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Sample records for tension screw geometry

  1. Cannulated screw and cable are superior to modified tension band in the treatment of transverse patella fractures.

    Science.gov (United States)

    Tian, Yun; Zhou, Fang; Ji, Hongquan; Zhang, Zhishan; Guo, Yan

    2011-12-01

    Although the modified tension band technique (eg, tension band supplemented by longitudinal Kirschner wires) has long been the mainstay for fixation of transverse fractures of the patella, it has shortcomings, such as bad reduction, loosening of implants, and skin irritation. We conducted a retrospective comparison of the modified tension band technique and the titanium cable-cannulated screw tension band technique. We retrospectively reviewed 101 patients aged 22 to 85 years (mean, 56.6 years) with AO/OTA 34-C1 fractures (n = 68) and 34-C2 fractures (n = 33). Fifty-two patients were in the modified tension band group and 49 were in the titanium cable-cannulated screw tension band group. Followup was at least 1 year (range, 1-3 years). Comparison criteria were fracture reduction, fracture healing time, and the Iowa score for knee function. The titanium cable-cannulated screw tension band group showed improved fracture reduction, reduced healing time, and better Iowa score, compared with the modified tension band group. In the modified tension band group, eight patients experienced wire migration, three of these requiring a second operation. There were no complications in the titanium cable-cannulated screw tension band group. The titanium cable-cannulated screw tension band technique showed superior results and should be considered as an alternative method for treatment of transverse patellar fractures. Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

  2. Internal Fixation of Transverse Patella Fractures Using Cannulated Cancellous Screws with Anterior Tension Band Wiring

    Directory of Open Access Journals (Sweden)

    Khan I

    2016-07-01

    Full Text Available Aims: To evaluate the effectiveness and safety of anterior tension band wiring technique using two cannulated cancellous screws in patients with transverse (AO34-C1 or transverse with mildly comminuted (AO34-C2 patellar fractures. Materials and Methods: This is a prospective study of 25 patients with transverse fracture or transverse fracture with mildly comminuted patella fractures. All the patients were treated with open reduction and internal fixation using two parallel cannulated screws and 18G stainless steel wire as per the tension band principle. Results: There were eighteen males (72% and seven females (28%. The age group ranged from 24 to 58 years, with mean age of 38 years. The most common mode of injury was fall (72% followed by road traffic accident (20% and violent quadriceps contraction (8%. Transverse fracture was present in 60% and transverse fracture with mild comminution in 40% of patients. Mean time to achieve union was 10.7 weeks (range 8-12 weeks. Mean ROM at three months was 113.8 degree (90-130 and at final follow up this improved to 125.4 degrees (range 100-140. There was one case of knee stiffness and no case of implant failure was observed. Patients were evaluated using Bostman scoring, the mean score at three months being 26.04 which improved to 27.36 at the end of final follow up at one year. Conclusion: Cannulated cancellous screws with anterior tension band wiring is a safe, reliable and reproducible method in management of transverse patellar fractures, with less chances of implant failure and soft tissue irritation.

  3. Open reduction and internal fixation of patellar fractures with tension band wiring through cannulated screws.

    Science.gov (United States)

    Malik, Mudasir; Halwai, Manzoor Ahmad

    2014-10-01

    The purpose of this study was to evaluate effectiveness and safety of a relatively new technique of open reduction and internal fixation of displaced transverse patellar fractures with tension band wiring (TBW) through parallel cannulated compression screws. A total of 30 patients with displaced transverse patellar fracture were enrolled in this prospective study. Of the 30 patients, 20 patients had trauma due to fall, 5 due to road traffic accident, 2 due to fall of heavy object on the knee, 2 due to forced flexion of knee, and 1 had fracture due to being beaten. All 30 patients were treated with vertical skin exposure, fracture open reduction, and internal fixation by anterior TBW through 4.0 mm cannulated screws. The postoperative rehabilitation protocol was standardized. The patients were followed postsurgery to evaluate time required for radiographic bone union, knee joint range of motion (ROM), loss of fracture reduction, material failure, and the overall functional result of knee using Bostman scoring. All the fractures healed radiologically, at an average time of 10.7 weeks (range, 8-12 weeks). The average ROM arc was 129.7 degrees (range, 115-140 degrees). No patient had loss of fracture reduction, implant migration, or material failure. The average Bostman score was 28.6 out of 30. Anterior TBW through cannulated screws for displaced transverse fractures is safe and effective alternative treatment. Good functional results and recovery can be expected. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  4. Additional Tension Screws Improve Stability in Elastic Stable Intramedullary Nailing: Biomechanical Analysis of a Femur Spiral Fracture Model.

    Science.gov (United States)

    Zachert, Gregor; Rapp, Marion; Eggert, Rebecca; Schulze-Hessing, Maaike; Gros, Nina; Stratmann, Christina; Wendlandt, Robert; Kaiser, Martin M

    2015-08-01

    For pediatric femoral shaft fractures, elastic stable intramedullary nailing (ESIN) is an accepted method of treatment. But problems regarding stability with shortening or axial deviation are well known in complex fracture types and heavier children. Biomechanical in vitro testing was performed to determine whether two modified osteosyntheses with an additional tension screw fixation or screw fixation alone without nails could significantly improve the stability in comparison to classical ESIN. A total of 24 synthetic adolescent-sized femoral bone models (Sawbones, 4th generation; Vashon, Washington, United States) with an identical spiral fracture (length 100 mm) were used. All grafts underwent retrograde fixation with two C-shaped steel nails (2C). Of the 24, 8 osteosyntheses were supported by one additional tension screw (2C1S) and another 8 by two screws (2S) in which the intramedullary nails were removed before testing. Each configuration underwent biomechanical testing in 4-point bending, external rotation (ER) and internal rotation (IR). Furthermore, the modifications were tested in axial physiological 9 degrees position for shifting and dynamic compression as well as dynamic load. Both screw configurations (2C1S and 2S) demonstrated a significantly higher stability in comparison to the 2C configuration in 4-point bending (anterior-posterior, 0.95 Nm/mm [2C] spiral fracture model, the stability of ESIN could be significantly improved by two modifications with additional tension screws. If transferred in clinical practice, these modifications might offer earlier weight bearing and less problems of shortening or axial deviation. Georg Thieme Verlag KG Stuttgart · New York.

  5. Indentation of a floating elastic sheet: geometry versus applied tension.

    Science.gov (United States)

    Box, Finn; Vella, Dominic; Style, Robert W; Neufeld, Jerome A

    2017-10-01

    The localized loading of an elastic sheet floating on a liquid bath occurs at scales from a frog sitting on a lily pad to a volcano supported by the Earth's tectonic plates. The load is supported by a combination of the stresses within the sheet (which may include applied tensions from, for example, surface tension) and the hydrostatic pressure in the liquid. At the same time, the sheet deforms, and may wrinkle, because of the load. We study this problem in terms of the (relatively weak) applied tension and the indentation depth. For small indentation depths, we find that the force-indentation curve is linear with a stiffness that we characterize in terms of the applied tension and bending stiffness of the sheet. At larger indentations, the force-indentation curve becomes nonlinear and the sheet is subject to a wrinkling instability. We study this wrinkling instability close to the buckling threshold and calculate both the number of wrinkles at onset and the indentation depth at onset, comparing our theoretical results with experiments. Finally, we contrast our results with those previously reported for very thin, highly bendable membranes.

  6. Investigation of the Geometry of Metal Tube Walls after Necking in Uniaxial Tension

    Directory of Open Access Journals (Sweden)

    Chong Li

    2017-03-01

    Full Text Available Abstract: In order to characterize the deformation and true stress–strain relation of metal tubes, the geometry of tube walls after necking in uniaxial tension need to be determined. The paper investigated the necking process of metal tube. A large number of tensile tests and finite element analysis of 1Cr18Ni9Ti tubes with different sizes were conducted. It was found that the geometry of outer tube wall in the necking region can be described using a logistic regression model. The final geometry of the tube is determined by original tube diameter and wall thickness. The offset of tube walls are affected by two competing factors: volume constancy and necking. The offset distances of outer and inner walls are mainly affected by original wall thickness. The length of the necking zone is more influenced by original tube diameter. Tube elongation at fracture increases slightly as tube diameter gets larger, while the wall thickness has almost no impact on the elongation.

  7. Isolated olecranon fractures in children affected by osteogenesis imperfecta type I treated with single screw or tension band wiring system: Outcomes and pitfalls in relation to bone mineral density.

    Science.gov (United States)

    Persiani, Pietro; Ranaldi, Filippo M; Graci, Jole; De Cristo, Claudia; Zambrano, Anna; D'Eufemia, Patrizia; Martini, Lorena; Villani, Ciro

    2017-05-01

    The purpose of this study is to compare the results of 2 techniques, tension band wiring (TBW) and fixation with screws, in olecranon fractures in children affected with osteogenesis imperfecta (OI) type I. Between 2010 and 2014, 21 olecranon fractures in 18 children with OI (average age: 12 years old) were treated surgically. Ten patients were treated with the screw fixation and 11 with TBW. A total of 65% of olecranon fractures occurred as a result of a spontaneous avulsion of the olecranon during the contraction of the triceps muscle. The average follow-up was 36 months. Among the children treated with 1 screw, 5 patients needed a surgical revision with TBW due to a mobilization of the screw. In this group, the satisfactory results were 50%. In patients treated with TBW, the satisfactory results were 100% of the cases. The average Z-score, the last one recorded in the patients before the trauma, was -2.53 in patients treated with screw fixation and -2.04 in those treated with TBW. TBW represents the safest surgical treatment for patients suffering from OI type I, as it helps to prevent the rigidity of the elbow through an earlier recovery of the range of motion, and there was no loosening of the implant. In analyzing the average Z-score before any fracture, the fixation with screws has an increased risk of failure in combination with low bone mineral density.

  8. Geometries

    CERN Document Server

    Sossinsky, A B

    2012-01-01

    The book is an innovative modern exposition of geometry, or rather, of geometries; it is the first textbook in which Felix Klein's Erlangen Program (the action of transformation groups) is systematically used as the basis for defining various geometries. The course of study presented is dedicated to the proposition that all geometries are created equal--although some, of course, remain more equal than others. The author concentrates on several of the more distinguished and beautiful ones, which include what he terms "toy geometries", the geometries of Platonic bodies, discrete geometries, and classical continuous geometries. The text is based on first-year semester course lectures delivered at the Independent University of Moscow in 2003 and 2006. It is by no means a formal algebraic or analytic treatment of geometric topics, but rather, a highly visual exposition containing upwards of 200 illustrations. The reader is expected to possess a familiarity with elementary Euclidean geometry, albeit those lacking t...

  9. Geometry

    Indian Academy of Sciences (India)

    . In the previous article we looked at the origins of synthetic and analytic geometry. More practical minded people, the builders and navigators, were studying two other aspects of geometry- trigonometry and integral calculus. These are actually ...

  10. Geometry

    CERN Document Server

    Prasolov, V V

    2015-01-01

    This book provides a systematic introduction to various geometries, including Euclidean, affine, projective, spherical, and hyperbolic geometries. Also included is a chapter on infinite-dimensional generalizations of Euclidean and affine geometries. A uniform approach to different geometries, based on Klein's Erlangen Program is suggested, and similarities of various phenomena in all geometries are traced. An important notion of duality of geometric objects is highlighted throughout the book. The authors also include a detailed presentation of the theory of conics and quadrics, including the theory of conics for non-Euclidean geometries. The book contains many beautiful geometric facts and has plenty of problems, most of them with solutions, which nicely supplement the main text. With more than 150 figures illustrating the arguments, the book can be recommended as a textbook for undergraduate and graduate-level courses in geometry.

  11. Determination of enthalpy, temperature, surface tension and geometry of the material transfer in PGMAW for the system argon–iron

    International Nuclear Information System (INIS)

    Siewert, E; Schein, J; Forster, G

    2013-01-01

    The metal transfer is a fundamental process in gas metal arc welding, which substantially determines the shape of the weld seam and strongly influences arc formation and stability. In this investigation the material transfer from the wire electrode (anode) to the workpiece (cathode) is analysed experimentally with high accuracy using various innovative diagnostic techniques for a pulsed gas metal arc welding (PGMAW) process. A high-speed two-colour pyrometer, a calorimeter, thermocouples, a stereo optical setup and a droplet oscillation technique are used to analyse a precisely defined PGMAW process. Thus, results obtained are verified by different measurement techniques and enable a comprehensive description of the material transfer procedure. The surface temperature of both electrodes as well as the droplet temperature, enthalpy and surface tension were determined. Furthermore, the geometry of the arc, wire, droplets and weld pool were extracted in three dimensions in order to describe the interaction between the material transfer and the formation of the weld seam. The experiments are performed using argon as shielding gas and pure iron as filler and base material to reduce complex chemical processes. It turned out that the wire feed rate has the biggest influence on droplet temperature and detachment. A correlation between weld pool formation and weld pool surface temperature gradient was observed, which is mainly a function of welding speed and wire feed rate. The experimental results obtained provide a detailed data pool for use in modelling. (paper)

  12. Geometry

    CERN Document Server

    Pedoe, Dan

    1988-01-01

    ""A lucid and masterly survey."" - Mathematics Gazette Professor Pedoe is widely known as a fine teacher and a fine geometer. His abilities in both areas are clearly evident in this self-contained, well-written, and lucid introduction to the scope and methods of elementary geometry. It covers the geometry usually included in undergraduate courses in mathematics, except for the theory of convex sets. Based on a course given by the author for several years at the University of Minnesota, the main purpose of the book is to increase geometrical, and therefore mathematical, understanding and to he

  13. Molecular dynamics modeling on the role of initial void geometry in a thin aluminum film under uniaxial tension

    International Nuclear Information System (INIS)

    Cui, Yi; Chen, Zengtao

    2015-01-01

    The effect of initial void geometry on damage progression in a thin aluminum film under uniaxial load is studied via molecular dynamics (MD) method. The embedded voids are with different initial geometries regarding shape, porosity and intervoid ligament distance (ILD). Major simulations are run upon twelve MD geometries with each containing 8–27 million atoms. The corresponding stress–strain relation is monitored during the microstructure evolution of the specimens. The critical stress to trigger the dislocation emission is found in line with the prediction of the Lubarda model. The simulation results reveal that the initial void geometry has substantial impact on the stress–strain relation especially for a specimen with larger initial porosity. (paper)

  14. In vitro validation of a novel mechanical model for testing the anchorage capacity of pedicle screws using physiological load application.

    Science.gov (United States)

    Liebsch, Christian; Zimmermann, Julia; Graf, Nicolas; Schilling, Christoph; Wilke, Hans-Joachim; Kienle, Annette

    2018-01-01

    Biomechanical in vitro tests analysing screw loosening often include high standard deviations caused by high variabilities in bone mineral density and pedicle geometry, whereas standardized mechanical models made of PU foam often do not integrate anatomical or physiological boundary conditions. The purpose of this study was to develop a most realistic mechanical model for the standardized and reproducible testing of pedicle screws regarding the resistance against screw loosening and the holding force as well as to validate this model by in vitro experiments. The novel mechanical testing model represents all anatomical structures of a human vertebra and is consisting of PU foam to simulate cancellous bone, as well as a novel pedicle model made of short carbon fibre filled epoxy. Six monoaxial cannulated pedicle screws (Ø6.5 × 45mm) were tested using the mechanical testing model as well as human vertebra specimens by applying complex physiological cyclic loading (shear, tension, and bending; 5Hz testing frequency; sinusoidal pulsating forces) in a dynamic materials testing machine with stepwise increasing load after each 50.000 cycles (100.0N shear force + 20.0N per step, 51.0N tension force + 10.2N per step, 4.2Nm bending moment + 0.8Nm per step) until screw loosening was detected. The pedicle screw head was fixed on a firmly clamped rod while the load was applied in the vertebral body. For the in vitro experiments, six human lumbar vertebrae (L1-3, BMD 75.4 ± 4.0mg/cc HA, pedicle width 9.8 ± 0.6mm) were tested after implanting pedicle screws under X-ray control. Relative motions of pedicle screw, specimen fixture, and rod fixture were detected using an optical motion tracking system. Translational motions of the mechanical testing model experiments in the point of load introduction (0.9-2.2mm at 240N shear force) were reproducible within the variation range of the in vitro experiments (0.6-3.5mm at 240N shear force). Screw loosening occurred continuously in

  15. Análisis de tensiones en árboles de geometría compleja. // Stress analysis in complex geometry shafts.

    Directory of Open Access Journals (Sweden)

    M. Sánchez Noa

    2001-07-01

    Full Text Available En el presente trabajo se exponen los resultados del análisis realizado en árboles de compleja geometría pertenecientes a unmultiplicador planetario tipo 2KH-A destinado a emplearse en aerogeneradores de electricidad. En el mismo, se presentanlos modelos físico-matemáticos de dichos árboles para ser analizados mediante el método de los elementos finitos,considerando el estado de carga que surge al funcionar el mecanismo y contemplando el efecto adicional de las cargasgiroscópicas. Se muestran las zonas de conflicto de tensiones y se analizan propuestas de diseño que permitan, garantizandola resistencia y rigidez, realizar variaciones dimensionales y mejorar la compacidad de los elementos, disminuyendo a lavez el peso de los mismos.Palabras claves: Elementos finitos, multiplicador planetario, diseño de árbol, resistencia mecánica.____________________________________________________________________________AbstractThe results of the analysis in shafts of complex geometry, belonging to a planetary multiplier type 2KH-AM to be usedin wind generators is presented. The physical-mathematical models of these shafts are analyzed by means of finiteelement method. Can increasing of load when the mechanism is working and contemplating the additional effect of thegyroscopic loads. The tension distribution are shown and design proposals are analyzed to improve the resistance, rigidityand to improve the compactness of the elements. This analysis constitutes an application of the the finite element methodof which reference doesn't existKey Words: Finite elements method, planetary gear unit, shaft design, mechanical strength.

  16. Enhancing the performance of a tensioned metastable fluid detector based active interrogation system for the detection of SNM in interrogation source in moderated/reflected geometries

    Science.gov (United States)

    Grimes, T. F.; Hagen, A. R.; Archambault, B. C.; Taleyarkhan, R. P.

    2018-03-01

    This paper describes the development of a SNM detection system for interrogating 1m3 cargos via the combination of a D-D neutron interrogation source (with and without reflectors) and tensioned metastable fluid detectors (TMFDs). TMFDs have been previously shown (Taleyarkhan et al., 2008; Grimes et al., 2015; Grimes and Taleyarkhan, 2016; Archambault et al., 2017; Hagen et al., 2016) to be capable of using Threshold Energy Neutron Analysis (TENA) techniques to reject the ∼2.45 MeV D-D interrogating neutrons while still remaining sensitive to >2.45 MeV neutrons resulting from fission in the target (HEU) material. In order to enhance the performance, a paraffin reflector was included around the accelerator head. This reflector was used to direct neutrons into the package to increase the fission signal, lower the energy of the interrogating neutrons to increase the fission cross-section with HEU, and, also to direct interrogating neutrons away from the detectors in order to enhance the required discrimination between interrogating and fission neutrons. Experiments performed with a 239 Pu-Be neutron source and MnO2 indicated that impressive performance gains could be made by placing a parabolic paraffin moderator between the interrogation source and an air-filled cargo container with HEU placed at the center. However, experiments with other cargo fillers (as specified in the well-known ANSI N42.41-2007 report), and with HEU placed in locations other than the center of the package indicated that other reflector geometries might be superior due to over-"focusing" and the increased solid angle effects due to the accommodation of the moderator geometry. The best performance for the worst case of source location and box fill was obtained by placing the reflector only behind the D-D neutron source rather than in front of it. Finally, it was shown that there could be significant gains in the ability to detect concealed SNM by operating the system in multiple geometric

  17. Comparison of surgical techniques of 111 medial malleolar fractures classified by fracture geometry.

    Science.gov (United States)

    Ebraheim, Nabil A; Ludwig, Todd; Weston, John T; Carroll, Trevor; Liu, Jiayong

    2014-05-01

    Evaluation of operative techniques used for medial malleolar fractures by classifying fracture geometry has not been well documented. One hundred eleven patients with medial malleolar fractures (transverse n = 63, oblique n = 29, vertical n = 7, comminuted n = 12) were included in this study. Seventy-two patients had complicating comorbidities. All patients were treated with buttress plate, lag screw, tension band, or K-wire fixation. Treatment outcomes were evaluated on the basis of radiological outcome (union, malunion, delayed union, or nonunion), need for operative revision, presence of postoperative complications, and AOFAS Ankle-Hindfoot score. For transverse fractures, tension band fixation showed the highest rate of union (79%), highest average AOFAS score (86), lowest revision rate (5%), and lowest complication rate (16%). For oblique fractures, lag screws showed the highest rate of union (71%), highest average AOFAS score (80), lowest revision rate (19%), and lowest complication rate (33%) of the commonly used fixation techniques. For vertical fractures, buttress plating was used in every case but 1, achieving union (whether normal or delayed) in all cases with an average AOFAS score of 84, no revisions, and a 17% complication rate. Comminuted fractures had relatively poor outcomes regardless of fixation method. The results of this study suggest that both tension bands and lag screws result in similar rates of union for transverse fractures of the medial malleolus, but that tension band constructs are associated with less need for revision surgery and fewer complications. In addition, our data demonstrate that oblique fractures were most effectively treated with lag screws and that vertical fractures attained superior outcomes with buttress plating. Level III, retrospective comparative series.

  18. Drag and Torque on Locked Screw Propeller

    Directory of Open Access Journals (Sweden)

    Tomasz Tabaczek

    2014-09-01

    Full Text Available Few data on drag and torque on locked propeller towed in water are available in literature. Those data refer to propellers of specific geometry (number of blades, blade area, pitch and skew of blades. The estimation of drag and torque of an arbitrary propeller considered in analysis of ship resistance or propulsion is laborious. The authors collected and reviewed test data available in the literature. Based on collected data there were developed the empirical formulae for estimation of hydrodynamic drag and torque acting on locked screw propeller. Supplementary CFD computations were carried out in order to prove the applicability of the formulae to modern moderately skewed screw propellers.

  19. Tension Headache

    Science.gov (United States)

    ... tight band around your head. A tension headache (tension-type headache) is the most common type of headache, and ... Headache after a head injury, especially if the headache gets worse ... tension or stress. But research suggests muscle contraction isn't the ...

  20. Sacroiliac Screw Fixation

    NARCIS (Netherlands)

    E.W. van den Bosch

    2003-01-01

    textabstractThe aim of this thesis is to evaluate three major aspects of the use of sacroiliac screws in patients with unstable pelvic ring fractures: the optimal technique for sacroiliac screw fixation, the reliability of peroperative fluoroscopy and the late results. We focused on the questions

  1. Multiaxial pedicle screw designs: static and dynamic mechanical testing.

    Science.gov (United States)

    Stanford, Ralph Edward; Loefler, Andreas Herman; Stanford, Philip Mark; Walsh, William R

    2004-02-15

    Randomized investigation of multiaxial pedicle screw mechanical properties. Measure static yield and ultimate strengths, yield stiffness, and fatigue resistance according to an established model. Compare these measured properties with expected loads in vivo. Multiaxial pedicle screws provide surgical versatility, but the complexity of their design may reduce their strength and fatigue resistance. There is no published data on the mechanical properties of such screws. Screws were assembled according to a vertebrectomy model for destructive mechanical testing. Groups of five assemblies were tested in static tension and compression and subject to three cyclical loads. Modes of failure, yield, and ultimate strength, yield stiffness, and cycles to failure were determined for six designs of screw. Static compression yield loads ranged from 217.1 to 388.0 N and yield stiffness from 23.7 to 38.0 N/mm. Cycles to failure ranged from 42 x 10(3) to 4,719 x 10(3) at 75% of static ultimate load. There were significant differences between designs in all modes of testing. Failure occurred at the multiaxial link in static and cyclical compression. Bending yield strengths just exceeded loads expected in vivo. Multiaxial designs had lower static bending yield strength than fixed screw designs. Five out of six multiaxial screw designs achieved one million cycles at 200 N in compression bending. "Ball-in-cup" multiaxial locking mechanisms were vulnerable to fatigue failure. Smooth surfaces and thicker material appeared to be protective against fatigue failure.

  2. Ball Screw Actuator Including a Compliant Ball Screw Stop

    Science.gov (United States)

    Wingett, Paul T. (Inventor); Hanlon, Casey (Inventor)

    2017-01-01

    An actuator includes a ball nut, a ball screw, and a ball screw stop. The ball nut is adapted to receive an input torque and in response rotates and supplies a drive force. The ball screw extends through the ball nut and has a first end and a second end. The ball screw receives the drive force from the ball nut and in response selectively translates between a retract position and a extend position. The ball screw stop is mounted on the ball screw proximate the first end to translate therewith. The ball screw stop engages the ball nut when the ball screw is in the extend position, translates, with compliance, a predetermined distance toward the first end upon engaging the ball nut, and prevents further rotation of the ball screw upon translating the predetermined distance.

  3. Complications of syndesmotic screw removal

    NARCIS (Netherlands)

    Schepers, Tim; van Lieshout, Esther M. M.; de Vries, Mark R.; van der Elst, Maarten

    2011-01-01

    Currently, the metallic syndesmotic screw is the gold standard in the treatment of syndesmotic disruption. Whether or not this screw needs to be removed remains debatable. The aim of the current study was to determine the complications which occur following routine removal of the syndesmotic screw

  4. Analysis of Modeling Parameters on Threaded Screws.

    Energy Technology Data Exchange (ETDEWEB)

    Vigil, Miquela S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brake, Matthew Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vangoethem, Douglas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-06-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry cause issues when generating a mesh of the model. This paper will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  5. Tension headache.

    Science.gov (United States)

    Ziegler, D K

    1978-05-01

    Headache is an extremely common symptom, and many headaches undoubtedly have a relationship to stressful situations. The clear definition, however, of a "tension headache" complex and its differentiation from migraine in some patients is difficult. The problems are in the identification of a specific headache pattern induced by stress or "tension" and the relationship of the symptom to involuntary contraction of neck and scalp muscles. Treatment consists of analgesics and occasionally mild tranquilizers. Psychotherapy consists of reassurance and often other supportive measures, including modification of life styles. Various feedback techniques have been reported of value, but their superiority to suggestion and hypnosis is still problematic.

  6. Spinning geometry = Twisted geometry

    International Nuclear Information System (INIS)

    Freidel, Laurent; Ziprick, Jonathan

    2014-01-01

    It is well known that the SU(2)-gauge invariant phase space of loop gravity can be represented in terms of twisted geometries. These are piecewise-linear-flat geometries obtained by gluing together polyhedra, but the resulting geometries are not continuous across the faces. Here we show that this phase space can also be represented by continuous, piecewise-flat three-geometries called spinning geometries. These are composed of metric-flat three-cells glued together consistently. The geometry of each cell and the manner in which they are glued is compatible with the choice of fluxes and holonomies. We first remark that the fluxes provide each edge with an angular momentum. By studying the piecewise-flat geometries which minimize edge lengths, we show that these angular momenta can be literally interpreted as the spin of the edges: the geometries of all edges are necessarily helices. We also show that the compatibility of the gluing maps with the holonomy data results in the same conclusion. This shows that a spinning geometry represents a way to glue together the three-cells of a twisted geometry to form a continuous geometry which represents a point in the loop gravity phase space. (paper)

  7. Mini-Fragment Fixation Is Equivalent to Bicortical Screw Fixation for Horizontal Medial Malleolus Fractures.

    Science.gov (United States)

    Wegner, Adam M; Wolinsky, Philip R; Robbins, Michael A; Garcia, Tanya C; Amanatullah, Derek F

    2018-05-01

    Horizontal fractures of the medial malleolus occur through application of valgus or abduction force through the ankle that creates a tension failure of the medial malleolus. The authors hypothesize that mini-fragment T-plates may offer improved fixation, but the optimal fixation construct for these fractures remains unclear. Forty synthetic distal tibiae with identical osteotomies were randomized into 4 fixation constructs: (1) two parallel unicortical cancellous screws; (2) two parallel bicortical cortical screws; (3) a contoured mini-fragment T-plate with 2 unicortical screws in the fragment and 2 bicortical screws in the shaft; and (4) a contoured mini-fragment T-plate with 2 bicortical screws in the fragment and 2 unicortical screws in the shaft. Specimens were subjected to offset axial tension loading on a servohydraulic testing system and tracked using high-resolution video. Failure was defined as 2 mm of articular displacement. Analysis of variance followed by a Tukey-Kramer post hoc test was used to assess for differences between groups, with significance defined as Pfragment T-plate constructs (239±83 N/mm and 190±37 N/mm) and the bicortical screw construct (240±17 N/mm) were not statistically different. The mean stiffness values of both mini-fragment T-plate constructs and the bicortical screw construct were higher than that of a parallel unicortical screw construct (102±20 N/mm). Contoured T-plate constructs provide stiffer initial fixation than a unicortical cancellous screw construct. The T-plate is biomechanically equivalent to a bicortical screw construct, but may be superior in capturing small fragments of bone. [Orthopedics. 2018; 41(3):e395-e399.]. Copyright 2018, SLACK Incorporated.

  8. Positioning device for screwing or unscrewing screw nut

    International Nuclear Information System (INIS)

    Sevelinge, G.

    1987-01-01

    This automatic positioning device for screwing or unscrewing a screw nut on a closure stud has a drawed socket and means for axially centre and angularly by wedge the socket on the closure stud and generate a continuous spiral between the socket and the closure stud [fr

  9. Scaphoid Fracture Fixation with an Acutrak? Screw

    OpenAIRE

    Loving, Vilert A.; Richardson, Michael L.

    2015-01-01

    We report a case of fixation of a scaphoid fracture using an Acutrak? screw. This screw is cannulated and headless, which allows it to be implanted below the surface of the bone. It uses the same concept of variable thread pitch as the Herbert screw, but unlike the Herbert screw, is fully threaded, with continuously varying pitch along its length. This variable pitch creates constant compression across a fracture as the screw is advanced, and gives the screw its unique appearance. This featur...

  10. Complications of syndesmotic screw removal

    NARCIS (Netherlands)

    T. Schepers (Tim); E.M.M. van Lieshout (Esther); M.R. de Vries (Mark); M. van der Elst (Maarten)

    2011-01-01

    textabstractBackground: Currently, the metallic syndesmotic screw is the gold standard in the treatment of syndesmotic disruption. Whether or not this screw needs to be removed remains debatable. The aim of the current study was to determine the complications which occur following routine removal of

  11. Frictional performance of ball screw

    International Nuclear Information System (INIS)

    Nakashima, Katuhiro; Takafuji, Kazuki

    1985-01-01

    As feed screws, ball screws have become to be adopted in place of trapezoidal threads. The structure of ball screws is complex, but those are the indispensable component of NC machine tools and machining centers, and are frequently used for industrial robots. As the problems in the operation of ball screws, there are damage, life and the performance related to friction. As to the damage and life, though there is the problem of the load distribution on balls, the results of the research on rolling bearings are applied. The friction of ball screws consists of the friction of balls and a spiral groove, the friction of a ball and a ball, the friction in a ball-circulating mechanism and the viscous friction of lubricating oil. It was decided to synthetically examine the frictional performance of ball screws, such as driving torque, the variation of driving torque, efficiency, the formation of oil film and so on, under the working condition of wide range, using the screws with different accuracy and the nuts of various circuit number. The experimental setup and the processing of the experimental data, the driving performance of ball screws and so on are reported. (Kako, I.)

  12. Studies on positive conveying in helically channeled single screw extruders

    Directory of Open Access Journals (Sweden)

    L. Pan

    2012-07-01

    Full Text Available A solids conveying theory called double-flight driving theory was proposed for helically channeled single screw extruders. In the extruder, screw channel rotates against static barrel channel, which behaves as cooperative embedded twin-screws for the positive conveying. They turn as two parallel arc plates, between which an arc-plate solid-plug was assumed. By analyzing the forces on the solid-plug in the barrel channel and screw channel, the boundary conditions when the solid-plug is waived of being cut off on barrel wall, were found to have the capacity of the positive conveying. Experimental data were obtained using a specially designed extruder with a helically channeled barrel in the feeding zone and a pressure-adjustable die. The effects of the barrel channel geometry and friction coefficients on the conveying mechanism were presented and compared with the experimental results. The simulations showed that the positive conveying could be achieved after optimizing extruder designs. Compared with the traditional design with the friction-drag conveying, the throughput is higher while screw torque and energy consumption are decreased. Besides, the design criteria of the barrel channel were also discussed.

  13. Theoretical investigation of flash vaporisation in a screw expander

    Science.gov (United States)

    Vasuthevan, Hanushan; Brümmer, Andreas

    2017-08-01

    In the present study flash vaporisation of liquid injection in a twin screw expander for a Trilateral Flash Cycle (TFC) is examined theoretically. The TFC process comprises a pressure increase in the working fluid, followed by heating the liquid close to boiling point. The hot liquid is injected into the working chamber of a screw expander. During this process the pressure of the liquid drops below the saturation pressure, while the temperature of the liquid remains virtually constant. Hence the liquid is superheated and in a metastable state. The liquid jet seeks to achieve a stable state in thermodynamic equilibrium and is therefore partially vaporised. This effect is referred to as flash vaporisation. Accordingly, a two-phase mixture, consisting of vapour and liquid, exists in the working chamber. Thermodynamic simulations were carried out using water as the working fluid for representative screw expander geometry. The simulations presented are performed from two different aspects during the filling process of a screw expander. The first case is the vaporisation of the injected liquid in a state of thermodynamic equilibrium, whereby the two-phase mixture is treated entirely as a compressible and homogeneous gas. The second case considers flashing efficiency. It describes the quantity of flashed vapour and consists of a liquid and vapour domain. Both models are compared and analysed with respect to the operational behaviour of a screw expander.

  14. Gas flow through the clearances of screw spindle vacuum pumps; Gasspaltstroemungen in Schraubenspindel-Vakuumpumpen

    Energy Technology Data Exchange (ETDEWEB)

    Kauder, K.; Wenderott, D. [Dortmund Univ. (Germany). FG Fluidenergiemaschinen

    1998-12-31

    The documentation `Schraubenmaschinen` deals with the subject `screw spindle vacuum pump` for the first time. Therefore, this paper presents the type of maschine `screw spindle vacuum pump`, fixes its limits to the better known screw type compressor and finally classifies it in the crossover of vacuum-technology, characteristic geometry and the numerical simulation. The suggested reflections to choose a proper model of flow are based on the geometry of the screw spindle vacuum pump and fundamentals concerning the vacuum-technology and the state of flow. (orig.) [Deutsch] Die Schriftenreihe `Schraubenmaschinen` behandelt erstmals das Thema `Schraubenspindel-Vakuumpumpe`. Aus diesem Grund stellt der vorliegende Beitrag den Maschinentyp Schraubenspindel-Vakuumpumpe vor, grenzt ihn zur bekannteren Schraubenmaschine ab und ordnet ihn in der Schnittmenge aus Vakuumtechnik, charakteristischer Maschinengeometrie und der Simulation ein. Auf den vakuumtechnischen und stroemungstechnischen Grundlagen sowie geometrischen Betrachtungen basieren die genannten Ueberlegungen zur Auswahl geeigneter Stroemungsmodelle. (orig.)

  15. Magnetic tension and gravitational collapse

    International Nuclear Information System (INIS)

    Tsagas, Christos G

    2006-01-01

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

  16. The screw propeller

    Science.gov (United States)

    Larrabee, E. E.

    1980-07-01

    Marine and air screw propellers are considered in terms of theoretical hydrodynamics as developed by Joukowsky, Prandtl, and Betz. Attention is given to the flow around wings of finite span where spanwise flow exists and where lift and the bound vorticity must all go smoothly to zero at the wing tips. The concept of a trailing vortex sheet made up of infinitesimal line vortexes roughly aligned with the direction of flight is discussed in this regard. Also considered is induced velocity, which tends to convect the sheet downward at every stage in the roll-up process, the vortex theory of propellers and the Betz-Prandtl circulation distribution. The performance of the Gossamer Albatross and of a pedal-driven biplane called the Chrysalis are also discussed.

  17. The pullout performance of pedicle screws

    CERN Document Server

    Demir, Teyfik

    2015-01-01

    This brief book systematically discusses all subjects that affect the pullout strength of pedicle screws. These screws are used in spinal surgeries to stabilize the spine. The holding strength of the pedicle screw is vital since loosening of the pedicle screws can cause revision surgeries. Once the pedicle screw is pulled out, it is harder to obtain same stabilization for the fused vertebrae. The book reviews the effect of screw designs, application techniques, cement augmentation, coating of the screw and test conditions on the pullout strength. The studies with finite element analysis were also included.

  18. Deformations of the spin currents by topological screw dislocation and cosmic dispiration

    International Nuclear Information System (INIS)

    Wang, Jianhua; Ma, Kai; Li, Kang; Fan, Huawei

    2015-01-01

    We study the spin currents induced by topological screw dislocation and cosmic dispiration. By using the extended Drude model, we find that the spin dependent forces are modified by the nontrivial geometry. For the topological screw dislocation, only the direction of spin current is bent by deforming the spin polarization vector. In contrast, the force induced by cosmic dispiration could affect both the direction and magnitude of the spin current. As a consequence, the spin-Hall conductivity does not receive corrections from screw dislocation.

  19. Deformations of the spin currents by topological screw dislocation and cosmic dispiration

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jianhua [School of Physics Science, Shaanxi University of Technology, Hanzhong 723000, Shaanxi (China); Ma, Kai, E-mail: makainca@gmail.com [School of Physics Science, Shaanxi University of Technology, Hanzhong 723000, Shaanxi (China); Li, Kang [Department of Physics, Hangzhou Normal University, Hangzhou 310036, Zhejiang (China); Fan, Huawei [School of Physics and Information Technology, Shaanxi Normal University, Xian 710000, Shaanxi (China)

    2015-11-15

    We study the spin currents induced by topological screw dislocation and cosmic dispiration. By using the extended Drude model, we find that the spin dependent forces are modified by the nontrivial geometry. For the topological screw dislocation, only the direction of spin current is bent by deforming the spin polarization vector. In contrast, the force induced by cosmic dispiration could affect both the direction and magnitude of the spin current. As a consequence, the spin-Hall conductivity does not receive corrections from screw dislocation.

  20. Geothermal ORC Systems Using Large Screw Expanders

    OpenAIRE

    Biederman, Tim R.; Brasz, Joost J.

    2014-01-01

    Geothermal ORC Systems using Large Screw Expanders Tim Biederman Cyrq Energy Abstract This paper describes a low-temperature Organic Rankine Cycle Power Recovery system with a screw expander a derivative of developed of Kaishan's line of screw compressors, as its power unit. The screw expander design is a modified version of its existing refrigeration compressor used on water-cooled chillers. Starting the ORC development program with existing refrigeration screw compre...

  1. Development of a high speed extrusion concept using a floating screw sleeve for solid-melt-separation

    Science.gov (United States)

    Karrenberg, Gregor; Wortberg, Johannes

    2015-05-01

    The High-Speed-S-Truder with floating screw sleeve is an alternative extrusion concept with solid-melt-separation. A fairly conventional 35 mm screw with a length of 21 D, which is accelerated by a 75 kW gearless, water cooled synchronous drive, conveys the resin into a 60 mm screw sleeve with a length of 10 D. Inside the sleeve the material is plasticizied and discharged into the outer screw channel of the sleeve through radial bores. Only the solid bed remains inside. The development of a melt pool - and thus a decrease of the plasticizing capacity - is avoided. The sleeve is rotated by drag forces only (approximately 10 - 15 % of the screw speed). Due to the low speed of the screw sleeve molten material is conveyed to a 4 D Dynamic Mixing Ring in a gentle manner. The DMRs floating ring and the screw sleeve are directly coupled. The granules in the screw channel are stopped by a barrier on the screw in front of the mixing device. So nearly no unmelted material can pass the system. For temperature management in the plastification and mixing zone a 3-zone heating/air-cooling system is used. Various kinds of experiments with the High-Speed S-Truder were conducted. Reachable throughputs with different types of material (LDPE, LLDPE, PP, PS) have been tested. Also three screw geometries, which are mainly varying in the channel depth, were compared. Experimental results and theoretical background will be described in this paper.

  2. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System

    OpenAIRE

    Sim, Bo Kyun; Kim, Bongju; Kim, Min Jeong; Jeong, Guk Hyun; Ju, Kyung Won; Shin, Yoo Jin; Kim, Man Yong; Lee, Jong-Ho

    2017-01-01

    The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access ...

  3. Removal torque of nail interlocking screws is related to screw proximity to the fracture and screw breakage.

    Science.gov (United States)

    White, Alexander A; Kubacki, Meghan R; Samona, Jason; Telehowski, Paul; Atkinson, Patrick J

    2016-06-01

    Studies have shown that titanium implants can be challenging to explant due to the material's excellent biocompatibility and resulting osseointegration. Clinically, titanium alloy nail interlocking screws may require removal to dynamize a construct or revise the nail due to nonunion, infection, pain, or periprosthetic fracture. This study was designed to determine what variables influence the removal torque for titanium alloy interlocking screws. An intramedullary nail with four interlocking screws was used to stabilize a 1-cm segmental femoral defect in a canine model for 16 weeks. The animals were observed to be active following a several-day recovery after surgery. In six animals, the femora and implanted nail/screws were first tested to failure in torsion to simulate periprosthetic fracture of an implant after which the screws were then removed. In four additional animals, the screws were removed without mechanical testing. Both intraoperative insertional and extraction torques were recorded for all screws. Mechanical testing to failure broke 10/24 screws. On average, the intact screws required 70% of the insertional torque during removal while broken screws only required 16% of the insertional torque (p torque than the outboard distal screw (p torque was ∼80°. The peak axial load did not significantly correlate with the torque required to remove the screws. On average, the removal torque was lower than at the time of insertion, and less torque was required to remove broken screws and screws remote to the fracture. However, broken screws will require additional time to retrieve the remaining screw fragment. This study suggests that broken screws and screws in prematurely active patients will require less torque to remove. © IMechE 2016.

  4. Misplaced Cervical Screws Requiring Reoperation.

    Science.gov (United States)

    Peterson, Jeremy C; Arnold, Paul M; Smith, Zachary A; Hsu, Wellington K; Fehlings, Michael G; Hart, Robert A; Hilibrand, Alan S; Nassr, Ahmad; Rahman, Ra'Kerry K; Tannoury, Chadi A; Tannoury, Tony; Mroz, Thomas E; Currier, Bradford L; De Giacomo, Anthony F; Fogelson, Jeremy L; Jobse, Bruce C; Massicotte, Eric M; Riew, K Daniel

    2017-04-01

    A multicenter, retrospective case series. In the past several years, screw fixation of the cervical spine has become commonplace. For the most part, this is a safe, low-risk procedure. While rare, screw backout or misplaced screws can lead to morbidity and increased costs. We report our experiences with this uncommon complication. A multicenter, retrospective case series was undertaken at 23 institutions in the United States. Patients were included who underwent cervical spine surgery from January 1, 2005, to December 31, 2011, and had misplacement of screws requiring reoperation. Institutional review board approval was obtained at all participating institutions, and detailed records were sent to a central data center. A total of 12 903 patients met the inclusion criteria and were analyzed. There were 11 instances of screw backout requiring reoperation, for an incidence of 0.085%. There were 7 posterior procedures. Importantly, there were no changes in the health-related quality-of-life metrics due to this complication. There were no new neurologic deficits; a patient most often presented with pain, and misplacement was diagnosed on plain X-ray or computed tomography scan. The most common location for screw backout was C6 (36%). This study represents the largest series to tabulate the incidence of misplacement of screws following cervical spine surgery, which led to revision procedures. The data suggest this is a rare event, despite the widespread use of cervical fixation. Patients suffering this complication can require revision, but do not usually suffer neurologic sequelae. These patients have increased cost of care. Meticulous technique and thorough knowledge of the relevant anatomy are the best means of preventing this complication.

  5. Novel free-hand T1 pedicle screw method: Review of 44 consecutive cases

    Directory of Open Access Journals (Sweden)

    Mark A Rivkin

    2014-01-01

    Full Text Available Summary of Background Data: Multilevel posterior cervical instrumented fusions are becoming more prevalent in current practice. Biomechanical characteristics of the cervicothoracic junction may necessitate extending the construct to upper thoracic segments. However, fixation in upper thoracic spine can be technically demanding owing to transitional anatomy while suboptimal placement facilitates vascular and neurologic complications. Thoracic instrumentation methods include free-hand, fluoroscopic guidance, and CT-based image guidance. However, fluoroscopy of upper thoracic spine is challenging secondary to vertebral geometry and patient positioning, while image-guided systems present substantial financial commitment and are not readily available at most centers. Additionally, imaging modalities increase radiation exposure to the patient and surgeon while potentially lengthening surgical time. Materials and Methods: Retrospective review of 44 consecutive patients undergoing a cervicothoracic fusion by a single surgeon using the novel free-hand T1 pedicle screw technique between June 2009 and November 2012. A starting point medial and cephalad to classic entry as well as new trajectory were utilized. No imaging modalities were employed during screw insertion. Postoperative CT scans were obtained on day 1. Screw accuracy was independently evaluated according to the Heary classification. Results: In total, 87 pedicle screws placed were at T1. Grade 1 placement occurred in 72 (82.8% screws, Grade 2 in 4 (4.6% screws and Grade 3 in 9 (10.3% screws. All Grade 2 and 3 breaches were <2 mm except one Grade 3 screw breaching 2-4 mm laterally. Only two screws (2.3% were noted to be Grade 4, both breaching medially by less than 2 mm. No new neurological deficits or returns to operating room took place postoperatively. Conclusions: This modification of the traditional starting point and trajectory at T1 is safe and effective. It attenuates additional bone

  6. Hyperbolic geometry

    CERN Document Server

    Iversen, Birger

    1992-01-01

    Although it arose from purely theoretical considerations of the underlying axioms of geometry, the work of Einstein and Dirac has demonstrated that hyperbolic geometry is a fundamental aspect of modern physics

  7. Twistor geometry

    NARCIS (Netherlands)

    van den Broek, P.M.

    1984-01-01

    The aim of this paper is to give a detailed exposition of the relation between the geometry of twistor space and the geometry of Minkowski space. The paper has a didactical purpose; no use has been made of differential geometry and cohomology.

  8. Analysis of Eyring-Powell Fluid in Helical Screw Rheometer

    Directory of Open Access Journals (Sweden)

    A. M. Siddiqui

    2014-01-01

    Full Text Available This paper aims to study the flow of an incompressible, isothermal Eyring-Powell fluid in a helical screw rheometer. The complicated geometry of the helical screw rheometer is simplified by “unwrapping or flattening” the channel, lands, and the outside rotating barrel, assuming the width of the channel is larger as compared to the depth. The developed second order nonlinear differential equations are solved by using Adomian decomposition method. Analytical expressions are obtained for the velocity profiles, shear stresses, shear at wall, force exerted on fluid, volume flow rates, and average velocity. The effect of non-Newtonian parameters, pressure gradients, and flight angle on the velocity profiles is noticed with the help of graphical representation. The observation confirmed the vital role of involved parameters during the extrusion process.

  9. Thermal homogeneity of plastication processes in single-screw extruders

    Science.gov (United States)

    Bu, L. X.; Agbessi, Y.; Béreaux, Y.; Charmeau, J.-Y.

    2018-05-01

    Single-screw plastication, used in extrusion and in injection moulding, is a major way of processing commodity thermoplastics. During the plastication phase, the polymeric material is melted by the combined effects of shear-induced self-heating (viscous dissipation) and heat conduction coming from the barrel. In injection moulding, a high level of reliability is usually achieved that makes this process ideally suited to mass market production. Nonetheless, process fluctuations still appear that make moulded part quality control an everyday issue. In this work, we used a combined modelling of plastication, throughput calculation and laminar dispersion, to investigate if, and how, thermal fluctuations could propagate along the screw length and affect the melt homogeneity at the end of the metering section. To do this, we used plastication models to relate changes in processing parameters to changes in the plastication length. Moreover, a simple model of throughput calculation is used to relate the screw geometry, the polymer rheology and the processing parameters to get a good estimate of the mass flow rate. Hence, we found that the typical residence time in a single screw is around one tenth of the thermal diffusion time scale. This residence time is too short for the dispersion coefficient to reach a steady state, but too long to be able to neglect radial thermal diffusion and resort to a purely convective solution. Therefore, a full diffusion/convection problem has to be solved with a base flow described by the classic pressure and drag velocity field. Preliminary results already show the major importance of the processing parameters in the breakthrough curve of an arbitrary temperature fluctuation at the end of the metering section of injection moulding screw. When the flow back-pressure is high, the temperature fluctuation is spread more evenly with time, whereas a pressure drop in the flow will results in a breakthrough curve which presents a larger peak of

  10. Simple New Screw Insertion Technique without Extraction for Broken Pedicle Screws.

    Science.gov (United States)

    Kil, Jin-Sang; Park, Jong-Tae

    2018-05-01

    Spinal transpedicular screw fixation is widely performed. Broken pedicle screw rates range from 3%-7.1%. Several techniques have been described for extraction of broken pedicle screws. However, most of these techniques require special instruments. We describe a simple, modified technique for management of broken pedicle screws without extraction. No special instruments or drilling in an adjacent pedicle are required. We used a high-speed air drill with a round burr. With C-arm fluoroscopy guidance, the distal fragment of a broken pedicle screw was palpated using free-hand technique through the screw entry hole. A high-speed air drill with a round burr (not a diamond burr) was inserted through the hole. Drilling began slowly and continued until enough space was obtained for new screw insertion. Using this space, we performed new pedicle screw fixation medially alongside the distal fragment of the broken pedicle screw. We performed the insertion with a previously used entry hole and pathway in the pedicle. The same size pedicle screw was used. Three patients were treated with this modified technique. New screw insertion was successful in all cases after partial drilling of the distal broken pedicle screw fragment. There were no complications, such as screw loosening, dural tears, or root injury. We describe a simple, modified technique for management of broken pedicle screws without extraction. This technique is recommended in patients who require insertion of a new screw. Copyright © 2017. Published by Elsevier Inc.

  11. Behaviour and Modelling of Self-piercing Screw and Self-piercing Rivet Connections: An Experimental and Numerical Investigation

    OpenAIRE

    Sønstabø, Johan Kolstø; Holmstrøm, Petter Henrik

    2013-01-01

    Accurate and reliable models of connections are essential for the design of aluminium parts in cars. Today, there exist a few models customized for self-piercing rivets (SPR), but none for self-piercing screws (SPS). This thesis presents an experimental and numerical study on the behaviour of SPR and SPS connections for different loading situations. For the rolled base material, AA6016 in the T4 condition, uniaxial tension, plane strain tension and in-plane single shear tests were performe...

  12. Modified tension band wiring of medial malleolar ankle fractures.

    Science.gov (United States)

    Georgiadis, G M; White, D B

    1995-02-01

    Twenty-two displaced medial malleolar ankle fractures that were treated surgically using the modified tension band method of Cleak and Dawson were retrospectively reviewed at an average follow-up of 25 months. The technique involves the use of a screw to anchor a figure-of-eight wire. There were no malreductions and all fractures healed. Problems with the technique included technical errors with hardware placement, medial ankle pain, and asymptomatic wire migration. Despite this, modified tension band wiring remains an acceptable method for fixation of selected displaced medial malleolar fractures. It is especially suited for small fracture fragments and osteoporotic bone.

  13. Reactor vessel stud tensioner

    International Nuclear Information System (INIS)

    Malandra, L.J.; Beer, R.W.; Salton, R.B.; Spiegelman, S.R.; Cognevich, M.L.

    1982-01-01

    A quick-acting stud tensioner, for facilitating the loosening or tightening of a stud nut on a reactor vessel stud, has gripper jaws which when the tensioner is lowered into engagement with the upper end of the stud are moved inwards to grip the upper end and which when the tensioner is lifted move outward to release the upper end. (author)

  14. Molecular geometry

    CERN Document Server

    Rodger, Alison

    1995-01-01

    Molecular Geometry discusses topics relevant to the arrangement of atoms. The book is comprised of seven chapters that tackle several areas of molecular geometry. Chapter 1 reviews the definition and determination of molecular geometry, while Chapter 2 discusses the unified view of stereochemistry and stereochemical changes. Chapter 3 covers the geometry of molecules of second row atoms, and Chapter 4 deals with the main group elements beyond the second row. The book also talks about the complexes of transition metals and f-block elements, and then covers the organometallic compounds and trans

  15. In vitro evaluation of allogeneic bone screws for use in internal fixation of transverse fractures created in proximal sesamoid bones obtained from equine cadavers.

    Science.gov (United States)

    Sasaki, Naoki; Takakuwa, Jun; Yamada, Haruo; Mori, Ryuji

    2010-04-01

    To evaluate effectiveness of allogeneic bone screws and pins for internal fixation of midbody transverse fractures of equine proximal sesamoid bones (PSBs) in vitro. 14 forelimbs from cadavers of 3-year-old Thoroughbreds. Allogeneic cortical bone fragments were collected from the limbs of a male Thoroughbred, and cortical bone screws were prepared from the tissue by use of a precision desktop microlathe programmed with the dimensions of a metal cortical bone screw. A midbody transverse osteotomy of each PSB was performed by use of a bone-shaping oscillating saw and repaired via 1 of 3 internal fixation techniques: 1 allogeneic bone screw with 1 allogeneic bone pin (type I; n = 6 PSBs), 2 allogeneic bone screws (type II; 8), or 1 stainless steel cortical bone screw (control repair; 6). Mechanical tension measurements were obtained by use of a commercially available materials testing system. Mean +/- SD tensile strength (TS) was 668.3 +/- 216.6 N for type I repairs, 854.4 +/- 253.2 N for type II repairs, and 1,150.0 +/- 451.7 N for control repairs. Internal fixation of PSB fractures by the use of allogeneic bone screws and bone pins was successful. Although mean TS of control repairs with stainless steel cortical bone screws was greater than the mean TS of type I and type II repairs, the difference between type II and control repairs was not significant. Allogeneic screws may advance healing and result in fewer complications in a clinical setting.

  16. Comparison of Neck Screw and Conventional Fixation Techniques in Mandibular Condyle Fractures Using 3-Dimensional Finite Element Analysis.

    Science.gov (United States)

    Conci, Ricardo Augusto; Tomazi, Flavio Henrique Silveira; Noritomi, Pedro Yoshito; da Silva, Jorge Vicente Lopes; Fritscher, Guilherme Genehr; Heitz, Claiton

    2015-07-01

    To compare the mechanical stress on the mandibular condyle after the reduction and fixation of mandibular condylar fractures using the neck screw and 2 other conventional techniques according to 3-dimensional finite element analysis. A 3-dimensional finite element model of a mandible was created and graphically simulated on a computer screen. The model was fixed with 3 different techniques: a 2.0-mm plate with 4 screws, 2 plates (1 1.5-mm plate and 1 2.0-mm plate) with 4 screws, and a neck screw. Loads were applied that simulated muscular action, with restrictions of the upper movements of the mandible, differentiation of the cortical and medullary bone, and the virtual "folds" of the plates and screws so that they could adjust to the condylar surface. Afterward, the data were exported for graphic visualization of the results and quantitative analysis was performed. The 2-plate technique exhibited better stability in regard to displacement of fractures, deformity of the synthesis materials, and minimum and maximum tension values. The results with the neck screw were satisfactory and were similar to those found when a miniplate was used. Although the study shows that 2 isolated plates yielded better results compared with the other groups using other fixation systems and methods, the neck screw could be an option for condylar fracture reduction. Copyright © 2015 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.

  17. Optical geometry

    International Nuclear Information System (INIS)

    Robinson, I.; Trautman, A.

    1988-01-01

    The geometry of classical physics is Lorentzian; but weaker geometries are often more appropriate: null geodesics and electromagnetic fields, for example, are well known to be objects of conformal geometry. To deal with a single null congruence, or with the radiative electromagnetic fields associated with it, even less is needed: flag geometry for the first, optical geometry, with which this paper is chiefly concerned, for the second. The authors establish a natural one-to-one correspondence between optical geometries, considered locally, and three-dimensional Cauchy-Riemann structures. A number of Lorentzian geometries are shown to be equivalent from the optical point of view. For example the Goedel universe, the Taub-NUT metric and Hauser's twisting null solution have an optical geometry isomorphic to the one underlying the Robinson congruence in Minkowski space. The authors present general results on the problem of lifting a CR structure to a Lorentz manifold and, in particular, to Minkowski space; and exhibit the relevance of the deviation form to this problem

  18. Modularity of Pressing Tools for Screw Press Producing Solid Biofuels

    Directory of Open Access Journals (Sweden)

    Miloš Matúš

    2012-01-01

    Full Text Available This paper focuses on the development of the newly-patented structure of a screw briquetting machine for compacting biomass into a solid biofuel. The design of the machine is based on the results of a comprehensive study of the complicated process of biomass compaction. The patented structure meets two main goals: the elimination of axial forces, leading to increased lifetime of the bearings, and the new modular design of a pressing chamber and tools with their geometry based on the application of a mathematical model.

  19. A CFD study of Screw Compressor Motor Cooling Analysis

    Science.gov (United States)

    Branch, S.

    2017-08-01

    Screw compressors use electric motors to drive the male screw rotor. They are cooled by the suction refrigerant vapor that flows around the motor. The thermal conditions of the motor can dramatically influence the performance and reliability of the compressor. The more optimized this flow path is, the better the motor performance. For that reason it is important to understand the flow characteristics around the motor and the motor temperatures. Computational fluid dynamics (CFD) can be used to provide a detailed analysis of the refrigerant’s flow behavior and motor temperatures to identify the undesirable hot spots in the motor. CFD analysis can be used further to optimize the flow path and determine the reduction of hot spots and cooling effect. This study compares the CFD solutions of a motor cooling model to a motor installed with thermocouples measured in the lab. The compressor considered for this study is an R134a screw compressor. The CFD simulation of the motor consists of a detailed breakdown of the stator and rotor components. Orthotropic thermal conductivity material properties are used to represent the simplified motor geometry. In addition, the analysis includes the motor casings of the compressor to draw heat away from the motor by conduction. The study will look at different operating conditions and motor speeds. Finally, the CFD study will investigate the predicted motor temperature change by varying the vapor mass flow rates and motor speed. Recommendations for CFD modeling of such intricate heat transfer phenomenon have thus been proposed.

  20. Architectural geometry

    KAUST Repository

    Pottmann, Helmut; Eigensatz, Michael; Vaxman, Amir; Wallner, Johannes

    2014-01-01

    Around 2005 it became apparent in the geometry processing community that freeform architecture contains many problems of a geometric nature to be solved, and many opportunities for optimization which however require geometric understanding. This area of research, which has been called architectural geometry, meanwhile contains a great wealth of individual contributions which are relevant in various fields. For mathematicians, the relation to discrete differential geometry is significant, in particular the integrable system viewpoint. Besides, new application contexts have become available for quite some old-established concepts. Regarding graphics and geometry processing, architectural geometry yields interesting new questions but also new objects, e.g. replacing meshes by other combinatorial arrangements. Numerical optimization plays a major role but in itself would be powerless without geometric understanding. Summing up, architectural geometry has become a rewarding field of study. We here survey the main directions which have been pursued, we show real projects where geometric considerations have played a role, and we outline open problems which we think are significant for the future development of both theory and practice of architectural geometry.

  1. Architectural geometry

    KAUST Repository

    Pottmann, Helmut

    2014-11-26

    Around 2005 it became apparent in the geometry processing community that freeform architecture contains many problems of a geometric nature to be solved, and many opportunities for optimization which however require geometric understanding. This area of research, which has been called architectural geometry, meanwhile contains a great wealth of individual contributions which are relevant in various fields. For mathematicians, the relation to discrete differential geometry is significant, in particular the integrable system viewpoint. Besides, new application contexts have become available for quite some old-established concepts. Regarding graphics and geometry processing, architectural geometry yields interesting new questions but also new objects, e.g. replacing meshes by other combinatorial arrangements. Numerical optimization plays a major role but in itself would be powerless without geometric understanding. Summing up, architectural geometry has become a rewarding field of study. We here survey the main directions which have been pursued, we show real projects where geometric considerations have played a role, and we outline open problems which we think are significant for the future development of both theory and practice of architectural geometry.

  2. Beautiful geometry

    CERN Document Server

    Maor, Eli

    2014-01-01

    If you've ever thought that mathematics and art don't mix, this stunning visual history of geometry will change your mind. As much a work of art as a book about mathematics, Beautiful Geometry presents more than sixty exquisite color plates illustrating a wide range of geometric patterns and theorems, accompanied by brief accounts of the fascinating history and people behind each. With artwork by Swiss artist Eugen Jost and text by acclaimed math historian Eli Maor, this unique celebration of geometry covers numerous subjects, from straightedge-and-compass constructions to intriguing configur

  3. Tricortical cervical inter-body screw fixation.

    Directory of Open Access Journals (Sweden)

    Goel A

    1997-01-01

    Full Text Available A new tricortical method of screw implantation for anterior cervical interbody plate fixation is described. The screws are placed obliquely such that they engage the anterior cortex of the body and traverse through the cortices adjoining the disc space. By this method the screws not only hold the plate firmly with a tricortical purchase, but by virtue of their course stabilize the two adjoining vertebral bodies by themselves. Sixteen patients were treated by this method. In three of these cases only tricortical screws without the metal plate were used for fixation. The advantages of the technique are discussed.

  4. Development of load calculation techniques on screw and screw press energy consumption

    OpenAIRE

    Татарьянц, Максим Сергеевич; Завинский, Сергей Иванович; Трошин, Алексей Георгиевич

    2015-01-01

    The process of pressing of wood chips in screw machines is researched. It is defined processes taking place in different parts of the screw, formulas allowing to calculate the loads acting on the screw flights, as well as to determine the power required for compression. The unit costs of energy consumption and raw materials in the degree of heat pressing are determined

  5. [Fracture of implant abutment screws and removal of a remaining screw piece

    NARCIS (Netherlands)

    Broeke, S.M. van den; Baat, C. de

    2008-01-01

    Fracture of the implant abutment screws is a complication which can render an implant useless. The prevalence of abutment screw fracture does not exceed 2.5% after 10 years. Causes are loosening of implant abutment screw, too few, too short or too narrow implants, implants not inserted perpendicular

  6. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System.

    Science.gov (United States)

    Sim, Bo Kyun; Kim, Bongju; Kim, Min Jeong; Jeong, Guk Hyun; Ju, Kyung Won; Shin, Yoo Jin; Kim, Man Yong; Lee, Jong-Ho

    2017-01-01

    The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA) and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.

  7. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System

    Directory of Open Access Journals (Sweden)

    Bo Kyun Sim

    2017-01-01

    Full Text Available The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA.

  8. Hollow Abutment Screw Design for Easy Retrieval in Case of Screw Fracture in Dental Implant System

    Science.gov (United States)

    Kim, Bongju; Shin, Yoo Jin

    2017-01-01

    The prosthetic component of dental implant is attached on the abutment which is connected to the fixture with an abutment screw. The abutment screw fracture is not frequent; however, the retrieval of the fractured screw is not easy, and it poses complications. A retrieval kit was developed which utilizes screw removal drills to make a hole on the fractured screw that provides an engaging drill to unscrew it. To minimize this process, the abutment screw is modified with a prefabricated access hole for easy retrieval. This study aimed to introduce this modified design of the abutment screw, the concept of easy retrieval, and to compare the mechanical strengths of the conventional and hollow abutment screws by finite element analysis (FEA) and mechanical test. In the FEA results, both types of abutment screws showed similar stress distribution in the single artificial tooth system. A maximum load difference of about 2% occurred in the vertical load by a mechanical test. This study showed that the hollow abutment screw may be an alternative to the conventional abutment screws because this is designed for easy retrieval and that both abutment screws showed no significant difference in the mechanical tests and in the FEA. PMID:29065610

  9. Analytische Geometrie

    Science.gov (United States)

    Kemnitz, Arnfried

    Der Grundgedanke der Analytischen Geometrie besteht darin, dass geometrische Untersuchungen mit rechnerischen Mitteln geführt werden. Geometrische Objekte werden dabei durch Gleichungen beschrieben und mit algebraischen Methoden untersucht.

  10. Algebraic geometry

    CERN Document Server

    Lefschetz, Solomon

    2005-01-01

    An introduction to algebraic geometry and a bridge between its analytical-topological and algebraical aspects, this text for advanced undergraduate students is particularly relevant to those more familiar with analysis than algebra. 1953 edition.

  11. Information geometry

    CERN Document Server

    Ay, Nihat; Lê, Hông Vân; Schwachhöfer, Lorenz

    2017-01-01

    The book provides a comprehensive introduction and a novel mathematical foundation of the field of information geometry with complete proofs and detailed background material on measure theory, Riemannian geometry and Banach space theory. Parametrised measure models are defined as fundamental geometric objects, which can be both finite or infinite dimensional. Based on these models, canonical tensor fields are introduced and further studied, including the Fisher metric and the Amari-Chentsov tensor, and embeddings of statistical manifolds are investigated. This novel foundation then leads to application highlights, such as generalizations and extensions of the classical uniqueness result of Chentsov or the Cramér-Rao inequality. Additionally, several new application fields of information geometry are highlighted, for instance hierarchical and graphical models, complexity theory, population genetics, or Markov Chain Monte Carlo. The book will be of interest to mathematicians who are interested in geometry, inf...

  12. Tension type headache

    Directory of Open Access Journals (Sweden)

    Debashish Chowdhury

    2012-01-01

    Full Text Available Tension type headaches are common in clinical practice. Earlier known by various names, the diagnosis has had psychological connotations. Recent evidence has helped clarify the neurobiological basis and the disorder is increasingly considered more in the preview of neurologists. The classification, clinical features, differential diagnosis and treatment of tension type headache are discussed in this paper.

  13. Tensions in Distributed Leadership

    Science.gov (United States)

    Ho, Jeanne; Ng, David

    2017-01-01

    Purpose: This article proposes the utility of using activity theory as an analytical lens to examine the theoretical construct of distributed leadership, specifically to illuminate tensions encountered by leaders and how they resolved these tensions. Research Method: The study adopted the naturalistic inquiry approach of a case study of an…

  14. Pedicle screw anchorage of carbon fiber-reinforced PEEK screws under cyclic loading.

    Science.gov (United States)

    Lindtner, Richard A; Schmid, Rene; Nydegger, Thomas; Konschake, Marko; Schmoelz, Werner

    2018-03-01

    Pedicle screw loosening is a common and significant complication after posterior spinal instrumentation, particularly in osteoporosis. Radiolucent carbon fiber-reinforced polyetheretherketone (CF/PEEK) pedicle screws have been developed recently to overcome drawbacks of conventional metallic screws, such as metal-induced imaging artifacts and interference with postoperative radiotherapy. Beyond radiolucency, CF/PEEK may also be advantageous over standard titanium in terms of pedicle screw loosening due to its unique material properties. However, screw anchorage and loosening of CF/PEEK pedicle screws have not been evaluated yet. The aim of this biomechanical study therefore was to evaluate whether the use of this alternative nonmetallic pedicle screw material affects screw loosening. The hypotheses tested were that (1) nonmetallic CF/PEEK pedicle screws resist an equal or higher number of load cycles until loosening than standard titanium screws and that (2) PMMA cement augmentation further increases the number of load cycles until loosening of CF/PEEK screws. In the first part of the study, left and right pedicles of ten cadaveric lumbar vertebrae (BMD 70.8 mg/cm 3  ± 14.5) were randomly instrumented with either CF/PEEK or standard titanium pedicle screws. In the second part, left and right pedicles of ten vertebrae (BMD 56.3 mg/cm 3  ± 15.8) were randomly instrumented with either PMMA-augmented or nonaugmented CF/PEEK pedicle screws. Each pedicle screw was subjected to cyclic cranio-caudal loading (initial load ranging from - 50 N to + 50 N) with stepwise increasing compressive loads (5 N every 100 cycles) until loosening or a maximum of 10,000 cycles. Angular screw motion ("screw toggling") within the vertebra was measured with a 3D motion analysis system every 100 cycles and by stress fluoroscopy every 500 cycles. The nonmetallic CF/PEEK pedicle screws resisted a similar number of load cycles until loosening as the contralateral standard

  15. Effects of Screw Configuration on the Preload Force of Implant-Abutment Screws.

    Science.gov (United States)

    Zipprich, Holger; Rathe, Florian; Pinz, Sören; Schlotmann, Luca; Lauer, Hans-Christoph; Ratka, Christoph

    The aim of this study was to investigate the effects of tightening torque, screw head angle, and thread number on the preload force of abutment screws. The test specimens consisted of three self-manufactured components (ie, a thread sleeve serving as an implant analog, an abutment analog, and an abutment screw). The abutment screws were fabricated with metric M1.6 external threads. The thread number varied between one and seven threads. The screw head angles were produced in eight varying angles (30 to 180 degrees). A sensor unit simultaneously measured the preload force of the screw and the torsion moment inside the screw shank. The tightening of the screw with the torque wrench was performed in five steps (15 to 35 Ncm). The torque wrench was calibrated before each step. Only the tightening torque and screw head angle affected the resulting preload force of the implant-abutment connection. The thread number had no effect. There was an approximately linear correlation between tightening torque and preload force. The tightening torque and screw head angle were the only study parameters that affected the resulting preload force of the abutment screw. The results obtained from this experiment are valid only for a single torque condition. Further investigations are needed that analyze other parameters that affect preload force. Once these parameters are known, it will add value for a strong, but detachable connection between the implant and abutment. Short implants and flat-to-flat connections especially will benefit significantly from this knowledge.

  16. Secure and documented screwing down of Castor containers

    International Nuclear Information System (INIS)

    Yilmaz, Asir; Junkers, Patrick

    2011-01-01

    The castor container is sealed using a multiple lid system comprising a primary lid and a secondary lid. The two lids are positioned one above the other and screwed securely to the body of the container. In addition, the tightness of the lids is guaranteed by a special metal seal. A further steel plate is screwed securely over the lids providing additional protection for the lids from moisture and various influences. The central element connecting the lids to the container comprises fixed threaded connections which must be accurately tightened with a torque of 900 Nm, 1500 Nm or more. The basic function of a threaded connection, in terms of a positive fit and detachable joint, is to join together two or more parts in such a way that they always behave as a single part whatever operational forces are present. This can only be achieved by means of an accurate and sufficient pre-tensioning force. This pretensioning force is transferred to the threaded connection with the help of a particular torque and presses the components together. This loading brought about by the pretensioning force is referred to as the prestress. In order to create a correct and high quality connection, this prestress must be arrived at in an optimum manner. The prestress must therefore be high enough to withstand the full loading for which the connection is designed. In addition the connection should not come loose unintentionally if it is exposed to externally acting forces. Since under no circumstances should threaded connections on a castor container fail, a suitable screwing process must guarantee that this does not happen. The securing of threaded joints can only be ensured by introducing and maintaining a constant and accurate prestress. VDI Guideline 2230, Part 1, mentions various threaded connection or tightening processes, including torque-controlled tightening, angle-controlled tightening and yield-controlled tightening. (orig.)

  17. Secure and documented screwing down of Castor containers

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, Asir; Junkers, Patrick [HYTORC - Barbarino und Kilp GmbH, Krailling (Germany)

    2011-07-01

    The castor container is sealed using a multiple lid system comprising a primary lid and a secondary lid. The two lids are positioned one above the other and screwed securely to the body of the container. In addition, the tightness of the lids is guaranteed by a special metal seal. A further steel plate is screwed securely over the lids providing additional protection for the lids from moisture and various influences. The central element connecting the lids to the container comprises fixed threaded connections which must be accurately tightened with a torque of 900 Nm, 1500 Nm or more. The basic function of a threaded connection, in terms of a positive fit and detachable joint, is to join together two or more parts in such a way that they always behave as a single part whatever operational forces are present. This can only be achieved by means of an accurate and sufficient pre-tensioning force. This pretensioning force is transferred to the threaded connection with the help of a particular torque and presses the components together. This loading brought about by the pretensioning force is referred to as the prestress. In order to create a correct and high quality connection, this prestress must be arrived at in an optimum manner. The prestress must therefore be high enough to withstand the full loading for which the connection is designed. In addition the connection should not come loose unintentionally if it is exposed to externally acting forces. Since under no circumstances should threaded connections on a castor container fail, a suitable screwing process must guarantee that this does not happen. The securing of threaded joints can only be ensured by introducing and maintaining a constant and accurate prestress. VDI Guideline 2230, Part 1, mentions various threaded connection or tightening processes, including torque-controlled tightening, angle-controlled tightening and yield-controlled tightening. (orig.)

  18. Simple Technique for Removing Broken Pedicular Screws

    Directory of Open Access Journals (Sweden)

    A Agrawal

    2014-03-01

    Full Text Available The procedure for removing a broken pedicle screw should ideally be technically easy and minimally invasive, as any damage to the pedicle, during removal of the broken screw, may weaken the pedicle, thus compromising on the success of re-instrumentation. We describe the case of a 32-year old man who had undergone surgery for traumatic third lumbar vertebral body fracture three years prior to current admission and had developed the complication of pedicle screw breakage within the vertebral body. The patient underwent re-exploration and removal of the distal screws. Through a paravertebral incision and muscle separation, the screws and rods were exposed and the implants were removed.

  19. Analytic geometry

    CERN Document Server

    Burdette, A C

    1971-01-01

    Analytic Geometry covers several fundamental aspects of analytic geometry needed for advanced subjects, including calculus.This book is composed of 12 chapters that review the principles, concepts, and analytic proofs of geometric theorems, families of lines, the normal equation of the line, and related matters. Other chapters highlight the application of graphing, foci, directrices, eccentricity, and conic-related topics. The remaining chapters deal with the concept polar and rectangular coordinates, surfaces and curves, and planes.This book will prove useful to undergraduate trigonometric st

  20. Geometry Revealed

    CERN Document Server

    Berger, Marcel

    2010-01-01

    Both classical geometry and modern differential geometry have been active subjects of research throughout the 20th century and lie at the heart of many recent advances in mathematics and physics. The underlying motivating concept for the present book is that it offers readers the elements of a modern geometric culture by means of a whole series of visually appealing unsolved (or recently solved) problems that require the creation of concepts and tools of varying abstraction. Starting with such natural, classical objects as lines, planes, circles, spheres, polygons, polyhedra, curves, surfaces,

  1. Vector geometry

    CERN Document Server

    Robinson, Gilbert de B

    2011-01-01

    This brief undergraduate-level text by a prominent Cambridge-educated mathematician explores the relationship between algebra and geometry. An elementary course in plane geometry is the sole requirement for Gilbert de B. Robinson's text, which is the result of several years of teaching and learning the most effective methods from discussions with students. Topics include lines and planes, determinants and linear equations, matrices, groups and linear transformations, and vectors and vector spaces. Additional subjects range from conics and quadrics to homogeneous coordinates and projective geom

  2. Noncommutative geometry

    CERN Document Server

    Connes, Alain

    1994-01-01

    This English version of the path-breaking French book on this subject gives the definitive treatment of the revolutionary approach to measure theory, geometry, and mathematical physics developed by Alain Connes. Profusely illustrated and invitingly written, this book is ideal for anyone who wants to know what noncommutative geometry is, what it can do, or how it can be used in various areas of mathematics, quantization, and elementary particles and fields.Key Features* First full treatment of the subject and its applications* Written by the pioneer of this field* Broad applications in mathemat

  3. Projective Geometry

    Indian Academy of Sciences (India)

    mathematicians are trained to use very precise language, and so find it hard to simplify and state .... thing. If you take a plane on which there are two such triangles which enjoy the above ... within this geometry to simplify things if needed.

  4. Geometry -----------~--------------RESONANCE

    Indian Academy of Sciences (India)

    Parallel: A pair of lines in a plane is said to be parallel if they do not meet. Mathematicians were at war ... Subsequently, Poincare, Klein, Beltrami and others refined non-. Euclidean geometry. ... plane divides the plane into two half planes and.

  5. Finite element analysis of the equivalent stress distribution in Schanz screws during the use of a femoral fracture distractor

    Directory of Open Access Journals (Sweden)

    Vincenzo Giordano

    Full Text Available ABSTRACT To evaluate the mechanical stress and elastic deformation exercised in the thread/shaft transition of Schanz screws in assemblies with different screw anchorage distances in the entrance to the bone cortex, through the distribution and location of tension in the samples. An analysis of 3D finite elements was performed to evaluate the distribution of the equivalent stress (triple stress state in a Schanz screw fixed bicortically and orthogonally to a tubular bone, using two mounting patterns: (1 thread/shaft transition located 20 mm from the anchorage of the Schanz screws in the entrance to the bone cortex and (2 thread/shaft transition located 3 mm from the anchorage of the Schanz screws in entrance to the bone cortex. The simulations were performed maintaining the same direction of loading and the same distance from the force vector in relation to the center of the hypothetical bone. The load applied, its direction, and the distance to the center of the bone were constant during the simulations in order to maintain the moment of flexion equally constant. The present calculations demonstrated linear behavior during the experiment. It was found that the model with a distance of 20 mm between the Schanz screws anchorage in the entrance to the bone cortex and the thread/shaft transition reduces the risk of breakage or fatigue of the material during the application of constant static loads; in this model, the maximum forces observed were higher (350 MPa. The distance between the Schanz screws anchorage at the entrance to the bone cortex and the smooth thread/shaft transition of the screws used in a femoral distractor during acute distraction of a fracture must be farther from the entrance to the bone cortex, allowing greater degree of elastic deformation of the material, lower mechanical stress in the thread/shaft transition, and minimized breakage or fatigue. The suggested distance is 20 mm.

  6. Parachute Cord Tension Sensor

    Data.gov (United States)

    National Aeronautics and Space Administration — To design and fabricate a light weight (few oz), very small (~2 inch length) parachute cord tension sensor demonstrator device.A major challenge for the CPAS (The...

  7. Leadership. Using Creative Tension.

    Science.gov (United States)

    Cook, David L.

    1986-01-01

    Leadership involves maintaining a balance of the variables which comprise leadership. Love and fear, types of power, success and effectiveness, and driving and restraining forces are discussed as sources of the creative tension a leader uses to influence others. (MT)

  8. Optic nerve oxygen tension

    DEFF Research Database (Denmark)

    la Cour, M; Kiilgaard, Jens Folke; Eysteinsson, T

    2000-01-01

    To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide.......To investigate the influence of acute changes in intraocular pressure on the oxygen tension in the vicinity of the optic nerve head under control conditions and after intravenous administration of 500 mg of the carbonic anhydrase inhibitor dorzolamide....

  9. Spontaneous tension haemopneumothorax

    OpenAIRE

    Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey

    2008-01-01

    Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such c...

  10. Screw-released roller brake

    Science.gov (United States)

    Vranish, John M. (Inventor)

    1999-01-01

    A screw-released roller brake including an input drive assembly, an output drive assembly, a plurality of locking sprags, a mechanical tripper nut for unlocking the sprags, and a casing therefor. The sprags consist of three dimensional (3-D) sprag members having pairs of contact surface regions which engage respective pairs of contact surface regions included in angular grooves or slots formed in the casing and the output drive assembly. The sprags operate to lock the output drive assembly to the casing to prevent rotation thereof in an idle mode of operation. In a drive mode of operation, the tripper is either self actuated or motor driven and is translated linearly up and down against a spline and at the limit of its travel rotates the sprags which unlock while coupling the input drive assembly to the output drive assembly so as to impart a turning motion thereto in either a clockwise or counterclockwise direction.

  11. Riemannian geometry

    CERN Document Server

    Petersen, Peter

    2016-01-01

    Intended for a one year course, this text serves as a single source, introducing readers to the important techniques and theorems, while also containing enough background on advanced topics to appeal to those students wishing to specialize in Riemannian geometry. This is one of the few Works to combine both the geometric parts of Riemannian geometry and the analytic aspects of the theory. The book will appeal to a readership that have a basic knowledge of standard manifold theory, including tensors, forms, and Lie groups. Important revisions to the third edition include: a substantial addition of unique and enriching exercises scattered throughout the text; inclusion of an increased number of coordinate calculations of connection and curvature; addition of general formulas for curvature on Lie Groups and submersions; integration of variational calculus into the text allowing for an early treatment of the Sphere theorem using a proof by Berger; incorporation of several recent results about manifolds with posit...

  12. Special geometry

    International Nuclear Information System (INIS)

    Strominger, A.

    1990-01-01

    A special manifold is an allowed target manifold for the vector multiplets of D=4, N=2 supergravity. These manifolds are of interest for string theory because the moduli spaces of Calabi-Yau threefolds and c=9, (2,2) conformal field theories are special. Previous work has given a local, coordinate-dependent characterization of special geometry. A global description of special geometries is given herein, and their properties are studied. A special manifold M of complex dimension n is characterized by the existence of a holomorphic Sp(2n+2,R)xGL(1,C) vector bundle over M with a nowhere-vanishing holomorphic section Ω. The Kaehler potential on M is the logarithm of the Sp(2n+2,R) invariant norm of Ω. (orig.)

  13. A geometrical introduction to screw theory

    International Nuclear Information System (INIS)

    Minguzzi, E

    2013-01-01

    This work introduces screw theory, a venerable but little known theory aimed at describing rigid body dynamics. This formulation of mechanics unifies in the concept of screw the translational and rotational degrees of freedom of the body. It captures a remarkable mathematical analogy between mechanical momenta and linear velocities, and between forces and angular velocities. For instance, it clarifies that angular velocities should be treated as applied vectors and that, under the composition of motions, they sum with the same rules of applied forces. This work provides a short and rigorous introduction to screw theory intended for an undergraduate and general readership. (paper)

  14. Vertical-Screw-Auger Conveyer Feeder

    Science.gov (United States)

    Walton, Otis (Inventor); Vollmer, Hubert J. (Inventor)

    2016-01-01

    A conical feeder is attached to a vertically conveying screw auger. The feeder is equipped with scoops and rotated from the surface to force-feed regolith the auger. Additional scoops are possible by adding a cylindrical section above the conical funnel section. Such then allows the unit to collect material from swaths larger in diameter than the enclosing casing pipe of the screw auger. A third element includes a flexible screw auger. All three can be used in combination in microgravity and zero atmosphere environments to drill and recover a wide area of subsurface regolith and entrained volatiles through a single access point on the surface.

  15. Development of a process map: A step towards a regime map for steady-state high shear wet twin screw granulation

    DEFF Research Database (Denmark)

    Kumar, Ashish; Dhondt, Jens; Vercruysse, Jurgen

    2016-01-01

    involves the combination of screw speed, material throughput and torque required to rotate the screws was correlated with the applied liquid-to-solid ratio to present process maps. The study suggested that, despite an increase in the granule size by the increasing liquid-to-solid ratio, most of the liquid...... contributes to formation of oversized granules. Therefore, keeping the liquid-to-solid ratio in a lower range and increasing the energy input to the system can be effectively used to lower the mean granule size. Changes in the screw geometry should also be explored to improve solid liquid mixing and breakage...

  16. General Geometry and Geometry of Electromagnetism

    OpenAIRE

    Shahverdiyev, Shervgi S.

    2002-01-01

    It is shown that Electromagnetism creates geometry different from Riemannian geometry. General geometry including Riemannian geometry as a special case is constructed. It is proven that the most simplest special case of General Geometry is geometry underlying Electromagnetism. Action for electromagnetic field and Maxwell equations are derived from curvature function of geometry underlying Electromagnetism. And it is shown that equation of motion for a particle interacting with electromagnetic...

  17. Extraction of sunflower oil by twin screw extruder: screw configuration and operating condition effects

    Energy Technology Data Exchange (ETDEWEB)

    Kartika, I.A. [FATETA-IPB, Bogor (Indonesia). Department of Agroindustrial Technology; Pontalier, P.Y.; Rigal, L. [Laboratoire de Chimie Agro-Industrielle, UMR 1010 INRA/INP-ENSIACET, Toulouse (France)

    2006-12-15

    The objective of this study was to investigate the screw configuration allowing oil extraction from sunflower seeds with a twin-screw extruder. Experiments were conducted using a co-rotating twin-screw extruder. Five screw profiles were examined to define the best performance (oil extraction yield, specific mechanical energy and oil quality) by studying the influence of operating conditions, barrel temperature, screw speed and feed rate. Generally, the position and spacing between two reversed screw elements affected oil extraction yield. An increase of oil extraction yield was observed as the reversed screw elements were moved with increased spacing between two elements and with smaller pitch elements. In addition, oil extraction yield increased as barrel temperature, screw speed and feed rate were decreased. Highest oil extraction yield (85%) with best cake meal quality (residual oil content lower than 13%) was obtained under operating conditions of 120 {sup o}C, 75 rpm and 19 kg/h. Furthermore, the operating parameters influenced energy input. A decrease in barrel temperature and feed rate followed by an increase in screw speed increased energy input, particularly specific mechanical energy input. Effect of the operating parameters on oil quality was less important. In all experiments tested, the oil quality was very good. The acid value was below 2 mg of KOH/g of oil and total phosphorus content was low, below 100 mg/kg. (author)

  18. Loosening torque of Universal Abutment screws after cyclic loading: influence of tightening technique and screw coating.

    Science.gov (United States)

    Bacchi, Atais; Regalin, Alexandre; Bhering, Claudia Lopes Brilhante; Alessandretti, Rodrigo; Spazzin, Aloisio Oro

    2015-10-01

    The purpose of this study was to evaluate the influence of tightening technique and the screw coating on the loosening torque of screws used for Universal Abutment fixation after cyclic loading. Forty implants (Titamax Ti Cortical, HE, Neodent) (n=10) were submerged in acrylic resin and four tightening techniques for Universal Abutment fixation were evaluated: A - torque with 32 Ncm (control); B - torque with 32 Ncm holding the torque meter for 20 seconds; C - torque with 32 Ncm and retorque after 10 minutes; D - torque (32 Ncm) holding the torque meter for 20 seconds and retorque after 10 minutes as initially. Samples were divided into subgroups according to the screw used: conventional titanium screw or diamond like carbon-coated (DLC) screw. Metallic crowns were fabricated for each abutment. Samples were submitted to cyclic loading at 10(6) cycles and 130 N of force. Data were analyzed by two-way ANOVA and Tukey's test (5%). The tightening technique did not show significant influence on the loosening torque of screws (P=.509). Conventional titanium screws showed significant higher loosening torque values than DLC (P=.000). The use of conventional titanium screw is more important than the tightening techniques employed in this study to provide long-term stability to Universal Abutment screws.

  19. Twin Screw Mixer/Fine Grind Facility

    Data.gov (United States)

    Federal Laboratory Consortium — The 40-mm Twin-Screw Mixer/Extruder (TSE) pilot plant is a continuous, remotely operated, flexible facility that can significantly enhance safety and environmental...

  20. Effect of screw position on single cycle to failure in bending and torsion of a locking plate-rod construct in a synthetic feline femoral gap model.

    Science.gov (United States)

    Niederhäuser, Simone K; Tepic, Slobodan; Weber, Urs T

    2015-05-01

    To evaluate the effect of screw position on strength and stiffness of a combination locking plate-rod construct in a synthetic feline femoral gap model. 30 synthetic long-bone models derived from beechwood and balsa wood. 3 constructs (2 locking plate-rod constructs and 1 locking plate construct; 10 specimens/construct) were tested in a diaphyseal bridge plating configuration by use of 4-point bending and torsion. Variables included screw position (near the fracture gap and far from the fracture gap) and application of an intramedullary pin. Constructs were tested to failure in each loading mode to determine strength and stiffness. Failure was defined as plastic deformation of the plate or breakage of the bone model or plate. Strength, yield angle, and stiffness were compared by use of a Wilcoxon test. Placement of screws near the fracture gap did not increase bending or torsional stiffness in the locking plate-rod constructs, assuming the plate was placed on the tension side of the bone. Addition of an intramedullary pin resulted in a significant increase in bending strength of the construct. Screw positioning did not have a significant effect on any torsion variables. Results of this study suggested that, in the investigated plate-rod construct, screw insertion adjacent to the fracture lacked mechanical advantages over screw insertion at the plate ends. For surgeons attempting to minimize soft tissue dissection, the decision to make additional incisions for screw placement should be considered with even more caution.

  1. Effect of Repeated Screw Joint Closing and Opening Cycles and Cyclic Loading on Abutment Screw Removal Torque and Screw Thread Morphology: Scanning Electron Microscopy Evaluation.

    Science.gov (United States)

    Arshad, Mahnaz; Mahgoli, Hosseinali; Payaminia, Leila

    To evaluate the effect of repeated screw joint closing and opening cycles and cyclic loading on abutment screw removal torque and screw thread morphology using scanning electron microscopy (SEM). Three groups (n = 10 in each group) of implant-abutment-abutment screw assemblies were created. There were also 10 extra abutment screws as new screws in group 3. The abutment screws were tightened to 12 Ncm with an electronic torque meter; then they were removed and removal torque values were recorded. This sequence was repeated 5 times for group 1 and 15 times for groups 2 and 3. The same screws in groups 1 and 2 and the new screws in group 3 were then tightened to 12 Ncm; this was also followed by screw tightening to 30 Ncm and retightening to 30 Ncm 15 minutes later. Removal torque measurements were performed after screws were subjected to cyclic loading (0.5 × 10⁶ cycles; 1 Hz; 75 N). Moreover, the surface topography of one screw from each group before and after cyclic loading was evaluated with SEM and compared with an unused screw. All groups exhibited reduced removal torque values in comparison to insertion torque in each cycle. However, there was a steady trend of torque loss in each group. A comparison of the last cycle of the groups before loading showed significantly greater torque loss value in the 15th cycle of groups 2 and 3 compared with the fifth cycle of group 1 (P abutment is definitively placed.

  2. Differential geometry

    CERN Document Server

    Ciarlet, Philippe G

    2007-01-01

    This book gives the basic notions of differential geometry, such as the metric tensor, the Riemann curvature tensor, the fundamental forms of a surface, covariant derivatives, and the fundamental theorem of surface theory in a selfcontained and accessible manner. Although the field is often considered a classical one, it has recently been rejuvenated, thanks to the manifold applications where it plays an essential role. The book presents some important applications to shells, such as the theory of linearly and nonlinearly elastic shells, the implementation of numerical methods for shells, and

  3. Screw piles for cold climate foundations

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, R.; Sakr, M. [Almita Manufacturing Ltd., Edmonton, AB (Canada)

    2008-07-01

    Almita Manufacturing is an Alberta-based company that designs and builds screw piles with its own installation teams. It also engineers and supplies piles to numerous other companies and independent installers. The company services industries such as oil and gas; power transmission and distribution; and commercial construction. This presentation discussed the design and technical aspects of screw piles. A screw pile was defined as a steel pipe shaft with a 45 degree cut at the bottom and a formed helical plate welded to the outside of the pipe near the base and at a selected point on the shaft. The pile is screwed into the ground with a planetary drive head of suitable torque rating. The helical plate or helix helps facilitate the installation of the pile and gives the screw pile increased bearing capacity and pull-out resistance over a traditional straight-shaft pile. Screw piles were compared against cast in place concrete piles and steel driven piles. Screw piles were reported to have no tailings; no concrete curing time; no rebar, anchor belts, and no liners; and no dewatering. Screw piles can also be installed in all types of weather. Rhe Cree Burn Camp case study near Fort McMurray, Alberta was also presented. This residential camp and recreation complex consists of pre-fabricated units that make up three storey housing buildings and a single floor multi-use building. The case study provided information on soil; design parameter inputs; load testing program and pile configuration; geotechnical and structural design results; compression load test arrangement; pile test setup; and test results. The presentation also discussed fabrication as well as installation equipment. Various applications were also presented through a series of project pictures. Last, the presentation provided a simple cost analysis. tabs., figs.

  4. Analysis of Third-Grade Fluid in Helical Screw Rheometer

    Directory of Open Access Journals (Sweden)

    M. Zeb

    2013-01-01

    Full Text Available The steady flow of an incompressible, third-grade fluid in helical screw rheometer (HSR is studied by “unwrapping or flattening” the channel, lands, and the outside rotating barrel. The geometry is approximated as a shallow infinite channel, by assuming that the width of the channel is large as compared to the depth. The developed second-order nonlinear coupled differential equations are reduced to single differential equation by using a transformation. Using Adomian decomposition method, analytical expressions are calculated for the the velocity profiles and volume flow rates. The results have been discussed with the help of graphs as well. We observed that the velocity profiles are strongly dependant on non-Newtonian parameter (β~, and with the increase in β~, the velocity profiles increase progressively, which conclude that extrusion process increases with the increase in β~. We also observed that the increase in pressure gradients in x- and z-direction increases the net flow inside the helical screw rheometer, which increases the extrusion process. We noticed that the flow increases as the flight angle increase.

  5. Spontaneous tension haemopneumothorax.

    Science.gov (United States)

    Patterson, Benjamin Oliver; Itam, Sarah; Probst, Fey

    2008-10-31

    We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported.Aetiology and current approach to spontaneous haemothorax are discussed briefly.

  6. Spontaneous tension haemopneumothorax

    Directory of Open Access Journals (Sweden)

    Itam Sarah

    2008-10-01

    Full Text Available Abstract We present a patient with sudden onset progressive shortness of breath and no history of trauma, who rapidly became haemodynamically compromised with a pneumothorax and pleural effusion seen on chest radiograph. He was treated for spontaneous tension pneumothorax but this was soon revealed to be a tension haemopneumothorax. He underwent urgent thoracotomy after persistent bleeding to explore an apical vascular abnormality seen on CT scanning. To our knowledge this is the first such case reported. Aetiology and current approach to spontaneous haemothorax are discussed briefly.

  7. Insertion profiles of 4 headless compression screws.

    Science.gov (United States)

    Hart, Adam; Harvey, Edward J; Lefebvre, Louis-Philippe; Barthelat, Francois; Rabiei, Reza; Martineau, Paul A

    2013-09-01

    In practice, the surgeon must rely on screw position (insertion depth) and tactile feedback from the screwdriver (insertion torque) to gauge compression. In this study, we identified the relationship between interfragmentary compression and these 2 factors. The Acutrak Standard, Acutrak Mini, Synthes 3.0, and Herbert-Whipple implants were tested using a polyurethane foam scaphoid model. A specialized testing jig simultaneously measured compression force, insertion torque, and insertion depth at half-screw-turn intervals until failure occurred. The peak compression occurs at an insertion depth of -3.1 mm, -2.8 mm, 0.9 mm, and 1.5 mm for the Acutrak Mini, Acutrak Standard, Herbert-Whipple, and Synthes screws respectively (insertion depth is positive when the screw is proud above the bone and negative when buried). The compression and insertion torque at a depth of -2 mm were found to be 113 ± 18 N and 0.348 ± 0.052 Nm for the Acutrak Standard, 104 ± 15 N and 0.175 ± 0.008 Nm for the Acutrak Mini, 78 ± 9 N and 0.245 ± 0.006 Nm for the Herbert-Whipple, and 67 ± 2N, 0.233 ± 0.010 Nm for the Synthes headless compression screws. All 4 screws generated a sizable amount of compression (> 60 N) over a wide range of insertion depths. The compression at the commonly recommended insertion depth of -2 mm was not significantly different between screws; thus, implant selection should not be based on compression profile alone. Conically shaped screws (Acutrak) generated their peak compression when they were fully buried in the foam whereas the shanked screws (Synthes and Herbert-Whipple) reached peak compression before they were fully inserted. Because insertion torque correlated poorly with compression, surgeons should avoid using tactile judgment of torque as a proxy for compression. Knowledge of the insertion profile may improve our understanding of the implants, provide a better basis for comparing screws, and enable the surgeon to optimize compression. Copyright

  8. Ball Screw Actuator Including a Stop with an Integral Guide

    Science.gov (United States)

    Wingett, Paul T. (Inventor); Perek, John (Inventor); Geck, Kellan (Inventor)

    2015-01-01

    An actuator includes a housing assembly, a ball nut, a ball screw, and a ball screw stop. The ball nut is rotationally mounted in the housing assembly, is adapted to receive an input torque, and is configured, upon receipt thereof, to rotate and supply a drive force. The ball screw is mounted within the housing assembly and extends through the ball nut. The ball screw has a first end and a second end, and is coupled to receive the drive force from the ball nut. The ball screw is configured, upon receipt of the drive force, to selectively translate between a stow position and a deploy position. The ball screw stop is mounted on the ball screw to translate therewith and is configured to at selectively engage the housing assembly while the ball screw is translating, and engage the ball nut when the ball screw is in the deploy position.

  9. Creating Tension in Writing.

    Science.gov (United States)

    Folta, Bernarr

    This paper discusses the rationale and teaching methods for a six-week unit, for a high school freshman English Class, on perception, semantics, and writing, which places special focus on developing tension in student writing. The first four objectives of the course focus on perception and the next two focus on semantics. The seventh…

  10. Tension-filled Governance?

    DEFF Research Database (Denmark)

    Celik, Tim Holst

    on the statesituated tension-filled functional relationship between legitimation and accumulation, the study both historically and theoretically reworks this approach and reapplies it for the post-1970s/1990s governance period. It asks whether and to what extent governance has served as a distinctive post- 1970s/1990s...

  11. Rein tension during canter

    NARCIS (Netherlands)

    Egenvall, Agneta; Eisersiö, Marie; Rhodin, Marie; van Weeren, P.R.; Roepstorff, Lars

    2015-01-01

    Riders generally use reins as a means for communication with the horse. At present, the signalling pattern is poorly understood. The aim of this study was to illustrate and analyse the rein tension patterns in a number of rider/horse combinations across a variety of exercises in the canter gait. Our

  12. Optic nerve oxygen tension

    DEFF Research Database (Denmark)

    Kiilgaard, Jens Folke; Pedersen, D B; Eysteinsson, T

    2004-01-01

    The authors have previously reported that carbonic anhydrase inhibitors such as acetazolamide and dorzolamide raise optic nerve oxygen tension (ONPO(2)) in pigs. The purpose of the present study was to investigate whether timolol, which belongs to another group of glaucoma drugs called beta...

  13. Tapping insertional torque allows prediction for better pedicle screw fixation and optimal screw size selection.

    Science.gov (United States)

    Helgeson, Melvin D; Kang, Daniel G; Lehman, Ronald A; Dmitriev, Anton E; Luhmann, Scott J

    2013-08-01

    There is currently no reliable technique for intraoperative assessment of pedicle screw fixation strength and optimal screw size. Several studies have evaluated pedicle screw insertional torque (IT) and its direct correlation with pullout strength. However, there is limited clinical application with pedicle screw IT as it must be measured during screw placement and rarely causes the spine surgeon to change screw size. To date, no study has evaluated tapping IT, which precedes screw insertion, and its ability to predict pedicle screw pullout strength. The objective of this study was to investigate tapping IT and its ability to predict pedicle screw pullout strength and optimal screw size. In vitro human cadaveric biomechanical analysis. Twenty fresh-frozen human cadaveric thoracic vertebral levels were prepared and dual-energy radiographic absorptiometry scanned for bone mineral density (BMD). All specimens were osteoporotic with a mean BMD of 0.60 ± 0.07 g/cm(2). Five specimens (n=10) were used to perform a pilot study, as there were no previously established values for optimal tapping IT. Each pedicle during the pilot study was measured using a digital caliper as well as computed tomography measurements, and the optimal screw size was determined to be equal to or the first size smaller than the pedicle diameter. The optimal tap size was then selected as the tap diameter 1 mm smaller than the optimal screw size. During optimal tap size insertion, all peak tapping IT values were found to be between 2 in-lbs and 3 in-lbs. Therefore, the threshold tapping IT value for optimal pedicle screw and tap size was determined to be 2.5 in-lbs, and a comparison tapping IT value of 1.5 in-lbs was selected. Next, 15 test specimens (n=30) were measured with digital calipers, probed, tapped, and instrumented using a paired comparison between the two threshold tapping IT values (Group 1: 1.5 in-lbs; Group 2: 2.5 in-lbs), randomly assigned to the left or right pedicle on each

  14. Transpedicular screw fixation in the thoracic and lumbar spine with a novel cannulated polyaxial screw system

    Directory of Open Access Journals (Sweden)

    Lutz Weise

    2008-10-01

    Full Text Available Lutz Weise, Olaf Suess, Thomas Picht, Theodoros KombosNeurochirurgische Klinik, Charité – Universitätsmedizin Berlin, Berlin, GermanyObjective: Transpedicular screws are commonly and successfully used for posterior fixation in spinal instability, but their insertion remains challenging. Even using navigation techniques, there is a misplacement rate of up to 11%. The aim of this study was to assess the accuracy of a novel pedicle screw system.Methods: Thoracic and lumbar fusions were performed on 67 consecutive patients for tumor, trauma, degenerative disease or infection. A total of 326 pedicular screws were placed using a novel wire-guided, cannulated, polyaxial screw system (XIA Precision®, Stryker. The accuracy of placement was assessed post operatively by CT scan, and the patients were followed-up clinically for a mean of 16 months.Results: The total medio-caudal pedicle wall perforation rate was 9.2% (30/326. In 19 of these 30 cases a cortical breakthrough of less than 2 mm occurred. The misplacement rate (defined as a perforation of 2 mm or more was 3.37% (11/326. Three of these 11 screws needed surgical revision due to neurological symptoms or CSF leakage. There have been no screw breakages or dislocations over the follow up-period.Conclusion: We conclude that the use of this cannulated screw system for the placement of pedicle screws in the thoracic and lumbar spine is accurate and safe. The advantages of this technique include easy handling without a time-consuming set up. Considering the incidence of long-term screw breakage, further investigation with a longer follow-up period is necessary.Keywords: spinal instrumentation, pedicle screws, misplacement, pedicle wall perforation

  15. Standard Waste Box Lid Screw Removal Option Testing

    International Nuclear Information System (INIS)

    Anast, Kurt Roy

    2016-01-01

    This report provides results from test work conducted to resolve the removal of screws securing the standard waste box (SWB) lids that hold the remediated nitrate salt (RNS) drums. The test work evaluated equipment and process alternatives for removing the 42 screws that hold the SWB lid in place. The screws were secured with a red Loctite thread locker that makes removal very difficult because the rivets that the screw threads into would slip before the screw could be freed from the rivet, making it impossible to remove the screw and therefore the SWB lid.

  16. Standard Waste Box Lid Screw Removal Option Testing

    Energy Technology Data Exchange (ETDEWEB)

    Anast, Kurt Roy [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-11

    This report provides results from test work conducted to resolve the removal of screws securing the standard waste box (SWB) lids that hold the remediated nitrate salt (RNS) drums. The test work evaluated equipment and process alternatives for removing the 42 screws that hold the SWB lid in place. The screws were secured with a red Loctite thread locker that makes removal very difficult because the rivets that the screw threads into would slip before the screw could be freed from the rivet, making it impossible to remove the screw and therefore the SWB lid.

  17. Coulomb string tension, asymptotic string tension, and the gluon chain

    OpenAIRE

    Greensite, Jeff; Szczepaniak, Adam P.

    2014-01-01

    We compute, via numerical simulations, the non-perturbative Coulomb potential of pure SU(3) gauge theory in Coulomb gauge. We find that that the Coulomb potential scales nicely in accordance with asymptotic freedom, that the Coulomb potential is linear in the infrared, and that the Coulomb string tension is about four times larger than the asymptotic string tension. We explain how it is possible that the asymptotic string tension can be lower than the Coulomb string tension by a factor of four.

  18. Biodegradable device applied in flatfoot surgery: Comparative studies between clinical and technological aspects of removed screws

    International Nuclear Information System (INIS)

    Ruozi, Barbara; Belletti, Daniela; Manfredini, Giuseppe; Tonelli, Massimo; Sena, Paola; Vandelli, Maria Angela; Forni, Flavio; Tosi, Giovanni

    2013-01-01

    Poly-L-lactide (PLLA) is one of the most used polymers for biomedical application; its use in sutures and other implants has been widely investigated. Although the knowledge of PLLA biodegradation and biocompatibility features is deep, PLLA screws used to correct the flat foot deformity have deserved attention since they are not degraded in most of cases after a long period of years (3–7) from the implantation. In this article, a clinical and radiological evaluation (NMR, histological and clinical outcomes) on patients was correlated with physico-chemical characterization (by SEM, DSC, GPC and XRD analysis at different temperatures) on both native and patient-recovered screws together with the theoretical degradation processes of PLLA-based implants. The data demonstrated the need for crossing the biodegradation and bioabsorption of the polymer with the characteristics of both the device (geometry, structure and fabrication process) and the implantation site. Highlights: ► Resorbable PLLA screws were proposed for arthroereisis in pediatric flatfoot. ► Satisfactory clinical results were obtained almost in the totality of patients. ► The bioabsorption period is slightly longer than what is expected. ► Patient-recovered screws were analyzed to evaluate the biodegradation stage. ► Degradability/structural integrity during implantation should be ameliorated

  19. Biodegradable device applied in flatfoot surgery: Comparative studies between clinical and technological aspects of removed screws

    Energy Technology Data Exchange (ETDEWEB)

    Ruozi, Barbara, E-mail: barbara.ruozi@unimore.it [Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, MO (Italy); Belletti, Daniela, E-mail: daniela.belletti@unimore.it [Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, MO (Italy); Manfredini, Giuseppe, E-mail: giuseppe626@virgilio.it [Orthopaedic and Traumatologic Clinic, University Hospital of Modena and Reggio Emilia, Modena Italy, Director Prof. F. Catani, Via del Pozzo 71, Policlinico, 41100 Modena, MO (Italy); Tonelli, Massimo, E-mail: massimo.tonelli@unimore.it [CIGS, University of Modena and Reggio Emilia, Via Campi 213/A, 41100 Modena, MO (Italy); Sena, Paola, E-mail: paola.sena@unimore.it [Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Via del Pozzo 71, Policlinico, 41100 Modena, MO (Italy); Vandelli, Maria Angela, E-mail: mariaangela.vandelli@unimore.it [Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, MO (Italy); Forni, Flavio, E-mail: flavio.forni@unimore.it [Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, MO (Italy); Tosi, Giovanni, E-mail: giovanni.tosi@unimore.it [Department of Life Sciences, University of Modena and Reggio Emilia, Via Campi 183, 41100 Modena, MO (Italy)

    2013-04-01

    Poly-L-lactide (PLLA) is one of the most used polymers for biomedical application; its use in sutures and other implants has been widely investigated. Although the knowledge of PLLA biodegradation and biocompatibility features is deep, PLLA screws used to correct the flat foot deformity have deserved attention since they are not degraded in most of cases after a long period of years (3–7) from the implantation. In this article, a clinical and radiological evaluation (NMR, histological and clinical outcomes) on patients was correlated with physico-chemical characterization (by SEM, DSC, GPC and XRD analysis at different temperatures) on both native and patient-recovered screws together with the theoretical degradation processes of PLLA-based implants. The data demonstrated the need for crossing the biodegradation and bioabsorption of the polymer with the characteristics of both the device (geometry, structure and fabrication process) and the implantation site. Highlights: ► Resorbable PLLA screws were proposed for arthroereisis in pediatric flatfoot. ► Satisfactory clinical results were obtained almost in the totality of patients. ► The bioabsorption period is slightly longer than what is expected. ► Patient-recovered screws were analyzed to evaluate the biodegradation stage. ► Degradability/structural integrity during implantation should be ameliorated.

  20. Twin screw wet granulation: Binder delivery.

    Science.gov (United States)

    Saleh, Mohammed F; Dhenge, Ranjit M; Cartwright, James J; Hounslow, Michael J; Salman, Agba D

    2015-06-20

    The effects of three ways of binder delivery into the twin screw granulator (TSG) on the residence time, torque, properties of granules (size, shape, strength) and binder distribution were studied. The binder distribution was visualised through the transparent barrel using high speed imaging as well as quantified using offline technique. Furthermore, the effect of binder delivery and the change of screw configuration (conveying elements only and conveying elements with kneading elements) on the surface velocity of granules across the screw channel were investigated using particle image velocimetry (PIV). The binder was delivered in three ways; all solid binder incorporated with powder mixture, 50% of solid binder mixed with powder mixture and 50% mixed with water, all the solid binder dissolved in water. Incorporation of all solid binder with powder mixture resulted in the relatively longer residence time and higher torque, narrower granule size distribution, more spherical granules, weaker big-sized granules, stronger small-sized granules and better binder distribution compared to that in other two ways. The surface velocity of granules showed variation from one screw to another as a result of uneven liquid distribution as well as shown a reduction while introducing the kneading elements into the screw configuration. Copyright © 2015. Published by Elsevier B.V.

  1. Minimally invasive tension band wiring technique for olecranon fractures.

    Science.gov (United States)

    Takada, Naoya; Kato, Kenji; Fukuta, Makoto; Wada, Ikuo; Otsuka, Takanobu

    2013-12-01

    Some types of implants, such as plates, screws, wires, and nails, have been used for open reduction and internal fixation of olecranon fractures. A ≥ 10 cm longitudinal incision is used for open reduction and internal fixation of olecranon fractures. According to previous studies, tension band wiring is a popular method that gives good results. However, back out of the wires after the surgery is one of the main postoperative complications. Moreover, if the Kirschner wires are inserted through the anterior ulnar cortex, they may impinge on the radial neck, supinator muscle, or biceps tendon. Herein, we describe the minimally invasive tension band wiring technique using Ring-Pin. This technique can be performed through a 2 cm incision. Small skin incisions are advantageous from an esthetic viewpoint. Ring-Pin was fixed by using a dedicated cable wire that does not back out unless the cable wire breaks or slips out of the dedicated metallic clamp. As the pins are placed in intramedullary canal, this technique does not lead to postoperative complications that may occur after transcortical fixation by conventional tension band wiring. Minimally invasive tension band wiring is one of the useful options for the treatment of olecranon fractures with some advantages.

  2. Kinematics of Planetary Roller Screw Mechanism considering Helical Directions of Screw and Roller Threads

    Directory of Open Access Journals (Sweden)

    Shangjun Ma

    2015-01-01

    Full Text Available Based on the differential principle of thread transmission, an analytical model considering helical directions between screw and roller threads in planetary roller screw mechanism (PRSM is presented in this work. The model is critical for the design of PRSM with a smaller lead and a bigger pitch to realize a higher transmission accuracy. The kinematic principle of planetary transmission is employed to analyze the PRSM with different screw thread and roller thread directions. In order to investigate the differences with different screw thread and roller thread directions, the numerical model is developed by using the software Adams to validate the analytical solutions calculated by the presented model. The results indicate, when the helical direction of screw thread is identical with the direction of roller thread, that the lead of PRSM is unaffected regardless of whether sliding between screw and rollers occurs or not. Only when the direction of screw thread is reverse to the direction of roller thread, the design of PRSM with a smaller lead can be realized under a bigger pitch. The presented models and numerical simulation method can be used to research the transmission accuracy of PRSM.

  3. The movement of screw dislocations in tungsten

    International Nuclear Information System (INIS)

    Tian Xiaogeng; Woo Chungho

    2004-01-01

    Using Acland potential for tungsten, the movement of 1/2a screw dislocation under shear stress was investigated by molecular dynamics simulation. Equilibrated core structure was obtained by relaxation of screw dislocation with proper boundary conditions. We found that the equilibrium dislocation core has three-fold symmetry and spread out in three direction on {1 1 0} planes. The screw dislocation core could not keep the original shape when the shear stress applied. The dislocation could not move until the shear stress became large enough. The dislocation moved in zigzag when the shear stress neared the Peierls stress. When the shear stress became larger, the dislocation moved in zigzag at the beginning and than moved almost in straight line in [2-bar11] direction. The large shear stress applied, the long distance moved before the dislocation stilled in z-direction and the large velocity in y-direction

  4. Screw expander for light duty diesel engines

    Science.gov (United States)

    1983-01-01

    Preliminary selection and sizing of a positive displacement screw compressor-expander subsystem for a light-duty adiabatic diesel engine; development of a mathematical model to describe overall efficiencies for the screw compressor and expander; simulation of operation to establish overall efficiency for a range of design parameters and at given engine operating points; simulation to establish potential net power output at light-duty diesel operating points; analytical determination of mass moments of inertia for the rotors and inertia of the compressor-expander subsystem; and preparation of engineering layout drawings of the compressor and expander are discussed. As a result of this work, it was concluded that the screw compressor and expander designed for light-duty diesel engine applications are viable alternatives to turbo-compound systems, with acceptable efficiencies for both units, and only a moderate effect on the transient response.

  5. Dual-worm screw compressors; Compresseurs bi-vis

    Energy Technology Data Exchange (ETDEWEB)

    Baleydier, J P [Bitzer France, 69 - Lyon (France)

    1998-12-31

    Low power worm-screw moto-compressors are used in any king of refrigerating machineries and more and more in air conditioning systems. This paper presents the principle of dual-screw moto-compressors: worm-screw technology, role of oil (lubrication, tightness, cooling), compression, internal pressure, power reduction, lubrication, economizer, operation, model selection and accessories. (J.S.)

  6. A Novel Pedicle Screw with Mobile Connection: A Pilot Study

    Directory of Open Access Journals (Sweden)

    Yasuaki Tokuhashi

    2014-01-01

    Full Text Available To prevent adjacent disc problems after spinal fusion, a pedicle screw with a mobile junction between the head and threaded shaft was newly developed. The threaded shaft of the screw has 10 degrees mobility in all directions, but its structure is to prevent abnormal translation and tilting. This screw was evaluated as follows: (1 endurance test: 106 times rotational stress was applied; (2 biological reactions: novel screws with a mobile head and conventional screws with a fixed head were inserted into the bilateral pedicles of the L3, L4, and L5 in two mini pigs with combination. Eight months after surgery, vertebral units with the screw rod constructs were collected. After CT scan, the soft and bony tissues around the screws were examined grossly and histologically. As a result, none of the screws broke during the endurance test stressing. The mean amount of abrasion wear was 0.0338 g. In the resected mini pig section, though zygapophyseal joints between fixed-head screws showed bony union, the amount of callus in the zygapophyseal joints connected with mobile-head screws was small, and joint space was confirmed by CT. No metalloses were noted around any of the screws. Novel screws were suggested to be highly durable and histologically safe.

  7. Dual-worm screw compressors; Compresseurs bi-vis

    Energy Technology Data Exchange (ETDEWEB)

    Baleydier, J.P. [Bitzer France, 69 - Lyon (France)

    1997-12-31

    Low power worm-screw moto-compressors are used in any king of refrigerating machineries and more and more in air conditioning systems. This paper presents the principle of dual-screw moto-compressors: worm-screw technology, role of oil (lubrication, tightness, cooling), compression, internal pressure, power reduction, lubrication, economizer, operation, model selection and accessories. (J.S.)

  8. Minimisation of pressure pulsations in the screw compressor discharge piping

    Energy Technology Data Exchange (ETDEWEB)

    Zaytsev, D. [Grasso GmbH Refrigeration Technology, Berlin (Germany). R and D Screw Compressors

    2006-07-01

    A problem of noise and vibration in the piping between the screw compressor and oil separator arises if the natural gas pulsations in the piping get in the resonance with the pulsations sent by the compressor. Several typical piping geometries such as a short and a long pipe with the open end and a short pipe with agglomerator have been studied to evaluate the natural frequency of the gas column. It was found that because of the wave reflection from the open pipe end the gas in such a pipe has several natural frequencies dependent on the sound speed and on the pipe length. Since the sound speed of various refrigerants differs significantly, the resonance pipe length will also vary strongly from one refrigerant to another. Hence, to avoid the resonance a separate examination for each refrigerant would be required at the compressor package design stage. Unlike open ended pipes, in the pipe with agglomerator the wave reflection at the agglomerator side is reduced. This allows using of one standard discharge pipe geometry resonance-free independent on the refrigerant. (orig.)

  9. Comparison of Expansive Pedicle Screw and Polymethylmethacrylate-Augmented Pedicle Screw in Osteoporotic Sheep Lumbar Vertebrae: Biomechanical and Interfacial Evaluations

    OpenAIRE

    Liu, Da; Zhang, Yi; Zhang, Bo; Xie, Qing-yun; Wang, Cai-ru; Liu, Jin-biao; Liao, Dong-fa; Jiang, Kai; Lei, Wei; Pan, Xian-ming

    2013-01-01

    BACKGROUND: It was reported that expansive pedicle screw (EPS) and polymethylmethacrylate-augmented pedicle screw (PMMA-PS) could be used to increase screw stability in osteoporosis. However, there are no studies comparing the two kinds of screws in vivo. Thus, we aimed to compare biomechanical and interfacial performances of EPS and PMMA-PS in osteoporotic sheep spine. METHODOLOGY/PRINCIPAL FINDINGS: After successful induction of osteoporotic sheep, lumbar vertebrae in each sheep were random...

  10. Percutaneous anterior C1/2 transarticular screw fixation: salvage of failed percutaneous odontoid screw fixation for odontoid fracture

    OpenAIRE

    Wu, Ai-Min; Jin, Hai-Ming; Lin, Zhong-Ke; Chi, Yong-Long; Wang, Xiang-Yang

    2017-01-01

    Background The objective of this study is to investigate the outcomes and safety of using percutaneous anterior C1/2 transarticular screw fixation as a salvage technique for odontoid fracture if percutaneous odontoid screw fixation fails. Methods Fifteen in 108 odontoid fracture patients (planned to be treated by percutaneous anterior odontoid screw fixation) were failed to introduce satisfactory odontoid screw trajectory. To salvage this problem, we chose the percutaneous anterior C1/2 trans...

  11. A phenomenological study on twin screw extruders

    NARCIS (Netherlands)

    Janssen, L.P.B.M.

    1976-01-01

    Although more and more twin screw extruders are being used in the polymer industry, the theoretical background is relatively undeveloped. The literature abounds in contradictions and often informs the reader that all extrusion problems can be solved if a certain new design is considered. The

  12. Sacroiliac screw fixation for tile B fractures.

    NARCIS (Netherlands)

    Bosch, E.W. van den; Zwienen, C.M. van; Hoek van Dijke, G.A.; Snijders, C.J.; Vugt, A.B. van

    2003-01-01

    BACKGROUND: The purpose of this comparative cadaveric study was to investigate whether the stability of partially unstable pelvic fractures can be improved by combining plate fixation of the symphysis with a posterior sacroiliac screw. METHODS: In six specimens, a Tile B1 (open-book) pelvic fracture

  13. Tension-type headache

    DEFF Research Database (Denmark)

    Bendtsen, Lars; Jensen, Rigmor; Bendtsen, Lars

    2009-01-01

    The substantial societal and individual burdens associated with tension-type headache (TTH) constitute a previously overlooked major public health issue. TTH is prevalent, affecting up to 78% of the general population, and 3% suffer from chronic TTH. Pericranial myofascial nociception probably...... is important for the pathophysiology of episodic TTH, whereas sensitization of central nociceptive pathways seems responsible for the conversion of episodic to chronic TTH. Headache-related disability usually can be reduced by identification of trigger factors combined with nonpharmacologic and pharmacologic...... treatments, but effective treatment modalities are lacking. Benefits can be gained by development of specific and effective treatment strategies....

  14. Accuracy of computer-assisted cervicle pedicle screw installation

    International Nuclear Information System (INIS)

    Zhang Honglei; Zhou Dongsheng; Jang Zhensong

    2009-01-01

    Objective: To investigate the accuracy of computer-assisted cervical pedicle screw installation and the reason of screw malposition. Methods: A total of 172 cervical pedicle screws were installed by computer-assisted navigation for 30 patients with lower cervical spinal diseases. All the patients were examined by X-ray and CT after operation. Screw's position and direction were measured on the sagittal and transectional images of intraoperative navigation and post-operative CT. Then linear regression analysis was taken between navigational and post-operative CT's images. Results: Two screws perforated the upper pedicle wall, 3 perforated the lateral pedicle wall.There was a positive linear correlation between navigational and post-operative CT's images. Conclusion: Computer-assisted navigation can provide the high accuracy of cervical pedicle screw installation and excursion phenomenon is reason of screw malposition. (authors)

  15. Graft fixation with predetermined tension using a new device, the double spike plate.

    Science.gov (United States)

    Shino, Konsei; Mae, Tatsuo; Maeda, Akira; Miyama, Takahide; Shinjo, Hirotaka; Kawakami, Hideo

    2002-10-01

    To biomechanically evaluate a new fixation device, DSP (Double Spike Plate; Meira Corp, Nagoya, Aichi, Japan), for pullout graft fixation. Biomechanical study. A porcine tibia in which 8-mm diameter drill holes had been made from the medial tibial metaphysis to the anterior cruciate ligament attachment was rigidly fixed to a tension analyzer. A quadrupled graft consisting of 2 double-looped bovine tendons was prepared with No. 3 polyester sutures placed distally. The graft was passed through the drill hole, and its proximal loop ends were rigidly fixed to a load cell for monitoring graft tension. The graft's distal ends were connected to the DSP by tying the sutures to the top hole in the DSP. The graft tension was predetermined at 49 N (n = 5) or 98 N (n = 5). This tension was maintained for 5 minutes with a suture passed through the bottom hole of the DSP. The plate was fixed to the tibia by hammering its spikes into the bone under the index tension. Finally, the fixation was completed by inserting a screw. Although the graft tension immediately increased to 69 +/- 11 N or 133 +/- 14 N during hammering, it gradually reduced to 49 +/- 10 N or 100 +/- 7 N 5 minutes later. This study shows that graft fixation under a predetermined tension can be achieved with the DSP.

  16. Complex analysis and geometry

    CERN Document Server

    Silva, Alessandro

    1993-01-01

    The papers in this wide-ranging collection report on the results of investigations from a number of linked disciplines, including complex algebraic geometry, complex analytic geometry of manifolds and spaces, and complex differential geometry.

  17. Non-Riemannian geometry

    CERN Document Server

    Eisenhart, Luther Pfahler

    2005-01-01

    This concise text by a prominent mathematician deals chiefly with manifolds dominated by the geometry of paths. Topics include asymmetric and symmetric connections, the projective geometry of paths, and the geometry of sub-spaces. 1927 edition.

  18. Double twist : Can-K's electric submersible twin screw pump is designed to handle the nastiest crudes

    Energy Technology Data Exchange (ETDEWEB)

    Byfield, M.

    2010-12-15

    This article described the Can-K Group of Companies' electric submersible twin screw pump (ESTSP) designed for pumping heavy crudes with high levels of asphaltenes, hydrogen sulphide, wax, and methane. The technology was awarded the 2010 winner of best production technology for a company with fewer than 100 employees. The ESTSP can pump at a greater depth than other lift technologies. The design challenges included making the pump small enough to fit inside the well casing while also able to generate the high pressures necessary for pumping heavy oil. The ESTSP can compete directly against other lift technologies, including electric submersible pumps (ESPs). In the design, two shafts are separated by a timing gear. Each shaft has short sections of interlocking screws that do not touch, which lessens tension and the need for torque, lowering electricity consumption. The ESTSP is more efficient than ESP systems, particularly in more viscous mediums with high gas-to-oil ratios. The positive displacement pump interprets only volume and does not distinguish between gas and oil, functioning with gas content up to 97 percent. ESTSP can also handle more sand than ESP because it does not rely on centrifugal force. A patented screw design also helps prevent pump seizure resulting from sand and other solids. The pump uses downhole electric motors from other manufacturers. The inherent efficiencies of twin screw pumps give the technology the potential to replace conventional ESPs. 2 figs.

  19. Geometry-Dependent Electrostatics near Contact Lines

    International Nuclear Information System (INIS)

    Chou, Tom

    2001-01-01

    Long-ranged electrostatic interactions in electrolytes modify contact angles on charged substrates in a scale and geometry-dependent manner. For angles measured at scales smaller than the typical Debye screening length, the wetting geometry near the contact line must be explicitly considered. Using variational and asymptotic methods, we derive new transcendental equations for the contact angle as functions of the electrostatic potential only at the three phase contact line. Analytic expressions are found in certain limits and compared with predictions for contact angles measured with lower resolution. An estimate for electrostatic contributions to line tension is also given

  20. Geometry of the Universe

    International Nuclear Information System (INIS)

    Gurevich, L.Eh.; Gliner, Eh.B.

    1978-01-01

    Problems of investigating the Universe space-time geometry are described on a popular level. Immediate space-time geometries, corresponding to three cosmologic models are considered. Space-time geometry of a closed model is the spherical Riemann geonetry, of an open model - is the Lobachevskij geometry; and of a plane model - is the Euclidean geometry. The Universe real geometry in the contemporary epoch of development is based on the data testifying to the fact that the Universe is infinitely expanding

  1. Are We Underestimating the Significance of Pedicle Screw Misplacement?

    Science.gov (United States)

    Sarwahi, Vishal; Wendolowski, Stephen F; Gecelter, Rachel C; Amaral, Terry; Lo, Yungtai; Wollowick, Adam L; Thornhill, Beverly

    2016-05-01

    A retrospective review of charts, x-rays (XRs) and computed tomography (CT) scans was performed. To evaluate the accuracy of pedicle screw placement using a novel classification system to determine potentially significant screw misplacement. The accuracy rate of pedicle screw (PS) placement varies from 85% to 95% in the literature. This demonstrates technical ability but does not represent the impact of screw misplacement on individual patients. This study quantifies the rate of screw misplacement on a per-patient basis to highlight its effect on potential morbidity. A retrospective review of charts, XRs and low-dose CT scans of 127 patients who underwent spinal fusion with pedicle screws for spinal deformity was performed. Screws were divided into four categories: screws at risk (SAR), indeterminate misplacements (IMP), benign misplacements (BMP), accurately placed (AP). A total of 2724 screws were placed in 127 patients. A total of 2396 screws were placed accurately (87.96%). A total of 247 screws (9.07%) were BMP, 52 (1.91%) were IMP, and 29 (1.06%) were considered SAR. Per-patient analysis showed 23 (18.11%) of patients had all screws AP. Thirty-five (27.56%) had IMP and 18 (14.17%) had SAR. Risk factor analysis showed smaller Cobb angles increased likelihood of all screws being AP. Sub-analysis of adolescent idiopathic scoliotic patients showed no curve or patient characteristic that correlated with IMP or SAR. Over 40% of patients had screws with either some/major concern. Overall reported screw misplacement is low, but it does not reflect the potential impact on patient morbidity. Per-patient analysis reveals more concerning numbers toward screw misplacement. With increasing pedicle screw usage, the number of patients with misplaced screws will likely increase proportionally. Better strategies need to be devised for evaluation of screw placement, including establishment of a national database of deformity surgery, use of intra-operative image guidance, and

  2. General definition of gravitational tension

    International Nuclear Information System (INIS)

    Harmark, T.; Obers, N.A.

    2004-01-01

    In this note we give a general definition of the gravitational tension in a given asymptotically translationally-invariant spatial direction of a space-time. The tension is defined via the extrinsic curvature in analogy with the Hawking-Horowitz definition of energy. We show the consistency with the ADM tension formulas for asymptotically-flat space-times, in particular for Kaluza-Klein black hole solutions. Moreover, we apply the general tension formula to near-extremal branes, constituting a check for non-asymptotically flat space-times. (author)

  3. The applicability of PEEK-based abutment screws.

    Science.gov (United States)

    Schwitalla, Andreas Dominik; Abou-Emara, Mohamed; Zimmermann, Tycho; Spintig, Tobias; Beuer, Florian; Lackmann, Justus; Müller, Wolf-Dieter

    2016-10-01

    The high-performance polymer PEEK (poly-ether-ether-ketone) is more and more being used in the field of dentistry, mainly for removable and fixed prostheses. In cases of screw-retained implant-supported reconstructions of PEEK, an abutment screw made of PEEK might be advantageous over a conventional metal screw due to its similar elasticity. Also in case of abutment screw fracture, a screw of PEEK could be removed more easily. M1.6-abutment screws of four different PEEK compounds were subjected to tensile tests to set their maximum tensile strengths in relation to an equivalent stress of 186MPa, which is aused by a tightening torque of 15Ncm. Two screw types were manufactured via injection molding and contained 15% short carbon fibers (sCF-15) and 40% (sCF-40), respectively. Two screw types were manufactured via milling and contained 20% TiO2 powder (TiO2-20) and >50% parallel orientated, continuous carbon fibers (cCF-50). A conventional abutments screw of Ti6Al4V (Ti; CAMLOG(®) abutment screw, CAMLOG, Wimsheim, Germany) served as control. The maximum tensile strength was 76.08±5.50MPa for TiO2-20, 152.67±15.83MPa for sCF-15, 157.29±20.11MPa for sCF-40 and 191.69±36.33MPa for cCF-50. The maximum tensile strength of the Ti-screws amounted 1196.29±21.4MPa. The results of the TiO2-20 and the Ti screws were significantly different from the results of the other samples, respectively. For the manufacturing of PEEK abutment screws, PEEK reinforced by >50% continuous carbon fibers would be the material of choice. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Chirality-controlled crystallization via screw dislocations.

    Science.gov (United States)

    Sung, Baeckkyoung; de la Cotte, Alexis; Grelet, Eric

    2018-04-11

    Chirality plays an important role in science from enantiomeric separation in chemistry to chiral plasmonics in nanotechnology. However, the understanding of chirality amplification from chiral building blocks to ordered helical superstructures remains a challenge. Here, we demonstrate that topological defects, such as screw dislocations, can drive the chirality transfer from particle to supramolecular structure level during the crystallization process. By using a model system of chiral particles, which enables direct imaging of single particle incorporation into growing crystals, we show that the crystallization kinetic pathway is the key parameter for monitoring, via the defects, the chirality amplification of the crystalline structures from racemic to predominantly homohelical. We provide an explanation based on the interplay between geometrical frustration, racemization induced by thermal fluctuations, and particle chirality. Our results demonstrate that screw dislocations not only promote the growth, but also control the chiral morphology and therefore the functionality of crystalline states.

  5. Calculating Characteristics of the Screws with Constant And Variable Step

    Directory of Open Access Journals (Sweden)

    B. N. Zotov

    2015-01-01

    Full Text Available This work is devoted to creating a technique for calculating power characteristics of the screws with constant and variable step for the centrifugal pumps. The technique feature is that the reverse currents, which are observed in screws working at low flow, are numerically taken into account. The paper presents a diagram of the stream in the screw with flow to the network Q=0, and the static pressure of the screw in this mode is computed according to reverse current parameters. Maximum flow of screw is determined from the known formulas. When calculating the power characteristics and computing the overall efficiency of the screw, for the first time a volumetric efficiency of the screw is introduced. It is defined as a ratio between the flow into the network and the sum of the reverse current flows and a flow into the network. This approach allowed us to determine the efficiency of the screw over the entire range of flows.A comparison of experimental characteristics of the constant step screw with those of calculated by the proposed technique shows their good agreement.The technique is also used in calculating characteristics of the variable step screws. The variable step screw is considered as a screw consisting of two screws with a smooth transition of the blades from the inlet to the outlet. Screws in which the step at the inlet is less than that of at the outlet as well as screws with the step at the inlet being more than that of at the outlet were investigated. It is shown that a pressure of the screw with zero step and the value of the reverse currents depend only on the parameters of the input section of the screw, and the maximum flow, if the step at the inlet is more than the step at the outlet, is determined by the parameters of the output part of the screw. Otherwise, the maximum flow is determined a little bit differently.The paper compares experimental characteristics with characteristics calculated by the technique for variable step

  6. Tension type headaches: a review

    African Journals Online (AJOL)

    Location of the pain:There is often a typical location for tension- type headaches, as ... Cranial nerve abnormalities, including papilloedema. • Signs of ... peripheral and central mechanisms underlie tension-type ... Physiotherapy has been shown to be an effective management option for .... Acupuncture in primary headache.

  7. Energy saving screw compressor technology; Energiebesparende schroefcompressortechnologie

    Energy Technology Data Exchange (ETDEWEB)

    Moeller, A. [RefComp, Lonigo (Italy); Neus, M. [Delta Technics Engineering, Breda (Netherlands)

    2011-03-15

    Smart solutions to reduce the energy consumption are continuously part of investigation in the refrigeration technology. This article subscribed the technology on which way energy can be saved at the operation of screw compressors which are used in air conditioners and refrigerating machinery. The combination of frequency control and Vi-control (intrinsic volumetric ratio) such as researched in the laboratory of RefComp is for the user attractive because the energy efficiency during part load operation is much better. Smart uses of thermodynamics, electric technology and electronic control are the basics of these applications. According to the manufacturer's information it is possible with these new generation screw compressors to save approx. 26% energy in comparison with the standard screw compressor. [Dutch] In dit artikel wordt de technologie omschreven waarmee veel energie bespaard kan worden bij schroefcompressoren die worden gebruikt in airconditioningsystemen en koel- en vriesinstallaties. De combinatie van frequentieregeling en Vi- regeling (Vi is de intrinsieke volumetrische verhouding) zoals onderzocht in het laboratorium van RefComp biedt de gebruiker veel voordelen doordat de energie-efficintie van de compressor tijdens deellast enorm wordt verbeterd. Slim gebruik van thermodynamika, elektrotechniek en elektronica vormen de basis van deze toepassing. Volgens de fabrikant kan met deze nieuwe generatie schroefcompressoren circa 26 procent op het energiegebruik tijdens deellast worden bespaard in vergelijking met de standaard serie schroefcompressoren.

  8. 2D and 3D assessment of sustentaculum tali screw fixation with or without Screw Targeting Clamp.

    Science.gov (United States)

    De Boer, A Siebe; Van Lieshout, Esther M M; Vellekoop, Leonie; Knops, Simon P; Kleinrensink, Gert-Jan; Verhofstad, Michael H J

    2017-12-01

    Precise placement of sustentaculum tali screw(s) is essential for restoring anatomy and biomechanical stability of the calcaneus. This can be challenging due to the small target area and presence of neurovascular structures on the medial side. The aim was to evaluate the precision of positioning of the subchondral posterior facet screw and processus anterior calcanei screw with or without a Screw Targeting Clamp. The secondary aim was to evaluate the added value of peroperative 3D imaging over 2D radiographs alone. Twenty Anubifix™ embalmed, human anatomic lower limb specimens were used. A subchondral posterior facet screw and a processus anterior calcanei screw were placed using an extended lateral approach. A senior orthopedic trauma surgeon experienced in calcaneal fracture surgery and a senior resident with limited experience in calcaneal surgery performed screw fixation in five specimens with and in five specimens without the clamp. 2D lateral and axial radiographs and a 3D recording were obtained postoperatively. Anatomical dissection was performed postoperatively as a diagnostic golden standard in order to obtain the factual screw positions. Blinded assessment of quality of fixation was performed by two surgeons. In 2D, eight screws were considered malpositioned when placed with the targeting device versus nine placed freehand. In 3D recordings, two additional screws were malpositioned in each group as compared to the golden standard. As opposed to the senior surgeon, the senior resident seemed to get the best results using the Screw Targeting Clamp (number of malpositioned screws using freehand was eight, and using the targeting clamp five). In nine out of 20 specimens 3D images provided additional information concerning target area and intra-articular placement. Based on the 3D assessment, five additional screws would have required repositioning. Except for one, all screw positions were rated equally after dissection when compared with 3D examinations

  9. In vitro evaluation of force-expansion characteristics in a newly designed orthodontic expansion screw compared to conventional screws

    Directory of Open Access Journals (Sweden)

    Oshagh Morteza

    2009-01-01

    Full Text Available Objective : Expansion screws like Hyrax, Haas and other types, produce heavy interrupted forces which are unfavorable for dental movement and could be harmful to the tooth and periodontium. The other disadvantage of these screws is the need for patient cooperation for their regular activation. The purpose of this study was to design a screw and compare its force- expansion curve with other types. Materials and Methods : A new screw was designed and fabricated in the same dimension, with conventional types, with the ability of 8 mm expansion (Free wire length: 12 mm, initial compression: 4.5 mm, spring wire diameter: 0.4 mm, spring diameter: 3 mm, number of the coils: n0 ine, material: s0 tainless steel. In this in vitro study, the new screw was placed in an acrylic orthodontic appliance, and after mounting on a stone cast, the force-expansion curve was evaluated by a compression test machine and compared to other screws. Results : Force-expansion curve of designed screw had a flatter inclination compared to other screws. Generally it produced a light continuous force (two to 3.5 pounds for every 4 mm of expansion. Conclusion : In comparison with heavy and interrupted forces of other screws, the newly designed screw created light and continuous forces.

  10. Experimental study of pedicle screw stability on low BMD vertebrae

    International Nuclear Information System (INIS)

    Li Qi; Yang Huilin; Tang Tiansi; Wu Yiwei; Wang Yijin

    2005-01-01

    Objective: To conduct biomechanical study of different pedicle screws stability on spinal specimen, discuss the relationship between design parameter of screw, insertion torgue and BMD, establish the theoretical foundation for application of pedicle screw on osteoporotic patients. Methods: Six fixed lumbar cadavers were collected, the effects of design parameter, insertion torque and etc on fixation stability were determined under various BMD by using biomechanical ways. Results: According to in vitro study: (1) There was a significant difference among pullout strength of all screws (P 2 >U 1 >SF 1 >SF 2 >RF. Conclusions: There is a close correlated between type of screw, BMD and stability. The U-type screw displays the best fixation effect on specimen of low BMD. (authors)

  11. Passage of an Anterior Odontoid Screw through Gastrointestinal Tract.

    Science.gov (United States)

    Leitner, L; Brückmann, C I; Gilg, M M; Bratschitsch, G; Sadoghi, P; Leithner, A; Radl, R

    2017-01-01

    Purpose . Anterior screw fixation has become a popular surgical treatment method for instable odontoid fractures. Screw loosening and migration are a rare, severe complication following anterior odontoid fixation, which can lead to esophagus perforation and requires revision operation. Methods . We report a case of screw loosening and migration after anterior odontoid fixation, which perforated the esophagus and was excreted without complications in a 78-year-old male patient. Results . A ventral dislocated anterior screw perforated through the esophagus after eight years after implantation and was excreted through the gastrointestinal (GI) tract. At a 6-month follow-up after the event the patient was asymptomatic. Conclusion . Extrusion via the GI tract is not safe enough to be considered as a treatment option for loosened screws. Some improvements could be implemented to prevent such an incident. Furthermore, this case is a fine example that recent preoperative imaging is mandatory before revision surgery for screw loosening.

  12. Passage of an Anterior Odontoid Screw through Gastrointestinal Tract

    Directory of Open Access Journals (Sweden)

    L. Leitner

    2017-01-01

    Full Text Available Purpose. Anterior screw fixation has become a popular surgical treatment method for instable odontoid fractures. Screw loosening and migration are a rare, severe complication following anterior odontoid fixation, which can lead to esophagus perforation and requires revision operation. Methods. We report a case of screw loosening and migration after anterior odontoid fixation, which perforated the esophagus and was excreted without complications in a 78-year-old male patient. Results. A ventral dislocated anterior screw perforated through the esophagus after eight years after implantation and was excreted through the gastrointestinal (GI tract. At a 6-month follow-up after the event the patient was asymptomatic. Conclusion. Extrusion via the GI tract is not safe enough to be considered as a treatment option for loosened screws. Some improvements could be implemented to prevent such an incident. Furthermore, this case is a fine example that recent preoperative imaging is mandatory before revision surgery for screw loosening.

  13. Hydraulic screw fastening devices - design, maintenance, operational experience

    International Nuclear Information System (INIS)

    Lachner.

    1976-01-01

    With hydraulic screw fastening devices, pretension values with a maximum deviation of +-2.5% from the rated value can be achieved. This high degree of pretension accuracy is of considerable importance with regard to the safety factor required for the screw connection between reactor vessel head and reactor vessel. The operating rhythm of a nuclear power station with its refuelling art regular intervals makes further demands on the screw fastening device, in particular in connection with the transport of screws and for nuts. The necessary installations extend the screw fastening device into a combination of a high-pressure hydraulic cylinder system with an electrical or pneumoelectrical driving unit and an electrical control unit. Maintenance work is complicated by the large number of identical, highly stressed structural elements in connection with an unfavourable relation operating time/outage time. The problems have been perpetually reduced by close cooperation between the manufacturers and users of screw fastening devices. (orig./AK) [de

  14. Tightening techniques for the retaining screws of universal abutment

    Directory of Open Access Journals (Sweden)

    Alexandre Wittcinski REGALIN

    Full Text Available Abstract Purpose This study evaluated the torque maintenance of universal abutment retaining screws using different tightening techniques, and coated or uncoated screws. Material and method The screws were tightened to implants as following: Control – 32 Ncm torque; H20 – holding 32 Ncm torque for 20 s; R – 32 Ncm torque, repeated after 10 min (retorque; and H20+R – combining the two tightening techniques. Titanium and coated screws were also evaluated. Result Statistical analysis showed higher maintained torque for titanium screws (p<0.001. The H20+R technique showed the highest maintained torque (p=0.003, but the H20 technique’s maintained torque was similar. Conclusion Titanium screws associating the two tightening techniques can improve maintained torque.

  15. Contribution to the study of screw dislocations; Contribution a l'etude des dislocations helicoidales

    Energy Technology Data Exchange (ETDEWEB)

    Grilhe, J [Commissariat a l' Energie Atomique, Fontenay aux Roses (France). Centre d' Etudes Nucleaires

    1965-03-01

    The aim of this work is to study the germination, growth and properties of screw dislocations. In the introduction (first chapter), we describe briefly the main experimental results obtained by various authors (observations of screws by Amelinckx and Bontinck in ionic crystals, by Dash in silicon crystals and by Thomas and Whelan in aluminium based alloys). We then make a few considerations concerning characteristic geometry of screws and the various methods used for calculating the energy of a dislocation. In the second chapter we study the problems involving only slip of the screw around its cylinder. We calculate the equilibrium step as a function of the forces acting on the extremities. We determine the critical stress required to disrupt the screw and study the interactions between the screw and other dislocations of the lattice. In the third chapter we consider the problem of the stability when the dislocation can climb by absorption or emission of vacancies. We study separately the stability of the size which only involves volume diffusion and the stability of the shape which depends only on the rearrangement of the vacancies along the dislocation. In chapter four we put forward a germination model for the screws: since the vacancies are not absorbed by the screw dislocations, they form clusters which take up a spiral form. The formation of these spirals is studied from the geometrical point of view in face-centered cubic systems. In chapter five we make use of the results obtained in chapters two and three for studying the growth of the spirals. (author) [French] Le but de ce travail est d'etudier la germination, la croissance et les proprietes des dislocations helico ales. Dans l'introduction (premier chapitre), nous exposons brievement les principaux resultats experimentaux obtenus par differents auteurs (observations d'helice par Amelinckx et Bontinck dans les cristaux ioniques, par Dash dans des cristaux de silicium et par Thomas et Whelan dans des

  16. Mathematical modeling and design parameters of crushing machines with variable-pitch helix of the screw

    Directory of Open Access Journals (Sweden)

    Pelenko V. V.

    2017-11-01

    Full Text Available From the point of view of the effectiveness of the top cutting unit, the helix angle in the end portion of the screw is the most important and characteristic parameter, as it determines the pressure of the meat material in the zone of interaction of a knife and grate. The importance of solving the problem of mathematical modeling of geometry is due to the need to address the problem of minimizing the reverse flow of the food material when injecting into the cutting zone, as the specified effect of "locking" significantly reduces the performance of the transfer process, increases energy consumption of the equipment and entails the deterioration of the quality of the raw materials output. The problem of determining the length of the helix variable pitch for screw chopper food materials has been formulated and solved by methods of differential geometry. The task of correct description of the law of changing the angle of helix inclination along its length has been defined in this case as a key to provide the required dependence of this angle tangent on the angle of the radius-vector of the circle. It has been taken into account that the reduction in the pitch of the screw in the direction of the product delivery should occur at a decreasing rate. The parametric equation of the helix has been written in the form of three functional dependencies of the corresponding cylindrical coordinates. Based on the wide range analysis and significant number of models of tops from different manufacturers the boundaries of possible changes in the angles of inclination of the helical line of the first and last turns of the screw have been identified. The auger screw length is determined mathematically in the form of an analytical relationship and both as a function of the variable angle of its rise, and as a function of the rotation angle of the radius-vector of the circle generatrix, which makes it possible to expand the design possibilities of this node. Along

  17. MUSCLE TENSION DYSPHONIA

    Directory of Open Access Journals (Sweden)

    Irena Hočevar Boltežar

    2004-07-01

    Full Text Available Background. Muscle tension dysphonia (MTD is the cause of hoarseness in almost one half of the patients with voice disorders. The otorhinolaryngologic examination discovers no evident organic lesions in the larynx at least in the beginning of the voice problems. The reason for the hoarse voice is a disordered and maladjusted activity of the muscles taking part in phonation and/or articulation. In some patients, the irregular function of the larynx results in mucosal lesions on vocal folds. The factors participating in the development of MTD, directly or indirectly influence the quality of laryngeal mucosa, the activity of the phonatory muscles and/or increase of the vocal load. In the diagnostics and treatment of the MTD a phoniatrician, a speech and language therapist and a psychologist closely cooperate with the patient who must take an active role. The treatment is a long-lasting one but resulted in a high percentage of clinical success.Conclusions. Most likely, MTD is not a special disease but only a reflection of any disorder in the complicated system of regulation and realization of phonation. The prognosis of treatment is good when all unfavourable factors participating in development of MTD are eliminated and a proper professional voice- and psychotherapy started.

  18. Translaminar screw fixation in the lumbar spine: technique, indications, results

    OpenAIRE

    Grob, D.; Humke, T.

    1998-01-01

    Translaminar screw fixation of the lumbar spine represents a simple and effective technique for short segment fusion in the degenerative spine. Clinical experience with 173 patients who underwent translaminar screw fixation revealed a fusion rate of 94%. The indications for translaminar screw fixation as a primary fixation procedure are: segmental dysfunction, lumbar spinal stenosis with painful degenerative changes, segmental revision surgery after discectomies, and painful disc-related synd...

  19. Economics of water injected air screw compressor systems

    OpenAIRE

    Madhav, K. V.; Kovacevic, A.

    2015-01-01

    There is a growing need for compressed air free of entrained oil to be used in industry. In many cases it can be supplied by oil flooded screw compressors with multi stage filtration systems, or by oil free screw compressors. However, if water injected screw compressors can be made to operate reliably, they could be more efficient and therefore cheaper to operate. Unfortunately, to date, such machines have proved to be insufficiently reliable and not cost effective. This paper describes an in...

  20. Process and apparatus for optimizing screwing position for closure stud

    International Nuclear Information System (INIS)

    Bourdonne, J.C.; Briand, A.

    1987-01-01

    The stud is fixed to a screwing and unscrewing device. The vertical position and alignment of the stud with the axis of the threated hole is checking. The stud is descended into the hole and rotated in the unscrewing direction. After detection of the point of engagement, the stud is rotated in the screwing direction. When a gamming is detected the descent is stopped and the screwing device is positioned in a new position. When the screwing couple returns below the disconnection couple, the stud is rotated with a reduced speed and then with a normal speed until the end [fr

  1. Accuracy of pedicle screw placement in patients with Marfan syndrome.

    Science.gov (United States)

    Qiao, Jun; Zhu, Feng; Xu, Leilei; Liu, Zhen; Sun, Xu; Qian, Bangping; Jiang, Qing; Zhu, Zezhang; Qiu, Yong

    2017-03-21

    There is no study concerning safety and accuracy of pedicle screw placement in Marfan syndrome. The objective of this study is to investigate accuracy and safety of pedicle screw placement in scoliosis associated with Marfan syndrome. CT scanning was performed to analyze accuracy of pedicle screw placement. Pedicle perforations were classified as medial, lateral or anterior and categorized to four grades: ≤ 2 mm as Grade 1, 2.1-4.0 mm as Grade 2, 4.1-6.0 mm as Grade 3, ≥6.1 mm as Grade 4. Fully contained screws or with medial wall perforation ≤ 2 mm or with lateral wall perforation ≤ 6 mm and without injury of visceral organs were considered acceptable, otherwise were unacceptable. 976 pedicle screws were placed, 713 screws (73.1%) were fully contained within the cortical boundaries of the pedicle. 924 (94.7%) screws were considered as acceptable, and 52 (5.3%) as unacceptable. The perforation rate was higher using free-hand technique than O-arm navigation technique (30.8% VS. 11.4%, P Marfan syndrome is accuracy and safe. O-arm navigation was an effective modality to ensure the safety and accuracy of screw placement. Special attention should be paid when screws were placed at the lumber spine and the concave side of spine deformity to avoid the higher rate of complications.

  2. Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

    Directory of Open Access Journals (Sweden)

    Jan-Helge Klingler

    2015-01-01

    Full Text Available Purpose. To describe the minimally invasive technique for cement augmentation of cannulated and fenestrated screws using an injection cannula as well as to report its safety and efficacy. Methods. A total of 157 cannulated and fenestrated pedicle screws had been cement-augmented during minimally invasive posterior screw-rod spondylodesis in 35 patients from January to December 2012. Retrospective evaluation of cement extravasation and screw loosening was carried out in postoperative plain radiographs and thin-sliced triplanar computed tomography scans. Results. Twenty-seven, largely prevertebral cement extravasations were detected in 157 screws (17.2%. None of the cement extravasations was causing a clinical sequela like a new neurological deficit. One screw loosening was noted (0.6% after a mean follow-up of 12.8 months. We observed no cementation-associated complication like pulmonary embolism or hemodynamic insufficiency. Conclusions. The presented minimally invasive cement augmentation technique using an injection cannula facilitates convenient and safe cement delivery through polyaxial cannulated and fenestrated screws during minimally invasive screw-rod spondylodesis. Nevertheless, the optimal injection technique and design of fenestrated screws have yet to be identified. This trial is registered with German Clinical Trials DRKS00006726.

  3. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    Science.gov (United States)

    Henderson, Sarah E.; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L.; Chou, Da-Tren; Kumta, Prashant N.; Almarza, Alejandro J.

    2014-01-01

    Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications. PMID:24384125

  4. Tension pneumocephalus: Mount Fuji sign

    Directory of Open Access Journals (Sweden)

    Pulastya Sanyal

    2015-01-01

    Full Text Available A 13-year-old male was operated for a space occupying lesion in the brain. A noncontrast computed tomography scan done in the late postoperative period showed massive subdural air collection causing compression of bilateral frontal lobes with widening of interhemispheric fissure and the frontal lobes acquiring a peak like configuration - causing tension pneumocephalus-"Mount Fuji sign." Tension pneumocephalus occurs when air enters the extradural or intradural spaces in sufficient volume to exert a mass or pressure effect on the brain, leading to brain herniation. Tension pneumocephalus is a surgical emergency, which needs immediate intervention in the form of decompression of the cranial cavity by a burr hole or needle aspiration. The Mount Fuji sign differentiates tension pneumocephalus from pneumocephalus.

  5. Geometry and its applications

    CERN Document Server

    Meyer, Walter J

    2006-01-01

    Meyer''s Geometry and Its Applications, Second Edition, combines traditional geometry with current ideas to present a modern approach that is grounded in real-world applications. It balances the deductive approach with discovery learning, and introduces axiomatic, Euclidean geometry, non-Euclidean geometry, and transformational geometry. The text integrates applications and examples throughout and includes historical notes in many chapters. The Second Edition of Geometry and Its Applications is a significant text for any college or university that focuses on geometry''s usefulness in other disciplines. It is especially appropriate for engineering and science majors, as well as future mathematics teachers.* Realistic applications integrated throughout the text, including (but not limited to): - Symmetries of artistic patterns- Physics- Robotics- Computer vision- Computer graphics- Stability of architectural structures- Molecular biology- Medicine- Pattern recognition* Historical notes included in many chapters...

  6. Algebraic geometry in India

    Indian Academy of Sciences (India)

    algebraic geometry but also in related fields like number theory. ... every vector bundle on the affine space is trivial. (equivalently ... les on a compact Riemann surface to unitary rep- ... tial geometry and topology and was generalised in.

  7. Spinorial Geometry and Branes

    International Nuclear Information System (INIS)

    Sloane, Peter

    2007-01-01

    We adapt the spinorial geometry method introduced in [J. Gillard, U. Gran and G. Papadopoulos, 'The spinorial geometry of supersymmetric backgrounds,' Class. Quant. Grav. 22 (2005) 1033 [ (arXiv:hep-th/0410155)

  8. Spinorial Geometry and Branes

    Energy Technology Data Exchange (ETDEWEB)

    Sloane, Peter [Department of Mathematics, King' s College, University of London, Strand, London WC2R 2LS (United Kingdom)

    2007-09-15

    We adapt the spinorial geometry method introduced in [J. Gillard, U. Gran and G. Papadopoulos, 'The spinorial geometry of supersymmetric backgrounds,' Class. Quant. Grav. 22 (2005) 1033 [ (arXiv:hep-th/0410155)

  9. Mitochondrial Respiration and Oxygen Tension.

    Science.gov (United States)

    Shaw, Daniel S; Meitha, Karlia; Considine, Michael J; Foyer, Christine H

    2017-01-01

    Measurements of respiration and oxygen tension in plant organs allow a precise understanding of mitochondrial capacity and function within the context of cellular oxygen metabolism. Here we describe methods that can be routinely used for the isolation of intact mitochondria, and the determination of respiratory electron transport, together with techniques for in vivo determination of oxygen tension and measurement of respiration by both CO 2 production and O 2 consumption that enables calculation of the respiratory quotient [CO 2 ]/[O 2 ].

  10. Hyperelastic tension of graphene

    Energy Technology Data Exchange (ETDEWEB)

    Saavedra Flores, E. I., E-mail: erick.saavedra@usach.cl [Departamento de Ingeniería en Obras Civiles, Universidad de Santiago de Chile, Av. Ecuador 3659, Santiago (Chile); Ajaj, R. M. [Aeronautics and Astronautics, University of Southampton, Southampton SO171BJ (United Kingdom); Adhikari, S.; Dayyani, I.; Friswell, M. I. [College of Engineering, Swansea University, Singleton Park, Swansea SA2 8PP (United Kingdom); Castro-Triguero, Rafael [Department of Mechanics, University of Cordoba, Campus de Rabanales, Cordoba CP 14071 (Spain)

    2015-02-09

    In this paper, we investigate the hyperelastic tensile behaviour of single layer graphene sheets (SLGSs). A one-term incompressible Ogden-type hyperelastic model is chosen to describe the mechanical response of C-C bonds. By establishing equality between the Ogden strain-energy and the variation of the Tersoff-Brenner interatomic potential, three different geometries of SLGSs are studied under tensile loading. We compute the Young's modulus, the finite-deformation Poisson's ratio, ultimate strains, total reactions, and the variation of the potential energy per carbon atom for large strains. Numerical simulations are compared with results obtained by molecular mechanics and molecular dynamics simulations, finite elements, continuum mechanics theory, and experiments. Our predictions are validated, revealing the potential predictive capabilities of the present hyperelastic framework for the analysis of graphene in the context of infinitesimal and large deformations. The good agreement found between our calculations and the published data suggests that graphene may be described as a hyperelastic material.

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

    International Nuclear Information System (INIS)

    Tsagas, Christos G

    2005-01-01

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

  12. Evaluation of two styles of slotted, flat-head screws

    International Nuclear Information System (INIS)

    Reeves, C.A. Jr.; Johnson, W.B.

    1979-01-01

    A series of torque tests were performed to evaluate the relative merits of two different flat-head screws fabricated from a uranium--6% niobium alloy. The screws tested were machined with both normal, straight-through slots in the head and with slots having radiused bottoms. Test results indicate that both designs easily surpass the required 20-inch-pound-proof torque

  13. Electromagnetic Lead Screw for Potential Wave Energy Application

    DEFF Research Database (Denmark)

    Lu, Kaiyuan; Wu, Weimin

    2014-01-01

    This paper presents a new type electromagnetic lead screw (EMLS) intended for wave energy application. Similar to the mechanical lead screw, this electromagnetic version can transfer slow linear motion to high-rotational motion, offering gearing effects. Compared with the existing pure magnetic...

  14. Geometry essentials for dummies

    CERN Document Server

    Ryan, Mark

    2011-01-01

    Just the critical concepts you need to score high in geometry This practical, friendly guide focuses on critical concepts taught in a typical geometry course, from the properties of triangles, parallelograms, circles, and cylinders, to the skills and strategies you need to write geometry proofs. Geometry Essentials For Dummies is perfect for cramming or doing homework, or as a reference for parents helping kids study for exams. Get down to the basics - get a handle on the basics of geometry, from lines, segments, and angles, to vertices, altitudes, and diagonals Conque

  15. The Analysis of Soil Resistance During Screw Displacement Pile Installation

    Science.gov (United States)

    Krasinski, Adam

    2015-02-01

    The application of screw displacement piles (SDP) is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque) during screw auger penetration in non-cohesive subsoil based on CPT is proposed.

  16. Ball Screw Actuator Including an Axial Soft Stop

    Science.gov (United States)

    Wingett, Paul T. (Inventor); Forrest, Steven Talbert (Inventor); Abel, Steve (Inventor); Woessner, George (Inventor); Hanlon, Casey (Inventor)

    2016-01-01

    An actuator includes an actuator housing, a ball screw, and an axial soft stop assembly. The ball screw extends through the actuator housing and has a first end and a second end. The ball screw is coupled to receive a drive force and is configured, upon receipt of the drive force, to selectively move in a retract direction and an extend direction. The axial soft stop assembly is disposed within the actuator housing. The axial soft stop assembly is configured to be selectively engaged by the ball screw and, upon being engaged thereby, to translate, with compliance, a predetermined distance in the extend direction, and to prevent further movement of the ball screw upon translating the predetermined distance.

  17. On Helical Projection and Its Application in Screw Modeling

    Directory of Open Access Journals (Sweden)

    Riliang Liu

    2014-04-01

    Full Text Available As helical surfaces, in their many and varied forms, are finding more and more applications in engineering, new approaches to their efficient design and manufacture are desired. To that end, the helical projection method that uses curvilinear projection lines to map a space object to a plane is examined in this paper, focusing on its mathematical model and characteristics in terms of graphical representation of helical objects. A number of interesting projective properties are identified in regard to straight lines, curves, and planes, and then the method is further investigated with respect to screws. The result shows that the helical projection of a cylindrical screw turns out to be a Jordan curve, which is determined by the screw's axial profile and number of flights. Based on the projection theory, a practical approach to the modeling of screws and helical surfaces is proposed and illustrated with examples, and its possible application in screw manufacturing is discussed.

  18. A four lumen screwing device for multiparametric brain monitoring.

    Science.gov (United States)

    Feuerstein, T H; Langemann, H; Gratzl, O; Mendelowitsch, A

    2000-01-01

    We describe multiparametric monitoring in severe head trauma using a new screwing device. Our aim was to create a screw which would make the implantation of the probes and thus multiparametric monitoring easier. The new screw allows us to implant 3 probes (microdialysis, Paratrend and an intracranial pressure device) through one burr hole. The screw has four channels, the fourth being for ventricular drainage. We monitored 13 patients with severe head trauma (GCS = 3-8) for up to 7 days. Brain tissue pO2, pCO2, pH, and temperature were measured on-line with the Paratrend 7 machine. The microdialytic parameters glucose, lactate, pyruvate and glutamate were determined semi on-line with a CMA 600 enzymatic analyser. There were no complications in any of the patients that could be ascribed to the screw.

  19. The Analysis of Soil Resistance During Screw Displacement Pile Installation

    Directory of Open Access Journals (Sweden)

    Krasinski Adam

    2015-02-01

    Full Text Available The application of screw displacement piles (SDP is still increasing due to their high efficiency and many advantages. However, one technological problem is a serious disadvantage of those piles. It relates to the generation of very high soil resistance during screw auger penetration, especially when piles are installed in non-cohesive soils. In many situations this problem causes difficulties in creating piles of designed length and diameter. It is necessary to find a proper method for prediction of soil resistance during screw pile installation. The analysis of screw resistances based on model and field tests is presented in the paper. The investigations were carried out as part of research project, financed by the Polish Ministry of Science and Higher Education. As a result of tests and analyses the empirical method for prediction of rotation resistance (torque during screw auger penetration in non-cohesive subsoil based on CPT is proposed.

  20. Arithmetic noncommutative geometry

    CERN Document Server

    Marcolli, Matilde

    2005-01-01

    Arithmetic noncommutative geometry denotes the use of ideas and tools from the field of noncommutative geometry, to address questions and reinterpret in a new perspective results and constructions from number theory and arithmetic algebraic geometry. This general philosophy is applied to the geometry and arithmetic of modular curves and to the fibers at archimedean places of arithmetic surfaces and varieties. The main reason why noncommutative geometry can be expected to say something about topics of arithmetic interest lies in the fact that it provides the right framework in which the tools of geometry continue to make sense on spaces that are very singular and apparently very far from the world of algebraic varieties. This provides a way of refining the boundary structure of certain classes of spaces that arise in the context of arithmetic geometry, such as moduli spaces (of which modular curves are the simplest case) or arithmetic varieties (completed by suitable "fibers at infinity"), by adding boundaries...

  1. Undertapping of Lumbar Pedicle Screws Can Result in Tapping With a Pitch That Differs From That of the Screw, Which Decreases Screw Pullout Force.

    Science.gov (United States)

    Bohl, Daniel D; Basques, Bryce A; Golinvaux, Nicholas S; Toy, Jason O; Matheis, Erika A; Bucklen, Brandon S; Grauer, Jonathan N

    2015-06-15

    Survey of spine surgeons and biomechanical comparison of screw pullout forces. To investigate what may be a suboptimal practice regularly occurring in spine surgery. In order for a tap to function in its intended manner, the pitch of the tap should be the same as the pitch of the screw. Undertapping has been shown to increase the pullout force of pedicle screws compared with line-to-line tapping. However, given the way current commercial lumbar pedicle screw systems are designed, undertapping may result in a tap being used that has a different pitch from that of the screw (incongruent pitch). A survey asked participants questions to estimate the proportion of cases each participant performed in the prior year using various hole preparation techniques. Participant responses were interpreted in the context of manufacturing specifications of specific instrumentation systems. Screw pullout forces were compared between undertapping with incongruent pitch and undertapping with congruent pitch using 0.16 g/cm polyurethane foam block and 6.5-mm screws. Of the 3679 cases in which participants reported tapping, participants reported line-to-line tapping in 209 cases (5%), undertapping with incongruent pitch in 1156 cases (32%), and undertapping with congruent pitch in 2314 cases (63%). The mean pullout force for undertapping with incongruent pitch was 56 N (8%) less than the mean pullout force for undertapping with congruent pitch. This is equivalent to 13 lb. This study estimates that for about 1 out of every 3 surgical cases with tapping of lumbar pedicle screws in the United States, hole preparation is being performed by undertapping with incongruent pitch. This study also shows that undertapping with incongruent pitch results in a decrease in pullout force by 8% compared with undertapping with congruent pitch. Steps should be taken to correct this suboptimal practice. 3.

  2. The Geometry Conference

    CERN Document Server

    Bárány, Imre; Vilcu, Costin

    2016-01-01

    This volume presents easy-to-understand yet surprising properties obtained using topological, geometric and graph theoretic tools in the areas covered by the Geometry Conference that took place in Mulhouse, France from September 7–11, 2014 in honour of Tudor Zamfirescu on the occasion of his 70th anniversary. The contributions address subjects in convexity and discrete geometry, in distance geometry or with geometrical flavor in combinatorics, graph theory or non-linear analysis. Written by top experts, these papers highlight the close connections between these fields, as well as ties to other domains of geometry and their reciprocal influence. They offer an overview on recent developments in geometry and its border with discrete mathematics, and provide answers to several open questions. The volume addresses a large audience in mathematics, including researchers and graduate students interested in geometry and geometrical problems.

  3. Safety and surgical techniques of C1 lateral mass screws

    International Nuclear Information System (INIS)

    Kubo, Shinichiro; Kuroki, Hiroshi; Hanado, Shoji; Hamanaka, Hideaki; Inomata, Naoki; Kuroki, Shuji; Chosa, Etsuo

    2010-01-01

    The objectives of this study were to evaluate the proper insertion techniques of C1 lateral mass screws. Eighteen consecutive patients were examined after upper cervical fusion using twenty-nine C1 lateral mass screws. Screws were placed by three different techniques; Goel's technique (4), Tan's technique (20), Notching technique (5). Pre and post-operative CT scans with multiplanar reconstruction were used to detect cortical breaches and direction of screws. No transverse foramen and vertebral groove violation was found in CT scans. Three had breached superior articular facet of the atlas. However, the range of motion (R.O.M) of atlanto-occipital joints had not changed postoperatively. Theses screws were inserted with Tan's technique and two of three were directed medially. It is feasible to safely insert C1 lateral mass screws when correct insertion point and direction are considered preoperatively. However, care should be taken because screws can violate the atlanto-occipital joint especially with Tan's technique. (author)

  4. Experiments on screw-pinch plasmas with elongated cross section

    International Nuclear Information System (INIS)

    Lassing, H.W.

    1989-01-01

    In this thesis experiments are described carried out with SPICA II, a toroidal screw-pinch plasma device. this device is the last one in a series of plasma machines of the toroidal screw-pinch differing from its predecessor in its race-track shaped section. In devices of the type toroidal screw-pinch stable confinement is possible of plasmas with larger β values than in a tokamak discharge. In a pinch the plasma is screwed up, during the formation, in such a way that in a relatively small volume a plasma is formated with a high pressure. During the screwing up the plasma is heated by shock heating as well as adiabatic compression. With the modified snowplow model the density and temperature after the formation can be calculated, starting from the initial conditions. When all ions arrive into the plasma column, the density in the column is determined by the volume compression. First purpose of the experiments was to find a stable discharge. Subsequently discharges have been made with a high as possible β in order to investigate at which maximum β it is possible to confine screw-pinch plasmas stably. When these had been found, the nature and importance could be investigated of the processes following which the screw-pinch plasma looses its energy. (author), 75 res.; 95 figs.; 8 tabs

  5. Economics of water injected air screw compressor systems

    Science.gov (United States)

    Venu Madhav, K.; Kovačević, A.

    2015-08-01

    There is a growing need for compressed air free of entrained oil to be used in industry. In many cases it can be supplied by oil flooded screw compressors with multi stage filtration systems, or by oil free screw compressors. However, if water injected screw compressors can be made to operate reliably, they could be more efficient and therefore cheaper to operate. Unfortunately, to date, such machines have proved to be insufficiently reliable and not cost effective. This paper describes an investigation carried out to determine the current limitations of water injected screw compressor systems and how these could be overcome in the 15-315 kW power range and delivery pressures of 6-10 bar. Modern rotor profiles and approach to sealing and cooling allow reasonably inexpensive air end design. The prototype of the water injected screw compressor air system was built and tested for performance and reliability. The water injected compressor system was compared with the oil injected and oil free compressor systems of the equivalent size including the economic analysis based on the lifecycle costs. Based on the obtained results, it was concluded that water injected screw compressor systems could be designed to deliver clean air free of oil contamination with a better user value proposition than the oil injected or oil free screw compressor systems over the considered range of operations.

  6. Positioning of pedicle screws in adolescent idiopathic scoliosis using electromyography

    Directory of Open Access Journals (Sweden)

    Bruno Moreira Gavassi

    2015-06-01

    Full Text Available OBJECTIVE: To analyze the occurrence of poor positioning of pedicle screws inserted with the aid of intraoperative electromyographic stimulation in the treatment of Adolescent Idiopathic Scoliosis (AIS.METHODS: This is a prospective observational study including all patients undergoing surgical treatment for AIS, between March and December 2013 at a single institution. All procedures were monitored by electromyography of the inserted pedicle screws. The position of the screws was evaluated by assessment of postoperative CT and classified according to the specific AIS classification system.RESULTS: Sixteen patients were included in the study, totalizing 281 instrumented pedicles (17.5 per patient. No patient had any neurological deficit or complaint after surgery. In the axial plane, 195 screws were found in ideal position (69.4% while in the sagittal plane, 226 screws were found in ideal position (80.4%. Considering both the axial and the sagittal planes, it was observed that 59.1% (166/281 of the screws did not violate any cortical wall.CONCLUSION: The use of pedicle screws proved to be a safe technique without causing neurological damage in AIS surgeries, even with the occurrence of poor positioning of some implants.

  7. Algorithms in Algebraic Geometry

    CERN Document Server

    Dickenstein, Alicia; Sommese, Andrew J

    2008-01-01

    In the last decade, there has been a burgeoning of activity in the design and implementation of algorithms for algebraic geometric computation. Some of these algorithms were originally designed for abstract algebraic geometry, but now are of interest for use in applications and some of these algorithms were originally designed for applications, but now are of interest for use in abstract algebraic geometry. The workshop on Algorithms in Algebraic Geometry that was held in the framework of the IMA Annual Program Year in Applications of Algebraic Geometry by the Institute for Mathematics and Its

  8. Revolutions of Geometry

    CERN Document Server

    O'Leary, Michael

    2010-01-01

    Guides readers through the development of geometry and basic proof writing using a historical approach to the topic. In an effort to fully appreciate the logic and structure of geometric proofs, Revolutions of Geometry places proofs into the context of geometry's history, helping readers to understand that proof writing is crucial to the job of a mathematician. Written for students and educators of mathematics alike, the book guides readers through the rich history and influential works, from ancient times to the present, behind the development of geometry. As a result, readers are successfull

  9. Fundamental concepts of geometry

    CERN Document Server

    Meserve, Bruce E

    1983-01-01

    Demonstrates relationships between different types of geometry. Provides excellent overview of the foundations and historical evolution of geometrical concepts. Exercises (no solutions). Includes 98 illustrations.

  10. Developments in special geometry

    International Nuclear Information System (INIS)

    Mohaupt, Thomas; Vaughan, Owen

    2012-01-01

    We review the special geometry of N = 2 supersymmetric vector and hypermultiplets with emphasis on recent developments and applications. A new formulation of the local c-map based on the Hesse potential and special real coordinates is presented. Other recent developments include the Euclidean version of special geometry, and generalizations of special geometry to non-supersymmetric theories. As applications we discuss the proof that the local r-map and c-map preserve geodesic completeness, and the construction of four- and five-dimensional static solutions through dimensional reduction over time. The shared features of the real, complex and quaternionic version of special geometry are stressed throughout.

  11. A power recirculating test rig for ball screw endurance tests

    Directory of Open Access Journals (Sweden)

    Giberti Hermes

    2016-01-01

    Full Text Available A conceptual design of an innovative test rig for endurance tests of ball screws is presented in this paper. The test rig layout is based on the power recirculating principle and it also allows to overtake the main critical issues of the ball screw endurance tests. Among these there are the high power required to make the test, the lengthy duration of the same and the high loads between the screw and the frame that holds it. The article describes the test rig designed scheme, the kinematic expedients to be adopted in order to obtain the required performance and functionality and the sizing procedure to choose the actuation system.

  12. Design of platform for removing screws from LCD display shields

    Science.gov (United States)

    Tu, Zimei; Qin, Qin; Dou, Jianfang; Zhu, Dongdong

    2017-11-01

    Removing the screws on the sides of a shield is a necessary process in disassembling a computer LCD display. To solve this issue, a platform has been designed for removing the screws on display shields. This platform uses virtual instrument technology with LabVIEW as the development environment to design the mechanical structure with the technologies of motion control, human-computer interaction and target recognition. This platform removes the screws from the sides of the shield of an LCD display mechanically thus to guarantee follow-up separation and recycle.

  13. Noninvasive method for retrieval of broken dental implant abutment screw

    Directory of Open Access Journals (Sweden)

    Jagadish Reddy Gooty

    2014-01-01

    Full Text Available Dental implants made of titanium for replacement of missing teeth are widely used because of ease of technical procedure and high success rate, but are not free of complications and may fail. Fracturing of the prosthetic screw continues to be a problem in restorative practice and great challenge to remove the fractured screw conservatively. This case report describes and demonstrates the technique of using an ultrasonic scaler in the removal of the fracture screw fragment as a noninvasive method without damaging the hex of implants.

  14. Grid deformation strategies for CFD analysis of screw compressors

    OpenAIRE

    Rane, S.; Kovacevic, A.; Stosic, N.; Kethidi, M.

    2013-01-01

    Customized grid generation of twin screw machines for CFD analysis is widely used by the refrigeration and air-conditioning industry today, but is currently not suitable for topologies such as those of single screw, variable pitch or tri screw rotors. This paper investigates a technique called key-frame re-meshing that supplies pre-generated unstructured grids to the CFD solver at different time steps. To evaluate its accuracy, the results of an isentropic compression-expansion process in a r...

  15. Analysis of Material Flow in Screw Extrusion of Aluminum

    International Nuclear Information System (INIS)

    Haugen, Bjoern; Oernskar, Magnus; Welo, Torgeir; Wideroee, Fredrik

    2010-01-01

    Screw extrusion of aluminum is a new process for production of aluminum profiles. The commercial potential could be large. Little experimental and numerical work has been done with respect to this process.The material flow of hot aluminum in a screw extruder has been analyzed using finite element formulations for the non-Newtonian Navier-Stokes equations. Aluminum material properties are modeled using the Zener-Holloman material model. Effects of stick-slip conditions are investigated with respect to pressure build up and mixing quality of the extrusion process.The numerical results are compared with physical experiments using an experimental screw extruder.

  16. Comparison of open reduction versus minimally invasive surgical approaches on screw position in canine sacroiliac lag-screw fixation.

    Science.gov (United States)

    Déjardin, Loïc M; Marturello, Danielle M; Guiot, Laurent P; Guillou, Reunan P; DeCamp, Charles E

    2016-07-19

    To compare accuracy and consistency of sacral screw placement in canine pelves treated for sacroiliac luxation with open reduction and internal fixation (ORIF) or minimally invasive osteosynthesis (MIO) techniques. Unilateral sacroiliac luxations created experimentally in canine cadavers were stabilized with an iliosacral lag screw applied via ORIF or MIO techniques (n = 10/group). Dorsoventral and craniocaudal screw angles were measured using computed tomography multiplanar reconstructions in transverse and dorsal planes, respectively. Ratios between pilot hole length and sacral width (PL/SW-R) were obtained. Data between groups were compared statistically (p sacroiliac luxations provides more accurate and consistent sacral screw placement than ORIF. With proper techniques, iatrogenic neurological damage can be avoided with both techniques. The PL /SW-R, which relates to safe screw fixation, also demonstrates that screw penetration of at least 60% of the sacral width is achievable regardless of surgical approach. These findings, along with the limited dissection needed for accurate sacral screw placement, suggest that MIO of sacroiliac luxations is a valid alternative to ORIF.

  17. Measurement of Tip Apex Distance and Migration of Lag Screws and Novel Blade Screw Used for the Fixation of Intertrochanteric Fractures.

    Directory of Open Access Journals (Sweden)

    Jesse Chieh-Szu Yang

    Full Text Available Fixation with a dynamic hip screw (DHS is one of the most common methods for stabilizing intertrochanteric fractures, except for unstable and reverse oblique fracture types. However, failure is often observed in osteoporotic patients whereby the lag screw effectively 'cuts out' through the weak bone. Novel anti-migration blades have been developed to be used in combination with a lag screw ('Blade Screw' to improve the fixation strength in osteoporotic intertrochanteric fractures. An in-vitro biomechanical study and a retrospective clinical study were performed to evaluate lag screw migration when using the novel Blade Screw and a traditional threaded DHS. The biomechanical study showed both the Blade Screw and DHS displayed excessive migration (≥10 mm before reaching 20,000 loading cycles in mild osteoporotic bone, but overall migration of the Blade Screw was significantly less (p ≤ 0.03. Among the patients implanted with a Blade Screw in the clinical study, there was no significant variation in screw migration at 3-months follow-up (P = 0.12. However, the patient's implanted with a DHS did display significantly greater migration (P<0.001 than those implanted with the Blade Screw. In conclusion, the Blade Screw stabilizes the bone fragments during dynamic loading so as to provide significantly greater resistance to screw migration in patients with mild osteoporosis.

  18. Comparison of effectiveness between cork-screw and peg-screw electrodes for transcranial motor evoked potential monitoring using the finite element method.

    Science.gov (United States)

    Tomio, Ryosuke; Akiyama, Takenori; Ohira, Takayuki; Yoshida, Kazunari

    2016-01-01

    Intraoperative monitoring of motor evoked potentials by transcranial electric stimulation is popular in neurosurgery for monitoring motor function preservation. Some authors have reported that the peg-screw electrodes screwed into the skull can more effectively conduct current to the brain compared to subdermal cork-screw electrodes screwed into the skin. The aim of this study was to investigate the influence of electrode design on transcranial motor evoked potential monitoring. We estimated differences in effectiveness between the cork-screw electrode, peg-screw electrode, and cortical electrode to produce electric fields in the brain. We used the finite element method to visualize electric fields in the brain generated by transcranial electric stimulation using realistic three-dimensional head models developed from T1-weighted images. Surfaces from five layers of the head were separated as accurately as possible. We created the "cork-screws model," "1 peg-screw model," "peg-screws model," and "cortical electrode model". Electric fields in the brain radially diffused from the brain surface at a maximum just below the electrodes in coronal sections. The coronal sections and surface views of the brain showed higher electric field distributions under the peg-screw compared to the cork-screw. An extremely high electric field was observed under cortical electrodes. Our main finding was that the intensity of electric fields in the brain are higher in the peg-screw model than the cork-screw model.

  19. AUTOGENIC THERAPY IN TENSION HEADACHE

    Science.gov (United States)

    Amruthraj, Brunda; Mishra, H.; Kumaraiah, V.

    1987-01-01

    SUMMARY Ten subjects diagnosed as Psychalgia were taken for study. A multiple baseline design was adapted and clients were subjected to 30 sessions of autogenic training. They were assessed using physiological (EMG and thermal change) and behavioural measures (Visual analogue scale and behavioural symptom checklist). Findings revealed autogenic therapy to be effective in reducing tension headache. PMID:21927245

  20. Tensions of Corporate Social Responsibility

    DEFF Research Database (Denmark)

    Strand, Robert

    , and formally rational tools like key performance indicators (KPIs) can be developed and employed in service of the selected substantively rational ends. I show how these KPIs can serve to highlight tensions between substantively rational ends. As such, I argue the CSR bureaucracy can create a space...

  1. AUTOGENIC THERAPY IN TENSION HEADACHE

    OpenAIRE

    Amruthraj, Brunda; Mishra, H.; Kumaraiah, V.

    1987-01-01

    SUMMARY Ten subjects diagnosed as Psychalgia were taken for study. A multiple baseline design was adapted and clients were subjected to 30 sessions of autogenic training. They were assessed using physiological (EMG and thermal change) and behavioural measures (Visual analogue scale and behavioural symptom checklist). Findings revealed autogenic therapy to be effective in reducing tension headache.

  2. Geometry of multihadron production

    Energy Technology Data Exchange (ETDEWEB)

    Bjorken, J.D.

    1994-10-01

    This summary talk only reviews a small sample of topics featured at this symposium: Introduction; The Geometry and Geography of Phase space; Space-Time Geometry and HBT; Multiplicities, Intermittency, Correlations; Disoriented Chiral Condensate; Deep Inelastic Scattering at HERA; and Other Contributions.

  3. Designs and finite geometries

    CERN Document Server

    1996-01-01

    Designs and Finite Geometries brings together in one place important contributions and up-to-date research results in this important area of mathematics. Designs and Finite Geometries serves as an excellent reference, providing insight into some of the most important research issues in the field.

  4. Geometry of multihadron production

    International Nuclear Information System (INIS)

    Bjorken, J.D.

    1994-10-01

    This summary talk only reviews a small sample of topics featured at this symposium: Introduction; The Geometry and Geography of Phase space; Space-Time Geometry and HBT; Multiplicities, Intermittency, Correlations; Disoriented Chiral Condensate; Deep Inelastic Scattering at HERA; and Other Contributions

  5. The Beauty of Geometry

    Science.gov (United States)

    Morris, Barbara H.

    2004-01-01

    This article describes a geometry project that used the beauty of stained-glass-window designs to teach middle school students about geometric figures and concepts. Three honors prealgebra teachers and a middle school mathematics gifted intervention specialist created a geometry project that covered the curriculum and also assessed students'…

  6. Correction Capability in the 3 Anatomic Planes of Different Pedicle Screw Designs in Scoliosis Instrumentation.

    Science.gov (United States)

    Wang, Xiaoyu; Aubin, Carl-Eric; Coleman, John; Rawlinson, Jeremy

    2017-05-01

    Computer simulations to compare the correction capabilities of different pedicle screws in adolescent idiopathic scoliosis (AIS) instrumentations. To compare the correction and resulting bone-screw forces associated with different pedicle screws in scoliosis instrumentations. Pedicle screw fixation is widely used in surgical instrumentation for spinal deformity treatment. Screw design, correction philosophies, and surgical techniques are constantly evolving to achieve better control of the vertebrae and correction of the spinal deformity. Yet, there remains a lack of biomechanical studies that quantify the effects and advantages of different screw designs in terms of correction kinematics. The correction capabilities of fixed-angle, multiaxial, uniaxial, and saddle axial screws were kinematically analyzed, simulated, and compared. These simulations were based on the screw patterns and correction techniques proposed by 2 experienced surgeons for 2 AIS cases. Additional instrumentations were assessed to compare the correction and resulting bone-screw forces associated with each type of screw. The fixed-angle, uniaxial and saddle axial screws had similar kinematic behavior and performed better than multiaxial screws in the coronal and transverse planes (8% and 30% greater simulated corrections, respectively). Uniaxial and multiaxial screws were less effective than fixed-angle and saddle axial screws in transmitting compression/distraction to the anterior spine because of their sagittal plane mobility between the screw head and shank. Only the saddle axial screws allow vertebra angle in the sagittal plane to be independently adjusted. Pedicle screws of different designs performed differently for deformity corrections or for compensating screw placement variations in different anatomic planes. For a given AIS case, screw types should be determined based on the particular instrumentation objectives, the deformity's stiffness and characteristics so as to make the best of

  7. Effects on Subtalar Joint Stress Distribution After Cannulated Screw Insertion at Different Positions and Directions.

    Science.gov (United States)

    Yuan, Cheng-song; Chen, Wan; Chen, Chen; Yang, Guang-hua; Hu, Chao; Tang, Kang-lai

    2015-01-01

    We investigated the effects on subtalar joint stress distribution after cannulated screw insertion at different positions and directions. After establishing a 3-dimensional geometric model of a normal subtalar joint, we analyzed the most ideal cannulated screw insertion position and approach for subtalar joint stress distribution and compared the differences in loading stress, antirotary strength, and anti-inversion/eversion strength among lateral-medial antiparallel screw insertion, traditional screw insertion, and ideal cannulated screw insertion. The screw insertion approach allowing the most uniform subtalar joint loading stress distribution was lateral screw insertion near the border of the talar neck plus medial screw insertion close to the ankle joint. For stress distribution uniformity, antirotary strength, and anti-inversion/eversion strength, lateral-medial antiparallel screw insertion was superior to traditional double-screw insertion. Compared with ideal cannulated screw insertion, slightly poorer stress distribution uniformity and better antirotary strength and anti-inversion/eversion strength were observed for lateral-medial antiparallel screw insertion. Traditional single-screw insertion was better than double-screw insertion for stress distribution uniformity but worse for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion was slightly worse for stress distribution uniformity than was ideal cannulated screw insertion but superior to traditional screw insertion. It was better than both ideal cannulated screw insertion and traditional screw insertion for anti-rotary strength and anti-inversion/eversion strength. Lateral-medial antiparallel screw insertion is an approach with simple localization, convenient operation, and good safety. Copyright © 2015 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  8. A Reduced Order Model of Force Displacement Curves for the Failure of Mechanical Bolts in Tension.

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Keegan J. [Univ. of Illinois, Urbana-Champaign, IL (United States); Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brake, Matthew Robert [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-12-01

    Assembled mechanical systems often contain a large number of bolted connections. These bolted connections (joints) are integral aspects of the load path for structural dynamics, and, consequently, are paramount for calculating a structure's stiffness and energy dissipation prop- erties. However, analysts have not found the optimal method to model appropriately these bolted joints. The complexity of the screw geometry causes issues when generating a mesh of the model. This report will explore different approaches to model a screw-substrate connec- tion. Model parameters such as mesh continuity, node alignment, wedge angles, and thread to body element size ratios are examined. The results of this study will give analysts a better understanding of the influences of these parameters and will aide in finding the optimal method to model bolted connections.

  9. A Lorentzian quantum geometry

    Energy Technology Data Exchange (ETDEWEB)

    Grotz, Andreas

    2011-10-07

    In this thesis, a formulation of a Lorentzian quantum geometry based on the framework of causal fermion systems is proposed. After giving the general definition of causal fermion systems, we deduce space-time as a topological space with an underlying causal structure. Restricting attention to systems of spin dimension two, we derive the objects of our quantum geometry: the spin space, the tangent space endowed with a Lorentzian metric, connection and curvature. In order to get the correspondence to classical differential geometry, we construct examples of causal fermion systems by regularizing Dirac sea configurations in Minkowski space and on a globally hyperbolic Lorentzian manifold. When removing the regularization, the objects of our quantum geometry reduce to the common objects of spin geometry on Lorentzian manifolds, up to higher order curvature corrections.

  10. Methods of information geometry

    CERN Document Server

    Amari, Shun-Ichi

    2000-01-01

    Information geometry provides the mathematical sciences with a new framework of analysis. It has emerged from the investigation of the natural differential geometric structure on manifolds of probability distributions, which consists of a Riemannian metric defined by the Fisher information and a one-parameter family of affine connections called the \\alpha-connections. The duality between the \\alpha-connection and the (-\\alpha)-connection together with the metric play an essential role in this geometry. This kind of duality, having emerged from manifolds of probability distributions, is ubiquitous, appearing in a variety of problems which might have no explicit relation to probability theory. Through the duality, it is possible to analyze various fundamental problems in a unified perspective. The first half of this book is devoted to a comprehensive introduction to the mathematical foundation of information geometry, including preliminaries from differential geometry, the geometry of manifolds or probability d...

  11. A Lorentzian quantum geometry

    International Nuclear Information System (INIS)

    Grotz, Andreas

    2011-01-01

    In this thesis, a formulation of a Lorentzian quantum geometry based on the framework of causal fermion systems is proposed. After giving the general definition of causal fermion systems, we deduce space-time as a topological space with an underlying causal structure. Restricting attention to systems of spin dimension two, we derive the objects of our quantum geometry: the spin space, the tangent space endowed with a Lorentzian metric, connection and curvature. In order to get the correspondence to classical differential geometry, we construct examples of causal fermion systems by regularizing Dirac sea configurations in Minkowski space and on a globally hyperbolic Lorentzian manifold. When removing the regularization, the objects of our quantum geometry reduce to the common objects of spin geometry on Lorentzian manifolds, up to higher order curvature corrections.

  12. Lumbar pedicle screw placement: Using only AP plane imaging

    Directory of Open Access Journals (Sweden)

    Anil Sethi

    2012-01-01

    Conclusion: Placement of pedicle screws under fluoroscopic guidance using AP plane imaging alone with tactile guidance is safe, fast, and reliable. However, a good understanding of the radiographic landmarks is a prerequisite.

  13. Hollow Mill for Extraction of Stripped Titanium Screws: An Easy ...

    African Journals Online (AJOL)

    countries. The known alternative in such condition is ... Key words: Hollow mill, stripped screws, titanium locked plates ... used a locally manufactured stainless steel hollow mill, ... head ‑ plate hole” assembly as a mono‑block single unit. In.

  14. scaphoid dimensions and appropriate screw sizes in a kenyan

    African Journals Online (AJOL)

    There were no side to side differences in the total length or the distal pole. Conclusion: Scaphoid screws .... gender differences in prehension may contribute to .... differences between males and females. Sports. Med Arthroscopy Review. 2002 ...

  15. Biomechanical analysis of titanium fixation plates and screws in ...

    African Journals Online (AJOL)

    hole Y plates with monocortical screws. 150 N incisal occlusal loads were simulated on the models. The commercial ANSYS software was utilized to calculate the Von Mises stresses on fixative appliances. Results: The highest Von Mises stress ...

  16. Effect of twin-screw extrusion parameters on mechanical hardness ...

    Indian Academy of Sciences (India)

    A 2-level–4-factor factorial experimental design was used to investigate the influ- ... ture content, screw speed and temperature are found to influence, while feed rate ... of the food product that can be adequately evaluated by the consumer.

  17. Intermaxillary Fixation Screw Morbidity in Treatment of Mandibular Fractures

    DEFF Research Database (Denmark)

    Florescu, Vlad-Andrei; Kofod, Thomas; Pinholt, Else Marie

    2016-01-01

    Purpose The aim of the present retrospective study was to investigate the morbidity of screws used for intermaxillary fixation (IMF) in the treatment of mandibular fractures. A review of the published data was also performed for a comparison of outcomes. Our hypothesis was that the use of screws...... for IMF of mandibular fractures would result in minimal morbidity. Materials and Methods Patients treated for mandibular fractures from 2007 to 2013, using screws for IMF, using the international diagnosis code for mandibular fracture, DS026, were anonymously selected (Department of Oral and Maxillofacial...... Surgery, Rigshospitalet, University Hospital of Copenhagen, Copenhagen, Denmark). The fracture type, radiographic findings, treatment modality, screw type and number, and root damage were recorded. For the outcome comparison, a review of the published data regarding iatrogenic dental root damage caused...

  18. Kinematic analysis of parallel manipulators by algebraic screw theory

    CERN Document Server

    Gallardo-Alvarado, Jaime

    2016-01-01

    This book reviews the fundamentals of screw theory concerned with velocity analysis of rigid-bodies, confirmed with detailed and explicit proofs. The author additionally investigates acceleration, jerk, and hyper-jerk analyses of rigid-bodies following the trend of the velocity analysis. With the material provided in this book, readers can extend the theory of screws into the kinematics of optional order of rigid-bodies. Illustrative examples and exercises to reinforce learning are provided. Of particular note, the kinematics of emblematic parallel manipulators, such as the Delta robot as well as the original Gough and Stewart platforms are revisited applying, in addition to the theory of screws, new methods devoted to simplify the corresponding forward-displacement analysis, a challenging task for most parallel manipulators. Stands as the only book devoted to the acceleration, jerk and hyper-jerk (snap) analyses of rigid-body by means of screw theory; Provides new strategies to simplify the forward kinematic...

  19. Probing and Tapping: Are We Inserting Pedicle Screws Correctly?

    Science.gov (United States)

    Prasad, Vishal; Mesfin, Addisu; Lee, Robert; Reigrut, Julie; Schmidt, John

    2016-11-01

    Although there are a significant number of research publications on the topic of bone morphology and the strength of bone, the clinical significance of a failed pedicle screw is often revision surgery and the potential for further postoperative complications; especially in elderly patients with osteoporotic bone. The purpose of this report is to quantify the mechanical strength of the foam-screw interface by assessing probe/pilot hole diameter and tap sizes using statistically relevant sample sizes under highly controlled test conditions. The study consisted of two experiments and used up to three different densities of reference-grade polyurethane foam (ASTM 1839), including 0.16, 0.24, and 0.32 g/cm 3 . All screws and rods were provided by K2M Inc. and screws were inserted to a depth of 25 mm. A series of pilot holes, 1.5, 2.2, 2.7, 3.2, 3.7, 4.2, 5.0, and 6.0 mm in diameter were drilled through the entire depth of the material. A 6.5 × 45-mm pedicle screw was inserted and axially pulled from the material (n = 720). A 3.0-mm pilot hole was drilled and tapped with: no tap, 3.5-, 4.5-, 5.5-, and 6.5-mm taps. A 6.5 × 45-mm pedicle screw was inserted and axially pulled from the material (n = 300). The size of the probe/pilot hole had a nonlinear, parabolic effect on pullout strength. This shape suggests an optimum-sized probe hole for a given size pedicle screw. Too large or too small of a probe hole causes a rapid falloff in pullout strength. The tap data demonstrated that not tapping and undertapping by two or three sizes did not significantly alter the pullout strength of the screws. The data showed an exponential falloff of pullout strength when as tap size increased to the diameter of the screw. In the current study, the data show that an ideal pilot hole size half the diameter of the screw is a starting point. Also, that if tapping was necessary, to use a tap two sizes smaller than the screw being implanted. A similar optimum pilot hole or tap size may be

  20. Comparative effect of implant-abutment connections, abutment angulations, and screw lengths on preloaded abutment screw using three-dimensional finite element analysis: An in vitro study

    Directory of Open Access Journals (Sweden)

    Krishna Chaitanya Kanneganti

    2018-01-01

    Conclusions: The present study suggests selecting appropriate implant-abutment connection based on the abutment angulation, as well as preferring long screws with more number of threads for effective preload retention by the screws.

  1. Geometry on the space of geometries

    International Nuclear Information System (INIS)

    Christodoulakis, T.; Zanelli, J.

    1988-06-01

    We discuss the geometric structure of the configuration space of pure gravity. This is an infinite dimensional manifold, M, where each point represents one spatial geometry g ij (x). The metric on M is dictated by geometrodynamics, and from it, the Christoffel symbols and Riemann tensor can be found. A ''free geometry'' tracing a geodesic on the manifold describes the time evolution of space in the strong gravity limit. In a regularization previously introduced by the authors, it is found that M does not have the same dimensionality, D, everywhere, and that D is not a scalar, although it is covariantly constant. In this regularization, it is seen that the path integral measure can be absorbed in a renormalization of the cosmological constant. (author). 19 refs

  2. Adjacent-segment disease after thoracic pedicle screw fixation.

    Science.gov (United States)

    Agarwal, Nitin; Heary, Robert F; Agarwal, Prateek

    2018-03-01

    OBJECTIVE Pedicle screw fixation is a technique widely used to treat conditions ranging from spine deformity to fracture stabilization. Pedicle screws have been used traditionally in the lumbar spine; however, they are now being used with increasing frequency in the thoracic spine as a more favorable alternative to hooks, wires, or cables. Although safety concerns, such as the incidence of adjacent-segment disease (ASD) after cervical and lumbar fusions, have been reported, such issues in the thoracic spine have yet to be addressed thoroughly. Here, the authors review the literature on ASD after thoracic pedicle screw fixation and report their own experience specifically involving the use of pedicle screws in the thoracic spine. METHODS Select references from online databases, such as PubMed (provided by the US National Library of Medicine at the National Institutes of Health), were used to survey the literature concerning ASD after thoracic pedicle screw fixation. To include the authors' experience at Rutgers New Jersey Medical School, a retrospective review of a prospectively maintained database was performed to determine the incidence of complications over a 13-year period in 123 consecutive adult patients who underwent thoracic pedicle screw fixation. Children, pregnant or lactating women, and prisoners were excluded from the review. By comparing preoperative and postoperative radiographic images, the occurrence of thoracic ASD and disease within the surgical construct was determined. RESULTS Definitive radiographic fusion was detected in 115 (93.5%) patients. Seven incidences of instrumentation failure and 8 lucencies surrounding the screws were observed. One patient was observed to have ASD of the thoracic spine. The mean follow-up duration was 50 months. CONCLUSIONS This long-term radiographic evaluation revealed the use of pedicle screws for thoracic fixation to be an effective stabilization modality. In particular, ASD seems to be less of a problem in the

  3. Pull out Strength of Dual Outer Diameter Pedicle Screws Compared to Uncemented and Cemented Standard Pedicle Screws: A Biomechanical in vitro Study.

    Science.gov (United States)

    Lorenz, Andrea; Leichtle, Carmen I; Frantz, Sandra; Bumann, Marte; Tsiflikas, Ilias; Shiozawa, Thomas; Leichtle, Ulf G

    2017-05-01

    To analyze the potential of the dual outer diameter screw and systematically evaluate the pull-out force of the dual outer diameter screw compared to the uncemented and cemented standard pedicle screws with special regard to the pedicle diameter and the vertebra level. Sixty vertebrae of five human spines (T 6 -L 5 ) were sorted into three study groups for pairwise comparison of the uncemented dual outer diameter screw, the uncemented standard screw, and the cemented standard screw, and randomized with respect to bone mineral density (BMD) and vertebra level. The vertebrae were instrumented, insertion torque was determined, and pull-out testing was performed using a material testing machine. Failure load was evaluated in pairwise comparison within each study group. The screw-to-pedicle diameter ratio was determined and the uncemented dual outer diameter and standard screws were compared for different ratios as well as vertebra levels. Significantly increased pull-out forces were measured for the cemented standard screw compared to the uncemented standard screw (+689 N, P dual outer diameter screw (+403 N, P dual outer diameter screw to the uncemented standard screw in the total study group, a distinct but not significant increase was measured (+149 N, P = 0.114). Further analysis of these two screws, however, revealed a significant increase of pull-out force for the dual outer diameter screw in the lumbar region (+247 N, P = 0.040), as well as for a screw-to-pedicle diameter ratio between 0.6 and 1 (+ 488 N, P = 0.028). For clinical application, cement augmentation remains the gold standard for increasing screw stability. According to our results, the use of a dual outer diameter screw is an interesting option to increase screw stability in the lumbar region without cement augmentation. For the thoracic region, however, the screw-to-pedicle diameter should be checked and attention should be paid to screw cut out, if the dual outer diameter screw is considered.

  4. Determination of wall tension in cerebral artery aneurysms by numerical simulation

    DEFF Research Database (Denmark)

    Isaksen, J.G.; Bazilevs, Y.; Kvamsdal, T.

    2008-01-01

    a computational model for simulation of fluid-structure interaction in cerebral aneurysms based on patient specific lesion geometry, with special emphasis on wall tension. METHODS: An advanced isogeometric fluid-structure analysis model incorporating flexible aneurysm wall based on patient specific computed...

  5. Modeling and Analyzing the Slipping of the Ball Screw

    Directory of Open Access Journals (Sweden)

    Nannan Xu

    Full Text Available AbstractThis paper aims to set up the ball systematic slipping model and analyze the slipping characteristics caused by different factors for a ball screw operating at high speeds. To investigate the ball screw slipping mechanism, transformed coordinate system should be established firstly. Then it is used to set up mathematical modeling for the ball slipping caused by the three main reasons and the speed of slipping can be calculated. Later, the influence of the contact angle, helix angle and screw diameter for ball screw slipping will be analyzed according to the ball slipping model and slipping speeds equation and the slipping analysis will be obtained. Finally, curve of slipping analysis and that of mechanical efficiency of the ball screw analysis by Lin are compared, which will indirectly verify the correctness of the slipping model. The slipping model and the curve of slipping analysis established in this paper will provide theory basis for reducing slipping and improving the mechanical efficiency of a ball screw operating at high speeds.

  6. Stress corrosion cracking lifetime prediction of spring screw

    International Nuclear Information System (INIS)

    Koh, S. K.; Ryu, C. H.

    2004-01-01

    A lifetime prediction of holddown spring screw in nuclear fuel assembly was performed using fracture mechanics approach. The spring screw was designed such that it was capable of sustaining the loads imposed by the initial tensile preload and operational loads. In order to investigate the cause of failure and to predict the stress corrosion cracking life of the screw, a stress analysis of the top nozzle spring assembly was done using finite element analysis. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Normalized stress intensity factors for PWSCC life prediction was proposed. Primary water stress corrosion cracking life of the Inconel 600 screw was predicted by using integration of the Scott model and resulted in 1.78 years, which was fairly close to the actual service life of the holddown spring screw

  7. Urinary incontinence - tension-free vaginal tape

    Science.gov (United States)

    ... ency/article/007377.htm Urinary incontinence - tension-free vaginal tape To use the sharing features on this page, please enable JavaScript. Placement of tension-free vaginal tape is surgery to help control stress urinary ...

  8. Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae - A cadaveric study

    Directory of Open Access Journals (Sweden)

    Shyam K Saraf

    2013-01-01

    Full Text Available Background: The objective of this cadaveric study was to analyze the effects of iatrogenic pedicle perforations from screw misplacement on the mean pullout strength of lower thoracic and lumbar pedicle screws. We also investigated the effect of bone mineral density (BMD, diameter of pedicle screws, and the region of spine on the pullout strength of pedicle screws. Materials and Methods: Sixty fresh human cadaveric vertebrae (D10-L2 were harvested. Dual-energy X-ray absorptiometry (DEXA scan of vertebrae was done for BMD. Titanium pedicle screws of different diameters (5.2 and 6.2 mm were inserted in the thoracic and lumbar segments after dividing the specimens into three groups: a standard pedicle screw (no cortical perforation; b screw with medial cortical perforation; and c screw with lateral cortical perforation. Finally, pullout load of pedicle screws was recorded using INSTRON Universal Testing Machine. Results: Compared with standard placement, medially misplaced screws had 9.4% greater mean pullout strength and laterally misplaced screws had 47.3% lesser mean pullout strength. The pullout strength of the 6.2 mm pedicle screws was 33% greater than that of the 5.2 mm pedicle screws. The pullout load of pedicle screws in lumbar vertebra was 13.9% greater than that in the thoracic vertebra ( P = 0.105, but it was not statistically significant. There was no significant difference between pullout loads of vertebra with different BMD ( P = 0.901. Conclusion: The mean pullout strength was less with lateral misplaced pedicle screws while medial misplaced pedicle screw had more pullout strength. The pullout load of 6.2 mm screws was greater than that of 5.2 mm pedicle screws. No significant correlation was found between bone mineral densities and the pullout strength of vertebra. Similarly, the pullout load of screw placed in thoracic and lumbar vertebrae was not significantly different.

  9. [Surgical treatment of inferior pole comminuted fractures of patella with new type tension band].

    Science.gov (United States)

    Sun, B; Zhang, Z S; Zhou, F; Tian, Y; Ji, H Q; Guo, Y; Lv, Y; Yang, Z W

    2015-04-18

    To study the effectiveness of inferior pole fracture of patella treating by the new tension band. From Dec. 2011 to Dec. 2013, 21 patients with inferior pole fracture of patella were treated with the new tension band which consisted of cannulated screw, titanium cable and shims. There were 21 patients[10 males, 11 females, the average age was 54 years(21 to 79)],of whom,all were "fell on knees". The average operation time was 89 min (57-197 min),the follow-up visits were done from 7-31 months (average 18 months), the bone healing time was from 8-12 weeks (average 10.5 weeks). The post operation assessment was done by Bostman score, from 20-30 (average 27),10 excellent,and 11 good. No complication occurred. The new tension band is the effective treatment for inferior pole fracture of patella. The internal fixation is reliable, it is simple to operate, and patients can take exercises as early as possible. Therefore, the new tension band has a better clinical value.

  10. Fixation strength of biocomposite wedge interference screw in ACL reconstruction: effect of screw length and tunnel/screw ratio. A controlled laboratory study

    Directory of Open Access Journals (Sweden)

    Herrera Antonio

    2010-06-01

    Full Text Available Abstract Background Primary stability of the graft is essential in anterior cruciate ligament surgery. An optimal method of fixation should be easy to insert and provide great resistance against pull-out forces. A controlled laboratory study was designed to test the primary stability of ACL tendinous grafts in the tibial tunnel. The correlation between resistance to traction forces and the cross-section and length of the screw was studied. Methods The tibial phase of ACL reconstruction was performed in forty porcine tibias using digital flexor tendons of the same animal. An 8 mm tunnel was drilled in each specimen and two looped tendons placed as graft. Specimens were divided in five groups according to the diameter and length of the screw used for fixation. Wedge interference screws were used. Longitudinal traction was applied to the graft with a Servohydraulic Fatigue System. Load and displacement were controlled and analyzed. Results The mean loads to failure for each group were 295,44 N (Group 1; 9 × 23 screw, 564,05 N (Group 2; 9 × 28, 614,95 N (Group 3; 9 × 35, 651,14 N (Group 4; 10 × 28 and 664,99 (Group 5; 10 × 35. No slippage of the graft was observed in groups 3, 4 and 5. There were significant differences in the load to failure among groups (ANOVA/P Conclusions Longer and wider interference screws provide better fixation in tibial ACL graft fixation. Short screws (23 mm do not achieve optimal fixation and should be implanted only with special requirements.

  11. Complex and symplectic geometry

    CERN Document Server

    Medori, Costantino; Tomassini, Adriano

    2017-01-01

    This book arises from the INdAM Meeting "Complex and Symplectic Geometry", which was held in Cortona in June 2016. Several leading specialists, including young researchers, in the field of complex and symplectic geometry, present the state of the art of their research on topics such as the cohomology of complex manifolds; analytic techniques in Kähler and non-Kähler geometry; almost-complex and symplectic structures; special structures on complex manifolds; and deformations of complex objects. The work is intended for researchers in these areas.

  12. Non-Euclidean geometry

    CERN Document Server

    Kulczycki, Stefan

    2008-01-01

    This accessible approach features two varieties of proofs: stereometric and planimetric, as well as elementary proofs that employ only the simplest properties of the plane. A short history of geometry precedes a systematic exposition of the principles of non-Euclidean geometry.Starting with fundamental assumptions, the author examines the theorems of Hjelmslev, mapping a plane into a circle, the angle of parallelism and area of a polygon, regular polygons, straight lines and planes in space, and the horosphere. Further development of the theory covers hyperbolic functions, the geometry of suff

  13. Early tension loss in an anterior cruciate ligament graft. A cadaver study of four tibial fixation devices.

    Science.gov (United States)

    Grover, Dustin M; Howell, Stephen M; Hull, Maury L

    2005-02-01

    The tensile force applied to an anterior cruciate ligament graft determines the maximal anterior translation; however, it is unknown whether the tensile force is transferred to the intra-articular portion of the graft and whether the intra-articular tension and maximal anterior translation are maintained shortly after ligament reconstruction. Ten cadaveric knees were reconstructed with a double-looped tendon graft. The graft was looped through a femoral fixation transducer that measured the resultant force on the proximal end of the graft. A pneumatic cylinder applied a tensile force of 110 N to the graft exiting the tibial tunnel with the knee in full extension. The graft was fixed sequentially with four tibial fixation devices (a spiked metal washer, double staples, a bioabsorbable interference screw, and a WasherLoc). Three cyclic loading treatments designed to conservatively load the graft and its fixation were applied. The combined loss in intra-articular graft tension from friction, insertion of the tibial fixation device, and three cyclic loading treatments was 50% for the spiked washer (p = 0.0004), 100% for the double staples (p < 0.0001), 64% for the interference screw (p = 0.0001), and 56% for the WasherLoc (p < 0.0001). The tension loss caused an increase in the maximal anterior translation from that of the intact knee of 2.0 mm for the spiked washer (p = 0.005), 7.8 mm for the double staples (p < 0.0001), 2.7 mm for the interference screw (p = 0.001), and 2.1 mm for the WasherLoc (p < 0.0001). The tensile force applied to a soft-tissue anterior cruciate ligament graft is not transferred intra-articularly and is not maintained during graft fixation. The loss in tension is caused by friction in the tibial tunnel and wrapping the graft around the shank of the screw of the spiked washer, insertion of the tibial fixation device, and cyclical loading of the knee. The amount of tension loss is sufficient to increase the maximal anterior translation.

  14. Robust Tensioned Kevlar Suspension Design

    Science.gov (United States)

    Young, Joseph B.; Naylor, Bret J.; Holmes, Warren A.

    2012-01-01

    One common but challenging problem in cryogenic engineering is to produce a mount that has excellent thermal isolation but is also rigid. Such mounts can be achieved by suspending the load from a network of fibers or strings held in tension. Kevlar fibers are often used for this purpose owing to their high strength and low thermal conductivity. A suite of compact design elements has been developed to improve the reliability of suspension systems made of Kevlar.

  15. Surface Tension Confines Cryogenic Liquid

    Science.gov (United States)

    Castles, Stephen H.; Schein, Michael E.

    1989-01-01

    New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

  16. Delayed Tension Pneumothorax During Surgery

    Directory of Open Access Journals (Sweden)

    Ying-Lun Chen

    2005-10-01

    Full Text Available Tension pneumothorax is a life-threatening emergency that rapidly results in cardiopulmonary arrest. It requires prompt diagnosis and treatment. We present 2 cases from our practice, 1 caused by blunt chest trauma and the other resulting from laparoscopic surgery. Both were successfully treated by insertion of a chest tube. The diagnosis and treatment of intraoperative pneumothorax is discussed together with a review of the literature.

  17. Thermodynamic Simulation on the Performance of Twin Screw Expander Applied in Geothermal Power Generation

    Directory of Open Access Journals (Sweden)

    Yuanqu Qi

    2016-08-01

    Full Text Available A three-dimensional (3D geometry model of twin screw expander has been developed in this paper to measure and analyze geometric parameters such as groove volume, suction port area, and leakage area, which can be described as functions of rotation angle of male rotor. Taking the suction loss, leakage loss, and real gas effect into consideration, a thermodynamic model is developed using continuity and energy conservation equation. The developed model is verified by comparing predicted results of power output and internal efficiency with experimental data. Based on the model, the relationship between mass flow rate through inlet port and leakage path with rotation angle of male rotor as well as effects of the inlet parameter and operating parameter on the performance of the expander are analyzed.

  18. Planning, guidance, and quality assurance of pelvic screw placement using deformable image registration

    Science.gov (United States)

    Goerres, J.; Uneri, A.; Jacobson, M.; Ramsay, B.; De Silva, T.; Ketcha, M.; Han, R.; Manbachi, A.; Vogt, S.; Kleinszig, G.; Wolinsky, J.-P.; Osgood, G.; Siewerdsen, J. H.

    2017-12-01

    Percutaneous pelvic screw placement is challenging due to narrow bone corridors surrounded by vulnerable structures and difficult visual interpretation of complex anatomical shapes in 2D x-ray projection images. To address these challenges, a system for planning, guidance, and quality assurance (QA) is presented, providing functionality analogous to surgical navigation, but based on robust 3D-2D image registration techniques using fluoroscopy images already acquired in routine workflow. Two novel aspects of the system are investigated: automatic planning of pelvic screw trajectories and the ability to account for deformation of surgical devices (K-wire deflection). Atlas-based registration is used to calculate a patient-specific plan of screw trajectories in preoperative CT. 3D-2D registration aligns the patient to CT within the projective geometry of intraoperative fluoroscopy. Deformable known-component registration (dKC-Reg) localizes the surgical device, and the combination of plan and device location is used to provide guidance and QA. A leave-one-out analysis evaluated the accuracy of automatic planning, and a cadaver experiment compared the accuracy of dKC-Reg to rigid approaches (e.g. optical tracking). Surgical plans conformed within the bone cortex by 3-4 mm for the narrowest corridor (superior pubic ramus) and  >5 mm for the widest corridor (tear drop). The dKC-Reg algorithm localized the K-wire tip within 1.1 mm and 1.4° and was consistently more accurate than rigid-body tracking (errors up to 9 mm). The system was shown to automatically compute reliable screw trajectories and accurately localize deformed surgical devices (K-wires). Such capability could improve guidance and QA in orthopaedic surgery, where workflow is impeded by manual planning, conventional tool trackers add complexity and cost, rigid tool assumptions are often inaccurate, and qualitative interpretation of complex anatomy from 2D projections is prone to trial

  19. Rapid optimization of tension distribution for cable-driven parallel manipulators with redundant cables

    Science.gov (United States)

    Ouyang, Bo; Shang, Weiwei

    2016-03-01

    The solution of tension distributions is infinite for cable-driven parallel manipulators(CDPMs) with redundant cables. A rapid optimization method for determining the optimal tension distribution is presented. The new optimization method is primarily based on the geometry properties of a polyhedron and convex analysis. The computational efficiency of the optimization method is improved by the designed projection algorithm, and a fast algorithm is proposed to determine which two of the lines are intersected at the optimal point. Moreover, a method for avoiding the operating point on the lower tension limit is developed. Simulation experiments are implemented on a six degree-of-freedom(6-DOF) CDPM with eight cables, and the results indicate that the new method is one order of magnitude faster than the standard simplex method. The optimal distribution of tension distribution is thus rapidly established on real-time by the proposed method.

  20. Experimental study of the density distribution of the particles of the material in screw installation

    Directory of Open Access Journals (Sweden)

    Demidov S. F.

    2017-02-01

    Full Text Available the experimental studies of density distribution of the particles of a mixture of wheat, oats, rye to feed pigs by infrared heating at the time of stay and temperature at the exit of the installation. The purpose of the work is to study the quality of treatment of the product with the settings with the screw and the screw with installed round jumper on the pen of the screw. Screw installations with infrared emitters of selected wavelength give the opportunity for intense and continuous heat treatment process. The authors used the optimal parameters of the process with the screw and the screw with installed round jumper on the pen of the screw. The parameters of screw installation during the study were the following: the number of revolutions of the screw was 10 rpm, density of heat flux was 12 kW/m2, output capacity – 250 kg/h.

  1. Lectures on coarse geometry

    CERN Document Server

    Roe, John

    2003-01-01

    Coarse geometry is the study of spaces (particularly metric spaces) from a 'large scale' point of view, so that two spaces that look the same from a great distance are actually equivalent. This point of view is effective because it is often true that the relevant geometric properties of metric spaces are determined by their coarse geometry. Two examples of important uses of coarse geometry are Gromov's beautiful notion of a hyperbolic group and Mostow's proof of his famous rigidity theorem. The first few chapters of the book provide a general perspective on coarse structures. Even when only metric coarse structures are in view, the abstract framework brings the same simplification as does the passage from epsilons and deltas to open sets when speaking of continuity. The middle section reviews notions of negative curvature and rigidity. Modern interest in large scale geometry derives in large part from Mostow's rigidity theorem and from Gromov's subsequent 'large scale' rendition of the crucial properties of n...

  2. Lectures on Symplectic Geometry

    CERN Document Server

    Silva, Ana Cannas

    2001-01-01

    The goal of these notes is to provide a fast introduction to symplectic geometry for graduate students with some knowledge of differential geometry, de Rham theory and classical Lie groups. This text addresses symplectomorphisms, local forms, contact manifolds, compatible almost complex structures, Kaehler manifolds, hamiltonian mechanics, moment maps, symplectic reduction and symplectic toric manifolds. It contains guided problems, called homework, designed to complement the exposition or extend the reader's understanding. There are by now excellent references on symplectic geometry, a subset of which is in the bibliography of this book. However, the most efficient introduction to a subject is often a short elementary treatment, and these notes attempt to serve that purpose. This text provides a taste of areas of current research and will prepare the reader to explore recent papers and extensive books on symplectic geometry where the pace is much faster. For this reprint numerous corrections and cl...

  3. Complex algebraic geometry

    CERN Document Server

    Kollár, János

    1997-01-01

    This volume contains the lectures presented at the third Regional Geometry Institute at Park City in 1993. The lectures provide an introduction to the subject, complex algebraic geometry, making the book suitable as a text for second- and third-year graduate students. The book deals with topics in algebraic geometry where one can reach the level of current research while starting with the basics. Topics covered include the theory of surfaces from the viewpoint of recent higher-dimensional developments, providing an excellent introduction to more advanced topics such as the minimal model program. Also included is an introduction to Hodge theory and intersection homology based on the simple topological ideas of Lefschetz and an overview of the recent interactions between algebraic geometry and theoretical physics, which involve mirror symmetry and string theory.

  4. Geometry and Combinatorics

    DEFF Research Database (Denmark)

    Kokkendorff, Simon Lyngby

    2002-01-01

    The subject of this Ph.D.-thesis is somewhere in between continuous and discrete geometry. Chapter 2 treats the geometry of finite point sets in semi-Riemannian hyperquadrics,using a matrix whose entries are a trigonometric function of relative distances in a given point set. The distance...... to the geometry of a simplex in a semi-Riemannian hyperquadric. In chapter 3 we study which finite metric spaces that are realizable in a hyperbolic space in the limit where curvature goes to -∞. We show that such spaces are the so called leaf spaces, the set of degree 1 vertices of weighted trees. We also...... establish results on the limiting geometry of such an isometrically realized leaf space simplex in hyperbolic space, when curvature goes to -∞. Chapter 4 discusses negative type of metric spaces. We give a measure theoretic treatment of this concept and related invariants. The theory developed...

  5. The geometry of geodesics

    CERN Document Server

    Busemann, Herbert

    2005-01-01

    A comprehensive approach to qualitative problems in intrinsic differential geometry, this text examines Desarguesian spaces, perpendiculars and parallels, covering spaces, the influence of the sign of the curvature on geodesics, more. 1955 edition. Includes 66 figures.

  6. Geometry and billiards

    CERN Document Server

    Tabachnikov, Serge

    2005-01-01

    Mathematical billiards describe the motion of a mass point in a domain with elastic reflections off the boundary or, equivalently, the behavior of rays of light in a domain with ideally reflecting boundary. From the point of view of differential geometry, the billiard flow is the geodesic flow on a manifold with boundary. This book is devoted to billiards in their relation with differential geometry, classical mechanics, and geometrical optics. The topics covered include variational principles of billiard motion, symplectic geometry of rays of light and integral geometry, existence and nonexistence of caustics, optical properties of conics and quadrics and completely integrable billiards, periodic billiard trajectories, polygonal billiards, mechanisms of chaos in billiard dynamics, and the lesser-known subject of dual (or outer) billiards. The book is based on an advanced undergraduate topics course (but contains more material than can be realistically taught in one semester). Although the minimum prerequisit...

  7. Introduction to tropical geometry

    CERN Document Server

    Maclagan, Diane

    2015-01-01

    Tropical geometry is a combinatorial shadow of algebraic geometry, offering new polyhedral tools to compute invariants of algebraic varieties. It is based on tropical algebra, where the sum of two numbers is their minimum and the product is their sum. This turns polynomials into piecewise-linear functions, and their zero sets into polyhedral complexes. These tropical varieties retain a surprising amount of information about their classical counterparts. Tropical geometry is a young subject that has undergone a rapid development since the beginning of the 21st century. While establishing itself as an area in its own right, deep connections have been made to many branches of pure and applied mathematics. This book offers a self-contained introduction to tropical geometry, suitable as a course text for beginning graduate students. Proofs are provided for the main results, such as the Fundamental Theorem and the Structure Theorem. Numerous examples and explicit computations illustrate the main concepts. Each of t...

  8. Rudiments of algebraic geometry

    CERN Document Server

    Jenner, WE

    2017-01-01

    Aimed at advanced undergraduate students of mathematics, this concise text covers the basics of algebraic geometry. Topics include affine spaces, projective spaces, rational curves, algebraic sets with group structure, more. 1963 edition.

  9. Development and Testing of X-Ray Imaging-Enhanced Poly-L-Lactide Bone Screws.

    Directory of Open Access Journals (Sweden)

    Wei-Jen Chang

    Full Text Available Nanosized iron oxide particles exhibit osteogenic and radiopaque properties. Thus, iron oxide (Fe3O4 nanoparticles were incorporated into a biodegradable polymer (poly-L-lactic acid, PLLA to fabricate a composite bone screw. This multifunctional, 3D printable bone screw was detectable on X-ray examination. In this study, mechanical tests including three-point bending and ultimate tensile strength were conducted to evaluate the optimal ratio of iron oxide nanoparticles in the PLLA composite. Both injection molding and 3D printing techniques were used to fabricate the PLLA bone screws with and without the iron oxide nanoparticles. The fabricated screws were implanted into the femoral condyles of New Zealand White rabbits. Bone blocks containing the PLLA screws were resected 2 and 4 weeks after surgery. Histologic examination of the surrounding bone and the radiopacity of the iron-oxide-containing PLLA screws were evaluated. Our results indicated that addition of iron oxide nanoparticles at 30% significantly decreased the ultimate tensile stress properties of the PLLA screws. The screws with 20% iron oxide exhibited strong radiopacity compared to the screws fabricated without the iron oxide nanoparticles. Four weeks after surgery, the average bone volume of the iron oxide PLLA composite screws was significantly greater than that of PLLA screws without iron oxide. These findings suggested that biodegradable and X-ray detectable PLLA bone screws can be produced by incorporation of 20% iron oxide nanoparticles. Furthermore, these screws had significantly greater osteogenic capability than the PLLA screws without iron oxide.

  10. CT provides precise size assessment of implanted titanium alloy pedicle screws.

    Science.gov (United States)

    Elliott, Michael J; Slakey, Joseph B

    2014-05-01

    After performing instrumented spinal fusion with pedicle screws, postoperative imaging using CT to assess screw position may be necessary. Stainless steel implants produce significant metal artifact on CT, and the degree of distortion is at least partially dependent on the cross-sectional area of the implanted device. If the same effect occurs with titanium alloy implants, ability to precisely measure proximity of screws to adjacent structures may be adversely affected as screw size increases. We therefore asked whether (1) CT provides precise measurements of true screw widths; and (2) precision degrades based on the size of the titanium implant imaged. CT scans performed on 20 patients after instrumented spinal fusion for scoliosis were reviewed. The sizes of 151 titanium alloy pedicle screws were measured and compared with known screw size. The amount of metal bloom artifact was determined for each of the four screw sizes. ANOVA with Tukey's post hoc test were performed to evaluate differences in scatter, and Spearman's rho coefficient was used to measure relationship between screw size and scatter. All screws measured larger than their known size, but even with larger 7-mm screws the size differential was less than 1 mm. The four different screw sizes produced scatter amounts that were different from each other (p titanium alloy pedicle screws produces minimal artifact, thus making this the preferred imaging modality to assess screw position after surgery. Although the amount of artifact increases with the volume of titanium present, the degree of distortion is minimal and is usually less than 1 mm.

  11. Implosions and hypertoric geometry

    DEFF Research Database (Denmark)

    Dancer, A.; Kirwan, F.; Swann, A.

    2013-01-01

    The geometry of the universal hyperkahler implosion for SU (n) is explored. In particular, we show that the universal hyperkahler implosion naturally contains a hypertoric variety described in terms of quivers. Furthermore, we discuss a gauge theoretic approach to hyperkahler implosion.......The geometry of the universal hyperkahler implosion for SU (n) is explored. In particular, we show that the universal hyperkahler implosion naturally contains a hypertoric variety described in terms of quivers. Furthermore, we discuss a gauge theoretic approach to hyperkahler implosion....

  12. Intermediate algebra & analytic geometry

    CERN Document Server

    Gondin, William R

    1967-01-01

    Intermediate Algebra & Analytic Geometry Made Simple focuses on the principles, processes, calculations, and methodologies involved in intermediate algebra and analytic geometry. The publication first offers information on linear equations in two unknowns and variables, functions, and graphs. Discussions focus on graphic interpretations, explicit and implicit functions, first quadrant graphs, variables and functions, determinate and indeterminate systems, independent and dependent equations, and defective and redundant systems. The text then examines quadratic equations in one variable, system

  13. d-geometries revisited

    CERN Document Server

    Ceresole, Anna; Gnecchi, Alessandra; Marrani, Alessio

    2013-01-01

    We analyze some properties of the four dimensional supergravity theories which originate from five dimensions upon reduction. They generalize to N>2 extended supersymmetries the d-geometries with cubic prepotentials, familiar from N=2 special K\\"ahler geometry. We emphasize the role of a suitable parametrization of the scalar fields and the corresponding triangular symplectic basis. We also consider applications to the first order flow equations for non-BPS extremal black holes.

  14. CMS geometry through 2020

    International Nuclear Information System (INIS)

    Osborne, I; Brownson, E; Eulisse, G; Jones, C D; Sexton-Kennedy, E; Lange, D J

    2014-01-01

    CMS faces real challenges with upgrade of the CMS detector through 2020 and beyond. One of the challenges, from the software point of view, is managing upgrade simulations with the same software release as the 2013 scenario. We present the CMS geometry description software model, its integration with the CMS event setup and core software. The CMS geometry configuration and selection is implemented in Python. The tools collect the Python configuration fragments into a script used in CMS workflow. This flexible and automated geometry configuration allows choosing either transient or persistent version of the same scenario and specific version of the same scenario. We describe how the geometries are integrated and validated, and how we define and handle different geometry scenarios in simulation and reconstruction. We discuss how to transparently manage multiple incompatible geometries in the same software release. Several examples are shown based on current implementation assuring consistent choice of scenario conditions. The consequences and implications for multiple/different code algorithms are discussed.

  15. Software Geometry in Simulations

    Science.gov (United States)

    Alion, Tyler; Viren, Brett; Junk, Tom

    2015-04-01

    The Long Baseline Neutrino Experiment (LBNE) involves many detectors. The experiment's near detector (ND) facility, may ultimately involve several detectors. The far detector (FD) will be significantly larger than any other Liquid Argon (LAr) detector yet constructed; many prototype detectors are being constructed and studied to motivate a plethora of proposed FD designs. Whether it be a constructed prototype or a proposed ND/FD design, every design must be simulated and analyzed. This presents a considerable challenge to LBNE software experts; each detector geometry must be described to the simulation software in an efficient way which allows for multiple authors to easily collaborate. Furthermore, different geometry versions must be tracked throughout their use. We present a framework called General Geometry Description (GGD), written and developed by LBNE software collaborators for managing software to generate geometries. Though GGD is flexible enough to be used by any experiment working with detectors, we present it's first use in generating Geometry Description Markup Language (GDML) files to interface with LArSoft, a framework of detector simulations, event reconstruction, and data analyses written for all LAr technology users at Fermilab. Brett is the other of the framework discussed here, the General Geometry Description (GGD).

  16. Introduction to combinatorial geometry

    International Nuclear Information System (INIS)

    Gabriel, T.A.; Emmett, M.B.

    1985-01-01

    The combinatorial geometry package as used in many three-dimensional multimedia Monte Carlo radiation transport codes, such as HETC, MORSE, and EGS, is becoming the preferred way to describe simple and complicated systems. Just about any system can be modeled using the package with relatively few input statements. This can be contrasted against the older style geometry packages in which the required input statements could be large even for relatively simple systems. However, with advancements come some difficulties. The users of combinatorial geometry must be able to visualize more, and, in some instances, all of the system at a time. Errors can be introduced into the modeling which, though slight, and at times hard to detect, can have devastating effects on the calculated results. As with all modeling packages, the best way to learn the combinatorial geometry is to use it, first on a simple system then on more complicated systems. The basic technique for the description of the geometry consists of defining the location and shape of the various zones in terms of the intersections and unions of geometric bodies. The geometric bodies which are generally included in most combinatorial geometry packages are: (1) box, (2) right parallelepiped, (3) sphere, (4) right circular cylinder, (5) right elliptic cylinder, (6) ellipsoid, (7) truncated right cone, (8) right angle wedge, and (9) arbitrary polyhedron. The data necessary to describe each of these bodies are given. As can be easily noted, there are some subsets included for simplicity

  17. The Improvement of Bone-Tendon Fixation by Porous Titanium Interference Screw: A Rabbit Animal Model.

    Science.gov (United States)

    Tsai, Pei-I; Chen, Chih-Yu; Huang, Shu-Wei; Yang, Kuo-Yi; Lin, Tzu-Hung; Chen, San-Yuan; Sun, Jui-Sheng

    2018-05-04

    The interference screw is a widely used fixation device in the anterior cruciate ligament (ACL) reconstruction surgeries. Despite the generally satisfactory results, problems of using interference screws were reported. By using additive manufacturing (AM) technology, we developed an innovative titanium alloy (Ti 6 Al 4 V) interference screw with rough surface and inter-connected porous structure designs to improve the bone-tendon fixation. An innovative Ti 6 Al 4 V interference screws were manufactured by AM technology. In vitro mechanical tests were performed to validate its mechanical properties. Twenty-seven New Zealand white rabbits were randomly divided into control and AM screw groups for biomechanical analyses and histological analysis at 4, 8 and 12 weeks postoperatively; while micro-CT analysis was performed at 12 weeks postoperatively. The biomechanical tests showed that the ultimate failure load in the AM interference screw group was significantly higher than that in the control group at all tested periods. These results were also compatible with the findings of micro-CT and histological analyses. In micro-CT analysis, the bone-screw gap was larger in the control group; while for the additive manufactured screw, the screw and bone growth was in close contact. In histological study, the bone-screw gaps were wider in the control group and were almost invisible in the AM screw group. The innovative AM interference screws with surface roughness and inter-connected porous architectures demonstrated better bone-tendon-implant integration, and resulted in stronger biomechanical characteristics when compared to traditional screws. These advantages can be transferred to future interference screw designs to improve their clinical performance. The AM interference screw could improve graft fixation and eventually result in better biomechanical performance of the bone-tendon-screw construct. The innovative AM interference screws can be transferred to future

  18. Sacroiliac secure corridor: analysis for safe insertion of iliosacral screws

    Directory of Open Access Journals (Sweden)

    Henrique Alves Cruz

    2013-08-01

    Full Text Available OBJECTIVE: Posterior pelvic lesions, especially of the sacral-iliac joint, have high mortality and morbidity risks. Definitive fixation is necessary for the joint stabilization, and one option is the sacral percutaneous pinning with screws. Proximity to important structures to this region brings risks to the fixation procedure; therefore, it is important to know the tridimensional anatomy of the pelvis posterior region. Deviations of the surgeon's hand of four degrees may target the screws to those structures; dimorphisms of the upper sacrum and a poor lesion reduction may redound in a screw malpositioning. This study is aimed to evaluate the dimensions of a safe surgical corridor for safe sacroiliac screw insertion and relations with age and sex of the patients. METHOD: One hundred randomly selected pelvis CTs of patients with no pelvic diseases, seen at a tertiary care teaching Hospital. Measurements were made by computer and the safest area for screw insertion was calculated by two methods. The results were expressed in mm (not in degrees, in order to be a further surgical reference. RESULTS: There was a significant size difference in the analyzed sacral vertebra, differing on a wider size in men than in women. There was no significant statistical difference between vertebral size and age. By both methods, a safe area for screw insertion could be defined. CONCLUSION: Age does not influence the width of the surgical corridor. The surgeon has a safe corridor considered narrower when inserting screws in a female pelvis than when in a male one. However, as the smallest vertebra found (feminine was considered for statics, it was concluded that this corridor is 20 mm wide in any direction, taking as a reference the centrum of the vertebra.

  19. History of Retractor Technologies for Percutaneous Pedicle Screw Fixation Systems.

    Science.gov (United States)

    Mobbs, Ralph J; Phan, Kevin

    2016-02-01

    Minimally invasive techniques aimed at minimizing surgery-associated risk and morbidity of spinal surgery have increased in popularity in recent years. Their potential advantages include reduced length of hospital stay, blood loss, and requirement for post-operative analgesia and earlier return to work. One such minimally invasive technique is the use of percutaneous pedicle screw fixation, which is paramount for promoting rigid and stable constructs and fusion in the context of trauma, tumors, deformity and degenerative disease. Percutaneous pedicle screw insertion can be an intimidating prospect for surgeons who have only been trained in open techniques. One of the ongoing challenges of this percutaneous system is to provide the surgeon with adequate access to the pedicle entry anatomy and adequate tactile or visual feedback concerning the position and anatomy of the rod and set-screw construct. This review article discusses the history and evolution of percutaneous pedicle screw retractor technologies and outlines the advances over the last decade in the rapidly expanding field of minimal access surgery for posterior pedicle screw based spinal stabilization. As indications for percutaneous pedicle screw techniques expand, the nuances of the minimally invasive surgery techniques and associated technologies will also multiply. It is important that experienced surgeons have access to tools that can improve access with a greater degree of ease, simplicity and safety. We here discuss the technical challenges of percutaneous pedicle screw retractor technologies and a variety of systems with a focus on the pros and cons of various retractor systems. © 2016 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

  20. Global aspects of complex geometry

    CERN Document Server

    Catanese, Fabrizio; Huckleberry, Alan T

    2006-01-01

    Present an overview of developments in Complex Geometry. This book covers topics that range from curve and surface theory through special varieties in higher dimensions, moduli theory, Kahler geometry, and group actions to Hodge theory and characteristic p-geometry.

  1. Preload, Coefficient of Friction, and Thread Friction in an Implant-Abutment-Screw Complex.

    Science.gov (United States)

    Wentaschek, Stefan; Tomalla, Sven; Schmidtmann, Irene; Lehmann, Karl Martin

    To examine the screw preload, coefficient of friction (COF), and tightening torque needed to overcome the thread friction of an implant-abutment-screw complex. In a customized load frame, 25 new implant-abutment-screw complexes including uncoated titanium alloy screws were torqued and untorqued 10 times each, applying 25 Ncm. Mean preload values decreased significantly from 209.8 N to 129.5 N according to the number of repetitions. The overall COF increased correspondingly. There was no comparable trend for the thread friction component. These results suggest that the application of a used implant-abutment-screw complex may be unfavorable for obtaining optimal screw preload.

  2. [Clinical efficacy of unilateral percutaneous transfacet screws combined with contralateral pedicle screw versus bilateral pedicle screws fixation in the treatment of the degenerative lumbar disease].

    Science.gov (United States)

    Hao, Rong-Xue; Zhou, Hui; Pan, Hao; Yue, Jun; Chen, Hui-Guo; Yang, He-Jie; Jia, Gao-Yong; Wang, Dong; Lin, Yan; Xu, Hua-Zi

    2017-09-25

    To investigate the surgical outcome of unilateral pedicle screw(UPS) after TLIF technique combined with contralateral percutaneous transfacet screw(PTS) fixation vs bilateral pedicle screws(BPS) fixation in treatment of degenerative lumbar disease. From January 2009 to June 2012, 46 patients with degenerative lumbar diseases, including 30 males and 16 females with an average age of 51.5 years old, who were divided into two groups according to different fixation methods. Twenty-two cases underwent UPS after TLIF technique combined with contralateral PTS fixation (group A), while the others underwent BPS fixation(group B). The relative data were analyzed, such as blood loss volume, operative time, fusion rate, ODI score, JOA score and so on. All the patients were followed up for 1 to 3 years with an average of 22 months. Except one case of each group was uncertainty fusion, the rest have obtained bony fusion, and the fusion rates in group A and B were 95.5% and 95.8%, respectively. No displacement and breakage of screw were found during follow-up. Operative time and blood loss volume in group A were better than of group B( P 0.05). Two approaches had similar clinical outcomes for degenerative lumbar disease with no severe instability. Compared with BPS fixation, the UPS after TLIF technique and contralateral PTS fixation has the advantages of less trauma, shorter operative time and less blood loss, and it is a safe and feasible surgical technique.

  3. Evaluation of the Effect of Fixation Angle between Polyaxial Pedicle Screw Head and Rod on the Failure of Screw-Rod Connection

    Directory of Open Access Journals (Sweden)

    Engin Çetin

    2015-01-01

    Full Text Available Introduction. Polyaxial screws had been only tested according to the ASTM standards (when they were perpendicularly positioned to the rod. In this study, effects of the pedicle screws angled fixation to the rod on the mechanical properties of fixation were investigated. Materials and Method. 30 vertically fixed screws and 30 screws fixed with angle were used in the study. Screws were used in three different diameters which were 6.5 mm, 7.0 mm, and 7.5 mm, in equal numbers. Axial pull-out and flexion moment tests were performed. Test results compared with each other using appropriate statistical methods. Results. In pull-out test, vertically fixed screws, in 6.5 mm and 7.0 mm diameter, had significantly higher maximum load values than angled fixed screws with the same diameters (P<0.01. Additionally, vertically fixed screws, in all diameters, had significantly greater stiffness according to corresponding size fixed with angle (P<0.005. Conclusion. Fixing the pedicle screw to the rod with angle significantly decreased the pull-out stiffness in all diameters. Similarly, pedicle screw instrumentation fixed with angle decreased the minimum sagittal angle between the rod and the screw in all diameters for flexion moment test but the differences were not significant.

  4. Preoperative CT planning of screw length in arthroscopic Latarjet.

    Science.gov (United States)

    Hardy, Alexandre; Gerometta, Antoine; Granger, Benjamin; Massein, Audrey; Casabianca, Laurent; Pascal-Moussellard, Hugues; Loriaut, Philippe

    2018-01-01

    The Latarjet procedure has shown its efficiency for the treatment of anterior shoulder dislocation. The success of this technique depends on the correct positioning and fusion of the bone block. The length of the screws that fix the bone block can be a problem. They can increase the risk of non-union if too short or be the cause of nerve lesion or soft tissue discomfort if too long. Suprascapular nerve injuries have been reported during shoulder stabilisation surgery up to 6 % of the case. Bone block non-union depending on the series is found around 20 % of the cases. The purpose of this study was to evaluate the efficiency of this CT preoperative planning to predict optimal screws length. The clinical importance of this study lies in the observation that it is the first study to evaluate the efficiency of CT planning to predict screw length. Inclusion criteria were patients with chronic anterior instability of the shoulder with an ISIS superior to 4. Exclusion criteria were patients with multidirectional instability or any previous surgery on this shoulder. Thirty patients were included prospectively, 11 of them went threw a CT planning, before their arthroscopic Latarjet. Optimal length of both screws was calculated, adding the size of the coracoid at 5 and 15 mm from the tip to the glenoid. Thirty-two-mm screws were used for patients without planning. On a post-operative CT scan with 3D reconstruction, the distance between the screw tip and the posterior cortex was measured. A one-sample Wilcoxon test was used to compare the distance from the tip of the screw to an acceptable positioning of ±2 mm from the posterior cortex. In the group without planning, screw 1 tended to differ from the acceptable positioning: mean 3.44 mm ± 3.13, med 2.9 mm, q1; q3 [0.6; 4.75] p = 0.1118, and screw 2 differed significantly from the acceptable position: mean 4.83 mm ± 4.11, med 3.7 mm, q1; q3 [1.7; 5.45] p = 0.0045. In the group with planning, position of

  5. The Study of Vibration Processes in Oil Flooded Screw Compressors

    Directory of Open Access Journals (Sweden)

    I. V. Filippov

    2014-01-01

    Full Text Available Vibration processes that accompany most of machines and mechanisms are of interest to the researcher, as a source of information about the technical condition and the nature of the business processes flow. Vibration-based diagnostics of oil flooded screw compressors allows us to estimate the deviation of their operation from the main mode in accordance with changing the settings of vibration processes.The oil flooded screw compressor transition from the main mode of operation to the abnormal one is accompanied by complex gas-dynamic phenomena i.e. the initial gaps and their decays. This leads to changes in the nature of vibration processes, prompting suggestions that there is a relationship to a change of vibration parameters and mode of compressor operation.Studies were conducted by combined method using an analytical calculation of the decay parameters of the initial discontinuity and an experimental one based on the measurement of acceleration on the body of the real oil flooded screw compressor. A virtually adequate reaction of the decay parameters of the initial gap and the peak values of vibration acceleration to the change of operation mode of oil flooded screw compressor has been received. The peak value of the vibration acceleration was selected by the method of Gating being time-coinciding with the beginning discharge phase of the oil flooded screw compressor, and therefore, with the decay time of the initial discontinuity.This indicates a large degree of hypothesis likelihood on an existing initial break in oil flooded screw compressor when operating in abnormal conditions. This work contains the study results of vibration processes and their relationship to the operating mode of the oil flooded screw compressor, which distinguish it from the other works studied vibration processes in reciprocating compressors. The vibration parameters control of operating oil flooded screw compressor allows us to create an automatic capacity control

  6. Locking screw apparatus and method for underwater remote replacement

    International Nuclear Information System (INIS)

    Balog, L.J.

    1987-01-01

    A method is described for locking in place a screw which secures together first and second structures in the internal region of a nuclear reactor core. The first structure has a screw bore with a counterbore portion formed in an outer surface. The method comprises the steps of: forming a lateral recess in the counterbore portion and spaced from the outer surface, providing an elongated screw having an enlarged shoulder flange and an angular drive head with a lateral width substantially less than that of the counterbore portion, disposing the screw through the screw bore in threaded engagement with the second structure and with the shoulder rotatably seated in the counterbore portion. This provides a locking member having an angular opening and disposing it in the counterbore portion against the flange with the drive head received in the opening for engagement with the locking member to prevent rotation. This deforms a portion of the locking member into the recess for engagement to prevent movement of the locking member with respect to the first structure

  7. Tests for the dynamic behavior of insulation valve screws

    International Nuclear Information System (INIS)

    Tulke, K.D.; Stoppler, W.; Stern, G.

    1994-01-01

    Thermal tensile tests were performed at a temperature of 270 C, with two new original insulation valve conical screws M30-Tx92,5 mm (material: 21 CrMo V 5 7)and two prestrained ones during the event on 27.12.92. In order to assure the results obtained with regard to the dynamic load on the insulation valve during ''quick opening'', in addition tensile impact tests were performed at 270 C with six original insulation valve conical screws. Impact velocity reached 13,5 m/s at four screws and 6 m/s at two screws. Test conditions regarding collision damping and mass distribution were adapted, by means of parameter studies, to the situation of the insulation valve. During thermal tensile tests, strength and deformation values, such as stress at flow start, tensile strength, fracture prolongation and strain, necking at fracture as well as energy absorption up to maximum force and up to rupture, were determined. During tensile impact tests, deformation values, such as elongation, strain and necking, and energy absorption by the screw, were determined. (orig.) [de

  8. Dorsal bridge plating or transarticular screws for Lisfranc fracture dislocations.

    Science.gov (United States)

    Kirzner, N; Zotov, P; Goldbloom, D; Curry, H; Bedi, H

    2018-04-01

    Aims The aim of this retrospective study was to compare the functional and radiological outcomes of bridge plating, screw fixation, and a combination of both methods for the treatment of Lisfranc fracture dislocations. Patients and Methods A total of 108 patients were treated for a Lisfranc fracture dislocation over a period of nine years. Of these, 38 underwent transarticular screw fixation, 45 dorsal bridge plating, and 25 a combination technique. Injuries were assessed preoperatively according to the Myerson classification system. The outcome measures included the American Orthopaedic Foot and Ankle Society (AOFAS) score, the validated Manchester Oxford Foot Questionnaire (MOXFQ) functional tool, and the radiological Wilppula classification of anatomical reduction. Results Significantly better functional outcomes were seen in the bridge plate group. These patients had a mean AOFAS score of 82.5 points, compared with 71.0 for the screw group and 63.3 for the combination group (p bridge plate group, 38.1 in the screw group, and 45.5 in the combination group (p bridge plating have better functional and radiological outcomes than those treated with transarticular screws or a combination technique. Cite this article: Bone Joint J 2018;100-B:468-74.

  9. Numerical simulation of a twin screw expander for performance prediction

    Science.gov (United States)

    Papes, Iva; Degroote, Joris; Vierendeels, Jan

    2015-08-01

    With the increasing use of twin screw expanders in waste heat recovery applications, the performance prediction of these machines plays an important role. This paper presents a mathematical model for calculating the performance of a twin screw expander. From the mass and energy conservation laws, differential equations are derived which are then solved together with the appropriate Equation of State in the instantaneous control volumes. Different flow processes that occur inside the screw expander such as filling (accompanied by a substantial pressure loss) and leakage flows through the clearances are accounted for in the model. The mathematical model employs all geometrical parameters such as chamber volume, suction and leakage areas. With R245fa as working fluid, the Aungier Redlich-Kwong Equation of State has been used in order to include real gas effects. To calculate the mass flow rates through the leakage paths formed inside the screw expander, flow coefficients are considered as constant and they are derived from 3D Computational Fluid Dynamic calculations at given working conditions and applied to all other working conditions. The outcome of the mathematical model is the P-V indicator diagram which is compared to CFD results of the same twin screw expander. Since CFD calculations require significant computational time, developed mathematical model can be used for the faster performance prediction.

  10. Percutaneous Iliac Screws for Minimally Invasive Spinal Deformity Surgery

    Directory of Open Access Journals (Sweden)

    Michael Y. Wang

    2012-01-01

    Full Text Available Introduction. Adult spinal deformity (ASD surgeries carry significant morbidity, and this has led many surgeons to apply minimally invasive surgery (MIS techniques to reduce the blood loss, infections, and other peri-operative complications. A spectrum of techniques for MIS correction of ASD has thus evolved, most recently the application of percutaneous iliac screws. Methods. Over an 18 months 10 patients with thoracolumbar scoliosis underwent MIS surgery. The mean age was 73 years (70% females. Patients were treated with multi-level facet osteotomies and interbody fusion using expandable cages followed by percutaneous screw fixation. Percutaneous iliac screws were placed bilaterally using the obturator outlet view to target the ischial body. Results. All patients were successfully instrumented without conversion to an open technique. Mean operative time was 302 minutes and the mean blood loss was 480 cc, with no intraoperative complications. A total of 20 screws were placed successfully as judged by CT scanning to confirm no bony violations. Complications included: two asymptomatic medial breaches at T10 and L5, and one patient requiring delayed epidural hematoma evacuation. Conclusions. Percutaneous iliac screws can be placed safely in patients with ASD. This MIS technique allows for successful caudal anchoring to stress-shield the sacrum and L5-S1 fusion site in long-segment constructs.

  11. Sources of hyperbolic geometry

    CERN Document Server

    Stillwell, John

    1996-01-01

    This book presents, for the first time in English, the papers of Beltrami, Klein, and Poincaré that brought hyperbolic geometry into the mainstream of mathematics. A recognition of Beltrami comparable to that given the pioneering works of Bolyai and Lobachevsky seems long overdue-not only because Beltrami rescued hyperbolic geometry from oblivion by proving it to be logically consistent, but because he gave it a concrete meaning (a model) that made hyperbolic geometry part of ordinary mathematics. The models subsequently discovered by Klein and Poincaré brought hyperbolic geometry even further down to earth and paved the way for the current explosion of activity in low-dimensional geometry and topology. By placing the works of these three mathematicians side by side and providing commentaries, this book gives the student, historian, or professional geometer a bird's-eye view of one of the great episodes in mathematics. The unified setting and historical context reveal the insights of Beltrami, Klein, and Po...

  12. Generalizing optical geometry

    International Nuclear Information System (INIS)

    Jonsson, Rickard; Westman, Hans

    2006-01-01

    We show that by employing the standard projected curvature as a measure of spatial curvature, we can make a certain generalization of optical geometry (Abramowicz M A and Lasota J-P 1997 Class. Quantum Grav. A 14 23-30). This generalization applies to any spacetime that admits a hypersurface orthogonal shearfree congruence of worldlines. This is a somewhat larger class of spacetimes than the conformally static spacetimes assumed in standard optical geometry. In the generalized optical geometry, which in the generic case is time dependent, photons move with unit speed along spatial geodesics and the sideways force experienced by a particle following a spatially straight line is independent of the velocity. Also gyroscopes moving along spatial geodesics do not precess (relative to the forward direction). Gyroscopes that follow a curved spatial trajectory precess according to a very simple law of three-rotation. We also present an inertial force formalism in coordinate representation for this generalization. Furthermore, we show that by employing a new sense of spatial curvature (Jonsson R 2006 Class. Quantum Grav. 23 1)) closely connected to Fermat's principle, we can make a more extensive generalization of optical geometry that applies to arbitrary spacetimes. In general this optical geometry will be time dependent, but still geodesic photons move with unit speed and follow lines that are spatially straight in the new sense. Also, the sideways experienced (comoving) force on a test particle following a line that is straight in the new sense will be independent of the velocity

  13. Development of structural schemes of parallel structure manipulators using screw calculus

    Science.gov (United States)

    Rashoyan, G. V.; Shalyukhin, K. A.; Gaponenko, EV

    2018-03-01

    The paper considers the approach to the structural analysis and synthesis of parallel structure robots based on the mathematical apparatus of groups of screws and on a concept of reciprocity of screws. The results are depicted of synthesis of parallel structure robots with different numbers of degrees of freedom, corresponding to the different groups of screws. Power screws are applied with this aim, based on the principle of static-kinematic analogy; the power screws are similar to the orts of axes of not driven kinematic pairs of a corresponding connecting chain. Accordingly, kinematic screws of the outlet chain of a robot are simultaneously determined which are reciprocal to power screws of kinematic sub-chains. Solution of certain synthesis problems is illustrated with practical applications. Closed groups of screws can have eight types. The three-membered groups of screws are of greatest significance, as well as four-membered screw groups [1] and six-membered screw groups. Three-membered screw groups correspond to progressively guiding mechanisms, to spherical mechanisms, and to planar mechanisms. The four-membered group corresponds to the motion of the SCARA robot. The six-membered group includes all possible motions. From the works of A.P. Kotelnikov, F.M. Dimentberg, it is known that closed fifth-order screw groups do not exist. The article presents examples of the mechanisms corresponding to the given groups.

  14. The Plastic Tension Field Method

    DEFF Research Database (Denmark)

    Hansen, Thomas

    2005-01-01

    This paper describes a calculation method for steel plate girders with transverse web stiffeners subjected to shear. It may be used for predicting the failure load or, as a design method, to determine the optimal amount of internal web stiffeners. The new method is called the plastic tension field...... method. The method is based on the theory of plasticity and is analogous to the so-called diagonal compression field method developed for reinforced concrete beams with transverse stirrups, which is adopted in the common European concrete code (Eurocode 2). Many other theories have been developed...

  15. Axelrod's model with surface tension

    Science.gov (United States)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  16. Computational synthetic geometry

    CERN Document Server

    Bokowski, Jürgen

    1989-01-01

    Computational synthetic geometry deals with methods for realizing abstract geometric objects in concrete vector spaces. This research monograph considers a large class of problems from convexity and discrete geometry including constructing convex polytopes from simplicial complexes, vector geometries from incidence structures and hyperplane arrangements from oriented matroids. It turns out that algorithms for these constructions exist if and only if arbitrary polynomial equations are decidable with respect to the underlying field. Besides such complexity theorems a variety of symbolic algorithms are discussed, and the methods are applied to obtain new mathematical results on convex polytopes, projective configurations and the combinatorics of Grassmann varieties. Finally algebraic varieties characterizing matroids and oriented matroids are introduced providing a new basis for applying computer algebra methods in this field. The necessary background knowledge is reviewed briefly. The text is accessible to stud...

  17. Discrete and computational geometry

    CERN Document Server

    Devadoss, Satyan L

    2011-01-01

    Discrete geometry is a relatively new development in pure mathematics, while computational geometry is an emerging area in applications-driven computer science. Their intermingling has yielded exciting advances in recent years, yet what has been lacking until now is an undergraduate textbook that bridges the gap between the two. Discrete and Computational Geometry offers a comprehensive yet accessible introduction to this cutting-edge frontier of mathematics and computer science. This book covers traditional topics such as convex hulls, triangulations, and Voronoi diagrams, as well as more recent subjects like pseudotriangulations, curve reconstruction, and locked chains. It also touches on more advanced material, including Dehn invariants, associahedra, quasigeodesics, Morse theory, and the recent resolution of the Poincaré conjecture. Connections to real-world applications are made throughout, and algorithms are presented independently of any programming language. This richly illustrated textbook also fe...

  18. Geometry and Cloaking Devices

    Science.gov (United States)

    Ochiai, T.; Nacher, J. C.

    2011-09-01

    Recently, the application of geometry and conformal mappings to artificial materials (metamaterials) has attracted the attention in various research communities. These materials, characterized by a unique man-made structure, have unusual optical properties, which materials found in nature do not exhibit. By applying the geometry and conformal mappings theory to metamaterial science, it may be possible to realize so-called "Harry Potter cloaking device". Although such a device is still in the science fiction realm, several works have shown that by using such metamaterials it may be possible to control the direction of the electromagnetic field at will. We could then make an object hidden inside of a cloaking device. Here, we will explain how to design invisibility device using differential geometry and conformal mappings.

  19. Lectures on discrete geometry

    CERN Document Server

    2002-01-01

    Discrete geometry investigates combinatorial properties of configurations of geometric objects. To a working mathematician or computer scientist, it offers sophisticated results and techniques of great diversity and it is a foundation for fields such as computational geometry or combinatorial optimization. This book is primarily a textbook introduction to various areas of discrete geometry. In each area, it explains several key results and methods, in an accessible and concrete manner. It also contains more advanced material in separate sections and thus it can serve as a collection of surveys in several narrower subfields. The main topics include: basics on convex sets, convex polytopes, and hyperplane arrangements; combinatorial complexity of geometric configurations; intersection patterns and transversals of convex sets; geometric Ramsey-type results; polyhedral combinatorics and high-dimensional convexity; and lastly, embeddings of finite metric spaces into normed spaces. Jiri Matousek is Professor of Com...

  20. Complex differential geometry

    CERN Document Server

    Zheng, Fangyang

    2002-01-01

    The theory of complex manifolds overlaps with several branches of mathematics, including differential geometry, algebraic geometry, several complex variables, global analysis, topology, algebraic number theory, and mathematical physics. Complex manifolds provide a rich class of geometric objects, for example the (common) zero locus of any generic set of complex polynomials is always a complex manifold. Yet complex manifolds behave differently than generic smooth manifolds; they are more coherent and fragile. The rich yet restrictive character of complex manifolds makes them a special and interesting object of study. This book is a self-contained graduate textbook that discusses the differential geometric aspects of complex manifolds. The first part contains standard materials from general topology, differentiable manifolds, and basic Riemannian geometry. The second part discusses complex manifolds and analytic varieties, sheaves and holomorphic vector bundles, and gives a brief account of the surface classifi...

  1. Geometry and symmetry

    CERN Document Server

    Yale, Paul B

    2012-01-01

    This book is an introduction to the geometry of Euclidean, affine, and projective spaces with special emphasis on the important groups of symmetries of these spaces. The two major objectives of the text are to introduce the main ideas of affine and projective spaces and to develop facility in handling transformations and groups of transformations. Since there are many good texts on affine and projective planes, the author has concentrated on the n-dimensional cases.Designed to be used in advanced undergraduate mathematics or physics courses, the book focuses on ""practical geometry,"" emphasi

  2. New concept single screw compressors and their manufacture technology

    Science.gov (United States)

    Feng, Q.; Liu, F.; Chang, L.; Feng, C.; Peng, C.; Xie, J.; van den Broek, M.

    2017-08-01

    Single screw compressors were generally acknowledged as one of the nearly perfect machines by compressor researchers and manufacturers. However the rapid wear of the star-wheel in a single screw compressor during operation is a key reason why it hasn’t previously joined the main current compressors’ market. After more than ten years of effective work, the authors of this paper have proposed a new concept single screw compressor whose mesh-couple profile is enveloped with multi-column. Also a new design method and manufacture equipment for this kind of compressor have been developed and are described in this paper. A lot of prototype tests and a long period of industrial operations under full loading conditions have shown that the mesh-couple profiles of the new concept single compressors have excellent anti-wearness.

  3. Internally Heated Screw Pyrolysis Reactor (IHSPR) heat transfer performance study

    Science.gov (United States)

    Teo, S. H.; Gan, H. L.; Alias, A.; Gan, L. M.

    2018-04-01

    1.5 billion end-of-life tyres (ELT) were discarded globally each year and pyrolysis is considered the best solution to convert the ELT into valuable high energy-density products. Among all pyrolysis technologies, screw reactor is favourable. However, conventional screw reactor risks plugging issue due to its lacklustre heat transfer performance. An internally heated screw pyrolysis reactor (IHSPR) was developed by local renewable energy industry, which serves as the research subject for heat transfer performance study of this particular paper. Zero-load heating test (ZLHT) was first carried out to obtain the operational parameters of the reactor, followed by the one dimensional steady-state heat transfer analysis carried out using SolidWorks Flow Simulation 2016. Experiments with feed rate manipulations and pyrolysis products analyses were conducted last to conclude the study.

  4. A modified transcondylar screw to accommodate anatomical skull base variations.

    Science.gov (United States)

    Ghaly, R F; Lissounov, A

    2017-01-01

    Occipitocervical instability may be attributed to congenital, bony/ligamentous abnormalities, trauma, neoplasm, degenerative bone disease, and failed atlantoaxial fixation. Indications for occipitocervical fixation include the prevention of disabling pain, cranial nerve dysfunction, paralysis, or even sudden death. The screw trajectory for the modified transcondylar screw (mTCS) is optimally planned utilizing a three-dimensional skull reconstructed image. The modified mTCS technique is helpful where there is a loss of bone, such as after prior suboccipital craniotomy and/or an inadequate occipital condyle. The new proposed technique is similar to the classical transcondylar screw placement but follows a deeper course along the bony lip of foramen magnum toward clivus from a dorsolateral approach. The modified mTCS technique allows for direct visualization and, therefore, helps to avoid damage to the hypoglossal nerve and lateral aspect of brain stem.

  5. Bioabsorbable metal screws in traumatology: A promising innovation

    Directory of Open Access Journals (Sweden)

    Roland Biber

    2017-04-01

    Full Text Available MAGNEZIX® CS (Syntellix AG, Hanover, Germany is a bioabsorbable compression screw made of a magnesium alloy (MgYREZr. Currently there are only two clinical studies reporting on a limited number of elective patients who received this screw in a hallux valgus operation. We applied MAGNEZIX® CS for fixation of distal fibular fracture in a trauma patient who had sustained a bimalleolar fracture type AO 44-B2.3. Clinical course was uneventful, fracture healing occurred within three months. Follow-up X-rays showed a radiolucent area around the implant for some months, yet this radiolucent area had disappeared in the 17-months follow-up X-ray. Keywords: Magnesium, Bioabsorbable, Compression screw, Osteosynthesis, Ankle fracture

  6. Update on normal tension glaucoma

    Directory of Open Access Journals (Sweden)

    Jyotiranjan Mallick

    2016-01-01

    Full Text Available Normal tension glaucoma (NTG is labelled when typical glaucomatous disc changes, visual field defects and open anterior chamber angles are associated with intraocular pressure (IOP constantly below 21 mmHg. Chronic low vascular perfusion, Raynaud's phenomenon, migraine, nocturnal systemic hypotension and over-treated systemic hypertension are the main causes of normal tension glaucoma. Goldmann applanation tonometry, gonioscopy, slit lamp biomicroscopy, optical coherence tomography and visual field analysis are the main tools of investigation for the diagnosis of NTG. Management follows the same principles of treatment for other chronic glaucomas: To reduce IOP by a substantial amount, sufficient to prevent disabling visual loss. Treatment is generally aimed to lower IOP by 30% from pre-existing levels to 12-14 mmHg. Betaxolol, brimonidine, prostaglandin analogues, trabeculectomy (in refractory cases, systemic calcium channel blockers (such as nifedipine and 24-hour monitoring of blood pressure are considered in the management of NTG. The present review summarises risk factors, causes, pathogenesis, diagnosis and management of NTG.

  7. Influence of bacterial colonization of the healing screws on peri-implant tissue

    Directory of Open Access Journals (Sweden)

    Simonetta D'Ercole

    2013-06-01

    Conclusion: The healing screws left in situ for a period of 90 days caused a peri-implant inflammation and the presence of periodontal pathogenic bacteria in the peri-implant sulcus, due to the plaque accumulation on screw surfaces.

  8. Hands, screws, triangles and absolute space

    Directory of Open Access Journals (Sweden)

    Filipović Nenad

    2009-01-01

    Full Text Available Hands and other incongruent counterparts are enough argument against relationist, at least Kant thought so, since some of his pre-critical writings. Arguments with incongruent counterparts are elegant and effective and they are quite attracted great attention of numerous authors who have criticized or defended the arguments in different ways. In a meanwhile discussions have gone too far from Kant's original argument, and from the spirit of that time, and received characteristics of modern philosophy and geometry. This text should show that Kant, as well as those who later defended him, did not achieve their goal - no conclusive argument against relationist have been brought by them.

  9. [Development of polyaxial locking plate screw system of sacroiliac joint].

    Science.gov (United States)

    Fan, Weijie; Xie, Xuesong; Zhou, Shuping; Zhang, Yonghu

    2014-09-01

    To develop an instrument for sacroiliac joint fixation with less injury and less complications. Firstly, 18 adult pelvic specimens (8 males and 10 females) were used to measure the anatomical data related to the locking plates and locking screws on the sacrum and ilium, and the polyaxial locking plate screw system of the sacroiliac joint was designed according to the anatomic data. This system was made of medical titanium alloy. Then 4 adult male plevic specimens were harvested and the experiment was divided into 3 groups: group A (normal pelvic), group B (the dislocated sacroiliac joint fixed with sacroiliac screws), and group C (the dislocated sacroiliac joint fixed with polyaxial locking plate screw system). The vertical displacement of sacroiliac joint under the condition of 0-700 N vertical load and the horizontal displacement on angle under the condition of 0-12 N·m torsional load were compared among the 3 groups by using the biological material test system. Finally, the simulated application test was performed on 1 adult male cadaveric specimen to observe soft tissue injury and the position of the locking plate and screw by X-ray films. According to the anatomic data of the sacrum and ilium, the polyaxial locking plate screw system of the sacroiliac joint was designed. The biomechanical results showed that the vertical displacement of the sacroiliac joint under the condition of 0-700 N vertical load in group A was significantly bigger than that in group B and group C (P 0.05). The horizontal displacement on angle under the condition of 0-12 N·m torsional load in group A was significantly less than that in group B and group C (P 0.05). The test of simulating application showed that the specimen suffered less soft tissue injury, and this instrument could be implanted precisely and safely. The polyaxial locking plate screw system of the sacroiliac joint has the advantages of smaller volume and less injury; polyaxial fixation enables flexible adjustment screw

  10. Idealized Compression Ratio for a Screw Briquetting Press

    Directory of Open Access Journals (Sweden)

    Peter Biath

    2012-01-01

    Full Text Available This paper deals with issues in determining the ideal compression ratio for a screw briquetting press. First, the principles of operation and a basic description of the main parts of a screw briquetting press are introduced. The next section describes the pressing space by means of 3D software. The pressing space was created using a Boolean subtract function. The final section of the paper measures the partial volumes of the pressing chamber in CATIA V5 by function of measuring. The measured values are substituted into the formula for the compression ratio, and the resulting evaluations are presented in the diagram in the conclusion of this paper.

  11. Accelerated Tooth Movement with Orthodontic Mini-Screws

    Directory of Open Access Journals (Sweden)

    S. Aksakalli

    2017-01-01

    Full Text Available This case report outlines the possibility of accelerated tooth movement with the combination of microosteoperforation and mini-screws. A 14-year-old male patient presented Class II malocclusion with maxillary incisor protrusion. Upper first premolars were extracted, and after leveling, accelerated canine distalization started. For pre- and postdistalization times, amount of distalization, periodontal health, and root resorption were assessed. Within the limitations of this case report, micro-osteoperforations with mini-screw have a potential for shortening the treatment time.

  12. Screw compressor analysis from a vibration point-of-view

    Science.gov (United States)

    Hübel, D.; Žitek, P.

    2017-09-01

    Vibrations are a very typical feature of all compressors and are given great attention in the industry. The reason for this interest is primarily the negative influence that it can have on both the operating staff and the entire machine's service life. The purpose of this work is to describe the methodology of screw compressor analysis from a vibration point-of-view. This analysis is an essential part of the design of vibro-diagnostics of screw compressors with regard to their service life.

  13. Flexible tension sensor based on poly(l-lactic acid) film with coaxial structure

    Science.gov (United States)

    Yoshida, Mitsunobu; Onishi, Katsuki; Tanimoto, Kazuhiro; Nishikawa, Shigeo

    2017-10-01

    We have developed a tension sensor with a coaxial structure using a narrow slit ribbon made of a uniaxially stretched poly(l-lactic acid) (PLLA) film for application to a wearable device. The tension sensor is produced as follows. We used tinsel wire as the center conductor of the sensor. The tinsel wire consists of a yarn of synthetic fibers arranged at the center, with a spirally wound rolled copper foil ribbon on the side surface. Next, slit ribbons obtained from a uniaxially oriented film of PLLA are wound helically on the side surface of the center conductor in the direction of a left-handed screw, at an angle of 45° to the central axis. The rolled copper foil is used as an outer conductor and covers the yarn without a gap. The prototype of the fabricated tension sensor has good flexibility, since the sensor is in the form of a filament and consists of a highly flexible material. For the 1 mm tension sensor, it was found that for a tension of 1 N, a charge of 14 pC was output. It was also found that the sensor maintained its room-temperature sensitivity up to 60 °C. Compared with an existing coaxial line sensor using poly(vinylidene fluoride) (PVDF), the sensor using PLLA does not exhibit pyroelectricity, meaning that no undesirable voltage is generated when in contact with body heat, which is a significant advantage as wearable sensors. The result has demonstrated the potential application of the PLLA film to wearable devices for detecting heartbeat and respiration.

  14. The study and design of tension controller

    Science.gov (United States)

    Jun, G.; Lamei, X.

    2018-02-01

    Tension control is a wide used technology in areas such as textiles, paper and plastic films. In this article, the tension control system release and winding process is analyzed and the mathematical model of tension control system is established, and a high performance tension controller is designed. In hardware design, STM32F130 single chip microcomputer is used as the control core, which has the characteristics of fast running speed and rich peripheral features. In software design, μC/OS-II operating system is introduced to improve the efficiency of single chip microcomputer, and enhance the independence of each module, and make development and maintenance more convenient. The taper tension control is adopted in the winding part, which can effectively solve the problem of rolling shrinkage. The results show that the tension controller has the characteristics of simple structure, easy operation and stable performance.

  15. Soft-tissue tension total knee arthroplasty.

    Science.gov (United States)

    Asano, Hiroshi; Hoshino, Akiho; Wilton, Tim J

    2004-08-01

    It is far from clear how best to define the proper strength of soft-tissue tensioning in total knee arthroplasty (TKA). We attached a torque driver to the Monogram balancer/tensor device and measured soft-tissue tension in full extension and 90 degrees flexion during TKA. In our surgical procedure, when we felt proper soft-tissue tension was being applied, the mean distraction force was noted to be 126N in extension and 121N in flexion. There was no significant correlation between soft-tissue tension and the postoperative flexion angle finally achieved. To the best of our knowledge, this is the first study to assess the actual distraction forces in relation to soft-tissue tension in TKA. Further study may reveal the most appropriate forces to achieve proper soft-tissue tension in the wide variety of circumstances presenting at knee arthroplasty.

  16. Stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture: a comparative finite element study.

    Science.gov (United States)

    Huang, Xiaowei; Zhi, Zhongzheng; Yu, Baoqing; Chen, Fancheng

    2015-11-25

    The purpose of this study is to compare the stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture. A three-dimensional (3D) finite element model of the medial tibial plateau fracture (Schatzker type IV fracture) was created. An axial force of 2500 N with a distribution of 60% to the medial compartment was applied to simulate the axial compressive load on an adult knee during single-limb stance. The equivalent von Mises stress, displacement of the model relative to the distal tibia, and displacement of the implants were used as the output measures. The mean stress value of the plate-screw fixation system was 18.78 MPa, which was significantly (P stress value of the triangular fragment in the plate-screw fixation system model was 42.04 MPa, which was higher than that in the screw fixation model (24.18 MPa). But the mean stress of the triangular fractured fragment in the screw fixation model was significantly higher in terms of equivalent von Mises stress (EVMS), x-axis, and z-axis (P < 0.001). This study demonstrated that the load transmission mechanism between plate-screw fixation system and screw fixation system was different and the stability provided by the plate-screw fixation system was superior to the screw fixation system.

  17. The effect of different screw-rod design on the anti-rotational torque: a biomechanical comparison of three conventional screw-rod constructs.

    Science.gov (United States)

    Huang, Zifang; Wang, Chongwen; Fan, Hengwei; Sui, Wenyuan; Li, Xueshi; Wang, Qifei; Yang, Junlin

    2017-07-28

    Screw-rod constructs have been widely used to correct spinal deformities, but the effects of different screw-rod systems on anti-rotational torque have not been determined. This study aimed to analyze the biomechanical effect of different rod-screw constructs on anti-rotational torque. Three conventional spinal screw-rod systems (Legacy, RF-F-10 and USSII) were used to test the anti-rotational torque in the material test machine. ANOVA was performed to evaluate the anti-rotational capacity of different pedicle screws-rod constructs. The anti-rotational torque of Legacy group, RF-F-10 group and USSII group were 12.3 ± 1.9 Nm, 6.8 ± 0.4 Nm, and 3.9 ± 0.8 Nm, with a P value lower than 0.05. This results indicated that the Legacy screws-rod construct could provide a highest anti-rotation capacity, which is 68% and 210% greater than RF-F-10 screw-rod construct and USSII screw-rod respectively. The anti-rotational torque may be mainly affected by screw cap and groove design. Our result showed the anti-rotational torque are: Legacy system > RF-F-10 system > USSII system, suggesting that appropriate rod-screw constructs selection in surgery may be vital for anti-rotational torque improvement and preventing derotation correction loss.

  18. Towards relativistic quantum geometry

    Energy Technology Data Exchange (ETDEWEB)

    Ridao, Luis Santiago [Instituto de Investigaciones Físicas de Mar del Plata (IFIMAR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata (Argentina); Bellini, Mauricio, E-mail: mbellini@mdp.edu.ar [Departamento de Física, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Funes 3350, C.P. 7600, Mar del Plata (Argentina); Instituto de Investigaciones Físicas de Mar del Plata (IFIMAR), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Mar del Plata (Argentina)

    2015-12-17

    We obtain a gauge-invariant relativistic quantum geometry by using a Weylian-like manifold with a geometric scalar field which provides a gauge-invariant relativistic quantum theory in which the algebra of the Weylian-like field depends on observers. An example for a Reissner–Nordström black-hole is studied.

  19. Multiplicity in difference geometry

    OpenAIRE

    Tomasic, Ivan

    2011-01-01

    We prove a first principle of preservation of multiplicity in difference geometry, paving the way for the development of a more general intersection theory. In particular, the fibres of a \\sigma-finite morphism between difference curves are all of the same size, when counted with correct multiplicities.

  20. Spacetime and Euclidean geometry

    Science.gov (United States)

    Brill, Dieter; Jacobson, Ted

    2006-04-01

    Using only the principle of relativity and Euclidean geometry we show in this pedagogical article that the square of proper time or length in a two-dimensional spacetime diagram is proportional to the Euclidean area of the corresponding causal domain. We use this relation to derive the Minkowski line element by two geometric proofs of the spacetime Pythagoras theorem.

  1. Physics and geometry

    International Nuclear Information System (INIS)

    Konopleva, N.P.

    2009-01-01

    The basic ideas of description methods of physical fields and elementary particle interactions are discussed. One of such ideas is the conception of space-time geometry. In this connection experimental measurement methods are analyzed. It is shown that measure procedures are the origin of geometrical axioms. The connection between space symmetry properties and the conservation laws is considered

  2. Origami, Geometry and Art

    Science.gov (United States)

    Wares, Arsalan; Elstak, Iwan

    2017-01-01

    The purpose of this paper is to describe the mathematics that emanates from the construction of an origami box. We first construct a simple origami box from a rectangular sheet and then discuss some of the mathematical questions that arise in the context of geometry and algebra. The activity can be used as a context for illustrating how algebra…

  3. Gravity is Geometry.

    Science.gov (United States)

    MacKeown, P. K.

    1984-01-01

    Clarifies two concepts of gravity--those of a fictitious force and those of how space and time may have geometry. Reviews the position of Newton's theory of gravity in the context of special relativity and considers why gravity (as distinct from electromagnetics) lends itself to Einstein's revolutionary interpretation. (JN)

  4. Towards a Nano Geometry?

    DEFF Research Database (Denmark)

    Booss-Bavnbek, Bernhelm

    2011-01-01

    This paper applies I.M. Gelfand's distinction between adequate and non-adequate use of mathematical language in different contexts to the newly opened window of model-based measurements of intracellular dynamics. The specifics of geometry and dynamics on the mesoscale of cell physiology are elabo...

  5. Diophantine geometry an introduction

    CERN Document Server

    Hindry, Marc

    2000-01-01

    This is an introduction to diophantine geometry at the advanced graduate level. The book contains a proof of the Mordell conjecture which will make it quite attractive to graduate students and professional mathematicians. In each part of the book, the reader will find numerous exercises.

  6. Sliding vane geometry turbines

    Science.gov (United States)

    Sun, Harold Huimin; Zhang, Jizhong; Hu, Liangjun; Hanna, Dave R

    2014-12-30

    Various systems and methods are described for a variable geometry turbine. In one example, a turbine nozzle comprises a central axis and a nozzle vane. The nozzle vane includes a stationary vane and a sliding vane. The sliding vane is positioned to slide in a direction substantially tangent to an inner circumference of the turbine nozzle and in contact with the stationary vane.

  7. History of analytic geometry

    CERN Document Server

    Boyer, Carl B

    2012-01-01

    Designed as an integrated survey of the development of analytic geometry, this study presents the concepts and contributions from before the Alexandrian Age through the eras of the great French mathematicians Fermat and Descartes, and on through Newton and Euler to the "Golden Age," from 1789 to 1850.

  8. Non-euclidean geometry

    CERN Document Server

    Coxeter, HSM

    1965-01-01

    This textbook introduces non-Euclidean geometry, and the third edition adds a new chapter, including a description of the two families of 'mid-lines' between two given lines and an elementary derivation of the basic formulae of spherical trigonometry and hyperbolic trigonometry, and other new material.

  9. Topics in Riemannian geometry

    International Nuclear Information System (INIS)

    Ezin, J.P.

    1988-08-01

    The lectures given at the ''5th Symposium of Mathematics in Abidjan: Differential Geometry and Mechanics'' are presented. They are divided into four chapters: Riemannian metric on a differential manifold, curvature tensor fields on a Riemannian manifold, some classical functionals on Riemannian manifolds and questions. 11 refs

  10. Geometry Euclid and beyond

    CERN Document Server

    Hartshorne, Robin

    2000-01-01

    In recent years, I have been teaching a junior-senior-level course on the classi­ cal geometries. This book has grown out of that teaching experience. I assume only high-school geometry and some abstract algebra. The course begins in Chapter 1 with a critical examination of Euclid's Elements. Students are expected to read concurrently Books I-IV of Euclid's text, which must be obtained sepa­ rately. The remainder of the book is an exploration of questions that arise natu­ rally from this reading, together with their modern answers. To shore up the foundations we use Hilbert's axioms. The Cartesian plane over a field provides an analytic model of the theory, and conversely, we see that one can introduce coordinates into an abstract geometry. The theory of area is analyzed by cutting figures into triangles. The algebra of field extensions provides a method for deciding which geometrical constructions are possible. The investigation of the parallel postulate leads to the various non-Euclidean geometries. And ...

  11. The Equilibrium Spreading Tension of Pulmonary Surfactant

    OpenAIRE

    Dagan, Maayan P.; Hall, Stephen B.

    2015-01-01

    Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γe) with the bulk phase from which they form. For individual phospholipids, γe is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γe therefo...

  12. Comparison of the Mechanical Characteristics of a Universal Small Biplane Plating Technique Without Compression Screw and Single Anatomic Plate With Compression Screw.

    Science.gov (United States)

    Dayton, Paul; Ferguson, Joe; Hatch, Daniel; Santrock, Robert; Scanlan, Sean; Smith, Bret

    2016-01-01

    To better understand the mechanical characteristics of biplane locked plating in small bone fixation, the present study compared the stability under cyclic cantilever loading of a 2-plate locked biplane (BPP) construct without interfragmentary compression with that of a single-plate locked construct with an additional interfragmentary screw (SPS) using surrogate bone models simulating Lapidus arthrodesis. In static ultimate plantar bending, the BPP construct failed at significantly greater load than did the SPS construct (556.2 ± 37.1 N versus 241.6 ± 6.3 N, p = .007). For cyclic failure testing in plantar bending at a 180-N starting load, the BPP construct failed at a significantly greater number of cycles (158,322 ± 50,609 versus 13,718 ± 10,471 cycles) and failure load (242.5 ± 25.0 N versus 180.0 ± 0.0 N) than the SPS construct (p = .002). For cyclic failure testing in plantar bending at a 120-N starting load, the results were not significantly different between the BPP and SPS constructs for the number of cycles (207,646 ± 45,253 versus 159,334 ± 69,430) or failure load (205.0 ± 22.4 N versus 185.0 ± 33.5 N; p = .300). For cyclic testing with 90° offset loading (i.e., medial to lateral bending) at a 120-N starting load, all 5 BPP constructs (tension side) and 2 of the 5 SPS constructs reached 250,000 cycles without failure. Overall, the present study found the BPP construct to have superior or equivalent stability in multiplanar orientations of force application in both static and fatigue testing. Thus, the concept of biplane locked plating, using 2 low profile plates and unicortical screw insertion, shows promise in small bone fixation, because it provides consistent stability in multiplanar orientations, making it universally adaptable to many clinical situations. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  13. Posterior cervical spine arthrodesis with laminar screws. A report of two cases

    International Nuclear Information System (INIS)

    Nakanishi, Kazuo; Tanaka, Masato; Sugimoto, Yoshihisa; Ozaki, Toshifumi

    2007-01-01

    We performed fixation using laminar screws in 2 patients in whom lateral mass screws, pedicle screws or transarticular screws could not be inserted. One was a 56-year-old woman who had anterior atlantoaxial subluxation (AAS). When a guide wire was inserted using an imaging guide, the hole bled massively. We thought the re-insertion of a guide wire or screw would thus increase the risk of vascular injury, so we used laminar screws. The other case was an 18-year-old man who had a hangman fracture. Preoperative magnetic resonance angiography showed occlusion of the left vertebral artery. A laminar screw was inserted into the patent side (i.e., the right side of C2). Cervical pedicle screws are the most biomechanically stable screws. However, their use carries a high risk of neurovascular complications during screw insertion, because the cervical pedicle is small and is adjacent laterally to the vertebral artery, medially to the spinal cord, and vertically to the nerve roots. Lateral mass screws are also reported to involve a risk of neurovascular injuries. The laminar screw method was thus thought to be useful, since arterial injuries could thus be avoided and it could also be used as a salvage modality for the previous misinsertion. (author)

  14. The best location for proximal locking screw for femur interlocking nailing: A biomechanical study

    Directory of Open Access Journals (Sweden)

    Ahmet A Karaarslan

    2016-01-01

    Conclusion: According to our findings, there is twice as much difference in locking screw bending resistance between these two application levels. To avoid proximal locking screw deformation, locking screws should be placed in the level of the lesser trochanter in nailing of 1/3 middle and distal femur fractures.

  15. Actin filaments as tension sensors.

    Science.gov (United States)

    Galkin, Vitold E; Orlova, Albina; Egelman, Edward H

    2012-02-07

    The field of mechanobiology has witnessed an explosive growth over the past several years as interest has greatly increased in understanding how mechanical forces are transduced by cells and how cells migrate, adhere and generate traction. Actin, a highly abundant and anomalously conserved protein, plays a large role in forming the dynamic cytoskeleton that is so essential for cell form, motility and mechanosensitivity. While the actin filament (F-actin) has been viewed as dynamic in terms of polymerization and depolymerization, new results suggest that F-actin itself may function as a highly dynamic tension sensor. This property may help explain the unusual conservation of actin's sequence, as well as shed further light on actin's essential role in structures from sarcomeres to stress fibers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  16. Microfluidic step-emulsification in axisymmetric geometry.

    Science.gov (United States)

    Chakraborty, I; Ricouvier, J; Yazhgur, P; Tabeling, P; Leshansky, A M

    2017-10-25

    Biphasic step-emulsification (Z. Li et al., Lab Chip, 2015, 15, 1023) is a promising microfluidic technique for high-throughput production of μm and sub-μm highly monodisperse droplets. The step-emulsifier consists of a shallow (Hele-Shaw) microchannel operating with two co-flowing immiscible liquids and an abrupt expansion (i.e., step) to a deep and wide reservoir. Under certain conditions the confined stream of the disperse phase, engulfed by the co-flowing continuous phase, breaks into small highly monodisperse droplets at the step. Theoretical investigation of the corresponding hydrodynamics is complicated due to the complex geometry of the planar device, calling for numerical approaches. However, direct numerical simulations of the three dimensional surface-tension-dominated biphasic flows in confined geometries are computationally expensive. In the present paper we study a model problem of axisymmetric step-emulsification. This setup consists of a stable core-annular biphasic flow in a cylindrical capillary tube connected co-axially to a reservoir tube of a larger diameter through a sudden expansion mimicking the edge of the planar step-emulsifier. We demonstrate that the axisymmetric setup exhibits similar regimes of droplet generation to the planar device. A detailed parametric study of the underlying hydrodynamics is feasible via inexpensive (two dimensional) simulations owing to the axial symmetry. The phase diagram quantifying the different regimes of droplet generation in terms of governing dimensionless parameters is presented. We show that in qualitative agreement with experiments in planar devices, the size of the droplets generated in the step-emulsification regime is independent of the capillary number and almost insensitive to the viscosity ratio. These findings confirm that the step-emulsification regime is solely controlled by surface tension. The numerical predictions are in excellent agreement with in-house experiments with the axisymmetric

  17. Biomechanical evaluation of a second generation headless compression screw for ankle arthrodesis in a cadaver model.

    Science.gov (United States)

    Somberg, Andrew Max; Whiteside, William K; Nilssen, Erik; Murawski, Daniel; Liu, Wei

    2016-03-01

    Many types of screws, plates, and strut grafts have been utilized for ankle arthrodesis. Biomechanical testing has shown that these constructs can have variable stiffness. More recently, headless compression screws have emerged as an evolving method of achieving compression in various applications but there is limited literature regarding ankle arthrodesis. The aim of this study was to determine the biomechanical stability provided by a second generation fully threaded headless compression screw compared to a standard headed, partially threaded cancellous screw in a cadaveric ankle arthrodesis model. Twenty fresh frozen human cadaver specimens were subjected to simulated ankle arthrodesis with either three standard cancellous-bone screws (InFix 7.3mm) or with three headless compression screws (Acumed Acutrak 2 7.5mm). The specimens were subjected to cyclic loading and unloading at a rate of 1Hz, compression of 525 Newtons (N) and distraction of 20N for a total of 500 cycles using an electromechanical load frame (Instron). The amount of maximum distraction was recorded as well as the amount of motion that occurred through 1, 10, 50, 100, and 500 cycles. No significant difference (p=0.412) was seen in the amount of distraction that occurred across the fusion site for either screw. The average maximum distraction after 500 cycles was 201.9μm for the Acutrak 2 screw and 235.4μm for the InFix screw. No difference was seen throughout each cycle over time for the Acutrak 2 screw (p-value=0.988) or the InFix screw (p-value=0.991). Both the traditional InFix type screw and the second generation Acumed Acutrak headless compression screws provide adequate fixation during ankle arthrodesis under submaximal loads. There is no demonstrable difference between traditional cannulated partially threaded screws and headless compression screws studied in this model. Copyright © 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

  18. Enhancement of Orthodontic Anchor Screw Stability Under Immediate Loading by Ultraviolet Photofunctionalization Technology.

    Science.gov (United States)

    Takahashi, Maiko; Motoyoshi, Mitsuru; Inaba, Mizuki; Hagiwara, Yoshiyuki; Shimizu, Noriyoshi

    Ultraviolet (UV)-mediated photofunctionalization technology is intended to enhance the osseointegration capability of titanium implants. There are concerns about orthodontic anchor screws loosening under immediate loading protocols in adolescent orthodontic treatment. The purpose of this in vivo study was to evaluate the effects of photofunctionalization on the intrabony stability of orthodontic titanium anchor screws and bone-anchor screw contact under immediate loading in growing rats. Custom-made titanium anchor screws (1.4 mm in diameter and 4.0 mm in length) with or without photofunctionalization pretreatment were placed on the proximal epiphysis of the tibial bone in 6-week-old male Sprague-Dawley rats and were loaded immediately after placement. After 2 weeks of loading, the stability of the anchor screws was evaluated using a Periotest device, and the bone-anchor screw contact ratio (BSC) was assessed by a histomorphometric analysis using field-emission scanning electron microscopy. In the unloaded group, Periotest values (PTVs) were ~25 for UV-untreated screws and 13 for UVtreated screws (P < .01), while in the immediate-loading group, PTVs were 28 for UV-untreated screws and 16 for UV-treated screws (P < .05). Significantly less screw mobility was observed in both UV-treated groups regardless of the loading protocol. The BSC was increased ~1.8 fold for UV-treated screws, compared with UV-untreated screws, regardless of the loading protocol. Photofunctionalization enhanced the intrabony stability of orthodontic anchor screws under immediate loading in growing rats by increasing bone-anchor screw contact.

  19. Direct access to polyisocyanide screw sense using vibrational circular dichroism

    NARCIS (Netherlands)

    Schwartz, E.; Domingos, S.R.; Vdovin, A.; Koepf, M.; Buma, W.J.; Cornelissen, J.J.L.M.; Rowan, A.E.; Nolte, R.J.M.; Woutersen, S.

    2010-01-01

    We show that the screw sense of polyisocyanide helices can be determined in a simple manner from the vibrational circular dichroism (VCD) of their CN-stretching mode. The relation between VCD and molecular structure is obtained using the coupled-oscillator approximation. It is shown that since the

  20. Residence time distribution in twin-screw extruders

    NARCIS (Netherlands)

    Jager, T.

    1992-01-01

    For the twin-screw extruders used in the food industry at short time high temperature processes the knowledge of their reactor properties is incomplete for mass- and heat flow. Therefore each process change such as: scale-up or product development requires a great number of measurements

  1. Kinematics and Dynamic Evaluation of the Screw Conveyor of a ...

    African Journals Online (AJOL)

    An analysis of the vortex motion in a horizontal screw conveyor of a Cassava Centrifuge Dewatering Machine is presented. It is shown that the vortex motion is characterised by the tangential component of the absolute grain velocity being constant with the radial position of a point on the blade. On this basis, an expression ...

  2. Kinematics of a Hybrid Manipulator by Means of Screw Theory

    International Nuclear Information System (INIS)

    Gallardo-Alvarado, J

    2005-01-01

    In this work the kinematics of a hybrid manipulator, namely a fully parallel-serial manipulator, with a particular topology is approached by means of the theory of screws. Given the length of the six independent limbs, the forward position analysis of the mechanism under study, indeed the computation of the resulting pose, position and orientation, of the end-platform with respect to the fixed platform, is carried out in closed-form solution. Therefore conveniently this initial analysis avoids the use of a numerical technique such as the Newton-Raphson method. Writing in screw form the reduced acceleration state of the translational platform, with respect to the fixed platform, a simple expression for the computation of the acceleration of the translational platform is derived by taking advantage of the properties of reciprocal screws, via the Klein form, a bilinear symmetric form of the Lie algebra e(3). Following a similar procedure, a simple expression for the computation of the angular acceleration of the end-platform, with respect to the translational platform, is easily derived. Naturally, as an intermediate step, this contribution also provides the forward and inverse velocity analyses of the chosen parallel-serial manipulator. Finally, in order to prove the versatility of the expressions obtained via screw theory for solving the kinematics, up to the acceleration analysis, of the proposed spatial mechanism, a numerical example is solved with the help of commercial computer codes

  3. Sacroiliac screw fixation: A mini review of surgical technique

    Directory of Open Access Journals (Sweden)

    Hernando Raphael Alvis-Miranda

    2014-01-01

    Full Text Available The sacral percutaneous fixation has many advantages but can be associated with a significant exposure to X-ray radiation. Currently, sacroiliac screw fixation represents the only minimally invasive technique to stabilize the posterior pelvic ring. It is a technique that should be used by experienced surgeons. We present a practical review of important aspects of this technique.

  4. Biomechanical analysis of titanium fixation plates and screws in ...

    African Journals Online (AJOL)

    Conclusions: It was concluded that the use of double 4-hole straight plates provided the sufficient stability on the osteotomy site when compared with the other rigid fixation methods used in this study. Key words: Bone plates, bone screws, finite element analysis, jaw fixation techniques, mandible, mandibular osteotomy ...

  5. Resorbable screws for fixation of autologous bone grafts

    NARCIS (Netherlands)

    Raghoebar, GM; Liem, RSB; Bos, RRM; van der Wal, JE; Vissink, A

    The aim of this study was to evaluate the suitability of resorbable screws made of poly (D,L-lactide) acid (PDLLA) for fixation of autologous bone grafts related to graft regeneration and osseointegration of dental implants. In eight edentulous patients suffering from insufficient retention of their

  6. Modeling The Effect Of Extruder Screw Speed On The Mechanical ...

    African Journals Online (AJOL)

    Modeling The Effect Of Extruder Screw Speed On The Mechanical Properties Of High Density Polyethylene Blown Film. ... Journal of Modeling, Design and Management of Engineering Systems ... Two sets of multiple linear regression models were developed to predict impact failure weight and tenacity respectively.

  7. Multivariate calculus and geometry

    CERN Document Server

    Dineen, Seán

    2014-01-01

    Multivariate calculus can be understood best by combining geometric insight, intuitive arguments, detailed explanations and mathematical reasoning. This textbook has successfully followed this programme. It additionally provides a solid description of the basic concepts, via familiar examples, which are then tested in technically demanding situations. In this new edition the introductory chapter and two of the chapters on the geometry of surfaces have been revised. Some exercises have been replaced and others provided with expanded solutions. Familiarity with partial derivatives and a course in linear algebra are essential prerequisites for readers of this book. Multivariate Calculus and Geometry is aimed primarily at higher level undergraduates in the mathematical sciences. The inclusion of many practical examples involving problems of several variables will appeal to mathematics, science and engineering students.

  8. Transformational plane geometry

    CERN Document Server

    Umble, Ronald N

    2014-01-01

    Axioms of Euclidean Plane Geometry The Existence and Incidence Postulates The Distance and Ruler Postulates The Plane Separation Postulate The Protractor Postulate The Side-Angle-Side Postulate and the Euclidean Parallel Postulate Theorems of Euclidean Plane Geometry The Exterior Angle Theorem Triangle Congruence Theorems The Alternate Interior Angles Theorem and the Angle Sum Theorem Similar Triangles Introduction to Transformations, Isometries, and Similarities Transformations Isometries and SimilaritiesAppendix: Proof of Surjectivity Translations, Rotations, and Reflections Translations Rotations Reflections Appendix: Geometer's Sketchpad Commands Required by Exploratory Activities Compositions of Translations, Rotations, and Reflections The Three Points Theorem Rotations as Compositions of Two Reflections Translations as Compositions of Two Halfturns or Two Reflections The Angle Addition Theorem Glide Reflections Classification of Isometries The Fundamental Theorem and Congruence Classification of Isometr...

  9. Multilevel geometry optimization

    Science.gov (United States)

    Rodgers, Jocelyn M.; Fast, Patton L.; Truhlar, Donald G.

    2000-02-01

    Geometry optimization has been carried out for three test molecules using six multilevel electronic structure methods, in particular Gaussian-2, Gaussian-3, multicoefficient G2, multicoefficient G3, and two multicoefficient correlation methods based on correlation-consistent basis sets. In the Gaussian-2 and Gaussian-3 methods, various levels are added and subtracted with unit coefficients, whereas the multicoefficient Gaussian-x methods involve noninteger parameters as coefficients. The multilevel optimizations drop the average error in the geometry (averaged over the 18 cases) by a factor of about two when compared to the single most expensive component of a given multilevel calculation, and in all 18 cases the accuracy of the atomization energy for the three test molecules improves; with an average improvement of 16.7 kcal/mol.

  10. Multilevel geometry optimization

    Energy Technology Data Exchange (ETDEWEB)

    Rodgers, Jocelyn M. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States); Fast, Patton L. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States); Truhlar, Donald G. [Department of Chemistry and Supercomputer Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431 (United States)

    2000-02-15

    Geometry optimization has been carried out for three test molecules using six multilevel electronic structure methods, in particular Gaussian-2, Gaussian-3, multicoefficient G2, multicoefficient G3, and two multicoefficient correlation methods based on correlation-consistent basis sets. In the Gaussian-2 and Gaussian-3 methods, various levels are added and subtracted with unit coefficients, whereas the multicoefficient Gaussian-x methods involve noninteger parameters as coefficients. The multilevel optimizations drop the average error in the geometry (averaged over the 18 cases) by a factor of about two when compared to the single most expensive component of a given multilevel calculation, and in all 18 cases the accuracy of the atomization energy for the three test molecules improves; with an average improvement of 16.7 kcal/mol. (c) 2000 American Institute of Physics.

  11. Geometry and Destiny

    OpenAIRE

    Krauss, Lawrence M.; Turner, Michael S.

    1999-01-01

    The recognition that the cosmological constant may be non-zero forces us to re-evaluate standard notions about the connection between geometry and the fate of our Universe. An open Universe can recollapse, and a closed Universe can expand forever. As a corollary, we point out that there is no set of cosmological observations we can perform that will unambiguously allow us to determine what the ultimate destiny of the Universe will be.

  12. Complex geometries in wood

    DEFF Research Database (Denmark)

    Tamke, Martin; Ramsgaard Thomsen, Mette; Riiber Nielsen, Jacob

    2009-01-01

    The versatility of wood constructions and traditional wood joints for the production of non standard elements was in focus of a design based research. Herein we established a seamless process from digital design to fabrication. A first research phase centered on the development of a robust...... parametric model and a generic design language a later explored the possibilities to construct complex shaped geometries with self registering joints on modern wood crafting machines. The research was carried out as collaboration with industrial partners....

  13. Electroweak vacuum geometry

    International Nuclear Information System (INIS)

    Lepora, N.; Kibble, T.

    1999-01-01

    We analyse symmetry breaking in the Weinberg-Salam model paying particular attention to the underlying geometry of the theory. In this context we find two natural metrics upon the vacuum manifold: an isotropic metric associated with the scalar sector, and a squashed metric associated with the gauge sector. Physically, the interplay between these metrics gives rise to many of the non-perturbative features of Weinberg-Salam theory. (author)

  14. Comparison of accuracy of lag screw placement in cephalocondylic nails and sliding hip screw plate fixation for extracapsular fractures of the neck of femur

    OpenAIRE

    Shyam Kumar, A. J.; Parmar, V.; Bankart, J.; Williams, S. C.; Harper, W. M.

    2006-01-01

    This study compared the accuracy of lag screw placement between extracapsular femoral fractures fixed with sliding hip screw plate systems and those fixed with cephalocondylic nails. It involved 75 retrospective radiographs of fractures fixed with either a cephalocondylic nail (32) or a sliding hip screw plate system (43). Postoperative anteroposterior and lateral radiographs of the hip were scanned using a digital X-ray scanner and measured using computer software. Measurements were conducte...

  15. Comparative effect of implant-abutment connections, abutment angulations, and screw lengths on preloaded abutment screw using three-dimensional finite element analysis: An in vitro study

    OpenAIRE

    Krishna Chaitanya Kanneganti; Dileep Nag Vinnakota; Srinivas Rao Pottem; Mahesh Pulagam

    2018-01-01

    Purpose: The purpose of this study is to compare the effect of implant-abutment connections, abutment angulations, and screw lengths on screw loosening (SL) of preloaded abutment using three dimensional (3D) finite element analysis. Materials and Methods: 3D models of implants (conical connection with hex/trilobed connections), abutments (straight/angulated), abutment screws (short/long), and crown and bone were designed using software Parametric Technology Corporation Creo and assembled t...

  16. Continuously graded extruded polymer composites for energetic applications fabricated using twin-screw extrusion processing technology

    Science.gov (United States)

    Gallant, Frederick M.

    A novel method of fabricating functionally graded extruded composite materials is proposed for propellant applications using the technology of continuous processing with a Twin-Screw Extruder. The method is applied to the manufacturing of grains for solid rocket motors in an end-burning configuration with an axial gradient in ammonium perchlorate volume fraction and relative coarse/fine particle size distributions. The fabrication of functionally graded extruded polymer composites with either inert or energetic ingredients has yet to be investigated. The lack of knowledge concerning the processing of these novel materials has necessitated that a number of research issues be addressed. Of primary concern is characterizing and modeling the relationship between the extruder screw geometry, transient processing conditions, and the gradient architecture that evolves in the extruder. Recent interpretations of the Residence Time Distributions (RTDs) and Residence Volume Distributions (RVDs) for polymer composites in the TSE are used to develop new process models for predicting gradient architectures in the direction of extrusion. An approach is developed for characterizing the sections of the extrudate using optical, mechanical, and compositional analysis to determine the gradient architectures. The effects of processing on the burning rate properties of extruded energetic polymer composites are characterized for homogeneous formulations over a range of compositions to determine realistic gradient architectures for solid rocket motor applications. The new process models and burning rate properties that have been characterized in this research effort will be the basis for an inverse design procedure that is capable of determining gradient architectures for grains in solid rocket motors that possess tailored burning rate distributions that conform to user-defined performance specifications.

  17. W-geometry

    International Nuclear Information System (INIS)

    Hull, C.M.

    1993-01-01

    The geometric structure of theories with gauge fields of spins two and higher should involve a higher spin generalisation of Riemannian geometry. Such geometries are discussed and the case of W ∝ -gravity is analysed in detail. While the gauge group for gravity in d dimensions is the diffeomorphism group of the space-time, the gauge group for a certain W-gravity theory (which is W ∝ -gravity in the case d=2) is the group of symplectic diffeomorphisms of the cotangent bundle of the space-time. Gauge transformations for W-gravity gauge fields are given by requiring the invariance of a generalised line element. Densities exist and can be constructed from the line element (generalising √detg μν ) only if d=1 or d=2, so that only for d=1,2 can actions be constructed. These two cases and the corresponding W-gravity actions are considered in detail. In d=2, the gauge group is effectively only a subgroup of the symplectic diffeomorphisms group. Some of the constraints that arise for d=2 are similar to equations arising in the study of self-dual four-dimensional geometries and can be analysed using twistor methods, allowing contact to be made with other formulations of W-gravity. While the twistor transform for self-dual spaces with one Killing vector reduces to a Legendre transform, that for two Killing vectors gives a generalisation of the Legendre transform. (orig.)

  18. Integral geometry and valuations

    CERN Document Server

    Solanes, Gil

    2014-01-01

    Valuations are finitely additive functionals on the space of convex bodies. Their study has become a central subject in convexity theory, with fundamental applications to integral geometry. In the last years there has been significant progress in the theory of valuations, which in turn has led to important achievements in integral geometry. This book originated from two courses delivered by the authors at the CRM and provides a self-contained introduction to these topics, covering most of the recent advances. The first part, by Semyon Alesker, is devoted to the theory of convex valuations, with emphasis on the latest developments. A special focus is put on the new fundamental structures of the space of valuations discovered after Alesker's irreducibility theorem. Moreover, the author describes the newly developed theory of valuations on manifolds. In the second part, Joseph H. G. Fu gives a modern introduction to integral geometry in the sense of Blaschke and Santaló, based on the notions and tools presented...

  19. CBM RICH geometry optimization

    Energy Technology Data Exchange (ETDEWEB)

    Mahmoud, Tariq; Hoehne, Claudia [II. Physikalisches Institut, Giessen Univ. (Germany); Collaboration: CBM-Collaboration

    2016-07-01

    The Compressed Baryonic Matter (CBM) experiment at the future FAIR complex will investigate the phase diagram of strongly interacting matter at high baryon density and moderate temperatures in A+A collisions from 2-11 AGeV (SIS100) beam energy. The main electron identification detector in the CBM experiment will be a RICH detector with a CO{sub 2} gaseous-radiator, focusing spherical glass mirrors, and MAPMT photo-detectors being placed on a PMT-plane. The RICH detector is located directly behind the CBM dipole magnet. As the final magnet geometry is now available, some changes in the RICH geometry become necessary. In order to guarantee a magnetic field of 1 mT at maximum in the PMT plane for effective operation of the MAPMTs, two measures have to be taken: The PMT plane is moved outwards of the stray field by tilting the mirrors by 10 degrees and shielding boxes have been designed. In this contribution the results of the geometry optimization procedure are presented.

  20. Comparison of cannulated screw and dynamic hip screw for the treatment of femoral neck fractures

    Directory of Open Access Journals (Sweden)

    Mehmet Gem

    2015-09-01

    Full Text Available Objective: We aimed to compare the results of surgeries for intracapsular femoral neck fractures with cannulated screws(CS and dynamic hip screw(DHS, due to lack of evidence which implant for internal fixation of femoral neck fractures is better . Methods: In our clinic between September 2005 and November 2009, 38 patients were operated with intracapsular transcervical fracture of collum femoris between17 to 65 years of age. Eighteen were operated with DHS(47.4% and 20 were operated with CS fixation(52.6%. Results: 16 patients (42.1% were female and 22 (57.9% were male and the mean age was 37.13 (17-65 years. The mean duration of follow-up was 18.05 (2-57 months. 26 patients were operated in 1st -3rd day (68.4%, 9 patients were operated in 4 to 7 day (23.7%, 3 patients were operated in after 7th day (7.9%. In the DHS group, 9 (50% patients had avascular necrosis (AVN, 6 (33.3% patients had implant failure, 3 (16.7% patients had delayed union, 5 (27.8% patients had nonunion, 1 (5.6% patient had infection, and 1 (5.6% patient had myositis ossificans. According to the criteria of Salvati Wilson hip joint assessment, in the DHS group 8 patients (44.4% were very good, 5 patients (27.8% were good, 5 patients (27.8% were moderate. Salvati score was evaluated as average of 28 points (16-40. İn the CS group, 8 (40% patients had AVN, 1 (5% had delayed union, 3 (15% of the cases had nonunion and 1 (5% patients infection was detected. According to the criteria of the Salvati-Wilson, in the CS group13 (65% of them are very good, 5 (25% were good, 2 (10% were assessed as moderate. Salvati score was evaluated as average of 33 points (18-40. In the CS group none of the patients had implant failure, in the DHS group 6 patients had implant failure (33.3% (p<0,05. Conclusion: Except for the high rate of implant failure detection in the DHS group method, no significant difference between complications and functional results between two groups. J Clin Exp Invest

  1. Conceptual design of ball-screw type control element drive mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji Ho; Kim, Jong In; Huh, Hyung [Korea Atomic Energy Research Institute, Taejon (Korea)

    1999-10-01

    In this report, the design features of ball-screw type CEDM with fine-step movement capability are described. The contents of this report are as follows: -Review of Design Requirements for Ball-screw type CEDM -System Description for Ball-screw type CEDM -Design of Ball Bearing and Ball-screw Assembly -Detail Design of Rotary Step Motor -Detail Design of Angular Position Indicator -Materials. The Ball-screw type CEDM described in this report is to be utilized as the starting point for design development of CEDM for SMART. 11 refs., 43 figs., 3 tabs. (Author)

  2. The improvement of screw compressor performance using a newly developed rotor profile

    International Nuclear Information System (INIS)

    Kishi, Takayuki; Nishio, Toshio; Matsui, Akira; Ino, Nobumi

    1994-01-01

    An oil-compression phenomenon occurs at two portions of a conventional oil injected screw compressor that degrades the isothermal efficiency of the screw compressor. Hence a new screw rotor profile and lubricant have been developed in order to avoid the above oil-compression phenomena. Mycom and Fermi National Accelerator Laboratory have measured the performance of a new Mycom compound type screw compressor 2016C using the new profile rotors and the new lubricant. In the experiments, a 33% enhancement rate in the isothermal efficiency of the new screw compressor installed in Fermilab was achieved

  3. Mechanical comparison between lengthened and short sacroiliac screws in sacral fracture fixation: a finite element analysis.

    Science.gov (United States)

    Zhao, Y; Zhang, S; Sun, T; Wang, D; Lian, W; Tan, J; Zou, D; Zhao, Y

    2013-09-01

    To compare the stability of lengthened sacroiliac screw and standard sacroiliac screw for the treatment of unilateral vertical sacral fractures; to provide reference for clinical applications. A finite element model of Tile type C pelvic ring injury (unilateral Denis type II fracture of the sacrum) was produced. The unilateral sacral fractures were fixed with lengthened sacroiliac screw and sacroiliac screw in six different types of models respectively. The translation and angle displacement of the superior surface of the sacrum (in standing position on both feet) were measured and compared. The stability of one lengthened sacroiliac screw fixation in S1 or S2 segment is superior to that of one sacroiliac screw fixation in the same sacral segment. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one sacroiliac screw fixation in S1 and S2 segments respectively. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one lengthened sacroiliac screw fixation in S1 or S2 segment. The stability of one sacroiliac screw fixation in S1 and S2 segments respectively is markedly superior to that of one sacroiliac screw fixation in S1 or S2 segment. The vertical and rotational stability of lengthened sacroiliac screw fixation and sacroiliac screw fixation in S2 is superior to that of S1. In a finite element model of type C pelvic ring disruption, S1 and S2 lengthened sacroiliac screws should be utilized for the fixation as regularly as possible and the most stable fixation is the combination of the lengthened sacroiliac screws of S1 and S2 segments. Even if lengthened sacroiliac screws cannot be systematically used due to specific conditions, one sacroiliac screw fixation in S1 and S2 segments respectively is recommended. No matter which kind of sacroiliac screw is used, if only one screw can be implanted, the fixation in S2 segment is more recommended

  4. A technique for the management of screw access opening in cement-retained implant restorations

    Directory of Open Access Journals (Sweden)

    Hamid Kermanshah

    2014-01-01

    Full Text Available Introduction: Abutment screw loosening has been considered as a common complication of implant-supported dental prostheses. This problem is more important in cement-retained implant restorations due to their invisible position of the screw access opening. Case Report: This report describes a modified retrievability method for cement-retained implant restorations in the event of abutment screw loosening. The screw access opening was marked with ceramic stain and its porcelain surface was treated using hydrofluoric acid (HF, silane, and adhesive to bond to composite resin. Discussion: The present modified technique facilitates screw access opening and improves the bond between the porcelain and composite resin.

  5. Covering the screw-access holes of implant restorations in the esthetic zone: a clinical report.

    Directory of Open Access Journals (Sweden)

    Abolfazl Saboury

    2014-12-01

    Full Text Available Screw-retained implant restorations have an advantage of predictable retention as well as retrievability, and obviate the risk of excessive sub-gingival cement commonly associated with cement retained implant restorations. Screw-retained restorations generally have screw access holes, which can compromise esthetics and weaken the porcelain around the holes. The purpose of this study is to describe the use of a separate overcasting crown design to cover the screw access hole of implant screw-retained prosthesis for improved esthetics.

  6. Normal-tension glaucoma (Low-tension glaucoma)

    Science.gov (United States)

    Anderson, Douglas R

    2011-01-01

    Glaucoma is now considered an abnormal physiology in the optic nerve head that interacts with the level of intraocular pressure (IOP), with the degree and rate of damage depending on the IOP and presumably the degree of abnormal physiology. Diagnosis of normal-tension glaucoma (NTG), defined as glaucoma without a clearly abnormal IOP, depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visual field loss. Among the findings are a halo or crescent of absence of retinal pigment epithelium around the disc, bilateral pre-chiasmal visual field defects, splinter hemorrhages at the disc margin, vascular dysregulation (low blood pressure, cold hands and feet, migraine headache with aura, and the like), or a family history of glaucoma. Possibly relevant, is a history of hemodynamic crisis, arterial obstructive disease, or sleep apnea. Neurological evaluation with imaging is needed only for atypical cases or ones that progress unexpectedly. Management follows the same principle of other chronic glaucomas, to lower the IOP by a substantial amount, enough to prevent disabling visual loss. However, many NTG cases are non-progressive. Therefore, it may often be wisein mild cases to determine whether the case is progressive and the rate of progression before deciding on how aggressivene to be with therapy. Efforts at neuroprotection and improvement in blood flow have not yet been shown effective. PMID:21150042

  7. Normal-tension glaucoma (Low-tension glaucoma

    Directory of Open Access Journals (Sweden)

    Anderson Douglas

    2011-12-01

    Full Text Available Glaucoma is now considered an abnormal physiology in the optic nerve head that interacts with the level of intraocular pressure (IOP, with the degree and rate of damage depending on the IOP and presumably the degree of abnormal physiology. Diagnosis of normal-tension glaucoma (NTG, defined as glaucoma without a clearly abnormal IOP, depends on recognizing symptoms and signs associated with optic nerve vulnerability, in addition to absence of other explanations for disc abnormality and visual field loss. Among the findings are a halo or crescent of absence of retinal pigment epithelium around the disc, bilateral pre-chiasmal visual field defects, splinter hemorrhages at the disc margin, vascular dysregulation (low blood pressure, cold hands and feet, migraine headache with aura, and the like, or a family history of glaucoma. Possibly relevant, is a history of hemodynamic crisis, arterial obstructive disease, or sleep apnea. Neurological evaluation with imaging is needed only for atypical cases or ones that progress unexpectedly. Management follows the same principle of other chronic glaucomas, to lower the IOP by a substantial amount, enough to prevent disabling visual loss. However, many NTG cases are non-progressive. Therefore, it may often be wisein mild cases to determine whether the case is progressive and the rate of progression before deciding on how aggressivene to be with therapy. Efforts at neuroprotection and improvement in blood flow have not yet been shown effective.

  8. Introducing geometry concept based on history of Islamic geometry

    Science.gov (United States)

    Maarif, S.; Wahyudin; Raditya, A.; Perbowo, K. S.

    2018-01-01

    Geometry is one of the areas of mathematics interesting to discuss. Geometry also has a long history in mathematical developments. Therefore, it is important integrated historical development of geometry in the classroom to increase’ knowledge of how mathematicians earlier finding and constructing a geometric concept. Introduction geometrical concept can be started by introducing the Muslim mathematician who invented these concepts so that students can understand in detail how a concept of geometry can be found. However, the history of mathematics development, especially history of Islamic geometry today is less popular in the world of education in Indonesia. There are several concepts discovered by Muslim mathematicians that should be appreciated by the students in learning geometry. Great ideas of mathematicians Muslim can be used as study materials to supplement religious character values taught by Muslim mathematicians. Additionally, by integrating the history of geometry in teaching geometry are expected to improve motivation and geometrical understanding concept.

  9. Traumatic tension pneumocephalus: Two case reports

    Directory of Open Access Journals (Sweden)

    Abubaker Al-Aieb

    2017-01-01

    Conclusions: These are two rare cases with posttraumatic tension pneumocephalus treated conservatively with a favorable outcome. Early diagnosis of tension pneumocephalus is a crucial step to facilitate early recovery; however, the associated injuries need attention as they could influence the hospital course.

  10. Embracing Tensions in Feminist Organizational Communication Pedagogies

    Science.gov (United States)

    Linabary, Jasmine R.; Long, Ziyu; Mouton, Ashton; Rao, Ranjani L.; Buzzanell, Patrice M.

    2017-01-01

    Feminist pedagogies hold potential to create more inclusive and transformative classrooms. Adopting a tension-centered approach, we draw on our individual and collective reflections on the design and instruction of a multi-section undergraduate organizational communication course to build an autoethnographic account of the tensions associated with…

  11. Tending the tensions in co-creation

    DEFF Research Database (Denmark)

    Phillips, Professor MSO Louise; Nordentoft, Helle Merete; Pedersen, Lektor Christina Hee

    -for-granted positive value. In the panel we de-romanticise “co-creation” and explore how it is enacted in particular organisational contexts, concentrating on context-specific tensions arising in the meeting between different knowledge forms and interests. These include tensions BETWEEN dialogic views of knowledge co-creation...

  12. Post-tensioning system surveillance program

    International Nuclear Information System (INIS)

    Drew, G.E.

    1979-01-01

    Nuclear power plant containment structure post-tensioning system tendon surveillance program is described in detail. Data collected over three yearly post-tensioning system Surveillance Programs is presented and evaluated to correlate anticipated stress losses with actual losses. In addition corrosion protected system performance is analyzed

  13. Tension and robustness in multitasking cellular networks.

    Directory of Open Access Journals (Sweden)

    Jeffrey V Wong

    Full Text Available Cellular networks multitask by exhibiting distinct, context-dependent dynamics. However, network states (parameters that generate a particular dynamic are often sub-optimal for others, defining a source of "tension" between them. Though multitasking is pervasive, it is not clear where tension arises, what consequences it has, and how it is resolved. We developed a generic computational framework to examine the source and consequences of tension between pairs of dynamics exhibited by the well-studied RB-E2F switch regulating cell cycle entry. We found that tension arose from task-dependent shifts in parameters associated with network modules. Although parameter sets common to distinct dynamics did exist, tension reduced both their accessibility and resilience to perturbation, indicating a trade-off between "one-size-fits-all" solutions and robustness. With high tension, robustness can be preserved by dynamic shifting of modules, enabling the network to toggle between tasks, and by increasing network complexity, in this case by gene duplication. We propose that tension is a general constraint on the architecture and operation of multitasking biological networks. To this end, our work provides a framework to quantify the extent of tension between any network dynamics and how it affects network robustness. Such analysis would suggest new ways to interfere with network elements to elucidate the design principles of cellular networks.

  14. Tension Pneumothorax following an Accidental Kerosene Poisoning ...

    African Journals Online (AJOL)

    Tension pneumothorax is a rare complication following an accidental kerosene poisoning. In such situation, a bed-side needle thoracocentesis is performed because of its potential of becoming fatal; hence its clinical importance. A case of 15 month old boy with tension pneumothorax following accidental kerosene ...

  15. Oral mucosa tissue response to titanium cover screws.

    Science.gov (United States)

    Olmedo, Daniel G; Paparella, María L; Spielberg, Martín; Brandizzi, Daniel; Guglielmotti, María B; Cabrini, Rómulo L

    2012-08-01

    Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

  16. Do screws and screw holes affect osteolysis in cementless cups using highly crosslinked polyethylene? A 7 to 10-year follow-up case-control study.

    Science.gov (United States)

    Taniguchi, N; Jinno, T; Takada, R; Koga, D; Ando, T; Okawa, A; Haro, H

    2018-05-01

    The use of screws and the presence of screw holes may cause acetabular osteolysis and implant loosening in cementless total hip arthroplasty (THA) using conventional polyethylene. In contrast, this issue is not fully understood using highly crosslinked polyethylene (HXLPE), particularly in large comparative study. Therefore, we performed a case-control study to assess the influence of screw usage and screw holes on: (1) implant fixation and osteolysis and (2) polyethylene steady-state wear rate, using cases with HXLPE liners followed up for 7-10 years postoperatively. The screw usage and screw holes adversely affect the implant fixation and incidence of wear-related osteolysis in THA with HXLPE. We reviewed 209 primary cementless THAs performed with 26-mm cobalt-chromium heads on HXLPE liners. To compare the effects of the use of screws and the presence of screw holes, the following groups were established: (1) with-screw (n=140); (2) without-screw (n=69); (3) no-hole (n=27) and (4) group in which a cup with screw holes, but no screw was used (n=42). Two adjunct groups (no-hole cups excluded) were established to compare the differences in the two types of HXLPE: (5) remelted group (n=100) and (6) annealed group (n=82). Implant stability and osteolysis were evaluated by plain radiography and computed tomography. The wear rate from 1 year to the final evaluation was measured using plain X-rays and PolyWare Digital software. All cups and stems achieved bony fixation. On CT-scan, no acetabular osteolysis was found, but there were 3 cases with a small area of femoral osteolysis. The mean steady-state wear rate of each group was (1) 0.031±0.022, (2) 0.033±0.035, (3) 0.031±0.024, (4) 0.029±0.018, (5) 0.030±0.018 and (6) 0.034±0.023mm/year, respectively. A comparison of the effects of screw usage or screw holes found no significant between-group differences in the implant stability, prevalence of osteolysis [no acetabular osteolysis and 3/209 at femoral side (1

  17. Comparative effect of implant-abutment connections, abutment angulations, and screw lengths on preloaded abutment screw using three-dimensional finite element analysis: An in vitro study.

    Science.gov (United States)

    Kanneganti, Krishna Chaitanya; Vinnakota, Dileep Nag; Pottem, Srinivas Rao; Pulagam, Mahesh

    2018-01-01

    The purpose of this study is to compare the effect of implant-abutment connections, abutment angulations, and screw lengths on screw loosening (SL) of preloaded abutment using three dimensional (3D) finite element analysis. 3D models of implants (conical connection with hex/trilobed connections), abutments (straight/angulated), abutment screws (short/long), and crown and bone were designed using software Parametric Technology Corporation Creo and assembled to form 8 simulations. After discretization, the contact stresses developed for 150 N vertical and 100 N oblique load applications were analyzed, using ABAQUS. By assessing damage initiation and shortest fatigue load on screw threads, the SL for 2.5, 5, and 10 lakh cyclic loads were estimated, using fe-safe program. The obtained values were compared for influence of connection design, abutment angulation, and screw length. In straight abutment models, conical connection showed more damage (14.3%-72.3%) when compared to trilobe (10.1%-65.73%) at 2.5, 5, and 10 lakh cycles for both vertical and oblique loads, whereas in angulated abutments, trilobe (16.1%-76.9%) demonstrated more damage compared to conical (13.5%-70%). Irrespective of the connection type and abutment angulation, short screws showed more percentage of damage compared to long screws. The present study suggests selecting appropriate implant-abutment connection based on the abutment angulation, as well as preferring long screws with more number of threads for effective preload retention by the screws.

  18. Condensation in complex geometries

    International Nuclear Information System (INIS)

    Lauro, F.

    1975-01-01

    A mathematical evaluation of the condensation exchange coefficient can only succeds for well specified cases: small upright or inclined plates, horizontal tubes, small height vertical tubes. Among the main hypotheses accounted for this mathematical development in the case of the condensate, a laminar flow and uniform surface temperature are always considered. In practice certain shapes of surfaces significantly increase the heat transfer during the vapor condensation on a surface wet by the condensate. Such surfaces are rough surfaces such as the condensate is submitted to surface tension effects, negligeable for plane or large curvature surfaces, and the nature of the material may play an important role (temperature gradients). Results from tests on tubes with special shapes, performed in France or out of France, are given [fr

  19. Screw-worm eradication in the Americas - Overview

    International Nuclear Information System (INIS)

    Wyss, John H.

    2000-01-01

    Screw-worms (Cochliomyia hominivorax, Coquerel) are found only in the Americas, and are known, therefore, as the New World Screw-worm (NWS). The larval stages of the fly feed on the living flesh of their host. A screw-worm infestation can kill an adult animal in 7-10 days if not treated. All warm-blooded animals are affected including man. Although screw-worms had long been recognised as a severe pest of animals in the southwestern United States, they had never been detected east of the Mississippi River before 1933. In July 1933, screw-worms were transported on infested cattle to Georgia and became established east of the Mississippi River. Screw-worms spread quickly in the southeastern United States and were able to overwinter in southern Florida. Being new to the region, they were quickly recognised as a severe pest with a tremendous economic impact on livestock production. The livestock owners in the southeastern United States immediately noticed an increase in the number of animal deaths and increased costs of insecticides, veterinary medicines, veterinary services, inspection and handling. At the same time, they observed a decrease in animal weights and in milk production. Due to these observations, the livestock industry in the southeastern United States requested help in controlling screw-worms. Because of these requests, the research community became interested in control and eradication measures for this pest. Early work by Crushing and Patton in 1933 recognised that C. hominivorax was an obligatory animal parasite and different from the secondary blowfly, Cochliomyia macellaria. In 1934, the US Department of Agriculture (USDA), Agricultural Research Service (ARS) opened a research station in Valdosa, Georgia, and E.W. Laake and E.F. Knipling were assigned to work there. In September 1935, R.C. Bushland was hired by ARS to do research related to screw-worms at an ARS Research Laboratory in Dallas, Texas. Melvin and Bushland in 1936 developed artificial

  20. Initial tension loss in cerclage cables.

    Science.gov (United States)

    Ménard, Jérémie; Émard, Maxime; Canet, Fanny; Brailovski, Vladimir; Petit, Yvan; Laflamme, George Y

    2013-10-01

    Cerclage cables, frequently used in the management of fractures and osteotomies, are associated with a high failure rate and significant loosening during surgery. This study compared the capacity to maintain tension of different types of orthopaedic cable systems. Multifilament Cobalt-Chrome (CoCr) cables with four different crimp/clamp devices (DePuy, Stryker, Zimmer and Smith&Nephew) and one non-metallic Nylon (Ny) cable from Kinamed were instrumented with a load cell to measure tension during insertion. Significant tension loss was observed with crimping for all cables (Ptensioner led to an additional unexpected tension loss (CoCr-DePuy: 18%, CoCr-Stryker: 29%, CoCr-Smith&Nephew: 33%, Ny: 46%, and CoCr-Zimmer: 52%). The simple CoCr (DePuy) cable system outperformed the more sophisticated locking devices due to its significantly better ability to prevent tension loss. Copyright © 2013 Elsevier Inc. All rights reserved.

  1. A rationale method for evaluating unscrewing torque values of prosthetic screws in dental implants

    Directory of Open Access Journals (Sweden)

    Felipe Miguel Saliba

    2011-02-01

    Full Text Available OBJECTIVES: Previous studies that evaluated the torque needed for removing dental implant screws have not considered the manner of transfer of the occlusal loads in clinical settings. Instead, the torque used for removal was applied directly to the screw, and most of them omitted the possibility that the hexagon could limit the action of the occlusal load in the loosening of the screws. The present study proposes a method for evaluating the screw removal torque in an anti-rotational device independent way, creating an unscrewing load transfer to the entire assembly, not only to the screw. MATERIAL AND METHODS: Twenty hexagonal abutments without the hexagon in their bases were fixed with a screw to 20 dental implants. They were divided into two groups: Group 1 used titanium screws and Group 2 used titanium screws covered with a solid lubricant. A torque of 32 Ncm was applied to the screw and then a custom-made wrench was used for rotating the abutment counterclockwise, to loosen the screw. A digital torque meter recorded the torque required to loosen the abutment. RESULTS: There was a significant difference between the means of Group 1 (38.62±6.43 Ncm and Group 2 (48.47±5.04 Ncm, with p=0.001. CONCLUSION: This methodology was effective in comparing unscrewing torque values of the implant-abutment junction even with a limited sample size. It confirmed a previously shown significant difference between two types of screws.

  2. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone

    Directory of Open Access Journals (Sweden)

    Eduardo Aloisio Fleck NEUMANN

    2014-08-01

    Full Text Available Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1, polyetheretherketone (PEEK screws (Group 2, and 30% carbon fiber-reinforced PEEK screws (Group 3. The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey’s range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05. Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  3. Fracture resistance of abutment screws made of titanium, polyetheretherketone, and carbon fiber-reinforced polyetheretherketone.

    Science.gov (United States)

    Neumann, Eduardo Aloisio Fleck; Villar, Cristina Cunha; França, Fabiana Mantovani Gomes

    2014-01-01

    Fractured abutment screws may be replaced; however, sometimes, the screw cannot be removed and the entire implant must be surgically removed and replaced. The aim of this study was to compare the fracture resistance of abutment retention screws made of titanium, polyetheretherketone (PEEK) and 30% carbon fiber-reinforced PEEK, using an external hexagonal implant/UCLA-type abutment interface assembly. UCLA-type abutments were fixed to implants using titanium screws (Group 1), polyetheretherketone (PEEK) screws (Group 2), and 30% carbon fiber-reinforced PEEK screws (Group 3). The assemblies were placed on a stainless steel holding apparatus to allow for loading at 45o off-axis, in a universal testing machine. A 200 N load (static load) was applied at the central point of the abutment extremity, at a crosshead speed of 5 mm/minute, until failure. Data was analyzed by ANOVA and Tukey's range test. The titanium screws had higher fracture resistance, compared with PEEK and 30% carbon fiber-reinforced PEEK screws (p 0.05). Finally, visual analysis of the fractions revealed that 100% of them occurred at the neck of the abutment screw, suggesting that this is the weakest point of this unit. PEEK abutment screws have lower fracture resistance, in comparison with titanium abutment screws.

  4. Bioresorbable screws reinforced with phosphate glass fibre: manufacturing and mechanical property characterisation.

    Science.gov (United States)

    Felfel, R M; Ahmed, I; Parsons, A J; Rudd, C D

    2013-01-01

    Use of bioresorbable screws could eliminate disadvantages associated with metals such as removal operations, corrosion, MRI interference and stress shielding. Mechanical properties of bioresorbable polymers alone are insufficient for load bearing applications application as screws. Thus, reinforcement is necessary to try and match or surpass the mechanical properties of cortical bone. Phosphate based glass fibres were used to reinforce polylactic acid (PLA) in order to produce unidirectionally aligned (UD) and unidirectionally plus randomly distributed (UD/RM) composite screws (P40 UD and P40 UD/RM). The maximum flexural and push-out properties for the composite screws (P40 UD and P40 UD/RM) increased by almost 100% in comparison with the PLA screws. While the pull-out strength and stiffness of the headless composite screws were ∼80% (strength) and ∼130% (stiffness) higher than for PLA, those with heads exhibited properties lower than those for PLA alone as a result of failure at the heads. An increase in the maximum shear load and stiffness for the composite screws (∼30% and ∼40%) in comparison to the PLA screws was also seen. Maximum torque for the PLA screws was ∼1000 mN m, while that for the composite screws were slightly lower. The SEM micrographs for P40 UD and P40 UD/RM screws revealed small gaps around the fibres, which were suggested to be due to buckling of the UD fibres during the manufacturing process. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Screw Remaining Life Prediction Based on Quantum Genetic Algorithm and Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Xiaochen Zhang

    2017-01-01

    Full Text Available To predict the remaining life of ball screw, a screw remaining life prediction method based on quantum genetic algorithm (QGA and support vector machine (SVM is proposed. A screw accelerated test bench is introduced. Accelerometers are installed to monitor the performance degradation of ball screw. Combined with wavelet packet decomposition and isometric mapping (Isomap, the sensitive feature vectors are obtained and stored in database. Meanwhile, the sensitive feature vectors are randomly chosen from the database and constitute training samples and testing samples. Then the optimal kernel function parameter and penalty factor of SVM are searched with the method of QGA. Finally, the training samples are used to train optimized SVM while testing samples are adopted to test the prediction accuracy of the trained SVM so the screw remaining life prediction model can be got. The experiment results show that the screw remaining life prediction model could effectively predict screw remaining life.

  6. Process and remote device for unscrewing and extracting an assembly screw

    International Nuclear Information System (INIS)

    Lagarrigue, F.

    1990-01-01

    The device comprises a C-shaped frame, with two parallel arms and a joining section fixed at one end of a long support, an extraction screw engaged in a hole through one arm and having one end made of a centre punch directed towards the inside of the frame and a remote mean for screwed or unscrewed the extraction screw. A supporting and centering piece can also be fixed to the second branch of the frame. The screw is extracted by exerting a moment about the axis of the screw through the support and frame after tightening the extraction screw. This device can be used particularly for the unscrewing and the extraction of the screw of the springs of a nuclear fuel assembly [fr

  7. Two lectures on D-geometry and noncommutative geometry

    International Nuclear Information System (INIS)

    Douglas, M.R.

    1999-01-01

    This is a write-up of lectures given at the 1998 Spring School at the Abdus Salam ICTP. We give a conceptual introduction to D-geometry, the study of geometry as seen by D-branes in string theory, and to noncommutative geometry as it has appeared in D-brane and Matrix theory physics. (author)

  8. Surface Tension of Multi-phase Flow with Multiple Junctions Governed by the Variational Principle

    International Nuclear Information System (INIS)

    Matsutani, Shigeki; Nakano, Kota; Shinjo, Katsuhiko

    2011-01-01

    We explore a computational model of an incompressible fluid with a multi-phase field in three-dimensional Euclidean space. By investigating an incompressible fluid with a two-phase field geometrically, we reformulate the expression of the surface tension for the two-phase field found by Lafaurie et al. (J Comput Phys 113:134–147, 1994) as a variational problem related to an infinite dimensional Lie group, the volume-preserving diffeomorphism. The variational principle to the action integral with the surface energy reproduces their Euler equation of the two-phase field with the surface tension. Since the surface energy of multiple interfaces even with singularities is not difficult to be evaluated in general and the variational formulation works for every action integral, the new formulation enables us to extend their expression to that of a multi-phase (N-phase, N ≥ 2) flow and to obtain a novel Euler equation with the surface tension of the multi-phase field. The obtained Euler equation governs the equation for motion of the multi-phase field with different surface tension coefficients without any difficulties for the singularities at multiple junctions. In other words, we unify the theory of multi-phase fields which express low dimensional interface geometry and the theory of the incompressible fluid dynamics on the infinite dimensional geometry as a variational problem. We apply the equation to the contact angle problems at triple junctions. We computed the fluid dynamics for a two-phase field with a wall numerically and show the numerical computational results that for given surface tension coefficients, the contact angles are generated by the surface tension as results of balances of the kinematic energy and the surface energy.

  9. Dynamical modeling of surface tension

    International Nuclear Information System (INIS)

    Brackbill, J.U.; Kothe, D.B.

    1996-01-01

    In a recent review it is said that free-surface flows ''represent some of the difficult remaining challenges in computational fluid dynamics''. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin. This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin are discussed

  10. Bilateral tension pneumothorax after acupuncture.

    Science.gov (United States)

    Mohammad, Nurashikin

    2018-04-19

    Acupuncture is an ancient complementary medicine which is currently used worldwide. Many serious adverse events have been reported which include a spectrum of mild-to-fatal complications. However, the level of awareness with regard to complications is still low both to physicians and patients. We report a 63-year-old who presented with acute shortness of breath 2 hours after having had acupuncture. On examination, there was absent breath sound heard on the left lung and slightly reduced breath sound on the right lung. She had type 1 respiratory failure. Urgent chest radiograph confirmed bilateral pneumothorax which was more severe on the left with tension pneumothorax and mediastinal shift. Chest tubes were inserted bilaterally after failed needle aspiration attempts. Subsequently, the pneumothoraces resolved, and she was discharged well. The bilateral pneumothoraces caused by acupuncture were curable but could have been potentially fatal if diagnosis was delayed. This case report adds to the limited current literature on the complications of acupuncture leading to bilateral pneumothoraces. © BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

  11. Multibreath alveolar oxygen tension imaging.

    Science.gov (United States)

    Clapp, Justin; Hamedani, Hooman; Kadlecek, Stephen; Xin, Yi; Shaghaghi, Hoora; Siddiqui, Sarmad; Rossman, Milton D; Rizi, Rahim R

    2016-10-01

    This study tested the ability of a multibreath hyperpolarized HP (3) He MRI protocol to increase the accuracy of regional alveolar oxygen tension (PA O2 ) measurements by lessening the influence of gas-flow artifacts. Conventional single-breath PA O2 measurement has been susceptible to error induced by intervoxel gas flow, particularly when used to study subjects with moderate-to-severe chronic obstructive pulmonary disease (COPD). Both single-breath and multibreath PA O2 imaging schemes were implemented in seven human subjects (one healthy, three asymptomatic smokers, and three COPD). The number and location of voxels with nonphysiologic PA O2 values generated by intervoxel gas flow were compared between the two protocols. The multibreath scheme resulted in a significantly lower total percentage of nonphysiologic PA O2 values (6.0%) than the single-breath scheme (13.7%) (P = 0.006). PA O2 maps showed several patterns of gas-flow artifacts that were present in the single-breath protocol but mitigated by the multibreath approach. Multibreath imaging also allowed for the analysis of slow-filling areas that presented no signal after a single breath. A multibreath approach enhances the accuracy and completeness of noninvasive PA O2 measurement by significantly lessening the proportion of nonphysiologic values generated by intervoxel gas flow. Magn Reson Med 76:1092-1101, 2016. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.

  12. Geometry of Quantum States

    International Nuclear Information System (INIS)

    Hook, D W

    2008-01-01

    A geometric framework for quantum mechanics arose during the mid 1970s when authors such as Cantoni explored the notion of generalized transition probabilities, and Kibble promoted the idea that the space of pure quantum states provides a natural quantum mechanical analogue for classical phase space. This central idea can be seen easily since the projection of Schroedinger's equation from a Hilbert space into the space of pure spaces is a set of Hamilton's equations. Over the intervening years considerable work has been carried out by a variety of authors and a mature description of quantum mechanics in geometric terms has emerged with many applications. This current offering would seem ideally placed to review the last thirty years of progress and relate this to the most recent work in quantum entanglement. Bengtsson and Zyczkowski's beautifully illustrated volume, Geometry of Quantum States (referred to as GQS from now on) attempts to cover considerable ground in its 466 pages. Its topics range from colour theory in Chapter 1 to quantum entanglement in Chapter 15-to say that this is a whirlwind tour is, perhaps, no understatement. The use of the work 'introduction' in the subtitle of GQS, might suggest to the reader that this work be viewed as a textbook and I think that this interpretation would be incorrect. The authors have chosen to present a survey of different topics with the specific aim to introduce entanglement in geometric terms-the book is not intended as a pedagogical introduction to the geometric approach to quantum mechanics. Each of the fifteen chapters is a short, and mostly self-contained, essay on a particular aspect or application of geometry in the context of quantum mechanics with entanglement being addressed specifically in the final chapter. The chapters fall into three classifications: those concerned with the mathematical background, those which discuss quantum theory and the foundational aspects of the geometric framework, and

  13. Analysis of crack opening stresses for center- and edge-crack tension specimens

    Directory of Open Access Journals (Sweden)

    Tong Di-Hua

    2014-04-01

    Full Text Available Accurate determination of crack opening stress is of central importance to fatigue crack growth analysis and life prediction based on the crack-closure model. This paper studies the crack opening behavior for center- and edge-crack tension specimens. It is found that the crack opening stress is affected by the crack tip element. By taking the crack tip element into account, a modified crack opening stress equation is given for the center-crack tension specimen. Crack surface displacement equations for an edge crack in a semi-infinite plate under remote uniform tension and partially distributed pressure are derived by using the weight function method. Based on these displacements, a crack opening stress equation for an edge crack in a semi-infinite plate under uniform tension has been developed. The study shows that the crack opening stress is geometry-dependent, and the weight function method provides an effective and reliable tool to deal with such geometry dependence.

  14. Functional integration over geometries

    International Nuclear Information System (INIS)

    Mottola, E.

    1995-01-01

    The geometric construction of the functional integral over coset spaces M/G is reviewed. The inner product on the cotangent space of infinitesimal deformations of M defines an invariant distance and volume form, or functional integration measure on the full configuration space. Then, by a simple change of coordinates parameterizing the gauge fiber G, the functional measure on the coset space M/G is deduced. This change of integration variables leads to a Jacobian which is entirely equivalent to the Faddeev--Popov determinant of the more traditional gauge fixed approach in non-abelian gauge theory. If the general construction is applied to the case where G is the group of coordinate reparameterizations of spacetime, the continuum functional integral over geometries, i.e. metrics modulo coordinate reparameterizations may be defined. The invariant functional integration measure is used to derive the trace anomaly and effective action for the conformal part of the metric in two and four dimensional spacetime. In two dimensions this approach generates the Polyakov--Liouville action of closed bosonic non-critical string theory. In four dimensions the corresponding effective action leads to novel conclusions on the importance of quantum effects in gravity in the far infrared, and in particular, a dramatic modification of the classical Einstein theory at cosmological distance scales, signaled first by the quantum instability of classical de Sitter spacetime. Finite volume scaling relations for the functional integral of quantum gravity in two and four dimensions are derived, and comparison with the discretized dynamical triangulation approach to the integration over geometries are discussed. Outstanding unsolved problems in both the continuum definition and the simplicial approach to the functional integral over geometries are highlighted

  15. Kinematic geometry of gearing

    CERN Document Server

    Dooner, David B

    2012-01-01

    Building on the first edition published in 1995 this new edition of Kinematic Geometry of Gearing has been extensively revised and updated with new and original material. This includes the methodology for general tooth forms, radius of torsure', cylinder of osculation, and cylindroid of torsure; the author has also completely reworked the '3 laws of gearing', the first law re-written to better parallel the existing 'Law of Gearing" as pioneered by Leonard Euler, expanded from Euler's original law to encompass non-circular gears and hypoid gears, the 2nd law of gearing describing a unique relat

  16. From geometry to topology

    CERN Document Server

    Flegg, H Graham

    2001-01-01

    This excellent introduction to topology eases first-year math students and general readers into the subject by surveying its concepts in a descriptive and intuitive way, attempting to build a bridge from the familiar concepts of geometry to the formalized study of topology. The first three chapters focus on congruence classes defined by transformations in real Euclidean space. As the number of permitted transformations increases, these classes become larger, and their common topological properties become intuitively clear. Chapters 4-12 give a largely intuitive presentation of selected topics.

  17. Torsional heterotic geometries

    International Nuclear Information System (INIS)

    Becker, Katrin; Sethi, Savdeep

    2009-01-01

    We construct new examples of torsional heterotic backgrounds using duality with orientifold flux compactifications. We explain how duality provides a perturbative solution to the type I/heterotic string Bianchi identity. The choice of connection used in the Bianchi identity plays an important role in the construction. We propose the existence of a much larger landscape of compact torsional geometries using string duality. Finally, we present some quantum exact metrics that correspond to NS5-branes placed on an elliptic space. These metrics describe how torus isometries are broken by NS flux.

  18. Geometrie verstehen: statisch - kinematisch

    Science.gov (United States)

    Kroll, Ekkehard

    Dem Allgemeinen steht begrifflich das Besondere gegenüber. In diesem Sinne sind allgemeine Überlegungen zum Verstehen von Mathematik zu ergänzen durch Untersuchungen hinsichtlich des Verstehens der einzelnen mathematischen Disziplinen, insbesondere der Geometrie. Hier haben viele Schülerinnen und Schüler Probleme. Diese rühren hauptsächlich daher, dass eine fertige geometrische Konstruktion in ihrer statischen Präsentation auf Papier nicht mehr die einzelnen Konstruktionsschritte erkennen lässt; zum Nachvollzug müssen sie daher ergänzend in einer Konstruktionsbeschreibung festgehalten werden.

  19. Elementary algebraic geometry

    CERN Document Server

    Kendig, Keith

    2015-01-01

    Designed to make learning introductory algebraic geometry as easy as possible, this text is intended for advanced undergraduates and graduate students who have taken a one-year course in algebra and are familiar with complex analysis. This newly updated second edition enhances the original treatment's extensive use of concrete examples and exercises with numerous figures that have been specially redrawn in Adobe Illustrator. An introductory chapter that focuses on examples of curves is followed by a more rigorous and careful look at plane curves. Subsequent chapters explore commutative ring th

  20. Local analytic geometry

    CERN Document Server

    Abhyankar, Shreeram Shankar

    1964-01-01

    This book provides, for use in a graduate course or for self-study by graduate students, a well-motivated treatment of several topics, especially the following: (1) algebraic treatment of several complex variables; (2) geometric approach to algebraic geometry via analytic sets; (3) survey of local algebra; (4) survey of sheaf theory. The book has been written in the spirit of Weierstrass. Power series play the dominant role. The treatment, being algebraic, is not restricted to complex numbers, but remains valid over any complete-valued field. This makes it applicable to situations arising from

  1. Geometry of conics

    CERN Document Server

    Akopyan, A V

    2007-01-01

    The book is devoted to the properties of conics (plane curves of second degree) that can be formulated and proved using only elementary geometry. Starting with the well-known optical properties of conics, the authors move to less trivial results, both classical and contemporary. In particular, the chapter on projective properties of conics contains a detailed analysis of the polar correspondence, pencils of conics, and the Poncelet theorem. In the chapter on metric properties of conics the authors discuss, in particular, inscribed conics, normals to conics, and the Poncelet theorem for confoca

  2. Geometry and trigonometry

    CERN Document Server

    2015-01-01

    This stimulating volume offers a broad collection of the principles of geometry and trigonometry and contains colorful diagrams to bring mathematical principles to life. Subjects are enriched by references to famous mathematicians and their ideas, and the stories are presented in a very comprehensible way. Readers investigate the relationships of points, lines, surfaces, and solids. They study construction methods for drawing figures, a wealth of facts about these figures, and above all, methods to prove the facts. They learn about triangle measure for circular motion, sine and cosine, tangent

  3. Geometry I essentials

    CERN Document Server

    REA, The Editors of

    2012-01-01

    REA's Essentials provide quick and easy access to critical information in a variety of different fields, ranging from the most basic to the most advanced. As its name implies, these concise, comprehensive study guides summarize the essentials of the field covered. Essentials are helpful when preparing for exams, doing homework and will remain a lasting reference source for students, teachers, and professionals. Geometry I includes methods of proof, points, lines, planes, angles, congruent angles and line segments, triangles, parallelism, quadrilaterals, geometric inequalities, and geometric

  4. A Biomechanical Analysis of 2 Constructs for Metacarpal Spiral Fracture Fixation in a Cadaver Model: 2 Large Screws Versus 3 Small Screws.

    Science.gov (United States)

    Eu-Jin Cheah, Andre; Behn, Anthony W; Comer, Garet; Yao, Jeffrey

    2017-12-01

    Surgeons confronted with a long spiral metacarpal fracture may choose to fix it solely with lagged screws. A biomechanical analysis of a metacarpal spiral fracture model was performed to determine whether 3 1.5-mm screws or 2 2.0-mm screws provided more stability during bending and torsional loading. Second and third metacarpals were harvested from 12 matched pairs of fresh-frozen cadaveric hands and spiral fractures were created. One specimen from each matched pair was fixed with 2 2.0-mm lagged screws whereas the other was fixed with 3 1.5-mm lagged screws. Nine pairs underwent combined cyclic cantilever bending and axial compressive loading followed by loading to failure. Nine additional pairs were subjected to cyclic external rotation while under a constant axial compressive load and were subsequently externally rotated to failure under a constant axial compressive load. Paired t tests were used to compare cyclic creep, stiffness, displacement, rotation, and peak load levels. Average failure torque for all specimens was 7.2 ± 1.7 Nm. In cyclic torsional testing, the group with 2 screws exhibited significantly less rotational creep than the one with 3 screws. A single specimen in the group with 2 screws failed before cyclic bending tests were completed. No other significant differences were found between test groups during torsional or bending tests. Both constructs were biomechanically similar except that the construct with 2 screws displayed significantly less loosening during torsional cyclic loading, although the difference was small and may not be clinically meaningful. Because we found no obvious biomechanical advantage to using 3 1.5-mm lagged screws to fix long spiral metacarpal fractures, the time efficiency and decreased implant costs of using 2-2.0 mm lagged screws may be preferred. Copyright © 2017 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

  5. Graded geometry and Poisson reduction

    OpenAIRE

    Cattaneo, A S; Zambon, M

    2009-01-01

    The main result of [2] extends the Marsden-Ratiu reduction theorem [4] in Poisson geometry, and is proven by means of graded geometry. In this note we provide the background material about graded geometry necessary for the proof in [2]. Further, we provide an alternative algebraic proof for the main result. ©2009 American Institute of Physics

  6. Liquid metal actuator driven by electrochemical manipulation of surface tension

    Science.gov (United States)

    Russell, Loren; Wissman, James; Majidi, Carmel

    2017-12-01

    We examine the electrocapillary properties of a fluidic actuator composed of a liquid metal droplet that is submerged in electrolytic solution and attached to an elastic beam. The beam deflection is controlled by electrochemically driven changes in the surface energy of the droplet. The metal is a eutectic gallium-indium alloy that is liquid at room temperature and forms an nm-thin Ga2O3 skin when oxidized. The effective surface tension of the droplet changes dramatically with oxidation and reduction, which are reversibly controlled by applying low voltage to the electrolytic bath. Wetting the droplet to two copper pads allows for a controllable tensile force to be developed between the opposing surfaces. We demonstrate the ability to reliably control force by changing the applied oxidizing voltage. Actuator forces and droplet geometries are also examined by performing a computational fluid mechanics simulation using Surface Evolver. The theoretical predictions are in qualitative agreement with the experimental measurements and provide additional confirmation that actuation is driven by surface tension.

  7. Gastrothorax or tension pneumothorax: A diagnostic dilemma

    Directory of Open Access Journals (Sweden)

    Singh Sarvesh

    2011-01-01

    Full Text Available Gastrothorax, a rare complication following thoracoabdominal aortic aneurysm repair, is reported. The clinical features of a gastrothorax and tension pneumothorax are similar and thus, a gastrothorax can masquerade as a tension pneumothorax. The diagnosis is made by a high level of clinical suspicion, chest X-ray shows a distended stomach with air fluid levels and a computerised tomography is useful in assessing the diaphragm and establishing the positions of the various intra-abdominal organs. Also, the risk of an intercostal drainage tube placement and the role of nasogastric tube in avoiding the development of a tension gastrothorax is highlighted.

  8. Retrograde lag screw placement in anterior acetabular column with regard to the anterior pelvic plane and midsagittal plane -- virtual mapping of 260 three-dimensional hemipelvises for quantitative anatomic analysis.

    Science.gov (United States)

    Ochs, Bjoern Gunnar; Stuby, Fabian Maria; Ateschrang, Atesch; Stoeckle, Ulrich; Gonser, Christoph Emanuel

    2014-10-01

    Percutaneous screw placement can be used for minimally invasive treatment of none or minimally displaced fractures of the anterior column. The complex pelvic geometry can pose a major challenge even for experienced surgeons. The present study examined the preformed bone stock of the anterior column in 260 hemipelvises (130 male and 130 female). Screws were virtually implanted using iPlan(®) CMF (BrainLAB AG, Feldkirchen, Germany); the maximal implant length and the maximal implant diameter were assessed. The study showed, that 6.5mm can generally be used in men; in women however individual planning is essential in regard to the maximal implant diameter since we found that in 15.4% of women, screws with a diameter less than 6.5mm were necessary. The virtual analysis of the preformed bone stock corridor of the anterior column showed two constrictions of crucial clinical importance. These can be found after 18% and 55% (men) respectively 16% and 55% (women) measured from the entry point along the axis of the implant. The entry point of the retrograde anterior column screw in our collective was located lateral of tuberculum pubicum at the level of the superior-medial margin of foramen obturatum. In female patients, the entry point was located significantly more lateral of symphysis and closer to the cranial margin of ramus superior ossis pubis. The mean angle between the screw trajectory and the anterior pelvic plane in sagittal section was 31.6 ± 5.5°, the mean angle between the screw trajectory and the midsagittal plane in axial section was 55.9 ± 4.6° and the mean angle between the screw trajectory and the midsagittal plane in coronal section was 42.1 ± 3.9° with no significant deviation between both sexes. The individual angles formed by the screw trajectory and the anterior pelvic and midsagittal plane are independent from anthropometric parameters sex, age, body length and weight. Therefore, they can be used for orientation in lag screw placement keeping

  9. Comparison of migration behavior between single and dual lag screw implants for intertrochanteric fracture fixation

    Directory of Open Access Journals (Sweden)

    Katonis Pavlos G

    2009-05-01

    Full Text Available Abstract Background Lag screw cut-out failure following fixation of unstable intertrochanteric fractures in osteoporotic bone remains an unsolved challenge. This study tested if resistance to cut-out failure can be improved by using a dual lag screw implant in place of a single lag screw implant. Migration behavior and cut-out resistance of a single and a dual lag screw implant were comparatively evaluated in surrogate specimens using an established laboratory model of hip screw cut-out failure. Methods Five dual lag screw implants (Endovis, Citieffe and five single lag screw implants (DHS, Synthes were tested in the Hip Implant Performance Simulator (HIPS of the Legacy Biomechanics Laboratory. This model simulated osteoporotic bone, an unstable fracture, and biaxial rocking motion representative of hip loading during normal gait. All constructs were loaded up to 20,000 cycles of 1.45 kN peak magnitude under biaxial rocking motion. The migration kinematics was continuously monitored with 6-degrees of freedom motion tracking system and the number of cycles to implant cut-out was recorded. Results The dual lag screw implant exhibited significantly less migration and sustained more loading cycles in comparison to the DHS single lag screw. All DHS constructs failed before 20,000 cycles, on average at 6,638 ± 2,837 cycles either by cut-out or permanent screw bending. At failure, DHS constructs exhibited 10.8 ± 2.3° varus collapse and 15.5 ± 9.5° rotation around the lag screw axis. Four out of five dual screws constructs sustained 20,000 loading cycles. One dual screw specimens sustained cut-out by medial migration of the distal screw after 10,054 cycles. At test end, varus collapse and neck rotation in dual screws implants advanced to 3.7 ± 1.7° and 1.6 ± 1.0°, respectively. Conclusion The single and double lag screw implants demonstrated a significantly different migration resistance in surrogate specimens under gait loading simulation with

  10. Process and device for the ultrasonic testing of slotted screws screwed into a head of a nuclear reactor fuel element for cracks

    International Nuclear Information System (INIS)

    Scharpenberg, R.

    1986-01-01

    To achieve correct echo signals, a test head is set separately on each area limited by a slot of the top of the slotted screw and the screw head is ultrasonically sounded in the direction of the suspected cracks. (orig./HP) [de

  11. Biomechanical comparison of 3.0 mm headless compression screw and 3.5 mm cortical bone screw in a canine humeral condylar fracture model.

    Science.gov (United States)

    Gonsalves, Mishka N; Jankovits, Daniel A; Huber, Michael L; Strom, Adam M; Garcia, Tanya C; Stover, Susan M

    2016-09-20

    To compare the biomechanical properties of simulated humeral condylar fractures reduced with one of two screw fixation methods: 3.0 mm headless compression screw (HCS) or 3.5 mm cortical bone screw (CBS) placed in lag fashion. Bilateral humeri were collected from nine canine cadavers. Standardized osteotomies were stabilized with 3.0 mm HCS in one limb and 3.5 mm CBS in the contralateral limb. Condylar fragments were loaded to walk, trot, and failure loads while measuring construct properties and condylar fragment motion. The 3.5 mm CBS-stabilized constructs were 36% stiffer than 3.0 mm HCS-stabilized constructs, but differences were not apparent in quality of fracture reduction nor in yield loads, which exceeded expected physiological loads during rehabilitation. Small residual fragment displacements were not different between CBS and HCS screws. Small fragment rotation was not significantly different between screws, but was weakly correlated with moment arm length (R² = 0.25). A CBS screw placed in lag fashion provides stiffer fixation than an HCS screw, although both screws provide similar anatomical reduction and yield strength to condylar fracture fixation in adult canine humeri.

  12. Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing.

    Directory of Open Access Journals (Sweden)

    Sophie Le Cann

    Full Text Available The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age of the animal, the level of the vertebrae (lumbar or thoracic and the type of screw anchorage (mono- or bi-cortical on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level, the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout.

  13. Pedicle Screw Fixation Study in Immature Porcine Spines to Improve Pullout Resistance during Animal Testing.

    Science.gov (United States)

    Le Cann, Sophie; Cachon, Thibaut; Viguier, Eric; Miladi, Lotfi; Odent, Thierry; Rossi, Jean-Marie; Chabrand, Patrick

    2015-01-01

    The porcine model is frequently used during development and validation of new spinal devices, because of its likeness to the human spine. These spinal devices are frequently composed of pedicle screws with a reputation for stable fixation but which can suffer pullouts during preclinical implantation on young animals, leading to high morbidity. With a view to identifying the best choices to optimize pedicle screw fixation in the porcine model, this study evaluates ex vivo the impact of weight (age) of the animal, the level of the vertebrae (lumbar or thoracic) and the type of screw anchorage (mono- or bi-cortical) on pedicle screw pullouts. Among the 80 pig vertebrae (90- and 140-day-old) tested in this study, the average screw pullout forces ranged between 419.9N and 1341.2N. In addition, statistical differences were found between test groups, pointing out the influence of the three parameters stated above. We found that the the more caudally the screws are positioned (lumbar level), the greater their pullout resistance is, moreover, screw stability increases with the age, and finally, the screws implanted with a mono-cortical anchorage sustained lower pullout forces than those implanted with a bi-cortical anchorage. We conclude that the best anchorage can be obtained with older animals, using a lumbar fixation and long screws traversing the vertebra and inducing bi-cortical anchorage. In very young animals, pedicle screw fixations need to be bi-cortical and more numerous to prevent pullout.

  14. Numerical study of internal flow in twin screw extruder and its mixing performance analysis

    International Nuclear Information System (INIS)

    Kim, Nak Soo; Kim, Hong Bum; Lee, Jae Wook

    2006-01-01

    We analyzed the non-Newtonian and non-isothermal flow in the melt conveying zone in co-rotating and counter-rotating screw extruder system with the commercial code, STAR-CD, and compared the mixing performance with respect to screw speed and rotating direction. The viscosity of fluid was described by power-law model. The dynamics of mixing was studied numerically by tracking the motion of particles in a twin screw extruder system. The extent of mixing was characterized in terms of the residence time distribution and average strain. The results showed that high screw speed decreases the residence time but increases the shear rate. Therefore higher screw speed increases the strain and has better mixing performance. Counter-rotating screw extruder system and co-rotating screw extruder has the similar shear rate with the same screw speed in spite of different rotating direction. However, the counter-rotating screw has good mixing performance, which is resulted from longer residence time than that of co-rotating screw extruder

  15. Stress corrosion cracking life estimation of hold-down spring screw for nuclear fuel assembly

    International Nuclear Information System (INIS)

    Koh, S.K.

    2005-01-01

    Hold-down spring screw fractures due to primary water stress corrosion cracking were observed in nuclear fuel assemblies. The screw fastens hold-down springs that are required to maintain the nuclear fuel assembly in contact with upper core plate and permit thermal and irradiation-induced length changes. In order to investigate the primary causes of the screw fractures, the finite element stress analysis and fracture mechanics analysis were performed on the hold-down spring assembly. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded the yield strength of the screw material, resulting in local plastic deformation. Preloading on the screw applied for tightening had beneficial effects on the screw strength by reducing the stress level at the critical regions, compared to the screw without preload. Calculated deflections and strains at the hold-down springs using the finite element analysis were in very close agreements with the experimentally measured deflections and strains. Primary water stress corrosion cracking (PWSCC) life of the Inconel 600 screw was predicted by integrating the Scott's model and resulted in a life of 1.42 years, which was fairly close to the field experience. Cracks were expected to originate at the threaded region of the screw and propagated to the opposite side of the spring, which was confirmed by the fractographic analysis of the fractured screws. (orig.)

  16. BIOMECHANICAL EVALUATION OF THE INFLUENCE OF CERVICAL SCREWS TAPPING AND DESIGN.

    Science.gov (United States)

    Silva, Patricia; Rosa, Rodrigo César; Shimano, Antonio Carlos; Albuquerque de Paula, Francisco José; Volpon, José Batista; Aparecido Defino, Helton Luiz

    2009-01-01

    To assess if the screw design (self-drilling/self-tapping) and the pilot hole tapping could affect the insertion torque and screw pullout strength of the screw used in anterior fixation of the cervical spine. Forty self-tapping screws and 20 self-drilling screws were inserted into 10 models of artificial bone and 10 cervical vertebrae of sheep. The studied parameters were the insertion torque and pullout strength. The following groups were created: Group I-self-tapping screw insertion after pilot hole drilling and tapping; Group II-self-tapping screw insertion after pilot hole drilling without tapping; Group III-self-drilling screw insertion without drilling and tapping. In Groups I and II, the pilot hole had 14.0 mm in depth and was made with a 3mmn drill, while tapping was made with a 4mm tap. The insertion torque was measured and the pullout test was performed. The comparison between groups was made considering the mean insertion torque and the maximum mean pullout strength with the variance analysis (ANOVA; p≤ 0.05). Previous drilling and tapping of pilot hole significantly decreased the insertion torque and the pullout strength. The insertion torque and pullout strength of self-drilling screws were significantly higher when compared to self-tapping screws inserted after pilot hole tapping.

  17. Effectiveness of screw surface coating on the stability of zirconia abutments after cyclic loading.

    Science.gov (United States)

    Basílio, Mariana de Almeida; Butignon, Luis Eduardo; Arioli Filho, João Neudenir

    2012-01-01

    Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading. Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 X 106 cycles was defined. Group means were calculated and compared using analysis of variance and the F test (α = .05). Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P = .021). After cyclic loading, there was no significant difference between them (P = .499). Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload.

  18. Determination of Screw and Nail Withdrawal Resistance of Some Important Wood Species

    Directory of Open Access Journals (Sweden)

    Alper Aytekin

    2008-04-01

    Full Text Available In this study, screw and nail withdrawal resistance of fir (Abies nordmanniana, oak (Quercus robur L. black pine (Pinus nigra Arnold and Stone pine (Pinus pinea L. wood were determined and compared. The data represent the testing of withdrawal resistance of three types of screws as smart, serrated and conventional and common nails. The specimens were prepared according to TS 6094 standards. The dimensions of the specimens were 5x5x15cm and for all of the directions. Moreover, the specimens were conditioned at ambient room temperature and 65±2% relative humidity. The screws and nails were installed according to ASTM-D 1761 standards. Nail dimensions were 2.5mm diameter and 50 mm length, conventional screws were 4x50mm, serrated screws were 4x45mm and smart screws were 4x50mm. Results show that the maximum screw withdrawal resistance value was found in Stone pine for the serrated screw. There were no significant differences between Stone pine and oak regarding screw withdrawal resistance values. Conventional screw yielded the maximum screw withdrawal resistance value in oak, followed by Stone pine, black pine and fir. Oak wood showed the maximum screw withdrawal resistance value for the smart screw, followed by Stone pine, black pine, and fir. Oak wood showed higher nail withdrawal resistances than softwood species. It was also determined that oak shows the maximum nail withdrawal resistance in all types. The nail withdrawal resistances at the longitudinal direction are lower with respect to radial and tangential directions.

  19. Pedicle Screw Insertion Accuracy Using O-Arm, Robotic Guidance, or Freehand Technique: A Comparative Study.

    Science.gov (United States)

    Laudato, Pietro Aniello; Pierzchala, Katarzyna; Schizas, Constantin

    2018-03-15

    A retrospective radiological study. The aim of this study was to evaluate the accuracy of pedicle screw insertion using O-Arm navigation, robotic assistance, or a freehand fluoroscopic technique. Pedicle screw insertion using either "O-Arm" navigation or robotic devices is gaining popularity. Although several studies are available evaluating each of those techniques separately, no direct comparison has been attempted. Eighty-four patients undergoing implantation of 569 lumbar and thoracic screws were divided into three groups. Eleven patients (64 screws) had screws inserted using robotic assistance, 25 patients (191 screws) using the O-arm, while 48 patients (314 screws) had screws inserted using lateral fluoroscopy in a freehand technique. A single experienced spine surgeon assisted by a spinal fellow performed all procedures. Screw placement accuracy was assessed by two independent observers on postoperative computed tomography (CTs) according to the A to D Rampersaud criteria. No statistically significant difference was noted between the three groups. About 70.4% of screws in the freehand group, 69.6% in the O arm group, and 78.8% in the robotic group were placed completely within the pedicle margins (grade A) (P > 0.05). About 6.4% of screws were considered misplaced (grades C&D) in the freehand group, 4.2% in the O-arm group, and 4.7% in the robotic group (P > 0.05). The spinal fellow inserted screws with the same accuracy as the senior surgeon (P > 0.05). The advent of new technologies does not appear to alter accuracy of screw placement in our setting. Under supervision, spinal fellows might perform equally well to experienced surgeons using new tools. The lack of difference in accuracy does not imply that the above-mentioned techniques have no added advantages. Other issues, such as surgeon/patient radiation, fiddle factor, teaching suitability, etc., outside the scope of our present study, need further assessment. 3.

  20. Numerical Simulation and Performance Analysis of Twin Screw Air Compressors

    Directory of Open Access Journals (Sweden)

    W. S. Lee

    2001-01-01

    Full Text Available A theoretical model is proposed in this paper in order to study the performance of oil-less and oil-injected twin screw air compressors. Based on this model, a computer simulation program is developed and the effects of different design parameters including rotor profile, geometric clearance, oil-injected angle, oil temperature, oil flow rate, built-in volume ratio and other operation conditions on the performance of twin screw air compressors are investigated. The simulation program gives us output variables such as specific power, compression ratio, compression efficiency, volumetric efficiency, and discharge temperature. Some of the above results are then compared with experimentally measured data and good agreement is found between the simulation results and the measured data.

  1. PERFORMANCE OPTIMIZATION OF AN ORGANIC MUD AGITATOR SCREW

    Directory of Open Access Journals (Sweden)

    Mircea Dimitrie CAZACU

    2009-11-01

    Full Text Available Due to the special performances obtained by means of the optimisation method applied to the axial runners of run-of-river hydraulic turbines and of wind turbines, as well as in the case of the screws for boat propulsion, perfected by the first of the authors [1] - [10], in this work one extend the application of this method at the case of an organic mud agitator screw for fermentation and biogas production. One presents the obtaining of the bio liquid circulation minimal velocity in the two possible cases [3]: extracting the fluid velocity from the peripheral force exerted by the runner, as well as from the mechanical power consumed for its driving. After the obtaining of the optimal relative peripheral angle one determines also the optimal incidence angles of the profile for other blade radii. This method permits in the same time to find the optimal profile, using the multitude of the profile characteristics, experimentally studied.

  2. Range of motion, sacral screw and rod strain in long posterior spinal constructs: a biomechanical comparison between S2 alar iliac screws with traditional fixation strategies.

    Science.gov (United States)

    Sutterlin, Chester E; Field, Antony; Ferrara, Lisa A; Freeman, Andrew L; Phan, Kevin

    2016-12-01

    S1 screw failure and L5/S1 non-union are issues with long fusions to S1. Improved construct stiffness and S1 screw offloading can help avoid this. S2AI screws have shown to provide similar stiffness to iliac screws when added to L3-S1 constructs. We sought to examine and compare the biomechanical effects on an L2-S1 pedicle screw construct of adding S2AI screws, AxiaLIF, L5-S1 interbody support via transforaminal lumbar interbody fusion (TLIF), and to examine the effect of the addition of cross connectors to each of these constructs. Two S1 screws and one rod with strain gauges (at L5/S1) were used in L2-S1 screw-rod constructs in 7 L1-pelvis specimens (two with low BMD). ROM, S1 screw and rod strain were assessed using a pure-moment flexibility testing protocol. Specimens were tested intact, and then in five instrumentation states consisting of: (I) Pedicle screws (PS) L2-S1; (II) PS + S2AI screws; (III) PS + TLIF L5/S1; (IV) PS + AxiaLIF L5/S1; (V) PS + S2AI + AxiaLIF L5/S1. The five instrumentation conditions were also tested with crosslinks at L2/3 and S1/2. Tests were conducted in flexion-extension, lateral bending and axial torsion with no compressive preload. S2A1 produces reduced S1 screw strain for flexion-extension, lateral bending and axial torsion, as well as reduced rod strain in lateral bending and axial torsion in comparison to AxiaLIF and interbody instrumentation, at the expense of increased rod flexion-extension strain. Cross-connectors may have a role in further reduction of S1 screw and rod strain. From a biomechanical standpoint, the use of the S2AI technique is at least equivalent to traditional iliac screws, but offers lower prominence and ease of assembly compared to conventional sacroiliac stabilization.

  3. Fatigue life prediction of pedicle screw for spinal surgery

    Czech Academy of Sciences Publication Activity Database

    Major, Štěpán; Kocour, Vladimír; Cyrus, P.

    2016-01-01

    Roč. 10, č. 35 (2016), s. 379-388 ISSN 1971-8993. [European Conference on Fracture. ECF21. Catania, 20.06.2015-20.06.2015] Institutional support: RVO:68378297 Keywords : pedicle-screw * titan alloy * fatigue life * finite element analysis Subject RIV: JK - Corrosion ; Surface Treatment of Materials http://www.fracturae.com/index.php/fis/article/view/IGF-ESIS.35.43

  4. Outcomes of Distal Femur Fracture Treated with Dynamic Condylar Screw

    International Nuclear Information System (INIS)

    Razaq, M. N. U.; Muhammad, T.; Ahmed, A.; Adeel, M.; Ahmad, S.; Ahmad, S.; Sultan, S.

    2016-01-01

    Background: Implants for open reduction and internal fixation of distal femoral fracture includes angle blade plate, rush nails, enders nail and interlocking nails. But all these devices are technically demanding and less effective in providing inter-fragmentary compression in osteoporotic bones. These problems can be solved with dynamic condylar screw (DCS).The objective of the study was to determine the frequency of different outcomes of distal femoral fracture treated with dynamic condylar screw Methods: This case series study was carried out in the Department of Trauma and Orthopaedics, Ayub Teaching Hospital Abbottabad from 1st October 2014 to August 2015, after approval of the ethical committee of the institution. Data of all patients with distal femoral fractures aged 20-70 years, recruited through emergency, OPD or consultant clinic collected on a proforma. Standard treatment of trauma was given to the patients. Detailed history was taken including the past medical and surgical history. Detailed examination including air-way, breathing and circulation, general physical examination and abdomino-pelvic examination was done in each patient. Investigations including urinalysis, haemoglobin percent, full blood count, X-ray (both AP and lateral view) of the involved femur (including hip and knee) was done. Results: Mean age of the patients was 43.18±14.647 ranging from 20 to 70 years. Mean duration of hospital stay in days was 2.21±1.111 ranging from 1 to 6 days. Patients follow-up assessment after 4 months of surgery for union of femoral fracture treated with dynamic condylar screw was found in 96 (94.1 percent), wound infection was found in 7 (6.9 percent), knee stiffness was found in 21 (20.6 percent) and limb shortening was found in 7 (6.9 percent). Conclusion: Dynamic condylar screw is an easy, scientifically less difficult and satisfying method of treatment for fractures of femur. (author)

  5. Screw-in forces during instrumentation by various file systems.

    Science.gov (United States)

    Ha, Jung-Hong; Kwak, Sang Won; Kim, Sung-Kyo; Kim, Hyeon-Cheol

    2016-11-01

    The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems. Forty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS- k , DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%. Reciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest ( p files with smaller cross-sectional area for higher flexibility is recommended.

  6. External jig in the placement of distal interlocking screws | Ikem ...

    African Journals Online (AJOL)

    Retrograde (52.2%) was the commonest surgical approach used for femur. The main indication for SIGN interlocking surgery was recent fracture 77.8%. Open reduction 97.8% was the commonest method of reduction used. The mean±SD bone union time was 3.58±0.56 months and range 3-5 months. Distal screw insertion ...

  7. CFD Modelling in Screw Compressors With Complex Multi Rotor Configurations

    OpenAIRE

    Rane, Sham Ramchandra; Kovacevic, Ahmed; Kethidi, Madhulika

    2012-01-01

    Computational Fluid Dynamics (CFD) of screw compressors is challenging due to the positive displacement nature of the process, existence of very fine fluid leakage paths, coexistence of working fluid and lubricant or coolant, fluid injection and most importantly the lack of methodologies available to generate meshes required for the full three dimensional transient simulations. In this paper, currently available technology of grid remeshing has been used to demonstrate the CFD simulations of ...

  8. Comparison of the Pullout Strength of Different Pedicle Screw Designs and Augmentation Techniques in an Osteoporotic Bone Model.

    Science.gov (United States)

    Kiyak, Gorkem; Balikci, Tevfik; Heydar, Ahmed Majid; Bezer, Murat

    2018-02-01

    Mechanical study. To compare the pullout strength of different screw designs and augmentation techniques in an osteoporotic bone model. Adequate bone screw pullout strength is a common problem among osteoporotic patients. Various screw designs and augmentation techniques have been developed to improve the biomechanical characteristics of the bone-screw interface. Polyurethane blocks were used to mimic human osteoporotic cancellous bone, and six different screw designs were tested. Five standard and expandable screws without augmentation, eight expandable screws with polymethylmethacrylate (PMMA) or calcium phosphate augmentation, and distal cannulated screws with PMMA and calcium phosphate augmentation were tested. Mechanical tests were performed on 10 unused new screws of each group. Screws with or without augmentation were inserted in a block that was held in a fixture frame, and a longitudinal extraction force was applied to the screw head at a loading rate of 5 mm/min. Maximum load was recorded in a load displacement curve. The peak pullout force of all tested screws with or without augmentation was significantly greater than that of the standard pedicle screw. The greatest pullout force was observed with 40-mm expandable pedicle screws with four fins and PMMA augmentation. Augmented distal cannulated screws did not have a greater peak pullout force than nonaugmented expandable screws. PMMA augmentation provided a greater peak pullout force than calcium phosphate augmentation. Expandable pedicle screws had greater peak pullout forces than standard pedicle screws and had the advantage of augmentation with either PMMA or calcium phosphate cement. Although calcium phosphate cement is biodegradable, osteoconductive, and nonexothermic, PMMA provided a significantly greater peak pullout force. PMMA-augmented expandable 40-mm four-fin pedicle screws had the greatest peak pullout force.

  9. Managing Tensions And Forging Creative Synergies Between ...

    African Journals Online (AJOL)

    Managing Tensions And Forging Creative Synergies Between Indigenous And Modern Settlement Planning Concepts And Practices: Lessons For The Design And Planning For Sustainable Settlements And Built-Forms In Southern Africa.

  10. Tension perturbations of black brane spacetimes

    International Nuclear Information System (INIS)

    Traschen, Jennie; Fox, Daniel

    2004-01-01

    We consider black brane spacetimes that have at least one spatial translation Killing field that is tangent to the brane. A new parameter, the tension of a spacetime, is defined. The tension parameter is associated with spatial translations in much the same way that the ADM mass is associated with the time translation Killing field. In this work, we explore the implications of the spatial translation symmetry for small perturbations around a background black brane. For static-charged black branes we derive a law which relates the tension perturbation to the surface gravity times the change in the horizon area, plus terms that involve variations in the charges and currents. We find that as a black brane evaporates the tension decreases. We also give a simple derivation of a first law for black brane spacetimes. These constructions hold when the background stress-energy is governed by a Hamiltonian, and the results include arbitrary perturbative stress-energy sources

  11. Notch effects in uniaxial tension specimens

    International Nuclear Information System (INIS)

    Delph, T.J.

    1979-03-01

    Results of a literature survey on the effect of notches on the time-dependent failure of uniaxial tension specimens at elevated temperatures are presented. Particular attention is paid to the failure of notched specimens containing weldments

  12. Tension waves in tethered satellite cables

    Science.gov (United States)

    Lallman, F. J.

    1984-01-01

    A one-degree-of-freedom simulation of the Tethered Satellite System (TSS) was programmed using a distributed system model of the tether based on the one-dimensional wave equation. This model represents the time varying tension profile along the tether as the sum of two traveling waves of tension moving in opposite directions. A control loop was devised which combines a deployment rate command with the measured tension at the deployer to produce a smooth, stable rate of deployment of the subsatellite. Simulation results show a buildup of periodic bursts of high frequency oscillation in tension. This report covers the mathematical modelling and simulation results and explains the reason for the observed oscillations. The design of a possible vibration damping device is discussed.

  13. Mechanical characteristics of connection for GFRP plates using tapping screws

    Science.gov (United States)

    Inoue, Yuya; Duong, Nguyen Ngoc; Satake, Chito; Matsumoto, Yukihiro

    2017-10-01

    FRP material has good characteristics such as light-weight, high-strength and high-corrosion resistance. Light-weight structure possesses some advantages over the rational constructing procedure such as self-building structures. In recent years, mechanical characteristics of FRP joints using bolts and/or rivet are investigated in detail, and they are used in many FRP structures. However, the bolts lack bearing strength compared with material strength and the joint needs the prepared bolt hole. In this paper, an alternative joint system for FRP structures using tapping screw is proposed and mechanical characteristics are investigated through experiment. Tapping screw has some advantages; easy-to-use, light-weight and high bearing strength. Then, the results of double-lapped tensile shear tests having one, four and eight tapping screws along longitudinal direction are shown. Moreover, it is shown that longitudinal stress distribution is approximately corresponding to the theoretical stress distribution of double-lapped adhesively bonded joints. Based on these, it is proposed that joint strength can be estimated by using the present calculation method.

  14. Optimization and Numerical Simulation of Outlet of Twin Screw Extruder

    Directory of Open Access Journals (Sweden)

    Zhang Yuan

    2018-01-01

    Full Text Available In view of the unreasonable design of non-intermeshing counter-rotating twin screw extruder die, the problem of productivity reduction was discussed. Firstly, the mathematical model of extruder productivity was established. The extruder die model was improved. Secondly, the force analysis of twin screw extruder physical model was carried out. Meanwhile, A combination of mechanical analysis and numerical simulation was adopted. The velocity field, pressure field and viscosity field were calculated by Mini-Element interpolation method, linear interpolation method and Picard iterative convergence method respectively. The influence of die model on the quantity of each field before and after improvement was analyzed. The results show that the improved model had increased the rheological parameters of the flow field, the leakage and reverse flow decreased. Through post-processing calculation, the productivity of the third dies extruder was 10% higher than before. The research results provide a theoretical basis for the design and optimization of die model of non intermeshing counter-rotating twin screw extruder.

  15. Real algebraic geometry

    CERN Document Server

    Bochnak, Jacek; Roy, Marie-Françoise

    1998-01-01

    This book is a systematic treatment of real algebraic geometry, a subject that has strong interrelation with other areas of mathematics: singularity theory, differential topology, quadratic forms, commutative algebra, model theory, complexity theory etc. The careful and clearly written account covers both basic concepts and up-to-date research topics. It may be used as text for a graduate course. The present edition is a substantially revised and expanded English version of the book "Géometrie algébrique réelle" originally published in French, in 1987, as Volume 12 of ERGEBNISSE. Since the publication of the French version the theory has made advances in several directions. Many of these are included in this English version. Thus the English book may be regarded as a completely new treatment of the subject.

  16. Critique of information geometry

    International Nuclear Information System (INIS)

    Skilling, John

    2014-01-01

    As applied to probability, information geometry fails because probability distributions do not form a metric space. Probability theory rests on a compelling foundation of elementary symmetries, which also support information (aka minus entropy, Kullback-Leibler) H(p;q) as the unique measure of divergence from source probability distribution q to destination p. Because the only compatible connective H is from≠to asymmetric, H(p;q)≠H(q;p), there can be no compatible geometrical distance (which would necessarily be from=to symmetric). Hence there is no distance relationship compatible with the structure of probability theory. Metrics g and densities sqrt(det(g)) interpreted as prior probabilities follow from the definition of distance, and must fail likewise. Various metrics and corresponding priors have been proposed, Fisher's being the most popular, but all must behave unacceptably. This is illustrated with simple counter-examples

  17. Geometry from Gauge Theory

    International Nuclear Information System (INIS)

    Correa, Diego H.; Silva, Guillermo A.

    2008-01-01

    We discuss how geometrical and topological aspects of certain (1/2)-BPS type IIB geometries are captured by their dual operators in N = 4 Super Yang-Mills theory. The type IIB solutions are characterized by arbitrary droplet pictures in a plane and we consider, in particular, axially symmetric droplets. The 1-loop anomalous dimension of the dual gauge theory operators probed with single traces is described by some bosonic lattice Hamiltonians. These Hamiltonians are shown to encode the topology of the droplets. In appropriate BMN limits, the Hamiltonians spectrum reproduces the spectrum of near-BPS string excitations propagating along each of the individual edges of the droplet. We also study semiclassical regimes for the Hamiltonians. For droplets having disconnected constituents, the Hamiltonian admits different complimentary semiclassical descriptions, each one replicating the semiclassical description for closed strings extending in each of the constituents

  18. Emergent geometry of membranes

    Energy Technology Data Exchange (ETDEWEB)

    Badyn, Mathias Hudoba de; Karczmarek, Joanna L.; Sabella-Garnier, Philippe; Yeh, Ken Huai-Che [Department of Physics and Astronomy, University of British Columbia,6224 Agricultural Road, Vancouver (Canada)

    2015-11-13

    In work http://dx.doi.org/10.1103/PhysRevD.86.086001, a surface embedded in flat ℝ{sup 3} is associated to any three hermitian matrices. We study this emergent surface when the matrices are large, by constructing coherent states corresponding to points in the emergent geometry. We find the original matrices determine not only shape of the emergent surface, but also a unique Poisson structure. We prove that commutators of matrix operators correspond to Poisson brackets. Through our construction, we can realize arbitrary noncommutative membranes: for example, we examine a round sphere with a non-spherically symmetric Poisson structure. We also give a natural construction for a noncommutative torus embedded in ℝ{sup 3}. Finally, we make remarks about area and find matrix equations for minimal area surfaces.

  19. Geometry through history Euclidean, hyperbolic, and projective geometries

    CERN Document Server

    Dillon, Meighan I

    2018-01-01

    Presented as an engaging discourse, this textbook invites readers to delve into the historical origins and uses of geometry. The narrative traces the influence of Euclid’s system of geometry, as developed in his classic text The Elements, through the Arabic period, the modern era in the West, and up to twentieth century mathematics. Axioms and proof methods used by mathematicians from those periods are explored alongside the problems in Euclidean geometry that lead to their work. Students cultivate skills applicable to much of modern mathematics through sections that integrate concepts like projective and hyperbolic geometry with representative proof-based exercises. For its sophisticated account of ancient to modern geometries, this text assumes only a year of college mathematics as it builds towards its conclusion with algebraic curves and quaternions. Euclid’s work has affected geometry for thousands of years, so this text has something to offer to anyone who wants to broaden their appreciation for the...

  20. Tension Hydrothorax Related to Disseminated Endometriosis

    Directory of Open Access Journals (Sweden)

    AnnaKate Deal, MD

    2016-01-01

    Full Text Available We present the case of a 34-year-old woman presenting to the emergency department (ED with dyspnea, cough, and fever. She was found to have a tension hydrothorax and was treated with ultrasound-guided thoracentesis in the ED. Subsequent inpatient evaluation showed the patient had disseminated endometriosis. Tension hydrothorax has not been previously described in the literature as a complication of this disease.

  1. Density and surface tension of ionic liquids.

    Science.gov (United States)

    Kolbeck, C; Lehmann, J; Lovelock, K R J; Cremer, T; Paape, N; Wasserscheid, P; Fröba, A P; Maier, F; Steinrück, H-P

    2010-12-30

    We measured the density and surface tension of 9 bis[(trifluoromethyl)sulfonyl]imide ([Tf(2)N](-))-based and 12 1-methyl-3-octylimidazolium ([C(8)C(1)Im](+))-based ionic liquids (ILs) with the vibrating tube and the pendant drop method, respectively. This comprehensive set of ILs was chosen to probe the influence of the cations and anions on density and surface tension. When the alkyl chain length in the [C(n)C(1)Im][Tf(2)N] series (n = 1, 2, 4, 6, 8, 10, 12) is increased, a decrease in density is observed. The surface tension initially also decreases but reaches a plateau for alkyl chain lengths greater than n = 8. Functionalizing the alkyl chains with ethylene glycol groups results in a higher density as well as a higher surface tension. For the dependence of density and surface tension on the chemical nature of the anion, relations are only found for subgroups of the studied ILs. Density and surface tension values are discussed with respect to intermolecular interactions and surface composition as determined by angle-resolved X-ray photoelectron spectroscopy (ARXPS). The absence of nonvolatile surface-active contaminants was proven by ARXPS.

  2. Oxygen tension level and human viral infections

    Energy Technology Data Exchange (ETDEWEB)

    Morinet, Frédéric, E-mail: frederic.morinet@sls.aphp.fr [Centre des Innovations Thérapeutiques en Oncologie et Hématologie (CITOH), CHU Saint-Louis, Paris (France); Université Denis Diderot, Sorbonne Paris Cité Paris, Paris (France); Casetti, Luana [Institut Cochin INSERM U1016, Paris (France); François, Jean-Hugues; Capron, Claude [Institut Cochin INSERM U1016, Paris (France); Laboratoire d' Hématologie, Hôpital Ambroise Paré, Boulogne (France); Université de Versailles Saint-Quentin en Yvelynes, Versailles (France); Pillet, Sylvie [Laboratoire de Bactériologie-Virologie-Hygiène, CHU de Saint-Etienne, Saint-Etienne (France); Université de Lyon et Université de Saint-Etienne, Jean Monnet, GIMAP EA3064, F-42023 Saint-Etienne, Lyon (France)

    2013-09-15

    The role of oxygen tension level is a well-known phenomenon that has been studied in oncology and radiotherapy since about 60 years. Oxygen tension may inhibit or stimulate propagation of viruses in vitro as well as in vivo. In turn modulating oxygen metabolism may constitute a novel approach to treat viral infections as an adjuvant therapy. The major transcription factor which regulates oxygen tension level is hypoxia-inducible factor-1 alpha (HIF-1α). Down-regulating the expression of HIF-1α is a possible method in the treatment of chronic viral infection such as human immunodeficiency virus infection, chronic hepatitis B and C viral infections and Kaposi sarcoma in addition to classic chemotherapy. The aim of this review is to supply an updating concerning the influence of oxygen tension level in human viral infections and to evoke possible new therapeutic strategies regarding this environmental condition. - Highlights: • Oxygen tension level regulates viral replication in vitro and possibly in vivo. • Hypoxia-inducible factor 1 (HIF-1α) is the principal factor involved in Oxygen tension level. • HIF-1α upregulates gene expression for example of HIV, JC and Kaposi sarcoma viruses. • In addition to classical chemotherapy inhibition of HIF-1α may constitute a new track to treat human viral infections.

  3. d = 2 transverse-field Ising model under the screw-boundary condition: an optimization of the screw pitch

    International Nuclear Information System (INIS)

    Nishiyama, Yoshihiro

    2011-01-01

    A length-N spin chain with the √N(=v)th neighbor interaction is identical to a two-dimensional (d = 2) model under the screw-boundary (SB) condition. The SB condition provides a flexible scheme to construct a d ≥ 2 cluster from an arbitrary number of spins; the numerical diagonalization combined with the SB condition admits a potential applicability to a class of systems intractable with the quantum Monte Carlo method due to the negative-sign problem. However, the simulation results suffer from characteristic finite-size corrections inherent in SB. In order to suppress these corrections, we adjust the screw pitch v(N) so as to minimize the excitation gap for each N. This idea is adapted to the transverse-field Ising model on the triangular lattice with N ≤ 32 spins. As a demonstration, the correlation-length critical exponent ν is analyzed in some detail

  4. Toward a general psychological model of tension and suspense.

    Science.gov (United States)

    Lehne, Moritz; Koelsch, Stefan

    2015-01-01

    Tension and suspense are powerful emotional experiences that occur in a wide variety of contexts (e.g., in music, film, literature, and everyday life). The omnipresence of tension and suspense suggests that they build on very basic cognitive and affective mechanisms. However, the psychological underpinnings of tension experiences remain largely unexplained, and tension and suspense are rarely discussed from a general, domain-independent perspective. In this paper, we argue that tension experiences in different contexts (e.g., musical tension or suspense in a movie) build on the same underlying psychological processes. We discuss key components of tension experiences and propose a domain-independent model of tension and suspense. According to this model, tension experiences originate from states of conflict, instability, dissonance, or uncertainty that trigger predictive processes directed at future events of emotional significance. We also discuss possible neural mechanisms underlying tension and suspense. The model provides a theoretical framework that can inform future empirical research on tension phenomena.

  5. On organizing principles of discrete differential geometry. Geometry of spheres

    International Nuclear Information System (INIS)

    Bobenko, Alexander I; Suris, Yury B

    2007-01-01

    Discrete differential geometry aims to develop discrete equivalents of the geometric notions and methods of classical differential geometry. This survey contains a discussion of the following two fundamental discretization principles: the transformation group principle (smooth geometric objects and their discretizations are invariant with respect to the same transformation group) and the consistency principle (discretizations of smooth parametrized geometries can be extended to multidimensional consistent nets). The main concrete geometric problem treated here is discretization of curvature-line parametrized surfaces in Lie geometry. Systematic use of the discretization principles leads to a discretization of curvature-line parametrization which unifies circular and conical nets.

  6. Higher geometry an introduction to advanced methods in analytic geometry

    CERN Document Server

    Woods, Frederick S

    2005-01-01

    For students of mathematics with a sound background in analytic geometry and some knowledge of determinants, this volume has long been among the best available expositions of advanced work on projective and algebraic geometry. Developed from Professor Woods' lectures at the Massachusetts Institute of Technology, it bridges the gap between intermediate studies in the field and highly specialized works.With exceptional thoroughness, it presents the most important general concepts and methods of advanced algebraic geometry (as distinguished from differential geometry). It offers a thorough study

  7. Micro-CT evaluation and histological analysis of screw-bone interface of expansive pedicle screw in osteoporotic sheep.

    Science.gov (United States)

    Wan, Shi-yong; Lei, Wei; Wu, Zi-xiang; Lv, Rong; Wang, Jun; Fu, Suo-chao; Li, Bo; Zhan, Ce

    2008-04-01

    To investigate the properties of screw-bone interface of expansive pedicle screw (EPS) in osteoporotic sheep by micro-CT and histological observation. Six female sheep with bilateral ovariectomy-induced osteoporosis were employed in this experiment. After EPS insertion in each femoral condyle, the sheep were randomly divided into two groups: 3 sheep were bred for 3 months (Group A), while the other 3 were bred for 6 months (Group B). After the animals being killed, the femoral condyles with EPS were obtained, which were three-dimensionally-imaged and reconstructed by micro-CT. Histological evaluation was made thereafter. The trabecular microstructure was denser at the screw-bone interface than in the distant parts in expansive section, especially within the spiral marking. In the non-expansive section, however, there was no significant difference between the interface and the distant parts. The regions of interest (ROI) adjacent to EPS were reconstructed and analyzed by micro-CT with the same thresholds. The three-dimensional (3-D) parameters, including tissue mineral density (TMD), bone volume fraction (BVF, BV/TV), bone surface/bone volume (BS/BV) ratio, trabecular thickness (Tb.Th), and trabecular separation (Tb.Sp), were significantly better in expansive sections than non-expansive sections (P less than 0.05). Histologically, newly-formed bony trabeculae crawled along the expansive fissures and into the center of EPS. The newly-formed bones, as well as the bones at the bone-screw interface, closely contacted with the EPS and constructed four compartments. The findings of the current study, based on micro-CT and histological evaluation, suggest that EPS can significantly provide stabilization in osteoporotic cancellous bones.

  8. Failure analysis of top nozzle holddown spring screw for nuclear fuel assembly

    International Nuclear Information System (INIS)

    Koh, S. K.; Ryu, C. H.; Na, E. G.; Baek, T. H.; Jeon, K. L.

    2003-01-01

    A failure analysis of holddown spring screw was performed using fracture mechanics approach. The spring screw was designed such that it was capable of sustaining the loads imposed by the initial tensile preload and operational loads. In order to investigate the cause of failure, a stress analysis of the top nozzle spring assembly was done using finite element analysis and a life prediction of the screw was made using a fracture mechanics approach. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Primary water stress corrosion cracking life of the Inconel 600 screw was predicted by using integration of the Scott model and resulted in 1.42 years, which was fairly close to the actual service life of the holddown spring screw

  9. Decrease in Hydrogen Embrittlement Susceptibility of 10B21 Screws by Bake Aging

    Directory of Open Access Journals (Sweden)

    Kuan-Jen Chen

    2016-08-01

    Full Text Available The effects of baking on the mechanical properties and fracture characteristics of low-carbon boron (10B21 steel screws were investigated. Fracture torque tests and hydrogen content analysis were performed on baked screws to evaluate hydrogen embrittlement (HE susceptibility. The diffusible hydrogen content within 10B21 steel dominated the fracture behavior of the screws. The fracture torque of 10B21 screws baked for a long duration was affected by released hydrogen. Secondary ion mass spectroscopy (SIMS result showed that hydrogen content decreased with increasing baking duration, and thus the HE susceptibility of 10B21 screws improved. Diffusible hydrogen promoted crack propagation in high-stress region. The HE of 10B21 screws can be prevented by long-duration baking.

  10. CT-based bone density assessment for iliosacral screw trajectories

    Directory of Open Access Journals (Sweden)

    Andreas Schicho

    2016-01-01

    Full Text Available Introduction: Sacroiliac screw placement is one standard treatment option for stabilization of posterior pelvic ring injuries encountering high intra- and inter-individual variations of bone stock quality as well as a vast variety and prevalence of sacral dysmorphism. An individual, easy-to-use preoperative bone stock quality estimation would be of high value for the surgeon. Materials and Methods: We analyzed 36 standard computed tomography datasets with the uninjured pelvic ring. Using a two-plane cross-referencing technique, we assessed the Hounsfield unit (HU mean values as well as standard deviation and minimum/maximum values within selected region of interests (ROIs at five key areas: os ilium left and right, massa lateralis of os sacrum left and right, and central vertebral body on levels S1 and S2. Results: Results showed no difference in mean HU at any ROI when comparing male and female data. For all ROIs set on S1 and S2, there was an age-related decline of HU with a calculated slope significantly different from zero. There was no statistical difference of slopes when comparing S1- and S2-level with respect to any distinct ROI. Comparison of levels S1 and S2 revealed differences at the vertebral body and at the right os ilium. The right and left massa lateralis of os sacrum had lower bone density than the center of the vertebral body, the right, or left os ilium on S1; right and left massa lateralis density did not differ significantly. On level S2, results were comparable with no difference of massa lateralis density. Conclusion: With our easy-to-use preoperative assessment of bone density of five key areas of sacroiliac screw anchoring we were able to find the lowest bone density in both the left and right massa lateralis on levels S1 and S2 with high inter- and intra-individual variations. Significantly lower bone density was found in the center of the vertebral bodies S2 in comparison to S1, which both are crucial for iliosacral

  11. An introduction to incidence geometry

    CERN Document Server

    De Bruyn, Bart

    2016-01-01

    This book gives an introduction to the field of Incidence Geometry by discussing the basic families of point-line geometries and introducing some of the mathematical techniques that are essential for their study. The families of geometries covered in this book include among others the generalized polygons, near polygons, polar spaces, dual polar spaces and designs. Also the various relationships between these geometries are investigated. Ovals and ovoids of projective spaces are studied and some applications to particular geometries will be given. A separate chapter introduces the necessary mathematical tools and techniques from graph theory. This chapter itself can be regarded as a self-contained introduction to strongly regular and distance-regular graphs. This book is essentially self-contained, only assuming the knowledge of basic notions from (linear) algebra and projective and affine geometry. Almost all theorems are accompanied with proofs and a list of exercises with full solutions is given at the end...

  12. Performance Characteristics of a 4 × 6 Oil-Free Twin-Screw Compressor

    OpenAIRE

    Sun-Seok Byeon; Jae-Young Lee; Youn-Jea Kim

    2017-01-01

    The screw compressor in the early stage of development is generally known as the oil-injection type. However, escalating environmental problems and advances in electronic components have spurred continuous R & D to minimize the oil content in compressed air. The oil-free twin-screw compressor is continuously compressed by inner volumetric change between rotors and casing. For this reason, in order to predict the overall performance of the screw compressor at the early stage of the design ...

  13. Hollow Mill for Extraction of Stripped Titanium Screws: An Easy, Quick, and Safe Technique

    OpenAIRE

    Gupta, Ravi; Singh, Harpreet; Singh, Amit; Garg, Sudhir

    2014-01-01

    Removal of jammed titanium screws can be difficult due to the problem of stripping of the hexagonal heads of the screws. We present a technique of extraction of stripped screws with the use of a standard 4.5 mm stainless steel hollow mill in a patient of peri-implant fracture of the radius fixed with a titanium locking plate 2 years back. The technique is quick, safe, and cost effective.

  14. In Vivo Evaluation of Immediately Loaded Stainless Steel and Titanium Orthodontic Screws in a Growing Bone

    OpenAIRE

    Gritsch, Kerstin; Laroche, Norbert; Bonnet, Jeanne-Marie; Exbrayat, Patrick; Morgon, Laurent; Rabilloud, Muriel; Grosgogeat, Brigitte

    2013-01-01

    The present work intends to evaluate the use of immediate loaded orthodontic screws in a growing model, and to study the specific bone response. Thirty-two screws (half of stainless steel and half of titanium) were inserted in the alveolar bone of 8 growing pigs. The devices were immediately loaded with a 100 g orthodontic force. Two loading periods were assessed: 4 and 12 weeks. Both systems of screws were clinically assessed. Histological observations and histomorphometric analysis evaluate...

  15. Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes.

    Science.gov (United States)

    Kennon, Justin C; Lu, Caroline; McGee-Lawrence, Meghan E; Crosby, Lynn A

    2017-06-01

    Reverse total shoulder arthroplasty (RTSA) is a viable treatment option for rotator cuff tear arthropathy but carries a complication risk of scapular fracture. We hypothesized that using screws above the central glenoid axis for metaglene fixation creates a stress riser contributing to increased scapula fracture incidence. Clinical type III scapular fracture incidence was determined with screw placement correlation: superior screw vs. screws placed exclusively below the glenoid midpoint. Cadaveric RTSA biomechanical modeling was employed to analyze scapular fractures. We reviewed 318 single-surgeon single-implant RTSAs with screw correlation to identify type III scapular fractures. Seventeen cadaveric scapula specimens were matched for bone mineral density, metaglenes implanted, and fixation with 2 screw configurations: inferior screws alone (group 1 INF ) vs. inferior screws with one additional superior screw (group 2 SUP ). Biomechanical load to failure was analyzed. Of 206 patients, 9 (4.4%) from the superior screw group experienced scapula fractures (type III); 0 fractures (0/112; 0%) were identified in the inferior screw group. Biomechanically, superior screw constructs (group 2 SUP ) demonstrated significantly (P < .05) lower load to failure (1077 N vs. 1970 N) compared with constructs with no superior screws (group 1 INF ). There was no significant age or bone mineral density discrepancy. Clinical scapular fracture incidence significantly decreased (P < .05) for patients with no screws placed above the central cage compared with patients with superior metaglene screws. Biomechanical modeling demonstrates significant construct compromise when screws are used above the central cage, fracturing at nearly half the ultimate load of the inferior screw constructs. We recommend use of inferior screws, all positioned below the central glenoid axis, unless necessary to stabilize the metaglene construct. Copyright © 2016 Journal of Shoulder and Elbow Surgery

  16. Casimir forces and geometry

    International Nuclear Information System (INIS)

    Buescher, R.

    2005-01-01

    Casimir interactions are interactions induced by quantum vacuum fluctuations and thermal fluctuations of the electromagnetic field. Using a path integral quantization for the gauge field, an effective Gaussian action will be derived which is the starting point to compute Casimir forces between macroscopic objects analytically and numerically. No assumptions about the independence of the material and shape dependent contributions to the interaction are made. We study the limit of flat surfaces in further detail and obtain a concise derivation of Lifshitz' theory of molecular forces. For the case of ideally conducting boundaries, the Gaussian action will be calculated explicitly. Both limiting cases are also discussed within the framework of a scalar field quantization approach, which is applicable for translationally invariant geometries. We develop a non-perturbative approach to calculate the Casimir interaction from the Gaussian action for periodically deformed and ideally conducting objects numerically. The obtained results reveal two different scaling regimes for the Casimir force as a function of the distance between the objects, their deformation wavelength and -amplitude. The results confirm that the interaction is non-additive, especially in the presence of strong geometric deformations. Furthermore, the numerical approach is extended to calculate lateral Casimir forces. The results are consistent with the results of the proximity-force approximation for large deformation wavelengths. A qualitatively different behaviour between the normal and lateral force is revealed. We also establish a relation between the boundary induced change of the of the density of states for the scalar Helmholtz equation and the Casimir interaction using the path integral method. For statically deformed boundaries, this relation can be expressed as a novel trace formula, which is formally similar to the so-called Krein-Friedel-Lloyd formula. While the latter formula describes the

  17. Planetary Image Geometry Library

    Science.gov (United States)

    Deen, Robert C.; Pariser, Oleg

    2010-01-01

    The Planetary Image Geometry (PIG) library is a multi-mission library used for projecting images (EDRs, or Experiment Data Records) and managing their geometry for in-situ missions. A collection of models describes cameras and their articulation, allowing application programs such as mosaickers, terrain generators, and pointing correction tools to be written in a multi-mission manner, without any knowledge of parameters specific to the supported missions. Camera model objects allow transformation of image coordinates to and from view vectors in XYZ space. Pointing models, specific to each mission, describe how to orient the camera models based on telemetry or other information. Surface models describe the surface in general terms. Coordinate system objects manage the various coordinate systems involved in most missions. File objects manage access to metadata (labels, including telemetry information) in the input EDRs and RDRs (Reduced Data Records). Label models manage metadata information in output files. Site objects keep track of different locations where the spacecraft might be at a given time. Radiometry models allow correction of radiometry for an image. Mission objects contain basic mission parameters. Pointing adjustment ("nav") files allow pointing to be corrected. The object-oriented structure (C++) makes it easy to subclass just the pieces of the library that are truly mission-specific. Typically, this involves just the pointing model and coordinate systems, and parts of the file model. Once the library was developed (initially for Mars Polar Lander, MPL), adding new missions ranged from two days to a few months, resulting in significant cost savings as compared to rewriting all the application programs for each mission. Currently supported missions include Mars Pathfinder (MPF), MPL, Mars Exploration Rover (MER), Phoenix, and Mars Science Lab (MSL). Applications based on this library create the majority of operational image RDRs for those missions. A

  18. Initiation to global Finslerian geometry

    CERN Document Server

    Akbar-Zadeh, Hassan

    2006-01-01

    After a brief description of the evolution of thinking on Finslerian geometry starting from Riemann, Finsler, Berwald and Elie Cartan, the book gives a clear and precise treatment of this geometry. The first three chapters develop the basic notions and methods, introduced by the author, to reach the global problems in Finslerian Geometry. The next five chapters are independent of each other, and deal with among others the geometry of generalized Einstein manifolds, the classification of Finslerian manifolds of constant sectional curvatures. They also give a treatment of isometric, affine, p

  19. Computed tomography fluoroscopy-guided placement of iliosacral screws in patients with unstable posterior pelvic fractures

    International Nuclear Information System (INIS)

    Iguchi, Toshihiro; Ogawa, Ken-Ichi; Doi, Takeshi; Munetomo, Kazuo; Miyasho, Koji; Hiraki, Takao; Kanazawa, Susumu; Ozaki, Toshifumi

    2010-01-01

    The purpose of this study was to evaluate retrospectively the safety and effectiveness of the computed tomography (CT) fluoroscopy-guided placement of iliosacral screws in patients with unstable posterior pelvic fractures. Six patients (four women and two men; mean age 55.8 years; range 35-77 years) with unstable posterior pelvic fractures underwent iliosacral screw placement under CT fluoroscopy guidance between November 2007 and August 2008. Unstable pelvic ring injury (AO types B and C) was the indication for this procedure. In all the six patients except one, CT fluoroscopy-guided placement had been technically successful. In one patient, a second screw had been inserted, with a tilt to the caudal site, and slightly advanced into the extrasacral body; afterward, it could be exchanged safely for a shorter screw. Five patients and one patient underwent placement of two screws and one screw, respectively. The mean duration of the procedure was 15.0 min (range 9-30 min) per screw; the duration was 12.3 min and 18.2 min for the first and second screws, respectively. No complications requiring treatment occurred during or after the procedure. The mean clinical and radiologic follow-up period was 14 months (range 6-21 months). All pelvic injuries had healed satisfactorily, without complication, and all patients are now doing well clinically and can walk. CT fluoroscopy-guided placement of iliosacral screws is a safe and effective treatment in patients with unstable posterior pelvic fractures. (orig.)

  20. The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?

    Science.gov (United States)

    Paik, Haines; Kang, Daniel G; Lehman, Ronald A; Gaume, Rachel E; Ambati, Divya V; Dmitriev, Anton E

    2013-11-01

    Rod contouring is frequently required to allow for appropriate alignment of pedicle screw-rod constructs. When residual mismatch is still present, a rod persuasion device is often used to achieve further rod reduction. Despite its popularity and widespread use, the biomechanical consequences of this technique have not been evaluated. To evaluate the biomechanical fixation strength of pedicle screws after attempted reduction of a rod-pedicle screw mismatch using a rod persuasion device. Fifteen 3-level, human cadaveric thoracic specimens were prepared and scanned for bone mineral density. Osteoporotic (n=6) and normal (n=9) specimens were instrumented with 5.0-mm-diameter pedicle screws; for each pair of comparison level tested, the bilateral screws were equal in length, and the screw length was determined by the thoracic level and size of the vertebra (35 to 45 mm). Titanium 5.5-mm rods were contoured and secured to the pedicle screws at the proximal and distal levels. For the middle segment, the rod on the right side was intentionally contoured to create a 5-mm residual gap between the inner bushing of the pedicle screw and the rod. A rod persuasion device was then used to engage the setscrew. The left side served as a control with perfect screw/rod alignment. After 30 minutes, constructs were disassembled and vertebrae individually potted. The implants were pulled in-line with the screw axis with peak pullout strength (POS) measured in Newton (N). For the proximal and distal segments, pedicle screws on the right side were taken out and reinserted through the same trajectory to simulate screw depth adjustment as an alternative to rod reduction. Pedicle screws reduced to the rod generated a 48% lower mean POS (495±379 N) relative to the controls (954±237 N) (p.05). In circumstances where a rod is not fully seated within the pedicle screw, the use of a rod persuasion device decreases the overall POS and work energy to failure of the screw or results in outright

  1. Screw engine used as an expander in ORC for low-potential heat utilization

    Science.gov (United States)

    Richter, Lukáš

    2017-09-01

    This paper deals with a screw motor that is used as an expander in an ORC (Organic Rankin Cycle) system, whose organic working substance allows the transformation of low-potential heat (waste heat, solar and geothermal energy) into electrical energy. The article describes the specific properties of an organic substance and a screw motor that must be considered when designing and assembling a complete power unit. Screw machines are not commonly used as expansion devices, so it is necessary to perform an analysis that makes it possible to adapt the screw machine to the expansion process in terms of profiling and design.

  2. A novel approach to pipeline tensioner modeling

    Energy Technology Data Exchange (ETDEWEB)

    O' Grady, Robert; Ilie, Daniel; Lane, Michael [MCS Software Division, Galway (Ireland)

    2009-07-01

    As subsea pipeline developments continue to move into deep and ultra-deep water locations, there is an increasing need for the accurate prediction of expected pipeline fatigue life. A significant factor that must be considered as part of this process is the fatigue damage sustained by the pipeline during installation. The magnitude of this installation-related damage is governed by a number of different agents, one of which is the dynamic behavior of the tensioner systems during pipe-laying operations. There are a variety of traditional finite element methods for representing dynamic tensioner behavior. These existing methods, while basic in nature, have been proven to provide adequate forecasts in terms of the dynamic variation in typical installation parameters such as top tension and sagbend/overbend strain. However due to the simplicity of these current approaches, some of them tend to over-estimate the frequency of tensioner pay out/in under dynamic loading. This excessive level of pay out/in motion results in the prediction of additional stress cycles at certain roller beds, which in turn leads to the prediction of unrealistic fatigue damage to the pipeline. This unwarranted fatigue damage then equates to an over-conservative value for the accumulated damage experienced by a pipeline weld during installation, and so leads to a reduction in the estimated fatigue life for the pipeline. This paper describes a novel approach to tensioner modeling which allows for greater control over the velocity of dynamic tensioner pay out/in and so provides a more accurate estimation of fatigue damage experienced by the pipeline during installation. The paper reports on a case study, as outlined in the proceeding section, in which a comparison is made between results from this new tensioner model and from a more conventional approach. The comparison considers typical installation parameters as well as an in-depth look at the predicted fatigue damage for the two methods

  3. Emergency percutaneous needle decompression for tension pneumoperitoneum

    Directory of Open Access Journals (Sweden)

    Körner Markus

    2011-05-01

    Full Text Available Abstract Background Tension pneumoperitoneum as a complication of iatrogenic bowel perforation during endoscopy is a dramatic condition in which intraperitoneal air under pressure causes hemodynamic and ventilatory compromise. Like tension pneumothorax, urgent intervention is required. Immediate surgical decompression though is not always possible due to the limitations of the preclinical management and sometimes to capacity constraints of medical staff and equipment in the clinic. Methods This is a retrospective analysis of cases of pneumoperitoneum and tension pneumoperitoneum due to iatrogenic bowel perforation. All patients admitted to our surgical department between January 2005 and October 2010 were included. Tension pneumoperitoneum was diagnosed in those patients presenting signs of hemodynamic and ventilatory compromise in addition to abdominal distension. Results Between January 2005 and October 2010 eleven patients with iatrogenic bowel perforation were admitted to our surgical department. The mean time between perforation and admission was 36 ± 14 hrs (range 30 min - 130 hrs, between ER admission and begin of the operation 3 hrs and 15 min ± 47 min (range 60 min - 9 hrs. Three out of eleven patients had clinical signs of tension pneumoperitoneum. In those patients emergency percutaneous needle decompression was performed with a 16G venous catheter. This improved significantly the patients' condition (stabilization of vital signs, reducing jugular vein congestion, bridging the time to the start of the operation. Conclusions Hemodynamical and respiratory compromise in addition to abdominal distension shortly after endoscopy are strongly suggestive of tension pneumoperitoneum due to iatrogenic bowel perforation. This is a rare but life threatening condition and it can be managed in a preclinical and clinical setting with emergency percutaneous needle decompression like tension pneumothorax. Emergency percutaneous decompression is no

  4. Ostrich eggs geometry

    Directory of Open Access Journals (Sweden)

    Šárka Nedomová

    2013-01-01

    Full Text Available Precise quantification of the profile of egg can provide a powerful tool for the analysis of egg shape for various biological problems. A new approach to the geometry of a Ostrich’s egg profile is presented here using an analysing the egg’s digital photo by edge detection techniques. The obtained points on the eggshell counter are fitted by the Fourier series. The obtained equations describing an egg profile have been used to calculate radii of curvature. The radii of the curvature at the important point of the egg profile (sharp end, blunt end and maximum thickness are independent on the egg shape index. The exact values of the egg surface and the egg volume have been obtained. These quantities are also independent on the egg shape index. These quantities can be successively estimated on the basis of simplified equations which are expressed in terms of the egg length, L¸ and its width, B. The surface area of the eggshells also exhibits good correlation with the egg long circumference length. Some limitations of the most used procedures have been also shown.

  5. Nonperturbative quantum geometries

    International Nuclear Information System (INIS)

    Jacobson, T.; California Univ., Santa Barbara; Smolin, L.; California Univ., Santa Barbara

    1988-01-01

    Using the self-dual representation of quantum general relativity, based on Ashtekar's new phase space variables, we present an infinite dimensional family of quantum states of the gravitational field which are exactly annihilated by the hamiltonian constraint. These states are constructed from Wilson loops for Ashtekar's connection (which is the spatial part of the left handed spin connection). We propose a new regularization procedure which allows us to evaluate the action of the hamiltonian constraint on these states. Infinite linear combinations of these states which are formally annihilated by the diffeomorphism constraints as well are also described. These are explicit examples of physical states of the gravitational field - and for the compact case are exact zero eigenstates of the hamiltonian of quantum general relativity. Several different approaches to constructing diffeomorphism invariant states in the self dual representation are also described. The physical interpretation of the states described here is discussed. However, as we do not yet know the physical inner product, any interpretation is at this stage speculative. Nevertheless, this work suggests that quantum geometry at Planck scales might be much simpler when explored in terms of the parallel transport of left-handed spinors than when explored in terms of the three metric. (orig.)

  6. Matrix Information Geometry

    CERN Document Server

    Bhatia, Rajendra

    2013-01-01

    This book is an outcome of the Indo-French Workshop on Matrix Information Geometries (MIG): Applications in Sensor and Cognitive Systems Engineering, which was held in Ecole Polytechnique and Thales Research and Technology Center, Palaiseau, France, in February 23-25, 2011. The workshop was generously funded by the Indo-French Centre for the Promotion of Advanced Research (IFCPAR).  During the event, 22 renowned invited french or indian speakers gave lectures on their areas of expertise within the field of matrix analysis or processing. From these talks, a total of 17 original contribution or state-of-the-art chapters have been assembled in this volume. All articles were thoroughly peer-reviewed and improved, according to the suggestions of the international referees. The 17 contributions presented  are organized in three parts: (1) State-of-the-art surveys & original matrix theory work, (2) Advanced matrix theory for radar processing, and (3) Matrix-based signal processing applications.  

  7. Surface tension in soap films: revisiting a classic demonstration

    International Nuclear Information System (INIS)

    Behroozi, F

    2010-01-01

    We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)

  8. Surface tension in soap films: revisiting a classic demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Behroozi, F [Department of Physics, University of Northern Iowa, Cedar Falls, IA 50614 (United States)], E-mail: behroozi@uni.edu

    2010-01-15

    We revisit a classic demonstration for surface tension in soap films and introduce a more striking variation of it. The demonstration shows how the film, pulling uniformly and normally on a loose string, transforms it into a circular arc under tension. The relationship between the surface tension and the string tension is analysed and presented in a useful graphical form. (letters and comments)

  9. Mentoring Preservice Teachers: Identifying Tensions and Possible Resolutions

    Science.gov (United States)

    Hudson, Peter; Hudson, Sue

    2018-01-01

    Tensions can occur in the mentor-mentee relationship during school-based professional experiences that require problem solving. What are the tensions for mentor teachers in preservice teacher education and how might these tensions be resolved? This qualitative study collected data from 31 high school mentor teachers about tensions experienced with…

  10. Exploratory experimental investigations on post-tensioned structural glass beams

    DEFF Research Database (Denmark)

    Louter, C.; Nielsen, Jens Henrik; Belis, J.

    2013-01-01

    This paper discusses two projects on post-tensioned glass beams, performed at EPFL and DTU, respectively. In these projects small scale glass beams (length of 1.5m and 1m) are post-tensioned by means of steel threaded rods tensioned at the beam ends. The purpose of post-tensioning glass beams...

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

    Science.gov (United States)

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

    2006-05-01

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

  12. The accuracy and safety of fluoroscopically guided percutaneous pedicle screws in the lumbosacral junction and the lumbar spine: a review of 880 screws.

    Science.gov (United States)

    Chiu, C K; Kwan, M K; Chan, C Y W; Schaefer, C; Hansen-Algenstaedt, N

    2015-08-01

    We undertook a retrospective study investigating the accuracy and safety of percutaneous pedicle screws placed under fluoroscopic guidance in the lumbosacral junction and lumbar spine. The CT scans of patients were chosen from two centres: European patients from University Medical Center Hamburg-Eppendorf, Germany, and Asian patients from the University of Malaya, Malaysia. Screw perforations were classified into grades 0, 1, 2 and 3. A total of 880 percutaneous pedicle screws from 203 patients were analysed: 614 screws from 144 European patients and 266 screws from 59 Asian patients. The mean age of the patients was 58.8 years (16 to 91) and there were 103 men and 100 women. The total rate of perforation was 9.9% (87 screws) with 7.4% grade 1, 2.0% grade 2 and 0.5% grade 3 perforations. The rate of perforation in Europeans was 10.4% and in Asians was 8.6%, with no significant difference between the two (p = 0.42). The rate of perforation was the highest in S1 (19.4%) followed by L5 (14.9%). The accuracy and safety of percutaneous pedicle screw placement are comparable to those cited in the literature for the open method of pedicle screw placement. Greater caution must be taken during the insertion of L5 and S1 percutaneous pedicle screws owing to their more angulated pedicles, the anatomical variations in their vertebral bodies and the morphology of the spinal canal at this location. ©2015 The British Editorial Society of Bone & Joint Surgery.

  13. Regional surface geometry of the rat stomach based on three-dimensional curvature analysis

    Energy Technology Data Exchange (ETDEWEB)

    Liao Donghua [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark); Zhao Jingbo [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark); Gregersen, Hans [Center of Excellence in Visceral Biomechanics and Pain, Aalborg Hospital, DK-9100 Aalborg (Denmark)

    2005-01-21

    A better understanding of gastric accommodation and gastric perception requires knowledge of regional gastric geometry and local gastric tension throughout the stomach. An analytic method based on medical imaging data was developed in this study to describe the three-dimensional (3D) rat stomach geometry and tension distribution. The surface principal radii of curvatures were simulated and the surface tension was calculated in the glandular and non-glandular region of the stomach at pressures from 0 Pa to 800 Pa. The radii of curvature and tension distribution in the stomach were non-homogeneous. The radii of curvature in the glandular stomach were larger than those in the non-glandular region at pressures less than 100 Pa (P < 0.001). When the pressure increased to more than 200 Pa, the radii of curvature in the non-glandular stomach was larger than in the glandular stomach (P < 0.05). The curvature and tension distribution mapping using medical imaging technology and 3D models can be used to characterize and distinguish the physical behaviour in separate regions of the stomach.

  14. Regional surface geometry of the rat stomach based on three-dimensional curvature analysis

    International Nuclear Information System (INIS)

    Liao Donghua; Zhao Jingbo; Gregersen, Hans

    2005-01-01

    A better understanding of gastric accommodation and gastric perception requires knowledge of regional gastric geometry and local gastric tension throughout the stomach. An analytic method based on medical imaging data was developed in this study to describe the three-dimensional (3D) rat stomach geometry and tension distribution. The surface principal radii of curvatures were simulated and the surface tension was calculated in the glandular and non-glandular region of the stomach at pressures from 0 Pa to 800 Pa. The radii of curvature and tension distribution in the stomach were non-homogeneous. The radii of curvature in the glandular stomach were larger than those in the non-glandular region at pressures less than 100 Pa (P < 0.001). When the pressure increased to more than 200 Pa, the radii of curvature in the non-glandular stomach was larger than in the glandular stomach (P < 0.05). The curvature and tension distribution mapping using medical imaging technology and 3D models can be used to characterize and distinguish the physical behaviour in separate regions of the stomach

  15. On relation between the quark-gluon bag surface tension and the colour tube string tension

    International Nuclear Information System (INIS)

    Bugaev, K.A.; Zinovjev, G.M.

    2010-01-01

    We revisit the bag phenomenology of deconfining phase transition aiming to replenish it by introducing systematically the bag surface tension. Comparing the free energies of such bags and the strings confining the static quark-antiquark pair, we express the string tension in terms of the bag surface tension and the bulk pressure in order to estimate the bag characteristics using the lattice QCD (LQCD) data. Our analysis of the bag entropy density demonstrates that the surface tension coefficient is amazingly negative at the cross-over (continuous transition). The approach developed allows us to naturally account for an origin of a pronounced maximum (observed in the LQCD studies) in the behaviour of heavy quark-antiquark pair entropy. The vicinity of the (tri-)critical endpoint is also analyzed to clarify the meaning of vanishing surface tension coefficient.

  16. Using three-dimensional rapid prototyping in the design and development of orthopaedic screws in standardised pull-out tests.

    Science.gov (United States)

    Leslie, Laura Jane; Connolly, Ashley; Swadener, John G; Junaid, Sarah; Theivendran, Kanthan; Deshmukh, Subodh C

    2018-05-01

    The majority of orthopaedic screws are designed, tested and manufactured by existing orthopaedics companies and are predominantly developed with healthy bone in mind. The timescales and costs involved in the development of a new screw design, for example, for osteoporotic bone, are high. In this study, standard wood screws were used to analyse the concept of using three-dimensional printing, or rapid prototyping, as a viable stage of development in the design of a new bone screw. Six wood screws were reverse engineered and printed in polymeric material using stereolithography. Three of the designs were also printed in Ti6Al4V using direct metal laser sintering; however, these were not of sufficient quality to test further. Both the original metal screws (metal) and polymeric rapid prototyping screws were then tested using standard pull-out tests from low-density polyurethane blocks (Sawbones). Results showed the highest pull-out strengths for screws with the longest thread length and the smallest inner diameter. Of the six screw designs tested, five showed no more than a 17% variance between the metal and rapid prototyping results. A similar pattern of results was shown between the screw designs for both the metal and rapid prototyping screws in five of the six cases. While not producing fully comparable pull-out results to orthopaedic screws, the results from this study do provide evidence of the potential usefulness and cost-effectiveness of rapid prototyping in the early stages of design and testing of orthopaedic screws.

  17. GPS: Geometry, Probability, and Statistics

    Science.gov (United States)

    Field, Mike

    2012-01-01

    It might be said that for most occupations there is now less of a need for mathematics than there was say fifty years ago. But, the author argues, geometry, probability, and statistics constitute essential knowledge for everyone. Maybe not the geometry of Euclid, but certainly geometrical ways of thinking that might enable us to describe the world…

  18. Surrogate Modeling for Geometry Optimization

    DEFF Research Database (Denmark)

    Rojas Larrazabal, Marielba de la Caridad; Abraham, Yonas; Holzwarth, Natalie

    2009-01-01

    A new approach for optimizing the nuclear geometry of an atomic system is described. Instead of the original expensive objective function (energy functional), a small number of simpler surrogates is used.......A new approach for optimizing the nuclear geometry of an atomic system is described. Instead of the original expensive objective function (energy functional), a small number of simpler surrogates is used....

  19. Kaehler geometry and SUSY mechanics

    International Nuclear Information System (INIS)

    Bellucci, Stefano; Nersessian, Armen

    2001-01-01

    We present two examples of SUSY mechanics related with Kaehler geometry. The first system is the N = 4 supersymmetric one-dimensional sigma-model proposed in hep-th/0101065. Another system is the N = 2 SUSY mechanics whose phase space is the external algebra of an arbitrary Kaehler manifold. The relation of these models with antisymplectic geometry is discussed

  20. A prediction for bubbling geometries

    OpenAIRE

    Okuda, Takuya

    2007-01-01

    We study the supersymmetric circular Wilson loops in N=4 Yang-Mills theory. Their vacuum expectation values are computed in the parameter region that admits smooth bubbling geometry duals. The results are a prediction for the supergravity action evaluated on the bubbling geometries for Wilson loops.

  1. Molecular motion in restricted geometries

    Indian Academy of Sciences (India)

    Molecular dynamics in restricted geometries is known to exhibit anomalous behaviour. Diffusion, translational or rotational, of molecules is altered significantly on confinement in restricted geometries. Quasielastic neutron scattering (QENS) offers a unique possibility of studying molecular motion in such systems. Both time ...

  2. Fate of the syndesmotic screw--Search for a prudent solution.

    Science.gov (United States)

    Kaftandziev, Igor; Spasov, Marko; Trpeski, Simon; Zafirova-Ivanovska, Beti; Bakota, Bore

    2015-11-01

    Ankle fractures are common injuries. Since the recognition of the importance of syndesmotic injury in ankle fractures, much of the scientific work has been focused on concomitant syndesmotic injury. Despite the invention of novel devices for restoration and maintenance of the congruent syndesmosis following syndesmotic injury, the metallic syndesmotic screw is still considered to be the "gold standard". The aim of this study was to compare the clinical results in patients who retained the syndesmosis screw with those in whom the screw was removed following open reduction and internal fixation of the malleolar fracture associated with syndesmosis disruption. This was a retrospective study of 82 patients. Minimum follow-up was 12 months. Clinical evaluation included American Orthopaedic Foot and Ankle Society (AOFAS) score and Visual Analogue Scale (VAS) for patient general satisfaction. The condition of the screw (removed, intact or broken), presence of radiolucency around the syndesmotic screw and the tibiofibular clear space were recorded using final follow-up radiographs. Three cortices were engaged in 66 patients (80%) and quadricortical fixation was performed in the remaining 16 patients (20%). The number of engaged cortices did not correlate with the clinical outcome and screw fracture. A single syndesmotic screw was used in 71 patients (86%. The mean AOFAS score in the group with intact screw (I) was 83; the scores in the group with broken screw (B) and removed screw (R) were 92.5 and 85.5, respectively. There was a statistically significant difference between the three groups: this was due to the difference between groups I and B; the difference between groups I and R and groups B and R were not statistically significant. There were no statistically significant differences in VAS results. There were no statistically significant differences in clinical outcome between the group with the screw retained and the group in which the screw was removed; however, the

  3. Comparative Analysis of Effect of Density, Insertion Angle and Reinsertion on Pull-Out Strength of Single and Two Pedicle Screw Constructs Using Synthetic Bone Model

    OpenAIRE

    Krishnan, Venkatesh; Varghese, Vicky; Kumar, Gurunathan Saravana

    2016-01-01

    Study Design Biomechanical study. Purpose To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. Overview of Literature Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the single screw construct may lead to using expensive implants or increasing the fusion levels specifically i...

  4. Ipsilateral proximal femur and shaft fractures treated with hip screws and a reamed retrograde intramedullary nail.

    Science.gov (United States)

    Ostrum, Robert F; Tornetta, Paul; Watson, J Tracy; Christiano, Anthony; Vafek, Emily

    2014-09-01

    Although not common, proximal femoral fractures associated with ipsilateral shaft fractures present a difficult management problem. A variety of surgical options have been employed with varying results. We investigated the use of hip screws and a reamed retrograde intramedullary (IM) nail for the treatment of this combined fracture pattern in terms of postoperative alignment (malunion), nonunion, and complications. Between May 2002 and October 2011, a total of 95 proximal femoral fractures with associated shaft fractures were treated at three participating Level 1 trauma centers; all were treated with hip screw fixation (cannulated screws or sliding hip screws) and retrograde reamed IM nails. The medical records of these patients were reviewed retrospectively for alignment, malunion, nonunion, and complications. Followup was available on 92 of 95 (97%) of the patients treated with hip screws and a retrograde nail. Forty were treated with a sliding hip screw, and 52 were treated with cannulated screws. There were five proximal malunions in this series (5%). The union rate was 98% (90 of 92) for the femoral neck fractures and 91.3% (84 of 92) for the femoral shaft fractures after the initial surgery. There were two nonunions of comminuted femoral neck fractures after cannulated screw fixation. There was no difference in femoral neck union or alignment when comparing cannulated screws to a sliding hip screw. Four open comminuted femoral shaft fractures went on to nonunion and required secondary surgery to obtain union, and one patient developed symptomatic avascular necrosis. The treatment of ipsilateral proximal femoral neck and shaft fractures with hip screw fixation and a reamed retrograde nail demonstrated a high likelihood of union for the femoral neck fractures and a low risk of malunion. Comminution and initial displacement of the proximal femoral fracture may still lead to a small incidence of malunion or nonunion, and open comminuted femoral shaft fractures

  5. What caused the failures of the solenoid valve screws

    International Nuclear Information System (INIS)

    Vassallo, T.P.; Mumford, J.R.; Hossain, F.

    2001-01-01

    At Seabrook Station on May 5,1998 following a lengthy purge of the pressurizer steam space through Containment isolation sample valve 1-RC-FV-2830, the UL status light associated with this solenoid valve did not come on when the valve was closed from the plant's main control board. The UL status light is used to confirm valve closure position to satisfy the plant's Technical Specification requirements. The incorrect valve position indication on the main control board was initially believed to have resulted from excessive heat from a failed voltage control module that did not reduce the voltage to the valve's solenoid coil. This conclusion was based on a similar event that occurred in November of 1996. Follow-up in-plant testing of the valve determined that the voltage control module had not failed and was functioning satisfactorily. Subsequent investigations determined the root cause of the event to be excessive heat-up of the valve caused by high process fluid temperature and an excessively long purge of the pressurizer. The excessive heat-up of the valve from the high temperature process fluid weakened the magnetic field strength of the valve stem magnet to the extent that the UL status light reed switch would not actuate when the valve was closed. Since the voltage control module was tested and found to be functioning properly it was not replaced. Only the UL status light reed switch was replaced with a more sensitive reed that would respond better to a reduced magnetic field strength that results from a hot magnet. During reed switch replacement, three terminal block screws in the valve housing were found fractured and three other terminal block screws fractured during determination of the electrical conductors. This paper describes the initial plant event and ensuing laboratory tests and examinations that were performed to determine the root cause of the failure of the terminal block screws from the Containment isolation sample solenoid valve. (author)

  6. Open reduction and internal fixation: Screw injury - Retrospective study

    Directory of Open Access Journals (Sweden)

    Preetha Balaji

    2017-01-01

    Full Text Available Background/Aims: Open reduction and internal fixation (ORIF is a standard surgical procedure in jaw trauma and in orthognathic surgery. Insertion of screws is a significant risk for accidental tooth root injury with varying outcomes. Contrary evidences are found in literature due to a variety of study designs. This study was undertaken to address the lacunae and possibly estimate the difference in occurrence of tooth damage during or after ORIF between trauma and planned osteotomies. Materials and Methods: In this retrospective study, the data of ORIF in either trauma or orthognathic surgery fulfilling inclusion and exclusion criteria were collected and analyzed. Results: There were 1632 patients fulfilling the inclusion and exclusion criteria and formed the study group, of which 663 were in orthognathic surgery, of whom 210 had bimaxillary orthognathic surgery. In the trauma group, 358 patients had fractures involving both jaws whereas 272 had maxilla alone and 339 had mandibular fractures alone. On comparing the outcome, of the 9073 screws studied, 93.40% were not involved in any contact with the teeth, 6.3% were in category of potential hits (near apices or the root surfaces, and only 0.28% had evidence of root damage with the screws. It is observed that molar and premolar had a significant difference in terms of the type of surgery (P ≤ 0.05 whereas canine (P = 0.75 and incisor (P = 0.67 showed no statistical difference. Conclusion: ORIF when used as mentioned is a safe way for the management of fractures. The incidence of root injury is not uncommon but can be avoided with careful planning and execution.

  7. Evaluation of the stiffness characteristics of rapid palatal expander screws

    Directory of Open Access Journals (Sweden)

    Luca Lombardo

    2016-11-01

    Full Text Available Abstract Background The aim of this study is to evaluate the mechanical properties of the screws used for rapid expansion of the upper jaw. Methods Ten types of expansion screw were assessed, seven with four arms: Lancer Philosophy 1, Dentaurum Hyrax Click Medium, Forestadent Anatomic Expander type “S”, Forestadent Anatomic Expander type “S” for narrow palates, Forestadent Memory, Leone A 2620-10 with telescopic guide, and Leone A 0630-10 with orthogonal arms; and three with two arms: Dentaurum Variety S.P., Target Baby REP Veltri, and Leone A 362113. A test expander with the mean dimensions taken from measurements on a sample of 100 expanders was constructed for each screw. The test expanders were connected to the supports of an Instron 4467 (Instron Corp., USA mechanical testing machine equipped with a 500 N load cell, and the compression force exerted after each activation was measured. The mean forces expressed by the two- and four-arm expanders were then compared. Results After five activations, the forces expressed by the two-arm devices were double than those expressed by the four-arm devices on average (224 ± 59.9 N vs. 103 ± 32.9 N, and such values remained high after subsequent activations. Conclusions The expanders tested demonstrated stiffness characteristics compatible with opening of the palatine sutures in pre-adolescent patients. The stiffness of such devices can be further increased during the construction phase.

  8. Basic algebraic geometry, v.2

    CERN Document Server

    Shafarevich, Igor Rostislavovich

    1994-01-01

    Shafarevich Basic Algebraic Geometry 2 The second edition of Shafarevich's introduction to algebraic geometry is in two volumes. The second volume covers schemes and complex manifolds, generalisations in two different directions of the affine and projective varieties that form the material of the first volume. Two notable additions in this second edition are the section on moduli spaces and representable functors, motivated by a discussion of the Hilbert scheme, and the section on Kähler geometry. The book ends with a historical sketch discussing the origins of algebraic geometry. From the Zentralblatt review of this volume: "... one can only respectfully repeat what has been said about the first part of the book (...): a great textbook, written by one of the leading algebraic geometers and teachers himself, has been reworked and updated. As a result the author's standard textbook on algebraic geometry has become even more important and valuable. Students, teachers, and active researchers using methods of al...

  9. Optical geometry across the horizon

    International Nuclear Information System (INIS)

    Jonsson, Rickard

    2006-01-01

    In a recent paper (Jonsson and Westman 2006 Class. Quantum Grav. 23 61), a generalization of optical geometry, assuming a non-shearing reference congruence, is discussed. Here we illustrate that this formalism can be applied to (a finite four-volume) of any spherically symmetric spacetime. In particular we apply the formalism, using a non-static reference congruence, to do optical geometry across the horizon of a static black hole. While the resulting geometry in principle is time dependent, we can choose the reference congruence in such a manner that an embedding of the geometry always looks the same. Relative to the embedded geometry the reference points are then moving. We discuss the motion of photons, inertial forces and gyroscope precession in this framework

  10. Fatigue in tension perpendicular to the grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Bo Uhre; Hoffmeyer, Preben

    1999-01-01

    Traditinally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduce in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In order to test the predictive validity of the result from the small tension specimens, fatigue experiments...

  11. Fatigue In Tension Perpendicular to the Grain

    DEFF Research Database (Denmark)

    Clorius, Christian Odin; Pedersen, Martin Uhre; Hoffmeyer, Preben

    2004-01-01

    Traditionally fatigue resistance is quantified as number of cycles to failure at a given stress level. A previous study by the authors showed that fatigue in compression parallel to the grain is governed partly by duration of load and partly by an effect of loading, i.e. a combination of a creep...... mechanism and a mechanism connected to damage introduced in the loading sequences. The purpose of the present study is to disentangle the effect of duration of load from the effect of load oscillation in fatigue in tension perpendicular to the grain. Fatigue experiments are made on small specimens...... and on dowel type joints with slotted in steel plates. In series of ten, the small specimens are taken to fatigue failure in uniform tension at square wave shaped load cycles at 0.01 Hz and 0.1 Hz. In arder to test the predictive validity of the result from the small tension specimens, fatigue experiments...

  12. Tensions between Teams and Their Leaders

    Directory of Open Access Journals (Sweden)

    J. David Johnson

    2016-10-01

    Full Text Available The intersection of teamwork and leadership results in tensions, dilemmas, and paradoxes for both individuals and for institutions such as simultaneously empowering individuals at the same time it frustrates them when our naive, cultural understanding of leadership centralizes power and values leaders who can impose their will and vision on others. Perhaps the fundamental paradox of teamwork and leadership is that the more leadership is focused on an individual the less likely a team’s potential will be realized. Six specific domains where tensions arise are: at team boundaries; culture; who is in charge, rationality/cognition; diversity; and collaborations. Three approaches - clarifying different levels of analysis, temporal factors, and overarching concepts - to resolving tensions are discussed. New conceptions of leadership and the importance of the larger cultural frame within which they are embedded are needed for the management of technology and innovation.

  13. Cellular control of connective tissue matrix tension.

    Science.gov (United States)

    Langevin, Helene M; Nedergaard, Maiken; Howe, Alan K

    2013-08-01

    The biomechanical behavior of connective tissue in response to stretching is generally attributed to the molecular composition and organization of its extracellular matrix. It also is becoming apparent that fibroblasts play an active role in regulating connective tissue tension. In response to static stretching of the tissue, fibroblasts expand within minutes by actively remodeling their cytoskeleton. This dynamic change in fibroblast shape contributes to the drop in tissue tension that occurs during viscoelastic relaxation. We propose that this response of fibroblasts plays a role in regulating extracellular fluid flow into the tissue, and protects against swelling when the matrix is stretched. This article reviews the evidence supporting possible mechanisms underlying this response including autocrine purinergic signaling. We also discuss fibroblast regulation of connective tissue tension with respect to lymphatic flow, immune function, and cancer. Copyright © 2013 Wiley Periodicals, Inc.

  14. Surface tension of normal and heavy water

    International Nuclear Information System (INIS)

    Straub, J.; Rosner, N.; Grigull, V.

    1980-01-01

    A Skeleton Table and simple interpolation equation for the surface tension of light water was developed by the Working Group III of the International Association for the Properties of Steam and is recommended as an International Standard. The Skeleton Table is based on all known measurements of the surface tension and individual data were weighted corresponding to the accuracy of the measurements. The form of the interpolation equation is based on a physical concept. It represents an extension of van der Waals-equation, where the exponent conforms to the 'Scaling Laws'. In addition for application purposes simple relations for the Laplace-coefficient and for the density difference between the liquid and gaseous phases of light water are given. The same form of interpolation equation for the surface tension can be used for heavy water, for which the coefficients are given. However, this equation is based only on a single set of data. (orig.) [de

  15. Tension Stiffened and Tendon Actuated Manipulator

    Science.gov (United States)

    Doggett, William R. (Inventor); Dorsey, John T. (Inventor); Ganoe, George G. (Inventor); King, Bruce D. (Inventor); Jones, Thomas C. (Inventor); Mercer, Charles D. (Inventor); Corbin, Cole K. (Inventor)

    2015-01-01

    A tension stiffened and tendon actuated manipulator is provided performing robotic-like movements when acquiring a payload. The manipulator design can be adapted for use in-space, lunar or other planetary installations as it is readily configurable for acquiring and precisely manipulating a payload in both a zero-g environment and in an environment with a gravity field. The manipulator includes a plurality of link arms, a hinge connecting adjacent link arms together to allow the adjacent link arms to rotate relative to each other and a cable actuation and tensioning system provided between adjacent link arms. The cable actuation and tensioning system includes a spreader arm and a plurality of driven and non-driven elements attached to the link arms and the spreader arm. At least one cable is routed around the driven and non-driven elements for actuating the hinge.

  16. Dual head screw hip nailing for trochanteric fractures

    Science.gov (United States)

    Mavrogenis, Andreas F.; Igoumenou, Vasilios G.; Megaloikonomos, Panayiotis D.; Panagopoulos, George N.; Galanopoulos, Ioannis P.; Vottis, Christos Th.; Karamanis, Eirinaios; Koulouvaris, Panayiotis; Papagelopoulos, Panayiotis J.

    2017-01-01

    Introduction: There are limited information and inconclusive results for dual head screw intramedullary hip nails for trochanteric fractures. Therefore, we performed a prospective study to evaluate the healing of fractures, and survival, function, and complications of patients operated with this implant. Methods: We prospectively studied 79 patients (61 women and 18 men; mean age: 84.7 years; range: 65–96 years) with a low-energy trochanteric fracture, treated with a dual head screw intramedullary hip nail from 2013 to 2016. The mean follow-up was 2.1 years (range: 1–3 years); seven patients were lost to follow up. This left 72 patients for further analysis. We evaluated the healing of fractures, and survival, function, and complications of patients. Results: Fracture healing was evident in 70 patients (97.2%) at 2–3 months postoperatively. One patient experienced cut-out and z-effect phenomenon of the head screws. Another patient experienced a periprosthetic femoral diaphysis fracture at the distal tip of the nail. A third patient experienced an acute postoperative superficial skin infection that was treated successfully with wound dressing changes and a course of antibiotics. Sixteen patients (22.2%) deceased within 12 months postoperatively. In the remaining patients, the Harris Hip Score (HHS) at 12 months postoperatively was excellent in 16 (28.6%), good in 23 (41.1%), fair in 10 (17.8%), and poor in 7 patients (12.5%). The function declined after the patients’ fracture. Fair and poor results were related to age > 85 years, poor pre-fracture level of function, and AO/OTA-31-A3 fracture types. Conclusion: The dual head screw intramedullary hip nail is associated with high healing and low complication rates for intertrochanteric fractures. The function of the patients is good or excellent in most cases; however, it declines, especially for those patients with age > 85 years, poor pre-fracture level of function, and AO/OTA-31-A3 fracture types

  17. Dual head screw hip nailing for trochanteric fractures

    Directory of Open Access Journals (Sweden)

    Mavrogenis Andreas F.

    2017-01-01

    Full Text Available Introduction: There are limited information and inconclusive results for dual head screw intramedullary hip nails for trochanteric fractures. Therefore, we performed a prospective study to evaluate the healing of fractures, and survival, function, and complications of patients operated with this implant. Methods: We prospectively studied 79 patients (61 women and 18 men; mean age: 84.7 years; range: 65–96 years with a low-energy trochanteric fracture, treated with a dual head screw intramedullary hip nail from 2013 to 2016. The mean follow-up was 2.1 years (range: 1–3 years; seven patients were lost to follow up. This left 72 patients for further analysis. We evaluated the healing of fractures, and survival, function, and complications of patients. Results: Fracture healing was evident in 70 patients (97.2% at 2–3 months postoperatively. One patient experienced cut-out and z-effect phenomenon of the head screws. Another patient experienced a periprosthetic femoral diaphysis fracture at the distal tip of the nail. A third patient experienced an acute postoperative superficial skin infection that was treated successfully with wound dressing changes and a course of antibiotics. Sixteen patients (22.2% deceased within 12 months postoperatively. In the remaining patients, the Harris Hip Score (HHS at 12 months postoperatively was excellent in 16 (28.6%, good in 23 (41.1%, fair in 10 (17.8%, and poor in 7 patients (12.5%. The function declined after the patients’ fracture. Fair and poor results were related to age > 85 years, poor pre-fracture level of function, and AO/OTA-31-A3 fracture types. Conclusion: The dual head screw intramedullary hip nail is associated with high healing and low complication rates for intertrochanteric fractures. The function of the patients is good or excellent in most cases; however, it declines, especially for those patients with age > 85 years, poor pre-fracture level of function, and AO/OTA-31-A3

  18. A novel magnetic lead screw active suspension system for vehicles

    DEFF Research Database (Denmark)

    Berg, Nick Ilsø; Holm, Rasmus Koldborg; Rasmussen, Peter Omand

    2014-01-01

    This paper encompasses a detailed study of the redesign of a novel Magnetic Lead Screw (MLS) active suspension system for possible regeneration of the energy dispatched in the suspension system and active control of vehicle body movement. The MLS converts a low speed high force linear motion...... of a translator into a high speed low torque rotational motion of a rotor through helically shaped magnets. The paper describes the drawback of the first MLS prototype v1.0 developed for active suspension system, which lead to a new design of the MLS prototype named v1.5. Furthermore the paper introduces detailed...

  19. Anomalous behaviour of screw dislocations in quenched indium antimonide monocrystals

    International Nuclear Information System (INIS)

    Alekseenko, V.I.; Mostovoj, V.M.

    1991-01-01

    Anomalies of screw dislocation mobility in indium antimonide single crystals quenched after annealing were detected experimentally. Taking into accout specific nature of thermal treatment an enhanced attention is paid to the technique of the experiment. It is shown that the observed peculiarities can be explained using a model of thermoactivated movement of excessive bends over stoppers at the dislocation line. Proceeding from the assumption on the nature of stoppers, the values of stopper energy barriers overcome by an excessive bend are determined on the basis of the above model of excessive bend movement

  20. Titanium mesh as a low-profile alternative for tension-band augmentation in patella fracture fixation: A biomechanical study.

    Science.gov (United States)

    Dickens, Aaron J; Salas, Christina; Rise, LeRoy; Murray-Krezan, Cristina; Taha, Mahmoud Reda; DeCoster, Thomas A; Gehlert, Rick J

    2015-01-01

    We performed a simple biomechanical study to compare the fixation strength of titanium mesh with traditional tension-band augmentation, which is a standard treatment for transverse patella fractures. We hypothesised that titanium mesh augmentation is not inferior in fixation strength to the standard treatment. Twenty-four synthetic patellae were tested. Twelve were fixed with stainless steel wire and parallel cannulated screws. Twelve were fixed with parallel cannulated screws, augmented with anterior titanium mesh and four screws. A custom test fixture was developed to simulate a knee flexed to 90°. A uniaxial force was applied to the simulated extensor mechanism at this angle. A non-inferiority study design was used to evaluate ultimate force required for failure of each construct as a measure of fixation strength. Stiffness of the bone/implant construct, fracture gap immediately prior to failure, and modes of failure are also reported. The mean difference in force at failure was -23.0 N (95% CI: -123.6 to 77.6N) between mesh and wire constructs, well within the pre-defined non-inferiority margin of -260 N. Mean stiffness of the mesh and wire constructs were 19.42 N/mm (95% CI: 18.57-20.27 N/mm) and 19.49 N/mm (95% CI: 18.64-20.35 N/mm), respectively. Mean gap distance for the mesh constructs immediately prior to failure was 2.11 mm (95% CI: 1.35-2.88 mm) and 3.87 mm (95% CI: 2.60-5.13 mm) for wire constructs. Titanium mesh augmentation is not inferior to tension-band wire augmentation when comparing ultimate force required for failure in this simplified biomechanical model. Results also indicate that stiffness of the two constructs is similar but that the mesh maintains a smaller fracture gap prior to failure. The results of this study indicate that the use of titanium mesh plating augmentation as a low-profile alternative to tension-band wiring for fixation of transverse patella fractures warrants further investigation. Copyright © 2015 Elsevier Ltd. All

  1. Stationary bubbles and their tunneling channels toward trivial geometry

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Pisin; Yeom, Dong-han [Leung Center for Cosmology and Particle Astrophysics, National Taiwan University, Taipei 10617, Taiwan (China); Domènech, Guillem; Sasaki, Misao, E-mail: pisinchen@phys.ntu.edu.tw, E-mail: guillem.domenech@yukawa.kyoto-u.ac.jp, E-mail: misao@yukawa.kyoto-u.ac.jp, E-mail: innocent.yeom@gmail.com [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2016-04-01

    In the path integral approach, one has to sum over all histories that start from the same initial condition in order to obtain the final condition as a superposition of histories. Applying this into black hole dynamics, we consider stable and unstable stationary bubbles as a reasonable and regular initial condition. We find examples where the bubble can either form a black hole or tunnel toward a trivial geometry, i.e., with no singularity nor event horizon. We investigate the dynamics and tunneling channels of true vacuum bubbles for various tensions. In particular, in line with the idea of superposition of geometries, we build a classically stable stationary thin-shell solution in a Minkowski background where its fate is probabilistically given by non-perturbative effects. Since there exists a tunneling channel toward a trivial geometry in the entire path integral, the entire information is encoded in the wave function. This demonstrates that the unitarity is preserved and there is no loss of information when viewed from the entire wave function of the universe, whereas a semi-classical observer, who can see only a definitive geometry, would find an effective loss of information. This may provide a resolution to the information loss dilemma.

  2. The use of blocking screws with internal lengthening nail and reverse rule of thumb for blocking screws in limb lengthening and deformity correction surgery.

    Science.gov (United States)

    Muthusamy, Saravanaraja; Rozbruch, S Robert; Fragomen, Austin T

    2016-11-01

    Internal lengthening nail (ILN) is a recent development in limb lengthening and deformity correction specialty. The ILN has the distinct advantage of combining acute deformity correction with gradual lengthening of bone. While using ILN, the short metaphyseal bone fragment may develop a deformity at the time of osteotomy and nail insertion or during bone lengthening because of the wide medullary canal. These deformities are typically predictable, and blocking screws (Poller screws) are helpful in these situations. This manuscript describes the common deformities that occur in femur and tibia with osteotomies at different locations while using ILN in antegrade and retrograde nailing technique. Also, a systematic approach to the appropriate use of blocking screws in these deformities is described. In addition, the "reverse rule of thumb" is introduced as a quick reference to determine the ideal location(s) and number of blocking screws. These principles are applicable to limb lengthening and deformity correction as well as fracture fixation using intramedullary nails.

  3. End-threaded intramedullary positive profile screw ended self-tapping pin (Admit pin) - A cost-effective novel implant for fixing canine long bone fractures.

    Science.gov (United States)

    Chanana, Mitin; Kumar, Adarsh; Tyagi, Som Prakash; Singla, Amit Kumar; Sharma, Arvind; Farooq, Uiase Bin

    2018-02-01

    The current study was undertaken to evaluate the clinical efficacy of end-threaded intramedullary pinning for management of various long bone fractures in canines. This study was conducted in two phases, managing 25 client-owned dogs presented with different fractures. The technique of application of end-threaded intramedullary pinning in long bone fractures was initially standardized in 6 clinical patients presented with long bone fractures. In this phase, end-threaded pins of different profiles, i.e., positive and negative, were used as the internal fixation technique. On the basis of results obtained from standardization phase, 19 client-owned dogs clinically presented with different fractures were implanted with end-threaded intramedullary positive profile screw ended self-tapping pin in the clinical application phase. The patients, allocated randomly in two groups, when evaluated postoperatively revealed slight pin migration in Group-I (negative profile), which resulted in disruption of callus site causing delayed union in one case and large callus formation in other two cases whereas no pin migration was observed in Group-II (positive profile). Other observations in Group-I was reduced muscle girth and delayed healing time as compared to Group-II. In clinical application, phase 21 st and 42 nd day post-operative radiographic follow-up revealed no pin migration in any of the cases, and there was no bone shortening or fragment collapse in end-threaded intramedullary positive profile screw ended self-tapping pin. The end-threaded intramedullary positive profile screw ended self-tapping pin used for fixation of long bone fractures in canines can resist pin migration, pin breakage, and all loads acting on the bone, i.e., compression, tension, bending, rotation, and shearing to an extent with no post-operative complications.

  4. Fast neutron spectroscopy with tensioned metastable fluid detectors

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, T.F.; Taleyarkhan, R.P., E-mail: rusi@purdue.edu

    2016-09-11

    This paper describes research into development of a rapid-turnaround, neutron-spectroscopy capable (gamma-beta blind), high intrinsic efficiency sensor system utilizing the tensioned metastable fluid detector (TMFD) architecture. The inability of prevailing theoretical models (developed successfully for the classical bubble chamber) to adequately predict detection thresholds for tensioned metastable fluid conditions is described. Techniques are presented to overcome these inherent shortcomings, leading thereafter, to allow successful neutron spectroscopy using TMFDs – via the newly developed Single Atom Spectroscopy (SAS) approach. SAS also allows for a unique means for rapidly determining neutron energy thresholds with TMFDs. This is accomplished by simplifying the problem of determining Cavitation Detection Events (CDEs) arising from neutron interactions with one in which several recoiling atom species contribute to CDEs, to one in which only one dominant recoil atom need be considered. The chosen fluid is Heptane (C{sub 7}H{sub 16}) for which only recoiling C atoms contribute to CDEs. Using the SAS approach, the threshold curve for Heptane was derived using isotope neutron source data, and then validated against experiments with mono-energetic (2.45/14 MeV) neutrons from D-D and D-T accelerators. Thereafter the threshold curves were used to produce the response matrix for various geometries. The response matrices were in turn combined with experimental data to recover the continuous spectra of fission (Cf-252) and (α,n) Pu–Be isotopic neutron sources via an unfolding algorithm. A generalized algorithm is also presented for performing neutron spectroscopy using any other TMFD fluid that meets the SAS approach assumptions.

  5. Active Tension Network model reveals an exotic mechanical state realized in epithelial tissues

    Science.gov (United States)

    Noll, Nicholas; Mani, Madhav; Heemskerk, Idse; Streicha, Sebastian; Shraiman, Boris

    Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behavior remains an open problem. Here we formulate and analyze the Active Tension Network (ATN) model, which assumes that mechanical balance of cells is dominated by cortical tension and introduces tension dependent active remodeling of the cortex. We find that ATNs exhibit unusual mechanical properties: i) ATN behaves as a fluid at short times, but at long times it supports external tension, like a solid; ii) its mechanical equilibrium state has extensive degeneracy associated with a discrete conformal - ''isogonal'' - deformation of cells. ATN model predicts a constraint on equilibrium cell geometry, which we demonstrate to hold in certain epithelial tissues. We further show that isogonal modes are observed in a fruit fly embryo, accounting for the striking variability of apical area of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, understanding which helps understand biological phenomena.

  6. Active tension network model suggests an exotic mechanical state realized in epithelial tissues

    Science.gov (United States)

    Noll, Nicholas; Mani, Madhav; Heemskerk, Idse; Streichan, Sebastian J.; Shraiman, Boris I.

    2017-12-01

    Mechanical interactions play a crucial role in epithelial morphogenesis, yet understanding the complex mechanisms through which stress and deformation affect cell behaviour remains an open problem. Here we formulate and analyse the active tension network (ATN) model, which assumes that the mechanical balance of cells within a tissue is dominated by cortical tension and introduces tension-dependent active remodelling of the cortex. We find that ATNs exhibit unusual mechanical properties. Specifically, an ATN behaves as a fluid at short times, but at long times supports external tension like a solid. Furthermore, an ATN has an extensively degenerate equilibrium mechanical state associated with a discrete conformal--`isogonal'--deformation of cells. The ATN model predicts a constraint on equilibrium cell geometries, which we demonstrate to approximately hold in certain epithelial tissues. We further show that isogonal modes are observed in the fruit fly embryo, accounting for the striking variability of apical areas of ventral cells and helping understand the early phase of gastrulation. Living matter realizes new and exotic mechanical states, the study of which helps to understand biological phenomena.

  7. The Research of Screw Thread Parameter Measurement Based on Position Sensitive Detector and Laser

    International Nuclear Information System (INIS)

    Tong, Q B; Ding, Z L; Chen, J C; Ai, L L; Yuan, F

    2006-01-01

    A technique and system of measuring screw thread parameter based on the theory of laser measurement is presented in this paper, which can be carried out the automated measurement of screw thread parameter. An inspection instrument was designed and produced, which included exterior imaging system of optical path, transverse displacement measurement system, axial displacement measurement system, and a module to deal with, control and assess the data in the upper system. The inspection and estimate of the screw thread contour curve were completed by using position sensitive device (PSD) as photoelectric detector to measure the coordinate data of the screw thread contour curve in the transverse section, and using precise raster to measure the axial displacement of the precision worktable under the screw thread test criterion., computer can gives a measured result according to coordinate data of the screw thread obtained by PSD. The relation between measured spot and image is established, and optimum design of the system organization are introduced, including the image length of receiving lens focal length optical system and the choice of PSD , and some main factor affected measuring precision are analyzed. The experimental results show that the measurement uncertainty of screw thread minor diameter can reach 0. 5μm, which can meet most requests for the measurement of screw thread parameter

  8. To retain or remove the syndesmotic screw: a review of literature

    NARCIS (Netherlands)

    T. Schepers (Tim)

    2011-01-01

    textabstractIntroduction: Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this

  9. To retain or remove the syndesmotic screw: a review of literature

    NARCIS (Netherlands)

    Schepers, T.

    2011-01-01

    Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this study, the recent

  10. Screw-System-Based Mobility Analysis of a Family of Fully Translational Parallel Manipulators

    Directory of Open Access Journals (Sweden)

    Ernesto Rodriguez-Leal

    2013-01-01

    Full Text Available This paper investigates the mobility of a family of fully translational parallel manipulators based on screw system analysis by identifying the common constraint and redundant constraints, providing a case study of this approach. The paper presents the branch motion-screws for the 3-RP̲C-Y parallel manipulator, the 3-RCC-Y (or 3-RP̲RC-Y parallel manipulator, and a newly proposed 3-RP̲C-T parallel manipulator. Then the paper determines the sets of platform constraint-screws for each of these three manipulators. The constraints exerted on the platforms of the 3-RP̲C architectures and the 3-RCC-Y manipulators are analyzed using the screw system approach and have been identified as couples. A similarity has been identified with the axes of couples: they are perpendicular to the R joint axes, but in the former the axes are coplanar with the base and in the latter the axes are perpendicular to the limb. The remaining couples act about the axis that is normal to the base. The motion-screw system and constraint-screw system analysis leads to the insightful understanding of the mobility of the platform that is then obtained by determining the reciprocal screws to the platform constraint screw sets, resulting in three independent instantaneous translational degrees-of-freedom. To validate the mobility analysis of the three parallel manipulators, the paper includes motion simulations which use a commercially available kinematics software.

  11. Screwing or unscrewing device for studs or bolls of big dimension

    International Nuclear Information System (INIS)

    Sevelinge, G.; Bourdonne, J.C.

    1988-01-01

    The device for screwing or unscrewing large studs or bolts has a system determining the optimun screwing position and orientation of the bolt, a variable speed bidirectional drive a pin holding the bolt axially and system compensating the weight of the bolt with an hydraulic jack with a pressure detector to which the drive is slaved [fr

  12. Strength evaluation of top nozzle holddown spring screw for nuclear fuel assembly

    International Nuclear Information System (INIS)

    Koh, S. K.; Won, S. Y.; Ryu, C. H.; Kim, Y. J.; Lee, K. S.; Jeon, K. L.

    2002-01-01

    Holddown springs are required to maintain the nuclear fuel assembly in contact with lower core plate and permit thermal and irradiation-induced length changes. Therefore, the holddown spring screw must be designed such that it is capable of sustaining the loads imposed by the initial tensile preload and operational loads. Prior to assessing the structural integrity of the spring screw in the corrosive and irradiating environment throughout the design lifetime of the fuel assembly, the strength evaluation of screw was made in this paper using the mechanics of materials and finite element methods. Calculations based on the mechanics of materials, showed that the preloaded screw with an operating holddown force had a quite large margin of safety in strength. However, the elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Preloading on the screw applied for tightening had beneficial effects on the screw strength by reducing the stress level at the critical regions, compared to the screw without preload. Calculated spring deflection using the finite element analysis was in close agreement with the experimentally measured deflection

  13. Percutaneous Intramedullary Screw Fixation of Distal Fibula Fractures: A Case Series and Systematic Review

    NARCIS (Netherlands)

    Loukachov, Vladimir V.; Birnie, Merel F. N.; Dingemans, Siem A.; de Jong, Vincent M.; Schepers, Tim

    2017-01-01

    The current reference standard for unstable ankle fractures is open reduction and internal fixation using a plate and lag screws. This approach requires extensive dissection and wound complications are not uncommon. The use of intramedullary screw fixation might overcome these issues. The aim of our

  14. Locking screw-plate interface stability in carbon-fibre reinforced polyetheretherketone proximal humerus plates.

    Science.gov (United States)

    Hak, David J; Fader, Ryan; Baldini, Todd; Chadayammuri, Vivek B S

    2017-09-01

    Carbon-fibre reinforced polyetheretherketone (CFR-PEEK) plates have recently been introduced for proximal humerus fracture treatment. The purpose of this study was to compare the locking screw-plate interface stability in CFR-PEEK versus stainless steel (SS) proximal humerus plates. Locking screw mechanical stability was evaluated independently in proximal and shaft plate holes. Stiffness and load to failure were tested for three conditions: (1) on-axis locking screw insertion in CFR-PEEK versus SS plates, (2) on-axis locking screw insertion, removal, and reinsertion in CFR-PEEK plates, and (3) 10-degree off-axis locking screw insertion in CFR-PEEK plates. Cantilever bending at a rate of 1 mm/minute was produced by an Instron machine and load-displacement data recorded. Shaft locking screw load to failure was significantly greater in CFR-PEEK plates compared to SS plates (746.4 ± 89.7 N versus 596.5 ± 32.6 N, p PEEK plates (p PEEK plates. The mechanical stability of locking screws in CFR-PEEK plates is comparable or superior to locking screws in SS plates.

  15. Treating Simple Tibia Fractures with Poly-DL-Lactic Acid Screw as a ...

    African Journals Online (AJOL)

    Purpose: To investigate the curative effect of poly-DL-lactic acid (PDLLA) absorbable screw as a locked intramedullary nail for simple tibia fractures. Methods: In this study, 35 patients treated with the PDLLA screw were observed, and another 35 patients treated with a traditional locking intramedullary nail were treated as ...

  16. Atomistic simulations of cross-slip of jogged screw dislocations in copper

    DEFF Research Database (Denmark)

    Vegge, T.; Rasmussen, T.; Leffers, T.

    2001-01-01

    We have performed atomic-scare simulations of cross-slip processes of screw dislocations in copper, simulating jog-free dislocations as well as different types of jogged screw dislocations. Minimum-energy paths and corresponding transition state energies are obtained using the nudged-elastic...

  17. Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement.

    Science.gov (United States)

    Hou, Yang; Shi, Jiangang; Lin, Yanping; Chen, Huajiang; Yuan, Wen

    2018-06-01

    The cervical screw placement is one of the most difficult procedures in spine surgery, which often needs a long period of repeated practices and could cause screw placement-related complications. We performed this cadaver study to investigate the effectiveness of virtual surgical training system (VSTS) on cervical pedicle screw instrumentation for residents. A total of ten novice residents were randomly assigned to two groups: the simulation training (ST) group (n = 5) and control group (n = 5). The ST group received a surgical training of cervical pedicle screw placement on VSTS and the control group was given an introductory teaching session before cadaver test. Ten fresh adult spine specimens including 6 males and 4 females were collected, and were randomly allocated to the two groups. The bilateral C3-C6 pedicle screw instrumentation was performed in the specimens of the two groups, respectively. After instrumentation, screw positions of the two groups were evaluated by image examinations. There was significantly statistical difference in screw penetration rates between the ST (10%) and control group (62.5%, P VSTS as an advanced training tool exhibited promising effects on improving performance of novice residents in cervical pedicle screw placement compared with the traditional teaching methods.

  18. Ball tip method for thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis

    International Nuclear Information System (INIS)

    Watanabe, Kota; Matsumoto, Morio; Iizuka, Shingo

    2008-01-01

    The purpose of this study was to evaluate the efficacy of ball tip method for thoracic pedicle screw placements in idiopathic scoliosis patients. 24 patients with adolescent idiopathic scoliosis were included in this study. Conventional method was performed in 12 patients. Ball tip method was performed in 12 patients. Accuracy of the pedicle screw placement was evaluated based on the postoperative CT. In the ball tip method, a probe which was consisted of ball tip with flexible shaft was used. After removing of cortical bone at a starting point, the probe was inserted manually or sometimes with gently tapping by hammer. During the maneuver, the probe will gradually progress into cancellous bone in the pedicle, without perforating cortical bone in the pedicle. Following expansion of the hole by a rigid gear shift probe, screw was placed in the pedicle. 65.1% of screws were located within pedicle in the conventional group and 86.5% in the ball tip group. 5.3% of screws were located out of pedicle within 2 mm in the conventional group and 8.2% in the ball tip group. 15.8% of screws were located out of pedicle beyond 2 mm and 1.8% in the ball tip group. The ball tip method enhanced the accuracy of thoracic pedicle screw placements in adolescent idiopathic scoliosis patients. The ball tip method may be effective for accurate pedicle screw placement in patients with adolescent idiopathic scoliosis. (author)

  19. Four quadrant parallel peripheral screw fixation for displaced femoral neck fractures in elderly patients

    Directory of Open Access Journals (Sweden)

    Bhava RJ Satish

    2013-01-01

    Conclusion: Closed reduction and cannulated cancellous screw fixation gives satisfactory functional results in large group of elderly patients. The four quadrant parallel peripheral (FQPP screw fixation technique gives good stability, allows controlled collapse, avoids fixation failure and achieves predictable bone healing in displaced femoral neck fracture in patients ≥50 years of age.

  20. [Measurement of screw length through drilling technique in osteosynthesis of the proximal humerus fractures].

    Science.gov (United States)

    Avcı, Cem Coşkun; Gülabi, Deniz; Sağlam, Necdet; Kurtulmuş, Tuhan; Saka, Gürsel

    2013-01-01

    This study aims to investigate the efficacy of screw length measurement through drilling technique on the reduction of intraarticular screw penetration and fluoroscopy time in osteosynthesis of proximal humerus fractures. Between January 2008 and June 2012, 98 patients (34 males, 64 females; mean age 64.4 years; range 35 to 81 years) who underwent osteosynthesis using locking anatomical proximal humerus plates (PHILOS) in our clinic with the diagnosis of Neer type 2, 3 or 4 were included. Two different surgical techniques were used to measure proximal screw length in the plate and patients were divided into two groups based on the technique used. In group 1, screw length was determined by a 3 mm blunt tipped Kirschner wire without fluoroscopic control. In group 2, bilateral fluoroscopic images for each screw at least were obtained. Intraarticular screw penetration was detected in five patients (10.6%) in group 1, and in 19 patients (37.3%) in group 2. The mean fluoroscopic imaging time was 10.6 seconds in group 1 and 24.8 seconds in group 2, indicating a statistically significant difference. Screw length measurement through the drilling technique significantly reduces the intraarticular screw penetration and fluoroscopy time in osteosynthesis of proximal humerus fractures using PHILOS plates.