vegetation composition as well as the mean annual air temperatures. Aim is to achieve a deeper understanding of the factors determining the site-specific thermal regime, as well as the spatially limited and temporally highly variable permafrost occurrences in vegetated talus slopes. Focus is not solely on the question of why permafrost exists at these sites, but also why permafrost does not exist in the immediate surroundings. To detect the temporal variability and spatial heterogeneity of the permafrost occurrences, electrical resistivity tomography monitoring, seismic refraction tomography monitoring, and quasi-3D ERT were applied. To determine the ground thermal regime, air-, ground surface-, and humus temperatures, as well as temperatures within vents of the chimneys were recorded. Furthermore, humus characteristics (thickness, -temperature and -moisture) were mapped in permafrost-affected slope areas and in the immediate surroundings. To test the correlation between solar radiation, permafrost distribution, and humus/vegetation composition, digital elevation models were used to calculate the income of solar radiation. The areal extent of the permafrost bodies coincide precisely with slope sections where the organic layer is thickest, a consistent moss cover is present, and where temperatures at the transition between humus layer and talus material are lowest. The interaction of factors driving the ground thermal regime turned out to be more complex than assumed with differences between the investigated sites. Besides convective heat transport of the chimney effect, conductive heat flow within the humus layer strongly influences the ground thermal regime. Supercooling of the talus material in winter and autumn is aggravated by a high thermal conductivity of the organic material under frozen and wet conditions. The preservation of permafrost is favoured by the high insulation capacity of dry organic material in summer and by a prolonged zero-curtain period of up to 3 months - driven by high water-storage capacity of the organic material - that buffers the propagation of warm temperatures into the subsurface in spring. The income of solar radiation at the foot of the slope does not state a major driving factor for the occurrence of permafrost. Variability is low between areas with and without permafrost. In fact, differences were detected upslope, below the rock-walls, with summer-values being lowest in areas above the permafrost occurrences. It must be assumed that this affects the thermal circulation of the chimney effect during summer and favours the persistence of frozen ground in spatially limited slope areas.

Schwindt, Daniel; Kneisel, Christof

2013-04-01

2

Paediatric talus fracture.  

Science.gov (United States)

Paediatric talus fractures are rare injuries resulting from axial loading of the talus against the anterior tibia with the foot in dorsiflexion. Skeletally immature bone is less brittle, with higher elastic resistance than adult bone, thus the paediatric talus can sustain higher forces before fractures occur. However, displaced paediatric talus fractures and those associated with high-energy trauma have been associated with complications including avascular necrosis, arthrosis, delayed union, neurapraxia and the need for revision surgery. The authors present the rare case of a talar neck fracture in a skeletally immature young girl, initially missed on radiological review. However, clinical suspicion on the part of the emergency physician, repeat examination and further radiographic imaging revealed this rare paediatric injury. PMID:22605852

Byrne, Ann-Maria; Stephens, Michael

2012-01-01

3

Reef talus: A popular misconception  

Science.gov (United States)

Reef fronts have traditionally been regarded as comprising debris derived by contemporaneous erosion of 'the reef'. However, evidence from wave transport indicates that on present-day reefs the bulk of the debris generated in this way accumulates in the back-reef area, with only finer-grained sediment carried off-reef by retreating flows or by overwash. Nevertheless, in contrast to this observation, 'fore-reef' debris slopes are commonly considered "characteristic" of Phanerozoic reefs. This apparent error reflects the conflation of processes defining contemporary growth and accretion of the reef, and the corresponding long-term accretion of the carbonate platform on which it rests. Present-day reefs are commonly (although not exclusively) additions to long-lived carbonate platforms. Growth of the latter is intermittent and has been moderated by changes in sea-level that, for recent reefs, have been on time scales of less than 100 ka. During low sea-level stands, growth ceases or is translated downslope and earlier deposits are subject to lithification and subaerial erosion. Similar changes are applied on a larger scale to the aggrading growth of carbonate platforms, but the bulk accretion of these includes quite different processes and reflects far longer timescales. During low sea-level stands, the margins of platforms commonly become unstable, with instability reflected in slope failure and in the shedding of blocks, ranging from metres to kilometres in diameter, associated with the generation of debris flows and turbidites. It is argued that these are the materials that are commonly described as 'reef talus' in ancient structures, although their formation is largely independent of any contemporary reef growth. Difficulties arise where 'the reef' and 'the platform' are treated as a single functional entity. It is important to recognize the conceptual distinction between them, 'reef talus' is a misleading description of the debris predominantly generated by platform erosion and slope failure.

Braithwaite, Colin J. R.

2014-01-01

4

Fracture Bilateral Talus in Children  

Directory of Open Access Journals (Sweden)

Full Text Available Talar body injuries are rare, particularly in children. To our knowledge, there has not been a single case report of bilateral talus fracture in a child till date. We report two cases of fracture bilateral talus in children. The first case is of a fracture separation of the distal tibial epiphysis and a fracture of the body of the talus with subluxation of ankle on right side and a fracture neck of talus on left side. The second is fracture bilateral talus with epiphyseal injury of left distal tibia. A minimal or undisplaced fracture of talus is less likely to undergo avascular necrosis than a displaced fracture but even with optimal treatment, avascular necrosis may still occur. It is of prime significance that these fractures should be diagnosed well in time to avert complications. Therefore an appropriate length of follow-up is required.

Vinit Verma

2013-08-01

5

Polli talus tehakse maailmatasemel kultuuri / Kaire Korpe  

Index Scriptorium Estoniae

Polli talu perenaine Marika Blossfeldt korraldab kolmandat suve oma talus kursusi, loenguid ja tantsuetendusi. Viimased kolm nädalat olid Polli talus õppelaagris koreograafid Baltimaadest ja Ida-Euroopast

Korpe, Kaire

2001-01-01

6

Talus fracture management.  

Science.gov (United States)

Talar head and fracture injuries are not easily recognized and can create significant long-term disability when missed. Careful investigation of any injury about the ankle requires both clinical and radiographic examination. A computed tomography scan is extremely helpful in diagnosing and treating talus fractures. Displaced fractures require open reduction of the major joint surfaces and internal fixation. Prolonged non-weight bearing and immobilization is the norm. Despite aggressive management, complications involving avascular necrosis and posttraumatic arthritis to both the subtalar and tibiotalar joints occurs frequently. PMID:19013400

Early, John S

2008-12-01

7

[Talus partitus. A case report].  

Science.gov (United States)

An ankle bone consisting of several fragments is a rare anatomical variant of the talus, in the literature described as talus partitus or frontal split. On radiographs or CT scans it presents as two or more relatively large fragments. The term talus partitus is sometimes incorrectly used for an accessory bone that occasionally develops behind the ankle bone and is called os trigonum. Talus partitus is an unusual developmental anomaly in which the talus is partitioned although it ossifies from a single centre. The cause of its split has not been explained although this may also be due to a previous unrecognized injury. In the Slovak medical literature no report of this anomaly has been found. Here we resent the case of a 30-year-old man in whom the ankle bone split was an incidental finding. This patient also had ipsilateral developmental dysplasia of the hip. This is the first report of a patient with the two concurrently found anomalies. PMID:22405555

Chandoga, I; Vajcziková, S

2012-01-01

8

Closed total talus dislocation: a case report.  

Science.gov (United States)

Total dislocation of the talus is caused by a high-energy trauma, that dislocates the talus from all its surrounding articulations. Most cases reported are open talus dislocations; closed dislocations are rarely seen. Complications include avascular necrosis, posttraumatic osteoarthritis and infection. The vascularisation of the talus is delicate and the soft tissue attachments surrounding the talus are important for the blood supply. Closed talus dislocations, closed reduction and careful surgical dissection in case of open reduction respect more soft tissue attachments and potentially reduce the incidence of avascular of necrosis. We describe the case of a 46-year old male patient who sustained a closed total dislocation of the right talus associated with small fractures of the lateral and medial malleolus. The talus could not be reduced by closed means. The malleolar fractures were treated by open reduction and internal fixation. PMID:22308633

Heylen, Steven; De Baets, Thierry; Verstraete, Patricia

2011-12-01

9

Surgical approaches to the talus.  

Science.gov (United States)

Surgical approaches to the talus should allow access for fracture fixation, resection of osteophytes, treatment of osteochondral lesions, removal of painful os trigonum, and resection of hindfoot coalitions. This article describes the specific approaches to these conditions as well the structures at risk during surgery. PMID:15498701

Weinfeld, Steven B

2004-12-01

10

Osteogenic sarcoma of the talus  

International Nuclear Information System (INIS)

Observation presenting the interest due to rare localization of osteogenous sarcoma (talus) detected in an elderly patient of 62 years old as a primary malignant tumor is presented. Metastases in distal epimetaphysis of a tibial bone are detected in roentgenograms and scintigrams with 99mTc pyrophosphate

11

[Posterior dislocation of the talus].  

Science.gov (United States)

This report presents a rare case of an open total talar extrusion. The patient was treated by reduction and transarticular Kirschner-wire fixation of the talus, suture of an associated Achilles tendon rupture and plaster cast immobilisation. The plaster cast and Kirschner wires were removed after 6 weeks. At 10 weeks after injury, the patient started to walk with full weight-bearing of the operated extremity. At 18 months after injury, the patient was free from subjective complaints, with persisting slight restriction of ankle dorsiflexion range of motion and recurrent perimalleolar oedema. Neither MRI nor radiographic examination showed any avascular necrosis of the talus. The authors discuss the aetiology, diagnosis, therapeutic options and the most serious complications of this injury. PMID:24750970

Sebesta, P; Hach, J; Tlustý St, Z

2013-01-01

12

Osteochondral Allograft of the Talus  

Science.gov (United States)

Osteochondral lesions of the talus are being recognized as an increasingly common injury. They are most commonly located postero-medially or antero-laterally, while centrally located lesions are uncommon. Large osteochondral lesions have significant biomechanical consequences and often require resurfacing with osteochondral autograft transfer, mosaicplasty, autologous chondrocyte implantation (or similar methods) or osteochondral allograft transplantation. Allograft procedures have become popular due to inherent advantages over other resurfacing techniques. Cartilage viability is one of the most important factors for successful clinical outcomes after transplantation of osteochondral allografts and is related to storage length and intra-operative factors. While there is abundant literature about osteochondral allograft transplantation in the knee, there are few papers about this procedure in the talus. Failure of non-operative management, initial debridement, curettage or microfractures are an indication for resurfacing. Patients should have a functional ankle motion, closed growth plates, absence of cartilage lesions on the tibial side. This paper reviews the published literature about osteochondral allograft transplantation of the talus focusing on indications, pre-operative planning, surgical approaches, postoperative management, results and complications of this procedure.

Bisicchia, Salvatore; Rosso, Federica; Amendola, Annunziato

2014-01-01

13

Chance fracture of the talus and calcaneum.  

Science.gov (United States)

Combined talus and calcaneum fractures are rare in themselves. We report the case of an unusual fracture pattern of the talus and calcaneum in an otherwise, healthy 17-year-old male. Plain radiographic images of the foot revealed a fracture through the neck of the talus. Additional computed tomography imaging showed the fracture line extending through the talus and entire calcaneum. The fracture was open and associated with rupture of the tibialis anterior and extensor hallucis longus tendons. The patient underwent debridement with open reduction and internal fixation of the talar component of the fracture using 2 screws. The calcaneal component was treated conservatively. The soft tissue injuries to the 2 tendons were also repaired. The patient made good progress with this management. PMID:23621978

Lancaster, Sarah; Harries, William

2013-01-01

14

Lopsakalt rahvuslik mood Pulga talus / Tanel Veenre  

Index Scriptorium Estoniae

Eesti Moekunstnike Ühenduse näitus "Lillemotiiv moevormil" Eesti Vabaõhumuuseumi Pulga talus. Osalevad Anne Metsis, Anneliis Vabul, Diana Denissova, Monika Kisand, Juta Piirlaid, Anu Hint ja moekunsti õppejõud Yumiko Okazaki Jaapanist. Eksponeeritud rõivamudelid on kaunistatud rahvuslikest tikanditest inspireeritud stiliseeritud kujunditega

Veenre, Tanel, 1977-

2009-01-01

15

Magus suvelõpp Saare talus / Kaja Kurg  

Index Scriptorium Estoniae

Saare talus Vändra lähistel Lüüste külas kasvatavad omanikud Harri Poom, Aivar ja Kaja Saar nii kilehoonetes kui avamaal mitmeid lõunamaa vilju, mis esindatud mitmete sortidega. Saare-Tõrvaaugu aiand pakub õppepäevadel degusteerimiseks meloneid, arbuuse, viinamarju, tomateid, kartuleid.

Kurg, Kaja, 1959-

2011-01-01

16

Vanad sõbrad: Poola president õhtustas Ärma talus  

Index Scriptorium Estoniae

President Toomas Hendrik Ilves võõrustas 28. märtsil 2011 Viljandimaal Ärma talus Poola presidenti Bronislaw Komorowskit. Poola riigipea abikaasa Anna Komorowska ja proua Evelin Ilves külastasid Tallinnas ka lastekirjanduse keskust, kus esitleti raamatut "Väike Chopin" ning tegid ekskursiooni Tallinna vanalinnas

2011-01-01

17

Posttraumatic avascular necrosis of the talus.  

Science.gov (United States)

Avascular necrosis of the talus is one the most challenging problems encountered in posttraumatic reconstruction of the hindfoot. Since the first description of the talus injury in 1608 by Fabricius of Hilden, our knowledge of the talar anatomy, injuries, sequelae, and management has increased significantly. Adequate knowledge of the etiology, the extent of the disease, and the degree of patient symptoms are required to determine optimal treatment. PMID:19013407

Léduc, Stephane; Clare, Michael P; Laflamme, G Yves; Walling, Arthur K

2008-12-01

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Expandable Membrane Ground Anchors in Talus  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Expander Body (EB) tieback anchors were installed in talus material in Glenwood Canyon and evaluated as to their ease of installation and performance. The EB consists of a steel tube with thin, folded walls which is expanded in the soil by injection of cement grout. The EB system can be expanded in coarse, angular materials at high pressure without rupturing. It, therefore, can be successfully used to limit grout take in permeable materials. Based on the results of this study, the EB sy...

United States Department Of Transportation, Federal Highway Administration

1989-01-01

19

14C age of the talus deposits distributed in the middle course of the river Obirashibe, northern Hokkaido, Japan  

International Nuclear Information System (INIS)

The samples for the determination of the 14C age of the talus deposit were collected from Takinoshita, Obira town, Rumoe district, Hokkaido. The stratigraphy and the sequence of deposits were as follows: 1) T1 terrace deposit, 2) mud flow deposit, 3) T2 terrace deposit (lake deposit), 4) talus deposit, 5) large rock slide. The obtained 14C age of 23750+-620 Y.B.P. showed the lower limit of talus deposit and the upper limit of lake deposit. The 14C age 29060+-2180 Y.B.P. of the mud flow deposit was regarded as the lower limit of the lake deposit. The formation of lake deposit was estimated to be in the period of 29000-24000 years ago. The obtained age showed good correspondence with the results of pollen analysis which indicated the climate-mitigating period in last glacial epoch. Consequently, the lake deposit of this area was regarded as to be formed in the similar weather condition mentioned above. Talus deposit contained wood pieces in its basement, but fossil pollens and the relics of lage plants were not found. This means that the talus deposit was formed continuously without vegetation. The weather condition in which the deposits were formed are as follows. 1) Mud flow deposit was formed by the large collapse of mountain side slope in the last stage of [Biraotori moor period]. 2) Lake deposit was formed in the period of weather mitigation of 29000-26000 years ago. 3) Talus deposit was formed under the cold and dry periglacial condition 24000 years ago and on. (Ishimitsu, A.)

20

Closed total talus dislocation without fracture: a case report.  

Science.gov (United States)

Total dislocation of the talus from all of its joints is a rare injury specially when the talus and malleoli are not fractured and frequently it is as a result of a high-energy trauma. It usually leads to degenerative changes in neighboring joints and frequently avascular necrosis is a predictable outcome. We present a case of total talus dislocation because of a high-energy trauma in association with other major fractures resulting from a fall from height, but no fracture could be detected in the talus and any of malleols. Closed reduction was unsuccessful and we performed open reduction. At 6 month post operation follow-up, the talus didn't show subluxation and avascular necrosis could not be detected. PMID:20062649

Sharifi, Seyed Reza; Ebrahimzadeh, Mohamad H; Ahmadzadeh-Chabok, Hosein; Khajeh-Mozaffari, Javad

2009-01-01

 
 
 
 
21

Simultaneous Bilateral Fracture Dislocation of the Talus: A Case Report  

Directory of Open Access Journals (Sweden)

Full Text Available Introduction: Fracture - dislocations of the talus are typically due to high energy injuries. Displaced fracture - dislocations of the talus have poor outcomes in general and complications are common. Although talar fracture is common and comprises the second most common tarsal fracture, bilateral fracture - dislocations of the talus are rare. Not many reports regarding the subject can be found in the literature.Case Presentation: We report a patient with bilateral fracture - dislocations of the talus treated by open reduction and internal fixation. This patient was a 25 year-old man who sustained bilateral fracture - dislocation of the talus due to a motor vehicle accident.Conclusions: Bilateral talar fracture - dislocation is rare. The surgical approach discussed together with the pathomechanics of this injury can yield good short term results.

Mohammad Hosein Taraz-Jamshidi

2013-09-01

22

Tibiotalar arthrodesis for injuries of the talus  

Directory of Open Access Journals (Sweden)

Full Text Available Background: Fracture-dislocation of the talus is one of the most severe injuries of the ankle. Opinion varies widely as to the proper treatment of this injury. Since Blair?s original description of the tibiotalar fusion in 1943, there is little mention in the literature of his method. The present study reports the results of tibiotalar arthrodesis with modification in Blair?s technique. Materials and Methods: Eleven cases of modified Blair ? s tibiotalar arthrodesis were retrospectively studied. The average age was 32.4 years (range, 26-51 years. Six patients had posttraumatic avascular necrosis; five had neglected fracture-dislocation of the talus. Results: The mean followup is 8 years (range 3-12 years. Tibiotalar fusion was achieved in all the ankles at an average of 20.5 weeks (range 16-28 weeks. Nine cases having 15°-20° tibiopedal motion had excellent results and two ankles having 10°-15° of tibiopedal motion had good result. Conclusion: We achieved good long term results with tibiotalar arthrodesis with modification in Blair technique. The principal modification in the present study is retention of the talar body while performing arthrodesis with anterior sliding graft. The retention of the talar body provides intraoperative stability and in the long term, the retained talar body shares the load transmitted to the anterior and middle subtalar joints thus resulting in improved hind foot function and gait.

Singh Jaswant

2008-01-01

23

Closed total talus dislocation without fracture: a case report  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Total dislocation of the talus from all of its joints is a rare injury specially when the talus and malleoli are not fractured and frequently it is as a result of a high-energy trauma. It usually leads to degenerative changes in neighboring joints and frequently avascular necrosis is a predictable outcome. We present a case of total talus dislocation because of a high-energy trauma in association with other major fractures resulting from a fall from height, but no fracture could be detected i...

Sharifi, Seyed Reza; Ebrahimzadeh, Mohamad H.; Ahmadzadeh-chabok, Hosein; Khajeh-mozaffari, Javad

2009-01-01

24

Analysis of Cliff Retreat and Rockfall Talus Deposition Patterns through Geomorphologic Analysis, Physical Modeling and Numerical Simulation  

Science.gov (United States)

During storms or earthquakes, Rockfall is a frequent mishap in mountain areas. Reviewing the histories of rockfall disasters in Taiwan, as the cluster of rockfall consists of simultaneous movements, it might cause serious disasters, which had occurred in Central Cross-lsland highway, Nanyali, Maijin road of Jilong City, Taidong Zhiben river, and the landslide-blocked lake of Longquan river. Such disasters have threatened the safety of life and need to be concerned. Whereas, this research study the relationship of talus deposits development induced by various cliff retreat types in Hungtsaiping rockfall area. In the present paper, we analyzed the geomorphologic changes of cliffs and talus deposits based on the findings from the topographic maps and interpreting aerial photos. The physical modeling was then carried out which was helpful to understand the relationship of cliff retreat and talus deposition patterns. The results of physical modeling were compared with those produced by numerical simulation (Application of discrete element method by PFC3D 3.0 program) so that the correctness of the numerical simulation could be justified. Subsequently, calibrated numerical methods adopted in the small-scale model were used to simulate the full-scale model. The simulation results should be as close to reality as much as possible. Finally, the shape function of talus deposition topographic patterns and the cluster of rockfall influence area for various cliff retreat types. Furthermore, the shape function reflects the deposits characteristic of main factors (the factor includes the slope angle of movement area, the fall height, rockfall amount, the joints spacing, the mean roughness height of deposition area, cliff retreat type) through the full-scale model simulation and physical modeling tests. The shape function are helpful for rockfall hazard zonation and developing reasonable and scientifically sound guidelines while giving land use assessment and protection engineering sited in rockfall area. Keywords: rockfall disaster, cliff retreat, talus deposits, geomorphologic analysis, physical modeling, numerical simulation, shape function

Lin, Ming-Lang; Lo, Chia-Ming; Lien, Tsun-Kai

2010-05-01

25

Reimplantation of a totally extruded talus: a case report.  

Science.gov (United States)

Total extrusion of the talus is an unusual injury, and the obvious risks of reimplantation of the extruded bone include infection and avascular necrosis. In this article, the authors present the case of a 34-year-old man who sustained an open ankle injury with complete extrusion of the talus. The talus was recovered at the scene of the accident, and subsequently reimplanted along with ankle stabilization with pins and an external fixator. At 6 weeks following the osseous surgery, final soft tissue reconstruction with a suralis flap was performed. At 3 years after the injury, radiographs revealed spontaneous fusion of the tibiotalar and subtalar joints, and the clinical examination and history indicated satisfactory weight-bearing function of the involved foot and ankle. The definitive treatment of this serious lower extremity injury remains controversial, and the use of large allogeneic bone grafts, vascularized bone grafts, and tibiocalcaneal fusion, as well as reimplantation of the extruded talus have been recommended. PMID:20015667

Mnif, Hichem; Zrig, Makram; Koubaa, Mustapha; Jawahdou, Rafik; Hammouda, Imed; Abid, Abderrazek

2010-01-01

26

A rare case of Aneurysmal Bone Cyst of the Talus  

Directory of Open Access Journals (Sweden)

Full Text Available Talus bone is an unusual location for Aneurysmal Bone Cysts. Although considered benign, it has a locally aggressive behavior making it difficult both from diagnostic and therapeutic point of view. It becomes even more challenging when unusual sites are encountered. We report a rare and challenging case of Aneurysmal Bone Cyst in Talus in a young male patient who was treated with curettage and bone grafting. [Cukurova Med J 2014; 39(4.000: 932-937

Sandesh S. Madi

2014-08-01

27

Intra-osseous lipoma of the talus: a case report.  

Science.gov (United States)

Intra-osseous lipomas are rare benign tumours. We report one such case in the talus of a 60-year-old man. The patient underwent curettage and bone grafting. At the 22-month follow-up, radiographs of the talus showed dense sclerosis with multiple cortical breaks in the anterior process and no evidence of local recurrence or avascular necrosis. The patient had a painless ankle joint with normal range of movement. PMID:22535830

Rajmane, Shivkumar; Kulkarni, P N; Patil, Adish; Patil, V C; Rajmane, Vijaya

2012-04-01

28

Treatment of osteochondral defects of the talus.  

Science.gov (United States)

This review article provides a current concepts overview of osteochondral defects of the talus, with special emphasis on treatment options, their indications and future developments. Osteochondral defects of the talar dome are mostly caused by a traumatic event. They may lead to deep ankle pain on weight-bearing, prolonged swelling, diminished range of motion and synovitis. Plain radiographs may disclose the lesion. For further diagnostic evaluation, computed tomography (CT) and magnetic resonance imaging (MRI) have demonstrated similar accuracy. Computed tomography is preferred for preoperative planning. Treatment options are diverse and up to the present there is no consensus. Based on the current literature, we present a treatment algorithm that is mainly guided by the size of the lesion. Asymptomatic or low-symptomatic lesions are treated nonoperatively. The primary surgical treatment of defects up to 15 mm in diameter consists of arthroscopic debridement and bone marrow stimulation. For large cystic talar lesions, retrograde drilling combined with a bone graft is an important alternative. In adolescents or in (sub)acute situations, in which the fragment is 15 mm or larger, fixation of the fragment is preferred. Osteochondral autograft transfer and autologous chondrocyte implantation (ACI), with or without a cancellous bone graft, are recommended for secondary cases as well as large lesions. PMID:19046699

van Bergen, C J A; de Leeuw, P A J; van Dijk, C N

2008-12-01

29

Mixed approach (numerical modeling / equilibrium analysis) for slope stability analysis: development and application to the dams and open pit mining; Une approche mixte (numerique/equilibre limite) pour le calcul de stabilite des ouvrages en terre: developpement et application aux barrages et talus miniers  

Energy Technology Data Exchange (ETDEWEB)

The determination of the sliding surface of slope (dam, slope natural..) is one of the important and complicated problems in geotechnics. The Analyze of stability by the methods of Limit Equilibrium like the method of slices are the most used methods. They are able to determine a safety factor for a geometrically defined failure surface. These methods well adapted to the homogeneous mediums, have been developed a lot but they do not integrate the basic relations of mechanics (stress-strain). The numerical methods are better adapted to mediums having more complexity (effect of water, seismicity, fracturing,..). But, they are seldom used to determine a sliding surface and a safety factor. Each family offers appreciable advantages in the analysis of slope stability. For that purpose, we have developed a method that combines the advantages of the numerical methods as well as those of Limit Equilibrium allowing obtaining a slip surface determined by the calculated constraints. This slip surface may be imposed or better optimized, thus providing a minimal safety factor. Methods of operation research are used to obtain this surface. They are search methods by level, dynamic research.. or both at the same time. We integrated these developments in an existing computer code based on the method of Finite Differences known as FLAC. The stresses are determined for a linear behavior and for nonlinear. Interfaces and graphic tools are also produced to facilitate the analysis of stability. The validity of this approach was carried out for a standard case of slope, we analyzed and compared the results with the methods of Limit Equilibrium. The parametric study shows that this approach takes account of different parameters, which influences stability. We also kept a particular place for the application on real cases presenting slopes of different nature (dams, mining slops,...). (author)

Kourdey, A.

2002-09-15

30

[The results of the surgical treatment for total talus dislocation].  

Science.gov (United States)

The purpose of the research was to study the results of surgical treatment for rare and severe injury, such as the total talus dislocation and determine the causes of complications. The study was based on findings from dynamic observations of 15 patients with this type of musculoskeletal pathology, who underwent surgical treatment in three multi-profile medical facilities of Kutaisi during 2005-2013 years. Statistical results were as follows: men - 12, women -3. Patients age range 29-51 years. Trauma was mainly caused by motor vehicle accidents and falls. Three patients had a sports injury. There were 6 cases of an open dislocation of the talus. Complex surgical treatment strategy has been discussed. The author has studied the early and late complications of the surgical reduction of total talus dislocation during treatment and rehabilitation periods. Based on the observations and the data obtained from the reviewed literature we have concluded that outcomes of the surgical treatment of total talus dislocation in most cases are not satisfactory and often become the cause of limb dysfunction and repeated reconstructive surgery due to the later developed aseptic necrosis and arthrosis. Given the anatomical specificity of the talus, satisfactory results of the treatment are directly depended on a timely surgical intervention after the trauma as well as on a comprehensive postoperative rehabilitation. PMID:24632641

2014-02-01

31

Osteonecrosis of the talus after talonavicular arthrodesis: a case report and review of the literature.  

Science.gov (United States)

Avascular necrosis of the talus is a well-documented complication following fractures, although less is known about this complication following reconstructive foot and ankle surgery. Knowledge of the blood supply of the talus is necessary for surgical dissection of the talus, especially when the approach traverses the sinus tarsi. In this article, we describe a rare case of avascular necrosis of the talus after talonavicular arthrodesis, using a medial surgical approach. PMID:21406330

Hermus, Joris P S

2011-01-01

32

Bilateral talus fracture dislocation: is avascular necrosis inevitable?  

Science.gov (United States)

Bilateral simultaneous fracture dislocation of the talus is a very rare injury. It occurs usually following high-velocity injuries. We report a 45-year-old man who presented with bilateral talar fracture dislocation following a heavy stone falling on him. On his right side, he had open talus dislocation with lateral process fracture and on his left side he had closed talar neck fracture dislocation. He underwent immediate debridement and external fixator application for his right side and open reduction and internal fixation for his left talus. At the end of 34?months' follow-up, he was able to walk up to 2?km without pain. His ankle range of movements were restricted bilaterally. Radiographs revealed bilateral avascular necrosis with right side showing complete collapse. We present this case for its rare presentation of bilateral talar fracture dislocation with bilateral avascular necrosis with sequential radiographs. PMID:25155493

Balaji G, Gopisankar; Arockiaraj, Justin

2014-01-01

33

Ephemeral skin-flows on talus affected by permafrost degradation (Corral del Veleta, Spain)  

Science.gov (United States)

In mountain environments, talus formed at the foot of valley sides are frequently affected by hillslope processes, such as skin-flows. The main characteristic of this type of flow is that it only causes the movement of a thin layer of soil, regolith or debris over an inclined plane parallel to the topographical surface of the talus. Some examples of this movement have already been described (Rapp, 1960; Akerman; 1984; White, 1981, Benedict, 1970; Jahn, 1967; Söderman, 1980; Lewkowicz, 1988, Harris, 1987). The causes of the formation of these movements vary, but in general they have been linked primarily with rapid snow melt and/or with degraded permafrost levels (Jahn, 1967; Nyberg, 1991; Rapp and Nyberg, 1988; Strömquist, 1985; Hall, 1985; Thorn, 1988; McRoberts and Morgenstern, 1974, Caine, 1976). Within this context, the aims of this paper are: first, to present and describe the characteristics and temporal and geomorphological evolution of a series of skin-flows which have occurred on the talus which lies at the foot of the Corral del Veleta glacial cirque, and second, to analyze the factors that appear to have triggered them. The Pico del Veleta mountain (3398 m a.s.l.) is one of the main summits in the Sierra Nevada Massif, a group of mountains forming part of the Cordilleras Béticas, in SE Spain (37°03´N, 3°22´W). The Corral del Veleta is a glacial cirque on the northeastern face of the Pico del Veleta, c. 600 m long in a NW-SE direction, with a head is formed by a steep wall which falls more than 250 meters to meet with a wide and irregular talus. The cirque headwall is composed of metamorphic rocks (mainly micaschist), lined up in structural steps or shelves tilted towards the NNW. One of these shelves forms the base of the cirque, on which a series of moraine ridges, tardiglacial or from the Little Ice Age, which close off the cirque towards the North (Gómez et al., 2001). The talus is formed from abundant debris resulting from weathering (gelifraction) and hillslope dynamics (rockfall activity) which affect the headwall (Gómez et al., 2003) and is formed mainly by various talus cones which are irregular in shape and stepped as the accumulated debris covers the remains of the stepped structural shelves which were not destroyed by the glacial erosion. Although the talus debris is basically made up of blocks, it is important to point out the abundant presence of fine material, produced by the weathering of the micaschist. (Castillo and Fedeli, 2002; Gómez et al., 2003). Field work carried out over the last ten years (1998-2008) has allowed observation of the triggering and formation in some years of various skin flows in different sectors of the talus, especially in the late summer of 2002 when four skin flows occurred. Within this timeframe monitoring and analysis of this kind of skin flow has been carried out. On the one hand, the description of the morphology, morphometry and sedimentology of each flow has been completed with the production of detailed geomorphological mapping and from sedimentological analysis. The geomorphological mapping has, in turn, allowed the observation of the geomorphological evolution of the flows from the time they occurred. On the other hand, a study has been made of the variables or factors which seem a priori to control the triggering of the skin flow landslips: the snow melt and the presence of permafrost in the detrital talus. The former has been monitored through photographic control of the snow cover at the end of the summer season, so that for each date analyzed a map was obtained of the snow cover, superimposing in turn the location of the skin flows at that date. A GIS processing of the different snow covers has also allowed a map to be produced with the areas of maximum summer snow cover, which was compared with the sites of the skin flow landslips. The existence of permafrost and its presence in the detrital slope has been detected through the monitoring of the ground temperature (BTS measurements, miniature temperature dataloggers) and geophysical surveys (Gó

Tanarro, L. M.; Palacios, D.; Zamorano, J. J.; Gómez, A.

2009-04-01

34

President Ilves võõrustas Ärma talus Poola riigipead / Raimo Poom  

Index Scriptorium Estoniae

Poola president Lech Kaczynski ja tema abikaasa Maria Kaczynska külastasid president Toomas Hendrik Ilvest ja proua Evelin Ilvest Ärma talus Viljandimaal. Eesti riigipea rõhutas kohtumisel peamiselt Euroopa Liidu ja NATO teemasid ning väljendas rahulolematust Ignalina tuumajaama projekti kulgemise viisi ja tempo üle

Poom, Raimo

2008-01-01

35

Closed total dislocation of talus without any accompanying fractures.  

Science.gov (United States)

Total talar dislocation, ie, disruption of the talus from the calcaneus, navicula, and tibia, is a rare and severe injury. We present a case of closed peritalar dislocation without any accompanying fractures and, thus, discuss the conflicts encountered in this rare injury. A 25-year-old male patient presented with severe pain, swelling, and deformity in his right ankle within 30 minutes of a fall from a height. There were no wounds around the ankle. Radiographs revealed that the talus was disrupted from the calcaneus, navicula, and tibia moving in the anterolateral direction. No accompanying fractures were seen in the talus or in surrounding bones. After an unsuccessful closed reduction attempt, a further decision was open reduction. It was seen that the interposed joint capsula was preventing reduction. After reduction, stability of the ankle was checked and found to be satisfactory, so no fixation material was used. It has been 2 years since the first injury, and the patient is functioning well, with no pain. The ankle has the same range of motion as the unaffected side. No sign of an avascular necrosis or sclerosis is seen on the final radiographs. Closed total dislocation of the talus without any accompanying fractures is a rare entity. The injury is open to various important complications, such as avascular necrosis, infection in patients with open wounds, and arthritic changes. To achieve a good outcome, early reduction of the dislocation has key importance. PMID:23328856

Gursu, Sarper; Sahin, Vedat; Demir, Bilal; Yildirim, Timur

2013-01-01

36

Raba talus tähistati "Vallatute kurvide" juubelit / Tõnis Tõnisson  

Index Scriptorium Estoniae

Raplamaal Mahtra külas Raba talus organiseeris Tallinnfilmi mängufilmis "Vallatud kurvid" keskset kaksikrolli mänginud Terje Luik filmi 50. juubelit (film esilinastus 28. 12. 1959) tähistava ürituse. Terje Luige elust. Muuseumitoas on väljas Saima Randjärv-Berlokko Kehtna kunstide koolis juhendatavate laste filmiainelised joonistused

Tõnisson, Tõnis, 1945-

2009-01-01

37

A Case Report of Sequela of Operation of Talus Osteonecrosis  

Directory of Open Access Journals (Sweden)

Full Text Available Objective : The clinic study or report about Oriental Medical treatment about osteonecrosis is very insufficient. Therefore, we report a case about a sequela of operation of talus osteonecrosis treated by Oriental Medical treatments. Methods : The patient was managed by bee venom and Carthami Flos Herbal-Acupuncture, Sa-am and body acupucture, oxibustion, physical theraphy and herbal medicine. We evaluated the patient through Visual Analogue Scale(VAS. Results : After 25 days of treatment, the patient showed that clinical symptoms was decreased and VAS changed from 10 to 2. Conclusion : In this case, Oriental Medical treatments for a sequela of operation of talus osteonecrosis was effective. But further studies are required to confirm the effect of these methods

Choi Sung-Hun

2006-02-01

38

Ostéome ostéoïde du talus gauche chez l'enfant  

Digital Repository Infrastructure Vision for European Research (DRIVER)

La localisation de l'ostéome ostéoïde au niveau de la cheville est rare. Nous rapportons le cas d'une jeune fille qui présentait un ostéome ostéoïde du talus gauche dont le diagnostic a été évoqué par la TDM et dont l'exérèse a été réalisée à ciel ouvert. L'examen histologique de la pièce a confirmé le diagnostic. Les suites opératoires ont été simples avec une disparition complète des douleurs sans recidives après un recul de 3 ans.

Mahmoudi, Abdelhalim; Bendahou, Mouhcine; Rami, Mohamed; Khattala, Khalid; Amarti, Afaf; Youssef, Bouabdallah; Afifi, My Abderrahmane

2013-01-01

39

Nonoperative treatment of closed total talus dislocation without fracture: A case report and literature review  

Science.gov (United States)

Complete dislocation of the talus not accompanied by a fracture is a very rare injury. Most cases reported are open talus dislocations; closed dislocations are rarely seen. The functional prognosis is poor due to osteonecrosis of the talus which develops in the majority of cases. We present a case of lateral dislocation of the left talus in a 29-year-old road accident victim, but no fracture could be detected in the talus and any of malleolus. Reduction of dislocation had been performed in emergency by external manipulation. At 1-year follow-up, the right ankle was pain free and stable. Motion was satisfactory: 15° dorsal flexion, 30° plantar flexion; the talus didn't show subluxation and avascular necrosis could not be detected.

Rhanim, Abdelkarim; Zanati, Rachid El; Younes Ouchrif; Hassani, Zouhir Ameziane; Kharmaz, Mohammed; Berrada, Mohammed Saleh

2014-01-01

40

[Computerized tomography of osteochondral diseases of the talus dome].  

Science.gov (United States)

The definition "osteochondritis dissecans" of the talus improperly includes a variety of diseases involving the chondral surface of the talus dome and the relative subchondral bone. To investigate the CT diagnostic potentials in the study of these conditions, 35 patients complaining of a "painful ankle" were examined with plain radiography and axial and direct paracoronal CT over a 2-year period. Twelve patients were then examined with double contrast CT arthrography with air and iodated contrast agents. CT diagnostic accuracy was assessed evaluating the following parameters: the presence and extent of the subchondral bone fragment, the presence of residual bone fragment attachment at the lesion base or its intraarticular dislocation, the presence of subchondral bone cysts, of chondral surface lesions and, finally, of capsular and ligamentous damage. All the patients with CT findings of osteochondral conditions of the talus dome were submitted to arthroscopic examination/treatment and/or surgical arthrotomy. Baseline CT exams accurately depicted all the lesions, except for early (grade I) lesions. Moreover, the administration of intraarticular contrast agent (CT arthrography) increased the diagnostic accuracy in articular cartilage studies. Therefore, the authors believe baseline CT on the orthogonal planes to represent an effective tool for the staging of osteochondral talar lesions and for accurate treatment planning. PMID:9122454

Ragozzino, A; Rossi, G; Esposito, S; Giovine, S; Tuccillo, M

1996-12-01

 
 
 
 
41

[Medial dislocation of the talus. Medium term evolution].  

Science.gov (United States)

Fifty-seven year old patient with open medial dislocation of the left talus, with suprasyndesmotic fracture of the fibula, due to indirect traumatism. The following were carried out: washing, cleaning the talus and the soft parts, Friedrich, reduction, fixing with Kirschner needles, suture of the deltoid ligament, and osteosynthesis of the fibula. There were neither surface nor deep post-operational infections. The patient underwent six weeks of immobilisation and spent three months on discharge. Two years later there were no radiological signs of avascular necrosis. In the osseous gammagraphy carried out 18 months after the lesion, partial avascular necrosis of the talus was observed. Three years after the lesion, the patient was able to carry out a normal life, without pain in repose but with pain whilst moving, and mobility with limitation of dorsoinflection (-20 masculine). Five and a half years after the lesion, the patient presented sinking of the talar dome due to avascular necrosis, with painful symptomatology whilst moving, and tibiofibular distal diastasis, which required ankle arthrodesis. PMID:19430516

García Mata, S; Hidalgo-Ovejero, A; Martínez de Lecea, F

2009-01-01

42

Considerations on the chronological and causal relationships between talus flatirons and palaeoclimatic changes in central and northeastern Spain  

Science.gov (United States)

Talus flatirons are relatively common landforms in arid and semiarid areas. They are frequent in the Duero, Tajo and Ebro Tertiary Basins in Spain. The generation of a flatiron requires the alternation of periods with a prevalence of accumulation processes followed by periods with a preponderance of erosion processes. In the three Tertiary basins considered here talus flatirons have been found in numerous places and up to five stages of slope evolution have been recognised in some locations. The second youngest stage (S 2) has been dated in several places in the Ebro and Duero Basins through 14C. The age of this stage ranges from 2529 ± 52 to 3590 ± 40 14C yBP. The third youngest stage (S 3) has yielded dates of 27,862 ± 444 radiocarbon years BP in the Ebro Basin, and 28,550 ± 130 14C yBP in the Duero Basin. S 4 has been dated in the Ebro Basin to 35,570 ± 490 14C yBP. The S 2 slope facets correspond to the Iron and Bronze Age Cold Stages. The S 3 and S 4 flatirons may be correlated with the Heinrich events H 3 and H 4. These dates may indicate that the accumulation periods on the slopes correspond to cold global events. The dates obtained for the stages S 3 and S 4 in the central and northeastern sectors of Spain and their good correlation with Heinrich events suggest that flatirons could be related to climatic sequences in the Upper Pleistocene and Holocene.

Gutiérrez, M.; Gutiérrez, F.; Desir, G.

2006-01-01

43

Arthroscopic treatment of post-traumatic cysts of the talus.  

Science.gov (United States)

We report on 9 patients with persistent ankle pain and radiographic evidence of a cystic lesion on the talus. All had a history of an inversion-type of ankle injury. Radiographs were initially negative, but a cyst developed about 6 months after the injury. Arthroscopic debridement revealed extrusion of viscid gelatinous material from the cyst. The cavity was arthroscopically abraded to bleeding base. Follow-up of these patients at an average of 26 months showed statistically significant improvement in terms of pain, swelling, stiffness, limp, and activity level. Bone grafting may not be necessary in the treatment of post-traumatic cysts. PMID:10705333

Ogilvie-Harris, D J; Sarrosa, E A

2000-03-01

44

Morphometric Changes in Talus of Club Foot A Gross Observation in Human Foetuses / Cambios Morfométricos en Talus del Pie Zambo, una Observación Macroscópica en Fetos Humanos  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Para su estudio morfológico fueron disecados ambos pies de seis fetos humanos de distintas edades, uno de los pies era zambo. Seis parámetros morfométricos fueron considerados para la comparación de graves alteraciones anatómicas en los pies normales y deformes; estos fueron: 1. Longitud máxima del [...] talus, 2. Dimensión longitudinal de la cabeza del talus, 3. Ancho troclear anterior, 4. Altura medial máxima del talus, 5. Cuello talar y ángulo calcáneo, 6. Ángulo talocalcáneo. Todos los fetos con pie zambo congénito tienen una deformidad similar del esqueleto del pie. Las anomalías graves observadas fueron el menor tamaño del talus del pie zambo, aumento de la desviación media y retraso en el crecimiento plantar, deformación de la cabeza y región del cuello talar. También se observó una subluxación medial plantar del hueso navicular, con un consecuente deformidad de las facetas articulares de la cabeza del talus. La uniformidad y consistencia de las anomalías anatómicas fueron los rasgos más llamativos en este estudio. Abstract in english Both the feet of six human foetuses of different age groups having unilateral club feet, were dissected for morphological study. Six morphometric parameters considered for comparing gross anatomical changes in normal and deformed feet, were 1-Maximum length of the talus, 2-Longitudinal dimension of [...] head of talus, 3-Anterior trochlear breadth, 4-Maximum medial talar height, 5-Talar neck and calcaneal angle, 6-Talocalcaneal angle. All the foetuses with congenital club feet have almost similar deformity of foot skeleton. The gross anomalies observed were the smaller size of club foot talus and increased medial and planter deviation of a stunted, misshapen head and neck region. A medial plantar subluxation of the navicular bone with a consequent deformity of the articular facets of the talar head was also observed. Uniformity and consistency of anatomical abnormalities were striking features in present study.

, Fazal-ur-Rehman; Nafis A, Faruqi.

2012-03-01

45

Morphometric Changes in Talus of Club Foot A Gross Observation in Human Foetuses Cambios Morfométricos en Talus del Pie Zambo, una Observación Macroscópica en Fetos Humanos  

Directory of Open Access Journals (Sweden)

Full Text Available Both the feet of six human foetuses of different age groups having unilateral club feet, were dissected for morphological study. Six morphometric parameters considered for comparing gross anatomical changes in normal and deformed feet, were 1-Maximum length of the talus, 2-Longitudinal dimension of head of talus, 3-Anterior trochlear breadth, 4-Maximum medial talar height, 5-Talar neck and calcaneal angle, 6-Talocalcaneal angle. All the foetuses with congenital club feet have almost similar deformity of foot skeleton. The gross anomalies observed were the smaller size of club foot talus and increased medial and planter deviation of a stunted, misshapen head and neck region. A medial plantar subluxation of the navicular bone with a consequent deformity of the articular facets of the talar head was also observed. Uniformity and consistency of anatomical abnormalities were striking features in present study.Para su estudio morfológico fueron disecados ambos pies de seis fetos humanos de distintas edades, uno de los pies era zambo. Seis parámetros morfométricos fueron considerados para la comparación de graves alteraciones anatómicas en los pies normales y deformes; estos fueron: 1. Longitud máxima del talus, 2. Dimensión longitudinal de la cabeza del talus, 3. Ancho troclear anterior, 4. Altura medial máxima del talus, 5. Cuello talar y ángulo calcáneo, 6. Ángulo talocalcáneo. Todos los fetos con pie zambo congénito tienen una deformidad similar del esqueleto del pie. Las anomalías graves observadas fueron el menor tamaño del talus del pie zambo, aumento de la desviación media y retraso en el crecimiento plantar, deformación de la cabeza y región del cuello talar. También se observó una subluxación medial plantar del hueso navicular, con un consecuente deformidad de las facetas articulares de la cabeza del talus. La uniformidad y consistencia de las anomalías anatómicas fueron los rasgos más llamativos en este estudio.

Fazal-ur-Rehman

2012-03-01

46

Morphometric Changes in Talus of Club Foot A Gross Observation in Human Foetuses / Cambios Morfométricos en Talus del Pie Zambo, una Observación Macroscópica en Fetos Humanos  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Para su estudio morfológico fueron disecados ambos pies de seis fetos humanos de distintas edades, uno de los pies era zambo. Seis parámetros morfométricos fueron considerados para la comparación de graves alteraciones anatómicas en los pies normales y deformes; estos fueron: 1. Longitud máxima del [...] talus, 2. Dimensión longitudinal de la cabeza del talus, 3. Ancho troclear anterior, 4. Altura medial máxima del talus, 5. Cuello talar y ángulo calcáneo, 6. Ángulo talocalcáneo. Todos los fetos con pie zambo congénito tienen una deformidad similar del esqueleto del pie. Las anomalías graves observadas fueron el menor tamaño del talus del pie zambo, aumento de la desviación media y retraso en el crecimiento plantar, deformación de la cabeza y región del cuello talar. También se observó una subluxación medial plantar del hueso navicular, con un consecuente deformidad de las facetas articulares de la cabeza del talus. La uniformidad y consistencia de las anomalías anatómicas fueron los rasgos más llamativos en este estudio. Abstract in english Both the feet of six human foetuses of different age groups having unilateral club feet, were dissected for morphological study. Six morphometric parameters considered for comparing gross anatomical changes in normal and deformed feet, were 1-Maximum length of the talus, 2-Longitudinal dimension of [...] head of talus, 3-Anterior trochlear breadth, 4-Maximum medial talar height, 5-Talar neck and calcaneal angle, 6-Talocalcaneal angle. All the foetuses with congenital club feet have almost similar deformity of foot skeleton. The gross anomalies observed were the smaller size of club foot talus and increased medial and planter deviation of a stunted, misshapen head and neck region. A medial plantar subluxation of the navicular bone with a consequent deformity of the articular facets of the talar head was also observed. Uniformity and consistency of anatomical abnormalities were striking features in present study.

, Fazal-ur-Rehman; Nafis A, Faruqi.

47

Combined ankle and talus fractures--a case report.  

Science.gov (United States)

A 50-year-old male patient sustained a supination-adduction type ankle fracture with an associated sagittal split fracture of the talus. The patient was treated initially in a short leg splint, and upon presentation to an orthopaedic surgeon, an external fixator was applied. After the soft tissue swelling improved enough to permit open reduction and internal fixation, the patient was brought back to the operating room for definitive treatment with removal of the external fixator and open reduction and placement of internal fixation. The patient's postoperative course was uncomplicated. At the 6-week follow-up visit, he was noted to have a radiographic Hawkin's sign in the dome of the talus. At 3 months postoperatively, he was weightbearing as tolerated with radiographic evidence of fracture healing, and his ankle range of motion was from 30° of plantar flexion to 15° of dorsiflexion. At 6 months postoperatively, the patient had no complaints and was ambulating in a regular shoe. His plantar flexion was 35° and his dorsiflexion was 15°. His subtalar motion was from 5° of eversion to 10° of inversion. He returned for his one-year follow-up doing well without complaints, and he had returned to his previous activities. PMID:24032619

Weatherall, Justin; Schwarzkopf, Ran; Sheskier, Steven

2013-01-01

48

CT for diagnosing fractures of the undersurface of the talus and mechanism of injury  

Energy Technology Data Exchange (ETDEWEB)

Talus fractures whose fracture lines extend to the subtalar joint, except fractures of the neck and the body of the talus, are defined as fractures of the lower portion of the talus. It is difficult to make a correctly diagnosis of inferior fractures of the talus by plain radiography or tomography alone. The author encountered 12 cases of inferior fractures of the talus between 1989 and 1997, and CT imaging in 2 directions, in the horizontal and frontal plane, was useful in making the diagnosis. The correct diagnosis rate was 100%, and differentiation of the site and extent of the fractures was possible. Based on the CT findings, the fractures were classified into 8 types (fractures of the lateral process of the talus, fractures of the medial tubercle, fractures of the posterior process, and combinations of the above, and comminuted fractures). The mechanism of the injuries was also investigated, and the fractures of the lateral process of the talus seemed to have been caused by excessive eversion force on the ankle joint, with the lateral process becoming trapped between the fibula and the calcaneus. Medial tubercle fractures also seemed to be caused by forcible inversion of the ankle, with the tip of the medial malleous impacting and the medial tubercle being trapped between it and the sustentaculum tali. The comminuted fractures seem to have been caused by axial compression added to various of external forces. (K.H.)

Okamoto, Hideaki; Shibata, Yoshimori; Nishi, Genzaburo; Tago, Kyoji; Tsuchiya, Daiji; Chiba, Takehiro; Okumura, Hisashi [Aichiken Koseiren Kainan Hospital, Yatomi (Japan); Ikeda, Takeshi; Wada, Ikuo

2000-02-01

49

Effect of anterior translation of the talus on outcomes of three-component total ankle arthroplasty  

Science.gov (United States)

Background Ankle osteoarthritis commonly involves sagittal malalignment with anterior translation of the talus relative to the tibia. Total ankle arthroplasty has become an increasingly popular treatment for patients with symptomatic ankle osteoarthritis. However, no comprehensive study has been conducted on the outcomes of total ankle arthroplasty for osteoarthritis with preoperative sagittal malalignment. The purpose of this study was to evaluate the effect of anterior translation of the talus on outcomes of three-component total ankle arthroplasty. Methods One hundred and four osteoarthritic ankles in 104 patients who underwent three-component total ankle arthroplasty were included in this study. The 104 ankles were divided into 2 groups: ankles with anteriorly translated talus (50 ankles), and ankles with non-translated talus (54 ankles). Clinical and radiographic outcomes were assessed in both groups. The mean follow-up duration was 42.8?±?17.9 months (range, 24 to 95 months). Results Forty-six (92%) of 50 ankles with anterior translation of the talus showed relocation of the talus within the mortise at 6 months, and 48 (96%) ankles were relocated at 12 months after total ankle arthroplasty. But, 2 (4%) ankles were not relocated until the final follow-up. The AOFAS scores, ankle range of motion, and radiographic outcomes showed no significant difference between the two groups at the final follow-up (p?>?0.05 for each). Conclusions In majority of cases, the anteriorly translated talus in osteoarthritic ankles was restored to an anatomical position within 6 months after successful three-component total ankle arthroplasty. The clinical and radiographic outcomes in the osteoarthritic ankles with anteriorly translated talus group were comparable with those in non-translated talus group. PMID:24007555

2013-01-01

50

39 - Glenshane Slopes  

...Roe Basin38 - Eastern Binevenagh Slopes39 - Glenshane SlopesGlenshane Slopes LandscapeGlenshane Slopes Geodiversity...Digital DatasetsStrategic Environmental Assessment (SEA)39 - Glenshane SlopesLast updated: 9 February 2007This...

51

Talocalcaneal transfixation in total dislocation of the talus and subtalar dislocations.  

Science.gov (United States)

We present 4 cases of talus dislocation. In one case we had open total lateral dislocation of the talus and in 3 other cases we had closed subtalar dislocation (disruption of the talocalcaneal and talonavicular joints). Reposition of the dislocation was made and talocalcaneal transfixation completed with 3 Kirschner wires, placed like a spread fan, under fluoroscopic control. Reoccurring dislocations were not experienced nor were there signs of avascular necrosis in these 4 cases. PMID:19354102

Pavi?, Roman

2009-03-01

52

Percutaneous core decompression: a successful method of treatment of Stage I avascular necrosis of the talus.  

Science.gov (United States)

The talus is a bone uncommonly affected by avascular necrosis (AVN) [1]. Factors such as trauma and pre-existing inflammatory arthropathy (particularly with concomitant steroid use) increase the risk of development of AVN. We report a case of resolution of Stage I AVN, diagnosed clinically and on magnetic resonance imaging (MRI), treated successfully by percutaneous core decompression of the talus. An MRI 12 weeks post-operatively showed complete resolution of the appearances of AVN. PMID:22017911

Grice, John; Cannon, Les

2011-12-01

53

Impact of land-use change on soil degradation by establishment of terraces with subtropical orchards in sloping areas (Granada, SE Spain)  

Energy Technology Data Exchange (ETDEWEB)

In the coast of Granada, an intensive irrigated agriculture based on subtropical crops has been established. These trees have been planted in highly sloped areas, by the construction of terraces. In this fragile Mediterranean agroecosystem, the removal of native spontaneous vegetation cover and substitution by orchards, increase the susceptibility to soil degradation and eventually brings up the destruction of these structures by rainfall events. To study this net change, we monitored the soil loss and runoff over a two-year period in the taluses of terraces with a mature mango (Mangifera indica L.) orchard. The studied treatments were bare soil (BS) and spontaneous vegetation (NSV), each twice replicated. The erosion plots were 4 m x 4 m in area and were located in the taluses of orchard in the taluses of orchard terraces (65 degree centigrade slope). The average annual soil loss by erosion for BS and NSV was 2.5 and 0.3 Mg ha{sup -}1 yr{sup -}1, and for runoff 34.1 and 6.8 mm yr{sup -}1, respectively. Therefore, soil erosion and runoff from BS plot were 8- and 5-times higher than in NSV, showing the importance of plant covers in the taluses of terraces in reducing this impact. Thus, the removal of plant cover from the taluses under these conditions, represent a high risk of slump and collapse, causing serious environmental and economic problems for farmers of subtropical crops. (Author) 11 refs.

Rodriguez Pleguezuelo, C. R.; Duran Zuzo, V. H.; Martin Peinado, F. J.; Franco Tarifa, D.

2009-07-01

54

Osteochondral lesions of the talus: aspects of current management.  

Science.gov (United States)

Osteochondral lesions (OCLs) occur in up to 70% of sprains and fractures involving the ankle. Atraumatic aetiologies have also been described. Techniques such as microfracture, and replacement strategies such as autologous osteochondral transplantation, or autologous chondrocyte implantation are the major forms of surgical treatment. Current literature suggests that microfracture is indicated for lesions up to 15 mm in diameter, with replacement strategies indicated for larger or cystic lesions. Short- and medium-term results have been reported, where concerns over potential deterioration of fibrocartilage leads to a need for long-term evaluation. Biological augmentation may also be used in the treatment of OCLs, as they potentially enhance the biological environment for a natural healing response. Further research is required to establish the critical size of defect, beyond which replacement strategies should be used, as well as the most appropriate use of biological augmentation. This paper reviews the current evidence for surgical management and use of biological adjuncts for treatment of osteochondral lesions of the talus. PMID:24493179

Hannon, C P; Smyth, N A; Murawski, C D; Savage-Elliott, I; Deyer, T W; Calder, J D F; Kennedy, J G

2014-02-01

55

Congenital vertical talus in four generations of the same family  

Energy Technology Data Exchange (ETDEWEB)

This paper presents four generations of a family with radiographically demonstrated congenital vertical talus (CVT) in whom a HOXD10 gene mutation was identified. Some members of the family with this mutation exhibited cavo-varus foot deformity consistent with a Charcot-Marie-Tooth (CMT)-like disorder. Physical examination was performed on nearly all of the affected and unaffected family members. DNA was extracted from blood obtained from 14 subjects who showed radiographic and clinical features of CVT (two of whom also had CMT), from two subjects with features of CMT but not CVT, and from 20 related family members who were clinically normal. Radiographs show the appearance of uncorrected CVT in infancy, in childhood, and in adulthood. DNA analysis revealed a mutation in a HOXD10gene located on chromosome 2 in all of the affected but none of the unaffected family members. There is an autosomal-dominant-inherited mutation with complete penetrance which is found in all members of a pedigree with CVT, some of whom exhibit a CMT-like foot disorder. Radiologic findings vary depending on the severity of involvement, treatment provided and age of the patient. (orig.)

Levinsohn, E. Mark [Crouse Hospital, Department of Medical Imaging, Syracuse (United States); Shrimpton, Antony E. [SUNY Upstate Medical University, Department of Clinical Pathology, Syracuse (United States); Cady, Robert B. [SUNY Upstate Medical University, Department of Pediatrics, Syracuse (United States); Packard, David S. [SUNY Upstate Medical University, Department of Cell and Developmental Biology, Syracuse (United States); Hootnick, David R. [SUNY Upstate Medical University, Department of Pediatrics, Syracuse (United States); SUNY Upstate Medical University, Department of Cell and Developmental Biology, Syracuse (United States); SUNY Upstate Medical University, Department of Orthopedic Surgery, Syracuse (United States)

2004-11-01

56

Congenital vertical talus in four generations of the same family  

International Nuclear Information System (INIS)

This paper presents four generations of a family with radiographically demonstrated congenital vertical talus (CVT) in whom a HOXD10 gene mutation was identified. Some members of the family with this mutation exhibited cavo-varus foot deformity consistent with a Charcot-Marie-Tooth (CMT)-like disorder. Physical examination was performed on nearly all of the affected and unaffected family members. DNA was extracted from blood obtained from 14 subjects who showed radiographic and clinical features of CVT (two of whom also had CMT), from two subjects with features of CMT but not CVT, and from 20 related family members who were clinically normal. Radiographs show the appearance of uncorrected CVT in infancy, in childhood, and in adulthood. DNA analysis revealed a mutation in a HOXD10gene located on chromosome 2 in all of the affected but none of the unaffected family members. There is an autosomal-dominant-inherited mutation with complete penetrance which is found in all members of a pedigree with CVT, some of whom exhibit a CMT-like foot disorder. Radiologic findings vary depending on the severity of involvement, treatment provided and age of the patient. (orig.)

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77 - Iveagh Slopes  

...75 - Mourne Mountains76 - Ballyroney Basin77 - Iveagh SlopesIveagh Slopes LandscapeIveagh Slopes Geodiversity...Digital DatasetsStrategic Environmental Assessment (SEA)77 - Iveagh SlopesLast updated: 9 February 2007This...

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Arthroscopic Particulated Juvenile Cartilage Allograft Transplantation for the Treatment of Osteochondral Lesions of the Talus  

Science.gov (United States)

Several options exist for the treatment of osteochondral lesions of the talus. Particulated juvenile cartilage allograft transplantation (PJCAT) has become a viable treatment modality for osteochondral lesions of the talus that are not amenable to microfracture or for which microfracture has failed. Arthroscopic placement of this type of graft obviates the need for osteotomy or plafondplasty and does not prevent additional procedures from being performed through an anterior approach. Special instrumentation and setup are not required to perform this procedure. Our arthroscopic technique for placement of particulated juvenile cartilage into osteochondral lesions of the talus is described. Case series and outcomes after arthroscopic ankle PJCAT are currently not reported within the literature; however, it is believed that the outcomes are at least similar to those of open ankle PJCAT.

Adams, Samuel B.; Demetracopoulos, Constantine A.; Parekh, Selene G.; Easley, Mark E.; Robbins, Justin

2014-01-01

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Arthroscopic Particulated Juvenile Cartilage Allograft Transplantation for the Treatment of Osteochondral Lesions of the Talus.  

Science.gov (United States)

Several options exist for the treatment of osteochondral lesions of the talus. Particulated juvenile cartilage allograft transplantation (PJCAT) has become a viable treatment modality for osteochondral lesions of the talus that are not amenable to microfracture or for which microfracture has failed. Arthroscopic placement of this type of graft obviates the need for osteotomy or plafondplasty and does not prevent additional procedures from being performed through an anterior approach. Special instrumentation and setup are not required to perform this procedure. Our arthroscopic technique for placement of particulated juvenile cartilage into osteochondral lesions of the talus is described. Case series and outcomes after arthroscopic ankle PJCAT are currently not reported within the literature; however, it is believed that the outcomes are at least similar to those of open ankle PJCAT. PMID:25264516

Adams, Samuel B; Demetracopoulos, Constantine A; Parekh, Selene G; Easley, Mark E; Robbins, Justin

2014-08-01

60

Modified Blair tibiotalar arthrodesis for post-traumatic avascular necrosis of the talus: a case report.  

Science.gov (United States)

Surgical treatment of post-traumatic avascular necrosis of the talus coupled with collapse often results in limited treatment options. Of those options, the Blair tibiotalar arthrodesis has been beneficial in preserving limb length and subtalar motion. The complications associated with Blair tibiotalar arthrodesis have led to modifications to improve stability and functional outcomes with rigid internal fixation. We present the case of a 29-year-old female with a history of an open fracture dislocation of the talus 10 years previously, with subsequent development of avascular necrosis of the talus. The purpose of the present case report was to describe the surgical approach and use of an anterior compression plate to augment the modified Blair tibiotalar arthrodesis. PMID:24160724

Ross, Justin S; Rush, Shannon M; Todd, Nicholas W; Jennings, Meagan M

2013-01-01

 
 
 
 
61

An unusual cause of a cystic lesion with an osteochondral defect in the talus: intraosseous lipoma.  

Science.gov (United States)

An intraosseous lipoma is a rare benign bone lesion that proliferates from mature lipocytes. It occurs most frequently in the lower limb, particularly in the calcaneus. The talus is an unusual location for this rare lesion. A review of the literature produced only two reports with talar intraosseous lipomas under the name of intraosseous lipomatosis, which described multiple lipomas in different areas. We describe a 38-year-old male patient who had an isolated intraosseous lipoma with an osteochondral defect in the talus and was treated with autologous osteochondral graft transplantation by medial malleolar osteotomy. He could walk with full weightbearing without any assistance at the end of 12 months. Intraosseous lipoma localized in the talus may be confused radiologically with other bone lesions, especially with unicameral bone cyst, if it is associated with an osteochondral defect. Autologous osteochondral graft transplantation is a successful treatment method for talar intraosseous lipoma. PMID:21622640

Atay, Evren Fehmi; Güven, Melih; Cakar, Murat; Ba?sorgun, Cumhur Ibrahim; Akman, Budak; Bes, Cemal

2011-01-01

62

Reimplantation of a completely extruded talus 8 days following injury: a case report.  

Science.gov (United States)

We present the case of a 28-year-old female with 45 months follow-up after reimplantation of a completely extruded talus 8 days following the injury. The extruded talus was recovered at the site of the motor vehicle accident, where it had been embedded in the wreckage and subsequently transported to hospital 3 hours later. Thereafter, the talus was washed in an iodine solution for 5 hours and frozen for a period of 8 days at -80 °C, after which reimplantation surgery was undertaken. Throughout the extended follow-up period, no evidence of infection ever developed. Three years following her injury, the patient underwent fusion of the subtalar and talonavicular joints. At 45 months postoperative, imaging revealed avascular necrosis of the talar dome without substantial collapse. The patient progressed to the point where, at last follow-up, she was working in an administrative job and was able to bear full weight on the involved foot, despite development of mild pain on physical exertion. Despite the pain, moreover, she remained able to snow ski and to regularly walk 2 kilometers for cardiovascular fitness. We believe this case demonstrates that, in the apparent absence of deep infection, the development of avascular necrosis need not necessarily lead to a poor clinical outcome. Furthermore, this case showed that even after a period of 8 days in the freezer, and following antiseptic cleansing, the extruded talus could be reimplanted with a reasonable degree of clinical success. PMID:21106409

Burston, Johnny L; Brankov, Boris; Zellweger, Rene

2011-01-01

63

The flake fracture of the talus - diagnosis and follow up study by direct radiologic magnification technique  

International Nuclear Information System (INIS)

With regard to 26 cases with a flake fracture of the talus we could demonstrate that in selected cases the primary diagnosis of the lesion is easier, when the direct radiologic magnification technique is performed. This technique, however, should be mainly used for follow up studies after an operation or a conservative therapy. (orig.)

64

[Neonatal osteomyelitis of the talus due to methicillin-resistant Staphylococcus epidermidis].  

Science.gov (United States)

Acute osteomyelitis is a relatively rare disorder in the neonatal period, with considerable morbidity and mortality. Early diagnosis and prompt treatment are essential for a successful outcome. In this report we present a case of acute osteomyelitis of the talus due to methicillin-resistant Staphylococcus epidermidis, observed in a 30-day-old infant. PMID:23774980

Pampinella, Diego; Serra, Gregorio; Giordano, Salvatore; Dones, Piera; Di Gangi, Maria; Failla, Maria Concetta; Corsello, Giovanni

2013-06-01

65

Aggressive giant cell tumour of talus with pulmonary metastasis-a rare presentation.  

Science.gov (United States)

Giant cell tumour (GCT) is a primary benign neoplasm of bone. It is classically described as a locally invasive tumour that occurs close to the joint of a mature bone. It accounts for 5% of all skeletal tumours. It usually originates from long bones. Giant Cell Tumour of the small bones of the hand and foot are relatively uncommon. Giant Cell Tumour of talus is a rare occurrence. We report a rare presentation of giant cell tumour of the talus in a 62-year-old farmer treated by talectomy and tibiocalcaneal fusion, who later presented with features suggestive of recurrence and secondaries in chest within six months following surgical resection of the primary. Below knee amputation was performed to manage the recurrence. At two years follow-up the patient showed no further progression of pulmonary metastasis or local recurrence. PMID:25177585

Kumar, B Udaya; Sharma, P Ravi; Ram, G Santhosh; Kumar, P Varun

2014-07-01

66

Simultaneous bilateral fracture-dislocation of the talus: a case report.  

Science.gov (United States)

A bilateral talar body fracture-dislocation in a 29-year-old multitrauma patient is presented. There was a comminuted fracture associated with an ankle, subtalar and talonavicular subluxation on the right lower limb and an open fracture with complete dislocation of the body of talus on the left side. We performed a minimal invasive reduction and stabilization of the fractures with the use of K-wires, due to severe contamination of the wounds and the patient's poor general condition. After a 28-month follow-up there were signs of posttraumatic arthritis but no signs of avascular necrosis of the talus bilaterally. The range of motion in both ankle joints was limited but the patient had a satisfactory level of activity. PMID:20307463

Sayegh, F E; Nikolaides, A P; Anagnostidis, K S; Kapetanos, G A

2009-06-01

67

Estimação dos parâmetros do modelo do motor de indução usando o algoritmo Talus  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the algorithm Talus is applied to problem of parameter estimation of induction motor. The solution of the estimation problem is achieved minimizing a quadratic cost function. The data source used in the algorithm is the measured value of current end power in standard laboratory. The estimated parameters are compared with classical test (no-load and locked rotor either by simulation and experimentally

Eurico Souza Filho Bezerra de

2004-01-01

68

Medial subtalar dislocation associated with fracture of the posterior process of the talus.  

Science.gov (United States)

A 17-year-old male sustained a medial subtalar fracture dislocation while playing basketball. The dislocation of the subtalar joint was reduced by closed means, but a large, comminuted, displaced posterior process fracture remained. Open reduction and internal fixation through a posteromedial approach was used to restore congruity to the subtalar joint. MRI at 12 months after injury showed no signs of avascular necrosis in the talus. PMID:22331059

Liu, Zhenjiang; Zhao, Qun; Zhang, Lijun

2012-09-01

69

Talar neck fracture associated with talonavicular dislocation and fracture of posteromedial process of talus.  

Science.gov (United States)

Canale and Kelly modified the Hawkins classification of talar neck fractures by adding a type IV fracture dislocation to the original 3 types described. Type IV injury occurs rarely and is the only type involving dislocation of the talonavicular joint. To our knowledge, only 2 unusual cases have been described in published studies in which a fracture of neck of the talus occurred in association with talonavicular dislocation but the ankle and subtalar joints remained intact. We describe a very unusual case of an adult male with a fracture of the neck of the talus with talonavicular dislocation, subtalar subluxation, an intact ankle joint, and a fracture of the posteromedial tubercle of talus. Open reduction and internal fixation of the talar neck and posteromedial tubercle was undertaken. The talar neck fracture united without any evidence of avascular necrosis, but the posteromedial tubercle remained un-united. Such an injury is unusual, and the injury pattern is unique and cannot be classified using existing systems. PMID:21920783

Kapoor, Sudhir K; Patra, Satya Ranjan

2011-01-01

70

Fracture of the lateral process of the talus: a report of two cases.  

Science.gov (United States)

Fracture of the lateral process of the talus is a rare lesion commonly described in snowboarding injuries. Nevertheless, several conditions can lead to this injury, which is often misdiagnosed as a severe ankle sprain because of the difficulty in detecting it on standard radiographic views. Computed tomography is very helpful for the assessment of this injury. The type of treatment will depend on the size and degree of the displacement of the fracture. This injury can also lead to subtalar joint osteoarthritis. We report 2 cases of fracture of the lateral process of the talus. In the first case, a young male sustained a combined inversion and dorsiflexion strain of his right foot when he fell from a ladder. In the second case, a woman broke the lateral process of her right talus by the same mechanism when she was sledding. In the 2 situations, we opted for an open reduction and internal fixation using 2.4-mm cannulated screws. Both patients were allowed walking with partial weightbearing with a walker boot (VACOped(®)) for 6 weeks. At 1 year, both showed a consolidated fracture and had regained their preinjury level of activity. PMID:24618244

Lunebourg, Alexandre; Zermatten, Philippe

2014-01-01

71

Simulation of River Bluffs and Slip-Off Slopes With a Discrete Particle-Based Model  

Science.gov (United States)

A discrete particle-based model simulates evolution of two-dimensional valley cross sections similar to those produced by bedrock meandering rivers and thereby suggests that characteristic features such as overhanging cliffs and talus slopes are dependent on specific relationships among process rates. Discrete coordinates on a gridded cross-section define locations of particles of intact bedrock, sediment (loose material with half the bulk density of bedrock), water, or air on that grid, and each particle of rock or sediment has a unique (or zero) concentration of terrestrial cosmogenic nuclides (TCNs). Stochastic processes determine both the possible locations of process actions and the results of those actions. Stochastic discharges generate boundary shear stresses, calculated by an approximation to the ray-isovel model, that determine removal probabilities for candidate particles of bedrock or sediment from the boundary of a self-formed channel. An asymmetric probability distribution governs the selection of candidate particles on the wetted perimeter and drives asymmetric fluvial erosion and transport that can undermine adjacent slopes, so that the channel migrates laterally. Sediment is produced from intact bedrock by weathering and rock fall. The latter acts only on candidate bedrock particles that are undermined and exposed at the surface. Weathering produces two sediment particles from one of bedrock, and thereby inflates the surface, when slope-normal random walks from candidate sites on the surface end at bedrock particles, so that the sediment-bedrock interface is irregular and discontinuous. Diffusive transport moves candidate particles on random walks in random directions along the surface, where transition probabilities depend on local topography. TCNs are produced when the randomly situated and oriented random walks of cosmic rays end at bedrock or sediment, and not water, particles. The model produces asymmetric channels and valley cross sections, where the two slopes have contrasting bedrock lowering rates, regolith thicknesses, TCN concentrations, and gradients. In simulated valleys, talus-mantled slopes grade smoothly into steep outer channel banks at the bases of overhanging cliffs, all with small TCN concentrations, and thickly mantled slip-off slopes grade smoothly into shallow inner banks similar to point bars, all with large TCN concentrations. Dimensional analysis suggests, and simulations confirm, relationships that can be tested in the field: cliffs form when bedrock lowering due to weathering is small relative to fluvial bedrock and weathering rate is small relative to fluvial transport capacity; for a given slope length, smaller rock-fall rates produce greater cliff heights; and greater fluvial transport capacity relative to sediment production by bedrock lowering produces thinner talus.

Lancaster, S. T.; Zunka, J. P.; Tucker, G. E.

2013-12-01

72

Talus cone activity recorded by tree-rings of Arctic dwarf shrubs: a study case from SW Spitsbergen, Norway  

Science.gov (United States)

Dendrochronological methods were used to determine talus cone activity in the Arctic area. Talus cones are one of the most characteristic geomorphological features of the Svalbad Archipelago. Two species of dwarf shrubs, Salix polaris and Salix reticulata, which belong to the Willow family (Salicaceae), were collected from two talus cones located in the SW Spitsbergen Island. These small creeping shrubs (less than 10 cm tall with stem diameters ranging from 0.5 cm to 1.1 cm) have well developed tree-rings which allow them to be used for dendrochronological research. The age of the dwarf shrubs showed the minimum time during which the cones were disturbed by mass movements. Observations and material analysis indicate that currently the talus cones are active, but their development through debris flow, creep and rock particle slide is observed only episodically. An increased rate of vegetation colonization during the 1980s indicates that geomorphic events were less active in the talus cone area during this time.

Owczarek, Piotr

2010-12-01

73

Effect of Talus Deposit Excavations on Hydrogeochemical Characteristics of Kuvars Spring Water, Maltepe, Istanbul, Turkey  

Directory of Open Access Journals (Sweden)

Full Text Available Spring waters consumed for drinking purposes should be clean and quality. These waters with balanced mineral distribution, which do not contain organic substances, whose physical and chemical caharacteristics comply with certain quality parameters and which do not negatively affect human health are identified as healthy water. Kuvars water is a spring water which is pumped out from the draw well at the Camurluk stream basin of Maltepe province of Istanbul and filled into bottles. The Camurluk stream basin is approximately 4.5 km2. The Camurluk stream basin is sedimentary rocks and talus deposit outcrops. Reaching of trace elements, which is found more in the talus deposit samples than outcropping quartzarenite at the basin, to underground aquifer as ions under effect of rains, water rock interaction, leakage and filtration, is prevented by illite type clay levels existing within the talus deposit stack, which have upto 20 cm thickness. However, negative effects of the excavation that were made at the talus deposit reflect on the hydrologic cycle and chemical compositions of well waters. This effect was at first negatively affected the physical characteristics of the well waters. During the rainy periods, the water in the excavated area which was enriched with respect to the suspended sediments was percolated into the groundwaters from the joints and cracks of the quartzarenite. The turbidity value measured in the well waters of K2 and K3 were determined as 40.3 NTU and 34.2 NTU respectively. Although at the basin, the aquifer of underground water and the well waters being managed are quartzarenite, the fact that water types belonging to well waters differ (they are not same according to the Piper diagram and when the heavy metal content of the water of well numbered KS1 is taken as basis, that some heavy metals such as Al3+, Fe2+, Ni2+, Mn2+ and Cu2+ be enriched 3 to 40 times in KS2 and KS3 well waters, are caused by talus deposit—water interaction at the excavation area. After a rainfall, in the water that became turbid with the water-talus deposit interaction at the excavation area, the water-mineral interaction has caused the limit value for drinking water suggested by World Health Organization (WHO to be exceeded with the Al3+ concentration of 189 ppb detected in KS2 well water and Fe2+ concentration of 185 ppb has caused to approach the drinking water limit value of 200 ppb permitted by World Health Organization (WHO, United States Environmental Protection Agency (EPA, European Union (EU and Turkish Standards (TS. Therefore, at the water basins where bottled spring waters consumed for drinking purposes are produced, technical undertakings that shall disturb the stability of geological units should not be permitted.

Deniz Key

2012-05-01

74

Lesson 4: Slope  

Science.gov (United States)

Treating slope as a rate of change of two quantities with different units. There are both applications based examples and non contextual examples. Slope is found both from a graph and from the relationship between two quantities given in a context.

2011-01-01

75

Hawkins Group I fracture of neck of talus and Salter Harris Type III tibial epiphyseal injury of medial malleolus.  

Science.gov (United States)

We are reporting an unusual combination of Hawkins Group I fracture of the neck of left talus in association with Salter Harris Type III distal tibial epiphyseal injury of medial malleolus in a child with cerebral palsy and hemiplegia of contralateral limbs and discussed the possible mechanism as well as management. Fractures of medial malleolus usually occur in Hawkins Group III fracture-dislocations in adults. Forced dorsiflexion of talus against the anterior edge of tibia appears to be the accepted common mechanism, despite limited experimental and clinical evidence incriminating axial compression. Fracture of medial malleolus implicates supination. We managed this unusual pattern of injury conservatively. At 15 months, the child was asymptomatic with no radiological evidence of avascular necrosis of body of talus or growth disturbance of distal tibial epiphysis. PMID:23639364

Prasad, Kodali Siva R K; Vali, Hamza; Hussain, Altaf

2013-01-01

76

Dysplasia epiphysealis hemimelica (trevor syndrome) of talus in a 21-year old woman; case report.  

Science.gov (United States)

Dysplasia epiphysealis hemimelica is a rare nonhereditary epiphyseal disease that mimics synovial chondromatosis and osteochondroma of the joints. The disease mainly involves long bones of the lower extremities and tarsal bones. Herein we report 21-year old woman who presented with pain and limited range of ankle motion, who underwent surgical excision of talus exostosis after preoperative imaging and careful planning. after that she was discharged and her problem improved and she have no problem in three year follow up. pathologic examination of specimen confirm the diagnosis. PMID:25207317

Sadeghifar, Amir R; Heshmati, Afshin Ahmadzadeh

2014-03-01

77

Groundwater flow and storage within an alpine meadow-talus complex  

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Full Text Available The different types of geological deposits and rock formations found in alpine watersheds play key roles in regulating the rate and timing of runoff to mountain rivers. Talus and alpine meadows are dominant features in these areas, but scant data exist for their capacity to store and transmit groundwater. To gain further understanding of these processes, we have undertaken a combined geophysical and hydrological study of a small (2100 m2 alpine meadow and surrounding talus within the Lake O'Hara watershed in the Canadian Rockies. Several intersecting ground-penetrating radar (GPR and electrical resistivity tomography (ERT profiles and a seismic refraction profile were acquired to map the thickness of the talus and to image the topography of the bedrock basin that underlies the meadow. From analysis of the GPR and seismic profiles, we estimate that the talus deposits are relatively thin (<6 m. Combined interpretations from the GPR and ERT data show that the fine-grained sediment comprising the meadow basin has a total volume of ca. 3300 m3 and has a maximum thickness of ca. 4 m. Annual snow surveys and stream gauging reveal that the total input volume of snowmelt and rainfall to the meadow basin is several times larger than its groundwater storage capacity, giving rise to low total-dissolved species concentrations (14–21 mg/L within the meadow groundwater. Observations from four piezometers established on the meadow show that the water table fluctuates rapidly in response to spring snowmelt and precipitation events but otherwise maintains a relatively stable depth of 0.3–0.4 m below the meadow surface during summer months. A slug test performed on one of the piezometers indicated that the saturated hydraulic conductivity of the shallow meadow sediments is 2.5×10?7 m/s. We suggest that a bedrock saddle imaged underneath the southern end of the meadow forms a natural constriction to subsurface flow out of the basin and helps to maintain the stable water-table depth.

A. F. McClymont

2010-06-01

78

Groundwater flow and storage within an alpine meadow-talus complex  

Directory of Open Access Journals (Sweden)

Full Text Available The different types of geological deposits and rock formations found in alpine watersheds play key roles in regulating the rate and timing of runoff to mountain rivers. Talus and alpine meadows are dominant features in these areas, but scant data exist for their capacity to store and transmit groundwater. To gain further understanding of these processes, we have undertaken a combined geophysical and hydrological study of a small (2100 m2 alpine meadow and surrounding talus within the Lake O'Hara watershed in the Canadian Rockies. Several intersecting ground-penetrating radar (GPR and electrical resistivity tomography (ERT profiles and a seismic refraction profile were acquired to map the thickness of the talus and to image the topography of the bedrock basin that lies under the meadow. From analysis of the GPR and seismic profiles, we estimate that the talus deposits are relatively thin (<6 m. Combined interpretations from the GPR and ERT data show that the fine-grained sediment, that the meadow basin is comprised of, has a total volume of ca. 3300 m3 and has a maximum thickness of ca. 4 m. Annual snow surveys and stream gauging reveal that the total input volume of snowmelt and rainfall to the meadow basin is several times larger than its groundwater storage capacity, giving rise to low total-dissolved species concentrations (14–21 mg/L within the meadow groundwater. Observations from four piezometers established on the meadow show that the water table fluctuates rapidly in response to spring snowmelt and precipitation events but otherwise maintains a relatively stable depth of 0.3–0.4 m below the meadow surface during summer months. A slug test performed on one of the piezometers indicated that the saturated hydraulic conductivity of the shallow meadow sediments is 2.5×10?7 m/s. We suggest that a bedrock saddle imaged underneath the southern end of the meadow forms a natural constriction to subsurface flow out of the basin and helps to maintain the stable water-table depth.

A. F. McClymont

2010-02-01

79

Recurrent parosteal osteosarcoma of the talus in a 2-year-old child  

International Nuclear Information System (INIS)

Parosteal osteosarcoma is an uncommon, low-grade malignant bone tumor and is found in an older age group than conventional osteosarcoma. We present a talar parosteal osteosarcoma that recurred twice in a 2-year-old child. To our knowledge, this is the youngest patient reported with a parosteal osteosarcoma. The talus is an unusual site for parosteal osteosarcoma. Inadequate resection due to a diagnosis of juxtacortical chondroma resulted in recurrence of the tumor. The age of the patient, the thick cartilaginous cap, and well-differentiated trabecular bone all contributed to the critical erroneous diagnosis. (orig.)

80

Epidemiological study on talus fractures / Estudo epidemiológico das fraturas do tálus  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Objetivo: Analisar as características dos indivíduos e das lesões encontradas em pacientes com fraturas de tálus. Métodos: Análise retrospectiva dos pacientes internados no Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo de 200 [...] 6 a 2011 com fratura de tálus. Foram estudados parâmetros associados ao perfil do paciente e fatores de risco, características da fratura, dados do tratamento e complicações agudas. Resultados: A análise dos 23 casos mostrou que os homens foram mais afetados do que as mulheres, com uma relação de 4,8:1. O mecanismo de trauma mais frequente foram os acidentes de trânsito, seguido pelas quedas de altura. O tipo de fratura mais frequente foi a do colo do tálus, com 17 casos. Dos 23 casos, sete apresentavam luxação peritalar no momento da apresentação, quatro tinham fratura exposta e 11 apresentavam outras fraturas associadas. O tempo médio entre o trauma e o tratamento definitivo foi de seis dias, enquanto o tempo médio de permanência hospitalar foi de 11 dias. Houve três pacientes que apresentaram complicações pós-operatórias agudas. Conclusão: A fratura do tálus foi mais comum na região do colo e mais frequente em jovens do gênero masculino que sofreram traumatismos de alta energia. Em quase metade dos casos houve fraturas associadas e o tempo de permanência hospitalar foi de 11 dias. Abstract in english Objective: To analyze the characteristics of patients with talus fractures and the injuries that they present. Methods: Retrospective analysis on patients hospitalized in the Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine of the University of São Paulo, betwe [...] en 2006 and 2011, with talus fractures. Patient profile parameters, risk factors, fracture characteristics, treatment data and acute complications were analyzed. Results: Analysis on 23 cases showed that men were more affected than women, with a ratio of 4.8:1. The most frequent trauma mechanism was traffic accidents, followed by falls from a height. The most frequent type of fracture was at the neck of the talus, with 17 cases. Among the 23 cases, seven had peritalar dislocation at the time of presentation, four had exposed fractures and 11 presented other associated fractures. The mean length of time between the trauma and the definitive treatment was six days, while the mean length of hospital stay was 11 days. Three patients presented acute postoperative complications. Conclusion: Talus fractures occurred most commonly in the region of the talar neck and most frequently in young males who suffered high-energy trauma. In almost half of the cases, there were other associated fractures. The length of hospital stay was 11 days.

Marcos Hideyo, Sakaki; Guilherme Honda, Saito; Rafael Garcia de, Oliveira; Rafael Trevisan, Ortiz; Jorge dos Santos, Silva; Túlio Diniz, Fernandes; Alexandre Leme Godoy dos, Santos.

2014-07-01

 
 
 
 
81

Epidemiological study on talus fractures / Estudo epidemiológico das fraturas do tálus  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese Objetivo: Analisar as características dos indivíduos e das lesões encontradas em pacientes com fraturas de tálus. Métodos: Análise retrospectiva dos pacientes internados no Instituto de Ortopedia e Traumatologia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo de 200 [...] 6 a 2011 com fratura de tálus. Foram estudados parâmetros associados ao perfil do paciente e fatores de risco, características da fratura, dados do tratamento e complicações agudas. Resultados: A análise dos 23 casos mostrou que os homens foram mais afetados do que as mulheres, com uma relação de 4,8:1. O mecanismo de trauma mais frequente foram os acidentes de trânsito, seguido pelas quedas de altura. O tipo de fratura mais frequente foi a do colo do tálus, com 17 casos. Dos 23 casos, sete apresentavam luxação peritalar no momento da apresentação, quatro tinham fratura exposta e 11 apresentavam outras fraturas associadas. O tempo médio entre o trauma e o tratamento definitivo foi de seis dias, enquanto o tempo médio de permanência hospitalar foi de 11 dias. Houve três pacientes que apresentaram complicações pós-operatórias agudas. Conclusão: A fratura do tálus foi mais comum na região do colo e mais frequente em jovens do gênero masculino que sofreram traumatismos de alta energia. Em quase metade dos casos houve fraturas associadas e o tempo de permanência hospitalar foi de 11 dias. Abstract in english Objective: To analyze the characteristics of patients with talus fractures and the injuries that they present. Methods: Retrospective analysis on patients hospitalized in the Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine of the University of São Paulo, betwe [...] en 2006 and 2011, with talus fractures. Patient profile parameters, risk factors, fracture characteristics, treatment data and acute complications were analyzed. Results: Analysis on 23 cases showed that men were more affected than women, with a ratio of 4.8:1. The most frequent trauma mechanism was traffic accidents, followed by falls from a height. The most frequent type of fracture was at the neck of the talus, with 17 cases. Among the 23 cases, seven had peritalar dislocation at the time of presentation, four had exposed fractures and 11 presented other associated fractures. The mean length of time between the trauma and the definitive treatment was six days, while the mean length of hospital stay was 11 days. Three patients presented acute postoperative complications. Conclusion: Talus fractures occurred most commonly in the region of the talar neck and most frequently in young males who suffered high-energy trauma. In almost half of the cases, there were other associated fractures. The length of hospital stay was 11 days.

Marcos Hideyo, Sakaki; Guilherme Honda, Saito; Rafael Garcia de, Oliveira; Rafael Trevisan, Ortiz; Jorge dos Santos, Silva; Túlio Diniz, Fernandes; Alexandre Leme Godoy dos, Santos.

82

Elastic slopes and diffraction  

International Nuclear Information System (INIS)

It is well known that elastic hadronic slopes grow with energy and appear sizeably larger when measured very close to t=0 than at intermediate t-values. This has been confirmed by the recent anti-p p measurements at the CERN SPS-Collider. By comparing the data with a formula derived recently which gives the slope as a function of the four momentum transfer squared t and of the average multiplicity we argue that all the basic properties of hadronic slopes may be attributed to the role of multiparticle unitarity, i.e. to diffraction

83

An uncommon treatment of totally extruded and lost talus: a case report  

Science.gov (United States)

Introduction Total extrusion and loss of the talus is a rare injury with a wide choice of appropriate treatment, but rarely resulting in a fully functional recovery. We report on an uncommon case, both for the severity of the injury and for the uncommon treatment due to the patient’s rejection of secondary surgery. Case presentation We treated a 16-year-old Caucasian man with the most extreme variant of a totally extruded and lost talus, accompanied with complex injury of the soft tissues of the ankle and foot. The treatment included urgent microvascular foot reimplantation, microvascular muscle free flap transfer, and temporary fixation. This kind of injury should typically be treated by tibiocalcaneal arthrodesis. However, this was not performed, as after the successful early stages of the treatment he strongly objected to another surgery due to his fully functional status and the successful therapeutic results of our early treatment. Conclusions The injury described in this case study would ordinarily be treated by amputation, but due to the well-executed treatment in the early stages after the injury, the outcome was satisfying. Surprisingly and against our expectations, the late results of the treatment were successful even without arthrodesis. He is now 37 years old and has a functional foot 21 years after the injury. PMID:25266945

2014-01-01

84

Heterogeneity of Holocene clinothems: Significance for the exploitation of ancient slope deposits  

Energy Technology Data Exchange (ETDEWEB)

Inclined margin deposits (clinothems) of ancient carbonate platforms and reef complexes are known to be important hydrocarbon reservoirs and may function as conduits for the migration of oil from basin to reef. Recent work in the Tongue of the Ocean (TOTO), Bahamas, provides new insight into the depositional anatomy of Holocene clinothems. Observations from 94 dives in a research submersible in the TOTO indicates that modern carbonate slopes of 30-40{degree} are forming by the synsedimentary amalgamation of linear trains of sediment and talus blocks derived from the margin of the platform. Sand-sized sediment is transported downslope by various gravity induced mechanisms and deposited in topographic lows between linear ridges where it is rapidly lithified by submarine cementation. These sediment lobes are decimeters thick, and extend across and down the slope for a few meters and tens of meters, respectively. Repeated episodes of deposition and cementation result in the amalgamation of individual sediment packages that are linear in shape and discontinuous in both lateral and vertical dimensions along the slope. Progressive slope accretion of this nature will result in a heterogeneous texture and composition, further complicated by a complex internal facies geometry. Awareness of the internal heterogeneity of modern slope deposits may be a critical factor when evaluating the potential of ancient slope deposits to act as conduits for the migration of hydrocarbons or to be economically viable reservoirs.

Grammer, G.M.; Ginsburg, R.N.; McNeill, D.F. (Univ. of Miami, FL (USA))

1990-05-01

85

Dark Slope Streaks  

Science.gov (United States)

13 March 2004 Martian slope streaks occur in the regions most heavily mantled by fine, dry dust, particularly Tharsis, Arabia, and the knobby areas between Amazonis and Cerberus. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some examples of dark slope streaks off of buttes, mesas, and massifs in a dust-mantled crater in central Arabia Terra. New slope streaks form from time to time in the modern martian environment; the streaks in this image probably formed within the past decade. To create them, dust slid or avalanched down the slopes in an almost liquid-like manner. The image is located near 6.8oN, 321.7oW. The picture covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

2004-01-01

86

Glenshane Slopes Landscape  

...and form a striking landscape pattern on some slopes...have a more diverse landscape pattern, with a transition to the...form extensive, homogeneous blocks which camouflage the subtle variations of colour...

87

Iveagh Slopes Landscape  

...Strong horizontal field pattern on upper slopes.Sparsely settled...often emphasised by the hedgerow pattern, which radiates from the centre...is a distinctive elongated field pattern, with hedgerows running parallel to...

88

Linear Functions and Slope  

Science.gov (United States)

This session on linear function and slope contains five parts, multiple problems and videos, and interactive activities geared to help students recognize and understand linear relationships, explore slope and dependent and independent variables in graphs of linear relationships, and develop an understanding of rates and how they are related to slopes and equations. Throughout the session, students use spreadsheets to complete the work, and are encouraged to think about the ways technology can aid in teaching and understanding. The solutions for all problems are given, and many allow students to have a hint or tip as they solve. There is even a homework assignment with four problems for students after they have finished all five parts of the session.

2008-03-06

89

Narrowing the critical region for congenital vertical talus in patients with interstitial 18q deletions.  

Science.gov (United States)

Interstitial deletions of 18q lead to a number of phenotypic features, including multiple types of foot deformities. Many of these associated phenotypes have had their critical regions narrowly defined. Here we report on three patients with small overlapping deletions of chromosome 18q determined by microarray analysis (chr18:72493281-73512553 hg19 coordinates). All of the patients have congenital vertical talus (CVT). Based on these findings and previous reports in the literature and databases, we narrow the critical region for CVT to a minimum of five genes (ZNF407, ZADH2, TSHZ1, C18orf62, and ZNF516), and propose that TSHZ1 is the likely causative gene for CVT in 18q deletion syndrome. PMID:23495172

Mark, Paul R; Radlinski, Brian C; Core, Nathalie; Fryer, Alan; Kirk, Edwin P; Haldeman-Englert, Chad R

2013-05-01

90

Osteochondritis dissecans of the talus and knee: prospective comparison of MR and arthroscopic classifications.  

Science.gov (United States)

The primary objective of this study was to determine if magnetic resonance (MR) could accurately predict the arthroscopic stage of osteochondritis dissecans lesions of the knee and ankle. Twelve patients, who were indicated for arthroscopy on either clinical or radiographic findings, underwent an MR examination prior to arthroscopy. All scans were performed on a 0.35 T magnet using the same spin echo sequence: repetition time 1,000 ms and echo time 40 ms. Magnetic resonance scans were interpreted prospectively (D.W.N.) and retrospectively (J.S.) by the radiologists without knowledge of the arthroscopic findings. Both radiologists predicted the exact grade in 11 of 12 patients. A single Grade 2 lesion was called Grade 3 by both radiologists. An MR staging classification has been developed that allows accurate preoperative staging of osteochondritis dissecans lesions of the talus and knee. PMID:2398165

Nelson, D W; DiPaola, J; Colville, M; Schmidgall, J

1990-01-01

91

Western Slope Colorado  

International Nuclear Information System (INIS)

A conference on the geology and geologic resources of the Western Slope of western Colorado and eastern Utah is presented. Fourteen papers from the conference have been abstracted and indexed for the Department of Energy's Energy Data Base. These papers covered such topics as uranium resources, oil shale deposits, coal resources, oil and gas resources, and geothermal resources of the area

92

Slope Stability Analysis Program  

Science.gov (United States)

This site provides information as well as a downloadable demo version of a slope stability and reinforced soil analysis and design software. The software includes an analysis option which analyzes strata profile and groundwater conditions, surcharge loads and earthquake forces, slip surfaces, and reinforced soil options. Data input and editing can also be performed as well as output from the program and graphics.

2008-07-17

93

Slope filtrations revisited  

CERN Document Server

We give a "second generation" exposition of the slope filtration theorem for modules with Frobenius action over the Robba ring, providing a number of simplifications in the arguments. Some of these are inspired by parallel work of Hartl and Pink, which points out some analogies with the formalism of stable vector bundles.

Kedlaya, K S

2005-01-01

94

Snowboard, wakeboard, dashboard? Isolated fracture of the lateral process of the talus in a high-speed road traffic accident.  

LENUS (Irish Health Repository)

We present a 23-year-old man who sustained an isolated fracture of the lateral process of the talus (LPT) in a head-on vehicle collision at a combined speed of 200 km\\/h. The driver of the other vehicle sustained fatal injuries at the scene. The LPT was openly reduced and fixed with successful outcome at 3 months. This case is unusual in the method of injury, in particular in relation to the isolated relatively minor injury sustained.

Ng, Evangeline Shimei

2013-01-01

95

Low-grade fibromyxoid sarcoma of the talus: a case report.  

Science.gov (United States)

Low-grade fibromyxoid sarcoma is a rare tumor, which most commonly arises from the deep soft tissues of the lower extremities in young men. Diagnosis of this tumor can be difficult because of its deceptively benign histopathologic appearance. Specifically, the lesion is characterized by alternating fibrous and myxoid areas with variable cellularity and a whorled growth pattern. Like many soft tissue tumors, low-grade fibromyxoid sarcoma is also characterized by strong immunoreactivity to the human proto-oncogene BCL-2. Cytogenetically, the lesion has also been associated with the t (7,16) (q33;p11) translocation, with the characteristic resultant FUS and CREB3L2 fusion gene. In this report, we describe the rare case of a low-grade fibromyxoid sarcoma that appeared to develop as a primary malignancy in the neck of the talus of a young man who presented with recurrent ankle pain after a previous surgery for a cystic lesion at the same site. PMID:20510633

Dhillon, Mandeep Singh; Mootha, Aditya Krishna; Kumar, Vishal; Saini, Raghav; Bharti, Sreekant

2010-01-01

96

[Visualization of radiographically occult osteochondrosis dissecans of the talus using MRI].  

Science.gov (United States)

Posttraumatic disorders of the ankle are a common cause of chronic pain. Magnetic resonance imaging (MRI) has proved to be highly useful in clarifying a wide spectrum of underlying lesions which frequently cannot be detected on radiographs. Even if the assessment of the lateral collateral ligaments of the ankle is not regarded as a primary indication for MRI, it allows the diagnosis of subchondral contusions or cysts, anterolateral impingement syndrome, sinus tarsi syndrome, osteochondral fractures and osteochondrosis dissecans of the talus (ODT),which may not be detected with other imaging modalities. A 42 year old female patient suffered from persisting non-specific pain following an inversion trauma 4 months previously. MRI enabled the detection of an ODT which was not diagnosed on plain radiographs and which was verified upon arthroscopy. A superficial cartilage defect, as shown arthroscopically,was not delineated using MRI. Our observations indicate that MRI may be useful in patients with unclear persisting pain following ankle trauma and that it may contribute to the early detection of lesions which require surgical intervention. PMID:12658342

Wirth, S; Wieser, A; Witt, S N; Mutschler, W; Reiser, M

2003-03-01

97

[Tibiocalcaneal arthrodesis with retrograde nails. Description of a hindfoot procedure after massive talus destruction].  

Science.gov (United States)

Following loss of the talus, tibiocalcaneal fusion is often the only available means of obtaining weight-bearing ability in the lower limb. Length discrepancy may be managed with an allograft. This casuistic describes 6 patients with tibiocalcaneal fusion (mean age 64 years) who had received a structural femoral head allograft fusion for failed total ankle arthroplasty (3 cases), Charcot arthropathy (2 cases) and osteomyelitis (1 case). The mean follow-up was 33 months and all limbs could be salvaged. There were two cases of non-union (one with infection). The mean AOFAS score was 51 and the mean Mazur score was 37. In the SF-36 the mean PCS was 34.4 and the mean MCS was 48.4. It was shown that in the hindfoot, as at other sites, allografts may be used for the filling of major bone defects; however, the patient function will still be massively impaired. Therefore, the procedure should be confined to cases where less complex and less invasive techniques are unlikely to be of benefit. PMID:23624611

Klos, K; Lange, A; Matziolis, G; Wagner, A

2013-05-01

98

MRI-guided percutaneous retrograde drilling of osteochondritis dissecans of the talus: a feasibility study  

International Nuclear Information System (INIS)

The purpose of this study was to evaluate the feasibility of MRI guidance for percutaneous retrograde drilling in the treatment of osteochondritis dissecans of the talus (OCDT). Four patients, one juvenile and three adults, with one OCDT lesion each and persisting ankle pain after conservative treatment, were treated with MRI-guided retrograde drilling. All lesions were stable and located in the middle or posterior medial third of the talar dome. Pain relief and the ability to return to normal activities were assessed during clinical follow-up. MRI and plain film radiographs were used for imaging follow-up. Technical success was 100 % with no complications and with no damage to the overlying cartilage. All patients experienced some clinical benefit, although only one had complete resolution of pain and one had a relapse leading to surgical treatment. Changes in the pathological imaging findings were mostly very slight during the follow-up period. MRI guidance seems accurate, safe and technically feasible for retrograde drilling of OCDT. Larger series are needed to reliably assess its clinical value. (orig.)

99

MRI-guided percutaneous retrograde drilling of osteochondritis dissecans of the talus: a feasibility study  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this study was to evaluate the feasibility of MRI guidance for percutaneous retrograde drilling in the treatment of osteochondritis dissecans of the talus (OCDT). Four patients, one juvenile and three adults, with one OCDT lesion each and persisting ankle pain after conservative treatment, were treated with MRI-guided retrograde drilling. All lesions were stable and located in the middle or posterior medial third of the talar dome. Pain relief and the ability to return to normal activities were assessed during clinical follow-up. MRI and plain film radiographs were used for imaging follow-up. Technical success was 100 % with no complications and with no damage to the overlying cartilage. All patients experienced some clinical benefit, although only one had complete resolution of pain and one had a relapse leading to surgical treatment. Changes in the pathological imaging findings were mostly very slight during the follow-up period. MRI guidance seems accurate, safe and technically feasible for retrograde drilling of OCDT. Larger series are needed to reliably assess its clinical value. (orig.)

Kerimaa, Pekka; Ojala, Risto; Markkanen, Paula; Tervonen, Osmo; Blanco Sequeiros, Roberto [Oulu University Hospital, Department of Radiology, Oulu (Finland); Sinikumpu, Juha-Jaakko; Korhonen, Jussi [Oulu University Hospital, Department of Paediatric Surgery, Oulu (Finland); Hyvoenen, Pekka [Oulu University Hospital, Department of Surgery, Oulu (Finland)

2014-07-15

100

Slope constrained Topology Optimization  

DEFF Research Database (Denmark)

The problem of minimum compliance topology optimization of an elastic continuum is considered. A general continuous density-energy relation is assumed, including variable thickness sheet models and artificial power laws. To ensure existence of solutions, the design set is restricted by enforcing pointwise bounds on the density slopes. A finite element discretization procedure is described, and a proof of convergence of finite element solutions to exact solutions is given, as well as numerical examples obtained by a continuation/SLP (sequential linear programming) method. The convergence proof implies that checkerboard patterns and other numerical anomalies will not be present, or at least, that they can be made arbitrarily weak. (C) 1998 John Wiley & Sons, Ltd.

Sigmund, Ole

1998-01-01

 
 
 
 
101

Exceptional surgery and boundary slopes  

CERN Document Server

Let X be a norm curve in the SL(2,C)-character variety of a knot exterior M. Let t = || b || / || a || be the ratio of the Culler-Shalen norms of two distinct non-zero classes a, b in H_1(\\partial M, Z). We demonstrate that either X has exactly two associated strict boundary slopes \\pm t, or else there are strict boundary slopes r_1 and r_2 with |r_1| > t and |r_2| < t. As a consequence, we show that there are strict boundary slopes near cyclic, finite, and Seifert slopes. We also prove that the diameter of the set of strict boundary slopes can be bounded below using the Culler-Shalen norm of those slopes.

Ishikawa, M; Shimokawa, K; Ishikawa, Masaharu; Mattman, Thomas W.; Shimokawa, Koya

2002-01-01

102

Using Submarine Landslides to Predict Slope Stability  

Science.gov (United States)

Students use detailed bathymetric maps to find submarine landslides and compare the slope of these slides to the slope of hills near school and home. By comparing the slopes they can consider slope failure, especially during earthquakes.

Doan, Shawn

103

Enucleación medial de astrágalo abierta: Evolución a medio plazo Medial dislocation of the talus: Medium term evolution  

Directory of Open Access Journals (Sweden)

Full Text Available Paciente de 57 años con enucleación abierta medial del astrágalo izquierdo, con fractura suprasindesmal de peroné, por traumatismo indirecto. Se realizó lavado, limpieza del astrágalo y partes blandas, Friedrich, reducción, fijación con agujas de kirschner, sutura del ligamento deltoideo y osteosíntesis del peroné. No hubo infección superficial ni profunda postoperatoria. Permaneció seis semanas de inmovilización y tres meses en descarga. Dos años después no había signos radiológicos de necrosis avascular. En gammagrafía ósea realizada a los 18 meses de la lesión se observaba necrosis avascular parcial astragalina. Tres años después de la lesión realizaba vida normal, sin dolor en reposo pero sí a la marcha y movilidad con limitación de la dorsiflexión (-20º. Cinco años y medio después de la lesión presentaba hundimiento de cúpula astragalina por la necrosis avascular con sintomatología dolorosa a la marcha y diástasis tibio-peronea distal, que requirió realizar artrodesis tibio-astragalina.Fifty-seven year old patient with open medial dislocation of the left talus, with suprasyndesmotic fracture of the fibula, due to indirect traumatism. The following were carried out: washing, cleaning the talus and the soft parts, Friedrich, reduction, fixing with Kirschner needles, suture of the deltoid ligament, and osteosynthesis of the fibula. There were neither surface nor deep post-operational infections. The patient underwent six weeks of immobilisation and spent three months on discharge. Two years later there were no radiological signs of avascular necrosis. In the osseous gammagraphy carried out 18 months after the lesion, partial avascular necrosis of the talus was observed. Three years after the lesion, the patient was able to carry out a normal life, without pain in repose but with pain whilst moving, and mobility with limitation of dorsoinflection (-20º. Five and a half years after the lesion, the patient presented sinking of the talar dome due to avascular necrosis, with painful symptomatology whilst moving, and tibiofibular distal diastasis, which required ankle arthrodesis.

S. García Mata

2009-04-01

104

Rafferty Dam upstream slope rehabilitation  

Energy Technology Data Exchange (ETDEWEB)

Constructed over a three-year period stretching from 1988 to 1990, the Rafferty Dam is located approximately 220 kilometres southeast of Regina, Saskatchewan. The presence of soft, highly plastic clays up to 23 metres deep in the central portion of the valley and approximately 6 metres deep toward the abutments had a major influence over the design of the dam. To expedite the consolidation of the foundation clays, wick drains were installed, resulting in the considerable settling of the embankment during and after construction. A 2:1 (horizontal to vertical) upper slope followed by a 3:1 lower slope which intersected with a berm made up a typical as-built cross-section. In 1997 and 1998, along the upstream and downstream shoulders of the dam crest, several cracks were detected. A vertical drop of 300 millimetres of the downstream slope at the crest shoulder was noted, and it forced the monitoring and reassessment of the embankment slopes. The upper slope was as steep as 1.2:1 on the upstream side and 1.8:1 on the downstream side, as a survey of the slopes revealed. Despite the uneven settlement, the lower slopes on either side were close to design values. The movement along a shallow plane by the downstream slope did not present a threat to the safety of the dam, and subsequent efforts were concentrated on the upstream slope. Stability analyses of the upstream slopes were conducted, and the results indicated factors of safety of less than one for all loading conditions, using the current configuration of the embankment slopes. To increase the factors of safety, the decision was made to flatten the slope, which could only be economically accomplished through the installation of additional rip-rap, as the upstream slope is rock rip-rapped. The fall of 2000 saw the work being completed. The results of the slope stability analyses, the design of remedial measures, and the successful construction of the project are all presented by the author in this paper. 13 refs., 5 tabs., 15 figs.

Rahman, M.G. [Saskatchewan Water Corp., Moose Jaw, SK (Canada)

2001-10-01

105

Closed subtalar dislocation with non-displaced fractures of talus and navicular: a case report and review of the literature.  

Science.gov (United States)

Closed subtalar dislocations associated with talus and navicular fractures are rare injuries. We report on a case of a 43-year-old builder man with medial subtalar dislocation that was further complicated by minimally displaced talar and navicular fractures. Successful closed reduction under general anesthesia was followed by non-weight bearing and ankle immobilization with a below-knee cast for 6 ;weeks. At 3 years post-injury, the subtalar joint was stable, the foot and ankle mobility was in normal limits and the patient could still work as a builder. However, he complained for occasionally mild pain due to the development of post-traumatic arthritis in subtalar and ankle joints. Our search in literature revealed that conservative treatment of all the successfully reduced and minimally displaced subtalar fracture-dislocations has given superior results compared to surgical management. However, even in cases with no or slight fracture displacement, avascular necrosis of the talus or arthritis of the surrounding joints can compromise the final functional outcome. PMID:19918402

Fotiadis, Elias; Lyrtzis, Christos; Svarnas, Theodoros; Koimtzis, Miltos; Akritopoulou, Kiriaki; Chalidis, Byron

2009-01-01

106

Functional anatomy of the calcaneum and talus in Cercopithecinae (Mammalia, Primates, Cercopithecidae  

Directory of Open Access Journals (Sweden)

Full Text Available Among the species of the order Primates exist a huge variety of forms and habitats. This heterogeneity has encouraged the evolution and development of a great number of locomotor adaptations to different environments. Thus, nowadays there are both arboreal and terrestrial groups within the order. The subfamily Cercopithecinae present taxa with both kinds of locomotor behaviours, although the most of them are adapted to a ground life-style. This group probably has an arboreal ancestor and its radiation is relatively recent. Consequently, species belonged to this group present mixed features or sometimes not too much derived ones. Likewise, it is important the fact that the evolutionary history and phylogeny of the group could influence in some characteristics. Both the calcaneum and the talus are two of the largest bones of the foot and are good for inferring the kind of locomotion. For this reason, it has been used these two tarsal bones to study the morphology of eight species of cercopithecines and then deduce functional implications of the kind of locomotion.

Dentro del orden Primates existe una gran variedad de especies distribuidas a lo largo de hábitats muy diversos. Dicha heterogeneidad ha fomentado la evolución y desarrollo de un gran número de adaptaciones locomotoras a los diferentes ambientes en los que habitan. Así, existen en la actualidad tanto grupos arborícolas como terrestres. La subfamilia Cercopithecinae agrupa una serie de taxones que representan ambos comportamientos locomotores, aunque la mayoría de las especies están adaptadas a una vida en el suelo. Se supone que este grupo desciende de un ancestro arborícola y que su radiación es relativamente reciente. En consecuencia, las especies de este grupo presentan características mixtas o poco derivadas en algunas ocasiones. Asimismo, es importante tener en cuenta la influencia que la herencia filogenética puede tener sobre alguno de estos rasgos. El calcáneo y el astrágalo son dos de los huesos más grandes del pie y ambos son buenos indicadores del tipo de locomoción. Por este motivo, se han utilizado estos dos tarsales para llevar a cabo el estudio de la morfología de ocho especies de cercopitecoideos, de tal manera que luego se ha podido hacer una serie de inferencias funcionales en cuanto al tipo de locomocón de las mismas.

Pina, M.

2011-12-01

107

Interior Slopes of Copernican Craters  

Science.gov (United States)

The Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) routinely acquires high resolution (50 to 200 cm pixel scales) stereo pairs from adjacent orbits through spacecraft slews; parallax angles are typically >20°, and the local incidence angle between 40° and 65°. These observations are reduced to digital elevation models (DEM) using a combination of ISIS (USGS) and SOCET Set (BAE Systems). For this study DEMs originally sampled at 2 m scales were reduced (averaging technique) to 5 m scales to provide slopes calculated over 3x3 pixel boxes (15 m x 15 m). The upper 50% of interior walls of Copernican craters (2 to 20 km diameter) typically have average slopes of 36°, with slopes locally above 40° not uncommon (i.e. Fig 1: 2.3 km diam, 17.68°S, 144.41°E). Giordano Bruno (GB; 35.97N°, 102.86°E) is likely the youngest 20-km diameter class crater on the Moon. Its floor is dominated by impact forms (ponds and flows), and inner walls exhibit a series of coalesced flow lobes emanating from steep upper slopes. The lobes appear to be composed of dry granular material based on the observation of boulder trails superposed on many examples. The upper slopes average 36° or more, with some slopes above 40°. For much of GB, slopes exceed 30° all the way to the crater floor (especially in the SE). The high slopes imply angular grains, some level of cohesion, and/or higher angles of repose due to the Moon's relatively low gravity. Larmor Q (28.56°N, 176.33°E), another large Copernican crater, is elliptical in plan (23 x 18 km diameter), with an interior floor dominated by large slump blocks. Like GB its walls exhibit overlapping lobes (granular materials) emanating from interior wall slopes that range from 30° to 36°. Other Copernican craters exhibit similar steep slopes on interior walls: Moore F (23 km diam), Necho (30 km), and two unnamed craters (9 km,13.31°S, 257.55°E; 9 km, 15.72°, 177.39°E). Slopes of the central peaks of Tycho crater (0.1 by age) are equally steep (24° to 36°). The central peaks of Tsiolkovskiy crater (>3.0 by age) have slopes significantly shallower (20°) than younger counterparts, likely due to eons of micrometorite bombardment. High resolution (2-5 m pixel scales) LROC NAC topographic maps of impact craters are enabling characterization of slopes across a broad population of fresh and degraded craters; key information for improving numeric models of crater formation and subsequent erosion processes.

Robinson, M. S.; Burns, K.; Stelling, R.; Speyerer, E.; Mahanti, P.

2012-12-01

108

Car Depreciation (rate and slope)  

Science.gov (United States)

The purpose of this activity is for students to use the concept of the rate of depreciation in a real world situation to investigate the relationship between rate and slope. Students create ordered pairs, graph depreciating car values, and calculate rates of depreciation, then identify that the rate of depreciation = slope of the line. Using the equation they then solve for future values and times.

2010-01-01

109

North Slope (Wahluke Slope) expedited response action cleanup plan  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this action is to mitigate any threat to public health and the environment from hazards on the North Slope and meet the expedited response action (ERA) objective of cleanup to a degree requiring no further action. The ERA may be the final remediation of the 100-I-3 Operable Unit. A No Action record of decision (ROD) may be issued after remediation completion. The US Department of Energy (DOE) currently owns or administers approximately 140 mi{sup 2} (about 90,000 acres) of land north and east of the Columbia River (referred to as the North Slope) that is part of the Hanford Site. The North Slope, also commonly known as the Wahluke Slope, was not used for plutonium production or support facilities; it was used for military air defense of the Hanford Site and vicinity. The North Slope contained seven antiaircraft gun emplacements and three Nike-Ajax missile positions. These military positions were vacated in 1960--1961 as the defense requirements at Hanford changed. They were demolished in 1974. Prior to government control in 1943, the North Slope was homesteaded. Since the initiation of this ERA in the summer of 1992, DOE signed the modified Hanford Federal Agreement and Consent Order (Tri-Party Agreement) with the Washington Department of Ecology (Ecology) and the US Environmental Protection Agency (EPA), in which a milestone was set to complete remediation activities and a draft closeout report by October 1994. Remediation activities will make the North Slope area available for future non-DOE uses. Thirty-nine sites have undergone limited characterization to determine if significant environmental hazards exist. This plan documents the results of that characterization and evaluates the potential remediation alternatives.

1994-02-01

110

North Slope (Wahluke Slope) expedited response action cleanup plan  

International Nuclear Information System (INIS)

The purpose of this action is to mitigate any threat to public health and the environment from hazards on the North Slope and meet the expedited response action (ERA) objective of cleanup to a degree requiring no further action. The ERA may be the final remediation of the 100-I-3 Operable Unit. A No Action record of decision (ROD) may be issued after remediation completion. The US Department of Energy (DOE) currently owns or administers approximately 140 mi2 (about 90,000 acres) of land north and east of the Columbia River (referred to as the North Slope) that is part of the Hanford Site. The North Slope, also commonly known as the Wahluke Slope, was not used for plutonium production or support facilities; it was used for military air defense of the Hanford Site and vicinity. The North Slope contained seven antiaircraft gun emplacements and three Nike-Ajax missile positions. These military positions were vacated in 1960--1961 as the defense requirements at Hanford changed. They were demolished in 1974. Prior to government control in 1943, the North Slope was homesteaded. Since the initiation of this ERA in the summer of 1992, DOE signed the modified Hanford Federal Agreement and Consent Order (Tri-Party Agreement) with the Washington Department of Ecology (Ecology) and the US Environmental Protection Agency (EPA), in which a milestone was set to complete remediation activities and a draft closeout report by October 1994. Remediation activities will make the North Slope area available for future non-DOE uses. Thirty-nine sites have undergone limited characterization to determine if significant environmental hazards exist. This plan documents the results of that characterization and evaluates the potential remediation alternatives

111

Enucleación medial de astrágalo abierta: Evolución a medio plazo / Medial dislocation of the talus: Medium term evolution  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Paciente de 57 años con enucleación abierta medial del astrágalo izquierdo, con fractura suprasindesmal de peroné, por traumatismo indirecto. Se realizó lavado, limpieza del astrágalo y partes blandas, Friedrich, reducción, fijación con agujas de kirschner, sutura del ligamento deltoideo y osteosínt [...] esis del peroné. No hubo infección superficial ni profunda postoperatoria. Permaneció seis semanas de inmovilización y tres meses en descarga. Dos años después no había signos radiológicos de necrosis avascular. En gammagrafía ósea realizada a los 18 meses de la lesión se observaba necrosis avascular parcial astragalina. Tres años después de la lesión realizaba vida normal, sin dolor en reposo pero sí a la marcha y movilidad con limitación de la dorsiflexión (-20º). Cinco años y medio después de la lesión presentaba hundimiento de cúpula astragalina por la necrosis avascular con sintomatología dolorosa a la marcha y diástasis tibio-peronea distal, que requirió realizar artrodesis tibio-astragalina. Abstract in english Fifty-seven year old patient with open medial dislocation of the left talus, with suprasyndesmotic fracture of the fibula, due to indirect traumatism. The following were carried out: washing, cleaning the talus and the soft parts, Friedrich, reduction, fixing with Kirschner needles, suture of the de [...] ltoid ligament, and osteosynthesis of the fibula. There were neither surface nor deep post-operational infections. The patient underwent six weeks of immobilisation and spent three months on discharge. Two years later there were no radiological signs of avascular necrosis. In the osseous gammagraphy carried out 18 months after the lesion, partial avascular necrosis of the talus was observed. Three years after the lesion, the patient was able to carry out a normal life, without pain in repose but with pain whilst moving, and mobility with limitation of dorsoinflection (-20º). Five and a half years after the lesion, the patient presented sinking of the talar dome due to avascular necrosis, with painful symptomatology whilst moving, and tibiofibular distal diastasis, which required ankle arthrodesis.

S., García Mata; A., Hidalgo Ovejero; F., Martínez de Lecea.

2009-04-01

112

Enucleación medial de astrágalo abierta: Evolución a medio plazo / Medial dislocation of the talus: Medium term evolution  

Scientific Electronic Library Online (English)

Full Text Available SciELO Spain | Language: Spanish Abstract in spanish Paciente de 57 años con enucleación abierta medial del astrágalo izquierdo, con fractura suprasindesmal de peroné, por traumatismo indirecto. Se realizó lavado, limpieza del astrágalo y partes blandas, Friedrich, reducción, fijación con agujas de kirschner, sutura del ligamento deltoideo y osteosínt [...] esis del peroné. No hubo infección superficial ni profunda postoperatoria. Permaneció seis semanas de inmovilización y tres meses en descarga. Dos años después no había signos radiológicos de necrosis avascular. En gammagrafía ósea realizada a los 18 meses de la lesión se observaba necrosis avascular parcial astragalina. Tres años después de la lesión realizaba vida normal, sin dolor en reposo pero sí a la marcha y movilidad con limitación de la dorsiflexión (-20º). Cinco años y medio después de la lesión presentaba hundimiento de cúpula astragalina por la necrosis avascular con sintomatología dolorosa a la marcha y diástasis tibio-peronea distal, que requirió realizar artrodesis tibio-astragalina. Abstract in english Fifty-seven year old patient with open medial dislocation of the left talus, with suprasyndesmotic fracture of the fibula, due to indirect traumatism. The following were carried out: washing, cleaning the talus and the soft parts, Friedrich, reduction, fixing with Kirschner needles, suture of the de [...] ltoid ligament, and osteosynthesis of the fibula. There were neither surface nor deep post-operational infections. The patient underwent six weeks of immobilisation and spent three months on discharge. Two years later there were no radiological signs of avascular necrosis. In the osseous gammagraphy carried out 18 months after the lesion, partial avascular necrosis of the talus was observed. Three years after the lesion, the patient was able to carry out a normal life, without pain in repose but with pain whilst moving, and mobility with limitation of dorsoinflection (-20º). Five and a half years after the lesion, the patient presented sinking of the talar dome due to avascular necrosis, with painful symptomatology whilst moving, and tibiofibular distal diastasis, which required ankle arthrodesis.

S., García Mata; A., Hidalgo Ovejero; F., Martínez de Lecea.

113

Percutaneous osteoplasty for the treatment of a painful osteochondral lesion of the talus: a case report and literature review.  

Science.gov (United States)

An osteochondral lesion of the talus (OLT) is a lesion involving the talar articular cartilage and its subchondral bone. OLT is a known cause of chronic ankle pain after ankle sprains in the active population. The lesion causes deep ankle pain associated with weight-bearing, impaired function, limited range of motion, stiffness, catching, locking, and swelling. There are 2 common patterns of OLTs. Anterolateral talar dome lesions result from inversion and dorsiflexion injuries of the ankle at the area impacting against the fibula. Posteromedial lesions result from inversion, plantar flexion, and external rotation injuries of the ankle at the area impacting against the tibial ceiling of the ankle joint. Early diagnosis of an OLT is particularly important because the tibiotalar joint is exposed to more compressive load per unit area than any other joint in the body. Failure of diagnosis can lead to the evolution of a small, stable lesion into a larger lesion or an unstable fragment, which can result in chronic pain, joint instability, and premature osteoarthritis. A 43-year-old man, with a history of ankle sprain one year previously, visited our pain clinic for continuous right ankle pain after walking or standing for more than 30 minutes. There was a focal tenderness on the posteromedial area of the right talus. Imaging studies revealed a posteromedial OLT classified as having a geode form according to the FOG (fractures, osteonecroses, geodes) radiological classification and categorized as a stage 2a lesion on magnetic resonance imaging. The patient was scheduled for aspiration and osteoplasty with hydroxyapatite under arthroscopic and fluoroscopic guidance. A 26-gauge needle was inserted to infiltrate local anesthetics into the skin over the cyst and ankle joint. An arthroscope was placed into the joint to approach the OLT. The arthroscopic view showed that there was no connection between the OLT and the cyst of the talus body. A 13-gauge bone biopsy needle was inserted into the cyst, and aspiration was performed. Aspirated fluid from the cyst was originally white and clear; however, it changed to a blood-tinged, reddish color due to mixing with the incisional blood. After aspiration, contrast medium was injected, and the shape of the spread was observed. Bone cement comprising hydroxyapatite was injected to fill the bone defect of the cyst. A 1.5 mL volume of cement was injected into the talus under vigilant fluoroscopic and arthroscopic monitoring to prevent its dissemination into the joint. There was no cement leakage into the vessels or articular space. Postoperative fluoroscopy and computed tomography images showed bone cement filling of the defect. In the present case, arthroscopic and fluoroscopic guidance was used for aspiration of an OLT and for performing percutaneous osteoplasty with hydroxyapatite for one defect; this treatment decreased pain upon weight bearing and enabled a return to work without any restrictions one week after the procedure. The purpose of this report was to highlight the presence of OLT in chronic ankle pain and to review its management strategies. PMID:22996869

Seo, Sung-Suk; Park, Joo-Yeon; Kim, Hae-Jin; Yoon, Ji-Wook; Park, Sang-Hyun; Kim, Kyung-Hoon

2012-01-01

114

Anatomy of gravitationally deformed slopes  

Science.gov (United States)

Deep-seated gravitational slope deformation is the deformation of rocks as well as slope surfaces, but the internal structures have not been well observed and described before. This is mainly due to the difficulty in obtaining undisturbed samples from underground. We analyzed the internal deformational structures of gravitationally deformed slopes by using high quality drilled cores obtained by hybrid drilling technique, which has been recently developed and can recover very fragile materials that could not be taken by the conventional drilling techniques. Investigated slopes were gravitationally deformed out-facing slopes of pelitic schist and shale. The slope surfaces showed deformational features of small steps, depressions, knobs, and linear depressions, but had no major main scarp and landslide body with well-defined outline. This is indicative of slow, deep-seated gravitational deformation. Most of these small deformational features are hidden by vegetations, but they are detected by using airborne laser scanner. Drilled cores showed that the internal deformation is dominated by the slip and tearing off along foliations. Slippage along foliations is conspicuous in pelitic schist: Pelitic schist is sheared, particularly along black layers, which are rich in graphite and pyrite. Graphite is known to be a solid lubricant in material sciences, which seems to be why shearing occurs along the black layers. Rock mass between two slip layers is sheared, rotated, fractured, and pulverized; undulation of bedding or schistosity could be the nucleation points of fracturing. Tearing off along foliations is also the major deformation mode, which forms jagged morphology of rock fragments within shear zones. Rock fragments with jagged surface are commonly observed in "gouge", which is very different from tectonic gouge. This probably reflects the low confining pressures during their formation. Microscopic to mesoscopic openings along fractures are commonly observed with fractures, which also suggests the low confining pressures. Vertical distribution of gravitational deformation with above features indicates that gravitational shear zones are nucleated in a distributed manner, then gradually connected to each other, and finally cut through the whole slope. This is the transition of gravitational mass rock creep to rock slide. First nucleation points seem to be controlled by the heterogeneity of rock properties. Thick black layers in pelitic schist, shale near thick sandstone beds in sedimentary rocks, were such nuclear points. The geometrical relationships between the distribution of fracture zones and the slope morphology suggest that they are formed in accordance to the valley incision and resultant slope destabilization.

Chigira, Masahiro; Yamasaki, Shintaro; Hariyama, Takehiro

2010-05-01

115

The surgical treatment of children with congenital convex foot (vertical talus): evaluation of midtarsal surgical release and open reduction.  

Science.gov (United States)

In this study we evaluated the results of midtarsal release and open reduction for the treatment of children with convex congenital foot (CCF) (vertical talus) and compared them with the published results of peritalar release. Between 1977 and 2009, a total of 22 children (31 feet) underwent this procedure. In 15 children (48%) the CCF was isolated and in the remainder it was not (seven with arthrogryposis, two with spinal dysraphism, one with a polymalformative syndrome and six with an undefined neurological disorder). Pre-operatively, the mean tibiotalar angle was 150.2° (106° to 175°) and the mean calcaneal pitch angle was -19.3° (-72° to 4°). The procedure included talonavicular and calcaneocuboid joint capsulotomies, lengthening of tendons of tibialis anterior and the extensors of the toes, allowing reduction of the midtarsal joints. Lengthening of the Achilles tendon was necessary in 23 feet (74%). The mean follow-up was 11 years (2 to 21). The results, as assessed by the Adelaar score, were good in 24 feet (77.4%), fair in six (19.3%) and poor in one foot (3.3%), with no difference between those with isolated CCF and those without. The mean American Orthopaedic Foot and Ankle Society midfoot score was 89.9 (54 to 100) and 77.8 (36 to 93) for those with isolated CCF and those without, respectively. At the final follow-up, the mean tibiotalar (120°; 90 to 152) and calcaneal pitch angles (4°; -13 to 22) had improved significantly (p avascular necrosis of the talus. Midtarsal joint release and open reduction is a satisfactory procedure, which may provide better results than peritalar release. Complications include the development of pes planovalgus and persistent dorsal subluxation of the talonavicular joint. PMID:24891587

Ramanoudjame, M; Loriaut, P; Seringe, R; Glorion, C; Wicart, P

2014-06-01

116

Slope stability in surface mining  

Energy Technology Data Exchange (ETDEWEB)

The volume contains a total of 49 invited papers in four sections entitled: rock slope design considerations; case studies in rock slope stability; stability of waste rock embankments; and tailings and heap leaching. Three papers are directly relevant to coal mining: coal mine highwall stability by Ben Seegmiller; construction and operation of a major mined-rock disposal facility at Elkview Coal Corporation, British Colombia by Brent Zeitz; and steepened spoil slopes at Bridger Coal Company, by William Gerhard. The papers were invited in the long time lapse between the 3rd and 4th international conference on stability in open pit mining to supplement earlier proceedings. Immediately following the publication of this volume, a symposium was held in conjunction with the 2001 SME annual meeting in Denver, Colorado, USA.

Hustrulid, W.A.; McCarter, M.K.; Van Zyl, D.J.A. (eds.)

2000-07-01

117

Exploring Slope with Stairs & Steps  

Science.gov (United States)

As much as ever before, mathematics teachers are searching for ways to connect mathematics to real-life scenarios within STEM contexts. As students develop skill in proportional reasoning, they examine graphical representations of linear functions, learn to associate "slope" with "steepness" and rate of change, and develop…

Smith, Toni M.; Seshaiyer, Padmanabhan; Peixoto, Nathalia; Suh, Jennifer M.; Bagshaw, Graham; Collins, Laurena K.

2013-01-01

118

Radioecological reliability of slope ecosystem  

International Nuclear Information System (INIS)

Natural and technogenic cataclysms taking place in Ukraine bring to the forefront the problem of estimation and forecast of different ecosystems type. Theory and models of the radio capacity and reliability developed by us allow to describe adequately regularities of radionuclide migration and redistribution in slope ecosystems, and carry out mathematical modeling of investigated phenomena. That will give the possibility to use special countermeasures

119

Did talus-derived rock glaciers and cirque glaciers co-exist during MIS 3 and 2 in coastal northern Norway?  

Science.gov (United States)

Evidence of past activity of talus-derived rock glaciers and cirque glaciers, nearly down to the present-day sea level in northern Norway, can be taken as proof of extreme climate in the past. The geology of Andøya (69 N 16 E) has been explored for a long time, and suites of onshore and offshore landforms have been investigated in order to reveal the ice age history. The continental shelf is less than 15 km wide off northwestern Andøya, and the current knowledge of the LGM ice margin position at Andøya suggests that perhaps the Ålesund (38.5-34.5 ka) and Austnes (44-42 ka) Interstadials should be present in the (morpho-) stratigraphic record. Pinpointing the time of landform formation and/or stagnation (inactivation) can provide details of past local or regional patterns of temperature, precipitation and prevailing wind directions. Crucial in this context is the ability to precisely date the landforms, and to understand what phase (if any) of the landform's history the date reflects (e.g. inception, inactivation, stabilisation). This study has investigated the temporal relationship between activity of cirque glaciers and talus-derived rock glaciers on northern Andøya using cosmogenic 10Be surface exposure dating. If active at the same time, talus-derived rock glaciers and cirque glaciers must reflect a delicate balance in the local climate between temperature, precipitation and wind direction, allowing both types to co-exist. If active at different times, talus-derived rock glaciers and cirque glaciers in the same region could reflect shifting climatic conditions (temperature, precipitation, wind direction). Ages of these landforms could provide valuable palaeoclimate information prior to the 'onset' of biogenic production and/or older than the time range of radiocarbon dating.

Linge, H.; Dahl, S.

2012-12-01

120

Shallow viscoplastic flows on slopes  

Science.gov (United States)

Evolving viscoplastic flows on slopes are an important idealization of many geophysical flows for which yield stresses are thought to play a role. For such models, asymptotic expansions suitable for slowly moving, shallow fluid layers (lubrication theory) reduce the governing equations to a simpler problem for the fluid thickness. We consider the version of this theory for the Herschel-Bulkley fluid model and provide a variety of solutions, both numerical and analytical.

Balmforth, Neil; Craster, Richard

2001-11-01

 
 
 
 
121

High slope waste dumps – a proven possibility  

Directory of Open Access Journals (Sweden)

Full Text Available This paper is an overview of dumping operations on High Slope Waste Dump at Veliki Krivelj open pit copper mine, RTB Bor, Serbia. The High Slope Waste Dump in Bor is the highest single slope waste dump in the world with the slope height of 405 m. The paper gives the basics and limitations of the designed dumping technology, the redesigned technology, gives an overview of the 13 year long operation and gathered experiences and addresses the main issues of dumping operations in high slope conditions as well as the present condition of the High Slope Waste Dump.

Igor Svrkota

2013-11-01

122

Human talus bones from the Middle Pleistocene site of Sima de los Huesos (Sierra de Atapuerca, Burgos, Spain).  

Science.gov (United States)

Here we present and describe comparatively 25 talus bones from the Middle Pleistocene site of the Sima de los Huesos (SH) (Sierra de Atapuerca, Burgos, Spain). These tali belong to 14 individuals (11 adult and three immature). Although variation among Middle and Late Pleistocene tali tends to be subtle, this study has identified unique morphological characteristics of the SH tali. They are vertically shorter than those of Late Pleistocene Homo sapiens, and show a shorter head and a broader lateral malleolar facet than all of the samples. Moreover, a few shared characters with Neanderthals are consistent with the hypothesis that the SH population and Neanderthals are sister groups. These shared characters are a broad lateral malleolar facet, a trochlear height intermediate between modern humans and Late Pleistocene H. sapiens, and a short middle calcaneal facet. It has been possible to propose sex assignment for the SH tali based on their size. Stature estimates based on these fossils give a mean stature of 174.4 cm for males and 161.9 cm for females, similar to that obtained based on the long bones from this same site. PMID:23706407

Pablos, Adrián; Martínez, Ignacio; Lorenzo, Carlos; Gracia, Ana; Sala, Nohemi; Arsuaga, Juan Luis

2013-07-01

123

Geotechnical system reliability of slopes  

International Nuclear Information System (INIS)

In slope stability analysis it is customary to search for the critical slip surface considering the conventional factor of safety as an index of stability. With the development of reliability analysis approaches within a probabilistic framework, alternative definitions of the critical slip surface can be adopted. Thus one may define a critical slip surface as one with the lowest reliability index or one with the highest probability of failure. However, it is important to consider the slope stability problem in terms of a system of many potential slip surfaces. For such a system, the calculation of system reliability is appropriate and desirable. In this paper, system reliability bounds are calculated within a probabilistic framework. The 'system reliability' or the 'system probability of failure' must be estimated for comparison with the corresponding reliability or probability of failure with respect to a 'critical' slip surface. The general slope stability problem involving non-zero internal friction angle involves a non-linear performance function. Moreover, the expression for factor of safety is usually inexplicit except for the ordinary method of slices which is not accurate except when 'oe = 0'. This paper addresses the system reliability for inexplicit and non-linear performance functions as well as for linear and explicit ones. Any version of the method of slices may be used although the proposed approach is presented on the basis of the Bishop simplified method. It is shown that the upper bound system failure probability is higher than the failure probability associated with a critical slip surface. The difference increases as the coefficient of variation of the shear strength parameters increases

124

A simple limit for slope instability  

CERN Document Server

Ross and Thomas have shown that subschemes can K-destabilise polarised varieties, yielding a notion known as slope (in)stability for varieties. Here we describe a special situation in which slope instability for varieties (for example of general type) corresponds to a slope instability type condition for certain bundles, making the computations almost trivial.

Stoppa, J

2009-01-01

125

Survey observation of opencast slopes and interpretation  

Energy Technology Data Exchange (ETDEWEB)

This paper discusses the monitoring of the static stabilities of slopes and slope systems by mine survey in the open-pit forefield, at open-pit slopes within the grown and dumped rock masses as well as on the surface and at the foot of heaps. (In German)

Fisenko, G.L.

1977-01-01

126

Evolving Viscoplastic Flows Upon Slopes  

Science.gov (United States)

Evolving viscoplastic flows upon slopes are an important idealization of many flows in a variety of geophysical situations where yield stress is thought to play a role. For such models, asymptotic expansions suitable for slowly moving, shallow fluid layers (lubrication theory) reduce the governing equations to a simpler problem in terms of the fluid thickness. We consider the version of the theory for fluids described by the Herschel-Bulkley constitutive law, and provide a variety of solutions to the reduced equation, both nu- merical and analytical. For extruded, inclined domes, we derive the characteristic tem- poral behaviour of measures of the dome's dimensions.

Balmforth, N. J.; Craster, R. V.; Sassi, R.

127

High slope waste dumps – a proven possibility  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper is an overview of dumping operations on High Slope Waste Dump at Veliki Krivelj open pit copper mine, RTB Bor, Serbia. The High Slope Waste Dump in Bor is the highest single slope waste dump in the world with the slope height of 405 m. The paper gives the basics and limitations of the designed dumping technology, the redesigned technology, gives an overview of the 13 year long operation and gathered experiences and addresses the main issues of dumping operations in high slope condi...

Igor Svrkota; Radoje Pantovi?; Miodrag Žiki?; Saša Stojadinovi?; Dejan Petrovi?

2013-01-01

128

Slope Stability Analysis Using Numerical Method  

Directory of Open Access Journals (Sweden)

Full Text Available Stability evaluations are regularly achieved in order to measure the safe and efficient design of man-made slope (e.g., open pit mining, road cuts, etc., and/or the stability conditions of a natural slope. It has been issue of concern to numerous previous investigators. The numerical technique chosen depends on both soil specifications and its situations and the potential mode of failure. Assessment has been made for slope system with different slope for both cohesive and cohesionless soil. Two-dimensional finite element approach has been used to simulate and analysis the whole geotechnical system. This study illustrated that the factor of safety in the structure of slope case decreased while the slope was increasing for both types of soils. In addition, the displacement in the points when the section is change (in the critical zone is increasing when the slope is increasing.

Jasim M. Abbas

2014-01-01

129

Slope filtrations for relative Frobenius  

CERN Document Server

The slope filtration theorem gives a partial analogue of the eigenspace decomposition of a linear transformation, for a Frobenius-semilinear endomorphism of a finite free module over the Robba ring (the ring of germs of rigid analytic functions on an unspecified open annulus of outer radius 1) over a discretely valued field. In this paper, we give a third-generation proof of this theorem, which both introduces some new simplifications (particularly the use of faithfully flat descent, to recover the theorem from a classification theorem of Dieudonne-Manin type) and extends the result to allow an arbitrary action on coefficients (previously the action on coefficients had to itself be a lift of an absolute Frobenius). This extension is relevant to a study of (phi, Gamma)-modules associated to families of p-adic Galois representations, presently being initiated by Berger and Colmez.

Kedlaya, K S

2006-01-01

130

When does the flat-top talus lesion occur in idiopathic clubfoot: evaluation with magnetic resonance imaging at three months of age.  

Science.gov (United States)

Flat-top talus has been described as a pathologic change secondary to idiopathic clubfoot condition and/or as a direct result of nonoperative manipulation involving forced dorsiflexion and molding of the cartilaginous talus. No definitive study, however, on the etiology and the timing of the flat-top talus deformity has been performed to date. The authors evaluated the magnetic resonance images of eleven patients with idiopathic clubfoot deformities treated with 2 to 3 months of casting to assess if flattening of the talar dome occurred at this age with this amount of casting. All children were 3 months of age, were casted for a maximum of 2 to 3 months, and sedated before MRI examination. The images were evaluated for maximum talar head height, maximum talar body height, and deviation of the talar body from a perfect circle. Maximum talar head height ranged from 4 to 9 mm, maximum talar body height ranged from 6 to 10 mm. Eight of the eleven had maximum talar body measurements 3 to 5mm greater than maximum talar head height. Three of the eleven patients had head and body size of equal proportion. Two of the eleven had a talar body that was within 1 mm of a perfect circle. The remaining nine patients had perfectly round talar bodies. In the senior author's (RSD) experience with treating clubfeet, a substantial increase has been seen at operation in flat-top tali among children that were casted for more than 1 year before surgical correction, compared to children casted for 3 months before surgical correction. The current investigation indicated that although tali of children with clubfeet are abnormally shaped, the talar body remains larger than the talar head and maintains its roundness after two to three months of corrective casting. Maintenance of cast treatment for more than three months may lead to the flat-top talus deformity. The authors recommend surgical intervention following three months of failed manipulation and casting to prevent this deformity. PMID:11428762

Sullivan, R J; Davidson, R S

2001-05-01

131

Dip-slope and Dip-slope Failures in Taiwan - a Review  

Science.gov (United States)

Taiwan is famous for dip-slope and dip-slope slides. Dip-slopes exist at many places in the fold-and-thrust belt of Taiwan. Under active cutting of stream channels and man-made excavations, a dip-slope may become unstable and susceptible for mass sliding. Daylight of a bedding parallel clay seam is the most dangerous type for dip-slope sliding. Buckling or shear-off features may also happen at toe of a long dip-slope. Besides, a dip-slope is also dangerous for shallow debris slides, if the slope angle is between 25 to 45 degrees and the debris (colluvium or slope wash) is thick (>1m). These unstable slopes may slide during a triggering event, earthquake or typhoon storm; or even slide without a triggering event, like the 2010 Tapu case. Initial buckling feature had been found in the dip-slope of the Feitsui arch dam abutment after detailed explorations. Shear-off feature have also been found in dip-slope located in right bank of the Nahua reservoir after field investigation and drilling. The Chiufengerhshan slide may also be shear-off type. On the other hand, the Tapu, the Tsaoling slides and others are of direct slide type. The Neihoo Bishan slide is a shallow debris slide on dip-slope. All these cases demonstrate the four different types of dip-slope slide. The hazard of a dip-slope should be investigated to cover these possible types of failure. The existence of bedding parallel clay seams is critical for the stability of a dip-slope, either for direct slide or buckling or shear-off type of failure, and is a hot point during investigation. Because, the stability of a dip-slope is changing with time, therefore, detailed explorations to including weathering and erosion rates are also very necessary to ensure the long-term stability of a dip-slope.

Lee, C.

2011-12-01

132

Analysis of Slope Stability Using Limit Equilibrium  

Directory of Open Access Journals (Sweden)

Full Text Available In achievement of slope load sustainability using mixed soil technique, is considered acceptable the method for slope construction technology. This paper deals with evaluation of mixed soil technique for construction of stable slope and proves the soil capability by analysis of computerized modeling, the revealed result of investigation, the possibility of using nearest local material, reducing project cost, solving the construction geotechnical problem and accurate understanding of soil property when it is developed under different types of geometry.

Abdoullah Namdar

2010-01-01

133

Error Reduction in Slope Stability Assessment  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Slopes in quarries and open pit mines, as well as all the types of embankments (stockpiles, tailing dams, waste dumps) resulting from mining and mineral processing activities, must be considered as "geotechnical structures". Therefore, the design and implementation of these structures must be conducted with all consideration.The main aim of this chapter is to highlight the basic principles of the slope design process, to review the methods of stability analysis and slope design, as well as th...

Fleurisson, Jean-alain; Cojean, Roger

2014-01-01

134

Slope Estimation from ICESat/GLAS  

Directory of Open Access Journals (Sweden)

Full Text Available We present a novel technique to infer ground slope angle from waveform LiDAR, known as the independent slope method (ISM. The technique is applied to large footprint waveforms (\\(\\sim\\ mean diameter from the Ice, Cloud and Land Elevation Satellite (ICESat Geoscience Laser Altimeter System (GLAS to produce a slope dataset of near-global coverage at \\(0.5^{\\circ} \\times 0.5^{\\circ}\\ resolution. ISM slope estimates are compared against high resolution airborne LiDAR slope measurements for nine sites across three continents. ISM slope estimates compare better with the aircraft data (R\\(^{2}=0.87\\ and RMSE\\(=5.16^{\\circ}\\ than the Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM inferred slopes (R\\(^{2}=0.71\\ and RMSE\\(=8.69^{\\circ}\\ ISM slope estimates are concurrent with GLAS waveforms and can be used to correct biophysical parameters, such as tree height and biomass. They can also be fused with other DEMs, such as SRTM, to improve slope estimates.

Craig Mahoney

2014-10-01

135

Slope factor and shallow landslide occurrence  

Science.gov (United States)

Elevations in a mature mountain are generally normally distributed and slope gradients do. Shallow landslides occur on hill slopes and involve only regolith on the slopes. The slope gradient distribution of shallow landslides (including rock falls) is also a normal distribution; similar to that of natural slopes in shape, but shifting to a higher gradient. A probability of failure curve, which is defined as the ratio of landslide cells and total cells at each interval of a factor, then shows a shape close to a cumulative normal distribution and may be fitted with a Weibull curve. The probability of failure curve commonly shows an increase of failure from gradient about 0.5 to about 1.5, and then become saturated. There are few landslides located at slope less than about 26 degrees and lost its correlation with slope when slope greater than about 56 degrees, indicating landslide type change (rock falls). This is true for the storm-induced landslides. As to the earthquake-induced landslides, there are differences to the storm-induced landslides both in distribution curve and probability of failure curve. Earthquake-induced landslides most occurred at slope gradient from 20 degrees to 54 degrees and shows a mode about 42 degrees, whereas storm-induced landslides most occurred at slope gradient from 20 degrees to 44 degrees and shows a mode about 33 degrees. There are fewer occurrences of rock falls in a storm event than that in an earthquake event. Also, earthquake-induced landslides do not show saturation at higher slope gradients in the probability of failure curve. Normally distributed topographic pattern may skew in young mountains, like those in southern Taiwan or hilly terrain in western Taiwan, and the characteristic Weibull-shaped probability of failure curve may change also. It even becomes not applicable when a very extreme storm event is involved, like typhoon Morakot event in 2009 in southern Taiwan.

Lee, Chyi-Tyi

2014-05-01

136

Contribution of magnetic resonance imaging in the diagnosis of talus skip metastases of Ewing's sarcoma of the calcaneus in a child: a case report  

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Full Text Available Abstract Introduction Ewing's sarcoma of the calcaneus is rare. About thirty cases with calcaneus involvement have been reported in the literature. Talus skip metastases have rarely been described in the available literature Case presentation We report a case of a 14-year-old Moroccan boy, who presented with Ewing's sarcoma of his right calcaneus, diagnosed by swelling of the calcaneus evolving over a year. Radiography, computed tomography and magnetic resonance imaging showed an important tumoral process of the calcaneus and talus skip metastases. The diagnosis was confirmed with histology after a biopsy. In spite of amputation and postoperative chemotherapy, our patient died six months later due to secondary respiratory distress after lung metastasis. Conclusion Imaging, especially magnetic resonance, is important in the diagnosis of Ewing sarcoma and skeletal skip metastases. Treatment of Ewing's sarcoma consists of chemotherapy, radiation therapy and surgical resection depending on the stage and extent of the disease. With the exception of lesions in the calcaneus, the prognosis for disease-free survival of Ewing's sarcoma of the foot is excellent.

Fikry Tarik

2011-09-01

137

Internal waves and temperature fronts on slopes  

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Full Text Available Time series measurements from an array of temperature miniloggers in a line at constant depth along the sloping boundary of a lake are used to describe the `internal surf zone' where internal waves interact with the sloping boundary. More small positive temperature time derivatives are recorded than negative, but there are more large negative values than positive, giving the overall distribution of temperature time derivatives a small negative skewness. This is consistent with the internal wave dynamics; fronts form during the up-slope phase of the motion, bringing cold water up the slope, and the return flow may become unstable, leading to small advecting billows and weak warm fronts. The data are analysed to detect `events', periods in which the temperature derivatives exceed a set threshold. The speed and distance travelled by `events' are described. The motion along the slope may be a consequence of (a instabilities advected by the flow (b internal waves propagating along-slope or (c internal waves approaching the slope from oblique directions. The propagation of several of the observed 'events' can only be explained by (c, evidence that the internal surf zone has some, but possibly not all, the characteristics of the conventional 'surface wave' surf zone, with waves steepening as they approach the slope at oblique angles.

Key words. Oceanography: general (benthic boundary layers; limnology, Oceanography: physical (internal and inertial waves

S. A. Thorpe

138

Eastern slopes grizzly bear project  

Energy Technology Data Exchange (ETDEWEB)

The cumulative effects of human activities on the grizzly bears in the central Canadian Rockies are not well known. As a result, a project was initiated in 1994 to address the urgent requirement for accurate scientific information on the habitat and populations of grizzly bears in the area of the Banff National Park and Kananaskis Country. This area is probably the most heavily used and developed area where the grizzly still survives. The information gathered throughout the course of this study will be used to better protect and manage the bears and other sensitive carnivores in the region. Using telemetry, researchers are monitoring 25 grizzly bears which were radio-collared in a 22,000 square-kilometer area in the upper Bow Valley drainage of the eastern Alberta slopes. The researchers involved in the project are working with representatives from Husky Oil and Talisman Energy on the sound development of the Moose Mountain oil and gas field without adversely affecting the grizzly bear population. Information collected over seven years indicated that the grizzly bears have few and infrequent offspring. Using the information gathered so far, the location of the Moose Mountain to Jumping Pound pipeline was carefully selected, since the bears recover very slowly from high mortality, and also considering that the food and cover had already been compromised by the high number of roads, trails and other human activities in the area. The status of the population and habitat of the grizzly bear will be assessed upon the conclusion of the field research phase in 2001. Models will be updated using the data obtained during eight years and will assist in the understanding of complex variables that affect grizzly bears.

NONE

2001-01-01

139

Automated sliding susceptibility mapping of rock slopes  

Science.gov (United States)

We present a suite of extensions for ARCVIEW GIS (ESRI) that allows to map the spatial distribution of first-order mechanical slope-properties in hard rock terrain, e.g. for large slope areas like water reservoir slopes. Besides digital elevation data, this expert-system includes regional continuous grid-based data on geological structures that might act as potential sliding or cutoff planes for rockslides. The system allows rapid automated mapping of geometrical and kinematical slope properties in hard rock, providing the basis for spatially distributed deterministic sliding-susceptibility evaluations on a pixel base. Changing hydrostatic slope conditions and rock mechanical parameters can be implemented and used for simple predictive static stability calculations. Application is demonstrated for a study area in the Harz Mts., Germany.

Günther, A.; Carstensen, A.; Pohl, W.

2004-03-01

140

Automated sliding susceptibility mapping of rock slopes  

Directory of Open Access Journals (Sweden)

Full Text Available We present a suite of extensions for ARCVIEW GIS™ (ESRI that allows to map the spatial distribution of first-order mechanical slope-properties in hard rock terrain, e.g. for large slope areas like water reservoir slopes. Besides digital elevation data, this expert-system includes regional continuous grid-based data on geological structures that might act as potential sliding or cutoff planes for rockslides. The system allows rapid automated mapping of geometrical and kinematical slope properties in hard rock, providing the basis for spatially distributed deterministic sliding-susceptibility evaluations on a pixel base. Changing hydrostatic slope conditions and rock mechanical parameters can be implemented and used for simple predictive static stability calculations. Application is demonstrated for a study area in the Harz Mts., Germany.

A. Günther

2004-01-01

 
 
 
 
141

Computer aided analysis of rock slope stability  

Science.gov (United States)

A computer program is written in basic language on a micro-computer to carrying out kinematic analysis of rock slope stability. The program is capable of handling plane sliding, wedge sliding and toppling of rock slopes. Applications of the program are demonstrated by examples on opencast mine excavations and highway cuts. The computer output are presented in the form of tables and illustrations for ease of interpretation. As micro-computers are readily available in design offices nowadays, the present work provides an efficient means for engineers to analyse and design rock slope excavations.

Leung, C. F.; Kheok, S. C.

1987-04-01

142

Database on unstable rock slopes in Norway  

Science.gov (United States)

Several large rockslides have occurred in historic times in Norway causing many casualties. Most of these casualties are due to displacement waves triggered by a rock avalanche and affecting coast lines of entire lakes and fjords. The Geological Survey of Norway performs systematic mapping of unstable rock slopes in Norway and has detected up to now more than 230 unstable slopes with significant postglacial deformation. This systematic mapping aims to detect future rock avalanches before they occur. The registered unstable rock slopes are stored in a database on unstable rock slopes developed and maintained by the Geological Survey of Norway. The main aims of this database are (1) to serve as a national archive for unstable rock slopes in Norway; (2) to serve for data collection and storage during field mapping; (3) to provide decision-makers with hazard zones and other necessary information on unstable rock slopes for land-use planning and mitigation; and (4) to inform the public through an online map service. The database is organized hierarchically with a main point for each unstable rock slope to which several feature classes and tables are linked. This main point feature class includes several general attributes of the unstable rock slopes, such as site name, general and geological descriptions, executed works, recommendations, technical parameters (volume, lithology, mechanism and others), displacement rates, possible consequences, hazard and risk classification and so on. Feature classes and tables linked to the main feature class include the run-out area, the area effected by secondary effects, the hazard and risk classification, subareas and scenarios of an unstable rock slope, field observation points, displacement measurement stations, URL links for further documentation and references. The database on unstable rock slopes in Norway will be publicly consultable through the online map service on www.skrednett.no in 2014. Only publicly relevant parts of the database will be shown in the online map service (e.g. processed results of displacement measurements), while more detailed data will not (e.g. raw data of displacement measurements). Factsheets with key information on unstable rock slopes can be automatically generated and downloaded for each site, a municipality, a county or the entire country. Selected data will also be downloadable free of charge. The present database on unstable rock slopes in Norway will further evolve in the coming years as the systematic mapping conducted by the Geological Survey of Norway progresses and as available techniques and tools evolve.

Oppikofer, Thierry; Nordahl, Bo; Bunkholt, Halvor; Nicolaisen, Magnus; Hermanns, Reginald L.; Böhme, Martina; Yugsi Molina, Freddy X.

2014-05-01

143

Quadratic integer programming and the slope conjecture  

CERN Document Server

The Slope Conjecture relates a quantum knot invariant, (the degree of the colored Jones polynomial of a knot) with a classical one (boundary slopes of incompressible surfaces in the knot complement). The degree of the colored Jones polynomial can be computed by a suitable (almost tight) state sum and the solution of a corresponding quadratic integer programming problem. We illustrate this principle for a 2-parameter family of 2-fusion knots. Combined with the results of Dunfield and the first author, this confirms the Slope Conjecture for the 2-fusion knots.

Garoufalidis, Stavros

2014-01-01

144

Delayed gadolinium-enhanced MRI of cartilage of the ankle joint: Results after autologous matrix-induced chondrogenesis (AMIC)-aided reconstruction of osteochondral lesions of the talus  

International Nuclear Information System (INIS)

Aim: To assess cartilage quality using delayed gadolinium-enhanced magnetic resonance imaging after repair of osteochondral lesions of the talus using autologous matrix-induced chondrogenesis (AMIC). Materials and methods: A three-dimensional (3D) spoiled gradient-echo (SGE) sequence at 3 T was used to obtain quantitative T1 relaxation times before and after Gd-DTPA2 (Magnevist, 0.2 mM/kg bod weight) administration to assess 23 cases of AMIC-aided repair of osteochondral lesions of the talus. Delta relaxation rates (?R1) for reference cartilage (RC) and repair tissue (RT), and the relative delta relaxation rate (r?R1) were calculated. The morphological appearance of the cartilage RT was graded on sagittal dual-echo steady-state (DESS) views according to the “magnetic resonance observation of cartilage repair tissue” (MOCART) protocol. The study was approved by the institutional review board and written consent from each patient was obtained. Results: The AMIC cases had a mean T1 relaxation time of 1.194 s (SD 0.207 s) in RC and 1.470 s (SD 0.384 s) in RT before contrast medium administration. The contrast-enhanced T1 relaxation time decreased to 0.480 s (SD 0.114 s) in RC and 0.411 s (SD 0.096 s) in RT. There was a significant difference (p > 0.05) between the ?R1 in RC (1.372 × 10?3/s, range 0.526–3.201 × 10?3/s, SD 0.666 × 10?3/s) and RT (1.856 × 10?3/s, range 0.93–3.336 × 10?3/s, SD 0.609 × 10?3/s). The mean r?R1 was 1.49, SD 0.45). The mean MOCART score at follow-up was 62.6 points (range 30–95, SD 15.3). Conclusion: The results of the present study suggest that repair cartilage resulting from AMIC-aided repair of osteochondral lesions of the talus has a significantly lower glycosaminoglycan (GAG) content than normal hyaline cartilage, but can be regarded as having hyaline-like properties

145

Green Alder Pattern in Relation to Slope-Area Scaling Regimes of a Headwater Basin in the Eastern Italian Alps  

Science.gov (United States)

The landscape of headwater alpine basins is strongly influenced by erosion processes. The scaling relationship between the local slope of a given point on the landscape and its drainage area reveals information about the dominant erosion process over geomorphic time scales. There has been significant research literature which documents how vegetation distribution is coupled with local topography. Understanding the interrelationship between the vegetation, especially between some plant species than others with local topography will help us to better understand how the landscape change due to a specific geomorphic process is related to vegetation change. In this paper a steep Alpine debris flow-landslide dominated headwater catchment with uniform lithology substrata, and vegetation characterized by various grass, shrub, and forest species has been considered. The basin was chosen as study area because it is representative of the lithological and physiographical conditions frequently observed in the Carnia region (Eastern Italian Alps). The work has focused on the analysis of scaling regimes of local slope versus contributing area in relation to each vegetation types with particular attention to the spatial distribution of Alnus viridis, the main shrub species present in the area. Alnus viridis, also known as Green Alder, is an early successional shrub growing up to 4 m that invades screes, landslide scree, avalanche debris on talus slopes, avalanche slide paths and pastures in the subalpine zone of the Alps. It is widespread on moist, north-exposed medium-steep slopes on silicious bedrock at an altitude ranging from 1500 to 2000 m a.s.l.. LiDAR-derived DSM (Digital Surface Model) served as the basis to evaluate the distribution of vegetation canopies. The LiDAR bare-ground elevation points were used for the DTM (Digital Terrain Model) interpolation at the same resolution of the DSM. The results revealed that there is significant relationship between the local slope and drainage area depicting the natural location of Green Alder and other vegetation types. Profound landslide/debris flow topographic signature is detected in areas where Green Alder prevails. Its pioneering ability to colonize the landslide scars and headwater channel hollows, makes it as a key species in the analysis of geomorphic processes at the hillslope/valley transition. The work has broad implications in geomorphology, landscape ecology, landscape evolution with vegetation dynamics for studies in high-altitude extreme-climate Alpine regions.

Tarolli, P.

2007-12-01

146

The critical slope angle for orographic rain  

Science.gov (United States)

Krishnamurti has shown that orographic rain depends on the slope of the windward terrain rather than just the total elevation gain. A simple physical model is proposed to account for the effect of slope. Based on the inhibiting effect of vortex (rotational) acceleration on entrainment, a critical slope angle is derived. If the rate of orographic lifting is sufficiently large, the enhanced buoyancy from latent heat release increases the acceleration parameter. As a consequence, the entrainment rate of under-saturated air is reduced. The critical slope corresponds to the situation where the rate of condensation in a rising adiabatic parcel just equals the rate of evaporation due to the entrainment of under-saturated air. The model is also applied to the trigger conditions for towering cumulus in general.

Breidenthal, R. E.; Zagar, N.

2013-12-01

147

3D geodetic monitoring slope deformations  

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Full Text Available For plenty of slope failures that can be found in Slovakia is necessary and very important their geodetic monitoring (because of their activity, reactivisations, checks. The paper gives new methodologies for these works, using 3D terrestrial survey technologies for measurements in convenient deformation networks. The design of an optimal type of deformation model for various kinds of landslides and their exact processing with an efficient testing procedure to determine the kinematics of the slope deformations are presented too.

Weiss Gabriel

1996-06-01

148

Electrokinetic Geotextile Stabilization Of Embankment Slopes  

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Full Text Available The choice of repair of slope depends on site conditions and cost. This includes reducing the slope, installing horizontal drains, soil nailing and providing stability by structural methods. All these methods have their limitations and some are very costly. Another alternative is the electrokinetic stabilization of slopes. EKG reinforcement or soil nails not only provide reinforcement, but also increase the shear strength of the soil in which they are placed as well as improving soil-reinforcement bond. The development of EKG materials offers slope stabilisation of embankments and cuttings in fine grained soils, which will significantly increase the factor of safety , address pore pressure changes and also avoids importing earthwork materials or aggregates. By inserting a grid of anodes and a cathode into the ground and applying an electrical potential difference across the slope drives water away, via the cathodes and creates physical changes in the embankment, promoting consolidation of the slope materials. Anodes and cathodes were connected to a DC power circuit and electrified for a calculated period based on water content, strength and electrode spacing. The conductive geotextile used was coir geotextile and it was woven with steel filament in weft direction only. The steel filament made the geotextile conductive. The geotextile used was natural geotextile and it is required after the end of construction of embankment only, till the completion of dissipation of pore pressure.

Mumtaz M

2014-12-01

149

Seasonal slope surface deformation measured with TLS  

Science.gov (United States)

In temperate European climates, soil water removal due to vegetation transpiration peaks in summer and soil rewetting from higher levels of precipitation occurs in winter. In clays of high plasticity, the seasonal cycles of drying and wetting cause the soil to experience a volumetric change, resulting in seasonal shrinking and swelling. For a clay slope exhibiting volume change, such behaviour can lead to excessive deformation and could contribute to strain-softening and progressive slope failure. This can in turn cause traffic disruption and loss of life if roads and railways are founded on or surrounded by such slopes. This paper discusses the driving forces of seasonal surface movement, in particular the role of vegetation, and presents the use of Terrestrial Laser Scanning (TLS) to measure the surface movement of a lightly vegetated London Clay slope near Newbury, UK. Two TLS scans were carried out in early and late summer respectively, representing relative wet and dry conditions of the slope. Continuous field measurements of soil water content in upper layers of the slope were obtained from TDR ThetaProbes already installed at the site. The water content data are used to support the results obtained from TLS by indicating the likely volumetric change in the soil due to loss of water.

Fan, L.; Smethurst, J.; Powrie, W.; Sellaiya, A.

2014-03-01

150

Establishing proof of concept: Platelet-rich plasma and bone marrow aspirate concentrate may improve cartilage repair following surgical treatment for osteochondral lesions of the talus  

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Full Text Available Osteochondral lesions of the talus are common injuries in the athletic patient. They present a challenging clinical problem as cartilage has a poor potential for healing. Current surgical treatments consist of reparative (microfracture or replacement (autologous osteochondral graft strategies and demonstrate good clinical outcomes at the short and medium term follow-up. Radiological findings and second-look arthroscopy however, indicate possible poor cartilage repair with evidence of fibrous infill and fissuring of the regenerative tissue following microfracture. Longer-term follow-up echoes these findings as it demonstrates a decline in clinical outcome. The nature of the cartilage repair that occurs for an osteochondral graft to become integrated with the native surround tissue is also of concern. Studies have shown evidence of poor cartilage integration, with chondrocyte death at the periphery of the graft, possibly causing cyst formation due to synovial fluid ingress. Biological adjuncts, in the form of platelet-rich plasma (PRP and bone marrow aspirate concentrate (BMAC, have been investigated with regard to their potential in improving cartilage repair in both in vitro and in vitro settings. The in vitro literature indicates that these biological adjuncts may increase chondrocyte proliferation as well as synthetic capability, while limiting the catabolic effects of an inflammatory joint environment. These findings have been extrapolated to in vitro animal models, with results showing that both PRP and BMAC improve cartilage repair. The basic science literature therefore establishes the proof of concept that biological adjuncts may improve cartilage repair when used in conjunction with reparative and replacement treatment strategies for osteochondral lesions of the talus.

Niall A Smyth

2012-01-01

151

30 CFR 716.2 - Steep-slope mining.  

Science.gov (United States)

...with an occasional steep slope through which the mining...mining operations on steep slopes where the operation...requirements on steep slopes to— (i) Improve...established to assure the stability, drainage, and configuration...general geotechnical analysis. (ii)...

2010-07-01

152

Putting beach slope prediction into perspective  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english The storage capacity of any given tailings storage facility (TSF) is a function of the volume available for the tailings, for which the geometry of the final upper surface of the tailings is most important. One of the advantages that can be obtained from thickening tailings prior to discharge is tha [...] t the tailings can be stacked at a steeper beach angle than is obtainable with conventional low-density slurries. However, there is at present no universally accepted method available for the accurate prediction of tailings beach slopes. This paper examines the current situation with the objective of putting the quest for a method for the accurate prediction of beach slopes into perspective. The paper references published reviews of the best-known beach slope prediction methods. However, there do not appear to be any independently verified projects or published references to projects on which a Class A prediction has been validated for any of these approaches, and in those instances where projects have been implemented correlation of actual with predicted slopes has been poor - often due to differences between the properties of the tailings assumed in the design and those actually achieved in the field. The author also concludes that flume-scale testing cannot be taken as a reliable indicator of full-scale performance, and suggests that the outcome of any current predictive method should be used by experienced practitioners as only one of a range of indicators in order to suggest a range of slope angles likely to result for any given operation. Practice has shown that it is possible to manipulate beach slopes by changes to the disposal technique, such as limiting the rate of discharge per discharge point and by increasing or decreasing yield stress, but the impact of these changes cannot readily be predicted. There are also newly emerging technologies, such as the injection of a polymer into the tailings at discharge, that will enhance the dewatering of tailings and hence expedite the consolidation of the tailings, that could well facilitate the development of steeper beach slopes. The overall conclusion is that with the current state of knowledge, the accurate prediction of beach slopes is not possible. Furthermore, in view of the inherent variability of the tailings parameters from any operation, it may well be of more value to concentrate on developing an understanding of the means by which the tailings parameters may be manipulated by the operators to achieve a given beach slope than to concentrate wholly on developing a generic beach slope prediction model.

R.J., Jewell.

153

Sedimentary Processes of a Slope Ridge on the Northern South China Sea Continental Slope  

Science.gov (United States)

In the context of source to sink, continental slope is generally regarded as a zone where sediments pass through from shelf to continental rise and deep sea basin. However, in the area offshore of southwestern Taiwan, the passive South China Sea continental margin receives considerable amount of terrigenous sediments that deposited on the continental shelf and lower continental slope. Morphological characters of the continental slope here are numerous short, straight submarine canyons which erode the slope surface to form a series of down-dip trending slope ridges. Most of the slope ridges are narrow, with width BSR are common within the sediment wave structures. Seismic images also reveal that the wide ridge consists of two basement highs, named the northeastern hill (NEH) and the southwestern hill (SWH), respectively. We interpret that these two hills could be formed by erosion and deposition processes. From morphology and seismic stratigraphic analyses, we propose two models for the formation of this wide ridge, one is that this ridge was formed by filling up a submarine canyon between two adjacent slope ridges, and the 2nd model is that this wide ridge is part of the continental slope which has not been incised. Further investigation will be conducted to better understand the relationship between erosion and deposition processes which shape the slope ridges in the study area.

Ni, J. J.; Liu, C. S.; Chen, S. C.

2012-04-01

154

Finite Element analyses of soil bioengineered slopes  

Science.gov (United States)

Soil Bioengineering methods are not only effective from an economical point of view, but they are also interesting as fully ecological solutions. The presented project is aimed to define a numerical model which includes the impact of vegetation on slope stability, considering both mechanical and hydrological effects. In this project, a constitutive model has been developed that accounts for the multi-phase nature of the soil, namely the partly saturated condition and it also includes the effects of a biological component. The constitutive equation is implemented in the Finite Element (FE) software Comes-Geo with an implicit integration scheme that accounts for the collapse of the soils structure due to wetting. The mathematical formulation of the constitutive equations is introduced by means of thermodynamics and it simulates the growth of the biological system during the time. The numerical code is then applied in the analysis of an ideal rainfall induced landslide. The slope is analyzed for vegetated and non-vegetated conditions. The final results allow to quantitatively assessing the impact of vegetation on slope stability. This allows drawing conclusions and choosing whenever it is worthful to use soil bioengineering methods in slope stabilization instead of traditional approaches. The application of the FE methods show some advantages with respect to the commonly used limit equilibrium analyses, because it can account for the real coupled strain-diffusion nature of the problem. The mechanical strength of roots is in fact influenced by the stress evolution into the slope. Moreover, FE method does not need a pre-definition of any failure surface. FE method can also be used in monitoring the progressive failure of the soil bio-engineered system as it calculates the amount of displacements and strains of the model slope. The preliminary study results show that the formulated equations can be useful for analysis and evaluation of different soil bio-engineering methods of slope stabilization.

Tamagnini, Roberto; Switala, Barbara Maria; Sudan Acharya, Madhu; Wu, Wei; Graf, Frank; Auer, Michael; te Kamp, Lothar

2014-05-01

155

Gravity currents propagating up a slope  

Science.gov (United States)

Bottom propagating gravity currents resulting from full- and partial-depth lock-release experiments are investigated as they approach and then propagate up a rising slope. Consistent with the prediction of a WKB-like theory, the gravity current front decelerates in a nearly uniform manner along the slope as 0.112g's(D/H)(2 - D/H), in which g' is the reduced gravity, s is the slope, D is the initial lock-fluid height, and H is the ambient fluid height. The shape of the gravity current as it decelerates over relatively steep slopes is found to be self similar with a nearly linear decrease of the head height between the start of the slope and up to 80% of the distance to the nose. Some deviation from self-similar behaviour is found in cases with small s because of the comparatively large volume of fluid in the gravity current tail that flows downslope while the front continues to advance upwards.

Marleau, Larissa J.; Flynn, Morris R.; Sutherland, Bruce R.

2014-04-01

156

Slope evolution at the Calvert Cliffs, Maryland -- measuring the change from eroding bluffs to stable slopes  

Science.gov (United States)

Despite a long history of geomorphic studies, it is difficult to ascertain the time required for slopes to change from near vertical exposures to relatively stable slopes due to inadequate age control. Actively eroding coastal bluffs along the western shore of the Chesapeake Bay provide a key for understanding the centennial-scale development of stable slopes from eroding bluff faces. The Calvert Cliffs are composed of sandy silts, silty sands, and clayey silts of Miocene-age. Active wave erosion at the bluff toes encourages rapid sloughing from bluff faces and maintains slope angles of 70-80 degrees and relatively constant bluff-retreat rates. Naturally stabilized slopes are preserved as a fossil bluff line inland from a prograding cuspate foreland at Cove Point. The foreland is migrating southward at a rate of ca. 1.5 m/yr. As it moves south, it progressively protects bluffs from wave action as new beaches are deposited at their toes. Wave erosion is reinitiated at the northern end of the complex as the landform passes. An incremental record of slope change is preserved along the fossil bluff line. 14C dating of swales between beach ridges shows the complex to span 1700 years of progressive migration history. We hypothesized that slopes would change from steep, eroding faces to low-angle slopes covered with vegetation and sought to document the rate of change. Our team measured slope angles at intervals along the fossil bluff line and dated profiles by interpolating 14C ages of adjacent beach ridges. There was no progressive decrease in slope with age. All slopes along the fossil bluff line were 30-40 degrees with a mean of 35 degrees. Constancy in slope angle suggests that steep, actively eroding bluffs were quickly changed to stable slopes by landslides and slumping once they were protected. Given the accuracy of our age control, we conclude that the time required to attain a stable slope under natural processes is less than one century. This indicates that once toe erosion is ended (naturally or through engineering) slopes are reduced to 35-degrees over a period of decades and not centuries.

Herzog, Martha; Larsen, Curtis E.; McRae, Michele

2002-01-01

157

Geomorphologic mapping in the Ny Ålesund area (Svalbard Island, Norway) for the analysis of geomorphologic effects on rock slopes induced by glacier retreat in climate sensitive High Arctic regions  

Science.gov (United States)

The geomorphological effects of glacial retreat, rapidly changing Arctic environments and consequent local temporary permafrost melting are several types of glacial and periglacial landforms (pingos, solifluction, drumlins, etc.) but also debris and rock falls, alluvial fan and glacial outwash development and scarp/slopes retreat and evolution. In this work we have realized a geomorphologic map of rockfalls, landslides, alluvial fans and the slopes and scarps of steep mountainsides in the Ny Ålesund area (Svalbard Island, Norway) focused on the analysis of rock falls as geomorphological effects of glacier retreat, permafrost degradation and higher temperatures on slope processes. The investigation is based on geological and geomorphological field survey, and remote sensing and aerial photo interpretation, The Ny Ålesund area landscape is characterized by rugged non-vegetated mountains only partially covered by glaciers, with steep flanks and rock scarps; the scarps are formed by different types of rocks (intrusive and effusive igneous rocks, marine sedimentary rocks); this landscape is highly affected by debris and rock falls (from scarps and slopes) forming wide talus slopes and by alluvial fan and fluvial outwash (from glaciers), which make the surface sedimentary cover of the island together with rock glaciers and moraine deposits and locally fluvial deposits. The work is focused on the comprehension of the role of different factors in inducing rock falls, alluvial fans, slope/scarps evolution in high geomorphological sensitivity environments (i.e. glacial, periglacial or mountain) including: orography, lithology, rock fracturation, morphostructural setting, meteorological context. The conclusions focus on the possible geomorphological hazards affecting the Ny Ålesund area.

Miccadei, Enrico; Piacentini, Tommaso; Casacchia, Ruggero; Sparapani, Roberto

2014-05-01

158

Centrifuge model test of rock slope failure caused by seismic excitation. Plane failure of dip slope  

International Nuclear Information System (INIS)

Recently, it is necessary to assess quantitatively seismic safety of critical facilities against the earthquake induced rock slope failure from the viewpoint of seismic PSA. Under these circumstances, it is essential to evaluate more accurately the possibilities of rock slope failure and the potential failure boundary, which are triggered by earthquake ground motions. The purpose of this study is to analyze dynamic failure characteristics of rock slopes by centrifuge model tests for verification and improvement of the analytical methods. We conducted a centrifuge model test using a dip slope model with discontinuities limitated by Teflon sheets. The centrifugal acceleration was 50G, and the acceleration amplitude of input sin waves increased gradually at every step. The test results were compared with safety factors of the stability analysis based on the limit equilibrium concept. Resultant conclusions are mainly as follows: (1) The slope model collapsed when it was excited by the sine wave of 400gal, which was converted to real field scale, (2) Artificial discontinuities were considerably concerned in the collapse, and the type of collapse was plane failure, (3) From response acceleration records observed at the slope model, we can say that tension cracks were generated near the top of the slope model during excitation, and that might be cause of the collapse, (4) By considering generation of the tension cracks in the stability analysis, correspondence of the analytical results and the experimental results improved. From the obtained results, we need to consider progressive failure in evaluating earthquake induced rock slope failure. (author)

159

Reinforcement of sloping banks in open cast mines: analysis of stability and dimensions from block models. Final report; Renforcement des talus de mines a ciel ouvert: analyse de stabilite et dimensionnement par models de blocs. Rapport final  

Energy Technology Data Exchange (ETDEWEB)

Resoblok software is a powerful computing tool which allows simulation of fracturing in rock formations from actual or statistically defined data. Combined with a method of analysis of the stability of isolated blocks, it becomes a means of predicting risks of instability and enables the calculation of a suitable bolt-propping system to remedy the problem. In general the choice of a bolt-propping plan is made by analysing various possible alternatives. The criterion used is the minimisation of the numbers and size of unstable blocks, but economic considerations and complementary technical solutions (grillage and concreting) are also taken into account. The relatively simple calculation method used speeds up the analysis of stability, and permits the study of various method of bolting for various types of fracturing geometries. Application to actual situations should be carried out progressively, comparing the model results with observations and measurements in situ, as well as continuously improving knowledge of the fracturing, the mechanical characteristics and the hypotheses of the calculation.

Paquette, Y. [INERIS, Paris (France)

1997-12-31

160

Radial slope measurement of dynamic transparent samples  

International Nuclear Information System (INIS)

An interferometric method to measure the radial slope of dynamic transparent samples is presented. We have implemented a simultaneous phase shifting Mach–Zehnder radial-shear interferometer (SPS-MZRI) using a phase grating to replicate the interference patterns and phase shifts modulated by polarization; the interferometer is capable of processing the optical phase data through the acquisition of n-interferograms captured simultaneously. The SPS-MZRI is capable of obtaining the radial phase derivative and associating it with its corresponding radial slope. The experimental results for static and dynamic samples are presented in this work, as well as the experimental evidence for the generation of spiral patterns. (paper)

 
 
 
 
161

Chirp slope keying for underwater communications  

Science.gov (United States)

This paper presents a novel broadband modulation method for digital underwater communications: Chirp Slope Keying (CSK). In its simplest form, the binary information modulates the slope of a linear chirp, with up-chirps representing ones and down-chirps representing zeros. Performance evaluation in the form of probability of error vs. SNR show that the system performs as expected for AWGN environments and very well for more realistic models for underwater acoustical communications, such as the Raylegih channel with Doppler, delays, phase offset, and multipath.

Kaminsky, Edit J.; Simanjuntak, Lastri

2005-05-01

162

Bootstrap methods for comparing independent regression slopes.  

Science.gov (United States)

In this study, we explore the effects of non-normality and heteroscedasticity when testing the hypothesis that the regression lines associated with multiple independent groups have the same slopes. The conventional approach involving the F-test and the t-test (F/t approach) is examined. In addition, we introduce two robust methods which allow simultaneous testing of regression slopes. Our results suggest that the F/t approach is extremely sensitive to violations of assumptions and tends to yield misleading conclusions. The new robust alternatives are recommended for general use. PMID:21827447

Ng, Marie; Wilcox, Rand R

2012-05-01

163

Slope monitoring key to maintaining pipeline integrity  

Energy Technology Data Exchange (ETDEWEB)

Two case histories describe instances in which operating pipelines have experienced stress or failure as a result of slope instability. Factors which led to pipeline distress and remedial actions in two actual cases are discussed in this second of two articles on pipeline terrain. Both sites are located very near each other within the west central area of Alberta. Each case history is unique, as were the remedial measures adopted to ensure pipeline integrity. This article is divided into the following areas: Early evidence; Spring thaw; Partial collapse; Another washout; Remediation; Simonette river; Northern slope site; Continued movement; Continued monitoring; and Global positioning survey.

Couperthwaite, S.L.; Marshall, R.G. (Nova, an Alberta Corp., AB (Canada))

1989-09-25

164

Evaluation of Slope Stability Performance in Different Methods  

Directory of Open Access Journals (Sweden)

Full Text Available The magnitude of liquefaction is changing respect to level of underground water, soil mechanical properties, time, direction and magnitude of forces. In this research work to understanding slope failure mechanism the limit equilibrium code employed to evaluating slope stability and assessing failure. The result revealed that thefailure of slope could be predicted if accurate slope behavior investigated. For increasing soil structure stability and loads mitigation this is essential of appropriate selection of slope geometry based on evaluating of slope at different slope geometry.

Abdoullah Namdar,

2010-07-01

165

Slope Stability, Triggering Events, Mass Wasting Events  

Science.gov (United States)

This article, authored by Professor Stephen A. Nelson of Tulane University, focuses on many aspects of slope stability. Some of these factors include: the role of water, troublesome earth materials, triggering events, and assessing and mitigating mass-wasting hazards. The article is filled with detailed diagrams along with accompanying textual descriptions that make a cohesive piece easily understood by many audiences.

Nelson, Stephen A.

2008-09-22

166

A Novel Way To Practice Slope.  

Science.gov (United States)

Presents examples of using a tic-tac-toe format to practice finding the slope and identifying parallel and perpendicular lines from various equation formats. Reports the successful use of this format as a review in both precalculus and calculus classes before students work with applications of analytic geometry. (JRH)

Kennedy, Jane B.

1997-01-01

167

Advance in prediction of soil slope instabilities  

Science.gov (United States)

Six generic soils (clays and sands) were systematically modeled with plane-strain finite elements (FE) at varying heights and inclinations. A dataset was generated in order to develop predictive relations of soil slope instabilities, in terms of co-seismic displacements (u), under strong motions with a linear multiple regression. For simplicity, the seismic loads are monochromatic artificial sinusoidal functions at four frequencies: 1, 2, 4, and 6 Hz, and the slope failure criterion used corresponds to near 10% Cartesian shear strains along a continuous region comparable to a slip surface. The generated dataset comprises variables from the slope geometry and site conditions: height, H, inclination, i, shear wave velocity from the upper 30 m, vs30, site period, Ts; as well as the input strong motion: yield acceleration, ay (equal to peak ground acceleration, PGA in this research), frequency, f; and in some cases moment magnitude, M, and Arias intensity, Ia, assumed from empirical correlations. Different datasets or scenarios were created: "Magnitude-independent", "Magnitude-dependent", and "Soil-dependent", and the data was statistically explored and analyzed with varying mathematical forms. Qualitative relations show that the permanent deformations are highly related to the soil class for the clay slopes, but not for the sand slopes. Furthermore, the slope height does not constrain the variability in the co-seismic displacements. The input frequency decreases the variability of the co-seismic displacements for the "Magnitude-dependent" and "Soil-dependent" datasets. The empirical models were developed with two and three predictors. For the sands it was not possible because they could not satisfy the constrains from the statistical method. For the clays, the best models with the smallest errors coincided with the simple general form of multiple regression with three predictors (e.g. near 0.16 and 0.21 standard error, S.E. and 0.75 and 0.55 R2 for the "M-independent" and "M-dependent" datasets correspondingly). From the models with two predictors, a 2nd-order polynom gave the best performance but with a not-significant parameter. The best models with both predictors significant have slightly larger error and smaller R2, e.g. 0.15 S.E., 44% R2 with ay and i. The predictive models obtained with the three scenarios from the clay slopes provide well-constrained predictions but low R2, suggesting the predictors are "not complete", most likely in relation to the simplicity used in the strong motion characterization. Nevertheless, the findings from this work demonstrate the potential from analytical methods in developing more precise predictions as well as the importance on treating different different ground types.

Sigarán-Loría, C.; Hack, R.; Nieuwenhuis, J. D.

2012-04-01

168

Prótese do tornozelo híbrida em um caso de necrose avascular pós-traumática do tálus Hybrid ankle prosthesis in a case of post-traumatic avascular necrosis of the talus  

Directory of Open Access Journals (Sweden)

Full Text Available As fraturas do astrágalo originam frequentemente artrose pós-traumática tardia. Nestes casos, a utilização de próteses do tornozelo não cimentadas de última geração tem sido evitada pela presença de necrose avascular. Relatamos o caso de um paciente com 65 anos que se apresenta quatro anos após uma fratura do colo do astrágalo. Apresentava uma artrose do tornozelo dolorosa (escala AOFAS do retropé e tornozelo 19 e necrose avascular com colapso de toda a cúpula astragalina. Dada a extensão da necrose, foi decidido cimentar o componente protésico astragalino. Um ano após a cirurgia, o paciente apresenta bom resultado clínico e radiológico (escala AOFAS do retropé e tornozelo 87 e está satisfeito com o procedimento. Não temos conhecimento de nenhum relato semelhante na literatura.Talus fractures often lead to late post-traumatic arthrosis. In such cases, the use of latest generation, cementless prostheses has been hindered by the presence of avascular necrosis. We report the case of a 65-year-old patient who presented four years after a talus neck fracture. He had painful ankle arthrosis (AOFAS ankle-hindfoot score 19 and avascular necrosis, with collapse of the entire talar dome. Given the extent of the necrosis, it was decided to cement the talus prosthetic component. One year after the surgery, the patient shows good clinical and radiological results (AOFAS ankle-hindfoot score 87 and is satisfied with the procedure. We are not aware of any similar reports in the literature.

Ricardo Jorge Gomes de Sousa

2011-01-01

169

Geological hazards investigation - relative slope stability map  

Energy Technology Data Exchange (ETDEWEB)

The Republic of Korea is a mountainous country; the mountains occupy about three quarters of her land area, an increasing urban development being taken place along the mountainside. For the reason, planners as well as developers and others must realize that some of the urban areas may be threaten by geologic hazards such as landslides and accelerated soil and rock creeps. For the purpose of environmental land-use planning, a mapping project on relative slope-stability was established in 1996. The selected area encompasses about 5,900 km{sup 2} including the topographic maps of Ulsan, Yongchon, Kyongju, Pulguksa, and Kampo, all at a scale of 1:50,000. Many disturbed and undisturbed soil samples, which were collected from the ares of the landslides and unstable slopes, were tested for their physical properties and shear strength. They were classified as GC, SP, SC, SM, SP-SM, SC-SM, CL, ML, and MH according to the Unified Soil Classification System, their liquid limit and plasticity index ranging from 25.3% to as high as 81.3% and from 4.1% to 41.5%, respectively. X-ray analysis revealed that many of the soils contained a certain amount of montmorillonite. Based on the available information as well as both field and laboratory investigation, it was found out that the most common types of slope failures in the study area were both debris and mud flows induced by the heavy rainfalls during the period of rainy season; the flows mostly occurred in the colluvial deposits at the middle and foot of mountains. Thus the deposits generally appear to be the most unstable slope forming materials in the study area. Produced for the study area were six different maps consisting of slope classification map, soil classification map, lineament density map, landslide distribution map, zonal map of rainfall, and geology map, most of them being stored as data base. Using the first four maps and GIS, two sheets of relative slope-stability maps were constructed, each at a scale of 1:100,000; the maps can be utilized for regional land-use planning. (author). 36 refs., 15 tabs., 83 figs., 2 maps.

Han, Dae Suk; Kim, Won Young; Yu, Il Hyon; Kim, Kyeong Su; Lee, Sa Ro; Choi, Young Sup [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

1997-12-01

170

Relief unity emulator and slope stability simulator applied to mass movement occurrence analysis in slope evolution  

Science.gov (United States)

This work refers to a part of my "Fellow" thesis "Geomorphosynthesis and Geomorphocinematic applied to slope stability and evolution" (Colangelo, 2007). Relief unity emulator (rue) is a device that permits to synthesize a slope unity by means of a single generatrix profile that determine the initial conditions for application of a set of a geotechnical, hydrological and morphological models. This initial profile is considered in equilibrium with original environmental conditions, and operates in an integrated manner with these models. The aim is to induce a boundary condition on initial profile and produce a new profile: a threshold profile. For this manner and by iterations we generate a set of new profiles that represents, each one, a meta-stable profile, or a descending profile. The evolution of these profiles is in according with the central geomorphologycal concepts of slope retreat, base level change and head retreat. This set of "descending profiles" will be now sliced at topographic equivalent points, that will linked for describe a "topographic equivalence line". The crossing of this kind of isolines with descending profiles composes a 3D slope unity. This descending slope unity is represented by a mesh built for the crossing of these new slope profiles with the topographic equivalence lines and, the result is a four-dimensional meta-stable object integrated to the slope stability simulator (sss). This composite "rue-sss" device operates with 10 main models and 16 variables. The models describe effective stress, shearing resistance, soil saturation level behavior, potential rupture surface depth, critical depth, potential rupture surface critical gradient, critical soil saturation level, top of percolation flow gradient and unit weight of soil. Of this manner, is possible to evaluate effective friction angles and cohesion, critical soil saturation levels, critical gradients for potential rupture surfaces, neutral stress, shear strength, shear stress, effective stress, water retention factor, vegetation canopy unit weight and height. All these considering variables were calculated for each cell in the synthetic slope system, that is defined laterally by crossing of equivalence topographic belt with inter-profile space and, vertically by soil surface and potential rupture surface, that may be soil-regolith or regolith-rock transition. Therefore, with this device is possible, from a single generatrix profile, to design infinity of slope evolution ways by means of definition of boundary value of the models. When in the "potential rupture surface" is produced an "effective potential rupture surface", factor of safety less than unity, the soil fails and the slope stability simulator generate a mass movement prototype. A number of interesting and verisimilar 3D mass movement digital experiments may be performed for an inferred neogenic slope evolution time scale.

Colangelo, Antonio C.

2010-05-01

171

The Moon’s surface slopes and slope-distributions from the Lunar Orbiter Laser Altimeter  

Science.gov (United States)

The Lunar Reconnaissance Orbiter (LRO) successfully entered orbit around the moon on June 23, 2009. Since then, the Moon’s topography has been sampled with unprecedented detail and coverage by the Lunar Orbiter Laser Altimeter (LOLA). Surface slopes are computed from comparison of measurements among the five illuminated spots on the surface from each laser shot, as well as across multiple shots along the ground profile. Slopes and slope distributions for the sampled areas are obtained, and preliminary properties of the lunar surface roughness over the range of length-scales from 10’s m to km’s will be presented. We focus on notable properties of the distribution computed locally of median and RMS slopes, correlation length, and Hurst exponent (relatable to the power spectral slope). Regional slope histograms are considered for characteristic terrain types such as mare plains, impacts basins, and the highlands. The high precision and high density of LOLA measurements allow a quantitative morphologic characterization of the lunar surface pertinent to studies of surface processes and evolution, as well as for possible future landing site selection.

Aharonson, O.; Rosenburg, M. A.; Smith, D. E.; Zuber, M. T.; Neumann, G. A.; Torrence, M. H.; Mazarico, E.

2009-12-01

172

Slope reinforcement design using geotextiles and geogrids  

Science.gov (United States)

A geotextile is defined by ASTM as: any permeable textile material used with foundation, soil, rock, earth, or any other geotechnical engineering related material, as a integral part of a man-made project, structure, or system. A geogrid is defined as: any geotextile-related material used in a similar manner to geotextiles. They are usually made of plastic, but can be metal or wood. Geotextiles and geogrids are collectively referred to as geosynthetics in this paper. Geosynthetic reinforcement of slopes is a relatively new option available to the civil engineer. Slope angles can be increased and 'poor' soil can be used to construct economical soil-geosynthetic facilities. Uncertainties exist in the complex interaction between the soil and the geosynthetic but there are numerous procedures which ignore this in the design. The design procedures available may be conservative yet still may be an economical alternative when compared to more conventional options.

Setser, Darrell M.

1990-08-01

173

In-Place Randomized Slope Selection  

DEFF Research Database (Denmark)

Slope selection is a well-known algorithmic tool used in the context of computing robust estimators for fitting a line to a collection P of n points in the plane. We demonstrate that it is possible to perform slope selection in expected O(nlogn) time using only constant extra space in addition to the space needed for representing the input. Our solution is based upon a space-efficient variant of Matoušek’s randomized interpolation search, and we believe that the techniques developed in this paper will prove helpful in the design of space-efficient randomized algorithms using samples. To underline this, we also sketch how to compute the repeated median line estimator in an in-place setting.

Blunck, Henrik; Vahrenhold, Jan

2006-01-01

174

The Salpeter Slope of the IMF Explained  

CERN Document Server

If we accept a paradigm that star formation is a self-similar, hierarchical process, then the Salpeter slope of the IMF for high-mass stars can be simply and elegantly explained as follows. If the instrinsic IMF at the smallest scales follows a simple -2 power-law slope, then the steepening to the -2.35 Salpeter value results when the most massive stars cannot form in the lowest-mass clumps of a cluster. It is stressed that this steepening MUST occur if clusters form hierarchically from clumps, and the lowest-mass clumps can form stars. This model is consistent with a variety of observations as well as theoretical simulations.

Oey, M S

2012-01-01

175

Clustering Moving Objects Using Segments Slopes  

Directory of Open Access Journals (Sweden)

Full Text Available Given a set of moving object trajectories, we show how to cluster them using k-meansclustering approach. Our proposed clustering algorithm is competitive with the k-means clusteringbecause it specifies the value of “k” based on the segment’s slope of the moving object trajectories. Theadvantage of this approach is that it overcomes the known drawbacks of the k-means algorithm, namely,the dependence on the number of clusters (k, and the dependence on the initial choice of the clusters’centroids, and it uses segment’s slope as a heuristic to determine the different number of clusters for thek-means algorithm. In addition, we use the standard quality measure (silhouette coefficient in order tomeasure the efficiency of our proposed approach. Finally, we present experimental results on both realand synthetic data that show the performance and accuracy of our proposed technique.

Mohamed E. El-Sharkawi

2011-03-01

176

Ocean processes at the Antarctic continental slope  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean–atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce wat...

Heywood, Karen J.; Schmidtko, Sunke; Heuze?, Ce?line; Kaiser, Jan; Jickells, Timothy D.; Queste, Bastien; Stevens, David P.; Wadley, Martin; Thompson, Andrew F.; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K.; Smith, Walker

2014-01-01

177

Ocean processes at the Antarctic continental slope.  

Science.gov (United States)

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An iron-cycling model embedded in an eddy-permitting ocean model reveals the importance of sedimentary iron in fertilizing parts of the Southern Ocean. Ocean gliders play a key role in improving our ability to observe and understand these small-scale processes at the continental shelf break. The Gliders: Excellent New Tools for Observing the Ocean (GENTOO) project deployed three Seagliders for up to two months in early 2012 to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. The glider data resolve small-scale exchange processes across the shelf-break front (the Antarctic Slope Front) and the front's biogeochemical signature. GENTOO demonstrated the capability of ocean gliders to play a key role in a future multi-disciplinary Southern Ocean observing system. PMID:24891389

Heywood, Karen J; Schmidtko, Sunke; Heuzé, Céline; Kaiser, Jan; Jickells, Timothy D; Queste, Bastien Y; Stevens, David P; Wadley, Martin; Thompson, Andrew F; Fielding, Sophie; Guihen, Damien; Creed, Elizabeth; Ridley, Jeff K; Smith, Walker

2014-07-13

178

Jurassic-Neocomian biostratigraphy, North Slope, Alaska  

Energy Technology Data Exchange (ETDEWEB)

The foraminiferal and palynological biostratigraphy of subsurface Jurassic and Neocomian (Early Cretaceous) age strata from the North Slope were investigated to better define biostratigraphic zone boundaries and to help clarify the correlation of the stratigraphic units in the National Petroleum Reserve in Alaska (NPRA). Through use of micropaleontologic data, eight principal biostratigraphic units have been identified. The Neocomian and Jurassic strata have each been subdivided into four main units.

Mickey, M.B.; Haga, H.

1985-04-01

179

3D geodetic monitoring slope deformations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For plenty of slope failures that can be found in Slovakia is necessary and very important their geodetic monitoring (because of their activity, reactivisations, checks). The paper gives new methodologies for these works, using 3D terrestrial survey technologies for measurements in convenient deformation networks. The design of an optimal type of deformation model for various kinds of landslides and their exact processing with an efficient testing procedure to determine the kinematics of the ...

Weiss Gabriel; Sütti Juraj

1996-01-01

180

Geosynthetic clay liners - slope stability field study  

International Nuclear Information System (INIS)

A field research project was developed to examine the internal shear performance of geosynthetic clay liners (GCLs). Several combinations of cross sections were assembled using GCL materials that were available at the time of project initiation. The cross sections utilized were intended to simulate landfill cover applications. Thirteen (13) resulting test plots were constructed on two different slope angles, and each plot is instrumented for physical displacement and soil moisture characteristics. Test plots were constructed in a manner that dictated the shear plane in the clay portion of the GCL product. The project purpose is to assess field performance and to verify design parameters associated with the application of GCLs in waste containment applications. Interim research data shows that test slopes on 2H:1V show global deformation, but little internal shear evidence, and the 3H:1V slopes show little deformation at approximately 650 days. The research is ongoing, and this paper presents the most recent information available from the project

 
 
 
 
181

Geosynthetic clay liners - slope stability field study  

Energy Technology Data Exchange (ETDEWEB)

A field research project was developed to examine the internal shear performance of geosynthetic clay liners (GCLs). Several combinations of cross sections were assembled using GCL materials that were available at the time of project initiation. The cross sections utilized were intended to simulate landfill cover applications. Thirteen (13) resulting test plots were constructed on two different slope angles, and each plot is instrumented for physical displacement and soil moisture characteristics. Test plots were constructed in a manner that dictated the shear plane in the clay portion of the GCL product. The project purpose is to assess field performance and to verify design parameters associated with the application of GCLs in waste containment applications. Interim research data shows that test slopes on 2H:1V show global deformation, but little internal shear evidence, and the 3H:1V slopes show little deformation at approximately 650 days. The research is ongoing, and this paper presents the most recent information available from the project.

Carson, D.A. [Environmental Protection Agency, Cincinnati, OH (United States); Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States); Koerner, R.M. [Geosynthetic Research Institute, Philadelphia, PA (United States); Bonaparte, R. [GeoSyntec Consultants, Atlanta, GA (United States)

1997-12-31

182

Geotechnical vs. Geophysical models for slope stability  

Science.gov (United States)

Current approaches to landslide forecasting are based either on empirical models, which search for correlations between rainfall data and landslide occurrences, or on physically based models, which combine hydrological models with slope stability analyses for the computation of the Factor of Safety. Traditionally, the calculation of the Factor of Safety is based on accurate geotechnical measurements, which provide information on the internal structure and the mechanical properties of the investigated soils through the analysis of samples of very reduced size. Hence, both empirical and physically based traditional approaches are based on point information, which refer to very small rainwater collecting areas of rain gauges and very small soil volumes around porous probes. To overcome the limit of point-sampled information, we propose a semi-empirical approach based on the use of a geophysical Factor of Safety introduced in terms of local resistivities and slope angles. Starting from two resistivity tomography surveys performed on a test area on Sarno Mountains (Southern Italy) during the autumnal and spring seasons, we present an application of the proposed geophysical approach and compared the results with those coming from the infinite slope analysis. Advantages and disadvantages of geotechnical and geophysical approaches are shown.

Piegari, E.; Di Maio, R.

2012-04-01

183

On Front Slope Stability of Berm Breakwaters  

DEFF Research Database (Denmark)

The short communication presents application of the conventional Van der Meer stability formula for low-crested breakwaters for the prediction of front slope erosion of statically stable berm breakwaters with relatively high berms. The method is verified (Burcharth, 2008) by comparison with the reshaping of a large Norwegian breakwater exposed to the North Sea waves. As a motivation for applying the Van der Meer formula a discussion of design parameters related to berm breakwater stability formulae is given. Comparisons of front erosion predicted by the use of the Van der Meer formula with model test results including tests presented in Sigurdarson and Van der Meer (2011) are discussed. A proposal is presented for performance of new model tests with the purpose of developing more accurate formulae for the prediction of front slope erosion as a function of front slope, relative berm height, relative berm width, method of armour stone placement, and hydraulic parameters. The formulae should cover the structure range from statically stable berm breakwaters to conventional double layer armoured breakwaters.

Burcharth, Hans F.

2013-01-01

184

Stability of nuclear crater slopes in rock  

International Nuclear Information System (INIS)

The United States Army Engineer Nuclear Cratering Group was established in 1962 to participate with the Atomic Energy Commission in a joint research and development program to develop nuclear engineering and construction technology. A major part of this research effort has been devoted to studies of the engineering properties of craters. The program to date has included field investigations of crater properties in various media over a broad range of chemical and nuclear explosive yields, studies of man-made and natural slopes, and studies directed toward the development of analytical and empirical methods of crater stability analysis. From this background, a general understanding has been developed of the effects of a cratering explosion on the surrounding medium and of physical nature of the various crater zones which are produced. The stability of nuclear crater slopes has been a subject of prime interest in the feasibility study being conducted for an Atlantic-Pacific sea-level canal. Based on experimental evidence assembled to date, nuclear crater slopes in dry dock and dry alluvium have an initially stable configuration. There have been five nuclear craters produced to date with yields of 0.4 kt or more on which observations are based and the initial configurations of these craters have remained stable for over seven years. The medium, yield, crater dimensions, and date of event for these craters are summarized. It is interesting to note that the Sedan Crater has been subjected to strong seismic motions from nearby detonations without adverse effects

185

Overview of gas hydrates in submarine slopes  

Energy Technology Data Exchange (ETDEWEB)

Gas hydrates are solid crystalline compounds consisting of hydrogen-bonded water molecules that form a rigid crystal lattice stabilized by encaged gas molecules. Their stability is confined to low-temperature, high-pressure regimes such as those found in permafrost regions and under the seafloor on continental slopes. In-situ natural gas hydrate deposits are typically located in marine sediments at temperatures of 5 to 10 degrees C. The critical factors influencing hydrate formation and stability are pressure, temperature, gas composition, volume of bulk free water, salinity, gas availability, sediment type, and the presence of catalysts or inhibitors. Circumstantial evidence suggests that large submarine landslides along the continental margins can be triggered by the weakening of hydrate bearing sediments. Hydrate dissociation results in loss of solid material, production of free gas, and increased fluid pressures, all which have the effect of reducing sediment strength. These underwater landslides have the potential to destroy offshore equipment, jeopardize safety of personnel, and generate tsunamis. This paper presented recent results and advances on the intersection of gas hydrates and submarine slope stability, with particular reference to the role of gas hydrates in triggering or propagating submarine mass movements. It was concluded that the cause of slope failures is not fully understood because of the complexities of gas hydrates and their interactions with the host sediment, combined with the high cost of laboratory and field investigations. 35 refs., 2 figs.

Grozic, J.L.H. [Calgary Univ., AB (Canada). Dept. of Civil Engineering

2009-07-01

186

Slope stability monitoring from microseismic field using polarization methodology  

Directory of Open Access Journals (Sweden)

Full Text Available Numerical simulation of seismoacoustic emission (SAE associated with fracturing in zones of shear stress concentration shows that SAE signals are polarized along the stress direction. The proposed polarization methodology for monitoring of slope stability makes use of three-component recording of the microseismic field on a slope in order to pick the signals of slope processes by filtering and polarization analysis. Slope activity is indicated by rather strong roughly horizontal polarization of the respective portion of the field in the direction of slope dip. The methodology was tested in microseismic observations on a landslide slope in the Northern Tien-Shan (Kyrgyzstan.

Yu. I. Kolesnikov

2003-01-01

187

30 CFR 716.2 - Steep-slope mining.  

Science.gov (United States)

...2010-07-01 false Steep-slope mining. 716.2 Section 716.2 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT...STANDARDS § 716.2 Steep-slope mining. The permittee conducting...

2010-07-01

188

Thermomechanical forcing of deep rock slope deformation: 1. Conceptual study of a simplified slope  

Science.gov (United States)

Thermo-elastic rock slope deformation is often considered to be of relatively minor importance and limited to shallow depths subject to seasonal warming and cooling. In this study, we demonstrate how thermomechanical (TM) effects can drive rock slope deformation at greater depths below the annual thermal active layer. Here in Part 1 of two companion papers, we present 2D numerical models of a simplified slope subject to annual surface temperature cycles. The slope geometry and discontinuity sets are loosely based on the Randa instability considered in detail in Part 2. Results show that near-surface thermo-elastic stresses can propagate to depths of 100 m and more as a result of topography and elasticity of the rock mass. Shear dislocation along discontinuities can have both a reversible component controlled by discontinuity compliance and, provided that the stress state is sufficiently close to the strength limit, an irreversible component (i.e., slip). Induced slip increments are followed by stress redistribution resulting in the propagation of slip fronts. Thus, deformation and progressive rock slope failure can be driven solely by thermomechanical forcing. The influence of TM-induced stress changes becomes stronger for increasing numbers of critically stressed discontinuities and is enhanced if failure of discontinuities involves slip-weakening. The net TM effect acts as a meso-scale fatigue process, involving incremental discontinuity slip and hysteresis driven by periodic loading.

Gischig, Valentin S.; Moore, Jeffrey R.; Evans, Keith F.; Amann, Florian; Loew, Simon

2011-12-01

189

Evaluation of Slope Assessment Systems for Predicting Landslides of Cut Slopes in Granitic and Meta-sediment Formations  

Directory of Open Access Journals (Sweden)

Full Text Available In Malaysia, slope assessment systems (SAS are widely used in assessing the instability of slope or the probability of occurrence and the likely severity of landslides. These SAS can be derived based on either one particular approach or combination of several approaches of landslide assessments and prediction. This study overviews four slope assessment systems (SAS developed in Malaysia for predicting landslide at a large-scale assessments. They are the Slope Maintenance System (SMS, Slope Priority Ranking System (SPRS, Slope Information Management System (SIMS and the Slope Management and Risk Tracking System (SMART. An attempt is made to evaluate the accuracy of the SAS in predicting landslides based on slope inventory data from 139 cut slopes in granitic formation and 47 cut slopes in meta-sediment formation, which are the two most common rock/soil formations found in Malaysia. Based on this study, it was found that none of existing SAS is satisfactory in predicting landslides of cut slopes in granitic formation, for various reasons such as the use of hazard score developed from another country, insufficient data base, oversimplified approach and use of data base derived from different rock/soil formations. However for the case of cut slope in meta-sediment, the Slope Management and Risk Tracking System (SMART was found to be satisfactory with 90% prediction accuracy. The current database of SMART is largely based on meta-sediment formation.

Suhaimi Jamaludin

2006-01-01

190

Mars Exploration Rover Landing Site Hectometer Slopes  

Science.gov (United States)

The Mars Exploration Rover (MER) airbag landing system imposes a maximum slope of 5 degrees over 100 m length-scales. This limit avoids dangerous changes in elevation over the horizontal travel distance of the lander on its parachute between the time of the last radar altimeter detection of the surface and the time the retro-rockets fire and the bridle to the airbags is cut. Stereo imagery from the MGS MOC can provide information at this length scale, but MOC stereo coverage is sparse, even when targeted to MER landing sites. Additionally, MGS spacecraft stability issues affect the DEMs at precisely the hectometric length-scale1. The MOLA instrument provides global coverage pulse-width measurements2 over a single MOLA-pulse footprint, which is about 100 m in diameter. However, the pulse spread only provides an upper bound on the 100 m slope. We chose another approach. We sample the inter-pulse root-mean-square (RMS) height deviations for MOLA track segments restricted to pixels of 0.1 deg latitude by 0.1 deg longitude. Then, under the assumption of self-affine topography, we determine the scale-dependence of the RMS deviations and extrapolate that behavior over the range of 300 m to 1.2 km downward to the 100 m scale. Shepard et al.3 clearly summarize the statistical properties of the RMS deviation (noting that it also goes by the name structure function, variogram or Allan deviation), and we follow their nomenclature. The RMS deviation is a useful measure in that it can be directly converted to RMS-slope for a given length-scale. We map the results of this self-affine extrapolation method for each of the proposed MER landing sites as well as Viking Lander 1 (VL1) and Pathfiner (MPF). In order of decreasing average hectometer RMS-slopes, Melas (about 4.5 degrees) > Elysium EP80 > Gusev > MPF > Elysium EP78 > VL1 > Athabasca > Isidis > Hematite (about 1 degree). We also map the scaling parameter (Hurst exponent); its behavior in the MER landing site regions is interesting in how it ties together the regional behavior of kilometer slopes (directly measured with MOLA) with the decameter and meter slopes (locally derived from stereo image analysis or radar scattering). 1Kirk, R. L., E. Howington-Kraus, and B. A. Archinal, Int. Arch. Photogramm. Remote Sens., XXVIII(B4), 476 (CD-ROM), 2001; Kirk, R. L., E. Howington-Kraus, and B. A. Archinal, Lunar Planet Sci., XXXIII, abs 1988, 2002. 2Garvin, J. B., and J. J. Frawley, Lunar Planet. Sci., XXXI, abs 1884, 2000. 3Shepard, M. K., R. A. Brackett, and R. E. Arvidson, J. Geophys. Res., 100, 11709-11718, 1995.; Shepard, M. K., et al., J. Geophys. Res., 106, 32777-32796, 2001.

Haldemann, A. F.; Anderson, F. S.

2002-12-01

191

Slope equalities for genus 5 surface fibrations  

CERN Document Server

K. Konno proved a slope equality for fibred surfaces with fibres of odd genus and general fibre of maximal gonality. More precisely he found a relation between the invariants of the fibration and certain weights of special fibres (called the Horikawa numbers). We give an alternative and more geometric proof in the case of a genus 5 fibration, under generality assumptions. In our setting we are able to prove that the fibre with positive Horikawa numbers are precisely the trigonal ones, we compute their weights explicitly and thus we exhibit explicit examples of regular surfaces with assigned invariants and Horikawa numbers.

Tenni, Elisa

2010-01-01

192

On comparing regression lines with unequal slopes.  

Science.gov (United States)

For the situation in which the slopes of two regression lines may differ, procedures are discussed for the comparison of the lines at a single X, simultaneous comparison at several values of X, and determination of the range of X for which the difference between the lines is large enough to be statistically significant. These useful procedures have previously been discussed but do not seem to be well known. Their usefulness in the analysis of physiological data is demonstrated with data arising from a study of pulmonary response to hypoxia. PMID:7065210

Zerbe, G O; Archer, P G; Banchero, N; Lechner, A J

1982-03-01

193

Western Ross Sea continental slope gravity currents  

Science.gov (United States)

Antarctic Bottom Water of the world ocean is derived from dense Shelf Water that is carried downslope by gravity currents at specific sites along the Antarctic margins. Data gathered by the AnSlope and CLIMA programs reveal the presence of energetic gravity currents that are formed over the western continental slope of the Ross Sea when High Salinity Shelf Water exits the shelf through Drygalski Trough. Joides Trough, immediately to the east, offers an additional escape route for less saline Shelf Water, while the Glomar Challenger Trough still farther east is a major pathway for export of the once supercooled low-salinity Ice Shelf Water that forms under the Ross Ice Shelf. The Drygalski Trough gravity currents increase in thickness from ˜100 to ˜400 m on proceeding downslope from ˜600 m (the shelf break) to 1200 m (upper slope) sea floor depth, while turning sharply to the west in response to the Coriolis force during their descent. The mean current pathway trends ˜35° downslope from isobaths. Benthic-layer current and thickness are correlated with the bottom water salinity, which exerts the primary control over the benthic-layer density. A 1-year time series of bottom-water current and hydrographic properties obtained on the slope near the 1000 m isobath indicates episodic pulses of Shelf Water export through Drygalski Trough. These cold (34.75) pulses correlate with strong downslope bottom flow. Extreme examples occurred during austral summer/fall 2003, comprising concentrated High Salinity Shelf Water (-1.9 °C; 34.79) and approaching 1.5 m s -1 at descent angles as large as ˜60° relative to the isobaths. Such events were most common during November-May, consistent with a northward shift in position of the dense Shelf Water during austral summer. The coldest, saltiest bottom water was measured from mid-April to mid-May 2003. The summer/fall export of High Salinity Shelf Water observed in 2004 was less than that seen in 2003. This difference, if real, may reflect the influence of the large iceberg C-19 over Drygalski Trough until its departure in mid-May 2003, when there was a marked decrease in the coldest, saltiest gravity current adjacent to Drygalski Trough. Northward transport of cold, saline, recently ventilated Antarctic Bottom Water observed in March 2004 off Cape Adare was ˜1.7 Sv, including ˜0.4 Sv of High Salinity Shelf Water.

Gordon, Arnold L.; Orsi, Alejandro H.; Muench, Robin; Huber, Bruce A.; Zambianchi, Enrico; Visbeck, Martin

2009-06-01

194

Slope stability of moraines, Cordillera Blanca, Peru  

Science.gov (United States)

Landslides originating from inner slopes of moraine dams are often capable of producing glacial lakes outburst floods (GLOFs). Therefore assessing stability conditions of the moraines is important for predicting this potentially damaging phenomenon. Characteristics of the basic mechanical properties of the material and geophysical investigations were applied to collect necessary information for slope stability assessment of the Palcacocha Lake moraine dam, Peru. The lake is situated in the Cordillera Blanca Mts. at the altitude of about 4,500m asl and produced catastrophic GLOF in 1941. Another minor flood originated in 2003 due to landslide impact into the lake. Detailed investigations of this landslide site included geomorphological mapping, geophysical investigations and characterization of basic mechanical properties of the forming material. Geomorphological mapping identified dormant landslide with scarp up to 2m high which developed on the edge of the inner moraine slope. It is conditioned by set of parallel extension trenches which also affected the origin of 2003 landslide. Within its scarp area, significant water bearing layer was noticed around 10 m bellow the moraine surface. Three profiles were investigated using electric resistivity tomography performed on 4poing light instrument with 24 electrodes and with spacing ranging from 1 to 4m. Results helped to verify geometry of the main shear plane of the mapped landslide as well as the spacing and depth of extension trenches. Significant heterogeneity in the moraine resistivity characteristics was found. The high resistivity regions are explained by rock block accumulation whereas the low resistivity may represent wet layers within the moraine body. Grain size distribution of 33 disturbed soil samples originating from moraine material within the Cordillera Blanca Mts., Peru were determined and classified according to the UCSC classification system. The samples were taken from moraine dams and slopes covered by moraine material. 11 samples were also tested for the angle of repose. These results were compared with literature data relating grains size distribution of similar soil types with measured shear strength characteristics to assess peak shear strength ?max of the analyzed samples. Rough estimates of these values indicate that the moraine material gains 35°-38o. These estimates are verified by measured angle of repose. Results of the grain size distribution were also used to estimate average hydraulic conductivity applying Hazen formula. This estimates show that investigated moraine material range from 6x10-6 to 3x10-4 m/s.

Klimes, J.; Novotny, J.

2012-12-01

195

Water budgets of martian recurring slope lineae  

Science.gov (United States)

Flowing water, possibly brine, has been suggested to cause seasonally reappearing, incrementally growing, dark streaks on steep, warm slopes on Mars. We modeled these Recurring Slope Lineae (RSL) as isothermal water flows in thin surficial layers driven by gravity and capillary suction, with input from sources in the headwall and loss to evaporation. The principal observables are flow duration and length. At 40% porosity, we find that flow thicknesses reaching saturation can be just 50 mm or so and freshwater RSL seasonally require 2-10 m3 of H2O per m of source headwall. Modeled water budgets are larger for brines because they are active for a longer part of each day, but this could be partly offset by lower evaporation rates. Most of the discharged water is lost to evaporation even while RSL are actively lengthening. The derived water volumes, while small, exceed those that can be supplied by annual melting of near-surface ice (0.2-2 m3/m for a 200-mm melt depth over 1-10 m height). RSL either tap a liquid reservoir startlingly close to the surface, or the actual water budget is several times smaller. The latter is possible if water never fully saturates RSL along their length. Instead, they would advance like raindrops on a window, as intermittent slugs of water that overrun prior parts of the flow at residual saturation. Annual recharge by vapor cold trapping might then be supplied from the atmosphere or subsurface.

Grimm, Robert E.; Harrison, Keith P.; Stillman, David E.

2014-05-01

196

Kinetics of cross-slope running.  

Science.gov (United States)

The purpose of the present study was to identify kinetic responses to running on mediolaterally elevated (cross-sloped) running surfaces. Ground reaction forces (GRFs), GRF lever arms and joint moment characteristics of 19 male runners were analyzed when running at 3.5m/s on a custom-made, tiltable runway. Tilt angles of 3° and 6° for medial and lateral elevation were analyzed using a 10 camera Vicon Nexus system and a force platform. The point of force application of the GRF showed a systematic shift in the order of 1-1.5cm to either the lateral or medial aspect of the foot for lateral or medial inclinations, respectively. Consequently, the strongest significant effects of tilt orientation and level on joint kinetics and ground reaction force lever arms were identified at the ankle, knee and hip joint in the frontal plane of movement. External eversion moments at the ankle were significantly increased by 35% for 6° of lateral elevation and decreased by 16% for 6° of medial elevation. Altering the cross-slope of the running surface changed the pattern of ankle joint moments in the transversal plane. Effect sizes were on average larger for laterally elevated conditions, indicating a higher sensitivity of kinetic parameters to this kind of surface tilt. These alterations in joint kinetics should be considered in the choice of the running environment, especially for specific risk groups, like runners in rehabilitation processes. PMID:24074942

Willwacher, Steffen; Fischer, Katina Mira; Benker, Rita; Dill, Stephan; Brüggemann, Gert-Peter

2013-11-15

197

Slope stability analysis of Valles Marineris, Mars  

Science.gov (United States)

Valles Marineris (VM) in the equatorial area of Mars exhibits several gravitational failures which resulted in a series of large landslides up to several hundred cubic kilometers in volume. Questions arise as to forces at play and rock strength in the stability of the walls of VM. In this work we address the stability analysis of the walls of VM by considering the strength of the materials of the chasma walls and the causes of landslides. Using finite element calculations and the limit analysis upper bound method, we explore the range of cohesion and friction angle values associated to realistic failure geometries, and compare predictions with the classical Culmann's wedge model. Our analysis is based both on synthetic, simplified slope profiles and also on the real shape of the walls of VM taken from the MOLA topographic data. Validation of the calibrated cohesion and friction angle values is performed by comparing the computed unstable cross sectional areas with the observed pre- and post-failure profiles and estimated failure surface geometry. This offers a link between rock mass properties, slope geometry and volume of the observed failure. Pseudo-static seismic analyses generated another set of dimensionless charts. Our pseudo-static analyses show that low seismicity events induced by meteoroids impacts compatible with the size of craters could be a cause for some of the observed landslides if poor rock properties for VM is assumed.

Vittorio De Blasio, Fabio; Battista Crosta, Giovanni; Castellanza, Riccardo; Utili, Stefano

2013-04-01

198

Slope evolution of GRB correlations and cosmology  

CERN Document Server

Gamma -ray bursts (GRBs) observed up to redshifts $z>9.4$ can be used as possible probes to test cosmological models. Here we show how changes of the slope of the {\\it luminosity $L^*_X$ -break time $T^*_a$} correlation in GRB afterglows, hereafter the LT correlation, affect the determination of the cosmological parameters. With a simulated data set of 101 GRBs with a central value of the correlation slope that differs on the intrinsic one by a $5\\sigma$ factor, we find an overstimated value of the matter density parameter, $\\Omega_M$, compared to the value obtained with SNe Ia, while the Hubble constant, $H_0$, best fit value is still compatible in 1$\\sigma$ compared to other probes. We show that this compatibility of $H_0$ is due to the large intrinsic scatter associated with the simulated sample. Instead, if we consider a subsample of high luminous GRBs ($HighL$), we find that both the evaluation of $H_0$ and $\\Omega_M$ are not more compatible in 1$\\sigma$ and $\\Omega_M$ is underestimated by the $13\\%$. Ho...

Dainotti, Maria Giovanna; Piedipalumbo, Ester; Capozziello, Salvatore

2013-01-01

199

Comparative three-dimensional structure of the trabecular bone in the talus of primates and its relationship to ankle joint loads generated during locomotion.  

Science.gov (United States)

The trabecular structure of the ankle bone in small to medium-bodied (60-5000 g) primates of distinct locomotor types was analyzed using high-resolution X-ray computed tomography. There are large inter-, intraspecific, and regional (medial vs. lateral) variations in the trabecular architecture of the talar body. Body mass has no effect on the bone volume fraction or on the fabric anisotropy. However, both the number and thickness of trabeculae seem to be body mass-dependent. All taxa show anisotropic trabecular bone, but the degree of anisotropy and elongation values vary, notably across the locomotion categories. The fabric orientation in the talar body indicates that, practically, all taxa studied display a generally consistent pattern of orientation restricted primarily to a dorsoplantar direction. We have observed a mediolateral difference in the bone volume fraction in most primates who are proficient or frequent climbers. This could reflect a specific reinforcement of the trabecular structure in response to the loads engendered in habitually sustained foot inversion. In contrast, tali of primates who are proficient or frequent leapers rather exhibit a different three-dimensional distribution of the material, which consists of a more anisotropic trabecular structure. This could reflect stronger unidirectional and stereotypical-loading conditions generated at the ankle joints during a leap. Finally, it appears that the talar trabecular bone structure has a good potential for predicting locomotion in extinct species. We have analyzed the trabecular bone structure of the talus of some Eocene European primates (Adapis, Leptadapis, and Necrolemur) and compared the functional signal of the external versus internal talar anatomy in these fossils. PMID:23109268

Hébert, David; Lebrun, Renaud; Marivaux, Laurent

2012-12-01

200

Tratamento das lesões osteocondrais do talo através da técnica de microperfurações assistidas por artroscopia Treatment of osteochondral lesions of the talus by means of thearthroscopy-assisted microperforation technique  

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Full Text Available OBJETIVO: Analisar pacientes acometidos por fratura osteocondral do talo tratados cirurgicamente através de microperfurações assistidas por artroscopia. MÉTODOS: Foi realizado um estudo retrospectivo de 24 pacientes com lesão osteocondral do talo submetidos à microperfurações assistidas por videoartroscopia do tornozelo. Todos os pacientes foram submetidos ao sistema de avaliação da American Orthopaedic Foot & Ankle Society (AOFAS no pré e pós-operatório. RESULTADOS: Foram observados 19 homens e cinco mulheres, com idade média de 35,3 anos (mínima de 17 anos e máxima de 54 anos. O tempo mínimo de seguimento foi de dois anos (máximo de 39 meses. Todos os pacientes apresentaram melhora do escore da AOFAS após o procedimento cirúrgico, com média de elevação do escore em torno de 22,5 pontos. CONCLUSÃO: A técnica de microperfurações assistidas por videoartroscopia consiste em boa opção para o tratamento das lesões osteocondrais do talo e fornece bons resultados funcionais.OBJECTIVE: To evaluate patients affected by osteochondral fractures of the talus who were treated surgically by means of arthroscopy-assisted microperforation. METHODS: A retrospective study was carried out on 24 patients with osteochondral lesions of the talus who underwent microperforation assisted by videoarthroscopy of the ankle. They were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS score system before and after the operation. RESULTS: There were 19 men and 5 women, with a mean age of 35.3 years (minimum of 17 years and maximum of 54 years. The minimum follow-up was two years (maximum of 39 months. All the patients showed an improvement in AOFAS score after surgery, with an average improvement of around 22.5 points. CONCLUSION: Videoarthroscopy-assisted microperforation is a good option for treating osteochondral lesions of the talus and provides good functional results.

Everton de Lima

2011-01-01

 
 
 
 
201

Prótese do tornozelo híbrida em um caso de necrose avascular pós-traumática do tálus / Hybrid ankle prosthesis in a case of post-traumatic avascular necrosis of the talus  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese As fraturas do astrágalo originam frequentemente artrose pós-traumática tardia. Nestes casos, a utilização de próteses do tornozelo não cimentadas de última geração tem sido evitada pela presença de necrose avascular. Relatamos o caso de um paciente com 65 anos que se apresenta quatro anos após uma [...] fratura do colo do astrágalo. Apresentava uma artrose do tornozelo dolorosa (escala AOFAS do retropé e tornozelo 19) e necrose avascular com colapso de toda a cúpula astragalina. Dada a extensão da necrose, foi decidido cimentar o componente protésico astragalino. Um ano após a cirurgia, o paciente apresenta bom resultado clínico e radiológico (escala AOFAS do retropé e tornozelo 87) e está satisfeito com o procedimento. Não temos conhecimento de nenhum relato semelhante na literatura. Abstract in english Talus fractures often lead to late post-traumatic arthrosis. In such cases, the use of latest generation, cementless prostheses has been hindered by the presence of avascular necrosis. We report the case of a 65-year-old patient who presented four years after a talus neck fracture. He had painful an [...] kle arthrosis (AOFAS ankle-hindfoot score 19) and avascular necrosis, with collapse of the entire talar dome. Given the extent of the necrosis, it was decided to cement the talus prosthetic component. One year after the surgery, the patient shows good clinical and radiological results (AOFAS ankle-hindfoot score 87) and is satisfied with the procedure. We are not aware of any similar reports in the literature.

Ricardo Jorge Gomes de, Sousa; Ricardo Pedro Ferreira Rodrigues, Pinto; Marta Maria Teixeira de Oliveira, Massada; Manuel Alexandre Negrais Pinho Gonçalves, Pereira; José Muras, Geada; Isabel Maria Gonçalves, Costa.

202

Seismic Stability of Reinforced Soil Slopes  

DEFF Research Database (Denmark)

Over recent decades increased research interest has been observed on the dynamic response and stability issues of earth walls and reinforced soil structures. The current study aims to provide an insight into the dynamic response of reinforced soil structures and the potential of the geosynthetics to prevent the development of slope instability taking advantage of their reinforcing effect. For this purpose, a onedimensional (SDOF) model, based on Newmark’s sliding block model as well as a two-dimensional (plane-strain) dynamic finite-element analyses are conducted in order to investigate the impact of the most significant parameters involved, such as the flexibility of the sliding system, the mechanical properties of the soil and of the geosynthetics material, the frequency content of the excitation and the interface shear strength.

Tzavara, I.; Zania, Varvara

2012-01-01

203

The dual-slope conversion improvement  

Directory of Open Access Journals (Sweden)

Full Text Available The dual-slope ADC (DSADC is a type of analog-to-digital conversion with low input bandwidths. It is pretty slow, but its ability to reject high-frequency noise and fixed low frequencies such as 50 Hz or 60 Hz makes it useful in noisy industrial environments and applications. It provides very good resolution. For the practical measurements in the Institutes laboratory an instrument is designed and realized. The base DSADC method is used, but improved by multiple conversions to make the measuring more precise and the time shorter. The special attention is paid to the problems occurred in practical realization and the way to overcome them. The paper describes the proposed and applied solutions, functional principles and achieved performances of the realized instrument. [Projekat Ministarstva nauke Republike Srbije, br. TR33037 i TR34005

Radeti? Radojle

2014-01-01

204

Nocturnal flow on a western Colorado slope  

International Nuclear Information System (INIS)

The Department of Energy sponsored Atomspheric Studies in Complex Terrain (ASCOT) program has conducted a research program designed to increase our knowledge and understanding of terrain-dominated flows with specific emphasis on nocturnal flows within mountain valleys. ASCOT has sponsored both field studies and numerical modeling efforts to improve our understanding of the wind, temperature and turbulence structure of nocturnal drainage flows. One of the most recent ASCOT sponsored field studies involves a study within the Mesa Creek Basin in western Colorado to investigate the seasonal frequency of occurrence of drainage flows along the sloped surfaces and within the basin, and to evaluate the effect of the ambient meteorology on their development. The Mesa Creek Basin, situated on the north slope of the Grand Mesa, encompasses a roughly 10 x 20 km area that is approximately 30 km east of Grand Junction. The observational segment of the study was undertaken jointly by the Lawrence Livermore National Laboratory and the NOAA Wave Propagation Laboratory, and involved the operation of network of eight meteorological towers and a monostatic sodar within the Mesa Creek study area over a period of one year that extended from December 1988 through November 1989. These measurements were augmented by tethersonde observations to define the vertical wind and temperature structure during a few nights. The modeling portion of the study is being undertaken by Lawrence Livermore Laboratory using a three-dimensional prognostic boundary layer model to gain further insight into the dynamics of the seasonal variations and the effect of cloud cover on the development of the drainage flows. It is the purpose of this paper to present preliminary results form a numerical simulation done as part of this study. 4 refs., 7 figs

205

Dendrogeomorphic approach to estimating slope retreat, Maxey Flats, Kentucky  

International Nuclear Information System (INIS)

A dendrogeomorphic study of slope retreat was conducted at the Maxey Flats nuclear-waste disposal site in northeastern Kentucky. Tree roots exposed by surface lowering were used as an indicator of ground surface at the time of germination. The amount of lowering was measured and divided by tree-ring-determined tree age. Surface lowering and slope degradation rates were estimated for three slopes below waste-burial trenches and compared with data obtained from sediment troughs and erosion frames at the site. Mean rates of slope retreat ranged from 1.92 to 3.16 mm/yr. Sediment-trough results are two to three orders of magnitude less than dendrogeomorphic and erosion-frame estimates of slope degradation, which suggests that piping and solution-weathering processes may be important in slope degradation. Slope aspect and declivity may be important factors affecting retreat of slopes with a uniform lithology. Dendrogeomorphic techniques provide results comparable to those in the literature and offer a rapid method for estimating slope retreat that integrates slope processes over many years

206

Design principles for optimizing an established survey slope monitoring system  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english When slope angles are designed during open pit optimization, there is a risk factor applied in steepening the slopes. The steepening of slope angles has implications for the safety and economics of the mining operation. The steeper the slope angles, the greater the probability of slope failure. Alth [...] ough a slope failure will result in added costs, the challenge is to compile an accurate cost-benefit exercise optimizing the economic benefits of the project without exposing mine workers and equipment to unacceptable risk of rockfalls. A balance between the safety of the operation and the economics of the investment is therefore required. The ideal situation is to have a slope monitoring system that will predict slope failure by detecting any ground movement before the actual failure occurs. This early warning will allow the risk factor to be applied with a high degree of confidence, knowing that the risk will be adequately mitigated. The objective of this paper is to provide guidelines on how to design an optimal survey slope monitoring system. It is the authors' view that for a survey monitoring system to yield desirable results, it should adhere to survey principles such as working from the whole to part and consistently cross-checking. The case study used is Jwaneng Mine, and the design strategy outlined can be used as a guideline for developing a new slope monitoring system or to optimize an existing one.

N, Mphathiwa; F.T, Cawood.

207

Design principles for optimizing an established survey slope monitoring system  

Scientific Electronic Library Online (English)

Full Text Available SciELO South Africa | Language: English Abstract in english When slope angles are designed during open pit optimization, there is a risk factor applied in steepening the slopes. The steepening of slope angles has implications for the safety and economics of the mining operation. The steeper the slope angles, the greater the probability of slope failure. Alth [...] ough a slope failure will result in added costs, the challenge is to compile an accurate cost-benefit exercise optimizing the economic benefits of the project without exposing mine workers and equipment to unacceptable risk of rockfalls. A balance between the safety of the operation and the economics of the investment is therefore required. The ideal situation is to have a slope monitoring system that will predict slope failure by detecting any ground movement before the actual failure occurs. This early warning will allow the risk factor to be applied with a high degree of confidence, knowing that the risk will be adequately mitigated. The objective of this paper is to provide guidelines on how to design an optimal survey slope monitoring system. It is the authors' view that for a survey monitoring system to yield desirable results, it should adhere to survey principles such as working from the whole to part and consistently cross-checking. The case study used is Jwaneng Mine, and the design strategy outlined can be used as a guideline for developing a new slope monitoring system or to optimize an existing one.

N, Mphathiwa; F.T, Cawood.

2014-06-01

208

Stability Analysis of Cut Slopes Using Continuous Slope Mass Rating and Kinematic Analysis in Rudraprayag District, Uttarakhand  

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Full Text Available In mountain terrains of Himalaya, road and highway networks play a vital role in remote areas for transportation, public network and all kind of socio-economic activities. The stability of rock slopes along the roads and highways is a major concern in these hilly regions. Any kind of slope failure may lead to disruption in traffic, loss of properties and lives/injuries as well as environmental degradation. The unplanned excavations of rock slopes for construction or widening purposes may undermine the stability of the slopes. The present study incorporates the stability analysis of road cut slopes along NH-109 which goes to holy shrine of Kedarnath. Slope failure is not only a phenomenon of rainy season but it has also been encountered even in dry season. The study area experiences high vehicular traffic especially from March to August due to pilgrims since it is the only road to Kedarnath. The distance of about 20 km between Rudraprayag and Agastmuni has been investigated. The continuous slope mass rating (CSMR technique has been used for slope stability analysis at five different locations. CSMR is modification of original slope mass rating (SMR proposed by Romana which is based on well established rock mass rating (RMR technique. Kinematic analysis was also carried out to evaluate these sites for types of failure and its potential failure directions. The potentially vulnerable sites were identified. The results indicate that the CSMR technique may be exploited to assess the stability of rock slopes in the Himalayan territory.

R. K. Umrao

2011-10-01

209

A slippery slope: estimated slant of hills increases with distance.  

Science.gov (United States)

The slopes of hills tend to be greatly overestimated. Previous studies have found that slope estimates are significantly greater when estimated verbally than with a proprioceptive measure. It has yet to be determined whether these estimates are made for the entire extent of the slope, or whether the estimates in closest proximity are estimated using a different process. Since some parietal cortex neurons respond differently to objects within arm's reach, short-distance slope estimation may utilize these or analogous neurons. Alternatively, greater implied effort might make longer slopes seem steeper. We determined that both verbal and proprioceptive reports of slope are overestimates that increase logarithmically with distance from the observer, contradicting both theories. Consistent with previous work, proprioceptive estimates were more accurate at all ranges. Our results can be interpreted as a function of the angle between the observer's gaze and the plane of the hill, modified by depth cues available at only near distances. PMID:25223107

Chiu, Eric M; Thomas, Kyle A; Persike, Malte; Quan, Joshua R; Bridgeman, Bruce

2014-01-01

210

Distinct Element Modelling of Mahabaleshwar Road Cut Hill Slope  

Directory of Open Access Journals (Sweden)

Full Text Available Reliable estimates of slope stability are essential for safe design and planning of road cut hill slopes which accommo-date a number of tourist destinations around the world. The failure of cut slopes along these hills puts human life in grave danger and it is also disastrous for the economy. In the present study, a section of 100 m high jointed basalt hill slope has been analyzed numerically in a distinct element code, which is apt for simulating the behavior for jointed rock. The analysis was carried out for both the dry and saturated conditions. The distinct element analysis of the hill slope demonstrates it to be marginally stable under dry condition, while for the saturated condition, the hill slope fails along well defined joint planes.

Ashutosh Kainthola

2012-10-01

211

STANDARDS OF SUSTAINABLE ARCHITECTURE: RESIDENTIAL BUILDING ON A SLOPE  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main subject of this graduation thesis are modern houses on a slope, in comparison with traditional building on countryside based on a long-term principal of sustainable architecture. In the first part of this thesis, a traditional Slovenian house on a slope is presented, so is an example of a typical Slovenian house in the defined architectural region, and the analysis of a modern Slovenian house on a slope are presented. Based on chosen criteria, the similarities and differences be...

Lambizer, Karin

2011-01-01

212

Effects of bilayer gelatin/?-tricalcium phosphate sponges loaded with mesenchymal stem cells, chondrocytes, bone morphogenetic protein-2, and platelet rich plasma on osteochondral defects of the talus in horses.  

Science.gov (United States)

Osteochondrosis (OC) is a common and clinically important joint disorder in horses. However, repair of the OC region is difficult because of the avascular nature of cartilage. This study aimed to evaluate the efficacy of bilayer gelatin/?-tricalcium phosphate (GT) sponges loaded with mesenchymal stem cells (MSCs), chondrocytes, bone morphogenetic protein-2 (BMP-2), and platelet rich plasma (PRP) for the repair of osteochondral defects of the talus in horses. Full-thickness osteochondral defects were created on both the lateral trochlear ridges of the talus (n = 6). In the test group, a basic GT sponge loaded with MSCs and BMP-2 (MSC/BMP2/GT) was inserted into the lower part of the defect, and an acidic GT sponge loaded with chondrocyte, MSCs, and PRP (Ch/MSC/PRP/GT) was inserted into the upper part of the defect. In the control group, the defect was treated only with bilayer GT sponges. Repair of osteochondral defects was assessed by radiography, quantitative computed tomography (QCT), and macroscopic and histological evaluation. The test group showed significantly higher radiographic, QCT, macroscopic, and histological scores than the control group. This study demonstrated that the bilayer scaffolds consisting of Ch/MSC/PRP/GT for the chondrogenic layer and MSC/BMP2/GT for the osteogenic layer promoted osteochondral regeneration in an equine model. The bilayer scaffolds described here may be useful for treating horses with OC. PMID:24054973

Seo, Jong-Pil; Tanabe, Takafumi; Tsuzuki, Nao; Haneda, Shingo; Yamada, Kazutaka; Furuoka, Hidefumi; Tabata, Yasuhiko; Sasaki, Naoki

2013-12-01

213

Sequelas a longo prazo de fracturas do corpo e colo do astrágalo Long-term results of body and neck talus fractures  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: As fracturas do colo e corpo do astrágalo são lesões infrequentes. O objectivo deste estudo é avaliar a prevalência de sequelas a longo prazo. MÉTODOS: Foi feita uma análise retrospectiva que incluiu um total de 11 doentes sujeitos a tratamento cirúrgico por fracturas do corpo ou colo do astrágalo entre Janeiro de 1997 e Dezembro de 2005. A avaliação final foi clínica (utilizando a escala AOFAS e radiológica. RESULTADOS: O seguimento médio foi 58,5 meses. A prevalência de lesões ósseas associadas foi de 60% (6/10. O resultado AOFAS médio foi 72 [19-100] pontos. A necrose avascular e/ou artrose pós-traumática ocorreu em metade dos doentes. A qualidade da redução cirúrgica, as fracturas do corpo e a ausência de alterações degenerativas relacionaram-se com melhores resultados funcionais. As fracturas do colo, a osteonecrose e a presença de artrose pós-traumática conduziram a piores resultados. CONCLUSÃO: Há um grande potencial para sequelas tardias e compromisso funcional devido a artrose e dor crónica após esse tipo de fracturas. A redução anatómica cirúrgica é a melhor hipótese de as evitar, mas não é infalível. A taxa de necrose avascular relaciona-se com o grau de desvio inicial da fractura, mas a sua ocorrência em cada caso específico é imprevisível.OBJECTIVES: Talar neck and body fractures are unusual fractures. The purpose of this study is to determine the prevalence of long term results. MATERIAL AND METHODS: A retrospective analysis was carried out including 11 patients that underwent surgical treatment for body or neck talus fractures between January 1997 and December 2005. Final follow-up examination included a clinical evaluation (AOFAS score and standard radiographs. RESULTS: The mean follow-up time was 58.5 months. The prevalence of associated fractures was 60% (6/10. Overall AOFAS score averaged 72 [19-100]. Avascular necrosis and posttraumatic arthritis were present in half of the patients. Quality of surgical reduction, body fractures and absence of degenerative changes were correlated with better functional results. Neck fractures, osteonecrosis and posttraumatic arthritis led to inferior results. CONCLUSION: There is a great potential for long term functional impairment due to posttraumatic arthritis and chronic pain in this kind of fracture. Anatomic surgical reduction is the best chance to avoid them but it is not infallible. The avascular necrosis rate correlates with initial fracture displacement, but its occurrence in each specific case is unpredictable.

Ricardo Jorge Gomes de Sousa

2009-10-01

214

Sequelas a longo prazo de fracturas do corpo e colo do astrágalo / Long-term results of body and neck talus fractures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: As fracturas do colo e corpo do astrágalo são lesões infrequentes. O objectivo deste estudo é avaliar a prevalência de sequelas a longo prazo. MÉTODOS: Foi feita uma análise retrospectiva que incluiu um total de 11 doentes sujeitos a tratamento cirúrgico por fracturas do corpo ou colo do a [...] strágalo entre Janeiro de 1997 e Dezembro de 2005. A avaliação final foi clínica (utilizando a escala AOFAS) e radiológica. RESULTADOS: O seguimento médio foi 58,5 meses. A prevalência de lesões ósseas associadas foi de 60% (6/10). O resultado AOFAS médio foi 72 [19-100] pontos. A necrose avascular e/ou artrose pós-traumática ocorreu em metade dos doentes. A qualidade da redução cirúrgica, as fracturas do corpo e a ausência de alterações degenerativas relacionaram-se com melhores resultados funcionais. As fracturas do colo, a osteonecrose e a presença de artrose pós-traumática conduziram a piores resultados. CONCLUSÃO: Há um grande potencial para sequelas tardias e compromisso funcional devido a artrose e dor crónica após esse tipo de fracturas. A redução anatómica cirúrgica é a melhor hipótese de as evitar, mas não é infalível. A taxa de necrose avascular relaciona-se com o grau de desvio inicial da fractura, mas a sua ocorrência em cada caso específico é imprevisível. Abstract in english OBJECTIVES: Talar neck and body fractures are unusual fractures. The purpose of this study is to determine the prevalence of long term results. MATERIAL AND METHODS: A retrospective analysis was carried out including 11 patients that underwent surgical treatment for body or neck talus fractures betw [...] een January 1997 and December 2005. Final follow-up examination included a clinical evaluation (AOFAS score) and standard radiographs. RESULTS: The mean follow-up time was 58.5 months. The prevalence of associated fractures was 60% (6/10). Overall AOFAS score averaged 72 [19-100]. Avascular necrosis and posttraumatic arthritis were present in half of the patients. Quality of surgical reduction, body fractures and absence of degenerative changes were correlated with better functional results. Neck fractures, osteonecrosis and posttraumatic arthritis led to inferior results. CONCLUSION: There is a great potential for long term functional impairment due to posttraumatic arthritis and chronic pain in this kind of fracture. Anatomic surgical reduction is the best chance to avoid them but it is not infallible. The avascular necrosis rate correlates with initial fracture displacement, but its occurrence in each specific case is unpredictable.

Ricardo Jorge Gomes de, Sousa; Marta Maria Teixeira de Oliveira, Massada; Manuel Alexandre Negrais Pinho Gonçalves, Pereira; Isabel Maria Gonçalves, Costa; José Fernando Souzellas da Costa e, Castro.

215

Sequelas a longo prazo de fracturas do corpo e colo do astrágalo / Long-term results of body and neck talus fractures  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese OBJETIVO: As fracturas do colo e corpo do astrágalo são lesões infrequentes. O objectivo deste estudo é avaliar a prevalência de sequelas a longo prazo. MÉTODOS: Foi feita uma análise retrospectiva que incluiu um total de 11 doentes sujeitos a tratamento cirúrgico por fracturas do corpo ou colo do a [...] strágalo entre Janeiro de 1997 e Dezembro de 2005. A avaliação final foi clínica (utilizando a escala AOFAS) e radiológica. RESULTADOS: O seguimento médio foi 58,5 meses. A prevalência de lesões ósseas associadas foi de 60% (6/10). O resultado AOFAS médio foi 72 [19-100] pontos. A necrose avascular e/ou artrose pós-traumática ocorreu em metade dos doentes. A qualidade da redução cirúrgica, as fracturas do corpo e a ausência de alterações degenerativas relacionaram-se com melhores resultados funcionais. As fracturas do colo, a osteonecrose e a presença de artrose pós-traumática conduziram a piores resultados. CONCLUSÃO: Há um grande potencial para sequelas tardias e compromisso funcional devido a artrose e dor crónica após esse tipo de fracturas. A redução anatómica cirúrgica é a melhor hipótese de as evitar, mas não é infalível. A taxa de necrose avascular relaciona-se com o grau de desvio inicial da fractura, mas a sua ocorrência em cada caso específico é imprevisível. Abstract in english OBJECTIVES: Talar neck and body fractures are unusual fractures. The purpose of this study is to determine the prevalence of long term results. MATERIAL AND METHODS: A retrospective analysis was carried out including 11 patients that underwent surgical treatment for body or neck talus fractures betw [...] een January 1997 and December 2005. Final follow-up examination included a clinical evaluation (AOFAS score) and standard radiographs. RESULTS: The mean follow-up time was 58.5 months. The prevalence of associated fractures was 60% (6/10). Overall AOFAS score averaged 72 [19-100]. Avascular necrosis and posttraumatic arthritis were present in half of the patients. Quality of surgical reduction, body fractures and absence of degenerative changes were correlated with better functional results. Neck fractures, osteonecrosis and posttraumatic arthritis led to inferior results. CONCLUSION: There is a great potential for long term functional impairment due to posttraumatic arthritis and chronic pain in this kind of fracture. Anatomic surgical reduction is the best chance to avoid them but it is not infallible. The avascular necrosis rate correlates with initial fracture displacement, but its occurrence in each specific case is unpredictable.

Ricardo Jorge Gomes de, Sousa; Marta Maria Teixeira de Oliveira, Massada; Manuel Alexandre Negrais Pinho Gonçalves, Pereira; Isabel Maria Gonçalves, Costa; José Fernando Souzellas da Costa e, Castro.

2009-10-01

216

Overpressure, Flow Focusing, Compaction and Slope Stability on the continental slope: Insights from IODP Expedition 308  

Science.gov (United States)

Integrated Ocean Drilling Program Expepedition 308 used direct measurements of pore pressure, analysis of hydromechanical properties, and geological analysis to illuminate how sedimentation, flow focusing, overpressure, and slope stability couple beneath the seafloor on the deepwater continental slope in the Gulf of Mexico. We used pore pressure penetrometers to measure severe overpressures (60% of the difference between lithostatic stress and hydrostatic pressure) that extend from the seafloor for 100’s of meters. We ran uniaxial consolidation experiments on whole core and found that although permeability is relatively high near the seafloor, the sediments are highly compressible. As a result, the coefficient of consolidation (the hydraulic diffusivity) is remarkably constant over a large range of effective stresses. This behavior accounts for the high overpressure that begins near the seafloor and extends to depth. Forward modeling suggests that flow is driven laterally along a permeable unit called the Blue Unit. Calculations suggest that soon after deposition, lateral flow lowered the effective stress and triggered the submarine landslides that we observe. Later in the evolution of this system, overpressure may have pre-conditioned the slope to failure by earthquakes. Results from IODP Expedition 308 illustrate how pore pressure and sedimentation control the large-scale form of continental margins, how submarine landslides form, and provide strategies for designing stable drilling programs.

Flemings, P. B.

2010-12-01

217

Analysis of rainfall infiltration law in unsaturated soil slope.  

Science.gov (United States)

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (?s - ?r), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process. PMID:24672332

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

218

Slope Stability and Exceptional Divisors of High Genus  

CERN Document Server

We study slope stability of smooth surfaces and its connection with exceptional divisors. We show that a surface containing an exceptional divisor with arithmetic genus at least two is slope unstable for some polarisation. In the converse direction we show that slope stability of surfaces can be tested with divisors, and prove that for surfaces with non-negative Kodaira dimension any destabilising divisor must have negative self-intersection and arithmetic genus at least two. We also prove that a destabilising divisor can never be nef, and as an application give an example of a surface that is slope stable but not K-stable.

Panov, Dmitri

2007-01-01

219

Degradation of terraced slopes in Mediterranean conditions  

Science.gov (United States)

Agricultural terraces with dry-stone walls take the largest area of all man-made landforms in Mediterranean mountain regions. Despite on that their contemporary morphodynamics have not been the subject of many studies. It is a significant problem both from a scientific and a practical point of view. The aim of the study was to estimate the influence of relief, lithology, climatic conditions, methods of wall construction and actual agricultural practice on the degradation of agricultural terraces. A field study was conducted in Greece on 7 plots with the overall area of over 42 000 m2 - on the east Crete and on two Aegean islands - Ikaria and Thera. The analysis was conducted on terraced slopes with gradient of 8-23o, built of granitoids, gneisses, crystalline schists, limestones, crystalline dolomites and volcanic tuffs. There was identified the types of terrace walls. Metrical features of terrace systems were ascertained on the basis of GPS RTK measurement. Terrace material petrography and grain size distribution was identified for regolith an soil samples taken from the selected outcrops which were recognized as being representative for 239 georadar profiles of the joint length of over 2500 m. On that basis the volume of each terrace material was defined. The rills cutting the fields and the walls were measured. The infiltration rate was also taken in 130 points. Reasearch showed that regardless of metrical features of terraces, soil grain size distribution and thickness of the terrace material, the most important reason for the destruction of terrace walls is the abandonment of cultivated areas. Changes in cultivation methods and the introduction of pasturage visibly accelerate the degradation processes. On areas unused for 30 years terrace walls are destroyed on over 25% of their length. It concerns both the areas on which filtration coefficient (k) reaches about 10-5m•s-1 as well as the ones where it is a 100 times lower. The least varied values (10-6-10-5m•s-1) came from the measurements of gneisses and granitogneisses, where muddy sandy and gravelly material prevail. On volcanic tuffs the k coefficient reached the order of magnitude of 10-7-10-5m•s-1. The most varied infiltration rates were observed on limestones and crystalline dolomites - depending on thickness of loamy soil material and density of cracks the k coefficient reached from 5•10-9m•s-1 up to 6•10-4m•s-1. An important factor of slope degradation is also the way of making terrace dry-stone walls, independently of the fact if they are 0,5 m or 3 m high. The walls with buried lower part or situated directly on solid rock which are wider at the foundation are far more lasting than the ones facing stones. In this last case damage takes up to 80% of the length of the walls even on the terraces used nowadays. On Ikaria Island during the field study period well constructed and preserved dry-stone walls survived daily precipitation of 300mm and stay intact.

Tsermegas, I.; D?u?ewski, M.; Biejat, K.; Szynkiewicz, A.

2012-04-01

220

Application of the Finite Element Method to Slope Stability  

Science.gov (United States)

This document outlines the capabilities of the finite element method in the analysis of slope stability problems. A description of the constitutive laws of material behavior such as the Mohr-Coulomb failure criterion, and material properties input parameters, required to adequately model slope failure is given as well.

2008-09-23

 
 
 
 
221

Recurring slope lineae in equatorial regions of Mars  

Science.gov (United States)

The presence of liquid water is a requirement of habitability on a planet. Possible indicators of liquid surface water on Mars include intermittent flow-like features observed on sloping terrains. These recurring slope lineae are narrow, dark markings on steep slopes that appear and incrementally lengthen during warm seasons on low-albedo surfaces. The lineae fade in cooler seasons and recur over multiple Mars years. Recurring slope lineae were initially reported to appear and lengthen at mid-latitudes in the late southern spring and summer and are more common on equator-facing slopes where and when the peak surface temperatures are higher. Here we report extensive activity of recurring slope lineae in equatorial regions of Mars, particularly in the deep canyons of Valles Marineris, from analysis of data acquired by the Mars Reconnaissance Orbiter. We observe the lineae to be most active in seasons when the slopes often face the sun. Expected peak temperatures suggest that activity may not depend solely on temperature. Although the origin of the recurring slope lineae remains an open question, our observations are consistent with intermittent flow of briny water. Such an origin suggests surprisingly abundant liquid water in some near-surface equatorial regions of Mars.

McEwen, Alfred S.; Dundas, Colin M.; Mattson, Sarah S.; Toigo, Anthony D.; Ojha, Lujendra; Wray, James J.; Chojnacki, Matthew; Byrne, Shane; Murchie, Scott L.; Thomas, Nicolas

2014-01-01

222

Writing a Slope-Intercept Equation from a Graph  

Science.gov (United States)

This step by step lesson from Math Ops demonstrates how to write a slope-intercept equation from a graph. Students can read the text on the slides or follow along as it is read aloud. The slope-intercept format of a line is explained as well as how to write an equation for a line. Three examples are given.

2011-01-01

223

The World Is Not Flat: Can People Reorient Using Slope?  

Science.gov (United States)

Studies of spatial representation generally focus on flat environments and visual input. However, the world is not flat, and slopes are part of most natural environments. In a series of 4 experiments, we examined whether humans can use a slope as a source of allocentric, directional information for reorientation. A target was hidden in a corner of…

Nardi, Daniele; Newcombe, Nora S.; Shipley, Thomas F.

2011-01-01

224

RMS slope of exponentially correlated surface roughness for radar applications  

DEFF Research Database (Denmark)

In radar signature analysis, the root mean square (RMS) surface slope is utilized to assess the relative contribution of multiple scattering effects. For an exponentially correlated surface, an effective RMS slope can be determined by truncating the high frequency tail of the roughness spectrum. The choice of the cutoff frequency and the effect on surface scattering simulations are discussed

Dierking, Wolfgang

2000-01-01

225

Culture of Sharing: North Slope Leaders Forge Trail into Future  

Science.gov (United States)

To create a strong local economy, the community needs a workforce. In Native communities, the workforce should be grounded in the local culture and values. On the North Slope of Alaska, this has long been a goal of leaders. To achieve this goal, North Slope leaders came together February 2010 in Barrow, Alaska, for the "Tumitchiat" Leadership…

Patkotak, Elise Sereni

2010-01-01

226

Investigation of Wetting Pattern Dimensions on Sloping Lands  

Directory of Open Access Journals (Sweden)

Full Text Available To study the effects of irrigation durations and land slopes on wetting pattern dimensions, some experiments were performed using an emitter with constant discharge of 4 liters per hour by 2, 4, and 6 hours irrigation durations. Experiments were conducted on lands with the slopes of 0, 5, 15 an 25 percent, with silty loam soil texture in 3 replications in Fathali region, Mogan plain, Iran. Results showed that increasing the land slope caused an increment in wetting pattern dimensions and bulk, in constant irrigation durations. When slope increased, the depth of infiltrated water along the emitter had a little decrease which wasn’t significant. The upstream and downstream components of wetting pattern were symmetrical on 0 percent slope but not on steep lands. So, optimizing the water use, which is saved in the soil, depends on the land slope and the crop should be planted 10 to 25 centimeters away from the dripper. The investigation of soil moisture distribution on wetting pattern in slope lands showed that contrary to the flat lands the main part of the moisture is accumulated in lower part of the emitter, and wetting pattern in these sloping lands was larger than in flat lands.

A. Mohammadi

2014-02-01

227

DESIGN INFORMATION REPORT: PROTECTION OF WASTEWATER LAGOON INTERIOR SLOPES  

Science.gov (United States)

A problem common to many wastewater treatment and storage lagoons is erosion of the interior slopes. Erosion may be caused by surface runoff and wind-induced wave action. The soils that compose the steep interior slopes of lagoons are especially susceptible to erosion and slumpin...

228

HIRESSS: a physically based slope stability simulator for HPC applications  

Digital Repository Infrastructure Vision for European Research (DRIVER)

HIRESSS (HIgh REsolution Slope Stability Simulator) is a physically based distributed slope stability simulator for analyzing shallow landslide triggering conditions in real time and on large areas using parallel computational techniques. The physical model proposed is composed of two parts: hydrological and geotechnical. The hydrological model receives the rainfall data as dynamical input and provi...

Rossi, G.; Catani, F.; Leoni, L.; Segoni, S.; Tofani, V.

2013-01-01

229

Eastern slopes grizzly bear project : project update  

Energy Technology Data Exchange (ETDEWEB)

This report updates a study to examine the cumulative effects of human activities on the grizzly bears in the central Canadian Rockies. The project was initiated in 1994 to acquire accurate scientific information on the habitat and populations of grizzly bears in the area of the Banff National Park and Kananaskis Country. This area is probably the most heavily used and developed area where the grizzly still survives. The information gathered throughout the course of the study is used to better protect and manage the bears and other sensitive carnivores in the region. Using telemetry, researchers monitored 25 grizzly bears which were radio-collared in a 22,000 square-kilometer area in the upper Bow Valley drainage of the eastern Alberta slopes. The researchers worked with representatives from Husky Oil and Rigel Energy on the development of the Moose Mountain oil and gas field without adversely affecting the grizzly bear population. Information collected over eight years indicates that the grizzly bears have few and infrequent offspring. Using the information gathered thus far, the location of the Moose Mountain to Jumping Pound pipeline was carefully selected, since the bears suffer from high mortality, and the food and cover had already been compromised by the high number of roads, trails and other human activities in the area. The research concluded in November 2001 provides sufficient information to accurately asses the status of the grizzly bear population and habitat. The data will be analyzed and integrated in 2002 into models that reflect the variables affecting grizzly bears and a final report will be published.

NONE

2002-01-01

230

?PPLICATION OF A METHOD OF INSURANCE PROTECTION AT RADIATING POLLUTION IN SLOPE`S ECOSYSTEMS  

Directory of Open Access Journals (Sweden)

Full Text Available The worked out chamber models of typical slope ecosystems allowed to conduct the estimationof collective dose and radiation risks for a population which uses these ecosystems. On this basisthe calculation of the expected losses is conducted from the dose loading estimation of collectiveand individual risks and losses. An algorithm and chart of insurance defence of population areoffered for this type of ecosystems. It is shown what an algorithm is offered it is possible to applyfor insurance defence people in other types of ecosystems and radiation situations

?. ???????????

2011-04-01

231

Research on the Slope Protection Mechanism of Roots  

Directory of Open Access Journals (Sweden)

Full Text Available This study aims to investigate the slope protection mechanism of roots. In ecological slope protection, plant roots can fix soil and protect slop through biological and mechanical action. However, previous studies on the slope protection mechanism are still not deep enough and inadequate. By taking four kinds of typical plant roots along Wu-Shen Expressway as the research object, through the indoor tensile test and root morphology observation analysis, the tensile strength and ultimate tension were studied and the influence to the stability of the slope was discussed in this study. The results show that the mean ultimate tension of roots is 7.19~29.96 N. The mean tension of shrub roots is 2~4 times greater than that of herb roots. The ultimate tension of the same plant roots increases with the diameter significantly. To the range of improvement, Shrub roots exceed herb ones. It also indicates that the mean tensile strength of roots are 24.48~74.25 MPa. Compared with the steel HRB235, the tensile strength of herb roots is as great as 1/5~1/3, while Shrub roots is about 1/10~1/5. The slope stability coefficient with plant growing is a positive correlation with roots tension and root number through the sliding surface and is a negative correlation with plants weight. In addition, the slope stability coefficient is related to plant density and root morphology. The test results demonstrate that the roots tension with acute angle or right angle to the landslide surface and the roots shear stiffness with obtuse angle can improve the performance of slope’s anti-slide. Four kinds of plants can improve the stability coefficient of shallow soil. As for the slope protection effect, herbage is superior to shrub. In general, grass-shrub mixed community is the ideal system for slope protection.

Juan Wan

2013-08-01

232

Is there a distinct continental slope fauna in the Antarctic?  

Science.gov (United States)

The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ˜3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (BIOdiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be a unique Antarctic slope fauna, but the paucity of our samples could not demonstrate this in the Scotia Sea. It is very likely that various ecological and evolutionary factors (such as topography, water-mass and sediment characteristics, input of particulate organic carbon (POC) and glaciological history) drive slope distinctness. Isopods showed greatest species richness at slope depths, whereas bryozoans and ostracods were more speciose at shelf depths; however, significance varied across Weddell Sea and Scotia Sea and depending on bathymetric vs. geomorphological definitions. Whilst the slope may harbour some source populations for localised shelf recolonisation, the absence of many shelf species, genera and even families (in a poorly dispersing taxon) from the continental slope indicate that it was not a universal refuge for Antarctic shelf fauna.

Kaiser, Stefanie; Griffiths, Huw J.; Barnes, David K. A.; Brandão, Simone N.; Brandt, Angelika; O'Brien, Philip E.

2011-02-01

233

Photogrammetry and altimetry: Part C: frequency distributions of lunar slopes  

Science.gov (United States)

The metric and panoramic cameras aboard the Apollo 16 spacecraft provided photographs on which photogrammetric techniques may be used to obtain precise measurements of horizontal distances and elevations. These measurements of horizontal distances and elevations. These measurements may in turn be used to obtain slope-frequency distributions of lunar surfaces at various slope lengths and for various types of terrain and geologic map units (ref. 30-4). Bistatic radar and photoclinometric methods have also been used to obtain slope-frequency distributions of lunar surfaces. The problem arises as to how well these varied methods correlate with one another (ref. 30-5).

Wu, Sherman S.C.; Moore, H.J.

1972-01-01

234

Free surface flows with large slopes: beyond lubrication theory  

CERN Document Server

The description of free surface flows can often be simplified to thin film (or lubrication) equations, when the slopes of the liquid-gas interface are small. Here we present a long wavelength theory that remains fully quantitative for steep interface slopes, by expanding about Stokes flow in a wedge. For small capillary numbers, the variations of the interface slope are slow and can be treated perturbatively. This geometry occurs naturally for flows with contact lines: we quantify the difference with ordinary lubrication theory through a numerical example and analytically recover the full Cox-Voinov asymptotic solution.

Snoeijer, J H

2006-01-01

235

Simulating the seismic behaviour of soil slopes and embankments  

DEFF Research Database (Denmark)

In the current study the clarification of the main assumptions, related to the two most commonly used methods of seismic slope stability analysis (pseudostatic and permanent deformation) is attempted. The seismic permanent displacements and the corresponding seismic coefficients were determined via parametric dynamic numerical analyses taking into account not only the main parameters dominating the seismic slope stability, but also the inherent assumptions of the applied approaches that affect the obtained results. The investigation conclude to a realistic procedure for seismic slope stability assessment based on the application of two simple methods taking into account the impact of the most important factors involved.

Zania, Varvara; Tsompanakis, Yiannis

2010-01-01

236

Interpretation of Schubert plot slopes for metal-humate systems  

International Nuclear Information System (INIS)

In this paper an error in the literature is identified pertaining to the interpretation of nonintegral slopes in Schubert plots for metal-humate and metal-fulvate systems. Equations are derived that correctly describe the behavior of these systems

237

Systems of pillarless working of adjacent, sloped and inclined seams  

Energy Technology Data Exchange (ETDEWEB)

An analysis is made (advantages and disadvantages) of existing and recommended (pillarless) systems of working adjacent, sloped, and inclined seams. The economic benefits, area and extent of those systems are indicated. 8 references, 4 figures.

Batmanov, Yu.K.; Bakhtin, A.F.; Bulavka, E.I.

1979-01-01

238

Newton slopes for Artin-Schreier-Witt towers  

DEFF Research Database (Denmark)

We fix a monic polynomial f(x) in Fq[x] over a finite field and consider the Artin-Schreier-Witt tower defined by f (x); this is a tower of curves · · · ? Cm ? Cm?1 ? ···?C0 =A1, with total Galois group Zp. We study the Newton slopes of zeta functions of this tower of curves. This reduces to the study of the Newton slopes of L-functions associated to characters of the Galois group of this tower. We prove that, when the conductor of the character is large enough, the Newton slopes of the L-function form arithmetic progressions which are independent of the conductor of the character. As a corollary, we obtain a result on the behavior of the slopes of the eigencurve associated to the Artin-Schreier-Witt tower, analogous to the result of Buzzard and Kilford.

Davis, Christopher James; Wan, Daqing

2014-01-01

239

Lunar Surface Roughness and Slope Statistics from LOLA  

Science.gov (United States)

The RMS slope and Hurst exponent over horizontal scales of ~56 meters to ~2.7 kilometers are calculated from LOLA altimetry measurements and used to quantitatively characterize the roughness properties of the lunar surface.

Rosenburg, M. A.; Aharonson, O.; Smith, D. E.; Zuber, M. T.; Neumann, G. A.; Torrence, M. H.; Mazarico, E.

2010-03-01

240

POTENTIALLY UNSTABLE SLOPE ABOVE ORE PROCESSING PLANT IN THE  

Directory of Open Access Journals (Sweden)

Full Text Available The complex engineering investigation, in the nearest surroun-dig of the conditionally stable high slope, close to ore processing facilities in the dolomite quarry »O?ura« near Lepoglava (North Croatia, was carried out. Studying the tectonic features of the rock mass, discontinuities referent to the slope stability, was found out. Rock fragment size was measured and data processed using statistical design. According to rock fragment mean values, velocity of the longitudinal seismic waves was predicted. This values was compared with velocities of the longitudinal seismic waves, determined using gcophisical refraction seismic method. Physical and mechanical properties of the dolomite rock mass, considering longitudinal and transversal seismic wave velocities, and »RMR«-classification was assesed. All the results indicate, that the slope above the ore processing facilities should be consider as conditionally stable, with real probability to get unstable under the vibrations caused by blasting, during the exploitation in the field, close behind the investigated slope.

Ivan Baturi?

1993-12-01

 
 
 
 
241

Impact Analysis of Blasting Vibration on the Slope and Dump  

Directory of Open Access Journals (Sweden)

Full Text Available As known that the blasting on the slope is very dangerous in the exploration of the mine andneeds complex analysis and calculation on the slope and dump. In the study it adopts the regression method in the analysis of important parameters of the vibration experiments of iron ore stope which influence the stability of slope and vibration velocity of mine blasting, vibration acceleration, etc., it makes the analysis of power spectrum and dynamic response. Through the model of landslide dynamic response it analyzes the rule of blasting vibration and the blasting vibration influence on the stability of slope, the research can provide a safety criterion in the exploitation of the iron ore.

Zhang De

2014-01-01

242

30 CFR 716.2 - Steep-slope mining.  

Science.gov (United States)

...OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT...716.2 Steep-slope mining. The permittee conducting surface coal mining and reclamation operations on natural...measures to protect the area from...

2010-07-01

243

Heat Transfer Energy Balance Model of Single Slope Solar Still  

Directory of Open Access Journals (Sweden)

Full Text Available Single slope solar still absorbs the thermal energy from sunlight to distillate polluted water into clean water in an enclosed space. Principal of heat transfer and energy balance were the governing equations for the operation of single slope solar still. A mathematical model was developed to express these thermodynamics behaviours. In the model, critical parameters had been identified, such as slope angle of glass cover, mass of water in basin and wind speed. Simulation had been carried out and results revealed the importance of the slope angle matching the latitude of the experimental location, the increasing of water mass in the basin leading to decreasing of clean water production and the presence of wind speed also increase the output only when the sunlight is still sufficient.

Kiam Beng Yeo

2014-01-01

244

Influence of Rainfall Patterns on the Instability of Slopes  

Directory of Open Access Journals (Sweden)

Full Text Available The assessment of rainstorm-induced shallow landslides is still a research topic of wide concern for scientists and engineers. This paper examined the effect of rainfall intensity distribution on shallow landslides. Four synthetic rainfall distributions comprising uniformed, delayed, centralized, and advanced, were selected to examine the effect of rainstorm patterns on slope failure. The infiltration was modeled using Green-Ampt equation, while an infinite slope was selected to model the shallow landslide. Monte Carlo Simulation was applied to analyze the failure probability of the slopes. Two landslide cases were selected to examine the proposed model. The results indicated that among the four representative rainstorm patterns, the advanced rainfall pattern caused worst slope stability. The advanced rainfall pattern resulted in the shortest rainfall duration threshold for landslide occurrence, followed by the central, uniform, and then delayed rainfall pattern. The probabilistic analysis method was suitable to estimate the time of failure for the evaluated landslide cases.

Muntohar A.S.

2013-01-01

245

30 CFR 785.15 - Steep slope mining.  

Science.gov (United States)

... 2010-07-01 false Steep slope mining. 785.15 Section 785.15 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND ENFORCEMENT, DEPARTMENT OF THE INTERIOR SURFACE COAL MINING AND RECLAMATION OPERATIONS PERMITS...

2010-07-01

246

Application of distinct element method to toppling failure of slopes  

International Nuclear Information System (INIS)

Recently, the stability of slopes during earthquakes has become to be an important engineering problem, especially in case of the earthquake-proof design of nuclear power plants. But, for fissured rock slopes, some problems are remained unresolved, because they can not be treated as continua. The authors have been investigating toppling failure of slopes, from a point of view which regards a fissured rock mass as an assemblage of rigid blocks. DEM (Distinct Element Method) proposed by Cundall (1974) seems to be very helpful to such a investigation. So, in this paper, the applicability of DEM to toppling failure of slopes is examined through the comparison between DEM results and theoretical or experimental results using 3 simple models. (author)

247

Effect of a weak layer in slope stability  

Energy Technology Data Exchange (ETDEWEB)

The objective of this paper is to present a practical method for calculating minimum safety factors of rock slopes with a horizontal layer of weak material. It is demonstrated that the most critical failure surface, in this case, is a bilinear surface composed of a horizontal failure surface inside the weak layer and an inclined surface inside the rock. The model presented in this paper shows that with a good approximation, the change in slope for the bilinear failure surface may occur directly below the slope crest. This assumption simplifies the calculation of safety factors considerably, because the most critical failure surface is located directly, and the trial computations for a number of failure surfaces are not necessary. Special parameters involved in slope stability analyses of highwalls in open-pit mines are discussed and, by an example calculation, the applicability of this method is demonstrated.

Vakili, J.

1984-01-01

248

Slope stability of geosynthetic clay liner test plots  

Energy Technology Data Exchange (ETDEWEB)

Fourteen full-scale field test plots containing five types of geosynthetic clay liners (GCLs) were constructed on 2H:1V and 3H:1V slopes for the purpose of assessing slope stability. The test plots were designed to simulate typical final cover systems for landfills. Slides occurred in two of the 2H:1V test plots along interfaces between textured geomembranes and the woven geotextile components of internally reinforced GCLs. One additional slide occurred within the unreinforced GCL component of a 2H:1V test plot, when the GCL unexpectedly became hydrated. All 3H:1V slopes have remained stable. Results of laboratory direct shear tests compared favorably with field observations, providing support for the current design procedures that engineers are using for assessing the stability of slopes containing GCLs.

Daniel, D.E. [Univ. of Illinois, Urbana, IL (United States); Koerner, R.M. [Drexel Univ., Philadelphia, PA (United States). Geosynthetic Research Inst.; Bonaparte, R. [GeoSyntec Consultants, Atlanta, GA (United States); Landreth, R.E. [Landreth, (Robert E.), West Chester, OH (United States); Carson, D.A. [Environmental Protection Agency, Cincinnati, OH (United States); Scranton, H.B. [Haley and Aldrich, Boston, MA (United States)

1998-07-01

249

Evaluation of the stability of anchor-reinforced slopes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The conventional methods of slices are commonly used for the analysis of slope stability. When anchor loads are involved, they are often treated as point loads, which may lead to abrupt changes in the normal stress distribution on the potential slip surface. As such abrupt changes are not reasonable and do not reflect reality in the field, an alternative approach based on the limit equilibrium principle is proposed for the evaluation of the stability of anchor-reinforced slopes. With this app...

Lee, Cf; Zhu, Dy; Chan, Dh; Jiang, Hd

2005-01-01

250

Model tests of geosynthetic reinforced slopes in a geotechnical centrifuge  

International Nuclear Information System (INIS)

rtant contribution to the stability of the slope models was provided by the overlapping of the geotextile layers. It has a secondary reinforcement effect when it was prolonged and passed through the shear surface. Moreover, the location of the shear surface observed with PIV analysis exactly matches the tears of the retrieved geotextiles measured carefully after the centrifuge testing. It is concluded that PIV is an efficient tool to instrument the slope failures in a geotechnical centrifuge.(author)

251

The effect of a single point on correlation and slope  

Directory of Open Access Journals (Sweden)

Full Text Available By augmenting a bivariate data set with one point, the correlation coefficient and/or the slope of the regression line can be changed to any prescribed values. For the target value of the correlation coefficient or the slope, the coordinates of the new point are found as a function of certain statistics of the original data. The location of this new point with respect to the original data is investigated.

David L. Farnsworth

1990-12-01

252

Exploring Benthic Biodiversity Patterns and Hotspots on European Margin Slopes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

There is increasing evidence that continental slope ecosystems represent one of the major repositories of benthic marine biodiversity. The enhanced levels of biodiversity along slopes are hypothesized to be a source of biodiversity for continental shelves and deeper basins. Continental margins are increasingly altered by human activities, but the consequences of these anthropogenic impacts on benthic biodiversity and ecosystem functioning are almost completely unknown. Thus, there is an urgen...

Roberto Danovaro; Miquel Canals; Serge Heussner; Nikolaos Lampadariou; Ann Vanreusel

2009-01-01

253

Geospatial Data Integration for Assessing Landslide Hazard on Engineered Slopes  

Science.gov (United States)

Road and rail networks are essential components of national infrastructures, underpinning the economy, and facilitating the mobility of goods and the human workforce. Earthwork slopes such as cuttings and embankments are primary components, and their reliability is of fundamental importance. However, instability and failure can occur, through processes such as landslides. Monitoring the condition of earthworks is a costly and continuous process for network operators, and currently, geospatial data is largely underutilised. The research presented here addresses this by combining airborne laser scanning and multispectral aerial imagery to develop a methodology for assessing landslide hazard. This is based on the extraction of key slope stability variables from the remotely sensed data. The methodology is implemented through numerical modelling, which is parameterised with the slope stability information, simulated climate conditions, and geotechnical properties. This allows determination of slope stability (expressed through the factor of safety) for a range of simulated scenarios. Regression analysis is then performed in order to develop a functional model relating slope stability to the input variables. The remotely sensed raster datasets are robustly re-sampled to two-dimensional cross-sections to facilitate meaningful interpretation of slope behaviour and mapping of landslide hazard. Results are stored in a geodatabase for spatial analysis within a GIS environment. For a test site located in England, UK, results have shown the utility of the approach in deriving practical hazard assessment information. Outcomes were compared to the network operator's hazard grading data, and show general agreement. The utility of the slope information was also assessed with respect to auto-population of slope geometry, and found to deliver significant improvements over the network operator's existing field-based approaches.

Miller, P. E.; Mills, J. P.; Barr, S. L.; Birkinshaw, S. J.

2012-07-01

254

The Influence of Earthquakes on Open-Pit Slope Stability  

Directory of Open Access Journals (Sweden)

Full Text Available Estimation of stability of natural slopes, embankments, dams and open-pit slopes during earthquakes are complex and non-linear problems, therefore physical modeling is used for decision of it. As a result of physical modeling the pattern of seismic vibrations impact based on the movement process of probable collapse prism delineated by the most stressed plane of sliding has been established. Particular recommendations on the basis of safety factors selection in seismoactive zones are given.

Sergei Vadimovich Tsirel

2012-09-01

255

Relating weak layer and slab properties to snow slope stability  

Science.gov (United States)

Snow slope stability evaluation requires considering weak layer as well as slab properties - and in particular their interaction. We developed a stability index from snow micro-penetrometer measurements and compared it to 129 concurrent point observations with the compression test (CT). The index considers the SMP-derived micro-structural strength and the additional load which depends on the hardness of the surface layers. The new quantitative measure of stability discriminated well between point observations rated as either "poor" or "fair" (CT gridded snow micro-penetrometer measurements from 11 snow slopes to explore the spatial structure and possibly relate it to slope stability. Stability distributions on the 11 slopes reflected various possible strength and load (stress) distributions that naturally can occur. Their relation to slope stability was poor possibly because the index does not consider crack propagation. Hence, the relation between spatial patterns of point stability and slope stability remains elusive. Whereas this is the first attempt of a truly quantitative measure of stability, future developments should consider a better reference of stability and incorporate a measure of crack propagation.

Schweizer, J.; Reuter, B.

2014-07-01

256

Alternative method for direct measurement of tibial slope  

Directory of Open Access Journals (Sweden)

Full Text Available Background/Aim. The tibial slope is one of the most frequently cited anatomical causes of anterior cruciate ligament trauma. The aim of this study was to determine the possibility of direct measuring of the tibial slope of the knee without prior soft tissue dissection in cadavers. Methods. Measurement was performed on the two groups of samples: osteological and cadaveric. The osteological group consisted of 102 matured tibiae and measurement was performed: indirectly by sagittal photographing of the tibia, and directly by a set of parallel bars. The cadaveric group consisted of 50 cadaveric knees and measurement was performed directly by a set of parallel bars. The difference and correlation between indirect and the direct measurements were observed, which included also measuring of the difference and correlation of the tibial slope on the medial and lateral condyles. Results. A statistically significant difference between the direct and indirect method of measuring (p 0.05. However, the slope on the medial condyle, as well as indirect measurement showed a statistically significant difference (p < 0.01. Conclusion. By the use of a set of parallel bars it is possible to measure the tibial slope directly without removal of the soft tissue. The results of indirect, photographic measurement did not statistically differ from the results of direct measurement of the tibial slope.

Stijak Lazar

2014-01-01

257

Relating weak layer and slab properties to snow slope stability  

Directory of Open Access Journals (Sweden)

Full Text Available Snow slope stability evaluation requires considering weak layer as well as slab properties – and in particular their interaction. We developed a stability index from snow micro-penetrometer measurements and compared it to 129 concurrent point observations with the compression test (CT. The index considers the SMP-derived micro-structural strength and the additional load which depends on the hardness of the surface layers. The new quantitative measure of stability discriminated well between point observations rated as either "poor" or "fair" (CT < 19 and those rated as "good" (CT ? 19. However, discrimination power within the intermediate range was low. We then applied the index to gridded snow micro-penetrometer measurements from 11 snow slopes to explore the spatial structure and possibly relate it to slope stability. Stability distributions on the 11 slopes reflected various possible strength and load (stress distributions that naturally can occur. Their relation to slope stability was poor possibly because the index does not consider crack propagation. Hence, the relation between spatial patterns of point stability and slope stability remains elusive. Whereas this is the first attempt of a truly quantitative measure of stability, future developments should consider a better reference of stability and incorporate a measure of crack propagation.

J. Schweizer

2014-07-01

258

Problems of definitive slopes mining at Doly Nastup Tusimice  

International Nuclear Information System (INIS)

The instability of slopes influents mining business in many aspects at open-cast mining. The temporary decrease of intended mined volumes due to land slips is common and sometimes there is necessary to change origin-mining plans. It has impact to economy and other essential costs for rehabilitation are required. In case of definitive slopes formation in contact to traffic and communication networks, watercourses and infrastructures of seats stability of slope security there is even more important. Monitoring of rock massive stability plays an important role. Everything which stability of slopes is concerned belongs to essential tasks for mining technicians at open-cast mining. The article explains what ways for definitive slope formation near mining boundary were selected at Severoceske doly j.s.c., Doly Nastup Tusimice mining site. The precautions refer to mining technology, preventive and reconstruction precautions for stabilization of slopes must to solve, are to described. Tasks, which mining engineers, surveyors, geologists and geotechnics have to solve are described. (authors)

259

Performance of the APS optical slope measuring system  

Energy Technology Data Exchange (ETDEWEB)

An optical slope measuring system (OSMS) was recently brought into operation at the Advanced Photon Source of the Argonne National Laboratory. This system is equipped with a precision autocollimator and a very accurate mirror-based pentaprism on a scanning stage and kept in an environment-controlled enclosure. This system has the capability to measure precision optics with sub-microradian rms slope errors as documented with a series of tests demonstrating accuracy, stability, reliability and repeatability. Measurements of a flat mirror with 0.2 ?rad rms slope error are presented which show that the variation of the slope profile measurements with the mirror setting at different locations along the scanning direction is only 60 nrad and the corresponding height error profile has 2 nm rms. -- Highlights: ? This is the first time to present the APS OSMS in publication. ? The APS OSMS is capable to measure flat and near flat mirrors with slope error <100 nrad rms. ? The accuracy of the slope error measurements of a 350 mm long mirror is less than 60 nrad rms.

Qian, Jun, E-mail: jqian@aps.anl.gov [Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, 60439 (United States); Sullivan, Joe; Erdmann, Mark; Khounsary, Ali; Assoufid, Lahsen [Advanced Photon Source, Argonne National Laboratory, 9700S. Cass Avenue, Argonne, 60439 (United States)

2013-05-11

260

Exploring Benthic Biodiversity Patterns and Hotspots on European Margin Slopes  

Directory of Open Access Journals (Sweden)

Full Text Available There is increasing evidence that continental slope ecosystems represent one of the major repositories of benthic marine biodiversity. The enhanced levels of biodiversity along slopes are hypothesized to be a source of biodiversity for continental shelves and deeper basins. Continental margins are increasingly altered by human activities, but the consequences of these anthropogenic impacts on benthic biodiversity and ecosystem functioning are almost completely unknown. Thus, there is an urgent need to gather sufficient information to enable us to understand patterns and drivers of deep-sea biodiversity along continental margins. Although the local diversity of some deep open slope ecosystems is moderately well documented, very little is known about the biodiversity of these systems at greater spatial scales. Topographic setting, hydrodynamic forcing, and the biogeochemical characteristics of the deep-sea floor may play key roles in promoting and sustaining high biodiversity along the open slopes of continental margins. HERMES provided the opportunity to acquire a significant volume of information on the biodiversity, trophic conditions, and topographic characteristics of open slopes across European margins, increasing our knowledge of the latitudinal, longitudinal, and bathymetric patterns of benthic biodiversity, and extending our comprehension of the mechanisms driving deep-sea biodiversity and its potential loss. Improved knowledge of these processes is needed to inform policy decisions for promoting sustainable management of open slopes and deep-sea ecosystems along continental margins.

Roberto Danovaro

2009-03-01

 
 
 
 
261

Behavior of heated water discharged on sloping beach  

International Nuclear Information System (INIS)

The characteristics of diffusion process of the heated water discharged on the sloping beach were investigated. In the coastal region, the diffusion process is influenced by various factors which are classified into basic three categories; discharge conditions, environmental factors and geographical features. In order to extract main factors which are important for the momentum dominant field of the diffusion process, dimensional analysis was employed. The dominant factors determined for this paticular region are the densimetric Froude number at outlet, discharge aspect ratio, discharge angle of heated water, crossflow parameter and bottom slope. Two series of experiments were performed forcusing the effects of the sloping bottom and oblique discharge of heated water. In order to investigate the change of both flow field and temperature field, the manner of decrease of velocity and temperature at the centerline of watrm water jet were examined as well as the width of the jet. It was found that the existence of sloping bottom highly inhibites the entrainment of ambient water and reduces the spread of the jet, as the slope of bottom becomes gentler or the water depth smaller. The most distingushing feature under the condition of the oblique discharge on the sloping bottom is that the jet trajectory bends toward shoreline. Such behavior of the warm water jet causes the stationarity of warm water patch along the coast. (author)

262

Katabatic Flow Mechanisms on a Low-Angle Slope  

Energy Technology Data Exchange (ETDEWEB)

Momentum and heat budget equations are written for katabatic flows on sloping surfaces. Terms in these equations are evaluated using wind and potential temperature data from four tethered balloon data collection systems on a 3-km line running down a 1.6° slope at the foot of the Oquirrh Mountains in Utah’s Salt Lake Valley. The analyses focus on the development with downslope distance of the katabatic flow and the associated negatively buoyant layer. Under conditions of strong stratification, the katabatic flow shows little variation between sites, suggesting a state close to local equilibrium. With weaker ambient stratification, the acceleration of the katabatic flow between two tethersonde sites is systematically larger than what would be predicted based on observed buoyancy. Comparison of observed flow direction with the local topographic gradient indicates that slope curvature, associated with small deviations from the basically planar slope, may be responsible for the anomalous increase. It is concluded that the assumption of cross-slope homogeneity of the flow which is assumed in simplified katabatic flow models is not even found on slopes which appear planar to the visual observer.

Haiden, Thomas S.; Whiteman, Charles D.

2005-01-01

263

Slope Morphology of Twin Peaks, Mars Pathfinder Landing Site  

Science.gov (United States)

Development of slope form over time has long been a concern of geomorphologists, although recently this concern has been moved to slope processes rather than form. There are two basic approaches. The first is theoretical, involving modeling of different types and rates of processes, and calculation of results in terms of slope evolution over time. Comparisons with real-life slopes can follow this approach [1], [2]. The second, inductive, approach involves field measurements to test ideas about slope evolution starting from the assumption that observed slopes represent different stages of an essentially similar evolution [3]. Space is substituted for time, and a number of slopes, assumed to be of increasing age, are measured and placed in an evolutionary sequence (e.g. [4], [5], [6]). [5] showed that slope angles are modally distributed, with the modal angles controlled by the materials (regolith) of which the slopes are formed, and by the processes operating on them. Data can be obtained directly from field work or from digital elevation models (DEM) derived from remote sensing investigations [7]. DEMs are particularly useful to study inaccessible planets, such as Mars, where on site observations are restricted to only a few landing sites. Here we present a study of slopes on the Twin Peaks, two small hills located 780 m north and 910 m south of the Mars Pathfinder landing site at the mouth of the Ares and Tiu flood channels. The presence of streamlined hills, jumbled surfaces and conglomerates suggested the region was modified by massive flooding 1.8 - 3.5 billion years ago [8], [9]. The streamlined forms and terraces of the Twin Peaks were taken to indicate catastrophic flood conditions that were believed to be prevalent in the area [8]. It was also suggested that the northernmost peak was topped by floodwater, causing its flatter appearance. Other researchers postulated alternative geomorphological origins for the features observed at the Pathfinder landing site. Processes such as ice flow or deposition were proposed as being the principal cause of most of observed features, by analogy with similar features observed on Earth [10]. Here we propose that the slopes on the Twin Peaks may provide an indication of the processes that shaped them after they were formed. This work shows the results of a detailed morphometric analysis of slopes on the southernmost peak, conducted to gain a greater understanding of past and present slope processes at work at the Pathfinder landing site. The southern Twin Peak is a conical hill rising 38 m above the local terrain. A portion of the Pathfinder super panorama was used to analyse the hill-slope morphology. The camera horizon was used as a baseline and all slope angles were measured from this. The hill comprises four separate regions including the top of the hill, which is convex in shape. The convex nature of the hilltop is a common if not ubiquitous feature of hills regardless of their origin. It is related to the creep processes that frequently dominate the tops of hill slopes. In this case it was probably caused by heating and cooling during the Martian diurnal cycle, by the action of soil water, or a combination of both. All slope sections were observed to be similar in length. The slopes nearest the hill top measure 21? and 22.5? respectively on the north and south sides of the Southern Twin Peak. Mid way down the hill the next sequence of slopes have north and south angles of 9? and 15? respectively. Shallow end-slopes measure 4? and 5? north and south respectively. Similarity of slope angles and lengths indicates symmetry, suggesting that the rocks are the same all around the hill. Our analysis suggests that slope angles are controlled by a combination of the materials of which they are formed and the processes that are operating on them. Their primarily symmetrical outlook indicates no structural control, suggesting that the hill is formed by flat-lying or massive homogeneous rocks. This being the case, slope morphology results from shallow processes related to mass was

Hobbs, Steven; Paine, Colin; Clarke, Jon; Caprarelli, Graziella

2010-05-01

264

The influence of preferential flow on slope stability  

Science.gov (United States)

Slope failures triggered by heavy rainfall are common geological disasters around the world, because rainfall caused pore-pressure increase will reduce the soil shear strength and influence the slope stability. Physically-based subsurface hydrological models are frequently integrated with slope stability analysis methods to evaluate which areas are susceptible for landslides. In structured soil, preferential flow can change the pattern of the infiltration process, resulting in more rapid and deeper water movement. For highly-heterogeneous slopes, the influence of preferential flow on the distribution of pore water pressure and slope stability has not been studied thoroughly yet. In this study, the COMSOL Multiphysics finite element software package is used to model the hydrological and soil mechanical processes. A two-dimensional hydro-mechanical model framework composed of a subsurface flow module and a slope stability analysis module was built to evaluate the influence of preferential flow on subsurface flow and consequent slope stability. The subsurface flow module consists of a dual-permeability model, which can be used to quantify the influence of preferential flow on distribution and timing of the pressure head in a slope. The dual-permeability model divides the soil into matrix domain and preferential flow domain, and the water flow is described by two coupled Richard's equations. The slope stability analysis module is composed of an elastic solid mechanics model and a local factor of safety algorithm. The total principle stress distribution is calculated by a solid mechanics module for plane-strain elastic analyses. The local factor of safety is defined as the ratio of the Coulomb stress at the current state of stress to the Coulomb stress of the potential failure state under the Mohr-Coulomb criterion. In this study the focus will be on the temporal and spatial distribution of the local factor of safety. Eventually, the influence of preferential flow on slope stability can be evaluated by comparing the results of the single-permeability model and the dual-permeability model.

Shao, Wei; Bogaard, Thom A.; Bakker, Mark

2013-04-01

265

Design of Overall Slope Angle and Analysis of Rock Slope Stability of Chadormalu Mine Using Empirical and Numerical Methods  

Directory of Open Access Journals (Sweden)

Full Text Available In engineering projects associated with rock mechanic science like open pit mines, assessment and slope stability of mine walls is one of the important performance in generate of these structures. Estimating and knowledge of stable slope angle is one of main parts that should be occurring to special attention in open pit mines studies phase. Considering the importance of economic costs in mining issues, the need for appropriate design slope angle that can cause an adverse minimize project costs and throws the other hand, the stability conditions in the safe walls of the mine life will provide essential and seems obvious. Therefore, in this study to determine the optimal slope angle of overall and bench of west wall of the Chadormalu ore iron mine, has been trying, first, done field studies on the discontinuity of western wall, engineering classification and geomechanical properties of rock masses of wall, then assess the amount of optimal slope angle using empirical method. Finally, in order to ensure stability and accuracy of the wall slope angle based on the obtained (empirical method tries to analysis is amount of Factor of Safety (FOS, displacements and mean stress condition atwalls calculated from drilling use Phase2D powerful software.

Mahdi Rasouli Maleki

2011-09-01

266

Slope stability along active and passive continental margins: a geotechnical approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Submarine mass movements are widespread at submarine slopes and play an important role in transporting sediments across the continental slope to the deep basin, as well as potential danger to both offshore infrastructures (e.g., pipeline, cables and platforms) and coastal areas (e.g., slope failure-induced tsunamis). Sliding of the sediments on continental slope takes place when the shear stress within sediments exceeds the shear strength thereby causing slope failure. Slope failures are gene...

Ai, Fei

2013-01-01

267

Geotechnical and numerical studies of slope instability in loess deposits  

Science.gov (United States)

The mass movements occurred in loess accumulations often cause catastrophic damages to infrastructure and lose to the human lives. The failure in loess deposits can occur in gently terrains as happened in Tajik Republic in 1989. The earthquake with magnitude 5.5 hit the suburb of town. During this event the liquefaction effects developed consequently to lead to the catastrophic landslides. The loess failure related case is Kainama landslide (Fergana Valley, Kyrgyzstan) that killed 33 people. Potential relation between site effects and pore pressure build up causing liquefaction is the main thrust of this research. Methodology of the seismic slope stability investigation included determination of the mechanical strength properties and numerical modelling of a slope failure. In order to simulate the slope it is essential to gather the strength parameters of soil that present the conditions of the material in the nature. The main emphasis has been put to the geotechnical studies. To better understand the slope failure in loess body the two landslide sites in Fergana Valley (Kyrgyzstan) were selected to collect the loess specimens. Mechanism of deformation of loess material determined in terms of standard geotechnical tests. The natural water content in specimens is low, ranging from 12,8 % to 21% . The first investigation site occurred in Tertiary sediments has a low mean of the plasticity index (12% - 16 %). The climate data were analysed in order to correlate with slope failure cases. The development of landslides in investigating areas is truly connected with variation of physical and mechanical properties of loess material that is respectively related to geological and tectonic conditions of an area. To arrange the connection between site effects and pore pressure build up we used the numerical modelling with a finite difference code (FLAC 2D and 3D). These simulations give an opportunity to better clarify site effect impact to the slope and its role to cause liquefaction effects regarding to the slope failure initiation.

Mamyrova, R.; Stahlmann, J.; Bourdeau, C.; Havenith, Hb.

2009-04-01

268

Impacts of Habitat Slope on Plant from of Astracantha adscendens  

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Full Text Available Astracantha adscendens is an endemic species in Iran growing on alpine and above alpine timberline habitats on the Zagross Mountain Range. These habitats are characterized by steep slopes, heavy snowfalls and long ice formation periods. The present study was carried out in Chelgerd, Bakhtiari, and Fereidan, Isfahan. Slopes, elevation above sea-level, and magnetic north azimuth were measured. The canopy cover was also measured along four radii in upward, downward, left and right directions. Regression analysis was performed for the measured values of plant and environmental factors. The results revealed that the upward radius had a high negative correlation with slope changes while the downward radius showed no relationship with slope variations. The two left and right radii had a high and positive relationship with each other, both reducing in length as the slope steepness increased. Shrub volume decreases with increasing slope steepness. Plant shape was classified into seven groups using Sorenson similarity index and constructing the dendrogram. Snow pressure bends the stem toward the soil surface. Snow gliding pressure scratches stem and its base buds above the bent stem. Soil and debris move downward the slope as a result of snow gliding and rainfall runoff as well as wildlife and domestic animals. Snow gliding along with other natural factors have various effects on A. adscendens plant form which can be grouped under three categories: direct mechanical effect of snow, physiological effect of snow, and indirect effect of precipitation and wildlife. The environmental factors and plant physiological responses to them change the A. adscendens plant form from a funnel or ob-conical shape to a semi-funnel or semi ob-conical form.

S.J. Khajeddin

2001-01-01

269

Simulation of a sloped solar chimney power plant in Lanzhou  

Energy Technology Data Exchange (ETDEWEB)

Research highlights: {yields} A sloped solar chimney power plant in Lanzhou, China is investigated. {yields} The configuration sizes are designed separately. {yields} The system has high periodicity and stability but low efficiency. {yields} The sloped solar chimney power system is of high value for Northwest China. -- Abstract: Solar chimney power system is one large-scale utilization style of solar energy, which has drawn high attentions worldwide. Though scholars all over the world have made many researches on the solar chimney power system, reports of sloped solar chimney power system are still few. A sloped solar chimney power plant, which is expected to provide electric power for remote villages in Northwest China, has been designed for Lanzhou City in this paper. The designed plant, in which the height and radius of the chimney are 252.2 m and 14 m respectively, the radius and angle of the solar collector are 607.2 m and 31{sup o} respectively, is designed to produce 5 MW electric power on a monthly average all year. The performances, such as the airflow temperature increase, pressure, the airflow speed, system efficiency and solar collector efficiency, of the built sloped solar chimney power plant are simulated and presented. Simulation results show that parameters of the sloped solar chimney power plant are symmetrical and stable; the power plant has better performances in spring and autumn days; the overall efficiency of the power plant is low. Considering the abundant solar radiation, environmental friendliness, easy management and low population density, the sloped solar chimney power system is of high value to Northwest China.

Cao, Fei [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an (China); Zhao, Liang, E-mail: lzhao@mail.xjtu.edu.c [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an (China); Guo, Liejin [State Key Laboratory of Multiphase Flow in Power Engineering, Xi' an Jiaotong University, Xi' an (China)

2011-06-15

270

Simulation of a sloped solar chimney power plant in Lanzhou  

International Nuclear Information System (INIS)

Research highlights: ? A sloped solar chimney power plant in Lanzhou, China is investigated. ? The configuration sizes are designed separately. ? The system has high periodicity and stability but low efficiency. ? The sloped solar chimney power system is of high value for Northwest China. -- Abstract: Solar chimney power system is one large-scale utilization style of solar energy, which has drawn high attentions worldwide. Though scholars all over the world have made many researches on the solar chimney power system, reports of sloped solar chimney power system are still few. A sloped solar chimney power plant, which is expected to provide electric power for remote villages in Northwest China, has been designed for Lanzhou City in this paper. The designed plant, in which the height and radius of the chimney are 252.2 m and 14 m respectively, the radius and angle of the solar collector are 607.2 m and 31o respectively, is designed to produce 5 MW electric power on a monthly average all year. The performances, such as the airflow temperature increase, pressure, the airflow speed, system efficiency and solar collector efficiency, of the built sloped solar chimney power plant are simulated and presented. Simulation results show that parameters of the sloped solar chimney power plant are symmetrical and stable; the power plant has better performances in spring and autumn days; the overall efficiency of the power plant is low. Considering the abundant solar radiation, environmental friendliness, easy management and low population density, the sloped solar chimney power system is of high value to Northwest China.

271

Slope Length Estimation of Topographic Factor in Watershed using GIS  

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Full Text Available Water erosion is a severe and extended issue affecting all over the Loess Plateau, Northwest China. In order to estimate soil loss in China, Chinese Soil Loss Equation (CSLE were used to estimate soil erosion in the Forth China Soil Erosion Survey. CSLE was developed at an individual farmstead scale according to the erosion environment of the Loess Plateau. The equation has a similar calculation way with the universal soil loss equation (USLE and its’ revised version the revised universal soil loss equation (RUSLE. However, a major limitation is the difficulty in extracting the Topographic factor. The extraction method of slope gradient is already widely used and integrated in some applications. How to extract slope length in watershed is still a big problem for applying the USLE, RUSLE and CSLE to calculate soil erosion. The unit contributing area-based estimation method (UCA converts slope length to unit contributing area for considering two-dimensional topography, however is not able to predict the different zones of soil erosion and deposition. The flowpath and cumulative cell length-based method (FCL overcomes this disadvantage but does not consider channel networks, flow convergence and divergence flow in three-dimensional topography. The aim of this paper is to propose an algorithm that extends the FCL method and revise its calculation algorithm for slope length. Using the concept of the multiple flow direction algorithm (MFD with a focus on the calculation of slope length including slope changes. A calculation process is shown and a comparison of results for slope length calculated by FCL and LS-TOOL method (this paper for Xiannangou catchment is presented.

Hongming Zhang

2013-06-01

272

Very rare Q-slope none overcome by electropolishing and baking  

International Nuclear Information System (INIS)

We discovered the very rare Q-slope none overcome by electropolishing and baking at 120degC for 48 hours. The Q-slope is not related to 'Hydrogen disease'. The Q-slope is not improved by the wiping and steam so that we recognize that the Q-slope is not caused by some cohesion things of the cavity's surface. The rare Q-slope is categorized a low, medium and high rare Q-slope. In this paper, we report the Rare Q-slope and the categorized rare Q-slope. (author)

273

Estimating Coastal Slopes Vulnerability in Dakar Peninsula, West Senegal  

Science.gov (United States)

Dakar Peninsula, where most of the economically active places in Senegal are concentrated, has been repeatedly subjected to rockfalls and coastal erosion on the stretch of coastline between Pointe des Abattoirs and Pointe de Dakar. Coastal scientists, engineers and political leaders are increasingly being called upon to assess the physical and socio-economic impacts of such slope degradation, and hence explore appropriate response strategies. The objective of this terrain hazard mapping study was to collect information to enable the prevention and control of slope failure and slope degradation to be made on a rational basis. The area to be investigated was defined and sub-areas were further subdivided into 12 individual sections and assigned hazard and risk categories or levels derived from the field data.The present study evaluated the risk of slope failure within a conventional probabilistic framework based on slope outcrop inventory and structural discontinuities measurements, geomorphological mapping combined with air photograph interpretation, review of pre-existing geotechnical data as well as the sampling of rock specimen for laboratory testing and analysis. Detailed sea level rise analysis reported elsewhere leads to the conclusion that the background geology of the area should be looked as the cause to the several coastal hazards, among which slope instability poses the most important urban management problems in Dakar. From the results of the study it was possible to infer that local rockfalls and degradation of rock slopes are closely linked to the geological setting of the area, notably local rock type and structure, local hydrogeological conditions, local topography and geomorphological processes, as well as a poor city planning and overpopulation. The results also showed that geomorphological mapping can provide an effective tool to the engineering geologist in anticipating the slope failure processes which may otherwise go unnoticed. Eventually the probabilistic method has been found to work consistently for this case study and therefore suggests that the orientation and distribution of structural discontinuities play a key role for assessing the risk of slope failure with acceptable degree of accuracy.

Diop, S.

2004-12-01

274

The influence of slope breaks on lava flow surface disruption  

Science.gov (United States)

in the underlying slope of a lava flow impart a significant fraction of rotational energy beyond the slope break. The eddies, circulation, and vortices caused by this rotational energy can disrupt the flow surface, having a significant impact on heat loss and thus the distance the flow can travel. A basic mechanics model is used to compute the rotational energy caused by a slope change. The gain in rotational energy is deposited into an eddy of radius R whose energy is dissipated as it travels downstream. A model of eddy friction with the ambient lava is used to compute the time-rate of energy dissipation. The key parameter of the dissipation rate is shown to be ?R2/?, where ? is the lava density and ? is the viscosity, which can vary by orders of magnitude for different flows. The potential spatial disruption of the lava flow surface is investigated by introducing steady state models for the main flow beyond the steepening slope break. One model applies to slow-moving flows with both gravity and pressure as the driving forces. The other model applies to fast-moving, low-viscosity, turbulent flows. These models provide the flow velocity that establishes the downstream transport distance of disrupting eddies before they dissipate. The potential influence of slope breaks is discussed in connection with field studies of lava flows from the 1801 Hualalai and 1823 Keaiwa Kilauea, Hawaii, and 2004 Etna eruptions.

Glaze, Lori S.; Baloga, Stephen M.; Fagents, Sarah A.; Wright, Robert

2014-03-01

275

High-Order FEM Formulation for 3-D Slope Instability  

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Full Text Available High-order finite element method (FEM formulation also referred to as spectral element method (SEM formulation is currently implemented in this paper for 3-dimensional (3-D elasto-plastic problems in stability assessment of large- scale slopes (vegetated and barren slopes in different instability conditions such as seismic and saturation. We have reviewed the SEM formulation, and have sought its applicability for vegetated slopes. Utilizing p (high-order polynomial degree or spectral degrees and h (mesh operation for quality meshing in required elemental budgets refining techniques in the existing FEM, the complexity of problem domain can be well addressed in greater numerical stability. Unlike the existing FEM formulation, this high-order FEM employs the same integration and interpolation points to achieve a progressive response of the instability, which drastically reduces the computational costs (formation of diagonalized mass matrix and offers significant benefits to slope instability computations for serial and parallel implementations. With this formulation, we have achieved the following three qualities in slope instability modeling: 1 geometric flexibility of the finite elements, 2 high computational efficiency, and 3 reliable spectral accuracy. A sample problem has also been presented in this paper, which has accommodated all aforesaid numerical qualities.

Yatabe Ryuichi

2013-05-01

276

Slope Stability Analysis of Itakpe Iron Ore Mine, Itakpe, Nigeria  

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Full Text Available The slope stability of the Itakpe Iron Ore Mine has been carried out using computer software, ROCKPACK III. One hundred and twenty three dip and dip direction values were obtained using compass clinometer. The Itakpe Iron Ore Mine was divided into four benches; 241 - 258 m, 263 - 275 m, 276 - 286 m and 308 - 312 m. Joints along the discontinuities were mapped. The data obtained were analyzed using ROCKPACK III. The results indicate that the discontinuities within the critical zone are potentially unstable and can lead to planar failure. The Markland test carried out for wedge failure indicates that the intersection of the discontinuities does not fall within the critical zone hence there cannot be any wedge failure of the slope within the level 241 - 258 m. The presence of discontinuities that plot within the toppling critical zone indicates that there is potential toppling failure on the slope at the 276 - 286 m level. In addition, the toppling failure test shows the absence of discontinuities that plot within the toppling critical zone and this indicates the absence of poten-tial toppling failure of the slope at the 308 - 312 m level. The result of the study will be useful to the man-agement of the Itakpe iron ore mine in having a proper understanding of the failure mechanism of the slopes.

Jide Muili Akande

2011-06-01

277

Slope stability analysis using limit equilibrium method in nonlinear criterion.  

Science.gov (United States)

In slope stability analysis, the limit equilibrium method is usually used to calculate the safety factor of slope based on Mohr-Coulomb criterion. However, Mohr-Coulomb criterion is restricted to the description of rock mass. To overcome its shortcomings, this paper combined Hoek-Brown criterion and limit equilibrium method and proposed an equation for calculating the safety factor of slope with limit equilibrium method in Hoek-Brown criterion through equivalent cohesive strength and the friction angle. Moreover, this paper investigates the impact of Hoek-Brown parameters on the safety factor of slope, which reveals that there is linear relation between equivalent cohesive strength and weakening factor D. However, there are nonlinear relations between equivalent cohesive strength and Geological Strength Index (GSI), the uniaxial compressive strength of intact rock ? ci , and the parameter of intact rock m i . There is nonlinear relation between the friction angle and all Hoek-Brown parameters. With the increase of D, the safety factor of slope F decreases linearly; with the increase of GSI, F increases nonlinearly; when ? ci is relatively small, the relation between F and ? ci is nonlinear, but when ? ci is relatively large, the relation is linear; with the increase of m i , F decreases first and then increases. PMID:25147838

Lin, Hang; Zhong, Wenwen; Xiong, Wei; Tang, Wenyu

2014-01-01

278

Retrieval of short ocean wave slope using polarimetric imaging  

International Nuclear Information System (INIS)

We present a passive optical remote sensing technique for recovering shape information about a water surface, in the form of a two-dimensional slope map. The method, known as polarimetric slope sensing (PSS), uses the relationship between surface orientation and the change in polarization of reflected light to infer the instantaneous two-dimensional slope across the field-of-view of an imaging polarimeter. For unpolarized skylight, the polarization orientation and degree of linear polarization of the reflected skylight provide sufficient information to determine the local surface slope vectors. A controlled laboratory experiment was carried out in a wave tank with mechanically generated gravity waves. A second study was performed from a pier on the Hudson River, near Lamont-Doherty Earth Observatory. We demonstrated that the two-dimensional slope field of short gravity waves could be recovered accurately without interfering with the fluid dynamics of the air or water, and water surface features appear remarkably realistic. The combined field and laboratory results demonstrate that the polarimetric camera gives a robust characterization of the fine-scale surface wave features that are intrinsic to wind-driven air–sea interaction processes

279

Retrieval of short ocean wave slope using polarimetric imaging  

Science.gov (United States)

We present a passive optical remote sensing technique for recovering shape information about a water surface, in the form of a two-dimensional slope map. The method, known as polarimetric slope sensing (PSS), uses the relationship between surface orientation and the change in polarization of reflected light to infer the instantaneous two-dimensional slope across the field-of-view of an imaging polarimeter. For unpolarized skylight, the polarization orientation and degree of linear polarization of the reflected skylight provide sufficient information to determine the local surface slope vectors. A controlled laboratory experiment was carried out in a wave tank with mechanically generated gravity waves. A second study was performed from a pier on the Hudson River, near Lamont-Doherty Earth Observatory. We demonstrated that the two-dimensional slope field of short gravity waves could be recovered accurately without interfering with the fluid dynamics of the air or water, and water surface features appear remarkably realistic. The combined field and laboratory results demonstrate that the polarimetric camera gives a robust characterization of the fine-scale surface wave features that are intrinsic to wind-driven air-sea interaction processes.

Zappa, Christopher J.; Banner, Michael L.; Schultz, Howard; Corrada-Emmanuel, Andres; Wolff, Lawrence B.; Yalcin, Jacob

2008-05-01

280

A preliminary pit slope stability study Kvanefjeld, South Greenland  

International Nuclear Information System (INIS)

On the basis of 1300 field measurements of joint planes, four individual structural regions have been outlined in the Kvanefjeld area. Potential failure planes and planes which are unlikely to be involved in slope failures are identified. Failures seem, not likely to occur on walls dipping SW or NE respectively, but may occur on walls dipping NM. The factors of safety for each region are calculated in order to determine the sensibility of the overall slope to different overall slope angles. The factors of safety does only exceed the required factor of safety of 1.5 in one of the structural regions. Changing the overall pit slope inclination from 55deg to 45deg improves the security, but even still not satisfactorily for two of the regions. At 45deg overall pit slope in parts of the pit implies additional 14.3 x 106 tonnes of non-mineralized material to be mined, thus resulting in a total mineralized- to non-mineralized material ratio about 1.0: 1.7. (author)

 
 
 
 
281

Receiver structures for underwater acoustical communications using chirp slope keying  

Science.gov (United States)

This paper presents several receiver structures for Chirp Slope Keying (CSK), a digital broadband modulation scheme we propose to use for underwater acoustical communications. In its simplest form, the binary information modulates the slope of a linear chirp, with up-chirps representing ones and down-chirps representing zeros. A time-domain receiver and a novel time-frequency receiver structure based on the Wigner distribution and the Radon Transform are discussed and evaluated in terms of the probability of error versus Signal-to-Noise (SNR) performance. Simulation results and plots are presented for the Additive White Gaussian Noise (AWGN) channel. Results show that if the detector at the receiver operates directly on the slope of the received signal, performance is improved at the expense of computational complexity.

Kaminsky, Edit J.; Barbu, Madalina

2006-05-01

282

A New Closure to Slice Model for Slope Stability Analysis  

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Full Text Available This paper presents a new closure to slice models for evaluating slopes. The discussion is based on the minimal inter-slice action (MIA hypothesis, which results in a new slice model without including artificially adjustable parameters. It has been realized that the new slice model predicts the minimum value of the safety factor, while all other slice models available always overestimate the value of the safety factor. Moreover, the gravity moment of each slice is found to be opposite to the overturning moment, which is different from the existing knowledge. In particular, the new slice model overcomes the situation where different assumptions of the inter-slice force function will give different safety factors to the same slope. The related numerical examples indicate that the new slice model can serve as a reliable tool for investigating geotechnical slope stability.

Chongbin Zhao

2012-07-01

283

Violating the General Density-Slope Anisotropy Inequality  

CERN Document Server

We examine the robustness of the well-known empirical relationship between the density slope and the velocity anisotropy of collisionless systems. This relation, known as the Global Density-Slope Anisotropy Inequality (GDSAI) (Ciotti & Morganti, 2010), posits that no collisionless system with a globally positive distribution function exists where the anisotropy exceeds half of the power-law of the density slope. We significantly extend previous indications that the GDSAI is not a universal rule by identifying a class of models where violation occurs. These models possess a globally positive DF, have an isotropic central core, but are not guaranteed to be stable. Our analysis suggests that stability criteria provide a stronger basis for determining if a DF represents an equilibrium solution for a collisionless system.

Barber, Jeremy A

2014-01-01

284

Forest harvesting influence on slope erosion in Baikal Basin Mountains  

Science.gov (United States)

Post-logging recovery of forest water protection and erosion prevention functions can occur different ways on slopes and in big river catchments. While erosion decreases several times during only three to five years after logging on slopes, as compared to its immediate post-logging rate, water silt load in big rivers can remain high for decades after forest logging in their catchments. Among other factors, this can be attributable to erosion of timber transportation roads and skidding trails, which become extremely eroded 10-15 years following forest logging. One should not underestimate a probable sediment load increase resulting from post-logging channel runoff changes. Disregarding this increase leads to contradictory conclusions about post-logging recovery of forest water protecting capability. Investigating this issue requires to clearly determine the type of the forest site of interest (a certain slope, an elementary or a complex catchments) and to consider the experience gained so far in estimating erosion rate changes depending on changing forest areas of continents. Therefore, hierarchical river catchments ranking should be recognized effective and useful for forest hydrology. This approach will allow systematizing the existing information and facilitating the development of fruitful analysis of water protection and erosion prevention functions of forest in areas of different ranks. This study used an approach that enabled a single-model description of the rate of soil erosion previously estimated by different models for areas of various ranks, from a micro slope to elementary catchments. An elementary catchments is defined as the smallest drainage area characterized by uniform surface, ground, and vegetation structures and having a single well-pronounced channel, with hydro network being practically absent. Using runoff slope length as the argument and introducing a dummy variable that describes specific investigation methodologies ensured high generality of this model. The model describing soil erosion rates on separate slopes and in elementary catchments is: ln M=-9,3+0,95lnX-0,064NlnL+0,069lnXlnm/lnL+5,03K+1,49lnI+ +0,0162ln((X-W)/In)i-0,00026ln((X-W)/In)i2 R2 =0,86; ?=1,04; F?=221; where M is sediment load module, t/km2; N is time since the last disturbance (fire or logging), years; X is precipitation amount, mm; I is precipitation rate, mm/min; m is soil mineralization level, %; L is length of slope where surface runoff occurs, m; W is forest floor moisture capacity, mm; In is soil water permeability, mm/min; i is slope, degrees; K is investigation methodology indicator (it is assumed to equal 1 in the case of area sprinkling and 2 in erosion observations on permanent runoff sample sites and in catchments); R² is multiple determination coefficient;?? is standard deviation, ton per km2; and F? is Fisher criterion. All coefficients are 95% confident. This model shows a monotonous increase in sediment load module with increasing total moisture in an area and soil mineralization on burned or harvested sites. This module decreases with increasing forest floor moisture capacity and soil water permeability. These trends, as well as slope-caused soil erosion changes, were reported by earlier studies. Our experimental data obtained by other methods did not impact the earlier identified relationships. Therefore, estimating slope length precipitation rate influences on sediment load and predicting soil erosion slowdown on disturbed sites present a great interest. Numerical experiments with this model showed the sediment load module to increase with increasing precipitation rate and to decrease with increasing slope length. This decrease might be attributable to soil particle re-deposition in the lower parts of a slope. Re-deposited erosion products do not get into streams and become involved again in soil development.

Onuchin, A. A.; Borisov, A. N.; Burenina, T. A.

2009-04-01

285

Model slope infiltration experiments for shallow landslides early warning  

Science.gov (United States)

Occurrence of fast landslides has become more and more dangerous during the last decades, due to the increased density of settlements, industrial plants and infrastructures. Such problem is particularly worrying in Campania (Southern Italy), where the fast population growth led a diffuse building activity without planning: indeed, recent flowslides caused hundreds of victims and heavy damages to buildings, roads and other infrastructures. Large mountainous areas in Campania are mantled by loose pyroclastic granular soils up to a depth of a few meters from top soil surface. These soils have usually a grain size that falls in the domain of silty sands, including pumice interbeds (gravelly sands), with saturated hydraulic conductivities up to the order of 10-1 cm/min. Such deposits often cover steep slopes, which stability is guaranteed by the apparent cohesion due to suction under unsaturated conditions, that are the most common conditions for these slopes [Olivares and Picarelli, 2001]. Whereas rainfall infiltration causes soil to approach saturation, suction vanishes and slope failure may occur. Besides soil physical properties, landslide triggering is influenced by several factors, such as rainfall intensity, soil initial moisture and suction, slope inclination, boundary conditions. Whereas slope failure occurs with soil close to being saturated, landslide may develop in form of fast and destructive flowslide. Calibration of reliable mathematical models of such a complex phenomenon requires availability of experimental observations of the major variables of interest, such as soil moisture and suction, soil deformation and displacements, pore water pressure, during the entire process of infiltration until slope failure. Due to the sudden trigger and extremely rapid propagation of such type of landslides, such data sets are rarely available for natural slopes where flowslides occurred. As a consequence landslide risk assessment and early warning in Campania rely on simple empirical models [Versace et al., 2003] based on correlation between some features of rainfall records (cumulated height, duration, season etc.) and the correspondent observed landslides. Laboratory experiments on instrumented small scale slope models represent an effective way to provide data sets [Eckersley, 1990; Wang and Sassa, 2001] useful for building up more complex models of landslide triggering prediction. At the Geotechnical Laboratory of C.I.R.I.AM. an instrumented flume to investigate on the mechanics of landslides in unsaturated deposits of granular soils is available [Olivares et al. 2003; Damiano, 2004; Olivares et al., 2007]. In the flume a model slope is reconstituted by a moist-tamping technique and subjected to an artificial uniform rainfall since failure happens. The state of stress and strain of the slope is monitored during the entire test starting from the infiltration process since the early post-failure stage: the monitoring system is constituted by several mini-tensiometers placed at different locations and depths, to measure suction, mini-transducers to measure positive pore pressures, laser sensors, to measure settlements of the ground surface, and high definition video-cameras to obtain, through a software (PIV) appositely dedicated, the overall horizontal displacement field. Besides, TDR sensors, used with an innovative technique [Greco, 2006], allow to reconstruct the water content profile of soil along the entire thickness of the investigated deposit and to monitor its continuous changes during infiltration. In this paper a series of laboratory tests carried out on model slopes in granular pyroclastic soils taken in the mountainous area north-eastern of Napoli, are presented. The experimental results demonstrate the completeness of information provided by the various sensors installed. In particular, very useful information is given by the coupled measurements of soil water content by TDR and suction by tensiometers. Knowledge of soil water content at the occurrence of slope failure is of key importance, since high soil mo

Damiano, E.; Greco, R.; Guida, A.; Olivares, L.; Picarelli, L.

2009-04-01

286

Wetting Front Advance From a Point Source in Sloping Fields  

Directory of Open Access Journals (Sweden)

Full Text Available To determine the effects of field slope, emitter discharge, irrigation water volume and soil texture on soil moisture profile and soil surface wetted shape from a point source, field data were collected on three different soil types, three emitter discharges (4, 8, and 12 lph, four slopes (0, 2, 5, and 10%, and five irrigation water volumes (10, 20, 30, 40, and 50 liters with three replications. The results showed that the surface-wetted area increases as the emitter discharge increases. The surface-wetted area decreased with a corresponding increase in emitter discharge in experimental fields with light-textured soils. In experimental fields with heavy textured soils and slopes greater than 5%, the changes in surface-wetted area due to the emitter discharge increases, were higher compared to slopes of less than 5%. Since, a higher emitter discharge would result in higher surface-wetted area, the results showed that for an equal volume of irrigation water, the soil moisture profile was deeper for lower emitter discharge. In general, the volume of wetted zone was higher for greater emitter discharges. It was found that as the volume of irrigation water increased, the volume of wetted zone would increase correspondingly. This effect is more prominent than that of emitter discharge. In general, the depth of wetting front was lower and the wetted surface area was greater for heavy textured soils as compared to the light textured soils. The wetted-surface area and the shape of wetting front in the direction of slope were affected by the soil infiltration, emitter discharge and volume of irrigation water where these effects were more critical in higher sloping lands.

Behrouz Mostafazadeh

1998-10-01

287

An Experimental Study of Submarine Canyon Evolution on Continental Slopes  

Science.gov (United States)

Submarine canyons define the morphology of many continental slopes and are conduits for the transport of sediment from shallow to deep water. Though the origin and evolution of submarine canyons is still debated, there is general agreement that sediment gravity flows play an important role. Here we present results from a simple, reduced-scale sandbox experiment designed to investigate how sediment gravity flows generate submarine canyons. In the experiments, gravity flows were modeled using either sediment-free or turbid saline currents. Unconfined flows were released onto an inclined bed of sand bounded on the downstream end by a movable floor that was incrementally lowered during the course of an experiment to produce an escarpment. This design was developed to represent the growth of relief across the continental slope. To monitor canyon evolution on the slope, we placed an overhead DSLR camera to record vivid time-lapse videos. At the end of each experimental stage we scanned the topography by imaging a series of submerged laser stripes, each projected from a motor-driven transverse laser sheet, onto a calibrated Cartesian coordinate system to produce high resolution bathymetry without draining the ambient water. In areas unaffected by the flows, we observe featureless, angle-of-repose submarine slopes formed by retrogressive breaching processes. In contrast, areas influenced by gravity flows cascading across the shelf break are deeply incised by submarine canyons with well-developed channel networks. Our results show that downslope gravity flows and submarine falling base level are both required to produce realistic canyon morphologies at laboratory scale. Though our mechanism for generating relief may be a rather crude analogue for the processes driving slope evolution, we hope our novel approach can stimulate new questions about the coevolution of canyons and slopes and motivate further experimental work to address them.

Lai, S. Y.; Gerber, T. P.; Amblas, D.

2013-12-01

288

Research on the seasonal snow of the Arctic Slope  

Energy Technology Data Exchange (ETDEWEB)

This project deals with the seasonal snow on Alaska's Arctic Slope. Although it is concentrated on snow of the R{sub 4}D project area, it is important to relate the snow cover of this area with the rest of the Arctic Slope. The goals include determination of the amount of precipitation which comes as snow, the wind transport of this snow and its depositional pattern as influenced by drifting, the physical properties of the snow, the physical processes which operate in it, the proportions of it which go into evaporation, infiltration and runoff, and the biological role of the snow cover.

Benson, C.S.

1991-01-01

289

Using waste to reduce slope erosion on road embankments  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Urban waste may be used to reduce slope erosion of highway embankments. Whereas different kinds of compost have been tested in the USA for highway revegetation, sewage sludge has been used only for agricultural purposes. This paper presents the results of research carried out in order to study the viability of the application of sewage sludge compared with compost. Test areas measuring 4 m 3 5 m were constructed on a new highway embankment with 2 : 1 and 3 : 2 side slopes in the south of Spai...

On?a, Juan; Osorio, Francisco

2006-01-01

290

Spatial distribution models of erosion on slopes cultivated with vineyards  

International Nuclear Information System (INIS)

Soils cultivated with vineyards have high rates of erosion. In the Mediterranean area, this is related to the environmental characteristics and the management of cultivation techniques. Indeed, in this region the rainfall intensity and the location of vineyards on slopes favour the erosive activity of runoff. The total area of vineyards in La Rioja (Spain) is currently almost 40,000 ha. Vineyards are located on hillsides between 400 and 60 m.a.s.l. Of the vineyards of La Rioja 81,7% are planted on slopes with a gradient between 3 degree centigrade and 9 degree centigrade. (Author) 5 refs.

291

Delay-slope-dependent stability results of recurrent neural networks.  

Science.gov (United States)

By using the fact that the neuron activation functions are sector bounded and nondecreasing, this brief presents a new method, named the delay-slope-dependent method, for stability analysis of a class of recurrent neural networks with time-varying delays. This method includes more information on the slope of neuron activation functions and fewer matrix variables in the constructed Lyapunov-Krasovskii functional. Then some improved delay-dependent stability criteria with less computational burden and conservatism are obtained. Numerical examples are given to illustrate the effectiveness and the benefits of the proposed method. PMID:21984499

Li, Tao; Zheng, Wei Xing; Lin, Chong

2011-12-01

292

Red Beans and Rice: Slope failure experimental modeling  

Science.gov (United States)

In this activity, students replicate the slope failure experiment presented by Densmore et al. (1997) in the journal Science. They are given the original article and the slope failure apparatus (along with all associated materials) and then they need to figure out how to replicate the experiment. Once they have completed an experimental run of sufficient length, they compile and analyze their data and compare it to the article's results. After completing this portion of the lab, the students read the discussion and reply (Aalto et al., 1998; Densmore et al., 1998) and critically evaluate they results of the experiment and its applicability to the real world and landscape evolution.

Hickson, Tom

293

On the slope of the elastic differential cross sections  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Making use of a model-independent analytical fit for the elastic hadron-hadron amplitude, recently developed, we investigate the slope of the proton-proton and antiproton-proton differential cross sections, as a function of the energy and the momentum transfer. We show that the predictions for these [...] quantities are in agreement with the experimental data available and discuss the effect of the slope position as function of the momentum transfer.

S. D., Campos; M. J., Menon; J., Montanha.

2007-03-01

294

Global High-Accuracy Intercomparison of Slope Measuring Instruments  

International Nuclear Information System (INIS)

from the SR-community, optical manufacturers and other interested parties. This initiative is intended to start an extensive comparison of various measurement principles and tools and will help to push the frontiers in metrology, and hence production, to a precision well below the current state-of-the-art limit of 0.5?rad rms for slope errors

295

Measurement of Pipe Slope with Laser Scanning Technique  

Energy Technology Data Exchange (ETDEWEB)

U.S. Nuclear Regulatory Commission (NRC) issued Generic Letter (GL) 2008-01 which provides recommendation and guidance to nuclear power plants for managing gas intrusion and accumulation in safety systems such as Emergency Core Cooling (ECC), Decay Heat Removal (DHR) and Containment Spray (CS) systems. Following the GL2008-01, Nuclear Energy Institute (NEI) reported NEI 09-10 that gives industry guidance for effective prevention and management of system gas accumulation. The location of gas accumulation is usually a high point of piping systems. The high point of system is easily identified by investigating as-built isometric drawings of the subjected systems. However, the real plant piping configuration such as a slope might be different from as-built drawings. If there is a small slope on pipe which is a horizontal configuration in as-built drawing, gas can be accumulated at the high point in pipes with wrong slope as shown in Fig. 1. This paper demonstrates a feasibility to measure the slope of piping systems by using the laser scanning and presents a simple example

Lee, D. Y.; Jeon, S. S.; Hong, S. J. [FNC Technology Co., Seoul National University, Seoul (Korea, Republic of); Park, S. C. [Enguard Co., Seoul (Korea, Republic of)

2011-10-15

296

Visibility of rms slope variations on the sea surface.  

Science.gov (United States)

A model relating viewing geometry, sky conditions, and statistical sea surface parameters to the luminance of the sea surface is developed. The model is used to estimate the relative visibility of surface perturbations manifested by a variation in the rms surface slope. These estimates are presented for a variety of geometries in the solar plane using two sky conditions (clear and overcast) and two wind speeds (~2 and 7 m/sec). The results of this analysis, applicable to a unidirectional radiometer with no temporal averaging, show comparable extrema in the visibility of surface perturbations for both the overcast and clear sky models. The visibility of surface perturbations is shown to be maximized by geometries with either large gradients in the slope-to-luminance transfer functions (within the glitter pattern for the clear sky and near the horizon for both sky models) or very small gradients in the slope-to-luminance transfer functions (90 degrees away from the glitter pattern for the clear sky and nadir directed for the overcast sky). It is shown that improvements in the estimated values of the luminance SNR sensitivity to rms surface slope variations can be obtained through spatial and/or temporal averaging. PMID:20332868

Chapman, R D

1981-06-01

297

Comparison of slope stability in two Brazilian municipal landfills  

International Nuclear Information System (INIS)

aluate the potential use of very simple stability analyses which can be used to study the potential for slumps and slides within the waste mass and which may represent a significant constraint on construction and development of the landfill, on reclamation and closure and on the feasibility of a LFGTE project. The stability analyses rely on site-specific but simple estimates of the unit weight of waste and the pore pressure conditions and use 'generic' published shear strength envelopes for municipal waste. Application of the slope stability analysis method is presented in a case study of two Brazilian landfill sites; the Cruz das Almas Landfill in Maceio and the Muribeca Landfill in Recife. The Muribeca site has never recorded a slope failure and is much larger and better-maintained when compared to the Maceio site at which numerous minor slumps and slides have been observed. Conventional limit-equilibrium analysis was used to calculate factors of safety for stability of the landfill side slopes. Results indicate that the Muribeca site is more stable with computed factors of safety values in the range 1.6-2.4 compared with computed values ranging from 0.9 to 1.4 for the Maceio site at which slope failures have been known to occur. The results suggest that this approach may be useful as a screening-level tool when considering the feasibility of implementing LFGTE projects

298

Experimental research on stability of covering blocks for sloping banks  

International Nuclear Information System (INIS)

In the case of constructing thermal and nuclear power stations facing open seas, usually the harbors for unloading fuel and others are constructed. In Japan, breakwaters are installed in the places of relatively shallow depth less than 20 m, and in such case, the sloping banks having the covering material of wave-controlling blocks made of concrete are mostly adopted as those are excellent in their function and economical efficiency, and are advantageous in the maintenance and management. Sloping banks are of such type that wave-controlling blocks cover the vertical front face of nonpermeating caissons, and the same type was adopted for breakwaters and others in Onagawa Nuclear Power Station, Tohoku Electric Power Co., Inc. As for the wave-controlling blocks, tetrapods and shake blocks were used. One of the most important problems in the design of sloping banks is how to estimate the stability of wave controlling blocks. In this paper, the results of the examination by hydraulic model experiment on the stability of covering blocks are reported, which are useful as the basic data for the rational and economical design of sloping banks. The experimental setup and a model bank, the generation of experimental waves and their characteristics, the experimental conditions and experimental method, and the results are reported. (Kako, I.)

299

Slope estimation and viewing distance of the observer.  

Science.gov (United States)

The overestimation of geographical slant is one of the most sizable visual illusions. However, in some cases estimates of close-by slopes within the range of the observer's personal space have been found to be rather accurate. We propose that the seemingly diverse findings can be reconciled when taking the viewing distance of the observer into account. The latter involves the distance of the observer from the slope (personal space, action space, and vista space) and also the eye-point relative to the slope. We separated these factors and compared outdoor judgments to those collected with a three-dimensional (3D) model of natural terrain, which was within arm's reach of the observer. Slope was overestimated in the outdoors at viewing distances between 2 m and 138 m. The 3D model reproduced the errors in monocular viewing; however, performance was accurate with stereoscopic viewing. We conclude that accurate slant perception breaks down as soon as the situation exits personal space, be it physically or be it by closing one eye. PMID:24927945

Hecht, Heiko; Shaffer, Dennis; Keshavarz, Behrang; Flint, Mariagrace

2014-08-01

300

Estimating Slope and Level Change in N = 1 Designs  

Science.gov (United States)

The current study proposes a new procedure for separately estimating slope change and level change between two adjacent phases in single-case designs. The procedure eliminates baseline trend from the whole data series before assessing treatment effectiveness. The steps necessary to obtain the estimates are presented in detail, explained, and…

Solanas, Antonio; Manolov, Rumen; Onghena, Patrick

2010-01-01

 
 
 
 
301

Behaviour of the slope parameter in the high elastic scattering  

International Nuclear Information System (INIS)

If the elastic pp total cross section grows as ln2 s, then so does the slope parameter B, measured inside the diffraction region. The apparent paradox arising from Martin's bound B(s, t) < C ln s at nearly fixed t is explained. (orig.)

302

Stability analysis of nonlinear systems with slope restricted nonlinearities.  

Science.gov (United States)

The problem of absolute stability of Lur'e systems with sector and slope restricted nonlinearities is revisited. Novel time-domain and frequency-domain criteria are established by using the Lyapunov method and the well-known Kalman-Yakubovich-Popov (KYP) lemma. The criteria strengthen some existing results. Simulations are given to illustrate the efficiency of the results. PMID:24592160

Liu, Xian; Du, Jiajia; Gao, Qing

2014-01-01

303

The Snowmass Points and Slopes: benchmarks for SUSY searches  

International Nuclear Information System (INIS)

The ''Snowmass Points and Slopes'' (SPS) are a set of benchmark points and parameter lines in the MSSM parameter space corresponding to different scenarios in the search for Supersymmetry at present and future experiments. This set of benchmarks was agreed upon at the 2001 ''Snowmass Workshop on the Future of Particle Physics'' as a consensus based on different existing proposals. (orig.)

304

Slope histogram distribution-based parametrisation of Martian geomorphic features  

Science.gov (United States)

The application of geomorphometric methods on the large Martian digital topographic datasets paves the way to analyse the Martian areomorphic processes in more detail. One of the numerous methods is the analysis is to analyse local slope distributions. To this implementation a visualization program code was developed that allows to calculate the local slope histograms and to compare them based on Kolmogorov distance criterion. As input data we used the digital elevation models (DTMs) derived from HRSC high-resolution stereo camera image from various Martian regions. The Kolmogorov-criterion based discrimination produces classes of slope histograms that displayed using coloration obtaining an image map. In this image map the distribution can be visualized by their different colours representing the various classes. Our goal is to create a local slope histogram based classification for large Martian areas in order to obtain information about general morphological characteristics of the region. This is a contribution of the TMIS.ascrea project, financed by the Austrian Research Promotion Agency (FFG). The present research is partly realized in the frames of TÁMOP 4.2.4.A/2-11-1-2012-0001 high priority "National Excellence Program - Elaborating and Operating an Inland Student and Researcher Personal Support System convergence program" project's scholarship support, using Hungarian state and European Union funds and cofinances from the European Social Fund.

Balint, Zita; Székely, Balázs; Kovács, Gábor

2014-05-01

305

The Perceptual Experience of Slope by Foot and by Finger  

Science.gov (United States)

Historically, the bodily senses have often been regarded as impeccable sources of spatial information and as being the teacher of vision. Here, the authors report that the haptic perception of slope by means of the foot is greatly exaggerated. The exaggeration is present in verbal as well as proprioceptive judgments. It is shown that this…

Hajnal, Alen; Abdul-Malak, Daniel T.; Durgin, Frank H.

2011-01-01

306

Stability Analysis of Nonlinear Systems with Slope Restricted Nonlinearities  

Science.gov (United States)

The problem of absolute stability of Lur'e systems with sector and slope restricted nonlinearities is revisited. Novel time-domain and frequency-domain criteria are established by using the Lyapunov method and the well-known Kalman-Yakubovich-Popov (KYP) lemma. The criteria strengthen some existing results. Simulations are given to illustrate the efficiency of the results. PMID:24592160

Du, Jiajia

2014-01-01

307

Late Cenzoic stratigraphy of the central Scotian Slope, eastern Canada  

Energy Technology Data Exchange (ETDEWEB)

High-resolution multichannel seismic profiles have been used to define the Quaternary seismic stratigraphy for the Scotian Slope in the area of the Acadia K-62 and Shubenacadie H-100 wells southwest of Sable Island Bank. Seven key reflectors are identified and correlated through much of the study area. The wells provide biostratigraphic control for this seismic stratigraphy. During the Neogene, sediments accumulated slowly and uniformly on the slope; these now give continuous, parallel acoustic reflectors. A broad, shallow, ancestral valley on the site of the present Verrill and Dawson canyons was cut during the earliest part of the Late Pliocene, reflecting a low stand of sea level. The valley was then filled by fine grained sediment. Subsequently, in the Late Pliocene, a further lowering of the sea level resulted in gully and canyon cutting and an increase in sedimentation rates of about 0.2 m/ka. In the Quaternary, continued canyon cutting led to much sediment bypassing of the continental slope and lower sedimentation rates (0.1 m/ka). High rates of sedimentation (0.4 m/ka) are found only in some intercanyon areas on levee-like accumulations and close to ice margin tills deposited on the upper slope. Implications of these findings for hydrocarbon development are briefly discussed. 25 refs., 8 figs., 1 tab.

Piper, D.J.W.; Normark, W.R.; Sparkes, R.

1987-03-01

308

Slope failure on Eros- Implications for regolith properties  

Science.gov (United States)

The physical properties of regolith record processes important in the surface evolution of asteroids. For example, grain size is affected by the rates and style of cratering, and in turn affects spectral properties. In this study, we combine results acquired from the NEAR laser rangefinder (NLR) and the multispectral imager (MSI) to gain insight into physical characteristics of the regolith. By comparing the most recent NLR shape model to MSI albedo maps of Eros, we can determine the regional slope at which regolith fails. High albedos have been identified by the MSI team primarily in regions of steep slope, and attributed to exposure of the subsurface by mass-wasting processes. We determine the angles at which slope failure occurs by mapping individual NLR transects through high albedo regions visible in the MSI images, and use slope stability analyses to estimate the range of regolith grain sizes required to obtain failure at the observed angle. Preliminary results suggest that the regolith of Eros associated with these failures is coarse and possibly gravel-sized.

Barnouin-Jha, O. S.; Murchie, S.; Cheng, A.; Robinson, M.

2001-12-01

309

Late Holocene Radiocarbon Variability in Northwest Atlantic Slope Waters  

Energy Technology Data Exchange (ETDEWEB)

Deep-sea gorgonian corals secrete a 2-part skeleton of calcite, derived from dissolved inorganic carbon at depth, and gorgonin, derived from recently fixed and exported particulate organic matter. Radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters, respectively. Using specimens collected from Northwest Atlantic slope waters, we generated radiocarbon records for surface and upper intermediate water layers spanning the pre- and post bomb-{sup 14}C eras. In Labrador Slope Water (LSW), convective mixing homogenizes the pre-bomb {Delta}{sup 14}C signature (-67 {+-} 4{per_thousand}) to at least 1000 m depth. Surface water bomb-{sup 14}C signals were lagged and damped (peaking at {approx} +45{per_thousand} in the early 1980s) relative to other regions of the northwest Atlantic, and intermediate water signals were damped further. Off southwest Nova Scotia, the vertical gradient in {Delta}{sup 14}C is much stronger. In surface water, pre-bomb {Delta}{sup 14}C averaged -75 {+-} 5{per_thousand}. At 250-475 m depth, prebomb {Delta}{sup 14}C oscillated quasi-decadally between -80 and -100{per_thousand}, likely reflecting interannual variability in the presence of Labrador Slope Water vs. Warm Slope Water (WSW). Finally, subfossil corals reveal no systematic changes in vertical {Delta}{sup 14}C gradients over the last 1200 years.

Sherwood, O; Edinger, E; Guilderson, T P; Ghaleb, B; Risk, M J; Scott, D B

2008-08-15

310

Recurring Slope Lineae and Future Exploration of Mars  

Science.gov (United States)

Recurring slope lineae (RSL) on Mars may be evidence for the seasonal flow or seepage of water on relatively warm slopes. RSL are narrow (MRO. The fans on which RSL terminate have distinctive color and spectral properties in MRO/CRISM, but lack distinctive water absorption bands [Ojha et al., 2013, GRL]. The first group of confirmed RSL appear and lengthen in the late southern spring through summer from 48° - 32°S latitude, favoring equator-facing slopes—times and places with peak surface temperatures ranging from >250 K to >300 K. Over the past Martian year we have monitored active RSL in equatorial (0°-15°S) regions of Mars, especially in the deep canyons of Valles Marineris [McEwen et al., 2014, Nature Geoscience]. These equatorial RSL are especially active on north-facing slopes in northern summer and spring and on south-facing slopes in southern spring and summer, following the most normal solar incidence angles on these steep slopes. More recently we have confirmed RSL near 35°N in the low-albedo and low-altitude Acidalia Planitia. All RSL locations have warm peak daily temperatures (typically >273 K at the surface) in the seasons when RSL are active, and occur on steep, rocky, low-albedo slopes. However, most times and places with these properties lack apparent RSL, so there are additional, unseen requirements. We do not know what time of day RSL are actively flowing. Seasonal variation in the atmospheric column abundance of water vapor does not match the RSL activity. Seasonal melting of shallow ice best explains the RSL observations, but the origin and replenishment of such ice is not understood, especially in the tropics. Laboratory experiments are consistent with two key MRO observations: (1) that seeping water darkens basaltic soils but may only produce weak water absorption bands undetectable in ratio spectra after partial dehydration during the low-humidity middle afternoon conditions when MRO observes; and (2) the flows are more linear than under terrestrial conditions and do not erode channels under Martian atmospheric pressures [Masse et al., 2014, LPSC]. No dry process is known to create such slowly creeping seasonal flows. The potential for equatorial water activity creates new exploration opportunities, to search for extant life, as well as challenges such as the definition of special regions for planetary protection.

McEwen, Alfred; Byrne, Shane; Chevrier, Vincent; Chojnacki, Matt; Dundas, Colin; Masse, Marion; Mattson, Sarah; Ojha, Lujendra; Pommerol, Antoine; Toigo, Anthony; Wray, James

2014-05-01

311

Consequence assessment of large rock slope failures in Norway  

Science.gov (United States)

Steep glacially carved valleys and fjords in Norway are prone to many landslide types, including large rockslides, rockfalls, and debris flows. Large rockslides and their secondary effects (rockslide-triggered displacement waves, inundation behind landslide dams and outburst floods from failure of landslide dams) pose a significant hazard to the population living in the valleys and along the fjords shoreline. The Geological Survey of Norway performs systematic mapping of unstable rock slopes in Norway and has detected more than 230 unstable slopes with significant postglacial deformation. This large number necessitates prioritisation of follow-up activities, such as more detailed investigations, periodic displacement measurements, continuous monitoring and early-warning systems. Prioritisation is achieved through a hazard and risk classification system, which has been developed by a panel of international and Norwegian experts (www.ngu.no/en-gb/hm/Publications/Reports/2012/2012-029). The risk classification system combines a qualitative hazard assessment with a consequences assessment focusing on potential life losses. The hazard assessment is based on a series of nine geomorphological, engineering geological and structural criteria, as well as displacement rates, past events and other signs of activity. We present a method for consequence assessment comprising four main steps: 1. computation of the volume of the unstable rock slope; 2. run-out assessment based on the volume-dependent angle of reach (Fahrböschung) or detailed numerical run-out modelling; 3. assessment of possible displacement wave propagation and run-up based on empirical relations or modelling in 2D or 3D; and 4. estimation of the number of persons exposed to rock avalanches or displacement waves. Volume computation of an unstable rock slope is based on the sloping local base level technique, which uses a digital elevation model to create a second-order curved surface between the mapped extent of the unstable rock slope. This surface represents the possible basal sliding surface of an unstable rock slope. The elevation difference between this surface and the topographic surface estimates the volume of the unstable rock slope. A tool has been developed for the present study to adapt the curvature parameters of the computed surface to local geological and structural conditions. The obtained volume is then used to define the angle of reach of a possible rock avalanche from the unstable rock slope by using empirical derived values of angle of reach vs. volume relations. Run-out area is calculated using FlowR; the software is widely used for run-out assessment of debris flows and is adapted here for assessment of rock avalanches, including their potential to ascend opposing slopes. Under certain conditions, more sophisticated and complex numerical run-out models are also used. For rock avalanches with potential to reach a fjord or a lake the propagation and run-up area of triggered displacement waves is assessed. Empirical relations of wave run-up height as a function of rock avalanche volume and distance from impact location are derived from a national and international inventory of landslide-triggered displacement waves. These empirical relations are used in first-level hazard assessment and where necessary, followed by 2D or 3D displacement wave modelling. Finally, the population exposed in the rock avalanche run-out area and in the run-up area of a possible displacement wave is assessed taking into account different population groups: inhabitants, persons in critical infrastructure (hospitals and other emergency services), persons in schools and kindergartens, persons at work or in shops, tourists, persons on ferries and so on. Exposure levels are defined for each population group and vulnerability values are set for the rock avalanche run-out area (100%) and the run-up area of a possible displacement wave (70%). Finally, the total number of persons within the hazard area is calculated taking into account exposure and vulnerability. The method for conse

Oppikofer, Thierry; Hermanns, Reginald L.; Horton, Pascal; Sandøy, Gro; Roberts, Nicholas J.; Jaboyedoff, Michel; Böhme, Martina; Yugsi Molina, Freddy X.

2014-05-01

312

Parallel processing for efficient 3D slope stability modelling  

Science.gov (United States)

We test the performance of the GIS-based, three-dimensional slope stability model r.slope.stability. The model was developed as a C- and python-based raster module of the GRASS GIS software. It considers the three-dimensional geometry of the sliding surface, adopting a modification of the model proposed by Hovland (1977), and revised and extended by Xie and co-workers (2006). Given a terrain elevation map and a set of relevant thematic layers, the model evaluates the stability of slopes for a large number of randomly selected potential slip surfaces, ellipsoidal or truncated in shape. Any single raster cell may be intersected by multiple sliding surfaces, each associated with a value of the factor of safety, FS. For each pixel, the minimum value of FS and the depth of the associated slip surface are stored. This information is used to obtain a spatial overview of the potentially unstable slopes in the study area. We test the model in the Collazzone area, Umbria, central Italy, an area known to be susceptible to landslides of different type and size. Availability of a comprehensive and detailed landslide inventory map allowed for a critical evaluation of the model results. The r.slope.stability code automatically splits the study area into a defined number of tiles, with proper overlap in order to provide the same statistical significance for the entire study area. The tiles are then processed in parallel by a given number of processors, exploiting a multi-purpose computing environment at CNR IRPI, Perugia. The map of the FS is obtained collecting the individual results, taking the minimum values on the overlapping cells. This procedure significantly reduces the processing time. We show how the gain in terms of processing time depends on the tile dimensions and on the number of cores.

Marchesini, Ivan; Mergili, Martin; Alvioli, Massimiliano; Metz, Markus; Schneider-Muntau, Barbara; Rossi, Mauro; Guzzetti, Fausto

2014-05-01

313

The dependence of sheet erosion velocity on slope angle  

Directory of Open Access Journals (Sweden)

Full Text Available The article presents a method for estimating the erosion velocity on forested natural area. As a research object for testing the methodology the authors selected Neskuchny Garden - a city Park on the Moskva river embankment, named after the cognominal Palace of Catherine's age. Here, an almost horizontal surface III of the Moskva river terrace above the flood-plain is especially remarkable, accentuated by the steep sides of the ravine parallel to St. Andrew's, but short and nameless. The crests of the ravine sides are sharp, which is the evidence of its recent formation, but the old trees on the slopes indicate that it has not been growing for at least 100 years. Earlier Russian researchers defined vertical velocity of sheet erosion for different regions and slopes with different parent (in relation to the soil rocks. The comparison of the velocities shows that climatic conditions, in the first approximation, do not have a decisive influence on the erosion velocity of silt loam soils. The velocities on the shores of Issyk-Kul lake and in Moscow proved to be the same. But the composition of the parent rocks strongly affects the sheet erosion velocity. Even low-strength rock material reduces the velocity by times. Phytoindication method gives a real, physically explainable sheet erosion velocities. The speed is rather small but it should be considered when designing long-term structures on the slopes composed of dispersive soils. On the slopes composed of rocky soils sheet erosion velocity is so insignificant that it shouldn't be taken into account when designing. However, there may be other geological processes, significantly disturbing the stability of slopes connected with cracks.

Chernyshev Sergey Nikolaevich

2014-09-01

314

Cooperative Three-Robot System for Traversing Steep Slopes  

Science.gov (United States)

Teamed Robots for Exploration and Science in Steep Areas (TRESSA) is a system of three autonomous mobile robots that cooperate with each other to enable scientific exploration of steep terrain (slope angles up to 90 ). Originally intended for use in exploring steep slopes on Mars that are not accessible to lone wheeled robots (Mars Exploration Rovers), TRESSA and systems like TRESSA could also be used on Earth for performing rescues on steep slopes and for exploring steep slopes that are too remote or too dangerous to be explored by humans. TRESSA is modeled on safe human climbing of steep slopes, two key features of which are teamwork and safety tethers. Two of the autonomous robots, denoted Anchorbots, remain at the top of a slope; the third robot, denoted the Cliffbot, traverses the slope. The Cliffbot drives over the cliff edge supported by tethers, which are payed out from the Anchorbots (see figure). The Anchorbots autonomously control the tension in the tethers to counter the gravitational force on the Cliffbot. The tethers are payed out and reeled in as needed, keeping the body of the Cliffbot oriented approximately parallel to the local terrain surface and preventing wheel slip by controlling the speed of descent or ascent, thereby enabling the Cliffbot to drive freely up, down, or across the slope. Due to the interactive nature of the three-robot system, the robots must be very tightly coupled. To provide for this tight coupling, the TRESSA software architecture is built on a combination of (1) the multi-robot layered behavior-coordination architecture reported in "An Architecture for Controlling Multiple Robots" (NPO-30345), NASA Tech Briefs, Vol. 28, No. 10 (October 2004), page 65, and (2) the real-time control architecture reported in "Robot Electronics Architecture" (NPO-41784), NASA Tech Briefs, Vol. 32, No. 1 (January 2008), page 28. The combination architecture makes it possible to keep the three robots synchronized and coordinated, to use data from all three robots for decision- making at each step, and to control the physical connections among the robots. In addition, TRESSA (as in prior systems that have utilized this architecture) , incorporates a capability for deterministic response to unanticipated situations from yet another architecture reported in Control Architecture for Robotic Agent Command and Sensing (NPO-43635), NASA Tech Briefs, Vol. 32, No. 10 (October 2008), page 40. Tether tension control is a major consideration in the design and operation of TRESSA. Tension is measured by force sensors connected to each tether at the Cliffbot. The direction of the tension (both azimuth and elevation) is also measured. The tension controller combines a controller to counter gravitational force and an optional velocity controller that anticipates the motion of the Cliffbot. The gravity controller estimates the slope angle from the inclination of the tethers. This angle and the weight of the Cliffbot determine the total tension needed to counteract the weight of the Cliffbot. The total needed tension is broken into components for each Anchorbot. The difference between this needed tension and the tension measured at the Cliffbot constitutes an error signal that is provided to the gravity controller. The velocity controller computes the tether speed needed to produce the desired motion of the Cliffbot. Another major consideration in the design and operation of TRESSA is detection of faults. Each robot in the TRESSA system monitors its own performance and the performance of its teammates in order to detect any system faults and prevent unsafe conditions. At startup, communication links are tested and if any robot is not communicating, the system refuses to execute any motion commands. Prior to motion, the Anchorbots attempt to set tensions in the tethers at optimal levels for counteracting the weight of the Cliffbot; if either Anchorbot fails to reach its optimal tension level within a specified time, it sends message to the other robots and the commanded motion is not executed. If any

Stroupe, Ashley; Huntsberger, Terrance; Aghazarian, Hrand; Younse, Paulo; Garrett, Michael

2009-01-01

315

Hydrological modelling of slopes from field monitoring data  

Science.gov (United States)

A simplified hydrological model of a steep slope covered with loose granular pyroclastic deposits is presented. The slope is located in the mountains northern of Naples, and the soil cover, constituted by layers of loose volcanic ashes and pumices with a total thickness of 2.5m, lays upon a fractured limestone bedrock. At the interface between the bedrock and the soil cover, a layer of weathered ashes, with significant clay fraction, is sometimes observed. The slope has a fairly regular inclination of 40°, and is covered by chestnut woods and thick brushwood growing in late spring. The inclination of the slope is comparable with the internal friction angle of the ashes, thus the equilibrium is possible thanks to the contribution offered to the shear strength by the soil suction in unsaturated conditions. Indeed, in December 1999, a landslide was triggered by prolonged and intense precipitations. As it frequently happens with similar pyroclastic covers, the triggered slide exhibited a flow-like behavior, covering 2km in few minutes, heavily hitting the nearby town of Cervinara (AV). Since then, the slope has been constantly monitored, and during the last two years an automated station with seven TDR probes for the measurement of soil water content, eight tensiometers for the measurement of soil suction, and a rain gauge, has been operating. The data, collected every two hours, allowed getting more insight of the hydrological behavior of the slope and building up an effective hydrological model. In the model, the layered soil profile has been replaced with a single homogeneous layer, with water retention curve estimated by coupling the values of water content and suction measured at various depths. A seasonal top boundary condition has been introduced, related to the annual cycle of the vegetation: the observed precipitations quickly caused changes of soil suction at the depth of -50cm during the entire year, with the exception of the period between the end of May and the early August. To reproduce the observed behavior of soil suction at the bottom of the profile, a linear reservoir model has been introduced as bottom boundary condition, related to the presence of a small aquifer in the fractured bedrock, which water table, affecting the hydraulic conditions of the soil cover, rapidly deepens during the dry season. The developed model, calibrated with the data of one year of observation, satisfactorily reproduces the observed soil hydraulic behaviour also during other periods.

Comegna, Luca; Damiano, Emilia; Greco, Roberto; Guida, Andrea; Olivares, Lucio; Picarelli, Luciano

2013-04-01

316

Bioengineering case studies sustainable stream bank and slope stabilization  

CERN Document Server

This unique volume describes and evaluates 30 projects from across the United States where bio-stabilization was employed to address a detrimental naturally occurring process or byproduct of the built environment. Bio-stabilization (or soil bioengineering) refers to the use of plant materials, primarily live cuttings, arranged in the ground in different arrays to reinforce soils and protect upland slopes and/or stream banks against surficial erosion and shallow slope failures. Examples included in the collection represent different regions of the country and their specific conditions and challenges. Each project is illustrated with a number of distinctive photographs to support the reader's understanding and showcase the wide scope of projects and techniques presented. This book also: ·         Presents a range of well-documented case studies on key techniques and best practices for bio-stabilization projects ·         Emphasizes evaluation and comparison of different techniques and challeng...

Goldsmith, Wendi; McCullah, John

2014-01-01

317

Evaluating thermal performance of a single slope solar still  

Science.gov (United States)

The distillation is one of the important methods of getting clean water from brackish and sea water using the free energy supply from the sun. An experimental work is conducted on a single slope solar still. The thermal performance of the single slope solar still is examined and evaluated through implementing the following effective parameters: (a) different insulation thicknesses of 1, 2.5 and 5 cm; (b) water depth of 2 and 3.5 cm; (c) solar intensity; (d) Overall heat loss coefficient (e) effective absorbtivity and transmissivity; and (f) ambient, water and vapor temperatures. Different effective parameters should be taken into account to increase the still productivity. A mathematical model is presented and compared with experimental results. The model gives a good match with experimental values.

Badran, Omar O.; Abu-Khader, Mazen M.

2007-08-01

318

Hydraulic Characteristics of a Stepped-slope Floating Breakwater  

International Nuclear Information System (INIS)

A stepped-slope floating breakwater is developed to provide wave protection to small ports and harbours. The width of the structure can be enhanced by increasing the number of breakwater units that are placed side-by-side to each other. This produces three types of test model, i.e. single-row, double-row and triple-row breakwaters. The test models have been tested in monochromatic waves in a wave flume to determine their hydraulic performance in various wave conditions. The incident and reflected wave profiles in the vicinity of the test models are recorded and analysed by using moving-probe method. The hydraulic performance of the test models are quantified by the coefficients of transmission, reflection and energy loss. The experimental results showed that the stepped-slope floating breakwater is an effective anti-reflection structure and a reasonably good wave attenuator.

319

Seismic distress and slope instability of municipal solid waste landfills  

DEFF Research Database (Denmark)

The impact of seismic loading on municipal solid waste landfills is investigated numerically in the current study. Initially, the role of the main parameters involved in the linear or nonlinear dynamic response of landfills is determined in terms of developed inertial acceleration. The most important factors are the geometry, the waste material properties, and the characteristics of the seismic excitation. Concerning the evaluation of the potential failure mechanisms, the effect of the main parameters on the slope stability is underlined, and a comparison between circular slope instability and base sliding is presented. Furthermore, according to the failure envelopes adopted in the literature for the shear strength of the waste material, a decoupled procedure is utilized to estimate the developed landfill deformations. Finally, the generation of parasitic vertical acceleration (due to the multidimensional nature of the problem) is taken into account in stability assessment, while its effect on the resulting deformation is determined.

Zania, Varvara; Tsompanakis, Yiannis

2008-01-01

320

Integration of Indoor Ski Slopes into the Urban Recreation System  

Directory of Open Access Journals (Sweden)

Full Text Available Indoor ski slope is an innovative type of active indoor recreation. This new urban character is simulating the concept of mountain ski resort and is considered to be a strong attraction point all year-round. Due to a big scale and complexity, sustainable integration into an urban context should be very carefully considered. Economical, social, environmental and aesthetic impact on surrounding territories is an important factor to be evaluated. International practice shows that the appropriate integration of the above mentioned typology into urban parks increase their popularity and use of the recreation zone. On the other hand, the alien architecture and egocentric dominance of complexes can cause conflict with the existing urban territories and natural environment. Having indoor ski slopes in mind at the stages of regional and town territorial planning is an important point. Only complex development can bring positive results for sustainable town development, town economy, tourism and social life. Article in Lithuanian

Inga Urbonait?

2011-03-01

 
 
 
 
321

Breaking of Waves over a Steep Bottom Slope  

DEFF Research Database (Denmark)

The thesis deals with the wave breaking process of waves propagating over a steep submerged bottom slope. The amount of energy dissipated in the wave breaking process is focused upon. An extensive number of experimental tests (>400) using regular and irregular waves breaking over a simulated reef in the hydraulic laboratory are performed. Based on the experimental tests several formulae developed. Formulae are capable of predicting the transmitted wave height and wave energy flux, respectively. Furthermore, a numerical wave model based on the extended Mild-Slope equation has been developed. The model is capable of generating progressive irregular waves. Wave breaking has been included using a modification of the Battjes and Janssen [1978] periodic bore approach. The results from this study be applicable in the design of coastal structures as submerged breakwaters or artificial reefs.

Jensen, Morten S.

2004-01-01

322

Relation between vertical movement velocity and dynamic syncline slope  

Energy Technology Data Exchange (ETDEWEB)

Deformation of the surface in the dynamic syncline is discussed. It is most intense above underground face dislocation. The deformations are analyzed on the basis of the results of theoretical and empirical studies. Relationships between velocity of the vertical ground subsidence in the profile of the dynamic syncline and the slope syncline are characterized. These relations are important not only for protecting buildings on the surface but also for proper location of mine surveying points in mining areas. (24 refs.) (In Polish)

Trojanowski, K.

1973-01-01

323

Relation between vertical movement velocity and dynamic syncline slope  

Energy Technology Data Exchange (ETDEWEB)

Deformation of the surface in the dynamic syncline is discussed. It is most intense above underground face dislocation. The deformations are analyzed on the basis of the results of theoretical and empirical studies. Relationships between velocity of the vertical ground subsidence in the profile of the dynamic syncline and the slope syncline are characterized. These relations are important not only for protecting buildings on the surface but also for proper location of mine surveying points in mining areas.

Trojanowski, K.

1973-01-01

324

Electric vehicle's electricity consumption on a road with different slope  

Science.gov (United States)

In this paper, we propose an extended car-following model and an electricity consumption model to study the effects of the road's slope on the electric vehicle's electricity consumption. The numerical results show that each electric vehicle's electricity consumption increases with the uphill's tilt angle and decreases with the downhill's tilt angle. In addition, each electric vehicle's electricity consumption increases with the uphill's (downhill's) length under a certain tilt angle.

Yang, S. C.; Li, M.; Lin, Y.; Tang, T. Q.

2014-05-01

325

Aerial Photogrammetric Analysis of a Scree Slope and Cliff  

Science.gov (United States)

Mapping the physical features of landslide tracks provides information about factors controlling landslide movement. The increasing availability of unmanned aerial vehicles (UAV) provides the opportunity to efficiently and cost effectively map terrain. The main goal of this field study is to create a streamlined work-flow from acquisition to interpretation for the photogrammetric analysis of landslide tracks. Here an open source software package MicMac is used for ortho-image and point-cloud creation. A series of two flights were conducted over a scree (rockfall) slope in Kolsas, Norway. The slope runs roughly 500 m north-south with a maximum width of 60 m. A cliff to the west is the source area for the scree. The cliff consists of conglomerate, basalt, and porphyry from bottom to top respectively. The grain size of boulders in the scree slope apparently varies due to lateral differences in the cliff composition. The flights were completed under cloud cover and consisted of multiple lengthwise passes over the scree field. There was a minimum of 75% overlap between images. During the first flight the altitude was roughly 100 m, the camera was positioned normal to the scree (60 degrees from horizontal), and the resolution was 2.7 cm per pixel. The second flight had an altitude of 200 m, the camera orientation was 30 degrees from horizontal, and the resolution was 4.0 cm per pixel. Using the Micmac engine, Ortho-photos and Digital Elevation Models (DEM) were created for both the scree and the cliff. This data will allow for analysis of grain-size, surface roughness, grain-shape, fracture plane orientation, as well as geological mapping. Further work will focus the quantitative assessment of the significance different camera altitudes and angles have on the results. The work-flow used in this study provides a repeatable method for aerial photogrammetric surveys of scree slopes.

Saunders, Greg; Galland, Olivier; Mair, Karen

2014-05-01

326

Slope failures on the flanks of the western Canary Islands  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Landslides have been a key process in the evolution of the western Canary Islands. The younger and more volcanically active Canary Islands, El Hierro, La Palma and Tenerife, show the clearest evidence of recent landslide activity. The evidence includes landslide scars on the island flanks, debris deposits on the lower island slopes, and volcaniclastic turbidites on the floor of the adjacent ocean basins. At least 14 large landslides have occurred on the flanks of the El Hierro, La Palma and T...

Masson, Dg; Watts, Ab; Gee, Mjr; Urgeles, R.; Mitchell, Nc; Le Bas, Tp; Canals, M.

2002-01-01

327

North Slope Decision Support for Water Resource Planning and Management  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project was to enhance the water resource decision-making process with respect to oil and gas exploration/production activities on Alaska’s North Slope. To this end, a web-based software tool was developed to allow stakeholders to assemble, evaluate, and communicate relevant information between and amongst themselves. The software, termed North Slope Decision Support System (NSDSS), is a visually-referenced database that provides a platform for running complex natural system, planning, and optimization models. The NSDSS design was based upon community input garnered during a series of stakeholder workshops, and the end product software is freely available to all stakeholders via the project website. The tool now resides on servers hosted by the UAF Water and Environmental Research Center, and will remain accessible and free-of-charge for all interested stakeholders. The development of the tool fostered new advances in the area of data evaluation and decision support technologies, and the finished product is envisioned to enhance water resource planning activities on Alaska’s North Slope.

Schnabel, William; Brumbelow, Kelly

2013-03-31

328

Climbing in hexapods: a plain model for heavy slopes.  

Science.gov (United States)

Usually, a climbing cockroach attaches with three legs to a substrate. According to a recent model study, pulling forces underneath the front leg are required at some critical slope angle in upward locomotion. This critical angle depends on the animal's anatomy and leg positioning. In this study, we asked especially how this critical angle can be biased by one parameter that may be controlled during climbing: the body height above the substrate. We found that the typical ratio between body height and length (0.2) adopted by cockroaches is slightly higher than the very ratio (0.15) at which the critical slope angle can be increased most strongly for a given decrease in body height. In other words, it is likely that a geometrical body design of cockroaches evolved, which enables a delicate reduction in body height perfectly suitable for preventing the danger of slipping or even falling over rearwards at steepening slopes (approaching the vertical). In that sense, our model predicts, not just for hexapods but rather for any three-point climber, that taking up a low ratio of body height to the distance between the foremost and the hindmost attachment point (very crouched posture) makes body height a good parameter for climbing control. PMID:22019507

Günther, Michael; Weihmann, Tom

2012-01-21

329

Some comments on dynamic stability of rock slopes  

Energy Technology Data Exchange (ETDEWEB)

Individual sedimentation cycles in the Miocene coal basin in Northwest Bohemia, where many of open-pit brown coal mines are situated, sometimes contain some sideritic mudstone interlayers. In order to facilitate continuous operation of the large excavators, these hard layers must be blasted prior to coal seam exploitation. Dynamic effects of these blasting operations on the rock slope stability are evaluated according to the critical values of particle velocities for sliding and failure of stripping slopes in the open-pit mines. The source of seismic waves was, in the experimental measurements, modelled by a cylindric charge of explosives which was put into the boreholes and tamped by sand. Seismic waves, namely radial component of particle velocities, generated by explosions were recorded at three sites of observation in the near zone of the seismic source using pairs of velocigraphs with different sensitivity at each of them. Resulting values of particle velocities were compared with macroscopic effects of individual explosions on the state of rock slopes which were documented by photos before and after every explosion. 3 refs., 4 figs.

Holub, K.; Stodulkova, S. [Academy of Sciences of the Czech Republic, Ostrava (Czech Republic). Inst. of Geonics

1999-11-01

330

Some comments on dynamic stability of rock slopes  

Energy Technology Data Exchange (ETDEWEB)

Individual sedimentation cycles in the Miocene coal basin in Northwest Bohemia, where many of open-pit brown coal mines are situated, sometimes contain some sideritic mudstone interlayers. In order to facilitate continuous operation of the large excavators, these hard layers must be blasted prior to coal seam exploitation. Dynamic effects of these blasting operations on the rock slope stability are evaluated according to the critical values of particle velocities for sliding and failure of stripping slopes in the open-pit mines. The source of seismic waves was, in the experimental measurements, modelled by a cylindric charge of explosives which was put into the boreholes and tamped by sand. Seismic waves, namely radial component of particle velocities, generated by explosions were recorded at three sites of observation in the near zone of the seismic source using pairs of velocigraphs with different sensitivity at each of them. Resulting values of particle velocities were compared with macroscopic effects of individual explosions on the state of rock slopes which were documented by photos before and after every explosion. 3 refs., 4 figs.

Holub, K.; Stodulkova, S. (Academy of Sciences of the Czech Republic, Ostrava (Czech Republic). Inst. of Geonics)

1999-01-01

331

Native plants for erosion control in urban river slopes  

Directory of Open Access Journals (Sweden)

Full Text Available Mechanical and structural erosion of soils is produced by the loss of the vegetal cover and the action of rain on unprotected surfaces. Raindrop impact, transport and sediment deposition leads to landslides and slope instability and soil loss. In Costa Rica, water bodies have been negatively impacted by urban development and both water resources and soils have become more vulnerable. This is the case of the Pirro river micro watershed where riverbed vegetation has been replaced by constructions producing erosion problems in its slopes. In order to evaluate how native plants favor sediment control and prevent this sediment from been deposited in the river, eight experimental plots were installed. Four treatments were established: A (Costus pulverulentus Presl, B (Heliconia tortuosa (Griggs Standl., C (Vetiveria zizanioides (L. Nash and D (control. Sediments were collected weekly during the rainy and transitional seasons. A clear relation between rainfall intensity and sediment production was determined, particularly for intensities higher than 50 mm h-1. Significant differences were also determined between the treatments and the efficiency order was B >A > C >D, with the native plants being the most efficient in terms of sediment control. The use of native plants is recommended for the management and rehabilitation of slopes near urban rivers due to their ecological value and their capability for sediment control.

Virginia Alvarado

2014-03-01

332

An Adaptive Slope Compensation Circuit and its Application  

Directory of Open Access Journals (Sweden)

Full Text Available To resolve over-compensation problem in the current mode PWM switch power, a new adaptive slope compensation circuit is proposed in this study. In the circuit, the difference between the output and input voltage is positive correlative with the duty cycle of switch signal which is used to generate the control signal varying with the duty ratio. The control signal is used to control the gate voltage of MOS operating in linear region which changes the linear drain-source resistance. With clamping circuit, a proportional ramp voltage with controllable slope is produced and amplified for compensation system by two stage amplifier. This compensation voltage is almost ideal which can reduce the negative effect of over-compensation farthest. This circuit is applied to an LED driver IC and simulated in Cadence with CSMC 0.5um BiCMOS library. The results show that the boost driver circuit using adaptive compensation has about 28% dynamic response time reducing compared with the settled slope compensation. Therefore the proposed compensation circuit can improve systems dynamic responsibility effectively.

Chen Guanghua

2013-01-01

333

Road surface drainage, channel initiation, and slope instability  

Science.gov (United States)

Field surveys of road drainage concentration at three sites in the western United States are used to test simple models relating channel initiation and shallow landsliding to ground slope and contributing area thresholds. The form of boundaries between data for locations where road drainage concentration is associated with either shallow landsliding, channel initiation by overland flow, or no observable geomorphic effect is consistent with theoretically derived drainage area-slope relations. Comparison of survey data with results of previous studies in these areas indicates that the drainage area required to support a channel head is smaller for road-related runoff than for undisturbed slopes. Contrary to current land management paradigms in the Pacific Northwest, drainage concentration from ridgetop roads may cause both landsliding and integration of the channel and road networks. Road drainage concentration increases the effective length of the channel network and strongly influences the distribution of erosional processes in each of the study areas. The approach of using field reconnaissance to establish thresholds for erosion associated with road drainage provides a useful method to define regional criteria for road design that should reduce impacts on downstream channel systems.

Montgomery, David R.

1994-06-01

334

The nuclear cusp slopes of dwarf elliptical galaxies  

CERN Document Server

We derive the light profiles for a sample of 25 dwarf elliptical galaxies observed by us with HST/WFPC2 in F555W and F814W. These profiles are fitted with Nuker, R^1/4, exponential, and Sersic laws, and are also used to derive the nuclear cusp slopes gamma. We discuss the correlation of nuclear cusp slope with galactic luminosity, presence of a nucleus, and type of light profile. The results are compared to those found in the literature for elliptical galaxies and the bulges of spiral galaxies. We find that as a class the nuclear regions of dwarf ellipticals are very similar to those of the exponential bulges of spiral galaxies, and have nuclear cusp slopes shallower than those of bulges that were well fitted by a de Vaucouleurs R^1/4 profile with the same luminosity. For the 14 nucleated galaxies in our sample this conclusion is less certain than for the 11 non-nucleated objects since it relies on an extrapolation of galaxy light under the nucleus. In terms of their light profiles and nuclear properties, mos...

Stiavelli, M; Ferguson, H C; Mack, J; Whitmore, B C; Lotz, J

2000-01-01

335

Quasi-stable Slope-Failure Dams in High Asia  

Science.gov (United States)

Collapses of steep mountain slopes in the Himalaya, Karakoram, Pamir, Hindu Kush, and Tibetan Plateau are well known as a result of:(1) generally high seismicity in active tectonic areas; (2) prior deglaciation leaving undercut, unstable cliffs; (3) present-day debuttressing of rock cliffs by glacial down-wasting in conditions of global warming; and (4) degradation of permafrost cohesion and water-ice cementation in high mountain slopes. Landslide dams across mountain rivers are also well known worldwide and generally do not endure for long because of the common landslide-lake outburst floods (LLOF) whose discharge is commonly sufficiently large to remove much of the dam in a short time. A number of massive slope-failure dams in south High Asia, however, have endured for centuries and require explanations for the length of duration, whereas recent examples require robust assessment for better predictive hazard analysis. Three main factors contribute to longevity of slope-failure dams: (1) mega-rocks >15-30 m that inhibit dam failure in overflow breaches; (2) mega-porosity wherein incoming discharge to the landslide lake is balanced by subterranean water through-flow within the landslide dam; (3) impermeable clay fills caused by remobilization of prior lacustrine-dammed sediment that impart dam strength to allow lasting integrity for a time, and (4) climate-change induced lake-level lowering. Several examples of long-lived or unusually stable, slope-failure dams associated with pronounced structural/tectonic associations include: (1) Pangong Tso, Ladakh and Tibet; (2) Lake Shewa, Afghanistan; (3) Sarez Lake, Tajikistan; and (4) Lake Hunza, Pakistan. Pangong Tso and Lake Shewa were emplaced thousands of years ago and only Lake Shewa shows some instability of the dam front where percolating water maintains lake level but may be causing new slumping. Sarez Lake behind the Usoi landslide dam was emplaced by an earthquake in 1911 and maintains its level by seepage. Lake Hunza developed behind a new landslide dam in 2010 but remobilized lacustrine clay from a prior damming event and large blocks have maintained dam integrity in spite of overflow beginning 29 May 2010. Character and condition of landslide dams clearly controls whether LLOF or stability will prevail.

Shroder, J. F.

2010-12-01

336

Asymmetric craters on Vesta: Impact on sloping surfaces  

Science.gov (United States)

Cratering processes on planetary bodies happen continuously and cause the formation of a large variety of impact crater morphologies. On Vesta whose surface has been imaged at high resolution during a 14 months orbital mission by the Dawn spacecraft we identified a substantial number of craters with an asymmetrical shape. These craters, in total a number of 2892 ranging in diameter from 0.3 km to 43 km, are characterized by a sharp crater rim on the uphill side and a smooth one on the downhill side. The formation of these unusual asymmetric impact craters is controlled by Vesta's remarkable topographic relief. In order to understand the processes creating such unusual crater forms on a planetary body with a topography like Vesta we carried out the following work packages: (1) the asymmetric craters show various morphologies and therefore can be subdivided into distinct classes by their specific morphologic details; (2) using a digital terrain model (DTM), the craters are grouped into bins of slope angles for further statistical analysis; (3) for a subset of these asymmetric craters, the size-frequency distributions of smaller craters superimposed on their crater floors and continuous ejecta are measured in order to derive cratering model ages for the selected craters and to constrain possible post-impact processes; (4) three-dimensional hydrocode simulations using the iSALE-3D code are applied to the data set in order to quantify the effects of topography on crater shape and ejecta distribution. We identified five different classes (A-E) of asymmetric craters. Primarily, we focus on class A in this work. The global occurrence of these crater classes compared with a slope map clearly shows that these asymmetric crater types exclusively form on slopes. We found that slopes, especially slopes >20°, prevent the deposition of ejected material in the uphill direction, and slumping material superimposed the deposit of ejecta on the downhill side. The combination of these two processes explains the local accumulation of material in this direction. In the subset of asymmetric craters which we used for crater counts, our results show that no post-impact processes have taken place since floors and continuous ejecta in each crater show comparable cratering model ages within the uncertainties of the cratering chronology model. Therefore the formation, or modification, of the asymmetric crater forms by processes other than impact can be excluded with some certainty.

Krohn, K.; Jaumann, R.; Elbeshausen, D.; Kneissl, T.; Schmedemann, N.; Wagner, R.; Voigt, J.; Otto, K.; Matz, K. D.; Preusker, F.; Roatsch, T.; Stephan, K.; Raymond, C. A.; Russell, C. T.

2014-11-01

337

Performance of the Bowen ratio systems on a 22 deg slope  

Science.gov (United States)

The Bowen ratio energy balance technique was used to assess the energy fluxes on inclined surfaces during the First ISLSCP Field Experiment (FIFE). Since air flow over sloping surface may differ from that over flat terrain, it is important to examine whether Bowen ratio measurements taken on sloping surfaces are valid. In this study, the suitability of using the Bowen ratio technique on sloping surfaces was tested by examining the assumptions that the technique requires for valid measurements. This was accomplished by studying the variation of Bowen ratio measurements along a selected slope at the FIFE site. In September 1988, four Bowen ratio systems were set up in a line along the 22 degree north-facing slope with northerly air flow (wind went up the slope). In July of 1989, six Bowen ratio systems were similarly installed with southerly air flow (the wind went down slope). Results indicated that, at distances between 10 to 40 meters from the top of the slope, no temperature or vapor pressure gradient parallel to the slope was detected. Uniform Bowen ratio values were obtained on the slope, and thus the sensible or latent heat flux should be similar along the slope. This indicates that the assumptions for valid flux measurements are reasonably met at the slope. The Bowen ratio technique should give the best estimates of the energy fluxes on slopes similar to that in this study.

Nie, D.; Flitcroft, I.; Kanemasu, E. T.

1990-01-01

338

Assessment of Rockfall Hazard along the Road Cut Slopes of State Highway-72, Maharashtra, India  

Directory of Open Access Journals (Sweden)

Full Text Available Rockfall is a major problem in high hill slopes and rocky mountainous regions and construction of highways at these rockfall prone areas often require stable slopes. The causes of rockfall are presence of discontinuities, high angle cut slopes, heavy rainfall, and unplanned slope geometry etc. Slope geometry is one of the most triggering parameters for rockfall, when there are variations in slope angle along the profile of slope. The Present study involves rockfall hazard assessment of road cut slopes for 15 km distance starting from Mahabaleshwar town along State Highway-72 (SH-72. The vertical to subvertical cut slopes are prone to instability due to unfavorable orientation of discontinuities in slope face of weathered and altered basaltic rockmass. The predominant type of instability has been found as wedge type failure involving medium to large size blocks. In order to investigate the existing stability conditions, analyses were carried out at two locations under different slope conditions. The kinematic analysis was performed using stereographic projection method. RockFall 4.0 numerical simulator software was used to calculate the maximum bounce heights, total kinetic energies and translational velocities of the falling rockmass blocks, and a comparative analysis is presented with increasing the mass of blocks and height of the slope. The result of numerical analysis shows that varying slope angle geometry creates more problems as compared to the mass of blocks in the scenario of rockfall.

M. Ahmad

2013-01-01

339

ANALYSIS OF EXISTING METHODS OF STUDY OF STRAIN-STRESS STATE OF ROCKS ON SLIP SLOPE  

Directory of Open Access Journals (Sweden)

Full Text Available The methods for analysis of strain-stress state of rocks on slip slope as well as the methods of study of engineering and geological properties of rocks that compose the slip slope are considered.

Ye. Ugnenko

2010-01-01

340

Trophic ecology of deepwater fishes associated with the continental slope of the eastern Norwegian Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In June 1995 and 1996 demersal fishes on the continental slope of the eastem Norwegian Sea were sampled to study distribution patterns and community structure. The diets of the more abundant slope species were characterised and linkages within the upper slope food-web identified. Few cases of predator-prey relationships between the typical slope fishes were found. Most of the smaller fishes fed on epibenthic crustaceans such as amphipods and mysids, while pelagic crustaceans and fish dominate...

Bergstad, Odd Aksel; Bjelland, Otte

1998-01-01

 
 
 
 
341

Vegetated Flow down a Slope under a Uniform Rainfall  

Science.gov (United States)

To understand the effect of vegetation on flow velocity and water depth, a semi-analytical approach was proposed to study flow passing over a finite thick vegetated area under a uniform rainfall event. In this study, the flow region is divided into three layers-- homogenous water layer, mixed water-plant layer and finite thick soil layer (briefly denoted by water layer, vegetation layer, and soil layer). The flow of the water layer is governed by the Navier-Stokes equations. The vegetation and soil layers are both regarded as porous media and a laminar model modified from Biot's theory of poroelasticity is applied. The semi-closed solutions were obtained via the Runge-Kutta method. The flow profiles on a vegetated slope with different slopes were graphed. Accordingly, the relation between vegetation and water depth was divided into three patterns-- submerged vegetation, emergent vegetation and submerged-emergent vegetation. The velocity profiles for these patterns at each location were estimated. The retardation of vegetation causes that the velocity in vegetation layer is much slower than that in water layer and thus an inflection point exists inside the vegetation layer. This phenomenon doesn't happen in the case of emergent vegetation. The nonzero velocity at the ground surface is also estimated, and the velocity in the soil layer decays quickly to a constant. The shear stress distribution for different diameters of vegetation in the case of submerged vegetation was estimated. There is a positive correlation between the diameter of vegetation and the retardation of vegetation. Therefore the shear stress is influenced by the diameter of vegetation. The shear stress inside the water layer increases with the diameter of vegetation while the shear stress inside the vegetation layer decreases with the diameter of vegetation. This implies that the vegetation on the slope can protect the soil erosion.

Hsieh, P.; Hu, S.

2012-12-01

342

Slopes To Prevent Trapping of Bubbles in Microfluidic Channels  

Science.gov (United States)

The idea of designing a microfluidic channel to slope upward along the direction of flow of the liquid in the channel has been conceived to help prevent trapping of gas bubbles in the channel. In the original application that gave rise to this idea, the microfluidic channels are parts of micro-capillary electrophoresis (microCE) devices undergoing development for use on Mars in detecting compounds indicative of life. It is necessary to prevent trapping of gas bubbles in these devices because uninterrupted liquid pathways are essential for sustaining the electrical conduction and flows that are essential for CE. The idea is also applicable to microfluidic devices that may be developed for similar terrestrial microCE biotechnological applications or other terrestrial applications in which trapping of bubbles in microfluidic channels cannot be tolerated. A typical microCE device in the original application includes, among other things, multiple layers of borosilicate float glass wafers. Microfluidic channels are formed in the wafers, typically by use of wet chemical etching. The figure presents a simplified cross section of part of such a device in which the CE channel is formed in the lowermost wafer (denoted the channel wafer) and, according to the present innovation, slopes upward into a via hole in another wafer (denoted the manifold wafer) lying immediately above the channel wafer. Another feature of the present innovation is that the via hole in the manifold wafer is made to taper to a wider opening at the top to further reduce the tendency to trap bubbles. At the time of reporting the information for this article, an effort to identify an optimum technique for forming the slope and the taper was in progress. Of the techniques considered thus far, the one considered to be most promising is precision milling by use of femtosecond laser pulses. Other similar techniques that may work equally well are precision milling using a focused ion beam, or a small diamond-tipped drill bit.

Greer, Harold E.; Lee, Michael C.; Smith, J. Anthony; Willis, Peter A.

2010-01-01

343

Numerical simulations of dense water cascading on a steep slope  

Science.gov (United States)

Flows of dense shelf waters down the continental slope - cascades - contribute to the formation of intermediate and bottom waters and are believed to be influential in the off-shelf transport of carbon and other suspended or dissolved matter. We study cascading over steep bottom topography in numerical experiments using POLCOMS, a 3-D ocean circulation model employing a terrain-following s-coordinate system. The model setup is based on a laboratory experiment of a continuous dense water flow from a central source on a steep conical slope (39° ) in a rotating tank. The descent of the dense water mass as characterised by the length of the plume as a function of time is studied for a range of experimental parameters, mainly the density difference between plume and ambient water, the flow rate and the speed of rotation. Very good agreement between the model and the laboratory results is shown in dimensional and nondimensional variables. Our results demonstrate that a hydrostatic model is capable of reproducing the essential physics of cascading on a very steep slope if the model correctly resolves velocity veering in the bottom boundary layer. Our 3-D modelling confirms findings previously obtained by reduced physics models for a 2-layer flow. We further explore the dynamics of cascading outside of the controlled laboratory conditions in model runs where viscosity and/or diffusivity are modified. The limits of the reduced physics theory are identified in simulations with increased diffusivity where the cascade has a blurred interface between plume and ambient water and can no longer be considered a 2-layer flow. We show that downslope transport is reduced when the plume interface is strongly diffused, but enhanced in a regime that simulates cascades with increased turbulence where diffusivity and viscosity are both increased. This work was partly funded by NERC's Core Research Programme Oceans 2025 and the EU FP7 MyOceans project.

Wobus, F.; Shapiro, G. I.; Maqueda, M. A. M.; Huthnance, J. M.

2012-04-01

344

Initial results of the 2011 Geoid Slope Validation Survey  

Science.gov (United States)

The National Oceanic and Atmospheric Administration's (NOAA), National Geodetic Survey (NGS) has embarked on a ten year project called GRAV-D (Gravity for the Redefinition of the American Vertical Datum).The purpose of this project is to replace the current official vertical datum, NAVD 88 (the North American Vertical Datum of 1988) with a geopotential reference system based on a new survey of the gravity field and a gravimetric geoid. As part of GRAV-D, NGS plans to execute a set of "geoid validation surveys" at various locations of the country.These will be surveys designed to independently measure the geoid to provide a check against both the data and theory used to create the final gravimetric geoid which will be used in the geopotential reference system. The first of these surveys, known as the Geoid Slope Validation Survey of 2011 (GSVS11) was executed between July and October, 2011 in the west central region of Texas.The survey took place over a 330 kilometer line running more or less north-south from Austin to Corpus Christi, Texas.Measurements were taken at 220 marks (one per mile) and included static GPS, RTN GPS, geodetic leveling, astro-geodetic deflections of the vertical using the Swiss DIADEM camera, absolute gravity, gravity gradients and LIDAR.This region was chosen for many factors including the availability of GRAV-D airborne gravity over the area, its relatively low elevation (220 meter orthometric height max), its geoid slope (about 130 cm over 300 km), lack of significant topographic relief, lack of large forestation, availability of good roads, clarity of weather and lack of large water crossings. This talk will outline the initial results of the survey, specifically the comparison of various geoid slopes over this region:gravimetric geoid models (with and without airborne gravity), minimally constrained GPS and leveling and from astro-geodetic deflections of the vertical.

Smith, D. A.

2011-12-01

345

29 CFR Appendix B to Subpart P of... - Sloping and Benching  

Science.gov (United States)

...with the requirements set forth in § 1926.652(b...classification. Soil and rock deposits shall be classified...allowable slope for a soil or rock deposit shall be determined...the slope shall be cut back to an actual slope which...for each layer as set forth below....

2010-07-01

346

Dynamic Slope Scaling Procedure to solve Stochastic Integer Programming Problem  

Directory of Open Access Journals (Sweden)

Full Text Available Stochastic programming deals with optimization under uncertainty. A stochastic programming problem with recourse is referred to as a two-stage stochastic problem. We consider the stochastic programming problem with simple integer recourse in which the value of the recourse variable is restricted to a multiple of a nonnegative integer. The algorithm of a dynamic slope scaling procedure to solve the problem is developed by using the property of the expected recourse function. The numerical experiments show that the proposed algorithm is quite efficient. The stochastic programming model defined in this paper is quite useful for a variety of design and operational problems.

Takayuki Shiina

2012-12-01

347

Ratio of slopes method for quantitative analysis in ceramic bodies  

International Nuclear Information System (INIS)

A quantitative x-ray diffraction analysis technique developed at University of Sheffield was adopted, rather than the previously widely used internal standard method, to determine the amount of the phases present in a reformulated whiteware porcelain and a BaTiO sub 3 electrochemical material. This method, although still employs an internal standard, was found to be very easy and accurate. The required weight fraction of a phase in the mixture to be analysed is determined from the ratio of slopes of two linear plots, designated as the analysis and reference lines, passing through their origins using the least squares method

348

Total Widths And Slopes From Complex Regge Trajectories  

CERN Document Server

Maximally complex Regge trajectories are introduced for which both Re positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to $\\epsilon$) goes to zero. A scaling formula for the total widths emerges: $\\Gamma_{TOT}/M\\to$ constant for large M, in very good agreement with data for mesons and baryons. The unitarity corrections also enhance the space-like slopes from their time-like values, thereby resolving an old problem with the $\\rho$ trajectory in $\\pi N$ charge exchange. Finally, the unitarily enhanced intercept, $\\alpha_{\\rho}\\approx 0.525$, \

Filipponi, S; Srivastava, Y N

1999-01-01

349

Conservation laws for shallow water waves on a sloping beach  

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Full Text Available Shallow water waves are governed by a pair of non-linear partial differential equations. We transfer the associated homogeneous and non-homogeneous systems, (corresponding to constant and sloping depth, respectively, to the hodograph plane where we find all the non-simple wave solutions and construct infinitely many polynomial conservation laws. We also establish correspondence between conservation laws and hodograph solutions as well as Bäcklund transformations by using the linear nature of the problems on the hodogrpah plane.

Yilmaz Akyildiz

1986-06-01

350

Application of reverse engineering for probabilistic assessment of slope stability  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents a back-analysis study of a landslide occurred on BR-153 Highway. The landslide history, the climate characteristics of the region and the geotechnical parameters obtained in a laboratory and field experimental program are presented. Retroanalysis shows that the rupture occurred due to groundwater rising to the soil surface. The estimated value of the rupture probability was influenced by the slope geometry, the groundwater position, position of critical surface and method of stability analysis, in addition to the variation in geotechnical parameters.

Paulo César de Almeida Maia

2010-05-01

351

Stability analysis of jointed rock slope by the block theory  

International Nuclear Information System (INIS)

The block theory to analyze three dimensional stability problems of discontinuous rock masses is applied to the actual discontinuous rock slope. Taking into consideration that the geometrical information about discontinuities generally increases according to progressive steps of rock investigation in field, the method adopted for analysis is divided into following two steps; 1) the statistical/probabilitical analysis using information from the primary investigation stage which mainly consists of that of natural rock outcrops, and 2) the deterministic analysis correspond to the secondary stage using exploration adits. (author)

352

Contrast Analysis on Fractional Order and Slope Correlation Accuracy  

Directory of Open Access Journals (Sweden)

Full Text Available In order to improve the correlation accuracy of correlation algorithm, the fractional order correlation algorithm of  uncertain time sequences is proposed in this paper. By taking advantage of the memory property of fractional order, the algorithm introduces the measurement of fractional order differential for the local trend of time sequence into the correlation algorithm and also analyzes the influences of differential order and noise upon correlation accuracy, provides selection relations between noise level and order. It has been proven with examples that the correlation accuracy of fractional order correlation algorithm has increased by one orders of magnitude as compared with slope correlation.

Mingliang Hou

2012-08-01

353

HDMR methods to assess reliability in slope stability analyses  

Science.gov (United States)

Stability analyses of complex rock-soil deposits shall be tackled considering the complex structure of discontinuities within rock mass and embedded soil layers. These materials are characterized by a high variability in physical and mechanical properties. Thus, to calculate the slope safety factor in stability analyses two issues must be taken into account: 1) the uncertainties related to structural setting of the rock-slope mass and 2) the variability in mechanical properties of soils and rocks. High Dimensional Model Representation (HDMR) (Chowdhury et al. 2009; Chowdhury and Rao 2010) can be used to carry out the reliability index within complex rock-soil slopes when numerous random variables with high coefficient of variations are considered. HDMR implements the inverse reliability analysis, meaning that the unknown design parameters are sought provided that prescribed reliability index values are attained. Such approach uses implicit response functions according to the Response Surface Method (RSM). The simple RSM can be efficiently applied when less than four random variables are considered; as the number of variables increases, the efficiency in reliability index estimation decreases due to the great amount of calculations. Therefore, HDMR method is used to improve the computational accuracy. In this study, the sliding mechanism in Polish Flysch Carpathian Mountains have been studied by means of HDMR. The Southern part of Poland where Carpathian Mountains are placed is characterized by a rather complicated sedimentary pattern of flysh rocky-soil deposits that can be simplified into three main categories: (1) normal flysch, consisting of adjacent sandstone and shale beds of approximately equal thickness, (2) shale flysch, where shale beds are thicker than adjacent sandstone beds, and (3) sandstone flysch, where the opposite holds. Landslides occur in all flysch deposit types thus some configurations of possible unstable settings (within fractured rocky-soil masses) resulting in sliding mechanisms have been investigated in this study. The reliability indices values drawn from the HDRM method have been compared with conventional approaches as neural networks: the efficiency of HDRM is shown in the case studied. References Chowdhury R., Rao B.N. and Prasad A.M. 2009. High-dimensional model representation for structural reliability analysis. Commun. Numer. Meth. Engng, 25: 301-337. Chowdhury R. and Rao B. 2010. Probabilistic Stability Assessment of Slopes Using High Dimensional Model Representation. Computers and Geotechnics, 37: 876-884.

Kozubal, Janusz; Pula, Wojciech; Vessia, Giovanna

2014-05-01

354

Triggering Mechanisms of Slope Instability Processes on the Gulf of Mexico Continental Slope: Preliminary Results From IODP Expedition 308  

Science.gov (United States)

The Ursa Basin lies ~100km downdip of the present mouth of the Mississippi River, northeastern Gulf of Mexico, at ~1000 m depth. In this area, large-scale Mass Transport Deposits (MTD) of Holocene and Pleistocene age were drilled at Sites U1322, U1323 and U1324 during IODP Expedition 308. Recent large landslides also occurred 1 to 10 km NE of the drilled sites. To illuminate the factors controlling initiation of past sediment failures and to characterize the hazard from future slope instabilities, a complete suite of logging data and direct measurements of moisture and density and undrained shear strength were acquired during Expedition 308. Preliminary results indicate that Ursa Basin has very high sedimentation rates, at least 10m/ky with peaks up to 25 m/ky. This has resulted in a particular porosity profile, with a relatively rapid decrease from 80% at seafloor to 55% at ~50 mbsf. Then, a gentler gradient is observed down to the bottom of the hole, with the lowest porosities at ~45%. Fluid overpressure estimated from the porosity profile and from pore pressure penetrometers indicates that the vertical effective stress is 50 to 60% lower than if hydrostatic conditions existed. The trends in density and undrained shear strength are relatively smoother at Site U1324 compared to Site U1322. At Site U1322 density and strength measurements show significant increases (up to 0.1 g/cm3 and 50 kPa respectively) associated with MTDs. This may indicate higher consolidation of MTD, which probably results from shearing and dewatering of the sediments during the landslide process. High sedimentation rates are a crucial factor leading to overpressure and slope instability at Ursa. The location, depth, thickness and amount of shearing in MTDs will further influence slope stability.

Urgeles, R.; Locat, J.; Flemings, P.; Behrmann, J.; John, C.

2005-12-01

355

Precision Tiltmeter as a Reference for Slope Measuring Instruments  

International Nuclear Information System (INIS)

The next generation of synchrotrons and free electron lasers require extremely high-performance x-ray optical systems for proper focusing. The necessary optics cannot be fabricated without the use of precise optical metrology instrumentation. In particular, the Long Trace Profiler (LTP) based on the pencil-beam interferometer is a valuable tool for low-spatial-frequency slope measurement with x-ray optics. The limitations of such a device are set by the amount of systematic errors and noise. A significant improvement of LTP performance was the addition of an optical reference channel, which allowed to partially account for systematic errors associated with wiggling and wobbling of the LTP carriage. However, the optical reference is affected by changing optical path length, non-homogeneous optics, and air turbulence. In the present work, we experimentally investigate the questions related to the use of a precision tiltmeter as a reference channel. Dependence of the tiltmeter performance on horizontal acceleration, temperature drift, motion regime, and kinematical scheme of the translation stage has been investigated. It is shown that at an appropriate experimental arrangement, the tiltmeter provides a slope reference for the LTP system with accuracy on the level of 0.1 (micro)rad (rms)

356

Storm size's effect on constant slope hydrograph separation method  

Science.gov (United States)

The two main components that make up stream flow are baseflow and runoff. Baseflow is important as it maintains flows during times of low precipitation and dryness. Its abundance is also an indicator of habitat. Hydrograph separation techniques are one of the methods used to determine the amount of baseflow in a gauged stream. One widely used and relatively simple hydrograph separation technique is the constant slope method. A limitation of this method is the problem associated with finding the inflection point which is determined by the equation N=A0.2 where N is the number of days past the peak of the hydrograph and A is the watershed area. The equation does not perform equally well in all watersheds and for all storm sizes. The objective of this project is to determine how sensitive the equation is to storm size. To determine this sensitivity, twenty storms ranging in size from (0.01 to 1 cm) were identified in two similarly sized gauged watersheds: the Kickapoo at La Farge (266 sq mi) and Pecatonica (273 sq mi). Hydrograph separation was done manually using the constant slope method and compared to inflection point determination using curve fitting software and USGS HYSEP minimum flow hydrograph separation.

Bowman, S. A.; Clancy, K. A.

2013-12-01

357

On the Landslide of Daigala Slope-Kurdistan-Iraq  

Directory of Open Access Journals (Sweden)

Full Text Available The strategic two-lane road (Erbil – Koya is the main link between Erbil and Suleymaniya governorates. It passes through Daigala bridge whose edge from Koya side is adjacent to a curved section which experienced a slope failure (Fig. 1 in the form of rotational sliding which progressed into a slump failure through the mechanism of “progressive failure” after the overburden soil and sediments were fully saturated with water due to some heavy rain storms which happened at the end of January 2013 leading to the loss of cohesive force and triggering that failure which was developed into a progressive failure by the action of additional loading which was imposed by the heavy traffic of big oil tankers which were running on the adjacent paved road. The research team tried to study and analyze this failure by collecting some soil samples (both disturbed and disturbed from the study area and performing different laboratory tests in addition to some in-situ field tests by using the “Inspection Vane Tester, H – 60” for the purpose of enabling this study and analysis. The location of the study area was described and illustrated by providing a location map and the geological settings were explained. As a theoretical background, the different modes of soil slopes failures and their conditions were presented. At the end, some conclusions of this study were outlined and few recommendations for future remedial measures were eventually made.

Assist. Prof. Dr. Hamed M. Jassim

2014-06-01

358

Sediment dispersal and accumulation in tectonic accommodation across the Gaoping Slope, offshore Southwestern Taiwan  

Science.gov (United States)

Distribution and architecture of slope basins across a continental slope vary as a consequence of accommodation forming, sediment dispersal rates, canyon cutting, sediment filling and different sediment transporting mechanisms. The area offshore Southwestern Taiwan is generally recognized as having active tectonics and high sediment deposition rates. In the Gaoping Slope, slope basins are formed by the developments of folds, faults and diapiric intrusions. Portions of the sediments discharged from the Taiwan mountain belt have been trapped in these basins in the Gaoping Shelf and Gaoping Slope. The rest of the sediments were transported to deep sea areas through submarine canyons. This complex system of folds, faults, diapirs, slope basins, submarine canyons, and sediment deposits has also readjusted the morphology of the Gaoping Slope. This study examines the linkage between accommodation spaces of tectonic and sedimentary processes in the Gaoping Slope through seismic facies analysis. Four seismic facies which include convergent-symmetrical facies, convergent-baselapping facies, chaotic facies, and parallel and drape facies, and different deposition patterns have been recognized in the Gaoping Slope basins. The thick mud layers which are regarded as the source of diapiric intrusions are first observed beneath the basin. Strata records show that the accommodation spaces in various slope basins have increased or decreased during different stages of basin evolution. Because of the competition between regional tectonism (accommodation space variations) and sediment routing distance from provenance to depository (sediment input variations), most under-filled basins lie in the lower slope domain in the Gaoping Slope, but also in the upper slope domain east of the Gaoping Submarine Canyon. This observation suggests that in the inner Gaoping Slope west of the Gaoping Submarine Canyon, sediment deposition rate is higher than the basin subsidence rate, the topography of the upper slope domain there is "healed", and most sediments are overfilled in the slope basins now. Besides the sequential steps of sedimentary disposal in the filling-and-spilling model, we have also observed evidences which indicate that mass movements and submarine canyons in the area have significantly changed the sediment dispersal patterns in the slope basins of the Gaoping Slope. We suggest that although filling-and-spilling is a key sedimentary process in the Gaoping Slope, tectonic activities, mass wasting events and canyon feeding processes have diversified sediment transporting mechanisms from the inner to outer slopes in the area offshore Southwest Taiwan.

Hsu, Ho-Han; Liu, Char-Shine; Yu, Ho-Shing; Chang, Jih-Hsin; Chen, Song-Chuen

2013-06-01

359

Variance-in-Mean Effects of the Long Forward-Rate Slope  

DEFF Research Database (Denmark)

This paper contains an empirical analysis of the dependence of the long forward-rate slope on the long-rate variance. The long forward-rate slope and the long rate are described by a bivariate GARCH-in-mean model. In accordance with theory, a negative long-rate variance-in-mean effect for the long forward-rate slope is documented. Thus, the greater the long-rate variance, the steeper the long forward-rate curve slopes downward (the long forward-rate slope is negative). The variance-in-mean effect is both statistically and economically significant.

Christiansen, Charlotte

2005-01-01

360

Large slope instabilities in Northern Chile and Southern Peru  

Science.gov (United States)

Deep canyon incision into Tertiary paleosurfaces and large slope instabilities along the canyon flanks characterize the landscape of western slope of the Andes of northern Chile and South Peru. This area belongs to the Coastal Escarpment and Precordillera and is formed by coarse-grained clastic and volcanoclastic formations. The area is characterized by intense seismicity and long-term hyperaridity (Atacama Desert). Landslides along the canyon flanks affect volumes generally up to 1 km3 and locally evolved in large rock avalanches. We prepared a landslide inventory covering an area of about 30,000 km2, extending from Iquique (Chile) to the South and Tacna (Peru) to the North. A total of 606 landslides have been mapped in the area by use of satellite images and direct field surveys, prevalently including large phenomena. The landslides range from 1 10-3 km2 to 464 km2 (Lluta landslide). The total landslide area, inclusive of the landslide scarp and of the deposit, amounts to about 2,130 km2 (about 7% of the area). The mega landslides can be classified as large block slides that can evolve in large rock avalanches (e.g. Minimini landslide). Their initiation seems to be strongly associated to the presence of secondary faults and large fractures transversal to the slope. These landslides show evidence suggesting a re-incision by the main canyon network. This seems particularly true for the Lluta collapse where the main 'landslide' mass is masked or deleted by the successive erosion. Other landslides have been mapped along the Coastal Escarpment and some of the major tectonic escarpments with an E-W trend. We examined area-frequency distributions of landslides by developing logarithmically binned, non-cumulative size frequency distributions that report frequency density as a function of landslide planar area A. The size frequency distribution presents a strong undersampling for smaller landslides, due to the extremely old age of the inventory. For landslides larger than 2 000 m2, the distribution exhibits a power-law behaviour with scaling exponent, ?, equal to -2.24. For comparison, we analysed the power-law behaviour of other earthquake-induced landslide inventories, obtaining similar results, although the geological and seismic conditions may have been very different (Buller, New Zealand, ? = -2.42; Iningahua, New Zealand, ? = -2.53; Northridge, USA, ? = -2.39; Chi-Chi, Taiwan, ? = -2.30; Wenchuan Earthquake, China, ? = -2.19). Volume estimates and slope stability modelling have been completed to characterize the phenomena and the possible triggering mechanisms. For volume estimate, we reconstructed the pre-failure surface for tens of landslides, in order to characterize the area-volume relationship. By using this relationship, we assigned a volume to all landslides of the inventory. The study area is subject to a high seismicity associated to earthquakes of different type: interplate (superficial and intermediate depth), subduction zone earthquakes, and earthquake along the Coastal Escarpment. By analysing the frequency size relationships for earthquake-induced landslides from literature, it is possible to observe that the higher the earthquake Magnitude, the higher the frequency density curve. To quantify this observation, we used the power-law relationships derived for each inventory to calculate the frequency density associated to selected areas, and we plotted these frequencies as a function of the magnitude of the respective earthquakes. By fitting these values, we derived the expected Magnitude required to generate the landslide distribution of the study area. In conclusion, we argue that the evolution of these landslides is controlled by: deep valley incision, canyon walls undercutting and lateral migration of the river controlled by valley flank instabilities, the Presence of weak lithologies and weak basal layers, the river incision debuttressing the slope toe and especially brings to daylighting the weak basal layers observed at some landslide sites, the possible deep groundwater flow above the deep imperm

Crosta, Giovanni B.; Hermanns, Reginald L.; Valbuzzi, Elena; Frattini, Paolo; Valagussa, Andrea

2014-05-01

 
 
 
 
361

Research on the Slope Green and Environment Protection Using Dynamical Game Theory  

Directory of Open Access Journals (Sweden)

Full Text Available This study aims to investigate the slope green and environment protection in China. In ecological slope protection, the plant roots can achieve the ecological vegetation restoration of the slope surface. Hence the slope environment can be protected significantly. However, there is still lack of efficient policy to support the implementation of nationwide slope green program to facilitate the development of slope green and environment protection technologies. Hence, the reasonable relationship between the slope green and environment protection and the national policy is very important. Literature review indicates that very little work has been done to address this issue. In order to investigate the relationship between the slope green and environment protection and the national policy, this study presents a new analysis method based on the dynamical Game theory. The game between the slope green and environment protection and the national policy can be regarded as a dynamical economic process, the optimized implementation strategy for the slope green and environment protection under the national support can be obtained by the use of dynamical game analysis. The stability analysis and the balance analysis have been discussed for the proposed game model. The analysis result shows that the government should increase financial support as well as establish corresponding punishment mechanism to encourage different policies and practices for slope green and environment protection and hence a win-win situation can be achieved.

Juan Wan

2013-10-01

362

Dynamic stability and failure modes of slopes in discontinuous rock mass  

International Nuclear Information System (INIS)

The stability of rock slopes during earthquakes are of great concern in rock engineering works such as highway, dam, and nuclear power station constructions. As rock mass in nature is usually discontinuous, the stability of rock slopes will be geverned by the spatial distribution of discontinuities in relation with the geometry of slope and their mechanical properties rather than the rock element. The authors have carried out some model tests on discontinuous rock slopes using three different model tests techniques in order to investigate the dynamic behaviour and failure modes of the slopes in discontinuous rock mass. This paper describes the findings and observations made on model rock slopes with various discontinuity patterns and slope geometry. In addition some stability criterions are developed and the calculated results are compared with those of experiments. (author)

363

Thresholds for the slope ratio in determining transition time and quantifying diffuser performance in situ  

DEFF Research Database (Denmark)

This study is concerned with an objective measure called the slope ratio that can detect acoustic defects due to unexpected pressure increases such as strong reflections and coincidental constructive interference. The slope ratio is the ratio of the instantaneous slope to the mean slope in a decay curve. The slope ratio was suggested for determining the room acoustic transition time experimentally, but its threshold criteria have not been thoroughly investigated. The thresholds for the slope ratio, particularly for applications such as determining the room acoustic transition time and quantifying in situ diffuseness, are examined for various room impulse responses. For the tested rooms, a slope ratio threshold of 11 gives the most consistent and systematic results.

Jeong, Cheol-Ho; Jacobsen, Finn

2012-01-01

364

Evaluation and forecast distribution of radionuclides and dose in the model slope ecosystems for landscape ukraine  

Directory of Open Access Journals (Sweden)

Full Text Available  For the analysis of ecological safety in typical of slope`s ecosystem the block-scheme of ecosystem is created. From nature  of data and on the basis of the theoretical analysis the parameters of speeds of transitions of pollutant (Cs-137 are chosen. On this basis modeling processes of migration and relocation of radionuclides  in a typical slope by a method of box models is carried out. Is shown, that actively and quickly enough redistributes radionuclides. As a result of modeling it is possible to estimate and  to prognose  of dynamics  of distribution radionuclides  in typical of slope`s  ecosystem and to establish probable   of dose   loading on the people, which use parts such  slope`s ecosystem.

?.?. ??????????

2006-02-01

365

Predicting Modes and Displacements of Seismic Rock Slope Failures  

Science.gov (United States)

Seismically induced rock slope failures have resulted in billions of dollars of economic damage and enormous loss of life throughout the world. Accurate prediction of the triggering and run out of these failures is elusive for a variety of reasons, including knowledge of the physical modes of failure. Our research explores the potential failure modes of an idealized rigid rock block and expands the modes typically considered to include not only sliding but also toppling (pure forward rotation) and slumping (combined backward rotation and translation). The yield acceleration (or minimum inertial acceleration to cause block movement) for slumping, similar to toppling, is found to be lower than for pure translational sliding. These yield accelerations indicate the initial modes of rock block failure; however, they do not always predict the ultimate failure mode. To predict the final failure modes, the results of discrete element numerical analyses were compared to pseudo static yield acceleration to develop a seismic failure mode decision-making chart based on block geometry and interface friction. With regard to seismic displacement predictions, current simplified models predicting ultimate displacement of a mass under seismic conditions are limited to purely translating, sliding blocks (i.e. Newmark's sliding block method). Our modeling introduces additional simplified analyses to predict ultimate displacement in toppling and slumping modes as well. Important findings from these new methods are that the magnitude of seismically-induced displacement is dependent on the size of the block (or failure mass) and that as the yield acceleration decreases the seismically induced displacements increase. We plan to map these tools into analyses that evaluate rock slope systems with complex geology and geotechnical characteristics. It is envisioned that the decision chart, which predicts the initial and ultimate modes of failure based on block geometry and interface friction, and the toppling and slumping displacement models can be used to enhance seismic hazard evaluations for rock slope failure at both regional and site-specific scales. Financial support for this research was provided by the United States National Science Foundation (NSF) under grant CMMI-1156413.

Gibson, M. D.; Wartman, J.; Keefer, D. K.; Maclaughlin, M.; Arnold, L.; Applegate, K. N.; Smith, S.; Adams, S.

2013-12-01

366

Weathering-related Slope Instabilities of The Calabrian Arc (italy)  

Science.gov (United States)

Weathered igneous and metamorphic rocks widely crop out in the Mediterranean area, where in recent years greater attention has been paid to weathering-related slope movements. Calabria, the southernmost region of the Italian peninsula, is one of the most challenging area where to study such topic. Many factors favoured during past times onset and development of the weathering processes in Calabria: huge geody- namic events, still active today as proved by regional seismicity; high uplifting rate; long history of exposition to weathering agents; aggressive climatic conditions, char- acterized by intense, locally clustered, rainfall. In the late '80s a wide research pro- gramme was started in Calabria with the aim of defining an integrated, multidisci- plinary method, suitable to analyse and interpret both the weathering processes and the related instability phenomena. Two were the main goals of the research: a) the engineering-geological characteristics of weathered terrains; and b) the understanding of typology, mechanisms and triggering causes of mass movements. The research was carried out on several test sites distributed over the Calabrian Arc, a complex chain formed by several massifs (Coastal Chain, Sila, Serre, Poro, Aspromonte), largely made up of crystalline rocks. Choice of the sites was also dictated by the presence of important man-made structures (settlements, dams, tunnels, etc.) and the conse- quent availability of specific geological and geotechnical data. A summary of the re- sults so far obtained in the definition of the weathering characteristics of Calabrian crystalline rocks, in type and frequency of slope movements in weathered materials, and in the understandings of the main relations between weathering and instability as well, is here presented. In general terms, weathering in Calabria shows a complex profile, characterized by pronounced irregularity in the spatial distribution of weath- ered horizons. The latter have been recognized up to a depth of 150-200 m from the ground surface, where only occasionally fresh volumes are present. Mass movements range from slide-flows to rock instabilities, including also deep-seated phenomena. Frequency and activity of slope movements seems to be strictly related to outcropping of the more weathered horizons.

Calcaterra, D.; Parise, M.

367

Check dams effects on sediment transport in steep slope flume  

Science.gov (United States)

Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the bed level. As long as they are not buried by too strong aggradation they allow a 'bed level independence' between reaches. On the long term, as the total inlet flux is kept constant, a decrease in transported volumes induces an increase in the erosion event frequency: sediment releases are more frequent but littler. As proposed by Poncet (1995), check dams participate efficiently in hazard mitigation because 'they release in retail what torrents would too abruptly delivered wholesale'. Reference : Poncet, A. "Restauration et conservation des terrains en montagne." Office national des forêts, Paris (1995).

Piton, Guillaume; Recking, Alain

2014-05-01

368

Biocorrosive Thermophilic Microbial Communities in Alaskan North Slope Oil Facilities  

Energy Technology Data Exchange (ETDEWEB)

Corrosion of metallic oilfield pipelines by microorganisms is a costly but poorly understood phenomenon, with standard treatment methods targeting mesophilic sulfatereducing bacteria. In assessing biocorrosion potential at an Alaskan North Slope oil field, we identified thermophilic hydrogen-using methanogens, syntrophic bacteria, peptideand amino acid-fermenting bacteria, iron reducers, sulfur/thiosulfate-reducing bacteria and sulfate-reducing archaea. These microbes can stimulate metal corrosion through production of organic acids, CO2, sulfur species, and via hydrogen oxidation and iron reduction, implicating many more types of organisms than are currently targeted. Micromolar quantities of putative anaerobic metabolites of C1-C4 n-alkanes in pipeline fluids were detected, implying that these low molecular weight hydrocarbons, routinely injected into reservoirs for oil recovery purposes, are biodegraded and provide biocorrosive microbial communities with an important source of nutrients.

Duncan, Kathleen E.; Gieg, Lisa M.; Parisi, Victoria A.; Tanner, Ralph S.; Green Tringe, Susannah; Bristow, Jim; Suflita, Joseph M.

2009-09-16

369

REVIEW OF HIGH FIELD Q SLOPE, CAVITY MEASUREMENTS  

Energy Technology Data Exchange (ETDEWEB)

One of the most interesting phenomenon occurring in superconducting radio-frequency (SRF) cavities made of bulk niobium is represented by a sharp decrease of the quality factor above peak surface magnetic field of about 90 mT and is referred to as "high field Q-slope" or "Q-drop". This phenomenon was observed first in 1997 and since then some effort was devoted to the understanding of the causes behind it. Still, no clear physical interpretation of the Q-drop has emerged, despite several attempts. In this contribution, I will review the experimental results for various cavities measured in many laboratories and I will try to identify common features and differences related to the Q-drop.

Gianluigi Ciovati

2008-01-23

370

Air-cushion tankers for Alaskan North Slope oil  

Science.gov (United States)

A concept is described for transporting oil from the Arctic to southern markets in 10,000-ton, chemically fueled air-cushion vehicles (ACV's) configured as tankers. Based on preliminary cost estimates the conceptual ACV tanker system as tailored to the transportation of Alaskan North Slope oil could deliver the oil for about the same price per barrel as the proposed trans-Alaska pipeline with only one-third of the capital investment. The report includes the description of the conceptual system and its operation; preliminary cost estimates; an appraisal of ACV tanker development; and a comparison of system costs, versatility, vulnerability, and ecological effect with those of the trans-Alaska pipeline.

Anderson, J. L.

1973-01-01

371

Biocorrosive thermophilic microbial communities in Alaskan North Slope oil facilities.  

Science.gov (United States)

Corrosion of metallic oilfield pipelines by microorganisms is a costly but poorly understood phenomenon, with standard treatment methods targeting mesophilic sulfate-reducing bacteria. In assessing biocorrosion potential at an Alaskan North Slope oil field, we identified thermophilic hydrogen-using methanogens, syntrophic bacteria, peptide- and amino acid-fermenting bacteria, iron reducers, sulfur/thiosulfate-reducing bacteria, and sulfate-reducing archaea. These microbes can stimulate metal corrosion through production of organic acids, CO2, sulfur species, and via hydrogen oxidation and iron reduction, implicating many more types of organisms than are currently targeted. Micromolar quantities of putative anaerobic metabolites of C1-C4 n-alkanes in pipeline fluids were detected, implying that these low molecular weight hydrocarbons, routinely reinjected into reservoirs for oil recovery purposes, are biodegraded and can provide biocorrosive microbial communities with an important source of nutrients. PMID:19921923

Duncan, Kathleen E; Gieg, Lisa M; Parisi, Victoria A; Tanner, Ralph S; Tringe, Susannah Green; Bristow, Jim; Suflita, Joseph M

2009-10-15

372

Investigation of continuously variable slope delta modulator/demodulator compatibility  

Science.gov (United States)

A computer model of the continuously variable slope delta voice encoding system specified in the draft STANAG on "Analogue/Digital Conversion of Speech Signals for Tactical, Digital Area Communication Systems", dated June 1978, is developed and implemented in FORTRAN IV. The model's performance is then characterized in terms of idle channel noise, total harmonic distortion, intermodulation distortion, signal-to-noise ratio, and frequency response. For each of these attributes, the system's performance is presented graphically and compared to the criteria established in the draft standard. The model is then exercised by varying the system parameters to the limits imposed by the standard and the resulting performance compared to the previously determined ideal system performance. The results show that the performance characteristics measured are most sensitive to the primary integrator response and output filter response when the system parameters are restricted to the range allowed by the draft NATO standard.

Lersch, J. A.

1980-12-01

373

Transformation of an Agulhas eddy near the continental slope  

Directory of Open Access Journals (Sweden)

Full Text Available The transformation of Agulhas eddies near the continental slope of southern Africa and their subsequent self-propagation are analyzed in both observational data and numerical simulations. Self-propagation results from a net dipole moment of a generalized heton structure consisting of a surface-intensified anticyclonic eddy and deep cyclonic pattern. Such Agulhas vortical structures can form near the retroflection region and further north along the western coast of southern Africa. We analyze nonlinear topographic wave generation, vortex deformations, and filament production as an important part in water mass exchange. Self-propagating structures provide a conduit for exchange between the deep ocean and shelf regions in the Benguela upwelling system.

S. Baker-Yeboah

2010-02-01

374

Transformation of an Agulhas eddy near the continental slope  

Directory of Open Access Journals (Sweden)

Full Text Available The transformation of Agulhas eddies near the continental slope of South Africa and their subsequent self-propagation are analyzed in both observational data and numerical simulations. Self-propagation results from a net dipole moment of a generalized heton structure consisting of a surface-intensified anticyclonic eddy and deep cyclonic pattern. Such Agulhas vortical structures can form near the retroflection region and further north along the western coast of South Africa. We analyze nonlinear topographic wave generation, vortex deformations, and filament production as an important part in water mass exchange. Self-propagating structures provide a conduit for exchange between the deep ocean and shelf regions in the Benguela upwelling system.

S. Baker-Yeboah

2009-08-01

375

Total widths and slopes from complex Regge trajectories  

Science.gov (United States)

Experimental data for mesons and baryons imply a scaling formula for the total widths ?tot/M-->const, for large M. This leads to both real and imaginary parts of Regge trajectories to grow asymptotically in the same way. For this purpose, maximally complex Regge trajectories are introduced for which both Re ?(s) and Im ?(s) grow as s1-? (? small and positive). Our expression reduces to the standard real linear form as the imaginary part (proportional to ?) goes to zero. The unitarity corrections also enhance the spacelike slopes from their timelike values, thereby resolving an old problem with the ? trajectory in ?N charge exchange. Finally, the unitarily enhanced intercept, ??~0.525, is in good accord with the Donnachie-Landshoff total cross section analysis.

Filipponi, S.; Pancheri, G.; Srivastava, Y.

1999-04-01

376

Global High-Accuracy Intercomparison of Slope Measuring Instruments  

Science.gov (United States)

The upcoming generation of high accuracy synchrotron radiation (SR) optics will be characterized by a slope deviation from ideal shape in the range of some 0.05?rad rms at a sampling interval of about 1mm. To certify and improve the measurement capabilities of metrology tools to inspect these stringent specifications, an essential step is a worldwide intercomparison of these measurements based on a set of transfer standards. It is the aim of these cross measurements to verify the "absolute" correctness and comparability of the measurement results obtained by the cooperating partners when measuring the topography of specific reference optics (ROs) using their latest metrology tools and methods. Organized by members of the SR-optics community, new national and international cross measurement comparisons of typical synchrotron radiation mirrors have been realized during the last few years: A round robin test by the European COST-program (BESSY, Elettra, ESRF, Soleil) during the years 2004-2005 and a similar cooperation realized by the APS, ESRF and Spring-8 have proceeded. The first results of both projects were presented at the "Optics & Photonics" conference in San Diego in August 2005. This work build upon earlier work. The participants of both groups and representatives of other SR-laboratories agreed to start a global cooperation bringing together the two round-robin projects and open these activities to other partners from the SR-community, optical manufacturers and other interested parties. This initiative is intended to start an extensive comparison of various measurement principles and tools and will help to push the frontiers in metrology, and hence production, to a precision well below the current state-of-the-art limit of 0.5?rad rms for slope errors.

Siewert, Frank; Assoufid, Lahsen; Cocco, Daniele; Hignette, Olivier; Irick, Steve; Lammert, Heiner; McKinney, Wayne; Ohashi, Haruhiko; Polack, Francois; Qian, Shinan; Rah, Seungyu; Rommeveaux, Amparo; Schönherr, Veit; Sostero, Giovani; Takacs, Peter; Thomasset, Muriel; Yamauchi, Kazuto; Yashchuk, Valeriy; Zeschke, Thomas

2007-01-01

377

Monte-Carlo Modeling of Some Niger Delta Slope Events  

Directory of Open Access Journals (Sweden)

Full Text Available Monte-Carlo modeling has been utilized in this study to simulate seismic P-wave events on four horizons (AA, BB, CC and DD in a Niger Delta Slope environment with the aim of generating AVO attributes. Monte-Carlo modeling undertaken on a well log from the Gulf of Mexico served as a generic model and control. Trends analysis regressions generated in the environment served as input for the models while default parameter in SAVIOR (fluid method was used for establishing reservoir fluid properties. Fourier velocity served as velocity function. The results of the modeling are presented as AVO crossplots for brine sand (background, residual hydrocarbon and commercial hydrocarbon. For each event, offset-dependent synthetic seismograms are also generated using Zoeppritz equations. The AA horizon is typified by incoherent orientations of AVO crossplots. The horizon is thus presumed unconsolidated. The synthetic seismogram generated shows no perceptible amplitude variation with offset on all the models. AVO crossplot of the encountered BB horizon show that most of the commercial hydrocarbon plots and some of the residual hydrocarbon plots fall on quadrant III (bright spot quadrant. Synthetic seismic generated for BB horizon exhibits positive AVO response (soft kick on the commercial hydrocarbon model. A similar but marginal response was obtained on brine saturated BB model. Brine saturated model of the AVO crossplot for CC horizon model plotted mostly on hard sand quadrant. Conversely, presumed commercial hydrocarbon saturated CC is split between the hard sand and soft sand quadrants with low background normal values. The DD horizon is similar to the deep model of the Gulf of Mexico and hence exhibits similar crossplot. Curiously, high background normal (Bn characterized residual hydrocarbon models while unconsolidated gas sand horizons exhibit anomalous characteristics. The AVO crossplot obtained from the Monte-Carlo model could be a robust tool for mapping reservoirs within the Niger Delta Slope.

M.I. Oladapo

2009-01-01

378

Limitations of Deterministic Modelling of Slope Stability on Volcanic Edifices  

Science.gov (United States)

The conditions leading to the 18 May 1980 sector collapse of Mount St Helens have been the subject of a number of detailed investigations. Preservation of the initial failure plane(s) allowed Voight et al. (1983) and Donnadieu et al. (2001) to undertake back analyses and determine a range of possible failure conditions. While the models proposed offer major insights into potential failure mechanisms, we will demonstrate that deterministic analyses are of limited usefulness because many of the model parameters, such as cohesion, internal friction and pore pressure, are very poorly constrained. This creates problems of non-uniqueness in the solution. An alternative approach involves a series of Monte Carlo simulations to identify potential combinations of parameters that will produce the observed failure plane. Initial input ranges are specified for each parameter and the predetermined model is run repeatedly, with the parameter values for each model selected at random from within the input ranges. The interaction between parameters can be examined in detail, providing a better understanding of the potential failure conditions. This approach, which has been tested initially on a theoretical slope with predetermined failure conditions, highlights the fact that it is impossible to generate a unique model that fits the data when the slope has poorly defined strength parameters. This has clear implications for the validity of commonly used deterministic approaches. This probabilistic back analysis approach has been used to reanalyse the conditions that led to the May 18 collapse on Mount St Helens. Donnadieu, F., Merle, O., and Besson, J.C., 2001, Volcanic edifice stability during cryptodome intrusion, Bulletin of Volcanology, vol 63, p61-72. Voight, B., Janda, R.J., Glicken, H., and Douglass, P.M., 1983, Nature and Mechanics of the Mount St-Helens Rockslide-Avalanche of 18 May 1980, Geotechnique, vol 33, p243-273.

Burrell, R. V.; Pinkerton, H.; Binley, A.

2004-12-01

379

The slope seismic response monitoring of Wenchuan aftershocks in Qingchuan  

Directory of Open Access Journals (Sweden)

Full Text Available This work reports some new progress of rock slope inside seismic response monitoring results in the area of Mountain Dong and Mountain Shizi (Qingchuan county, located more than 250 km NE of Yingxiu epicenter (2008 Wenchuan earthquake, Sichuan province. Five adits with the maximum depth of 15 m had been excavated in different elevation on both sides slope. Stations were emplaced at middle of the adits, from September 2009 to May 2010 more than 60 Wenchuan aftershocks had been monitored, 22 typical aftershocks had been analysis, whose magnitude varied between 2.3 ~ 5.2 and epicentral distance was from a few to 45 km. A comparison analysis of recordings provided evidence of the presence amplification effect at the Q4 station of Mt. Dong, which the peak horizontal acceleration amplification factor is between 1.0 ~ 2.5. But this amplification effect had no stronger at other stations. Comprehensive studies show that the relative height to riverbed is an important factor of Q4 seismic amplification effect. Otherwise the topography of Q4 site is conducive to horizontal amplification, not the vertical amplification. Moreover the calculation of Arias intensity (Ia had the same amplification effect as the PGA, only the amplification factor is between 1.0 ~ 3.47 much bigger than the latter. On the other hand, the calculation of horizontal to vertical spectral ratio (HVSR at Q4 shows the curves have multiple peaks corresponding with different dominant frequencies, which the amplification factor is always bigger than other stations at Mt. Dong. Sufficient evidence indicates that the Mt. Dong amplification effect is stronger than Mt. Shizi.

Y. H. Luo

2014-06-01

380

The slope seismic response monitoring of Wenchuan aftershocks in Qingchuan  

Science.gov (United States)

This work reports some new progress of rock slope inside seismic response monitoring results in the area of Mountain Dong and Mountain Shizi (Qingchuan county), located more than 250 km NE of Yingxiu epicenter (2008 Wenchuan earthquake), Sichuan province. Five adits with the maximum depth of 15 m had been excavated in different elevation on both sides slope. Stations were emplaced at middle of the adits, from September 2009 to May 2010 more than 60 Wenchuan aftershocks had been monitored, 22 typical aftershocks had been analysis, whose magnitude varied between 2.3 ~ 5.2 and epicentral distance was from a few to 45 km. A comparison analysis of recordings provided evidence of the presence amplification effect at the Q4 station of Mt. Dong, which the peak horizontal acceleration amplification factor is between 1.0 ~ 2.5. But this amplification effect had no stronger at other stations. Comprehensive studies show that the relative height to riverbed is an important factor of Q4 seismic amplification effect. Otherwise the topography of Q4 site is conducive to horizontal amplification, not the vertical amplification. Moreover the calculation of Arias intensity (Ia) had the same amplification effect as the PGA, only the amplification factor is between 1.0 ~ 3.47 much bigger than the latter. On the other hand, the calculation of horizontal to vertical spectral ratio (HVSR) at Q4 shows the curves have multiple peaks corresponding with different dominant frequencies, which the amplification factor is always bigger than other stations at Mt. Dong. Sufficient evidence indicates that the Mt. Dong amplification effect is stronger than Mt. Shizi.

Luo, Y. H.; Huang, R.; Wang, Y.

2014-06-01