Quantitative dual-energy CT for phantomless evaluation of cancellous bone mineral density of the vertebral pedicle: correlation with pedicle screw pull-out strength

Energy Technology Data Exchange (ETDEWEB)

Wichmann, Julian L.; Booz, Christian; Bauer, Ralf W.; Kerl, J.M.; Fischer, Sebastian; Lehnert, Thomas; Vogl, Thomas J.; Khan, M.F. [University Hospital Frankfurt, Department of Diagnostic and Interventional Radiology, Frankfurt am Main (Germany); Wesarg, Stefan [Fraunhofer IGD, Cognitive Computing and Medical Imaging, Darmstadt (Germany); Kafchitsas, Konstantinos [Spine Center, Asklepios Klinik Lindenlohe, Schwandorf (Germany)

2015-06-01

To evaluate quantitative dual-energy computed tomography (DECT) for phantomless analysis of cancellous bone mineral density (BMD) of vertebral pedicles and to assess the correlation with pedicle screw pull-out strength. Twenty-nine thoracic and lumbar vertebrae from cadaver specimens were examined with DECT. Using dedicated post-processing software, a pedicle screw vector was mapped (R1, intrapedicular segment of the pedicle vector; R2, intermediate segment; R3, intracorporal segment; global, all segments) and BMD was calculated. To invasively evaluate pedicle stability, pedicle screws were drilled through both pedicles and left pedicle screw pull-out strength was measured. Resulting values were correlated using the paired t test and Pearson's linear correlation. Average pedicle screw vector BMD (R1, 0.232 g/cm{sup 3}; R2, 0.166 g/cm{sup 3}; R3, 0.173 g/cm{sup 3}; global, 0.236 g/cm{sup 3}) showed significant differences between R1-R2 (P < 0.002) and R1-R3 (P < 0.034) segments while comparison of R2-R3 did not reach significance (P > 0.668). Average screw pull-out strength (639.2 N) showed a far stronger correlation with R1 (r = 0.80; P < 0.0001) than global BMD (r = 0.42; P = 0.025), R2 (r = 0.37; P = 0.048) and R3 (r = -0.33; P = 0.078) segments. Quantitative DECT allows for phantomless BMD assessment of the vertebral pedicle. BMD of the intrapedicular segment shows a significantly stronger correlation with pedicle screw pull-out strength than other segments. (orig.)

Carbonizing etc. , coal etc

Energy Technology Data Exchange (ETDEWEB)

Duckham, A M; Rider, D; Watts, J S

1924-01-17

In drying, carbonizing, and distilling coal, shale, etc., by passage through a heated retort, the material is spread in a thin layer over the heating surface by a conveying-screw with a shallow thread. The retort is heated by a bath of molten metal, and the conveyingscrew intermeshes with a scraper screw of smaller diameter, and of a different hand; the screws are mounted on shafts geared together by wheels. The material after passing through the retort is delivered into a chute closed at the bottom by an arc-shaped water seal carried on arms and opened periodically by a lever.

Feeder replacement tooling and processes

International Nuclear Information System (INIS)

Mallozzi, R.; Goslin, R.; Pink, D.; Askari, A.

2008-01-01

Primary heat transport system feeder integrity has become a concern at some CANDU nuclear plants as a result of thinning caused by flow accelerated corrosion (FAC). Feeder inspections are indicating that life-limiting wall thinning can occur in the region between the Grayloc hub weld and second elbow of some outlet feeders. In some cases it has become necessary to replace thinned sections of affected feeders to restore feeder integrity to planned end of life. Atomic Energy of Canada Limited (AECL) and Babcock and Wilcox Canada Ltd. (B and W) have developed a new capability for replacement of single feeders at any location on the reactor face without impacting or interrupting operation of neighbouring feeders. This new capability consists of deploying trained crews with specialized tools and procedures for feeder replacements during planned outages. As may be expected, performing single feeder replacement in the congested working environment of an operational CANDU reactor face involves overcoming many challenges with respect to access to feeders, available clearances for tooling, and tooling operation and performance. This paper describes some of the challenges encountered during single feeder replacements and actions being taken by AECL and B and W to promote continuous improvement of feeder replacement tooling and processes and ensure well-executed outages. (author)

Replacing by numbers - computer aided installation of ball screws in a CANDU

International Nuclear Information System (INIS)

Granz, R.; Georgas, J.

1992-01-01

Performing repair procedures on a commissioned nuclear reactor is a critical maintenance task and certainly not one suitable for on-the-job experimentation. That was our dilemma when the engineering staff developed what was thought would be a better way to replace the ball screws in the fuelling machine support bridges of a CANDU nuclear plant. The 40ft long ball screws must be installed vertically into square cavities that are less than 40ft from the ''ceiling'' of the room where they are located. Standard operating procedures for replacing the ball screw involve opening up the feeder cabinet located above to provide clearance. But this practice risks damage to delicate piping located inside the cabinet. The new concept involved walking the ball screw in by tilting it at a series of angles. Unfortunately, there was no simple way that we could determine with pencil and paper whether or not this approach would work or exactly how to do it in practice. Using the solid modelling capabilities of the Aries Concept Station mechanical computer-aided engineering system, we proved the new procedure and developed a series of illustrations offering step-by-step visual instructions to guide the maintenance crew performing the task. (Author)

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

Science.gov (United States)

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

2013-08-01

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

Corrosion protection pays off for coal-fired power plants

Energy Technology Data Exchange (ETDEWEB)

Hansen, T.

2006-11-15

Zinc has long been used to hot-dip galvanise steel to deliver protection in harsh environments. Powder River Basin or eastern coal-fired plants benefit from using galvanized steel for conveyors, vibratory feeders, coal hoppers, chutes, etc. because maintenance costs are essentially eliminated. When life cycle costs for this process are compared to an alternative three-coal paint system for corrosion protection, the latter costs 5-10 times more than hot-dip galvanizing. An AEP Power Plant in San Juan, Puerto Rico and the McDuffie Coal Terminal in Mobile, AL, USA have both used hot-dip galvanized steel. 1 fig., 1 tab.

In Developping a Bench-Scale Circulating Fluidized Bed Combustor to Burn High Ash Brazilian Coal-Dolomites Mixtures

Science.gov (United States)

Ramírez Behainne, Jhon Jairo; Hory, Rogério Ishikawa; Goldstein, Leonardo; Bernárdez Pécora, Araí Augusta

This work considers some of the questions in burning high ash Brazilian coal-dolomite mixtures in a bench-scale circulating fluidized bed combustor (CFBC). Experimental tests were performed with the CE4500 coal from Santa Catarina State, in southern Brazil, with a Sauter mean diameter d p =43 μm. The coal particles were mixed with dolomite particles of d p = 111 μm and this fuel mixture was fed into the circulating fluidized reactor, previously loaded with quartz sand particles of d p =353 μm. This inert material was previously heated by the combustion of liquefied petroleum gas up to the ignition temperature of the fuel mixture. The CFBC unit has a 100mm internal diameter riser, 4.0m high, as well as a 62.8mm internal diameter downcomer. The loop has a cyclone, a sampling valve to collect particles and a 62.8mm internal diameter L-valve to recirculate the particles in the loop. A screw feeder with a rotation control system was used to feed the fuel mixture to the reactor. The operational conditions were monitored by pressure taps and thermocouples installed along the loop. A data acquisition system showed the main operational conditions to control. Experimental tests performed put in evidence the problems found during bed operation, with special attention to the solids feed device, to the L-valve operation, to particle size, solids inventory, fluidized gas velocity, fuel mixture and recirculated solids feeding positions.

Feederism in a woman.

Science.gov (United States)

Terry, Lesley L; Vasey, Paul L

2011-06-01

Feederism is a fat fetish subculture in which individuals eroticize weight gain and feeding. Feeders are individuals who claim to become sexually aroused by feeding their partners and encouraging them to gain weight. Conversely, Feedees are individuals who claim to become sexually aroused by eating, being fed, and the idea or act of gaining weight. Very little is known about this population. This report describes a woman who self-identified as a Feedee. It is unclear, at present, whether female Feederism represents a unique paraphilia or a thematic variation of morphophilia or sexual masochism.

Co-firing straw with coal in a swirl-stabilized dual-feed burner: modelling and experimental validation

DEFF Research Database (Denmark)

Yin, Chungen; Kær, Søren Knudsen; Rosendahl, Lasse

2010-01-01

This paper presents a comprehensive computational fluid dynamics (CFD) modelling study of co-firing wheat straw with coal in a 150 kW swirl-stabilized dual-feed burner flow reactor, in which the pulverized straw particles (mean diameter of 451μm) and coal particles (mean diameter of 110.4μm...... conversion. It is found that for pulverized biomass particles of a few hundred microns in diameter the intra-particle heat and mass transfer is a secondary issue at most in their conversion, and the global four-step mechanism of Jones and Lindstedt may be better used in modelling volatiles combustion......-lean core zone; whilst the coal particles are significantly affected by secondary air jet and swirled into the oxygen-rich outer radius with increased residence time (in average, 8.1s for coal particles vs. 5.2s for straw particles in the 3m high reactor). Therefore, a remarkable difference in the overall...

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

Science.gov (United States)

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

2016-06-01

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

Design of apron feeders

Energy Technology Data Exchange (ETDEWEB)

Ramos, C.M.

1987-12-01

This paper discusses practical aspects of apron feeder design, and includes information on how to make the first selection. Various aspects of design such as feeder speed, material depth, chain-pitch, roller loading, wheels/sprockets and chain roller friction are elaborated in detail. 8 refs., 14 figs., 12 tabs.

Ball Screw Actuator Including a Compliant Ball Screw Stop

Science.gov (United States)

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

2017-01-01

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

The development and manufacture of size for size feeder pipe for feeder replacement

International Nuclear Information System (INIS)

Legate, G.; Schreiter, D.; Townley, N.

2008-01-01

The recently recognised problem of feeder pipe thinning created a unique sourcing problem. Operators require relatively small quantities of nuclear class 1 seamless feeder pipe for such replacement which prior to the introduction of this product in 2006 was not available. It was desired that the pipe be produced at the exact size of the pipe currently in use at the specific reactor site (feeder pipe size varies from site to site). Secondly the pipe had to be made in conformance to the original code year of issue and to conform to the intent of the original material specifications. Finally a supply strategy had to be implemented allowing for timely manufacture of replacement piping. This presentation will report upon how replacement size for size feeder tube was developed and is currently manufactured at Nu-Tech Precision Metals. The paper will also detail the current supply strategy to ensure timely manufacture of the product.

Survey of industrial coal conversion equipment capabilities: valves

Energy Technology Data Exchange (ETDEWEB)

Bush, W. A.; Slade, E. C.

1978-06-01

A survey of the industrial capabilities of the valve and valve-actuator industry to supply large, high-pressure stop valves for the future coal conversion industry is presented in this report. Also discussed are development and testing capabilities of valve and valve-actuator manufacturers and anticipated lead times required to manufacture advanced design valves for the most stringent service applications. Results indicate that the valve and valve-actuator industry is capable of manufacturing in quantity equipment of the size and for the pressure and temperature ranges which would be required in the coal conversion industry. Valve manufacturers do not, however, have sufficient product application experience to predict the continuing functional ability of valves used for lock-hopper feeders, slurry feeders, and slag-char letdown service. Developmental and testing efforts to modify existing valve designs or to develop new valve concepts for these applications were estimated to range from 1 to 6 years. A testing facility to simulate actuation of critical valves under service conditions would be beneficial.

Segregation in handling processes of blended industrial coal

Energy Technology Data Exchange (ETDEWEB)

Jones, M.G.; Marjanovic, P.; McGlinchy, D.; McLaren, R. [Glasgow Caledonian University, Glasgow (United Kingdom). Department of Physical Sciences, Centre for Industrial Bulk Solids Handling

1998-09-01

A comparison was made between two belt blending methods; using either a compartment hopper or feeder belts. The results indicated that in this case the system with feeder belts gave a more consistent proportioning of materials. Coal when formed into a heap was shown to segregate dependent on size fraction. The level of segregation for each size fraction was quantified using ANOVA statistics. Any measure taken to mitigate this segregation could then be properly assessed. Some aspects of the segregation evident in the heap arose in previous handling steps showing that such effects are transmittable along a process stream. Singles coal when pneumatically conveyed in dilute phase will segregate in the conveying pipeline. Segregation in the direction of travel was minimal in dense phase conveying although the materials tested separated through the depth of the pipe. A full scale experimental programme investigating segregation in both dense and dilute phase is currently underway. 7 refs., 2 figs., 4 tabs.

Screw-vector bond graphs for kinetic-static modelling and analysis of mechanisms

International Nuclear Information System (INIS)

Bidard, Catherine

1994-01-01

This dissertation deals with the kinetic-static modelling and analysis of spatial mechanisms used in robotics systems. A framework is proposed, which embodies a geometrical and a network approach for kinetic-static modelling. For this purpose we use screw theory and bond graphs. A new form of bond graphs is introduced: the screw-vector bond graph, whose power variables are defined to be wrenches and twists expressed as intrinsic screw-vectors. The mechanism is then identified as a network, whose components are kinematic pairs and whose topology is described by a directed graph. A screw-vector Simple Junction Structure represents the topological constraints. Kinematic pairs are represented by one-port elements, defined by two reciprocal screw-vector spaces. Using dual bases of screw-vectors, a generic decomposition of kinematic pair elements is given. The reduction of kinetic-static models of series and parallel kinematic chains is used in order to derive kinetic-static functional models in geometric form. Thereupon, the computational causality assignment is adapted for the graphical analysis of the mobility and the functioning of spatial mechanisms, based on completely or incompletely specified models. (author) [fr

Scoping Studies to Evaluate the Benefits of an Advanced Dry Feed System on the Use of Low-Rank Coal

Energy Technology Data Exchange (ETDEWEB)

Rader, Jeff; Aguilar, Kelly; Aldred, Derek; Chadwick, Ronald; Conchieri, John; Dara, Satyadileep; Henson, Victor; Leininger, Tom; Liber, Pawel; Liber, Pawel; Lopez-Nakazono, Benito; Pan, Edward; Ramirez, Jennifer; Stevenson, John; Venkatraman, Vignesh

2012-03-30

The purpose of this project was to evaluate the ability of advanced low rank coal gasification technology to cause a significant reduction in the COE for IGCC power plants with 90% carbon capture and sequestration compared with the COE for similarly configured IGCC plants using conventional low rank coal gasification technology. GE’s advanced low rank coal gasification technology uses the Posimetric Feed System, a new dry coal feed system based on GE’s proprietary Posimetric Feeder. In order to demonstrate the performance and economic benefits of the Posimetric Feeder in lowering the cost of low rank coal-fired IGCC power with carbon capture, two case studies were completed. In the Base Case, the gasifier was fed a dilute slurry of Montana Rosebud PRB coal using GE’s conventional slurry feed system. In the Advanced Technology Case, the slurry feed system was replaced with the Posimetric Feed system. The process configurations of both cases were kept the same, to the extent possible, in order to highlight the benefit of substituting the Posimetric Feed System for the slurry feed system.

A bend thickness sensitivity study of Candu feeder piping

International Nuclear Information System (INIS)

Li, M.; Aggarwal, M.L.; Meysner, A.; Micelotta, C.

2005-01-01

In CANDU reactors, feeder bends close to the connection at the fuel channel may be subjected to the highest Flow Accelerated Corrosion (FAC) and stresses. Feeder pipe stress analysis is crucial in the life extension of aging CANDU plants. Typical feeder pipes are interconnected by upper link plates and spacers. It is well known that the stresses at the bends are sensitive to the local bend thicknesses. It is also known from the authors' study (Li and et al, 2005) that feeder inter linkage effect is significant and cannot be ignored. The field measurement of feeder bend thickness is difficult and may be subjected to uncertainty in accuracy. Hence, it is desirable to know how the stress on a subject feeder could be affected by the bend thickness variation of the neighboring feeders. This effect cannot be evaluated by the traditional 'single' feeder model approach. In this paper, the 'row' and 'combined' models developed in the previous study (Li and et al, 2005), which include the feeder interactions, are used to investigate the sensitivity of bend thickness. A series of random thickness bounded by maximum and minimum measured values were applied to feeders in the model. The results show that an individual feeder is not sensitive to the bend thickness variation of the remaining feeders in the model, but depends primarily on its own bend thickness. The highest stress at a feeder always occurs when the feeder has the smallest possible bend thickness. A minimum acceptable bend thickness for individual feeders can be computed by an iterative computing process. The dependency of field thickness measurement and the amount of required analysis work can be greatly reduced. (authors)

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.

Development of an extruder-feeder biomass direct liquefaction process

Energy Technology Data Exchange (ETDEWEB)

White, D.H.; Wolf, D. (Arizona Univ., Tucson, AZ (United States). Dept. of Chemical Engineering)

1991-10-01

As an abundant, renewable, domestic energy resource, biomass could help the United States reduce its dependence on imported oil. Biomass is the only renewable energy technology capable of addressing the national need for liquid transportation fuels. Thus, there is an incentive to develop economic conversion processes for converting biomass, including wood, into liquid fuels. Through research sponsored by the US DOE's Biomass Thermochemical Conversion Program, the University of Arizona has developed a unique biomass direct liquefaction system. The system features a modified single-screw extruder capable of pumping solid slurries containing as high as 60 wt% wood flour in wood oil derived vacuum bottoms at pressures up to 3000 psi. The extruder-feeder has been integrated with a unique reactor by the University to form a system which offers potential for improving high pressure biomass direct liquefaction technology. The extruder-feeder acts simultaneously as both a feed preheater and a pumping device for injecting wood slurries into a high pressure reactor in the biomass liquefaction process. An experimental facility was constructed and following shakedown operations, wood crude oil was produced by mid-1985. By July 1988, a total of 57 experimental continuous biomass liquefaction runs were made using White Birch wood feedstock. Good operability was achieved at slurry feed rates up to 30 lb/hr, reactor pressures from 800 to 3000 psi and temperatures from 350{degree}C to 430{degree}C under conditions covering a range of carbon monoxide feed rates and sodium carbonate catalyst addition. Crude wood oils containing as little as 6--10 wt% residual oxygen were produced. 38 refs., 82 figs., 26 tabs.

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

Science.gov (United States)

Kil, Jin-Sang; Park, Jong-Tae

2018-05-01

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

Computational fluid dynamics simulation for chemical looping combustion of coal in a dual circulation fluidized bed

International Nuclear Information System (INIS)

Su, Mingze; Zhao, Haibo; Ma, Jinchen

2015-01-01

Highlights: • CFD simulation of a 5 kW_t_h CLC reactor of coal was conducted. • Gas leakage, flow pattern and combustion efficiency of the reactor was analyzed. • Optimal condition was achieved based on operation characteristics understanding. - Abstract: A dual circulation fluidized bed system is widely accepted for chemical looping combustion (CLC) for enriching CO_2 from the utilization of fossil fuels. Due to the limitations of the measurement, the details of multiphase reactive flows in the interconnected fluidized bed reactors are difficult to obtain. Computational Fluid Dynamics (CFD) simulation provides a promising method to understand the hydrodynamics, chemical reaction, and heat and mass transfers in CLC reactors, which are very important for the rational design, optimal operation, and scaling-up of the CLC system. In this work, a 5 kW_t_h coal-fired CLC dual circulation fluidized bed system, which was developed by our research group, was first simulated for understanding gas leakage, flow pattern and combustion efficiency. The simulation results achieved good agreement with the experimental measurements, which validates the simulation model. Subsequently, to improve the combustion efficiency, a new operation condition was simulated by increasing the reactor temperature and decreasing the coal feeding. An improvement in the combustion efficiency was attained, and the simulation results for the new operation condition were also validated by the experimental measurements in the same CLC combustor. All of the above processes demonstrated the validity and usefulness of the simulation results to improve the CLC reactor operation.

Workability of coal seams in the Upper Silesian Coal Basin

Energy Technology Data Exchange (ETDEWEB)

Sikora, W; Fels, M; Soltysik, K

1978-04-01

This paper presents results of an investigation on workability of coal seams of stratigraphic groups from 100 to 700 in the: Upper Silesian Coal Basin. Analyzed are 2900 petrographic logs taken in the longwall workings and in narrow openings as well as about 9000 individual samples. Workability of coal seams, floors and partings is determined. Workability is described by the indicator f, (according to the Protodyakonov shatter method) and the indicator U, (compression strength of the unshaped test samples). The mean percentage content of indivi dual petrographic groups of coal as well as the mean workability indicator, f, of coals in the stratigraphic groups of coal seams in Upper Silesia are also determined.

Primary investigation of a design for a dual energy gamma-ray transmission gauge to determine the ash content of coal on a conveyor belt

International Nuclear Information System (INIS)

Abedinzadeh, A.; Rahimi, H.; Rahimi, N.; Amini, A.; Naimpour, A.; Moafian, J.

1993-01-01

In order to design a dual energy γ-ray transmission gauge for measuring, on-line, the ash content of coal, an investigation was carried out to determine the relation between the theoretical mass absorption coefficient (μ-bar) and the % ash of coal in the Kerman District Coal Mines. Because coal, transported on a conveyor belt, may be a non-homogeneous mixture from one or more mines, it was decided to compare % ash in a mixture of coals from several mines with that from individual mines, the measurements being made whilst the coal was being transported on a conveyor belt. The investigation shows that the relation between the mass absorption coefficient and the % ash in a coal mixture from several mines cannot be used to assess, accurately, the value of μ-bar for coals from individual mines in this particular region. (author)

Rapid decompression and desorption induced energetic failure in coal

Directory of Open Access Journals (Sweden)

Shugang Wang

2015-06-01

Full Text Available In this study, laboratory experiments are conducted to investigate the rapid decompression and desorption induced energetic failure in coal using a shock tube apparatus. Coal specimens are recovered from Colorado at a depth of 610 m. The coal specimens are saturated with the strong sorbing gas CO2 for a certain period and then the rupture disc is suddenly broken on top of the shock tube to generate a shock wave propagating upwards and a rarefaction wave propagating downwards through the specimen. This rapid decompression and desorption has the potential to cause energetic fragmentation in coal. Three types of behaviors in coal after rapid decompression are found, i.e. degassing without fragmentation, horizontal fragmentation, and vertical fragmentation. We speculate that the characteristics of fracture network (e.g. aperture, spacing, orientation and stiffness and gas desorption play a role in this dynamic event as coal can be considered as a dual porosity, dual permeability, dual stiffness sorbing medium. This study has important implications in understanding energetic failure process in underground coal mines such as coal gas outbursts.

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

Science.gov (United States)

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

2018-03-01

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

EFFECT OF PILOT HOLE TAPPING ON PULLOUT STRENGTH AND INSERTION TORQUE OF DUAL CORE PEDICLE SCREWS.

Science.gov (United States)

Rosa, Rodrigo César; Silva, Patrícia; Falcai, Maurício José; Shimano, Antônio Carlos; Defino, Helton Luiz Aparecido

2010-01-01

To evaluate the influence of pilot hole tapping on pullout resistance and insertion torque of pedicle screws with a conical core. Mechanical tests using a universal testing machine were performed on pedicle screws with a conical core that were inserted into pedicles in the fifth lumbar vertebra of calves. The insertion torque was measured using a torque meter with a capacity of 10 Nm, which was considered to be the highest torque value. The pilot holes were prepared using a probe of external diameter 3.8 mm and tapping of the same dimensions and thread characteristics as the screw. Decreased insertion torque and pullout resistance were observed in the group with prior tapping of the pilot hole. Pilot hole tapping reduced the insertion torque and pullout resistance of pedicle screws with a conical core that had been inserted into the pedicle of the fifth lumbar vertebra of calves.

Dual inoculation with an Aarbuscular Mycorrhizal fungus and Rhizobium to facilitate the growth of alfalfa on coal mine substrates

Energy Technology Data Exchange (ETDEWEB)

Wu, F.Y.; Bi, Y.L.; Wong, M.H. [China University of Mining & Technology, Beijing (China)

2009-07-01

A pot experiment was conducted to investigate the effects of Glomus mosseae and Rhizobium on Medicago sativa grown on three types of coal mine substrates, namely a mixture of coal wastes and sands (CS), coal wastes and fly ash (CF), and fly ash (FA). Inoculation with Rhizobium alone did not result in any growth response but G. mosseae alone displayed a significant effect on plant growth. G. mosseae markedly increased the survival rate of M. sativa in CS substrate. In CF and FA substrates the respective oven dry weights of M. sativa inoculated with G. mosseae were 1.8 and 5.1 times higher than those without inoculation. Based on nitrogen (N), phosphorus (P) and potassium (K) uptake and legume growth, the results also show that dual inoculation in CS and CF substrates elicited a synergistic effect. This indicates that inoculation with arbuscular mycorrhizal (AM) fungi may be a promising approach for revegetation of coal mine substrates.

A study of inter linkage effects on Candu feeder piping

International Nuclear Information System (INIS)

Li, M.; Aggarwal, M.L.; Meysner, A.

2005-01-01

A CANDU (Canadian Deuterium Uranium) reactor core consists of a large number of fuel channels where heat is generated. Two feeder pipes are connected to each fuel channel to transport D 2 O coolant into and out of the reactor core. The feeder piping is designed to the requirements of Class 1 piping of Section III NB of the ASME Boiler and Pressure Vessel and CSA Codes. Feeder piping stress analysis is being performed to demonstrate the code compliance check and the fitness for service of feeders. In the past, stress analyses were conducted for each individual feeder without including interaction effects among connected feeders. Interaction effects occur as a result of linkages that exist between feeders to prevent fretting and impacting damage during normal, abnormal and accident conditions. In this paper, a 'combined' approach is adopted to include all feeders connected by inter linkages into one feeder piping model. MSC/NASTRAN finite element software was used in the stress simulation, which contains up to 127 feeder pipes. The ASME Class 1 piping analysis was conducted to investigate the effects of the linkages between feeders. Both seismic time history and broadened response spectra methods were used in the seismic stress calculation. The results show that the effect of linkages is significant in dynamic stresses for all feeder configurations, as well as in static stresses for certain feeder configurations. The single feeder analysis could either underestimate or overestimate feeder stresses depending on the pipe geometry and bend wall thickness. (authors)

An on-line identification device for coal and gangue based on dual-energy γ-ray transmission and microcontroller

International Nuclear Information System (INIS)

Chen Guojie; Zhu Xing

2004-01-01

The operating principle, hardware design, software design and stabled-spectrum method of on-line identification device for coal and gangue based on dual-energy γ-ray transmission and microcontroller are introduced. The integrated linear amplifier and integrated single channel pulse height analyzer are analyzed. The on-line identification device has advantages of small size, low cost as well stabilization. (authors)

Economic feeder for recharging and ``topping off''

Science.gov (United States)

Fickett, Bryan; Mihalik, G.

2000-04-01

Increasing the size of the melt charge significantly increases yield and reduces costs. Siemens Solar Industries is optimizing a method to charge additional material after meltdown (top-off) using an external feeder system. A prototype feeder system was fabricated consisting of a hopper and feed delivery system. The low-cost feeder is designed for simple operation and maintenance. The system is capable of introducing up to 60 kg of granular silicon while under vacuum. An isolation valve permits refilling of the hopper while maintaining vacuum in the growth furnace. Using the feeder system in conjunction with Siemens Solar Industries' energy efficient hot zone dramatically reduces power and argon consumption. Throughput is also improved as faster pull speeds can be attained. The increased pull speeds have an even greater impact when the charge size is increased. Further cost reduction can be achieved by refilling the crucible after crystal growth and pulling a second ingot run. Siemens Solar Industries is presently testing the feeder in production.

Pore pressure propagation in a permeable thin-layer coal seam based on a dual porosity model: A case of risk prediction of water inrush in coalmines

Science.gov (United States)

Zhu, B.; Gao, F.; Yang, J. W.; Zhou, G. Q.

2016-08-01

Thin-layer coal seams, a type of filling coal rock body, are considered aquifer systems made up of dual porosity medium with immediate floor. A numerical simulation for the pore pressure propagation along a thin-layer coal seam was carried out for the case of the Zhaogezhuang coalmine in China. By valuing the permeability (Kf ) of the thin-layer coal seam, pore pressure variation with time was simulated and compared to the analytical solutions of a dual porosity model (DPM). The main conclusions were drawn as follow: (1) Seepage in the thin-layer coal seam was predominant in the whole process, and the distance of seepage was lengthened and the pore pressure decreased with increased Kf , (2) A series of simulated hydraulic graphs demonstrated that the pore pressure characteristics of peak-occurring and time-lag effects agreed with the analytical solutions of DPM; (3) By adjusting the parameters of DPM, two results of analytical solutions and numerical solutions fit well, particularly in the thin-layer coal seam, (4) The power law relationship between the peak-values and lag time of pore pressure were derived statistically under consideration of the Kf parameter in the range of 10-8 to 10-10 m2/pa-s orders, and it was reasonable that the Kf of the thin-layer coal seam was in the range of 10-8 m2/pa-s orders. The results were significantly helpful in decision-making for mining water prevention and prediction in practice.

Human induced pluripotent stem cells on autologous feeders.

Directory of Open Access Journals (Sweden)

Kazutoshi Takahashi

Full Text Available BACKGROUND: For therapeutic usage of induced Pluripotent Stem (iPS cells, to accomplish xeno-free culture is critical. Previous reports have shown that human embryonic stem (ES cells can be maintained in feeder-free condition. However, absence of feeder cells can be a hostile environment for pluripotent cells and often results in karyotype abnormalities. Instead of animal feeders, human fibroblasts can be used as feeder cells of human ES cells. However, one still has to be concerned about the existence of unidentified pathogens, such as viruses and prions in these non-autologous feeders. METHODOLOGY/PRINCIPAL FINDINGS: This report demonstrates that human induced Pluripotent Stem (iPS cells can be established and maintained on isogenic parental feeder cells. We tested four independent human skin fibroblasts for the potential to maintain self-renewal of iPS cells. All the fibroblasts tested, as well as their conditioned medium, were capable of maintaining the undifferentiated state and normal karyotypes of iPS cells. Furthermore, human iPS cells can be generated on isogenic parental fibroblasts as feeders. These iPS cells carried on proliferation over 19 passages with undifferentiated morphologies. They expressed undifferentiated pluripotent cell markers, and could differentiate into all three germ layers via embryoid body and teratoma formation. CONCLUSIONS/SIGNIFICANCE: These results suggest that autologous fibroblasts can be not only a source for iPS cells but also be feeder layers. Our results provide a possibility to solve the dilemma by using isogenic fibroblasts as feeder layers of iPS cells. This is an important step toward the establishment of clinical grade iPS cells.

An RFID Based Smart Feeder for Hummingbirds.

Science.gov (United States)

Ibarra, Vicente; Araya-Salas, Marcelo; Tang, Yu-ping; Park, Charlie; Hyde, Anthony; Wright, Timothy F; Tang, Wei

2015-12-16

We present an interdisciplinary effort to record feeding behaviors and control the diet of a hummingbird species (Phaethornis longirostris, the long-billed hermit or LBH) by developing a Radio Frequency Identification (RFID) based smart feeder. The system contains an RFID reader, a microcontroller, and a servo-controlled hummingbird feeder opener; the system is presented as a tool for studying the cognitive ability of the LBH species. When equipped with glass capsule RFID tags (which are mounted on the hummingbird), the smart feeder can provide specific diets for predetermined sets of hummingbirds at the discretion of biologists. This is done by reading the unique RFID tag on the hummingbirds and comparing the ID number with the pre-programmed ID numbers stored in the smart feeder. The smart feeder records the time and ID of each hummingbird visit. The system data is stored in a readily available SD card and is powered by two 9 V batteries. The detection range of the system is approximately 9-11 cm. Using this system, biologists can assign the wild hummingbirds to different experimental groups and monitor their diets to determine if they develop a preference to any of the available nectars. During field testing, the smart feeder system has demonstrated consistent detection (when compared to detections observed by video-recordings) of RFID tags on hummingbirds and provides pre-designed nectars varying water and sugar concentrations to target individuals. The smart feeder can be applied to other biological and environmental studies in the future.

An RFID Based Smart Feeder for Hummingbirds

Directory of Open Access Journals (Sweden)

Vicente Ibarra

2015-12-01

Full Text Available We present an interdisciplinary effort to record feeding behaviors and control the diet of a hummingbird species (Phaethornis longirostris, the long-billed hermit or LBH by developing a Radio Frequency Identification (RFID based smart feeder. The system contains an RFID reader, a microcontroller, and a servo-controlled hummingbird feeder opener; the system is presented as a tool for studying the cognitive ability of the LBH species. When equipped with glass capsule RFID tags (which are mounted on the hummingbird, the smart feeder can provide specific diets for predetermined sets of hummingbirds at the discretion of biologists. This is done by reading the unique RFID tag on the hummingbirds and comparing the ID number with the pre-programmed ID numbers stored in the smart feeder. The smart feeder records the time and ID of each hummingbird visit. The system data is stored in a readily available SD card and is powered by two 9 V batteries. The detection range of the system is approximately 9–11 cm. Using this system, biologists can assign the wild hummingbirds to different experimental groups and monitor their diets to determine if they develop a preference to any of the available nectars. During field testing, the smart feeder system has demonstrated consistent detection (when compared to detections observed by video-recordings of RFID tags on hummingbirds and provides pre-designed nectars varying water and sugar concentrations to target individuals. The smart feeder can be applied to other biological and environmental studies in the future.

SAFIRE - a robotic inspection system for CANDU feeders

Energy Technology Data Exchange (ETDEWEB)

Buckingham, R. [OC Robotics, Bristol (United Kingdom)

2011-07-01

The condition of primary circuit feeder pipes in CANDU reactors is relevant to the commercial viability and plant life. One known wear mechanism is external fretting between feeder pipes and adjacent services or support structures, particularly within the Upper Feeder Cabinet (UFC). Fretting leads to wall thinning which must not exceed certain agreed limits. Chafe shields have been added to protect the feeder pipes. Regular inspections are required of the chafe shields, feeder pipes and other structures that may cause feeder damage. Historically, the dose received by inspectors conducting this work has been significant. For this reason Ontario Power Generation has invested in a remotely operated robot system to conduct visual inspections within the UFC. This system, called SAFIRE for 'Snake-Arm Feeder Inspection Robot Equipment' has been deployed at Pickering during 2010 and 2011 and has been used to inspect areas that are extremely difficult to inspect with existing manual techniques. The 2011 scope of work included inspection of a total of 660 feeder pipes in three UFC quadrants, in two reactors. The full scope was completed over a one-month period in Autumn 2011 in which SAFIRE was used during 23, twelve hour shifts. This included two periods each of 72 hours of continuous operation using multiple teams of operators. SAFIRE is remote controlled delivery system for multiple cameras to record still images and video. The main system elements include a snake-arm robot mounted on a mobile vehicle. It can be controlled from up to 500m away using a fibre/copper connection. The snake-arm is 2.2m long, 25mm wide and has 18 degrees of freedom. It is designed to snake between the rows of feeder pipes to inspect feeder/hanger interfaces, both above and below the feeder cabinet catwalks. Future upgrades offer the potential to add additional tools to increase functionality. This paper describes the SAFIRE development process from inception to operational experience

SAFIRE - a robotic inspection system for CANDU feeders

International Nuclear Information System (INIS)

Buckingham, R.

2011-01-01

The condition of primary circuit feeder pipes in CANDU reactors is relevant to the commercial viability and plant life. One known wear mechanism is external fretting between feeder pipes and adjacent services or support structures, particularly within the Upper Feeder Cabinet (UFC). Fretting leads to wall thinning which must not exceed certain agreed limits. Chafe shields have been added to protect the feeder pipes. Regular inspections are required of the chafe shields, feeder pipes and other structures that may cause feeder damage. Historically, the dose received by inspectors conducting this work has been significant. For this reason Ontario Power Generation has invested in a remotely operated robot system to conduct visual inspections within the UFC. This system, called SAFIRE for 'Snake-Arm Feeder Inspection Robot Equipment' has been deployed at Pickering during 2010 and 2011 and has been used to inspect areas that are extremely difficult to inspect with existing manual techniques. The 2011 scope of work included inspection of a total of 660 feeder pipes in three UFC quadrants, in two reactors. The full scope was completed over a one-month period in Autumn 2011 in which SAFIRE was used during 23, twelve hour shifts. This included two periods each of 72 hours of continuous operation using multiple teams of operators. SAFIRE is remote controlled delivery system for multiple cameras to record still images and video. The main system elements include a snake-arm robot mounted on a mobile vehicle. It can be controlled from up to 500m away using a fibre/copper connection. The snake-arm is 2.2m long, 25mm wide and has 18 degrees of freedom. It is designed to snake between the rows of feeder pipes to inspect feeder/hanger interfaces, both above and below the feeder cabinet catwalks. Future upgrades offer the potential to add additional tools to increase functionality. This paper describes the SAFIRE development process from inception to operational experience gained

Development of an in-line Raman spectroscopic method for continuous API quantification during twin-screw wet granulation.

Science.gov (United States)

Harting, Julia; Kleinebudde, Peter

2018-04-01

Raman spectroscopy was evaluated as a process analytical technology (PAT) tool for continuous API quantification during twin-screw wet granulation. Therefore, a Raman probe was implemented in front of the granulator barrel. This setup enabled the collection of Raman spectra upon a constant granule flow. To develop an in-line PLS calibration model, eight binary mixtures of the API and lactose monohydrate with API contents between 5 and 50% were pre-blended and granulated in a twin-screw granulator with a screw speed of 150 rpm and a powder feed rate of 40 g/min. Water was used as a granulation liquid with different liquid to solid ratios depending on the API content. Ibuprofen and diclofenac sodium were chosen as model drugs and separated PLS models were built for each API. The predictive performance of the developed PLS models was determined by granulating and monitoring new test samples containing different API concentrations. This evaluation showed that the models were able to predict the API concentration with an RMSEP of 0.59% for ibuprofen and 1.5% for diclofenac sodium. In a second part, the developed in-line Raman spectroscopic method was used to determine the API concentration during a split feeding process. Therefore, the API and lactose monohydrate were added by two independently adjustable feeders into the twin-screw granulator barrel. The in-line spectroscopy analysis which was verified by UV-analysis indicated that the mixing ability of the twin-screw granulator was good for the used settings and all adjusted API concentrations. Copyright © 2018 Elsevier B.V. All rights reserved.

Risk-informed prediction of feeder end of life

International Nuclear Information System (INIS)

Jyrkama, M.; Pandey, M.

2011-01-01

The operating life of feeder piping is negatively impacted by flow accelerated corrosion (FAC). In this study, an assessment of a large set of inspection data reveals that FAC in feeders is a relatively stationary process, with variability only at the local scale. Given the added uncertainty from inspection coverage, a new method for estimating the thinning rate and feeder EOL is developed using a probabilistic approach. The results of the study illustrate the benefits of the methodology in supporting risk-informed decision making at the station by quantifying the present and incremental risk in the feeder system over time. (author)

Risk-informed prediction of feeder end of life

Energy Technology Data Exchange (ETDEWEB)

Jyrkama, M.; Pandey, M. [Univ. of Waterloo, Ontario (Canada)

2011-07-01

The operating life of feeder piping is negatively impacted by flow accelerated corrosion (FAC). In this study, an assessment of a large set of inspection data reveals that FAC in feeders is a relatively stationary process, with variability only at the local scale. Given the added uncertainty from inspection coverage, a new method for estimating the thinning rate and feeder EOL is developed using a probabilistic approach. The results of the study illustrate the benefits of the methodology in supporting risk-informed decision making at the station by quantifying the present and incremental risk in the feeder system over time. (author)

Expectations of Cattle Feeding Investors in Feeder Cattle Placements

OpenAIRE

Kastens, Terry L.; Schroeder, Ted C.

1993-01-01

Cattle feeders appear irrational when they place cattle on feed when projected profits are negative. Long futures positions appear to offer superior returns to cattle feeding investment. Cattle feeder behavior suggests that they believe a downward bias in live cattle futures persists and that cattle feeders use different information than the live cattle futures market price when making placement decisions. This paper examines feeder cattle placement determinants and compares performance of ex...

Feeder density enhances house finch disease transmission in experimental epidemics.

Science.gov (United States)

Moyers, Sahnzi C; Adelman, James S; Farine, Damien R; Thomason, Courtney A; Hawley, Dana M

2018-05-05

Anthropogenic food provisioning of wildlife can alter the frequency of contacts among hosts and between hosts and environmental sources of pathogens. Despite the popularity of garden bird feeding, few studies have addressed how feeders influence host contact rates and disease dynamics. We experimentally manipulated feeder density in replicate aviaries containing captive, pathogen-naive, groups of house finches ( Haemorhous mexicanus ) and continuously tracked behaviours at feeders using radio-frequency identification devices. We then inoculated one bird per group with Mycoplasma gallisepticum (Mg), a common bacterial pathogen for which feeders are fomites of transmission, and assessed effects of feeder density on house finch behaviour and pathogen transmission. We found that pathogen transmission was significantly higher in groups with the highest density of bird feeders, despite a significantly lower rate of intraspecific aggressive interactions relative to the low feeder density groups. Conversely, among naive group members that never showed signs of disease, we saw significantly higher concentrations of Mg-specific antibodies in low feeder density groups, suggesting that birds in low feeder density treatments had exposure to subclinical doses of Mg. We discuss ways in which the density of garden bird feeders could play an important role in mediating the intensity of Mg epidemics.This article is part of the theme issue 'Anthropogenic resource subsidies and host-parasite dynamics in wildlife'. © 2018 The Author(s).

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

Science.gov (United States)

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

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

Colour preferences of UK garden birds at supplementary seed feeders.

Directory of Open Access Journals (Sweden)

Luke Rothery

Full Text Available Supplementary feeding of garden birds generally has benefits for both bird populations and human wellbeing. Birds have excellent colour vision, and show preferences for food items of particular colours, but research into colour preferences associated with artificial feeders is limited to hummingbirds. Here, we investigated the colour preferences of common UK garden birds foraging at seed-dispensing artificial feeders containing identical food. We presented birds simultaneously with an array of eight differently coloured feeders, and recorded the number of visits made to each colour over 370 30-minute observation periods in the winter of 2014/15. In addition, we surveyed visitors to a garden centre and science festival to determine the colour preferences of likely purchasers of seed feeders. Our results suggest that silver and green feeders were visited by higher numbers of individuals of several common garden bird species, while red and yellow feeders received fewer visits. In contrast, people preferred red, yellow, blue and green feeders. We suggest that green feeders may be simultaneously marketable and attractive to foraging birds.

Round-bale feeder design affects hay waste and economics during horse feeding.

Science.gov (United States)

Martinson, K; Wilson, J; Cleary, K; Lazarus, W; Thomas, W; Hathaway, M

2012-03-01

Many horse owners find round bales convenient, less labor intensive, and more affordable than other hay types, but report an inability to control horse BW gain and excessive hay waste. The objectives were to compare hay waste, hay intake, and payback of 9 round-bale feeders and a no-feeder control when used during horse feeding. Nine round-bale feeders were tested: Cinch Net, Cone, Covered Cradle, Hayhut, Hay Sleigh, Ring, Tombstone, Tombstone Saver, and Waste Less. Each feeder design was placed on the ground in a dirt paddock. Five groups of 5 horses were fed in rotation for a 4-d period with each feeder. Every fourth day, groups were rotated among paddocks and a new round bale was placed in each feeder. In the 5 paddocks used, 5 feeders were installed for d 1 through 20, and the remaining 4 feeders and no-feeder control were installed for d 21 through 40. Groups of horses were sequentially assigned to feeders using two 5 × 5 Latin squares, the first for d 1 through 20, the second for d 21 through 40. Horse groups of similar age, BW, breed, and sex were formed from 25 Quarter Horse and Thoroughbred geldings and open mares (means: 11 yr; 541 kg of BW). Hay on the ground surrounding the feeder was collected daily, dried, and weighed. The total amount of hay removed around each feeder for a 4-d period was considered waste. Dry matter intake was estimated as the difference between hay disappearance and waste. Number of months for the reduction in waste to repay feeder cost (payback) were calculated using hay valued at $110/t, and improved feeder efficiency over the control. Feeder design did not affect hay intake (P > 0.05); all feeders resulted in an estimated hay intake of 2.0 to 2.4% BW; the no-feeder control resulted in a reduced intake of 1.3% BW (P = 0.001). Mean percentage of hay waste differed among feeders (P feeder control, 57%. Feeder design also affected payback (P feeder design affected hay waste and payback, but not estimated hay intake or BW change

On-line nuclear ash gauge for coal based on gamma-ray transmission techniques

International Nuclear Information System (INIS)

Rizk, R.A.M.; El-Kateb, A.H.; Abdul-Kader, A.M.

1999-01-01

Developments and applications of on-line nuclear gauges in the coal industry are highly requested. A nuclear ash gauge for coal, based on γ-ray transmission techniques is developed. Single and dual energy γ-ray beams are used to determine the ash content of coal. The percentage ash content as a function of the γ-ray intensities transmitted through coal samples is measured and sensitivity curves are obtained. An empirical formulation relating the ash content values to the γ-ray intensities is derived. Preliminary results show that both single and dual energy γ-ray transmission techniques can be used to give a rapid on-line estimation of the ash concentration values in coal with low cost and reasonable accuracy, but the dual one is much preferable. (author)

Impact of flow accelerated corrosion (FAC) on feeder refurbishment planning

International Nuclear Information System (INIS)

Jyrkama, M.; Pandey, M.

2010-01-01

Feeder wall thinning due to flow accelerated corrosion (FAC) may result in a large number of feeder replacements in the future. In this study, the process of FAC is modelled using a probabilistic approach and used to predict the expected number of degraded feeders and their replacements in the future. Because of the high cost associated with feeder replacements, it may be optimal to replace the entire feeder population during a single refurbishment outage when the unit cost of replacement is likely to be less. The results of this study demonstrate, however, that the unit cost of feeder replacement must be sufficiently lower than the standard replacement cost and the refurbishment performed at an optimal time to realize the economic benefits associated with the refurbishment. (author)

in meat production III. Feeder - breeder dimorphism

African Journals Online (AJOL)

Feeder- breeder dimorphism is advantageous when large offspring for slaughter is obtained from small breeding animals. The effect of feeder- breeder dimorphism on herd efficiency is evaluated for terminal crossbreeding and growth modification by biotechnological or dietary means. Selection criteria for breeds or lines in ...

Positioning device for screwing or unscrewing screw nut

International Nuclear Information System (INIS)

Sevelinge, G.

1987-01-01

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

Leaky feeder: the communication backbone

Energy Technology Data Exchange (ETDEWEB)

NONE

1999-01-01

The need to communicate with all areas of the underground operation in monitoring the movement of men, materials and vehicles, as well as the optimum performance of conveyor systems, has been effectively met with the installation of a Flexcom leaky feeder cable network at a coliery in Mpumalanga. Installed by the South African subsidiary of Mine Radio Systems (MRS), based in Canada, Flexcom is an RF communications highway for underground mines. The system can provide up to 32 voice/data control channels and up to 16 video channels, all operating simultaneously. The system uses a series of bi-directional amplifiers (or signal boosters) spaced at 350 m intervals along the leaky feeder cable, with branching units and termination units added as required. Communication is possible within 50 m of the leaky feeder cable. MRS has 11 conveyors monitored via the SCADA program at the mine and the system produces reports as required which are accessible via cellphone from anywhere in the world. The wireless monitoring of miners and equipment contributes to mine safety. 3 figs.

Determination of representative CANDU feeder dimensions for engineering simulator

International Nuclear Information System (INIS)

Cho, S.; Muzumdar, A.

1996-01-01

This paper describes a logic for selection of representative channel groups and a methodology for determination of representative CANDU feeder dimensions and the pressure drops between inlet/outlet header and fuel channel in the primary loop. A code, MEDOC, was developed based on this logic and methodology and helps perform a calculation of representative feeder dimensions for a selected channel group on the basis of feeder geometry data (fluid volume, mass flow rate, loss factor) and given property data (pressure, quality, density) at inlet/outlet header. The representative feeder dimensions calculated based on this methodology will be useful for the engineering simulator for the CANDU type reactor. (author)

Assessment of CANDU feeders subject to flow accelerated corrosion

Energy Technology Data Exchange (ETDEWEB)

Iyer, S. [Atomic Energy of Canada Ltd., Mississauga, Ontario (Canada); Slade, J.P. [New Brunswick Power, Point Lepreau Generating Station, Lepreau, New Brunswick (Canada)

2003-07-01

'Full Text:' Inspections of CANDU feeders have indicated greater than expected wall thinning of outlet feeders. This wall thinning is attributed to Flow-Accelerated Corrosion (FAC). The rate of wall loss due to FAC is highest in the close radius bends near the end fitting. The minimum allowed thickness for a feeder pipes is based on design pressure during the design stage. Extended operation of the thinned feeders beyond their design basis, i.e., operation of feeders with thickness below design pressure based minimum thickness has economic benefits for the utilities. In such cases, it is important to establish the remaining life and evaluate the adequacy of the components for safe operation. ASME Code Case N-597 provides the guidelines for acceptance for continued service of Classes 2 and 3 piping components experiencing wall thinning during operation. However, for Class 1 systems, the Code Case recommends that the owner develop the methodology and criteria for the assessment of wall thinning. Therefore, under the CANDU Owner's Group's (COG) Feeder Integrity Joint Program (FIJP), the 'Fitness for Service Guidelines (FFSG) for Feeders Affected by Wall Thinning in Operating CANDU Reactors' was developed and subsequently conditionally approved by CNSC. This paper illustrates the underlying concepts in the FFSG methodology and its benefits to utilities. Specific examples of the application and benefits of the FFSG at Point Lepreau G.S. are described in this paper. The assessment of feeders is based on the requirements of the construction Code (Section III of the ASME Boiler and Pressure Vessel Code): The following points briefly describe the assessment methodology. Satisfying the requirements of NB-3650 for design and service loadings are sufficient for continued service and extended life if the predicted minimum wall thickness of the component is greater than or equal to 90% of the pressure based thickness calculated as per NB-3641. The B

Feeding Against Gravity with Spot Feeders in High Silicon Ductile Iron

DEFF Research Database (Denmark)

Vedel-Smith, Nikolaj Kjelgaard; Tiedje, Niels Skat

2014-01-01

and classified using X-ray imaging and ultrasound analysis. The effect of the different feeder configurations were classified in reference to defect location, sleeve material, and feeder type, modulus, and location. The analysis showed that exothermal feeder sleeves with the right configurations can feed up......-hill against gravity. This effect may contribute to the thermal expansion created by the exothermal reaction. It was also found that the optimum feeder size does not scale linearly with the casting modulus but that larger casting modulus requires relatively smaller modulus feeders. The thermal gradient created...

26 CFR 1.502-1 - Feeder organizations.

Science.gov (United States)

2010-04-01

... 26 Internal Revenue 7 2010-04-01 2010-04-01 true Feeder organizations. 1.502-1 Section 1.502-1...) INCOME TAXES (CONTINUED) Exempt Organizations § 1.502-1 Feeder organizations. (a) In the case of an organization operated for the primary purpose of carrying on a trade or business for profit, exemption is not...

Fluidised bed gasification of high-ash South African coals: An experimental and modelling study

CSIR Research Space (South Africa)

Engelbrecht, AS

2011-11-01

Full Text Available model (CeSFaMB). The predictive capability of the model was analysed in terms of the degree of variation between experimental and simulated results for each test. The calibrated model was used to design a 15 MW fluidised bed coal gasifier...-scale BFBG are given in Figure 1 and Table 1. Process description Coal, air, oxygen and steam are the input streams to the process which produce the output streams: gas and char (ash). Coal is fed to the gasifier by means of a screw conveyor at a...

Novel Methods to Determine Feeder Locational PV Hosting Capacity and PV Impact Signatures

Energy Technology Data Exchange (ETDEWEB)

Reno, Matthew J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Coogan, Kyle [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Seuss, John [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Broderick, Robert Joseph [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2017-05-01

Often PV hosting capacity analysis is performed for a limited number of distribution feeders. For medium - voltage distribution feeders, previous results generally analyze less than 20 feeders, and then the results are extrapolated out to similar types of feeders. Previous hosting capacity research has often focused on determining a single value for the hosting capacity for the entire feeder, whereas this research expands previous hosting capacity work to investigate all the regions of the feeder that may allow many different hosting capacity values wit h an idea called locational hosting capacity (LHC)to determine the largest PV size that can be interconnected at different locations (buses) on the study feeders. This report discusses novel methods for analyzing PV interconnections with advanced simulati on methods. The focus is feeder and location - specific impacts of PV that determine the locational PV hosting capacity. Feeder PV impact signature are used to more precisely determine the local maximum hosting capacity of individual areas of the feeder. T he feeder signature provides improved interconnection screening with certain zones that show the risk of impact to the distribution feeder from PV interconnections.

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

Science.gov (United States)

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

2017-01-01

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

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

NARCIS (Netherlands)

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

2008-01-01

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

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

Science.gov (United States)

Arshad, Mahnaz; Mahgoli, Hosseinali; Payaminia, Leila

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

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

Directory of Open Access Journals (Sweden)

Bo Kyun Sim

2017-01-01

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

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

Science.gov (United States)

Kim, Bongju; Shin, Yoo Jin

2017-01-01

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

A Dynamic and Heuristic Phase Balancing Method for LV Feeders

Directory of Open Access Journals (Sweden)

Samad Taghipour Boroujeni

2016-01-01

Full Text Available Due to the single-phase loads and their stochastic behavior, the current in the distribution feeders is not balanced. In addition, the single-phase loads are located in different positions along the LV feeders. So the amount of the unbalanced load and its location affect the feeder losses. An unbalanced load causes the feeder losses and the voltage drop. Because of time-varying behavior of the single-phase loads, phase balancing is a dynamic and combinatorial problem. In this research, a heuristic and dynamic solution for the phase balancing of the LV feeders is proposed. In this method, it is supposed that the loads’ tie could be connected to all phases through a three-phase switch. The aim of the proposed method is to make the feeder conditions as balanced as possible. The amount and the location of single-phase loads are considered in the proposed phase balancing method. Since the proposed method needs no communication interface or no remote controller, it is inexpensive, simple, practical, and robust. Applying this method provides a distributed and dynamic phase balancing control. In addition, the feasibility of reducing the used switches is investigated. The ability of the proposed method in the phase balancing of the LV feeders is approved by carrying out some simulations.

Structural integrity investigations of feeder pipe ice plugging procedures

International Nuclear Information System (INIS)

Flaman, M.T.; Shah, N.N.

1985-03-01

A procedure involving the use of a liquid nitrogen cooled heat exchanger to form internal ice plugs in feeder pipes is routinely used in nuclear generating stations. The use of this procedure has caused concerns with regard to the safety of station maintenance personnel, and in regard to the integrity of the feeder pipes. This report describes the results of laboratory stress and pressure measurements which were performed on a feeder pipe section during ice plugging operations to investigate these concerns. From the results of this study, and from the results of previous studies of material behaviour at low temperatures, it has been determined that the ice plugging procedure can be performed on feeder pipes in a safe and effective manner

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

OpenAIRE

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

2017-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2006-12-15

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

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.

Aerial Triangulation Close-range Images with Dual Quaternion

Directory of Open Access Journals (Sweden)

SHENG Qinghong

2015-05-01

Full Text Available A new method for the aerial triangulation of close-range images based on dual quaternion is presented. Using dual quaternion to represent the spiral screw motion of the beam in the space, the real part of dual quaternion represents the angular elements of all the beams in the close-range area networks, the real part and the dual part of dual quaternion represents the line elements corporately. Finally, an aerial triangulation adjustment model based on dual quaternion is established, and the elements of interior orientation and exterior orientation and the object coordinates of the ground points are calculated. Real images and large attitude angle simulated images are selected to run the experiments of aerial triangulation. The experimental results show that the new method for the aerial triangulation of close-range images based on dual quaternion can obtain higher accuracy.

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

OpenAIRE

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

2015-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

Frictional performance of ball screw

International Nuclear Information System (INIS)

Nakashima, Katuhiro; Takafuji, Kazuki

1985-01-01

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

Damping considerations in CANDU feeder pipe design and analysis

International Nuclear Information System (INIS)

Usmani, S.A.; Saleem, M.A.; So, G.

1990-01-01

Recent developments in pipe damping indicate a trend towards more realistic and less conservative values, which result in less rigid and safer pipe designs. The CANDU-PHW (Canada deuterium uranium, pressurized heavy water) reactor feeder pipe designs have applied similar approaches which permit seismic qualifications without overly restraining these compact arrays of pipes to cater for the large creep and thermal anchor movement. This paper reviews the feeder design aspects, especially pertaining to the design provisions, experimental verification and analytical modelling for seismic qualification in the light of recent pipe dynamic developments. Using illustrative examples, comparison of seismic analysis results is provided for the ASME Code Case N-411 dampings, and those traditionally used in the feeder seismic qualification. The results confirm acceptability of the traditional approach which permit simplified analysis to demonstrate seismic qualificationqualification of CANDU feeder pipes

Automation Selection and Sequencing of Traps for Vibratory Feeders

DEFF Research Database (Denmark)

Mathiesen, Simon; Ellekilde, Lars-Peter

2017-01-01

Vibratory parts feeders with mechanical orienting devices are used extensively in the assembly automation industry. Even so, the design process is based on trial-and-error approaches and is largely manual. In this paper, a methodology is presented for automatic design of this type of feeder....... The approach uses dynamic simulation for generating the necessary data for configuring a feeder with a sequence of mechanical orienting devices called traps, with the goal of reorienting all parts from a random to fixed orientation. Then, a fast algorithm for facilitating this configuration task automatically...

Urban Bird Feeders Dominated by a Few Species and Individuals

Directory of Open Access Journals (Sweden)

Josie A. Galbraith

2017-08-01

Full Text Available The practice of garden bird feeding is a global phenomenon, involving millions of people and vast quantities of food annually. Many people engage in the practice of feeding assuming that birds gain some benefit from the food they provide, yet recent studies have revealed the potential for detrimental impacts as well. However, there is still a paucity of information on the impacts of feeding, including the ubiquity of these impacts among and within feeder-visiting species. Consistency in feeder use among birds is likely an important determinant of this. Individual birds and species that make frequent use of feeders are more likely to experience both the benefits and detrimental impacts of supplementary food. We investigated patterns of feeder use by garden birds visiting experimental feeding stations in Auckland, New Zealand, with the specific aim of determining whether use of supplementary food was consistent or variable among individuals and species. We used camera traps as well as Radio Frequency Identification (RFID technology to examine intra- and interspecific feeder visitation patterns and to discern species associations. Eleven bird species were detected using feeding stations, however, two introduced species (house sparrow Passer domesticus and spotted dove Streptopelia chinensis dominated visitation events. These species were present at feeders most frequently, with the largest conspecific group sizes. Significant associations were detected among a number of species, suggesting interspecific interactions are important in determining feeder use. We also found within-species differences in feeder use for all focal species, with individual variation greatest in house sparrows. Furthermore, season had an important influence on most visitation parameters. The observed individual and species-specific differences in supplementary food resource use imply that the impacts of garden bird feeding are not universal. Crucially, particularly given

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

Directory of Open Access Journals (Sweden)

Shangjun Ma

2015-01-01

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

Neural stem cells achieve and maintain pluripotency without feeder cells.

Directory of Open Access Journals (Sweden)

Hyun Woo Choi

Full Text Available BACKGROUND: Differentiated cells can be reprogrammed into pluripotency by transduction of four defined transcription factors. Induced pluripotent stem cells (iPS cells are expected to be useful for regenerative medicine as well as basic research. Recently, the report showed that mouse embryonic fibroblasts (MEF cells are not essential for reprogramming. However, in using fibroblasts as donor cells for reprogramming, individual fibroblasts that had failed to reprogram could function as feeder cells. METHODOLOGY/PRINCIPAL FINDING: Here, we show that adult mouse neural stem cells (NSCs, which are not functional feeder cells, can be reprogrammed into iPS cells using defined four factors (Oct4, Sox2, Klf4, and c-Myc under feeder-free conditions. The iPS cells, generated from NSCs expressing the Oct4-GFP reporter gene, could proliferate for more than two months (passage 20. Generated and maintained without feeder cells, these iPS cells expressed pluripotency markers (Oct4 and Nanog, the promoter regions of Oct4 and Nanog were hypomethylated, could differentiated into to all three germ layers in vitro, and formed a germline chimera. These data indicate that NSCs can achieve and maintain pluripotency under feeder-free conditions. CONCLUSION/SIGNIFICANCE: This study suggested that factors secreted by feeder cells are not essential in the initial/early stages of reprogramming and for pluripotency maintenance. This technology might be useful for a human system, as a feeder-free reprogramming system may help generate iPS cells of a clinical grade for tissue or organ regeneration.

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

Science.gov (United States)

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

2015-10-01

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

Advances in technologies for feeder pipe inspections

Energy Technology Data Exchange (ETDEWEB)

Ten Grotenhuis, R.; Verma, Y.; Hitchcox, T.; Sakuta, A. [Ontario Power Generation, Inspection and Maintenance Div., Toronto, Ontario (Canada)

2014-07-15

The successful development of the Matrix Inspection Technique (MIT) for feeder weld area applications has been followed up with a project to leverage the technology to address other aspects of feeder inspection. The goal of the project is to adapt the technology to provide full circumferential inspection of feeder pipes for FAC thinning and, potentially, for axial cracking. The project necessitated evolving a new generation of high speed, high element count data acquisition instruments. It also required the development of custom inspection arrays, innovative approaches to sealing the water column, use of inertial motion sensors to synthesize encoder inputs, real-time visual feedback for the operator, and enhanced automated analysis software capable of plotting the inspected configuration in 3D. The individual components of the system are currently being integrated into a whole. The results obtained to date demonstrate the approach to be fundamentally sound. (author)

Generating a representative signal of coal moisture content to anticipate combustion control in thermal power stations

Energy Technology Data Exchange (ETDEWEB)

Prieto-Fernandez, Ismael; Luengo-Garcia, J. Carlos; Alonso-Hidalgo, Manuela; Ponte-Gutierrez, Daniel [Area de Maquinas y Motores Termicos, Universidad de Oviedo, Campus Universitario s/n 33203, Asturias Gijon (Spain)

2002-06-01

This article describes the possibilities of continuously measuring coal moisture in the boiler feeding circuit of a thermal power station so that the measurement can be used as a signal for the boiler combustion control system. To do so, in the first place, the point through which coal would be fed into the boiler was chosen. After studying the different parts of the circuit, the feeder was selected. Then, an installation was designed, at semi-industrial scale, faithfully reproducing the operation of a belt conveyor. In order to measure the moisture content, a microwave system was installed, and a large number of coal samples with different ranks and grain sizes was tested showing eventually the likelihood of the objective.

A Decentralized Storage Strategy for Residential Feeders with Photovoltaics

DEFF Research Database (Denmark)

Marra, Francesco; Yang, Guangya; Træholt, Chresten

2014-01-01

. The power sizing of the ESSs is performed with linear programming (LP) method, based on voltage sensitivity analysis. A Belgian residential LV feeder with private PV systems is used as a case study to demonstrate the effectiveness of the proposed strategy. Quantification of the required energy levels...... domestic energy storage systems (ESS). The traditional way of operating a domestic ESS to increase the local consumption rate does not take into account the need of voltage support in a feeder; the proposed storage concept improves the traditional one, by mitigating voltage rise due to PV in the feeder...

Sacroiliac Screw Fixation

NARCIS (Netherlands)

E.W. van den Bosch

2003-01-01

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

Material balance in coal. 2. Oxygen determination and stoichiometry of 33 coals

International Nuclear Information System (INIS)

Volborth, A.; Miller, G.E.; Garner, C.K.; Jerabek, P.A.

1977-01-01

The chemical analysis of coal can be supplemented by the determination of oxygen in high and low temperature ash, in coal as received and in coal dried at 105 0 C. The rapid method utilizes fast-neutron activation. The reaction 16 O(n,p) 16 N and counting of the 6.1 and 7.1 MeV gammas of 7.3 second half-life are used. A specially designed dual transfer and simultaneous counting system gives very accurate results. Oxygen in 33 coals ranging from lignite to low volatile bituminous coal is determined and compared with ''oxygen by difference.'' Considerable discrepancies are observed. Better stoichiometric results are obtained if oxygen in coal ash, in wet coal and in the dried coal is determined. This permits the estimation of the true material balances using data of the ultimate and the proximate coal analysis. The oxygen determination provides the coal chemist with an accurate basis and can be used to rank coal. The summation of the percent of carbon, nitrogen, hydrogen, sulfur, and oxygen becomes more meaningful and some errors can be detected and the state of completeness of coal analysis thus evaluated. Total sulfur can be estimated and oxidation effects during drying can be detected. These affect the moisture determination. It appears that after more data are collected, the interpretation of solid fuel analyses may be facilitated and will be stoichiometrically more meaningful. It is shown that it may be possible to simplify the present time-consuming methods of coal analysis

Complications of syndesmotic screw removal

NARCIS (Netherlands)

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

2011-01-01

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

Generating a representative signal of coal ash content to anticipate combustion control in a thermal power station

International Nuclear Information System (INIS)

Prieto-Fernandez, Ismael; Santurio-Diaz, J.M.; Folgueras-Diaz, B.; Lopez-Bobo, M. Rosario; Fernandez-Viar, P.

2004-01-01

This paper describes the possibilities of continuously measuring coal ash in the boiler feeding circuit of a thermal power station so that the measurement can be used as a signal for the boiler combustion control system. An installation was designed, at semi-industrial scale, that could faithfully reproduce the operation of a belt feeder. In order to measure the ash content, a natural radioactivity meter was installed and a large number of coal samples with different ranks and grain sizes were tested, eventually showing the possibility of achieving the objective

Effects of Feeder Cells on Dopaminergic Differentiation of Human Embryonic Stem Cells

Directory of Open Access Journals (Sweden)

Zhenqiang Zhao

2016-12-01

Full Text Available Mouse embryonic fibroblasts (MEFs and human foreskin fibroblasts (HFFs are used for the culture of human embryonic stem cells (hESCs. MEFs and HFFs differed in their capacity to support the proliferation and pluripotency of hESCs and could affect cardiac differentiation potential of hESCs. The aim of this study was to evaluate the effect of MEFs and HFFs feeders on dopaminergic differentiation of hESCs lines. To minimize the impact of culture condition variation, two hESCs lines were cultured on mixed feeder cells (MFCs, MEFs: HFFs =1:1 and HFFs feeder respectively, and then were differentiated into DA neurons under the identical protocol. Dopaminergic differentiation was evaluated by immunocytochemistry, quantitative fluorescent real-time PCR (qRT-PCR, transmission and scanning electron microscopy, and patch clamp. Our results demonstrated that these hESCs-derived neurons were genuine and functional DA neurons. However, compared to hESCs line on MFCs feeder, hESCs line on HFFs feeder had a higher proportion of TH positive cells and expressed higher levels of FOXA2, PITX3, NURR1 and TH genes. In addition, the values of threshold intensity and threshold membrane potential of DA neurons from hESCs line on HFFs feeder were lower than those of DA neurons from hESCs line on the MFCs feeder. In conclusion, HFFs feeder not only facilitated the differentiation of hESCs cells into dopaminergic neurons, but also induced hESCs-derived DA neurons to express higher electrophysiological excitability. Therefore, feeder cells could affect not only dopaminergic differentiation potential of different hESCs lines, but also electrophysiological properties of hESCs-derived DA neurons.

Object categorization by wild ranging birds-Winter feeder experiments.

Science.gov (United States)

Nováková, Nela; Veselý, Petr; Fuchs, Roman

2017-10-01

The object categorization is only scarcely studied using untrained wild ranging animals and relevant stimuli. We tested the importance of the spatial position of features salient for categorization of a predator using wild ranging birds (titmice) visiting a winter feeder. As a relevant stimulus we used a dummy of a raptor, the European sparrowhawk (Accipiter nisus), placed at the feeding location. This dummy was designed to be dismantled into three parts and rearranged with the head in the correct position, in the middle or at the bottom of the dummy. When the birds had the option of visiting an alternative feeder with a dummy pigeon, they preferred this option to visiting the feeder with the dummy sparrowhawk with the head in any of the three positions. When the birds had the option of visiting an alternative feeder with an un-rearranged dummy sparrowhawk, they visited both feeders equally often, and very scarcely. This suggests that the titmice considered all of the sparrowhawk modifications as being dangerous, and equally dangerous as the un-rearranged sparrowhawk. The position of the head was not the most important cue for categorization. The presence of the key features was probably sufficient for categorization, and their mutual spatial position was of lower importance. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Scaphoid Fracture Fixation with an Acutrak? Screw

OpenAIRE

Loving, Vilert A.; Richardson, Michael L.

2015-01-01

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

Stress analysis of feeder bends using neutrons: new results and cumulative impacts

Energy Technology Data Exchange (ETDEWEB)

Banks, D.; Donaberger, R. [Canadian Neutron Beam Centre, Chalk River, ON (Canada); Leitch, B. [Atomic Energy of Canada Limited, Chalk River, ON (Canada); Rogge, R.B. [Canadian Neutron Beam Centre, Chalk River, ON (Canada)

2014-07-01

Neutron diffraction has played a vital role in stress analysis of bends in carbon steel pipes, known as feeder pipes, in CANDU reactors. Due to incidents of cracking of feeders, extensive R&D programs to manage feeder cracking have been implemented over about ten years. We review the cumulative impacts of this research from the view point of the stress analysis using neutrons, and present new results by examining a feeder bend with a partial crack both experimentally using neutron diffraction and theoretically using a finite element model. (author)

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.

Impacting effects of seismic loading in feeder pipes of PHWR power plants

International Nuclear Information System (INIS)

Kumar, R.

1996-01-01

The core of a pressurized heavy water reactor (PHWR) consists of a large number of fuel channels. These fuel channels are connected to the feeder pipes through which the heavy water flows and transports heat from the reactor core to the steam generators. The feeder pipes are several hundreds in number. They run close to each other with small gaps and have several bends. Thus they represent a complex piping system. Under seismic loading, the adjacent feeder pipes may impact each other. In this paper a simplified procedure has been established to assess such impacting effects. The results of the proposed analysis include bending moment and impact force, which provide the stresses due to impacting effects. These results are plotted in nondimensional form so that they could be utilized for any set of feeder pipes. The procedure used for studying the impacting effects includes seismic analysis of individual feeder pipes without impacting effects, selection of pipes for impact analysis, and estimating their maximum impact velocity. Based on the static and dynamic characteristics of the selected feeder pipes, the maximum bending moment, impact force, and stresses are obtained. The results of this study are useful for quick evaluation of the impacting effects in feeder pipes

S08: investigation and repair of a cracked feeder at Point Lepreau GS

International Nuclear Information System (INIS)

A Celovsky, A.; Wright, M.D.; Gendron, T.S.

1997-01-01

Early in 1997 investigation of a low level leak in the Point Lepreau GS (PLGS) PHTS revealed that an outlet feeder, S08, was leaking. Ultrasonic inspection, and subsequent failure analysis, revealed that the leak was a consequence of a crack. Given the unusual nature of this event, and current concerns over feeder thinning, a detailed and careful removal and examination procedure was developed. The S08 outlet feeder was removed and shipped to Chalk River Laboratories for examination. The examination confirmed that the failure was a through-wall crack, most likely the consequence of stress corrosion cracking. A critical point of the analysis was to determine how the crack initiated, and subsequently propagated. High residual stresses and possible abnormal loading in conjunction with chemistry environments resulted in the Stress Corrosion Cracking (SCC) of the S08 outlet feeder bend. It is recognized that some of the causative factors implicated in the S08 failure apply to other outlet feeders. In particular, residual stresses in the non-stress-relieved, short-radius cold bent pipes will remain relatively high over the future life of the feeders. However, the risk of CANDU feeder failure by SCC is judged to be extremely low based on the evidence of the inspections carried out to date and the good performance record of feeder pipe in the CANDU industry. The channel was restored to its locked configuration, and the failed section of feeder replaced. (author)

Geothermal ORC Systems Using Large Screw Expanders

OpenAIRE

Biederman, Tim R.; Brasz, Joost J.

2014-01-01

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

Improvement of automatic fish feeder machine design

Science.gov (United States)

Chui Wei, How; Salleh, S. M.; Ezree, Abdullah Mohd; Zaman, I.; Hatta, M. H.; Zain, B. A. Md; Mahzan, S.; Rahman, M. N. A.; Mahmud, W. A. W.

2017-10-01

Nation Plan of action for management of fishing is target to achieve an efficient, equitable and transparent management of fishing capacity in marine capture fisheries by 2018. However, several factors influence the fishery production and efficiency of marine system such as automatic fish feeder machine could be taken in consideration. Two latest fish feeder machines have been chosen as the reference for this study. Based on the observation, it has found that the both machine was made with heavy structure, low water and temperature resistance materials. This research’s objective is to develop the automatic feeder machine to increase the efficiency of fish feeding. The experiment has conducted to testing the new design of machine. The new machine with maximum storage of 5 kg and functioning with two DC motors. This machine able to distribute 500 grams of pellets within 90 seconds and longest distance of 4.7 meter. The higher speed could reduce time needed and increase the distance as well. The minimum speed range for both motor is 110 and 120 with same full speed range of 255.

The applicability of PEEK-based abutment screws.

Science.gov (United States)

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

2016-10-01

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

Development of an extruder-feeder biomass direct liquefaction process. Volume 2, Parts 4--8: Final report

Energy Technology Data Exchange (ETDEWEB)

White, D.H.; Wolf, D. [Arizona Univ., Tucson, AZ (United States). Dept. of Chemical Engineering

1991-10-01

As an abundant, renewable, domestic energy resource, biomass could help the United States reduce its dependence on imported oil. Biomass is the only renewable energy technology capable of addressing the national need for liquid transportation fuels. Thus, there is an incentive to develop economic conversion processes for converting biomass, including wood, into liquid fuels. Through research sponsored by the US DOE`s Biomass Thermochemical Conversion Program, the University of Arizona has developed a unique biomass direct liquefaction system. The system features a modified single-screw extruder capable of pumping solid slurries containing as high as 60 wt% wood flour in wood oil derived vacuum bottoms at pressures up to 3000 psi. The extruder-feeder has been integrated with a unique reactor by the University to form a system which offers potential for improving high pressure biomass direct liquefaction technology. The extruder-feeder acts simultaneously as both a feed preheater and a pumping device for injecting wood slurries into a high pressure reactor in the biomass liquefaction process. An experimental facility was constructed and following shakedown operations, wood crude oil was produced by mid-1985. By July 1988, a total of 57 experimental continuous biomass liquefaction runs were made using White Birch wood feedstock. Good operability was achieved at slurry feed rates up to 30 lb/hr, reactor pressures from 800 to 3000 psi and temperatures from 350{degree}C to 430{degree}C under conditions covering a range of carbon monoxide feed rates and sodium carbonate catalyst addition. Crude wood oils containing as little as 6--10 wt% residual oxygen were produced. 38 refs., 82 figs., 26 tabs.

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

Science.gov (United States)

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

2015-06-15

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

A Feeder-Bus Dispatch Planning Model for Emergency Evacuation in Urban Rail Transit Corridors

Science.gov (United States)

Wang, Yun; Yan, Xuedong; Zhou, Yu; Zhang, Wenyi

2016-01-01

The mobility of modern metropolises strongly relies on urban rail transit (URT) systems, and such a heavy dependence causes that even minor service interruptions would make the URT systems unsustainable. This study aims at optimally dispatching the ground feeder-bus to coordinate with the urban rails’ operation for eliminating the effect of unexpected service interruptions in URT corridors. A feeder-bus dispatch planning model was proposed for the collaborative optimization of URT and feeder-bus cooperation under emergency situations and minimizing the total evacuation cost of the feeder-buses. To solve the model, a concept of dummy feeder-bus system is proposed to transform the non-linear model into traditional linear programming (ILP) model, i.e., traditional transportation problem. The case study of Line #2 of Nanjing URT in China was adopted to illustrate the model application and sensitivity analyses of the key variables. The modeling results show that as the evacuation time window increases, the total evacuation cost as well as the number of dispatched feeder-buses decrease, and the dispatched feeder-buses need operate for more times along the feeder-bus line. The number of dispatched feeder-buses does not show an obvious change with the increase of parking spot capacity and time window, indicating that simply increasing the parking spot capacity would cause huge waste for the emergent bus utilization. When the unbalanced evacuation demand exists between stations, the more feeder-buses are needed. The method of this study will contribute to improving transportation emergency management and resource allocation for URT systems. PMID:27676179

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

Directory of Open Access Journals (Sweden)

Jesse Chieh-Szu Yang

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

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

Science.gov (United States)

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

2016-01-01

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

Network Reduction Algorithm for Developing Distribution Feeders for Real-Time Simulators: Preprint

Energy Technology Data Exchange (ETDEWEB)

Nagarajan, Adarsh; Nelson, Austin; Prabakar, Kumaraguru; Hoke, Andy; Asano, Marc; Ueda, Reid; Nepal, Shaili

2017-06-15

As advanced grid-support functions (AGF) become more widely used in grid-connected photovoltaic (PV) inverters, utilities are increasingly interested in their impacts when implemented in the field. These effects can be understood by modeling feeders in real-time systems and testing PV inverters using power hardware-in-the-loop (PHIL) techniques. This paper presents a novel feeder model reduction algorithm using a Monte Carlo method that enables large feeders to be solved and operated on real-time computing platforms. Two Hawaiian Electric feeder models in Synergi Electric's load flow software were converted to reduced order models in OpenDSS, and subsequently implemented in the OPAL-RT real-time digital testing platform. Smart PV inverters were added to the real-time model with AGF responses modeled after characterizing commercially available hardware inverters. Finally, hardware inverters were tested in conjunction with the real-time model using PHIL techniques so that the effects of AGFs on the choice feeders could be analyzed.

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

Directory of Open Access Journals (Sweden)

Herrera Antonio

2010-06-01

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

Final report on the evolution of supporting conditions for the feeders of 500 MWe PHWR

International Nuclear Information System (INIS)

Mishra, Rajesh; Soni, R.S.; Kushawaha, H.S.; Mahajan, S.C.; Kakodkar, A.; Hariprasad, K.

1994-01-01

This report deals with the evolution of generic supporting conditions for the feeders of 500 MWe PHWR based on the analysis and qualification of a few representative feeders. There are 196 different feeder pipe configurations for a total of 748 feeders. The present analysis was aimed at evolving a generalised supporting criteria based on the analysis of some representative feeders. The analysis was carried out for various loadings viz. pressure, temperature, dead weight, operating basis earthquake (OBE), safe shutdown earthquake (SSE) and creep loadings. The analysis for OBE and SSE loadings were carried out using response spectrum method. The effect of spacers between various feeders was modelled using higher damping values than those prescribed in ASME code. Based on the above analyses, generic supporting arrangements for the feeders of various groups have been finalized. This report gives details about the mathematical modelling, the analysis approach, the optimised supporting criteria, finalization of grouping and fixing of boundaries between various groups of feeders. (author). 34 refs., 51 figs., 69 tabs

The blending and segregation of coal for the U.K. industrial market

Energy Technology Data Exchange (ETDEWEB)

McGlinchey, D.; Jones, M.G.; Marjanovic, P. [Glasgow Caledonian Univ. (United Kingdom). Dept. of Physical Sciences

1999-09-01

The two most common methods of 'blending' industrial coals is either by use of feeder belts discharging onto a central conveyor belt, or by a compartment hopper discharging onto a common belt. These two methodologies were shown to give very similar levels of variance in the proportioning of component coals, over a wide range of discharge conditions. Limited work suggested that belt sampling from the end of the belt gave similar results to the stopped belt and frame technique. The segregation found in heaps formed from binary mixtures of coals was quantified by various statistical methods. These results demonstrated that very high levels of segregation can be expected in almost any heap formed when material is discharged from the belt in either of the two 'blending' methods described above. This can reasonably be expected to be a major factor in the inconsistent supply of a specified blend to a consumer. (orig.)

Increasing flexibility of coal power plant by control system modifications

Directory of Open Access Journals (Sweden)

Marušić Ante

2016-01-01

Full Text Available Expanding implementation of intermittent renewable energy sources has already started to change the role of thermal power plants in energy systems across Europe. Traditionally base load plants are now forced to operate as peaking plants. A familiar transition in upcoming years is expected in Croatia and coal power plant operators are preparing accordingly. To evaluate cycling capabilities and control system operation for flexible operation of selected 210 MW coal plant, series of tests with different load gradients were performed and results were thoroughly analyzed. Two possible “bottlenecks” are identified, thermal stress in superheater header, and achievable ramping rate considering operational limitations of coal feeders, firing system and evaporator dynamics. Several unexpected readings were observed, usually caused by malfunctioning sensors and equipment, resulting in unexpected oscillations of superheated steam temperature. Based on superheater geometry and experimental data, maximal steam temperature gradient during ramping was evaluated. Since thermal stress was well inside the safety margins, the simulation model of the whole boiler was used to evaluate achievable ramping on electric side.

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

Science.gov (United States)

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

2016-07-19

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

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

OpenAIRE

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

2017-01-01

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

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

Directory of Open Access Journals (Sweden)

Engin Çetin

2015-01-01

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

limit loads for wall-thinning feeder pipes under combined bending and internal pressure

International Nuclear Information System (INIS)

Je, Jin Ho; Lee, Kuk Hee; Chung, Ha Joo; Kim, Ju Hee; Han, Jae Jun; Kim, Yun Jae

2009-01-01

Flow Accelerated Corrosion (FAC) during inservice conditions produces local wall-thinning in the feeder pipes of CANDU. The Wall-thinning in the feeder pipes is main degradation mechanisms affecting the integrity of piping systems. This paper discusses the integrity assessment of wall-thinned feeder pipes using limit load analysis. Based on finite element limit analyses, this paper compare limit loads for wall-thinning feeder pipes under combined bending and internal pressure with proposed limit loads. The limit loads are determined from limit analyses based on rectangular wall-thinning and elastic-perfectly-plastic materials using the large geometry change.

Standard Waste Box Lid Screw Removal Option Testing

International Nuclear Information System (INIS)

Anast, Kurt Roy

2016-01-01

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

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.

Feeder cells support the culture of induced pluripotent stem cells even after chemical fixation.

Directory of Open Access Journals (Sweden)

Xiao-Shan Yue

Full Text Available Chemically fixed mouse embryonic fibroblasts (MEFs, instead of live feeder cells, were applied to the maintenance of mouse induced pluripotent stem (miPS cells. Formaldehyde and glutaraldehyde were used for chemical fixation. The chemically fixed MEF feeders maintained the pluripotency of miPS cells, as well as their undifferentiated state. Furthermore, the chemically fixed MEF feeders were reused several times without affecting their functions. These results indicate that chemical fixation can be applied to modify biological feeders chemically, without losing their original functions. Chemically fixed MEF feeders will be applicable to other stem cell cultures as a reusable extracellular matrix candidate that can be preserved on a long-term basis.

Misplaced Cervical Screws Requiring Reoperation.

Science.gov (United States)

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

2017-04-01

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

Are We Underestimating the Significance of Pedicle Screw Misplacement?

Science.gov (United States)

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

2016-05-01

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

How can we reduce carbon in ash in firing pulverized coal

Energy Technology Data Exchange (ETDEWEB)

O' Keefe, W. (and others)

1992-12-01

The article discusses solutions to the problem of reducing carbon in ash in firing pulverized coal. Suggested solutions to the problem include: reviewing air flow through the mills; examining the pulverizers for coal fineness variations; investigating air distribution in the burners; review dual-firing equations; examining the burners for slag build up; checking coal fineness is appropriate to the boiler; increasing air flow; and checking instrumentation. 2 figs., 1 photo.

Tricortical cervical inter-body screw fixation.

Directory of Open Access Journals (Sweden)

Goel A

1997-01-01

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

Seismic analysis of ITER fourth PF (Poloidal Field Coil) feeder

International Nuclear Information System (INIS)

Liu, Sumei; Chen, Wei; Song, Yuntao; Ni, Xiaojun; Wang, Zhongwei; Chen, Yonghua; Gong, Chenyu

2014-01-01

The ITER feeder systems connect the ITER magnet systems located inside the main cryostat to the cryo-plant, power-supply and control system interfaces outside the cryostat. The main purpose of the feeders is to convey the cryogenic supply and electrical power to the coils as well as house the instrumentation wiring. The PF busbar which carries 52 kA current will suffer from high Lorentz force due to the background magnetic field inspired by the coils and the self-field between every pair of busbars. Except their mechanical strength and thermal insulation performance must be achieved, the dynamic mechanism on PF structure should be assessed. This paper presents the simulation and seismic analysis on ITER 4th PF feeder including the Coil Terminal Box and S-bend Box (CTB and SBB), the Cryostat Feed-through (CFT), the In-Cryostat-Feeder (ICF), especially for the ground supports and main outer-tube firstly. This analysis aims to study seismic resistance on system design under local seismograms with floor response spectrum, the structural response vibration mode and response duration results of displacement, membrane stress, and bending stress on structure under different directions actuating signals were obtained by using the single-seismic spectrum analysis and Dead Weight analysis respectively. Based on the simulative and analytical results, the system seismic resistance and the integrity of the support structure in the 4th PF feeder have been studied and the detail design confirmed

Improvement of Local Voltage in Feeders with Photovoltaic using Electric Vehicles

DEFF Research Database (Denmark)

Marra, Francesco; Yang, Guangya; Fawzy, Y. T.

2013-01-01

In low-voltage (LV) feeders with high penetration of photovoltaic (PV), a major issue to be solved is voltage rise due to the active power injection. If no measures are taken, this may lead to generation’s interruptions and to the malfunctioning of domestic appliances due to non-standard voltage...... profiles. This paper proposes a storage strategy to alleviate voltage rise in feeders with PV, using coordinated electric vehicle (EV) load as the storage solution. The voltage support strategy is easy to implement practically and it is demonstrated on a test feeder emulating a household with roof...

Accuracy of computer-assisted cervicle pedicle screw installation

International Nuclear Information System (INIS)

Zhang Honglei; Zhou Dongsheng; Jang Zhensong

2009-01-01

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

Decision Support for Optimal Repositioning of Containers in a Feeder System

Directory of Open Access Journals (Sweden)

Danijela Tuljak-Suban

2008-03-01

Full Text Available The transport of empty containers represents a seriousproblem in the fast growing sphere of maritime container transport.The most widespread type of container transport organizationin maritime transport is the hub and spoke mode, whichenables the transport of a great number of containers via largevessels between hub ports, from where feeder ships transport tosmaller ports that thus gravitate to the central hub port. The articlecontains a detailed analysis of the northern Adriatic portsand the feeder connections with the hub ports of the Mediterranean.A two-level VRPPD (Vehicle Routing Problem withPickup and Delivery problem is modelled on a graph, wherethe transport of full containers is privileged over the transport ofempty containers. This enables the simulation of the feeder systemin the n01them Adriatic, meaning that it shows the ship'soperator the movement programme with minimal transportcosts for the superfluous empty containers in the complex of theregular transports of full containers in the feeder system.

A Markov chain model for CANDU feeder pipe degradation

International Nuclear Information System (INIS)

Datla, S.; Dinnie, K.; Usmani, A.; Yuan, X.-X.

2008-01-01

There is need for risk based approach to manage feeder pipe degradation to ensure safe operation by minimizing the nuclear safety risk. The current lack of understanding of some fundamental degradation mechanisms will result in uncertainty in predicting the rupture frequency. There are still concerns caused by uncertainties in the inspection techniques and engineering evaluations which should be addressed in the current procedures. A probabilistic approach is therefore useful in quantifying the risk and also it provides a tool for risk based decision making. This paper discusses the application of Markov chain model for feeder pipes in order to predict and manage the risks associated with the existing and future aging-related feeder degradation mechanisms. The major challenge in the approach is the lack of service data in characterizing the transition probabilities of the Markov model. The paper also discusses various approaches in estimating plant specific degradation rates. (author)

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

OpenAIRE

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

2013-01-01

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

Protective and control relays as coal-mine power-supply ACS subsystem

Science.gov (United States)

Kostin, V. N.; Minakova, T. E.

2017-10-01

The paper presents instantaneous selective short-circuit protection for the cabling of the underground part of a coal mine and central control algorithms as a Coal-Mine Power-Supply ACS Subsystem. In order to improve the reliability of electricity supply and reduce the mining equipment down-time, a dual channel relay protection and central control system is proposed as a subsystem of the coal-mine power-supply automated control system (PS ACS).

Non-competitive market behaviour in the international coking coal market

International Nuclear Information System (INIS)

Graham, P.; Thorpe, S.; Hogan, L.

1999-01-01

In this paper, a primal dual programming model of international coking coal trade is constructed to test for non-competitive market behaviour. World trade in 1996 is simulated under perfect competition and various non-competitive market structures. Statistical tests are used to compare simulated trade flows with actual data. Assuming Cournot-Nash behaviour, an all consumer oligopsony market structure is preferred to alternative models. Under an all consumer oligopsony world coking coal prices and trade are lower than under perfect competition. Under an oligopsonistic structure welfare gains from productivity increases in Australian coal mines might largely accrue to coal buyers

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.

A novel method for decomposing electricity feeder load into elementary profiles from customer information

International Nuclear Information System (INIS)

Gerossier, Alexis; Barbier, Thibaut; Girard, Robin

2017-01-01

Highlights: •Use of aggregated electricity load profiles and customer description at feeder level. •Statistical recovery of elementary load profiles with customer categorization. •Generation of load demand profiles for unknown feeders and new local areas. •Relevancy of the different categorizations. -- Abstract: To plan a distribution grid involves making a long-term forecast of sub-hourly demand, which requires modeling the demand and its dynamics with aggregated measurement data. Distribution system operators (DSOs) have been recording electricity sub-hourly demand delivered by their medium-voltage feeders (around 1000—10,000 customers) for several years. Demand profiles differ widely among the various considered feeders. This is partly due to the varying mix of customer categories from one feeder to another. To overcome this issue, elementary demand profiles are often associated with customer categories and then combined according to a mix description. This paper presents a novel method to estimate elementary profiles that only requires several feeder demand curves and a description of customers. The method relies on a statistical blind source model and a new estimation procedure based on the augmented Lagrangian method. The use of feeders to estimate elementary profiles means that measurements are fully representative and continuously updated. We illustrate the proposed method through a case study comprising around 1000 feeder demand curves operated by the main French DSO Enedis. We propose an application o that uses the obtained profiles to evaluate the contribution of any set of new customers to a feeder peak load. We show that profiles enable a simulation of new unmeasured areas with errors of around 20%. We also show how our method can be used to evaluate the relevancy of different customer categorizations.

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

Science.gov (United States)

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

2017-07-28

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

Screw piles for cold climate foundations

Energy Technology Data Exchange (ETDEWEB)

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

2008-07-01

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

Complications of syndesmotic screw removal

NARCIS (Netherlands)

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

2011-01-01

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

BC Hydro's integrated approach on replacing underground feeder cables

Energy Technology Data Exchange (ETDEWEB)

Tarampi, D. [BC Hydro, Burnaby, BC (Canada)

2008-07-01

BC Hydro's integrated approach on replacing underground feeder cables was discussed. The feeder cables were all in ducts encased in concrete and splices were identified in concrete manholes. The feeder cables averaged 35 to 40 failures per year, with a large majority of failures occurring in manholes or near terminations. The age of the cables was not known. A graphical representation of a condition assessment was presented with reference to an electrical test, metallurgical test, hardness test, and dye penetrating test. Prioritization steps were also listed, including a condition index and replacement threshold. Steps in prioritizing the condition index included determining the insulation index based on electrical test results; determining the manhole condition based on metallurgical test results; determining the customer importance factor and feeder load factor; and calculating the overall condition index based on the indices. A process flowchart was also illustrated. A replacement strategy was then discussed and a cost comparison of two options was described. Option 1 was to replace only the unjacketed cables while option two involved selective replacement. tabs., figs.

Quantitative control of belt weighing feeder quick loading system%定量控制皮带称重式给料机快速装车系统

Institute of Scientific and Technical Information of China (English)

张荣轩

2012-01-01

This paper introduces a kind of belt weighing feeder quantitative control technology, which realizes the bulk material rapid loading design and widely used in coal metallurgy, chemical industry, building materials industry.%本文介绍了一种对皮带称重式给料机进行定量控制技术,实现散状物料快速装车的设计方案,广泛适用于煤炭、冶金、化工和建材等行业。

Expression and secretory profile of buffalo fetal fibroblasts and Wharton's jelly feeder layers.

Science.gov (United States)

Parmar, Mehtab S; Mishra, Smruti Ranjan; Somal, Anjali; Pandey, Sriti; Kumar, G Sai; Sarkar, Mihir; Chandra, Vikash; Sharma, G Taru

2017-05-01

The present study examined the comparative expression and secretory profile of vital signaling molecules in buffalo fetal fibroblasts (BFF) and Wharton's jelly (BWJ) feeder layers at different passages. Both feeder layers were expanded up to 8th passage. Signaling molecules viz. bone morphogenetic protein 4 (BMP4), fibroblast growth factor 2 (FGF2), leukemia inhibitory factor (LIF) and transforming growth factor beta 1 (TGFB1) and pluripotency-associated transcriptional factors (POU5F1, SOX2, NANOG, KLF4, MYC and FOXD3) were immunolocalized in the both feeder types. A clear variation in the expression pattern of key signaling molecules with passaging was registered in both feeders compared to primary culture (0 passage). The conditioned media (CM) was collected from different passages (2, 4, 6, 8) of both the feeder layers and was quantified using enzyme-linked immunosorbent assay (ELISA). Concomitant to expression profile, protein quantification also revealed differences in the concentration of signaling molecules at different time points. Conjointly, expression and secretory profile revealed that 2nd passage of BFF and 6th passage of BWJ exhibit optimal levels of key signaling molecules thus may be selected as best passages for embryonic stem cells (ESCs) propagation. Further, the effect of mitomycin-C (MMC) treatment on the expression profile of signaling molecules in the selected passages of BFF and BWJ revealed that MMC modulates the expression profile of these molecules. In conclusion, the results indicate that feeder layers vary in expression and secretory pattern of vital signaling molecules with passaging. Based on these findings, the appropriate feeder passages may be selected for the quality propagation of buffalo ESCs. Copyright © 2017 Elsevier B.V. All rights reserved.

Comparing the engineering program feeders from SiF and convention models

Science.gov (United States)

Roongruangsri, Warawaran; Moonpa, Niwat; Vuthijumnonk, Janyawat; Sangsuwan, Kampanart

2018-01-01

This research aims to compare the relationship between two types of engineering program feeder models within the technical education systems of Rajamangala University of Technology Lanna (RMUTL), Chiangmai, Thailand. To illustrate, the paper refers to two typologies of feeder models, which are the convention and the school in factory (SiF) models. The new SiF model is developed through a collaborative educational process between the sectors of industry, government and academia, using work-integrated learning. The research methodology were use to compared features of the the SiF model with conventional models in terms of learning outcome, funding budget for the study, the advantages and disadvantages from the point of view of students, professors, the university, government and industrial partners. The results of this research indicate that the developed SiF feeder model is the most pertinent ones as it meet the requirements of the university, the government and the industry. The SiF feeder model showed the ability to yield positive learning outcomes with low expenditures per student for both the family and the university. In parallel, the sharing of knowledge between university and industry became increasingly important in the process, which resulted in the improvement of industrial skills for professors and an increase in industrial based research for the university. The SiF feeder model meets its demand of public policy in supporting a skilled workforce for the industry, which could be an effective tool for the triple helix educational model of Thailand.

Effects of different feeder layers on culture of bovine embryonic stem cell-like cells in vitro.

Science.gov (United States)

Cong, Shan; Cao, Guifang; Liu, Dongjun

2014-12-01

To find a suitable feeder layer is important for successful culture conditions of bovine embryonic stem cell-like cells. In this study, expression of pluripotency-related genes OCT4, SOX2 and NANOG in bovine embryonic stem cell-like cells on mouse embryonic fibroblast feeder layers at 1-5 passages were monitored in order to identify the possible reason that bovine embryonic stem cell-like cells could not continue growth and passage. Here, we developed two novel feeder layers, mixed embryonic fibroblast feeder layers of mouse and bovine embryonic fibroblast at different ratios and sources including mouse fibroblast cell lines. The bovine embryonic stem cell-like cells generated in our study displayed typical stem cell morphology and expressed specific markers such as OCT4, stage-specific embryonic antigen 1 and 4, alkaline phosphatase, SOX2, and NANOG mRNA levels. When feeder layers and cell growth factors were removed, the bovine embryonic stem cell-like cells formed embryoid bodies in a suspension culture. Furthermore, we compared the expression of the pluripotent markers during bovine embryonic stem cell-like cell in culture on mixed embryonic fibroblast feeder layers, including mouse fibroblast cell lines feeder layers and mouse embryonic fibroblast feeder layers by real-time quantitative polymerase chain reaction. Results suggested that mixed embryonic fibroblast and sources including mouse fibroblast cell lines feeder layers were more suitable for long-term culture and growth of bovine embryonic stem cell-like cells than mouse embryonic fibroblast feeder layers. The findings may provide useful experimental data for the establishment of an appropriate culture system for bovine embryonic stem cell lines.

An evaluation of the choice of feeder cell growth arrest for the production of cultured epidermis.

Science.gov (United States)

Chugh, Rishi Man; Chaturvedi, Madhusudan; Yerneni, Lakshmana Kumar

2015-12-01

Growth arrested 3T3 cells have been used as feeder cells in human epidermal keratinocyte cultures to produce cultured epidermal autografts for the treatment of burns. The feeder cells were ideally growth-arrested by gamma-irradiation. Alternatively, growth arrest by mitomycin C treatment is a cost effective option. We compared the functional efficacy of these two approaches in keratinocyte cultures by colony forming efficiency, the net growth area of colonies, BrdU labeling and histological features of cultured epidermal sheets. The growth area estimation involved a semi-automated digital technique using the Adobe Photoshop and comprised of isolation and enumeration of red pixels in Rhodamine B-stained keratinocyte colonies. A further refinement of the technique led to the identification of critical steps to increasing the degree of accuracy and enabling its application as an extension of colony formation assay. The results on feeder cell functionality revealed that the gamma irradiated feeders influenced significantly higher colony forming efficiency and larger growth area than the mitomycin C treated feeders. The BrdU labeling study indicated significant stimulation of the overall keratinocyte proliferation by the gamma irradiated feeders. The cultured epidermal sheets produced by gamma feeders were relatively thicker than those produced by mitomycin C feeders. We discussed the clinical utility of mitomycin C feeders from the viewpoint of cost-effective burn care in developing countries. Copyright © 2015 Elsevier Ltd and ISBI. All rights reserved.

Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de La Muerte, Costa Rica

Directory of Open Access Journals (Sweden)

Gerardo Avalos

2012-03-01

Full Text Available Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis, dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads, and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon. Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of

Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de la Muerte, Costa Rica.

Science.gov (United States)

Avalos, Gerardo; Soto, Alejandra; Alfaro, Willy

2012-03-01

Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant) and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis), dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads), and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon). Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of captured

Optimal Design of the Feeder-Bus Network Based on the Transfer System

Directory of Open Access Journals (Sweden)

Lianbo Deng

2013-01-01

Full Text Available This paper studied the classic feeder-bus network design problem (FBNDP, which can be described as follows: for the passenger travel demand between rail stations and bus stops on a given urban transit network, it designs the optimal feeder bus routes and frequencies so as to minimize the passengers’ travel expense and the operator’s cost. We extended the demand pattern of M-to-1 in most existing researches to M-to-M. We comprehensively considered the passenger travel cost, which includes the waiting and riding cost on the bus, riding cost on rail, and transfer cost between these two transportation modes, and presented a new genetic algorithm that determines the optimal feeder-bus operating frequencies under strict constraint conditions. The numerical examples under different demand patterns have been experienced and analysed, which showed the robustness and efficiency of the presented algorithm. We also found that the distribution pattern of the travel demand has a significant influence on the feeder-bus network construction.

Calculating Characteristics of the Screws with Constant And Variable Step

Directory of Open Access Journals (Sweden)

B. N. Zotov

2015-01-01

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

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.

Minimally Invasive Technique for PMMA Augmentation of Fenestrated Screws

Directory of Open Access Journals (Sweden)

Jan-Helge Klingler

2015-01-01

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

Handling and feeding of biomass to pressurized reactors: safety engineering

Energy Technology Data Exchange (ETDEWEB)

Wilen, Carl; Rautalin, Aimo (Valtion Teknillinen Tutkimuskeskus, Espoo (Finland). Lab. of Fuel and Process Technology)

1993-01-01

There are rather few literature references to or experience of the feed of biomass into a pressurized space. Alternatives given in the literature usually concern handling and feeding technology for coal. Some screw- or piston-operated plug feeders and coal and concrete pump equipment have, however, also been tested with biomasses. Explosion characteristics of fuels and their susceptibility to spontaneous ignition have been studied at both atmospheric and elevated pressures. The maximum explosion pressure and maximum rate of pressure rise, being critical factors in the process design and in the choice of safety equipment, have been determined under these conditions. In pressurized processes, the maintenance of sufficient inertization in fuel-feed systems is an especially critical factor. Peat, bark, and forest residues were used as biofuels, and lignite was used as reference fuel. The results obtained with a dynamic method for spontaneous ignition were compared with experience obtained from the operation of a commercial pressurized peat gasifier of 140 MW. (author)

Mass transfer effects in feeder flow-accelerated corrosion wall thinning

International Nuclear Information System (INIS)

Pietralik, J.

2008-01-01

Flow conditions play a dominant role in Flow-Accelerated Corrosion (FAC) under certain conditions, e.g., in CANDU feeders. While chemistry and materials set the overall potential for FAC, flow conditions determine the local distribution of wall thinning. Recent plant data of feeders and laboratory tests confirms that there is a close relationship between local flow conditions, expressed by mass transfer coefficient, and FAC rate in CANDU feeder bends. The knowledge of local effects can be useful for minimizing the number of inspected components, predicting the location of the highest FAC rate for a given piping component, and determining what components or feeders should be replaced. A similar evaluation applies also to FAC in heat transfer equipment such as heat exchangers and steam generators. The objective of this paper is to examine the relationship between FAC rate and local mass transfer parameters. For FAC where the flow is dominant, the FAC rate is proportional to mass flux of ferrous ions. The mass flux is the product of the mass transfer coefficient and the concentration difference, or degree of saturation. The mass transfer coefficient describes the intensity of the transport of corrosion products (ferrous ions) from the oxide-water interface into the bulk water. Therefore, this parameter can be used for predicting the local distribution of FAC rate in the mass-transfer controlled FAC. The degree of saturation reduces the mass flux, thus reducing the FAC rate. This effect can be significant in long piping, e.g., in outlet feeders. The paper presents plant and laboratory evidence for the relationship between local mass transfer conditions and the FAC rate. It shows correlations for mass transfer coefficient in components that are highly susceptible to FAC and most important flow parameters that affect mass transfer coefficient. The role of surface roughness, wall shear stress, and local turbulence is also discussed. (author)

Insertion profiles of 4 headless compression screws.

Science.gov (United States)

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

2013-09-01

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

Evaluation of options for life cycle management of feeder cracking at the Point Lepreau Generating Station

International Nuclear Information System (INIS)

Gendron, T.S.; Slade, J.P.

2003-01-01

The CANDU industry has a predictive capability for most Heat Transport System (HTS) degradation issues that allows utilities to apply cost-effective maintenance programs. The standard approach for maintenance programs is focussed inspection and planned replacement. Some examples of degradation issues with deterministic failure rates are feeder thinning, and pressure tube elongation and deuterium ingress. However, the cracking observed in Point Lepreau Generating Station (PLGS) outlet feeder first bends is one notable exception to this behaviour. A predictive capability for feeder cracking does not currently exist for several reasons. First, the mechanism of feeder cracking, stress corrosion cracking (SCC), has to some degree a random nature. Second, although a probable environment causing cracking has been identified, the precise stress and environmental conditions for feeder crack initiation and propagation have not been defined. Finally, the very low incidence of feeder cracking observed to-date (four, all at PLGS) precludes a probabilistic or statistical prediction of failure rate. Generally, utilities select a Life Cycle Management Plan that ensures safe operation and has the lowest Net Present Value cost. In preparing a Feeder Life Cycle Management Plan, New Brunswick Power (NBP) has recognized that the Net Present Value cost is very sensitive to failure rate. Since the failure rate for feeder cracking is not well defined, the following three scenarios were considered to bound the probability of future failures at PLGS. (author)

Computational fluid dynamics analysis for flow accelerated corrosion in CANDU6 feeder pipes

International Nuclear Information System (INIS)

Catana, A.; Pauna, E.; Ioan, M.

2013-01-01

CANDU6 plant management over a long time period includes various ageing and degradation mechanisms like FAC manifested mainly at first and second elbow of CANDU6 outlet feeders. FAC take place at all CANDU6 built before 2000 year with feeders made from SA106 grade B low alloy carbon-steel (with chromium at 0.02%). CFD method is used in this paper to investigate the feeder's wall thinning process taking place mainly due local flow conditions in complex 3D geometrical configurations. The 380 outlet feeders grouped in 2.5'' (320) and 2.0'' feeders (60). The objective of this paper is to help, as much as possible, to focus investigation on most probable maximum thinning rate locations through 3D distribution of some TH parameters. Application of CFD methods in CANDU6 nuclear reactors implies the knowledge of real plant operating data like: long term time averaged channel power and mass flow as well as temperature, pressure, pHa etc allowing the optimization and cost reduction of wall thinning monitoring process at CANDU6 nuclear power plants. (authors)

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.

Ball Screw Actuator Including an Axial Soft Stop

Science.gov (United States)

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

2016-01-01

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

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

Science.gov (United States)

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

2017-12-01

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

Screw scale measurement requirements and test methods%螺旋秤的计量要求和试验方法

Institute of Scientific and Technical Information of China (English)

刘炜

2012-01-01

Through to the electronic spiral weighing feeder test, this article describes in detail on the basis of continuous totalizing automatic weighing instrument (belt) national standard (GBfF7721-2007) and test procedures (JJG195-2D02) corresponding to the terms of the screw scale test measurement requirements and test methods.%本文通过对电子螺旋称重给料机进行试验，详细地阐述了依据连续累计自动衡器（皮带秤）的国家标准（GB／T7721—2007）和检定规程~G195—2002）相应的条款对螺旋秤进行试验的计量要求和试验方法。

An imbalanced development of coal and electricity industries in China

International Nuclear Information System (INIS)

Wang, Bing

2007-01-01

China's coal and electricity industries have a strong reliance on each other, however, because of excessive invasion of government, it is difficult for these two industries to form a stable, reasonable, and transaction cost-saving relationships, but long-run disputes and quarrels. This paper discusses the pricing policies and transaction relationship between these two industries from the historical perspective. It begins with the discussion of coal. Coal market has become competitive since 1980 due to the system of dual track approach, but coal sold to electricity was still tightly controlled by government-guided pricing. Then the paper examines electricity investment and tariff reform. Unlike coal, entry to electricity generation sector was gradually relaxed but generation and retailing tariffs are still strictly regulated. As energy demand and prices soared after 2002, coal and electricity enterprises are all unsatisfied with the rule of price setting of coal sold to electricity industry. This paper concludes that the deliberate low coal price policy does protect electricity industry from fuel cost fluctuation but harm coal industry. Allocative and productive efficiency are difficult to achieve in the long run

Hydraulic screw fastening devices - design, maintenance, operational experience

International Nuclear Information System (INIS)

Lachner.

1976-01-01

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

Stress corrosion cracking lifetime prediction of spring screw

International Nuclear Information System (INIS)

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

2004-01-01

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

Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

Science.gov (United States)

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

2014-01-01

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

Tightening techniques for the retaining screws of universal abutment

Directory of Open Access Journals (Sweden)

Alexandre Wittcinski REGALIN

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

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

Science.gov (United States)

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

2018-05-01

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

A feeder-free culture using autogeneic conditioned medium for undifferentiated growth of human embryonic stem cells: Comparative expression profiles of mRNAs, microRNAs and proteins among different feeders and conditioned media

Directory of Open Access Journals (Sweden)

Chou Chi-Hsien

2010-10-01

Full Text Available Abstract Background Human embryonic stem (hES cell lines were derived from the inner cell mass of human blastocysts, and were cultured on mouse embryonic fibroblast (MEF feeder to maintain undifferentiated growth, extensive renewal capacity, and pluripotency. The hES-T3 cell line with normal female karyotype was previously used to differentiate into autogeneic fibroblast-like cells (T3HDF as feeder to support the undifferentiated growth of hES-T3 cells (T3/HDF for 14 passages. Results A feeder-free culture on Matrigel in hES medium conditioned by the autogeneic feeder cells (T3HDF was established to maintain the undifferentiated growth of hES-T3 cells (T3/CMHDF for 8 passages in this investigation. The gene expression profiles of mRNAs, microRNAs and proteins between the undifferentiated T3/HDF and T3/CMHDF cells were shown to be very similar, and their expression profiles were also found to be similar to those of T3/MEF and T3/CMMEF cells grown on MEF feeder and feeder-free Matrigel in MEF-conditioned medium, respectively. The undifferentiated state of T3/HDF and T3/CMHDF as well as T3/MEF andT3/CMMEF cells was evidenced by the very high expression levels of "stemness" genes and low expression levels of differentiation markers of ectoderm, mesoderm and endoderm in addition to the strong staining of OCT4 and NANOG. Conclusion The T3HDF feeder and T3HDF-conditioned medium were able to support the undifferentiated growth of hES cells, and they would be useful for drug development and toxicity testing in addition to the reduced risks of xenogeneic pathogens when used for medical applications such as cell therapies.

A geometrical introduction to screw theory

International Nuclear Information System (INIS)

Minguzzi, E

2013-01-01

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

Twin screw wet granulation: Binder delivery.

Science.gov (United States)

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

2015-06-20

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

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

Science.gov (United States)

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

2016-09-20

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

EV Charging Facilities and Their Application in LV Feeders with Photovoltaics

DEFF Research Database (Denmark)

Marra, Francesco; Yang, Guangya; Træholt, Chresten

2013-01-01

Low-voltage (LV) grid feeders with high penetration of photovoltaics (PVs) are often affected by voltage magnitude problems. To solve such issues, previous research has shown that reactive power methods, active power curtailment and grid reinforcement can be used for voltage support, yet showing...... several limits. We introduce the use of electric vehicle (EV) public charging stations with energy storage system (ESS) as a solution for voltage regulation in LV feeders with PV. A novel method is proposed to determine the ESS charging load required for voltage regulation and compare the results...... for the different locations in the feeder. With time-series simulations, we quantify the energy size required for a station ESS. A Belgian LV residential grid, modeled using real PV generation and load profiles, is used as case study. The method and simulation results show the effectiveness of using public EV...

Continuous powder feeding for pharmaceutical solid dosage form manufacture: a short review.

Science.gov (United States)

Blackshields, Caroline A; Crean, Abina M

2018-07-01

There has been a noticeable shift from pharmaceutical batch processing towards a more continuous mode of manufacture for solid oral dosage forms. Continuous solid oral dose processes would not be possible in the absence of a highly accurate feeding system. The performance of feeders defines the content of formulations and is therefore a critical operation in continuous manufacturing of solid dosage forms. It was the purpose of this review to review the role of the initial powder feeding step in a continuous manufacturing process. Different feeding mechanisms are discussed with a particular emphasis on screw controlled loss in weight (LIW) feeding. The importance of understanding the physical properties of the raw materials and its impact on the feeding process is reviewed. Prior knowledge of materials provides an initial indication of how the powders will behave through processing and facilitates in the selection of the most suitable (i) feeder (capacity), (ii) feeding mechanism, and (iii) in the case of screw feeder - screw type. The studies identified in this review focus on the impact of material on powder feeding performance.

Counseling in the Elementary Feeder Schools.

Science.gov (United States)

Dunham, Virginia

This brief paper presents the concept of transition counseling between a junior high school and its feeder school(s), designed to make the change from elementary into junior high less traumatic. Aside from routine sixth grade counseling, the counselors expanded their base of counseling to include all types of problems as well as all grade levels.…

Development of structural schemes of parallel structure manipulators using screw calculus

Science.gov (United States)

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

2018-03-01

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

Configuration System for Simulation Based Design of Vibratory Bowl Feeders

DEFF Research Database (Denmark)

Hansson, Michael Natapon; Mathiesen, Simon; Ellekilde, Lars-Peter

2017-01-01

Vibratory bowl feeders are still among the most commonly used production equipment for automated part feeding, where parts are correctly oriented for further manipulation by being conveyed through a set of orienting devices. Designing vibratory bowl feeders involves selecting and sequencing...... a number of these devices that either reorients or rejects the part until a desirable orientation is achieved. To aid the designer in this task, this work presents a configuration system where knowledge of the behaviour for each device is acquired through dynamic simulation, and used to solve...

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

Science.gov (United States)

Elliott, Michael J; Slakey, Joseph B

2014-05-01

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

Fate of the syndesmotic screw--Search for a prudent solution.

Science.gov (United States)

Kaftandziev, Igor; Spasov, Marko; Trpeski, Simon; Zafirova-Ivanovska, Beti; Bakota, Bore

2015-11-01

Ankle fractures are common injuries. Since the recognition of the importance of syndesmotic injury in ankle fractures, much of the scientific work has been focused on concomitant syndesmotic injury. Despite the invention of novel devices for restoration and maintenance of the congruent syndesmosis following syndesmotic injury, the metallic syndesmotic screw is still considered to be the "gold standard". The aim of this study was to compare the clinical results in patients who retained the syndesmosis screw with those in whom the screw was removed following open reduction and internal fixation of the malleolar fracture associated with syndesmosis disruption. This was a retrospective study of 82 patients. Minimum follow-up was 12 months. Clinical evaluation included American Orthopaedic Foot and Ankle Society (AOFAS) score and Visual Analogue Scale (VAS) for patient general satisfaction. The condition of the screw (removed, intact or broken), presence of radiolucency around the syndesmotic screw and the tibiofibular clear space were recorded using final follow-up radiographs. Three cortices were engaged in 66 patients (80%) and quadricortical fixation was performed in the remaining 16 patients (20%). The number of engaged cortices did not correlate with the clinical outcome and screw fracture. A single syndesmotic screw was used in 71 patients (86%. The mean AOFAS score in the group with intact screw (I) was 83; the scores in the group with broken screw (B) and removed screw (R) were 92.5 and 85.5, respectively. There was a statistically significant difference between the three groups: this was due to the difference between groups I and B; the difference between groups I and R and groups B and R were not statistically significant. There were no statistically significant differences in VAS results. There were no statistically significant differences in clinical outcome between the group with the screw retained and the group in which the screw was removed; however, the

Investigation of combustion and gasification mechanically activated coal fuel of various degrees of metamorphism on the 5-MW heat setup

Directory of Open Access Journals (Sweden)

Butakov Evgenii

2017-01-01

Full Text Available The technology of mechanochemical activation of combustion and gasification of coals is of unquestionable scientific and technical interest; an increase in chemical activity of coals at their mechanically activated grinding is associated with an increase in the rate of reaction of the coal substance. To study the combustion and gasification process, the reactor model with tangential scroll input of coal-air suspension and cylindrical reaction chamber was used at the 5-MW thermal power plant. The experiments were carried out with coals of G and SS grades of the Kuznetsk deposit. Coal, ground after the boiler’s standard mill, is fed by a feeder to the disintegrator; then, it enters the scroll inlet of the reactor burner with transport air. The suspension is ignited by a gas igniting device with the power of 50 kW. In experiments on combustion and gasification of fine coal performed at the temperature in the reaction chamber of 1000-1300°C and air excess α = 0.5-0.7, the data on concentrations of CO and H2 were obtained: for coal of grade G, concentration of H2 was 6.3% and concentration of CO was 15.3%; for coal of SS grade, concentration of H2 was 9.5% and concentration of CO was 15.6%.

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.

First Metatarsophalangeal Joint Arthrodesis: A Retrospective Comparison of Crossed-screws, Locking and Non-Locking Plate Fixation with Lag Screw

Directory of Open Access Journals (Sweden)

Leif Claassen

2017-07-01

Full Text Available Background:Locking plate fixation is increasingly used for first metatarsophalangeal joint (MTP-I arthrodesis. Still there is few comparable clinical data regarding this procedure. Methods:We retrospectively evaluated 60 patients who received an arthrodesis of the MTP-I between January 2008 and June 2010. With 20 patients each we performed a locking plate fixation with lag screw, arthrodesis with crossed-screwsor with a nonlocking plate with lag screw. Results: There were four non-unions in crossed-screws patients and one nonunion in non-locked plate group. All the patients in locking plate group achieved union. 90% of the patients were completely or mildly satisfied in locking plate group, whereas this rate was 80% for patients in both crossed screws and non-locking plate groups. Conclusions: Use of dorsal plating for arthrodesis of MTP1 joint either locking or non-locking were associated with high union rate and acceptable and comparable functional outcome. Although nonunion rate was high using two crossed screws but functional outcome was not significantly different compare to dorsal plating. Level of evidence:Ш, retrospective comparative study

Co-ordination of directional overcurrent protection with load current for parallel feeders

Energy Technology Data Exchange (ETDEWEB)

Wright, J.W.; Lloyd, G.; Hindle, P.J. [Alstom, Inc., Stafford (United Kingdom). T and D Protection and Control

1999-11-01

Directional phase overcurrent relays are commonly applied at the receiving ends of parallel feeders or transformer feeders. Their purpose is to ensure full discrimination of main or back-up power system overcurrent protection for a fault near the receiving end of one feeder. This paper reviews this type of relay application and highlights load current setting constraints for directional protection. Such constraints have not previously been publicized in well-known text books. A directional relay current setting constraint that is suggested in some text books is based purely on thermal rating considerations for older technology relays. This constraint may not exist with modern numerical relays. In the absence of any apparent constraint, there is a temptation to adopt lower current settings with modern directional relays in relation to reverse load current at the receiving ends of parallel feeders. This paper identifies the danger of adopting very low current settings without any special relay feature to ensure protection security with load current during power system faults. A system incident recorded by numerical relays is also offered to highlight this danger. In cases where there is a need to infringe the identified constraints an implemented and testing relaying technique is proposed.

Particle size distribution of fly ash from co-incineration of bituminous coal with municipal solid waste

Directory of Open Access Journals (Sweden)

Cieślik Ewelina

2018-01-01

Full Text Available One of the source of air pollutants is emission from local coal-fired boiler-houses and domestic heating boilers. The consequence of incineration of municipal waste is the introduction of additional pollutants into the atmosphere, including fly ash. The aim of this work was to evaluate the particle size distribution of fly ash emitted by coal combustion and co-incineration of coal with municipal waste in a domestic 18 kW central heating boiler equipped with an automatic fuel feeder. Mixtures of bituminous coal with different types of solid waste (5, 10 and 15% of mass fraction were used. Solid waste types consisted of: printed, colored PE caps, fragmented cable trunking, fragmented car gaskets and shredded tires from trucks. During the incineration of a given mixture of municipal waste with bituminous coal, the velocity of exhaust gas was specified, the concentration and mass flow of fly ash were determined together with the physico-chemical parameters of the exhaust gas, the samples of emitted fly ash were taken as the test material. Particle size analysis of fly ash was performed using laser particle sizer Fritch Analysette 22. The PM10 share from all fly ashes from incineration of mixtures was about 100%. Differences were noted between PM2.5 and PM1.

Particle size distribution of fly ash from co-incineration of bituminous coal with municipal solid waste

Science.gov (United States)

Cieślik, Ewelina; Konieczny, Tomasz; Bobik, Bartłomiej

2018-01-01

One of the source of air pollutants is emission from local coal-fired boiler-houses and domestic heating boilers. The consequence of incineration of municipal waste is the introduction of additional pollutants into the atmosphere, including fly ash. The aim of this work was to evaluate the particle size distribution of fly ash emitted by coal combustion and co-incineration of coal with municipal waste in a domestic 18 kW central heating boiler equipped with an automatic fuel feeder. Mixtures of bituminous coal with different types of solid waste (5, 10 and 15% of mass fraction) were used. Solid waste types consisted of: printed, colored PE caps, fragmented cable trunking, fragmented car gaskets and shredded tires from trucks. During the incineration of a given mixture of municipal waste with bituminous coal, the velocity of exhaust gas was specified, the concentration and mass flow of fly ash were determined together with the physico-chemical parameters of the exhaust gas, the samples of emitted fly ash were taken as the test material. Particle size analysis of fly ash was performed using laser particle sizer Fritch Analysette 22. The PM10 share from all fly ashes from incineration of mixtures was about 100%. Differences were noted between PM2.5 and PM1.

Selection experiments for the optimum combination of AMF-plant-substrate for the restoration of coal mines

Energy Technology Data Exchange (ETDEWEB)

Li-ping Wang; Wei-wei Zhang; Guang-xia Guo; Kui-mei Qian; Xiao-pei Huang [China University of Mining & Technology, Xuzhou (China). School of Environment and Spatial Informatics

2009-07-15

A complex substrate consisting of fly ash, coal gangue and excess sludge was used as an experimental soil in pot culture experiments. Different soil compositions were tested by observing the growth of arbuscular mycorrhizal (AM) fungi inoculated white clover, rye grass or corn. The biomass of the host plants, the mycorrhizal colonization (MC) rate and the mycorrhizal dependency (MD) were measured. The research addresses the preferable AMF-plant-substrate combination appropriate for restoration of coal mines. We used two inoculation methods: single-inoculation with Glomus versiforme or Glomus mosseae and a dual inoculation with both G.v and G.m. The results show that G.m is the preferable fungi and that dual inoculation does not show advantages for the restoration of coal mines. White clover inoculated with AM fungi is the most suitable condition for restoration of coal mines. The best weight ratio of fly ash, coal gangue and excess sludge was found to be 20:60:20. The optimum treatment conditions of AMF-plant-activated-substrate are described. 10 refs., 2 figs., 4 tabs.

An imbalanced development of coal and electricity industries in China

Energy Technology Data Exchange (ETDEWEB)

Wang, Bing [School of Public Administration, Huazhong University of Science and Technology, Wuhan (China)]. E-mail: wbyf@mail.hust.edu.cn

2007-10-15

China's coal and electricity industries have a strong reliance on each other, however, because of excessive invasion of government, it is difficult for these two industries to form a stable, reasonable, and transaction cost-saving relationships, but long-run disputes and quarrels. This paper discusses the pricing policies and transaction relationship between these two industries from the historical perspective. It begins with the discussion of coal. Coal market has become competitive since 1980 due to the system of dual track approach, but coal sold to electricity was still tightly controlled by government-guided pricing. Then the paper examines electricity investment and tariff reform. Unlike coal, entry to electricity generation sector was gradually relaxed but generation and retailing tariffs are still strictly regulated. As energy demand and prices soared after 2002, coal and electricity enterprises are all unsatisfied with the rule of price setting of coal sold to electricity industry. This paper concludes that the deliberate low coal price policy does protect electricity industry from fuel cost fluctuation but harm coal industry. Allocative and productive efficiency are difficult to achieve in the long run.

An imbalanced development of coal and electricity industries in China

Energy Technology Data Exchange (ETDEWEB)

Bing Wang [Huazhong University of Science and Technology, Wuhan (China). School of Public Administration

2007-10-15

China's coal and electricity industries have a strong reliance on each other, however, because of excessive invasion of government, it is difficult for these two industries to form a stable, reasonable, and transaction cost-saving relationships, but long-run disputes and quarrels. This paper discusses the pricing policies and transaction relationship between these two industries from the historical perspective. It begins with the discussion of coal. The coal market has become competitive since 1980 due to the system of dual track approach, but coal sold to electricity was still tightly controlled by government-guided pricing. The paper next examines electricity investment and tariff reform. Unlike coal, entry to the electricity generation sector was gradually relaxed but generation and retailing tariffs are still strictly regulated. As energy demand and prices soared after 2002, coal and electricity enterprises are all unsatisfied with the rule of price setting of coal sold to the electricity industry. It is concluded that the deliberate low coal price policy does protect the electricity industry from fuel cost fluctuation but harms the coal industry. Allocative and productive efficiency are difficult to achieve in the long run. 33 refs., 5 figs., 2 tabs.

Response of deposit-feeders to exclusion of epibenthic predators in a Mediterranean intertidal flat

NARCIS (Netherlands)

Como, S.; Rossi, F.; Lardicci, C.

2004-01-01

Deposit-feeders are common components of macrofaunal assemblages in intertidal soft sediments. Predation has been considered to have a central role in affecting their distribution and population dynamics. This study investigates the effect of epibenthic predators on deposit-feeders, inhabiting the

"The good into the pot, the bad into the crop!"--a new technology to free stem cells from feeder cells.

Directory of Open Access Journals (Sweden)

Annette Schneider

Full Text Available A variety of embryonic and adult stem cell lines require an initial co-culturing with feeder cells for non-differentiated growth, self renewal and maintenance of pluripotency. However for many downstream ES cell applications the feeder cells have to be considered contaminations that might interfere not just with the analysis of experimental data but also with clinical application and tissue engineering approaches. Here we introduce a novel technique that allows for the selection of pure feeder-freed stem cells, following stem cell proliferation on feeder cell layers. Complete and reproducible separation of feeder and embryonic stem cells was accomplished by adaptation of an automated cell selection system that resulted in the aspiration of distinct cell colonies or fraction of colonies according to predefined physical parameters. Analyzing neuronal differentiation we demonstrated feeder-freed stem cells to exhibit differentiation potentials comparable to embryonic stem cells differentiated under standard conditions. However, embryoid body growth as well as differentiation of stem cells into cardiomyocytes was significantly enhanced in feeder-freed cells, indicating a feeder cell dependent modulation of lineage differentiation during early embryoid body development. These findings underline the necessity to separate stem and feeder cells before the initiation of in vitro differentiation. The complete separation of stem and feeder cells by this new technology results in pure stem cell populations for translational approaches. Furthermore, a more detailed analysis of the effect of feeder cells on stem cell differentiation is now possible, that might facilitate the identification and development of new optimized human or genetically modified feeder cell lines.

harmonic load modeling: a case study of 33 kv abuja steel mill feeder

African Journals Online (AJOL)

HOD

techniques are adopted. This paper studied the harmonic orders of the 33 kV Abuja Steel Feeder modeled as a ... (ETAP) software package was deployed to perform Discrete Fast Transform (DFT) while the input ... and documented in research and development articles ... network with 33kV Abuja Steel feeder as case study.

Utilization of coal ash/coal combustion products for mine reclamation

International Nuclear Information System (INIS)

Dolence, R.C.; Giovannitti, E.

1997-01-01

Society's demand for an inexpensive fuel, combined with ignorance of the long term impacts, has left numerous scars on the Pennsylvania landscape. There are over 250,000 acres of abandoned surface mines with dangerous highwalls and water filled pits. About 2,400 miles of streams do not meet water quality standards because of drainage from abandoned mines. There are uncounted households without an adequate water supply due to past mining practices. Mine fires and mine subsidence plague many Pennsylvania communities. The estimated cost to reclaim these past scars is over $15 billion. The beneficial use of coal ash in Pennsylvania for mine reclamation and mine drainage pollution abatement projects increased during the past ten years. The increase is primarily due to procedural and regulatory changes by the Department of Environmental Protection (DEP). Prior to 1986, DEP required a mining permit and a separate waste disposal permit for the use of coal ash in backfilling and reclaiming a surface mine site. In order to eliminate the dual permitting requirements and promote mine reclamation, procedural changes now allow a single permit which authorize both mining and the use of coal ash in reclaiming active and abandoned pits. The actual ash placement, however, must be conducted in accordance with the technical specifications in the solid waste regulations

Impact of rent-seeking on productivity in Chinese coal mine safety supervision: A simulation study

International Nuclear Information System (INIS)

Chen, Hong; Feng, Qun; Zhu, Dandan; Han, Shuai; Long, Ruyin

2016-01-01

During the “golden decade” (2001–2011) of the coal industry in China, rent-seeking increased in coal mine safety supervision alongside significant improvements in coal mine safety status and increased economic benefits in the coal industry. To explore this internal relationship, we developed a Matlab simulation system and simulated the impact of rent-seeking from each level of the supervision department on coal mine productivity in different scenarios. The results showed the following. (1) Rent-seeking had no significant influence on the average level of material productivity but it had an adverse effect on the average level of mental productivity. Due to the effects of rent-seeking, productivity tended to exhibit unstable and destructive fluctuations, and rent-seeking had the dual effect of promoting and restraining productivity in a wide range with a high frequency. (2) In the supervision scenario, supervision by the high-level department was efficient, and productivity was promoted more by the national and provincial supervision department. (3) In the rent-seeking scenario, each level of the department had an intensity threshold above which coal mine accidents occurred. We also propose suggestions that focuses on the improved supervision of Chinese coal mine safety in three areas based on the “new normal” safety concept. - Highlights: •We discussed rent-seeking behavior in Chinese coal mine safety supervision. •We explored the characteristics of coal mine productivity. •We investigated the impact of rent-seeking on coal mine productivity in three scenarios. •We found rent-seeking led to great fluctuations in productivity with a dual effect. •We proposed a model strategy for Chinese coal mine safety supervision in three areas.

Screw-worm eradication in the Americas - Overview

International Nuclear Information System (INIS)

Wyss, John H.

2000-01-01

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

The accuracy and safety of fluoroscopically guided percutaneous pedicle screws in the lumbosacral junction and the lumbar spine: a review of 880 screws.

Science.gov (United States)

Chiu, C K; Kwan, M K; Chan, C Y W; Schaefer, C; Hansen-Algenstaedt, N

2015-08-01

We undertook a retrospective study investigating the accuracy and safety of percutaneous pedicle screws placed under fluoroscopic guidance in the lumbosacral junction and lumbar spine. The CT scans of patients were chosen from two centres: European patients from University Medical Center Hamburg-Eppendorf, Germany, and Asian patients from the University of Malaya, Malaysia. Screw perforations were classified into grades 0, 1, 2 and 3. A total of 880 percutaneous pedicle screws from 203 patients were analysed: 614 screws from 144 European patients and 266 screws from 59 Asian patients. The mean age of the patients was 58.8 years (16 to 91) and there were 103 men and 100 women. The total rate of perforation was 9.9% (87 screws) with 7.4% grade 1, 2.0% grade 2 and 0.5% grade 3 perforations. The rate of perforation in Europeans was 10.4% and in Asians was 8.6%, with no significant difference between the two (p = 0.42). The rate of perforation was the highest in S1 (19.4%) followed by L5 (14.9%). The accuracy and safety of percutaneous pedicle screw placement are comparable to those cited in the literature for the open method of pedicle screw placement. Greater caution must be taken during the insertion of L5 and S1 percutaneous pedicle screws owing to their more angulated pedicles, the anatomical variations in their vertebral bodies and the morphology of the spinal canal at this location. ©2015 The British Editorial Society of Bone & Joint Surgery.

Conceptual design of ball-screw type control element drive mechanism

Energy Technology Data Exchange (ETDEWEB)

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

1999-10-01

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

Urbanization affects neophilia and risk-taking at bird-feeders

Science.gov (United States)

Tryjanowski, Piotr; Møller, Anders Pape; Morelli, Federico; Biaduń, Waldemar; Brauze, Tomasz; Ciach, Michał; Czechowski, Paweł; Czyż, Stanisław; Dulisz, Beata; Goławski, Artur; Hetmański, Tomasz; Indykiewicz, Piotr; Mitrus, Cezary; Myczko, Łukasz; Nowakowski, Jacek J.; Polakowski, Michał; Takacs, Viktoria; Wysocki, Dariusz; Zduniak, Piotr

2016-06-01

Urban environments cover vast areas with a high density of humans and their dogs and cats causing problems for exploitation of new resources by wild animals. Such resources facilitate colonization by individuals with a high level of neophilia predicting that urban animals should show more neophilia than rural conspecifics. We provided bird-feeders across urban environments in 14 Polish cities and matched nearby rural habitats, testing whether the presence of a novel item (a brightly coloured green object made out of gum with a tuft of hair) differentially delayed arrival at feeders in rural compared to urban habitats. The presence of a novel object reduced the number of great tits Parus major, but also the total number of all species of birds although differentially so in urban compared to rural areas. That was the case independent of the potentially confounding effects of temperature, population density of birds, and the abundance of cats, dogs and pedestrians. The number of great tits and the total number of birds attending feeders increased in urban compared to rural areas independent of local population density of birds. This implies that urban birds have high levels of neophilia allowing them to readily exploit unpredictable resources in urban environments.

Passage of an Anterior Odontoid Screw through Gastrointestinal Tract.

Science.gov (United States)

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

2017-01-01

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

Passage of an Anterior Odontoid Screw through Gastrointestinal Tract

Directory of Open Access Journals (Sweden)

L. Leitner

2017-01-01

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

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

Science.gov (United States)

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

2016-12-01

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

Impact of Distribution Feeders that do not have Voltage Regulators on the number of Charged Electric Vehicles using IEEE 34 Bus Test Feeder

Energy Technology Data Exchange (ETDEWEB)

Allehyani, Ahmed [University of Southern California, Department of Electrical Engineering; Beshir, Mohammed [University of Southern California, Department of Electrical Engineering

2015-02-01

Voltage regulators help maintain an acceptable voltage profile for the system. This paper discusses the effect of installing voltage regulators to the system to fix the voltage drop resulting from the electrical vehicles loading increase when they are being charged. The effect will be studied in the afternoon, when the peak load occurs, using the IEEE 34 bus test feeder. First, only one spot node is used to charge the electric vehicles while a voltage regulator is present. Second, five spot nodes are loaded at the same time to charge the electric vehicles while voltage regulators are installed at each node. After that, the impact of electric vehicles on distribution feeders that do not have voltage regulators will appear.

Experimental study of pedicle screw stability on low BMD vertebrae

International Nuclear Information System (INIS)

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

2005-01-01

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

Safety and surgical techniques of C1 lateral mass screws

International Nuclear Information System (INIS)

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

2010-01-01

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

Vertical linear feeder to elliptical igneous saucer-shaped sills: evidences from structural observations, geochemistry and experimental modeling

Science.gov (United States)

Galerne, C. Y.; Galland, O.; Neumann, E. R.; Planke, S.

2009-12-01

The structural relationships between sills and their feeders are poorly documented because they are rarely observed in the field and difficult to image on seismic data. For instance, it is unclear whether sills are fed by pipes, dikes or other sills. Nevertheless, the geometrical relationships between sills and their feeders provide first-order constraints on magma emplacement mechanisms. Here, we investigate the structural and geochemical relationships between sills and potential feeder dikes in a remarkably well-preserved and exposed sill complex, the Golden Valley Sill Complex (GVSC), Karoo Basin, South Africa. The GVSC consists of five major saucer-shaped sills and six dikes. The Golden Valley sill itself is an elliptical saucer, with a N-S trend. A one meter thick dike (D4) crops out underneath the southern tip of the Golden Valley sill. The strike of this dike is parallel to the long axis of the Golden Valley sill. Detailed sampling and geochemical analyses of the GVSC show that each sill and dike exhibits a specific geochemical signature. The Golden Valley sill and its underlying dike D4 have identical signatures. Although there is no clear structural evidence, the consistent geometrical and geochemical relationships between the Golden Valley sill and the D4 dike suggest that this vertical linear structure is the feeder of the overlying saucer-shaped sill. In order to investigate the relationships between sills and feeders, we resorted to scaled laboratory experiments. The experiments consisted of a low-viscosity vegetable oil representing magma and a cohesive fine-grained silica flour representing brittle rocks. We placed a horizontal weak layer into the silica flour, just above the top of the inlet, to simulate strata. Such a weak layer controlled the formation of horizontal sill that subsequently turned into a transgressive sheet leading to the formation of a saucer geometry. We ran experiments with varying inlet shapes: 1) a point inlet representing a

Accuracy of pedicle screw placement in patients with Marfan syndrome.

Science.gov (United States)

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

2017-03-21

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

Process and remote device for unscrewing and extracting an assembly screw

International Nuclear Information System (INIS)

Lagarrigue, F.

1990-01-01

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

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

Science.gov (United States)

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

2015-11-25

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

The Use of Filter-feeders to Manage Disease in a Changing World.

Science.gov (United States)

Burge, Colleen A; Closek, Collin J; Friedman, Carolyn S; Groner, Maya L; Jenkins, Cody M; Shore-Maggio, Amanda; Welsh, Jennifer E

2016-10-01

Rapid environmental change is linked to increases in aquatic disease heightening the need to develop strategies to manage disease. Filter-feeding species are effective biofilters and can naturally mitigate disease risk to humans and wildlife. We review the role of filter-feeders, with an emphasis on bivalves, in altering disease outcomes via augmentation and reduction. Filtration can reduce transmission by removing pathogens from the water column via degradation and release of pathogens in pseudofeces. In other cases, filtration can increase pathogen transmission and disease risk. The effect of filtration on pathogen transmission depends on the selectivity of the filter-feeder, the degree of infectivity by the pathogen, the mechanism(s) of pathogen transmission and the ability of the pathogen to resist degradation. For example, some bacteria and viruses can resist degradation and accumulate within a filter-feeder leading to disease transmission to humans and other wildlife upon ingestion. Since bivalves can concentrate microorganisms, they are also useful as sentinels for the presence of pathogenic microorganisms. While somewhat less studied, other invertebrates, including ascidians and sponges may also provide ecosystem services by altering pathogen transmission. In all scenarios, climate change may affect the potential for filter-feeders to mitigate disease risk. We conclude that an assessment including empirical data and modeling of system-wide impacts should be conducted before selection of filter-feeders to mitigate disease. Such studies should consider physiology of the host and microbe and risk factors for negative impacts including augmentation of other pathogens. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

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

Science.gov (United States)

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

2009-01-01

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

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

International Nuclear Information System (INIS)

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

2007-01-01

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

High-speed optical feeder-link system using adaptive optics

Science.gov (United States)

Arimoto, Yoshinori; Hayano, Yutaka; Klaus, Werner

1997-05-01

We propose a satellite laser communication system between a ground station and a geostationary satellite, named high- speed optical feeder link system. It is based on the application of (a) high-speed optical devices, which have been developed for ground-based high-speed fiber-optic communications, and (b) the adaptive optics which compensates wavefront distortions due to atmospheric turbulences using a real time feedback control. A link budget study shows that a system with 10-Gbps bit-rate are available assuming the state-of-the-art device performance of the Er-doped fiber amplifier. We further discuss preliminary measurement results of the atmospheric turbulence at the telescope site in Tokyo, and present current study on the design of the key components for the feeder-link laser transceiver.

Modeling and Analyzing the Slipping of the Ball Screw

Directory of Open Access Journals (Sweden)

Nannan Xu

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

A hybrid evolutionary algorithm for distribution feeder reconfiguration

Indian Academy of Sciences (India)

the reconfiguration of distribution networks has been proposed by .... An effective strategy to increase the loading margin of heavily loaded feeders is to ... social animals such as a flock of birds, a school of fish or a group of people that pursue.

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

Science.gov (United States)

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

2018-01-01

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

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.

Digital optical feeder links system for broadband geostationary satellite

Science.gov (United States)

Poulenard, Sylvain; Mège, Alexandre; Fuchs, Christian; Perlot, Nicolas; Riedi, Jerome; Perdigues, Josep

2017-02-01

An optical link based on a multiplex of wavelengths at 1.55μm is foreseen to be a valuable solution for the feeder link of the next generation of high-throughput geostationary satellite. The main satellite operator specifications for such link are an availability of 99.9% over the year, a capacity around 500Gbit/s and to be bent-pipe. Optical ground station networks connected to Terabit/s terrestrial fibers are proposed. The availability of the optical feeder link is simulated over 5 years based on a state-of-the-art cloud mask data bank and an atmospheric turbulence strength model. Yearly and seasonal optical feeder link availabilities are derived and discussed. On-ground and on-board terminals are designed to be compliant with 10Gbit/s per optical channel data rate taking into account adaptive optic systems to mitigate the impact of atmospheric turbulences on single-mode optical fiber receivers. The forward and return transmission chains, concept and implementation, are described. These are based on a digital transparent on-off keying optical link with digitalization of the DVB-S2 and DVB-RCS signals prior to the transmission, and a forward error correcting code. In addition, the satellite architecture is described taking into account optical and radiofrequency payloads as well as their interfaces.

Experiments on screw-pinch plasmas with elongated cross section

International Nuclear Information System (INIS)

Lassing, H.W.

1989-01-01

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

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.

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

Science.gov (United States)

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

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

Probing and Tapping: Are We Inserting Pedicle Screws Correctly?

Science.gov (United States)

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

2016-11-01

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

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...

Adjacent-segment disease after thoracic pedicle screw fixation.

Science.gov (United States)

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

2018-03-01

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

Effects of different feeder layers on culture of bovine embryonic stem cell-like cells in vitro

OpenAIRE

Cong, Shan; Cao, Guifang; Liu, Dongjun

2014-01-01

To find a suitable feeder layer is important for successful culture conditions of bovine embryonic stem cell-like cells. In this study, expression of pluripotency-related genes OCT4, SOX2 and NANOG in bovine embryonic stem cell-like cells on mouse embryonic fibroblast feeder layers at 1–5 passages were monitored in order to identify the possible reason that bovine embryonic stem cell-like cells could not continue growth and passage. Here, we developed two novel feeder layers, mixed embryonic ...

Impact of feeder space on laying hen feeding behavior and production performance in enriched colony housing.

Science.gov (United States)

Oliveira, J L; Xin, H; Wu, H

2018-05-30

Current feeder space recommendations in laying hen welfare guidelines are inconsistent among and within countries. One determining criterion forming the recommendations (e.g. 12.0 cm/hen for the EU guideline) is that all birds can feed simultaneously. However, if there are other resources in the environment, as in enriched colony housing (ECH), it is unknown whether group-housed hens will choose to feed simultaneously. This study assesses the impact of feeder space on feeding behavior of 60 laying hens (W-36) in ECH using a ultra-high frequency radio-frequency identification-based tracking system. The feeder spaces investigated were 12.0, 9.5, 8.5 and 6.5 cm/hen, achieved by blocking portions of the overall feeder access to keep hens at the same stocking density. Each feeder space treatment, randomly assigned over the course of the experiment, lasted for 7 consecutive days. Feeding behaviors were characterized as daily time spent at the feeder (TS, min/hen-day), daily frequency of visits to the feeder (FV, #/hen-day), and maximum or average percentage of hens feeding simultaneously (MPB, APB, %). Group-average daily feed intake (FI, g/hen-day), water use (WU, g/hen-day), and hen-day egg production (HDEP, %) were also measured. The results revealed that at 12.0 cm/hen, where unoccupied feeder space was present, a maximum of 59.0±1.4% (average of 31.7±0.3%) hens fed simultaneously. No significant differences were detected among 12.0, 9.5 and 8.5 cm/hen in TS (293±10, 286±10 and 281±10 min/hen-day) and MPB (59.0±1.4, 57.3±1.4 and 53.3±1.4%) (P>0.05). The outcome of no significant differences also held true between 12.0 and 9.5 cm/hen in APB (31.7±0.3 v. 30.8±0.3%) and between 9.5 and 8.5 cm/hen in all response variables measured (P>0.05). However, there were significant differences in APB between 6.5 cm/hen and all other treatments; in TS and FV between 6.5 and 9.5 cm/hen; and in MPB between 6.5 and 12 cm/hen (P0.05). The results revealed that synchronous

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.

Preoperative CT planning of screw length in arthroscopic Latarjet.

Science.gov (United States)

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

2018-01-01

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

Irradiated murine fibroblasts as feeder layer used in human cell culture

International Nuclear Information System (INIS)

Almeida, Tiago L.; Klingbeil, Fatima G.; Yoshito, Daniele; Caproni, Priscila; Mathor, Monica B.; Herson, Marisa R.

2007-01-01

In 1975, Rheinwald and Green published an in vitro model for keratinocyte cell cultures in which the use of murine fibroblasts, as a feeder layer was introduced. These cells are modified fibroblasts, which presence render keratinocyte cells to remain proliferative for longer periods of time. This optimization of culture outputs has allowed for several clinical applications of confluent keratinocyte cultures as skin substitutes or wound dressings in situations such as post burn extensive skin loss, loss of oral mucosa, and other skin disorders. Nevertheless, proliferation of fibroblast in co-culture with keratinocytes must be controlled by anti-proliferative measures such as irradiation; at the same time, keratinocytes require specific nutrients in the culture medium, which may interfere with the fibroblast feeder layer viability. Therefore, the thorough understanding of the impact of different issues such as culture media composition, irradiation dose and pre-plating storage conditions of irradiated fibroblast to be used as feeder layer in these co-culture systems is important. In this work, changes as far as viability and proliferative rates of irradiated fibroblasts in culture were evaluated in relation to the type of culture medium used, dose of gamma radiation exposure, storage and timing of cell plating post irradiation. Results indicate that the type of culture medium used and time-lag between irradiation, refrigeration and plating of irradiated cells do not have significant impact in culture outcomes. However, the dose of gamma radiation administered to the cells may influence the final quality of these cells if to be used as a feeder layer. (author)

Demonstration of Market-Based Real-Time Electricity Pricing on a Congested Feeder

DEFF Research Database (Denmark)

Larsen, Emil Mahler; Pinson, Pierre; le Ray, Guillaume

2015-01-01

Congestion management can delay grid reinforcements needed due to the growth of distributed technologies like photovoltaics and electric vehicles. This paper presents a method of congestion management for low voltage feeders using indirect control from the smart grid demonstration EcoGrid EU, where...... prices to 1900 houses, with a virtual feeder of 28 houses receiving congestion pricing. Simulations are used to calculate the cost from using this congestion management method, while demonstration results indicate that congestion can be managed successfully....

Fabrication of corneal epithelial cell sheets maintaining colony-forming cells without feeder cells by oxygen-controlled method.

Science.gov (United States)

Nakajima, Ryota; Takeda, Shizu

2014-01-01

The use of murine 3T3 feeder cells needs to be avoided when fabricating corneal epithelial cell sheets for use in treating ocular surface diseases. However, the expression level of the epithelial stem/progenitor cell marker, p63, is down-regulated in feeder-free culture systems. In this study, in order to fabricate corneal epithelial cell sheets that maintain colony-forming cells without using any feeder cells, we investigated the use of an oxygen-controlled method that was developed previously to fabricate cell sheets efficiently. Rabbit limbal epithelial cells were cultured under hypoxia (1-10% O2) and under normoxia during stratification after reaching confluence. Multilayered corneal epithelial cell sheets were fabricated using an oxygen-controlled method, and immunofluorescence analysis showed that cytokeratin 3 and p63 was expressed in appropriate localization in the cell sheets. The colony-forming efficiency of the cell sheets fabricated by the oxygen-controlled method without feeder cells was significantly higher than that of cell sheets fabricated under 20% O2 without feeder cells. These results indicate that the oxygen-controlled method has the potential to achieve a feeder-free culture system for fabricating corneal epithelial cell sheets for corneal regeneration. Copyright © 2013 Elsevier Ltd. All rights reserved.

Study on pedicle screw fixation of cervical spine assisted CT-based navigation system compared with the individual cervical peddle screws placement technique

International Nuclear Information System (INIS)

He Xishun; Yang Huilin; Zhu Ruofu; Tan Xiangqi; Wang Genlin; Tang Tiansi

2008-01-01

Objective: To explore a safe and effective method for placing the cervical pedicle screws. Methods: There were ten adult cadaver specimens of cervica spine (C 1 -C 7 ) with intact structures including ligament and perivertebral muscles. The spiral computed tomography scan (Elscint CT Twin flash) at the section of 1 mm and three-dimensional reconstruction of all 10 cervical specimens were taken. By CT scan, the parameters of the cervical pedicles were measure,Then taking randomly 5 cervical specimens, according to the CT measurements, an appropriate screw was inserted into pedicle individually. In the other 5 human cadaver cervical vertebraes, Φ3.5 mm screws were inserted into the C 2 -C 7 pedicles by assisted by CT-based navigation system. Cortical integrity of every sample was examined by anatomic dissection, the spiral computed tomography scan and arrows,and coronal reconstruction. Results: Sixty screws was inserted into pedicle individually, and the achievement ratio was 90%, the perfectness ratio was 75%, 60 screws was placed into pedicle assisted by CT-based navigation system, and the achievement ratio was 96.6%, the perfectness ratio was 90%. By chi-square test for statistical analysis, there were no statistical significance between the accuracy rate of two methods(P>0.05). However there was statistical significance between the perfectness ratio between two methods(P<0.05). Conclusion: Compared with the individual cervical peddle screws placement technique, the perfectness ratio of pedicle screw fixation of cervical spine assisted by CT-based navigation system is higher, but there are no significant difference in accuracy. (authors)

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

Science.gov (United States)

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

2017-09-25

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

Multiaxial pedicle screw designs: static and dynamic mechanical testing.

Science.gov (United States)

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

2004-02-15

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

Development of a feeder device for logging residue for a drum chipper; Hakkurin syoetoen kehittaeminen energiapuulle

Energy Technology Data Exchange (ETDEWEB)

Leinonen, T.; Kemppainen, J P [Oulu Univ. (Finland). Dept. of Mechanical Engineering

1997-12-01

The aim of this project is to increase the productivity of a large drum chipper by developing a feeder device to be used especially when chipping logging residue. Logging residue from regeneration areas is the most important reserve of forest biomass for the production of renewable energy in Finland. It is possible ecologically and economically to use about 5 million m{sup 3} of logging residue yearly for energy purposes. Currently both large lorry based chippers and smaller forwarder based chippers are used for chipping logging residue. However even the latest versions of these chippers are not well equipped for chipping logging residue. The ball like shape of residue piles causes blockades, if too large amounts of residue are fed into the chipper. Keeping the material flow even is difficult. In this project a prototype of a feeder device will be designed and manufactured to exactly find out the problems, that occur when feeding logging residue to a chipper. The designed prototype is based on a tubular chassis, which supports a conveyor made of steel plates. Prototype also has a 2,5 m wide feeding table and a feeder roll, which is located above the conveyor just before the chipper opening. Both the conveyor and the feeder roll are powered by hydraulic motors. The maximum feeding force is 20 kN. For research purposes both hydraulic pressure and flow can be adjusted individually for both motors. During 1996 activities included designing and building the prototype feeder device. In 1997 the prototype will be tested to find out possible problems, which need to be cured. After problems are solved and other improvements are made, the feeder device will be installed to an existing chipper and then tested again to determine the productivity of the new feeder device compared to the old unit. (orig.)

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.

Accuracy of S2 Alar-Iliac Screw Placement Under Robotic Guidance.

Science.gov (United States)

Laratta, Joseph L; Shillingford, Jamal N; Lombardi, Joseph M; Alrabaa, Rami G; Benkli, Barlas; Fischer, Charla; Lenke, Lawrence G; Lehman, Ronald A

Case series. To determine the safety and feasibility of S2 alar-iliac (S2AI) screw placement under robotic guidance. Similar to standard iliac fixation, S2AI screws aid in achieving fixation across the sacropelvic junction and decreasing S1 screw strain. Fortunately, the S2AI technique minimizes prominent instrumentation and the need for offset connectors to the fusion construct. Herein, we present an analysis of the largest series of robotic-guided S2AI screws in the literature without any significant author conflicts of interest with the robotics industry. Twenty-three consecutive patients who underwent spinopelvic fixation with 46 S2AI screws under robotic guidance were analyzed from 2015 to 2016. Screws were placed by two senior spine surgeons, along with various fellow or resident surgical assistants, using a proprietary robotic guidance system (Renaissance; Mazor Robotics Ltd., Caesara, Israel). Screw position and accuracy was assessed on intraoperative CT O-arm scans and analyzed using three-dimensional interactive viewing and manipulation of the images. The average caudal angle in the sagittal plane was 31.0° ± 10.0°. The average horizontal angle in the axial plane using the posterior superior iliac spine as a reference was 42.8° ± 6.6°. The average S1 screw to S2AI screw angle was 11.3° ± 9.9°. Two violations of the iliac cortex were noted, with an average breach distance of 7.9 ± 4.8 mm. One breach was posterior (2.2%) and one was anterior (2.2%). The overall robotic S2AI screw accuracy rate was 95.7%. There were no intraoperative neurologic, vascular, or visceral complications related to the placement of the S2AI screws. Spinopelvic fixation achieved using a bone-mounted miniature robotic-guided S2AI screw insertion technique is safe and reliable. Despite two breaches, no complications related to the placement of the S2AI screws occurred in this series. Level IV, therapeutic. Copyright © 2017 Scoliosis Research Society. Published by Elsevier

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.

Biomechanical properties of a novel biodegradable magnesium-based interference screw

Directory of Open Access Journals (Sweden)

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.

Optimisation of Trap Design for Vibratory Bowl Feeders

DEFF Research Database (Denmark)

Mathiesen, Simon; Sørensen, Lars Carøe; Kraft, Dirk

2018-01-01

Vibratory bowl feeders (VBFs) are a widely used option for industrial part feeding, but their design is still largely manual. A subtask of VBF design is determining an optimal parameter set for the passive devices, called traps, which the VBF uses to ensure correct part orientation. This paper...

Convex relaxation of Optimal Power Flow in Distribution Feeders with embedded solar power

DEFF Research Database (Denmark)

Hermann, Alexander Niels August; Wu, Qiuwei; Huang, Shaojun

2016-01-01

There is an increasing interest in using Distributed Energy Resources (DER) directly coupled to end user distribution feeders. This poses an array of challenges because most of today’s distribution feeders are designed for unidirectional power flow. Therefore when installing DERs such as solar...... panels with uncontrolled inverters, the upper limit of installable capacity is quickly reached in many of today’s distribution feeders. This problem can often be mitigated by optimally controlling the voltage angles of inverters. However, the optimal power flow problem in its standard form is a large...... scale non-convex optimization problem, and thus can’t be solved precisely and also is computationally heavy and intractable for large systems. This paper examines the use of a convex relaxation using Semi-definite programming to optimally control solar power inverters in a distribution grid in order...

Coal pricing in China: Issues and reform strategy. World Bank discussion paper

International Nuclear Information System (INIS)

Albouy, Y.

1991-01-01

The study assesses the magnitude of coal price distortions left in place by the dual track pricing approach to price reform implemented by China in the 1980s; it examines the economic and financial costs of these distortions and identifies the potential winners and losers of pricing improvements. Finally the report outlines a strategy for gradual price adjustments and liberalization in the coal sector. (Copyright (c) 1991 The International Bank for Reconstruction and Development/The World Bank.)

Pose and Motion Estimation Using Dual Quaternion-Based Extended Kalman Filtering

Energy Technology Data Exchange (ETDEWEB)

Goddard, J.S.; Abidi, M.A.

1998-06-01

A solution to the remote three-dimensional (3-D) measurement problem is presented for a dynamic system given a sequence of two-dimensional (2-D) intensity images of a moving object. The 3-D transformation is modeled as a nonlinear stochastic system with the state estimate providing the six-degree-of-freedom motion and position values as well as structure. The stochastic model uses the iterated extended Kalman filter (IEKF) as a nonlinear estimator and a screw representation of the 3-D transformation based on dual quaternions. Dual quaternions, whose elements are dual numbers, provide a means to represent both rotation and translation in a unified notation. Linear object features, represented as dual vectors, are transformed using the dual quaternion transformation and are then projected to linear features in the image plane. The method has been implemented and tested with both simulated and actual experimental data. Simulation results are provided, along with comparisons to a point-based IEKF method using rotation and translation, to show the relative advantages of this method. Experimental results from testing using a camera mounted on the end effector of a robot arm are also given.

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

Science.gov (United States)

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

2015-01-01

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

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...

Effect of primary air content on formation of nitrogen oxides during combustion of Ehkibastuz coal

Energy Technology Data Exchange (ETDEWEB)

Kotler, V.R.; Imankulov, Eh.R.

1986-01-01

Investigations are discussed carried out in a pilot plant at the Kaz. Power Engineering Scientific Research Institute into the effect of the amount of primary air in coal-dust flame on the final concentration of nitrogen oxides in flue gases. The tests were carried out in a 7500 mm high, 1600 mm dia vertical cylindrical combustion chamber having type P-57 burner, and air dispersed fuel plus additional air supplies located at the top. Amounts of coal dust fed by a drum feeder along the air pipe varied from 100-600 kg/h. The required air was supplied by 5000 m/sup 3//h Type TK-700/5 blowers at 0.04 MPa. Ehkibastuz coal samples contained: 1.3% moisture; 48.1% ash; 38.02% carbon; 2.56% hydrogen; 0.73% sulfur; 0.60% nitrogen; heat of combustion was 14.3 MJ/kg. Results obtained indicate that variations in the amount of primary air in swirl flow burners affect formation of fuel nitrogen; there is an optimum volume at which minimum quantities of nitrogen oxides are formed. Either an increase or decrease in the primary air results in a rise in nitrogen oxide concentration. 3 references.

Real-Time Distribution Feeder Performance Monitoring, Advisory Control, and Health Management System

Energy Technology Data Exchange (ETDEWEB)

Stoupis, James; Mousavi, Mirrasoul

2014-09-30

New data collection system equipment was installed in Xcel Energy substations and data was collected from 6 substations and 20 feeders. During Phase I, ABB collected and analyzed 793 real-time events to date from 6 Xcel Energy substations and continues today. The development and integration of several applications was completed during the course of this project, including a model-based faulted segment identification algorithm, with very positive results validated with field-gathered data discussed and included in this report. For mostly underground feeders, the success rate is 90% and the overreach rate is 90%. For mostly overhead feeders, the success rate is 74% and the overreach rate is 50%. The developed method is producing very accurate results for mostly underground feeders. For mostly overhead feeders, due to the bad OMS data quality and varying fault resistance when arcing, the developed method is producing good results but with much room for improvement. One area where the algorithm can be improved is the accuracy for sub-cycle fault events. In these cases, the accuracy of the conventional signal processing methods suffers due to most of these methods being based on a one-cycle processing window. By improving the signal processing accuracy, the accuracy of the faulted segment identification algorithm will also improve significantly. ABB intends to devote research in this area in the near future to help solve this problem. Other new applications developed during the course of the project include volt/VAR monitoring, unbalanced capacitor switching detection, unbalanced feeder loading detection, and feeder overloading detection. An important aspect of the demonstration phase of the project is to show the ability to provide adequate “heads-up” time ahead of customer calls or AMI reports so that the operators are provided with the much needed time to collect information needed to address an outage. The advance notification feature of the demonstration system

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

Science.gov (United States)

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

2013-01-01

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

A feeder protection method against the phase-phase fault using symmetrical components

DEFF Research Database (Denmark)

Ciontea, Catalin-Iosif; Bak, Claus Leth; Blaabjerg, Frede

2017-01-01

generation and relatively reduced short-circuit currents, thus resembling the electric network on a ship. The simulation results demonstrate that the proposed method of protection provides an improved performance compared to the conventional OverCurrent relays in a radial feeder with variable short......The method of symmetrical components simplifies analysis of an electric circuit during the fault and represents an important tool for the protection engineers. In this paper, the symmetrical components of the fault current are used in a new feeder protection method for the maritime applications...

Tumorigenic risk of human induced pluripotent stem cell explants cultured on mouse SNL76/7 feeder cells

Energy Technology Data Exchange (ETDEWEB)

Kamada, Mizuna; Mitsui, Youji, E-mail: y-mitsui8310@hb.tp1.jp; Kumazaki, Tsutomu; Kawahara, Yuta; Matsuo, Taira; Takahashi, Tomoko, E-mail: t-takahashi@kph.bunri-u.ac.jp

2014-10-24

Highlights: • hiPS cell explants formed malignant tumors when SNL76/7 feeder cells were used. • Multi type tumors developed by interaction of SNL76/7 feeder cells with hiPS cells. • Tumorigenic risk occurs by co-culture of hiPS cells with SNL76/7 feeder cells. - Abstract: The potential for tumor formation from transplanted human induced pluripotent stem cell (hiPSC) derivatives represents a high risk in their application to regenerative medicine. We examined the genetic origin and characteristics of tumors, that were formed when 13 hiPSC lines, established by ourselves, and 201B7 hiPSC from Kyoto University were transplanted into severe combined immune-deficient (SCID) mice. Though teratomas formed in 58% of mice, five angiosarcomas, one malignant solitary fibrous tumor and one undifferentiated pleomorphic sarcoma formed in the remaining mice. Three malignant cell lines were established from the tumors, which were derived from mitomycin C (MMC)-treated SNL76/7 (MMC-SNL) feeder cells, as tumor development from fusion cells between MMC-SNL and hiPSCs was negative by genetic analysis. While parent SNL76/7 cells produced malignant tumors, neither MMC-SNL nor MMC-treated mouse embryo fibroblast (MEF) produced malignant tumors. When MMC-SNL feeder cells were co-cultured with hiPSCs, growing cell lines were generated, that expressed genes similar to the parent SNL76/7 cells. Thus, hiPSCs grown on MMC-SNL feeder cells have a high risk of generating feeder-derived malignant tumors. The possible mechanism(s) of growth restoration and the formation of multiple tumor types are discussed with respect of the interactions between MMC-SNL and hiPSC.

Process and apparatus for optimizing screwing position for closure stud

International Nuclear Information System (INIS)

Bourdonne, J.C.; Briand, A.

1987-01-01

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

Grid deformation strategies for CFD analysis of screw compressors

OpenAIRE

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

2013-01-01

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

Locking screw apparatus and method for underwater remote replacement

International Nuclear Information System (INIS)

Balog, L.J.

1987-01-01

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

Tests for the dynamic behavior of insulation valve screws

International Nuclear Information System (INIS)

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

1994-01-01

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

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

Science.gov (United States)

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

2017-05-01

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

Coal background paper. Coal demand

International Nuclear Information System (INIS)

1997-01-01

Statistical data are presented on coal demands in IEA and OECD member countries and in other countries. Coal coaking and coaking coal consumption data are tabulated, and IEA secretariat's coal demand projections are summarized. Coal supply and production data by countries are given. Finally, coal trade data are presented, broken down for hard coal, steam coal, coking coal (imports and export). (R.P.)

High effective inverse dynamics modelling for dual-arm robot

Science.gov (United States)

Shen, Haoyu; Liu, Yanli; Wu, Hongtao

2018-05-01

To deal with the problem of inverse dynamics modelling for dual arm robot, a recursive inverse dynamics modelling method based on decoupled natural orthogonal complement is presented. In this model, the concepts and methods of Decoupled Natural Orthogonal Complement matrices are used to eliminate the constraint forces in the Newton-Euler kinematic equations, and the screws is used to express the kinematic and dynamics variables. On this basis, the paper has developed a special simulation program with symbol software of Mathematica and conducted a simulation research on the a dual-arm robot. Simulation results show that the proposed method based on decoupled natural orthogonal complement can save an enormous amount of CPU time that was spent in computing compared with the recursive Newton-Euler kinematic equations and the results is correct and reasonable, which can verify the reliability and efficiency of the method.

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

International Nuclear Information System (INIS)

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

1994-01-01

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

Tumor Volume Decrease via Feeder Occlusion for Treating a Large, Firm Trigone Meningioma.

Science.gov (United States)

Nakashima, Takuma; Hatano, Norikazu; Kanamori, Fumiaki; Muraoka, Shinsuke; Kawabata, Teppei; Takasu, Syuntaro; Watanabe, Tadashi; Kojima, Takao; Nagatani, Tetsuya; Seki, Yukio

2018-01-01

Trigone meningiomas are considered a surgical challenge, as they tend to be considerably large and hypervascularized at the time of presentation. We experienced a case of a large and very hard trigone meningioma that was effectively treated using initial microsurgical feeder occlusion followed by surgery in stages. A 19-year-old woman who presented with loss of consciousness was referred to our hospital for surgical treatment of a brain tumor. Radiological findings were compatible with a left ventricular trigone meningioma extending laterally in proximity to the Sylvian fissure. At initial surgery using the transsylvian approach, main feeders originating from the anterior and lateral posterior choroidal arteries were occluded at the inferior horn; however, only a small section of the tumor could initially be removed because of its firmness. Over time, feeder occlusion resulted in tumor necrosis and a 20% decrease in its diameter; the mass effect was alleviated within 1 year. The residual meningioma was then totally excised in staged surgical procedures after resection became more feasible owing to ischemia-induced partial softening of the tumor. When a trigone meningioma is large and very hard, initial microsurgical feeder occlusion in the inferior horn can be a safe and effective option, and can lead to necrosis, volume decrease, and partial softening of the residual tumor to allow for its staged surgical excision.

Feeder Cell Type Affects the Growth of In Vitro Cultured Bovine Trophoblast Cells

Directory of Open Access Journals (Sweden)

Islam M. Saadeldin

2017-01-01

Full Text Available Trophectoderm cells are the foremost embryonic cells to differentiate with prospective stem-cell properties. In the current study, we aimed at improving the current approach for trophoblast culture by using granulosa cells as feeders. Porcine granulosa cells (PGCs compared to the conventional mouse embryonic fibroblasts (MEFs were used to grow trophectoderm cells from hatched bovine blastocysts. Isolated trophectoderm cells were monitored and displayed characteristic epithelial/cuboidal morphology. The isolated trophectoderm cells expressed mRNA of homeobox protein (CDX2, cytokeratin-8 (KRT8, and interferon tau (IFNT. The expression level was higher on PGCs compared to MEFs throughout the study. In addition, primary trophectoderm cell colonies grew faster on PGCs, with a doubling time of approximately 48 hrs, compared to MEFs. PGCs feeders produced a fair amount of 17β-estradiol and progesterone. We speculated that the supplementation of sex steroids and still-unknown factors during the trophoblasts coculture on PGCs have helped to have better trophectoderm cell’s growth than on MEFs. This is the first time to use PGCs as feeders to culture trophectoderm cells and it proved superior to MEFs. We propose PGCs as alternative feeders for long-term culture of bovine trophectoderm cells. This model will potentially benefit studies on the early trophoblast and embryonic development in bovines.

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

International Nuclear Information System (INIS)

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

2006-01-01

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

Economic Contribution of Regional Feeder Ports to The Local Economy In Indonesia

Directory of Open Access Journals (Sweden)

Ibnu Syabri

2017-07-01

Full Text Available Indonesia regional feeder ports’ main function is to serve marine transport activities between regency/city in a province in limited quantities. The intention of the government to make marine transportation as the backbone of national logistic transportation system puts these ports to an important position, as suppliers for the main and/or collector ports and as goods distribution centers for the region from the bigger ports. Not only as a provider of accessibility between regions, regional feeder ports should be seen as an investation to boost regional economy. This study aims to explain the influences of regional feeder ports on regency/city economy, based on the port types: (1 cargo ports, and (2 cargo & passengers ports. Results showed that both types of ports have positive influences on the regency/city economy, although it is not related to region’s economic base sector. Cargo ports which are mainly located on west area of Indonesia, supports the region’s economy more than cargo & passenger ports which are mainly located on the east.

The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?

Science.gov (United States)

Paik, Haines; Kang, Daniel G; Lehman, Ronald A; Gaume, Rachel E; Ambati, Divya V; Dmitriev, Anton E

2013-11-01

Rod contouring is frequently required to allow for appropriate alignment of pedicle screw-rod constructs. When residual mismatch is still present, a rod persuasion device is often used to achieve further rod reduction. Despite its popularity and widespread use, the biomechanical consequences of this technique have not been evaluated. To evaluate the biomechanical fixation strength of pedicle screws after attempted reduction of a rod-pedicle screw mismatch using a rod persuasion device. Fifteen 3-level, human cadaveric thoracic specimens were prepared and scanned for bone mineral density. Osteoporotic (n=6) and normal (n=9) specimens were instrumented with 5.0-mm-diameter pedicle screws; for each pair of comparison level tested, the bilateral screws were equal in length, and the screw length was determined by the thoracic level and size of the vertebra (35 to 45 mm). Titanium 5.5-mm rods were contoured and secured to the pedicle screws at the proximal and distal levels. For the middle segment, the rod on the right side was intentionally contoured to create a 5-mm residual gap between the inner bushing of the pedicle screw and the rod. A rod persuasion device was then used to engage the setscrew. The left side served as a control with perfect screw/rod alignment. After 30 minutes, constructs were disassembled and vertebrae individually potted. The implants were pulled in-line with the screw axis with peak pullout strength (POS) measured in Newton (N). For the proximal and distal segments, pedicle screws on the right side were taken out and reinserted through the same trajectory to simulate screw depth adjustment as an alternative to rod reduction. Pedicle screws reduced to the rod generated a 48% lower mean POS (495±379 N) relative to the controls (954±237 N) (p.05). In circumstances where a rod is not fully seated within the pedicle screw, the use of a rod persuasion device decreases the overall POS and work energy to failure of the screw or results in outright

Establishment of feeder-free culture system for human induced pluripotent stem cell on DAS nanocrystalline graphene

Science.gov (United States)

Lee, Hyunah; Nam, Donggyu; Choi, Jae-Kyung; Araúzo-Bravo, Marcos J.; Kwon, Soon-Yong; Zaehres, Holm; Lee, Taehee; Park, Chan Young; Kang, Hyun-Wook; Schöler, Hans R.; Kim, Jeong Beom

2016-02-01

The maintenance of undifferentiated human pluripotent stem cells (hPSC) under xeno-free condition requires the use of human feeder cells or extracellular matrix (ECM) coating. However, human-derived sources may cause human pathogen contamination by viral or non-viral agents to the patients. Here we demonstrate feeder-free and xeno-free culture system for hPSC expansion using diffusion assisted synthesis-grown nanocrystalline graphene (DAS-NG), a synthetic non-biological nanomaterial which completely rule out the concern of human pathogen contamination. DAS-NG exhibited advanced biocompatibilities including surface nanoroughness, oxygen containing functional groups and hydrophilicity. hPSC cultured on DAS-NG could maintain pluripotency in vitro and in vivo, and especially cell adhesion-related gene expression profile was comparable to those of cultured on feeders, while hPSC cultured without DAS-NG differentiated spontaneously with high expression of somatic cell-enriched adhesion genes. This feeder-free and xeno-free culture method using DAS-NG will facilitate the generation of clinical-grade hPSC.

Intermaxillary Fixation Screw Morbidity in Treatment of Mandibular Fractures

DEFF Research Database (Denmark)

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

2016-01-01

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

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.

The effect of space allowance and cage size on laying hens housed in furnished cages, Part II: Behavior at the feeder.

Science.gov (United States)

Widowski, T M; Caston, L J; Casey-Trott, T M; Hunniford, M E

2017-09-01

Standards for feeder (a.k.a. feed trough) space allowance (SA) are based primarily on studies in conventional cages where laying hens tend to eat simultaneously, limiting feeder space. Large furnished cages (FC) offer more total space and opportunities to perform a greater variety of behaviors, which may affect feeding behavior and feeder space requirements. Our objective was to determine the effects of floor/feeder SA on behavior at the feeder. LSL-Lite hens were housed in FC equipped with a nest, perches, and a scratch mat. Hens with SA of either 520 cm2 (Low; 8.9 cm feeder space/hen) or 748 cm2 (High; 12.8 cm feeder space/hen) per bird resulted in groups of 40 vs. 28 birds in small FC (SFC) and 80 vs. 55 in large FC (LFC). Chain feeders ran at 0500, 0800, 1100, 1400, and 1700 with lights on at 0500 and off at 1900 hours. Digital recordings of FC were scanned at chain feeder onset and every 15 min for one h after (5 scans × 5 feeding times × 2 d) to count the number of birds with their head in the feeder. All occurrences of aggressive pecks and displacements during 2 continuous 30-minute observations at 0800 h and 1700 h also were counted. Mixed model repeated analyses tested the effects of SA, cage size, and time on the percent of hens feeding, and the frequency of aggressive pecks and displacements. Surprisingly, the percent of birds feeding simultaneously was similar regardless of cage size (LFC: 23.0 ± 0.9%; SFC: 24.0 ± 1.0%; P = 0.44) or SA (Low: 23.8 ± 0.9%; High: 23.3 ± 1.0%; P = 0.62). More birds were observed feeding at 1700 h (35.3 ± 0.1%) than any at other time (P Feeder use differed by cage area (nest, middle, or scratch) over the d (P feeder competition at the Low SA in this study. © The Author 2017. Published by Oxford University Press on behalf of Poultry Science Association.

Identification of molecules derived from human fibroblast feeder cells that support the proliferation of human embryonic stem cells

DEFF Research Database (Denmark)

Anisimov, Sergey V.; Christophersen, Nicolaj S.; Correia, Ana S.

2011-01-01

The majority of human embryonic stem cell lines depend on a feeder cell layer for continuous growth in vitro, so that they can remain in an undifferentiated state. Limited knowledge is available concerning the molecular mechanisms that underlie the capacity of feeder cells to support both...... the proliferation and pluripotency of these cells. Importantly, feeder cells generally lose their capacity to support human embryonic stem cell proliferation in vitro following long-term culture. In this study, we performed large-scale gene expression profiles of human foreskin fibroblasts during early...... foreskin fibroblasts to serve as feeder cells for human embryonic stem cell cultures. Among these, the C-KIT, leptin and pigment epithelium-derived factor (PEDF) genes were the most interesting candidates....

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

OpenAIRE

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

2006-01-01

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

Faecal nitrogen of browser and mixed feeder game species during ...

African Journals Online (AJOL)

Faecal nitrogen of browser and mixed feeder game species during different seasons. ... A practical measure of assessing periods of potential nutritional stress of game species is needed in the management of ... AJOL African Journals Online.

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

International Nuclear Information System (INIS)

Scharpenberg, R.

1986-01-01

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

A probabilistic degradation model for the estimation of the remaining life distribution of feeders

International Nuclear Information System (INIS)

Yuan, X.-X.; Pandey, M.D.; Bickel, G.A.

2006-01-01

Wall thinning due to flow accelerated corrosion (FAC) is a pervasive form of degradation in the outlet feeder pipes of the primary heat transport system of CANDU reactors. The prediction of the end-of-life of a feeder from wall thickness measurement data is confounded by the sampling and temporal uncertainties associated with the FAC degradation phenomenon. Traditional regression-based statistical methods deal with only the sampling uncertainties, leaving the temporal uncertainties unresolved. This paper presents an advanced probabilistic model, which is able to integrate the temporal uncertainties into the prediction of lifetime. In particular, a random gamma process model is proposed to model the FAC process and it is calibrated with a set of wall thickness measurements using the method of maximum likelihood. This information can be used to establish an optimum strategy for inspection and replacement of feeders. (author)

Effect of diameter of the drill hole on torque of screw insertion and pushout strength for headless tapered compression screws in simulated fractures of the lateral condyle of the equine third metacarpal bone.

Science.gov (United States)

Carpenter, Ryan S; Galuppo, Larry D; Stover, Susan M

2006-05-01

To compare variables for screw insertion, pushout strength, and failure modes for a headless tapered compression screw inserted in standard and oversize holes in a simulated lateral condylar fracture model. 6 pairs of third metacarpal bones from horse cadavers. Simulated lateral condylar fractures were created, reduced, and stabilized with a headless tapered compression screw by use of a standard or oversize hole. Torque, work, and time for drilling, tapping, and screw insertion were measured during site preparation and screw implantation. Axial load and displacement were measured during screw pushout. Effects of drill hole size on variables for screw insertion and screw pushout were assessed by use of Wilcoxon tests. Drill time was 59% greater for oversize holes than for standard holes. Variables for tapping (mean maximum torque, total work, positive work, and time) were 42%, 70%, 73%, and 58% less, respectively, for oversize holes, compared with standard holes. Variables for screw pushout testing (mean yield load, failure load, failure displacement, and failure energy) were 40%, 40%, 47%, and 71% less, respectively, for oversize holes, compared with standard holes. Screws could not be completely inserted in 1 standard and 2 oversize holes. Enlarging the diameter of the drill hole facilitated tapping but decreased overall holding strength of screws. Therefore, holes with a standard diameter are recommended for implantation of variable pitch screws whenever possible. During implantation, care should be taken to ensure that screw threads follow tapped bone threads.

Dual-energy X-ray absorptiometry and force-plate analysis of gait in dogs with healed femora after leg-lengthening plate fixation

International Nuclear Information System (INIS)

Muir, P.; Markel, M.D.; Bogdanske, J.J.; Johnson, K.A.

1995-01-01

Dual-energy x-ray absorptiometry was used to measure bone mineral density of four regions in healed femora of nine dogs after fracture fixation with a leg-lengthening plate. Six to 85 months (mean, 46 months) after surgery, the bone mineral density of healed femora was not significantly different from the contralateral uninjured femora (P > .05; power = 0.8 at delta = 15%). Radiolucencies around the proximal screws, apparently associated with screw loosening, were seen on radiographic views of the healed femora of three dogs. In one of these dogs, one screw in the proximal metaphysis had broken. Force-plate analysis of gait was also performed on dogs at the time of bone mineral density measurement. Peak vertical force was decreased in the pelvic limb with the healed fracture compared with the contralateral unoperated limb (P < 0.05). Clinically apparent lameness in three dogs did not appear to be associated with altered bone mineral density and may have been caused by hip osteoarthritis, a nondisplaced hairline diaphyseal fracture, and screw loosening in conjunction with extensive post-traumatic soft tissue injury

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.

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

Science.gov (United States)

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

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

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

OpenAIRE

Grob, D.; Humke, T.

1998-01-01

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

Inspection and replacement of baffle assembly screws inside American reactor vessels

International Nuclear Information System (INIS)

Neal, K.; Chaumont, J.C.

1999-01-01

The baffle assembly inside the vessel of a 900 MWe reactor designed by Framatome, is made up of 44 plates fixed on 8 horizontal supports by a system of about 1000 screws. These plates undergo high neutron flux and the problem of screw cracking appeared at the end of the eighties in the first-generation reactors. The first operation on a large scale concerning the screws of a Westinghouse type reactor, was performed on the Tihange-1 power plant where Framatome controlled 960 screws and replaced 91. In 1997 as a consequence of the Belgian and French feedback experience, American plant operators launched a vast program of preventive actions: material analysis, inspection of baffle plate screws and replacement of defective screws. This program was held in cooperation with EPRI (electric power research institute) and under the control of NRC (nuclear regulatory commission). Framatome Technologies Inc (FTI) was in charge of the in-situ inspection and replacement of the screws. FTI designed special tools and equipment adapted to the 2-loop American reactors but the basis ideas were those applied on the Tihange reactor. The successful experience of FTI has allowed the firm to be commissioned for 6 2-loops American reactors. (A.C.)

Feederism: an exaggeration of a normative mate selection preference?

Science.gov (United States)

Terry, Lesley L; Suschinsky, Kelly D; Lalumière, Martin L; Vasey, Paul L

2012-02-01

Quinsey and Lalumière (1995) suggested that some, if not most, paraphilias are exaggerated manifestations of more normative and functional mate selection preferences. The present study tested whether Feederism, a fat fetish focused on erotic eating, feeding, and gaining weight, is an exaggeration of a sexual arousal pattern commonly seen in the general population. Thirty participants (15 men and 15 women) recruited from the general population were assessed using penile plethysmography and vaginal photoplethysmography, respectively. None of the participants were self-identified Feeders or Feedees. Participants were shown sexual, neutral, and feeding still images while listening to audio recordings of sexual, neutral, and feeding stories. Participants did not genitally respond to feeding stimuli. However, both men and women subjectively rated feeding stimuli as more sexually arousing than neutral stimuli. We discuss the discordance between physiological and self-reported sexual arousal in the context of sex differences in sexual concordance and implications for future research.

Experience of superconducting current feeders system of SST-1

International Nuclear Information System (INIS)

Gupta, N.C.; Garg, A.; Sonara, D.

2014-01-01

The superconducting current feeder system for SST-1 which has been installed and commissioned recently along with SST-1, felicitates to energize the SST-1. The CFS consists of ten pairs of 10,000 Ampere (A) rating helium vapor cooled conventional current leads, interconnecting Cu-SC joints, three numbers of cryo-compatible SC feeders ducts, current leads assembly chamber, hydraulic network and three numbers of joint boxes operated at different current rating to charge Toroidal Field and Poloidal Field coils separately. During the last three campaigns, it was possible to achieve a controlled cool down up to 4 K and showed its rated operational performance. Actively cooled liquid nitrogen shield showed temperature profile in the temperature range of 80-85K and the whole system was evacuated up to 6x10 -6 mbar. The measured LHe consumption rates from TF VCCL were 0.3 g/s and 0.35 g/s at zero current and 1 kA respectively. (author)

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

Directory of Open Access Journals (Sweden)

Eduardo Aloisio Fleck NEUMANN

2014-08-01

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

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

Science.gov (United States)

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

2014-01-01

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

Strength evaluation of top nozzle holddown spring screw for nuclear fuel assembly

International Nuclear Information System (INIS)

Koh, S. K.; Won, S. Y.; Ryu, C. H.; Kim, Y. J.; Lee, K. S.; Jeon, K. L.

2002-01-01

Holddown springs are required to maintain the nuclear fuel assembly in contact with lower core plate and permit thermal and irradiation-induced length changes. Therefore, the holddown spring screw must be designed such that it is capable of sustaining the loads imposed by the initial tensile preload and operational loads. Prior to assessing the structural integrity of the spring screw in the corrosive and irradiating environment throughout the design lifetime of the fuel assembly, the strength evaluation of screw was made in this paper using the mechanics of materials and finite element methods. Calculations based on the mechanics of materials, showed that the preloaded screw with an operating holddown force had a quite large margin of safety in strength. However, the elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Preloading on the screw applied for tightening had beneficial effects on the screw strength by reducing the stress level at the critical regions, compared to the screw without preload. Calculated spring deflection using the finite element analysis was in close agreement with the experimentally measured deflection

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

OpenAIRE

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

2018-01-01

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

Screw expander for light duty diesel engines

Science.gov (United States)

1983-01-01

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

Control of influence of a thread on a bending of screws

International Nuclear Information System (INIS)

Proskuriakov, N E; Lopa, I V; Trapeznikov, E V

2017-01-01

The influence of the threads and the bending of screw on their moments of inertia of the cross section considered. This problem is actual since existing methods exclude from calculations the influence of supporting the thread, using as the basic geometrical parameter such as the internal diameter of the thread (diameter of cavities). Fundamental difference of a bend of the screw from a bend of a smooth rod consists that moment of inertia of the screw is a variable. It is shown that the change in cross-section moment of inertia along the length of the screw are essential and have periodic character. Analytical interrelation of the bending of the screw and the decreasing of moment of inertia of its cross section is established and equation describing this phenomenon is suggested. The greatest decrease of the moment of inertia occurs in the middle of the screw length, and the lowest - at its ends. Function and approximate coefficients for the main types of thread are proposed, which take into account this change. (paper)

Bioabsorbable metal screws in traumatology: A promising innovation

Directory of Open Access Journals (Sweden)

Roland Biber

2017-04-01

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

Test Firing of chunk wood - Is it possible to automate the fuel supply?; Proveldning av knubbved - Aer det moejligt att automatisera braenslematningen?

Energy Technology Data Exchange (ETDEWEB)

Persson, Tomas; Danielsson, Bengt-Olof

2013-05-15

Chunk wood is a wood fuel with a fuel particle length typically between 50 and 150 mm. The ad-vantage of chunk wood compared to wood chips is that the fuel dry as fast as fuel wood, but can be produced and handled as wood chip. Technologies for efficient producing, drying and distribution of Chunk wood have been developed since the 1970:s and machines for manufacturing the fuel is available on the market, but still there is no small-scale heating equipment in operation to burn the fuel automatically. The aim of the study was to investigate how the feeding and firing of chunk wood works in a standard 200 kW biomass boiler for various types of biofuels. The main focus was on studying how the fuel feeding system works using chunk wood and if the combustion and emissions are satisfactory. The boiler have a main fuel feeding auger screw connected to the bottom of the fuel storage, followed by a cell feeder and another auger screw that is feeding the fuel into the combustion chamber. The power consumption for the fuel feeding auger screws and the CO-emissions were measured during the firing period. In order to obtain reference values for the stresses in the fuel feeding system and the CO-emissions, regular wood chips were initially fired followed by the chunk wood firing. During the chunk wood firing period several interruptions in the fuel feeding occurred, as the trigger mechanism for the motor protection stopped the fuel supply. Most of the interruptions, however, could be resolved through manual reversing of the fuel feeding auger screw. Only at two occasions the entrance to the auger screw were manually cleared from large fuel pieces. The cell feeder and the auger screw feeding the fuel into the combustion chamber were stopped twice, and to continue operating the boiler it was enough to restart the feeding system. However, as they are both operated by the same motor we do not know whether the two shutdowns that occurred were caused by feeding problems in the auger

The effect of space allowance and cage size on laying hens housed in furnished cages, Part II: Behavior at the feeder

Science.gov (United States)

Widowski, T. M; Caston, L. J; Casey-Trott, T. M; Hunniford, M. E

2017-01-01

Abstract Standards for feeder (a.k.a. feed trough) space allowance (SA) are based primarily on studies in conventional cages where laying hens tend to eat simultaneously, limiting feeder space. Large furnished cages (FC) offer more total space and opportunities to perform a greater variety of behaviors, which may affect feeding behavior and feeder space requirements. Our objective was to determine the effects of floor/feeder SA on behavior at the feeder. LSL-Lite hens were housed in FC equipped with a nest, perches, and a scratch mat. Hens with SA of either 520 cm2 (Low; 8.9 cm feeder space/hen) or 748 cm2 (High; 12.8 cm feeder space/hen) per bird resulted in groups of 40 vs. 28 birds in small FC (SFC) and 80 vs. 55 in large FC (LFC). Chain feeders ran at 0500, 0800, 1100, 1400, and 1700 with lights on at 0500 and off at 1900 hours. Digital recordings of FC were scanned at chain feeder onset and every 15 min for one h after (5 scans × 5 feeding times × 2 d) to count the number of birds with their head in the feeder. All occurrences of aggressive pecks and displacements during 2 continuous 30-minute observations at 0800 h and 1700 h also were counted. Mixed model repeated analyses tested the effects of SA, cage size, and time on the percent of hens feeding, and the frequency of aggressive pecks and displacements. Surprisingly, the percent of birds feeding simultaneously was similar regardless of cage size (LFC: 23.0 ± 0.9%; SFC: 24.0 ± 1.0%; P = 0.44) or SA (Low: 23.8 ± 0.9%; High: 23.3 ± 1.0%; P = 0.62). More birds were observed feeding at 1700 h (35.3 ± 0.1%) than any at other time (P < 0.001). Feeder use differed by cage area (nest, middle, or scratch) over the d (P < 0.001). The frequency of aggressive pecks was low overall and not affected by SA or cage size. Frequency of displacements was also low but greater at Low SA (P = 0.001). There was little evidence of feeder competition at the Low SA in this study. PMID:29050409

History of Retractor Technologies for Percutaneous Pedicle Screw Fixation Systems.

Science.gov (United States)

Mobbs, Ralph J; Phan, Kevin

2016-02-01

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

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

Science.gov (United States)

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

2018-05-04

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

The impact of small benthic passive suspension feeders in shallow marine ecosystems: the hydroids as an example

NARCIS (Netherlands)

Gili, J.-M.; Alvà, V.; Coma, R.; Orejas, C.; Pagès, F.; Ribes, M.; Zabala, M.; Arntz, W.; Bouillon, J.; Boero, F.; Hughes, R.G.

1998-01-01

Benthic suspension feeders are abundant in littoral and shallow sub-littoral ecosystems, where they feed on the plankton and on organic matter suspended in the water column. Recent studies indicate that active suspension feeders with powerful water filtration mechanisms (e.g., bivalve molluscs) may

Feeders of Free-Roaming Cats: Personal Characteristics, Feeding Practices, and Data on Cat Health and Welfare in an Urban Setting of Israel.

Science.gov (United States)

Gunther, Idit; Raz, Tal; Even Zor, Yehonatan; Bachowski, Yuval; Klement, Eyal

2016-01-01

Cat feeders serve as an important source of available food for free-roaming cats (FRCs) and can play a central role in providing data on FRC distribution, welfare, and health. Data on cat feeder personalities as well as a better understanding of their feeding practices offer relevance for decision making concerning FRC population control strategies. The current study surveyed 222 FRC feeders who responded to a municipal trap-neuter-return (TNR) campaign in an Israeli central urban setting. The aim of the study was to describe their personal characteristics, feeding practices, and the FRC populations they feed. Feeders were divided into four groups according to the number of cats they claimed to feed per day (group 1: fed up to 5 cats, group 2: fed 6-10 cats, group 3: fed 11-20 cats, and group 4: fed ≥21 cats). Most feeders were women (81%), with a median age of 58 years (range 18-81). The feeders reported an overall feeding of 3337 cats in 342 different feeding locations. Feeders of group 4 comprised 15.31% (n = 34) of all feeders but fed 56% (n = 1869) of the FRC in 37.42% (n = 128) of the feeding locations. "Heavy" feeders (groups 3 and 4) reported that they traveled significantly longer distances in order to feed the cats. Commercial dry food consisted of 90% of the food they provided, with 66% of them feeding once a day, with less food per cat per day than the other feeder groups. Interestingly, "heavy" feeders were usually singles, had on average fewer siblings, a clear preference for owning cats as pets, and lived in lower income neighborhoods. According to the feeders' reports on the FRC populations they fed, 69.7% (2325/3337) cats were neutered and 11.8% (395/3337) were kittens. In addition, they reported that 1.6% (54/3337) of the cats were limping, 2% (67/3337) suffered from a systemic disease, 4% (135/3337) had skin lesions, and 3.9% (130/3337) were suffering from a chronic disability. Abundance of kittens and morbidity rate were

Feeders of free-roaming cats: personal characteristics, feeding practices and data on cat health and welfare in an urban setting of Israel

Directory of Open Access Journals (Sweden)

Idit eGunther

2016-03-01

Full Text Available Cat feeders serve as an important source of available food for free-roaming cats (FRC and can play a central role in providing data on FRC distribution, welfare, and health. Data on cat feeder personalities as well as a better understanding of their feeding practices offer relevance for decision making concerning FRC population control strategies. The current study surveyed 222 FRC feeders who responded to a municipal trap-neuter-return (TNR campaign in an Israeli central urban setting. The aim of the study was to describe their personal characteristics, feeding practices and the FRC populations they feed. Feeders were divided into four groups according to the number of cats they claimed to feed per day (group 1: fed up to five cats; group 2: fed six to 10 cats; group 3: fed 11-20 cats; group 4: fed ≥21 cats. Most feeders were women (81%, with a median age of 58 years (range 18-81. The feeders reported an overall feeding of 3,337 cats in 342 different feeding locations. Feeders of group 4 comprised of 15.31% (n=34 of all feeders, but fed 56% (n=1869 of the FRC in 37.42% (n=128 of the feeding locations. 'Heavy' feeders (groups 3 and 4 reported that they traveled significantly longer distances in order to feed the cats. Commercial dry food consisted of 90% of the food they provided, with 66% of them feeding once a day, with less food per cat per day than the other feeder groups. Interestingly, 'heavy' feeders were usually singles, had on average fewer siblings, a clear preference for owning cats as pets and lived in lower income neighborhoods. According to the feeders' reports on the FRC populations they fed, 69.7% (2325/3337 cats were neutered and 11.8% (395/3337 were kittens. In addition, they reported that 1.6% (54/3337 of the cats were limping, 2% (67/3337 suffered from a systemic disease, 4% (135/3337 had skin lesions, and 3.9% (130/3337 were suffering from a chronic disability. Abundance of kittens and morbidity rate were significantly and

Developmental Competence of Buffalo (Bubalus bubalis) Pluripotent Embryonic Stem Cells Over Different Homologous Feeder Layers and the Comparative Evaluation with Various Extracellular Matrices.

Science.gov (United States)

Sharma, Manjinder; Dubey, Pawan K; Kumar, Rajesh; Nath, Amar; Kumar, G Sai; Sharma, G Taru

2013-05-01

Use of somatic cells as a feeder layer to maintain the embryonic stem cells (ESCs) in undifferentiated state limits the stem cell research design, since experimental data may result from a combined ESCs and feeder cell response to various stimuli. Therefore, present study was designed to evaluate the developmental competence of the buffalo ESCs over different homogenous feeders and compare with various extracellular matrices using different concentrations of LIF. Inner cell masses (ICMs) of in vitro hatched blastocysts were cultured onto homologous feeders viz. fetal fibroblast, granulosa and oviductal cell feeder layers and synthetic matrices viz. fibronectin, collagen type I and matrigel in culture medium. Developmental efficiency was found higher for ESCs cultured on fetal fibroblast and granulosa layers (83.33%) followed by fibronectin (77.78%) at 30 ng LIF. Oviductal feeder was found to be the least efficient feeder showing only 11.11% undifferentiated primary ESC colonies at 30 ng LIF. However, neither feeder layer nor synthetic matrix could support the development of primary colonies at 10 ng LIF. Expression of SSEA- 4, TRA-1-60 and Oct-4 were found positive in ESC colonies from all the feeders and synthetic matrices with 20 ng and 30 ng LIF. Fetal fibroblast and granulosa cell while, amongst synthetic matrices, fibronectin were found to be equally efficient to support the growth and maintenance of ESCs pluripotency with 30 ng LIF. This well-defined culture conditions may provide an animal model for culturing human embryonic stem cells in the xeno-free or feeder-free conditions for future clinical applications.

Coal-oil coprocessing at HTI - development and improvement of the technology

Energy Technology Data Exchange (ETDEWEB)

Stalzer, R.H.; Lee, L.K.; Hu, J.; Comolli, A. [Hydrocarbon Technologies, Inc., Lawrenceville, NJ (United States)

1995-12-31

Co-Processing refers to the combined processing of coal and petroleum-derived heavy oil feedstocks. The coal feedstocks used are those typically utilized in direct coal liquefaction: bituminous, subbituminous, and lignites. Petroleum-derived oil, is typically a petroleum residuum, containing at least 70 W% material boiling above 525{degrees}C. The combined coal and oil feedstocks are processed simultaneously with the dual objective of liquefying the coal and upgrading the petroleum-derived residuum to lower boiling (<525{degrees}C) premium products. HTI`s investigation of the Co-Processing technology has included work performed in laboratory, bench and PDU scale operations. The concept of co-processing technology is quite simple and a natural outgrowth of the work done with direct coal liquefaction. A 36 month program to evaluate new process concepts in coal-oil coprocessing at the bench-scale was begun in September 1994 and runs until September 1997. Included in this continuous bench-scale program are provisions to examine new improvements in areas such as: interstage product separation, feedstock concentrations (coal/oil), improved supported/dispersed catalysts, optimization of reactor temperature sequencing, and in-line hydrotreating. This does not preclude other ideas from DOE contracts and other sources that can lead to improved product quality and economics. This research work has led to important findings which significantly increased liquid yields, improved product quality, and improved process economics.

Meta-analysis on the effects of the physical environment, animal traits, feeder and feed characteristics on the feeding behaviour and performance of growing-finishing pigs.

Science.gov (United States)

Averós, X; Brossard, L; Dourmad, J Y; de Greef, K H; Edwards, S A; Meunier-Salaün, M C

2012-08-01

A meta-analysis, using information from 45 experiments on growing-finishing pigs published in 39 manuscripts, was carried out to determine the simultaneous effects of the physical environment (space allowance, group size, flooring conditions, temperature, presence of enrichment), pig traits (initial body weight (BW) for each studied time interval, sex, genetics), feeder characteristics (water provision within the feeder, feeder design (individual/collective), feeder places/pig, presence of feeder protection) and feed characteristics (feed allowance (ad libitum/restricted), net energy content, crude protein (CP) content), as well as their potential interactions, on the feeding behaviour and performance of growing-finishing pigs. The detrimental effect of low temperature on performance was particularly evident for restricted-fed pigs (P < 0.05). At reduced feeder space allowance, a reduction in the percentage of time spent eating was predicted when increasing initial BW, whereas the opposite was predicted for larger feeder space allowances (P < 0.001). The reduction in visit duration to the feeder in higher BW groups became gradually more important with increasing feeder space allowance (P < 0.01), whereas the increase in the ingestion rate and average daily feed intake (ADFI) with increasing initial BW became smaller with increasing feeder space (P < 0.05). The model predicted a reduction in feed conversion ratio (FCR) with increasing group size (P < 0.05) and floor space allowance (P < 0.01) and on solid floors with or without bedding (P < 0.05). In comparison with other feeders, wet/dry feeders were associated with more frequent but shorter feeder visits (P < 0.05), higher ingestion rates (P < 0.001) and higher ADFI (P < 0.10). The use of protection within individual feeders increased the time spent feeding (P < 0.001), reduced the number of visits per day (P < 0.01), the ingestion rate (P < 0.001) and FCR (P < 0.01) in comparison with other feeder types. Sex

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

International Nuclear Information System (INIS)

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

2003-01-01

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

The Study of Vibration Processes in Oil Flooded Screw Compressors

Directory of Open Access Journals (Sweden)

I. V. Filippov

2014-01-01

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

Effect of artificial feeders on pollen loads of the hummingbirds of Cerro de La Muerte, Costa Rica

Directory of Open Access Journals (Sweden)

Gerardo Avalos

2012-03-01

Full Text Available Although sugar-water feeders are commonly used by enthusiasts to attract hummingbirds, little is known about how they affect hummingbird behavior and flower use. We studied the highland hummingbird assemblage of Cerro de La Muerte, Costa Rica, both at a site with permanent feeders (La Georgina Restaurant and further from it. We examined how feeder use and monopolization affected seasonal changes in pollen loads during four sampling periods, including dry and wet seasons, from 2003-2005. We expected that species monopolizing the feeders would carry little or no pollen whatsoever, and would have pollen loads characterized by low floral diversity, in contrast with species less dependent on feeders. We obtained pollen samples from 183 individuals of four hummingbird species captured around the feeders using mist nets, which were compared with a pollen reference collection of plants with a pollination syndrome by hummingbirds. The same methods were implemented at a site 3km away from the feeders. Feeder usage was quantified by counting the number of times hummingbirds drank from the feeders in periods of 4min separated by 1min. The effects of hummingbird species and season on pollen load categories were assessed using a nominal logistic regression. The alpha species at the site, the Fiery-throated Hummingbird (Panterpe insignis, dominated the feeders during the dry season. Meanwhile, in the wet season, feeder usage was more evenly distributed across species, with the exception of the Volcano Hummingbird, Selasphorus flammula, which occupies the last place in the dominance hierarchy. Pollen loads of hummingbirds captured near feeders were low in abundance (more than 50% of captured individuals had zero or low pollen loads, and low in species richness (96% of the hummingbirds with pollen from only one plant genus, Centropogon. Overall pollen loads increased during the dry season coinciding with peaks in flower availability, although the majority of

Analysis of Material Flow in Screw Extrusion of Aluminum

International Nuclear Information System (INIS)

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

2010-01-01

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

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

Directory of Open Access Journals (Sweden)

Kuan-Jen Chen

2016-08-01

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

The movement of screw dislocations in tungsten

International Nuclear Information System (INIS)

Tian Xiaogeng; Woo Chungho

2004-01-01

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

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.

Ball Nut Preload Diagnosis of the Hollow Ball Screw through Support Vector Machine

Directory of Open Access Journals (Sweden)

Yi-Cheng Huang

2018-01-01

Full Text Available This paper studies the diagnostic results of hollow ball screws with different ball nut preload through the support vector machine (SVM process. The method is testified by considering the use of ball screw pretension and different ball nut preload. SVM was used to discriminate the hollow ball screw preload status through the vibration signals and servo motor current signals. Maximum dynamic preloads of 2%, 4%, and 6% ball screws were predesigned, manufactured, and conducted experimentally. Signal patterns with different preload features are separatedby SVM. The irregularity development of the ball screw driving motion current and rolling balls vibration of the ball screw can be discriminated via SVM based on complexity perception. The experimental results successfully show that the prognostic status of ball nut preload can be envisaged by the proposed methodology. The smart reasoning for the health of the ball screw is available based on classification of SVM. This diagnostic method satisfies the purposes of prognostic effectiveness on knowing the ball nut preload status

Locking screw-plate interface stability in carbon-fibre reinforced polyetheretherketone proximal humerus plates.

Science.gov (United States)

Hak, David J; Fader, Ryan; Baldini, Todd; Chadayammuri, Vivek B S

2017-09-01

Carbon-fibre reinforced polyetheretherketone (CFR-PEEK) plates have recently been introduced for proximal humerus fracture treatment. The purpose of this study was to compare the locking screw-plate interface stability in CFR-PEEK versus stainless steel (SS) proximal humerus plates. Locking screw mechanical stability was evaluated independently in proximal and shaft plate holes. Stiffness and load to failure were tested for three conditions: (1) on-axis locking screw insertion in CFR-PEEK versus SS plates, (2) on-axis locking screw insertion, removal, and reinsertion in CFR-PEEK plates, and (3) 10-degree off-axis locking screw insertion in CFR-PEEK plates. Cantilever bending at a rate of 1 mm/minute was produced by an Instron machine and load-displacement data recorded. Shaft locking screw load to failure was significantly greater in CFR-PEEK plates compared to SS plates (746.4 ± 89.7 N versus 596.5 ± 32.6 N, p PEEK plates (p PEEK plates. The mechanical stability of locking screws in CFR-PEEK plates is comparable or superior to locking screws in SS plates.

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...

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.

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

Science.gov (United States)

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

2014-09-01

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

[Effects of prefrontal ablations on the reaction of the active choice of feeder under different probability and value of the reinforcement on dog].

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Preobrazhenskaia, L A; Ioffe, M E; Mats, V N

2004-01-01

The role of the prefrontal cortex was investigated on the reaction of the active choice of the two feeders under changes value and probability reinforcement. The experiments were performed on 2 dogs with prefrontal ablation (g. proreus). Before the lesions the dogs were taught to receive food in two different feeders to conditioned stimuli with equally probable alimentary reinforcement. After ablation in the inter-trial intervals the dogs were running from the one feeder to another. In the answer to conditioned stimuli for many times the dogs choose the same feeder. The disturbance of the behavior after some times completely restored. In the experiments with competition of probability events and values of reinforcement the dogs chose the feeder with low-probability but better quality of reinforcement. In the experiments with equal value but different probability the intact dogs chose the feeder with higher probability. In our experiments the dogs with prefrontal lesions chose the each feeder equiprobably. Thus in condition of free behavior one of different functions of the prefrontal cortex is the reactions choose with more probability of reinforcement.

Current trends in pedicle screw stimulation techniques: lumbosacral, thoracic, and cervical levels.

Science.gov (United States)

Isley, Michael R; Zhang, Xiao-Feng; Balzer, Jeffrey R; Leppanen, Ronald E

2012-06-01

Unequivocally, pedicle screw instrumentation has evolved as a primary construct for the treatment of both common and complex spinal disorders. However an inevitable and potentially major complication associated with this type of surgery is misplacement of a pedicle screw(s) which may result in neural and vascular complications, as well as impair the biomechanical stability of the spinal instrumentation resulting in loss of fixation. In light of these potential surgical complications, critical reviews of outcome data for treatment of chronic, low-back pain using pedicle screw instrumentation concluded that "pedicle screw fixation improves radiographically demonstrated fusion rates;" however the expense and complication rates for such constructs are considerable in light of the clinical benefit (Resnick et al. 2005a). Currently, neuromonitoring using free-run and evoked (triggered) electromyography (EMG) is widely used and advocated for safer and more accurate placement of pedicle screws during open instrumentation procedures, and more recently, guiding percutaneous placement (minimally invasive) where the pedicle cannot be easily inspected visually. The latter technique, evoked or triggered EMG when applied to pedicle screw instrumentation surgeries, has been referred to as the pedicle screw stimulation technique. As concluded in the Position Statement by the American Society of Neurophysiological Monitoring (ASNM), multimodality neuromonitoring using free-run EMG and the pedicle screw stimulation technique was considered a practice option and not yet a standard of care (Leppanen 2005). Subsequently, the American Association of Neurological Surgeons/Congress of Neurological Surgeons (AANS/CNS) Joint Section on Disorders of the Spine and Peripheral Nerves published their "Guidelines for the Performance of Fusion Procedures for Degenerative Disease of the Lumbar Spine" (Heary 2005, Resnick et al. 2005a, Resnick et al. 2005b). It was concluded that the "primary

In vivo Study of the Accuracy of Dual-arch Impressions.

Science.gov (United States)

de Lima, Luciana Martinelli Santayana; Borges, Gilberto Antonio; Junior, Luiz Henrique Burnett; Spohr, Ana Maria

2014-06-01

This study evaluated in vivo the accuracy of metal (Smart®) and plastic (Triple Tray®) dual-arch trays used with vinyl polysiloxane (Flexitime®), in the putty/wash viscosity, as well as polyether (Impregum Soft®) in the regular viscosity. In one patient, an implant-level transfer was screwed on an implant in the mandibular right first molar, serving as a pattern. Ten impressions were made with each tray and impression material. The impressions were poured with Type IV gypsum. The width and height of the pattern and casts were measured in a profile projector (Nikon). The results were submitted to Student's t-test for one sample (α = 0.05). For the width distance, the plastic dual-arch trays with vinyl polysiloxane (4.513 mm) and with polyether (4.531 mm) were statistically wider than the pattern (4.489 mm). The metal dual-arch tray with vinyl polysiloxane (4.504 mm) and with polyether (4.500 mm) did not differ statistically from the pattern. For the height distance, only the metal dual-arch tray with polyether (2.253 mm) differed statistically from the pattern (2.310 mm). The metal dual-arch tray with vinyl polysiloxane, in the putty/wash viscosities, reproduced casts with less distortion in comparison with the same technique with the plastic dual-arch tray. The plastic or metal dual-arch trays with polyether reproduced cast with greater distortion. How to cite the article: Santayana de Lima LM, Borges GA, Burnett LH Jr, Spohr AM. In vivo study of the accuracy of dual-arch impressions. J Int Oral Health 2014;6(3):50-5.

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

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Krishna Chaitanya Kanneganti

2018-01-01

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

Accelerated Tooth Movement with Orthodontic Mini-Screws

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S. Aksakalli

2017-01-01

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

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

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Demidov S. F.

2017-02-01

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

Oral mucosa tissue response to titanium cover screws.

Science.gov (United States)

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

2012-08-01

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

International Coal Report's coal year 1991

Energy Technology Data Exchange (ETDEWEB)

McCloskey, G [ed.

1991-05-31

Following introductory articles on factors affecting trade in coal and developments in the freight market, tables are given for coal exports and coal imports for major countries worldwide for 1989 and 1990. Figures are also included for coal consumption in Canada and the Eastern bloc,, power station consumption in Japan, coal supply and demand in the UK, electric utility coal consumption and stocks in the USA, coal production in Australia, Canada and USA by state, and world hard coal production. A final section gives electricity production and hard coal deliveries in the EEC, sales of imported and local coal and world production of pig iron and steel.

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

Science.gov (United States)

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

2012-01-01

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

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

Science.gov (United States)

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

2013-09-01

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

A new coal-permeability model: Internal swelling stress and fracture-matrix interaction

Energy Technology Data Exchange (ETDEWEB)

Liu, H.H.; Rutqvist, J.

2009-10-01

We have developed a new coal-permeability model for uniaxial strain and constant confining stress conditions. The model is unique in that it explicitly considers fracture-matrix interaction during coal deformation processes and is based on a newly proposed internal-swelling stress concept. This concept is used to account for the impact of matrix swelling (or shrinkage) on fracture-aperture changes resulting from partial separation of matrix blocks by fractures that do not completely cut through the whole matrix. The proposed permeability model is evaluated with data from three Valencia Canyon coalbed wells in the San Juan Basin, where increased permeability has been observed during CH{sub 4} gas production, as well as with published data from laboratory tests. Model results are generally in good agreement with observed permeability changes. The importance of fracture-matrix interaction in determining coal permeability, demonstrated in this work using relatively simple stress conditions, underscores the need for a dual-continuum (fracture and matrix) mechanical approach to rigorously capture coal-deformation processes under complex stress conditions, as well as the coupled flow and transport processes in coal seams.

Replacement of murine fibroblasts by human fibroblasts irradiated in obtaining feeder layer for the culture of human keratinocytes

International Nuclear Information System (INIS)

Yoshito, Daniele; Sufi, Bianca S.; Santin, Stefany P.; Mathor, Monica B.; Altran, Silvana C.; Isaac, Cesar

2011-01-01

Human autologous epithelia cultivated in vitro, have been used successfully in treating damage to skin integrity. The methodology allowed the cultivation of these epithelia was described by Rheinwald and Green in 1975, this methodology consisted in seeding keratinocytes onto a feeder layer composed of lineage 3T3 murine fibroblasts, the proliferation rate is controlled through the action of ionizing radiation. However, currently there is a growing concern about the possibility of transmitting prions and murine viruses to transplanted patients. Taking into account this concern, in this present work, we replaced the feeder layer originally composed of murine fibroblasts by human fibroblasts. To obtain this new feeder layer was necessary to standardize the enough irradiation dose to inhibit the replication of human fibroblasts and the verification of effectiveness of the development of keratinocytes culture on a feeder layer thus obtained. According to the obtained results we can verify that the human fibroblasts irradiated at various tested doses (60, 70, 100, 200, 250 and 300 Gy) had their mitotic activity inactivated by irradiation, allowing the use of any of these doses to confection of the feeder layer, since these fibroblasts irradiated still showed viable until fourteen days of cultivation. In the test of colony formation efficiency was observed that keratinocytes seeded on irradiated human fibroblasts were able to develop satisfactorily, preserving their clonogenic potential. Therefore it was possible the replacement of murine fibroblasts by human fibroblasts in confection of the feeder layer, in order to eliminate this xenobiotic component of the keratinocytes culture. (author)

Replacement of murine fibroblasts by human fibroblasts irradiated in obtaining feeder layer for the culture of human keratinocytes

Energy Technology Data Exchange (ETDEWEB)

Yoshito, Daniele; Sufi, Bianca S.; Santin, Stefany P.; Mathor, Monica B. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Altran, Silvana C.; Isaac, Cesar [Universidade Sao Paulo (USP), Sao Paulo, SP (Brazil). Fac. de Medicina. Lab. de Microcirurgia Plastica; Esteves-Pedro, Natalia M. [Universidade Sao Paulo (USP), Sao Paulo, SP (Brazil). Fac. de Ciencias Farmaceuticas. Lab. de Controle Biologico; Herson, Marisa R. [DonorTissue Bank of Victoria (Australia)

2011-07-01

Human autologous epithelia cultivated in vitro, have been used successfully in treating damage to skin integrity. The methodology allowed the cultivation of these epithelia was described by Rheinwald and Green in 1975, this methodology consisted in seeding keratinocytes onto a feeder layer composed of lineage 3T3 murine fibroblasts, the proliferation rate is controlled through the action of ionizing radiation. However, currently there is a growing concern about the possibility of transmitting prions and murine viruses to transplanted patients. Taking into account this concern, in this present work, we replaced the feeder layer originally composed of murine fibroblasts by human fibroblasts. To obtain this new feeder layer was necessary to standardize the enough irradiation dose to inhibit the replication of human fibroblasts and the verification of effectiveness of the development of keratinocytes culture on a feeder layer thus obtained. According to the obtained results we can verify that the human fibroblasts irradiated at various tested doses (60, 70, 100, 200, 250 and 300 Gy) had their mitotic activity inactivated by irradiation, allowing the use of any of these doses to confection of the feeder layer, since these fibroblasts irradiated still showed viable until fourteen days of cultivation. In the test of colony formation efficiency was observed that keratinocytes seeded on irradiated human fibroblasts were able to develop satisfactorily, preserving their clonogenic potential. Therefore it was possible the replacement of murine fibroblasts by human fibroblasts in confection of the feeder layer, in order to eliminate this xenobiotic component of the keratinocytes culture. (author)

Correlation between classification and secondary screw penetration in proximal humeral fractures.

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Qiuke Wang

Full Text Available In this study, we investigated the correlation between fracture classification and secondary screw penetration.We retrospectively identified 189 patients with displaced proximal humeral fractures treated by ORIF at our hospital between June 2006 and June 2013. All fractures were classified radiographically before surgery and follow-up for least 2 years after surgery was recommended. At each follow-up, radiographs were taken in three orthogonal views to evaluate secondary screw penetration.The study population consisted of 189 patients. Of these, 70 were male and 119 female, with a mean age of 59.1 years; the mean follow-up time was 28.5 months. Secondary screw penetration occurred in 26 patients. The risk of developing secondary screw penetration was 11.3-fold higher in four-part fractures than two-part fractures (P 0.05.Patients with four-part fractures, type C fractures and medial hinges disruption are vulnerable to secondary screw penetration. This allows additional precautions to be instituted and measures to be taken as needed.

Percutaneous Iliac Screws for Minimally Invasive Spinal Deformity Surgery

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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.

Theoretical investigation of flash vaporisation in a screw expander

Science.gov (United States)

Vasuthevan, Hanushan; Brümmer, Andreas

2017-08-01

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

Sacroiliac secure corridor: analysis for safe insertion of iliosacral screws

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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.

Characterization of a new Hencken burner with a transition from a reducing-to-oxidizing environment for fundamental coal studies

Science.gov (United States)

Adeosun, Adewale; Huang, Qian; Li, Tianxiang; Gopan, Akshay; Wang, Xuebin; Li, Shuiqing; Axelbaum, Richard L.

2018-02-01

In pulverized coal burners, coal particles usually transition from a locally reducing environment to an oxidizing environment. The locally reducing environment in the near-burner region is due to a dense region of coal particles undergoing devolatilization. Following this region, the particles move into an oxidizing environment. This "reducing-to-oxidizing" transition can influence combustion processes such as ignition, particulate formation, and char burnout. To understand these processes at a fundamental level, a system is required that mimics such a transition. Hence, we have developed and characterized a two-stage Hencken burner to evaluate the effect of the reducing-to-oxidizing transition and particle-to-particle interaction (which characterizes dense region of coal particles) on ignition and ultrafine aerosol formation. The two-stage Hencken burner allows coal particles to experience a reducing environment followed by a transition to an oxidizing environment. This work presents the results of the design and characterization of the new two-stage Hencken burner and its new coal feeder. In a unique approach to the operation of the flat-flame of the Hencken burner, the flame configurations are operated as either a normal flame or inverse flame. Gas temperatures and oxygen concentrations for the Hencken burner are measured in reducing-to-oxidizing and oxidizing environments. The results show that stable flames with well-controlled conditions, relatively uniform temperatures, and species concentrations can be achieved in both flame configurations. This new Hencken burner provides an effective system for evaluating the effect of the reducing-to-oxidizing transition and particle-to-particle interaction on early-stage processes of coal combustion such as ignition and ultrafine particle formation.

Fast neutron activation analysis and radioisotope X-ray fluorescence study on KALEWA and NAMMA coal

Energy Technology Data Exchange (ETDEWEB)

Naing-Win, [Arts and Science University, Yangon (Myanmar)

1981-07-01

Kalewa coal was studied with Fast Neutron Activation Analysis (FNAA) technique, employing KAMAN A-710 neutron generator and HP(Ge) detector coupled to ``Canberra`` series 30 MCA. Sequential irradiation and dual aluminium foil monitoring method was employed. Simultaneous multielement analysis was carried out. Namma Coal was studied with radioisotope X-ray Fluorescence (XRF) technique, employing Co-57 exciter source and HP(Ge) detector coupled to ``Canberra`` series 40 MCA. In both FNAA and XRF study, the results obtained were compared to that obtained with Atomic Absorption Spectrophotometry (AAS) technique. Finally, the results were reviewed together with those obtained from similar work on coal with FNAA and XRF techniques. (author).

Fast neutron activation analysis and radioisotope X-ray fluorescence study on KALEWA and NAMMA coal

International Nuclear Information System (INIS)

Naing-Win

1981-07-01

Kalewa coal was studied with Fast Neutron Activation Analysis (FNAA) technique, employing KAMAN A-710 neutron generator and HP(Ge) detector coupled to ''Canberra'' series 30 MCA. Sequential irradiation and dual aluminium foil monitoring method was employed. Simultaneous multielement analysis was carried out. Namma Coal was studied with radioisotope X-ray Fluorescence (XRF) technique, employing Co-57 exciter source and HP(Ge) detector coupled to ''Canberra'' series 40 MCA. In both FNAA and XRF study, the results obtained were compared to that obtained with Atomic Absorption Spectrophotometry (AAS) technique. Finally, the results were reviewed together with those obtained from similar work on coal with FNAA and XRF techniques. (author)

Dorsal bridge plating or transarticular screws for Lisfranc fracture dislocations.

Science.gov (United States)

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

2018-04-01

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

Studies on positive conveying in helically channeled single screw extruders

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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.

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

Directory of Open Access Journals (Sweden)

Fei Guo

Full Text Available 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.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.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.The individualized 3D printing navigation template for pedicle screw fixation is easy and safe, with a high success rate in the upper cervical spine surgery.

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.

Design of platform for removing screws from LCD display shields

Science.gov (United States)

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

2017-11-01

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

[Three-dimensional computed tomography analysis and clinical application of sacroiliac screw placement].

Science.gov (United States)

Yin, Y C; Zhang, R P; Li, S L; Hou, Z Y; Chen, W; Zhang, Y Z

2018-03-01

Objective: To evaluate the possibility of transverse sacroiliac screw placement in different segments of the sacrum. Methods: Data of 80 pelvic CT scans (slice thickness ≤1.0 mm) archived in CT department of the Third Hospital of Hebei Medical University from September 2016 to October 2017 were retrospectively collected. Mimics software was used to rebuild the pelvis three-dimensional model. According to whether the sacral 1(S(1)) segment could place the transverse sacroiliac screws or not, all the sacrums were divided into normal group ( n =55) and dysmorphic group ( n =25). Simulation the S(1), sacral 2(S(2)) transverse sacroiliac screw placement in 3-Matic software. Analysis whether there was any difference in maximum diameter and length of S(2) transverse sacroiliac screw between the normal group and the dysmorphic group. The pelvic CT data of the dysmorphic group were measured, and the optimal tilt angle and length of the oblique S(1) screw were obtained. The feasibility of transverse sacroiliac screw insertion in sacral 3(S(3)) segment was evaluated. t -test, rank sum test, and χ(2) test was used to analyze data, respectively. Results: In the dysmorphic group, the largest diameter of the S(1) transverse screw was (4.9±1.6)mm, and the normal group was (13.6±3.6)mm ( t =-15.07, P =0.00). In the dysmorphic group, the largest diameter of S(2) transverse screw was (13.8±3.0)mm, and was (12.4±2.2)mm in the normal group( t =2.11, P =0.04). There was no significant difference in the length of S(2) transverse sacroiliac screw between the two groups ( t =0.47, P =0.64). In the dysmorphic group, the anterior vertebral height of S(1) was (23.1±4.0)mm, which was significantly higher than that of the normal group ((14.1±4.2)mm)( t =9.01, P =0.00). The angle of S(1)S(2) in the dysmorphic group was 10.9°(3.8°, 17.6°), which was significantly larger than that of the normal group (2.0°(1.0°, 2.0°) ( Z =-4.03, P =0.00). In the dysmorphic group, the incline angle

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

Science.gov (United States)

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

2008-04-01

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

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

International Nuclear Information System (INIS)

Koh, S.K.

2005-01-01

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

Biomechanical Comparison of External Fixation and Compression Screws for Transverse Tarsal Joint Arthrodesis.

Science.gov (United States)

Latt, L Daniel; Glisson, Richard R; Adams, Samuel B; Schuh, Reinhard; Narron, John A; Easley, Mark E

2015-10-01

Transverse tarsal joint arthrodesis is commonly performed in the operative treatment of hindfoot arthritis and acquired flatfoot deformity. While fixation is typically achieved using screws, failure to obtain and maintain joint compression sometimes occurs, potentially leading to nonunion. External fixation is an alternate method of achieving arthrodesis site compression and has the advantage of allowing postoperative compression adjustment when necessary. However, its performance relative to standard screw fixation has not been quantified in this application. We hypothesized that external fixation could provide transverse tarsal joint compression exceeding that possible with screw fixation. Transverse tarsal joint fixation was performed sequentially, first with a circular external fixator and then with compression screws, on 9 fresh-frozen cadaveric legs. The external fixator was attached in abutting rings fixed to the tibia and the hindfoot and a third anterior ring parallel to the hindfoot ring using transverse wires and half-pins in the tibial diaphysis, calcaneus, and metatarsals. Screw fixation comprised two 4.3 mm headless compression screws traversing the talonavicular joint and 1 across the calcaneocuboid joint. Compressive forces generated during incremental fixator foot ring displacement to 20 mm and incremental screw tightening were measured using a custom-fabricated instrumented miniature external fixator spanning the transverse tarsal joint. The maximum compressive force generated by the external fixator averaged 186% of that produced by the screws (range, 104%-391%). Fixator compression surpassed that obtainable with screws at 12 mm of ring displacement and decreased when the tibial ring was detached. No correlation was found between bone density and the compressive force achievable by either fusion method. The compression across the transverse tarsal joint that can be obtained with a circular external fixator including a tibial ring exceeds that

Microplastic in a macro filter feeder: humpback whale Megaptera novaeangliae

NARCIS (Netherlands)

Besseling, E.; Foekema, E.M.; Franeker, van J.A.; Leopold, M.F.; Bravo Rebolledo, E.; Kuehn, S.; Mielke, L.; Heberle-Bors, E.; Ijzer, J.; Kamminga, P.; Koelmans, A.A.

2015-01-01

Marine filter feeders are exposed to microplastic because of their selection of small particles as food source. Baleen whales feed by filtering small particles from large water volumes. Macroplastic was found in baleen whales before. This study is the first to show the presence of microplastic in

Microplastic in a macro filter feeder: Humpback whale Megaptera novaeangliae.

NARCIS (Netherlands)

E., Besseling,; E.M., Foekema,; J.A. van, Franeker; Leopold, Mardik F; Kuhn, S.; Bravo Rebolledo, E.L.; Hese, E.; Mielke, L.; IJzer, J.|info:eu-repo/dai/nl/304839663; Kamminga, P.; Koelmans, A.A.

2015-01-01

Marine filter feeders are exposed to microplastic because of their selection of small particles as food source. Baleen whales feed by filtering small particles from large water volumes. Macroplastic was found in baleen whales before. This study is the first to show the presence of microplastic in

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

Science.gov (United States)

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

2018-05-01

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

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.

A reliable and economical method for gaining mouse embryonic fibroblasts capable of preparing feeder layers.

Science.gov (United States)

Jiang, Guangming; Wan, Xiaoju; Wang, Ming; Zhou, Jianhua; Pan, Jian; Wang, Baolong

2016-08-01

Mouse embryonic fibroblasts (MEFs) are widely used to prepare feeder layers for culturing embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) in vitro. Transportation lesions and exorbitant prices make the commercially obtained MEFs unsuitable for long term research. The aim of present study is to establish a method, which enables researchers to gain MEFs from mice and establish feeder layers by themselves in ordinary laboratories. MEFs were isolated from ICR mouse embryos at 12.5-17.5 day post-coitum (DPC) and cultured in vitro. At P2-P7, the cells were inactivated with mitomycin C or by X-ray irradiation. Then they were used to prepare feeder layers. The key factors of the whole protocol were analyzed to determine the optimal conditions for the method. The results revealed MEFs isolated at 12.5-13.5 DPC, and cultured to P3 were the best choice for feeder preparation, those P2 and P4-P5 MEFs were also suitable for the purpose. The P3-P5 MEFs treated with 10 μg/ml of mitomycin C for 3 h, or irradiated with X-ray at 1.5 Gy/min for 25 Gy were the most suitable feeder cells. Treating MEFs with 10 μg/ml of mitomycin C for 2.5 h, 15 μg/ml for 2.0 h, or irradiating the cells with 20 Gy of X-ray at 2.0 Gy/min could all serve as alternative methods for P3-P4 cells. Our study provides a reliable and economical way to obtain large amount of qualified MEFs for long term research of ESCs or iPSCs.

Utilization of human amniotic mesenchymal cells as feeder layers to sustain propagation of human embryonic stem cells in the undifferentiated state.

Science.gov (United States)

Zhang, Kehua; Cai, Zhe; Li, Yang; Shu, Jun; Pan, Lin; Wan, Fang; Li, Hong; Huang, Xiaojie; He, Chun; Liu, Yanqiu; Cui, Xiaohui; Xu, Yang; Gao, Yan; Wu, Liqun; Cao, Shanxia; Li, Lingsong

2011-08-01

Human embryonic stem (ES) cells are usually maintained in the undifferentiated state by culturing on feeder cells layers of mouse embryonic fibroblasts (MEFs). However, MEFs are not suitable to support human ES cells used for clinical purpose because of risk of zoonosis from animal cells. Therefore, human tissue-based feeder layers need to be developed for human ES cells for clinical purpose. Hereof we report that human amniotic mesenchymal cells (hAMCs) could act as feeder cells for human ES cells, because they are easily obtained and relatively exempt from ethical problem. Like MEFs, hAMCs could act as feeder cells for human ES cells to grow well on. The self-renewal rate of human ES cells cultured on hAMCs feeders was higher than that on MEFs and human amniotic epithelial cells determined by measurement of colonial diameters and growth curve as well as cell cycle analysis. Both immunofluorescence staining and immunoblotting showed that human ES cells cultured on hAMCs expressed stem cell markers such as Oct-3/4, Sox2, and NANOG. Verified by embryoid body formation in vitro and teratoma formation in vivo, we found out that after 20 passages of culture, human ES cells grown on hAMCs feeders could still retain the potency of differentiating into three germ layers. Taken together, our data suggested hAMCs may be safe feeder cells to sustain the propagation of human ES cells in undifferentiated state for future therapeutic use.

Scoping Studies to Evaluate the Benefits of an Advanced Dry Feed System on the Use of Low-Rank Coal

Energy Technology Data Exchange (ETDEWEB)

Rader, Jeff; Aguilar, Kelly; Aldred, Derek; Chadwick, Ronald; Conchieri,; Dara, Satyadileep; Henson, Victor; Leininger, Tom; Liber, Pawel; Nakazono, Benito; Pan, Edward; Ramirez, Jennifer; Stevenson, John; Venkatraman, Vignesh

2012-11-30

This report describes the development of the design of an advanced dry feed system that was carried out under Task 4.0 of Cooperative Agreement DE-FE0007902 with the US DOE, “Scoping Studies to Evaluate the Benefits of an Advanced Dry Feed System on the use of Low- Rank Coal.” The resulting design will be used for the advanced technology IGCC case with 90% carbon capture for sequestration to be developed under Task 5.0 of the same agreement. The scope of work covered coal preparation and feeding up through the gasifier injector. Subcomponents have been broken down into feed preparation (including grinding and drying), low pressure conveyance, pressurization, high pressure conveyance, and injection. Pressurization of the coal feed is done using Posimetric1 Feeders sized for the application. In addition, a secondary feed system is described for preparing and feeding slag additive and recycle fines to the gasifier injector. This report includes information on the basis for the design, requirements for down selection of the key technologies used, the down selection methodology and the final, down selected design for the Posimetric Feed System, or PFS.

The use of blocking screws with internal lengthening nail and reverse rule of thumb for blocking screws in limb lengthening and deformity correction surgery

Directory of Open Access Journals (Sweden)

Saravanaraja Muthusamy

2016-09-01

Full Text Available Abstract Internal lengthening nail (ILN is a recent development in limb lengthening and deformity correction specialty. The ILN has the distinct advantage of combining acute deformity correction with gradual lengthening of bone. While using ILN, the short metaphyseal bone fragment may develop a deformity at the time of osteotomy and nail insertion or during bone lengthening because of the wide medullary canal. These deformities are typically predictable, and blocking screws (Poller screws are helpful in these situations. This manuscript describes the common deformities that occur in femur and tibia with osteotomies at different locations while using ILN in antegrade and retrograde nailing technique. Also, a systematic approach to the appropriate use of blocking screws in these deformities is described. In addition, the “reverse rule of thumb” is introduced as a quick reference to determine the ideal location(s and number of blocking screws. These principles are applicable to limb lengthening and deformity correction as well as fracture fixation using intramedullary nails.

The use of blocking screws with internal lengthening nail and reverse rule of thumb for blocking screws in limb lengthening and deformity correction surgery.

Science.gov (United States)

Muthusamy, Saravanaraja; Rozbruch, S Robert; Fragomen, Austin T

2016-11-01

Internal lengthening nail (ILN) is a recent development in limb lengthening and deformity correction specialty. The ILN has the distinct advantage of combining acute deformity correction with gradual lengthening of bone. While using ILN, the short metaphyseal bone fragment may develop a deformity at the time of osteotomy and nail insertion or during bone lengthening because of the wide medullary canal. These deformities are typically predictable, and blocking screws (Poller screws) are helpful in these situations. This manuscript describes the common deformities that occur in femur and tibia with osteotomies at different locations while using ILN in antegrade and retrograde nailing technique. Also, a systematic approach to the appropriate use of blocking screws in these deformities is described. In addition, the "reverse rule of thumb" is introduced as a quick reference to determine the ideal location(s) and number of blocking screws. These principles are applicable to limb lengthening and deformity correction as well as fracture fixation using intramedullary nails.

Research on energy conversion mechanism of a screw centrifugal pump under the water

International Nuclear Information System (INIS)

Quan, H; Li, R N; Han, W; Cheng, X R; Shen, Z J; Su, Q M

2013-01-01

In order to research screw centrifugal pump impeller power capability and energy conversion mechanism, we used Navier-Stokes equation and standard k-ε equation turbulence model on the basis of the Euler equations to carry out screw centrifugal pump internal flow numerical simulation. This was explored by simulating specific design conditions; the medium is water, variation of speed and pressure of flow filed under the action of the impeller, and the screw centrifugal impeller shroud line and wheel line segment take monitoring sites. The monitoring points are between dynamic head and static head change to analyze the energy conversion capability along the impeller corners of screw centrifugal pump. The results show that the energy of fluid of the screw centrifugal pump is provided by spiral segment, the spiral segment in front of the impeller has played a multi-level role, it has significant reference value to research the energy conversion mechanism of screw centrifugal pump under solid-liquid two phase

Posterior pelvic ring fractures: Closed reduction and percutaneous CT-guided sacroiliac screw fixation

International Nuclear Information System (INIS)

Jacob, Augustinus Ludwig; Messmer, Peter; Stock, Klaus-Wilhelm; Suhm, Norbert; Baumann, Bernard; Regazzoni, Pietro; Steinbrich, Wolfgang

1997-01-01

Purpose. To assess the midterm results of closed reduction and percutaneous fixation (CRPF) with computed tomography (CT)-guided sacroiliac screw fixation in longitudinal posterior pelvic ring fractures. Methods. Thirteen patients with 15 fractures were treated. Eleven patients received a unilateral, two a bilateral, screw fixation. Twenty-seven screws were implanted. Continuous on-table traction was used in six cases. Mean radiological follow-up was 13 months. Results. Twenty-five (93%) screws were placed correctly. There was no impingement of screws on neurovascular structures. Union occurred in 12 (80%), delayed union in 2 (13%), and nonunion in 1 of 15 (7%) fractures. There was one screw breakage and two axial dislocations. Conclusion. Sacroiliac CRPF of longitudinal fractures of the posterior pelvic ring is technically simple, minimally invasive, well localized, and stable. It should be done by an interventional/surgical team. CT is an excellent guiding modality. Closed reduction may be a problem and succeeds best when performed as early as possible

The Peierls stress of the moving [Formula: see text] screw dislocation in Ta.

Science.gov (United States)

Liu, Ruiping; Wang, Shaofeng; Wu, Xiaozhi

2009-08-26

The Peierls stress of the moving [Formula: see text] screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving [Formula: see text] screw dislocation in Ta is proposed to be planar.

The Peierls stress of the moving 1/2{110} screw dislocation in Ta

International Nuclear Information System (INIS)

Liu Ruiping; Wang Shaofeng; Wu Xiaozhi

2009-01-01

The Peierls stress of the moving 1/2 {110} screw dislocation with a planar and non-dissociated core structure in Ta has been calculated. The elastic strain energy which is associated with the discrete effect of the lattice and ignored in classical Peierls-Nabarro (P-N) theory has been taken into account in calculating the Peierls stress, and it can make the Peierls stress become smaller. The Peierls stress we obtain is very close to the experimental data. As shown in the numerical calculations and atomistic simulations, the core structure of the screw dislocation undergoes significant changes under the explicit stress before the screw dislocation moves. Moreover, the mechanism of the screw dislocation is revealed by our results and the experimental data that the screw dislocation retracts its extension in three {110} planes and transforms its dissociated core structure into a planar configuration. Therefore, the core structure of the moving 1/2 {110} screw dislocation in Ta is proposed to be planar.

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

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. 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 stability and no need to renovate; Type III, 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. 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. The individualized 3D printing navigation template for pedicle screw fixation is easy and safe

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

Science.gov (United States)

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

2018-02-01

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

Nanometre-sized pores in coal: Variations between coal basins and coal origin

Science.gov (United States)

Sakurovs, Richard; Koval, Lukas; Grigore, Mihaela; Sokolava, Anna; Ruppert, Leslie F.; Melnichenko, Yuri B.

2018-01-01

We have used small angle neutron scattering (SANS) to investigate the differences in methane and hexane penetration in pores in bituminous coal samples from the U.S., Canada, South Africa, and China, and maceral concentrates from Australian coals. This work is an extension of previous work that showed consistent differences between the extent of penetration by methane into 10–20 nm size pores in inertinite in bituminous coals from Australia, North America and Poland.In this study we have confirmed that there are differences in the response of inertinite to methane and hexane penetration in coals sourced from different coal basins. Inertinite in Permian Australian coals generally has relatively high numbers of pores in the 2.5–250 nm size range and the pores are highly penetrable by methane and hexane; coals sourced from Western Canada had similar penetrability to these Australian coals. However, the penetrability of methane and hexane into inertinite from the Australian Illawarra Coal Measures (also Permian) is substantially less than that of the other Australian coals; there are about 80% fewer 12 nm pores in Illawarra inertinite compared to the other Australian coals examined. The inertinite in coals sourced from South Africa and China had accessibility intermediate between the Illawarra coals and the other Australian coals.The extent of hexane penetration was 10–20% less than CD4 penetration into the same coal and this difference was most pronounced in the 5–50 nm pore size range. Hexane and methane penetrability into the coals showed similar trends with inertinite content.The observed variations in inertinite porosity between coals from different coal regions and coal basins may explain why previous studies differ in their observations of the relationships between gas sorption behavior, permeability, porosity, and maceral composition. These variations are not simply a demarcation between Northern and Southern Hemisphere coals.

Electromyogram synergy control of a dexterous artificial hand to unscrew and screw objects.

Science.gov (United States)

Kent, Benjamin A; Karnati, Nareen; Engeberg, Erik D

2014-03-21

Due to their limited dexterity, it is currently not possible to use a commercially available prosthetic hand to unscrew or screw objects without using elbow and shoulder movements. For these tasks, prosthetic hands function like a wrench, which is unnatural and limits their use in tight working environments. Results from timed rotational tasks with human subjects demonstrate the clinical need for increased dexterity of prosthetic hands, and a clinically viable solution to this problem is presented for an anthropomorphic artificial hand. Initially, a human hand motion analysis was performed during a rotational task. From these data, human hand synergies were derived and mapped to an anthropomorphic artificial hand. The synergy for the artificial hand is controlled using conventional dual site electromyogram (EMG) signals. These EMG signals were mapped to the developed synergy to control four joints of the dexterous artificial hand simultaneously.Five limb absent and ten able-bodied test subjects participated in a comparison study to complete a timed rotational task as quickly as possible with their natural hands (except for one subject with a bilateral hand absence), eight commercially available prosthetic hands, and the proposed synergy controller. Each test subject used two to four different artificial hands. With the able-bodied subjects, the developed synergy controller reduced task completion time by 177% on average. The limb absent subjects completed the task faster on average than with their own prostheses by 46%. There was a statistically significant improvement in task completion time with the synergy controller for three of the four limb absent participants with integrated prostheses, and was not statistically different for the fourth. The proposed synergy controller reduced average task completion time compared to commercially available prostheses. Additionally, the synergy controller is able to function in a small workspace and requires less physical

Cement Augmentation in Sacroiliac Screw Fixation Offers Modest Biomechanical Advantages in a Cadaver Model.

Science.gov (United States)

Osterhoff, Georg; Dodd, Andrew E; Unno, Florence; Wong, Angus; Amiri, Shahram; Lefaivre, Kelly A; Guy, Pierre

2016-11-01

Sacroiliac screw fixation in elderly patients with pelvic fractures is prone to failure owing to impaired bone quality. Cement augmentation has been proposed as a possible solution, because in other anatomic areas this has been shown to reduce screw loosening. However, to our knowledge, this has not been evaluated for sacroiliac screws. We investigated the potential biomechanical benefit of cement augmentation of sacroiliac screw fixation in a cadaver model of osteoporotic bone, specifically with respect to screw loosening, construct survival, and fracture-site motion. Standardized complete sacral ala fractures with intact posterior ligaments in combination with ipsilateral upper and lower pubic rami fractures were created in osteoporotic cadaver pelves and stabilized by three fixation techniques: sacroiliac (n = 5) with sacroiliac screws in S1 and S2, cemented (n = 5) with addition of cement augmentation, and transsacral (n = 5) with a single transsacral screw in S1. A cyclic loading protocol was applied with torque (1.5 Nm) and increasing axial force (250-750 N). Screw loosening, construct survival, and sacral fracture-site motion were measured by optoelectric motion tracking. A sample-size calculation revealed five samples per group to be required to achieve a power of 0.80 to detect 50% reduction in screw loosening. Screw motion in relation to the sacrum during loading with 250 N/1.5 Nm was not different among the three groups (sacroiliac: 1.2 mm, range, 0.6-1.9; cemented: 0.7 mm, range, 0.5-1.3; transsacral: 1.1 mm, range, 0.6-2.3) (p = 0.940). Screw subsidence was less in the cemented group (3.0 mm, range, 1.2-3.7) compared with the sacroiliac (5.7 mm, range, 4.7-10.4) or transsacral group (5.6 mm, range, 3.8-10.5) (p = 0.031). There was no difference with the numbers available in the median number of cycles needed until failure; this was 2921 cycles (range, 2586-5450) in the cemented group, 2570 cycles (range, 2500-5107) for the sacroiliac specimens, and

Evaluation of two styles of slotted, flat-head screws

International Nuclear Information System (INIS)

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

1979-01-01

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

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.

Screw-System-Based Mobility Analysis of a Family of Fully Translational Parallel Manipulators

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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.

Pre-treatment of Biomass By Rolling - A Combined Experimental and Numerical Analysis

DEFF Research Database (Denmark)

Hansen, Klaus Schütt; Ravn, Christian; Nielsen, Emil Krabbe

2017-01-01

Pre-treatment of bulk straw material by rolling is studied as a possible method to prepare for subsequent biogas production. A combined experimental and theoretical study is presented. A pilot rolling mill with a double screw feeder is designed and constructed for crushing of bulk straw. Experime...... process window for pre-treatment of wheat straw by roll pressing varying the feed, the roll gap, the roll speed and the moisture content of the bulk straw.......Pre-treatment of bulk straw material by rolling is studied as a possible method to prepare for subsequent biogas production. A combined experimental and theoretical study is presented. A pilot rolling mill with a double screw feeder is designed and constructed for crushing of bulk straw....... Experiments show that the roll speed and the roll reduction should be chosen within a specific range depending on the injection screw speed to avoid blocking or insufficient compaction. A mechanical testing procedure of the bulk straw material including closed die compaction testing as well as simple...

Intraoperative insertion torque of lumbar pedicle screw and postoperative radiographic evaluation. Short-term observation

International Nuclear Information System (INIS)

Mizuno, Koichi; Shinomiya, Kenichi; Otani, Kazuyuki

2005-01-01

The correlation between the insertion torque of a lumbar pedicle screw and the mechanical stability of the screw in the bone has been mentioned in in vitro studies. The purpose of this study was to confirm the factors affecting the insertion torque of such screws in vivo. Also, the contribution of insertion torque to the initial stability of the fusion area was to be analyzed in vivo. A series of 23 cases representing 50 lumbar vertebrae were included in this study, in which we examined bone mineral density using quantitative computed tomography (CT) prior to operation. Two screw shapes were utilized, with the insertion torque for each screw measured at two points in time. The correlation between insertion torque and mineral density was investigated. Screw positions were confirmed on postoperative CT scans, and the effect of the screw thread cutting into the cortex bone was investigated. Radiographic changes at three points during a period of 3 months were also measured, and we then evaluated the interrelations between these changes and insertion torque. Furthermore, the relation between insertion torque and instability at 3 months was investigated. Correlations of insertion torque and bone mineral density depended on screw shape. There was no correlation found with mineral density in the case of cylindrical screws. Insertion torque was not affected by the screw thread cutting into the cortex of bone. As for postoperative alignment changes, no definitive trends could be ascertained, and no interrelations with torque and alignment changes were observed. There is a possibility that insertion torque was related to early-stage stability, but no statistical relation could be determined. (author)

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...

[Measurement of screw length through drilling technique in osteosynthesis of the proximal humerus fractures].

Science.gov (United States)

Avcı, Cem Coşkun; Gülabi, Deniz; Sağlam, Necdet; Kurtulmuş, Tuhan; Saka, Gürsel

2013-01-01

This study aims to investigate the efficacy of screw length measurement through drilling technique on the reduction of intraarticular screw penetration and fluoroscopy time in osteosynthesis of proximal humerus fractures. Between January 2008 and June 2012, 98 patients (34 males, 64 females; mean age 64.4 years; range 35 to 81 years) who underwent osteosynthesis using locking anatomical proximal humerus plates (PHILOS) in our clinic with the diagnosis of Neer type 2, 3 or 4 were included. Two different surgical techniques were used to measure proximal screw length in the plate and patients were divided into two groups based on the technique used. In group 1, screw length was determined by a 3 mm blunt tipped Kirschner wire without fluoroscopic control. In group 2, bilateral fluoroscopic images for each screw at least were obtained. Intraarticular screw penetration was detected in five patients (10.6%) in group 1, and in 19 patients (37.3%) in group 2. The mean fluoroscopic imaging time was 10.6 seconds in group 1 and 24.8 seconds in group 2, indicating a statistically significant difference. Screw length measurement through the drilling technique significantly reduces the intraarticular screw penetration and fluoroscopy time in osteosynthesis of proximal humerus fractures using PHILOS plates.

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

Science.gov (United States)

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

2016-03-01

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

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

Science.gov (United States)

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

2018-03-15

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

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.

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

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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

Assessing the role of benthic filter feeders on phytoplankton production in a shellfish farming site: Mont Saint Michel Bay, France

Science.gov (United States)

Cugier, Philippe; Struski, Caroline; Blanchard, Michel; Mazurié, Joseph; Pouvreau, Stéphane; Olivier, Frédéric; Trigui, Jihane R.; Thiébaut, Eric

2010-07-01

The macrobenthic community of Mont Saint Michel Bay (English Channel, France) is mainly dominated by filter feeders, including cultivated species (oysters and mussels). An ecological model of the bay was developed, coupling a 2D hydro-sedimentary model and two biological models for primary production and filter-feeder filtration. The filter-feeder model includes three cultivated species ( Mytilus edulis, Crassostrea gigas and Ostrea edulis), one invasive species ( Crepidula fornicata) and eight wild native species ( Abra alba, Cerastoderma edule, Glycymeris glycymeris, Lanice conchilega, Macoma balthica, Paphia rhomboides, Sabellaria alveolata, andSpisula ovalis). For cultivated and invasive species, the production of biodeposits was computed to assess their role in restimulating primary production. Chlorophyll a concentrations appeared to be strongly controlled by the filter feeders. When the pressure of each benthic compartment on phytoplankton was estimated separately wild species and the invasive slipper limpet C.fornicata were shown to be key elements in the control of primary production. Conversely, the role of cultivated species, particularly oysters, was weaker. Feedback due to the mineralization of biodeposits also appears to be crucial to fully evaluate the role of filter feeders in primary production.

[Clinical application of atlas translaminar screws fixation in treatment of atlatoaxial instability].

Science.gov (United States)

Wang, Guoyou; Fu, Shijie; Shen, Huarui; Guan, Taiyuan; Xu, Ping

2013-10-01

To explore the effectiveness of fixation of atlas translaminar screws in the treatment of atlatoaxial instability. A retrospective analysis was made on the clinical data of 32 patients with atlatoaxial instability treated with atlantoaxial trans-pedicle screws between March 2007 and August 2009. Of them, 7 patients underwent atlas translaminar screws combined with axis transpedicle screws fixation because of fracture types, anatomic variation, and intraoperative reason, including 5 males and 2 females with an average age of 48.2 years (range, 35-69 years). A total of 9 translaminar screws were inserted. Injury was caused by traffic accident in 4 cases, falling from height in 2 cases, and crushing in 1 case. Two cases had simple odontoid fracture (Anderson type II), and 5 cases had odontoid fracture combined with other injuries (massa lateralis atlantis fracture in 2, atlantoaxial dislocation in 1, and Hangman fracture in 2). The interval between injury and operation was 4-9 days (mean, 6 days). The preoperative Japanese Orthopaedic Association (JOA) score was 8.29 +/- 1.60. The X-ray films showed good position of the screws. Healing of incision by first intention was obtained, and no patient had injuries of the spinal cord injury, nerve root, and vertebral artery. Seven cases were followed up 9-26 months (mean, 14 months). Good bone fusion was observed at 8 months on average (range, 6-11 months). No loosening, displacement, and breakage of internal fixation, re-dislocation and instability of atlantoaxial joint, or penetrating of pedicle screw into the spinal canal and the spinal cord occurred. The JOA score was significantly improved to 15.29 +/- 1.38 at 6 months after operation (t = 32.078, P = 0.000). Atlas translaminar screws fixation has the advantages of firm fixation, simple operating techniques, and relative safety, so it may be a remedial measure of atlatoaxial instability.

Clinical accuracy of three-dimensional fluoroscopy (IsoC-3D)-assisted upper thoracic pedicle screw insertion

International Nuclear Information System (INIS)

Sugimoto, Yoshihisa; Ito, Yasuo; Shimokawa, Tetsuya; Shiozaki, Yasuyuki; Mazaki, Tetsuro; Tomioka, Masao; Tanaka, Masato

2010-01-01

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. (author)

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

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Sophie Le Cann

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

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

Science.gov (United States)

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

2015-01-01

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

An electromagnetic screw and nut system for operating vertical motions along an axis

International Nuclear Information System (INIS)

Fehr, Henri.

1975-01-01

This invention concerns a magnetic screw and nut system for operating control rods, designed for vertical mounting and having no mobile or slide contacts. It makes it possible to rotate a screw located inside a sealed tubular containment that can have a very thick wall. All the electromagnetic components entering into the operation are outside this containment. The magnetic screw has a constant air gap. The tube, manufactured of a non-magnetic material, includes two added annular pole pieces forming part of its wall and whose internal surfaces have a thread corresponding to that of the screw. The two annular pole pieces are spaced axially from each other by an amount equal to an integral number of thread pitches. An external winding and magnetic armature associated to these pole pieces form the fixed magnetic nut. A multiphase non-synchronous motor is placed around the tube and near the nut, the stator is external, the rotor is the screw. An appliance for fixing the degree of axial displacement freedom of the screw can be provided [fr

Influence of abutment screw preload on stress distribution in marginal bone.

Science.gov (United States)

Khraisat, Ameen

2012-01-01

Changes in an implant assembly after abutment connection might possibly cause deformation in the implant/abutment joint and even in the marginal bone. The aim of this study was to evaluate the influence of abutment screw preload through the implant collar on marginal bone stress without external load application. Models of three implant parts made of titanium (implant, abutment, and abutment screw) and cortical bone were built and positioned with computer-aided design software. Meshing and generation of boundary conditions, loads, and interactions were performed. Each part was meshed independently. The sole load applied to the model was a torque of 32 Ncm on the abutment screw about its axis of rotation. The implant collar was deformed axially after the screw was tightened (3 μm). This deformation resulted in 60 MPa of stress in the marginal bone. Moreover, pressure on the marginal bone in a radial direction was observed. It can be concluded that, without any external load application, abutment screw preload exerts stresses on the implant collar and the marginal bone. These findings should help guide the development of new implant/abutment joint designs that exert less stress on the marginal bone.

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

Directory of Open Access Journals (Sweden)

Sun-Seok Byeon

2017-07-01

Full Text Available The screw compressor in the early stage of development is generally known as the oil-injection type. However, escalating environmental problems and advances in electronic components have spurred continuous R & D to minimize the oil content in compressed air. The oil-free twin-screw compressor is continuously compressed by inner volumetric change between rotors and casing. For this reason, in order to predict the overall performance of the screw compressor at the early stage of the design process, industry still relies on the empirical method. However, it is difficult using the existing empirical method to gain more information of the inner fluid flow of the twin-screw compressor. Flow simulation techniques using CFD are required. This study presents applications of a recently proposed overset grid method to the solution of the flow around a moving boundary. In order to analyze the performance of a 4 × 6 oil-free screw compressor, the 3-D, unsteady and compressible flow fields were numerically calculated with a shear stress transport (SST turbulence model, and implemented by the commercial software, Star-CCM+. The pressure distributions were calculated and graphically depicted. Results also showed that the volumetric and adiabatic efficiencies of the screw compressor measured by the experiments were 78% and 71%, respectively.

Bioresorbable composite screws manufactured via forging process: pull-out, shear, flexural and degradation characteristics.

Science.gov (United States)

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

2013-02-01

Bioresorbable screws have the potential to overcome some of the complications associated with metallic screws currently in use. Removal of metallic screws after bone has healed is a serious issue which can lead to refracture due to the presence of screw holes. Poly lactic acid (PLA), fully 40 mol% P(2)O(5) containing phosphate unidirectional (P40UD) and a mixture of UD and short chopped strand random fibre mats (P40 70%UD/30%RM) composite screws were prepared via forging composite bars. Water uptake and mass loss for the composite screws manufactured increased significantly to ∼1.25% (P=0.0002) and ∼1.1% (P<0.0001), respectively, after 42 days of immersion in PBS at 37 °C. The initial maximum flexural load for P40 UD/RM and P40 UD composite screws was ∼60% (P=0.0047) and ∼100% (P=0.0037) higher than for the PLA screws (∼190 N), whilst the shear load was slightly higher in comparison to PLA (∼2.2 kN). The initial pull-out strengths for the P40 UD/RM and PLA screws were similar whereas that for P40 UD screws was ∼75% higher (P=0.022). Mechanical properties for the composite screws decreased initially after 3 days of immersion and this reduction was ascribed to the degradation of the fibre/matrix interface. After 3 days interval the mechanical properties (flexural, shear and pull-out) maintained their integrity for the duration of the study (at 42 days). This property retention was attributed to the chemical durability of the fibres used and stability of the matrix properties during the degradation process. It was also deemed necessary to enhance the fibre/matrix interface via use of a coupling agent in order to maintain the initial mechanical properties acquired for the required period of time. Lastly, it is also suggested that the degrading reinforcement fibres may have the potential to buffer any acidic products released from the PLA matrix. Copyright © 2012 Elsevier Ltd. All rights reserved.

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.

New concept single screw compressors and their manufacture technology

Science.gov (United States)

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

2017-08-01

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

Screw engine used as an expander in ORC for low-potential heat utilization

Science.gov (United States)

Richter, Lukáš

2017-09-01

This paper deals with a screw motor that is used as an expander in an ORC (Organic Rankin Cycle) system, whose organic working substance allows the transformation of low-potential heat (waste heat, solar and geothermal energy) into electrical energy. The article describes the specific properties of an organic substance and a screw motor that must be considered when designing and assembling a complete power unit. Screw machines are not commonly used as expansion devices, so it is necessary to perform an analysis that makes it possible to adapt the screw machine to the expansion process in terms of profiling and design.

The Research of Screw Thread Parameter Measurement Based on Position Sensitive Detector and Laser

International Nuclear Information System (INIS)

Tong, Q B; Ding, Z L; Chen, J C; Ai, L L; Yuan, F

2006-01-01

A technique and system of measuring screw thread parameter based on the theory of laser measurement is presented in this paper, which can be carried out the automated measurement of screw thread parameter. An inspection instrument was designed and produced, which included exterior imaging system of optical path, transverse displacement measurement system, axial displacement measurement system, and a module to deal with, control and assess the data in the upper system. The inspection and estimate of the screw thread contour curve were completed by using position sensitive device (PSD) as photoelectric detector to measure the coordinate data of the screw thread contour curve in the transverse section, and using precise raster to measure the axial displacement of the precision worktable under the screw thread test criterion., computer can gives a measured result according to coordinate data of the screw thread obtained by PSD. The relation between measured spot and image is established, and optimum design of the system organization are introduced, including the image length of receiving lens focal length optical system and the choice of PSD , and some main factor affected measuring precision are analyzed. The experimental results show that the measurement uncertainty of screw thread minor diameter can reach 0. 5μm, which can meet most requests for the measurement of screw thread parameter

Parametric analysis and design of a screw extruder for slightly non-Newtonian (pseudoplastic materials

Directory of Open Access Journals (Sweden)

J.I. Orisaleye

2018-04-01

Full Text Available Extruders have found application in the food, polymer and pharmaceutical industries. Rheological characteristics of materials are important in the specification of design parameters of screw extruders. Biopolymers, which consist of proteins, nucleic acids and polysaccharides, are shear-thinning (pseudoplastic within normal operating ranges. However, analytical models to predict and design screw extruders for non-Newtonian pseudoplastic materials are rare. In this study, an analytical model suitable to design a screw extruder for slightly non-Newtonian materials was developed. The model was used to predict the performance of the screw extruder while processing materials with power law indices slightly deviating from unity (the Newtonian case. Using non-dimensional analysis, the effects of design and operational parameters were investigated. Expressions to determine the optimum channel depth and helix angle were also derived. The model is capable of predicting the performance of the screw extruder within the range of power law indices considered (1/2⩽n⩽1. The power law index influences the choice of optimum channel depth and helix angle of the screw extruder. Keywords: Screw extruder, Slightly non-Newtonian, Shear-thinning, Pseudoplastic, Biopolymer, Power law

Dynamic modelling and PID loop control of an oil-injected screw compressor package

Science.gov (United States)

Poli, G. W.; Milligan, W. J.; McKenna, P.

2017-08-01

A significant amount of time is spent tuning the PID (Proportional, Integral and Derivative) control loops of a screw compressor package due to the unique characteristics of the system. Common mistakes incurred during the tuning of a PID control loop include improper PID algorithm selection and unsuitable tuning parameters of the system resulting in erratic and inefficient operation. This paper details the design and development of software that aims to dynamically model the operation of a single stage oil injected screw compressor package deployed in upstream oil and gas applications. The developed software will be used to assess and accurately tune PID control loops present on the screw compressor package employed in controlling the oil pressures, temperatures and gas pressures, in a bid to improve control of the operation of the screw compressor package. Other applications of the modelling software will include its use as an evaluation tool that can estimate compressor package performance during start up, shutdown and emergency shutdown processes. The paper first details the study into the fundamental operational characteristics of each of the components present on the API 619 screw compressor package and then discusses the creation of a dynamic screw compressor model within the MATLAB/Simulink software suite. The paper concludes by verifying and assessing the accuracy of the created compressor model using data collected from physical screw compressor packages.

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.

Metal Artifacts Reduction of Pedicle Screws on Spine Computed Tomography Images Using Variable Thresholding Technique

International Nuclear Information System (INIS)

Kaewlek, T.; Koolpiruck, D.; Thongvigitmanee, S.; Mongkolsuk, M.; Chiewvit, P.; Thammakittiphan, S.

2012-01-01

Metal artifacts are one of significant problems in computed tomography (CT). The streak lines and air gaps arise from metal implants of orthopedic patients, such as prosthesis, dental bucket, and pedicle screws that cause incorrect diagnosis and local treatment planning. A common technique to suppressed artifacts is by adjusting windows, but those artifacts still remain on the images. To improve the detail of spine CT images, the variable thresholding technique is proposed in this paper. Three medical cases of spine CT images categorized by the severity of artifacts (screws head, one full screw, and two full screws) were investigated. Metal regions were segmented by k-mean clustering, then transformed into a sinogram domain. The metal sinogram was identified by the variable thresholding method, and then replaced the new estimated values by linear interpolation. The modified sinogram was reconstructed by the filtered back- projection algorithm, and added the metal region back to the modified reconstructed image in order to reproduce the final image. The image quality of the proposed technique, the automatic thresholding (Kalender) technique, and window adjustment technique was compared in term of noise and signal to noise ratio (SNR). The propose method can reduce metal artifacts between pedicle screws. After processing by our proposed technique, noise in the modified images is reduced (screws head 121.15 to73.83, one full screw 160.88 to 94.04, and two full screws 199.73 to 110.05 from the initial image) and SNR is increased (screws head 0.87 to 1.88, one full screw 1.54 to 2.82, and two full screws 0.32 to 0.41 from the initial image). The variable thresholding technique can identify the suitable boundary for restoring the missing data. The efficiency of the metal artifacts reduction is indicated on the case of partial and full pedicle screws. Our technique can improve the detail of spine CT images better than automatic thresholding (Kalender) technique, and

Effect of portion size and milk flow on the use of a milk feeder and the development of cross-sucking in dairy calves

DEFF Research Database (Denmark)

Nielsen, Per Peetz; Jensen, Margit Bak; Halekoh, Ulrich

2018-01-01

milk feeder in each pen, and exposed to four milk-feeding treatments in a cross-over design with four periods of 1 week. All four treatments involved a daily allowance of 8. L of whole milk, with variation in the maximum portion size and the rate at which milk entered the teat of the milk feeder......This study aimed to investigate whether reducing the milk flow and increasing the milk portion size of a computer-controlled milk feeder would lead to less cross-sucking and fewer unrewarded feeder visits in dairy calves. Five groups, each with 9 or 10 calves (n = 48), were housed in pens with one...

To retain or remove the syndesmotic screw: a review of literature

NARCIS (Netherlands)

T. Schepers (Tim)

2011-01-01

textabstractIntroduction: Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this

Atomistic simulations of cross-slip of jogged screw dislocations in copper

DEFF Research Database (Denmark)

Vegge, T.; Rasmussen, T.; Leffers, T.

2001-01-01

We have performed atomic-scare simulations of cross-slip processes of screw dislocations in copper, simulating jog-free dislocations as well as different types of jogged screw dislocations. Minimum-energy paths and corresponding transition state energies are obtained using the nudged-elastic...

Surgical strategies to improve fixation in the osteoporotic spine: the effects of tapping, cement augmentation, and screw trajectory.

Science.gov (United States)

Kuhns, Craig A; Reiter, Michael; Pfeiffer, Ferris; Choma, Theodore J

2014-02-01

Study Design Biomechanical study of pedicle screw fixation in osteoporotic bone. Objective To investigate whether it is better to tap or not tap osteoporotic bone prior to placing a cement-augmented pedicle screw. Methods Initially, we evaluated load to failure of screws placed in cancellous bone blocks with or without prior tapping as well as after varying the depths of tapping prior to screw insertion. Then we evaluated load to failure of screws placed in bone block models with a straight-ahead screw trajectory as well as with screws having a 23-degree cephalad trajectory (toward the end plate). These techniques were tested with nonaugmented (NA) screws as well as with bioactive cement (BioC) augmentation prior to screw insertion. Results In the NA group, pretapping decreased fixation strength in a dose-dependent fashion. In the BioC group, the tapped screws had significantly greater loads to failure (p tapping prior to cement augmentation will substantially improve fixation when compared with not tapping. Angulating screws more cephalad also seems to enhance aging spine fixation.

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

OpenAIRE

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

2017-01-01

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

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.

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.

Method and apparatus for monitoring the flow of solids

International Nuclear Information System (INIS)

Wyton, W.W.; Doeksen, G.

1977-01-01

The flow of particulate solids through a screw conveyor or a screw feeder is monitored by passing radiant energy from a source in a generally vertical path into a bed of the solids flowing through the conveyor, receiving by a detector radiation that is not absorbed or scattered by the solids or the conveyor, and transmitting amplified electrical signals from the detector to a recorder. The detector extends parallel to the shaft of the conveyor screw for at least about one pitch length of the screw. The path of radiaton from the source to the detector follows a plane that lies between the shaft and the conveyor casing on the lift side of the screw. Cyclic variations in radiation signals as tapered pitch-length segments of material move through the conveyor are averaged mechanically

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.

The improvement of the edge screw connection in OSB and conventional particleboard

Directory of Open Access Journals (Sweden)

Popović Mlađan

2006-01-01

Full Text Available This work presents the method for improvement of direct screw connection performance in conventional particleboard (PB and oriented strand board (OSB. It is conceived on adhesive insertion into the pilot hole prior to embedment of the screw. The tests were carried out on the PB and OSB, both presenting interior boards and with the same nominal thickness of 18 mm. Particleboard screws of the 5 mm in diameter were inserted in the edge of the board. Pilot hole diameters were 2,5 mm and 3,0 mm and the depth of embedment was 30 mm for all tests. The chosen PVAc adhesive (type 3 with the addition of wood flour as consolidator in the range from 3-10% was inserted into pilot-hole. Tests were also obtained after consequent reassembly of the screw connection in order to examine the ratio of loss in withdrawal forces in such case. It was found that the insertion of PVAc adhesive into the pilot hole and the addition of wood flour have the positive effects on the screw withdrawal force in the tested boards.

On-conveyor belt determination of ash in coal

International Nuclear Information System (INIS)

Sowerby, B.; Lim, C.S.; Abernethy, D.A.; Liu, Y.; Maguire, P.A.

1997-01-01

A laboratory feasibility study has been carried out on new and advanced neutron and gamma-ray analysis systems for the direct on-conveyor belt analysis of ash in coal without the need for sample by-lines. Such an analysis system could deliver the combined advantages of a direct on-conveyor configuration with new and accurate analysis techniques. An industry survey of 18 coal companies carried out in early 1996 indicated that accurate on-belt ash analysis is of the highest priority. Subsequent laboratory work has focussed on the investigation of methods with the potential for improving the accuracy of ash content measurement relative to existing on-belt ash analysers, the most widely-used of which are based on dual energy gamma-ray transmission (DUET), which is sensitive to variations in ash composition. The current work indicates that on-belt neutron/gamma-ray techniques combined with advanced spectral analysis techniques show promise for development into an on-belt ash analysis system which is significantly less sensitive to composition changes than DUET and which analyses a much larger proportion of coal on the belt, thus eliminating some key sources of analysis error

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.

Coal geopolitics

International Nuclear Information System (INIS)

Giraud, P.N.; Suissa, A.; Coiffard, J.; Cretin, D.

1991-01-01

This book divided into seven chapters, describes coal economic cycle. Chapter one: coals definition; the principle characteristics and properties (origin, calorific power, international classification...) Chapter two: the international coal cycle: coal mining, exploration, coal reserves estimation, coal handling coal industry and environmental impacts. Chapter three: the world coal reserves. Chapter four: the consumptions, productions and trade. Chapter five: the international coal market (exporting mining companies; importing companies; distributors and spot market operators) chapter six: the international coal trade chapter seven: the coal price formation. 234 refs.; 94 figs. and tabs [fr

Bone anchors or interference screws? A biomechanical evaluation for autograft ankle stabilization.

Science.gov (United States)

Jeys, Lee; Korrosis, Sotiris; Stewart, Todd; Harris, Nicholas J

2004-01-01

Autograft stabilization uses free semitendinosus tendon grafts to anatomically reconstruct the anterior talofibular ligament. Study aims were to evaluate the biomechanical properties of Mitek GII anchors compared with the Arthrex Bio-Tenodesis Screw for free tendon reconstruction of the anterior talofibular ligament. There are no differences in load to failure and percentage specimen elongation at failure between the 2 methods. Controlled laboratory study using porcine models. Sixty porcine tendon constructs were failure tested. Re-creating the pull of the anterior talofibular ligament, loads were applied at 70 degrees to the bones. Thirty-six tendons were fixed to porcine tali and tested using a single pull to failure; 10 were secured with anchors and No. 2 Ethibond, 10 with anchors and FiberWire, 10 with screws and Fiberwire, and 6 with partially gripped screws. Cyclic preloading was conducted on 6 tendons fixed by anchors and on 6 tendons fixed by screws before failure testing. Two groups of 6 components fixed to the fibula were also tested. The talus single-pull anchor group produced a mean load of 114 N and elongation of 37% at failure. The talus single-pull screw group produced a mean load of 227 N and elongation of 22% at failure (P anchors. The improved biomechanics of interference screws suggests that these may be more suited to in vivo reconstruction of the anterior talofibular ligament than are bone anchors.

To retain or remove the syndesmotic screw: a review of literature

NARCIS (Netherlands)

Schepers, T.

2011-01-01

Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this study, the recent

Fiscal 2001 achievement report. Development of coal gas production technology for fuel cells - Research using pilot test facility - for public release (Test result report - 2/3); 2001 nendo seika hokokusho (Kokai you). Nenryo denchi you sekitan gas seizo gijutsu kaihatsu - Pilot shiken setsubi ni yoru kenkyu (Shiken kekka hokokusho 2/3)

Energy Technology Data Exchange (ETDEWEB)

NONE

2002-03-01

For the development of a coal gasification furnace optimum for fuel cells, a pilot test facility was constructed, and the results of tests and inspections conducted therefor are put together. They include an individual test of the receiving pit hopper vibrator, individual test of the pulverized coal related rotary valve, individual test of the pretreatment compressed air fan, individual test of the coal pulverizer lubricating device, individual test of the coal pulverizer pressure device, individual test of the coal pulverizer, individual test of the coal pulverizer motor, individual test of the coal feeder, individual test of the pulverized coal bunker exhaust fan, individual test of the pulverized coal bunker exhaust fan motor, test of capacity for pulverized coal, individual test of the pulverized coal conveyer blower, test of the sequence of the same, test of pulverizer inert clearing, individual test of the pretreatment condensed water pump in the coal pretreatment device, test of airborne conveyance in the same, verification test of inter-hopper transfer in the same, test of coal pulverization in the same, test operation of the raw material air/low pressure nitrogen compressor in the air separation facility, test operation of the raw material air freezer in the same, and a test operation of the MS adsorber/MS regeneration electric heater. (NEDO)

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.

Ball tip method for thoracic pedicle screw placement in patients with adolescent idiopathic scoliosis

International Nuclear Information System (INIS)

Watanabe, Kota; Matsumoto, Morio; Iizuka, Shingo

2008-01-01

The purpose of this study was to evaluate the efficacy of ball tip method for thoracic pedicle screw placements in idiopathic scoliosis patients. 24 patients with adolescent idiopathic scoliosis were included in this study. Conventional method was performed in 12 patients. Ball tip method was performed in 12 patients. Accuracy of the pedicle screw placement was evaluated based on the postoperative CT. In the ball tip method, a probe which was consisted of ball tip with flexible shaft was used. After removing of cortical bone at a starting point, the probe was inserted manually or sometimes with gently tapping by hammer. During the maneuver, the probe will gradually progress into cancellous bone in the pedicle, without perforating cortical bone in the pedicle. Following expansion of the hole by a rigid gear shift probe, screw was placed in the pedicle. 65.1% of screws were located within pedicle in the conventional group and 86.5% in the ball tip group. 5.3% of screws were located out of pedicle within 2 mm in the conventional group and 8.2% in the ball tip group. 15.8% of screws were located out of pedicle beyond 2 mm and 1.8% in the ball tip group. The ball tip method enhanced the accuracy of thoracic pedicle screw placements in adolescent idiopathic scoliosis patients. The ball tip method may be effective for accurate pedicle screw placement in patients with adolescent idiopathic scoliosis. (author)

Computed tomography fluoroscopy-guided placement of iliosacral screws in patients with unstable posterior pelvic fractures

International Nuclear Information System (INIS)

Iguchi, Toshihiro; Ogawa, Ken-Ichi; Doi, Takeshi; Munetomo, Kazuo; Miyasho, Koji; Hiraki, Takao; Kanazawa, Susumu; Ozaki, Toshifumi

2010-01-01

The purpose of this study was to evaluate retrospectively the safety and effectiveness of the computed tomography (CT) fluoroscopy-guided placement of iliosacral screws in patients with unstable posterior pelvic fractures. Six patients (four women and two men; mean age 55.8 years; range 35-77 years) with unstable posterior pelvic fractures underwent iliosacral screw placement under CT fluoroscopy guidance between November 2007 and August 2008. Unstable pelvic ring injury (AO types B and C) was the indication for this procedure. In all the six patients except one, CT fluoroscopy-guided placement had been technically successful. In one patient, a second screw had been inserted, with a tilt to the caudal site, and slightly advanced into the extrasacral body; afterward, it could be exchanged safely for a shorter screw. Five patients and one patient underwent placement of two screws and one screw, respectively. The mean duration of the procedure was 15.0 min (range 9-30 min) per screw; the duration was 12.3 min and 18.2 min for the first and second screws, respectively. No complications requiring treatment occurred during or after the procedure. The mean clinical and radiologic follow-up period was 14 months (range 6-21 months). All pelvic injuries had healed satisfactorily, without complication, and all patients are now doing well clinically and can walk. CT fluoroscopy-guided placement of iliosacral screws is a safe and effective treatment in patients with unstable posterior pelvic fractures. (orig.)

The effect of stocking density and bin feeder space on performance ...

African Journals Online (AJOL)

The effect of stocking density and bin feeder space on performance in pigs. G.A. Lavers, N.S. Ferguson. Abstract. (South African J of Animal Science, 2000, 30, Supplement 1: 70-71). Full Text: EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

A Branch-and-Price Approach to the Feeder Network Design Problem

DEFF Research Database (Denmark)

Santini, Alberto; Plum, Christian Edinger Munk; Røpke, Stefan

2017-01-01

In this paper we consider the problem of designing a container liner shipping feeder network. The designer has to choose which port to serve during many rotations that start and end at a central hub. Many operational characteristics are considered, such as variable leg-by-leg speeds and cargo...

Virtual surgery simulation versus traditional approaches in training of residents in cervical pedicle screw placement.

Science.gov (United States)

Hou, Yang; Shi, Jiangang; Lin, Yanping; Chen, Huajiang; Yuan, Wen

2018-06-01

The cervical screw placement is one of the most difficult procedures in spine surgery, which often needs a long period of repeated practices and could cause screw placement-related complications. We performed this cadaver study to investigate the effectiveness of virtual surgical training system (VSTS) on cervical pedicle screw instrumentation for residents. A total of ten novice residents were randomly assigned to two groups: the simulation training (ST) group (n = 5) and control group (n = 5). The ST group received a surgical training of cervical pedicle screw placement on VSTS and the control group was given an introductory teaching session before cadaver test. Ten fresh adult spine specimens including 6 males and 4 females were collected, and were randomly allocated to the two groups. The bilateral C3-C6 pedicle screw instrumentation was performed in the specimens of the two groups, respectively. After instrumentation, screw positions of the two groups were evaluated by image examinations. There was significantly statistical difference in screw penetration rates between the ST (10%) and control group (62.5%, P VSTS as an advanced training tool exhibited promising effects on improving performance of novice residents in cervical pedicle screw placement compared with the traditional teaching methods.

Experimental results of single screw mechanical tests: a follow-up to SAND2005-6036.

Energy Technology Data Exchange (ETDEWEB)

Lee, Sandwook; Lee, Kenneth L.; Korellis, John S.; McFadden, Sam X.

2006-08-01

The work reported here was conducted to address issues raised regarding mechanical testing of attachment screws described in SAND2005-6036, as well as to increase the understanding of screw behavior through additional testing. Efforts were made to evaluate fixture modifications and address issues of interest, including: fabrication of 45{sup o} test fixtures, measurement of the frictional load from the angled fixture guide, employment of electromechanical displacement transducers, development of a single-shear test, and study the affect of thread start orientation on single-shear behavior. A286 and 302HQ, No.10-32 socket-head cap screws were tested having orientations with respect to the primary loading axis of 0{sup 0}, 45{sup o}, 60{sup o}, 75{sup o} and 90{sup o} at stroke speeds 0,001 and 10 in/sec. The frictional load resulting from the angled screw fixture guide was insignificant. Load-displacement curves of A286 screws did not show a minimum value in displacement to failure (DTF) for 60{sup o} shear tests. Tests of 302HQ screws did not produce a consistent trend in DTF with load angle. The effect of displacement rate on DTF became larger as shear angle increased for both A286 and 302HQ screws.

[Open double-row rotator cuff repair using the LASA-DR screw].

Science.gov (United States)

Schoch, C; Geyer, S; Geyer, M

2016-02-01

Safe and cost-effective rotator-cuff repair. All types of rotator cuff lesions. Frozen shoulder, rotator cuff mass defect, defect arthropathy. Extensive four-point fixation on the bony footprint is performed using the double-row lateral augmentation screw anchor (LASA-DR) with high biomechanical stability. Following mobilization of the tendons, these are refixed in the desired configuration first medially and then laterally. To this end, two drilling channels (footprint and lateral tubercle) are created for each screw. Using the shuttle technique, a suture anchor screw is reinforced with up to four pairs of threads. The medial row is then pierced and tied, and the sutures that have been left long are tied laterally around the screw heads (double row). 4 Weeks abduction pillow, resulting in passive physiotherapy, followed by initiation of active assisted physiotherapy. Full weight-bearing after 4-6 months. Prospective analysis of 35 consecutive Bateman-III lesions with excellent results and low rerupture rate (6%).

Utilization of new feeding technology in power production from biomass; safety aspects and techno-economic assessment

Energy Technology Data Exchange (ETDEWEB)

Wilen, C.; Rautalin, A. [VTT Energy, Espoo (Finland)

1998-12-31

Safety-technical characteristics of fuels, primarily biomass and, as reference, coal, have been studied at VTT Energy since the year 1993. The work has been related mainly to the development work of feeding and handling systems for pressurised gasification and combustion technology. Dust explosion and self-ignition characteristics of fuels have been determined in a number of research projects. Possible prevention of dust explosions with a suppression method immediately at ignition was studied in a project on suppression of dust explosions in biomass-utilising plants (Bioenergia Programme 1995). The first phase of dust explosion and suppression tests at elevated pressure were carried out in testing equipment of 5,6 m{sup 3} constructed, in particular, for these tests in Great Britain. Tests were made both with coal and wood powders by Coal Technology Development Division (British Coal Corporation) and Kidde Fire Protection. At the first stage of the test programme both coal and wood powder explosions were successfully suppressed at 10 bar pressure level. The current 1997-98 project includes the second phase of the explosion suppression tests, which will be carried out at 18 bar. If successful these tests would enable the extrapolation of the operation values to the pressure level of IGCC plants, i.e. to 20 - 25 bar. The boundary conditions set by safety factors on the design of pressurised (and atmospheric) feeding systems are fairly well-known due to data obtained from dust explosion and self-ignition experiments and from dust explosion suppression tests. The overall aim of the research is to compare pressurised system alternatives based primarily on lock-hopper feeding technology both technically and economically. A significant issue is how to arrange pressurisation and sufficient inertisation. New alternatives to produce inert gas will be assessed. The newest equipment, plug screw and piston feeders under development, will also be included in the study. The

Development of ceramic-free antenna feeder

International Nuclear Information System (INIS)

Moriyama, S.; Kimura, H.; Fujii, T.; Saigusa, M.; Arai, H.

1994-01-01

We have proposed a ceramics-free antenna feeder line employing a ridged waveguide as a local support for IC antenna of next-generation tokamaks. One fourth mock-up model of the all metal waveguide designed for the ITER ICRF system is fabricated and electrical characteristics of the model including the coaxial line - waveguide converter are measured. Power reflection coefficient of the model including the coax-waveguide converter to the input coaxial line is estimated to be less than 15% below the cut-off frequency of 107 MHz and less than 3% above the cut-off frequency. It is found that this ceramics-free antenna support employing a ridged waveguide is quite available for IC antenna of next-generation tokamaks. (author)

Design of Two Feeder Three Phase Four Wire Distribution System Utilizing Multi Converter UPQC with Fuzzy Logic Controller

Directory of Open Access Journals (Sweden)

Chandra Babu Paduchuri

2014-01-01

Full Text Available This paper proposes the instantaneous p-q theory based fuzzy logic controller (FLC for multi converter unified power quality conditioner (MC-UPQC to mitigate power quality issues in two feeders three-phase four-wire distribution systems. The proposed system is extended system of the existing one feeder three-phase four-wire distribution system, which is operated with UPQC. This system is employed with three voltage source converters, which are connected commonly to two feeder distribution systems. The performance of this proposed system used to compensate voltage sag, neutral current mitigation and compensation of voltage and current harmonics under linear and nonlinear load conditions. The neutral current flowing in series transformers is zero in the implementation of the proposed system. The simulation performance analysis is carried out using MATLAB.

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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.

Parameters Affecting the Extraction Process of Jatropha curcas Oil Using a Single Screw Extruder

Directory of Open Access Journals (Sweden)

Ali Nurrakhmad Siregar

2015-07-01

Full Text Available The most commonly used technique to separate oil and cake from J. curcas seeds is mechanical extraction. It uses simple tools such as a piston and a screw extruder to produce high pressure, driven by hand or by engine. A single screw extruder has one screw rotating inside the barrel and materials simultaneously flow from the feed to the die zone. The highest oil yield can be obtained by a well-designed oil press as well as finding the optimum conditions for all parameters involved during the extraction process. The influence of the parameters in a single screw extruder was studied using finite element analysis and computational fluid dynamics simulation with ANSYS POLYFLOW. The research focused on predicting the velocity, pressure and shear rate in the metering section that influenced the screw rotational speed and mass flow rate. The obtained results revealed that increasing the screw rotational speed will increase the pressure, velocity and shear rate. Meanwhile, increasing the mass flow rate results in decreasing the pressure while the velocity and shear rate remain constant.

Evolution of generic supporting conditions for feeders of 500 M We PHWR