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Sample records for friction factor correlations

  1. Modified friction factor correlation for CICC's based on a porous media analogy

    NASA Astrophysics Data System (ADS)

    Lewandowska, Monika; Bagnasco, Maurizio

    2011-09-01

    A modified correlation for the bundle friction factor in CICC's based on a porous media analogy is presented. The correlation is obtained by the analysis of the collected pressure drop data measured for 23 CICC's. The friction factors predicted by the proposed correlation are compared with those resulting from the pressure drop data for two CICC's measured recently using cryogenic helium in the SULTAN test facility at EPFL-CRPP.

  2. Development of colburn ` j' factor and fanning friction factor ` f' correlations for compact heat exchanger plain fins by using CFD

    NASA Astrophysics Data System (ADS)

    Bala Sundar Rao, R.; Ranganath, G.; Ranganayakulu, C.

    2013-07-01

    A numerical model has been developed for plain fin of plate fin heat exchanger. Plain fin performance has been analyzed with the help of CFD by changing the various parameters of the fin, Colburn ` j' and fanning friction ` f' factors are calculated. These values compared with the standard values. The correlations have been developed between Reynolds number Re, fin height h, fin thickness t, fin spacing s, Colburn factor ` j' and friction factor ` f'.

  3. A new friction factor correlation for laminar, single-phase flows through rock fractures

    NASA Astrophysics Data System (ADS)

    Nazridoust, Kambiz; Ahmadi, Goodarz; Smith, Duane H.

    2006-09-01

    SummarySingle-phase flow through fractured media occurs in various situations, such as transport of dissolved contaminants through geological strata, sequestration of carbon dioxide in depleted gas reservoirs, and in primary oil recovery. In the present study, fluid flows through a rock fracture were simulated. The fracture geometry was obtained from the CT scans of a rock fracture produced by the Brazilian method in a sandstone sample. A post-processing code using a CAD package was developed and used to generate the three-dimensional fracture from the CT scan data. Several sections along the fracture were considered and the Gambit™ code was used to generate unstructured grids for flow simulations. FLUENT™ was used to analyze the flow conditions through the fracture section for different flow rates. Because of the small aperture of the fractures, the gravitational effects could be neglected. It was confirmed that the pressure drop was dominated by the smallest aperture passages of the fracture. The accuracy of parallel plate models for estimating the pressure drops through fractures was studied. It was shown that the parallel plate flow model with the use of an appropriate effective fracture aperture and inclusion of the tortuosity factor could provide reasonable estimates for pressure drops in the fracture. On the basis of the CFD simulation data, a new expression for the friction factor for flows through fractures was developed. The new model predictions were compared with the simulation results and favorable agreement was found. It was shown that when the length of the fracture and the mean and standard deviation of the fracture are known, the pressure loss as a function of the flow rate could be estimated. These findings may prove useful for design of lab experiments, computational studied of flows through real rock fractures, or inclusions in simulators for large-scale flows in highly fractured rocks.

  4. A new friction factor correlation for laminar, single-phase flows through rock fractures

    SciTech Connect

    Nazridoust, K.; Ahmadi, G.; Smith, D.H.

    2006-09-30

    Single-phase flow through fractured media occurs in various situations, such as transport of dissolved contaminants through geological strata, sequestration of carbon dioxide in depleted gas reservoirs, and in primary oil recovery. In the present study, fluid flows through a rock fracture were simulated. The fracture geometry was obtained from the CT scans of a rock fracture produced by the Brazilian method in a sandstone sample. A post-processing code using a CAD package was developed and used to generate the three-dimensional fracture from the CT scan data. Several sections along the fracture were considered and the GambitTM code was used to generate unstructured grids for flow simulations. FLUENTTM was used to analyze the flow conditions through the fracture section for different flow rates. Because of the small aperture of the fractures, the gravitational effects could be neglected. It was confirmed that the pressure drop was dominated by the smallest aperture passages of the fracture. The accuracy of parallel plate models for estimating the pressure drops through fractures was studied. It was shown that the parallel plate flow model with the use of an appropriate effective fracture aperture and inclusion of the tortuosity factor could provide reasonable estimates for pressure drops in the fracture. On the basis of the CFD simulation data, a new expression for the friction factor for flows through fractures was developed. The new model predictions were compared with the simulation results and favorable agreement was found. It was shown that when the length of the fracture and the mean and standard deviation of the fracture are known, the pressure loss as a function of the flow rate could be estimated. These findings may prove useful for design of lab experiments, computational studied of flows through real rock fractures, or inclusions in simulators for large-scale flows in highly fractured rocks.

  5. Corrosion effects on friction factors

    SciTech Connect

    Magleby, H.L.; Shaffer, S.J.

    1996-03-01

    This paper presents the results of NRC-sponsored material specimen tests that were performed to determine if corrosion increases the friction factors of sliding surfaces of motor-operated gate valves, which could require higher forces to close and open safety-related valves when subjected to their design basis differential pressures. Friction tests were performed with uncorroded specimens and specimens subjected to accelerated corrosion. Preliminary tests at ambient conditions showed that corrosion increased the friction factors, indicating the need for additional tests duplicating valve operating parameters at hot conditions. The additional tests showed friction factors of corroded specimens were 0.1 to 0.2 higher than for uncorroded specimens, and that the friction factors of the corroded specimens were not very dependent on contact stress or corrosion film thickness. The measured values of friction factors for the three corrosion films tested (simulating three operating times) were in the range of 0.3 to 0.4. The friction factor for even the shortest simulated operating time was essentially the same as the others, indicating that the friction factors appear to reach a plateau and that the plateau is reached quickly.

  6. Friction factor for isothermal and nonisothermal flow through porous media

    NASA Technical Reports Server (NTRS)

    Koh, J. C.; Dutton, J. L.; Benson, B. A.; Fortini, A.

    1977-01-01

    Measurements were performed to determine the pressure drops for gaseous flow through porous materials of different microstructures, porosities, and thickness under isothermal and nonisothermal conditions at various temperature levels. Results were satisfactorily correlated by a simple equation relating the friction factor to the Reynolds number and porosities.

  7. Friction Factor Characterization for High-Porosity Random Fiber Regenerators

    NASA Technical Reports Server (NTRS)

    Thieme, Lanny G.

    2001-01-01

    NASA Glenn Research Center, the Department of Energy (DOE), and Stirling Technology Company (STC) of Kennewick, Washington are developing a Stirling convertor for a high-efficiency Stirling Radioisotope Power System to provide electric power for NASA Space Science Missions. STC is developing the 55-We Technology Demonstration Convertor (TDC) under contract to DOE. Steady-flow tests were completed to determine the friction factor for the high-porosity regenerators that are used in the TDC. STC fabricated a flow test fixture and three random fiber regenerator test samples, one each at approximately 80, 88, and 96 percent porosities. The flow tests were then completed by the NASA Glenn Flow Calibration Laboratory, and the data reduced to Reynolds number and friction factor. The results showed that the 80 and 88 percent porosity samples had similar characteristics while the 96 percent porosity sample had significantly higher friction factors for given Reynolds numbers compared to the samples with lower porosities. Comparisons were also made between the test data and existing correlations. STC used this data to derive a modified regenerator friction factor correlation for use in the Stirling design code GLIMPS for porosities greater than 88 percent. Using this new correlation, the final optimized regenerator design porosity was reduced from 96 to 90 percent.

  8. Friction-factor characteristics for narrow channels with honeycomb surfaces

    NASA Technical Reports Server (NTRS)

    Ha, T. W.; Morrison, G. L.; Childs, D. W.

    1992-01-01

    The experimental determination of friction-factors for the flow of air in a narrow channel lined with various honeycomb geometries has been carried out. Test results show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Reynolds number increases. This phenomenon can be characterized as a 'friction-factor jump'. Further investigations of the acoustic spectrum and friction-factor measurements for a broad range of Reynolds numbers indicate that the 'friction-factor jump' phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of 10,000. The purpose of this paper is to explain the friction-factor-jump phenomenon and friction-factor characteristics.

  9. Correlation of Preston-tube data with laminar skin friction

    NASA Technical Reports Server (NTRS)

    Reed, T. D.; Abu-Mostafa, A.; Steinle, F. W., Jr.

    1982-01-01

    Preston-tube data have been obtained on a sharp ten-degree cone in the NASA Ames Eleven-Foot Transonic Wind Tunnel. Data were obtained over a Mach number range of 0.30 to 0.95 and unit Reynolds numbers of 9.84, 13.1, and 16.4 million per meter. The portions of these data, that were obtained within laminar boundary layers, have been correlated with the corresponding values of theoretical skin friction. The rms scatter of skin-friction coefficient about the correlation is of the order of one percent, which is comparable to the reported accuracy for calibrations of Preston-tubes in incompressible pipe-flows. In contrast to previous works on Preston-tube/skin-friction correlations, which are based on the physical height of the probe's face, this very satisfactory correlation for compressible boundary-layer flows is achieved by accounting for the effects of a variable 'effective' height of the probe. The coefficients, which appear in the correlation, are dependent on the particular tunnel environment. The general procedure can be used to define correlations for other wind tunnels.

  10. United Formula for the Friction Factor in the Turbulent Region of Pipe Flow.

    PubMed

    Li, Shuolin; Huai, Wenxin

    2016-01-01

    Friction factor is an important element in both flow simulations and river engineering. In hydraulics, studies on the friction factor in turbulent regions have been based on the concept of three flow regimes, namely, the fully smooth regime, the fully rough regime, and the transitional regime, since the establishment of the Nikuradze's chart. However, this study further demonstrates that combining the friction factor with Reynolds number yields a united formula that can scale the entire turbulent region. This formula is derived by investigating the correlation between friction in turbulent pipe flow and its influencing factors, i.e., Reynolds number and relative roughness. In the present study, the formulae of Blasius and Stricklerare modified to rearrange the implicit model of Tao. In addition, we derive a united explicit formula that can compute the friction factor in the entire turbulent regimes based on the asymptotic behavior of the improved Tao's model. Compared with the reported formulae of Nikuradze, the present formula exhibits higher computational accuracy for the original pipe experiment data of Nikuradze. PMID:27136099

  11. United Formula for the Friction Factor in the Turbulent Region of Pipe Flow

    PubMed Central

    Li, Shuolin; Huai, Wenxin

    2016-01-01

    Friction factor is an important element in both flow simulations and river engineering. In hydraulics, studies on the friction factor in turbulent regions have been based on the concept of three flow regimes, namely, the fully smooth regime, the fully rough regime, and the transitional regime, since the establishment of the Nikuradze’s chart. However, this study further demonstrates that combining the friction factor with Reynolds number yields a united formula that can scale the entire turbulent region. This formula is derived by investigating the correlation between friction in turbulent pipe flow and its influencing factors, i.e., Reynolds number and relative roughness. In the present study, the formulae of Blasius and Stricklerare modified to rearrange the implicit model of Tao. In addition, we derive a united explicit formula that can compute the friction factor in the entire turbulent regimes based on the asymptotic behavior of the improved Tao’s model. Compared with the reported formulae of Nikuradze, the present formula exhibits higher computational accuracy for the original pipe experiment data of Nikuradze. PMID:27136099

  12. United Formula for the Friction Factor in the Turbulent Region of Pipe Flow.

    PubMed

    Li, Shuolin; Huai, Wenxin

    2016-01-01

    Friction factor is an important element in both flow simulations and river engineering. In hydraulics, studies on the friction factor in turbulent regions have been based on the concept of three flow regimes, namely, the fully smooth regime, the fully rough regime, and the transitional regime, since the establishment of the Nikuradze's chart. However, this study further demonstrates that combining the friction factor with Reynolds number yields a united formula that can scale the entire turbulent region. This formula is derived by investigating the correlation between friction in turbulent pipe flow and its influencing factors, i.e., Reynolds number and relative roughness. In the present study, the formulae of Blasius and Stricklerare modified to rearrange the implicit model of Tao. In addition, we derive a united explicit formula that can compute the friction factor in the entire turbulent regimes based on the asymptotic behavior of the improved Tao's model. Compared with the reported formulae of Nikuradze, the present formula exhibits higher computational accuracy for the original pipe experiment data of Nikuradze.

  13. Friction

    NASA Astrophysics Data System (ADS)

    Matsuo, Yoshihiro; Clarke, Daryl D.; Ozeki, Shinichi

    Friction materials such as disk pads, brake linings, and clutch facings are widely used for automotive applications. Friction materials function during braking due to frictional resistance that transforms kinetic energy into thermal energy. There has been a rudimentary evolution, from materials like leather or wood to asbestos fabric or asbestos fabric saturated with various resins such as asphalt or resin combined with pitch. These efforts were further developed by the use of woven asbestos material saturated by either rubber solution or liquid resin binder and functioned as an internal expanding brake, similar to brake lining system. The role of asbestos continued through the use of chopped asbestos saturated by rubber, but none was entirely successful due to the poor rubber heat resistance required for increased speeds and heavy gearing demands of the automobile industry. The use of phenolic resins as binder for asbestos friction materials provided the necessary thermal resistance and performance characteristics. Thus, the utility of asbestos as the main friction component, for over 100 years, has been significantly reduced in friction materials due to asbestos identity as a carcinogen. Steel and other fibrous components have displaced asbestos in disk pads. Currently, non-asbestos organics are the predominate friction material. Phenolic resins continue to be the preferred binder, and increased amounts are necessary to meet the requirements of highly functional asbestos-free disk pads for the automotive industry. With annual automobile production exceeding 70 million vehicles and additional automobile production occurring in developing countries worldwide and increasing yearly, the amount of phenolic resin for friction material is also increasing (Fig. 14.1). Fig. 14.1 Worldwide commercial vehicle production The Friction Factor in the Forchheimer Equation for Rock Fractures

    NASA Astrophysics Data System (ADS)

    Zhou, Jia-Qing; Hu, Shao-Hua; Chen, Yi-Feng; Wang, Min; Zhou, Chuang-Bing

    2016-08-01

    The friction factor is an important dimensionless parameter for fluid flow through rock fractures that relates pressure head loss to average flow velocity; it can be affected by both fracture geometry and flow regime. In this study, a theoretical formula form of the friction factor containing both viscous and inertial terms is formulated by incorporating the Forchheimer equation, and a new friction factor model is proposed based on a recent phenomenological relation for the Forchheimer coefficient. The viscous term in the proposed formula is inversely proportional to Reynolds number and represents the limiting case in Darcy flow regime when the inertial effects diminish, whereas the inertial term is a power function of the relative roughness and represents a limiting case in fully turbulent flow regime when the fracture roughness plays a dominant role. The proposed model is compared with existing friction factor models for fractures through parametric sensitivity analyses and using experimental data on granite fractures, showing that the proposed model has not only clearer physical significance, but also better predictive performance. By accepting proper percentages of nonlinear pressure drop to quantify the onset of Forchheimer flow and fully turbulent flow, a Moody-type diagram with explicitly defined flow regimes is created for rock fractures of varying roughness, indicating that rougher fractures have a large friction factor and are more prone to the Forchheimer flow and fully turbulent flow. These findings may prove useful in better understanding of the flow behaviors in rock fractures and improving the numerical modeling of non-Darcy flow in fractured aquifers.

  14. Assessments of fluid friction factors for use in leak rate calculations

    SciTech Connect

    Chivers, T.C.

    1997-04-01

    Leak before Break procedures require estimates of leakage, and these in turn need fluid friction to be assessed. In this paper available data on flow rates through idealized and real crack geometries are reviewed in terms of a single friction factor k It is shown that for {lambda} < 1 flow rates can be bounded using correlations in terms of surface R{sub a} values. For {lambda} > 1 the database is less precise, but {lambda} {approx} 4 is an upper bound, hence in this region flow calculations can be assessed using 1 < {lambda} < 4.

  15. Measurement and correlation of friction characteristic of flow through foam matrixes

    SciTech Connect

    Liu, J.F.; Wu, W.T.; Chiu, W.C.; Hsieh, W.H.

    2006-03-01

    A correlation of friction characteristic was developed based on the measured pressure drop of air through foam matrixes. The pressure drops of seven types of aluminum foams with different porosities and pore densities were measured. The Reynolds number based on the equivalent spherical diameter of the foam ranged from 32.05 to 1289.32. The range of porosity was 0.87-0.958. A empirical equation was developed to correlate the dimensionless pressure drop with the dimensionless flow velocity for all seven types of aluminum foams. The empirical correlation agreed well with experimental data. According to the empirical correlation and the measured data, the pressure drop introduced by foam matrixes was much lower than that by granular matrixes at the same Reynolds number. The relationship between the friction factor and Re of foam matrixes follows the trend of granular matrixes and can be classified into three regimes: Re<30, f{sub k}{proportional_to}(1-{epsilon})/Re; 30300, the value of f{sub k} approaches 0.22. (author)

  16. Contribution of velocity-vorticity correlations to the frictional drag in wall-bounded turbulent flows

    NASA Astrophysics Data System (ADS)

    Yoon, Min; Ahn, Junsun; Hwang, Jinyul; Sung, Hyung Jin

    2016-08-01

    The relationship between the frictional drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The frictional drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the frictional drag.

  17. Tripping Effects on the Friction Factor in Turbulent Pipe Flows

    NASA Astrophysics Data System (ADS)

    Al-Salaymeh, A.; Bayoumi, O. A.; Durst, F.; Gad-El-Hak, M.

    2004-11-01

    Tripping devices are usually installed at the entrance of laboratory-scale pipe test sections to obtain a fully developed turbulent flow sooner. The tripping of laminar flow to induce turbulence can be carried out in different ways, such as using cylindrical wires, sand papers, well-organized tape letters, fences, etc. Claims of tripping effects have been made periodically since the classical experiments of Nikuradse (1932), which covered a significant range of Reynolds numbers. NikuradseÂ's data have become the metric by which theories are established, and have also been the subject of intense scrutiny. Several subsequent experiments reported friction factors as much as 5% lower than those measured by Nikuradse, and the authors of those reports attributed the difference to tripping effects. In the present study, measurements with and without ring tripping devices of different blocking areas of 10%, 20%, 30% and 40% have been carried out to determine the effect of entrance condition on the developing flow field in pipes. Along with pressure drop measurements to compute the skin friction, both Pitot tube and hot-wire anemometry measurements have been used to accurately determine the mean velocity profile over the working test section at different Reynolds numbers in the range of 1× 10^5--4.5 × 10^5. The results we obtained suggest that the tripping technique has an insignificant effect on the wall friction factor, in agreement with Nikuradse's original data.

  18. Program helps friction factor for non-Newtonian fluid flow

    SciTech Connect

    Ohen, H.A. )

    1989-01-02

    A Fortran program has been developed that gives more accurate predictions for shear rates, effective viscosity, Reynold's number, and hence the friction factor from which frictional pressure losses for flowing non-Newtonian fluids can be obtained. The method presented can handle flow in smooth pipes, transition, and fully rough zones of turbulence. Two mathematical models, namely the power law and the Bingham have been widely used with drilling fluids and cement slurries for relating shear stress to shear rate, the most popular being Bingham. However, most non-Newtonian fluids are not correctly represented by either of these models. In fact, experience has shown that the consistency curves of most non-Newtonian fluids fall in between those predicted by these models.

  19. Correlation of ideal and actual shear strengths of metals with their friction properties

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1981-01-01

    The relation between the ideal and actual shear strengths and friction properties of clean metals in contact with clean diamond, boron nitride, silicon carbide, manganese-zinc ferrite, and the metals themselves in vacuum is discussed. An estimate of the ideal shear strength for metals is obtained from the shear modulus, the repeat distance of atoms in the direction of shear of the metal, and the interplanar spacing of the shearing planes. The coefficient of friction for metals is shown to be correlated with both the ideal and actual shear strength of metals. The higher the strength of the metal, the lower the coefficient of friction occurs.

  1. Influence of molecular weight on friction force microscopy of polystyrene and poly(methyl methacrylate) films: correlation between coefficient of friction and chain entanglement.

    PubMed

    Whittle, Tracie J; Leggett, Graham J

    2009-02-17

    The frictional properties of spun-cast films of polystyrene and poly(methyl methacrylate) (PMMA) have been characterized using friction force microscopy (FFM). In air, the friction-load relationship was found to obey Johnson-Kendall-Roberts mechanics, but under ethanol, it was found to fit Amontons' Law. The coefficient of friction measured under ethanol was found to increase with increasing molecular weight, up to a molecular weight close to the bulk critical molecular weight for entanglement. At greater values than this, the coefficient of friction changed comparatively little with molecular weight. It is suggested that at molecular weights below Mc, the frictional interaction is dominated by plowing of the tip between polymer molecules; as molecular weight increases, so the viscosity of the film increases and the coefficient of friction increases. After the onset of entanglement, the mechanism of energy dissipation changes to one in which the tip sticks in loops of polymer between entanglements, extending the chains until at a critical stress, the contact is broken. The frictional interaction is thus comparatively invariant with molecular weight. FFM was also used to investigate the kinetics of the UV-induced modification of PMMA. A progressive decrease in the coefficient of friction was observed as a function of the time that the film was exposed to UV light, a result which was correlated to a gradual reduction in the molecular weight of the polymer and, hence, the entanglement density of the system.

  2. Experimental, numerical and analytical studies of abrasive wear: correlation between wear mechanisms and friction coefficient

    NASA Astrophysics Data System (ADS)

    Mezlini, Salah; Zidi, M.; Arfa, H.; Ben Tkaya, Mohamed; Kapsa, Philippe

    2005-11-01

    The transport of granular material often generates severe damage. Understanding the correlation between the friction coefficient, particle geometry and wear mechanisms is of primary importance for materials undergoing abrasive wear. The aim of this study is to investigate the effect of particle geometry on wear mechanisms and the friction coefficient. Numerical and analytical simulations and experimental results have been compared. The process to be studied is the scratch made by a rigid cone with different attack angles on a 5xxx aluminium alloy (Al-Mg) flat surface. A scratch test was used and the wear mechanisms were observed for different attack angles. A numerical study with a finite element code was made in order to understand the effect of attack angle on the friction coefficient. The contact surface and the friction coefficient were also studied, and the results compared to the Bowden and Tabor model. The superposition of the numerical, analytical and experimental results showed a better correlation between the wear mechanisms and the friction coefficient. It also showed the importance of the model hypothesis used to simulate the scratch phenomenon. To cite this article: S. Mezlini et al., C. R. Mecanique 333 (2005).

  3. Correlations to predict frictional pressure loss of hydraulic-fracturing slurry in coiled tubing

    SciTech Connect

    Shah, S.; Zhoi, Y.X.; Bailey, M.; Hernandez, J.

    2009-08-15

    Compared with conventional-tubing fracturing, coiled-tubing (CT) fracturing has several advantages. CT fracturing has become an effective stimulation technique for multizone oil and gas wells. It is also an attractive production-enhancement method for multiseam coalbed-methane wells, and wells with bypassed zones. The excessive frictional pressure loss through CT has been a concern in fracturing. The small diameter of the string limits the cross-sectional area open to flow. Furthermore, the tubing curvature causes secondary flow and results in extra flow resistance. This increased frictional pressure loss results in high surface pumping pressure. The maximum possible pump rate and sand concentration, therefore, have to be reduced. To design a CT fracturing job properly, it is essential to predict the frictional pressure loss through the tubing accurately. This paper presents correlations for the prediction of frictional pressure loss of fracturing slurries in straight tubing and CT. They are developed on the basis of full-scale slurry-flow tests with 11/2-in. CT and slurries prepared with 35 lbm/1,000 gal of guar gel. The extensive experiments were conducted at the full-scale CT-flow test facility. The proposed correlations have been verified with the experimental data and actual field CT-fracturing data. Case studies of wells recently fractured are provided to demonstrate the application of the correlations. The correlations will be useful to the CT engineers in their hydraulics design calculations.

  4. Correlation of subjective slipperiness judgements with quantitative COF (Coefficient Of Friction) measurements for structural steel

    NASA Astrophysics Data System (ADS)

    Purswell, Jerry L.; Schlegel, Robert E.

    1988-06-01

    When there is no simple or accurate procedure for measuring the coefficient of friction (COF) at a job site, workers and/or supervisors involved must make subjective judgments about the slipperiness of the walking and climbing surfaces and in turn decide whether the surface presents a safe or an unsafe condition for work. This project was designed to determine whether these subjective judgment calls did in fact agree with the COF measurements obtained using a mechanical device. It was noted that the coatings chosen for study were subject to a polishing factor by the boot soles during the trials, causing the COF values to become lower as the trials continued. Poor correlation was obtained between subjective ratings of slipperiness and the COF values measured before the trials began. A relatively high correlation was obtained between subjective ratings and the COF values measured after the trials had been completed. A difference was noted in the subjective ratings for the effects of water on a coating for column climbing, but not for walking a beam, suggesting the effects of water on a coating are related to the type of task being performed in steel erection. An increase in the measured COF was noted for all of the coatings when they were wet as compared to the dry condition. The importance of clean shoe soles was clearly demonstrated.

  5. Friction factor data for flat plate tests of smooth and honeycomb surfaces. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Ha, Tae Woong

    1989-01-01

    Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.

  6. Friction-factor data for flat-plate tests of smooth and honeycomb surfaces

    NASA Technical Reports Server (NTRS)

    Ha, T. W.; Childs, Dara W.

    1992-01-01

    Friction factors for honeycomb surfaces were measured with a flat plate tester. The flat plate test apparatus was described and a method was discussed for determining the friction factor experimentally. The friction factor model was developed for the flat plate test based on the Fanno Line Flow. The comparisons of the friction factor were plotted for smooth surfaces and six-honeycomb surfaces with three-clearances, 6.9 bar to 17.9 bar range of inlet pressures, and 5,000 to 100,000 range of the Reynolds number. The optimum geometries for the maximum friction factor were found as a function of cell width to cell depth and cell width to clearance ratios.

  7. Correlation of Preston-tube data with laminar skin friction (Log No. J12984)

    NASA Technical Reports Server (NTRS)

    Reed, T. D.; Abu-Mostafa, A.; Steinle, F. W., Jr.

    1982-01-01

    Preston tube data within laminar boundary layers obtained on a sharp ten-degree cone in the NASA Ames eleven-foot transonic wind tunnel are correlated with the corresponding values of theoretical skin friction. Data were obtained over a Mach number range of 0.30 to 0.95 and unit Reynolds numbers of 9.84, 13.1, and 16.4 million per meter. The rms scatter of skin friction coefficient about the correlation is of the order of one percent, which is comparable to the reported accuracy for calibrations of Preston tubes in incompressible pipe flows. In contrast to previous works on Preston tube/skin friction correlations, which are based on the physical height of the probe's face, this satisfactory correlation for compressible boundary layer flows is achieved by accounting for the effects of a variable "effective" height of the probe. The coefficients, which appear in the correlation, are dependent on the particular tunnel environment. The general procedure can be used to define correlations for other wind tunnels.

  8. Friction Factor for Flow in Rectangular Ducts with One Side Rib-Roughened

    NASA Technical Reports Server (NTRS)

    Youn, B.; Yuen, C.; Mills, A. F.

    1994-01-01

    Numerical simulations of incompressible turbulent flow through rectangular ducts with one side rib-roughened were performed to determine pressure drop. The "PHOENICS " software package was used for the computations, which required provision of a wall function for transverse rib-roughened surfaces. The present study was conducted in the range of 10(exp 5) less than or equal to Reynolds number less than or equal to 10(exp 7), 0.01 less than or equal to rib height to hydraulic diameter ratio less than or equal to 0.04, 10 less than or equal to pitch to rib height ratio less than or equal to 40. Using the numerical results, friction factor charts for various aspect ratios were generated. The numerical results agreed well with experimental data that was obtained for 10(exp 5) less than Reynolds less than 2 x 10(exp 5). In addition, a scheme for predicting friction factor using existing correlations for smooth and rough walls was developed.

  9. Friction Factor Evaluation Using Experimental and Finite Element Methods for Al-4%Cu Preforms

    NASA Astrophysics Data System (ADS)

    Desalegn, Wogaso; Davidson, M. J.; Khanra, A. K.

    2014-08-01

    In this study, ring compression tests and finite element (FE) simulations have been utilized to evaluate the friction factor, m, under different lubricating conditions for powder metallurgical (P/M) Al-4%Cu preforms. A series of ring compression tests were carried out to obtain friction factor ( m) for a number of lubricating conditions, including zinc stearate, graphite, molybdenum disulfide powder, and unlubricated condition. FE simulations were used to analyze materials deformation, densification, and geometric changes, and to derive the friction calibration curves. The friction factor has been determined for various initial relative densities and different lubricating conditions, and a proper lubricant for cold forging of P/M Al-4%Cu preforms is found. Studies show that the use of lubricants has reduced the friction. However, increase in the number of pores in the preforms leads to excessive friction. The FE simulation results demonstrate a shift in the neutral plane distance from the axis of ring specimen, which occurred due to variations in the frictional conditions and initial relative densities. The load requirement for deformation, effective stress, and effective strain induced, and bulging phenomena obtained by FE simulations have a good agreement with the experimental data.

  10. Entrance and exit region friction factor models for annular seal analysis. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Elrod, David Alan

    1988-01-01

    The Mach number definition and boundary conditions in Nelson's nominally-centered, annular gas seal analysis are revised. A method is described for determining the wall shear stress characteristics of an annular gas seal experimentally. Two friction factor models are developed for annular seal analysis; one model is based on flat-plate flow theory; the other uses empirical entrance and exit region friction factors. The friction factor predictions of the models are compared to experimental results. Each friction model is used in an annular gas seal analysis. The seal characteristics predicted by the two seal analyses are compared to experimental results and to the predictions of Nelson's analysis. The comparisons are for smooth-rotor seals with smooth and honeycomb stators. The comparisons show that the analysis which uses empirical entrance and exit region shear stress models predicts the static and stability characteristics of annular gas seals better than the other analyses. The analyses predict direct stiffness poorly.

  11. Structure-Property Correlation of AA2014 Friction Stir Welds: Role of Tool Pin Profile

    NASA Astrophysics Data System (ADS)

    Ramanjaneyulu, K.; Madhusudhan Reddy, G.; Venugopal Rao, A.; Markandeya, R.

    2013-08-01

    The influence of rapid plastic deformation in the generation of welding heat during friction stir welding (FSW), supplementing the frictional heat generation by the tool shoulder, forms the thrust of the present investigation. Several researchers have highlighted the role of tool shoulder in the generation of frictional heat and suggested that the tool-material interface friction as the sole mechanism for heating. The configuration of tool pin profile is seldom studied for its contribution to welding heat through rapid plastic deformation at high strain rates (103/s), especially while welding thick plates. An attempt has been made to understand the dependence of deformation heat generation with different tool pin profiles in welding 5 mm thick AA2014-T6 aluminum alloy, maintaining the same swept volume during the tool rotation. An attempt has also been made to correlate the influence of process response variables such as force and torque acting on the tool pin. To quantify the physical influence of tool pin profile, temperature measurements were made in the region adjacent to the rotating pin, close to nugget in the thermo-mechanically affected zone (TMAZ). It has been observed that the temperature rises at a relatively rapid rate in the case of hexagonal tool pin compared to the welds produced employing other tool pin profiles. It is observed that during FSW, extensive deformation experienced at the nugget zone and the evolved microstructure strongly influences the mechanical properties of the joint. The present study is also aimed at understanding the influence of tool profile on the microstructural changes and the associated mechanical properties. Transverse tensile samples failed at the nugget/TMAZ boundary due to localized softening. Hexagonal tool pin profile welds have shown higher tensile strength, low TMAZ width, and high nugget hardness compared to other tool pin profile welds.

  12. Correlation between contact surface and friction during the optical glass polishing

    NASA Astrophysics Data System (ADS)

    Belkhir, N.; Aliouane, T.; Bouzid, D.

    2014-01-01

    This study aims to determine the correlation between the contact surface, the polishing pressure and the friction coefficient during the optical glass polishing. For this purpose, BK7 optical glass samples were polished and the mentioned parameters were measured to find a correlation between them. Several methods of characterization have been used; the mechanical profilometer, the AFM, and in addition setups for measuring forces and the contact surface have been developed and adapted to the polishing machine. The found results have shown the existence of a close relationship between the three parameters and the influence of each other. This have allowed to deduce that during the polishing process it is very important to control the contact pressure and the polisher form according to the pressure distribution in order to guarantee a very high quality of the polished surface.

  13. Correlation of transonic-cone preston-tube data and skin friction

    NASA Technical Reports Server (NTRS)

    Abu-Mostafa, A. S.; Reed, T. D.

    1984-01-01

    Preston-tube measurements obtained on the Arnold Engineering Development Center (AEDC) Transition Cone have been correlated with theoretical skin friction coefficients in transitional and turbulent flow. This has been done for the NASA Ames 11-Ft Transonic Wind Tunnel (11 TWT) and flight tests. The developed semi-empirical correlations of Preston-tube data have been used to derive a calibration procedure for the 11 TWT flow quality. This procedure has been applied to the corrected laminar data, and an effective freestream unit Reynolds number is defined by requiring a matching of the average Preston-tube pressure in flight and in the tunnel. This study finds that the operating Reynolds number is below the effective value required for a match in laminar Preston-tube data. The distribution of this effective Reynolds number with Mach number correlates well with the freestream noise level in this tunnel. Analyses of transitional and turbulent data, however, did not result in effective Reynolds numbers that can be correlated with background noise. This is a result of the fact that vorticity fluctuations present in transitional and turbulent boundary layers dominate Preston-tube pressure fluctuations and, therefore, mask the tunnel noise eff ects. So, in order to calibrate the effects of noise on transonic wind tunnel tests only laminar data should be used, preferably at flow conditions similar to those in flight tests. To calibrate the effects of transonic wind-tunnel noise on drag measurements, however, the Preston-tube data must be supplemented with direct measurements of skin friction.

  14. Investigations of rough surface effects on friction factors in turbulent pipe flow

    NASA Astrophysics Data System (ADS)

    Taylor, Robert P.; Coleman, Hugh W.; Scaggs, W. F.

    1988-02-01

    The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a discrete element roughness model which had been developed previously. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for eleven different rough surfaces, nine of which had uniform roughness elements and two of which were roughened nonuniformly. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data for both the uniform and nonuniform roughness cases.

  15. Measurement and prediction of rough wall effects on friction factor - Uniform roughness results

    NASA Astrophysics Data System (ADS)

    Scaggs, W. F.; Taylor, Robert P.; Coleman, Hugh W.

    The results of an experimental investigation of the effects of surface roughness on turbulent pipe flow friction factors are presented and compared with predictions from a previously published discrete element roughness model. Friction factor data were acquired over a pipe Reynolds number range from 10,000 to 600,000 for nine different uniformly rough surfaces. These surfaces covered a range of roughness element sizes, spacings and shapes. Predictions from the discrete element roughness model were in very good agreement with the data.

  16. An annular gas seal analysis using empirical entrance and exit region friction factors

    NASA Technical Reports Server (NTRS)

    Elrod, D. A.; Childs, D. W.; Nelson, C. C.

    1990-01-01

    Wall shear stress results from stationary-rotor flow tests of five annular gas seals are used to develop entrance and exit region friction factor models. The friction factor models are used in a bulk-flow seal analysis which predicts leakage and rotor-dynamic coefficients. The predictions of the analysis are compared to experimental results and to the predictions of Nelson's analysis (1985). The comparisons are for smooth-rotor seals with smooth and honeycomb-stators. The present analysis predicts the destabilizing cross-coupled stiffness of a seal better than Nelson's analysis. Both analyses predict direct damping well and direct stiffness poorly.

  17. Heat transfer and friction factors in the ribbed square convergent and divergent channels

    NASA Astrophysics Data System (ADS)

    Lee, M. S.; Ahn, S. W.

    2016-06-01

    Heat transfer and friction factors are reported for the measurements of turbulent flows in the convergent and divergent square channels with one-sided ribbed wall as well as two opposite in-line ribbed walls. The study covers three different hydraulic diameter ratios between inlet and exit at the test section such as Dho/Dhi = 0.75, 1.0, and 1.33 and Reynolds numbers in the range of 25,000-79,000. The channels, composing of ten isolated copper sections in the length of test section of 1 m, have the hydraulic diameter of 87.5 mm for the straight channel (Dho/Dhi = 1.0); the rib height-to-hydraulic diameter is 0.114; the rib pitch-to-height ratio equals 10. On the contrary to public opinion that the friction factor depends on the portion of the ribbed area, the total friction factor in the two opposite ribbed walls are lower than in the one-sided ribbed wall in the divergent channel of Dho/Dhi = 1.33 because the total pressure, summing positive dynamic and negative static pressures, is acted. The results show that the two opposite ribbed divergent channel of Dho/Dhi = 1.33 provides the best heat transfer enhancement and the two opposite ribbed convergent channel of Dho/Dhi = 0.75 provides the worst friction factor enhancement, and the ribbed divergent channels are generally recommended.

  18. Friction factor for turbulent flow in rough pipes from Heisenberg's closure hypothesis.

    PubMed

    Calzetta, Esteban

    2009-05-01

    We show that the main results of the analysis of the friction factor for turbulent pipe flow reported by Gioia and Chakraborty [Phys. Rev. Lett. 96, 044502 (2006)] can be recovered by assuming the Heisenberg closure hypothesis for the turbulent spectrum. This highlights the structural features of the turbulent spectrum underlying the analysis of Gioia and Chakraborty.

  19. Surface-specific flow factors for prediction of friction of cross-hatched surfaces

    NASA Astrophysics Data System (ADS)

    Leighton, M.; Rahmani, R.; Rahnejat, H.

    2016-06-01

    The paper presents a combined numerical and experimental study of generated sliding friction at low sliding speeds and high load intensity, typical of the top compression ring-cylinder liner conjunction at top dead centre in the compression stroke of high performance race engines. Frictional losses in the transition from compression to power stroke represent a significant portion of cyclic cylinder losses. The cylinder liner is cross-hatch honed with non-Gaussian topography, including larger groove features and a fairly smooth plateau roughness. Surface-specific flow factors are derived to closely represent the actual real rough conjunction. The predictions closely agree with the representative reported precision tribometric study of measured friction.

  20. Biomechanical risk factors and flexor tendon frictional work in the cadaveric carpal tunnel.

    PubMed

    Kociolek, Aaron M; Tat, Jimmy; Keir, Peter J

    2015-02-01

    Pathological changes in carpal tunnel syndrome patients include fibrosis and thickening of the subsynovial connective tissue (SSCT) adjacent to the flexor tendons in the carpal tunnel. These clinical findings suggest an etiology of excessive shear-strain force between the tendon and SSCT, underscoring the need to assess tendon gliding characteristics representative of repetitive and forceful work. A mechanical actuator moved the middle finger flexor digitorum superficialis tendon proximally and distally in eight fresh frozen cadaver arms. Eighteen experimental conditions tested the effects of three well-established biomechanical predictors of injury, including a combination of two wrist postures (0° and 30° flexion), three tendon velocities (50, 100, 150mm/sec), and three forces (10, 20, 40N). Tendon gliding resistance was determined with two light-weight load cells, and integrated over tendon displacement to represent tendon frictional work. During proximal tendon displacement, frictional work increased with tendon velocity (58.0% from 50-150mm/sec). There was a significant interaction between wrist posture and tendon force. In wrist flexion, frictional work increased 93.0% between tendon forces of 10 and 40N. In the neutral wrist posture, frictional work only increased 33.5% (from 10-40N). During distal tendon displacement, there was a similar multiplicative interaction on tendon frictional work. Concurrent exposure to multiple biomechanical work factors markedly increased tendon frictional work, thus providing a plausible link to the pathogenesis of work-related carpal tunnel syndrome. Additionally, our study provides the conceptual basis to evaluate injury risk, including the multiplicative repercussions of combined physical exposures. PMID:25553671

  1. Biomechanical risk factors and flexor tendon frictional work in the cadaveric carpal tunnel.

    PubMed

    Kociolek, Aaron M; Tat, Jimmy; Keir, Peter J

    2015-02-01

    Pathological changes in carpal tunnel syndrome patients include fibrosis and thickening of the subsynovial connective tissue (SSCT) adjacent to the flexor tendons in the carpal tunnel. These clinical findings suggest an etiology of excessive shear-strain force between the tendon and SSCT, underscoring the need to assess tendon gliding characteristics representative of repetitive and forceful work. A mechanical actuator moved the middle finger flexor digitorum superficialis tendon proximally and distally in eight fresh frozen cadaver arms. Eighteen experimental conditions tested the effects of three well-established biomechanical predictors of injury, including a combination of two wrist postures (0° and 30° flexion), three tendon velocities (50, 100, 150mm/sec), and three forces (10, 20, 40N). Tendon gliding resistance was determined with two light-weight load cells, and integrated over tendon displacement to represent tendon frictional work. During proximal tendon displacement, frictional work increased with tendon velocity (58.0% from 50-150mm/sec). There was a significant interaction between wrist posture and tendon force. In wrist flexion, frictional work increased 93.0% between tendon forces of 10 and 40N. In the neutral wrist posture, frictional work only increased 33.5% (from 10-40N). During distal tendon displacement, there was a similar multiplicative interaction on tendon frictional work. Concurrent exposure to multiple biomechanical work factors markedly increased tendon frictional work, thus providing a plausible link to the pathogenesis of work-related carpal tunnel syndrome. Additionally, our study provides the conceptual basis to evaluate injury risk, including the multiplicative repercussions of combined physical exposures.

  2. Tensile Strength and Hardness Correlations with Microscopy in Friction welded Aluminium to Copper

    NASA Astrophysics Data System (ADS)

    Satish, Rengarajan; Seshagiri Rao, Vaddi; Ananthapadmanaban, Dattaguru; Ravi, Balappa

    2016-01-01

    Aluminium and copper are good conductors of heat and electricity, copper being the better conductor, is a costly metal indeed. On the other hand, aluminium is cheap, easily available and also has a lower density than copper. Hence, worldwide efforts are being made to partially replace copper wire. Solid state welding should be used to join aluminium to copper. This is because the use of fusion welding results in brittle phases formed in the weld interface. One of the solid state welding techniques used for joining aluminium to copper is friction welding. In this paper, an attempt has been made to join aluminium to copper by friction welding by varying the friction welding parameters, namely friction pressure, upset pressure, burn-off length and speed of rotation of the workpiece. Nine different friction welding parameter combinations were used during welding in accordance with ASTM standards and results have been reported. Tensile strength and hardness tests were carried out for each parameter combination. Optimum friction welding parameter combination was identified with respect to tensile strength. Scanning Electron Microscopy and Electron dispersive spectroanalysis were obtained to identify modes of fracture and presence of intermetallic phases for each friction welding combination with the aim to narrow down friction welding parameters that give good properties on the whole.

  3. Internal friction Q factor measurements in lunar rocks

    NASA Technical Reports Server (NTRS)

    Tittmann, B. R.

    1977-01-01

    Investigations to aid in the interpretation of seismic data obtained below the lunar surface are reported. Fine grained basalt with about 1.0% open core porosity was encapsulated under hard vacuum and measured. A Q value just under 2,000 at 0.5 kbar was achieved for a terrestrial analog of lunar basalt. In contrast to the modulus which increases by as much as 10%, the quality factor Q shows little or no change with pressure (a well outgassed sample maintains a high Q, whereas one exposed to laboratory atmosphere maintains a low Q). This result suggests that the absence of volatiles plays an important role in determining the q factor even at a depth of 10 km below the lunar surface.

  4. Heat Transfer and Friction-Factor Methods Turbulent Flow Inside Pipes 3d Rough

    1994-01-21

    Three-dimensional roughened internally enhanced tubes have been shown to be one of the most energy efficient for turbulent, forced convection applications. However, there is only one prediction method presented in the open literature and that is restricted to three-dimensional sand-grain roughness. Other roughness types are being proposed: hemispherical sectors, truncated cones, and full and truncated pyramids. There are no validated heat-transfer and friction-factor prediction methods for these different roughness shapes that can be used inmore » the transition and fully rough region. This program calculates the Nusselt number and friction factor values, for a broad range of three-dimensional roughness types such as hemispherical sectors, truncated cones, and full and truncated pyramids. Users of this program are heat-exchangers designers, enhanced tubing suppliers, and research organizations or academia who are developing or validating prediction methods.« less

  5. Friction factor of two-dimensional rough-boundary turbulent soap film flows.

    PubMed

    Guttenberg, Nicholas; Goldenfeld, Nigel

    2009-06-01

    We use momentum-transfer arguments to predict the friction factor f in two-dimensional turbulent soap film flows with rough boundaries (an analog of three-dimensional pipe flow) as a function of Reynolds number Re and roughness r , considering separately the inverse energy cascade and the forward enstrophy cascade. At intermediate Re, we predict a Blasius-like friction factor scaling of f proportional, variant Re{-1/2} in flows dominated by the enstrophy cascade, distinct from the energy cascade scaling of Re{-1/4} . For large Re, f approximately r in the enstrophy-dominated case. We use conformal map techniques to perform direct numerical simulations that are in satisfactory agreement with theory and exhibit data collapse scaling of roughness-induced criticality, previously shown to arise in the three-dimensional pipe data of Nikuradse.

  6. Correlation of Fracture Behavior With Microstructure in Friction Stir Welded, and Spin Formed AI-Li 2195 Domes

    NASA Technical Reports Server (NTRS)

    Tayon, Wesley A.; Domack, Marcia S.; Hales, Stephen J.

    2012-01-01

    Single-piece, spin-formed domes manufactured from friction stir welded (FSW) plates of Al-Li alloy 2195 have the potential to reduce the cost of fabricating cryogenic propellant tanks. Mechanical properties in the completed domes can be related directly to the final material condition and the microstructures developed. However, these new fabrication techniques have resulted in unexpected material challenges, such as abnormal grain growth in the weld nugget and the propensity for fracture in the adjacent thermo-mechanically affected zone (TMAZ). In this study, the microstructure and texture transformations within the TMAZ are related to fracture location in the vicinity of the weldment. The texture variations in the TMAZ are caused primarily by the varying amounts of shear deformation introduced during the FSW process. Grain morphology and microtexture characteristics are examined as a function of location in the TMAZ via electron backscatter diffraction (EBSD). A strong correlation between fracture location and the presence of texture banding in the TMAZ is observed. The fracture path tends to follow a distinct region of low Taylor Factor (TF) grains.

  7. Correlation of tensile and shear strengths of metals with their friction properties

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1982-01-01

    The relation between the theoretical tensile and the shear strengths and the friction properties of metals in contact with diamond, boron nitride, silicon carbide, manganese-zinc ferrite, and the metals themselves in vacuum was investigated. The relationship between the actual shear strength and the friction properties of the metal was also investigated. An estimate of the theoretical uniaxial tensile strength was obtained in terms of the equilibrium surface energy, interplanar spacing of the planes perpendicular to the tensile axis, and the Young's modulus of elasticity. An estimate of the theoretical shear strength for metals was obtained from the shear modulus, the repeat distance of atoms in the direction of shear of the metal and the interplanar spacing of the shear planes. The coefficient of friction for metals was found to be related to the theoretical tensile, theoretical shear, and actual shear strengths of metals. The higher the strength of the metal, the lower the coefficient of friction.

  8. CFD analysis of heat transfer and friction factor charaterstics in a circular tube fitted with horizontal baffles twisted tape inserts

    NASA Astrophysics Data System (ADS)

    Salman, Sami D.; Kadhum, Abdul Amir H.; Takriff, Mohd S.; Bakar Mohamad, Abu

    2013-12-01

    Swirl/vortex flow generator is an important form of passive augmentation techniques. Twisted-tape is one of the most important members of this form which is used extensively in different type heat exchangers. This paper reports the effect of twisted tape inserts on heat transfer and friction factor characteristics in circular tube under constant heat flux and laminar flow conditions using CFD simulation. Plain twisted tape inserts with twist ratios (y = 2.93, 3.91) and baffled twisted tape inserts with twist ratio (y = 2.93) have been used for the simulation using Fluent version 6.3.26. The results obtained by simulation matched with the literature correlations for plain tube with the discrepancy of less than ± 8% for Nusselt number and ± 6.25% for friction factor. The results have also revealed that the heat transfer in term of the Nusselt number enhanced with increases of Reynolds number, decreases of twist ratio and baffle insert. Among the various twist ratios, the twisted tape with twist ratio of y=2.93 and baffle is offered a maximum heat transfer enhancement.

  9. Exploring factors affecting measurements of the static coefficient of friction: An application of fractional factorial experiment design

    NASA Astrophysics Data System (ADS)

    Folkerts, Timothy J.

    2004-10-01

    The common undergraduate experiment for determining the static coefficient of friction between a wooden block and a horizontal tabletop often produces inconsistent results. We show how several factors influence the measured magnitude and consistency of the coefficient of friction. We utilize a fractional factorial experimental design, which is a method that has been specifically developed to effectively and efficiently uncover key factors that most strongly influence experimental results.

  10. Factor Analysis of the Image Correlation Matrix.

    ERIC Educational Resources Information Center

    Kaiser, Henry F.; Cerny, Barbara A.

    1979-01-01

    Whether to factor the image correlation matrix or to use a new model with an alpha factor analysis of it is mentioned, with particular reference to the determinacy problem. It is pointed out that the distribution of the images is sensibly multivariate normal, making for "better" factor analyses. (Author/CTM)

  11. Single-Phase, Turbulent Heat-Transfer Friction-Factor Data Base Flow Enhanced Tb

    1994-01-21

    Heat-exchanger designers need to know what type of performance improvement can be obtained before they will consider enhanced tubes. In particular, they need access to the heat-transfer coefficients and friction-factor values of enhanced tube types that are commercially available. To compile these data from the numerous publications and reports in the open literature is a formidable task that can discourage the designer from using them. A computer program that contains a comprehensive data base withmore » a search feature would be a handy tool for the designer to obtain an estimate of the performance improvement that can be obtained with a particular enhanced tube geometry. In addition, it would be a valuable tool for researchers who are developing and/or validating new prediction methods. This computer program can be used to obtain friction-factor and/or heat-transfer data for a broad range of internally enhanced tube geometries with forced-convective turbulent flow. The program has search features; that is the user can select data for tubes with a particular enhancement geometry range or data obtained from a particular source or publication. The friction factor data base contains nearly 5,000 points and the heat-transfer data base contains more than 4,700 points. About 360 different tube geometries are included from the 36 different sources. Data for tubes with similar geometries and the same and/or different types can be easily extracted with the sort feature of this data base and compared. Users of the program are heat-exchanger designers, enhanced tubing suppliers, and research organizations or academia who are developing or validating prediction methods.« less

  12. The influence of void fraction on the submerged perforated sheet hydraulic friction factor

    NASA Astrophysics Data System (ADS)

    Blinkov, V. N.; Elkin, I. V.; Emelianov, D. A.; Melikhov, V. I.; Melikhov, O. I.; Nerovnov, A. A.; Nikonov, S. M.; Parfenov, Yu. V.

    2015-07-01

    The results from an experimental investigation of two-phase flow motion through a submerged perforated sheet (SPS) obtained at the Elektrogorsk Research Center test facility are presented. The test facility, the test section of which is a transverse "cutout" from the full-scale PGV-1000 steam generator with the models of vessel internals, is described in detail. The procedure for carrying out trial startups is outlined, and the system of instrument and control devices is described. The SPS used in all experimental modes of operation had the perforation ratio (the hole area to the sheet area ratio) equal to 5.7%. The pressure in the system was around 7 MPa, and the flow rate of supplied steam was varied from 4.23 to 7.94 t/h, which corresponded to the steam velocity at the evaporation surface equal to 0.15-0.29 m/s. Distributions of pressure difference across the SPS and void fractions under the SPS and above it are obtained. The SPS hydraulic friction factor for a two-phase flow is determined as a result of processing the experimental data. A correction for two-phase nature of the flow for the SPS operating conditions is determined by comparing the obtained SPS hydraulic friction factor for a two-phase flow with the SPS hydraulic friction factor to single-phase flow of steam. It is shown that this correction can be either greater than unity (at low void fractions) or less than unity (at high void fractions).

  13. Apparatus for measuring internal friction Q factors in brittle materials. [applied to lunar samples

    NASA Technical Reports Server (NTRS)

    Tittmann, B. R.; Curnow, J. M.

    1976-01-01

    A flexural analog of the torsion pendulum for measuring the Young's modulus and the internal friction Q factor of brittle materials has been developed for Q greater than 10 to the 3rd measurements at a zero static stress and at 10 to the -7th strains of brittle materials in the Hz frequency range. The present design was motivated by the desire to measure Q in fragile lunar return samples at zero static stress to shed light on the anomalously low attenuation of seismic waves on the moon. The use of the apparatus is demonstrated with data on fused silica and on a terrestrial analog of lunar basalt.

  14. Refinement of the dependences of the contact friction stresses in the deformation zone during cold rolling on the technological factors

    NASA Astrophysics Data System (ADS)

    Garber, E. A.; Yagudin, I. V.; Traino, A. I.

    2013-07-01

    The regression equation used to calculate the friction coefficient between a strip and rolls in the working stands of cold-rolling mills is refined using a database containing 580 friction coefficients. The reliability of this equation and the importance of the factors entering into it are proved by mathematical statistics methods. As compared to the calculations performed by alternative equations, the calculation of the rolling force by the refined formula decreases the difference between the calculated and experimental results more than twofold.

  15. Prediction of friction factor of pure water flowing inside vertical smooth and microfin tubes by using artificial neural networks

    NASA Astrophysics Data System (ADS)

    Çebi, A.; Akdoğan, E.; Celen, A.; Dalkilic, A. S.

    2016-06-01

    An artificial neural network (ANN) model of friction factor in smooth and microfin tubes under heating, cooling and isothermal conditions was developed in this study. Data used in ANN was taken from a vertically positioned heat exchanger experimental setup. Multi-layered feed-forward neural network with backpropagation algorithm, radial basis function networks and hybrid PSO-neural network algorithm were applied to the database. Inputs were the ratio of cross sectional flow area to hydraulic diameter, experimental condition number depending on isothermal, heating, or cooling conditions and mass flow rate while the friction factor was the output of the constructed system. It was observed that such neural network based system could effectively predict the friction factor values of the flows regardless of their tube types. A dependency analysis to determine the strongest parameter that affected the network and database was also performed and tube geometry was found to be the strongest parameter of all as a result of analysis.

  16. Friction and anchorage loading revisited.

    PubMed

    Dholakia, Kartik D

    2012-01-01

    Contemporary concepts of sliding mechanics explain that friction is inevitable. To overcome this frictional resistance, excess force is required to retract the tooth along the archwire (ie, individual retraction of canines, en masse retraction of anterior teeth), in addition to the amount of force required for tooth movement. The anterior tooth retraction force, in addition to excess force (to overcome friction), produces reciprocal protraction force on molars, thereby leading to increased anchorage loading. However, this traditional concept was challenged in recent literature, which was based on the finite element model, but did not bear correlation to the clinical scenario. This article will reinforce the fact that clinically, friction increases anchorage loading in all three planes of space, considering the fact that tooth movement is a quasistatic process rather than a purely continuous or static one, and that conventional ways of determining the effects of static or dynamic friction on anchorage load cannot be applied to clinical situations (which consist of anatomical resistance units and a complex muscular force system). The article does not aim to quantify friction and its effect on the amount of anchorage load. Rather, a new perspective regarding the role of various additional factors (which is not explained by contemporary concept) that may influence friction and anchorage loading is provided..

  17. Laminar heat transfer and friction factor characteristics of carbon nano tube/water nanofluids.

    PubMed

    Rathnakumar, P; Mayilsamy, K; Suresh, S; Murugesan, P

    2014-03-01

    This paper presents an experimental investigation on the convective heat transfer and friction factor characteristics of CNT/water nanofluid through a circular tube fitted with helical screw tape inserts with constant heat flux under laminar flow condition. Nanofluids of 0.1% and 0.2% volume fractions are prepared by two step method. Thermo-physical properties like thermal conductivity and viscosity are measured by using KD2 thermal property analyzer and Brooke field cone and plate viscometer respectively. From the measurements, it is found that the viscosity increase is substantially higher than the increase in the thermal conductivity. The helical screw tape insets with twist ratios Y = 3, 2.44 and 1.78 are used to study the convective heat transfer and friction factor characteristics under laminar flow in the Reynolds number range of 520-2500. It is observed that, in a plain tube, maximum enhancement in Nusselt number for 0.1% and 0.2% volume fractions of nanofluids compared to pure water is 15% and 32% respectively. With the use of inserts, maximum enhancement in Nusselt number corresponding to twist ratios of 1.78, 2.44 and 3 are obtained as 8%, 16% and 4.6% for 0.1% volume fraction of nanofluid and 5%, 4% and 12% for 0.2% volume fraction of nanofluid when compared with water in plain tube. Thermal performance factor evaluation revealed that the values at all Reynolds number for all twist ratios and both concentration of CNT nanofluid are greater than unity which indicates that helical screw tape inserts with twist ratios considered are feasible in terms of energy saving in laminar flow.

  18. Diminishing friction of joint surfaces as initiating factor for destabilising permafrost rocks?

    NASA Astrophysics Data System (ADS)

    Funk, Daniel; Krautblatter, Michael

    2010-05-01

    Degrading alpine permafrost due to changing climate conditions causes instabilities in steep rock slopes. Due to a lack in process understanding, the hazard is still difficult to asses in terms of its timing, location, magnitude and frequency. Current research is focused on ice within joints which is considered to be the key-factor. Monitoring of permafrost-induced rock failure comprises monitoring of temperature and moisture in rock-joints. The effect of low temperatures on the strength of intact rock and its mechanical relevance for shear strength has not been considered yet. But this effect is signifcant since compressive and tensile strength is reduced by up to 50% and more when rock thaws (Mellor, 1973). We hypotheisze, that the thawing of permafrost in rocks reduces the shear strength of joints by facilitating the shearing/damaging of asperities due to the drop of the compressive/tensile strength of rock. We think, that decreasing surface friction, a neglected factor in stability analysis, is crucial for the onset of destabilisation of permafrost rocks. A potential rock slide within the permafrost zone in the Wetterstein Mountains (Zugspitze, Germany) is the basis for the data we use for the empirical joint model of Barton (1973) to estimate the peak shear strength of the shear plane. Parameters are the JRC (joint roughness coefficient), the JCS (joint compressive strength) and the residual friction angle (φr). The surface roughness is measured in the field with a profile gauge to create 2D-profiles of joint surfaces. Samples of rock were taken to the laboratory to measure compressive strength using a high-impact Schmidt-Hammer under air-dry, saturated and frozen conditions on weathered and unweathered surfaces. Plugs where cut out of the rock and sand blasted for shear tests under frozen and unfrozen conditions. Peak shear strength of frozen and unfrozen rocks will be calculated using Barton's model. First results show a mean decrease of compressive

  19. Internal friction quality-factor Q under confining pressure. [of lunar rocks

    NASA Technical Reports Server (NTRS)

    Tittmann, B. R.; Ahlberg, L.; Nadler, H.; Curnow, J.; Smith, T.; Cohen, E. R.

    1977-01-01

    It has been found in previous studies that small amounts of adsorbed volatiles can have a profound effect on the internal friction quality-factor Q of rocks and other porous media. Pandit and Tozer (1970) have suggested that the laboratory-measured Q of volatile-free rocks should be similar to the in situ seismic Q values of near-surface lunar rocks which according to Latham et al. (1970) are in the range of 3000-5000. Observations of dramatic increases in Q with outgassing up to values approaching 2000 in the seismic frequency range confirm this supposition. Measurements under confining pressures with the sample encapsulated under hard vacuum are reported to aid in the interpretation of seismic data obtained below the lunar surface. It has been possible to achieve in the experiments Q values just under 2000 at about 1 kbar for a terrestrial analog of lunar basalt. It was found that a well-outgassed sample maintains a high Q whereas one exposed to moisture maintains a low Q as the confining pressure is raised to 2.5 kbar. This result suggests that volatiles can indeed affect Q when cracks are partially closed and the high lunar seismic Q values reported are concomitant with very dry rock down to depths of at least 50 km.

  20. An entrance region friction factor model applied to annular seal analysis - Theory versus experiment for smooth and honeycomb seals

    NASA Technical Reports Server (NTRS)

    Elrod, D.; Nelson, C.; Childs, D.

    1989-01-01

    A friction factor model is developed for the entrance-region of a duct. The model is used in an annular gas seal analysis similar to Nelson's (1984). Predictions of the analysis are compared to experimental results for a smooth-stator/smooth-rotor seal and three honeycomb-stator/smooth-rotor seals. The model predicts a leakage and direct damping well. The model overpredicts the dependence of cross-coupled stiffness on fluid prerotation. The model predicts direct stiffness poorly.

  1. Numerical investigation of heat transfer and friction factor characteristics in a circular tube fitted with V-cut twisted tape inserts.

    PubMed

    Salman, Sami D; Kadhum, Abdul Amir H; Takriff, Mohd S; Mohamad, Abu Bakar

    2013-01-01

    Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y = 2.93) and different cut depths (w = 0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y = 2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratio y = 2.93 and cut depth w = 0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration.

  2. Numerical Investigation of Heat Transfer and Friction Factor Characteristics in a Circular Tube Fitted with V-Cut Twisted Tape Inserts

    PubMed Central

    Salman, Sami D.; Kadhum, Abdul Amir H.; Takriff, Mohd S.; Mohamad, Abu Bakar

    2013-01-01

    Numerical investigation of the heat transfer and friction factor characteristics of a circular fitted with V-cut twisted tape (VCT) insert with twist ratio (y = 2.93) and different cut depths (w = 0.5, 1, and 1.5 cm) were studied for laminar flow using CFD package (FLUENT-6.3.26). The data obtained from plain tube were verified with the literature correlation to ensure the validation of simulation results. Classical twisted tape (CTT) with different twist ratios (y = 2.93, 3.91, 4.89) were also studied for comparison. The results show that the enhancement of heat transfer rate induced by the classical and V-cut twisted tape inserts increases with the Reynolds number and decreases with twist ratio. The results also revealed that the V-cut twisted tape with twist ratio y = 2.93 and cut depth w = 0.5 cm offered higher heat transfer rate with significant increases in friction factor than other tapes. In addition the results of V-cut twist tape compared with experimental and simulated data of right-left helical tape inserts (RLT), it is found that the V-cut twist tape offered better thermal contact between the surface and the fluid which ultimately leads to a high heat transfer coefficient. Consequently, 107% of maximum heat transfer was obtained by using this configuration. PMID:24078795

  3. Friction in orthodontics

    PubMed Central

    Prashant, P. S.; Nandan, Hemant; Gopalakrishnan, Meera

    2015-01-01

    Conventional wisdom suggests that resistance to sliding (RS) generated at the wire-bracket interface has a bearing on the force transmitted to the teeth. The relative importance of static and kinetic friction and also the effect of friction on anchorage has been a topic of debate. Lot of research work has been done to evaluate the various factors that affect friction and thus purportedly retards the rate of tooth movement. However, relevancy of these studies is questionable as the methodology used hardly simulates the oral conditions. Lately studies have concluded that more emphasis should be laid on binding and notching of archwires as these are considered to be the primary factors involved in retarding the tooth movement. This article reviews the various components involved in RS and the factors affecting friction. Further, research work should be carried out to provide cost effective alternatives aimed at reducing friction. PMID:26538873

  4. Design of exchange-correlation functionals through the correlation factor approach

    SciTech Connect

    Pavlíková Přecechtělová, Jana E-mail: Matthias.Ernzerhof@UMontreal.ca

    2015-10-14

    The correlation factor model is developed in which the spherically averaged exchange-correlation hole of Kohn-Sham theory is factorized into an exchange hole model and a correlation factor. The exchange hole model reproduces the exact exchange energy per particle. The correlation factor is constructed in such a manner that the exchange-correlation energy correctly reduces to exact exchange in the high density and rapidly varying limits. Four different correlation factor models are presented which satisfy varying sets of physical constraints. Three models are free from empirical adjustments to experimental data, while one correlation factor model draws on one empirical parameter. The correlation factor models are derived in detail and the resulting exchange-correlation holes are analyzed. Furthermore, the exchange-correlation energies obtained from the correlation factor models are employed to calculate total energies, atomization energies, and barrier heights. It is shown that accurate, non-empirical functionals can be constructed building on exact exchange. Avenues for further improvements are outlined as well.

  5. Personality factors correlate with regional cerebral perfusion.

    PubMed

    O'Gorman, R L; Kumari, V; Williams, S C R; Zelaya, F O; Connor, S E J; Alsop, D C; Gray, J A

    2006-06-01

    There is an increasing body of evidence pointing to a neurobiological basis of personality. The purpose of this study was to investigate the biological bases of the major dimensions of Eysenck's and Cloninger's models of personality using a noninvasive magnetic resonance perfusion imaging technique in 30 young, healthy subjects. An unbiased voxel-based analysis was used to identify regions where the regional perfusion demonstrated significant correlation with any of the personality dimensions. Highly significant positive correlations emerged between extraversion and perfusion in the basal ganglia, thalamus, inferior frontal gyrus and cerebellum and between novelty seeking and perfusion in the cerebellum, cuneus and thalamus. Strong negative correlations emerged between psychoticism and perfusion in the basal ganglia and thalamus and between harm avoidance and perfusion in the cerebellar vermis, cuneus and inferior frontal gyrus. These observations suggest that personality traits are strongly associated with resting cerebral perfusion in a variety of cortical and subcortical regions and provide further evidence for the hypothesized neurobiological basis of personality. These results may also have important implications for functional neuroimaging studies, which typically rely on the modulation of cerebral hemodynamics for detection of task-induced activation since personality effects may influence the intersubject variability for both task-related activity and resting cerebral perfusion. This technique also offers a novel approach for the exploration of the neurobiological correlates of human personality.

  6. Influence of tube-entrance configuration on average heat-transfer coefficients and friction factors for air flowing in an Inconel tube

    NASA Technical Reports Server (NTRS)

    Lowdermilk, Warren H; Grele, Milton D

    1950-01-01

    A heat-transfer investigation was conducted with air flowing through an electrically heated Inconel tube having either a long-approach or a right-angle-edge entrance, an inside diameter of 0.402 inch, and a length of 24 inches over a range of Reynolds numbers up to 375,000 and average inside-tube-wall temperatures up to 2000 degrees R. Good correlation of heat-transfer data was obtained for both entrances, which substantiates work previously reported. A fair correlation of friction data was obtained for both entrances. The entrance configuration had little effect on the average heat-transfer and friction coefficients.

  7. Correlations between ultrasonic and fracture toughness factors in metallic materials

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    A heuristic mathematical basis was proposed for the experimental correlations found between ultrasonic propagation factors and fracture toughness factors in metallic materials. A crack extension model was developed wherein spontaneous stress (elastic) waves produced during microcracking are instrumental in promoting the onset of unstable crack extension. Material microstructural factors involved in the process are measurable by ultrasonic probing. Experimental results indicate that ultrasonic attenuation and velocity measurements will produce significant correlations with fracture toughness properties and also yield strength.

  8. Factors controlling threshold friction velocity in semiarid and arid areas of the United States

    USGS Publications Warehouse

    Marticorena, Beatrice; Bergametti, G.; Belnap, Jayne

    1997-01-01

    A physical model was developed to explain threshold friction velocities u*t for particles of the size 60a??120 I?m lying on a rough surface in loose soils for semiarid and arid parts of the United States. The model corrected for the effect of momentum absorption by the nonerodible roughness. For loose or disturbed soils the most important parameter that controls u*t is the aerodynamic roughness height z 0. For physical crusts damaged by wind the size of erodible crust pieces is important along with the roughness. The presence of cyanobacteriallichen soil crusts roughens the surface, and the biological fibrous growth aggregates soil particles. Only undisturbed sandy soils and disturbed soils of all types would be expected to be erodible in normal wind storms. Therefore disturbance of soils by both cattle and humans is very important in predicting wind erosion as confirmed by our measurements.

  9. Local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a microchannel heat sink

    NASA Astrophysics Data System (ADS)

    Chabi, A. R.; Zarrinabadi, S.; Peyghambarzadeh, S. M.; Hashemabadi, S. H.; Salimi, M.

    2016-06-01

    Forced convective heat transfer in a microchannel heat sink (MCHS) using CuO/water nanofluids with 0.1 and 0.2 vol% as coolant was investigated. The experiments were focused on the heat transfer enhancement in the channel entrance region at Re < 1800. Hydraulic performance of the MCHS was also estimated by measuring friction factor and pressure drop. Results showed that higher convective heat transfer coefficient was obtained at the microchannel entrance. Maximum enhancement of the average heat transfer coefficient compared with deionized water was about 40 % for 0.2 vol% nanofluid at Re = 1150. Enhancement of the convective heat transfer coefficient of nanofluid decreased with further increasing of Reynolds number.

  10. PROCESSING, MICROSTRUCTURE AND MECHANICAL PROPERTY CORRELATION IN Al-B4C SURFACE COMPOSITE PRODUCED VIA FRICTION STIR PROCESSING

    SciTech Connect

    Komarasamy, Mageshwari; Mishra, Rajiv S.; Baumann, John A.; Grant, Glenn J.; Hovanski, Yuri

    2013-01-29

    Friction stir processing (FSP) was employed to prepare surface composites (SC) composed of B4C particles in 5024 Al matrix. The processing parameters, such as hole pattern and geometry,and the number of FSP passes, were optimized to obtain uniform powder distribution. The micrographs revealed a homogeneous distribution of the particles with good interfacial bonding. The hardness of the composite was uniform across the processed region which again indicates the uniformity of powder distribution. The modulus of the surface composite was measured using strain gage and showed a significant improvement. This improvement in modulus lies in the load sharing capability from the soft matrix to the hard particles.

  11. Correlation of transonic-cone Preston-tube data and skin friction. [characterizing the flow quality of a transonic wind tunnel

    NASA Technical Reports Server (NTRS)

    Reed, T. D.

    1981-01-01

    The distribution of Preston tube pressures within turbulent boundary layers along the surface of a sharp-nosed, ten degree cone was correlated with theoretical values of turbulent skin friction for freestream Mach numbers less than one. The mini-basic computer code, the Wu and Lock computer code, and the STAN-5 computer code were used to analyze the data and to solve the boundary layer conservation equations. The skin friction which results from using Preston tube pressures in the correlation equation, has a rms error of 1.125 percent. It was found that the effective center of the probe is not a constant but increases as the surface distance increases. For a specified unit Reynolds number, the effective center of the probe decreases as the Mach number increases. The variation of the fluid (air) properties across the face of the probe may be neglected for subsonic flows. The possible transverse errors caused by the use of the concept of a virtual origin for the turbulent boundary layer were investigated and found to be negligible.

  12. Fissile mass-multiplication factor correlation for Pu measurement

    SciTech Connect

    Lu, Ming-Shih; Teichmann, T.; De Ridder, P.; Verrecchia, G.P.D.; Chare, P.; Vocino, V.

    1993-06-01

    An empirical correlation between the fissile mass and the leakage multiplication factor, as determined by High Level Neutron Coincidence (HLNC) counting, was developed based on available measurement data. This correlation has been used successfully for the simulation of HLNC counting. With the singles count rate (totals), the correlation can be used to obtain a quick estimate of the plutonium mass of the sample in less time than required to measure the real coincidence count rate. The correlation can also be used to evaluate samples contaminated with ({alpha},n) sources such as fluorine.

  13. Orthopositronium decay form factors and two-photon correlations

    SciTech Connect

    Adkins, Gregory S.; Droz, Daniel R.; Rastawicki, Dominik; Fell, Richard N.

    2010-04-15

    We give results for the orthopositronium decay form factors through one-loop order. We use the form factors to calculate momentum correlations of the final-state photons and , including one-loop corrections, for ensembles of initial orthopositronium atoms having arbitrary polarization.

  14. Caregiver’s feeding styles questionnaire - new factors and correlates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Study objectives were to conduct exploratory factor analysis (EFA) of Caregiver’s Feeding Styles Questionnaire (CFSQ) and evaluate correlations between factors and maternal feeding practices, attitudes, and perceptions. Mothers (N = 144) were 43% minority race/ethnicity, 24% full-time employed, 54% ...

  15. Musculoskeletal symptoms, postural disorders and occupational risk factors: correlation analysis.

    PubMed

    Comper, Maria Luiza C; Macedo, Felipe; Padula, Rosimeire S

    2012-01-01

    Work-related musculoskeletal disorders (WRMSD) include a list of inflammatory and degenerative diseases characterized by the presence of musculoskeletal symptoms, compensatory posture changes and functional disabilities. The objective of this study was to evaluate the kinetic/functional characteristics of textile plant workers, their level of exposure to risk factors and the contribution these make to musculoskeletal symptoms. The sample of 42 workers answered the Nordic Questionnaire and the Job Factors Questionnaire. The kinetic/functional characteristics of each worker were verified by a blinded evaluator. Data were analyzed using descriptive statistics and Pearson's correlation. Musculoskeletal symptoms were more prevalent in the spinal region and upper limbs. The exposure levels to risk factors were identified as a serious problem. Postural disorders, musculoskeletal symptoms and risk factors were correlated (P ≤ 0.05).

  16. Bootstrap Confidence Intervals for Ordinary Least Squares Factor Loadings and Correlations in Exploratory Factor Analysis

    ERIC Educational Resources Information Center

    Zhang, Guangjian; Preacher, Kristopher J.; Luo, Shanhong

    2010-01-01

    This article is concerned with using the bootstrap to assign confidence intervals for rotated factor loadings and factor correlations in ordinary least squares exploratory factor analysis. Coverage performances of "SE"-based intervals, percentile intervals, bias-corrected percentile intervals, bias-corrected accelerated percentile intervals, and…

  17. Joint Winter Runway Friction Program Accomplishments

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.; Wambold, James C.; Henry, John J.; Andresen, Arild; Bastian, Matthew

    2002-01-01

    The major program objectives are: (1) harmonize ground vehicle friction measurements to report consistent friction value or index for similar contaminated runway conditions, for example, compacted snow, and (2) establish reliable correlation between ground vehicle friction measurements and aircraft braking performance. Accomplishing these objectives would give airport operators better procedures for evaluating runway friction and maintaining acceptable operating conditions, providing pilots information to base go/no go decisions, and would contribute to reducing traction-related aircraft accidents.

  18. Interstitial Fluid Pressure Correlates Clinicopathological Factors of Lung Cancer

    PubMed Central

    Koga, Takamasa; Shibata, Hidekatsu; Ikeda, Koei; Shiraishi, Kenji; Suzuki, Makoto; Iyama, Ken-ichi

    2015-01-01

    Purpose: Solid tumors show increased interstitial fluid pressure (IFP), which correlates to a number of pathophysiological features of tumors. There have been no reports on the usefulness of measuring IFP in lung cancer. The aim of this study was to examine the relationship between IFP and the clinicopathological characteristics of lung cancer. Methods: IFP was measured prospectively in 215 patients with 219 lesions showing solid or part-solid appearance. Four patients with double lung cancer were excluded from the analysis, resulting in 211 patients with lung cancer being analyzed for the correlation between IFP and computed tomography (CT) appearance, size, Tumor-node-metastasis (TNM) classification, maximal standardized uptake value (SUVmax), histological type, tumor grade, pleural and vessel invasion, Ki-67 index, and recurrence-free survival (RFS). Results: The mean IFP was 8.5 mmHg; IFP was significantly correlated with the tumor size, SUVmax, TNM, vessel and pleural invasion, and Ki-67 index. Low IFP was associated with a better RFS compared to high IFP. Multivariate analysis did not select IFP as independent prognostic factor. In subgroup analysis of patients with adenocarcinoma, IFP was selected as independent one. Conclusions: IFP correlates clinicopathological factors of lung cancer. IFP might be used as a prognostic factor for lung cancer. PMID:25641031

  19. [Correlations between wild Polygonatum odoratum quality and main ecological factors].

    PubMed

    Bu, Jing; Li, Deng-Wu; Wang, Dong-Mei

    2012-06-01

    By the methods of stepwise regression, principal component analysis, and grey relational grade analysis, this paper studied the correlations between the effective components (polysaccharides and water- and alcohol-soluble substances) contents and antioxidant activity of wild Polygonatum odoratum in different places and the ecological factors. Among the test ecological factors, the mean air temperature in January and in July, mean annual precipitation, frost-free period, and soil pH and total potassium were the main factors affecting the effective component contents of P. odoratum, with a contribution rate of 99.0%. As compared with soil factors, climatic factors made more contribution to the effective component contents. Soil total potassium was the key factor controlling the effective component contents, mean annual precipitation was the main decision factor, and mean air temperature in January was the main limiting factor. The plant polysaccharides and water-soluble substance contents were the key factors affecting the antioxidant activity of P. odoratum, and the capability of P. odoratum in excavating DPPH free radical increased with increasing contents of polysaccharides and water-soluble substances. PMID:22937629

  20. Coherence factor effects in the antisymmetrized LDOS correlators

    NASA Astrophysics Data System (ADS)

    Maltseva, Marianna; Coleman, P.

    2009-03-01

    Recent scanning tunneling experiments on underdoped cuprates by Hanaguri et al [1] show the appearance of coherence factor effects. Unlike conventional observables, we show that the tunneling density of states in a superconductor does not have a well defined coherence factor. However, by extracting the component that is either even, or odd in the bias voltage, we show that these separate components have well-defined coherence factors. These results are used to understand the appearance of coherence factor effects in the antisymmetrized local density of states correlators in recent scanning tunneling experiments. [3pt] [1] T. Hanaguri, Y. Kohsaka, M. Ono, M. Maltseva, P. Coleman, I. Yamada, M. Azuma, M. Takano, K. Ohishi and H. Takagi, to be published (2009).

  1. Experimental studies on heat transfer and friction factor characteristics of Al{sub 2}O{sub 3}/water nanofluid in a circular pipe under laminar flow with wire coil inserts

    SciTech Connect

    Chandrasekar, M.; Suresh, S.; Chandra Bose, A.

    2010-02-15

    In this paper, fully developed laminar flow convective heat transfer and friction factor characteristics of Al{sub 2}O{sub 3}/water nanofluid flowing through a uniformly heated horizontal tube with and without wire coil inserts is presented. For this purpose, Al{sub 2}O{sub 3} nanoparticles of 43 nm size were synthesized, characterized and dispersed in distilled water to form stable suspension containing 0.1% volume concentration of nanoparticles. The Nusselt number in the fully developed region were measured and found to increase by 12.24% at Re = 2275 for plain tube with nanofluid compared to distilled water. Two wire coil inserts made of stainless steel with pitch ratios 2 and 3 were used which increased the Nusselt numbers by 15.91% and 21.53% respectively at Re = 2275 with nanofluid compared to distilled water. The better heat transfer performance of nanofluid with wire coil insert is attributed to the effects of dispersion or back-mixing which flattens the temperature distribution and make the temperature gradient between the fluid and wall steeper. The measured pressure loss with the use of nanofluids is almost equal to that of the distilled water. The empirical correlations developed for Nusselt number and friction factor in terms of Reynolds/Peclet number, pitch ratio and volume concentration fits with the experimental data within {+-}15%. (author)

  2. Intelligent Flow Friction Estimation

    PubMed Central

    Brkić, Dejan; Ćojbašić, Žarko

    2016-01-01

    Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ). In the present study, a noniterative approach using Artificial Neural Network (ANN) was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Reynolds Number (Re) and the relative roughness of pipe (ε/D) were transformed to logarithmic scales. The 90,000 sets of data were fed to the ANN model involving three layers: input, hidden, and output layers with, 2, 50, and 1 neurons, respectively. This configuration was capable of predicting the values of friction factor in the Colebrook equation for any given values of the Reynolds number (Re) and the relative roughness (ε/D) ranging between 5000 and 108 and between 10−7 and 0.1, respectively. The proposed ANN demonstrates the relative error up to 0.07% which had the high accuracy compared with the vast majority of the precise explicit approximations of the Colebrook equation. PMID:27127498

  3. Intelligent Flow Friction Estimation.

    PubMed

    Brkić, Dejan; Ćojbašić, Žarko

    2016-01-01

    Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ). In the present study, a noniterative approach using Artificial Neural Network (ANN) was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Reynolds Number (Re) and the relative roughness of pipe (ε/D) were transformed to logarithmic scales. The 90,000 sets of data were fed to the ANN model involving three layers: input, hidden, and output layers with, 2, 50, and 1 neurons, respectively. This configuration was capable of predicting the values of friction factor in the Colebrook equation for any given values of the Reynolds number (Re) and the relative roughness (ε/D) ranging between 5000 and 10(8) and between 10(-7) and 0.1, respectively. The proposed ANN demonstrates the relative error up to 0.07% which had the high accuracy compared with the vast majority of the precise explicit approximations of the Colebrook equation.

  4. Intelligent Flow Friction Estimation.

    PubMed

    Brkić, Dejan; Ćojbašić, Žarko

    2016-01-01

    Nowadays, the Colebrook equation is used as a mostly accepted relation for the calculation of fluid flow friction factor. However, the Colebrook equation is implicit with respect to the friction factor (λ). In the present study, a noniterative approach using Artificial Neural Network (ANN) was developed to calculate the friction factor. To configure the ANN model, the input parameters of the Reynolds Number (Re) and the relative roughness of pipe (ε/D) were transformed to logarithmic scales. The 90,000 sets of data were fed to the ANN model involving three layers: input, hidden, and output layers with, 2, 50, and 1 neurons, respectively. This configuration was capable of predicting the values of friction factor in the Colebrook equation for any given values of the Reynolds number (Re) and the relative roughness (ε/D) ranging between 5000 and 10(8) and between 10(-7) and 0.1, respectively. The proposed ANN demonstrates the relative error up to 0.07% which had the high accuracy compared with the vast majority of the precise explicit approximations of the Colebrook equation. PMID:27127498

  5. Finite volume form factors and correlation functions at finite temperature

    NASA Astrophysics Data System (ADS)

    Pozsgay, Balázs

    2009-07-01

    In this thesis we investigate finite size effects in 1+1 dimensional integrable QFT. In particular we consider matrix elements of local operators (finite volume form factors) and vacuum expectation values and correlation functions at finite temperature. In the first part of the thesis we give a complete description of the finite volume form factors in terms of the infinite volume form factors (solutions of the bootstrap program) and the S-matrix of the theory. The calculations are correct to all orders in the inverse of the volume, only exponentially decaying (residual) finite size effects are neglected. We also consider matrix elements with disconnected pieces and determine the general rule for evaluating such contributions in a finite volume. The analytic results are tested against numerical data obtained by the truncated conformal space approach in the Lee-Yang model and the Ising model in a magnetic field. In a separate section we also evaluate the leading exponential correction (the μ-term) associated to multi-particle energies and matrix elements. In the second part of the thesis we show that finite volume factors can be used to derive a systematic low-temperature expansion for correlation functions at finite temperature. In the case of vacuum expectation values the series is worked out up to the third non-trivial order and a complete agreement with the LeClair-Mussardo formula is observed. A preliminary treatment of the two-point function is also given by considering the first nontrivial contributions.

  6. Interfacial Friction in Gas-Liquid Annular Flow: Analogies to Full and Transition Roughness

    SciTech Connect

    Bauer, R.C.; Beus, S.G.; Fore, L.B.

    1999-03-01

    New film thickness and pressure gradient data were obtained in a 5.08 by 101.6 mm duct for nitrogen and water in annular flow. Pressures of 3.4 and 17 atm and temperatures of 38 and 93 C were used to vary the gas density and liquid viscosity. These data are used to compute interfacial shear stresses and interfacial friction factors for comparison with several accepted literature correlations. These comparisons are reasonable for small values of the relative film thickness. However, the new data cover conditions not approached by the data used to construct those correlations. By combining the current data with the results of two other comprehensive modern experimental studies, a new correlation for the interfacial friction factor has been developed. This correlation adds elements of transition roughness to Wallis' fully-rough analogy to better predict interfacial friction factors over a wide range of gas Reynolds numbers and liquid film thicknesses.

  7. The Eysenckian personality factors and their correlations with academic performance.

    PubMed

    Poropat, Arthur E

    2011-03-01

    BACKGROUND. The relationship between personality and academic performance has long been explored, and a recent meta-analysis established that measures of the five-factor model (FFM) dimension of Conscientiousness have similar validity to intelligence measures. Although currently dominant, the FFM is only one of the currently accepted models of personality, and has limited theoretical support. In contrast, the Eysenckian personality model was developed to assess a specific theoretical model and is still commonly used in educational settings and research. AIMS. This meta-analysis assessed the validity of the Eysenckian personality measures for predicting academic performance. SAMPLE. Statistics were obtained for correlations with Psychoticism, Extraversion, and Neuroticism (20-23 samples; N from 8,013 to 9,191), with smaller aggregates for the Lie scale (7 samples; N= 3,910). METHODS. The Hunter-Schmidt random effects method was used to estimate population correlations between the Eysenckian personality measures and academic performance. Moderating effects were tested using weighted least squares regression. RESULTS. Significant but modest validities were reported for each scale. Neuroticism and Extraversion had relationships with academic performance that were consistent with previous findings, while Psychoticism appears to be linked to academic performance because of its association with FFM Conscientiousness. Age and educational level moderated correlations with Neuroticism and Extraversion, and gender had no moderating effect. Correlations varied significantly based on the measurement instrument used. CONCLUSIONS. The Eysenckian scales do not add to the prediction of academic performance beyond that provided by FFM scales. Several measurement problems afflict the Eysenckian scales, including low to poor internal reliability and complex factor structures. In particular, the measurement and validity problems of Psychoticism mean its continued use in academic

  8. [Bipolarity correlated factors in major depression: about 155 Tunisian inpatients].

    PubMed

    Gassab, L; Mechri, A; Gaha, L; Khiari, G; Zaafrane, F; Zougaghi, L

    2002-01-01

    The distinction between the depressive troubles according to their inclusion in bipolar disorders or in recurrent depressive disorders offers an evident practical interest. In fact, the curative and mainly the preventive treatment of these troubles are different. So it is necessary to identify the predictive factors of bipolar development in case of inaugural depressive episode. In 1983, Akiskal was the first who identified those factors: pharmacological hypomania, puerperal depression, onset at early age (<25 years), presence of psychotic characteristics, hypersomnia and psychomotor inhibition. Through this study, the authors try to compare the epidemiological, clinical and evolution characteristics of major depression in bipolar disorders to recurrent depressive disorders in order to indicate the correlated factors with bipolarity. It is a retrospective and comparative study based on about 155 inpatients for major depressive episode during the period between January 1994 and December 1998. These patients were divided into two groups according the DSM IV criteria: bipolar group (96 patients) and recurrent depressive group (59 patients). Both groups were compared according to socio-demographic data, life events in childhood, personal and family history, clinical and evolution characteristics of the index depressive episode. The predictive factors proposed by Akiskal were systematically examined. It was found out that the following factors were correlated with bipolarity: high rate of separation and divorce (17.7% versus 5.1%; p=0.02), family history of psychiatric disorders (56.3% versus 35.6%; p=0.012) especially bipolar ones (29.2% versus 3.4%; p=0,00008), onset at early age (mean age of onset: 24.8 8.2 years versus 34.1 12.6 years; p=0.000004), number of affective episode significantly more frequent (mean 3.6 versus 2.5; p=0.03), sudden onset of depressive episode (44.8% versus 15.9%; p=0.0003) and presence of psychotic characteristics (69.8% versus 16.7%; p=0

  9. Suicide during Perinatal Period: Epidemiology, Risk Factors, and Clinical Correlates

    PubMed Central

    Orsolini, Laura; Valchera, Alessandro; Vecchiotti, Roberta; Tomasetti, Carmine; Iasevoli, Felice; Fornaro, Michele; De Berardis, Domenico; Perna, Giampaolo; Pompili, Maurizio; Bellantuono, Cesario

    2016-01-01

    Perinatal period may pose a great challenge for the clinical management and treatment of psychiatric disorders in women. In fact, several mental illnesses can arise during pregnancy and/or following childbirth. Suicide has been considered a relatively rare event during the perinatal period. However, in some mental disorders (i.e., postpartum depression, bipolar disorder, postpartum psychosis, etc.) have been reported a higher risk of suicidal ideation, suicide attempt, or suicide. Therefore, a complete screening of mothers’ mental health should also take into account thoughts of suicide and thoughts about harming infants as well. Clinicians should carefully monitor and early identify related clinical manifestations, potential risk factors, and alarm symptoms related to suicide. The present paper aims at providing a focused review about epidemiological data, risk factors, and an overview about the main clinical correlates associated with the suicidal behavior during the pregnancy and postpartum period. Practical recommendations have been provided as well. PMID:27570512

  10. Suicide during Perinatal Period: Epidemiology, Risk Factors, and Clinical Correlates.

    PubMed

    Orsolini, Laura; Valchera, Alessandro; Vecchiotti, Roberta; Tomasetti, Carmine; Iasevoli, Felice; Fornaro, Michele; De Berardis, Domenico; Perna, Giampaolo; Pompili, Maurizio; Bellantuono, Cesario

    2016-01-01

    Perinatal period may pose a great challenge for the clinical management and treatment of psychiatric disorders in women. In fact, several mental illnesses can arise during pregnancy and/or following childbirth. Suicide has been considered a relatively rare event during the perinatal period. However, in some mental disorders (i.e., postpartum depression, bipolar disorder, postpartum psychosis, etc.) have been reported a higher risk of suicidal ideation, suicide attempt, or suicide. Therefore, a complete screening of mothers' mental health should also take into account thoughts of suicide and thoughts about harming infants as well. Clinicians should carefully monitor and early identify related clinical manifestations, potential risk factors, and alarm symptoms related to suicide. The present paper aims at providing a focused review about epidemiological data, risk factors, and an overview about the main clinical correlates associated with the suicidal behavior during the pregnancy and postpartum period. Practical recommendations have been provided as well. PMID:27570512

  11. Friction and Wear

    NASA Technical Reports Server (NTRS)

    Pomey, Jacques

    1952-01-01

    From the practical point of view, this analysis shows that each problem of friction or wear requires its particular solution. There is no universal solution; one or other of the factors predominates and defines the choice of the solution. In certain cases, copper alloys of great thermal conductivity are preferred; in others, plastics abundantly supplied with water. Sometimes, soft antifriction metals are desirable to distribute the load; at other times, hard metals with high resistance to abrasion or heat.

  12. A Two Factor ANOVA-like Test for Correlated Correlations: CORANOVA

    ERIC Educational Resources Information Center

    Bilker, Warren B.; Brensinger, Colleen; Gur, Ruben C.

    2004-01-01

    Testing homogeneity of correlations with Fisher's Z is inappropriate when correlations are themselves correlated. Suppose measurements of brain activation and performance are taken before and during a verbal memory task. Of interest are changes in activity gradients in specific regions, R1, R2, R3, and performance, V. The "correlated correlations"…

  13. Correlation between clonorchiasis incidences and climatic factors in Guangzhou, China

    PubMed Central

    2014-01-01

    Background Human infection with Clonorchis sinensis is still a big public health problem in Guangzhou. To investigate the correlation between clonorchiasis and climatic factors, we analyzed the clonorchiasis reported cases and simultaneous meteorological data during 2006–2012 in Guangzhou City, China. Findings Annual incidence rate of clonorchiasis from 2006 to 2012 was 166.76, 191.55, 247.37, 213.82, 246.03, 274.71, and 239.63 (per 100 000), respectively. Each 1°C rise of temperature corresponded to an increase of 1.18% (95% CI 0.88% to 1.48%) in the monthly number of cases, and a one millimeter rise of rainfall corresponded to increase of 0.03% (95% CI 0.01% to 0.04%). Whereas each one percent rise of relative humidity corresponded to a decrease in the number of cases by 1.51% (95% CI -1.75% to -1.27%). Conclusions We reported incidence rates of clonorchiasis showed an increasing trend by years. Temperature and rainfall were positively associated with clonorchiasis incidence, while relative humidity was inversely associated with clonorchiasis incidence. Our study provided evidence that climatic factors affect the occurrence of clonorchiasis in Guangzhou city, China. PMID:24428903

  14. Influence of epidermal hydration on the friction of human skin against textiles.

    PubMed

    Gerhardt, L-C; Strässle, V; Lenz, A; Spencer, N D; Derler, S

    2008-11-01

    Friction and shear forces, as well as moisture between the human skin and textiles are critical factors in the formation of skin injuries such as blisters, abrasions and decubitus. This study investigated how epidermal hydration affects the friction between skin and textiles.The friction between the inner forearm and a hospital fabric was measured in the natural skin condition and in different hydration states using a force plate. Eleven males and eleven females rubbed their forearm against the textile on the force plate using defined normal loads and friction movements. Skin hydration and viscoelasticity were assessed by corneometry and the suction chamber method, respectively.In each individual, a highly positive linear correlation was found between skin moisture and friction coefficient (COF). No correlation was observed between moisture and elasticity, as well as between elasticity and friction. Skin viscoelasticity was comparable for women and men. The friction of female skin showed significantly higher moisture sensitivity. COFs increased typically by 43% (women) and 26% (men) when skin hydration varied between very dry and normally moist skin. The COFs between skin and completely wet fabric were more than twofold higher than the values for natural skin rubbed on a dry textile surface.Increasing skin hydration seems to cause gender-specific changes in the mechanical properties and/or surface topography of human skin, leading to skin softening and increased real contact area and adhesion.

  15. Correlation Between Nuclear Factor E2-Related Factor 2 Expression and Gastric Cancer Progression

    PubMed Central

    Zheng, Hongyu; Nong, Zhiwei; Lu, Guohao

    2015-01-01

    Background Nuclear factor E2-related factor 2 (Nrf2) plays an anti-oxidative and phase II detoxification function via its up-regulation on various antioxidant response elements (ARE) genes. Nrf2 can protect both normal and cancer cells from damages of cell stress, thereby exerting a critical role in the development of cancer. The expression and significance of Nrf2 in gastric cancer, however, has not been reported. This study thus aimed to investigate the expression of Nrf2 in gastric cancer tissues via immunohistochemical (IHC) staining. Material/Methods Gastric carcinoma tissues from a total of 175 patients during surgical resection were examined for Nfr2 expression profiles using IHC staining on paraffin-embedded slides. Between-group-comparisons were performed by chi-square, Fisher’s exact, or Mann-Whitney U test. The correlation between Nfr2 expression and clinical indexes was further analyzed by Kaplan-Meier test, univariate/multivariate analysis, and log-rank test. Results Nrf2 is mainly expressed in nuclei of gastric carcinoma tissues, with significant correlation with clinical indexes, including tumor size, invasive depth, lymph node metastasis, and invasion. Patients with Nrf2-positive expression had significantly lower survival rates compared to those in the negative group (p<0.01), with chemo-resistance against 5-fluorouracil (5-FU) (p<0.05). Conclusions Nrf2 expression is positively correlated with invasive gastric cancer, suggesting its utility as a predictive index for unfavorable prognosis. PMID:26410168

  16. Temporal Stability, Correlates, and Longitudinal Outcomes of Career Indecision Factors

    ERIC Educational Resources Information Center

    Nauta, Margaret M.

    2012-01-01

    A confirmatory factor analysis (CFA) tested the fit of Kelly and Lee's six-factor model of career decision problems among 188 college students. The six-factor model did not fit the data well, but a five-factor (Lack of Information, Need for Information, Trait Indecision, Disagreement with Others, and Choice Anxiety) model did provide a good fit.…

  17. Mesh Size Control of Friction

    NASA Astrophysics Data System (ADS)

    Pitenis, Angela; Uruena, Juan Manuel; Schulze, Kyle D.; Cooper, Andrew C.; Angelini, Thomas E.; Sawyer, W. Gregory

    Soft, permeable sliding interfaces in aqueous environments are ubiquitous in nature but their ability to maintain high lubricity in a poor lubricant (water) has not been well understood. Hydrogels are excellent materials for fundamental soft matter and biotribology studies due to their high water content. While mesh size controls the material and transport properties of a hydrogel, its effects on friction were only recently explored. Polyacrylamide hydrogels slid in a Gemini (self-mated) interface produced low friction under low speeds, low pressures, macroscopic contact areas, and room temperature aqueous environments. The friction coefficients at these interfaces are lowest at low speeds and are speed-independent. This behavior is due to thermal fluctuations at the interface separating the surfaces, with water shearing in this region being the main source of dissipation. We found that mesh size had an inverse correlation with friction. We further investigated a transition from this behavior at higher speeds, and found that the transition speed correlated with the mesh size and relaxation time of the polymer network. Very soft and correspondingly large mesh size Gemini hydrogels show superlubricity under specific conditions with friction being less than 0.005.

  18. Frictional constitutive properties and related microstructures of albite, muscovite, biotite and talc

    NASA Astrophysics Data System (ADS)

    Scruggs, Valerie Jean

    Rock friction studies were conducted using a rotary shear, room temperature gas apparatus. The frictional behavior and constitutive parameters that model that behavior were determined and linked with specific microstructures. The velocity dependence of friction determines the stability of sliding in the laboratory and is found to correlate with changes in localization of strain. Material composition, velocity of sliding and initial conditions such as surface roughness were all found to affect the constitutive behavior. The work involves experiments on initially bare surfaces of albite, albite gouge and mica and talc gouges. The experimental results for frictional sliding on bare surfaces of albite show two distinct behaviors, one with lower friction that is slightly velocity negative and the other with higher friction that is more velocity negative. These two behaviors represent different styles of deformation, with the lower friction mechanism representing deformation on inclined Coulomb shear planes of fine-grained gouge generated during wear of the surface and the higher friction mechanism representing deformation on shears oriented parallel to the macroscopic shear plane. Microstructures of all materials are compared to frictional constitutive behavior. In both feldspar and mica gouge experiments, localization along boundary parallel shears correlates with negative velocity dependence, and is associated with a lower strength. Uniform distribution of strain within the gouge zone is associated with stable sliding for both micas and feldspar. At large displacements, talc and muscovite have a positive velocity dependence and slide stably, whereas biotite has a negative velocity dependence. Biotite becomes velocity strengthening at low velocities, similar to the transition to 'flow' behavior seen for serpentinites. Changes in velocity dependence with displacement are also seen in albite gouge. Two experimental factors affect this variability in behavior: the

  19. The Manifest Association Structure of the Single-Factor Model: Insights from Partial Correlations

    ERIC Educational Resources Information Center

    Salgueiro, Maria de Fatima; Smith, Peter W. F.; McDonald, John W.

    2008-01-01

    The association structure between manifest variables arising from the single-factor model is investigated using partial correlations. The additional insights to the practitioner provided by partial correlations for detecting a single-factor model are discussed. The parameter space for the partial correlations is presented, as are the patterns of…

  20. Comparison of friction and lubrication of different hip prostheses.

    PubMed

    Scholes, S C; Unsworth, A

    2000-01-01

    It is well documented that an important cause of osteolysis and subsequent loosening of replacement hip joints is polyethylene wear debris. To avoid this, interest has been renewed in metal-on-metal and ceramic-on-ceramic prostheses. Various workers have assessed the lubrication modes of different joints by measuring the friction at the bearing surfaces, using different lubricants. Measurements of friction factors of a series of hip prostheses were undertaken using carboxymethyl cellulose (CMC) fluids, silicone fluids, synovial fluid and different concentrations of bovine serum as the lubricant. The experimental results were compared with theoretical predictions of film thicknesses and lubrication modes. A strong correlation was observed between experiment and theory when employing CMC fluids or silicone fluids as the lubricant. Mixed lubrication was found to occur in the metal-on-metal (CoCrMo/CoCrMo) joints with all lubricants at a viscosity within the physiological range. This was also the case for the metal-on-plastic (CoCrMo/ultra-high molecular weight polyethylene) joints. The ceramic-on-ceramic (Al2O3/Al2O3) joints, however, exhibited full fluid film lubrication with the synthetic lubricants but mixed lubrication with the biological lubricants. Employing a biological fluid as the lubricant affected the friction to varying degrees when compared with the synthetic lubricants. In the case of the ceramic-on-ceramic joints it acted to increase the friction factor tenfold; however, for the metal-on-metal joints, biological fluids gave slightly lower friction than the synthetic lubricants did. This suggests that, when measuring friction and wear of artificial joints, a standard lubricant should be used.

  1. Effect of tumor microenvironmental factors on tumor growth dynamics modeled by correlated colored noises with colored cross-correlation

    NASA Astrophysics Data System (ADS)

    Idris, Ibrahim Mu'awiyya; Abu Bakar, Mohd Rizam

    2016-07-01

    The effect of non-immunogenic tumor microenvironmental factors on tumor growth dynamics modeled by correlated additive and multiplicative colored noises is investigated. Using the Novikov theorem, Fox approach and Ansatz of Hanggi, an approximate Fokker-Planck equation for the system is obtained and analytic expression for the steady state distribution Pst(x) is derived. Based on the numerical results, we find that fluctuations of microenvironmental factors within the tumor site with parameter θ have a diffusive effect on the tumor growth dynamics, and the tumor response to the microenvironmental factors with parameter α inhibits growth at weak correlation time τ. Moreover, at increasing correlation time τ the inhibitive effect of tumor response α is suppressed and instead a systematic growth promotion is noticed. The result also reveals that the strength of the correlation time τ has a strong influence on the growth effects exerted by the non-immunogenic component of tumor microenvironment on tumor growth.

  2. Rotational Uniqueness Conditions under Oblique Factor Correlation Metric

    ERIC Educational Resources Information Center

    Peeters, Carel F. W.

    2012-01-01

    In an addendum to his seminal 1969 article Joreskog stated two sets of conditions for rotational identification of the oblique factor solution under utilization of fixed zero elements in the factor loadings matrix (Joreskog in "Advances in factor analysis and structural equation models," pp. 40-43, 1979). These condition sets, formulated under…

  3. Environmental factors and cancer mortality in Italy: correlational exercise.

    PubMed

    Decarli, A; La Vecchia, C

    1986-01-01

    Mortality rates for 21 cancer sites in 20 Italian regions have been correlated with several economic and dietary variables (including alcohol and coffee consumption), patterns of cigarette smoking and reproductive habits. In both sexes, a large number of strong correlations emerged, the most notable ones being the strong positive coefficients between cigarettes sold in the early 1950s and lung cancer mortality in middle-aged males in the early 1970s, between gross internal product or meat consumption and cancer of the intestines in both sexes, between total per caput consumption and cancer of the prostate and between mean age at first birth, gross internal product and milk consumption and cancer of the breast. Cancer of the ovary was positively correlated with mean age at the first birth, and negatively with average number of births. Among the unexpected correlations observed, the most remarkable ones were the strong positive coefficient between skin cancer mortality and latitude (which can however be explained in terms of different constitutional characteristics of skin color in various Italian regions), and the pattern of coefficients emerging for gastric cancer, showing positive correlations with gross internal product or meat and negative ones with bread, pasta or fish. These and other results (including the analysis of several first-order partial correlation coefficients) are discussed with regard to their limitations and major points of interest, and in comparison with similar studies conducted on different populations. PMID:3951786

  4. Friction, wear, and lubrication in vacuum

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1971-01-01

    A review of studies and observations on the friction, wear, and lubrication behavior of materials in a vacuum environment is presented. The factors that determine and influence friction and wear are discussed. They include topographical, physical, mechanical, and the chemical nature of the surface. The effects of bulk properties such as deformation characteristics, fracture behavior, and structure are included.

  5. Are "g" and the General Factor of Personality (GFP) Correlated?

    ERIC Educational Resources Information Center

    Irwing, Paul; Booth, Tom; Nyborg, Helmuth; Rushton, J. Philippe

    2012-01-01

    We examined whether the General Factor of Personality (GFP) is related to the "g" factor of cognitive ability using data from the Vietnam Experience Study which randomly sampled 4462 Vietnam War veterans from a total sample of about five million Vietnam era army veterans. Exclusionary criteria included passing a fitness test, achieving a final…

  6. Near-Edge X-ray Absorption Fine Structure Imaging of Spherical and Flat Counterfaces of Ultrananocrystalline Diamond Tribological Contacts: A Correlation of Surface Chemistry and Friction

    SciTech Connect

    A Konicek; C Jaye; M Hamilton; W Sawyer; D Fischer; R Carpick

    2011-12-31

    A recently installed synchrotron radiation near-edge X-ray absorption fine structure (NEXAFS) full field imaging electron spectrometer was used to spatially resolve the chemical changes of both counterfaces from an ultra-nanocrystalline diamond (UNCD) tribological contact. A silicon flat and Si{sub 3}N{sub 4} sphere were both coated with UNCD, and employed to form two wear tracks on the flat in a linear reciprocating tribometer. The first wear track was produced using a new, unconditioned sphere whose surface was thus conditioned during this first experiment. This led to faster run-in and lower friction when producing a second wear track using the conditioned sphere. The large depth of field of the magnetically guided NEXAFS imaging detector enabled rapid, large area spectromicroscopic imaging of both the spherical and flat surfaces. Laterally resolved NEXAFS data from the tribological contact area revealed that both substrates had an as-grown surface layer that contained a higher fraction of sp{sup 2}-bonded carbon and oxygen which was mechanically removed. Unlike the flat, the film on the sphere showed evidence of having graphitic character, both before and after sliding. These results show that the graphitic character of the sphere is not solely responsible for low friction and short run-in. Rather, conditioning the sphere, likely by removing asperities and passivating dangling bonds, leads to lower friction with less chemical modification of the substrate in subsequent tests. The new NEXAFS imaging spectroscopy detector enabled a more complete understanding of the tribological phenomena by imaging, for the first time, the surface chemistry of the spherical counterface which had been in continual contact during wear track formation.

  7. Factors, Correlates, Emotional Barriers Affecting Career Decisions of College Students.

    ERIC Educational Resources Information Center

    O'Neil, James M.; And Others

    The correlates of career choice and the problem areas affecting career decisions are important to counseling psychologists. They are important to understanding the complexities of vocational behavior, facilitating differential treatment in counseling, and developing preventive career programs for men, women, and special groups. The effects of the…

  8. Factors Correlated with the Interactional Diversity of Community College Students

    ERIC Educational Resources Information Center

    Jones, Willis A.

    2016-01-01

    This study used data from the Community College Survey of Student Engagement (CCSSE) to examine how student background characteristics, student engagement, and institutional characteristics correlate with the frequency of interactional diversity among community college students. Given the current lack of research on interactional diversity among…

  9. Orthogonal Connectivity Factorization: Interpretable Decomposition of Variability in Correlation Matrices.

    PubMed

    Hyvärinen, Aapo; Hirayama, Jun-ichiro; Kiviniemi, Vesa; Kawanabe, Motoaki

    2016-03-01

    In many multivariate time series, the correlation structure is nonstationary, that is, it changes over time. The correlation structure may also change as a function of other cofactors, for example, the identity of the subject in biomedical data. A fundamental approach for the analysis of such data is to estimate the correlation structure (connectivities) separately in short time windows or for different subjects and use existing machine learning methods, such as principal component analysis (PCA), to summarize or visualize the changes in connectivity. However, the visualization of such a straightforward PCA is problematic because the ensuing connectivity patterns are much more complex objects than, say, spatial patterns. Here, we develop a new framework for analyzing variability in connectivities using the PCA approach as the starting point. First, we show how to analyze and visualize the principal components of connectivity matrices by a tailor-made rank-two matrix approximation in which we use the outer product of two orthogonal vectors. This leads to a new kind of transformation of eigenvectors that is particularly suited for this purpose and often enables interpretation of the principal component as connectivity between two groups of variables. Second, we show how to incorporate the orthogonality and the rank-two constraint in the estimation of PCA itself to improve the results. We further provide an interpretation of these methods in terms of estimation of a probabilistic generative model related to blind separation of dependent sources. Experiments on brain imaging data give very promising results. PMID:26735746

  10. Friction measurement in a hip wear simulator.

    PubMed

    Saikko, Vesa

    2016-05-01

    A torque measurement system was added to a widely used hip wear simulator, the biaxial rocking motion device. With the rotary transducer, the frictional torque about the drive axis of the biaxial rocking motion mechanism was measured. The principle of measuring the torque about the vertical axis above the prosthetic joint, used earlier in commercial biaxial rocking motion simulators, was shown to sense only a minor part of the total frictional torque. With the present method, the total frictional torque of the prosthetic hip was measured. This was shown to consist of the torques about the vertical axis above the joint and about the leaning axis. Femoral heads made from different materials were run against conventional and crosslinked polyethylene acetabular cups in serum lubrication. Regarding the femoral head material and the type of polyethylene, there were no categorical differences in frictional torque with the exception of zirconia heads, with which the lowest values were obtained. Diamond-like carbon coating of the CoCr femoral head did not reduce friction. The friction factor was found to always decrease with increasing load. High wear could increase the frictional torque by 75%. With the present system, friction can be continuously recorded during long wear tests, so the effect of wear on friction with different prosthetic hips can be evaluated.

  11. Correlations between metabolic syndrome, serologic factors, and gallstones

    PubMed Central

    Sang, Jae Hong; Ki, Nam Kyun; Cho, Jae Hwan; Ahn, Jae Ouk; Sunwoo, Jae Gun

    2016-01-01

    [Purpose] This study investigated the serologic factors associated with metabolic syndrome and gallstones. [Subjects and Methods] The study evaluated subjects who visited a health promotion center in Seoul from March 2, 2013 to February 28, 2014, and had undergone abdominal ultrasonography. Height, weight, and blood pressure were measured. Blood sampling was performed for high-density lipoprotein cholesterol, triglyceride, fasting blood glucose, total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, uric acid, total cholesterol, low-density lipoprotein cholesterol, thyroid stimulating hormone, and red and white blood cell counts. We conducted logistic regression analysis to assess the risk factors associated with metabolic syndrome. [Results] The risk factors for metabolic syndrome in men, in order of decreasing weight, were red blood cell count, body mass index, maximum size of gallstones, white blood cell count, waist circumference, and uric acid level. The factors in women, in order of decreasing weight, were red blood cell count, presence/absence of gallstones, uric acid level, body mass index, fasting blood glucose, and waist circumference. [Conclusion] Most serum biochemical factors and gallstone occurrence could be used to indicate the presence or absence of metabolic syndrome, independent of gender. PMID:27630427

  12. Correlations between metabolic syndrome, serologic factors, and gallstones

    PubMed Central

    Sang, Jae Hong; Ki, Nam Kyun; Cho, Jae Hwan; Ahn, Jae Ouk; Sunwoo, Jae Gun

    2016-01-01

    [Purpose] This study investigated the serologic factors associated with metabolic syndrome and gallstones. [Subjects and Methods] The study evaluated subjects who visited a health promotion center in Seoul from March 2, 2013 to February 28, 2014, and had undergone abdominal ultrasonography. Height, weight, and blood pressure were measured. Blood sampling was performed for high-density lipoprotein cholesterol, triglyceride, fasting blood glucose, total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, uric acid, total cholesterol, low-density lipoprotein cholesterol, thyroid stimulating hormone, and red and white blood cell counts. We conducted logistic regression analysis to assess the risk factors associated with metabolic syndrome. [Results] The risk factors for metabolic syndrome in men, in order of decreasing weight, were red blood cell count, body mass index, maximum size of gallstones, white blood cell count, waist circumference, and uric acid level. The factors in women, in order of decreasing weight, were red blood cell count, presence/absence of gallstones, uric acid level, body mass index, fasting blood glucose, and waist circumference. [Conclusion] Most serum biochemical factors and gallstone occurrence could be used to indicate the presence or absence of metabolic syndrome, independent of gender.

  13. Correlations between metabolic syndrome, serologic factors, and gallstones.

    PubMed

    Sang, Jae Hong; Ki, Nam Kyun; Cho, Jae Hwan; Ahn, Jae Ouk; Sunwoo, Jae Gun

    2016-08-01

    [Purpose] This study investigated the serologic factors associated with metabolic syndrome and gallstones. [Subjects and Methods] The study evaluated subjects who visited a health promotion center in Seoul from March 2, 2013 to February 28, 2014, and had undergone abdominal ultrasonography. Height, weight, and blood pressure were measured. Blood sampling was performed for high-density lipoprotein cholesterol, triglyceride, fasting blood glucose, total bilirubin, direct bilirubin, indirect bilirubin, aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, uric acid, total cholesterol, low-density lipoprotein cholesterol, thyroid stimulating hormone, and red and white blood cell counts. We conducted logistic regression analysis to assess the risk factors associated with metabolic syndrome. [Results] The risk factors for metabolic syndrome in men, in order of decreasing weight, were red blood cell count, body mass index, maximum size of gallstones, white blood cell count, waist circumference, and uric acid level. The factors in women, in order of decreasing weight, were red blood cell count, presence/absence of gallstones, uric acid level, body mass index, fasting blood glucose, and waist circumference. [Conclusion] Most serum biochemical factors and gallstone occurrence could be used to indicate the presence or absence of metabolic syndrome, independent of gender. PMID:27630427

  14. Large Friction Anisotropy of a Polydiacetylene Monolayer

    SciTech Connect

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-05-11

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.

  15. The effect of wall friction on magnetohydrodynamic generator performance

    NASA Technical Reports Server (NTRS)

    Bishop, A. R.

    1972-01-01

    The effect of wall friction on magnetohydrodynamic generator performance is determined by introduction of a wall friction factor into the one-dimensional generator equations. This addition should be useful in improving generator analysis and determining optimum generator geometry. The curves presented can be used to determine the effects of changes in wall friction and generator performance. Wall friction has an increasing effect on the Mach number increases and a decreasing effect as the pressure drop across the generator increase.

  16. Frictional behavior of large displacement experimental faults

    USGS Publications Warehouse

    Beeler, N.M.; Tullis, T.E.; Blanpied, M.L.; Weeks, J.D.

    1996-01-01

    The coefficient of friction and velocity dependence of friction of initially bare surfaces and 1-mm-thick simulated fault gouges (400 mm at 25??C and 25 MPa normal stress. Steady state negative friction velocity dependence and a steady state fault zone microstructure are achieved after ???18 mm displacement, and an approximately constant strength is reached after a few tens of millimeters of sliding on initially bare surfaces. Simulated fault gouges show a large but systematic variation of friction, velocity dependence of friction, dilatancy, and degree of localization with displacement. At short displacement (<10 mm), simulated gouge is strong, velocity strengthening and changes in sliding velocity are accompanied by relatively large changes in dilatancy rate. With continued displacement, simulated gouges become progressively weaker and less velocity strengthening, the velocity dependence of dilatancy rate decreases, and deformation becomes localized into a narrow basal shear which at its most localized is observed to be velocity weakening. With subsequent displacement, the fault restrengthens, returns to velocity strengthening, or to velocity neutral, the velocity dependence of dilatancy rate becomes larger, and deformation becomes distributed. Correlation of friction, velocity dependence of friction and of dilatancy rate, and degree of localization at all displacements in simulated gouge suggest that all quantities are interrelated. The observations do not distinguish the independent variables but suggest that the degree of localization is controlled by the fault strength, not by the friction velocity dependence. The friction velocity dependence and velocity dependence of dilatancy rate can be used as qualitative measures of the degree of localization in simulated gouge, in agreement with previous studies. Theory equating the friction velocity dependence of simulated gouge to the sum of the friction velocity dependence of bare surfaces and the velocity

  17. On the Genetic and Environmental Correlations between Trait Emotional Intelligence and Vocational Interest Factors.

    PubMed

    Schermer, Julie Aitken; Petrides, Konstantinos V; Vernon, Philip A

    2015-04-01

    The phenotypic (observed), genetic, and environmental correlations were examined in a sample of adult twins between the four factors and global score of the trait emotional intelligence questionnaire (TEIQue) and the seven vocational interest factors of the Jackson Career Explorer (JCE). Multiple significant correlations were found involving the work style vocational interest factor (consisting of job security, stamina, accountability, planfulness, and interpersonal confidence) and the social vocational interest factor (which included interests in the social sciences, personal services, teaching, social services, and elementary education), both of which correlated significantly with all of the TEIQue variables (well-being, self-control, emotionality, sociability, and global trait EI). Following bivariate genetic analyses, most of the significant phenotypic correlations were found to also have significant genetic correlations as well as significant non-shared (unique) environmental correlations.

  18. On the Genetic and Environmental Correlations between Trait Emotional Intelligence and Vocational Interest Factors.

    PubMed

    Schermer, Julie Aitken; Petrides, Konstantinos V; Vernon, Philip A

    2015-04-01

    The phenotypic (observed), genetic, and environmental correlations were examined in a sample of adult twins between the four factors and global score of the trait emotional intelligence questionnaire (TEIQue) and the seven vocational interest factors of the Jackson Career Explorer (JCE). Multiple significant correlations were found involving the work style vocational interest factor (consisting of job security, stamina, accountability, planfulness, and interpersonal confidence) and the social vocational interest factor (which included interests in the social sciences, personal services, teaching, social services, and elementary education), both of which correlated significantly with all of the TEIQue variables (well-being, self-control, emotionality, sociability, and global trait EI). Following bivariate genetic analyses, most of the significant phenotypic correlations were found to also have significant genetic correlations as well as significant non-shared (unique) environmental correlations. PMID:25743745

  19. Tactile texture and friction of soft sponge surfaces.

    PubMed

    Takahashi, Akira; Suzuki, Makoto; Imai, Yumi; Nonomura, Yoshimune

    2015-06-01

    We evaluated the tactile texture and frictional properties of five soft sponges with various cell sizes. The frictional forces were measured by a friction meter containing a contact probe with human-finger-like geometry and mechanical properties. When the subjects touched these sponges with their fingers, hard-textured sponges were deemed unpleasant. This tactile feeling changed with friction factors including friction coefficients, their temporal patterns, as well as mechanical and shape factors. These findings provide useful information on how to control the tactile textures of various sponges.

  20. Nanotribology and Nanoscale Friction

    SciTech Connect

    Guo, Yi; Qu, Zhihua; Braiman, Yehuda; Zhang, Zhenyu; Barhen, Jacob

    2008-01-01

    Tribology is the science and technology of contacting solid surfaces in relative motion, including the study of lubricants, lubrication, friction, wear, and bearings. It is estimated that friction and wear cost the U.S. economy 6% of the gross national product (Persson, 2000). For example, 5% of the total energy generated in an automobile engine is lost to frictional resistance. The study of nanoscale friction has a technological impact in reducing energy loss in machines, in microelectromechanical systems (MEMS), and in the development of durable, low-friction surfaces and ultra-thin lubrication films.

  1. The friction of explanted hip prostheses.

    PubMed

    Hall, R M; Unsworth, A; Wroblewski, B M; Siney, P; Powell, N J

    1997-01-01

    Charnley prostheses, retrieved at revision surgery, were studied to assess the effects of friction on the total hip replacement procedure. Frictional resistance was measured using the Durham hip function simulator under both dry and lubricated conditions. The friction factor values (f) for the explanted prostheses were found to have a non-Gaussian distribution with medians of 0.13 [inter-quartile range (IQR) 0.10-0.16] and 0.06 (IQR 0.005-0.08) for dry and lubricated (n = 0.01 Pa s) regimes, respectively. New Charnley prostheses had values of f equal to 0.11 +/- 0.025 and 0.04 +/- 0.01 under the same conditions, and showed no large deviation from a Gaussian distribution. There was found to be a statistically significant difference in the medians of the friction factors for new and retrieved prostheses in the lubricated regime. Ingression of cement into the worn region of the cup was found to increase the friction factor significantly under dry conditions. There was no evidence of an increase in the friction factor or torque for those joints that had a loose socket with respect to those that were fixed at revision. A decrease in the frictional torque against number of cycles undergone by the joint in vivo may indicate that a fatigue-type process may have a role in the loosening of the socket. However, this relationship was found not to be significant for friction measured under lubricated conditions and it seems unlikely that the frictional torque generated in this type of prosthesis will contribute significantly to the long-term loosening of the socket.

  2. Micromachine friction test apparatus

    DOEpatents

    deBoer, Maarten P.; Redmond, James M.; Michalske, Terry A.

    2002-01-01

    A microelectromechanical (MEM) friction test apparatus is disclosed for determining static or dynamic friction in MEM devices. The friction test apparatus, formed by surface micromachining, is based on a friction pad supported at one end of a cantilevered beam, with the friction pad overlying a contact pad formed on the substrate. A first electrostatic actuator can be used to bring a lower surface of the friction pad into contact with an upper surface of the contact pad with a controlled and adjustable force of contact. A second electrostatic actuator can then be used to bend the cantilevered beam, thereby shortening its length and generating a relative motion between the two contacting surfaces. The displacement of the cantilevered beam can be measured optically and used to determine the static or dynamic friction, including frictional losses and the coefficient of friction between the surfaces. The test apparatus can also be used to assess the reliability of rubbing surfaces in MEM devices by producing and measuring wear of those surfaces. Finally, the friction test apparatus, which is small in size, can be used as an in situ process quality tool for improving the fabrication of MEM devices.

  3. Generic expansion of the Jastrow correlation factor in polynomials satisfying symmetry and cusp conditions

    SciTech Connect

    Lüchow, Arne; Sturm, Alexander; Schulte, Christoph; Haghighi Mood, Kaveh

    2015-02-28

    Jastrow correlation factors play an important role in quantum Monte Carlo calculations. Together with an orbital based antisymmetric function, they allow the construction of highly accurate correlation wave functions. In this paper, a generic expansion of the Jastrow correlation function in terms of polynomials that satisfy both the electron exchange symmetry constraint and the cusp conditions is presented. In particular, an expansion of the three-body electron-electron-nucleus contribution in terms of cuspless homogeneous symmetric polynomials is proposed. The polynomials can be expressed in fairly arbitrary scaling function allowing a generic implementation of the Jastrow factor. It is demonstrated with a few examples that the new Jastrow factor achieves 85%–90% of the total correlation energy in a variational quantum Monte Carlo calculation and more than 90% of the diffusion Monte Carlo correlation energy.

  4. A new detrended semipartial cross-correlation analysis: Assessing the important meteorological factors affecting API

    NASA Astrophysics Data System (ADS)

    Shen, Chen-Hua

    2015-12-01

    To analyze the unique contribution of meteorological factors to the air pollution index (API), a new method, the detrended semipartial cross-correlation analysis (DSPCCA), is proposed. Based on both a detrended cross-correlation analysis and a DFA-based multivariate-linear-regression (DMLR), this method is improved by including a semipartial correlation technique, which is used to indicate the unique contribution of an explanatory variable to multiple correlation coefficients. The advantages of this method in handling nonstationary time series are illustrated by numerical tests. To further demonstrate the utility of this method in environmental systems, new evidence of the primary contribution of meteorological factors to API is provided through DMLR. Results show that the most important meteorological factors affecting API are wind speed and diurnal temperature range, and the explanatory ability of meteorological factors to API gradually strengthens with increasing time scales. The results suggest that DSPCCA is a useful method for addressing environmental systems.

  5. Load-Dependent Friction Hysteresis on Graphene.

    PubMed

    Ye, Zhijiang; Egberts, Philip; Han, Gang Hee; Johnson, A T Charlie; Carpick, Robert W; Martini, Ashlie

    2016-05-24

    Nanoscale friction often exhibits hysteresis when load is increased (loading) and then decreased (unloading) and is manifested as larger friction measured during unloading compared to loading for a given load. In this work, the origins of load-dependent friction hysteresis were explored through atomic force microscopy (AFM) experiments of a silicon tip sliding on chemical vapor deposited graphene in air, and molecular dynamics simulations of a model AFM tip on graphene, mimicking both vacuum and humid air environmental conditions. It was found that only simulations with water at the tip-graphene contact reproduced the experimentally observed hysteresis. The mechanisms underlying this friction hysteresis were then investigated in the simulations by varying the graphene-water interaction strength. The size of the water-graphene interface exhibited hysteresis trends consistent with the friction, while measures of other previously proposed mechanisms, such as out-of-plane deformation of the graphene film and irreversible reorganization of the water molecules at the shearing interface, were less correlated to the friction hysteresis. The relationship between the size of the sliding interface and friction observed in the simulations was explained in terms of the varying contact angles in front of and behind the sliding tip, which were larger during loading than unloading.

  6. Simultaneous measurement of friction and wear in hip simulators.

    PubMed

    Haider, Hani; Weisenburger, Joel N; Garvin, Kevin L

    2016-05-01

    We propose and have evaluated a method to measure hip friction during wear testing on a popular multi-station hip simulator. A 6-degree-of-freedom load cell underneath the specimen sensed forces and torques during implant wear testing of simulated walking. This included internal-external and adduction-abduction rotations which are often neglected during friction testing on pendulum-type machines. Robust mathematical analysis and data processing provided friction estimates in three simultaneous orthogonal rotations, over extended multi-million cycle wear tests. We tested various bearing couples including metal-on-plastic, ceramic-on-plastic, and metal-on-metal material couples. In one test series, new and intentionally scratched CoCrMo 40-mm-diameter femoral heads were tested against conventional ultrahigh-molecular-weight polyethylene, highly cross-linked, and highly cross-linked with vitamin E versions. The scratching significantly increased friction and doubled the wear of all groups. Before scratching, friction levels for the aforementioned plastic groups were 0.056 ± 0.0060, 0.062 ± 0.0080, and 0.070 ± 0.0045, respectively, but after scratching increased to 0.088 ± 0.018, 0.076 ± 0.0066, and 0.082 ± 0.0049, respectively, all statistically significant increases (p = 0.00059, 0.00005, 0.0115, respectively). In another test series of 44-mm femoral head diameter hips, metal-on-plastic hips with conventional ultrahigh-molecular-weight polyethylene showed the lowest friction at 0.045 ± 0.0085, followed by highly cross-linked with 0.046 ± 0.0035 (not significantly different). In a ceramic-on-plastic design with conventional ultrahigh-molecular-weight polyethylene, higher friction 0.079 ± 0.0070 was measured likely due to that ceramic surface being rougher than usual. Metal-on-metal hips were compared without and with a TiN coating, resulting in 0.049 ± 0.014 and 0.097 ± 0.020 friction factors, respectively

  7. Simultaneous measurement of friction and wear in hip simulators.

    PubMed

    Haider, Hani; Weisenburger, Joel N; Garvin, Kevin L

    2016-05-01

    We propose and have evaluated a method to measure hip friction during wear testing on a popular multi-station hip simulator. A 6-degree-of-freedom load cell underneath the specimen sensed forces and torques during implant wear testing of simulated walking. This included internal-external and adduction-abduction rotations which are often neglected during friction testing on pendulum-type machines. Robust mathematical analysis and data processing provided friction estimates in three simultaneous orthogonal rotations, over extended multi-million cycle wear tests. We tested various bearing couples including metal-on-plastic, ceramic-on-plastic, and metal-on-metal material couples. In one test series, new and intentionally scratched CoCrMo 40-mm-diameter femoral heads were tested against conventional ultrahigh-molecular-weight polyethylene, highly cross-linked, and highly cross-linked with vitamin E versions. The scratching significantly increased friction and doubled the wear of all groups. Before scratching, friction levels for the aforementioned plastic groups were 0.056 ± 0.0060, 0.062 ± 0.0080, and 0.070 ± 0.0045, respectively, but after scratching increased to 0.088 ± 0.018, 0.076 ± 0.0066, and 0.082 ± 0.0049, respectively, all statistically significant increases (p = 0.00059, 0.00005, 0.0115, respectively). In another test series of 44-mm femoral head diameter hips, metal-on-plastic hips with conventional ultrahigh-molecular-weight polyethylene showed the lowest friction at 0.045 ± 0.0085, followed by highly cross-linked with 0.046 ± 0.0035 (not significantly different). In a ceramic-on-plastic design with conventional ultrahigh-molecular-weight polyethylene, higher friction 0.079 ± 0.0070 was measured likely due to that ceramic surface being rougher than usual. Metal-on-metal hips were compared without and with a TiN coating, resulting in 0.049 ± 0.014 and 0.097 ± 0.020 friction factors, respectively

  8. Enhanced nanoscale friction on fluorinated graphene.

    PubMed

    Kwon, Sangku; Ko, Jae-Hyeon; Jeon, Ki-Joon; Kim, Yong-Hyun; Park, Jeong Young

    2012-12-12

    Atomically thin graphene is an ideal model system for studying nanoscale friction due to its intrinsic two-dimensional (2D) anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro- and nanomechanical devices. Here, we report unexpectedly enhanced nanoscale friction on chemically modified graphene and a relevant theoretical analysis associated with flexural phonons. Ultrahigh vacuum friction force microscopy measurements show that nanoscale friction on the graphene surface increases by a factor of 6 after fluorination of the surface, while the adhesion force is slightly reduced. Density functional theory calculations show that the out-of-plane bending stiffness of graphene increases up to 4-fold after fluorination. Thus, the less compliant F-graphene exhibits more friction. This indicates that the mechanics of tip-to-graphene nanoscale friction would be characteristically different from that of conventional solid-on-solid contact and would be dominated by the out-of-plane bending stiffness of the chemically modified graphene. We propose that damping via flexural phonons could be a main source for frictional energy dissipation in 2D systems such as graphene. PMID:22720882

  9. Friction and nonlinear dynamics

    NASA Astrophysics Data System (ADS)

    Manini, N.; Braun, O. M.; Tosatti, E.; Guerra, R.; Vanossi, A.

    2016-07-01

    The nonlinear dynamics associated with sliding friction forms a broad interdisciplinary research field that involves complex dynamical processes and patterns covering a broad range of time and length scales. Progress in experimental techniques and computational resources has stimulated the development of more refined and accurate mathematical and numerical models, capable of capturing many of the essentially nonlinear phenomena involved in friction.

  10. Statistics of Frictional Families

    NASA Astrophysics Data System (ADS)

    Shen, Tianqi; Papanikolaou, Stefanos; O'Hern, Corey S.; Shattuck, Mark D.

    2014-09-01

    We develop a theoretical description for mechanically stable frictional packings in terms of the difference between the total number of contacts required for isostatic packings of frictionless disks and the number of contacts in frictional packings, m=Nc0-Nc. The saddle order m represents the number of unconstrained degrees of freedom that a static packing would possess if friction were removed. Using a novel numerical method that allows us to enumerate disk packings for each m, we show that the probability to obtain a packing with saddle order m at a given static friction coefficient μ, Pm(μ), can be expressed as a power series in μ. Using this form for Pm(μ), we quantitatively describe the dependence of the average contact number on the friction coefficient for static disk packings obtained from direct simulations of the Cundall-Strack model for all μ and N.

  11. Confirmatory factor analysis and job burnout correlates of the Health Professions Stress Inventory.

    PubMed

    Akhtar, Syed; Lee, Jenny S Y

    2002-02-01

    Previous research in 1994 by Gupchup and Wolfgang identified four factors from Wolfgang's Health Professions Stress Inventory (1988) that were common among a sample of practicing pharmacists. The factors were labeled Professional Recognition. Patient Care Responsibilities, Job Conflicts, and Professional Uncertainty, respectively. We used confirmatory factor analysis to assess whether this factor structure was generalizable to nurses. To examine concurrent validity, we correlated the factors with Maslach and Jackson's three dimensions of job burnout, i.e., Emotional Exhaustion, Depersonalization, and Personal Accomplishment. Data were collected through a questionnaire survey of a random sample of 9,380 nurses from across 43 public hospitals in Hong Kong, from which 2,267 (24.2%) responded. Analysis indicated statistically acceptable goodness of fit indices for the four-factor solution. Except for the factor Patient Care Responsibilities. all other factors had moderate correlations between .44 and .53 with Emotional Exhaustion and Depersonalization. Correlations between the factors of Stress Inventory and Personal Accomplishment were small but significant, ranging from -.25 to .13. Areas for further improving the psychometric properties of the inventory are discussed.

  12. Heat transfer from high-temperature surfaces to fluids II : correlation of heat-transfer and friction data for air flowing in inconel tube with rounded entrance

    NASA Technical Reports Server (NTRS)

    Lowdermilk, Warren H; Grele, Milton D

    1949-01-01

    A heat transfer investigation, which was an extension of a previously reported NACA investigation, was conducted with air flowing through an electrically heated inconel tube with a rounded entrance,an inside diameter of 0.402 inch, and a length of 24 inches over a range of conditions, which included Reynolds numbers up to 500,000, average surface temperatures up to 2050 degrees R, and heat-flux densities up to 150,000 Btu per hour per square foot. Conventional methods of correlating heat-transfer data wherein properties of the air were evaluated at the average bulk, film, and surface temperatures resulted in reductions of Nusselt number of about 38, 46, and 53 percent, respectively, for an increase in surface temperature from 605 degrees to 2050 degrees R at constant Reynolds number. A modified correlation method in which the properties of air were based on the surface temperature and the Reynolds number was modified by substituting the product of the density at the inside tube wall and the bulk velocity for the conventional mass flow per unit cross-sectional area, resulted in a satisfactory correlation of the data for the extended ranges of conditions investigated.

  13. Factors controlling the correlation between ozone and CO in the North American continental boundary layer

    NASA Astrophysics Data System (ADS)

    Cheng, Y.

    2015-12-01

    Previous research has reported good correlation between O3 and CO over continental outflow regions. The correlation is often considered as an indication of anthropogenic emissions. In this study, a Regional chEmical trAnsport Model (REAM) was used to study the correlation between boundary layer O3 and CO. The observed correlation during the DISCOVER-AQ 2011 campaign was reproduced in the model and revealed that biogenic emissions made a significant contribution to the observed correlation and slope between O3 and CO in that experiment. In order to quantify source contributions to the observed linear correlation of O3 and CO in the continental boundary layer, CO sources were separated into four different categories: anthropogenic emission, chemical production from anthropogenic VOC oxidation, production of biogenic isoprene oxidation, and transport from lateral boundaries. The tagged tracer simulations reveal that biogenic isoprene is the main factor determining the correlation and slope between O3 and CO and those between O3 and CH2O near the surface and in the continental boundary layer. In the outflow region (western North Atlantic), both biogenic isoprene and anthropogenic emissions are significant factors. This finding implies that estimate of continental O3 export on the basis of O3 and CO correlation must account for the biogenic contribution and that satellite observations of CH2O and CO can be applied to provide observational constraints on the distribution of surface O3.

  14. Extended ion pumped vacuum friction test

    NASA Technical Reports Server (NTRS)

    Hammel, R. L.

    1971-01-01

    Boundary layer friction data under ion pumped vacuum was taken for sixteen material couples. The test series was an extension of a previous study of the effects of modified ion pumped environments. Sliding distances imposed in the present effort greatly exceeded any studied in the previous contiguous, flight or ground tests. Wear out of specific couples, in particular, thin film lubricants was noted. The behavior of the test hardware including wear out of the mechanisms was noted. As a result, the impact of test interruption was observed for several test couples. Recovery of the friction upon re-establishing sliding in vacuum was generally rapid. The results of the extended sliding study reinforce the previous conclusion that sliding distance (mechanical history) is the primary factor in establishing the force limiting boundary layer friction. General friction value under the extended sliding confirm those observed in previous orbital and the related ground test studies.

  15. Communication: A Jastrow factor coupled cluster theory for weak and strong electron correlation

    SciTech Connect

    Neuscamman, Eric

    2013-11-14

    We present a Jastrow-factor-inspired variant of coupled cluster theory that accurately describes both weak and strong electron correlation. Compatibility with quantum Monte Carlo allows for variational energy evaluations and an antisymmetric geminal power reference, two features not present in traditional coupled cluster that facilitate a nearly exact description of the strong electron correlations in minimal-basis N{sub 2} bond breaking. In double-ζ treatments of the HF and H{sub 2}O bond dissociations, where both weak and strong correlations are important, this polynomial cost method proves more accurate than either traditional coupled cluster or complete active space perturbation theory. These preliminary successes suggest a deep connection between the ways in which cluster operators and Jastrow factors encode correlation.

  16. Environmental factors correlated with size of bacterial populations in a polluted stream.

    PubMed

    Brasfeild, H

    1972-09-01

    Samples of water were taken from a polluted zone of the Gallinas River and analyzed as to numbers of total bacteria, coliforms, and fecal streptococci. Environmental factors measured were temperature, pH and concentrations of detergent, nitrate plus nitrite nitrogen, sulfate, chloride, bicarbonate, and phosphate. Thirty-two observations were made from 12 March through 22 July 1971. Stepwise multiple linear regression analyses of the data were carried out by computer to determine which of the environmental factors were significantly correlated with numbers of bacteria present. A multiple linear regression equation was constructed for each bacteriological parameter as a function of significant variables only. Log total bacteria was correlated positively with bicarbonate, phosphate, and detergent concentrations. Log coliforms was correlated positively with phosphate and sulfate concentrations and negatively with chloride concentration. Log fecal streptococci was correlated positively with bicarbonate and chloride concentrations.

  17. Environmental Factors Correlated with Size of Bacterial Populations in a Polluted Stream

    PubMed Central

    Brasfeild, Helen

    1972-01-01

    Samples of water were taken from a polluted zone of the Gallinas River and analyzed as to numbers of total bacteria, coliforms, and fecal streptococci. Environmental factors measured were temperature, pH and concentrations of detergent, nitrate plus nitrite nitrogen, sulfate, chloride, bicarbonate, and phosphate. Thirty-two observations were made from 12 March through 22 July 1971. Stepwise multiple linear regression analyses of the data were carried out by computer to determine which of the environmental factors were significantly correlated with numbers of bacteria present. A multiple linear regression equation was constructed for each bacteriological parameter as a function of significant variables only. Log total bacteria was correlated positively with bicarbonate, phosphate, and detergent concentrations. Log coliforms was correlated positively with phosphate and sulfate concentrations and negatively with chloride concentration. Log fecal streptococci was correlated positively with bicarbonate and chloride concentrations. PMID:4627965

  18. [Correlation between chemical constituents and ecological factors of Astragalus membranaceus var. mongholicus].

    PubMed

    Yang, Qing-zhen; Wang, Zeng-hui; Fu, Juan; Liu, De-wang; Huang, Lin-fang

    2015-03-01

    Principal component analysis (PCA) and correlation analysis (CA) were applied to analyze the correlation of the main chemical components in Astragalus membranaceus var. mongholicus and ecological factors. The results showed that the contents of astragaloside, campanulin, ononin, kaempferol and astragalus polysaccharides (APS) of A. membranaceus var. mongholicus produced. in Shanxi were significantly higher than in Inner Mongolia and Gansu. The main climatic factors for affecting the contents of chemical ingredients in A. membranaceus var. mongholicus were annual average relative humidity, sunshine hours and average July temperature. Calcium was the main factor in the soil affecting the chemical ingredient contents, and calcium was negatively correlated with the contents of calycosin glycosides, kaempferol, ononin, quercetin and APS in A. membranaceus var. mongholicus within a certain range. PMID:26211053

  19. In vitro friction and lubrication of large bearing hip prostheses.

    PubMed

    Flanagan, S; Jones, E; Birkinshaw, C

    2010-01-01

    New material combinations and designs of artificial hip implants are being introduced in an effort to improve proprioception and functional longevity. Larger joints in particular are being developed to improve joint stability, and it is thought that these larger implants will be more satisfactory for younger and more physically active patients. The study detailed here used a hip friction simulator to assess the friction and lubrication properties of large-diameter hip bearings of metal-on-metal and ceramic-on-reinforced-polymer couplings. Joints of different diameters were evaluated to determine what effect, if any, bearing diameter had on lubrication. In addition, the effects of lubricant type are considered, using carboxymethyl cellulose and bovine calf serum, and the physiological lubricant is shown to be considerably more effective at reducing friction. The frictional studies showed that the metal-on-metal joints worked under a mixed lubrication regime, producing similar friction factor values to each other. The addition of bovine calf serum (BCS) reduced the friction. The ceramic-on-reinforced-polymer samples were shown to operate with high friction factors and mixed lubrication. When tested with BCS, the larger-diameter bearings showed a decrease in friction compared with the smaller-size bearings, and the addition of BCS resulted in an increase in friction, unlike the metal-on-metal system. The study demonstrated that the component's diameter had little or no influence on the lubrication and friction of the large bearing combinations tested.

  20. Spouse correlations in cardiovascular risk factors and the effect of marriage duration.

    PubMed

    Knuiman, M W; Divitini, M L; Bartholomew, H C; Welborn, T A

    1996-01-01

    Spouse correlations in cardiovascular risk factors were investigated using data on 2,836 spouse pairs collected in the Busselton Population Health Surveys over the period 1966-1981. The risk factors considered were systolic blood pressure, diastolic blood pressure, body mass index, triceps fatfold, cholesterol, and forced expiratory volume (1 second). Statistically significant positive correlations (p < 0.01) were found for all (age-adjusted) variables. There was a statistically significant decreasing trend in the correlations for systolic blood pressure with marriage duration (trend p < 0.01). Although no other variables showed statistically significant trends, the correlations for diastolic blood pressure (p = 0.29), body mass index (p = 0.14), and forced expiratory volume (p = 0.16) also decreased with marriage duration, and correlations for cholesterol (p = 0.61) and triceps fatfold (p = 0.99) increased with marriage duration. These results suggest that there is spousal concordance in cardiovascular risk factors. The lack of consistent increasing trends in the correlations with marriage duration suggests that assortative mating may be a more likely explanation than the sharing of a common environment.

  1. Scanning laser edema index: a reliable tool to correlate with diabetic retinopathy and systemic risk factors?

    PubMed

    Peyman, Mohammadreza; Tajunisah, Iqbal; Loo, Angela; Chuah, Khai Choon; Subrayan, Visvaraja

    2012-01-01

    To correlate Heidelberg Retina Tomograph (HRT) derived macular edema (DME) index with severity of diabetic retinopathy and systemic factors. A total of 300 diabetic patients were recruited for the study for each of them a value for the macular edema index was obtained using the HRT II. Patients' age, gender, duration and type of diabetes mellitus, latest HbA1c result and presence or absence of co-morbid factors (hypertension, ischemic heart disease, nephropathy) were recorded together with the stage of diabetic retinopathy. These were correlated with DME. Out of 300 patients, HRT defined macula edema was seen in 68 patients (22.6%). There is a wider and higher range (95% percentile) of macula edema index in the severe non proliferative diabetic retinopathy (NPDR) group. Independent samples t test showed significant difference between the severe NPDR group and no DR group (p<0.001), mild NPDR group (p<0.05) and moderate NPDR group (p<0.05). A higher macula edema index was also found to have a low degree of correlation with more advanced stages of retinopathy (r=0.310; p<0.001). Also nephropathy showed a strong and significant correlation with DME. Hypertension had moderately significant correlation with DME. This study found no correlation between ischemic heart disease and DME. HRT derived scanning laser edema index is a reliable objective tool to evaluate diabetic retinopathy and systemic risk factors. PMID:22520399

  2. Iliotibial band friction syndrome.

    PubMed

    Lavine, Ronald

    2010-07-20

    Published articles on iliotibial band friction syndrome have been reviewed. These articles cover the epidemiology, etiology, anatomy, pathology, prevention, and treatment of the condition. This article describes (1) the various etiological models that have been proposed to explain iliotibial band friction syndrome; (2) some of the imaging methods, research studies, and clinical experiences that support or call into question these various models; (3) commonly proposed treatment methods for iliotibial band friction syndrome; and (4) the rationale behind these methods and the clinical outcome studies that support their efficacy.

  3. Iliotibial band friction syndrome

    PubMed Central

    2010-01-01

    Published articles on iliotibial band friction syndrome have been reviewed. These articles cover the epidemiology, etiology, anatomy, pathology, prevention, and treatment of the condition. This article describes (1) the various etiological models that have been proposed to explain iliotibial band friction syndrome; (2) some of the imaging methods, research studies, and clinical experiences that support or call into question these various models; (3) commonly proposed treatment methods for iliotibial band friction syndrome; and (4) the rationale behind these methods and the clinical outcome studies that support their efficacy. PMID:21063495

  4. Is there a genetic correlation between general factors of intelligence and personality?

    PubMed

    Loehlin, John C; Bartels, Meike; Boomsma, Dorret I; Bratko, Denis; Martin, Nicholas G; Nichols, Robert C; Wright, Margaret J

    2015-06-01

    We tested a hypothesis that there is no genetic correlation between general factors of intelligence and personality, despite both having been selected for in human evolution. This was done using twin samples from Australia, the United States, the Netherlands, Great Britain, and Croatia, comprising altogether 1,748 monozygotic and 1,329 same-sex dizygotic twin pairs. Although parameters in the model-fitting differed among the twin samples, the genetic correlation between the two general factors could be set to zero, with a better fit if the U.S. sample was excepted.

  5. Evaluating the Dynamic Character of Friction During Metal Forming

    SciTech Connect

    Stoudt, M.R.; Mates, S.P.; Hubbard, J.B.; Pitchure, D.J.

    2005-08-05

    The inhomogeneous distribution of surface asperities generated by deformation induces variability in the friction and initiates strain localizations during metal forming. The friction literature generally does not account for the strong influence localized variations in material properties have on the friction behavior. A prototype apparatus was developed that measures the friction behavior under simulated forming conditions and enables detailed characterization of the influences of the microstructure and the topographical conditions that occur under those conditions. The results demonstrate that the measurement system can resolve subtle real-time changes in the dynamic friction coefficient, and that a correlation could exist between the largest surface asperities and the largest variations in the measured friction coefficient.

  6. Science 101: What Causes Friction?

    ERIC Educational Resources Information Center

    Robertson, Bill

    2014-01-01

    Defining friction and asking what causes it might seem like a trivial question. Friction seems simple enough to understand. Friction is a force between surfaces that pushes against things that are moving or tending to move, and the rougher the surfaces, the greater the friction. Bill Robertson answers this by saying, "Well, not exactly".…

  7. GMDH-type neural network modeling and genetic algorithm-based multi-objective optimization of thermal and friction characteristics in heat exchanger tubes with wire-rod bundles

    NASA Astrophysics Data System (ADS)

    Rahimi, Masoud; Beigzadeh, Reza; Parvizi, Mehdi; Eiamsa-ard, Smith

    2016-08-01

    The group method of data handling (GMDH) technique was used to predict heat transfer and friction characteristics in heat exchanger tubes equipped with wire-rod bundles. Nusselt number and friction factor were determined as functions of wire-rod bundle geometric parameters and Reynolds number. The performance of the developed GMDH-type neural networks was found to be superior in comparison with the proposed empirical correlations. For optimization, the genetic algorithm-based multi-objective optimization was applied.

  8. Friction stir welding tool

    DOEpatents

    Tolle; Charles R. , Clark; Denis E. , Barnes; Timothy A.

    2008-04-15

    A friction stir welding tool is described and which includes a shank portion; a shoulder portion which is releasably engageable with the shank portion; and a pin which is releasably engageable with the shoulder portion.

  9. Compound hierarchical correlated beta mixture with an application to cluster mouse transcription factor DNA binding data.

    PubMed

    Dai, Hongying; Charnigo, Richard

    2015-10-01

    Modeling correlation structures is a challenge in bioinformatics, especially when dealing with high throughput genomic data. A compound hierarchical correlated beta mixture (CBM) with an exchangeable correlation structure is proposed to cluster genetic vectors into mixture components. The correlation coefficient, [Formula: see text], is homogenous within a mixture component and heterogeneous between mixture components. A random CBM with [Formula: see text] brings more flexibility in explaining correlation variations among genetic variables. Expectation-Maximization (EM) algorithm and Stochastic Expectation-Maximization (SEM) algorithm are used to estimate parameters of CBM. The number of mixture components can be determined using model selection criteria such as AIC, BIC and ICL-BIC. Extensive simulation studies were conducted to compare EM, SEM and model selection criteria. Simulation results suggest that CBM outperforms the traditional beta mixture model with lower estimation bias and higher classification accuracy. The proposed method is applied to cluster transcription factor-DNA binding probability in mouse genome data generated by Lahdesmaki and others (2008, Probabilistic inference of transcription factor binding from multiple data sources. PLoS One, 3: , e1820). The results reveal distinct clusters of transcription factors when binding to promoter regions of genes in JAK-STAT, MAPK and other two pathways.

  10. The Knowledge of Memory Aging Questionnaire: Factor Structure and Correlates in a Lifespan Sample

    PubMed Central

    Calamia, Matthew; Reese-Melancon, Celinda; Cherry, Katie E.; Hawley, Karri S.; Jazwinski, S. Michal

    2016-01-01

    The authors examined the factor structure of the Knowledge of Memory Aging Questionnaire (KMAQ) [1] using confirmatory factor analysis in a lifespan sample of 933 individuals who ranged in age from 18 to 101. Participants were college students at Louisiana State University and adults from the community enrolled in the Louisiana Healthy Aging Study (LHAS). A two-factor solution was expected, consistent with the normal and pathological memory aging dimensions that comprise the KMAQ. A bi-factor solution with items loading on a general response bias factor and either a normal or pathological knowledge-specific factor showed good model fit. Knowledge scores were correlated with demographic and cognitive performance variables. Implications of these data for clinical settings and research are considered. PMID:27505021

  11. The Knowledge of Memory Aging Questionnaire: Factor Structure and Correlates in a Lifespan Sample.

    PubMed

    Calamia, Matthew; Reese-Melancon, Celinda; Cherry, Katie E; Hawley, Karri S; Jazwinski, S Michal

    2016-03-01

    The authors examined the factor structure of the Knowledge of Memory Aging Questionnaire (KMAQ) [1] using confirmatory factor analysis in a lifespan sample of 933 individuals who ranged in age from 18 to 101. Participants were college students at Louisiana State University and adults from the community enrolled in the Louisiana Healthy Aging Study (LHAS). A two-factor solution was expected, consistent with the normal and pathological memory aging dimensions that comprise the KMAQ. A bi-factor solution with items loading on a general response bias factor and either a normal or pathological knowledge-specific factor showed good model fit. Knowledge scores were correlated with demographic and cognitive performance variables. Implications of these data for clinical settings and research are considered. PMID:27505021

  12. Friction Stir Weld Tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  13. Friction stir weld tools

    NASA Technical Reports Server (NTRS)

    Carter, Robert W. (Inventor); Payton, Lewis N. (Inventor)

    2007-01-01

    A friction stir weld tool sleeve is supported by an underlying support pin. The pin material is preferably selected for toughness and fracture characteristics. The pin sleeve preferably has a geometry which employs the use of an interrupted thread, a plurality of flutes and/or eccentric path to provide greater flow through. Paddles have been found to assist in imparting friction and directing plastic metal during the welding process.

  14. Mobility and Balance and Their Correlation with Physiological Factors in Elderly with Different Foot Postures

    PubMed Central

    Mohd Said, Aisyah; Manaf, Haidzir; Bukry, Saiful Adli; Justine, Maria

    2015-01-01

    This study determines (1) the correlation between mobility and balance performances with physiological factors and (2) the relationship between foot postures with anthropometric characteristics and lower limb characteristics among elderly with neutral, pronated, and supinated foot. A cross-sectional observational study was conducted in community-dwelling elderly (age: 69.86 ± 5.62 years). Participants were grouped into neutral (n = 16), pronated (n = 14), and supinated (n = 14) foot based on the foot posture index classification. Anthropometric data (height, weight, and BMI), lower limb strength (5-STS) and endurance (30 s chair rise test), mobility (TUG), and balance (FSST) were determined. Data were analyzed using Spearman's correlation coefficient. Body weight was negatively and moderately correlated (rs = −0.552, P < 0.05) with mobility in supinated foot; moderate-to-high positive linear rank correlation was found between lower limb strength and mobility (rs = 0.551 to 0.804, P < 0.05) for pronated and neutral foot. Lower limb endurance was negatively and linearly correlated with mobility in pronated (rs = −0.699) and neutral (rs = −0.573) foot. No correlation was observed in balance performance with physiological factors in any of the foot postures. We can conclude that muscle function may be the most important feature to make movement possible in older persons regardless of the type of foot postures. PMID:26583104

  15. Do Pre-Service Elementary School Teachers Still Have Mathematics Anxiety? Some Factors and Correlates

    ERIC Educational Resources Information Center

    Çatlioglu, Hakan; Gürbüz, Ramazan; Birgin, Osman

    2014-01-01

    This study aims to provide new evidence from Turkish pre-service elementary school (PES) teachers and to identify some correlations and factors associated with mathematics anxiety (MA). 480 Turkish PES teachers participated in this study. Data was collected using a "Personal Information Form," "Mathematics Anxiety Scale," and…

  16. Angiogenic growth factors correlate with disease severity in young patients with autosomal dominant polycystic kidney disease

    PubMed Central

    Reed, Berenice; Masoumi, Amirali; Elhassan, Elwaleed; McFann, Kim; Cadnapaphornchai, Melissa; Maahs, David; Snell-Bergeon, Janet; Schrier, Robert W.

    2013-01-01

    Renal cysts, pain and hematuria are common presentations of autosomal dominant polycystic kidney disease (ADPKD) in children. Renal function, however, is typically preserved in these patients despite increased renal volume. Since angiogenesis has been implicated in promotion of renal cyst growth in ADPKD we measured the serum level of various angiogenic factors and early renal structural changes and cardiovascular parameters in 71 patients with ADPKD with a mean age of 16 years. Renal structure and left ventricular mass index were measured by magnetic resonance imaging or by echocardiogram. Renal function was assessed by creatinine clearance, and urinary protein excretion. Serum growth factor levels were measured by enzyme-linked immunosorbent assay. Because of skewed distributions, the various parameters are reported as log10. Serum Log10 vascular endothelial growth factor was positively correlated with renal and cardiac structure, but negatively correlated with creatinine clearance. Serum angiopoietin 1 levels significantly correlated with structural change in both the kidney and the heart and with urinary protein. Thus, the correlation between angiogenic growth factors with both renal and cardiac disease severity is compatible with a possible role for angiogenesis in the early progression of disease in ADPKD. PMID:20881939

  17. Quantum correlation dynamics of two qubits in noisy environments: The factorization law and beyond

    SciTech Connect

    Zhang, Guo-Feng; Ji, Ai-Ling; Fan, Heng; Liu, Wu-Ming

    2012-09-15

    We investigate the quantum correlations of two qubits under conditions of single-sided and two-sided noisy channels when the initial state of the system belongs to a subclass of X structured ones in terms of measurement-induced nonlocality, measurement-induced disturbance and quantum discord. The results show that measurement-induced nonlocality has a factorization law, regardless of whether there are single-sided or two-sided noisy channels. However, there is no simple factorization relation for measurement-induced disturbance and quantum discord. Also, we compare the evolution of these quantum correlations as functions of time. For the four Bell initial states, we find that the measurement-induced disturbance evolution equations are the same when the channel is single-sided, but they will be divided into two categories when the channel is two-sided. Quantum correlations decay more quickly when the channel is two-sided. Furthermore, quantum discord presents sudden change in the derivative of its time evolution. - Highlights: Black-Right-Pointing-Pointer The quantum correlation dynamics of two qubits under noisy environmental conditions is investigated. Black-Right-Pointing-Pointer Measurement-induced nonlocality has a factorization law, regardless of whether there are single-sided or two-sided noisy channels. Black-Right-Pointing-Pointer There is no simple factorization relation for measurement-induced disturbance and quantum discord.

  18. Web Link Counts Correlate with ISI Impact Factors: Evidence from Two Disciplines.

    ERIC Educational Resources Information Center

    Vaughan, Liwen; Thelwall, Mike

    2002-01-01

    Reports on a study that compared counts of links to the Web home pages of academic journals with the citation based Journal Impact Factor (JIF) for two disciplines: library and information science, and law. Highlights include compiling the lists of journals (which are appended); locating Web pages; and correlations between JIF and link counts.…

  19. Respiratory syncytial virus infection in infants and correlation with meteorological factors and air pollutants

    PubMed Central

    2013-01-01

    Background Respiratory Syncytial Virus (RSV) is the most important cause of severe respiratory infections in infants with seasonal epidemics. Environmental factors (temperature, humidity, air pollution) could influence RSV epidemics through their effects on virus activity and diffusion. Methods We conducted a retrospective study on a paediatric population who referred to our Paediatric Emergency Unit in order to analyze the correlation between weekly incidence of RSV positive cases during winter season in Bologna and meteorological factors and air pollutants concentration. Results We observed a significant correlation between the incidence of RSV infections and the mean minimum temperature registered during the same week and the previous weeks. The weekly number of RSV positive cases was also correlated to the mean PM10 concentration of the week before. Conclusions RSV epidemic trend in Bologna (Italy) is related to the mean minimum temperature, and the mean PM10 concentration. PMID:23311474

  20. Using frictional power to model LSST removal with conventional abrasives

    NASA Astrophysics Data System (ADS)

    Allen, Richard G.; Hubler, William H.

    2015-08-01

    The stressed lap on the Large Polishing Machine (LPM) at the University of Arizona Richard F. Caris Mirror Lab has recently been used to polish the M1 and M3 surfaces of the 8.4-m mirror for the Large Synoptic Survey Telescope (LSST). Loadcells in the three 4-bar links that connect this lap to the spindle of the machine allow the translational forces and torque on the lap to be measured once a second. These force readings and all other available machine parameters are recorded in history files that can be used to create a 2D removal map from one or more polishing runs. While the Preston equation has been used for many years to predict removal in a conventional polishing process, we have adopted a new equation that assumes that removal is proportional to the energy that is transferred from the lap to the substrate via friction. Specifically, the instantaneous removal rate at any point is defined to be the product of four parameters - an energy conversion factor which we call the Allen coefficient, the coefficient of friction, the lap pressure, and the speed of the lap. The Allen coefficient is the ratio of volumetric removal to frictional energy for a particular combination of pad material, abrasive, and substrate. Because our calculations take into account changes in the coefficient of friction between the lap and mirror, our 2D removal maps usually correlate well with optical data. Removal maps for future polishing strokes are created in simulations that track the position and speed of individual lap pads.

  1. Sagittal abdominal diameter shows better correlation with cardiovascular risk factors than waist circumference and BMI

    PubMed Central

    2013-01-01

    Background Obesity (abdominal adiposity) is a risk factor for cardiovascular diseases and the most used methods to measure the adiposity are body mass index (BMI), waist circumference (WC), and sagittal abdominal diameter (SAD). Objective To correlate BMI, WC, and SAD with biochemical parameters and blood pressure in adults. Methods A non-experimental exploratory/descriptive and cross sectional study was developed and it was assessed 133 subjects (59 men and 74 women) aging between 18 and 87 years. It was registered the patients’ weight (kg), height (m), BMI (kg/m2), WC (cm) and SAD (cm), and these parameters were correlated with glycemia, triglycerides, total cholesterol, HDL-c, LDL-c and blood pressure. Results After adjustment for gender and age, it was observed a positive correlation between SAD and systolic arterial blood pressure (r = 0.20), glycemia (r = 0.20), triglycerides (r = 0.32), LDL (r = 0.26), total cholesterol (TC) (r = 0.33), and a negative correlation with HDL-c (r = −0.21) (p < 0.05). It was observed a positive correlation between WC and systolic arterial blood pressure (r = 0.14), triglycerides (r = 0.31), total cholesterol (r = 0.21), and a negative correlation with HDL-c (r = −0.24) (p < 0.05). BMI showed a positive correlation with systolic arterial blood pressure (r = 0.22), total cholesterol (r = 0.20), and triglycerides (r = 0.23) (p < 0.05). Conclusion SAD correlated with almost all the cardiovascular risk factors analyzed and it might be considered the best predictor of abdominal fat and cardiovascular risk. PMID:23856008

  2. X-ray photoelectron spectroscopy study of radiofrequency sputtered chromium bromide, molybdenum disilicide, and molybdenum disulfide coatings and their friction properties

    NASA Technical Reports Server (NTRS)

    Wheeler, D. R.; Brainard, W. A.

    1977-01-01

    Radiofrequency sputtered coatings of CRB2, MOSI2, and MOS2 were examined by X-ray photoelectron spectroscopy. The effects of sputtering target history, deposition time, RF power level, and substrate bias on film composition were studied. Friction tests were run on RF sputtered surfaces of 440-C steel to correlate XPS data with lubricating properties. Significant deviations from stoichiometry and high oxide levels for all three compounds were related to target outgassing. The effect of biasing on these two factors depended on the compound. Improved stoichiometry correlated well with good friction and wear properties.

  3. Linear Confirmatory Factor Models To Evaluate Multitrait-Multimethod Matrices: The Effects of Number of Indicators and Correlation among Methods.

    ERIC Educational Resources Information Center

    Tomas, Jose M.; Hontangas, Pedro M.; Oliver, Amparo

    2000-01-01

    Assessed two models for confirmatory factor analysis of multitrait-multimethod data through Monte Carlo simulation. The correlated traits-correlated methods (CTCM) and the correlated traits-correlated uniqueness (CTCU) models were compared. Results suggest that CTCU is a good alternative to CTCM in the typical multitrait-multimethod matrix, but…

  4. Correlating clinical manifestations with factor levels in rare bleeding disorders: a report from Southern India.

    PubMed

    Viswabandya, A; Baidya, S; Nair, S C; Abraham, A; George, B; Mathews, V; Chandy, M; Srivastava, A

    2012-05-01

    Data on the clinical manifestations of patients with clotting factor defects other than Haemophilia A, B and von Willebrand disease are limited because of their rarity. Due to their autosomal recessive nature of inheritance, these diseases are more common in areas where there is higher prevalence of consanguinity. There is no previous large series reported from southern India where consanguinity is common. Our aim was to analyze clinical manifestations of patients with rare bleeding disorders and correlate their bleeding symptoms with corresponding factor level. Data were collected in a standardized format from our centre over three decades on 281 patients who were diagnosed with rare bleeding disorders (fibrinogen, prothrombin, factor V (FV), FVII, FX, FXI, FXIII and combined FV or FVIII deficiency). Patients with liver dysfunction or those on medications which can affect factor level were excluded. All patients with <50% factor levels were included in this analysis. Patients were analysed for their salient clinical manifestations and it was correlated with their factor levels. The data shows that FXIII deficiency is the commonest and FXI deficiency is the rarest in Southern India. There was no significant difference in bleeding symptoms among those who were < or >1% factor coagulant activities among all disorders, except for few symptoms in FVII and FX deficiency. An international collaborative study is essential to find out the best way of classifying severity in patients with rare bleeding disorders.

  5. Factor structure and external correlates of posttraumatic stress disorder symptoms among African American firefighters

    PubMed Central

    Arbona, Consuelo; Fan, Weihua; Noor, Nausheen

    2016-01-01

    This study compared the relative goodness of fit of three well-established factorial models of posttraumatic stress disorder (PTSD) symptoms among 477 African American male firefighters in a large city in the US. The compared models were the two four-factor emotional numbing and dysphoria models and a five-factor dysphoric arousal model. The study also examined the convergent and discriminant validity of PTSD symptom clusters in relation to depression and alcohol dependence symptoms. Both the emotional numbing and dysphoric arousal PTSD models provided a superior fit to the data compared to the dysphoria model. Findings also indicated a good fit for factor models that included PTSD, depression, and alcohol dependence latent factors, which provides support for the specificity of PTSD symptom clusters. Depression symptoms were more strongly correlated with PTSD symptom clusters than alcohol dependence. In the dysphoric arousal model, depression and alcohol dependence were equally related to the emotional numbing and dysphoric arousal clusters; however, both depression and alcohol dependence were more highly correlated with dysphoric arousal than with anxious arousal. Even though the emotional numbing and dysphoric arousal models demonstrated a superior fit to the data, the four-factor dysphoria model may provide a more parsimonious representation of PTSD’s latent structure than the five-factor dysphoric arousal model. In conclusion, this study extends support for the well-established PTSD symptom factor models among African Americans, a population with whom these models had not been examined earlier. PMID:27563263

  6. Factor structure and external correlates of posttraumatic stress disorder symptoms among African American firefighters.

    PubMed

    Arbona, Consuelo; Fan, Weihua; Noor, Nausheen

    2016-01-01

    This study compared the relative goodness of fit of three well-established factorial models of posttraumatic stress disorder (PTSD) symptoms among 477 African American male firefighters in a large city in the US. The compared models were the two four-factor emotional numbing and dysphoria models and a five-factor dysphoric arousal model. The study also examined the convergent and discriminant validity of PTSD symptom clusters in relation to depression and alcohol dependence symptoms. Both the emotional numbing and dysphoric arousal PTSD models provided a superior fit to the data compared to the dysphoria model. Findings also indicated a good fit for factor models that included PTSD, depression, and alcohol dependence latent factors, which provides support for the specificity of PTSD symptom clusters. Depression symptoms were more strongly correlated with PTSD symptom clusters than alcohol dependence. In the dysphoric arousal model, depression and alcohol dependence were equally related to the emotional numbing and dysphoric arousal clusters; however, both depression and alcohol dependence were more highly correlated with dysphoric arousal than with anxious arousal. Even though the emotional numbing and dysphoric arousal models demonstrated a superior fit to the data, the four-factor dysphoria model may provide a more parsimonious representation of PTSD's latent structure than the five-factor dysphoric arousal model. In conclusion, this study extends support for the well-established PTSD symptom factor models among African Americans, a population with whom these models had not been examined earlier. PMID:27563263

  7. Correlation of climatic factors and dengue incidence in Metro Manila, Philippines.

    PubMed

    Su, Glenn L Sia

    2008-06-01

    Dengue is a serious public health problem in Metro Manila, Philippines. Increasing dengue incidence has been attributed to climate change; however, contradicting reports show inconclusive relationships between dengue and climatic factors. This study investigates temperature and rainfall as climatic factors affecting dengue incidence in Metro Manila from 1996 to 2005. Monthly dengue incidence and climatic data for Metro Manila were collected over a 10-y period (1996-2005). Climatic factors temperature and rainfall were linked with dengue incidence through regression analysis. A predictive model equation plots dengue incidence (Y) versus rainfall (X), which suggests that rainfall is significantly correlated to dengue incidence (r2 = 0.377, p < 0.05). No significant correlation between dengue incidence and temperature was established (p > 0.05). Evidence shows dengue incidence in Metro Manila varies with changing rainfall patterns. Intensified surveillance and control of mosquitoes during periods with high rainfall are recommended.

  8. Friction in volcanic environments

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie E.; Lavallée, Yan

    2016-04-01

    Volcanic landscapes are amongst the most dynamic on Earth and, as such, are particularly susceptible to failure and frictional processes. In rocks, damage accumulation is frequently accompanied by the release of seismic energy, which has been shown to accelerate in the approach to failure on both a field and laboratory scale. The point at which failure occurs is highly dependent upon strain-rate, which also dictates the slip-zone properties that pertain beyond failure, in scenarios such as sector collapse and pyroclastic flows as well as the ascent of viscous magma. High-velocity rotary shear (HVR) experiments have provided new opportunities to overcome the grand challenge of understanding faulting processes during volcanic phenomena. Work on granular ash material demonstrates that at ambient temperatures, ash gouge behaves according to Byerlee's rule at low slip velocities, but is slip-weakening, becoming increasingly lubricating as slip ensues. In absence of ash along a slip plane, rock-rock friction induces cataclasis and heating which, if sufficient, may induce melting (producing pseudotachylyte) and importantly, vesiculation. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The shear-thinning behaviour and viscoelasticity of frictional melts yield a tendency for extremely unstable slip, and occurrence of frictional melt fragmentation. This velocity-dependence acts as an important feedback mechanism on the slip plane, in addition to the bulk composition, mineralogy and glass content of the magma, that all influence frictional behaviour. During sector collapse events and in pyroclastic density currents it is the frictional properties of the rocks and ash that, in-part, control the run-out distance and associated risk. In addition, friction plays an important role in the eruption of viscous magmas: In the conduit, the rheology of magma is integral

  9. Friction-Induced Fluid Heating in Nanoscale Helium Flows

    SciTech Connect

    Li Zhigang

    2010-05-21

    We investigate the mechanism of friction-induced fluid heating in nanoconfinements. Molecular dynamics simulations are used to study the temperature variations of liquid helium in nanoscale Poiseuille flows. It is found that the fluid heating is dominated by different sources of friction as the external driving force is changed. For small external force, the fluid heating is mainly caused by the internal viscous friction in the fluid. When the external force is large and causes fluid slip at the surfaces of channel walls, the friction at the fluid-solid interface dominates over the internal friction in the fluid and is the major contribution to fluid heating. An asymmetric temperature gradient in the fluid is developed in the case of nonidentical walls and the general temperature gradient may change sign as the dominant heating factor changes from internal to interfacial friction with increasing external force.

  10. Does spinal stenosis correlate with MRI findings and pain, psychologic factor and quality of life?

    PubMed Central

    Lee, Mi Young; Jung, Sung Won; Lee, Su Yong

    2015-01-01

    Background To investigate and analyze MRI findings in relation to visual analogue scale (VAS), Oswestry Disability Index (ODI), psychological-factor, sleep-quality, and Short-Form Health Survey (SF-36) scores among patients with central lumbar spinal stenosis (LSS) for the purpose of elucidating a correlation. Methods From July 2013 to May 2014, 117 consecutive patients with central LSS were included in this study. All of the MRIs were evaluated by one of the authors, and the evaluated items were the dural sac cross-sectional area (DSCSA), the number of stenotic levels, and the presence and levels of spondylolisthesis. The ODI, VAS, 36-item SF-36, Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), and Pittsburgh Sleep Quality Index (PSQI) questionnaires were used to evaluate the participants. Results There are no correlations between the ODI, VAS, BDI, BAI, PSQI, and SF-36 scores and the minimum DSCSA; however, a significant correlation was found between the ODI scores and multilevel LSS. The BDI, BAI, and PSQI scores are higher for multilevel LSS compared with single-level LSS, but the difference of this mean value is not statistically significant. Conclusions A significant correlation was shown between those patients with multilevel LSS and the ODI scores; however, significant correlations were not found between the MRI findings and the psychological factors pertaining to sleep and life qualities. PMID:26495059

  11. A statistical method for studying correlated rare events and their risk factors

    PubMed Central

    Xue, Xiaonan; Kim, Mimi Y; Wang, Tao; Kuniholm, Mark H; Strickler, Howard D

    2016-01-01

    Longitudinal studies of rare events such as cervical high-grade lesions or colorectal polyps that can recur often involve correlated binary data. Risk factor for these events cannot be reliably examined using conventional statistical methods. For example, logistic regression models that incorporate generalized estimating equations often fail to converge or provide inaccurate results when analyzing data of this type. Although exact methods have been reported, they are complex and computationally difficult. The current paper proposes a mathematically straightforward and easy-to-use two-step approach involving (i) an additive model to measure associations between a rare or uncommon correlated binary event and potential risk factors and (ii) a permutation test to estimate the statistical significance of these associations. Simulation studies showed that the proposed method reliably tests and accurately estimates the associations of exposure with correlated binary rare events. This method was then applied to a longitudinal study of human leukocyte antigen (HLA) genotype and risk of cervical high grade squamous intraepithelial lesions (HSIL) among HIV-infected and HIV-uninfected women. Results showed statistically significant associations of two HLA alleles among HIV-negative but not HIV-positive women, suggesting that immune status may modify the HLA and cervical HSIL association. Overall, the proposed method avoids model nonconvergence problems and provides a computationally simple, accurate, and powerful approach for the analysis of risk factor associations with rare/uncommon correlated binary events. PMID:25854937

  12. Optimization of conical hydrostatic bearing for minimum friction.

    NASA Technical Reports Server (NTRS)

    Nypan, L. J.; Hamrock, B. J.; Scibbe, H. W.; Anderson, W. J.

    1971-01-01

    Equations for the flow rate, load capacity, and friction torque for a conical hydrostatic bearing were developed. These equations were solved by a digital computer program to determine bearing configurations for minimum friction torque. Design curves are presented that show optimal bearing dimensions for minimum friction torque as a function of dimensionless flow rate for a range of dimensionless load capacity. Results are shown for both laminar and turbulent flow conditions. The results indicate that hydrostatic pocket friction is a significant portion of the total friction torque. However, the bearing dimensions for a minimum friction design are affected very little by inclusion of pocket friction in the analysis. For laminar flow the values of the outer-land radius ratio X3 and outer bearing radius ratio X4 did not change significantly with increasing friction factor. For turbulent flow, the outer bearing radius ratio X4 did not change with increasing friction factor; therefore the value determined for X4 in the laminar flow case is valid for all turbulent flows.

  13. Chirality-dependent friction of bulk molecular solids.

    PubMed

    Yang, Dian; Cohen, Adam E

    2014-08-26

    We show that the solid-solid friction between bulk chiral molecular solids can depend on the relative chirality of the two materials. In menthol and 1-phenyl-1-butanol, heterochiral friction is smaller than homochiral friction, while in ibuprofen, heterochiral friction is larger. Chiral asymmetries in the coefficient of sliding friction vary with temperature and can be as large as 30%. In the three compounds tested, the sign of the difference between heterochiral and homochiral friction correlated with the sign of the difference in melting point between racemate (compound or conglomerate) and pure enantiomer. Menthol and ibuprofen each form a stable racemic compound, while 1-phenyl-1-butanol forms a racemic conglomerate. Thus, a difference between heterochiral and homochiral friction does not require the formation of a stable interfacial racemic compound. Measurements of chirality-dependent friction provide a unique means to distinguish the role of short-range intermolecular forces from all other sources of dissipation in the friction of bulk molecular solids.

  14. [Greenhouse tomato transpiration and its affecting factors: correlation analysis and model simulation].

    PubMed

    Yao, Yong-Zhe; Li, Jian-Ming; Zhang, Rong; Sun, San-Jie; Chen, Kai-Li

    2012-07-01

    A pot experiment was conducted to study the correlations between the daily transpiration of greenhouse tomato and the related affecting factors such as total leaf area per plant, soil relative moisture content, air temperature, relative humidity, and solar radiation under different treatments of supplementary irrigation. A regression model for the daily transpiration of greenhouse tomato was established. There existed significant linear correlations between the daily transpiration and the test affecting factors, and the affecting factors had complicated mutual effects. Soil relative moisture content was the main decision factor of the transpiration, with the decision coefficient being 27.4%, and daily minimum relative humidity was the main limiting factor, with the decision coefficient being -119.7%. The square value of the regression coefficient (R2) between the predicted and measured tomato daily transpiration was 0.81, root mean squared error (RMSE) was 68.52 g, and relative prediction error (RE) was 19.4%, suggesting that the regression model established by using the main affecting factors selected through path analysis could better simulate the daily transpiration of greenhouse tomato. PMID:23173461

  15. [Greenhouse tomato transpiration and its affecting factors: correlation analysis and model simulation].

    PubMed

    Yao, Yong-Zhe; Li, Jian-Ming; Zhang, Rong; Sun, San-Jie; Chen, Kai-Li

    2012-07-01

    A pot experiment was conducted to study the correlations between the daily transpiration of greenhouse tomato and the related affecting factors such as total leaf area per plant, soil relative moisture content, air temperature, relative humidity, and solar radiation under different treatments of supplementary irrigation. A regression model for the daily transpiration of greenhouse tomato was established. There existed significant linear correlations between the daily transpiration and the test affecting factors, and the affecting factors had complicated mutual effects. Soil relative moisture content was the main decision factor of the transpiration, with the decision coefficient being 27.4%, and daily minimum relative humidity was the main limiting factor, with the decision coefficient being -119.7%. The square value of the regression coefficient (R2) between the predicted and measured tomato daily transpiration was 0.81, root mean squared error (RMSE) was 68.52 g, and relative prediction error (RE) was 19.4%, suggesting that the regression model established by using the main affecting factors selected through path analysis could better simulate the daily transpiration of greenhouse tomato.

  16. Measuring anisotropic friction on WTe2 using atomic force microscopy in the force-distance and friction modes.

    PubMed

    Watson, Gregory S; Myhra, Sverre; Watson, Jolanta A

    2010-04-01

    Layered materials which can be easily cleaved have proved to be excellent samples for the study of atomic scale friction. The layered transition metal dichalcogenides have been particularly popular. These materials exhibit a number of interesting properties ranging from superconductivity to low frictional coefficients. In this paper we have investigated the tribology of the dichalcogenide-WTe2. The coefficient of friction is less than 0.040 along the Te rows and increases to over 0.045 across the rows. The frictional forces almost doubled at normal loads of 5000 nN when scanning in the [010] direction in comparison to the [100] direction. The frictional responses of the AFM probe have been monitored in the frictional force and force-versus-distance (f-d) mode. A comparison between the outcomes using the two different modes demonstrates the factors which need to be considered for accurate measurements. PMID:20355449

  17. Measuring anisotropic friction on WTe2 using atomic force microscopy in the force-distance and friction modes.

    PubMed

    Watson, Gregory S; Myhra, Sverre; Watson, Jolanta A

    2010-04-01

    Layered materials which can be easily cleaved have proved to be excellent samples for the study of atomic scale friction. The layered transition metal dichalcogenides have been particularly popular. These materials exhibit a number of interesting properties ranging from superconductivity to low frictional coefficients. In this paper we have investigated the tribology of the dichalcogenide-WTe2. The coefficient of friction is less than 0.040 along the Te rows and increases to over 0.045 across the rows. The frictional forces almost doubled at normal loads of 5000 nN when scanning in the [010] direction in comparison to the [100] direction. The frictional responses of the AFM probe have been monitored in the frictional force and force-versus-distance (f-d) mode. A comparison between the outcomes using the two different modes demonstrates the factors which need to be considered for accurate measurements.

  18. Angiogenic growth factors correlate with disease severity in young patients with autosomal dominant polycystic kidney disease.

    PubMed

    Reed, Berenice Y; Masoumi, Amirali; Elhassan, Elwaleed; McFann, Kim; Cadnapaphornchai, Melissa A; Maahs, David M; Snell-Bergeon, Janet K; Schrier, Robert W

    2011-01-01

    Renal cysts, pain, and hematuria are common presentations of autosomal dominant polycystic kidney disease (ADPKD) in children. Renal function, however, is typically preserved in these patients despite increased renal volume. Since angiogenesis has been implicated in promotion of renal cyst growth in ADPKD, we measured the serum level of various angiogenic factors and early renal structural changes and cardiovascular parameters in 71 patients with ADPKD, with a mean age of 16 years. Renal structure and left ventricular mass index were measured by magnetic resonance imaging or by echocardiogram. Renal function was assessed by creatinine clearance and urinary protein excretion. Serum growth factor levels were measured by enzyme-linked immunosorbent assay. Because of skewed distributions, the various parameters are reported as log(10). Serum log(10) vascular endothelial growth factor was positively correlated with renal and cardiac structure, but negatively with creatinine clearance. Serum angiopoietin 1 levels significantly correlated with structural change in both the kidney and the heart and with urinary protein. Thus, the correlation between angiogenic growth factors with both renal and cardiac disease severity is compatible with a possible role for angiogenesis in the early progression of disease in ADPKD. PMID:20881939

  19. Correlations between environmental factors and wild bee behavior on alfalfa (Medicago sativa) in northwestern China.

    PubMed

    Wang, Xiaojuan; Liu, Hongping; Li, Xiaoxia; Song, Yu; Chen, Li; Jin, Liang

    2009-10-01

    To discover the effect of environmental factors on pollinator visitation to flowering Medicago sativa, several field experiments were designed to examine the diurnal movement patterns of wild bee species in the Hexi Corridor of northwestern China. Our study results showed that Megachile abluta, M. spissula, and Xylocopa valga showed unimodal diurnal foraging behavior, whereas Andrena parvula and Anthophora melanognatha showed bimodal diurnal foraging behavior. Correlation analysis indicated that diurnal foraging activities of pollinators were significantly correlated with environmental factors. Correlations of foraging activities versus environmental factors for M. abluta, M. spissula, and X. valga best fit a linear model, whereas those of A. parvula and A. melanognatha best fit a parallel quadratic model. Results of this study indicated that solitary wild bees such as M. abluta, M. spissula, X. valga, A. parvula, and A. melanognatha are potential alfalfa pollinators in the Hexi Corridor. An understanding of the environmental factors that affect the behaviors of different wild bees foraging in alfalfa are basic to the utilization of solitary wild bees in a practical way for increased, or more consistent, pollination of alfalfa for seed production. PMID:19825303

  20. CAM/LIFTER forces and friction

    NASA Astrophysics Data System (ADS)

    Gabbey, D. J.; Lee, J.; Patterson, D. J.

    1992-02-01

    This report details the procedures used to measure the cam/lifter forces and friction. The present effort employed a Cummins LTA-10, and focuses on measurements and dynamic modeling of the injector train. The program was sponsored by the US Department of Energy in support of advanced diesel engine technology. The injector train was instrumented to record the instantaneous roller speed, roller pin friction torque, pushrod force, injector link force, and cam speed. These measurements, together with lift profiles for pushrod and injector link displacement, enabled the friction work loss in the injector train to be determined. Other significant design criteria such as camshaft roller follower slippage and maximum loads on components were also determined. Future efforts will concentrate on the dynamic model, with tests run as required for correlation.

  1. Friction of Aviation Engines

    NASA Technical Reports Server (NTRS)

    Sparrow, S W; Thorne, M A

    1928-01-01

    The first portion of this report discusses measurements of friction made in the altitude laboratory of the Bureau of Standards between 1920 and 1926 under research authorization of the National Advisory Committee for Aeronautics. These are discussed with reference to the influence of speed, barometric pressure, jacket-water temperature, and throttle opening upon the friction of aviation engines. The second section of the report deals with measurements of the friction of a group of pistons differing from each other in a single respect, such as length, clearance, area of thrust face, location of thrust face, etc. Results obtained with each type of piston are discussed and attention is directed particularly to the fact that the friction chargeable to piston rings depends upon piston design as well as upon ring design. This is attributed to the effect of the rings upon the thickness and distribution of the oil film which in turn affects the friction of the piston to an extent which depends upon its design.

  2. Symptoms of post-traumatic stress disorder in bereaved children and adolescents: factor structure and correlates.

    PubMed

    Boelen, Paul A; Spuij, Mariken

    2013-10-01

    This study investigated the factor structure and correlates of posttraumatic stress-disorder (PTSD) symptoms among children and adolescents confronted with the death of a loved one. Three hundred thirty-two bereaved children and adolescents (aged 8-18; 56.9 % girls) who all received some form of psychosocial support after their loss, completed self-report measures of PTSD, together with measures tapping demographic and loss-related variables, depression, prolonged grief, and functional impairment. Parent-rated indices of impairment were also collected. We first evaluated the fit of six alternative models of the factor structure of PTSD symptoms, using confirmatory factor analyses. Outcomes showed that the 4-factor numbing model from King et al. (Psychological Assessment 10, 90-96, 1998), with distinct factors of reexperiencing, avoidance, emotional numbing, and hyperarousal fit the data best. Of all participants, 51.5 % met DSM-IV criteria for PTSD. PTSD-status and scores on the PTSD factors varied as a function of age and gender, but were unrelated to other demographic and loss-related variables. PTSD-status and scores on the PTSD factors were significantly associated symptom-levels of depression, prolonged grief, and functional impairment. Findings complement prior evidence that the DSM-IV model of the factor structure of PTSD symptoms may not represent the best conceptualization of these symptoms and highlight the importance of addressing PTSD symptoms in children and adolescents seeking help after bereavement.

  3. One-factor model for the cross-correlation matrix in the Vietnamese stock market

    NASA Astrophysics Data System (ADS)

    Nguyen, Quang

    2013-07-01

    Random matrix theory (RMT) has been applied to the analysis of the cross-correlation matrix of a financial time series. The most important findings of previous studies using this method are that the eigenvalue spectrum largely follows that of random matrices but the largest eigenvalue is at least one order of magnitude higher than the maximum eigenvalue predicted by RMT. In this work, we investigate the cross-correlation matrix in the Vietnamese stock market using RMT and find similar results to those of studies realized in developed markets (US, Europe, Japan) [9-18] as well as in other emerging markets[20,21,19,22]. Importantly, we found that the largest eigenvalue could be approximated by the product of the average cross-correlation coefficient and the number of stocks studied. We demonstrate this dependence using a simple one-factor model. The model could be extended to describe other characteristics of the realistic data.

  4. Dynamical correlation effects on structure factor of spin-polarized two-dimensional electron gas

    SciTech Connect

    Singh, Gurvinder; Moudgil, R. K.; Kumar, Krishan; Garg, Vinayak

    2015-06-24

    We report a theoretical study on static density structure factor S(q) of a spin-polarized two-dimensional electron gas over a wide range of electron number density r{sub s}. The electron correlations are treated within the dynamical version of the self-consistent mean-field theory of Singwi, Tosi, Land, and Sjolander, the so-called qSTLS approach. The calculated S(q) exhibits almost perfect agreement with the quantum Monte Carlo simulation data at r{sub s}=1. However, the extent of agreement somewhat diminishes with increasing r{sub s}, particularly for q around 2k{sub F}. Seen in conjunction with the success of qSTLS theory in dealing with correlations in the unpolarized phase, our study suggests that the otherwise celebrated qSTLS theory is not that good in treating the like-spin correlations.

  5. Skin friction balance

    NASA Technical Reports Server (NTRS)

    Ping, Tcheng (Inventor); Supplee, Frank H., Jr. (Inventor)

    1989-01-01

    A skin friction balance uses a parallel linkage mechanism to avoid inaccuracies in skin friction measurement attributable to off-center normal forces. The parallel linkage mechanism includes a stationary plate mounted in a cage, and an upper and lower movable plate which are linked to each other and to the stationary plate throught three vertical links. Flexure pivots are provided for pivotally connecting the links and the plates. A sensing element connected to the upper plate moves in response to skin friction, and the lower plate moves in the opposite direction of the upper plate. A force motor maintains a null position of the sensing element by exerting a restoring force in response to a signal generated by a linear variable differential transformer (LVDT).

  6. Correlation between molybdenum target mammography signs and pathological prognostic factors of breast cancer.

    PubMed

    Zhang, Y; Ma, A D; Jia, H X

    2016-01-01

    This study explores the correlation between molybdenum target (mo-target) mammography signs and pathological prognostic factors of breast cancer. We selected 320 breast cancer patients who were treated between January 2014 and January 2016; using single-factor and multiple-factor logistic regression method, we made correlation analysis on their clinical features, pathological features and mo-target mammography signs. Among mo-target mammography signs, lumps accompanied with calcification and blurry edge were associated with high histologic grades; lumps accompanied with calcification and clear edge were associated with Ki-67 positive; compared with the patients who had lumps with non-stellate edges, positive rates of estrogen receptor (ER) and progesterone receptor (PR) were significantly higher for the patients who had lumps with stellate edges (p < 0.01), while positive rate of human epidermal growth factor receptor-2 (HER-2) and tumor proliferative activity were significantly lower (p < 0.05, p < 0.01). According to the study, we can conclude that mo-target mammography signs mainly include lumps and calcification. Mo-target mammography can improve the accuracy of diagnosis and reduce misdiagnosis or missed diagnosis. Part of mo-target mammography signs are associated with clinical pathology prognostic factors; by grasping the relation, breast cancer patient conditions are expected to be relieved.

  7. Variation of correlations between factors and culturable airborne bacteria and fungi

    NASA Astrophysics Data System (ADS)

    Gao, Min; Yan, Xu; Qiu, Tianlei; Han, Meilin; Wang, Xuming

    2016-03-01

    Bioaerosols, including their characteristics and overall changes correlated with environmental factors, have the potential to impact human health and influence atmospheric dynamics. In this study, the varying interrelationship between the concentration and diameter of culturable bioaerosols and twelve factors including PM2.5 (AQI), PM10 (AQI), sampling time, sampling season, temperature, relative humidity, dew, pressure, wind, O3, NO2, and SO2 is determined for twelve months during non-haze and haze days in Beijing. Results of principal component analysis (PCA) indicated that the influence of factors on culturable bioaerosols is mainly associated with haze levels, sampling time, and season. Multiple linear regressions showed that the correlation between PM10 (AQI) or temperature and culturable bioaerosols varied at different haze levels. The seasonal influence of PM2.5 (AQI) was observed in culturable bioaerosol concentrations, but not their diameters. A temporal relationship between PM10 (AQI) and culturable bioaerosol concentration was detected during rush hour. SO2 and NO2 show positive and negative correlations with culturable bioaerosol concentrations in the morning/evening and mid-day, respectively. These results are useful for accurately evaluating the health effects of exposure to bioaerosols.

  8. Beyond Correlates: A Review of Risk and Protective Factors for Adolescent Dating Violence Perpetration

    PubMed Central

    Vagi, Kevin J.; Rothman, Emily; Latzman, Natasha E.; Tharp, Andra Teten; Hall, Diane M.; Breiding, Matthew J.

    2013-01-01

    Dating violence is a serious public health problem. In recent years, the U.S. Centers for Disease Control and Prevention (CDC) and other entities have made funding available to community based agencies for dating violence prevention. Practitioners who are tasked with developing dating violence prevention strategies should pay particular attention to risk and protective factors for dating violence perpetration that have been established in longitudinal studies. This has been challenging to date because the scientific literature on the etiology of dating violence is somewhat limited, and because there have been no comprehensive reviews of the literature that clearly distinguish correlates of dating violence perpetration from risk or protective factors that have been established through longitudinal research. This is problematic because prevention programs may then target factors that are merely correlated with dating violence perpetration, and have no causal influence, which could potentially limit the effectiveness of the programs. In this article, we review the literature on risk and protective factors for adolescent dating violence perpetration and highlight those factors for which temporal precedence has been established by one or more studies. This review is intended as a guide for researchers and practitioners as they formulate prevention programs. We reviewed articles published between 2000–2010 that reported on adolescent dating violence perpetration using samples from the United States or Canada. In total, 53 risk factors and six protective factors were identified from 20 studies. Next steps for etiological research in adolescent dating violence are discussed, as well as future directions for prevention program developers. PMID:23385616

  9. Is frictional healing slip-dependent?

    NASA Astrophysics Data System (ADS)

    Bhattacharya, P.; Rubin, A. M.; Ryan, K. L.; Riviere, J. V.; Marone, C.

    2015-12-01

    Frictional re-strengthening of bare rock surfaces at very low stresses and near zero slip rate, as observed in the laboratory, is traditionally interpreted as showing support for purely time-dependent healing as embodied in the Aging law. However, while slide-hold-slide experiments on bare surfaces do show an apparent (purely) time-dependent increase in the static friction upon reslide, we show that the stress minima attained during the preceding holds show a strong slip-dependence which contradict the Aging law. A velocity strengthening Slip law explains such data much better. We also show that, large velocity step decreases, which drive the system far below steady state just like long holds, clearly support the slip-dependent response of the Slip law over the time-dependent healing contained in the Aging law. But, while time-dependent healing has an intuitive physical picture in terms of growth of the 'real contact area' with time, it is more difficult to ascribe one to slip-dependent healing. Here, we explore the possibility that the slip-dependence arises out of an interplay between contact `quality' and `quantity' at the scale of the asperity contacts. First, to further study the slip-dependence of healing, we carry out large velocity step decreases and sequences of long slide-hold-slides on both bare rock and gouge. Secondly, to probe the micro-mechanical origins of healing, we complement our mechanical data with amplitudes and travel time data of ultrasonic P- and S- waves transmitted across the sliding interface. While ultrasonic P-wave transmissivity has been used as a proxy for 'real contact area' in friction experiments by Nagata et al. (2012, 2014) before, the simultaneous use of P- and S-phases in our experiments is designed specifically to probe contact rheology. Initial results show strong correlations between changes in friction, transmitted wave amplitudes and travel times in response to changes in slip rate. We also observe important differences

  10. Increase in friction force with sliding speed

    NASA Astrophysics Data System (ADS)

    Cross, Rod

    2005-09-01

    A block sliding down an inclined plane normally accelerates. However, if the friction force increases with speed, then the block can slide at a constant terminal speed in a manner similar to the fall of an object through a fluid. Measurements of the increase in the coefficient of friction for tennis ball cloth sliding on a smooth surface are described over speeds varying by a factor of 9000. For the low speed measurements, the ball cloth was attached to the bottom of a weighted box and pulled along a horizontal surface by a constant horizontal force. Results at higher speeds were obtained by bouncing a tennis ball off the surface.

  11. Hepatoma-derived growth factor upregulation is correlated with prognostic factors of early-stage cervical adenocarcinoma.

    PubMed

    Tsai, Ching-Chou; Huang, Shun-Chen; Tai, Ming Hong; Chien, Chan-Chao Chang; Huang, Chao-Cheng; Hsu, Yi-Chiang

    2014-11-21

    Hepatoma-derived growth factor (HDGF) is a unique nuclear/growth factor that plays an important role in the progression of different types of cancer. A total of 63 patients with early-stage cervical adenocarcinoma (Cx) were enrolled in this retrospective study. The expression of HDGF was significantly increased compared with adjacent non-tumor tissue samples (p < 0.001). Moreover, elevated nuclear HDGF levels were correlated with lymph-vascular space invasion (LVSI; p < 0.05), lymph node metastasis (LNM; p < 0.001), recurrence (p < 0.001) and advanced grade (AG; p < 0.001). The growth of cervical cancer cells (Hela cells) was enhanced by HDGF treatment. The HDGF mRNA and protein level were significantly higher in malignant cervical cancer cells compared with primary ones. By adenovirus gene delivery, HDGF overexpression enhanced, whereas HDGF knockdown perturbed the tumorigenic behaviors of cervical cancer cells. HDGF overexpression is common in early-stage cervical adenocarcinoma and is involved in the carcinogenesis of cervical adenocarcinoma. Cytoplasmic HDGF expression is strongly correlated with pelvic lymph node metastasis and recurrence, indicating that HDGF may serve as a novel prognostic marker for patients with Cx.

  12. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles.

    PubMed

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism. PMID:27447515

  13. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism.

  14. Universal Aging Mechanism for Static and Sliding Friction of Metallic Nanoparticles.

    PubMed

    Feldmann, Michael; Dietzel, Dirk; Tekiel, Antoni; Topple, Jessica; Grütter, Peter; Schirmeisen, André

    2016-07-01

    The term "contact aging" refers to the temporal evolution of the interface between a slider and a substrate usually resulting in increasing friction with time. Current phenomenological models for multiasperity contacts anticipate that such aging is not only the driving force behind the transition from static to sliding friction, but at the same time influences the general dynamics of the sliding friction process. To correlate static and sliding friction on the nanoscale, we show experimental evidence of stick-slip friction for nanoparticles sliding on graphite over a wide dynamic range. We can assign defined periods of aging to the stick phases of the particles, which agree with simulations explicitly including contact aging. Additional slide-hold-slide experiments for the same system allow linking the sliding friction results to static friction measurements, where both friction mechanisms can be universally described by a common aging formalism.

  15. Temperature dependence of nanoscale friction for Fe on YBCO

    NASA Astrophysics Data System (ADS)

    Altfeder, Igor; Krim, Jacqueline

    2012-05-01

    A magnetic probe microscopy study of levitation and atomic-scale friction is reported for Fe on YBCO (Tc = 92.5 K) in the temperature range 65-293 K. Below Tc, the friction coefficient is constant and exhibits no correlation with the strength of superconducting levitation forces. Above Tc, the friction coefficient increases progressively, and nearly doubles between Tc and room temperature. The results are discussed within the context of the underlying atomic-scale electronic and phononic mechanisms that give rise to friction, and it is concluded that contact electrification and static electricity may play a significant role in the non-superconducting phase. Given that the properties of YBCO can be finely tuned, the results point the way to a variety of interesting studies of friction and superconductors.

  16. Skin friction measurement with partially exposed polymer dispersed liquid crystals

    NASA Technical Reports Server (NTRS)

    Parmar, D. S.; Holmes, H. K.

    1993-01-01

    Partially exposed polymer dispersed liquid crystal thin film (10-25 microns) deposited on a flat glass substrate has been used for the first time to measure skin friction. Utilizing the shear-stress-induced director reorientation in the partially exposed liquid-crystal droplets, optical transmission under crossed polarization has been measured as a function of the air flow differential pressure. Direct measurement of the skin friction with a skin friction drag balance, under the same aerodynamic conditions, lets us correlate the skin friction with optical transmission. This provides a unique technique for the direct measurement of skin friction from the transmitted light intensity. The results are in excellent agreement with the model suggested in this paper.

  17. Friction enhancement in concertina locomotion of snakes.

    PubMed

    Marvi, Hamidreza; Hu, David L

    2012-11-01

    Narrow crevices are challenging terrain for most organisms and biomimetic robots. Snakes move through crevices using sequential folding and unfolding of their bodies in the manner of an accordion or concertina. In this combined experimental and theoretical investigation, we elucidate this effective means of moving through channels. We measure the frictional properties of corn snakes, their body kinematics and the transverse forces they apply to channels of varying width and inclination. To climb channels inclined at 60°, we find snakes use a combination of ingenious friction-enhancing techniques, including digging their ventral scales to double their frictional coefficient and pushing channel walls transversely with up to nine times body weight. Theoretical modelling of a one-dimensional n-linked crawler is used to calculate the transverse force factor of safety: we find snakes push up to four times more than required to prevent sliding backwards, presumably trading metabolic energy for an assurance of wall stability.

  18. Friction enhancement in concertina locomotion of snakes

    PubMed Central

    Marvi, Hamidreza; Hu, David L.

    2012-01-01

    Narrow crevices are challenging terrain for most organisms and biomimetic robots. Snakes move through crevices using sequential folding and unfolding of their bodies in the manner of an accordion or concertina. In this combined experimental and theoretical investigation, we elucidate this effective means of moving through channels. We measure the frictional properties of corn snakes, their body kinematics and the transverse forces they apply to channels of varying width and inclination. To climb channels inclined at 60°, we find snakes use a combination of ingenious friction-enhancing techniques, including digging their ventral scales to double their frictional coefficient and pushing channel walls transversely with up to nine times body weight. Theoretical modelling of a one-dimensional n-linked crawler is used to calculate the transverse force factor of safety: we find snakes push up to four times more than required to prevent sliding backwards, presumably trading metabolic energy for an assurance of wall stability. PMID:22728386

  19. Magnetic Low-Friction Track

    NASA Astrophysics Data System (ADS)

    Paetkau, Mark; Bahniwal, Manpreet; Gamblen, James

    2008-05-01

    The standard low-friction tracks used to test Newton's laws are the air track and the low-friction cart track. Both are commercially available and provide low-friction environments to test various physics concepts. At a recent science fair, one of the authors (JG) presented a magnetically levitated cart and track. A literature search found no previous testing of magnetically levitated carts. This paper compares a magnetically levitated cart against the two standard low-friction tracks.

  20. Frictional melt and seismic slip

    NASA Astrophysics Data System (ADS)

    Nielsen, S.; di Toro, G.; Hirose, T.; Shimamoto, T.

    2008-01-01

    Frictional melt is implied in a variety of processes such as seismic slip, ice skating, and meteorite combustion. A steady state can be reached when melt is continuously produced and extruded from the sliding interface, as shown recently in a number of laboratory rock friction experiments. A thin, low-viscosity, high-temperature melt layer is formed resulting in low shear resistance. A theoretical solution describing the coupling of shear heating, thermal diffusion, and extrusion is obtained, without imposing a priori the melt thickness. The steady state shear traction can be approximated at high slip rates by the theoretical form τss = σn1/4 (A/?) ? under a normal stress σn, slip rate V, radius of contact area R (A is a dimensional normalizing factor and W is a characteristic rate). Although the model offers a rather simplified view of a complex process, the predictions are compatible with experimental observations. In particular, we consider laboratory simulations of seismic slip on earthquake faults. A series of high-velocity rotary shear experiments on rocks, performed for σn in the range 1-20 MPa and slip rates in the range 0.5-2 m s-1, is confronted to the theoretical model. The behavior is reasonably well reproduced, though the effect of radiation loss taking place in the experiment somewhat alters the data. The scaling of friction with σn, R, and V in the presence of melt suggests that extrapolation of laboratory measures to real Earth is a highly nonlinear, nontrivial exercise.

  1. Quantum theory of friction

    SciTech Connect

    Barnett, Stephen M.; Cresser, James D.

    2005-08-15

    We present a Markovian quantum theory of friction. Our approach is based on the idea that collisions between a Brownian particle and single molecules of the surrounding medium constitute, as far as the particle is concerned, instantaneous simultaneous measurements of its position and momentum.

  2. Internal Friction within the Earth and Seismic Attenuation

    NASA Astrophysics Data System (ADS)

    Morozov, I. B.

    2012-12-01

    The existing theory of internal friction within the Earth uses viscosity for its fluids and "viscoelastic quality factor" (Q) for solids. Despite its broad acceptance, it is rarely noticed that this model also faces serious theoretical and practical difficulties. Such difficulties arise in cases of heterogeneous media, which are most important in seismology. For example, for a long-period Love wave, the viscoelastic model violates the energy balance and overestimates the attenuation by ~ 5-12 %. In all existing Q models, fluid layers such as the outer core unrealistically contribute zero dissipation of free oscillations, seismic waves, and tides. For fluids, internal friction (Q-1) is directly proportional to viscosity, whereas from comparing seismic observations with geodynamics, this empirical correlation is opposite for the upper mantle. The viscoelastic model also produces nonphysical solutions and incorrect phases of acoustic impedances in heterogeneous media. These problems need to be addressed in order o understand the meaning of Q shown in many attenuation models. Fortunately, an alternate approach to internal friction is well known in continuum mechanics and thermodynamics. This approach is free from the above problems. Instead of Q and "material memory", it considers several specific mechanisms of energy dissipation: 1) viscosity for both solids or fluids, which can be Newtonian or non-Newtonian, 2) thermoelasticity, 3) scattering and variations of geometric spreading, and 4) kinetic transformations within the material. Here, we apply this approach to field and lab observations of seismic attenuation. As an example, we invert the Love-wave QL observed on the surface at 20-200-s periods for physical parameters 1)-3) above. With the exception of thermoelasticity on small heterogeneities, each of these mechanisms explains the observed frequency dependence of QL very closely. For several mechanisms, Love-wave attenuation is dominated by mantle layers at ~70

  3. Diffusion Weighted MR Imaging of Breast and Correlation of Prognostic Factors in Breast Cancer

    PubMed Central

    Kızıldağ Yırgın, İnci; Arslan, Gözde; Öztürk, Enis; Yırgın, Hakan; Taşdemir, Nihat; Gemici, Ayşegül Akdoğan; Kabul, Fatma Çelik; Kaya, Eyüp

    2016-01-01

    Background: Through Diffusion Weighted Imaging (DWI), information related to early molecular changes, changes in the permeability of cell membranes, and early morphologic and physiologic changes such as cell swelling can be obtained. Aims: We investigated the correlation between the prognostic factors of breast cancer and apparent diffusion coefficient (ADC) in DWI sequences of malignant lesions. Study Design: Retrospective cross-sectional study. Methods: Patients who were referred to our clinic between September 2012 and September 2013, who underwent dynamic breast MRI before or after biopsy and whose biopsy results were determined as malignant, were included in our study. Before the dynamic analysis, DWI sequences were taken. ADC relationship with all prognostic factors was investigated. Pearson correlation test was used to compare the numerical data, while Spearman correlation and Fisher exact tests were used to compare the categorical data. The advanced relationships were evaluated with linear regression analysis and univariate analysis. The efficiency of the parameters was evaluated using ROC analysis. The significance level (P) was accepted as 0.05. Results: In total, 41 female patients with an average age of 49.4 years (age interval 21–77) and 44 lesions were included into the study. In the Pearson correlation test, no statistically significant difference was determined between ADC and the patient’s age and tumor size. In the Spearman correlation test, a statistically significant difference was determined between nuclear grade (NG) and ADC (r=−0.424, p=0.04); no statistically significant correlation was observed between the other prognostic factors with each other and ADC values. In the linear regression analysis, the relationship of NG with ADC was found to be more significant alone than when comparing all parameters (corrected r2=0.196, p=0.005). Further evaluations between the NG and ADC correlation were carried out with ROC analysis. A

  4. Expression of neu protein, epidermal growth factor receptor, and transforming growth factor alpha in breast cancer. Correlation with clinicopathologic parameters.

    PubMed Central

    Lundy, J.; Schuss, A.; Stanick, D.; McCormack, E. S.; Kramer, S.; Sorvillo, J. M.

    1991-01-01

    The major objectives of this study were twofold: to determine 1) if growth factors or growth factor receptors were expressed similarly or differently in a clinically well-characterized group of breast cancer patients and 2) if these phenotypic characteristics were associated with any of the commonly used prognostic parameters. Formalin-fixed paraffin-embedded tumor tissue from 51 node-positive breast cancer patients were analyzed for the expression of neu, epidermal growth factor-receptor (EGF-R), and transforming growth factor alpha (TGF alpha) using immunoperoxidase staining. Positive membranous staining for neu was observed in 15 (29%) tumors. Over-expression of neu was observed in high-grade, estrogen-receptor-negative tumors (P less than 0.05). Epidermal growth factor receptor was expressed in 22 (43%) of the tumors analyzed and found to a greater degree in estrogen-receptor-negative and high-grade tumors (P less than 0.025). A significant correlation between neu and EGF-R expression was also noted. Tumors expressing membranous staining of neu had a greater than 70% chance of expressing EGF-R (P less than 0.01). Expression of TGF alpha was found in 68% of tumors and TGF alpha was detected in grade 1 and 2 tumor to a greater degree than EGF-R. The authors conclude that assaying tumors for these antigens may give additional phenotypic characteristics that can give further insight into the biology of breast cancer. Images Figure 1 Figure 2 Figure 3 PMID:1711294

  5. Correlation Analysis of Potential Factors Influencing Graft Maturity After Anterior Cruciate Ligament Reconstruction

    PubMed Central

    Li, Hong; Chen, Shuang; Tao, Hongyue; Li, Hongyun; Chen, Shiyi

    2014-01-01

    Background: Postoperatively, signal changes of the reconstructed anterior cruciate ligament (ACL) graft on magnetic resonance imaging (MRI) images commonly occurs, which may be a cause for concern. The signal intensity changes are usually expressed by signal/noise quotient (SNQ) value, representing graft maturity. To date, little is known about the factors influencing the SNQ value of the reconstructed ACL graft. Purpose: To evaluate ACL graft SNQ value and associated factors after ACL reconstruction. Study Design: Case series; Level of evidence, 4. Methods: Male patients who underwent ACL reconstruction using autograft or allograft tendon from September 2004 to September 2011 were randomly invited to take part in this investigation, including functional scores, physical examination, and MRI scan. The femoral side graft was fixed with Endobutton CL or Rigidfix pins, and the tibial side graft was fixed with a bio-intrafix. SNQ values of each graft were measured on MRI to represent graft maturity. Sagittal ACL angle, ACL–Blumensaat line angle, and medial and lateral posterior tibial slope (PTS) were measured using MRI 3-dimensional dual-echo steady-state images. Potential risk factors, including age, body mass index, postoperative time, Tegner activity scale (TAS), sagittal ACL angle, ACL–Blumensaat line angle, medial PTS, lateral PTS, and primary graft diameter, were tested for their association with the graft SNQ value by multivariate stepwise regression analysis. Results: A total of 104 male subjects (mean follow-up, 30.7 months) were examined, including 62 allograft and 42 autograft reconstructions. There was a significant association between graft SNQ and postoperative time (r = −0.431, P < .001), TAS (r = 0.295, P = .002), and ACL–Blumensaat line angle (r = −0.304, P = .002). Univariate regression analysis showed that TAS (β = 6.15, P < .001) positively correlated, postoperative time (β = −0.26, P < .001) negatively correlated, and ACL

  6. An IL6-correlated signature in serous epithelial ovarian cancer associates with growth factor response

    PubMed Central

    2013-01-01

    Background Epithelial ovarian cancer (EOC) is one of the most lethal gynecological cancers; the majority of EOC is the serous histotype and diagnosed at advanced stage. IL6 is the cytokine that has been found most frequently associated with carcinogenesis and progression of serous EOCs. IL6 is a growth-promoting and anti-apoptotic factor, and high plasma levels of IL6 in advanced stage EOCs correlate with poor prognosis. The objective of the present study was to identify IL6 co-regulated genes and gene network/s in EOCs. Results We applied bioinformatics tools on 7 publicly available data sets containing the gene expression profiles of 1262 EOC samples. By Pearson's correlation analysis we identified, in EOCs, an IL6-correlated gene signature containing 40 genes mainly associated with proliferation. 33 of 40 genes were also significantly correlated in low malignant potential (LMP) EOCs, while 7 genes, named C5AR1, FPR1, G0S2, IL8, KLF2, MMP19, and THBD were IL6-correlated only in advanced stage EOCs. Among the 40-gene signature EGFR ligand HBEGF, genes of the EGR family members and genes encoding for negative feedback regulators of growth factor signaling were included. The results obtained by Gene Set Enrichment and Ingenuity Pathway Analyses enabled the identification, respectively, of gene sets associated with ‘early growth factor response’ for the 40-gene signature, and a biological network related to ‘thrombosis and cardiovascular disease’ for the 7-gene signature. In agreement with these results, selected genes from the identified signatures were validated in vitro by real time RT-PCR in serous EOC cell lines upon stimulation with EGF. Conclusions Serous EOCs, independently of their aggressiveness, co-regulate IL6 expression together with that of genes associated to growth factor signaling, arguing for the hypothesis that common mechanism/s driven by EGFR ligands characterize both advanced-stage and LMP EOCs. Only advanced-stage EOCs appeared to be

  7. Residential Greenness and Birth Outcomes: Evaluating the Influence of Spatially Correlated Built-Environment Factors

    PubMed Central

    Davies, Hugh W.; Frank, Lawrence; Van Loon, Josh; Gehring, Ulrike; Tamburic, Lillian; Brauer, Michael

    2014-01-01

    Background: Half the world’s population lives in urban areas. It is therefore important to identify characteristics of the built environment that are beneficial to human health. Urban greenness has been associated with improvements in a diverse range of health conditions, including birth outcomes; however, few studies have attempted to distinguish potential effects of greenness from those of other spatially correlated exposures related to the built environment. Objectives: We aimed to investigate associations between residential greenness and birth outcomes and evaluate the influence of spatially correlated built environment factors on these associations. Methods: We examined associations between residential greenness [measured using satellite-derived Normalized Difference Vegetation Index (NDVI) within 100 m of study participants’ homes] and birth outcomes in a cohort of 64,705 singleton births (from 1999–2002) in Vancouver, British Columbia, Canada. We also evaluated associations after adjusting for spatially correlated built environmental factors that may influence birth outcomes, including exposure to air pollution and noise, neighborhood walkability, and distance to the nearest park. Results: An interquartile increase in greenness (0.1 in residential NDVI) was associated with higher term birth weight (20.6 g; 95% CI: 16.5, 24.7) and decreases in the likelihood of small for gestational age, very preterm (< 30 weeks), and moderately preterm (30–36 weeks) birth. Associations were robust to adjustment for air pollution and noise exposures, neighborhood walkability, and park proximity. Conclusions: Increased residential greenness was associated with beneficial birth outcomes in this population-based cohort. These associations did not change after adjusting for other spatially correlated built environment factors, suggesting that alternative pathways (e.g., psychosocial and psychological mechanisms) may underlie associations between residential greenness and

  8. Auto-correlation of journal impact factor for consensus research reporting statements: a cohort study

    PubMed Central

    2016-01-01

    Background. The Journal Citation Reports journal impact factors (JIFs) are widely used to rank and evaluate journals, standing as a proxy for the relative importance of a journal within its field. However, numerous criticisms have been made of use of a JIF to evaluate importance. This problem is exacerbated when the use of JIFs is extended to evaluate not only the journals, but the papers therein. The purpose of this study was therefore to investigate the relationship between the number of citations and journal IF for identical articles published simultaneously in multiple journals. Methods. Eligible articles were consensus research reporting statements listed on the EQUATOR Network website that were published simultaneously in three or more journals. The correlation between the citation count for each article and the median journal JIF over the published period, and between the citation count and number of article accesses was calculated for each reporting statement. Results. Nine research reporting statements were included in this analysis, representing 85 articles published across 58 journals in biomedicine. The number of citations was strongly correlated to the JIF for six of the nine reporting guidelines, with moderate correlation shown for the remaining three guidelines (median r = 0.66, 95% CI [0.45–0.90]). There was also a strong positive correlation between the number of citations and the number of article accesses (median r = 0.71, 95% CI [0.5–0.8]), although the number of data points for this analysis were limited. When adjusted for the individual reporting guidelines, each logarithm unit of JIF predicted a median increase of 0.8 logarithm units of citation counts (95% CI [−0.4–5.2]), and each logarithm unit of article accesses predicted a median increase of 0.1 logarithm units of citation counts (95% CI [−0.9–1.4]). This model explained 26% of the variance in citations (median adjusted r2 = 0.26, range 0.18–1.0). Conclusion. The impact

  9. Two speed factors of visual recognition independently correlated with fluid intelligence.

    PubMed

    Tachibana, Ryosuke; Namba, Yuri; Noguchi, Yasuki

    2014-01-01

    Growing evidence indicates a moderate but significant relationship between processing speed in visuo-cognitive tasks and general intelligence. On the other hand, findings from neuroscience proposed that the primate visual system consists of two major pathways, the ventral pathway for objects recognition and the dorsal pathway for spatial processing and attentive analysis. Previous studies seeking for visuo-cognitive factors of human intelligence indicated a significant correlation between fluid intelligence and the inspection time (IT), an index for a speed of object recognition performed in the ventral pathway. We thus presently examined a possibility that neural processing speed in the dorsal pathway also represented a factor of intelligence. Specifically, we used the mental rotation (MR) task, a popular psychometric measure for mental speed of spatial processing in the dorsal pathway. We found that the speed of MR was significantly correlated with intelligence scores, while it had no correlation with one's IT (recognition speed of visual objects). Our results support the new possibility that intelligence could be explained by two types of mental speed, one related to object recognition (IT) and another for manipulation of mental images (MR).

  10. Internal rotor friction instability

    NASA Technical Reports Server (NTRS)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  11. Micro Surface Texturing for Friction Control

    NASA Astrophysics Data System (ADS)

    Rashwan, Ola

    Recently, surface texturing has gained momentum as a way to control the friction which is involved in various applications and systems, such as components of internal combustion engines, dies and punches of the metal forming processes and Micro-electrical-mechanical Systems (MEMS). This dissertation demonstrates that under dry sliding, there is a specific significant surface texturing parameter at which the coefficient of friction should be at a minimum. This dissertation met this objective through an extensive study of the relevant literature on surface texturing and friction, analysing the friction mechanisms involved in dry sliding, and highlighting the key factors that control friction as the real area of contact and material properties. An analytical proof is derived demonstrating that a minimum friction force exists if the two components of the friction force, adhesion and mechanical deformation, are differentiated with respect to the real contact area. In addition, numerical simulations and experimental work were performed to test this hypothesis. In the two and three dimensional finite element models, normal and sliding contact between a rigid indenter and elastic-plastic surfaces, which are textured by circular and hexagonal dimples of different sizes and densities, are simulated and analysed. Circular craters of different sizes and densities, are fabricated using laser ablation on hardened tool steel samples, while the hexagonal dimples are fabricated using photo-lithography. The dimples are arranged in adjacent equilateral triangles layout. Coefficients of friction were measured using a scratch tester under dry sliding conditions and constant load. In addition, adhesion forces were estimated using an Atomic Force Microscope (AFM). The adhesion force is found to be exponentially decreasing with the increase of the spatial texture density. The dimensionless quantity, spatial texture density (D/L) was identified as the most significant texturing parameter

  12. PEBBLES Simulation of Static Friction and New Static Friction Benchmark

    SciTech Connect

    Joshua J. Cogliati; Abderrafi M. Ougouag

    2010-05-01

    Pebble bed reactors contain large numbers of spherical fuel elements arranged randomly. Determining the motion and location of these fuel elements is required for calculating certain parameters of pebble bed reactor operation. This paper documents the PEBBLES static friction model. This model uses a three dimensional differential static friction approximation extended from the two dimensional Cundall and Strack model. The derivation of determining the rotational transformation of pebble to pebble static friction force is provided. A new implementation for a differential rotation method for pebble to container static friction force has been created. Previous published methods are insufficient for pebble bed reactor geometries. A new analytical static friction benchmark is documented that can be used to verify key static friction simulation parameters. This benchmark is based on determining the exact pebble to pebble and pebble to container static friction coefficients required to maintain a stable five sphere pyramid.

  13. LORENTZ-FACTOR-ISOTROPIC-LUMINOSITY/ENERGY CORRELATIONS OF GAMMA-RAY BURSTS AND THEIR INTERPRETATION

    SciTech Connect

    Lue Jing; Zou Yuanchuan; Lei Weihua; Wu Qingwen; Wang Dingxiong; Zhang Bing; Lue Houjun; Liang Enwei E-mail: leiwh@hust.edu.cn

    2012-05-20

    The bulk Lorentz factor of the gamma-ray burst (GRB) ejecta ({Gamma}{sub 0}) is a key parameter to understanding GRB physics. Liang et al. have discovered a correlation between {Gamma}{sub 0} and isotropic {gamma}-ray energy: {Gamma}{sub 0}{proportional_to}E{sup 0.25}{sub {gamma},iso,52}. By including more GRBs with updated data and more methods to derive {Gamma}{sub 0}, we confirm this correlation and obtain {Gamma}{sub 0} {approx_equal} 91E{sup 0.29}{sub {gamma},iso,52}. Evaluating the mean isotropic {gamma}-ray luminosities L{sub {gamma},iso} of the GRBs in the same sample, we discover an even tighter correlation {Gamma}{sub 0} {approx_equal} 249L{sup 0.30}{sub {gamma},iso,52}. We propose an interpretation to this later correlation. Invoking a neutrino-cooled hyperaccretion disk around a stellar mass black hole as the central engine of GRBs, we derive jet luminosity powered by neutrino annihilation and baryon loading from a neutrino-driven wind. Applying beaming correction, we finally derive {Gamma}{sub 0}{proportional_to}L{sup 0.22}{sub {gamma},iso}, which is consistent with the data. This suggests that the central engine of long GRBs is likely a stellar mass black hole surrounded by a hyper-accreting disk.

  14. Clinical factors correlated with the success rate of miniscrews in orthodontic treatment

    PubMed Central

    Topouzelis, Nikolaos; Tsaousoglou, Phoebus

    2012-01-01

    Miniscrews offer a reliable alternative for anchorage during orthodontic treatment, particularly for non-cooperative patients or periodontal patients with alveolar bone loss. The study aims at assessing the correlation of various clinical indicators with the success or failure of miniscrews used for anchorage during orthodontic treatment. Thirty-four consecutive patients with a cumulative total of 82 miniscrews implanted participated in the study. Generalized Estimating Equations were used to assess the correlation of various factors with success rates. The miniscrew was considered the unit of analysis clustered within site and within patient. The overall success rate of miniscrews was 90.2%. For every additional miniscrew used in a patient's oral cavity, the success rate was reduced by 67%. Retromandibular triangle and palatal placement and in movable mucosa resulted in lower success rate. The miniscrew length and diameter were found to correlate with success rates. Orthodontic force applied on miniscrews for uprighting purposes showed a lower success rate than that used for retraction. This study revealed that miniscrews present high success rates. The number of miniscrews used per patient, the miniscrew site placement, the soft tissue type of placement, the miniscrew length and diameter as well as the orthodontic force applied on the miniscrew showed significant correlation with success rates. PMID:22241373

  15. Analysis of thoracic epidurography and correlating factors affecting the extent of contrast medium spread

    PubMed Central

    Oh, Jung Hue; Park, Ki Bum

    2016-01-01

    Background Thoracic epidural anesthesia is frequently used to maintain intraoperative and postoperative analgesia. Frequently, 3 ml of local anesthetic is used as a test dose, or for intermittent epidural injection. We assessed the extent of the spread of 3 ml of contrast medium in the thoracic epidural space and attempted to identify any correlating factors affecting the epidurography. Methods A total of 70 patients were enrolled in the study, and thoracic epidural catheterizations were performed under fluoroscopic guidance. Using 3 ml of contrast medium, epidurography was evaluated to confirm the number of spinal segments covered by the contrast medium. Correlation analysis was performed between patient characteristics (sex, age, body mass index, weight, height, and location of catheter tip) and the extent of the contrast spread. Results The mean number of vertebral segments evaluated by contrast medium was 7.9 ± 2.2 using 3 ml of contrast medium. The contrast spread in the cranial direction showed more extensive distribution than that in the caudal direction, with statistical significance (P < 0.01). Patient height demonstrated a negative correlation with the extent of distribution of contrast medium (r = −0.311, P < 0.05). Conclusions Thoracic epidurography using 3 ml of contrast medium results in coverage of a mean of 7.9 ± 2.2 spinal segments, with more extensive cranial spread, and patient height showed a weak negative correlation with the distribution of contrast medium. PMID:27738504

  16. Patterns and correlates of multiple risk factors for adult-onset cancer among adolescents

    PubMed Central

    MAYS, DARREN; PESHKIN, BETH N.; WALKER, LESLIE R.; ABRAHAM, ANISHA A.; HAWKINS, KIRSTEN B.; TERCYAK, KENNETH P.

    2012-01-01

    We investigated patterns and correlates of multiple, adult-onset cancer risk factors (MCRFs) among adolescents. Baseline data from an intervention efficacy trial were analyzed to examine patterns of co-occurring MCRFs and sociodemographic and theoretical (e.g., prevention self-efficacy) correlates of MCRFs among adolescents (N = 50) age 13 – 21. The mean total MCRFs was 4.6 (SD = 1.6; range 0–9). The most common risk factors were intentions to use alcohol (n = 40, 80%), < 5 daily servings of fruits/vegetables (n = 40, 80%), and lifetime alcohol use (n = 38, 76%). MCRFs commonly co-occurred, suggesting a clustered risk profile. Greater age (B = 0.19 95% CI 0.01, 0.38) and lower prevention self-efficacy (B = −0.16, 95% CI −0.02, −0.30) were significantly (p < 0.05) associated with MCRFs. Multiple health behavior change interventions are needed to prevent accumulation of risk factors as youth mature. Self-efficacy may be an important target for prevention interventions. PMID:22363044

  17. Factorization of correlations in two-dimensional percolation on the plane and torus

    NASA Astrophysics Data System (ADS)

    Ziff, Robert M.; Simmons, Jacob J. H.; Kleban, Peter

    2011-02-01

    Recently, Delfino and Viti have examined the factorization of the three-point density correlation function P3 at the percolation point in terms of the two-point density correlation functions P2. According to conformal invariance, this factorization is exact on the infinite plane, such that the ratio R(z1, z2, z3) = P3(z1, z2, z3)/[P2(z1, z2)P2(z1, z3)P2(z2, z3)]1/2 is not only universal but also a constant, independent of zi and in fact an operator product expansion coefficient. Delfino and Viti analytically calculated its value (1.022 013...) for percolation, in agreement with the numerical value 1.022 found previously in a study of R on the conformally equivalent cylinder. In this paper we confirm the factorization on the plane numerically using periodic lattices (tori) of very large size, which locally approximate a plane. We also investigate the general behavior of R on the torus, and find a minimum value of R ≈ 1.0132 when the three points are maximally separated. In addition, we present a simplified expression for R on the plane as a function of the SLE parameter κ.

  18. Correlates for Legal Help-Seeking: Contextual Factors for Battered Women in Shelter

    PubMed Central

    Wright, Caroline Vaile; Johnson, Dawn M.

    2010-01-01

    Legal redress can play a critical role in interrupting the pattern of domination and control inherent in intimate partner violence (IPV), yet it remains an infrequent strategy among battered women. The current study employed a contextual framework for investigating the correlates for engagement in the criminal justice system for a sample of 227 sheltered battered women. Results indicated that individual, relational, and system-level factors were all associated with two legal help-seeking behaviors: having a civil protection order and criminal prosecution. In particular, posttraumatic stress disorder (PTSD) symptomatology, social support, and prior experience with police officers were significant correlates for legal help-seeking. Results highlight the need for a coordinated community response to IPV, addressing both legal needs and psychological needs simultaneously. PMID:20055214

  19. Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy.

    PubMed

    Peckys, Diana B; de Jonge, Niels

    2015-09-11

    This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM) of whole cells in hydrated state. Fluorescent quantum dots (QDs) were coupled to EGFR via a two-step labeling protocol, providing an efficient and specific protein labeling, while avoiding label-induced clustering of the receptor. Fluorescence microscopy provided overview images of the cellular locations of the EGFR. The scanning transmission electron microscopy (STEM) detector was used to detect the QD labels with nanoscale resolution. The resulting correlative images provide data of the cellular EGFR distribution, and the stoichiometry at the single molecular level in the natural context of the hydrated intact cell. ESEM-STEM images revealed the receptor to be present as monomer, as homodimer, and in small clusters. Labeling with two different QDs, i.e., one emitting at 655 nm and at 800 revealed similar characteristic results.

  20. Studying the Stoichiometry of Epidermal Growth Factor Receptor in Intact Cells using Correlative Microscopy

    PubMed Central

    Peckys, Diana B.; de Jonge, Niels

    2015-01-01

    This protocol describes the labeling of epidermal growth factor receptor (EGFR) on COS7 fibroblast cells, and subsequent correlative fluorescence microscopy and environmental scanning electron microscopy (ESEM) of whole cells in hydrated state. Fluorescent quantum dots (QDs) were coupled to EGFR via a two-step labeling protocol, providing an efficient and specific protein labeling, while avoiding label-induced clustering of the receptor. Fluorescence microscopy provided overview images of the cellular locations of the EGFR. The scanning transmission electron microscopy (STEM) detector was used to detect the QD labels with nanoscale resolution. The resulting correlative images provide data of the cellular EGFR distribution, and the stoichiometry at the single molecular level in the natural context of the hydrated intact cell. ESEM-STEM images revealed the receptor to be present as monomer, as homodimer, and in small clusters. Labeling with two different QDs, i.e., one emitting at 655 nm and at 800 revealed similar characteristic results. PMID:26383083

  1. Glassy properties and viscous slowing down: An analysis of the correlation between nonergodicity factor and fragility.

    PubMed

    Niss, Kristine; Dalle-Ferrier, Cécile; Giordano, Valentina M; Monaco, Giulio; Frick, Bernhard; Alba-Simionesco, Christiane

    2008-11-21

    We present an extensive analysis of the proposed relationship [T. Scopigno et al., Science 302, 849 (2003)] between the fragility of glass-forming liquids and the nonergodicity factor as measured by inelastic x-ray scattering. We test the robustness of the correlation through the investigation of the relative change under pressure of the speed of sound, nonergodicity factor, and broadening of the acoustic exitations of a molecular glass former, cumene, and of a polymer, polyisobutylene. For polyisobutylene, we also perform a similar study by varying its molecular weight. Moreover, we have included new results on liquids presenting an exceptionally high fragility index m under ambient conditions. We show that the linear relation, proposed by Scopigno et al. [Science 302, 849 (2003)] between fragility, measured in the liquid state, and the slope alpha of the inverse nonergodicity factor as a function of T/T(g), measured in the glassy state, is not verified when increasing the data base. In particular, while there is still a trend in the suggested direction at atmospheric pressure, its consistency is not maintained by introducing pressure as an extra control parameter modifying the fragility: whatever is the variation in the isobaric fragility, the inverse nonergodicity factor increases or remains constant within the error bars, and one observes a systematic increase in the slope alpha when the temperature is scaled by T(g)(P). To avoid any particular aspects that might cause the relation to fail, we have replaced the fragility by other related properties often evoked, e.g., thermodynamic fragility, for the understanding of its concept. Moreover, we find, as previously proposed by two of us [K. Niss and C. Alba-Simionesco, Phys. Rev. B 74, 024205 (2006)], that the nonergodicity factor evaluated at the glass transition qualitatively reflects the effect of density on the relaxation time even though in this case no clear quantitative correlations appear. PMID:19026072

  2. Factors correlating with significant differences between X-ray structures of myoglobin

    SciTech Connect

    Rashin, Alexander A.; Domagalski, Marcin J.; Zimmermann, Michael T.; Minor, Wladek; Chruszcz, Maksymilian; Jernigan, Robert L.

    2014-02-01

    Conformational differences between myoglobin structures are studied. Most structural differences in whale myoglobin beyond the uncertainty threshold can be correlated with a few specific structural factors. There are always exceptions and a search for additional factors is needed. The results might have serious implications for biological insights from conformational differences. Validation of general ideas about the origins of conformational differences in proteins is critical in order to arrive at meaningful functional insights. Here, principal component analysis (PCA) and distance difference matrices are used to validate some such ideas about the conformational differences between 291 myoglobin structures from sperm whale, horse and pig. Almost all of the horse and pig structures form compact PCA clusters with only minor coordinate differences and outliers that are easily explained. The 222 whale structures form a few dense clusters with multiple outliers. A few whale outliers with a prominent distortion of the GH loop are very similar to the cluster of horse structures, which all have a similar GH-loop distortion apparently owing to intermolecular crystal lattice hydrogen bonds to the GH loop from residues near the distal histidine His64. The variations of the GH-loop coordinates in the whale structures are likely to be owing to the observed alternative intermolecular crystal lattice bond, with the change to the GH loop distorting bonds correlated with the binding of specific ‘unusual’ ligands. Such an alternative intermolecular bond is not observed in horse myoglobins, obliterating any correlation with the ligands. Intermolecular bonds do not usually cause significant coordinate differences and cannot be validated as their universal cause. Most of the native-like whale myoglobin structure outliers can be correlated with a few specific factors. However, these factors do not always lead to coordinate differences beyond the previously determined uncertainty

  3. Engineered epidermal growth factor mutants with faster binding on-rates correlate with enhanced receptor activation

    PubMed Central

    Lahti, Jennifer L.; Lui, Bertrand H.; Beck, Stayce E.; Lee, Stephen S.; Ly, Daphne P.; Longaker, Michael T.; Yang, George P.; Cochran, Jennifer R.

    2011-01-01

    Receptor tyrosine kinases (RTKs) regulate critical cell signaling pathways, yet the properties of their cognate ligands that influence receptor activation are not fully understood. There is great interest in parsing these complex ligand-receptor relationships using engineered proteins with altered binding properties. Here we focus on the interaction between two engineered epidermal growth factor (EGF) mutants and the EGF receptor (EGFR), a model member of the RTK superfamily. We found that EGF mutants with faster kinetic on-rates stimulate increased EGFR activation compared to wild-type EGF. These findings support previous predictions that faster association rates correlate with enhanced receptor activity. PMID:21439278

  4. Measuring stress intensity factors with a camera: Integrated digital image correlation (I-DIC)

    NASA Astrophysics Data System (ADS)

    Hild, François; Roux, Stéphane

    2006-01-01

    A novel 'integrated' approach coupling image correlation and elastic displacement field identification provides a powerful and accurate tool to evaluate mode I and II stress intensity factors. This technique is applied to silicon carbide subjected to a sandwiched three-point bend test, using digital pictures obtained in optical microscopy where the pixel physical scale is about 2 μm. A crack whose maximum opening is 500 nm can be detected and its geometry identified. The toughness is determined well within a 10%uncertainty. To cite this article: F. Hild, S. Roux, C. R. Mecanique 334 (2006).

  5. Rigid Cluster Decomposition Reveals Criticality in Frictional Jamming

    NASA Astrophysics Data System (ADS)

    Henkes, Silke; Quint, David A.; Fily, Yaouen; Schwarz, J. M.

    2016-01-01

    We study the nature of the frictional jamming transition within the framework of rigidity percolation theory. Slowly sheared frictional packings are decomposed into rigid clusters and floppy regions with a generalization of the pebble game including frictional contacts. Our method suggests a second-order transition controlled by the emergence of a system-spanning rigid cluster accompanied by a critical cluster size distribution. Rigid clusters also correlate with common measures of rigidity. We contrast this result with frictionless jamming, where the rigid cluster size distribution is noncritical.

  6. Rigid Cluster Decomposition Reveals Criticality in Frictional Jamming.

    PubMed

    Henkes, Silke; Quint, David A; Fily, Yaouen; Schwarz, J M

    2016-01-15

    We study the nature of the frictional jamming transition within the framework of rigidity percolation theory. Slowly sheared frictional packings are decomposed into rigid clusters and floppy regions with a generalization of the pebble game including frictional contacts. Our method suggests a second-order transition controlled by the emergence of a system-spanning rigid cluster accompanied by a critical cluster size distribution. Rigid clusters also correlate with common measures of rigidity. We contrast this result with frictionless jamming, where the rigid cluster size distribution is noncritical. PMID:26824572

  7. Adiabatic molecular-dynamics-simulation-method studies of kinetic friction

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Sokoloff, J. B.

    2005-06-01

    An adiabatic molecular-dynamics method is developed and used to study the Muser-Robbins model for dry friction (i.e., nonzero kinetic friction in the slow sliding speed limit). In this model, dry friction between two crystalline surfaces rotated with respect to each other is due to mobile molecules (i.e., dirt particles) adsorbed at the interface. Our adiabatic method allows us to quickly locate interface potential-well minima, which become unstable during sliding of the surfaces. Since dissipation due to friction in the slow sliding speed limit results from mobile molecules dropping out of such unstable wells, our method provides a way to calculate dry friction, which agrees extremely well with results found by conventional molecular dynamics for the same system, but our method is more than a factor of 10 faster.

  8. Frictional effect of ultrasonic-vibration on upsetting.

    PubMed

    Hung, Jung-Chung; Tsai, Yu-Chung; Hung, Chinghua

    2007-06-01

    The ultrasonic-vibration ring compression test and finite element analysis were performed on aluminum alloy specimens to explore the frictional effect of superimposing ultrasonic-vibration during upsetting. The extrapolated compression test was first adopted to obtain the frictionless material properties for finite element analysis. Experimental results of extrapolated compression test also indicate that ultrasonic-vibration can reduce the compressive force when friction is eliminated and can increase the temperatures of a material at the same time. The following results of the hot extrapolated compression test and the hot ring compression test reveal that increasing temperature by ultrasonic-vibration may reduce the flow stress and increase the interfacial friction. Finally, finite element analysis was conducted to derive the friction calibration curves and to evaluate the friction factor.

  9. Propagation factors of cosine-Gaussian-correlated Schell-model beams in non-Kolmogorov turbulence.

    PubMed

    Xu, Hua-Feng; Zhang, Zhou; Qu, Jun; Huang, Wei

    2014-09-22

    Based on the extended Huygens-Fresnel principle and second-order moments of the Wigner distribution function (WDF), we have studied the relative root-mean-square (rms) angular width and the propagation factor of cosine-Gaussian-correlated Schell-model (CGSM) beams propagating in non-Kolmogorov turbulence. It has been found that the CGSM beam has advantage over the Gaussian Schell-model (GSM) beam for reducing the turbulence-induced degradation, and this advantage will be more obvious for the beams with larger parameter n and spatial coherence δ or under the condition of stronger fluctuation of turbulence. The CGSM beam with larger parameter n or smaller spatial coherence δ will be less affected by the turbulence. In addition, the effects of the slope-parameter α, inner and outer scale and the refractive-index structure constant of the non-Kolmogorov's power spectrum on the propagation factor are also analyzed in detailed.

  10. [Correlation analysis between meteorological factors, biomass, and active components of Salvia miltiorrhiza in different climatic zones].

    PubMed

    Zhang, Chen-lu; Liang, Zong-suo; Guo, Hong-bo; Liu, Jing-ling; Liu, Yan; Liu, Feng-hua; Wei, Lang-zhu

    2015-02-01

    In this study, the growth and accumulation of active components of Salvia miltiorrhiza in twenty two experimental sites which crossing through three typical climate zones. The S. miltiorrhiza seedlings with the same genotype were planted in each site in spring, which were cultivated in fields with uniform management during their growing seasons till to harvest. The diterpene ketones (dihydrotanshinone, cryptotanshinone, tanshinone I and tanshinone II(A)) in S. miltiorrhiza root samples were determined by using high-performance liquid chromatography (HPLC) method. The biomass of root (root length, number of root branches, root width and dry weight) was also measured. The results showed that tanshinone II(A) in all samples of each site were higher than the standards required by China Pharmacopoeia. It has been found there is a relationship between root shape and climate change. The correlation analysis between active components and meteorological factors showed that the accumulation of tanshinones were effected by such meteorological factors as average relative humidity from April to October > average vapor pressure from April to October > average temperature difference day and night from April to October > annual average temperature and so on. The correlation analysis between root biomass and meteorological factors exhibited that root shape and accumulation of dry matter were affected by those factors, such as average annual aboveground (0-20 cm) temperature from April to October > annual average temperature > average vapor pressure from April to October > annual active accumulated temperature > annual average temperature > average vapor pressure from April to October. The accumulation of tanshinones and biomass was increased with the decrease of latitude. At the same time, the dry matter and diameter of root decreased if altitude rises. In addition, S. miltiorrhiza required sunlight is not sophisticated, when compared with humid and temperature. To sum up, S

  11. Friction at small displacement.

    NASA Technical Reports Server (NTRS)

    Campbell, W. E.; Aronstein, J.

    1972-01-01

    Low contact resistance between metal surfaces is often observed in spite of interposed lubricant and/or oxide films. To study this effect an apparatus is used with which normal force and tangential microdisplacement are applied between a small lead rider and a gold flat with various surface film conditions. Under nonoxidized and nonlubricated conditions, and with either oxide or stearic acid lubricant film alone, friction is high and contact resistance is low. With oxide and lubricant together, friction is much lower and slide is smooth, but contact resistance remains low and Ohm's law is obeyed. The results are consistent with Greenwood's theory of contact resistance for a cluster of minute metallic contact spots within the load-supporting area. The contact resistance of such a cluster is indistinguishable, for practical purposes, from that given by complete metallic contact.

  12. Friction-reducing device

    SciTech Connect

    Dollison, W.W.

    1990-04-24

    This patent describes a sucker rod coupling adapted to reduce friction within production tubing in a well bore. It comprises: a substantially cylindrical body member and roller assemblies; the body member comprising means at each end thereof for attaching the coupling to a sucker rod, and axially and circumferentially spaced recesses, each recess containing a roller guide connected to the body, and each recess being further adapted to receive and support a roller assembly around the roller guide in such manner that the roller assembly can revolve around the roller guide; the roller assemblies each comprising rollers rotatably mounted on and linked by a chain, the rollers being adapted to reduce frictional contact between the body member and the tubing by rotating between the roller guide and the tubing while the chain revolves around the roller guide.

  13. Friction in rail guns

    NASA Technical Reports Server (NTRS)

    Kay, P. K.

    1984-01-01

    The influence of friction is included in the present equations describing the performance of an inductively driven rail gun. These equations, which have their basis in an empirical formulation, are applied to results from two different experiments. Only an approximate physical description of the problem is attempted, in view of the complexity of details in the interaction among forces of this magnitude over time periods of the order of milisecs.

  14. The correlation between perceived social support, cortisol and brain derived neurotrophic factor levels in healthy women.

    PubMed

    Ma, Doy Yung; Chang, Wei Hung; Chi, Mei Hung; Tsai, Hsin Chun; Yang, Yen Kuang; Chen, Po See

    2016-05-30

    In this study, the role of brain derived neurotrophic factor (BDNF) in stress resilience was investigated. With a focus on healthy subjects, we explored whether plasma BDNF levels are correlated with the dexamethasone suppression test (DST) and subjectively perceived social support status. Moreover, we examined the possible interacting effect of DST status and perceived social support on BDNF levels. Seventy-two healthy volunteers, 44 females and 28 males, were recruited from the community and completed the perceived routine support subscale of Measurement of Support Function (PRS_MSF) questionnaire. Plasma BDNF levels and DST suppression rate with the low dose DST were measured. There was a significant positive correlation between BDNF and DST suppression rate in the female subjects. This was also true for the plasma BDNF levels and PRS_MSF in the female subjects. The positive correlation between BDNF and PRS_MSF was significant only in female subjects with low DST suppression rates. Plasma BDNF levels were associated with stress resilience in a sex-specific manner. Subjects' belief in social support might buffer the biological stress reactions. Differences in social perception and the biological stress response between men and women merits further investigation. PMID:27137977

  15. The influence of anxiety and personality factors on comfort and reachability space: a correlational study.

    PubMed

    Iachini, Tina; Ruggiero, Gennaro; Ruotolo, Francesco; Schiano di Cola, Armando; Senese, Vincenzo Paolo

    2015-09-01

    Although the effects of several personality factors on interpersonal space (i.e. social space within personal comfort area) are well documented, it is not clear whether they also extend to peripersonal space (i.e. reaching space). Indeed, no study has directly compared these spaces in relation to personality and anxiety factors even though such a comparison would help to clarify to what extent they share similar mechanisms and characteristics. The aim of the present paper was to investigate whether personality dimensions and anxiety levels are associated with reaching and comfort distances. Seventy university students (35 females) were administered the Big Five Questionnaire and the State-Trait Anxiety Inventory; afterwards, they had to provide reachability- and comfort-distance judgments towards human confederates while standing still (passive) or walking towards them (active). The correlation analyses showed that both spaces were positively related to anxiety and negatively correlated with the Dynamism in the active condition. Moreover, in the passive condition higher Emotional Stability was related to shorter comfort distance, while higher cognitive Openness was associated with shorter reachability distance. The implications of these results are discussed.

  16. Quantifying the dynamics of the oligomeric transcription factor STAT3 by pair correlation of molecular brightness

    PubMed Central

    Hinde, Elizabeth; Pandžić, Elvis; Yang, Zhengmin; Ng, Ivan H. W.; Jans, David A.; Bogoyevitch, Marie A.; Gratton, Enrico; Gaus, Katharina

    2016-01-01

    Oligomerization of transcription factors controls their translocation into the nucleus and DNA-binding activity. Here we present a fluorescence microscopy analysis termed pCOMB (pair correlation of molecular brightness) that tracks the mobility of different oligomeric species within live cell nuclear architecture. pCOMB amplifies the signal from the brightest species present and filters the dynamics of the extracted oligomeric population based on arrival time between two locations. We use this method to demonstrate a dependence of signal transducer and activator of transcription 3 (STAT3) mobility on oligomeric state. We find that on entering the nucleus STAT3 dimers must first bind DNA to form STAT3 tetramers, which are also DNA-bound but exhibit a different mobility signature. Examining the dimer-to-tetramer transition by a cross-pair correlation analysis (cpCOMB) reveals that chromatin accessibility modulates STAT3 tetramer formation. Thus, the pCOMB approach is suitable for mapping the impact oligomerization on transcription factor dynamics. PMID:27009358

  17. Angiogenesis in Breast Cancer and its Correlation with Estrogen, Progesterone Receptors and other Prognostic Factors

    PubMed Central

    Rani, Poonam; Kamal, Vinay; Agarwal, Prem Narayan

    2015-01-01

    Purpose: The aim of study is to evaluate angiogenesis using CD34, in estrogen, progesterone positive and negative breastcancer and to correlate the microvessel density with known histological prognostic factors, morphological type of breast carcinoma and lymph node metastasis. Materials and Methods: Twenty eight untreated cases of breast cancer were included in the study and paraffin embedded sections were obtained from representative mastectomy specimen of breast cancer patient. The sections were stained with hematoxylin and eosin stain and immunohistochemistry was performed using CD34, estrogen, progesterone, cytokeratin and epithelial membrane antigen antibody. Angiogenesis was analysed using CD 34 antibody. For statistical analysis, cases were grouped into estrogen, progesterone positive and negative receptors. Results: Mean microvessel density in ER-/PR-, ER-/ PR+, ER+/PR-, ER+/PR+ was 15.45, 14.83, 11, 10.89 respectively. A significant correlation was found between ER receptors and mean vascular density with p-value (< 0.05). A significant difference was observed in mean vascular density between the four groups comprising (p-value < 0.05). Infiltrating duct carcinoma (NOS) grade III has got the highest mean microvessel density (14.17) followed by grade II (12.93) and grade I (12.33). Conclusion: Information about prognostic factors in breast cancer patients may lead to better ways to identify those patients at high risk who might benefit from adjuvant therapies. PMID:25737993

  18. High Speed Ice Friction

    NASA Astrophysics Data System (ADS)

    Seymour-Pierce, Alexandra; Sammonds, Peter; Lishman, Ben

    2014-05-01

    Many different tribological experiments have been run to determine the frictional behaviour of ice at high speeds, ostensibly with the intention of applying results to everyday fields such as winter tyres and sports. However, experiments have only been conducted up to linear speeds of several metres a second, with few additional subject specific studies reaching speeds comparable to these applications. Experiments were conducted in the cold rooms of the Rock and Ice Physics Laboratory, UCL, on a custom built rotational tribometer based on previous literature designs. Preliminary results from experiments run at 2m/s for ice temperatures of 271 and 263K indicate that colder ice has a higher coefficient of friction, in accordance with the literature. These results will be presented, along with data from further experiments conducted at temperatures between 259-273K (in order to cover a wide range of the temperature dependent behaviour of ice) and speeds of 2-15m/s to produce a temperature-velocity-friction map for ice. The effect of temperature, speed and slider geometry on the deformation of ice will also be investigated. These speeds are approaching those exhibited by sports such as the luge (where athletes slide downhill on an icy track), placing the tribological work in context.

  19. Solvent friction effects propagate over the entire protein molecule through low-frequency collective modes.

    PubMed

    Moritsugu, Kei; Kidera, Akinori; Smith, Jeremy C

    2014-07-24

    Protein solvation dynamics has been investigated using atom-dependent Langevin friction coefficients derived directly from molecular dynamics (MD) simulations. To determine the effect of solvation on the atomic friction coefficients, solution and vacuum MD simulations were performed for lysozyme and staphylococcal nuclease and analyzed by Langevin mode analysis. The coefficients thus derived are roughly correlated with the atomic solvent-accessible surface area (ASA), as expected from the fact that friction occurs as the result of collisions with solvent molecules. However, a considerable number of atoms with higher friction coefficients are found inside the core region. Hence, the influence of solvent friction propagates into the protein core. The internal coefficients have large contributions from the low-frequency modes, yielding a simple picture of the surface-to-core long-range damping via solvation governed by collective low-frequency modes. To make use of these findings in implicit-solvent modeling, we compare the all-atom friction results with those obtained using Langevin dynamics (LD) with two empirical representations: the constant-friction and the ASA-dependent (Pastor-Karplus) friction models. The constant-friction model overestimates the core and underestimates the surface damping whereas the ASA-dependent friction model, which damps protein atoms only on the solvent-accessible surface, reproduces well the friction coefficients for both the surface and core regions observed in the explicit-solvent MD simulations. Therefore, in LD simulation, the solvent friction coefficients should be imposed only on the protein surface. PMID:24999844

  20. Solvent friction effects propagate over the entire protein molecule through low-frequency collective modes.

    PubMed

    Moritsugu, Kei; Kidera, Akinori; Smith, Jeremy C

    2014-07-24

    Protein solvation dynamics has been investigated using atom-dependent Langevin friction coefficients derived directly from molecular dynamics (MD) simulations. To determine the effect of solvation on the atomic friction coefficients, solution and vacuum MD simulations were performed for lysozyme and staphylococcal nuclease and analyzed by Langevin mode analysis. The coefficients thus derived are roughly correlated with the atomic solvent-accessible surface area (ASA), as expected from the fact that friction occurs as the result of collisions with solvent molecules. However, a considerable number of atoms with higher friction coefficients are found inside the core region. Hence, the influence of solvent friction propagates into the protein core. The internal coefficients have large contributions from the low-frequency modes, yielding a simple picture of the surface-to-core long-range damping via solvation governed by collective low-frequency modes. To make use of these findings in implicit-solvent modeling, we compare the all-atom friction results with those obtained using Langevin dynamics (LD) with two empirical representations: the constant-friction and the ASA-dependent (Pastor-Karplus) friction models. The constant-friction model overestimates the core and underestimates the surface damping whereas the ASA-dependent friction model, which damps protein atoms only on the solvent-accessible surface, reproduces well the friction coefficients for both the surface and core regions observed in the explicit-solvent MD simulations. Therefore, in LD simulation, the solvent friction coefficients should be imposed only on the protein surface.

  1. Lithification facilitates frictional instability in argillaceous subduction zone sediments

    NASA Astrophysics Data System (ADS)

    Trütner, Sebastian; Hüpers, Andre; Ikari, Matt J.; Yamaguchi, Asuka; Kopf, Achim J.

    2015-12-01

    Previous work suggests that in subduction zones, the onset of large earthquake nucleation at depths > ~ 5-10 km is likely driven by a combination of factors associated with the process of lithification. At these depths, lithification processes affect the entire fault system by modifying the mechanical properties of both the plate boundary fault zone and the wall-rock. To test the hypothesis that lithification of subduction zone sediments produces rocks capable of earthquake nucleation via diagenesis and low-grade metamorphism, we conducted friction experiments on fossil subduction zone sediments recovered from exposures in the Shimanto Belt in SW Japan. These meta-sediments represent accreted and subducted material which has experienced maximum temperatures of 125 to 225 °C, which are representative of seismogenic depths along the active Nankai subduction megathrust in the foreland of the Shimanto Belt. We find that intact Shimanto rock samples, which preserve the influence of diagenetic and metamorphic processes, exhibit the potential for unstable slip under in-situ pressure conditions. Powdered versions of the same samples tested under the same conditions exhibit only velocity-strengthening friction, thus demonstrating that destroying the lithification state also removes the potential for unstable slip. Using advanced porosity loss to quantify the lithification process, we demonstrate that increased velocity weakening correlates with increasingly advanced lithification. In combination with documented frictionally stable behavior of subduction zone sediments from shallower depths, our results provide evidence that the sediment lithification hypothesis can explain the depth-dependent onset of large earthquake nucleation along subduction zone megathrusts.

  2. Factors correlating with significant differences between X-ray structures of myoglobin.

    PubMed

    Rashin, Alexander A; Domagalski, Marcin J; Zimmermann, Michael T; Minor, Wladek; Chruszcz, Maksymilian; Jernigan, Robert L

    2014-02-01

    Validation of general ideas about the origins of conformational differences in proteins is critical in order to arrive at meaningful functional insights. Here, principal component analysis (PCA) and distance difference matrices are used to validate some such ideas about the conformational differences between 291 myoglobin structures from sperm whale, horse and pig. Almost all of the horse and pig structures form compact PCA clusters with only minor coordinate differences and outliers that are easily explained. The 222 whale structures form a few dense clusters with multiple outliers. A few whale outliers with a prominent distortion of the GH loop are very similar to the cluster of horse structures, which all have a similar GH-loop distortion apparently owing to intermolecular crystal lattice hydrogen bonds to the GH loop from residues near the distal histidine His64. The variations of the GH-loop coordinates in the whale structures are likely to be owing to the observed alternative intermolecular crystal lattice bond, with the change to the GH loop distorting bonds correlated with the binding of specific `unusual' ligands. Such an alternative intermolecular bond is not observed in horse myoglobins, obliterating any correlation with the ligands. Intermolecular bonds do not usually cause significant coordinate differences and cannot be validated as their universal cause. Most of the native-like whale myoglobin structure outliers can be correlated with a few specific factors. However, these factors do not always lead to coordinate differences beyond the previously determined uncertainty thresholds. The binding of unusual ligands by myoglobin, leading to crystal-induced distortions, suggests that some of the conformational differences between the apo and holo structures might not be `functionally important' but rather artifacts caused by the binding of `unusual' substrate analogs. The causes of P6 symmetry in myoglobin crystals and the relationship between crystal and

  3. Factors correlating with significant differences between X-ray structures of myoglobin.

    PubMed

    Rashin, Alexander A; Domagalski, Marcin J; Zimmermann, Michael T; Minor, Wladek; Chruszcz, Maksymilian; Jernigan, Robert L

    2014-02-01

    Validation of general ideas about the origins of conformational differences in proteins is critical in order to arrive at meaningful functional insights. Here, principal component analysis (PCA) and distance difference matrices are used to validate some such ideas about the conformational differences between 291 myoglobin structures from sperm whale, horse and pig. Almost all of the horse and pig structures form compact PCA clusters with only minor coordinate differences and outliers that are easily explained. The 222 whale structures form a few dense clusters with multiple outliers. A few whale outliers with a prominent distortion of the GH loop are very similar to the cluster of horse structures, which all have a similar GH-loop distortion apparently owing to intermolecular crystal lattice hydrogen bonds to the GH loop from residues near the distal histidine His64. The variations of the GH-loop coordinates in the whale structures are likely to be owing to the observed alternative intermolecular crystal lattice bond, with the change to the GH loop distorting bonds correlated with the binding of specific `unusual' ligands. Such an alternative intermolecular bond is not observed in horse myoglobins, obliterating any correlation with the ligands. Intermolecular bonds do not usually cause significant coordinate differences and cannot be validated as their universal cause. Most of the native-like whale myoglobin structure outliers can be correlated with a few specific factors. However, these factors do not always lead to coordinate differences beyond the previously determined uncertainty thresholds. The binding of unusual ligands by myoglobin, leading to crystal-induced distortions, suggests that some of the conformational differences between the apo and holo structures might not be `functionally important' but rather artifacts caused by the binding of `unusual' substrate analogs. The causes of P6 symmetry in myoglobin crystals and the relationship between crystal and

  4. A comprehensive evaluation of high friction overlay systems on bridge decks in cold climate regions

    NASA Astrophysics Data System (ADS)

    Kostick, Robert D.

    In recent history the Minnesota Department of Transportation has looked to improve the safety of bridge decks by installing high friction overlays (HFO). A comprehensive study researched four different proprietary HFO systems placed on fourteen bridge decks throughout Minnesota. Research was split into three separate tasks: (1) laboratory testing of aggregate properties, (2) field observations and testing, and (3) a comprehensive analysis of crash data investigated crash rates on bridges with HFO systems. Field observations and testing revealed that the use of snowplows quickly abrades HFO systems. Abrasion, among other factors, causes a reduction in surface friction values, and reduces the life of HFO systems. Furthermore, improving crash rate trends cannot be directly correlated to the installation of HFO systems. Research concludes that HFO systems should not be used in Minnesota. Other cold climate transportation agencies should conduct research emulated after this study to assess HFO systems in their jurisdiction.

  5. Bioinspired orientation-dependent friction.

    PubMed

    Xue, Longjian; Iturri, Jagoba; Kappl, Michael; Butt, Hans-Jürgen; del Campo, Aránzazu

    2014-09-23

    Spatular terminals on the toe pads of a gecko play an important role in directional adhesion and friction required for reversible attachment. Inspired by the toe pad design of a gecko, we study friction of polydimethylsiloxane (PDMS) micropillars terminated with asymmetric (spatular-shaped) overhangs. Friction forces in the direction of and against the spatular end were evaluated and compared to friction forces on symmetric T-shaped pillars and pillars without overhangs. The shape of friction curves and the values of friction forces on spatula-terminated pillars were orientation-dependent. Kinetic friction forces were enhanced when shearing against the spatular end, while static friction was stronger in the direction toward the spatular end. The overall friction force was higher in the direction against the spatula end. The maximum value was limited by the mechanical stability of the overhangs during shear. The aspect ratio of the pillar had a strong influence on the magnitude of the friction force, and its contribution surpassed and masked that of the spatular tip for aspect ratios of >2.

  6. Prediction of Very High Reynolds Number Compressible Skin Friction

    NASA Technical Reports Server (NTRS)

    Carlson, John R.

    1998-01-01

    Flat plate skin friction calculations over a range of Mach numbers from 0.4 to 3.5 at Reynolds numbers from 16 million to 492 million using a Navier Stokes method with advanced turbulence modeling are compared with incompressible skin friction coefficient correlations. The semi-empirical correlation theories of van Driest; Cope; Winkler and Cha; and Sommer and Short T' are used to transform the predicted skin friction coefficients of solutions using two algebraic Reynolds stress turbulence models in the Navier-Stokes method PAB3D. In general, the predicted skin friction coefficients scaled well with each reference temperature theory though, overall the theory by Sommer and Short appeared to best collapse the predicted coefficients. At the lower Reynolds number 3 to 30 million, both the Girimaji and Shih, Zhu and Lumley turbulence models predicted skin-friction coefficients within 2% of the semi-empirical correlation skin friction coefficients. At the higher Reynolds numbers of 100 to 500 million, the turbulence models by Shih, Zhu and Lumley and Girimaji predicted coefficients that were 6% less and 10% greater, respectively, than the semi-empirical coefficients.

  7. Factors Affecting Depression During Pregnancy and the Correlation Between Social Support and Pregnancy Depression

    PubMed Central

    Aktas, Songul; Yesilcicek Calik, Kiymet

    2015-01-01

    Background: Women are seriously subjected to psychiatric diseases during pregnancy and depression is the most prevailing one among these diseases. There is a relation between the social support and depression in pregnancy whose predisposing factors are genetic, psychological, biological, environmental, and hormonal. Objectives: This study aimed to determine the frequency of depression symptoms, and its risk factors. Also it studied the correlation between social support and pregnancy depression. Patients and Methods: This research is a descriptive cross-sectional study. It was conducted on 266 pregnant women selected by simple random method from all pregnant women admitted at the Maternity Hospital of Trabzon, Turkey from May 21 to June 13, 2008. The data were collected with a questionnaire form, the Beck depression inventory (BDI), and the multidimensional scale of perceived social support (MSPSS). Results: The mean BDI score of the pregnant women was 11.12 ± 6.65. According to the BDI, 46.2% of the pregnant women had no depression symptoms, 34.59% of them had mild, 13.91% had moderate, and 4.89% had severe level of depression symptoms. It was found that such factors as the educational level of the pregnant women and their husbands, having an undesired pregnancy, suffering from a chronic disease before pregnancy, presence of pregnancy-related problems, having a child with disability or having relatives whose children had disability, and smoking during pregnancy were the risk factors affecting the severity of the depression symptoms and these results were statistically significant (P < 0.05). On the other hand, the mean MSPSS score was 67.89 ± 14.26 and it was found that the pregnant women got the highest social support from their husbands. It was found that there was a significant correlation between BDI and MSPSS total score and its subscale scores (P < 0.05). Conclusions: According to this study, one-fifth of pregnant women were found to experience depressive

  8. Recidivism risk factors are correlated with a history of psychiatric hospitalization among sex offenders.

    PubMed

    Lee, Seung C; Hanson, R Karl

    2016-08-01

    Sexual offenders are more likely to have a history of psychiatric hospitalization compared with the general population. This finding suggests that a history of psychiatric hospitalization is a plausible risk factor for the initiation of sexual crimes. It is less clear, however, whether psychiatric hospitalization is associated with risk factors for criminal recidivism. Consequently, the current study examined the correlates of psychiatric hospitalization and its relevance for risk assessment in a sample of sexual offenders on community supervision (N = 947). In this sample, a history of psychiatric hospitalization significantly increased the rate of sexual recidivism (hazard ratio = 1.95). After controlling for well-established risk factors, however, the association was no longer statistically significant. Consequently, this study supported an indirect effect of a history of psychiatric hospitalization, such that the association between psychiatric symptoms and recidivism was mediated by criminogenic needs (e.g., poor general self-regulation, loneliness, and social rejection). Replication studies are needed to confirm this association, and to further understand the link between mental illness and recidivism for sexual offenders. (PsycINFO Database Record PMID:27504645

  9. Recidivism risk factors are correlated with a history of psychiatric hospitalization among sex offenders.

    PubMed

    Lee, Seung C; Hanson, R Karl

    2016-08-01

    Sexual offenders are more likely to have a history of psychiatric hospitalization compared with the general population. This finding suggests that a history of psychiatric hospitalization is a plausible risk factor for the initiation of sexual crimes. It is less clear, however, whether psychiatric hospitalization is associated with risk factors for criminal recidivism. Consequently, the current study examined the correlates of psychiatric hospitalization and its relevance for risk assessment in a sample of sexual offenders on community supervision (N = 947). In this sample, a history of psychiatric hospitalization significantly increased the rate of sexual recidivism (hazard ratio = 1.95). After controlling for well-established risk factors, however, the association was no longer statistically significant. Consequently, this study supported an indirect effect of a history of psychiatric hospitalization, such that the association between psychiatric symptoms and recidivism was mediated by criminogenic needs (e.g., poor general self-regulation, loneliness, and social rejection). Replication studies are needed to confirm this association, and to further understand the link between mental illness and recidivism for sexual offenders. (PsycINFO Database Record

  10. Quantitative structure-activity relationship correlation between molecular structure and the Rayleigh enantiomeric enrichment factor.

    PubMed

    Jammer, S; Rizkov, D; Gelman, F; Lev, O

    2015-08-01

    It was recently demonstrated that under environmentally relevant conditions the Rayleigh equation is valid to describe the enantiomeric enrichment - conversion relationship, yielding a proportional constant called the enantiomeric enrichment factor, εER. In the present study we demonstrate a quantitative structure-activity relationship model (QSAR) that describes well the dependence of εER on molecular structure. The enantiomeric enrichment factor can be predicted by the linear Hansch model, which correlates biological activity with physicochemical properties. Enantioselective hydrolysis of sixteen derivatives of 2-(phenoxy)propionate (PPMs) have been analyzed during enzymatic degradation by lipases from Pseudomonas fluorescens (PFL), Pseudomonas cepacia (PCL), and Candida rugosa (CRL). In all cases the QSAR relationships were significant with R(2) values of 0.90-0.93, and showed high predictive abilities with internal and external validations providing QLOO(2) values of 0.85-0.87 and QExt(2) values of 0.8-0.91. Moreover, it is demonstrated that this model enables differentiation between enzymes with different binding site shapes. The enantioselectivity of PFL and PCL was dictated by electronic properties, whereas the enantioselectivity of CRL was determined by lipophilicity and steric factors. The predictive ability of the QSAR model demonstrated in the present study may serve as a helpful tool in environmental studies, assisting in source tracking of unstudied chiral compounds belonging to a well-studied homologous series.

  11. Friction and wear of plasma-deposited diamond films

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Wu, Richard L. C.; Garscadden, Alan; Barnes, Paul N.; Jackson, Howard E.

    1993-01-01

    Reciprocating sliding friction experiments in humid air and in dry nitrogen and unidirectional sliding friction experiments in ultrahigh vacuum were conducted with a natural diamond pin in contact with microwave-plasma-deposited diamond films. Diamond films with a surface roughness (R rms) ranging from 15 to 160 nm were produced by microwave-plasma-assisted chemical vapor deposition. In humid air and in dry nitrogen, abrasion occurred when the diamond pin made grooves in the surfaces of diamond films, and thus the initial coefficients of friction increased with increasing initial surface roughness. The equilibrium coefficients of friction were independent of the initial surface roughness of the diamond films. In vacuum the friction for diamond films contacting a diamond pin arose primarily from adhesion between the sliding surfaces. In these cases, the initial and equilibrium coefficients of friction were independent of the initial surface roughness of the diamond films. The equilibrium coefficients of friction were 0.02 to 0.04 in humid air and in dry nitrogen, but 1.5 to 1.8 in vacuum. The wear factor of the diamond films depended on the initial surface roughness, regardless of environment; it increased with increasing initial surface roughness. The wear factors were considerably higher in vacuum than in humid air and in dry nitrogen.

  12. Friction laws for lubricated nanocontacts

    NASA Astrophysics Data System (ADS)

    Buzio, R.; Boragno, C.; Valbusa, U.

    2006-09-01

    We have used friction force microscopy to probe friction laws for nanoasperities sliding on atomically flat substrates under controlled atmosphere and liquid environment, respectively. A power law relates friction force and normal load in dry air, whereas a linear relationship, i.e., Amontons' law, is observed for junctions fully immersed in model lubricants, namely, octamethylciclotetrasiloxane and squalane. Lubricated contacts display a remarkable friction reduction, with liquid and substrate specific friction coefficients. Comparison with molecular dynamics simulations suggests that load-bearing boundary layers at junction entrance cause the appearance of Amontons' law and impart atomic-scale character to the sliding process; continuum friction models are on the contrary of limited predictive power when applied to lubrication effects. An attempt is done to define general working conditions leading to the manifestation of nanoscale lubricity due to adsorbed boundary layers.

  13. Solid friction between soft filaments.

    PubMed

    Ward, Andrew; Hilitski, Feodor; Schwenger, Walter; Welch, David; Lau, A W C; Vitelli, Vincenzo; Mahadevan, L; Dogic, Zvonimir

    2015-06-01

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments. Yet the nature of the sliding friction between two aligned filaments interacting through multiple contacts remains largely unexplored. Here, by directly measuring the sliding forces between two bundled F-actin filaments, we show that these frictional forces are unexpectedly large, scale logarithmically with sliding velocity as in solid-like friction, and exhibit complex dependence on the filaments' overlap length. We also show that a reduction of the frictional force by orders of magnitude, associated with a transition from solid-like friction to Stokes's drag, can be induced by coating F-actin with polymeric brushes. Furthermore, we observe similar transitions in filamentous microtubules and bacterial flagella. Our findings demonstrate how altering a filament's elasticity, structure and interactions can be used to engineer interfilament friction and thus tune the properties of fibrous composite materials.

  14. Friction surfaced Stellite6 coatings

    SciTech Connect

    Rao, K. Prasad; Damodaram, R.; Rafi, H. Khalid; Ram, G.D. Janaki; Reddy, G. Madhusudhan; Nagalakshmi, R.

    2012-08-15

    Solid state Stellite6 coatings were deposited on steel substrate by friction surfacing and compared with Stellite6 cast rod and coatings deposited by gas tungsten arc and plasma transferred arc welding processes. Friction surfaced coatings exhibited finer and uniformly distributed carbides and were characterized by the absence of solidification structure and compositional homogeneity compared to cast rod, gas tungsten arc and plasma transferred coatings. Friction surfaced coating showed relatively higher hardness. X-ray diffraction of samples showed only face centered cubic Co peaks while cold worked coating showed hexagonally close packed Co also. - Highlights: Black-Right-Pointing-Pointer Stellite6 used as coating material for friction surfacing. Black-Right-Pointing-Pointer Friction surfaced (FS) coatings compared with casting, GTA and PTA processes. Black-Right-Pointing-Pointer Finer and uniformly distributed carbides in friction surfaced coatings. Black-Right-Pointing-Pointer Absence of melting results compositional homogeneity in FS Stellite6 coatings.

  15. Empirical correlations for the modeling of R-134a flow through adiabatic capillary tubes

    SciTech Connect

    Melo, C.; Neto, C.B.; Silva Ferreira, R.T. da

    1999-07-01

    This paper presents the results of an experimental study on capillary tubes commonly used as an expansion device in household refrigerators and freezers. The experiments were performed with the hydrofluorocarbon R-134a at different condensing pressures and levels of subcooling. The pressure and temperature profiles along the capillary tubes were measured in each test run. The data set was then used to evaluate the suitability of some equations previously reported in the literature for the single-phase friction factor, the underpressure of vaporization, and the entrance contraction loss factor. Correlations for the average and local two-phase friction factors were also developed based on the measured data.

  16. In-process discontinuity detection during friction stir welding

    NASA Astrophysics Data System (ADS)

    Shrivastava, Amber

    The objective of this work is to develop a method for detecting the creation of discontinuities (e.g., voids) during friction stir welding. Friction stir welding is inherently cost-effective, however, the need for significant weld inspection can make the process cost-prohibitive. A new approach to weld inspection is required -- where an in-situ characterization of weld quality can be obtained, reducing the need for post-process inspection. Friction stir welds with discontinuity and without discontinuity were created. In this work, discontinuities are generated by reducing the friction stir tool rotation frequency and increasing the tool traverse speed in order to create "colder" welds. During the welds, forces are measured. Discontinuity sizes for welds are measured by computerized tomography. The relationship between the force transients and the discontinuity sizes indicate that the force measurement during friction stir welding can be effectively used for detecting discontinuities in friction stir welds. The normalized force transient data and normalized discontinuity size are correlated to develop a criterion for discontinuity detection. Additional welds are performed to validate the discontinuity detection method. The discontinuity sizes estimated by the force measurement based method are in good agreement with the discontinuity sizes measured by computerized tomography. These results show that the force measurement based discontinuity detection model method can be effectively used to detect discontinuities during friction stir welding.

  17. The Friction of Piston Rings

    NASA Technical Reports Server (NTRS)

    Tischbein, Hans W

    1945-01-01

    The coefficient of friction between piston ring and cylinder liner was measured in relation to gliding acceleration, pressure, temperature, quantity of oil and quality of oil. Comparing former lubrication-technical tests, conclusions were drawn as to the state of friction. The coefficients of friction as figured out according to the hydrodynamic theory were compared with those measured by tests. Special tests were made on "oiliness." The highest permissible pressure was measured and the ratio of pressure discussed.

  18. Measurement of friction between pulley and flexor tendon.

    PubMed

    An, K N; Berglund, L; Uchiyama, S; Coert, J H

    1993-01-01

    When tendon excursion takes place through the pulley, friction and drag are encountered at the interface. Repetitive exposure to such friction and attrition of the tendon has been considered one of the important factors causing cumulative trauma and leading to disorders such as tendinitis and tenosynovitis. In this study, development of an experimental method to evaluate friction and drag between the pulley and tendon under different loading conditions and joint configurations is considered. Verification of the model under an ideal situation of sutures across a mechanical pulley was performed.

  19. Elongation factor 1 alpha concentration is highly correlated with the lysine content of maize endosperm.

    PubMed Central

    Habben, J E; Moro, G L; Hunter, B G; Hamaker, B R; Larkins, B A

    1995-01-01

    Lysine is the most limiting essential amino acid in cereals, and for many years plant breeders have attempted to increase its concentration to improve the nutritional quality of these grains. The opaque2 mutation in maize doubles the lysine content in the endosperm, but the mechanism by which this occurs is unknown. We show that elongation factor 1 alpha (EF-1 alpha) is overexpressed in opaque2 endosperm compared with its normal counterpart and that there is a highly significant correlation between EF-1 alpha concentration and the total lysine content of the endosperm. This relationship is also true for two other cereals, sorghum and barley. It appears that genetic selection for genotypes with a high concentration of EF-1 alpha can significantly improve the nutritional quality of maize and other cereals. Images Fig. 1 Fig. 2 PMID:7567989

  20. Correlations between psychosocial factors and psychological trauma symptoms among rescue personnel.

    PubMed

    Soffer, Yechiel; Wolf, Jonathan Jacob; Ben-Ezra, Menachem

    2011-06-01

    During large-scale, sudden-onset disasters, rescue personnel experience severe stress due to the brief window of opportunity for saving lives. Following the earthquake in Haiti, rescue personnel worked in Port-au-Prince under harsh conditions in order to save lives and extricate bodies. Reactions to this disaster among rescue personnel were examined using self-report questionnaires. Correlations between psychosocial factors and psychological trauma (dissociation and post-traumatic stress disorder (PTSD) symptoms) were examined in a sample of 20 rescue personnel who worked in Haiti. The study indicated that negative affect and crisis of meaning were associated with higher levels of dissociative and PTSD symptoms. The results suggest that rescue personnel who are overwhelmed by the destruction and number of bodies being extricated may exhibit negative affect and loss of meaning along with dissociative and PTSD symptoms.

  1. Computation of the factorized error covariance of the difference between correlated estimators

    NASA Technical Reports Server (NTRS)

    Wolff, Peter J.; Mohan, Srinivas N.; Stienon, Francis M.; Bierman, Gerald J.

    1990-01-01

    A state estimation problem where some of the measurements may be common to two or more data sets is considered. Two approaches for computing the error covariance of the difference between filtered estimates (for each data set) are discussed. The first algorithm is based on postprocessing of the Kalman gain profiles of two correlated estimators. It uses UD factors of the covariance of the relative error. The second algorithm uses a square root information filter applied to relative error analysis. In the absence of process noise, the square root information filter is computationally more efficient and more flexible than the Kalman gain (covariance update) method. Both the algorithms (covariance and information matrix based) are applied to a Venus orbiter simulation, and their performances are compared.

  2. Correlations between risk factors and functional evolution in patients with spastic quadriplegia

    PubMed Central

    Rogoveanu, OC; Tuțescu, NC; Kamal, D; Alexandru, DO; Kamal, C; Streba, L; Trăistaru, MR

    2016-01-01

    Cerebral palsy is the most common cause of developing neuro-motor disability in children, in many cases, the triggering cause remaining unknown. Quadriplegia is the most severe spastic cerebral palsy, characterized by severe mental retardation and bi-pyramidal syndrome. The purpose of this paper was to demonstrate the importance of knowing the risk factors and the psychosomatic ones, determining to what extent they influence the functional evolution in patients diagnosed with spastic quadriplegia. 23 children diagnosed with spastic quadriplegia were included in the study, being aged between 1 year and half and 12 years. Patients were assessed at baseline (T1), at one year (T2) and after two years at the end of the study (T3). Patients received a comprehensive rehabilitation program for the motor and sensory deficits throughout the study. Initially, a comprehensive evaluation (etiopathogenic, clinical and functional) that started from a thorough medical history of children (the older ones), was conducted but chose parents to identify the risk factors, and a complete physical exam. At each assessment, joint and muscle balance was conducted. To assess functionality, the gross motor function classification systems (GMFCS) and manual ability (MACS) were used. Many risk factors that were classified according to the timeline in prenatal factors, perinatal and postnatal, were identified from a thorough history. A direct correlation was noticed between the decrease of coarse functionality and manual ability, both initially and in dynamic and low APGAR scores, low gestational age, low birth weight and a higher body mass index of the mother. A direct link was observed between the gross motor function and the manual ability. A significant improvement in the MACS score was noticed in patients with a better GMFCS score. PMID:27453749

  3. Correlations between risk factors and functional evolution in patients with spastic quadriplegia.

    PubMed

    Rogoveanu, O C; Tuțescu, N C; Kamal, D; Alexandru, D O; Kamal, C; Streba, L; Trăistaru, M R

    2016-01-01

    Cerebral palsy is the most common cause of developing neuro-motor disability in children, in many cases, the triggering cause remaining unknown. Quadriplegia is the most severe spastic cerebral palsy, characterized by severe mental retardation and bi-pyramidal syndrome. The purpose of this paper was to demonstrate the importance of knowing the risk factors and the psychosomatic ones, determining to what extent they influence the functional evolution in patients diagnosed with spastic quadriplegia. 23 children diagnosed with spastic quadriplegia were included in the study, being aged between 1 year and half and 12 years. Patients were assessed at baseline (T1), at one year (T2) and after two years at the end of the study (T3). Patients received a comprehensive rehabilitation program for the motor and sensory deficits throughout the study. Initially, a comprehensive evaluation (etiopathogenic, clinical and functional) that started from a thorough medical history of children (the older ones), was conducted but chose parents to identify the risk factors, and a complete physical exam. At each assessment, joint and muscle balance was conducted. To assess functionality, the gross motor function classification systems (GMFCS) and manual ability (MACS) were used. Many risk factors that were classified according to the timeline in prenatal factors, perinatal and postnatal, were identified from a thorough history. A direct correlation was noticed between the decrease of coarse functionality and manual ability, both initially and in dynamic and low APGAR scores, low gestational age, low birth weight and a higher body mass index of the mother. A direct link was observed between the gross motor function and the manual ability. A significant improvement in the MACS score was noticed in patients with a better GMFCS score. PMID:27453749

  4. Correlations between risk factors and functional evolution in patients with spastic quadriplegia.

    PubMed

    Rogoveanu, O C; Tuțescu, N C; Kamal, D; Alexandru, D O; Kamal, C; Streba, L; Trăistaru, M R

    2016-01-01

    Cerebral palsy is the most common cause of developing neuro-motor disability in children, in many cases, the triggering cause remaining unknown. Quadriplegia is the most severe spastic cerebral palsy, characterized by severe mental retardation and bi-pyramidal syndrome. The purpose of this paper was to demonstrate the importance of knowing the risk factors and the psychosomatic ones, determining to what extent they influence the functional evolution in patients diagnosed with spastic quadriplegia. 23 children diagnosed with spastic quadriplegia were included in the study, being aged between 1 year and half and 12 years. Patients were assessed at baseline (T1), at one year (T2) and after two years at the end of the study (T3). Patients received a comprehensive rehabilitation program for the motor and sensory deficits throughout the study. Initially, a comprehensive evaluation (etiopathogenic, clinical and functional) that started from a thorough medical history of children (the older ones), was conducted but chose parents to identify the risk factors, and a complete physical exam. At each assessment, joint and muscle balance was conducted. To assess functionality, the gross motor function classification systems (GMFCS) and manual ability (MACS) were used. Many risk factors that were classified according to the timeline in prenatal factors, perinatal and postnatal, were identified from a thorough history. A direct correlation was noticed between the decrease of coarse functionality and manual ability, both initially and in dynamic and low APGAR scores, low gestational age, low birth weight and a higher body mass index of the mother. A direct link was observed between the gross motor function and the manual ability. A significant improvement in the MACS score was noticed in patients with a better GMFCS score.

  5. Identification of Transcription Factor Genes and Their Correlation with the High Diversity of Stramenopiles

    PubMed Central

    Buitrago-Flórez, Francisco Javier; Restrepo, Silvia; Riaño-Pachón, Diego Mauricio

    2014-01-01

    The biological diversity among Stramenopiles is striking; they range from large multicellular seaweeds to tiny unicellular species, they embrace many ecologically important autothrophic (e.g., diatoms, brown algae), and heterotrophic (e.g., oomycetes) groups. Transcription factors (TFs) and other transcription regulators (TRs) regulate spatial and temporal gene expression. A plethora of transcriptional regulatory proteins have been identified and classified into families on the basis of sequence similarity. The purpose of this work is to identify the TF and TR complement in diverse species belonging to Stramenopiles in order to understand how these regulators may contribute to their observed diversity. We identified and classified 63 TF and TR families in 11 species of Stramenopiles. In some species we found gene families with high relative importance. Taking into account the 63 TF and TR families identified, 28 TF and TR families were established to be positively correlated with specific traits like number of predicted proteins, number of flagella and number of cell types during the life cycle. Additionally, we found gains and losses in TF and TR families specific to some species and clades, as well as, two families with high abundance specific to the autotrophic species and three families with high abundance specific to the heterotropic species. For the first time, there is a systematic search of TF and TR families in Stramenopiles. The attempts to uncover relationships between these families and the complexity of this group may be of great impact, considering that there are several important pathogens of plants and animals, as well as, important species involved in carbon cycling. Specific TF and TR families identified in this work appear to be correlated with particular traits in the Stramenopiles group and may be correlated with the high complexity and diversity in Stramenopiles. PMID:25375671

  6. Proliferating cell nuclear antigen in oesophageal diseases; correlation with transforming growth factor alpha expression.

    PubMed Central

    Jankowski, J; McMenemin, R; Yu, C; Hopwood, D; Wormsley, K G

    1992-01-01

    This study was designed to correlate mucosal proliferation in Barrett's oesophagus with expression of a growth promoting peptide, transforming growth factor alpha (TGF alpha). Oesophageal mucosa was studied from 50 patients with oesophageal disease who had been treated by oesophagectomy. Histological analysis showed a range of oesophageal pathology - 18 patients had gastric type Barrett's mucosa, 18 had intestinal type Barrett's mucosa, and 14 had oesophageal adenocarcinomas. Sections were stained immunohistochemically for proliferating cell nuclear antigen (PCNA) (an index of cellular proliferation) and TGF alpha. PCNA immunostaining was seen mainly in the basal cells of the neck/foveolar epithelial compartment of the glands in Barrett's oesophagus. However, in mucosa with high grade dysplasia, the proliferative compartment extended upwards into the superficial layers of the glands. At least 2000 cells were counted in each patient to determine the proportion with PCNA immunoreactivity (PCNA labelling index). The labelling index was highest in adenocarcinoma (25%) and in Barrett's intestinal type mucosa with high grade dysplasia (26%) compared with intestinal type mucosa with no significant dysplasia (20%) and Barrett's gastric type mucosa (12%). There was a significant positive correlation between PCNA labelling indices and TGF alpha expression in Barrett's mucosa (p less than 0.01). In glands showing high grade dysplasia, TGF alpha immunoreactivity was seen in the same regions of the glands as PCNA immunoreactivity, indicating the possibility of involvement of TGF alpha in (pre) neoplastic proliferation in Barrett's oesophagus. Images Figure 2 Figure 5 PMID:1351861

  7. Correlation between expression of NF-E2-related factor 2 and progression of gastric cancer

    PubMed Central

    Bao, Jie; Li, Jiansheng; Li, Dongying; Li, Zhenjie

    2015-01-01

    Objective: Nuclear factor E2-related factor 2 (Nrf2) plays a part in antioxidant and phase II detoxification enzymes in cells by the up regulation of many antioxidant response elements (ARE) related gene transcription. Nrf2 not only protect the normal cells, but also can protect cancer cells from the effect of cell stress, which is helpful to the survival of cancer cell. Some studies show that the expression of Nrf2 has important clinical significance in cancer patients, but the analysis of gastrointestinal tumor Nrf2 comprehensive expression has not been reported. The aim of this study is to evaluate the expression of Nrf2 in gastric cancer by immunohistochemistry and analyze its related clinical significance. Methods: 180 cases of gastric cancer patients receive the gastrectomy and lymphadenectomy, and the resection of tissue is expressesd in paraffin embedded sections by immunohistochemical analysis of Nrf2. And the difference between groups use χ2 (chi-square criterion) test, and will be analyzed by Fisher’s exact test and Mann-Whitney U test. Use univariate and multivariate analysis, Kaplan-Meier curve and log-rank to test and evaluate the correlation between the expression of Nrf2 and the clinical pathological features. Results: The immune reaction of Nrf2 is mainly found in gastric cancer cell nucleus, which positive expression is closely related to the tumor size, depth of invasion, lymph node metastasis, lymphatic invasion and histological analysis (all P<0.05). The log-rank test shows that the survival rate of Nrf2 positive expression group is significantly lower than that of the negative expression group (P<0.01). The Nrf2 positive expression is closely related to the drug resistance of adjuvant chemotherapy on the basis of 5FU (P=0.022). Conclusion: There is a positive correlation between the expression of Nrf2 and the invasion of gastric cancer, which can be used as a potential indicator of patients’ poor prognosis. PMID:26550248

  8. Friction phenomena and their impact on the shear behaviour of granular material

    NASA Astrophysics Data System (ADS)

    Suhr, Bettina; Six, Klaus

    2016-06-01

    In the discrete element simulation of granular materials, the modelling of contacts is crucial for the prediction of the macroscopic material behaviour. From the tribological point of view, friction at contacts needs to be modelled carefully, as it depends on several factors, e.g. contact normal load or temperature to name only two. In discrete element method (DEM) simulations the usage of Coulomb's law of friction is state of the art in modelling particle-particle contacts. Usually in Coulomb's law, for all contacts only one constant coefficient of friction is used, which needs to reflect all tribological effects. Thus, whenever one of the influence factors of friction varies over a wide range, it can be expected that the usage of only one constant coefficient of friction in Coulomb's law is an oversimplification of reality. For certain materials, e.g. steel, it is known that a dependency of the coefficient of friction on the contact normal load exists. A more tribological tangential contact law is implemented in DEM, where the interparticle friction coefficient depends on the averaged normal stress in the contact. Simulations of direct shear tests are conducted, using steel spheres of different size distributions. The strong influence of interparticle friction on the bulk friction is shown via a variation of the constant interparticle friction coefficient. Simulations with constant and stress-dependent interparticle friction are compared. For the stress-dependent interparticle friction, a normal stress dependency of the bulk friction is seen. In the literature, measurements of different granular materials and small normal loads also show a stress dependency of the bulk friction coefficient. With increasing applied normal stress, the bulk friction coefficient reduces both in the experiments and in the simulations.

  9. Improved Skin Friction Interferometer

    NASA Technical Reports Server (NTRS)

    Westphal, R. V.; Bachalo, W. D.; Houser, M. H.

    1986-01-01

    An improved system for measuring aerodynamic skin friction which uses a dual-laser-beam oil-film interferometer was developed. Improvements in the optical hardware provided equal signal characteristics for each beam and reduced the cost and complexity of the system by replacing polarization rotation by a mirrored prism for separation of the two signals. An automated, objective, data-reduction procedure was implemented to eliminate tedious manual manipulation of the interferometry data records. The present system was intended for use in two-dimensional, incompressible flows over a smooth, level surface without pressure gradient, but the improvements discussed are not limited to this application.

  10. Iliotibial band friction syndrome.

    PubMed

    Kirk, K L; Kuklo, T; Klemme, W

    2000-11-01

    Overuse knee injuries are common, but ITBFS is often overlooked as a cause of lateral knee pain in an active population. Iliotibial band friction syndrome is an overuse injury usually seen in long distance runners, cyclists, and military personnel. The exact incidence of the syndrome has been estimated to range from 1.6%-52% depending on the population studied. The diagnosis is often made from a thorough history and clinical examination with an infrequent need for additional studies. Treatment is mostly conservative consisting of rest and anti-inflammatory agents, with only the refractory cases requiring surgical resection of the impinging portion of the ITB.

  11. Friction loss in straight pipes of unplasticized polyvinyl chloride.

    PubMed

    Iwasaki, T; Ojima, J

    1996-01-01

    In order to design proper ductwork for a local exhaust system, airflow characteristics were investigated in straight pipes of unplasticized polyvinyl chloride (PVC). A linear decrease in static pressure was observed downstream at points from the opening of the VU pipes (JIS K 6741) located at distances greater than 10 times the pipe diameter, for velocities ranging between 10.18-36.91 m/s. Roughness inside pipes with small diameters was found to be 0.0042-0.0056 mm and the friction factor was calculated on the basis of Colebrook's equation for an airflow transition zone. An extended friction chart was then constructed on the basis of the roughness value and the friction factor. This chart can be applied when designing a local exhaust system with the ducts of diameters ranging from 40 to 900 mm. The friction loss of the PVC pipe was found to be approximately 2/3 of that of a galvanized steel pipe. PMID:8768669

  12. Friction loss in straight pipes of unplasticized polyvinyl chloride.

    PubMed

    Iwasaki, T; Ojima, J

    1996-01-01

    In order to design proper ductwork for a local exhaust system, airflow characteristics were investigated in straight pipes of unplasticized polyvinyl chloride (PVC). A linear decrease in static pressure was observed downstream at points from the opening of the VU pipes (JIS K 6741) located at distances greater than 10 times the pipe diameter, for velocities ranging between 10.18-36.91 m/s. Roughness inside pipes with small diameters was found to be 0.0042-0.0056 mm and the friction factor was calculated on the basis of Colebrook's equation for an airflow transition zone. An extended friction chart was then constructed on the basis of the roughness value and the friction factor. This chart can be applied when designing a local exhaust system with the ducts of diameters ranging from 40 to 900 mm. The friction loss of the PVC pipe was found to be approximately 2/3 of that of a galvanized steel pipe.

  13. General theory of frictional heating with application to rubber friction

    NASA Astrophysics Data System (ADS)

    Fortunato, G.; Ciaravola, V.; Furno, A.; Lorenz, B.; Persson, B. N. J.

    2015-05-01

    The energy dissipation in the contact regions between solids in sliding contact can result in high local temperatures which may strongly effect friction and wear. This is the case for rubber sliding on road surfaces at speeds above 1 mm s-1. We derive equations which describe the frictional heating for solids with arbitrary thermal properties. The theory is applied to rubber friction on road surfaces and we take into account that the frictional energy is partly produced inside the rubber due to the internal friction of rubber and in a thin (nanometer) interfacial layer at the rubber-road contact region. The heat transfer between the rubber and the road surface is described by a heat transfer coefficient which depends on the sliding speed. Numerical results are presented and compared to experimental data. We find that frictional heating results in a kinetic friction force which depends on the orientation of the sliding block, thus violating one of the two basic Leonardo da Vinci ‘laws’ of friction.

  14. General theory of frictional heating with application to rubber friction.

    PubMed

    Fortunato, G; Ciaravola, V; Furno, A; Lorenz, B; Persson, B N J

    2015-05-01

    The energy dissipation in the contact regions between solids in sliding contact can result in high local temperatures which may strongly effect friction and wear. This is the case for rubber sliding on road surfaces at speeds above 1 mm s(-1). We derive equations which describe the frictional heating for solids with arbitrary thermal properties. The theory is applied to rubber friction on road surfaces and we take into account that the frictional energy is partly produced inside the rubber due to the internal friction of rubber and in a thin (nanometer) interfacial layer at the rubber-road contact region. The heat transfer between the rubber and the road surface is described by a heat transfer coefficient which depends on the sliding speed. Numerical results are presented and compared to experimental data. We find that frictional heating results in a kinetic friction force which depends on the orientation of the sliding block, thus violating one of the two basic Leonardo da Vinci 'laws' of friction.

  15. Osteoporosis in the jawbones: a correlative factor of primary trigeminal neuralgia?

    PubMed

    Liu, Li; Wang, Hu; Liu, Na; Yang, Qianmei; Luo, En

    2014-01-01

    Trigeminal neuralgia (TN), a neuropathic disorder of one or both of the trigeminal nerves, occurs most often in people over age 50. Extreme, sporadic, sudden burning or shock-like face pain in common activities greatly lowers quality of life. The precise cause of primary TN remains unknown, but it may be caused by vascular pressing on the trigeminal nerve in its root entry zone (REZ), demyelinization of trigeminal sensory fibers, or jawbone cavity. Accordingly, many treatments carry risks of adverse effects, recurrence, and complications. TN and osteoporosis have similar high-risk populations and a common influential factor - emotional stress - is also closed related to primary TN for calcitonin gene-related peptide and calcitonin. Jawbone cavity, which is a possible pathogenesis of TN, may be another form of jawbone osteoporosis. Therefore, we hypothesized that osteoporosis in jaws could be a correlative factor of primary TN. If this hypothesis is verified, it may suggest specific new ideas for the early preventive treatment of primary TN. PMID:25141822

  16. Partition coefficients of organic compounds in lipid-water systems and correlations with fish bioconcentration factors

    USGS Publications Warehouse

    Chiou, C.T.

    1985-01-01

    Triolein-water partition coefficients (KtW) have been determined for 38 slightly water-soluble organic compounds, and their magnitudes have been compared with the corresponding octanol-water partition coefficients (KOW). In the absence of major solvent-solute interaction effects in the organic solvent phase, the conventional treatment (based on Raoult's law) predicts sharply lower partition coefficients for most of the solutes in triolein because of its considerably higher molecular weight, whereas the Flory-Huggins treatment predicts higher partition coefficients with triolein. The data are in much better agreement with the Flory-Huggins model. As expected from the similarity in the partition coefficients, the water solubility (which was previously found to be the major determinant of the KOW) is also the major determinant for the Ktw. When the published BCF values (bioconcentration factors) of organic compounds in fish are based on the lipid content rather than on total mass, they are approximately equal to the Ktw, which suggests at least near equilibrium for solute partitioning between water and fish lipid. The close correlation between Ktw and Kow suggests that Kow is also a good predictor for lipid-water partition coefficients and bioconcentration factors.

  17. High prevalence of cardiometabolic risk factors in Hispanic adolescents: correlations with adipocytokines and markers of inflammation.

    PubMed

    Pérez, Cynthia M; Ortiz, Ana P; Fuentes-Mattei, Enrique; Velázquez-Torres, Guermarie; Santiago, Damarys; Giovannetti, Katya; Bernabe, Raúl; Lee, Mong-Hong; Yeung, Sai-Ching J

    2014-10-01

    This study assessed the association of cardiometabolic risk factors with systemic inflammation, insulin resistance, and adypocytokines in a Hispanic adolescent subgroup. A clinic-based sample of 101 Puerto Rican adolescents, 48 of whom were overweight or obese based on body mass index percentiles for age and sex, was recruited during 2010. Data were collected through interviews, blood pressure and anthropometric measurements, and blood drawing. Overall prevalence of the metabolic syndrome was 16.8 % and increased to 37.5 % among overweight/obese youth. The overweight/obese group exhibited significantly (p < 0.05) higher values for abdominal obesity measures, systolic blood pressure, triglycerides, insulin resistance, C peptide, high-sensitivity C reactive protein, fibrinogen, leptin, and IL-6 and lower levels of high density lipoprotein cholesterol, adiponectin, and IGF-1. Total adiponectin significantly correlated with most cardiovascular risk factors independent of sex, Tanner stage, and adiposity. Altered cardiometabolic and adipocytokine profiles were present in this Hispanic subgroup, reinforcing the need to strengthen strategies addressing childhood obesity. PMID:23828626

  18. Fragility and hysteretic creep in frictional granular jamming

    NASA Astrophysics Data System (ADS)

    Bandi, M. M.; Rivera, M. K.; Krzakala, F.; Ecke, R. E.

    2013-04-01

    The granular jamming transition is experimentally investigated in a two-dimensional system of frictional, bidispersed disks subject to quasistatic, uniaxial compression without vibrational disturbances (zero granular temperature). Three primary results are presented in this experimental study. First, using disks with different static friction coefficients (μ), we experimentally verify numerical results that predict jamming onset at progressively lower packing fractions with increasing friction. Second, we show that the first compression cycle measurably differs from subsequent cycles. The first cycle is fragile—a metastable configuration with simultaneous jammed and unjammed clusters—over a small packing fraction interval (ϕ1<ϕ<ϕ2) and exhibits simultaneous exponential rise in pressure and exponential decrease in disk displacements over the same packing fraction interval. This fragile behavior is explained through a percolation mechanism of stressed contacts where cluster growth exhibits spatial correlation with disk displacements and contributes to recent results emphasizing fragility in frictional jamming. Control experiments show that the fragile state results from the experimental incompatibility between the requirements for zero friction and zero granular temperature. Measurements with several disk materials of varying elastic moduli E and friction coefficients μ show that friction directly controls the start of the fragile state but indirectly controls the exponential pressure rise. Finally, under repetitive loading (compression) and unloading (decompression), we find the system exhibits pressure hysteresis, and the critical packing fraction ϕc increases slowly with repetition number. This friction-induced hysteretic creep is interpreted as the granular pack's evolution from a metastable to an eventual structurally stable configuration. It is shown to depend on the quasistatic step size Δϕ, which provides the only perturbative mechanism in the

  19. Slow frictional waves

    NASA Astrophysics Data System (ADS)

    Viswanathan, Koushik; Sundaram, Narayan; Chandrasekar, Srinivasan

    Stick-slip, manifest as intermittent tangential motion between two dry solid surfaces, is a friction instability that governs diverse phenomena from automobile brake squeals to earthquakes. We show, using high-speed in situ imaging of an adhesive polymer interface, that low velocity stick-slip is fundamentally of three kinds, corresponding to passage of three different surface waves -- separation pulses, slip pulses and the well-known Schallamach waves. These waves, traveling much slower than elastic waves, have clear distinguishing properties. Separation pulses and Schallamach waves involve local interface separation, and propagate in opposite directions while slip pulses are characterized by a sharp stress front and do not display any interface detachment. A change in the stick-slip mode from separation to slip pulse is effected simply by increasing the normal force. Together, these three waves constitute all possible stick-slip modes in adhesive friction and are shown to have direct analogues in muscular locomotory waves in soft bodied invertebrates. A theory for slow wave propagation is also presented which is capable of explaining the attendant interface displacements, velocities and stresses.

  20. Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Nunes, Arthur C., Jr.

    2008-01-01

    Friction stir welding (FSW) is a solid state welding process invented in 1991 at The Welding Institute in the United Kingdom. A weld is made in the FSW process by translating a rotating pin along a weld seam so as to stir the sides of the seam together. FSW avoids deleterious effects inherent in melting and promises to be an important welding process for any industries where welds of optimal quality are demanded. This article provides an introduction to the FSW process. The chief concern is the physical effect of the tool on the weld metal: how weld seam bonding takes place, what kind of weld structure is generated, potential problems, possible defects for example, and implications for process parameters and tool design. Weld properties are determined by structure, and the structure of friction stir welds is determined by the weld metal flow field in the vicinity of the weld tool. Metal flow in the vicinity of the weld tool is explained through a simple kinematic flow model that decomposes the flow field into three basic component flows: a uniform translation, a rotating solid cylinder, and a ring vortex encircling the tool. The flow components, superposed to construct the flow model, can be related to particular aspects of weld process parameters and tool design; they provide a bridge to an understanding of a complex-at-first-glance weld structure. Torques and forces are also discussed. Some simple mathematical models of structural aspects, torques, and forces are included.

  1. Fibroblast growth factor receptor 4 promotes progression and correlates to poor prognosis in cholangiocarcinoma

    SciTech Connect

    Xu, Yun-Fei; Yang, Xiao-Qing; Lu, Xiao-Fei; Guo, Sen; Liu, Yi; Iqbal, Mohammad; Ning, Shang-Lei; Yang, Hui; Suo, Ning; Chen, Yu-Xin

    2014-03-28

    Highlights: • FGFR4 is significantly related with N stage in IHCC, with T stage and TNM stage in PHCC. • FGFR4 is an independent prognostic factor in IHCC and PHCC. • FGFR4 promotes proliferation, invasion and EMT in cholangiocarinoma cell lines. • Inhibitor AP24354 can decrease proliferation, invasion and induce apoptosis of CCA. - Abstract: Fibroblast growth factor receptor 4 (FGFR4) is related to poor prognosis of several cancers, but the correlation between FGFR4 expression and cholangiocarcinoma (CCA) has not been well elucidated. We investigated the expression of FGFR4 in 83 intrahepatic cholangiocarcinomas (IHCCs), 75 perihilar cholangiocarcinomas (PHCCs) and 41 distal cholangiocarcinomas (DCCs) by immunohistochemistry (IHC), and subsequently evaluated association of FGFR4 with clinicopathologic parameters and survival rate. The rate of FGFR4 higher expression was 61.4% (51/83) in IHCCs, 53.3% (40/75) in PHCCs and 56.1% (23/41) in DCCs. FGFR4 expression was significantly related to poor prognosis of IHCC (P = 0.002) and PHCC (P = 0.019) with univariate analysis, and also identified as an independent prognostic factor in IHCC (P = 0.045) and PHCC (P = 0.049) with multivariate analysis. Additionally, with functional assays in vitro, we found FGFR4 can induce proliferation, invasion and epithelial–mesenchymal transition (EMT) of CCA cell lines with FGF19 stimulation. Moreover, FGFR4 inhibitor AP24354 can suppress proliferation, invasion and induce apoptosis of CCA cells. In conclusion, FGFR4 expression can be identified as a significant independent prognostic biomarker of IHCC and PHCC. FGFR4 played a pivotal role in proliferation, invasion and EMT of CCA. FGFR4 inhibitor can suppress proliferation, invasion and induce apoptosis of CCA, indicating that FGFR4 may act as a potential therapeutic target.

  2. Factor Analysis of the Stewart Personality Inventory Research Form and Its Correlations with Some Other Personality Instruments.

    ERIC Educational Resources Information Center

    Stewart, Robert A. C.; Ahmed, S. M. S.

    1984-01-01

    Administered the 80-item Stewart Personality Inventory (SPI) to 193 college students. Factor analysis yielded a factor structure similar to a previous study. Presents a summary of the inventory, scoring methods, and correlations of subscales to other personality inventories. Results support the SPI's validity. (BH)

  3. Frictional action at lower limb/prosthetic socket interface.

    PubMed

    Zhang, M; Turner-Smith, A R; Roberts, V C; Tanner, A

    1996-04-01

    The frictional action at stump/socket interface is discussed by a simplified model and finite element model analyses and clinical pressure measurements. The friction applied to the stump skin produces stresses within tissue and these stresses may damage the tissues and affect their normal functions. The combination of normal and shear stresses is considered to be a critical factor leading to amputee's discomfort and tissue damage. However, friction at the stump/socket interface has a beneficial action. A simplified residual limb model and a finite element model using real geometry have been developed to analyse the support action of friction. Both results show that the friction plays a critical role both in supporting the load of the amputee's body during the support phase of the gait cycle and in preventing the prosthesis from slipping off the limb during swing phase. Pressure at the below-knee socket during walking were measured with conditions of different friction. The results reveal that a larger pressures was produced at the lubricated interface than at the normal interface. A proper choice of coefficient of friction will balance the requirements of relief of load stress and reduction of slip with the general ability to support loads.

  4. Reduction of friction stress of ethylene glycol by attached hydrogen ions

    PubMed Central

    Li, Jinjin; Zhang, Chenhui; Deng, Mingming; Luo, Jianbin

    2014-01-01

    In the present work, it is shown that the friction stress of ethylene glycol can decrease by an order of magnitude to achieve superlubricity if there are hydrogen ions attached on the friction surfaces. An ultra-low friction coefficient (μ = 0.004) of ethylene glycol between Si3N4 and SiO2 can be obtained with the effect of hydrogen ions. Experimental result indicates that the hydrogen ions adsorbed on the friction surfaces forming a hydration layer and the ethylene glycol in the contact region forming an elastohydrodynamic film are the two indispensable factors for the reduction of friction stress. The mechanism of superlubricity is attributed to the extremely low shear strength of formation of elastohydrodynamic film on the hydration layer. This finding may introduce a new approach to reduce friction coefficient of liquid by attaching hydrogen ions on friction surfaces. PMID:25428584

  5. Elastic model of dry friction

    SciTech Connect

    Larkin, A. I.; Khmelnitskii, D. E.

    2013-09-15

    Friction of elastic bodies is connected with the passing through the metastable states that arise at the contact of surfaces rubbing against each other. Three models are considered that give rise to the metastable states. Friction forces and their dependence on the pressure are calculated. In Appendix A, the contact problem of elasticity theory is solved with adhesion taken into account.

  6. ISG15 expression correlates with HIV-1 viral load and with factors regulating T cell response.

    PubMed

    Scagnolari, Carolina; Monteleone, Katia; Selvaggi, Carla; Pierangeli, Alessandra; D'Ettorre, Gabriella; Mezzaroma, Ivano; Turriziani, Ombretta; Gentile, Massimo; Vullo, Vincenzo; Antonelli, Guido

    2016-02-01

    Given the multifactorial nature of action of type I interferon (IFN) in HIV-1 infection and the need to firmly establish the action of key components of IFN pathways, we compared the IFN stimulated gene (ISG)15 expression with that of other well-characterized ISGs, evaluating its relationship with immunosuppressive factors regulating T-cell response in HIV-1 patients. PBMC from 225 subjects were included: healthy donors (n=30), naïve (n=93) and HAART treated HIV-1 subjects (n=102). Levels of ISG15-mRNA, ISG56-mRNA, APOBEC3G/3F-mRNA, TRAIL-mRNA, IDO-mRNA, proviral load andISG15 (rs15842 and rs1921) SNPs were evaluated by using TaqMan assays. We found that ISG15, ISG56, APOBEC3G/3F levels were increased in untreated HIV-1 patients compared to healthy donors, being ISG15 the highest ISG expressed. The amount of ISG15 correlated with viral load and with CD4+ T cell counts whereas no relationship was found between all ISGs analyzed and proviral load or HIV-1 tropism. ISG15 expression was reduced following long-term antiretroviral therapy. In addition, ISG15 levels were correlated with those of TRAIL and IDO in HIV-1 viremic patients. Lastly, ISG15 SNPs had no influence on ISG15 levels. We demonstrates that ISG15 is elevated in viremic HIV-1 patients and is associated with high TRAIL and IDO levels. PMID:26563749

  7. Computed Tomography Appearance of Early Radiation Injury to the Lung: Correlation With Clinical and Dosimetric Factors

    SciTech Connect

    Jenkins, Peter; Welsh, Anne

    2011-09-01

    Purpose: To systematically assess the spectrum of radiologic changes in the lung after radiation therapy for non-small-cell lung cancer. Methods and Materials: We reviewed the cases of 146 patients treated with radical radiotherapy at our institution. All patients had computed tomography (CT) scans performed 3 months after completion of therapy. Radiographic appearances were categorized using a standard grading system. The association of these abnormalities with pretreatment factors and clinical radiation pneumonitis (RP) was investigated. Results: New intrapulmonary abnormalities were seen in 92 patients (63%). These were ground-glass opacity in 16 (11%), patchy consolidation in 19 (13%), and diffuse consolidation in 57 (39%). Twenty-five patients (17%) developed clinical symptoms of RP. Although 80% of the patients with RP had areas of consolidation seen on the posttreatment CT scan, the majority (74%) of patients with such radiographic changes were asymptomatic. For patients with lung infiltrates, the minimum isodose encompassing the volume of radiologic abnormality was usually {>=}27 Gy. Traditional dose-volume metrics, pulmonary function tests, and the coadministration of angiotensin converting enzyme inhibitors (ACE-I) were all strongly correlated with the presence of radiologic injury on univariate analysis (p {<=} 0.002). There was also an inverse correlation between prior smoking history and CT scan changes (p = 0.02). On multivariate analysis, dosimetric parameters and the use of ACE-I retained significance (p = 0.005). Conclusions: Our findings suggest that there is substantial interindividual variation in lung radiosensitivity. ACE-I prevented the radiologic changes seen after high-dose radiation therapy, and their role as radioprotectants warrants further investigation.

  8. Crystallographic controls on the frictional behavior of dry and water-saturated sheet structure minerals

    USGS Publications Warehouse

    Moore, Diane E.; Lockner, D.A.

    2004-01-01

    We compare the frictional strengths of 17 sheet structure mineral powders, measured under dry and water-saturated conditions, to identify the factors that cause many of them to be relatively weak. The dry coefficient of friction ?? ranges upward from 0.2 for graphite, leveling off at 0.8 for margarite, clintonite, gibbsite, kaolinite, and lizardite. The values of ?? (dry) correlate directly with calculated (001) interlayer bond strengths of the minerals. This correlation occurs because shear becomes localized along boundary and Riedel shears and the platy minerals in them rotate into alignment with the shear planes. For those gouges with ?? (dry) < 0.8, shear occurs by breaking the interlayer bonds to form new cleavage surfaces. Where ?? (dry) = 0.8, consistent with Byerlee's law, the interlayer bonds are sufficiently strong that other frictional processes dominate. The transition in dry friction mechanisms corresponds to calculated surface energies of 2-3 J/m2. Adding water causes ?? to decrease for every mineral tested except graphite. If the minerals are separated into groups with similar crystal structures, ?? (wet) increases with increasing interlayer bond strength within each group. This relationship also holds for the swelling clay montmorillonite, whose water-saturated strength is consistent with the strengths of nonswelling clays of similar crystal structure. Water in the saturated gouges forms thin, structured films between the plate surfaces. The polar water molecules are bonded to the plate surfaces in proportion to the mineral's surface energy, and ?? (wet) reflects the stresses required to shear through the water films. Copyright 2004 by the American Geophysical Union.

  9. Determination of basic friction angle using various laboratory tests.

    NASA Astrophysics Data System (ADS)

    Jang, Bo-An

    2016-04-01

    The basic friction angle of rock is an important factor of joint shear strength and is included within most shear strength criteria. It can be measured by direct shear test, triaxial compression test and tilt test. Tilt test is mostly used because it is the simplest method. However, basic friction angles measured using tilt test for same rock type or for one sample are widely distributed and often do not show normal distribution. In this research, the basic friction angles for the Hangdeung granite form Korea and Berea sandstone from USA are measured accurately using direct shear test and triaxial compression test. Then basic friction angles are again measured using tilt tests with various conditions and are compared with those measured using direct shear test and triaxial compression test to determine the optimum condition of tilt test. Three types of sliding planes, such as planes cut by saw and planes polished by #100 and #600 grinding powders, are prepared. When planes are polished by #100 grinding powder, the basic friction angles measured using direct shear test and triaxial compression test are very consistent and show narrow ranges. However, basic friction angles show wide ranges when planes are cut by saw and are polished by #600 grinding powder. The basic friction angle measured using tilt test are very close to those measured using direct shear test and triaxial compression test when plane is polished by #100 grinding powder. When planes are cut by saw and are polished by #600 grinding powder, basic friction angles measured using tilt test are slightly different. This indicates that tilt test with plane polished by #100 grinding powder can yield an accurate basic friction angle. In addition, the accurate values are obtained not only when planes are polished again after 10 times of tilt test, but values are averaged by more 30 times of tests.

  10. Finger pad friction and its role in grip and touch

    PubMed Central

    Adams, Michael J.; Johnson, Simon A.; Lefèvre, Philippe; Lévesque, Vincent; Hayward, Vincent; André, Thibaut; Thonnard, Jean-Louis

    2013-01-01

    Many aspects of both grip function and tactile perception depend on complex frictional interactions occurring in the contact zone of the finger pad, which is the subject of the current review. While it is well established that friction plays a crucial role in grip function, its exact contribution for discriminatory touch involving the sliding of a finger pad is more elusive. For texture discrimination, it is clear that vibrotaction plays an important role in the discriminatory mechanisms. Among other factors, friction impacts the nature of the vibrations generated by the relative movement of the fingertip skin against a probed object. Friction also has a major influence on the perceived tactile pleasantness of a surface. The contact mechanics of a finger pad is governed by the fingerprint ridges and the sweat that is exuded from pores located on these ridges. Counterintuitively, the coefficient of friction can increase by an order of magnitude in a period of tens of seconds when in contact with an impermeably smooth surface, such as glass. In contrast, the value will decrease for a porous surface, such as paper. The increase in friction is attributed to an occlusion mechanism and can be described by first-order kinetics. Surprisingly, the sensitivity of the coefficient of friction to the normal load and sliding velocity is comparatively of second order, yet these dependencies provide the main basis of theoretical models which, to-date, largely ignore the time evolution of the frictional dynamics. One well-known effect on taction is the possibility of inducing stick–slip if the friction decreases with increasing sliding velocity. Moreover, the initial slip of a finger pad occurs by the propagation of an annulus of failure from the perimeter of the contact zone and this phenomenon could be important in tactile perception and grip function. PMID:23256185

  11. Finger pad friction and its role in grip and touch.

    PubMed

    Adams, Michael J; Johnson, Simon A; Lefèvre, Philippe; Lévesque, Vincent; Hayward, Vincent; André, Thibaut; Thonnard, Jean-Louis

    2013-03-01

    Many aspects of both grip function and tactile perception depend on complex frictional interactions occurring in the contact zone of the finger pad, which is the subject of the current review. While it is well established that friction plays a crucial role in grip function, its exact contribution for discriminatory touch involving the sliding of a finger pad is more elusive. For texture discrimination, it is clear that vibrotaction plays an important role in the discriminatory mechanisms. Among other factors, friction impacts the nature of the vibrations generated by the relative movement of the fingertip skin against a probed object. Friction also has a major influence on the perceived tactile pleasantness of a surface. The contact mechanics of a finger pad is governed by the fingerprint ridges and the sweat that is exuded from pores located on these ridges. Counterintuitively, the coefficient of friction can increase by an order of magnitude in a period of tens of seconds when in contact with an impermeably smooth surface, such as glass. In contrast, the value will decrease for a porous surface, such as paper. The increase in friction is attributed to an occlusion mechanism and can be described by first-order kinetics. Surprisingly, the sensitivity of the coefficient of friction to the normal load and sliding velocity is comparatively of second order, yet these dependencies provide the main basis of theoretical models which, to-date, largely ignore the time evolution of the frictional dynamics. One well-known effect on taction is the possibility of inducing stick-slip if the friction decreases with increasing sliding velocity. Moreover, the initial slip of a finger pad occurs by the propagation of an annulus of failure from the perimeter of the contact zone and this phenomenon could be important in tactile perception and grip function.

  12. Spatial and Temporal Patterns of Global NDVI Trends: Correlations with Climate and Human Factors

    NASA Astrophysics Data System (ADS)

    LIU, Y.; Li, S.

    2015-12-01

    Abstract: Changes in vegetation activity are driven by multiple natural and anthropogenic factors, which can be reflected by Normalized Difference Vegetation Index (NDVI) derived from satellite. In this paper, NDVI trends from 1982 to 2012 are first estimated by the Theil-Sen median slope method to explore their spatial and temporal patterns. Then the impact of climate variables and human activity on the observed NDVI trends is analyzed. Our results show on average NDVI increased by 0.46×10-3 per year from 1982 to 2012 globally with decadal variations. For most regions of the world, a greening (increasing) - browning(decreasing) - greening (G-B-G) trend is observed over the periods 1982-2004, 1995-2004, and 2005-2012, respectively. A positive partial correlation of NDVI and temperature is observed in the first period but it decreases and occasionally becomes negative in the following periods, especially in the Humid Temperate and Dry Domain Regions. This suggests a weakened effect of temperature on vegetation growth. Precipitation, on the other hand, is found to have a positive impact on the NDVI trend. This effect becomes stronger in the third period of 1995-2004, especially in the Dry Domain Region. Anthropogenic effects and human activities, derived here from the Human Footprint Dataset and the associated Human Influence Index (HII), have varied impacts on the magnitude (absolute value) of the NDVI trends across continents. Significant positive effects are found in Asia, Africa, and Europe, suggesting that intensive human activity could accelerate the change in NDVI and vegetation. A more accurate attribution of vegetation change to specific climatic and anthropogenic factors is instrumental to understand vegetation dynamics and requires further research.

  13. Correlation between the 1.6 A crystal structure and mutational analysis of keratinocyte growth factor.

    PubMed Central

    Osslund, T. D.; Syed, R.; Singer, E.; Hsu, E. W.; Nybo, R.; Chen, B. L.; Harvey, T.; Arakawa, T.; Narhi, L. O.; Chirino, A.; Morris, C. F.

    1998-01-01

    A comprehensive deletion, mutational, and structural analysis of the native recombinant keratinocyte growth factor (KGF) polypeptide has resulted in the identification of the amino acids responsible for its biological activity. One of these KGF mutants (delta23KGF-R144Q) has biological activity comparable to the native protein, and its crystal structure was determined by the multiple isomorphous replacement plus anomalous scattering method (MIRAS). The structure of KGF reveals that it folds into a beta-trefoil motif similar to other members of fibroblast growth factor (FGF) family whose structures have been resolved. This fold consists of 12 anti-parallel beta-strands in which three pairs of the strands form a six-stranded beta-barrel structure and the other three pairs of beta-strands cap the barrel with hairpin triplets forming a triangular array. KGF has 10 well-defined beta strands, which form five double-stranded anti-parallel beta-sheets. A sixth poorly defined beta-strand pair is in the loop between residues 133 and 144, and is defined by only a single hydrogen bond between the two strands. The KGF mutant has 10 additional ordered amino terminus residues (24-33) compared to the other FGF structures, which are important for biological activity. Based on mutagenesis, thermal stability, and structural data we postulate that residues TRP125, THR126, and His127 predominantly confer receptor binding specificity to KGF. Additionally, residues GLN152, GLN138, and THR42 are implicated in heparin binding. The increased thermal stability of delta23KGF-R144Q can structurally be explained by the additional formation of hydrogen bonds between the GLN side chain and a main-chain carbonyl on an adjoining loop. The correlation of the structure and biochemistry of KGF provides a framework for a rational design of this potentially important human therapeutic. PMID:10082365

  14. Rolling friction robot fingers

    NASA Technical Reports Server (NTRS)

    Vranish, John M. (Inventor)

    1992-01-01

    A low friction, object guidance, and gripping finger device for a robotic end effector on a robotic arm is disclosed, having a pair of robotic fingers each having a finger shaft slideably located on a gripper housing attached to the end effector. Each of the robotic fingers has a roller housing attached to the finger shaft. The roller housing has a ball bearing mounted centering roller located at the center, and a pair of ball bearing mounted clamping rollers located on either side of the centering roller. The object has a recess to engage the centering roller and a number of seating ramps for engaging the clamping rollers. The centering roller acts to position and hold the object symmetrically about the centering roller with respect to the X axis and the clamping rollers act to position and hold the object with respect to the Y and Z axis.

  15. Eliminating friction with friction: 2D Janssen effect in a friction-driven system.

    PubMed

    Karim, M Yasinul; Corwin, Eric I

    2014-05-01

    The Janssen effect is a unique property of confined granular materials experiencing gravitational compaction in which the pressure at the bottom saturates with an increasing filling height due to frictional interactions with side walls. In this Letter, we replace gravitational compaction with frictional compaction. We study friction-compacted 2D granular materials confined within fixed boundaries on a horizontal conveyor belt. We find that even with high-friction side walls the Janssen effect completely vanishes. Our results demonstrate that gravity-compacted granular systems are inherently different from friction-compacted systems in at least one important way: vibrations induced by sliding friction with the driving surface relax away tangential forces on the walls. Remarkably, we find that the Janssen effect can be recovered by replacing the straight side walls with a sawtooth pattern. The mechanical force introduced by varying the sawtooth angle θ can be viewed as equivalent to a tunable friction force. By construction, this mechanical friction force cannot be relaxed away by vibrations in the system. PMID:24856724

  16. Mars - Wind friction speeds for particle movement

    NASA Technical Reports Server (NTRS)

    Greeley, R.; Leach, R.; White, B.; Iversen, J.; Pollack, J.

    1976-01-01

    Wind friction threshold speeds for particle movement were determined in a low pressure boundary layer wind tunnel at an atmospheric pressure of 5.3 mb. The results imply that for comparable pressures on Mars, the minimum wind friction threshold speed is about 2.5 m/sec, which would require free-stream winds of 50 to 135 m/sec, depending on the character of the surface and the atmospheric conditions. The corresponding wind speeds at the height of the Viking lander meteorology instrument would be about a factor of two less than the free-stream wind speed. The particle size most easily moved by winds on Mars is about 160 microns; particles both larger and smaller than this (at least down to about 5 microns) require stronger winds to initiate movement.

  17. Correlation of genetic polymorphism of vascular endothelial growth factor gene with susceptibility to lung cancer.

    PubMed

    Liu, C; Zhou, X; Gao, F; Qi, Z; Zhang, Z; Guo, Y

    2015-06-01

    The aim of the study is to study the correlation of genetic polymorphism of vascular endothelial growth factor (VEGF) gene with susceptibility to primary lung cancer. A total of 414 patients with primary lung cancer and 338 healthy volunteers were enrolled in this case-control study from September 2008 to October 2011. Gene identification with PCR-RFLP (polymerase chain reaction-based restriction fragment length polymorphism) was used to detect in white blood cells from the subjects the single-nucleotide polymorphisms (SNP) of VEGF gene, including +405G/C, -460 T/C, -1154G/A, -2578C/A sites. Association of genotypes or haplotypes with susceptibility of lung cancer was analyzed with unconditional logistic regression adjusted by gender and age. Smoking was significantly associated with increased risk of lung cancer. Gene phenotypic analysis demonstrated that C allele of +405G/C in VEGF gene was significantly associated increased risk of lung cancer in males (P=0.0094, odds ratio=1.634.3), as that with carrying GCTC haplotype (odds ratio=1.349), whereas carrying GACG had decreased risk for lung cancer (odds ratio=0.044). No relationship existed between 460 T/C, -1154G/A, -2578C/A alleles of VEGF gene and risk of lung cancer. VEGF gene polymorphism may have a role in the development of lung cancer.

  18. The leucocyte count: correlates and relationship to coronary risk factors: the CARDIA study.

    PubMed

    Friedman, G D; Tekawa, I; Grimm, R H; Manolio, T; Shannon, S G; Sidney, S

    1990-12-01

    Correlates of the leucocyte count (WBC) and its relationships to other coronary heart disease (CHD) risk factors were assessed in 4981 black and white young adults. Mean WBC was higher in women than men, higher in whites than blacks, and higher in those aged 18-24 than aged 25-30 years. It also varied by season with the highest levels in the autumn. Other characteristics with persistent statistically significant direct associations with the WBC after multivariate adjustments were cigarette smoking, marijuana use, geographical location (possibly an inter-laboratory artifact), use of birth control pills, body mass index, pulse rate, and systolic blood pressure; height, physical fitness and high density lipoprotein cholesterol (HDL-C) level were inversely associated with the WBC. The negative association of WBC with HDL-C was too small to explain the association of WBC with CHD found elsewhere. The WBC is a commonly performed clinical test; yet much remains to be learned about its variation in the general population and its value as a predictor rather than merely an indicator of disease.

  19. Correlations between zooplankton assemblages and environmental factors in the downtown rivers of Shanghai, China

    NASA Astrophysics Data System (ADS)

    Yu, Na; Li, Erchao; Feng, Dexiang; Xiao, Baicai; Wei, Chaoqun; Zhang, Meiling; Chen, Liqiao

    2014-11-01

    Most urban rivers play an important role in urban flood control and drainage in China, but pollution is fast becoming an issue of greater importance in water management. In this study, 63 zooplankton species were recorded in four downtown rivers in Shanghai between November 2007 and October 2008. Of these, 44 species belonged to the Rotifera, 13 to Cladocera, and six to Copepoda. The three most frequently occurring zooplankton ( Brachionus calyciflorus, Microcyclops leuckarti, and Asplanchna priodonta) accounted for 80.00%, 76.84%, and 53.68%, respectively. Rotifera were found to be dominant, comprising 86.26% of total zooplankton, while cladoceran and copepod abundance amounted to 5.08% and 8.67%, respectively. Water temperature, salinity, electrical conductivity, and total nitrogen were of the greatest significance in the occurrence of zooplankton. Two species ( Schmackeria forbesi and Lepadella ovalis) were notably more sensitive to environmental factors such as salinity and electrical conductivity than other species. The population size and community were inversely correlated with the increasing nutrient levels of the four rivers, suggesting that the water quality of the four rivers had been gradually recovering from a severe eutrophic state and that water conditions of the rivers had been gradually improved.

  20. Friction and wear of some ferrous-base metallic glasses

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1983-01-01

    Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminum oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.

  1. Friction and wear of some ferrous-base metallic glasses

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1984-01-01

    Sliding friction experiments, X-ray photoelectron spectroscopy (XPS) analysis, and electron microscopy and diffraction studies were conducted with ferrous base metallic glasses (amorphous alloys) in contact with aluminium oxide at temperatures to 750 C in a vacuum. Sliding friction experiments were also conducted in argon and air atmospheres. The results of the investigation indicate that the coefficient of friction increases with increasing temperature to 350 C in vacuum. The increase in friction is due to an increase in adhesion resulting from surface segregation of boric oxide and/or silicon oxide to the surface of the foil. Above 500 C the coefficient of friction decreased rapidly. The decrease correlates with the segregation of boron nitride to the surface. Contaminants can come from the bulk of the material to the surface upon heating and impart boric oxide and/or silicon oxide at 350 C and boron nitride above 500 C. The segregation of contaminants is responsible for the friction behavior. The amorphous alloys have superior wear resistance to crystalline 304 stainless steel. The relative concentrations of the various constituents at the surfaces of the amorphous alloys are very different from the nominal bulk compositions.

  2. Physically representative atomistic modeling of atomic-scale friction

    NASA Astrophysics Data System (ADS)

    Dong, Yalin

    interesting physical process is buried between the two contact interfaces, thus makes a direct measurement more difficult. Atomistic simulation is able to simulate the process with the dynamic information of each single atom, and therefore provides valuable interpretations for experiments. In this, we will systematically to apply Molecular Dynamics (MD) simulation to optimally model the Atomic Force Microscopy (AFM) measurement of atomic friction. Furthermore, we also employed molecular dynamics simulation to correlate the atomic dynamics with the friction behavior observed in experiments. For instance, ParRep dynamics (an accelerated molecular dynamic technique) is introduced to investigate velocity dependence of atomic friction; we also employ MD simulation to "see" how the reconstruction of gold surface modulates the friction, and the friction enhancement mechanism at a graphite step edge. Atomic stick-slip friction can be treated as a rate process. Instead of running a direction simulation of the process, we can apply transition state theory to predict its property. We will have a rigorous derivation of velocity and temperature dependence of friction based on the Prandtl-Tomlinson model as well as transition theory. A more accurate relation to prediction velocity and temperature dependence is obtained. Furthermore, we have included instrumental noise inherent in AFM measurement to interpret two discoveries in experiments, suppression of friction at low temperature and the attempt frequency discrepancy between AFM measurement and theoretical prediction. We also discuss the possibility to treat wear as a rate process.

  3. The frictional response of patterned soft polymer surfaces

    NASA Astrophysics Data System (ADS)

    Rand, Charles J.

    2008-10-01

    Friction plays an intricate role in our everyday lives, it is therefore critical to understand the underlying features of friction to better help control and manipulate the response anywhere two surfaces in contact move past each other by a sliding motion. Here we present results targeting a thorough understanding of soft material friction and how it can be manipulated with patterns. We found that the naturally occurring length scale or periodicity (lambda) of frictionally induced patterns, Schallamach waves, could be described using two materials properties (critical energy release rate Gc and complex modulus (E*), i.e. lambdainfinity Gc /E*). Following this, we evaluated the effect of a single defect at a sliding interface. Sliding over a defect can be used to model the sliding from one feature to another in a patterned surface. Defects decreased the sliding frictional force by as much as 80% sliding and this decrease was attributed to changes in tangential stiffness of the sliding interface. The frictional response of surface wrinkles, where multiple edges or defects are acting in concert, was also evaluated. Wrinkles were shown to decrease friction (F) and changes in contact area (A) could not describe this decrease. A tangential stiffness correction factor (fx) and changes in the critical energy release rate were used to describe this deviation (F infinity Gc *A*fx/ℓ, where ℓ is a materials defined length scale of dissipation). This scaling can be used to describe the friction of any topographically patterned surface including the Gecko's foot, where the feature size is smaller than ℓ and thus replaces ℓ, increasing the friction compared to a flat surface. Also, mechanically-induced surface defects were used to align osmotically driven surface wrinkles by creating stress discontinuities that convert the global biaxial stress state to local uniaxial stresses. Defect spacing was used to control the alignment process at the surface of the wrinkled rigid

  4. Flow Friction or Spontaneous Ignition?

    NASA Technical Reports Server (NTRS)

    Stoltzfus, Joel M.; Gallus, Timothy D.; Sparks, Kyle

    2012-01-01

    "Flow friction," a proposed ignition mechanism in oxygen systems, has proved elusive in attempts at experimental verification. In this paper, the literature regarding flow friction is reviewed and the experimental verification attempts are briefly discussed. Another ignition mechanism, a form of spontaneous combustion, is proposed as an explanation for at least some of the fire events that have been attributed to flow friction in the literature. In addition, the results of a failure analysis performed at NASA Johnson Space Center White Sands Test Facility are presented, and the observations indicate that spontaneous combustion was the most likely cause of the fire in this 2000 psig (14 MPa) oxygen-enriched system.

  5. REDUCED ENGINE FRICTION AND WEAR

    SciTech Connect

    Ron Matthews

    2005-05-01

    This Final Technical Report discusses the progress was made on the experimental and numerical tasks over the duration of this project regarding a new technique for decreasing engine friction and wear via liner rotation. The experimental subtasks involved quantifying the reduction in engine friction for a prototype rotating liner engine relative to a comparable baseline engine. Both engine were single cylinder conversions of nominally identical production four-cylinder engines. Hot motoring tests were conducted initially and revealed that liner rotation decreased engine friction by 20% under motoring conditions. A well-established model was used to estimate that liner rotation should decrease the friction of a four-cylinder engine by 40% under hot motoring conditions. Hot motoring tear-down tests revealed that the crankshaft and valve train frictional losses were essentially the same for the two engines, as expected. However, the rotating liner engine had much lower (>70%) piston assembly friction compared to the conventional engine. Finally, we used the Instantaneous IMEP method to compare the crank-angle resolved piston assembly friction for the two engines. Under hot motoring conditions, these measurements revealed a significant reduction in piston assembly friction, especially in the vicinity of compression TDC when the lubrication regime transitions from hydrodynamic through mixed and into boundary friction. We have some remaining problems with these measurements that we expect to solve during the next few weeks. We will then perform these measurements under firing conditions. We also proposed to improve the state-of-the-art of numerical modeling of piston assembly friction for conventional engines and then to extend this model to rotating liner engines. Our research team first modeled a single ring in the Purdue ring-liner test rig. Our model showed good agreement with the test rig data for a range of speeds and loads. We then modeled a complete piston

  6. On laminar and turbulent friction

    NASA Technical Reports Server (NTRS)

    Von Karman, TH

    1946-01-01

    Report deals, first with the theory of the laminar friction flow, where the basic concepts of Prandtl's boundary layer theory are represented from mathematical and physical points of view, and a method is indicated by means of which even more complicated cases can be treated with simple mathematical means, at least approximately. An attempt is also made to secure a basis for the computation of the turbulent friction by means of formulas through which the empirical laws of the turbulent pipe resistance can be applied to other problems on friction drag. (author)

  7. Stress-dependent grain size evolution of nanocrystalline Ni-W and its impact on friction behavior

    DOE PAGESBeta

    Argibay, N.; Furnish, T. A.; Boyce, B. L.; Clark, B. G.; Chandross, M.

    2016-06-07

    The friction behavior of ultra-nanocrystalline Ni-W coatings was investigated. A critical stress threshold was identified below which friction remained low, and above which a time-dependent evolution toward higher friction behavior occurred. Founded on established plasticity models we propose a correlation between surface grain size and applied stress that can be used to predict the critical stress separating the two friction regimes. Lastly, this interpretation of plasticity models suggests that macro-scale low and high friction regimes are respectively associated with the nano-scale mechanisms of grain boundary and dislocation-mediated plasticity.

  8. Fault Wear and Friction Evolution: Experimental Analysis

    NASA Astrophysics Data System (ADS)

    Boneh, Y.; Chang, J. C.; Lockner, D. A.; Reches, Z.

    2011-12-01

    -body' structure that acts to lubricate the fault (Reches & Lockner, 2010). The steady-state stage is characterized by (1) relatively low wear-rate (approximately 10% of running-in wear-rate) and (2) quasi-constant friction coefficient. These observations suggest only small changes in the gouge layer in term of thickness (100 to 200 microns) and strength in this final stage. The present study indicates that (1) wear by plowing and asperity failure initiate early, during the first few millimeters of slip; and (2) wear and associated gouge formation appear as the controlling factors of friction evolution and fault weakening.

  9. Effects of Different Ligature Materials on Friction in Sliding Mechanics

    PubMed Central

    Khamatkar, Aparna; Sonawane, Sushma; Narkhade, Sameer; Gadhiya, Nitin; Bagade, Abhijit; Soni, Vivek; Betigiri, Asha

    2015-01-01

    Background: During orthodontic tooth movement friction occurs at the bracket wire interface. Out of the total force applied to the tooth movement, some of it is dissipated as friction, and the remainder is transferred to the supporting structures of the tooth to mediate tooth movement. However many factors affect friction, and method of arch wire ligation being an important contributing factor. Hence, this study was carried out to evaluate the effects of different ligature materials on friction in sliding mechanics and to compare the effect of environment (dry and wet) on friction produced in sliding mechanics. Materials and Methods: The evaluation of friction between the bracket and the archwire consisted of a simulated half arch fixed appliance with archwire ligated in a vertical position. Four 0.022” maxillary stainless steel premolar brackets having a - 0° torque and 0° angulation were aligned with a 0.019” × 0.025” stainless steel arch wire onto a rigid Plexiglass sheet. The movable test bracket was fitted with a 10 mm long, 0.045” thick stainless steel power arm on the bonding surface. Testing was performed on a Hounsfield material testing machine. A total of 100 g weight was suspended from the power arm and the load needed to move the bracket over the distance of not <4 mm across the central span was recorded separately. Fifteen representative readings were taken with one reading per test sample. Results: The results showed that the mean frictional force of different groups in dry and wet state was statistically significantly different. The mean frictional force in a dry state was statistically significantly higher than wet state in elastomeric group. Conclusion: The type of ligation material and environment significantly affected the degree of friction generated during sliding mechanics. Teflon coated stainless steel ligatures produced the least friction among the materials tested in both dry and wet conditions and there was no significant effect

  10. A clinicopathologic correlation of mammographic parenchymal patterns and associated risk factors for human mammary carcinoma.

    PubMed

    Bland, K I; Kuhns, J G; Buchanan, J B; Dwyer, P A; Heuser, L F; O'Connor, C A; Gray, L A; Polk, H C

    1982-05-01

    screened population. An equal distribution frequency of the XM classification existed for screenees 50 years of age or older with cancer (p = 0.50), while screenees 35-49 years of age were more often observed to have the high-risk P(2), DY patterns (p <0.001). Analysis of 1,759 histologic characteristics in biopsies of 863 patients with FCDB revealed ductal and lobular hyperplastic lesions, sclerosing adenosis, or epithelial cyst(s) to be the major constituents of 64-69% of the high-risk P(2) (P(2f), P(2n), P(2c)) image (p < 0.001). These data suggest that XM parenchymal patterns observed in asymptomatic screenees incompletely correlate with known pathologic variables and risk factors. Additionally, benefit for recognition of these preinvasive proliferative pathologic factors and carcinomas appears restricted to the younger screenee. The clinical integration of these risk factors with XM patterns may allow preselection of patients deserving of frequent follow-up for breast cancer; however, these data do not support the contention that Wolfe XM patterns are predictors for screening strategies or that they decisively enhance patient management.

  11. Multimodal Friction Ignition Tester

    NASA Technical Reports Server (NTRS)

    Davis, Eddie; Howard, Bill; Herald, Stephen

    2009-01-01

    The multimodal friction ignition tester (MFIT) is a testbed for experiments on the thermal and mechanical effects of friction on material specimens in pressurized, oxygen-rich atmospheres. In simplest terms, a test involves recording sensory data while rubbing two specimens against each other at a controlled normal force, with either a random stroke or a sinusoidal stroke having controlled amplitude and frequency. The term multimodal in the full name of the apparatus refers to a capability for imposing any combination of widely ranging values of the atmospheric pressure, atmospheric oxygen content, stroke length, stroke frequency, and normal force. The MFIT was designed especially for studying the tendency toward heating and combustion of nonmetallic composite materials and the fretting of metals subjected to dynamic (vibrational) friction forces in the presence of liquid oxygen or pressurized gaseous oxygen test conditions approximating conditions expected to be encountered in proposed composite material oxygen tanks aboard aircraft and spacecraft in flight. The MFIT includes a stainless-steel pressure vessel capable of retaining the required test atmosphere. Mounted atop the vessel is a pneumatic cylinder containing a piston for exerting the specified normal force between the two specimens. Through a shaft seal, the piston shaft extends downward into the vessel. One of the specimens is mounted on a block, denoted the pressure block, at the lower end of the piston shaft. This specimen is pressed down against the other specimen, which is mounted in a recess in another block, denoted the slip block, that can be moved horizontally but not vertically. The slip block is driven in reciprocating horizontal motion by an electrodynamic vibration exciter outside the pressure vessel. The armature of the electrodynamic exciter is connected to the slip block via a horizontal shaft that extends into the pressure vessel via a second shaft seal. The reciprocating horizontal

  12. Friction microprobe investigation of particle layer effects on sliding friction

    SciTech Connect

    Blau, P.J.

    1993-01-01

    Interfacial particles (third-bodies), resulting from wear or external contamination, can alter and even dominate the frictional behavior of solid-solid sliding in the absence of effective particle removal processes (e.g., lubricant flow). A unique friction microprobe, developed at Oak Ridge National Laboratory, was used to conduct fine- scale friction studies using 1.0 mm diameter stainless steel spheres sliding on several sizes of loose layers of fine aluminum oxide powders on both aluminum and alumina surfaces. Conventional, pin-on-disk experiments were conducted to compare behavior with the friction microprobe results. The behavior of the relatively thick particle layers was found to be independent of the nature of underlying substrate, substantiating previous work by other investigators. The time-dependent behavior of friction, for a spherical macrocontact starting from rest, could generally be represented by a series of five rather distinct phases involving static compression, slider breakaway, transition to steady state, and dynamic layer instability. A friction model for the steady state condition, which incorporates lamellar powder layer behavior, is described.

  13. Outcomes of pediatric glioblastoma treated with adjuvant chemoradiation with temozolomide and correlation with prognostic factors

    PubMed Central

    Mallick, Supriya; Gandhi, Ajeet Kumar; Joshi, Nikhil P.; Kumar, Anupam; Puri, Tarun; Sharma, Daya Nand; Haresh, Kunhi Parambath; Gupta, Subhash; Julka, Pramod Kumar; Rath, Goura Kisor; Sarkar, Chitra

    2015-01-01

    Background: Pediatric glioblastoma (pGBM) patients are underrepresented in major trials for this disease. We aimed to explore the outcome of pGBM patients treated with concurrent and adjuvant temozolomide (TMZ). Materials and Methods: 23 patients of pGBM treated from 2004 to 2010 were included in this retrospective analysis. Adjuvant therapy included conformal radiation 60 gray at 2 gray/fraction daily over 6 weeks with concurrent TMZ 75 mg/m2 followed by six cycles of adjuvant TMZ 150-200 mg/m2 (day 1-5) every 4 weeks. Kaplan-Meier estimates of overall survival (OS) were determined. Univariate analysis with log-rank test was used to determine the impact of prognostic variables on survival. Results: Median age at presentation was 11.5 years (range: 7-19 years) and M:F ratio was 15:8. All patients underwent maximal safe surgical resection; 13 gross total resection and 10 sub-total resection. At a median follow-up of 18 months (range: 2.1-126 months), the estimated median OS was 41.9 months. The estimated median OS for patients receiving only concurrent TMZ was 8 months while that for patients receiving concurrent and adjuvant TMZ was 41.9 months (P = 0.081). Estimated median OS for patients who did not complete six cycles of adjuvant TMZ was 9.5 months versus not reached for those who completed at least six cycles (P = 0.0005). Other prognostic factors did not correlate with survival. Conclusions: Our study shows the benefit of TMZ for pGBM patients. Both concurrent and adjuvant TMZ seem to be important for superior OS in this group of patients. PMID:26157286

  14. Correlation of Clinical and Dosimetric Factors With Adverse Pulmonary Outcomes in Children After Lung Irradiation

    SciTech Connect

    Venkatramani, Rajkumar; Kamath, Sunil; Wong, Kenneth; Malvar, Jemily; Sposto, Richard; Goodarzian, Fariba; Freyer, David R.; Keens, Thomas G.; and others

    2013-08-01

    Purpose: To identify the incidence and the risk factors for pulmonary toxicity in children treated for cancer with contemporary lung irradiation. Methods and Materials: We analyzed clinical features, radiographic findings, pulmonary function tests, and dosimetric parameters of children receiving irradiation to the lung fields over a 10-year period. Results: We identified 109 patients (75 male patients). The median age at irradiation was 13.8 years (range, 0.04-20.9 years). The median follow-up period was 3.4 years. The median prescribed radiation dose was 21 Gy (range, 0.4-64.8 Gy). Pulmonary toxic chemotherapy included bleomycin in 58.7% of patients and cyclophosphamide in 83.5%. The following pulmonary outcomes were identified and the 5-year cumulative incidence after irradiation was determined: pneumonitis, 6%; chronic cough, 10%; pneumonia, 35%; dyspnea, 11%; supplemental oxygen requirement, 2%; radiographic interstitial lung disease, 40%; and chest wall deformity, 12%. One patient died of progressive respiratory failure. Post-irradiation pulmonary function tests available from 44 patients showed evidence of obstructive lung disease (25%), restrictive disease (11%), hyperinflation (32%), and abnormal diffusion capacity (12%). Thoracic surgery, bleomycin, age, mean lung irradiation dose (MLD), maximum lung dose, prescribed dose, and dosimetric parameters between V{sub 22} (volume of lung exposed to a radiation dose ≥22 Gy) and V{sub 30} (volume of lung exposed to a radiation dose ≥30 Gy) were significant for the development of adverse pulmonary outcomes on univariate analysis. MLD, maximum lung dose, and V{sub dose} (percentage of volume of lung receiving the threshold dose or greater) were highly correlated. On multivariate analysis, MLD was the sole significant predictor of adverse pulmonary outcome (P=.01). Conclusions: Significant pulmonary dysfunction occurs in children receiving lung irradiation by contemporary techniques. MLD rather than prescribed

  15. Correlation between genetic variability and virulence factors in clinical strains of Malassezia pachydermatis of animal origin.

    PubMed

    Buommino, Elisabetta; Nocera, Francesca Paola; Parisi, Annamaria; Rizzo, Antonietta; Donnarumma, Giovanna; Mallardo, Karina; Fiorito, Filomena; Baroni, Adone; De Martino, Luisa

    2016-09-01

    Malassezia pachydermatis is a yeast belonging to the microbiota of the skin and mucous membranes of dog and cat, but it can also act as pathogen, causing dermatitis. The aim of this work was to evaluate the genetic variability of M. pachydermatis strains isolated from symptomatic dogs and cats and determine a correlation between genotype and phenotype. For this purpose eleven strains of M. pachydermatis were molecularly classified by nested-polymerase chain reaction (nested-PCR) based on ITS-1 and ITS-2 regions, specific for fungal rRNA genes. Furthermore, random amplification of polymorphic DNA (RAPD) was applied for genetic typing of M. pachydermatis isolates identifying four different genotypes. Strains belonging to genotype 1 produced the highest amount of biofilm and phospholipase activity. The inflammatory response induced by M. pachydermatis strains in immortalized human keratinocytes (HaCat cells) was significantly different when we compared the results obtained from each strain. In particular, HaCat cells infected with the strains belonging to genotypes 1 and 2 triggered the highest levels of increase in TLR-2, IL-1β, IL-6, IL-8, COX-2 and MMP-9 expression. By contrast, cells infected with the strains of genotype 3 and those of genotype 4 did not significantly induce TLR-2 and cytokines. The results obtained might suggest a possible association between genotype and virulence factors expressed by M. pachydermatis strains. This highlights the need for a more accurate identification of the yeast to improve the therapeutic approach and to monitor the onset of human infections caused by this emergent zoonotic pathogen. PMID:27602421

  16. Correlational study on mitochondrial DNA mutations as potential risk factors in breast cancer

    PubMed Central

    Zhang, Weiyun; Liao, Yang; Chen, Jianyun; Sun, Zhaohui

    2016-01-01

    The presented study performed an mtDNA genome-wide association analysis to screen the peripheral blood of breast cancer patients for high-risk germline mutations. Unlike previous studies, which have used breast tissue in analyzing somatic mutations, we looked for germline mutations in our study, since they are better predictors of breast cancer in high-risk groups, facilitate early, non-invasive diagnoses of breast cancer and may provide a broader spectrum of therapeutic options. The data comprised 22 samples of healthy group and 83 samples from breast cancer patients. The sequencing data showed 170 mtDNA mutations in the healthy group and 393 mtDNA mutations in the disease group. Of these, 283 mtDNA mutations (88 in the healthy group and 232 in the disease group) had never been reported in the literature. Moreover, correlation analysis indicated there was a significant difference in 32 mtDNA mutations. According to our relative risk analysis of these 32 mtDNA mutations, 27 of the total had odds ratio values (ORs) of less than 1, meaning that these mutations have a potentially protective role to play in breast cancer. The remaining 5 mtDNA mutations, RNR2-2463 indelA, COX1-6296 C>A, COX1-6298 indelT, ATP6-8860 A>G, and ND5-13327 indelA, whose ORs were 8.050, 4.464, 4.464, 5.254 and 4.853, respectively, were regarded as risk factors of increased breast cancer. The five mutations identified here may serve as novel indicators of breast cancer and may have future therapeutic applications. In addition, the use of peripheral blood samples was procedurally simple and could be applied as a non-invasive diagnostic technique. PMID:27121313

  17. Frictional slip of granite at hydrothermal conditions

    USGS Publications Warehouse

    Blanpied, M.L.; Lockner, D.A.; Byerlee, J.D.

    1995-01-01

    To measure the strength, sliding behavior, and friction constitutive properties of faults at hydrothermal conditions, laboratory granite faults containing a layer of granite powder (simulated gouge) were slid. The mechanical results define two regimes. The first regime includes dry granite up to at least 845?? and wet granite below 250??C. In this regime the coefficient of friction is high (?? = 0.7 to 0.8) and depends only modestly on temperature, slip rate, and PH2O. The second regime includes wet granite above ~350??C. In this regime friction decreases considerably with increasing temperature (temperature weakening) and with decreasing slip rate (velocity strengthening). These regimes correspond well to those identified in sliding tests on ultrafine quartz. The results highlight the importance of fluid-assisted deformation processes active in faults at depth and the need for laboratory studies on the roles of additional factors such as fluid chemistry, large displacements, higher concentrations of phyllosilicates, and time-dependent fault healing. -from Authors

  18. Size Scaling of Static Friction

    NASA Astrophysics Data System (ADS)

    Braun, O. M.; Manini, Nicola; Tosatti, Erio

    2013-02-01

    Sliding friction across a thin soft lubricant film typically occurs by stick slip, the lubricant fully solidifying at stick, yielding and flowing at slip. The static friction force per unit area preceding slip is known from molecular dynamics (MD) simulations to decrease with increasing contact area. That makes the large-size fate of stick slip unclear and unknown; its possible vanishing is important as it would herald smooth sliding with a dramatic drop of kinetic friction at large size. Here we formulate a scaling law of the static friction force, which for a soft lubricant is predicted to decrease as fm+Δf/Aγ for increasing contact area A, with γ>0. Our main finding is that the value of fm, controlling the survival of stick slip at large size, can be evaluated by simulations of comparably small size. MD simulations of soft lubricant sliding are presented, which verify this theory.

  19. Rubber friction: comparison of theory with experiment.

    PubMed

    Lorenz, B; Persson, B N J; Dieluweit, S; Tada, T

    2011-12-01

    We have measured the friction force acting on a rubber block slid on a concrete surface. We used both unfilled and filled (with carbon black) styrene butadiene (SB) rubber and have varied the temperature from -10 °C to 100 °C and the sliding velocity from 1 μm/s to 1000 μm/s. We find that the experimental data at different temperatures can be shifted into a smooth master-curve, using the temperature-frequency shifting factors obtained from measurements of the bulk viscoelastic modulus. The experimental data has been analyzed using a theory which takes into account the contributions to the friction from both the substrate asperity-induced viscoelastic deformations of the rubber, and from shearing the area of real contact. For filled SB rubber the frictional shear stress σ(f) in the area of real contact results mainly from the energy dissipation at the opening crack on the exit side of the rubber-asperity contact regions. For unfilled rubber we instead attribute σ(f) to shearing of a thin rubber smear film, which is deposited on the concrete surface during run in. We observe very different rubber wear processes for filled and unfilled SB rubber, which is consistent with the different frictional processes. Thus, the wear of filled SB rubber results in micrometer-sized rubber particles which accumulate as dry dust, which is easily removed by blowing air on the concrete surface. This wear process seams to occur at a steady rate. For unfilled rubber a smear film forms on the concrete surface, which cannot be removed even using a high-pressure air stream. In this case the wear rate appears to slow down after some run in time period.

  20. Factors determining the precision of the correlated firing generated by a monosynaptic connection in the cat visual pathway

    PubMed Central

    Veredas, Francisco J; Vico, Francisco J; Alonso, Jose-Manuel

    2005-01-01

    Across the visual pathway, strong monosynaptic connections generate a precise correlated firing between presynaptic and postsynaptic neurons. The precision of this correlated firing is not the same within thalamus and visual cortex. While retinogeniculate connections generate a very narrow peak in the correlogram (peak width < 1 ms), the peaks generated by geniculocortical and corticocortical connections have usually a time course of several milliseconds. Several factors could explain these differences in timing precision such as the amplitude of the monosynaptic EPSP (excitatory postsynaptic potential), its time course or the contribution of polysynaptic inputs. While it is difficult to isolate the contribution of each factor in physiological experiments, a first approximation can be done in modelling studies. Here, we simulated two monosynaptically connected neurons to measure changes in their correlated firing as we independently modified different parameters of the connection. Our results suggest that the precision of the correlated firing generated by strong monosynaptic connections is mostly determined by the EPSP time course of the connection and much less by other factors. In addition, we show that a polysynaptic pathway is unlikely to emulate the correlated firing generated by a monosynaptic connection unless it generates EPSPs with very small latency jitter. PMID:16020458

  1. Radiation friction versus ponderomotive effect

    NASA Astrophysics Data System (ADS)

    Fedotov, A. M.; Elkina, N. V.; Gelfer, E. G.; Narozhny, N. B.; Ruhl, H.

    2014-11-01

    The concept of ponderomotive potential is upgraded to a regime in which radiation friction becomes dominant. The radiation friction manifests itself in long-term capturing of the particles released at the focus and impenetrability of the focus from the exterior. We apply time scale separation to the Landau-Lifshitz equation splitting the particle motion into quivering and slow drift of a guiding center. The drift equation is deduced by averaging over fast motion.

  2. Tire/runway friction interface

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.

    1990-01-01

    An overview is given of NASA Langley's tire/runway pavement interface studies. The National Tire Modeling Program, evaluation of new tire and landing gear designs, tire wear and friction tests, and tire hydroplaning studies are examined. The Aircraft Landing Dynamics Facility is described along with some ground friction measuring vehicles. The major goals and scope of several joint FAA/NASA programs are identified together with current status and plans.

  3. [Correlation analysis on normalized difference vegetation index (NDVI) of different vegetations and climatic factors in Southwest China].

    PubMed

    Zhang, Yuan-Dong; Zhang, Xiao-He; Liu, Shi-Rong

    2011-02-01

    Based on the 1982-2006 NDVI remote sensing data and meteorological data of Southwest China, and by using GIS technology, this paper interpolated and extracted the mean annual temperature, annual precipitation, and drought index in the region, and analyzed the correlations of the annual variation of NDVI in different vegetation types (marsh, shrub, bush, grassland, meadow, coniferous forest, broad-leaved forest, alpine vegetation, and cultural vegetation) with corresponding climatic factors. In 1982-2006, the NDVI, mean annual temperature, and annual precipitation had an overall increasing trend, and the drought index decreased. Particularly, the upward trend of mean annual temperature was statistically significant. Among the nine vegetation types, the NDVI of bush and mash decreased, and the downward trend was significant for bush. The NDVI of the other seven vegetation types increased, and the upward trend was significant for coniferous forest, meadow, and alpine vegetation, and extremely significant for shrub. The mean annual temperature in the areas with all the nine vegetation types increased significantly, while the annual precipitation had no significant change. The drought index in the areas with marsh, bush, and cultural vegetation presented an increasing trend, that in the areas with meadow and alpine vegetation decreased significantly, and this index in the areas with other four vegetation types had an unobvious decreasing trend. The NDVI of shrub and coniferous forest had a significantly positive correlation with mean annual temperature, and that of shrub and meadow had significantly negative correlation with drought index. Under the conditions of the other two climatic factors unchanged, the NDVI of coniferous forest, broad-leaved forest, and alpine vegetation showed the strongest correlation with mean annual temperature, that of grass showed the strongest correlation with annual precipitation, and the NDVI of mash, shrub, grass, meadow, and cultural

  4. Nanotribology fundamentals: Predicting the viscous coefficient of friction

    NASA Astrophysics Data System (ADS)

    Coffey, Tonya S.

    In this work, I have used the Quartz Crystal Microbalance (QCM) to study nanoscale friction of monolayer adsorbates on (111) metals. The friction of these systems is viscous friction, defined as Ff = etanu = ( mt )nu. Here, eta is the viscous coefficient of friction, nu is the velocity of the adsorbate, m is adsorbate mass, and tau is the slip time, which is the time required for the film's speed to fall to 1/e of its original value. The main focus of this dissertation is to determine the factors that control eta, the viscous coefficient of friction. I have examined three different parameters in order to determine their effect on eta. An equation for predicting the viscous coefficient of friction has been proposed: eta = etasubs + aU2o . Here, etasubs is the damping of adsorbate sliding energy within the substrate, a is a constant depending on mainly temperature and adsorbate film coverage, and Uo is the atomic-scale surface corrugation. I have examined the sliding friction of n-octane on Cu(111) vs. Pb(11I) surfaces, which have gamma = 0.45 meV and gamma = 0.26 meV, respectively. I have observed that the slip time for a monolayer of n-octane/Cu(111) is 0.94 ns +/- 0.36 ns, and the slip time of noctane/Pb(111) is 0.59 ns +/- 0.13 ns. I therefore observe no direct evidence of a link between the damping of perpendicular FT modes and sliding friction. It is still possible, however, that the damping of the parallel FT phonon mode affects sliding friction. Finally, I studied the slippage of monolayer methanol films at room temperature on rotating, rigid, and slowly ratcheting C60 substrates, to examine the effect that the molecular rotation of the substrate surface has on the sliding friction of an adsorbate. I found that at all coverages, the slip time for methanol on rigid and slowly ratcheting C60 was longer (hence lower friction) than the slip time for methanol on rotating C 60, defying the ball bearing analogy. (Abstract shortened by UMI.)

  5. Modelling environmental factors correlated with podoconiosis: a geospatial study of non-filarial elephantiasis

    PubMed Central

    2014-01-01

    Introduction The precise trigger of podoconiosis — endemic non-filarial elephantiasis of the lower legs — is unknown. Epidemiological and ecological studies have linked the disease with barefoot exposure to red clay soils of volcanic origin. Histopathology investigations have demonstrated that silicon, aluminium, magnesium and iron are present in the lower limb lymph node macrophages of both patients and non-patients living barefoot on these clays. We studied the spatial variation (variations across an area) in podoconiosis prevalence and the associated environmental factors with a goal to better understanding the pathogenesis of podoconiosis. Methods Fieldwork was conducted from June 2011 to February 2013 in 12 kebeles (administrative units) in northern Ethiopia. Geo-located prevalence data and soil samples were collected and analysed along with secondary geological, topographic, meteorological and elevation data. Soil data were analysed for chemical composition, mineralogy and particle size, and were interpolated to provide spatially continuous information. Exploratory, spatial, univariate and multivariate regression analyses of podoconiosis prevalence were conducted in relation to primary (soil) and secondary (elevation, precipitation, and geology) covariates. Results Podoconiosis distribution showed spatial correlation with variation in elevation and precipitation. Exploratory analysis identified that phyllosilicate minerals, particularly clay (smectite and kaolinite) and mica groups, quartz (crystalline silica), iron oxide, and zirconium were associated with podoconiosis prevalence. The final multivariate model showed that the quantities of smectite (RR = 2.76, 95% CI: 1.35, 5.73; p = 0.007), quartz (RR = 1.16, 95% CI: 1.06, 1.26; p = 0.001) and mica (RR = 1.09, 95% CI: 1.05, 1.13; p < 0.001) in the soil had positive associations with podoconiosis prevalence. Conclusions More quantities of smectite, mica and quartz within the soil

  6. Friction and stress coupling on the subduction interfaces

    NASA Astrophysics Data System (ADS)

    Tan, E.; Lavier, L.; van Avendonk, H.

    2011-12-01

    At a subduction zone, the down-going oceanic plate slides underneath the overriding plate. The frictional resistance to the relative motion between the plates generates great earthquakes along the subduction interface, which can cause tremendous damage in the civil life and property. There is a strong incentive to understand the frictional strength of the subduction interface. One fundamental question of mechanics of subuction is the degree of coupling between the plates, which is linked to the size of earthquakes. It has been noted that the trench-parallel (along-strike) gravity variation correlates positively with the trench-parallel topography anomaly and negatively with the activity of great earthquake (Song and Simons, 2003). Regions with a negative trench-parallel gravity anomaly are more likely to have great earthquakes. The interpretation of such correlation is that strong coupling along subduction interface will drag down the for-arc region of the overriding plate, which generates the gravity and topography anomalies, and could store more strain energy to be released during a great earthquake. We developed a 2D numerical thermo-mechanical code for modeling subduction. The numerical method is based on an explicit finite element method similar to the Fast Lagrangian Analysis of Continua (FLAC) technique. The constitutive law is visco-elasti-plastic with strain weakening. The cohesion and friction angle are reduced with increasing plastic strain after yielding. To track different petrologic phases, Lagrangian particles are distributed in the domain. Basalt-eclogite, sediment-schist and peridotite-serpentinite phase changes are included in the model. Our numerical models show that the degree of coupling negatively correlates with the coefficient of friction. In the low friction case, the subduction interface has very shallow dipping angle, which helps to elastically couple the downing plate with the overriding plate. The topography and gravity anomalies of the

  7. Friction-induced skin injuries-are they pressure ulcers? An updated NPUAP white paper.

    PubMed

    Brienza, David; Antokal, Steven; Herbe, Laura; Logan, Susan; Maguire, Jeanine; Van Ranst, Jennifer; Siddiqui, Aamir

    2015-01-01

    Friction injuries are often misdiagnosed as pressure ulcers. The reason for the misdiagnosis may be a misinterpretation of classic pressure ulcer literature that reported friction increased the susceptibility of the skin to pressure damage. This analysis assesses the classic literature that led to the inclusion of friction as a causative factor in the development of pressure ulcers in light of more recent research on the effects of shear. The analysis in this article suggests that friction can contribute to pressure ulcers by creating shear strain in deeper tissues, but friction does not appear to contribute to pressure ulcers in the superficial layers of the skin. Injuries to the superficial layers of the skin caused by friction are not pressure ulcers and should not be classified or treated as such.

  8. The influence of high temperatures on the tribological properties of automotive friction materials

    NASA Astrophysics Data System (ADS)

    Savage, Luke

    Temperatures of over 800C can be generated at the frictional interface within the brake systems of large vehicles, such high temperatures result in severe wear at the frictional interface, and can also lead to a very dangerous condition known as brake fade, characterised by a sharp fall in the coefficient of friction between the pad and disc, resulting in a catastrophic loss of braking efficiency. Common friction materials are very specialised composites often containing up to 15 components bound together within a phenolic resin matrix. The high temperature behaviour of the various constituents of friction materials were investigated using thermogravimetric analysis, focusing in particular on the thermal decomposition of the phenolic resin matrix material, where it has been firmly established that the thermal decomposition products of phenolic resin are the primary cause of brake fade. This has lead to the development of a novel approach for reducing fade in conventional resin based friction materials, involving a partial carbonisation to 400C. The high temperature wear characteristics of both modified and conventional friction materials were examined using standard dynamometer tests, as well as a 'continuous drag' type test machine, equipped with a heating facility. During this study a number of factors were identified as the main influences on the overall wear behaviour of friction materials. These included test temperature, sample test history, and the various effects of friction films, which were the subject of a detailed analysis. The formation of friction films was found to be an important facet of a successful friction material, producing a reduction in wear at the frictional interface. Films were examined and analysed using EDX, SEM, and X-ray diffraction techniques, which revealed the presence of a high proportion of magnetite (Fe3O4), containing iron which originated from the disc surface. It was established that the incorporation of iron in friction

  9. Rotation Criteria and Hypothesis Testing for Exploratory Factor Analysis: Implications for Factor Pattern Loadings and Interfactor Correlations

    ERIC Educational Resources Information Center

    Schmitt, Thomas A.; Sass, Daniel A.

    2011-01-01

    Exploratory factor analysis (EFA) has long been used in the social sciences to depict the relationships between variables/items and latent traits. Researchers face many choices when using EFA, including the choice of rotation criterion, which can be difficult given that few research articles have discussed and/or demonstrated their differences.…

  10. Experimental Research Into Generation of Acoustic Emission Signals in the Process of Friction of Hadfield Steel Single Crystals

    NASA Astrophysics Data System (ADS)

    Lychagin, D. V.; Filippov, A. V.; Novitskaia, O. S.; Kolubaev, E. A.; Sizova, O. V.

    2016-08-01

    The results of experimental research into dry sliding friction of Hadfield steel single crystals involving registration of acoustic emission are presented in the paper. The images of friction surfaces of Hadfield steel single crystals and wear grooves of the counterbody surface made after completion of three serial experiments conducted under similar conditions and friction regimes are given. The relation of the acoustic emission waveform envelope to the changing friction factor is revealed. Amplitude-frequency characteristics of acoustic emission signal frames are determined on the base of Fast Fourier Transform and Short Time Fourier Transform during the run-in stage of tribounits and in the process of stable friction.

  11. Frictional Heterogeneities Along Carbonate Faults

    NASA Astrophysics Data System (ADS)

    Collettini, C.; Carpenter, B. M.; Scuderi, M.; Tesei, T.

    2014-12-01

    The understanding of fault-slip behaviour in carbonates has an important societal impact as a) a significant number of earthquakes nucleate within or propagate through these rocks, and b) half of the known petroleum reserves occur within carbonate reservoirs, which likely contain faults that experience fluid pressure fluctuations. Field studies on carbonate-bearing faults that are exhumed analogues of currently active structures of the seismogenic crust, show that fault rock types are systematically controlled by the lithology of the faulted protolith: localization associated with cataclasis, thermal decomposition and plastic deformation commonly affect fault rocks in massive limestone, whereas distributed deformation, pressure-solution and frictional sliding along phyllosilicates are observed in marly rocks. In addition, hydraulic fractures, indicating cyclic fluid pressure build-ups during the fault activity, are widespread. Standard double direct friction experiments on fault rocks from massive limestones show high friction, velocity neutral/weakening behaviour and significant re-strengthening during hold periods, on the contrary, phyllosilicate-rich shear zones are characterized by low friction, significant velocity strengthening behavior and no healing. We are currently running friction experiments on large rock samples (20x20 cm) in order to reproduce and characterize the interaction of fault rock frictional heterogeneities observed in the field. In addition we have been performing experiments at near lithostatic fluid pressure in the double direct shear configuration within a pressure vessel to test the Rate and State friction stability under these conditions. Our combination of structural observations and mechanical data have been revealing the processes and structures that are at the base of the broad spectrum of fault slip behaviors recently documented by high-resolution geodetic and seismological data.

  12. Dynamical friction in pairs of elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Prugniel, Philippe; Combes, Francoise

    1990-01-01

    The authors present numerical experiments on dynamical friction in pairs of elliptical galaxies of unequal mass. They confirm that the self-gravity of the response is not important and show the drastic effect of the deformability of the companion which reduces the decay time by more than a factor of 2. Almost the same amount of orbital energy is dissipated within the satellite as within the large galaxy. Finally, the authors discuss the importance of distant encounters for the dynamical evolution of systems of galaxies.

  13. Adhesion energy between mica surfaces: Implications for the frictional coefficient under dry and wet conditions

    NASA Astrophysics Data System (ADS)

    Sakuma, Hiroshi

    2013-12-01

    frictional strength of faults is a critical factor that contributes to continuous fault slip and earthquake occurrence. Frictional strength can be reduced by the presence of sheet-structured clay minerals. In this study, two important factors influencing the frictional coefficient of minerals were quantitatively analyzed by a newly developed computational method based on a combination of first-principles study and thermodynamics. One factor that helps reduce the frictional coefficient is the low adhesion energy between the layers under dry conditions. Potassium ions on mica surfaces are easily exchanged with sodium ions when brought into contact with highly concentrated sodium-halide solutions. We found that the surface ion exchange with sodium ions reduces the adhesion energy, indicating that the frictional coefficient can be reduced under dry conditions. Another factor is the lubrication caused by adsorbed water films on mineral surfaces under wet conditions. Potassium and sodium ions on mica surfaces have a strong affinity for water molecules. In order to remove the adsorbed water molecules confined between mica surfaces, a differential compressive stress of the order of tens of gigapascals was necessary at room temperature. These water molecules inhibit direct contact between mineral surfaces and reduce the frictional coefficient. Our results imply that the frictional coefficient can be modified through contact with fluids depending on their salt composition. The low adhesion energy between fault-forming minerals and the presence of an adsorbed water film is a possible reason for the low frictional coefficient observed at continuous fault slip zones.

  14. General regularities of explosion initiation in determining impact and friction sensitivity of an explosive

    SciTech Connect

    Kondrikov, B.N.

    1995-09-01

    The impact and friction sensitivities of explosives were measured by 12 methods used in Russia and abroad. Correlations between explosion frequency on devices No. 1 and No. 2 with a {open_quotes}lower sensitivity limit{open_quotes} according to Russian standard 4545-88 and {open_quotes}critical clamping pressure{close_quotes} for the I-6-2 device are obtained. Almost all results are well correlated with critical stress p{sub 1} thus representing a good base for explanation of experimental results for impact and friction. The values we obtained determining friction sensitivity are often proportional to p{sub 1}. The regularities obtained are explained.

  15. Instantaneous engine frictional torque, its components and piston assembly friction

    SciTech Connect

    Nichols, F.A. ); Henein, N.A. . Center for Automotive Research)

    1992-05-01

    The overall goal of this report is to document the work done to determine the instantaneous frictional torque of internal combustion engine by using a new approach known as (P-[omega]) method developed at Wayne State University. The emphasis has been to improve the accuracy of the method, and apply it to both diesel and gasoline engines under different operating conditions. Also work included an investigation to determine the effect of using advanced materials and techniques to coat the piston rings on the instantaneous engine frictional torque and the piston assembly friction. The errors in measuring the angular velocity, [omega], have been determined and found to be caused by variations in the divisions within one encoder, encoder-to-encoder variations, misalignment within the encoder itself and misalignment between the encoder and crankshaft. The errors in measuring the cylinder gas pressure, P, have been determined and found to be caused by transducer-to-transducer variations, zero drift, thermal stresses and lack of linearity. The ability of the (P-[omega]) method in determining the frictional torque of many engine components has been demonstrated. These components include valve train, fuel injection pump with and without fuel injection, and piston with and without different ring combinations. The emphasis in this part of the research program has been on the piston-ring assembly friction. The effects of load and other operating variables on IFT have been determined. The motoring test, which is widely used in industry to measure engine friction has been found to be inaccurate. The errors have been determined at different loads.

  16. Versatile Friction Stir Welding/Friction Plug Welding System

    NASA Technical Reports Server (NTRS)

    Carter, Robert

    2006-01-01

    A proposed system of tooling, machinery, and control equipment would be capable of performing any of several friction stir welding (FSW) and friction plug welding (FPW) operations. These operations would include the following: Basic FSW; FSW with automated manipulation of the length of the pin tool in real time [the so-called auto-adjustable pin-tool (APT) capability]; Self-reacting FSW (SRFSW); SR-FSW with APT capability and/or real-time adjustment of the distance between the front and back shoulders; and Friction plug welding (FPW) [more specifically, friction push plug welding] or friction pull plug welding (FPPW) to close out the keyhole of, or to repair, an FSW or SR-FSW weld. Prior FSW and FPW systems have been capable of performing one or two of these operations, but none has thus far been capable of performing all of them. The proposed system would include a common tool that would have APT capability for both basic FSW and SR-FSW. Such a tool was described in Tool for Two Types of Friction Stir Welding (MFS- 31647-1), NASA Tech Briefs, Vol. 30, No. 10 (October 2006), page 70. Going beyond what was reported in the cited previous article, the common tool could be used in conjunction with a plug welding head to perform FPW or FPPW. Alternatively, the plug welding head could be integrated, along with the common tool, into a FSW head that would be capable of all of the aforementioned FSW and FPW operations. Any FSW or FPW operation could be performed under any combination of position and/or force control.

  17. Slow rupture of frictional interfaces

    NASA Astrophysics Data System (ADS)

    Bar Sinai, Yohai; Brener, Efim A.; Bouchbinder, Eran

    2012-02-01

    The failure of frictional interfaces and the spatiotemporal structures that accompany it are central to a wide range of geophysical, physical and engineering systems. Recent geophysical and laboratory observations indicated that interfacial failure can be mediated by slow slip rupture phenomena which are distinct from ordinary, earthquake-like, fast rupture. These discoveries have influenced the way we think about frictional motion, yet the nature and properties of slow rupture are not completely understood. We show that slow rupture is an intrinsic and robust property of simple non-monotonic rate-and-state friction laws. It is associated with a new velocity scale cmin, determined by the friction law, below which steady state rupture cannot propagate. We further show that rupture can occur in a continuum of states, spanning a wide range of velocities from cmin to elastic wave-speeds, and predict different properties for slow rupture and ordinary fast rupture. Our results are qualitatively consistent with recent high-resolution laboratory experiments and may provide a theoretical framework for understanding slow rupture phenomena along frictional interfaces.

  18. Airborne and allergenic fungal spores of the Karachi environment and their correlation with meteorological factors.

    PubMed

    Hasnain, Syed M; Akhter, Tasneem; Waqar, Muhammad A

    2012-03-01

    Airborne fungal spores are well known to cause respiratory allergic diseases particularly bronchial asthma, allergic rhinitis, rhino-conjunctivitis and allergic broncho-pulmonary aspergillosis in both adults and children. In order to monitor and analyze airborne fungal flora of the Karachi environment, an aeromycological study was conducted using a Burkard 7-Day Recording Volumetric Spore Trap from January to December 2010. The data recorded from the Spore Trap was further analyzed for percent catch determination, total spores concentration, seasonal periodicities and diurnal variations. Cladosporium spp (44.8%), Alternaria spp. (15.5%), Periconia spp (6.1%), Curvularia spp (2.1%), Stemphylium spp (1.3%) and Aspergillus/Penicillium type (1%) emerged to be major components constituting more than 70% of the airborne fungal flora. Cladosporium, Curvularia and Stemphylium displayed a clear seasonal trend, while there were no clear seasonal trends for other fungal spore types. Diurnal variations were observed to be mainly having daytime maxima. Spearman Rank Correlation Coefficient analysis was conducted using various weather parameters. The various fungal types showed a negative correlation with heat index, dew point, wind velocity and wind chill. However, a positive correlation was found with humidity, rain and barometric pressure. In fact, Alternaria, Bipolaris and Periconia showed a negative correlation with temperature, while Cladosporium and Periconia showed a negative correlation with heat index, dew point, wind velocity and wind chill. The barometric pressure was positively correlated with Cladosporium. On the basis of these findings, it can be concluded that a number of fungal spores are present in the atmosphere of Karachi throughout the year, with certain atmospheric conditions influencing the release, dispersion, and sedimentation processes of some genera. It is expected that clinicians will use the identified fungal flora for diagnosis and treatment and

  19. Factors Influencing the Estimates of Correlation between Motor Unit Activities in Humans

    PubMed Central

    Negro, Francesco; Farina, Dario

    2012-01-01

    Background Alpha motoneurons receive common synaptic inputs from spinal and supraspinal pathways. As a result, a certain degree of correlation can be observed between motoneuron spike trains during voluntary contractions. This has been studied by using correlation measures in the time and frequency domains. These measures are interpreted as reflecting different types of connectivity in the spinal networks, although the relation between the degree of correlation of the output motoneuron spike trains and of their synaptic inputs is unclear. Methodology/Principal Findings In this study, we analyze theoretically this relation and we complete this analysis by simulations and experimental data on the abductor digiti minimi muscle. The results demonstrate that correlation measures between motoneuron output spike trains are inherently influenced by the discharge rate and that this influence cannot be compensated by normalization. Because of the influence of discharge rate, frequency domain measures of correlation (coherence) do not identify the full frequency content of the common input signal when computed from pairs of motoneurons. Rather, an increase in sampling rate is needed by using cumulative spike trains of several motoneurons. Moreover, the application of averaging filters to the spike trains influences the magnitude of the estimated correlation levels calculated in the time, but not in the frequency domain (coherence). Conclusions It is concluded that the analysis of coherence in different frequency bands between cumulative spike trains of a sufficient number of motoneurons provides information on the spectrum of the common synaptic input. Nonetheless, the absolute values of coherent peaks cannot be compared across conditions with different cumulative discharge rates. PMID:23049762

  20. Airborne and allergenic fungal spores of the Karachi environment and their correlation with meteorological factors.

    PubMed

    Hasnain, Syed M; Akhter, Tasneem; Waqar, Muhammad A

    2012-03-01

    Airborne fungal spores are well known to cause respiratory allergic diseases particularly bronchial asthma, allergic rhinitis, rhino-conjunctivitis and allergic broncho-pulmonary aspergillosis in both adults and children. In order to monitor and analyze airborne fungal flora of the Karachi environment, an aeromycological study was conducted using a Burkard 7-Day Recording Volumetric Spore Trap from January to December 2010. The data recorded from the Spore Trap was further analyzed for percent catch determination, total spores concentration, seasonal periodicities and diurnal variations. Cladosporium spp (44.8%), Alternaria spp. (15.5%), Periconia spp (6.1%), Curvularia spp (2.1%), Stemphylium spp (1.3%) and Aspergillus/Penicillium type (1%) emerged to be major components constituting more than 70% of the airborne fungal flora. Cladosporium, Curvularia and Stemphylium displayed a clear seasonal trend, while there were no clear seasonal trends for other fungal spore types. Diurnal variations were observed to be mainly having daytime maxima. Spearman Rank Correlation Coefficient analysis was conducted using various weather parameters. The various fungal types showed a negative correlation with heat index, dew point, wind velocity and wind chill. However, a positive correlation was found with humidity, rain and barometric pressure. In fact, Alternaria, Bipolaris and Periconia showed a negative correlation with temperature, while Cladosporium and Periconia showed a negative correlation with heat index, dew point, wind velocity and wind chill. The barometric pressure was positively correlated with Cladosporium. On the basis of these findings, it can be concluded that a number of fungal spores are present in the atmosphere of Karachi throughout the year, with certain atmospheric conditions influencing the release, dispersion, and sedimentation processes of some genera. It is expected that clinicians will use the identified fungal flora for diagnosis and treatment and

  1. Correlation analysis of lung cancer and urban spatial factor: based on survey in Shanghai

    PubMed Central

    Xu, Wangyue; Tang, Jian; Jiang, Xiji

    2016-01-01

    Background The density of particulate matter (PM) in mega-cities in China such as Beijing and Shanghai has exceeded basic standards for health in recent years. Human exposure to PMs has been identified as traceable and controllable factor among all complicated risk factors for lung cancer. While the improvement of air quality needs tremendous efforts and time, certain revision of PM’s density might happen associated with the adjustment of built environment. It is also proved that urban built environment is directly relevant to respiratory disease. Studies have respectively explored the indoor and outdoor factors on respiratory diseases. More comprehensive spatial factors need to be analyzed to understand the cumulative effect of built environment upon respiratory system. This interdisciplinary study examines the impact of both indoor (including age of housing, interval after decoration, indoor humidity etc.) and outdoor spatial factors (including density, parking, green spaces etc.) on lung cancer. Methods A survey of lung cancer patients and a control group has been conducted in 2014 and 2015. A total of 472 interviewees are randomly selected within a pool of local residents who have resided in Shanghai for more than 5 years. Data are collected including their socio-demographic factors, lifestyle factors, and external and internal residential area factors. Regression models are established based on collected data to analyze the associations between lung cancer and urban spatial factors. Results Regression models illustrate that lung cancer presents significantly associated with a number of spatial factors. Significant outdoor spatial factors include external traffic volume (P=0.003), main plant type (P=0.035 for trees) of internal green space, internal water body (P=0.027) and land use of surrounding blocks (P=0.005 for residential areas of 7-9 floors, P=0.000 for residential areas of 4-6 floors, P=0.006 for business/commercial areas over 10 floors, P=0.005 for

  2. [Correlation analysis of regional vegetation seasonal fluctuation and climate factors based on MODIS-EVI].

    PubMed

    Peng, Dai-liang; Huang, Jing-feng; Wang, Xiu-zhen

    2007-05-01

    Taking Zhejiang Province as study area, and based on the data of MODIS-EVI, daily mean air temperature and daily precipitation from 52 weather stations, and actual land use in 2001-2004, the time lag cross-correlation analysis was made to relate the seasonal fluctuations of enhanced vegetation index (EVI) of farmland, woodland and garden plot with air temperature and precipitation. The results indicated that in most areas of Zhejiang, EVI had no time lag to air temperature, but about one month lag to precipitation. The time that air temperature or precipitation significantly influenced the seasonal fluctuation of most areas EVI lasted about 50 days. The correlation coefficients of the EVI of farmland, woodland and garden plot with air temperature and precipitation differed with time lags. When the time lag was zero, the correlation coefficient decreased in the sequence of woodland > garden plot > farmland, and when the time lag was not zero, it changed in adverse. The EVI of these three land-use types all had stronger correlation with air temperature than with precipitation, indicating that air temperature had more influence on the seasonal fluctuation of EVI. PMID:17650845

  3. A Correlational Study of the Factors that Influence Lifelong Learning in the Army Civilian Corps

    ERIC Educational Resources Information Center

    Godinez, Eileen U.

    2010-01-01

    The purpose of this qualitative, correlational study was to determine if a relationship existed between employee value for learning, supervisor support for training, education, and leader development, perceived access to learning opportunities, demographic characteristics, and pursuit of lifelong learning. A researcher-generated survey was used to…

  4. Finding the "g"-Factor in Brain Structure Using the Method of Correlated Vectors

    ERIC Educational Resources Information Center

    Colom, Roberto; Jung, Rex E.; Haier, Richard J.

    2006-01-01

    It is unclear whether brain mechanisms underlying human intelligence are distributed throughout the brain or mainly concentrated in the frontal lobes. Data are inconsistent possibly due, at least in part, to the different ways the construct of intelligence is measured. Here we apply the method of correlated vectors to determine how the general…

  5. Factorization of event-plane correlations over transverse momentum in relativistic heavy ion collisions in a multiphase transport model

    NASA Astrophysics Data System (ADS)

    Xiao, Kai; Yi, Li; Liu, Feng; Wang, Fuqiang

    2016-08-01

    Momentum-space azimuthal harmonic event planes (EP) are constructed from final-state midrapidity particles binned in transverse momentum (pT) in √{sN N}=200 GeV Au+Au collisions in a multiphase transport (AMPT) model. The EP correlations between pT bins, corrected by EP resolutions, are smaller than unity. This indicates that the EP's decorrelate over pT in AMPT, qualitatively consistent with data and hydrodynamic calculations. It is further found that the EP correlations approximately factorize into single pT-bin EP correlations to a common plane. This common plane appears to be the momentum-space EP integrated over all pT, not the configuration-space participant plane (PP).

  6. Direct Measurements of Skin Friction

    NASA Technical Reports Server (NTRS)

    Dhawan, Satish

    1953-01-01

    A device has been developed to measure local skin friction on a flat plate by measuring the force exerted upon a very small movable part of the surface of the flat plate. These forces, which range from about 1 milligram to about 100 milligrams, are measured by means of a reactance device. The apparatus was first applied to measurements in the low-speed range, both for laminar and turbulent boundary layers. The measured skin-friction coefficients show excellent agreement with Blasius' and Von Karman's results. The device was then applied to high-speed subsonic flow and the turbulent-skin-friction coefficients were determined up to a Mach number of about 0.8. A few measurements in supersonic flow were also made. This paper describes the design and construction of the device and the results of the measurements.

  7. Advanced friction simulation of standardized friction tests: a numerical and experimental demonstrator

    NASA Astrophysics Data System (ADS)

    Hol, J.; Wiebenga, J. H.; Hörning, M.; Dietrich, F.; Dane, C.

    2016-08-01

    For the characterization of friction conditions under sheet metal forming process conditions, different friction test set-ups are being used in industry. However, different friction tests and test set-ups are known to result in scattering friction results. In this work, the TriboForm software is utilized to numerically model the frictional behavior. The simulated coefficients of friction are experimentally validated using friction results from a standardized strip drawing friction test set-up. The experimental and simulation results of the friction behavior show a good overall agreement. This demonstrates that the TriboForm software enables simulating friction conditions for varying tribology conditions, i.e. resulting in a generally applicable approach for friction characterization under industrial sheet metal forming process conditions.

  8. Pigment epithelium-derived factor expression is down-regulated in bladder tumors and correlates with vascular endothelial growth factor and matrix metalloproteinase-9.

    PubMed

    Feng, Chen-Chen; Ding, Qiang; Zhang, Yuan-Fang; Jiang, Hao-Wen; Wen, Hui; Wang, Pao-Hsun; Wu, Zhong

    2011-06-01

    Growth of solid tumor depends on angiogenesis, a process regulated by the balance of pro- and anti-angiogenic factors. We investigated the expression of anti-angiogenic factor pigment epithelium-derived factor (PEDF) and proangiogenic factors vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) with immunohistochemistry in 64 bladder tumor samples and 23 normal controls. Compared with normal urothelium, we identified decreased PEDF expression (P = 0.000) whereas increased expression of VEGF (P = 0.000) and MMP-9 (P = 0.000) in tumorous tissue as well as in papillary urothelial neoplasm of low malignant potential (PUNLMP) (P = 0.009 and P = 0.000 accordingly) but MMP-9 (P = 0.704). Decreased PEDF expression was revealed with higher tumor grade (P = 0.014) but stage (P = 0.687). There was no age or gender preference in PEDF, VEGF or MMP-9 expression. Negative correlation of expression in tumorous and cancerous tissue regarding PEDF and VEGF (P = 0.000, r = -0.56, and P = 0.000, r = -0.50, respectively), PEDF and MMP-9 (P = 0.002, r = -0.39, and P = 0.032, r = -0.30, respectively) was identified. There was a negative correlation of expression between PEDF and VEGF (P = 0.016, r = -0.677) and no correlation between PEDF and MMP-9 (P = 0.147, r = -0.45) in PUNLMP. Decreased PEDF and increased VEGF and MMP-9 expression may play considerable roles in differentiation and invasion of bladder tumor.

  9. Erythropoietin Levels Increase during Cerebral Malaria and Correlate with Heme, Interleukin-10 and Tumor Necrosis Factor-Alpha in India.

    PubMed

    Dalko, Esther; Tchitchek, Nicolas; Pays, Laurent; Herbert, Fabien; Cazenave, Pierre-André; Ravindran, Balachandran; Sharma, Shobhona; Nataf, Serge; Das, Bidyut; Pied, Sylviane

    2016-01-01

    Cerebral malaria (CM) caused by Plasmodium falciparum parasites often leads to the death of infected patients or to persisting neurological sequelae despite anti-parasitic treatments. Erythropoietin (EPO) was recently suggested as a potential adjunctive treatment for CM. However diverging results were obtained in patients from Sub-Saharan countries infected with P. falciparum. In this study, we measured EPO levels in the plasma of well-defined groups of P. falciparum-infected patients, from the state of Odisha in India, with mild malaria (MM), CM, or severe non-CM (NCM). EPO levels were then correlated with biological parameters, including parasite biomass, heme, tumor necrosis factor (TNF)-α, interleukin (IL)-10, interferon gamma-induced protein (IP)-10, and monocyte chemoattractant protein (MCP)-1 plasma concentrations by Spearman's rank and multiple correlation analyses. We found a significant increase in EPO levels with malaria severity degree, and more specifically during fatal CM. In addition, EPO levels were also found correlated positively with heme, TNF-α, IL-10, IP-10 and MCP-1 during CM. We also found a significant multivariate correlation between EPO, TNF-α, IL-10, IP-10 MCP-1 and heme, suggesting an association of EPO with a network of immune factors in CM patients. The contradictory levels of circulating EPO reported in CM patients in India when compared to Africa highlights the need for the optimization of adjunctive treatments according to the targeted population. PMID:27441662

  10. Erythropoietin Levels Increase during Cerebral Malaria and Correlate with Heme, Interleukin-10 and Tumor Necrosis Factor-Alpha in India

    PubMed Central

    Dalko, Esther; Tchitchek, Nicolas; Pays, Laurent; Herbert, Fabien; Cazenave, Pierre-André; Ravindran, Balachandran; Sharma, Shobhona; Nataf, Serge; Das, Bidyut; Pied, Sylviane

    2016-01-01

    Cerebral malaria (CM) caused by Plasmodium falciparum parasites often leads to the death of infected patients or to persisting neurological sequelae despite anti-parasitic treatments. Erythropoietin (EPO) was recently suggested as a potential adjunctive treatment for CM. However diverging results were obtained in patients from Sub-Saharan countries infected with P. falciparum. In this study, we measured EPO levels in the plasma of well-defined groups of P. falciparum-infected patients, from the state of Odisha in India, with mild malaria (MM), CM, or severe non-CM (NCM). EPO levels were then correlated with biological parameters, including parasite biomass, heme, tumor necrosis factor (TNF)-α, interleukin (IL)-10, interferon gamma-induced protein (IP)-10, and monocyte chemoattractant protein (MCP)-1 plasma concentrations by Spearman’s rank and multiple correlation analyses. We found a significant increase in EPO levels with malaria severity degree, and more specifically during fatal CM. In addition, EPO levels were also found correlated positively with heme, TNF-α, IL-10, IP-10 and MCP-1 during CM. We also found a significant multivariate correlation between EPO, TNF-α, IL-10, IP-10 MCP-1 and heme, suggesting an association of EPO with a network of immune factors in CM patients. The contradictory levels of circulating EPO reported in CM patients in India when compared to Africa highlights the need for the optimization of adjunctive treatments according to the targeted population. PMID:27441662

  11. Friction of total hip replacements with different bearings and loading conditions.

    PubMed

    Brockett, Claire; Williams, Sophie; Jin, Zhongmin; Isaac, Graham; Fisher, John

    2007-05-01

    Metal-on-ultra-high molecular weight polyethylene (UHMWPE) total hip replacements have been the most popular and clinically successful implants to date. However, it is well documented that the wear debris from these prostheses contributes to osteolysis and ultimate failure of the prosthesis, hence alternative materials have been sought. A range of 28 mm diameter bearings were investigated using a hip friction simulator, including conventional material combinations such as metal-on-UHWMPE, ceramic-on-ceramic (CoC), and metal-on-metal (MoM), as well as novel ceramic-on-metal (CoM) pairings. Studies were performed under different swing-phase load and lubricant conditions. The friction factors were lowest in the ceramic bearings, with the CoC bearing having the lowest friction factor in all conditions. CoM bearings also had low friction factors compared with MoM, and the trends were similar to CoC bearings for all test conditions. Increasing swing phase load was shown to cause an increase in friction factor in all tests. Increased serum concentration resulted in increased friction factor in all material combinations, except MoM, where increased serum concentration produced a significant reduction in friction factor.

  12. Generating correlation matrices with model error for simulation studies in factor analysis: a combination of the Tucker-Koopman-Linn model and Wijsman's algorithm.

    PubMed

    Hong, S

    1999-11-01

    Most simulation studies in factor analysis follow a process of constructing population correlation matrices from the common-factor model and generating sample correlation matrices from the population matrices. In the common-factor model, the population correlation matrix is perfectly fit by the model's containing common and unique factors. However, since no mathematical model accounts exactly for the real-world phenomena that it is intended to represent, the Tucker-Koopman-Linn model (1969) is more realistic for generating correlation matrices than the conventional common-factor model because the former incorporates model error. In this paper, a procedure for generating population and sample correlation matrices with model error by combining the Tucker-Koopman-Linn model and Wijsman's algorithm (1959) is presented. The SAS/IML program for generating correlation matrices is described, and an example is also provided.

  13. Thermal form factor approach to the ground-state correlation functions of the XXZ chain in the antiferromagnetic massive regime

    NASA Astrophysics Data System (ADS)

    Dugave, Maxime; Göhmann, Frank; Kozlowski, Karol K.; Suzuki, Junji

    2016-09-01

    We use the form factors of the quantum transfer matrix in the zero-temperature limit in order to study the two-point ground-state correlation functions of the XXZ chain in the antiferromagnetic massive regime. We obtain novel form factor series representations of the correlation functions which differ from those derived either from the q-vertex-operator approach or from the algebraic Bethe Ansatz approach to the usual transfer matrix. We advocate that our novel representations are numerically more efficient and allow for a straightforward calculation of the large-distance asymptotic behaviour of the two-point functions. Keeping control over the temperature corrections to the two-point functions we see that these are of order {T}∞ in the whole antiferromagnetic massive regime. The isotropic limit of our result yields a novel form factor series representation for the two-point correlation functions of the XXX chain at zero magnetic field. Dedicated to the memory of Petr Petrovich Kulish.

  14. Potentially harmful microalgal distribution in an area of the NW Adriatic coastline: Sampling procedure and correlations with environmental factors

    NASA Astrophysics Data System (ADS)

    Penna, Antonella; Ingarao, Cristina; Ercolessi, Manuela; Rocchi, Marco; Penna, Nunzio

    2006-10-01

    In this study, the trend of potentially Harmful Algal (HA) taxa (genera and species), was analysed along a coastal area of the NW Adriatic Sea on a monthly scale. The study included the use of a phytoplankton net for sample collection. The investigation was carried out in four sampling stations characterised by different ecological features. The composition of potentially HA phytoplankton taxa and their succession were related to the environmental factors. The potentially HA group abundance accounted for 8% of all the phytoplankton taxa considered. Multivariate analyses of environmental factors suggested that potentially HA taxa are sensitive to phosphate content: potential DSP-YTX (Diarrhetic Shellfish Poisoning-Yessotoxin) producers were positively correlated with P content ( p = 0.023), while potential ASP (Amnesic Shellfish Poisoning) producers were negatively correlated with P content ( p = 0.006). Phosphorus could be considered to be the limiting factor for phytoplankton taxa density in the NW Adriatic Sea. There was a highly positive correlation between the occurrences of potentially HA taxa and low values of salinity ( p = 0.001 for potential producers of ASP, p = 0.029 for potential DSP-YTX producers). The counting of potential HA dinoflagellates in net samples represented a more accurate estimation of potential HA abundances in the water column making it possible to concentrate a greater number of potential HA dinoflagellate cells by net sampling along the entire water column rather than by sampling only at the surface as in routine monitoring procedures.

  15. Frictional Properties of Single Crystalline and Quasicrystalline Surfaces

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew

    2000-03-01

    undergo plastic deformation when brought into contact and yet it is possible for these ultra-thin layers of adsorbed molecules to reduce friction and lubricate the interface. There are a number of measurements which show that friction and adhesion between crystalline materials can be anisotropic in the sense that they depend on the relative crystallographic orientations of the two surfaces. For the most part these have been made between surfaces in elastic contact and the understanding of the source of the anisotropy is based on the commensurability of the overlapping crystal surface lattices. In the case of metal surfaces which undergo plastic deformation when brought into contact it is not so clear that the commensurability of the surface lattices is the determining factor in friction anisotropy. Three sets of experiments have been performed in which pairs of Ni(100) surfaces have been brought onto contact and sheared with different orientations of the surface lattices. In the first experiment the Ni(100) surfaces were clean. In the second they were modified by adsorption of 1/2 monolayer of sulfur atoms ordered into a c(2x2) lattice. In this case the two surface lattices are rotated by 45o with respect to the original Ni(100) lattice. Finally, in the third set of experiments the surfaces were modified by adsorption of 2 monolayers of ethanol. Adsorbed ethanol forms an overlayer with no long range order. The basic point of these surface modifications is that they either rotate or eliminate the surface lattice periodicity while leaving the bulk lattices of the Ni(100) crystals in the same relative orientations. In all three cases friction anisotropy is observed as the two bulk crystal lattices are rotated with respect to one another. The interesting thing is that a minimum in the friction is observed when the two are rotated by 45^o with respect to one another. The fact that this is observed for all three modifications of the surface lattice suggests that it is the

  16. Brain Structure Correlates of Urban Upbringing, an Environmental Risk Factor for Schizophrenia

    PubMed Central

    Haddad, Leila; Schäfer, Axel; Streit, Fabian; Lederbogen, Florian; Grimm, Oliver; Wüst, Stefan; Deuschle, Michael; Kirsch, Peter; Tost, Heike; Meyer-Lindenberg, Andreas

    2015-01-01

    Urban upbringing has consistently been associated with schizophrenia, but which specific environmental exposures are reflected by this epidemiological observation and how they impact the developing brain to increase risk is largely unknown. On the basis of prior observations of abnormal functional brain processing of social stress in urban-born humans and preclinical evidence for enduring structural brain effects of early social stress, we investigated a possible morphological correlate of urban upbringing in human brain. In a sample of 110 healthy subjects studied with voxel-based morphometry, we detected a strong inverse correlation between early-life urbanicity and gray matter (GM) volume in the right dorsolateral prefrontal cortex (DLPFC, Brodmann area 9). Furthermore, we detected a negative correlation of early-life urbanicity and GM volumes in the perigenual anterior cingulate cortex (pACC) in men only. Previous work has linked volume reductions in the DLPFC to the exposure to psychosocial stress, including stressful experiences in early life. Besides, anatomical and functional alterations of this region have been identified in schizophrenic patients and high-risk populations. Previous data linking functional hyperactivation of pACC during social stress to urban upbringing suggest that the present interaction effect in brain structure might contribute to an increased risk for schizophrenia in males brought up in cities. Taken together, our results suggest a neural mechanism by which early-life urbanicity could impact brain architecture to increase the risk for schizophrenia. PMID:24894884

  17. Tribological behavior of a friction couple functioning with selective mass transfer

    NASA Astrophysics Data System (ADS)

    Ilie, Filip

    2016-06-01

    Experimental researches on different lubricated friction couples, have confirmed that it is useful to investigate thermodynamic processes which are unstable in lubricant and on the friction couples surfaces in the first stage of the friction process. This presupposes that, in operating conditions, physical-chemical processes which are favourable to friction, such as: polymerization, formation of colloids, formation of other active substances at the contact surfaces and of other compounds with low resistance to shear take place. Friction in such conditions takes place with selective mass transfer, and it is used there where the friction of the mixed and adherence layers is not safe enough, or the durability of the friction couples is not assured. The selective mass transfer allows the transfer of some elements of the materials in contact from one surface to the other, covering them with a thin, superficial layer, with superior properties at minimal friction and wear. The aim of this paper is to analyse the physical-chemical factors and the proper processes for achieving the selective mass transfer for the couple steel/bronze, which in optimal conditions, forms a thin layer of copper on the contact surfaces areas. Also, it presents some studies and researches concerning the tribological behaviour of the surfaces of a friction couple with linear contact (roll/roll) which operates with selective mass transfer, tested on Amsler tribometer.

  18. Finite Element Analysis of the Amontons-Coulomb's Model using Local and Global Friction Tests

    SciTech Connect

    Oliveira, M. C.; Menezes, L. F.; Ramalho, A.; Alves, J. L.

    2011-05-04

    In spite of the abundant number of experimental friction tests that have been reported, the contact with friction modeling persists to be one of the factors that determine the effectiveness of sheet metal forming simulation. This difficulty can be understood due to the nature of the friction phenomena, which comprises the interaction of different factors connected to both sheet and tools' surfaces. Although in finite element numerical simulations friction models are commonly applied at the local level, they normally rely on parameters identified based on global experimental tests results. The aim of this study is to analyze the applicability of the Amontons-Coulomb's friction coefficient identified using complementary tests: (i) load-scanning, at the local level and (ii) draw-bead, at the global level; to the numerical simulation of sheet metal forming processes.

  19. Dynamical Behaviors between the PM10 and the meteorological factor using the detrended cross-correlation analysis method

    NASA Astrophysics Data System (ADS)

    Kim, Kyungsik; Lee, Dong-In

    2013-04-01

    There is considerable interest in cross-correlations in collective modes of real data from atmospheric geophysics, seismology, finance, physiology, genomics, and nanodevices. If two systems interact mutually, that interaction gives rise to collective modes. This phenomenon is able to be analyzed using the cross-correlation of traditional methods, random matrix theory, and the detrended cross-correlation analysis method. The detrended cross-correlation analysis method was used in the past to analyze several models such as autoregressive fractionally integrated moving average processes, stock prices and their trading volumes, and taxi accidents. Particulate matter is composed of the organic and inorganic mixtures such as the natural sea salt, soil particle, vehicles exhaust, construction dust, and soot. The PM10 is known as the particle with the aerodynamic diameter (less than 10 microns) that is able to enter the human respiratory system. The PM10 concentration has an effect on the climate change by causing an unbalance of the global radiative equilibrium through the direct effect that blocks the stoma of plants and cuts off the solar radiation, different from the indirect effect that changes the optical property of clouds, cloudiness, and lifetime of clouds. Various factors contribute to the degree of the PM10 concentration. Notable among these are the land-use types, surface vegetation coverage, as well as meteorological factors. In this study, we analyze and simulate cross-correlations in time scales between the PM10 concentration and the meteorological factor (among temperature, wind speed and humidity) using the detrended cross-correlation analysis method through the removal of specific trends at eight cities in the Korean peninsula. We divide time series data into Asian dust events and non-Asian dust events to analyze the change of meteorological factors on the fluctuation of PM10 the concentration during Asian dust events. In particular, our result is

  20. Attitudinal barriers to participation in oncology clinical trials: factor analysis and correlates of barriers

    PubMed Central

    MANNE, S.; KASHY, D.; ALBRECHT, T.; WONG, Y.-N.; FLAMM, A. LEDERMAN; BENSON, A. B.; MILLER, S.M.; FLEISHER, LINDA; BUZAGLO, J.; ROACH, N.; KATZ, M.; ROSS, E.; COLLINS, M.; POOLE, D.; RAIVITCH, S.; MILLER, D.M.; KINZY, T.G.; LIU, T.; MEROPOL, N.J.

    2015-01-01

    Patient participation in cancer clinical trials is low. Little is known about attitudinal barriers to participation, particularly among patients who may be offered a trial during an imminent initial oncology consult. The aims of the present study were to confirm the presence of proposed subscales of a recently developed cancer clinical trial attitudinal barriers measure, describe the most common cancer clinical trials attitudinal barriers, and evaluate socio-demographic, medical and financial factors associated with attitudinal barriers. A total of 1256 patients completed a survey assessing demographic factors, perceived financial burden, prior trial participation and attitudinal barriers to clinical trials participation. Results of a factor analysis did not confirm the presence of the proposed four attitudinal barriers subscale/factors. Rather, a single factor represented the best fit to the data. The most highly-rated barriers were fear of side-effects, worry about health insurance and efficacy concerns. Results suggested that less educated patients, patients with non-metastatic disease, patients with no previous oncology clinical trial participation, and patients reporting greater perceived financial burden from cancer care were associated with higher barriers. These patients may need extra attention in terms of decisional support. Overall, patients with fewer personal resources (education, financial issues) report more attitudinal barriers and should be targeted for additional decisional support. PMID:24467411

  1. Correlation of vascular endothelial growth factor expression with fibroblast growth factor-8 expression and clinico-pathologic parameters in human prostate cancer

    PubMed Central

    West, A F; O'Donnell, M; Charlton, R G; Neal, D E; Leung, H Y

    2001-01-01

    Vascular endothelial growth factor (VEGF) mediates neo-angiogenesis during tumour progression and is known to cooperate with the fibroblast growth factor (FGF) system to facilitate angiogenesis in a synergistic manner. In view of this, we have investigated VEGF expression in 67 cases of prostate cancer previously characterized for fibroblast growth factor-8 (FGF-8) expression. Cytoplasmic VEGF staining was detected in malignant cells in 45 out of 67 cases. Cytoplasmic staining was found in adjacent stromal cells in 32 cases, being particularly strong around nests of invasive tumour. Positive VEGF immunoreactivity in benign glands was restricted to basal epithelium. A significant association was observed between tumour VEGF and FGF-8 expression (P = 0.004). We identified increased VEGF immunoreactivity in both malignant epithelium and adjacent stroma and both were found to be significantly associated with high tumour stage (P = 0.0047 and P = 0.0002, respectively). VEGF expression also correlated with increased serum PSA levels (P = 0.01). Among positively stained tumours, VEGF expression showed a significant association with Gleason score (P = 0.04). Cases showing positive VEGF immunoreactivity in the stroma had a significantly reduced survival rate compared to those with negative staining (P = 0.037). Cases with tumours expressing both FGF-8 in the malignant epithelium and VEGF in the adjacent stroma had a significantly worse survival rate than those with tumours negative for both, or only expressing one of the two growth factors (P = 0.029). Cox multivariate regression analysis of survival demonstrated that stromal VEGF and tumour stage were the most significant independent predictors of survival. In conclusion, we report for the first time a correlation of both tumour and stromal VEGF expression in prostate cancer with clinical parameters as well as its correlation to FGF-8 expression. © 2001 Cancer Research Campaign http://www.bjcancer.com PMID:11506499

  2. Atomistic simulation of the load dependence of nanoscale friction on suspended and supported graphene.

    PubMed

    Ye, Zhijiang; Martini, Ashlie

    2014-12-16

    Suspended graphene exhibits distinct behavior in which nanoscale friction first increases and then decreases with load; this is in contrast to the monotonic increase of friction with load exhibited by most materials, including graphene supported by a substrate. In this work, these friction trends are reproduced for the first time using molecular dynamics simulations of a nanoscale probe scanning on suspended and supported graphene. The atomic-scale detail available in the simulations is used to correlate friction trends to the presence and size of a wrinkle on the graphene surface in front of the probe. The simulations also provide information about how frictional load dependence is affected by the size of the graphene, the size of the probe, and the strength of the interaction between graphene and probe.

  3. The friction behavior of semiconductors Si and GaAs in contact with pure metals

    NASA Technical Reports Server (NTRS)

    Mishina, H.

    1984-01-01

    The friction behavior of the semiconductors silicon and gallium arsenide in contact with pure metals was studied. Five transition and two nontransition metals, titanium, tantalum, nickel, palladium, platinum, copper, and silver, slid on a single crystal silicon (111) surface. Four metals, indium, nickel, copper and silver, slid on a single crystal gallium arsenide (100) surface. Experiments were conducted in room air and in a vacuum of 10 to the minus 7th power N/sq cm (10 to the minus 9th power torr). The results indicate that the sliding of silicon on the transition metals exhibits relatively higher friction than for the nontransition metals in contact with silicon. There is a clear correlation between friction and Schottky barrier height formed at the metal silicon interface for the transition metals. Transition metals with a higher barrier height on silicon had a lower friction. The same effect of barrier height was found for the friction of gallium arsenide in contact with metals.

  4. Exploring the role of internal friction in the dynamics of unfolded proteins using simple polymer models.

    PubMed

    Cheng, Ryan R; Hawk, Alexander T; Makarov, Dmitrii E

    2013-02-21

    Recent experiments showed that the reconfiguration dynamics of unfolded proteins are often adequately described by simple polymer models. In particular, the Rouse model with internal friction (RIF) captures internal friction effects as observed in single-molecule fluorescence correlation spectroscopy (FCS) studies of a number of proteins. Here we use RIF, and its non-free draining analog, Zimm model with internal friction, to explore the effect of internal friction on the rate with which intramolecular contacts can be formed within the unfolded chain. Unlike the reconfiguration times inferred from FCS experiments, which depend linearly on the solvent viscosity, the first passage times to form intramolecular contacts are shown to display a more complex viscosity dependence. We further describe scaling relationships obeyed by contact formation times in the limits of high and low internal friction. Our findings provide experimentally testable predictions that can serve as a framework for the analysis of future studies of contact formation in proteins.

  5. Electronic friction at the atomic scale: Conduction, electrostatic and magnetic effects

    NASA Astrophysics Data System (ADS)

    Krim, Jacqueline; Altfeder, Igor

    2013-03-01

    We have performed a magnetic probe microscopy study of levitation and atomic-scale friction for Fe on YBCO (Tc = 92.5K) in the temperature range 65 - 293 K, to explore electronic contributions to friction at the atomic scale. The samples were prepared with oxygen-depleted surfaces, with thin semiconducting surface layers present atop the bulk. Below Tc, the friction coefficient was observed to be constant at 0.19 and exhibited no correlation with the strength of superconducting levitation forces observed below Tc. The friction coefficient exhibited a change in slope within experimental error of Tc that increased progressively above Tc and reached 0.33 by room temperature. The results were analyzed within the context of underlying atomic-scale electronic and phononic mechanisms that give rise to friction we conclude that contact electrification and static electricity play a significant role above Tc. Supported by NSF and AFOSR.

  6. A correlational and factor analysis of anticipatory and consummatory measures of sexual behavior in the male rat.

    PubMed

    Pfaus, J G; Mendelson, S D; Phillips, A G

    1990-01-01

    This study investigated the relationship among measures of anticipatory and consummatory sexual behavior displayed by male rats in the bilevel chambers designed by Mendelson and Gorzalka (1987). Normative data from a standard test of sexual behavior were gathered from 80 intact, sexually experienced male Long-Evans rats and subjected to multiple correlational and factor analyses. The correlational analysis confirmed that several consummatory measures of copulation were related significantly, whereas the anticipatory measure, level changing, was statistically independent of consummatory measures. Factor analysis using orthogonal rotations revealed five factors that accounted for 95% of the intersubject variance for all measures: Copulatory Rate, Initiation, Hit Rate, Mount Count, and Anticipation. These results indicate that at least five conceptual mechanisms are required in any theoretical description of male sexual behavior in the bilevel chamber. In particular, the extraction of separate anticipation and initiation factors indicates that these aspects of male sexual behavior are distinct. The use of bilevel chambers thus may facilitate the identification of potential neurochemical or endocrine mechanisms associated with different aspects of male sexual motivation. In addition, several statistical techniques are discussed with the aim of reducing the elevated experiment-wise error that can occur when related measures of sexual behavior are analyzed independently. PMID:2101959

  7. Evaluation of MAGE-1 Cancer-Testis Antigen Expression in Invasive Breast Cancer and its Correlation with Prognostic Factors

    PubMed Central

    Rastgoosalami, Mojtaba; Memar, Bahram; Aledavood, Seyed Amir; Fanipakdel, Azar

    2016-01-01

    Background Aberrant expression of cancer-testis antigens (CTA) in breast carcinoma tissue, and its natural expression in the testis, the tissue away from the immune system, makes them good candidates for cancer immunotherapy and vaccines designing. Objectives The aim of this study was to assess the expression of a CTA (MAGE-1) in invasive breast cancer and its correlation with prognostic factors. Methods Paraffin blocks of breast cancer tissues from 113 patients operated in 2011 - 2013 were stained for MAGE-1expression by immunohistochemistry (IHC). The associations of MAGE-1 expression with known prognostic factors were assessed by statistical analysis using SPSS 16. Results MAGE-1 expression was found in cancer cell cytoplasms of 30.1% of patients, with different degrees of intensity, (23.9% moderate and 6.2% strong). Nuclear staining turned positive in 31.8%, stratified from moderate in 26.5%to to strong in 5.3%. There was a significant association between the number of lymph nodes involved and both nuclear (P = 0.042) and cytoplasmic (P = 0.003) MAGE-1 expression. There was also a significant correlation between the nuclear expression of MAGE-1 and tumor size (P = 0.018). Cytoplasmic expression of MAGE-1 increased with increasing pathologic grade of tumors although the association was not statistically significant (P = 0.119). Conclusions CTA MAGE-1 has significant association with some prognostic factors in breast cancer and may have the role of a prognostic factor. PMID:27761208

  8. IFCI 7.0 Models and Correlations

    SciTech Connect

    Reed, A.W.; Schmidt, R.C.; Young, M.F.

    1999-05-01

    The Integrated Fuel-Coolant Interaction Code (IFCI) is a best-estimate computer program for analysis of phenomena related to mixing of molten nuclear reactor core material with reactor coolant (water). The stand-alone version of the code, IFCI 7.0, has been designed for analysis of small- and intermediate-scale experiments in order to gain insight into the physics (including scaling effects) of molten fuel-coolant interactions. The code's methods, models, and correlations are being assessed. This report describes the flow regime, friction factor, and heat-transfer models used in the current version of IFCI (IFCI 7.0).

  9. Reducing Sliding Friction with Liquid-Impregnated Surfaces

    NASA Astrophysics Data System (ADS)

    Habibi, Mohammad; Collier, C. Patrick; Boreyko, Jonathan; Nature Inspired Fluids; Interfaces Team; CenterNanophase Materials Sciences Team

    2015-11-01

    Liquid-impregnated surfaces are fabricated by infusing a lubricating liquid into the micro/nano roughness of a textured substrate, such that the surface is slippery for any deposited liquid immiscible with the lubricant. To date, liquid-impregnated surfaces have almost exclusively focused on repelling liquids by minimizing the contact angle hysteresis. Here, we demonstrate that liquid-impregnated surfaces are also capable of reducing sliding friction for solid objects. Ordered arrays of silicon micropillars were infused with lubricating liquids varying in viscosity by two orders of magnitude. Five test surfaces were used: two different micropillared surfaces with and without liquid infusion and a smooth, dry control surface. The static and kinetic coefficients of friction were measured using a polished aluminum cube as the sliding object. Compared to the smooth control surface, the sliding friction was reduced by at least a factor of two on the liquid-impregnated surfaces.

  10. Low-Friction Joint for Robot Fingers

    NASA Technical Reports Server (NTRS)

    Ruoff, C. F.

    1985-01-01

    Mechanical linkage allows adjacent parts to move relative to each other with low friction and with no chatter, slipping, or backlash. Low-friction joint of two surfaces in rolling contact, held in alinement by taut flexible bands. No sliding friction or "stick-slip" motion: Only rolling-contact and bending friction within bands. Proposed linkage intended for finger joints in mechanical hands for robots and manipulators.

  11. Showing Area Matters: A Work of Friction

    ERIC Educational Resources Information Center

    Van Domelen, David

    2010-01-01

    Typically, we teach the simplified friction equation of the form F[subscript s] = [mu][subscript s]N for static friction, where F[subscript s] is the maximum static friction, [mu][subscript s] is the coefficient of static friction, and "N" is the normal force pressing the surfaces together. However, this is a bit too simplified, and doesn't work…

  12. Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.

    SciTech Connect

    Dechant, Lawrence; Smith, Justin

    2016-01-01

    Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by

  13. Clinical Correlates of Hachinski Ischemic Score and Vascular Factors in Cognitive Function of Elderly

    PubMed Central

    Kim, Youn Ho

    2014-01-01

    The aim of this study is to investigate the relationship between Hachinski ischemic score (HIS) and vascular factors as well as between HIS and the cognitive function in elderly community. Demographic characteristics, such as sex, age, education, history of drinking and smoking, family history of dementia and stroke, diabetes mellitus, hypertension, hyperlipidemia, cardiovascular disease, stroke, and dementia, were surveyed. Neurological examination was administered to every subject and HIS was checked by a neurologist. From a total of 392 participants aged 65 and over in a rural community, 348 completed the survey and were finally enrolled. Among the vascular factors, history of hypertension (P = 0.008), history of stroke (P < 0.001), family history of dementia (P = 0.01), and history of cardiac diseases (P = 0.012) showed a significant relationship with HIS. In the cognitive function tests, both Korean version of the Mini-Mental State Examination and the Clinical Dementia Rating (Global and Sum of Boxes) had a significant relationship with HIS. Our study suggested HIS may have an association with some vascular factors and cognitive scales in community dwelling elderly. In this study, the HIS seemed to contribute to the evaluation of the quantity of vascular factors and to the prediction of status of cognitive function. PMID:25247189

  14. Prevalence of Internet Addiction and Correlations with Family Factors among South Korean Adolescents

    ERIC Educational Resources Information Center

    Park, Soo Kyung; Kim, Jae Yop; Cho, Choon Bum

    2008-01-01

    This study investigated the prevalence of Internet addiction among South Korean adolescents and explored family factors associated with such addiction. The study participants were middle and high school students residing in Seoul. One-tenth (10.7%) of the 903 adolescents surveyed scored at least 70 on the Internet Addiction Scale. These youths…

  15. Factor Structure and Correlates of the Dissociative Experiences Scale in a Large Offender Sample

    ERIC Educational Resources Information Center

    Ruiz, Mark A.; Poythress, Norman G.; Lilienfeld, Scott O.; Douglas, Kevin S.

    2008-01-01

    The authors examined the psychometric properties, factor structure, and construct validity of the Dissociative Experiences Scale (DES) in a large offender sample (N = 1,515). Although the DES is widely used with community and clinical samples, minimal work has examined offender samples. Participants were administered self-report and interview…

  16. Teacher-Related Factors as Correlates of Pupils' Achievement in Social Studies in Southwestern Nigeria

    ERIC Educational Resources Information Center

    Adeyemi, Babatunde

    2010-01-01

    Introduction: The teacher plays a significant role in the intellectual development of the pupils, using various assessment and teaching styles to improve pupils' performance in school subjects. The study therefore investigated the effect of some teacher related factors: teacher level of awareness of assessment style, teacher assessment style,…

  17. Turbine blade friction damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1985-01-01

    A lumped parameter method, implemented on a VAX 11/780 computer shows that the primary parameters affecting the performance of the friction damper of the first stage turbine of the SSME high pressure fuel pump are: the damper-blade coefficient of friction; the normal force applied to the friction interface; the amplitude of the periodic forcing function; the relative phase angle of the forcing functions for adjacent blades bridged by a damper (effectively, the engine order of the forcing function); and the amount of hysteretic damping that acts to limit the vibration amplitude of the blade in its resonance modes. The low order flexural resonance vibration modes of HPFTP blades without dampers, with production dampers, and with two types of lightweight experimental dampers were evaluated in high speed spin pit tests. Results agree with those of the analytical study in that blades fitted with production friction dampers experienced the airfoil-alone flexural resonance mode, while those without dampers or with lighter weight dampers did not. No blades fitted with dampers experienced the whole blade flexural resonance mode during high speed tests, while those without dampers did.

  18. Deformation During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    White, Henry J.

    2002-01-01

    Friction Stir Welding (FSW) is a solid state welding process that exhibits characteristics similar to traditional metal cutting processes. The plastic deformation that occurs during friction stir welding is due to the superposition of three flow fields: a primary rotation of a radially symmetric solid plug of metal surrounding the pin tool, a secondary uniform translation, and a tertiary ring vortex flow (smoke rings) surrounding the tool. If the metal sticks to the tool, the plug surface extends down into the metal from the outer edge of the tool shoulder, decreases in diameter like a funnel, and closes up beneath the pin. Since its invention, ten years have gone by and still very little is known about the physics of the friction stir welding process. In this experiment, an H13 steel weld tool (shoulder diameter, 0.797 in; pin diameter, 0.312 in; and pin length, 0.2506 in) was used to weld three 0.255 in thick plates. The deformation behavior during friction stir welding was investigated by metallographically preparing a plan view sections of the weldment and taking Vickers hardness test in the key-hole region.

  19. Dynamical friction in cuspy galaxies

    SciTech Connect

    Arca-Sedda, M.; Capuzzo-Dolcetta, R.

    2014-04-10

    In this paper, we treat the problem of the dynamical friction decay of a massive object moving in an elliptical galaxy with a cuspidal inner distribution of the mass density. We present results obtained by both self-consistent, direct summation, N-body simulations, as well as by a new semi-analytical treatment of dynamical friction valid in such cuspy central regions of galaxies. A comparison of these results indicates that the proposed semi-analytical approximation is the only reliable one in cuspy galactic central regions, where the standard Chandrasekhar's local approximation fails and also gives estimates of decay times that are correct at 1% with respect to those given by N-body simulations. The efficiency of dynamical friction in cuspy galaxies is found definitively higher than in core galaxies, especially on more radially elongated satellite orbits. As another relevant result, we find a proportionality of the dynamical friction decay time to the –0.67 power of the satellite mass, M, shallower than the standardly adopted M {sup –1} dependence.

  20. Improved Coulomb-Friction Damper

    NASA Technical Reports Server (NTRS)

    Campbell, G. E.

    1985-01-01

    Equal damping provided on forward and reverse strokes. Improved damper has springs and wedge rings symmetrically placed on both ends of piston wedge, so friction force same in both directions of travel. Unlike conventional automotive shock absorbers, they resemble on outside, both versions require no viscous liquid and operate over wide temperature range.

  1. Autosomal Factors with Correlated Effects on the Activities of the Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenases in DROSOPHILA MELANOGASTER

    PubMed Central

    Laurie-Ahlberg, C. C.; Williamson, J. H.; Cochrane, B. J.; Wilton, A. N.; Chasalow, F. I.

    1981-01-01

    Isogenic lines, in which chromosomes sampled from natural populations of D. melanogaster are substituted into a common genetic background, were used to detect and partially characterize autosomal factors that affect the activities of the two pentose phosphate pathway enzymes, glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). The chromosome 3 effects on G6PD and 6PGD are clearly correlated; the chromosome 2 effects, which are not so great, also appear to be correlated, but the evidence in this case is not so strong. Examination of activity variation of ten other enzymes revealed that G6PD and 6PGD are not the only pair of enzymes showing a high positive correlation, but it is among the highest in both sets of lines. In addition, there was some evidence that the factor(s) affecting G6PD and 6PGD may also affect two other metabolically related enzymes, transaldolase and phosphoglucose isomerase.—Rocket immunoelectrophoresis was used to estimate specific CRM levels for three of the enzymes studied: G6PD, 6PGD and ME. This experiment shows that a large part of the activity variation is accounted for by variation in CRM level (especially for chromosome 3 lines), but there remains a significant fraction of the genetic component of activity variation that is not explained by CRM level.—These results suggest that the autosomal factors are modifiers involved in regulation of the expression of the X-linked structural genes for G6PD and 6PGD, but a role in determining part of the enzymes' primary structure cannot be excluded with the present evidence. PMID:6804300

  2. Spatial Correlations of Malaria Incidence Hotspots with Environmental Factors in Assam, North East India

    NASA Astrophysics Data System (ADS)

    Handique, Bijoy K.; Khan, Siraj A.; Dutta, Prafulla; Nath, Manash J.; Qadir, Abdul; Raju, P. L. N.

    2016-06-01

    Malaria is endemic and a major public health problem in north east (NE) region of India and contributes about 8-12 % of India's malaria positives cases. Historical morbidity pattern of malaria in terms of API (Annual Parasite Incidence) in the state of Assam has been used for delineating the malaria incidence hotspots at health sub centre (HSC) level. Strong spatial autocorrelation (p < 0.01) among the HSCs have been observed in terms of API (Annual Parasite Incidence). Malaria incidence hot spots in the state could be identified based on General G statistics and tested for statistical significance. Spatial correlation of malaria incidence hotspots with physiographic and climatic parameters across 6 agro-climatic zones of the state reveals the types of land cover pattern and the range of elevation contributing to the malaria outbreaks. Analysis shows that villages under malaria hotspots are having more agricultural land, evergreen/semi-evergreen forests with abundant waterbodies. Statistical and spatial analyses of malaria incidence showed a significant positive correlation with malaria incidence hotspots and the elevation (p < 0.05) with villages under malaria hotspots are having average elevation ranging between 17 to 240 MSL. This conforms to the characteristics of two dominant mosquito species in the state Anopheles minimus and An. baimai that prefers the habitat of slow flowing streams in the foot hills and in forest ecosystems respectively.

  3. Neurophysiological correlates of embodiment and motivational factors during the perception of virtual architectural environments.

    PubMed

    Vecchiato, Giovanni; Jelic, Andrea; Tieri, Gaetano; Maglione, Anton Giulio; De Matteis, Federico; Babiloni, Fabio

    2015-09-01

    The recent efforts aimed at providing neuroscientific explanations of how people perceive and experience architectural environments have largely justified the initial belief in the value of neuroscience for architecture. However, a systematic development of a coherent theoretical and experimental framework is missing. To investigate the neurophysiological reactions related to the appreciation of ambiances, we recorded the electroencephalographic (EEG) signals in an immersive virtual reality during the appreciation of interior designs. Such data have been analyzed according to the working hypothesis that appreciated environments involve embodied simulation mechanisms and circuits mediating approaching stimuli. EEG recordings of 12 healthy subjects have been performed during the perception of three-dimensional interiors that have been simulated in a CAVE system and judged according to dimensions of familiarity, novelty, comfort, pleasantness, arousal and presence. A correlation analysis on personal judgments returned that scores of novelty, pleasantness and comfort are positively correlated, while familiarity and novelty are in negative way. Statistical spectral maps reveal that pleasant, novel and comfortable interiors produce a de-synchronization of the mu rhythm over left sensorimotor areas. Interiors judged more pleasant and less familiar generate an activation of left frontal areas (theta and alpha bands), along an involvement of areas devoted to spatial navigation. An increase in comfort returns an enhancement of the theta frontal midline activity. Cerebral activations underlying appreciation of architecture could involve different mechanisms regulating corporeal, emotional and cognitive reactions. Therefore, it might be suggested that people's experience of architectural environments is intrinsically structured by the possibilities for action.

  4. Correlation between ambulatory function and clinical factors in hemiplegic patients with intact single lateral corticospinal tract

    PubMed Central

    Hong, Ji Seong; Kim, Jong Moon; Kim, Hyoung Seop

    2016-01-01

    Abstract To define the relationship between the complete destruction of 1 lateral corticospinal tract (CST), as demonstrated by diffusion tensor imaging (DTI) tractography, and ambulatory function 6 months following stroke. Twenty-six adults (17 male, 9 female) with poststroke hemiplegia who were transferred to the physical medicine and rehabilitation department. Participants underwent DTI tractography, which showed that 1 lateral CST had been clearly destroyed. Functional ambulation classification (FAC) scores at admission, discharge, and 6 months after discharge were used to evaluate the patients’ ability to walk. The National Institutes of Health Stroke Scale (NIHSS) and the Korean version of the modified Barthel index (K-MBI) at admission, discharge, and 6 months after discharge were used to evaluate the degree of functional recovery. Of the 26 patients, 18 were nonambulatory (FAC level 1–3), and 8 were able to walk without support (FAC level 4–6). The type of stroke (infarction or hemorrhage), site of the lesion, spasticity of lower extremities, cranioplasty, and the time taken from onset to MRI were not statistically significantly correlated with the ability to walk. However, statistically significant correlations were found in relation to age, K-MBI scores, and initial NIHSS scores. Despite the complete damage to the lesion site and the preservation of 1 unilateral CST, as shown by DTI, good outcomes can be predicted on the basis of younger age, low NIHSS scores, and high MBI scores at onset. PMID:27495041

  5. Friction of ice on ice

    NASA Astrophysics Data System (ADS)

    Schulson, Erland M.; Fortt, Andrew L.

    2012-12-01

    New measurements have been made of the friction coefficient of freshwater polycrystalline ice sliding slowly (5 × 10-8 to 1 × 10-3 m s-1) upon itself at temperatures from 98 to 263 K under low normal stresses (≤98 kPa). Sliding obeys Coulomb's law: the shear stress is directly proportional to the normal stress across the interface, while cohesion offers little contribution to frictional resistance. The coefficient of kinetic friction of smooth surfaces varies from μk = 0.15 to 0.76 and, at elevated temperatures (≥223 K), exhibits both velocity strengthening at lower velocities (<10-5 to 10-4 m s-1) and velocity weakening at higher velocities. Strengthening and weakening are attributed to creep deformation of asperities and localized melting, respectively. At intermediate temperatures of 173 and 133 K, the kinetic coefficient appears to not exhibit significant dependence upon velocity. However, at the low temperature of 98 K the coefficient of kinetic friction exhibits moderate velocity strengthening at both the lowest and the highest velocities but velocity independence over the range of intermediate velocities. No effect was detected of either grain size or texture. Over the range of roughness 0.4 × 10-6 m ≤ Ra ≤ 12 × 10-6 m, a moderate effect was detected, where μk ∝ Ra0.08. Slide-hold-slide experiments revealed that the coefficient of static friction increases by an amount that scales logarithmically with holding time. Implications of the results are discussed in relation to shearing across "tiger stripe" faults within the icy crust of Saturn's Enceladus, sliding of the arctic sea ice cover and brittle compressive failure of cold ice.

  6. Translationally invariant calculations of form factors, nucleon densities and momentum distributions for finite nuclei with short-range correlations included

    NASA Astrophysics Data System (ADS)

    Shebeko, A. V.; Grigorov, P. A.; Iurasov, V. S.

    2012-11-01

    Relying upon our previous treatment of the density matrices for nuclei (in general, nonrelativistic self-bound finite systems) we are studying a combined effect of center-of-mass motion and short-range nucleon-nucleon correlations on the nucleon density and momentum distributions in light nuclei (4He and 16O). Their intrinsic ground-state wave functions are constructed in the so-called fixed center-of-mass approximation, starting with mean-field Slater determinants modified by some correlator ( e.g., after Jastrow or Villars). We develop the formalism based upon the Cartesian or boson representation, in which the coordinate and momentum operators are linear combinations of the creation and annihilation operators for oscillatory quanta in the three different space directions, and get the own "Tassie-Barker" factors for each distribution and point out other model-independent results. After this separation of the center-of-mass motion effects we propose additional analytic means in order to simplify the subsequent calculations ( e.g., within the Jastrow approach or the unitary correlation operator method). The charge form factors, densities and momentum distributions of 4He and 16O evaluated by using the well-known cluster expansions are compared with data, our exact (numerical) results and microscopic calculations.

  7. Demonstration of the preclinical correlate of protection for Staphylococcus aureus clumping factor A in a murine model of infection.

    PubMed

    Scully, Ingrid L; Timofeyeva, Yekaterina; Keeney, David; Matsuka, Yury V; Severina, Elena; McNeil, Lisa K; Nanra, Jasdeep; Hu, George; Liberator, Paul A; Jansen, Kathrin U; Anderson, Annaliesa S

    2015-10-01

    The Staphylococcus aureus virulence factor clumping factor A (ClfA) is a component of an investigational S. aureus prophylactic vaccine. ClfA enables S. aureus to bind to fibrinogen and platelets during the initial stages of invasive disease. Here we demonstrate that ectopic expression of ClfA is sufficient to render nonpathogenic Lactococcus lactis lethal in a murine model of systemic infection. In contrast, L. lactis expressing ClfAY338A, which cannot bind fibrinogen, did not cause death in the mice. Pathogenicity was also prevented by immunization with ClfA. This model was then used to define a preclinical correlate of protection by measuring functional antibody in a S. aureus fibrinogen binding inhibition assay (FBI) and correlating that titer with protective outcomes. Although many humans have pre-existing antibodies that bind to ClfA, only sera with a threshold functional titer in the FBI were protective in this preclinical model. This confirms that fibrinogen binding is critical for ClfA-mediated pathogenesis and demonstrates that functional antibodies against ClfA are sufficient to protect against ClfA-mediated pathogenesis in vivo, enabling the definition of a preclinical correlate of protection for ClfA-containing vaccines based on FBI titer.

  8. Demonstration of the preclinical correlate of protection for Staphylococcus aureus clumping factor A in a murine model of infection.

    PubMed

    Scully, Ingrid L; Timofeyeva, Yekaterina; Keeney, David; Matsuka, Yury V; Severina, Elena; McNeil, Lisa K; Nanra, Jasdeep; Hu, George; Liberator, Paul A; Jansen, Kathrin U; Anderson, Annaliesa S

    2015-10-01

    The Staphylococcus aureus virulence factor clumping factor A (ClfA) is a component of an investigational S. aureus prophylactic vaccine. ClfA enables S. aureus to bind to fibrinogen and platelets during the initial stages of invasive disease. Here we demonstrate that ectopic expression of ClfA is sufficient to render nonpathogenic Lactococcus lactis lethal in a murine model of systemic infection. In contrast, L. lactis expressing ClfAY338A, which cannot bind fibrinogen, did not cause death in the mice. Pathogenicity was also prevented by immunization with ClfA. This model was then used to define a preclinical correlate of protection by measuring functional antibody in a S. aureus fibrinogen binding inhibition assay (FBI) and correlating that titer with protective outcomes. Although many humans have pre-existing antibodies that bind to ClfA, only sera with a threshold functional titer in the FBI were protective in this preclinical model. This confirms that fibrinogen binding is critical for ClfA-mediated pathogenesis and demonstrates that functional antibodies against ClfA are sufficient to protect against ClfA-mediated pathogenesis in vivo, enabling the definition of a preclinical correlate of protection for ClfA-containing vaccines based on FBI titer. PMID:26319743

  9. Factors correlated with fatigue in disease-free breast cancer patients: application of the Cancer Fatigue Scale.

    PubMed

    Okuyama, T; Akechi, T; Kugaya, A; Okamura, H; Imoto, S; Nakano, T; Mikami, I; Hosaka, T; Uchitomi, Y

    2000-05-01

    Fatigue is one of the most frequent symptoms in cancer patients. However, the precise causes of this fatigue are still unknown, and this situation makes it difficult to combat the problem. The present study was conducted to investigate factors correlated with fatigue in disease-free breast cancer patients. A group of 134 randomly selected ambulatory breast cancer patients who had undergone successful surgical treatment participated. They completed the Cancer Fatigue Scale, the Hospital Anxiety and Depression Scale, the Mental Adjustment to Cancer Scale, and an ad hoc questionnaire detailing physical symptoms, social support, and demographic variables at home and returned them by mail the following day. Multiple regression analysis revealed that fatigue was significantly correlated with dyspnea, insufficient sleep, and depression, and that these three variables accounted for a total of 46% of variance in fatigue. Factors concerned with the cancer and treatment, such as disease stage, lymph node metastasis, number of days since operation, past intravenous chemotherapy, radiotherapy, current use of fluoropyrimidine compounds, and current use of tamoxifen citrate were not correlated with fatigue. The results suggest that fatigue in this population is determined by current physical and psychological distress rather than by the cancer itself and prior cancer treatments, and that the management of dyspnea, insomnia, and depression might be important in reducing fatigue in this population.

  10. A frictional study of total hip joint replacements

    NASA Astrophysics Data System (ADS)

    Scholes, S. C.; Unsworth, A.; Goldsmith, A. A. J.

    2000-12-01

    Polymeric wear debris produced by articulation of the femoral head against the ultra-high-molecular-weight polyethylene socket of a total hip replacement has been implicated as the main cause of osteolysis and subsequent failure of these implants. Potential solutions to this problem are to employ hard bearing surface combinations such as metal-on-metal or ceramic-on-ceramic prostheses. The aim of this study was to investigate the difference in lubrication modes and friction of a range of material combinations using synthetic and biological fluids as the lubricants. The experimental results were compared with theoretical predictions of film thicknesses and lubrication modes. A strong correlation was observed between experiment and theory when employing carboxy methyl cellulose (CMC) fluids as the lubricant. Under these conditions the ceramic-on-ceramic joints showed full fluid film lubrication while the metal-on-metal, metal-on-plastic, diamond-like carbon-coated stainless steel (DLC)-on-plastic and ceramic-on-plastic prostheses operated under a mixed lubrication regime. With bovine serum as the lubricant in the all ceramic joints, however, the full fluid film lubrication was inhibited due to adsorbed proteins. In the metal-on-metal joints this adsorbed protein layer acted to reduce the friction while in the ceramic coupling the friction was increased. The use of bovine serum as the lubricant also significantly increased the friction in both the metal-on-plastic and ceramic-on-plastic joints. The friction produced by the DLC-on-plastic joints depended on the quality of the coating. Those joints with a less consistent coating and therefore a higher surface roughness gave significantly higher friction than the smoother, more consistently coated heads.

  11. Molecular Specificities of R Factor-Determined Beta-Lactamases: Correlation with Plasmid Compatibility

    PubMed Central

    Hedges, R. W.; Datta, Naomi; Kontomichalou, Polyxeni; Smith, J. T.

    1974-01-01

    Beta (β)-lactamases determined by 29 ampicillin resistance plasmids could be divided into two types. One, TEM-type, was very uniform with respect to substrate specificity but heterogeneous in absolute levels of β-lactamase activity. The TEM-type β-lactamase was determined by R factors of compatibility groups FII, Iα, Iε, N, C, A, T, W, P, L, and X, and by prophage φ Amp. The other type, characterized by the ability to hydrolyze oxacillin, was less common, showed lower absolute levels of activity, and was heterogeneous as regards substrate specificities. Oxacillin-hydrolyzing β-lactamases were determined by R factors of compatibility groups FI, Iα, N, C, and O. PMID:4587613

  12. The correlation between the Glycated hemoglobin (HbA1c) in non-diabetics and cardiovascular risk factors.

    PubMed

    Wu, Xinling; Zhao, Youmin; Chai, Jianwen; Hao, Dongqin

    2016-01-01

    This study aimed to discuss the relativity between the glycated hemoglobin (HbA1c) in non-diabetics and cardiovascular risk factors and definite the significance of predicting the cardiovascular risk factors through cross-sectional research method. There were 2007 cases volunteers (including 650 cases of male, 1357 cases of female) from city community with complete information involved in the research of diabetes. The value of HbA1c 6.5% was set as the diagnose boundary of the diabetes. Differences were considered to be statistically significant at P<0.05. Hypertension, dyslipidemi, being overweight or obesity, age (male was over 45 years old and female was over 55 years old.), HbA1c 6.0% and fasting blood glucose (FBG) 6.1mmol/L were regarded as cardiovascular risk factors. Then we analyzed the number of risk factors for individuals in different HbA1c groups. Meanwhile, patients were grouped into zero, one, two, three, four or more groups with reference to the number of risk factors they had in order to compare the values of risk factors in different groups through Logistic regression. The results showed that (1) For those people who had no less than three risk factors, the frequency of risk factors was on the rise with the increase of HbA1c levels. (2) The value of HbA1c in different groups of risk factors rose with the increasing number of risk factors. There was a significant difference (P<0.001) between groups. (3) The Regression analysis showed that there was a stronger correlation between HbA1c levels and impaired glucose tolerance (IGT), fasting blood glucose (FBG) rather than age. So Non-diabetics whose HbA1c levels ranged from 6.0% to 6.5% were at high risk of cardiovascular risk factors. HbA1c levels, which can be a prediction index for cardiovascular risk factors dependent from other cardiovascular risk factors for non-diabetics, and it were highly relevant with impaired glucose tolerance (IGT) and impaired fasting blood glucose (FBG).

  13. The correlation between the Glycated hemoglobin (HbA1c) in non-diabetics and cardiovascular risk factors.

    PubMed

    Wu, Xinling; Zhao, Youmin; Chai, Jianwen; Hao, Dongqin

    2016-01-01

    This study aimed to discuss the relativity between the glycated hemoglobin (HbA1c) in non-diabetics and cardiovascular risk factors and definite the significance of predicting the cardiovascular risk factors through cross-sectional research method. There were 2007 cases volunteers (including 650 cases of male, 1357 cases of female) from city community with complete information involved in the research of diabetes. The value of HbA1c 6.5% was set as the diagnose boundary of the diabetes. Differences were considered to be statistically significant at P<0.05. Hypertension, dyslipidemi, being overweight or obesity, age (male was over 45 years old and female was over 55 years old.), HbA1c 6.0% and fasting blood glucose (FBG) 6.1mmol/L were regarded as cardiovascular risk factors. Then we analyzed the number of risk factors for individuals in different HbA1c groups. Meanwhile, patients were grouped into zero, one, two, three, four or more groups with reference to the number of risk factors they had in order to compare the values of risk factors in different groups through Logistic regression. The results showed that (1) For those people who had no less than three risk factors, the frequency of risk factors was on the rise with the increase of HbA1c levels. (2) The value of HbA1c in different groups of risk factors rose with the increasing number of risk factors. There was a significant difference (P<0.001) between groups. (3) The Regression analysis showed that there was a stronger correlation between HbA1c levels and impaired glucose tolerance (IGT), fasting blood glucose (FBG) rather than age. So Non-diabetics whose HbA1c levels ranged from 6.0% to 6.5% were at high risk of cardiovascular risk factors. HbA1c levels, which can be a prediction index for cardiovascular risk factors dependent from other cardiovascular risk factors for non-diabetics, and it were highly relevant with impaired glucose tolerance (IGT) and impaired fasting blood glucose (FBG). PMID:27005508

  14. Autoimmune manifestations in human myelodysplasia: a positive correlation with interferon regulatory factor-1 (IRF-1) expression

    PubMed Central

    Giannouli, S; Tzoanopoulos, D; Ritis, K; Kartalis, G; Moutsopoulos, H; Voulgarelis, M

    2004-01-01

    Background: Patients with myelodysplasia may have autoimmune manifestations (AIM). Interferon regulatory factor-1 (IRF-1) is a transcription factor involved in interferon signalling, leukaemogenesis, and the development of the immune system. Objectives: To determine whether IRF-1 is implicated in the pathophysiology of AIM in myelodysplasia. Methods: 14 patients with myelodysplasia were studied, seven with AIM and seven without. Five patients with vasculitis and seven normal subjects served as controls. The expression of IRF-1 was studied in bone marrow mononuclear cells taken from patients and controls, using a relative quantitative reverse transcriptase polymerase chain reaction. Results: A 10-fold reduction in full length IRF-1 mRNA was detected in the myelodysplasia patients without AIM compared with the normal controls. In contrast, the group with AIM had increased IRF-1 transcripts, to a level almost equal to that observed in patients with vasculitis and normal controls. Conclusions: Myelodysplasia patients without IRF-1 expression had a decreased incidence of AIM. Thus the absence of IRF-1 transcription factor appears to protect against the development of autoimmunity in myelodysplasia. PMID:15082491

  15. Factors correlated with traffic accidents as a basis for evaluating Advanced Driver Assistance Systems.

    PubMed

    Staubach, Maria

    2009-09-01

    This study aims to identify factors which influence and cause errors in traffic accidents and to use these as a basis for information to guide the application and design of driver assistance systems. A total of 474 accidents were examined in depth for this study by means of a psychological survey, data from accident reports, and technical reconstruction information. An error analysis was subsequently carried out, taking into account the driver, environment, and vehicle sub-systems. Results showed that all accidents were influenced by errors as a consequence of distraction and reduced activity. For crossroad accidents, there were further errors resulting from sight obstruction, masked stimuli, focus errors, and law infringements. Lane departure crashes were additionally caused by errors as a result of masked stimuli, law infringements, expectation errors as well as objective and action slips, while same direction accidents occurred additionally because of focus errors, expectation errors, and objective and action slips. Most accidents were influenced by multiple factors. There is a safety potential for Advanced Driver Assistance Systems (ADAS), which support the driver in information assimilation and help to avoid distraction and reduced activity. The design of the ADAS is dependent on the specific influencing factors of the accident type. PMID:19664441

  16. Factors correlated with traffic accidents as a basis for evaluating Advanced Driver Assistance Systems.

    PubMed

    Staubach, Maria

    2009-09-01

    This study aims to identify factors which influence and cause errors in traffic accidents and to use these as a basis for information to guide the application and design of driver assistance systems. A total of 474 accidents were examined in depth for this study by means of a psychological survey, data from accident reports, and technical reconstruction information. An error analysis was subsequently carried out, taking into account the driver, environment, and vehicle sub-systems. Results showed that all accidents were influenced by errors as a consequence of distraction and reduced activity. For crossroad accidents, there were further errors resulting from sight obstruction, masked stimuli, focus errors, and law infringements. Lane departure crashes were additionally caused by errors as a result of masked stimuli, law infringements, expectation errors as well as objective and action slips, while same direction accidents occurred additionally because of focus errors, expectation errors, and objective and action slips. Most accidents were influenced by multiple factors. There is a safety potential for Advanced Driver Assistance Systems (ADAS), which support the driver in information assimilation and help to avoid distraction and reduced activity. The design of the ADAS is dependent on the specific influencing factors of the accident type.

  17. The effect of chalk on the finger-hold friction coefficient in rock climbing.

    PubMed

    Amca, Arif Mithat; Vigouroux, Laurent; Aritan, Serdar; Berton, Eric

    2012-11-01

    The main purpose of this study was to examine the effect of chalk on the friction coefficient between climber's fingers and two different rock types (sandstone and limestone). The secondary purpose was to investigate the effects of humidity and temperature on the friction coefficient and on the influence of chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed. Participants hung from holds which were fixed on a specially designed hang board. The inclination of the hang board was progressively increased until the climber's hand slipped from the holds. The angle of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient was calculated at the moment of slip. The results showed that there was a significant positive effect of chalk on the coefficient of friction (+18.7% on limestone and +21.6% on sandstone). Moreover sandstone had a higher coefficient of friction than limestone (+15.6% without chalk, +18.4% with chalk). These results confirmed climbers' belief that chalk enhances friction. However, no correlation with humidity/temperature and friction coefficient was noted which suggested that additional parameters should be considered in order to understand the effects of climate on finger friction in rock climbing.

  18. Correlation Between Hepatocyte Growth Factor (HGF) and Gamma-Aminobutyric Acid (GABA) Plasma Levels in Autistic Children.

    PubMed

    Russo, Anthony J

    2013-01-01

    There is much support for the role of Gamma-Aminobutyric acid (GABA) in the etiology of autism. Recent research has shown that hepatocyte growth factor (HGF) modulates GABAergic inhibition and seizure susceptibility. This study was designed to determine and correlate plasma levels of HGF, GABA, as well as symptom severity, in autistic children and neurotypical controls. Plasma from 48 autistic children and 29 neurotypical controls was assessed for HGF and GABA concentration using ELISAs. Symptom severity was assessed in these autistic individuals and compared to HGF and GABA concentrations. We previously reported that autistic children had significantly decreased levels of HGF. In this study, the same autistic children had significantly increased plasma levels of GABA (P = 0.002) and decreased HGF levels correlated with these increased GABA levels (r = 0.3; P = 0.05). High GABA levels correlated with increasing hyperactivity (r = 0.6; P = 0.0007) and impulsivity severity (r = 0.5; P = 0.007), tip toeing severity (r = 0.35; P = 0.03), light sensitivity (r = 0.4; P = 0.02), and tactile sensitivity (r = 0.4; P = 0.01). HGF levels did not correlate significantly with any symptom severity. These results suggest an association between HGF and GABA levels and suggest that plasma GABA levels are related to symptom severity in autistic children.

  19. Cognitive factors correlating with the metacognition of the phenomenal properties of experience

    PubMed Central

    Mogi, Ken

    2013-01-01

    The awareness of the phenomenal qualities of one's experiences can be considered as an instance of metacognition. Although some people take qualia (sensory qualities such as the redness of red) as salient features of phenomenal experience, others have expressed views that doubt or deny the central importance of qualia. How do such cognitive heterogeneities occur? What parameters influence them? Here I examine the relationship between the awareness of the phenomenal qualities of subjective experience (qualia and free will) and general cognitive tendencies. The awareness of qualia was found to be more varied among subjects compared to the belief in free will. Various cognitive tendencies correlated with the metacognition of phenomenal experience. The awareness of qualia was found to increase significantly with age, suggesting a continuous learning process. These results suggest that heterogeneities in the metacognition of phenomenal properties of experience are important constraints in human cognition. PMID:24284832

  20. Neurophysiological correlates of embodiment and motivational factors during the perception of virtual architectural environments.

    PubMed

    Vecchiato, Giovanni; Jelic, Andrea; Tieri, Gaetano; Maglione, Anton Giulio; De Matteis, Federico; Babiloni, Fabio

    2015-09-01

    The recent efforts aimed at providing neuroscientific explanations of how people perceive and experience architectural environments have largely justified the initial belief in the value of neuroscience for architecture. However, a systematic development of a coherent theoretical and experimental framework is missing. To investigate the neurophysiological reactions related to the appreciation of ambiances, we recorded the electroencephalographic (EEG) signals in an immersive virtual reality during the appreciation of interior designs. Such data have been analyzed according to the working hypothesis that appreciated environments involve embodied simulation mechanisms and circuits mediating approaching stimuli. EEG recordings of 12 healthy subjects have been performed during the perception of three-dimensional interiors that have been simulated in a CAVE system and judged according to dimensions of familiarity, novelty, comfort, pleasantness, arousal and presence. A correlation analysis on personal judgments returned that scores of novelty, pleasantness and comfort are positively correlated, while familiarity and novelty are in negative way. Statistical spectral maps reveal that pleasant, novel and comfortable interiors produce a de-synchronization of the mu rhythm over left sensorimotor areas. Interiors judged more pleasant and less familiar generate an activation of left frontal areas (theta and alpha bands), along an involvement of areas devoted to spatial navigation. An increase in comfort returns an enhancement of the theta frontal midline activity. Cerebral activations underlying appreciation of architecture could involve different mechanisms regulating corporeal, emotional and cognitive reactions. Therefore, it might be suggested that people's experience of architectural environments is intrinsically structured by the possibilities for action. PMID:26224275

  1. A Lack of Correlation between Brain-Derived Neurotrophic Factor Serum Level and Verbal Memory Performance in Healthy Polish Population.

    PubMed

    Wilkosc, Monika; Markowska, Anita; Zajac-Lamparska, Ludmila; Skibinska, Maria; Szalkowska, Agnieszka; Araszkiewicz, Aleksander

    2016-01-01

    Brain derived neurotrophic factor (BDNF) is considered to be connected with memory and learning through the processes of long term synaptic potentiation and synaptic plasticity. The aim of the study was to examine the relationship between precursor BDNF (proBNDF) and mature BDNF (mBDNF) serum levels and performance on Rey Auditory-Verbal Learning Test (RAVLT) in 150 healthy volunteers. In addition, we have verified the relationships between serum concentration of both forms of BDNF and RAVLT with sociodemographic and lifestyle factors.We found no strong evidence for the correlation of proBDNF and mBDNF serum levels with performance on RAVLT in healthy Polish population in early and middle adulthood. We observed the mBDNF serum concentration to be higher in women compared with men. Moreover, we revealed higher mBDNF level to be connected with lower body mass index (BMI). In turn, the results of RAVLT correlated with sociodemographic and lifestyle factors, such as: age, education, gender, BMI and smoking. PMID:27242447

  2. Probing the kinetic landscape of Hox transcription factor-DNA binding in live cells by massively parallel Fluorescence Correlation Spectroscopy.

    PubMed

    Papadopoulos, Dimitrios K; Krmpot, Aleksandar J; Nikolić, Stanko N; Krautz, Robert; Terenius, Lars; Tomancak, Pavel; Rigler, Rudolf; Gehring, Walter J; Vukojević, Vladana

    2015-11-01

    Hox genes encode transcription factors that control the formation of body structures, segment-specifically along the anterior-posterior axis of metazoans. Hox transcription factors bind nuclear DNA pervasively and regulate a plethora of target genes, deploying various molecular mechanisms that depend on the developmental and cellular context. To analyze quantitatively the dynamics of their DNA-binding behavior we have used confocal laser scanning microscopy (CLSM), single-point fluorescence correlation spectroscopy (FCS), fluorescence cross-correlation spectroscopy (FCCS) and bimolecular fluorescence complementation (BiFC). We show that the Hox transcription factor Sex combs reduced (Scr) forms dimers that strongly associate with its specific fork head binding site (fkh250) in live salivary gland cell nuclei. In contrast, dimers of a constitutively inactive, phospho-mimicking variant of Scr show weak, non-specific DNA-binding. Our studies reveal that nuclear dynamics of Scr is complex, exhibiting a changing landscape of interactions that is difficult to characterize by probing one point at a time. Therefore, we also provide mechanistic evidence using massively parallel FCS (mpFCS). We found that Scr dimers are predominantly formed on the DNA and are equally abundant at the chromosomes and an introduced multimeric fkh250 binding-site, indicating different mobilities, presumably reflecting transient binding with different affinities on the DNA. Our proof-of-principle results emphasize the advantages of mpFCS for quantitative characterization of fast dynamic processes in live cells.

  3. Importance of Relativistic Effects and Electron Correlation in Structure Factors and Electron Density of Diphenyl Mercury and Triphenyl Bismuth.

    PubMed

    Bučinský, Lukáš; Jayatilaka, Dylan; Grabowsky, Simon

    2016-08-25

    This study investigates the possibility of detecting relativistic effects and electron correlation in single-crystal X-ray diffraction experiments using the examples of diphenyl mercury (HgPh2) and triphenyl bismuth (BiPh3). In detail, the importance of electron correlation (ECORR), relativistic effects (REL) [distinguishing between total, scalar and spin-orbit (SO) coupling relativistic effects] and picture change error (PCE) on the theoretical electron density, its topology and its Laplacian using infinite order two component (IOTC) wave functions is discussed. This is to develop an understanding of the order of magnitude and shape of these different effects as they manifest in the electron density. Subsequently, the same effects are considered for the theoretical structure factors. It becomes clear that SO and PCE are negligible, but ECORR and scalar REL are important in low- and medium-order reflections on absolute and relative scales-not in the high-order region. As a further step, Hirshfeld atom refinement (HAR) and subsequent X-ray constrained wavefunction (XCW) fitting have been performed for the compound HgPh2 with various relativistic and nonrelativistic wave functions against the experimental structure factors. IOTC calculations of theoretical structure factors and relativistic HAR as well as relativistic XCW fitting are presented for the first time, accounting for both scalar and spin-orbit relativistic effects. PMID:27434184

  4. Risk factor correlates of platelet and leukocyte markers assessed by flow cytometry in a population-based sample

    PubMed Central

    Folsom, Aaron R.; Aleksic, Nena; Sanhueza, Antonio; Boerwinkle, Eric

    2008-01-01

    Background Platelet and leukocyte products are involved in atherothrombosis. However, the determinants of of platelet and leukocyte markers assessed by flow cytometry have not been documented in a population-based sample. Methods and results We performed flow cytometry on blood from participants (n=1,894) in the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study. Cellular aggregates and multiple platelet and leukocyte markers, such as myeloperoxidase in granulocytes and toll-like receptor-4, CD14, and CD45 in monocytes, were quantified. Their cross-sectional associations with demographic and risk factors were assessed using multiple linear regression. Mean values of most cellular markers and aggregates were considerably higher in blacks than whites (p<0.01). There were some differences in cellular markers between men and women, but little association with age. LDL-cholesterol was associated positively with several markers (toll-like receptor-4 and myeloperoxidase in granulocytes and CD162 in lymphocytes). Lipid lowering therapy tended to show opposite associations. Smokers had much higher granulocyte myeloperoxidase than nonsmokers. However, most other correlations between risk factors and cellular markers were nonsignificant. Conclusions Race/ethnicity, sex, and to a lesser degree LDL-cholesterol and lipid-lowering therapy, but few other risk factors, were correlated with markers of cellular activation in this population-based study. PMID:19124123

  5. Importance of Relativistic Effects and Electron Correlation in Structure Factors and Electron Density of Diphenyl Mercury and Triphenyl Bismuth.

    PubMed

    Bučinský, Lukáš; Jayatilaka, Dylan; Grabowsky, Simon

    2016-08-25

    This study investigates the possibility of detecting relativistic effects and electron correlation in single-crystal X-ray diffraction experiments using the examples of diphenyl mercury (HgPh2) and triphenyl bismuth (BiPh3). In detail, the importance of electron correlation (ECORR), relativistic effects (REL) [distinguishing between total, scalar and spin-orbit (SO) coupling relativistic effects] and picture change error (PCE) on the theoretical electron density, its topology and its Laplacian using infinite order two component (IOTC) wave functions is discussed. This is to develop an understanding of the order of magnitude and shape of these different effects as they manifest in the electron density. Subsequently, the same effects are considered for the theoretical structure factors. It becomes clear that SO and PCE are negligible, but ECORR and scalar REL are important in low- and medium-order reflections on absolute and relative scales-not in the high-order region. As a further step, Hirshfeld atom refinement (HAR) and subsequent X-ray constrained wavefunction (XCW) fitting have been performed for the compound HgPh2 with various relativistic and nonrelativistic wave functions against the experimental structure factors. IOTC calculations of theoretical structure factors and relativistic HAR as well as relativistic XCW fitting are presented for the first time, accounting for both scalar and spin-orbit relativistic effects.

  6. Analysis of HIV Correlated Factors in Chinese and Vietnamese Female Sex Workers in Hekou, Yunnan Province, a Chinese Border Region

    PubMed Central

    Wang, Junjie; Ding, Guowei; Zhu, Zhibin; Zhou, Chunlian; Wang, Ning

    2015-01-01

    Objectives To assess the prevalence and correlated factors of HIV-1 among Chinese and Vietnamese female sex workers (FSW) in the border county of Hekou, Yunnan province, China. Methods A cross-sectional survey was conducted collecting information on demographics, sexual behavior, medical history, and drug use. Blood samples were obtained to test for HIV/STIs. Multivariate logistic regression model was used to examine associations between factors and HIV-1 infection. Results Of 345 FSWs who participated in this study, 112 (32.5%) were Chinese and 233 (67.5) were Vietnamese. Vietnamese FSWs were significantly more likely to be HIV-1 positive (7.7%) compared with Chinese FSWs (0.9%) (p = 0.009). In multivariate analysis, sexual debut at age≤16 (OR 3.8: 95% CI: 1.4, 10.6), last client’s payment <150 RMB ($22 USD) (OR: 5.2, 95% CI; 1.7, 16.6), and HSV-2 (OR: 12.3; 95% CI: 1.6, 94.8) were significant for HIV-1 infection. Conclusions Differences in HIV prevalence in Vietnamese and Chinese FSWs may be indicative of differential risk. It is important to characterize the nature of trans-border transmission in order to gain a better understanding of the potential impact on the international HIV epidemic. Understanding the correlated factors for HIV in Vietnamese and Chinese FSWs is important for designing interventions for this vulnerable population. PMID:26053040

  7. A Lack of Correlation between Brain-Derived Neurotrophic Factor Serum Level and Verbal Memory Performance in Healthy Polish Population

    PubMed Central

    Wilkosc, Monika; Markowska, Anita; Zajac-Lamparska, Ludmila; Skibinska, Maria; Szalkowska, Agnieszka; Araszkiewicz, Aleksander

    2016-01-01

    Brain derived neurotrophic factor (BDNF) is considered to be connected with memory and learning through the processes of long term synaptic potentiation and synaptic plasticity. The aim of the study was to examine the relationship between precursor BDNF (proBNDF) and mature BDNF (mBDNF) serum levels and performance on Rey Auditory-Verbal Learning Test (RAVLT) in 150 healthy volunteers. In addition, we have verified the relationships between serum concentration of both forms of BDNF and RAVLT with sociodemographic and lifestyle factors.We found no strong evidence for the correlation of proBDNF and mBDNF serum levels with performance on RAVLT in healthy Polish population in early and middle adulthood. We observed the mBDNF serum concentration to be higher in women compared with men. Moreover, we revealed higher mBDNF level to be connected with lower body mass index (BMI). In turn, the results of RAVLT correlated with sociodemographic and lifestyle factors, such as: age, education, gender, BMI and smoking. PMID:27242447

  8. Pressure and Friction Injuries in Primary Care.

    PubMed

    Phillips, Shawn; Seiverling, Elizabeth; Silvis, Matthew

    2015-12-01

    Pressure and friction injuries are common throughout the lifespan. A detailed history of the onset and progression of friction and pressure injuries is key to aiding clinicians in determining the underlying mechanism behind the development of the injury. Modifying or removing the forces that are creating pressure or friction is the key to both prevention and healing of these injuries. Proper care of pressure and friction injuries to the skin is important to prevent the development of infection. Patient education on positioning and ergonomics can help to prevent recurrence of pressure and friction injuries.

  9. Piston ring designs for reduced friction

    SciTech Connect

    Hill, S.H.; Newman, B.A.

    1984-01-01

    To reduce parasitic losses, a project was initiated to design, develop and bring to production a piston ring set which reduces engine friction while maintaining ring performance. In this paper, theoretical considerations affecting piston ring friction, and their implication in ring design, are discussed. An estimate of friction reduction and fuel economy improvement which can be achieved is calculated. Features of the resulting designs are reviewed, and friction, dynamometer, and vehicle test results are presented. Future ring design changes for reduced friction are reviewed.

  10. The Internalized Homophobia Scale for Vietnamese Sexual Minority Women: Conceptualization, Factor Structure, Reliability, and Associations With Hypothesized Correlates.

    PubMed

    Nguyen, Trang Quynh; Poteat, Tonia; Bandeen-Roche, Karen; German, Danielle; Nguyen, Yen Hai; Vu, Loan Kieu-Chau; Nguyen, Nam Thi-Thu; Knowlton, Amy R

    2016-08-01

    We developed the first Vietnamese Internalized Homophobia (IH) scale for use with Vietnamese sexual minority women (SMW). Drawing from existing IH scales in the international literature and based on prior qualitative research about SMW in the Viet Nam context, the scale covers two domains: self-stigma (negative attitudes toward oneself as a sexual minority person) and sexual prejudice (negative attitudes toward homosexuality/same-sex relations in general). Scale items, including items borrowed from existing scales and items based on local expressions, were reviewed and confirmed by members of the target population. Quantitative evaluation used data from an anonymous web-based survey of Vietnamese SMW, including those who identified as lesbian (n = 1187), or as bisexual (n = 641) and those who were unsure about their sexual identity (n = 353). The scale was found to consist of two highly correlated factors reflecting self-stigma (not normal/wholesome and self-reproach and wishing away same-sex sexuality) and one factor reflecting sexual prejudice, and to have excellent internal consistency. Construct validity was evidenced by subscale associations with a wide range of hypothesized correlates, including perceived sexual stigma, outness, social support, connection to other SMW, relationship quality, psychological well-being, anticipation of heterosexual marriage, and endorsement of same-sex marriage legalization. Self-stigma was more strongly associated with psychosocial correlates, and sexual prejudice was more associated with endorsement of legal same-sex marriage. The variations in these associations across the hypothesized correlates and across sexual identity groups were consistent with the minority stress model and the IH literature, and exhibited context-specific features, which are discussed. PMID:27007469

  11. The Internalized Homophobia Scale for Vietnamese Sexual Minority Women: Conceptualization, Factor Structure, Reliability, and Associations With Hypothesized Correlates.

    PubMed

    Nguyen, Trang Quynh; Poteat, Tonia; Bandeen-Roche, Karen; German, Danielle; Nguyen, Yen Hai; Vu, Loan Kieu-Chau; Nguyen, Nam Thi-Thu; Knowlton, Amy R

    2016-08-01

    We developed the first Vietnamese Internalized Homophobia (IH) scale for use with Vietnamese sexual minority women (SMW). Drawing from existing IH scales in the international literature and based on prior qualitative research about SMW in the Viet Nam context, the scale covers two domains: self-stigma (negative attitudes toward oneself as a sexual minority person) and sexual prejudice (negative attitudes toward homosexuality/same-sex relations in general). Scale items, including items borrowed from existing scales and items based on local expressions, were reviewed and confirmed by members of the target population. Quantitative evaluation used data from an anonymous web-based survey of Vietnamese SMW, including those who identified as lesbian (n = 1187), or as bisexual (n = 641) and those who were unsure about their sexual identity (n = 353). The scale was found to consist of two highly correlated factors reflecting self-stigma (not normal/wholesome and self-reproach and wishing away same-sex sexuality) and one factor reflecting sexual prejudice, and to have excellent internal consistency. Construct validity was evidenced by subscale associations with a wide range of hypothesized correlates, including perceived sexual stigma, outness, social support, connection to other SMW, relationship quality, psychological well-being, anticipation of heterosexual marriage, and endorsement of same-sex marriage legalization. Self-stigma was more strongly associated with psychosocial correlates, and sexual prejudice was more associated with endorsement of legal same-sex marriage. The variations in these associations across the hypothesized correlates and across sexual identity groups were consistent with the minority stress model and the IH literature, and exhibited context-specific features, which are discussed.

  12. The effect of surface waviness on friction between Neolite and quarry tiles.

    PubMed

    Chang, Wen-Ruey; Grönqvist, Raoul; Hirvonen, Mikko; Matz, Simon

    2004-06-22

    Friction is widely used as an indicator of surface slipperiness in preventing accidents in slips and falls. Surface texture affects friction, but it is not clear which surface characteristics are better correlated with friction. Highly correlated surface characteristics could be used as potential interventions to prevent slip and fall accidents. The dynamic friction between quarry tiles and a commonly used sole testing material, Neolite, using three different mixtures of glycerol and water as contaminants at the interface was correlated with the surface parameters of the tile surfaces. The surface texture was quantified with various surface roughness and surface waviness parameters using three different cut-off lengths to filter the measured profiles for obtaining the profiles of either surface roughness or surface waviness. The correlation coefficients between the surface parameters and the measured friction were affected by the glycerol contents and cut-off lengths. Surface waviness parameters could potentially be better indicators of friction than commonly used surface roughness parameters, especially when they were measured with commonly used cut-off lengths or when the viscosity of the liquid contaminant was high.

  13. Friction properties of novel PVP/PVA blend hydrogels as artificial cartilage.

    PubMed

    Ma, Ruyin; Xiong, Dangsheng; Miao, Feng; Zhang, Jinfeng; Peng, Yan

    2010-06-01

    In this work, novel polyvinylpyrrolidone (PVP)/polyvinylalcohol (PVA) blend hydrogels were prepared by repeated freezing-thawing cycles. The factors that influenced friction properties of blend hydrogels, such as PVP content, contact load, sliding speed, and lubrication condition, were mainly studied by sliding with stainless steel ball. The results showed that friction coefficients of the PVP/PVA blend hydrogels were definitely dependent on such influence factors. The friction system consisting of blend hydrogel and stainless steel ball nearly exhibited a mixed lubrication regime especially under bovine serum lubrication, and it can be proposed as a promising method to reduce wear of the prosthesis.

  14. Frictional constraints on crustal faulting

    USGS Publications Warehouse

    Boatwright, J.; Cocco, M.

    1996-01-01

    We consider how variations in fault frictional properties affect the phenomenology of earthquake faulting. In particular, we propose that lateral variations in fault friction produce the marked heterogeneity of slip observed in large earthquakes. We model these variations using a rate- and state-dependent friction law, where we differentiate velocity-weakening behavior into two fields: the strong seismic field is very velocity weakening and the weak seismic field is slightly velocity weakening. Similarly, we differentiate velocity-strengthening behavior into two fields: the compliant field is slightly velocity strengthening and the viscous field is very velocity strengthening. The strong seismic field comprises the seismic slip concentrations, or asperities. The two "intermediate" fields, weak seismic and compliant, have frictional velocity dependences that are close to velocity neutral: these fields modulate both the tectonic loading and the dynamic rupture process. During the interseismic period, the weak seismic and compliant regions slip aseismically, while the strong seismic regions remain locked, evolving into stress concentrations that fail only in main shocks. The weak seismic areas exhibit most of the interseismic activity and aftershocks but can also creep seismically. This "mixed" frictional behavior can be obtained from a sufficiently heterogenous distribution of the critical slip distance. The model also provides a mechanism for rupture arrest: dynamic rupture fronts decelerate as they penetrate into unloaded complaint or weak seismic areas, producing broad areas of accelerated afterslip. Aftershocks occur on both the weak seismic and compliant areas around a fault, but most of the stress is diffused through aseismic slip. Rapid afterslip on these peripheral areas can also produce aftershocks within the main shock rupture area by reloading weak fault areas that slipped in the main shock and then healed. We test this frictional model by comparing the

  15. Insulin-like growth factor-1 content and pattern of expression correlates with histopathologic grade in diffusely infiltrating astrocytomas.

    PubMed

    Hirano, H; Lopes, M B; Laws, E R; Asakura, T; Goto, M; Carpenter, J E; Karns, L R; VandenBerg, S R

    1999-04-01

    Studies of experimental tumorigenesis have strongly implicated signaling of the insulin-like growth factor 1 (IGF-1) as a key component in astrocytic neoplasia; however, its role in the growth of low-grade and malignant human tumors is not well understood. Correlative analyses of IGF-1, p53, and Ki-67 (MIB-1) immunohistochemistry and IGF-1 receptor (IGF-1R) mRNA expression were performed to examine the cellular pattern of IGF-1 signaling in 39 cases of astrocytoma (World Health Organization grades II-IV). Tumor cells expressing IGF-1 and IGF-1R were present in all tumor grades. The proportion of tumor cells that expressed IGF-1 correlated with both histopathologic grade and Ki-67 labeling indices, while expression of IGF-1R mRNA correlated with Ki-67 indices. In cases where stereotactic tissue sampling could be identified with a specific tumor area by neuroimaging features, the numbers of IGF-1 immunoreactive cells correlated with the tumor zones of highest cellularity and Ki-67 labeling. In glioblastomas, the localization of IGF-1 immunoreactivity was notable for several features: frequent accentuation in the perivascular tumor cells surrounding microvascular hyperplasia; increased levels in reactive astrocytes at the margins of tumor infiltration; and selective expression in microvascular cells exhibiting endothelial/pericytic hyperplasia. IGF-1R expression was particularly prominent in tumor cells adjacent to both microvascular hyperplasia and palisading necrosis. These data suggest that IGF-1 signaling occurs early in astroglial tumorigenesis in the setting of cell proliferation. The distinctive correlative patterns of IGF-1 and IGF-1R expression in glioblastomas also suggest that IGF-1 signaling has an association with the development of malignant phenotypes related to aberrant angiogenesis and invasive tumor interactions with reactive brain.

  16. Tracking transcription factor mobility and interaction in Arabidopsis roots with fluorescence correlation spectroscopy

    PubMed Central

    Clark, Natalie M; Hinde, Elizabeth; Winter, Cara M; Fisher, Adam P; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N; Sozzani, Rosangela

    2016-01-01

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction with its downstream target SCARECROW (SCR) control root patterning and cell fate specification. However, quantitative information about the spatio-temporal dynamics of SHR movement and SHR-SCR interaction is currently unavailable. Here, we quantify parameters including SHR mobility, oligomeric state, and association with SCR using a combination of Fluorescent Correlation Spectroscopy (FCS) techniques. We then incorporate these parameters into a mathematical model of SHR and SCR, which shows that SHR reaches a steady state in minutes, while SCR and the SHR-SCR complex reach a steady-state between 18 and 24 hr. Our model reveals the timing of SHR and SCR dynamics and allows us to understand how protein movement and protein-protein stoichiometry contribute to development. DOI: http://dx.doi.org/10.7554/eLife.14770.001 PMID:27288545

  17. Tracking transcription factor mobility and interaction in Arabidopsis roots with fluorescence correlation spectroscopy.

    PubMed

    Clark, Natalie M; Hinde, Elizabeth; Winter, Cara M; Fisher, Adam P; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N; Sozzani, Rosangela

    2016-01-01

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction with its downstream target SCARECROW (SCR) control root patterning and cell fate specification. However, quantitative information about the spatio-temporal dynamics of SHR movement and SHR-SCR interaction is currently unavailable. Here, we quantify parameters including SHR mobility, oligomeric state, and association with SCR using a combination of Fluorescent Correlation Spectroscopy (FCS) techniques. We then incorporate these parameters into a mathematical model of SHR and SCR, which shows that SHR reaches a steady state in minutes, while SCR and the SHR-SCR complex reach a steady-state between 18 and 24 hr. Our model reveals the timing of SHR and SCR dynamics and allows us to understand how protein movement and protein-protein stoichiometry contribute to development. PMID:27288545

  18. Tracking transcription factor mobility and interaction in Arabidopsis roots with fluorescence correlation spectroscopy.

    PubMed

    Clark, Natalie M; Hinde, Elizabeth; Winter, Cara M; Fisher, Adam P; Crosti, Giuseppe; Blilou, Ikram; Gratton, Enrico; Benfey, Philip N; Sozzani, Rosangela

    2016-06-11

    To understand complex regulatory processes in multicellular organisms, it is critical to be able to quantitatively analyze protein movement and protein-protein interactions in time and space. During Arabidopsis development, the intercellular movement of SHORTROOT (SHR) and subsequent interaction with its downstream target SCARECROW (SCR) control root patterning and cell fate specification. However, quantitative information about the spatio-temporal dynamics of SHR movement and SHR-SCR interaction is currently unavailable. Here, we quantify parameters including SHR mobility, oligomeric state, and association with SCR using a combination of Fluorescent Correlation Spectroscopy (FCS) techniques. We then incorporate these parameters into a mathematical model of SHR and SCR, which shows that SHR reaches a steady state in minutes, while SCR and the SHR-SCR complex reach a steady-state between 18 and 24 hr. Our model reveals the timing of SHR and SCR dynamics and allows us to understand how protein movement and protein-protein stoichiometry contribute to development.

  19. Correlations between Microbial Indicators, Pathogens, and Environmental Factors in a Subtropical Estuary

    PubMed Central

    Ortega, Cristina; Solo-Gabriele, Helena M.; Abdelzaher, Amir; Wright, Mary; Deng, Yang; Stark, Lillian M.

    2009-01-01

    The objective of this study was to evaluate whether indicator microbes and physical-chemical parameters were correlated with pathogens within a tidally influenced estuary. Measurements included the analysis of physical-chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, E. coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L).. Notable physical-chemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31 °C). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites. PMID:19464704

  20. A Model for Static and Dry Friction

    NASA Astrophysics Data System (ADS)

    Daly, Christopher

    2005-03-01

    It will be shown that the Muser-Robbins (MR) model, consisting of mobile molecules trapped between two incommensurate crystalline solids, exhibits many of the qualitative features of friction between macroscopic solids, such as the result that the static friction is greater than the kinetic friction, stick-slip motion and a force of static friction which increases as a function of the time that the two solids are in contact and stationary. At zero temperature, the kinetic friction is highly sensitive to the direction of sliding, but this sensitivity decreases markedly as the temperature rises. At low temperatures (with the surfaces stationary for a relatively long time), the model gives a static friction approximately 3 times larger than the kinetic friction for sufficiently slow velocities, but this ratio decreases steadily as the temperature is increased.

  1. Friction and Wear of Carbonate Rocks Under High Velocity Sliding

    NASA Astrophysics Data System (ADS)

    Boneh, Y.; Sagy, A.; Reches, Z.

    2012-12-01

    We experimentally investigated the relations between friction and wear-rate during steady-state, high-velocity slip along carbonate faults. Our observations demonstrate a systematic reduction of both friction coefficient and wear-rate with increase of both slip-velocity and normal stress. The experiments were conducted with a rotary shear apparatus on solid, ring-shaped rock samples that slipped for displacements up to tens of meters, with continuous monitoring of stresses, wear and temperature. We performed 107 experiments on experimental faults made of Kasota dolomite, Dover limestone and a fault made of rock-pair Kasota dolomite and Blue quartzite. The friction/wear analysis is focused on the steady-state stage under slip velocity range of 0.002 to 0.96 m/s, and normal stress from 0.25 to 6.9 MPa. The experiments reveal a combined effect of slip-velocity and normal stress on the wear-rate. Under relatively low velocities (V < 0.5 m/s for limestone and V < 0.12 m/s for dolomite-quartzite pair), the wear-rate is proportional to the normal stress, in agreement with Archard (1953) model. On the other hand, in the higher velocity range of V ~ 0.5 - 1 m/s, the wear-rate is not proportional to the normal stress and it reduces with increasing slip-velocity. Further, the velocity effect on the wear-rate becomes stronger with increasing normal stress approaching negligible wear production. The experiments indicate that the steady-state frictional strength of these carbonate samples is best correlated with the power-density (= shear stress * slip-velocity, MW/m2). The observed friction/power-density relation show three regimes: (1) high (μ ~ 0.9), quasi-constant friction coefficient under low power-density of < 0.05 MW/m2; (2) low (μ ~ 0.3), quasi-constant friction coefficient under high power-density > 0.4 MW/m2; and (3) transition zone of friction coefficient dropping from ~ 0.9 to ~ 0.3 for intermediated power density ranging 0.05 - 0.4 MW/m2. During experiments with

  2. Correlations for perceived family environmental factors with substance use among adolescents in South Africa.

    PubMed

    Madu, S N; Matla, M P

    2003-04-01

    Perceived family environmental factors were used to predict self-reported use of substances (drugs or alcohol) among adolescents in South Africa. 435 high school students (ages 15 to 19 years, M=17.2 yr., SD=1.34) answered a questionnaire which included questions on demographic variables, the Family Environmental Scale, and questions on substances used (drugs or alcohol). Logistic regression analysis indicated that scores on family conflict and low family moral-religious emphasis were significantly associated with drug use (57.9% of the variance was accounted for) and use of alcohol (62.3% of the variance was accounted for). Programmes for the reduction of substance use among adolescents should include activities designed to reduce family conflict and strengthen family moral-religious emphasis.

  3. Factor structure and clinical correlates of the Food Thought Suppression Inventory within treatment seeking obese women with binge eating disorder.

    PubMed

    Barnes, Rachel D; Sawaoka, Takuya; White, Marney A; Masheb, Robin M; Grilo, Carlos M

    2013-01-01

    Prior research on the relations among eating behaviors and thought suppression is limited to a measure of general thought suppression, the White Bear Suppression Inventory. To address this limitation, researchers recently validated the Food Thought Suppression Inventory (FTSI). Analyses using this measure suggest that food thought suppression is distinct from and is more predictive of eating disorder psychopathology than is general thought suppression. The FTSI, however, has not yet been validated in clinical samples. The purpose of the current study is to examine the factor structure and clinical correlates of the FTSI within treatment seeking obese women with binge eating disorder (BED; N=128). Analyses revealed a valid and reliable one-factor measure of food thought suppression that was related to higher levels of eating and general psychopathology. The findings provide evidence for the use of the FTSI with obese women with BED. Future research should examine the psychometric properties of the FTSI within larger and more diverse samples.

  4. The Impact of Childhood Bullying among HIV-Positive Men: Psychosocial Correlates and Risk Factors

    PubMed Central

    Kamen, Charles; Bergstrom, Jessica; Vorasarun, Chaniga; Mardini, Mona; Patrick, Rudy; Lee, Susanne; Lazar, Rachael; Koopman, Cheryl; Gore-Felton, Cheryl

    2012-01-01

    Objectives While some studies have examined the deleterious effects of childhood bullying on adults, no studies to date have focused on the effects of bullying on Persons Living with HIV (PLH), a particularly at-risk population. PLH experience higher rates of childhood and adulthood physical and sexual abuse than the population at large, and experience of childhood abuse appears to be predictive of sexual and other risk behaviors in this population. Thus it remains critical to examine rates of childhood bullying and correlates of bullying in adult PLH. Methods A sample of 171 HIV-positive men over 18 years of age were recruited from the San Francisco Bay Area. All participants reported experiencing symptoms of traumatic stress. The participants were recruited as part of a larger study assessing a group intervention for individuals with HIV and symptoms of trauma. Self-report questionnaires were administered to assess participants’ exposure to bullying in childhood and trauma symptoms in adulthood. Results Bullying was commonly reported by men in the current sample, with 91% of the sample endorsing having experienced some level of bullying before age 18. Having been bullied in childhood was significantly (p < .05) associated with methamphetamine use in adulthood, difficulties with mood, and with symptoms of trauma. Results of a hierarchical regression equation found that report of bullying in childhood predicted additional, unique variance in trauma symptoms in adulthood above and beyond the effect of exposure to other forms of trauma, resulting in a better-fitting model. Conclusions The current study highlights the association between rate of childhood bullying and symptoms of trauma in adulthood, accounting for the effect of exposure to other forms of trauma. Given the impact of trauma symptoms on disease progression in PLH, exposure to bullying must be considered in any intervention aiming to reduce trauma symptoms or improve mental or physical health among HIV

  5. Stick-slip friction and wear of articular joints

    PubMed Central

    Lee, Dong Woog; Banquy, Xavier; Israelachvili, Jacob N.

    2013-01-01

    Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps—separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints. PMID:23359687

  6. Stick-slip friction and wear of articular joints.

    PubMed

    Lee, Dong Woog; Banquy, Xavier; Israelachvili, Jacob N

    2013-02-12

    Stick-slip friction was observed in articular cartilage under certain loading and sliding conditions and systematically studied. Using the Surface Forces Apparatus, we show that stick-slip friction can induce permanent morphological changes (a change in the roughness indicative of wear/damage) in cartilage surfaces, even under mild loading and sliding conditions. The different load and speed regimes can be represented by friction maps--separating regimes of smooth and stick-slip sliding; damage generally occurs within the stick-slip regimes. Prolonged exposure of cartilage surfaces to stick-slip sliding resulted in a significant increase of surface roughness, indicative of severe morphological changes of the cartilage superficial zone. To further investigate the factors that are conducive to stick-slip and wear, we selectively digested essential components of cartilage: type II collagen, hyaluronic acid (HA), and glycosaminoglycans (GAGs). Compared with the normal cartilage, HA and GAG digestions modified the stick-slip behavior and increased surface roughness (wear) during sliding, whereas collagen digestion decreased the surface roughness. Importantly, friction forces increased up to 2, 10, and 5 times after HA, GAGs, and collagen digestion, respectively. Also, each digestion altered the friction map in different ways. Our results show that (i) wear is not directly related to the friction coefficient but (ii) more directly related to stick-slip sliding, even when present at small amplitudes, and that (iii) the different molecular components of joints work synergistically to prevent wear. Our results also suggest potential noninvasive diagnostic tools for sensing stick-slip in joints.

  7. One-year neurodevelopmental outcome of very and late preterm infants: Risk factors and correlation with maternal stress.

    PubMed

    Coletti, Maria Franca; Caravale, Barbara; Gasparini, Corinna; Franco, Francesco; Campi, Francesca; Dotta, Andrea

    2015-05-01

    Although "late preterm" (LP) newborns (33-36 weeks of gestational age) represent more than 70% of all preterm labors, little is known about the relation between certain risk factors and developmental outcomes in LP compared to "very preterm" (≤32 weeks) children (VP). This study investigates: (1) LP and VP infants' development at 12 months of corrected age (CA) using the Bayley Scales of Infant Development - 3rd Edition (BSID-III); (2) correlation between BSID-III performances and maternal stress (using Parenting Stress Index-Short Form, PSI-SF) among LP and VP at 12 months CA; and (3) the link between known neonatal and demographic risk factors and developmental outcomes of LP and VP infants. For both LP and VP infants the Mean Cognitive (LP: 102.69±7.68; VP: 103.63±10.68), Language (LP: 96.23±10.08; VP: 99.10±10.37) and Motor (LP: 91.11±10.33; VP: 93.85±10.17) composite scores were in the normal range, without significant differences between the groups. Correlations between PSI-SF and BSID-III showed that in the VP group (but not LP), Language score was negatively related to the PSI-SF 'Difficult Child' scale (r=-.34, p<.05). Regression models revealed that cognitive performance was significantly predicted by physical therapy in LP and by cesarean section in VP infants. For VP only maternal education and length of stay predicted Language score, whereas physical therapy predicted Motor score. Results of the study underline the importance of considering cognitive, language and motor developments separately when assessing a preterm child's development. Prediction models of developmental performance confirm the influence of some known neonatal risk factors and indicate the need for further research on the role of sociodemographic risk factors.

  8. One-year neurodevelopmental outcome of very and late preterm infants: Risk factors and correlation with maternal stress.

    PubMed

    Coletti, Maria Franca; Caravale, Barbara; Gasparini, Corinna; Franco, Francesco; Campi, Francesca; Dotta, Andrea

    2015-05-01

    Although "late preterm" (LP) newborns (33-36 weeks of gestational age) represent more than 70% of all preterm labors, little is known about the relation between certain risk factors and developmental outcomes in LP compared to "very preterm" (≤32 weeks) children (VP). This study investigates: (1) LP and VP infants' development at 12 months of corrected age (CA) using the Bayley Scales of Infant Development - 3rd Edition (BSID-III); (2) correlation between BSID-III performances and maternal stress (using Parenting Stress Index-Short Form, PSI-SF) among LP and VP at 12 months CA; and (3) the link between known neonatal and demographic risk factors and developmental outcomes of LP and VP infants. For both LP and VP infants the Mean Cognitive (LP: 102.69±7.68; VP: 103.63±10.68), Language (LP: 96.23±10.08; VP: 99.10±10.37) and Motor (LP: 91.11±10.33; VP: 93.85±10.17) composite scores were in the normal range, without significant differences between the groups. Correlations between PSI-SF and BSID-III showed that in the VP group (but not LP), Language score was negatively related to the PSI-SF 'Difficult Child' scale (r=-.34, p<.05). Regression models revealed that cognitive performance was significantly predicted by physical therapy in LP and by cesarean section in VP infants. For VP only maternal education and length of stay predicted Language score, whereas physical therapy predicted Motor score. Results of the study underline the importance of considering cognitive, language and motor developments separately when assessing a preterm child's development. Prediction models of developmental performance confirm the influence of some known neonatal risk factors and indicate the need for further research on the role of sociodemographic risk factors. PMID:25779697

  9. Fault rheology beyond frictional melting.

    PubMed

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E; Hess, Kai-Uwe; Dingwell, Donald B

    2015-07-28

    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or "pseudotachylytes." It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics. PMID:26124123

  10. Fault rheology beyond frictional melting

    PubMed Central

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E.; Hess, Kai-Uwe; Dingwell, Donald B.

    2015-01-01

    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or “pseudotachylytes.” It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics. PMID:26124123

  11. Fault rheology beyond frictional melting.

    PubMed

    Lavallée, Yan; Hirose, Takehiro; Kendrick, Jackie E; Hess, Kai-Uwe; Dingwell, Donald B

    2015-07-28

    During earthquakes, comminution and frictional heating both contribute to the dissipation of stored energy. With sufficient dissipative heating, melting processes can ensue, yielding the production of frictional melts or "pseudotachylytes." It is commonly assumed that the Newtonian viscosities of such melts control subsequent fault slip resistance. Rock melts, however, are viscoelastic bodies, and, at high strain rates, they exhibit evidence of a glass transition. Here, we present the results of high-velocity friction experiments on a well-characterized melt that demonstrate how slip in melt-bearing faults can be governed by brittle fragmentation phenomena encountered at the glass transition. Slip analysis using models that incorporate viscoelastic responses indicates that even in the presence of melt, slip persists in the solid state until sufficient heat is generated to reduce the viscosity and allow remobilization in the liquid state. Where a rock is present next to the melt, we note that wear of the crystalline wall rock by liquid fragmentation and agglutination also contributes to the brittle component of these experimentally generated pseudotachylytes. We conclude that in the case of pseudotachylyte generation during an earthquake, slip even beyond the onset of frictional melting is not controlled merely by viscosity but rather by an interplay of viscoelastic forces around the glass transition, which involves a response in the brittle/solid regime of these rock melts. We warn of the inadequacy of simple Newtonian viscous analyses and call for the application of more realistic rheological interpretation of pseudotachylyte-bearing fault systems in the evaluation and prediction of their slip dynamics.

  12. Friction Stir Process Mapping Methodology

    NASA Technical Reports Server (NTRS)

    Kooney, Alex; Bjorkman, Gerry; Russell, Carolyn; Smelser, Jerry (Technical Monitor)

    2002-01-01

    In FSW (friction stir welding), the weld process performance for a given weld joint configuration and tool setup is summarized on a 2-D plot of RPM vs. IPM. A process envelope is drawn within the map to identify the range of acceptable welds. The sweet spot is selected as the nominal weld schedule. The nominal weld schedule is characterized in the expected manufacturing environment. The nominal weld schedule in conjunction with process control ensures a consistent and predictable weld performance.

  13. Friction force reduction triggers feet grooming behaviour in beetles.

    PubMed

    Hosoda, Naoe; Gorb, Stanislav N

    2011-06-01

    In insects, cleaning (grooming) of tarsal attachment devices is essential for maintaining their adhesive ability, necessary for walking on a complex terrain of plant surfaces. How insects obtain information on the degree of contamination of their feet has remained, until recently, unclear. We carried out friction force measurements on walking beetles Gastrophysa viridula (Coleoptera, Chrysomelidae) and counted grooming occurrence on stiff polymer substrata with different degrees of nanoroughness (root mean square: 28-288 nm). Since nanoscopically, rough surfaces strongly reduced friction and adhesion without contaminating feet, we were able to demonstrate, for the first time to our knowledge, that friction force between tarsal attachment pads and the substrate provides an insect with information on the degree of contamination of its attachment structures. We have shown that foot grooming occurrence correlates not only with the degree of contamination but also with the decrease of friction force. This result indicates that insects obtain information about the degree of contamination, not statically but rather dynamically and, presumably, use mechanoreceptors monitoring either tensile/compressive forces in the cuticle or tensile forces between leg segments.

  14. In-flight and laboratory vacuum-friction test results

    NASA Technical Reports Server (NTRS)

    Devine, E. J.; Evans, H. E.; Leasure, W. A.

    1973-01-01

    Coefficient of friction measurements were made for six unlubricated metal couples exposed to the space environment aboard the OV-1-13 spacecraft and exposed to laboratory vacuum. Materials studied included mutually soluble, partially soluble, and insoluble metal combinations. Two samples of each material couple were tested in space and in the laboratory using the disk and rider technique. Linear velocity was 0.10 cm/s (2.5 in/min) and rider normal load was 4.45 N (1 lb) for the gold versus silver couples and 8.90 N (2lb) for the other combinations. Results showed that friction data obtained in a clean ion-pumped laboratory vacuum of 10 to the minus 10 power materials with low mutual solubility can be correlated to operation in the vicinity of a typical scientific spacecraft that is exposed to an ambient pressure as low as 10 to the minus 12 power torr. The expected increase in coefficient of friction with solubility was shown. Material couples with high mutual solubility present the hazard of unpredictable drastic friction increase in orbit which may not be evident in laboratory testing at levels down to 10 to the minus 10 power torr. It was also shown that gross cold welding of unlubricated metals exposed to a satellite environment does not occur.

  15. Brownian motion and the hydrodynamic friction tensor for colloidal particles of complex shape.

    PubMed

    Kraft, Daniela J; Wittkowski, Raphael; ten Hagen, Borge; Edmond, Kazem V; Pine, David J; Löwen, Hartmut

    2013-11-01

    We synthesize colloidal particles with various anisotropic shapes and track their orientationally resolved Brownian trajectories using confocal microscopy. An analysis of appropriate short-time correlation functions provides direct access to the hydrodynamic friction tensor of the particles revealing nontrivial couplings between the translational and rotational degrees of freedom. The results are consistent with calculations of the hydrodynamic friction tensor in the low-Reynolds-number regime for the experimentally determined particle shapes.

  16. Adhesion, Deformation and Friction for Self-Assembled Monolayers on Au and Si Surfaces

    SciTech Connect

    Houston, J.E.; Hsung, R.P.; Kiely, J.D.; Mulder, J.A.; Zhu, X.Y.

    1999-07-07

    Using Interracial Force Microscopy (IFM), we investigated the tribological behavior of hexadecanethiol monolayer on Au and films of octadecyltrichlorosilane (ODTS), perfluorodecyltrichlorosilane (PFTS) and dodecane on Si. We observe a strong correlation between hysteresis in a compression cycle (measured via nanoindentation) and friction. Additionally, we suggest that the amount of hysteresis and friction in each film is related to its detailed molecular structure, especially the degree of molecular packing.

  17. Structural and phase transformations in Hadfield steel upon frictional loading in liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Korshunov, L. G.; Sagaradze, V. V.; Chernenko, N. L.

    2016-08-01

    Structural transformations that occur in 110G13 steel (Hadfield) upon sliding friction in liquid nitrogen (-196°C) have been investigated by metallographic, electron-microscopic, and X-ray diffraction methods. The frictional action was performed through the reciprocating sliding of a cylindrical indenter of quenched 110G13 steel over a plate of the studied steel. A like friction pair was immersed into a bath with liquid nitrogen. It has been shown that the Hadfield steel quenched from 1100°C under the given temperature conditions of frictional loading retains the austenitic structure completely. The frictional action forms in a surface layer up to 10 μm thick the nanocrystalline structure with austenite grains 10-50 nm in size and a hardness 6 GPa. Upon subsequent low-temperature friction, the tempering of steel at 400°C (3 h) and at 600°C (5 min and 5 h) brings about the formation of a large amount (tens of vol %) of ɛ (hcp) martensite in steel. The formation of this phase under friction is supposedly a consequence of the reduction in the stacking fault energy of Hadfield steel, which is achieved due to the combined action of the following factors: low-temperature cooling, a decrease in the carbon content in the austenite upon tempering, and the presence of high compressive stresses in the friction-contact zone.

  18. Prognostic Factors for Anastomotic Urinary Leakage Following Retropubic Radical Prostatectomy and Correlation With Voiding Outcomes.

    PubMed

    Cormio, Luigi; Di Fino, Giuseppe; Scavone, Carmen; Maroscia, Domenico; Mancini, Vito; Ruocco, Nicola; Bellanti, Francesco; Selvaggio, Oscar; Sanguedolce, Francesca; Lucarelli, Giuseppe; Carrieri, Giuseppe

    2016-04-01

    This study aimed to determine the occurrence and grade of cystographically detected urinary leakage (UL) in a contemporary series of open retropubic radical prostatectomy (RP), whether patients' clinical variables predict occurrence of UL, and whether occurrence of UL correlates with patients' voiding outcomes in terms of urinary continence and anastomotic stricture (AS). Enrolled patients underwent cystography 7 days after retropubic RP; in case of UL, the catheter was left in situ and cystography repeated at 7 days intervals until demonstrating absence of UL. Leakage was classified as grade I = extraperitoneal leak <6 cm, grade II = extraperitoneal leak >6 cm, grade III = leak freely extending in the small pelvis. Voiding was evaluated at 3, 6, and 12 months after RP using the 24-hour pad test and uroflowmetry; in cases of maximum flow rate <10 mL/s, urethrocystoscopy was carried out to determine presence and location of an AS. The first postoperative cystogram showed UL in 52.6% of patients (grade I in 48.1%, grade II in 21.5%, and grade III in 30.4% of the cases). Multivariate analysis demonstrated that patients with UL had significantly greater prostate volume (64.5 vs 34.8 cc, P < 0.001), loss of serum hemoglobin (4.77 vs 4.19 g/dL, P < 0.001), lower postoperative serum total proteins (4.85 vs 5.4 g/dL, P < 0.001), and higher rate of AS (20.6% vs. 2.8%, p < 0.001) than those without UL. Continence rate at 3, 6, and 12 months postoperatively was 34.2%, 76%, and 90%, respectively, in patients with UL compared with 77.5%, 80.3%, and 93% in patients without UL; such difference was statistically significant (P < 0.001) only at 3 months follow-up. ROC curve analysis showed that prostate volume and postoperative serum total proteins had the best AUC (0.821 and 0.822, respectively) and when combined, their positive and negative predictive values for UL were 90% and 93%, respectively. In conclusion, half of the patients undergoing open

  19. Prognostic Factors for Anastomotic Urinary Leakage Following Retropubic Radical Prostatectomy and Correlation With Voiding Outcomes

    PubMed Central

    Cormio, Luigi; Di Fino, Giuseppe; Scavone, Carmen; Maroscia, Domenico; Mancini, Vito; Ruocco, Nicola; Bellanti, Francesco; Selvaggio, Oscar; Sanguedolce, Francesca; Lucarelli, Giuseppe; Carrieri, Giuseppe

    2016-01-01

    Abstract This study aimed to determine the occurrence and grade of cystographically detected urinary leakage (UL) in a contemporary series of open retropubic radical prostatectomy (RP), whether patients’ clinical variables predict occurrence of UL, and whether occurrence of UL correlates with patients’ voiding outcomes in terms of urinary continence and anastomotic stricture (AS). Enrolled patients underwent cystography 7 days after retropubic RP; in case of UL, the catheter was left in situ and cystography repeated at 7 days intervals until demonstrating absence of UL. Leakage was classified as grade I = extraperitoneal leak <6 cm, grade II = extraperitoneal leak >6 cm, grade III = leak freely extending in the small pelvis. Voiding was evaluated at 3, 6, and 12 months after RP using the 24-hour pad test and uroflowmetry; in cases of maximum flow rate <10 mL/s, urethrocystoscopy was carried out to determine presence and location of an AS. The first postoperative cystogram showed UL in 52.6% of patients (grade I in 48.1%, grade II in 21.5%, and grade III in 30.4% of the cases). Multivariate analysis demonstrated that patients with UL had significantly greater prostate volume (64.5 vs 34.8 cc, P < 0.001), loss of serum hemoglobin (4.77 vs 4.19 g/dL, P < 0.001), lower postoperative serum total proteins (4.85 vs 5.4 g/dL, P < 0.001), and higher rate of AS (20.6% vs. 2.8%, p < 0.001) than those without UL. Continence rate at 3, 6, and 12 months postoperatively was 34.2%, 76%, and 90%, respectively, in patients with UL compared with 77.5%, 80.3%, and 93% in patients without UL; such difference was statistically significant (P < 0.001) only at 3 months follow-up. ROC curve analysis showed that prostate volume and postoperative serum total proteins had the best AUC (0.821 and 0.822, respectively) and when combined, their positive and negative predictive values for UL were 90% and 93%, respectively. In conclusion, half of the patients

  20. Organic geochemical correlation of Oklahoma crude oils using R- and Q-mode factor analysis

    SciTech Connect

    Engel, M.H.; Imbus, S.W. ); Zumberge, J.E. )

    1988-01-01

    For the past several decades, there has been a significant amount of crude oil exploration and production throughout the state of Oklahoma. Publications with respect to biological marker compound distributions and stable isotopic compositions of Oklahoma crude oils, their potential genetic relationships and possible sources have, however, been very limited. In this study, a detailed organic geochemical investigation of 46 crude oils from throughout the state of Oklahoma is presented. In addition to assessing similarities and differences of the oils with respect to reservoir ages and geologic provinces, an attempt was made to establish possible genetic relationships on the basis of combined R- and Q-mode factor analysis of source-related geochemical parameters. While the oils from throughout the state were found to be remarkably similar in chemical and stable isotopic composition, four genetic families of oils have been delineated based on this statistical approach. The possible effects of thermal alteration, migration, and multiple sources, i.e. mixing of the oil groups, are discussed.

  1. Considerations on risk factors correlated to the occurrence of gastric stump cancer

    PubMed Central

    Păduraru, DN; Nica, A; Ion, D; Handaric, M; Andronic, O

    2016-01-01

    Gastric stump cancer (GSC) is the malignant tumor that develops in the gastric remnant after partial gastrectomy was performed both for benign and malignant lesions. This paper presents the results of the case studies from the scientific literature, which focused on GSC, and has been published in the last 10 years. The search was performed with the help of the specific tools offered by the international databases. The subject was approached because of the constant rising incidence of GSC in the past few years, now reaching values between 1% and 7%. The outcome report is consistent and similar to the period that ended approximately 25 years ago, when general surgeons dedicated a significant part of their activity to treating gastric ulcer. Statistics revealed that the main risk factors are the following: the type of reconstruction after distal gastrectomy (Billroth I or Billroth II), the presence of duodenogastric reflux, the time between gastric resections, and the moment of diagnosis of gastric stump cancer, the initial pathology for which partial gastrectomy was performed, gender, age, helicobacter pylori infection, Epstein Barr virus infection and the presence of vagotomy. All the authors have significantly contributed to the article and have been involved in the writing of the manuscript in draft and any revision stages, and have read and approved the final version. PMID:27453741

  2. Considerations on risk factors correlated to the occurrence of gastric stump cancer.

    PubMed

    Păduraru, D N; Nica, A; Ion, D; Handaric, M; Andronic, O

    2016-01-01

    Gastric stump cancer (GSC) is the malignant tumor that develops in the gastric remnant after partial gastrectomy was performed both for benign and malignant lesions. This paper presents the results of the case studies from the scientific literature, which focused on GSC, and has been published in the last 10 years. The search was performed with the help of the specific tools offered by the international databases. The subject was approached because of the constant rising incidence of GSC in the past few years, now reaching values between 1% and 7%. The outcome report is consistent and similar to the period that ended approximately 25 years ago, when general surgeons dedicated a significant part of their activity to treating gastric ulcer. Statistics revealed that the main risk factors are the following: the type of reconstruction after distal gastrectomy (Billroth I or Billroth II), the presence of duodenogastric reflux, the time between gastric resections, and the moment of diagnosis of gastric stump cancer, the initial pathology for which partial gastrectomy was performed, gender, age, helicobacter pylori infection, Epstein Barr virus infection and the presence of vagotomy. All the authors have significantly contributed to the article and have been involved in the writing of the manuscript in draft and any revision stages, and have read and approved the final version. PMID:27453741

  3. The correlated factors of the uneven performances of the CDM host countries

    NASA Astrophysics Data System (ADS)

    Zhu, Jinshan

    2012-03-01

    The Kyoto Protocol’s Clean Development Mechanism (CDM) has experienced a rapid growth. Up to 2010, 2763 projects have been registered, standing for about 433 million ton CO2 equivalent (CO2-eq.) of annual carbon credits. However, the performances of CDM host countries are remarkably unbalanced. Previous literature suggested that economic and investment conditions, energy intensity, energy structure, the share of annual carbon credits from high global warming potential (GWP) green house gas (GHG), capacity and institutional buildings of domestic CDM governance can play important roles in promoting CDM. This quantitative analysis shows that domestic economic and investment conditions are the most decisive factors determining the performance of the CDM host countries. Additionally, the influence of carbon intensity of energy consumption is relatively modest, and energy intensity of GDP as well as the share of annual carbon credits from high GWP GHG is less significant. Moreover, several leading CDM countries are not as successful as they seem to be, when the influences of their vast territories, distinguished economic and investment conditions are excluded. Therefore, to simply transplant the CDM governances of these countries can hardly guarantee that other countries will boost their carbon credit outputs.

  4. Analysis on factors affecting household customers decision in using electricity at peak time and its correlation towards saving electricity

    NASA Astrophysics Data System (ADS)

    Pasasa, Linus; Marbun, Parlin; Mariza, Ita

    2015-09-01

    The purpose of this paper is to study and analyse the factors affecting customer decisions in using electricity at peak-load hours (between 17.00 to 22.00 WIB) and their behaviors towards electricity conservation in Indonesian household. The underlying rationale is to influence a reduction in energy consumption by stimulating energy saving behaviors, thereby reducing the impact of energy use on the environment. How is the correlation between the decisions in using electricity during peak load hours with the household customer's behavior towards saving electricity? The primary data is obtained by distributing questionnaires to customers of PT. PLN Jakarta Raya and Tangerang Distribution from Household segment. The data is analysed using the Structural Equation Model (SEM) and AMOS Software. The research is finding that all factors (Personal, Social, PLN Services, Psychological, and Cultural) are positively influence customer decision in using electricity at peak load hours. There is a correlation between the decisions in using electricity during peak load hours with the household customer's behavior towards saving electricity.

  5. Obesity-associated insulin resistance is correlated to adipose tissue vascular endothelial growth factors and metalloproteinase levels

    PubMed Central

    2012-01-01

    Background The expansion of adipose tissue is linked to the development of its vasculature, which appears to have the potential to regulate the onset of obesity. However, at present, there are no studies highlighting the relationship between human adipose tissue angiogenesis and obesity-associated insulin resistance (IR). Results Our aim was to analyze and compare angiogenic factor expression levels in both subcutaneous (SC) and omentum (OM) adipose tissues from morbidly obese patients (n = 26) with low (OB/L-IR) (healthy obese) and high (OB/H-IR) degrees of IR, and lean controls (n = 17). Another objective was to examine angiogenic factor correlations with obesity and IR. Here we found that VEGF-A was the isoform with higher expression in both OM and SC adipose tissues, and was up-regulated 3-fold, together with MMP9 in OB/L-IR as compared to leans. This up-regulation decreased by 23% in OB/-H-IR compared to OB/L-IR. On the contrary, VEGF-B, VEGF-C and VEGF-D, together with MMP15 was down-regulated in both OB/H-IR and OB/L-IR compared to lean patients. Moreover, MMP9 correlated positively and VEGF-C, VEGF-D and MMP15 correlated negatively with HOMA-IR, in both SC and OM. Conclusion We hereby propose that the alteration in MMP15, VEGF-B, VEGF-C and VEGF-D gene expression may be caused by one of the relevant adipose tissue processes related to the development of IR, and the up-regulation of VEGF-A in adipose tissue could have a relationship with the prevention of this pathology. PMID:22471305

  6. Linear regression models of floor surface parameters on friction between Neolite and quarry tiles.

    PubMed

    Chang, Wen-Ruey; Matz, Simon; Grönqvist, Raoul; Hirvonen, Mikko

    2010-01-01

    For slips and falls, friction is widely used as an indicator of surface slipperiness. Surface parameters, including surface roughness and waviness, were shown to influence friction by correlating individual surface parameters with the measured friction. A collective input from multiple surface parameters as a predictor of friction, however, could provide a broader perspective on the contributions from all the surface parameters evaluated. The objective of this study was to develop regression models between the surface parameters and measured friction. The dynamic friction was measured using three different mixtures of glycerol and water as contaminants. Various surface roughness and waviness parameters were measured using three different cut-off lengths. The regression models indicate that the selected surface parameters can predict the measured friction coefficient reliably in most of the glycerol concentrations and cut-off lengths evaluated. The results of the regression models were, in general, consistent with those obtained from the correlation between individual surface parameters and the measured friction in eight out of nine conditions evaluated in this experiment. A hierarchical regression model was further developed to evaluate the cumulative contributions of the surface parameters in the final iteration by adding these parameters to the regression model one at a time from the easiest to measure to the most difficult to measure and evaluating their impacts on the adjusted R(2) values. For practical purposes, the surface parameter R(a) alone would account for the majority of the measured friction even if it did not reach a statistically significant level in some of the regression models.

  7. Knee muscle strength correlates with joint cartilage T2 relaxation time in young participants with risk factors for osteoarthritis.

    PubMed

    Macías-Hernández, Salvador Israel; Miranda-Duarte, Antonio; Ramírez-Mora, Isabel; Cortés-González, Socorro; Morones-Alba, Juan Daniel; Olascoaga-Gómez, Andrea; Coronado-Zarco, Roberto; Soria-Bastida, María de Los Angeles; Nava-Bringas, Tania Inés; Cruz-Medina, Eva

    2016-08-01

    The objective of this study is to correlate T2 relaxation time (T2RT), measured by magnetic resonance imaging (MRI) with quadriceps and hamstring strength in young participants with risk factors for knee osteoarthritis (OA). A descriptive cross-sectional study was conducted with participants between 20 and 40 years of age, without diagnosis of knee OA. Their T2 relaxation time was measured through MRI, and their muscle strength (MS) was measured with an isokinetic dynamometer. Seventy-one participants were recruited, with an average age of 28.3 ± 5.5 years; 39 (55 %) were females. Negative correlations were found between T2RT and quadriceps peak torque (QPT) in males in the femur r = -0.46 (p = 0.01), tibia r = -0.49 (p = 0.02), and patella r = -0.44 (p = 0.01). In women, correlations were found among the femur r = -0.43 (p = 0.01), tibia r = -0.61 (p = 0.01), and patella r = -0.32 (p = 0.05) and among hamstring peak torque (HPT), in the femur r = -0.46 (p = 0.01), hamstring total work (HTW) r = -0.42 (p = 0.03), and tibia r = -0.33 (p = 0.04). Linear regression models showed good capacity to predict T2RT through QPT in both genders. The present study shows that early changes in femoral, tibial, and patellar cartilage are significantly correlated with MS, mainly QPT, and that these early changes might be explained by MS, which could play an important role in pre-clinical phases of the disease.

  8. Coseismic slip and early afterslip of the 2015 Illapel, Chile, earthquake: Implications for frictional heterogeneity and coastal uplift

    NASA Astrophysics Data System (ADS)

    Barnhart, William D.; Murray, Jessica R.; Briggs, Richard W.; Gomez, Francisco; Miles, Charles P. J.; Svarc, Jerry; Riquelme, Sebastian; Stressler, Bryan J.

    2016-08-01

    Great subduction earthquakes are thought to rupture portions of the megathrust, where interseismic coupling is high and velocity-weakening frictional behavior is dominant, releasing elastic deformation accrued over a seismic cycle. Conversely, postseismic afterslip is assumed to occur primarily in regions of velocity-strengthening frictional characteristics that may correlate with lower interseismic coupling. However, it remains unclear if fixed frictional properties of the subduction interface, coseismic or aftershock-induced stress redistribution, or other factors control the spatial distribution of afterslip. Here we use interferometric synthetic aperture radar and Global Position System observations to map the distribution of coseismic slip of the 2015 Mw 8.3 Illapel, Chile, earthquake and afterslip within the first 38 days following the earthquake. We find that afterslip overlaps the coseismic slip area and propagates along-strike into regions of both high and moderate interseismic coupling. The significance of these observations, however, is tempered by the limited resolution of geodetic inversions for both slip and coupling. Additional afterslip imaged deeper on the fault surface bounds a discrete region of deep coseismic slip, and both contribute to net uplift of the Chilean Coastal Cordillera. A simple partitioning of the subduction interface into regions of fixed frictional properties cannot reconcile our geodetic observations. Instead, stress heterogeneities, either preexisting or induced by the earthquake, likely provide the primary control on the afterslip distribution for this subduction zone earthquake. We also explore the occurrence of coseismic and postseismic coastal uplift in this sequence and its implications for recent hypotheses concerning the source of permanent coastal uplift along subduction zones.

  9. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Bares, Jonathan; Dijksman, Joshua; Ren, Jie; Zheng, Hu; Behringer, Robert

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ~ 0 . 6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how changing friction affects shear jamming. By applying a homogeneous simple shear, we study the effect of friction by using photoelastic disks either wrapped with Teflon to reduce friction or with fine teeth on the edge to increase friction. Shear jamming is still observed; however, the difference ϕJ -ϕS is smaller with lower friction. We also observe larger fluctuations due to initial configurations both at the lowest and the highest friction systems studied. Ongoing work is to use particles made of gelatin to reduce the friction coefficient to the order of 0.01. We acknowledge support from NSF Grant DMR1206351, NASA Grant NNX15AD38G and the William M. Keck Foundation.

  10. Effect of friction on shear jamming

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Bares, Jonathan; Dijksman, Joshua; Ren, Jie; Zheng, Hu; Behringer, Robert

    2015-11-01

    Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient μ ~ 0 . 6. Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ϕ between ϕJ (isotropic jamming) and a lowest ϕS for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how changing friction affects shear jamming. By applying a homogeneous simple shear, we study the effect of friction by using photoelastic disks either wrapped with Teflon to reduce friction or with fine teeth on the edge to increase friction. Shear jamming is still observed; however, the difference ϕJ -ϕS is smaller with lower friction. We also observe larger fluctuations due to initial configurations both at the lowest and the highest friction systems studied. Ongoing work is to characterize response from different friction systems under shear with information at local scale. We acknowledge support from NSF-DMR1206351, NASA NNX15AD38G and W.M. Keck Foundation.

  11. Correlation and periodicity analysis between herbage yields and climatic factors in the Tianshan Mountain,China in 22 year periods.

    NASA Astrophysics Data System (ADS)

    Jianlong, L.

    2009-04-01

    To analyze the relationship between herbage yields and climatic factors, 22 years of herbage yields and climate data were collected on the northern slope of the Tianshan Mountains region of western China. Using multiple regression analysis, maximum entropy spectrum analysis and cross spectrum analysis, it was clarified that fluctuation of climatic factors affected herbage yields and their periodical variation. The herbage yields were correlated significantly to the four climate factors including annual precipitation, annual means of relative humidity, absolute humidity and percentage of sunshine, but unrelated to the trend variable (the former year yield has little effects on the later) and other climatic factors. These clarified that long term variation of grassland productivity responded directly to changes of some climate factors in typical zone of arid continental climate. The results in co-spectrum and quadrature spectrum analysis revealed that the herbage yields had 4-year period similar to some moisture factors, and with 1/4 period delay. These findings demonstrated further that the fluctuation of some climatic elements (precipitation particularly) was the crucial factor affecting the variations of herbage yields of natural grassland in arid and semiarid ecosystem. The periodical change of vegetation and correlation with climate provide us a way to predict the herbage production according to the climate change, and it was important for the herdsmen to arrange predictively their animal production including rectifying their livestock population in natural grazing land and storing up the supply of forage timely for livestock use in cold season. Our finding in periodical variation of climatic element and plant yield further demonstrated the crucial driver of some climate factors on formation of herbage yields. The same or similar quasi-4-year period in climatic element and vegetation was due to that periodical variation of climatic element (especially

  12. Correlation between growth differentiation factor-15 and collagen metabolism indicators in patients with myocardial infarction and heart failure

    PubMed Central

    Wang, Fang-Fang; Chen, Bao-Xia; Yu, Hai-Yi; Mi, Lin; Li, Zi-Jian; Gao, Wei

    2016-01-01

    Background Growth differentiation factor (GDF)-15, a divergent member of the transforming growth factor beta super-family does appear to be up-regulated in response to experimental pressure overload and progression of heart failure (HF). HF frequently develops after myocardial infarction (MI), contributing to worse outcome. The aim of this study is to assess the correlation between GDF-15 levels and markers related to collagen turnover in different stages of HF. Methods The study consists of a cohort of 179 patients, including stable angina pectoris patients (AP group, n = 50), old MI patients without HF (OMI group, n = 56), old MI patients with HF (OMI-HF group, n = 38) and normal Control group (n = 35). Both indicators reflecting the synthesis and degradation rates of collagen including precollagen I N-terminal peptide (PINP), type I collagen carboxy-terminal peptide (ICTP), precollagen III N-terminal peptide (PIIINP) and GDF-15 were measured using an enzyme-linked inmunosorbent assay. Results The plasma GDF-15 level was higher in OMI-HF group (1373.4 ± 275.4 ng/L) than OMI group (1036.1 ± 248.6 ng/L), AP group (784.6 ± 222.4 ng/L) and Control group (483.8 ± 186.4 ng/L) (P < 0.001). The indicators of collagen turnover (ICTP, PINP, PIIINP) all increased in the OMI-HF group compared with Control group (3.03 ± 1.02 µg/L vs. 2.08 ± 0.95 µg/L, 22.2 ± 6.6 µg/L vs. 16.7 ± 5.1 µg/L and 13.2 ± 7.9 µg/L vs. 6.4 ± 2.1 µg/L, respectively; P < 0.01). GDF-15 positively correlated with ICTP and PIIINP (r = 0.302, P < 0.001 and r = 0.206, P = 0.006, respectively). GDF-15 positively correlated to the echocardiographic diastolic indicators E/Em and left atrial pressure (r = 0.349 and r = 0.358, respectively; P < 0.01), and inversely correlated to the systolic indicators left ventricular ejection fraction and the average of peak systolic myocardial velocities (Sm) (r = −0.623 and r = −0.365, respectively; P < 0.01). Conclusion Plasma GDF-15 is associated with

  13. Friction Forces during Sliding of Various Brackets for Malaligned Teeth: An In Vitro Study

    PubMed Central

    Crincoli, Vito; Di Bisceglie, Maria Beatrice; Balsamo, Antonio; Serpico, Vitaliano; Chiatante, Francesco; Pappalettere, Carmine; Boccaccio, Antonio

    2013-01-01

    Aims. To measure the friction force generated during sliding mechanics with conventional, self-ligating (Damon 3 mx, Smart Clip, and Time 3) and low-friction (Synergy) brackets using different archwire diameters and ligating systems in the presence of apical and buccal malalignments of the canine. Methods. An experimental setup reproducing the right buccal segment of the maxillary arch was designed to measure the friction force generated at the bracket/wire and wire/ligature interfaces of different brackets. A complete factorial plan was drawn up and a three-way analysis of variance (ANOVA) was carried out to investigate whether the following factors affect the values of friction force: (i) degree of malalignment, (ii) diameter of the orthodontic wire, and (iii) bracket/ligature combination. Tukey post hoc test was also conducted to evaluate any statistically significant differences between the bracket/ligature combinations analyzed. Results. ANOVA showed that all the above factors affect the friction force values. The friction force released during sliding mechanics with conventional brackets is about 5-6times higher than that released with the other investigated brackets. A quasilinear increase of the frictional forces was observed for increasing amounts of apical and buccal malalignments. Conclusion. The Synergy bracket with silicone ligature placed around the inner tie-wings appears to yield the best performance. PMID:23533364

  14. SRM propellant, friction/ESD testing

    NASA Technical Reports Server (NTRS)

    Campbell, L. A.

    1989-01-01

    Following the Pershing 2 incident in 1985 and the Peacekeeper ignition during core removal in 1987, it was found that propellant can be much more sensitive to Electrostatic Discharges (ESD) than ever before realized. As a result of the Peacekeeper motor near miss incident, a friction machine was designed and fabricated, and used to determine friction hazards during core removal. Friction testing with and electrical charge being applied across the friction plates resulted in propellant ignitions at low friction pressures and extremely low ESD levels. The objective of this test series was to determine the sensitivity of solid rocket propellant to combined friction pressure and electrostatic stimuli and to compare the sensitivity of the SRM propellant to Peacekeeper propellant. The tests are fully discussed, summarized and conclusions drawn.

  15. Friction Anisotropy with Respect to Topographic Orientation

    PubMed Central

    Yu, Chengjiao; Wang, Q. Jane

    2012-01-01

    Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties. PMID:23248751

  16. Friction coefficient dependence on electrostatic tribocharging

    PubMed Central

    Burgo, Thiago A. L.; Silva, Cristiane A.; Balestrin, Lia B. S.; Galembeck, Fernando

    2013-01-01

    Friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The literature presents a wealth of information on the electronic contributions to friction in metals and semiconductors but the effect of triboelectricity on friction coefficients of dielectrics is as yet poorly defined and understood. In this work, friction coefficients were measured on tribocharged polytetrafluoroethylene (PTFE), using three different techniques. As a result, friction coefficients at the macro- and nanoscales increase many-fold when PTFE surfaces are tribocharged, but this effect is eliminated by silanization of glass spheres rolling on PTFE. In conclusion, tribocharging may supersede all other contributions to macro- and nanoscale friction coefficients in PTFE and probably in other insulating polymers. PMID:23934227

  17. Friction coefficient dependence on electrostatic tribocharging.

    PubMed

    Burgo, Thiago A L; Silva, Cristiane A; Balestrin, Lia B S; Galembeck, Fernando

    2013-01-01

    Friction between dielectric surfaces produces patterns of fixed, stable electric charges that in turn contribute electrostatic components to surface interactions between the contacting solids. The literature presents a wealth of information on the electronic contributions to friction in metals and semiconductors but the effect of triboelectricity on friction coefficients of dielectrics is as yet poorly defined and understood. In this work, friction coefficients were measured on tribocharged polytetrafluoroethylene (PTFE), using three different techniques. As a result, friction coefficients at the macro- and nanoscales increase many-fold when PTFE surfaces are tribocharged, but this effect is eliminated by silanization of glass spheres rolling on PTFE. In conclusion, tribocharging may supersede all other contributions to macro- and nanoscale friction coefficients in PTFE and probably in other insulating polymers.

  18. Friction anisotropy with respect to topographic orientation.

    PubMed

    Yu, Chengjiao; Wang, Q Jane

    2012-01-01

    Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties.

  19. Static friction between rigid fractal surfaces

    NASA Astrophysics Data System (ADS)

    Alonso-Marroquin, Fernando; Huang, Pengyu; Hanaor, Dorian A. H.; Flores-Johnson, E. A.; Proust, Gwénaëlle; Gan, Yixiang; Shen, Luming

    2015-09-01

    Using spheropolygon-based simulations and contact slope analysis, we investigate the effects of surface topography and atomic scale friction on the macroscopically observed friction between rigid blocks with fractal surface structures. From our mathematical derivation, the angle of macroscopic friction is the result of the sum of the angle of atomic friction and the slope angle between the contact surfaces. The latter is obtained from the determination of all possible contact slopes between the two surface profiles through an alternative signature function. Our theory is validated through numerical simulations of spheropolygons with fractal Koch surfaces and is applied to the description of frictional properties of Weierstrass-Mandelbrot surfaces. The agreement between simulations and theory suggests that for interpreting macroscopic frictional behavior, the descriptors of surface morphology should be defined from the signature function rather than from the slopes of the contacting surfaces.

  20. Modeling of rock friction 2. Simulation of preseismic slip

    USGS Publications Warehouse

    Dieterich, J.H.

    1979-01-01

    The constitutive relations developed in the companion paper are used to model detailed observations of preseismic slip and the onset of unstable slip in biaxial laboratory experiments. The simulations employ a deterministic plane strain finite element model to represent the interactions both within the sliding blocks and between the blocks and the loading apparatus. Both experiments and simulations show that preseismic slip is controlled by initial inhomogeneity of shear stress along the sliding surface relative to the frictional strength. As a consequence of the inhomogeneity, stable slip begins at a point on the surface and the area of slip slowly expands as the external loading increases. A previously proposed correlation between accelerating rates of stable slip and growth of the area of slip is supported by the simulations. In the simulations and in the experiments, unstable slip occurs shortly after a propagating slip event traverses the sliding surface and breaks out at the ends of the sample. In the model the breakout of stable slip causes a sudden acceleration of slip rates. Because of velocity dependency of the constitutive relationship for friction, the rapid acceleration of slip causes a decrease in frictional strength. Instability occurs when the frictional strength decreases with displacement at a rate that exceeds the intrinsic unloading characteristics of the sample and test machine. A simple slider-spring model that does not consider preseismic slip appears to approximate the transition adequately from stable sliding to unstable slip as a function of normal stress, machine stiffness, and surface roughness for small samples. However, for large samples and for natural faults the simulations suggest that the simple model may be inaccurate because it does not take into account potentially large preseismic displacements that will alter the friction parameters prior to instability. Copyright ?? 1979 by the American Geophysical Union.

  1. Modelling cohesive, frictional and viscoplastic materials

    NASA Astrophysics Data System (ADS)

    Alehossein, Habib; Qin, Zongyi

    2016-06-01

    Most materials in mining and civil engineering construction are not only viscoplastic, but also cohesive frictional. Fresh concrete, fly ash and mining slurries are all granular-frictional-visco-plastic fluids, although solid concrete is normally considered as a cohesive frictional material. Presented here is both a formulation of the pipe and disc flow rates as a function of pressure and pressure gradient and the CFD application to fresh concrete flow in L-Box tests.

  2. Investigation of squeal noise under positive friction characteristics condition provided by friction modifiers

    NASA Astrophysics Data System (ADS)

    Liu, Xiaogang; Meehan, Paul A.

    2016-06-01

    Field application of friction modifiers on the top of rail has been shown to effectively curb squeal and reduce lateral forces, but performance can be variable, according to other relevant research. Up to now, most investigations of friction modifiers were conducted in the field, where it is difficult to control or measure important parameters such as angle of attack, rolling speed, adhesion ratio etc. In the present investigation, the effect of different friction modifiers on the occurrence of squeal was investigated on a rolling contact two disk test rig. In particular, friction-creep curves and squeal sound pressure levels were measured under different rolling speeds and friction modifiers. The results show friction modifiers can eliminate or reduce the negative slope of friction-creep curves, but squeal noise still exists. Theoretical modelling of instantaneous creep behaviours reveals a possible reason why wheel squeal still exists after the application of friction modifiers.

  3. Friction, Wear, and Surface Damage of Metals as Affected by Solid Surface Films

    NASA Technical Reports Server (NTRS)

    Bisson, Edmond E; Johnson, Robert L; Swikert, Max A; Godfrey, Douglas

    1956-01-01

    As predicted by friction theory, experiments showed that friction and surface damage of metals can be reduced by solid surface films. The ability of materials to form surface films that prevent welding was a very important factor in wear of dry and boundary lubricated surfaces. Films of graphitic carbon on cast irons, nio on nickel alloys, and feo and fe sub 3 o sub 4 on ferrous materials were found to be beneficial. Abrasive films such as fe sub 2 o sub 3 or moo sub 3 were definitely detrimental. It appears that the importance of oxide films to friction and wear processes has not been fully appreciated.

  4. BLCA1 expression is associated with angiogenesis of bladder cancer and is correlated with common pro-angiogenic factors

    PubMed Central

    Feng, Chenchen; Wang, Lujia; Ding, Guanxiong; Jiang, Haowen; Ding, Qiang; Wu, Zhong

    2015-01-01

    Aim: To study the association between expression of BLCA1 and clinicopathological parameters of bladder cancer. Method: Seventy-seven bladder cancer tissue samples were collected and primary antibody of BLCA1 was generated via animal inoculation. Immunohistochemical staining of BLCA1 and several pro-angiogenic factors were performed and evaluated semi-quantitatively. Statistical analyses were used to reveal the associations therein. Results: Expression of BLCA-1 was not associated with tumor characteristics such as occurrence, size, or onset pattern, but was associated with progression of tumor grade, stage, and with muscle invasion. BLCA1 expression was correlated with expression of VEGF, MMP9, IL1α, IL8, and microvessel density (MVD), but not with TNFα expression. Conclusion: BLCA1 is associated with progression of bladder cancer and paly a role in angiogenesis in bladder cancer. PMID:26629142

  5. Clinical correlates of plasma brain-derived neurotrophic factor in post-traumatic stress disorder spectrum after a natural disaster.

    PubMed

    Stratta, Paolo; Sanità, Patrizia; Bonanni, Roberto L; de Cataldo, Stefano; Angelucci, Adriano; Rossi, Rodolfo; Origlia, Nicola; Domenici, Luciano; Carmassi, Claudia; Piccinni, Armando; Dell'Osso, Liliana; Rossi, Alessandro

    2016-10-30

    Clinical correlates of plasma Brain-Derived Neurotrophic Factor (BDNF) have been investigated in a clinical population with Post Traumatic Stress Disorder (PTSD) symptoms and healthy control subjects who survived to the L'Aquila 2009 earthquake. Twenty-six outpatients and 14 control subjects were recruited. Assessments included: Structured Clinical Interview for DSM-IV Axis-I disorders Patient Version, Trauma and Loss Spectrum-Self Report (TALS-SR) for post-traumatic spectrum symptoms. Thirteen patients were diagnosed as Full PTSD and 13 as Partial PTSD. The subjects with full-blown PTSD showed lower BDNF level than subjects with partial PTSD and controls. Different relationship patterns of BDNF with post-traumatic stress spectrum symptoms have been reported in the three samples. Our findings add more insight on the mechanisms regulating BDNF levels in response to stress and further proofs of the utility of the distinction of PTSD into full and partial categories.

  6. Clinical correlates of plasma brain-derived neurotrophic factor in post-traumatic stress disorder spectrum after a natural disaster.

    PubMed

    Stratta, Paolo; Sanità, Patrizia; Bonanni, Roberto L; de Cataldo, Stefano; Angelucci, Adriano; Rossi, Rodolfo; Origlia, Nicola; Domenici, Luciano; Carmassi, Claudia; Piccinni, Armando; Dell'Osso, Liliana; Rossi, Alessandro

    2016-10-30

    Clinical correlates of plasma Brain-Derived Neurotrophic Factor (BDNF) have been investigated in a clinical population with Post Traumatic Stress Disorder (PTSD) symptoms and healthy control subjects who survived to the L'Aquila 2009 earthquake. Twenty-six outpatients and 14 control subjects were recruited. Assessments included: Structured Clinical Interview for DSM-IV Axis-I disorders Patient Version, Trauma and Loss Spectrum-Self Report (TALS-SR) for post-traumatic spectrum symptoms. Thirteen patients were diagnosed as Full PTSD and 13 as Partial PTSD. The subjects with full-blown PTSD showed lower BDNF level than subjects with partial PTSD and controls. Different relationship patterns of BDNF with post-traumatic stress spectrum symptoms have been reported in the three samples. Our findings add more insight on the mechanisms regulating BDNF levels in response to stress and further proofs of the utility of the distinction of PTSD into full and partial categories. PMID:27479108

  7. Elevated LRP6 levels correlate with vascular endothelial growth factor in the vitreous of proliferative diabetic retinopathy

    PubMed Central

    Gao, Xinxiao; Ma, Kai; Lu, Ning; Xu, Yongsheng; Hong, Tingting

    2015-01-01

    Purpose To measure intravitreal low-density lipoprotein receptor-related protein 6 (LRP6) and vascular endothelial growth factor (VEGF) levels in the eyes of patients with proliferative diabetic retinopathy (PDR) and to observe their correlation with PDR activity. Methods Fifty-five eyes of 55 patients were enrolled consecutively. Vitreous samples from 30 eyes with PDR and 25 eyes with nondiabetic macular disease were collected. Active PDR was present in 16 patients and quiescent PDR in 14 patients according to retinal neovascularization. LRP6 and VEGF concentrations in samples were determined using enzyme-linked immunosorbent assay (ELISA). Results ELISA revealed significant increases in the vitreous levels of VEGF in eyes affected with PDR compared to the controls (p<0.001). The mean concentrations of LRP6 were also higher in the vitreous samples from patients with PDR compared to the nondiabetic controls: 39.85 ng/ml and 15.48 ng/ml, respectively (p=0.002). In addition, the vitreous levels of LRP6 and VEGF were significantly higher in active PDR than in quiescent PDR (p=0.022 and p=0.015, respectively). Furthermore, a significant positive correlation was found between intravitreal levels of LRP6 and VEGF in patients with PDR (r=0.567, p=0.001). However, comparison of patients with PDR with controls revealed that the plasma levels of LRP6 were not significantly different between the two groups (p=0.636). Conclusions LRP6 and VEGF levels in the vitreous body from patients with PDR were increased and correlated mutually. LRP6 may be a good diagnostic biomarker and a new therapeutic target for PDR. PMID:26120271

  8. Positive correlations of age and parity with plasma concentration of macrophage migration inhibitory factor in Japanese black cows

    PubMed Central

    KOIZUMI, Motoya; NAHAR, Asrafun; YAMABE, Ryusei; KADOKAWA, Hiroya

    2016-01-01

    Plasma Macrophage migration inhibitory factor (MIF) concentration correlates positively with age, and negatively with self-rated health in women, and optimal MIF concentration may promote proper reproductive function. This study was conducted to evaluate the hypotheses that plasma MIF concentration changes with parturition or postpartum first ovulation, and that age in months and parity correlate with plasma MIF concentration in Japanese black cows. Western blotting utilizing an anti-MIF mouse monoclonal antibody of various tissues and plasma from females indicated that MIF expression was stronger in the anterior pituitary than in other tissues. We developed a competitive EIA utilizing the same anti-MIF mouse monoclonal antibody with sufficient sensitivity and reliable performance for measuring bovine plasma samples. We then measured MIF concentrations in bovine plasma collected from 4 weeks before parturition to 4 weeks after postpartum first ovulation. There was no significant difference in plasma MIF concentration pre- and post-parturition, or before and after the postpartum first ovulation. Plasma MIF concentrations were positively correlated (P < 0.01) with parity (r = 0.703), age in months on the day of parturition (r = 0.647), and age in months on the day of the postpartum first ovulation (r = 0.553) when we used almost all data, except for that from a third-parity cow with an abnormally high plasma MIF concentration. We therefore concluded that plasma MIF concentrations may increase with age in months and parity, but do not change either before and after parturition or before and after postpartum first ovulation in Japanese black cows. PMID:26853787

  9. How to teach friction: Experiments and models

    NASA Astrophysics Data System (ADS)

    Besson, Ugo; Borghi, Lidia; De Ambrosis, Anna; Mascheretti, Paolo

    2007-12-01

    Students generally have difficulty understanding friction and its associated phenomena. High school and introductory college-level physics courses usually do not give the topic the attention it deserves. We have designed a sequence for teaching about friction between solids based on a didactic reconstruction of the relevant physics, as well as research findings about student conceptions. The sequence begins with demonstrations that illustrate different types of friction. Experiments are subsequently performed to motivate students to obtain quantitative relations in the form of phenomenological laws. To help students understand the mechanisms producing friction, models illustrating the processes taking place on the surface of bodies in contact are proposed.

  10. Effect of grafted oligopeptides on friction.

    PubMed

    Iarikov, Dmitri D; Ducker, William A

    2013-05-14

    Frictional and normal forces in aqueous solution at 25 °C were measured between a glass particle and oligopeptide films grafted from a glass plate. Homopeptide molecules consisting of 11 monomers of either glutamine, leucine, glutamic acid, lysine, or phenylalanine and one heteropolymer were each "grafted from" an oxidized silicon wafer using microwave-assisted solid-phase peptide synthesis. The peptide films were characterized using X-ray photoelectron spectroscopy and secondary ion mass spectrometry. Frictional force measurements showed that the oligopeptides increased the magnitude of friction compared to that on a bare hydrophilic silicon wafer but that the friction was a strong function of the nature of the monomer unit. Overall we find that the friction is lower for more hydrophilic films. For example, the most hydrophobic monomer, leucine, exhibited the highest friction whereas the hydrophilic monomer, polyglutamic acid, exhibited the lowest friction at zero load. When the two surfaces had opposite charges, there was a strong attraction, adhesion, and high friction between the surfaces. Friction for all polymers was lower in phosphate-buffered saline than in pure water, which was attributed to lubrication via hydrated salt ions.

  11. Measurement of Gear Tooth Dynamic Friction

    NASA Technical Reports Server (NTRS)

    Rebbechi, Brian; Oswald, Fred B.; Townsend, Dennis P.

    1996-01-01

    Measurements of dynamic friction forces at the gear tooth contact were undertaken using strain gages at the root fillets of two successive teeth. Results are presented from two gear sets over a range of speeds and loads. The results demonstrate that the friction coefficient does not appear to be significantly influenced by the sliding reversal at the pitch point, and that the friction coefficient values found are in accord with those in general use. The friction coefficient was found to increase at low sliding speeds. This agrees with the results of disc machine testing.

  12. Epidermal growth factor, oestrogen and progesterone receptor expression in primary ovarian cancer: correlation with clinical outcome and response to chemotherapy.

    PubMed Central

    Scambia, G.; Benedetti-Panici, P.; Ferrandina, G.; Distefano, M.; Salerno, G.; Romanini, M. E.; Fagotti, A.; Mancuso, S.

    1995-01-01

    The expression of epidermal growth factor receptor (EGFR), oestrogen receptor (ER) and progesterone receptor (PR) was assayed by a radioreceptor method in 117 primary ovarian cancers. EGFR was not significantly related to any of the clinicopathological parameters examined. In patients with stage II-IV disease who underwent second-look surgery after primary chemotherapy, a significant correlation between high EGFR levels and poor response to chemotherapy was demonstrated (P = 0.031). Moreover, post-operative residual tumour showed an independent role in predicting chemotherapy response (P = 0.0007) and EGFR status showed a borderline significance (P = 0.052) in the multivariate analysis. No correlation between steroid hormone receptors and clinicopathological parameters was observed. Whereas a significant relationship was shown between EGFR positivity and a shorter overall survival (OS) (P = 0.0022) and progression-free survival (PFS) (P = 0.0033), patient survival was not related to steroid hormone receptor status. Among the parameters tested only stage, ascites and EGFR status retained an independent prognostic value in the multivariate analysis. PMID:7640219

  13. Unraveling transcription factor interactions with heterochromatin protein 1 using fluorescence lifetime imaging microscopy and fluorescence correlation spectroscopy

    PubMed Central

    Siegel, Amanda P.; Hays, Nicole M.

    2013-01-01

    Abstract. The epigenetic control of heterochromatin deposition is achieved through a network of protein interactions mediated by the heterochromatin protein 1 (HP1). In earlier studies, we showed that the CCAAT/enhancer-binding protein alpha (C/EBPα), a transcription factor that controls cell differentiation, localizes to heterochromatin, and interacts with HP1α. Here, deletion and mutagenesis are combined with live-cell imaging approaches to characterize these protein interactions. The results demonstrate that the basic region and leucine zipper (BZip) domain of C/EBPα is sufficient for the interaction with HP1α in regions of heterochromatin. Fluorescence correlation spectroscopy and cross-correlation (FCS and FCCS) revealed very different diffusion profiles for HP1α and the BZip protein, and co-expression studies indicated that the mobile fractions of these nuclear proteins diffuse independently of one another. The steady-state interactions of these proteins in regions of heterochromatin were monitored using Förster resonance energy transfer (FRET). A point mutation in HP1α, W174A, which disrupts the interactions with proteins containing the common PxVxL motif did not affect the interaction with the BZip protein. In contrast, the HP1α W41A mutation, which prevents binding to methylated histones, exhibited greatly reduced FRET efficiency when compared to the wild type HP1α or HP1αW174A. The functional significance of these interactions is discussed. PMID:23392382

  14. Annoyance Caused by Noise and Air Pollution during Pregnancy: Associated Factors and Correlation with Outdoor NO2 and Benzene Estimations.

    PubMed

    Fernández-Somoano, Ana; Llop, Sabrina; Aguilera, Inmaculada; Tamayo-Uria, Ibon; Martínez, María Dolores; Foraster, Maria; Ballester, Ferran; Tardón, Adonina

    2015-06-18

    This study aimed to describe the degree of annoyance among pregnant women in a Spanish cohort and to examine associations with proximity to traffic, NO2 and benzene exposure. We included 2457 participants from the Spanish Childhood and Environment study. Individual exposures to outdoor NO2 and benzene were estimated, temporally adjusted for pregnancy. Interviews about sociodemographic variables, noise and air pollution were carried out. Levels of annoyance were assessed using a scale from 0 (none) to 10 (strong and unbearable); a level of 8 to 10 was considered high. The reported prevalence of high annoyance levels from air pollution was 11.2% and 15.0% from noise; the two variables were moderately correlated (0.606). Significant correlations between NO2 and annoyance from air pollution (0.154) and that from noise (0.181) were observed. Annoyance owing to noise and air pollution had a low prevalence in our Spanish population compared with other European populations. Both factors were associated with proximity to traffic. In multivariate models, annoyance from air pollution was related to NO2, building age, and country of birth; annoyance from noise was only related to the first two. The health burden of these exposures can be increased by stress caused by the perception of pollution sources.

  15. Annoyance Caused by Noise and Air Pollution during Pregnancy: Associated Factors and Correlation with Outdoor NO2 and Benzene Estimations

    PubMed Central

    Fernández-Somoano, Ana; Llop, Sabrina; Aguilera, Inmaculada; Tamayo-Uria, Ibon; Martínez, María Dolores; Foraster, Maria; Ballester, Ferran; Tardón, Adonina

    2015-01-01

    This study aimed to describe the degree of annoyance among pregnant women in a Spanish cohort and to examine associations with proximity to traffic, NO2 and benzene exposure. We included 2457 participants from the Spanish Childhood and Environment study. Individual exposures to outdoor NO2 and benzene were estimated, temporally adjusted for pregnancy. Interviews about sociodemographic variables, noise and air pollution were carried out. Levels of annoyance were assessed using a scale from 0 (none) to 10 (strong and unbearable); a level of 8 to 10 was considered high. The reported prevalence of high annoyance levels from air pollution was 11.2% and 15.0% from noise; the two variables were moderately correlated (0.606). Significant correlations between NO2 and annoyance from air pollution (0.154) and that from noise (0.181) were observed. Annoyance owing to noise and air pollution had a low prevalence in our Spanish population compared with other European populations. Both factors were associated with proximity to traffic. In multivariate models, annoyance from air pollution was related to NO2, building age, and country of birth; annoyance from noise was only related to the first two. The health burden of these exposures can be increased by stress caused by the perception of pollution sources. PMID:26095869

  16. Separable projection integrals for higher-order correlators of the cosmic microwave sky: Acceleration by factors exceeding 100

    NASA Astrophysics Data System (ADS)

    Briggs, J. P.; Pennycook, S. J.; Fergusson, J. R.; Jäykkä, J.; Shellard, E. P. S.

    2016-04-01

    We present a case study describing efforts to optimise and modernise "Modal", the simulation and analysis pipeline used by the Planck satellite experiment for constraining general non-Gaussian models of the early universe via the bispectrum (or three-point correlator) of the cosmic microwave background radiation. We focus on one particular element of the code: the projection of bispectra from the end of inflation to the spherical shell at decoupling, which defines the CMB we observe today. This code involves a three-dimensional inner product between two functions, one of which requires an integral, on a non-rectangular domain containing a sparse grid. We show that by employing separable methods this calculation can be reduced to a one-dimensional summation plus two integrations, reducing the overall dimensionality from four to three. The introduction of separable functions also solves the issue of the non-rectangular sparse grid. This separable method can become unstable in certain scenarios and so the slower non-separable integral must be calculated instead. We present a discussion of the optimisation of both approaches. We demonstrate significant speed-ups of ≈100×, arising from a combination of algorithmic improvements and architecture-aware optimisations targeted at improving thread and vectorisation behaviour. The resulting MPI/OpenMP hybrid code is capable of executing on clusters containing processors and/or coprocessors, with strong-scaling efficiency of 98.6% on up to 16 nodes. We find that a single coprocessor outperforms two processor sockets by a factor of 1.3× and that running the same code across a combination of both microarchitectures improves performance-per-node by a factor of 3.38×. By making bispectrum calculations competitive with those for the power spectrum (or two-point correlator) we are now able to consider joint analysis for cosmological science exploitation of new data.

  17. Examination of fungi in domestic interiors by using factor analysis: Correlations and associations with home factors. [Cladosporium, Alternaria, Epicoccum, Aureobasidium, Aspergillus; Penicillium

    SciTech Connect

    Su, H.J.; Rotnitzky, A.; Spengler, J.D. ); Burge, H.A. )

    1992-01-01

    Factor analysis was utilized to investigate correlations among airborne microorganisms collected with Andersen samplers from homes in Topeka, Kans., during the winter of 1987 to 1988. The factors derived were used to relate microbial concentrations with categorical, questionnaire-derived descriptions of housing conditions. This approach successfully identified groups of common aboveground decay fungi including Cladosporium, Alternaria, Epicoccum, and Aureobasidium spp. The common soil fungi Aspergillus and Penicillium spp. were also separated as a group. These previously known ecological groupings were confirmed with air sampling data by a quantitative evaluation technique. The above ground decay fungi sampled indoors in winter were present at relatively high concentrations in homes with gas stoves for cooking, suggesting a possible association between these fungi and increased humidity from the combustion process. Elevated concentrations of the soil fungi were significantly associated with the dirt floor, crawl-space type of basement. Elevated concentrations of water-requiring fungi, such as Fusarium spp., were shown to be associated with water collection in domestic interiors. Also, elevated mean concentrations for the group of fungi including Cladosporium, Epicoccum, Aureobasidium, and yeast spp. were found to be associated with symptoms reported on a health questionnaire. This finding was consistent with the authors previous study of associations between respiratory health and airborne microorganisms by univariate logistic regression analysis.

  18. A statistical model for road surface friction forecasting applying optical road weather measurements

    NASA Astrophysics Data System (ADS)

    Hippi, M.; Juga, I.; Nurmi, P.

    2009-09-01

    Road surface friction is defined as the grip between car tyre and underlying surface. Poor friction often plays a crucial role in wintertime car accidents. Friction can decrease dramatically during snowfall or when wet road surface temperature falls below zero. Even a thin layer of ice or snow can decrease friction substantially increasing the risk of accidents. Many studies have shown that road surface temperature, road conditions and friction can fluctuate dramatically within short distances under specific weather situations. Friction or grip can be improved with road maintenance activities like salting and gritting. Salting will melt the ice or snow layer, whereas gritting will improve the grip. Salting is effective only above -5C temperatures. Light snowfall together with low temperatures can result in very slippery driving conditions. Finnish Road Administration's observing network covers c. 500 road weather stations in Finland. Almost 100 of them are equipped with optical sensors (in winter 2008-2009). The number of optical sensors has increased remarkably during past few years. The optical measuring devices are Vaisala DSC111 sensors which measure the depth of water, snow and ice on the road surface and also produce an estimate of the state of road and prevailing friction. Observation data from road weather stations with optical sensors were collected from winter 2007/08, and a couple of representative (from a weather perspective) stations were selected for detailed statistical analysis. The purpose of the study was to find a statistical relationship between the observed values and, especially, the correlation between friction and other road weather parameters. Consequently, a model based on linear regression was developed. With the model friction being the dependent variable, the independent variables having highest correlations were the composite of ice and snow (water content) on the road, and the road surface temperature. In the case of a wet road

  19. Hydrodynamic skin-friction reduction

    NASA Technical Reports Server (NTRS)

    Reed, Jason C. (Inventor); Bushnell, Dennis M. (Inventor); Weinstein, Leonard M. (Inventor)

    1991-01-01

    A process for reducing skin friction, inhibiting the effects of liquid turbulence, and decreasing heat transfer in a system involving flow of a liquid along a surface of a body includes applying a substantially integral sheet of a gas, e.g., air, immediately adjacent to the surface of the body, e.g., a marine vehicle, which has a longitudinally grooved surface in proximity with the liquid and with a surface material having high contact angle between the liquid and said wall to reduce interaction of the liquid, e.g., water, with the surface of the body, e.g., the hull of the marine vehicle.

  20. Fractional trajectories: Decorrelation versus friction

    NASA Astrophysics Data System (ADS)

    Svenkeson, A.; Beig, M. T.; Turalska, M.; West, B. J.; Grigolini, P.

    2013-11-01

    The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation of a fractional trajectory, that being an average over an ensemble of stochastic trajectories. Heretofore what has been interpreted as intrinsic friction, a form of non-Markovian dissipation that automatically arises from adopting the fractional calculus, is shown to be a manifestation of decorrelations between trajectories. We apply the general theory developed herein to the Lotka-Volterra ecological model, providing new insight into the final equilibrium state. The relaxation time to achieve this state is also considered.

  1. Epidermal growth factor receptor and B7-H3 expression in esophageal squamous tissues correlate to patient prognosis

    PubMed Central

    Song, Jianxiang; Shi, Woda; Zhang, Yajun; Sun, Mingzhong; Liang, Xiaodong; Zheng, Shiying

    2016-01-01

    Biomarkers that can serve as diagnostic and prognostic indicators of esophageal squamous cell carcinoma (ESCC) are urgently needed to help improve patient outcomes. Here, the expression of epidermal growth factor receptor (EGFR) and costimulatory molecule B7-H3, both of which have been implicated in tumor onset and progression in certain tumors, was investigated in relation to the clinical characteristics and survival outcomes of patients with ESCC. ESCC tissue samples were analyzed for 100 patients. Tumor and patient characteristics were recorded. Tissues were investigated for EGFR and B7-H3 staining by immunohistochemistry. Patients were followed for up to 96 months to determine overall survival (OS) and progression-free survival (PFS). High expression for EGFR (68.0%) and B7-H3 (66.0%) was observed in the majority of cases. High expression of either EGFR or B7-H3 was correlated with tumor invasion depth and clinical stage (P<0.05). Further, high expression of either EGFR or B7-H3 was correlated with worse survival outcomes. The estimated OS (38.1 months) and PFS (13.4 months) of patients with high expression of EGFR were lower than those of patients with low expression (69.3 and 68.1 months, P<0.05). The estimated OS (31.1 months) and PFS (13.1 months) of patients with high expression of B7-H3 were also lower than those of patients with low expression (69.3 and 66.6 months, P<0.05). Indeed, Cox multiple regression showed that OS and PFS were correlated with EGFR (relative risk =1.853, 1.875, respectively) and B7-H3 (relative risk =1.886, 2.061, respectively) (all P<0.05) expression level. Thus, EGFR and B7-H3 are highly expressed in tumor tissues of patients with ESCC. Their expression levels are correlated with tumor severity and survival, and therefore these may be viable biomarkers to aid in prognosis determination. PMID:27785073

  2. Direct observation of frictional contacts: New insights for state-dependent properties

    USGS Publications Warehouse

    Dieterich, J.H.; Kilgore, B.D.

    1994-01-01

    Rocks and many other materials display a rather complicated, but characteristic, dependence of friction on sliding history. These effects are well-described by empirical rate- and state-dependent constitutive formulations which have been utilized for analysis of fault slip and earthquake processes. We present a procedure for direct quantitative microscopic observation of frictional contacts during slip. The observations reveal that frictional state dependence represents an increase of contact area with contact age. Transient changes of sliding resistance correlate with changes in contact area and arise from shifts of contact population age. Displacement-dependent replacement of contact populations is shown to cause the diagnostic evolution of friction over a characteristic sliding distance that occurs whenever slip begins or sliding conditions change. ?? 1994 Birkha??user Verlag.

  3. Plasma levels of tumour necrosis factor and its soluble receptors correlate with clinical features and outcome of Hodgkin's disease patients.

    PubMed Central

    Warzocha, K.; Bienvenu, J.; Ribeiro, P.; Moullet, I.; Dumontet, C.; Neidhardt-Berard, E. M.; Coiffier, B.; Salles, G.

    1998-01-01

    A prospective study was performed to assess the use of plasma measurement of tumour necrosis factor (TNF), lymphotoxin alpha (LT alpha) and their soluble receptors (p55 and p75) for prognostic risk assignment in 61 patients with Hodgkin's disease. Plasma levels of TNF, p55 and p75, but not of LT alpha, were higher in Hodgkin's disease patients than in healthy controls. Plasma levels of TNF, p55 and p75 were associated with several prognostic factors for Hodgkin's disease, including those related to the host (age, performance status) and to the tumour (disease stage, extranodal site involvement, bulky tumour, serum levels of LDH and beta2-microglobulin, histology). Elevated plasma levels of TNF, p55 and p75 were also associated with several parameters reflecting an immune activation, including the presence of B symptoms, elevated serum levels of gammaglobulins, alkaline phosphatase and fibrinogen, as well as peripheral monocytosis, anaemia and low serum albumin levels. Finally, elevated TNF ligand receptor plasma markers were associated with a lower incidence of complete response to therapy and predicted shorter free-from-progression survival and overall survival of the patients. These results indicate that the plasma levels of TNF and its soluble receptors correlate with clinical features and outcome of patients with Hodgkin's disease. PMID:9649158

  4. The Impact of Gate Width Setting and Gate Utilization Factors on Plutonium Assay in Passive Correlated Neutron Counting

    DOE PAGESBeta

    Henzlova, Daniela; Menlove, Howard Olsen; Croft, Stephen; Favalli, Andrea; Santi, Peter Angelo

    2015-06-15

    In the field of nuclear safeguards, passive neutron multiplicity counting (PNMC) is a method typically employed in non-destructive assay (NDA) of special nuclear material (SNM) for nonproliferation, verification and accountability purposes. PNMC is generally performed using a well-type thermal neutron counter and relies on the detection of correlated pairs or higher order multiplets of neutrons emitted by an assayed item. To assay SNM, a set of parameters for a given well-counter is required to link the measured multiplicity rates to the assayed item properties. Detection efficiency, die-away time, gate utilization factors (tightly connected to die-away time) as well as optimummore » gate width setting are among the key parameters. These parameters along with the underlying model assumptions directly affect the accuracy of the SNM assay. In this paper we examine the role of gate utilization factors and the single exponential die-away time assumption and their impact on the measurements for a range of plutonium materials. In addition, we examine the importance of item-optimized coincidence gate width setting as opposed to using a universal gate width value. Finally, the traditional PNMC based on multiplicity shift register electronics is extended to Feynman-type analysis and application of this approach to Pu mass assay is demonstrated.« less

  5. Life Satisfaction Index among Elderly People Residing in Gorgan and Its Correlation with Certain Demographic Factors in 2013

    PubMed Central

    Chehregosha, Maryam; Bastaminia, Amir; Vahidian, Fatemeh; Mohammadi, Azam; Aghaeinejad, Aliakbar; Jamshidi, Ensiyeh; Ghasemi, Afsaneh

    2016-01-01

    Background: Aging is a universal phenomenon that will present itself as a dominant social and welfare challenge. Aim: This study was to examine life satisfaction among people residing in Gorgan and its correlation with certain demographic factors in 2013. Methods: A total of 250 elder people were selected for the study through the convenience sampling during 4 months. Data collected through life satisfaction index-A (LSIA). This instrument consists of 5 subscales, including, zest for life, resolution and fortitude, congruence between desired and achieved goals, positive self-concept and mood tone. The Multiple Linear Regression analysis was used in order to determine factors influencing the overall LSIA. Results: The overall LSIA score was 22.1 ± 7.5 with the maximum and minimum mean scores pertaining to the resolution and fortitude (6.1 ± 2.5) and the positive self-concept (3.1 ± 1.2) subscales, respectively. Level of education, type of living and gender were variables influencing the overall LSIA (P<0.05). Conclusion: Given the overall LSIA, it appears that future plans for this age group should be seriously revised along with cultural plans for promoting reverence for old age in the general public. PMID:27045397

  6. The Impact of Gate Width Setting and Gate Utilization Factors on Plutonium Assay in Passive Correlated Neutron Counting

    SciTech Connect

    Henzlova, Daniela; Menlove, Howard Olsen; Croft, Stephen; Favalli, Andrea; Santi, Peter Angelo

    2015-06-15

    In the field of nuclear safeguards, passive neutron multiplicity counting (PNMC) is a method typically employed in non-destructive assay (NDA) of special nuclear material (SNM) for nonproliferation, verification and accountability purposes. PNMC is generally performed using a well-type thermal neutron counter and relies on the detection of correlated pairs or higher order multiplets of neutrons emitted by an assayed item. To assay SNM, a set of parameters for a given well-counter is required to link the measured multiplicity rates to the assayed item properties. Detection efficiency, die-away time, gate utilization factors (tightly connected to die-away time) as well as optimum gate width setting are among the key parameters. These parameters along with the underlying model assumptions directly affect the accuracy of the SNM assay. In this paper we examine the role of gate utilization factors and the single exponential die-away time assumption and their impact on the measurements for a range of plutonium materials. In addition, we examine the importance of item-optimized coincidence gate width setting as opposed to using a universal gate width value. Finally, the traditional PNMC based on multiplicity shift register electronics is extended to Feynman-type analysis and application of this approach to Pu mass assay is demonstrated.

  7. Phenomenological Blasius-type friction equation for turbulent power-law fluid flows

    NASA Astrophysics Data System (ADS)

    Anbarlooei, H. R.; Cruz, D. O. A.; Ramos, F.; Silva Freire, A. P.

    2015-12-01

    We propose a friction formula for turbulent power-law fluid flows, a class of purely viscous non-Newtonian fluids commonly found in applications. Our model is derived through an extension of the friction factor analysis based on Kolmogorov's phenomenology, recently proposed by Gioia and Chakraborty. Tests against classical empirical data show excellent agreement over a significant range of Reynolds number. Limits of the model are also discussed.

  8. Phenomenological Blasius-type friction equation for turbulent power-law fluid flows.

    PubMed

    Anbarlooei, H R; Cruz, D O A; Ramos, F; Silva Freire, A P

    2015-12-01

    We propose a friction formula for turbulent power-law fluid flows, a class of purely viscous non-Newtonian fluids commonly found in applications. Our model is derived through an extension of the friction factor analysis based on Kolmogorov's phenomenology, recently proposed by Gioia and Chakraborty. Tests against classical empirical data show excellent agreement over a significant range of Reynolds number. Limits of the model are also discussed.

  9. Kozai Cycles and Tidal Friction

    SciTech Connect

    L, K; P.P., E

    2009-07-17

    Several studies in the last three years indicate that close binaries, i.e. those with periods of {approx}< 3 d, are very commonly found to have a third body in attendance. We argue that this proves that the third body is necessary in order to make the inner period so short, and further argue that the only reasonable explanation is that the third body causes shrinkage of the inner period, from perhaps a week or more to the current short period, by means of the combination of Kozai cycles and tidal friction (KCTF). In addition, once KCTF has produced a rather close binary, magnetic braking also combined with tidal friction (MBTF) can decrease the inner orbit further, to the formation of a contact binary or even a merged single star. Some of the products of KCTF that have been suggested, either by others or by us, are W UMa binaries, Blue Stragglers, X-ray active BY Dra stars, and short-period Algols. We also argue that some components of wide binaries are actually merged remnants of former close inner pairs. This may include such objects as rapidly rotating dwarfs (AB Dor, BO Mic) and some (but not all) Be stars.

  10. Comparison of Frictional Heating Models

    SciTech Connect

    Davies, Nicholas R; Blau, Peter Julian

    2013-10-01

    The purpose of this work was to compare the predicted temperature rises using four well-known models for frictional heating under a few selected conditions in which similar variable inputs are provided to each model. Classic papers by Archard, Kuhlmann-Wilsdorf, Lim and Ashby, and Rabinowicz have been examined, and a spreadsheet (Excel ) was developed to facilitate the calculations. This report may be used in conjunction with that spreadsheet. It explains the background, assumptions, and rationale used for the calculations. Calculated flash temperatures for selected material combinations, under a range of applied loads and sliding speeds, are tabulated. The materials include AISI 52100 bearing steel, CDA 932 bronze, NBD 200 silicon nitride, Ti-6Al-4V alloy, and carbon-graphite material. Due to the assumptions made by the different models, and the direct way in which certain assumed quantities, like heat sink distances or asperity dimensions, enter into the calculations, frictional hearing results may differ significantly; however, they can be similar in certain cases in light of certain assumptions that are shared between the models.

  11. Glassy dynamics of Brownian particles with velocity-dependent friction

    NASA Astrophysics Data System (ADS)

    Yazdi, Anoosheh; Sperl, Matthias

    2016-09-01

    We consider a two-dimensional model system of Brownian particles in which slow particles are accelerated while fast particles are damped. The motion of the individual particles is described by a Langevin equation with Rayleigh-Helmholtz velocity-dependent friction. In the case of noninteracting particles, the time evolution equations lead to a non-Gaussian velocity distribution. The velocity-dependent friction allows negative values of the friction or energy intakes by slow particles, which we consider active motion, and also causes breaking of the fluctuation dissipation relation. Defining the effective temperature proportional to the second moment of velocity, it is shown that for a constant effective temperature the higher the noise strength, the lower the number of active particles in the system. Using the Mori-Zwanzig formalism and the mode-coupling approximation, the equations of motion for the density autocorrelation function are derived. The equations are solved using the equilibrium structure factors. The integration-through-transients approach is used to derive a relation between the structure factor in the stationary state considering the interacting forces, and the conventional equilibrium static structure factor.

  12. Correlation between vascular endothelial growth factor and long-term prognosis in patients with acute myocardial infarction

    PubMed Central

    NIU, JIAMIN; HAN, XIA; QI, HUAXIN; YIN, JIE; ZHANG, ZHIQIANG; ZHANG, ZENGTANG

    2016-01-01

    The aim of the present study was to investigate the correlation between plasma the levels of vascular endothelial growth factor (VEGF) and major adverse cardiovascular events (MACE) in patients with acute myocardial infarction (AMI). A total of 124 patients with AMI undergoing emergency percutaneous coronary intervention (PCI) were selected, and plasma VEGF levels were measured 7 days after the onset of AMI using an enzyme-linked immunosorbent assay. The patients were divided into the L (≤190 pg/ml VEGF) and H (>190 pg/ml VEGF) groups, and were followed up every 2 months for an average of 12 months. MACE were recorded during follow-up. On the basis of these results, the patients were further divided into the MACE and non-MACE (N-MACE) groups, and the serum VEGF concentration was compared between the two groups. At the 6-month follow-up, the incidence of MACE in the H group was found to be significantly reduced compared with the L group. The serum VEGF concentration in the N-MACE group was significantly higher compared with the MACE group. Multinomial logistic regression revealed that reduced VEGF levels (β=1.243; 95% CI, 1.018–1.326; P=0.026) were independent risk factors for MACE. In conclusion, high plasma VEGF levels at 7 days after AMI onset facilitate the long-term prognosis in the same infarct zone in patients with AMI, while low plasma VEGF levels are independent risk factors for MACE. PMID:27347081

  13. Tumor necrosis factor inhibitor therapy in ankylosing spondylitis: differential effects on pain and fatigue and brain correlates.

    PubMed

    Wu, Qi; Inman, Robert D; Davis, Karen D

    2015-02-01

    Ankylosing spondylitis is associated with back pain and fatigue and impacts mobility but can be treated with tumor necrosis factor inhibitors (TNFi). The differential effects of TNFi treatment on multiple symptoms and the brain is not well delineated. Thus, we conducted a 2-part study. In study 1, we conducted a retrospective chart review in 129 ankylosing spondylitis patients to assess TNFi effects on pain, fatigue, motor function, mobility, and quality of life (QoL). After at least 10 weeks of TNFi treatment, patients had clinically significant improvements (>30%) in pain (including neuropathic pain), most disease and QoL factors, and normalized sensory detection thresholds. However, residual fatigue (mean = 5.3) was prominent. Although 60% of patients had significant relief of pain, only 22% of patients had significant relief of both pain and fatigue. Therefore, the preferential TNFi treatment effect on pain compared with fatigue could contribute to suboptimal effects on QoL. Part 2 was a prospective study in 14 patients to identify TNFi treatment effects on pain, fatigue, sensory and psychological factors, and brain cortical thickness based on 3T magnetic resonance imaging. Centrally, TNFi was associated with statistically significant cortical thinning of motor, premotor, and posterior parietal regions. Pain intensity reduction was associated with cortical thinning of the secondary somatosensory cortex, and pain unpleasantness reduction was associated with the cortical thinning of motor areas. In contrast, fatigue reduction correlated with cortical thinning of the insula, primary sensory cortex/inferior parietal sulcus, and superior temporal polysensory areas. This indicates that TNFi treatment produces changes in brain areas implicated in sensory, motor, affective, and cognitive functions.

  14. Correlation of Spatio-Temporal Contaminant Distribution, Land Use, and Hydrogeological Factors in the Karst Aquifers of Northern Puerto Rico

    NASA Astrophysics Data System (ADS)

    Torres Torres, N. I.; Padilla, I. Y.

    2015-12-01

    Karst aquifers are characterized by caves, springs, and sinkholes, and typified by interconnected fissures, fractures and conduits. These characteristics make these aquifers highly productive, and vulnerable to contamination. Previous studies in the northern karst aquifers of Puerto Rico have shown significant distribution of contaminants, including volatile organic compounds, phthalates and other contaminants of emerging concern, beyond demarked sources of contamination. This study develops spatial-temporal distributions of phthalate contaminants in the karst system of northern Puerto Rico and assesses statistical correlations between hydrogeologic factors and groundwater contamination with phthalates. Geographic Information Systems (GIS) tools and technologies, and statistical models are applied to attain these objectives. Results show that there is an extensive contamination with phthalates that varies with time. Contamination is present in the confined and shallow aquifers. Di-(2-ethylhexyl) phthalate (DEHP) is the most detected contaminant (20.6% of the sites). Diethyl phthalate and and dibutyl phthalate are also detected in 6.7% and 8.24% of the sites, respectively. Phthalates detected as mixtures components are significantly detected in areas of high urban and industrial development. They are also detected in areas within 5 miles of superfund sites and landfills. The results indicate that phthalate contamination is highly related to land use. Statistical models show that the hydraulic conductivity of the aquifers, sinkholes density, and time are significantly related to the presence of phthalates in groundwater. The extensive spatio-temporal contamination suggests that contaminants can persist in the environment for long periods of time, and that land use and hydrogeological factors are important factors contributing to the presence of emerging contaminants in karst systems.

  15. Modeling of friction-induced deformation and microstructures.

    SciTech Connect

    Michael, Joseph Richard; Prasad, Somuri V.; Jungk, John Michael; Cordill, Megan J.; Bammann, Douglas J.; Battaile, Corbett Chandler; Moody, Neville Reid; Majumdar, Bhaskar Sinha (New Mexico Institure of Mining and Technology)

    2006-12-01

    mechanical response of wear surfaces. Coatings are often required to mitigate friction and wear. Amongst other factors, plastic deformation of the substrate determines the coating-substrate interface reliability. Finite element modeling has been applied to predict the plastic deformation for the specific case of diamond-like carbon (DLC) coated Ni alloy substrates.

  16. Lubrication and friction prediction in metal-on-metal hip implants

    NASA Astrophysics Data System (ADS)

    Wang, F. C.; Brockett, C.; Williams, S.; Udofia, I.; Fisher, J.; Jin, Z. M.

    2008-03-01

    A general methodology of mixed lubrication analysis and friction prediction for a conforming spherical bearing in hip implants was developed, with particular reference to a typical metal-on-metal hip replacement. Experimental measurement of frictional torque for a similar implant was carried out to validate the theoretical prediction. A ball-in-socket configuration was adopted to represent the articulation between the femoral head and the acetabular cup under cyclic operating conditions of representative load and motion. The mixed lubrication model presented in this study was first applied to identify the contact characteristics on the bearing surfaces, consisting of both fluid-film and boundary lubricated regions. The boundary lubricated contact was assumed to occur when the predicted fluid film thickness was less than a typical boundary protein layer absorbed on the bearing surfaces. Subsequently, the friction was predicted from the fluid-film lubricated region with viscous shearing due to both Couette and Poiseuille flows and the boundary protein layer contact region with a constant coefficient of friction. The predicted frictional torque of the typical metal-on-metal hip joint implant was compared with the experimental measurement conducted in a functional hip simulator and a reasonably good agreement was found. The mixed lubrication regime was found to be dominant for the conditions considered. Although the percentage of the boundary lubricated region was quite small, the corresponding contribution to friction was quite large and the resultant friction factor was quite high.

  17. Lubrication and friction prediction in metal-on-metal hip implants.

    PubMed

    Wang, F C; Brockett, C; Williams, S; Udofia, I; Fisher, J; Jin, Z M

    2008-03-01

    A general methodology of mixed lubrication analysis and friction prediction for a conforming spherical bearing in hip implants was developed, with particular reference to a typical metal-on-metal hip replacement. Experimental measurement of frictional torque for a similar implant was carried out to validate the theoretical prediction. A ball-in-socket configuration was adopted to represent the articulation between the femoral head and the acetabular cup under cyclic operating conditions of representative load and motion. The mixed lubrication model presented in this study was first applied to identify the contact characteristics on the bearing surfaces, consisting of both fluid-film and boundary lubricated regions. The boundary lubricated contact was assumed to occur when the predicted fluid film thickness was less than a typical boundary protein layer absorbed on the bearing surfaces. Subsequently, the friction was predicted from the fluid-film lubricated region with viscous shearing due to both Couette and Poiseuille flows and the boundary protein layer contact region with a constant coefficient of friction. The predicted frictional torque of the typical metal-on-metal hip joint implant was compared with the experimental measurement conducted in a functional hip simulator and a reasonably good agreement was found. The mixed lubrication regime was found to be dominant for the conditions considered. Although the percentage of the boundary lubricated region was quite small, the corresponding contribution to friction was quite large and the resultant friction factor was quite high.

  18. High-velocity frictional strength across the Tohoku-Oki megathrust determined from surface drilling torque

    NASA Astrophysics Data System (ADS)

    Ujiie, Kohtaro; Inoue, Tomoya; Ishiwata, Junya

    2016-03-01

    High-velocity frictional strength is one of the primary factors controlling earthquake faulting. The Japan Trench Fast Drilling Project drilled through the shallow plate boundary fault, where displacement was ~50 m during the 2011 Tohoku-Oki earthquake. To determine downhole frictional strength, we analyzed the surface drilling torque data acquired at rotation rates equivalent to seismic slip rates (0.8-1.3 m/s). The results show a clear contrast in high-velocity frictional strength across the plate boundary fault: the apparent friction coefficient of frontal prism sediments (hemipelagic mudstones) in the hanging wall is 0.1-0.3, while that of the underthrust sediments (mudstone, laminar pelagic claystone, and chert) in the footwall increases to 0.2-0.4. The apparent friction coefficient of the smectite-rich pelagic clay in the plate boundary fault is 0.08-0.19, which is consistent with that determined from high-velocity (1.1-1.3 m/s) friction experiments. This suggests that surface drilling torque is useful in obtaining downhole frictional strength.

  19. Intraoral corrosion of self-ligating metallic brackets and archwires and the effect on friction

    NASA Astrophysics Data System (ADS)

    Tima, Lori Lynn

    The purpose of this study was to investigate how the frictional coefficient was affected due to intraoral use. A secondary aim of this study was to determine whether or not there was a relationship between corrosion of orthodontic alloys and friction via scanning electron microscopic qualitative analysis. Orthodontic brackets and 0.019 x 0.025 inch stainless steel archwires were collected and divided into three groups of n=10: used bracket and used wires (UBUW), used brackets and new wires (UBNW), and new brackets and new wires (NBNW). New materials were as-received from the manufacturer, and used materials were clinically used bracket and wires collected from patients following orthodontic treatment. Archwires were pulled through bracket slots at a rate of 0.5mm/min while friction forces were measured. Following a cleaning process, the surface topography of the bracket slots was examined under a scanning electron microscope (SEM). Based on a 1-factor MANOVA, there was no significant group effect (all p>0.05) on frictional forces. Partial eta squared values indicated that intraoral exposure had only a small effect on frictional forces (≤ 3%). Qualitative analysis of SEM images did not show an association between surface characteristics of the bracket slots and magnitude of frictional force. Results suggest that surface corrosion from intraoral use does not significantly affect friction at the bracket wire interface.

  20. Environmental effects on friction and wear of diamond and diamondlike carbon coatings

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Wu, Richard L. C.; Garscadden, Alan

    1992-01-01

    Reciprocating sliding friction experiments were conducted with a natural diamond flat, diamond film, and low and high density diamondlike carbon (DLC) films in contact with pin specimens of natural diamond and silicon nitride (Si3N4) both in humid air and dry air nitrogen. The results indicated that for natural diamond pin contacts the diamond films and the natural diamond flat were not susceptible to moisture but that moisture could increase both the coefficient of friction and the wear factors of the DLC films. The coefficients of friction and wear factors of the diamond films were generally similar to those of the natural diamond flat both in humid air and dry air nitrogen. In dry nitrogen the coefficients of friction of the high density DLC films in contact with pin specimens of both diamond and Si3N4 were generally low (about 0.02) and similar to those of the natural diamond flat and the diamond films. The wear factors of the materials in contact with both natural diamond and Si3N4 were generally in the ascending order of natural diamond flat, diamond film, high density DLC film, and low density DLC film. The moisture in the environment increased the coefficients of friction for Si3N4 pins in contact with all the materials. This increase in friction is due to the silicon oxide film produced on the surface of Si3N4 pins in humid air.