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Sample records for carbonate interference screw

  1. Carbon nanotube Archimedes screws.

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    Oroszlány, László; Zólyomi, Viktor; Lambert, Colin J

    2010-12-28

    Recently, nanomechanical devices composed of a long stationary inner carbon nanotube and a shorter, slowly rotating outer tube have been fabricated. In this paper, we study the possibility of using such devices as nanoscale transducers of motion into electricity. When the outer tube is chiral, we show that such devices act like quantum Archimedes screws, which utilize mechanical energy to pump electrons between reservoirs. We calculate the pumped charge from one end of the inner tube to the other, driven by the rotation of a chiral outer nanotube. We show that the pumped charge can be greater than one electron per 360° rotation, and consequently, such a device operating with a rotational frequency of 10 MHz, for example, would deliver a current of ≈1 pAmp.

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

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    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.

  3. Biomechanical properties of a novel biodegradable magnesium-based interference screw

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    Marco Ezechieli

    2016-06-01

    Full Text Available Magnesium-based interference screws may be an alternative in anterior/posterior cruciate ligament reconstruction. The well-known osteoconductive effects of biodegradable magnesium alloys may be useful. It was the purpose of this study to evaluate the biomechanical properties of a magnesium based interference screw and compare it to a standard implant. A MgYREZr-alloy interference screw and a standard implant (Milagro®; De Puy Mitek, Raynham, MA, USA were used for graft fixation. Specimens were placed into a tensile loading fixation of a servohydraulic testing machine. Biomechanical analysis included pretensioning of the constructs at 20 N for 1 min following cyclic pretensioning of 20 cycles between 20 and 60 N. Biomechanical elongation was evaluated with cyclic loading of 1000 cycles between 50 and 200 N at 0.5 Hz. Maximum load to failure was 511.3±66.5 N for the Milagro® screw and 529.0±63.3 N for magnesium-based screw (ns, P=0.57. Elongations after preload, during cyclical loading and during failure load were not different between the groups (ns, P>0.05. Stiffness was 121.1±13.8 N/mm for the magnesiumbased screw and 144.1±18.4 for the Milagro® screw (ns, P=0.32. MgYREZr alloy interference screws show comparable results in biomechanical testing to standard implants and may be an alternative for anterior cruciate reconstruction in the future.

  4. Interference Screw vs. Suture Anchor Fixation for Open Subpectoral Biceps Tenodesis: Does it Matter?

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    Gobezie Reuben

    2008-09-01

    Full Text Available Abstract Background Bioabsorbable interference screw fixation has superior biomechanical properties compared to suture anchor fixation for biceps tenodesis. However, it is unknown whether fixation technique influences clinical results. Hypothesis We hypothesize that subpectoral interference screw fixation offers relevant clinical advantages over suture anchor fixation for biceps tenodesis. Study Design Case Series. Methods We performed a retrospective review of a consecutive series of 88 patients receiving open subpectoral biceps tenodesis with either interference screw fixation (34 patients or suture anchor fixation (54 patients. Average follow up was 13 months. Outcomes included Visual Analogue Pain Scale (0–10, ASES score, modified Constant score, pain at the tenodesis site, failure of fixation, cosmesis, deformity (popeye and complications. Results There were no failures of fixation in this study. All patients showed significant improvement between their preoperative and postoperative status with regard to pain, ASES score, and abbreviated modified Constant scores. When comparing IF screw versus anchor outcomes, there was no statistical significance difference for VAS (p = 0.4, ASES score (p = 0.2, and modified Constant score (P = 0.09. One patient (3% treated with IF screw complained of persistent bicipital groove tenderness, versus four patients (7% in the SA group (nonsignificant. Conclusion Subpectoral biceps tenodesis reliably relieves pain and improves function. There was no statistically significant difference in the outcomes studied between the two fixation techniques. Residual pain at the site of tenodesis may be an issue when suture anchors are used in the subpectoral location.

  5. Bacterial adherence to titanium, poly-L-lactic acid, and composite hydroxyapatite and poly-L-lactic acid interference screws.

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    Masini, Brendan D; Stinner, Daniel J; Waterman, Scott M; Wenke, Joseph C; Gerlinger, Tad L

    2012-01-01

    This study investigates a potential site of bacterial adherence, the implant surface, comparing titanium, poly-L-lactic acid (PLLA), and composite hydroxyapatite and poly-L-lactic acid (PLLA-HA) interference screws using a bioluminescent in vitro model. Interference screws of three materials, titanium (Arthrex, Naples, FL), bioabsorbable poly-L-lactic acid (BIORCI, Smith & Nephew, Andover, MA), and bioabsorbable composite hydroxyapatite and poly-L-lactic acid (BIORCI-HA, Smith & Nephew, Andover, MA) were immersed in a broth of bioluminescent Staphylococcus aureus. The screws were irrigated and then imaged with a photon-capturing camera system yielding a total photon count correlating with residual adherent bacteria. The titanium screws had the lowest mean total bacterial counts followed by the PLLA-HA screws and with the PLLA screws having the highest mean total counts. The difference in means between the titanium group and the PLLA group was statistically significant (p bacterial adherence than comparable bioabsorbable PLLA screws.

  6. The Biocompatibility of Degradable Magnesium Interference Screws: An Experimental Study with Sheep

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    Ulrich Thormann

    2015-01-01

    Full Text Available Screws for ligament reconstruction are nowadays mostly made of poly-L-lactide (PLLA. However, magnesium-based biomaterials are gathering increased interest in this research field because of their good mechanical property and osteoanabolic influence on bone metabolism. The aim of this pilot study was to evaluate the biocompatibility of an interference screw for ligament reconstruction made of magnesium alloy W4 by diecasting and milling and using different PEO-coatings with calcium phosphates. PLLA and titanium screws were used as control samples. The screws were implanted in the femur condyle of the hind leg of a merino sheep. The observation period was six and twelve weeks and one year. Histomorphometric, immunohistochemical, immunofluorescence, and molecular biological evaluation were conducted. Further TEM analysis was done. In all magnesium screws a clinically relevant gas formation in the vicinity of the biomaterial was observed. Except for the PLLA and titanium control samples, no screw was fully integrated in the surrounding bone tissue. Regarding the fabrication process, milling seems to produce less gas liberation and has a better influence on bone metabolism than diecasting. Coating by PEO with calcium phosphates could not reduce the initial gas liberation but rather reduced the bone metabolism in the vicinity of the biomaterial.

  7. Magnetic resonance imaging analysis of the bioabsorbable Milagro interference screw for graft fixation in anterior cruciate ligament reconstruction.

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    Frosch, K-H; Sawallich, T; Schütze, G; Losch, A; Walde, T; Balcarek, P; Konietschke, F; Stürmer, K M

    2009-10-01

    Ligament graft fixation with bioabsorbable interference screws is a standard procedure in cruciate ligament replacement. Previous screw designs may resorb incompletely, and can cause osteolysis and sterile cysts despite being implanted for several years. The aim of this study was to examine the in vivo degradation and biocompatibility of the new Milagro interference screw (Mitek, Norderstedt, Germany). The Milagro interference screw is made of 30% ss-TCP (TriCalcium phosphate) and 70% PLGA (Poly-lactic-co-glycolic acid). In the period between June 2005 and February 2006, 38 patients underwent graft fixation with Milagro screws in our hospital. Arthroscopic ACL reconstruction was performed using hamstring tendon grafts in all the patients. MR imaging was performed on 12 randomly selected patients out of the total of 38 at 3, 6 and 12 months after surgery. During the examination, the volume loss of the screw, tunnel enlargement, presence of osteolysis, fluid lines, edema and postoperative screw replacement by bone tissue were evaluated. There was no edema or signs of inflammation around the bone tunnels. At 3, 6 and 12 months, the tibial screws showed an average volume loss of 0, 8.1% (+/-7.9%) and 82.6% (+/-17.2%, P Milagro screw is closely linked to the graft healing process. The screws were rapidly resorbed after 6 months and, at 12 months, only the screw remnants were detectable. Moreover, the Milagro screw is biocompatible and osteoconductive, promoting bone ingrowth during resorption. Tunnel enlargement is not prevented in the first months but is reduced by bone ingrowth after 12 months.

  8. Tibial inlay press-fit fixation versus interference screw in posterior cruciate ligament reconstruction

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    Max Ettinger

    2013-11-01

    Full Text Available Reconstruction of the posterior cruciate ligament (PCL by a tibial press-fit fixation of the patellar tendon with an accessory bone plug is a promising approach because no foreign materials are required. Until today, there is no data about the biomechanical properties of such press-fit fixations. The aim of this study was to compare the biomechanical qualities of a bone plug tibial inlay technique with the commonly applied interference screw of patellar tendon PCL grafts. Twenty patellar tendons including a bone block were harvested from ten human cadavers. The grafts were implanted into twenty legs of adult German country pigs. In group P, the grafts were attached in a press-fit technique with accessory bone plug. In group S, the grafts were fixed with an interference screw. Each group consisted of 10 specimens. The constructs were biomechanically analyzed in cyclic loading between 60 and 250 N for 500 cycles recording elongation. Finally, ultimate failure load and failure mode were analyzed. Ultimate failure load was 598.6±36.3 N in group P and 653.7±39.8 N in group S (not significant, P>0.05. Elongation during cyclic loading between the 1st and the 20th cycle was 3.4±0.9 mm for group P and 3.1±1 mm for group S. Between the 20th and the 500th cycle, elongation was 4.2±2.3 mm in group P and 2.5±0.9 mm in group S (not significant, P>0.05. This is the first study investigating the biomechanical properties of tibial press-fit fixation of the patellar tendon with accessory bone plug in posterior cruciate ligament reconstruction. The implant-free tibial inlay technique shows equal biomechanical characteristics compared to an interference screw fixation. Further in vivo studies are desirable to compare the biological behavior and clinical relevance of this fixation device.

  9. Painful knee joint after ACL reconstruction using biodegradable interference screws- SPECT/CT a valuable diagnostic tool? A case report

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    Hirschmann Michael T

    2010-09-01

    Full Text Available Abstract With the presented case we strive to introduce combined single photon emission computerized tomography and conventional computer tomography (SPECT/CT as new diagnostic imaging modality and illustrate the possible clinical value in patients after ACL reconstruction. We report the case of a painful knee due to a foreign body reaction and delayed degradation of the biodegradable interference screws after ACL reconstruction. The MRI showed an intact ACL graft, a possible tibial cyclops lesion and a patella infera. There was no increased fluid collection within the bone tunnels. The 99mTc-HDP-SPECT/CT clearly identified a highly increased tracer uptake around and within the tibial and femoral tunnels and the patellofemoral joint. On 3D-CT out of the SPECT/CT data the femoral graft attachment was shallow (50% along the Blumensaat's line and high in the notch. At revision arthroscopy a diffuse hypertrophy of the synovium, scarring of the Hoffa fat pad and a cyclops lesion of the former ACL graft was found. The interference screws were partially degraded and under palpation and pressure a grey fluid-like substance drained into the joint. The interference screws and the ACL graft were removed and an arthrolysis performed. In the case presented it was most likely a combination of improper graft placement, delayed degradation of the interference screws and unknown biological factors. The too shallow and high ACL graft placement might have led to roof impingement, chronic intraarticular inflammation and hence the delayed degradation of the screws. SPECT/CT has facilitated the establishment of diagnosis, process of decision making and further treatment in patients with knee pain after ACL reconstruction. From the combination of structural (tunnel position in 3D-CT and metabolic information (tracer uptake in SPECT/CT the patient's cause of the pain was established.

  10. Carbon nanostructure composite for electromagnetic interference shielding

    Indian Academy of Sciences (India)

    Anupama Joshi; Suwarna Datar

    2015-06-01

    This communication reviews current developments in carbon nanostructure-based composite materials for electromagnetic interference (EMI) shielding. With more and more electronic gadgets being used at different frequencies, there is a need for shielding them from one another to avoid interference. Conventionally, metal-based shielding materials have been used. But due to the requirement of light weight, corrosion resistive materials, lot of work is being done on composite materials. In this research the forerunner is the nanocarbon-based composite material whose different forms add different characteristics to the composite. The article focusses on composites based on graphene, graphene oxide, carbon nanotubes, and several other novel forms of carbon.

  11. Interference screw versus Endoscrew fixation for anterior cruciate ligament reconstruction: A biomechanical comparative study in sawbones and porcine knees

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    Chu-Chih Hung

    2014-04-01

    Full Text Available Interference screw fixation is one of the most common methods for ligament reconstruction. Although the advantages and clinical outcomes of this procedure have been widely reported, post-surgical complications often arise. The purpose of this study was to evaluate a new femoral fixation device, the Endoscrew, for anterior cruciate ligament (ACL reconstruction. We performed a mechanical test in accordance with American Society for Testing and Materials (ASTM standards and an in vitro biomechanical study. An axial pullout test was conducted to evaluate the mechanical properties of the new device and the interference screw when implanted in solid rigid polyurethane foam test blocks. The biomechanical test used porcine femora to evaluate the initial fixation strength between these two implants. The maximum pullout force of the interference screw group [722.05 ± 130.49 N (N] was significantly greater (p < 0.01 than the Endoscrew group (440.79 ± 26.54 N when implanted in polyurethane foam 320 kg/m3 density. With polyurethane foam 160 kg/m3 density, the maximum pullout forces were (242.61 ± 37.36 N (p < 0.001 and (99.33 ± 30.01 N for the interference screw group and Endoscrew group, respectively. In the in vitro mechanical study, the Endoscrew (646.39 ± 72.38 N required a significantly greater ultimate load prior to failure (p < 0.05 when compared with the interference screw (489.72 ± 138.64 N. With regard to pullout stiffness, there was no statistically significant difference (p < 0.13 between the Endoscrew group (99.15 ± 12.16 N/mm and the interference screw group (87.96 ± 11.12 N/mm. The cyclic stiffness was also not significantly different (p < 0.44 between the Endoscrew group (93.09 ± 16.07 N/mm and the interference screw group (85.78 ± 14.76 N/mm. The axial pullout test showed that the strength of the Endoscrew was close to the fixation strength required for daily activities, but it is

  12. Secondary Electron Interference from Trigonal Warping in Clean Carbon Nanotubes

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    Dirnaichner, A.; del Valle, M.; Götz, K. J. G.; Schupp, F. J.; Paradiso, N.; Grifoni, M.; Strunk, Ch.; Hüttel, A. K.

    2016-10-01

    We investigate Fabry-Perot interference in an ultraclean carbon nanotube resonator. The conductance shows a clear superstructure superimposed onto conventional Fabry-Perot oscillations. A sliding average over the fast oscillations reveals a characteristic slow modulation of the conductance as a function of the gate voltage. We identify the origin of this secondary interference in intervalley and intravalley backscattering processes which involve wave vectors of different magnitude, reflecting the trigonal warping of the Dirac cones. As a consequence, the analysis of the secondary interference pattern allows us to estimate the chiral angle of the carbon nanotube.

  13. Wear resistance of thick diamond like carbon coatings against polymeric materials used in single screw plasticizing technology

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    Zitzenbacher, G.; Liu, K.; Forsich, C.; Heim, D.

    2015-05-01

    Wear on the screw and barrel surface accompany polymer single screw plasticizing technology from the beginning. In general, wear on screws can be reduced by using nitrided steel surfaces, fused armour alloys on the screw flights and coatings. However, DLC-coatings (Diamond Like Carbon) comprise a number of interesting properties such as a high hardness, a low coefficient of friction and an excellent corrosion resistance due to their amorphous structure. The wear resistance of about 50 µm thick DLC-coatings against polyamide 6.6, polybutylene terephthalate and polypropylene is investigated in this paper. The tribology in the solids conveying zone of a single screw extruder until the beginning of melting is evaluated using a pin on disc tribometer and a so called screw tribometer. The polymeric pins are pressed against coated metal samples using the pin on disc tribometer and the tests are carried out at a defined normal force and sliding velocity. The screw tribometer is used to perform tribological experiments between polymer pellets and rotating coated metal shafts simulating the extruder screw. Long term experiments were performed to evaluate the wear resistance of the DLC-coating. A reduction of the coefficient of friction can be observed after a frictional distance of about 20 kilometers using glass fibre reinforced polymeric materials. This reduction is independent on the polymer and accompanied by a black layer on the wear surface of the polymeric pins. The DLC-coated metal samples show an up to 16 µm deep wear track after the 100 kilometer test period against the glass fiber filled materials only.

  14. DLC screw preload. Loosening prevention

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    Ivete Aparecida de Mattias Sartori

    2008-01-01

    Full Text Available The screw loosening is a reason to prosthetic rehabilitation failure. However, the DLC (Diamond-like carbon screw treatment lead thefriction decrease and sliding between the components, which increases the screw preload benefit and decreases the chance of looseningoccurrence. This case shows a clinical indication of the association of the correct preload applied and the DLC screw, which can be considered an optimized protocol to solve screw loosening recidivate of unitary prosthesis in anterior maxillary site.

  15. Electrical and Thermal Properties of Twin-Screw Extruded Multiwalled Carbon Nanotube/Epoxy Composites

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    Karippal, Jeena Jose; Narasimha Murthy, H. N.; Rai, K. S.; Krishna, M.; Sreejith, M.

    2010-11-01

    This paper presents the experimental results of dispersing multiwalled carbon nanotubes (MWNTs) into epoxy (space grade structural adhesive) nanocomposites using co-rotating twin screw extrusion process. Two sets of specimens were prepared; set 1 with ultrasonication for predispersing MWNT before extrusion and set 2 direct dispersion of MWNT in the extruder. MWNT was loaded up to 8 vol.% in both the sets. The specimens were characterized for room temperature volume and surface resistivities as per ASTM D257 using Keithley Model 6517 and for thermal conductivity in the temperature range -50 to 150 °C as per ASTM E 1530 using Thermal Conductivity Instrument (TCI) 2022 SX211. The volume resistivity of sets 1 and 2 decreased to an extent of 1011 and 109 respectively. The surface resistivity drop was of the order of 109 for both the sets. These drops corresponded to the maximum MWNT loading of 8 vol.%. Electrical conductivity values of the specimens were fitted into the Power Law Model to evaluate the critical exponent. Both sets 1 and 2 showed increase in thermal conductivity with increase in temperature in the testing range. Thermal conductivity increased with increase in filler loading and the maximum increase was 60% at 150 °C in case of 8 vol.% MWNT nanocomposites for set 1. The corresponding value for the set 2 was 25%. Thermal conductivity values were predicted using Lewis Nielson model. DSC of the specimens showed increase in glass transition temperature with increase in filler loading. The dispersion of the nanofillers was studied using SEM and the surface morphology using AFM.

  16. Carbon cycle and climate commitments from early human interference

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    Zickfeld, K.; Solomon, S.

    2015-12-01

    According to the early anthropogenic hypothesis proposed by Ruddiman (2003), human influence on Earth's climate began several thousand years before the beginning of the industrial era. Agriculture and deforestation starting around 8000 years before present (BP) and slowly increasing over the Holocene, would have led to an increase in atmospheric methane (CH4) and carbon dioxide (CO2) concentration, preventing a natural cooling of Earth's climate. Here, the emphasis is not on testing Ruddiman's hypothesis, but rather on exploring the carbon cycle and climate commitment from potential early CH4 and CO2 emissions. In contrast to modern greenhouse gas emissions, early emissions occurred over millennia, allowing the climate system to come to near-equilibrium with the applied forcing. We perform two transient Holocene simulations with an Earth system model of intermediate complexity - the University of Victoria Earth System Climate Model (UVic ESCM). The first simulation is a standard transient Holocene simulation, forced with reconstructed changes in CO2 and CH4 concentrations and orbital and volcanic forcing. The second simulation is forced with CO2 and CH4 concentrations corrected for the net anthropogenic contribution postulated by Ruddiman (2007), with other forcings evolving as in the standard simulation. The difference in diagnosed emissions between the two simulations allows us to determine the anthropogenic emissions. After year 1850, anthropogenic CO2 and CH4 emissions are set to zero and the simulations continued for several hundred years. In this paper, we analyze the carbon cycle and climate response to the applied forcings, and quantify the resulting (post 1850) commitment from early anthropogenic interference.

  17. Postoperative evaluation of the position of interference screws, boneblocks and ligamentum patellae autografts in anterlor cruciate ligament replacement; Evaluierung von Knochenblockposition, Interferenzschraubenlage und Ersatzplastik des vorderen Kreuzbandes nach Ligamentum patellae-Transplantat mittels CT

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    Bauer, R, [Leipzig Univ. (Germany). FUSt 8/Radiologie; Kolbus, F.; Brueckner, B. [Leipzig Univ. (Germany). Abt. 2/Chirurgie des Bundeswehrkrankenhauses Leipzig

    2000-06-01

    Purpose: Evaluation of arthroscopically assisted reconstruction of the anterior cruciate ligament using ligamentum patellae autografts in the bone-tendon-bone technique with special regard to the position of blocks and interference screws. Material and methods: In a prospective study 28 patients were included after undergoing arthroscopic anterior cruciate ligament replacement surgery. Data thus obtained were correlated with the postoperatively determined functional parameters of the affected joint. Results: Interference screws, bone-blocks and ligamentous transplants could be well imaged using CT. In a comparison of our data with clinical results there was a statistically highly significant correlation between clinical outcome and the position of bone-blocks and interference screws in the tibia. Angles between screw and bone-block exceeding a standard deviation led to significantly worse results, while a divergence in femoral angles did not lead to significantly worse results. (orig./AJ) [German] Ziel: Evaluation der arthroskopischen Ersatzplastik des vorderen Kreuzbandes unter besonderer Beruecksichtigung der Lage der Knochenbloecke, Interferenzschrauben und Bohrkanaele mittels CT und Vergleich der radiologischen Daten mit klinischen und funktionellen Parametern. Material und Methodik: In einer prospektiven Studie wurden 28 Patienten nach arthroskopischer Ersatzplastik des vorderen Kreuzbandes mittels Lig. patellae-Transplantat im CT untersucht. Anschliessend erfolgte die Pruefung der Korrelation mit postoperativ erhobenen klinisch-funktionellen Parametern des Kniegelenks. Ergebnisse: Die Interferenzschrauben, Bohrkanaele und Knochenbloecke sowie das Transplantat konnten in allen Faellen gut dargestellt werden. Bei einem Vergleich unserer Daten mit den klinischen Untersuchungsergebnissen der Chirurgen zeigte sich ein statistisch hochsignifikanter Zusammenhang mit den Winkeldivergenzen zwischen Interferenzschraube und Bohrkanal im Bereich der Tibia. Divergenzen

  18. Novo sistema para acoplamento de parafusos de interferência: ensaio biomecânico de torção New coupling system for interference screws: biomechanical resistance to torsion

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    Aloísio Fernandes Bonavides Júnior

    2011-01-01

    Full Text Available OBJETIVO: Apresentar um novo sistema de acoplamento solidário entre chave e parafuso de interferência, assim como ensaios biomecânicos que avaliem a segurança de sua utilização. MÉTODOS: O novo sistema foi submetido a ensaios biomecânicos de torção. Foram realizados dois tipos de análise: torque máximo de inserção manual dos parafusos em osso bovino; ensaios destrutivos de torção do sistema em máquina INSTRON 55MT. Os mesmos testes foram realizados em um grupo controle utilizando um sistema de acoplamento já disponível no mercado. (Acufex® RESULTADOS: Nos ensaios de inserção em fêmures bovinos as médias de valores aferidos com torquímetro digital foram 1,958 N/m para Acufex® e 2,563 N/m para FMRP. Considerando p0,05. Ao avaliar a deformação angular, não houve diferença significativa entre os grupos de parafuso (p=0,15. CONCLUSÃO: O novo sistema de acoplamento para parafusos de interferência desenvolvido na FMRP-USP revelou resistência à torção comparável a sistema já disponível no mercado e regulamentado para uso internacional.OBJECTIVE: To introduce a new coupling system between screw driver and interference screw, and biomechanical tests that validate the safety of its application. METHODS: The new system was submitted to biomechanical torsion assays. Two types of analysis were performed: maximum torque of manual insertion of the screws into bovine bone; destructive assays of torsion of the system using an INSTRON 55MT machine. The same tests were also performed on a control group, using a commercially available interference screw coupling system (Acufex®. RESULTS: In the tests on manual insertion of screws in bovine femurs, the average values found with a digital torque meter were 1.958 N/m for Acufex® and 2.563 N/m for FMRP. Considering p>0.05, there were no statistical differences between the two groups (p=0.02 in the values for maximum torque of insertion, in the two systems studied. The average

  19. Interference and Interaction in multi-wall carbon nanotubes

    Science.gov (United States)

    Schönenberger, C.; Bachtold, A.; Strunk, C.; Salvetat, J.-P.; Forró, L.

    We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance. The phase-coherence (lφ)and elastic-scattering lengths (le)are deduced. Because le is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall tube. As a function of temperature T the resistance increases on decreasing T and saturates at 1-10 Kfor all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small voltage scale of the order 10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.

  20. Interference and interaction in multi-wall carbon nanotubes

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    Schoenenberger, C.; Bachtold, A.; Strunk, C. [Basel Univ. (Switzerland). Inst. fuer Physik; Salvetat, J.P.; Forro, L. [Institut de Genie Atomique, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland)

    1999-09-01

    We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance. The phase-coherence (l{sub {phi}})and elastic-scattering lengths (l{sub e})are deduced. Because l{sub e} is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall tube. As a function of temperature T the resistance increases on decreasing T and saturates at {approx}1-10 Kfor all measured nanotubes. R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects. On a relatively small voltage scale of the order {approx}10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results. (orig.) With 8 figs., 66 refs.

  1. EXPERIMENTAL EVALUATION OF A CONICAL-SCREW BRIQUETTING MACHINE FOR THE BRIQUETTING OF CARBONIZED COTTON STALKS IN SUDAN

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    YOUSIF A. ABAKR

    2006-12-01

    Full Text Available Briquetting of the carbonized agricultural residues represents one of the possible solutions to the local energy shortages in many developing countries. It constitutes a positive solution to the problem of increasing rates of desertification in many areas worldwide. Agricultural residues are not attractive as a household fuel source for urban areas because they are very bulky and have low energy intensity. Also, to eliminate the smoke generation when burning agricultural residues requires processing it by carbonization before being used as a house-hold indoor fuel. Previously investigated, briquetting machines lacked high productivity and were of complicated designs. The present study puts forward a machine of simple design which could be manufactured locally in Sudan and of much higher productivity. The local Sudanese briquetting experience was overviewed, studying all the alternative available options and the market potential. The study presents a detailed design study of the new briquetting machine. The prototype was made and tested in the field at Al-Gazeera area in Sudan. The investigation results show that the new machine has a production rate better than all the previous alternatives. This low pressure screw briquetting machine was found to have a production rate equivalent to about eight times better than the production rate of the best local competitor. The production cost was found to be lower due to the lower binder requirement for the new machine, which is lower by about 65%. The initial moisture content of the feed stock required for this machine is lower by about 30 % compared to the best alternative, which results in shorter drying time for the fuel briquettes produced. The quality of the produced briquettes was found to be better and of lower smoke generation when burned due to the lower binder content.

  2. Adsorption interference in mixtures of trace contaminants flowing through activated carbon adsorber beds

    Science.gov (United States)

    Madey, R.; Photinos, P. J.

    1980-01-01

    Adsorption interference in binary and ternary mixtures of trace contaminants in a helium carrier gas flowing through activated carbon adsorber beds are studied. The isothermal transmission, which is the ratio of the outlet to the inlet concentration, of each component is measured. Interference between co-adsorbing gases occurs when the components are adsorbed strongly. Displacement of one component by another is manifested by a transmission greater than unity for the displaced component over some range of eluted volume. Interference is evidenced not only by a reduction of the adsorption capacity of each component in the mixture in comparison with the value obtained in a single-component experiment, but also by a change in the slope of the transmission curve of each component experiment.

  3. Pectoralis Major Tear with Retracted Tendon: How to Fill the Gap? Reconstruction with Hamstring Autograft and Fixation with an Interference Screw

    Directory of Open Access Journals (Sweden)

    L. Baverel

    2017-01-01

    Full Text Available Rupture of the pectoralis major tendon is considered an uncommon injury and a significant number of ruptures are missed or diagnosed late, leading to a chronic tear. We report an open reconstruction technique and its outcomes in a case of chronic and retracted PM tear. At the last follow-up (12 months, the patient was pain-free, with a visual analogic scale at 0 all the time. He was very satisfied concerning the cosmetic and clinical results. The constant score was 93%, the SST value 95%, and the Quick DASH score 4.5. MRI performed one year postoperatively confirmed the continuity between PM tendon and graft, even if the aspect of the distal tendon seemed to be thinner than normal PM tendon. The excellent clinical outcomes at one-year follow-up suggest that PM tear with major tendon retraction can be reliably reconstructed with hamstring autograft, using a bioabsorbable screw to optimize the fixation device. This technique has proven its simplicity and efficiency to fill the gap.

  4. Surface Characterization of Carbon Fiber Polymer Composites and Aluminum Alloys After Laser Interference Structuring

    Science.gov (United States)

    Sabau, Adrian S.; Greer, Clayton M.; Chen, Jian; Warren, Charles D.; Daniel, Claus

    2016-07-01

    The increasing use of carbon fiber-reinforced polymer matrix composites (CFPC) and aluminum alloys as lightweight materials in the automotive and aerospace industries demands enhanced surface preparation and control of surface morphology prior to joining. In this study, surfaces of both composite and aluminum were prepared for joining using an Nd:YAG laser in a two-beam interference setup, enabling the (1) structuring of the AL 5182 surface, (2) removal of the resin layer on top of carbon fibers, and (3) structuring of the carbon fibers. CFPC specimens of T700S carbon fiber, Prepreg—T83 epoxy, 5 ply thick, 0°/90° plaques were used. The effects of laser fluence, scanning speed, and number of shots-per-spot were investigated on the removal rate of the resin without an excessive damage of the fibers. Optical micrographs, 3D imaging, and scanning electron microscope imaging were used to study the effect of the laser processing on the surface morphology. It was found that an effective resin ablation and a low density of broken fibers for CFPC specimens was attained using laser fluences of 1-2 J/cm2 and number of 2-4 pulses per spot. A relatively large area of periodic line structures due to energy interference were formed on the aluminum surface at laser fluences of 12 J/cm2 and number of 4-6 pulses per spot.

  5. Electromagnetic Interference Shielding Properties of Electroless Nickel-coated Carbon Fiber Paper Reinforced Epoxy Composites

    Institute of Scientific and Technical Information of China (English)

    CHEN Wei; WANG Jun; WANG Tao; WANG Junpeng; XU Renxin; YANG Xiaoli

    2014-01-01

    Carbon fibers (CFs) were coated with a nickel-phosphorus (Ni-P) film using an electroless plating process. The morphology, elemental composition and phases in the coating layer of the CFs were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. Wet paper-making method was used to prepare nickle coated carbon fiber paper (NCFP). Vacuum assisted infusion molding process (VAIMP) was employed to manufacture the NCFP reinforced epoxy composites, and carbon fiber paper (CFP) reinforced epoxy composites were also produced as a comparison. Electromagnetic interference (EMI) shielding properties of the composites were measured in the 3.22-4.9 GHz frequency range using waveguide method. Both NCFP and CFP reinforced epoxy composites of 0.5 mm thickness exhibited high EMI shielding effectiveness (SE) at 8wt%fiber content, 35 dB and 30 dB, respectively, and reflection was the dominant shielding mechanism.

  6. Role of inter-tube coupling and quantum interference on electrical transport in carbon nanotube junctions

    Science.gov (United States)

    Tripathy, Srijeet; Bhattacharyya, Tarun Kanti

    2016-09-01

    Due to excellent transport properties, Carbon nanotubes (CNTs) show a lot of promise in sensor and interconnect technology. However, recent studies indicate that the conductance in CNT/CNT junctions are strongly affected by the morphology and orientation between the tubes. For proper utilization of such junctions in the development of CNT based technology, it is essential to study the electronic properties of such junctions. This work presents a theoretical study of the electrical transport properties of metallic Carbon nanotube homo-junctions. The study focuses on discerning the role of inter-tube interactions, quantum interference and scattering on the transport properties on junctions between identical tubes. The electronic structure and transport calculations are conducted with an Extended Hückel Theory-Non Equilibrium Green's Function based model. The calculations indicate conductance to be varying with a changing crossing angle, with maximum conductance corresponding to lattice registry, i.e. parallel configuration between the two tubes. Further calculations for such parallel configurations indicate onset of short and long range oscillations in conductance with respect to changing overlap length. These oscillations are attributed to inter-tube coupling effects owing to changing π orbital overlap, carrier scattering and quantum interference of the incident, transmitted and reflected waves at the inter-tube junction.

  7. Screw holding capability of larch wood members′end reinforced using powdered carbon fibers%落叶松木构件碳纤维增强端部的握钉性能

    Institute of Scientific and Technical Information of China (English)

    杨小军; 杨茵; 陈炼; 王正; 孙友富

    2016-01-01

    为提高木构件端部握钉性能,采用粉状碳纤维对木构件端面进行增强,研究了增强端部握钉性能。结果表明:在木构件端面复合碳纤维可有效增强木构件端部的握钉性能;木构件内部木材截面面内力学性能优于端面,采用开口方法可在一定程度上提高木构件端部握钉力;木螺钉直径越大木构件端部握钉力越大,木构件增强端部宜选用较大直径螺钉;采用碳纤维增强端面的方法可使木构件薄弱的端面获得与径向木材同等水平的握钉力,可使木构件端部十字槽头木螺钉及六角头木螺钉握钉力分别提高了24.98%和28.11%。这对木构件连接设计及安全服役具有重要的指导意义。%To improve the wood endscrew holding performance. Powdered carbon fibers were used to reinforce wood members′end. The results showed that carbon fiber reinforced wood end′s screw holding capability was significantly greater than that of the normal wood end. In-plane mechanical performance of wood members′interior section was better than that of the end face. The opening way adopted could improve the screw holding capability of wood members′end in a certain extent. Large diameter screw was suitable for reinforcing carbon fibers in wood members′end, for larger diameter screw could make screw holding capability stronger. The method of wood members′end reinforced by carbon fibers could help weak wood end obtain the same level of screw holding capability as radial wood does. Meanwhile, the method also could make holding capability of cross recessed countersunk head wood screw and hexagon head wood screw increase by 24. 98% and 28. 11% respectively. Such method is of important guiding significance to help improve wood connection design and safe service.

  8. Electromagnetic Interference Behavior of Multiwall Carbon Nanotubes and Carbon Nanofibers Composites Under Fatigue

    Science.gov (United States)

    2012-03-01

    This led to the use of composite structures made of Kevlar /epoxy and graphite/epoxy. The U.S. military today are researching and testing...Laboratory. The first discovery of a carbon nano scaled molecule was in 1985 with fullerenes by Kroto, Smalley, and Curl at Rice University. A fullerene

  9. Comparação entre parafuso de interferência e transcondilar na reconstrução do LCA Comparison of interference screw and transcondilar in the ACL reconstruction

    Directory of Open Access Journals (Sweden)

    Marcus Vinicius Danieli

    2011-01-01

    Full Text Available OBJETIVO: A fixação femoral na reconstrução do Ligamento Cruzado Anterior (LCA com enxerto de tendões flexores pode variar muito de acordo com a disposição dos materiais e a experiência do cirurgião. Porém os trabalhos que comparam os sistemas de fixação são efetuados na maioria das vezes em cadáveres ou em animais, sem avaliar os resultados clínicos, prejudicando sua comparação com pacientes humanos vivos. Neste artigo avaliamos o resultado clínico de dois métodos de fixação do enxerto ao fêmur (parafuso de interferência de titânio e parafuso transcondilar de titânio para saber se, do ponto de vista clinico e subjetivo, há diferença entre estes métodos. MÉTODOS: Foram selecionados 40 pacientes com lesão do LCA sendo que 20 pacientes tiveram seu enxerto fixado ao fêmur com parafuso de interferência e 20 com parafuso transcondilar. Todos foram reavaliados com no mínimo dois anos de pós operatório para medição da gaveta anterior, Pivot Shift e teste de Lachman, além da obtenção dos questionário de Lysholm e IKDC (International Knee Documentation Committee. RESULTADOS: Os resultados não foram estatisticamente diferentes para os critérios avaliados. CONCLUSÃO: As duas formas de fixação são eficientes para esta técnica dentro dos parâmetros estabelecidos. Nível de Evidência II, Estudo Prospectivo Comparativo.OBJECTIVE: Femoral fixation in ACL reconstruction with flexor tendon grafts can vary greatly according to the provision of materials and the surgeon's experience. But studies comparing fixation systems are most often performed on cadavers or animals, without evaluating the clinical results, which affects their comparison with live human patients. This article evaluates the clinical and subjective outcomes of two methods of graft fixation to the femur (Titanium interference screw and titanium transcondilar device to determine whether there is any difference between these methods. METHODS: Forty

  10. Enhanced electromagnetic interference shielding effectiveness of polyaniline functionalized carbon nanotubes filled polystyrene composites

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Parveen, E-mail: pksaini@nplindia.org [CSIR-National Physical Laboratory, Polymeric and Soft Materials Section (India); Choudhary, Veena [Indian Institute of Technology, Centre for Polymer Science and Engineering (India)

    2013-01-15

    Multiwall carbon nanotubes (MWCNTs)/polystyrene composites were fabricated by solution processing route using non-covalently functionalized (polyaniline coated) MWCNTs. These composites exhibit an extremely low percolation threshold (0.12 vol.% MWCNT) along with micro porosity and are found to have potential applications in the areas of electromagnetic interference (EMI) shielding and electrostatic dissipation (ESD) with an ESD time of 0.78 s and shielding effectiveness of -23.3 dB (>99 % attenuation). The EMI shielding was found to be dominated by absorption (-18.7 dB) with a nominal contribution from reflection (-4.6 dB) that can explained in terms of multiple internal reflection phenomenon driven by high conductivity and the porous structure.

  11. Electrical conductivity and electromagnetic interference shielding characteristics of multiwalled carbon nanotube filled polyurethane composite films

    Science.gov (United States)

    Son Hoang, Anh

    2011-06-01

    Multiwalled carbon nanotubes (MWCNTs) were homogeneously dispersed in a pure polyurethane resin by grinding in a planetary ball mill. The structure and surface morphology of the MWCNTs and MWCNT/polyurethane composites were studied by filed emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) methods. The electrical conductivity at room temperature and electromagnetic interference (EMI) shielding effectiveness (SE) of the composite films with different MWCNT loadings were investigated and the measurement of EMI SE was carried out in a frequency range of 8-12 GHz (X-band). The experimental results show that with a low MWCNT concentration the composite films could achieve a high conductivity and their EMI SE has a strong dependence on MWCNT content. For the composite films with 22 wt% of MWCNTs, the EMI SE attained an average value of 20 dB, so that the shielding effect reduced the penetrating power to 1%.

  12. Interference of iron as a coagulant on MIB removal by powdered activated carbon adsorption for low turbidity waters.

    Science.gov (United States)

    Seckler, Ferreira Filho Sidney; Margarida, Marchetto; Rosemeire, Alves Laganaro

    2013-08-01

    Powered activated carbon (PAC) is widely used in water treatment plants to minimize odors in drinking water. This study investigated the removal of 2-methylisoborneol (MIB) by PAC adsorption, combined with coagulation using iron as a coagulant. The adsorption and coagulation process were studied through different case scenarios of jar tests. The analysis evaluated the effect of PAC dosing in the liquid phase immediately before or after the coagulant addition. Ferric sulphate was used as the coagulant with dosages from 10 to 30 mg/L, and PAC dosages varied from 10 to 40 mg/L. The highest MIB removal efficiency (about 70%) was achieved without the coagulant addition and with the highest PAC dosage (40 mg/L). Lower MIB removal efficiencies were observed in the presence of coagulant, showing a clear interference of the iron precipitate or coagulant in the adsorption process. The degree of interference of the coagulation process in the MIB removal was proportional to the ratio of ferric hydroxide mass to the PAC mass. For both cases of PAC dosing, upstream and downstream of the coagulant injection point, the MIB removal efficiency was similar. However, MIB removal efficiency was 15% lower when compared with experiments without the coagulant application. This interference in the MIB adsorption occurs potentially because the coagulant coats the surface of the carbon and interferes with the MIB coming in contact with the carbon's surface and pores. This constraint requires an increase of the PAC dosage to provide the same efficiency observed without coagulation.

  13. An experimental study of adsorption interference in binary mixtures flowing through activated carbon

    Science.gov (United States)

    Madey, R.; Photinos, P. J.

    1983-01-01

    The isothermal transmission through activated carbon adsorber beds at 25 C of acetaldehyde-propane and acetylene-ethane mixtures in a helium carrier gas was measured. The inlet concentration of each component was in the range between 10 ppm and 500 ppm. The constant inlet volumetric flow rate was controlled at 200 cc (STP)/min in the acetaldehyde-propane experiments and at 50 cc (STP)/min in the acetaldehyde-ethane experiments. Comparison of experimental results with the corresponding single-component experiments under similar conditions reveals interference phenomena between the components of the mixtures as evidenced by changes in both the adsorption capacity and the dispersion number. Propane was found to displace acetaldehyde from the adsorbed state. The outlet concentration profiles of propane in the binary mixtures tend to become more diffuse than the corresponding concentration profiles of the one-component experiments. Similar features were observed with mixtures of acetylene and ethane; however, the displacement of acetylene by ethane is less pronounced.

  14. Interference of iron as a coagulant on MIB removal by powdered activated carbon adsorption for low turbidity waters

    Institute of Scientific and Technical Information of China (English)

    Ferreira Filho SIDNEY SECKLER; Marchetto MARGARIDA; Alves Laganaro ROSEMEIRE

    2013-01-01

    Powered activated carbon (PAC) is widely used in water treatment plants to minimize odors in drinking water.This study investigated the removal of 2-methylisoborneol (MIB) by PAC adsorption,combined with coagulation using iron as a coagulant.The adsorption and coagulation process were studied through different case scenarios of jar tests.The analysis evaluated the effect of PAC dosing in the liquid phase immediately before or after the coagulant addition.Ferric sulphate was used as the coagulant with dosages from 10 to 30 mg/L,and PAC dosages varied from 10 to 40 mg/L.The highest MIB removal efficiency (about 70%) was achieved without the coagulant addition and with the highest PAC dosage (40 mg/L).Lower MIB removal efficiencies were observed in the presence of coagulant,showing a clear interference of the iron precipitate or coagulant in the adsorption process.The degree of interference of the coagulation process in the MIB removal was proportional to the ratio of ferric hydroxide mass to the PAC mass.For both cases of PAC dosing,upstream and downstream of the coagulant injection point,the MIB removal efficiency was similar.However,MIB removal efficiency was 15% lower when compared with experiments without the coagulant application.This interference in the MIB adsorption occurs potentially because the coagulant coats the surface of the carbon and interferes with the MIB coming in contact with the carbon's surface and pores.This constraint requires an increase of the PAC dosage to provide the same efficiency observed without coagulation.

  15. Intrafix与界面螺钉在前交叉韧带重建中的生物力学研究%Biomechanical evaluation of tendon graft fixation at the tibial site in anterior cruciate ligament reconstruction with intrafix and bioabsorbable interference screw

    Institute of Scientific and Technical Information of China (English)

    王俊良; 刘玉杰; 王爱媛; 杨玉明; 李海峰; 李众利; 王志刚

    2009-01-01

    目的 探讨胭绳肌腱移植重建前交叉韧带(ACL)胫骨端界面螺钉与Intrafix固定的生物力学.方法 新鲜冰冻尸体膝关节标本14具,采用四股腘绳肌腱移植重建ACL,胫骨端分别采用可吸收界面螺钉(n=7)和Intrafix(n=7)固定,测试最大载荷、100 kg·m·s-2和400 kg·m·s-2位移、抗拉刚度、失败模式等数据并进行统计学分析.结果 Intrafix固定组的最大载荷大于可吸收界面螺钉组,两组间差异有统计学意义(t=0.003,P0.05),抗拉刚度两组间差异无统计学意义(t=0.0967,P>0.05).结论 四股胭绳肌腱移植重建ACL,胫骨端采用可吸收界面螺钉和Intrafix固定均可满足ACL初期固定强度的需求;Intrafix固定强度大于可吸收界面螺钉.%Objective The fixation strength of the hamstring tendon graft on the tibial side is considered the weak point in anterior eruciate ligament (ACL) reconstruction. This work tested the hypotheses that some of these devices will resist graft slippage under loads better than others, and that some will have higher ultimate strength than others. Methods Fourteen flesh frozen human cadaver knees underwent fixation of the hamstring tendon harvested from the knee to be used as graft material to reconstruct the ACL and were divided into two equal groups based on the fixation methods: bioabsorbable interference screw group and Intrafix group. A MTS 858 MiniBionix Ⅱ testing machine was used to carry out tensile testing under an axial load parallel to the tibial tunnel with a velocity of 10 mm/min. Ultimate failure load, displacement of 100N, displacement of 4OON, stiffness and mode of failure were recorded respectively. Results The maximum load for the lntrafix fixation group was (719. 094 ± 160. 478) kg · m · s-2, significantly higher than that of the bioabsorbable interference screw fixation group [(476. 640 ± 64. 226) kg · m · s-2, P 0. 05], and the stiffness of the Intratix fixation group was (96. 770 ±36. 848) kg · m-1

  16. Biomechanical comparison of cervical transfacet pedicle screws versus pedicle screws

    Institute of Scientific and Technical Information of China (English)

    LIU Guan-yi; XU Rong-ming; MA Wei-hu; SUN Shao-hua; HUANG Lei; YING Jiang-wei; JIANG Wei-yu

    2008-01-01

    Background Transfacet pedicle screws provide another alternative for standard pedicle screw placement for plate fixation in the Iumbar spine. However, few studies looking at transfacet pedicle screw fixation in the cervical spine are available. Therefore, cervical transfacet pedicle screw fixation and standard pedicle screw fixation techniques were biomechanically compared in this study.Methods Ten fresh human cadaveric cervical spines were harvested. On one side, transfacet pedicle screws were placed at the C3-4, C5-6, and C7-T1 levels. On the other side, pedicle screws were placed at the C3, C5, and C7 levels. The screw insertion technique at each level was randomized for right or left. The starting point for the transfacet pedicle screw insertion was located at the midpoint of the inferolateral quadrant of the lateral mass and the direction of the screw was about 50° caudally in the sagittal plane and about 45° toward the midline in the axial plane. Screws were placed from the inferior articular process, across the facet complex and the pedicle into the body of the caudal vertebra. The entry point for the pedicle screw was located at the midpoint of the superolateral quadrant of the lateral mass, and the direction of the screw was about 45° toward the midline in the axial plane and toward the upper third of the vertebral body in the sagittal plane. After screw placement we performed axial pullout testing.Results All the cervical transfacet pedicle screws and the pedicle screws were inserted successfully. The mean pullout strength for the transfacet pedicle screws was 694 N, while for the pedicle screws 670 N (P=-0.013). In all but six instances (10%), the pedicle screw pullout values exceeded the values for the transfacet pedicle screws; this occurred three times at the C3/C4 level, twice at the C5/C6 level and once at the C7/T1 level. The greatest pullout strength difference at a single level was observed at the C5/C6 level, with a mean difference of 38 N (t

  17. 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.

  18. Carbon Disulfide (CS2) Interference in Glucose Metabolism from Unconventional Oil and Gas Extraction and Processing Emissions.

    Science.gov (United States)

    Rich, Alisa L; Patel, Jay T; Al-Angari, Samiah S

    2016-01-01

    Carbon disulfide (CS2) has been historically associated with the manufacturing of rayon, cellophane, and carbon tetrachloride production. This study is one of the first to identify elevated atmospheric levels of CS2 above national background levels and its mechanisms to dysregulate normal glucose metabolism. Interference in glucose metabolism can indirectly cause other complications (diabetes, neurodegenerative disease, and retinopathy), which may be preventable if proper precautions are taken. Rich et al found CS2 and 12 associated sulfide compounds present in the atmosphere in residential areas where unconventional shale oil and gas extraction and processing operations were occurring. Ambient atmospheric concentrations of CS2 ranged from 0.7 parts per billion by volume (ppbv) to 103 ppbv over a continuous 24-hour monitoring period. One-hour ambient atmospheric concentrations ranged from 3.4 ppbv to 504.6 ppbv. Using the U.S. Environmental Protection Agency Urban Air Toxic Monitoring Program study as a baseline comparison for atmospheric CS2 concentrations found in this study, it was determined that CS2 atmospheric levels were consistently elevated in areas where unconventional oil and gas extraction and processing occurred. The mechanisms by which CS2 interferes in normal glucose metabolism by dysregulation of the tryptophan metabolism pathway are presented in this study. The literature review found an increased potential for alteration of normal glucose metabolism in viscose rayon occupational workers exposed to CS2. Occupational workers in the energy extraction industry exposed to CS2 and other sulfide compounds may have an increased potential for glucose metabolism interference, which has been an indicator for diabetogenic effect and other related health impacts. The recommendation of this study is for implementation of regular monitoring of blood glucose levels in CS2-exposed populations as a preventative health measure.

  19. Chloride interference in the analysis of dissolved organic carbon by the wet oxidation method

    Science.gov (United States)

    Aiken, G.R.

    1992-01-01

    The presence of Cl- in concentrations greater than 0.02 M is shown to interfere with the analysis of aqueous DOC concentrations by the wet oxidation method of analysis when a reaction time of 5 min is employed. Chloride competes with DOC for S2O82-, lowering the overall oxidation efficiency. The resulting HOCl from the oxidation of Cl- reacts with DOC, producing significant amounts of chlorinated intermediate compounds in addition to CO2. These compounds were found in the waste effluent from the reaction chamber and in the gas stream transporting CO2 to the detector. While a possible Cl- effect has been noted for DOC measurements in the past, it has not previously been demonstrated to be a source of error at the concentrations reported in this paper. The interference can be overcome either by increasing the digestion time or by diluting samples to contain less than 0.02 M Cl-.

  20. A review of the interference of carbon containing fly ash with air entrainment in concrete

    DEFF Research Database (Denmark)

    Pedersen, Kim Hougaard; Jensen, Anker Degn; Skjøth-Rasmussen, Martin Skov;

    2008-01-01

    Industrial utilization of fly ash from pulverized coal combustion plays an important role in environmentally clean and cost effective power generation. Today, the primary market for fly ash utilization is as pozzolanic additive in the production of concrete. However, the residual carbon in fly ash...... on the adsorption capacity of AEAs. The type of fuel used in the combustion process influences the amount and properties of the residual carbon. Fly ash derived from bituminous coal has generally higher carbon content compared with fly ash produced from subbituminous coal or lignite, but shows a lower AEA......-treatment methods applied to improve fly ash quality are described in the review. Ozonation, thermal treatment and physical cleaning of carbon have been found to improve the fly ash performance for concrete utilization. Ultimately, recommendations for further work are outlined in the discussion....

  1. Cellulose aerogels decorated with multi-walled carbon nanotubes: preparation, characterization, and application for electromagnetic interference shielding

    Directory of Open Access Journals (Sweden)

    Jian LI,Caichao WAN

    2015-12-01

    Full Text Available Electromagnetic wave pollution has attracted extensive attention because of its ability to affect the operation of electronic machinery and endanger human health. In this work, the environmentally-friendly hybrid aerogels consisting of cellulose and multi-walled carbon nanotubes (MWCNTs were fabricated. The aerogels have a low bulk density of 58.17 mg·cm-3. The incorporation of MWCNTs leads to an improvement in the thermal stability. In addition, the aerogels show a high electromagnetic interference (EMI SEtotal value of 19.4 dB. Meanwhile, the absorption-dominant shielding mechanism helps a lot to reduce secondary radiation, which is beneficial to develop novel eco-friendly EMI shielding materials.

  2. Screw bondgraph contact dynamics

    NARCIS (Netherlands)

    Visser, Martijn; Stramigioli, Stefano; Heemskerk, Cock

    2002-01-01

    This paper presents an elegant contact dynamics model in screw bondgraph form. It can model the contact between any two objects of finite curvature. It does so by defining a Gauss frame on the surfaces of both objects in the points that are closest to each other. Then it describes how the Gauss fram

  3. RNA Interference

    Science.gov (United States)

    ... NIGMS Home > Science Education > RNA Interference Fact Sheet RNA Interference Fact Sheet Tagline (Optional) Middle/Main Content Area What is RNA interference? RNA interference (RNAi) is a natural process ...

  4. NUT SCREW MECHANISMS

    Science.gov (United States)

    Glass, J.A.F.

    1958-07-01

    A reactor control mechanism is described wherein the control is achieved by the partial or total withdrawal of the fissile material which is in the form of a fuel rod. The fuel rod is designed to be raised and lowered from the reactor core area by means of two concentric ball nut and screw assemblies that may telescope one within the other. These screw mechanisms are connected through a magnetic clutch to a speed reduction gear and an accurately controllable prime motive source. With the clutch energized, the fuel rod may be moved into the reactor core area, and fine adjustments may be made through the reduction gearing. However, in the event of a power failure or an emergency signal, the magnetic clutch will become deenergized, and the fuel rod will drop out of the core area by the force of gravity, thus shutting down the operation of the reactor.

  5. Electromagnetic interference (EMI) shielding of ordered mesoporous carbon (OMC)/paraffin composites.

    Science.gov (United States)

    Wu, Hongjing; Wang, Liuding; Zhang, Jiangdong; Wei, Gao; Guo, Shaoli; Shen, Zhongyuan

    2014-08-01

    The ordered mesoporous carbon (OMC)/paraffin composites were successfully prepared by a facile physical mixing method and an EMI SE of 21-23 dB was achieved at the OMC loading of 5.69 wt.% in the X band. This indicates that the composites are very suitable for an application as effective and lightweight EMI shielding materials. The EMI shielding of the composite shows an absorption-dominant mechanism, i.e., a contribution shift from reflection to absorption is observed with the increase in OMC loading and frequency. This could be explained by the intrinsic properties (electrical conductivity, complex permittivity and potential large defects) and novel structure of the composites.

  6. ROTARY SCREW SYSTEMS IN CEMENT

    OpenAIRE

    2016-01-01

    The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometr...

  7. 87Sr/86Sr isotope ratio measurements by laser ablation multicollector inductively coupled plasma mass spectrometry: Reconsidering matrix interferences in bioapatites and biogenic carbonates

    Science.gov (United States)

    Irrgeher, Johanna; Galler, Patrick; Prohaska, Thomas

    2016-11-01

    This study is dedicated to the systematic investigation of the effect of interferences on Sr isotopic analyses in biological apatite and carbonate matrices using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC ICP-MS). Trends towards higher 87Sr/86Sr ratios for LA-MC ICP-MS compared to solution-nebulization based MC ICP-MS when analysing bioapatite matrices (e.g. human teeth) and lower ratios in case of calcium carbonates (e.g. fish ear stones) were observed. This effect can be related to the presence of significant matrix-related interferences such as molecular ions (e.g. (40Ca-31P-16O)+, (40Ar-31P-16O)+, (42Ca-44Ca)+, (46Ca40Ar)+) as well as in many cases concomitant atomic ions (e.g. 87Rb+, 174Hf2 +). Direct 87Sr/86Sr ratio measurements in Ca-rich samples are conducted without the possibility of prior sample separation, which can be accomplished routinely for solution-based analysis. The presence of Ca-Ar and Ca-Ca molecular ion interferences in the mass range of Sr isotopes is shown using the mass resolving capabilities of a single collector inductively coupled plasma sector field mass spectrometer operated in medium mass resolution when analysing bioapatites and calcium carbonate samples. The major focus was set on analysing human tooth samples, fish hard parts and geological carbonates. Potential sources of interferences were identified and corrected for. The combined corrections of interferences and adequate instrumental isotopic fractionation correction procedures lead to accurate data even though increased uncertainties have to be taken into account. The results are discussed along with approaches presented in literature for data correction in laser ablation analysis.

  8. A screwing device for handling and assembly of micro screws

    DEFF Research Database (Denmark)

    Gegeckaite, Asta; Hansen, Hans Nørgaard; Eriksson, Torbjörn Gerhard

    2007-01-01

    Nowadays, the application of specially designed handling devices in micro technology is an important topic and a necessity for the industry. Conventional methods for screwing can not be applied directly to micro screws. This is caused by the 3D micro object geometry and dimensions which inducing ...

  9. Scalable Fabrication of Natural-Fiber Reinforced Composites with Electromagnetic Interference Shielding Properties by Incorporating Powdered Activated Carbon

    Directory of Open Access Journals (Sweden)

    Changlei Xia

    2015-12-01

    Full Text Available Kenaf fiber—polyester composites incorporated with powdered activated carbon (PAC were prepared using the vacuum-assisted resin transfer molding (VARTM process. The product demonstrates the electromagnetic interference (EMI shielding function. The kenaf fibers were retted in a pressured reactor to remove the lignin and extractives in the fiber. The PAC was loaded into the freshly retted fibers in water. The PAC loading effectiveness was determined using the Brunauer-Emmett-Teller (BET specific surface area analysis. A higher BET value was obtained with a higher PAC loading. The transmission energies of the composites were measured by exposing the samples to the irradiation of electromagnetic waves with a variable frequency from 8 GHz to 12 GHz. As the PAC content increased from 0% to 10.0%, 20.5% and 28.9%, the EMI shielding effectiveness increased from 41.4% to 76.0%, 87.9% and 93.0%, respectively. Additionally, the EMI absorption increased from 21.2% to 31.7%, 44.7% and 64.0%, respectively. The ratio of EMI absorption/shielding of the composite at 28.9% of PAC loading was increased significantly by 37.1% as compared with the control sample. It was indicated that the incorporation of PAC into the composites was very effective for absorbing electromagnetic waves, which resulted in a decrease in secondary electromagnetic pollution.

  10. SU-E-T-609: Perturbation Effects of Pedicle Screws On Radiotherapy Dose Distributions

    Energy Technology Data Exchange (ETDEWEB)

    Bar-Deroma, R; Borzov, E; Nevelsky, A [Rambam Medical Center, Haifa (Israel)

    2015-06-15

    Purpose: Radiation therapy in conjunction with surgical implant fixation is a common combined treatment in case of bone metastases. However, metal implants generally used in orthopedic implants perturb radiation dose distributions. Carbon-Fiber Reinforced (CFR) PEEK material has been recently introduced for production of intramedullary screws and plates. Gold powder can be added to the CFR-PEEK material in order to enhance visibility of the screws during intraoperative imaging procedures. In this work, we investigated the perturbation effects of the pedicle screws made of CFR-PEEK, CFR-PEEK with added gold powder (CFR-PEEK-AU) and Titanium (Ti) on radiotherapy dose distributions. Methods: Monte Carlo (MC) simulations were performed using the EGSnrc code package for 6MV beams with 10×10 fields at SSD=100cm. By means of MC simulations, dose distributions around titanium, CFR- PEEK and CFR-PEEK-AU screws (manufactured by Carbo-Fix Orthopedics LTD, Israel) placed in a water phantom were calculated. The screw axis was either parallel or perpendicular to the beam axis. Dose perturbation (relative to dose in homogeneous water phantom) was assessed. Results: Maximum overdose due to backscatter was 10% for the Ti screws, 5% for the CFR-PEEK-AU screws and effectively zero for the CFR-PEEK screws. Maximum underdose due to attenuation was 25% for the Ti screws, 15% for the CFR-PEEK-AU screws and 5% for the CFR-PEEK screws. Conclusion: Titanium screws introduce the largest distortion on the radiation dose distribution. The gold powder added to the CFR-PEEK material improves visibility at the cost of increased dose perturbation. CFR-PEEK screws caused minimal alteration on the dose distribution. This can decrease possible over and underdose of adjacent tissue and thus favorably influence treatment efficiency. The use of such implants has potential clinical advantage in the treatment of neoplastic bone disease.

  11. Do Newer-Generation Bioabsorbable Screws Become Incorporated into Bone at Two Years After ACL Reconstruction with Patellar Tendon Graft?

    Science.gov (United States)

    Cox, Charles L.; Spindler, Kurt P.; Leonard, James P.; Morris, Brent J.; Dunn, Warren R.; Reinke, Emily K.

    2014-01-01

    Background: Bioabsorbable interference screws are used frequently for graft fixation in ACL (anterior cruciate ligament) reconstruction. The resorption properties of many available screws that are marketed as bioabsorbable are not well defined. The CALAXO (Smith & Nephew Endoscopy) and MILAGRO (DePuy Synthes) bioabsorbable screws contain polymers of poly(lactic-co-glycolic acid) (PLGA) plus additives to encourage osseointegration over time. The purpose of this study was to evaluate radiographic and magnetic resonance imaging (MRI) properties and compare patient-reported outcomes at a minimum of two years of follow-up after ACL reconstruction using CALAXO or MILAGRO bioabsorbable interference screws. Methods: A cohort of patients who underwent ACL reconstruction in which the fixation used was either CALAXO or MILAGRO screws returned for repeat radiographs for evaluation of tunnel widening, repeat MRI for evaluation of graft integrity and screw breakdown, and completion of the pain and symptom items of the KOOS (Knee injury and Osteoarthritis Outcome Score) questionnaire. Results: At a mean of three years (range, 2.5 to 4.0 years) after surgery, thirty-one patients with sixty-two CALAXO screws and thirty-six patients with seventy-two MILAGRO screws returned for repeat evaluation. Two blinded, independent reviewers found no significant differences between the two screw types when comparing radiographs for tibial or femoral tunnel widening or MRIs for graft integrity, tibial and femoral foreign body reactions, or femoral screw degradation. Both reviewers found a significant difference between the two screw types when comparing tibial screw degradation properties (p MILAGRO screws were more likely to be rated as intact. No significant differences were noted between the two screw types when comparing the two KOOS subscales. Conclusions: CALAXO screws in the tibial tunnel were more likely to be rated as degraded or partially degraded compared with MILAGRO screws at a mean

  12. Influence of screw length and diameter on tibial strain energy density distribution after anterior cruciate ligament reconstruction

    Science.gov (United States)

    Yao, Jie; Kuang, Guan-Ming; Wong, Duo Wai-Chi; Niu, Wen-Xin; Zhang, Ming; Fan, Yu-Bo

    2014-04-01

    Postoperative tunnel enlargement has been frequently reported after anterior cruciate ligament (ACL) reconstruction. Interference screw, as a surgical implant in ACL reconstruction, may influence natural loading transmission and contribute to tunnel enlargement. The aims of this study are (1) to quantify the alteration of strain energy den sity (SED) distribution after the anatomic single-bundle ACL reconstruction; and (2) to characterize the influence of screw length and diameter on the degree of the SED alteration. A validated finite element model of human knee joint was used. The screw length ranging from 20 to 30mm with screw diameter ranging from 7 to 9 mm were investigated. In the post-operative knee, the SED increased steeply at the extra-articular tunnel aperture under compressive and complex loadings, whereas the SED decreased beneath the screw shaft and nearby the intra-articular tunnel aperture. Increasing the screw length could lower the SED deprivation in the proximal part of the bone tunnel; whereas increasing either screw length or diameter could aggravate the SED deprivation in the distal part of the bone tunnel. Decreasing the elastic modulus of the screw could lower the bone SED deprivation around the screw. In consideration of both graft stability and SED alteration, a biodegradable interference screw with a long length is recommended, which could provide a beneficial mechanical environment at the distal part of the tunnel, and meanwhile decrease the bone-graft motion and synovial fluid propagation at the proximal part of the tunnel. These findings together with the clinical and histological factors could help to improve surgical outcome, and serve as a preliminary knowledge for the following study of biodegradable interference screw. [Figure not available: see fulltext.

  13. Adsorption of mercury from water by modified multi-walled carbon nanotubes: adsorption behaviour and interference resistance by coexisting anions.

    Science.gov (United States)

    Chen, Paris Honglay; Hsu, Cheng-Feng; Tsai, David Dah-wei; Lu, Yen-Ming; Huang, Winn-Jung

    2014-08-01

    This investigation reports the use of modified multi-walled carbon nanotubes (MWCNTs) with various functional groups for adsorbing inorganic divalent mercury (Hg(II)) from water samples. To elucidate the behaviours and mechanisms of Hg(II) adsorption by modified MWCNTs, their adsorption capacity was studied by considering adsorption isotherms and kinetics. Particular attention was paid to interference of coexisting inorganic ions with Hg(II) adsorption. The results reveal that functionalization with oxygen-containing groups improved the Hg(II) adsorption capacity of the MWCNTs. Kinetic analysis demonstrated that the adsorption of Hg(II) by MWCNTs was closely described by the pseudo-second-order and Elovich models, suggesting that the adsorption of Hg(II) by MWCNTs was significantly affected by chemical adsorption. The kinetic results were also analysed using the intraparticle diffusion model, which revealed that intraparticle diffusion was not the only rate-controlling mechanism. The adsorption of Hg(II) on MWCNTs fell drastically as the ionic strength increased from 0 to 1.0mol/L chloride ions, and declined significantly as the pH increased from 2.2 to 10.5. The elemental maps obtained by energy-dispersive spectrometer (EDS) revealed the formation of surface complexes of chloride ions with functional groups on MWCNTs, which reduced the number of available sites for the adsorption of Hg(II) and strengthened the repulsive forces between Hg(II) and MWCNTs. The EDS results suggest that chloride ions are important in controlling Hg(II) speciation and adsorption on the surfaces of MWCNTs.

  14. Avaliação dos resultados da tenodese artroscópica do bíceps, utilizando-se parafuso de interferência bioabsorvível Evaluation of arthroscopic tenodesis of the biceps using a bioabsorbable interference screw

    Directory of Open Access Journals (Sweden)

    Sérgio Luiz Checchia

    2007-08-01

    Full Text Available OBJETIVO: Avaliar os resultados obtidos com a realização da tenodese da cabeça longa do bíceps (CLB pela técnica artroscópica, com a utilização de parafuso de interferência bioabsorvível biotenodese Arthrex®. MÉTODOS: Entre março de 2004 e abril de 2005, 16 ombros de 16 pacientes foram submetidos a tenodese da CLB com essa técnica. O seguimento mínimo foi de 12 meses, com média de 19,5 meses. A idade variou de 32 a 69 anos, com média de 56,1 anos. Houve predomínio do sexo masculino em 75% dos casos. O membro dominante foi acometido em 62,5% dos pacientes. Foi encontrada lesão parcial da CLB em 75% dos pacientes e instabilidade em 25%. Houve associação com lesão do manguito rotador (LMR em 93,75% dos casos. A avaliação clínica foi feita por meio dos critérios da University of California at Los Angeles (UCLA. RESULTADOS: Observamos excelentes resultados em todos os casos. Não foi observado em nenhum caso sinal de retração do músculo bíceps (sinal do Popeye, caracterizando soltura da tenodese. CONCLUSÃO: A tenodese da CLB pela técnica artroscópica, com a utilização de parafuso de interferência bioabsorvível biotenodese Arthrex® mostrou-se uma técnica eficiente para o tratamento das alterações da CLB.OBJECTIVE: To evaluate results obtained with arthroscopic tenodesis of the long head of the biceps (LHB using a bioabsorbable interference screw Arthrex® biotenodesis. METHODS: Between March 2004 and April 2005, 16 shoulders of 16 patients were submitted to LHB tenodesis using this technique. Minimum follow-up was 12 months, with a mean of 19.5 months. Age ranged from 32 to 69 years, mean of 56.1 years. Male patients prevailed, with 75% of the cases. The dominant limb was involved in 62.5% of the patients. Partial lesion of the LHB was found in 75% of the patients, and instability in 25%. Association to rotator cuff lesion (RCL was found in 93.75% of the cases. Clinical evaluation was based on the University of

  15. 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.

  16. 关节镜下RetroButton-同种异体肌腱-界面螺钉重建前交叉韧带的近期疗效%SHORT-TERM EFFECTIVENESS OF ARTHROSCOPIC ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WITH RetroButton-ALLOGENEIC TENDON-INTERFERENCE SCREW

    Institute of Scientific and Technical Information of China (English)

    陈竞青; 陈百成; 高石军; 李彤; 邵德成

    2011-01-01

    目的 探讨关节镜下应用RetroButton-同种异体肌腱-界面螺钉重建前交叉韧带的手术方法与近期疗效.方法 2009年6月-10月,于关节镜下采用RetroButton-同种异体肌腱-界面螺钉重建23例前交叉韧带损伤.男15例,女8例;年龄19~46岁,平均32.5岁.左膝17例,右膝6例.致伤原因:运动伤13例,交通事故伤8例,坠落伤2例.急性损伤(6周)16例.合并单纯内侧半月板损伤11例,单纯外侧半月板损伤6例,内、外侧半月板同时损伤3例,关节软骨损伤5例.患者均无后交叉韧带、内外侧副韧带或后外侧结构损伤.受伤至手术时间3周~32个月.按照Lysholm评分和国际膝关节评分委员会(IKDC)膝关节评分标准进行主观评估;采用Lachman 试验和KT-1000关节测量仪检查进行客观评估.结果 术后患者切口均Ⅰ期愈合,患膝关节失稳症状明显改善.无高热、感染或明显排斥反应.1例患者术后发生顽固性滑膜炎,关节内反复积液,3周内经关节腔灌洗7次后稳定.患者均获随访,随访时间10~17个月,平均14.7个月.末次随访时IKDC评分、Lyrsholm评分、Lachman试验及KT-1000检测与术前比较,差异均有统计学意义(P<0.05).结论 关节镜下应用RetroButton-同种异体肌腱-界面螺钉重建前交叉韧带手术操作安全、简便,近期疗效满意.%Objective To investigate the method and short-term effectiveness of arthroscopic reconstruction of anterior cruciate ligament (ACL) using RetroButton-allogeneic tendon-interference screw. Methods Between June 2009 and October 2009, 23 patients with ACL rupture were treated by arthroscopic reconstruction with RetroButton-allogeneic tendon-interference screw. There were 15 males and 8 females with an average age of 32.5 years (range, 19-46 years), including 17 left knees and 6 right knees. The injury causes were sport trauma (13 cases), traffic accident (8 cases), and falling injury (2 cases). There were 7 acute cases (< 6 weeks

  17. Self-energized screw coupling

    Science.gov (United States)

    Lefever, A. E.; Totah, R. S.

    1980-01-01

    Threaded coupling carries its own store of rotational energy. Originally developed to ease task of astronauts assembling structures in space, coupling offers same advantages in other hazardous operations, such as underwater and in and around nuclear reactors. Coupling consists of two parts: crew portion and receptacle. When screw portion is inserted into receptacle and given slight push by operator, trigger pins release ratchet, allowing energy stored in springs to rotate screw into nut in receptacle.

  18. Effectiveness of electromagnetic interference shielding of carbon nanofiber/poly(vinylidene fluoride) composites as a function of heat treatment temperature and time

    Energy Technology Data Exchange (ETDEWEB)

    Kim, M.S.; Lee, B.O.; Woo, W.J. [Myoungji Univeristy, Yongin (Korea); An, K.H. [Agency for Technology and Standards, Kwacheon (Korea)

    2001-05-01

    The electromagnetic interference (EMI) shielding effectiveness (SE) of poly(vinylidene fluoride) (PVDF) composites was investigated using carbon nanofiber fillers prepared by catalytic chemical vapor deposition of various carbon-containing gases over Ni and Ni-Cu catalysts. The electrical conductivity of carbon nanofiber which was regarded as the key property of filler for the application of EMI shielding ranged from 4.2 to 22.4 S/cm at a pressure of 10000 psi. The electrical conductivity of carbon nanofiber/PVDF composites ranged from 0.22 to 2.46 S/cm and the EMI SE of those was in the range of 2{approx}13 dB. The electrical conductivity of carbon nanofibers increased with the increase in heat treatment temperature and time, while the electrical conductivity of the composites increased rapidly at the initial heat treatment and then approached a certain value with the further increase of heat treatment. The SE of the composites showed a maximum at the medium heat treatment and was proportional to the electrical conductivity of the composites. It was concluded that the specific surface area of carbon nanofibers decreased with the continual heat treatment and the specific surface area of filler was an important factor for the SE of the composites. (author). 16 refs., 4 tabs., 5 figs.

  19. Measurement of Analyzing Power for Proton-Carbon Elastic Scattering in the Coulomb-Nuclear Interference Region with a 22-GeV/c Polarized Proton Beam

    CERN Document Server

    Tojo, J; Bai, M; Bassalleck, B; Bunce, G M; Deshpande, A A; Doskow, J; Eilerts, S W; Fields, D E; Goto, Y; Huang, H; Hughes, V; Imai, K; Ishihara, M; Kanavets, V P; Kurita, K; Kwiatkowski, K K; Lewis, B; Lozowski, W R; Makdisi, Y I; Meyer, H O; Morozov, B V; Nakamura, M; Von Przewoski, B; Rinckel, T; Roser, T; Rusek, A; Saitô, N; Smith, B; Svirida, D N; Syphers, M J; Taketani, A; Thomas, T L; Underwood, D; Wolfe, D; Yamamoto, K; Zhu, L

    2002-01-01

    The analyzing power for proton-carbon elastic scattering in the coulomb-nuclear interference region of momentum transfer, $9.0\\times10^{-3}<-t<4.1\\times10^{-2}$ (GeV/$c)^{2}$, was measured with a 21.7 GeV/$c$ polarized proton beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory. The ratio of hadronic spin-flip to non-flip amplitude, $r_5$, was obtained from the analyzing power to be $\\text{Re} r_5=0.088\\pm 0.058$ and $\\text{Im} r_5=-0.161\\pm 0.226$.

  20. 拇长屈肌腱转位结合挤压螺钉重建KuwadaⅣ型陈旧性跟腱断裂%Flexor hallucis tendon transfer combined with an interference screw reconstruction for chronic Achilles tendon rup-ture of Kuwada IV

    Institute of Scientific and Technical Information of China (English)

    杜俊锋; 朱仰义

    2015-01-01

    Objective:To explore the clinical effect of interference screw and flexor hallucis longus tendon as augmenta⁃tion material in repair of chronic Achilles tendon rupture. Methods:From September 2010 to June 2012,26 patients with chronic Achilles tendon rupture were treated,including 18 males and 8 females with an average age of 44.2 years old(20 to 66 years old). All patients were unilateral damage. MRI showed the Achilles tendon ends' distance was 6.0 to 9.0 cm. The postoperative complications were observed. The curative effect was assessed by American Orthopedic Foot and Ankle Society and Leppilahti score. Results:All the 26 patients were followed up for 18 to 68 months(means 30.4 months). No neurological injury and infection of incision occurred,all patients were stage I incision healing. The shape and function of the ankle were re⁃covered well. The average AOFAS score increased from 52.27±12.30 preoperatively to 90.92±6.36 postoperatively. Leppilahti Achilles Tendon Repair score increased from 34.23 ± 12.86 preoperatively to 90.00 ± 5.10 postoperatively. Conclusion:The flexor hallucis tendon transfer with an interference screw technique for repairing the chronic Achilles tendon rupture of type IV of Kuwada had advantages of simple operation,quick recovery,firm tendon fixation,and less complications.%目的:探讨拇长屈肌腱转位后应用挤压螺钉重建陈旧性KuwadaⅣ型跟腱断裂的临床效果。方法:回顾性分析2010年9月至2012年6月,拇长屈肌腱转位后采用挤压螺钉固定重建26例陈旧性跟腱断裂患者的临床资料,其中男18例,女8例;年龄20~66岁,平均44.2岁。所有患者为单侧损伤。MRI显示跟腱断端距离为6.0~9.0 cm。观察术后并发症情况,并采用美国足踝外科协会(American Orthopaedic Foot and Ankle Society,AOFAS)踝与后足评分及Leppilahti跟腱修复评分进行评价疗效。结果:26例获得随访,时间18~68个月,平均30.4个月。

  1. Carbon-Neutral Energy Supply and Energy Demand-Reduction Technology Needed for Continued Economic Growth Without Dangerous Interference in the Climate System

    Science.gov (United States)

    Hoffert, M. I.; Caldeira, K.

    2007-12-01

    Stabilization of atmospheric CO2 at levels likely to avoid unacceptable climate risk will require a major transformation in the ways we produce and use energy. Most of our energy will need to come from sources that do not emit carbon dioxide to the atmosphere and that energy will need to be used efficiently. The required reduction of carbon dioxide emissions as global energy consumption and GDP grow imposes quantitative requirements on some combination of carbon-neutral primary power and energy demand reduction. (Emission reductions are expressed relative to an implicit or explicit baseline; explicit being better for policy-making. Energy demand reduction involves both efficiency improvements and lifestyle changes.) These requirements can be expressed as CO2 emission reductions needed, or as carbon-neutral primary power production needed combined with power not used by virtue of increased energy end use efficiency or lifestyle changes ("negawatts"), always subject to some reasonably well-characterized uncertainty limits. Climatic changes thus far have been closer to the more extreme zone of the climatic uncertainty envelope of global warming indicating the potential for disastrous impacts by mid-century and beyond for business-as-usual. Emission reductions needed to avoid "dangerous interference in the climate system" imply a revolutionary change in the global energy system beginning now; particularly ominous are massive conventional coal-fired electric power energy infrastructures under construction by the US, China & India. Strong arguments, based on physical science considerations, exist for prompt measures such as (1) an immediate moratorium on coal-fired plants that don't sequester CO2, (2) a gradually increasing price on carbon emissions and (3) regulatory standards, for example, that would encourage utilities and car manufacturers to improve efficiency, and (4) Apollo-scale R & D projects beginning now to develop sustainable carbon-neutral power that can be

  2. Biodegradable Magnesium Screws Accelerate Fibrous Tissue Mineralization at the Tendon-Bone Insertion in Anterior Cruciate Ligament Reconstruction Model of Rabbit

    Science.gov (United States)

    Wang, Jiali; Xu, Jiankun; Fu, Weimin; Cheng, Wenxiang; Chan, Kaiming; Yung, Patrick Shu-hang; Qin, Ling

    2017-01-01

    The incorporation of tendon graft into bone tunnel is one of the most challenging clinical issues in anterior cruciate ligament (ACL) reconstruction. As a biodegradable metal, Mg has appropriate mechanical strength and osteoinductive effects, thus may be a promising alternative to commercialized products used for graft fixation. Therefore, it was hypothesized that Mg based interference screws would promote tendon graft-bone junction healing when compared to Ti screws. Herein, we compared the effects of Mg and Ti screws on tendon graft healing in rabbits with ACL reconstruction via histological, HR-pQCT and mechanical analysis. The histological results indicated that Mg screws significantly improved the graft healing quality via promoting mineralization at the tendon graft enthesis. Besides, Mg screws significantly promoted bone formation in the peri-screw region at the early healing stage. Importantly, Mg screws exhibited excellent corrosion resistance and the degradation of Mg screws did not induce bone tunnel widening. In tensile testing, there were no significant differences in the load to failure, stress, stiffness and absorption energy between Mg and Ti groups due to the failure mode at the midsubstance. Our findings demonstrate that Mg screws can promote tendon graft healing after ACL reconstruction, implying a potential alternative to Ti screws for clinical applications. PMID:28071744

  3. Cancellous Screws Are Biomechanically Superior to Cortical Screws in Metaphyseal Bone.

    Science.gov (United States)

    Wang, Tim; Boone, Christopher; Behn, Anthony W; Ledesma, Justin B; Bishop, Julius A

    2016-09-01

    Cancellous screws are designed to optimize fixation in metaphyseal bone environments; however, certain clinical situations may require the substitution of cortical screws for use in cancellous bone, such as anatomic constraints, fragment size, or available instrumentation. This study compares the biomechanical properties of commercially available cortical and cancellous screw designs in a synthetic model representing various bone densities. Commercially available, fully threaded, 4.0-mm outer-diameter cortical and cancellous screws were tested in terms of pullout strength and maximum insertion torque in standard-density and osteoporotic cancellous bone models. Pullout strength and maximum insertion torque were both found to be greater for cancellous screws than cortical screws in all synthetic densities tested. The magnitude of difference in pullout strength between cortical and cancellous screws increased with decreasing synthetic bone density. Screw displacement prior to failure and total energy absorbed during pullout strength testing were also significantly greater for cancellous screws in osteoporotic models. Stiffness was greater for cancellous screws in standard and osteoporotic models. Cancellous screws have biomechanical advantages over cortical screws when used in metaphyseal bone, implying the ability to both achieve greater compression and resist displacement at the screw-plate interface. Surgeons should preferentially use cancellous over cortical screws in metaphyseal environments where cortical bone is insufficient for fixation. [Orthopedics.2016; 39(5):e828-e832.].

  4. On the interference of 86Kr2+ during carbon isotope analysis of atmospheric methane using continuous flow combustion – isotope ratio mass spectrometry

    Directory of Open Access Journals (Sweden)

    T. Röckmann

    2013-02-01

    Full Text Available Stable carbon isotope analysis of methane (δ13C of CH4 on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography isotope ratio mass spectrometry coupled to a combustion-preconcentration unit. This report shows that the atmospheric trace gas krypton can severely interfere during the mass spectrometric measurement leading to significant biases in δ13C of CH4 if krypton is not sufficiently separated during the analysis. The effect comes about by the lateral tailing of the peak of doubly charged 86Kr in the neighbouring m/z, 44, 45, and 46 Faraday cups. Accordingly, the introduced bias is dependent on the chromatographic separation, the Kr to CH4 mixing ratio in the sample, the mass spectrometer source tuning as well as the detector configuration and can amount to up to several permil in δ13C. Apart from technical solutions to avoid this interference we present correction routines to a posteriori remove the bias.

  5. MODIFIED PERIODONTAL EXPLORER FOR EXPANSION SCREW ACTIVATION

    Directory of Open Access Journals (Sweden)

    Srinivasan

    2012-08-01

    Full Text Available INTRODUCTION: Accidents with expansion screw activation keys are r eported in the literature 1,2 . A simple method to prevent such accident is to use a modified periodontal explorer as a key for expansion screw activation. A no.17 per iodontal explorer (fig 1 is cut at its first terminal bend (fig 2. The second section is bent m ore vertically to the long axis of the shaft (fig 3. This part which is tapered and stiff enough to ac tivate the screw is tried extra orally into the screw. It is further trimmed in such a way that onl y a mm of instrument can project through the screw hole (fig 4. Now a safe key for activating t he maxillary expansion screw is ready to use (fig 5. Once the patient’s parent or guardian succes sfully repeat the activation procedure in office, the instrument can be given to them for hom e use

  6. A strategy to achieve enhanced electromagnetic interference shielding at low concentration with a new generation of conductive carbon black in a chlorinated polyethylene elastomeric matrix.

    Science.gov (United States)

    Mondal, Subhadip; Ganguly, Sayan; Rahaman, Mostafizur; Aldalbahi, Ali; Chaki, Tapan K; Khastgir, Dipak; Das, Narayan Ch

    2016-09-21

    The fabrication of scalable and affordable conductive Ketjen carbon black (K-CB)-elastomer composites for adjustable electromagnetic interference (EMI) shielding remains a difficult challenge. Herein, chlorinated polyethylene (CPE)-K-CB composites have been developed by single step solution mixing to achieve high EMI shielding performance associated with absorption dominance potency by conductive dissipation as well as the reflection of electromagnetic waves. The dispersion of K-CB inside the CPE matrix has been corroborated by electron micrographs and atomic force microscopy (AFM). The K-CB filler and CPE polymer interaction has been investigated through the bound rubber content (Bdr) and the dynamic mechanical properties. The relatively low loading of K-CB with respect to other conventional carbon fillers contributes to a promising low percolation threshold (9.6 wt% K-CB) and a reasonably high EMI shielding effectiveness (EMI SE) value of 38.4 dB (at 30 wt% loading) in the X-band region (8.2 to 12.4 GHz). Classical percolation theory reveals that the electrical conduction behavior through the composite system is quasi-two dimensional in nature. Our belief lies in the promotion of scalable production of flexible and cost-effective K-CB-CPE composites of superior EMI SE to avoid electromagnetic radiation pollution.

  7. Shock-Absorbent Ball-Screw Mechanism

    Science.gov (United States)

    Hirr, Otto A., Jr.; Meneely, R. W.

    1986-01-01

    Actuator containing two ball screws in series employs Belleville springs to reduce impact loads, thereby increasing life expectancy. New application of springs increases reliability of equipment in which ball screws commonly used. Set of three springs within lower screw of ball-screw mechanism absorbs impacts that result when parts reach their upper and lower limits of movement. Mechanism designed with Belleville springs as shock-absorbing elements because springs have good energy-to-volume ratio and easily stacked to attain any stiffness and travel.

  8. Quantum interference in polyenes

    Science.gov (United States)

    Tsuji, Yuta; Hoffmann, Roald; Movassagh, Ramis; Datta, Supriyo

    2014-12-01

    The explicit form of the zeroth Green's function in the Hückel model, approximated by the negative of the inverse of the Hückel matrix, has direct quantum interference consequences for molecular conductance. We derive a set of rules for transmission between two electrodes attached to a polyene, when the molecule is extended by an even number of carbons at either end (transmission unchanged) or by an odd number of carbons at both ends (transmission turned on or annihilated). These prescriptions for the occurrence of quantum interference lead to an unexpected consequence for switches which realize such extension through electrocyclic reactions: for some specific attachment modes the chemically closed ring will be the ON position of the switch. Normally the signs of the entries of the Green's function matrix are assumed to have no physical significance; however, we show that the signs may have observable consequences. In particular, in the case of multiple probe attachments - if coherence in probe connections can be arranged - in some cases new destructive interference results, while in others one may have constructive interference. One such case may already exist in the literature.

  9. Quantum interference in polyenes

    Energy Technology Data Exchange (ETDEWEB)

    Tsuji, Yuta; Hoffmann, Roald, E-mail: rh34@cornell.edu [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853 (United States); Movassagh, Ramis [Department of Mathematics, Northeastern University, Boston, Massachusetts 02115, USA and Department of Mathematics, Massachusetts Institute of Technology, Building E18, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States); Datta, Supriyo [School of Electrical and Computer Engineering, Purdue University, Electrical Engineering Building, 465 Northwestern Ave., West Lafayette, Indiana 47907-2035 (United States)

    2014-12-14

    The explicit form of the zeroth Green's function in the Hückel model, approximated by the negative of the inverse of the Hückel matrix, has direct quantum interference consequences for molecular conductance. We derive a set of rules for transmission between two electrodes attached to a polyene, when the molecule is extended by an even number of carbons at either end (transmission unchanged) or by an odd number of carbons at both ends (transmission turned on or annihilated). These prescriptions for the occurrence of quantum interference lead to an unexpected consequence for switches which realize such extension through electrocyclic reactions: for some specific attachment modes the chemically closed ring will be the ON position of the switch. Normally the signs of the entries of the Green's function matrix are assumed to have no physical significance; however, we show that the signs may have observable consequences. In particular, in the case of multiple probe attachments – if coherence in probe connections can be arranged – in some cases new destructive interference results, while in others one may have constructive interference. One such case may already exist in the literature.

  10. Metalworking defects in surgery screws as a possible cause of post-surgical infections

    Science.gov (United States)

    Spector, Mario; Peretti, Leandro E.; Romero, Gustavo

    2016-04-01

    In the first phase of this work, surface defects (metalworking) in stainless steel implantable prostheses and their possible relation to infections that can be generated after surgery was studied. In a second phase, the results obtained in the aforementioned stage were applied to knee cruciate ligaments surgery screws, considering the fact that a substantial number of Mucormycetes infections have been reported after arthroscopic surgery in Argentina since the year 2005. Two types of screws, transverse and interference screws, were analyzed. The Allen heads presented defects such as burrs and metalworking bending as a result of the machining process. These defects allow the accumulation of machining oil, which could be contaminated with fungal spores. When this is the case, the gaseous sterilization by ethylene oxide may be jeopardized. Cortical screws were also analyzed and were found to present serious metalworking defects inside their heads. To reduce the risk of infection in surgery, the use of screws with metalworking defects on the outer surface, analyzed with stereomicroscope and considering the inside part of the Allen as an outer surface, should be avoided altogether.

  11. Anatomic comparison of transarticular screws with lateral mass screws in cervical vertebrae

    Institute of Scientific and Technical Information of China (English)

    LIU Guan-yi; XU Rong-ming; MA Wei-hu; RUAN Yong-ping; SUN Shao-hua; HUANG Lei

    2007-01-01

    Objective: To compare the potential incidence of nerve root (ventral and dorsal ramus) injury caused by cervical transarticular screws and Roy-Camille lateral mass screws.Methods: Insertion techniques with Klekamp transarticular screws and Roy-Camille lateral mass screws were respectively performed in this study. Each technique involved four specimens and 40 screws, which were inserted from C3 to C7. And 20-mm-long screws were used to overpenetrate the ventral cortex. The anterolateral aspect of the cervical spine was carefully dissected to allow observation of the screw-ramus relationship.Results: The overall percentage of nerve invasion was significantly lower with Klekamp (45%) technique than with Roy-Camille (85%) technique (P<0.05). The largest percentage of nerve invasion for Klekamp transarticular screws was found at the dorsal ramus (25%), followed by the ventral ramus (15%) and the bifurcation of the ventral dorsal ramus (5%). The largest percentage of nerve invasion for Roy-Camille lateral mass screws was found at the ventral ramus (80%).Conclusion: The potential risk of nerve root invasion is lower with Klekamp transarticular screws than with Roy-Camille lateral mass screws.

  12. Twin-Screw Extruders in Ceramic Extrusion

    Science.gov (United States)

    Wiedmann, Werner; Hölzel, Maria

    The machines mainly used for compounding plastics, chemicals and food are co-rotating, closely intermeshing twin-screw extruders. Some 30 000 such extruders are in use worldwide, about 1/3 are ZSKs from Coperion Werner & Pfleiderer, Stuttgart. In the chemical industry more and more batch mixers are being replaced by continuous twin-screw kneaders.

  13. Toponymic interferences

    Directory of Open Access Journals (Sweden)

    Marius Ilie Oros

    1985-12-01

    Full Text Available The study of linguistic interferences has been greatly extended lately. It comprises all language sections. In onomastics great attention was paid to to the study of macrotoponyms of foreign origin. I would like to mention in this respect the research concerning the toponyms of Slavic origin in Romania and Greece, the toponyms of Romance origin in Yugoslavia etc. The studies referring to the interferences in microtoponymy are more rare. These call for the collecting of all microtoponyms through inquiries made in plaees inhabited by mixed populetion from the ethnic point of view. The microtoponymy of these places off ers a very interesting material as far as the interactiong the reciprocal in.fluences of two or more toponymic systems is concerned.

  14. Twin screw granulation: steps in granule growth.

    Science.gov (United States)

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

    2012-11-15

    The present work focuses on the study of the progression of granules in different compartments along the length of screws in a twin screw granulator (TSG). The effects of varying powder feed rate; liquid to solid ratio and viscosity of granulation liquid on properties of granules was studied. The bigger granules produced at the start of the process were found to change in terms of size, shape and strength along the screw length at all the conditions investigated. The granules became more spherical and their strength increased along the screw length. Tracer granules were also introduced in order to understand the role of kneading and conveying elements in the TSG. The kneading elements promoted consolidation and breakage while the conveying elements led to coalescence, breakage and some consolidation. The results presented here help to provide a qualitative and quantitative understanding of the twin screw granulation process.

  15. 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.

  16. Twin screw subsurface and surface multiphase pumps

    Energy Technology Data Exchange (ETDEWEB)

    Dass, P. [CAN-K GROUP OF COMPANIES, Edmonton, Alberta (Canada)

    2011-07-01

    A new subsurface twin screw multiphase pump has been developed to replace ESP and other artificial lift technologies. This technology has been under development for a few years, has been field tested and is now going for commercial applications. The subsurface twin screw technology consists of a pair of screws that do not touch and can be run with a top drive or submersible motor; and it carries a lot of benefits. This technology is easy to install and its low slippage makes it highly efficient with heavy oil. In addition twin screw multiphase pumps are capable of handling high viscosity fluids and thus their utilization can save water when used in thermal applications. It also induces savings of chemicals because asphaltenes do not break down easily as well as a reduction in SOR. The subsurface twin screw multiphase pump presented herein is an advanced technology which could be used in thermal applications.

  17. The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

    Science.gov (United States)

    Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

    2012-06-01

    Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

  18. Electromagnetic interference shielding effectiveness of composite carbon nanotube macro-film at a high frequency range of 40 GHz to 60 GHz

    Directory of Open Access Journals (Sweden)

    Zi Ping Wu

    2015-06-01

    Full Text Available The electromagnetic interference (EMI shielding effectiveness (SE of carbon nanotube (CNT macro-film that is adhered to common cloth to maintain the light weight, silk-like quality, and smooth surface of the material for EMI shielding is investigated. The results show that a high and stable EMI SE of 48 dB to 57 dB at 40 GHz to 60 GHz was obtained by the macro-film with a thickness of only ∼4 μm. The composite CNT macro-film is easily manipulated, and its EMI property is significantly different from that of traditional electromagnetic shielding materials that show a lower EMI SE with increasing frequency. For example, the EMI SE of Cu foils decrease from 75 dB to 35 dB as frequency increases from 25 GHz to 60 GHz. Considering their stable and outstanding EMI SE and easy manipulation, the composite CNT macro-films are expected to have potential applications in shielding against millimeter waves.

  19. Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase.

    Science.gov (United States)

    Wray, Steven; Mimran, Ronnie; Vadapalli, Sasidhar; Shetye, Snehal S; McGilvray, Kirk C; Puttlitz, Christian M

    2015-05-01

    OBJECT Low bone mineral density in patients undergoing lumbar spinal surgery with screws is an especially difficult challenge because poor bone quality can severely compromise the maximum achievable purchase of the screws. A relatively new technique, the cortical bone screw trajectory, utilizes a medialized trajectory in the caudocephalad direction to engage a greater amount of cortical bone within the pars interarticularis and pedicle. The objectives of this cadaveric biomechanical study were to 1) evaluate a cortical screw system and compare its mechanical performance to the traditional pedicle screw system; 2) determine differences in bone quality associated with the cortical screw trajectory versus the normal pedicle screw insertion technique; 3) determine the cortical wall breach rate with both the cortical and traditional screw trajectories; and 4) determine the performance of the traditional screw in the cortical screw trajectory. METHODS Fourteen fresh frozen human lumbar spine sections (L1-5) were used in this study (mean age 57 ± 19 years). The experimental plan involved drilling and tapping screw holes for 2 trajectories under navigation (a traditional pedicle screw and a cortical screw) in both high-and low-quality vertebrae, measuring the bone quality associated with these trajectories, placing screws in the trajectories, and evaluating the competence of the screw purchase via 2 mechanical tests (pullout and toggle). The 3 experimental variants were 1) traditional pedicle screws placed in the traditional pedicle screw trajectory, 2) traditional pedicle screws placed in the cortical screw trajectory, and 3) cortical screws placed in the cortical screw trajectory. RESULTS A statistically significant increase in bone quality was observed for the cortical trajectories with a cortical screw (42%; p parameter comparisons (screw type and trajectory) between high-quality and lowquality samples were significant (p parameters determined from pullout and toggle

  20. A geometrical introduction to screw theory

    Science.gov (United States)

    Minguzzi, E.

    2013-05-01

    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.

  1. A Biomechanical Comparison of Expansive Pedicle Screws for Severe Osteoporosis: The Effects of Screw Design and Cement Augmentation.

    Directory of Open Access Journals (Sweden)

    Ching-Lung Tai

    Full Text Available Expansive pedicle screws significantly improve fixation strength in osteoporotic spines. However, the previous literature does not adequately address the effects of the number of lengthwise slits and the extent of screw expansion on the strength of the bone/screw interface when expansive screws are used with or without cement augmentation. Herein, four designs for expansive pedicle screws with different numbers of lengthwise slits and different screw expansion levels were evaluated. Synthetic bones simulating severe osteoporosis were used to provide a comparative platform for each screw design. The prepared specimens were then tested for axial pullout failure. Regardless of screw design, screws with cement augmentation demonstrated significantly higher pullout strength than pedicle screws without cement augmentation (p 0.05. Taken together, our results show that pedicle screws combined with cement augmentation may greatly increase screw fixation regardless of screws with or without expansion. An increase in both the number of slits and the extent of screw expansion had little impact on the screw-anchoring strength. Cement augmentation is the most influential factor for improving screw pullout strength.

  2. 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...

  3. 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.

  4. Design and biomechanical study of a modified pedicle screw

    Institute of Scientific and Technical Information of China (English)

    LIU Tao; ZHENG Wen-jie; LI Chang-qing; LIU Guo-dong; ZHOU Yue

    2010-01-01

    Objective: In pedicle screw fixation,the heads of monoaxial screws need to be directed in the same straight line to accommodate the rod placement by backing out during operation, which decreases the insertional torque and internal fixation strength. While polyaxial screws facilitate the assembly of the connecting rod, but its ball-in-cup locking mechanism reduces the static compressive bending yield strength as compared with monoaxial screws. Our study aimed to assess the mechanical performance of a modified pedicle screw.Methods: In this study, the tail of the screw body of the modified pedicle screw was designed to be a cylindershaped structure that well matched the inner wall of the screw head and the screw head only rotated around the cyclinder. Monoaxial screws, modified screws and polyaxial screws were respectively assembled into 3 groups ofvertebrectomy models simulated by ultra high molecular weight polyethylene (UHMWPE) blocks. This model was developed according to a standard for destructive mechanical testing published by the American Society for Testing Materials (ASTM F1717-04). Each screw design had 6 subgroups, including 3 for static tension, load compression and torsion tests, and the rest for dynamic compression tests. In dynamic tests, the cyclic loads were 25%, 50%, and 75% of the compressive bending ultimate loads respectively.Yield load, yield ultimate load, yield stiffness, torsional stiffness, cycles to failure and modes of failure for the 3 types of screws were recorded. The results of modified screws were compared with those ofmonoaxial and polyaxial screws.Results: In static tests, results of bending stiffness,yield load, yield torque and torsional stiffness indicated no significant differences between the modified and monoaxial screws (P>0.05), but both differed significantly from those ofpolyaxial screws (P<0.05). In dynamic compression tests,both modified and monoaxial screws showed failures that occurred at the insertion point of screw

  5. Flow characteristics of screws and special mixing enhancers in a co-rotating twin screw extruder

    NARCIS (Netherlands)

    Brouwer, T.; Todd, D.B.; Janssen, L.P.B.M.

    2002-01-01

    The flow behavior of a Newtonian fluid through special mixing enhancers in a modular intermeshing co-rotating twin screw extruder has been examined. The mixing enhancers are slotted screws and gear mixing elements. Particular attention has been directed to drag and pressure flow characteristics and

  6. Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

    Directory of Open Access Journals (Sweden)

    Lee Yen-Chen

    2011-02-01

    Full Text Available Abstract Background Pedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined. Method The Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine. Results The results revealed the following 1 Regardless of the screw outer geometry (conical or cylindrical, solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws. 2 For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling, no significant difference in pullout strength was found between conical and cylindrical screws (p >0.05. 3 Cement infiltration into the open cell of

  7. 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.

  8. 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

  9. 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.

  10. Magnesium-Based Absorbable Metal Screws for Intra-Articular Fracture Fixation

    Directory of Open Access Journals (Sweden)

    Roland Biber

    2016-01-01

    Full Text Available MAGNEZIX® (Syntellix AG, Hanover, Germany is a biodegradable magnesium-based alloy (MgYREZr which is currently used to manufacture bioabsorbable compression screws. To date, there are very few studies reporting on a limited number of elective foot surgeries using this innovative implant. This case report describes the application of this screw for osteochondral fracture fixation at the humeral capitulum next to a loose radial head prosthesis, which was revised at the same time. The clinical course was uneventful. Degradation of the magnesium alloy did not interfere with fracture healing. Showing an excellent clinical result and free range-of-motion, the contour of the implant was still visible in a one-year follow-up.

  11. [Cement augmentation of pedicle screws : Pros and cons].

    Science.gov (United States)

    Schnake, K J; Blattert, T R; Liljenqvist, U

    2016-09-01

    Cement augmentation of pedicle screws biomechanically increases screw purchase in the bone. However, clinical complications may occur. The pros and cons of the technique are discussed from different clinical perspectives.

  12. Impact of screw configuration on the particle size distribution of granules produced by twin screw granulation.

    Science.gov (United States)

    Vercruysse, J; Burggraeve, A; Fonteyne, M; Cappuyns, P; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2015-02-01

    Twin screw granulation (TSG) has been reported by different research groups as an attractive technology for continuous wet granulation. However, in contrast to fluidized bed granulation, granules produced via this technique typically have a wide and multimodal particle size distribution (PSD), resulting in suboptimal flow properties. The aim of the current study was to evaluate the impact of granulator screw configuration on the PSD of granules produced by TSG. Experiments were performed using a 25 mm co-rotating twin screw granulator, being part of the ConsiGma™-25 system (a fully continuous from-powder-to-tablet manufacturing line from GEA Pharma Systems). Besides the screw elements conventionally used for TSG (conveying and kneading elements), alternative designs of screw elements (tooth-mixing-elements (TME), screw mixing elements (SME) and cutters) were investigated using an α-lactose monohydrate formulation granulated with distilled water. Granulation with only conveying elements resulted in wide and multimodal PSD. Using kneading elements, the width of the PSD could be partially narrowed and the liquid distribution was more homogeneous. However, still a significant fraction of oversized agglomerates was obtained. Implementing additional kneading elements or cutters in the final section of the screw configuration was not beneficial. Furthermore, granulation with only TME or SME had limited impact on the width of the PSD. Promising results were obtained by combining kneading elements with SME, as for these configurations the PSD was narrower and shifted to the size fractions suitable for tableting.

  13. A modified technique for removing a failed abutment screw from an implant with a custom guide tube.

    Science.gov (United States)

    Taira, Yohsuke; Sawase, Takashi

    2012-04-01

    Fracture of abutment screw is a serious prosthodontic complication. When the abutment screw is fractured at the junction of the screw shank and screw thread, removal of the fractured screw fragment from the screw hole can be difficult. This article describes a modified technique for removing the failed abutment screw with a custom guide tube and tungsten carbide bur. The failed screw can be removed speedily without damaging the screw hole of the implant body or the screw threads.

  14. A processing method for orthodontic mini-screws reuse

    Directory of Open Access Journals (Sweden)

    Saeed Noorollahian

    2012-01-01

    Conclusion: Cleaning of used mini-screws with phosphoric acid 37% (10 minutes and sodium hypochlorite 5.25% (30 minutes reduces tissue remnants to the level of as-received mini-screws. So it can be suggested as a processing method of used mini-screws. Previous insertion of mini-screws into the bone and above-mentioned processing method and resterilization with autoclave had no adverse effects on insertion, removal, and fracture torque values as mechanical properties indices.

  15. A geometrical introduction to screw theory

    CERN Document Server

    Minguzzi, E

    2012-01-01

    Since the addition of applied forces must take into account the line of action, applied forces do not belong to a vector space. Screw theory removes this geometrical limitation and solves other mechanical problems by unifying, in a single concept, the translational and rotational degrees of freedom. Although venerable this theory is little known. By introducing some innovations, I show how screw theory can help us to rapidly develop several standard and less standard results in classical mechanics. The connection with the Lie algebra of the group of rigid maps is clarified.

  16. 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.

  17. Screw Extruder for Pellet Injection System

    Directory of Open Access Journals (Sweden)

    Sharadkumar K. Chhantbar

    2014-05-01

    Full Text Available Solid hydrogenic pellets are used as fuel for fusion energy reactor. A technique for continuous production of solid hydrogen and its isotopes by a screw extruder is suggested for the production of an unlimited number of pellets. The idea was developed and patented by PELIN laboratories, Inc. (Canada. A Gifford McMahon cryocooler is used for the generation of solid hydrogenic fluid pellets. Requirements of the pellets is depends upon the energy to be produced by tokamak. This review paper focuses on the model for the screw extruder for solidification of hydrogen ice having high injection reliability.

  18. 21 CFR 872.4880 - Intraosseous fixation screw or wire.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Intraosseous fixation screw or wire. 872.4880... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Surgical Devices § 872.4880 Intraosseous fixation screw or wire. (a) Identification. An intraosseous fixation screw or wire is a metal device intended to be...

  19. The additon of screws and the axodes of gear pairs

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-xiang

    2001-01-01

    In the light of screw addition, the distribution of instantaneous axes along the common perpendicular of the two screws is determined and all possible sorts of axodes are derived cinematically with the pitch of the relative-motio n screw in the gear pair as the basis and the transmission ratio i as an inde pendent variable.

  20. The additon of screws and the axodes of gear pairs

    Institute of Scientific and Technical Information of China (English)

    张文祥

    2001-01-01

    In the light of screw addition, the distribution of instantaneous axes along the common perpendicular of the two screws is determined and all possible sorts of axodes are derived cinematically with the pitch of the relative-motion screw in the gear pair as the basis and the transmission ratio i as an independent variable.

  1. Biomechanical evaluation of an expansive pedicle screw in calf vertebrae

    Institute of Scientific and Technical Information of China (English)

    雷伟; 吴子祥

    2005-01-01

    Objective: To obtain a comprehensive understanding of the effect of the improvement of fixation strength of a newly designed expansive pedicle screw through biomechanical analyses.Metheds: 100 (200 pedicles) fresh calf lumber vertebrae were used. A total of four instrumentation systems were tested including CDH (CD Horizon), USS (Universal Spine System pedicle screw), Tenor (Sofamor Denek) and expansive pedicle screw (EPS). Pullout and turning-back tests were performed to compare the holding strength of the expansive pedicle screw with conventional screws, i.e. USS, CDH and Tenor. Revision tests were performed to evaluate the mechanical properties of the expansive pedicle screw as a "rescue" revision screw. A fatigue simulation using perpendicular load up to 1 500 000 cycles was carried out.Results: The turning back torque (Tmax) and pull-out force (Fmax) of EPS were significantly greater than those of USS, Tenor and CDH screws (6.5 mm×40 mm). In revision tests, the Fmax of both kinds of EPS (6.5 mm×40 mm; 7.0 mm×40 mm) were greater than that of CDH, USS and Tenor screws significantly (P<0.05). No screws were broken or bent at the end of fatigue tests.Conclusions: EPS can significantly improve the bone purchase and the pull-out strength compared to USS, Tenor and CDH screws with similar dimensions before and after failure simulation. The fatigue characteristic of EPS is similar to that of CDH, USS and Tenor screws.

  2. 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.

  3. 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.)

  4. Design of a magnetic lead screw for wave energy conversion

    DEFF Research Database (Denmark)

    Holm, Rasmus Koldborg; Berg, Nick Ilsø; Rasmussen, Peter Omand

    2012-01-01

    This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state-of-the-art regarding linear PM generators and magnetic lead screws is given, leading to an introduction of the magnetic lead screw and a presentation of the results from...

  5. Clinical pedicle screw accuracy and deviation from planning in robot-guided spine surgery: robot-guided pedicle screw accuracy

    NARCIS (Netherlands)

    Dijk, van Joris D.; Ende, Roy P.J.; Stramigioli, Stefano; Köchling, Matthias; Höss, Norbert

    2015-01-01

    STUDY DESIGN: A retrospective chart review was performed for 112 consecutive minimally invasive spinal surgery patients who underwent pedicular screw fixation in a community hospital setting. OBJECTIVE: To assess the clinical accuracy and deviation in screw positions in robot-assisted pedicle screw

  6. Nylon screws make inexpensive coil forms

    Science.gov (United States)

    Aucoin, G.; Rosenthal, C.

    1978-01-01

    Standard nylon screws act as coil form copper wire laid down in spiral thread. Completed coil may be bonded to printed-circuit board. However, it is impossible to tune coil by adjusting spacing between windings, technique sometimes used with air-core coils.

  7. 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 develop

  8. IETS and quantum interference

    DEFF Research Database (Denmark)

    Jørgensen, Jacob Lykkebo; Gagliardi, Alessio; Pecchia, Alessandro

    2014-01-01

    Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low...... suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference....

  9. The effect of insertion angle on orthodontic mini-screw torque

    Directory of Open Access Journals (Sweden)

    Seyed Hamid Raji

    2014-01-01

    Full Text Available Background: Primary stability is an important factor for the clinical success of orthodontic mini-screws. The present study made an attempt to evaluate the effect of insertion angle changes on the maximum insertion and removal torque of orthodontic mini-screws. Materials and Methods: In this experimental study, 72 mini-screws (Dual Top Anchor System, Jeil, 1.6 mm diameter, 8 mm length were used. They were randomly divided into four equal groups and inserted in poly-carbonate plates with 3 mm thickness. Then, their maximum insertion torque (MIT and maximum removal torque (MRT were recorded using a digital torque tester/screwdriver. Each group had a different insertion angle (90°, 75°, 60° and 45°. The data were analyzed by SPSS software (version 18 using one-way ANOVA and post-hoc Tukey′s tests. The level of significance was set at 0.05. Results: The maximum MIT was observed in 45° insertion angle (14.84 Ncm and the minimum MIT was reported in 75° insertion angle (12.66 Ncm. The maximum MRT was observed in 45° insertion angle (23.21 Ncm and the minimum MRT was reported in the 90° insertion angle (17.43 Ncm. Conclusion: Oblique insertion of the mini-screws results in higher insertion and removal torques and probably more primary stability compared to the vertical insertion.

  10. Atlantoaxial stabilization using multiaxial C-1 posterior arch screws.

    Science.gov (United States)

    Donnellan, Michael B; Sergides, Ioannis G; Sears, William R

    2008-12-01

    The authors present a novel technique of atlantoaxial fixation using multiaxial C-1 posterior arch screws. The technique involves the insertion of bilateral multiaxial C-1 posterior arch screws, which are connected by crosslinked rods to bilateral multiaxial C-2 pars screws. The clinical results are presented in 3 patients in whom anomalies of the vertebral arteries, C-1 lateral masses, and/or posterior arch of C-1 presented difficulty using existing fixation techniques with transarticular screws, C-1 lateral mass screws, or posterior wiring. The C-1 posterior arch screws achieved solid fixation and their insertion appeared to be technically less demanding than that of transarticular or C-1 lateral mass screws. This technique may reduce the risk of complications compared with existing techniques, especially in patients with anatomical variants of the vertebral artery, C-1 lateral masses, or C-1 posterior arch. This technique may prove to be an attractive fixation option in patients with normal anatomy.

  11. Rotational Efficiency of Photo-Driven Archimedes Screws for Micropumps

    Directory of Open Access Journals (Sweden)

    Chih-Lang Lin

    2015-06-01

    Full Text Available In this study, we characterized the rotational efficiency of the photo-driven Archimedes screw. The micron-sized Archimedes screws were fabricated using the two-photon polymerization technique. Free-floating screws trapped by optical tweezers align in the laser irradiation direction and rotate spontaneously. The influences of the screw pitch and the number of screw blades have been investigated in our previous studies. In this paper, the blade thickness and the central rod of the screw were further investigated. The experimental results indicate that the blade thickness contributes to rotational stability, but not to rotational speed, and that the central rod stabilizes the rotating screw but is not conducive to rotational speed. Finally, the effect of the numerical aperture (NA of the optical tweezers was investigated through a demonstration. The NA is inversely proportional to the rotational speed.

  12. A Review of Screw Conveyors Performance Evaluation During Handling Process

    Directory of Open Access Journals (Sweden)

    Hemad Zareiforoush

    2010-04-01

    Full Text Available This paper reviews recent work on screw conveyors performance evaluation during handling process, especially in the case of agricultural grains and bulk materials. Experimental work has been mainly carried out to determine a range of parameters, such as auger dimension, screw rotational speed, screw clearance, conveyor intake length and conveying angle for horizontal, inclined and vertical screw conveyors. Several measurement techniques including theoretical models and DEM have been utilized to study the screw conveyors performance. However, each of these techniques is limited in its application. Difficulties in representing vortex motion and interactions among conveying grains and between the particles and screw rotating flight have so far limited the success of advanced modeling. Further work is needed to be conducted on screw augers performance to understand and improve the agricultural grains and bulk materials handling process.

  13. Research and application of absorbable screw in orthopedics: a clinical review comparing PDLLA screw with metal screw in patients with simple medial malleolus fracture

    Directory of Open Access Journals (Sweden)

    TANG Jin

    2013-02-01

    Full Text Available 【Abstract】Objective: To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics. Methods: A total of 129 patients with simple medial malleolus fracture were studied. Among them, 64 patients were treated with poly-D, L-lactic acid (PDLLA absorbable screws, while the others were treated with metal screws. All the patients were followed up for 12-20 months (averaged 18.4 months and the therapeutic effect was evaluated ac-cording to the American Orthopaedic Foot and Ankle Soci-ety clinical rating systems. Results: In absorbable screw group, we obtained excel-lent and good results in 62 cases (96.88%; in steel screw group, 61 cases (93.85% achieved excellent and good results. There was no significant difference between the two groups. Conclusion: In the treatment of malleolus fracture, absorbable screw can achieve the same result compared with metal screw fixation. Absorbable screw is preferred due to its advantages of safety, cleanliness and avoiding the removal procedure associated with metallic implants. Key words: Ankle; Bone screws; Fractures, bone

  14. Opportunistic Interference Alignment in MIMO Interference Channels

    CERN Document Server

    Perlaza, Samir Medina; Lasaulce, Samson; Chaufray, Jean Marie

    2008-01-01

    We present two interference alignment techniques such that an opportunistic point-to-point multiple input multiple output (MIMO) link can reuse, without generating any additional interference, the same frequency band of a similar pre-existing primary link. In this scenario, we exploit the fact that under power constraints, although each radio maximizes independently its rate by water-filling on their channel transfer matrix singular values, frequently, not all of them are used. Therefore, by aligning the interference of the opportunistic radio it is possible to transmit at a significant rate while insuring zero-interference on the pre-existing link. We propose a linear pre-coder for a perfect interference alignment and a power allocation scheme which maximizes the individual data rate of the secondary link. Our numerical results show that significant data rates are achieved even for a reduced number of antennas.

  15. Impact of screw elements on continuous granulation with a twin-screw extruder.

    Science.gov (United States)

    Djuric, Dejan; Kleinebudde, Peter

    2008-11-01

    The influence of different screw element types on wet granulation process with a twin-screw extruder was investigated. Lactose granules were prepared with different screw configurations such as conveying, combing mixer and kneading elements. The use of kneading blocks led to an almost complete agglomeration of lactose, whereas kneading and combing mixer elements resulted in smaller granules in comparison. Granule porosity varied between 17.4% and 50.6%. Granule friability values ranged from 1.2% to 38.5%. Conveying elements led to the most porous and friable granules, whereas kneading blocks produced the densest and least friable granules. Combing mixer elements produced granules with median properties. A linear correlation between granule porosity and the natural logarithm of granule friability was detected. Flowability of granules was also influenced by the element type. Compressed granules with higher granule porosities resulted in tablets with higher tensile strength values and vice versa. Twin-screw extruders proved to be a versatile tool for wet granulation. By the choice of a suitable screw element granule and tablet characteristics were influenced.

  16. 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.

  17. Translaminar facetal screw (magerl′s fixation

    Directory of Open Access Journals (Sweden)

    Rajasekaran S

    2005-01-01

    Full Text Available Translaminar facet screw fixation (TLFS achieves stabilization of the vertebral motion segment by screws inserted at the base of the spinous process, through the opposite lamina, traversing the facet joint, and ending in the base of the transverse process. It is simple, does not require any specialized equipment, and has the advantages of being a procedure of lesser magnitude, lesser operative time, less cost and few complication rate. Recently there is growing interest in this technique to augment the anterior lumbar fusions to achieve global fusion less invasively. In this review article, we discuss the clinical and biomechanical considerations, surgical technique, indications, contraindications and recent developments of TLFS fixation in lumbar spine fusion.

  18. Twin screw granulation - review of current progress.

    Science.gov (United States)

    Thompson, M R

    2015-01-01

    Twin screw granulation (TSG) is a new process of interest to the pharmaceutical community that can continuously wet granulate powders, doing so at lower liquid concentrations and with better product consistency than found by a high shear batch mixer. A considerable body of research has evolved over the short time since this process was introduced but generally with little comparison of results. A certain degree of confidence has been developed through these studies related to how process variables and many attributes of machinery configuration will affect granulation but some major challenges still lay ahead related to scalability, variations in the processing regimes related to degree of channel fill and the impact of wetting and granulation of complex powder formulations. This review examines the current literature for wet granulation processes studied in twin screw extrusion machinery, summarizing the influences of operational and system parameters affecting granule properties as well as strives to provide some practical observations to newly interested users of the technique.

  19. MOVING SCREW DISLOCATION IN CUBIC QUASICRYSTAL

    Institute of Scientific and Technical Information of China (English)

    ZHOU Wang-min; SONG Yu-hai

    2005-01-01

    The elasticity theory of the dislocation of cubic quasicrystals is developed.The governing equations of anti-plane elasticity dynamics problem of the quasicrystals were reduced to a solution of wave equations by introducing displacement functions,and the analytical expressions of displacements, stresses and energies induced by a moving screw dislocation in the cubic quasicrystalline and the velocity limit of the dislocation were obtained. These provide important information for studying the plastic deformation of the new solid material.

  20. 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.

  1. Research and application of absorbable screw in orthopedics: a clinical review comparing PDLLA screw with metal screw in patients with simple medial malleolus fracture

    Institute of Scientific and Technical Information of China (English)

    TANG Jin; HU Jin-feng; GUO Wei-chun; YU Ling; ZHAO Sheng-hao

    2013-01-01

    Objective:To observe the therapeutic effect of absorbable screw in medial malleolus fracture and discuss its clinical application in orthopedics.Methods:A total of 129 patients with simple medial malleolus fracture were studied.Among them,64 patients were treated with poly-D,L-lactic acid (PDLLA) absorbable screws,while the others were treated with metal screws.All the patients were followed up for 12-20 months (averaged 18.4 months) and the therapeutic effect was evaluated according to the American Orthopaedic Foot and Ankle Society clinical rating systems.Results:In absorbable screw group,we obtained excellent and good results in 62 cases (96.88%); in steel screw group,61 cases (93.85%) achieved excellent and good results.There was no significant difference between the two groups.Conclusion:In the treatment of malleolus fracture,absorbable screw can achieve the same result compared with metal screw fixation.Absorbable screw is preferred due to its advantages of safety,cleanliness and avoiding the removal procedure associated with metallic implants.

  2. Double insurance transfacetal screws for lumbar spinal stabilization

    Directory of Open Access Journals (Sweden)

    Atul Goel

    2014-01-01

    Full Text Available Aim: The authors report experience with 14 cases where two screws or ′′double insurance′′ screws were used for transfacetal fixation of each joint for stabilization of the lumbar spinal segment. The anatomical subtleties of the technique of insertion of screws are elaborated. Materials and Methods: During the period March 2011 to June 2014, 14 patients having lumbar spinal segmental instability related to lumbar canal stenosis were treated by insertion of two screws into each articular assembly by transfacetal technique. After a wide surgical exposure, the articular cartilage was denuded and bone chips were impacted into the joint cavity. For screw insertion in an appropriate angulation, the spinous process was sectioned at its base. The screws (2.8 mm in diameter and 18 mm in length were inserted into the substance of the medial or inferior articular facet of the rostral vertebra via the lateral limit of the lamina approximately 6-8 mm away from the edge of the articular cavity. The screws were inserted 3 mm below the superior edge and 5 mm above the inferior edge of the medial (inferior facets and directed laterally and traversed through the articular cavity into the lateral (superior articular facet of the caudal vertebra toward and into the region of junction of base of transverse process and of the pedicle. During the period of follow-up all treated spinal levels showed firm bone fusion. There was no complication related to insertion of the screws. There was no incidence of screw misplacement, displacementor implant rejection. Conclusions: Screw insertion into the firm and largely cortical bones of facets of lumbar spine can provide robust fixation and firm stabilization of the spinal segment. The large size of the facets provides an opportunity to insert two screws at each spinal segment. The firm and cortical bone material and absence on any neural or vascular structure in the course of the screw traverse provides strength and

  3. Finite Element Analysis of Reciprocating Screw for Injection Molding Machine

    Directory of Open Access Journals (Sweden)

    Nagsen B. Nagrale

    2011-06-01

    Full Text Available This paper deals with, the solution of problem occurred for reciprocating screw of Injection molding machine. It identifies and solves the problem by using the modeling and simulation techniques. The problem occurred in the reciprocating screw of machine which was wearing of threads due to affect of temperature of mold materials(flow materials i.e. Nylon, low density polypropylene, polystyrene, PVC etc., The main work was to model the components of machine with dimensions, assemble those components and then simulate the whole assembly for rotation of the screw. The modeling software used is PRO-E wildfire 4.0 for modeling the machine components like body, movable platen, fixed platen, barrel, screw, nozzle, etc. The analysis software ANSYS is used to analyze the reciprocating screws. The objectives involved are:- • To model all the components using modeling software Pro-E 4.0 • To assemble all the components of the machine in the software. • To make the assembly run in Pro-E software.• Analysis of screw of machine using Ansys 11.0 software. • To identify the wearing of threads and to provide the possible solutions.This problem is major for all industrial injection molding machines which the industries are facing and they need the permanent solution, so if the better solution is achieved then the industries will think for implementing it. The industries are having temporary solution but it will affect the life of the screw, because the stresses will be more in machined screw on lathe machine as compared to normal screw. Also if the screw will fail after some years of operation, the new screw available in the market will have the same problem. Also the cost associated with new screw and its mounting is much more as it is the main component of machine.

  4. 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...

  5. Discrete element modelling of screw conveyor-mixers

    Directory of Open Access Journals (Sweden)

    Jovanović Aca

    2015-01-01

    Full Text Available Screw conveyors are used extensively in food, plastics, mineral processing, agriculture and processing industries for elevating and/or transporting bulk materials over short to medium distances. Despite their apparent simplicity in design, the transportation action is very complex for design and constructors have tended to rely heavily on empirical performance data. Screw conveyor performance is affected by its operating conditions (such as: the rotational speed of the screw, the inclination of the screw conveyor, and its volumetric fill level. In this paper, horizontal, several single-pitch screw conveyors with some geometry variations in screw blade was investigated for mixing action during transport, using Discrete Element Method (DEM. The influence of geometry modifications on the performance of screw conveyor was examined, different screw designs were compared, and the effects of geometrical variations on mixing performances during transport were explored. During the transport, the particle tumbles down from the top of the helix to the next free surface and that segment of the path was used for auxiliary mixing action. The particle path is dramatically increased with the addition of three complementary helices oriented in the same direction as screw blades (1458.2 mm compared to 397.6 mm in case of single flight screw conveyor Transport route enlarges to 1764.4 mm, when installing helices oriented in the opposite direction from screw blades. By addition of straight line blade to single flight screw conveyor, the longest particle path is being reached: 2061.6 mm [Projekat Ministarstva nauke Republike Srbije, br. TR-31055

  6. On the interference of Kr during carbon isotope analysis of methane using continuous-flow combustion–isotope ratio mass spectrometry

    NARCIS (Netherlands)

    Schmitt, J.; Seth, B.; Bock, M; van der Veen, C.; Möller, L.; Sapart, C.J.; Prokopiou, M.; Sowers, T.; Röckmann, T.; Fischer, H

    2013-01-01

    Stable carbon isotope analysis of methane ( 13C of CH4) on atmospheric samples is one key method to constrain the current and past atmospheric CH4 budget. A frequently applied measurement technique is gas chromatography (GC) isotope ratio mass spectrometry (IRMS) coupled to a combustion-preconcentra

  7. Fluid Flow Phenomenon in a Three-Bladed Power-Generating Archimedes Screw Turbine

    OpenAIRE

    2016-01-01

    Experimental studies of the Archimedes screw turbine are applied as a micro hydro power plant for low head focused on the fluid flow. Fluid flow on a screw turbine is not completely filled water flow there is still a free surface between the water fluid and atmospheric air. Except the screw geometry, the turbine screw free surface allows the flow phenomena that are important in the process of turbine screw power generation. The Archimedes screw turbine main driving force is the fl...

  8. Wet granulation in a twin-screw extruder: implications of screw design.

    Science.gov (United States)

    Thompson, M R; Sun, J

    2010-04-01

    Wet granulation in twin-screw extrusion machinery is an attractive technology for the continuous processing of pharmaceuticals. The performance of this machinery is integrally tied to its screw design yet little fundamental knowledge exists in this emerging field for granulation to intelligently create, troubleshoot, and scale-up such processes. This study endeavored to systematically examine the influence of different commercially available screw elements on the flow behavior and granulation mechanics of lactose monohydrate saturated at low concentration (5-12%, w/w) with an aqueous polyvinyl-pyrrolidone binder. The results of the work showed that current screw elements could be successfully incorporated into designs for wet granulation, to tailor the particle size as well as particle shape of an agglomerate product. Conveying elements for cohesive granular flows were shown to perform similar to their use in polymer processing, as effective transport units with low specific mechanical energy input. The conveying zones provided little significant change to the particle size or shape, though the degree of channel fill in these sections had a significant influence on the more energy-intensive mixing elements studied. The standard mixing elements for this machine, kneading blocks and comb mixers, were found to be effective for generating coarser particles, though their mechanisms of granulation differed significantly.

  9. Comparison between Bilateral C2 Pedicle Screwing and Unilateral C2 Pedicle Screwing, Combined with Contralateral C2 Laminar Screwing, for Atlantoaxial Posterior Fixation

    OpenAIRE

    Miyakoshi, Naohisa; HONGO, MICHIO; Kobayashi, Takashi; Suzuki, Tetsuya; Abe, Eiji; Shimada, Yoichi

    2014-01-01

    Study Design A retrospective study. Purpose To compare clinical and radiological outcomes between bilateral C2 pedicle screwing (C2PS) and unilateral C2PS, combined with contralateral C2 laminar screwing (LS), for posterior atlantoaxial fixation. Overview of Literature Posterior fixation with C1 lateral mass screwing (C1LMS) and C2PS (C1LMS-C2PS method) is an accepted procedure for rigid atlantoaxial stabilization. However, conventional bilateral C2PS is not always allowed in this method due ...

  10. Reliability of predictors for screw cutout in intertrochanteric hip fractures

    NARCIS (Netherlands)

    K.M.J. de Bruijn (Kirstin); D. den Hartog (Dennis); W.E. Tuinebreijer (Wim); G.R. Roukema (Gert)

    2012-01-01

    textabstractBackground: Following internal fixation of intertrochanteric hip fractures, tip apex distance, fracture classification, position of the screw in the femoral head, and fracture reduction are known predictors for screw cutout, but the reliability of these measurements is unknown. We invest

  11. 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...

  12. KINEMATICS OF 3-DOF PYRAMID MANIPULATOR BY PRINCIPAL SCREWS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Kinematics of a 3-RPS parallel pyramid manipulator are investigated by principal screw. Firstly, the principal screws are identified by quadric degeneration. The planar conics representing the relations between the pitches and the three linear inputs are described, and the three-dimensional distribution of the axes of all the twists is illustrated. Finally, a numerical example is given successfully.

  13. [Loosening of a Calcaneo-Stop Screw after Trampolining].

    Science.gov (United States)

    Trieb, K; Fingernagel, T; Petershofer, A; Hofstaetter, S G

    2015-06-01

    Flexible flatfoot is a common malalignment in the paediatric population. Arthroereisis with a calcaneo-stop screw is an effective surgical procedure for treating juvenile flexible flatfoot after conservative measures have been fully exploited. In the present report, we describe the case of a loosening of a calcaneo-stop screw in a 12-year-old youth after excessive trampolining.

  14. OPTIMAL DISTAL SCREW ALIGNMENT IN THE GAMMA NAIL

    Institute of Scientific and Technical Information of China (English)

    Ching-KongChao; Chun-ChingHsiao; Po-QuangChen

    2002-01-01

    The effect of stress distribution due to the changes of the distal screw alignment in relation to the Gamma nail and the femoral shaft is thoroughly studied in this paper. Failure of the Gamma nail composite occurs through the cranial aperture of the distal screws and the insertion hole for the lag screw due to nonunion, delayed-union and continued weight-bearing. A three-dimensional finite element model was used to study the fractured femur, the Gamma nail, the lag screw and the distal locking screws. The first and the second distal screws were inserted into the Gamma nail in four different configurations. We found that the stress of the Gamma nail composite was substantially reduced with the two screws configured in the anterior to posterior direction. This alignment can bear greater loading in the more demanding fracture types. In the subtrochanteric fracture or the comminuted fractures at the proximal femur, the optimal alignment of the two distal screws was in the anterior to posterior direction.

  15. Determination of the of rate cross slip of screw dislocations

    DEFF Research Database (Denmark)

    Vegge, Tejs; Rasmussen, Torben; Leffers, Torben;

    2000-01-01

    The rate for cross slip of screw dislocations during annihilation of screw dipoles in copper is determined by molecular dynamics simulations. The temperature dependence of the rate is seen to obey an Arrhenius behavior in the investigated temperature range: 225-375 K. The activation energy...

  16. 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.

  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. 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.

  19. 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.

  20. Lumbar pedicle cortical bone trajectory screw

    Institute of Scientific and Technical Information of China (English)

    Song Tengfei; Wellington K Hsu; Ye Tianwen

    2014-01-01

    Objective The purpose of this study was to demonstrate the lumbar pedicle cortical bone trajectory (CBT) screw fixation technique,a new fixation technique for lumbar surgery.Data sources The data analyzed in this review are mainly from articles reported in PubMed published from 1994 to 2014.Study selection Original articles and critical reviews relevant to CBT technique and lumbar pedicle fixation were selected.Results CBT technique was firstly introduced as a new fixation method for lumbar pedicle surgery in 2009.The concepts,morphometric study,biomechanical characteristics and clinical applications of CBT technique were reviewed.The insertional point of CBT screw is located at the lateral point of the pars interarticularis,and its trajectory follows a caudocephalad path sagittally and a laterally directed path in the transverse plane.CBT technique can be used for posterior fixation during lumbar fusion procedures.This technique is a minimally invasive surgery,which affords better biomechanical stability,fixation strength and surgical safety.Therefore,CBT technique has the greatest benefit in lumbar pedicle surgery for patients with osteoporosis and obesity.Conclusion CBT technique is a better alternative option of lumbar pedicle fixation,especially for patients with osteoporosis and obesity.

  1. Asymmetric distribution in twin screw granulation.

    Science.gov (United States)

    Chan Seem, Tim; Rowson, Neil A; Gabbott, Ian; de Matas, Marcel; Reynolds, Gavin K; Ingram, Andy

    2016-09-01

    Positron Emission Particle Tracking (PEPT) was successfully employed to validate measured transverse asymmetry in material distribution in the conveying zones of a Twin Screw Granulator (TSG). Flow asymmetry was established to be a property of the granulator geometry and dependent on fill level. The liquid distribution of granules as a function of fill level was determined. High flow asymmetry at low fill level negatively affects granule nucleation leading to high variance in final uniformity. Wetting of material during nucleation was identified as a critical parameter in determining final granule uniformity and fill level is highlighted as a crucial control factor in achieving this. Flow asymmetry of dry material in conveying zones upstream of binder fluid injection leads to poor non-uniform wetting at nucleation and results in heterogeneous final product. The granule formation mechanism of 60°F kneading blocks is suggested to be primarily breakage of agglomerates formed during nucleation. Optimisation of screw configuration would be required to provide secondary growth. This work shows how fill dependent flow regimes affect granulation mechanisms.

  2. Supermassive screwed cosmic string in dilaton gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bezerra, V B [Departamento de Fisica, Universidade Federal da ParaIba, 58059-970, Joao Pessoa, PB (Brazil); Ferreira, Cristine N [Nucleo de Fisica, Centro Federal de Educacao Tecnologica de Campos, Rua Dr Siqueira, 273-Parque Dom Bosco, 28030-130, Campos dos Goytacazes, RJ (Brazil); Cuesta, H J Mosquera [Instituto de Cosmologia, Relatividade e AstrofIsica (ICRA-BR), Centro Brasileiro de Pesquisas Fisicas, Rua Dr Xavier Sigaud 150, Urca 22290-180, Rio de Janeiro, RJ (Brazil)

    2006-06-21

    The early universe might have undergone phase transitions at energy scales much higher than the one corresponding to the grand unified theories (GUT) scales. At these higher energy scales, the transition at which gravity separated from all other interactions, the so-called Planck era, more massive strings called supermassive cosmic strings could have been produced, with energy of about 10{sup 19} GeV. The dynamics of strings formed with this energy scale cannot be described by means of the weak-field approximation, as in the standard procedure for ordinary GUT cosmic strings. As suggested by string theories, at this extreme energy, gravity may be transmitted by some kind of scalar field (usually called the dilaton) in addition to the tensor field of Einstein's theory of gravity. It is then permissible to tackle the issue regarding the dynamics of supermassive cosmic strings within this framework. With this aim, we obtain the gravitational field of a supermassive screwed cosmic string in a scalar-tensor theory of gravity. We show that for the supermassive configuration, exact solutions of scalar-tensor screwed cosmic strings can be found in connection with the Bogomol'nyi limit. We show that the generalization of Bogomol'nyi arguments to the Brans-Dicke theory is possible when torsion is present and we obtain an exact solution in this supermassive regime, with the dilaton solution obtained by consistency with internal constraints.

  3. Dark Matter Interference

    DEFF Research Database (Denmark)

    Del Nobile, Eugenio; Kouvaris, Christoforos; Sannino, Francesco

    2012-01-01

    We study different patterns of interference in WIMP-nuclei elastic scattering that can accommodate the DAMA and CoGeNT experiments via an isospin violating ratio $f_n/f_p=-0.71$. We study interference between the following pairs of mediators: Z and Z', Z' and Higgs, and two Higgs fields. We show...

  4. How does interference fall?

    CERN Document Server

    Orlando, Patrick J; Modi, Kavan

    2016-01-01

    We study how single- and double-slit interference patterns fall in the presence of gravity. First, we demonstrate that universality of free fall still holds in this case, i.e., interference patterns fall just like classical objects. Next, we explore lowest order relativistic effects in the Newtonian regime by employing a recent quantum formalism which treats mass as an operator. This leads to interactions between non-degenerate internal degrees of freedom (like spin in an external magnetic field) and external degrees of freedom (like position). Based on these effects, we present an unusual phenomenon, in which a falling double slit interference pattern periodically decoheres and recoheres. The oscillations in the visibility of this interference occur due to correlations built up between spin and position. Finally, we connect the interference visibility revivals with non-Markovian quantum dynamics.

  5. Optimization of Twin-Screw Superchargers for Combined Compressor - Expander Performance (SCREW); Optimierung von Schraubenladern fuer den kombinierten Verdichtungs- und Expansionsbetrieb (SCREW)

    Energy Technology Data Exchange (ETDEWEB)

    Romba, M. [Dortmund Univ. (Germany). Fachgebiet Fluidenergiemaschinen

    2005-07-01

    During the last years the use of mechanical superchargers has gained increasing interest in a bid to combine attractive emission- and fuel consumption values with dynamic driving performance. Based on an analysis of available supercharging systems the development potential of twin screw superchargers is assessed. A concept using inlet slide valves is developed which allows at the same time to control the mass flow delivered by the supercharger and achieve an expansion of the transported charge under part load conditions when the delivered pressure is lower than ambient pressure, achieving a reduction in necessary shaft power or even the delivery of shaft power. To distinguish it from conventional superchargers the new device is called ''SCREW'' - screw type machine with compressor respectively expander working mode. The effect of several design parameters on the SCREW'S performance is evaluated by extensive simulation calculations, showing that a suitable design varies considerably from conventional supercharger designs and that a significant amount of further research, especially covering the development of rotor profiles suited for the specific task, is still needed to fully utilize the concept's potential. As a proof of concept prototype SCREW'S, based on a conventional twin screw supercharger, have been built and tested. The results obtained made clear the general suitability of the concept but also underlined the shortcomings of the prototype as they had already been predicted by the simulations. (orig.)

  6. Electrocatalytic Reduction of Hydrogen Peroxide on Palladium-Gold Codeposits on Glassy Carbon: Applications to the Design of Interference-Free Glucose Biosensor

    Directory of Open Access Journals (Sweden)

    Elena Horozova

    2011-01-01

    Full Text Available Following our previous studies on the catalytic activity electrochemically codeposited on graphite Pd-Pt electrocatalysts for hydrogen peroxide electroreduction, a series of glassy carbon electrodes were modified with Pd or (Pd+Au deposits aiming at the development of even more efficient electrocatalysts for the same process. The resulting electrodes were found to be very effective at low applied potentials (−100 and −50 mV versus Ag/AgCl, 1 M KCl. The surface topography of the electrode modified with Pd+Au mixed in proportions 90% : 10%, exhibiting optimal combination of sensitivity and linear dynamic range towards hydrogen peroxide electrochemical reduction, was studied with SEM and AFM. The applicability of the same electrode as transducer in an amperometric biosensor for glucose assay was demonstrated. At an applied potential of −50 mV, the following were determined: detection limit (S/N=3 of 6×10−6 M glucose, electrode sensitivity of 0.15 μA μM−1, and strict linearity up to concentration of 3×10−4 M.

  7. Engineering Aspects of Single- and Twin-screw Extrusion-cooking of Biopolymers

    NARCIS (Netherlands)

    Zuilichem, D.J. van; Stolp, W.; Janssen, L.P.B.M.

    1983-01-01

    A survey is given of the properties of single- and twin-screw extruders. The influence on the design of the different leakage gaps existing in co-rotating, counter-rotating, self-wiping, twin-screw extruders and single-screw equipment is discussed. The mixing effects in single- and twin-screw equipm

  8. 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.

  9. 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.

  10. Comparison of expansive pedicle screw and polymethylmethacrylate-augmented pedicle screw in osteoporotic sheep lumbar vertebrae: biomechanical and interfacial evaluations.

    Directory of Open Access Journals (Sweden)

    Da Liu

    Full Text Available 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 randomly divided into three groups. The conventional pedicle screw (CPS was inserted directly into vertebrae in CPS group; PMMA was injected prior to insertion of CPS in PMMA-PS group; and the EPS was inserted in EPS group. Sheep were killed and biomechanical tests, micro-CT analysis and histological observation were performed at both 6 and 12 weeks post-operation. At 6-week and 12-week, screw stabilities in EPS and PMMA-PS groups were significantly higher than that in CPS group, but there were no significant differences between EPS and PMMA-PS groups at two study periods. The screw stability in EPS group at 12-week was significantly higher than that at 6-week. The bone trabeculae around the expanding anterior part of EPS were more and denser than that in CPS group at 6-week and 12-week. PMMA was found without any degradation and absorption forming non-biological "screw-PMMA-bone" interface in PMMA-PS group, however, more and more bone trabeculae surrounded anterior part of EPS improving local bone quality and formed biological "screw-bone" interface. CONCLUSIONS/SIGNIFICANCE: EPS can markedly enhance screw stability with a similar effect to the traditional method of screw augmentation with PMMA in initial surgery in osteoporosis. EPS can form better biological interface between screw and bone than PMMA-PS. In addition, EPS have no risk of thermal injury, leakage and compression caused by PMMA. We propose EPS has a great application potential in augmentation of

  11. Recovery of dynamic interference

    CERN Document Server

    Baghery, Mehrdad; Rost, Jan M

    2016-01-01

    We develop general quantitative criteria for dynamic interference, a manifestation of double-slit interference in time which should be realizable with brilliant state-of-the-art high-frequency laser sources. Our analysis reveals that the observation of dynamic interference hinges upon maximizing the difference between the dynamic polarization of the initial bound and the final continuum state of the electron during the light pulse, while keeping depletion of the initial state small. Confirmed by numerical results, we predict that this is impossible for the hydrogen ground-state but feasible with excited states explicitly exemplified with the hydrogen 2p-state.

  12. Group Based Interference Alignment

    CERN Document Server

    Ma, Yanjun; Chen, Rui; Yao, Junliang

    2010-01-01

    in $K$-user single-input single-output (SISO) frequency selective fading interference channels, it is shown that the achievable multiplexing gain is almost surely $K/2$ by using interference alignment (IA). However when the signaling dimensions is limited, allocating all the resource to all the users simultaneously is not optimal. According to this problem, a group based interference alignment (GIA) scheme is proposed and a search algorithm is designed to get the group patterns and the resource allocation among them. Analysis results show that our proposed scheme achieves a higher multiplexing gain when the resource is limited.

  13. Preliminary Design on Screw Press Model of Palm Oil Extraction Machine

    Science.gov (United States)

    Firdaus, Muhammad; Salleh, S. M.; Nawi, I.; Ngali, Z.; Siswanto, W. A.; Yusup, E. M.

    2017-01-01

    The concept of the screw press is to compress the fruit bunch between the main screw and travelling cones to extract the palm oil. Visual inspection, model development and simulation of screw press by using Solidworks 2016 and calculation of design properties were performed to support the investigation. The project aims to analyse different design of screw press which improves in reducing maintenance cost and increasing lifespan. The currently existing of screw press can endure between 500 to 900 hours and requires frequent maintenance. Different configurations have been tried in determination of best design properties in screw press. The results specify that screw press with tapered inner shaft has more total lifespan (hours) compared existing screw press. The selection of the screw press with tapered inner shaft can reduce maintenance cost and increase lifespan of the screw press.

  14. Simulation and analysis of resin flow in injection machine screw

    Institute of Scientific and Technical Information of China (English)

    Ling-feng LI; Samir MEKID

    2008-01-01

    A method with simulation and analysis of the resin flow in a screw is presented to ease the control of some problems that may affect the efficiency and the quality of the product among existing screws in an injection machine. The physical model of a screw is established to represent the stress, the strain, the relationship between velocity and stress, and the temperature of the cells. In this paper, a working case is considered where the velocity and the temperature distributions at any section of the flow are obtained. The analysis of the computational results shows an ability to master various parameters depending on the specifications.

  15. 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.

  16. 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...... lead screw (MLS) employing permanent magnets only, the new EMLS proposed uses dc current to provide the required helical-shape magnetic field, offering a much simpler, robust structure compared with the MLS. The working principle and the performances of this EMLS are analyzed in this paper. Comparison...

  17. 3D CFD analysis of a twin screw expander

    OpenAIRE

    Kovacevic, A.; S Rane

    2013-01-01

    Twin screw machines can be used as expanders for variety of applications. This paper describes how the performance of an oil free twin screw air expander of 3/5 lobe configuration was estimated by use of full 3D Computational Fluid Dynamics (CFD) applying a procedure similar to that used for screw compressors. The grid generator SCORG© was employed for pre-processing of the moving domains between the rotors while the stationary grids for the ports were derived from a commercial grid generator...

  18. 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.

  19. Test Research on Special Sucker Rod for Screw Pump

    Institute of Scientific and Technical Information of China (English)

    Zhang Mingyi; Chen Mingzhan; Li Zhi

    2006-01-01

    @@ According to the statistics of straight thread sucker rods' application in screw pump in Daqing Oilfield before2000, the proportion of sucker rods' yearly breakaway reached to 41.6%, taking up 70% of the total wells that were checked. Thus it can be seen that the rods breakaway problem was becoming the main barrier restricting screw pump large-scale population and application. Since then,the development work on the special sucker rods for screw pump had been carried on. Through the analysis on the failure position and failure form of the sucker rods',the following conclusions arepresented:

  20. Migration of polyethylene fixation screw after total knee arthroplasty.

    Science.gov (United States)

    Cho, Woo-Shin; Youm, Yoon-Seok

    2009-08-01

    Duracon (Howmedica, Rutherford, NJ) posterior stabilized total knee system has a snap fit locking mechanism of a tibial polyethylene, including an additional locking screw for further fixation of polyethylene. We report 13 cases of locking screw migration from tibial component after Duracon posterior stabilized primary total knee arthroplasty. Among 13 knees, screw migration in 10 asymptomatic cases was incidentally detected during regular follow-up, and they were just observed in the outpatient clinic. Only 3 knees had moderate pain, swelling, and instability, and revision was done on 2 of 3 knees.

  1. Understanding of edge and screw dislocations in nanostructures by modeling and simulations

    Science.gov (United States)

    Dontsova, Evgeniya

    The role of the extended dislocation defects in nanostructures only recently began to be explored. In bulk materials, dislocations are modeled only away from their cores within the framework of the continuum mechanics. It is known that applying continuum modeling in the core region leads to divergences. In nanostructures, the core region dominates and new investigation methods are needed. This work contributes to the fundamental understanding of the role of dislocations in important carbon and zinc oxide nanostructures, by using atomistic investigation methods. In quasi-zero-dimensional structures, thesis describes the first attempt to rationalize dislocation processes in carbon nano-onions. Experiments show that carbon nano-onions exhibit an unusual dislocation dynamics with unexpected attraction of outer edge dislocation towards the core. Atomistic calculations combined with rigorous energy analysis attribute this behavior to an unusual inward driving force on the outer edge dislocation associated with a reduction in the number of dangling bonds. Moving on to quasi-one-dimensional nanostructures, we study the stability of screw-dislocated zinc oxide structures in the wurtzite phase with a symmetry-adapted molecular dynamics methodology, which introduces a significant simplification in the simulation domain size by accounting for the helical symmetry explicitly. The goal is to provide the theoretical support for a universal screw-dislocation-driven growth mechanism suggested by recent experiments. Moreover, the effects of axial screw dislocations on the electronic properties in helical zinc oxide nanowires and nanotubes are explored. We demonstrate significant screw-dislocation-induced band gap modifications that originate in the highly distorted cores. Finally, using the same objective technique, we investigate the stability against torsional deformations of quasi-one-dimensional graphene nanoribbons with bare, F-, and OH-saturated armchair edges. The prevalence

  2. Centrifuging Step-Screw Conveyor for Regolith Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A variety of ISRU operations will utilize lunar regolith as feedstock. The proposed centrifuging step-screw conveyor concept will provide a well controlled robust,...

  3. Screw-matrix method in dynamics of multibody systems

    Science.gov (United States)

    Yanzhu, Liu

    1988-05-01

    In the present paper the concept of screw in classical mechanics is expressed in matrix form, in order to formulate the dynamical equations of the multibody systems. The mentioned method can retain the advantages of the screw theory and avoid the shortcomings of the dual number notation. Combining the screw-matrix method with the tool of graph theory in Roberson/Wittenberg formalism. We can expand the application of the screw theory to the general case of multibody systems. For a tree system, the dynamical equations for each j-th subsystem, composed of all the outboard bodies connected by j-th joint can be formulated without the constraint reaction forces in the joints. For a nontree system, the dynamical equations of subsystems and the kinematical consistency conditions of the joints can be derived using the loop matrix. The whole process of calculation is unified in matrix form. A three-segment manipulator is discussed as an example.

  4. 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...

  5. 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.

  6. 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.

  7. Pedicle screw fixation against burst fracture of thoracolumbar vertebrae

    Institute of Scientific and Technical Information of China (English)

    L(U) Fu-xin; HUANG Yong; ZHANG Qiang; SHI Feng-lei; ZHAO Dong-sheng; HU Qiao

    2007-01-01

    Objective: To analyze the application of vertebral pedicle screw fixation in the treatment of burst fracture of thoracolumbar vertebrae.Methods: A total of 48 cases (31 males and 17 females, aged from 18-72 years, mean: 41.3 years) with thoracolumbar vertebrae burst fracture were treated by pedicle screw system since January 2004. According to the AO classification of thoracolumbar vertebrae fracture,there are 36 cases of Type A, 9 of Type B and 3 of Type C.Results: All patients were followed up for 6-25 months (average 12 months ), no secondary nerve root injury, spinal cord injury, loosening or breakage of pedicle screw were observed. The nerve function of 29 patients with cauda equina nerve injury was restored to different degrees. The vertebral body height returned to normal level and posterior process angle was rectified after operation.Conclusions: The vertebral pedicle screw internal fixation was technologically applicable, which can efficiently reposition and stablize the bursting fractured vertabrae,indirectly decompress canalis spinalis, maintain spine stablity, scatter stress of screw system, reduce the risk of loosening or breakage of screw and loss of vertebral height,and prevent the formation of posterior convex after operation.

  8. Rapid prototyping drill guide template for lumbar pedicle screw placement

    Institute of Scientific and Technical Information of China (English)

    LU Sheng; XU Yong-qing; ZHANG Yuan-zhi; LI Yan-bing; SHI Ji-hong; CHEN Guo-ping; CHEN Yu-bing

    2009-01-01

    To develop a novel method of spinal pedical stereotaxy by reverse engineering and rapid prototyping techniques, and to validate its accuracy by experimental and clinical studies. Methods: A 3D reconstruction model for the desired lumbar vertebra was generated by using the Mimics 10.11 software, and the optimal screw size and orientation were determined using the reverse engineering software. Afterwards, a drill template was created by reverse engi-neering principle, whose surface was the antitemplate of the vertebral surface. The drill template and its correspond-ing vertebra were manufactured using the rapid prototyping technique. Results: The accuracy of the drill template was con-firmed by drilling screw trajectory into the vertebral biomodel preoperatively. This method also showed its ability to cus-tomize the placement and size of each screw based on the unique morphology of the lumbar vertebra.The drill tem-plate fits the postural surface of the vertebra very well in the cadaver experiment. Postoperative CT scans for controlling the pedicle bore showed that the personalized template had a high precision in cadaver experiment and clinical application. No misplacement occurred by using the per-sonalized template. During surgery, no additional computer assistance was needed.Conclusions: The authors have developed a novel drill template for lumbar pedicle screw placement with good applicability and high accuracy. The potential use of drill templates to place lumbar pedicle screws is promising. Our methodology appears to provide an accurate technique and trajectory for pedicle screw placement in the lumbar spine.

  9. Robot-assisted Anterior Odontoid Screw Fixation: A Case Report.

    Science.gov (United States)

    Tian, Wei; Wang, Han; Liu, Ya-Jun

    2016-08-01

    Anterior odontoid screw fixation has been proved to be effective but technically challenging because the difficult approach is associated with high risks of screw malposition and damage to surrounding vital structures. Navigation techniques are therefore increasingly being used to improve safety and accuracy. However, no robot-assisted odontoid screw fixation has yet been reported. We here report a 61-year-old woman with a type II dens fracture on whom anterior odontoid screw fixation was performed under the guidance of a newly developed robotic system (TiRobot, co-designed by Beijing Jishuitan Hospital and TINAVI Medical Technologies). One odontoid screw was safely and accurately placed, the calculated deviation between the planned and actual positions being 0.9 mm. No intraoperative complications were identified and the patient was discharged on Day 5. Follow-up studies after 2 weeks showed good clinical and radiological results. We believe this is the first reported case of robot-assisted anterior odontoid screw fixation. We consider that complicated procedures can become feasible, safe and accurate using TiRobot systems.

  10. Far cortical locking screws in distal femur fractures.

    Science.gov (United States)

    Adams, John D; Tanner, Stephanie L; Jeray, Kyle J

    2015-03-01

    Distal femur fractures routinely heal by secondary bone healing, which relies on interfragmentary motion. Periarticular locking plates are commonly used for fixation in distal femur fractures but are associated with a high nonunion rate, likely due to the stiffness of the constructs. Far cortical locking (FCL) screws are designed to allow micromotion at the near cortex while maintaining purchase in only the far cortex. Although clinical data are limited, these screws have been shown in biomechanical studies to provide excellent interfragmentary motion, and animal models have shown increased callus formation compared with traditional locking screws. The purpose of this study was to examine the clinical effects that FCL screws have on healing in distal femur fractures treated with locked constructs. In this retrospective case series, 15 patients with a distal femur fracture treated with MotionLoc screws (Zimmer, Warsaw, Indiana) were analyzed. Serial radiographs were evaluated for callus presence and time to union. All fractures were either 33-A3 or 33-C2 according to the AO classification system, and 5 (33%) were open. Bone loss was recorded in 2 patients. There were no nonunions, and average time to union was 24 weeks. There were no implant failures, and all 5 open fractures, including the 2 with bone loss, healed without intervention. There was 1 reoperation due to painful hardware. Although this is a small case series, these results are promising. Far cortical locking screws may provide the answer to the high nonunion rate associated with distal femur fractures treated with traditional locked constructs.

  11. Prediction of Deformity Correction by Pedicle Screw Instrumentation in Thoracolumbar Scoliosis Surgery

    Science.gov (United States)

    Kiriyama, Yoshimori; Yamazaki, Nobutoshi; Nagura, Takeo; Matsumoto, Morio; Chiba, Kazuhiro; Toyama, Yoshiaki

    In segmental pedicle screw instrumentation, the relationship between the combinations of pedicle screw placements and the degree of deformity correction was investigated with a three-dimensional rigid body and spring model. The virtual thoracolumbar scoliosis (Cobb’s angle of 47 deg.) was corrected using six different combinations of pedicle-screw placements. As a result, better correction in the axial rotation was obtained with the pedicle screws placed at or close to the apical vertebra than with the screws placed close to the end vertebrae, while the correction in the frontal plane was better with the screws close to the end vertebrae than with those close to the apical vertebra. Additionally, two screws placed in the convex side above and below the apical vertebra provided better correction than two screws placed in the concave side. Effective deformity corrections of scoliosis were obtained with the proper combinations of pedicle screw placements.

  12. Usefulness of absorbable screws in the Sauvé-Kapandji procedure for rheumatoid wrist reconstruction.

    Science.gov (United States)

    Nakamura, K; Oda, H; Tanaka, S; Kuga, Y; Yamamoto, M; Nishikawa, T; Juji, T; Shimizu, M

    2002-06-01

    Abstract  In the Sauvé-Kapandji (S-K) procedure for rheumatoid wrist reconstruction, the distal end of the ulna is fixed to the radius with screws. Recently, absorbable screws have increasingly been used instead of metal ones. However, the clinical usefulness of absorbable screws in S-K procedures for rheumatoid patients is still unknown. The purpose of this article is to evaluate the effect of absorbable screws in this procedure by comparing their clinical results with those of metal screws. Poly-l-lactic acid (PLLA) absorbable screws were used in 23 wrists, and metal screws were used in 20 wrists. We evaluated the presence of general or local reactions to PLLA, the stability of the ulnar head, the time to bone union, changes in the shape of the distal ulna, and the presence of bone resorption around the screws. There were no complications with the use of PLLA screws, and their fixation stability was adequate to form sufficient bone union. In five cases in the metal screw group, bone resorption around the screws occurred between 1 and 2 years after surgery. Bone resorption around the PLLA screws was not observed. We conclude that absorbable screws may be more useful than metal screws in the S-K procedure for rheumatoid wrist reconstruction.

  13. 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.

  14. The influence of screw configuration on the pretreatment performance of a continuous twin screw-driven reactor (CTSR).

    Science.gov (United States)

    Choi, Chang Ho; Um, Byung-Hwan; Oh, Kyeong Keun

    2013-03-01

    A combination of a continuous twin screw-driven reactor (CTSR) and a dilute acid pretreatment was used for the pretreatment of biomass with a high cellulose content and high monomeric xylose hydrolyzate. With the newly modified CTSR screw configuration (Config. 3), the influences of the screw rotational speed (30-60 rpm), of the pretreatment conditions such as acid concentration (1-5%) and reaction temperature (160-175 °C) at the operating condition of biomass feeding rate (1.0 g/min) and acid feeding rate (13.4 mL/min) on the pretreatment performance were investigated. The cellulose content in the pretreated rape straw was 67.1% at the following optimal conditions: barrel temperature of 165 °C, acid concentration of 3.0% (w/v), and screw rotational speed of 30 rpm. According to the three screw configurations, the glucose yields from enzymatic hydrolysis were 70.1%, 72.9%, and 78.7% for screw Configs. 1, 2, and 3, respectively.

  15. Investigation of an 11mm diameter twin screw granulator: Screw element performance and in-line monitoring via image analysis.

    Science.gov (United States)

    Sayin, Ridade; Martinez-Marcos, Laura; Osorio, Juan G; Cruise, Paul; Jones, Ian; Halbert, Gavin W; Lamprou, Dimitrios A; Litster, James D

    2015-12-30

    As twin screw granulation (TSG) provides one with many screw element options, characterization of each screw element is crucial in optimizing the screw configuration in order to obtain desired granule attributes. In this study, the performance of two different screw elements - distributive feed screws and kneading elements - was studied in an 11 mm TSG at different liquid-to-solid (L/S) ratios. The kneading element configuration was found to break large granules more efficiently, leading to narrower granule size distributions. While pharmaceutical industry shifts toward continuous manufacturing, inline monitoring and process control are gaining importance. Granules from an 11 mm TSG were analysed using the Eyecon™, a real-time high speed direct imaging system, which has been used to capture accurate particle size distribution and particle count. The size parameters and particle count were then assessed in terms of their ability to be a suitable control measure using the Shewhart control charts. d10 and particle count were found to be good indicators of the change in L/S ratio. However, d50 and d90 did not reflect the change, due to their inherent variability even when the process is at steady state.

  16. Ipsilateral pedicle screw placement with contralateral percutaneous facet screws: Early results with an alternative in lumbar arthrodesis

    Directory of Open Access Journals (Sweden)

    Richard B Rhiew

    2009-03-01

    Full Text Available Richard B Rhiew, Sunil Manjila, Andrew M Lozen, David Hong, Murali Guthikonda, S S RengacharyDepartment of Neurosurgery, Wayne State University, Detroit, MI, USAAbstract: Transforaminal lumbar interbody fusion (TLIF is a widely used method of surgical treatment for a variety of lumbar spinal disorders. Bilateral transpedicular instrumentation is routinely used in conjunction with an interbody graft to provide additional stability. In this technical note, we describe our fusion construct using ipsilateral pedicle screw placement on the side of TLIF and contralateral facet screw placement. We performed this construct at six levels in four patients. Suggested advantages include: low morbidity, small incision and lower cost. Outcomes parameters included radiographic evidence of solid union at four months and improvement in Oswestry Disability Index. A mean improvement from a preoperative score of 73 to 26 after surgery was observed at one-year follow-up. There were no instrument-related complications. In conclusion, this hybrid screw system minimizes contralateral dissection and is an attractive alternative to standard bilateral pedicle screw fixation.Keywords: TLIF, facet screw, pedicle screw, lumbar spine fusion

  17. Understanding ghost interference

    Science.gov (United States)

    Qureshi, Tabish; Chingangbam, Pravabati; Shafaq, Sheeba

    2016-08-01

    The ghost interference observed for entangled photons is theoretically analyzed using wave-packet dynamics. It is shown that ghost interference is a combined effect of virtual double-slit creation due to entanglement, and quantum erasure of which-path information for the interfering photon. For the case where the two photons are of different color, it is shown that fringe width of the interfering photon depends not only on its own wavelength, but also on the wavelength of the other photon which it is entangled with.

  18. Helical Screw Expander Evaluation Project. Final report

    Energy Technology Data Exchange (ETDEWEB)

    McKay, R.

    1982-03-01

    A functional 1-MW geothermal electric power plant that featured a helical screw expander was produced and then tested in Utah in 1978 to 1979 with a demonstrated average performance of approximately 45% machine efficiency over a wide range of test conditions in noncondensing operation on two-phase geothermal fluids. The Project also produced a computer-equipped data system, an instrumentation and control van, and a 1000-kW variable load bank, all integrated into a test array designed for operation at a variety of remote test sites. Additional testing was performed in Mexico in 1980 under a cooperative test program using the same test array, and machine efficiency was measured at 62% maximum with the rotors partially coated with scale, compared with approximately 54% maximum in Utah with uncoated rotors, confirming the importance of scale deposits within the machine on performance. Data are presented for the Utah testing and for the noncondensing phases of the testing in Mexico. Test time logged was 437 hours during the Utah tests and 1101 hours during the Mexico tests.

  19. PEACH POMACE PROCESSING USING TWIN SCREW EXTRUSION

    Directory of Open Access Journals (Sweden)

    Preetam Sarkar

    2014-02-01

    Full Text Available Fruit by-products have found limited applications in the food industry. They have been primarily used as animal feed, applied to agricultural land for soil amendment or composted and applied to farms for growing crops. Some of these disposal methods are not environment friendly, while others are costly. This study was undertaken to examine the possibility of utilizing peach pomace as a source of soluble dietary fiber in expanded extruded food products. Peach pomace was combined with rice flour at four different levels. The four blends were mixed, dried to a moisture level of 13.5% (w/w and ground to flour. These blends were extruded in a twin-screw extruder (Clextral EV-25 at a feed flow rate of 15 kg/h. The extruded products were analyzed for physical and textural properties. The apparent and true densities for the extrudates decreased from 183.93 to 133.94 kg/m3 and 1275.31 to 1171.2 kg/m3, respectively. A linear increase in extrudate porosity (85.11-88.54% and radial expansion ratio (13.5-19.3 and a steady decrease in breaking strength (104-50.74 kPa were observed with increasing peach pomace level in the blends. This study demonstrates the potential of extrusion processing as a tool for fruit by-product utilization, which will not only enhance consumption of soluble dietary fiber but will also increase the overall fruit utilization.

  20. 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.

  1. Destructive Interference of Dualities

    CERN Document Server

    Wotzasek, C

    1998-01-01

    We show that the fusion of two (diffeomorphism) invariant self-dual scalars described by right and left chiral-WZW actions, produces a Hull non-mover field. After fusion, right and left moving modes disappear from the spectrum, displaying in this way the phenomenon of (destructive) quantum interference of dualities.

  2. Downlink Interference Alignment

    CERN Document Server

    Suh, Changho; Tse, David

    2010-01-01

    We develop an interference alignment (IA) technique for a downlink cellular system. In the uplink, IA schemes need channel-state-information exchange across base-stations of different cells, but our downlink IA technique requires feedback only within a cell. As a result, the proposed scheme can be implemented with a few changes to an existing cellular system where the feedback mechanism (within a cell) is already being considered for supporting multi-user MIMO. Not only is our proposed scheme implementable with little effort, it can in fact provide substantial gain especially when interference from a dominant interferer (base-station) is significantly stronger than the remaining interference: it is shown that in the two-isolated cell layout, our scheme provides four-fold gain in throughput performance over a standard multi-user MIMO technique. We show through simulations that our technique provides respectable gain under more realistic scenarios: it gives approximately 55% and 20% gain for a linear cell layou...

  3. Interference Alignment for Secrecy

    CERN Document Server

    Koyluoglu, Onur Ozan; Lai, Lifeng; Poor, H Vincent

    2008-01-01

    This paper studies the frequency/time selective $K$-user Gaussian interference channel with secrecy constraints. Two distinct models, namely the interference channel with confidential messages and the one with an external eavesdropper, are analyzed. The key difference between the two models is the lack of channel state information (CSI) about the external eavesdropper. Using interference alignment along with secrecy pre-coding, it is shown that each user can achieve non-zero secure Degrees of Freedom (DoF) for both cases. More precisely, the proposed coding scheme achieves $\\frac{K-2}{2K-2}$ secure DoF {\\em with probability one} per user in the confidential messages model. For the external eavesdropper scenario, on the other hand, it is shown that each user can achieve $\\frac{K-2}{2K}$ secure DoF {\\em in the ergodic setting}. Remarkably, these results establish the {\\em positive impact} of interference on the secrecy capacity region of wireless networks.

  4. Interference and radioastronomy

    Science.gov (United States)

    Thompson, A. R.; Vanden Bout, Paul A.; Gergely, Tomas E.

    1991-11-01

    The vulnerabilty of radio astronomy to the growing flood of interfering sources ranging from garage door openers to digital audio broadcast satellites is reviewed. Technical solutions to these problems are briefly examined, and work that needs to be done in the international regulatory system to ameliorate the interference is addressed. An overview is given of existing regulations.

  5. A biomechanical study of two different pedicle screw methods for fixation in osteoporotic and nonosteoporotic vertebrae.

    Science.gov (United States)

    Higashino, Kosaku; Kim, Jin Hwan; Horton, William C; Hutton, William C

    2012-01-01

    In reconstruction of the osteoporotic spine, patients often show poor outcome because of pedicle screw failure. This study used osteoporotic and nonosteoporotic vertebrae to determine the difference in fixation strength between pedicle screws inserted straight forward and pedicle screws inserted in an upward trajectory toward the superior end plate (i.e., end-plate screws). There is some evidence to suggest that end-plate screws have a strength advantage. The particular focus was on osteoporotic vertebrae. Thirty-three vertebrae (T10-L2) were harvested. The bone mineral density (BMD) was measured: 15 vertebrae were greater than 0.8 g/cm(2) and designated as nonosteoporotic (average BMD 1.146 ± 0.186 g/cm(2)) and 18 vertebrae were designated as osteoporotic (average BMD 0.643 ± 0.088 g/cm(2)). On one pedicle the screw was inserted straight forward and on the other pedicle the screw was inserted as an end-plate screw. The torque of insertion was measured (Proto 6106 torque screwdriver). Using an MTS Mini Bionix, two types of mechanical testing were carried out on each pedicle: (a) cephalocaudad toggling was first carried out to simulate some physiological type loading: 500 cycles at 0.3 Hz, at ±50 N; and (b) then each pedicle screw was pulled out at a displacement rate of 12.5 cm/min.There was no difference in pullout force between the pedicle screws inserted straight forward and the pedicle screws inserted as end-plate screws. This result applies whether the vertebrae were osteoporotic or nonosteoporotic. For both the straight-forward screws and the end-plate screws, a statistically significant correlation was observed between torque of insertion and pullout force. The results of this experiment indicate that pedicle screws inserted as end-plate screws do not provide a strength advantage over pedicle screws inserted straight forward, whether the vertebrae are osteoporotic or not.

  6. Interfragmentary compression forces of scaphoid screws in a sawbone cylinder model.

    Science.gov (United States)

    Hausmann, J T; Mayr, W; Unger, E; Benesch, T; Vécsei, V; Gäbler, C

    2007-07-01

    Various screws have been developed to stabilise fractures of the scaphoid. Commonly used are the Herbert, the HBS, the 3-mm AO and the Acutrak screws. Not long ago a new screw, the Twin Fix, was introduced. This is cannulated and similar in shape and appearance to the classical Herbert screw. In our test series we compared the maximum achievable compression forces of the Twin Fix screw with that of three other screws (AO, HBS and Acutrak screws). To avoid the variations of density, stiffness and rigidity in natural bone, a polyurethane sawbone-based test setup was used. The test series included 10 screws of each type. The compression force was measured using a special strain gauge. The mean compression force was significantly higher for the Twin Fix screw (8+/-1N) and the Acutrak screw (7.6+/-0.4/0.6N) in relation to the AO screw (6.8+/-1.0/1.4N) and HBS screw (2+/-1N). We found the Twin Fix and Acutrak screws to be promising in the treatment of scaphoid fractures.

  7. 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.

  8. 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.

  9. Numerical and experimental study of an Archimedean Screw Generator

    Science.gov (United States)

    Dellinger, G.; Garambois, P.-A.; Dufresne, M.; Terfous, A.; Vazquez, J.; Ghenaim, A.

    2016-11-01

    Finding new, safe and renewable energy is becoming more and more of a priority with global warming. One solution that is gaining popularity is the Archimedean Screw Generator (ASG). This kind of hydroelectric plant allows transforming potential energy of a fluid into mechanical energy and is convenient for low-head hydraulic sites. As it is a new and growing technology, there are few references dealing with their design and performance optimization. The present contribution proposes to investigate experimentally and numerically the ASG performances. The experimental study is performed for various flow conditions and a laboratory scale screw device installed at the fluid mechanics laboratory of the INSA of Strasbourg. The first results show that the screw efficiencies are higher than 80% for various hydraulic conditions. In order to study the structure of 3D turbulent flows and energy losses in a screw, the 3D Navier Stokes equations are solved with the k-w SST turbulence model. The exact geometry of the laboratory-scale screw was used in these simulations. Interestingly, the modeled values of efficiency are in fairly good agreement with experimental results while any friction coefficient is involved.

  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. Treatment of scaphoid waist fractures with the HCS screw

    Directory of Open Access Journals (Sweden)

    Gehrmann, Sebastian V.

    2014-11-01

    Full Text Available The aim of the study was to evaluate the clinical results of the Headless Compression Screw (HCS, Synthes when used for treatment of acute scaphoid waist fractures. The new screw design generates interfragmentary compression with use of a compression sleeve. Twenty-one patients were treated for acute scaphoid waist fractures type B2 with HCS screws. The average time to the final follow-up examination was 12.8 months. All 21 fractures united after a mean time of 7.2 weeks. The mean DASH score was 7.1. The average motion of the wrist in extension was 61°, flexion was 46°, radial abduction reached 25° and the ulnar abduction was 31°. The maximally achieved grip strength was 86% compared to the uninjured side. Treatment of type B2 scaphoid fractures with the Headless Compression Screw showed good functional and radiographic results. The results are similar to those identified using other screw fixation systems.

  12. Screw dislocations in GaN grown by different methods

    Energy Technology Data Exchange (ETDEWEB)

    Liliental-Weber, Z.; Zakharov, D.; Jasinski, J.; O' Keefe, M.A.; Morkoc, H.

    2003-05-27

    A study of screw dislocations in Hydride-Vapor-Phase-Epitaxy (HVPE) template and Molecular-Beam-Epitaxy (MBE) over-layers was performed using Transmission Electron Microscopy (TEM) in plan-view and in cross-section. It was observed that screw dislocations in the HVPE layers were decorated by small voids arranged along the screw axis. However, no voids were observed along screw dislocations in MBE overlayers. This was true both for MBE samples grown under Ga-lean and Ga-rich conditions. Dislocation core structures have been studied in these samples in the plan-view configuration. These experiments were supported by image simulation using the most recent models. A direct reconstruction of the phase and amplitude of the scattered electron wave from a focal series of high-resolution images was applied. It was shown that the core structures of screw dislocations in the studied materials were filled. The filed dislocation cores in an MBE samples were stoichiometric. However, in HVPE materials, single atomic columns show substantial differences in intensities and might indicate the possibility of higher Ga concentration in the core than in the matrix. A much lower intensity of the atomic column at the tip of the void was observed. This might suggest presence of lighter elements, such as oxygen, responsible for their formation.

  13. Screw theoretic view on dynamics of spatially compliant beam

    Institute of Scientific and Technical Information of China (English)

    Xi-lun DING; J.M.SELIG

    2010-01-01

    Beams with spatial compliance can be deformed as bending in a plane,twisting,and extending.In terms of the screw theory on rigid body motions,the concept of"deflection screw"is introduced,a spatial compliant beam theory via the deflection screw is proposed,and the spatial compliance of such a beam system is presented and analysed based on the material theory and fundamental kinematic assumptions.To study the dynamics of the spatially compliant beam,the potential energy and the kinetic energy of the beam are discussed by using the screw theory to obtain the Lagrangian.The Rayleigh-Ritz method is used to compute the vibrational frequencies based on discussions of boundary conditions and shape functions.The eigenfrequencies of the beam with spatial compliance are compared with those of individual deformation cases,pure bending,extension,or torsion.Finally,dynamics of a robot with two spatial compliant links and perpendicular joints is studied using the spatial compliant beam theory.Coupling between the joint rigid body motions and the deformations of spatial compliant links can easily be found in dynamic simulation.The study shows the effectiveness of using the screw theory to deal with the problems of dynamic modeling and analysis of mechanisms with spatially compliant links.

  14. Interference Decoding for Deterministic Channels

    CERN Document Server

    Bandemer, Bernd

    2010-01-01

    An inner bound to the capacity region of a class of three user pair deterministic interference channels is presented. The key idea is to simultaneously decode the combined interference signal and the intended message at each receiver. It is shown that this interference decoding inner bound is strictly larger than the inner bound obtained by treating interference as noise, which includes interference alignment for deterministic channels. The gain comes from judicious analysis of the number of combined interference sequences in different regimes of input distributions and message rates.

  15. Screw Performance Degradation Assessment Based on Quantum Genetic Algorithm and Dynamic Fuzzy Neural Network

    Directory of Open Access Journals (Sweden)

    Xiaochen Zhang

    2015-01-01

    Full Text Available To evaluate the performance of ball screw, screw performance degradation assessment technology based on quantum genetic algorithm (QGA and dynamic fuzzy neural network (DFNN is studied. The ball screw of the CINCINNATIV5-3000 machining center is treated as the study object. Two Kistler 8704B100M1 accelerometers and a Kistler 8765A250M5 three-way accelerometer are installed to monitor the degradation trend of screw performance. First, screw vibration signal features are extracted both in time domain and frequency domain. Then the feature vectors can be obtained by principal component analysis (PCA. Second, the initialization parameters of the DFNN are optimized by means of QGA. Finally, the feature vectors are inputted to DFNN for training and then get the screw performance degradation model. The experiment results show that the screw performance degradation model could effectively evaluate the performance of NC machine screw.

  16. Transmission of Correlated Messages over Interference Channels with Strong Interference

    Science.gov (United States)

    Choi, Suhan; Yoon, Eunchul; Moon, Hichan

    Transmission of correlated messages over interference channels with strong interference is considered. As a result, an achievable rate region is presented. It is shown that if the messages are correlated, the achievable rate region can be larger than the capacity region given by Costa and El Gamal. As an example, the Gaussian interference channel is considered.

  17. Instantaneous screws of weight-bearing knee: what can the screws tell us about the knee motion.

    Science.gov (United States)

    Wolf, Alon

    2014-07-01

    There are several ways to represent a given object's motion in a 3D space having 6DOF i.e., three translations and three rotations. Some of the methods that are used are mathematical and do not provide any geometrical insight into the nature of the motion. Screw theory is a mathematical, while at the same time, geometrical method in which the 6DOF motion of an object can be represented. We describe the 6DOF motion of a weight-bearing knee by its screw parameters, that are extracted from 3D Optical Reflective motion capture data. The screw parameters which describe the transformation of the shank with respect to the thigh in each two successive frames, is represented as the instantaneous screw axis of the motion given in its Plücker line coordinate, along with its corresponding pitch and intensity values. Moreover, the Striction curve associated with the motion provides geometrical insight into the nature of the motion and its repeatability. We describe the theoretical background and demonstrate what the screw can tell us about the motion of healthy subjects' knee.

  18. Odontoid screw fixation for fresh and remote fractures

    Directory of Open Access Journals (Sweden)

    Rao Ganesh

    2005-01-01

    Full Text Available Fractures of the odontoid process are common, accounting for 10% to 20% of all cervical spine fractures. Odontoid process fractures are classified into three types depending on the location of the fracture line. Various treatment options are available for each of these fracture types and include application of a cervical orthosis, direct anterior screw fixation, and posterior cervical fusion. If a patient requires surgical treatment of an odontoid process fracture, the timing of treatment may affect fusion rates, particularly if direct anterior odontoid screw fixation is selected as the treatment method. For example, type II odontoid fractures treated within the first 6 months of injury with direct anterior odontoid screw fixation have an 88% fusion rate, whereas fractures treated after 18 months have only a 25% fusion rate. In this review, we discuss the etiology, biomechanics, diagnosis, and treatment (including factors affecting fusion such as timing and fracture orientation options available for odontoid process fractures.

  19. [Midcarpal fusion using break-away compression screw].

    Science.gov (United States)

    Maire, N; Facca, S; Gouzou, S; Liverneaux, P

    2012-02-01

    Indication of midcarpal fusion is SNAC or SLAC wrist grade 3. The main complication of circular plate (most common technique) is non-union. In this context, the purpose of our work was to propose the use of break-away compression screws to decrease the rate of non-union. Our series included ten patients. The fusion was fixed using two break-away compression screws (2mm diameter). No bone graft was used. As assessment, subjective (pain, Quick-DASH) and objective (strength, mobility) criteria were reviewed at follow-up. All the criteria were significantly improved after operation except mobility. Among the complications, we noticed one delayed bone-healing with a good outcome and a radiological consolidation. Midcarpal fusion by dorsal approach using break-away compression screws appears to us a technique of interest, not requiring a bone graft, with good cost effectiveness.

  20. Error Analysis of Robotic Assembly System Based on Screw Theory

    Institute of Scientific and Technical Information of China (English)

    韩卫军; 费燕琼; 赵锡芳

    2003-01-01

    Assembly errors have great influence on assembly quality in robotic assembly systems. Error analysis is directed to the propagations and accumula-tions of various errors and their effect on assembly success.Using the screw coordinates, assembly errors are represented as "error twist", the extremely compact expression. According to the law of screw composition, relative position and orientation errors of mating parts are computed and the necessary condition of assembly success is concluded. A new simple method for measuring assembly errors is also proposed based on the transformation law of a screw.Because of the compact representation of error, the model presented for error analysis can be applied to various part- mating types and especially useful for error analysis of complexity assembly.

  1. Optically driven Archimedes micro-screws for micropump application.

    Science.gov (United States)

    Lin, Chih-Lang; Vitrant, Guy; Bouriau, Michel; Casalegno, Roger; Baldeck, Patrice L

    2011-04-25

    Archimedes micro-screws have been fabricated by three-dimensional two-photon polymerization using a Nd:YAG Q-switched microchip laser at 532nm. Due to their small sizes they can be easily manipulated, and made to rotate using low power optical tweezers. Rotation rates up to 40 Hz are obtained with a laser power of 200 mW, i.e. 0.2 Hz/mW. A photo-driven micropump action in a microfluidic channel is demonstrated with a non-optimized flow rate of 6 pL/min. The optofluidic properties of such type of Archimedes micro-screws are quantitatively described by the conservation of momentum that occurs when the laser photons are reflected on the helical micro-screw surface.

  2. Augmentation of Pedicle Screw Fixation with Calcium Phosphate Cement

    Institute of Scientific and Technical Information of China (English)

    YANG Shu-hua; FU De-hao; LI Jin; XU Wei-hua; YANG Cao; YE Zhe-wei; ZUO Xiao-yan

    2004-01-01

    To determine whether a biodegradable calcium phosphate cement(CPC) provides significant augmentation of pedicle screw fixation or not,an in vitro biomechanical study was carried out to evaluate the biomechanical effect of CPC in the restoration and augmentation of pedicle screw fixation.Axial pullout test and cyclic bending resistance test were employed in the experiment,and polymethylmethacrylate (PMMA) was chosen as control.The results demonstrate that the pullout strengths following CPC restoration and augmentation are 74% greater on an average than those of the control group,but less than those of PMMA restoration group and augmentation group respectively (increased by 126% versus control).In cyclic bending resistance test,the CPC augmented screws are found to withstand a greater number of cycles or greater loading with less displacement before loosening,but the augmentation effect of PMMA is greater than that of CPC.

  3. Free-hand thoracic pedicle screws placed by neurosurgery residents: a CT analysis

    OpenAIRE

    Wang, Vincent Y.; Chin, Cynthia T.; Lu, Daniel C.; Smith, Justin S.; Chou, Dean

    2010-01-01

    Free-hand thoracic pedicle screw placement is becoming more prevalent within neurosurgery residency training programs. This technique implements anatomic landmarks and tactile palpation without fluoroscopy or navigation to place thoracic pedicle screws. Because this technique is performed by surgeons in training, we wished to analyze the rate at which these screws were properly placed by residents by retrospectively reviewing the accuracy of resident-placed free-hand thoracic pedicle screws u...

  4. Nanoporous nanocomposite membranes via hybrid twin-screw extrusion-multijet electrospinning.

    Science.gov (United States)

    Senturk-Ozer, Semra; Aktas, Seda; He, Jing; Fisher, Frank T; Kalyon, Dilhan M

    2017-01-13

    Non-woven nanoporous membranes of poly(caprolactone), PCL, incorporated with multi-walled carbon nanotubes, CNTs, could be fabricated via an industrially-scalable hybrid twin screw extrusion and electrospinning process. The utilization of a spinneret with multiple nozzles allowed the increase of the flow rate beyond what is possible with conventional electrospinning using a single nozzle, albeit at the expense of difficulties in the control of the thickness distributions of the nanofibrous membranes. The thickness and orientation distributions and the resulting mechanical properties of the membranes could be modified via changes in voltage, angular velocity of the collector mandrel and separation distance of the collector from the spinneret. The increases in crystallinity due to the presence of the CNTs and the preferential alignment of the nanofibers via rotation of the collecting mandrel led to increases in the tensile properties of the nanoporous membranes. The use of poly(ethylene oxide), PEO, together with PCL, followed by the dissolution of the PEO, rendered the nanofibers themselves nanoporous with typical surface porosity values of around 50% and pore sizes of about 220 nm. The demonstrated versatility of the hybrid twin screw extrusion and electrospinning process and the manipulation of mesh dimensions and properties are indicative of the applicability of the hybrid process for fabrication of nanoporous membranes for myriad diverse industrial applications ranging from water treatment to tissue engineering applications.

  5. Nanoporous nanocomposite membranes via hybrid twin-screw extrusion—multijet electrospinning

    Science.gov (United States)

    Senturk-Ozer, Semra; Aktas, Seda; He, Jing; Fisher, Frank T.; Kalyon, Dilhan M.

    2017-01-01

    Non-woven nanoporous membranes of poly(caprolactone), PCL, incorporated with multi-walled carbon nanotubes, CNTs, could be fabricated via an industrially-scalable hybrid twin screw extrusion and electrospinning process. The utilization of a spinneret with multiple nozzles allowed the increase of the flow rate beyond what is possible with conventional electrospinning using a single nozzle, albeit at the expense of difficulties in the control of the thickness distributions of the nanofibrous membranes. The thickness and orientation distributions and the resulting mechanical properties of the membranes could be modified via changes in voltage, angular velocity of the collector mandrel and separation distance of the collector from the spinneret. The increases in crystallinity due to the presence of the CNTs and the preferential alignment of the nanofibers via rotation of the collecting mandrel led to increases in the tensile properties of the nanoporous membranes. The use of poly(ethylene oxide), PEO, together with PCL, followed by the dissolution of the PEO, rendered the nanofibers themselves nanoporous with typical surface porosity values of around 50% and pore sizes of about 220 nm. The demonstrated versatility of the hybrid twin screw extrusion and electrospinning process and the manipulation of mesh dimensions and properties are indicative of the applicability of the hybrid process for fabrication of nanoporous membranes for myriad diverse industrial applications ranging from water treatment to tissue engineering applications.

  6. Posterior atlantoaxial transpedicle screw fixation for traumatic atlatoaxial instability

    Directory of Open Access Journals (Sweden)

    Zheng-lei WANG

    2015-10-01

    Full Text Available Objective To explore the clinical efficacy of posterior atlantoaxial pedicle screw fixation for traumatic atlantoaxial instability. Methods From September 2009 to March 2013, 17 patients with atlantoaxial instability received posterior atlantoaxial pedicle screw fixation. There were 12 males and 5 females, with a mean age of 42 years old (ranged from 19 to 63 years old. Transpedicle screw fixation was employed in 8 patients with atlantoaxial fracture and dislocation, in 2 with traumatic disruption of transverse atlantal ligament, and in 7 with odontoid fracture. The Japanese Orthopaedic Association (JOA score before operation was from 5 to 14, with a mean of 11.2. Preoperative CT, MRI and radiographs, as well as intraoperative screw placement and bone graft were administered in all the patients. Results In all the patients, complete reduction was achieved without injury to the vertebral artery, spinal cord or never root, and they started to be ambulatory on the first day after the operation. The patients were followed up for 6-36 months (mean 21 months, and clinical symptoms were seen to be improved significantly. Imaging reexamination 6 months after the surgery showed satisfactory healing of implanted bone and position of all the screws without loosening of the implant. The mean JOA scores was 15.5(11.0-17.0 twelve months after the operation. Conclusion Atlantoaxial pedicle screw fixation for traumatic atlantoaxial instability is safe and reliable with a favorable clinical result. DOI: 10.11855/j.issn.0577-7402.2015.09.14

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

    Science.gov (United States)

    2016-01-01

    Objectives The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems. Materials and Methods 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%. Results 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 < 0.05). Conclusions Geometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended. PMID:27847752

  8. Virtual estimates of fastening strength for pedicle screw implantation procedures

    Science.gov (United States)

    Linte, Cristian A.; Camp, Jon J.; Augustine, Kurt E.; Huddleston, Paul M.; Robb, Richard A.; Holmes, David R.

    2014-03-01

    Traditional 2D images provide limited use for accurate planning of spine interventions, mainly due to the complex 3D anatomy of the spine and close proximity of nerve bundles and vascular structures that must be avoided during the procedure. Our previously developed clinician-friendly platform for spine surgery planning takes advantage of 3D pre-operative images, to enable oblique reformatting and 3D rendering of individual or multiple vertebrae, interactive templating, and placement of virtual pedicle implants. Here we extend the capabilities of the planning platform and demonstrate how the virtual templating approach not only assists with the selection of the optimal implant size and trajectory, but can also be augmented to provide surrogate estimates of the fastening strength of the implanted pedicle screws based on implant dimension and bone mineral density of the displaced bone substrate. According to the failure theories, each screw withstands a maximum holding power that is directly proportional to the screw diameter (D), the length of the in-bone segm,ent of the screw (L), and the density (i.e., bone mineral density) of the pedicle body. In this application, voxel intensity is used as a surrogate measure of the bone mineral density (BMD) of the pedicle body segment displaced by the screw. We conducted an initial assessment of the developed platform using retrospective pre- and post-operative clinical 3D CT data from four patients who underwent spine surgery, consisting of a total of 26 pedicle screws implanted in the lumbar spine. The Fastening Strength of the planned implants was directly assessed by estimating the intensity - area product across the pedicle volume displaced by the virtually implanted screw. For post-operative assessment, each vertebra was registered to its homologous counterpart in the pre-operative image using an intensity-based rigid registration followed by manual adjustment. Following registration, the Fastening Strength was computed

  9. 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.

  10. Posterior cervical spine arthrodesis with laminar screws: a report of two cases

    Directory of Open Access Journals (Sweden)

    Sugimoto,Yoshihisa

    2007-04-01

    Full Text Available 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.

  11. 46 CFR 154.524 - Piping joints: Welded and screwed couplings.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 5 2010-10-01 2010-10-01 false Piping joints: Welded and screwed couplings. 154.524... Equipment Cargo and Process Piping Systems § 154.524 Piping joints: Welded and screwed couplings. Pipe... warmer. (d) Screwed couplings are allowed for instrumentation and control piping that meets §...

  12. Holographic interference filters

    Science.gov (United States)

    Diehl, Damon W.

    Holographic mirrors have wavelength-selection properties and thus qualify as a class of interference filters. Two theoretical methods for analyzing such structures are developed. The first method uses Hill's matrix method to yield closed-forms solutions in terms of the Floquet-Bloch waves within a periodic structure. A process is developed for implementing this solution method on a computer, using sparse-matrix memory allocation, numerical root-finding algorithms, and inverse-iteration techniques. It is demonstrated that Hill's matrix method is valid for the analysis of finite and multi-periodic problems. The second method of theoretical analysis is a transfer-matrix technique, which is herein termed thin-film decomposition. It is shown that the two methods of solution yield results that differ by, at worst, a fraction of a percent. Using both calculation techniques, a number of example problems are explored. Of key importance is the construction of a set of curves that are useful for the design and characterization of holographic interference filters. In addition to the theoretical development, methods are presented for the fabrication of holographic interference filters using DuPont HRF-800X001 photopolymer. Central to the exposure system is a frequency-stabilized, tunable dye laser. The types of filters fabricated include single-tone reflection filters, two types of multitone reflection filters, and reflection filters for infrared wavelengths. These filters feature index profiles that are not easily attainable through other fabrication methods. As a supplement to the body of the dissertation, the computer algorithms developed to implement Hill's matrix method and thin-film decomposition are also included as an appendix. Further appendices provide more information on Floquet's theorem and Hill's matrix method. A final appendix presents a design for an infrared laser spectrophotometer.

  13. RNA interference in Lepidoptera

    DEFF Research Database (Denmark)

    Terenius, Ole; Papanicolaou, Alexie; Garbutt, Jennie S.

    2011-01-01

    Gene silencing through RNA interference (RNAi) has revolutionized the study of gene function, particularly in non-model insects. However, in Lepidoptera (moths and butterflies) RNAi has many times proven to be difficult to achieve. Most of the negative results have been anecdotal and the positive...... is particularly successful in the family Saturniidae and in genes involved in immunity. On the contrary, gene expression in epidermal tissues seems to be most difficult to silence. In addition, gene silencing by feeding dsRNA requires high concentrations for success. Possible causes for the variability of success...

  14. Role of rod diameter in comparison between only screws versus hooks and screws in posterior instrumentation of thoracic curve in idiopathic scoliosis.

    Science.gov (United States)

    Lamartina, Claudio; Petruzzi, Maria; Macchia, Marcello; Stradiotti, Paola; Zerbi, Alberto

    2011-05-01

    Since the introduction of Cotrel-Dubousset instrumentation in 1984, the correction techniques in scoliosis surgery have changed from Harrington principles of concave distraction to segmental realignment to a variety of possibilities including the rod rotation manoeuvres, and to segmental approximation via cantilever methods. Additionally, pedicle screw utilization in lumbar curves enhanced correction and stabilization of various deformities, and various studies have strongly supported the clinical advantages of lumbar pedicle screws versus conventional hook instrumentation. Pedicle screw constructs have become increasingly popular in the treatment of patients with spinal deformity. When applied to adolescent idiopathic scoliosis patients, pedicle screw fixation has demonstrated increased corrective ability compared with traditional hook/hybrid instrumentation. In our study, we do a retrospective review of idiopathic scoliosis patients (King 2-Lenke 1 B/C) treated with a selective thoracic posterior fusion using an all-screw construct versus a hybrid (pedicle screws and hooks) construct and, compare the percentage of correction of the scoliotic curves obtained with screws alone and screws and hooks. Special attention was given to the rod diameter and correction technique. Our results show that the percentage of correction of idiopathic thoracic scoliosis is similar when treating the scoliosis with rods and screws alone or with rods, screws and hooks; therefore, we and the majority of authors in the literature do not consider the rod section. This can be an important parameter in the evaluation of the superiority of treatment with screws only or screws and hooks. In our study, even if not of statistical significance, the better thoracic curve correction obtained with the hybrid group should be ascribed to the fact that in this group mostly 6 mm rods were used.

  15. Partial Interference Alignment for K-user MIMO Interference Channels

    CERN Document Server

    Huang, Huang

    2011-01-01

    In this paper, we consider a Partial Interference Alignment and Interference Detection (PIAID) design for $K$-user quasi-static MIMO interference channels with discrete constellation inputs. Each transmitter has M antennas and transmits L independent data streams to the desired receiver with N receive antennas. We focus on the case where not all K-1 interfering transmitters can be aligned at every receiver. As a result, there will be residual interference at each receiver that cannot be aligned. Each receiver detects and cancels the residual interference based on the constellation map. However, there is a window of unfavorable interference profile at the receiver for Interference Detection (ID). In this paper, we propose a low complexity Partial Interference Alignment scheme in which we dynamically select the user set for IA so as to create a favorable interference profile for ID at each receiver. We first derive the average symbol error rate (SER) by taking into account of the non-Guassian residual interfere...

  16. STRUCTURE SYNTHESIS OF 4-DOF PARALLEL ROBOT MECHANISMS BASED ON SCREW THEORY

    Institute of Scientific and Technical Information of China (English)

    Fang Hairong; Fang Yuefa; Guo Sheng

    2004-01-01

    Structural synthesis for 4-DOF parallel manipulators using screw theory is systematically studied. Motion properties and constraint conditions of 4-DOF parallel manipulators according to the relationship between screw and reciprocal screw are analyzed. Mathematical expressions for constraint screws and twist screws of moving platform are constructed, and all possible limbs, which provide one or more force constraints, are enumerated. Finally, a parallel manipulator with 3-rotation-DOF and 1-translation-DOF is used as an example to describe the synthesis procedure for symmetrical and non-symmetrical 4-DOF parallel manipulators.

  17. Use of computational fluid dynamics simulations for design of a pretreatment screw conveyor reactor.

    Science.gov (United States)

    Berson, R Eric; Hanley, Thomas R

    2005-01-01

    Computational fluid dynamics simulations were employed to compare performance of various designs of a pretreatment screw conveyor reactor. The reactor consisted of a vertical screw used to create cross flow between the upward conveying solids and the downward flow of acid. Simulations were performed with the original screw design and a modified design in which the upper flights of the screw were removed. Results of the simulations show visually that the modified design provided favorable plug flow behavior within the reactor. Pressure drop across the length of the reactor without the upper screws in place was predicted by the simulations to be 5 vs 40 kPa for the original design.

  18. Effects of lag screw design and lubrication on sliding in trochanteric nails.

    Science.gov (United States)

    Kummer, Frederick J

    2010-01-01

    This study compared the sliding characteristics of three lag screw designs used with trochanteric nails and determined the effects of lubrication on sliding. They were tested by an established method to measure initiation and ease of lag screw sliding. These tests were then repeated with calf serum lubrication. There were significant differences (p Lubrication did not affect either parameter. Lag screw design aspects, such as diameter and, particularly, surface finish, affect sliding. Due to the small contact area between the lag screw and nail creating high interface stresses, lubrication had no effect on lag screw sliding.

  19. 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.

  20. 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.

  1. Kinematics Analysis Based on Screw Theory of a Humanoid Robot

    Institute of Scientific and Technical Information of China (English)

    MAN Cui-hua; FAN Xun; LI Cheng-rong; ZHAO Zhong-hui

    2007-01-01

    A humanoid robot is a complex dynamic system for its idiosyncrasy. This paper aims to provide a mathematical and theoretical foundation for the design of the configuration, kinematics analysis of a novel humanoid robot. It has a simplified configuration and design for entertainment purpose. The design methods, principle and mechanism are discussed. According to the design goals of this research, there are ten degrees of freedom in the two bionic arms.Modularization, concurrent design and extension theory methods were adopted in the configuration study and screw theory was introduced into the analysis of humanoid robot kinematics. Comparisons with other methods show that: 1) only two coordinates need to be established in the kinematics analysis of humanoid robot based on screw theory; 2) the spatial manipulator Jacobian obtained by using twist and exponential product formula is succinct and legible; 3) adopting screw theory to resolve the humanoid robot arms kinematics question can avoid singularities; 4) using screw theory can solve the question of specification insufficiency.

  2. [Posterior atlantoaxial fixation using vertex multiaxial screw system].

    Science.gov (United States)

    Zhong, Dejun; Song, Yueming

    2007-06-01

    This study aims to assess the effectiveness and advantages of Vertex multiaxial screw system in use for stabilizing the atlanto-axial junction. The entry point of the atlas was located 18-20 mm lateral to the midline and 2.0 mm superior to the inferior border of posterior arch, and the direction of screw was chosen to be about 10 degrees medial to the sagittal plane and about 5 degrees cephalad to the transverse plane. In odontoid vertebra (C2), the direction of the drill bit was guided directly by the medial and superior aspect of the individual C2 pedicle. All screws were placed properly without incidence of nerve or blood vessel injury, and no complication appeared in operation and after surgery. All cases were followed up for an average of 9 months, all cases achieved well reposition and fixation of atlantoaxial joint, average JOA grade was 9.6 before preoperation and 15.9 after operation. Fixation of the atlantoaxial complex using Vertex multiaxial screw system seemed to be a reliable technique and should be considered a good alternative in atlantoaxial fusion. The technique could be used in young patiens.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gallardo-Alvarado, J [Department of Mechanical Engineering, Instituto Tecnologico de Celaya (Mexico)

    2005-11-15

    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.

  4. Optimisation of acoustic silencer for the screw compressor system

    NARCIS (Netherlands)

    Swamy, M.; Lier, L.J. van; Smeulers, J.P.M.

    2014-01-01

    In one of the screw compressor system, designed silencer was not optimal. A great challenge was the large variation in operating conditions, especially the variation of the molecular weight of the gas. There was need to optimize the silencer. This paper describes the acoustic modelling tools to opti

  5. Granulation of increasingly hydrophobic formulations using a twin screw granulator.

    Science.gov (United States)

    Yu, Shen; Reynolds, Gavin K; Huang, Zhenyu; de Matas, Marcel; Salman, Agba D

    2014-11-20

    The application of twin screw granulation in the pharmaceutical industry has generated increasing interest due to its suitability for continuous processing. However, an understanding of the impact of formulation properties such as hydrophobicity on intermediate and finished product quality has not yet been established. Hence, the current work investigated the granulation behaviour of three formulations containing increasing amounts of hydrophobic components using a Consigma™-1 twin screw granulator. Process conditions including powder feed rate, liquid to solid ratio, granulation liquid composition and screw configuration were also evaluated. The size of the wet granules was measured in order to enable exploration of granulation behaviour in isolation without confounding effects from downstream processes such as drying. The experimental observations indicated that the granulation process was not sensitive to the powder feed rate. The hydrophobicity led to heterogeneous liquid distribution and hence a relatively large proportion of un-wetted particles. Increasing numbers of kneading elements led to high shear and prolonged residence time, which acted to enhance the distribution of liquid and feeding materials. The bimodal size distributions considered to be characteristic of twin screw granulation were primarily ascribed to the breakage of relatively large granules by the kneading elements.

  6. Are inclined screw blades for vertical grain augers advantageous?

    NARCIS (Netherlands)

    Rademacher, F.J.C.

    1978-01-01

    Due to modern technology, screw blades are often manufactured by rolling them out of one single strip of steel. When simultaneously some blade inclination is applied, less residual stresses and/or larger possible ratios between outer and shaft diameter are claimed by some manufacturers, which seems

  7. 21 CFR 888.3070 - Pedicle screw spinal system.

    Science.gov (United States)

    2010-04-01

    ... treatment of the following acute and chronic instabilities or deformities of the thoracic, lumbar, and... conditions are significant mechanical instability or deformity of the thoracic, lumbar, and sacral spine... screw spinal system because this is a technically demanding procedure presenting a risk of...

  8. 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 before an ac

  9. Coupled Thermodynamic Behavior of New Screw Compressors Rotors Profile

    Directory of Open Access Journals (Sweden)

    Arístides Rivera Torres

    2010-05-01

    Full Text Available The article displays an evaluation of the thermodynamic behavior of screw compressor rotors with new profiles, obtained with the help of the Scorpath 2000 software. This allows predicting precisely the operation of the compressor, as well as its thermodynamic evaluation, under equal conditions, with the work of other compressors fitted with rotor profiles of other kinds.

  10. 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.

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

    Science.gov (United States)

    Alvis-Miranda, Hernando Raphael; Farid-Escorcia, Hector; Alcalá-Cerra, Gabriel; Castellar-Leones, Sandra Milena; Moscote-Salazar, Luis Rafael

    2014-01-01

    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. PMID:25336831

  12. Ankle fusion using a 2-incision, 3-screw technique

    NARCIS (Netherlands)

    R.P.M. Hendrickx; G.M.M.J. Kerkhoffs; S.A.S. Stufkens; C.N. van Dijk; R.K. Marti

    2011-01-01

    Reliable fusion and optimal correction of the alignment of the ankle joint using a 2-incision, 3-screw technique. Symptomatic osteoarthritis of the ankle joint after insufficient other treatment, severe deformity of the osteoarthritic ankle joint, or salvation procedure after failed arthroplasty. Ac

  13. Atomistic simulations of jog migration on extended screw dislocations

    DEFF Research Database (Denmark)

    Vegge, T.; Leffers, T.; Pedersen, O.B.;

    2001-01-01

    We have performed large-scale atomistic simulations of the migration of elementary jogs on dissociated screw dislocations in Cu. The local crystalline configurations, transition paths. effective masses. and migration barriers for the jogs are determined using an interatomic potential based on the...

  14. Design of a magnetic lead screw for wave energy conversion

    DEFF Research Database (Denmark)

    Holm, Rasmus Koldborg; Berg, Nick Ilsoe; Walkusch, Morten

    2013-01-01

    This paper deals with the development of a magnetic lead screw (MLS) for wave energy conversion. Initially, a brief state of the art regarding linear permanent-magnet generators and MLSs is given, leading to an introduction of the MLS and a presentation of the results from a finite-element analysis...

  15. The general theory of blade screws including propellers, fans, helicopter screws, helicoidal pumps, turbo-motors, and different kinds of helicoidal blades

    Science.gov (United States)

    De Bothezat, George

    1920-01-01

    Report presents a theory which gives a complete picture and an exact quantitative analysis of the whole phenomenon of the working of blade screws, but also unites in a continuous whole the entire scale of states of work conceivable for a blade screw. Chapter 1 is devoted to the establishment of the system of fundamental equations relating to the blade screw. Chapter 2 contains the general discussion of the 16 states of work which may establish themselves for a blade screw. The existence of the vortex ring state and the whirling phenomenon are established. All the fundamental functions which enter the blade-screw theory are submitted to a general analytical discussion. The general outline of the curve of the specific function is examined. Two limited cases of the work of the screw, the screw with a zero constructive pitch and the screw with an infinite constructive pitch, are pointed out. Chapter 3 is devoted to the study of the propulsive screw or propeller. (author)

  16. 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.

  17. 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.

  18. Evaluation of different screw fixation techniques and screw diameters in sagittal split ramus osteotomy: finite element analysis method.

    Science.gov (United States)

    Sindel, A; Demiralp, S; Colok, G

    2014-09-01

    Sagittal split ramus osteotomy (SSRO) is used for correction of numerous congenital or acquired deformities in facial region. Several techniques have been developed and used to maintain fixation and stabilisation following SSRO application. In this study, the effects of the insertion formations of the bicortical different sized screws to the stresses generated by forces were studied. Three-dimensional finite elements analysis (FEA) and static linear analysis methods were used to investigate difference which would occur in terms of forces effecting onto the screws and transmitted to bone between different application areas. No significant difference was found between 1·5- and 2-mm screws used in SSRO fixation. Besides, it was found that 'inverted L' application was more successful compared to the others and that was followed by 'L' and 'linear' formations which showed close rates to each other. Few studies have investigated the effect of thickness and application areas of bicortical screws. This study was performed on both advanced and regressed jaws positions.

  19. Subaxial cervical pedicle screw insertion with newly defined entry point and trajectory: accuracy evaluation in cadavers.

    Science.gov (United States)

    Zheng, Xiujun; Chaudhari, Rahul; Wu, Chunhui; Mehbod, Amir A; Transfeldt, Ensor E

    2010-01-01

    Successful placement of cervical pedicle screws requires accurate identification of both entry point and trajectory. However, literature has not provided consistent recommendations regarding the direction of pedicle screw insertion and entry point location. The objective of this study was to define a guideline regarding the optimal entry point and trajectory in placing subaxial cervical pedicle screws and to evaluate the screw accuracy in cadaver cervical spines. The guideline for entry point and trajectory for each vertebra was established based on the recently published morphometric data. Six fresh frozen cervical spines (C3-C7) were used. There were two men and four women. After posterior exposure, the entry point was determined and the cortical bone of the entry point was removed using a 2-mm burr. Pilot holes were created with a cervical probe based on the guideline using fluoroscopy. After tapping, 3.5-mm screws with appropriate length were inserted. After screw insertion, every vertebra was dissected and inspected for pedicle breach. The pedicle width, height, pedicle transverse angulation and actual screw insertion angle were measured. A total of 60 pedicle screws were inserted. No statistical difference in pedicle width and height was found between the left and right sides for each level. The overall accuracy of pedicle screws was 83.3%. The remaining 13.3% screws had noncritical breach, and 3.3% had critical breach. The critical breach was not caused by the guideline. There was no statistical difference between the pedicle transverse angulation and the actual screw trajectory created using the guideline. There was statistical difference in pedicle width between the breach and non-breach screws. In conclusion, high success rate of subaxial cervical pedicle screw placement can be achieved using the recently proposed operative guideline and oblique views of fluoroscopy. However, careful preoperative planning and good surgical skills are still required to

  20. Biomechanical Evaluation of Plate Versus Lag Screw Only Fixation of Distal Fibula Fractures.

    Science.gov (United States)

    Misaghi, Amirhossein; Doan, Josh; Bastrom, Tracey; Pennock, Andrew T

    2015-01-01

    Traditional fixation of unstable Orthopaedic Trauma Association type B/C ankle fractures consists of a lag screw and a lateral or posterolateral neutralization plate. Several studies have demonstrated the clinical success of lag screw only fixation; however, to date no biomechanical comparison of the different constructs has been performed. The purpose of the present study was to evaluate the biomechanical strength of these different constructs. Osteotomies were created in 40 Sawbones(®) distal fibulas and reduced using 1 bicortical 3.5-mm stainless steel lag screw, 2 bicortical 3.5-mm lag screws, 3 bicortical 3.5-mm lag screws, or a single 3.5-mm lag screw coupled with a stainless steel neutralization plate with 3 proximal cortical and 3 distal cancellous screws. The constructs were tested to determine the stiffness in lateral bending and rotation and failure torque. No significant differences in lateral bending or rotational stiffness were detected between the osteotomies fixed with 3 lag screws and a plate. Constructs fixed with 1 lag screw were weaker for both lateral bending and rotational stiffness. Osteotomies fixed with 2 lag screws were weaker in lateral bending only. No significant differences were found in the failure torque. Compared with lag screw only fixation, plate fixation requires larger incisions and increased costs and is more likely to require follow-up surgery. Despite the published clinical success of treating simple Orthopaedic Trauma Association B/C fractures with lag screw only fixation, many surgeons still have concerns about stability. For noncomminuted, long oblique distal fibula fractures, lag screw only fixation techniques offer construct stiffness similar to that of traditional plate and lag screw fixation.

  1. Accuracy of robot-assisted pedicle screw placement for adolescent idiopathic scoliosis in the pediatric population.

    Science.gov (United States)

    Macke, Jeremy J; Woo, Raymund; Varich, Laura

    2016-06-01

    This is a retrospective review of pedicle screw placement in adolescent idiopathic scoliosis (AIS) patients under 18 years of age who underwent robot-assisted corrective surgery. Our primary objective was to characterize the accuracy of pedicle screw placement with evaluation by computed tomography (CT) after robot-assisted surgery in AIS patients. Screw malposition is the most frequent complication of pedicle screw placement and is more frequent in AIS. Given the potential for serious complications, the need for improved accuracy of screw placement has spurred multiple innovations including robot-assisted guidance devices. No studies to date have evaluated this robot-assisted technique using CT exclusively within the AIS population. Fifty patients were included in the study. All operative procedures were performed at a single institution by a single pediatric orthopedic surgeon. We evaluated the grade of screw breach, the direction of screw breach, and the positioning of the patient for preoperative scan (supine versus prone). Of 662 screws evaluated, 48 screws (7.2 %) demonstrated a breach of greater than 2 mm. With preoperative prone position CT scanning, only 2.4 % of screws were found to have this degree of breach. Medial malposition was found in 3 % of screws, a rate which decreased to 0 % with preoperative prone position scanning. Based on our results, we conclude that the proper use of image-guided robot-assisted surgery can improve the accuracy and safety of thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis. This is the first study to evaluate the accuracy of pedicle screw placement using CT assessment in robot-assisted surgical correction of patients with AIS. In our study, the robot-assisted screw misplacement rate was lower than similarly constructed studies evaluating conventional (non-robot-assisted) procedures. If patients are preoperatively scanned in the prone position, the misplacement rate is further

  2. Graphene quantum interference photodetector

    Directory of Open Access Journals (Sweden)

    Mahbub Alam

    2015-03-01

    Full Text Available In this work, a graphene quantum interference (QI photodetector was simulated in two regimes of operation. The structure consists of a graphene nanoribbon, Mach–Zehnder interferometer (MZI, which exhibits a strongly resonant transmission of electrons of specific energies. In the first regime of operation (that of a linear photodetector, low intensity light couples two resonant energy levels, resulting in scattering and differential transmission of current with an external quantum efficiency of up to 5.2%. In the second regime of operation, full current switching is caused by the phase decoherence of the current due to a strong photon flux in one or both of the interferometer arms in the same MZI structure. Graphene QI photodetectors have several distinct advantages: they are of very small size, they do not require p- and n-doped regions, and they exhibit a high external quantum efficiency.

  3. Sensing via optical interference

    Directory of Open Access Journals (Sweden)

    Ryan C. Bailey

    2005-04-01

    Full Text Available Chemical and biological sensing are problems of tremendous contemporary technological importance in multiple regulatory and human health contexts, including environmental monitoring, water quality assurance, workplace air quality assessment, food quality control, many aspects of biodiagnostics, and, of course, homeland security. Frequently, what is needed, or at least wanted, are sensors that are simultaneously cheap, fast, reliable, selective, sensitive, robust, and easy to use. Unfortunately, these are often conflicting requirements. Over the past few years, however, a number of promising ideas based on optical interference effects have emerged. Each is based to some extent on advances in the design and fabrication of functional materials. Generally, the advances are of two kinds: chemo- and bio-selective recognition and binding, and efficient methods for micropatterning or microstructuring.

  4. Graphene quantum interference photodetector.

    Science.gov (United States)

    Alam, Mahbub; Voss, Paul L

    2015-01-01

    In this work, a graphene quantum interference (QI) photodetector was simulated in two regimes of operation. The structure consists of a graphene nanoribbon, Mach-Zehnder interferometer (MZI), which exhibits a strongly resonant transmission of electrons of specific energies. In the first regime of operation (that of a linear photodetector), low intensity light couples two resonant energy levels, resulting in scattering and differential transmission of current with an external quantum efficiency of up to 5.2%. In the second regime of operation, full current switching is caused by the phase decoherence of the current due to a strong photon flux in one or both of the interferometer arms in the same MZI structure. Graphene QI photodetectors have several distinct advantages: they are of very small size, they do not require p- and n-doped regions, and they exhibit a high external quantum efficiency.

  5. Quantum Interference in Graphene Nanoconstrictions.

    Science.gov (United States)

    Gehring, Pascal; Sadeghi, Hatef; Sangtarash, Sara; Lau, Chit Siong; Liu, Junjie; Ardavan, Arzhang; Warner, Jamie H; Lambert, Colin J; Briggs, G Andrew D; Mol, Jan A

    2016-07-13

    We report quantum interference effects in the electrical conductance of chemical vapor deposited graphene nanoconstrictions fabricated using feedback controlled electroburning. The observed multimode Fabry-Pérot interferences can be attributed to reflections at potential steps inside the channel. Sharp antiresonance features with a Fano line shape are observed. Theoretical modeling reveals that these Fano resonances are due to localized states inside the constriction, which couple to the delocalized states that also give rise to the Fabry-Pérot interference patterns. This study provides new insight into the interplay between two fundamental forms of quantum interference in graphene nanoconstrictions.

  6. 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

  7. Cytotoxicity of a new antimicrobial coating for surgical screws: an in vivo study

    Science.gov (United States)

    Güzel, Yunus; Elmadag, Mehmet; Uzer, Gokcer; Yıldız, Fatih; Bilsel, Kerem; Tuncay, İbrahim

    2017-01-01

    INTRODUCTION The risk of surgery-related infection is a persistent problem in orthopaedics and infections involving implants are particularly difficult to treat. This study explored the responses of bone and soft tissue to antimicrobial-coated screws. We investigated whether such screws, which have never been used to fix bony tissues, would result in a cytotoxic effect. We hypothesised that the coated screws would not be toxic to the bone and that the likelihood of infection would be reduced since bacteria are not able to grow on these screws. METHODS Titanium screws were inserted into the left supracondylar femoral regions of 16 rabbits. The screws were either uncoated (control group, n = 8) or coated with a polyvinylpyrrolidone-polyurethane interpolymer with tertiary amine functional groups (experimental group, n = 8). At Week 6, histological samples were obtained and examined. The presence of necrosis, fibrosis and inflammation in the bony tissue and the tissue surrounding the screws was recorded. RESULTS Live, cellular bone marrow was present in all the rabbits from the experimental group, but was replaced with connective tissue in four rabbits from the control group. Eight rabbits from the control group and two rabbits from the experimental group had necrosis in fatty bone marrow. Inflammation was observed in one rabbit from the experimental group and five rabbits from the control group. CONCLUSION Titanium surgical screws coated with polyvinylpyrrolidone-polyurethane interpolymer were associated with less necrosis than standard uncoated screws. The coated screws were also not associated with any cytotoxic side effect. PMID:26805670

  8. PROSPECTS OF USE OF RELATIVE SCREW AND COMBINED REELS FOR MIXING BULKS

    Directory of Open Access Journals (Sweden)

    Marchenko A. Y.

    2015-11-01

    Full Text Available The article reveals a possibility of using equipment based on relative screw and combined drums for mixing of bulks. Change of relative positioning of flat elements of sidewalls of internal surfaces in relative screw drums allows operating the difficult and spatial movement of streams of bulks. In relative screw drums we have developed effective processes of mixing and sets of the equipment, which are characterized by that fact the difficult and spatial screw movement taking place in relative screw drums is dismembered on rather simple, in the kinematic relation, in the movements. The difficult and spatial screw movement with a big amplitude of 15-1000 mm and more, in the offered equipment constructions on the basis of relative screw or combined drums, is reported to bulks by elements of the relative screw or combined drums of various parameters and configurations which becomes complicated also screw lines on perimeter of a relative screw drum with various number of calling and the directions from each other or rounds of the springs fixed in the relative combined drums

  9. 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.

  10. Interference in ballistic motor learning - is motor interference really sensory?

    DEFF Research Database (Denmark)

    Lundbye-Jensen, Jesper; Petersen, Tue Hvass; Rothwell, John C

    Skill gained after a short period of practice in one motor task can be abolished if a second task is learned shortly afterwards. We hypothesised that interference requires the same circuits to be engaged in the two tasks and provoke competing processes of synaptic plasticity. To test this, subjects...... not require learning. Repeated transcranial magnetic stimulation (rTMS) of corticospinal motor output at intensities below ankle movement threshold did not cause interference, whereas suprathreshold rTMS did. Furthermore, electrical stimulation of the peripheral nerve to the plantarflexors (but not extensors......) caused interference. We conclude that interference is remarkably specific for circuits involved in a specific movement direction / activation of individual muscles and depends crucially on sensory error signals. One possible mechanism of interference may be disruption of early motor memory consolidation....

  11. Scattering and interference in epitaxial graphene.

    Science.gov (United States)

    Rutter, G M; Crain, J N; Guisinger, N P; Li, T; First, P N; Stroscio, J A

    2007-07-13

    A single sheet of carbon, graphene, exhibits unexpected electronic properties that arise from quantum state symmetries, which restrict the scattering of its charge carriers. Understanding the role of defects in the transport properties of graphene is central to realizing future electronics based on carbon. Scanning tunneling spectroscopy was used to measure quasiparticle interference patterns in epitaxial graphene grown on SiC(0001). Energy-resolved maps of the local density of states reveal modulations on two different length scales, reflecting both intravalley and intervalley scattering. Although such scattering in graphene can be suppressed because of the symmetries of the Dirac quasiparticles, we show that, when its source is atomic-scale lattice defects, wave functions of different symmetries can mix.

  12. Modeling the Parker instability in a rotating plasma screw pinch

    CERN Document Server

    Khalzov, I V; Katz, N; Forest, C B; 10.1063/1.3684240

    2012-01-01

    We analytically and numerically study the analogue of the Parker (magnetic buoyancy) instability in a uniformly rotating plasma screw pinch confined in a cylinder. Uniform plasma rotation is imposed to create a centrifugal acceleration, which mimics the gravity required for the classical Parker instability. The goal of this study is to determine how the Parker instability could be unambiguously identified in a weakly magnetized, rapidly rotating screw pinch, in which the rotation provides an effective gravity and a radially varying azimuthal field is controlled to give conditions for which the plasma is magnetically buoyant to inward motion. We show that an axial magnetic field is also required to circumvent conventional current driven magnetohydrodynamic (MHD) instabilities such as the sausage and kink modes that would obscure the Parker instability. These conditions can be realized in the Madison Plasma Couette Experiment (MPCX). Simulations are performed using the extended MHD code NIMROD for an isothermal...

  13. 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.

  14. Analysis of Eyring-Powell fluid in helical screw rheometer.

    Science.gov (United States)

    Siddiqui, A M; Haroon, T; Zeb, M

    2014-01-01

    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.

  15. HA/UHMWPE Nanocomposite Produced by Twin-screw Extrusion

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The HA/UHMWPE nanocomposite is compounded by twin-screw extrusion of the HA and UHMWPE powder mixture in paraffin oil and then compression molded to a sheet form. TGA measurement shows the HA weight loss after processing is about 1%-2% . FTIR spectra indicate the paraffin oil residue is trivial and UHMWPE is not oxidized. SEM reveals the HA nano particles are homogeneously dispersed by twin- screw extrusion and the inter-particle spaces are penetrated with UHMWPE fibrils by swelling treatment. HRTEM image indicates the HA particles and UHMWPE are intimately contacted by mechanical interlocking. Compared with the unfilled UHMWPE, stiffness of the composite with the HA volume fraction 0.23 was significantly enhanced to 9 times without detriment of the yield strength and the ductility.

  16. 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.

  17. Accuracy of spinal navigation for Magerl-screws

    CERN Document Server

    Herz, T

    2001-01-01

    Study design: assessment of the accuracy of frameless stereotactic navigation at the second cervical vertebra. Objectives: to assess the influence of the protocol of preoperative CT-scan and the registration technique on the accuracy of navigation for implanting Magerl-screws. Summary of background data: the use of navigation systems for implanting Magerl-screws could help to decrease the risk of complications and to reduce the required skin incision. Two parameters conceivably affecting the accuracy are the protocol of the preoperative CT-scan and the registration technique. Methods: four cervical spine segments of human cadavers were scanned with two different protocols (3 mm slice thickness/2 mm table increment, 1 mm slice thickness/1 mm table increment). Registration was performed either based on anatomical landmarks or using a specially designed percutaneous registration device. For the accuracy-check, the pointer tip was exactly placed on markers. The distance between the pointer and the marker displaye...

  18. Femoral and Tibial Tunnel Diameter and Bioabsorbable Screw Findings After Double-Bundle ACL Reconstruction in 5-Year Clinical and MRI Follow-up

    Science.gov (United States)

    Kiekara, Tommi; Paakkala, Antti; Suomalainen, Piia; Huhtala, Heini; Järvelä, Timo

    2017-01-01

    Background: Tunnel enlargement is frequently seen in short-term follow-up after anterior cruciate ligament reconstruction (ACLR). According to new evidence, tunnel enlargement may be followed by tunnel narrowing, but the long-term evolution of the tunnels is currently unknown. Hypothesis/Purpose: The hypothesis was that tunnel enlargement is followed by tunnel narrowing caused by ossification as seen in follow-up using magnetic resonance imaging (MRI). The purpose of this study was to evaluate the ossification pattern of the tunnels, the communication of the 2 femoral and 2 tibial tunnels, and screw absorption findings in MRI. Study Design: Case series; Level of evidence, 4. Methods: Thirty-one patients underwent anatomic double-bundle ACLR with hamstring grafts and bioabsorbable interference screw fixation and were followed with MRI and clinical evaluation at 2 and 5 years postoperatively. Results: The mean tunnel enlargement at 2 years was 58% and reduced to 46% at 5 years. Tunnel ossification resulted in evenly narrowed tunnels in 44%, in conical tunnels in 48%, and fully ossified tunnels in 8%. Tunnel communication increased from 13% to 23% in the femur and from 19% to 23% in the tibia between 2 and 5 years and was not associated with knee laxity. At 5 years, 54% of the screws were not visible, with 35% of the screws replaced by a cyst and 19% fully ossified. Tunnel cysts were not associated with worse patient-reported outcomes or knee laxity. Patients with a tibial anteromedial tunnel cyst had higher Lysholm scores than patients without a cyst (93 and 84, P = .03). Conclusion: Tunnel enlargement was followed by tunnel narrowing in 5-year follow-up after double-bundle ACLR. Tunnel communication and tunnel cysts were frequent MRI findings and not associated with adverse clinical evaluation results. PMID:28203605

  19. Output Interference in Recognition Memory

    Science.gov (United States)

    Criss, Amy H.; Malmberg, Kenneth J.; Shiffrin, Richard M.

    2011-01-01

    Dennis and Humphreys (2001) proposed that interference in recognition memory arises solely from the prior contexts of the test word: Interference does not arise from memory traces of other words (from events prior to the study list or on the study list, and regardless of similarity to the test item). We evaluate this model using output…

  20. Sleep can reduce proactive interference.

    Science.gov (United States)

    Abel, Magdalena; Bäuml, Karl-Heinz T

    2014-01-01

    Sleep has repeatedly been connected to processes of memory consolidation. While extensive research indeed documents beneficial effects of sleep on memory, little is yet known about the role of sleep for interference effects in episodic memory. Although two prior studies reported sleep to reduce retroactive interference, no sleep effect has previously been found for proactive interference. Here we applied a study format differing from that employed by the prior studies to induce a high degree of proactive interference, and asked participants to encode a single list or two interfering lists of paired associates via pure study cycles. Testing occurred after 12 hours of diurnal wakefulness or nocturnal sleep. Consistent with the prior work, we found sleep in comparison to wake did not affect memory for the single list, but reduced retroactive interference. In addition we found sleep reduced proactive interference, and reduced retroactive and proactive interference to the same extent. The finding is consistent with the view that arising benefits of sleep are caused by the reactivation of memory contents during sleep, which has been suggested to strengthen and stabilise memories. Such stabilisation may make memories less susceptible to competition from interfering memories at test and thus reduce interference effects.

  1. Twin screw two-phase expanders in large chiller units

    Energy Technology Data Exchange (ETDEWEB)

    Smith, I.K.; Stosic, N.; Aldis, C.A.; Kovacevic, A. [City Univ., Dept. of Mechanical Engineering and Aeronautics, London (United Kingdom)

    1999-07-01

    An investigation was carried out to determine the feasibility of the use of a twin screw expander as a throttle valve replacement in a 500 ton chiller. The aim was to produce a demonstration unit with an overall machine adiabatic efficiency of not less that 70%. The efficiency target was effectively met but further analytical work is needed to predict mass flow rates reliably and hence the exact machine size required when refrigerant enters the expander as subcooled liquid. (Author)

  2. The human sacrum and safe approaches for screw placement.

    Science.gov (United States)

    Arman, Candan; Naderi, Sait; Kiray, Amaç; Aksu, Funda Taştekin; Yilmaz, Hakan Sinan; Tetik, Süleyman; Korman, Esin

    2009-08-01

    The human sacrum is the target of lumbosacral instrumentation and decompression procedures. Such surgical interventions require detailed knowledge of the anatomy of the human sacrum. The aim of this study was to measure surgically relevant parameters. Several factors, including the one-piece composition of the sacrum, the angles of the sacral pedicles and the anteroposterior diameter of the sacral vertebral bodies distinguish the sacrum from other parts of spine. Thirty-two measurements of shape, angles and distances between parts were taken of the sacra of 100 adult West Anatolian people using a Vernier caliper accurate to 0.1 mm and goniometer. According to this morphometric study, when measured from the sagittal, the S1 facet angle was measured as 35.71 degrees +/-9.59 and 34.70 degrees +/-9.66, the sacral pedicle anteromedial screw trajectory angle was 35.65 degrees +/-4.73 and 31.95 degrees +/-3.95 and the anterolaterally oriented sacral wing screw trajectory angle was 32.65 degrees +/-3.51 and 29.10 degrees +/-3.14, on the right and left sides, respectively. The distance of the midline oriented S1 pedicle screw was 51.12 mm and 51.26 mm on the right and left side, respectively. The distance for sacral wing oriented screw placement was 50.13 mm and 50.46 mm on the right and left side, respectively. The anteroposterior and transverse diameter of the sacral spinal canal were 21.81 mm and 31.31 mm, respectively. Thus, this study describes anatomical specifications of the sacrum. These defined morphometric details should be taken into consideration during surgical procedures. This study also describes anatomical landmarks which will allow injury of the sacrum during surgery to be avoided.

  3. The RNA interference revolution

    Directory of Open Access Journals (Sweden)

    G. Lenz

    2005-12-01

    Full Text Available The discovery of double-stranded RNA-mediated gene silencing has rapidly led to its use as a method of choice for blocking a gene, and has turned it into one of the most discussed topics in cell biology. Although still in its infancy, the field of RNA interference has already produced a vast array of results, mainly in Caenorhabditis elegans, but recently also in mammalian systems. Micro-RNAs are short hairpins of RNA capable of blocking translation, which are transcribed from genomic DNA and are implicated in several aspects from development to cell signaling. The present review discusses the main methods used for gene silencing in cell culture and animal models, including the selection of target sequences, delivery methods and strategies for a successful silencing. Expected developments are briefly discussed, ranging from reverse genetics to therapeutics. Thus, the development of the new paradigm of RNA-mediated gene silencing has produced two important advances: knowledge of a basic cellular mechanism present in the majority of eukaryotic cells and access to a potent and specific new method for gene silencing.

  4. Fluid Flow Phenomenon in a Three-Bladed Power-Generating Archimedes Screw Turbine

    Directory of Open Access Journals (Sweden)

    Tineke Saroinsong

    2016-05-01

    Full Text Available Experimental studies of the Archimedes screw turbine are applied as a micro hydro power plant for low head focused on the fluid flow. Fluid flow on a screw turbine is not completely filled water flow there is still a free surface between the water fluid and atmospheric air. Except the screw geometry, the turbine screw free surface allows the flow phenomena that are important in the process of turbine screw power generation. The Archimedes screw turbine main driving force is the fluid-gravity weight, which is affected by the inflow depth, inflow velocity and the turbine shaft’s slope. The dimensionless parameter Froude number (Fr is connected to analyze the screw turbine efficiency. The purpose of this study is to figure out the fluid flow role when power generated by a three blades Archimedes screw turbine observed visualized, and also observed the turbine rotation and torque. The observed parameters are varied in inflow depth as the characteristic length (y of Froude Number, inflow velocity (co, and the turbine shaft slope (α. The screw turbine model, were made under a laboratory scale and made from acrylic material. The geometric form is the three bladed screws which have seven screw respectively, the number of helix turns is 21, the angle of screw blade is 30°, radius ratio of 0.54 with a pitch distance of 2,4 Ro. The result from this study revealed a phenomenon of fluid flow between the screw blades a whirlpool wave occurs or vortex due to the linear momentum in a form of the hydrostatic force against the blade screw which occurs in two opposite directions and the effect of the turbine shaft angular momentum. The vortex would affect the screw turbine power generation process as most of the kinetic energy that goes into the screw turbine sucked into the vortex between the screw blades, but this phenomenon can be reduced by reducing the turbine shaft slope. The highest turbine efficiency of 89% occurred in the turbine shaft’s slope of 25

  5. Communications in interference limited networks

    CERN Document Server

    2016-01-01

    This book offers means to handle interference as a central problem of operating wireless networks. It investigates centralized and decentralized methods to avoid and handle interference as well as approaches that resolve interference constructively. The latter type of approach tries to solve the joint detection and estimation problem of several data streams that share a common medium. In fact, an exciting insight into the operation of networks is that it may be beneficial, in terms of an overall throughput, to actively create and manage interference. Thus, when handled properly, "mixing" of data in networks becomes a useful tool of operation rather than the nuisance as which it has been treated traditionally. With the development of mobile, robust, ubiquitous, reliable and instantaneous communication being a driving and enabling factor of an information centric economy, the understanding, mitigation and exploitation of interference in networks must be seen as a centrally important task.

  6. Coating of carbon fiber-reinforced polyetheretherketone implants with titanium to improve bone apposition.

    Science.gov (United States)

    Devine, Declan M; Hahn, Joachim; Richards, R Geoffery; Gruner, Heiko; Wieling, Ronald; Pearce, Simon G

    2013-05-01

    Carbon fiber-reinforced polyetheretherketone (CF/PEEK) is a thermoplastic composite biomaterial exhibiting properties suitable for load-bearing orthopedic implants. However, the hydrophobic surface of CF/PEEK implants induces the deposition of a peri-implant fibrous tissue capsule preventing bone apposition. However, if bone apposition was improved, the use of CF/PEEK in orthopedics could be increased as it has many advantages compared with metallic implants. In this study, CF/PEEK screws were coated with titanium (Ti) using two different techniques, namely vacuum plasma spraying (VPS) and physical vapor deposition (PVD) with uncoated screws as controls. These coatings were characterized and implanted in a loaded sheep tibia model. In the characterization of the screw surfaces using microscopy techniques, the uncoated screws were seen to have an irregular surface. The PVD coating appeared smooth and consistent, whereas the VPS coating appeared to be a rough coating with some inhomogeneities, which did not cover the entire surface area. Nevertheless, in the ex vivo analysis the VPS-coated screws had a screw removal torque which was statistically greater than uncoated and PVD-coated screws (p ≤ 0.002 for both comparisons). Additionally, the VPS-coated screws had a statistically higher bone contact area than the uncoated screws (p = 0.006), whereas no statistical difference was detected between VPS and PVD coating types (p = 0.11). Thereby illustrating that Ti coating of CF/PEEK screws significantly improve bone apposition and removal torque compared with uncoated CF/PEEK screws.

  7. 重载滚珠丝杠副可靠性设计与试验方法研究%Research on the Reliability Design and Test Method for the Heavy Load Ball Screw

    Institute of Scientific and Technical Information of China (English)

    沈嘉禾; 陶卫军; 冯虎田; 屠国俊

    2013-01-01

    To meet the reliability requirements of heavy load ball screw, its main failure modes are analyzed and a reliability design method of heavy load ball screw is proposed based on stressstrength interference and truncated distribution theory. Combined with the developed running test bench, the reliability test method of is designed. The test results show that the proposed reliability design and test methods are reasonable and effective for heavy load ball screw and are also suitable for the product development and reliability inspection of heavy load ball screw.%从满足重载滚珠丝杠副可靠性要求出发,对其主要失效模式进行了分析,提出了一种基于应力——强度干涉模型和截尾分布理论的重载滚珠丝杠副可靠性设计方法;结合所开发的跑合试验台设计了重载滚珠丝杠副可靠性试验方法.试验结果表明,所提出的重载滚珠丝杠副可靠性设计与试验方法正确有效,适用于重载滚珠丝杠副新产品开发与可靠性检验.

  8. A new scale-up approach for dispersive mixing in twin-screw compounding

    Science.gov (United States)

    Fukuda, Graeme; Bigio, David I.; Andersen, Paul; Wetzel, Mark

    2015-05-01

    Scale-up rules in polymer processing are critical in ensuring consistency in product quality and properties when transitioning from low volume laboratory mixing processes to high volume industrial compounding. The scale-up approach investigated in this study evaluates the processes with respect to dispersive mixing. Demand of polymer composites with solid additives, such as carbon microfibers and nanotubes, has become increasingly popular. Dispersive mixing breaks down particles that agglomerate, which is paramount in processing composites because solid additives tend to collect and clump. The amount of stress imparted on the material governs the degree of dispersive mixing. A methodology has been developed to characterize the Residence Stress Distribution (RSD) within a twin-screw extruder in real time through the use of polymeric stress beads. Through this technique, certain mixing scale-up rules can be analyzed. The following research investigated two different scale-up rules. The industry standard for mixing scale-up takes the ratio of outer diameters cubed to convert the volumetric flow rate from the smaller process to a flow rate appropriate in the larger machine. This procedure then resolves both operating conditions since shear rate remains constant. The second rule studied is based on percent drag flow, or the fraction of pumping potential, for different elements along the screw configuration. The percent drag flow rule aims to bring greater focus to operating conditions when scaling-up with respect to dispersive mixing. Through the use of the RSD methodology and a Design of Experiment (DOE) approach, rigorous statistical analysis was used to determine the validity between the scale-up rules of argument.

  9. INVESTIGATION ON KANE DYNAMIC EQUATIONS BASED ON SCREW THEORY FOR OPENCHAIN MANIPULATORS

    Institute of Scientific and Technical Information of China (English)

    LIU Wu-fa; GONG Zhen-bang; WANG Qin-que

    2005-01-01

    First, screw theory, product of exponential formulas and Jacobian matrix are introduced. Then definitions are given about active force wrench, inertial force wrench, partial velocity twist, generalized active force, and generalized inertial force according to screw theory. After that Kane dynamic equations based on screw theory for open-chain manipulators have been derived. Later on how to compute the partial velocity twist by geometrical method is illustrated. Finally the correctness of conclusions is verified by example.

  10. 3D CFD analysis of an oil injected twin screw expander

    OpenAIRE

    Papeš, Iva; Degroote, Joris; Vierendeels, Jan

    2014-01-01

    Small scale Organic Rankine Cycle (ORC) systems have a big potential for waste heat recovery in the market. Due to the smaller volume flows inside these systems, non-conventional expansion technologies such as screw expanders become more interesting. Recent economic studies have shown the important role of screw machines in such cycles. However, in order to get a better understanding of the expansion behaviour in an ORC, appropriate simulation models of screw expanders are necessary. The flow...

  11. Screw in the aorta: minimally invasive graft replacement for chronic aortic erosion by spinal instrument.

    Science.gov (United States)

    Fukuda, Wakako; Aoki, Chikashi; Daitoku, Kazuyuki; Taniguchi, Satoshi; Fukuda, Ikuo

    2013-01-01

    Intra-and early post-operative aortic injury by pedicle screw is not a rare complication in orthopedic surgery, but aortic penetration by a screw head over a long time period is considered as an uncommon case. There are various surgical management options for thoracic aortic injury caused by malpositioned spinal instruments. We report a case of a patient who underwent minimally invasive graft replacement of the descending thoracic artery for pedicle screw penetration.

  12. Accuracy and complications of transpedicular C2 screw placement without the use of spinal navigation.

    Science.gov (United States)

    Mueller, Christian-Andreas; Roesseler, Lukas; Podlogar, Martin; Kovacs, Attlila; Kristof, Rudolf Andreas

    2010-05-01

    The objective of the study was to describe the technique, accuracy of placement and complications of transpedicular C2 screw fixation without spinal navigation. Patients treated by C2 pedicle screw fixations were identified from the surgical log book of the department. Clinical data were extracted retrospectively from the patients' charts. Pedicle screw placement accuracy was assessed on postoperative CT scans according to Gertzbein and Robbins (GRGr). A total of 27 patients were included in the study. The mean age of the patients was 56 +/- 22.0 years; 51.9% of them were female. As much as 17 patients suffered from trauma, 5 of degenerative disease, 3 of inflammations and 2 of metastatic disease. A total of 47 C2 transpedicular screw fixations were performed. The canulated screws were inserted under visual control following the preparation of the superior surface of the isthmus and of the medial surface of the pedicles of the C2. Intraoperative fluoroscopy was additionally used. The postoperative CT findings showed in 55.3% GRGr 1, in 27.7% GRGr 2, in 10.6% GRGr 3, and in 6.3% GRGr 4 pedicle screw insertion accuracy. Screw insertions GRGr 5 were not observed. Screw malpositioning (i.e., GRGr 3 and 4) was significantly associated with thin (C2 fractures. In the three patients with screw insertions GRGr 4, postoperative angiographies were performed to exclude vertebral artery affections. In one of these three cases, the screw caused a clinically asymptomatic vertebral artery compression. Hardware failures did not occur. In one patient, postoperative pneumonia resulted in the death of the patient. Careful patient selection and surgical technique is necessary to avoid vertebral artery injury in C2 pedicle screw fixation without spinal navigation. A slight opening of the vertebral artery canal (Gertzbein and Robbins grade C2 pedicle screw insertions.

  13. Accuracy and safety of pedicle screw placement in neuromuscular scoliosis with free-hand technique.

    Science.gov (United States)

    Modi, Hitesh N; Suh, Seung Woo; Fernandez, Harry; Yang, Jae Hyuk; Song, Hae-Ryong

    2008-12-01

    It is a retrospective analytic study of 1,009 transpedicular screws (689 thoracic and 320 lumbosacral), inserted with free-hand technique in neuromuscular scoliosis using postoperative CT scan. The aim of paper was to determine the accuracy and safety of transpedicular screw placement with free-hand technique in neuromuscular scoliosis and to compare the accuracy at different levels in such population. All studies regarding accuracy and safety of pedicle screw in scoliosis represent idiopathic scoliosis using various techniques such as free-hand, navigation, image intensifier, etc., for screw insertion. Anatomies of vertebrae and pedicle are distorted in scoliosis, hence accurate and safe placement of pedicle screw is prerequisite for surgery. Between 2004 and 2006, 37 consecutive patients, average age 20 years (9-44 years), of neuromuscular scoliosis were operated with posterior pedicle screw fixation using free-hand technique. Accuracy of pedicle screws was studied on postoperative CT scan. Placement up to 2 mm medial side and 4 mm lateral side was considered within-safe zone. Of the 1,009 screws, 273 screws were displaced medially, laterally or on the anterior side showing that 73% screws (68% in thoracic and 82.5% in lumbar spine) were accurately placed within pedicle. Considering the safe zone, 93.3% (942/1009, 92.4% in thoracic and 95.3% in lumbar spine) of the screws were within the safe zone. Comparing accuracy according to severity of curve, accuracy was 75% in group 1 (curve 90 degrees) with a safety of 94.8 and 91.2%, respectively (P = 0.35). Comparing the accuracy at different thoracic levels, it showed 67, 64 and 72% accuracy in upper, middle and lower thoracic levels with safety of 96.6, 89.2 and 93.1%, respectively, exhibiting no statistical significant difference (P = 0.17). Pedicle screw placement in neuromuscular scoliosis with free-hand technique is accurate and safe as other conditions.

  14. Twin screw wet granulation: the study of a continuous twin screw granulator using Positron Emission Particle Tracking (PEPT) technique.

    Science.gov (United States)

    Lee, Kai T; Ingram, Andy; Rowson, Neil A

    2012-08-01

    In this paper, Positron Emission Particle Tracking (PEPT) techniques are utilised to track the trajectory of single particles through the mixing and conveying zones of a Twin Screw Granulator (TSG). A TSG consisting of conveying zones and mixing zones is used in this study. The mixing zones are arranged with kneading discs at an angle of 30°, 60° or 90°. Experiments were carried out using different mixing configurations with various screw speed and total mass flow rate. The PEPT data obtained were then utilised to obtain the residence time distribution (RTD) and the Peclet number in an attempt to gain some insight into the mixing of the process. The fill level of the granulator was also estimated to study the mechanism of granulation. As might be expected, it was shown that the residence time of the granulation process increases with decreasing screw speed. It also increases with increasing angle of the arrangement of kneading blocks in the mixing zones, but will decreases when powder feed rate is increased. The fill level of the mixing zone in particular increases when the screw speed decreases or when powder feed rate increases. Furthermore, the fill level of the granulator will increase when the mixing zone configuration changes from 30° to 90°. It is shown that the granulator is never fully filled, even using 90° mixer elements implying limited compaction which may explain why the granules produced are porous compared with those from a high shear mixer. Interestingly, the RTD analysis reveals that the extent of axial mixing in the mixing zone of the granulator does not change significantly for different configurations and process conditions. There is evidence of a tail in the RTD which implies some material hold up and channelling.

  15. 螺旋输送机螺旋体优化设计%Optimization Design of Screw in Screw Conveyor

    Institute of Scientific and Technical Information of China (English)

    王铁流; 郭晓梅; 陈仙明

    2012-01-01

    The process of finite element analysis and optimization design of screw for screw conveyor with the Pro/Engineer is discussed, the main steps and methods are also introduced. Subject to the requirements of the structural parameters and design objectives, the optimal design is realized efficiently and rapidly. A practical method is improved for the design quality of screw.%应用Pro/Engineer软件,研究了螺旋输送机螺旋体的有限元分析和优化设计方法和过程,介绍了设计过程的主要步骤和方法.在满足结构参数和设计目标要求的前提下,快捷、有效地实现了优化设计,提高了设计质量,为螺旋体的设计提供了一种有效的方法.

  16. Design of Formed Milling Cutter for Double-Helix Screw Based on Noninstantaneous Envelope Method

    Directory of Open Access Journals (Sweden)

    Yun Li

    2013-01-01

    Full Text Available The design theory and method of formed milling cutter for double-helix screw of progressing cavity pump are presented. Through analyzing the shape and characteristic parameters of double-helix screw, the helicoids equation and axial curve equation of double-helix screw were established. According to the relative position relations between formed milling cutter and double-helix screw in the machining process, the geometric mapping relationship of screw coordinate system and formed milling cutter coordinate system was established by using the coordinate transformation theory. Based on noninstantaneous envelope method and the meshing conditions between formed milling cutter and double-helix screw, the contact line equations were established by minimum value method. By analyzing the machining errors caused by resharpening the formed milling cutter, the tooth back curve equation was established based on spiral of Archimedes, and the profile equation of formed milling cutter with constant back angle was got. On this basis, the formed milling cutter of processing double-helix screw was designed, and the cutter head and tool post were manufactured, respectively. The measuring results have shown that this method can satisfy the requirements of machining accuracy for double-helix screw. So this is an effective method to get formed milling cutter profile for double-helix screw.

  17. Innovative approach in the development of computer assisted algorithm for spine pedicle screw placement.

    Science.gov (United States)

    Solitro, Giovanni F; Amirouche, Farid

    2016-04-01

    Pedicle screws are typically used for fusion, percutaneous fixation, and means of gripping a spinal segment. The screws act as a rigid and stable anchor points to bridge and connect with a rod as part of a construct. The foundation of the fusion is directly related to the placement of these screws. Malposition of pedicle screws causes intraoperative complications such as pedicle fractures and dural lesions and is a contributing factor to fusion failure. Computer assisted spine surgery (CASS) and patient-specific drill templates were developed to reduce this failure rate, but the trajectory of the screws remains a decision driven by anatomical landmarks often not easily defined. Current data shows the need of a robust and reliable technique that prevents screw misplacement. Furthermore, there is a need to enhance screw insertion guides to overcome the distortion of anatomical landmarks, which is viewed as a limiting factor by current techniques. The objective of this study is to develop a method and mathematical lemmas that are fundamental to the development of computer algorithms for pedicle screw placement. Using the proposed methodology, we show how we can generate automated optimal safe screw insertion trajectories based on the identification of a set of intrinsic parameters. The results, obtained from the validation of the proposed method on two full thoracic segments, are similar to previous morphological studies. The simplicity of the method, being pedicle arch based, is applicable to vertebrae where landmarks are either not well defined, altered or distorted.

  18. Interference in motor learning - is motor interference sensory?

    DEFF Research Database (Denmark)

    Jensen, Jesper Lundbye; Petersen, Tue Hvass; Rothwell, John C

    Skill gained after a short period of practice in one motor task can be abolished if a second task is learned shortly afterwards, but not all motor activities cause interference. After all it is not necessary to remain completely still after practicing a task for learning to occur. Here we ask which...... mechanisms determine whether or not interference occurs. We hypothesised that interference requires the same neural circuits to be engaged in the two tasks and provoke competing processes of synaptic plasticity. To test this, subjects learned a ballistic ankle plantarflexion task. Early motor memory...... learning of the primary task, no interference was observed. Previous studies have suggested that primary motor cortex (M1) may be involved in early motor memory consolidation. 1Hz Repetitive Transcranial Magnetic Stimulation (rTMS) of corticospinal motor output at intensities below ankle movement threshold...

  19. Carbon Fiber Biocompatibility for Implants

    OpenAIRE

    Richard Petersen

    2016-01-01

    Carbon fibers have multiple potential advantages in developing high-strength biomaterials with a density close to bone for better stress transfer and electrical properties that enhance tissue formation. As a breakthrough example in biomaterials, a 1.5 mm diameter bisphenol-epoxy/carbon-fiber-reinforced composite rod was compared for two weeks in a rat tibia model with a similar 1.5 mm diameter titanium-6-4 alloy screw manufactured to retain bone implants. Results showed that carbon-fiber-rein...

  20. Optical interference with digital holograms

    Science.gov (United States)

    Gossman, David; Perez-Garcia, Benjamin; Hernandez-Aranda, Raul I.; Forbes, Andrew

    2016-07-01

    In 1804, Thomas Young reported the observation of fringes in the intensity of light, and attributed it to the concept of interference between coherent sources. In this paper, we revisit this famous experiment and show how it can easily be demonstrated with digital holography. We look closely at the concept of interference with light and ask, "fringes in what?" We then show that depending on how light interferes, fringe patterns in observables other than intensity can be seen. We explain this conceptually and demonstrate it experimentally. We provide a holistic approach to the topic, aided by modern laboratory practices for a straightforward demonstration of the underlying physics.

  1. C2 laminar screw and C1-2 transarticular screw combined with C1 laminar hooks for atlantoaxial instability with unilateral vertebral artery injury.

    Science.gov (United States)

    Guo, Qunfeng; Liu, Jun; Ni, Bin; Lu, Xuhua; Zhou, Fengjin

    2011-09-01

    Transarticular screw fixation (TASF) is technically demanding, with high risk of vertebral artery (VA) injury. How to manage intraoperative VA injury and choose optimal alternative fixation becomes a concern of spinal surgeons. In this study, the management strategy for a patient with suspected intraoperative VA injury was analyzed. A 53-year-old woman developed type II odontoid fracture and brain stem injury due to a motor vehicle accident 3 months earlier. After conservative treatments, the brain stem injury improved, but with residual ocular motility defect in the right eye. The odontoid fracture did not achieve fusion with displacement and absorption of fracture fragments. After admission, atlantoaxial fixation using bilateral C1-2 transarticular screws (TASs) combined with C1 laminar hooks was planed. The first TAS was inserted successfully. Unfortunately, suspected VA injury developed during tapping the tract for the second TAS. Considering the previous brain stem injury and that directly inserting the screw to tamponade the hemorrhage might cause VA stenosis or occlusion, we blocked the screw trajectory with bone wax. C2 laminar screw was implanted instead of intended TAS on the injured side. The management strategy for suspected VA injury should depend on intraoperative circumstances and be tailored to patients. Blocking screw trajectory with bone wax is a useful method to stop bleeding. Atlantoaxial fixation using C2 laminar screw and C1-2 TAS combined with C1 laminar hooks is an ideal alternative procedure.

  2. Multipolar interference effects in nanophotonics

    CERN Document Server

    Liu, Wei

    2016-01-01

    Scattering of electromagnetic waves by an arbitrary nanoscale object can be characterized by a multipole decomposition of the electromagnetic field that allows to describe the scattering intensity and radiation pattern through interferences of dominating excited multipole modes. In modern nanophotonics, both generation and interference of multipole modes start to play an indispensable role, and they enable nanoscale manipulation of light with many related applications. Here we review the multipolar interference effects in metallic, metal-dielectric, and dielectric nanostructures, and suggest a comprehensive view on many phenomena involving the interferences of electric, magnetic and toroidal multipoles, which drive a number of recently discussed effects in nanophotonics such as unidirectional scattering, effective optical antiferromagnetism, generalized Kerker scattering with controlled angular patterns, generalized Brewster angle, and nonradiating optical anapoles. We further discuss other types of possible ...

  3. Interference of Quantum Market Strategies

    CERN Document Server

    Piotrowski, E W; Syska, J

    2003-01-01

    Recent development in quantum computation and quantum information theory allows to extend the scope of game theory for the quantum world. The paper is devoted to the analysis of interference of quantum strategies in quantum market games.

  4. Interference Phenomena in Quantum Information

    CERN Document Server

    Stefanak, Martin

    2010-01-01

    One of the key features of quantum mechanics is the interference of probability amplitudes. The reason for the appearance of interference is mathematically very simple. It is the linear structure of the Hilbert space which is used for the description of quantum systems. In terms of physics we usually talk about the superposition principle valid for individual and composed quantum objects. So, while the source of interference is understandable it leads in fact to many counter-intuitive physical phenomena which puzzle physicists for almost hundred years. The present thesis studies interference in two seemingly disjoint fields of physics. However, both have strong links to quantum information processing and hence are related. In the first part we study the intriguing properties of quantum walks. In the second part we analyze a sophisticated application of wave packet dynamics in atoms and molecules for factorization of integers. The main body of the thesis is based on the original contributions listed separately...

  5. Interference, reduced action, and trajectories

    OpenAIRE

    2006-01-01

    Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichroma...

  6. Biomechanical impact of C2 pedicle screw length in an atlantoaxial fusion construct

    Directory of Open Access Journals (Sweden)

    Risheng Xu

    2014-01-01

    Full Text Available Background: Posterior, atlantoaxial (AA fusions of the cervical spine may include either standard (26 mm or short (16 mm C2 pedicle screws. This manuscript focused on an in vitro biomechanical comparison of standard versus short C2 pedicle screws to perform posterior C1-C2 AA fusions. Methods: Twelve human cadaveric spines underwent C1 lateral mass screw and standard C2 pedicle screw (n = 6 versus short C2 pedicle screw (n = 6 fixation. Six additional controls were not instrumented. The peak torque, peak rotational interval, and peak stiffness of the constructs were analyzed to failure levels. Results: The peak torque to construct failure was not statistically significantly different among the control spine (12.2 Nm, short pedicle fixation (15.5 Nm, or the standard pedicle fixation (11.6 Nm, P = 0.79. While the angle at the peak rotation statistically significantly differed between the control specimens (47.7° of relative motion and the overall instrumented specimens (P < 0.001, the 20.7° of relative rotation in the short C2 pedicle screw specimens was not statistically significantly higher than the 13.7° of relative rotation in the standard C2 pedicle screw specimens (P = 0.39. Similarly, although the average stiffness was statistically significantly lower in control group (0.026 Nm/degree versus the overall instrumented specimens (P = 0.001, the standard C2 pedicle screws (2.54 Nm/degree did not differ from the short C2 pedicle screws (1.69 Nm/degree (P = 0.30. Conclusions: Both standard and short C2 pedicle screws allow for equally rigid fixation of C1 lateral mass-C2 AA fusions. Usage of a short C2 pedicle screw may be an acceptable method of stabilization in carefully selected patient populations.

  7. Anatomic Study of Anterior Transdiscal Axial Screw Fixation for Subaxial Cervical Spine Injuries.

    Science.gov (United States)

    Ji, Wei; Zheng, Minghui; Qu, Dongbin; Zou, Lin; Chen, Yongquan; Chen, Jianting; Zhu, Qingan

    2016-08-01

    Anterior transdiscal axial screw (ATAS) fixation is an alternative or supplement to the plate and screw constructs for the upper cervical spine injury. However, no existing literatures clarified the anatomic feasibility of this technique for subaxial cervical spine. Therefore, the objective of this study was to evaluate the anatomical feasibility and to establish guidelines for the use of the ATAS fixation for the subaxial cervical spine injury.Fifty normal cervical spines had radiographs to determine the proposed screw trajectory (the screw length and insertion angle) and the interbody graft-related parameters (the disc height and depth, and the distance between anterior vertebral margin and the screw) for all levels of the subaxial cervical spine. Following screw insertion in 8 preserved human cadaver specimens, surgical simulation and dissection verified the feasibility and safety of the ATAS fixation.Radiographic measurements showed the mean axial screw length and cephalic incline angle of all levels were 41.2 mm and 25.2°, respectively. The suitable depth of the interbody graft was >11.7 mm (the distance between anterior vertebral margin and the screw), but C2-C3, C3-C4, C4-C5, and C5-C6 levels, but impossible at C6-C7 due to the obstacle of the sternum. All screws were placed accurately. None of the screws penetrated into the spinal canal and caused fractures determined by dissecting the specimens.The anterior transdiscal axial screw fixation, as an alternative or supplementary instrumentation for subaxial cervical spine injuries, is feasible and safe with meticulous surgical planning.

  8. Multipolar interference effects in nanophotonics.

    Science.gov (United States)

    Liu, Wei; Kivshar, Yuri S

    2017-03-28

    Scattering of electromagnetic waves by an arbitrary nanoscale object can be characterized by a multipole decomposition of the electromagnetic field that allows one to describe the scattering intensity and radiation pattern through interferences of dominating multipole modes excited. In modern nanophotonics, both generation and interference of multipole modes start to play an indispensable role, and they enable nanoscale manipulation of light with many related applications. Here, we review the multipolar interference effects in metallic, metal-dielectric and dielectric nanostructures, and suggest a comprehensive view on many phenomena involving the interferences of electric, magnetic and toroidal multipoles, which drive a number of recently discussed effects in nanophotonics such as unidirectional scattering, effective optical antiferromagnetism, generalized Kerker scattering with controlled angular patterns, generalized Brewster angle, and non-radiating optical anapoles. We further discuss other types of possible multipolar interference effects not yet exploited in the literature and envisage the prospect of achieving more flexible and advanced nanoscale control of light relying on the concepts of multipolar interference through full phase and amplitude engineering.This article is part of the themed issue 'New horizons for nanophotonics'.

  9. Morphological character of cervical spine for anterior transpedicular screw fixation

    Directory of Open Access Journals (Sweden)

    Rong-Ping Zhou

    2013-01-01

    Full Text Available Background: Anterior cervical interbody grafts/cages combined with a plate were frequently used in multilevel discectomies/corpectomies. In order to avoid additional posterior stabilization in patients who undergo anterior reconstructive surgery, an anterior cervical transpedicular screw fixation, which offers higher stability is desirable. We investigated in this study the anatomical (morphologic characters for cervical anterior transpedicular screw fixation. Materials and Methods: Left pedicle parameters were measured on computed tomography (CT images based on 36 cervical spine CT scans from healthy subjects. The parameters included outer pedicle width (Distance from lateral to medial pedicle surface in the coronal plane, outer pedicle height (OPH (Distance from upper to lower pedicle surface in the sagittal plane, maximal pedicle axis length (MPAL, distance transverse insertion point (DIP, distance of the insertion point to the upper end plate (DIUP, pedicle sagittal transverse angle (PSTA and pedicle transverse angle (PTA at C3 to C7. Results: The values of outer pedicle width and MPAL in males were larger than in females from C3 to C7. The OPH in males was larger than in females at C3 to C6, but there was no difference at C7. The DIP and PTA were significantly greater in males than in females at C3, but there was no difference in the angle at C4-7. The PSTA was not statistically different between genders at C3, 4, 7, but this value in males was larger than females at C5, 6. The DIUP was significantly greater in males at C3, 4, 6, 7 but was non significant at C5. Conclusions: The placement of cervical anterior transpedicular screws should be individualized for each patient and based on a detailed preoperative planning.

  10. A Technique for Removal of Forearm Dynamic Compression Plate with Stripped Screws: A Report of Three Cases

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    CK Lee

    2009-05-01

    Full Text Available Removal of plates is a procedure commonly performed by orthopaedic surgeons and stripped screws are probably the most common problem encountered during this procedure. Stripped screws are caused by slippage between the screwdriver and the screw. Due to the inherent difficulty in removing such screws, surgeons should be knowledgeable in techniques for their removal and should be equipped with the proper instruments to expedite the procedure. There are few published articles about such techniques. This report describes a technique for removal of plates with stripped screws. The tip of a stripped screw is approached from the far cortex and then reamed with a trephine reamer in the direction of the screw until both cortices are cleared. The plate is then removed with stripped screws attached. All the removals utilizing this technique to date have been successful with no complications, and this method is safe, efficient and technically easy to learn.

  11. New Tools for Computational Geometry and Rejuvenation of Screw Theory

    Science.gov (United States)

    Hestenes, David

    Conformal Geometric Algebraic (CGA) provides ideal mathematical tools for construction, analysis, and integration of classical Euclidean, Inversive & Projective Geometries, with practical applications to computer science, engineering, and physics. This paper is a comprehensive introduction to a CGA tool kit. Synthetic statements in classical geometry translate directly to coordinate-free algebraic forms. Invariant and covariant methods are coordinated by conformal splits, which are readily related to the literature using methods of matrix algebra, biquaternions, and screw theory. Designs for a complete system of powerful tools for the mechanics of linked rigid bodies are presented.

  12. A description of the dynamics of manipulators using screw theory

    Science.gov (United States)

    Akselrod, B. V.

    1985-04-01

    The paper is concerned with the derivation of Lagrange equations of the second kind for a manipulator consisting of N links each of which is coupled with the preceding link (except for the first link, which is coupled with a fixed base) through a single-degree-of-freedom joint. The joints can be translational or rotational; each joint is treated as a rigid body, and the possibility of allowing for elasticity in the hinges and joints is demonstrated. The kinetic energy is determined using the theory of kinematic screws.

  13. Pedicle Screw-Based Posterior Dynamic Stabilization: Literature Review

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    Dilip K. Sengupta

    2012-01-01

    Full Text Available Posterior dynamic stabilization (PDS indicates motion preservation devices that are aimed for surgical treatment of activity related mechanical low back pain. A large number of such devices have been introduced during the last 2 decades, without biomechanical design rationale, or clinical evidence of efficacy to address back pain. Implant failure is the commonest complication, which has resulted in withdrawal of some of the PDS devices from the market. In this paper the authors presented the current understanding of clinical instability of lumbar motions segment, proposed a classification, and described the clinical experience of the pedicle screw-based posterior dynamic stabilization devices.

  14. RESEARCH OF A HIGH EFFICIENCY SLIDING SCREW DRIVER

    Institute of Scientific and Technical Information of China (English)

    Hu Xiaowei; Lu Huailiang; Huang Shuhuai

    2004-01-01

    A high efficiency sliding screw driver is introduced. It can improve driving efficiency obviously. As the material strength of the nut in this structure is low and the nut is the most dangerous part, so it is important to master the structure's characters of deformation and stress. The deformation and stress of this structure are researched by finite element method(FEM), and the changing law of stress concentration coefficient of the structure is gained. So the exact stress of nut teeth with highest load can be calculated directly based on this result.

  15. Reduction in radiation (fluoroscopy while maintaining safe placement of pedicle screws during lumbar spine fusion

    Directory of Open Access Journals (Sweden)

    Christopher D. Chaput

    2013-01-01

    Full Text Available OBJECTIVE: The purpose of this study is to report the results using PediGuard (electrical conductivity device to reduce radiation exposure while drilling the pilot hole for pedicle screw placement. METHOD: Eighteen patients diagnosed with a degenerative lumbar spine, that required a posterior spinal fusion. Average age of the patients were 55 ± 12 years. Patients received postoperative CT scans of all screws. Scans were reviewed by an independent reviewer grading 'in' 2 mm of breach. In a randomized fashion, the surgeon created pilot holes with either his standard technique or by using the PediGuard. Fluoroscopy was used for each drilling as necessary. Once the pilot hole was created, the surgeon inserted titanium screws into the pedicle pilot holes. A total of 78 screws (39 standard probe and 39 PediGuard were analyzed. RESULTS: 78 screws (39 standard probe and 39 PediGuard were analyzed. No significant difference in breach rate > 2mm by either method (p=1.000, with one screw out in each group. Fluoroscopy shots averaged 5.2 (range, 0 to 15, average decrease of 2.3 (30% per screw in the PediGuard group vs. 7.5 (range, 2 to 17 in the standard group (p< .001. CONCLUSION: This trial to assess pedicle probe location within the pedicle and vertebral body showed the number of fluoroscopy shots were reduced by 30%, compared to a standard probe while maintaining a 97.5% screw placement accuracy.

  16. Application of Richards Sliding Hip Screw in Treatment of Intertrochanteric Femoral Fractures

    Institute of Scientific and Technical Information of China (English)

    PING Jinzhong; SHEN Hongsheng; QIU Song

    2002-01-01

    @@ Richards Sliding Hip Screw is an effective method for the treatment of subtrochanteric and intertrochanteric femoral fractures. We applied the screw to treat the above- mentioned fractures from 1994 and obtained satisfying results in our hospital. All the cases were followed up. We reported it as follows.

  17. Is there enough evidence to regularly apply bone screws for intermaxillary fixation in mandibular fractures?

    NARCIS (Netherlands)

    A. Bins; M.A.E. Oomens; P. Boffano; T. Forouzanfar

    2015-01-01

    Purpose Intermaxillary fixation (IMF) is traditionally achieved with arch bars; however, this method has several well-known disadvantages and other techniques, such as bone screws, are available. This study evaluated current evidence regarding these IMF screws (IMFSs) for mandibular trauma and to as

  18. Pyrolysis of cassava rhizome in a counter-rotating twin screw reactor unit.

    Science.gov (United States)

    Sirijanusorn, Somsak; Sriprateep, Keartisak; Pattiya, Adisak

    2013-07-01

    A counter-rotating twin screw reactor unit was investigated for its behaviour in the pyrolysis of cassava rhizome biomass. Several parameters such as pyrolysis temperature in the range of 500-700°C, biomass particle size of twin screw reactor was relatively low, whereas the solids content was relatively high, compared to some other reactor configurations.

  19. A biomechanical study on fixation stability with twin hook or lag screw in artificial cancellous bone.

    Science.gov (United States)

    Olsson, O; Tanner, K E; Ceder, L; Ryd, L

    2002-01-01

    The twin hook has been developed as an alternative to the conventional lag screw to be combined with a barrelled side-plate in the treatment of trochanteric hip fractures. With two oppositely directed apical hooks introduced into the subchondral bone of the femoral head, the twin hook provides different stabilising properties to the lag screw. The femoral head purchase of the twin hook and the lag screw were compared in a biomechanical study using artificial cancellous bone, and responses to axial and torsional loading was determined. A distinct yield point in load and torque was noted for the lag screw, representing failure of the laminas supporting the threads. For the twin hook, gradual increase of load and torque occurred during impaction of the bone supporting the hooks. The peak loads and torques were higher for the lag screw, but were similar for both devices after 8 mm deformation. The stiffness was higher for the lag screw, but in counter-clockwise rotation the stiffness for the lag screw was negligible. The twin hook appeared to provide fixation stability comparable to that offered by the lag screw, but with conceivable advantages in terms of a deformation response involving bone impaction and gradually increasing stability.

  20. Complications of pedicle screws in lumbar and lumbosacral fusions in 105 consecutive primary operations

    NARCIS (Netherlands)

    Jutte, PC

    2002-01-01

    Pedicle screw fixation is technically demanding and associated with high complication rates. The aim of this study was to identify and quantify the pedicle screw-related complications in 105 consecutive operations. We retrospectively analysed 105 consecutive primary operations. We found complication

  1. 29 CFR 1926.305 - Jacks-lever and ratchet, screw, and hydraulic.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 8 2010-07-01 2010-07-01 false Jacks-lever and ratchet, screw, and hydraulic. 1926.305... Power § 1926.305 Jacks—lever and ratchet, screw, and hydraulic. (a) General requirements. (1) The... secured at once. (ii) Hydraulic jacks exposed to freezing temperatures shall be supplied with an...

  2. Robot assisted navigated drilling for percutaneous pedicle screw placement: A preliminary animal study

    Directory of Open Access Journals (Sweden)

    Hongwei Wang

    2015-01-01

    Conclusions: The preliminary study supports the view that computer assisted pedicle screw fixation using spinal robot is feasible and the robot can decrease the intraoperative fluoroscopy time during the minimally invasive pedicle screw fixation surgery. As spine robotic surgery is still in its infancy, further research in this field is worthwhile especially the accuracy of spine robot system should be improved.

  3. Comparison of two-transsacral-screw fixation versus triangular osteosynthesis for transforaminal sacral fractures.

    Science.gov (United States)

    Min, Kyong S; Zamorano, David P; Wahba, George M; Garcia, Ivan; Bhatia, Nitin; Lee, Thay Q

    2014-09-01

    Transforaminal pelvic fractures are high-energy injuries that are translationally and rotationally unstable. This study compared the biomechanical stability of triangular osteosynthesis vs 2-transsacral-screw fixation in the repair of a transforaminal pelvic fracture model. A transforaminal fracture model was created in 10 cadaveric lumbopelvic specimens. Five of the specimens were stabilized with triangular osteosynthesis, which consisted of unilateral L5-to-ilium lumbopelvic fixation and ipsilateral iliosacral screw fixation. The remaining 5 were stabilized with a 2-transsacral-screw fixation technique that consisted of 2 transsacral screws inserted across S1. All specimens were loaded cyclically and then loaded to failure. Translation and rotation were measured using the MicroScribe 3D digitizing system (Revware Inc, Raleigh, North Carolina). The 2-transsacral-screw group showed significantly greater stiffness than the triangular osteosynthesis group (2-transsacral-screw group, 248.7 N/mm [standard deviation, 73.9]; triangular osteosynthesis group, 125.0 N/mm [standard deviation, 66.9]; P=.02); however, ultimate load and rotational stiffness were not statistically significant. Compared with triangular osteosynthesis fixation, the use of 2 transsacral screws provides a comparable biomechanical stability profile in both translation and rotation. This newly revised 2-transsacral-screw construct offers the traumatologist an alternative method of repair for vertical shear fractures that provides biplanar stability. It also offers the advantage of percutaneous placement in either the prone or supine position.

  4. 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.

  5. Effect of Welding Methods on the Structure and Mechanical Properties of Welded Joints of Screw Piles

    Science.gov (United States)

    Golikov, N. I.; Sidorov, M. M.; Stepanova, K. V.

    2016-11-01

    Mechanical properties and characteristics of the structure of welded joints of screw piles are studied. It is shown that cast tips from steel 25L do not meet the performance specifications for operation in the Northern climatic zone. Quality welded joints of screw piles can be obtained by semiautomatic welding in an environment of CO2 with Sv-08G2S welding wire.

  6. Foreign body reaction after PLC reconstruction caused by a broken PLLA screw.

    Science.gov (United States)

    Kim, Tae-Kwon; Jeong, Tae-Wan; Lee, Dae-Hee

    2014-12-01

    Foreign body reactions may occur in patients who receive bioabsorbable implants during orthopedic surgery for fractures and ligament repair. The authors describe a 34-year-old man who presented with a palpable tender mass on the lateral aspect of the left knee of 1 month's duration. He underwent posterior cruciate ligament and posterolateral corner reconstruction 3 years earlier. Physical examination showed a 1×1-cm soft, nontender mass without localized warmth on the lateral epicondyle of the distal femur. Magnetic resonance imaging showed a broken screw fragment surrounded by a cyst-like mass. Under general anesthesia, the surgeon excised the screw fragment and the fibrotic mass, enclosing it in the subcutaneous tissue at the lateral epicondyle, the site at which a poly-L-lactic acid bioabsorbable screw had been inserted to fix the graft for posterolateral corner reconstruction. Histologic evaluation showed a foreign body reaction to the degraded screw particles. To the authors' knowledge, this report is the first description of a patient presenting with a delayed foreign body reaction to a broken poly-L-lactic acid bioabsorbable screw at the lateral femoral epicondyle after posterolateral corner reconstruction. Because delayed foreign body reactions can occur at any site of poly-L-lactic acid bioabsorbable screw insertion, care should be taken to avoid screw protrusion during ligament reconstruction because it can lead to screw breakage and delayed foreign body reaction.

  7. Determining the residence time distribution of various screw elements in a co-rotating twin-screw extruder by means of fluorescence spectroscopy

    Science.gov (United States)

    Lepschi, Alexander; Gerstorfer, Gregor; Miethlinger, Jürgen

    2015-05-01

    The Residence Time Distribution (RTD) is key to optimizing the mixing ability of an extruder. For both sensitive and reactive materials, it is important to know how long particles remain in the barrel and how long the polymer remains, for instance, in a kneading element. To assess the influence of different screw configurations on the RTD, a low-concentration tracer particle was injected into the feeding section and measured inline by fluorescence spectroscopy1 both inside the barrel and at the extruder exit. The measurements were conducted using polypropylene with different amounts of organic peroxide. Measuring the residence time at various positions along the screw allows the RTD to be determined for just one screw element. Furthermore, we show the influence of different screw configurations on the polydispersity of polypropylene.

  8. Are two retrograde 3.5 mm screws superior to one 7.3 mm screw for anterior pelvic ring fixation in bones with low bone mineral density?

    Science.gov (United States)

    Zderic, I.; Grechenig, S.; Richards, R. G.; Schmitz, P.; Gueorguiev, B.

    2017-01-01

    Objectives Osteosynthesis of anterior pubic ramus fractures using one large-diameter screw can be challenging in terms of both surgical procedure and fixation stability. Small-fragment screws have the advantage of following the pelvic cortex and being more flexible. The aim of the present study was to biomechanically compare retrograde intramedullary fixation of the superior pubic ramus using either one large- or two small-diameter screws. Materials and Methods A total of 12 human cadaveric hemipelvises were analysed in a matched pair study design. Bone mineral density of the specimens was 68 mgHA/cm3 (standard deviation (sd) 52). The anterior pelvic ring fracture was fixed with either one 7.3 mm cannulated screw (Group 1) or two 3.5 mm pelvic cortex screws (Group 2). Progressively increasing cyclic axial loading was applied through the acetabulum. Relative movements in terms of interfragmentary displacement and gap angle at the fracture site were evaluated by means of optical movement tracking. The Wilcoxon signed-rank test was applied to identify significant differences between the groups Results Initial axial construct stiffness was not significantly different between the groups (p = 0.463). Interfragmentary displacement and gap angle at the fracture site were also not statistically significantly different between the groups throughout the evaluated cycles (p ⩾ 0.249). Similarly, cycles to failure were not statistically different between Group 1 (8438, sd 6968) and Group 2 (10 213, sd 10 334), p = 0.379. Failure mode in both groups was characterised by screw cutting through the cancellous bone. Conclusion From a biomechanical point of view, pubic ramus stabilisation with either one large or two small fragment screw osteosynthesis is comparable in osteoporotic bone. However, the two-screw fixation technique is less demanding as the smaller screws deflect at the cortical margins. Cite this article: Y. P. Acklin, I. Zderic, S. Grechenig, R. G. Richards, P

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

    Institute of Scientific and Technical Information of China (English)

    WAN Shi-yong; LEI Wei; WU Zi-xiang; L(U) Rong; WANG Jun; FU Suo-chao; LI Bo; ZHAN Ce

    2008-01-01

    To investigate the properties of screwbone interface of expansive pedicle screw(EPS)in osteoporotic sheep by micro-CT and histological observation.Methods:Six female sheep with bilateral ovariectomyinduced osteoporosis were employed in this experiment.After EPS insertion in each femoral condvle, 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.Results: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 nonexpansive 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<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.Conclusions:The findings of the current study,based on micro-CT and histological evaluation, suggest that EPS can significantly provide stabilization in osteoporotic cancellous bones.

  10. Use of the channel fill level in defining a design space for twin screw wet granulation.

    Science.gov (United States)

    Gorringe, L J; Kee, G S; Saleh, M F; Fa, N H; Elkes, R G

    2017-03-15

    Twin screw wet granulation is a key process in the continuous manufacture of oral solid dosage forms. Previous research has qualitatively suggested that the channel fill level influences the granules produced. In this paper a quantitative measure of the total volumetric fraction of the conveying element channels of the screw filled with powder (φ) was used. Experimental results are shown which demonstrate that very similar particle size distributions can be obtained at the same φ with the same material and screw configuration but radically different solids feed rates and screw speeds. Morphology of the granules also correlates with φ. This is consistent with previous observations in the literature correlating granule attributes with powder feed rate and screw speed but also considers the two parameters in combination. A process design space approach based on φ is proposed. This can be determined empirically, and potentially has value in setting process control strategies, assuring process robustness and allowing process flexibility during the product lifecycle.

  11. EFFECT OF THE SCREW TORQUE LEVEL ON THE INTERFRAGMENTARY STRAIN AND THE INTERFRAGMENTARY MODULUS

    Directory of Open Access Journals (Sweden)

    Boonthum Wongchai

    2013-01-01

    Full Text Available The screw torque is applied at the screw head to fix the plate and the bone. It generates the compressive force between the plate and the bone to stabilize them. The interfragmentary strain is the main factor for healing the bone fractured. The screw torque level affects the interfragmentary strain and the stability of the fixation between the plates an the bone. The interfragmentary modulus is the new factor of the plate fixation stability and it is affected by the torque level. This research is proposed to study the effect of the screw torque level on the interfragmentary strain and the interfragmentary modulus. The interfragmentary strain and the interfragmentary modulus decrease by increasing the screw torque level.

  12. Connection of Screw Instability with Electric Current in an Accretion Disc around a Black Hole

    Institute of Scientific and Technical Information of China (English)

    LAN Xiao-Xia; WANG Ding-Xiong; GAN Zhao-Ming

    2005-01-01

    @@ The screw instability of the magnetic field is discussed based on its poloidal configuration generated by a single toroidal electric current flowing in the equatorial plane of a Kerr Mack hole (BH). The rotation of the BH relative to the disc induces an electromotive force, which in turn results in a poloidal electric current. By using Ampere's law, we calculate the toroidal component of the magnetic field and derive a criterion for the screw instability of the magnetic field connecting the rotating BH with its surrounding disc. It is determined that the screw instability is related to two parameters: the radius of the disc and the BH spin. The occurrence of screw instability is depicted in a parameter space. In addition, we discuss the effect of the screw instability on magnetic extraction of energy from the rotating BH.

  13. Evaluation of contributions of orthodontic mini-screw design factors based on FE analysis and the Taguchi method.

    Science.gov (United States)

    Lin, Chun-Li; Yu, Jian-Hong; Liu, Heng-Liang; Lin, Chih-Hao; Lin, Yang-Sung

    2010-08-10

    This study determines the relative effects of changes in bone/mini-screw osseointegration and mini-screw design factors (length, diameter, thread shape, thread depth, material, head diameter and head exposure length) on the biomechanical response of a single mini-screw insertion. Eighteen CAD and finite element (FE) models corresponding to a Taguchi L(18) array were constructed to perform numerical simulations to simulate mechanical responses of a mini-screw placed in a cylindrical bone. The Taguchi method was employed to determine the significance of each design factor in controlling strain. Simulation results indicated that mini-screw material, screw exposure length and screw diameter were the major factors affecting bone strain, with percentage contributions of 63%, 24% and 7%, respectively. Bone strain decreased obviously when screw material had the high elastic modulus of stainless/titanium alloys, a small exposure length and a large diameter. Other factors had no significant on bone strain. The FE analysis combined with the Taguchi method efficiently identified the relative contributions of several mini-screw design factors, indicating that using a strong stainless/titanium alloys as screw material is advantageous, and increase in mechanical stability can be achieved by reducing the screw exposure length. Simulation results also revealed that mini-screw and bone surface contact can provide sufficient mechanical retention to perform immediately load in clinical treatment.

  14. Posterior thoracic segmental pedicle screw instrumentation: Evolving methods of safe and effective placement

    Directory of Open Access Journals (Sweden)

    Zeiller S

    2005-01-01

    Full Text Available The use of pedicle screw instrumentation in the spine has evolved over the last two decades. The initial use of pedicle screws began in the lumbar spine. As surgeons have become more comfortable with the complex anatomy required for accurate screw placement, the use of pedicle instrumentation has evolved to include their use in the thoracolumbar and thoracic spine. The impetus behind their increased use is a result of the many advantages that pedicle screw anchorage offers over traditional hook and rod constructs. Improved deformity correction and overall construct rigidity are two important advantages of pedicle screw instrumentation due its three-column control over the spinal elements. First, pedicle screw instrumentation obviates the need to place instrumentation within the spinal canal with its inherent risk of neurologic injury. Second, the placement of pedicle screws is independent of facet or laminar integrity and thus has been extremely useful in traumatic, neoplastic, and degenerative conditions. The benefits of pedicle screws in the thoracic spine has been tempered by the potential for catastrophic neurological or soft tissue injuries due to the close proximity of these structures. The narrow and inconsistent shape of the thoracic pedicles, especially in spinal deformity, makes their placement technically challenging. As a result, surgeons have employed a number of techniques to ensure the safe and efficacious placement of thoracic pedicle screws. Detailed anatomic landmarks used to determine pedicle location, intraoperative imaging including navigation, and neurophysiological monitoring are some of the techniques currently used by surgeons. The implementation of these techniques and a thorough understanding of the complex three-dimensional anatomy have allowed surgeons to successfully place thoracic and thoracolumbar pedicle screws.

  15. 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

  16. Study of Bone-screw Surface Fixation in Lumbar Dynamic Stabilization

    Directory of Open Access Journals (Sweden)

    Yun-Gang Luo

    2015-01-01

    Full Text Available Background: We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with surrounding bone, and determine whether pedicle screws achieve good mechanical stability in the vertebrae. Methods: Twenty-four goats aged 2-3 years had Cosmic ® pedicle screws implanted into both sides of the L2-L5 pedicles. Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5. Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine. The side that was not implanted with fixation rods was used as a static control group. Results: In the static control group, new bone was formed around the pedicle screw and on the screw surface. In the unilateral and bilateral dynamic fixation groups, large amounts of connective tissue formed between and around the screw threads, with no new bone formation on the screw surface; the pedicle screws were loose after the fixed rods were removed. The bone mineral density and morphological parameters of the region of interest (ROI in the unilateral and bilateral dynamic fixation group were not significantly different (P > 0.05, but were lower in the fixed groups than the static control group (P 0.05; however the maximum pull force of the fixation groups was significantly less than the static control group (P < 0.01. Conclusions: Fibrous connective tissue formed at the bone-screw interface under unilateral and bilateral pedicle dynamic fixation, and the pedicle screws lost mechanical stability in the vertebrae.

  17. Augmentation of screw fixation with injectable calcium sulfate bone cement in ovariectomized rats.

    Science.gov (United States)

    Yu, Xiao-Wei; Xie, Xin-Hui; Yu, Zhi-Feng; Tang, Ting-Ting

    2009-04-01

    The objective of this study was to determine the effect of augmenting screw fixation with an injectable calcium sulfate cement (CSC) in the osteoporotic bone of ovariectomized rats. The influence of the calcium sulfate (CS) on bone remodeling and screw anchorage in osteoporotic cancellous bone was systematically investigated using histomorphometric and biomechanical analyses. The femoral condyles of 55 Sprague-Dawley ovariectomized rats were implanted with screw augmented with CS, while the contralateral limb received a nonaugmented screw. At time intervals of 2, 4, 8, 12, and 16 weeks, 11 rats were euthanized. Six pair-matched samples were used for histological analysis, while five pair-matched samples were preserved for biomechanical testing. Histomorphometric data showed that CS augmented screws activated cancellous bone formation, evidenced by a statistically higher (p < 0.05) percentage of osteoid surface at 2, 4, and 8 weeks and a higher rate of bone mineral apposition at 12 weeks compared with nonaugmented screws. The amount of the bone-screw contact at 2, 8, and 12 weeks and of bone ingrowth on the threads at 4 and 8 weeks was greater in the CS group than in the nonaugmented group (p < 0.05), although these parameters increased concomitantly with time for both groups. The CS was resorbed completely at 8 weeks without stimulating fibrous encapsulation on the screw surface. Also, the cement significantly increased the screw pull-out force and the energy to failure at 2, 4, 8, and 12 weeks after implantation, when compared with the control group (p < 0.05). These results imply that augmentation of screw fixation with CS may have the potential to decrease the risk of implant failure in osteoporotic bone.

  18. Energy consumption analysis for a single screw extruder

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jing; Harkin-Jones, Eileen; Price, Mark; Karnachi, Nayeem [Queen' s Univ., Belfast (United Kingdom). School of Mechanical and Aerospace Engineering; Li, Kang [Queen' s Univ., Belfast (United Kingdom). School of Electronics, Electrical Engineering and Computer Science; Fei, Minrui [Shanghai Univ. (China). School of Mechatronic Engineering and Automation

    2013-07-01

    Polymer extrusion is regarded as an energy intensive production process, the real-time monitoring of both thermal energy and motor drive energy consumption becomes necessary for the development of energy efficient management system. The use of power meter is a simple and easy way to achieve this, however the cost sometimes can be high. Mathematical models based on the process settings provide an affordable alternative, but the resultant models cannot be easily extended to other extruders with different geometry. In this paper, simple and accurate energy real-time monitoring methods are developed for the analysis of energy consumption of the thermal heating and motor drive respectively. This is achieved by looking inside the controller, and use the control variables to calculate the power consumption. The developed methods are then adopted to study the effects of operating settings on the energy efficiency. These include the barrel heating temperature, water cooling temperature, and screw speed. The experimental results on Killion KTS-100 extruder show that the barrel heating temperature has a negative effect on energy efficiency, while the water cooling setting affects the energy efficiency positively but insignificantly. Undoubtedly, screw speed has the most significant effect on energy efficiency.

  19. SURVEY SUBAXIAL CERVICAL VERTEBRAE FOR TRANSPEDICULAR SCREW FIXATION

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Objective In this study, the pedicles of subaxial vertebrae from C3 to C7 were measured to provide some morphometric data for cervical transpedicular screw fixation. Methods 20 dried bone cervical spinal columns (C3-C7), pedicle dimensions (pedicle height, width, length), and transverse and sagittal angles of the pedicles were performed with vernier in linear and angular measurements. Results The obtained data revealed that the mean values were approximately ranging from 6.7 to 7.2 mm for pedicle height, 4.4 to 4.9 mm for pedicle width, 22.2 to 27.7 mm for pedicle axis length, 42.3° to 51.5° for transverse angle, and 5.2° to 14.1° for sagittal angle. Conclusion Linear measurements of pedicle dimensions and also axial angles from horizontal and vertical planes may provide some anatomic limitations for subaxial cervical transpedicular screw fixation, and also contribute to the safety of the surgical procedure.

  20. 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.

  1. Prosopis pubescens (screw bean mesquite) seedlings are hyperaccumulators of copper.

    Science.gov (United States)

    Zappala, Marian N; Ellzey, Joanne T; Bader, Julia; Peralta-Videa, Jose R; Gardea-Torresdey, Jorge

    2013-08-01

    Due to health reasons, toxic metals must be removed from soils contaminated by mine tailings and smelter activities. The phytoremediation potential of Prosopis pubescens (screw bean mesquite) was examined by use of inductively-coupled plasma optical emission spectroscopy. Transmission electron microscopy was used to observe ultrastructural changes of parenchymal cells of leaves in the presence of copper. Elemental analysis was used to localize copper within leaves. A 600-ppm copper sulfate exposure to seedlings for 24 days resulted in 31,000 ppm copper in roots, 17,000 ppm in stems, 11,000 in cotyledons and 20 ppm in the true leaves. For a plant to be considered a hyperaccumulator, the plant must accumulate a leaf-to-root ratio <1. Screw bean mesquite exposed to copper had a leaf-to-root ratio of 0.355 when cotyledons were included. We showed that P. pubescens grown in soil is a hyperaccumulator of copper. We recommend that this plant should be field tested.

  2. Demonstrations of Beats as Moving Interference Patterns.

    Science.gov (United States)

    Stein, T. S.; Dishman, L. G.

    1982-01-01

    Describes a ripple tank demonstration that displays interference patterns responsible for producing beats and provides photographs of computer simulations of various beat interference patterns. Includes programs for the computer simulation and equations of constructive interference paths in beat interference patterns. (Author/SK)

  3. Whirling waves in Interference experiments

    Science.gov (United States)

    Sinha, Urbasi; Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna

    2014-03-01

    In a double slit interference experiment, the wave function at the screen with both slits open is not exactly the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well- known text books in quantum mechanics implicitly and/or explicitly use this assumption, the wave function hypothesis, which is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from non-classical paths in interference experiments which provide a measurable deviation from the wave function hypothesis. A direct experimental demonstration for the existence of these non-classical paths is hard. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence. I will also describe some ongoing experimental efforts towards testing our theoretical findings.

  4. Transmission Techniques for Relay-Interference Networks

    CERN Document Server

    Mohajer, Soheil; Fragouli, Christina; Tse, David N C

    2008-01-01

    In this paper we study the relay-interference wireless network, in which relay (helper) nodes are to facilitate competing information flows over a wireless network. We examine this in the context of a deterministic wireless interaction model, which eliminates the channel noise and focuses on the signal interactions. Using this model, we show that almost all the known schemes such as interference suppression, interference alignment and interference separation are necessary for relay-interference networks. In addition, we discover a new interference management technique, which we call interference neutralization, which allows for over-the-air interference removal, without the transmitters having complete access the interfering signals. We show that interference separation, suppression, and neutralization arise in a fundamental manner, since we show complete characterizations for special configurations of the relay-interference network.

  5. "Quantum Interference with Slits" Revisited

    CERN Document Server

    Rothman, Tony

    2010-01-01

    Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.

  6. Interference of diffusive light waves.

    Science.gov (United States)

    Schmitt, J M; Knüttel, A; Knutson, J R

    1992-10-01

    We examine interference effects resulting from the superposition of photon-density waves produced by coherently modulated light incident upon a turbid medium. Photon-diffusion theory is used to derive expressions for the ac magnitude and phase of the aggregate diffusive wave produced in full- and half-space volumes by two sources. Using a frequency-domain spectrometer operating at 410 MHz, we verify interference patterns predicted by the model in scattering samples having optical properties similar to those of skin tissue. Potential imaging applications of interfering diffusive waves are discussed in the context of the theoretical and experimental results.

  7. Interference, Reduced Action, and Trajectories

    Science.gov (United States)

    Floyd, Edward R.

    2007-09-01

    Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the trajectories of the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichromatic wave function’s trajectory. The quantum effective mass renders insight into the behavior of the trajectory. The trajectory in turn renders insight into quantum nonlocality.

  8. Interference, reduced action, and trajectories

    CERN Document Server

    Floyd, E R

    2006-01-01

    Instead of investigating the interference between two stationary, rectilinear wave functions in a trajectory representation by examining the two rectilinear wave functions individually, we examine a dichromatic wave function that is synthesized from the two interfering wave functions. The physics of interference is contained in the reduced action for the dichromatic wave function. As this reduced action is a generator of the motion for the dichromatic wave function, it determines the dichromatic wave function's trajectory. The quantum effective mass renders insight into the behavior of the trajectory. The trajectory in turn renders insight into quantum nonlocality.

  9. Individualized 3D printing navigation template for pedicle screw fixation in upper cervical spine

    Science.gov (United States)

    Guo, Fei; Dai, Jianhao; Zhang, Junxiang; Ma, Yichuan; Zhu, Guanghui; Shen, Junjie; Niu, Guoqi

    2017-01-01

    Purpose Pedicle screw fixation in the upper cervical spine is a difficult and high-risk procedure. The screw is difficult to place rapidly and accurately, and can lead to serious injury of spinal cord or vertebral artery. The aim of this study was to design an individualized 3D printing navigation template for pedicle screw fixation in the upper cervical spine. Methods Using CT thin slices data, we employed computer software to design the navigation template for pedicle screw fixation in the upper cervical spine (atlas and axis). The upper cervical spine models and navigation templates were produced by 3D printer with equal proportion, two sets for each case. In one set (Test group), pedicle screws fixation were guided by the navigation template; in the second set (Control group), the screws were fixed under fluoroscopy. According to the degree of pedicle cortex perforation and whether the screw needed to be refitted, the fixation effects were divided into 3 types: Type I, screw is fully located within the vertebral pedicle; Type II, degree of pedicle cortex perforation is 1 mm or with the poor internal fixation stability and in need of renovation. Type I and Type II were acceptable placements; Type III placements were unacceptable. Results A total of 19 upper cervical spine and 19 navigation templates were printed, and 37 pedicle screws were fixed in each group. Type I screw-placements in the test group totaled 32; Type II totaled 3; and Type III totaled 2; with an acceptable rate of 94.60%. Type I screw placements in the control group totaled 23; Type II totaled 3; and Type III totaled 11, with an acceptable rate of 70.27%. The acceptability rate in test group was higher than the rate in control group. The operation time and fluoroscopic frequency for each screw were decreased, compared with control group. Conclusion The individualized 3D printing navigation template for pedicle screw fixation is easy and safe, with a high success rate in the upper cervical spine

  10. When Planning Screw Fracture Fixation Why the 5.5 mm Screw is the Goldilocks Screw. An Observational Computer Tomographic Study of Fifth Metatarsal Bone Anatomy in a Sample of Patients.

    Science.gov (United States)

    Iselin, Lukas D; Ramawat, Sunil; Hanratty, Brian; Klammer, Georg; Stavrou, Peter

    2015-05-01

    We wanted to verify our clinical experience that the 5.5 mm screw was ideal in the majority of fifth metatarsal fracture fixation. The size of a screw is important for the successful surgical treatment of these fractures in order to obtain the maximal stability while reducing the risk for iatrogenic fracture.A sample of patients undergoing computer tomographic imaging of the foot for investigation other than fifth metatarsal pathology were recruited. The parameters of the fifth metatarsal bone anatomy were measured.These parameters of the 5.5 mm screw were correlated with this data. The upper parameter (the diameter of the threads) was 5.5 and the lower parameter (the diameter of the shank) was 4.0 mm.Twenty seven patients were recruited.The proximal third internal diameter ranged from 3.6 to 7.0 mm with a mean of 5.0 mm. 93% of the metatarsals could easily accommodate the 5.5 mm screw. Two of the metatarsals had an internal diameter of < 4 mm (7%).It is our belief that the 5.5 mm screw may be used safely in the majority of patients with fifth metatarsal fractures.

  11. Use of self-tapping metal screws for temporary fixation of a resorbable plate system in maxillofacial surgery.

    Science.gov (United States)

    Iwai, Toshinori; Omura, Susumu; Aoki, Noriaki; Tohnai, Iwai

    2015-05-01

    Resorbable plate systems have been used in maxillofacial surgery to obviate the need for plate removal. However, resorbable plates and screws are very costly, and refixation with additional screws may be necessary when reduction or repositioning of the bone segment is inaccurate. Here we report the use of self-tapping metal screws for temporary fixation of a resorbable plating system in maxillofacial surgery to avoid the use of additional screws following inaccurate fixation or the reuse of resorbable screws, which may result in loosening.

  12. The biomechanical effect of artificial and human bone density on stopping and stripping torque during screw insertion.

    Science.gov (United States)

    Tsuji, Matthew; Crookshank, Meghan; Olsen, Michael; Schemitsch, Emil H; Zdero, Rad

    2013-06-01

    Orthopedic surgeons apply torque to metal screws manually by "subjective feel" to obtain adequate fracture fixation, i.e. stopping torque, and attempt to avoid accidental over-tightening that leads to screw-bone interface failure, i.e. stripping torque. Few studies have quantified stripping torque in human bone, and only one older study from 1980 reported stopping/ stripping torque ratio. The present aim was to measure stopping and stripping torque of cortical and cancellous screws in artificial and human bone over a wide range of densities. Sawbone blocks were obtained having densities from 0.08 to 0.80g/cm(3). Sixteen fresh-frozen human femurs of known standardized bone mineral density (sBMD) were also used. Using a torque screwdriver, 3.5-mm diameter cortical screws and 6.5-mm diameter cancellous screws were inserted for adequate tightening as determined subjectively by an orthopedic surgeon, i.e. stopping torque, and then further tightened until failure of the screw-bone interface, i.e. stripping torque. There were weak (R=0.25) to strong (R=0.99) linear correlations of absolute and normalized torque vs. density or sBMD. Maximum stopping torques normalized by screw thread area engaged by the host material were 15.2N/mm (cortical screws) and 13.4N/mm (cancellous screws) in sawbone blocks and 20.9N/mm (cortical screws) and 6.1N/mm (cancellous screws) in human femurs. Maximum stripping torques normalized by screw thread area engaged by the host material were 23.4N/mm (cortical screws) and 16.8N/mm (cancellous screws) in sawbone blocks and 29.3N/mm (cortical screws) and 8.3N/mm (cancellous screws) in human femurs. Combined average stopping/ stripping torque ratios were 80.8% (cortical screws) and 76.8% (cancellous screws) in sawbone blocks, as well as 66.6% (cortical screws) and 84.5% (cancellous screws) in human femurs. Surgeons should be aware of stripping torque limits for human femurs and monitor stopping torque during surgery. This is the first study of the

  13. "Quantum Interference with Slits" Revisited

    Science.gov (United States)

    Rothman, Tony; Boughn, Stephen

    2011-01-01

    Marcella has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his…

  14. Political Interference in Climate Science

    Science.gov (United States)

    Kumar, Mohi

    2007-02-01

    ``All of us have a right to our own views about the seriousness of global warming,'' U.S. Rep. Henry Waxman (D-Calif.), chair of the House Oversight and Government Reform Committee, said at a 30 January committee hearing held to examine political interference in climate science. ``But we don't have a right to our own science.''

  15. Spinal pedicle screw planning using deformable atlas registration

    Science.gov (United States)

    Goerres, J.; Uneri, A.; De Silva, T.; Ketcha, M.; Reaungamornrat, S.; Jacobson, M.; Vogt, S.; Kleinszig, G.; Osgood, G.; Wolinsky, J.-P.; Siewerdsen, J. H.

    2017-04-01

    Spinal screw placement is a challenging task due to small bone corridors and high risk of neurological or vascular complications, benefiting from precision guidance/navigation and quality assurance (QA). Implicit to both guidance and QA is the definition of a surgical plan—i.e. the desired trajectories and device selection for target vertebrae—conventionally requiring time-consuming manual annotations by a skilled surgeon. We propose automation of such planning by deriving the pedicle trajectory and device selection from a patient’s preoperative CT or MRI. An atlas of vertebrae surfaces was created to provide the underlying basis for automatic planning—in this work, comprising 40 exemplary vertebrae at three levels of the spine (T7, T8, and L3). The atlas was enriched with ideal trajectory annotations for 60 pedicles in total. To define trajectories for a given patient, sparse deformation fields from the atlas surfaces to the input (CT or MR image) are applied on the annotated trajectories. Mean value coordinates are used to interpolate dense deformation fields. The pose of a straight trajectory is optimized by image-based registration to an accumulated volume of the deformed annotations. For evaluation, input deformation fields were created using coherent point drift (CPD) to perform a leave-one-out analysis over the atlas surfaces. CPD registration demonstrated surface error of 0.89  ±  0.10 mm (median  ±  interquartile range) for T7/T8 and 1.29  ±  0.15 mm for L3. At the pedicle center, registered trajectories deviated from the expert reference by 0.56  ±  0.63 mm (T7/T8) and 1.12  ±  0.67 mm (L3). The predicted maximum screw diameter differed by 0.45  ±  0.62 mm (T7/T8), and 1.26  ±  1.19 mm (L3). The automated planning method avoided screw collisions in all cases and demonstrated close agreement overall with expert reference plans, offering a potentially valuable tool in support

  16. Occipital condyle screw placement and occipitocervical instrumentation using three-dimensional image-guided navigation.

    Science.gov (United States)

    Le, Tien V; Burkett, Clint; Ramos, Edwin; Uribe, Juan S

    2012-05-01

    Occipital condyle (OC) screws are an alternative cephalad fixation point in occipitocervical fusion. Safe placement of occipital, C1 lateral mass, and C2 pars screws have been described previously, but not OC screws. The craniocervical junction is complex, and a thorough understanding of the anatomy is needed. Three-dimensional (3D) image-guided navigation was used in six patients. There were no complications related to image-guided navigation during the placement of 12 OC screws and we found that this navigation can serve as a useful adjunct when placing an OC screw. Technical considerations of placing OC and C1 lateral mass screws are discussed with particular reference to patient positioning and the StealthStation® S7™ image-guided navigational platform (Medtronic, Minneapolis, MN, USA). The reference arc is attached to the head-clamp and faces forward. The optical camera and monitor are positioned at the head of the table for a direct, non-obstructed line-of-sight. To minimize intersegmental movement, the OC should not be drilled until all other screws have been placed. We conclude that 3D image-guided navigation is a useful adjunct that can be safely and effectively used for placement of instrumentation of the upper cervical spine including the OC.

  17. Investigation of a Ball Screw Feed Drive System Based on Dynamic Modeling for Motion Control

    Directory of Open Access Journals (Sweden)

    Yi-Cheng Huang

    2017-06-01

    Full Text Available This paper examines the frequency response relationship between the ball screw nut preload, ball screw torsional stiffness variations and table mass effect for a single-axis feed drive system. Identification for the frequency response of an industrial ball screw drive system is very important for the precision motion when the vibration modes of the system are critical for controller design. In this study, there is translation and rotation modes of a ball screw feed drive system when positioning table is actuated by a servo motor. A lumped dynamic model to study the ball nut preload variation and torsional stiffness of the ball screw drive system is derived first. The mathematical modeling and numerical simulation provide the information of peak frequency response as the different levels of ball nut preload, ball screw torsional stiffness and table mass. The trend of increasing preload will indicate the abrupt peak change in frequency response spectrum analysis in some mode shapes. This study provides an approach to investigate the dynamic frequency response of a ball screw drive system, which provides significant information for better control performance when precise motion control is concerned.

  18. Experimental investigation of granule size and shape dynamics in twin-screw granulation.

    Science.gov (United States)

    Kumar, Ashish; Vercruysse, Jurgen; Bellandi, Giacomo; Gernaey, Krist V; Vervaet, Chris; Remon, Jean Paul; De Beer, Thomas; Nopens, Ingmar

    2014-11-20

    A twin-screw granulator (TSG), a promising equipment for continuous high shear wet granulation (HSWG), achieves the desired level of mixing by a combination of the appropriate screw configuration and a suitable set of process settings (e.g. feed rate, screw speed, etc.), thus producing a certain granule size and shape distribution (GSSD). However, the primary sizing and shaping mechanism behind the resulting distribution is not well understood due to the opacity of the multiphase system in the granulator. This study experimentally characterised the GSSD dynamics along the TSG barrel length in order to understand the function of individual screw modules and process settings, as well as their interaction. Particle size analysis of granules collected at the outlet of the TSG suggested significant interaction between the process and screw configuration parameters influencing the heterogeneity in the GSSD. By characterising the samples collected along the screw length, a variable influence of the screw modules at different process conditions was observed. At low liquid-to-solid ratio (L/S), the first kneading module seemed to play a significant role in mixing, whereas the second kneading module was found to be more involved in reshaping the granules. At high L/S and high throughput, aggregation mainly took place in the second kneading module changing the GSSD. The results obtained from this study will be further used for the calibration and validation of a mechanistic model and, hence, support future development of a more detailed understanding of the HSWG process in a TSG.

  19. Management of Cannulated Screw Failure and Recurrent SCFE Displacement – Case Report

    Directory of Open Access Journals (Sweden)

    Nathan A Jacobson

    2014-01-01

    Full Text Available Introduction: SCFE occurs in 10 per 100,000 in some regions of the United States with the incidence continuing to increase. Percutaneous screw fixation is a well-accepted treatment for this disorder for over 20 years but management of complications is not well elucidated in the literature. Case Report: We describe a case where a traumatic unstable SCFE that was initially treated with closed reduction and fixation with a single transphyseal screw went on to hardware failure with recurrence of the deformity. The complication was successfully treated with closed reduction and re- cannulating the fractured screw within the epiphysis and extracting it using a conical extraction screw commonly referred to as an “easy out.” Three trans physeal screws were then placed for improved fixation strength. Follow-up at 9 months demonstrates a fused physis and no signs of avascular necrosis of the femoral head. Conclusion: Percutaneous management of SCFE screw breakage is possible utilizing specialized instruments and a precise and gentle manipulation preventing the need for more invasive treatments with their obligatory potential complications profile. Keywords: Hardware Failure, Slip Recurrence, SCFE, Complication, Conical Extraction Screw, Easy Out.

  20. The effect of screw insertion torque on tendons fixed with spiked washers.

    Science.gov (United States)

    Beynnon, B D; Meriam, C M; Ryder, S H; Fleming, B C; Johnson, R J

    1998-01-01

    The long-term success of a hamstring tendon graft depends not only on the type of device that is used for fixation but also on the mechanical interlocking of the soft tissue between the fixation device and bone. The purpose of this study was to evaluate the effect of screw insertion torque on the structural properties of soft tissue fixed to bone with a spiked metal washer. Two bovine tendons, one similar in size to a human semitendinosus tendon and the other similar in size to a human gracilis tendon, were secured to a bovine femur using a figure-of-8 technique with screws and metal spiked washers. A single load to failure was applied at 25 mm/sec. A significant positive linear correlation was observed between fixation screw insertion torque magnitude and the ultimate failure load value. An increase in the fixation screw insertion torque produced an increase in the ultimate failure load value. Similarly, there was a significant positive linear correlation between fixation screw insertion torque magnitude and the average maximum linear load value. No relationship was detected between screw insertion torque magnitude and the linear stiffness values of the tendon-fixation construct, indicating that a reproducible model was used. This study demonstrates that screw insertion torque is an important variable that controls the initial strength of soft tissue fixation to bone.

  1. Mechanical Comparison of Headless Screw Fixation and Locking Plate Fixation for Talar Neck Fractures.

    Science.gov (United States)

    Karakasli, Ahmet; Hapa, Onur; Erduran, Mehmet; Dincer, Cemal; Cecen, Berivan; Havitcioglu, Hasan

    2015-01-01

    For talar neck fractures, open reduction and internal fixation have been thought to facilitate revascularization and prevent osteonecrosis. Newer screw systems allow for placement of cannulated headless screws, which provide compression by virtue of a variable pitch thread. The present study compared the biomechanical fixation strength of cannulated headless variable-pitch screw fixation and locking plate fixation. A reproducible talar neck fracture was created in 14 fresh cadaver talar necks. Talar head fixation was then performed using 2 cannulated headless variable-pitch 4-mm/5-mm diameter (4/5) screws (Acutrak; Acumed, Hillsboro, OR) and locking plate fixation. Headless variable-pitch screw fixation had lower failure displacement than did locking plate fixation. No statistically significant differences were found in failure stiffness, yield stiffness (p = .655), yield load (p = .142), or ultimate load between the 2 fixation techniques. Cannulated headless variable-pitch screw fixation resulted in better failure displacement than locking plate fixation in a cadaveric talus model and could be considered a viable option for talus fracture fixation. Headless, fully threaded, variable-pitch screw fixation has inherent advantages compared with locking plate fixation, because it might cause less damage to the articular surface and can compress the fracture for improved reduction. Additionally, plate fixation can increase the risk of avascular necrosis owing to the wider incision and dissection of soft tissues.

  2. Factors influencing success of cement versus screw-retained implant restorations: a clinical review

    Directory of Open Access Journals (Sweden)

    Ahmad Manawar

    2012-10-01

    Full Text Available Aim: As more and more dental practitioners are focusing on implant-supported fixed restorations, some clinicians favor the use of cement retained restorations while others consider screw retained prosthesis to be the best choice. Discussion: In screw-retained restorations, the fastening screw provides a solid joint between the restoration and the implant abutment, while in cement-retained prostheses the restorative screw is eliminated to enhance esthetics, occlusal stability, and passive fit of the restorations. The factors that influence the type of fixation of the prostheses to the implants like passivity of the framework, ease of fabrication, occlusion, esthetics, accessibility, retention and retrievability are discussed in this article with scientific studies demonstrating superior outcomes of one technique over another. Screwretained implant restorations have an advantage of predictable retention, retrievability and lack of potentially retained subgingival cement. However, a few disadvantages exist such as precise placement of the implant for optimal and esthetic location of the screw access hole and obtaining passive fit. On the other hand, cement retained restorations eliminate unesthetic screw access holes, have passive fit of castings, reduced complexity of clinical and lab procedures, enhanced esthetics, reduced cost factors and non disrupted morphology of the occlusal table. Conclusion: This article compares the advantages, potential disadvantages and limitations of screw and cement retained restorations and their specific implications in the most common clinical situation.

  3. The use of bovine screws to promote bone formation using a tibia model in dogs

    Science.gov (United States)

    Bianchini, Marco Aurélio; Pontual, Marco Antônio B; Bez, Leonardo; Benfatti, César Augusto M; Boabaid, Fernanda; Somerman, Martha J; Magini, Ricardo S

    2013-01-01

    The objective of this study was to evaluate the use of a unique resorbable bovine bone screw, to stimulate bone formation. Bovine bone screws were inserted in the tibia beagle dogs. Each animal received 8 screws, divided into Groups A (screws + no membranes), B (screws + titanium reinforced membranes) and C (bone defects treated with autogenous bone grafts). Animals were sacrificed at 2, 4 and 6 months. New bone was measured with a periodontal probe and reported an average of 7.4 mm in vertical bone gain for Group B, 3.6 mm for Group A and 1.7 mm for Group C. Submission to Kruskal-Wallis test showed statistical differences between groups (p<0,05). Histological examination revealed an intimate contact between the newly formed bone and the resorbing bone screws. Conclusion: Bovine bone screws provide environment for new bone formation and thus may provide an alternative therapy for enhancing bone formation vertically, including for regenerative procedures as well as prior to implant therapy. PMID:23058228

  4. Evaluations of Flow and Mixing Efficiency in the Kneading Disks of a Novel Tri-Screw Extruder

    Directory of Open Access Journals (Sweden)

    X. Z. Zhu

    2016-01-01

    Full Text Available The forward or backward stagger angles of the kneading disks have great effects on configures of the special center region along axial length in a novel tri-screw extruder. In this paper, the flow and mixing of a nonNewtonian polyethylene in kneading disks of a tri-screw extruder were simulated using three-dimensional finite element modeling based on mesh superposition technique. Three types of kneading disks, neutral stagger, staggered 30° forward and staggered 30° reverse were considered for the tri-screw extruder. The effects of stagger angles of kneading disks on the flow pattern in the tri-screw extruder were investigated. Moreover, at different stagger angles, the dispersive and distributive mixing efficiencies in the kneading disks of the tri-screw extruder and the twin-screw extruder were calculated and compared by means of mean shear rate, stretching rates, maximal stress magnitudes, mixing index, residence time distribution (RTD and logarithm of area stretch. It is found that increasing the stagger angles decreases the axial velocities of polymer melt in the center region for the tri-screw extruder. The staggered 30° reverse is relatively reasonable for the tri-screw extruder and neutral stagger for the twin-screw extruder for the mixing efficiency. In comparison, the kneading disks in the tri-screw extruder have higher distributive and dispersive mixing efficiencies than those in the twin-screw extruder with the same stagger angles.

  5. Atomistic modeling of carbon Cottrell atmospheres in bcc iron

    Science.gov (United States)

    Veiga, R. G. A.; Perez, M.; Becquart, C. S.; Domain, C.

    2013-01-01

    Atomistic simulations with an EAM interatomic potential were used to evaluate carbon-dislocation binding energies in bcc iron. These binding energies were then used to calculate the occupation probability of interstitial sites in the vicinity of an edge and a screw dislocation. The saturation concentration due to carbon-carbon interactions was also estimated by atomistic simulations in the dislocation core and taken as an upper limit for carbon concentration in a Cottrell atmosphere. We obtained a maximum concentration of 10 ± 1 at.% C at T = 0 K within a radius of 1 nm from the dislocation lines. The spatial carbon distributions around the line defects revealed that the Cottrell atmosphere associated with an edge dislocation is denser than that around a screw dislocation, in contrast with the predictions of the classical model of Cochardt and colleagues. Moreover, the present Cottrell atmosphere model is in reasonable quantitative accord with the three-dimensional atom probe data available in the literature.

  6. Error rate of multi-level rapid prototyping trajectories for pedicle screw placement in lumbar and sacral spine

    Institute of Scientific and Technical Information of China (English)

    Matjaz Merc; Igor Drstvensek; Matjaz Vogrin; Tomaz Brajlih; Tomaz Friedrich; Gregor Recnik

    2014-01-01

    Objective:Free-hand pedicle screw placement has a high incidence of pedicle perforation which can be reduced with fluoroscopy,navigation or an alternative rapid prototyping drill guide template.In our study the error rate of multi-level templates for pedicle screw placement in lumbar and sacral regions was evaluated.Methods:A case series study was performed on 11 patients.Seventy-two screws were implanted using multilevel drill guide templates manufactured with selective laser sintering.According to the optimal screw direction preoperatively defined,an analysis of screw misplacement was performed.Displacement,deviation and screw length difference were measured.The learning curve was also estimated.Results:Twelve screws (17%) were placed more than 3.125 mm out of its optimal position in the centre of pedicle.The tip of the 16 screws (22%) was misplaced more than 6.25 mm out of the predicted optimal position.According to our predefined goal,19 screws (26%) were implanted inaccurately.In 10 cases the screw length was selected incorrectly:1 (1%) screw was too long and 9 (13%) were too short.No clinical signs of neurovascular lesion were observed.Learning curve was insignificantly noticeable (P=0.129).Conclusion:In our study,the procedure of manufacturing and applying multi-level drill guide templates has a 26% chance of screw misplacement.However,that rate does not coincide with pedicle perforation incidence and neurovascular injury.These facts along with a comparison to compatible studies make it possible to summarize that multi-level templates are satisfactorily accurate and allow precise screw placement with a clinically irrelevant mistake factor.Therefore templates could potentially represent a useful tool for routine pedicle screw placement.

  7. Bicortical screw fixation of distal fibula fractures with a lateral plate: an anatomic and biomechanical study of a new technique.

    Science.gov (United States)

    Milner, Brenton F; Mercer, Deana; Firoozbakhsh, Keikhosrow; Larsen, Kenna; Decoster, Thomas A; Miller, Richard A

    2007-01-01

    One of the potential drawbacks of lateral plating of distal fibula fractures is less than satisfactory fixation of unicortical screws commonly placed in the distal fragment to avoid implant penetration of the ankle joint. This study examines the anatomy of the distal fibula, proposes new techniques for bicortical screw fixation and radiographic evaluation of screw placement, and compares pullout strength of unicortical versus bicortical screws in this area. Sixteen pairs of human cadaver feet were used in this study. It was found that a large percentage of the surface area of the distal fibula is nonarticular and that the distal fibula could be divided into 3 zones with distinct anatomic features. Zone I is defined as the distal most 1.5 cm of the fibula, zone II is the next 1 cm of fibula proximal to zone I, and zone III is defined as the fibula above the ankle joint, starting at just over 2.5 cm proximal to the tip of the fibula. We determined a safe corridor for bicortical screw placement by means of a lateral plate in each zone. An improved radiographic view is described for confirmation of extraarticular screw placement. Screw pullout testing was performed on 8 pairs of fresh-frozen human cadaver fibulas. In both zone I and zone II, the bicortical screw fixation was significantly stronger than the unicortical screw fixation. In zone I, the average pullout strength for the bicortical screw fixation was 2.3 times higher than the unicortical screw fixation. In zone II, the average pullout strength for the bicortical screw fixation was 3.3 times higher than the unicortical screw fixation. This study shows that not only is bicortical screw placement in the distal fibula technically feasible, but it is also biomechanically stronger than unicortical placement in this area.

  8. Applied anatomy of the lower cervical pedicle screw insertion

    Institute of Scientific and Technical Information of China (English)

    LI Xing-guo; LIU Zong-liang; HE Yun; ZHAO Yan; ZOU Zhi-rong; ZHANG Peng; LUO Ji-hong; GUO Yong-fu; ZHANG Yang-jie; ZHANG Yu-ran

    2007-01-01

    Objective: To ascertain an accurate approach to inserting the pedicle screw into C3-C7 segments of the cervical vertebra.Methods: Anatomic morphology of lateral mass and pedicle, and their anatomic relationship with the adjacent tissue were observed on C3-C7 segments of 25 adult embalmed cadavers (50 sides).Results: 1 ) The inferior edge of the base of the posterior tubercle of the transverse process and the inferior edge of the pedicle were connected with each other on 25 adult embalmed cadavers (50 sides ). The transverse section which passed through the median point between the superior edge and the inferior edge of the base of the posterior tubercle of the transverse process, and the transverse section which passed through the central axis between the superior edge and the inferior edge of the pedicle, were in the same horizontal plane. The superior and inferior position of placing the pedicle screw was determined by this transverse section, which passed through the median point between the superior and the inferior edge of the base of the posterior tubercle of the transverse process. 2 ) There was a directed internaldownwards "triangular sulcule" between the base of the posterior tubercle of the transverse process and the anterolateral edge of the inferior articular process. The anterior wall of the triangular sulcule was the base of the posterior tubercle of the transverse process, the posterior wall was the anterolateral edge of the inferior articular process, and the bottom of the sulcule was connected with the interior edge of the pedicle. The vertical length between the top of triangle and the planes of inferior edge of the pedicle was (2.78 ± 1.71 ) mm. The inferior edge of the cervical pedicle could be detected using a blunt probe along the "triangular sulcule" between the base of the posterior tubercle of the transverse process and the anterolateral edge of the inferior articular process in surgical operation. 3 )The lateral fovea of the articular

  9. Rotating Optical Tubes: An Archimedes' Screw for Atoms

    CERN Document Server

    Rsheed, Anwar Al; Aldossary, Omar M; Lembessis, Vassilis E

    2016-01-01

    The classical dynamics of a cold atom trapped inside a vertical rotating helical optical tube (HOT) is investigated by taking also into account the gravitational field. The resulting equations of motion are solved numerically. The rotation induces a vertical motion for an atom initially at rest. The motion is a result of the action of two inertial forces, namely the centrifugal force and the Coriolis force. Both inertial forces force the atom to rotate in a direction opposite to that of the angular velocity of the HOT. The frequency and the turning points of the atom's global oscillation can be controlled by the value and the direction of the angular velocity of the HOT. However, at large values of the angular velocity of the HOT the atom can escape from the global oscillation and be transported along the axis of the HOT. In this case, the rotating HOT operates as an Optical Archimedes' Screw (OAS) for atoms.

  10. [Mechanical circulatory assist using a miniaturized Archimedes screw].

    Science.gov (United States)

    von Segesser, L K; Bisang, B; Leskosek, B; Turina, M

    1991-01-01

    An axial flow blood pump (Archimedes screw) for intraarterial left ventricular assist was evaluated in comparison to standard roller pump left heart bypass (LHBP) in 13 bovine experiments (bodyweight 74 +/- 15 kg). Full systemic heparinization (ACT greater than 500 s) was used for LHBP in comparison to limited systemic heparinization (ACT greater than 180 s) for axial. A standard battery of blood samples was taken before and at regular intervals throughout perfusion: (table; see text) Transarterial access and relatively limited blood trauma appear to be the main advantages of the evaluated axial flow blood pump. However, the impossibility to assess the pump flow may be a major problem for the management of the failing left ventricle.

  11. Assessment of a percutaneous iliosacral screw insertion simulator

    CERN Document Server

    Tonetti, J; Girard, P; Dubois, M; Merloz, P; Troccaz, Jocelyne; 10.1016/j.otsr.2009.07.005

    2009-01-01

    BACKGROUND: Navigational simulator use for specialized training purposes is rather uncommon in orthopaedic and trauma surgery. However, it reveals providing a valuable tool to train orthopaedic surgeons and help them to plan complex surgical procedures. PURPOSE: This work's objective was to assess educational efficiency of a path simulator under fluoroscopic guidance applied to sacroiliac joint percutaneous screw fixation. MATERIALS AND METHODS: We evaluated 23 surgeons' accuracy inserting a guide-wire in a human cadaver experiment, following a pre-established procedure. These medical trainees were defined in three prospective respects: novice or skilled; with or without theoretical knowledge; with or without surgical procedure familiarity. Analysed criteria for each tested surgeon included the number of intraoperative X-rays taken in order to achieve the surgical procedure as well as an iatrogenic index reflecting the surgeon's ability to detect any hazardous trajectory at the time of performing said procedu...

  12. Computer-Aided Design System for CP Single-Screw Compressor

    Institute of Scientific and Technical Information of China (English)

    SHEN Jing-feng; YAO Fu-sheng

    2006-01-01

    To design various optimum parameters and simulate the working process of CP single-screw compressor,the Computer-Aided Design(CAD)system for the CP singlescrew compressor has been established.A new method based on computer graphics technology,database technology,object-oriented programming technology,and visual simulation technology has been adopted in this CAD system.The system has integrated solid modeling function with parameterization design function and animator simulation function based on analyzing the working principle of the CP single-screw compressor.The experimental results show fhat the CAD system for the CP single-screw compressor is practical and feasible.

  13. Subtrochanteric femur fracture after removal of screws for femoral neck fracture in a child.

    Science.gov (United States)

    Song, Kwang Soon; Lee, Si Wook

    2015-01-01

    Displaced femoral neck fractures are rare in children and are associated with a high rate of complications. Subtrochanteric fractures after cannulated screw fixation of femoral neck fractures in adults are well recognized, and there are several reports on the topic. However, there are no reports on complications related to hardware or subtrochanteric fractures after removal of the screws in the treatment of femoral neck fractures in children. Here we report the case of a 10-year-old boy who sustained a subtrochanteric fracture after the screw removal and healing that followed a femoral neck fracture.

  14. The use of twin screw extruders for feeding coal against pressures of up to 1500 PSI

    Science.gov (United States)

    Wiedmann, W.; Mack, W. A.

    1977-01-01

    Recent tests with a twin-screw, co-rotating extruder which was successfully used to convey and feed coal against pressures of up to 1500 psi are described. Intermeshing and self-wiping, co-rotating twin-screws give greatly improved conveying and pressure built-up capabilities and avoid hangup and eventual decomposition of coal particles in the screw flights. The conveying action of intermeshing, self-wiping, co-rotating extruder systems approaches that of a positive displacement pump. With this feature, it is possible to maintain very accurate control over all aspects of product conveyance in the extruder, i.e., intake, conveyance and pressure buildup.

  15. Analysis of Indicator Diagrams of a Water Injected Twin-shaft Screw-type Expander

    OpenAIRE

    Nikolov, Alexander; Brümmer, Andreas

    2016-01-01

    Twin-shaft screw-type expanders offer a high potential for energy conversion in the lower and medium power range, for instance as expansion engines in Rankine cycles for exhaust heat recovery. With regard to minimizing internal leakages and lubricating moving machine parts, an auxiliary liquid or liquid working fluid can be fed to the screw expander. In this paper, indicator diagrams of a twin-shaft screw-type expander prototype designed at the Chair of Fluidics at TU Dortmund University are ...

  16. Pedicale screw system plus ACPC perfusion to treat fractures of thoracolumbar vertebrae

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@In recent years the pedicle screw system has been widely used in treating thoracolumbar vertebral fractures. The effect to recover the injured vertebrae height, the spinal physiological curve and to decompress vertebral canal has been confirmed. But the problems of internal fixation bending, loosening and breaking, which result in the loss of the vertebral height and spinal angulation deformity, are quite common and cause a lot of difficulties for surgeons. To solve these problems and decrease the sequelae from treating thoracolumbar vertebrae fractures with vertebral pedicle screw system, we have tried using vertebral pedicle screw system plus ACPC perfusion to treat 18patients with thoracolumbar vertebral fractures.Satisfactory results have been obtained.

  17. 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.

  18. Plastification of polymers in twin-screw-extruders: New visualization technic using high-speed imaging

    Energy Technology Data Exchange (ETDEWEB)

    Knieper, A., E-mail: Alexander.Knieper@lbf.fraunhofer.de, E-mail: Christian.Beinert@lbf.fraunhofer.de; Beinert, C., E-mail: Alexander.Knieper@lbf.fraunhofer.de, E-mail: Christian.Beinert@lbf.fraunhofer.de [Group Polymer Processing, Division Plastics, Fraunhofer-Institute LBF (Germany)

    2014-05-15

    The initial melting of the first granules through plastic energy dissipation (PED) at the beginning of the melting zone, in the co-rotating twin-screw extruder is visualized in this work. The visualization was created through the use of a high speed camera in the cross section of the melting zone. The parameters screw speed, granule-temperature, temperature-profile, type of polymer and back pressure were examined. It was shown that the screw speed and the temperature-profile have significant influence on the rate of initial melting.

  19. Posterior lumbar inter-body fusion (PLIF) using autogenous bone and cage with pedicle screw instrumentation versus PLIF using cage with pedicle screw instrumentation in adult spondylolisthesis

    Institute of Scientific and Technical Information of China (English)

    Dou Yusheng; Hao Dingjun; Wen Shiming

    2005-01-01

    Objective: To compare the clinical outcomes of PLIF using autogenous bone and cage with pedicle screw fixation (group 2) and simple cage fusion with pedicle screw fixation (group 1) in adult spondylolisthesis.Methods: 27 patients with minimum follow-up of 24 months, treated by inter-body fusion with pedicle screw fixation were prospectively studied. Disc space height, degree of slippage and fusion rate had been compared before and after operation between the two groups. Results: After minimum 24 month's follow-up, there was no significant difference between the two groups in terms of the amount of blood loss, duration of hospital stay, back pain,radiating pain, fusion rate, or complication (P>0.05). however, there was a significant difference between the two groups in terms of disc space height and percentage of slippage (P<0.05). Conclusion: PLIF using autogenous bone and cage with pedicle screw fixation more beneifical to improve fusion rate and prevent long-term instabilities than simple cage fusion with pedicle screw fixation in adult spondylolisthesis.

  20. Monoaxial Pedicle Screws Are Superior to Polyaxial Pedicle Screws and the Two Pin External Fixator for Subcutaneous Anterior Pelvic Fixation in a Biomechanical Analysis

    Directory of Open Access Journals (Sweden)

    Rahul Vaidya

    2013-01-01

    Full Text Available Purpose. Comparison of monoaxial and polyaxial screws with the use of subcutaneous anterior pelvic fixation. Methods. Four different groups each having 5 constructs were tested in distraction within the elastic range. Once that was completed, 3 components were tested in torsion within the elastic range, 2 to torsional failure and 3 in distraction until failure. Results. The pedicle screw systems showed higher stiffness (4.008 ± 0.113 Nmm monoaxial, 3.638 ± 0.108 Nmm Click-x; 3.634 ± 0.147 Nmm Pangea than the exfix system (2.882 ± 0.054 Nmm in distraction. In failure testing, monoaxial pedicle screw system was stronger (360 N than exfixes (160 N and polyaxial devices which failed if distracted greater than 4 cm (157 N Click-x or 138 N Pangea. The exfix had higher peak torque and torsional stiffness than all pedicle systems. In torsion, the yield strengths were the same for all constructs. Conclusion. The infix device constructed with polyaxial or monoaxial pedicle screws is stiffer than the 2 pin external fixator in distraction testing. In extreme cases, the use of reinforcement or monoaxial systems which do not fail even at 360 N is a better option. In torsional testing, the 2 pin external fixator is stiffer than the pedicle screw systems.

  1. REM sleep rescues learning from interference.

    Science.gov (United States)

    McDevitt, Elizabeth A; Duggan, Katherine A; Mednick, Sara C

    2015-07-01

    Classical human memory studies investigating the acquisition of temporally-linked events have found that the memories for two events will interfere with each other and cause forgetting (i.e., interference; Wixted, 2004). Importantly, sleep helps consolidate memories and protect them from subsequent interference (Ellenbogen, Hulbert, Stickgold, Dinges, & Thompson-Schill, 2006). We asked whether sleep can also repair memories that have already been damaged by interference. Using a perceptual learning paradigm, we induced interference either before or after a consolidation period. We varied brain states during consolidation by comparing active wake, quiet wake, and naps with either non-rapid eye movement sleep (NREM), or both NREM and REM sleep. When interference occurred after consolidation, sleep and wake both produced learning. However, interference prior to consolidation impaired memory, with retroactive interference showing more disruption than proactive interference. Sleep rescued learning damaged by interference. Critically, only naps that contained REM sleep were able to rescue learning that was highly disrupted by retroactive interference. Furthermore, the magnitude of rescued learning was correlated with the amount of REM sleep. We demonstrate the first evidence of a process by which the brain can rescue and consolidate memories damaged by interference, and that this process requires REM sleep. We explain these results within a theoretical model that considers how interference during encoding interacts with consolidation processes to predict which memories are retained or lost.

  2. Parasitic interference in nulling interferometry

    CERN Document Server

    Matter, Alexis; Danchi, William C; Lopez, Bruno; Absil, Olivier

    2013-01-01

    Nulling interferometry aims to detect faint objects close to bright stars. Its principle is to produce a destructive interference along the line-of-sight so that the stellar flux is rejected, while the flux of the off-axis source can be transmitted. In practice, various instrumental perturbations can degrade the nulling performance. Any imperfection in phase, amplitude, or polarization produces a spurious flux that leaks to the interferometer output and corrupts the transmitted off-axis flux. One of these instrumental pertubations is the crosstalk phenomenon, which occurs because of multiple parasitic reflections inside transmitting optics, and/or diffraction effects related to beam propagation along finite size optics. It can include a crosstalk of a beam with itself, and a mutual crosstalk between different beams. This can create a parasitic interference pattern, which degrades the intrinsic transmission map - or intensity response - of the interferometer. In this context, we describe how this instrumental ...

  3. Silicon superconducting quantum interference device

    Energy Technology Data Exchange (ETDEWEB)

    Duvauchelle, J. E.; Francheteau, A.; Marcenat, C.; Lefloch, F., E-mail: francois.lefloch@cea.fr [Université Grenoble Alpes, CEA - INAC - SPSMS, F-38000 Grenoble (France); Chiodi, F.; Débarre, D. [Université Paris-sud, CNRS - IEF, F-91405 Orsay - France (France); Hasselbach, K. [Université Grenoble Alpes, CNRS - Inst. Néel, F-38000 Grenoble (France); Kirtley, J. R. [Center for probing at nanoscale, Stanford University, Palo Alto, California 94305-4045 (United States)

    2015-08-17

    We have studied a Superconducting Quantum Interference Device (SQUID) made from a single layer thin film of superconducting silicon. The superconducting layer is obtained by heavily doping a silicon wafer with boron atoms using the gas immersion laser doping technique. The SQUID is composed of two nano-bridges (Dayem bridges) in a loop and shows magnetic flux modulation at low temperature and low magnetic field. The overall behavior shows very good agreement with numerical simulations based on the Ginzburg-Landau equations.

  4. Interference Mitigation in Cognitive Femtocells

    DEFF Research Database (Denmark)

    Da Costa, Gustavo Wagner Oliveira; Cattoni, Andrea Fabio; Alvarez Roig, Victor;

    2010-01-01

    in densely deployed femto scenarios. In this paper, two key elements of cognitive femtocells are combined: a power control algorithm and a fully distributed dynamic spectrum allocation method. The resulting solution was evaluated through system-level simulations and compared to the separate algorithms...... and fixed frequency reuses. The outage throughput performance of the combined algorithm exceeds all other options, proving the efficiency of the method in reducing inter-cell interference....

  5. RNA干扰%RNA Interference

    Institute of Scientific and Technical Information of China (English)

    陈颖; 朱明华

    2003-01-01

    RNA干扰(RNA interference,RNAi)是一种古老的生物抗病毒机制,能介导序列特异性的mRNA降解,是基因功能研究和蛋白组学的有效工具,在药物靶基因的筛选、抗病毒、肿瘤基因治疗等领域有很好的发展前景.

  6. CRISPR interference: a structural perspective

    Science.gov (United States)

    Reeks, Judith; Naismith, James H.; White, Malcolm F.

    2013-01-01

    CRISPR (cluster of regularly interspaced palindromic repeats) is a prokaryotic adaptive defence system, providing immunity against mobile genetic elements such as viruses. Genomically encoded crRNA (CRISPR RNA) is used by Cas (CRISPR-associated) proteins to target and subsequently degrade nucleic acids of invading entities in a sequence-dependent manner. The process is known as ‘interference’. In the present review we cover recent progress on the structural biology of the CRISPR/Cas system, focusing on the Cas proteins and complexes that catalyse crRNA biogenesis and interference. Structural studies have helped in the elucidation of key mechanisms, including the recognition and cleavage of crRNA by the Cas6 and Cas5 proteins, where remarkable diversity at the level of both substrate recognition and catalysis has become apparent. The RNA-binding RAMP (repeat-associated mysterious protein) domain is present in the Cas5, Cas6, Cas7 and Cmr3 protein families and RAMP-like domains are found in Cas2 and Cas10. Structural analysis has also revealed an evolutionary link between the small subunits of the type I and type III-B interference complexes. Future studies of the interference complexes and their constituent components will transform our understanding of the system. PMID:23805973

  7. Improved Linear Parallel Interference Cancellers

    CERN Document Server

    Srikanth, T; Chockalingam, A; Milstein, L B

    2007-01-01

    In this paper, taking the view that a linear parallel interference canceller (LPIC) can be seen as a linear matrix filter, we propose new linear matrix filters that can result in improved bit error performance compared to other LPICs in the literature. The motivation for the proposed filters arises from the possibility of avoiding the generation of certain interference and noise terms in a given stage that would have been present in a conventional LPIC (CLPIC). In the proposed filters, we achieve such avoidance of the generation of interference and noise terms in a given stage by simply making the diagonal elements of a certain matrix in that stage equal to zero. Hence, the proposed filters do not require additional complexity compared to the CLPIC, and they can allow achieving a certain error performance using fewer LPIC stages. We also extend the proposed matrix filter solutions to a multicarrier DS-CDMA system, where we consider two types of receivers. In one receiver (referred to as Type-I receiver), LPIC...

  8. The results of ankle arthrodesis with screws for end stage ankle arthrosis.

    Science.gov (United States)

    Torudom, Yingyong

    2010-02-01

    Aim of this study was to evaluate the results of ankle arthrodesis with screws in patients with ankle arthrosis. The author studied 19 patients (20 feet) who had been treated by ankle arthrodesis with screws from 2003 to 2008. Ten patients were men (11 feet) and nine (9 feet) were women. Their mean age was 56 years (30 to 65), and the average duration of follow-up was four years (2 to 6). Two compression screws were used in all feet. Union was achieved in 19 of the 20 feet (95%). Average scores for pain and clinical condition are increase after operation. One re-operation was performed for nonunion. Author conclude that ankle arthrodesis with screws was effective treatment for ankle arthrosis.

  9. Screw fixation for atlantoaxial dislocation related to Down syndrome in children younger than 5 years.

    Science.gov (United States)

    Ito, Kenyu; Imagama, Shiro; Ito, Zenya; Ando, Kei; Kobayashi, Kazuyoshi; Hida, Tetsuro; Ishikawa, Yoshimoto; Ishiguro, Naoki

    2017-01-01

    The aim of this study was to present cases of upper cervical fixation in Down syndrome patients younger than 5 years. In two cases, C1 lateral mass screws were installed. However, owing to the irreducible atlantoaxial dislocation, the screw backed out and fractured. Therefore, O-C2 fusion was performed. Furthermore, C2 bilateral lamina screws were added to the C2 pedicle screw for reinforcement. C1-C2 fusion is an option for Down syndrome patients younger than 5 years with atlantoaxial dislocation, when the dislocation is reducible. If the dislocation is irreducible, or the implant cannot be firmly secured, the fixation range should be expanded to O-C2 or below.

  10. 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.)

  11. Extracapsular hip fractures: fixation with a twin hook or a lag screw?

    Science.gov (United States)

    Olsson, O; Ceder, L; Lunsjö, K; Hauggaard, A

    2000-01-01

    The twin hook, which has 2 oppositely directed apical hooks, is an alternative to the lag screw for use with a 'dynamic plate' in the fixation of trochanteric hip fractures. In this prospective study lasting 1 year, 102 consecutive patients with trochanteric hip fractures were treated by 19 surgeons with either a twin hook or a lag screw combined with a conventional sliding hip screw plate or a Medoff sliding plate. Seven intraoperative errors were made with the twin hook but postoperative migration did not differ significantly between the 2 groups. Postoperative fixation failures were equally distributed between the 2 groups. The twin hook provides adequate fixation, which is comparable to that produced by a lag screw.

  12. A study of the bone healing kinetics of plateau versus screw root design titanium dental implants.

    LENUS (Irish Health Repository)

    Leonard, Gary

    2009-03-01

    This study was designed to compare the bone healing process around plateau root from (PRF) and screw root from (SRF) titanium dental implants over the immediate 12 week healing period post implant placement.

  13. Magnesium-Based Compression Screws: A Novelty in the Clinical Use of Implants

    Science.gov (United States)

    Seitz, Jan-Marten; Lucas, Arne; Kirschner, Martin

    2016-04-01

    Magnesium alloys are currently subject to much research for use in biodegradable implant applications. The challenge in this field of material development comprises the design of an alloy that provides adequate mechanical and corrosion properties combined with an excellent biocompatibility. While there are many approaches in current literature only one Mg-based application shows the potential to hit the market. MAGNEZIX® Compression Screws are the world's first approved/CE-certified magnesium-based implants designed for use in biodegradable osteosyntheses applications in humans. Therefore, this paper focusses on challenges and current clinical results achieved by means of degradable compression screws. Insights into the screws' process chain and approval processes are given. As these innovative screws have already been on the market for 2 years long-term results based on their use in surgery are discussed.

  14. ADOLESCENT IDIOPATHIC SCOLIOSIS: EVALUATION ON THE EFFECT OF SCREW DENSITY IN THE CORRECTION

    Directory of Open Access Journals (Sweden)

    Enguer Beraldo Garcia

    2016-03-01

    Full Text Available ABSTRACT Objective: The objective was to investigate implant density or the number of screws correlated with the correction of the main curve in patients undergoing surgery for adolescent idiopathic scoliosis (AIS. Methods: We evaluated 112 medical records: 33 patients with screw density of up to 50%, and 79 patients with a density of 100%; all patients underwent surgical correction by posterior approach with transpedicular fixation. Results: In the group of patients with screw density of up to 50% the residual Cobb median was 10°; in the group with 100% density, the median was 7°. Conclusion: Biostatistical analysis showed that the group with up to 50% of screw density presented correction rate of 82.1% and the group with 100% density had correction of about 86.8%. It is therefore concluded that the difference is statistically significant in favor of the fixation with 100% density (p =0.010.

  15. In vivo study of extracellular matrix coating enhancing fixation of the pedicle screw-bone's interface

    Institute of Scientific and Technical Information of China (English)

    LIU Guo-min; ZHANG Xing-yi; XU Chuan-jie; ZHU Xiao-min; WANG Jun; LIU Yi

    2011-01-01

    Background Based on in vivo research on the effect of the coating of the extracellular matrix composition of pedicle screws on the conduction and induction of bone formation in young sheep,the aim of this study was to investigate the application of coated pedicle screws in sheep with scoliosis whose spines are under constant development.Methods Four groups of pedicle screws were randomly implanted into bilateral L2-L5 pedicles of 2.5- to 3-month-old sheep.A static experiment was performed on one side and a loading test was performed on the other side by implanting connecting rods at the L2-L3 and L4-L5 segments.The changes in the force on the coated screws and the combination of the surface of the coated screws with the surrounding bone in the growth process of young sheep's spines with aging were observed.After 3 months,the lumbar vertebrae with the screws were removed and examined by micro-CT,histological,and biomechanical analyses.Results Under nonloading conditions,there is bone formation around the surfaces of coated screws.The bone forming on the surface of collagen/chondroitin sulfate/hydroxyapatite coating of pedicle screws is the most,the one of the collagen / chondrcitin sulfate coating and hydroxyapatite coating is followed,and no significant difference between the two groups.In terms of the trabecular bone morphology parameters of the region of interest around the surface of the pedicle screws,such as bone mineral content,bone mineral density,tissue mineral content,tissue bone mineral density,bone volume fraction,and connection density,those associated with collagen/chondroitin sulfate/hydroxyapatite coatings are largest and those unassociated with coatings are smallest.Under nonloading conditions,the pullout strength of the collagen/chondroitin sulfate/hydroxyapatite-coated screws was largest,and that of the uncoated screws was minimal (P <0.01).Under loading conditions,the maximum pullout strength of each group of pedicle screws was less than that

  16. 49 CFR 193.2633 - Interference currents.

    Science.gov (United States)

    2010-10-01

    ...: FEDERAL SAFETY STANDARDS Maintenance § 193.2633 Interference currents. (a) Each component that is subject to electrical current interference must be protected by a continuing program to minimize...

  17. Study of Bone-screw Surface Fixation in Lumbar Dynamic Stabilization

    Institute of Scientific and Technical Information of China (English)

    Yun-Gang Luo; Tao Yu; Guo-Min Liu; Nan Yang

    2015-01-01

    Background:We aimed to use the animal model of dynamic fixation to examine the interaction of the pedicle screw surface with surrounding bone,and determine whether pedicle screws achieve good mechanical stability in the vertebrae.Methods:Twenty-four goats aged 2-3 years had Cosmic(R) pedicle screws implanted into both sides of the L2-L5 pedicles.Twelve goats in the bilateral dynamic fixation group had fixation rods implanted in L2-L3 and L4-L5.Twelve goats in the unilateral dynamic fixation group had fixation rods randomly fixed on one side of the lumbar spine.The side that was not implanted with fixation rods was used as a static control group.Results:In the static control group,new bone was formed around the pedicle screw and on the screw surface.In the unilateral and bilateral dynamic fixation groups,large amounts of connective tissue formed between and around the screw threads,with no new bone formation on the screw surface; the pedicle screws were loose after the fixed rods were removed.The bone mineral density and morphological parameters of the region of interest (ROI) in the unilateral and bilateral dynamic fixation group were not significantly different (P > 0.05),but were lower in the fixed groups than the static control group (P < 0.05).This showed the description bone of the ROI in the static control group was greater than in the fixation groups.Under loading conditions,the pedicle screw maximum pull force was not significantly different between the bilateral and unilateral dynamic fixation groups (P > 0.05); however the maximum pull force of the fixation groups was significantly less than the static control group (P < 0.01).Conclusions:Fibrous connective tissue formed at the bone-screw interface under unilateral and bilateral pedicle dynamic fixation,and the pedicle screws lost mechanical stability in the vertebrae.

  18. Interference of processing variables on the mechanical behavior of nano composites HDPE/clay; Interferencia das variaveis de processamento no comportamento mecanico de nanocompositos PEAD/argila

    Energy Technology Data Exchange (ETDEWEB)

    Barbosa, R. [Universidade Federal do Piaui, Teresina, PI (Brazil); Souza, D.D.; Nobrega, K.C.; Araujo, E.M.; Melo, T.J. [Universidade Federal de Campina Grande - UAEMa Campina Grande, PB (Brazil)

    2010-07-01

    Nano composites were processed using the technique of melt intercalation, starting from a concentrated polar compatibilizer / organo clay (PE-g-MA / organo clay) prepared in an internal mixer. The concentrate was incorporated into the matrix of PEAD by two methods: (I) twin screw contrarrotational extruder and (II) twin screw corrotational extruder, using two thread profiles (ROS and 2KB90), after extrusion, the specimens of the extruded composites were injection molded. The diffraction of X-ray was used to analyze the degree of expansion of the clays prepared, and the degree of exfoliation of nano composites developed. The interference of processing variables on mechanical properties was studied by the behavior of the modulus and tensile strength of nano composite systems. Observed similar behavior in the use of thread (or 2KB90 ROS) of the nano composites, with a reduction in modulus and tensile strength. (author)

  19. Distributed Interference Alignment with Low Overhead

    CERN Document Server

    Ma, Yanjun; Chen, Rui

    2011-01-01

    Based on closed-form interference alignment (IA) solutions, a low overhead distributed interference alignment (LOIA) scheme is proposed in this paper for the $K$-user SISO interference channel, and extension to multiple antenna scenario is also considered. Compared with the iterative interference alignment (IIA) algorithm proposed by Gomadam et al., the overhead is greatly reduced. Simulation results show that the IIA algorithm is strictly suboptimal compared with our LOIA algorithm in the overhead-limited scenario.

  20. Canceling Stationary Interference Signals Exploiting Secondary Data

    OpenAIRE

    Swärd, Johan; Jakobsson, Andreas

    2014-01-01

    In this paper, we propose a novel interference cancellation method that exploits secondary data to estimate stationary interference components present in both the primary and the secondary data sets, thereby allowing for the removal of such interference from the data sets, even when these components share frequencies with the signal of interest. The algorithm estimates the present interference components one frequency at a time, thus enabling for a computationally efficient algorithm, that re...

  1. Design of three-dimensional visualization based on the posterior lumbar pedicle screw fixation

    Directory of Open Access Journals (Sweden)

    Kai XU

    2011-09-01

    Full Text Available Objective To establish a three-dimensional visualization model of posterior lumbar pedicle screw fixation.Methods A patient with lumbar intervertebral disc hernia and another patient with compression fracture of lumbar vertebra were involved in the present study.Both patients underwent multi-slice spiral CT scan before and after lumbar pedicle screw fixation.The degree of preoperative vertebral compression,vertebral morphology before and after surgery,postoperative pedicle screw position,and decompression effects were observed.The original data of the multi-slice spiral CT were inputted into the computer.The three-dimensional reconstructed images of the lumbar and implanted screws were obtained using the software Amira 4.1 to show the three-dimensional shape of the lumbar vertebrae before and after surgery and the location of the implanted screws.Results The morphology and structure of the lumbar vertebrae before and after surgery and of the implanted screws were reconstructed using the digital navigation platform.The reconstructed 3D images could be displayed in multicolor,transparent,or arbitrary combinations.In the 3D surface reconstruction images,the location and structure of the implanted screws could be clearly observed,and the decompression of the spinal cord or nerve roots and the severity of the fracture and the compression of lumbar vertebrae could be fully evaluated.The reconstructed images before operation revealed the position of the vertebral pedicles and provided reference for intraoperative localization.Conclusions The three-dimensional computerized reconstructions of lumbar pedicle screw fixation may be valuable in basic research,clinical experiment,and surgical planning.The software Amira is one of the bases of three-dimensional reconstruction.

  2. Mechanical behaviour of aluminum screws. Pt. 2. Cyclic behaviour; Tragfaehigkeit von Aluminiumschrauben. T. 2. Zyklische Tragfaehigkeit

    Energy Technology Data Exchange (ETDEWEB)

    Weber, J.O. [Deutscher Schraubenverband, Hagen (Germany); Marx, T. [Adam Opel AG, Ruesselsheim (Germany); Berger, C. [Zentrum fuer Konstruktionswerkstoffe, Institut fuer Werkstoffkunde der Technischen Universitaet Darmstadt (Germany); Arz, U.

    2011-03-15

    This article is the second part of a description of the mechanical behaviour of aluminum screws. The first part describes the mechanical behaviour under static conditions, while the second part details the cyclic behaviour. An overview of the influences to the cyclic behaviour of high strength aluminum screws made of the wrought alloys EN AW 6013, EN AW 6056 and EN AW 7075 is given. In some cases values for EN AW 6082 are presented.

  3. Pseudoaneurysm of profunda femoris artery following dynamic hip screw fixation for intertrochanteric femoral fracture

    Institute of Scientific and Technical Information of China (English)

    Shailendra Singh; Sumit Arora; Ankit Thora; Ram Mohan; Sumit Sural; Anil Dhal

    2013-01-01

    Dynamic hip screw fixation is a commonly performed procedure for internal fixation of intertrochanteric femoral fractures.Arterial injury following the operative fixation is a rare but serious event.We present a patient who developed pseudoaneurysm of profunda femoris artery after internal fixation of intertrochanteric fracture with a dynamic hip screw.The diagnosis was confirmed by angiographic study and it was successfully treated by coil embolization.

  4. Analysis of human mandibular mechanics based on screw theory and in vivo data.

    Science.gov (United States)

    Gal, J A; Gallo, L M; Palla, S; Murray, G; Klineberg, I

    2004-09-01

    In this paper the mechanics of human mandibular function is described in terms of the associated screws. The two distinct, yet related features of jaw mechanics, involving the motion itself as well as the forces, are both functions of the anatomical constraints, namely the contact areas that exist within the temporomandibular joint, and the forces of the muscles and tendons that allow motion to occur. The relationships that exist between these two aspects of jaw-motion are identified in this paper showing that muscle forces can be uniquely represented in terms of the action screw. This new approach to analyzing the mechanics of jaw-motion also incorporates the previously studied motion screw or helical axis. A consistent dynamic model is formulated where the action screw is used to represent the action of the closing muscle forces while the moment arms of the muscle forces are determined about the motion screw representing mandibular kinematics. The action screw formulation is verified using in vivo motion data and MR image information for a single asymptomatic subject. The results confirm the feasibility of the method and its application in dental research. A general increase in the mechanical advantage of most muscles, in the distance between action and motion screws as well as in the expended energy towards the end of the jaw-closing phase was observed. Asymmetries in the distribution of muscle force magnitudes appeared to influence the resultant force and moment of the action screw but had little effect on its spatial location. The method presented is intended to facilitate understanding of mandibular function and dysfunction.

  5. Edge screw withdrawal resistance in conventional particleboard and OSB: Influence of the particles type

    Directory of Open Access Journals (Sweden)

    Miljković Jovan

    2007-01-01

    Full Text Available This research was based on presumption that the changes in size and shape of wood particles are expected to have certain impact on the particleboard quality in general. Since the conventional particleboard (PB and oriented strand board (OSB were built of the quite diverse wood particles, they present interesting specimens in the comparison tests. In this work, the influence of the wood particles type on the edge screw holding performance of conventional particleboard and OSB was investigated. Those tests were obtained with the screw diameters of 4.0 mm, 4.5 mm and 5 mm. Depth of embedment was 30 mm for all tests and with the pilot-hole diameter kept in the range of 80-90% in respect of the screw root diameter. Additional tests of the thickness density profile and tensile strength perpendicular to the surface of the board were conducted. Since the middle layer structure of the particleboard embeds the screw body, both mentioned parameters are considered important in the aspect of the quality of the edge screw holding performance. In order to have further insight into the conformation of the middle layer the image survey was obtained on the split board section presenting the surface of the middle layer. Significant differences in the SWR performance of OSB and PB was recorded at all screw diameters. For the screw withdrawal tests parameters OSB samples showed 56-73% superior mean values then conventional PB. On the other hand, the OSB showed wider dispersions of measured withdrawal forces at all screw diameters, which might present some of the problems in certain engineering and project calculations.

  6. Degradation behaviour of LAE442-based plate–screw-systems in an in vitro bone model

    Energy Technology Data Exchange (ETDEWEB)

    Wolters, Leonie [Small Animal Clinic, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559 Hannover (Germany); Besdo, Silke [Institute of Continuum Mechanics, Leibniz Universität Hannover, Appelstraße 11, 30167 Hannover (Germany); Angrisani, Nina [Small Animal Clinic, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559 Hannover (Germany); Wriggers, Peter [Institute of Continuum Mechanics, Leibniz Universität Hannover, Appelstraße 11, 30167 Hannover (Germany); Hering, Britta [Institute of Production Engineering and Machine Tools, Leibniz Universität Hannover, An der Universität 2, 30823 Garbsen (Germany); Seitz, Jan-Marten [Institute of Materials Science, Leibniz Universität Hannover, An der Universität 2, 30823 Garbsen (Germany); Reifenrath, Janin, E-mail: janin.reifenrath@tiho-hannover.de [Small Animal Clinic, University of Veterinary Medicine Hannover, Foundation, Bünteweg 9, 30559 Hannover (Germany)

    2015-04-01

    The use of absorbable implant materials for fixation after bone fracture helps to avoid a second surgery for implant removal and the risks and costs involved. Magnesium (Mg) is well known as a potential metallic material for degradable implants. The aim of the present in vitro study was to evaluate if degradable LAE442-based magnesium plate–screw-systems are suitable candidates for osteosynthesis implants in load-bearing bones. The corrosion behaviour was tested concerning the influence of different surface treatments, coatings and screw torques. Steel plates and screws of the same size served as control. Plates without special treatment screwed on up to a specified torque of 15 cNm or 7 cNm, NaOH treated plates (15 cNm), magnesium fluoride coated plates (15 cNm) and steel plates as control (15 cNm) were examined in pH-buffered, temperature-controlled SBF solution for two weeks. The experimental results indicate that the LAE442 plates and screws coated with magnesium fluoride revealed a lower hydrogen evolution in SBF solution as well as a lower weight loss and volume decrease in μ-computed tomography (μCT). The nanoindentation and SEM/EDX measurements at several plate areas showed no significant differences. Summarized, the different screw torques did not affect the corrosion behaviour differently. Also the NaOH treatment seemed to have no essential influence on the degradation kinetics. The plates coated with magnesium fluoride showed a decreased corrosion rate. Hence, it is recommended to consider this coating for the next in vivo study. - Highlights: • Mg-based plate screw systems were examined in an in vitro corrosion setup. • Different screw torques did not affect the corrosion behaviour. • Pretreatment with NaOH showed no increase in corrosion resistance. • Fluoride coating slowed down the corrosion rate of plates. • Fluoride coating might be an alternative for decrease of corrosion rate in vivo.

  7. Selected Methods for Locking Screw Joints, Including the Use of Adhesives, Used in the Helicopter Construction

    Science.gov (United States)

    Rudawska, Anna; Cisz, Sławomir; Warda, Tomasz

    2014-12-01

    The paper presents the problems of preventing screw joints from self-loosening on one of helicopter. The research examines selected locking methods used in aircraft produced by different manufacturers. Experimental tests were performed to investigate the loosening torque of screw joints locked by various devices: cotter pin, locknut, centre punching, self-locking nut and adhesive. A comparative analysis of the investigated locking methods is made with respect to their locking strength and efficiency.

  8. Posterior fixation and fusion with atlas pedicle screw system for upper cervical diseases

    Institute of Scientific and Technical Information of China (English)

    LI Lei; ZHOU Feng-hua; WANG Huan; CUI Shao-qian

    2008-01-01

    Objective: To evaluate the feasibility, safety and efficacy of atlas pedicle screws system fixation and fusion for the treatment of upper cervical diseases. Methods: Twenty-three consecutive patients with up-per cervical disorders requiring stabilization, including 19 cases of atlantoaxial dislocation (4 congenital odontoid disconnections, 6 old odontoid fractures, 4 fresh odontoid fractures of Aderson Ⅱ C, 3 ruptures of the C1 transverse ligament, and 2 fractures ofC1), 2 cases ofC2 tumor (instability after the resection of the tumors), and 2 giant neurilemomas of C2-C3(instability after resection of the tumors), were treated by posterior fixation and fusion with the atlas pedicle screw system, in which the screws were inserted through the posterior arch of Cr The operative time, bleeding volume and complications were reported. All patients were immobilized without external fixation or with rigid cervical collars for 1-3 months. All patients were followed up and evaluated with radiographs and CT. Results: In the 23 patients, 46 C1 pedicle screws, 42 C2 pedicle screws and 6 lower cervical lateral mass screws and 2 lower cervical pedicle screws were placed. The mean operative time and bleeding volume was 2.7 hours and 490 ml respectively. No intraoperative complications were directly related to surgical technique. No neurological, vascular or infective complications were encountered. All patients were followed up for 3-36 months (average 15 months). Firm bony fusion was documented in all patients after 3-6 months. One patient with atlas fracture showed anterior occipitocervical fusion. There was no implant failure. Conclusions: Posterior fixation and fusion of the atlas pedicle screw system is feasible and safe for the treatment of upper cervical diseases, and may be applicable to a larger number of patients.

  9. Treatment of fractures of the condylar head with resorbable pins or titanium screws: an experimental study.

    Science.gov (United States)

    Schneider, Matthias; Loukota, Richard; Kuchta, Anne; Stadlinger, Bernd; Jung, Roland; Speckl, Katrin; Schmiedekampf, Robert; Eckelt, Uwe

    2013-07-01

    We aimed to compare in vivo the stability of fixation of condylar fractures in sheep using sonic bone welding and standard titanium screws. We assessed stability of the osteosynthesis and maintenance of the height of the mandibular ramus. Height decreased slightly in both groups compared with the opposite side. The volume of the condyle increased considerably in both groups mainly because callus had formed. The results showed no significant disadvantages for pin fixation compared with osteosynthesis using titanium screws.

  10. Comparison of organic rankine cycle systems under varying conditions using turbine and twin-screw expanders

    OpenAIRE

    Read, M. G.; Smith, I K; Stosic, N.; Kovacevic, A.

    2016-01-01

    A multi-variable optimization program has been developed to investigate the performance of Organic Rankine Cycles (ORCs) for low temperature heat recovery applications using both turbine and twin-screw expanders when account is taken of performance variation due to changes in ambient conditions. The cycle simulation contains thermodynamic models of both types of expander. In the case of the twin-screw machine, the methods used to match the operation of the expander to the requirements of the ...

  11. Pedicle screw placement accuracy of bone-mounted miniature robot system

    Science.gov (United States)

    Tsai, Tai-Hsin; Tzou, Rong-Dar; Su, Yu-Feng; Wu, Chieh-Hsin; Tsai, Cheng-Yu; Lin, Chih-Lung

    2017-01-01

    Abstract This article describes factors affecting the accuracy of transpedicle screw placements performed with the Renaissance robot-guided system and reviews the relevant literature. Between January 2013 and January 2015, Renaissance robot-guided spinal surgery was performed in 125 patients at Kaohsiung Medical University Hospital in Kaohsiung, Taiwan. The surgeries included 662 transpedicle screw implants and 49 Kirschner wire (K-wire) reimplants performed by intraoperative repositioning. The lead author evaluated the accuracy of all K-wire insertions and classified their accuracy into 3 categories relative to the preoperative plan for transpedicle screw placement. For cases in which screws required repositioning after the registration step, factors affecting pedicle screw placement were determined according to the consensus of 3 experienced spinal surgeons. According to the scheme developed by Kuo et al (PLoS One 2016;11:e0153235), the K-wire placement accuracies before and after repositioning were respectively classified as follows: 76.1% and 77.6% in type I; 12.2% and 17.7% in type IIa; 4.3% and 4.5% in type IIb; 6.4% and 0% in type IIIa; and 1% and 1% in type IIIb. The percentage of screws requiring repositioning due to drilling error was 85.7% (42/49). Comparisons of preoperative and postoperative function showed significantly improved accuracy. This study showed that inaccurate pedicle screw placement mainly results from errors in preoperative planning, mounting, registration, drilling, and robot assembly. Pedicle screw placement using a bone-mounted miniature robot system requires meticulous preoperative planning to minimize these errors. PMID:28099339

  12. Design of Cold-Formed Steel Screw Connections with Gypsum Sheathing at Ambient and Elevated Temperatures

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2016-09-01

    Full Text Available Load-bearing cold-formed steel (CFS walls sheathed with double layers of gypsum plasterboard on both sides have demonstrated good fire resistance and attracted increasing interest for use in mid-rise CFS structures. As the main connection method, screw connections between CFS and gypsum sheathing play an important role in both the structural design and fire resistance of this wall system. However, studies on the mechanical behavior of screw connections with double-layer gypsum sheathing are still limited. In this study, 200 monotonic tests of screw connections with single- or double-layer gypsum sheathing at both ambient and elevated temperatures were conducted. The failure of screw connections with double-layer gypsum sheathing in shear was different from that of single-layer gypsum sheathing connections at ambient temperature, and it could be described as the breaking of the loaded sheathing edge combined with significant screw tilting and the loaded sheathing edge flexing fracture. However, the screw tilting and flexing fracture of the loaded sheathing edge gradually disappear at elevated temperatures. In addition, the influence of the loaded edge distance, double-layer sheathing and elevated temperatures is discussed in detail with clear conclusions. A unified design formula for the shear strength of screw connections with gypsum sheathing is proposed for ambient and elevated temperatures with adequate accuracy. A simplified load–displacement model with the post-peak branch is developed to evaluate the load–displacement response of screw connections with gypsum sheathing at ambient and elevated temperatures.

  13. Alkaline-assisted screw press pretreatment affecting enzymatic hydrolysis of wheat straw.

    Science.gov (United States)

    Yan, Qingqi; Wang, Yumei; Rodiahwati, Wawat; Spiess, Antje; Modigell, Michael

    2017-02-01

    Screw press processing of biomass can be considered as a suitable mechanically based pretreatment for biofuel production since it disrupts the structure of lignocellulosic biomass with high shear and pressure forces. The combination with chemical treatment has been suggested to increase the conversion of lignocellulosic biomass to fermentable sugars. Within the study, the synergetic effect of alkaline (sodium hydroxide, NaOH) soaking and screw press pretreatment on wheat straw was evaluated based on, e.g., sugar recovery and energy efficiency. After alkaline soaking (at 0.1 M for 30 min) and sequential screw press pretreatment with various screw press configurations and modified screw barrel, the lignin content of pretreated wheat straw was quantified. In addition, the structure of pretreated wheat straw was investigated by scanning electron microscopy and measurement of specific surface area. It could be shown that removal of lignin is more important than increase of surface area of the biomass to reach a high sugar recovery. The rate constant of the enzymatic hydrolysis increased from 1.1 × 10(-3) 1/h for the non-treated material over 2.3 × 10(-3) 1/h for the alkaline-soaked material to 26.9 × 10(-3) 1/h for alkaline-assisted screw press pretreated material, indicating a nearly 25-fold improvement of the digestibility by the combined chemo-mechanical pretreatment. Finally, the screw configuration was found to be an important factor for improving the sugar recovery and for reducing the specific energy consumption of the screw press pretreatment.

  14. Cervical pedicle screw fixation at C6 and C7 A cadaveric study

    Directory of Open Access Journals (Sweden)

    Ye Li

    2015-01-01

    Conclusion: The intersection of the horizontal line through the midpoint of the transverse process root and vertical line through the intersection of the posterolateral and posterior planes of the isthmus can be used as an entry point for C6 and C7 pedicle screw fixation. The screws should be inserted at 60 or 90° with the posterolateral isthmus in the horizontal plane and at 75° with the posterior isthmus in the sagittal plane. The LSC should not exceed 30 mm.

  15. Initial experience with extreme angle cervical screw for treatment of trauma and cervical spondylosis.

    Science.gov (United States)

    Mehta, Ankit I; Babu, Ranjith; Bagley, Carlos A; Grossi, Peter M; Gottfried, Oren N

    2014-03-01

    In this study, we have described our initial experience and surgical technique of extreme angle screw placement in the cervical and upper thoracic spine of a cohort of patients undergoing posterior fusion. This extreme angle screw facilitates rod placement without need for any coronal contouring of the rod or offset connectors despite the varied entry site locations for posterior instrumentation and the different trajectories and pathways of these screws. From ruary 2011 to July 2011, extreme angle screws were placed in twenty consecutive adult patients who underwent posterior cervical, occipital-cervical or cervical-thoracic fusions. The primary diagnosis was cervical spondylotic myelopathy (13), trauma (4), and pseudoarthrosis with stenosis (3). Eight patients had gross instability. A total of 196 screws were placed; half of the cases involved instrumentation at or within the C3-7 segments (10) and the others included constructs extending to occipital bone, C2, T1, or T2 (10). Of all twenty cases, there were no perioperative hardware complications. At long-term follow-up, two patients required reoperation, one for hardware failure and the other for single level symptomatic pseudoarthrosis. We conclude that extreme angle screw use in the posterior cervical spine provides an evolution in posterior instrumentation that maximizes the biomechanical strength of a construct, allows for easy rod placement, and may improve the restoration of sagittal alignment. Overall, extreme angle screws facilitate rod placement even for screws offset from the natural plane of the rod, thereby avoiding the need for coronal contouring or placement of offset connectors.

  16. An accumulator model of semantic interference

    NARCIS (Netherlands)

    van Maanen, Leendert; van Rijn, Hedderik

    2007-01-01

    To explain latency effects in picture-word interference tasks, cognitive models need to account for both interference and stimulus onset asynchrony (SOA) effects. As opposed to most models of picture-word interference, which model the time course during the task in a ballistic manner, the RACE model

  17. Comparative analysis of pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis surgery

    Science.gov (United States)

    Rafi, Sohail; Munshi, Naseem; Abbas, Asad; Shaikh, Rabia Hassan; Hashmi, Imtiaz

    2016-01-01

    Introduction: Adolescent idiopathic scoliosis is the most common type of scoliosis. A Cobb angle of 50° will progress beyond the age of spinal maturity. Surgery over bracing is advised at a Cobb angle above or equal to 50°. The aim of surgery is to bring the Cobb angle down below 50° to prevent reprogression as well as improve the quality of life. The objective of the study is to analyze the efficacy and significance in lifestyle improvement of pedicle screw-only fixation system versus the more common hybrid instrumentation system used for the surgical treatment of adolescent idiopathic scoliosis. Materials and Methods: A prospective cohort study was conducted involving two groups of patients were included in the study. One group was operated with pedicle screw-only method while the other with hybrid instrumentation system. The pre- and post-operative Cobb's angles were taken across a follow-up of 4 years. An SRS-30 questionnaire was given in a yearly follow-up to assess the lifestyle improvement of the patient. Results: Pedicle screw-only method was significantly more effective in reducing Cobb's angle (P = 0.0487). It was showed less loss of correction (P = 0.009) pedicle screw-only surgery was also better at reducing thoracic curves (P = 0.001). There seemed a better recovery time with pedicle screw surgery (P = 0.003). Conclusion: Pedicle screws are more effective and durable than hybrid systems at when treating adolescent idiopathic scoliosis. PMID:27695235

  18. Recognizing knee pathologies by classifying instantaneous screws of the six degrees-of-freedom knee motion.

    Science.gov (United States)

    Wolf, Alon; Degani, Amir

    2007-05-01

    We address the problem of knee pathology assessment by using screw theory to describe the knee motion and by using the screw representation of the motion as an input to a machine learning classifier. The flexions of knees with different pathologies are tracked using an optical tracking system. The instantaneous screw parameters which describe the transformation of the tibia with respect to the femur in each two successive observation is represented as the instantaneous screw axis of the motion given in its Plücker line coordinates along with its corresponding pitch. The set of instantaneous screw parameters associated with a particular knee with a given pathology is then identified and clustered in R(6) to form a "signature" of the motion for the given pathology. Sawbones model and two cadaver knees with different pathologies were tracked, and the resulting screws were used to train a classifier system. The system was then tested successfully with new, never-trained-before data. The classifier demonstrated a very high success rate in identifying the knee pathology.

  19. Anterior transarticular screw fixation as a conventional operation for rigid stabilization

    Directory of Open Access Journals (Sweden)

    Manabu Sasaki

    2014-01-01

    Full Text Available Background: Anterior transarticular screw (ATS fixation is a useful surgical option for atlantoaxial (AA stabilization. This report presents a revised ATS method for AA fusion. Methods: A 79-year-old male presented with AA instability attributed both to an old odontoid fracture and severe degeneration of the lateral atlantoaxial joints (LAAJs. ATS fixation was performed through the conventional anterior cervical approach. The longest screw trajectories were planned preoperatively using multiplanar reconstruction computed tomography (CT scans, with entry points of the screws situated at the midpoint on the inferior border of the axial body. The surgical exposure was limited to opening at the entry points alone. Our retractor of choice was the Cusco speculum; it sufficiently secured space for utilizing the required instruments for screw placement while offering sufficient protection of soft tissues. Cannulated full-threaded bicortical screws stabilized the LAAJs. Screw insertion required a significant amount of coronal angulation up to the superior articular process of the atlas under open-mouth and lateral fluoroscopy image guidance. After ATS fixation, bone grafting was performed between the posterior laminae of the axis and the atlas through a conventional posterior approach. Results: Bony fusion between the atlas and the axis was confirmed radiographically. Arthrodesis of the LAAJs occurred despite no bone grafting. Conclusions: Rigid fixation of the LAAJs was obtained by our ATS technique, indicating that it is an alternative method for AA fixation when posterior rigid internal fixation is not applicable.

  20. Progressive slip after removal of screw fixation in slipped capital femoral epiphysis: two case reports

    Directory of Open Access Journals (Sweden)

    Engelsma Yde

    2012-11-01

    Full Text Available Abstract Introduction In slipped capital femoral epiphysis the femoral neck displaces relative to the head due to weakening of the epiphysis. Early recognition and adequate surgical fixation is essential for a good functional outcome. The fixation should be secured until the closure of the epiphysis to prevent further slippage. A slipped capital femoral epiphysis should not be confused with a femoral neck fracture. Case presentation Case 1 concerns a 15-year-old boy with an adequate initial screw fixation of his slipped capital femoral epiphysis. Unfortunately, it was thought that the epiphysis had healed and the screw was removed after 11 weeks. This caused new instability with a progressive slip of the femoral epiphysis and subsequently re-fixation and a subtrochanteric correction osteotomy was obligatory. Case 2 concerns a 13-year-old girl with persistent hip pain after screw fixation for slipped capital femoral epiphysis. The screw was removed as lysis was seen around the screw on the hip X-ray. This operation created a new unstable situation and the slip progressed resulting in poor hip function. A correction osteotomy with re-screw fixation was performed with a good functional result. Conclusion A slipped epiphysis of the hip is not considered ‘healed’ after a few months. Given the risk of progression of the slip the fixation material cannot be removed before closure of the growth plate.

  1. Conceptual framework for model-based analysis of residence time distribution in twin-screw granulation.

    Science.gov (United States)

    Kumar, Ashish; Vercruysse, Jurgen; Vanhoorne, Valérie; Toiviainen, Maunu; Panouillot, Pierre-Emmanuel; Juuti, Mikko; Vervaet, Chris; Remon, Jean Paul; Gernaey, Krist V; De Beer, Thomas; Nopens, Ingmar

    2015-04-25

    Twin-screw granulation is a promising continuous alternative for traditional batchwise wet granulation processes. The twin-screw granulator (TSG) screws consist of transport and kneading element modules. Therefore, the granulation to a large extent is governed by the residence time distribution within each module where different granulation rate processes dominate over others. Currently, experimental data is used to determine the residence time distributions. In this study, a conceptual model based on classical chemical engineering methods is proposed to better understand and simulate the residence time distribution in a TSG. The experimental data were compared with the proposed most suitable conceptual model to estimate the parameters of the model and to analyse and predict the effects of changes in number of kneading discs and their stagger angle, screw speed and powder feed rate on residence time. The study established that the kneading block in the screw configuration acts as a plug-flow zone inside the granulator. Furthermore, it was found that a balance between the throughput force and conveying rate is required to obtain a good axial mixing inside the twin-screw granulator. Although the granulation behaviour is different for other excipients, the experimental data collection and modelling methods applied in this study are generic and can be adapted to other excipients.

  2. Validation of a continuous granulation process using a twin-screw extruder.

    Science.gov (United States)

    Van Melkebeke, B; Vervaet, C; Remon, J P

    2008-05-22

    Using twin-screw granulation as particle size enlargement technique, the effect of modifying the screw configuration (number of mixing zones, configuration of kneading block) on granule quality, tablet properties and mixing efficiency was investigated. The amount of oversized agglomerates and yield was significantly influenced by the presence of an extra conveying element at the screw end. Changing the staggering angle of the kneading block significantly affected yield and granule friability. The 90 degrees configuration resulted in a lower yield and granule friability. Disintegration time was the only tablet property significantly influenced by the screw configuration as disintegration was significantly faster when an extra conveying element was placed at the screw end. The influence of tracer addition method (wet vs. dry) on mixing efficiency inside the extruder barrel was investigated by means of different tracers: riboflavin (0.05%) suspended in the granulation liquid and hydrochlorothiazide (2.5%) added separately as powder. Mixing efficiency in function of time and granule size (above and below 1400 microm) was tested using riboflavine sodium phosphate (0.05%) dissolved in the granulation liquid. Since a good mixing efficiency was obtained independent of tracer addition method, tracer solubility, granulation time and granule size, continuous granulation using a twin-screw extruder was identified as a robust process.

  3. Numerical and Experimental Investigation of Pressure Losses at Suction of a Twin Screw Compressor

    Science.gov (United States)

    Arjeneh, M.; Kovacevic, A.; Rane, S.; Manolis, M.; Stosic, N.

    2015-08-01

    Rotary twin screw machines are used in the wide range of industrial applications and are capable of handling single and multiphase fluids as compressors, expanders and pumps. Concentration of liquid in the inlet flow can influence the performance of the machine significantly. Characteristics of the multiphase flow at the suction of a screw compressor depend on the local flow velocities and concentration. Local flow velocity measurements inside the screw compressors are difficult to obtain. However other flow properties such as local pressures are easier to attain. It is therefore useful to carry out experiments with local pressure variations in the suction which can be used to validate the 3D numerical Computational Fluid Dynamic (CFD) models that could help in studying the single and multiphase flow behaviour in screw compressors. This paper presents experimental efforts to measure the local pressure losses inside the suction plenum of the screw compressor. Pressure variations are measured at 23 locations in the suction port at various operating conditions and compared with 3D CFD model. The grid generator SCORGTM was used for generating numerical mesh of rotors. The flow calculations were carried out using commercial 3D solver ANSYS CFX. It was found that the local pressure changes predicted by the CFD model are in the good agreement with measured pressures. This validated the use of CFD for modelling of the single phase flows in suction of screw machines.

  4. "Rolling" phenomenon in twin screw granulation with controlled-release excipients.

    Science.gov (United States)

    Thompson, M R; O'Donnell, K P

    2015-03-01

    The developed knowledge regarding use of twin screw granulators for continuous wet granulation has been primarily limited to immediate release formulations in the literature. The present study highlights an issue previously unreported for wet granulation with twin screw extruders when using formulations containing controlled-release (CR) excipients. Long (3-10 mm), twisted noodle-like granules can be produced in the presence of these excipients that are difficult to control and are anticipated to create complications in downstream unit operations to the granulator. Working with two different CR excipients, METHOCEL™ K4M and Kollidon® SR, each blended at different ratios with a mixture of 80% α-lactose monohydrate/20% microcrystalline cellulose, these unique particles were found to be produced in the conveying elements of the extruder, arising from a rolling action at the top of the screw flights. The CR excipients adhesively strengthen the wetted mass, forming this undesired granule shape such that they persisted to the exit of the machine; the shape appeared most strongly affected by screw speed, producing particles of higher aspect ratio as speed was increased. Adjusting the concentration of these CR excipients in the formulation, the flow rate or the type of compression element used in the screws proved ineffective in controlling the problem. Rather, a re-design of the extruder screws was required to prevent generation of these extended-form granules.

  5. Biomechanical evaluation of Caspar cervical screws: comparative stability under cyclical loading.

    Science.gov (United States)

    Gallagher, M R; Maiman, D J; Reinartz, J; Pintar, F; Yoganandan, N

    1993-12-01

    Anterior cervical instrumentation is used as an adjunct to bone fusion; however, definitive biomechanical data to support some applications and techniques are lacking. In the absence of supportive experimental data, posterior cortical penetration has been recommended with the Caspar system. Previously, we compared the axial pull-out strength of Caspar screws with and without posterior cortical penetration. This study compares the stability of unicortical versus bicortical screw penetration groups under cyclical loading simulating physiological flexion-extension. Caspar screws were placed in human cadaveric vertebrae with or without posterior cortical purchase. Each screw was separately tested, simulating flexion-extension to 200 cycles. Deformation time data allowed a direct comparison of screw "wobble" with and without posterior cortical purchase. The mean deformation differences between subcortical and bicortical groups were statistically significant and increased over time within both groups. Enhanced stability was noted with bicortical purchase throughout most of the examined range, becoming more pronounced over longer periods of cyclical loading. Significant (P < 0.05) increases in deformation over time were noted for both groups, suggesting potentially significant deterioration at the screw-bone interface, despite bicortical purchase. Such deterioration with repeated flexion-extension loading may be of concern in the use of Caspar plates in the presence of multicolumn instability.

  6. Preliminary experimental results of radiofrequency-cement-augmented and cannulated pedicle screws

    Directory of Open Access Journals (Sweden)

    Goost H

    2011-01-01

    Full Text Available The risk of cut-out of a pedicle screw is high in the presence of osteoporotic bone. In cadaver studies it was found that cement augmentation of pedicle screws markedly increases pullout forces. However, the use of conventional low viscosity vertebroplasty or kyphoplasty cement is associated with the risk of cement extravasation. The risk might be reduced by using high viscosity, radiofrequency-activated bone cement. After performing DEXA scans, six fresh-frozen vertebral bodies of different bone densities were obtained from cadavers. Two pedicle screws (WSI Expertise-Inject, Peter Brehm, Germany were placed in the pedicles. About 3 ml of radiofrequency-activated, ultra-high viscosity cement (ER2 Bone Cement, DFine Europe GmbH, Germany was injected through the right pedicle. The left pedicle screw was left uncemented and served as control. Axial pullout tests were performed using a material testing device (Zwick/Roell Zmartpro, Ulm, Germany. The tests revealed that cementaugmented pedicle screws were able to withstand markedly higher pullout forces. Extravasation of cement did not occur. The value of the study is limited by the fact that only six samples were investigated. Further cadaver studies and clinical evaluation will be needed in the future. However, this pilot study showed that combining cannulated pedicle screws with ultra-high viscosity bone cement is a successful approach. Revision due to cut-out and complications secondary to cement extravasation can be reduced by this method.

  7. Analysis of Sheet Metal Tapping Screw Fabrication Using a Finite Element Method

    Directory of Open Access Journals (Sweden)

    Shao-Yi Hsia

    2016-10-01

    Full Text Available The malformation of sheet metal tapping screw threads in the screw threading process increases the cost of screw threading dies and their maintenance. Die factories do not reveal their screw threading die design techniques, so production and maintenance processes are established by trial-and-error or worker experience and passing down such techniques and documenting quality control is difficult. In this study, screw thread forming design and process analysis were carried out by combining computer-aided design software with computer-aided metal forming analysis software. Simulation results were verified in an actual forming process. The sheet metal tapping screw forging size error was less than 0.90%, except at a sharp angle, which was associated with an error of 3.075%, thereby demonstrating the accuracy of the simulated forming process. The numerical analysis process can be utilized to shorten forming development time; to reduce the number of die tests, and to improve product quality and die service life, reducing the cost of development and promoting the overall competitiveness of the company.

  8. Management of Cannulated Screw Failure and Recurrent SCFE Displacement – Case Report

    Science.gov (United States)

    Jacobson, Nathan A; Feierabend, Siegfried P; Lee, Christopher L

    2014-01-01

    Introduction: SCFE occurs in 10 per 100,000 in some regions of the United States with the incidence continuing to increase. Percutaneous screw fixation is a well-accepted treatment for this disorder for over 20 years but management of complications is not well elucidated in the literature. Case Report: We describe a case where a traumatic unstable SCFE that was initially treated with closed reduction and fixation with a single transphyseal screw went on to hardware failure with recurrence of the deformity. The complication was successfully treated with closed reduction and re-cannulating the fractured screw within the epiphysis and extracting it using a conical extraction screw commonly referred to as an “easy out.” Three trans physeal screws were then placed for improved fixation strength. Follow-up at 9 months demonstrates a fused physis and no signs of avascular necrosis of the femoral head. Conclusion: Percutaneous management of SCFE screw breakage is possible utilizing specialized instruments and a precise and gentle manipulation preventing the need for more invasive treatments with their obligatory potential complications profile. PMID:27298941

  9. Simulation of Polymer Melt Flow Fields in Intermeshing Co-Rotating Three-Screw Extruders

    Institute of Scientific and Technical Information of China (English)

    HU Dong-dong; CHEN Jin-nan

    2006-01-01

    Three-dimension isothermal flows of polymer melt in the kneading blocks of triangularly-arranged and parallelly-arranged intermeshing co-rotating three-screw extruders are simulated using the finite element package POLYFLOW. Based on the velocity fields calculated, the particle trajectories in both machines are visualized using particle tracking technique. The numerical results indicate that the flow patterns in three-screw extruders are similar to those in twin-screw extruders. The triangularly-arranged three-screw extruder has the largest pumping capacity and also the highest extrusion stability in terms of flowrate fluctuation with screw rotation. The instantaneous mixing and cumulative residence time distribution (RTD) characteristics are also analyzed and compared with traditional intermeshing co-rotating twin-screw extruders. It is shown that the start section of the cumulative RTD curve for the triangularly-arranged machine has a small shoulder, which is attributed to the faster flow in the central region of this type of extruder.

  10. The Axial Nonlinear Vibration Analysis of Ball-screw about Machine Tool Feeding System

    Institute of Scientific and Technical Information of China (English)

    ZENG Hao-ran; LIU Nian-cong; YANG Jia-rui; CHEN Jian-long; GENG Wei-tao

    2016-01-01

    The forced state of the ball⁃screw of machine tool feeding system is analyzed. The ball⁃screw is simplified as Timoshenko beam and the differential equation of motion for the ball⁃screw is built. To obtain the axial vibration equation, the differential equation of motion is simplified using the assumed mode method. Axial vibration equation is in form of Duffing equation and has the characteristics of nonlinearity. The numerical simulation of Duffing equation is proceeded by MATLAB/Simulink. The effect of screw length, exciting force and damping coefficient are researched, and the axial vibration phase track diagram and Poincare section are obtained. The stability and period of the axial vibration are analyzed. The limit cycle of phase track diagram is enclosed. Axial vibration has two type⁃center singularity distributions on both sides of the origin. The singularity attracts vibration to reach a stable state, and Poincare section shows that axial vibration appears chaotic motion and quasi periodic motion or periodic motion. Singularity position changes with the vibration system parameters, while the distribution doesn′t change. The period of the vibration is enhanced with increasing frequency and damping coefficient. Test of the feeding system ball⁃screw axial vibration exists chaos movement. This paper provides a certain theoretical basis for the dynamic characteristic analysis of machine feeding system ball⁃screw and optimization of structural parameters.

  11. Comparative analysis of pedicle screw versus hybrid instrumentation in adolescent idiopathic scoliosis surgery

    Directory of Open Access Journals (Sweden)

    Sohail Rafi

    2016-01-01

    Full Text Available Introduction: Adolescent idiopathic scoliosis is the most common type of scoliosis. A Cobb angle of 50° will progress beyond the age of spinal maturity. Surgery over bracing is advised at a Cobb angle above or equal to 50°. The aim of surgery is to bring the Cobb angle down below 50° to prevent reprogression as well as improve the quality of life. The objective of the study is to analyze the efficacy and significance in lifestyle improvement of pedicle screw-only fixation system versus the more common hybrid instrumentation system used for the surgical treatment of adolescent idiopathic scoliosis. Materials and Methods: A prospective cohort study was conducted involving two groups of patients were included in the study. One group was operated with pedicle screw-only method while the other with hybrid instrumentation system. The pre- and post-operative Cobb's angles were taken across a follow-up of 4 years. An SRS-30 questionnaire was given in a yearly follow-up to assess the lifestyle improvement of the patient. Results: Pedicle screw-only method was significantly more effective in reducing Cobb's angle (P = 0.0487. It was showed less loss of correction (P = 0.009 pedicle screw-only surgery was also better at reducing thoracic curves (P = 0.001. There seemed a better recovery time with pedicle screw surgery (P = 0.003. Conclusion: Pedicle screws are more effective and durable than hybrid systems at when treating adolescent idiopathic scoliosis.

  12. 干式螺杆真空泵的螺杆设计与计算%Screw design and computing of dry twin-screw vacuum pump

    Institute of Scientific and Technical Information of China (English)

    周宝洪

    2001-01-01

    The article introduces design and computing of main parts of screw rotor of dry screw vacuum pump, and give the relative formula. Many modal products can be computed conveniently, if the data are substituted into the computing formula.%叙述了干式螺杆真空泵的核心零件螺杆的设计与计算,并导出了计算的有关公式,只要将参数代入,即可方便地计算出多规格产品。

  13. DEVELOPMENT OF ARCHIMEDEAN’S PIPE-SCREW FOR THAI SAIL WINDPUMP

    Directory of Open Access Journals (Sweden)

    Ronnakorn Thepwong

    2014-01-01

    Full Text Available This study describes new considerations in the design and development of Archimedean’s Pipe-Screw especially for water pumping in case of low head high volume form open farm pond at Rajamangala University of Technology Rattanakosin, Thailand. The objectives of this research is to develop an Archimedean’s Pipe-Screw especially for water pumping in case of low head high volume form open farm pond used for water pumping with Thai sail windmill, at any location of low wind speed of Thailand and tests the performance of an Archimedean’s Pipe-Screw Model (APSM. The experimental was carried out on diameter of Archimedean’s Pipe-Screw is Φ5/8”, the pitch Archimedean’s Pipe-Screw (P is 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8 and 2.0 D for angle slope of the screw with the horizontal (α is 20, 25, 30°C in laboratory scale Archimedean’s Pipe-Screw model. Archimedean’s Pipe-Screw tests were conducted to assess the performance of characteristics of Archimedean’s Pipe-Screw model. A model of pump has been manufactured; 1.0 m long with the blade small rubber tube was constructed. The output of the experiments recommenced for development the prototype of Archimedean’s Pipe-Screw for the Thai sail wind pump. The prototype of pump has been manufactured, 4.0 m long, 8 m diameter. This wind pump has twelve triangular sails sweeping a circle of 8 m diameter. For the construction of this Archimedean’s Pipe-Screw wind pump all efforts were made to use maximize materials and local parts available in the market for large scale of Archimedean’s screw-pipe for Thai sail wind pump. The cost of material and parts is 145,000 Baht excluding the cost of machining and fabrication. Water discharge was in the range 0.005-0.081 lps. It can be seen maximum water discharge of pitch Archimedean’s Pipe-Screw (P is 1.4D at 80 rpm for α = 20° was 0.081 lps. For the result of prototype of Archimedean’s Pipe-Screw for Thai sail wind pump, it was found that the

  14. MANAGEMENT OF DISTAL FEMORAL FRACTURES USING DYNAMIC CONDYLAR SCREWS

    Directory of Open Access Journals (Sweden)

    Ambrish

    2015-11-01

    Full Text Available BACKGROUND Fractures of distal end of femur are complex injuries which are difficult to manage & are unstable and comminuted. Despite advances in implants treatment of distal femoral fractures remains a challenge. AIMS This study was done to analyze the functional outcome & complications associated with surgical management of fractures of distal end of femur in adults using Dynamic Condylar Screw (DCS. SETTINGS & DESIGN It was a prospective clinical study done at BMCH, Chitradurga. METHODS The present study included 25 patients with 13 Supracondylar and 12 Intercondylar fractures of femur. They were operated after stabilization using Dynamic Condylar Screw. RESULTS The study showed maximum presentation between 4th and 5th decade with mean age of 39.2 years with sex incidence of 11.5:1 (M:F. Mode of injury was RTA in 17, simple fall in 5, fall from height in 2 and assault in 1 patient. Patients presented to hospital within 0 to 4 days of injury. Left side was involved in 12 and right side in 13 cases. There were 9-A1, 3-A2, 1-A3, 2-C1, 8-C2 and 2-C3 fractures. Six patients had compound fracture. Patients were operated from 3 days to 40 days after admission at an average of 12.36 days. Results were found to be excellent in 8, good in 9, moderate in 3 and poor in 5 patients. Complication in form of valgus angulation, shortening, splintering of proximal femoral fragment, deep infection, Implant failure and lateral angulation at fracture site, Non-union with deep infection were noticed. Average range of knee flexion was 1040 and average time to radiological union was 13.42 weeks. CONCLUSION This study showed that DCS is a good method of treating closed type A1, A2, A3, C1 and C2 fractures. Type C3 and compound fractures treated by this method had more poor results. DCS provides rigid fixation and good purchase in osteoporotic bone. Early mobilization prevents knee stiffness.

  15. Codebook-based interference alignment for uplink MIMO interference channels

    KAUST Repository

    Lee, Hyun Ho

    2014-02-01

    In this paper, we propose a codebook-based interference alignment (IA) scheme in the constant multiple-input multipleoutput (MIMO) interference channel especially for the uplink scenario. In our proposed scheme, we assume cooperation among base stations (BSs) through reliable backhaul links so that global channel knowledge is available for all BSs, which enables BS to compute the transmit precoder and inform its quantized index to the associated user via limited rate feedback link.We present an upper bound on the rate loss of the proposed scheme and derive the scaling law of the feedback load tomaintain a constant rate loss relative to IA with perfect channel knowledge. Considering the impact of overhead due to training, cooperation, and feedback, we address the effective degrees of freedom (DOF) of the proposed scheme and derive the maximization of the effective DOF. From simulation results, we verify our analysis on the scaling law to preserve the multiplexing gain and confirm that the proposed scheme is more effective than the conventional IA scheme in terms of the effective DOF. © 2014 KICS.

  16. INTERFERENCE CANCELLATION FOR MOBILE DISPERSIVE CHANNELS

    Institute of Scientific and Technical Information of China (English)

    Kazi Takpaya

    2003-01-01

    A robust interference canceller for Multi-Carrier Code Division Multiple Access(MC-CDMA) using Orthogonal Frequency Division Multiplexing (OFDM) in Rayleigh fading isproposed. This interference canceller is robust in the sense that it cancels Inter-Carriers Inter-ference (ICI) and is suitable for use in dispersive channels. To come up the effects of the signaldispersion, Doppler shifts and delay spreads on the performance of MC-CDMA systems over mo-bile fading channels, this interference canceller exploits the merit of the orthogonal signaling andpilot signals to evaluate the channel parameters. This interface canceller is well suited to work initerative turbo interference cancellation.

  17. Embracing interference in wireless systems

    CERN Document Server

    Gollakota, Shyamnath

    2014-01-01

    The wireless medium is a shared resource. If nearby devices transmit at thesame time, their signals interfere, resulting in a collision. In traditionalnetworks, collisions cause the loss of the transmitted information. For thisreason, wireless networks have been designed with the assumption thatinterference is intrinsically harmful and must be avoided.This book, a revised version of the author's award-winning Ph.D.dissertation, takes an alternate approach: Instead of viewing interferenceas an inherently counterproductive phenomenon that should to be avoided, wedesign practical systems that tra

  18. Interference Mitigation in Large Random Wireless Networks

    CERN Document Server

    Aldridge, Matthew

    2011-01-01

    A central problem in the operation of large wireless networks is how to deal with interference -- the unwanted signals being sent by transmitters that a receiver is not interested in. This thesis looks at ways of combating such interference. In Chapters 1 and 2, we outline the necessary information and communication theory background, including the concept of capacity. We also include an overview of a new set of schemes for dealing with interference known as interference alignment, paying special attention to a channel-state-based strategy called ergodic interference alignment. In Chapter 3, we consider the operation of large regular and random networks by treating interference as background noise. We consider the local performance of a single node, and the global performance of a very large network. In Chapter 4, we use ergodic interference alignment to derive the asymptotic sum-capacity of large random dense networks. These networks are derived from a physical model of node placement where signal strength d...

  19. Assessment of life interference in anxious children

    DEFF Research Database (Denmark)

    Rapee, Ronald; Thastum, Mikael; Chavira, Denise

    life interference derived from symptoms of anxiety. Broader and more general life interference measures tend to have minimal relevance for children with anxiety disorders. The current paper will describe two measures of life interference that have been developed at the Centre for Emotional Health...... directed at children and adolescents. One measure, the Children's Anxiety Life Interference Scale (CALIS) was developed to assess interference directly associated with symptoms of anxiety in children and adolescents, while the other, the Adolescent Life Interference Scale (ALIS) is a broader measure....... This imbalance has particularly characterised research on child anxiety where few studies have examined either the impact of anxiety disorders on children's lives or the effects of treatments on life interference. To some extent this lack of attention has come from a lack of well developed measures to assess...

  20. Cooperative Feedback for MIMO Interference Channels

    CERN Document Server

    Huang, Kaibin

    2010-01-01

    Multi-antenna precoding effectively mitigates the interference in wireless networks. However, the precoding efficiency can be significantly degraded by the overhead due to the required feedback of channel state information (CSI). This paper addresses such an issue by proposing a systematic method of designing precoders for the two-user multiple-input-multiple-output (MIMO) interference channels based on finite-rate CSI feedback from receivers to their interferers, called cooperative feedback. Specifically, each precoder is decomposed into inner and outer precoders for nulling interference and improving the data link array gain, respectively. The inner precoders are further designed to suppress residual interference resulting from finite-rate cooperative feedback. To regulate residual interference due to precoder quantization, additional scalar cooperative feedback signals are designed to control transmitters' power using different criteria including applying interference margins, maximizing sum throughput, an...

  1. Intra-operative computer navigation guided cervical pedicle screw insertion in thirty-three complex cervical spine deformities

    Directory of Open Access Journals (Sweden)

    S Rajasekaran

    2010-01-01

    Full Text Available Background: Cervical pedicle screw fixation is challenging due to the small osseous morphometrics and the close proximity of neurovascular elements. Computer navigation has been reported to improve the accuracy of pedicle screw placement. There are very few studies assessing its efficacy in the presence of deformity. Also cervical pedicle screw insertion in children has not been described before. We evaluated the safety and accuracy of Iso-C 3D-navigated pedicle screws in the deformed cervical spine. Materials and Methods: Thirty-three patients including 15 children formed the study group. One hundred and forty-five cervical pedicle screws were inserted using Iso-C 3D-based computer navigation in patients undergoing cervical spine stabilization for craniovertebral junction anomalies, cervico-thoracic deformities and cervical instabilities due to trauma, post-surgery and degenerative disorders. The accuracy and containment of screw placement was assessed from postoperative computerized tomography scans. Results: One hundred and thirty (89.7% screws were well contained inside the pedicles. Nine (6.1% Type A and six (4.2% Type B pedicle breaches were observed. In 136 levels, the screws were inserted in the classical description of pedicle screw application and in nine deformed vertebra, the screws were inserted in a non-classical fashion, taking purchase of the best bone stock. None of them had a critical breach. No patient had any neurovascular complications. Conclusion: Iso-C navigation improves the safety and accuracy of pedicle screw insertion and is not only successful in achieving secure pedicle fixation but also in identifying the best available bone stock for three-column bone fixation in altered anatomy. The advantages conferred by cervical pedicle screws can be extended to the pediatric population also.

  2. Combining of small fragment screws and large fragment plates for open reduction and internal fixation of periprosthetic humeral fractures.

    Science.gov (United States)

    Seybold, Dominik; Citak, Mustafa; Königshausen, Matthias; Gessmann, Jan; Schildhauer, Thomas A

    2011-10-01

    Operative treatment of periprosthetic humeral fractures in elderly patients with osteoporotic bone requires a stable fixations technique. The combination of 3.5 cortical screws with washers in a 4.5 Arbeitsgemeinschaft für Osteosynthesefragen, Limited-contact dynamic compression plate or Locking plate, allows a stable periprosthetic fixation with the small 3.5 screws and 4.5 screws above and below the prosthesis, respectively. This combination is a cost-effective technique to treat periprosthetic humeral fractures.

  3. Comparative endurance testing of the Biomet Matthews Nail and the Dynamic Compression Screw, in simulated condylar and supracondylar femoral fractures

    OpenAIRE

    Davies Benjamin M; Davidson Jerome A; O'Connor-Read Laurence M; Matthews Michael G; Smirthwaite Paul

    2008-01-01

    Abstract Background The dynamic compression screw is a plate and screws implant used to treat fractures of the distal femur. The Biomet Matthews Nail is a new retrograde intramedullary nail designed as an alternative surgical option to treat these fractures. The objective of this study was to assess the comparative endurance of both devices. Method The dynamic compression screw (DCS) and Biomet Matthews Nail (BMN) were implanted into composite femurs, which were subsequently cyclically loaded...

  4. Applied thermal pyrolysis of cogongrass in twin screw reactor

    Science.gov (United States)

    Promdee, K.; Vitidsant, T.

    2014-08-01

    Thermal pyrolysis by heat transfer model can be solved the control temperature in twin screw feeder for produce bio-oil from Cogongrass by novel continuous pyrolysis reactor. In this study, all yield were expressed on a dry and their values were taken as the average of the thermal controlled. Thermal of pyrolysis were carried out at 400-500°C. The products yield calculation showed that the liquid yield of Cogongrass by pyrolysis was higher than that solid and gas yield, as highest of 52.62%, at 500°C, and the other of liquid yield obtained from Cogongrass were 40.56, and 46.45%, at 400, and 450°C, respectively. When separate liquid phase be composed of the bio-oil was highest 37.39%, at 500°C. Indicated that biomass from Cogongrass had good received yields because of low solid yield average and gas yield and high liquid yield average. The compounds detected in bio-oil from Cogongrass showed the functional group, especially; Phenol, Phenol 2,5-dimethyl, Benzene 1-ethyl-4-methoxy, 2-Cyclopenten-1-one, 2,3-dimethyl, Benzene 1-ethyl-3-methyl.

  5. Encapsulation of liquids using a counter rotating twin screw extruder.

    Science.gov (United States)

    Tackenberg, Markus W; Krauss, Ralph; Marmann, Andreas; Thommes, Markus; Schuchmann, Heike P; Kleinebudde, Peter

    2015-01-01

    Until now extrusion is not applied for pharmaceutical encapsulation processes, whereas extrusion is widely used for encapsulation of flavours within food applications. Based on previous mixing studies, a hot melt counter-rotating extrusion process for encapsulation of liquid active pharmaceutical ingredients (APIs) was investigated. The mixing ratio of maltodextrin to sucrose as matrix material was adapted in first extrusion trials. Then the number of die holes was investigated to decrease expansion and agglutination of extrudates to a minimum. At a screw speed of 180 min(-1) the product temperature was decreased below 142 °C, resulting in extrudates of cylindrical shape with a crystalline content of 9-16%. Volatile orange terpenes and the nonvolatile α-tocopherol were chosen as model APIs. Design of experiments were performed to investigate the influences of barrel temperature, powder feed rate, and API content on the API retentions. A maximum of 9.2% α-tocopherol was encapsulated, while the orange terpene encapsulation rate decreased to 6.0% due to evaporation after leaving the die. During 12 weeks of storage re-crystallization of sucrose occurred; however, the encapsulated orange terpene amount remained unchanged.

  6. Analyze The Turn of the Screw from Cultural Criticism

    Institute of Scientific and Technical Information of China (English)

    YANG Yan

    2016-01-01

    Henry James is one of the most important novelists and critics in British and American literature. He spent much of his youth in plenty of European countries where he studied with tutors and governesses. Since the 1980s, more and more Western critics have started to use various critical theories such as political sociology, gender identity, and racial discrimination to study his novels. The author attempts to analyze The Turn of the Screw from cultural criticism. Cultural Criticism is not an independent theory. It is often interwoven with social, political, psychological, and historical contexts of a novel. The author first uses political sociology to analyze class division and power structure of the Victorian time. And then use social psychology to analyze the psyche of the governess and proves that it is the governess’sexual hysteria that leads to the fall of the two children.The author argues that Cul-tural Criticism seems to be a more suitable and effective way to analyze the story.

  7. Adolescent idiopathic scoliosis: sagital plane and low density pedicle screws

    Directory of Open Access Journals (Sweden)

    Rodrigo Augusto do Amaral

    2014-03-01

    Full Text Available OBJECTIVE: To examine the sagittal curves of patients treated with CD instrumentation using exclusively pedicle screws. METHODS: Image analysis of medical records of 27 patients (26 M and 1 F with a minimum follow-up of 6 months, who underwent surgical treatment in our service between January 2005 and December 2010. The curves were evaluated on coronal and sagittal planes, taking into account the potential correction of the technique. RESULTS: In the coronal plan the following curves were evaluated: proximal thoracic (TPx, main thoracic (TPp, and thoracolumbar; lumbar (TL, L, and the average flexibility was 52%, 52%, and 92% and the capacity of correction was 51%, 72%, and 64%, respectively. In the sagittal plane there was a mean increase in thoracic kyphosis (CT of 41% and an average reduction of lumbar lordosis (LL of 17%. Correlation analysis between variables showed Pearson coefficient of correlation of 0.053 and analysis of dispersion of R2 = <0.001. CONCLUSION: The method has shown satisfactory results with maintenance of kyphosis correction in patients with normal and hyper kyphotic deformities.

  8. Motor interference in interactive contexts

    Directory of Open Access Journals (Sweden)

    Eris eChinellato

    2015-06-01

    Full Text Available Action observation and execution share overlapping neural substrates, so that simultaneous activation by observation and execution modulates motor performance. Previous literature on simple prehension tasks has revealed that motor influence can be two-sided: facilitation for observed and performed congruent actions and interference for incongruent actions. But little is known of the specific modulations of motor performance in complex forms of interaction. Is it possible that the very same observed movement can lead either to interference or facilitation effects on a temporally overlapping congruent executed action, depending on the context? To answer this question participants were asked to perform a reach-to-grasp movement adopting a precision grip (PG while: (i observing a fixation cross, (ii observing an actor performing a PG with interactive purposes, (iii observing an actor performing a PG without interactive purposes. In particular, in the interactive condition the actor was shown trying to pour some sugar on a large cup located out of her reach but close to the participant watching the video, thus eliciting in reaction a complementary whole-hand grasp. Notably, fine-grained kinematic analysis for this condition revealed a specific delay in the grasping and reaching components and an increased trajectory deviation despite the observed and executed movement’s congruency. Moreover, early peaks of trajectory deviation seem to indicate that socially relevant stimuli are acknowledged by the motor system very early. These data suggest that interactive contexts can determine a prompt modulation of stimulus–response compatibility effects.

  9. Modal interference in spiky nanoshells.

    Science.gov (United States)

    Hastings, Simon P; Qian, Zhaoxia; Swanglap, Pattanawit; Fang, Ying; Engheta, Nader; Park, So-Jung; Link, Stephan; Fakhraai, Zahra

    2015-05-04

    Near-field enhancement of the electric field by metallic nanostructures is important in non-linear optical applications such as surface enhanced Raman scattering. One approach to producing strong localization of the electric field is to couple a dark, non-radiating plasmonic mode with a broad dipolar resonator that is detectable in the far-field. However, characterizing or predicting the degree of the coupling between these modes for a complicated nanostructure can be quite challenging. Here we develop a robust method to solve the T-matrix, the matrix that predicts the scattered electric fields of the incident light, based on finite-difference time-domain (FDTD) simulations and least square fitting algorithms. This method allows us to simultaneously calculate the T-matrix for a broad spectral range. Using this method, the coupling between the electric dipole and quadrupole modes of spiky nanoshells is evaluated. It is shown that the built-in disorder in the structure of these nanoshells allows for coupling between the dipole modes of various orientations as well as coupling between the dipole and the quadrupole modes. A coupling strength of about 5% between these modes can explain the apparent interference features observed in the single particle scattering spectrum. This effect is experimentally verified by single particle backscattering measurements of spiky nanoshells. The modal interference in disordered spiky nanoshells can explain the origin of the spectrally broad quadrupole resonances that result in strong Quadrupole Enhanced Raman Scattering (QERS) in these nanoparticles.

  10. 粒煤螺旋输送特性实验研究%Screw conveying characteristics of granular coal from screw conveyor

    Institute of Scientific and Technical Information of China (English)

    陈汝超; 陈晓平; 蔡佳莹; 刘道银; 梁财

    2012-01-01

    The screw conveying characteristics of granular coal from an screw conveyor was investigated.The results show that coal particle size,moisture content and conveying angle have significant effects on the screw conveying characteristics of granular coal.Screw velocity increases with the increasing of particle size of granular coal and decreases with the increasing of moisture content of granular coal.Increasing the conveying angle leads to serious sliding of the granular coal,and the filling coefficient increases.The filling coefficient increases with the increasing of particle size and moisture content of granular coal.%在自行设计的粒煤螺旋输送系统上对粒煤的螺旋输送特性进行了研究。结果表明:粒煤的粒径、外水分及螺旋倾角对其输送特性有显著影响。粒煤的平均粒径越大,外水分越小,其输送速率越大;螺旋倾角越大,输送过程中物料的滑移现象越严重,填充系数越大;粒煤的外水分越大,平均粒径越大,输送过程中的填充系数越大。

  11. Functionality Evaluation of a Novel Smart Expandable Pedicle Screw to Mitigate Osteoporosis Effect in Bone Fixation: Modeling and Experimentation

    Directory of Open Access Journals (Sweden)

    Ahmadreza Eshghinejad

    2013-01-01

    Full Text Available This paper proposes a novel expandable-retractable pedicle screw and analyzes its functionality. A specially designed pedicle screw is described which has the ability to expand and retract using nitinol elements. The screw is designed to expand in body temperature and retract by cooling the screw. This expansion-retraction function is verified in an experiment designed in larger scale using a nitinol antagonistic assembly. The results of this experiment are compared to the results of a finite element model developed in Abaqus in combination with a user material subroutine (UMAT. This code has been developed to analyze the nonlinear thermomechanical behavior of shape memory alloy materials. The functionality of the proposed screw is evaluated with simulation and experimentation in a pullout test as well. The pullout force of a normal screw inserted in a normal bone was simulated, and the result is compared with the results of the expandable screw in osteoporotic bone. Lastly, strength of the designed pedicle screw in a foam block is also verified with experiment. The reported finite element simulations and experiments are the proof for the concept of nitinol expandable-retractable elements on a pedicle screw which validate the functionality in a pullout test.

  12. Core properties and mobility of the basal screw dislocation in wurtzite GaN: a density functional theory study

    Science.gov (United States)

    Belabbas, I.; Chen, J.; Heggie, M. I.; Latham, C. D.; Rayson, M. J.; Briddon, P. R.; Nouet, G.

    2016-10-01

    We have performed first principles simulations, based on density functional theory (DFT), to investigate the core properties of the basal a -type screw dislocation in wurtzite gallium nitride. Our calculations demonstrate that the fully coordinated shuffle core configuration is the most energetically favourable. The calculated electronic structure of the a -type screw dislocation was found to exhibit exclusively shallow gap states which are not associated with any extended metallization. This may explain why a -type screw dislocations are less detrimental to the performance of GaN based electronic devices than c -type screw dislocations.

  13. Clinical Accuracy of Three-Dimensional Fluoroscopy (IsoC-3D-Assisted Upper Thoracic Pedicle Screw Insertion

    Directory of Open Access Journals (Sweden)

    Sugimoto,Yoshihisa

    2010-06-01

    Full Text Available Correct screw placement is especially difficult in the upper thoracic vertebrae. At the cervicothoracic junction (C7-T2, problems can arise because of the narrowness of the pedicle and the difficulty of using a lateral image intensifier there. Other upper thoracic vertebrae (T3-6 pose a problem for screw insertion also because of the narrower pedicle. We inserted 154 pedicle screws into 78 vertebrae (C7 to T6 in 38 patients. Screws were placed using intraoperative data acquisition by an isocentric C-arm fluoroscope (Siremobile Iso-C3D and computer navigation. Out of 90 pedicle screws inserted into 45 vertebrae between C7 and T2, 87 of the 90 (96.7% screws were classified as grade 1 (no perforation. Of 64 pedicle screws inserted into 33 vertebrae between T3 and T6, 61 of 64 (95.3% screws were classified as grade 1. In this study, we reduced pedicle screw misplacement at the level of the C7 and upper thoracic (T1-6 vertebrae using the three-dimensional fluoroscopy navigation system.

  14. Pseudohypobicarbonatemia caused by an endogenous assay interferent: a new entity.

    Science.gov (United States)

    Goldwasser, Philip; Manjappa, Nagarathna G; Luhrs, Carol A; Barth, Robert H

    2011-10-01

    Serum total carbon dioxide, measured using a chemistry analyzer, and gas panel-derived plasma bicarbonate, calculated from the pH and partial pressure of carbon dioxide, often are used interchangeably for clinical purposes. When they disagree, there is a tendency to accept total carbon dioxide and discredit gas panel-derived plasma bicarbonate values. We report a patient who, during a 5-month hospitalization, had persistently low total carbon dioxide levels (12.4 ± 2.7 [standard deviation] mEq/L [12.4 ± 2.7 mmol/L]), measured using an enzymatic/photometric assay, and a high anion gap (19.2 ± 3.1 mEq/L [19.2 ± 3.1 mmol/L]), suggesting high-anion-gap metabolic acidosis, but who had gas panel-derived plasma bicarbonate (24.0 ± 0.9 mEq/L [24.0 ± 0.9 mmol/L]) and arterial pH values in the reference range. Organic anion levels in blood and urine were unremarkable. Negative interference with the enzymatic assay by the patient's serum was shown by the findings that total carbon dioxide level was 7.0 ± 0.1 mEq/L (7.0 ± 0.1 mmol/L) higher when measured using the electrode-based method than using the enzymatic method (P < 0.01), and the patient's serum, but not control serum, altered the reaction kinetics of the enzymatic assay by producing turbidity, resulting in an initial increase in absorbance and a falsely low total carbon dioxide value. The turbidity may have resulted from precipitation of 1 of 2 paraproteins in the patient's serum or an endogenous antibody binding with an animal protein included in the assay reagents. In summary, a discrepancy between total carbon dioxide level measured using an enzymatic assay and gas panel-derived plasma bicarbonate level was found to be the result of turbidity caused by an endogenous interferent with the total carbon dioxide assay, a novel artifact. When total carbon dioxide and gas panel-derived plasma bicarbonate values disagree, measurement error in total carbon dioxide level should be considered.

  15. Calcium phosphate cement augmentation of cancellous bone screws can compensate for the absence of cortical fixation.

    Science.gov (United States)

    Stadelmann, Vincent A; Bretton, Elise; Terrier, Alexandre; Procter, Philip; Pioletti, Dominique P

    2010-11-16

    An obvious means to improve the fixation of a cancellous bone screw is to augment the surrounding bone with cement. Previous studies have shown that bone augmentation with Calcium Phosphate (CaP) cement significantly improves screw fixation. Nevertheless, quantitative data about the optimal distribution of CaP cement is not available. The present study aims to show the effect of cement distribution on the screw fixation strength for various cortical thicknesses and to determine the conditions at which cement augmentation can compensate for the absence of cortical fixation in osteoporotic bone. In this study, artificial bone materials were used to mimic osteoporotic cancellous bone and cortical bone of varying thickness. These bone constructs were used to test the fixation strength of cancellous bone screws in different cortical thicknesses and different cement augmentation depths. The cement distribution was measured with microCT. The maximum pullout force was measured experimentally. The microCT analysis revealed a pseudo-conic shape distribution of the cement around the screws. While the maximum pullout strength of the screws in the artificial bone only was 30±7N, it could increase up to approximately 1000N under optimal conditions. Cement augmentation significantly increased pullout force in all cases. The effect of cortical thickness on pullout force was reduced with increased cement augmentation depth. Indeed, cement augmentation without cortical fixation increased pullout forces over that of screws without cement augmentation but with cortical fixation. Since cement augmentation significantly increased pullout force in all cases, we conclude that the loss of cortical fixation can be compensated by cement augmentation.

  16. Repair of microdamage in osteonal cortical bone adjacent to bone screw.

    Directory of Open Access Journals (Sweden)

    Lei Wang

    Full Text Available Up to date, little is known about the repair mode of microdamage in osteonal cortical bone resulting from bone screw implantation. In this study, self-tapping titanium cortical bone screws were inserted into the tibial diaphyses of 24 adult male rabbits. The animals were sacrificed at 1 day, 2 weeks, 1 month and 2 months after surgery. Histomorphometric measurement and confocal microscopy were performed on basic fuchsin stained bone sections to examine the morphological characteristics of microdamage, bone resorption activity and spatial relationship between microdamage and bone resorption. Diffuse and linear cracks were coexisted in peri-screw bone. Intracortical bone resorption was significantly increased 2 weeks after screw installation and reach to the maximum at 1 month. There was no significant difference in bone resorption between 1-month and 2-months groups. Microdamage was significantly decreased within 1 month after surgery. Bone resorption was predisposed to occur in the region of <100 µm from the bone-screw interface, where had extensive diffuse damage mixed with linear cracks. Different patterns of resorption cavities appeared in peri-screw bone. These data suggest that 1 the complex microdamage composed of diffuse damage and linear cracks is a strong stimulator for initiating targeted bone remodeling; 2 bone resorption activities taking place on the surfaces of differently oriented Haversian and Volkmann canals work in a team for the repair of extensive microdamage; 3 targeted bone remodeling is a short-term reaction to microdamage and thereby it may not be able to remove all microdamage resulting from bone screw insertion.

  17. 螺旋叶片对垂直螺旋输送机性能的影响%Influence of screw blade of performance for vertical screw conveyor

    Institute of Scientific and Technical Information of China (English)

    余书豪; 谌永祥

    2016-01-01

    为了研究在垂直螺旋输送机物料输送过程中的细观甚至微观特征,降低颗粒输送过程中近轴处的涡流引起的能耗,增大近壁面处的轴向速度,考察不同母线形状的螺旋叶片,借助颗粒仿真软件EDEM 2.5进行数值试验,模拟垂直螺旋输送机内颗粒速度、功率消耗、能量耗散、质量流量等性能指标,通过数据处理软件Origin Pro 8.0作图分析各项指标的变化情况.结果表明:与传统直线型母线的螺旋叶片相比,弯曲型母线的螺旋叶片在近轴处的切向速度减小73.87%,大大降低近轴处的涡流效应;近壁面处的轴向速度在高转速时增大12.34%,完成预定输送任务基础上,有效地降低额外的能量消耗,提升整机性能.%In order to figure out the meso and microscopic characteristics during bulk material being conveyed within the vertical screw conveyor and reduce the swirl flow near the screw shag and increase the axial velocity of particles near the wall during the particulate being conveyed,the different shape screw blades were surveyed,by means of the software of particle simulation EDEM 2.5,numerical test was done,the standards of performance such as particle velocity,power consumption,energy dissipation and average mass flow rate within the vertical screw conveyor were simulated.The trend charts were plotted based on the data processing software Origin Pro 8.0,to analysis the changes of indicators.The result shows that compared with the line type screw blade,the curved screw blade of tangential velocity near the shaft is reduce by 73.87%,the vortex motion decreases evidently.The axial velocity near the wall is increased by 12.34%,the extra energy dissipation effectively reduces on the basis of finishing the intended work,which promotes the whole performance of vertical screw conveyor

  18. RNA interference as a gene knockdown technique.

    Science.gov (United States)

    Shan, Ge

    2010-08-01

    Not many scientific breakthroughs bring significant advances simultaneously in both basic research and translational applications like the discovery of RNA interference. Along with the elucidation of the RNA interference pathway and the discovery of its participation in crucial biological events, a branch of science has grown to utilize the RNA interference pathway as a biotechnology for both basic and applied research. Small interference RNA, plasmid-, and virus-encoded short-hairpin RNA are now regular reagents in the tool box of biologists to knockdown the expression of specific genes posttranscriptionally. Efforts have also been made to develop RNA interference based therapeutics into reality. Many concerns about the RNA interference technique have now been answered through research and development, although hurdles are still present. In this review, the RNA interference/microRNA pathway is briefly introduced followed with a detailed summary about the design and application of the RNA interference experiments, along with examples of the utilization of the RNA interference technology in animal cells and model organisms. Recent progresses and current concerns are also highlighted. Two techniques, namely morpholino and external guide sequence, are discussed as complementary gene knockdown technology. RNA interference technology, along with several other alternative gene knockdown techniques, is now indispensable to modern biological and medical research.

  19. Posterior lumbar interbody fusion with cortical bone trajectory screw fixation versus posterior lumbar interbody fusion using traditional pedicle screw fixation for degenerative lumbar spondylolisthesis: a comparative study.

    Science.gov (United States)

    Sakaura, Hironobu; Miwa, Toshitada; Yamashita, Tomoya; Kuroda, Yusuke; Ohwada, Tetsuo

    2016-11-01

    OBJECTIVE Several biomechanical studies have demonstrated the favorable mechanical properties of the cortical bone trajectory (CBT) screw. However, no reports have examined surgical outcomes of posterior lumbar interbody fusion (PLIF) with CBT screw fixation for degenerative spondylolisthesis (DS) compared with those after PLIF using traditional pedicle screw (PS) fixation. The purposes of this study were thus to elucidate surgical outcomes after PLIF with CBT screw fixation for DS and to compare these results with those after PLIF using traditional PS fixation. METHODS Ninety-five consecutive patients underwent PLIF with CBT screw fixation for DS (CBT group; mean followup 35 months). A historical control group consisted of 82 consecutive patients who underwent PLIF with traditional PS fixation (PS group; mean follow-up 40 months). Clinical status was assessed using the Japanese Orthopaedic Association (JOA) scale score. Fusion status was assessed by dynamic plain radiographs and CT. The need for additional surgery and surgery-related complications was also evaluated. RESULTS The mean JOA score improved significantly from 13.7 points before surgery to 23.3 points at the latest follow-up in the CBT group (mean recovery rate 64.4%), compared with 14.4 points preoperatively to 22.7 points at final follow-up in the PS group (mean recovery rate 55.8%; p fusion was achieved in 84 patients from the CBT group (88.4%) and in 79 patients from the PS group (96.3%, p > 0.05). Symptomatic adjacent-segment disease developed in 3 patients from the CBT group (3.2%) compared with 9 patients from the PS group (11.0%, p fusion rate tended to be lower in the CBT group than in the PS group, although the difference was not statistically significant between the 2 groups.

  20. Pyrolysis of aseptic packages (tetrapak) in a laboratory screw type reactor and secondary thermal/catalytic tar decomposition.

    Science.gov (United States)

    Haydary, J; Susa, D; Dudáš, J

    2013-05-01

    Pyrolysis of aseptic packages (tetrapak cartons) in a laboratory apparatus using a flow screw type reactor and a secondary catalytic reactor for tar cracking was studied. The pyrolysis experiments were realized at temperatures ranging from 650 °C to 850 °C aimed at maximizing of the amount of the gas product and reducing its tar content. Distribution of tetrapak into the product yields at different conditions was obtained. The presence of H2, CO, CH4, CO2 and light hydrocarbons, HCx, in the gas product was observed. The Aluminum foil was easily separated from the solid product. The rest part of char was characterized by proximate and elemental analysis and calorimetric measurements. The total organic carbon in the tar product was estimated by elemental analysis of tars. Two types of catalysts (dolomite and red clay marked AFRC) were used for catalytic thermal tar decomposition. Three series of experiments (without catalyst in a secondary cracking reactor, with dolomite and with AFRC) at temperatures of 650, 700, 750, 800 and 850 °C were carried out. Both types of catalysts have significantly affected the content of tars and other components in pyrolytic gases. The effect of catalyst on the tetrapack distribution into the product yield on the composition of gas and on the total organic carbon in the tar product is presented in this work.

  1. A novel cleaning process for industrial production of xylose in pilot scale from corncob by using screw-steam-explosive extruder.

    Science.gov (United States)

    Zhang, Hong-Jia; Fan, Xiao-Guang; Qiu, Xue-Liang; Zhang, Qiu-Xiang; Wang, Wen-Ya; Li, Shuang-Xi; Deng, Li-Hong; Koffas, Mattheos A G; Wei, Dong-Sheng; Yuan, Qi-Peng

    2014-12-01

    Steam explosion is the most promising technology to replace conventional acid hydrolysis of lignocellulose for biomass pretreatment. In this paper, a new screw-steam-explosive extruder was designed and explored for xylose production and lignocellulose biorefinery at the pilot scale. We investigated the effect of different chemicals on xylose yield in the screw-steam-explosive extrusion process, and the xylose production process was optimized as followings: After pre-impregnation with sulfuric acid at 80 °C for 3 h, corncob was treated at 1.55 MPa with 9 mg sulfuric acid/g dry corncob (DC) for 5.5 min, followed by countercurrent extraction (3 recycles), decoloration (activated carbon dosage 0.07 g/g sugar, 75 °C for 40 min), and ion exchange (2 batches). Using this process, 3.575 kg of crystal xylose was produced from 22 kg corncob, almost 90 % of hemicellulose was released as monomeric sugar, and only a small amount of by-products was released (formic acid, acetic acid, fural, 5-hydroxymethylfurfural, and phenolic compounds were 0.17, 1.14, 0.53, 0.19, and 1.75 g/100 g DC, respectively). All results indicated that the screw-steam-explosive extrusion provides a more effective way to convert hemicellulose into xylose and could be an alternative method to traditional sulfuric acid hydrolysis process for lignocellulose biorefinery.

  2. Comparison study of the pullout strength of conventional spinal pedicle screws and a novel design in full and backed-out insertions using mechanical tests.

    Science.gov (United States)

    Amaritsakul, Yongyut; Chao, Ching-Kong; Lin, Jinn

    2014-03-01

    Recently, new pedicle screw designs have been developed. However, these designs' performances are still unclear, especially when backed out after insertion. The objective of this study was to investigate the performances of different screw designs when backed out from full insertion. Seven conventional designs of the pedicle screw and one novel design were inserted into polyurethane foam (0.32 g/cm(3)). All screws were first fully inserted (43 mm) and were backed out 360°. Axial pullout tests were performed and the reaction force was measured. The results showed that the conical screw of type 1 with a small inner diameter provided the highest pullout strength in both full insertion and backed-out insertion (2401.85 and 2169.82 N, respectively). However, this screw's pullout strength significantly decreased (9.7%) when backed out from full insertion. There was no significant difference between the conical screw of type 1 with a small inner diameter and double duo core screw (p > 0.01) in backed-out insertion. The cylindrical screw with a small diameter, dual inner core screw and double dual core screw also provided good results in both full insertion (2115.44, 2182.99 and 2226.93 N, respectively) and backed-out conditions (2065.80, 2014.28 and 1941.29 N, respectively). The increased pullout strength of the conical design could be due to the effect of bone compaction. However, the screw exhibited less consistent pullout strength when backed out when compared with the other designs. The conical screw should be inserted to the precise position without turning back, especially in osteoporosis patients. The dual inner core screw and double dual core screw could provide greater stability in both conditions. Care should be taken when using both the cylindrical screw with a small thread depth and the dual outer core screw.

  3. Ramsey Interference with Single Photons

    Science.gov (United States)

    Clemmen, Stéphane; Farsi, Alessandro; Ramelow, Sven; Gaeta, Alexander L.

    2016-11-01

    Interferometry using discrete energy levels of nuclear, atomic, or molecular systems is the foundation for a wide range of physical phenomena and enables powerful techniques such as nuclear magnetic resonance, electron spin resonance, Ramsey-based spectroscopy, and laser or maser technology. It also plays a unique role in quantum information processing as qubits may be implemented as energy superposition states of simple quantum systems. Here, we demonstrate quantum interference involving energy states of single quanta of light. In full analogy to the energy levels of atoms or nuclear spins, we implement a Ramsey interferometer with single photons. We experimentally generate energy superposition states of a single photon and manipulate them with unitary transformations to realize arbitrary projective measurements. Our approach opens the path for frequency-encoded photonic qubits in quantum information processing and quantum communication.

  4. RNA interference and antiviral therapy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    RNA interference (RNAi) is an evolutionally conserved gene silencing mechanism present in a variety of eukaryotic species. RNAi uses short double-stranded RNA (dsRNA) to trigger degradation or translation repression of homologous RNA targets in a sequence-specific manner. This system can be induced effectively in vitro and in vivo by direct application of small interfering RNAs (siRNAs), or by expression of short hairpin RNA (shRNA) with non-viral and viral vectors. To date, RNAi has been extensively used as a novel and effective tool for functional genomic studies, and has displayed great potential in treating human diseases, including human genetic and acquired disorders such as cancer and viral infections. In the present review, we focus on the recent development in the use of RNAi in the prevention and treatment of viral infections. The mechanisms,strategies, hurdles and prospects of employing RNAi in the pharmaceutical industry are also discussed.

  5. Ramsey interference with single photons

    CERN Document Server

    Clemmen, Stéphane; Ramelow, Sven; Gaeta, Alexander L

    2016-01-01

    Interferometry using discrete energy levels in nuclear, atomic or molecular systems is the foundation for a wide range of physical phenomena and enables powerful techniques such as nuclear magnetic resonance, electron spin resonance, Ramsey-based spectroscopy and laser/maser technology. It also plays a unique role in quantum information processing as qubits are realized as energy superposition states of single quantum systems. Here, we demonstrate quantum interference of different energy states of single quanta of light in full analogy to energy levels of atoms or nuclear spins and implement a Ramsey interferometer with single photons. We experimentally generate energy superposition states of a single photon and manipulate them with unitary transformations to realize arbitrary projective measurements, which allows for the realization a high-visibility single-photon Ramsey interferometer. Our approach opens the path for frequency-encoded photonic qubits in quantum information processing and quantum communicati...

  6. RNA干扰%RNA interference

    Institute of Scientific and Technical Information of China (English)

    江舸; 金由辛

    2003-01-01

    RNA干扰(RNA interference,RNAi)现象是指,当与内源性mRNA编码区某段序列同源的双链RNA(dsRNA)导入细胞后,该mRNA发生特异性的降解,而导致该基因表达的沉寂.这可能反映了生物防范病毒或转座子诱导DNA突变的一种防御机制.RNA干扰已经成为一种重要的研究基因功能的有力工具,并且有希望在对疾病的防御及治疗中发挥重要的作用.

  7. RNA干扰%RNA interference

    Institute of Scientific and Technical Information of China (English)

    陈凌; 郑祥雄

    2003-01-01

    @@ 1998年,Fire等人首次发现双链RNA(dsRNA)能够特异地抑制秀丽新小杆线虫中的纹状肌细胞unc-22基因的表达,这种抑制效能比单独应用正义或反义 RNA强十几倍;进一步研究还发现,用少量dsRNA处理的线虫就能呈现基因沉默的现象,并且该抑制现象可以传给第二代.他们将这一现象称为RNA干扰(RNA interference,RNAi)+[1].因为RNAi作用发生在转录后水平,所以又被称为转录后基因沉默(post-transcriptional gene silencing,PTGS).

  8. CDMA with interference cancellation for multiprobe missions

    Science.gov (United States)

    Divsalar, D.; Simon, M. K.

    1995-01-01

    Code division multiple-access spread spectrum has been proposed for use in future multiprobe/multispacecraft missions. This article considers a general parallel interference-cancellation scheme that significantly reduces the degradation effect of probe (user) interference but with a lesser implementation complexity than the maximum-likelihood technique. The scheme operates on the fact that parallel processing simultaneously removes from each probe (user) the total interference produced by the remaining most reliably received probes (users) accessing the channel. The parallel processing can be done in multiple stages. The proposed scheme uses tentative decision devices with different optimum thresholds at the multiple stages to produce the most reliably received data for generation and cancellation of probe/spacecraft interference. The one-stage interference cancellation was analyzed for two types of tentative decision devices, namely, hard and null zone decisions. Simulation results are given for one- and two-stage interference cancellation for equal as well as unequal received power probes.

  9. Conversion of low density polyethylene into petrochemical feedstocks using a continuous screw kiln reactor

    Energy Technology Data Exchange (ETDEWEB)

    Serrano, D.P.; Aguado, J.; Escola, J.M. [ESCET, Rey Juan Carlos University, c/Tulipan s/n, 28933 Mostoles, Madrid (Spain); Garagorri, E. [Chemical Engineering Department, Complutense University of Madrid, Av. Complutense s/n, 28040 Madrid (Spain)

    2001-04-01

    Thermal and catalytic degradation of low-density polyethylene (LDPE) has been investigated using a screw kiln reactor provided with two zones of reaction temperature. Thermal degradation experiments carried out at different temperatures and screw speeds have shown that this continuous system is suitable for the LDPE degradation, product outputs up to c.a. 100 g/h being obtained. Compared to a conventional batch reactor, the screw kiln system leads to a lower formation of gaseous products, whereas overcracking of the heavy fractions is also reduced. These differences are probably originated by the intimate contact and the same residence times for all the product fractions that exist within the screw reactor, which is in contrast with the selective and fast withdrawal of volatile products taking place in the batch system. In the catalytic experiments, a mesoporous MCM-41 type aluminosilicate has been used as catalyst, being continuously fed to the screw reactor mixed with the raw plastic material. In these conditions, yields up to 80% towards hydrocarbons within the gasoline range (C{sub 5}-C{sub 12}) have been obtained. Moreover, high amounts of C{sub 7} and C{sub 8} hydrocarbons are present in the gasoline fractions, which is assigned to catalytic oligomerization reactions that selectively affect to C{sub 3} and C{sub 4} gaseous hydrocarbons.

  10. Design of Nano Screw Pump for Water Transport and its Mechanisms

    Science.gov (United States)

    Wang, LiYa; Wu, HengAn; Wang, FengChao

    2017-01-01

    Nanopumps conducting fluids through nanochannels have attracted considerable interest for their potential applications in nanofiltration, water desalination and drug delivery. Here, we demonstrate by molecular dynamics (MD) simulations that a nano screw pump is designed with helical nanowires embedded in a nanochannel, which can be used to drive unidirectional water flow. Such helical nanowires have been successfully synthesized in many experiments. By investigating the water transport mechanism through nano screw pumps with different configuration parameters, three transport modes were observed: cluster-by-cluster, pseudo-continuous, and linear-continuous, in which the water flux increases linearly with the rotating speed. The influences of the nanowires’ surface energy and the screw’s diameter on water transport were also investigated. Results showed that the water flux rate increases as the decreasing wettability of helical nanowires. The deviation in water flux in screw pumps with smaller radius is attributed to the weak hydrogen bonding due to space confinement and the hydrophobic blade. Moreover, we also proposed that such screw pumps with appropriate diameter and screw pitch can be used for water desalination. The study provides an insight into the design of multifunctional nanodevices for not only water transport but water desalination in practical applications. PMID:28155898

  11. Design of Nano Screw Pump for Water Transport and its Mechanisms

    Science.gov (United States)

    Wang, Liya; Wu, Hengan; Wang, Fengchao

    2017-02-01

    Nanopumps conducting fluids through nanochannels have attracted considerable interest for their potential applications in nanofiltration, water desalination and drug delivery. Here, we demonstrate by molecular dynamics (MD) simulations that a nano screw pump is designed with helical nanowires embedded in a nanochannel, which can be used to drive unidirectional water flow. Such helical nanowires have been successfully synthesized in many experiments. By investigating the water transport mechanism through nano screw pumps with different configuration parameters, three transport modes were observed: cluster-by-cluster, pseudo-continuous, and linear-continuous, in which the water flux increases linearly with the rotating speed. The influences of the nanowires’ surface energy and the screw’s diameter on water transport were also investigated. Results showed that the water flux rate increases as the decreasing wettability of helical nanowires. The deviation in water flux in screw pumps with smaller radius is attributed to the weak hydrogen bonding due to space confinement and the hydrophobic blade. Moreover, we also proposed that such screw pumps with appropriate diameter and screw pitch can be used for water desalination. The study provides an insight into the design of multifunctional nanodevices for not only water transport but water desalination in practical applications.

  12. Continuous twin screw granulation: influence of process variables on granule and tablet quality.

    Science.gov (United States)

    Vercruysse, J; Córdoba Díaz, D; Peeters, E; Fonteyne, M; Delaet, U; Van Assche, I; De Beer, T; Remon, J P; Vervaet, C

    2012-09-01

    The aim of the current study was to screen theophylline (125 mg) tablets manufactured via twin screw granulation in order to improve process understanding and knowledge of process variables that determine granule and tablet quality. A premix of theophylline anhydrate, α-lactose monohydrate and PVP (ratio: 30/67.5/2.5,w/w) was granulated with demineralized water. Experiments were done using the high-shear wet granulation module (based on twin screw granulation) of the ConsiGma™-25 unit (a continuous tablet manufacturing system) for particle size enlargement. After drying, granules were compressed using a MODUL™ P tablet press (compression force: 10 kN, tablet diameter: 12 mm). Using a D-optimal experimental design, the effect of several process variables (throughput (10-25 kg/h), screw speed (600-950 rpm), screw configuration (number (2, 4, 6 and 12) and angle (30°, 60° and 90°) of kneading elements), barrel temperature (25-40°C) and method of binder addition (dry versus wet)) on the granulation process (torque and temperature increase in barrel wall), granule (particle size distribution, friability and flowability) and tablet (tensile strength, porosity, friability, disintegration time and dissolution) quality was evaluated. The results showed that the quality of granules and tablets can be optimized by adjusting specific process variables (number of kneading elements, barrel temperature and binder addition method) during a granulation process using a continuous twin screw granulator.

  13. Dissolving cellulose with twin-screw extruder in a NaOH complex aqueous solution

    Science.gov (United States)

    Yang, Y. P.; Zhang, Y.; Dawelbeit, A.; Yu, M. H.

    2016-07-01

    Novel cellulose dissolution method with twin-screw extruder was developed in order to improve the dissolution property, to simplify production procedure and to produce cellulose spinning dope which is stable and which has a higher concentration of cellulose. Therefore, the extrusion conditions on the cellulose dissolution in NaOH/thiourea/urea were extensively studied in this work. The resulted extrudates of twin-screw extruder dissolution method were characterized by polarized optical microscope image, the solubility experiment and the apparent viscosity. The results revealed that the screw revolution speed of such process could improve the solubility value (S a) of cellulose, and the solubility of cellulose reached a maximum value of 7.5 wt% at higher revolutions 450 rpm. On the other hand, the cellulose solutions were more transparent and balanced with its apparent viscosity values lower and more stable compare to stirring method, which indicated dissolving cellulose with twin-screw extruder was reliable. Moreover, the whole dissolving time is quite short, and the process is simple. The soluble effect of twin screw extrusion was far superior to traditional stirring, and the most suitable temperature was -2°C.

  14. Artificial neural network modelling of continuous wet granulation using a twin-screw extruder.

    Science.gov (United States)

    Shirazian, Saeed; Kuhs, Manuel; Darwish, Shaza; Croker, Denise; Walker, Gavin M

    2017-04-15

    Computational modelling of twin-screw granulation was conducted by using an artificial neural network (ANN) approach. Various ANN configurations were considered with changing hidden layers, nodes and activation functions to determine the optimum model for the prediction of the process. The neural networks were trained using experimental data obtained for granulation of pure microcrystalline cellulose using a 12mm twin-screw extruder. The experimental data were obtained for various liquid binder (water) to solid ratios, screw speeds, material throughputs, and screw configurations. The granulate particle size distribution, represented by d-values (d10, d50, d90) were considered the response in the experiments and the ANN model. Linear and non-linear activation functions were taken into account in the simulations and more accurate results were obtained for non-linear function in terms of prediction. Moreover, 2 hidden layers with 2 nodes per layer and 3-Fold cross-validation method gave the most accurate simulation. The results revealed that the developed ANN model is capable of predicting granule size distribution in high-shear twin-screw granulation with a high accuracy in different conditions, and can be used for implementation of model predictive control in continuous pharmaceutical manufacturing.

  15. Root contact with maxillomandibular fixation screws in orthognathic surgery: incidence and consequences.

    Science.gov (United States)

    Camargo, I B; Van Sickels, J E; Laureano Filho, J R; Cunningham, L L

    2016-08-01

    The use of maxillomandibular fixation (MMF) screws in orthognathic surgery has become common in recent years. The risk of injury to adjacent roots with their placement in this population has not been studied extensively. The aim of this study was to review the incidence and consequences of root contact/injury in patients undergoing orthognathic surgery. A retrospective analysis of the treatment and radiographic records of patients who underwent orthognathic surgery between January 2013 and September 2014 at a university in Kentucky, USA was performed. The mean number of screws used was correlated to the mean number of roots affected using Spearman's test, set to a level of significance of 5%. Of 125 patients who underwent orthognathic surgery, 15 (12%) had evidence of root contact. Subsequent radiographs showed resolution of the bone defects. There was no clinical evidence of pulpal necrosis or pain during follow-up. The average number of screws used was 3.14±0.35 per patient, with an average of 0.17±0.52 root contacts per patient. There was no correlation between the number of screws used and the number of roots injured (P=0.279). Based on these results, MMF screws can safely be used to establish interim fixation during orthognathic surgery. Caution should be taken during placement to avoid direct injury to the roots of teeth.

  16. Lower cervical spine injury treated with lateral mass plates and pedicle screws through posterior approach

    Institute of Scientific and Technical Information of China (English)

    ZHAO Xue-ling; ZHAO Hong-bin; WANG Bin; ZHU Xiao-song; LI Lin-zhi; ZHANG Chun-qiang

    2005-01-01

    Objective: To treat injury of the lower cervical spine C6 to C7 with cervical lateral mass plates and T1 pedicle screws through posterior approach. Methods: The data of 8 patients with lower cervical spine C6 or C7 injury (6 patients with fracture and dislocation in C6 and C7 and 2 with fracture in C7) were analyzed retrospectively in this study. For the preoperative American Spinal Injury Association (ASIA) classification, Grade C was found in 3 cases and Grade D in 5 cases. Screws were placed on the lateral masses and the first thoracic pedicle with Margerl technique. Lamina or facet bone allografting was used to achieve a long-term stability. Results: All the 8 patients were followed up for 5-37 months (mean: 15 months). No operative death occurred. There were no examples of aggravation of spinal cord injury or vertebral artery injury, cerebrospinal fluid leak, nerve roots injury, screw malposition or back-out, loose of alignment or implant failure. Clinical symptoms and ASIA classification were improved in all the patients. Postoperative MRI scanning confirmed the satisfactory screw placement in all the cases. Conclusions: Lateral mass plates and pedicle screws through posterior approach are safe and beneficial for patients with lower cervical spine C6 or C7 injury.

  17. Study on Hardware-in-loop Simulation of Twin-screw Extruder Experiment System

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    <正>In order to facilitate the teaching of industrial processes and experiments on the twin-screw extruder control debugging,and be closer to the actual testing,to reduce the debugging costs and the risk of debugging process,the paper designs a hardware-in-loop simulation of twin-screw extruder experiment system which is closer to scene,low cost and high safety.The system through the establishment of twin-screw extruder’s mathematical model on computer to simulate the realistic system and there is hardware practicality in the computer simulation loop.The hardware based on C8051F020 can operate in the simulation loop in real time.In computer software design, we desigh man-machine interface that is intuitive and easy to operate,can reflect twin-screw extruder main operation information vividly.Finally,twin-screw extruder’s 3 heater temperature mathematical model and PID incremental control algorithm are presented.

  18. Computational fluid dynamics simulation and redesign of a screw conveyor reactor.

    Science.gov (United States)

    Wan, Yinkun; Hanley, Thomas R

    2004-01-01

    National Renewable Energy Laboratory (NREL) designed a shrinking-bed reactor to maintain a constant bulk packing density of cellulosic biomass. The high solid-to-liquid ratio in the pretreatment process allows a high sugar yield and avoids the need to flush large volumes of solution through the reactor. To scale up the shrinking-bed reactor, NREL investigated a pilot-scale screw conveyor reactor in which an interrupted flight between screws was employed to mimic the "shrinking-bed" effect. In the experiments with the screw conveyor reactor, overmixing and uneven flow occurred. These phenomena produce negative effects on biomass hydrolysis. The flow behavior inside the reactor was analyzed to allow redesign of the screw to achieve adequate mixing and even flow. In the present study, computational fluid dynamics (CFD) was utilized to simulate the fluid flow in the porous media, and a new screw design was proposed. CFD analysis performed on the redesigned reactor indicated that an even flow pattern was achieved.

  19. Designs and Techniques That Improve the Pullout Strength of Pedicle Screws in Osteoporotic Vertebrae: Current Status

    Directory of Open Access Journals (Sweden)

    Thomas M. Shea

    2014-01-01

    Full Text Available Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant’s trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device’s effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein.

  20. Designs and techniques that improve the pullout strength of pedicle screws in osteoporotic vertebrae: current status.

    Science.gov (United States)

    Shea, Thomas M; Laun, Jake; Gonzalez-Blohm, Sabrina A; Doulgeris, James J; Lee, William E; Aghayev, Kamran; Vrionis, Frank D

    2014-01-01

    Osteoporosis is a medical condition affecting men and women of different age groups and populations. The compromised bone quality caused by this disease represents an important challenge when a surgical procedure (e.g., spinal fusion) is needed after failure of conservative treatments. Different pedicle screw designs and instrumentation techniques have been explored to enhance spinal device fixation in bone of compromised quality. These include alterations of screw thread design, optimization of pilot hole size for non-self-tapping screws, modification of the implant's trajectory, and bone cement augmentation. While the true benefits and limitations of any procedure may not be realized until they are observed in a clinical setting, axial pullout tests, due in large part to their reproducibility and ease of execution, are commonly used to estimate the device's effectiveness by quantifying the change in force required to remove the screw from the body. The objective of this investigation is to provide an overview of the different pedicle screw designs and the associated surgical techniques either currently utilized or proposed to improve pullout strength in osteoporotic patients. Mechanical comparisons as well as potential advantages and disadvantages of each consideration are provided herein.

  1. Sextant percutaneous pedicle screw fixation for correcting single-segment thoracolumbar fractures

    Institute of Scientific and Technical Information of China (English)

    Ming Jiang-hua; Zheng Hui-feng; Zhao Qi; Chen Qing; Wang Gang

    2014-01-01

    BACKGROUND:Though the effects of conservative or traditional open reduction and internal fixation in the treatment of thoracolumbar fractures are reliable and satisfactory for most cases, two methods also have shortages. Minimal-invasive percutaneous pedicle screw system provides a new available method. OBJECTIVE:To investigate the clinical effect of Sextant percutaneous pedicle screw system in the treatment of thoracolumbar fractures. METHODS:A total of 55 patients, who had undergone percutaneous pedicle screw fixation using Sextant system (25 patients) or traditional open internal fixation (30 patients) for single-level vertebral body compression fractures in Department of Orthopedics of Renmin Hospital of Wuhan University from February 2011 to January 2013, were enrol ed in this study. RESULTS AND CONCLUSION:Except two patients in traditional open internal fixation group were lost after discharge, al other patients were fol owed up for 8-14 months. Operative time, intraoperative blood loss, postoperative drainage amount and hospital day were better in percutaneous pedicle screw fixation group than in the traditional open internal fixation group (P0.05). The results show that percutaneous pedicle screw fixation using Sextant system has a satisfactory outcome in the treatment of thoracolumbar fractures. However, obeying indication strictly is very important for clinical application.

  2. Filtering algorithm for dotted interferences

    Energy Technology Data Exchange (ETDEWEB)

    Osterloh, K., E-mail: kurt.osterloh@bam.de [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Buecherl, T.; Lierse von Gostomski, Ch. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany); Zscherpel, U.; Ewert, U. [Federal Institute for Materials Research and Testing (BAM), Division VIII.3, Radiological Methods, Unter den Eichen 87, 12205 Berlin (Germany); Bock, S. [Technische Universitaet Muenchen, Lehrstuhl fuer Radiochemie, Walther-Meissner-Str. 3, 85748 Garching (Germany)

    2011-09-21

    An algorithm has been developed to remove reliably dotted interferences impairing the perceptibility of objects within a radiographic image. This particularly is a major challenge encountered with neutron radiographs collected at the NECTAR facility, Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II): the resulting images are dominated by features resembling a snow flurry. These artefacts are caused by scattered neutrons, gamma radiation, cosmic radiation, etc. all hitting the detector CCD directly in spite of a sophisticated shielding. This makes such images rather useless for further direct evaluations. One approach to resolve this problem of these random effects would be to collect a vast number of single images, to combine them appropriately and to process them with common image filtering procedures. However, it has been shown that, e.g. median filtering, depending on the kernel size in the plane and/or the number of single shots to be combined, is either insufficient or tends to blur sharp lined structures. This inevitably makes a visually controlled processing image by image unavoidable. Particularly in tomographic studies, it would be by far too tedious to treat each single projection by this way. Alternatively, it would be not only more comfortable but also in many cases the only reasonable approach to filter a stack of images in a batch procedure to get rid of the disturbing interferences. The algorithm presented here meets all these requirements. It reliably frees the images from the snowy pattern described above without the loss of fine structures and without a general blurring of the image. It consists of an iterative, within a batch procedure parameter free filtering algorithm aiming to eliminate the often complex interfering artefacts while leaving the original information untouched as far as possible.

  3. Visualization and understanding of the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging.

    Science.gov (United States)

    Vercruysse, Jurgen; Toiviainen, Maunu; Fonteyne, Margot; Helkimo, Niko; Ketolainen, Jarkko; Juuti, Mikko; Delaet, Urbain; Van Assche, Ivo; Remon, Jean Paul; Vervaet, Chris; De Beer, Thomas

    2014-04-01

    Over the last decade, there has been increased interest in the application of twin screw granulation as a continuous wet granulation technique for pharmaceutical drug formulations. However, the mixing of granulation liquid and powder material during the short residence time inside the screw chamber and the atypical particle size distribution (PSD) of granules produced by twin screw granulation is not yet fully understood. Therefore, this study aims at visualizing the granulation liquid mixing and distribution during continuous twin screw granulation using NIR chemical imaging. In first instance, the residence time of material inside the barrel was investigated as function of screw speed and moisture content followed by the visualization of the granulation liquid distribution as function of different formulation and process parameters (liquid feed rate, liquid addition method, screw configuration, moisture content and barrel filling degree). The link between moisture uniformity and granule size distributions was also studied. For residence time analysis, increased screw speed and lower moisture content resulted to a shorter mean residence time and narrower residence time distribution. Besides, the distribution of granulation liquid was more homogenous at higher moisture content and with more kneading zones on the granulator screws. After optimization of the screw configuration, a two-level full factorial experimental design was performed to evaluate the influence of moisture content, screw speed and powder feed rate on the mixing efficiency of the powder and liquid phase. From these results, it was concluded that only increasing the moisture content significantly improved the granulation liquid distribution. This study demonstrates that NIR chemical imaging is a fast and adequate measurement tool for allowing process visualization and hence for providing better process understanding of a continuous twin screw granulation system.

  4. Opportunistic Interference Alignment for Random Access Networks

    OpenAIRE

    Jin, Hu; Jeon, Sang-Woon; Jung, Bang Chul

    2015-01-01

    An interference management problem among multiple overlapped random access networks (RANs) is investigated, each of which operates with slotted ALOHA protocol. Assuming that access points and users have multiple antennas, a novel opportunistic interference alignment~(OIA) is proposed to mitigate interference among overlapped RANs. The proposed technique intelligently combines the transmit beamforming technique at the physical layer and the opportunistic packet transmission at the medium acces...

  5. Interference Coordination for Dense Wireless Networks

    DEFF Research Database (Denmark)

    Soret, Beatriz; Pedersen, Klaus I.; Jørgensen, Niels T.K.;

    2015-01-01

    The promise of ubiquitous and super-fast connectivity for the upcoming years will be in large part fulfilled by the addition of base stations and spectral aggregation. The resulting very dense networks (DenseNets) will face a number of technical challenges. Among others, the interference emerges...... simply react to an identified interference problem. As an example, we propose two algorithms to apply time domain and frequency domain small cell interference coordination in a DenseNet....

  6. Quantum interference from remotely trapped ions

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, S; Rotter, D; Hennrich, M; Blatt, R [Institute for Experimental Physics, University of Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Rohde, F; Schuck, C; Almendros, M; Gehr, R; Dubin, F; Eschner, J [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, Av del Canal OlImpic, E-08860 Castelldefels (Spain)], E-mail: francois.dubin@icfo.es

    2009-01-15

    We observe quantum interference of photons emitted by two continuously laser-excited single ions, independently trapped in distinct vacuum vessels. High contrast two-photon interference is observed in two experiments with different ion species, Ca{sup +} and Ba{sup +}. Our experimental findings are quantitatively reproduced by Bloch equation calculations. In particular, we show that the coherence of the individual resonance fluorescence light field is determined from the observed interference.

  7. Using Interference to Block RFID Tags

    DEFF Research Database (Denmark)

    Krigslund, Rasmus; Popovski, Petar; Pedersen, Gert Frølund

    We propose a novel method to block RFID tags from responding, using intentional interference. We focus on the experimental evaluation, where we impose interference on the download and uplink, respectively. The results are positive, where modulated CCI shows most effective to block a tag.......We propose a novel method to block RFID tags from responding, using intentional interference. We focus on the experimental evaluation, where we impose interference on the download and uplink, respectively. The results are positive, where modulated CCI shows most effective to block a tag....

  8. Impact of MIMO Co-Channel Interference

    DEFF Research Database (Denmark)

    Rahman, Muhammad Imadur; De Carvalho, Elisabeth; Prasad, Ramjee

    2007-01-01

    to cellular interference of some specific Multiple Input Multiple Output (MIMO) schemes on the same and other MIMO schemes. The goal is to study the impact of interference from MIMO schemes at a user located in the cell edge. Semi-Analytical evaluations of Signal to Interference and Noise Ratio (SINR) is done...... to find out the SINR statistics of different combinations of desired and interfering links. We have studied linear combining receivers for all the link combinations. Based on the current analysis, it is found that Space-Time Block Code (STBC) is a severe interferer compared to others, and specific...

  9. Electromagnetic Interference (EMI) and TEMPEST Test Facility

    Data.gov (United States)

    Federal Laboratory Consortium — Electromagnetic Interference (EMI), Electromagnetic Compatibility (EMC) and TEMPEST testing are conducted at EPG's Blacktail Canyon Test Facility in one of its two...

  10. Interference Alignment Using Variational Mean Field Annealing

    DEFF Research Database (Denmark)

    Badiu, Mihai Alin; Guillaud, Maxime; Fleury, Bernard Henri

    2014-01-01

    We study the problem of interference alignment in the multiple-input multiple- output interference channel. Aiming at minimizing the interference leakage power relative to the receiver noise level, we use the deterministic annealing approach to solve the optimization problem. In the corresponding...... for interference alignment. We also show that the iterative leakage minimization algorithm by Gomadam et al. and the alternating minimization algorithm by Peters and Heath, Jr. are instances of our method. Finally, we assess the performance of the proposed algorithm through computer simulations....

  11. Totally absorbable screws in fixation of subtalar extra articular arthrodesis in children with spastic neuromuscular disease: preliminary report of a randomized prospective study of fourteen arthrodeses fixed with absorbable or metallic screws.

    Science.gov (United States)

    Partio, E K; Merikanto, J; Heikkilä, J T; Ylinen, P; Mäkelä, E A; Vainio, J; Törmälä, P; Rokkanen, P

    1992-01-01

    Seven patients with spastic neuromuscular disease and severe hindfoot valgus deformity were treated by subtalar arthrodesis. Arthrodesis was performed in both feet at the same operation and fixed on one side with a self-reinforced poly-L-lactide (SR-PLLA) screw, and with a standard AO screw on the other side. The functional status state was improved, and radiographic union of the arthrodesis occurred in all feet. The radiograph showed better solid fusion in five feet treated with PLLA screws, similar fusion in both sides in one patient, and one slower fusion in the side treated initially with a PLLA screw. Totally absorbable SR-PLLA screws appear to be firm enough for fixation of subtalar extraarticular arthrodesis in children.

  12. Sensorless compensation system for thermal deformations of ball screws in machine tools drives

    Science.gov (United States)

    Kowal, Michał

    2016-12-01

    The article presents constructional, technological and operational issues associated with the compensation of thermal deformations of ball screw drives. Further, it demonstrates the analysis of a new sensorless compensation method relying on coordinated computation of data fed directly from the drive and the control system in combination with the information pertaining to the operational history of the servo drive, retrieved with the use of an artificial neural networks (ANN)-based learning system. Preliminary ANN-based models, developed to simulate energy dissipation resulting from the friction in the screw-cap assembly and convection of heat are expounded upon, as are the processes of data selection and ANN learning. In conclusion, the article presents the results of simulation studies and preliminary experimental evidence confirming the applicability of the proposed method, efficiently compensating for the thermal elongation of the ball screw in machine tool drives.

  13. Mobility analysis of parallel mechanisms based on screw theory and mechanism topology

    Directory of Open Access Journals (Sweden)

    Liping Wang

    2015-11-01

    Full Text Available A practical method for mobility analysis of mechanisms is presented in this article, which is based on the screw theory and the topology structure of mechanisms. The proposed method can be summarized as one core principle and two key techniques. The core principle is that the series connection of kinematic pairs is equivalent to the superposition of corresponding degrees of freedom, and the parallel connection of kinematic pairs is equivalent to the superposition of corresponding constraints. The first key technique for analyzing the mobility of mechanisms is to correctly identify the series and parallel connection relationship between all kinematic pairs, that is, the mechanism topology structure. Another key technique is transforming the screws and reciprocal screws from local coordinate systems to the global coordinate system. First, the above-mentioned method is presented in theory. Then, several examples are analyzed using it, which validate its effectiveness and universality.

  14. Thermal Analysis of Ball screw Systems by Explicit Finite Difference Method

    Energy Technology Data Exchange (ETDEWEB)

    Min, Bog Ki [Hanyang Univ., Seoul (Korea, Republic of); Park, Chun Hong; Chung, Sung Chong [KIMM, Daejeon (Korea, Republic of)

    2016-01-15

    Friction generated from balls and grooves incurs temperature rise in the ball screw system. Thermal deformation due to the heat degrades positioning accuracy of the feed drive system. To compensate for the thermal error, accurate prediction of the temperature distribution is required first. In this paper, to predict the temperature distribution according to the rotational speed, solid and hollow cylinders are applied for analysis of the ball screw shaft and nut, respectively. Boundary conditions such as the convective heat transfer coefficient, friction torque, and thermal contact conductance (TCC) between balls and grooves are formulated according to operating and fabrication conditions of the ball screw. Explicit FDM (finite difference method) is studied for development of a temperature prediction simulator. Its effectiveness is verified through numerical analysis.

  15. Twin Boundaries merely as Intrinsically Kinematic Barriers for Screw Dislocation Motion in FCC Metals

    Science.gov (United States)

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-03-01

    Metals with nanoscale twins have shown ultrahigh strength and excellent ductility, attributed to the role of twin boundaries (TBs) as strong barriers for the motion of lattice dislocations. Though observed in both experiments and simulations, the barrier effect of TBs is rarely studied quantitatively. Here, with atomistic simulations and continuum based anisotropic bicrystal models, we find that the long-range interaction force between coherent TBs and screw dislocations is negligible. Further simulations of the pileup behavior of screw dislocations in front of TBs suggest that screw dislocations can be blocked kinematically by TBs due to the change of slip plane, leading to the pileup of subsequent dislocations with the elastic repulsion actually from the pinned dislocation in front of the TB. Our results well explain the experimental observations that the variation of yield strength with twin thickness for ultrafine-grained copper follows the Hall-Petch relationship.

  16. Examining drug hydrophobicity in continuous wet granulation within a twin screw extruder.

    Science.gov (United States)

    Li, H; Thompson, M R; O'Donnell, K P

    2015-12-30

    The influence of active pharmaceutical ingredient (API) hydrophobicity on continuous wet granulation was studied in twin screw granulation utilizing foamed binder delivery. The APIs examined were caffeine, acetaminophen, ibuprofen and griseofulvin and the drug load was maintained constant at 15 wt%. In order to understand the impact of these APIs on the granulation process, API and binder distribution, particle size, porosity, and fracture strength were analyzed on samples collected along the screw length. It was found that the API and binder distributions were uniform along the screws regardless of the hydrophobicity of the formulation, in contrast to literature results with liquid injection. The absence of de-mixing of the hydrophobic ingredient was hypothesized to be a result of the high spread-to-soak ratio of a foamed binder that 'cages' those particles within the mass of local hydrophilic solids.

  17. [APPLICATION OF COMPRESSION MINI-SCREWS IN TREATMENT OF PATIENTS WITH INJURY OF ELBOW JOINT BONES].

    Science.gov (United States)

    Neverov, V A; Egorov, K S

    2015-01-01

    A case report presents the experience of application of compression pileateless mini-screws (Gerbert's screws) in treatment of intra-articular fractures, which formed the elbow joint (44 cases). There were performed 32 operations concerning fracture of head of radius, 10 operations on the occasion of fractures of distal section of the humerus and 2 operations on the coronoid process. Long-term treatment results were followed-up in 31 patients during more than 6 months. On basis of analysis of treatment results the authors made a conclusion that the application of mini-screws in case of bone fractures, which formed the elbow joint, allowed realization of stable osteosynthesis after anatomic reposition of articular surfaces, obtaining good anatomical and functional result and shortened the terms of patient's treatment.

  18. Malposition and revision rates of different imaging modalities for percutaneous iliosacral screw fixation following pelvic fractures

    DEFF Research Database (Denmark)

    Zwingmann, Jörn; Hauschild, Oliver; Bode, Gerrit;

    2013-01-01

    INTRODUCTION: Percutaneous iliosacral screw placement following pelvic trauma is associated with high rates of revisions, screw malpositioning, the risk of neurological damage and inefficient stability. The correct entry point and the small target corridor may be difficult to visualize using only...... an image intensifier. Therefore, 2D and 3D image-based navigation and reconstruction techniques could be helpful tools. The aim of this systematic review and meta-analysis was to evaluate the best available evidence regarding the rate of malpositioning and revisions using different techniques for screw...... implantation, i.e., conventional, 2D and 3D image-based navigation and reconstruction techniques, CT navigation. METHODS: A systematic review and meta-analysis were performed using the data available on Ovid Medline. 430 studies published between 1/1948 and 2/2011 were identified by two independent...

  19. ANALYSIS OF SPATIAL COMPLIANCE BEHAVIOR OF COILED SPRINGS VIA SCREW THEORY

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new method is presented to describe and analyze the spatial compliance of coiled springs using screw theory.After an abbreviated description for the deformation of a beam element using screw theory, the spatial compliance den-sity for a beam element is derived based on the fundamental material theory and reasonable assumptions, and the spatialcompliance of the beam with finite length is obtained by integral. The spatial compliance of coiled springs is furtheranalyzed using the spatial compliance density of the beam element. By calculating the eigencompliance and Ball's prin-ciple screws for the whole compliance of system, the compliance properties varying with the basic physical parameters ofthe system are illustrated in detail. The basic ideas can be used for the design and application of the coiled springs and theother compliant mechanisms with spatial compliant beam element.

  20. Twin Boundaries merely as Intrinsically Kinematic Barriers for Screw Dislocation Motion in FCC Metals.

    Science.gov (United States)

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-03-10

    Metals with nanoscale twins have shown ultrahigh strength and excellent ductility, attributed to the role of twin boundaries (TBs) as strong barriers for the motion of lattice dislocations. Though observed in both experiments and simulations, the barrier effect of TBs is rarely studied quantitatively. Here, with atomistic simulations and continuum based anisotropic bicrystal models, we find that the long-range interaction force between coherent TBs and screw dislocations is negligible. Further simulations of the pileup behavior of screw dislocations in front of TBs suggest that screw dislocations can be blocked kinematically by TBs due to the change of slip plane, leading to the pileup of subsequent dislocations with the elastic repulsion actually from the pinned dislocation in front of the TB. Our results well explain the experimental observations that the variation of yield strength with twin thickness for ultrafine-grained copper follows the Hall-Petch relationship.

  1. Corrosion of magnesium alloy AZ31 screws is dependent on the implantation site

    Energy Technology Data Exchange (ETDEWEB)

    Willbold, E. [Laboratory for Biomechanics and Biomaterials, Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Strasse 1-7, D - 30625 Hannover (Germany); Kaya, A.A. [Mugla University, Engineering Faculty, Metallurgy and Materials Engineering Department, Mugla (Turkey); Kaya, R.A. [MedicalPark Hospital, Kueltuer Sok No:1, 34160 Bahcelievler, Istanbul (Turkey); Beckmann, F. [Helmholtz-Zentrum Geesthacht, Institute of Materials Research, Max-Planck-Str.1, D - 21502 Geesthacht (Germany); Witte, F., E-mail: witte.frank@mh-hannover.de [Laboratory for Biomechanics and Biomaterials, Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Strasse 1-7, D - 30625 Hannover (Germany)

    2011-12-15

    The corrosion of biodegradable materials is a crucial issue in implant development. Among other materials, magnesium and magnesium based alloys are one of the most promising candidates. Since the corrosion of biodegradable materials depends on different physiological parameters like pH or ion concentrations, the corrosion might be different in different biological environments. To investigate this issue, we produced screws from magnesium alloy AZ31 and implanted them into the hip bone of 14 sheep. After 3 and 6 months, the screws were explanted and analyzed with synchrotron-radiation based micro-computed tomography and hard tissue histology. We found considerable differences in the corrosion behavior of the magnesium screws with respect to its original tissue location. However, we could detect a normal immunological tissue response.

  2. Replacement screws valve operating under Trunnion; Substituicao de parafusos de valvulas Trunnion em regime de operacao

    Energy Technology Data Exchange (ETDEWEB)

    Souza Netto, Charles de; Santos, Rogerio Andre Zolin dos; Arnhold, Diego [Companhia de Gas do Estado do Rio Grande do Sul (SULGAS), Porto Alegre, RS (Brazil); Jacques, Rodrigo das Neves [Guidotti e Vieira Manutencao Industrial Ltda., Canoas, RS (Brazil)

    2012-07-01

    The report shows the process created for the substitution and extraction of bearing screws of the Trunnion valves, in operation. The methodology was developed at the 'Companhia de Gas do Estado do Rio Grande do Sul - SULGAS', with the objective of avoiding failure emergency situations, and or sudden breaking of the screws of fixation of the lid of the inferior bearing of the Trunnion valves. it is a preventive process of substitution of these screws, that after a great period of use in atmospheres with high potential of oxidation present structural failure. The breaking of these components creates a leaking process by the inferior lid of the valves, fact that is intended to be avoided with the application of the technical procedure of this report, guaranteeing the integrity of the valves that are vital components for the continuous operation of the gas pipe line. (author)

  3. A finite element modeling of posterior atlantoaxial fixation and biomechanical analysis of C2 intralaminar screw fixation

    Institute of Scientific and Technical Information of China (English)

    Ma Xuexiao; Peng Xianbo; Xiang Hongfei; Zhang Yan; Zhang Guoqing; Chen Bohua

    2014-01-01

    Background The objective of this study was to use three-dimensional finite element (FE) models to analyze the stability and the biomechanics of two upper cervical fixation methods:the C2 intralaminar screw method and the C2 pedicle screw method.Methods From computed tomography images,a nonlinear three-dimensional FE model from C0 (occiput) to C3 was developed with anatomic detail.The C2 intralaminar screw and the C2 pedicle screw systems were added to the model,in parallel to establish the interlaminar model and the pedicle model.The two models were operated with all possible states of motion and physiological loads to simulate normal movement.Results Both the C2 intralaminar screw method and the C2 pedicle screw method significantly reduced motion compared with the intact model.There were no statistically significant differences between the two methods.The Von Mises stresses of the internal and external laminar walls were similar between the two methods.Stability was also similar.Conclusions The C2 intralaminar screw method can complement but cannot completely replace the C2 pedicle screw method.Clinicians would need to assess and decide which approach to adopt for the best therapeutic effect.

  4. Percutaneous Cement-Augmented Screws Fixation in the Fractures of the Aging Spine: Is It the Solution?

    Directory of Open Access Journals (Sweden)

    Sébastien Pesenti

    2014-01-01

    Full Text Available Introduction. Management of elderly patients with thoracolumbar fractures is still challenging due to frequent osteoporosis and risk of screws pull-out. The aim of this study was to evaluate results of a percutaneous-only procedure to treat these fragile patients using cement-augmented screws. Methods. 12 patients diagnosed with a thoracolumbar fracture associated with an important loss of bone stock were included in this prospective study. Surgical procedure included systematically a percutaneous osteosynthesis using cemented fenestrated screws. When necessary, additional anterior support was performed using a kyphoplasty procedure. Clinical and radiographic evaluations were performed using CT scan. Results. On the whole series, 15 fractures were diagnosed and 96 cemented screws were inserted. The difference between the pre- and postoperative vertebral kyphosis was statistically significant (12.9° versus 4.4°, P=0.0006. No extrapedicular screw was reported and one patient was diagnosed with a cement-related pulmonary embolism. During follow-up period, no infectious complications, implant failures, or pull-out screws were noticed. Discussion. Aging spine is becoming an increasing public health issue. Management of these patients requires specific attention due to the augmented risk of complications. Using percutaneous-only screws fixation with cemented screw provides satisfactory results. A rigorous technique is mandatory in order to achieve best outcomes.

  5. Magnesium inference screw supports early graft incorporation with inhibition of graft degradation in anterior cruciate ligament reconstruction

    Science.gov (United States)

    Cheng, Pengfei; Han, Pei; Zhao, Changli; Zhang, Shaoxiang; Zhang, Xiaonong; Chai, Yimin

    2016-05-01

    Patients after anterior cruciate ligament (ACL) reconstruction surgery commonly encounters graft failure in the initial phase of rehabilitation. The inhibition of graft degradation is crucial for the successful reconstruction of the ACL. Here, we used biodegradable high-purity magnesium (HP Mg) screws in the rabbit model of ACL reconstruction with titanium (Ti) screws as a control and analyzed the graft degradation and screw corrosion using direct pull-out tests, microCT scanning, and histological and immunohistochemical staining. The most noteworthy finding was that tendon graft fixed by HP Mg screws exhibited biomechanical properties substantially superior to that by Ti screws and the relative area of collagen fiber at the tendon-bone interface was much larger in the Mg group, when severe graft degradation was identified in the histological analysis at 3 weeks. Semi-quantitative immunohistochemical results further elucidated that the MMP-13 expression significantly decreased surrounding HP Mg screws with relatively higher Collagen II expression. And HP Mg screws exhibited uniform corrosion behavior without displacement or loosening in the femoral tunnel. Therefore, our results demonstrated that Mg screw inhibited graft degradation and improved biomechanical properties of tendon graft during the early phase of graft healing and highlighted its potential in ACL reconstruction.

  6. 基于无瞬心包络法的偏心螺杆成型铣刀研究%Study of Formed Milling Cutter for Processing Eccentric Screw Based on Non-Instantaneous Envelope Method

    Institute of Scientific and Technical Information of China (English)

    李云; 范晋伟; 陈东菊; 王晓峰; 刘勇军

    2012-01-01

    根据偏心螺杆的形状和特征参数,建立了偏心螺杆的螺旋曲面方程;基于无瞬心包络法,从成型铣刀与偏心螺杆的相对运动关系出发,依据成型铣刀与螺杆的啮合条件,建立其接触线方程.由接触线围绕铣刀轴线回转形成回转面的轴向截形,推导出铣刀刀刃的廓形方程.进一步分析了成型铣刀用钝重磨后引起加工误差的原因,以阿基米德螺线为基础建立铣刀的齿背曲线方程,得到具有恒定后角的铣刀廓形方程.仿真结果表明,成型铣刀的廓形与偏心螺杆螺旋曲面吻合良好,设计的成型铣刀廓形方程符合加工要求.%The design theory and method of formed milling cutter for eccentric screw is presented. Through analyzing the shape and characteristic parameters of eccentric screw, the spiral surface equation of eccentric screw was established. Considering the relative motion and the meshing conditions between formed milling cutter and eccentric screw, the contact line equation was established based on non-instantaneous envelope method. Further, from the cross-section shape of the rotary surface formed by the contact line around the axis of cutter, the profile equation of formed milling cutter was deduced. By analyzing the causes of processing errors after wear of formed milling cutter, the tooth back curve equation was achieved in accordance with spiral of Archimedes and got the profile equation of formed milling cutter with constant back edge was gotten. Finally, the interference for profile equation of formed milling cutter was checked. Simulation shows that the profile of formed milling cutter coincides with the spiral surface of eccentric screw and the designed profile equation of formed milling cutter conforms to the requirements of the processing. This work provides a theoretical foundation for the design and manufacture of formed milling cutter.

  7. Biomechanical and clinical study on screw hook fixation after direct repair of lumbar spondylolysis

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jian; LIU Fan; SHI Hong-guang; FAN Jian; ZHAO Wei-dong; WANG You-hua; CAI Yu-hui

    2006-01-01

    Objective: To evaluate the biomechanical effect and clinical results of hook screw fixation after direct repair of lumbar spondylous defects in the pars interarticularis.Methods: L2-L6 spines of 8 fresh-frozen and thawed calf cadavers were used for mechanical testing. Bilateral spondylous defects were created in the L4 vertebra. The intervertebral rotation ranges between L4 and Ls were scanned and computerized in various states of motion, such as flexion/extension, lateral bending and torsional loadings applied on the intact spine and the spondylous spine when the spondylous spine was fixed with modified Scott's fixation, hook screw fixation and Buck's fixation sequentially and respectively. Between July 2002 and February 2004, 14 young male patients (aged 15-31 years)suffering from symptomatic lumbar spondylolysis were treated with TSRH hook screw fixation after direct repair of the defects. MacNab criteria1 were used to assess their preand post-operative status.Results: Each fixation technique could significantly increase the intervertebral rotational stiffness and made the stiffness return to nearly the intact level. Hook screw technique provided more rotational stability than the others. Hook screw and Buck's techniques provided more flexion/extension stability than modified Scott's technique.Neither complication nor instrumental failure was observed in this study. The mean follow-up period was 21 months.All the patients except one acquired union during the follow-up period. Thirteen patients had a "good" or "excellent" result according to MacNab criteria.Conclusions: Hook screw fixation shows biomechanical advantages and is safe and effective for young patients with lumbar spondylolysis.

  8. Proximal migration of hardware in patients undergoing midcarpal fusion with headless compression screws.

    Science.gov (United States)

    Shifflett, Grant D; Athanasian, Edward A; Lee, Steve K; Weiland, Andrew J; Wolfe, Scott W

    2014-11-01

    Background Scaphoid excision and limited intercarpal fusion is a common surgical procedure performed for degenerative disorders of the wrist including scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC) wrist deformities. Postoperative screw migration is a rare but devastating complication that can result in severe degenerative changes in the radiocarpal joint. Questions/Purposes The purpose of this study is to report on a series of patients who developed proximal migration of their hardware following limited intercarpal fusions with headless compression screws. Patients and Methods Four patients were identified between 2001 and 2012 who were indicated for and underwent scaphoid excision and midcarpal fusions with headless compression screw fixation and subsequently developed hardware migration with screw protrusion into the radiocarpal joint. Detailed chart review was performed. Results Mean age at surgery was 64 years (57-69 years). All patients had the diagnosis of SLAC wrist. Mean time to detection of failure was 6 months (4-8 months). All patients demonstrated radiographic union prior to failure based on plain films. Radiographs revealed screw backout with erosion of the radial lunate facet in all patients. Calculated carpal height ratios demonstrated a drop from an average 44.2% to 39.5% at the time of hardware migration. All four patients underwent hardware removal. One patient was not indicated for any further surgery, and two patients underwent further revision surgery. All three patients reported complete pain relief. One patient refused a salvage procedure and had subsequent persistent pain. Conclusions This study reports a serious complication of scaphoid excision and midcarpal fusion performed with headless compression screws. We advise surgeons to be aware of this potential complication and consider employing methods to reduce the risk of hardware migration. Additionally, we recommend at least 8 months of

  9. The calcar screw in angular stable plate fixation of proximal humeral fractures - a case study

    Directory of Open Access Journals (Sweden)

    Simmen Hans-Peter

    2011-09-01

    Full Text Available Abstract Background With new minimally-invasive approaches for angular stable plate fixation of proximal humeral fractures, the need for the placement of oblique inferomedial screws ('calcar screw' has increasingly been discussed. The purpose of this study was to investigate the influence of calcar screws on secondary loss of reduction and on the occurrence of complications. Methods Patients with a proximal humeral fracture who underwent angular stable plate fixation between 01/2007 and 07/2009 were included. On AP views of the shoulder, the difference in height between humeral head and the proximal end of the plate were determined postoperatively and at follow-up. Additionally, the occurrence of complications was documented. Patients with calcar screws were assigned to group C+, patients without to group C-. Results Follow-up was possible in 60 patients (C+ 6.7 ± 5.6 M/C- 5.0 ± 2.8 M. Humeral head necrosis occurred in 6 (C+, 15.4% and 3 (C-, 14.3% cases. Cut-out of the proximal screws was observed in 3 (C+, 7.7% and 1 (C-, 4.8% cases. In each group, 1 patient showed delayed union. Implant failure or lesions of the axillary nerve were not observed. In 44 patients, true AP and Neer views were available to measure the head-plate distance. There was a significant loss of reduction in group C- (2.56 ± 2.65 mm compared to C+ (0.77 ± 1.44 mm; p = 0.01. Conclusions The placement of calcar screws in the angular stable plate fixation of proximal humeral fractures is associated with less secondary loss of reduction by providing inferomedial support. An increased risk for complications could not be shown.

  10. Sol-gel derived titania coating with immobilized bisphosphonate enhances screw fixation in rat tibia.

    Science.gov (United States)

    Linderbäck, Paula; Areva, Sami; Aspenberg, Per; Tengvall, Pentti

    2010-08-01

    A variety of surface modifications have been tested for the enhancement of screw fixation in bone, and locally delivered anti-osteoporosis drugs such as bisphosphonates (BP) are then of interest. In this in vivo study, the impact of surface immobilized BP was compared with systemic BP delivery and screws with no BP. After due in vitro characterization, differently treated stainless steel (SS) screws were divided into four groups with 10 rats each. Three of the groups received screws coated with sol-gel derived TiO(2) and calcium phosphate (SS+TiO(2)+CaP). One of these had no further treatment, one had alendronate (BP) adsorbed to calcium phosphate mineral, and one received systemic BP treatment. The fourth group received uncoated SS screws and no BP (control). The screw pullout force was measured after 4 weeks of implantation in rat tibiae. The immobilized amount and release rate of alendronate could be controlled by different immersion times. The SS+TiO(2)+CaP coating did not increase the pullout force compared to SS alone. Surface delivered alendronate enhanced the pullout force by 93% [p = 0.000; 95% Confidence Interval (CI): 67-118%] compared to SS, and by 39% (p = 0.044; 95% CI: 7-71%) compared to systemic alendronate delivery. Both surface immobilized and systemically delivered alendronate improved implant fixation. Also, locally delivered, that is, surface immobilized alendronate showed a better fixation than systemically delivered. Using sol-gel derived TiO(2) as a platform, it is possible to administer controllable amounts of a variety of BPs.

  11. Comparison between two pedicle screw augmentation instrumentations in adult degenerative scoliosis with osteoporosis

    Directory of Open Access Journals (Sweden)

    Xie Yang

    2011-12-01

    Full Text Available Abstract Background The operative treatment of adult degenerative scoliosis combined with osteoporosis increase following the epidemiological development. Studies have confirmed that screws in osteoporotic spines have significant lower-screw strength with more frequent screw movements within the vertebra than normal spines. Screws augmented with Polymethylmethacrylate (PMMA or with autogenous bone can offer more powerful corrective force and significant advantages. Methods A retrospective analysis was conducted on 31 consecutive patients with degenerative lumbar scoliosis combined with osteoporosis who had surgery from December 2000. All had a minimum of 2-year follow-up. All patients had posterior approach surgery. 14 of them were fixed with pedicle screw by augmentation with Polymethylmethacrylate (PMMA and the other 17 patients with autogenous bone. Age, sex and whether smoking were similar between the two groups. Surgical time, blood loss, blood transfusion, medical cost, post surgery ICU time, hospital day, length of oral pain medicines taken, Pre-and postoperative Oswestry disability index questionnaire and surgical revision were documented and compared. Preoperative, postoperative and final follow up Cobb angle, sagittal lumbar curve, correction rate, and Follow up Cobb loss were also compared. Results No significant differences were found between the autogenous bone group and Polymethylmethacrylate group with regards to all the targets above except for length of oral pain medicines taken and surgery cost. 2 patients were seen leakage during operation, but there is neither damage of nerve nor symptom after operation. No revision was needed. Conclusion Both augmentation pedicle screw with Polymethylmethacrylate (PMMA and autogenous bone treating degenerative lumbar scoliosis combined with osteoporosis can achieve a good surgical result. Less oral pain medicines taken are the potential benefits of Polymethylmethacrylate augmentation, but

  12. INTERFERENCE OF COUNTERPROPAGATING SHOCK WAVES

    Directory of Open Access Journals (Sweden)

    P. V. Bulat

    2015-03-01

    -dynamic discontinuities, the intensities corresponding to the transition from regular to irregular interference were described. Numerical calculations of the shock-wave structure transformation in the conditions of hysteresis were performed. The results were compared with the experiments carried out by hydraulic analogy method. Practical significance. Results of the work complement well the theory of stationary gas-dynamic discontinuities interference and can be used at designing of perspective images of supersonic and hypersonic aircraft.

  13. Estudo histomorfométrico da interface óssea do parafuso expansor cervical Histomorphometric analysis of bone-screw interface of expansive cervical screw

    Directory of Open Access Journals (Sweden)

    Leandro Sérgio da Silva

    2008-03-01

    experimental study for the Histomorphometric analysis of the bone interface of expansive screws used in the anterior cervical spine fixation system. METHODS: Five sheep cervical vertebrae (C4 were used in the study, in which screws were inserted. The 18.5 mm long and 5.0 mm outer diameter expansive screws (Ulrich were inserted in both sides of the C4 vertebra. On the left side, the screw was inserted without the internal expansive screw, which was used on the right side. A pilot hole was made on the lower portion of the vertebra with a 2.5 mm bore, but no implant was introduced. The vertebral region containing the screws and the pilot hole was prepared for a histological study of the interface between implants and bone screws, and of the pilot hole wall. Histomorphometric analysis evaluated total bone density, external bone density (outside the screw thread, internal density (inside the screw thread and the linear measurement of the contact between bone tissue and the implant. RESULTS: Total bone density was greater in group I (expansive screw as compared to group III (control. External bone density was greater in groups I (expansive screw and II (non-expansive screw when compared to group III. Internal bone density was greater in group I when compared to groups II and III, and greater in group II when compared to group III. Linear contact was greater in group I when compared to groups II and III. CONCLUSION: structural changes around expansive screws detected immediately after their application provide subsidies for a better understanding of the greater tearing resistance of the implant, which could be related to the compacting of cancellous bone around the implant, while providing a larger contact area between the implant and the bone tissue.

  14. Vortex conception of rotor and mutual effect of screw/propellers

    Science.gov (United States)

    Lepilkin, A. M.

    1986-01-01

    A vortex theory of screw/propellers with variable circulation according to the blade and its azimuth is proposed, the problem is formulated and circulation is expanded in a Fourier series. Equations are given for inductive velocities in space for crews, including those with an infinitely large number of blades and expansion of the inductive velocity by blade azimuth of a second screw. Multiparameter improper integrals are given as a combination of elliptical integrals and elementary functions, and it is shown how to reduce elliptical integrals of the third kind with a complex parameter to integrals with a real parameter.

  15. Positioning of Screw Holes Group Based on Digital Camera and Digital Control Drilling

    Institute of Scientific and Technical Information of China (English)

    FENG Wenhao; LI Jiansong; YAN Li; SU Guozhong; YUAN Xiuxiao; ZHONG Shengzhang; JI Huiming

    2004-01-01

    Positioning of screw holes is an important production procedure for steel construction connecting with bolts. In this paper, a new production method is presented, in which the digital camera is used for taking pictures of screw holes and other techniques are advanced. This paper also indicates that the pixels of CCD chip in photogrammetry should be chosen as all geometric units in an image, such as interior elements and all kinds of distortions. The measure can also simplify the camera calibration for determining the size of non-square pixel.

  16. Analysis of jacobian and singularity of planar parallel robots using screw theory

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jung Hyun; Lee, Jeh Won; Lee, Hyuk Jin [Yeungnam Univ., Gyeongsan (Korea, Republic of)

    2012-11-15

    The Jacobian and singularity analysis of parallel robots is necessary to analyze robot motion. The derivations of the Jacobian matrix and singularity configuration are complicated and have no geometrical earning in the velocity form of the Jacobian matrix. In this study, the screw theory is used to derive the Jacobian of parallel robots. The statics form of the Jacobian has a geometrical meaning. In addition, singularity analysis can be performed by using the geometrical values. Furthermore, this study shows that the screw theory is applicable to redundantly actuated robots as well as non redundant robots.

  17. The Accuracy of Screw Axis Analysis Using Position Data from Anatomical Motion Studies.

    Science.gov (United States)

    1980-05-05

    Hip Motion ........ . 57 7-2 Screw Axis Analysis for the Sacro -iliac Joint. 57 viii " LIST OF FIGURES Figure Title Page 2-1 Systems Anthropometry Data...The piercing point selected for this test was an arbitrary point. The screw axis direction was selected so that there would be equal components in all...analyzed are the hip, and the sacro -iliac joint. The bone movements analyzed are the femur moving relative to the left inominate for hip motion, and the

  18. DEVELOPMENT OF ARCHIMEDEAN’S PIPE-SCREW FOR THAI SAIL WINDPUMP

    OpenAIRE

    Ronnakorn Thepwong; Issaree Hansacharoonroj; Joseph Khedari; Tawit Chitsomboon; Jongjit Hirunlabh; Sombat Teekasap

    2014-01-01

    This study describes new considerations in the design and development of Archimedean’s Pipe-Screw especially for water pumping in case of low head high volume form open farm pond at Rajamangala University of Technology Rattanakosin, Thailand. The objectives of this research is to develop an Archimedean’s Pipe-Screw especially for water pumping in case of low head high volume form open farm pond used for water pumping with Thai sail windmill, at any location of low wind speed of Th...

  19. A new technique for insertion of barrel plate over dynamic hip/compression lag screw:a case report

    Institute of Scientific and Technical Information of China (English)

    Sameer Naranje; Vivek Trikha

    2012-01-01

    Dynamic hip/compression screw (DHS/DCS) is one of the most commonly performed surgeries in orthopaedic practice.Sliding barrel plate over the DHS/DCS lag screw is one of the very crucial and at times uncomfortable and time consuming steps of DHS/DCS surgery especially when it comes to inexperienced surgeons and residents.Also in developing countries where not all standard instrumentation is always available,this crucial step becomes more time consuming.Here we present a case report of 58-year-old male patient with intertrochanteric fracture,in which we used a new device for insertion of barrel plate over DHS/DCS lag screw and found that a small DHS/DCS lag screw extension (sliding jig of barrel plate)can be very helpful to slide barrel plate over the DHS/DCS lag screw.

  20. Automated detection of fiducial screws from CT/DVT volume data for image-guided ENT surgery.

    Science.gov (United States)

    Zheng, Guoyan; Gerber, Nicolas; Widmer, Daniel; Stieger, Christof; Caversaccio, Marco; Nolte, Lutz-Peter; Weber, Stefan

    2010-01-01

    This paper presents an automated solution for precise detection of fiducial screws from three-dimensional (3D) Computerized Tomography (CT)/Digital Volume Tomography (DVT) data for image-guided ENT surgery. Unlike previously published solutions, we regard the detection of the fiducial screws from the CT/DVT volume data as a pose estimation problem. We thus developed a model-based solution. Starting from a user-supplied initialization, our solution detects the fiducial screws by iteratively matching a computer aided design (CAD) model of the fiducial screw to features extracted from the CT/DVT data. We validated our solution on one conventional CT dataset and on five DVT volume datasets, resulting in a total detection of 24 fiducial screws. Our experimental results indicate that the proposed solution achieves much higher reproducibility and precision than the manual detection. Further comparison shows that the proposed solution produces better results on the DVT dataset than on the conventional CT dataset.