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Sample records for lateral talar dome

  1. Arthroscopic intralesional curettage for large benign talar dome cysts

    PubMed Central

    El Shazly, Ossama; Abou El Soud, Maged M.; Nasef Abdelatif, Nasef Mohamed

    2015-01-01

    Introduction: Surgical management of large talar dome cysts is challenging due to increased morbidity by associated cartilage damage and malleolar osteotomy. The purpose of this study is to evaluate the clinical and radiological outcome of endoscopic curettage and bone graft for large talar dome cysts. Methods: This is a retrospective analysis of data for eight patients (eight feet) who were treated by arthroscopic curettage and grafting for large talar dome cysts. Seven cases were treated by posterior ankle arthroscopy as the lesion was located posteriorly while one case was treated by anterior ankle arthroscopy as the lesion was breached anteriorly. Results: The final diagnosis, was; large osteochondral lesion of talus (two cases), aneurysmal bone cyst (ABC) (two case), intra-osseous ganglion (two cases), Chronic infection in talus (one case) and angiomatous lesion of the talus (one case). The mean follow up period was 18.3 (±3.06 SD) months (range 16–25 months). The median preoperative AOFAS score was 74.5 (±5.34 SD) points. The mean postoperative AOFAS score at one year follow up was 94.6 (±2.97 SD) points. None of the patient had recurrence of the lesion during follow up. Return to normal daily activity was achieved at 11.25 (±2.37 SD) weeks. Discussion: In this short case series study, large talar dome bony cysts of different pathologies including aneurysmal bone cysts could be treated effectively by endoscopic curettage and bone grafting with no recurrence no complications during the follow-up period. PMID:27163087

  2. Arthroscopic management of talar dome lesions using a transmalleolar approach.

    PubMed

    Grady, John; Hughes, David

    2006-01-01

    Surgical treatment of posteromedial talar dome lesions is frequently necessary for Berndt and Harty grade IV osteochondral defects and nondisplaced osteochondral fragments resistant to conservative modalities. When operative intervention is indicated, the approach and management can be complicated by the location and extent of the injury. The operative technique we advocate allows direct exposure of the lesion and minimizes damage to healthy articular cartilage and surrounding soft tissue. Use of a drill guide assists the surgeon in precisely placing a transmalleolar portal through the tibia for subchondral drilling of osteochondral defects when the lesions are inaccessible through traditional arthroscopic portals. PMID:16707640

  3. Osteochondritis Dissecans of the Talar Dome in a Collegiate Swimmer: A Case Report

    PubMed Central

    Smith, Michelle; Chang, Cindy J.

    1998-01-01

    Objective: To present the case of an intercollegiate swimmer with a stage IV lateral talar dome injury and associated bony fragments. Background: Lack of distinct diagnostic symptoms, low index of clinical suspicion, and the difficulty of visualizing the early stages of this injury on standard x-rays cause frequent misdiagnosis of talar dome lesions. Differential Diagnosis: Ganglion cyst, with inflammatory synovitis secondary to rupture of cyst; loose bodies from previous occult fracture; osteochondral fracture. Treatment: Initial treatment with nonsteroidal antiinflammatory drugs and a posterior splint for comfort, followed by arthroscopic excision of loose bodies with abrasion and drilling arthroplasty. Uniqueness: Patient presented to the team physician for care of acute left medial ankle pain after the athletic trainer had attempted to rupture a ganglion cyst on the anterolateral aspect of the patient's ankle. Conclusions: Increased clinical suspicion is necessary to correctly diagnose osteochondral lesions, particularly in the early stages. Aggressive treatment of talar dome lesions has a good success rate and may be an attractive option for competitive athletes. ImagesFigure 2.Figure 3.Figure 4.Figure 5. PMID:16558537

  4. Novel metallic implantation technique for osteochondral defects of the medial talar dome

    PubMed Central

    van Bergen, Christiaan J A

    2010-01-01

    Background and purpose A metallic inlay implant (HemiCAP) with 15 offset sizes has been developed for the treatment of localized osteochondral defects of the medial talar dome. The aim of this study was to test the following hypotheses: (1) a matching offset size is available for each talus, (2) the prosthetic device can be reproducibly implanted slightly recessed in relation to the talar cartilage level, and (3) with this implantation level, excessive contact pressures on the opposite tibial cartilage are avoided. Methods The prosthetic device was implanted in 11 intact fresh-frozen human cadaver ankles, aiming its surface 0.5 mm below cartilage level. The implantation level was measured at 4 margins of each implant. Intraarticular contact pressures were measured before and after implantation, with compressive forces of 1,000–2,000 N and the ankle joint in plantigrade position, 10° dorsiflexion, and 14° plantar flexion. Results There was a matching offset size available for each specimen. The mean implantation level was 0.45 (SD 0.18) mm below the cartilage surface. The defect area accounted for a median of 3% (0.02–18) of the total ankle contact pressure before implantation. This was reduced to 0.1% (0.02–13) after prosthetic implantation. Interpretation These results suggest that the implant can be applied clinically in a safe way, with appropriate offset sizes for various talar domes and without excessive pressure on the opposite cartilage. PMID:20515434

  5. Arthroscopically assisted autologous osteochondral transplantation for osteochondral lesions of the talar dome: an MRI and clinical follow-up study.

    PubMed

    Assenmacher, J A; Kelikian, A S; Gottlob, C; Kodros, S

    2001-07-01

    Osteochondral Lesions of the Talar Dome (OLT) are common problems encountered in orthopedics. Although the etiology remains uncertain, a myriad of treatment options exists. The authors describe arthroscopically assisted autologous osteochondral graft (OCG) transplantation procedures in the treatment of unstable OLTs in nine patients. The patients underwent standard preoperative MRI examination to assess fragment stability (using De Smet criteria for stability). Intraoperative arthroscopy was used to correlate the preoperative MRI assessment (using Cheng/Ferkel grading). After transplantation procedures, MRI (using De Smet criteria for stability) assessed graft incorporation for stability at an average of 9.3 months after the procedure. Preoperative MRI correlated highly with arthroscopic findings of OLT instability (sensitivity = 1.0). This has been demonstrated in the current orthopedic literature. The post transplantation MRI demonstrated stable graft osteointegration by De Smet criteria in all patients. Postoperative visual analogue pain scales showed significant improvement from preoperative assessment. Postoperative AOFAS Ankle-Hindfoot scores averaged 80.2 (S.D. +/- 18.9). Our favorable early results and those of other authors using similar techniques may validate OCG transplantation as a viable alternative for treating unstable osteochondral defects in the talus that are refractive to more commonly used surgical techniques. PMID:11503978

  6. Fracture of the lateral tubercle of the posterior talar process caused by a rock-climbing fall: a case report.

    PubMed

    Blanchette, Marc-André; Grenier, Julie-Marthe

    2014-09-01

    The purpose of this case report is to describe the clinical presentation of a patient who suffered from a fracture of the lateral tubercle of the posterior talar process caused by a fall while rock-climbing. The initial evaluation revealed diffuse ankle swelling, tenderness, and pain at the distal aspect of both malleoli. Plain film radiography revealed a fracture of the posterior process of the talus. Computed tomography (CT) outlined the extension of the fracture line in the postero-lateral aspect of the body of the talus with minimal displacement. The patient was treated conservatively with an Aircast© walking boot for 6 weeks (non-weight-bearing) followed by a 2-week period of partial weight bearing. At the 8 week follow-up, he reported minimal tenderness and normal ankle function. Clinicians should be aware that talar fracture identification on plain films is difficult and computed tomography or magnetic resonance imaging may be required. PMID:25202157

  7. Fracture of the lateral tubercle of the posterior talar process caused by a rock-climbing fall: a case report

    PubMed Central

    Blanchette, Marc-André; Grenier, Julie-Marthe

    2014-01-01

    The purpose of this case report is to describe the clinical presentation of a patient who suffered from a fracture of the lateral tubercle of the posterior talar process caused by a fall while rock-climbing. The initial evaluation revealed diffuse ankle swelling, tenderness, and pain at the distal aspect of both malleoli. Plain film radiography revealed a fracture of the posterior process of the talus. Computed tomography (CT) outlined the extension of the fracture line in the postero-lateral aspect of the body of the talus with minimal displacement. The patient was treated conservatively with an Aircast© walking boot for 6 weeks (non–weight-bearing) followed by a 2-week period of partial weight bearing. At the 8 week follow-up, he reported minimal tenderness and normal ankle function. Clinicians should be aware that talar fracture identification on plain films is difficult and computed tomography or magnetic resonance imaging may be required. PMID:25202157

  8. Talar Dome Lesion

    MedlinePlus

    ... side of the ankle. This condition often... Barefoot Running Barefoot running is running while barefoot, without wearing any shoes on the feet. Running in thin-soled, flexible shoes is related but ...

  9. Talar Dome Lesion

    MedlinePlus

    ... be helpful in reducing the pain and inflammation. Physical therapy . Range-of-motion and strengthening exercises are beneficial once the lesion is adequately healed. Physical therapy may also include techniques to reduce pain and ...

  10. Assessment of Ankle and Hindfoot Stability and Joint Pressures Using a Human Cadaveric Model of a Large Lateral Talar Process Excision

    PubMed Central

    Sands, Andrew; White, Charles; Blankstein, Michael; Zderic, Ivan; Wahl, Dieter; Ernst, Manuela; Windolf, Markus; Hagen, Jennifer E.; Richards, R. Geoff; Stoffel, Karl; Gueorguiev, Boyko

    2015-01-01

    Abstract Lateral talar process fragment excision may be followed by hindfoot instability and altered biomechanics. There is controversy regarding the ideal fragment size for internal fixation versus excision and a concern that excision of a large fragment may lead to significant instability. The aim of this study was to assess the effect of a simulated large lateral talar process excision on ankle and subtalar joint stability. A custom-made seesaw rig was designed to apply inversion/eversion stress loading on 7 fresh-frozen human cadaveric lower legs and investigate them in pre-excision, 5 cm3 and 10 cm3 lateral talar process fragment excision states. Anteroposterior radiographs were taken to assess ankle and subtalar joint tilt and calculate angular change from neutral hindfoot alignment to 10-kg forced inversion/eversion. Ankle joint pressures and contact areas were measured under 30-kg axial load in neutral hindfoot alignment. In comparison to the pre-excision state, no significantly different mediolateral angular change was observed in the subtalar joint after 5 and 10 cm3 lateral talar process fragment excision in inversion and eversion. With respect to the ankle joint, 10-cm3 fragment excision produced significantly bigger inversion tibiotalar tilt compared with the pre-excision state, P = .04. No significant change of the ankle joint pressure and contact area was detected after 5 and 10-cm3 excision in comparison with the pre-excison state. An excision of up to 10 cm3 of the lateral talar process does not cause a significant instability at the level of the subtalar joint but might be a destabilizing factor at the ankle joint under inversion stress. The latter could be related to extensive soft tissue dissection required for resection. PMID:25789950

  11. Talar Fractures and Dislocations: A Radiologist's Guide to Timely Diagnosis and Classification.

    PubMed

    Melenevsky, Yulia; Mackey, Robert A; Abrahams, R Brad; Thomson, Norman B

    2015-01-01

    The talus, the second largest tarsal bone, has distinctive imaging characteristics and injury patterns. The predominantly extraosseous vascular supply of the talus predisposes it to significant injury in the setting of trauma. In addition, the lack of muscular attachments and absence of a secondary blood supply can lead to subsequent osteonecrosis. Although talar fractures account for less than 1% of all fractures, they commonly result from high-energy trauma and may lead to complications and long-term morbidity if not recognized and managed appropriately. While initial evaluation is with foot and ankle radiographs, computed tomography (CT) is often performed to evaluate the extent of the fracture, displacement, comminution, intra-articular extension, and associated injuries. Talar fractures are divided by anatomic region: head, neck, and body. Talar head fractures can be treated conservatively if nondisplaced, warranting careful radiographic and CT evaluation to assess rotation, displacement, and extension into the neck. The modified Hawkins-Canale classification of talar neck fractures is most commonly used due to its simplicity, usefulness in guiding treatment, and prognostic value, as it correlates associated malalignment with risk of subsequent osteonecrosis. Isolated talar body fractures may be more common than previously thought. The Sneppen classification further divides talar body fractures into osteochondral talar dome, lateral and posterior process, and shear and crush comminuted central body fractures. Crush comminuted central body fractures carry a poor prognosis due to nonanatomic reduction, bone loss, and subsequent osteonecrosis. Lateral process fractures can be radiographically occult and require a higher index of suspicion for successful diagnosis. Subtalar dislocations are often accompanied by fractures, necessitating postreduction CT. Familiarity with the unique talar anatomy and injury patterns is essential for radiologists to facilitate

  12. Talar neck fractures.

    PubMed

    Berlet, G C; Lee, T H; Massa, E G

    2001-01-01

    Clinical management of talar neck fractures is complex and fraught with complications. As Gaius Julius Caesar stated: "The die is cast"; often the outcome of a talar neck fracture is determined at the time of injury. The authors believe, however, that better results can be achieved by following some simple guidelines. The authors advocate prompt and precise anatomic surgical reduction, preferring the medial approach with secondary anterolateral approach. Preservation of blood supply can be achieved by a thorough understanding of vascular pathways and efforts to stay within appropriate surgical intervals. The authors advocate bone grafting of medial neck comminution (if present) to prevent varus malalignment and rigid internal fixation to allow for joint mobilization postoperatively. These guidelines may seem simple, but when dealing with the complexity of talar neck fractures, the foot and ankle surgeon needs to focus and rely on easily grasped concepts to reduce poor outcomes. PMID:11465133

  13. Ecological divergence and talar morphology in gorillas.

    PubMed

    Dunn, Rachel H; Tocheri, Matthew W; Orr, Caley M; Jungers, William L

    2014-04-01

    Gorillas occupy a variety of habitats from the west coast to eastern central Africa. These habitats differ considerably in altitude, which has a pronounced effect on forest ecology. Although all gorillas are obligate terrestrial knuckle-walking quadrupeds, those that live in lowland habitats eat fruits and climb more often than do those living in highland habitats. Here we test the hypothesis that gorilla talus morphology falls along a morphocline that tracks locomotor function related to a more inverted or everted foot set. This proposed morphocline predicts that gorillas living in lowland habitats may have a talocrural joint configured to facilitate a more medially oriented foot during climbing, suggesting that they may be more adaptively committed to arboreality than gorillas living in highland habitats. To quantify the relative set of the foot in gorillas, we chose two three-dimensional measurements of the talocrural joint: mediolateral curvature of the trochlea and relative surface area of the lateral malleolus. Our results show that, in comparison to their eastern counterparts, western gorillas have talar features that reflect a more medially directed sole of the foot. This morphology likely facilitates foot placement in a wider range of positions and minimization of shearing stresses across the joint when the foot is loaded on more curved or vertically oriented substrates as occurs during climbing and other arboreal behaviors. In contrast, eastern gorilla talar morphology is consistent with habitual placement of the foot with the sole directed more inferiorly, suggesting more effective loading during plantigrade push-off on terrestrial substrates. PMID:24374860

  14. Misdiagnosis of Talar Body or Neck Fractures as Ankle Sprains in Low Energy Traumas

    PubMed Central

    Young, Ki-Won; Kim, Jin-Su; Cho, Hun-Ki; Choo, Ho-Sik; Park, Jang-Ho

    2016-01-01

    Background The talus has a very complex anatomical morphology and is mainly fractured by a major force caused by a fall or a traffic accident. Therefore, a talus fracture is not common. However, many recent reports have shown that minor injuries, such as sprains and slips during sports activities, can induce a talar fracture especially in the lateral or posterior process. Still, fractures to the main parts of the talus (neck and body) after ankle sprains have not been reported as occult fractures. Methods Of the total 102 cases from January 2005 to December 2012, 7 patients had confirmed cases of missed/delayed diagnosis of a talus body or neck fracture and were included in the study population. If available, medical records, X-rays, computed tomography scans, and magnetic resonance imaging of the confirmed cases were retrospectively reviewed and analyzed. Results In the 7-patient population, there were 3 talar neck fractures and 4 talar body fractures (coronal shearing type). The mechanisms of injuries were all low energy trauma episodes. The causes of the injuries included twisting of the ankle during climbing (n = 2), jumping to the ground from a 1-m high wall (n = 2), and twisting of the ankle during daily activities (n = 3). Conclusions A talar body fracture and a talar neck fracture should be considered in the differential diagnosis of patients with acute and chronic ankle pain after a minor ankle injury. PMID:27583114

  15. Arthroscopic Treatment of Talar Body Fractures

    PubMed Central

    Jorgensen, Nicholas B.; Lutz, Michael

    2014-01-01

    Talar fractures can be severe injuries with complications leading to functional disability. Open reduction–internal fixation remains the treatment of choice for displaced talar fractures. Arthroscopic evaluation of the fracture and articular surfaces can play an important role in the treatment of these fractures. Arthroscopic reduction–internal fixation (ARIF) is increasingly used for certain intra-articular fracture types through the body. The minimally invasive nature of ARIF and high accuracy are enviable attributes of an evolving technique. This technical note describes arthroscopic evaluation of 2 intra-articular talar head fractures, using posterior portals, with ARIF performed in 1 case and excision of the fracture fragments in the other case. PMID:24904775

  16. Arthroscopic Debridement of Pediatric Accessory Anterolateral Talar Facet Causing Impingement.

    PubMed

    Neumann, Julie A; Mannava, Sandeep; Gross, Christopher E; Wooster, Benjamin M; Busch, Michael T

    2016-04-01

    Symptomatic subfibular and/or lateral talocalcaneal impingement in pediatric patients may result from an accessory anterolateral talar facet (AALTF). This impingement may cause pain and disability and may limit athletic performance in high-level athletes. We report the case of a 12-year-old female competitive gymnast who had refractory, lateral-sided right ankle pain for 4 months and underwent right ankle arthroscopic resection of the AALTF causing impingement. Standard medial and anterolateral portals with the addition of an accessory anterolateral-distal portal were used in conjunction with a 30° 2.7-mm-diameter arthroscope. The AALTF was resected with a combination of a shaver and a motorized rasp. Intraoperative fluoroscopy was used to verify successful debridement of the bony facet. This case illustrates that arthroscopic debridement is a technique to treat subfibular and/or talocalcaneal impingement associated with an AALTF. PMID:27462543

  17. The pleasure dome with caves of ice. Cerebral lateralization, creativity, and the drug experience.

    PubMed

    Kaplan, C D

    1988-09-01

    The drug experience is not a phenomenon of isolated interest to the neurosciences. The investigation of the phases of the drug experience can tell us much about the process of stimulating and losing creativity. This paper aimed to present a human model of creativity and the drug experience to complement the existing animal models. It remains for future research to reject or confirm the hypotheses sketched here. The exploration of these hypotheses would give us better insight into the control mechanisms determining the delicate process of creating functional forms that link words and images to feelings (for example, art). The examination of the drug experience from the point of view of cerebral lateralization provides a better understanding of how the quest for art may be tied up with the consequences of self-destruction. As Luria has noted, the gnostic disturbances associated with damages of the right hemisphere are "the remarkable absence of perception of the patient of his own defects; . . . such patients have unimpaired speech but they lack the precise analysis of the direct flow of information about their own body." Perhaps this was intuitively known by Coleridge, who in 1803 had already passed into the maintenance phase and wrote the fragment "Reality's Dark Dream": I know 'tis but a dream, yet feel more anguish Than if 'twere truth. It has been often so: Must I die under it? Is no one near? Will no one hear these stifled groans and wake me? PMID:3067227

  18. Talar Neck Fracture after United Tibiotalar Fusion

    PubMed Central

    Platt, W.; Welck, M.; Rudge, B.

    2015-01-01

    Tibiotalar arthrodesis is a well-established treatment for tibiotalar arthritis, for example, in younger high demand patients. Talar neck fractures are less common though well-recognised sequelae of foot ankle trauma. Here we present the clinical case of a 69-year-old male who presented to our institution with a nonunion of a talar neck fracture, having undergone a left tibiotalar fusion 24 years previously. To the authors' knowledge, this injury has only been described once previously in the literature. However, the original case described a fracture sustained in the very early postoperative period following tibiotalar fusion, postulated to be secondary to postimmobilisation osteopaenia or stress risers from metalwork. The aetiology in this case is likely due to axial compression transmitted to the talar neck via the calcaneus. The predisposing factors for nonunion are discussed, highlighting the importance of vigilance for this injury in any patient with concomitant tibiotalar fusion and foot trauma. The management of this patient is discussed. PMID:26491589

  19. Talar Neck Fracture after United Tibiotalar Fusion.

    PubMed

    Platt, W; Welck, M; Rudge, B

    2015-01-01

    Tibiotalar arthrodesis is a well-established treatment for tibiotalar arthritis, for example, in younger high demand patients. Talar neck fractures are less common though well-recognised sequelae of foot ankle trauma. Here we present the clinical case of a 69-year-old male who presented to our institution with a nonunion of a talar neck fracture, having undergone a left tibiotalar fusion 24 years previously. To the authors' knowledge, this injury has only been described once previously in the literature. However, the original case described a fracture sustained in the very early postoperative period following tibiotalar fusion, postulated to be secondary to postimmobilisation osteopaenia or stress risers from metalwork. The aetiology in this case is likely due to axial compression transmitted to the talar neck via the calcaneus. The predisposing factors for nonunion are discussed, highlighting the importance of vigilance for this injury in any patient with concomitant tibiotalar fusion and foot trauma. The management of this patient is discussed. PMID:26491589

  20. Open Reduction for AO/OTA 81-B3 (Hawkins 3) Talar Neck Fractures: The Natural Delivery Method.

    PubMed

    Simpson, R B; Auston, Darryl A

    2016-03-01

    Fractures of the talar neck with subtalar and tibiotalar joint dislocation (AO/OTA 81-B3) represent a treatment challenge for the orthopedic surgeon. The magnitude of deformity and complexity of the pathoanatomy adds to concerns for soft tissue embarrassment to convey an urgency of surgical intervention. Previous studies have described the several techniques for talar reduction, including medial malleolar osteotomy, posterior Schanz pin manipulation, or posteromedial incision to facilitate relocation at the time of definitive open treatment. We describe a simple technique for stepwise surgical intervention using adjuncts to reduction on the surgical field that facilitate an atraumatic relocation of the displaced body fragment through a standard lateral incision, simplifying fixation of the residual talar neck fracture. A reasonable metaphor for the technique is its similarity to reducing an obstetric shoulder dystocia in the delivery of a newborn infant. PMID:26709817

  1. Dome Schools.

    ERIC Educational Resources Information Center

    Cirulli, Carol

    1999-01-01

    Back in 1988, Emmett, Idaho, built the first monolithic dome school. Now, school boards in Arizona, Missouri, Florida, Minnesota, and New Mexico are among those that have voted to build domed school buildings. A monolithic dome is a steel- reinforced, concrete structure with a smooth, round surface that is inspired by the shape of an egg. (MLF)

  2. Monolithic Domes.

    ERIC Educational Resources Information Center

    Lanham, Carol

    2002-01-01

    Describes how the energy savings, low cost, and near-absolute protection from tornadoes provided by monolithic domes is starting to appeal to school districts for athletic and other facilities, including the Italy (Texas) Independent School District. Provides an overview of monolithic dome construction. (EV)

  3. Three-dimensional geometric morphometric analysis of talar morphology in extant gorilla taxa from highland and lowland habitats.

    PubMed

    Knigge, Ryan P; Tocheri, Matthew W; Orr, Caley M; Mcnulty, Kieran P

    2015-01-01

    Western gorillas (Gorilla gorilla) are known to climb significantly more often than eastern gorillas (Gorilla beringei), a behavioral distinction attributable to major differences in their respective habitats (i.e., highland vs. lowland). Genetic evidence suggests that the lineages leading to these taxa began diverging from one another between approximately 1 and 3 million years ago. Thus, gorillas offer a special opportunity to examine the degree to which morphology of recently diverged taxa may be "fine-tuned" to differing ecological requirements. Using three-dimensional (3D) geometric morphometrics, we compared talar morphology in a sample of 87 specimens including western (lowland), mountain (highland), and grauer gorillas (lowland and highland populations). Talar shape was captured with a series of landmarks and semilandmarks superimposed by generalized Procrustes analysis. A between-group principal components analysis of overall talar shape separates gorillas by ecological habitat and by taxon. An analysis of only the trochlea and lateral malleolar facet identifies subtle variations in trochlear shape between western lowland and lowland grauer gorillas, potentially indicative of convergent evolution of arboreal adaptations in the talus. Lastly, talar shape scales differently with centroid size for highland and lowland gorillas, suggesting that ankle morphology may track body-size mediated variation in arboreal behaviors differently depending on ecological setting. Several of the observed shape differences are linked biomechanically to the facilitation of climbing in lowland gorillas and to stability and load-bearing on terrestrial substrates in the highland taxa, providing an important comparative model for studying morphological variation in groups known only from fossils (e.g., early hominins). PMID:25338937

  4. Recent Advances in Egypt for Treatment of Talar Osteochondral Lesions.

    PubMed

    Haleem, Amgad M; AbouSayed, Mostafa M; Gomaa, Mohammed

    2016-06-01

    Treatment of osteochondral defects (OCLs) of the talus is a challenging orthopedic surgery. Treatment of talar OCLs has evolved through the 3 "R" paradigm: reconstruction, repair, and replacement. This article highlights current state-of-the-art techniques and reviews recent advances in the literature about articular cartilage repair using various novel tissue engineering approaches, including various scaffolds, growth factors, and cell niches; which include chondrocytes and culture-expanded bone marrow-derived mesenchymal stem cells. PMID:27261813

  5. Diagnosis and treatment of talar dislocation fractures illustrated by 3 case reports and review of literature

    PubMed Central

    Haverkort, J.J.M.; Leenen, L.P.H.; Wessem, K.J.P. van

    2015-01-01

    Introduction Talar fractures are a rare type of fractures (less than 1%). They are difficult to treat and outcome is often complicated by arthritis and avascular necrosis. In this article three cases are presented with different types of dislocated talar neck fractures. Anatomy of the talus, treatment, outcome and follow up of these fractures are discussed. Further, review of literature and guidelines for treatment and follow up for dislocated talar neck fractures are discussed. Discussion The risk of developing arthritis or avascular necrosis of the talus after dislocated talar neck fractures depends on the initial trauma with vascular compromise due to dislocation of the talus. The modified Hawkins classification gives an insight in the risk of developing avascular necrosis. During follow up the Hawkins sign can be an indication of a vital talus. To diagnose avascular necrosis MRI is the only suitable diagnostic tool. Conclusion Reduction of a dislocated talar fracture is a medical emergency in an effort to reduce the vascular compromise of the talus. Definitive fixation can be delayed but should be performed by an experienced surgeon to achieve an optimal reconstruction of the talar surface. Long-term follow up is important to evaluate signs of arthritis and avascular necrosis. PMID:26451643

  6. Late Oligocene to early Miocene lateral extrusion at the eastern border of the Lepontine dome of the central Alps (Bergell and Insubric areas, eastern central Alps)

    NASA Astrophysics Data System (ADS)

    Ciancaleoni, Laurent; Marquer, Didier

    2008-07-01

    How the internal domain of the central Alps deformed during late stages of the continental collision remains poorly understood. To fill this gap in knowledge, we present new data constraining the late Alpine brittle and brittle-ductile tectonics in Oligocene intrusions of the Bergell Alps (eastern central Alps). Syncollisional late normal faulting is widespread at all investigated scales, but part of the deformation observed is also associated with oblique-slip and transcurrent displacements. The faults are explained by stress permutations in space and time implying the three principal stress axes and correspond to different homoaxial states of stress of one single transtensive tectonic event. Motion on these faults accommodated coeval orogen-parallel extension and orogen-perpendicular contraction, during oblique indentation by the Southern alpine crust. Extensional and transcurrent structures likely formed by lateral extrusion of the Bergell Alps via distributed eastward extrusion of imbricated wedge-shaped crustal blocks, during the late Oligocene and lower Miocene. A first-order wedge-shaped crustal block in the Bergell Alps is represented by three coeval segments of the Periadriatic Fault System (namely the Tonale, Engadine, and Forcola faults). The eastern central segment of the Alpine belt appears to have deformed during the late Oligocene and lower Miocene in a similar way to its extremities where lateral escape tectonics occurred at least until the upper Miocene, according to free boundary availabilities.

  7. A Pediatric Comminuted Talar Fracture Treated by Minimal K-Wire Fixation Without Using a Tourniquet

    PubMed Central

    Inal, Sermet; Inal, Canan

    2014-01-01

    Background Pediatric comminuted talar fractures are reported to be rare, and treatment options such as minimal internal K-wire fixation without using a tourniquet to prevent avascular necrosis have not previously been investigated. Case Description We report a case of a comminuted talar body and a non-displaced neck fracture with dislocation of the tibiotalar, talonavicular and subtalar joints with bimalleolar epiphyseal fractures in an 11-year-old boy due to a fall from height. We present radiological findings, the surgical procedure and clinical outcomes of minimal internal K-wire fixation without using a tourniquet. Literature Review Avascular necrosis rates are reported to be between 0 % and 66 % after fractures of the neck of the talus and the talar body in children. The likelihood of developing avascular necrosis increases with the severity of the fracture. Clinical Relevance To avoid avascular necrosis in a comminuted talar fracture accompanied by tibiotalar, talonavicular, subtalar dislocations and bimalleolar epiphyseal fractures, a minimal internal K-wire fixation without the use of a tourniquet was performed. The outcome was evaluated by the American Orthopedic Foot and Ankle Society score (AOFAS). A score of 90 (excellent) was found at the end of the second year of follow up. Radiology revealed preservation of the joint with no evidence of avascular necrosis, and clinical findings revealed a favorable functional outcome after two years. Level of Evidence 4 PMID:25328479

  8. Closed Talar Dislocation without Associated Fracture a Very Rare Injury, a Case Report

    PubMed Central

    Kumar, Yashavntha C; Reddy, Sandeep; Golla, Dinesh Kumar; Ganesh, Niranthara

    2014-01-01

    Introduction: Total talar dislocations are uncommon injuries and usually seen following high velocity injuries. Total talar dislocations (missing talus) without fractures around the ankle are extremely rare. There are no consensuses on the best treatment of such injuries. To best of our knowledge very few cases have been reported in literature. We hereby report a closed total talar dislocation in a 25 year old male without an associated fracture around ankle. He was managed with emergency closed reduction and below knee splint. At one year follow up there were no complications. Case Report: A 25 year old male presented to orthopaedic causality with injury to right ankle following a road traffic accident. Patient complained of severe pain and deformity of ankle following injury. On examination ankle was deformed and swollen. Plain radiographs of right ankle joint revealed total anterolateral dislocation of talus without any accompanying ankle fracture. CT scan with 3D reconstruction also confirmed our radiographic findings. Under spinal anaesthesia and fluoroscopic guidance closed reduction was performed. To maintain reduction a 3mm K-wire was passed from calcaneum to tibia through talus. A posterior below knee splint was applied. Patient was followed every three months till one year. At one year follow up patient had good range of motion at ankle and subtalar joint. Conclusion: Total talar dislocations are very rare injuries and should be treated as impending open fractures. There is no consensus on treatment of such complex injuries as very few cases have been reported in literature. PMID:27298950

  9. Modular combustor dome

    NASA Technical Reports Server (NTRS)

    Glynn, Christopher Charles (Inventor); Halila, Ely Eskenazi (Inventor); Bibler, John David (Inventor); Morris, David Byron (Inventor)

    2001-01-01

    A combustor dome module includes a mixer tube having a hollow heat shield sealingly joined around the outlet end thereof. The modules may then be assembled in an array for defining the combustor dome, with each module being individually removable therefrom.

  10. What factors control the superficial lava dome explosivity?

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoit; Morgan, Daniel J.

    2015-04-01

    Dome-forming eruption is a frequent eruptive style; lava domes result from intermittent, slow extrusion of viscous lava. Most dome-forming eruptions produce highly microcrystallized and highly- to almost totally-degassed magmas which have a low explosive potential. During lava dome growth, recurrent collapses of unstable parts are the main destructive process of the lava dome, generating concentrated pyroclastic density currents (C-PDC) channelized in valleys. These C-PDC have a high, but localized, damage potential that largely depends on the collapsed volume. Sometimes, a dilute ash cloud surge develops at the top of the concentrated flow with an increased destructive effect because it may overflow ridges and affect larger areas. In some cases, large lava dome collapses can induce a depressurization of the magma within the conduit, leading to vulcanian explosions. By contrast, violent, laterally directed, explosions may occur at the base of a growing lava dome: this activity generates dilute and turbulent, highly-destructive, pyroclastic density currents (D-PDC), with a high velocity and propagation poorly dependent on the topography. Numerous studies on lava dome behaviors exist, but the triggering of lava dome explosions is poorly understood. Here, seven dome-forming eruptions are investigated: in the Lesser Antilles arc: Montagne Pelée, Martinique (1902-1905, 1929-1932 and 650 y. BP eruptions), Soufrière Hills, Montserrat; in Guatemala, Santiaguito (1929 eruption); in La Chaîne des Puys, France (Puy de Dome and Puy Chopine eruptions). We propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by these key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite

  11. ANALYSIS OF CLINICAL AND FUNCTIONAL OUTCOME AND COMPLICATIONS OF TALAR NECK FRACTURES

    PubMed Central

    Bastos, Leonardo Ribeiro; Ferreira, Ricardo Cardenuto; Mercadante, Marcelo Tomanik

    2015-01-01

    Objective: To evaluate the clinical, functional and radiographic results from talar neck fractures in patients treated at the Foot and Ankle Surgery Group of Santa Casa de Sao Paulo. Method: We evaluated 20 patients. The mean follow-up time was 71 months. One fracture was classified as Hawkins Type I, 12 as Hawkins type II, five as Hawkins type III, two as Hawkins type IV and four fractures were open. Results: One patient was treated conservatively, 16 were treated with open reduction and internal fixation (three with primary subtalar arthrodesis), one was treated with talectomy and two with tibiotalocalcaneal arthrodesis. The reduction obtained was anatomical in seven feet, acceptable in six feet and poor in four. Seven patients had early complications. There was one case of delayed consolidation and four of talar body osteonecrosis. Four patients required secondary reconstruction procedures. No significant radiographic impairment of the ankle joint was found in 62% of the patients and of the subtalar joint in 25%. Of the patients who did not undergo secondary procedures, 81% complained about the treated foot, 37.5% showed some deformity, 44% presented diminished sensitivity and 50% had to retire from work. The mean loss of motion in the ankle was 49%, and in the subtalar joint, 80%. The average AOFAS score was 73 points. Conclusion: Talar neck fractures are associated with high rates of clinical, functional and radiographic complications. PMID:27022565

  12. Pancakelike domes on Venus

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-10-01

    A comparison between the shape of seven large domes on the plains of Venus (volumes between 100 and 1000 cu cm) and that of an axisymmetric gravity current spreading over a rigid horizontal surface is presented. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the synthetic aperture radar images agree well with the theoretical similarity solution for a Newtonian fluid but not with the shape calculated for a rigid-plastic rheology or with that for a static model with a strong skin. The stress induced by the flow in the plains material below is obtained, and is found to be large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constant if spreading is possible only when the fluid is hot and lies between 10 exp 14 and 10 exp 17 Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 to 700 C in dry rhyolitic magmas. It is shown that dome development can be understood using simple fluid dynamical ideas and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  13. Pancakelike domes on Venus

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-12-01

    The shape of seven large domes on the plains of Venus, with volumes between 100 and 1000 cu km, is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the SAR images agree well with the theoretical similarity solution for a newtonian fluid, but not with the shape calculated for a rigid-plastic rheology, nor with that for a static model with a strong skin. As a viscous current spreads, it generates an isotropic strain rate tensor whose magnitude is independent of radius. Such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes. The stress induced by the flow in the plains material below is obtained, and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot, and lies between 1014 and 1017 Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 - 690 C in dry rhyolitic magmas. These temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite. These results show that the development of the domes can be understood using simple fluid dynamical ideas, and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  14. Pancakelike domes on Venus

    NASA Technical Reports Server (NTRS)

    Mckenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-01-01

    The shape of seven large domes on the plains of Venus, with volumes between 100 and 1000 cu km, is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the SAR images agree well with the theoretical similarity solution for a newtonian fluid, but not with the shape calculated for a rigid-plastic rheology, nor with that for a static model with a strong skin. As a viscous current spreads, it generates an isotropic strain rate tensor whose magnitude is independent of radius. Such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes. The stress induced by the flow in the plains material below is obtained, and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot, and lies between 10(exp 14) and 10(exp 17) Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 - 690 C in dry rhyolitic magmas. These temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite. These results show that the development of the domes can be understood using simple fluid dynamical ideas, and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  15. Three-dimensional shape variation of talar surface morphology in hominoid primates.

    PubMed

    Parr, W C H; Soligo, C; Smaers, J; Chatterjee, H J; Ruto, A; Cornish, L; Wroe, S

    2014-07-01

    The hominoid foot is of particular interest to biological anthropologists, as changes in its anatomy through time reflect the adoption of terrestrial locomotion, particularly in species of Australopithecus and Homo. Understanding the osteological morphology associated with changes in whole foot function and the development of the plantar medial longitudinal foot arch are key to understanding the transition through habitual bipedalism in australopithecines to obligate bipedalism and long-distance running in Homo. The talus is ideal for studying relationships between morphology and function in this context, as it is a major contributor to the adduction-abduction, plantar-dorsal flexion and inversion-eversion of the foot, and transmits all forces encountered from the foot to the leg. The talar surface is predominantly covered by articular facets, which have different quantifiable morphological characters, including surface area, surface curvature and orientation. The talus also presents challenges to the investigator, as its globular shape is very difficult to quantify accurately and reproducibly. Here we apply a three-dimensional approach using type 3 landmarks (slid semilandmarks) that are geometrically homologous to determine overall talar shape variations in a range of living and fossil hominoid taxa. Additionally, we use novel approaches to quantify the relative orientations and curvatures of talar articular facets by determining the principal vectors of facet orientation and fitting spheres to articular facets. The resulting metrics are analysed using phylogenetic regressions and principal components analyses. Our results suggest that articular surface curvatures reflect locomotor specialisations with, in particular, orangutans having more highly curved facets in all but the calcaneal facet. Similarly, our approach to quantifying articular facet orientation appears to be effective in discriminating between extant hominoid species, and may therefore provide a

  16. Three-dimensional shape variation of talar surface morphology in hominoid primates

    PubMed Central

    Parr, W C H; Soligo, C; Smaers, J; Chatterjee, H J; Ruto, A; Cornish, L; Wroe, S

    2014-01-01

    The hominoid foot is of particular interest to biological anthropologists, as changes in its anatomy through time reflect the adoption of terrestrial locomotion, particularly in species of Australopithecus and Homo. Understanding the osteological morphology associated with changes in whole foot function and the development of the plantar medial longitudinal foot arch are key to understanding the transition through habitual bipedalism in australopithecines to obligate bipedalism and long-distance running in Homo. The talus is ideal for studying relationships between morphology and function in this context, as it is a major contributor to the adduction–abduction, plantar–dorsal flexion and inversion–eversion of the foot, and transmits all forces encountered from the foot to the leg. The talar surface is predominantly covered by articular facets, which have different quantifiable morphological characters, including surface area, surface curvature and orientation. The talus also presents challenges to the investigator, as its globular shape is very difficult to quantify accurately and reproducibly. Here we apply a three-dimensional approach using type 3 landmarks (slid semilandmarks) that are geometrically homologous to determine overall talar shape variations in a range of living and fossil hominoid taxa. Additionally, we use novel approaches to quantify the relative orientations and curvatures of talar articular facets by determining the principal vectors of facet orientation and fitting spheres to articular facets. The resulting metrics are analysed using phylogenetic regressions and principal components analyses. Our results suggest that articular surface curvatures reflect locomotor specialisations with, in particular, orang-utans having more highly curved facets in all but the calcaneal facet. Similarly, our approach to quantifying articular facet orientation appears to be effective in discriminating between extant hominoid species, and may therefore

  17. Spontaneous talar and calcaneal fracture in rheumatoid arthritis: a case report

    PubMed Central

    Spina, Antonio; Clemente, Alberto; Vancini, Chiara; Fejzo, Majlinda; Campioni, Paolo

    2011-01-01

    Rheumatoid arthritis (RA) leads to a progressive weakening of the skeleton which may result in bone fractures. However, spontaneous fractures (exclusive of stress fractures, vertebral collapse, and superficial articular fragmentation) in patients with rheumatoid arthritis have been only occasionally reported in the medical literature. A case of spontaneous talar and calcaneal fracture in rheumatoid arthritis is described. Bone lesions were identified on radiographs, MR images and scintigraphy in a patient with right ankle pain. The absence of episodes of acute trauma, and the presence of acute clinical manifestations should guide the clinical suspicion. PMID:22470803

  18. The optics of ellipsoidal domes

    NASA Astrophysics Data System (ADS)

    Ellis, Kenneth Scott

    An ellipsoidal dome is a conformal optical element used to replace a hemispherical dome on a missile to enhance its performance by reducing its aerodynamic drag. Conformal optics are a general class of optical systems in which the optical elements are shaped to optimize something other than image quality, such as aerodynamics. An ellipsoidal dome has lower aerodynamic drag than a comparably sized hemispherical dome. On a missile, lower drag improves its aerodynamic performance by increasing its range and fuel efficiency but degrades the quality of the transmitted wavefront. In particular, an ellipsoidal dome introduces a varying aberration component that depends on the orientation of the aperture stop, which is pivoted about a fixed axis inside the dome. The transmitted ray bundle is incident only on a portion of the dome surface, and the included area lacks axial symmetry. To better understand the imaging characteristics of an ellipsoidal dome in this application, the first- and third-order optical properties of a constant thickness dome are investigated. Particular emphasis is placed on the geometry and symmetry of an ellipse, which impose certain constraints on the form of the aberration coefficients. The geometry is defined in terms of the aerodynamic fineness ratio, outer diameter, and center thickness of the dome. Emphasis is placed on third-order astigmatism and coma, which are shown to be the dominant aberration terms. The effects of varying the fineness ratio, thickness, and index of refraction of a dome are also investigated.

  19. Removal of osteoblastoma of the talar neck using standard anterior ankle Arthroscopy:A case report

    PubMed Central

    Duan, Xiao-jun; Yang, Liu

    2016-01-01

    Introduction Osteoblastoma of the talus, a benign tumor, is rare in orthopedics. The choice of treatment is usually open surgery for excision of tumor. Limited data is available concerning arthroscopic approaches. Presentation of case A 36-year-old male patient was evaluated for pain and swelling of the left ankle joint. Based on the findings of physical examination, X-rays and MRI investigations, the tumor was isolated. Standard anterior arthroscopic surgery was performed due to ankle pain. A diagnosis of osteoblastoma of the talar neck was made following the pathological survey. He had no recurrent pain and normal joint mobility 5 years postoperatively during he was regularly followed up. Discussion Osteoblastoma of the talar neck is slowly progressive and it is a palpable painful mass. Open or arthroscopic surgery can be performed. Treatment strategies are decided on according to the tumor's location, extent and size. Some advantages of arthroscopic surgery are wide visualization areas, minimally invasion, low morbidity, no necessity for casting and immobilization, early rehabilitation and quick recovery. Conclusion In conclusion, arthroscopic management can be successful in selected patients with small benign tumor localized to the ankle joint. PMID:27100951

  20. Lava flows and domes

    SciTech Connect

    Fink, J. )

    1989-01-01

    This book discusses emplacement of silicic domes and mafic lava flows. The authors have utilized the combination of field, experimental and theoretical methods to constrain various characteristics of recently-emplaced lavas, including dimensions, growth rates, surface morphology, deformation styles, rheology, and volatile contents. Filed measurements from numerous volcanoes are presented. Focus is on data from Mount St. Helens. The value of such investigations is addressed.

  1. Cyclic pressurisation of lava dome rocks. Laboratory results and implications for lava dome monitoring

    NASA Astrophysics Data System (ADS)

    Dainty, M. L.; Smith, R.; Sammonds, P.; Meredith, P. G.

    2009-12-01

    Lava domes are frequently subjected to cyclic heating and pressurisation. These processes may weaken the dome rocks, leading to collapse of the lava dome or explosion and extrusion events caused by unplugging of the magma conduit. By subjecting lava dome rocks to cyclic loading and heating in the laboratory, we can investigate how these processes affect the elastic moduli and strength of the dome rocks. These elastic moduli are crucial parameters for determining how the deformation measured at a volcano relates to the pressurisation and stress. Recording acoustic emissions (AE) during these cyclic loading tests can reveal when the cracking and damage occurs and indicate expected patterns in seismicity during cyclic pressurisation of lava domes. For this laboratory investigation of cyclic loading and heating of lava dome rocks, samples with four different extrusion dates within the 2004-2008 eruption of Mount St Helens were used. This allowed us to also investigate how the mechanical properties of this lava dome changed with time. For each timed sample, four 62.5 mm long x 25 mm diameter cores were deformed in uniaxial compression. The first sample was simply loaded to failure at a constant rate, to obtain the strength and elastic moduli. Of the remaining three cores from each sample, one was slowly heated and cooled to 900°C and one to 600°C (and the other not heated). The three cores from each sample were then initially loaded to 40 MPa at a constant rate and then unloaded to 5 MPa. They were then sequentially reloaded and unloaded at the same rate with the peak stress in each cycle increased by 5 MPa until failure. For all samples, the core loaded to failure with no cycling was stronger than those subjected to cyclic loading. However, there was no weakening or reduction in elastic moduli seen for the samples subjected to a heating cycle before cyclic loading. The sample extruded in 2004 compared to the later ones from 2005 and 2006, was the weakest at 60 to 70

  2. Interspecific scaling patterns of talar articular surfaces within primates and their closest living relatives

    PubMed Central

    Yapuncich, Gabriel S; Boyer, Doug M

    2014-01-01

    The articular facets of interosseous joints must transmit forces while maintaining relatively low stresses. To prevent overloading, joints that transmit higher forces should therefore have larger facet areas. The relative contributions of body mass and muscle-induced forces to joint stress are unclear, but generate opposing hypotheses. If mass-induced forces dominate, facet area should scale with positive allometry to body mass. Alternatively, muscle-induced forces should cause facets to scale isometrically with body mass. Within primates, both scaling patterns have been reported for articular surfaces of the femoral and humeral heads, but more distal elements are less well studied. Additionally, examination of complex articular surfaces has largely been limited to linear measurements, so that ‘true area' remains poorly assessed. To re-assess these scaling relationships, we examine the relationship between body size and articular surface areas of the talus. Area measurements were taken from microCT scan-generated surfaces of all talar facets from a comprehensive sample of extant euarchontan taxa (primates, treeshrews, and colugos). Log-transformed data were regressed on literature-derived log-body mass using reduced major axis and phylogenetic least squares regressions. We examine the scaling patterns of muscle mass and physiological cross-sectional area (PCSA) to body mass, as these relationships may complicate each model. Finally, we examine the scaling pattern of hindlimb muscle PCSA to talar articular surface area, a direct test of the effect of mass-induced forces on joint surfaces. Among most groups, there is an overall trend toward positive allometry for articular surfaces. The ectal (= posterior calcaneal) facet scales with positive allometry among all groups except ‘sundatherians', strepsirrhines, galagids, and lorisids. The medial tibial facet scales isometrically among all groups except lemuroids. Scaling coefficients are not correlated with sample

  3. Evolution of Enzymatic Activities int he Enolase Superfamily: L-Talarate/Galactarate Dehydratase from Salmonella typhimurium LT2

    SciTech Connect

    Yew,W.; Fedorov, A.; Fedorov, E.; Almo, S.; Gerlt, J.

    2007-01-01

    We assigned L-talarate dehydratase (TalrD) and galactarate dehydratase (GalrD) functions to a group of orthologous proteins in the mechanistically diverse enolase superfamily, focusing our characterization on the protein encoded by the Salmonella typhimurium LT2 genome (GI:16766982; STM3697). Like the homologous mandelate racemase, L-fuconate dehydratase, and D-tartrate dehydratase, the active site of TalrD/GalrD contains a general acid/base Lys 197 at the end of the second {beta}-strand in the ({beta}/{alpha}){sub 7}{beta}-barrel domain, Asp 226, Glu 252, and Glu 278 as ligands for the essential Mg{sup 2+} at the ends of the third, fourth, and fifth {sup {beta}}-strands, a general acid/base His 328-Asp 301 dyad at the ends of the seventh and sixth {beta}-strands, and an electrophilic Glu 348 at the end of the eighth {beta}-strand. We discovered the function of STM3697 by screening a library of acid sugars; it catalyzes the efficient dehydration of both L-talarate (k{sub cat} = 2.1 s{sup -1}, k{sub cat}/K{sub m} = 9.1 x 10{sup 3} M{sup -1} s{sup -1}) and galactarate (k{sub cat} = 3.5 s{sup -1}, k{sub cat}/K{sub m} = 1.1 x 10{sup 4} M{sup -1} s{sup -1}). Because L-talarate is a previously unknown metabolite, we demonstrated that S. typhimurium LT2 can utilize L-talarate as carbon source. Insertional disruption of the gene encoding STM3697 abolishes this phenotype; this disruption also diminishes, but does not eliminate, the ability of the organism to utilize galactarate as carbon source. The dehydration of L-talarate is accompanied by competing epimerization to galactarate; little epimerization to L-talarate is observed in the dehydration of galactarate. On the basis of (1) structures of the wild type enzyme complexed with L-lyxarohydroxamate, an analogue of the enolate intermediate, and of the K197A mutant complexed with L-glucarate, a substrate for exchange of the {alpha}-proton, and (2) incorporation of solvent deuterium into galactarate in competition with

  4. Europa Ridges, Hills and Domes

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This moderate-resolution view of the surface of one of Jupiter's moons, Europa, shows the complex icy crust that has been extensively modified by fracturing and the formation of ridges. The ridge systems superficially resemble highway networks with overpasses, interchanges and junctions. From the relative position of the overlaps, it is possible to determine the age sequence for the ridge sets. For example, while the 8-kilometer-wide (5-mile) ridge set in the lower left corner is younger than most of the terrain seen in this picture, a narrow band cuts across the set toward the bottom of the picture, indicating that the band formed later. In turn, this band is cut by the narrow 2- kilometer-wide (1.2-mile) double ridge running from the lower right to upper left corner of the picture. Also visible are numerous clusters of hills and low domes as large as 9 kilometers (5.5 miles) across, many with associated dark patches of non-ice material. The ridges, hills and domes are considered to be ice-rich material derived from the subsurface. These are some of the youngest features seen on the surface of Europa and could represent geologically young eruptions.

    This area covers about 140 kilometers by 130 kilometers (87 miles by 81 miles) and is centered at 12.3 degrees north latitude, 268 degrees west longitude. Illumination is from the east (right side of picture). The resolution is about 180 meters (200 yards) per pixel, meaning that the smallest feature visible is about a city block in size. The picture was taken by the Solid State Imaging system on board the Galileo spacecraft on February 20, 1997, from a distance of 17,700 kilometers (11,000 miles) during its sixth orbit around Jupiter.

    The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at http://galileo.jpl.nasa.gov.

  5. Geodesic Domes in the Classroom.

    ERIC Educational Resources Information Center

    Lund, Charles

    1978-01-01

    Some practical, hands-on ways in which ideas about geodesic domes can be used in secondary school mathematics are described. Instructions for constructing a one-frequency geodesic sphere are given. (MP)

  6. Factors controlling lava dome morphology

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan; Bridges, Nathan; Griffiths, Ross

    1991-01-01

    Research suggests that variations in lava dome morphology on different planets will depend much more critically on local gravity and the style of eruption than on the magma composition, ambient temperature, or the relative roles of convective and radiative cooling. Eruption style in turn reflects differences in tectonic conditions and the ability of magma to exsolve volatiles. Observed crude correlations between silica content and calculated yield strengths for terrestrial lava flows and domes probably are do to differences in extrusion rate and volatile solubility, rather than intrinsic rheological properties. Thus, even after taking the known effect of gravity into account, observed differences in gross dome morphology on different planets cannot by themselves be directly related to composition. Additional information such as the distribution of surface textures and structures, or spectroscopic data will be needed to conclusively establish dome compositions.

  7. A Dome Amidst the Hexagons

    ERIC Educational Resources Information Center

    American School and University, 1976

    1976-01-01

    Describes the design of the gymnasium of York (South Carolina) Comprehensive High School, a circular 12,000 square foot structure with a prefabricated domed roof constructed of steel hubs and curved wooden beams. (JG)

  8. Estimating dome seeing for LSST

    NASA Astrophysics Data System (ADS)

    Sebag, Jacques; Vogiatzis, Konstantinos

    2014-08-01

    Begin Dome seeing is a critical effect influencing the optical performance of ground based telescopes. A previously reported combination of Computational Fluid Dynamics (CFD) and optical simulations to model dome seeing was implemented for the latest LSST enclosure geometry. To this end, high spatial resolution thermal unsteady CFD simulations were performed for three different telescope zenith angles and four azimuth angles. These simulations generate time records of refractive index values along the optical path, which are post-processed to estimate the image degradation due to dome seeing. This method allows us to derive the distribution of seeing contribution along the different optical path segments that composed the overall light path between the entrance of the dome up to the LSST science camera. These results are used to recognize potential problems and to guide the observatory design. In this paper, the modeling estimates are reviewed and assessed relative to the corresponding performance allocation, and combined with other simulator outputs to model the dome seeing impact during LSST operations.

  9. Sensitivity of storage field performance to geologic and cavern design parameters in salt domes.

    SciTech Connect

    Ehgartner, Brian L.; Park, Byoung Yoon; Herrick, Courtney Grant

    2010-06-01

    A sensitivity study was performed utilizing a three dimensional finite element model to assess allowable cavern field sizes in strategic petroleum reserve salt domes. A potential exists for tensile fracturing and dilatancy damage to salt that can compromise the integrity of a cavern field in situations where high extraction ratios exist. The effects of salt creep rate, depth of salt dome top, dome size, caprock thickness, elastic moduli of caprock and surrounding rock, lateral stress ratio of surrounding rock, cavern size, depth of cavern, and number of caverns are examined numerically. As a result, a correlation table between the parameters and the impact on the performance of a storage field was established. In general, slower salt creep rates, deeper depth of salt dome top, larger elastic moduli of caprock and surrounding rock, and a smaller radius of cavern are better for structural performance of the salt dome.

  10. Sensitivity of storage field performance to geologic and cavern design parameters in salt domes.

    SciTech Connect

    Ehgartner, Brian L.; Park, Byoung Yoon

    2009-03-01

    A sensitivity study was performed utilizing a three dimensional finite element model to assess allowable cavern field sizes for strategic petroleum reserve salt domes. A potential exists for tensile fracturing and dilatancy damage to salt that can compromise the integrity of a cavern field in situations where high extraction ratios exist. The effects of salt creep rate, depth of salt dome top, dome size, caprock thickness, elastic moduli of caprock and surrounding rock, lateral stress ratio of surrounding rock, cavern size, depth of cavern, and number of caverns are examined numerically. As a result, a correlation table between the parameters and the impact on the performance of storage field was established. In general, slower salt creep rates, deeper depth of salt dome top, larger elastic moduli of caprock and surrounding rock, and a smaller radius of cavern are better for structural performance of the salt dome.

  11. New insights on kinematics and deformation within lava domes

    NASA Astrophysics Data System (ADS)

    Buisson, C.

    2003-04-01

    Highly viscous magma extrusions, such as lava domes, constitute a major volcanic risk, essentially because of their cataclysmal disruption occurring during or after emplacement. It is clear that destabilisation process depends mostly on lava domes growth setting and especially internal kinematics and deformation. This particular topic has never been tackled before. Simple scaled experiments have been conducted with a viscous fluid vertically injected from a reservoir into a feeding conduit and flowing on a planar base. Silicone putty is used as analogue magma. On models section, we can determine internal particle paths trough time, velocity gradients, sense of shearing and attitude of the flattening plane. The overall geometry is characterised by a prominent upper cupola located in the centre and corresponding to an injection field versus a gravity one, situated in dome periphery. Spatial distribution between these two zones evolves with time. A dome can be termed mature once the central domain has achieved its definitive shape. Then, dome growth is only expressed by lateral gravity field growth. Displacements are radial in plan and parabolic in section. The highest strain zone is situated above the feeding conduit. In cross-sections, stretch trajectories are remarkably concentric. To the lateral margins, a triple junction of stretch trajectories defines an isotropic point in the strain field. In the main central part of the dome, an intermediate zone of reversed sense of shearing is observed and attributed to velocity gradients variations. We complete analogues models by numerical approach intended to calculate the orientation and shape of the strain ellipsoid in the three dimensions of space. They reveal that the principal stretch, 1, is radial at the base, thus parallel to the flow direction and concentric, thus perpendicular to the flow direction, at the summit. In all the domes, deformation patterns are the results of a combination between pure shear and two

  12. 'Heat Dome' Heats Up United States

    MedlinePlus

    ... news/fullstory_160028.html 'Heat Dome' Heats Up United States Much of the country to be under ... As a massive "heat dome" stretches across the United States this week, sending temperatures and humidity levels ...

  13. The lunar Gruithuisen silicic extrusive domes: Topographic configuration, morphology, ages, and internal structure

    NASA Astrophysics Data System (ADS)

    Ivanov, M. A.; Head, J. W.; Bystrov, A.

    2016-07-01

    alternated with possible explosive activity (fine-grained materials). The spatial association of the Gruithuisen domes with the highland lava plains resembles the situation in which bimodal volcanism occur on Earth. The terrestrial association can be due to either fractional crystallization in basaltic magma reservoirs or remelting of high-silica crustal materials. In the first case, the evolved melts appear in later stages of volcanic activity and in the second case these melts are formed near the beginning of evolution of the magmatic systems. The age estimates of the Gruithuisen domes and the surrounding volcanic plains are more consistent with the crustal remelting scenario. However, remelting of primary anorthositic crust cannot readily produce the silica-rich melts and requires the presence of pre-existing granite-like materials. Formation of the domes by fractional crystallization avoids this difficulty but requires explanation of the older age of the domes relative to the volcanic plains in the surroundings. A third option is that the domes are unrelated genetically to the mare deposits.

  14. The Effectiveness of Modified Vertical Dome Division Technique in Reducing Nasal Tip Projection in Rhinoplasty

    PubMed Central

    Gandomi, Behrooz; Arzaghi, Mohammad Hossein; Rafatbakhsh, Mohammad

    2011-01-01

    Background: The technique of vertical dome division or tip defining, involves incising the lateral crura and vestibular skin at or lateral to the dome or tip defining point. The incision divides the lower lateral cartilage into a lateral segment and a medial segment, which are advanced anteriorly and sutured together to increase tip projection. The present study aimed at assessing a new vertical dome division, which is a modified version of vertical dome technique to decrease nasal tip projection, and increase or decrease nasal tip rotation and other tip deformities. Methods: The medical files of patients undergone rhinoplasty from 2003 to 2008 were retrospectively analyzed. The files were selected from a computerized rhinoplasty database of patients, who had been operated using a modified vertical dome technique and followed-up for one year or more after the surgery. Results: A total of 3756 patients were operated. Complications related to the nasal tip such as bossae, bifidity, persistent tip projection or tip asymmetry was seen in 81 patients (2.1%). Revisions for tip-related problems were performed in 42 patients (1.1%). Conclusions: The findings suggest that the modified vertical dome technique is an effective method for nasal tip deprojection and narrowing via an open approach. The length of follow-up and the large sample size support effectiveness of the technique. PMID:23359623

  15. Photogrammetric monitoring of lava dome growth during the 2009 eruption of Redoubt Volcano

    NASA Astrophysics Data System (ADS)

    Diefenbach, Angela K.; Bull, Katharine F.; Wessels, Rick L.; McGimsey, Robert G.

    2013-06-01

    The 2009 eruption of Redoubt Volcano, Alaska, began with a phreatic explosion on 15 March followed by a series of at least 19 explosive events and growth and destruction of at least two, and likely three, lava domes between 22 March and 4 April. On 4 April explosive activity gave way to continuous lava effusion within the summit crater. We present an analysis of post-4 April lava dome growth using an oblique photogrammetry approach that provides a safe, rapid, and accurate means of measuring dome growth. Photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed-wing volcanic gas surveys produced a series of digital elevation models (DEMs) of the lava dome from 16 April to 23 September. The DEMs were used to calculate estimates of volume and time-averaged extrusion rates and to quantify morphological changes during dome growth. Effusion rates ranged from a maximum of 35 m3 s- 1 during the initial two weeks to a low of 2.2 m3 s- 1 in early summer 2009. The average effusion rate from April to July was 9.5 m3 s- 1. Early, rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater. In mid-to-late April the volume of the dome had reached 36 × 106 m3, roughly half of the total volume, and dome growth within the summit crater began to be limited by confining crater walls to the south, east, and west. Once the dome reached the steep, north-sloping gorge that breaches the crater, growth decreased to the south, but the dome continued to inflate and extend northward down the gorge. Effusion slowed during 16 April-1 May, but in early May the rate increased again. This rate increase was accompanied by a transition to exogenous dome growth. From mid-May to July the effusion rate consistently declined. The decrease is consistent with observations of reduced seismicity, gas emission, and thermal anomalies, as well as declining rates of geodetic deflation or inflation. These trends

  16. Foldable dome climate measurements and thermal properties

    NASA Astrophysics Data System (ADS)

    Sliepen, Guus; Jägers, Aswin P. L.; Hammerschlag, Robert H.; Bettonvil, Felix C. M.

    2010-07-01

    As part of a larger project for measuring various aspects of foldable domes in the context of EST and with support of the Dutch Technology Foundation STW, we have collected over a year of continuous temperature and humidity measurements, both inside and outside the domes of the Dutch Open Telescope (DOT) on La Palma5 and the GREGOR telescope on Tenerife.6 In addition, we have measured the wind field around each dome. Although the structure of both domes is similar, the DOT dome has a single layer of cloth, and is situated on top of an open tower. In contrast, the GREGOR dome has a double layer of cloth, and is situated on top of a tower-shaped building. These differences result in large differences in temperature and humidity insulation when the dome is closed. We will present the changes in temperature and humidity one can expect for each dome within one day, and the statistics for the variations throughout a year. In addition, we will show that the main advantage of a foldable dome is the near instantaneous equilibration of the air inside the volume originally enclosed by the dome and that of the environment outside the dome. This property allows one to operate a telescope without needing expensive air conditioning and dome skin temperature control in order to limit dome and shell seeing effects. The measurements give also information about the weather fluctuations at the sites of the domes. It was observed that on small time scales the temperature fluctuations are significantly greater during the day than during the night.

  17. Arthroscopic Excision of Bone Fragments in a Neglected Fracture of the Lateral Process of the Talus in a Junior Soccer Player

    PubMed Central

    Funasaki, Hiroki; Kato, Soki; Hayashi, Hiroteru; Marumo, Keishi

    2014-01-01

    Fractures of the lateral process of the talus are uncommon and often overlooked. Typically, they are found in adult snowboarders. We report the case of an 11-year-old male soccer player who complained of lateral ankle pain after an inversion injury 6 months earlier. He did not respond to conservative treatment and thus underwent arthroscopic excision of fragments of the talar lateral process. The ankle was approached through standard medial and anterolateral portals. A 2.7-mm-diameter 30° arthroscope was used. Soft tissues around the talus were cleared with a motorized shaver, and the lateral aspect of the talar process was then visualized. The lateral process presented as an osseous overgrowth, and a loose body was impinged between the talus and the calcaneus. The osseous overgrowth was resected piece by piece with a punch, and the loose body was removed en block. The patient returned to soccer 5 weeks after the operation. This case exemplifies 2 important points: (1) This type of fracture can develop even in children and not only in snowboarders. (2) Arthroscopic excision of talar lateral process fragments can be accomplished easily, and return to sports can be achieved in a relatively short time. PMID:25126497

  18. What factors control superficial lava dome explosivity?

    PubMed Central

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J.

    2015-01-01

    Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management. PMID:26420069

  19. What factors control superficial lava dome explosivity?

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J.

    2015-09-01

    Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management.

  20. Programmable shape transformation of elastic spherical domes.

    PubMed

    Abdullah, Arif M; Braun, Paul V; Hsia, K Jimmy

    2016-07-20

    We investigate mismatch strain driven programmable shape transformation of spherical domes and report the effects of different geometric and structural characteristics on dome behavior in response to applied mismatch strain. We envision a bilayer dome design where the differential swelling of the inner layer with respect to the passive outer layer in response to changes in dome surroundings (such as the introduction of an organic solvent) introduces mismatch strain within the bilayer system and causes dome shape transformation. Finite element analysis reveals that, in addition to snap-through, spherical domes undergo bifurcation buckling and eventually gradual bending to morph into cylinders with increasing mismatch strain. Besides demonstrating how the snap-through energy barrier depends on the spherical dome shape, our analysis identifies three distinct groups of dome geometries based on their mismatch strain-transformed configuration relationships. Our experiments with polymer-based elastic bilayer domes that exhibit differential swelling in organic solvents qualitatively confirm the finite element predictions. We establish that, in addition to externally applied stimuli (mismatch strain), bilayer spherical dome morphing can be tuned and hence programmed through its geometry and structural characteristics. Incorporation of an elastic instability mechanism such as snap-through within the framework of stimuli-responsive functional devices can improve their response time which is otherwise controlled by diffusion. Hence, our proposed design guidelines can be used to realize deployable, multi-functional, reconfigurable, and therefore, adaptive structures responsive to a diverse set of stimuli across multiple length scales. PMID:27435451

  1. A Radar Survey of Lunar Dome Fields

    NASA Technical Reports Server (NTRS)

    Carter, Lynn M.; Campbell, Bruce A.; Hawke, B. Ray; Bussey, Ben

    2011-01-01

    The near side of the Moon has several areas with a high concentration of volcanic domes. These low relief structures are considerably different in morphology from terrestrial cinder cones, and some of the domes may be similar to some terrestrial shields formed through Hawaiian or Strombolian eruptions from a central pipe vent or small fissure [1]. The domes are evidence that some volcanic lavas were more viscous than the mare flood basalts that make up most of the lunar volcanic flows. It is still not known what types of volcanism lead to the creation of specific domes, or how much dome formation may have varied across the Moon. Prior work has shown that some domes have unusual radar polarization characteristics that may indicate a surface or subsurface structure that is different from that of other domes. Such differences might result from different styles of late-stage volcanism for some of the domes, or possibly from differences in how the erupted materials were altered over time (e.g. by subsequent volcanism or nearby cratering events). For example, many of the domes in the Marius Hills region have high circular polarization ratios (CPRs) in S-band (12.6 cm wavelength) and/or P-band (70 cm wavelength) radar data [2]. The high CPRs are indicative of rough surfaces, and suggest that these domes may have been built from overlapping blocky flows that in some cases have been covered by meters of regolith [2, 3]. In other cases, domes have low circular polarization ratios indicative of smooth, rock-poor surfaces or possibly pyroclastics. The 12 km diameter dome Manilius 1 in Mare Vaporum [1], has a CPR value of 0.20, which is significantly below values for the surrounding basalts [4]. To better understand the range of surface properties and styles of volcanism associated with the lunar domes, we are currently surveying lunar dome fields including the Marius Hills, Cauchy/Jansen dome field, the Gruithuisen domes, and domes near Hortensius and Vitruvius.

  2. Sustainable Outreach: Lessons Learned from Space Update and Discovery Dome

    NASA Astrophysics Data System (ADS)

    Reiff, P. H.; Sumners, C.; Law, C. C.

    2009-12-01

    A sustainable program lives on past its initial funding cycle, and develops a network of users that ensures continued life, either by fees, advertising revenue, or by making the program more successful in later sponsored grants. Teachers like free things, so having a sponsor for products such as lithographs or CD-Roms is key to wide distribution. In 1994 we developed “Space Update®”, under the NASA “Public Use of the Internet” program. It has new editions annually, with over 40,000 distributed so far (many purchased but most free at teacher and student workshops). In 1996 we created a special edition “Space Weather®”, which includes the space weather module from Space Update plus other resources. Initially developed with funding from the IMAGE mission, it is now sponsored by Cluster and MMS. A new edition is published annually and distributed in the “Sun-Earth Day” packet; total distribution now exceeds 180,000. “Earth Update” was created in 1999 under cooperative agreement “Museums Teaching Planet Earth”. It now has a total distribution of over 20,000. Both Earth Update and Space Update were developed to be museum kiosk software, and more than 15 museums have them on display. Over 4,000 users are active in our e-Teacher network and 577 in our museum educator network. Although these can certainly be considered successful because of their longevity and user base, we have had a far more dramatic sustainable program arise in the last six years… the “Discovery Dome®”. Invented at HMNS and developed under NASA Cooperative Agreement “Immersive Earth”, this dome was the first digital portable planetarium that also showed fulldome movies with an interactive interface (first shown to the public at the Dec 2003 AGU meeting). The Discovery Dome network (tinyurl.com/DiscDome) has spun those initial 6 NASA-funded domes into over 90 installations in 22 states and 23 countries. Creating high quality content is quite expensive and so needs

  3. Rehabilitation and return-to-sports activity after debridement and bone marrow stimulation of osteochondral talar defects.

    PubMed

    van Eekeren, Inge C M; Reilingh, Mikel L; van Dijk, C Niek

    2012-10-01

    An osteochondral defect (OD) is a lesion involving the articular cartilage and the underlying subchondral bone. ODs of the talus can severely impact on the quality of life of patients, who are usually young and athletic. The primary treatment for ODs that are too small for fixation, consists of arthroscopic debridement and bone marrow stimulation. This article delineates levels of activity, determines times for return to activity and reviews the factors that affect rehabilitation after arthroscopic debridement and bone marrow stimulation of a talar OD. Articles for review were obtained from a search of the MEDLINE database up to January 2012 using the search headings 'osteochondral defects', 'bone marrow stimulation', 'sports/activity', 'rehabilitation', various other related factors and 'talus'. English-, Dutch- and German-language studies were evaluated.The review revealed that there is no consensus in the existing literature about rehabilitation times or return-to-sports activity times, after treatment with bone marrow stimulation of ODs in the talus. Furthermore, scant research has been conducted on these issues. The literature also showed that potential factors that aid rehabilitation could include youth, lower body mass index, smaller OD size, mobilization and treatment with growth factors, platelet-rich plasma, biphosphonates, hyaluronic acid and pulse electromagnetic fields. However, most studies have been conducted in vitro or on animals. We propose a scheme, whereby return-to-sports activity is divided into four phases of increasing intensity: walking, jogging, return to non-contact sports (running without swerving) and return to contact sports (running with swerving and collision). We also recommend that research, conducted on actual sportsmen, of recovery times after treatment of talar ODs is warranted. PMID:22963224

  4. FIRST OBSERVATIONS OF A DOME-SHAPED LARGE-SCALE CORONAL EXTREME-ULTRAVIOLET WAVE

    SciTech Connect

    Veronig, A. M.; Muhr, N.; Kienreich, I. W.; Temmer, M.; Vrsnak, B.

    2010-06-10

    We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imager instrument on board STEREO-B on 2010 January 17. The main arguments that the observed structure is the wave dome (and not the coronal mass ejection, CME) are (1) the spherical form and sharpness of the dome's outer edge and the erupting CME loops observed inside the dome; (2) the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; (3) the lateral extent of the expanding dome which is much larger than that of the coronal dimming; and (4) the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome (v {approx} 650 km s{sup -1}) is larger than that of the lateral expansion of the wave (v {approx} 280 km s{sup -1}), indicating that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r {sup -2.5{+-}0.3}, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.

  5. The hydrothermal alteration of cooling lava domes

    NASA Astrophysics Data System (ADS)

    Ball, Jessica L.; Stauffer, Philip H.; Calder, Eliza S.; Valentine, Greg A.

    2015-12-01

    Hydrothermal alteration is a recognized cause of volcanic instability and edifice collapse, including that of lava domes or dome complexes. Alteration by percolating fluids transforms primary minerals in dome lavas to weaker secondary products such as clay minerals; moreover, secondary mineral precipitation can affect the porosity and permeability of dome lithologies. The location and intensity of alteration in a dome depend heavily on fluid pathways and availability in conjunction with heat supply. Here we investigate postemplacement lava dome weakening by hydrothermal alteration using a finite element numerical model of water migration in simplified dome geometries. This is combined with the rock alteration index (RAI) to predict zones of alteration and secondary mineral precipitation. Our results show that alteration potential is highest at the interface between the hot core of a lava dome and its clastic talus carapace. The longest lived alteration potential fields occur in domes with persistent heat sources and permeabilities that allow sufficient infiltration of water for alteration processes, but not so much that domes cool quickly. This leads us to conclude that alteration-induced collapses are most likely to be shallow seated and originate in the talus or talus/core interface in domes which have a sustained supply of magmatic heat. Mineral precipitation at these zones of permeability contrast could create barriers to fluid flow, potentially causing gas pressurization which might promote deeper seated and larger volume collapses. This study contributes to our knowledge of how hydrothermal alteration can affect lava domes and provides constraints on potential sites for alteration-related collapses, which can be used to target hazard monitoring.

  6. Ruemker Hills - A lunar volcanic dome complex

    NASA Technical Reports Server (NTRS)

    Smith, E. I.

    1974-01-01

    The Ruemker Hills, a volcanic dome-flow complex in the northern Oceanus Procellarum, is characterized by overlapping plains-forming units with lobate scarps, volcanic domes, a 60-km ring, and a scarp which separates the plateau from surrounding mare materials. Plains-forming units are interpreted as fluid volcanic flows, and domes as viscous extrusions. One dome may be a stratovolcano. The ring system is discordant with regional structural trends and probably has a local origin. The Ruemker Hills is the closest lunar analog to the large Martian shield structures revealed on the Mariner 9 photographs of Mars.

  7. Dome cities for extreme environments

    NASA Technical Reports Server (NTRS)

    Leonard, Raymond S.; Schwartz, Milton

    1992-01-01

    Extreme environments whether they be the frigid nights of the polar regions, the burning sands of the desert, or the harsh environment of space pose interesting challenges to the architect, the engineer, and the constructor in their efforts to create habitats for mankind. In space, the goals are to provide radiation protection while also providing an aesthetic living environment for long duration missions. Because of the need to provide both radiation protection and options for expansion of base facilities, a unique structural system which separates the radiation protection systems from the pressure envelope of the habitats was created. The system uses cable networks in a tensioned structural system, which supports the lunar regolith used for shielding above the facilities. The system is modular, easily expandable, and simple to construct. Additional innovations include the use of rock melting perpetrators for piles and anchoring deadmen, and various sized craters to provide side shielding. The reflective properties of the fabric used in the membrane are utilized to provide diffuse illumination. The use of craters along with the suspended shielding allows the dome to be utilized in fashions similar to those proposed by various designers unaware of the Moon's hostile radiation environment. Additional topics addressed deal with construction techniques for large domes, i.e., on the order of 100's to 1000's of meters, thermal control, the integration of tertiary water treatment schemes with architectural design, human factors, and its implications for the design of habitats for long term use in extreme environments.

  8. Dome cities for extreme environments

    NASA Astrophysics Data System (ADS)

    Leonard, Raymond S.; Schwartz, Milton

    Extreme environments whether they be the frigid nights of the polar regions, the burning sands of the desert, or the harsh environment of space pose interesting challenges to the architect, the engineer, and the constructor in their efforts to create habitats for mankind. In space, the goals are to provide radiation protection while also providing an aesthetic living environment for long duration missions. Because of the need to provide both radiation protection and options for expansion of base facilities, a unique structural system which separates the radiation protection systems from the pressure envelope of the habitats was created. The system uses cable networks in a tensioned structural system, which supports the lunar regolith used for shielding above the facilities. The system is modular, easily expandable, and simple to construct. Additional innovations include the use of rock melting perpetrators for piles and anchoring deadmen, and various sized craters to provide side shielding. The reflective properties of the fabric used in the membrane are utilized to provide diffuse illumination. The use of craters along with the suspended shielding allows the dome to be utilized in fashions similar to those proposed by various designers unaware of the Moon's hostile radiation environment. Additional topics addressed deal with construction techniques for large domes, i.e., on the order of 100's to 1000's of meters, thermal control, the integration of tertiary water treatment schemes with architectural design, human factors, and its implications for the design of habitats for long term use in extreme environments.

  9. Environmental assessment: Richton Dome site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. These evaluations were reported in draft environmental assessments (EAs), which were issued for public review and comment. After considering the comments received on the draft EAs, the DOE prepared the final EAs. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. This setting contains two other potentially acceptable sites--the Cypress Creek Dome site in Mississippi and the Vacherie Dome site in Louisiana. Although the Cypress Creek Dome and the Vacherie Dome sites are suitable for site characterization, the DOE has concluded that the Richton Dome site is the preferred site in the Gulf interior region. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines.

  10. Environmental assessment: Richton Dome Site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. These evaluations were reported in draft environmental assessments (EAs), which were issued for public review and comment. After considering the comments received on the draft EAs, the DOE prepared the final EAs. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. This setting contains two other potentially acceptable sites--the Cypress Creek Dome site in Mississippi and the Vacherie Dome site in Louisiana. Although the Cypress Creek Dome and the Vacherie Dome sites are suitable for site characterization, the DOE has concluded that the Richton Dome site is the preferred site in the Gulf interior region. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines.

  11. Submarine Analogs to Venusian Pancake Domes

    NASA Technical Reports Server (NTRS)

    Bridges, Nathan T.

    1995-01-01

    The morphology and dimensions of the large diameter, steep-sided, flat-topped "pancake domes" on Venus make them unlike any type of terrestrial subaerial volcano. Comparisons between images of Hawaiian seamounts and pancake domes show similarities in shapes and secondary features. The morphometry of pancake domes is closer to that of Pacific seamounts than subaerial lava domes. Considering both morphology and morphometry, seamounts seem a better analog to the pancake domes. The control of volatile exsolution by pressure on Venus and the seafloor can cause lavas to have similar viscosities and densities, although the latter will be counteracted by high buoyancy underwater. However, analogous effects of the Venusian and seafloor alone are probably not sufficient to produce similar volcanoes. Rather, Venusian lavas of various compositions may behave like basalt on the seafloor if appropriate rates and modes of extrusion and planetary thermal structure are also considered.

  12. Forecasting Lava Dome Eruptions from High Frequency Seismicity

    NASA Astrophysics Data System (ADS)

    Smith, R.; Kilburn, C. R.; Sammonds, P. R.

    2005-12-01

    Following its plinian eruption on 18 May 1980, Mount St Helens (Washington State, U.S.A.) entered a period of intermittent lava-dome extrusion until 1986. A re-analysis of the timing of volcano-tectonic (VT) earthquakes and eruptions indicates that: (1) all VT crises resulted in an eruption within 3 weeks (usually less than 10 days), (2) the majority of eruptions had VT precursors, and (3) patterns of precursory seismicity showed significant variations. Thus, although these seismic events could be used to warn of an impending eruption, specific forecasts were subject to significant uncertainty. It is proposed that: (1) Increased seismicity prior to later eruptions are a result of a larger more solidified dome acting as a greater impediment to magma ascent; (2) the consistency of seismic swarms resulting in an eruption indicate that stresses high enough to initiate fracturing in the country rock and lava dome carapace were only achieved once the approach to an eruption had already begun; and (3) discrepancies between models of accelerating rock fracture and the observed seismicity may arise due to a significant amount of the material failing and deforming through ductile mechanisms rather than seismogenic fracture.

  13. A comparison between semi-spheroid- and dome-shaped quantum dots coupled to wetting layer

    SciTech Connect

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad

    2014-06-15

    During the epitaxial growth method, self-assembled semi-spheroid-shaped quantum dots (QDs) are formed on the wetting layer (WL). However for sake of simplicity, researchers sometimes assume semi-spheroid-shaped QDs to be dome-shaped (hemisphere). In this work, a detailed and comprehensive study on the difference between electronic and transition properties of dome- and semi-spheroid-shaped quantum dots is presented. We will explain why the P-to-S intersubband transition behaves the way it does. The calculated results for intersubband P-to-S transition properties of quantum dots show two different trends for dome-shaped and semi-spheroid-shaped quantum dots. The results are interpreted using the probability of finding electron inside the dome/spheroid region, with emphasis on the effects of wetting layer. It is shown that dome-shaped and semi-spheroid-shaped quantum dots feature different electronic and transition properties, arising from the difference in lateral dimensions between dome- and semi-spheroid-shaped QDs. Moreover, an analogy is presented between the bound S-states in the quantum dots and a simple 3D quantum mechanical particle in a box, and effective sizes are calculated. The results of this work will benefit researchers to present more realistic models of coupled QD/WL systems and explain their properties more precisely.

  14. Repair of acute injuries of the lateral ligament complex of the ankle by suture anchors

    PubMed Central

    Liu, Xiang-Fei; Fang, Yang; Cao, Zhong-Hua; Li, Guang-Feng; Yang, Guo-Qing

    2015-01-01

    Objective: The objective of this study was to investigate the clinical curative effect of stage I repair of acute injuries of the lateral ligament complex of the ankle by the application of suture anchors. Methods: We retrospectively analyzed 18 cases of III degree acute injuries of the lateral ligament complex of the ankle. Results: There were statistically significant differences in preoperative and last follow-up VAS pain scores and AOFAS ankle hind-foot function scores. The X-ray talus displacement values in the anterior drawer test and pressure anteroposterior X-ray talar tilt in the ankle talar tilt test also showed statistically significant differences. Complications occurred in 2 patients, incision surface infection in one, and postoperative lateral dorsal skin numbness in one. All these cases were cured after symptomatic treatment. At the last follow-up all patients’ ankle joint activity recovered to their preinjury function levels. Conclusion: The application of suture anchors for small incision stage I repair of the lateral collateral ligament of ankle joint degree III injury, can effectively restored the stability of ankle joint, and prevent the occurrence of chronic ankle instability complications. It is effective and feasible for the treatment of ankle joint lateral collateral ligament injuries. PMID:26885144

  15. Emplacement Scenarios for Volcanic Domes on Venus

    NASA Technical Reports Server (NTRS)

    Glaze, Lori S.; Baloga, Steve M.; Stofan, Ellen R.

    2012-01-01

    One key to understanding the history of resurfacing on Venus is better constraints on the emplacement timescales for the range of volcanic features visible on the surface. A figure shows a Magellan radar image and topography for a putative lava dome on Venus. 175 such domes have been identified with diameters ranging from 19 - 94 km, and estimated thicknesses as great as 4 km. These domes are thought to be volcanic in origin and to have formed by the flow of viscous fluid (i.e., lava) on the surface.

  16. Pressure Dome for High-Pressure Electrolyzer

    NASA Technical Reports Server (NTRS)

    Norman, Timothy; Schmitt, Edwin

    2012-01-01

    A high-strength, low-weight pressure vessel dome was designed specifically to house a high-pressure [2,000 psi (approx. = 13.8 MPa)] electrolyzer. In operation, the dome is filled with an inert gas pressurized to roughly 100 psi (approx. = 690 kPa) above the high, balanced pressure product oxygen and hydrogen gas streams. The inert gas acts to reduce the clamping load on electrolyzer stack tie bolts since the dome pressure acting axially inward helps offset the outward axial forces from the stack gas pressure. Likewise, radial and circumferential stresses on electrolyzer frames are minimized. Because the dome is operated at a higher pressure than the electrolyzer product gas, any external electrolyzer leak prevents oxygen or hydrogen from leaking into the dome. Instead the affected stack gas stream pressure rises detectably, thereby enabling a system shutdown. All electrical and fluid connections to the stack are made inside the pressure dome and require special plumbing and electrical dome interfaces for this to be accomplished. Further benefits of the dome are that it can act as a containment shield in the unlikely event of a catastrophic failure. Studies indicate that, for a given active area (and hence, cell ID), frame outside diameter must become ever larger to support stresses at higher operating pressures. This can lead to a large footprint and increased costs associated with thicker and/or larger diameter end-plates, tie-rods, and the frames themselves. One solution is to employ rings that fit snugly around the frame. This complicates stack assembly and is sometimes difficult to achieve in practice, as its success is strongly dependent on frame and ring tolerances, gas pressure, and operating temperature. A pressure dome permits an otherwise low-pressure stack to operate at higher pressures without growing the electrolyzer hardware. The pressure dome consists of two machined segments. An O-ring is placed in an O-ring groove in the flange of the bottom

  17. Silicic lava dome growth in the 1934-1935 Showa Iwo-jima eruption, Kikai caldera, south of Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Maeno, Fukashi; Taniguchi, Hiromitsu

    2006-06-01

    The 1934-1935 Showa Iwo-jima eruption started with a silicic lava extrusion onto the floor of the submarine Kikai caldera and ceased with the emergence of a lava dome. The central part of the emergent dome consists of lower microcrystalline rhyolite, grading upward into finely vesicular lava, overlain by coarsely vesicular lava with pumice breccia at the top. The lava surface is folded, and folds become tighter toward the marginal part of the dome. The dome margin is characterized by two zones: a fracture zone and a breccia zone. The fracture zone is composed of alternating layers of massive lava and welded oxidized breccia. The breccia zone is the outermost part of the dome, and consists of glassy breccia interpreted to be hyaloclastite. The lava dome contains lava with two slightly different chemical compositions; the marginal part being more dacitic and the central part more rhyolitic. The fold geometry and chemical compositions indicate that the marginal dacite had a slightly higher temperature, lower viscosity, and lower yield stress than the central rhyolite. The high-temperature dacite lava began to effuse in the earlier stage from the central crater. The front of the dome came in contact with seawater and formed hyaloclastite. During the later stage, low-temperature rhyolite lava effused subaerially. As lava was injected into the growing dome, the fracture zone was produced by successive fracturing, ramping, and brecciation of the moving dome front. In the marginal part, hyaloclastite was ramped above the sea surface by progressive increments of the new lava. The central part was folded, forming pumice breccia and wrinkles. Subaerial emplacement of lava was the dominant process during the growth of the Showa Iwo-jima dome.

  18. Internal fabric development in complex lava domes

    NASA Astrophysics Data System (ADS)

    Závada, Prokop; Kratinová, Zuzana; Kusbach, Vladimír; Schulmann, Karel

    2009-03-01

    Viscous lava extrusions were modeled using plaster of Paris with admixed magnetite dust which served as a tracer of the internal anisotropy of magnetic susceptibility fabric in model lava domes. Used analogue material showed pseudoplastic behavior and yield strength level proportional to increasing mixing ratio of plaster powder and water. A series of models ranging from simple gravity flows to complex lava domes showing combined endogenous and exogenous growth were created by intrusion of plaster into a sandbox. The similarity of model bodies is compared with natural lava domes on the basis of dynamic scaling analysis. Growth dynamics, exogenous growth and internal fabric development in natural lava domes is critically discussed using the experimental results.

  19. Environmental assessment overview: Richton Dome site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines. On the basis of these findings, the DOE is nominating the Richton Dome site as one of five sites suitable for characterization. 3 figs.

  20. 'Heat Dome' Not Budging Until Week's End

    MedlinePlus

    ... fullstory_160083.html 'Heat Dome' Not Budging Until Week's End Eastern part of country still in its ... not be budging before the end of the week, weather forecasters said Tuesday. "With no strong pushes ...

  1. Yukimarimo at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Petenko, Igor

    2015-04-01

    Natural frostballs called "yukimarimo" were observed at at Dome C, Antarctica, during the winter of 2014. Frostballs have spheroidal or lightly oblate form. Four cases of the yukimarimo were observed in the period April - August. The characteristics concerning their sizes, density, distribution over the surface varied for different cases. The diameters ranged from several millimetres to 120 mm, the density ranged from 15 to 60 kg/m3 . The heaviest one weighted 14 g and had a diameter of ≈90 mm. The initial "material" from which they formed resembles candy floss or fluff. In one case, only the initial stage of the small-yukimarimo formation was observed; the further development was interrupted. The meteorological conditions observed diuring the yukimarimo were not particular. The near-surface temperature varied between -70° and -60°C. Winds favouring to the yukimarimo formation were low, but not less than 2 m/s^1. A two-step mechanism of their formation and development is assumed: 1) at the initial stage, an electrostatic attraction favours the clumping of ice crystals to form some ice mass resembling floss structured in spherical pieces; 2) some pieces of ice floss are rolled by the wind and collect more ice crystals and increase in size like to a tumbleweed. Special comprehensive studies of electrical properties of the frost during the initial stage are necessary. Videos of moving yukimarimo at different stages of their formation are available.

  2. The design research of a spinel dome

    NASA Astrophysics Data System (ADS)

    Zhao, Hongwei; Hou, Tianjin; Zhu, Bin; Huang, Qiu; Gao, Zhifeng

    2011-08-01

    Based on the aerodynamic heating simulated results of a spinel middle-infrared (Mid IR) image guide missile dome flying at supersonic speed, a series of experiments are made and some methods of eliminating aero-heating effect are carried out successfully. First, a simulation experiment on the ground discarding an outside protective shell of a spinel dome is accomplished in order to inspect the withstanding impact ability of the dome. Second, an arc wind tunnel experiment is fulfilled to obtain thermal mechanics characteristic of the spinel dome, and a method to buildup obviously mechanics intensity is approved which is coating diamond protective layer on the external wall of the spinel dome. Third, two heated dome imaging experiments on the ground are made to study the aero-optical phenomenon. Finally, a rocket sled experiment of a guide missile head is made successfully. Experimental results show that when the guide missile head flies in a supersonic, by adjusting the frame integration time of detector etc. the aero-optic effect would decrease greatly.

  3. Beware the Emergency Ankle Fracture Referral: An Unusual Case of Lateral Subtalar Joint Dislocation Secondary to Calcaneal Fracture with associated Lateral Malleolus Fracture

    PubMed Central

    Colegate-Stone, TJ; James, SE; Koka, SR

    2015-01-01

    Introduction: The referral of a lateral malleolus fracture is one of the commonest orthopaedic trauma presentations. Failure to fully assess the patient and radiography can lead to missing associated injuries in the hindfoot. Case Report: We describe an unusual hindfoot injury with an atypical combination of lateral subtalar dislocation and calcaneal fracture with associated lateral malleolus fracture that was initially not appreciated by the referring emergency department. This case is of particular interest as subtalar dislocation is a rare injury and lateral subtalar dislocation is even rarer. Conclusion: Failure to fully assess such injuries and manage non-operatively leads to early degenerative tibia-talar, hindfoot and midfoot changes and a difficult situation for the surgeon to salvage. We advocate early CT scan and open reduction with fixation for such cases. PMID:27299009

  4. Dome, Sweet Dome--Geodesic Structures Teach Math, Science, and Technology Principles

    ERIC Educational Resources Information Center

    Shackelford, Ray; Fitzgerald, Michael

    2007-01-01

    Today, geodesic domes are found on playgrounds, homes, over radar installations, storage facilities, at Disney's Epcot Center, and at World's Fairs. The inventor of the design, Buckminster Fuller, thought that geodesic domes could be used to cover large areas and even designed one to cover all of New York's Manhattan Island. This article details…

  5. Statistical forecasting of repetitious dome failures during the waning eruption of Redoubt Volcano, Alaska, February-April 1990

    USGS Publications Warehouse

    Page, R.A.; Lahr, J.C.; Chouet, B.A.; Power, J.A.; Stephens, C.D.

    1994-01-01

    successful forecasts and two false alarms; no events would have been missed. On closer examination, the intervals between successive dome failures are not uniform but tend to increase with time. This increase attests to the continuous, slowly decreasing supply of magma to the surface vent during the waning phase of the eruption. The domes formed in a precarious position in a breach in the summit crater rim where they were susceptible to gravitational collapse. The instability of the February 15-April 21 domes relative to the earlier domes is attributed to reaming the lip of the vent by a laterally directed explosion during the major dome-destroying eruption of February 15, a process which would leave a less secure foundation for subsequent domes. ?? 1994.

  6. Statistical forecasting of repetitious dome failures during the waning eruption of Redoubt Volcano, Alaska, February April 1990

    NASA Astrophysics Data System (ADS)

    Page, Robert A.; Lahr, John C.; Chouet, Bernard A.; Power, John A.; Stephens, Christopher D.

    1994-08-01

    successful forecasts and two false alarms; no events would have been missed. On closer examination, the intervals between successive dome failures are not uniform but tend to increase with time. This increase attests to the continuous, slowly decreasing supply of magma to the surface vent during the waning phase of the eruption. The domes formed in a precarious position in a breach in the summit crater rim where they were susceptible to gravitational collapse. The instability of the February 15-April 21 domes relative to the earlier domes is attributed to reaming the lip of the vent by a laterally directed explosion during the major dome-destroying eruption of February 15, a process which would leave a less secure foundation for subsequent domes.

  7. Dome forming eruptions: a global hazards database

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Loughlin, S.; Calder, E. S.; Ortiz, N.

    2009-12-01

    The analysis of global datasets of historical eruptions is a powerful tool for decision-making as well as for scientific discovery. Lava dome forming eruptions are common throughout the world, can extend for significant periods of time and have many associated hazards, thus providing a rich source of data to mine. A database on dome forming eruptions is under development with the view to aiding comparative studies, providing scientists with valuable data for analysis, and enabling advances in modeling of associated hazards. For new eruptive episodes in particular, and in the absence of monitoring data or a knowledge of a volcano’s eruptive history, global analysis can provide a method of understanding what might be expected based on similar eruptions in the past. Important scientific information has already been gleaned from disparate collections of dome-forming eruption hazard information, such as variation in the mobility of different types of pyroclastic flows, magma ascent and extrusion dynamics, and mechanisms of lava dome collapse. Further, modeling (both empirically-based and geophysically-based) of volcanic phenomena requires extensive data for development, calibration and validation. This study investigates the relationship between large explosive eruptions (VEI ≥ 4) and lava dome-growth from 1000 CE to present by development of a world-wide database of all relevant information, including dome growth duration, pauses between episodes of dome growth, and extrusion rates. Data sources include the database of volcanic activity maintained by the Smithsonian Institute (Global Volcanism Program) and all relevant published review papers, research papers and reports. For example, nearly all dome-forming eruptions have been associated with some level of explosive activity. Most explosions are vulcanian with eruption plumes reaching less than 15 km, and with a Volcanic Explosivity Index (VEI) <3. However large Plinian explosions with a VEI ≥ 4 can also occur

  8. Holodeck: Telepresence Dome Visualization System Simulations

    NASA Technical Reports Server (NTRS)

    Hite, Nicolas

    2012-01-01

    This paper explores the simulation and consideration of different image-projection strategies for the Holodeck, a dome that will be used for highly immersive telepresence operations in future endeavors of the National Aeronautics and Space Administration (NASA). Its visualization system will include a full 360 degree projection onto the dome's interior walls in order to display video streams from both simulations and recorded video. Because humans innately trust their vision to precisely report their surroundings, the Holodeck's visualization system is crucial to its realism. This system will be rigged with an integrated hardware and software infrastructure-namely, a system of projectors that will relay with a Graphics Processing Unit (GPU) and computer to both project images onto the dome and correct warping in those projections in real-time. Using both Computer-Aided Design (CAD) and ray-tracing software, virtual models of various dome/projector geometries were created and simulated via tracking and analysis of virtual light sources, leading to the selection of two possible configurations for installation. Research into image warping and the generation of dome-ready video content was also conducted, including generation of fisheye images, distortion correction, and the generation of a reliable content-generation pipeline.

  9. Geology of Damon Mound Salt Dome, Texas

    SciTech Connect

    Collins, E.W.

    1989-01-01

    Geological investigation of the stratigraphy, cap-rock characteristics, deformation and growth history, and growth rate of a shallow coastal diapir. Damon Mound salt dome, located in Brazoria County, has salt less than 600 feet and cap rock less than 100 feet below the surface; a quarry over the dome provides excellent exposures of cap rock as well as overlying Oligocene to Pleistocene strata. These conditions make it ideal as a case study for other coastal diapirs that lack bedrock exposures. Such investigations are important because salt domes are currently being considered by chemical waste disposal companies as possible storage and disposal sites. In this book, the author reviews previous research, presents additional data on the subsurface and surface geology at Damon Mound, and evaluates Oligocene to post-Pleistocene diapir growth.

  10. Isotopic analysis of northern Himalayan gneiss domes

    NASA Astrophysics Data System (ADS)

    Hassett, W. C.

    2010-12-01

    The Leo Pargil, Renbu, and Yalashangbo gneiss domes are among the western and eastern most in the chain of north Himalayan gneiss domes. The processes of gneiss dome formation are still debated, but there is a growing consensus that they result from the diapiric rise of pooled melt from a mid-crustal, ductile channel (Whitney et al., 2004). Under the channel flow model, the ductile channel is exhumed towards the southern Himalayan range front and is exposed as the Greater Himalayan Sequence (GHS) (Beaumont et al., 2004). Gneiss domes should have a petrogenetic relationship to the GHS if the channel flow theory is correct. Geochemical investigation of these gneiss domes can therefore help to determine their provenance and mode of origin. Leo Pargil is composed of high-grade metamorphic rocks consisting of schists, phyllites, metasiltstone, metagraywacke, and subordinate quartzites, with numerous cm-m scale two-mica granite, tourmaline granite, and leucogranite dikes that constitute between 10% and 50% of the host rock (Thiede, 2006). The Renbu gneiss dome consists of an undeformed two-mica leucogranite pluton intruded into Triassic shales, and lies on the west side of a northerly trending graben belonging to the Yadong-Gulu rift system (Miller, unpublished). The Yalashangbo gneiss dome consists of muscovite-biotite granite pluton, with common pegmatite dikes and gneisses (Zhang et al., 2007). Leo Pargil has relict U/Pb zircon core ages ranging from Late Archean to Middle Paleozoic (2.8 Ga to 400 Ma) and Middle Eocene to Middle Miocene ages (49 Ma to 15 Ma) for zircon rims. The Renbu dome has relict U/Pb zircon core ages ranging from Late Archean to Late Triassic (2.5 Ga to 200 Ma) and Late Eocene to Late Miocene ages (39 Ma to 7 Ma) for zircon rims. Yalashangbo has relict U/Pb zircon core ages ranging from Late Paleoproterozoic to Middle Cretaceous (1.8 Ga to 115 Ma), but has no zircon rim ages and therefore does not record the timing of most recent magmatism

  11. Environmental assessment, Richton Dome site, Mississippi (US)

    SciTech Connect

    none,

    1986-05-01

    The Nuclear Waste Policy Act of 1982 (42 USC Sections 10101-10226) requires the environmental assessment of a potential site to include a statement of the basis for the nomination of a site as suitable for characterization. Volume 2 of this environmental assessment provides a detailed evaluation of the Richton Dome Site and its suitability as the site for a radioactive waste disposal facility under DOE siting guidelines, as well as a comparison of the Richton Dome site with other proposed sites. Evaluation of the Richton Dome site is based on the reference repository design, but the evaluation will not change if based on the Mission Plan repository concept. The comparative evaluation of proposed sites is required under DOE guidelines, but is not intended to directly support the subsequent recommendation of three sites for characterization as candidate sites. 428 refs., 24 figs., 62 tabs. (MHB)

  12. Internal ballistics model update for ASRM dome

    NASA Technical Reports Server (NTRS)

    Bowden, Mark H.; Jenkins, Billy Z.

    1991-01-01

    A previous report (no. 5-32279, contract NAS8-36955, DO 51) describes the measures taken to adapt the NASA Complex Burning Region Model and code so that is was applicable to the Advanced Solid Rocket Motor as envisioned at that time. The code so modified was called the CBRM-A. CBRM-A could calculate the port volume and burning area for the star, transition, and cylindrically perforated regions of the motor. Described here is a subsequent effort to add computation of port volume and burning area for the Advanced Solid Rocket Motor head dome. Sample output, input, and overview of the models are included. The software was configured in two forms - a stand alone head dome code and a code integrating the head dome solution with the CBRM-A.

  13. Mount Unzen dome continues to grow

    NASA Astrophysics Data System (ADS)

    Volcanic activity on Japan's Mount Unzen, which erupted on June 3 killing 41 people, continues to build, according to latest reports. Dome extrusion and pyroclastic-flow formation continued at Unzen as of June 24. On June 14, the dome was 100 m wide and 50 m high; it grew another 20 m in height by June 16. Cracks in the dome emitted gas to 200-300 m height, and periodic explosions produced 1-km-high ash columns. The evacuation area was expanded on June 17, bringing the total number of evacuees to more than 10,000. The following report on recent activity at Unzen was provided by the Smithsonian Institution's Global Volcanism Network. All times are local (= UT + 9 hours).

  14. The longevity of lava dome eruptions

    NASA Astrophysics Data System (ADS)

    Wolpert, Robert L.; Ogburn, Sarah E.; Calder, Eliza S.

    2016-02-01

    Understanding the duration of past, ongoing, and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of ongoing and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding, we show that probability distributions for dome eruption durations are both heavy tailed and composition dependent. We construct objective Bayesian statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and ongoing eruptions that depend on both eruption duration to date and composition. Our Bayesian predictive distributions reflect both uncertainty about model parameter values (epistemic uncertainty) and the natural variability of the geologic processes (aleatoric uncertainty). The results are illustrated by presenting likely trajectories for 14 dome-building eruptions ongoing in 2015. Full representation of the uncertainty is presented for two key eruptions, Soufriére Hills Volcano in Montserrat (10-139 years, median 35 years) and Sinabung, Indonesia (1-17 years, median 4 years). Uncertainties are high but, importantly, quantifiable. This work provides for the first time a quantitative and transferable method and rationale on which to base long-term planning decisions for lava dome-forming volcanoes, with wide potential use and transferability to forecasts of other types of eruptions and other adverse events across the geohazard spectrum.

  15. Treatment of complete rupture of the lateral ligaments of the ankle: a randomized clinical trial comparing cast immobilization with functional treatment.

    PubMed

    Ardèvol, Jordi; Bolíbar, Ignasi; Belda, Víctor; Argilaga, Sílvia

    2002-11-01

    This study compared the therapeutic efficacy between cast immobilization and functional treatment of grade III ruptures of the lateral ankle ligaments. Subjects ( n=121) had closed physeal cartilage, age under 35 years, grade III rupture without previous or associated injuries, and practiced regular sports. Patients were randomized into an immobilization group (21 days plaster cast) or a functional one (15 days strapping plus early controlled mobilization). Symptoms (pain, swelling, stiffness, subjective instability), joint laxity, return to preinjury activity (time and level) and rate of reinjury were assessed 3, 6, and 12 months after sprain. Objective joint laxity was related to constitutional laxity, creating a new variable [talar tilt at injury - talar tilt at control]/contralateral talar tilt. The functional group showed significantly earlier and better return to physical activity, fewer symptoms at 3 and 6 months but no intergroup difference at 12 months. Functional treatment also showed better decrease in joint laxity. No intergroup differences were found in the reinjury rate. We conclude that functional treatment is safe, associated with a more rapid recovery, and particularly suitable in athletic populations. PMID:12444517

  16. Domes Made the Difference At Valley R-6.

    ERIC Educational Resources Information Center

    Graves, Larry

    2000-01-01

    Describes the development from conception through construction of three domes in the Valley R-6 School District (Washington County, Missouri). Arguments for, and investigations into, building monolithic domes, funding issues, and efforts to gain voter approval are discussed. (GR)

  17. Water recycling at the Millennium Dome.

    PubMed

    Hills, S; Smith, A; Hardy, P; Birks, R

    2001-01-01

    Thames Water is working with the New Millennium Experience Company to provide a water recycling system for the Millennium Dome which will supply 500 m3/d of reclaimed water for WC and urinal flushing. The system will treat water from three sources: rainwater--from the Dome roof greywater--from handbasins in the toilet blocks groundwater--from beneath the Dome site The treatment technologies will range from "natural" reedbeds for the rainwater, to more sophisticated options, including biological aerated filters and membranes for the greywater and groundwater. Pilot scale trials were used to design the optimum configuration. In addition to the recycling system, water efficient devices will be installed in three of the core toilet blocks as part of a programme of research into the effectiveness of conservation measures. Data on water usage and customer behaviour will be collected via a comprehensive metering system. Information from the Dome project on the economics and efficiency of on-site recycling at large scale and data on water efficient devices, customer perception and behaviour will be of great value to the water industry. For Thames Water, the project provides vital input to the development of future water resource strategies. PMID:11436793

  18. After-Hours Science: Gee, A Dome!

    ERIC Educational Resources Information Center

    Santos, John G.

    1984-01-01

    Nature's Classroom (Southbridge, MA), which provides field experiences, academic classes, and activities in the natural sciences, has been recognized as an outstanding program by the National Science Teachers Association's Search for Excellence in Science Education project. Various program activities (including building a geodesic dome) are…

  19. Geodesic Dome Activity Provides Serious Fun!

    ERIC Educational Resources Information Center

    Anderson, Richard

    2009-01-01

    After the author's class completed last year's 44'-long timber-framed covered bridge project, he was pondering what other learning challenge he could pose to his students. He came across an article on geodesic dome construction in the September 2007 issue of "Tech Directions" and, he had his answer. In this article, the author and his students…

  20. Conformal dome correction with counterrotating phase plates

    NASA Astrophysics Data System (ADS)

    Sparrold, Scott W.; Mills, James P.; Knapp, David J.; Ellis, Kenneth S.; Mitchell, Thomas A.; Manhart, Paul K.

    2000-07-01

    Windows and domes that are shaped to aerodynamic requirements can increase range and speed for the host platform. This class of optical systems is referred to as conformal optics. The solution discussed here is intended for conformal missile systems having gimbals that point the optical line of sight through different parts of the dome. A conformal dome induces large amounts of varying aberration, tens to hundreds of waves across gimbal angle, and therefore requires dynamic correction. Space is very constricted in missile sensors, and it is therefore highly desirable to limit the number of motors used for aberration correction. This paper describes the performance of a new class of optical systems that employ counterrotating phase prisms to correct conformal dome aberrations while gimbaling the optical system. The phase surfaces on the prisms are described by Zernike circular polynomials. Since the shear across the phase surfaces is rotational, the only aberrations that are generated are those without rotational symmetry, such as tilt, coma, or astigmatism. Using this approach, CODE VTM was used to analyze and design a compact, high-performance conformal optical system.

  1. Mississippian oolites on West Virginia dome

    SciTech Connect

    Koehler, B.; Smosna, R. )

    1989-08-01

    The West Virginia dome, a positive feature during the Early Mississippian, was submerged during a Meramec-Chester transgression and became the site for ooid sedimentation. The dome's axis trended eastwest through Randolph County, West Virginia, where four outcrops of the lower Pickaway Limestone (Greenbrier Group) were studied. Pickaway oolites formed as mobile sand belts that paralleled the dome's axis. In detail, these belts consisted of sand waves up to 2 m in height that migrated north and south under the influence of tidal currents. Along the crest, both flood and ebb currents moved the sediment, whereas farther away flood tides dominated. Sand bodies shoaled upward with time, the sediment becoming coarser grained and better sorted to the top; large wedge-shaped cross-bed sets gave way to planar bedding; and frequently the ooid shoals were subaerially exposed. Ooids and other grains have been extensively micritized, indicating a slow sedimentation rate, and small-scale ripples record the effect of minor wave action. North of the dome, muddy skeletal sands accumulated in a somewhat restricted gulf. To the south along a very gentle sea floor, the ooid shoals passed into fully marine skeletal sands. On the east, a nearby landmass supplied locally large volumes of detrital quartz. The lower Pickaway was deposited during a single rise and fall of sea level that produced two oolites at each outcrop separated by off-shore sediments. This stratigraphic sequence constitutes a fifth-order cycle 7-26 m thick.

  2. CMB Observations from DomeC

    NASA Astrophysics Data System (ADS)

    de Bernardis, P.

    DomeC is likely to be the best site in the world for mm and sub-mm observations. In this paper we focus on what can be done from DomeC to investigate the detailed properties of the Cosmic Microwave Background (CMB). Two experiment typologies are particularly promising: precision measurements of the polarization of the CMB, to confirm the presence of an inflation phase in the very early universe, and high resolution measurements of the Sunyaev-Zeldovich effect (SZE) in clusters of galaxies, which can be used to investigate dark energy and dark matter in the Universe. Several important teams are currently carrying out experiments of the first kind; DomeC is the location of the BRAIN experiment, which uses bolometric interferometry as the tool to produce sensitive measurements with low systematic effects, and certainly orthogonal to the systematic effects of all other instruments currently developed to this purpose. DomeC will be an ideal location for a large dish telescope for mm and sub-mm measurements. In addition to cutting-edge sub-mm science, a telescope complementing SPT (in size and/or in frequency) will be ideal for special CMB observation, like the detection of non-Gaussian features, the measurement of relativistic effects in SZE, the measurement of the SZE resulting from the decay products of super-symmetric dark matter in selected clusters.

  3. The Urban Dust Dome: A Demonstration Model

    ERIC Educational Resources Information Center

    Cross, Ralph D.

    1973-01-01

    Working plans for an inexpensive urban dust dome model are presented together with some generalizations about urban atmosphere pollution. Theories and principles of atmospheric pollution which are introduced can be made meaningful to elementary students through classroom use of this model. (SM)

  4. Dome Storage of Farmer Stock Peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The small-scale farmer stock storage research facility at the National Peanut Research Laboratory in Dawson, GA consisting of four warehouses and four monolithic domes was used to conduct a 3-yr study looking at the effects of storing peanuts through the summer months following harvest. The study wa...

  5. Capabilites of an arch element for correcting conformal optical domes

    NASA Astrophysics Data System (ADS)

    Sparrold, Scott W.; Knapp, David J.; Manhart, Paul K.; Elsberry, Kevin W.

    1999-10-01

    This paper presents an approach for correcting conformal missile domes with a non-rotationally symmetric optical element called an arch. A parametric study in terms of aerodynamics, fineness ratio, maximum seeker look angle and dome index of refraction will demonstrate its capabilities for correcting conformal domes. A nomograph for trading optical performance versus relative missile range will also be presented.

  6. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY... Specifications for Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have...

  7. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  8. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  9. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  10. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  11. Finite Element Model of a Two-Phase Non-Newtonian Thixotropic Fluid: Mount St. Helens Lava Dome

    NASA Astrophysics Data System (ADS)

    Vincent, P.; Zevada, P.

    2011-12-01

    Extrusion of highly viscous lavas that spread laterally and form lava domes in the craters of large volcanoes is associated with significant volcanic hazards. Gas overpressure driven fragmentation of the lava dome or collapse and slumping of marginal sections or the entire mass of the dome can trigger dangerous pyroclastic flows that threaten surrounding populations up to tens of kilometers away. The rate of lava dome growth in the mature state of the dome evolution is often oscillatory. Relatively quiescent episodes are terminated by renewed extrusion and emplacement of exogenous "lobes" or "spines" of lava on the surface of the dome. Emplacement of new lobes is preceded by pressurization of magma in the magmatic conduit that can trigger volcanic eruptions and is preceded by crater floor deformation (e.g. Swanson and Holcombe, 1990). This oscillatory behavior was previously attributed primarily to crystallization kinetics and gas exsolution generating cyclic overpressure build-ups. Analogue modeling of the lava domes has revealed that the oscillatory growth rate can be reproduced by extrusion of isothermal, pseudoplastic and thixotropic plaster of Paris (analogue material for the magma) on a sand layer (analogue material for the unconsolidated deposits of the crater floor). The patterns of dome growth of these models closely correspond to both the 1980-1985 and 2004-2005 growth episodes of Mt. St. Helens lava dome (Swanson and Holcombe, 1990; Major et al., 2005). They also suggest that the oscillatory growth dynamics of the lavas can be explained by the mechanical interaction of the non-Newtonian magma with the frictional and deformable substrate below the lava dome rather than complex crystallization kinetics (e.g. Melnik and Sparks, 1999). In addition, these results suggest that the renewed growth episode of Mt. St. Helens dome in 2006 could be associated with an even higher degree of magma pressurization in the conduit than occurred during the 1980 - 1986

  12. Experimental Compaction of Pumiceous Dome Lavas

    NASA Astrophysics Data System (ADS)

    Kendrick, J.; Ashwell, P. A.; Lavalleé, Y.; Kennedy, B. M.; Hess, K. U.; Cole, J.; Dingwell, D. B.

    2012-04-01

    Lava dome stability is reliant on pore pressure, which varies according to the evolution of the permeable porous network. Here, we present experimental results of porosity and permeability evolution during compaction of aphiric (from Ngongotaha volcano) and crystal-bearing (from Tarawera volcano) pumiceous, rhyolitic lavas from Taupo Volcanic Zone, New Zealand. The Ngongotaha sample has 55 % porosity and is from the crystal-free dome carapace erupted ~200 ka following caldera collapse at Rotorua Caldera. Two sample sets from Tarawera are crystalline, pumiceous clasts from a dome-collapse generated block and ash flow at Okataina Caldera ~1314 AD, and contain 50 and 25 % pores. This study tests the validity of the 'permeable foam' model by comparing properties of the experimentally compacted pumice to denser material seen in the exposed cores of Tarawera and Ngongotaha. Cylindrical samples were deformed under conditions similar to lava dome settings, under a constant, low axial stress of 2.8 MPa at 800-900oC (above the measured calorimetric glass transition temperatures). Deformation ensued to a total axial strain of 60% and the porosity and permeability of the samples were measured at strain increments of 10 %. Samples display different resultant strains under the same applied stress and exhibit strain-hardening behaviour during compaction. The development of textures and microstructures is characterised using petrographic analysis and x-ray computed tomography. Porosity reduces steadily with increasing strain, but reaches a minimum of 20 % porosity at 40-50 % strain (irrespective of starting porosity or crystallinity), after which further strain is accommodated by barrelling of the sample. A rapid reduction in permeability along the primary axis occurs during the initial stage of compression and continues to decrease with increasing strain and densification of the lava. Permeability development differs between lava types due to the influence of crystallinity on the

  13. Posterior talar fracture with dislocation of both talo-navicular and subtalar joints: a variant type II of the Sneppens classification

    PubMed Central

    Galanopoulos, Ilias; Fogg, Quentin; Ashwood, Neil

    2012-01-01

    A 63-year-old man fell from a ladder, thus causing an axial compression injury to the right ankle. Severe deformity was evident and the ankle could not be reduced by simple manipulation. The skin was tented and appearing critically contused. Radiographs revealed an oblique fracture of the posterior aspect of the talar body with dislocation of both the talo-navicular and subtalar joints, an injury previously not described in the literature. The fracture–dislocation was anatomically reduced within 3 h of presentation and stability achieved with two headless buried compression screws. CT scan confirmed anatomical reduction and the patient remained non-weight bearing in a cast for 6 weeks. One year postoperatively, the patient remains pain-free with no radiological signs of avascular necrosis of the talus. This injury is unique and despite its severity and soft tissue compromise good quality reduction and internal fixation resulted in an excellent clinical outcome. PMID:22847568

  14. Historical review: viruses, crystals and geodesic domes.

    PubMed

    Morgan, Gregory J

    2003-02-01

    In the mid 1950s, Francis Crick and James Watson attempted to explain the structure of spherical viruses. They hypothesized that spherical viruses consist of 60 identical equivalently situated subunits. Such an arrangement has icosahedral symmetry. Subsequent biophysical and electron micrographic data suggested that many viruses had >60 subunits. Drawing inspiration from architecture, Donald Caspar and Aaron Klug discovered a solution to the problem - they proposed that spherical viruses were structured like miniature geodesic domes. PMID:12575996

  15. Remote Control of the CFHT Dome Shutter

    NASA Astrophysics Data System (ADS)

    Look, Ivan; Roberts, Larry; Vermeulen, Tom; Taroma, Ralph; Matsushige, Grant

    2011-03-01

    Several years ago CFHT proposed developing a Remote Observing Environment aimed at producing Science Observations at their Facility on Mauna Kea from their Headquarters in Waimea, HI. This Remote Observing Project commonly referred to as OAP (Observatory Automation Project) was completed at the end of January 2011 and has been providing the majority of Science Data since. My poster will attempt to provide Design Information on the Dome Shutter, which is both Controlled and Monitored Remotely from Waimea. The Dome Shutter Control System incorporates an upgraded Allen-Bradley PLC processor (SLC 5/05), which provides Remote Operation and Monitoring of the existing System. Several earlier upgrade projects were integrated to provide improvement to the Shutter System such as PLC Control, System Feedback, and Safety Features. This particular upgrade provides Remote capability, CFHT developed Control GUI, and Remote monitoring that promise to deliver a more versatile, visual, and safer Shutter Operation. The Dome Shutter Control System provides three modes of Operation namely; Remote, Integration, and Local. The Control GUI is used to operate the Shutter remotely. Integration mode is provided to develop PLC software code and is performed by connecting a Laptop directly to the Shutter Control Panel. Local mode is retained to provide Remote Lockout (No Remote Control), which allows Shutter control ONLY via the existing Electrical Panel. This mode is primarily intended for Shutter maintenance and troubleshooting. The Dome Shutter remains the first Line-of-Defense for Telescope protection due to inclement weather and so special attention was considered during Remote development. The Shutter has been equipped with an Autonomous Shutdown sequence in the event of Power or Network failure. If Loss of HELCO Power or Start-up of our Stand-by Diesel Generator is detected; a planned timing sequence will Close the Shutter Automatically. Likewise, an internal CFHT Network heartbeat was

  16. Fabric and texture at Siple Dome, Antarctica

    USGS Publications Warehouse

    Diprinzio, C.L.; Wilen, L.A.; Alley, R.B.; Fitzpatrick, J.J.; Spencer, M.K.; Gow, A.J.

    2005-01-01

    Preferred c-axis orientations are present in the firn at Siple Dome, West Antarctica, and recrystallization begins as shallow as 200 m depth in ice below -20??C, based on digital analysis of c-axis fabrics, grain-sizes and other characteristics of 52 vertical thin sections prepared in the field from the kilometer-long Siple Dome ice core. The shallowest section analyzed, from 22 m, shows clustering of c axes toward the vertical. By 200 m depth, girdle fabric and other features of recrystallized ice are evident in layers (or regions), separated by layers (regions) of typically finer-grained ice lacking evidence of recrystallization. Ice from about 700-780 m depth, which was deposited during the last ice age, is especially fine-grained, with strongly vertical c axes, but deeper ice shows much larger crystals and strong evidence of recrystallization. Azimuthal asymmetry of some c-axis fabrics, trends in grain-size, and other indicators reveal additional information on processes and history of ice flow at Siple Dome.

  17. Underwater Calibration of Dome Port Pressure Housings

    NASA Astrophysics Data System (ADS)

    Nocerino, E.; Menna, F.; Fassi, F.; Remondino, F.

    2016-03-01

    Underwater photogrammetry using consumer grade photographic equipment can be feasible for different applications, e.g. archaeology, biology, industrial inspections, etc. The use of a camera underwater can be very different from its terrestrial use due to the optical phenomena involved. The presence of the water and camera pressure housing in front of the camera act as additional optical elements. Spherical dome ports are difficult to manufacture and consequently expensive but at the same time they are the most useful for underwater photogrammetry as they keep the main geometric characteristics of the lens unchanged. Nevertheless, the manufacturing and alignment of dome port pressure housing components can be the source of unexpected changes of radial and decentring distortion, source of systematic errors that can influence the final 3D measurements. The paper provides a brief introduction of underwater optical phenomena involved in underwater photography, then presents the main differences between flat and dome ports to finally discuss the effect of manufacturing on 3D measurements in two case studies.

  18. The association of lava dome growth with major explosive activity (VEI ≥ 4): DomeHaz, a global dataset

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Loughlin, S. C.; Calder, E. S.

    2015-05-01

    Investigation of the global eruptive records of particular types of volcanoes is a fundamental and valuable method of understanding what style of activity can be anticipated in the future and can highlight what might be expected or unusual in particular settings. This paper investigates the relationship between large explosions (volcanic explosivity index, VEI ≥ 4) and lava dome growth from 1000 AD to present and develops the DomeHaz database. DomeHaz contains information from 397 dome-forming episodes, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude (VEI) of associated large explosions. Major explosive activity, when associated with dome growth, is more likely to occur before dome growth rather than during, or at the end of, dome-forming eruptions. In most cases where major explosive activity has been associated with dome growth, the eruptions occurred at basaltic andesite to andesitic volcanoes (the most common type of dome-forming volcano), but a greater proportion of dacitic and rhyolitic dome growth episodes were associated with large explosions. High extrusion rates (>10 m3 s-1) seem to be associated with large explosions and may inhibit degassing or destabilize existing domes, leading to explosive decompression. Large explosions may, alternatively, be followed by dome growth, which represents the clearing of residual magma from the conduit. Relationships extracted from the global record can be used to construct probability trees for new and ongoing dome-forming eruptions or can be used in conjunction with other types of event trees to aid in forecasting volcanic hazards during a crisis, especially for volcanoes where data are sparse.

  19. [PARTICULAR QUALITIES OF DIAGNOSTIC ACUTE LATERAL ANKLE LIGAMENT INJURIES].

    PubMed

    Krasnoperov, S N; Shishka, I V; Golovaha, M L

    2015-01-01

    Delayed diagnosis of acute lateral ankle ligaments injury and subsequent inadequate treatment leads to the development of chronic instability and rapid progression of degenerative processes in the joint. The aim of our work was to improve treatment results by developing an diagnostic algorithm and treatment strategy of acute lateral ankle ligament injuries. The study included 48 patients with history of acute inversion ankle injury mechanism. Diagnostic protocol included clinical and radiological examination during 48 hours and after 7-10 days after injury. According to the high rate of inaccurate clinical diagnosis in the first 48 hours of the injury a short course of conservative treatment for 7-10 days is needed with follow-up and controlling clinical and radiographic instability tests. Clinical symptoms of ankle inversion injury showed that the combination of local tenderness in the projection of damaged ligaments, the presence of severe periarticular hematoma in the lateral department and positive anterior drawer and talar tilt tests in 7-10 days after the injury in 87% of cases shows the presence of ligament rupture. An algorithm for diagnosis of acute lateral ankle ligament injury was developed, which allowed us to determine differential indications for surgical repair of the ligaments and conservative treatment of these patients. PMID:27089717

  20. The Velay dome (French Massif Central): melt generation and granite emplacement during orogenic evolution

    NASA Astrophysics Data System (ADS)

    Ledru, P.; Courrioux, G.; Dallain, C.; Lardeaux, J. M.; Montel, J. M.; Vanderhaeghe, O.; Vitel, G.

    2001-12-01

    This paper is a synthesis of available data on the Velay dome that include both small- and large-scale lithologic and structural mapping, strain analysis, isotope geochemistry, geochronology and pressure-temperature estimates. The Velay dome, one of the largest granite-migmatite domes of the Variscan Belt, formed during orogenic collapse at around 300 Ma. Its study allows an assessment of the thermal and geodynamic context leading to voluminous crustal anatexis of the Variscan orogenic crust. A first melting stage developed in connection with south-verging thrust zones during the Early Carboniferous, leading to a crustal thickening estimated at 20 km minimum. The involvement of fertile lithologies and the intrusion of plutons of deep origin contributed to the development of water-saturated melts. The volume of biotite granite extracted from melt during this period was limited. The second phase of melting, corresponded to generalized melting of gneiss achieved by biotite-dehydration melting reactions and accompanied by the generation of cordierite-bearing granites. At this stage, crustal-scale detachment faults were active and partially obliterated the earlier structures. The new structures were progressively tilted to the vertical at the margin of the Velay dome due to the southward and lateral ballooning of the granitic dome. The reconstructed P, T path indicate that the large volume of melt produced was a consequence of a significant increase in temperature at the onset of biotite dehydration melting. At the base of the crust, this melting event is coeval with granulite facies metamorphism associated to underplating of mantle-derived magmas as suggested by the geochemical signature of Late Paleozoic lower crustal xenoliths sampled by Cenozoic volcanoes and with the isotopic signature of the late granitic intrusions. Accordingly, it is proposed that asthenospheric upwelling was responsible for the temperature increase favoring melting of hydrous minerals.

  1. Spatial and temporal patterns of dome extrusion during the 2004-2008 eruption of Mount St. Helens

    NASA Astrophysics Data System (ADS)

    Salzer, J. T.; Denlinger, R. P.; Diefenbach, A. K.; Walter, T. R.

    2014-12-01

    Extensive efforts by the USGS Cascades Volcano Observatory in response to the 2004-2008 dome building eruption at Mount St. Helens recorded the extrusion of seven dacite spines. Efforts included a network of time-lapse cameras. Published studies of decimated data from these cameras show strong correlations between (long-term) extrusion velocities determined from the camera imagery and ancillary geophysical data, such as dome tilt and RSAM seismicity. However, more detailed analysis of these data should provide better constraints on physical processes behind dome extrusion. Here we apply modern computer vision techniques to explore the spatiotemporal variability and interactions occurring during spine extrusion and dome growth. Digital Image Correlation (DIC) delineates the deformation field in a series of images at sub-pixel level, and quantifies dome, talus and glacier deformation at unprecedented resolution, revealing spatiotemporal variability of the strain field on the time scale of hours. We identify sharp boundaries between the vertically extruding spine, laterally displaced material, and downward-creeping talus. The spine growth at Mount St. Helens appears locally constrained and structurally separated into distinct segments. The velocities of different dome segments are generally correlated, but displacement patterns of the talus are more complex. We identify short term fluctuations with periods of hours to days superimposed on longer term fluctuations having periods of several weeks. The short term episodes of high displacement rates are often associated with strongly degassing plumes observed in the camera imagery. Over longer periods (days to weeks), extrusion rates form a sinusoidal fluctuating pattern, marked by sharp increases and gradual decreases in velocity. These observations substantiate the correlations with seismic and geodetic data shown in previous studies, but more closely constrain the velocity fluctuations of each spine. These fluctuations

  2. Petrology of sapphirine-bearing gedrite-cordierite gneiss, Okanogan dome, Washington USA, and implications for gneiss dome tectonics

    NASA Astrophysics Data System (ADS)

    Kruckenberg, S. C.; Whitney, D. L.

    2007-12-01

    The northern Cordilleran migmatite domes (Thor-Odin, Valhalla, Okanogan) contain Mg-Al-rich (Si-poor) orthoamphibole-cordierite gneiss as layers and lenses surrounded by quartzofeldspathic migmatite. The Mg-Al- rich rocks contain assemblages and reaction textures that provide information about metamorphic conditions during the tectonic evolution of the migmatite dome. In the Okanogan dome, gedrite + anorthite + cordierite + spinel + sapphirine +/- kyanite +/- hornblende assemblages of the Tunk Creek Amphibolite indicate T > 700- 800 degrees C. This Okanogan unit structurally overlies a migmatite domain dominated by diatexite. In contrast to gedrite-cordierite gneiss in other northern Cordilleran domes, the Okanogan rocks occur in a discontinuous kilometer-scale unit rather than small pods; are more calcic; and lack garnet. In addition, kyanite did not transform to sillimanite, and spinel occurs most commonly as a blocky matrix phase rather than as vermicules in symplectite. The differences in textures of gedrite-cordierite gneiss in the Cordilleran domes may in part be related to differences in bulk composition, but are also likely related to differences in tectonic evolution. The Okanogan dome is located at a greater distance from the Rocky Mountain foreland-hinterland boundary, a major crustal boundary that localized and therefore maximized vertical flow (decompression) in domes adjacent to it. The Okanogan dome, ~200 km west of the boundary, may have experienced less isothermal decompression during dome emplacement compared to domes located closer to the boundary, and therefore contains relict kyanite and only minor corona/symplectite development.

  3. Identifying suitable "piercement" salt domes for nuclear waste storage sites

    SciTech Connect

    Kehle, R.

    1980-08-01

    Piercement salt domes of the northern interior salt basins of the Gulf of Mexico are being considered as permanent storage sites for both nuclear and chemically toxic wastes. The suitable domes are stable and inactive, having reached their final evolutionary configuration at least 30 million years ago. They are buried to depths far below the level to which erosion will penetrate during the prescribed storage period and are not subject to possible future reactivation. The salt cores of these domes are themselves impermeable, permitting neither the entry nor exit of ground water or other unwanted materials. In part, a stable dome may be recognized by its present geometric configuration, but conclusive proof depends on establishing its evolutionary state. The evolutionary state of a dome is obtained by reconstructing the growth history of the dome as revealed by the configuration of sedimentary strata in a large area (commonly 3,000 square miles or more) surrounding the dome. A high quality, multifold CDP reflection seismic profile across a candidate dome will provide much of the necessary information when integrated with available subsurface control. Additional seismic profiles may be required to confirm an apparent configuration of the surrounding strata and an interpreted evolutionary history. High frequency seismic data collected in the near vicinity of a dome are also needed as a supplement to the CDP data to permit accurate depiction of the configuration of shallow strata. Such data must be tied to shallow drill hole control to confirm the geologic age at which dome growth ceased. If it is determined that a dome reached a terminal configuration many millions of years ago, such a dome is incapable of reactivation and thus constitutes a stable storage site for nuclear wastes.

  4. Siple Dome: Is it in Steady State?

    NASA Astrophysics Data System (ADS)

    Pettit, E. C.; Waddington, E. D.; Nereson, N. A.; Zumberge, M. A.; Hamilton, G. S.

    2001-12-01

    Changes in the West Antarctic Ice Sheet since the end of the last ice age have implications for how we interpret its present behavior, in terms of both its stability and its record of climate history. Siple Dome, the ridge between Ice Streams C and D, is not presently thinning and is close to being in balance with present environmental conditions. We present three independent measurements of ice thickness change in the divide region of Siple Dome: a GPS surface horizontal strain network, fiber optic vertical strain measurements at depth, and precision GPS measurements of vertical motion of near-surface ice ("coffee-can" method). From the horizontal strain network, we calculate the divergence of the horizontal velocity. This divergence is equal to the gradient of vertical velocity at the surface and, with some assumptions about the distribution of strain rates with depth, we can calculate the vertical velocity at the surface. For steady state, the vertical velocity must be balanced by the local accumulation rate. The fiber optic instruments provide a profile of the relative vertical velocity with depth. We fit a theoretical vertical velocity pattern to these data and extrapolate to find the surface vertical velocity. Our third method (coffee-can) directly measures the vertical motion of a marker 20 meters deep using precision GPS and compares it with the local long-term rate of snow accumulation to calculate the net rate of ice sheet thickness change. All three methods reach the same conclusion: Siple Dome is currently very close to being in steady state. This result has two implications. First, ice dynamics models developed to interpret radar images or ice core data can assume steady state behavior, simplifying the models. Second, our result suggests that the central part of the Ross Embayment may have had a low-elevation profile during the late Holocene, even though other areas of the WAIS may have been thicker.

  5. The Sequential Emplacement of the Chaos Crags Dome Complex in Lassen National Park and a Subsequent Avalanche Event Revealing the Internal Structure of a Crystal-Rich Lava Dome

    NASA Astrophysics Data System (ADS)

    Watts, R. B.; Clynne, M. A.; Sparks, R. S.; Christiansen, R. L.

    2013-12-01

    The Chaos Crags are an aptly named and spectacularly well-preserved nest of 6 crystal-rich rhyodacitic lava domes that lie in the shadow of the renowned Lassen Peak in Lassen National Park, northern California. Each of the domes is composed of a precarious pile of large angular lava blocks indicative of a relatively fast extrusion rate. However, the 2 southernmost domes (i.e. Group 1) exhibit a coulée-like appearance with asymmetric appearance, a thick, glassy basal breccia and distinct concentric flow ridges on the upper surface. The 4 northernmost domes (i.e. Group 2) are notably more dome-like, lacking lateral flow-features and any basal breccia but displaying steeper, blocky flanks and overall low Aspect Ratio. Petrologically, the 2 Groups are very similar in whole-rock composition except there is a distinct difference in the amount of mafic inclusions present - that is ~2 vol% (Group1 domes) and ~10vol% (Group 2 domes). The age of emplacement of the Crags has been previously determined as between 1125 and 375 years B.P (Clynne & Muffler, 1989). Following a period of quiescence, a series of 3 rock-fall avalanches, most likely triggered by a tectonic earthquake, collapsed away from one of the Group 2 domes to produce the 'Jumbles Avalanche' deposit. This impressive deposit (total volume of ~7km2) spilled across the northeastern landscape focused away from the base of Dome C, one of the Group 2 domes. The avalanche events left behind a near-vertical scarp composed of shattered, massive lava riddled with closely-spaced sigmoidal cooling joints to produce a very unstable ~250 meter high and ~300 meter wide metastable structure. On its upper surface, the remnants of a smooth semi-cylindical surface scored with striations is evident. Sampling from this surface and other points away from this surface highlighted the presence of highly fragmented lava with broken jigsaw-style phenocrysts up to one meter away from the smooth surface. Samples taken from a larger

  6. Dispersive thermohaline convection near salt domes: a case at Napoleonville Dome, southeast Louisiana, USA

    NASA Astrophysics Data System (ADS)

    Jamshidzadeh, Zahra; Tsai, Frank T.-C.; Ghasemzadeh, Hasan; Mirbagheri, Seyed Ahmad; Barzi, Majid Tavangari; Hanor, Jeffrey S.

    2015-08-01

    Density-driven flow around salt domes is strongly influenced by salt concentration and temperature gradients. In this study, a thermohaline convection numerical modeling is developed to investigate flow, salinity, and heat transport around salt domes under the impact of fluid dispersivity and variable density and viscosity. `Dispersive fluid flux of total fluid mass' is introduced to the density-driven flow equation to improve thermohaline modeling in porous media. The dispersive fluid flux term is derived to account for an additional fluid flux driven by the density gradient and mechanical dispersion. The model is first tested by a hypothetical salt-dome problem, where a circulation of flow is induced by an overpressure and density effect. The result shows a distinct salt-transport change due to the inclusion of the dispersive fluid flux and temperature effect. Then, the model is applied to investigate changes of groundwater flow, salinity, and heat transport near the west of Napoleonville salt dome, southeastern Louisiana, USA, due to a salt cavern failure. The result shows that an instant overpressure assumed to be created by the salt-cavern wall breach has little impact on salinity near the ground surface within a period of 3 months. However, salinity is significantly elevated near the breach area of the salt cavern, caused by strong flow velocities.

  7. Physical Volcanology of Obsidian Dome, California: A Complex Record of Emplacement of a Youthful Lava Dome

    NASA Astrophysics Data System (ADS)

    Kingsbury, Cole G.

    Obsidian Dome is a 550-650 year old, 1.5 by 1.8 km extrusion of high silica rhyolite situated along the Inyo Craters in eastern California. Field, and observations of drill core, reveals discrete metre-scale thick zones of rhyolitic glass exposed along the margin of Obsidian Dome as well as within its interior. Millimetre-scale flow-banded obsidian, pumice and rhyolite range from planar to chaotically folded, the latter a product of ductile, compressive deformation. Fractures, some of which display en-echelon splitting patterns are a result of brittle failure. Taken together, these features along with others, result from flow during lava dome growth and suggest complex emplacement patterns signified by vesiculation, crystallization and repeated brittle-ductile deformation, owing to episodic crossing of the glass transition. Evidence further shows that gas loss from the system occurred due to explosions, pumice formation and also brecciation of the melt as it episodically crossed the glass transition. Loss of gas by these mechanisms along with the inherent high viscosity of rhyolite melt explains the large amount of glass found on and within Obsidian Dome and other similar rhyolite extrusions in comparison to less silica-rich systems.

  8. The Vaasa migmatitic complex: the birth, growth and death of a thermal dome

    NASA Astrophysics Data System (ADS)

    Chopin, Francis; Korja, Annakaisa; Hölttä, Pentti; Eklund, Olav; Tapani Rämö, Osmo

    2015-04-01

    The Vaasa migmatitic complex, or Vaasa dome, is cored by diatexite migmatites and S-type granitoids and gradually mantled by metatexite migmatites and mica schist with thin metabasite-andesite intercalations. Previous geochemical studies have demonstrated that the metasediments are the sources of the melted core: it have been suggested that the complex have been formed by in-situ melting of a basin. Field work studies highlight the formation of a gently dipping metamorphic fabric with a lateral increase of the in-situ melt content towards the core of the dome (D1). This early layered and partially melted fabric is then affected by a regional N-S shortening forming km- to outcrop-scale E-W striking folds and new sub-vertical foliation (D2). Late sub-vertical shearing is visible along the dome border and within the diatexitic zone (D3). No late detachment structures have been observed. In the metamorphic belt, the grade increases from medium-T amphibolite facies to low-P granulite facies towards the core of the dome. Pseudosections in the MnNCKFMASHTO system have been performed in one mica schist (Grt+BtPl+Qz±Std+Sill+And) and one metatexite migmatite (Bt+Liq+Crd+Pl+Kfs+Grt+Qz±Sill+And). The metamorphic peaks are bracketed at 560°C at 5 kbar and 750-770°C at 4.5-5 kbar, respectively. The retrograde condition is situated at 540°C and <3 kbar for both lithologies. This implies an isobaric increase of the metamorphic grade towards the core of the dome. An isothermal decompression for the schist and a retrograde PT path for the migmatites are observed. Existing and new U/Pb monazite ages from mica schists, migmatites and clustered at 1860-1865 Ma whereas U/Pb ages from metamorphic and magmatic zircons are older and clustered at 1875 Ma. The latter might represent the peak of melting process and associated metamorphism whereas monazites ages might be related to the cooling of the orogenic middle crust. It has to be noticed that few monazites from metamorphic rocks of

  9. Precipitation regime and stable isotopes at Dome C and Dome Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Dittmann, Anna; Stenni, Barbara; Masson-Delmotte, Valerie; Powers, Jordan G.; Manning, Kevin W.; Raphael, Marilyn; Fujita, Koji; Werner, Martin; Valt, Mauro; Cagnati, Anselmo

    2016-04-01

    Dome Fuji and Dome C, both deep ice-core drilling sites in East Antarctica, are the only stations, for which direct daily precipitation measurements and stable isotope ratios of the precipitation samples are available. Whereas the Dome F series encompasses only one year of measurements, the Dome C series has been started in 2006 and is ongoing. For Dome C, the type of precipitation (diamond dust, hoar frost, snowfall) was determined based on crystal type analysis. The weather situations causing precipitation at the stations were analysed using data from the Antarctic Mesoscale Prediction System (AMPS). At both sites, major snowfall events were always related to an amplification of Rossby waves in the circumpolar westerlies, which led to an increased meridional transport of moisture and energy. Furthermore, increased amounts of diamond dust were observed after such event-type precipitation. The stable isotope data of the precipitation samples were related to the different weather situations and precipitation types and also simulated using a simple Rayleigh-type model (MCIM) and compared to output from the global isotopic-enhanced model ECHAM5wiso. Possible moisture sources were estimated using the synoptic analysis combined with back-trajectory calculation. MCIM was better in reproducing the annual cycle of deuterium excess, whereas ECHAM5wiso generally showed a smaller bias of the isotope ratios. Hoar frost shows isotope signals very different from diamond dust and snowfall, which hints at a more local cycle of sublimation and deposition for this type of precipitation, whereas both snowfall and diamond dust are related to large-scale moisture transport. Contrary to the literature, a more northern moisture source was found to be not necessarily associated with more depleted snowfall. This is explained by the strong warm air advection accompanying snowfall events, which decreases the temperature difference between source area and deposition site and thus leads to

  10. DOME: operational metrics under one roof

    NASA Astrophysics Data System (ADS)

    Primas, F.; Marteau, S.; Tacconi-Garman, L. E.; Mainieri, V.; Rejkuba, M.; Mysore, S.

    2012-09-01

    Thirteen VLT/I instruments plus some extra critical components like the block-scheduling of the Laser Guide Star Facility and VLTI baselines make for a rather complex machine that constantly challenges our operational efficiencies. DOME (Dashboard for Operational Metrics at ESO) is an ongoing project developed, implemented and maintained by the ESO User Support Department. It aims at providing an ESO-internal dashboard where key operational metrics are published and updated at regular intervals. Here, we will present the project and report on the indicators that have been looked at until now.ty and VLTI baselines make for a rather complex machine that constantly challenges our operational efficiencies. DOME (Dashboard for Operational Metrics at ESO) is an ongoing project developed, implemented and maintained by the ESO User Support Department. It aims at providing an ESO-internal dashboard where key operational metrics are published and updated at regular intervals. Here, we will present the project and report on the indicators that have been looked at until now.

  11. Evaluation of the structure and stratigraphy over Richton Dome, Mississippi

    SciTech Connect

    Werner, M.L.

    1986-05-01

    The structure and stratigraphy over Richton Salt Dome, Mississippi, have been evaluated from 70 borings that were completed to various depths above the dome. Seven lithologic units have been identified and tentatively correlated with the regional Tertiary stratigraphy. Structure-contour and thickness maps of the units show the effects of dome growth from Eocene through early Pliocene time. Growth of the salt stock from late Oligocene through early Pliocene is estimated to have averaged 0.6 to 2.6 centimeters (0.2 to 1.1 inches) per 1000 years. No dome growth has occurred since the early Pliocene. The late Oligocene to early Pliocene strata over and adjacent to the dome reflect arching over the entire salt stock; some additional arching over individual centers may represent pre-Quaternary differential movement in the salt stock. The lithology and structure of the caprock at the Richton Salt Dome indicate that the caprock probably was completely formed by late Oligocene. In late Oligocene, the caprock was fractured by arching and altered by gypsum veining. Since late Oligocene, there are no indications of significant hydrologic connections through the caprock - that is, there are no indications of dissolution collapse or further anhydrite caprock accumulation. This structural and stratigraphic analysis provides insights on dome growth history, dome geometry, and neardome hydrostratigraphy that will aid in planning site characterization field activities, including an exploratory shaft, and in the conceptual design of a high-level waste (HLW) repository.

  12. SOLUTION MINING IN SALT DOMES OF THE GULF COAST EMBAYMENT

    SciTech Connect

    Griswold, G. B.

    1981-02-01

    Following a description of salt resources in the salt domes of the gulf coast embayment, mining, particularly solution mining, is described. A scenario is constructed which could lead to release of radioactive waste stored in a salt dome via inadvertent solution mining and the consequences of this scenario are analyzed.

  13. Astronaut Alan Bean doing acrobatics in OWS dome area

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Astronaut Alan L. Bean, Skylab 3 commander, doing acrobatics in the dome area of the Orbital Workshop (OWS) on the space station cluster in Earth orbit. The dome area is about 22 feet in diameter and 19 feet from top to bottom.

  14. Astronaut Jack Lousma doing acrobatics in OWS dome area

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Astronaut Jack R. Lousma, Skylab 3 pilot, doing acrobatics in the dome area of the Orbital Workshop (OWS) on the space station cluster in Earth orbit. The dome area is about 22 feet in diameter and 19 feet from top to bottom.

  15. Baseline design and requirements for the LSST rotating enclosure (dome)

    NASA Astrophysics Data System (ADS)

    Neill, D. R.; DeVries, J.; Hileman, E.; Sebag, J.; Gressler, W.; Wiecha, O.; Andrew, J.; Schoening, W.

    2014-07-01

    The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter) wide-field (3.5 degree) survey telescope, which will be located on the Cerro Pachón summit in Chile. As a result of the wide field of view, its optical system is unusually susceptible to stray light; consequently besides protecting the telescope from the environment the rotating enclosure (Dome) also provides indispensible light baffling. All dome vents are covered with light baffles which simultaneously provide both essential dome flushing and stray light attenuation. The wind screen also (and primarily) functions as a light screen providing only a minimum clear aperture. Since the dome must operate continuously, and the drives produce significant heat, they are located on the fixed lower enclosure to facilitate glycol water cooling. To accommodate day time thermal control, a duct system channels cooling air provided by the facility when the dome is in its parked position.

  16. Phase competition in trisected superconducting dome

    NASA Astrophysics Data System (ADS)

    Vishik, Inna

    2012-02-01

    The momentum-resolved nature of angle-resolved photoemission spectroscopy (ARPES) has made it a key probe of emergent phases in the cuprates, such as superconductivity and the pseudogap, which have anisotropic momentum-space structure. ARPES can be used to infer the origin of spectral gaps from their distinct phenomenology---temperature, doping, and momentum dependence, and this principle has been used to argue that the pseudogap is a distinct phase from superconductivity, rather than a precursor [1]. We have studied Bi2Sr2CaCu2O8+δ (Bi-2212) using laser-ARPES, and our data give evidence for three distinct quantum phases comprising the superconducting ground state, accompanied by abrupt changes at p˜0.076 and p˜0.19 in the doping-and-temperature dependence of the gaps near the bond-diagonal (nodal) direction [2]. The latter doping likely marks the quantum critical point of the pseudogap, while the former represents a distinct competing phase at the edge of the superconducting dome. Additionally, we find that the pseudogap advances closer towards the node when superconductivity is weak, just below Tc or at low doping, and retreats towards the antinode well below Tc and at higher doping. This phase competition picture together with the two critical doping are synthesized into our proposed phase diagram, which also reconciles conflicting phase diagrams commonly used in the field. Our results underscore the importance of quantum critical phenomena to cuprate superconductivity, provide a microscopic picture of phase competition in momentum space, and predict the existence of phase boundaries inside the superconducting dome which are different from simple extrapolations from outside the dome. [4pt] [1] I. M. Vishik, W. S. Lee, R.-H. He, M. Hashimoto, Z. Hussain, T. P. Devereaux, and Z.-X. Shen. New J. Phys. 12, 105008 (2010). [0pt] [2] I. M. Vishik, M. Hashimoto, R.-H. He, W. S. Lee, F. Schmitt, D. H. Lu, R.G. Moore, C. Zhang, W. Meevasana, T. Sasagawa, S. Uchida, K

  17. Models of the geomorphology, hydrology, and development of domed peat bodies

    SciTech Connect

    Winston, R.B.

    1994-12-01

    Because peat accumulates only beneath the water table, the shape of a peat body should reflect the shape of its water table and thus the hydrology of the peat body. Three different models successfully reproduce the observed peat dome morphology, including a central bog plain. In the first model, the bog plain develops because peat accumulation is limited by anaerobic decay of peat beneath the water table. With certain simplifying assumptions, an analytic solution for this model can be obtained. The other two models are more easily investigated numerically. In the first model, the initial peat accumulation rate is limited only by plant growth and decay and is the maximum rate observed during peat dome development. As a peat dome expands laterally, peat accumulation slows because the water table ceases to rise fast enough to preserve all the available plant material. Eventually, anaerobic decay beneath the water table matches the rate of peat addition to the top of the peat body, and net peat accumulation ceases. 17 refs., 2 tabs.

  18. Emplacement of Volcanic Domes on Venus and Europa

    NASA Technical Reports Server (NTRS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Steve M.

    2015-01-01

    Placing firmer constraints on the emplacement timescales of visible volcanic features is essential to obtaining a better understanding of the resurfacing history of Venus. Fig. 1 shows a Magellan radar image and topography for a putative venusian lava dome. 175 such domes have been identified, having diameters that range from 19 - 94 km, and estimated thicknesses as great as 4 km [1-2]. These domes are thought to be volcanic in origin [3], having formed by the flow of a viscous fluid (i.e., lava) onto the surface. Among the unanswered questions surrounding the formation of Venus steep-sided domes are their emplacement duration, composition, and the rheology of the lava. Rheologically speaking, maintenance of extremely thick, 1-4 km flows necessitates higher viscosity lavas, while the domes' smooth upper surfaces imply the presence of lower viscosity lavas [2-3]. Further, numerous quantitative issues, such as the nature and duration of lava supply, how long the conduit remained open and capable of supplying lava, the volumetric flow rate, and the role of rigid crust in influencing flow and final morphology all have implications for subsurface magma ascent and local surface stress conditions. The surface of Jupiter's icy moon Europa exhibits many putative cryovolcanic constructs [5-7], and previous workers have suggested that domical positive relief features imaged by the Galileo spacecraft may be volcanic in origin [5,7-8] (Fig. 2). Though often smaller than Venus domes, if emplaced as a viscous fluid, formation mechanisms for europan domes may be similar to those of venusian domes [7]. Models for the emplacement of venusian lava domes (e.g. [9-10]) have been previously applied to the formation of putative cryolava domes on Europa [7].

  19. Geologic study of Kettle dome, northeast Washington. Final report

    SciTech Connect

    Not Available

    1980-10-01

    This geologic study of Kettle dome, northeast Washington, encompasses an area of approximately 800 square miles (2048 sq km). The evaluation of uranium occurrences associated with the igneous and metamorphic rocks of the dome and the determination of the relationship between uranium mineralization and stratigraphic, structural, and metamorphic features of the dome are the principal objectives. Evaluation of the validity of a gneiss dome model is a specific objective. The principal sources of data are detailed geologic mapping, surface radiometric surveys, and chemical analyses of rock samples. Uranium mineralization is directly related to the presence of pegmatite dikes and sills in biotite gneiss and amphibolite. Other characteristics of the uranium occurrences include the associated migmatization and high-grade metamorphism of wallrock adjacent to the pegmatite and the abrupt decrease in uranium mineralization at the pegmatite-gneiss contact. Subtle chemical characteristics found in mineralized pegmatites include: (1) U increase as K/sub 2/O increases, (2) U decreases as Na/sub 2/O increases, and (3) U increases as CaO increases at CaO values above 3.8%. The concentration of uranium occurrences in biotite gneiss and amphibolite units results from the preferential intrusion of pegmitites into these well-foliated rocks. Structural zones of weakness along dome margins permit intrusive and migmatitic activity to affect higher structural levels of the dome complex. As a result, uranium mineralization is localized along dome margins. The uranium occurrences in the Kettle dome area are classified as pegmatitic. Sufficient geologic similarities exist between Kettle dome and the Rossing uranium deposit to propose the existence of economic uranium targets within Kettle dome.

  20. The Discovery Dome: A Tool for Increasing Student Engagement

    NASA Astrophysics Data System (ADS)

    Brevik, Corinne

    2015-04-01

    The Discovery Dome is a portable full-dome theater that plays professionally-created science films. Developed by the Houston Museum of Natural Science and Rice University, this inflatable planetarium offers a state-of-the-art visual learning experience that can address many different fields of science for any grade level. It surrounds students with roaring dinosaurs, fascinating planets, and explosive storms - all immersive, engaging, and realistic. Dickinson State University has chosen to utilize its Discovery Dome to address Earth Science education at two levels. University courses across the science disciplines can use the Discovery Dome as part of their curriculum. The digital shows immerse the students in various topics ranging from astronomy to geology to weather and climate. The dome has proven to be a valuable tool for introducing new material to students as well as for reinforcing concepts previously covered in lectures or laboratory settings. The Discovery Dome also serves as an amazing science public-outreach tool. University students are trained to run the dome, and they travel with it to schools and libraries around the region. During the 2013-14 school year, our Discovery Dome visited over 30 locations. Many of the schools visited are in rural settings which offer students few opportunities to experience state-of-the-art science technology. The school kids are extremely excited when the Discovery Dome visits their community, and they will talk about the experience for many weeks. Traveling with the dome is also very valuable for the university students who get involved in the program. They become very familiar with the science content, and they gain experience working with teachers as well as the general public. They get to share their love of science, and they get to help inspire a new generation of scientists.

  1. Transdomes: Emplacement of Migmatite Domes in Oblique Tectonic Settings

    NASA Astrophysics Data System (ADS)

    Teyssier, C. P.; Rey, P. F.; Whitney, D. L.; Mondy, L. S.; Roger, F.

    2014-12-01

    Many migmatite domes are emplaced within wrench corridors in which a combination of strike-slip and extensional detachment zones (pull-apart, extensional relay, or transfer zones) focus deep-crust exhumation. The Montagne Noire dome (France, Variscan Massif Central) exemplifies wrench-related dome formation and displays the following structural, metamorphic, and geochronologic characteristics of a 'transdome': the dome is elongate in the direction of extension; foliation outlines a double dome separated by a high-strain zone; lineation is shallowly plunging with a fairly uniform trend that parallels the strike of the high-strain zone; subdomes contain recumbent structures overprinted by upright folds that affected upward by flat shear zones associated with detachment tectonics; domes display a large syn-deformation metamorphic gradient from core (upper amphibolite facies migmatite) to margin (down to greenschist facies mylonite); some rocks in the dome core experienced isothermal decompression revealed by disequilibrium reaction textures, particularly in mafic rocks (including eclogite); and results of U-Pb geochrononology indicate a narrow range of metamorphic crystallization from core to mantling schist spanning ~10 Myr. 3D numerical modeling of transdomes show that the dome solicits a larger source region of partially molten lower crust compared to 2D models; this flowing crust creates a double-dome architecture as in 2D models but there are differences in the predicted thermal history and flow paths. In a transtension setting, flow lines converge at depth (radial-centripetal flow) toward the zone of extension and diverge at shallow levels in a more uniform direction that is imposed by upper crust motion and deformation. This evolution produces a characteristic pattern of strain history, progressive fabric overprint, and P-T paths that are comparable to observed dome rocks.

  2. Miocene lava flows and domes, cooling fractures, carapace breccia, and avalanche deposits near Goldstone, California

    NASA Astrophysics Data System (ADS)

    Buesch, D.

    2013-12-01

    Mapping and petrography of volcanic rocks in western Fort Irwin (FI), California, provide insights into the cooling history of lava flows and domes and the formation of associated carapace breccia and avalanche deposits. The rocks formed on the eastern margin of the 19-16 Ma Eagle Crags volcanic field (Sabin and others, 1994). Lava compositions range from porphyritic olivine basalt to aphyric rhyolite. Basalt flows are 1-5 m thick and <1-2 km long, and sequences 5-50 m thick are traceable for >7 km. Andesite to rhyolite flows are 30-80 m thick and <1-3 km long, and domes have 100-300 m relief and radial length of 0.6-1.2 km. Cooling fractures, identified by occurrence of margins and geometry, are in all lava flows and domes. Similar to a 'rim' (Buesch and others, 1996 & 1999; Buesch, 2006), a 'margin' is a region along a fracture wall with a finer texture or different type of crystallinity or vesicularity compared to rock inward from the fracture. At FI, margins occur on many fractures and typically are 0.5-3 mm wide. They indicate that a fracture formed during initial cooling, before the bulk of the rock crystallized. Planarity and surface roughness are used to analyze fractures (Buesch and others, 1996). Typically at FI, cooling fractures are planar and smooth, and post-cooling fractures are slightly irregular and slightly rough. Typically, plan views of cooling fractures are 5-6 sided in olivine basalt, and 4-sided in andesite to rhyolite. Fracture sets are mostly perpendicular to the original surface of a flow, and some bend toward the interior. Many lava flows and domes have lateral and capping breccias referred to as carapace breccia. Similar breccia also cloaks individual lobes of composite domes. Carapace breccia can grade down into a non-brecciated interior, but in some cases, compositionally similar late-stage flow-banded lava was injected beneath the breccia, Breccia fragments are vitric or crystallized, and many have margins that do not match those of

  3. Tensile strength of dome rocks and lavas at Santiaguito dome complex, Guatemala

    NASA Astrophysics Data System (ADS)

    Hornby, Adrian; Lamb, Oliver; Lamur, Anthony; Lavallée, Yan

    2015-04-01

    Lava domes are inherently unstable structures, subject to intense gas flux and rapid variations in the state of stress. At shallow depths confining stresses are minimal and deformation is dilatant, occurring predominantly through tensile fractures. This fracture mode facilitates outgassing and contributes to the development of gas-and-ash activity as well as vulcanian eruptions. However, there is a paucity of tensile strength data for volcanic materials in the published literature, and we know of no paper which addresses this at high temperatures. We study the tensile strength of dome rocks collected at the Santiaguito dome complex, Guatemala, over a porosity range of 3-25%. Indirect tensile (Brazilian) tests were conducted on 40-mm diameter cores, by imposing a compressive displacement rate (radial to the core) of 4 micron/s at room temperature as well as an eruptive temperature of ca. 850 °C. An acoustic monitoring system is employed to track the nucleation, propagation and coalescence of fractures leading to complete sample failure. We find that the rocks' tensile strength exhibits a nonlinear decrease with porosity. Preliminary tests at high temperature indicate that some rocks exhibit a higher tensile strength (than at room temperature); in these experiments, samples containing a higher fraction of interstitial melt revealed an additional component of viscous flow. Further experiments conducted at higher strain rates will define the brittle response of the liquid during tensile failure. The data is compared against similar datasets for volcanic rocks. We will discuss implications for shallow volcanic processes ranging from dilation bands and tuffisite formation to gas-and-ash explosions and dome structural stability.

  4. Structural review of the Vredefort dome

    NASA Technical Reports Server (NTRS)

    Colliston, W. P.; Reimold, W. U.

    1992-01-01

    The structure of the older-than-3.2-Ga Archean basement and Archean-to-Precambrian sedimentary/volcanic rocks (3.07 to ca. 2.2 Ga) in the center of the Witwatersrand Basin to the southwest of Johannesburg (South Africa) is dominated by the ca. 2.0-Ga megascopic Vredefort 'Dome' structure. The effect of the 'Vredefort event' is demonstrably large and is evident within a northerly arc of about 100 km radius around the granitic core of the structure. Northerly asymmetric overturning of the strata is observed within the first 17 km (strata is horizontal in the south), followed by a 40-km-wide rim synclinorium. Fold and fault structures (normal, reverse, and strike-slip) are locally as well as regionally concentrically arranged with respect to the northern and western sides of the structure. The unusual category of brittle deformation, the so-called 'shock deformation', observed in the collar strata has attracted worldwide attention over the past two decades. These deformation phenomena include the presence of coesite and stishovite, mylonites, and pseudotachylites, cataclasis at a microscopic scale, and the ubiquitous development of multiply striated joint surfaces (which include shatter cones, orthogonal, curviplanar, and conjugate fractures). The macroscopic to microscopic deformation features have led to the formulation of various hypotheses to account for the origin of the Vredefort structure: (1) tectonic hypotheses--deep crustal shear model, doming and N-directed thrust fault model, fold interference model, and diapir model; (2) the exogenous bolide impact hypothesis; and (3) the endogenous cryptoexplosion model.

  5. Geohydrology of the Keechi, Mount Sylvan, Oakwood, and Palestine salt domes in the northeast Texas salt-dome basin

    USGS Publications Warehouse

    Carr, Jerry E.; Halasz, Stephen J.; Peters, Henry B.

    1980-01-01

    Additional problems concerning the hydrologic stability of Oakwood and Palestine Salt Domes have resulted from the disposal of oil-field salinewater in the cap rock at the Oakwood Dome and previous solution mining of salt at the Palestine Dome Additional investigations are needed to determine if a selected dome is hydrologically stable. Needed investigations include: (1) A more complete comparative analysis of the regional and local geohydrologic system; (2) a site-specific drilling and sampling program to analyze the cap rock-aquifer boundary, sediment distribution, hydraulic-parameter variations, hydraulic-head relationships, and hydrochemical patterns; and (3) mass-transport computer modeling of ground-water flow at the domes.

  6. Domes, pits, and small chaos on Europa produced by water sills

    NASA Astrophysics Data System (ADS)

    Michaut, Chloé; Manga, Michael

    2014-03-01

    Pits, domes, and small chaos on Europa's surface are quasi-circular features a few to a few tens of kilometers in diameter. We examine if injection of water sills into Europa's ice shell and their subsequent evolution can induce successive surface deformations similar to the morphologies of these features. We study the dynamics of water spreading within the elastic part of the ice shell and show that the mechanical properties of ice exert a strong control on the lateral extent of the sill. At shallow depths, water makes room for itself by lifting the overlying ice layer and water weight promotes lateral spreading of the sill. In contrast, a deep sill bends the underlying elastic layer and its weight does not affect its spreading. In that case, the sill lateral extent is limited by the fracture toughness of ice and the sill can thicken substantially. After emplacement, cooling of the sill warms the surrounding ice and thins the overlying elastic ice layer. As a result, preexisting stresses in the elastic part of the ice shell increase locally to the point that they may disrupt the ice above the sill (small chaos). Disruption of the surface also allows for partial isostatic compensation of water weight, leading to a topographic depression at the surface (pit), of the order of ~102 m. Complete water solidification finally causes expansion of the initial sill volume and results in an uplifted topography (dome) of ~102m.

  7. Analysis of aerothermal loads on spherical dome protuberances

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Smith, R. E.

    1983-01-01

    Hypersonic flow over spherical dome protuberances was investigated to determine increased pressure and heating loads to the surface. The configuration was mathematically modeled in a time-dependent three-dimensional analysis of the conservation of mass, momentum (Navier-Stokes), and energy equations. A boundary mapping technique was used to obtain a rectangular parallelepiped computational domain, a MacCormack explicit time-split predictor-corrector finite difference algorithm was used to obtain solutions. Results show local pressures and heating rates for domes one-half, one, and two boundary layer thicknesses high were increased by factors on the order of 1.4, 2, and 6, respectively. Flow over the lower dome was everywhere attached while flow over the intermediate dome had small windward and leeside separations. The higher dome had an unsteady windward separation region and a large leeside separation region. Trailing vortices form on all domes with intensity increasing with dome height. Discussion of applying the results to a thermally bowed thermal protection system are presented.

  8. First field identification of the Cuonadong dome in southern Tibet: implications for EW extension of the North Himalayan gneiss dome

    NASA Astrophysics Data System (ADS)

    Fu, Jiangang; Li, Guangming; Wang, Genhou; Huang, Yong; Zhang, Linkui; Dong, Suiliang; Liang, Wei

    2016-07-01

    The Cuonadong dome exposes in east-southern margin of the North Himalayan gneiss domes (NHGD), which is reported first time in this study. The Cuonadong dome is located at the southern part of the Zhaxikang ore concentration area, which is divided into three tectono-lithostratigraphic units by two curved faults around the dome geometry from upper to lower (or from outer to inner): the upper unit, middle unit and lower unit, and the outer fault is Nading fault, while the inner fault is Jisong fault. The Cuonadong dome is a magmatic orthogneiss and leucogranite mantled by orthogneiss and metasedimentary rocks, which in turn are overlain by Jurassic metasedimentary and sedimentary rocks. The grades of metamorphism and structural deformation increase towards the core, which is correspondence with the Ridang Formation low-metamorphic schist, tourmaline granitic-biotite gneiss, garnet-mica gneiss and mylonitic quartz-mica gneiss. The Cuonadong dome preserves evidences for four major deformational events: firstly top-to-S thrust (D1), early approximately N-S extensional deformation (D2), main approximately E-W extensional deformation (D3), and late collapse structural deformation (D4) around the core of the Cuonadong dome, which are consistent to three groups lineation: approximately N-S-trending lineation including L1 and L2, E-W trending L3, and L4 with plunging towards outside of the dome, respectively. The formation of the Cuonadong dome was probably resulted from the main E-W extensional deformation which is a result of eastward flow of middle or lower crust from beneath Tibet accommodated by northward oblique underthrusting of Indian crust beneath Tibet. The establishment of the Cuonadong dome enhanced the E-W extension of the NHGD, which is further divided into two structural dome zones according to the different extensional directions: approximately N-S extensional North Himalayan gneiss domes (NS-NHGD) and E-W extensional North Himalayan gneiss domes (EW

  9. Maximum potential erosion and inundation of seven interior salt domes

    SciTech Connect

    Aronow, S.

    1982-08-01

    Seven interior salt domes have been evaluated in regard to erosion or inundation due to natural events. The most likely possibility of either event occurring would be associated with continental glaciation. The domes were evaluated based on maximum previous sea level changes due to glaciation and effects caused by melting of existing ice sheets. Results are listed for each of the seven domes. Past history indicates a likelihood of returning to a glacial period. The subsequent fall of sea level may cause regrading of streams in the area. A conservative evaluation of this phenomenon was performed and the results are reported.

  10. Merkel cells and touch domes: More than mechanosensory functions?

    PubMed Central

    Xiao, Ying; Williams, Jonathan S.; Brownell, Isaac

    2014-01-01

    The touch dome is an innervated structure in the epidermis of mammalian skin. Composed of specialized keratinocytes and neuroendocrine Merkel cells, the touch dome has distinct molecular characteristics compared to the surrounding epidermal keratinocytes. Much of the research on Merkel cell function has focused on their role in mechanosensation, specifically light-touch. Recently, more has been discovered about Merkel cell molecular characteristics and their cells of origin. Here we review Merkel cell and touch dome biology, and discuss potential functions beyond mechanosensation. PMID:24862916

  11. Extrusion cycles during dome-building eruptions

    NASA Astrophysics Data System (ADS)

    de' Michieli Vitturi, M.; Clarke, A. B.; Neri, A.; Voight, B.

    2013-06-01

    We identify and quantify controls on the timescales and magnitudes of cyclic (periodic) volcanic eruptions using the numerical model DOMEFLOW (de' Michieli Vitturi et al., 2010) which was developed by the authors for magma systems of intermediate composition. DOMEFLOW treats the magma mixture as a liquid continuum with dispersed gas bubbles and crystals in thermodynamic equilibrium with the melt and assumes a modified Poiseuille form of the viscous term for fully developed laminar flow in a conduit of cylindrical cross-section. During ascent, magma pressure decreases and water vapor exsolves and partially degasses from the melt as the melt simultaneously crystallizes, causing changes in mixture density and viscosity. Two mechanisms previously proposed to cause periodic eruption behavior have been implemented in the model and their corresponding timescales explored. The first applies a stick-slip model in which motion of a shallow solid plug is resisted by static/dynamic friction, as described in Iverson et al. (2006). For a constant magma supply rate at depth, this mechanism yields cyclic extrusion with timescales of seconds to tens of seconds with values generally depending on assumed friction coefficients. The second mechanism does not consider friction but treats the plug as a high-viscosity Newtonian fluid. During viscous resistance, pressure beneath the degassed plug can increase sufficiently to overcome dome overburden, plug weight, and viscous forces, and ultimately drive the plug from the conduit. In this second model cycle periods are on the order of hours, and decrease with increasing magma supply rate until a threshold is reached, at which point periodicity disappears and extrusion rate becomes steady (vanishingly short periods). Magma volatile content for fixed chamber pressure has little effect on cycle timescales, but increasing volatile content increases mass flow rate and cycle magnitude as defined by the difference between maximum and minimum

  12. 2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO THE RIGHT, LOOKING NORTHWEST. - Mill Valley Air Force Station, Consolidated Open Mess, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA

  13. 4. FACING EAST ACROSS BRIDGE AT HALF DOME WITH BICYCLE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. FACING EAST ACROSS BRIDGE AT HALF DOME WITH BICYCLE PATH MARKERS IN FOREGROUND AND ELECTRICAL TRANSFORMER FOR CAMPGROUND TO RIGHT. - Ahwahnee Bridge, Spanning Merced River on service road, Yosemite Village, Mariposa County, CA

  14. Fourth floor rooftop corner detail, looking south. Note Capitol Dome ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Fourth floor rooftop corner detail, looking south. Note Capitol Dome and Washington Monument in distance. - Chesapeake & Potomac Telephone Company Warehouse, 1111 North Capitol Street, NE, Washington, District of Columbia, DC

  15. 4. WASHBURN POINT VISTA AREA. HALF DOME AT CENTER REAR. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. WASHBURN POINT VISTA AREA. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-37 43 13.7 / W-119 34 23.0 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  16. 1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-36 43 45.8 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  17. 5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. LOOKING E. GIS: N-37 42 43.8 / W-119 35 12.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  18. SURVEY AND EVALUATION OF FINE BUBBLE DOME DIFFUSER AERATION EQUIPMENT

    EPA Science Inventory

    This research project was initiated with the overall objective of better defining the oxygen transfer performance, operation and maintenance (O&M) requirements, and proper design approaches for fine bubble dome diffuser aeration systems used in activated sludge wastewater treatme...

  19. INTERIOR STRUCTURAL DETAIL, INSIDE OF DRUM UNDER DOME ON STAIRS, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    INTERIOR STRUCTURAL DETAIL, INSIDE OF DRUM UNDER DOME ON STAIRS, LOOKING SOUTH. - Colt Fire Arms Company, East Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

  20. DOME, NORTH ARMORY ON LEFT, OBLIQUE VIEW FROM SOUTHWEST. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DOME, NORTH ARMORY ON LEFT, OBLIQUE VIEW FROM SOUTHWEST. - Colt Fire Arms Company, East Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

  1. 8. Detail view of steam dome attached to top of ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. Detail view of steam dome attached to top of Lancashire double flue boiler. - Hacienda Azucarera El Coto, Sugar Mill Ruins, .5 Mi. SW of Rt. 347 Bridge Over Guanajibo River, San German, San German Municipio, PR

  2. View of Statue of Freedom atop the Capitol Dome but ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View of Statue of Freedom atop the Capitol Dome but under scaffolding - U.S. Capitol, Statue of Freedom, Intersection of North, South, & East Capitol Streets & Capitol Mall, Washington, District of Columbia, DC

  3. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  4. Snodar: 2009 performance at Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Bonner, Colin S.; Ashley, Michael C. B.; Bradley, Stuart G.; Cui, Xiangqun; Feng, Longlong; Gong, Xuefei; Lawrence, Jon S.; Luong-van, Daniel M.; Shang, Zhaohui; Storey, John W. V.; Wang, Lifan; Yang, Huigen; Yang, Ji; Zhou, Xu; Zhu, Zhenxi

    2010-07-01

    Snodar is a high resolution acoustic radar designed specifically for profiling the atmospheric boundary layer on the high Antarctic plateau. Snodar profiles the atmospheric temperature structure function constant to a vertical resolution of 1 m or better with a minimum sample height of 8 m. The maximum sampling height is dependent on atmospheric conditions but is typically at least 100 m. Snodar uses a unique in-situ intensity calibration method that allows the instrument to be autonomously recalibrated throughout the year. The instrument is initially intensity calibrated against tower-mounted differential microthermal sensors. A calibration sphere is located in the near-field of the antenna to provide a fixed echo of known intensity, allowing the instrument to be continuously re-calibrated once deployed. This allows snow accumulation, transducer wear and system changes due to temperature to be monitored. Year-round power and communications are provided by the PLATO facility. This allows processed data to be downloaded every 6 hours while raw data is stored on-site for collection the following summer. Over 4 million processed samples have been downloaded through PLATO to date. We present signal attenuation from accumulation of snow and ice on Snodar's parabolic reflector during the 2009 at Dome A.

  5. Phase competition in trisected superconducting dome

    PubMed Central

    Vishik, I. M.; Hashimoto, M.; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui; Moore, R. G.; Zhang, C.; Meevasana, W.; Sasagawa, T.; Uchida, S.; Fujita, Kazuhiro; Ishida, S.; Ishikado, M.; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Hussain, Zahid; Devereaux, Thomas P.; Shen, Zhi-Xun

    2012-01-01

    A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi2Sr2CaCu2O8+δ, covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below Tc and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome. PMID:23093670

  6. Emplacement and composition of steep-sided domes on Venus

    NASA Astrophysics Data System (ADS)

    Stofan, Ellen R.; Anderson, Steven W.; Crown, David A.; Plaut, Jeffrey J.

    2000-11-01

    Steep-sided domes on Venus have surface characteristics that can provide information on their emplacement, including relatively smooth upper surfaces, radial and polygonal fracture patterns, and pits. These characteristics indicate that domes have surface crusts which are relatively unbroken, have mobile interiors after emplacement, and preserve fractures from only late in their history in response to endogenous growth or sagging of the dome surface. We have calculated the time necessary to form a 12-cm-thick crust for basalt and rhyolite under current terrestrial and Venusian ambient conditions. A 12-cm-thick crust will form in all cases in <10 hours. Although Venusian lava flows should develop a brittle carapace during emplacement, only late-stage brittle fractures are preserved at steep-sided domes. We favor an emplacement model where early-formed surface crusts are entrained or continually annealed as they deform to accommodate dome growth. Entrainment and annealing of fractures are not mutually exclusive processes and thus may both be at work during steep-sided dome emplacement. Our results are most consistent with basaltic compositions, as rhyolitic lavas would quickly form thick crusts which would break into large blocks that would be difficult to entrain or anneal. However, if Venus has undergone large temperature excursions in the past (producing ambient conditions of 800-1000 K [e.g., Bullock and Grinspoon, 1996, 1998]), rhyolitic lavas would be unable to form crusts at high surface temperatures and could produce domes with surface characteristics consistent with those of Venusian steep-sided domes.

  7. Dome houses and energy conservation: an introductory bibliography. [38 references to dome efficiency

    SciTech Connect

    Not Available

    1983-01-01

    The appearance of geodesic domes in conventional neighborhoods is recent. The current popularity of these spherical designs is due to their energy efficiency. Some manufacturers have claimed over 40% efficiency improvement over conventional homes of the same size. A host of low utility bills across the country is now backing up these claims. This bibliography concentrates on the period from 1960 to the present, although there are a few entries from earlier periods. Most of the material is available in articles rather than books.

  8. Development of Core Complex Domes Due to Along-Axis Variation in Diking

    NASA Astrophysics Data System (ADS)

    Buck, W. R.; Choi, E.; Tian, X.

    2014-12-01

    Continental and oceanic core complexes are characterized by fairly smooth, unfaulted, but corrugated surfaces of high grade rocks often domed both along and orthogonal to the transport direction. The corrugations, or mega-mullions, are remarkably continuous in the transport direction and may be tens of kilometers long. Spencer [1999] suggests that corrugations with across-transport wavelengths of millimeter to ~25 km scales are formed when the lower plate of a large-offset normal fault is "continuously cast," as warm, ductile mantle and gabbro is pulled up against the cooler upper plate. Continuous casting is widely accepted as a mechanism to form the shorter wavelength corrugations as a result of irregularities of the brittle upper plate surface. However, doming is generally ascribed to upflow of buoyant diapirs or transtensional deformation of the lithosphere. We suggest that doming of core complexes can be a product of continuous casting when a large-offset fault evolves to be curved in plan-view. For oceanic core complexes along-axis variation in magmatism can lead to lateral offset of a detachment fault relative to the spreading axis. We assume that near-ridge normal faults form relatively straight and consider that horizontal offsets in the along-axis position of a large-offset fault (or detachment) result from variations in the rate of magmatic diking. Assuming a sinusoidal variation in the rate of dike opening with distance along the axis the evolution of fault offset and the plan-view shape of the active fault is easy to describe. Because the fault length increases as it is offset, the work to slip on the fault increases with time. Eventually, it should be easier to slip in a new straight fault and the conditions for this can be described with an approximate analytic model. We are developing 3D numerical models to test the predictions of this analytic model and show how the topographic amplitude of the domes depends the fault dip, the amplitude of the

  9. Subsidence at Boling salt dome: results of multiple resource production

    SciTech Connect

    Mullican, W.F. III

    1988-02-01

    Boling dome (Wharton and Fort Bend Counties) has experienced more overall subsidence and collapse than any other dome in Texas. These processes are directly related to production of sulfur and hydrocarbons from the southeastern quadrant of the dome. Greatest vertical movement due to subsidence and collapse is 35 ft (based on the Boling 7.5 min topographic map, last surveyed in 1953). Most of the subsidence (83%) is attributed to sulfur production, whereas only 11 to 12% can be linked to hydrocarbon production. Reservoir compaction is the dominant mechanism of land subsidence in areas of hydrocarbon production at Boling dome. Trough subsidence, chimneying, plug caving, and piping are the characteristic mechanisms over sulfur fields developed at the salt dome. The structural and hydrologic stability of the surface and subsurface at Boling dome is compromised by these active deformation processes. Damage to pipelines and well-casing strings may result in costly leaks which have the potential of being uncontrollable and catastrophic. Reduction in hydrologic stability may result if natural aquitards are breached and fresh water mixes with saline water or if hydrologic conduits to the diapir are opened, allowing unrestricted dissolution of the salt stock.

  10. Atmospheric Transmission at Dome C between 0 and 10 THz

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Minier, V.; Durand, G.; Tremblin, P.; Urban, J.; Baron, P.

    We present model calculations of the atmospheric transmission for DOME C in Antarctica for frequencies up to 10 THz (30 μm) using the forward model MOLIERE-5. Measurements of precipitable water vapor (pwv), obtained by the SUMMIT radiometer installed at the Concordia station during 2008 and working at a wavelength of 200 μm, are translated into atmospheric transmission using MOLIERE. Quartiles of transmission, calculated from 200 μm data are extrapolated to 350 μm and compared to the CCAT (Cornell-Caltech Atacama Telescope) site in Chile. It turns out that for 25% of the time at DOME C (CCAT), the transmission is around 20% (5%) at 200 μm. This corresponds to a pwv of 0.18 mm for DOME C. At 350 μm, for 50% of time at DOME C (CCAT) the transmission is around 55% (25%). This corresponds to a pwv of 0.22 mm for DOME C. These results show that DOME C is one of the best observing sites on Earth for submm-astronomy with respect to high atmospheric transmission over long time periods.

  11. Developments in the finishing of domes and conformal optics

    NASA Astrophysics Data System (ADS)

    Shorey, Aric B.; Kordonski, William; Tracy, Justin; Tricard, Marc

    2007-04-01

    The final finish and characterization of windows and domes presents a number of difficult challenges. Furthermore, there is a desire to incorporate conformal shapes into next generation imaging and surveillance systems to provide significant advantages in overall component performance. Unfortunately, their constantly changing curvature and steep slopes make fabrication of such shapes incompatible with most conventional polishing and metrology solutions. Two novel types of polishing technology, Magnetorheological Finishing (MRF®) and Magnetorheological Jet (MR Jet TM), along with metrology provided by the Sub-aperture Stitching Interferometer (SSI®) have several unique attributes that give them advantages in enhancing fabrication of hemispherical domes and even conformal shapes. The advantages that MRF brings to the precision finishing of a wide range of shapes such as flats, spheres (including hemispheres), cylinders, aspheres and even freeform optics, has been well documented. The recently developed MR Jet process provides additional benefits, particularly in the finishing the inside of steep concave domes and other irregular shapes. Combining these technologies with metrology techniques, such as the SSI, provides a solution for finishing current and future windows and domes. Recent exciting developments in the finishing of such shapes with these technologies will be presented. These include new advances such as the ability to use the SSI to characterize a range of shapes such as domes and aspheres, as well as progress in using MRF and MR Jet for finishing conventional and conformal windows and domes.

  12. Unique dome design for the SOAR telescope project

    NASA Astrophysics Data System (ADS)

    Teran, Jose U.; Porter, David S.; Hileman, Edward A.; Neff, Daniel H.

    2000-08-01

    The SOAR telescope dome is a 20 meter diameter 5/8 spherical structure built on a rotating steel frame with an over the top nesting shutter and covered with a fiberglass panel system. The insulated fiberglass panel system can be self- supporting and is typically used for radomes on ground based tracking systems. The enclosed observing area is ventilated using a down draft ventilation system. The rotating steel frame is comprised of a ring beam and dual arch girders to provide support to the panel system sections and guide the shutter. The dual door shutter incorporates a unique differential drive system that reduces the complexity of the control system. The dome, shutter and windscreen `track' the telescope for maximum wind protection. The dome rotates on sixteen fixed compliant bogie assemblies. The dome is designed for assembly in sections off the facility and lifted into place for minimal impact on assembly of other telescope systems. The expected cost of the complete dome; including structure, drives, and controls is under 1.7 million. The details covered in this paper are the initial trade-offs and rationale required by SOAR to define the dome, the detailed design performed by M3 Engineering and Technology, and the choices made during the design.

  13. Anomalous zones in Gulf Coast Salt domes with special reference to Big Hill, TX, and Weeks Island, LA

    SciTech Connect

    Neal, J.T.; Magorian, T.R.; Thoms, R.L.; Autin, W.J.; McCulloh, R.P.; Denzler, S.; Byrne, K.O.

    1993-07-01

    Anomalous features in Gulf Coast Salt domes exhibit deviations from normally pure salt and vary widely in form from one dome to the next, ranging considerably in length and width. They have affected both conventional and solution mining in several ways. Gas outbursts, insolubles, and potash (especially carnallite) have led to the breakage of tubing in a number of caverns, and caused irregular shapes of many caverns through preferential leaching. Such anomalous features essentially have limited the lateral extent of conventional mining at several salt mines, and led to accidents and even the closing of several other mines. Such anomalous features, are often aligned in anomalous zones, and appear to be related to diapiric processes of salt dome development. Evidence indicates that anomalous zones are found between salt spines, where the differential salt intrusion accumulates other materials: Anhydrite bands which are relatively strong, and other, weaker impurities. Shear zones and fault displacement detected at Big Hill and Weeks Island domes have not yet had any known adverse impacts on SPR oil storage, but new caverns at these sites conceivably may encounter some potentially adverse conditions. Seismic reflection profiles at Big Hill dome have shown numerous fractures and faults in the caprock, and verified the earlier recognition of a major shear zone transecting the entire salt stock and forming a graben in the overlying caprock. Casing that is placed in such zones can be at risk. Knowledge of these zones should create awareness of possible effects rather than preclude the future emplacement of caverns. To the extent possible, major anomalous zones and salt stock boundaries should be avoided. Shear zones along overhangs may be particularly hazardous, and otherwise unknown valleys in the top of salt may occur along shear zones. These zones often can be mapped geophysically, especially with high-resolution seismic techniques.

  14. Rock fracture as a precursor to lava dome eruptions at Mount St Helens from June 1980 to October 1986

    NASA Astrophysics Data System (ADS)

    Smith, R.; Kilburn, C. R. J.; Sammonds, P. R.

    2007-04-01

    Following its plinian eruption on 18 May 1980, Mount St Helens (Washington State, USA) entered a period of intermittent lava-dome extrusion until 1986. Renewed extrusion was frequently preceded by accelerating rates of seismicity, with more precursory seismicity observed prior to eruptions later in the sequence. Here the failure forecasting method (FFM) is used to investigate changes in the observed rate of volcano tectonic (VT) seismicity. The analysis indicates that: (1) all VT crises resulted in an eruption within 3 weeks (usually less than 10 days), (2) the majority of eruptions had VT precursors, and (3) patterns of precursory seismicity showed fluctuations about the ideal model trend. Thus, although these seismic events could be used to warn of an impending eruption, specific forecasts were subject to an uncertainty of weeks or more. It is proposed that: (1) increased seismicity prior to later eruptions is a result of a larger and more solidified dome acting as a greater impediment to magma ascent; (2) the consistency of seismic swarms resulting in an eruption indicates that stresses high enough to initiate fracturing in the country rock and lava dome carapace were only achieved once the approach to an eruption had already begun; and (3) discrepancies between models of accelerating rock fracture and the observed seismicity may arise due to a significant amount of the rocks deforming through ductile mechanisms rather than seismogenic fracture.

  15. Record of Miocene sea-floor dome volcanism, Cabo de Gata, Spain

    NASA Astrophysics Data System (ADS)

    Riggs, N. R.; Soriano Clemente, C.

    2008-12-01

    The Cabo de Gata volcanic field comprises a 200 km2 succession of andesitic and dacitic dome complexes, together with possibly caldera-related facies and minor . Detailed investigation of exposures in the Vela Blanca to Cala Genoveses area in the southwest of the field, together with new 40Ar/39Ar groundmass ages, reveal a complex succession of andesitic to rhyolitic facies erupted as domes on a relatively shallow sea floor to emergent setting within ~1 m.y. The succession youngs from southwest to northeast. At Vela Blanca, an andesitic complex is represented by strongly columnar jointed lava; other evidence of marine emplacement is weakest in this area, suggesting an at least partially subaerial setting. The andesites are in uncertain stratigraphic relation with rhyolitic pumice breccia: more recent debris avalanches have disrupted original stratigraphy. Andesite is overlain by a dacitic succession that is the oldest well-dated unit in the area (13.36±0.13 Ma). These rocks represent a growing dacitic dome that disrupted ambient, fine-grained shallow-marine sedimentation in the area. The basal flow from the dome has a pseudo-eutaxitic texture that may represent an upper carapace; the non-vesicular nature of "fiamme" suggests a complex attenuation of flow bands. The dacite is overlain by a highly variable, intermixed hyaloclastite and flow unit called the andesite of el Barronal. Vertically flow-banded and columnar-jointed andesite grades into hyaloclastite that comprises brecciated columnar-jointed fragments. Elsewhere, flow banding in lava is sub-horizontal, grading laterally, in the seaward direction, into hyaloclastite and shoreward into dense dome material. We interpret this succession as representing a dome that spread through lava flows on the seafloor, but that may have had a subaerial component as well. Farther east, andesite crops out as radially columnar-jointed lava that represents mega-pillows or lava tubes. The pillowed horizon grades into a zone of

  16. Geostrophic circulation between the Costa Rica Dome and Central America

    NASA Astrophysics Data System (ADS)

    Brenes, C. L.; Lavín, M. F.; Mascarenhas, Affonso S.

    2008-05-01

    The geostrophic circulation between the Costa Rica Dome and Central America is described from CTD observations collected in two surveys: (a) The Wet Cruise in September-October 1993, and the Jet Cruise in February-March 1994. Poleward coastal flow was present on both occasions, but the transition from flow around the dome to the poleward Costa Rica Coastal Current flow was quite tortuous because of the presence of mesoscale eddies. In particular, a warm anticyclonic eddy was found off the Gulf of Fonseca during both cruises, at an almost identical position and with similar dimensions (150 m deep, 250 km in diameter) and surface speed (0.5 m s -1). In the Gulf of Panama, poleward flow was also observed, weaker in February-March 1994 than in September-October 1993, when it penetrated to 600 m depth and transported 8.5 Sv. In September-October 1993, the current between the dome and the coast was mostly ˜100 m deep and weak (˜0.15 m s -1), although in its southern side it was deeper (˜450 m) and faster at 0.3 m s -1. The poleward transport between the dome and the coast was ˜7 Sv. In February-March 1994 the Costa Rica Dome was a closed ring adjacent to the continental shelf, ˜500 km in diameter, at least 400 m deep, had geostrophic surface speeds ˜0.25 m s -1, and subsurface maximum speed (0.15-0.20 m s -1) at ˜180 m depth; the associated uplift of the isotherms was ˜150 m. The flow in the south part of the dome splits into two branches, the weakest one going around the dome and the strongest one continuing east and turning south before reaching the Gulf of Panama.

  17. Wind tunnel study of an observatory dome with a circular aperture

    NASA Technical Reports Server (NTRS)

    Zilliac, Gregory G.; Cliffton, Ethan W.

    1990-01-01

    Results of a wind tunnel test of a new concept in observatory dome design, the Fixed Shutter Dome are presented. From an aerodynamic standpoint, the new dome configuration is similar in overall shape to conventional observatory domes, with the exception of the telescope viewing aperture. The new design consists of a circular aperture of reduced area in contrast to conventional domes with rectangular or slotted openings. Wind tunnel results of a side-by-side comparison of the new dome with a conventional dome demonstrate that the mean and fluctuating velocity through the aperture and in the center of the new dome configuration are lower than those of conventional domes, thus reducing the likelihood of telescope flow-induced vibration.

  18. M cells and granular mononuclear cells in Peyer's patch domes of mice depleted of their lymphocytes by total lymphoid irradiation.

    PubMed Central

    Ermak, T. H.; Steger, H. J.; Strober, S.; Owen, R. L.

    1989-01-01

    The cytoarchitecture of Peyer's patches that were depleted of their lymphocytes by total lymphoid irradiation (TLI) was examined with particular attention to the effects on M cells in the follicle epithelium and on mononuclear cells in follicle domes underlying the epithelium. Five-month-old, specific pathogen-free Balb/c mice were irradiated with 200-250 rad/day, five times a week to a total dose of 3400-4250, and their Peyer's patches were either fixed for electron microscopy or frozen for immunohistochemistry 1-4 days after completion of irradiation. Control mice were examined at the same time intervals. Follicle domes of TLI mice had approximately one fourth the epithelial surface area of domes of control mice. Within the epithelium, lymphoid cells were virtually depleted after TLI, and yet the epithelium contained M cells. In control mice, most M cells were accompanied by lymphoid cells in invaginations of the apical-lateral cell membrane. In TLI mice, most M cells did not have such apical-lateral invaginations and were columnar shaped. Other than lacking lymphocytes, these cells appeared to be mature M cells. Some M cells did have lymphoid cells or granular mononuclear cells below their basal membranes, adjacent to the basal lamina. Below the epithelium, the proportion of granular mononuclear cells was greatly increased following TLI. The retention of M cells and the increase in proportion of granular mononuclear cells in follicle domes are consistent with selective depletion of lymphocytes following TLI. Persistence of M cells without lymphocytic invaginations after TLI suggests that M cells can differentiate in the absence of, or at least in the presence of very few, lymphocytes, and that invagination by lymphocytes is not necessary to maintain mature M cell morphology. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:2923183

  19. Lateral blasts at Mount St. Helens and hazard zonation

    USGS Publications Warehouse

    Crandell, D.R.; Hoblitt, R.P.

    1986-01-01

    Lateral blasts at andesitic and dacitic volcanoes can produce a variety of direct hazards, including ballistic projectiles which can be thrown to distances of at least 10 km and pyroclastic density flows which can travel at high speed to distances of more than 30 km. Indirect effect that may accompany such explosions include wind-borne ash, pyroclastic flows formed by the remobilization of rock debris thrown onto sloping ground, and lahars. Two lateral blasts occurred at a lava dome on the north flank of Mount St. Helens about 1200 years ago; the more energetic of these threw rock debris northeastward across a sector of about 30?? to a distance of at least 10 km. The ballistic debris fell onto an area estimated to be 50 km2, and wind-transported ash and lapilli derived from the lateral-blast cloud fell on an additional lobate area of at least 200 km2. In contrast, the vastly larger lateral blast of May 18, 1980, created a devastating pyroclastic density flow that covered a sector of as much as 180??, reached a maximum distance of 28 km, and within a few minutes directly affected an area of about 550 km2. The May 18 lateral blast resulted from the sudden, landslide-induced depressurization of a dacite cryptodome and the hydrothermal system that surrounded it within the volcano. We propose that lateral-blast hazard assessments for lava domes include an adjoining hazard zone with a radius of at least 10 km. Although a lateral blast can occur on any side of a dome, the sector directly affected by any one blast probably will be less than 180??. Nevertheless, a circular hazard zone centered on the dome is suggested because of the difficulty of predicting the direction of a lateral blast. For the purpose of long-term land-use planning, a hazard assessment for lateral blasts caused by explosions of magma bodies or pressurized hydrothermal systems within a symmetrical volcano could designate a circular potential hazard area with a radius of 35 km centered on the volcano

  20. Upheaval Dome, An Analogue Site for Gale Center

    NASA Technical Reports Server (NTRS)

    Conrad, P. G.; Eignebrode, J. L.

    2011-01-01

    We propose Upheaval Dome in southeastern Utah as an impact analogue site on Earth to Mars Science Laboratory candidate landing site Gale Crater. The genesis of Upheaval Dome was a mystery for some time--originally thought to be a salt dome. The 5 km crater was discovered to possess shocked quartz and other shock metamorphic features just a few years ago, compelling evidence that the crater was formed by impact, although the structural geology caused Shoemaker and Herkenhoff to speculate an impact origin some 25 years earlier. The lithology of the crater is sedimentary. The oldest rocks are exposed in the center of the dome, upper Permian sandstones, and progressively younger units are well exposed moving outward from the center. These are Triassic sandstones, siltstones and shales, which are intruded by clastic dikes. There are also other clay-rich strata down section, as is the case with Gale Crater. There is significant deformation in the center of the crater, with folding and steeply tilted beds, unlike the surrounding Canyonlands area, which is relatively undeformed. The rock units are well exposed at Upheaval Dome, and there are shatter cones, impactite fragments, shocked quartz grains and melt rocks present. The mineral shock features suggest that the grains were subjected to dynamic pressures> 10 GPa.

  1. The behaviour of repaired composite domes subjected to external pressure

    NASA Astrophysics Data System (ADS)

    Mistry, J.; Levy-Neto, F.

    1992-07-01

    Six hemispherical and four torispherical composite plastic domes reinforced with either carbon or E-glass woven fabrics or a combination of both have been tested under external pressure. The domes were prepared using male or female moulds and employed the hand lay-up/vacuum bag method for their manufacture. The domes were observed to fail either by buckling or as a result of material failure. Both modes of failure were usually located at the meridian having the minimum average thickness. These domes were then repaired using a recommended technique and retested. It has been shown that the integrity of the repaired zones was guaranteed and further damage to the domes during retesting moved to new locations usually corresponding to the areas of the new minimum average thickness meridian. Two computer programs based on finite difference and finite element methods were employed to predict the critical buckling or material failure loads. The theoretical predictions were shown to correlate very well with the experimental results.

  2. Fracture fillings and intrusive pyroclasts, Inyo Domes, California

    SciTech Connect

    Heiken, G.; Wohletz, K.; Eichelberger, J.

    1988-05-10

    Fractures containing juvenile magmatic pyroclasts were encountered during drilling into a 600-year-old feeder dike beneath the Inyo Domes chain, California. The Inyo Domes consist of a north-south trending, 10-km-long chain of domes, rhyolitic tuff rings, and phreatic craters. Boreholes were cored through the 51-m-diameter conduit of Obsidian Dome, the largest of the Inyo Domes, and through an unvented portion of the intrusion (dike) 1 km to the south. Pyroclast-bearing fractures were intersected in both holes: (1) 7- to 40-cm-thick fractures in welded basaltic scoria and quartz monzonite country rock are adjacent to the conduit at depths of 400--411 m and 492--533 m; they contain gray, clastic deposits, which show truncated cross bedding and convolute bedding; (2) adjacent to the dike, massive fracture fillings occur at depths of 289--302 m (129 m east of the dike) and 366--384 m (95--87 m east of the dike).

  3. Contemporary doming of the Adirondack mountains: Further evidence from releveling

    USGS Publications Warehouse

    Isachsen, Y.W.

    1981-01-01

    The Adirondack Mountains constitute an anomalously large, domical uplift on the Appalachian foreland. The dome has a NNE-SSW axis about 190 km long, and an east-west dimension of about 140 km. It has a structural relief of at least 1600 m, and a local topographic relief of up to 1200 m. First-order leveling in 1955, and again in 1973 along a north-south line at the eastern margin of the Adirondack shows an uplift rate of 2.2 mm/yr at the latitude of the center of the dome and a subsidence rate of 2.8 mm/yr at the northern end of the line near the Canadian border. The net amount of arching along this releveled line is 9 cm ?? 2 cm (Isachsen, 1975). To test the idea that this arching represented an "edge effect" of contemporary doming of the Adirondacks as a whole, the National Geodetic Survey was encouraged to relevel a 1931 north-south line between Utica and Fort Covington (near the Canadian border) which crosses the center of the dome. The releveling showed that the mountain mass is undergoing contemporary domical uplift at a rate which reaches 3.7 mm/yr near the center of the dome (compare with 1 mm/yr for the Swiss Alps). Three other releveled lines in the area support this conclusion. ?? 1981.

  4. Explosive activity associated with the growth of volcanic domes

    USGS Publications Warehouse

    Newhall, C.G.; Melson, W.G.

    1983-01-01

    Domes offer unique opportunities to measure or infer the characteristics of magmas that, at domes and elsewhere, control explosive activity. A review of explosive activity associated with historical dome growth shows that: 1. (1) explosive activity has occurred in close association with nearly all historical dome growth; 2. (2) whole-rock SiO2 content, a crude but widely reported indicator of magma viscosity, shows no systematic relationship to the timing and character of explosions; 3. (3) the average rate of dome growth, a crude indicator of the rate of supply of magma and volatiles to the near-surface enviornment, shows no systematic relationship to the timing or character of explosions; and 4. (4) new studies at Arenal and Mount St. Helens suggest that water content is the dominant control on explosions from water-rich magmas, whereas the crystal content and composition of the interstitial melt (and hence magma viscosity) are equally or more important controls on explosions from water-poor magmas. New efforts should be made to improve current, rather limited techniques for monitoring pre-eruption volatile content and magma viscosity, and thus the explosive potential of magmas. ?? 1983.

  5. Two types of superconducting domes in unconventional superconductors

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Panagopoulos, Christos

    In this talk, we present a comprehensive analysis of the SC properties and phase diagrams across several families of unconventional superconductors within the copper-oxides, heavy-fermions, organics, and the recently discovered iron-pnictides, iron-chalcogenides, and oxybismuthides. We find that there are two types of SC domes present in all families of SC materials, arising sometimes as completely isolated, or merged into one, or in some materials only any one of them appears. One of the SC dome appearing at or near a possible QCP usually possesses a lower transition temperature (Tc) . The other SC dome appearing at a different value of the tuning parameter around a non-Fermi liquid (NFL) state often has higher Tc. Both SC domes are not necessarily linked to each other, and so does the QCP and NFL state. In materials, where both domes are present, they can be isolated by multiple tuning (such as such as disorder, or pressure, or magnetic field in addition to doping, and vice versa), giving a unique opportunity to decouple the relationship between QCP, NFL, and their role on superconductivity. The systematic study the NFL state might be a generic route to higher-Tc superconductivity.

  6. Dry Creek salt dome, Mississippi Interior Salt basin

    SciTech Connect

    Montgomery, S.L.; Ericksen, R.L.

    1997-03-01

    Recent drilling of salt dome flanks in the Mississippi Salt basin has resulted in important new discoveries and the opening of a frontier play. This play is focused on gas/condensate reserves in several Cretaceous formations, most notably the Upper Cretaceous Eutaw and lower Tuscaloosa intervals and Lower Cretaceous Paluxy and Hosston formations. As many as eight domes have been drilled thus far; sandstones in the upper Hosston Formation comprise the primary target. Production has been as high as 3-5 Mcf and 500-1200 bbl of condensate per day, with estimated ultimate reserves in the range of 0.2 to 1.5 MBOE (million barrels oil equivalent) per well. As typified by discovery at Dry Creek salt dome, traps are related to faulting, unconformities, and updip loss of permeability. Previous drilling at Dry Creek, and in the basin generally, avoided the flank areas of most domes, due to geologic models that predicted latestage (Tertiary) piercement and breached accumulations. Recent data from Dry Creek and other productive domes suggest that growth was episodic and that piercement of Tertiary strata did not affect deeper reservoirs charged with hydrocarbons in the Late Cretaceous.

  7. Magma Dynamics in Dome-Building Volcanoes

    NASA Astrophysics Data System (ADS)

    Kendrick, J. E.; Lavallée, Y.; Hornby, A. J.; Schaefer, L. N.; Oommen, T.; Di Toro, G.; Hirose, T.

    2014-12-01

    The frequent and, as yet, unpredictable transition from effusive to explosive volcanic behaviour is common to active composite volcanoes, yet our understanding of the processes which control this evolution is poor. The rheology of magma, dictated by its composition, porosity and crystal content, is integral to eruption behaviour and during ascent magma behaves in an increasingly rock-like manner. This behaviour, on short timescales in the upper conduit, provides exceptionally dynamic conditions that favour strain localisation and failure. Seismicity released by this process can be mimicked by damage accumulation that releases acoustic signals on the laboratory scale, showing that the failure of magma is intrinsically strain-rate dependent. This character aids the development of shear zones in the conduit, which commonly fracture seismogenically, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. High-velocity rotary shear (HVR) experiments demonstrate that at ambient temperatures, gouge behaves according to Byerlee's rule at low slip velocities. At rock-rock interfaces, mechanical work induces comminution of asperities and heating which, if sufficient, may induce melting and formation of pseudotachylyte. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The bulk composition, mineralogy and glass content of the magma all influence frictional behaviour, which supersedes buoyancy as the controlling factor in magma ascent. In the conduit of dome-building volcanoes, the fracture and slip processes are further complicated: slip-rate along the conduit margin fluctuates. The shear-thinning frictional melt yields a tendency for extremely unstable slip thanks to its pivotal position with regard to the glass transition. This thermo-kinetic transition bestows the viscoelastic melt with the ability to either flow or

  8. An assessment of hydrothermal alteration in the Santiaguito lava dome complex, Guatemala: implications for dome collapse hazards

    USGS Publications Warehouse

    Ball, Jessica L.; Calder, Eliza S.; Hubbard, Bernard E.; Bernstein, Marc L.

    2013-01-01

    A combination of field mapping, geochemistry, and remote sensing methods has been employed to determine the extent of hydrothermal alteration and assess the potential for failure at the Santiaguito lava dome complex, Guatemala. The 90-year-old complex of four lava domes has only experienced relatively small and infrequent dome collapses in the past, which were associated with lava extrusion. However, existing evidence of an active hydrothermal system coupled with intense seasonal precipitation also presents ideal conditions for instability related to weakened clay-rich edifice rocks. Mapping of the Santiaguito dome complex identified structural features related to dome growth dynamics, potential areas of weakness related to erosion, and locations of fumarole fields. X-ray diffraction and backscattered electron images taken with scanning electron microscopy of dacite and ash samples collected from around fumaroles revealed only minor clay films, and little evidence of alteration. Mineral mapping using ASTER and Hyperion satellite images, however, suggest low-temperature (<150 °C) silicic alteration on erosional surfaces of the domes, but not the type of pervasive acid-sulfate alteration implicated in collapses of other altered edifices. To evaluate the possibility of internal alteration, we re-examined existing aqueous geochemical data from dome-fed hot springs. The data indicate significant water–rock interaction, but the Na–Mg–K geoindicator suggests only a short water residence time, and δ18O/δD ratios show only minor shifts from the meteoric water line with little precipitation of secondary (alteration) minerals. Based on available data, hydrothermal alteration on the dome complex appears to be restricted to surficial deposits of hydrous silica, but the study has highlighted, importantly, that the 1902 eruption crater headwall of Santa María does show more advanced argillic alteration. We also cannot rule out the possibility of advanced alteration

  9. Folding retractable protective dome for space vehicle equipment

    NASA Technical Reports Server (NTRS)

    Clark, Paul R. (Inventor); Messinger, Ross H. (Inventor)

    2008-01-01

    A folding, retractable dome for protecting a feature, such as a docking mechanism, a hatch or other equipment at an exterior surface of a space vehicle, includes a plurality of arcuate ribs, each having opposite ends respectively pinioned at opposite sides of the feature at the surface of the vehicle for rotational movement about an axis of rotation extending through the opposite ends and through an arcuate path of revolution extending over the feature, and a flexible cover attached to each of the ribs such that, in a deployed configuration of the dome, in which adjacent ribs are rotated apart from each other at a maximum relative angle therebetween, the cover is stretched generally tangentially between the adjacent ribs to form a generally arcuate shield over the feature, and in a retracted position of the dome, in which adjacent ribs are rotated together at a minimum relative angle therebetween, the cover is collapsed to define folded pleats between the adjacent ribs.

  10. Geodesic-dome tank roof cuts water contamination, vapor losses

    SciTech Connect

    Barrett, A.E. )

    1989-07-10

    Colonial Pipeline Co. has established an ongoing program for using geodesic-dome roofs on tanks in liquid petroleum-product service. As its standard, Colonial adopted geodesicodone roofs, in conjunction with internal floating decks, to replace worn external floating roofs on existing tanks used in gasoline service and for use on new tanks in all types of product service. Geodesic domes are clear-span structures requiring no internal-support columns. This feature allows the associated use of a floating deck that is as vapor tight as is possible to construct. Further, geodesic domes can practically eliminate rainwater contamination, eliminate wind-generated vapor losses, and greatly reduce filling losses associated with conventional external floating roofs.

  11. Dome-shaped PDC cutters drill harder rock effectively

    SciTech Connect

    Moran, D.P. )

    1992-12-14

    This paper reports that rock mechanics and sonic travel time log data indicate that bits with convex-shaped polycrystalline diamond compact (PDC) cutters can drill harder rock formations than comparable bits with flat PDC cutters. The Dome-shaped cutters have drilled carbonate formations with sonic travel times as small as 50 [mu]sec/ft, compared to the standard cutoff of 75 [mu]sec/ft for flat PCD cutters. Recent field data from slim hole wells drilled in the Permian basin have shown successful applications of the 3/8-in. Dome cutter in the Grayburg dolomite with its sonic travel times as low as 50-55 [mu]sec/ft and compressive strengths significantly greater than the standard operating range for PDC bit applications. These field data indicate that the Dome cutters can successfully drill hard rock. The convex cutter shape as good impact resistance, cuttings removal, heat dissipation, and wear resistance.

  12. Numerical modelling of lithospheric extension: doming vs. thermal condition

    NASA Astrophysics Data System (ADS)

    Schenker, Filippo Luca; Gerya, Taras; Kaus, Boris; Burg, Jean-Pierre

    2010-05-01

    Structural aspects of extensional doming have been modelled numerically using simplified 2D visco-plastic models (e.g. Huismans et al. 2005, Buiter et al. 2008) concentrating mainly on symmetric/asymmetric doming, fault tectonics and deformation of domes and surrounding rocks. Recent works focus their attention to the influence of geotherms on the rheology (Tirel et al. 2008), even taking into account melting (Rey et al., 2009). However, thermal aspects remain difficult to compute because of the coupled interaction between mechanical forces and temperature. This coupling is fundamental, because it provides a link between modelling and thermochronometry. Indeed, cooling ages of extensional dome flanks can constrain time, size, and patterns of metamorphic overprints simulated in thermo-mechanical models. We treat mechanical and thermal aspects together (including modelling of metamorphic P-T-time paths of crustal rocks), using a visco-elasto-plastic rheology in a four layer setup (upper crust, lower crust, lithospheric mantle and asthenospheric mantle). The asthenospheric mantle is considered in order to predict the bending effect of the lithosphere. We employed I2ELVIS, a numerical 2D computer code designed for conservative finite differences method. The model domain is 300 km wide and 160 km deep. We observed two modes of dome development and geometry, depending on first order parameters such as temperature at the Moho and thickness of the crust: (i) Lower crustal doming: with a hot Moho (TMOHO > 700 °C) and/or a thick crust, strain is localized in the upper crust and distributed in the mantle. At these conditions partial melting in the lower crust forms the core of the dome and maintains a flat Moho. (ii) Asthenospheric-triggered doming: with a cold Moho (TMOHO < 700 °C), strain is distributed in the crust and localized in the lithospheric mantle, which allows upwelling of the asthenosphere. The migmatite "core complexes" develop after the upwelling of the

  13. Late Oligocene and Early Miocene Muroidea of the Zinda Pir Dome

    PubMed Central

    Lindsay, Everett H.; Flynn, Lawrence J.

    2016-01-01

    A series of Oligocene through Early Miocene terrestrial deposits preserved in the foothills of the Zinda Pir Dome of western Pakistan produce multiple, superposed fossil mammal localities. These include small mammal assemblages that shed light on the evolution of rodent lineages, especially Muroidea, in South Asia. Nine small mammal localities span approximately 28–19 Ma, an interval encompassing the Oligocene–Miocene boundary. The Early Miocene rodent fossil assemblages are dominated by muroid rodents, but muroids are uncommon and archaic in earlier Oligocene horizons. The Zinda Pir sequence includes the evolutionary transition to modern Muroidea at about the Oligocene–Miocene boundary. We review the muroid record for the Zinda Pir Dome, which includes the early radiation of primitive bamboo rats (Rhizomyinae) and early members of the modern muroid radiation, which lie near crown Cricetidae and Muridae. The Zinda Pir record dates diversification of modern muroids in the Indian Subcontintent and establishment by 19 Ma of muroid assemblages characteristic of the later Siwaliks. PMID:26681836

  14. Exploring Learning through Audience Interaction in Virtual Reality Dome Theaters

    NASA Astrophysics Data System (ADS)

    Apostolellis, Panagiotis; Daradoumis, Thanasis

    Informal learning in public spaces like museums, science centers and planetariums is increasingly popular during the last years. Recent advancements in large-scale displays allowed contemporary technology-enhanced museums to get equipped with digital domes, some with real-time capabilities like Virtual Reality systems. By conducting extensive literature review we have come to the conclusion that little to no research has been carried out on the leaning outcomes that the combination of VR and audience interaction can provide in the immersive environments of dome theaters. Thus, we propose that audience collaboration in immersive virtual reality environments presents a promising approach to support effective learning in groups of school aged children.

  15. Prediction of Limit Strains in Limiting Dome Height Formability Test

    NASA Astrophysics Data System (ADS)

    Zadpoor, Amir A.; Sinke, Jos; Benedictus, Rinze

    2007-04-01

    In this paper, the Marciniak-Kunczynski (MK) method is combined with the Storen-Rice analysis in order to improve accuracy of the predicted limit strains in Limiting Dome Height (LDH) test. FEM simulation is carried out by means of a commercial FEM code (ABAQUS) and FEM results are postprocessed by using an improved MK code. It has been shown that while original MK method considerably misspredicts the limit strains, a combination of MK method and Storen-Rice analysis can predict the dome height with a very good accuracy.

  16. Analysis and test of low profile aluminum aerospace tank dome

    NASA Astrophysics Data System (ADS)

    Ahmed, R.; Wilhelm, J. M.

    1993-12-01

    In order to increase the structural performance of cryogenic tanks, the aerospace industry is beginning to employ low-profile bulkheads in new generation launch vehicle designs. This report details the analysis and test of one such dome made from 2219 aluminum. Such domes have two potential failure modes under internal pressure, general tensile failure and hoop compression buckling (in regions near the equator). The test determined the buckling load and ultimate tensile load of the hardware and showed that both compared well with the analysis predictions. This effort was conducted under the auspices of NASA and the General Dynamics Cryogenic Tank Technology Program (CTTP).

  17. Analysis and test of low profile aluminum aerospace tank dome

    NASA Technical Reports Server (NTRS)

    Ahmed, R.; Wilhelm, J. M.

    1993-01-01

    In order to increase the structural performance of cryogenic tanks, the aerospace industry is beginning to employ low-profile bulkheads in new generation launch vehicle designs. This report details the analysis and test of one such dome made from 2219 aluminum. Such domes have two potential failure modes under internal pressure, general tensile failure and hoop compression buckling (in regions near the equator). The test determined the buckling load and ultimate tensile load of the hardware and showed that both compared well with the analysis predictions. This effort was conducted under the auspices of NASA and the General Dynamics Cryogenic Tank Technology Program (CTTP).

  18. Gravitational Collapse of Lava Domes Triggered by Volcanic Fluids

    NASA Astrophysics Data System (ADS)

    Elsworth, D.; Voight, B.; Taron, J.; Thompson, G.; Vinciguerra, S.; Simmons, J.

    2005-12-01

    Excess fluid pressures exert important controls on the stability of lava domes and of the flanks of volcanoes. Migrating overpressures reduce the shear strength of the edifice and may control the timing, morphology, and energetics of failure. Excess pressures may be developed both directly from magma degassing, and indirectly from the interaction of magma with infiltrating rainwater or groundwater. Interior gases influence the strength of the volcanic pile, and hence its stability, in at least two ways. In the fractured and solidified outer carapace high gas contents reduce effective stresses and concomitantly lower shear strength. In the dome interior, magmas which avoid the off-gassing of volatiles exhibit a low and primarily cohesive strength. Signatures of these various processes are evident in the extensive record of collapses which chart the episodic growth and destruction of the lava dome at Soufriere Hills volcano, Montserrat. Mechanisms include (1) interior pressurization by magma degassing, (2) the interaction of rainwater with the hot dome rind, and (3) the segregation of magmas extruded into the dome resulting in a relatively weak and potentially gas overpressured core. The influence of gas overpressures applied interior to a brittle carapace is typified by the response to episodes of cyclic inflation, where collapse may be delayed and may be triggered at inferred pressures below the peak reached in the prior cycle. Similar influences on timing, and in collapse style are present for rainfall-triggered events where deluges beyond a given intensity and duration are required to promote failure, and the style of collapse is influenced by the antecedent conditions of gas pressurization within the lava dome. In all instances, interior gas overpressures or the presence of a segregated plastic core are both viable mechanisms to promote a switch between shallow instability of the dome carapace to deep transaction of the dome core. Such switching to a more

  19. FLAMMABLE GAS DIFFUSION THROUGH SINGLE SHELL TANK (SST) DOMES

    SciTech Connect

    MEACHAM, J.E.

    2003-11-10

    This report quantified potential hydrogen diffusion through Hanford Site Single-Shell tank (SST) domes if the SSTs were hypothetically sealed airtight. Results showed that diffusion would keep headspace flammable gas concentrations below the lower flammability limit in the 241-AX and 241-SX SST. The purpose of this document is to quantify the amount of hydrogen that could diffuse through the domes of the SSTs if they were hypothetically sealed airtight. Diffusion is assumed to be the only mechanism available to reduce flammable gas concentrations. The scope of this report is limited to the 149 SSTs.

  20. Mount St. Helens Lava Domes, Then and Now

    NASA Astrophysics Data System (ADS)

    Fink, J.; Anderson, S. W.

    2004-12-01

    When the Mount St. Helens (MSH) lava dome grew from 1980-1986, little was known about how volatiles, vesicularity or crystallinity were distributed in domes, or about overall patterns of growth. Six years of MSH observations, coupled with comparative petrologic, structural, and analog laboratory studies of domes at Soufriere of St. Vincent, Augustine, Redoubt, Merapi, Montserrat, Santiaguito, and elsewhere have provided a much better foundation for evaluating the 2004 eruptive activity. One of the main goals of the earlier studies was to differentiate intrusive processes from those operating when magma ascends near and onto the volcano's surface. Here we use some of our earlier isotopic, petrographic and remote sensing observations of textures and volatiles to speculate about the processes operating in 2004. We earlier linked variations in lava textures to degassing processes operating during ascent and emplacement. MSH lava was extruded in a relatively dense state. When the water content was high enough, hot, ductile lava beneath the quenched outer rind of the dome vesiculated during surface flow, creating a 1 to 2 meter thick scoriaceous carapace. Post-1983 lavas lacked this scoria because the dome had reached a critical size and strength, resulting in lower short-term eruption rates and extensive degassing of lava en route to the surface. Observations of a dense "fin" in October 2004 suggest that this initial dome-building magma experienced thorough degassing as it broke a new path to the crater floor. We also used hydrogen isotope analyses of water in 1980-86 dome samples to infer degassing processes occurring in the source magma chamber and conduit system. Water content and hydrogen isotopic values of dome samples varied according to texture, position on the flow, and repose period prior to eruption. We saw two trends: (1) lava from lobes emplaced after longer repose intervals were deuterium-enriched, and (2) within individual lobes, relatively dry, smooth

  1. Shapes of Venusian 'pancake' domes imply episodic emplacement and silicic composition

    NASA Astrophysics Data System (ADS)

    Fink, J. H.; Bridges, N. T.; Grimm, R. E.

    1993-02-01

    The main evidence available for constraining the composition of the large circular 'pancake' domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of Venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 Venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.

  2. LAMELLA DOME FRAMING DETAIL. NOTE CATWALK AT 12 O'CLOCK AND ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LAMELLA DOME FRAMING DETAIL. NOTE CATWALK AT 12 O'CLOCK AND SUSPENDED PENTAGONAL LIGHT RING GONDOLA. ALSO NOTE COMPRESSION RING AT CROWN OF DOME. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  3. Shapes of Venusian 'pancake' domes imply episodic emplacement and silicic composition

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan H.; Bridges, Nathan T.; Grimm, Robert E.

    1993-01-01

    The main evidence available for constraining the composition of the large circular 'pancake' domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of Venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 Venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.

  4. Steep-sided domes on Venus - Characteristics, geologic setting, and eruption conditions from Magellan data

    NASA Technical Reports Server (NTRS)

    Pavri, Betina; Head, James W., III; Klose, K. B.; Wilson, Lionel

    1992-01-01

    A survey of more than 95 percent of the Venus surface reveals 145 steep-sided domes which can be subdivided into a variety of morphologic forms, the most common being shaped like inverted bowls or flat-topped domes. Results of a preliminary analysis of the distribution and geologic setting of the domes are presented. The relation of the domes to analogous terrestrial features is examined, and possible models for their mode of emplacement are outlined.

  5. [Analysis of the Basic Stress Pathway Above Acetabular Dome].

    PubMed

    Nie, Yong; Ma, Jun; Haung, Qiang; Hu, Qinsheng; Shi, Xiaojun; Pei, Fuxing

    2015-08-01

    The basic stress pathway above the acetabular dome is important for the maintenance of implant stability in acetabular reconstruction of total hip arthroplasty (THA). The purpose of this study was to describe the basic stress pathway to provide evidence for clinical acetabular reconstruction guidance of THA. A subject-specific finite element (FE) model was developed from CT data to generate 3 normal hip models and a convergence study was conducted to determine the number of pelvic trabecular bone material properties using 5 material assignment plans. In addition, in the range of 0 to 20 mm above the acetabular dome, the models were sectioned and the stress pathway was defined as two parts, i.e., 3D, trabecular bone stress distribution and quantified cortical bone stress level. The results showed that using 100 materials to define the material property of pelvic trabecular bone could assure both the accuracy and efficiency of the FE model. Under the same body weight condition, the 3D trabecular bone stress distributions above the acetabular dome were consistent, and especially the quantified cortical bone stress levels were all above 20 MPa and showed no statistically significant difference (P>0.05). Therefore, defining the basic stress pathway above the acetabular dome under certain body weight condition contributes to design accurate preoperative plan for acetabular reconstruction, thus helping restore the normal hip biomechanics and preserve the stability of the implants. PMID:26710451

  6. Determining the coordinates of lamps in an illumination dome

    NASA Astrophysics Data System (ADS)

    MacDonald, Lindsay W.; Ahmadabadian, Ali H.; Robson, Stuart

    2015-05-01

    The UCL Dome consists of an acrylic hemisphere of nominal diameter 1030 mm, fitted with 64 flash lights, arranged in three tiers of 16, one tier of 12, and one tier of 4 lights at approximately equal intervals. A Nikon D200 digital camera is mounted on a rigid steel frame at the `north pole' of the dome pointing vertically downwards with its optical axis normal to the horizontal baseboard in the `equatorial' plane. It is used to capture sets of images in pixel register for visualisation and surface reconstruction. Three techniques were employed for the geometric calibration of flash light positions in the dome: (1) the shadow cast by a vertical pin onto graph paper; (2) multi-image photogrammetry with retro-reflective targets; and (3) multi-image photogrammetry using the flash lights themselves as targets. The precision of the coordinates obtained by the three techniques was analysed, and it was found that although photogrammetric methods could locate individual targets to an accuracy of 20 μm, the uncertainty of locating the centroids of the flash lights was approximately 1.5 mm. This result was considered satisfactory for the purposes of using the dome for photometric imaging, and in particular for the visualisation of object surfaces by the polynomial texture mapping (PTM) technique.

  7. 19. View of satcom communication dome with TR radome in ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    19. View of satcom communication dome with TR radome in background right. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  8. 14. PHOTOCOPY OF PHOTOGRAPH: DOMED CEILING OF AUDITORIUM, Date unknown. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    14. PHOTOCOPY OF PHOTOGRAPH: DOMED CEILING OF AUDITORIUM, Date unknown. from FOURTH CHURCH OF CHRIST, SCIENTIST ARCHIVE (used with permission) E. S. Cheney and R. B. Bird, Photographers, Cheney Photo Adv. Co., Oakland, California. - Fourth Church of Christ, Scientist, 1330 Lakeshore Avenue, Oakland, Alameda County, CA

  9. Power production with two-phase expansion through vapor dome

    SciTech Connect

    Amend, W.E.; Toner, S.J.

    1984-08-07

    In a system wherein a fluid exhibits a regressive vapor dome in a T-S diagram, the following are provided: a two-phase nozzle receiving the fluid in pressurized and heated liquid state and expanding the received liquid into saturated or superheated vapor state, and apparatus receiving the saturated or superheated vapor to convert the kinetic energy thereof into power.

  10. Key variables influencing patterns of lava dome growth and collapse

    NASA Astrophysics Data System (ADS)

    Husain, T.; Elsworth, D.; Voight, B.; Mattioli, G. S.; Jansma, P. E.

    2013-12-01

    Lava domes are conical structures that grow by the infusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Dome growth can be characterized by repeated cycles of growth punctuated by collapse, as the structure becomes oversized for its composite strength. Within these cycles, deformation ranges from slow long term deformation to sudden deep-seated collapses. Collapses may range from small raveling failures to voluminous and fast-moving pyroclastic flows with rapid and long-downslope-reach from the edifice. Infusion rate and magma rheology together with crystallization temperature and volatile content govern the spatial distribution of strength in the structure. Solidification, driven by degassing-induced crystallization of magma leads to the formation of a continuously evolving frictional talus as a hard outer shell. This shell encapsulates the cohesion-dominated soft ductile core. Here we explore the mechanics of lava dome growth and failure using a two-dimensional particle-dynamics model. This meshless model follows the natural evolution of a brittle carapace formed by loss of volatiles and rheological stiffening and avoids difficulties of hour-glassing and mesh-entangelment typical in meshed models. We test the fidelity of the model against existing experimental and observational models of lava dome growth. The particle-dynamics model follows the natural development of dome growth and collapse which is infeasible using simple analytical models. The model provides insight into the triggers that lead to the transition in collapse mechasnism from shallow flank collapse to deep seated sector collapse. Increase in material stiffness due to decrease in infusion rate results in the transition of growth pattern from endogenous to exogenous. The material stiffness and strength are strongly controlled by the magma infusion rate. Increase in infusion rate decreases the time available for degassing induced crystallization leading to a

  11. Textural evidence for origin of salt dome anhydrite cap rocks, Winnfield Dome, Louisiana

    SciTech Connect

    Ulrich, M.R.; Kyle, J.R.; Price, P.E.

    1985-02-01

    Textures within anhydrite cap rock are products of repeated cycles of halie dissolution and residual anhydrite accretion at tops of salt stocks. Quarrying operations at Winnfield dome have exposed extensive portions of the anhydrite cap rock zone. This zone is composed primarily of unoriented, xenoblastic anhydrite crystals in laminae less than 1 mm to several centimeters thick. Laminations are defined by thin, dark sulfide accumulations and pressure solution of anhydrite. Deformed, banded anhydrite clasts are contained locally within laminae. Multiple-laminated, concave downward anhydrite mounds occur along some horizons. They may contain anhydrite breccia fragments or sulfides. Coarsely crystalline salt mounds, containing disseminated idioblastic anhydrite also occur along horizons. Mound morphologies vary from tall and thin to broad and squat; maximum dimensions range from less than 0.5 to about 2.0 m. These moundlike structures are related spatially and genetically. Moundlike structures are believed to form from salt spines along the salt-anhydrite contact. As the spine dissolves through several cycles of dissolution and accretion, a laminated anhydrite mound is preserved; if the spine becomes isolated from dissolution, then a salt inclusion is preserved. Anhydrite beds within the Louann Salt, deformed during diapirism, are preserved as deformed anhydrite clasts. Steeply dipping, bedded anhydrite zones within the salt stock may produce brecciated anhydrite mounds when incorporated into the cap rock. Sulfides record the movement of metalliferous fluids through the salt-anhydrite contact.

  12. Geology of the Upheaval Dome impact structure, southeast Utah

    USGS Publications Warehouse

    Kriens, B.J.; Shoemaker, E.M.; Herkenhoff, K. E.

    1999-01-01

    Two vastly different phenomena, impact and salt diapirism, have been proposed for the origin of Upheaval Dome, a spectacular scenic feature in southeast Utah. Detailed geologic mapping and seismic refraction data indicate that the dome originated by collapse of a transient cavity formed by impact. Evidence is as follows: (1) sedimentary strata in the center of the structure are pervasively imbricated by top-toward-the-center thrust faulting and are complexly folded as well; (2) top-toward-the-center normal faults are found at the perimeter of the structure; (3) clastic dikes are widespread; (4) the top of the underlying salt horizon is at least 500 m below the surface at the center of the dome, and there are no exposures of salt or associated rocks of the Paradox Formation in the dome to support the possibility that a salt diapir has ascended through it; and (5) planar microstructures in quartz grains, fantailed fracture surfaces (shatter surfaces), and rare shatter cones are present near the center of the structure. We show that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, are largely a consequence of this motion. We have also detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding near the perimeter of the structure. The observed deformation corresponds to the central uplift and the encircling ring structural depression seen in complex impact craters. Copyright 1999 by the American Geophysical Union.

  13. Granitoid magmatism of Alarmaut granite-metamorphic dome, West Chukotka, NE Russia

    NASA Astrophysics Data System (ADS)

    Luchitskaya, M. V.; Sokolov, S. D.; Bondarenko, G. E.; Katkov, S. M.

    2009-04-01

    Main tectonic elements of West Chukotka are Alazey-Oloy, South-Anyui and Anyui-Chukotka fold systems, formed as a result of collision between structures of North-Asian continent active margin and Chukotka microcontinent [1-3]. South-Anyui fold system, separating Alazey-Oloy and Anyui-Chukotka systems, is considered as suture zon, formed as a result of oceanic basin closing [4-6]. Continent-microcontinent collision resulted in formation of large orogen with of northern and southern vergent structures, complicated by strike-slip deformations [7, 8]. Within Anyui-Chukotka fold system several rises, where most ancient deposits (crystalline basement and Paleozoic cover of Chukotka microcontinent) are exposed, were distinguished [2, 9-11]. Later they were considered as granite-metamorphic domes [12-14]. Alarmaut dome is located at West Chukotka to the north from Bilibino city and is traced from south to north in more than 120 km. General direction of structure is discordant to prevailing NW extensions of tectonic elements of the region. Paleozoic-Triassic deposits are exposed within the Alarmaut dome: 1) D3-C1 - crystalline schists, quartz-feldspar metasandstones, quartzites, marbles (700 m) [11]; 2) C1 - marblized limestones, quartz-feldspar metasandstones, quartzites, amphibole-pyroxene crystalline schists. Limestones contain corals, indicating Visean age of deposits [11]. Metamorphism reaches amphibolite facies, maximum P-T conditions are 660°С and 5 kbar. Migmatites, indicating in situ partial melting, are observed. Intensity of deformations of Paleozoic rocks increases at the boundary with Triassic deposits [11]; in the western part of dome slices of Pz rocks are separated by blastomylonite horizons [14]. Within Alramaut dome granitoids of Lupveem batholith (central part of dome), Bystrinsky pluton (southeastern part), and small Koyvel' and Kelil'vun plutons were studied. New U-Pb SHRIMP zircon data indicate Early Cretaceous (117-112 m.a.) age of granitoids [15

  14. Cooling History in Mabja Dome, Southern Tibet: Implications for the Tectonic Evolution of the North Himalayan Gneiss Domes

    NASA Astrophysics Data System (ADS)

    Lee, J.; Wang, Y.; McWilliams, M.; Hourigan, J.; Blythe, A.; McClelland, W.

    2001-12-01

    The Mabja Dome (MD), southern Tibet, is one of a series of gneiss domes, called the North Himalayan Gneiss Domes, located south of the Indus-Tsangpo suture zone and north of the high Himalaya. The MD consists of an ~25 km diameter doubly plunging antiform cored by migmatitic K-feldspar augen biotite orthogneiss which is mantled by high grade metapelites and granitic orthogneisses. These rocks record two primary deformational events: an older deformational event, D1, characterized by ~EW-trending folds of S0 with an associated moderately N-dipping axial planar foliation, S1, and a younger event, D2, characterized by a domed mylonitic foliation, S2, and associated NS-trending mineral stretching lineation. Peak metamorphism is pre- to early syntectonic with D2 structures and defines a set of isograds that are subparallel to structure. Two-mica granites, one of which yielded an U/Pb monazite age of 14.5+/-0.1 Ma, were emplaced during the latest stages of D2 deformation. Mica and kspar Ar/Ar and apatite fission track (AFT) analyses were completed on orthogneisses, metasediments, and two-mica granites to shed light on the timing and mechanism of cooling of these rocks. Muscovite yielded Ar/Ar cooling ages of ~12.7 Ma on the northern flank of the dome, increasing to ~17.0 Ma in metapelite and orthogneiss at deeper structural levels, and decreasing to ~13.5 Ma within migmatite at the deepest structural levels. Biotites are disturbed and yield total gas ages that are slightly younger than muscovite on the flanks of the dome, but older within the core. Analyses of four kspars from orthogneiss and migmatite yielded complex spectra with old apparent ages at the lowest temperature steps, followed by ages that climb slowly from 12.5-13.0 Ma over the first 30% of 39Ar released, which in turn is followed by ages that climb to 100 Ma (orthogneiss) and 15-18 Ma (migmatite) at high temperature steps. AFT analyses from orthogneiss and migmatite yielded a mean age of 9.5 Ma indicating

  15. Debris avalanches and slumps on the margins of volcanic domes on Venus: Characteristics of deposits

    NASA Technical Reports Server (NTRS)

    Bulmer, M. H.; Guest, J. E.; Beretan, K.; Michaels, Gregory A.; Saunders, R. Stephen

    1992-01-01

    Modified volcanic domes, referred to as collapsed margin domes, have diameters greater than those of terrestrial domes and were therefore thought to have no suitable terrestrial analogue. Comparison of the collapsed debris using the Magellan SAR images with volcanic debris avalanches on Earth has revealed morphological similarities. Some volcanic features identified on the seafloor from sonar images have diameters similar to those on Venus and also display scalloped margins, indicating modification by collapse. Examination of the SAR images of collapsed dome features reveals a number of distinct morphologies to the collapsed masses. Ten examples of collapsed margin domes displaying a range of differing morphologies and collapsed masses have been selected and examined.

  16. RADIOGRAPHIC ABNORMALITIES OF THE TALUS IN PATIENTS WITH CLUBFOOT AFTER SURGICAL RELEASE USING THE MCKAY TECHNIQUE

    PubMed Central

    Pinto, José Antonio; Hernandes, Andréa Canizares; Buchaim, Thais Paula; Blumetti, Francesco Camara; Chertman, Carla; Yamane, Patrícia Corey; da Rocha Corrêa Fernandes, Artur

    2015-01-01

    Objective: To analyze morphological abnormalities of the talus in patients with clubfoot after surgical treatment using the McKay technique. Method: Lateral standing-position radiographs of the feet of 14 patients with unilateral clubfoot who underwent treatment by means of the doubleincision McKay technique were retrospectively analyzed. All the patients were operated by the same surgeon, with an average of 6.53 years between surgery and the radiograph. We compared the radiographic characteristics of the talus between the operated and the contralateral foot. We assessed the presence of deformity of the talar dome and head (sphericity evaluation); the talar length and height; the percentage and degree of navicular subluxation; abnormalities of the Gissane angle; and the trabecular bone pattern. Results: Abnormalities of the talar head occurred in 92.8% of the patients; of the talar dome in 92.8%; and of the trabecular pattern in 100%. The talar length ratio between the operated and the contralateral foot ranged from 0.61 to 0.88 (mean 0.79; SD = 0.09), while the height ratio ranged from 0.57 to 0.98 (mean 0.82; SD = 0.12). The Gissane angle was greater in all of the operated feet, and all of them also showed navicular subluxation, at a rate ranging from 6.43 to 59.75% (mean 26.34%; SD = 16.66%). Conclusion: Talar abnormalities occurred in 100% of the feet treated using the McKay technique. It was shown that establishing radiographic parameters to describe and quantify these deformities was feasible, through simple and easy-to-perform techniques. PMID:27047821

  17. Site testing for submillimetre astronomy at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Minier, V.; Schneider, N.; Durand, G. Al.; Ashley, M. C. B.; Lawrence, J. S.; Luong-van, D. M.; Storey, J. W. V.; Durand, G. An.; Reinert, Y.; Veyssiere, C.; Walter, C.; Ade, P.; Calisse, P. G.; Challita, Z.; Fossat, E.; Sabbatini, L.; Pellegrini, A.; Ricaud, P.; Urban, J.

    2011-11-01

    Aims: Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. We also present some solutions to the challenges of operating in the harsh polar environment. Methods: The 200-μm atmospheric opacity was measured with a tipper. The forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval) was used to calculate the atmospheric transmission and to evaluate the precipitable water vapour content (PWV) from the observed sky opacity. These results have been compared with satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A, with balloon humidity sondes and with results obtained by a ground-based microwave radiometer (HAMSTRAD). In addition, a series of experiments has been designed to study frost formation on surfaces, and the temporal and spatial evolution of thermal gradients in the low atmosphere. Results: Dome C offers exceptional conditions in terms of absolute atmospheric transmission and stability for submillimetre astronomy. Over the austral winter the PWV exhibits long periods during which it is stable and at a very low level (0.1 to 0.3 mm). Higher values (0.2 to 0.8 mm) of PWV are observed during the short summer period. Based on observations over three years, a transmission of around 50% at 350 μm is achieved for 75% of the time. The 200-μm window opens with a typical transmission of 10% to 15% for 25% of the time. Conclusions: Dome C is one of the best accessible sites on Earth for submillimetre astronomy. Observations at 350 or 450 μm are possible all year round, and the 200-μm window opens long enough and with a

  18. Timescales of texture development in a cooling lava dome

    NASA Astrophysics Data System (ADS)

    von Aulock, F. W.; Nichols, A. R. L.; Kennedy, B. M.; Oze, C.

    2013-08-01

    Crystal growth and crack development in cooling lava domes are both capable of redistributing and mobilizing water. Cracking and hydration decrease the stability of a dome, which may lead to hazards including partial dome collapse and block and ash flows. By examining the distribution of water around crystals and cracks, we identify and confine temperature and timescales of texture development in glassy rocks of volcanic domes. Four generations of textures have been identified: type a: spherulites, type b: cracks associated with spherulite growth, type c: perlitic cracks, and type d: disparate cracks. High-resolution imaging using Fourier Transform Infrared Spectroscopy (FTIR) performed on samples from the Ngongotaha dome, New Zealand, show an increase in H2O of up to 450% along gradients of around 100 μm up to 300 μm in length from perlitic cracks, spherulitic cracks and in haloes around spherulites. No gradients in water concentrations across the disparate cracks are present. Water diffusion models show potential timescale-temperature couples that coincide with textural observations and previous studies, and allow us to develop a conceptual model of spherulite growth and cracking in a cooling lava dome. Spherulite growth starts around the glass transition temperature (Tg) when the viscous melt cools to a brittle solid and proceeds with cracking related to volume changes at slightly lower temperatures and shorter timescales (days to weeks) compared to spherulite growth. Perlitic cracking happens at T≪Tg, allowing hydration of a permeable network within weeks to months. Low temperature (≲50 °C) cracks could not be hydrated in the time since eruption (≃230 ka). Our data show that textures in cooling glass develop during cooling below Tg within days, producing cracks and crystals that create inhomogeneities in the spatial distribution of water. The lengthscales of water diffusion away from spherulites, spherulite cracks, and perlite cracks suggest that most

  19. Geological evaluation of Gulf Coast salt domes: overall assessment of the Gulf Interior Region

    SciTech Connect

    1981-10-01

    The three major phases in site characterization and selection are regional studies, area studies, and location studies. This report characterizes regional geologic aspects of the Gulf Coast salt dome basins. It includes general information from published sources on the regional geology; the tectonic, domal, and hydrologic stability; and a brief description the salt domes to be investigated. After a screening exercise, eight domes were chosen for further characterization: Keechi, Oakwood, and Palestine Domes in Texas; Vacherie and Rayburn's domes in North Louisiana; and Cypress Creek and Richton domes in Mississippi. A general description of each, maps of the location, property ownership, and surface geology, and a geologic cross section were presented for each dome.

  20. Lateral orientation (image)

    MedlinePlus

    A lateral orientation is a position away from the midline of the body. For instance, the arms are lateral to the ... ears are lateral to the head. A medial orientation is a position toward the midline of the ...

  1. Advanced imaging techniques III: a scalable and modular dome illumination system for scientific microphotography on a budget

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs ...

  2. Characterization of Atmospheric Ekman Spirals at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Rysman, Jean-François; Lahellec, Alain; Vignon, Etienne; Genthon, Christophe; Verrier, Sébastien

    2016-03-01

    We use wind speed and temperature measurements taken along a 45-m meteorological tower located at Dome C, Antarctica (75.06° S, 123.19° E) to highlight and characterize the Ekman spiral. Firstly, temperature records reveal that the atmospheric boundary layer at Dome C is stable during winter and summer nights (i.e., > 85 % of the time). The wind vector, in both speed and direction, also shows a strong dependence with elevation. An Ekman model was then fitted to the measurements. Results show that the wind vector follows the Ekman spiral structure for more than 20 % of the year (2009). Most Ekman spirals have been detected during summer nights, that is, when the boundary layer is slightly stratified. During these episodes, the boundary-layer height ranged from 25 to 100 m, the eddy viscosity from 0.004 to 0.06 m^2 s^{-1} , and the Richardson number from zero to 1.6.

  3. A Fourier transform spectrometer for site testing at Dome A

    NASA Astrophysics Data System (ADS)

    Li, Xin-Xing; Paine, Scott; Yao, Qi-Jun; Shi, Sheng-Cai; Matsuo, Hiroshi; Yang, Ji; Zhang, Qi-Zhou

    2009-07-01

    Observations in tera-hertz astronomy can only be done at a site with good atmospheric transmission at millimeter and submillimeter wavelengths. With extremely dry weather and calm atmosphere resulted by high altitude and cold temperature, Dome A (or Dome Argus), Antarctica, is possibly the best site on this earth for THz astronomy. To evaluate the site condition there, we are constructing a Fourier Transform Spectrometer (FTS) based on Martin-Puplett interferometer to measure the atmospheric transmission in the frequency range of 0.75~15THz. The whole FTS system is designed for unattended and outdoor (temperatures even below -70 degrees Celsius) operation. Its total power consumption is estimated to be approximately 200W. This contribution will give a brief overview of this FTS development.

  4. Nanocomposite optical ceramics for infrared windows and domes

    NASA Astrophysics Data System (ADS)

    Stefanik, Todd; Gentilman, Richard; Hogan, Patrick

    2007-04-01

    Currently available IR transparent materials typically exhibit a trade-off between optical performance and mechanical strength. For instance, sapphire domes are very strong, but lack full transparency throughout the 3-5 micron mid-wave IR band. Yttria is fully transparent from 3-5 microns, but lacks sufficient strength, hardness, and thermal shock resistance for the most demanding aero-thermal applications. Missile system designers must limit system performance in order to accommodate the shortcomings of available window and dome materials. Recent work in the area of nanocomposite ceramics may produce new materials that exhibit both excellent optical transparency and high strength, opening the door to improved missile performance. The requirements for optical nanocomposite ceramics will be presented and recent work in producing such materials will be discussed.

  5. Boscovich as an engineer: the statics of masonry domes

    NASA Astrophysics Data System (ADS)

    Corradi Dell'Acqu, L.

    The collection of writings by Ruggiero Boscovich contains a certain number of studies that can be considered of ``engineering'' character, mostly focusing on problems of hydraulics and structural mechanics. Nevertheless, such studies hardly can be regarded as part of Boscovich's direct interest. They were usually meant at answering specific questions, when Boscovich was acting as a consultant for people that were facing serious problems of different kind and asked his advise, considered as precious because of the prestige that Boscovich enjoyed in his time. In this paper attention is focused on one problem, the statics of masonry domes, which Boscovich faced twice in two different contexts. In these studies he employed, to my knowledge for the first time for computation purposes, a failure mechanism that at the end of the century became the basis for systematic and rigorous methods for the analysis of arches, vaults and domes. Boscovich work can be regarded as anticipating these results.

  6. SCIDAR: an optical turbulence profiler for Dome A

    NASA Astrophysics Data System (ADS)

    Liu, Li-Yong; Yao, Yong-Qiang; Vernin, Jean; Chadid, Merieme; Wang, Hong-Shuai; Wang, Yi-Ping

    2013-01-01

    This paper introduces a plan to detect turbulence profiles at Dome A with a Single Star Scidar (SSS), to enhance our understanding of the characteristics of the site. The development of a portable monitor for profiling vertical atmospheric optical turbulence and wind speed is presented. By analyzing the spatial auto and cross-correlation functions of very short exposure images of single star scintillation patterns, the SSS can provide the vertical profiles of turbulence intensity C 2 n (h) and wind speed V(h). A SSS prototype is already operational at Ali in Tibet which will be improved in order to become fully robotic and adapted to extreme weather conditions that prevail at Dome A in Antarctica.

  7. Linear and nonlinear optical absorption coefficients of spherical dome shells

    NASA Astrophysics Data System (ADS)

    Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi

    2015-08-01

    Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.

  8. Mini-dome Fresnel lens photovoltaic concentrator development

    NASA Technical Reports Server (NTRS)

    Oneill, Mark J.; Piszczor, Michael F., Jr.

    1991-01-01

    Since 1986 work on a new high-performance, light-weight space photovoltaic concentration array has been conducted. An update on the mini-dome lens concentrator array development program is provided. Recent prototype cell and lens test results indicate that near-term array performance goals of 300 w/sq m and 100 w/kg are feasible, and that a longer-term goal of 200 w/kg is reasonable.

  9. Glacier geophysical studies at Taylor Dome: Your three

    SciTech Connect

    Morse, D.L.; Waddington, E.D. )

    1993-01-01

    Taylor Dome is the site of an ongoing ice core/paleoclimate project. The main activities of the 1992-1993 season included surveys by ground-based optical methods, surveys using satellite receivers, radio-echo sounding of bedrock topography, and depositional environment characterization. Monitoring continued of accumulation rate and three cores were sampled to detect the depths of atmospheric nuclear test fallout products. 5 refs., 1 fig.

  10. Analysis of the TMI-2 dome radiation monitor

    SciTech Connect

    Murphy, M B; Mueller, G M; Jernigan, W C

    1985-08-01

    Questions have been raised regarding the accuracy of the in-containment radiation readings from the LOCA qualified, dome radiation monitor, HP-R-214 during the March 28, 1979 accident at the Three Mile Island Unit 2 Reactor. This report discusses the accuracy of the readings, gives the results of examining the radiation monitor itself, and estimates the radiation environment inside containment during the accident.

  11. LDV measurements in lateral model aneurysms of various sizes

    NASA Astrophysics Data System (ADS)

    Liou, T.-M.; Chang, W.-C.; Liao, C.-C.

    Laser Doppler velocimetry (LDV) measurements are presented of three-dimensional flow fields in lateral model aneurysms arising from a straight parent vessel at a 90° angle. The flow considered was pulsatile and the aneurysm wall was rigid. The mean, peak, and minimal Reynolds numbers based on the bulk average velocity and diameter of the parent vessel were 550, 790, and 375, respectively. Comparisons among present in vitro studies, previous in vitro studies, computational simulations, and in vivo studies were made. It was found that the inflow angle into the lateral aneurysm, the maximum wall shear stress acting on the distal lip of the lateral aneurysm, and the intra-aneurysmal vortical motion increased with decreasing aneurysm size. This fact together with the impingement bifurcation of the inflow at the aneurysm dome provide possible hemodynamic factors for the rupture of the lateral aneurysm at small critical size.

  12. Cybersickness Following Repeated Exposure to DOME and HMD Virtual Environments

    NASA Technical Reports Server (NTRS)

    Taylor, Laura C.; Harm, Deborah L.; Kennedy, Robert S.; Reschke, Millard F.; Loftin, R. Bowen

    2011-01-01

    Virtual environments (VE) offer unique training opportunities, including training astronauts to preadapt them to the novel sensory conditions of microgravity. However, one unresolved issue with VE use is the occurrence of cybersickness during and following exposure to VE systems. Most individuals adapt and become less ill with repeated interaction with VEs. The goal of this investigation was to compare motion sickness symptoms (MSS) produced by dome and head-mounted (HMD) displays and to examine the effects of repeated exposures on MSS. Sixty-one subjects participated in the study. Three experimental sessions were performed each separated by one day. The subjects performed a navigation and pick and place task in either a dome or HMD VE. MSS were measured using a Simulator Sickness Questionnaire before, immediately after, and at 1, 2, 4 and 6 hours following exposure to the VEs. MSS data were normalized by calculating the natural log of each score and an analysis of variance was performed. We observed significant main effects for day and time and a significant day by time interaction for total sickness and for each of the subscales, nausea, oculomotor and disorientation. However, there was no significant main effect for device. In conclusion, subjects reported a large increase in MSS immediately following exposure to both the HMD and dome, followed by a rapid recovery across time. Sickness severity also decreased over days, which suggests that subjects become dual-adapted over time making VE training a viable pre-flight countermeasure for space motion sickness.

  13. Upgrading, monitoring and operation of a dome drive system

    NASA Astrophysics Data System (ADS)

    Bauman, Steven E.; Cruise, Bill; Look, Ivan; Matsushige, Grant; Roberts, Larry; Salmon, Derrick; Taroma, Ralph; Vermeulen, Tom; Richards, Krieg

    2014-08-01

    CFHT's decision to move away from classical observing prompted the development of a remote observing environment aimed at producing science observations from headquarters facility in Waimea, HI. This remote observing project commonly referred to as the Observatory Automation Project (OAP ) was completed at the end of January 2011 and has been providing the majority of science data ever since. A comprehensive feasibility study was conducted to determine the options available to achieve remote operations of the observatory dome drive system. After evaluation, the best option was to upgrade the original hydraulic system to utilize variable frequency drive (VFD) technology. The project upgraded the hydraulic drive system, which initially utilized a hydraulic power unit and three (3) identical drive units to rotate the dome. The new electric drive system replaced the hydraulic power unit with electric motor controllers, and each drive unit reuses the original drive and swaps one for one the original hydraulic motors with an electric motor. The motor controllers provide status and monitoring parameters for each drive unit which convey the functionality and health of the system. This paper will discuss the design upgrades to the dome drive rotation system, as well as some benefits, control, energy savings, and monitoring.

  14. Winter sky brightness and cloud cover at Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Moore, Anna M.; Yang, Yi; Fu, Jianning; Ashley, Michael C. B.; Cui, Xiangqun; Feng, Long Long; Gong, Xuefei; Hu, Zhongwen; Lawrence, Jon S.; Luong-Van, Daniel M.; Riddle, Reed; Shang, Zhaohui; Sims, Geoff; Storey, John W. V.; Tothill, Nicholas F. H.; Travouillon, Tony; Wang, Lifan; Yang, Huigen; Yang, Ji; Zhou, Xu; Zhu, Zhenxi

    2013-01-01

    At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction.

  15. Lunar Gruithuisen and Mairan domes: Rheology and mode of emplacement

    NASA Astrophysics Data System (ADS)

    Wilson, Lionel; Head, James W.

    2003-02-01

    The lunar steep-sided Gruithuisen and Mairan domes are morphologically and spectrally distinctive structures and appear similar to terrestrial extrusive volcanic features characterized by viscous magma. We use the basic morphologic and morphometric characteristics of the domes to estimate the yield strengths (~105 Pa), plastic viscosities (~109 Pa s), and effusion rates (~50 m3/s) of the magmas which formed them. These values are similar to those of terrestrial rhyolites, dacites, and basaltic andesites and support the hypothesis that these domes are an unusual variation of typical highlands and mare compositions. The dikes which formed them are predicted to have had widths of ~50 m and lengths of about 15 km. The magma rise speed implied by this geometry is very low, ~7 × 10-5 m/s, and the Reynolds number of the motion is ~2 × 10-8, implying a completely laminar flow regime. Estimates of emplacement duration range from one to several decades. These new calculations confirm the unusual nature of these features and support previous qualitative suggestions that they were formed from magmas with significantly higher viscosity than those typical of mare basalts.

  16. Radially fractured domes: A comparison of Venus and the Earth

    NASA Technical Reports Server (NTRS)

    Janes, Daniel M.; Squyres, Steven W.

    1993-01-01

    Radially fractured domes are large, tectonic and topographic features discovered on the surface of Venus by the Magellan spacecraft. They are thought to be due to uplift over mantle diapirism, and to date are known to occur only on Venus. Since Venus and the Earth are grossly similar in size, composition and structure, we seek to understand why these features have not been seen on the Earth. We model the uplift and fracturing over a mantle diapir as functions of lithospheric thickness and diapir size and depth. We find that lithospheres of the same thickness on the Earth and Venus should respond similarly to the same sized diapir, and that radially fractured domes should form most readily in thin oceanic lithospheres on Earth if diapiric activity is similar on the two planets. However, our current knowledge of the Earth's oceanic floors is insufficient to confirm or deny the presence of radially fractured domes. We compute the expected dimensions for these features on the Earth and suggest a search for them to determine whether mantle diapirism operates similarly on the Earth and Venus.

  17. Ice crystal precipitation at Dome C site (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Santachiara, G.; Belosi, F.; Prodi, F.

    2016-01-01

    For the first time, falling ice crystals were collected on glass slides covered with a thin layer of 2% formvar in chloroform at the Dome Concordia site (Dome C), Antarctica. Samplings were performed in the framework of the 27th Italian Antarctica expedition of the Italian National Program for Research in Antarctica in the period 21 February-6 August 2012. Events of clear-sky precipitations and precipitations from clouds were considered and the replicas obtained were examined under Scanning Electron Microscope (SEM). Several shapes of ice crystals were identified, including "diamond dust" (plates, pyramids, hollow and solid columns), and crystal aggregates varying in complexity. Single events often contained both small (10 μm to 50 μm) and large (hundreds of microns) crystals, suggesting that crystals can form simultaneously near the ground (height of a few hundred metres) and at higher layers (height of thousands of metres). Images of sampled crystal replicas showed that single bullets are not produced separately, but by the disintegration of combinations of bullets. Rimed ice crystals were absent in the Dome C samples, i.e. the only mode of crystal growth was water vapour diffusion. On considering the aerosol in the sampled crystals, we reached the conclusion that inertial impaction, interception and Brownian motion were insufficient to explain the scavenged aerosol. We therefore presume that phoretic forces play a role in scavenging during the crystal growth process.

  18. Cristobalite in a rhyolitic lava dome: evolution of ash hazard

    NASA Astrophysics Data System (ADS)

    Horwell, Claire J.; Le Blond, Jennifer S.; Michnowicz, Sabina A. K.; Cressey, Gordon

    2010-03-01

    Prolonged and heavy exposure to particles of respirable, crystalline silica-rich volcanic ash could potentially cause chronic, fibrotic disease, such as silicosis, in individuals living in areas of frequent ash fall. Here, we show that the rhyolitic ash erupted from Chaitén volcano, Chile, in its dome-forming phase, contains increased levels of the silica polymorph cristobalite, compared to its initial plinian eruption. Ash erupted during the initial, explosive phase (2-5 May 2008) contained approximately 2 wt.% cristobalite, whereas ash generated after dome growth began (from 21 May 2008) contains 13-19 wt.%. The work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time-scales of days to months, probably through vapour-phase crystallisation on the walls of degassing pathways, rather than through spherulitic growth in glassy obsidian. The ash is fine-grained (9.7-17.7 vol.% <4 µm in diameter, the respirable range) and the particles are mostly angular. Sparse, fibre-like particles were confirmed to be feldspar or glass.

  19. Small domes on Venus: probable analogs of Icelandic lava shields

    USGS Publications Warehouse

    Garvin, James B.; Williams, Richard S., Jr.

    1990-01-01

    On the basis of observed shapes and volumetric estimates, we interpret small, dome-like features on radar images of Venus to be analogs of Icelandic lava-shield volcanoes. Using morphometric data for venusian domes in Aubele and Slyuta (in press), as well as our own measurements of representative dome volumes and areas from Tethus Regio, we demonstrate that the characteristic aspect ratios and flank slopes of these features are consistent with a subclass of low Icelandic lava-shield volcanoes (LILS ). LILS are slightly convex in cross-section with typical flank slopes of ∼3°. Plausible lava-shield-production rates for the venusian plains suggest formation of ∼53 million shields over the past 0.25 Ga. The cumulative global volume of lava that would be associated with this predicted number of lava shields is only a factor of 3–4 times that of a single oceanic composite shield volcano such as Mauna Loa. The global volume of all venusian lava shields in the 0.5–20-km size range would only contribute a meter of resurfacing over geologically significant time scales. Thus, venusian analogs to LILS may represent the most abundant landform on the globally dominant plains of Venus, but would be insignificant with regard to the global volume of lava extruded. As in Iceland, associated lavas from fissure eruptions probably dominate plains volcanism and should be evident on the higher resolution Magellan radar images.

  20. Radar scattering properties of steep-sided domes on Venus

    NASA Technical Reports Server (NTRS)

    Ford, Peter G.

    1994-01-01

    More than 100 quasi-circular steep-sided volcanic domes, with diameters ranging from 6 to 60 km, have been observed on the surface of Venus by the Magellan radar mapper. Assuming that they have the shape of a solidified high-viscosity Newtonian fluid, their radar scattering properties can be studied in detail from Magellan images, since a typical radar swath resolves each dome into several tens of thousands of measurements of radar cross section at incidence angles varying fom 15 deg to 55 deg. Through examination of 20 domes in detail, it appears that many of those situated on lava plains scatter radar in a manner that is indistinguishable from that of the surrounding material, suggesting that either (1) they were formed of a relatively high-density high-viscosity material, e.g., andesite, rather than a lower-density one, e.g., rhyolite or dacite; or (2) that their surfaces share a common origin with those of their surroundings, e.g., through in situ weathering or aeolian deposition.

  1. The dome-shaped Fresnel-Köhler concentrator

    NASA Astrophysics Data System (ADS)

    Zamora, P.; Benitez, P.; Li, Y.; Miñano, J. C.; Mendes-Lopes, J.; Araki, K.

    2012-10-01

    Manufacturing tolerances, along with a high concentration ratio, are key issues in order to obtain cheap CPV systems for mass production. Consequently, this manuscript presents a novel tolerant and cost effective concentrator optic: the domed-shaped Fresnel-Köhler, presenting a curved Fresnel lens as Primary Optical Element (POE). This concentrator is based on two previous successful CPV designs: the FK concentrator, based on a flat Fresnel lens, and the dome-shaped Fresnel lens system developed by Daido Steel, resulting on a superior concentrator. The manuscript shows outstanding simulation results for geometrical concentration factor of Cg = 1,230x: high tolerance and high optical efficiency, achieving acceptance angles of 1.18° (dealing to a CAP*=0.72) and efficiencies over 85% (without any anti-reflective coating). Moreover, Köhler integration provides good irradiance uniformity on the cell surface without increasing system complexity by means of any extra element. Daido Steel advanced technique for demolding injected plastic pieces will allow for easy manufacture of the dome-shaped POE of DFK concentrator.

  2. An Operationally Based Vision Assessment Simulator for Domes

    NASA Technical Reports Server (NTRS)

    Archdeacon, John; Gaska, James; Timoner, Samson

    2012-01-01

    The Operational Based Vision Assessment (OBVA) simulator was designed and built by NASA and the United States Air Force (USAF) to provide the Air Force School of Aerospace Medicine (USAFSAM) with a scientific testing laboratory to study human vision and testing standards in an operationally relevant environment. This paper describes the general design objectives and implementation characteristics of the simulator visual system being created to meet these requirements. A key design objective for the OBVA research simulator is to develop a real-time computer image generator (IG) and display subsystem that can display and update at 120 frame s per second (design target), or at a minimum, 60 frames per second, with minimal transport delay using commercial off-the-shelf (COTS) technology. There are three key parts of the OBVA simulator that are described in this paper: i) the real-time computer image generator, ii) the various COTS technology used to construct the simulator, and iii) the spherical dome display and real-time distortion correction subsystem. We describe the various issues, possible COTS solutions, and remaining problem areas identified by NASA and the USAF while designing and building the simulator for future vision research. We also describe the critically important relationship of the physical display components including distortion correction for the dome consistent with an objective of minimizing latency in the system. The performance of the automatic calibration system used in the dome is also described. Various recommendations for possible future implementations shall also be discussed.

  3. Charged nano-domes and bubbles in epitaxial graphene.

    PubMed

    Trabelsi, A Ben Gouider; Kusmartsev, F V; Robinson, B J; Ouerghi, A; Kusmartseva, O E; Kolosov, O V; Mazzocco, R; Gaifullin, Marat B; Oueslati, M

    2014-04-25

    For the first time, new epitaxial graphene nano-structures resembling charged 'bubbles' and 'domes' are reported. A strong influence, arising from the change in morphology, on the graphene layer's electronic, mechanical and optical properties has been shown. The morphological properties of these structures have been studied with atomic force microscopy (AFM), ultrasonic force microscopy (UFM) and Raman spectroscopy. After initial optical microscopy observation of the graphene, a detailed description of the surface morphology, via AFM and nanomechanical UFM measurements, was obtained. Here, graphene nano-structures, domes and bubbles, ranging from a few tens of nanometres (150–200 nm) to a few μm in size have been identified. The AFM topographical and UFM stiffness data implied the freestanding nature of the graphene layer within the domes and bubbles, with heights on the order of 5–12 nm. Raman spectroscopy mappings of G and 2D bands and their ratio confirm not only the graphene composition of these structures but also the existence of step bunching, defect variations and the carrier density distribution. In particular, inside the bubbles and substrate there arises complex charge redistribution; in fact, the graphene bubble–substrate interface forms a charged capacitance. We have determined the strength of the electric field inside the bubble–substrate interface, which may lead to a minigap of the order of 5 meV opening for epitaxial graphene grown on 4H-SiC face-terminated carbon. PMID:24675237

  4. A Finite-Element Ice Flow Model for the Vicinity of Dome Fuji With Induced Anisotropy and Fabric Evolution

    NASA Astrophysics Data System (ADS)

    Seddik, H.; Greve, R.; Placidi, L.; Zwinger, T.; Gagliardini, O.

    2007-12-01

    A three-dimensional, thermo-mechanically coupled flow model with induced anisotropy has been developed and applied to the vicinity of Dome Fuji, Antarctica. The model implements the full Stokes equations for the ice dynamics, and the system is solved with the finite-element method (FEM) using the open source multi-physics package Elmer (http://www.csc.fi/elmer/). The finite-element mesh for the computational domain has been created with two data sets, the fine resolution data obtained at Dome Fuji and the coarse resolution data sets RAMPDEM V2 and BEDMAP which cover the entire Antarctic ice sheet. The fine data which represent a 60 x 60 km area around the Dome Fuji station have been merged to the coarse data sets to create a single domain of about 200 x 200 km size. The mesh consists of a coarse resolution near the boundaries (20 km) and a mesh resolution refinement (up to 500 m) towards the position of the borehole located at the center of the domain. This procedure has been carried out in order to keep the lateral boundaries sufficiently far away from the dome, so that shallow- ice stresses can be prescribed there. At the base, no-slip conditions are assumed, and on the surface, the temperature is prescribed to be constant everywhere on the domain. A Continuum-mechanical, Anisotropic Flow model, based on an anisotropic Flow Enhancement factor (CAFFE model) is used for taking into account the flow-induced anisotropy in ice. The flow law is implemented in Elmer by means of second and fourth order orientation tensors that describe the c-axis orientation of the fabric. Similarly, the fabric evolution equation is written in terms of the evolution of the second order tensor, and it is solved with a Discontinuous Galerkin method using Picard type iterations for the non-linearity. Since the fabric evolution equation also depends on the fourth order orientation tensor, the IBOF (Invariant-Based Optimal Fitting) closure function is used for the computation of its

  5. Lunar Mare Dome Identification and Morphologic Properties Analysis Using Chang'E-2 Lunar Data

    NASA Astrophysics Data System (ADS)

    Zeng, Xingguo; Mu, Lingli; Li, Chunlai; Liu, Jianjun; Ren, Xin; Wang, Yuanyuan

    2016-04-01

    Identify the lunar mare dome and study the morphologic properties to know more knowledge about the structure will enhance the study of lunar volcanism. Traditionally, most lunar domes are identified by the scientists from exploring the images or topographic maps of the lunar surface with manual method, which already found out a bunch of lunar domes in specific local areas. For the purpose of getting more knowledge about global lunar dome, it is necessary to identify the lunar dome from the global lunar mare. However, it is hard to find new lunar domes from the global lunar mare only with manual method, since in that case, the large volume lunar data is needed and such work is too time consumed, so that, there are few researchers who have indentified and study the properties of the lunar dome from the perspective of lunar global scale. To solve the problem mentioned above, in this approach , CE-2 DEM, DOM data in 7m resolution were used in the detection and morphologic analysis of the lunar domes and a dome detection method based on topographic characteristics were developed.We firstly designed a method considering the morphologic characteristics to identify the lunar dome with Chang'E2(CE-2) lunar global data, after that, the initial identified result with properties is analyzed, and finally, by integrating the result with lunar domes already found by former researchers, we made some maps about the spatial distribution of the global lunar mare dome. With the CE-2 data covering the former lunar domes and the new found lunar domes, we surveyed and calculated some morphologic properties, and found that, lunar domes are circular or eclipse shaped, obviously different from background in topography,which has a average diameter between 3-25km, circular degree less than 1.54, with a average slope less than 10°, average height less than 650m and diameter/height less than 0.065. Almost all of the lunar domes are located in the extent of 58°N~54°S,167°W~180°E,and nearly

  6. Dome design and coupled thermal-mechanical analysis of supersonic missile

    NASA Astrophysics Data System (ADS)

    Ai, Xing-qiao; Wei, Qun; Jia, Hong-guang

    2009-11-01

    A review of high-speed flow pressure and aerodynamic heating effect on Supersonic missile's dome is given. The dome should have excellent properties in optical, mechanical and chemical characteristics. A design of dome on supersonic mode is described according to tactical guide line of a missile. The dome made of quartz which is about 8mm thick and 141mm in window diameter. To check up the reliability of the dome, a reasonable finite element model (FEM) of dome is established, and a thermal-mechanical Analysis to the dome by finite element software NASTRAN has carried on, through these can obtained the distribution of temperature field and stress field when the speed is 2.3Ma. The results indicated that the stress was concentrated in the joint of the dome end and the Missile Section, and the maximum stress was 16.4Mpa. The stress of other nodes was smaller than the allowable stress of quartz glass. Reference to the results of the analysis, a lightweight revision to the dome structural dimension and a new method of dome fixing have put forward, which can reduce the stress concentration.

  7. Design and Development of a Composite Dome for Experimental Characterization of Material Permeability

    NASA Technical Reports Server (NTRS)

    Estrada, Hector; Smeltzer, Stanley S., III

    1999-01-01

    This paper presents the design and development of a carbon fiber reinforced plastic dome, including a description of the dome fabrication, method for sealing penetrations in the dome, and a summary of the planned test series. This dome will be used for the experimental permeability characterization and leakage validation of composite vessels pressurized using liquid hydrogen and liquid nitrogen at the Cryostat Test Facility at the NASA Marshall Space Flight Center (MSFC). The preliminary design of the dome was completed using membrane shell analysis. Due to the configuration of the test setup, the dome will experience some flexural stresses and stress concentrations in addition to membrane stresses. Also, a potential buckling condition exists for the dome due to external pressure during the leak testing of the cryostat facility lines. Thus, a finite element analysis was conducted to assess the overall strength and stability of the dome for each required test condition. Based on these results, additional plies of composite reinforcement material were applied to local regions on the dome to alleviate stress concentrations and limit deflections. The dome design includes a circular opening in the center for the installation of a polar boss, which introduces a geometric discontinuity that causes high stresses in the region near the hole. To attenuate these high stresses, a reinforcement system was designed using analytical and finite element analyses. The development of a low leakage polar boss system is also investigated.

  8. Effective pine bark composting with the Dome Aeration Technology

    SciTech Connect

    Trois, Cristina . E-mail: troisc@ukzn.ac.za; Polster, Andreas

    2007-07-01

    In South Africa garden refuse is primarily disposed of in domestic landfills. Due to the large quantities generated, any form of treatment would be beneficial for volume reduction, waste stabilization and resource recovery. Dome Aeration Technology (DAT) is an advanced process for aerobic biological degradation of garden refuse and general waste [Paar, S., Brummack, J., Gemende, B., 1999a. Advantages of dome aeration in mechanical-biological waste treatment. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Cagliari, 4-8 October 1999; Paar, S., Brummack, J., Gemende, B., 1999b. Mechanical-biological waste stabilization by the dome aeration method. Environment Protection Engineering 25 (3/99). Mollekopf, N., Brummack, J., Paar, S., Vorster, K., 2002. Use of the Dome Aeration Technology for biochemical stabilization of waste prior to landfilling. In: Proceedings of the Wastecon 2002, Waste Congress and Exhibition, Durban, South Africa.]. It is a non-reactor open windrow composting process, with the main advantage being that the input material needs no periodic turning. A rotting time of only 3-4 months indicates the high efficiency. Additionally, the low capital/operational costs, low energy inputs and limited plant requirements provide potential for use in aerobic refuse stabilization. The innovation in the DAT process is the passive aeration achieved by thermally driven advection through open windrows caused by temperature differences between the degrading material and the outside environment. This paper investigates the application of Dome Aeration Technology to pine bark composting as part of an integrated waste management strategy. A full-scale field experiment was performed at the Bisasar Road Landfill Site in Durban to assess the influence of climate, waste composition and operational conditions on the process. A test windrow was constructed and measurements of temperature and airflow through the material were taken. The process

  9. Integrated field and numerical modeling investigation of crustal flow mechanisms and trajectories in migmatite domes

    NASA Astrophysics Data System (ADS)

    Whitney, Donna; Teyssier, Christian; Rey, Patrice

    2016-04-01

    Integrated field-based and modeling studies provide information about the driving mechanisms and internal dynamics of migmatite domes, which are important structures for understanding the rheology of the lithosphere in orogens. Dome-forming processes range from extension (isostasy) driven flow to density (buoyancy) driven systems. Vertical flow (up or down) is on the scale of tens of km. End-member buoyancy-driven domes are typically Archean (e.g., Pilbara, Australia). Extension-driven systems include the migmatite domes in metamorphic core complexes of the northern North American Cordillera, as well as some domes in Variscan core complexes. The Entia dome of central Australia is a possible hybrid dome in which extension and density inversion were both involved in dome formation. The Entia is a "double dome", comprised of a steep high-strain zone bordered by high melt-fraction migmatite (subdomes). Field and numerical modeling studies show that these are characteristics of extension-driven domes, which form when flowing deep crust ascends beneath normal faults in the upper crust. Entia dome migmatite shows abundant evidence for extension, in addition to sequences of cascading, cuspate folds (well displayed in amphibolite) that are not present in the carapace of the dome, that do not have a consistent axial planar fabric, and that developed primarily at subsolidus conditions. We propose that these folds developed in mafic layers that had a density contrast with granodioritic migmatite, and that they formed during sinking of a denser layer above the rising migmatite subdomes. Extension-driven flow of partially molten (granodioritic) crust was therefore accompanied by sinking of a dense, mafic, mid-crustal layer, resulting in complex P-T-d paths of different lithologic units within the dome. This scenario is consistent with field and 2D modeling results, which together show how a combination of structural geology, metamorphic petrology, and modeling can illuminate the

  10. Fry spacing of deformed and undeformed modeled and natural salt domes

    SciTech Connect

    Roennlund, P.; Koyi, H.

    1988-05-01

    Fry's center-point spacing strain analysis is applied to experiments of gravity-driven overturn of horizontal fluid layers on scales of centimeters or decimeters, and to natural salt diapirs on scales of kilometers to tens of kilometers. Laboratory experiments in which about 100 diapirs formed from initially plane horizontal layers resulted in laterally isotropic spacing and yielded an open circle on a Fry plot with a radius equal to the wavelength (W). Lateral deformation and initial departures from horizontal layers with uniform properties may influence W. Sample experiments of diapirism with and without lateral deformation are compared to natural equivalents. The spacing of post-Late Triassic diapirs in the Zechstein salt of Germany and of post-Jurassic diapirs in the Hormuz salt of Arabia yields circles on Fry plots which indicate that these gravity structures developed without additional lateral forces. Fry plots of the spacing of salt diapirs in the Zagros Mountains define a strain ellipse with the long axis (=W in Arabia) parallel and the short axis perpendicular to post-Miocene regional fold axes. The ratio of the Zagros strain ellipse is about 1.7, which suggests a northeast-southwest shortening of 41%, rather than 10%-21% as estimated from folding alone. This mismatch may be a result of unquantified shortening due to thrusts and/or layer-parallel shortening. Center-point spacing of post-Late Triassic domes of Zechstein salt in the central North Sea also gives an ellipse. Here, the long axis coincides with the direction of Middle Jurassic to Cretaceous extension. The axial ratio of the North Sea strain ellipse is about 2.8, compared to estimates of about 1.5-2.0 by Sclater and Christie, and 1.8 by Wood and Barton.

  11. Structural analysis of the collar of the Vredefort Dome, South Africa—Significance for impact-related deformation and central uplift formation

    NASA Astrophysics Data System (ADS)

    Wieland, Frank; Gibson, Roger L.; Reimold, Wolf Uwe

    2005-10-01

    Landsat TM, aerial photograph image analysis, and field mapping of Witwatersrand supergroup meta-sedimentary strata in the collar of the Vredefort Dome reveals a highly heterogeneous internal structure involving folds, faults, fractures, and melt breccias that are interpreted as the product of shock deformation and central uplift formation during the 2.02 Ga Vredefort impact event. Broadly radially oriented symmetric and asymmetric folds with wavelengths ranging from tens of meters to kilometers and conjugate radial to oblique faults with strike-slip displacements of, typically, tens to hundreds of meters accommodated tangential shortening of the collar of the dome that decreased from ˜17% at a radius from the dome center of 21 km to <5% at a radius of 29 km. Ubiquitous shear fractures containing pseudotachylitic breccia, particularly in the metapelitic units, display local slip senses consistent with either tangential shortening or tangential extension; however, it is uncertain whether they formed at the same time as the larger faults or earlier, during the shock pulse. In addition to shatter cones, quartzite units show two fracture types—a cmspaced rhomboidal to orthogonal type that may be the product of shock-induced deformation and later joints accomplishing tangential and radial extension. The occurrence of pseudotachylitic breccia within some of these later joints, and the presence of radial and tangential dikes of impact melt rock, confirm the impact timing of these features and are suggestive of late-stage collapse of the central uplift.

  12. DomeHaz, a Global Hazards Database: Understanding Cyclic Dome-forming Eruptions, Contributions to Hazard Assessments, and Potential for Future Use and Integration with Existing Cyberinfrastructure

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Calder, E.; Loughlin, S.

    2013-12-01

    Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly all dome-forming eruptions have been associated with some level of explosive activity. Large Plinian explosions with a VEI ≥ 4 sometimes occur in association with dome-forming eruptions. Many of the most significant volcanic events of recent history are in this category. The 1902-1905 eruption of Mt. Pelée, Martinique; the 1980-1986 eruption of Mount St. Helens, USA; and the 1991 eruption of Mt. Pinatubo, Philippines all demonstrate the destructive power of VEI ≥ 4 dome-forming eruptions. Global historical analysis is a powerful tool for decision-making as well as for scientific discovery. In the absence of monitoring data or a knowledge of a volcano's eruptive history, global analysis can provide a method of understanding what might be expected based on similar eruptions. This study investigates the relationship between large explosive eruptions and lava dome growth and develops DomeHaz, a global database of dome-forming eruptions from 1000 AD to present. It is currently hosted on VHub (https://vhub.org/groups/domedatabase/), a community cyberinfrastructure for sharing data, collaborating, and modeling. DomeHaz contains information about 367 dome-forming episodes, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude of associated explosions. Data sources include the The Smithsonian Institution Global Volcanism Program (GVP), Bulletin of the Global Volcanism Network, and all relevant published review papers, research papers, and reports. This database builds upon previous work (e.g Newhall and Melson, 1983) in light of newly available data for lava dome eruptions. There have been 46 new dome-forming eruptions, 13 eruptions that continued past 1982, 151 new dome-growth episodes, and 8 VEI ≥ 4 events since Newhall and Melson's work in 1983. Analysis using DomeHaz provides useful information regarding the

  13. Geologic technical assessment of the Stratton Ridge salt dome, Texas, for potential expansion of the U.S. strategic petroleum reserve.

    SciTech Connect

    Rautman, Christopher Arthur; Snider, Anna C.; Looff, Karl M.

    2006-11-01

    difficult to come by, widely accepted industry rumors are that numerous existing caverns have experienced major operational problems, including salt falls, sheared casings, and unintended releases of stored product(s). Many of these difficulties may be related to on-going differential movement of individual salt spines or to lateral movement at the caprock-salt interface. The history of operational problems, only some of which appear to be a matter of public record, combined with the potential for encountering escaped product from other operations, renders the Stratton Ridge salt dome a less-than-desirable site for SPR purposes.

  14. Optimized design of the inside surface of supersonic missile's elliptical dome

    NASA Astrophysics Data System (ADS)

    Wei, Qun; Bai, Yang; Liu, Hui; Jia, Hongguang; Xuan, Ming

    2009-07-01

    Dome is the head of a missile which has such a strong effect on the missile's drag. When missiles attack at high speed, the drag caused by sphere dome is 50%~60% of whole missile's drag [1]. In order to reduce the dome's drag, the idea of "conformal optics" is studied in some papers. The state of the art of conformal optics is described in James P.Mils paper [2]. But most people's work focus on the outside of dome's shape design. This paper presents a way to design the dome's inside surface. This paper is composed by three main parts. The first part expands the calculation of dome's outflow and the shock wave. The second section describes how the optical optimizing function made. Finally, the last section shows the result.

  15. Conceptual model for regional radionuclide transport from a salt dome repository: a technical memorandum

    SciTech Connect

    Kier, R.S.; Showalter, P.A.; Dettinger, M.D.

    1980-05-30

    Disposal of high-level radioactive wastes is a major environmental problem influencing further development of nuclear energy in this country. Salt domes in the Gulf Coast Basin are being investigated as repository sites. A major concern is geologic and hydrologic stability of candidate domes and potential transport of radionuclides by groundwater to the biosphere prior to their degradation to harmless levels of activity. This report conceptualizes a regional geohydrologic model for transport of radionuclides from a salt dome repository. The model considers transport pathways and the physical and chemical changes that would occur through time prior to the radionuclides reaching the biosphere. Necessary, but unknown inputs to the regional model involve entry and movement of fluids through the repository dome and across the dome-country rock interface and the effect on the dome and surrounding strata of heat generated by the radioactive wastes.

  16. Venus pancake dome formation: Morphologic effects of a cooling-induced variable viscosity during emplacement

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Zuber, M. T.

    1993-01-01

    The distinctive steep-sided 'pancake' domes discovered in the Magellan images of Venus have morphologies that suggest formation by a single continuous emplacement of a high viscosity magma. A resemblance of the venusian domes to much smaller terrestrial rhyolite and dacite volcanic domes has prompted some authors to suggest that the domes on Venus also have high silica compositions and thus, high viscosities. However, viscosity is a function of crystallinity as well as silica content in a magma, and thus increases as a result of magmatic cooling. To investigate the effect of a cooling-induced viscosity increase on dome morphology, we have modeled the domes as radial viscous gravity currents that cool during emplacement. Various aspects of the investigation are discussed.

  17. Emplacement of the final lava dome of the 2009 eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Bull, Katharine F.; Anderson, Steven W.; Diefenbach, Angela K.; Wessels, Rick L.; Henton, Sarah M.

    2013-06-01

    After more than 8 months of precursory activity and over 20 explosions in 12 days, Redoubt Volcano, Alaska began to extrude the fourth and final lava dome of the 2009 eruption on April 4. By July 1 the dome had filled the pre-2009 summit crater and ceased to grow. By means of analysis and annotations of time-lapse webcam imagery, oblique-image photogrammetry techniques and capture and analysis of forward-looking infrared (FLIR) images, we tracked the volume, textural, effusive-style and temperature changes in near-real time over the entire growth period of the dome. The first month of growth (April 4-May 4) produced blocky intermediate- to high-silica andesite lava (59-62.3 wt.% SiO2) that initially formed a round dome, expanding by endogenous growth, breaking the surface crust in radial fractures and annealing them with warmer, fresh lava. On or around May 1, more finely fragmented and scoriaceous andesite lava (59.8-62.2 wt.% SiO2) began to appear at the top of the dome coincident with increased seismicity and gas emissions. The more scoriaceous lava spread radially over the dome surface, while the dome continued to expand from endogenous growth and blocky lava was exposed on the margins and south side of the dome. By mid-June the upper scoriaceous lava had covered 36% of the dome surface area. Vesicularity of the upper scoriaceous lava range from 55 to 66%, some of the highest vesicularity measurements recorded from a lava dome. We suggest that the stability of the final lava dome primarily resulted from sufficient fracturing and clearing of the conduit by preceding explosions that allowed efficient degassing of the magma during effusion. The dome was thus able to grow until it was large enough to exceed the magmastatic pressure in the chamber, effectively shutting off the eruption.

  18. The geology and mechanics of formation of the Fort Rock Dome, Yavapai County, Arizona

    USGS Publications Warehouse

    Fuis, Gary S.

    1996-01-01

    The Fort Rock Dome, a craterlike structure in northern Arizona, is the erosional product of a circular domal uplift associated with a Precambrian shear zone exposed within the crater and with Tertiary volcanism. A section of Precambrian to Quaternary rocks is described, and two Tertiary units, the Crater Pasture Formation and the Fort Rock Creek Rhyodacite, are named. A mathematical model of the doming process is developed that is consistent with the history of the Fort Rock Dome.

  19. A decade of dome growth at Mount St. Helens, 1980-90

    USGS Publications Warehouse

    Swanson, D.A.

    1990-01-01

    The growth of the dacite dome at Mount St. Helens between 1980 and 1986 has been more intensively studied than that of any other dome-building eruption. The growth has been complex in detail, but remarkably regular overall. This paper summarizes some of what has been learned and provides many references to additional information. Whether dome building has ended is an open question, particularly in view of the renewed, though minor, explosive activity of late 1989 and early 1990. -Author

  20. Cyclic pressurisation of Mount St Helens dacites and basalt. Laboratory results and implications for lava dome monitoring

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie; Dainty, Matthew; Smith, Rosanna; Sammonds, Peter; Pallister, John; Meredith, Phillip

    2010-05-01

    Lava domes are frequently subjected to cyclic heating and pressurisation, which may weaken the dome rocks, leading to renewed extrusion, explosions or collapse. These heating and loading cycles can be recreated in the laboratory, allowing the level of crack damage caused by these cycles to be established through analysing elastic moduli. Acoustic emissions (AEs) indicate the timing of cracking, and can also be used to interpret precursory seismicity for eruption prediction. Experiment samples are from Mount St. Helens, USA: 3 dacites from the Pine Creek eruptive period (2.9-2.55 ka), a Castle Creek age basalt (2.55-1.895 ka), and 4 dacites from the 2004-2008 eruption. Each sample was cut into several cylindrical cores (25 mm diameter and 62.5-70 mm long). Some samples were then heated and cooled at 1˚C/ minute to a target temperature of 600o C or 900o C, and held for 2 hours to achieve thermal equilibrium. This heating can cause cracking due to contrasts in thermal expansion of different minerals. Dynamic elastic moduli were calculated for each sample using ultrasonic wave velocity, density and porosity for later comparison to static elastic moduli gathered during deformation. One core of each sample was loaded to failure in uniaxial compression in order to find the short term strength of the sample. For all cyclic loading tests, conducted on pre-heated and unheated cores, samples were loaded at 10-5 s-1 strain rate then unloaded to 5MPa. Subsequent cycles had an increasing peak load. Most had the same rate for unloading, with a few samples unloaded instantaneously. Axial, radial and volumetric strain were determined from the recorded displacement throughout the experiment and used with the axial stress measurements to calculate static elastic moduli. Samples loaded to failure with no cycling generally failed at higher stresses than their cyclically loaded counter-parts, whilst rapid unloading increased their strength. Failure stresses of the dacite lava dome

  1. A Scalable and Modular Dome Illumination System for Scientific Microphotography on a Budget

    PubMed Central

    Kawada, Ricardo; Buffington, Matthew L.

    2016-01-01

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs remain expensive and inflexible with respect to new LED technology. Further, a one-size-fits-all dome cannot accommodate the large breadth of insect size encountered in nature, forcing the photographer to adapt, in some cases, to a less than ideal dome design. The dome described here is scalable, as it is based on a isodecahedron, and the template for the dome is available as a downloaded file from the internet that can be printed on any printer, on the photographer’s choice of media. As a result, a photographer can afford, using this design, to produce a series of domes of various sizes and materials, and LED ring lights of various sizes and color temperatures, depending on the need. PMID:27138573

  2. Identifying and inventorying cypress domes in the Florida panhandle using Landsat imagery

    NASA Astrophysics Data System (ADS)

    Calaminus, Andre Kyle

    Cypress domes are swamp ecosystems dominated by pond cypress (Taxodium ascendens), a conifer native to North America. Cypress domes can be found in flatland depressions throughout the southeast United States, hydrologically separated from other water bodies. Threatened by urbanization and land use change, these unique ecosystems have experienced degradation, destruction, and habitat loss over the past few decades. While many domes have been identified in central and southern Florida, literature is lacking on cypress domes found in the Florida panhandle. Cypress domes within the Florida panhandle were located, inventoried, and analyzed for landscape patterns, including size and shape. Additionally, the cypress dome areas were subject to pixel change detection for temporal comparison of dome size from 2000 to 2013. Using satellite imagery from the Landsat 8 spacecraft, support vector machine classification, and publicly available data, a total of 1,568 cypress domes were found to exist in the Florida panhandle, with a mean area of 1.28 hectares, ranging from a minimum of 0.13 ha to a maximum of 4.95 ha, occupying 19.79 km2, or 0.078% of the panhandle study area. A change detection analysis over the 13 year period show a net gain of 284.63 ha in cypress dome growth.

  3. A Scalable and Modular Dome Illumination System for Scientific Microphotography on a Budget.

    PubMed

    Kawada, Ricardo; Buffington, Matthew L

    2016-01-01

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs remain expensive and inflexible with respect to new LED technology. Further, a one-size-fits-all dome cannot accommodate the large breadth of insect size encountered in nature, forcing the photographer to adapt, in some cases, to a less than ideal dome design. The dome described here is scalable, as it is based on a isodecahedron, and the template for the dome is available as a downloaded file from the internet that can be printed on any printer, on the photographer's choice of media. As a result, a photographer can afford, using this design, to produce a series of domes of various sizes and materials, and LED ring lights of various sizes and color temperatures, depending on the need. PMID:27138573

  4. Longitudinal biases in the Seychelles Dome simulated by 35 ocean-atmosphere coupled general circulation models

    NASA Astrophysics Data System (ADS)

    Nagura, Motoki; Sasaki, Wataru; Tozuka, Tomoki; Luo, Jing-Jia; Behera, Swadhin K.; Yamagata, Toshio

    2013-02-01

    Seychelles Dome refers to the shallow climatological thermocline in the southwestern Indian Ocean, where ocean wave dynamics efficiently affect sea surface temperature, allowing sea surface temperature anomalies to be predicted up to 1-2 years in advance. Accurate reproduction of the dome by ocean-atmosphere coupled general circulation models (CGCMs) is essential for successful seasonal predictions in the Indian Ocean. This study examines the Seychelles Dome as simulated by 35 CGCMs, including models used in phase five of the Coupled Model Intercomparison Project (CMIP5). Among the 35 CGCMs, 14 models erroneously produce an upwelling dome in the eastern half of the basin whereas the observed Seychelles Dome is located in the southwestern tropical Indian Ocean. The annual mean Ekman pumping velocity in these models is found to be almost zero in the southern off-equatorial region. This result is inconsistent with observations, in which Ekman upwelling acts as the main cause of the Seychelles Dome. In the models reproducing an eastward-displaced dome, easterly biases are prominent along the equator in boreal summer and fall, which result in shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and a spurious upwelling dome in the region. Compared to the CMIP3 models, the CMIP5 models are even worse in simulating the dome longitudes.

  5. A preliminary report of the geohydrology of the Mississippi Salt-Dome Basin

    USGS Publications Warehouse

    Spiers, C.A.; Gandl, L.A.

    1980-01-01

    The U.S. Department of Energy is investigating the suitability of salt domes in the Mississippi salt-dome basin as repositories for storing radioactive wastes. The Department of Energy has requested that the U.S. Geological Survey describe the groundwater hydrology of the Mississippi salt-dome basin, giving special attention to direction and rate of movement of water. In this first part of a continuing investigation the data obtained from one year of extensive literature search and data compilation are summarized. The regional groundwater hydrology in the salt-dome basin is defined with respect to (1) groundwater flow, (2) facies changes, (3) geological structure, (4) recharge and discharge, (5) freshwater-saltwater relations, and (6) identification of localities where additional data are needed. From the 50 piercement-type salt domes in the Mississippi salt-dome basin three domes (Richton, Cypress Creek, and Lampton) were selected for more intensive study. To further evaluate the geohydrology of Richton, Lampton, and Cypress Creek domes as possible sites for storage of radioactive waste, an intensive geohydrologic study based on a comprehensive test drilling program near the domes is planned. (USGS)

  6. A detailed gravity study of the Chattolanee Baltimore Gneiss Dome, Maryland, U.S.A.

    NASA Astrophysics Data System (ADS)

    Kodama, Kenneth P.; Chapin, David A.

    1984-05-01

    A detailed gravity survey over the Chattolanee Baltimore Gneiss Dome in the Maryland Piedmont suggests that the dome is an arched recumbent fold. The Baltimore Gneiss, which cores the dome, has a negative density contrast with the surrounding Cambro-Ordovician marbles and schists and is coincident with a large minimum in the simple Bouguer gravity. Three north-south profiles, which cut across the east-west-trending surface exposure of the dome were modeled two-dimensionally. The models suggest that the Baltimore Gneiss is thickest and tightly folded in an inverted V shape to the east and thinner and broadly arched to the west. It is also possible to fit the gravity data with a mushroom-shaped body at the easternmost profile, which could suggest a diapiric origin for the dome, but this interpretation is not favored based on geological arguments. The Baltimore Mafic Complex, located to the south of the Chattolanee Dome, can be modeled as an approximately 1 km thick slab with a subhorizontal base, suggesting that it is a thrust sheet. By analogy with the Phoenix Baltimore Gneiss Dome, mapped by Crowley [2], the Cambro-Ordovician sediments surrounding the Chattolanee Dome may also be involved in the recumbent folding which would suggest that the dome was formed during the Ordovician Taconic orogeny.

  7. Deterministic precision finishing of domes and conformal optics

    NASA Astrophysics Data System (ADS)

    Shorey, Aric; Kordonski, William; Tricard, Marc

    2005-05-01

    In order to enhance missile performance, future window and dome designs will incorporate shapes with improved aerodynamic performance compared with the more traditional flats and spheres. Due to their constantly changing curvature and steep slopes, these shapes are incompatible with most conventional polishing and metrology solutions. Two types of a novel polishing technology, Magnetorheological Finishing (MRF®) and Magnetorheological (MR) Jet, could enable cost-effective manufacturing of free-form optical surfaces. MRF, a deterministic sub-aperture magnetically assisted polishing method, has been developed to overcome many of the fundamental limitations of traditional finishing. MRF has demonstrated the ability to produce complex optical surfaces with accuracies better than 30 nm peak-to-valley (PV) and surface micro-roughness less than 1 nm rms on a wide variety of optical glasses, single crystals, and glass-ceramics. The polishing tool in MRF perfectly conforms to the optical surface making it well suited for finishing this class of optics. A newly developed magnetically assisted finishing method MR JetTM, addresses the challenge of finishing the inside of steep concave domes and other irregular shapes. An applied magnetic field coupled with the properties of the MR fluid allow for stable removal rate with stand-off distances of tens of centimeters. Surface figure and roughness values similar to traditional MRF have been demonstrated. Combining these technologies with metrology techniques, such as Sub-aperture Stitching Interferometer (SSI®) and Asphere Stitching Interferometer (ASI®), enable higher precision finishing of the windows and domes today, as well as the finishing of future conformal designs.

  8. Seafloor doming driven by active mantle degassing offshore Naples (Italy)

    NASA Astrophysics Data System (ADS)

    Ventura, Guido; Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Caliro, Stefano; Chiodini, Giovanni; Sacchi, Marco; Rizzo, Andrea

    2016-04-01

    Structures and processes associated with shallow water hydrothermal fluid discharges on continental shelves are poorly known. We report geomorphological, geophysical, and geochemical evidences of a 5.5 x 5.3 km seabed doming located 5 km offshore the Naples harbor (Italy). The dome lies between 100 and 170 m of water depth and it is 15-20 m higher than the surrounding seafloor. It is characterized by a hummocky morphology due to 280 sub-circular to elliptical mounds, about 660 cones, and 30 pockmarks. The mounds and pockmarks alignments follow those of the main structural discontinuity affecting the Gulf of Naples. The seafloor swelling and breaching require relatively low pressures (about 2-3 MPa), and the sub-seafloor structures, which consists of 'pagodas' affecting the present-day seabed, record the active upraise, pressurization, and release of magmatic fluids. The gas composition of the sampled submarine emissions is consistent with that of the emissions from the hydrothermal systems of Ischia, CampiFlegrei and Somma-Vesuvius active volcanoes, and CO2 has a magmatic/thermometamorphic origin. The 3He/4He ratios (1.66-1.96 Ra) are slightly lower than in the Somma-Vesuvius and Campi Flegrei volcanoes (~2.6-3.0 Ra) indicating the contamination of fluids originated from the same magmatic source by crustal-derived radiogenic 4He. All these evidences concur to hypothesize an extended magmatic reservoir beneath Naples and its offshore. Seabed doming, faulting, and hydrothermal discharges are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions. We conclude that seabed deformations and hydrothermal discharge must be included in the coastal hazard studies.

  9. Winter sky brightness & cloud cover over Dome A

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Moore, A. M.; Fu, J.; Ashley, M.; Cui, X.; Feng, L.; Gong, X.; Hu, Z.; Laurence, J.; LuongVan, D.; Riddle, R. L.; Shang, Z.; Sims, G.; Storey, J.; Tothill, N.; Travouillon, T.; Wang, L.; Yang, H.; Yang, J.; Zhou, X.; Zhu, Z.; Burton, M. G.

    2014-01-01

    At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical Observatories. The Gattini DomeA project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fish-eye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R), however, the absence of tracking systems, together with the ultra large field of view 85 degrees) and strong distortion have driven us to seek a unique way to build our data reduction pipeline. We present here the first measurements of sky brightness in the photometric B, V, and R band, cloud cover statistics measured during the 2009 winter season and an estimate of the transparency. In addition, we present example light curves for bright targets to emphasize the unprecedented observational window function available from this ground-based location. A ~0.2 magnitude agreement of our simultaneous test at Palomar Observatory with NSBM(National Sky Brightness Monitor), as well as an 0.04 magnitude photometric accuracy for typical 6th magnitude stars limited by the instrument design, indicating we obtained reasonable results based on our ~7mm effective aperture fish-eye lens.

  10. Domed Fresnel lens concentrator technology for space application

    NASA Technical Reports Server (NTRS)

    Piszczor, Michael F., Jr.; Oneill, Mark J.

    1989-01-01

    Over the past three years, NASA Lewis and Entech, Inc. have been investigating the use of high efficiency refractive photovoltaic concentrators for use in space. The design currently under investigation uses a square domed Fresnel lens to focus light on a GaAs concentrator cell. A prismatic cell cover, which directs light away from the front contacts and thus eliminates metalization losses, is applied to the top of the GaAs cell to further enhance array efficiency. The latest experimental results based on testing the GaAs cell/prism cover assembly at standard and operating conditions are presented.

  11. Near-automatic generation of lava dome DEMs from photos

    NASA Astrophysics Data System (ADS)

    James, M. R.; Varley, N.

    2012-04-01

    Acquiring accurate digital elevation models (DEMs) of growing lava domes is critical for hazard assessment. However, most techniques require expertise and time (e.g. photogrammetry) or expensive equipment (e.g. laser scanning and radar-based techniques). Here, we use a photo-based approach developed within the computer vision community that offers the potential for near-automatic DEM construction using a consumer-grade digital camera and freely available software. The technique is based on a combination of structure-from-motion and multi-view stereo algorithms (SfM-MVS) and can generate dense 3D point clouds (millions of points) from multiple photographs of a scene taken from different positions. Processing is carried out by automated 'reconstruction pipeline' software downloadable from the internet, e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/. Such reconstructions are initally un-scaled and un-oriented so additional software (http://www.lancs.ac.uk/ staff/jamesm/software/sfm_georef.htm) has been developed to permit scaling or full georeferencing. Although this step requires the presence of some control points or knowledge of scale within the scene, it does not have the relatively strict image acquisition and control requirements of traditional photogrammetry. For accuracy and to allow error analysis, georeferencing observations are made within the image set, rather than requiring feature matching within the point cloud. Here we demonstrate the results of using the technique for deriving 3D models of the Volcán de Colima lava dome. 5 image sets have been collected by different people over a period of 12 months during overflights in a light aircraft. Although the resulting imagery is of variable quality for 3D reconstruction, useful data can be extracted from each set. Scaling and georeferencing is carried out using a combination of ortho-imagery (downloaded from Bing) and a few GPS points. Overall precisions are ~1 m and DEM qualities

  12. Field Survey of Cactus Crater Storage Facility (Runit Dome)

    SciTech Connect

    Douglas Miller, Terence Holland

    2008-10-31

    The US Department of Energy, Office of Health and Safety (DOE/HS-10), requested that National Security Technologies, LLC, Environmental Management directorate (NSTec/EM) perform a field survey of the Cactus Crater Storage Facility (Runit Dome), similar to past surveys conducted at their request. This field survey was conducted in conjunction with a Lawrence Livermore National Laboratory (LLNL) mission on Runit Island in the Enewetak Atoll in the Republic of the Marshall Islands (RMI). The survey was strictly a visual survey, backed up by digital photos and a written description of the current condition.

  13. Motivations for Imaging Spectroscopy atDomeC

    NASA Astrophysics Data System (ADS)

    Kelz, A.

    Antarctica offers unique conditions for ground-based observations, such as low sky background in the infrared, improved seeing, and low turbulence and scintillation noise. These properties are particularly beneficial to imaging, precision photometry, and infrared observations. It may be less clear if Antarctica offers equally compelling advantages for spectroscopy, in particular in the optical domain. However, scientific programmes that make use of imaging (or 3D) spectroscopy for selected follow-up studies of IR surveys, long-term monitoring of extended targets and resolved stellar population studies in crowded fields, also benefit from the site conditions at DomeC.

  14. Accuracy of 3d Reconstruction in AN Illumination Dome

    NASA Astrophysics Data System (ADS)

    MacDonald, Lindsay; Toschi, Isabella; Nocerino, Erica; Hess, Mona; Remondino, Fabio; Robson, Stuart

    2016-06-01

    The accuracy of 3D surface reconstruction was compared from image sets of a Metric Test Object taken in an illumination dome by two methods: photometric stereo and improved structure-from-motion (SfM), using point cloud data from a 3D colour laser scanner as the reference. Metrics included pointwise height differences over the digital elevation model (DEM), and 3D Euclidean differences between corresponding points. The enhancement of spatial detail was investigated by blending high frequency detail from photometric normals, after a Poisson surface reconstruction, with low frequency detail from a DEM derived from SfM.

  15. Static analysis of a sonar dome rubber window

    NASA Technical Reports Server (NTRS)

    Lai, J. L.

    1978-01-01

    The application of NASTRAN (level 16.0.1) to the static analysis of a sonar dome rubber window (SDRW) was demonstrated. The assessment of the conventional model (neglecting the enclosed fluid) for the stress analysis of the SDRW was made by comparing its results to those based on a sophisticated model (including the enclosed fluid). The fluid was modeled with isoparametric linear hexahedron elements with approximate material properties whose shear modulus was much smaller than its bulk modulus. The effect of the chosen material property for the fluid is discussed.

  16. Bayesian Inversion using Physics-based Models Applied to Dome Extrusion at Mount St. Helens 2004-2008

    NASA Astrophysics Data System (ADS)

    Wong, Y. Q.; Segall, P.; Anderson, K. R.; Bradley, A. M.

    2015-12-01

    Physics-based models of volcanic eruptions have grown more sophisticated over the past few decades. These models, combined with Bayesian inversion, offer the potential of integrating diverse geological and geophysical datasets to better understand volcanic systems. Using a Markov Chain Monte Carlo (MCMC) algorithm with a physics-based conduit model, we invert data from the 2004-2008 dome-forming eruption at Mount St. Helens, USA. We extend the 1D cylindrical conduit model of Anderson and Segall [2011] to include vertical and lateral gas loss from the magma, as well as equilibrium crystallization. The melt viscosity increases strongly with crystal content. Magma permeability obeys the Kozeny-Carman law with a threshold porosity. Excess pressure in the magma chamber drives Newtonian flow of magma upwards until the viscous resistance to flow exceeds the rate-dependent frictional strength on the conduit wall, at which point the magma transitions from viscous flow to plug flow. We investigate the steady-state solutions for lava dome growth between March and December 2005, in which magma chamber pressure, initial water content, permeability and friction parameters are unknown model parameters. These parameters are constrained by: dome rock porosity, extrusion rate from photogrammetry, plug depth from drumbeat earthquakes, and crystallization pressure from petrologic studies. Posterior probability density functions (PDFs) reveal the constraints on the model parameters and their correlations. Assuming lithostatic normal stress on the plug, low coefficients of friction (0.1-0.3) are required to allow extrusion at the observed rate while maintaining reasonable magma chamber pressures. Lower effective normal stress or melt viscosity could allow for larger friction coefficients. Future work will investigate the time-dependent system, thereby allowing us to incorporate time-evolving geodetic and eruption rate data into the inversion.

  17. Accessory lateral discoid meniscus.

    PubMed

    Saygi, Baransel; Yildirim, Yakup; Senturk, Salih; Sezgin Ramadan, Saime; Gundes, Hakan

    2006-12-01

    The lateral meniscus tends to have more developmental variation than the medial counterpart. This is a report of an accessory discoid layer of lateral meniscus. All arthroscopic, magnetic resonance imaging and histopathological views are presented. PMID:16710729

  18. Amyotrophic lateral sclerosis

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/000688.htm Amyotrophic lateral sclerosis To use the sharing features on this page, please enable JavaScript. Amyotrophic lateral sclerosis, or ALS, is a disease of the nerve ...

  19. Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Parrenin, F.; Severi, M.; Motoyama, H.; Wolff, E.

    2015-02-01

    Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were synchronized to better understand their chronology. A total of 1401 volcanic tie points were identified covering the past 216 kyr. DFO2006, the chronology for the DF core characterized by strong constraining by the O2/N2 age markers, was compared with AICC2012, the chronology for 5 cores including the EDC core, and characterized by glaciological approaches combining ice flow modelling with various age markers. The age gaps between the two chronologies are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of the gap of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, ratios of duration DFO2006/AICC2012 are 85% at a period from the late stage of MIS 6 to MIS 5d and 114% at a period from MIS 5d to 5b. We then compared the DFO2006 with another chronology of the DF core, DFGT2006, characterized by glaciological approaches with weaker constraining by age markers. Features of the DFO2006/DFGT2006 age gaps are very similar to those of the DFO2006/AICC2012 age gaps. This fact lead us to hypothesize that a cause of the systematic DFO2006/AICC2012 age gaps at MIS 5 are associated with differences in the dating approaches. Besides, ages of speleothem records from China agreed well with DFO2006 at MIS 5c and 5d but not at MIS 5b. Thus, we hypothesize at least at MIS 5c and 5d, major sources of the gaps are systematic errors in surface mass balance estimation in the glaciological approach. Compatibility of the age markers should be carefully assessed in future.

  20. Formation of the giant Shakhdara migmatitic gneiss dome, Pamir, India-Asia collision zone

    NASA Astrophysics Data System (ADS)

    Stübner, Konstanze; Ratschbacher, Lothar; Hacker, Bradley; Dunkl, István; Gloaguen, Richard

    2013-04-01

    Cenozoic gneiss domes comprise one third of the surface exposure of the Pamir Mountains and provide a window into deep crustal processes of the India-Asia collision. The largest of these is the 350 × 90 km Shakhdara-Alichur composite dome of the southern Pamir, Tajikistan and Afghanistan. The Shakhdara and Alichur domes formed by footwall exhumation of two low-angle detachments: In the larger Shakhdara dome the top-to-S South Pamir shear zone (SPSZ) exhumed crust from 30-40 km depth; in the Alichur dome the top-to-N Alichur shear zone exhumed upper crustal rocks. The subdomes are separated by a low-strain horst. Non-coaxial shear in the Shakhdara dome is pervasive over the ~4 km thick SPSZ. The top of the shear zone is preserved at mountain peaks, the base is incised by the Panj gorge, which exposes the 'core' of the dome; total erosion is less than 4 km throughout most of the dome. We use a comprehensive geo-thermochronologic dataset of titanite, monazite, and zircon U/Th-Pb, mica Rb-Sr and 40Ar/39Ar, zircon and apatite fission track, and zircon (U-Th)/He ages to constrain the exhumation history of the southern Pamir domes. Doming started at ~21 Ma by crustal buckling and activation of a top-to-N normal shear zone (Gunt shear zone) along the northern rim of the Shakhdara dome, resulting in exhumation and cooling. The bulk of the exhumation was accomplished by northward extrusion of the SPSZ footwall, which was active from ~18-15 Ma to ~2 Ma; exhumation rates were 1-3 mm/yr. Erosion rates during and after the end of doming were 0.3-0.5 mm/yr within the domes and 0.1-0.3 mm/yr in the horst and in the SE Pamir plateau; incision rates of the major drainages were up to 1.0 mm/yr. Doming by footwall exhumation of the SPSZ resulted in up to 90 km N-S extension, coeval with ongoing N-S convergence between India and Asia. Extension opposes shortening along and above the reactivated Rushan-Pshart suture zone, a wide fold-thrust belt north of the Shakhdara-Alichur domes

  1. Measurement of air quality within storage domes in technical area 54, areas G and L

    SciTech Connect

    Anderson, E.

    1994-03-15

    The concentrations of volatile organic compounds (VOCs) and tritium inside of storage domes at TA-54 were measured to assess worker exposure and support the Area G site characterization, including the Radioactive Air Emissions Management (RAEM) program. Samples were collected at 2-3 locations within Domes 48, 49, and 153 on up to six days during the summer of 1994. Samples were collected to evaluate three scenarios: (1) normal working activities with the domes open; (2) after domes were closed overnight; and (3) after domes were closed for three days. Eight-hour integrated samples were collected and analyzed in Radian`s Austin laboratories. Tritium activities from 17.1 to 69,900 pCi/m{sup 3} were measured. About two dozen individual VOCs were identified in each sample, but most of the concentration levels were very low (e.g.; < 1 to 10 ppbv). The highest concentrations measured were bromomethane (56.5 ppbv), 1, 1,1-trichloroethane (75.4 ppbv), propane (958 ppbv), methylene chloride (1,450 ppbv), and toluene (22.8). The measured VOC concentrations were well below the action levels developed by the New Mexico Environment Department and the measured tritium concentrations were well below the DOE`s derived air concentration (DAC). The variability in concentration within a dome during a single sampling episode was small. The concentrations were about an order of magnitude (i.e., 10x) higher after the domes had been closed overnight compared with the domes when open. Closing the domes over the weekend did not result in significantly higher concentrations (e.g.; > 20%) than when the domes were closed only overnight. The data were used to generate estimated annual dome emission rates of 0.3 Ci/yr of tritium and less than 100 lbs/yr of VOCs. The measured VOC concentrations were collected during the warmest months of the year and therefore should represent worst-case air impacts.

  2. Highly Symmetric and Congruently Tiled Meshes for Shells and Domes

    PubMed Central

    Rasheed, Muhibur; Bajaj, Chandrajit

    2016-01-01

    We describe the generation of all possible shell and dome shapes that can be uniquely meshed (tiled) using a single type of mesh face (tile), and following a single meshing (tiling) rule that governs the mesh (tile) arrangement with maximal vertex, edge and face symmetries. Such tiling arrangements or congruently tiled meshed shapes, are frequently found in chemical forms (fullerenes or Bucky balls, crystals, quasi-crystals, virus nano shells or capsids), and synthetic shapes (cages, sports domes, modern architectural facades). Congruently tiled meshes are both aesthetic and complete, as they support maximal mesh symmetries with minimal complexity and possess simple generation rules. Here, we generate congruent tilings and meshed shape layouts that satisfy these optimality conditions. Further, the congruent meshes are uniquely mappable to an almost regular 3D polyhedron (or its dual polyhedron) and which exhibits face-transitive (and edge-transitive) congruency with at most two types of vertices (each type transitive to the other). The family of all such congruently meshed polyhedra create a new class of meshed shapes, beyond the well-studied regular, semi-regular and quasi-regular classes, and their duals (platonic, Catalan and Johnson). While our new mesh class is infinite, we prove that there exists a unique mesh parametrization, where each member of the class can be represented by two integer lattice variables, and moreover efficiently constructable. PMID:27563368

  3. Unzen Dome Dacite Density: Influence On Fragmentation Behaviour

    NASA Astrophysics Data System (ADS)

    Küppers, U.; Spieler, O.; Dingwell, D. B.

    Preliminary experimental investigations of the fragmentation of dome lava from Un- zen volcano, Kyushu Island (Japan), have indicated that fragmentation is influenced by density. Two field campaigns (2000 and 2001) have been conducted to obtain extensive density information on the pyroclastic flow deposits of the 1990 to 1995 eruption. This allows the characterisation of the pre-collapse dome density. Such density data enable us to evaluate the effect and influence of transport processes on the density distribution inside the deposits. Experiments have been performed to determine the fragmentation threshold of hot, pressurised rock cylinders (60 x 26 mm) due to rapid decompression. The cylinders are pressurised using argon gas. The fragmentation bomb simulates the conditions for volcanic fragmentation induced by rapid decompression. At 850 C dense dacite with an open porosity of 3.76 % requires an initial pressure difference of 22.5 MPa to overcome the threshold. The threshold value decreases steeply with increasing porosity. At porosities greater than 12 % the rate of decrease of threshold value is reduced. The results presented here correlate with those obtained from Merapi, Montserrat and Mt. St. Helens (Spieler, 2001). Natural pyroclastics and pyroclastics generated experimentally have been compared using a laser particle size analyzer to correlate our experimental trends with data from natural products.

  4. The AST3 project: Antarctic Survey Telescopes for Dome A

    NASA Astrophysics Data System (ADS)

    Yuan, Xiangyan; Cui, Xiangqun; Gu, Bozhong; Yang, Shihai; Du, Fujia; Li, Xiaoyan; Wang, Daxing; Li, Xinnan; Gong, Xuefei; Wen, Haikun; Li, Zhengyang; Lu, Haiping; Xu, Lingzhe; Zhang, Ru; Zhang, Yi; Wang, Lifan; Shang, Zhaohui; Hu, Yi; Ma, Bin; Liu, Qiang; Wei, Peng

    2014-07-01

    The AST3 project consists of three large field of view survey telescopes with 680mm primary mirror, mainly for observations of supernovas and extrasolar planets searching from Antarctic Dome A where is very likely to be the best astronomical site on earth for astronomical observations from optical wavelength to thermal infrared and beyond, according to the four years site testing works by CCAA, UNSW and PRIC. The first AST3 was mounted on Dome A in Jan. 2012 and automatically run from March to May 2012. Based on the onsite winterization performance of the first AST3, some improvements such as the usage of high resolution encoders, defrosting method, better thermal control and easier onsite assembly et al were done for the second one. The winterization observation of AST3-2 in Mohe was carried on from Nov. 2013 to Apr. 2014, where is the most northern and coldest part of China with the lowest temperature around -50°. The technical modifications and testing observation results will be given in this paper. The third AST3 will be optimized from optical to thermal infrared aiming diffraction limited imaging with K band. Thus the whole AST3 project will be a good test bench for the development of future larger aperture optical/infrared Antarctic telescopes such as the proposed 2.5m Kunlun Dark Universe Survey Telescope project.

  5. Characterization of Atmospheric Ekman Spirals at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Rysman, Jean-François; Lahellec, Alain; Vignon, Etienne; Genthon, Christophe; Verrier, Sébastien

    2016-08-01

    We use wind speed and temperature measurements taken along a 45-m meteorological tower located at Dome C, Antarctica (75.06°S, 123.19°E) to highlight and characterize the Ekman spiral. Firstly, temperature records reveal that the atmospheric boundary layer at Dome C is stable during winter and summer nights (i.e., >85 % of the time). The wind vector, in both speed and direction, also shows a strong dependence with elevation. An Ekman model was then fitted to the measurements. Results show that the wind vector follows the Ekman spiral structure for more than 20 % of the year (2009). Most Ekman spirals have been detected during summer nights, that is, when the boundary layer is slightly stratified. During these episodes, the boundary-layer height ranged from 25 to 100 m, the eddy viscosity from 0.004 to 0.06 m^2 s^{-1}, and the Richardson number from zero to 1.6.

  6. Performance limits of planar phased array with dome lens

    NASA Astrophysics Data System (ADS)

    Geren, W. P.; Taylor, Michael

    1998-10-01

    Communication systems based on low-earth-orbit (LEO) satellites have generated a requirement for high-performance phased array antennas with exceptional gain, sidelobe levels, and axial ratio over broad scan angles and 360 degree azimuth coverage. One approach to mitigating the effects of scan dependence is to cover the planar array with a hemispherical lens, or dome, which implements passive or active phase correction of the scanned beam. The phase correction over the dome surface may be represented as the function (Delta) (Phi) ((theta) , (phi) ), with (theta) and (phi) the polar and azimuth angles in a coordinate system having z-axis normal to the array. The purpose of this study was to determine the performance improvement achievable with such an ideal lens. Three cases were considered: a conventional lens with fixed optimum phase correction, an active lens with scan-dependent phase correction a function of polar angle only, and an active lens with phase correction a function of polar and azimuthal angles. In all cases, the planar array distribution had a fixed radial Taylor amplitude distribution and a phase taper consisting of a linear beam-pointing term and a non-linear focusing term.

  7. Sediment distribution about salt domes and ridges on Louisiana slope

    SciTech Connect

    Lowrie, A.

    1984-09-01

    Salt ridges and domes underlie much of the present Louisiana slope. The bathymetric expression of underlying salt could be either a mound or a flattening of the normal rate of descent down the slope. The mounded salt features form barriers to the gravity-driven sediments from the shelf break. Much industrial research has been done in the search for reservoir sands about such an obstruction. Parallel-bedded sediments from foredrifts on the upcurrent side of a seamount. These foredrift sediments were deposited where the prevailing ocean bottom currents were locally decelerated by the obstructing seamount. Moats are found on the sides of the obstruction and are the result of erosion or nondeposition owing to acceleration of deflected waters. Leedrifts are found on the downcurrent side of the obstruction. Current gyres result from deceleration of accelerated currents along the obstruction's flanks, and a complex sedimentation pattern results. Flow over the obstruction's top is determined by size and shape of the obstruction relative to size and velocity of the bottom-following current. A turbulent wave will be set up which may have sufficient amplitude to influence sedimentation on the downcurrent side. If ocean bottoms currents equal gravity-driven terrigenous sediment movement and seamounts equal salt domes and ridges, then the result of deep ocean surveys are directly applicable to sedimentation on slopes with underlying salt basement. The salt-related sedimentation pattern of the present slope should be applicable to similar paleoenvironments.

  8. Exceptional astronomical seeing conditions above Dome C in Antarctica.

    PubMed

    Lawrence, Jon S; Ashley, Michael C B; Tokovinin, Andrei; Travouillon, Tony

    2004-09-16

    One of the most important considerations when planning the next generation of ground-based optical astronomical telescopes is to choose a site that has excellent 'seeing'--the jitter in the apparent position of a star that is caused by light bending as it passes through regions of differing refractive index in the Earth's atmosphere. The best mid-latitude sites have a median seeing ranging from 0.5 to 1.0 arcsec (refs 1-5). Sites on the Antarctic plateau have unique atmospheric properties that make them worth investigating as potential observatory locations. Previous testing at the US Amundsen-Scott South Pole Station has, however, demonstrated poor seeing, averaging 1.8 arcsec (refs 6, 7). Here we report observations of the wintertime seeing from Dome C (ref. 8), a high point on the Antarctic plateau at a latitude of 75 degrees S. The results are remarkable: the median seeing is 0.27 arcsec, and below 0.15 arcsec 25 per cent of the time. A telescope placed at Dome C would compete with one that is 2 to 3 times larger at the best mid-latitude observatories, and an interferometer based at this site could work on projects that would otherwise require a space mission. PMID:15372024

  9. PHOTOMETRY OF VARIABLE STARS FROM DOME A, ANTARCTICA

    SciTech Connect

    Wang Lingzhi; Macri, Lucas M.; Krisciunas, Kevin; Wang Lifan; Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Storey, John W. V.; Cui Xiangqun; Gong Xuefei; Yuan Xiangyan; Feng Longlong; Yang Ji; Zhu Zhenxi; Liu Qiang; Zhou Xu; Pennypacker, Carl R.; Shang Zhaohui; Yang Huigen; York, Donald G.

    2011-11-15

    Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present high-cadence time-series aperture photometry of 10,000 stars with i < 14.5 mag located in a 23 deg{sup 2} region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly uninterrupted synoptic coverage, we found six times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% were unclassified, 27% were likely binaries, and 17% were likely pulsating stars. The latter category includes {delta} Scuti, {gamma} Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.

  10. Unfinished business: the rebirth of the ALPO Lunar Dome Survey

    NASA Astrophysics Data System (ADS)

    Huddleston, Marvin W.

    2004-05-01

    The ALPO board of directors approved the revival of the Lunar Dome Survey during their annual board meeting in the summer of 2003. The initial LDS program was conceived by Harry Jamieson in the early 1960's and headed by him when the British Astronomical Assn. (BAA) was invited to join the program, which they did. The joint effort between the ALPO and BAA lunar sections lasted for approximately 14 years, ending officially around 1976 due to a decline in interest. The program was again revived in 1987 under the direction of Jim Phillips and lasted until the mid-1990's. All told, this program has been one of the longest running programs in the history of the Lunar Section of ALPO. The revived program will concentrate on cleaning up the existing catalog, classification and confirmation of the objects contained therein, and analysis of the database created in the process. It is hoped that, as in the past, much of the newly revived Lunar Dome Survey will be an international effort.

  11. Charged nano-domes and bubbles in epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Ben Gouider Trabelsi, A.; Kusmartsev, F. V.; Robinson, B. J.; Ouerghi, A.; Kusmartseva, O. E.; Kolosov, O. V.; Mazzocco, R.; Gaifullin, Marat B.; Oueslati, M.

    2014-04-01

    For the first time, new epitaxial graphene nano-structures resembling charged ‘bubbles’ and ‘domes’ are reported. A strong influence, arising from the change in morphology, on the graphene layer’s electronic, mechanical and optical properties has been shown. The morphological properties of these structures have been studied with atomic force microscopy (AFM), ultrasonic force microscopy (UFM) and Raman spectroscopy. After initial optical microscopy observation of the graphene, a detailed description of the surface morphology, via AFM and nanomechanical UFM measurements, was obtained. Here, graphene nano-structures, domes and bubbles, ranging from a few tens of nanometres (150-200 nm) to a few μm in size have been identified. The AFM topographical and UFM stiffness data implied the freestanding nature of the graphene layer within the domes and bubbles, with heights on the order of 5-12 nm. Raman spectroscopy mappings of G and 2D bands and their ratio confirm not only the graphene composition of these structures but also the existence of step bunching, defect variations and the carrier density distribution. In particular, inside the bubbles and substrate there arises complex charge redistribution; in fact, the graphene bubble-substrate interface forms a charged capacitance. We have determined the strength of the electric field inside the bubble-substrate interface, which may lead to a minigap of the order of 5 meV opening for epitaxial graphene grown on 4H-SiC face-terminated carbon.

  12. Lateral flow strip assay

    SciTech Connect

    Miles, Robin R.; Benett, William J.; Coleman, Matthew A.; Pearson, Francesca S.; Nasarabadi, Shanavaz L.

    2011-03-08

    A lateral flow strip assay apparatus comprising a housing; a lateral flow strip in the housing, the lateral flow strip having a receiving portion; a sample collection unit; and a reagent reservoir. Saliva and/or buccal cells are collected from an individual using the sample collection unit. The sample collection unit is immersed in the reagent reservoir. The tip of the lateral flow strip is immersed in the reservoir and the reagent/sample mixture wicks up into the lateral flow strip to perform the assay.

  13. Generation of pyroclastic flows and surges by hot-rock avalanches from the dome of Mount St. Helens volcano, USA

    USGS Publications Warehouse

    Mellors, R.A.; Waitt, R.B.; Swanson, D.A.

    1988-01-01

    Several hot-rock avalanches have occurred during the growth of the composite dome of Mount St. Helens, Washington between 1980 and 1987. One of these occurred on 9 May 1986 and produced a fan-shaped avalanche deposit of juvenile dacite debris together with a more extensive pyroclastic-flow deposit. Laterally thinning deposits and abrasion and baking of wooden and plastic objects show that a hot ash-cloud surge swept beyond the limits of the pyroclastic flow. Plumes that rose 2-3 km above the dome and vitric ash that fell downwind of the volcano were also effects of this event, but no explosion occurred. All the facies observed originated from a single avalanche. Erosion and melting of craterfloor snow by the hot debris caused debris flows in the crater, and a small flood that carried juvenile and other clasts north of the crater. A second, broadly similar event occured in October 1986. Larger events of this nature could present a significant volcanic hazard. ?? 1988 Springer-Verlag.

  14. Application of CryoSat-2 data product for DEM generation in Dome-A summit area, Antarctica

    NASA Astrophysics Data System (ADS)

    fang, W.; Cheng, X.; Hui, F.

    2012-12-01

    Currently available Digital Elevation Models (DEMs) of Dome A were originally derived from radar altimetry data (ERS-1/2, GLAS/ICESat), and later improved by GPS measurements. The relatively low resolution and coverage poses a problem, especially for the regional research. CryoSat-2 with SIRAL (SAR/Interferometric Altimeter) was launched on 8 April 2010, providing an alternative for high-density and high-accuracy acquisition of terrain point data. The inclination of the satellite's orbit is 92°, and the orbit can approach latitude of 88°. The repeat period of 369 days provides a high orbit crossover density (10 crossovers km-2 year-1 at 87°) with a 30-day sub-cycle. In this study, we collected ten months (March to December 2011) of successive CryoSat-2 Low Rate Mode level 2 (LRM L2) datasets. Two types of filters were applied to remove additional elevation outliers. These filtering procedures excluded 5.95% of the original data. According to the distribution of the point data, terrain modeling of grid DEM, interpolation method of Kriging (ordinary Kriging), and a grid resolution of 200m is chosen for DEM generation in this study. Finally, we used the satellite's monthly revisits with non-repeated coverage and present a novel DEM of 900 km2 in the Dome A region centered at Kunlun Station (80°25‧01″S, 77°06‧58″E). It shows that the topography of the Dome A region is saddle-shaped, with a northern peak and a southern peak. We used a subtraction method to compare the novel DEM with the previous DEM of GPS measurements. The elevation differences exhibit a positive average elevation bias. It may be due to the penetration of the Ku-band radar wave into the soft snow. As a first approximation based on the statistics of the height differences, we estimate that the average penetration depth of the CryoSat-2 Ku-band wave in this area is 1 m. Map of surface topography over the Dome A region generated from CryoSat-2 data. Contours are smoothed. The contour interval

  15. Mechanical and spatial determinants of cytoskeletal geodesic dome formation in cardiac fibroblasts.

    PubMed

    Entcheva, Emilia; Bien, Harold

    2009-02-01

    This study tests the hypothesis that the cell cytoskeletal (CSK) network can rearrange from geodesic dome type structures to stress fibers in response to microenvironmental cues. The CSK geodesic domes are highly organized actin microarchitectures within the cell, consisting of ordered polygonal elements. We studied primary neonatal rat cardiac fibroblasts. The cues used to trigger the interconversion between the two CSK architectures (geodesic domes and stress fibers) included factors affecting spatial order and the degree of CSK tension in the cells. Microfabricated three-dimensional substrates with micrometre sized grooves and peaks were used to alter the spatial order of cell growth in culture. CSK tension was modified by 2,3-butanedione 2-monoxime (BDM), cytochalasin D and the hyphae of Candida albicans. CSK geodesic domes occurred spontaneously in about 20% of the neonatal rat cardiac fibroblasts used in this study. Microfabricated structured surfaces produced anisotropy in the cell CSK and effectively converted geodesic domes into stress fibers in a dose-dependent manner (dependence on the period of the features). Affectors of actin structure, inhibitors of CSK tension and cell motility, e.g. BDM, cytochalasin D and the hyphae of C. albicans, suppressed or eliminated the geodesic domes. Our data suggest that the geodesic domes, similar to actin stress fibers, require maintenance of CSK integrity and tension. However, microenvironments that promote structural anisotropy in tensed cells cause the transformation of the geodesic domes into stress fibers, consistent with topographic cell guidance and some previous CSK model predictions. PMID:20023805

  16. Mechanical and spatial determinants of cytoskeletal geodesic dome formation in cardiac fibroblasts

    PubMed Central

    Bien, Harold

    2015-01-01

    This study tests the hypothesis that the cell cytoskeletal (CSK) network can rearrange from geodesic dome type structures to stress fibers in response to microenvironmental cues. The CSK geodesic domes are highly organized actin microarchitectures within the cell, consisting of ordered polygonal elements. We studied primary neonatal rat cardiac fibroblasts. The cues used to trigger the interconversion between the two CSK architectures (geodesic domes and stress fibers) included factors affecting spatial order and the degree of CSK tension in the cells. Microfabricated three-dimensional substrates with micrometre sized grooves and peaks were used to alter the spatial order of cell growth in culture. CSK tension was modified by 2,3-butanedione 2-monoxime (BDM), cytochalasin D and the hyphae of Candida albicans. CSK geodesic domes occurred spontaneously in about 20% of the neonatal rat cardiac fibroblasts used in this study. Microfabricated structured surfaces produced anisotropy in the cell CSK and effectively converted geodesic domes into stress fibers in a dose-dependent manner (dependence on the period of the features). Affectors of actin structure, inhibitors of CSK tension and cell motility, e.g. BDM, cytochalasin D and the hyphae of C. albicans, suppressed or eliminated the geodesic domes. Our data suggest that the geodesic domes, similar to actin stress fibers, require maintenance of CSK integrity and tension. However, microenvironments that promote structural anisotropy in tensed cells cause the transformation of the geodesic domes into stress fibers, consistent with topographic cell guidance and some previous CSK model predictions. PMID:20023805

  17. The ongoing dome emplacement and destruction cyclic process at Popocatépetl volcano, Central Mexico

    NASA Astrophysics Data System (ADS)

    Gómez-Vazquez, Angel; De la Cruz-Reyna, Servando; Mendoza-Rosas, Ana Teresa

    2016-09-01

    The ongoing eruptive activity of Popocatépetl volcano has been characterized by emplacement and subsequent destruction of a succession of lava domes. Between the onset of the current eruption in 1994 and the time of this submission, 38 episodes of lava dome formation and removal have been identified. Each dome has showed particular features related to the magma extrusion process. Among other manifestations, dome-emplacement events have been usually accompanied by relatively low-intensity, protracted explosions referred to as exhalations. After variable times of residence, emplacements have ended in partial or total destruction of the domes by strong vulcanian explosions that produced sizeable ash plumes, with most of them also ejecting incandescent debris onto the volcano flanks. Here, we present a detailed account for the observed activity related to the domes' growth and destruction, related seismic monitoring signals, and morphological features of the domes based on 19 years of visual observations and image analysis. We then discuss a model for the process of dome growth and destruction and its hazard implications.

  18. Lateral canthal surgery.

    PubMed

    Chong, Kelvin Kam-Lung; Goldberg, Robert A

    2010-08-01

    The lateral canthus is a delicate and complicated three-dimensional structure with function relevant to the health of the ocular surface. Dysfunction of the lateral canthus, due to aging changes or iatrogenic trauma, results in ocular morbidity ranging from chronic irritation to tearing to recalcitrant keratopathy. From an aesthetic standpoint, symmetric, normally positioned lateral canthi are cornerstones of youthful periorbital appearance, disruption of which leads to cosmetically significant deformity or asymmetry. Reconstruction of the lateral canthus is important in the rehabilitation of the aging eyelid and an unfortunate necessity after failed lateral canthal surgery. The common methods for improving or maintaining position, tone, and shape of the lower eyelid and lateral canthus use tightening or shortening the lower eyelid horizontally, keeping the canthal angle in an appropriate vertical level, and hugging the ocular surface. Many techniques have been described for the reconstruction of the lateral canthus in functional conditions or for aesthetic purposes. These methods have met with varying success. In this article, we begin with a discussion of the anatomy and physiology of the lateral canthus, followed by clinical examples of lateral canthal abnormalities and underlying pathophysiologies. A review of surgical options for the lateral canthus is presented with concluding remarks on postoperative complications. PMID:20524167

  19. Fabrication of conformal ZnS domes by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Goela, Jitendra S.; Askinazi, Joel

    1999-07-01

    Aspheric shape ZnS domes were fabricated by a scalable and cost-effective chemical vapor deposition (CVD) process to demonstrate the feasibility of producing aerodynamic domes that conform to the shape of the missile body. These domes provide enhanced performance by substantially reducing the missile drag, although they also present issues of CVD deposition, optical fabrication to the required figure and finish, particularly the inside surface, and metrology. Domes were fabricated on 'male' mandrels in a CVD chamber to produce net-shape or precision replicated inside surface and then diamond turned to produce surfaces with figure of a fraction of a wave and finish of 180 angstrom RMS. Important issues involved in near-net-shaping and precision replication of ZnS domes are discussed and data on mandrel and release coating materials, degree of replication achieved and mandrel durability are presented.

  20. A structural outline of the Yenkahe volcanic resurgent dome (Tanna Island, Vanuatu Arc, South Pacific)

    NASA Astrophysics Data System (ADS)

    Merle, O.; Brothelande, E.; Lénat, J.-F.; Bachèlery, P.; Garaébiti, E.

    2013-12-01

    A structural study has been conducted on the resurgent Yenkahe dome (5 km long by 3 km wide) located in the heart of the Siwi caldera of Tanna Island (Vanuatu arc, south Pacific). This spectacular resurgent dome hosts a small caldera and a very active strombolian cinder cone - the Yasur volcano - in the west and exhibits an intriguing graben in its central part. Detailed mapping and structural observations make it possible to unravel the volcano-tectonic history of the dome. It is shown that, following the early formation of a resurgent dome in the west, a complex collapse (caldera plus graben) occurred and this was associated with the recent uplift of the eastern part of the present dome. Eastward migration of the underlying magma related to regional tectonics is proposed to explain this evolution.

  1. Strategic Petroleum Reserve (SPR) geological site characterization report, Big Hill Salt Dome

    SciTech Connect

    Hart, R.J.; Ortiz, T.S.; Magorian, T.R.

    1981-09-01

    Geological and geophysical analyses of the Big Hill Salt Dome were performed to determine the suitability of this site for use in the Strategic Petroleum Reserve (SPR). Development of 140 million barrels (MMB) of storage capacity in the Big Hill Salt Dome is planned as part of the SPR expansion to achieve 750 MMB of storage capacity. Objectives of the study were to: (1) Acquire, evaluate, and interpret existing data pertinent to geological characterization of the Big Hill Dome; (2) Characterize the surface and near-surface geology and hydrology; (3) Characterize the geology and hydrology of the overlying cap rock; (4) Define the geometry and geology of the dome; (5) Determine the feasibility of locating and constructing 14 10-MMB storage caverns in the south portion of the dome; and (6) Assess the effects of natural hazards on the SPR site. Recommendations are included. (DMC)

  2. Venusian pancake domes: Insights from terrestrial voluminous silicic lavas and thermal modeling

    NASA Technical Reports Server (NTRS)

    Manley, Curtis R.

    1993-01-01

    The so-called 'pancake' domes, and several other volcanoes on Venus, appear to represent large extrusions of silicic lava. Similar voluminous rhyolite lava flows, often associated with mantle plumes, are known on Earth. Venus' high ambient temperature, and insulation by the dome's brecciated carapace, both act to prolong cooling of a dome's interior, allowing for episodic lava input over an extended period of time. Field relations and aspect ratios of terrestrial voluminous rhyolite lavas imply continuous, non-episodic growth, reflecting tapping of a large volume of dry, anatectic silicic magma. Petrogenetically, the venusian domes may be analogous to chains of small domes on Earth, which represent 'leakage' of evolved material from magma bodies fractionating from much more mafic liquids.

  3. Isotope Fractionation of Modern Air In Dome C (antarctica) Polar Firn.

    NASA Astrophysics Data System (ADS)

    Landais, A.; Leuenberger, M.; Caillon, N.; Schwander, J.; Jouzel, J.

    Air bubbles trapped in ice cores are unique archives of the past atmospheric com- position. Recent paleoclimatic studies have taken advantage of the effects of thermal and gravitational diffusion occurring in the firn to quantify past abrupt temperature changes. In order to better quantify the thermal diffusion, we have analysed modern air samples pumped within the FIRETRACC European Project at different depths along the firn (upper 100 m of the ice cap) of Dome C polar station (Antarctica). Air bottles were then directly analysed for the isotopic composition of N2, O2 and Ar with mass spectrometer either in Saclay (LSCE) or in Bern (Climate Institute). Similar results were obtained in the two laboratories, which is a validation of the analytical method. The strong seasonal temperature gradient in the upper 30 m of the firn leads to a clear thermal diffusion anomaly for each isotope which is superimposed on the gravitational signal. Comparison of the different magnitudes of these thermally driven anomalies for 15N/14N, 18O/16O and 40Ar/36Ar enables us then to estimate the thermal diffu- sion factors for each isotope pair and use it for later studies in paleothermometry.

  4. Exhumation Depths of the Lower Crustal Domes of the Pamir

    NASA Astrophysics Data System (ADS)

    McGraw, J. L.; Hacker, B. R.; Ratschbacher, L.

    2009-12-01

    Large-scale orogenic plateaux are important geodynamic features within continental collision systems. In this context, the indo-asian collision and the Tibetan plateau have been the focus of numerous studies aimed at understanding the development of these areas of over-thickened crust. However, the Pamir plateau may provide a better opportunity to understand the mechanics of plateau formation. Because of greater exhumation within the Pamir in the Cenozoic, deeper crustal rocks are exposed which may shed light on the crustal-scale processes occurring within the plateau interior. Examination of lower crustal exposures within the Pamir therefore provides an opportunity to understand the pressure-temperature history of the lower crust that is otherwise not directly observable in the Tibetan Plateau. Samples from three lower crustal domes from the Pamir plateau were analyzed by electron probe microanalysis. The sampled Kurgovat, Yazgulem, and Shakdhara domes likely formed diachronously as the Pamir grew northward, as they are dispersed north to south across the western half of the plateau. Exhumation depths determined from the pressure-temperature history of the rocks were obtained through quantitative thermobarometry. Well-established thermobarometers such as GASP, GHPQ, GBMP and GARB were used on the mainly metapelitic rocks. The typical peak pressure assemblage, garnet + kyanite + biotite + An20 plagioclase ± K-white mica, replaced staurolite, and is itself overgrown by sillimanite and more anorthitic plagioclase. Garnet cores are chemically homogeneous and rims are partially resorbed with long-wavelength rimward increases in Mn. Preliminary data indicate south to north variation in peak metamorphic pressures, which range from 9-11 kbar at temperatures of 700-800°C in the south to ~5 kbar at 500°C in the north; exhumation from peak pressures to 4-6 kbar occurred at temperatures of 500-700°C. These data imply exhumation depths of 32-40 km in the south and ~20 km

  5. Emplacement age of leucogranite in the Kampa Dome, southern Tibet

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Chi; Wu, Fu-Yuan; Yu, Liang-Jun; Liu, Zhi-Chao; Ji, Wei-Qiang; Wang, Jian-Gang

    2016-01-01

    Himalayan leucogranite is an important rock to decipher the orogenic evolution of the Himalayan orogen. It has been recognized that the leucogranite occurred as two separate, but parallel belts within Himalaya. Leucogranite in the north belt is mainly exposed an intrusion component within the gneissic dome. Although most domes have been intensively studied, the Kampa Dome, located in the east of Southern Tibet, is less investigated due to its inaccessibility. In this study, we conducted a comprehensive set of U(-Th)-Pb zircon, monazite and xenotime dating and trace element composition analyses using laser ablation technique, in order to constrain the emplacement age and lithological nature of the Kampa leucogranite. Zircons from gneiss are mainly magmatic and define a protolith age of ca. 498 Ma, but no Cenozoic age is documented. Zircons from leucogranite display inherited magmatic core overgrown by thin dark rim, which occasionally gives a much younger age of 27.7 ± 1.0 Ma. However, monazites from leucogranite yield a Th-Pb age of 25.7 ± 0.5 Ma to 26.8 ± 0.4 Ma, which is comparable to the U-Pb age of 24.8 ± 0.4 Ma obtained from xenotimes. For the granitic gneiss into which the leucogranite intruded, monazites and xenotimes give ages of 25.8 ± 0.6 Ma to 26.6 ± 0.8 Ma and 25.0 ± 0.4 Ma to 26.0 ± 1.0 Ma, respectively. These ages are comparable to those obtained from the leucogranite, and suggest that the metamorphic monazite and xenotime from gneiss formed during the leucogranite emplacement. Trace element analyses indicated that zircons from leucogranite have high P (up to 3721 ppm) and REE concentrations, but have low in Th/U ratios (0.04-0.16). Similarly, monazites from leucogranite generally show extreme HREE depletion and significant negative Eu anomaly with some displaying significantly tetrad effect. These geochemical features indicated that the Kampa leucogranite was highly fractionated during its evolution.

  6. Long-term landscape evolution in the Hangay Dome, Mongolia

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Ancuta, L. D.; Smith, S. G.; Idleman, B. D.; Wegmann, K. W.; Zeitler, P. K.

    2013-12-01

    The Hangay Dome in central Mongolia is an example of high-elevation (>3000 m), low-relief topography in a continental interior between the thick Siberian craton to the north and the active Himalaya deformation belt to the far south. Detrital and granitic bedrock apatite (U-Th)/He samples yield ages of ~85-200 Ma and ~95-120 Ma, respectively. These low-temperature data in conjunction with K-feldspar 40Ar/39Ar ages of ~200-225 Ma, raise questions about when this preserved, epeirogenic landscape was uplifted and how it has responded to minimal exhumation since the Mesozoic. Alpine cirques and intact moraine deposits are indicative of a more recent, climate-driven erosional signal in the higher elevation regions of the Hangay. Pecube modeling indicates that a recent, regional uplift signal produces younger, Early-Mid Cenozoic cooling ages in lower elevations of the Selenga River drainage basin to the north of the Hangay Dome. Modeled low exhumation rates of 0.038 mm/yr over 122 Ma generate cooling ages in agreement with preliminary geomorphic and geochronologic results. Basalt total fusion 40Ar/39Ar ages constrain the earliest surface exposure of the landscape to ~30 Ma in the Hangay, with flows as young as ~5 Ka present in a few areas. Geomorphic observations coupled with age-constrained basalt stratigraphy allow us to calculate minimum incision rates in the eastern Hangay for the Miocene and Late Pliocene-Holocene of 0.032 mm/yr and 0.039 mm/yr, respectively. In addition, basalt-bedrock contact mapping in one area places a ~10 Ma old basal flow erupted onto an undulated bedrock surface, suggesting the existence of topography at the time of eruption. Volumetric analysis reveals that rock removed in the past ~6 Ma (uppermost basalt flow age) yields a net erosion rate of 0.037 mm/yr. This rate is also comparable to our 10Be basin-averaged erosion rates from samples collected in adjacent drainages. In contrast to previous inferences that central Mongolia has undergone

  7. The Hangay Dome, central Mongolia: A relict Mesozoic landscape

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Zeitler, P. K.; Ancuta, L. D.; Idleman, B. D.; Boulton, S. L.; Wegmann, K. W.

    2014-12-01

    The Hangay Dome is a broad upland in central Mongolia characterized by a high elevation (>3000-4000 m), low relief landscape within the greater Mongolian Plateau (~2000 m avg. elevation) of central Asia. We have assessed the long-term, large-scale landscape evolution of the region using thermochronologic analysis. Detrital apatite (U-Th-Sm)/He samples from the Selenga River (n = 55) and Orkhon River (n = 15) basins north of the Hangay Dome yield central ages of 134.2 ± 6 and 131.3 ± 9.8 (1σ) Ma, respectively. The regional granitic bedrock apatite (U-Th-Sm)/He single grain age distribution is approximately 95 to 200 Ma, with a homogenized grain central age of 131.2 ± 6.1 Ma. These low-temperature data, in conjunction with K-feldspar MDD 40Ar/39Ar ages of ~200-230 Ma, suggest regional exhumation in the Mesozoic. HeFTy (Ketcham, 2005) modeling corroborates these data and suggests cooling rates of ~3°C/Ma from 220-185 Ma, and applying a geothermal gradient of 21 ± 3°C/km for central Mongolia (Lysak and Dorofeeva, 2003), rock uplift rates from Late Triassic to Mid-Late Jurassic are approximately 100 m/My and from the Early Cretaceous (130 Ma) to the present approximately ≤ 30 m/My. Regional bedrock age patterns, detrital age populations, and thermal modeling suggest that significant recent, rapid rock uplift in central Mongolia is unlikely. Pecube thermo-kinematic models (Braun, 2003) indicate that any rapid (> 500 m/My) event in the Late Miocene-Pliocene would produce Early-Mid Cenozoic cooling ages in lower elevations of the Selenga River drainage basin, which is not supported by the detrital age signal. Pecube modeling of slow rock uplift rates of <50 m/My since the Early Triassic produce regional ages in agreement with geomorphic and geochronologic data. Regional apatite helium age-elevation patterns suggest long-term thermal stability of the upper crust and possible lowering of relief since Mesozoic exhumation. Basalt total fusion 40Ar/39Ar ages

  8. Lateral intercrural suture in the caucasian nose: Decreased domal divergence angle in endonasal rhinoplasty without delivery

    PubMed Central

    Berger, Cezar Augusto Sarraf; Mocelin, Marcos; Soares, Caio Márcio Correia; Pasinato, Rogério; Frota, Andreia Ellery

    2012-01-01

    Summary Introduction: Several techniques can be performed to improve nasal tip definition such as cartilage resection, tip grafts, or sutures. Objctive: To evaluate the outcome of lateral intercrural suture at the lower lateral cartilage by endonasal rhinoplasty with a basic technique without delivery in decreasing the angle of domal divergence and improving the nasal tip definition. Method: This prospective study was performed in 64 patients in which a suture was made on the board head of the lower lateral cartilage in the joint between the dome and lateral crus, using polydioxanone (PDS) with sharp, curved needle. Results: In all of the cases, better definition of the nasal tip was achieved by intercrural suturing for at least 6 months postoperatively. Conclusion: Lateral intercrural suture of the lower lateral cartilage provides improved nasal tip definition and can be performed by endonasal rhinoplasty without delivery in the Caucasian nose. PMID:25991941

  9. Prospective Type Ia Supernova Surveys From Dome A

    SciTech Connect

    Kim, A.; Bonissent, A.; Christiansen, J.L.; Ealet, A.; Faccioli, L.; Gladney, L.; Kushner, G.; Linder, E.; Stoughton, C.; Wang, L.; /Texas A-M /Purple Mountain Observ.

    2010-02-01

    Dome A, the highest plateau in Antarctica, is being developed as a site for an astronomical observatory. The planned telescopes and instrumentation and the unique site characteristics are conducive toward Type Ia supernova surveys for cosmology. A self-contained search and survey over five years can yield a spectro-photometric time series of {approx}1000 z < 0.08 supernovae. These can serve to anchor the Hubble diagram and quantify the relationship between luminosities and heterogeneities within the Type Ia supernova class, reducing systematics. Larger aperture ({approx}>4-m) telescopes are capable of discovering supernovae shortly after explosion out to z {approx} 3. These can be fed to space telescopes, and can isolate systematics and extend the redshift range over which we measure the expansion history of the universe.

  10. Heavy metals in Antarctic ice from Law Dome: Initial results

    SciTech Connect

    Hong, S. |; Boutron, C.F. |; Edwards, R.; Morgan, V.I.

    1998-08-01

    Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values {approximately} two- to four-fold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea salt spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.

  11. Prospective Type Ia supernova surveys from Dome A

    SciTech Connect

    Kim, A.; Bonissent, A.; Christiansen, J. L.; Ealet, A.; Faccioli, L.; Gladney, L.; Kushner, G.; Linder, E.; Stoughton, C.; Wang, L.

    2010-03-10

    Dome A, the highest plateau in Antarctica, is being developed as a site for an astronomical observatory. The planned telescopes and instrumentation and the unique site characteristics are conducive toward Type Ia supernova surveys for cosmology. A self-contained search and survey over 5 years can yield a spectro-photometric time series of ~;; 1000 z< 0:08 supernovae. These can serve to anchor the Hubble diagram and quantify the relationship between luminosities and heterogeneities within the Type Ia supernova class, reducing systematics. Larger aperture (>=4-m) telescopes are capable of discovering supernovae shortly after explosion out to z ~;; 3. These can be fed to space telescopes, and can isolate systematics and extend the redshift range over which we measure the expansion history of the universe.

  12. Precision CMB Polarization from Dome-C: the BRAIN experiment

    NASA Astrophysics Data System (ADS)

    Masi, S.; de Bernardis, P.; Giordano, C.; Nati, F.; Piacentini, F.; Polenta, G.; Veneziani, M.; Gervasi, M.; Sironi, G.; Tartari, A.; Zannoni, M.; Peterzen, S.; Bartlett, J.; Giraud-Heraud, Y.; Piat, M.; Rosset, C.; Giard, M.; Pons, R.; Maffei, B.; Ade, P.; Gear, W.; Mauskopf, P.; Piccirillo, L.; Pisano, G.; Savini, G.

    In the current cosmological scenario, part of the linearly polarized emission of the CMB is expected to be rotational (B-modes). This component is due to tensor perturbations of the metric produced by primordial gravitational waves, which are generated a split-second after the Big Bang. The signal expected is of the order of ≲ 0.1 μ K, well below the non-rotational component of the polarization signal (E-modes), and beyond the sensitivity of present generation instruments. New, more sensitive instruments are developed in several labs, with the goal to measure the B-modes. Control of systematics and foregrounds will be the key to make the results of these experiments believable. In this paper we shortly outline BRAIN, a bolometric interferometer devoted to B-modes research, and its pathfinder experiment, devoted to test the Dome-C site.

  13. Numerical Simulation of Textile Composite Stamping On Double Dome

    SciTech Connect

    Xiongqi Peng; Zia Ur Rehman

    2011-05-04

    Stamping is one of the most effective ways to form textile composites in industry for providing high-strength, low-weight and cost-effective products. This paper presents a fully continuum mechanics-based approach for stamping simulation of textile fiber reinforced composites by using finite element (FE) method. A previously developed non-orthogonal constitutive model is used to represent the anisotropic mechanical behavior of textile composites under large deformation during stamping. Simulation are performed on a balanced plain weave composite with 0 deg./90 deg. and {+-}45 deg. as initial yarn orientation over a benchmark double dome device. Simulation results show good agreement with experimental output in terms of a number of parameters selected for comparison.

  14. Sojourner Rover View of Shark and Half Dome

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The rounded knobs (arrows) up to 3 or 4 cm wide on Shark (left; approximately 70 cm wide)) and Half Dome (upper right) and in the foreground could be pebbles in a cemented matrix of clays, silts, and sands; such rocks are called conglomerates. Well-rounded objects like these were not seen at the Viking sites.

    NOTE: original caption as published in Science Magazine.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  15. Disruption of the PV-PPV Phase Transition by a Dome-like Upwelling Beneath Alaska

    NASA Astrophysics Data System (ADS)

    Sun, D.; Helmberger, D. V.; Miller, M. S.

    2014-12-01

    The lowermost mantle region, D", represents one of the most dramatic thermal andcompositional layers within our planet. Global tomographic models display relatively fast patchsalong the circum-Pacific which is generally attributed to slab-debris. Such cold patches interactwith the PV-PPV phase boundary to generate particularly strong heterogeneity at their edges.Most seismic observations for the D" come from the lower mantle S wave triplication (Scd).However, the sampling regions concentrated beneath Central America, where intensive studies,including migration methods and array analysis, have been accomplished. Beneath the centralAmerica, the D" can have a step variation of ~ 100 km, which argues strong lateral temperaturevariations or possible chemical variations. However, the common used ray paths between SouthAmerican events and seismic stations in US sample such sharp boundary azimuthally, whichmake the modeling difficult. Here, we exploit the USArray waveform data to examine one ofthese sharp transitions beneath Alaska. From west to east beneath Alaska, we observed threedifferent type of D": West region with strong Scd requiring sharp δVS = 2% increase;Middle region with no clear Scd indicating lack of D"; East region with strong Scd requiring gradientδVS increase. To explain such strong lateral variation, chemical variations must be involved. Wesuggested that West region represents a normal mantle. In contrast, the east region is dominated bysubducted slab. At the Middle region, we discovered a strong upwelling structure that disrupts the phaseboundary. A distinct pattern of travel time delays, waveform distortions, and amplitude patternsreveal a circular anomaly about 5° across which can be modeled synthetically as a dome about400 km high with a shear velocity reduction of ~5%. Geodynamic modeling indicates thatthis structure could be the base of an upwelling and/or a hot Fe-rich oxide hill.

  16. Acoustic and Elastodynamic Redatuming for VSP Salt Dome Flank Imaging

    NASA Astrophysics Data System (ADS)

    Lu, R.; Willis, M.; Toksoz, N.

    2007-12-01

    We apply an extension of the concept of Time Reversed Acoustics (TRA) for imaging salt dome flanks using Vertical Seismic Profile (VSP) data. We demonstrate its performance and capabilities on both synthetic acoustic and elastic seismic data from a Gulf of Mexico (GOM) model. This target-oriented strategy eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove the effects of the salt canopy and surrounding overburden. In this study, we use data from surface shots recorded in a well from a walkaway VSP survey. The method, called redatuming, creates a geometry as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process generates effective downhole shot gathers without any knowledge of the overburden velocity structure. The resulting shot gathers are less complex since the VSP ray paths from the surface source are shortened and moved to be as if they started in the borehole, then reflected off the salt flank region and captured in the borehole. After redatuming, we apply multiple passes of prestack migration from the reference datum of the borehole. In our example, the first pass migration, using only simple vertical velocity gradient model, reveals the outline of the salt edge. A second pass of reverse-time prestack depth migration using the full, two-way wave equation, is performed with an updated velocity model that now consists of the velocity gradient and the salt dome. The second pass migration brings out the dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank forming prismatic reflections.

  17. Cambrian to Holocene structural and burial history of Nashville dome

    SciTech Connect

    Stearns, R.G.; Reesman, A.L.

    1986-02-01

    About 14,000 ft (4270 m) of strata covered basement over the present crest of the Nashville dome by the end of the Paleozoic (calculated by estimating the geothermal gradient, and using temperatures of veins in Stones River Group and Knox Dolomite). At least 7500 ft (2290 m) of post-Devonian strata have been removed by subsequent erosion. Estimates of other erosional episodes include 350 ft (107 m) of upper Knox (during the Middle Ordovician) and 500 ft (152 m) of Devonian-Ordovician (during the Late Devonian). Mesozoic to Holocene uplift was at least 6350 ft (1940 m), 1500 ft or 460 m (25%) of which occurred in the latest 100 m.y. and 450 ft or 140 m (7%) during the latest 2 m.y., a rate ranging from about 15 ft/m.y. (4.6 m/m.y.) for the longer term to over 225 ft/m.y. (70 m/m.y.) in the Pleistocene to Holocene. Earliest structure of the area was a series of elongate basins, probably rifts synchronous with Reelfoot rift to the west. Uplifts trending N10/sup 0/E moved about 40 mi (65 km) westward during the Middle Ordovician. These may relate to similar trending (and moving) Appalachian orogenic events. A change to uplifts trending N50/sup 0/E (parallel to strikes of Appalachian thrusts) occurred in the Late Ordovician and continued to the Devonian; this may reflect a similar Late Ordovician change in the orientation of Appalachian tectonism. In the interval from post-Mississippian to Late Cretaceous, the dome curved westward to join the Pascola arch in response to Ouachita activity. 11 figures, 3 tables.

  18. Behaviour of Atmospheric Boundary Layer Height at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Pietroni, I.; Argentini, S.

    2009-09-01

    The Antarctic Atmospheric Boundary Layer presents characteristics which are substantially different from the mid-latitudes ABLs. On the Antarctic plateau two different extreme situations are observed. During the summer a mixing height develops during the warmer hours of the day although the sensible heat flux is reduced compared to that at mid-latitudes. During the winter a long lived stable boundary layer is continuously present, the residual layer is never observed, consequently the inversion layer is connected at the free atmosphere. To understand the stable ABL process the STABLEDC (Study of the STAble Boundary Layer Environmental at Dome C) experimental field was held at Concordia, the French Italian plateau station at Dome C, during 2005. In the same period the RMO (Routine Measurements Observations) started. The data included turbulence data at the surface, temperature profiles by a microwave profiler (MTP-5P), a mini-sodar and radio-soundings. In this work we will show the results of a comparison of the ABL height at Concordia (3233 m a.s.l) during the summer and the winter using direct measurements and parameterization. The winter ABL height was estimated directly using experimental data (radio-soundings and radiometer temperature and wind velocity profiles) and different methods proposed in literature. The stable ABL height was also estimated using the formulation proposed by Zilitinkevich et al. (2007) for the long-lived stable boundary layer. The correlation of ABL height with the temperature and wind speed is also shown. The summer mixing height was instead estimated by mini-sodar data and compared with the height given by the model suggested by Batchvarova and Gryning (1991) which use as input the turbulence data.

  19. Designing the SALT facility to minimize dome seeing effects

    NASA Astrophysics Data System (ADS)

    de Kock, Mariana; Venter, Sarel J.

    2003-02-01

    Aspects of the design and experience of the Hobby-Eberly Telescope (HET) were incorporated in the SALT facility design. The characteristics of the local environment were taken into account to ensure a building that is cost effective and functional. The effect of heat from the control room and other warm areas were studied and their locations changed to limit thermal effects. A steel false floor, incorporating forced ventilation and extending around the telescope azimuth pier, was installed. This prevents heat radiating from large concrete surfaces with temperatures potentially higher than ambient. Because site testing (i.e. micro thermal measurements) indicated high turbulence within ~5 m of the ground level, the telescope and pier were raised to improve dome seeing. The SALT site is significantly windy all year round (median velocity = 4.8 m/s), and this was utilized to design better ventilation of the facility using adjustable louvers for natural ventilation. Results of a computational fluid dynamic analysis (CFD) are presented which show an adequate temperature distribution at wind speeds as low as 0.5 m/s. The telescope chamber and dome are build out of insulation panels to ensure low thermal losses during the day when the chamber is air conditioned and thus limit electricity consumption and thermal gradients. Large equipment that emit heat or vibration are housed in a separate utility building 50 m from the telescope in the non-prevailing wind direction in order to limit their effect on the telescope. Vented air from the building is also released at this site.

  20. Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Parrenin, F.; Severi, M.; Motoyama, H.; Wolff, E. W.

    2015-10-01

    Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d-6. Therefore, we hypothesize that the causes of the DFO2006-AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d-6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, -230 years (minimum) at MIS 7a and +60

  1. The 2005 and 2010 dome collapse driven block and ash flows on Shiveluch volcano, Kamchatka: Morphological analysis using satellite- and field-based data

    NASA Astrophysics Data System (ADS)

    Krippner, J.; Belousov, A.; Belousova, M.; Ramsey, M. S.

    2015-12-01

    A new multi-scale investigation of recent block and ash flow deposits on Shiveluch volcano, Kamchatka, using satellite- and field-based data has produced a detailed description of the surface deposits. In February, 2005 and October, 2010 Shiveluch produced large dome-collapse block and ash flows that travelled more than 19 km down the southern flanks. These deposits have now been interpreted using high-resolution (~0.5 m) WorldView-02 and QuickBird-02 panchromatic satellite data to describe surficial morphologies, block distributions, forest devastation and the subsequent tree deposition. These data reveal complex deposits composed of overlapping flows and lobes with diverse morphologies including channel and levee structures, varying lobate terminations, compaction features, ridges, small hummock-like features, arcuate scarps, as well as post-depositional erosion and reworking, which were later investigated in the field. The deposits are composed of poorly sorted, porphyritic, dome material which is largely oxidized with rare evidence of hydrothermal alteration, as well as lithics eroded from older deposits, all within an ash-lapilli matrix. Large dome blocks up to 12 m in diameter are deposited to the distal edges of the deposit and are dominantly sub-rounded, and composed of banded, porphyritic, poorly vesicular, variably oxidized dome material with mafic xenolith inclusions. Many of these display fracturing and impact scours. This study links satellite-based interpretations of large block and ash flow deposits to field observations, allowing the remote identification of morphological features. This multi-scale investigation of these morphologies can be applied elsewhere for the rapid and safe identification of fresh deposits in dangerous or remote locations.

  2. A model for submarine rhyolite dome growth: Ponza Island (central Italy)

    NASA Astrophysics Data System (ADS)

    DeRita, Donatella; Giordano, Guido; Cecili, Alessandro

    2001-07-01

    The Late Pliocene rhyolitic submarine volcanic rocks of Ponza island (Italy) can be interpreted as the subaqueous equivalent of subaerial dome complexes in terms of geometry and structure. Three coalescing domes of about 1 km radius and aligned along a NE-trending regional fracture have been identified. The main difference between subaqueous and subaerial lava domes is that in a subaqueous environment, lava is likely to undergo pervasive hyaloclastic brecciation, so that domes are mainly composed of variously brecciated, in situ to clast-rotated hyaloclastite rather than coherent lava. We suggest that the shape and rheologic behaviour through time of submarine domes are closely controlled by the development and thickness of the particulate hyaloclastic carapace, which assumes the role of the solid crust of domes in subaerial environment. The thickness of the hyaloclastic carapace at Ponza is greater than 150 m and emplaced during several different pulses (or eruptions). In the earliest pulses, lava is directly extruded on the seafloor and produces hyaloclastite, the degree of brecciation of which decreases inward to the coherent flow-banded rhyolite lava of the feeder dike. Once the hyaloclastic carapace is formed, further pulses of magma, combined with increase in height of the dome result in a local stress pattern characterised by a vertical σ1≫ σ2= σ3, producing concentric and radial fractures and normal faults. The newly rising magma, shielded by the hyaloclastic carapace, can intrude along these fault and fracture systems and invade previously emplaced but still water-saturated hyaloclastite. This produces the characteristic pattern of dikes observed at Ponza as a series of concentric dikes that are progressively less inclined outward with respect to the dome centre. These late stage dikes in turn produce hyaloclastite at their margins, but generally less fragmented than the embedding hyaloclastite, probably because the ascending magma is better shielded

  3. Ordered domain lateral location, symmetry, and thermal stability in Ge:Si islands

    SciTech Connect

    Richard, M.-I.; Schülli, T. U.; Zhong, Z.; Metzger, T. H.; Renaud, G.

    2015-01-05

    Compositional atomic ordering is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report on a method based on x-ray diffuse scattering close to basis forbidden Bragg reflections to infer the lateral location, the symmetry, and the thermal stability of ordered domains in GeSi dome-shaped islands on Si(001) after growth and during annealing. We observe that atomic ordering does not disappear after annealing, demonstrating that it is a resilient metastable phenomenon.

  4. Performance and applicability of a 2.5-D ice-flow model in the vicinity of a dome

    NASA Astrophysics Data System (ADS)

    Passalacqua, Olivier; Gagliardini, Olivier; Parrenin, Frédéric; Todd, Joe; Gillet-Chaulet, Fabien; Ritz, Catherine

    2016-07-01

    Three-dimensional ice flow modelling requires a large number of computing resources and observation data, such that 2-D simulations are often preferable. However, when there is significant lateral divergence, this must be accounted for (2.5-D models), and a flow tube is considered (volume between two horizontal flowlines). In the absence of velocity observations, this flow tube can be derived assuming that the flowlines follow the steepest slope of the surface, under a few flow assumptions. This method typically consists of scanning a digital elevation model (DEM) with a moving window and computing the curvature at the centre of this window. The ability of the 2.5-D models to account properly for a 3-D state of strain and stress has not clearly been established, nor their sensitivity to the size of the scanning window and to the geometry of the ice surface, for example in the cases of sharp ridges. Here, we study the applicability of a 2.5-D ice flow model around a dome, typical of the East Antarctic plateau conditions. A twin experiment is carried out, comparing 3-D and 2.5-D computed velocities, on three dome geometries, for several scanning windows and thermal conditions. The chosen scanning window used to evaluate the ice surface curvature should be comparable to the typical radius of this curvature. For isothermal ice, the error made by the 2.5-D model is in the range 0-10 % for weakly diverging flows, but is 2 or 3 times higher for highly diverging flows and could lead to a non-physical ice surface at the dome. For non-isothermal ice, assuming a linear temperature profile, the presence of a sharp ridge makes the 2.5-D velocity field unrealistic. In such cases, the basal ice is warmer and more easily laterally strained than the upper one, the walls of the flow tube are not vertical, and the assumptions of the 2.5-D model are no longer valid.

  5. Discoid lateral meniscus.

    PubMed

    Fritschy, D; Gonseth, D

    1991-01-01

    Discoid meniscus is uncommon and usually affects the lateral meniscus. We present 16 patients (8 male and 6 female) with tears of a discoid lateral meniscus occurring in 1800 arthroscopies. We carried out an arthroscopic partial meniscectomy leaving an intact peripheral rim. This is biomechanically satisfactory and the early results are encouraging. PMID:1917190

  6. [Semidiscoid lateral meniscus].

    PubMed

    Araki, Y; Ishida, T; Ootani, M; Yamamoto, H; Yamamoto, T; Nakamura, H; Tsukaguchi, I

    1992-12-25

    We propose a new entity known as "semidiscoid lateral meniscus" of the knee. The diagnostic criteria for semidiscoid lateral meniscus is the appearance on a thin-sliced axial 3-D image of a crescent-shaped meniscus whose transverse width is within 11.6 mm to 14.3 mm on the coronal image. These numerical values were calculated by discriminant analysis. A retrospective review of MR examinations of the knees revealed 15 patients (15 knees) with this entity. These patients were our subjects. Of these 15 patients, complicated lateral meniscal tears were seen in only three cases. Nine knees were free from complications, and five were asymptomatic. Six patients were examined with MR on the contralateral side, and discoid lateral menisci were revealed in all cases. Thus semidiscoid lateral meniscus shows a cross-relationship with discoid menisci. PMID:1488290

  7. Real-Time Measurements of Aft Dome Insulation Erosion on Space Shuttle Reusable Solid Rocket Motor

    NASA Technical Reports Server (NTRS)

    McWhorter, Bruce; Ewing, Mark; Albrechtsen, Kevin; Noble, Todd; Longaker, Matt

    2004-01-01

    Real-time erosion of aft dome internal insulation was measured with internal instrumentation on a static test of a lengthened version of the Space Shuffle Reusable Solid Rocket Motor (RSRM). This effort marks the first time that real-time aft dome insulation erosion (Le., erosion due to the combined effects of thermochemical ablation and mechanical abrasion) was measured in this kind of large motor static test [designated as Engineering Test Motor number 3 (ETM3)I. This paper presents data plots of the erosion depth versus time. The data indicates general erosion versus time behavior that is in contrast to what would be expected from earlier analyses. Engineers have long known that the thermal environment in the aft dome is severe and that the resulting aft dome insulation erosion is significant. Models of aft dome erosion involve a two-step process of computational fluid dynamics (CFD) modeling and material ablation modeling. This modeling effort is complex. The time- dependent effects are difficult to verify with only prefire and postfire insulation measurements. Nozzle vectoring, slag accumulation, and changing boundary conditions will affect the time dependence of aft dome erosion. Further study of this data and continued measurements on future motors will increase our understanding of the aft dome flow and erosion environment.

  8. The annual cycle and biological effects of the Costa Rica Dome

    NASA Astrophysics Data System (ADS)

    Fiedler, Paul C.

    2002-02-01

    The Costa Rica Dome is similar to other tropical thermocline domes in several respects: it is part of an east-west thermocline ridge associated with the equatorial circulation, surface currents flow cyclonically around it, and its seasonal evolution is affected by large-scale wind patterns. The Costa Rica Dome is unique because it is also forced by a coastal wind jet. Monthly climatological fields of thermocline depth and physical forcing variables (wind stress curl and surface current divergence) were analyzed to examine the structure and seasonal evolution of the dome. The annual cycle of the dome can be explained by wind forcing in four stages: (1) coastal shoaling of the thermocline off the Gulf of Papagayo during February-April, forced by Ekman pumping on the equatorward side of the Papagayo wind jet; (2) separation from the coast during May-June when the intertropical convergence zone (ITCZ) moves north to the countercurrent thermocline ridge, the wind jet stops, and the North Equatorial Countercurrent extends toward the coast on the equatorward flank of the ridge; (3) countercurrent thermocline ridging during July-November, when the dome expands to the west as the countercurrent thermocline ridge shoals beneath a band of cyclonic wind stress curl on the poleward side of the ITCZ; and (4) deepening during December-January when the ITCZ moves south and strong trade winds blow over the dome. Coastal eddies may be involved in the coastal shoaling observed during February-March. A seasonally predictable, strong, and shallow thermocline makes the Costa Rica Dome a distinct biological habitat where phytoplankton and zooplankton biomass are higher than in surrounding tropical waters. The physical structure and biological productivity of the dome affect the distribution and feeding of whales and dolphins, probably through forage availability.

  9. Formation of dome and basin structures: Results from scaled experiments using non-linear rock analogues

    NASA Astrophysics Data System (ADS)

    Zulauf, J.; Zulauf, G.; Zanella, F.

    2016-09-01

    Dome and basin folds are structures with circular or slightly elongate outcrop patterns, which can form during single- and polyphase deformation in various tectonic settings. We used power-law viscous rock analogues to simulate single-phase dome-and-basin folding of rocks undergoing dislocation creep. The viscosity ratio between a single competent layer and incompetent matrix was 5, and the stress exponent of both materials was 7. The samples underwent layer-parallel shortening under bulk pure constriction. Increasing initial layer thickness resulted in a decrease in the number of domes and basins and an increase in amplitude, A, arc-length, L, wavelength, λ, and layer thickness, Hf. Samples deformed incrementally show progressive development of domes and basins until a strain of eY=Z = -30% is attained. During the dome-and-basin formation the layer thickened permanently, while A, L, and λ increased. A dominant wavelength was not attained. The normalized amplitude (A/λ) increased almost linearly reaching a maximum of 0.12 at eY=Z = -30%. During the last increment of shortening (eY=Z = -30 to -40%) the domes and basins did not further grow, but were overprinted by a second generation of non-cylindrical folds. Most of the geometrical parameters of the previously formed domes and basins behaved stable or decreased during this phase. The normalized arc-length (L/Hf) of domes and basins is significantly higher than that of 2D cylindrical folds. For this reason, the normalized arc length can probably be used to identify domes and basins in the field, even if these structures are not fully exposed in 3D.

  10. Analysis of the imaging performance of panoramic annular lens with conic conformal dome

    NASA Astrophysics Data System (ADS)

    Huang, Xiao; Bai, Jian

    2015-10-01

    Panoramic annular lens (PAL) is a kind of the specific wide angle lenses which is widely applied in panoramic imaging especially in aerospace field. As we known, to improve the aerodynamic performance of the aircraft, conformal dome, which notably reduces the drag of an aircraft, is also functioning as an optical window for the inbuilt optical system. However, there is still no report of the specific analysis of the imaging performance of PAL with conformal dome, which is imperative in its aerospace-related applications. In this paper, we propose an analysis of the imaging performance of a certain PAL with various conic conformal domes. Working in visible wavelength, the PAL in our work observes 360° surroundings with a large field of view (FOV) ranging from 30° ~105° . Meanwhile, various thicknesses, half-vertex angles, materials of the conic dome and the central distances between the dome and PAL are considered. The imaging performances, mainly indicated by modulation transfer function (MTF) as well as RMS radius of the spot diagram, are systematically compared. It is proved that, on the contrary to the general cases, the dome partly contributes to the imaging performance of the inbuilt PAL. In particular, with a conic conformal dome in material of K9 glass with a half-vertex angle of 25° and a thickness of 6mm, the maximum MTF at 100lp/mm could be improved by 6.68% with nearly no degeneration of the minimum MTF, and the RMS radius could be improved by 14.76% to 19.46% in different FOV. It is worth to note that the PAL is adaptive to panoramic aerospace applications with conic or quasi-conic conformal dome and the co-design of both PAL and the dome is very important.

  11. Magma ascent dynamic through Ti diffusion in magnetites. Application to lava dome-forming eruptions. Implications to lava dome superifical explosivity.

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Morgan, Dan J.

    2016-04-01

    Superficial lava dome explosivity represents a major hazard during lava dome growth. But the origin of this explosive activity remains unclear until recently. By using geochemical (residual water content, silica abundance) and textural (vesicularity, microcristallinity) data, we constrain the occurrence of such hazard to the beginning of the lava dome activity. During the first stages of growth, the lava dome is small enough to develop an impermeable carapace that isolates a less degassed batch of magma inside, thus allowing an internal overpressurization of the volcano (Boudon et al., 2015). This study more precisely details the petrology and the texture of titano-magnetites as archive of magma ascent dynamic within the conduit. Titano-magnetites may exhibit two types of textures: exsolved or "limpid". When they are exsolved, no time constrain may be extracted as they re-equilibrate. On the contrary, when they are unexsolved, major element distribution, in particular Ti, may act as a powerful tool to decipher magma dynamic (differentiation, mixing) and estimate time that corresponds to the magma ascent time. The composition and elemental diffusion profiles are acquired by EPMA, following textural investigations by SEM. The time is then obtained by modelling the profile as a diffusion profile using the intracristalline diffusion coefficients published in literature. We applied this methodology to examples of lava dome superficial explosivity on Montagne Pelée in Martinique (Lesser Antilles Arc), and on Puy Chopine volcano in La Chaine des Puys, (French Massif Central). More precisely, the first phase of the Puy Chopine lava dome growth experienced a superficial explosion, as for Montagne Pelée, the first stages of the 1902 eruption (several superficial explosions occurred) and the 650 y. BP eruption (two superficial explosions destroyed the growing lava dome). We show that, for a single event, the vesiculated, undegassed batch of magma responsible of the

  12. Design and Test of Low-Profile Composite Aerospace Tank Dome

    NASA Technical Reports Server (NTRS)

    Ahmed, R.

    1999-01-01

    This report summarizes the design, analysis, manufacture, and test of a subscale, low-profile composite aerospace dome under internal pressure. A low-profile dome has a radius-to-height ratio greater than the square root of two. This effort demonstrated that a low-profile composite dome with a radius-to-height ratio of three was a feasible design and could adequately withstand the varying stress states resulting from internal pressurization. Test data for strain and displacement versus pressure are provided to validate the design.

  13. A history of semi-active laser dome and window materials

    NASA Astrophysics Data System (ADS)

    Sullivan, Roger M.

    2014-05-01

    Semi-Active Laser (SAL) guidance systems were developed starting in the mid-1960's and today form an important class of precision guided weapons. The laser wavelengths generally fall in the short wave infrared region of the spectrum. Relative to passive, image based, infrared seekers the optical demands placed on the domes or windows of SAL seekers is very modest, allowing the use of low cost, easily manufactured materials, such as polycarbonate. This paper will examine the transition of SAL window and dome science and technology from the laboratory to battlefield, with special emphasis on the story of polycarbonate domes.

  14. Preliminary investigation of gold mineralization in the Pedro Dome-Cleary Summit area, Fairbanks district, Alaska

    USGS Publications Warehouse

    Pilkington, H.D.; Forbes, R.B.; Hawkins, D.B.; Chapman, R.M.; Swainbank, R.C.

    1969-01-01

    Anomalous gold values in mineralized veins and hydrothermally altered quartz-mica schist in the Pedro Dome-Cleary Summit area of the Fairbanks district suggest the presence of numerous small low- to high-grade lodes. Anomalous concentrations of gold were found to exist in the wall rocks adjacent to mineralized veins. In general, the gold concentration gradients in these wall rocks are much too steep to increase appreciably the mineable width of the veins. Anomalous gold values were also detected in bedrock samples taken by means of a power auger on the Murphy Dome Road along the southwest extension of the Pedro Dome-Cleary Summit mineralized belt.

  15. Finite element analysis/hydroburst test data correlation for reverse dome integrated stage application

    NASA Astrophysics Data System (ADS)

    Burson, K. S.; Nowakowski, M.; Tiwari, S.

    1993-02-01

    The U.S. Army's Missile Integrated Stage ('MIST') program has undertaken the development of an advanced strategic interceptor booster's solid-fueled rocket motor. The primary structural components of this booster are a composite case with full-diameter aft closure opening, a titanium reverse dome, and a forced-deflection nozzle plug housing. Attention is presently given to the correlation between the analytical models used in this program and the hydroburst test data obtained for the MIST reverse dome. It is found that the reverse dome exceeded the minimum required burst pressure of 2300 psig.

  16. High-resolution ground layer turbulence from inside the CFHT dome using a lunar scintillometer

    NASA Astrophysics Data System (ADS)

    Pfrommer, T.; Hickson, P.

    2015-04-01

    For ground layer adaptive optics systems, knowledge of the local height- and time- resolved ground layer (GL) turbulence is crucial to link local topography with optical turbulence. Such turbulence profiles have been obtained in the years 2009 and 2010 over 250 hours on Mauna Kea, Hawaii. Results from measurements inside the Canada-France-Hawaii Telescope (CFHT) dome indicate severe degradation of image quality due to a poorly vented dome and thus provide input for dome modifications and design aspects for a new ground layer adaptive optics system. The outside median GL seeing above 6 metres was determined to be 0.48±0.01”.

  17. Amyotrophic Lateral Sclerosis

    MedlinePlus

    Amyotrophic lateral sclerosis (ALS) is a nervous system disease that attacks nerve cells called neurons in your ... people with ALS die from respiratory failure. The disease usually strikes between age 40 and 60. More ...

  18. Amyotrophic Lateral Sclerosis

    MedlinePlus

    Amyotrophic lateral sclerosis (ALS) is a nervous system disease that attacks nerve cells called neurons in your brain and spinal cord. These neurons ... breathing machine can help, but most people with ALS die from respiratory failure. The disease usually strikes ...

  19. Primary Lateral Sclerosis

    MedlinePlus

    ... synthesizers, and wheelchairs ma help some people retain independence.. Speech therapy may be useful for those with ... prevent, and ultimately cure these devastating diseases. NIH Patient Recruitment for Primary Lateral Sclerosis Clinical Trials At ...

  20. Were the world's youngest eclogites (NW D'Entrecasteaux Islands, Papua New Guinea) exhumed in rising gneiss domes or by shear on a deep-seated fault?

    NASA Astrophysics Data System (ADS)

    Little, T. A.; Hacker, B.; Seward, G.

    2008-12-01

    nearly plate-motion parallel. Shear indicators diverge across the dome crests, suggesting of an inward flow of deeper rocks into the dome; or are locally variable, consistent with bulk irrotational deformation. In the gneisses (both core and carapace), conjugate shear-band microstructures and near-orthorhombic quartz LPOs, and back-rotation of mantled porphyroclasts indicate that ductile strain in domes was near plane, but that it was not simple shear (and included significant vertical shortening). The LPO's of the deepest rocks record activity of the high-T prism-[c] and prism- slip systems, whereas the outermost carapace rocks record basal- and rhomb- slip. The data reveal that deformational temperatures increased toward the dome centers, rather than outwardly into the carapace. Quartz LPO's in both dome and carapace are of uniformly modest intensity (~2-3 times random). Feldspar LPO's suggest slip on the (010)[001] or (010)[100] systems, and in some cases a shear sense opposite to quartz. While we cannot resolve how the eclogitic rocks ascended isothermally from the mantle into the lower crust, the simplest model invokes diapiric ascent (with decompression melting), ponding and lateral spreading along the Moho during early Woodlark Basin rifting. Subsequent exhumation of these rocks from the lower crust involved continued upward movement and vertical shortening of the gneisses combined with subhorizontal rift-parallel flow. Finally, normal faulting and minor erosion exhumed these rocks through the ultramafic cover to their present levels.

  1. Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Dittmann, Anna; Schlosser, Elisabeth; Masson-Delmotte, Valérie; Powers, Jordan G.; Manning, Kevin W.; Werner, Martin; Fujita, Koji

    2016-06-01

    A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of δ18O. During the measurement period, 21 synoptically caused precipitation events caused 60 % of the total annual precipitation, whereas the remaining 40 % were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55° S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of δ18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the

  2. Internal Convection on Ceres: A Possible Explanation for Dome Formation

    NASA Astrophysics Data System (ADS)

    Travis, B. J.; Feldman, W. C.; Sizemore, H. G.; O'Brien, D. P.; Sykes, M. V.

    2015-12-01

    Numerical 2-D whole-body simulations of the evolution of Ceres' internal dynamics and thermal structure over its history indicate that hydrothermal activity is very strong throughout the first half of Ceres' history, gradually weakening thereafter, but still active even today (Travis et al, 2015, 46th LPSC). Large-scale upwelling plumes of muddy water extend from the porous, permeable rocky core through an ocean layer and impinge on the bottom of the ice shell. These upwellings are very long-lasting. In addition, small scale, shorter-lived plumes frequently develop on the upper regions of the large plumes. The large-scale plumes occur at roughly +/- 25 o latitude. Recently, 3-D simulations of a sector of Ceres shows that the upwellings are indeed plumes and not sheets. In the 3-D model, plume diameters in the model are as small as 15-20 km in diameter, up to several 10s of km or more. Relating internal dynamics to surface features is challenging. Linkage to mounds seen on the surface may be possible. There appear to be two classes of mounds: Large domes (10s of km diameter) and small (<15 km diameter). Morphological evidence such as embayment relations imply that large mounds may be extrusive. The source of the small domes is less clear. They could be extrusive, or they could be pingo-like structures that form when large areas of melt are extruded or produced by impact, although they are larger than terrestrial or martian structures. Mound heights are typically no more than 1 - 5 km. One mechanism for generation of these mounds suggested by our modeling is extrusion of mud through fractures in the icy crust. Over-pressuring of upwelling plumes at the base of the icy crust from freezing of neighboring downwellings could generate fractures in a frozen mud crust. As plumes and icy crust cool, a significant volume expansion occurs due to freezing of water to ice. This pressurization is not uniform in space; the still-liquid upwellings will experience overpressure in

  3. Pathways of lateral spreading.

    PubMed

    Jacobi, U; Schanzer, S; Weigmann, H-J; Patzelt, A; Vergou, T; Sterry, W; Lademann, J

    2011-01-01

    In the case of topically applied substances, usually both lateral spreading and competitive penetration into the skin occur in parallel. In the present study, the pathways of lateral spreading were studied quantitatively and visually. The local distribution and lateral spreading of the UV filter substance butyl methoxydibenzoylmethane applied in an o/w emulsion was studied on the forearm and the back. The tape stripping procedure was used to determine the recovery rates inside and outside the area of application. The skin characteristics of transepidermal water loss, pH value, hydration of the stratum corneum and sebum rate were determined at both anatomic sites. Photography and laser scanning microscopy were used to visually investigate the lateral spreading of topically applied dyes. On the back, a preferred direction of lateral spreading parallel to the body axis was observed. This result was caused by differences in the network of furrows. The furrows functioned as a pathway for lateral spreading, whereas the follicles formed a reservoir for the topically applied substance. PMID:21455016

  4. Water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine salt domes, northeast Texas salt-dome basin

    USGS Publications Warehouse

    Carr, Jerry E.; Halasz, Stephen J.; Liscum, Fred

    1980-01-01

    This report contains water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine Salt Domes, in the northeast Texas salt-dome basin. Water-quality data were compiled for aquifers in the Wilcox Group, the Carrizo Sand, and the Queen City Sand. The data include analyses for dissolved solids, pH, temperature, hardness, calcium, magnesium, sodium, bicarbonate, chloride, and sulfate. Water-quality and streamflow data were obtained from 63 surface-water sites in the vicinity of the domes. These data include water discharge, specific conductance, pH, water temperature, and dissolved oxygen. Samples were collected at selected sites for analysis of principal and selected minor dissolved constituents.

  5. Long-lasting tectonic activities of the Lepontine Dome. New evidence from low-temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Elfert, Simon; Reiter, Wolfgang; Spiegel, Cornelia

    2013-11-01

    To investigate the Neogene exhumation history of the central European Alps, we apply low-temperature thermochronology in combination with thermal history modelling. Fission track and (U-Th-Sm)/He ages on apatites from the central Lepontine Dome (Ticino, Switzerland) indicate higher exhumation rates in the centre of the dome and rather moderate exhumation at the northern and southern boundaries since Neogene times. We present a model for explaining the latest stage exhumation of the central Lepontine Dome and show that (I) both episodic and continuous exhumations are found on small-scale throughout the Neogene, (II) compressional tectonics control the exhumation until the Late Neogene, (III) the exhumation regime changes between 6 and 4 Ma and (IV) increasing hinterland exhumation rates at the Mio-Pliocene boundary cannot be related to tectonic structures of the dome and they are thus explained by climatic changes.

  6. Rheology of Lava Flows on Europa and the Emergence of Cryovolcanic Domes

    NASA Technical Reports Server (NTRS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Steve M.

    2015-01-01

    There is ample evidence that Europa is currently geologically active. Crater counts suggest that the surface is no more than 90 Myr old, and cryovolcanism may have played a role in resurfacing the satellite in recent geological times. Europa's surface exhibits many putative cryovolcanic features, and previous investigations have suggested that a number of domes imaged by the Galileo spacecraft may be volcanic in origin. Consequently, several Europa domes have been modeled as viscous effusions of cryolava. However, previous models for the formation of silicic domes on the terrestrial planets contain fundamental shortcomings. Many of these shortcomings have been alleviated in our new modeling approach, which warrants a re-assessment of the possibility of cryovolcanic domes on Europa.

  7. Mixing in the dome region of a staged gas turbine combustor

    NASA Astrophysics Data System (ADS)

    Sowa, W. A.; Brady, R. A.; Samuelsen, G. S.

    1992-07-01

    To lower NO(x) emissions from gas-turbine engines the effect of dome design and operational changes on the mixing quality in the fuel-rich region is studied. A statistical analysis is employed to establish the parametric sensitivity in this complex flow. A mixing-effectiveness index is defined and used to optimize the gas-species uniformity and the extent of reaction at the exit plane of the dome. Mixing effectiveness is tied to the fuel and air injection locations, the macroscale structure of the dome aerodynamics, and the level of turbulence. Increases in nozzle/air to fuel ratio, reference velocities, and the dome expansion angle increased the level of turbulence. The optimum configuration featured counter-swirling fuel and air streams and produced a strong torroidal recirculation zone, an effective spray angle of 45 degrees, and azimuthal velocities that decayed to zero inside of two duct diameters. The results underscore the system specific nature of mixing optimization.

  8. Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films.

    PubMed

    Song, Can-Li; Zhang, Hui-Min; Zhong, Yong; Hu, Xiao-Peng; Ji, Shuai-Hua; Wang, Lili; He, Ke; Ma, Xu-Cun; Xue, Qi-Kun

    2016-04-15

    We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-T_{c} dome, whereas in the heavily electron-doped higher-T_{c} dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ∼14  meV, irrespective of film thickness, verifying the higher-T_{c} superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors. PMID:27127981

  9. Tithonium Chasma Domes: A Result of Salt Diapirism by Means of Thin-skinned Extension?

    NASA Astrophysics Data System (ADS)

    Popa, C. I.; Esposito, F.; Ori, G. G.; Marinangeli, L.; Colangeli, L.

    2007-03-01

    The study focuses on the origin and evolution of the salt bearing deposits in Tithonium Chasma. We tested the hypothesis of domes as result of diapirism upraise in thin-skinned extension conditions from a previously deposited salt layer.

  10. Hydrogen-isotope evidence for extrusion mechanisms of the Mount St Helens lava dome

    NASA Technical Reports Server (NTRS)

    Anderson, Steven W.; Fink, Jonathan H.

    1989-01-01

    Hydrogen isotope analyses were used to determine water content and deuterium content for 18 samples of the Mount St Helens dome dacite in an attempt to identify the triggering mechanisms for periodic dome-building eruptions of lava. These isotope data, the first ever collected from an active lava dome, suggest a steady-state process of magma evolution combining crystallization-induced volatile production in the chamber with three different degassing mechanisms: closed-system volatile loss in the magma chamber, open-system volatile release during ascent, and kinetically controlled degassing upon eruption at the surface. The data suggest the future dome-building eruptions may require a new influx of volatile-rich magma into the chamber.

  11. Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films

    NASA Astrophysics Data System (ADS)

    Song, Can-Li; Zhang, Hui-Min; Zhong, Yong; Hu, Xiao-Peng; Ji, Shuai-Hua; Wang, Lili; He, Ke; Ma, Xu-Cun; Xue, Qi-Kun

    2016-04-01

    We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-Tc dome, whereas in the heavily electron-doped higher-Tc dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ˜14 meV , irrespective of film thickness, verifying the higher-Tc superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors.

  12. Blue Mountain and The Gas Rocks: Rear-Arc Dome Clusters on the Alaska Peninsula

    USGS Publications Warehouse

    Hildreth, Wes; Fierstein, Judy; Calvert, Andrew T.

    2007-01-01

    Behind the single-file chain of stratovolcanoes on the Alaska Peninsula, independent rear-arc vents for mafic magmas are uncommon, and for silicic magmas rarer still. We report here the characteristics, compositions, and ages of two andesite-dacite dome clusters and of several nearby basaltic units, all near Becharof Lake and 15 to 20 km behind the volcanic front. Blue Mountain consists of 13 domes (58-68 weight percent SiO2) and The Gas Rocks of three domes (62-64.5 weight percent SiO2) and a mafic cone (52 weight percent SiO2). All 16 domes are amphibole-biotite-plagioclase felsite, and nearly all are phenocryst rich and quartz bearing. Although the two dome clusters are lithologically and chemically similar and only 25 km apart, they differ strikingly in age. The main central dome of Blue Mountain yields an 40Ar/39Ar age of 632?7 ka, and two of the Gas Rocks domes ages of 25.7?1.4 and 23.3?1.2 ka. Both clusters were severely eroded by glaciation; surviving volumes of Blue Mountain domes total ~1 km3, and of the Gas Rocks domes 0.035 km3. Three basaltic vents lie close to The Gas Rocks, another lies just south of Blue Mountain, and a fifth is near the north shore of Becharof Lake. A basaltic andesite vent 6 km southeast of The Gas Rocks appears to be a flank vent of the arc-front center Mount Peulik. The basalt of Ukinrek Maars has been called transitionally alkalic, but all the other basaltic rocks are subalkaline. CO2-rich gas emissions near the eponymous Gas Rocks domes are not related to the 25-ka dacite dome cluster but, rather, to intracrustal degassing of intrusive basalt, one batch of which erupted 3 km away in 1977. The felsic and mafic vents all lie along or near the Bruin Bay Fault where it intersects a broad transverse structural zone marked by topographic, volcanologic, and geophysical discontinuities.

  13. First single star scidar measurements at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Vernin, J.; Chadid, M.; Aristidi, E.; Agabi, A.; Trinquet, H.; van der Swaelmen, M.

    2009-06-01

    Aims: We investigate the first operational running of the Single Star Scidar (SSS instrument) under harsh weather conditions at Dome C in Antarctica and examine continuous monitoring of the optical turbulence and wind speed profiles throughout the atmosphere. Methods: SSS is mainly composed of commercially available light-weight components and a 16 inch telescope installed on an equatorial mount. Scintillation patterns were computed (auto and cross-correlations) in real time and analyzed off line to retrieve continuously vertical profiles of optical turbulence C_N^2(h) and wind speed V(h), from the ground up to 20 km. Results: Using a simulated annealing method, we have analyzed about 6.5 h of observations, revealing the strong surface layer contribution to seeing degradation. SSS results show a good seeing agreement with simultaneous measurements with a Differential Image Motion Monitor, even under very good seeing as low as 0.2 arcsec, as well as wind speed agreement when compared to the weather archive from NOAA. Conclusions: SSS has shown its usefulness for site characterization since it simultaneously measures C_N2 and V profiles, from which most adaptative optic parameters are deduced, such as isoplanatic angle and coherence time of the wavefront. Due to its small size, it is well adapted for site characterization, even when low infrastructure is available.

  14. High precision metrology of domes and aspheric optics

    NASA Astrophysics Data System (ADS)

    Murphy, Paul E.; Fleig, Jon; Forbes, Greg; Tricard, Marc

    2005-05-01

    Many defense systems have a critical need for high-precision, complex optics. However, fabrication of high quality, advanced optics is often seriously hampered by the lack of accurate and affordable metrology. QED's Subaperture Stitching Interferometer (SSI®) provides a breakthrough technology, enabling the automatic capture of precise metrology data for large and/or strongly curved (concave and convex) parts. QED"s SSI complements next-generation finishing technologies, such as Magnetorheological Finishing (MRF®), by extending the effective aperture, accuracy and dynamic range of a phase-shifting interferometer. This workstation performs automated sub-aperture stitching measurements of spheres, flats, and mild aspheres. It combines a six-axis precision stage system, a commercial Fizeau interferometer, and specially developed software that automates measurement design, data acquisition, and the reconstruction of the full-aperture figure error map. Aside from the correction of sub-aperture placement errors (such as tilts, optical power, and registration effects), our software also accounts for reference-wave error, distortion and other aberrations in the interferometer"s imaging optics. The SSI can automatically measure the full aperture of high numerical aperture surfaces (such as domes) to interferometric accuracy. The SSI extends the usability of a phase measuring interferometer and allows users with minimal training to produce full-aperture measurements of otherwise untestable parts. Work continues to extend this technology to measure aspheric shapes without the use of dedicated null optics. This SSI technology will be described, sample measurement results shown, and various manufacturing applications discussed.

  15. Hard transparent domes and windows from magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    DiGiovanni, Anthony A.; Fehrenbacher, Larry; Roy, Don W.

    2005-05-01

    Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the everincreasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands. Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology - to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

  16. Time domain astronomy from Dome C: results from ASTEP

    NASA Astrophysics Data System (ADS)

    Rivet, J.-P.; Abe, L.; Agabi, K.; Barbieri, M.; Crouzet, N.; Goncalves, I.; Guillot, T.; Mekarnia, D.; Szulagyi, J.; Daban, J.-B.; Gouvret, C.; Fantei-Caujolle, Y.; Schmider, F.-X.; Furth, T.; Erikson, A.; Rauer, H.; Fressin, F.; Alapini, A.; Pont, F.; Aigrain, S.

    2013-01-01

    ASTEP (Antarctic Search for Transiting Exo Planets) is a research program funded mainly by French ANR grants and by the French Polar Institute (IPEV), dedicated to the photometric study of exoplanetary transits from Antarctica. The preliminary ``pathfinder'' instrument ASTEP-South is described in another communication (Crouzet et al., these proceedings), and we focus in this presentation on the main instrument of the ASTEP program: ``ASTEP-400'', a 40 cm robotized and thermally-controlled photometric telescope operated from the French-Italian Concordia station (Dome C, Antarctica). ASTEP-400 has been installed at Concordia during the 2009-2010 summer campaign. Since, the telescope has been operated in nominal conditions during 2010 and 2011 winters, and the 2012 winterover is presently in progress. Data from the first two winter campaigns are available and processed. We give a description of the ASTEP-400 telescope from the mechanical, optical and thermal point of view. Control and software issues are also addressed. We end with a discussion of some astronomical results obtained with ASTEP-400.

  17. Three-dimensional representations of salt-dome margins at four active strategic petroleum reserve sites.

    SciTech Connect

    Rautman, Christopher Arthur; Stein, Joshua S.

    2003-01-01

    Existing paper-based site characterization models of salt domes at the four active U.S. Strategic Petroleum Reserve sites have been converted to digital format and visualized using modern computer software. The four sites are the Bayou Choctaw dome in Iberville Parish, Louisiana; the Big Hill dome in Jefferson County, Texas; the Bryan Mound dome in Brazoria County, Texas; and the West Hackberry dome in Cameron Parish, Louisiana. A new modeling algorithm has been developed to overcome limitations of many standard geological modeling software packages in order to deal with structurally overhanging salt margins that are typical of many salt domes. This algorithm, and the implementing computer program, make use of the existing interpretive modeling conducted manually using professional geological judgement and presented in two dimensions in the original site characterization reports as structure contour maps on the top of salt. The algorithm makes use of concepts of finite-element meshes of general engineering usage. Although the specific implementation of the algorithm described in this report and the resulting output files are tailored to the modeling and visualization software used to construct the figures contained herein, the algorithm itself is generic and other implementations and output formats are possible. The graphical visualizations of the salt domes at the four Strategic Petroleum Reserve sites are believed to be major improvements over the previously available two-dimensional representations of the domes via conventional geologic drawings (cross sections and contour maps). Additionally, the numerical mesh files produced by this modeling activity are available for import into and display by other software routines. The mesh data are not explicitly tabulated in this report; however an electronic version in simple ASCII format is included on a PC-based compact disk.

  18. Why there was a useful plausible analogy between geodesic domes and spherical viruses.

    PubMed

    Morgan, Gregory J

    2006-01-01

    In 1962, Donald Caspar and Aaron Klug published their classic theory of virus structure. They developed their theory with an explicit analogy between spherical viruses and Buckminster Fuller's geodesic domes. In this paper, I use the spherical virus-geodesic dome case to develop an account of analogy and deductive analogical inference based on the notion of an isomorphism. I also consider under what conditions there is a good reason to claim an experimentally untested analogy is plausible. PMID:17702504

  19. Technologies for precision manufacture of current and future windows and domes

    NASA Astrophysics Data System (ADS)

    Hallock, Bob; Shorey, Aric

    2009-05-01

    The final finish and characterization of windows and domes presents a number of challenges in achieving desired precision with acceptable cost and schedule. This becomes more difficult with advanced materials and as window and dome shapes and requirements become more complex, including acute angle corners, transmitted wavefront specifications, aspheric geometries and trending toward conformal surfaces. Magnetorheological Finishing (MRF®) and Magnetorheological Jet (MR Jet®), along with metrology provided by Sub-aperture Stitching Interferometry (SSI®) have several unique attributes that provide them advantages in enhancing fabrication of current and next generation windows and domes. The advantages that MRF brings to the precision finishing of a wide range of shapes such as flats, spheres (including hemispheres), cylinders, aspheres and even freeform optics, has been well documented. Recent advancements include the ability to finish freeform shapes up to 2-meters in size as well as progress in finishing challenging IR materials. Due to its shear-based removal mechanism in contrast to the pressure-based process of other techniques, edges are not typically rolled, in particular on parts with acute angle corners. MR Jet provides additional benefits, particularly in the finishing of the inside of steep concave domes and other irregular shapes. The ability of MR Jet to correct the figure of conformal domes deterministically and to high precision has been demonstrated. Combining these technologies with metrology techniques, such as SSI provides a solution for finishing current and future windows and domes in a reliable, deterministic and cost-effective way. The ability to use the SSI to characterize a range of shapes such as domes and aspheres, as well as progress in using MRF and MR Jet for finishing conventional and conformal windows and domes with increasing size and complexity of design will be presented.

  20. Laterally closed lattice homomorphisms

    NASA Astrophysics Data System (ADS)

    Toumi, Mohamed Ali; Toumi, Nedra

    2006-12-01

    Let A and B be two Archimedean vector lattices and let be a lattice homomorphism. We call that T is laterally closed if T(D) is a maximal orthogonal system in the band generated by T(A) in B, for each maximal orthogonal system D of A. In this paper we prove that any laterally closed lattice homomorphism T of an Archimedean vector lattice A with universal completion Au into a universally complete vector lattice B can be extended to a lattice homomorphism of Au into B, which is an improvement of a result of M. Duhoux and M. Meyer [M. Duhoux and M. Meyer, Extended orthomorphisms and lateral completion of Archimedean Riesz spaces, Ann. Soc. Sci. Bruxelles 98 (1984) 3-18], who established it for the order continuous lattice homomorphism case. Moreover, if in addition Au and B are with point separating order duals (Au)' and B' respectively, then the laterally closedness property becomes a necessary and sufficient condition for any lattice homomorphism to have a similar extension to the whole Au. As an application, we give a new representation theorem for laterally closed d-algebras from which we infer the existence of d-algebra multiplications on the universal completions of d-algebras.

  1. Laterally bendable belt conveyor

    DOEpatents

    Peterson, William J.

    1985-01-01

    An endless, laterally flexible and bendable belt conveyor particularly adapted for coal mining applications in facilitating the transport of the extracted coal up- or downslope and around corners in a continuous manner is disclosed. The conveying means includes a flat rubber belt reinforced along the middle portion thereof along which the major portion of the belt tension is directed so as to cause rotation of the tubular shaped belt when trammed around lateral turns thus preventing excessive belt bulging distortion between adjacent belt supports which would inhibit belt transport. Pretension induced into the fabric reinforced flat rubber belt by conventional belt take-up means supports the load conveyed when the belt conveyor is making lateral turns. The carrying and return portions of the belt are supported and formed into a tubular shape by a plurality of shapers positioned along its length. Each shaper is supported from above by a monorail and includes clusters of idler rollers which support the belt. Additional cluster rollers in each shaper permit the belt supporting roller clusters to rotate in response to the belt's operating tension imposed upon the cluster rollers by induced lateral belt friction forces. The freely rotating roller clusters thus permit the belt to twist on lateral curves without damage to itself while precluding escape of the conveyed material by effectively enclosing it in the tube-shaped, inner belt transport length.

  2. Reconnaissance and deep-drill site selection on Taylor Dome, Antarctica

    NASA Technical Reports Server (NTRS)

    Grootes, Pieter M.; Waddington, Edwin D.

    1993-01-01

    Taylor Dome is a small ice dome near the head of Taylor Valley, Southern Victoria Land. The location of the dome, just west of the Transantarctic Mountains, is expected to make the composition of the accumulating snow sensitive to changes in the extent of the Ross Ice Shelf. Thus, it is linked to the discharge of the West Antarctic Ice Sheet but protected against direct influences of glacial-interglacial sea-level rise. The record of past climatic and environmental changes in the ice provides a valuable complement to the radiocarbon-dated proxy record of climate derived from perched deltas, strandlines, and moraines that have been obtained in the nearby Dry Valleys. We carried out a reconnaissance of the Taylor Dome area over the past two field seasons to determine the most favorable location to obtain a deep core to bedrock. A stake network has been established with an 80-km line roughly along the crest of Taylor Dome, and 40-km lines parallel to it and offset by 10 km. These lines have been surveyed 1990/91, and the positions of 9 grid points have been determined with geoceivers. A higher density stake network was placed and surveyed around the most likely drill area in the second year. Ground-based radar soundings in both years provided details on bedrock topography and internal layering of the ice in the drill area. An airborne radar survey in January 1992, completed the radar coverage of the Taylor Dome field area.

  3. A user`s perspective on aluminum dome roofs for aboveground tanks

    SciTech Connect

    Myers, P.E.

    1995-12-31

    There is a trend in the petroleum industry to install aluminum dome roofs on storage tanks of all kinds. Although most dome roofs have been installed on floating roof tanks, there is a trend to install them on fixed roof tanks as well, substituting the familiar shallow fixed cone roof with a geodesic dome. In part, this trend has been caused by EPA requirements causing a greater number of closed tanks to be vented to vapor recovery or vapor destruction systems. Both the aluminum roof manufacturing community and the user have moved into a whole new set of problems associated with the change in dome roof applications from atmospheric to those requiring internal pressure. New problems are just now being dealt with and solved because cost factors tend to make the aluminum dome an economic solution for many cases where sealed tank systems must be used. Because of the increased numbers of geodesic domes as either an alternative to a fixed cone roof tank or as a way to convert an external floating roof tank to an internal floating roof tank or as their potential to serve as tools in the environmental arena, it is the intent of this paper to examine them from the user`s perspective. In addition, some areas of research that should resolve some reliability and safety issues are presented for consideration and research by not only manufacturers but the users as well.

  4. Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae)

    PubMed Central

    Peterson, Joseph E.; Dischler, Collin; Longrich, Nicholas R.

    2013-01-01

    Pachycephalosaurids are small, herbivorous dinosaurs with domed skulls formed by massive thickening of the cranial roof. The function of the dome has been a focus of debate: the dome has variously been interpreted as the product of sexual selection, as an adaptation for species recognition, or as a weapon employed in intraspecific combat, where it was used in butting matches as in extant ungulates. This last hypothesis is supported by the recent identification of cranial pathologies in pachycephalosaurids, which appear to represent infections resulting from trauma. However, the frequency and distribution of pathologies have not been studied in a systematic fashion. Here, we show that pachycephalosaurids are characterized by a remarkably high incidence of cranial injury, where 22% of specimens have lesions on the dome. Frequency of injury shows no significant difference between different genera, but flat-headed morphs (here interpreted as juveniles or females) lack lesions. Mapping of injuries onto a digitial pachycephalosaurid skull shows that although lesions are distributed across the dome, they cluster near the apex, which is consistent with the hypothesis that the dome functioned for intraspecific butting matches. PMID:23874691

  5. Performance analysis of the retractable dome for the Chinese Large Telescope.

    PubMed

    Nian, Pan; Wen-Li, Ma

    2015-10-01

    In order to quantitatively assess the influence of the retractable dome on the observational performance of the 4-m Chinese Large Telescope (CLT), an integrated analysis method based on computational fluid dynamics (CFD) and sub-harmonic phase screen is proposed in this paper. The pressure, the temperature, and the speed of air surrounding the retractable dome are attained by CFD simulations, and then the fluctuation of refractive index of air is calculated. Based on sub-harmonic phase screen algorithm, three kinds of performance evaluation parameters are presented: irradiance, phase of the target, and Full Width Half Maximum (FWHM). The wind tunnel tests (WT) with a 1:120 scaled model of the retractable dome for the CLT are conducted to verify the calculated precision of the CFD. The results show that the fluctuation of air refractive index surrounding the CLT is mainly caused by the inhomogeneous distribution of temperature and speed, and with the help of pier's height the impact of inhomogeneous air temperature from the ground layer on the fluctuation of air refractive index can be effectively decreased. Furthermore, the lower of the air speed is, the better performance of the retractable dome will be, and when the speed of air is less than 5m/s, the dome seeing induced by the retractable dome on the observational wave front is less than 0.13 arcsec. PMID:26480059

  6. A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development

    PubMed Central

    Thoresen, Daniel T.; Miao, Lingling; Williams, Jonathan S.; Wang, Chaochen; Atit, Radhika P.; Wong, Sunny Y.

    2016-01-01

    The Sonic hedgehog (Shh) signaling pathway regulates developmental, homeostatic, and repair processes throughout the body. In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. The developmental signaling requirements for touch dome specification are largely unknown. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. Moreover, Merkel cells formed in Fgf20 mutant skin where primary hair formation was defective but Shh production was preserved. Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors. Shh signaling often demonstrates pleiotropic effects within a structure over time. In postnatal skin, Shh is known to regulate the self-renewal, but not the differentiation, of touch dome stem cells. Our findings relate the varied effects of Shh in the touch dome to the ligand source, with locally produced Shh acting as a morphogen essential for lineage specification during development and neural Shh regulating postnatal touch dome stem cell maintenance. PMID:27414798

  7. Features of Bayou Choctaw SPR caverns and internal structure of the salt dome.

    SciTech Connect

    Munson, Darrell E.

    2007-07-01

    The intent of this study is to examine the internal structure of the Bayou Choctaw salt dome utilizing the information obtained from graphical representations of sonar survey data of the internal cavern surfaces. Many of the Bayou Choctaw caverns have been abandoned. Some existing caverns were purchased by the Strategic Petroleum Reserve (SPR) program and have rather convoluted histories and complex cavern geometries. In fact, these caverns are typically poorly documented and are not particularly constructive to this study. Only two Bayou Choctaw caverns, 101 and 102, which were constructed using well-controlled solutioning methods, are well documented. One of these was constructed by the SPR for their use while the other was constructed and traded for another existing cavern. Consequently, compared to the SPR caverns of the West Hackberry and Big Hill domes, it is more difficult to obtain a general impression of the stratigraphy of the dome. Indeed, caverns of Bayou Choctaw show features significantly different than those encountered in the other two SPR facilities. In the number of abandoned caverns, and some of those existing caverns purchased by the SPR, extremely irregular solutioning has occurred. The two SPR constructed caverns suggest that some sections of the caverns may have undergone very regular solutioning to form uniform cylindrical shapes. Although it is not usually productive to speculate, some suggestions that point to the behavior of the Bayou Choctaw dome are examined. Also the primary differences in the Bayou Choctaw dome and the other SPR domes are noted.

  8. A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development.

    PubMed

    Xiao, Ying; Thoresen, Daniel T; Miao, Lingling; Williams, Jonathan S; Wang, Chaochen; Atit, Radhika P; Wong, Sunny Y; Brownell, Isaac

    2016-07-01

    The Sonic hedgehog (Shh) signaling pathway regulates developmental, homeostatic, and repair processes throughout the body. In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. The developmental signaling requirements for touch dome specification are largely unknown. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. Moreover, Merkel cells formed in Fgf20 mutant skin where primary hair formation was defective but Shh production was preserved. Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors. Shh signaling often demonstrates pleiotropic effects within a structure over time. In postnatal skin, Shh is known to regulate the self-renewal, but not the differentiation, of touch dome stem cells. Our findings relate the varied effects of Shh in the touch dome to the ligand source, with locally produced Shh acting as a morphogen essential for lineage specification during development and neural Shh regulating postnatal touch dome stem cell maintenance. PMID:27414798

  9. Diaphragm dome surface segmentation in CT data sets: a 3D active appearance model approach

    NASA Astrophysics Data System (ADS)

    Beichel, Reinhard; Gotschuli, Georg; Sorantin, Erich; Leberl, Franz W.; Sonka, Milan

    2002-05-01

    Knowledge about the location of the diaphragm dome surface, which separates the lungs and the heart from the abdominal cavity, is of vital importance for applications like automated segmentation of adjacent organs (e.g., liver) or functional analysis of the respiratory cycle. We present a new 3D Active Appearance Model (AAM) approach to segmentation of the top layer of the diaphragm dome. The 3D AAM consists of three parts: a 2D closed curve (reference curve), an elevation image and texture layers. The first two parts combined represent 3D shape information and the third part image intensity of the diaphragm dome and the surrounding layers. Differences in height between dome voxels and a reference plane are stored in the elevation image. The reference curve is generated by a parallel projection of the diaphragm dome outline in the axial direction. Landmark point placement is only done on the (2D) reference curve, which can be seen as the bounding curve of the elevation image. Matching is based on a gradient-descent optimization process and uses image intensity appearance around the actual dome shape. Results achieved in 60 computer generated phantom data sets show a high degree of accuracy (positioning error -0.07+/-1.29 mm). Validation using real CT data sets yielded a positioning error of -0.16+/-2.95 mm. Additional training and testing on in-vivo CT image data is ongoing.

  10. Final report on decommissioning boreholes and wellsite restoration, Gulf Coast Interior Salt Domes of Mississippi

    SciTech Connect

    Not Available

    1989-04-01

    In 1978, eight salt domes in Texas, Louisiana, and Mississippi were identified for study as potential locations for a nuclear waste repository as part of the National Waste Terminal Storage (NWTS) program. Three domes were selected in Mississippi for ``area characterization`` phase study as follows: Lampton Dome near Columbia, Cypress Creek Dome near New Augusta, and Richton Dome near Richton. The purpose of the studies was to acquire geologic and geohydrologic information from shallow and deep drilling investigations to enable selection of sites suitable for more intensive study. Eleven deep well sites were selected for multiple-well installations to acquire information on the lithologic and hydraulic properties of regional aquifers. In 1986, the Gulf Coast salt domes were eliminated from further consideration for repository development by the selection of three candidate sites in other regions of the country. In 1987, well plugging and restoration of these deferred sites became a closeout activity. The primary objectives of this activity are to plug and abandon all wells and boreholes in accordance with state regulations, restore all drilling sites to as near original condition as feasible, and convey to landowners any wells on their property that they choose to maintain. This report describes the activities undertaken to accomplish these objectives, as outlines in Activity Plan 1--2, ``Activity Plan for Well Plugging and Site Restoration of Test Hole Sites in Mississippi.``

  11. Percutaneous Ethanol Injection via an Artificially Induced Right Hydrothorax for Hepatocellular Carcinoma in the Hepatic Dome

    SciTech Connect

    Kume, Akimichi Nimura, Yuji; Kamiya, Junichi; Nagino, Masato; Kito, Yasushi

    2003-11-15

    To evaluate the efficacy of sonographically (US) guided percutaneous ethanol injection (PEI) via an artificially induced right hydrothorax (transthoracic PEI) to treat US-invisible hepatocellular carcinoma (HCC) in the hepatic dome. Five cirrhotic patients with US-invisible HCC in the hepatic dome, who were poor surgical candidates, underwent transthoracic PEI. An artificial right hydrothorax was created by instilling 500 ml saline, and absolute ethanol was injected transhydrothoracically into the hepatic dome lesion under local anesthesia. The success and complications were assessed radiologically. The patients were followed up serologically and radiologically for 12-44 (mean 28.4) months. Twenty-five hydrothoraces were induced. All hydrothoraces enabled US visualization of the entire hepatic dome. Eight of the nine small lesions were treated successfully by the treatment. Two of the three local recurrences were eradicated by repeat transthoracic PEI. One large lesion was treated by a combination of transthoracic and regular PEI. The only complication was one clinically insignificant pneumothorax. Induction of a right hydrothorax is feasible and safe. The hydrothorax enables US visualization of the entire hepatic dome and permits US-guided PEI for HCC in the hepatic dome that otherwise would not be possible.

  12. Time-delayed source and interferometric measurement of domes and windows

    NASA Astrophysics Data System (ADS)

    Kuhn, William P.; Dubin, Matthew

    2007-04-01

    Measurement of the transmitted wavefront of domes and windows is a long-standing problem. One may use a large return sphere and measure the interference cavity without the dome present and again with the dome present. The difference between the two measurements is a double-pass measurement of the transmitted wavefront of the dome. Even so, the long coherence length of the source results in many extraneous fringe patterns. Windows may be tested by using a collimated source and return flat. A time-delayed source (TDS) having a short-coherence length is used to obtain a single interference pattern due only to interference of light reflected by the two surfaces of a dome or window. Standard phase shifting algorithms may be used with the TDS to measure the optical thickness of a dome or window without errors due to multiple reflections. Since most of the interferometer is common-path, environmental sensitivity is reduced and alignment is straightforward compared to typical interferometers. Finally, since there is no reference surface, stitching of sub-aperture measurements is simplified.

  13. Costa Rica's Chain of laterally collapsed volcanoes.

    NASA Astrophysics Data System (ADS)

    Duarte, E.; Fernandez, E.

    2007-05-01

    From the NW extreme to the SW end of Costa Rica's volcanic backbone, a number of laterally collapsed volcanoes can be observed. Due to several factors, attention has been given to active volcanoes disregarding the importance of collapsed features in terms of assessing volcanic hazards for future generations around inhabited volcanoes. In several cases the typical horseshoe shape amphitheater-like depression can be easily observed. In other cases due to erosion, vegetation, topography, seismic activity or drastic weather such characteristics are not easily recognized. In the order mentioned above appear: Orosi-Cacao, Miravalles, Platanar, Congo, Von Frantzius, Cacho Negro and Turrialba volcanoes. Due to limited studies on these structures it is unknown if sector collapse occurred in one or several phases. Furthermore, in the few studied cases no evidence has been found to relate collapses to actual eruptive episodes. Detailed studies on the deposits and materials composing dome-like shapes will shed light on unsolved questions about petrological and chemical composition. Volume, form and distance traveled by deposits are part of the questions surrounding most of these collapsed volcanoes. Although most of these mentioned structures are extinct, at least Irazú volcano (active volcano) has faced partial lateral collapses recently. It did presented strombolian activity in the early 60s. Collapse scars show on the NW flank show important mass removal in historic and prehistoric times. Moreover, in 1994 a minor hydrothermal explosion provoked the weakening of a deeply altered wall that holds a crater lake (150m diameter, 2.6x106 ). A poster will depict images of the collapsed volcanoes named above with mayor descriptive characteristics. It will also focus on the importance of deeper studies to assess the collapse potential of Irazú volcano with related consequences. Finally, this initiative will invite researchers interested in such topic to join future studies in

  14. Mechanisms for rainfall-concurrent lava dome collapses at Soufrière Hills Volcano, 2000 2002

    NASA Astrophysics Data System (ADS)

    Taron, Joshua; Elsworth, Derek; Thompson, Glenn; Voight, Barry

    2007-02-01

    The evolution of rainfall-concurrent dome collapses at Soufrière Hills volcano is followed using a limit equilibrium model for rain infiltration into a hot lava carapace. Magma infusing into the dome both supplies heat and builds the slopes. The dome rocks are cooled by episodic rain infiltration and climatic cooling. Rainfall infiltrates fractures that develop in the hot dome carapace, occludes the void space, and staunches effusive gas flow. Gases may originate from juvenile de-gassing of the dome interior, or result from the vaporization of infiltrating water. Gas pressures build in cracks blocked-off by rain, and may destabilize the dome. The effects of dome growth, heating by magma infusion, and cooling by rain infiltration and climatic influences, are combined to follow the growth of the dome towards ultimate collapse. For a fixed suite of strength and transport parameters, and for measured magma influx rates, the evolution of instability may be followed. The evolving factor of safety tracks the observed March 2000 and July 2001 rainfall-concurrent collapse events, which evolve over months. However, the resolution of the hindcast is unable to discriminate between the effects of closely-timed rainfall events (order of hours). The heightening of the dome is shown to exert the principal influence on average slopes and in the evolution of instability. Collapse removes the over-heightened dome, and temporarily restores stability.

  15. Infrared lateral shearing interferometers

    NASA Astrophysics Data System (ADS)

    Kwon, O.

    1980-04-01

    Recently IR interferometry has received much attention for its special capabilities of testing IR materials, diamond-turned metal mirrors, deep aspherics, unpolished rough surface optics, and other unconventional optics. A CW CO2 laser is used as a coherent light source at 10.6 microns, and germanium and zinc selenide optics are used for lenses and beam splitters. A pyroelectric vidicon (PEV) detects the modulated interference pattern through a TV monitor and video recorder-player. This paper presents three methods of IR lateral shear interferometry using (1) a germanium plane-parallel plate, (2) a Ronchi ruling, and (3) a double-grating lateral shear interferometer.

  16. Lateral Thinking of Prospective Teachers

    ERIC Educational Resources Information Center

    Lawrence, A. S. Arul; Xavier, S. Amaladoss

    2013-01-01

    Edward de Bono who invented the term "lateral thinking" in 1967 is the pioneer of lateral thinking. Lateral thinking is concerned with the generation of new ideas. Liberation from old ideas and the stimulation of new ones are twin aspects of lateral thinking. Lateral thinking is a creative skills from which all people can benefit…

  17. Growth of intra-caldera lava domes controlled by various modes of caldera collapse, the Štiavnica volcano-plutonic complex, Western Carpathians

    NASA Astrophysics Data System (ADS)

    Tomek, Filip; Žák, Jiří; Holub, František V.; Chlupáčová, Marta; Verner, Kryštof

    2016-02-01

    The Štiavnica volcano-plutonic complex is an erosional relic of Miocene caldera-stratovolcano in the Western Carpathians. The complex exposes a vertical section from the volcano basement through subvolcanic intrusions and a ring fault to volcanic edifice, comprising mostly andesitic lava flows and domes. This paper examines internal structure, magnetic fabric as derived from the anisotropy of magnetic susceptibility (AMS), and emplacement dynamics of three intra-caldera andesite domes (referred to as Domes 1-3) located near the presumed ring fault. Magnetic fabrics, carried by multi-domain titanomagnetite and titanomaghemite, are interpreted as recording various mechanisms of dome growth controlled by active caldera collapse. Dome 1 is explained as a lava coulée, fed by conduits located along the ring fault, with a long lava outflow down the sloping caldera floor. Dome 2 represents an elongated, ring fault-parallel dome wherein the lava flowed a short distance over a flat floor. Dome 3 is interpreted as a composite dome fed from multiple linear fissures opened at a high angle to the ring fault. Subsequently, the dome was intruded by ring fault-parallel dikes that may have potentially fed overlying, now largely eroded lava domes and flows. Finally, we suggest that all domes formed during collapse of the Štiavnica caldera and the various mechanisms of their growth reflect different stages of the caldera evolution from piston (Dome 2) through trap-door (Dome 1) to piecemeal (Dome 3).

  18. In Situ Production of Methyl Chloride in Siple Dome and WAIS Divide Ice Cores from Antarctica

    NASA Astrophysics Data System (ADS)

    Frausto-Vicencio, I.; Verhulst, K. R.; Aydin, M.; Saltzman, E. S.

    2013-12-01

    Methyl chloride (CH3Cl) is a naturally-occurring halocarbon with a global mean abundance of 550 pmol mol-1 and a lifetime of about 1 year. It constitutes about 16% of the total chlorine burden in the stratosphere. The sources of methyl chloride are mainly natural and include tropical vegetation, oceans and biomass burning. Oxidation with the hydroxyl radical is the primary removal mechanism with additional loss via microbial degradation in soils and in the oceans. Previous measurements suggest ice cores from cold Antarctic sites (Dome Fuji, South Pole, Taylor Dome) preserve a record of atmospheric CH3Cl variability during the Holocene (Saito et al., 2007; Williams et al., 2007; Verhulst et al., in review). However, measurements at Siple Dome displayed evidence of in situ enhancement (Saltzman et al., 2009). This study involves new CH3Cl measurements in 117 ice core samples from the West Antarctic Ice Sheet Divide (WAIS-D) 06A ice core. Measurements from the Holocene are compared with earlier CH3Cl measurements from Taylor Dome and Siple Dome. In Late Holocene ice (5-0 ky BP), the WAIS-D and Siple Dome show evidence of in situ CH3Cl enrichment. The mean level and scatter are both larger than in Taylor Dome ice of the same age. The in situ enrichment is not time or depth-dependent. Interestingly, for most of the Early Holocene (11-5 ky BP), Siple Dome and WAIS-D exhibit less scatter and are closer to the Taylor Dome ice core data. In situ CH3Cl production may be purely chemical or involve biological reactions. Here, we investigate whether the excess CH3Cl in the Siple Dome and the WAIS-D ice cores can be explained by differences in ice chemistry between the various Antarctic sites. The results of this research will help establish the causes of CH3Cl production in ice cores and provide a basis to assess the possibility of studying long-term atmospheric CH3Cl variability using ice core data.

  19. 238U-230Th crystallization ages for the oldest domes of the Mono Craters, eastern California

    NASA Astrophysics Data System (ADS)

    Marcaida, M.; Vazquez, J. A.

    2014-12-01

    The Mono Craters volcanic chain is one of the youngest areas of rhyolitic volcanism in the Mono Lake-Long Valley region of eastern California. Located just south of Mono Lake, the Mono Craters comprise at least 28 individual domes and flows (numbered 3-30, north to south); however, the timing and frequency of eruptions remain poorly resolved. The earliest signs of volcanic activity are preserved as numerous tephra layers (Ashes 1-19, top to bottom) in the late Pleistocene Wilson Creek formation of ancestral Mono Lake, which indicate that rhyolitic volcanism from Mono Craters began by at least ca. 62 ka [1]. Although the current chronology indicates that most of the Mono Craters are younger than ca. 20 ka [2-4], similar compositions of titanomagnetite from both pumice and lava potentially correlate several Wilson Creek tephras to porphyritic biotite-bearing domes 11, 24, and 19 of the Mono Craters [5], suggesting that multiple domes in the Mono Craters chain reflect volcanism older than ca. 20 ka. Ash 3 is correlated to dome 11 based on similar ca. 20 ka ages and titanomagnetite compositions [6]. More recently, we performed ion microprobe 238U-230Th dating of unpolished rims of allanite and zircon from domes 24 and 19, yielding isochron ages of ca. 38 ka and ca. 42 ka, respectively. The age of dome 24 is consistent with the ca. 38 ka age of its potential correlative tephra layers [1, 5], indicating that dome 24 is likely the extrusive equivalent of Ashes 9-10. Dome 19 has titanomagnetite crystals with similar bimodal chemistry to titanomagnetites from Ash 15 [5]. The age of dome 19 is indistinguishable from the 238U-230Th age of Ash 15 [1], which erupted during a prominent geomagnetic excursion, originally designated as the "Mono Lake" excursion. Combining geochronological and titanomagnetite compositional data confirms that Ash 15 and its extrusive equivalent, dome 19, erupted during the Laschamp excursion. [1] Vazquez, J.A. and Lidzbarski, M.I. (2012) EPSL 357

  20. Topaz rhyolites of Nathrop, Colorado: Lava domes or rheomorphic flows?

    NASA Astrophysics Data System (ADS)

    Hernandez, B. M.; Panter, K. S.; Van Der Voo, R.

    2013-12-01

    Deposits of topaz-bearing rhyolite at Ruby and Sugarloaf Mountains in central Colorado are considered to be remnants of lava domes. The deposits are part of the Late Eocene-Oligocene Central Colorado Volcanic Field [1] that lies along the eastern margin of the Arkansas Graben of the Rio Grande Rift. Topaz-bearing rhyolite lava domes and flows have been identified elsewhere in Colorado and the western U.S., but an assortment of geomorphological, lithostratigraphical, and textural features of Ruby and Sugarloaf Mountains call into question their strict classification as such. Alternatively, the lava flows may be interpreted as rheomorphic ignimbrites. The volcanic deposits encompass a sequence of steeply (~70°) west-dipping units that form two N-S elongated edifices ~0.5 km long and a few hundred meters high. Their common lithostratigraphy from bottom to top is tuff breccia, vitrophyre, and flow-banded rhyolite. The tuff breccia includes large (up to ~1 m) pumice blocks and lithics that vary from nearly absent to moderately abundant (10-20%). At Sugarloaf lithics include rare cobble-sized clasts of granite, but the majority consists of flow-banded rhyolite. The tuff breccia grades normally upward into the vitrophyre with increased welding and a eutaxitic fabric defined by fiamme with increasing aspect ratios. Lithics are abundant in the vitrophyre at Sugarloaf but are rare or absent in the vitrophyre at Ruby Mountain. The transition from the vitrophyre to the flow-banded rhyolite is abrupt (<1 m) at both locations, though the lower rhyolite is less competent. The flow-banded rhyolite at Sugarloaf is crystal-rich (up to 50%), containing plagioclase, sanidine, smoky quartz, and biotite, while at Ruby the rhyolite is relatively crystal poor (2-3%) and biotite is absent. Pumiceous zones and lithophysae occur within the rhyolite at both locations. Zones of auto-brecciation are often associated with convoluted flow banding, especially along a vertical contact with

  1. Late Miocene uplift and doming of Madagascar: topographic implications

    NASA Astrophysics Data System (ADS)

    Delaunay, Antoine; Robin, Cecile; Guillocheau, François; Dall'Asta, Massimo; Calves, Gérôme

    2016-04-01

    and (3) a major stepping of dated planation surfaces. (3) The end result of this uplift is a convex up shape pattern for the end Cretaceous surface weathered during Eocene times, creating the present-day dome morphology (with a central plateau) of Madagascar. (4) The amplitude of this uplift can be estimated based on the present-day elevation of Late Eocene lagoonal sediments located 100 km north-east of Toliara and now at an elevation of 900m. If the absolute sea level was around 50 m (Miller et al., 2005) above present-day sea level during Late Eocene times, this means a surface uplift of around 850 m. (5) The mechanism of this uplift has to explain a very long wavelength deformation (x1000 km) necessary due to mantle dynamics. The relationships with the other East African domes (Ethiopia, East Africa, South Africa) are discussed. This study was founded by TOTAL and IFREMER in the frame of the research project PAMELA (Passive Margin Exploration Laboratories).

  2. Public Education and Outreach Through Full-Dome Video Technology

    NASA Astrophysics Data System (ADS)

    Pollock, John

    2009-03-01

    My long-term goal is to enhance public understanding of complex systems that can be best demonstrated through richly detailed computer graphic animation displayed with full-dome video technology. My current focus is on health science advances that focus on regenerative medicine, which helps the body heal itself. Such topics facilitate science learning and health literacy. My team develops multi-media presentations that bring the scientific and medical advances to the public through immersive high-definition video animation. Implicit in treating the topics of regenerative medicine will be the need to address stem cell biology. The topics are clarified and presented from a platform of facts and balanced ethical consideration. The production process includes communicating scientific information about the excitement and importance of stem cell research. Principles of function are emphasized over specific facts or terminology by focusing on a limited, but fundamental set of concepts. To achieve this, visually rich, biologically accurate 3D computer graphic environments are created to illustrate the cells, tissues and organs of interest. A suite of films are produced, and evaluated in pre- post-surveys assessing attitudes, knowledge and learning. Each film uses engaging interactive demonstrations to illustrate biological functions, the things that go wrong due to disease and disability, and the remedy provided by regenerative medicine. While the images are rich and detailed, the language is accessible and appropriate to the audience. The digital, high-definition video is also re-edited for presentation in other ``flat screen'' formats, increasing our distribution potential. Show content is also presented in an interactive web space (www.sepa.duq.edu) with complementing teacher resource guides and student workbooks and companion video games.

  3. Eclipsing Binaries From the CSTAR Project at Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Yang, Ming; Zhang, Hui; Wang, Songhu; Zhou, Ji-Lin; Zhou, Xu; Wang, Lingzhi; Wang, Lifan; Wittenmyer, R. A.; Liu, Hui-Gen; Meng, Zeyang; Ashley, M. C. B.; Storey, J. W. V.; Bayliss, D.; Tinney, Chris; Wang, Ying; Wu, Donghong; Liang, Ensi; Yu, Zhouyi; Fan, Zhou; Feng, Long-Long; Gong, Xuefei; Lawrence, J. S.; Liu, Qiang; Luong-Van, D. M.; Ma, Jun; Wu, Zhenyu; Yan, Jun; Yang, Huigen; Yang, Ji; Yuan, Xiangyan; Zhang, Tianmeng; Zhu, Zhenxi; Zou, Hu

    2015-04-01

    The Chinese Small Telescope ARray (CSTAR) has observed an area around the Celestial South Pole at Dome A since 2008. About 20,000 light curves in the i band were obtained during the observation season lasting from 2008 March to July. The photometric precision achieves about 4 mmag at i = 7.5 and 20 mmag at i = 12 within a 30 s exposure time. These light curves are analyzed using Lomb-Scargle, Phase Dispersion Minimization, and Box Least Squares methods to search for periodic signals. False positives may appear as a variable signature caused by contaminating stars and the observation mode of CSTAR. Therefore, the period and position of each variable candidate are checked to eliminate false positives. Eclipsing binaries are removed by visual inspection, frequency spectrum analysis, and a locally linear embedding technique. We identify 53 eclipsing binaries in the field of view of CSTAR, containing 24 detached binaries, 8 semi-detached binaries, 18 contact binaries, and 3 ellipsoidal variables. To derive the parameters of these binaries, we use the Eclipsing Binaries via Artificial Intelligence method. The primary and secondary eclipse timing variations (ETVs) for semi-detached and contact systems are analyzed. Correlated primary and secondary ETVs confirmed by false alarm tests may indicate an unseen perturbing companion. Through ETV analysis, we identify two triple systems (CSTAR J084612.64-883342.9 and CSTAR J220502.55-895206.7). The orbital parameters of the third body in CSTAR J220502.55-895206.7 are derived using a simple dynamical model.

  4. Transiting planet candidates with ASTEP 400 at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Mékarnia, D.; Guillot, T.; Rivet, J.-P.; Schmider, F.-X.; Abe, L.; Gonçalves, I.; Agabi, A.; Crouzet, N.; Fruth, T.; Barbieri, M.; Bayliss, D. D. R.; Zhou, G.; Aristidi, E.; Szulagyi, J.; Daban, J.-B.; Fanteï-Caujolle, Y.; Gouvret, C.; Erikson, A.; Rauer, H.; Bouchy, F.; Gerakis, J.; Bouchez, G.

    2016-08-01

    ASTEP 400, the main instrument of the ASTEP (Antarctica Search for Transiting ExoPlanets) programme, is a 40-cm telescope, designed to withstand the harsh conditions in Antarctica, achieving a photometric accuracy of a fraction of milli-magnitude on hourly timescales for planet-hosting southern bright (R˜12 mag) stars. We review the performances of this instrument, describe its operating conditions, and present results from the analysis of observations obtained during its first three years (2010-2012) of operation, before its repatriation in 2014. During this time, we observed a total of 22 stellar fields (1° × 1° FoV). Each field, in which we measured stars up to magnitude R=18 mag, was observed continuously during ˜7 to ˜30 days. More than 200 000 frames were recorded and 310 000 stars processed, using an implementation of the optimal image subtraction (OIS) photometry algorithm. We found 43 planetary transit candidates. Twenty of these candidates were observed using spectroscopic follow-ups including four targets classified as good planet candidates. Our results demonstrate that accurate near-continuous photometric observations are achievable from the Concordia station at Dome C in Antarctica, even if we were not able to reach the nominal photometric precision of the instrument. We conducted a correlation analysis between the RMS noise and a large number of external parameters and found that source of the ˜1 mmag correlated noise is not obvious and does not depend on a single parameter. However, our analysis provided some hints and guidance to increase the photometric accuracy of the instrument. These improvements should equip any future telescope operating in Antarctica.

  5. Low-temperature thermochronologic constraints on cooling and exhumation trends along conjugate margins, within core complexes and eclogite-bearing gneiss domes of the Woodlark rift system of eastern Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Fitzgerald, P. G.; Baldwin, S.; Bermudez, M. A.; Miller, S. R.; Webb, L. E.; Little, T.

    2012-12-01

    Ma) and have mean lengths that are typically longer (11-13 μm). The CTLD's indicate cooling, then residence in an apatite partial annealing zone (PAZ) and significant partial annealing followed by rapid cooling. Inverse thermal models do not constrain well the timing of initial cooling into the PAZ, but core zone samples from higher elevations cooled earlier. Later thermal annealing was initiated ca 2-4 Ma (core earlier than shear zone) coincident with granodiorite intrusion, with subsequent very rapid cooling initiated ~0.5 Ma. This thermochronologic dataset indicates a complex thermal history and is being used to constrain thermokinematic models (PeCube) in order to test the relative roles of buoyancy and normal faulting during exhumation of eclogite-bearing domes within the Woodlark rift system.

  6. The giant Shakhdara migmatitic gneiss dome, Pamir, India-Asia collision zone: 1. Geometry and kinematics

    NASA Astrophysics Data System (ADS)

    Stübner, Konstanze; Ratschbacher, Lothar; Rutte, Daniel; Stanek, Klaus; Minaev, Vladislav; Wiesinger, Maria; Gloaguen, Richard

    2013-07-01

    Cenozoic gneiss domes comprise one third of the surface exposure of the Pamir and provide a window into the deep crustal processes of the India-Asia collision. The largest of these are the doubly vergent, composite Shakhdara-Alichur domes of the southwestern Pamir, Tajikistan, and Afghanistan; they are separated by a low-strain horst. Top-to-SSE, noncoaxial pervasive flow over the up to 4 km thick South Pamir shear zone exhumed crust from 30-40 km depth in the ~250 × 80 km Shakhdara dome; the top-to-NNE Alichur shear zone exposed upper crustal rocks in the ~125 × 25 km Alichur dome. The Gunt shear zone bounds the Shakhdara dome in the north and records alternations of normal shear and dextral transpression; it contributed little to bulk exhumation. Footwall exhumation along two low-angle, normal-sense detachments resulted in up to 90 km syn-orogenic ~N-S extension. Extension in the southwestern Pamir opposes shortening in a fold-thrust belt north of the domes and in particular in the Tajik depression, where an evaporitic décollement facilitated upper crustal shortening. Gravitational collapse of the Pamir-plateau margin drove core-complex formation in the southwestern Pamir and shortening of the weak foreland adjacent to the plateau. Overall, this geometry defines a "vertical extrusion" scenario, comprising frontal and basal underthrusting and thickening, and hanging gravitationally driven normal shear. In contrast to the Himalayan vertical extrusion scenario, erosion in the Pamir was minor, preserving most of the extruded deep crust, including the top of the South Pamir shear zone at peak elevations throughout the dome.

  7. Impact of hydrothermal alteration on lava dome stability: a numerical modelling approach

    NASA Astrophysics Data System (ADS)

    Detienne, Marie; Delmelle, Pierre

    2016-04-01

    Lava domes are a common feature of many volcanoes worldwide. They represent a serious volcanic hazard as they are prone to repeated collapses, generating devastating debris avalanches and pyroclastic flows. While it has long been known that hydrothermal alteration degrades rock properties and weakens rock mass cohesion and strength, there is still little quantitative information allowing the description of this effect and its consequences for assessing the stability of a volcanic rock mass such as a lava dome. In this study, we use the finite difference numerical model FLAC 3D to investigate the impact of hydrothermal alteration on the stability of a volcanic dome lying on a flat surface. Different hydrothermal alteration distributions were tested to encompass the variability observed in natural lava domes. Rock shear strength parameters (minimum, maximum and mean cohesion "c" and friction angle "φ" values) representative of various degrees of hydrothermal rock alteration were used in the simulations. The model predicts that reduction of the basement rock's shear strength decreases the factor of safety significantly. A similar result is found by increasing the vertical and horizontal extension of hydrothermal alteration in the basement rocks. In addition, pervasive hydrothermal alteration within the lava dome is predicted to exert a strong negative influence on the factor of safety. Through reduction of rock porosity and permeability, hydrothermal alteration may also affect pore fluid pressure within a lava dome. The results of new FLAC 3D runs which simulate the effect of hydrothermal alteration-induced pore pressure changes on lava dome stability will be presented.

  8. Flexure and faulting of sedimentary host rocks during growth of igneous domes, Henry Mountains, Utah

    USGS Publications Warehouse

    Jackson, M.D.; Pollard, D.D.

    1990-01-01

    A sequence of sedimentary rocks about 4 km thick was bent, stretched and uplifted during the growth of three igneous domes in the southern Henry Mountains. Mount Holmes, Mount Ellsworth and Mount Hillers are all about 12 km in diameter, but the amplitudes of their domes are about 1.2, 1.85 and 3.0 km, respectively. These mountains record successive stages in the inflation of near-surface diorite intrusions that are probably laccolithic in origin. The host rocks deformed along networks of outcrop-scale faults, or deformation bands, marked by crushed grains, consolidation of the porous sandstone and small displacements of sedimentary beds. Zones of deformation bands oriented parallel to the beds and formation contacts subdivided the overburden into thin mechanical layers that slipped over one another during doming. Measurements of outcrop-scale fault populations at the three mountains reveal a network of faults that strikes at high angles to sedimentary beds which themselves strike tangentially about the domes. These faults have normal and reverse components of slip that accommodated bending and stretching strains within the strata. An early stage of this deformation is displayed at Mount Holmes, where states of stress computed from three fault samples correlate with the theoretical distribution of stresses resulting from bending of thin, circular, elastic plates. Field observations and analysis of frictional driving stresses acting on horizontal planes above an opening-mode dislocation, as well as the paleostress analysis of faulting, indicate that bedding-plane slip and layer flexure were important components of the early deformation. As the amplitude of doming increased, radial and circumferential stretching of the strata and rotation of the older faults in the steepening limbs of the domes increased the complexity of the fault patterns. Steeply-dipping, map-scale faults with dip-slip displacements indicate a late-stage jostling of major blocks over the central

  9. Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation

    PubMed Central

    Schott, Ryan K.; Evans, David C.; Goodwin, Mark B.; Horner, John R.; Brown, Caleb Marshall; Longrich, Nicholas R.

    2011-01-01

    Historically, studies of pachycephalosaurs have recognized plesiomorphically flat-headed taxa and apomorphically domed taxa. More recently, it has been suggested that the expression of the frontoparietal dome is ontogenetic and derived from a flat-headed juvenile morphology. However, strong evidence to support this hypothesis has been lacking. Here we test this hypothesis in a large, stratigraphically constrained sample of specimens assigned to Stegoceras validum, the best known pachycephalosaur, using multiple independent lines of evidence including conserved morphology of ornamentation, landmark-based allometric analyses of frontoparietal shape, and cranial bone histology. New specimens show that the diagnostic ornamentation of the parietosquamosal bar is conserved throughout the size range of the sample, which links flat-headed specimens to domed S. validum. High-resolution CT scans of three frontoparietals reveal that vascularity decreases with size and document a pattern that is consistent with previously proposed histological changes during growth. Furthermore, aspects of dome shape and size are strongly correlated and indicative of ontogenetic growth. These results are complementary and strongly support the hypothesis that the sample represents a growth series of a single taxon. Cranial dome growth is positively allometric, proceeds from a flat-headed to a domed state, and confirms the synonymy of Ornatotholus browni as a juvenile Stegoceras. This dataset serves as the first detailed model of growth and variation in a pachycephalosaur. Flat-headed juveniles possess three characters (externally open cranial sutures, tuberculate dorsal surface texture, and open supratemporal fenestrae) that are reduced or eliminated during ontogeny. These characters also occur in putative flat-headed taxa, suggesting that they may also represent juveniles of domed taxa. However, open cranial sutures and supratemporal fenestrae are plesiomorphic within Ornithischia, and thus

  10. [Adult lateral meniscus].

    PubMed

    Beaufils, P; Hardy, P; Chambat, P; Clavert, P; Djian, P; Frank, A; Hulet, C; Potel, J-F; Verdonk, R

    2006-09-01

    Meniscal lesion does not mean meniscectomy and this is particularly true for the lateral meniscus. The reputation of mildness of the meniscectomy is usurped. The rate of joint space narrowing after lateral meniscectomy is of 40% at a follow-up of 13 years compared to 28% for the medial meniscus (symposium SFA 1996). Several arguments explain those results: biomechanical: the lateral meniscus contributes to the congruence; particularly the lateral meniscus is the zone where antero-posterior translational during knee flexion is 12 mm. The pejorative effects of lateral meniscectomy have conducted, more though to the medial meniscus, to the concept of meniscal economy. Lateral meniscectomy must be as partial as possible. Particularly, a discoid meniscus presenting a complete tear should be treated by a meniscoplasty in order to shape the meniscus in a more anatomic form than a total meniscectomy. Lateral meniscectomy is indicated in complex or horizontal cleavage, symptomatic, on stable knees. A particular case is the cyst of the lateral meniscus. It is a cystic subcutaneous formation, usual consequence of a horizontal cleaved meniscus of which the particularity is that it opens besides the articulation. The strategy must not consist in the isolated treatment of the cyst. This pathology should be addressed by an arthroscopic meniscectomy reaching the meniscosynovial junction at the level of the cyst. Meniscal repair must be proposed every time if possible. Criteria of reparability are better studied on MRI. Preoperatively MRI is the first choice radiological exam. Two essential indications can be held back: the vertical peripheral longitudinal lesion is on the non-vascularized area, and the horizontal cleaving of the junior athlete (if the cleaving remains purely intra meniscal). Meniscal repair is highly performed when the meniscal tear is associated to a rupture of the ACL (simultaneous reconstruction of the LCA). Postoperative outcome is different of that of a

  11. Coeval doming and stretching of the eastern end of the India-Asia collision zone - Namche Barwa Syntaxis, Tibet

    NASA Astrophysics Data System (ADS)

    Scharf, A.; Handy, M. R.; Crupi, P.

    2013-12-01

    The eastern part of the India-Asia collisional zone is marked by a N-plunging, non-cylindrical fold, the Namche Barwa Syntaxis (NBS) with a topographic relief of >7 km. The NBS exposes rapidly exhuming Indian- and parts of the overlying Asian crust. Structural, paleomagnetic and GPS studies reveal clockwise rotation of the crust and mantle around a steep axis located close to the mutual borders of India, China and Myanmar (e.g. Sol et al. 2007; Liebke et al. 2011). Teleseismic tomography beneath the NBS reveals 170 km thick Indian lithosphere that is not connected with a slab anomaly to the N beneath the Tibetan Plateau, but that appears laterally continuous with north and E-dipping slab anomalies along strike of the Himalayan chain, respectively, to the W and E of the NBS (Zhang et al. 2012). A closer look at available structural, geochronological, and petrological data reveals Late Oligocene, N-directed subduction of Indian continental lithosphere followed by two stages of pronounced exhumation in Late Oligocene to Miocene time and unroofing in Pliocene time. This history is intimately related to the mantle structure imaged beneath the NBS. Timing of subduction is not constraint in the NBS, but Booth et al. (2009) suggest Palaeocene to Eocene ages for subduction-related plutonism along strike of the India/Asia suture zone. High-pressure (HP) conditions in granulites in the western NBS at 25-24 Ma preceded decompression beginning no later than 18 Ma (Su et al. 2012). These granulites are separated from granulites without HP assemblages by a moderately W-dipping mylonitic fault, indicating that this fault was a thrust (Xu et al. 2012) which accommodated S to E directed exhumation of the HP granulites in its hangingwall. This first stage of exhumation coincided with peak temperatures at ~10 Ma (Booth et al. 2009). The granulites and their intervening thrust fault are folded by the NBS (Geng et al. 2006), indicating that this first stage of exhumation preceded doming

  12. Lateral flow assays

    PubMed Central

    Koczula, Katarzyna M.

    2016-01-01

    Lateral flow assays (LFAs) are the technology behind low-cost, simple, rapid and portable detection devices popular in biomedicine, agriculture, food and environmental sciences. This review presents an overview of the principle of the method and the critical components of the assay, focusing on lateral flow immunoassays. This type of assay has recently attracted considerable interest because of its potential to provide instantaneous diagnosis directly to patients. The range and interpretation of results and parameters used for evaluation of the assay will also be discussed. The main advantages and disadvantages of LFAs will be summarized and relevant future improvements to testing devices and strategies will be proposed. Finally, the major recent advances and future diagnostic applications in the LFA field will be explored. PMID:27365041

  13. Conjugal amyotrophic lateral sclerosis

    PubMed Central

    Dewitt, John D.; Kwon, Julia; Burton, Rebecca

    2012-01-01

    Amyotrophic lateral sclerosis (ALS) is a disease characterized by progressive degeneration of motor neurons in the motor cortex, brainstem, and spinal cord. The incidence of sporadic ALS is 1.5 to 2.7 in 100,000, and the prevalence is 5.2 to 6.0 in 100,000. Conjugal ALS is even rarer than sporadic ALS. We report a case of conjugal ALS encountered in our outpatient neurology clinic. PMID:22275781

  14. Petrology and emplacement dynamics of the intrusive and extrusive rhyolites of Obsidian Dome Inyo Craters volcanic chain, eastern California

    SciTech Connect

    Vogel, T.A.; Schuraytz, B.C.; Eichelberger, J.C.; Stockman, H.W.; Westrich, H.R.; Younker, L.W.; Horkowitz, J.P.

    1989-01-01

    Drilling at Obsidian Dome has provided continuous core samples of the distal and proximal portions of Obsidian Dome, its conduit, and an associated feeder dike. Both the dome and conduit are chemically and mineralogically zoned and consist of a finely porphyritic, high-Ba, low-silica rhyolite occurring in the basal portion of the dome and margins of the conduit and a finely porphyritic, low-Ba, higher silica rhyolite in the upper portion of the dome and center of the conduit. The high-Ba rhyolite contains two distinct phenocrysts assemblages with two distinct compositions, and represents mingled magmas. The low-Ba rhyolite in the dome and conduit contains significantly fewer disequilibrium phenocrysts and is only slightly mingled. The dike, sampled at 600 m depth, as well as a related tephra fall from Obsidian Dome vent, are entirely low-Ba rhyolite that contain no evidence of magma mingling. End members of the mingled magma, calculated using two different methods, are a 63 percent silica end member, and a silicic end member identical in composition to the dike and tephra fall from Obsidian Dome vent. This silicic end member was the first magma emplaced in the dike, and comprised much or all of the first magma vented to the surface during formation of the Obsidian Dome vent when eruption rates were high. Magma mingling of mafic and rhyolite magmas occurred during formation of the conduit. 59 refs., 16 figs., 10 tabs.

  15. Observations of dome growth and lava flow development as determined by pixel offsets in photographs of the 2006 Merapi eruption

    NASA Astrophysics Data System (ADS)

    Walter, Thomas R.; Ratdomopurbo, Antonius; Subandriyo, Subandriyo; Aisyah, Nurnaning; Sri Brotopusptio, Kirbani; Salzer, Jacqueline; Lühr, Birger

    2013-04-01

    Viscous domes of explosive volcanoes commonly form by extrusion and are destroyed by collapses of the talus region. Although the growth and development of silicic domes and the associated flow and collapse mechanisms are of vital importance for understanding the occurrence and scale of pyroclastic flows, quantitative measurements of dome deformations are limited. We report on a sequence of photographs taken of a growing and deforming dome. Photographs of Mount Merapi in 2006, taken from similar camera positions, allow a digital image correlation algorithm to be applied to detect and explore the temporal evolution of pixel offsets. The results suggest that the dome underwent deformation in two regions between September and October 2006: (i) dome growth and spreading at the volcano summit and (ii) coulée flow through a narrow canyon. The latter is associated with strain localization and flow acceleration, which indicates that the displacements and flow velocities at silicic domes are governed by the topographic structure into which the flows develop. The downslope motion of the distal parts of the flow and apron slumps continue during episodes of dome extrusion by gravitational spreading. An analysis of the 2006 Merapi dome and coulée displacement also provides insights into processes of the newly established southerly eruption direction, which also controlled the 2010 eruption.

  16. Hemispheric lateralization in reasoning.

    PubMed

    Turner, Benjamin O; Marinsek, Nicole; Ryhal, Emily; Miller, Michael B

    2015-11-01

    A growing body of evidence suggests that reasoning in humans relies on a number of related processes whose neural loci are largely lateralized to one hemisphere or the other. A recent review of this evidence concluded that the patterns of lateralization observed are organized according to two complementary tendencies. The left hemisphere attempts to reduce uncertainty by drawing inferences or creating explanations, even at the cost of ignoring conflicting evidence or generating implausible explanations. Conversely, the right hemisphere aims to reduce conflict by rejecting or refining explanations that are no longer tenable in the face of new evidence. In healthy adults, the hemispheres work together to achieve a balance between certainty and consistency, and a wealth of neuropsychological research supports the notion that upsetting this balance results in various failures in reasoning, including delusions. However, support for this model from the neuroimaging literature is mixed. Here, we examine the evidence for this framework from multiple research domains, including an activation likelihood estimation analysis of functional magnetic resonance imaging studies of reasoning. Our results suggest a need to either revise this model as it applies to healthy adults or to develop better tools for assessing lateralization in these individuals. PMID:26426534

  17. Fragmentation and Cataclasis of Lava Domes: Field Evidence of Conduit-Margin Faulting and Cryptodome Unloading at Mount St. Helens

    NASA Astrophysics Data System (ADS)

    Pallister, J. S.; Hagstrum, J.; Cashman, K.; Tuffen, H.

    2007-12-01

    for many of the earthquakes at MSH. Additionally, grain-flow textures in the bounding ultracataclasite fault zones suggest that observed periods of aseismic extrusion were accommodated by creep on these faults. In contrast, Pine Creek age (~2.5 ka) dome dacite exposed over a large area at the mouth of the MSH crater is pervasively fractured over paleo-depths of >300m. Like the dacite of the current eruption, this rock has a microcrystalline groundmass, indicative of extensive shallow crystallization and subsurface solidification. However, the extent and character of fragmentation is unrelated to shear along conduit margins. Instead, a multi- stage history of brittle deformation consists of: 1) early 10-20cm thick subhorizontal zones of sandy cataclasite that repeat at intervals of meters to tens of meters within pervasively shattered dacite, 2) early cross-cutting high- angle faults with slickensides and <1mm pseudotachylite seams, and 3) later cross-cutting planar faults. We suggest that early cataclasis was produced by rapid unloading of the still-hot dome during a Pine-Creek age sector collapse and that the early high-angle faults represent boundaries of large mega-blocks that had begun to detach within the source dome. Together with mapped Pine Creek avalanche deposts nearby (Hausback, 2000), these features suggest that a transition from avalanche to still-intact Pine-Creek age cryptodome is exposed in the mouth of the MSH crater.

  18. Structure and Kinematics of a Complex Crater: Upheaval Dome, Southeast, Utah

    NASA Technical Reports Server (NTRS)

    Kriens, B. J.; Herkenhoff, K. E.; Shoemaker, E. M.

    1997-01-01

    Two vastly different phenomena, extraterrestrial impact and salt diapirism, have been proposed for the origin of Upheaval Dome. Upheaval Dome is a about 2.5-km-diameter structural dome surrounded by a 5-km-diameter ring structural depression, which is in turn flanked by extensive, nearly flat-lying Colorado Plateau strata. Seismic refraction data and geologic mapping indicate that the dome originated by the collapse of a transient cavity formed by impact; data also show that rising salt has had a negligible influence on dome development. Evidence for this includes several factors: (1) a rare lag deposit of impactite is present; (2) fan-tailed fracture surfaces (shatter surfaces) and a few shattercones are present; (3) the top of the underlying salt horizon is at least 500 m below the center of the dome, with no exposures of salt in the dome to support the possibility that a salt diapir has ascended through it; (4) sedimentary strata in the center are significantly imbricated by top-to-the-center thrust faulting and are complexly folded; (5) top-to-the-center low-angle normal faults are found at the perimeter of the structure; and (6) clastic dikes are widespread. The scarcity of melt rocks and shock fabrics is attributed to approximately 0.5 km of erosion; the structures of the dome reflect processes of complex crater development at a depth of about 0.5 km below the crater floor. Based on mapping and kinematic analysis, we infer that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, largely resulted from this motion. In addition, we have detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding in the perimeter of the structure. Collectively, the observed deformation accounts for the creation of both the central uplift and the encircling ring syncline.

  19. Alteration minerals on the Santiaguito lava dome complex, Santa María volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Ball, J. L.; Calder, E. S.; Giese, R.

    2010-12-01

    Santiaguito is a relatively young complex of four lava domes located at the foot of the Santa María volcano in Guatemala. The domes have been erupting intermittently since 1922, and have shown various degrees of hydrothermal activity throughout their development. Hydrothermal systems in older volcanic edifices (Casita in Nicaragua, La Soufriere of Guadeloupe) are known to weaken rock and promote collapses, but their effects and development in young lava domes is less well constrained. Santiaguito has experienced several relatively small dome collapses (≦ 3 million m3) in the past, but it is unclear what role hydrothermal processes have played in these collapses. Currently, low-temperature active fumaroles are present on the domes, indicating the presence of a hydrothermal system. Samples of unconsolidated ash and sediment and rock chips were collected from the interior of fumaroles on the El Brujo lava dome to determine if hydrothermal alteration minerals were present. X-ray diffraction (XRD) was used to identify the presence of clay minerals in the powdered samples. Additional semi-quantitative identification was obtained using backscattered electron images (BSE) collected with a scanning electron microscope (SEM). Both analyses were performed at the University at Buffalo. Preliminary XRD analyses were unable to conclusively detect alteration minerals in powdered samples; however, BSE images of the same samples appeared to show alteration minerals (montmorillonite, saponite) adhering to individual ash grains. Further SEM analyses are being conducted on thin sections of the rock chips to determine if alteration minerals are present in dome rock as well as in the unconsolidated material. Development of alteration minerals on the relatively young (~50-90 year old) Santiaguito lava domes may indicate an increased risk for alteration-driven instabilities and collapses. Altered volcanic rocks are less competent, have lower shear strength and are more susceptible to

  20. New approaches to inferences for steep-sided domes on Venus

    NASA Astrophysics Data System (ADS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Stephen M.; Stofan, Ellen R.

    2016-06-01

    New mathematical approaches for the relaxation and emplacement of viscous lava domes are presented and applied to steep-sided domes on Venus. A similarity solution approach is applied to the governing equation for fluid flow in a cylindrical geometry for two distinct scenarios. In the first scenario, dome relaxation is explored assuming a constant volume of fluid (i.e. lava) has been rapidly emplaced onto the surface. Cooling of lava is represented by a time-variable viscosity and singularities inherent in previous models for dome relaxation have been eliminated. At the onset of relaxation, bulk dynamic viscosities lie in the range between 1010-1016 Pa s, consistent with basaltic-andesite to rhyolitic compositions. Plausible relaxation times range from 5 to 5000 years, depending on initial lava viscosity. The first scenario, however, is only valid during the final stages of dome relaxation and does not consider the time taken for lava to be extruded onto the surface. In the second scenario, emplacement and growth of a steep-sided dome is considered when the volume of lava on the surface increases over time (i.e. time-variable volume approach). The volumetric flowrate may depend on an arbitrary power of the dome thickness, thus embracing Newtonian as well as other rheologies for describing terrestrial and planetary mass flows. The approach can be used to distinguish between basic flowrate models for fluid emplacement. The formalism results in radial expansion of a dome proportional to t1/2, consistent with the diffusive nature of the governing equation. The flow at the front is shown to thicken as the front advances for a constant rate of lava supply. Emplacement times are intimately correlated with the bulk rheology. Comparison of the theoretical profiles with the shape of a typical dome on Venus indicates that a Newtonian bulk rheology is most appropriate, consistent with prior studies. However, results here suggest a bulk dynamic viscosity of 1012-1013 Pa s and

  1. Long-period earthquakes and co-eruptive dome inflation seen with particle image velocimetry.

    PubMed

    Johnson, Jeffrey B; Lees, Jonathan M; Gerst, Alexander; Sahagian, Dork; Varley, Nick

    2008-11-20

    Dome growth and explosive degassing are fundamental processes in the cycle of continental arc volcanism. Because both processes generate seismic energy, geophysical field studies of volcanic processes are often grounded in the interpretation of volcanic earthquakes. Although previous seismic studies have provided important constraints on volcano dynamics, such inversion results do not uniquely constrain magma source dimension and material properties. Here we report combined optical geodetic and seismic observations that robustly constrain the sources of long-period volcanic earthquakes coincident with frequent explosive eruptions at the volcano Santiaguito, in Guatemala. The acceleration of dome deformation, extracted from high-resolution optical image processing, is shown to be associated with recorded long-period seismic sources and the frequency content of seismic signals measured across a broadband network. These earthquake sources are observed as abrupt subvertical surface displacements of the dome, in which 20-50-cm uplift originates at the central vent and propagates at approximately 50 m s(-1) towards the 200-m-diameter periphery. Episodic shifts of the 20-80-m thick dome induce peak forces greater than 10(9) N and reflect surface manifestations of the volcanic long-period earthquakes, a broad class of volcano seismic activity that is poorly understood and observed at many volcanic centres worldwide. On the basis of these observations, the abrupt mass shift of solidified domes, conduit magma or magma pads may play a part in generating long-period earthquakes at silicic volcanic systems. PMID:19020619

  2. Detailed studies of selected, well-exposed fracture zones in the Adirondack Mountains dome, New York

    SciTech Connect

    Wiener, R.W.; Isachsen, Y.W.

    1987-01-01

    The Adirondack Mountains constitute a relatively young (Mesozoic, Cenozoic) dome on the craton. The dome is undergoing contemporary uplift, based on geodetic releveling, and is seismically active. The breached dome provides a very large window through Paleozoic cover and thus permits ground study of the fracture systems that characterize the seismogenic basement and influence the patterns of brittle deformation that are found in overlying Paleozoic rocks of the platform. The predominant fracture zones are linear valleys that trend NNE to NE, parallel to the long axis of the dome. The 36 field studies of the lineament segments discussed in this report suggest that the prominent NE to NNE fracture systems in the eastern Adirondacks are dominantly high angle faults down-stepped to the east, whereas those in the central Adirondacks are dominantly zero-displacement crackle zones. The origin of these features is related to the rapid uplift of the Adirondack dome. Similar features can be expected to be found in other areas of domal uplift or rapid regional uplift.

  3. Conceptual design of a 5-m terahertz telescope at Dome A

    NASA Astrophysics Data System (ADS)

    Yang, Dehua; Wang, Hai; Zhang, Yong; Chen, Yi; Zhou, Guohua; Cheng, Jingquan; Li, Guoping

    2012-09-01

    A 5-meter terahertz telescope is proposed by the Chinese Center for Antarctic Astronomy (CCAA) for the East Antarctica site of the Dome A plateau. The Dome A 5-m terahertz telescope (DATE 5) will be operated at sub-millimeter waveband taking the unique advantage of the transparent atmospheric windows between 200 and 350 μm wavelengths at Dome A. A preliminary design has been conducted according to the given technical requirements and the special environmental conditions at Dome A. A symmetric R-C Cassegrain optical system is designed for the telescope, with a primary f-ratio of 0.4 and a wide field of view of 10 arcmin. The magnification of the sub-reflector is 9.4, leading to the final focal ratio of 3.76 and the focus 0.2 m below the vertex of the primary reflector. To ensure surface accuracy of the reflectors precise as small as 10 um RMS, we consider using Carbon Fiber Reinforced Plastics (CFRP) to build the backup structure (BUS) of the primary reflector and the sub-reflector itself. An alt-azimuthal mounting is adopted and a tall base structure beneath the telescope is set up to lift the telescope above the low atmosphere turbulent layer. All the mechanics, as well as control electronics, are strictly designed to fit the lower temperature operation in the Dome A environment. This paper is to generally present the mentioned systematic optical, structural and electronic design of the DATE 5 telescope.

  4. Crocodile-inspired dome-shaped pressure receptors for passive hydrodynamic sensing.

    PubMed

    Kanhere, Elgar; Wang, Nan; Kottapalli, Ajay Giri Prakash; Asadnia, Mohsen; Subramaniam, Vignesh; Miao, Jianmin; Triantafyllou, Michael

    2016-01-01

    Passive mechanosensing is an energy-efficient and effective recourse for autonomous underwater vehicles (AUVs) for perceiving their surroundings. The passive sensory organs of aquatic animals have provided inspiration to biomimetic researchers for developing underwater passive sensing systems for AUVs. This work is inspired by the 'integumentary sensory organs' (ISOs) which are dispersed on the skin of crocodiles and are equipped with slowly adapting (SA) and rapidly adapting (RA) receptors. ISOs assist crocodiles in locating the origin of a disturbance, both on the water surface and under water, thereby enabling them to hunt prey even in a dark environment and turbid waters. In this study, we construct SA dome receptors embedded with microelectromechanical systems (MEMS) piezoresistive sensors to measure the steady-state pressures imparted by flows and RA dome receptors embedded with MEMS piezoelectric sensors to detect oscillatory pressures in water. Experimental results manifest the ability of SA and RA dome receptors to sense the direction of steady-state flows and oscillatory disturbances, respectively. As a proof of concept, the SA domes are tested on the hull of a kayak under various pressure variations owing to different types of movements of the hull. Our results indicate that the dome receptors are capable of discerning the angle of attack and speed of the flow. PMID:27545614

  5. Siple Dome Ice Cores: Implications for West Antarctic Climate and ENSO Events

    NASA Astrophysics Data System (ADS)

    Jones, T.; White, J. W.

    2010-12-01

    Ice cores at Siple Dome, West Antarctic receive the majority of their precipitation from Pacific Ocean moisture sources. Pacific climate patterns, particularly the El Niño-Southern Oscillation, affect the local temperature, atmospheric circulation, and snow accumulation at Siple Dome, as well as isotopic signals (∂D and ∂18O). We examined isotopes, accumulation and borehole temperatures from a number of shallow ice cores distributed 60km across the Dome. The data reveal a strong microclimate heavily influenced by South Pacific climate and the location of the Amundsen Sea Low Pressure Area. The Dome Summit and Pacific Flank respond to La Niña conditions by warming, increasing isotope ratios and increased snowfall. The Inland Flank responds to El Niño conditions and cold interior air masses by cooling, decreasing isotope ratios and decreased snowfall. Spectral analysis of the ∂D record shows a distinct shift in ocean-atmosphere climate dynamics in the late 19th century, where scattered bi-decadal to decadal periodicities change to include more intensely grouped and decreasing periodicities as low as two years at the end of the 20th century. Similar changes are seen in South Pacific coral isotope records. Map of Siple Dome including local grid locations for the seven shallow cores B-H. Note the Pacific Ocean and Inland (South Pole) oriented cores. [Modified after Bertler et al., 2006].

  6. Analysis of thermal shock strength and quality factor with infrared optical domes

    NASA Astrophysics Data System (ADS)

    Gao, Youtang; Liu, Shuo; Xu, Yuan; Chang, Benkang

    2012-11-01

    The development of infrared optical materials is always closely related to the research and exploration of material science. The infrared optical domes bears shock and produces stress when the infrared optical domes mounted on the missile moving at a high speed is shocked by high temperature. According to principle of energy balance in fracture mechanics proposed by D.P.H. Hasselman, the author analyzed the crack extension and derived the relationship between Infrared optical materials window model and thermal shock quality factor. Meanwhile, strong or weak of thermal shock for different samples whether they are thin or thick are compared through the operation of queuing algorithm. The conclusion is the internal surface of the domes isn't heated when the window model is the thermal shock quality factor of thick sample and the heating time is between heating time constant and diffusion time constant. On the other hand, the internal surface of the domes is being heated when the window model is the thermal shock quality factor of thin sample and the heating time is between the two time constants. The most optical domes parts in practice is belong the thin model. For the thin model, reducing the thickness of optical parts can improve their thermal shock ability but mechanical impact stress factor should be considered comprehensively to design optical parts.

  7. An aerodynamic study of the CFHT dome using water tunnel tests and CFD

    NASA Astrophysics Data System (ADS)

    Baril, Marc; Benedict, Tom; Thanjavur, Karun; Salmon, Derrick; Vogiatzis, Konstantinos; Racine, Rene; Breidenthal, Robert

    2012-09-01

    Studies of astronomical seeing at the Canada France Hawaii Telescope (CFHT) site, from both inside and outside the dome, show that the full potential of the excellent seeing conditions at the CFHT site has never been fully exploited. These studies indicate that this is due to the classical unvented hemispherical CFHT dome. Tests have been performed to identify the causes of the “pathologies” revealed by these seeing studies and to find ways of mitigating them. In particular, we have investigated installing vents in the dome skin to improve air exchange between outside and inside the enclosure. A number of vent geometries were tested using water tunnel models at the University of Washington Aerodynamics Laboratory (UWAL). Relative flushing times for various dome slit to prevailing wind directions were compared for the different vent geometries. The general flow characteristics observed with these low Reynolds number tests were compared with computational fluid dynamics (CFD) simulations of the CFHT dome performed in collaboration with the Thirty Meter Telescope (TMT) project, as well as low-speed wind-tunnel tests and visualization of the flow around the actual observatory building.

  8. Improved manufacturing techniques for RF and laser hardening of missile domes. Phase I. Technical report

    SciTech Connect

    Pawlewicz, W.T.; Mann, I.B.; Martin, P.M.; Hays, D.D.; Graybeal, A.G.

    1982-07-01

    This report summarizes key results and accomplishements during the first year of a Manufacturing Methods and Technology project to adapt an existing Pacific Northwest Laboratory (PNL) optical coating capability developed for high-power fusion-laser applications to the case of rf and laser hardening of plastic missile domes used by the US Army (MICOM). The primary objective of the first year's work was to demonstrate rf hardening of Hellfire and Copperhead 1.06-micron missile domes by use of transparent conductive Indium Tin Oxide (ITO) coatings. The project thus involved adaptation of a coating material and process developed for flat glass components used in fusion lasers to the case of hemispherical or conical heat-sensitive plastic domes used on laser-guided missiles. Specific ITO coating property goals were an electrical sheet resistance of 10 Ohms/square, a coated-dome transmission of 80% or more at 1.06 micron wavelength (compared to 90% for a bare dome), and good adhesion. The sheet resistance goal of 10 Ohms/square was expected to result in an rf attenuation of 30 dB at the frequencies of importance.

  9. Shape and thermal modeling of the possible cryovolcanic dome Ganesa Macula on Titan: Astrobiological implications

    NASA Astrophysics Data System (ADS)

    Neish, C. D.; Lorenz, R. D.; O'Brien, D. P.; Cassini RADAR Team

    2005-08-01

    Observations of Titan by the Cassini spacecraft have revealed to us a world with an intricate and varied geology. In particular, there is evidence of extensive cryovolcanism. The 180 km structure Ganesa Macula observed in SAR imaging from Cassini's TA encounter in October 2004 resembles the pancake domes seen on Venus by the Magellan spacecraft and is comparable (in terms of years of planetary heatflow required to melt the lava volume) with the Deccan Traps on Earth. Cryovolcanism has important astrobiological implications, as it provides a means of exposing surface organics to liquid water. Aqueous chemistry permits Titan's hydrocarbons and nitriles to form more evolved and oxidized prebiotic species, such as amino acids and pyrimidines. In this work, we use Titan's observed backscatter function to model the radar appearance of domes of various shapes and heights to compare with the image of Ganesa: the SAR data are better fit by a ``spreading viscous drop" (``Huppert") shape than by one constrained by a skin strength (``Nye"). We then model the freezing of the model dome using a finite-element heat conduction code. Estimation of the dome height is presently underway, but even a dome only 1 km in height takes some 5 x 103 years to freeze for lava made entirely of liquid water, and 12 x 103 years for lava made of ammonia dihydrate. These timescales open a window for prebiotic chemistry far wider than can be explored in terrestrial laboratory experiments. This work was supported by the Cassini project.

  10. Degradation of dome cutting minerals in Hanford waste

    SciTech Connect

    Reynolds, Jacob G.; Huber, Heinz J.; Cooke, Gary A.

    2013-01-11

    At the Hanford Tank Farms, recent changes in retrieval technology require cutting new risers in several single-shell tanks. The Hanford Tank Farm Operator is using water jet technology with abrasive silicate minerals such as garnet or olivine to cut through the concrete and rebar dome. The abrasiveness of these minerals, which become part of the high-level waste stream, may enhance the erosion of waste processing equipment. However, garnet and olivine are not thermodynamically stable in Hanford waste, slowly degrading over time. How likely these materials are to dissolve completely in the waste before the waste is processed in the Waste Treatment and Immobilization Plant can be evaluated using theoretical analysis for olivine and collected direct experimental evidence for garnet. Based on an extensive literature study, a large number of primary silicates decompose into sodalite and cancrinite when exposed to Hanford waste. Given sufficient time, the sodalite also degrades into cancrinite. Even though cancrinite has not been directly added to any Hanford tanks during process times, it is the most common silicate observed in current Hanford waste. By analogy, olivine and garnet are expected to ultimately also decompose into cancrinite. Garnet used in a concrete cutting demonstration was immersed in a simulated supernate representing the estimated composition of the liquid retrieving waste from Hanford tank 241-C-107 at both ambient and elevated temperatures. This simulant was amended with extra NaOH to determine if adding caustic would help enhance the degradation rate of garnet. The results showed that the garnet degradation rate was highest at the highest NaOH concentration and temperature. At the end of 12 weeks, however, the garnet grains were mostly intact, even when immersed in 2 molar NaOH at 80 deg C. Cancrinite was identified as the degradation product on the surface of the garnet grains. In the case of olivine, the rate of degradation in the high-pH regimes

  11. Degradation of Dome Cutting Minerals in Hanford Waste - 13100

    SciTech Connect

    Reynolds, Jacob G.; Cooke, Gary A.; Huber, Heinz J.

    2013-07-01

    At the Hanford Tank Farms, recent changes in retrieval technology require cutting new risers in several single-shell tanks. The Hanford Tank Farm Operator is using water jet technology with abrasive silicate minerals such as garnet or olivine to cut through the concrete and rebar dome. The abrasiveness of these minerals, which become part of the high-level waste stream, may enhance the erosion of waste processing equipment. However, garnet and olivine are not thermodynamically stable in Hanford waste, slowly degrading over time. How likely these materials are to dissolve completely in the waste before the waste is processed in the Waste Treatment and Immobilization Plant can be evaluated using theoretical analysis for olivine and collected direct experimental evidence for garnet. Based on an extensive literature study, a large number of primary silicates decompose into sodalite and cancrinite when exposed to Hanford waste. Given sufficient time, the sodalite also degrades into cancrinite. Even though cancrinite has not been directly added to any Hanford tanks during process times, it is the most common silicate observed in current Hanford waste. By analogy, olivine and garnet are expected to ultimately also decompose into cancrinite. Garnet used in a concrete cutting demonstration was immersed in a simulated supernate representing the estimated composition of the liquid retrieving waste from Hanford tank 241-C-107 at both ambient and elevated temperatures. This simulant was amended with extra NaOH to determine if adding caustic would help enhance the degradation rate of garnet. The results showed that the garnet degradation rate was highest at the highest NaOH concentration and temperature. At the end of 12 weeks, however, the garnet grains were mostly intact, even when immersed in 2 molar NaOH at 80 deg. C. Cancrinite was identified as the degradation product on the surface of the garnet grains. In the case of olivine, the rate of degradation in the high

  12. Effects of anomalous salt features on caverns in Gulf Coast domes

    SciTech Connect

    Not Available

    1992-01-01

    Early solution miners encountered occasional difficulties with nonsymmetric caverns (including wings'' and chimneys''), gas releases, insoluble stringers, and excessive anhydrite sands.'' Apparently there was no early recognition of trends for these encounters, although certain areas were avoided after problems appeared consistently within them. Solution mining has now matured, and an accumulation of experience indicates that anomalous salt features occur on a number of Gulf Coast domes. Trends incorporating concentrations of anomalous features will be referred to as anomalous zones,'' or AZs (after Kupfer). The main objective of this Project is to determine the effects of AZ encounters on solution-mined caverns and related storage operations in domes. Geological features of salt domes related directly to cavern operations and AZs will be described briefly, but discussions of topics related generally to the evolution of Gulf Coast salt structures are beyond the scope of this Project.

  13. Effects of anomalous salt features on caverns in Gulf Coast domes

    SciTech Connect

    Not Available

    1992-10-01

    Early solution miners encountered occasional difficulties with nonsymmetric caverns (including ``wings`` and ``chimneys``), gas releases, insoluble stringers, and excessive anhydrite ``sands.`` Apparently there was no early recognition of trends for these encounters, although certain areas were avoided after problems appeared consistently within them. Solution mining has now matured, and an accumulation of experience indicates that anomalous salt features occur on a number of Gulf Coast domes. Trends incorporating concentrations of anomalous features will be referred to as ``anomalous zones,`` or AZs (after Kupfer). The main objective of this Project is to determine the effects of AZ encounters on solution-mined caverns and related storage operations in domes. Geological features of salt domes related directly to cavern operations and AZs will be described briefly, but discussions of topics related generally to the evolution of Gulf Coast salt structures are beyond the scope of this Project.

  14. Characterization of the Marquez Dome buried impact crater using gravity and magnetic data

    NASA Technical Reports Server (NTRS)

    Wong, A. M.; Reid, A. M.; Hall, S. A.; Sharpton, V. L.

    1993-01-01

    The buried impact crater, Marquez Dome, located in Leon County in east central Texas, is an approximately 15 km diameter structure whose central uplift is now partially exposed due to headward erosion of the post-impact cover. The central uplift is approximately 3 km in diameter and the rocks within it have been uplifted more than 1200 m above their regional level. The crater rim remains buried and previous attempts to determine its location have had to rely on seismic reflection data and geologic well logs. These attempts have been somewhat successful in mapping the extent of the disturbed zone around Marquez Dome, but more limited in their ability to image the shallow buried rim. In an attempt to define accurately the whole Marquez Dome structure and assist in the selection of drilling sites, a geophysical investigation involving gravity and magnetic data over the central uplift and the surrounding area has been undertaken.

  15. Volumetric Changes of the Bezymianny Dome: Insights on the Eruptive Behavior

    NASA Astrophysics Data System (ADS)

    Ushakov, S. V.; Dvigalo, V. N.; Izbekov, P. E.

    2010-12-01

    Bezymianny Volcano, Kamchatka erupted explosively on March 30, 1956 after ca. 1000 period of quiescence. The collapse of the eastern flank of the volcano followed by a directed blast and 4-hour-long explosive activity excavated a 1.3x2.5 km horse-shoe crater open to the East. The eruption continued through extrusive activity, which by the end of the 1956 formed a 300-m-tall dome in the middle of the crater. The extrusive dome growth accompanied by frequent partial collapses and block-and-ash flows dominated through mid 70s, when short vigorous explosions from central vent followed by effusions of viscous lava flows gradually became the prevailed eruption mechanisms. The volumetric changes of the Bezymianny dome have been measured by routine aerial surveys and stereophotogrammetry since 1956. In early 90s the observations has been interrupted due to the lack of funding. Support from the PIRE-Kamchatka project allowed us to resume Bezymianny dome aerial surveys and make three consecutive measurements on June 31, 2006, September 5, 2009, and July 24, 2010. The acquired data was used to generate high resolution digital elevation models of the dome area and to determine morphological and volumetric changes in response to the most recent eruptive activity. Our observations indicate that by 2005-2006 a new crater formed at the summit of the dome. This crater served as a vent for each of seven explosive-effusive events that occurred during 2006-2010. Volumetric changes due to extrusive activity between early 90s and 2006 and during 2006-2010 have been minimal and only occurred in the crater area. At present the dome is entirely covered by lava flows and pyroclastic flow deposits erupted from the central vent. The average annual increase of the dome volume for the 2006-2010 period was 6.8x10^6 cubic meters. Pyroclastic deposits filled the area between the dome and the 1956 crater rim, elevated the flow of the 1956 crater, and reduced the height of the rim above the floor to

  16. Metamorphism on the Moon: A terrestrial analogue in the Vredefort dome, South Africa?

    NASA Astrophysics Data System (ADS)

    Gibson, Roger L.; Reimold, W. Uwe; Ashley, Andrew J.; Koeberl, Christian

    2002-05-01

    A new model is proposed to explain the origin of enigmatic fine-grained granulite facies rocks sampled from the Moon, based on observations from the Vredefort dome, South Africa. The dome is the deeply eroded central uplift of the ˜300-km-diameter Vredefort impact structure. In the dome, fine-grained granulites displaying poikilitic or granoblastic microstructures were formed by relatively slow cooling of shock ± friction melts derived at T > 1350 °C. Slow cooling was achieved owing to the >7 km depth of burial of the rocks following the impact. At least some of the lunar granulitic impactites may also have formed by shock heating and slow cooling at deep levels within the central uplifts of large impact structures, without the need for additional heating by younger intrusive or impact melt bodies.

  17. A Neogene structural dome in the Klamath Mountains, California and Oregon

    NASA Astrophysics Data System (ADS)

    Mortimer, N.; Coleman, R. G.

    1985-04-01

    Regional structural doming of Neogene age has affected rocks of the Klamath and Cascade mountains near the California-Oregon border. Evidence for this is seen in (1) subannular outcrop patterns of pre-Cretaceous lithotectonic units, (2) a crude pattern of radially oriented high-angle faults, (3) tilted Jurassic plutons, (4) tilted Cretaceous to Miocene strata, and (5) various geomorphological features. The age of doming is constrained by a major middle Miocene to earliest Pliocene angular unconformity within the Cascade Mountains and uplifted upper Miocene marine beds on the western edge of the Klamath Mountains. Uplift and doming may be the result of shortening in the Cascade fore-arc region or, more speculatively, the recent accretion of subducted material to the North American plate beneath the Klamath Mountains. *Present addresses: Mortimer, Department of Geological Sciences, University of British Columbia, Vancouver, British Columbia V6T 2B4, Canada; Coleman, U.S. Geological Survey, Menlo Park, California 94025

  18. Advances in freeform optics fabrication for conformal window and dome applications

    NASA Astrophysics Data System (ADS)

    DeGroote Nelson, Jessica; Gould, Alan; Smith, Nathan; Medicus, Kate; Mandina, Michael

    2013-06-01

    Freeform optical shapes or optical surfaces that are designed with non-symmetric features are gaining popularity with lens designers and optical system integrators. This enabling technology allows for conformal sensor windows and domes that provide enhanced aerodynamic properties as well as environmental and ballistic protection. In order to provide ballistic and environmental protection, these conformal windows and domes are typically fabricated from hard ceramic materials. Hard ceramic conformal windows and domes provide two challenges to the optical fabricator. The material hardness, polycrystalline nature and non-traditional shape demand creative optical fabrication techniques to produce these types of optics cost-effectively. This paper will overview a complete freeform optical fabrication process that includes ultrasonic generation of hard ceramic surfaces, high speed VIBE polishing, sub-aperture figure correction of polycrystalline materials and final testing of freeform surfaces. This paper will highlight the progress made to each of the processes as well as the challenges associated with each of them.

  19. Intrusive and extrusive growth of the Mount St Helens lava dome

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan H.; Malin, Michael C.; Anderson, Steven W.

    1990-01-01

    High-resolution, digital topographic maps of the Mount St. Helens dome derived from aerial photographs are used here to make a quantitative assessment of the partitioning of magma into endogenous intrusion and exogenous lobes. The endogenous growth is found to be predictable, which shows that the cooling dome controls its own development independently of such deep-seated factors as magma overpressure and extrusion rate. The observed regular decrease in exogenous growth rate also allows volume prediction. Knowledge of the volume can be used to determine when an ongoing eruptive event should end. Finally, the observed transition from predominantly exogenous to predominantly endogenous growth reflects the increase in crust thickness, which in turn seems to depend on long repose periods rather than some fundamental change in the character of the dome.

  20. TECHNICAL NOTE: Observations on the use of a viscoelastic joint to provide noise reduced sonar domes

    NASA Astrophysics Data System (ADS)

    House, J. R.

    1997-10-01

    This paper concerns the noise and vibration advantages of an energy absorbing composite joint and its relevance to noise reduced glass reinforced polyester (GRP) sonar domes. Once installed on an operational boat, hydrodynamic flow and supporting structural induced vibrations cause the dome to vibrate, thus radiating noise and interfering with sonar sensor response. The results of a vibration transmissibility study on a GRP - steel interface are discussed as the first step in designing a composite viscoelastic joint that can act as a vibration sink to absorb flow generated and structure borne noise within GRP sonar domes. Preliminary investigations concerning the absorption of compressional waves by use of a tapered viscoelastic interlayer are discussed. It is shown that a tapered viscoelastic interlayer placed between a GRP beam and steel supporting substrate can produce a significant absorption of vibrational energy, reducing water borne radiated noise and providing a significantly quieter noise platform than conventional sonar jointing technology.

  1. Arthroscopic Anatomy of the Ankle Joint.

    PubMed

    Ray, Ronald G

    2016-10-01

    There are a number of variations in the intra-articular anatomy of the ankle which should not be considered pathological under all circumstances. The anteromedial corner of the tibial plafond (between the anterior edge of the tibial plafond and the medial malleolus) can have a notch, void of cartilage and bone. This area can appear degenerative arthroscopically; it is actually a normal variant of the articular surface. The anterior inferior tibiofibular ligament (AITF) can possess a lower, accessory band which can impinge on the anterolateral edge of the talar dome. In some cases it can cause irritation along this area of the talus laterally. If it is creating local irritation it can be removed since it does not provide any additional stabilization to the syndesmosis. There is a beveled region at the anterior leading edge of the lateral and dorsal surfaces of the talus laterally. This triangular region is void of cartilage and subchondral bone. The lack of talar structure in this region allows the lower portion of the AITF ligament to move over the talus during end range dorsiflexion of the ankle, preventing impingement. The variation in talar anatomy for this area should not be considered pathological. PMID:27599433

  2. The 2006 lava dome eruption of Merapi Volcano (Indonesia): Detailed analysis using MODIS TIR

    NASA Astrophysics Data System (ADS)

    Carr, Brett B.; Clarke, Amanda B.; Vanderkluysen, Loÿc

    2016-02-01

    Merapi is one of Indonesia's most active and dangerous volcanoes. Prior to the 2010 VEI 4 eruption, activity at Merapi during the 20th century was characterized by the growth and collapse of a series of lava domes. Periods of very slow growth were punctuated by short episodes of increased eruption rates characterized by dome collapse-generated pyroclastic density currents (PDCs). An eruptive event of this type occurred in May-June, 2006. For effusive eruptions such as this, detailed extrusion rate records are important for understanding the processes driving the eruption and the hazards presented by the eruption. We use thermal infrared (TIR) images from the Moderate Resolution Imaging Spectrometer (MODIS) instrument on NASA's Aqua and Terra satellites to estimate extrusion rates at Merapi Volcano during the 2006 eruption using the method of Harris and Ripepe (2007). We compile a set of 75 nighttime MODIS images of the eruptive period to produce a detailed time series of thermal radiance and extrusion rate that reveal multiple phases of the 2006 eruption. These data closely correspond to the published ground-based observational record and improve observation density and detail during the eruption sequence. Furthermore, additional analysis of radiance values for thermal anomalies in Band 21 (λ = 3.959 μm) of MODIS images results in a new framework for detecting different styles of activity. We successfully discriminate among slow dome growth, rapid dome growth, and PDC-producing dome collapse. We also demonstrate a positive correlation between PDC frequency and extrusion rate, and provide evidence that extrusion rate can increase in response to external events such as dome collapses or tectonic earthquakes. This study represents a new method of documenting volcanic activity that can be applied to other similar volcanic systems.

  3. Subaqueous, basaltic lava dome and carapace breccia on King George Island, South Shetland Islands, Antarctica

    NASA Astrophysics Data System (ADS)

    Smellie, J. L.; Millar, I. L.; Rex, D. C.; Butterworth, P. J.

    On King George Island during latest Oligocene/earliest Miocene time, submarine eruptions resulted in the emplacement of a small (ca. 500m estimated original diameter) basalt lava dome at Low Head. The dome contains a central mass of columnar rock enveloped by fractured basalt and basalt breccia. The breccia is crystalline and is a joint-block deposit (lithic orthobreccia) interpreted as an unusually thick dome carapace breccia cogenetic with the columnar rock. It was formed in situ by a combination of intense dilation, fracturing and shattering caused by natural hydrofracturing during initial dome effusion and subsequent endogenous emplacement of further basalt melt, now preserved as the columnar rock. Muddy matrix with dispersed hyaloclastite and microfossils fills fractures and diffuse patches in part of the fractured basalt and breccia lithofacies. The sparse glass-rich clasts formed by cooling-contraction granulation during interaction between chilled basalt crust and surrounding water. Together with muddy sediment, they were injected into the dome by hydrofracturing, local steam fluidisation and likely explosive bulk interaction. The basalt lava was highly crystallised and degassed prior to extrusion. Together with a low effusion temperature and rapid convective heat loss in a submarine setting, these properties significantly affected the magma rheology (increased the viscosity and shear strength) and influenced the final dome-like form of the extrusion. Conversely, high heat retention was favoured by the degassed state of the magma (minimal undercooling), a thick breccia carapace and viscous shear heating, which helped to sustain magmatic (eruption) temperatures and enhanced the mobility of the flow.

  4. Lateral Lumbar Interbody Fusion

    PubMed Central

    Hughes, Alexander; Girardi, Federico; Sama, Andrew; Lebl, Darren; Cammisa, Frank

    2015-01-01

    The lateral lumbar interbody fusion (LLIF) is a relatively new technique that allows the surgeon to access the intervertebral space from a direct lateral approach either anterior to or through the psoas muscle. This approach provides an alternative to anterior lumbar interbody fusion with instrumentation, posterior lumbar interbody fusion, and transforaminal lumbar interbody fusion for anterior column support. LLIF is minimally invasive, safe, better structural support from the apophyseal ring, potential for coronal plane deformity correction, and indirect decompression, which have has made this technique popular. LLIF is currently being utilized for a variety of pathologies including but not limited to adult de novo lumbar scoliosis, central and foraminal stenosis, spondylolisthesis, and adjacent segment degeneration. Although early clinical outcomes have been good, the potential for significant neurological and vascular vertebral endplate complications exists. Nevertheless, LLIF is a promising technique with the potential to more effectively treat complex adult de novo scoliosis and achieve predictable fusion while avoiding the complications of traditional anterior surgery and posterior interbody techniques. PMID:26713134

  5. Lateral Lumbar Interbody Fusion.

    PubMed

    Pawar, Abhijit; Hughes, Alexander; Girardi, Federico; Sama, Andrew; Lebl, Darren; Cammisa, Frank

    2015-12-01

    The lateral lumbar interbody fusion (LLIF) is a relatively new technique that allows the surgeon to access the intervertebral space from a direct lateral approach either anterior to or through the psoas muscle. This approach provides an alternative to anterior lumbar interbody fusion with instrumentation, posterior lumbar interbody fusion, and transforaminal lumbar interbody fusion for anterior column support. LLIF is minimally invasive, safe, better structural support from the apophyseal ring, potential for coronal plane deformity correction, and indirect decompression, which have has made this technique popular. LLIF is currently being utilized for a variety of pathologies including but not limited to adult de novo lumbar scoliosis, central and foraminal stenosis, spondylolisthesis, and adjacent segment degeneration. Although early clinical outcomes have been good, the potential for significant neurological and vascular vertebral endplate complications exists. Nevertheless, LLIF is a promising technique with the potential to more effectively treat complex adult de novo scoliosis and achieve predictable fusion while avoiding the complications of traditional anterior surgery and posterior interbody techniques. PMID:26713134

  6. Creativity in later life.

    PubMed

    Price, K A; Tinker, A M

    2014-08-01

    The ageing population presents significant challenges for the provision of social and health services. Strategies are needed to enable older people to cope within a society ill prepared for the impacts of these demographic changes. The ability to be creative may be one such strategy. This review outlines the relevant literature and examines current public health policy related to creativity in old age with the aim of highlighting some important issues. As well as looking at the benefits and negative aspects of creative activity in later life they are considered in the context of the theory of "successful ageing". Creative activity plays an important role in the lives of older people promoting social interaction, providing cognitive stimulation and giving a sense of self-worth. Furthermore, it is shown to be useful as a tool in the multi-disciplinary treatment of health problems common in later life such as depression and dementia. There are a number of initiatives to encourage older people to participate in creative activities such as arts-based projects which may range from visual arts to dance to music to intergenerational initiatives. However, participation shows geographical variation and often the responsibility of provision falls to voluntary organisations. Overall, the literature presented suggests that creative activity could be a useful tool for individuals and society. However, further research is needed to establish the key factors which contribute to patterns of improved health and well-being, as well as to explore ways to improve access to services. PMID:24974278

  7. Aft segment dome-to-stiffener factory joint insulation void elimination

    NASA Technical Reports Server (NTRS)

    Jensen, S. K.

    1991-01-01

    Since the detection of voids in the internal insulation of the dome-to-stiffener factory joint of the 15B aft segment, all aft segment dome-to-stiffener factory joints were x-rated and all were found to contain voids. Using a full-scale process simulation article (PSA), the objective was to demonstrate that the proposed changes in the insulation layup and vacuum bagging processes will greatly reduce or eliminate voids without adversely affecting the configuration of performance of the insulation which serves as a primary seal over the factory joint. The PSA-8 aft segment was insulated and cured using standard production processes.

  8. Drilling investigation of a young magmatic intrusion beneath Inyo Dome, Long Valley Caldera, California. Progress report

    SciTech Connect

    Vogel, T.A.

    1985-01-01

    Progress to date indicates: (1) the conduit and lava flow at Obsidian Dome consist of two magma types; (2) the more mafic magma occurs at the base of Obsidian Dome and at the margins of the conduit and was emplaced first; (3) the more silicic magma occurs in the center of the conduit and in the dike; (4) the ilmenite-magnetite and orthopyroxene-augite geothermometers have not reequilibrated in the conduit or dike; (5) the more mafic magma's emplacement temperature was 974/sup 0/C compared to the silicic magma's 951/sup 0/C; and (6) trace elements are characteristic of each magma type. (ACR)

  9. Volcanism on Venus: Large shields and major accumulations of small domes

    NASA Technical Reports Server (NTRS)

    Schaber, Gerald G.; Kozak, Richard C.

    1989-01-01

    The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.

  10. Exploring the possibility of developing a plastic missile dome for near-infrared transmission

    NASA Astrophysics Data System (ADS)

    Leuw, David H.

    1993-08-01

    The possibility was investigated of developing a missile dome from a transparent plastic for near infra-red transmission by which the windows form an integral part of it. The environmental requirements of the dome were severe as it had to stand up to a velocity in excess of 2 Mach at zero altitude without diminishing its transparency and thus, its optical performance. Several promising plastic candidates were investigated in a hot-wind tunnel and their eventual optical degradation was measured. Special coatings against EMI and reflection losses were applied resisting the high temperature and aero-dynamic pressure occurring during flight. Results of these experiments are given.

  11. The design of missile's dome that fits both optical and aerodynamic needs

    NASA Astrophysics Data System (ADS)

    Wei, Qun; Zhang, Xin; Jia, Hongguang

    2010-10-01

    Optical guidance missiles requires a dome which fits both optical and aerodynamic needs when they attack at 3 Ma. In this study, ellipse is the figure chosen to be the dome's shape. The ellipticity ɛ is the main variable should to be decided. The optimized function was built by optical and aerodynamic performance function multiply by their weights. The optical and aerodynamic functions were all obtained by computational fluid dynamic (CFD) simulation's results after normalization. In this study, the optical and aerodynamic performances have equal weights, after optimzing the ellipticity ɛis 2 for the missile.

  12. The origin of the silicic domes in the Macolod Corridor, Philippines

    NASA Astrophysics Data System (ADS)

    Flood, T. P.; Patino, L. C.; Vogel, T. A.; Arcilla, C.; Stimac, J. A.; Maximo, R. R.; Arpa, M. B.

    2002-12-01

    The petrogenesis of silicic magmas in areas that do not contain continental crust is often unclear. This study examines the composition of domes associated with Mount Makiling stratovolcano, Philippines, to understand the generation of silicic magmas, in an island arc setting. Makiling volcano and associated domes are located in the Macolod Corridor. The corridor is a tectonic depression between the West Luzon Arc (produced by east dipping South China Sea plate) and the East Luzon Arc (produced by the west dipping Philippine Sea plate) with numerous volcanic features. The volcanism in this part of the Macolod Corridor has occurred sporadically over at least the past million years. Sampling of Makiling volcano indicates a continuous range in composition from basaltic andesite to dacite. The range in composition in the domes is wider, from basalt to rhyolite. The chemical variation in samples from individual domes is small, and may be an indication of monogenetic nature of the magmatic activity. Howerver, most of the domes have similar compositions, with SiO2 modes of 70% and with little variation of other chemical parameters that may indicate derivation from a larger silicic magma system. At least one dome has bimodal composition, one set of samples ranges in composition form basalts-basaltic andesite and the other set of samples consists of dacites. There is a dubious association among the magmas from the Macolod corridor with subduction zone magmatism, the rocks from Makiling volcano and most of those sampled from the domes are calc-alkaline with large Nb and Ti depletion on spider diagrams. Conversely, one dome has tholeiitic characteristics with higher FeO/MgO ratios for a given SiO2 content. The major and minor elements data in the samples from Makiling volcano plot on trends that show little scatter. All the samples follow on a single trend for Mg, Fe, and Ca. Though, for other elements (Ti, Al, Sr, Na, K, Rb, and Zr) the samples from the northeastern part of

  13. Volumes and eruption rates for the 2008-2009 Chaitén rhyolite lava dome

    NASA Astrophysics Data System (ADS)

    Pallister, J. S.; Diefenbach, A. K.; Griswold, J.; Muñoz, J.; Lara, L. E.; Valenzuela, C.; Burton, W. C.; Keeler, R.

    2010-12-01

    The 2008 eruption of Chaitén caldera, southern Chile, was one of the most explosive on Earth in the past two decades. The eruption began early on 2 May 2008 (UTC) and produced sub-plinian to plinian ash columns between 2 May and 9 May, before transitioning from explosive eruption of tephra to effusive eruption of rhyolite lava. A series of lava flow lobes accumulated within the caldera between late May and the end of the year, burying most of Chaitén’s prehistoric lava dome. A prominent lava spine was also extruded, starting in late 2008. The spine collapsed on 19 February 2009, producing a pyroclastic flow that extended out of the caldera and 7 km down the Río Chaitén. Dome growth continued through 2009, filling in much of the spine-collapse area and further expanding the composite dome through endogenous growth. Dome volumes are computed and eruption rates estimated using satellite data from 2008-10, photogrammetric analysis of oblique aerial photographs taken in January 2010, and digital elevation models derived from ASTER, SRTM, LIDAR and topographic maps. The 2008-10 dome has a total volume of approximately 0.8 km3. About 0.5 km3 erupted within the first four months, when extrusion rates were in the range 10-100 m3s-1. Extrusion rates decreased exponentially over the eruptive period. The 2008-10 dome is similar in volume and composition to the prehistoric lava dome, which has a volume of at least 0.5 km3. Together the two domes constitute about 20-40% of the 3.5-7 km3 collapse volume of the prehistoric caldera. The unusually rapid extrusion rates during the first four months are among the highest ever measured for silicic lava. Chaitén’s 2008-10 lava is obsidian and microcrystalline rhyolite with 75.35+/-0.02% SiO2. A large volume of low viscosity crystal-poor magma (about 0.1% phenocrysts) coupled with high extrusion pressures during the extended transition from explosive to effusive eruption style resulted in these exceptionally high extrusion rates.

  14. Volcanism on Venus: Large shields and major accumulations of small domes

    NASA Astrophysics Data System (ADS)

    Schaber, Gerald G.; Kozak, Richard C.

    The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.

  15. A Review of Optical Sky Brightness and Extinction at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Kenyon, S. L.; Storey, J. W. V.

    2006-03-01

    The recent discovery of exceptional seeing conditions at Dome C, Antarctica, raises the possibility of constructing an optical observatory there with unique capabilities. However, little is known from an astronomer's perspective about the optical sky brightness and extinction at Antarctic sites. We review the contributions to sky brightness at high-latitude sites and calculate the amount of usable dark time at Dome C. We also explore the implications of the limited sky coverage of high-latitude sites and review optical extinction data from the South Pole. Finally, we examine the proposal of Baldry & Bland-Hawthorn to extend the amount of usable dark time through the use of polarizing filters.

  16. The Dome C Gattini sky brightness cameras: results from the first year of operation

    NASA Astrophysics Data System (ADS)

    Moore, A. M.; Leslie, T.; Ashley, M. C. B.; Aristidi, E.; Bedding, T.; Briguglio, R.; Busso, M.; Candidi, M.; Cutispoto, G.; Distefano, E.; Everett, J.; Kenyon, S.; Lawrence, J.; Le Roux, B.; Luong-van, D.; Phillips, A.; Ragazzoni, R.; Sabbatini, L.; Salinari, P.; Stello, D.; Storey, J. W. V.; Taylor, M.; Tosti, G.; Travouillon, T.

    The Gattini-DomeC project, part of the IRAIT site testing campaign and ongoing since January 2006, consists of two cameras for the measurement of optical sky brightness, large area cloud cover, and auroral detection above the DomeC site, home of the French-Italian Concordia station. The cameras are transit in nature and are virtually identical except for the nature of the lenses. The cameras have operated throughout the past two Antarctic winter seasons and here we present the results obtained from the 2006 winter-time dataset of the wide field “All-sky camera".

  17. Growth of single-layer boron nitride dome-shaped nanostructures catalysed by iron clusters.

    PubMed

    Torre, A La; Åhlgren, E H; Fay, M W; Ben Romdhane, F; Skowron, S T; Parmenter, C; Davies, A J; Jouhannaud, J; Pourroy, G; Khlobystov, A N; Brown, P D; Besley, E; Banhart, F

    2016-08-11

    We report on the growth and formation of single-layer boron nitride dome-shaped nanostructures mediated by small iron clusters located on flakes of hexagonal boron nitride. The nanostructures were synthesized in situ at high temperature inside a transmission electron microscope while the e-beam was blanked. The formation process, typically originating at defective step-edges on the boron nitride support, was investigated using a combination of transmission electron microscopy, electron energy loss spectroscopy and computational modelling. Computational modelling showed that the domes exhibit a nanotube-like structure with flat circular caps and that their stability was comparable to that of a single boron nitride layer. PMID:27486917

  18. Potentiometric-level monitoring program, Mississippi and Louisiana: Annual status report for fiscal year 1985. [Richton and Cypress Creek Domes, M5 and Vacherie Dome, LA

    SciTech Connect

    Not Available

    1986-10-01

    Potentiometric-level data presented in this report were collected at 82 wells in Mississippi and Louisiana from October 1984 through September 1985. These wells are located near Richton and Cypress Creek Domes in Mississippi and Vacherie dome in Louisiana. Three wells were reinstated to the program during this period. Two previously destroyed wells were deleted from the program. Protective barriers were installed around 26 shallow borings in Mississippi. Cursory analysis of the data in Mississippi indicated minimal, if any, change in potentiometric level during the past year in the Citronelle, Hattiesburg, Cockfield, Sparta, and Wilcox Formations. A slight decline, on the order of 0.3 meter (1 foot), occurred during the past year in well MCCG-1, which is screened in the caprock of Cypress Creek Dome. The potentiometric level in well MRIG-9, in the caprock of Richton Dome, stabilized during fiscal year 1985 following 5 years of increase. The Catahoula Formation experienced a continuing decline of about 0.3 meter/year (1 foot/year). Well MH-5C, screened in the Cook Mountain Formation, showed a continuing, long-term, upward trend on the order of 1.5 meters (4.9 feet) during the past year. The potentiometric level of well MH-8C, screened in the Cook Mountain Formation, stabilized during fiscal year 1985, following 5 years of large annual increases. Wells screened in the Austin Formation in Louisiana showed a downward trend of 0.3 to 1 meter (1 to 3.3 feet) during fiscal year 1985. Other formations in Louisiana generally showed no change in potentiometric level.

  19. Magnitude and timing of downstream channel aggradation and degradation in response to a dome-building eruption at Mount Hood, Oregon

    USGS Publications Warehouse

    Pierson, Thomas C.; Pringle, Patrick T.; Cameron, Kenneth A.

    2011-01-01

    A dome-building eruption at Mount Hood, Oregon, starting in A.D. 1781 and lasting until ca. 1793, produced dome-collapse lithic pyroclastic flows that triggered lahars and intermittently fed 108 m3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the Sandy River. Mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river (depositional reach), 61-87 km from the source. Stratigraphic and sedimentologic relations in the alluvial fill, together with dendrochronologic dating of degradation terraces, demonstrate that (1) channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less; (2) the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome-building eruption; (3) fluvial sediment transport and deposition, augmented by one lahar, achieved a minimum average aggradation rate of ~2 m/yr; (4) the degradation phase of the cycle was more prolonged than the aggradation phase, requiring more than half a century for the river to reach its present bed elevation; and (5) the present longitudinal profile of the Sandy River in this reach is at least 3 m above the pre-eruption profile. The pattern and rate of channel response and recovery in the Sandy River following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs. The magnitude of channel aggradation in the lower Sandy River, greater than that achieved at other volcanoes following much larger eruptions, was likely enhanced by lateral confinement of the channel within a narrow incised valley. A combination of at least one lahar and winter floods from frequent moderate-magnitude rainstorms and infrequent very large

  20. Kinematics of Deformation in West-Central Walker Lane; Paleomagnetic Testing of Fault-Block Rotation and Doming Models, Eastern California and Western Nevada

    NASA Astrophysics Data System (ADS)

    Fredrickson, S. M.; Pluhar, C. J.; Carlson, C. W.

    2013-12-01

    Walker Lane is a broad (~100-200 km) zone of dextral shear located between the Sierra Nevada microplate and the Basin and Range Province. We consider Bodie Hills a part of the greater Walker Lane because it has experienced clockwise, vertical-axis rotation of crustal blocks due to dextral shear accommodation. This strain is variable, resulting in rotations ranging from ~10°-70° depending on location. The Miocene Eureka Valley Tuff (EVT) is an ideal strain marker, because it is a geologically instantaneous and laterally extensive unit. We use paleomagnetic analysis of ignimbrites to improve the resolution of strain domain boundaries as well as test for doming in Bodie Hills. EVT site mean directions were compared to reference directions of the Tollhouse Flat and By Day Members collected from the stable Sierra Nevada to determine magnitudes of vertical-axis rotation. Three new sites and three previously sampled sites define a high-rotation domain including Bridgeport Valley and the East Walker River Canyon with an average clockwise rotation of ~50°-60°. We define the eastern boundary of this high-rotation domain as coinciding with a mapped fault exhibiting 11.7°×7.9° rotation of the presumed footwall. Our data corroborates and improves on Carlson's (2012) kinematic model in which the greater Bodie Hills has rotated clockwise ~30° since EVT emplacement. Eutaxitic textures, dipping up to 90°, are gross indicators of true tilt, but are also influenced by original dips in some localities, complicating interpretations. John et al. (2012) describe a simple doming model of Bodie Hills since EVT emplacement, supported by the high elevation of outflow channels compared to source areas. Our paleomagnetic data does not support simple doming, suggesting that there is either no doming of Bodie Hills, or that vertical crustal displacements have occurred without large-scale folding. John et al. (2012) dated undifferentiated EVT in Bodie Hills at ~9.4 Ma; using

  1. 8. UPPER INSIDE CHORD, VERTICAL, LATERAL STRUT, UPPER LATERAL & ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. UPPER INSIDE CHORD, VERTICAL, LATERAL STRUT, UPPER LATERAL & GUSSET PLATE, ONE DIAGONAL BRACE - Enterprise Parker Truss Bridge, Spanning Smoky Hill River on K-43 Highway, Enterprise, Dickinson County, KS

  2. 7. UPPER INSIDE CHORD, VERTICAL, LATERAL STRUT, UPPER LATERAL & ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. UPPER INSIDE CHORD, VERTICAL, LATERAL STRUT, UPPER LATERAL & GUSSET PLATE, TWO DIAGONAL BRACES - Enterprise Parker Truss Bridge, Spanning Smoky Hill River on K-43 Highway, Enterprise, Dickinson County, KS

  3. Development of in-structure design spectra for dome mounted equipment on underground waste storage tanks at the Hanford Site

    SciTech Connect

    Julyk, L.J.

    1995-09-01

    In-structure response spectra for dome mounted equipment on underground waste storage tanks at the Hanford Site are developed on the basis of recent soil-structure-interaction analyses. Recommended design spectra are provided for various locations on the tank dome.

  4. Exhumation of high-pressure rocks in a Variscan migmatite dome (Montagne Noire, France)

    NASA Astrophysics Data System (ADS)

    Whitney, Donna; Roger, Francoise; Rey, Patrice; Teyssier, Christian

    2015-04-01

    The Variscan orogen contains numerous domal structures composed mostly of migmatitic gneiss and granite, with lesser amounts of mafic rock. In the Montagne Noire (MN) migmatite dome of the southern Massif Central (France), some mafic rocks record eclogite facies metamorphism that contrasts with the low-pressure/high-temperature (LP/HT) conditions recorded by host gneiss. To understand the relationship of eclogite to migmatite/gneiss evolution, we determined P-T-time conditions of eclogite and gneiss and evaluated the location of HP rocks within the dome in the context of dome dynamics. Migmatite and granite in the dome commonly contain sillimanite and/or cordierite, and the schist carapace also contains index minerals of LP/HT metamorphism (andalusite, cordierite, sillimanite). There is sparse evidence, however, for earlier HP conditions: relict kyanite in schist and gneiss. The age of this metamorphism is not known but the LP/HT metamorphism and migmatite/granite crystallization was ~315-300 Ma (monazite, zircon U-Pb). Most MN eclogites have been significantly retrogressed. We focused our study on a relatively fresh eclogite (Terme de Fourcaric locality) containing omphacite (Jd36) + zoned pyrope-rich garnet (up to prp50 at the rim) + rutile + zircon. P-T conditions determined from a pseudosection and from Zr-in-rutile and grt-cpx thermometry indicates T = 700-800 C at P ~ 1.5 GPa. U-Pb dating of zircon by LA-ICP-MS reveals core ages of ~360 Ma and rim ages of ~315 Ma. The zircon core age is similar to results obtained by Faure et al. (2014) for eclogite from the same general locality using a Sm-Nd grt-cpx-whole rock isochron (interpreted as age of eclogite metamorphism). The rim age is similar to their U-Pb zircon and rutile results that they interpreted as the age of "hydrothermal" metamorphism. The interpretation of Faure is consistent with regional geologic age information, although the lack of retrogression in the Fourcaric eclogite and the high prp content

  5. Lateral conduction infrared photodetector

    DOEpatents

    Kim, Jin K.; Carroll, Malcolm S.

    2011-09-20

    A photodetector for detecting infrared light in a wavelength range of 3-25 .mu.m is disclosed. The photodetector has a mesa structure formed from semiconductor layers which include a type-II superlattice formed of alternating layers of InAs and In.sub.xGa.sub.1-xSb with 0.ltoreq.x.ltoreq.0.5. Impurity doped regions are formed on sidewalls of the mesa structure to provide for a lateral conduction of photo-generated carriers which can provide an increased carrier mobility and a reduced surface recombination. An optional bias electrode can be used in the photodetector to control and vary a cut-off wavelength or a depletion width therein. The photodetector can be formed as a single-color or multi-color device, and can also be used to form a focal plane array which is compatible with conventional read-out integrated circuits.

  6. Laterality and language experience.

    PubMed

    Hull, Rachel; Vaid, Jyotsna

    2006-09-01

    A meta-analysis was conducted on studies that examined hemispheric functional asymmetry for language in brain-intact monolingual and bilingual adults. Data from 23 laterality studies that directly compared bilingual and monolingual speakers on the same language were analysed (n = 1234). Variables examined were language experience (monolingual, bilingual), experimental paradigm (dichotic listening, visual hemifield presentation, and dual task) and, among bilinguals, the influence of second language proficiency (proficient vs nonproficient) and onset of bilingualism (early, or before age 6; and late, or after age 6). Overall, monolinguals and late bilinguals showed reliable left hemisphere dominance, while early bilinguals showed reliable bilateral hemispheric involvement. Within bilinguals, there was no reliable effect of language proficiency when age of L2 acquisition was controlled. The findings indicate that early learning of one vs. two languages predicts divergent patterns of cerebral language lateralisation in adulthood. PMID:16882556

  7. Lateral Flow Immunoassay.

    PubMed

    Ching, Kathryn H

    2015-01-01

    Lateral flow immunoassays (LFIAs) are a staple in the field of rapid diagnostics. These small handheld devices require no specialized training or equipment to operate, and generate a result within minutes of sample application. They are an ideal format for many types of home test kits, for emergency responders and for food manufacturers and producers looking for a quick evaluation of a given sample. LFIAs rely on high quality monoclonal antibodies that recognize the analyte of interest. As monoclonal antibody technology becomes more accessible to smaller laboratories, there has been increased interest in developing LFIA prototypes for potential commercial manufacture. In this chapter, the basics of designing and building an LFIA prototype are described. PMID:26160571

  8. Dome growth at Mount Cleveland, Aleutian Arc, quantified by time-series TerraSAR-X imagery

    USGS Publications Warehouse

    Wang, Teng; Poland, Michael; Lu, Zhong

    2016-01-01

    Synthetic aperture radar imagery is widely used to study surface deformation induced by volcanic activity; however, it is rarely applied to quantify the evolution of lava domes, which is important for understanding hazards and magmatic system characteristics. We studied dome formation associated with eruptive activity at Mount Cleveland, Aleutian Volcanic Arc, in 2011–2012 using TerraSAR-X imagery. Interferometry and offset tracking show no consistent deformation and only motion of the crater rim, suggesting that ascending magma may pass through a preexisting conduit system without causing appreciable surface deformation. Amplitude imagery has proven useful for quantifying rates of vertical and areal growth of the lava dome within the crater from formation to removal by explosive activity to rebirth. We expect that this approach can be applied at other volcanoes that host growing lava domes and where hazards are highly dependent on dome geometry and growth rates.

  9. Robotic Manufacturing of 5.5 Meter Cryogenic Fuel Tank Dome Assemblies for the NASA Ares I Rocket

    NASA Technical Reports Server (NTRS)

    Jones, Ronald E.

    2012-01-01

    The Ares I rocket is the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration's (NASA's) Constellation program. A series of full-scale Ares I development articles have been constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7-axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This presentation will focus on the friction stir welding of 5.5m diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome (LH2 MDA), the common bulkhead manufacturing development articles (CBMDA) and the thermal protection system demonstration dome (TPS Dome). The LH2 MDA was the first full-scale, flight-like Ares I hardware produced under the Constellation Program. It is a 5.5m diameter elliptical dome assembly consisting of eight gore panels, a y-ring stiffener and a manhole fitting. All components are made from aluminumlithium alloy 2195. Conventional and self-reacting friction stir welding was used on this article. An overview of the manufacturing processes will be discussed. The LH2 MDA is the first known fully friction stir welded dome ever produced. The completion of four Common Bulkhead Manufacturing Development Articles (CBMDA) and the TPS Dome will also be highlighted. Each CBMDA and the TPS Dome consists of a 5.5m diameter spun-formed dome friction stir welded to a y-ring stiffener. The domes and y-rings are made of aluminum 2014 and 2219 respectively. The TPS Dome has an additional aluminum alloy 2195 barrel section welded to the y-ring. Manufacturing solutions will be discussed including "fixtureless" welding with self reacting friction stir welding.

  10. Log analysis of six boreholes in conjunction with geologic characterization above and on top of the Weeks Island salt dome

    SciTech Connect

    Sattler, A.R.

    1996-04-01

    Six boreholes were drilled during the geologic characterization and diagnostics of the Weeks Island sinkhole that is over the two-tiered salt mine which was converted for oil storage by the US Strategic Petroleum Reserve. These holes were drilled to provide for geologic characterization of the Weeks Island Salt Dome and its overburden in the immediate vicinity of the sinkhole (mainly through logs and core); to establish a crosswell configuration for seismic tomography; to establish locations for hydrocarbon detection and tracer injection; and to Provide direct observations of sinkhole geometry and material properties. Specific objectives of the logging program were to: (1) identify the top of and the physical state of the salt dome; (2) identify the water table; (3) obtain a relative salinity profile in the aquifer within the alluvium, which ranges from the water table directly to the top of the Weeks Island salt dome; and (4) identify a reflecting horizon seen on seismic profiles over this salt dome. Natural gamma, neutron, density, sonic, resistivity and caliper logs were run. Neutron and density logs were run from inside the well casing because of the extremely unstable condition of the deltaic alluvium overburden above the salt dome. The logging program provided important information about the salt dome and the overburden in that (1) the top of the salt dome was identified at {approximately}189 ft bgl (103 ft msl), and the top of the dome contains relatively few fractures; (2) the water table is approximately 1 ft msl, (3) this aquifer appears to become steadily more saline with depth; and (4) the water saturation of much of the alluvium over the salt dome is shown to be influenced by the prevalent heavy rainfall. This logging program, a part of the sinkhole diagnostics, provides unique information about this salt dome and the overburden.

  11. Interaction between an emerging flux region and a pre-existing fan-spine dome observed by IRIS and SDO

    NASA Astrophysics Data System (ADS)

    Jiang, Fayu; Zhang, Jun; Yang, Shuhong

    2015-08-01

    We present multiwavelength observations of a fan-spine dome in the active region NOAA 11996 with the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO) on 2014 March 9. The destruction of the fan-spine topology owing to the interaction between its magnetic fields and a nearby emerging flux region (EFR) is observed for the first time. The line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board the SDO reveal that the dome is located on the mixed magnetic fields, with its rim rooted in the redundant positive polarity surrounding the minority parasitic negative fields. The fan surface of the dome consists of a filament system and recurring jets are observed along its spine. The jet occurring around 13:54 UT is accompanied by a quasi-circular ribbon that brightens in the clockwise direction along the bottom rim of the dome, which may indicate an occurrence of slipping reconnection in the fan-spine topology. The EFR emerges continuously and meets with the magnetic fields of the dome. Magnetic cancellations take place between the emerging negative polarity and the outer positive polarity of the dome's fields, which lead to the rise of the loop connecting the EFR and brightenings related to the dome. A single Gaussian fit to the profiles of the IRIS Si IV 1394 Å line is used in the analysis. It appears that there are two rising components along the slit, in addition to the rise in the line-of-sight direction. The cancellation process repeats again and again. Eventually the fan-spine dome is destroyed and a new connectivity is formed. We suggest that magnetic reconnection between the EFR and the magnetic fields of the fan-spine dome is responsible for the destruction of the dome.

  12. Geochronology of the Sleeper deposit, Humboldt County, Nevada: epithermal gold-silver mineralization following emplacement of a silicic flow-dome complex

    USGS Publications Warehouse

    Conrad, J.E.; McKee, E.H.; Rytuba, J.J.; Nash, J.T.; Utterback, W.C.

    1993-01-01

    The high-grade gold-silver deposits at the Sleeper mine are low sulfidation, quartz-adularia-type epithermal deposits, formed during the final stages of igneous hydrothermal activity of a small middle Miocene silicic flow-dome complex in north-central Nevada. There were multiple pulses of alteration and mineralization but all occurred within a period of less than 2 m.y. Later supergene alteration formed opal and alunite about 5.4 Ma but produced no Au or Ag mineralization other than some remobilization to produce locally rich pockets of secondary Au and Ag enrichment and is unrelated to the older magmatic hydrothermal system. The Sleeper deposit in the northern part of the Great Basin is genetically related to bimodal volcanism that followed a long period of arc-related andesitic volcanism in the same general region. -from Authors

  13. Density-Thermal-Driven Groundwater Flow and Brine Transport Near Salt Domes

    NASA Astrophysics Data System (ADS)

    Jamshidzadeh, Z.; Tsai, F. T.; Mirbagheri, S.; Ghasemzadeh, H.

    2012-12-01

    A major environmental and economic concern in many parts of the world is progressive salinization of groundwater system. Therefore, understanding the sources and flow patterns of encroachment of saline or brine water into freshwater aquifers is necessary for groundwater resources management. Flow patterns near salt domes in deep formation is of interest in this study because of complexity of different driving forces from salt concentration, thermal, and fluid pressure gradients. Because of rock formation and relative high temperature in the vicinity of salt domes, fluid salinity is much higher than seawater and density variation in the brine waters exceeds 20% with respect to fresh water. Groundwater flow, salt transport and heat transport equations are strongly coupled. Moreover, it is necessary to include the dispersive flux of total fluid mass in the flow equation. In this study, a two-dimensional density-thermal-driven groundwater flow induced by salt mass fraction gradient and temperature gradient near a hypothetical salt dome is considered. A fully implicit finite difference method has been developed to solve three coupled governing equations. The classical Elder problems and the Henry problem were used as benchmarks to verify the numerical code for solving the coupled flow and heat equations and the coupled flow and transport equations. Then, the numerical model is applied to a hypothetical salt dome problem to simulate upward density-thermal-driven groundwater flow and brine transport.

  14. A new design of Delclos dome cylinders using standard Cs-137 sources

    SciTech Connect

    Sharma, S.C.; Bhandare, N. )

    1991-07-01

    Surface dose rates around the currently-marketed Delclos uterine-vaginal afterloading dome (hemispherical) cylinders were calculated and measured for linear standard 3M cesium tube sources. Measurements were carried out using thin thermoluminescent lithium fluoride Chips on the surface of the cylinder and calculations at the same points were generated using a treatment planning computer. Wide surface dose variations were found for 2 to 3.5 cm diameter cylinders, but relatively small variation for 4 to 4.5 cm diameter cylinders. Attempting to achieve a uniform dose distribution around the entire dome surface of the cylinder, we have developed a new ellipsoidal design for the dome component that better conforms to the shape of the isodoses arising from the distal-most source. Thermoluminescent dosimetry indicates that the surface doses for the newly constructed cylinders are quite uniform, with variation within {plus minus} 5%. The effect on surface dose is discussed when the ellipsoidal dome cylinder in combination with vaginal cylinders is used and multiple sources are laid end to end to treat the added areas of the vaginal wall.

  15. The eastern Central Pamir Gneiss Domes: temporal and spatial geometry of burial and exhumation

    NASA Astrophysics Data System (ADS)

    Rutte, Daniel; Stearns, Michael; Ratschbacher, Lothar

    2013-04-01

    We present a structural and thermochronologic study of the Gneiss Domes and their cover in the Central Pamir. Emphasis is laid on presentation and discussion of new 40Ar-39Ar dates embedded in two structural profiles through the central Muskol and western Shatput domes. The structure of the Central Pamir is dominated by Cenozoic deformation related to the India-Asia collision. Only few structures of the Phanerozoic amalgamation of the Pamir were not reactivated. The Cenozoic structural development of the Central Pamir can be simplified into three phases: 1) Between initial collision of India and Asia to 28-20 Ma (peak metamorphism, U-Pb monazite) the emplacement of large thrust sheets led to strong north-south shortening;" in the eastern Central Pamir the major thrust sheet has a minimum displacement of 35 km. The stratigraphic thickness of this nappe is ~7 km but its internal structure and thus its true thickness is weakly constrained by the available data. Klippen of Early Paleozoic strata of this thrust sheet south of the Central Pamir Muskol and Shatput domes cover Carboniferous to Triassic strata of the footwall; they can be linked to the Akbaital nappe previously mapped by Russian geologists north of the domes. In the Sasaksu valley of the Muskol dome, the thrust sheet is intruded by a ~36 Ma granodiorite (new U-Pb zircon dates). (2) This crustal imbricate stack is cut by east-trending normal faults and shear zones that define the Central Pamir Gneiss Domes. Normal shear is concentrated along the northern margin of the domes and was the main process associated with exhumation of the domes from ~30 km depth at 20-15 Ma (U-Th/Pb titanite and monazite, Ar-Ar, fission-track geo-thermochronology). One granite at ~35 Ma (U-Pb zircon) pre-dates exhumation while three leucocratic dykes (18-20 Ma U-Pb monazite and zircon) are dated to be coeval with the initial stages of exhumation. Detrital U-Pb zircon ages of the high-grade metasediments indicate that the protoliths

  16. LOFT. West side of containment building and dome (TAN650). Camera ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    LOFT. West side of containment building and dome (TAN-650). Camera is atop earth -shield control building (TAN-630), facing east. Vertical structure at right of view (with light affixed) is west end of railroad door shroud. Date: May 2004. INEEL negative no. HD-39-19-1 - Idaho National Engineering Laboratory, Test Area North, Scoville, Butte County, ID

  17. Dome C: the best accessible site on Earth for submillimetre astronomy

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Schneider, N.; Minier, V.; Durand, G.; Reinert, Y.; Busso, M.; Sabbatini, L.; Storey, J. W. V.; Urban, J.; Calisse, P.; Veyssière, C.

    We present preliminary results of the measurements of sky transparency conducted at Dome C during the winter 2008. Using MOLIERE modeling, we estimate a low precipitable water vapour content above Concordia station, which is very promising for future submillimetre wave observations on the Antarctic Plateau.

  18. The PLATO Dome A site-testing observatory: Power generation and control systems

    NASA Astrophysics Data System (ADS)

    Lawrence, J. S.; Ashley, M. C. B.; Hengst, S.; Luong-van, D. M.; Storey, J. W. V.; Yang, H.; Zhou, X.; Zhu, Z.

    2009-06-01

    The atmospheric conditions above Dome A, a currently unmanned location at the highest point on the Antarctic plateau, are uniquely suited to astronomy. For certain types of astronomy Dome A is likely to be the best location on the planet, and this has motivated the development of the Plateau Observatory (PLATO). PLATO was deployed to Dome A in early 2008. It houses a suite of purpose-built site-testing instruments designed to quantify the benefits of Dome A site for astronomy, and science instruments designed to take advantage of the observing conditions. The PLATO power generation and control system is designed to provide continuous power and heat, and a high-reliability command and communications platform for these instruments. PLATO has run and collected data throughout the winter 2008 season completely unattended. Here we present a detailed description of the power generation, power control, thermal management, instrument interface, and communications systems for PLATO, and an overview of the system performance for 2008.

  19. Carboniferous tectonic history of the eastern flank of the Ozark dome

    SciTech Connect

    Nelson, W.J. )

    1993-03-01

    Detailed geologic mapping in southwestern Illinois and southeastern Missouri indicates that the eastern flank of the Ozark dome was a low positive area throughout Carboniferous (Mississippian and Pennsylvanian) time. Rock units of this age consistently thin onto the flank of the dome, and are punctuated by numerous disconformities. Effects of shoaling are prominent in Chesterian strata, which change from dominantly subtidal in the proto-Illinois basin to shallow subtidal, intertidal and supratidal on the flank of the dome. Although the dome probably was exposed subaerially for much of Carboniferous time, it contributed little sediment eastward. The exposed rocks were largely carbonates, which weathered by solution. Several long-lived basement structures on the east flank of the Ozarks were active during the Carboniferous. Chief among them were the Lincoln and Waterloo-Dupo anticlines, the Du Quoin monocline, and the Ste. Genevieve fault zone. All are high-angle reverse faults that strike north to northwest, and are overlain by sharp folds in sedimentary cover. Major displacements took place in late Valmeyeran to Atokan time, and addition deformation occurred in Desmoinesian through post-Pennsylvanian time. The compressional deformation probably is a product of the Ouachita orogeny.

  20. A Symbol of Peace and Peace Education: The Genbaku Dome in Hiroshima

    ERIC Educational Resources Information Center

    Ide, Kanako

    2007-01-01

    There are numerous paintings expressing both the glory and horror of war. These pictures are a powerful medium in peace education. In this article, the author focuses on a symbol of Hiroshima called the Genbaku Dome, a United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Site. She believes that images of the…

  1. The head dome: a simplified method for human exposures to inhaled air pollutants.

    PubMed

    Bowes, S M; Frank, R; Swift, D L

    1990-05-01

    Acute controlled exposures of human subjects to air pollutants are customarily carried out with whole-body chambers, masks, or mouthpieces. The use of these methods may be limited by cost or technical considerations. To permit a study involving a highly unstable pollutant, artificial acid fog, administered to subjects during natural breathing, a head-only exposure chamber, called a head dome, was developed. It consists of a transparent cylinder with a neck seal which fits over the subject's head and rests lightly on his shoulders. The head dome does not constrain the upper airways or impede exercise on a bicycle ergometer. Ventilation can be monitored accurately and unobtrusively with a pneumotachograph at the exhaust port of the dome. A thermocouple may be used to monitor the onset and persistence of oronasal breathing. For short-term exposures to unstable or reactive pollutants lasting up to several hours, the head dome is an effective alternative to a whole-body chamber and probably superior to a face mask or mouthpiece. PMID:2346113

  2. The Energy Dome. Social Studies Packet-Grades 4, 5, 6.

    ERIC Educational Resources Information Center

    National Science Teachers Association, Washington, DC.

    This teacher's guide contains a unit of study for teaching about energy in grades four, five, and six. The guide is self-contained and includes the fact sheets students need to work out the activity problems. The unit is organized around the theme of the domed athletic stadium. The students begin by surveying the energy it takes to travel from…

  3. The head dome: A simplified method for human exposures to inhaled air pollutants

    SciTech Connect

    Bowes, S.M. III; Frank, R.; Swift, D.L. )

    1990-05-01

    Acute controlled exposures of human subjects to air pollutants are customarily carried out with whole-body chambers, masks, or mouthpieces. The use of these methods may be limited by cost or technical considerations. To permit a study involving a highly unstable pollutant, artificial acid fog, administered to subjects during natural breathing, a head-only exposure chamber, called a head dome, was developed. It consists of a transparent cylinder with a neck seal which fits over the subject's head and rests lightly on his shoulders. The head dome does not constrain the upper airways or impede exercise on a bicycle ergometer. Ventilation can be monitored accurately and unobtrusively with a pneumotachograph at the exhaust port of the dome. A thermocouple may be used to monitor the onset and persistence of oronasal breathing. For short-term exposures to unstable or reactive pollutants lasting up to several hours, the head dome is an effective alternative to a whole-body chamber and probably superior to a face mask or mouthpiece.

  4. SURVEY AND EVALUATION OF FINE BUBBLE DOME AND DISC DIFFUSER AERATION SYSTEMS IN NORTH AMERICA

    EPA Science Inventory

    The research project was undertaken with the overall objective of better defining the oxygen transfer performance, operation and maintenance (O and M) requirements, and proper design approaches for ceramic fine bubble dome and disc diffuser aeration systems used in activated slud...

  5. Estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes

    NASA Astrophysics Data System (ADS)

    Fink, Jonathan H.; Kieffer, Susan W.

    1993-06-01

    APPARENTLY benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction, as happened recently at Mount Unzen in Japan1. Two sources have been proposed for the energy that propels such 'Peléan' or 'Merapi'-type2 pyroclastic flows: gravitational col-lapse (supplemented by heating and expansion of air) and sudden expansion of pressurized gases from inside the lava flow. If gravity controls the energy transfer, then areas likely to be affected can be predicted on the basis of topography3, and the resulting deposits will bear a simple relationship to the part of the lava flow from which they issued. But if gas pressure adds a significant contribution, hazard assessment becomes more difficult because gas decompression adds velocities beyond those acquired by gravitational forces, putting much larger areas at risk and forming pyroclastic deposits that are much more difficult to relate to their source. Here we estimate the initial velocities of pyroclastic flows generated by dome disintegration for a range of lava compositions and volatile contents, and offer a conceptual framework for correlating the dynamics of dome-front collapse with the resulting sediment record. Our results indicate that explosive decompression at distal portions of domes can cause velocities comparable to gravitational collapse, especially in cases where volatiles become locally concentrated above equilibrium values.

  6. The Southwest Indian Ocean thermocline dome in CMIP5 models: Historical simulation and future projection

    NASA Astrophysics Data System (ADS)

    Zheng, Xiao-Tong; Gao, Lihui; Li, Gen; Du, Yan

    2016-04-01

    Using 20 models of the Coupled Model Intercomparison Project Phase 5 (CMIP5), the simulation of the Southwest Indian Ocean (SWIO) thermocline dome is evaluated and its role in shaping the Indian Ocean Basin (IOB) mode following El Ni˜no investigated. In most of the CMIP5 models, due to an easterly wind bias along the equator, the simulated SWIO thermocline is too deep, which could further influence the amplitude of the interannual IOB mode. A model with a shallow (deep) thermocline dome tends to simulate a strong (weak) IOB mode, including key attributes such as the SWIO SST warming, antisymmetric pattern during boreal spring, and second North Indian Ocean warming during boreal summer. Under global warming, the thermocline dome deepens with the easterly wind trend along the equator in most of the models. However, the IOB amplitude does not follow such a change of the SWIO thermocline among the models; rather, it follows future changes in both ENSO forcing and local convection feedback, suggesting a decreasing effect of the deepening SWIO thermocline dome on the change in the IOB mode in the future.

  7. Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

    NASA Technical Reports Server (NTRS)

    Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

    2010-01-01

    Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

  8. Toward a large telescope facility for submm/FIR astronomy at Dome C

    NASA Astrophysics Data System (ADS)

    Durand, Gilles Alphonse; Minier, Vincent; Lagage, Pierre-Olivier; Daddi, Emanuele; El Khouloudi, Samir; Schneider-Bontemps, Nicola; Talvard, Michel; Veyssière, Christian; Durand, Gilles André; Walter, Christian; Sabbatini, Lucia; Challita, Zalpha; Storey, John W. V.; Calisse, Paolo; Pierre, Alain; Busso, Maurizio

    2008-07-01

    Submillimetre astronomy is the prime technique to unveil the birth and early evolution of stars and galaxies in the local and distant Universe. Preliminary meteorological studies and atmospheric transmission models tend to demonstrate that Dome C might offer atmosphere conditions that open the 200-μm atmospheric windows, and could potentially be a site for a large ground-based telescope facility. However, Antarctic climate conditions might also severely impact and deform any telescope mirror and hardware. We present prerequisite conditions and their associate experiments for defining a large telescope facility for submillimetre astronomy at Dome C: (1) Whether the submm/THz atmospheric windows open from 200 μm during a large and stable fraction of time; (2) The knowledge of thermal gradient and (3) icing formation and their impact on a telescope mirror and hardware. This paper will present preliminary results on current experiments that measure icing, thermal gradient and sky opacity at Dome C. We finally discuss a possible roadmap toward the deployment of a large telescope facility at Dome C.

  9. Annually-resolved temperature reconstructions of the past 2000 years from Dome-Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi; Motoyama, Hideaki

    2016-04-01

    We present annually-resolved temperature and SST reconstructions of the past 2000 years based on water (oxygen and deuterium) isotope measurement on a shallow ice core drilled in 2010 at Dome Fuji station, East Antarctica. These time series records will be an essential contribution to the PAGES 2k project from sparse data area in Antarctica. Dome Fuji station is located on a summit of Dronning Maud Land at an altitude of 3810 m a.s.l. (above sea level) (77o19'01'' S, 39o42'12'' E) in East Antarctica. The 10 m depth mean snow temperature at Dome Fuji is ‑57.3oC1). The inland area around Dome Fuji has been recognized to be especially unique: The snow and ice there contain much stratospheric information. The direct evidence for this comes from tritium contents originated from the nuclear bomb tests in the 1960s; the tritium fallout at the Dome Fuji site is outstandingly high among 16 snow pit samples widely collected over Antarctica2). To date the concerned Dome Fuji ice core, we applied volcanic signature matching to transfer the West Antarctic Ice Sheet (WAIS) Divide ice core chronology constructed by annual layer counting as used in the study by Sigl et al. (2014)3). In our presentation, we confine ourselves to discuss the oscillation periodicity that we observed in the oxygen isotope record in our data: The periods of approximately 10, 20, and 200 years were found. We will present the time series analyses for this in detail, and will discuss the origin of this periodicity. References: 1) Kameda, T., Motoyama, H., Fujita, S., and Takahashi, S.: "Past temporal and spatial variability of surface mass balance at Dome Fuji", East Antarctica, by the stake method from 1995 to 2006, J. Glaciol., 54, 107-116, 2008. 2) Fourre, E., Jean-Baptiste, P., Dapoigny, A., Baumier, D., Petit, J.-R., and Jouzel, J.: "Past and recent tritium levels in Arctic and Antarctic polar caps", Earth Planet. Sc. Lett., 245, 56-64, 2006. 3) Sigl, M., J. McConnell, M. Toohey, M. Curran, S. Das

  10. Solitary Waves, Magma Migration and Dome Building Eruptions at Mt. St. Helens, Washington

    NASA Astrophysics Data System (ADS)

    Ryan, M. P.; Stanley, B.; Plasker, M.

    2007-12-01

    Solitary waves have first-order attributes that include shape and volume conserving packets of fluid that migrate with characteristic wavelengths, amplitudes, wave numbers, and pulse durations. To ascend through dike-like, magma-filled fractures or sub-circular conduits, the solitary wave pulse duration is directly proportional to the conduit wall region viscosity and inversely proportional to the density contrast that drives the flow. Solitary waves are produced by the collapse of conduit wall rocks following the passage of a magma batch. The 1980-current eruptions at Mt. St. Helens display a variable time-series in their erupted volumes, as well as lava dome \\(or spine\\) heights / volumes and vent flow rates. Inter-eruption repose periods, however, have often shown broad regularity over extended periods. The rhythmic 'beat' of eruptive episodes within a long-lived series and their roughly regular repose periods arises directly from the solitary wave migration mechanism. Composite domes are suggested to be the products of solitary wave incremental additions of dacite, as in the 1980-1983 composite dome resulting from at least 9 such solitary wave-controlled additions. The 18 May 1980 dacite cryptodome may now be interpreted as a composite of several solitary wave-based intrusions leading to the climatic eruption volume. Domes may be either solitary or composite but are built up of one or several batches of evolving magma that ascend individually from the 8 to 1 km depth storage reservoir as solitary waves. Analytical calculations of wave speed, wave length, batch volume, parcel shapes and repose periods reveal the dependence on material properties appropriate for Mt. St. Helens intrusions and dome-building eruptions. Predicted solitary wave volumes and flow rates are in good agreement with observed values for dacitic dome and spine-building eruptions from 1980-1986 and from 2004-2007. Conduit dimensions are inferred to vary over the range R=2 to R=20 m. Magma

  11. Paroxysmal dome explosion during the Merapi 2010 eruption: Processes and facies relationships of associated high-energy pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Komorowski, Jean-Christophe; Jenkins, Susanna; Baxter, Peter J.; Picquout, Adrien; Lavigne, Franck; Charbonnier, Sylvain; Gertisser, Ralf; Preece, Katie; Cholik, Noer; Budi-Santoso, Agus; Surono

    2013-07-01

    An 11-minute sequence of laterally-directed explosions and retrogressive collapses on 5 November 2010 at Merapi (Indonesia) destroyed a rapidly-growing dome and generated high-energy pyroclastic density currents (PDCs) spreading over 22 km2 with a runout of 8.4 km while contemporaneous co-genetic valley-confined PDCs reached 15.5 km. This event formed Stage 4 of the multi-stage 2010 eruption, the most intense eruptive episode at Merapi since 1872. The deposits and the widespread devastating impact of associated high-energy PDCs on trees and buildings show striking similarities with those from historical volcanic blasts (Montagne Pelée, Martinique, Bezymianny, Russia, Mount St. Helens, USA, Soufrière Hills, Montserrat). We provide data from stratigraphic and sedimentologic analyses of 62 sections of the first unequivocal blast-like deposits in Merapi's recent history. We used high resolution satellite imagery to map eruptive units and flow direction from the pattern of extensive tree blowdown. The stratigraphy of Stage 4 consists of three depositional units (U0, U1, U2) that we correlate to the second, third and fourth explosions of the seismic record. Both U1 and U2 show a bi-partite layer stratigraphy consisting each of a lower L1 layer and an upper L2 layer. The lower L1 layer is typically very coarse-grained, fines-poor, poorly-sorted and massive, and was deposited by the erosive waxing flow head. The overlying L2 layer is much finer grained, fines-rich, moderately to well-sorted, with laminar to wavy stratification. L2 was deposited from the waning upper part and wake of the PDC. Field observations indicate that PDC height reached ~ 330 m with an internal velocity of ~ 100 m s- 1 within 3 km from the source. The summit's geometry and the terrain morphology formed by a major transversal ridge and a funneling deep canyon strongly focused PDC mass towards a major constriction, thereby limiting the loss of kinetic energy. This favored elevated PDC velocities and

  12. Laterally oscillating nitinol engine

    SciTech Connect

    Banks, R.

    1987-09-08

    This patent describes a laterally oscillating nitinol engine comprising: a first L-shaped drive member journalled for pivoting horizontal oscillation about the juncture of the legs of the L-shaped member, a second drive member journalled for pivoting about a point proximate the outboard end of the shorter leg of the L-shaped member at a distance from the pivot journal of the L-shaped member, a bearing block secured to the end of longer leg of the L-shaped and having a guide hole. The second member extending through the guide hole and arranged to reciprocate therein, a shape memory alloy power element disposed in flexure secured at its ends to the bearing block and to the second member intermediate the sliding connection with the bearing block and the pivotal connection of the second member, means for disposing different temperature baths below the element whereby as the drive members oscillate about their journals the element alternately dips into one bath and then the other, and means for absorbing a portion of the energy developed by the engine and moving the power element from the cold bath to the hot bath.

  13. Beryllium-10 in the Taylor Dome ice core: Applications to Antarctic glaciology and paleoclimatology

    SciTech Connect

    Steig, E.J.

    1996-12-31

    An ice core was drilled at Taylor dome, East Antarctica, reaching to bedrock at 554 meters. Oxygen-isotope measurements reveal climatic fluctuations through the last interglacial period. To facilitate comparison of the Taylor Dome paleoclimate record with geologic data and results from other deep ice cores, several glaciological issues need to be addressed. In particular, accumulation data are necessary as input for numerical ice-flow-models, for determining the flux of chemical constituents from measured concentrations, and for calculation of the offset in age between ice and trapped air in the core. The analysis of cosmogenic beryllium-10 provides a geochemical method for constraining the accumulation-rate history at Taylor Dome. High-resolution measurements were made in shallow firn cores and snow pits to determine the relationship among beryllium-10 concentrations, wet and dry deposition mechanisms, and snow-accumulation rates. Comparison between theoretical and measured variations in deposition over the last 75 years constrains the relationship between beryllium-10 deposition and global average production rates. The results indicate that variations in geomagnetically-modulated production-rate do not strongly influence beryllium-10 deposition at Taylor Dome. Although solar modulation of production rate is important for time scales of years to centuries, snow-accumulation rate is the dominant control on ice-core beryllium-10 concentrations for longer periods. Results show that the Taylor Dome core can be used to provide new constraints on regional climate over the last 130,000 years, complementing the terrestrial and marine geological record from the Dry Valley, Transantarctic Mountains and western Ross Sea.

  14. Intensity and polarization of the atmospheric emission at millimetric wavelengths at Dome Concordia

    NASA Astrophysics Data System (ADS)

    Battistelli, E. S.; Amico, G.; Baù, A.; Bergé, L.; Bréelle, É.; Charlassier, R.; Collin, S.; Cruciani, A.; de Bernardis, P.; Dufour, C.; Dumoulin, L.; Gervasi, M.; Giard, M.; Giordano, C.; Giraud-Héraud, Y.; Guglielmi, L.; Hamilton, J.-C.; Landé, J.; Maffei, B.; Maiello, M.; Marnieros, S.; Masi, S.; Passerini, A.; Piacentini, F.; Piat, M.; Piccirillo, L.; Pisano, G.; Polenta, G.; Rosset, C.; Salatino, M.; Schillaci, A.; Sordini, R.; Spinelli, S.; Tartari, A.; Zannoni, M.

    2012-06-01

    Atmospheric emission is a dominant source of disturbance in ground-based astronomy at millimetric wavelengths. The Antarctic plateau is recognized as an ideal site for millimetric and submillimetric observations, and the French/Italian base of Dome Concordia (Dome C) is among the best sites on Earth for these observations. In this paper, we present measurements at Dome C of the atmospheric emission in intensity and polarization at a 2-mm wavelength. This is one of the best observational frequencies for cosmic microwave background (CMB) observations when considering cosmic signal intensity, atmospheric transmission, detector sensitivity and foreground removal. Using the B-mode radiation interferometer (BRAIN)-pathfinder experiment, we have performed measurements of the atmospheric emission at 150 GHz. Careful characterization of the airmass synchronous emission has been performed, acquiring more than 380 elevation scans (i.e. 'skydip') during the third BRAIN-pathfinder summer campaign in 2009 December/2010 January. The extremely high transparency of the Antarctic atmosphere over Dome C is proven by the very low measured optical depth, <τI>= 0.050 ± 0.003 ± 0.011, where the first error is statistical and the second is the systematic error. Mid-term stability, over the summer campaign, of the atmosphere emission has also been studied. Adapting the radiative transfer atmosphere emission model am to the particular conditions found at Dome C, we also infer the level of the precipitable water vapor (PWV) content of the atmosphere, which is notoriously the main source of disturbance in millimetric astronomy (? mm). Upper limits on the airmass correlated polarized signal are also placed for the first time. The degree of circular polarization of atmospheric emission is found to be lower than 0.2 per cent [95 per cent confidence level (CL)], while the degree of linear polarization is found to be lower than 0.1 per cent (95 per cent CL). These limits include signal

  15. Thermal infrared investigation of the pyroclastic flow deposits and dome region of Bezymianny volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Carter, A. J.; Ramsey, M. S.; van Manen, S. M.

    2007-12-01

    Bezymianny (Kamchatka, Russia) is an active stratovolcano that contains a summit lava dome and pyroclastic flow (PF) sheet to the southeast. Two recent eruptions (24 December 2006 and 11 May 2007) generated fresh pyroclastic flows on the southeastern flank. During the winter of 2006, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) collected several day- and night-time images to monitor the December eruption deposits and subsequent events. A field campaign in August 2007 was conducted to investigate recent changes at the lava dome and to map the new PF deposits. Within the cloud-free night time ASTER image from 30 June 2007, seven ASTER thermal infrared (TIR) 90 m pixels were identified as being thermally-anomalous and were investigated in the field. Both handheld Forward Looking Infrared Radiometer (FLIR) and thermocouple probe data were obtained and compared to the satellite TIR data. Helicopter- and ground-based FLIR surveys revealed thermally-elevated PF deposits that contained warm blocks and fumaroles. The maximum fumarole temperature within the December 2006 PF deposit was 377C at a distance of five kilometers from the lava dome. At the terminus of the 24 December 2006 PF, seven kilometers from the dome, the maximum temperature recorded was 228C. This suggests that eight months after the December 2006 eruption, the deposit was of a sufficient thickness in this area to retain heat. In addition, the thickness of the deposit probably increased as the slope angle decreased approximately 4 kilometers from dome, which may explain the high temperatures observed. We present spaceborne, airborne and ground-based thermal data in order to compare direct and remote thermal observations of ongoing activity and provide the first ground-based TIR data of actively cooling PF deposits at Bezymianny.

  16. Permeability development during compaction of pumiceous dome lavas: testing the permeable foam collapse model

    NASA Astrophysics Data System (ADS)

    Ashwell, P.; Kendrick, J. E.; Lavallee, Y.; kennedy, B.; Hess, K.; von Aulock, F. W.; Cole, J. W.; Dingwell, D. B.

    2011-12-01

    The evolution of the porous network during lava dome extrusions is commonly perceived as the key control on the permeability which regulates the pore pressure, thereby challenging the stability of the dome. Here, we present experimental results of porosity and permeability evolution during compaction of aphiric and crystal-bearing rhyolitic, pumiceous (porosity ~60 %) lavas from Tarawera and Ngongotaha volcanoes (Taupo Volcanic Zone, New Zealand), respectively. The The Ngongotaha sample is from the crystal-free dome carapace (erupted ~200 ka following caldera collapse at Rotorua Caldera), while the Tarawera sample is a crystalline, pumiceous clast from a dome-collapse generated block and ash flow (at Okataina Caldera ~1314 AD). This study tests the validity of the 'permeable foam' model by comparing properties of the experimentally compacted pumice to denser material seen in the exposed cores of Tarawera and Ngongotaha. Cylindrical samples were deformed under an axial stress of 2.8 MPa at 650-750°C (above their calorimetric glass transition temperature) up a total axial strain of 50 %. The porosity and permeability of the samples were characterized at strain increments of 10 %. The samples exhibit strain hardening during compaction. A rapid reduction in permeability along the primary axis occurs during the initial stage of compression and continues to decrease with increasing strain and densification of the lava. Development of permeability of each lava differs as the crystallinity affects the compaction process. The development of textures and microstructures is characterised using petrographic analysis and neutron computed tomography. The findings from the study are then put into the context of lava dome growth at Tarawera and Ngongotaha volcanoes.

  17. Diamond heteroepitaxial lateral overgrowth

    NASA Astrophysics Data System (ADS)

    Tang, Yung-Hsiu

    This dissertation describes improvements in the growth of single crystal diamond by microwave plasma-assisted chemical vapor deposition (CVD). Heteroepitaxial (001) diamond was grown on 1 cm. 2 a-plane sapphiresubstrates using an epitaxial (001) Ir thin-film as a buffer layer. Low-energy ion bombardment of the Ir layer, a process known as bias-enhanced nucleation, is a key step in achieving a high density of diamond nuclei. Bias conditions were optimized to form uniformly-high nucleation densities across the substrates, which led to well-coalesced diamond thin films after short growth times. Epitaxial lateral overgrowth (ELO) was used as a means of decreasing diamond internal stress by impeding the propagation of threading dislocations into the growing material. Its use in diamond growth requires adaptation to the aggressive chemical and thermal environment of the hydrogen plasma in a CVD reactor. Three ELO variants were developed. The most successful utilized a gold (Au) mask prepared by vacuum evaporation onto the surface of a thin heteroepitaxial diamond layer. The Au mask pattern, a series of parallel stripes on the micrometer scale, was produced by standard lift-off photolithography. When diamond overgrows the mask, dislocations are largely confined to the substrate. Differing degrees of confinement were studied by varying the stripe geometry and orientation. Significant improvement in diamond quality was found in the overgrown regions, as evidenced by reduction of the Raman scattering linewidth. The Au layer was found to remain intact during diamond overgrowth and did not chemically bond with the diamond surface. Besides impeding the propagation of threading dislocations, it was discovered that the thermally-induced stress in the CVD diamond was significantly reduced as a result of the ductile Au layer. Cracking and delamination of the diamond from the substrate was mostly eliminated. When diamond was grown to thicknesses above 0.1 mm it was found that

  18. Thinking laterally about genomes.

    PubMed

    Ragan, Mark A

    2009-10-01

    Perhaps the most-surprising discovery of the genome era has been the extent to which prokaryotic and many eukaryotic genomes incorporate genetic material from sources other than their parent(s). Lateral genetic transfer (LGT) among bacteria was first observed about 100 years ago, and is now accepted to underlie important phenomena including the spread of antibiotic resistance and ability to degrade xenobiotics. LGT is invoked, perhaps too readily, to explain a breadth of awkward data including compositional heterogeneity of genomes, disagreement among gene-sequence trees, and mismatch between physiology and systematics. At the same time many details of LGT remain unknown or controversial, and some key questions have scarcely been asked. Here I critically review what we think we know about the existence, extent, mechanism and impact of LGT; identify important open questions; and point to research directions that hold particular promise for elucidating the role of LGT in genome evolution. Evidence for LGT in nature is not only inferential but also direct, and potential vectors are ubiquitous. Genetic material can pass between diverse habitats and be significantly altered during residency in viruses, complicating the inference of donors, In prokaryotes about twice as many genes are interrupted by LGT as are transferred intact, and about 5Short protein domains can be privileged units of transfer. Unresolved phylogenetic issues include the correct null hypothesis, and genes as units of analysis. Themes are beginning to emerge regarding the effect of LGT on cellular networks, but I show why generalization is premature. LGT can associate with radical changes in physiology and ecological niche. Better quantitative models of genome evolution are needed, and theoretical frameworks remain to be developed for some observations including chromosome assembly by LGT. PMID:20180279

  19. Geologic technical assessment of the Chacahoula Salt Dome, Louisiana, for potential expansion of the U.S. strategic petroleum reserve.

    SciTech Connect

    Snider, Anna C.; Rautman, Christopher Arthur; Looff, Karl M.

    2006-03-01

    The Chacahoula salt dome, located in southern Louisiana, approximately 66 miles southwest of New Orleans, appears to be a suitable site for a 160-million-barrel-capacity expansion facility for the U.S. Strategic Petroleum Reserve, comprising sixteen 10-million barrel underground storage caverns. The overall salt dome appears to cover an area of some 1800 acres, or approximately 2.8 square miles, at a subsea elevation of 2000 ft, which is near the top of the salt stock. The shallowest known salt is present at 1116 ft, subsea. The crest of the salt dome is relatively flatlying, outward to an elevation of -4000 ft. Below this elevation, the flanks of the dome plunge steeply in all directions. The dome appears to comprise two separate spine complexes of quasi-independently moving salt. Two mapped areas of salt overhang, located on the eastern and southeastern flanks of the salt stock, are present below -8000 ft. These regions of overhang should present no particular design issues, as the conceptual design SPR caverns are located in the western portion of the dome. The proposed cavern field may be affected by a boundary shear zone, located between the two salt spines. However, the large size of the Chacahoula salt dome suggests that there is significant design flexibility to deal with such local geologic issues.

  20. Cosmetic Lateral Canthoplasty: Preserving the Lateral Canthal Angle.

    PubMed

    Kim, Yeon-Jun; Lee, Kyu Ho; Choi, Hong Lim; Jeong, Eui Cheol

    2016-07-01

    Cosmetic lateral canthoplasty, in which the size of the eye is increased by extending the palpebral fissure and decreasing the degree of the eye slant, has become a prevalent procedure for East Asians. However, it is not uncommon for there to be complications or unfavorable results after the surgery. With this in mind, the authors have designed a surgical method to reduce complications in cosmetic lateral canthoplasty by preserving the lateral canthal angle. We discuss here the anatomy required for surgery, the surgical methods, and methods for reducing complications during cosmetic lateral canthoplasty. PMID:27462563

  1. Cosmetic Lateral Canthoplasty: Preserving the Lateral Canthal Angle

    PubMed Central

    Lee, Kyu Ho; Choi, Hong Lim; Jeong, Eui Cheol

    2016-01-01

    Cosmetic lateral canthoplasty, in which the size of the eye is increased by extending the palpebral fissure and decreasing the degree of the eye slant, has become a prevalent procedure for East Asians. However, it is not uncommon for there to be complications or unfavorable results after the surgery. With this in mind, the authors have designed a surgical method to reduce complications in cosmetic lateral canthoplasty by preserving the lateral canthal angle. We discuss here the anatomy required for surgery, the surgical methods, and methods for reducing complications during cosmetic lateral canthoplasty. PMID:27462563

  2. Electrical resistivity tomography applied to a complex lava dome: 2D and 3D models comparison

    NASA Astrophysics Data System (ADS)

    Portal, Angélie; Fargier, Yannick; Lénat, Jean-François; Labazuy, Philippe

    2015-04-01

    The study of volcanic domes growth (e.g. St. Helens, Unzen, Montserrat) shows that it is often characterized by a succession of extrusion phases, dome explosions and collapse events. Lava dome eruptive activity may last from days to decades. Therefore, their internal structure, at the end of the eruption, is complex and includes massive extrusions and lava lobes, talus and pyroclastic deposits as well as hydrothermal alteration. The electrical resistivity tomography (ERT) method, initially developed for environmental and engineering exploration, is now commonly used for volcano structure imaging. Because a large range of resistivity values is often observed in volcanic environments, the method is well suited to study the internal structure of volcanic edifices. We performed an ERT survey on an 11ka years old trachytic lava dome, the Puy de Dôme volcano (French Massif Central). The analysis of a recent high resolution DEM (LiDAR 0.5 m), as well as other geophysical data, strongly suggest that the Puy de Dôme is a composite dome. 11 ERT profiles have been carried out, both at the scale of the entire dome (base diameter of ~2 km and height of 400 m) on the one hand, and at a smaller scale on the summit part on the other hand. Each profile is composed of 64 electrodes. Three different electrode spacing have been used depending on the study area (35 m for the entire dome, 10 m and 5 m for its summit part). Some profiles were performed with half-length roll-along acquisitions, in order to keep a good trade-off between depth of investigation and resolution. Both Wenner-alpha and Wenner-Schlumberger protocols were used. 2-D models of the electrical resistivity distribution were computed using RES2DINV software. In order to constrain inversion models interpretation, the depth of investigation (DOI) method was applied to those results. It aims to compute a sensitivity index on inversion results, illustrating how the data influence the model and constraining models

  3. Amyotrophic lateral sclerosis

    PubMed Central

    Wijesekera, Lokesh C; Leigh, P Nigel

    2009-01-01

    Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterised by progressive muscular paralysis reflecting degeneration of motor neurones in the primary motor cortex, corticospinal tracts, brainstem and spinal cord. Incidence (average 1.89 per 100,000/year) and prevalence (average 5.2 per100,000) are relatively uniform in Western countries, although foci of higher frequency occur in the Western Pacific. The mean age of onset for sporadic ALS is about 60 years. Overall, there is a slight male prevalence (M:F ratio~1.5:1). Approximately two thirds of patients with typical ALS have a spinal form of the disease (limb onset) and present with symptoms related to focal muscle weakness and wasting, where the symptoms may start either distally or proximally in the upper and lower limbs. Gradually, spasticity may develop in the weakened atrophic limbs, affecting manual dexterity and gait. Patients with bulbar onset ALS usually present with dysarthria and dysphagia for solid or liquids, and limbs symptoms can develop almost simultaneously with bulbar symptoms, and in the vast majority of cases will occur within 1–2 years. Paralysis is progressive and leads to death due to respiratory failure within 2–3 years for bulbar onset cases and 3–5 years for limb onset ALS cases. Most ALS cases are sporadic but 5–10% of cases are familial, and of these 20% have a mutation of the SOD1 gene and about 2–5% have mutations of the TARDBP (TDP-43) gene. Two percent of apparently sporadic patients have SOD1 mutations, and TARDBP mutations also occur in sporadic cases. The diagnosis is based on clinical history, examination, electromyography, and exclusion of 'ALS-mimics' (e.g. cervical spondylotic myelopathies, multifocal motor neuropathy, Kennedy's disease) by appropriate investigations. The pathological hallmarks comprise loss of motor neurones with intraneuronal ubiquitin-immunoreactive inclusions in upper motor neurones and TDP-43 immunoreactive inclusions in

  4. Volcano dome dynamics at Mount St. Helens: Deformation and intermittent subsidence monitored by seismicity and camera imagery pixel offsets

    NASA Astrophysics Data System (ADS)

    Salzer, J. T.; Thelen, W. A.; James, M. R.; Walter, T. R.; Moran, S. C.; Denlinger, R. P.

    2015-12-01

    The morphology of a volcanic lava dome and its rate of change play key roles in the estimation of dome stability. While long term variations of dome morphology can be quantified using aerial remote sensing, changes over shorter time scales and smaller spatial scales are more difficult to determine. However, intermittent destabilization of the dome, in particular on flanks of the domes, can be significant. This study focuses on short term deformation associated with earthquakes and tremor at Mount St. Helens, observed over a 6 week period in the summer of 2006. We use Digital Image Correlation (DIC) to compute the displacement field between successive optical images acquired by multiple fixed cameras with clear views of the dome. The results of the these calculations are compared to the occurrence of seismic events. A systematic time-series DIC analysis of image pairs showed no sharp changes in the dome morphology during periods without seismic events. However, the results reveal that the steady dome growth at Mount St. Helens was interrupted by short term displacements reaching magnitudes on the order of a meter. These displacements are only observed in association with low frequency, large magnitude seismic events, followed by tremor with frequencies between 5 Hz and likely exceeding 30 Hz. For selected events that coincide with the timing of the acquisition of an accurate DEM of the crater floor, we reproject the displacement fields obtained from two cameras onto the topography. This enables 3D displacement vectors to be derived, showing that the co-seismic deformation is marked by subsidence of the dome in a segmented fashion, the central region displaying mainly vertical motion, while the displacements on the talus are more slope-parallel. The exact relationship between the recorded seismic energy and the observed deformation of the dome can not be resolved because the cameras were only sampling every 15 - 60 minutes. However, our analysis suggests that the

  5. Lava Dome Growth at Volcan de Fuego MEXICO (Colima Volcano), October 2001 to May 2002

    NASA Astrophysics Data System (ADS)

    Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Reyes-Davila, G. A.

    2002-12-01

    The Volcan de Fuego (19.512 N, 103.617 W) is located on the border between the States of Jalisco and Colima, Mexico, it is also known as Colima Volcano or Zapotl n Volcano, is a stratovolcano rising nearly 4000 m above sea level, and is the most active volcano in Mexico. Recent activity has been characterized by at least 3 different phases since January 1998 when seismic swarms began and ended with the extrusion of blocky lava in November 22, 1998 by the West vent as the 1991 eruptive process. That extrusive period lasted until the end of January, 1999 when was possible to observe a change in the seismic pattern, which mark the beginning of a new eruptive regime, an explosive one. On February 10, 1999 at approximately 0154 local time, 0754 gmt, an explosive event happens at the summit dome of Volc n de Fuego, four more big explosions took place at the summit the last one at dawn February 22, 2001. These explosions opened a new crater at the summit with a elliptical form with radius of 260 x 225 m and depth between 40 m and 15 m. A small dome structure inside the new crater was reported by March 2001. A reconnaissance flight in August 2001 shows two main features in the main crater an steep-sided mound(scoria cone) over the West vent and an inner crater on the NE vent. On October 31 Civil Defense members at Nevado Base on Nevado de Colima observed a neddle over the main crater rim, reconnaissance flight shows a spiny, 40 m high with a diameter of 20 m grows from the NE vent, the spiny seems to formed by material of the 1976 eruption. Continuous aerial observations allow us to follow the growth of a new dome pushing out the spiny. On November 23 the dimensions of the dome under the spiny were a radius of about 14 m and 21 m high for a total extrusion of 86,000 m3 which implies a extrusion rate of 0.027m3 /seg. By December the dome push out the spiny and began to grow from the NW vent. By December 29 an increase in the rate of extrusion was observed reaching a value

  6. Tremors in the Bayou: The Events on the Napoleonville Salt Dome, Louisiana

    NASA Astrophysics Data System (ADS)

    Ellsworth, W. L.; Horton, S.; Benz, H.; Hickman, S.; Leeds, A.; Leith, W. S.; Meremonte, M.; Rubinstein, J. L.; Withers, M. M.; Herrmann, R. B.

    2012-12-01

    Beginning in early June, 2012, an extended series of earth tremors were reported by residents of Bayou Corne in Assumption Parish, Louisiana, and at well control facilities on the nearby Napoleonville salt dome. The salt dome contains numerous caverns resulting from solution mining; some are used to store LPG and natural gas while others produce saltwater brine. Residents also reported natural gas bubbling at nearby locations in Bayou Corne and Grand Bayou. Some of the tremors were large enough to produce "cracks in sheet rock and foundations" (The Advocate, Baton Rouge, July 5, 2012). It was thus quite surprising to find that no earthquakes were detected in this region by either the USGS NEIC or the USArray Array Network Facility despite the presence of Transportable Array station 544A only 10 km from Bayou Corne. Careful inspection of the seismograms at 544A did reveal multiple events characterized by virtually no body wave energy and strong surface waves at the times of reported tremors. In response to a request for assistance from the State of Louisiana six temporary seismic stations with Trillium broad band sensors were deployed in the immediate epicentral region by the USGS and University of Memphis starting on July 12. Seismograms recorded by the temporary stations revealed a variable rate of tremor activity, with several hundred events registered on active days. Even at very close distance (S-P < 0.5 s) the body waves are weak and surface waves prominent, indicating a very shallow source depth. Precise location of the events is complicated by the presence of the high-seismic velocity and steep-sided Napoleonville salt dome that reaches to within 220 m of the surface and is overlain and surrounded by very low velocity sediments. Following several repositionings of the seismic network we have determined that the source region lies on the western edge of the salt dome top at very shallow depth and in the vicinity of an abandoned brine supply cavern. Tremor

  7. Blowing off steam: Tuffisite formation as a regulator for lava dome eruptions

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie; Lavallée, Yan; Varley, Nick; Wadsworth, Fabian; Lamb, Oliver; Vasseur, Jérémie

    2016-04-01

    Tuffisites are veins of variably sintered, pyroclastic particles that form in conduits and lava domes as a result of localized fragmentation events during gas-and-ash explosions. Those observed in-situ on the active 2012 lava dome of Volcán de Colima range from voids with intra-clasts showing little movement and interpreted to be failure-nuclei, to sub-parallel lenses of sintered granular aggregate interpreted as fragmentation horizons, through to infilled fractures with evidence of viscous remobilization. All tuffisites show evidence of sintering. Further examination of the complex fracture-and-channel patterns reveals viscous backfill by surrounding magma, suggesting that lava fragmentation was followed by stress relaxation and continued viscous deformation as the tuffisites formed. The natural tuffisites are more permeable than the host andesite, and have a wide range of porosity and permeability compared to a narrower window for the host rock, and gauging from their significant distribution across the dome, we posit that the tuffisite veins may act as important outgassing pathways. To investigate tuffisite formation we crushed and sieved andesite from the lava dome and sintered it at magmatic temperatures for different times. We then assessed the healing and sealing ability by measuring porosity and permeability, showing that sintering reduces both over time. During sintering the porosity-permeability reduction occurs due to the formation of viscous necks between adjacent grains, a process described by the neck-formation model of Frenkel (1945). This process leads the granular starting material to a porosity-permeability regime anticipated for effusive lavas, and which describes the natural host lava as well as the most impervious of natural tuffisites. This suggests that tuffisite formation at Volcán de Colima constructed a permeable network that enabled gas to bleed passively from the magma. We postulate that this progressively reduced the lava dome

  8. Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

    NASA Astrophysics Data System (ADS)

    Husain, Taha Murtuza

    Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

  9. Analysis Methodologies and Ameliorative Techniques for Mitigation of the Risk in Churches with Drum Domes

    SciTech Connect

    Zingone, Gaetano; Licata, Vincenzo; Calogero, Cucchiara

    2008-07-08

    The present work fits into the interesting theme of seismic prevention for protection of the monumental patrimony made up of churches with drum domes. Specifically, with respect to a church in the historic area of Catania, chosen as a monument exemplifying the typology examined, the seismic behavior is analyzed in the linear field using modern dynamic identification techniques. The dynamically identified computational model arrived at made it possible to identify the macro-element most at risk, the dome-drum system. With respect to this system the behavior in the nonlinear field is analyzed through dynamic tests on large-scale models in the presence of various types of improving reinforcement. The results are used to appraise the ameliorative contribution afforded by each of them and to choose the most suitable type of reinforcement, optimizing the stiffness/ductility ratio of the system.

  10. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride

    NASA Astrophysics Data System (ADS)

    Pan, Xing-Chen; Chen, Xuliang; Liu, Huimei; Feng, Yanqing; Wei, Zhongxia; Zhou, Yonghui; Chi, Zhenhua; Pi, Li; Yen, Fei; Song, Fengqi; Wan, Xiangang; Yang, Zhaorong; Wang, Baigeng; Wang, Guanghou; Zhang, Yuheng

    2015-07-01

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 T. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides.

  11. Localization of electrons in dome-shaped GeSi/Si islands

    SciTech Connect

    Yakimov, A. I.; Kirienko, V. V.; Bloshkin, A. A.; Armbrister, V. A.; Kuchinskaya, P. A.; Dvurechenskii, A. V.

    2015-01-19

    We report on intraband photocurrent spectroscopy of dome-shaped GeSi islands embedded in a Si matrix with n{sup +}-type bottom and top Si layers. An in-plane polarized photoresponse in the 85–160 meV energy region has been observed and ascribed to the optical excitation of electrons from states confined in the strained Si near the dome apexes to the continuum states of unstrained Si. The electron confinement is caused by a modification of the conduction band alignment induced by inhomogeneous tensile strain in Si around the buried GeSi quantum dots. Sensitivity of the device to the normal incidence radiation proves a zero-dimensional nature of confined electronic wave functions.

  12. Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride

    PubMed Central

    Pan, Xing-Chen; Chen, Xuliang; Liu, Huimei; Feng, Yanqing; Wei, Zhongxia; Zhou, Yonghui; Chi, Zhenhua; Pi, Li; Yen, Fei; Song, Fengqi; Wan, Xiangang; Yang, Zhaorong; Wang, Baigeng; Wang, Guanghou; Zhang, Yuheng

    2015-01-01

    Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 T. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides. PMID:26203922

  13. Seafloor doming driven by degassing processes unveils sprouting volcanism in coastal areas

    PubMed Central

    Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Chiodini, Giovanni; Caliro, Stefano; Sacchi, Marco; Rizzo, Andrea Luca; Ventura, Guido

    2016-01-01

    We report evidences of active seabed doming and gas discharge few kilometers offshore from the Naples harbor (Italy). Pockmarks, mounds, and craters characterize the seabed. These morphologies represent the top of shallow crustal structures including pagodas, faults and folds affecting the present-day seabed. They record upraise, pressurization, and release of He and CO2 from mantle melts and decarbonation reactions of crustal rocks. These gases are likely similar to those that feed the hydrothermal systems of the Ischia, Campi Flegrei and Somma-Vesuvius active volcanoes, suggesting the occurrence of a mantle source variously mixed to crustal fluids beneath the Gulf of Naples. The seafloor swelling and breaching by gas upraising and pressurization processes require overpressures in the order of 2–3 MPa. Seabed doming, faulting, and gas discharge are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions. PMID:26925957

  14. Geometric and Optic Characterization of a Hemispherical Dome Port for Underwater Photogrammetry

    PubMed Central

    Menna, Fabio; Nocerino, Erica; Fassi, Francesco; Remondino, Fabio

    2016-01-01

    The popularity of automatic photogrammetric techniques has promoted many experiments in underwater scenarios leading to quite impressive visual results, even by non-experts. Despite these achievements, a deep understanding of camera and lens behaviors as well as optical phenomena involved in underwater operations is fundamental to better plan field campaigns and anticipate the achievable results. The paper presents a geometric investigation of a consumer grade underwater camera housing, manufactured by NiMAR and equipped with a 7′′ dome port. After a review of flat and dome ports, the work analyzes, using simulations and real experiments, the main optical phenomena involved when operating a camera underwater. Specific aspects which deal with photogrammetric acquisitions are considered with some tests in laboratory and in a swimming pool. Results and considerations are shown and commented. PMID:26729133

  15. Compactional deformation bands in Wingate Sandstone; additional evidence of an impact origin for Upheaval Dome, Utah

    NASA Astrophysics Data System (ADS)

    Okubo, Chris H.; Schultz, Richard A.

    2007-04-01

    Field and microstructural observations from Upheaval Dome, in Canyonlands National Park, Utah, show that inelastic strain of the Wingate Sandstone is localized along compactional deformation bands. These bands are tabular discontinuities (< 0.5 cm thick) that accommodate inelastic shear and compaction of inter-granular volume. Measurements of porosity and grain size from non-deformed samples are used to define a set of capped strength envelopes for the Wingate Sandstone. These strength envelopes reveal that compactional deformation bands require at least ca. 0.7 GPa (and potentially more than 2.3 GPa) of effective mean stress in order to nucleate within this sandstone. We find that the most plausible geologic process capable of generating these required magnitudes of mean stress is a meteoritic impact. Therefore the compactional deformation bands observed within the Wingate Sandstone are additional evidence of an impact event at Upheaval Dome and support a post-Wingate (post-Early Jurassic) age for this impact.

  16. Seafloor doming driven by degassing processes unveils sprouting volcanism in coastal areas.

    PubMed

    Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Chiodini, Giovanni; Caliro, Stefano; Sacchi, Marco; Rizzo, Andrea Luca; Ventura, Guido

    2016-01-01

    We report evidences of active seabed doming and gas discharge few kilometers offshore from the Naples harbor (Italy). Pockmarks, mounds, and craters characterize the seabed. These morphologies represent the top of shallow crustal structures including pagodas, faults and folds affecting the present-day seabed. They record upraise, pressurization, and release of He and CO2 from mantle melts and decarbonation reactions of crustal rocks. These gases are likely similar to those that feed the hydrothermal systems of the Ischia, Campi Flegrei and Somma-Vesuvius active volcanoes, suggesting the occurrence of a mantle source variously mixed to crustal fluids beneath the Gulf of Naples. The seafloor swelling and breaching by gas upraising and pressurization processes require overpressures in the order of 2-3 MPa. Seabed doming, faulting, and gas discharge are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions. PMID:26925957

  17. Geometric and Optic Characterization of a Hemispherical Dome Port for Underwater Photogrammetry.

    PubMed

    Menna, Fabio; Nocerino, Erica; Fassi, Francesco; Remondino, Fabio

    2016-01-01

    The popularity of automatic photogrammetric techniques has promoted many experiments in underwater scenarios leading to quite impressive visual results, even by non-experts. Despite these achievements, a deep understanding of camera and lens behaviors as well as optical phenomena involved in underwater operations is fundamental to better plan field campaigns and anticipate the achievable results. The paper presents a geometric investigation of a consumer grade underwater camera housing, manufactured by NiMAR and equipped with a 7'' dome port. After a review of flat and dome ports, the work analyzes, using simulations and real experiments, the main optical phenomena involved when operating a camera underwater. Specific aspects which deal with photogrammetric acquisitions are considered with some tests in laboratory and in a swimming pool. Results and considerations are shown and commented. PMID:26729133

  18. Scalloped margin domes: What are the processes responsible and how do they operate?

    NASA Technical Reports Server (NTRS)

    Bulmer, M. H.; Guest, J. E.; Michaels, G.; Saunders, S.

    1993-01-01

    Studies of scalloped margin domes (SMD) indicate the scallops are the result of slope failure. SMD's have similar but smaller average diameters (26.5 km) to unmodified domes (29.8 km), and the majority plot at altitudes ranging from 0.5-4.7 km, relative to the mean planetary diameter. A range of morphological types exist from those least modified to those that show heavy modification. Of the 200 SMD's examined, 33 have clearly discernible debris aprons. Examination and comparison of debris aprons with mass movement features on the Moon, Mars, and in sub-aerial and submarine environments on Earth using H/L against area (km(sup 2)), suggests there are three main types of failure; debris avalanche, slumps, and debris flow. The five examples representing the morphological range within the SMD's, show the different modified forms and the different types of slope failures that have occurred.

  19. Metal-insulator quantum critical point beneath the high Tc superconducting dome

    PubMed Central

    Sebastian, Suchitra E.; Harrison, N.; Altarawneh, M. M.; Mielke, C. H.; Liang, Ruixing; Bonn, D. A.; Lonzarich, G. G.; Hardy, W. N.

    2010-01-01

    An enduring question in correlated systems concerns whether superconductivity is favored at a quantum critical point (QCP) characterized by a divergent quasiparticle effective mass. Despite such a scenario being widely postulated in high Tc cuprates and invoked to explain non-Fermi liquid transport signatures, experimental evidence is lacking for a critical divergence under the superconducting dome. We use ultrastrong magnetic fields to measure quantum oscillations in underdoped YBa2Cu3O6+x, revealing a dramatic doping-dependent upturn in quasiparticle effective mass at a critical metal-insulator transition beneath the superconducting dome. Given the location of this QCP under a plateau in Tc in addition to a postulated QCP at optimal doping, we discuss the intriguing possibility of two intersecting superconducting subdomes, each centered at a critical Fermi surface instability. PMID:20304800

  20. Seafloor doming driven by degassing processes unveils sprouting volcanism in coastal areas

    NASA Astrophysics Data System (ADS)

    Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Chiodini, Giovanni; Caliro, Stefano; Sacchi, Marco; Rizzo, Andrea Luca; Ventura, Guido

    2016-03-01

    We report evidences of active seabed doming and gas discharge few kilometers offshore from the Naples harbor (Italy). Pockmarks, mounds, and craters characterize the seabed. These morphologies represent the top of shallow crustal structures including pagodas, faults and folds affecting the present-day seabed. They record upraise, pressurization, and release of He and CO2 from mantle melts and decarbonation reactions of crustal rocks. These gases are likely similar to those that feed the hydrothermal systems of the Ischia, Campi Flegrei and Somma-Vesuvius active volcanoes, suggesting the occurrence of a mantle source variously mixed to crustal fluids beneath the Gulf of Naples. The seafloor swelling and breaching by gas upraising and pressurization processes require overpressures in the order of 2-3 MPa. Seabed doming, faulting, and gas discharge are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions.