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Sample records for friction factor correlations

  1. Simple LMFBR axial-flow friction-factor correlation

    SciTech Connect

    Chan, Y.N.; Todreas, N.E.

    1982-12-01

    Complicated LMFBR axial lead-length averaged friction-factor correlations are reduced to an easy, ready-to-use function of bundle Reynolds number for wire-wrapped bundles. The function together with the power curves to calculate the associated constants are incorporated in a computer preprocessor, EZFRIC. The constants required for the calculation of the subchannels and bundle friction factors are derived and correlated into power curves of geometrical parameters. A computer program, FRIC, which can alternatively be used to accurately calculate these constants is also included. The accurate values of the constants and the corresponding values predicted by the power curves and percentage error of prediction are tabulated for a wide variety of geometries of interest.

  2. 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.

  3. 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'.

  4. 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.

  5. Correlation between friction and thickness of vanadium-pentoxide nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Taekyeong

    2015-11-01

    We investigated the correlation between friction and thickness of vanadium-pentoxide nanowires (V2O5 NWs) by using friction/atomic force microscopy (FFM/AFM). We observed that the friction signal generally increased with thickness in the FFM/AFM image of the V2O5 NWs. We constructed a two-dimensional (2D) correlation distribution of the frictional force and the thickness of the V2O5 NWs and found that they are strongly correlated; i.e., thicker NWs had higher friction. We also generated a histogram for the correlation factors obtained from each distribution and found that the most probable factor is ~0.45. Furthermore, we found that the adhesion force between the tip and the V2O5 NWs was about -3 nN, and that the friction increased with increasing applied load for different thicknesses of V2O5 NWs. Our results provide an understanding of tribological and nanomechanical studies of various one-dimensional NWs for future fundamental research.

  6. 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.

  7. 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.

  8. Heat transfer and friction correlations for wavy plate fin-and-tube heat exchangers

    SciTech Connect

    Kim, N.H.; Youn, J.H.; Webb, R.L.

    1996-12-31

    This paper deals with heat exchangers having plate fins of herringbone wave configuration. Correlations are developed to predict the air-side heat transfer coefficient and friction factor as a function of flow conditions and geometric variables of the heat exchanger. Correlations are provided for both staggered and in-line arrays of circular tubes. A multiple regression technique was used to correlate 41 wavy fin geometries by Beecher and Fagan (1987), Wang et al. (1995) and Beecher (1968). For the staggered layout, 92% of the heat transfer data are correlated within {+-}10%, and 91% of the friction data are correlated within {+-}15%.

  9. Correlation between frictional force and surface roughness of orthodontic archwires.

    PubMed

    Choi, Samjin; Hwang, Eun-Young; Park, Hun-Kuk; Park, Young-Guk

    2015-01-01

    Lateral force microscopy measures the lateral bending of the cantilever depending on the frictional force acting between the tip and surface. The aim of this study was to investigate and compare the relationship between the surface roughness and frictional resistance of four archwire and bracket combinations consisting of the 0.016-inch NiTi and 0.019 × 0.025-inch stainless steel archwires interacting clinically with two representative self-ligating brackets, active-type Clippy-C(®) ceramic self-ligating brackets, and passive-type Damon(®) stainless steel self-ligating brackets, using the lateral force microscopy technique. A 0.016-inch NiTi archwire interacting with passive-type Damon(®) stainless steel self-ligating brackets showed the smoothest surface roughness and the lowest frictional resistance compared to other combinations. The archwires interacting with passive-type Damon(®) stainless steel self-ligating brackets showed significantly lower surface roughness and frictional resistance than those interacting with active-type Clippy-C(®) ceramic self-ligating brackets. The frictional force in the in vivo archwire and bracket system increased with increasing surface roughness of the archwire. This positive correlation suggests that surface roughness can be used as an evaluating marker for estimating the efficiency of orthodontic treatment, rather than the direct measurement of frictional force. PMID:26018223

  10. Aircraft and ground vehicle friction correlation test results obtained under winter runway conditions during joint FAA/NASA Runway Friction Program

    NASA Technical Reports Server (NTRS)

    Yager, Thomas J.; Vogler, William A.; Baldasare, Paul

    1988-01-01

    Aircraft and ground vehicle friction data collected during the Joint FAA/NASA Runway Friction Program under winter runway conditions are discussed and test results are summarized. The relationship between the different ground vehicle friction measurements obtained on compacted snow- and ice-covered conditions is defined together with the correlation to aircraft tire friction performance under similar runway conditions.

  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. PMID:27136099

  13. 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. 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 Charge/mass dynamic structure factors of water and applications to dielectric friction and electroacoustic conversion.

    PubMed

    Sedlmeier, Felix; Shadkhoo, Shahriar; Bruinsma, Robijn; Netz, Roland R

    2014-02-01

    We determine time correlation functions and dynamic structure factors of the number and charge density of liquid water from molecular dynamics simulations. Using these correlation functions we consider dielectric friction and electro-acoustic coupling effects via linear response theory. From charge-charge correlations, the drag force on a moving point charge is derived and found to be maximal at a velocity of around 300 m/s. Strong deviations in the resulting friction coefficients from approximate theory employing a single Debye relaxation mode are found that are due to non-Debye-like resonances at high frequencies. From charge-mass cross-correlations the ultrasonic vibration potential is derived, which characterizes the conversion of acoustic waves into electric time-varying potentials. Along the dispersion relation for normal sound waves in water, the ultrasonic vibration potential is shown to strongly vary and to increase for larger wavelengths. PMID:24511957

  16. 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.

  17. 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).

  18. 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.

  19. Correlations for heat transfer and flow friction characteristics of compact plate-type heat exchangers

    NASA Astrophysics Data System (ADS)

    Tinaut, F. V.; Melgar, A.; Rahman Ali, A. A.

    1992-07-01

    Correlations for heat transfer and flow friction coefficients are provided for plane parallel plates and offset strip-fin plates over the ranges used in compact heat exchangers. Closed form expressions have been used to present these correlations. The proposed correlations allow one to adequately predict experimental data available for the heat exchanged and pressure losses in compact plate-type heat exchangers. The correlation cover continuously the full range from laminar to turbulent flow, for both short and long pipes. Suggestions to extend the correlations to other flow conditions are provided.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Fluid dynamics of airlift reactors; Two-phase friction factors

    SciTech Connect

    Garcia-Calvo, E. )

    1992-10-01

    Airlift loop reactors (ALR) are useful equipment in biotechnology in a wide range of uses, however their design is not a simple task since prediction of fluid dynamics in these reactors is difficult. Most of the different strategies found in the literature in order to predict two main parameters, namely, gas holdup and liquid velocity, are based on energy or momentum balances. The balances include frictional effects, and it is not yet clear how to predict these effects. The objective of this article is to show how criteria corresponding to one-phase flow may be used in order to predict the frictional effects in ALRs. Based on a model proposed by Garcia-Calvo (1989, 1991), we simulated experimental data of liquid velocity profiles and gas holdup obtained by Young et al. in an ALR with two different configurations. Experimental data obtained in other three external ALRs with different shapes and sizes are also simulated.

  7. Molecular simulation studies of nanoscale friction between phosphorylcholine self-assembled monolayer surfaces: Correlation between surface hydration and friction

    NASA Astrophysics Data System (ADS)

    He, Yi; Chen, Shengfu; Hower, Jason C.; Bernards, Matthew T.; Jiang, Shaoyi

    2007-08-01

    We performed all-atom molecular dynamics simulations to study the friction between surfaces covered with two phosphorylcholine self-assembled monolayers (PC-SAM) under shear. PC-SAM surfaces with a √7×√7R19° lattice structure and a parallel arrangement of the head groups were used as model zwitterionic surfaces. They provide a full representation of the zwitterionic nature of phospholipid surfaces, which are believed to play an important role in the lubrication of biological joints such as knees and hips. The surfaces were immersed in aqueous solutions and kept in contact with two regions of bulk water. Sodium chloride and potassium chloride solutions at various concentrations were employed to study the effects of the presence of ions on friction. The results show a strong relationship between surface hydration and friction. Higher ionic concentrations or ions with shorter Debye lengths cause a larger disruption to the hydration around the zwitterionic surfaces, leading to larger friction forces. In addition, the results show that under nanoscale confinement, the friction coefficients of PC-SAM surfaces in pure water are directly proportional to both shear velocity and surface separation distance. These results are comparable to previously published experimental studies.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. What Factors Does Friction Depend On? A Socio-Cognitive Teaching Intervention with Young Children

    ERIC Educational Resources Information Center

    Ravanis, Konstantinos; Koliopoulos, Dimitris; Hadzigeorgiou, Yannis

    2004-01-01

    The objective of this study was to investigate the effect of a socio-cognitive teaching strategy on young children. It tests their understanding of the factors that friction depends on when an object is projected across a horizontal surface. The study was conducted in three phases: pre-test, teaching intervention, and post-test. The sample…

  14. 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.

  15. 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

  16. 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.

  17. 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.

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

    Energy Science and Technology Software Center (ESTSC)

    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

  19. 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.

  20. 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.

  1. 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.

  2. 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)

  3. Patellofemoral Friction Syndrome: MRI correlation of morphologic and T2 cartilage imaging

    PubMed Central

    Subhawong, Ty K.; Thakkar, Rashmi S.; Padua, Abraham; Flammang, Aaron; Chhabra, Avneesh; Carrino, John A.

    2014-01-01

    OBJECTIVE To investigate whether patellofemoral T2 cartilage changes are associated with lateral patellofemoral friction syndrome (PFS), as indicated by edema-like signal within the superolateral infrapatellar (Hoffa) fat pad. METHODS In this IRB-approved retrospective study of 510 consecutive patients, 49 patients with 50 knee MR imaging exams demonstrating normal or low-grade patellofemoral cartilage abnormalities (WORMS score ≤2) were included. 22 exams with PFS (cases) were compared with an age- and gender-matched cohort of 28 exams without PFS (controls). 3T MR imaging was performed with multi-echo, spin echo T2 mapping. Two readers measured in consensus malalignment parameters, including patellar height index, tibial tuberosity to trochlear groove distance (TT-TG), and sulcus angle. Bulk T2 cartilage values in the lateral and medial patellofemoral compartment, central weight-bearing medial and lateral femoral condyles were measured independently. Interobserver agreement was quantified using concordance correlation coefficients (CCC). Demographics, anatomic measurements, WORMS scores, and cartilage T2 values were compared between cases and controls using Fisher’s exact test, Wilcoxon rank-sum, and mixed effects models. RESULTS Cases demonstrated higher patellar height index (p=0.002) and TT-TG (p=0.02). Interobserver agreement for T2 values was good overall (CCC range: 0.65–0.93). Cases demonstrated higher medial facet patellar bulk T2 (38.1±7.5 ms) versus controls (33.6±7.3 ms) (p=0.02); otherwise there were no significant differences in regional T2 values. CONCLUSION T2 mapping in patients with PFS demonstrates increased cartilage T2 in the medial patellar facet, possibly reflecting collagen alteration from early chondromalacia (softening) or increased water content related to altered contact pressures. PMID:24448504

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

    Energy Science and Technology Software Center (ESTSC)

    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

  5. 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).

  6. 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.

  7. What factors does friction depend on? A socio-cognitive teaching intervention with young children

    NASA Astrophysics Data System (ADS)

    Ravanis, Konstantinos; Koliopoulos, Dimitris; Hadzigeorgiou, Yannis

    2004-08-01

    The objective of this study was to investigate the effect of a socio-cognitive teaching strategy on young children. It tests their understanding of the factors that friction depends on when an object is projected across a horizontal surface. The study was conducted in three phases: pre-test, teaching intervention, and post-test. The sample consisted of 68 preschool children who were assigned to two groups according to age and cognitive ability, based on their responses to a pre-test. The children in the experimental group participated in activities that were approached from a socio-cognitive perspective while the children in the control group participated in the same activities but from a Piagetian perspective. A statistically significant difference was found (Mann-Whitney U-test), between the pre-test and the post-test, providing evidence for the effect of the socio-cognitive strategy on children's understanding of a 'precursor model' for the concept of friction.

  8. 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.

  9. One-dimensional, steady compressible flow with friction factor and uniform heat flux at the wall specified

    SciTech Connect

    Landram, C.S.

    1997-10-27

    The purpose of this work is to present generalized graphical results to readily permit passage design for monatomic gases, the results including accommodation of any independently specified friction factor, heat transfer coefficient, and wall heat flux. Only constant area passages are considered, and the specified wall heat flux is taken to be uniform.

  10. Mercury bioaccumulation factors and spurious correlations.

    PubMed

    Pollman, Curtis D; Axelrad, Donald M

    2014-10-15

    While bioaccumulation factors (BAF) - the ratio of biota contaminant concentrations (Cbiota) to aqueous phase contaminant concentrations (Cw) - are useful in evaluating the accumulation of mercury (Hg) and other contaminants for various trophic levels in aquatic ecosystems, reduction of the underlying relationship between Cbiota and Cw to a single ratio (BAF) has inherent risks, including spurious correlation. Despite a long and rich history of remonstrations in the literature, several very recent publications evaluating Hg-related BAFs have suffered from false conclusions based on spurious correlation, and thus it seems that periodic reminders of the causes and risks of these errors are required. Herein we cite examples and explanations for unsupported conclusions from publications where authors using BAF-Cw relationships fail to recognize the underlying statistical significance (or lack thereof) of direct relationships between Cw and Cbiota. This fundamental error leads to other problems, including ascribing mechanistic significance (e.g., mechanisms related to biota contaminant uptake) to "inverse" BAF-Cw relationships that reflect nothing more than regressing the log transformed inverse of Cw (i.e., negative log) against itself (i.e., positive log transformed), and using such regression models of BAF-Cw relationships that appear significant for predictive purposes, but are misleading. Spurious correlation arising in the analysis of BAF relationships can potentially appear in more subtle forms as well, including regressing variables such as dissolved organic carbon (DOC) that are correlated with Cw. We conclude that conducting a direct analysis by examining the relationship between Cbiota and Cw (or Cbiota and other variables) rather than evaluating a ratio (BAF) is less ambiguous and subject to error, more easily interpreted, and would lead to more supportable conclusions. PMID:25087751

  11. 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

  12. Is internal friction friction?

    USGS Publications Warehouse

    Savage, J.C.; Byerlee, J.D.; Lockner, D.A.

    1996-01-01

    Mogi [1974] proposed a simple model of the incipient rupture surface to explain the Coulomb failure criterion. We show here that this model can plausibly be extended to explain the Mohr failure criterion. In Mogi's model the incipient rupture surface immediately before fracture consists of areas across which material integrity is maintained (intact areas) and areas across which it is not (cracks). The strength of the incipient rupture surface is made up of the inherent strength of the intact areas plus the frictional resistance to sliding offered by the cracked areas. Although the coefficient of internal friction (slope of the strength versus normal stress curve) depends upon both the frictional and inherent strengths, the phenomenon of internal friction can be identified with the frictional part. The curvature of the Mohr failure envelope is interpreted as a consequence of differences in damage (cracking) accumulated in prefailure loading at different confining pressures.

  13. Laminar flow of constant-flux released gravity currents: Friction factor-Reynolds number relationship

    NASA Astrophysics Data System (ADS)

    Testik, Firat; Yilmaz, Nazli; Chowdhury, Mijanur

    2012-11-01

    This study aims to provide a relationship for the friction factor, Cf, in terms of the Reynolds number, Re, for two-dimensional constant-flux release gravity currents during viscous-buoyancy propagation phase. Motivation of this study was related to the pipeline disposal of high-concentration dredged fluid-mud. Such disposal operations form non-Newtonian gravity currents that propagate over the coastal seafloor. Our theoretical and experimental analysis resulted in Cf-Re relationships for both Newtonian (e.g. saline solution) and power-law (e.g. non-Newtonian fluid mud) fluids. A large number of experiments were conducted with different concentrations of both fluid mud mixtures (Kaolinite clay mixed with tap water) and saline solutions in a laboratory tank [dimensions: 4.3 m × 0.25 m × 0.5 m]. In the experiments, different depths of ambient fluid (tap water) were considered. To determine the experimental Cf values for the viscous-buoyancy propagation phase, theoretical analysis was conducted to relate Cf to the experimental measurables. Based upon experimental observations, Cf is shown to relate to Re of the gravity currents inversely for both Newtonian and power-law fluids. While Newtonian gravity currents revealed a single value of the constant of proportionality for the Cf-Re relationship, power-law gravity currents revealed multiple values of the constant of proportionality that depends on the fluid-mud concentration.

  14. 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.

  15. Interfacial friction in cocurrent upward annular flow

    NASA Astrophysics Data System (ADS)

    Hossfeld, L. M.; Bharathan, D.; Wallis, G. B.; Richter, H. J.

    1982-03-01

    Cocurrent upward annular flow is investigated, with an emphasis on correlating and predicting pressure drop. Attention is given to the characteristics of the liquid flow in the film, and the interaction of the core with the film. Alternate approaches are discussed for correlating suitably defined interfacial friction factors. Both approaches are dependent on knowledge of the entrainment in order to make predictions. Dimensional analysis is used to define characteristic parameters of the flow and an effort is made to determine, to the extent possible, the influences of these parameters on the interfacial friction factor.

  16. 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

  17. Five key factors determining pairwise correlations in visual cortex

    PubMed Central

    Sahani, Maneesh; Carandini, Matteo

    2015-01-01

    The responses of cortical neurons to repeated presentation of a stimulus are highly variable, yet correlated. These “noise correlations” reflect a low-dimensional structure of population dynamics. Here, we examine noise correlations in 22,705 pairs of neurons in primary visual cortex (V1) of anesthetized cats, during ongoing activity and in response to artificial and natural visual stimuli. We measured how noise correlations depend on 11 factors. Because these factors are themselves not independent, we distinguished their influences using a nonlinear additive model. The model revealed that five key factors play a predominant role in determining pairwise correlations. Two of these are distance in cortex and difference in sensory tuning: these are known to decrease correlation. A third factor is firing rate: confirming most earlier observations, it markedly increased pairwise correlations. A fourth factor is spike width: cells with a broad spike were more strongly correlated amongst each other. A fifth factor is spike isolation: neurons with worse isolation were more correlated, even if they were recorded on different electrodes. For pairs of neurons with poor isolation, this last factor was the main determinant of correlations. These results were generally independent of stimulus type and timescale of analysis, but there were exceptions. For instance, pairwise correlations depended on difference in orientation tuning more during responses to gratings than to natural stimuli. These results consolidate disjoint observations in a vast literature on pairwise correlations and point towards regularities of population coding in sensory cortex. PMID:26019310

  18. 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.

  19. Friction factors and heat transfer coefficients in turbulated cooling passages of different aspect ratios. I - Experimental results

    NASA Astrophysics Data System (ADS)

    Taslim, M. E.; Spring, S. D.

    1987-06-01

    In advanced turbine airfoil cooling designs where multiple-pass cooling circuits are used, a range of cooling passage aspect ratios (height/width) are encountered. The objective of this experimental investigation was to determine the effect that increasing aspect ratios have on friction factors and Nusselt numbers in internal cooling passages with rib-roughened (turbulated) surfaces. Aspect ratios ranging from 0.5 to 3.5 were tested over a Reynolds number range of 30,000 to 190,000. Each aspect ratio was tested at three different turbulator-height/hydraulic-diameter ratios and at a constant turbulator-height/pitch ratio of 0.10.

  20. 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

  1. 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.

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

    NASA Technical Reports Server (NTRS)

    Vary, A.

    1978-01-01

    A heuristic mathematical basis is proposed for the experimental correlations found between ultrasonic propagation factors and fracture toughness factors in metallic materials. A crack extension model is proposed wherein spontaneous stress (elastic) waves produced during microcracking are instrumental in promoting the onset of unstable crack extension. Material microstructural factors involved in this 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.

  3. Correlation and the mechanism of lithium ion diffusion with the crystal structure of Li7La3Zr2O12 revealed by an internal friction technique.

    PubMed

    Wang, X P; Gao, Y X; Xia, Y P; Zhuang, Z; Zhang, T; Fang, Q F

    2014-04-21

    The correlation and transport mechanism of lithium ions with the crystal structure of a fast lithium ion conductor Li7La3Zr2O12 are mainly investigated by internal friction (IF) and AC impedance spectroscopy techniques. Compared with the poor conductivity of tetragonal Li7La3Zr2O12, the Al stabilized cubic phase exhibits a good ionic conductivity that can be up to 1.9 × 10(-4) S cm(-1) at room temperature, which can be ascribed to the disordered distribution of lithium ions in the cubic phase. A well-pronounced relaxation IF peak (labeled as peak PC) is observed in the cubic phase while a very weak IF peak (labeled as PT) is observed in the tetragonal phase, further evidencing the difference in lithium ion migration in the two phases. Peak PC can be decomposed into two sub-peaks with the activation energy and the pre-exponential factor of relaxation time being E1 = 0.41 eV and τ01 = 1.2 × 10(-14) s for the lower temperature peak PC1 and E2 = 0.35 eV and τ02 = 1.9 × 10(-15) s for the higher temperature PC2 peak, respectively. Based on the crystalline structure of a cubic garnet-type Li7La3Zr2O12 compound, an atomistic mechanism of lithium ion diffusion via vacancies is suggested, i.e. 48g(96h) ↔ 48g(96h) for peak PC1 and 48g(96h) ↔ 24d for peak PC2, respectively. The weak PT peak in the tetragonal phase is preliminarily interpreted as due to the short jump process among neighboring octahedral sites and vacant tetrahedral sites. PMID:24604069

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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% ...

  10. Friction welding.

    NASA Technical Reports Server (NTRS)

    Moore, T. J.

    1972-01-01

    Results of an exploratory study of the structure and properties of friction welds in Udimet 700 (U-700) and TD-nickel (TD-Ni) bar materials, as well as dissimilar U-700/TD-Ni friction welds. Butt welds were prepared by friction welding 12.7-mm-diam U-700 bars and TD-Ni bars. Specimens for elevated temperature tensile and stress rupture testing were machined after a postweld heat treatment. Friction welding of U-700 shows great potential because the welds were found to be as strong as the parent metal in stress rupture and tensile tests at 760 and 980 C. In addition, the weld line was not detectable by metallographic examination after postheating. Friction welds in TD-Ni or between U-700 and TD-Ni were extremely weak at elevated temperatures. The TD-Ni friction welds could support only 9% as much stress as the base metal for 10-hour stress rupture life at 1090 C. The U-700/TD-Ni weld could sustain only 15% as much stress as the TD-Ni parent metal for a 10-hour stress rupture life at 930 C. Thus friction welding is not a suitable joining method for obtaining high-strength TD-Ni or U-700/TD-Ni weldments.

  11. Understanding Correlation: Factors that Affect the Size of r

    ERIC Educational Resources Information Center

    Goodwin, Laura D.; Leech, Nancy L.

    2006-01-01

    The authors describe and illustrate 6 factors that affect the size of a Pearson correlation: (a) the amount of variability in the data, (b) differences in the shapes of the 2 distributions, (c) lack of linearity, (d) the presence of 1 or more "outliers," (e) characteristics of the sample, and (f) measurement error. Also discussed are ways to…

  12. Adolescents Who Drive Under the Influence: Correlates and Risk Factors.

    ERIC Educational Resources Information Center

    Mayton, Daniel M., II; And Others

    This study was designed to determine the correlates or potential risk factors which predict whether an adolescent who drinks or uses drugs will refrain from driving under the influence, or will drive in this condition. A group of 426 rural high school seniors completed a questionnaire which assessed drug use patterns and previously identified risk…

  13. Correlations of MMPI factor scales with measures of the five factor model of personality.

    PubMed

    Costa, P T; Busch, C M; Zonderman, A B; McCrae, R R

    1986-01-01

    Two recent item factor analyses of the Minnesota Multiphasic Personality Inventory (MMPI) classified the resulting factors according to a conceptual scheme offered by Norman's (1963) five factor model. The present article empirically evaluates those classifications by correlating MMPI factor scales with self-report and peer rating measures of the five factor model in a sample of 153 adult men and women. Both sets of predictions were generally supported, although MMPI factors derived in a normal sample showed closer correspondences with the five normal personality dimensions. MMPI factor scales were also correlated with 18 scales measuring specific traits within the broader domains of Neuroticism, Extraversion, and Openness. The nine Costa, Zonderman, McCrae, and Williams (1985) MMPI factor scales appear to give useful global assessments of four of the five factors; other instruments are needed to provide detailed information on more specific aspects of normal personality. The use of the five factor model in routine clinical assessment is discussed. PMID:3820053

  14. 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…

  15. Explicitly correlated local second-order perturbation theory with a frozen geminal correlation factor.

    PubMed

    Manby, Frederick R; Werner, Hans-Joachim; Adler, Thomas B; May, Andrew J

    2006-03-01

    The recently introduced MP2-R122*A(loc) and LMP2-R122*A(loc) methods are modified to use a short-range correlation factor expanded as a fixed linear combination of Gaussian geminals. Density fitting is used to reduce the effort for integral evaluation, and local approximations are introduced to improve the scaling of the computational resources with molecular size. The MP2-F122*A(loc) correlation energies converge very rapidly with respect to the atomic orbital basis set size. Already with the aug-cc-pVTZ basis the correlation energies computed for a set of 21 small molecules are found to be within 0.5% of the MP2 basis set limit. Furthermore the short-range correlation factor leads to an improved convergence of the resolution of the identity, and eliminates problems with long-range errors in density fitting caused by the linear r12 factor. The DF-LMP2-F122*A(loc) method is applied to compute second-order correlation energies for molecules with up to 49 atoms and more than 1600 basis functions. PMID:16526841

  16. [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

  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. 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)

  19. 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

  20. 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

  1. Shape Factor Correlations of Hydraulic Conductance in Noncircular Capillaries.

    PubMed

    Patzek, T. W.; Kristensen, J. G.

    2001-04-15

    In Part I of this paper, we introduced the Mason-Morrow shape factor and the corner half-angles to capture the part of geometry of angular capillaries essential in pore network calculations of single- and two-phase flow in drainage and imbibition. We then used this shape factor to obtain simple expressions for the hydraulic conductance in single-phase flow through triangular, rectangular, and oval capillaries. In Part II, we study two-phase fluid flow along angular capillaries. The nonwetting fluid occupies the central part of the capillary, whereas the wetting liquid fills the corners. First, we verify the numerical solution obtained by Ransohoff-Radke for concave corner menisci by using a high-resolution finite element method with zero and infinite surface shear viscosity. We present new numerical results for corner flow domains bounded by convex menisci, i.e., for pinned contact lines and forced imbibition. We also present numerical solutions for two-phase flow with momentum transfer across the interface. We introduce a dimensionless hydraulic conductance of wetting fluid in the corners and correlate it with the corner filament shape factor, corner half-angle, and contact angle. By appropriate scaling, we obtain an accurate universal curve for flow conductance in the corners of an arbitrary angular capillary and for arbitrary contact angles. We give error estimates of the Ransohoff-Radke flow resistance factors, of the Zhou et al. analytical expressions for the resistance factors, and of our universal curves for the hydraulic conductance with no-slip and perfect-slip boundary conditions at the interface. Our expressions for the hydraulic conductance in corner flow of wetting liquid not only are valid for both concave and convex fluid interfaces but also are more accurate than any other published correlation. Copyright 2001 Academic Press. PMID:11401378

  2. 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

  3. 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.

  4. 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

  5. [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

  6. 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

  7. Child Psychological Maltreatment and Its Correlated Factors in Chinese Families.

    PubMed

    Zhang, Wenjing; Ma, Yating; Chen, Jingqi

    2016-01-01

    The present study aimed to explore the prevalence and frequency of child psychological maltreatment and its correlated factors in Chinese families. A cross-sectional investigation was conducted among 1,002 parents of primary school students in Yuncheng City, China. Data were collected using the self-report questionnaire anonymously. Results showed that 696 (69.5%) surveyed parents had different extents of psychological maltreatment toward their children in the past 3 months. The high prevalence of parental psychology maltreatment was significantly associated with high scores on parental over-reactivity and low scores on recognition of child psychology maltreatment. These findings indicate that it is urgent to develop cultural interventions to raise parents' awareness of preventing child psychological maltreatment and to help parents use nonviolent child rearing in China. PMID:27030213

  8. 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

  9. 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"…

  10. Correlation between B type natriuretic peptide and metabolic risk factors

    PubMed Central

    Zhu, Wen-Hua; Chen, Li-Ying; Dai, Hong-Lei; Chen, Jian-Hua; Chen, Yan

    2016-01-01

    Introduction It has been shown that B type natriuretic peptide (BNP) level can indicate cardiovascular disease. However, the association between BNP and metabolic risk factors is unknown. The aim of this study was to investigate the correlation between N-terminal pro-B type natriuretic peptide (NT-proBNP) and metabolic risk factors. Material and methods A total of 11,508 subjects were selected from those who underwent health examinations in our hospital. NT-proBNP, waist circumference, blood pressure, fasting plasma glucose and lipid profile were measured. The level of NT-proBNP was measured and classified into four stratifications (BNP ≥ 20 pg/ml, ≥ 40 pg/ml, ≥ 60 pg/ml, and ≥ 80 pg/ml) to analyze the relationship between BNP and metabolic risk factors. Results B type natriuretic peptide increased gradually with increasing age (p < 0.001). The BNP levels were significantly higher in women than in men (p < 0.001). Multivariate regression analysis showed a positive association between NT-proBNP levels and systolic blood pressure (p < 0.001), fasting plasma glucose (p < 0.05), and total cholesterol (p < 0.001 in women). The NT-proBNP levels were inversely associated with diastolic blood pressure, waist circumference, triglyceride, high-density lipoprotein, and LDL cholesterol. Logistic regression analysis demonstrated a close relationship between NT-proBNP and systolic blood pressure, fasting plasma glucose, and total cholesterol. In the BNP ≥ 60 pg/ml group, odds ratio (OR) values were 1.80, 1.56 and 1.54 (female) and 3.74, 1.59 and 1.51 (male), respectively. In the BNP ≥ 80 pg/ml group, OR values were 2.45, 1.65 and 1.84 (female) and 4.61, 1.66 and 1.75 (male), respectively. Conclusions NT-proBNP was independently associated with the main metabolic risk factors (systolic blood pressure, fasting plasma glucose, and total cholesterol). These findings suggest that the combined determination of NT-proBNP and the main metabolic risk factors could be

  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. Giardia intestinalis genotypes: Risk factors and correlation with clinical symptoms.

    PubMed

    Mohammed Mahdy, A K; Surin, Johari; Wan, K L; Mohd-Adnan, A; Al-Mekhlafi, M S Hesham; Lim, Y A L

    2009-10-01

    This study was conducted to identify genotypes related risk factors of Giardia intestinalis in an Orang Asli (aboriginal) community in Pahang, Malaysia. Stool samples were collected from 321 individuals aged between 2 and 76 years old, of whom 160 were males and 161 were females. Faecal samples were processed with trichrome staining technique for the primary identification of G. intestinalis. Molecular identification was carried out by the amplification of a partial SSU rRNA gene using nested PCR. PCR products were purified and genotyped. 42 samples successfully amplified from the 76 positive faecal samples, only 1 was Assemblage A, the rest were Assemblage B. Risk analysis based on the detected genotypes of Giardia using univariate analysis and logistic regression identified three significant risk factors of giardiasis caused by assemblage B which included children correlated with clinical symptoms of giardiasis (OR=2.4, 95% CI=1.13-5.12, p=0.019). Females infected with Assemblage B were at higher risk of manifesting gastroenteritis signs and symptoms (OR=3.9, 95% CI=1.50-10.31, p=0.004). It has been concluded that giardiasis is still a public health problem in Orang Asli community and most commonly caused by assemblage B. The dynamic of transmission is most probably anthroponotic which is human to human either directly or indirectly through contaminated food. This route of transmission should be considered in the control strategy of the disease. Mass treatment together with health education could be the most practical intervention for reducing the infection. Those at high risk should receive more attention from public health authorities. PMID:19560431

  13. 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.…

  14. 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…

  15. 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.

  16. 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…

  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. Measurements of heat transfer coefficients and friction factors in rib-roughened channels simulating leading-edge cavities of a modern turbine blade

    SciTech Connect

    Taslim, M.E.; Li, T.; Spring, S.D.

    1997-07-01

    Leading edge cooling cavities in modern gas turbine blades play an important role in maintaining the leading edge temperature at levels consistent with air foil design life. These cavities often have a complex cross-sectional shape to be compatible with the external contour of the blade at the leading edge. A survey of many existing geometries shows that, for analytical as well as experimental analyses, such cavities can be simplified in shape by a four-sided polygon with one curved side similar to the leading edge curvature, a rectangle with one semicircular side (often the smaller side) or a trapezoid, the smaller base of which is replaced by a semicircle. Furthermore, to enhance the heat transfer coefficient in these cavities, they are mostly roughened on three sides with ribs of different geometries. Experimental data on friction factors and heat transfer coefficients in such cavities are rare if not nonexistent. A liquid crystal technique was used in this experimental investigation to measure heat transfer coefficients in six test sections representing the leading-edge cooling cavities. Both straight and tapered ribs were configured on the two opposite sidewalls in a staggered arrangement with angles of attack to the mainstream flow, {alpha}, of 60 and 90 deg. The ribs on the curved surface were of constant cross section with an angle of attack 90 deg to the flow. Heat transfer measurements were performed on the straight sidewalls, as well as on the round surface adjacent to the blade leading edge. Effects such as rib angle of attack to the mainstream flow and constant versus tapered rib cross-sectional areas were also investigated. Nusselt numbers, friction factors, and thermal performances are reported for nine rib geometries in six test sections.

  19. Analysis of factors correlating with medical radiological examination frequencies.

    PubMed

    Jahnen, A; Järvinen, H; Olerud, H; Vassilieva, J; Vogiatzi, S; Shannoun, F; Bly, R

    2015-07-01

    The European Commission (EC) funded project Dose Datamed 2 (DDM2) had two objectives: to collect available data on patient doses from the radiodiagnostic procedures (X-ray and nuclear medicine) in Europe, and to facilitate the implementation of the Radiation Protection 154 Guidelines (RP154). Besides the collection of frequency and dose data, two questionnaires were issued to gather information about medical radiological imaging. This article analyses a possible correlation between the collected frequency data, selected variables from the results of the detailed questionnaire and national economic data. Based on a 35 countries dataset, there is no correlation between the gross domestic product (GDP) and the total number of X-ray examinations in a country. However, there is a significant correlation (p < 0.01) between the GDP and the overall CT examination frequency. High income countries perform more CT examinations per inhabitant. That suggests that planar X-ray examinations are replaced by CT examinations. PMID:25813479

  20. 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…

  1. 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…

  2. 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…

  3. Multifractal detrended cross-correlation analysis between PM2.5 and meteorological factors

    NASA Astrophysics Data System (ADS)

    Zhang, Chen; Ni, Zhiwei; Ni, Liping

    2015-11-01

    PM2.5 pollution has become one of the most serious air pollution in China. The cross-correlations between PM2.5 concentration and meteorological factors (i.e., temperature, air pressure, relative humidity and wind speed) in Beijing and Hong Kong are discussed in this paper. We use the multifractal detrended cross-correlation analysis (MF-DCCA) to analyze the cross-correlations, and study further the asymmetric characteristics of cross-correlations by multifractal asymmetric detrended cross-correlation analysis (MF-ADCCA). The experimental results show that the cross-correlations between PM2.5 concentration and four meteorological factors are multifractal and anti-persistent, and the strength of multifractality of Beijing is stronger than that of Hong Kong. Meanwhile, the cross-correlations between PM2.5 concentration and meteorological factors are asymmetric, and the asymmetric cross-correlations are multifractal.

  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. 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

  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. 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.

  8. Dissection of genomic correlation matrices of US Holsteins using multivariate factor analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aim of the study was to compare correlation matrices between direct genomic predictions for 31 production, fitness and conformation traits both at genomic and chromosomal level in US Holstein bulls. Multivariate factor analysis was used to quantify basic features of correlation matrices. Factor extr...

  9. 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

  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. PMID:27160557

  11. 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.

  12. 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

  13. 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. PMID:25884490

  14. [Vulvovaginitis: correlation with predisposing factors, clinical manifestations and microbiological studies].

    PubMed

    Fosch, S; Fogolín, N; Azzaroni, E; Pairetti, N; Dana, L; Minacori, H; Tita, I; Redona, M; Gribaudo, G

    2006-01-01

    Vaginitis (V) and bacterial vaginosis (BV) are one of the most common reasons the middle class patient has to consult a gynaecologist. The purpose of this work is to analyse samples of vaginal fluid targeting the infection etiology and its relationship to related factors: (intrauterine devices, contraceptive pills, condoms, use of antibiotics), symptoms and signs. From November 1, 2001 to October 30, 2003, a cross-section study was carried out of 400 nonpregnant, sexually active women in an age range of 15 to 55. Vaginal secretions were analysed by Gram and Giemsa stains and culturing was used. Interpreting: (1) normal--no observable changes, absence of the infecting agents studied here; (2) infected--changes observed: bacterial vaginosis, vaginal candidiasis (CV) and trichomoniasis (TC) and (3) imbalance in vagina ecology, with medium alterations (D). Results obtained: (1) normal: 209 (52.2%); infected: 115 (28.8%) including 13.5% VB, 12.5% CV, 2.8% TC, and (3) 76 (19%) with imbalance of vagina ecology. Bacterial vaginosis and flora imbalance were related to the use of intrauterine devices, and candidiasis to contraceptive pills and previous antibiotic use. The number of symptoms increased in patients with vaginal candidiasis and trichomoniasis. PMID:17370572

  15. Active Dynamic Frictional Probes

    NASA Astrophysics Data System (ADS)

    Steimel, Joshua; Aragones, Juan; Alexander-Katz, Alfredo

    2015-03-01

    In biological systems there are a myriad of interactions occurring instantaneously and these interactions can vary drastically in the strength of the interaction, the speed at which this interaction occurs, and the duration of the interaction. When multiple interactions occur any of these factors can determine which particular interaction is dominant. However, currently it is extremely difficult to measure binding affinity, Kon, and Koff rates in a relatively high throughput manner. Here we propose a novel and versatile system that will be able to detect differences in binding affinity of wide range of transient interactions and will be able to extract the relevant time scales of these interactions. Our system will utilize ferromagnetic particles that can be easily functionalized with a receptor of interest and the substrate will be coated in the corresponding ligand. A rotating magnetic field will cause particles, henceforth referred to as rollers, to rotate and this rotational motion will be converted into translational motion via the effective frictional force induced by interaction that is being probed. By measuring the translation of the rollers to a baseline, where only hydrodynamic friction occurs, we can measure the relative strength of the interactions. We can also potentially measure kinetic information by changing the frequency at which the magnetic field rotates, since changing the frequency at which the bead rotates is akin to changing the time allowed for bond formation. We will measure a wide range of interaction including ionic, metal-ion coordination, IgG-Protein A complex, and biotin-streptavidin complex.

  16. Frictional Characteristics of graphene

    NASA Astrophysics Data System (ADS)

    Lee, Changgu; Carpick, Robert; Hone, James

    2009-03-01

    The frictional characteristics of graphene were characterized using friction force microscopy (FFM). The frictional force for monolayer graphene is more than twice that of bulk graphite, with 2,3, and 4 layer samples showing a monotonic decrease in friction with increasing sample thickness. Measurements on suspended graphene membranes show identical results, ruling out substrate effects as the cause of the observed variation. Likewise, the adhesion force is identical for all samples. The frictional force is independent of load within experimental uncertainty, consistent with previous measurements on graphite. We consider several possible explanations for the origin of the observed thickness dependence.

  17. 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.

  18. 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.

  19. 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.

  20. The Measurement and Analysis Risk Factors Dependence Correlation in Software Project

    NASA Astrophysics Data System (ADS)

    Jianjie, Ding; Hong, Hou; Kegang, Hao; Xiaoqun, Guo

    The complexity of software process leads to that there are all kinds of fuzzy correlations among different process management risk factors, such as dependence correlation among software risk factors. It’s difficult to analyze risk data directly by mathematic tools because that risk data is uncertain and rough. Based on the rough set theory and the data in risk management library, the risk factors dependence correlation analysis system(RFDCAS) is established, and the dependence coefficient and its calculate formula on the base of equivalence class is suggested. The RFDCAS unveils the dependence correlation among risk factors contribute to risk management, and can help discover the problems in the software process improvement management.

  1. Correlation of Lithium Ionic Diffusion with Nb Concentration in Li7-xLa3Zr2-xNbxO12 Evaluated by an Internal Friction Method

    NASA Astrophysics Data System (ADS)

    Xia, Yu; Wang, Xian-Ping; Gao, Yun-Xia; Hu, Jing; Zhuang, Zhong; Guo, Li-Jun; Fang, Qian-Feng; Liu, Chang-Song

    2014-01-01

    Solid lithium-ion conductors Li7-xLa3Zr2-xNbxO12 (x = 0.25, 0.5, 1, 1.5) with cubic garnet structure are successfully prepared by a solid state reaction method, and the effects of Nb concentration on lithium ion diffusion are investigated by means of internal friction (IF) technique. A prominent relaxation-type IF peak (actually composed of two components) is observed in each Nb doped Li7La3Zr2O12 compound: with apeak PL at lower temperature and a peak PH at higher temperature. The mechanisms of the two components are suggested to be associated with two diffusion processes of lithium ions via vacancies: 48g ↔ 48g and 48g ↔ 24d. The relaxational strength of the IF peak gradually decreases, which is accompanied by the activation energy increasing from 0.45 eV to 0.64 eV with the increasing Nb doping level. The corresponding mechanism is ascribed to originate from lattice contraction as well as the lower concentration of diffusion ions induced by the substitution of Zr4+ by Nb5+.

  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. PIV-based investigation of the skin friction of the flow over random fibrous media

    NASA Astrophysics Data System (ADS)

    Mirbod, Parisa; Gheisari, Reza

    2015-11-01

    Finite Reynolds number (Re<20) flow over fibrous medium inside a rectangular duct was studied using a planar 2D PIV system. Three different fibrous materials with different porosities were used. Fibrous material lined the bottom wall of the duct along the length of the duct. The flow regime for all tests was laminar, and measurements were all done when the flow reached a steady state. Error and uncertainty sources in the experiments were also discussed. Shear rates were estimated at the surface of the fibrous media. As a conclusion to this study skin friction factor were calculated at the interface of all fibrous media at selected Reynolds number. Then using power function, curve fits with the Cf = a/Re form were found which could closely correlate skin friction and Reynolds number. To weaken the effect of near-wall errors in estimated shear rates and consequently skin friction, an average of shear rate estimation in a layer with thickness of 5 mm was calculated which was used to calculate an average skin friction. Correlations of average skin friction with average Reynolds number were also presented.

  4. 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. PMID:27110836

  5. Friction of rocks

    USGS Publications Warehouse

    Byerlee, J.

    1978-01-01

    Experimental results in the published literature show that at low normal stress the shear stress required to slide one rock over another varies widely between experiments. This is because at low stress rock friction is strongly dependent on surface roughness. At high normal stress that effect is diminished and the friction is nearly independent of rock type. If the sliding surfaces are separated by gouge composed of Montmorillonite or vermiculite the friction can be very low. ?? 1978 Birkha??user Verlag.

  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. 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.

  8. Friction and nonlinear dynamics.

    PubMed

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

    2016-07-27

    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. PMID:27249652

  9. 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.

  10. 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

  11. Statistics of frictional families.

    PubMed

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

    2014-09-19

    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. PMID:25279647

  12. Friction plug welding

    NASA Technical Reports Server (NTRS)

    Takeshita, Riki (Inventor); Hibbard, Terry L. (Inventor)

    2001-01-01

    Friction plug welding (FPW) usage is advantageous for friction stir welding (FSW) hole close-outs and weld repairs in 2195 Al--Cu--Li fusion or friction stir welds. Current fusion welding methods of Al--Cu--Li have produced welds containing varied defects. These areas are found by non-destructive examination both after welding and after proof testing. Current techniques for repairing typically small (<0.25) defects weaken the weldment, rely heavily on welders' skill, and are costly. Friction plug welding repairs increase strength, ductility and resistance to cracking over initial weld quality, without requiring much time or operator skill. Friction plug welding while pulling the plug is advantageous because all hardware for performing the weld can be placed on one side of the workpiece.

  13. High energy factorization in nucleus-nucleus collisions III. Long range rapidity correlations

    SciTech Connect

    Venugopalan, R.; Gelis, F., Lappi, T.

    2009-10-27

    We obtain a novel result in QCD for long range rapidity correlations between gluons produced in the collision of saturated high energy hadrons or nuclei. This result, obtained in a high energy factorization framework, provides strong justification for the Glasma flux tube picture of coherent strong color fields. Our formalism can be applied to 'near side ridge' events at the Relativistic Heavy Ion Collider and in future studies of long range rapidity correlations at the LHC.

  14. High energy factorization in nucleus-nucleus collisions. III. Long range rapidity correlations

    SciTech Connect

    Gelis, Francois

    2009-05-01

    We obtain a novel result in QCD for long range rapidity correlations between gluons produced in the collision of saturated high energy hadrons or nuclei. This result, obtained in a high energy factorization framework, provides strong justification for the Glasma flux tube picture of coherent strong color fields. Our formalism can be applied to 'near side ridge' events at the Relativistic Heavy Ion Collider and in future studies of long range rapidity correlations at the LHC.

  15. Symptom correlates and factor structure of the Health Professions Stress Inventory.

    PubMed

    Eells, T D; Lacefield, P; Maxey, J

    1994-12-01

    Generalizability, psychological symptom correlates, and the factor structure of the Health Professions Stress Inventory were assessed with a sample of 92 geriatric nurses. The inventory was designed to measure the sources and frequency of stress among nurses, physicians, and pharmacists; little is known, however, of the extent to which scores correlate with psychological symptoms or of the underlying dimensions of stress measured. Analyses showed high correspondence between responses of the geriatric nurses and the normative nurses as measured by mean values and Cronbach alpha. Factor analysis of the intercorrelations among items yielded 4 factors contributing to work-related stress, i.e., Lack of Perceived Enrichment Potential, Patient Care, Interpersonal Conflict, and Family Responsibility Conflict. Scores on the inventory correlated significantly with those of all SCL-90--R scales. PMID:7886181

  16. Smart friction driven systems

    NASA Astrophysics Data System (ADS)

    Nitsche, Rainer; Gaul, Lothar

    2005-02-01

    Vibration properties of most assembled mechanical systems depend on frictional damping in joints. The nonlinear transfer behavior of the frictional interfaces often provides the dominant damping mechanism in a built-up structure and plays an important role in the vibratory response of the structure (Gaul and Nitsche 2001 Appl. Mech. Rev. 54 93-105). For improving the performance of systems, many studies have been carried out to predict, measure and/or enhance the energy dissipation of friction. To enhance the friction damping in joint connections a semi-active joint is investigated. A rotational joint connection is designed and manufactured such that the normal force in the friction interface can be influenced with a piezoelectric stack disc. With the piezoelectric device the normal force and thus the friction damping in the joint connection can be controlled. A control design method, namely semi-active control, is investigated. The recently developed LuGre friction model is used to describe the nonlinear transfer behavior of joints. This model is based on a bristle model and turns out to be highly suitable for systems assembled by such smart joints. Those systems can also be regarded as friction driven systems, since the energy flow is controlled by smart joints. The semi-active method is well suited for large space structures since the friction damping in joints turned out to be a major source of damping. To show the applicability of the proposed concept to large space structures a two-beam system representing a part of a large space structure is considered. Two flexible beams are connected with a semi-active joint connection. It can be shown that the damping of the system can be improved significantly by controlling the normal force in the semi-active joint connection. Experimental results validate the damping improvement due to the semi-active friction damping.

  17. Type 1 Diabetes Patients Using Continuous Subcutaneous Insulin Infusion Therapy: Feeling Burdened Correlated with Factors

    PubMed Central

    Nishio, Ikuko; Chujo, Masami

    2015-01-01

    Background The purpose of this study was to investigate factors related to feelings of being burdened in type 1 diabetes patients using continuous subcutaneous insulin infusion (CSII) therapy. Methods Participants were 106 subscribers to the Diabetes Network’s e-mail newsletter. An online survey was used. Eligible participants were aged at least 20 years, had type 1 diabetes, and were using CSII. Survey questions concerned whether participants found CSII burdensome, and seven potential reasons for feelings of burden. Analysis calculated correlations among participants’ demographic and treatment-related factors, and among participants’ reasons for feeling CSII to be burdensome. Results Regarding demographic and treatment-related factors, gender was found to be weakly negatively correlated with the following variables: employment status, and whether participants had discussed their concerns with a doctor. Employment status was found to be weakly correlated with diabetes duration; employment status and diabetes duration were found to be weakly correlated with age. Regarding reasons for finding CSII therapy burdensome, “It takes too much time” was found to be strongly positively correlated with “It interferes with work responsibilities”; 16 weak positive correlations were also found. Conclusion To explain our results, we suggest that medical expenses, glycemic control, scheduling outpatient visits around home and work responsibilities, and interacting with medical staff may have caused participants to find CSII therapy burdensome. Most participants had never discussed their treatment concerns with a doctor. This suggests that nurses may be able to mitigate feeling burdened in participants using CSII therapy. PMID:26538798

  18. 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

  19. Factors controlling degree of correlation between ISEE 1 and ISEE 3 interplanetary magnetic field measurements

    NASA Technical Reports Server (NTRS)

    Crooker, N. U.; Siscoe, G. L.; Russell, C. T.; Smith, E. J.

    1982-01-01

    Correlation variability between ISEE 1 and 3 IMF measurements is investigated, and factors governing the variability are discussed. About 200 two-hour periods when correlation was good, and 200 when correlation was poor, are examined, and both IMF variance and spacecraft separation distance in the plane perpendicular to the earth-sun line exert substantial control. The scale size of magnetic features is larger when variance is high, and abrupt changes in the correlation coefficient from poor to good or good to poor in adjacent two-hour intervals appear to be governed by the sense of change of IMF variance and vice versa. During periods of low variance, good correlations are most likely to occur when the distance between ISEE 1 and 3 perpendicular to the IMF is less than 20 earth radii.

  20. Kirkwood correlation factors in liquid mixtures from an extended Onsager-Kirkwood-Fröhlich equation.

    PubMed

    Reis, João Carlos R; Iglesias, T P

    2011-06-14

    Two approaches for applying the Onsager-Kirkwood-Fröhlich equation to liquid mixtures are revisited at the light of recent developments leading to the estimation of relative permittivities and refractive indices of thermodynamically ideal liquid mixtures. From the one-liquid approach, the squared permanent dipole moment of the mixture molecular-equivalent species M is demonstrated to be a mole-fraction average of squared permanent dipole moments of the components. An expression is obtained for calculating the ideal Kirkwood correlation factor of M at any composition by using only pure-constituent properties. From the two-liquid approach (Böttcher's equation), equations are obtained to describe the dependence on composition of the Kirkwood correlation factor of both components in the ideal mixture, even in mixtures of Onsager liquids. This dependency is tentatively ascribed to London dispersion forces acting between unlike molecules. It is demonstrated that Böttcher's equation can only be applied to mixtures where the relative permittivity of each component is larger than the squared refractive index of the other component. From the interplay of one- and two-liquid approaches, the ideal Kirkwood correlation factor of M and of both constituents are inter-related. Thermodynamic expressions are given for the calculation of excess Kirkwood correlation factors. In the case where permanent dipole moments are unknown, the ratio excess/ideal, termed the relative excess Kirkwood correlation factor for components and species M can still be evaluated. These ratios are related to more conventional excess properties. Density, relative permittivity and refractive index data are reported for binary mixtures of 2,2,2-trifluoroethanol with mono-, di-, tri- or tetra-glyme over the whole composition range at 288 K and 298 K. For these systems, ideal, excess and relative excess and Kirkwood correlation factors are calculated and discussed. In particular, by regarding Kirkwood

  1. Genotype-phenotype correlation in combined deficiency of factor V and factor VIII

    PubMed Central

    Spreafico, Marta; Zheng, Chunlei; Yang, Angela; Platzer, Petra; Callaghan, Michael U.; Avci, Zekai; Ozbek, Namik; Mahlangu, Johnny; Haw, Tabitha; Kaufman, Randal J.; Marchant, Kandice; Tuddenham, Edward G. D.; Seligsohn, Uri; Peyvandi, Flora; Ginsburg, David

    2008-01-01

    Combined deficiency of factor V and factor VIII (F5F8D) is caused by mutations in one of 2 genes, either LMAN1 or MCFD2. Here we report the identification of mutations for 11 additional F5F8D families, including 4 novel mutations, 2 in MCFD2 and 2 in LMAN1. We show that a novel MCFD2 missense mutation identified here (D81Y) and 2 previously reported mutations (D89A and D122V) abolish MCFD2 binding to LMAN1. Measurement of platelet factor V (FV) levels in 7 F5F8D patients (4 with LMAN1 and 3 with MCFD2 mutations) demonstrated similar reductions to those observed for plasma FV. Combining the current data together with all previous published reports, we performed a genotype-phenotype analysis comparing patients with MCFD2 mutations with those with LMAN1 mutations. A previously unappreciated difference is observed between these 2 classes of patients in the distribution of plasma levels for FV and factor VIII (FVIII). Although there is considerable overlap, the mean levels of plasma FV and FVIII in patients with MCFD2 mutations are significantly lower than the corresponding levels in patients with LMAN1 mutations. No differences in distribution of factor levels are observed by sex. These data suggest that MCFD2 may play a primary role in the export of FV and FVIII from the ER, with the impact of LMAN1 mediated indirectly through its interaction with MCFD2. PMID:18391077

  2. 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.

  3. 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

  4. 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

  5. Low-temperature internal friction in quenched amorphous selenium films

    NASA Astrophysics Data System (ADS)

    Metcalf, Thomas; Liu, Xiao; Abernathy, Matthew; Stephens, Richard

    Using ultra-high-quality-factor silicon mechanical resonators, we have measured the internal friction and shear modulus of amorphous selenium (a-Se) films at liquid helium temperatures. The glass transition temperature of selenium lies at a conveniently accessible 40 -50° C, facilitating a series of in- and ex-situ annealing and quench cycles. The a-Se films exhibit the low-temperature internal friction plateau (10-4 <=Q-1 <=10-3) found in almost all amorphous solids, which is a result of (and direct measure of) a broad distribution of two-level tunneling systems (TLS), whose origin is still unknown. We find a clear correlation between the post-anneal quench rate and the value of this plateau. The implications of these observations for understanding the microscopic origin of TLS will be discussed. Principally, the observed changes in the internal friction plateau could show the way in which the density of TLS could be manipulated or suppressed in other amorphous systems. Work supported by the Office of Naval Research and the University of Pennsylvania Materials Research Science and Engineering Center.

  6. Friction mediated by redox-active supramolecular connector molecules.

    PubMed

    Bozna, B L; Blass, J; Albrecht, M; Hausen, F; Wenz, G; Bennewitz, R

    2015-10-01

    We report on a friction study at the nanometer scale using atomic force microscopy under electrochemical control. Friction arises from the interaction between two surfaces functionalized with cyclodextrin molecules. The interaction is mediated by connector molecules with (ferrocenylmethyl)ammonium end groups forming supramolecular complexes with the cyclodextrin molecules. With ferrocene connector molecules in solution, the friction increases by a factor of up to 12 compared to control experiments without connector molecules. The electrochemical oxidation of ferrocene to ferrocenium causes a decrease in friction owing to the lower stability of ferrocenium-cyclodextrin complex. Upon switching between oxidative and reduction potentials, a change in friction by a factor of 1.2-1.8 is observed. Isothermal titration calorimetry reveals fast dissociation and rebinding kinetics and thus an equilibrium regime for the friction experiments. PMID:26367352

  7. 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

  8. 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.

  9. Correlates of Parental Differential Treatment: Parental and Contextual Factors during Middle Childhood

    ERIC Educational Resources Information Center

    Atzaba-Poria, Naama; Pike, Alison

    2008-01-01

    The current study examined whether parental and contextual risk factors contribute to mothers' and fathers' differential treatment (MDT/FDT) when accounting for sibling dyad characteristics. Also explored was whether family type (single mothers vs. 2 parents) moderated the links between the parental and contextual correlates and MDT. One hundred…

  10. 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…

  11. 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

  12. 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.…

  13. Parental Factors Correlated with Developmental Outcome in the Migrant Head Start Child.

    ERIC Educational Resources Information Center

    Siantz, Mary Lou de Leon; Smith, M. Shelton

    1994-01-01

    Examined parental factors correlated with developmental outcomes among 60 Mexican American migrant farmworker children. Found that maternal parenting style accounted for a significant amount of the variance in child behavior problems reported by the mothers, whereas maternal social support helped to explain the variance in peer acceptance reported…

  14. 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

  15. 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.

  16. Expression of molecular factors correlated with metastasis in small cell lung cancer and their significance

    PubMed Central

    Li, Xiao-Xia; Li, Rui-Jian; Zhao, Lu-Jun; Liu, Ning-Bo; Wang, Ping

    2015-01-01

    Distant metastasis continues to be a fatal threat to quality of life in patients with small cell lung caner (SCLC). The purpose of this work is to analyze the expressions of chemokine receptor four (CXCR4), matrix metalloproteinase-9 (MMP-9), transforming growth factor-b1 (TGF-β1), N-cadherin and vascular endothelial growth factor (VEGF) in small cell lung caner (SCLC), and to explore their correlations with the prognosis and metastasis. Sixty-five consecutive patients with stage I-III SCLC who received operation in our hospital from Jan 2003 to Oct 2009 were retrospectively analyzed. The expression of CXCR4 was found significantly correlated with bone metastasis (P = 0.004), and were marginally correlated with brain metastasis (P = 0.068) and lymph node metastasis (P = 0.085). The expression of MMP-9 was significantly associated with pathological staging (P = 0.048). Univariate analysis suggested surgical approach, clinical stage, lymph node metastasis were significantly associated with OS and PFS (P < 0.05), high expression of CXCR4 was significantly correlated with worse OS (P = 0.004) and PFS (P = 0.005). Multivariate analysis suggested surgical approach, TGF-β1, CXCR4 and lymph node metastasis were independent prognostic factor for PFS. In conclusion, High expression of CXCR4, MMP-9, TGF-β1 and VEGF were found in SCLC. High expression of MMP-9 was significantly associated with pathological staging, and high expression of CXCR4 was correlated with bone metastasis and also might correlate with brain metastasis. CXCR4 were independent prognostic factor for survival in SCLC and expanded samples should be further explored in the future. PMID:26823791

  17. High energy factorization in nucleus-nucleus collisions. II. Multigluon correlations

    SciTech Connect

    Gelis, Francois; Lappi, Tuomas

    2008-09-01

    We extend previous results from the preceding paper on factorization in high energy nucleus-nucleus collisions by computing the inclusive multigluon spectrum to next-to-leading order. The factorization formula is strictly valid for multigluon emission in a slice of rapidity of width {delta}Y{<=}{alpha}{sub s}{sup -1}. Our results shows that often neglected disconnected graphs dominate the inclusive multigluon spectrum, and are crucial in order to achieve factorization for this quantity. These results provide a dynamical framework for the Glasma flux tube picture of the striking ''ridge''-like correlation seen in heavy ion collisions.

  18. 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

  19. 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…

  20. 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".…

  1. 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.

  2. 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

  3. 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.

  4. Role of diquark correlations and the pion cloud in nucleon elastic form factors

    NASA Astrophysics Data System (ADS)

    Cloët, Ian C.; Bentz, Wolfgang; Thomas, Anthony W.

    2014-10-01

    Electromagnetic form factors of the nucleon in the spacelike region are investigated within the framework of a covariant and confining Nambu-Jona-Lasinio model. The bound-state amplitude of the nucleon is obtained as the solution of a relativistic Faddeev equation, where diquark correlations appear naturally as a consequence of the strong coupling in the color 3¯ qq channel. Pion degrees of freedom are included as a perturbation to the "quark-core" contribution obtained using the Poincaré covariant Faddeev amplitude. While no model parameters are fit to form-factor data, excellent agreement is obtained with the empirical nucleon form factors (including the magnetic moments and radii) where pion loop corrections play a critical role for Q2≲1GeV2. Using charge symmetry, the nucleon form factors can be expressed as proton quark sector form factors. The latter are studied in detail, leading, for example, to the conclusion that the d-quark sector of the Dirac form factor is much softer than the u-quark sector, a consequence of the dominance of scalar diquark correlations in the proton wave function. On the other hand, for the proton quark sector Pauli form factors we find that the effect of the pion cloud and axial-vector diquark correlations overcomes the effect of scalar diquark dominance, leading to a larger d-quark anomalous magnetic moment and a form factor in the u-quark sector that is slightly softer than in the d-quark sector.

  5. 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.

  6. 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.

  7. Rotor internal friction instability

    NASA Technical Reports Server (NTRS)

    Bently, D. E.; Muszynska, A.

    1985-01-01

    Two aspects of internal friction affecting stability of rotating machines are discussed. The first role of internal friction consists of decreasing the level of effective damping during rotor subsynchronous and backward precessional vibrations caused by some other instability mechanisms. The second role of internal frication consists of creating rotor instability, i.e., causing self-excited subsynchronous vibrations. Experimental test results document both of these aspects.

  8. On the correlation factor of pure polar fluids whose molecules dimerize to nonpolar dimers

    NASA Astrophysics Data System (ADS)

    Mognaschi, E. R.; Laboranti, L. M.; Chierico, A.

    The dipolar correlation of pure polar fluids whose molecules undergo dimerization, resulting in the formation of nonpolar ring dimers and polar monomers in statistical equilibrium, has been studied. Such a system has been treated as a solution of polar molecules (monomers) in an apolar solvent (dimers). This approach allowed us to introduce a new parameter that accounts for the correlation among polar monomers, besides the well known Kirkwood-Fröhlich correlation factor. A relation between the two correlation factors, involving the degree of association, has been established. The above summarized model was applied to the case of five monocarboxylic fatty acids: propionic, n-butyric, n-valeric, caprylic, and pelargonic. On going from high to low molecular mass terms the room temperature static dielectric constant of the considered series of acids increases together with the degree of association, obtained from adiabatic compressibility data on the hypothesis that only dimerization occurs. This behaviour of the static dielectric constant, unexpected on the basis of the decrease of polar monomer density due to the increase of the degree of association, has been interpreted taking into account the dipolar correlation among monomers.

  9. 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.

  10. The correlation between bioactive components of Fallopia multiflora root and environmental factors.

    PubMed

    Yan, Han-Jing; Fang, Zhi-Jian; Fu, Jun; Yu, Shi-Xiao

    2010-01-01

    Fallopia multiflora (Thunb.) Harald, a traditional Chinese medicinal plant, is used in treating dizziness. In this study, the samples of F. multiflora from ten different locations were collected, and five bioactive components (2, 3, 5, 4'-tetrahydroxystilbene-2-O-beta-D-glucoside, emodin, emodin-8-O-beta-D-glucoside, physcion and physcion-8-O-beta-D-glucoside) were quantified by high performance liquid chromatography. The correlations between 17 environmental factors and 5 bioactive components were analyzed. The results showed that the highest contents of bioactive components were in samples from Deqing, and the lowest in samples from Tianyang, which indicated that the quality of F. multiflora grown in Deqing was superior, while that grown in Tianyang was inferior. Emodin content was negatively correlated with the average temperature in January (p < 0.01) and the accumulated temperature (p < 0.01). Physician content was also negatively correlated with the average temperature in January (P < 0.01), the accumulated temperature (p < 0.05) and the organic matter (p < 0.05). However, emodin was positively correlated with the soil available K (p < 0.05) and Zn (p < 0.01). The results of stepwise regression showed that the accumulated temperature was the main factor influencing the contents of emodin and physcion. However, none of the environmental factors had significant correlation with 2, 3, 5, 4'-tetrahydroxystilbene-2-O-beta-D-glucoside, emodin-8- O-beta-D-glucoside and physcion-8-O-beta-D-glucoside. In conclusion, some environmental factors have significant influence on the content of dissociated anthraquinones, while some have no influence on that of combined anthraquinones. PMID:20503466

  11. 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.

  12. 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

  13. Friction Laws Based on Monotonic and Cyclic Rotary Shear Tests

    NASA Astrophysics Data System (ADS)

    Lai, C. J.; Dong, J. J.; Togo, T.; Yang, C. M.; Lee, C. T.; Shimamoto, T.

    2014-12-01

    Rotary-shear friction experiments have been successfully used to study the earthquake dynamics and catastrophic landslides in the past two decades. Recent studies indicated that the friction behaviors of fault gouge materials under oscillatory shear are different from those under monotonic shear. Experimental results revealed that the accelerating and decelerating motion caused weakening and strengthening, while undergoing overall slip weakening. In this study, we try to approximate the temporal variation of friction coefficient during accelerating/decelerating slip based on a velocity-displacement dependent friction law derived from monotonic rotary shear tests. The approximated results show a full strength recovery behavior when the slip velocity equals to zero, which cannot depict the experimental results. A frequency dependent factor was introduced into the friction law to improve the approximation. The mechanisms behind the differences of friction behaviors between the oscillatory and monotonic rotary shear tests will be explored.

  14. 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.

  15. 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.

  16. 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. PMID:23612882

  17. Correlation factors for impurity diffusion on the sublattice of dodecahedral sites in garnet

    NASA Astrophysics Data System (ADS)

    Carlson, William D.; Wilson, Clark R.

    2016-05-01

    The method of Koiwa and Ishioka (Philos Mag A 47:927-938, 1983) is used, with slight modification, to evaluate the correlation factor for vacancy-mediated diffusion of impurity atoms on the sublattice of dodecahedral sites in garnet, as a function of the relevant vacancy-jump frequencies. The required values of the lattice Green's function were obtained from multiple Monte Carlo simulations in lattices of progressively larger size, extrapolated to an infinite lattice using a model that linearizes the dependence of the functional value on lattice size. As Online Resources, codes are provided that permit evaluation of the correlation factor for any chosen set of vacancy-jump frequencies, for implementation in either M athematica ® or M atlab ®.

  18. Factors related to job satisfaction and autonomy as correlates of potential job retention for rural nurses.

    PubMed

    Hanson, C M; Jenkins, S; Ryan, R

    1990-07-01

    This study of 167 nurses in 10 rural Georgia agencies examines the relationships among personal characteristics, factors of job satisfaction, autonomy, and job retention. The findings indicate that, contrary to expectations, personal characteristics (e.g., age, education, salary, marital status, and number of dependents) are not strong predictors of job retention in this sample. Some of the factors of job satisfaction do correlate negatively with indicators of impending job change, but the strongest relationships were those related to nursing autonomy. The study concludes that, of the variables studied, autonomy was the most effective predictor of job satisfaction and intention to remain in the current position. PMID:10105941

  19. 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.

  20. Examining the correlates of the coldheartedness factor of the Psychopathic Personality Inventory-Revised.

    PubMed

    Berg, Joanna M; Hecht, Lisa K; Latzman, Robert D; Lilienfeld, Scott O

    2015-12-01

    Coldheartedness is a subscale of the Psychopathic Personality Inventory-Revised (PPI-R) that does not load onto either of the PPI-R's two traditional higher order factors (Fearless Dominance [FD] and Self-Centered Impulsivity [SCI]). As a result, it has been omitted from analyses in many studies. However, owing to Coldheartedness's associations with lack of empathy, guilt, and deep-seated social emotions, this subscale may be highly relevant to the construct of psychopathy. In a sample of 1,158 undergraduates, we attempted to clarify Coldheartedness's correlates within the context of a nomological network of psychopathology and personality; in addition, we examined Coldheartedness's contributions to psychopathy above and beyond FD and SCI. Coldheartedness demonstrated negative correlations with the Big Five personality factors, mixed correlations with indices of impulsivity, and largely negative correlations with measures of depression and anxiety. Regressions suggested that Coldheartedness displays substantial overlap with both FD and SCI but also contains psychologically important unique variance. Although the nature of this variance requires clarification, further research and perhaps an expansion of the Coldheartedness subscale may move the field toward a clearer understanding of the construct assessed by this measure. PMID:25915788

  1. CAM/LIFTER forces and friction

    SciTech Connect

    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.

  2. 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.

  3. Glutathione-related factors are not correlated with sensitivity of human tumour cells to actinomycin D.

    PubMed

    Zhang, K; Yang, E B; Zhao, Y N; Wong, K P; Mack, P

    2000-02-28

    Glutathione (GSH) contents and activities of glutathione S-transferases (GST), glutathione reductase (GSH-RD), glutathione peroxidase (GSHpx) and glutathione conjugate export pump (GS-X pump) were determined in eight human tumour cell lines with different sensitivities to melphalan, a substrate of glutathione conjugation, and actinomycin D which has not been shown to be detoxified by glutathione-related mechanisms. Chang liver cells with highest GSH content and highest activities of GST, GSH-RD, GSHpx and GS-X pump were found to be most resistant to melphalan. Statistical analysis showed significant correlations between sensitivities of the human tumour cells to melphalan and the glutathione-related factors (r = 0.72-0.79; except for GST, r = 0.65, P = 0.08), while there were no significant correlations observed between sensitivities of the human tumour cells to actinomycin D and all the glutathione-related factors tested (r = -0.25-0.14). Significant correlations of the glutathione-related factors to resistance of human tumour cells to melphalan, a substrate of glutathione conjugation, but not to resistance of the human tumour cells to actinomycin D which has not been shown to be detoxified by glutathione-related mechanisms suggested that glutathione-related mechanisms contribute to drug resistance by increased detoxification of the drugs involved. PMID:10737727

  4. 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

  5. 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

  6. Correlation between quantitative fit factors and workplace protection factors measured in actual workplace environments at a steel foundry.

    PubMed

    Zhuang, Ziqing; Coffey, Christopher C; Jensen, Paul A; Campbell, Donald L; Lawrence, Robert B; Myers, Warren R

    2003-01-01

    Past studies have found little or no correlation between workplace protection factors (WPFs) and quantitative fit factors (FFs). This study investigated the effect of good- and poor-fitting half-facepiece, air-purifying respirators on protection in actual workplace environments at a steel foundry and the correlation between WPFs and FFs. Fifteen burners and welders, who wore respirators voluntarily, and chippers participated in this study. Each subject was fit-tested with two respirator models each with three sizes, for a total of six fit-tests. Models and sizes were assigned this way to provide a wide range of FFs among study participants. Each worker donned the respirator twice per day (at the beginning of the shift and following the lunch break) for 2 days. Quantitative FFs were first obtained for each donning using the PortaCount Plus trade mark in a separate room. Without redonning the respirators, workers performed normal work for 1 to 2 hours, and WPFs were measured by collecting ambient and in-facepiece samples simultaneously. A second fit-test was conducted without disturbing the respirator. FFs were obtained by averaging the results from the first and second fit-tests. The resulting FFs had a geometric mean (GM) of 400 (range=10-6010) and a geometric standard deviation (GSD) of 6.1. Of the 55 valid donnings, 43 were good fitting (FFs> or =100) and 12 were poor fitting (FFs<100). The WPFs had a GM of 920 (range=13-230,000) and a GSD of 17.8. The WPFs were found to be significantly correlated with the FFs (R(2)=.55 and p-value=.0001). Therefore, FF was shown to be a meaningful indicator of respirator performance in actual workplace environments. PMID:14674806

  7. 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).

  8. Selected factors correlated to athletic performance in adults with mental retardation.

    PubMed

    Franciosi, Emanuele; Baldari, Carlo; Gallotta, Maria Chiara; Emerenziani, Gian Pietro; Guidetti, Laura

    2010-04-01

    The aims of this study were to assess the contribution of selected factors to the athletic performance in adults with mental retardation (MR) and to analyze the correlation of each factor with subjects' MR levels. Twenty-nine trained athletes with MR aged 20-45 years were recruited. The fundamental factors included anthropometric measurements, flexibility, muscular strength and endurance, explosive leg power, cardiovascular endurance, and motor coordination. The athletic performances were as follows: 60 m, 300 m, 400 m in walking, standing long jump, and vortex throw (Level I) or 100-m run, shot put, and long jump (Level II). Motor coordination and body weight had significant contributions to 60 m (p < 0.01) and the %body fat had significant contribution to 300 m and 100 m (p < 0.05). The explosive leg power had significant contribution to vortex throw and standing long jump (p < 0.05). The upper-body strength and muscular endurance had significant contribution in shot put (p < 0.05). The body weight had significant contribution in long jump (p < 0.05). MR level was positively correlated to motor coordination (p < 0.05) and negatively to abdominal muscular strength and endurance (p < 0.05). In conclusion, the results showed the possibility to determine the contributions of selected factors to the athletic performance. This should be addressed in athletics training to help athletes with MR to perform successfully in their competitions. PMID:20300018

  9. Seasonal distribution of systemic lupus erythematosus activity and its correlation with climate factors.

    PubMed

    Yang, Jie; Lu, Yu-Wei; Pan, Hai-Feng; Tao, Jin-Hui; Zou, Yan-Feng; Bao, Wei; Ye, Dong-Qing

    2012-08-01

    Systemic lupus erythematosus (SLE) is a complex autoimmune disease with a variety of clinical manifestations. Although inter-individual variations exist with respect to susceptibility to develop SLE, no study has been carried out to determine the role of different climate conditions in predisposing the susceptible individuals to SLE. The objective of this study was to investigate the role of different seasons and climate factors on SLE activity. From 2000 to 2009, the seasonal distribution of 2,802 active SLE patients recruited from Anhui Provincial Hospital and the First Affiliated Hospital of Anhui Medical University was analyzed retrospectively. The climate data were provided by the Institute of Geographical Sciences and Resources, Chinese Academy of Sciences. The correlation between climate factors and SLE activity was also analyzed. The proportion of active SLE patients in winter, spring, summer, and autumn was 10.06, 10.31, 9.74, and 8.66‰, respectively. In autumn, the proportion was much lower than that in winter and spring (P < 0.05). The proportion among winter, spring, and summer had no statistical difference (P > 0.05). The number of active SLE patients had no correlation with air temperature (r = 0.483, P > 0.05), relative humidity (r = -0.294, P > 0.05), and sunshine percentage (r = 0.503, P > 0.05), but it had positive correlation with amount of precipitation (r = 0.601, P < 0.05), wind velocity (r = 0.713, P < 0.01), and sunshine duration (r = 0.769, P < 0.01) and negative correlation with barometric pressure (r = -0.664, P < 0.05). The disease activity of patients with SLE is affected by seasons and climate factors. PMID:21667078

  10. Overflow: Facts on Friction

    NASA Technical Reports Server (NTRS)

    Lawrence, Scott

    1999-01-01

    This paper presents results of three minor studies into the behavior of the OVERFLOW with respect to the prediction of skin friction drag on wing bodies at cruise Mach number and wind tunnel Reynolds number. The studies include a preliminary assessment of the behavior of the two new 2-equation turbulence models introduced with the latest version of OVERFLOW (v. 1.8f), an investigation into potential improvements in the matrix dissipation scheme currently implemented in OVERFLOW, and an analysis of the observed sensitivity of the code's skin friction predictions to grid stretching at solid surface boundaries.

  11. 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

  12. First Europe-wide correlation analysis identifying factors best explaining the total nitrogen concentration in mosses

    NASA Astrophysics Data System (ADS)

    Schröder, Winfried; Holy, Marcel; Pesch, Roland; Harmens, Harry; Fagerli, Hilde; Alber, Renate; Coşkun, Mahmut; De Temmerman, Ludwig; Frolova, Marina; González-Miqueo, Laura; Jeran, Zvonka; Kubin, Eero; Leblond, Sébastien; Liiv, Siiri; Maňkovská, Blanka; Piispanen, Juha; Santamaría, Jesús M.; Simonèiè, Primož; Suchara, Ivan; Yurukova, Lilyana; Thöni, Lotti; Zechmeister, Harald G.

    2010-09-01

    In this study, the indicative value of mosses as biomonitors of atmospheric nitrogen (N) depositions and air concentrations on the one hand and site-specific and regional factors which explain best the total N concentration in mosses on the other hand were investigated for the first time at a European scale using correlation analyses. The analyses included data from mosses collected from 2781 sites across Europe within the framework of the European moss survey 2005/6, which was coordinated by the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops (ICP Vegetation). Modelled atmospheric N deposition and air concentration data were calculated using the Unified EMEP Model of the European Monitoring and Evaluation Programme (EMEP) of the Convention on Long-range Transboundary Air Pollution (CLRTAP). The modelled deposition and concentration data encompass various N compounds. In order to assess the correlations between moss tissue total N concentrations and the chosen predictors, Spearman rank correlation analysis and Classification and Regression Trees (CART) were applied. The Spearman rank correlation analysis showed that the total N concentration in mosses and modelled N depositions and air concentrations are significantly correlated (0.53 ≤ r s ≤ 0.68, p < 0.001). Correlations with other predictors were lower than 0.55. The CART analysis indicated that the variation in the total N concentration in mosses was best explained by the variation in NH 4+ concentrations in air, followed by NO 2 concentrations in air, sampled moss species and total dry N deposition. The total N concentrations in mosses mirror land use-related atmospheric concentrations and depositions of N across Europe. In addition to already proven associations to measured N deposition on a local scale the study at hand gives a scientific prove on the association of N concentration in mosses and modelled deposition at the European scale.

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

    PubMed

    Shanahan, Daniel R

    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 r (2) = 0.26, range 0.18-1.0). Conclusion. The impact factor of the

  14. 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

  15. 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

  16. 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

  17. 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

  18. Socio-Economic Factors of Bacillary Dysentery Based on Spatial Correlation Analysis in Guangxi Province, China

    PubMed Central

    Nie, Chengjing; Li, Hairong; Yang, Linsheng; Zhong, Gemei; Zhang, Lan

    2014-01-01

    Background In the past decade, bacillary dysentery was still a big public health problem in China, especially in Guangxi Province, where thousands of severe diarrhea cases occur every year. Methods Reported bacillary dysentery cases in Guangxi Province were obtained from local Centers for Diseases Prevention and Control. The 14 socio-economic indexes were selected as potential explanatory variables for the study. The spatial correlation analysis was used to explore the associations between the selected factors and bacillary dysentery incidence at county level, which was based on the software of ArcGIS10.2 and GeoDA 0.9.5i. Results The proportion of primary industry, the proportion of younger than 5-year-old children in total population, the number of hospitals per thousand persons and the rates of bacillary dysentery incidence show statistically significant positive correlation. But the proportion of secondary industry, per capital GDP, per capital government revenue, rural population proportion, popularization rate of tap water in rural area, access rate to the sanitation toilets in rural, number of beds in hospitals per thousand persons, medical and technical personnel per thousand persons and the rate of bacillary dysentery incidence show statistically significant negative correlation. The socio-economic factors can be divided into four aspects, including economic development, health development, medical development and human own condition. The four aspects were not isolated from each other, but interacted with each other. PMID:25036182

  19. Hypoxia-inducible factor-1alpha expression in experimental cirrhosis: correlation with vascular endothelial growth factor expression and angiogenesis.

    PubMed

    Bozova, Sevgi; Elpek, Gülsüm Ozlem

    2007-07-01

    Angiogenesis progresses together with fibrogenesis during chronic liver injury. Hypoxia-inducible factor-1alpha (HIF-1alpha), a master regulator of homeostasis, plays a pivotal role in hypoxia-induced angiogenesis through its regulation of vascular endothelial growth factor (VEGF). The association between hypoxia, angiogenesis and VEGF expression has been demonstrated in experimental cirrhosis. However, expression of HIF-1alpha has yet to be reported. The aim of this study was to investigate the significance of HIF-1alpha expression during experimental liver fibrosis and the relationships between HIF-1alpha expression, VEGF expression and angiogenesis. Cirrhosis was induced in male Wistar rats by intraperitoneal administration of diethyl nitrosamine (DEN) (100 mg/kg, once a week). The serial sections from liver tissues were stained with anti-HIF-1alpha, anti-VEGF and anti-CD34 antibodies before being measured by light microscopy. Our results showed that HIF-1alpha expression gradually increases according to the severity of fibrosis (p<0.01). Moreover, its expression was found to be correlated with angiogenesis (r=0.916) and VEGF expression (r=0.969). The present study demonstrates that HIF-1alpha might have a role in the development of angiogenesis via regulation of VEGF during experimental liver fibrogenesis and suggests that this factor could be a potential target in the manipulation of angiogenesis in chronic inflammatory diseases of the liver. PMID:17614845

  20. Spatial Heterogeneity Induces Scale Dependent Rock Friction

    NASA Astrophysics Data System (ADS)

    Yamashita, F.; Fukuyama, E.; Xu, S.; Takizawa, S.; Mizoguchi, K.; Kawakata, H.; Passelègue, F. X.; Schubnel, A.

    2014-12-01

    We carried out large-scale biaxial friction experiments (Fukuyama et al., 2012; 2014) using a pair of meter-sized Indian gabbro as specimens, whose contacting area was 1.5 × 0.1 m2, normal stress was up to 6.7 MPa and loading velocity was up to 3 × 10-2 m/s. After each experiment, we found localized damages (i.e. grooves) were generated on the fault surface and gouges were distributed around them. We confirmed work rate dependency of rock friction as revealed by centimeter-sized rock samples (Di Toro et al., 2011), but further found that the meter-sized rock friction starts to decrease at one order of magnitude smaller work rate than that of the centimeter sized rock (Yamashita et al., 2013, AGU fall meeting). Here, we concluded that this difference is caused by stress localization and associated increase in heterogeneity on the fault as shown by: 1) Total amount of deviations of each local shear stress from the average, which were monitored by strain gauge array, increased with the decrease in friction. 2) Friction coefficients were negatively correlated with degree of spatial heterogeneity evaluated from the distribution of grooves and gouges. 3) Melt textures were found in the collected gouges by microscopic observation using HRSEM. Based on these observations, we propose a stress localization model; the fault surfaces are composed of patched and non-patched areas with high and low normal stress, respectively. The high normal stress patch leads to high shear stress, high mechanical work and thus production of much wear material (gouge), which further causes additional increase in normal stress. Assuming that the local friction follows the results by centimeter-sized gabbro experiments, we numerically simulated a slip-dependent friction for both patched and non-patched areas, and successively reproduced a weakening in macroscopic friction. We confirmed that the work rate dependency of simulated friction was consistent with that of biaxial experiments (Fig. 1

  1. 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

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. Maternal Beliefs and Socioeconomic Correlated Factors on Child Mortality from Drowning in Caspian Sea Coastline

    PubMed Central

    Davoudi-Kiakalayeh, Ali; Mohammadi, Reza; Yousefzade-Chabok, Shahrokh

    2014-01-01

    Objective: To investigate maternal beliefs, practices about causes and determinant factors on drowning and maternal socioeconomic correlated factors on child mortality from drowning. Methods: From March 2005 to March 2009, in a register-based cohort study and household survey, individual records utilizing drowning registry data of northern Iran were enrolled.   Mothers (n=276) who responded to multiple questions in a household survey were included. The patterns, interrelationships and effects of socioeconomic correlated factors on child mortality were analyzed. Results: A significant difference in relation to mother's educational level and age and family income distribution was noticed. Participants in household survey also reported that establishment of a multi-sectorial collaboration, integration of public health messages into local television, additional rescue stations and lifeguard, hazard environment fencing, increasing adult supervision, more support on increasing swimming ability among the children were all effective on reducing of drowning death. Conclusion: Due to the high rate of drowning in children and lack of attention among olders, a greater emphasis should be placed on educating mothers to assist a better supervision on their children. PMID:27162872

  8. Comprehensive Analysis of Stop Codon Usage in Bacteria and Its Correlation with Release Factor Abundance*

    PubMed Central

    Korkmaz, Gürkan; Holm, Mikael; Wiens, Tobias; Sanyal, Suparna

    2014-01-01

    We present a comprehensive analysis of stop codon usage in bacteria by analyzing over eight million coding sequences of 4684 bacterial sequences. Using a newly developed program called “stop codon counter,” the frequencies of the three classical stop codons TAA, TAG, and TGA were analyzed, and a publicly available stop codon database was built. Our analysis shows that with increasing genomic GC content the frequency of the TAA codon decreases and that of the TGA codon increases in a reciprocal manner. Interestingly, the release factor 1-specific codon TAG maintains a more or less uniform frequency (∼20%) irrespective of the GC content. The low abundance of TAG is also valid with respect to expression level of the genes ending with different stop codons. In contrast, the highly expressed genes predominantly end with TAA, ensuring termination with either of the two release factors. Using three model bacteria with different stop codon usage (Escherichia coli, Mycobacterium smegmatis, and Bacillus subtilis), we show that the frequency of TAG and TGA codons correlates well with the relative steady state amount of mRNA and protein for release factors RF1 and RF2 during exponential growth. Furthermore, using available microarray data for gene expression, we show that in both fast growing and contrasting biofilm formation conditions, the relative level of RF1 is nicely correlated with the expression level of the genes ending with TAG. PMID:25217634

  9. 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.

  10. 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

  11. Participation in transvaginal ovarian cancer screening: compliance, correlation factors, and costs.

    PubMed

    Pavlik, E J; van Nagell, J R; DePriest, P D; Wheeler, L; Tatman, J M; Boone, M; Sollars, S; Rayens, M K; Kryscio, R K

    1995-06-01

    The objective was to identify factors influencing participation in screening for ovarian cancer using transvaginal sonography in the free experimental program at the University of Kentucky over its 6+ year history. Database records for screenings, performed from 1987 to June 1994, were utilized. Computer sorts, 1990 census information as predictors, and stepwise multiple regression analysis were employed. Participation in the model ovarian screening program took 3-4 years to approach > 300 screens/month, with repeat screenings exceeding new subject participation in this time period. A number of participants traveled > 200 miles for screening on both initial and repeat encounters. Analysis of distance to the screening site, median family income, county physician population, and education levels indicated that distance and then education correlated best with participation. Unit screening cost shrank from $45 to under $25 when maximal participation was achieved. Distance and education correlated with participation. Expenses compare favorably with diagnostic procedures for other diseases. PMID:7774844

  12. Correlates for legal help-seeking: contextual factors for battered women in shelter.

    PubMed

    Wright, Caroline Vaile; Johnson, Dawn M

    2009-01-01

    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

  13. Effect of frictional heating on brake materials

    NASA Technical Reports Server (NTRS)

    Ho, T.-L.; Peterson, M. B.; Ling, F. F.

    1974-01-01

    An exploratory study of the properties of aircraft brake materials was made to determine ways of improving friction and wear behavior while minimizing surface temperatures. It is found that frictional variation at high temperature involves material softening and metal transfer, formation of oxides, and surface melting. The choice of proper materials to combat these effects is discussed. Minimum surface temperatures are found to result from use of materials with large density-specific heat and density-specific heat-conductivity factors, use of a higher load-lower friction system, and maximization of the contact area. Some useful trade-off criteria for the size of brake disks against weight considerations are suggested. Additional information on material behavior and peak braking temperatures was gathered from an inspection of used brake pads and rotor disks.

  14. 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

  15. 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.

  16. 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

  17. 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.

  18. Expression of mitochondrial transcription factor A in endometrial carcinomas: clinicopathologic correlations and prognostic significance.

    PubMed

    Toki, Naoyuki; Kagami, Seiji; Kurita, Tomoko; Kawagoe, Toshinori; Matsuura, Yusuke; Hachisuga, Toru; Matsuyama, Atsuji; Hashimoto, Hiroshi; Izumi, Hiroto; Kohno, Kimitoshi

    2010-04-01

    Mitochondrial transcription factor A (mtTFA) is necessary for both transcription and maintenance of mitochondrial DNA. This study was conducted to elucidate the clinicopathologic and prognostic significance of mtTFA in patients with endometrial carcinoma. This study investigated the relationship between the immunohistochemical expression of mtTFA and various clinicopathological variables in 276 endometrial carcinomas, including 245 endometrioid adenocarcinomas and 31 nonendometrioid carcinomas (21 serous carcinomas and 10 clear cell adenocarcinomas). Both uni- and multivariate regression analyses were performed. The mtTFA labeling index of endometrioid adenocarcinomas ranged from 0% to 98%, with a median value of 32%, which was selected as the cut-off point for mtTFA expression. The mtTFA expression in endometrioid adenocarcinomas was significantly associated with the surgical stage, myometrial invasion, lymphovascular space invasion, cervical invasion, and lymph node metastasis. In contrast, no correlation between clinicopathologic variables and mtTFA expression was found in nonendometrioid carcinomas. Correlation analysis between mtTFA and p53 expression by using the Pearson test showed significant correlation in endometrioid adenocarcinomas (P = 0.007), but no significant correlation in nonendometrioid carcinomas (P = 0.947). A univariate survival analysis showed that the 10-year overall survival rate of the patients with mtTFA-positive endometrioid adenocarcinoma was significantly worse than that of patients with mtTFA-negative endometrioid adenocarcinoma (80.8% vs. 93.8%, P = 0.012). However, the multivariate analysis revealed that mtTFA expression in endometrioid adenocarcinomas was no independent prognostic factor. The positive mtTFA expression is a useful maker for progression of the tumors and the poor prognosis of the patients in endometrioid adenocarcinomas. PMID:20232213

  19. Friction induced skin tags.

    PubMed

    Allegue, Francisco; Fachal, Carmen; Pérez-Pérez, Lidia

    2008-01-01

    Skin tags are common benign neoplasm located predominantly in intertriginous skin. Generally of cosmetic concern, they can be easily treated with cryotherapy, electrodessication or snip-excision. Despite their high incidence data about their etiopathogenesis are scarce in the medical literature. We describe a patient who developed multiple skin tags arranged in a linear fashion suggesting an etiopathogenic role for friction. PMID:18627719

  20. 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.

  1. Friction-Testing Machine

    NASA Technical Reports Server (NTRS)

    Benz, F. J.; Dixon, D. S.; Shaw, R. C.

    1986-01-01

    Testing machine evaluates wear and ignition characteristics of materials in rubbing contact. Offers advantages over other laboratory methods of measuring wear because it simulates operating conditions under which material will actually be used. Machine used to determine wear characteristics, rank and select materials for service with such active oxidizers as oxygen, halogens, and oxides of nitrogen, measure wear characteristics, and determine coefficients of friction.

  2. Exploring the factors contributing to sibling correlations in BMI: a study using the Panel Study of Income Dynamics.

    PubMed

    Brown, Heather W; Roberts, Jennifer

    2012-05-01

    Understanding the mechanisms contributing to correlated BMI outcomes in a social network such as siblings will help policy makers reduce the burden of disease associated with obesity. There are two potential mechanisms explaining correlated BMI outcomes in a biologically related social network: (i) time constant factors such as genetic heritability and habits formed during childhood and (ii) factors that change over time some of which are dependent on the frequency of interactions between the social network, for example, social norms shaped by the social network's shifting attitudes towards weight and behaviors related to weight, or environmental factors like opportunities for exercise. This study aims to distinguish between time constant factors from factors that are likely to change over time to gain a better understanding of the mechanisms explaining the correlation in sibling BMI. We exploit data from the Panel Study of Income Dynamics (PSID) over 1999-2007 estimating the correlation in BMI for adult siblings who currently live in separate households but grew-up in the same household and adolescent siblings currently living in the same household to isolate the influence of factors that change over time. The findings indicate that time constant factors explain some of the overall correlation in sibling BMI for both cohorts of siblings. Factors that change over time only significantly impact on the overall correlation in BMI for adolescent siblings suggesting if there is a social network influence on correlations in BMI this is facilitated by sharing the same household. PMID:22173572

  3. Analysis of angiogenic factors and cyclooxygenase-2 expression in cartilaginous tumors – clinical and histological correlation

    PubMed Central

    Cintra, Francisco Fontes; Etchebehere, Mauricio; Gonçalves, José Carlos Barbi; Cassone, Alejandro Enzo; Amstalden, Eliane Maria Ingrid

    2011-01-01

    OBJECTIVES: To study the role of angiogenesis and cyclooxygenase-2 expression in cartilaginous tumors and correlate these factors with prognosis. INTRODUCTION: For chondrosarcoma, the histological grade is the current standard for predicting tumor outcome. However, a low-grade chondrosarcoma can follow an aggressive course—as monitored by sequential imaging techniques—even when it is histologically indistinguishable from an enchondroma. Therefore, additional tools are needed to help identify the biological potential of these tumors. The degree of angiogenesis that is induced by the tumor could assist in this task. Angiogenesis can be quantified by measuring the expression of vascular endothelial growth factor and CD34, and cyclooxygenase-2 can induce angiogenesis by stimulating the production of pro-angiogenic factors. METHODS: In total, 21 enchondromas and 58 conventional chondrosarcomas were studied by examining the clinical and histopathological findings in conjunction with the immunostaining markers of angiogenesis and cyclooxygenase-2 expression. RESULTS: The significant variables that were associated with poor outcome were 1) higher-grade chondrosarcomas, 2) tumors that developed in flat bones, and 3) over-expression of CD34 (with a median count that was higher than 5.9 vessels in 5 high power fields). Moreover, CD34 expression (measured using the Chalkley method) revealed significantly higher microvessel density in flat bone chondrosarcomas. DISCUSSION: Previous studies have shown a positive correlation between Chalkley microvessel density and histological grade; however, in our sample, we found that the former is predictive of the outcome. Chondrosarcomas in flat bones have been shown to correlate with a poor prognosis. We also found that CD34 microvessel density values were significantly higher in flat-bone chondrosarcomas. This could explain—at least in part—the more aggressive biological course that is taken by these tumors. CONCLUSIONS: These

  4. 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

  5. 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.

  6. 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.

  7. Quantum friction and fluctuation theorems

    NASA Astrophysics Data System (ADS)

    Intravaia, F.; Behunin, R. O.; Dalvit, D. A. R.

    2014-05-01

    We use general concepts of statistical mechanics to compute the quantum frictional force on an atom moving at constant velocity above a planar surface. We derive the zero-temperature frictional force using a nonequilibrium fluctuation-dissipation relation, and we show that in the large-time, steady-state regime, quantum friction scales as the cubic power of the atom's velocity. We also discuss how approaches based on Wigner-Weisskopf and quantum regression approximations fail to predict the correct steady-state zero-temperature frictional force, mainly due to the low-frequency nature of quantum friction.

  8. Long noncoding RNAs are spatially correlated with transcription factors and regulate lung development

    PubMed Central

    Herriges, Michael J.; Swarr, Daniel T.; Morley, Michael P.; Rathi, Komal S.; Peng, Tien; Stewart, Kathleen M.; Morrisey, Edward E.

    2014-01-01

    Long noncoding RNAs (lncRNAs) are thought to play important roles in regulating gene transcription, but few have well-defined expression patterns or known biological functions during mammalian development. Using a conservative pipeline to identify lncRNAs that have important biological functions, we identified 363 lncRNAs in the lung and foregut endoderm. Importantly, we show that these lncRNAs are spatially correlated with transcription factors across the genome. In-depth expression analyses of lncRNAs with genomic loci adjacent to the critical transcription factors Nkx2.1, Gata6, Foxa2 (forkhead box a2), and Foxf1 mimic the expression patterns of their protein-coding neighbor. Loss-of-function analysis demonstrates that two lncRNAs, LL18/NANCI (Nkx2.1-associated noncoding intergenic RNA) and LL34, play distinct roles in endoderm development by controlling expression of critical developmental transcription factors and pathways, including retinoic acid signaling. In particular, we show that LL18/NANCI acts upstream of Nkx2.1 and downstream from Wnt signaling to regulate lung endoderm gene expression. These studies reveal that lncRNAs play an important role in foregut and lung endoderm development by regulating multiple aspects of gene transcription, often through regulation of transcription factor expression. PMID:24939938

  9. 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

  10. 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. PMID:26232194

  11. Enhanced Expression of Keratinocyte Growth Factor and Its Receptor Correlates with Venous Invasion in Pancreatic Cancer

    PubMed Central

    Cho, Kazumitsu; Ishiwata, Toshiyuki; Uchida, Eiji; Nakazawa, Nando; Korc, Murray; Naito, Zenya; Tajiri, Takashi

    2007-01-01

    Keratinocyte growth factor (KGF) and KGF receptor (KGFR) have been implicated in cancer growth as well as tissue development and repair. In this study, we examined whether KGF and KGFR have a role in human pancreatic ductal adenocarcinoma (PDAC). KGFR mRNA was expressed in eight pancreatic cancer cell lines, whereas the KGF mRNA was detected in seven of the cell lines and was absent in MIA PaCa-2 cells. KGFR and KGF immunoreactivity were localized in the cancer cells in 41.5 and 34.0% of patients, respectively. There was a significant correlation between KGFR or KGF immunoreactivity and venous invasion and a significant correlation between the presence of both markers and venous invasion, vascular endothelial growth factor (VEGF)-A expression, and poor prognosis. Exogenous KGF increased VEGF-A expression and release in MIA PaCa-2 cells, and PANC-1 cells stably transfected to overexpress KGF-exhibited increased VEGF-A expression. Moreover, short hairpin-KGFR transfection in MIA PaCa-2 cells reduced the stimulatory effect of exogenous KGF on VEGF-A expression. Short hairpin-KGF transfection in KLM-1 cells reduced VEGF-A expression in the cells. KGFR and KGF may act to promote venous invasion and tumor angiogenesis in PDAC, raising the possibility that they may serve as novel therapeutic targets in anti-angiogenic strategies in PDAC. PMID:17525264

  12. 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

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

    PubMed

    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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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. PMID:26153539

  20. 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.

  1. 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.

  2. 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.

  3. 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

  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. PMID:27453749

  5. Identification of transcription factor genes and their correlation with the high diversity of stramenopiles.

    PubMed

    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. 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

  7. Uranium mass and neutron multiplication factor estimates from time-correlation coincidence counts

    NASA Astrophysics Data System (ADS)

    Xie, Wenxiong; Li, Jiansheng; Zhu, Jianyu

    2015-10-01

    Time-correlation coincidence counts of neutrons are an important means to measure attributes of nuclear material. The main deficiency in the analysis is that an attribute of an unknown component can only be assessed by comparing it with similar known components. There is a lack of a universal method of measurement suitable for the different attributes of the components. This paper presents a new method that uses universal relations to estimate the mass and neutron multiplication factor of any uranium component with known enrichment. Based on numerical simulations and analyses of 64 highly enriched uranium components with different thicknesses and average radii, the relations between mass, multiplication and coincidence spectral features have been obtained by linear regression analysis. To examine the validity of the method in estimating the mass of uranium components with different sizes, shapes, enrichment, and shielding, the features of time-correlation coincidence-count spectra for other objects with similar attributes are simulated. Most of the masses and multiplications for these objects could also be derived by the formulation. Experimental measurements of highly enriched uranium castings have also been used to verify the formulation. The results show that for a well-designed time-dependent coincidence-count measuring system of a uranium attribute, there are a set of relations dependent on the uranium enrichment by which the mass and multiplication of the measured uranium components of any shape and size can be estimated from the features of the source-detector coincidence-count spectrum.

  8. Application of Canonical Correlation Analysis for Detecting Risk Factors Leading to Recurrence of Breast Cancer

    PubMed Central

    Sadoughi, Farahnaz; Lotfnezhad Afshar, Hadi; Olfatbakhsh, Asiie; Mehrdad, Neda

    2016-01-01

    Background: Advances in treatment options of breast cancer and development of cancer research centers have necessitated the collection of many variables about breast cancer patients. Detection of important variables as predictors and outcomes among them, without applying an appropriate statistical method is a very challenging task. Because of recurrent nature of breast cancer occurring in different time intervals, there are usually more than one variable in the outcome set. For the prevention of this problem that causes multicollinearity, a statistical method named canonical correlation analysis (CCA) is a good solution. Objectives: The purpose of this study was to analyze the data related to breast cancer recurrence of Iranian females using the CCA method to determine important risk factors. Patients and Methods: In this cross-sectional study, data of 584 female patients (mean age of 45.9 years) referred to Breast Cancer Research Center (Tehran, Iran) were analyzed anonymously. SPSS and NORM softwares (2.03) were used for data transformation, running and interpretation of CCA and replacing missing values, respectively. Data were obtained from Breast Cancer Research Center, Tehran, Iran. Results: Analysis showed seven important predictors resulting in breast cancer recurrence in different time periods. Family history and loco-regional recurrence more than 5 years after diagnosis were the most important variables among predictors and outcomes sets, respectively. Conclusions: Canonical correlation analysis can be used as a useful tool for management and preparing of medical data for discovering of knowledge hidden in them. PMID:27231580

  9. 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.

  10. Solid friction between soft filaments

    NASA Astrophysics Data System (ADS)

    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.

  11. 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.

  12. 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. PMID:25730393

  13. Centrosome movements in vivo correlate with specific neurite formation downstream of LIM homeodomain transcription factor activity.

    PubMed

    Andersen, Erica F; Halloran, Mary C

    2012-10-01

    Neurons must develop complex structure to form proper connections in the nervous system. The initiation of axons in defined locations on the cell body and their extension to synaptic targets are critical steps in neuronal morphogenesis, yet the mechanisms controlling axon formation in vivo are poorly understood. The centrosome has been implicated in multiple aspects of neuronal morphogenesis; however, its function in axon development is under debate. Conflicting results from studies of centrosome function in axonogenesis suggest that its role is context dependent and underscore the importance of studying centrosome function as neurons develop in their natural environment. Using live imaging of zebrafish Rohon-Beard (RB) sensory neurons in vivo, we discovered a spatiotemporal relationship between centrosome position and the formation of RB peripheral, but not central, axons. We tested centrosome function by laser ablation and found that centrosome disruption inhibited peripheral axon outgrowth. In addition, we show that centrosome position and motility are regulated by LIM homeodomain transcription factor activity, which is specifically required for the development of RB peripheral axons. Furthermore, we show a correlation between centrosome mislocalization and ectopic axon formation in bashful (laminin alpha 1) mutants. Thus, both intrinsic transcription factor activity and extracellular cues can influence centrosome position and axon formation in vivo. This study presents the first positive association between the centrosome and axon formation in vivo and suggests that the centrosome is important for differential neurite formation in neurons with complex axonal morphologies. PMID:22899847

  14. 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.

  15. SNP-revealed genetic diversity in wild emmer wheat correlates with ecological factors

    PubMed Central

    2013-01-01

    Background Patterns of genetic diversity between and within natural plant populations and their driving forces are of great interest in evolutionary biology. However, few studies have been performed on the genetic structure and population divergence in wild emmer wheat using a large number of EST-related single nucleotide polymorphism (SNP) markers. Results In the present study, twenty-five natural wild emmer wheat populations representing a wide range of ecological conditions in Israel and Turkey were used. Genetic diversity and genetic structure were investigated using over 1,000 SNP markers. A moderate level of genetic diversity was detected due to the biallelic property of SNP markers. Clustering based on Bayesian model showed that grouping pattern is related to the geographical distribution of the wild emmer wheat. However, genetic differentiation between populations was not necessarily dependent on the geographical distances. A total of 33 outlier loci under positive selection were identified using a FST-outlier method. Significant correlations between loci and ecogeographical factors were observed. Conclusions Natural selection appears to play a major role in generating adaptive structures in wild emmer wheat. SNP markers are appropriate for detecting selectively-channeled adaptive genetic diversity in natural populations of wild emmer wheat. This adaptive genetic diversity is significantly associated with ecological factors. PMID:23937410

  16. Hypoxia-Inducible Factor-1α and CD271 inversely correlate with melanoma invasiveness.

    PubMed

    Marconi, Alessandra; Borroni, Riccardo G; Truzzi, Francesca; Longo, Caterina; Pistoni, Federica; Pellacani, Giovanni; Pincelli, Carlo

    2015-05-01

    Melanoma is characterized, among other features, by microenvironmental factors and by an altered apoptotic machinery. Melanoma cell response to a hypoxic environment is transcriptionally regulated by the Hypoxia-Inducible Factor (HIF)-1α. p75 neurotrophin receptor (p75(NTR) ), also called CD271, mediates apoptosis in several cell systems. The purpose of this study was to analyze the expression of HIF-1α and CD271 in melanomas at different phases of progression, as evaluated by histology and reflectance confocal microscopy (RCM). By RCM, 41.67% tumors were characterized by the presence of a population of dendritic and pleomorphic cells (D+P), corresponding to in situ melanoma; 25% exhibited a predominantly round-cell (RN) proliferation with histologic features of superficial melanoma, and 33.33% showed the presence of cells aggregated in nests (DN), typical of invasive melanoma. HIF-1α was scarcely detected in D+P and in RN melanomas, while it was highly expressed in DN tumors. By contrast, CD271 positive cells were mostly detected in D+P population, and barely observed in the other subtypes. This work demonstrates that CD271 expression inversely correlates with hypoxia in melanoma, and that the two markers may be used in the future as diagnostic/prognostic tools for this neoplasm. PMID:25739328

  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. Area of hock hair loss in dairy cows: risk factors and correlation with a categorical scale.

    PubMed

    Lim, P Y; Huxley, J N; Green, M J; Othman, A R; Potterton, S L; Brignell, C J; Kaler, J

    2015-02-01

    Data from 3691 dairy cows from 76 farms were used to investigate the risk factors associated with the area of hair loss over the lateral aspect of the hock and the correlation between the area of hair loss (as calculated using a hock map) and hock lesion scores determined using a pre-existing categorical scale. Six factors were associated with a greater area of hair loss, including cows with locomotion score 3, a cleanliness score (10/28 to 18/28), high daily milk yield (25.1-58.1 kg), poor body condition score (1-1.5), duration of winter housing (≥41 days) and some combinations of cubicle base and bedding materials. Compared with cows housed in cubicles with a concrete base and whole straw or rape straw bedding, cows housed in cubicles with concrete bases with sand or chopped straw bedding had smaller areas of hair loss and cows housed on a mattress base with whole straw or rape straw bedding had larger areas of hair loss. Area of hair loss, as measured on hock maps, was not significantly different between cows with score 1 (median 23.6 cm(2)) and score 2 (median 20.3 cm(2)) on the categorical scale for hock lesions. This suggests that the categorical scale was not reflecting the extent of hair loss and that hock maps are a good alternative for studying the dynamics of hock lesions over time. PMID:25577022

  19. Prevalence, Distribution, and Risk Factor Correlates of High Thoracic Periaortic Fat in the Framingham Heart Study

    PubMed Central

    Britton, Kathryn A.; Pedley, Alison; Massaro, Joseph M.; Corsini, Erin M.; Murabito, Joanne M.; Hoffmann, Udo; Fox, Caroline S.

    2012-01-01

    Background Thoracic periaortic adipose tissue (TAT) is associated with atherosclerosis and cardiovascular disease (CVD) risk factors and may play a role in obesity‐mediated vascular disease. We sought to determine the prevalence, distribution, and risk factor correlates of high TAT. Methods and Results Participants from the Framingham Heart Study (n=3246, 48% women, mean age 51.1 years) underwent multidetector computed tomography; high TAT and visceral adipose tissue (VAT) were defined on the basis of sex‐specific 90th percentiles in a healthy referent sample. The prevalence of high TAT was 38.1% in women and 35.7% in men. Among individuals without high VAT, 10.1% had high TAT. After adjustment for age and VAT, both women and men with high TAT in the absence of high VAT were older and had a higher prevalence of CVD (P<0.0001) compared with those without high TAT. In addition, men in this group were more likely to be smokers (P=0.02), whereas women were more likely to have low high‐density lipoprotein cholesterol (P=0.005). Conclusions Individuals in our community‐based sample with high TAT in the absence of high VAT were characterized by an adverse cardiometabolic profile. This adipose tissue phenotype may identify a subset of individuals with distinct metabolic characteristics. PMID:23316328

  20. Ultrasound measurement of peripheral endothelial dysfunction in type 2 diabetic patients: correlation with risk factors.

    PubMed

    Bosevski, Marijan; Georgievska-Ismail, Ljubica

    2010-05-01

    The purpose of the study was to assess the endothelial dysfunction (ED) in type 2 diabetic patients ultrasonographically and estimate the correlation of ED with glycemia and other cardio-metabolic risk factors. 171 patient (age 60.0 + 8.5 years) with diagnosed type 2 diabetes and coronary artery disease (CAD) were randomly included in a cross sectional study. B-mode ultrasound system with a linear transducer of 7.5 MHz was used for evaluation of flow-mediated vasodilation in brachial artery (FMV). FMV was presented as a change of brachial artery diameter at rest and after limb ischemia, previously provoked by cuff inflation. Peripheral ED was found in 77.2% (132 patients). Multivariate logistic regression model defined: age (OR 1.071, 95% CI 1.003 1,143) and plasma cholesterol (OR 4.083 95% CI 1.080 17,017) as determinants for ED. Linear multivariate analysis presented duration of diabetes (Beta 0.173, Sig 0.024), and glycemia (Beta 0.132, Sig 0.044) to be associated independently with FMV value. Estimated factors influencing FMV, might be potential therapeutic targets for presented endothelial dysfunction in type 2 diabetic patients with coronary artery disease. PMID:20507285

  1. Determination of simple correlated wave functions for few-electron systems using a Jastrow factor

    SciTech Connect

    Umezawa, N.; Sarsa, A.; Le Sech, C.; Chikyow, T.

    2006-01-15

    Compact Jastrow-Slater-type correlated wave functions for three- and four-electron atoms and ions (Li, Be{sup +}, B{sup 2+}, C{sup 3+}, Be, B{sup +}, and C{sup 2+}) are proposed. The Jastrow factor we employed consists of one-body and two-body functions including only two variational parameters in total. We found that a one-body Jastrow function with one variational parameter, which is responsible for the screening effect around the nucleus, is effective for reproducing good total energies of the three- and four-electron atomic systems if hydrogenoid orbitals are adopted in the Slater determinant. On the other hand, a determinant composed of Hartree-Fock orbitals multiplied by the same Jastrow factor was found to give rather worse results than that composed of hydrogenoid orbitals. This result clearly indicates that analytic hydrogenoid orbitals coupled with the one-body Jastrow function are useful for describing simple wave functions and understanding the physical properties of these systems.

  2. 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.

  3. 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.

  4. Fluctuations and friction

    NASA Astrophysics Data System (ADS)

    Raine, Derek

    2005-11-01

    Einstein's 1905 (Einstein 1905 Ann. Phys. 17 549) paper on Brownian motion is his most cited work, yet in terms of the scope of its application, apparently the least understood. In this brief note, I look at some examples of problems involving frictional forces that have puzzled school teachers, university lecturers and students, all of which can be understood from a proper appreciation of the relation between fluctuations and dissipation. For completeness I shall first give a simple derivation of a fluctuation-dissipation theorem, followed by three examples.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Correlation between heart rate variability and pulmonary function adjusted by confounding factors in healthy adults.

    PubMed

    Bianchim, M S; Sperandio, E F; Martinhão, G S; Matheus, A C; Lauria, V T; da Silva, R P; Spadari, R C; Gagliardi, A R T; Arantes, R L; Romiti, M; Dourado, V Z

    2016-03-01

    The autonomic nervous system maintains homeostasis, which is the state of balance in the body. That balance can be determined simply and noninvasively by evaluating heart rate variability (HRV). However, independently of autonomic control of the heart, HRV can be influenced by other factors, such as respiratory parameters. Little is known about the relationship between HRV and spirometric indices. In this study, our objective was to determine whether HRV correlates with spirometric indices in adults without cardiopulmonary disease, considering the main confounders (e.g., smoking and physical inactivity). In a sample of 119 asymptomatic adults (age 20-80 years), we evaluated forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). We evaluated resting HRV indices within a 5-min window in the middle of a 10-min recording period, thereafter analyzing time and frequency domains. To evaluate daily physical activity, we instructed participants to use a triaxial accelerometer for 7 days. Physical inactivity was defined as <150 min/week of moderate to intense physical activity. We found that FVC and FEV1, respectively, correlated significantly with the following aspects of the RR interval: standard deviation of the RR intervals (r =0.31 and 0.35), low-frequency component (r =0.38 and 0.40), and Poincaré plot SD2 (r =0.34 and 0.36). Multivariate regression analysis, adjusted for age, sex, smoking, physical inactivity, and cardiovascular risk, identified the SD2 and dyslipidemia as independent predictors of FVC and FEV1 (R2=0.125 and 0.180, respectively, for both). We conclude that pulmonary function is influenced by autonomic control of cardiovascular function, independently of the main confounders. PMID:26840706

  11. Correlation between heart rate variability and pulmonary function adjusted by confounding factors in healthy adults

    PubMed Central

    Bianchim, M.S.; Sperandio, E.F.; Martinhão, G.S.; Matheus, A.C.; Lauria, V.T.; da Silva, R.P.; Spadari, R.C.; Gagliardi, A.R.T.; Arantes, R.L.; Romiti, M.; Dourado, V.Z.

    2016-01-01

    The autonomic nervous system maintains homeostasis, which is the state of balance in the body. That balance can be determined simply and noninvasively by evaluating heart rate variability (HRV). However, independently of autonomic control of the heart, HRV can be influenced by other factors, such as respiratory parameters. Little is known about the relationship between HRV and spirometric indices. In this study, our objective was to determine whether HRV correlates with spirometric indices in adults without cardiopulmonary disease, considering the main confounders (e.g., smoking and physical inactivity). In a sample of 119 asymptomatic adults (age 20-80 years), we evaluated forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). We evaluated resting HRV indices within a 5-min window in the middle of a 10-min recording period, thereafter analyzing time and frequency domains. To evaluate daily physical activity, we instructed participants to use a triaxial accelerometer for 7 days. Physical inactivity was defined as <150 min/week of moderate to intense physical activity. We found that FVC and FEV1, respectively, correlated significantly with the following aspects of the RR interval: standard deviation of the RR intervals (r =0.31 and 0.35), low-frequency component (r =0.38 and 0.40), and Poincaré plot SD2 (r =0.34 and 0.36). Multivariate regression analysis, adjusted for age, sex, smoking, physical inactivity, and cardiovascular risk, identified the SD2 and dyslipidemia as independent predictors of FVC and FEV1 (R 2=0.125 and 0.180, respectively, for both). We conclude that pulmonary function is influenced by autonomic control of cardiovascular function, independently of the main confounders. PMID:26840706

  12. 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.

  13. 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.

  14. 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.

  15. Orbital friction stir weld system

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeffrey (Inventor); Carter, Robert W. (Inventor)

    2001-01-01

    This invention is an apparatus for joining the ends of two cylindrical (i.e., pipe-shaped) sections together with a friction stir weld. The apparatus holds the two cylindrical sections together and provides back-side weld support as it makes a friction stir weld around the circumference of the joined ends.

  16. Friction in a Moving Car

    ERIC Educational Resources Information Center

    Goldberg, Fred M.

    1975-01-01

    Describes an out-of-doors, partially unstructured experiment to determine the coefficient of friction for a moving car. Presents the equation which relates the coefficient of friction to initial velocity, distance, and time and gives sample computed values as a function of initial speed and tire pressure. (GS)

  17. Measurement of mixed-mode stress intensity factors using digital image correlation method

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; He, Lingfeng

    2012-07-01

    Applications of the digital image correlation method (DIC) for the determination of the mixed-mode stress intensity factors (SIF) is investigated in this paper. Experiments were performed on an edge fatigue cracked aluminum specimen using a special loading device, which is an appropriate apparatus for experimental mixed-mode fracture analysis. The full-field displacements around the crack-tip region of the test sample were calculated using DIC. And then the SIF associated with unavoidable rigid-body displacement motion were calculated simultaneously from the experimental data. The effect of the rigid body motion on the measured displacements was then eliminated using the computed rigid body translation and rotation. A coarse-fine searching method was developed to determine the crack-tip location. For validation, the SIF thus determined is compared with theoretical results, confirming the effectiveness and accuracy of the proposed technique. Therefore it reveals that the DIC is a practical and effective tool for full-field deformation and SIF measurement.

  18. Musashi-1 Expression is a Prognostic Factor in Ovarian Adenocarcinoma and Correlates with ALDH-1 Expression.

    PubMed

    Chen, Pu-xiang; Li, Qiao-yan; Yang, Zhulin

    2015-09-01

    The presence of cancer stem-like cells (CSCs) has been demonstrated to be associated with tumor metastasis, chemoresistance, and rapid recurrence of various tumors. The impact of CSC-related markers in the metastasis and prognosis of ovarian cancer has not been well established. In this study, the protein expression of musashi-1 and ALDH1 was measured using immunohistochemistry. Results demonstrated that the percentage of positive musashi-1 and ALDH1 expression were significantly higher in ovarian serous adenocarcinomas, mucinous adenocarcinomas and clear cell adenocarcinomas than in cystadenomas and normal tissues. The percentage of positive musashi-1 and ALDH1 expression were significantly lower in patients identified with clinical stage I or II ovarian adenocarcinomas without lymph node metastasis compared to patients with clinical stage III or IV tumors and lymph node metastasis. The expression of musashi-1 and ALDH1 was found to be highly consistent in ovarian adenocarcinomas. Univariate Kaplan-Meier analysis showed a negative correlation between musashi-1 or ALDH1 expression and overall survival. Multivariate Cox regression analysis showed that positive expression of musashi-1 or ALDH1 in ovarian adenocarcinoma was an independent predictor of poor prognosis. Our study suggested that musashi-1 and ALDH1 expression are closely related to metastasis of ovarian adenocarcinoma. The positive expression of musashi-1 and ALDH1 might be a poor-prognostic factor of ovarian adenocarcinoma. PMID:25971681

  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. Variability and Trends in Long Term Time Series and Correlations with Climate Factors

    NASA Astrophysics Data System (ADS)

    Pietrafesa, L. J.; Yan, T.; Bao, S.; Gayes, P. T.

    2014-12-01

    Employing credible data archives, we investigate 350 years of European land/atmospheric time series and 135 years of global oceanic and land/atmospheric time series. We reveal significant non-stationary and non-linear internal modes in the temporal data sets that include prominent signals at seasonal, annual, inter-annual, multi-annual, decadal, multi-decadal and trans-century time scales. We find an overall planetary warming. The overall trend is upwards, but the Global Surface Temperature Anomaly displays rates ranging from 0.8 oC/Century in 1659 to 0.0 in 1800 to 0.3 in 1880 and now at 1.0oC/Century; in deference to the IPCC 2007 Report which claimed ~ 2oC/Century. We relate the long term trends and variability of the temperature records correlatively with climate factors, such as the North Atlantic, Pacific Decadal, Atlantic Multi-Decadal, El Niño Southern, Arctic, Solar, Western Boundary Current, and other "Oscillations" and possible spatial-temporal links; and with the trend of fossil fuel burning.

  1. Encapsidation of Host-Derived Factors Correlates with Enhanced Infectivity of Sindbis Virus

    PubMed Central

    Sokoloski, Kevin J.; Snyder, Anthony J.; Liu, Natalia H.; Hayes, Chelsea A.

    2013-01-01

    The genus Alphavirus consists of a group of enveloped, single-stranded RNA viruses, many of which are transmitted by arthropods to a wide range of vertebrate host species. Here we report that Sindbis virus (SINV) produced from a representative mammalian cell line consists of at least two unique particle subpopulations, separable on the basis of virion density. In contrast, mosquito-derived SINV consists of a homogeneous population of particles. Our findings indicate that the denser particle subpopulation, SINVHeavy, is more infectious on a per-particle basis than SINVLight. SINV produced in mosquito cell lines (SINVC6/36) exhibited particle-to-PFU ratios similar to those observed for SINVHeavy. In mammalian cells, viral RNA was synthesized and accumulated more rapidly following infection with SINVHeavy or SINVC6/36 than following infection with SINVLight, due partly to enhanced translation of viral genomic RNA early in infection. Analysis of the individual particle subpopulations indicated that SINVHeavy and SINVC6/36 contain host-derived factors whose presence correlates with the enhanced translation, RNA synthesis, and infectivity observed for these particles. PMID:24006438

  2. Circulating tumour necrosis factor is highly correlated with brainstem serotonin transporter availability in humans.

    PubMed

    Krishnadas, Rajeev; Nicol, Alice; Sassarini, Jen; Puri, Navesh; Burden, A David; Leman, Joyce; Combet, Emilie; Pimlott, Sally; Hadley, Donald; McInnes, Iain B; Cavanagh, Jonathan

    2016-01-01

    Preclinical studies demonstrate that pro-inflammatory cytokines increase serotonin transporter availability and function, leading to depressive symptoms in rodent models. Herein we investigate associations between circulating inflammatory markers and brainstem serotonin transporter (5-HTT) availability in humans. We hypothesised that higher circulating inflammatory cytokine concentrations, particularly of tumour necrosis factor (TNF-α), would be associated with greater 5-HTT availability, and that TNF-α inhibition with etanercept (sTNFR:Fc) would in turn reduce 5-HTT availability. In 13 neurologically healthy adult women, plasma TNF-α correlated significantly with 5-HTT availability (rho=0.6; p=0.03) determined by [(123)I]-beta-CIT SPECT scanning. This association was replicated in an independent sample of 12 patients with psoriasis/psoriatic arthritis (rho=0.76; p=0.003). Indirect effects analysis, showed that there was a significant overlap in the variance explained by 5-HTT availability and TNF-α concentrations on BDI scores. Treatment with etanercept for 6-8weeks was associated with a significant reduction in 5-HTT availability (Z=2.09; p=0.03; r=0.6) consistent with a functional link. Our findings confirm an association between TNF-α and 5-HTT in both the basal physiological and pathological condition. Modulation of both TNF-α and 5-HTT by etanercept indicate the presence of a mechanistic pathway whereby circulating inflammatory cytokines are related to central nervous system substrates underlying major depression. PMID:26255693

  3. 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

  4. 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.

  5. Mother-daughter correlation of central obesity and other noncommunicable disease risk factors: Tehran Lipid and Glucose Study.

    PubMed

    Heidari, Zahra; Hosseinpanah, Farhad; Barzin, Maryam; Safarkhani, Maryam; Azizi, Fereidoun

    2015-03-01

    This study aimed to investigate the mother-daughter correlation for central obesity and other noncommunicable disease risk factors. The authors used metabolic and anthropometric data from the Tehran Lipid and Glucose Study, enrolling 1041 mother-daughter pairs for the current study. Three age strata were defined: 3 to 9 years for childhood (146 mother-daughter pairs), 10 to 17 years for adolescence (395 mother-daughter pairs), and 18 to 25 years for early adulthood (500 mother-daughter pairs). Familial associations for central obesity and other noncommunicable disease risk factors were assessed. The prevalence of central obesity was 44.7% in mothers and 11.2% in daughters (6.2% in the 3-9, 19.2% in the 10-17, and 6.4% in the 18-25 years groups). Mothers with central obesity were more likely than nonobese mothers to have daughters with central obesity (10.5% and 1.7%, respectively; P = .0001). Central obesity indices among daughters were positively correlated with those of their mothers in all 3 age strata. Correlations for other noncommunicable disease risk factors were analyzed before and after adjusting the risk factor levels for mothers' and daughters' waist circumferences (WCs) within each group to determine whether risk factor correlations were, in part, a result of the central obesity correlations. After the non-communicable disease risk factor levels of participants were adjusted for their WCs, the mother-daughter correlations remained significant. The consistent association of central obesity between mothers and daughters may indicate the key role that could be played by the mother in the primary prevention of central obesity, particularly in high-risk families. PMID:22500034

  6. ICF-based functional components and contextual factors as correlates of perceived quality of life for youth with chronic conditions

    PubMed Central

    Wright, Virginia; DeWit, David; Miller, Linda

    2014-01-01

    Purpose: To explore International Classification of Functioning, Disability and Health (ICF)-based functional components and contextual factors associated with perceived quality of life (QOL) for youth with chronic conditions from the perspective of youth and parents. Method: Baseline data were obtained from a longitudinal study examining predictors of changes in perceived QOL for youth with chronic conditions. 439 youth aged 11–17 (and one of their parents) completed a questionnaire. Standardized tools were used to measure youth functioning, contextual factors and perceived QOL. Multivariate linear regression analyses, controlling for socio-demographic and health information, were conducted to explore correlations among youth functioning/contextual factors and youth and parent perceptions of youth QOL. Results: Significant (p ≤ 0.05) negative correlates with both youth and parent perceptions of youth QOL included pain/other physical symptoms and emotional symptoms. Significant factors positively correlated with youth and parent perceptions of youth QOL included school productivity and spirituality. Other significant positive correlates of youth perspectives were family social support and school belongingness/safety. Family functioning was positively correlated, and youth social anxiety and environmental barriers were negatively correlated, with parent perceptions of youth QOL. Conclusions: This study provides preliminary evidence of factors upon which services aimed at improving perceived QOL of youth with chronic conditions could be based. Implications for Rehabilitation This study supports the utility of clinicians assessing the QOL of youth with chronic conditions in terms of youths' and their families' perspectives. This is the first study to identify key factors that impact perceived QOL at one point in time across a group of youth with chronic conditions, offering clinicians a main starting-point for considering youths' strengths and needs and the

  7. 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

  8. 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.

  9. 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

  10. Eliminating Friction with Friction: 2D Janssen Effect in a Friction-Driven System

    NASA Astrophysics Data System (ADS)

    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.

  11. Personality disorders in substance abusers: Validation of the DIP-Q through principal components factor analysis and canonical correlation analysis

    PubMed Central

    Hesse, Morten

    2005-01-01

    Background Personality disorders are common in substance abusers. Self-report questionnaires that can aid in the assessment of personality disorders are commonly used in assessment, but are rarely validated. Methods The Danish DIP-Q as a measure of co-morbid personality disorders in substance abusers was validated through principal components factor analysis and canonical correlation analysis. A 4 components structure was constructed based on 238 protocols, representing antagonism, neuroticism, introversion and conscientiousness. The structure was compared with (a) a 4-factor solution from the DIP-Q in a sample of Swedish drug and alcohol abusers (N = 133), and (b) a consensus 4-components solution based on a meta-analysis of published correlation matrices of dimensional personality disorder scales. Results It was found that the 4-factor model of personality was congruent across the Danish and Swedish samples, and showed good congruence with the consensus model. A canonical correlation analysis was conducted on a subset of the Danish sample with staff ratings of pathology. Three factors that correlated highly between the two variable sets were found. These variables were highly similar to the three first factors from the principal components analysis, antagonism, neuroticism and introversion. Conclusion The findings support the validity of the DIP-Q as a measure of DSM-IV personality disorders in substance abusers. PMID:15910688

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. Influence of snow properties on dense avalanche friction parameters

    NASA Astrophysics Data System (ADS)

    Mohamed, Naaim

    2013-04-01

    The values of the Voellmy friction parameters of 735 historical avalanches that occurred along 26 paths in the Chamonix valley since 1958 are back-analysed with a depth-averaged hydraulic model including sub models for erosion, entrainment and deposition. For each path, the longitudinal and crosswise topographic profiles were derived from a high resolution digital elevation model acquired by laser scanning. The initial snow depth and snow cohesion, as well as various physical properties of snow, were computed from numerical simulations of the detailed snowpack model Crocus fed by the SAFRAN meteorological analysis. For each event, the full ranges of the two friction parameters were scanned and the pairs of friction parameters for which the run-out altitude is found close enough to the observed one (with an uncertainty of 5m), were retained. Statistical class analysis was used to investigate the correlation between the obtained friction coefficients and the snow physical properties. Concerning the inertial friction coefficient, no evident trend with the snow parameters was found. For the static friction coefficient, an increasing trend with the temperature and the density was observed, as well as a decreasing trend with the liquid water content and the initial snow depth.

  17. 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.

  18. Frictional heating, fluid pressure, and the resistance to fault motion

    NASA Astrophysics Data System (ADS)

    Lachenbruch, Arthur H.

    1980-11-01

    Expansion of pore fluid caused by frictional heating might have an important effect on the factional resistance and temperature during an earthquake and a controlling influence on the physics of the earthquake process. When confined water is heated, the pressure increases rapidly (≳10 bars/°C). As Sibson (1973) has pointed out, this could cause a sharp reduction of effective normal stress and dynamic friction on the fault surface. Whether or not this transient stress reduction occurs depends upon the tandem operation of several processes, any of which can break the chain that links frictional heat to frictional stress: the friction must cause an appreciable temperature rise (imposing conditions on the width of the shear zone and rate of conductive transport); the temperature rise must cause an appreciable fluid pressure rise (imposing conditions on the rate of pore dilatation or hydrofracturing, and the rate of Darcian transport); the fluid pressure rise must cause an appreciable reduction of friction (requiring the presence of a continuous fluid phase). Each process depends upon event duration, particle velocity, and the initial value of dynamic friction. With the present uncertainty in the controlling parameters (principally permeability, width of the shear zone, initial stress, and factors controlling transient hydrofracture and pore dilatation) a wide variety of fault behavior is possible. Limits to fault behavior for various ranges of the controlling parameters can be estimated from the governing equations, however, and results can be summarized graphically. If the effective stress law applies and pore dilatation is unimportant, dynamic friction would drop from an initial value of 1 kbar to ˜100 bars when shear strain reached 10 for most earthquakes if the permeability were less than 0.1 μdarcy; the maximum temperature rise would be only ˜150°C irrespective of final strain. If the permeability were ≳100 mdarcies, however, friction would be unaffected

  19. 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

  20. 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)

  1. 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

  2. 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.

  3. Flexure Bearing Reduces Startup Friction

    NASA Technical Reports Server (NTRS)

    Clingman, W. Dean

    1991-01-01

    Design concept for ball bearing incorporates small pieces of shim stock, wire spokes like those in bicycle wheels, or other flexing elements to reduce both stiction and friction slope. In flexure bearing, flexing elements placed between outer race of ball bearing and outer ring. Elements flex when ball bearings encounter small frictional-torque "bumps" or even larger ones when bearing balls encounter buildups of grease on inner or outer race. Flexure of elements reduce high friction slopes of "bumps", helping to keep torque between outer ring and inner race low and more nearly constant. Concept intended for bearings in gimbals on laser and/or antenna mirrors.

  4. 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.

  5. 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.

  6. Coincidence gate utilization factors for neutron correlation counters with up to three components in the die-away profile

    SciTech Connect

    Croft, S.; McElroy, R.D.; Kane, S.C.

    2007-07-01

    We present analytical expressions for the gate utilization factors (GUFs), up to fourth order, for both signal triggered and random triggered histograms based on a three-component capture time profile. These are useful for refined design performance calculations of passive neutron multiplicity counters using shift register correlation analysis. To our knowledge, these expressions are new. (authors)

  7. 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

  8. 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

  9. 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.

  10. Using distance correlation and SS-ANOVA to assess associations of familial relationships, lifestyle factors, diseases, and mortality.

    PubMed

    Kong, Jing; Klein, Barbara E K; Klein, Ronald; Lee, Kristine E; Wahba, Grace

    2012-12-11

    We present a method for examining mortality as it is seen to run in families, and lifestyle factors that are also seen to run in families, in a subpopulation of the Beaver Dam Eye Study. We observe that pairwise distance between death age in related persons is on average less than pairwise distance in death age between random pairs of unrelated persons. Our goal is to examine the hypothesis that pairwise differences in lifestyle factors correlate with the observed pairwise differences in death age that run in families. Szekely and Rizzo [Szekely GJ, Rizzo ML (2009) Ann Appl Stat 3(4): 1236-1265] have recently developed a method called distance correlation, which is suitable for this task with some enhancements. We build a Smoothing Spline ANOVA (SS-ANOVA) model for predicting death age based on four major lifestyle factors generally known to be related to mortality and four major diseases contributing to mortality, to develop a lifestyle mortality risk vector and a disease mortality risk vector. We then examine to what extent pairwise differences in these scores correlate with pairwise differences in mortality as they occur between family members and between unrelated persons. We find significant distance correlations between death ages, lifestyle factors, and family relationships. Considering only sib pairs compared with unrelated persons, distance correlation between siblings and mortality is, not surprisingly, stronger than that between more distantly related family members and mortality. The methodological approach here adapts to exploring relationships between multiple clusters of variables with observable (real-valued) attributes, and other factors for which only possibly nonmetric pairwise dissimilarities are observed. PMID:23175793

  11. 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

  12. 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

  13. Rubber friction and tire dynamics.

    PubMed

    Persson, B N J

    2011-01-12

    We propose a simple rubber friction law, which can be used, for example, in models of tire (and vehicle) dynamics. The friction law is tested by comparing numerical results to the full rubber friction theory (Persson 2006 J. Phys.: Condens. Matter 18 7789). Good agreement is found between the two theories. We describe a two-dimensional (2D) tire model which combines the rubber friction model with a simple mass-spring description of the tire body. The tire model is very flexible and can be used to accurately calculate μ-slip curves (and the self-aligning torque) for braking and cornering or combined motion (e.g. braking during cornering). We present numerical results which illustrate the theory. Simulations of anti-blocking system (ABS) braking are performed using two simple control algorithms. PMID:21406818

  14. Rubber friction and tire dynamics

    NASA Astrophysics Data System (ADS)

    Persson, B. N. J.

    2011-01-01

    We propose a simple rubber friction law, which can be used, for example, in models of tire (and vehicle) dynamics. The friction law is tested by comparing numerical results to the full rubber friction theory (Persson 2006 J. Phys.: Condens. Matter 18 7789). Good agreement is found between the two theories. We describe a two-dimensional (2D) tire model which combines the rubber friction model with a simple mass-spring description of the tire body. The tire model is very flexible and can be used to accurately calculate μ-slip curves (and the self-aligning torque) for braking and cornering or combined motion (e.g. braking during cornering). We present numerical results which illustrate the theory. Simulations of anti-blocking system (ABS) braking are performed using two simple control algorithms.

  15. 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.

  16. Normal faults, normal friction?

    NASA Astrophysics Data System (ADS)

    Collettini, Cristiano; Sibson, Richard H.

    2001-10-01

    Debate continues as to whether normal faults may be seismically active at very low dips (δ < 30°) in the upper continental crust. An updated compilation of dip estimates (n = 25) has been prepared from focal mechanisms of shallow, intracontinental, normal-slip earthquakes (M > 5.5; slip vector raking 90° ± 30° in the fault plane) where the rupture plane is unambiguously discriminated. The dip distribution for these moderate-to-large normal fault ruptures extends from 65° > δ > 30°, corresponding to a range, 25° < θr < 60°, for the reactivation angle between the fault and inferred vertical σ1. In a comparable data set previously obtained for reverse fault ruptures (n = 33), the active dip distribution is 10° < δ = θr < 60°. For vertical and horizontal σ1 trajectories within extensional and compressional tectonic regimes, respectively, dip-slip reactivation is thus restricted to faults oriented at θr ≤ 60° to inferred σ1. Apparent lockup at θr ≈ 60° in each dip distribution and a dominant 30° ± 5° peak in the reverse fault dip distribution, are both consistent with a friction coefficient μs ≈ 0.6, toward the bottom of Byerlee's experimental range, though localized fluid overpressuring may be needed for reactivation of less favorably oriented faults.

  17. Rolling-Friction Robotic Gripper

    NASA Technical Reports Server (NTRS)

    Vranish, John M.

    1992-01-01

    Robotic gripper using rolling-friction fingers closes in on object with interface designed to mate with rollers somewhat misaligned initially, aligns object with respect to itself, then holds object securely in uniquely determined position and orientation. Operation of gripper causes minimal wear and burring of gripper and object. Exerts minimal friction forces on object when grasping and releasing. Releases object easily and reliably even when side forces and torques are between itself and object.

  18. 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.

  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. PMID:22139094

  20. Higher Order Factor Structure of a Self-Control Test: Evidence from Confirmatory Factor Analysis with Polychoric Correlations.

    ERIC Educational Resources Information Center

    Flora, David B.; Finkel, Eli J.; Foshee, Vangie A.

    2003-01-01

    Studied the higher order factor structure of a self-control test developed by H. Grasmick and others (1993). Results for 1,966 eighth and ninth graders show that the self-control test may provide more valid measurement of the constructs it was designed to measure than previous research suggested. (SLD)

  1. 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.…

  2. Experiment study on friction drive

    NASA Astrophysics Data System (ADS)

    Wang, Guomin; Ma, Lisheng; Yao, Zhengqiu; Li, Guoping

    2004-09-01

    In the past years, friction drive was developed to overcome the inherent deficiencies in both worm drive and gear drive. No periodical error and free of backlash are the main advantages of friction drive. With the trend towards bigger and bigger aperture of the optical telescopes, there are some reports about friction drive employed to drive the telescopes. However friction drive has its own deficiencies, such as slippage and creepage. This report here describes the study on the friction drive finished in an experiment arranged by LAMOST project. It comprises three main parts. First, it introduces the experiment apparatus and proposes a new kind of measurement and adjustment mechanisms. Secondly, the report gives the analysis of friction drive characteristics theoretically, such as slippage, creepage and gives the results of corresponding experiments. The experiment shows that the lowest stable speed reaches 0.05″/s with precision of 0.009″(RMS), the preload has little influence on the drive precision in the case of constant velocity and the variable velocity when the angle acceleration is less than 5″/s2 with close loop control and the creepage velocity of this experiment system is 1.47″/s. Lastly, the analysis in the second section lists some measures to improve the precision and stability further. These measures have been actually conducted in the testing system and proved to be reliable.

  3. Solid friction between soft filaments

    PubMed Central

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

    2015-01-01

    Any macroscopic deformation of a filamentous bundle is necessarily accompanied by local sliding and/or stretching of the constituent filaments1,2. 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. PMID:25730393

  4. The Effect of Friction on Penetration in Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Rapp, Steve

    2002-01-01

    "Friction stir butt welding," as it was originally termed by Wayne Thomas and Christopher Dawes, in the early 1990s, but now commonly called "friction stir welding," has made great progress as a new welding technique. Marshall Space Flight Center has been investigating the use of FSW for assembly of the Shuttle's external fuel tank since the late 1990s and hopes to have the process in use by the summer of 2002. In FSW, a cylindrical pin tool of hardened steel, is rotated and plunged into the abutting edges of the parts to be joined. The tool is plunged into the weldment to within about .050 in of the bottom to assure full penetration. As the tool moves along the joint, the tool shoulder helps produce frictional heating, causing the material to plasticize. The metal of the two abutting plates flows from the front of the tool to the back where it cools and coalesces to form a weld in the solid phase. One quarter inch thick plates of aluminum alloy 2219 were used in this study. Two samples, each consisting of two 4 in x 12 in plates, were friction stir welded. The anvil for one sample was coated with molybdenum sulfide, while for the other sample a sheet of roughened stainless steel was placed between the anvil and the sample. The retractable pin tool was used so that the depth of the pin tool penetration could be varied. As welding proceeded, the length of the pin tool was gradually increased from the starting point. The purpose of this investigation is to find out at what point, in the down ramp, penetration occurs. Differences in root structure of the friction stir weld due to differences in anvil friction will be observed. These observations will be analyzed using friction stir weld theory.

  5. 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.)

  6. The ultra-low speed research on friction drive of large telescope

    NASA Astrophysics Data System (ADS)

    Du, Fujia; Wang, Daxing

    2006-06-01

    No periodical error and free of backlash are the main advantages of friction drive. So friction drive is applied in many ultra-low speed systems in the past years. With the trend that the aperture of optical telescope becomes bigger and bigger, there are some reports about friction drive employed to drive the telescopes. However friction drive also brings up challenge to control system because the inherent nonlinear characteristics of friction drive. This report describes the study on the friction drive finished in an experiment arranged by LAMOST project. It comprises three main parts. First, it introduces the experiment apparatus and presents a friction nonlinear curve to indicate the nonlinear characteristics of friction drive. Subsequently, this report illuminates the negative result that influenced by the nonlinear characteristic. Secondly, this report use nonlinear PID control algorithm to control friction drive. It achieves ultra-low speed and high precision position control. The ultra-low velocity is 0.2"/S and error is 0.032"(RMS). This report also lists some factors that influence the precision of speed. Lastly, this report gives the analysis fluctuating speed of friction drive and applies acceleration feedback to diminish this fluctuating.

  7. 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

  8. High speed friction microscopy and nanoscale friction coefficient mapping

    NASA Astrophysics Data System (ADS)

    Bosse, James L.; Lee, Sungjun; Andersen, Andreas Sø; Sutherland, Duncan S.; Huey, Bryan D.

    2014-11-01

    As mechanical devices in the nano/micro length scale are increasingly employed, it is crucial to understand nanoscale friction and wear especially at technically relevant sliding velocities. Accordingly, a novel technique has been developed for friction coefficient mapping (FCM), leveraging recent advances in high speed AFM. The technique efficiently acquires friction versus force curves based on a sequence of images at a single location, each with incrementally lower loads. As a result, true maps of the coefficient of friction can be uniquely calculated for heterogeneous surfaces. These parameters are determined at a scan velocity as fast as 2 mm s-1 for microfabricated SiO2 mesas and Au coated pits, yielding results that are identical to traditional speed measurements despite being ~1000 times faster. To demonstrate the upper limit of sliding velocity for the custom setup, the friction properties of mica are reported from 200 µm s-1 up to 2 cm s-1. While FCM is applicable to any AFM and scanning speed, quantitative nanotribology investigations of heterogeneous sliding or rolling components are therefore uniquely possible, even at realistic velocities for devices such as MEMS, biological implants, or data storage systems.

  9. Pulmonary Hypertension an Independent Risk Factor for Death in Intensive Care Unit: Correlation of Hemodynamic Factors with Mortality

    PubMed Central

    Saydain, Ghulam; Awan, Aamir; Manickam, Palaniappan; Kleinow, Paul; Badr, Safwan

    2015-01-01

    OBJECTIVE Critically ill patients with pulmonary hypertension (PH) pose additional challenges due to the existence of right ventricular (RV) dysfunction. The purpose of this study was to assess the impact of hemodynamic factors on the outcome. METHODS We reviewed the records of patients with a diagnosis of PH admitted to the intensive care unit. In addition to evaluating traditional hemodynamic parameters, we defined severe PH as right atrial pressure >20 mmHg, mean pulmonary artery pressure >55 mmHg, or cardiac index (CI) <2 L/min/m2. We also defined the RV functional index (RFI) as pulmonary artery systolic pressure (PASP) adjusted for CI as PASP/CI; increasing values reflect RV dysfunction. RESULTS Fifty-three patients (mean age 60 years, 72% women, 79% Blacks), were included in the study. Severe PH was present in 68% of patients who had higher Sequential Organ Failure Assessment (SOFA) score (6.8 ± 3.3 vs 3.8 ± 1.6; P = 0.001) and overall in-hospital mortality (36% vs 6%; P = 0.02) compared to nonsevere patients, although Acute Physiology and Chronic Health Evaluation (APACHE) II scores (19.9 ± 7.5 vs 18.5 ± 6.04; P = 0.52) were similar and sepsis was more frequent among nonsevere PH patients (31 vs 64%; P = 0.02). Severe PH (P = 0.04), lower mean arterial pressure (P = 0.04), and CI (P = 0.01); need for invasive ventilation (P = 0.02) and vasopressors (P = 0.03); and higher SOFA (P = 0.001), APACHE II (P = 0.03), pulmonary vascular resistance index (PVRI) (P = 0.01), and RFI (P = 0.004) were associated with increased mortality. In a multivariate model, SOFA [OR = 1.45, 95% confidence interval (C.I.) = 1.09–1.93; P = 0.01], PVRI (OR = 1.12, 95% C.I. = 1.02–1.24; P = 0.02), and increasing RFI (OR = 1.06, 95% C.I. = 1.01–1.11; P = 0.01) were independently associated with mortality. CONCLUSION PH is an independent risk factor for mortality in critically ill patients. Composite factors rather than individual hemodynamic parameters are better predictors of

  10. Simple rule can be used to calculate friction loss in piping

    SciTech Connect

    Durand, A.A.

    1997-05-26

    A simple rule for calculating friction loss in piping has been developed. Called the Rule of Fours, it is designed to be easily memorized for use in the field. For determining pressure loss in piping, friction-loss tables are often more convenient than calculating the Reynolds number or finding the friction factor on a Moody chart, then calculating the friction loss by the Darcy or Fanning relationships. Friction-loss tables can be found in the Crane Technical Paper, Hydraulic Institute Engineering Data Book, and several other references. There are occasions, however, when such tables are not readily available to the engineer trying to estimate pressure drop in fluid flowing through pipelines. Because friction loss is essentially a point function, it is only necessary to determine the pressure drop for a given set of conditions. The author has developed a simple rule for such calculations.

  11. 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. PMID:25549310

  12. Identification of maximum road friction coefficient and optimal slip ratio based on road type recognition

    NASA Astrophysics Data System (ADS)

    Guan, Hsin; Wang, Bo; Lu, Pingping; Xu, Liang

    2014-09-01

    The identification of maximum road friction coefficient and optimal slip ratio is crucial to vehicle dynamics and control. However, it is always not easy to identify the maximum road friction coefficient with high robustness and good adaptability to various vehicle operating conditions. The existing investigations on robust identification of maximum road friction coefficient are unsatisfactory. In this paper, an identification approach based on road type recognition is proposed for the robust identification of maximum road friction coefficient and optimal slip ratio. The instantaneous road friction coefficient is estimated through the recursive least square with a forgetting factor method based on the single wheel model, and the estimated road friction coefficient and slip ratio are grouped in a set of samples in a small time interval before the current time, which are updated with time progressing. The current road type is recognized by comparing the samples of the estimated road friction coefficient with the standard road friction coefficient of each typical road, and the minimum statistical error is used as the recognition principle to improve identification robustness. Once the road type is recognized, the maximum road friction coefficient and optimal slip ratio are determined. The numerical simulation tests are conducted on two typical road friction conditions(single-friction and joint-friction) by using CarSim software. The test results show that there is little identification error between the identified maximum road friction coefficient and the pre-set value in CarSim. The proposed identification method has good robustness performance to external disturbances and good adaptability to various vehicle operating conditions and road variations, and the identification results can be used for the adjustment of vehicle active safety control strategies.

  13. Correlation between Sun Protection Factor and Antioxidant Activity, Phenol and Flavonoid Contents of some Medicinal Plants

    PubMed Central

    Ebrahimzadeh, Mohammad Ali; Enayatifard, Reza; Khalili, Masoumeh; Ghaffarloo, Mahdieh; Saeedi, Majid; Yazdani Charati, Jamshid

    2014-01-01

    Long exposure of UV radiation increases risk of skin diseases such as cancer and photoallergic reactions. UV-B (280-320 nm) radiation is mainly responsible for inducing the skin problems. Skin protection is a suitable method against ultraviolet radiation-induced damage. Various synthetic agents have been used as photo protective but because of their potential toxicity in humans, they have limited usage. Natural substances have been recently considered as potential sunscreen resources due to their absorption in the UV region and their antioxidant activity. In the present study, the UV protective effects of 20 extracts from four common medicinal plants were evaluated. Their phenol and flavonoid contents and antioxidant activities were determined and correlation between SPF and these contents were evaluated. SPFs were between 0.102 and 24.470. The highest value was reached with ultrasonic extract of Crataegus pentagyna (SPF = 24.47) followed by methanolic extract of Feijoa sellowiana (SPF = 1.30). Good correlation was found between SPF and phenolic contents (Correlation Coefficient = 0.55 and p = 0.01) but no correlations were found between SPF and flavonoid contents or antioxidant activity. These extracts can be used alone or as additives in other sun screen formulations to enhance their SPF. PMID:25276206

  14. 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…

  15. Correlation between Sun Protection Factor and Antioxidant Activity, Phenol and Flavonoid Contents of some Medicinal Plants.

    PubMed

    Ebrahimzadeh, Mohammad Ali; Enayatifard, Reza; Khalili, Masoumeh; Ghaffarloo, Mahdieh; Saeedi, Majid; Yazdani Charati, Jamshid

    2014-01-01

    Long exposure of UV radiation increases risk of skin diseases such as cancer and photoallergic reactions. UV-B (280-320 nm) radiation is mainly responsible for inducing the skin problems. Skin protection is a suitable method against ultraviolet radiation-induced damage. Various synthetic agents have been used as photo protective but because of their potential toxicity in humans, they have limited usage. Natural substances have been recently considered as potential sunscreen resources due to their absorption in the UV region and their antioxidant activity. In the present study, the UV protective effects of 20 extracts from four common medicinal plants were evaluated. Their phenol and flavonoid contents and antioxidant activities were determined and correlation between SPF and these contents were evaluated. SPFs were between 0.102 and 24.470. The highest value was reached with ultrasonic extract of Crataegus pentagyna (SPF = 24.47) followed by methanolic extract of Feijoa sellowiana (SPF = 1.30). Good correlation was found between SPF and phenolic contents (Correlation Coefficient = 0.55 and p = 0.01) but no correlations were found between SPF and flavonoid contents or antioxidant activity. These extracts can be used alone or as additives in other sun screen formulations to enhance their SPF. PMID:25276206

  16. 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…

  17. 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).

  18. Correlation Between Cyclo-oxygenase-2 and Vascular Endothelial Growth Factor Expression in Canine and Feline Squamous Cell Carcinomas.

    PubMed

    Millanta, F; Andreani, G; Rocchigiani, G; Lorenzi, D; Poli, A

    2016-05-01

    Overexpression of cyclo-oxygenase (COX)-2 is involved in tumour growth and spread by modulating the production of angiogenic factors such as vascular endothelial growth factor (VEGF). Expression of COX-2 and VEGF was investigated immunohistochemically in 51 canine and feline cutaneous and non-cutaneous squamous cell carcinomas (SCCs) and the correlation between expression of these molecules and clinicopathological variables was evaluated. COX-2 and VEGF expression was not observed in normal skin keratinocytes. COX-2 overexpression occurred in 53% and 61% of the canine and feline SCCs, respectively. The expression of both markers was higher in cutaneous compared with non-cutaneous SCCs. In both species COX-2 and VEGF expression was correlated with the progression of the disease, but not with the presence of lymphatic invasion, tumour grading or tumour classification in the cutaneous tumours. Further study will be required to understand the role of the COX-2 pathway in angiogenesis in SCC. PMID:27012907

  19. Frictional Melting of Peridotite and Seismic Slip

    NASA Astrophysics Data System (ADS)

    di Toro, G.; Del Gaudio, P.; Han, R.; Hirose, T.; Nielsen, S.; Shimamoto, T.; Cavallo, A.

    2008-12-01

    The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is one of the main factors controlling earthquake mechanics. In particular, friction-induced rock melting and melt lubrication during seismic slip may be typical at mantle depths, based on field studies, seismological evidence, torsion experiments and theoretical studies. To investigate the (1) dynamic strength of faults and (2) the frictional melting processes in mantle rocks, we performed 20 experiments with the Balmuccia peridotite in a high- velocity rotary shear apparatus. Experiments were conducted on cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4 to 16.1 MPa), slip rates (0.23 to 1.14 m/s) and displacements (1.5 to 71 m). The dynamic strength of experimental faults evolved with displacement: after a peak (first strengthening) at the initiation of slip, fault strength abruptly decreased (first weakening), then increased (second strengthening) and eventually decreased (second weakening) towards a steady-state value. The microstructural and geochemical (FE-SEM, EPMA and EDS) investigation of the slipping zone from experiments interrupted at different displacements, revealed that second strengthening was associated with the production of a grain-supported melt-poor layer, while second weakening and steady-state with the formation of a continuous melt-rich layer. The temperature of the frictional melt was up to 1780 Celsius. Microstructures formed during the experiments were identical to those found in natural ultramafic pseudotachylytes. By performing experiments for increasing normal stresses and slip rates, steady-state shear stress slightly increased with increasing normal stress (friction coefficient of 0.15) and, for a given normal stress, decreased with increasing slip rate. The dependence of steady-state shear stress with normal stress and slip rate is described by a constitutive equation for melt lubrication. The presence of

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Modeling of Instabilities and Self-organization at the Frictional Interface

    NASA Astrophysics Data System (ADS)

    Mortazavi, Vahid

    The field of friction-induced self-organization and its practical importance remains unknown territory to many tribologists. Friction is usually thought of as irreversible dissipation of energy and deterioration; however, under certain conditions, friction can lead to the formation of new structures at the interface, including in-situ tribofilms and various patterns at the interface. This thesis studies self-organization and instabilities at the frictional interface, including the instability due to the temperature-dependency of the coefficient of friction, the transient process of frictional running-in, frictional Turing systems, the stick-and-slip phenomenon, and, finally, contact angle (CA) hysteresis as an example of solid-liquid friction and dissipation. All these problems are chosen to bridge the gap between fundamental interest in understanding the conditions leading to self-organization and practical motivation. We study the relationship between friction-induced instabilities and friction-induced self-organization. Friction is usually thought of as a stabilizing factor; however, sometimes it leads to the instability of sliding, in particular when friction is coupled with another process. Instabilities constitute the main mechanism for pattern formation. At first, a stationary structure loses its stability; after that, vibrations with increasing amplitude occur, leading to a limit cycle corresponding to a periodic pattern. The self-organization is usually beneficial for friction and wear reduction because the tribological systems tend to enter a state with the lowest energy dissipation. The introductory chapter starts with basic definitions related to self-organization, instabilities and friction, literature review, and objectives. We discuss fundamental concepts that provide a methodological tool to investigate, understand and enhance beneficial processes in tribosystems which might lead to self-organization. These processes could result in the ability of a

  7. 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.

  8. Tuning frictions between graphene layers via Li ion intercalation

    NASA Astrophysics Data System (ADS)

    Lu, Aijiang; Wan, Jiayu; Li, Teng; Hu, Liangbing; Univerisyt of Maryland, College Park Team

    Graphite intercalated with Li ions are widely studied and applied in Li ion batteries. It was revealed in experiments that, the Li ion intercalation leads to a phase transition of the graphite with about 10% volume expansion. The increased interlayer distance should contribute to decrease the frictions between the grahene layers, but the Li ion intercalation would take an opposite effect. In order to show the total effect of the Li ion interalation, we studied the frictions between graphene layers with and without lithiation, based on density functional theory (DFT). In a sandwich-like model, slipping of the middle sheet of the graphene was simulated. Displacements between layers were fixed and the other parts were relaxed, thus the energies were record to estimate the energy barriers accordingly. We found that the frictions between the graphene layers with the Li ion intercalation are higher than those without intercalation. The energy barrier appears correlated with the concentration of the intercalated ions. As the atomic ratio between lithium and carbon increases from 0 (no intercalation) to 1:6, the energy barriers increase from 0.01 eV/atom to 0.05 eV/atom or so. Such an interesting result indicates that, just via ion intercalation, we can effectively tune the friction between graphene layers. Tuning frictions between graphene layers via Li ion intercalation.

  9. A pilot study: a descriptive correlational study of factors associated with weight in college nursing students.

    PubMed

    Singleton, Enrica Kinchen; Bienemy, Cynthia; Hutchinson, Sharon W; Dellinger, Amy; Rami, Janet S

    2011-01-01

    From a convenience sample consisting of junior level nursing students enrolled in a research class at a southern Historically Black College and University (HBCU), this pilot study investigated the percent of participants who were overweight as determined by Body Mass Index (BMI) measurements, and the percent satisfied with their body image as measured by the Strunkard Body Image Scale. BMI measurements were correlated with self esteem, body image, self care, and self efficacy in the regulation of eating habits and exercise regimens. The study found that students with greater BMIs had lower self efficacy beliefs about regulating their exercise habits. Self care, post the self directed intervention, significantly correlated with the pre and post intervention scores of self efficacy to regulate exercise, and with the post intervention scores of self efficacy to regulate eating habits. However, the study found that students' self care capacity was significantly different at the end of the study period. PMID:22165569

  10. Correlation of ER, PR and HER-2/Neu with other Prognostic Factors in Infiltrating Ductal Carcinoma of Breast

    PubMed Central

    Siadati, Sepideh; Sharbatdaran, Majid; Nikbakhsh, Novin; Ghaemian, Naser

    2015-01-01

    Background and Objectives: Breast cancer is the most common malignancy among women in the world. The aim of this study was to assess estrogen receptor (ER), progesterone receptor (PR) and HER-2/neu of infiltrating ductal carcinoma (IDC) with tumor size, histologic grade, lymph node metastasis and age. Methods: This study was carried out on 300 tissue blocks of patients with IDC who underwent mastectomy from 2007 to 2011 in Shahid Beheshti Hospital, affiliated to Babol University of Medical Sciences, Babol, Iran. Data including age, tumor size, and histologic grade and lymph node status retrieved from pathology department. Result: The mean age of the patients was 40.2±2.3 (ranged 19-82 years). ER and PR were positively correlated with each other ( P = 0.001) and they inversely correlated with HER-2/neu ( P =0.001). We observed correlation between ER and PR expression and low histologic grade ( P = 0.001) and HER-2/neu expression and high histologic grade ( P = 0.003). There was correlation between HER-2/neu expression and lymph node involvement ( P =0.03). None of these makers showed correlation with age and tumor size ( P > 0.05). Conclusion: Our findings indicate the importance of ER, PR and HER-2/neu expression as prognostic factors for therapeutic decision. PMID:26351488

  11. 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

  12. 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

  13. 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

  14. 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.

  15. Correlation of fiber composite tensile strength with the ultrasonic stress wave factor

    NASA Technical Reports Server (NTRS)

    Vary, A.; Lark, R. F.

    1978-01-01

    An ultrasonic-acoustic technique was used to indicate the strength variations of tensile specimens of a graphite-epoxy composite. A 'stress wave factor' was determined and its value was found to depend on variations of the fiber-resin bonding as well as fiber orientation. The fiber orientations studied were 0 deg (longitudinal), 10 deg (off-axis), 90 deg (transverse), (0 deg/+ or - 45 deg/0) symmetrical, and (+ or - 45 deg) symmetrical. The stress wave factor can indicate variations of the tensile and shear strengths of composite materials. The stress wave factor was also found to be sensitive to strength variations associated with microporosity and differences in fiber-resin ratio.

  16. Correlation of Fiber Composite Tensile Strength with the Ultrasonic Stress Wave Factor

    NASA Technical Reports Server (NTRS)

    Vary, A.; Lark, R. F.

    1978-01-01

    An ultrasonic-acoustic technique was used to indicate the strength variations of tensile specimens of a graphite-epoxy composite. A stress wave factor was determined and its value was found to depend on variations of the fiber-resin bonding as well as fiber orientation. The fiber orientations studied were 0 deg (longitudinal), 10 deg (off-axis), 90 deg (transverse), 0 deg + or - 45 deg/0 deg symmetrical, and + or - 45 deg] symmetrical. The stress wave factor can indicate variations of the tensile and shear strengths of composite materials. The stress wave factor was also found to be sensitive to strength variations associated with microporosity and differences in fiber-resin ratio.

  17. 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

  18. Frictional melting of peridotite and seismic slip

    NASA Astrophysics Data System (ADS)

    Del Gaudio, P.; di Toro, G.; Han, R.; Hirose, T.; Nielsen, S.; Shimamoto, T.; Cavallo, A.

    2009-06-01

    The evolution of the frictional strength along a fault at seismic slip rates (about 1 m/s) is a key factor controlling earthquake mechanics. At mantle depths, friction-induced melting and melt lubrication may influence earthquake slip and seismological data. We report on laboratory experiments designed to investigate dynamic fault strength and frictional melting processes in mantle rocks. We performed 20 experiments with Balmuccia peridotite in a high-velocity rotary shear apparatus and cylindrical samples (21.8 mm in diameter) over a wide range of normal stresses (5.4-16.1 MPa), slip rates (0.23-1.14 m/s), and displacements (1.5-71 m). During the experiments, shear stress evolved with cumulative displacement in five main stages (stages 1-5). In stage 1 (first strengthening), the coefficient of friction μ increased up to 0.4-0.7 (first peak in friction). In stage 2 (abrupt first weakening), μ decreased to about 0.25-0.40. In stage 3 (gradual second strengthening), shear stress increased toward a second peak in friction (μ = 0.30-0.40). In stage 4 (gradual second weakening), the shear stress decreased toward a steady state value (stage 5) with μ = 0.15. Stages 1 and 2 are of too short duration to be investigated in detail with the current experimental configuration. By interrupting the experiments during stages 3, 4, and 5, microstructural (Field Emission Scanning Electron Microscope) and geochemical (Electron Probe Micro-Analyzer and Energy Dispersive X-Ray Spectroscopy) analysis of the slipping zone suggest that second strengthening (stage 3) is associated with the production of a grain-supported melt-poor layer, while second weakening (stage 4) and steady state (stage 5) are associated with the formation of a continuous melt-rich layer with an estimated temperature up to 1780°C. Microstructures formed during the experiments were very similar to those found in natural ultramafic pseudotachylytes. By performing experiments at different normal stresses and slip

  19. [Geographic patterns and ecological factors correlates of snake species richness in China].

    PubMed

    Cai, Bo; Huang, Yong; Chen, Yue-Ying; Hu, Jun-Hua; Guo, Xian-Guang; Wang, Yue-Zhao

    2012-08-01

    Understanding large-scale geographic patterns of species richness as well its underlying mechanisms are among the most significant objectives of macroecology and biogeography. The ecological hypothesis is one of the most accepted explanations of this mechanism. Here, we studied the geographic patterns of snakes and investigated the relationships between species richness and ecological factors in China at a spatial resolution of 100 km×100 km. We obtained the eigenvector-based spatial filters by Principal Coordinates Neighbor Matrices, and then analyzed ecological factors by multiple regression analysis. The results indicated several things: (1) species richness of snakes showed multi-peak patterns along both the latitudinal and longitudinal gradient. The areas of highest richness of snake are tropics and subtropical areas of Oriental realm in China while the areas of lowest richness are Qinghai-Tibet Plateau, the grasslands and deserts in northern China, Yangtze-Huai Plain, Two-lake Plain, and the Poyang-lake Plain; (2) results of multiple regression analysis explained a total of 56.5% variance in snake richness. Among ecological factors used to explore the species richness patterns, we found the best factors were the normalized difference vegetation index, precipitation in the coldest quarter and temperature annual range ; (3) our results indicated that the model based on the significant variables that (P<0.05) uses a combination of precipitation of coldest quarter, normalized difference vegetation index and temperature annual range is the most parsimonious model for explaining the mechanism of snake richness in China. This finding demonstrates that different ecological factors work together to affect the geographic distribution of snakes in China. Studying the mechanisms that underlie these geographic patterns are complex, so we must carefully consider the choice of impact-factors and the influence of human activities. PMID:22855440

  20. Frictional processes in volcanic conduits

    NASA Astrophysics Data System (ADS)

    Lavallee, Y.; Kendrick, J. E.; Petrakova, L.; Mitchell, T. M.; Heap, M. J.; Hirose, T.; Di Toro, G.; Hess, K.; Dingwell, D. B.

    2012-12-01

    The ascent of high-viscosity magma in upper conduits proceeds via the development of shear zones, which commonly fracture, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. Frictional slip in conduits may occur along magma-rock, rock-rock and magma-magma interfaces, with or without the presence of gouge material. During slip, frictional work is converted to heat, which may result in strong geochemical disequilibria as well as rheological variations, with important consequences on the dynamics of magma ascent. Here, we present a thermo-mechanical study on the ability of volcanic rocks (with different proportions of interstitial glass, crystals and vesicles) to sustain friction, and in some cases to melt, using a high-velocity rotary apparatus. The friction experiments were conducted at a range of slip velocities (1.3 mm/s to 1.3 m/s) along a (fault) plane subjected to different normal stresses (0.5-10 MPa). We observe that the behaviour of volcanic rocks during slip events varies remarkably. Frictional slip along dense crystal-rich rocks is characterized by the occurrence of comminution, commonly followed by melting. In contrast, slip along dense glass rocks rarely proceeds along a discrete plane - a glass subjected to slip tends to shatter as temperature enters the glass transition interval. Alternatively, glass can be slipped against a crystalline material. In the case of porous material, slip generally results in rapid abrasion of the porous material, producing a high amount of ash particles. The inability of the material to preserve its slip surface inhibits the generation of significant heat. Finally, during experiments in which ash gouge occupies the slip zone, friction generates a modest amount of heat and does not induce significant comminution along the slip plane. Mechanically, the frictional coefficients of the tested volcanic material vary significantly, depending whether the material may sustain slip (and

  1. Correlating the anatomical site of injury and work-related factors with sick leave duration following minor musculoskeletal injuries.

    PubMed

    Alshameeri, Zeiad; Mohammed, Mustafa; Malkan, Dilip

    2011-01-01

    Many factors are associated with long sick leaves and therefore, reliance solely on disease-related factors can potentially underestimate sick leave durations. Here, we wanted to assess the association between the injury sites, work-related factors, and the length of sick leaves. Comprehensive medical legal reports of workers with pure minor musculoskeletal injuries were reviewed. 2029 reports of workers were included. 32.8% had sick leaves of less than a week in duration. Lower limb injuries were associated with longer sick leaves only in patients performing strenuous jobs. Public sector workers sustaining an injury at work and performing strenuous jobs were associated with longer sick leaves. Senior workers returned earlier to work, but age and gender were not strongly correlated with long sick leaves. There was a weak but significant association between sick leave duration and the period spent refraining from hobby activities, and almost all patients returned to their work before their hobbies. PMID:21337182

  2. Enhanced translation initiation factor 4G levels correlate with production levels of monoclonal antibodies in recombinant CHO cell lines.

    PubMed

    Pavitt, Graham D

    2016-03-15

    Using cells to manufacture protein-based therapeutics or biopharmaceuticals is a rapidly expanding industrial activity. Chinese hamster ovary (CHO) cells are the most frequently used mammalian host-expression system for the manufacture of biopharmaceuticals. Over the past ∼30 years academic and industrial researchers have studied cell expression characteristics with aims to improve product yield, quality, scalability and reproducibility. Although many steps in the gene expression and secretion pathways have been optimized, little attention has been paid to optimizing protein synthesis factors and regulators during this process. A new study in Biochemical Journal by Mead et al., provides a first systematic study of several protein synthesis factors and finds that the expression level of eIF4G1 correlates with the level of recombinant protein expressed in cultures. Optimizing levels and activities of protein synthesis factors may help to enhance recombinant protein expression of biopharmaceuticals. PMID:26965386

  3. Correlations between the Five Factor Model of Personality and Problem Behavior in Children

    ERIC Educational Resources Information Center

    Masood, Ambrin Faraz

    2009-01-01

    The validity of the Five Factor Model of personality traits has been mainly assessed with adults and late adolescents. Research has shown that adolescents are able to give reliable self-reports regarding their personality dispositions, but only a few studies have explored self-ratings in children younger than 12 years. Consistent patterns of…

  4. Factors affecting job satisfaction and their correlation with educational standards among dental assistants.

    PubMed

    Al Jazairy, Yousra H; Halawany, Hassan Suliman; Hussainan, Nawaf Al; Maflehi, Nassr Al; Abraham, Nimmi Biju; Jacob, Vimal

    2014-01-01

    A disparity exists in the educational qualifications of dental assistants working in various public and private institutions in Riyadh, Saudi Arabia. The aim of this study was to assess the influence of professional and personal characteristics on job satisfaction among dental assistants. A cross-sectional survey was performed among dental assistants using a 24-item self-administered questionnaire. Multinomial logistic regression was used to assess the relationship between overall job satisfaction and other variables. The overall response rate was 72.1%. Factor analysis suggested that five underlying factors were related to job satisfaction. The mean score for overall job satisfaction was 3.86 (satisfied) out of 5. Among the work environment factors, the highest mean score, 4.26 (satisfied), was obtained for quality of service, and the lowest mean score, 2.78 (neutral), was obtained for the perception of income. The income and general prospects of the profession was significantly associated with overall job satisfaction. This study suggests that for dental assistants, professional and personal life, quality of service, perception of income and prestige and self-respect are important factors for job satisfaction. Despite differences in professional formation standards, in general, the study participants were considerably satisfied with their jobs. PMID:24747371

  5. 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…

  6. Parametric Study to Correlate the Applied Factors and Abrasive Wear Resistance of HVOF Coating

    NASA Astrophysics Data System (ADS)

    Sharma, Satpal

    2012-12-01

    Co-Ni-base powder was modified with the addition of CeO2 to study the effect of CeO2 addition on microstructure, hardness, and abrasive wear behavior of the unmodified (without CeO2) and modified (with CeO2) HVOF sprayed coatings. To investigate the abrasive wear behavior of coatings statistical response surface methodology (RSM) with four factors such as load, abrasive size, sliding distance, and temperature with three levels of each factor were used. Analysis of variance (ANOVA) was carried out to determine the significant factors and their interactions. Thus abrasive wear model was developed in terms of main factors and their significant interactions. The validity of the model was evaluated by conducting experiments under different wear conditions. A comparison of modeled and experimental results showed 2-8% error. The wear resistance of coatings increased with the addition of CeO2. This is due to increase in hardness with the addition of CeO2 in Co-Ni-base coatings.

  7. 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,…

  8. Factors Affecting Job Satisfaction and Their Correlation with Educational Standards among Dental Assistants

    PubMed Central

    JAZAIRY, Yousra H. AL; HALAWANY, Hassan Suliman; HUSSAINAN, Nawaf AL; MAFLEHI, Nassr AL; ABRAHAM, Nimmi Biju; JACOB, Vimal

    2014-01-01

    A disparity exists in the educational qualifications of dental assistants working in various public and private institutions in Riyadh, Saudi Arabia. The aim of this study was to assess the influence of professional and personal characteristics on job satisfaction among dental assistants. A cross-sectional survey was performed among dental assistants using a 24-item self-administered questionnaire. Multinomial logistic regression was used to assess the relationship between overall job satisfaction and other variables. The overall response rate was 72.1%. Factor analysis suggested that five underlying factors were related to job satisfaction. The mean score for overall job satisfaction was 3.86 (satisfied) out of 5. Among the work environment factors, the highest mean score, 4.26 (satisfied), was obtained for quality of service, and the lowest mean score, 2.78 (neutral), was obtained for the perception of income. The income and general prospects of the profession was significantly associated with overall job satisfaction. This study suggests that for dental assistants, professional and personal life, quality of service, perception of income and prestige and self-respect are important factors for job satisfaction. Despite differences in professional formation standards, in general, the study participants were considerably satisfied with their jobs. PMID:24747371

  9. 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

  10. 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…

  11. Microsatellite diversity correlated with ecological-edaphic and genetic factors in three microsites of wild emmer wheat in North Israel.

    PubMed

    Li, Y; Fahima, T; Korol, A B; Peng, J; Röder, M S; Kirzhner, V; Beiles, A; Nevo, E

    2000-06-01

    This study was conducted to test the effects of internal (genetic) and external factors on allelic diversity at 27 dinucleotide microsatellite (simple sequence repeat [SSR]) loci in three Israeli natural populations of Triticum dicoccoides from Ammiad, Tabigha, and Yehudiyya, north of the Sea of Galilee. The results demonstrated that SSR diversity is correlated with the interaction of ecological and genetic factors. Genetic factors, including genome (A vs. B), chromosome, motif, and locus, affected average repeat number (ARN), variance in repeat number (sigma), and number of alleles (NA) of SSRs, but the significance of some factors varied among populations. Genome effect on SSR variation may result from different motif types, particularly compound (or imperfect) versus perfect motifs, which may be related to different evolutionary histories of genomes A and B. Ecological factors significantly affected SSR variation. Soil-unique and soil-specific alleles were found in two edaphic groups dwelling on terra rossa and basalt soils across macro- and microgeographical scales. The largest contributions of genetic and ecological effects were found for diversity of ARN and NA, respectively. Multiple regression indicated that replication slippage and unequal crossing over could be important mutational mechanisms, but their significance varied among motifs. Edaphic stresses may affect the probability of replication errors and recombination intermediates and thus control diversity level and divergence of SSRs. The results may indicate that SSR diversity is adaptive, channeled by natural selection and influenced by both internal and external factors and their interactions. PMID:10833191

  12. 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

  13. The Rate of Physicochemical Incompatibilities, Administration Errors. Factors Correlating with Nurses' Errors.

    PubMed

    Fahimi, Fanak; Sefidani Forough, Aida; Taghikhani, Sepideh; Saliminejad, Leila

    2015-01-01

    Medication errors are commonly encountered in hospital setting. Intravenous medications pose particular risks because of their greater complexity and the multiple steps required in their preparation, administration and monitoring. We aimed to determine the rate of errors during the preparation and administration phase of intravenous medications and the correlation of these errors with the demographics of nurses involved in the process. One hundred patients who were receiving IV medications were monitored by a trained pharmacist. The researcher accompanied the nurses during the preparation and administration process of IV medications. Collected data were compared with the acceptable guidelines. A checklist was filled for each IV medication. Demographic data of the nurses were collected as well. A total of 454 IV medications were recorded. Inappropriate administration rate constituted a large proportion of errors in our study (35.3%). No significant or life threatening drug interaction was recorded during the study. Evaluating the impact of the nurses' demographic characteristics on the incidence of medication errors showed that there is a direct correlation between nurses' employment status and the rate of medication errors, while other characteristics did not show a significant impact on the rate of administration errors. Administration errors were significantly higher in temporary 1-year contract group than other groups (p-value < 0.0001). Study results show that there should be more vigilance on administration rate of IV medications to prevent negative consequences especially by pharmacists. Optimizing the working conditions of nurses may play a crucial role. PMID:26185509

  14. The Rate of Physicochemical Incompatibilities, Administration Errors. Factors Correlating with Nurses' Errors

    PubMed Central

    Fahimi, Fanak; Sefidani Forough, Aida; Taghikhani, Sepideh; Saliminejad, Leila

    2015-01-01

    Medication errors are commonly encountered in hospital setting. Intravenous medications pose particular risks because of their greater complexity and the multiple steps required in their preparation, administration and monitoring. We aimed to determine the rate of errors during the preparation and administration phase of intravenous medications and the correlation of these errors with the demographics of nurses involved in the process. One hundred patients who were receiving IV medications were monitored by a trained pharmacist. The researcher accompanied the nurses during the preparation and administration process of IV medications. Collected data were compared with the acceptable guidelines. A checklist was filled for each IV medication. Demographic data of the nurses were collected as well. A total of 454 IV medications were recorded. Inappropriate administration rate constituted a large proportion of errors in our study (35.3%). No significant or life threatening drug interaction was recorded during the study. Evaluating the impact of the nurses’ demographic characteristics on the incidence of medication errors showed that there is a direct correlation between nurses’ employment status and the rate of medication errors, while other characteristics did not show a significant impact on the rate of administration errors. Administration errors were significantly higher in temporary 1-year contract group than other groups (p-value < 0.0001). Study results show that there should be more vigilance on administration rate of IV medications to prevent negative consequences especially by pharmacists. Optimizing the working conditions of nurses may play a crucial role. PMID:26185509

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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

  20. 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).

  1. Correlations Between the Incidence of National Notifiable Infectious Diseases and Public Open Data, Including Meteorological Factors and Medical Facility Resources

    PubMed Central

    Jang, Jin-Hwa; Lee, Ji-Hae; Je, Mi-Kyung; Cho, Myeong-Ji; Bae, Young Mee; Son, Hyeon Seok; Ahn, Insung

    2015-01-01

    Objectives: This study was performed to investigate the relationship between the incidence of national notifiable infectious diseases (NNIDs) and meteorological factors, air pollution levels, and hospital resources in Korea. Methods: We collected and stored 660 000 pieces of publicly available data associated with infectious diseases from public data portals and the Diseases Web Statistics System of Korea. We analyzed correlations between the monthly incidence of these diseases and monthly average temperatures and monthly average relative humidity, as well as vaccination rates, number of hospitals, and number of hospital beds by district in Seoul. Results: Of the 34 NNIDs, malaria showed the most significant correlation with temperature (r=0.949, p<0.01) and concentration of nitrogen dioxide (r=-0.884, p<0.01). We also found a strong correlation between the incidence of NNIDs and the number of hospital beds in 25 districts in Seoul (r=0.606, p<0.01). In particular, Geumcheon-gu was found to have the lowest incidence rate of NNIDs and the highest number of hospital beds per patient. Conclusions: In this study, we conducted a correlational analysis of public data from Korean government portals that can be used as parameters to forecast the spread of outbreaks. PMID:26265666

  2. Childhood atopic dermatitis-Brain-derived neurotrophic factor correlates with serum eosinophil cationic protein and disease severity.

    PubMed

    Fölster-Holst, R; Papakonstantinou, E; Rüdrich, U; Buchner, M; Pite, H; Gehring, M; Kapp, A; Weidinger, S; Raap, U

    2016-07-01

    Several studies have shown that neurotrophins including brain-derived neurotrophic factor (BDNF) play a role in chronic inflammatory skin diseases such as atopic dermatitis (AD). BDNF is increased in the serum samples of adults with AD. Interestingly, eosinophils of these patients can release and produce BDNF. We analyzed BDNF serum levels with ELISA and their correlation with SCORAD score, eosinophil cationic protein (ECP), total IgE, IL-4, IL-13 and IL-31 in children with AD (n = 56) compared to nonatopic healthy children (n = 25). In addition, we analyzed FLG loss-of-function mutations in 17 children with AD and their connection to BDNF. BDNF serum levels were significantly higher in children with AD. Further, BDNF correlated with disease activity, serum ECP, and total IgE serum levels in AD. There was no difference in BDNF levels of filaggrin-positive or filaggrin-negative children with AD, and there was no correlation of BDNF with IL-31 and Th2 cytokines including IL-4 and IL-13. Together, our data add new insights into the pathophysiology of AD, suggesting that serum BDNF which correlates with disease severity contributes to the regulation of inflammation in an eosinophil-, but not Th2-dependent manner. PMID:27087278

  3. Computational analysis reveals a correlation of exon-skipping events with splicing, transcription and epigenetic factors.

    PubMed

    Ye, Zhenqing; Chen, Zhong; Lan, Xun; Hara, Stephen; Sunkel, Benjamin; Huang, Tim H-M; Elnitski, Laura; Wang, Qianben; Jin, Victor X

    2014-03-01

    Alternative splicing (AS), in higher eukaryotes, is one of the mechanisms of post-transcriptional regulation that generate multiple transcripts from the same gene. One particular mode of AS is the skipping event where an exon may be alternatively excluded or constitutively included in the resulting mature mRNA. Both transcript isoforms from this skipping event site, i.e. in which the exon is either included (inclusion isoform) or excluded (skipping isoform), are typically present in one cell, and maintain a subtle balance that is vital to cellular function and dynamics. However, how the prevailing conditions dictate which isoform is expressed and what biological factors might influence the regulation of this process remain areas requiring further exploration. In this study, we have developed a novel computational method, graph-based exon-skipping scanner (GESS), for de novo detection of skipping event sites from raw RNA-seq reads without prior knowledge of gene annotations, as well as for determining the dominant isoform generated from such sites. We have applied our method to publicly available RNA-seq data in GM12878 and K562 cells from the ENCODE consortium and experimentally validated several skipping site predictions by RT-PCR. Furthermore, we integrated other sequencing-based genomic data to investigate the impact of splicing activities, transcription factors (TFs) and epigenetic histone modifications on splicing outcomes. Our computational analysis found that splice sites within the skipping-isoform-dominated group (SIDG) tended to exhibit weaker MaxEntScan-calculated splice site strength around middle, 'skipping', exons compared to those in the inclusion-isoform-dominated group (IIDG). We further showed the positional preference pattern of splicing factors, characterized by enrichment in the intronic splice sites immediately bordering middle exons. Finally, our analysis suggested that different epigenetic factors may introduce a variable obstacle in the

  4. The occurrence rate and correlation factors of thumb-in-palm posture in newborns.

    PubMed

    Hua, Y M; Hung, C H; Yuh, Y S

    2000-03-01

    Bilateral fisting of hands, including adduction and infolding of the thumbs (cortical thumbs), is an expected finding in term infants. Clinically, the cortical thumb position is a transient and normal, but not general, hand posture in newborns. The aim of this study was to analyze the rate of occurrence and the factors possibly affecting the cortical thumb (thumb-in-palm) posture in term newborns. We enrolled 197 low-risk term newborns and observed the posture of their hands once daily from the day of birth for 3 consecutive days. The occurrence rates of the thumb-in-palm posture of the right hand on the first, second, and third days were 62.8%, 60.9%, and 50%, respectively, and those of the left hand were 60.3%, 55.8% and 53.2%, respectively. There was a significant reduction on a day-to-day basis in the right hand and an insignificant reduction in that of the left hand. Factors including sex, gestation age, birth weight, method of delivery, and alertness were analyzed, and no relationship was evident between these factors and the occurrence rates of the cortical thumb posture. Our observations suggest that the cortical thumb posture is indeed a predominant hand posture in our hospital, yet it is not a general phenomenon in all term newborns. PMID:10734252

  5. CORRELATION BETWEEN MAMMOGRAPHY DETECTED BREAST ARTERIAL CALCIFICATIONS AND LIFESTYLE RISK FACTORS.

    PubMed

    Kosović, Vilma; Krolo, Ivan; Zadravec, Dijana; Drviš, Petar

    2015-06-01

    The aim of the study was to investigate the association between some lifestyle-attributable risk factors of atherosclerosis, such as body mass index (BMI), oral contraceptives, hormone replacement therapy, smoking and alcohol consumption with breast arterial calcification (BAC) and its intensity on mammograms, and to assess the impact of these lifestyle risk factors on mammography findings of BAC. This prospective study included 300 women aged 47-69, i.e. a group of 149 women with BAC on mammograms and control group of 151 women without BAC. Self-reported BMI, use of oral contraceptives, hormone replacement therapy, smoking and alcohol consumption were recorded by medical interview. The presence of BAC and its intensity on mammography was compared according to the presence of high BMI and use of hormone therapy, smoking and alcohol consumption. The results showed the highest proportion of smokers (28.9%) in the group with mild BAC as compared with the groups without calcification (14.6%) and with intense calcification (12.1%). Women taking oral contraceptives had a higher level of calcified breast arteries but no significant between-group difference was found for high BMI, hormone therapy and alcohol consumption. Thus, study results showed the mammographic finding of BAC to be inadequate to identify women with some lifestyle-attributable risk factors such as BMI, hormone replacement therapy, smoking and alcohol consumption. PMID:26415310

  6. 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

  7. Correlation of geophysical factors with results of gravity wave detection experiments

    SciTech Connect

    Sazeeva, N.N.

    1986-04-01

    The possible influence of variations in the daily-average sunspot number (W) and geomagnetic-wave amplitude (Ap) on the detections of gravitational-radiation events (GREs) reported by Brown et al. (1982) for a 440-d period in 1979-1981 is investigated statistically. An era-superposition technique is applied to compare 18 GRE periods and 20 non-GRE periods of 7 d each. Both Ap and W are found to be correlated with the GRE signals (the Ap peaking on the day of the GRE), and a bias toward daylight hours for GRE detection (62 percent of GREs in daylight and 43 percent of those between 10 AM and 2 PM local time) is noted. It is inferred that shielded gravitational-wave antennas may be subject to atmospheric EM noise too weak to be detected with available magnetometers. 10 references.

  8. 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.

  9. Exploring the role of internal friction in the dynamics of unfolded proteins using simple polymer models

    NASA Astrophysics Data System (ADS)

    Cheng, Ryan R.; Hawk, Alexander T.; Makarov, Dmitrii E.

    2013-02-01

    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.

  10. Rubber friction for tire tread compound on road surfaces

    NASA Astrophysics Data System (ADS)

    Lorenz, B.; Persson, B. N. J.; Fortunato, G.; Giustiniano, M.; Baldoni, F.

    2013-03-01

    We have measured the surface topography and calculated the surface roughness power spectrum for an asphalt road surface. For the same surface we have measured the friction for a tire tread compound for velocities 10-6 m s-1 < v < 10-3 m s-1 at three different temperatures (at -8 °C, 20 °C and 48 °C). The friction data was shifted using the bulk viscoelasticity shift factor aT to form a master curve. We have measured the effective rubber viscoelastic modulus at large strain and calculated the rubber friction coefficient (and contact area) during stationary sliding and compared it to the measured friction coefficient. We find that for the low velocities and for the relatively smooth road surface we consider, the contribution to friction from the area of real contact is very important, and we interpret this contribution as being due to shearing of a very thin confined rubber smear film.

  11. Rubber friction for tire tread compound on road surfaces.

    PubMed

    Lorenz, B; Persson, B N J; Fortunato, G; Giustiniano, M; Baldoni, F

    2013-03-01

    We have measured the surface topography and calculated the surface roughness power spectrum for an asphalt road surface. For the same surface we have measured the friction for a tire tread compound for velocities 10(-6) m s(-1) < v < 10(-3) m s(-1) at three different temperatures (at -8 °C, 20 °C and 48 °C). The friction data was shifted using the bulk viscoelasticity shift factor a(T) to form a master curve. We have measured the effective rubber viscoelastic modulus at large strain and calculated the rubber friction coefficient (and contact area) during stationary sliding and compared it to the measured friction coefficient. We find that for the low velocities and for the relatively smooth road surface we consider, the contribution to friction from the area of real contact is very important, and we interpret this contribution as being due to shearing of a very thin confined rubber smear film. PMID:23334507

  12. 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

  13. 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.

  14. 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…

  15. Apparatus for measurement of coefficient of friction

    NASA Technical Reports Server (NTRS)

    Slifka, A. J.; Siegwarth, J. D.; Sparks, L. L.; Chaudhuri, Dilip K.

    1990-01-01

    An apparatus designed to measure the coefficient of friction in certain controlled atmospheres is described. The coefficient of friction observed during high-load tests was nearly constant, with an average value of 0.56. This value is in general agreement with that found in the literature and also with the initial friction coefficient value of 0.67 measured during self-mated friction of 440C steel in an oxygen environment.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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

  1. Annoyance of noise stimuli in relation to the spatial factors extracted from the interaural cross-correlation function

    NASA Astrophysics Data System (ADS)

    Sato, Shin-ichi; Kitamura, Toshihiro; Ando, Yochi

    2004-10-01

    While considering auditory-brain model for subjective responses, effects of spatial factors extracted from the interaural cross-correlation function (IACF) on annoyance of noise stimuli are examined. The previously developed indices to measure sound pressure levels (SPL) and frequency characteristics cannot fully explain the psychological effects of noise. In the first experiment, subjects judged their annoyance by changing fluctuations in the magnitude of interaural cross-correlation function (IACC) and the SPL. In the second, they judged their annoyance by changing fluctuations in the interaural time delay (τIACC) and the SPL. Results show that: (1) annoyance increased by increasing the fluctuations of IACC as well as the SPL, (2) annoyance increased by increasing the fluctuations of τIACC as well as the SPL.

  2. 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

  3. Increased Neutrophil/Lymphocyte Ratio in Patients with Depression is Correlated with the Severity of Depression and Cardiovascular Risk Factors

    PubMed Central

    Aydin Sunbul, Esra; Yanartas, Omer; Cengiz, Fatma; Bozbay, Mehmet; Sari, Ibrahim; Gulec, Huseyin

    2016-01-01

    Objective Chronic inflammation is associated with cardiovascular (CV) risk factors and psychiatric disorders. The neutrophil to lymphocyte ratio (NLR) has been investigated as a new biomarker for systemic inflammatory response. The aim of the study is to investigate the relation of NLR with severity of depression and CV risk factors. Methods The study population consisted of 256 patients with depressive disorder. Patients were evaluated with the Hamilton Rating Scale for Depression (HAM-D). Patients were classified into four groups according to their HAM-D score such as mild, moderate, severe, and very severe depression. Patients were also evaluated in terms of CV risk factors. Results Patients with higher HAM-D score had significantly higher NLR levels compared to patients with lower HAM-D score. Correlation analysis revealed that severity of depression was associated with NLR in depressive patients (r=0.333, p<0.001). Patients with one or more CV risk factors have significantly higher NLR levels. Correlation analysis revealed that CV risk factors were associated with NLR in depressive patients (r=0.132, p=0.034). In logistic regression analyses, NLR levels were an independent predictor of severe or very severe depression (odds ratio: 3.02, 95% confidence interval: 1.867-4.884, p<0.001). A NLR of 1.57 or higher predicted severe or very severe depression with a sensitivity of 61.4% and specificity of 61.2%. Conclusion Higher HAM-D scores are associated with higher NLR levels in depressive patients. NLR more than 1.57 was an independent predictor of severe or very severe depression. A simple, cheap white blood cell count may give an idea about the severity of depression. PMID:26766954

  4. 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.

  5. Critical Length Limiting Superlow Friction

    NASA Astrophysics Data System (ADS)

    Ma, Ming; Benassi, Andrea; Vanossi, Andrea; Urbakh, Michael

    2015-02-01

    Since the demonstration of superlow friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micromechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nanomanipulation and can serve as a theoretical basis for designing nanodevices with superlow friction, such as carbon nanotubes.

  6. 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.

  7. Friction-formed liquid droplets

    NASA Astrophysics Data System (ADS)

    Lockwood, A. J.; Anantheshwara, K.; Bobji, M. S.; Inkson, B. J.

    2011-03-01

    The formation of nanoscale liquid droplets by friction of a solid is observed in real-time. This is achieved using a newly developed in situ transmission electron microscope (TEM) triboprobe capable of applying multiple reciprocating wear cycles to a nanoscale surface. Dynamical imaging of the nanoscale cyclic rubbing of a focused-ion-beam (FIB) processed Al alloy by diamond shows that the generation of nanoscale wear particles is followed by a phase separation to form liquid Ga nanodroplets and liquid bridges. The transformation of a two-body system to a four-body solid-liquid system within the reciprocating wear track significantly alters the local dynamical friction and wear processes. Moving liquid bridges are observed in situ to play a key role at the sliding nanocontact, interacting strongly with the highly mobile nanoparticle debris. In situ imaging demonstrates that both static and moving liquid droplets exhibit asymmetric menisci due to nanoscale surface roughness. Nanodroplet kinetics are furthermore dependent on local frictional temperature, with solid-like surface nanofilaments forming on cooling. TEM nanotribology opens up new avenues for the real-time quantification of cyclic friction, wear and dynamic solid-liquid nanomechanics, which will have widespread applications in many areas of nanoscience and nanotechnology.

  8. 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.

  9. Tool Wear in Friction Drilling

    SciTech Connect

    Miller, Scott F; Blau, Peter Julian; Shih, Albert J.

    2007-01-01

    This study investigated the wear of carbide tools used in friction drilling, a nontraditional hole-making process. In friction drilling, a rotating conical tool uses the heat generated by friction to soften and penetrate a thin workpiece and create a bushing without generating chips. The wear of a hard tungsten carbide tool used for friction drilling a low carbon steel workpiece has been investigated. Tool wear characteristics were studied by measuring its weight change, detecting changes in its shape with a coordinate measuring machine, and making observations of wear damage using scanning electron microscopy. Energy dispersive spectroscopy was applied to analyze the change in chemical composition of the tool surface due to drilling. In addition, the thrust force and torque during drilling and the hole size were measured periodically to monitor the effects of tool wear. Results indicate that the carbide tool is durable, showing minimal tool wear after drilling 11000 holes, but observations also indicate progressively severe abrasive grooving on the tool tip.

  10. 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.

  11. Measuring Adhesion And Friction Forces

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa

    1991-01-01

    Cavendish balance adapted to new purpose. Apparatus developed which measures forces of adhesion and friction between specimens of solid materials in vacuum at temperatures from ambient to 900 degrees C. Intended primarily for use in studying adhesion properties of ceramics and metals, including silicon carbide, aluminum oxide, and iron-base amorphous alloys.

  12. Correlation between advanced glycation end-products and the expression of fatty inflammatory factors in type II diabetic cardiomyopathy

    PubMed Central

    Guo, Zhengdong; Huang, Donghui; Tang, Xiange; Han, Jingjing; Li, Jing

    2015-01-01

    Diabetic cardiomyopathy (DCM) is one of the most severe complications of diabetes without a clear pathogenesis. This study investigated the adiponectin (APN) and leptin levels in type II DCM, as well as their correlation with advanced glycation end-products (AGEs). From 2011–2013, 78 type II diabetes mellitus (T2DM) cases (40–65 years old) in the Taian region were randomly selected. Based on the results of colour Doppler ultrasonography and coronary angiography, the cases were divided into a simple T2DM group (40 cases) and a DCM group (38 cases). Forty healthy subjects were used as normal control (NC). An enzyme-linked immunosorbent assay was performed to determine the levels of fatty inflammatory factors such as APN, leptin and AGEs, and a correlation analysis was conducted. In the T2DM group, the APN levels were decreased but the leptin and AGE levels were significantly increased compared to the NC group. In the DCM group, the APN levels were decreased but the leptin and AGE levels were significantly increased (P<0.01) compared to the T2DM group. The AGE levels were positively correlated with disease progression and with fasting plasma glucose levels, glycated haemoglobin, insulin resistance and leptin, but were negatively correlated with APN levels. Additionally, the APN and leptin levels were independently related to the AGE levels. Fatty inflammatory factors play a significant role in the progression of both simple T2DM and DCM. The results of this study revealed the pathogenesis of DCM and indicated the potential significance of AGEs in DCM prevention and treatment. PMID:26614846

  13. 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

  14. Agroecological factors correlated to soil DNA concentrations of Rhizoctonia in dryland wheat production zones of Washington state, USA.

    PubMed

    Okubara, Patricia A; Schroeder, Kurtis L; Abatzoglou, John T; Paulitz, Timothy C

    2014-07-01

    The necrotrophic soilborne fungal pathogens Rhizoctonia solani AG8 and R. oryzae are principal causal agents of Rhizoctonia root rot and bare patch of wheat in dryland cropping systems of the Pacific Northwest. A 3-year survey of 33 parcels at 11 growers' sites and 60 trial plots at 12 Washington State University cereal variety test locations was undertaken to understand the distribution of these pathogens. Pathogen DNA concentrations in soils, quantified using real-time polymerase chain reaction, were correlated with precipitation, temperature maxima and minima, and soil texture factors in a pathogen-specific manner. Specifically, R. solani AG8 DNA concentration was negatively correlated with precipitation and not correlated with temperature minima, whereas R. oryzae concentration was correlated with temperature minima but not with precipitation. However, both pathogens were more abundant in soils with higher sand and lower clay content. Principal component analysis also indicated that unique groups of meteorological and soil factors were associated with each pathogen. Furthermore, tillage did not affect R. oryzae but affected R. solani AG8 at P = 0.06. Lower soil concentrations of R. solani AG8 but not R. oryzae occurred when the previously planted crop was a broadleaf (P < 0.05). Our findings showed that R. solani AG8 concentrations were consistent with the general distribution of bare patch symptoms, based on field observations and surveys of other pathogens, but was present at many sites in which bare patch symptoms were not evident. Management of Rhizoctonia root rot and bare patch should account for the likelihood that each pathogen is affected by a unique group of agroecological variables. PMID:24915426

  15. Preface: Friction at the nanoscale

    NASA Astrophysics Data System (ADS)

    Fusc, Claudio; Smith, Roger; Urbakh, Michael; Vanossi, Andrea

    2008-09-01

    Interfacial friction is one of the oldest problems in physics and chemistry, and certainly one of the most important from a practical point of view. Everyday operations on a broad range of scales, from nanometer and up, depend upon the smooth and satisfactory functioning of countless tribological systems. Friction imposes serious constraints and limitations on the performance and lifetime of micro-machines and, undoubtedly, will impose even more severe constraints on the emerging technology of nano-machines. Standard lubrication techniques used for large objects are expected to be less effective in the nano-world. Novel methods for control and manipulation are therefore needed. What has been missing is a molecular level understanding of processes occurring between and close to interacting surfaces to help understand, and later manipulate friction. Friction is intimately related to both adhesion and wear, and all three require an understanding of highly non-equilibrium processes occurring at the molecular level to determine what happens at the macroscopic level. Due to its practical importance and the relevance to basic scientific questions there has been major increase in activity in the study of interfacial friction on the microscopic level during the last decade. Intriguing structural and dynamical features have been observed experimentally. These observations have motivated theoretical efforts, both numerical and analytical. This special issue focusses primarily on discussion of microscopic mechanisms of friction and adhesion at the nanoscale level. The contributions cover many important aspects of frictional behaviour, including the origin of stick-slip motion, the dependence of measured forces on the material properties, effects of thermal fluctuations, surface roughness and instabilities in boundary lubricants on both static and kinetic friction. An important problem that has been raised in this issue, and which has still to be resolved, concerns the

  16. Initial Friction Compensation by Disturbance Observer Based on Rolling Friction Model

    NASA Astrophysics Data System (ADS)

    Maeda, Yoshihiro; Iwasaki, Makoto

    This paper presents a rolling friction model-based initial friction compensation (IFC) by a disturbance observer for the fast and precise positioning of ball-screw-driven table systems. The effects of rolling friction in mechanisms should be suppressed in order to the achieve required control performance. In this study, therefore, a rolling friction model is adopted to compensate for the initial friction, so that delay-free friction estimation becomes possible. The proposed initial friction compensation method has been verified experimentally by using a prototype of industrial positioning devices.

  17. Sustained frictional instabilities on nanodomed surfaces: stick-slip amplitude coefficient.

    PubMed

    Quignon, Benoit; Pilkington, Georgia A; Thormann, Esben; Claesson, Per M; Ashfold, Michael N R; Mattia, Davide; Leese, Hannah; Davis, Sean A; Briscoe, Wuge H

    2013-12-23

    Understanding the frictional properties of nanostructured surfaces is important because of their increasing application in modern miniaturized devices. In this work, lateral force microscopy was used to study the frictional properties between an AFM nanotip and surfaces bearing well-defined nanodomes comprising densely packed prolate spheroids, of diameters ranging from tens to hundreds of nanometers. Our results show that the average lateral force varied linearly with applied load, as described by Amontons' first law of friction, although no direct correlation between the sample topographic properties and their measured friction coefficients was identified. Furthermore, all the nanodomed textures exhibited pronounced oscillations in the shear traces, similar to the classic stick-slip behavior, under all the shear velocities and load regimes studied. That is, the nanotextured topography led to sustained frictional instabilities, effectively with no contact frictional sliding. The amplitude of the stick-slip oscillations, σf, was found to correlate with the topographic properties of the surfaces and scale linearly with the applied load. In line with the friction coefficient, we define the slope of this linear plot as the stick-slip amplitude coefficient (SSAC). We suggest that such stick-slip behaviors are characteristics of surfaces with nanotextures and that such local frictional instabilities have important implications to surface damage and wear. We thus propose that the shear characteristics of the nanodomed surfaces cannot be fully described by the framework of Amontons' laws of friction and that additional parameters (e.g., σf and SSAC) are required, when their friction, lubrication, and wear properties are important considerations in related nanodevices. PMID:24219790

  18. Diurnal variation in endotoxin-induced mortality in mice: correlation with proinflammatory factors.

    PubMed

    Marpegan, Luciano; Leone, María Juliana; Katz, Marcelo E; Sobrero, Patricio M; Bekinstein, Tristan A; Golombek, Diego A

    2009-10-01

    Many immune parameters exhibit daily and circadian oscillations, including the number of circulating cells and levels of cytokines in the blood. Mice also have a differential susceptibility to lipopolysaccharide (LPS or endotoxin)-induced endotoxic shock, depending on the administration time in the 24 h light-dark (LD) cycle. We replicated these results in LD, but we did not find temporal differences in LPS-induced mortality in constant darkness (DD). Animals challenged with LPS showed only transient effects on their wheel locomotor activity rhythm without modification of circadian period and phase. Levels of several key factors involved in the pathology of sepsis and septic shock were tested in LD. We found that LPS-induced levels of interleukin (IL)-1beta, IL-6, JE (MCP-1), and MIP1alpha were significantly higher at zeitgeber time (ZT) 11 (time of increased mortality) than at ZT19 (ZT12 = time of lights-off in the animal quarters for the 12L:12D condition). Our results indicate that the differences found in mortality that are dependent on the time of LPS-challenge are not directly related to an endogenous circadian clock, and that some relevant immune factors in the development of sepsis are highly induced at ZT11, the time of higher LPS-induced mortality, compared to ZT19. PMID:19916840

  19. [Analysis of prognostic correlated factors of 49 patients with mucosa-associated lymphoid tissue lymphoma].

    PubMed

    Jing, Hong-Mei; Ke, Xiao-Yan; Dong, Fei

    2007-12-01

    The aim of this study was to investigate the clinical feature of mucosa-associated lymphoid tissue lymphoma and clarify the relationship between the pathological, clinical features, the expression of API2-MALT1 and the prognosis. A number of factors including pathological characters, grade, stage, prognosis and treatment of 49 cases of MALT lymphoma were analyzed, and the API2-MALT1 rearrangement was detected by RT-PCR. The results showed that 49 patients were diagnosed as MALT lymphoma, in which median age was 52.4 years. The percentage of patients older than 50 years was 67.3%. The majority of tumors were found in stomach (22 cases), intestine (13 cases), thyroid (6 cases) and so on. Among 49 patients, stage I, II was 77. 6%, stage III, IV was 22.4%. API2-MALT1 rearrangement were found 38.1% in low grade, and 12.5% in transform type. Among 18 patients with gastric MALT lymphoma, 9 cases (50.0%) were helicobacter pylori (HP) positive and received antibiotic treatment. The 3 years overall survival was 93.8%. It is concluded that MALT lymphoma is often seen in older patients, most of them were in low grade with slow progression. The site, grade, stage and molecular genetic changes are important prognostic factors, which can contribute to choosing suitable treatment for patients with MALT lymphoma. The antibiotic treatment is effective for patients with positive HP. PMID:18088487

  20. Volume overload correlates with cardiovascular risk factors in patients with chronic kidney disease.

    PubMed

    Hung, Szu-Chun; Kuo, Ko-Lin; Peng, Ching-Hsiu; Wu, Che-Hsiung; Lien, Yu-Chung; Wang, Yi-Chun; Tarng, Der-Cherng

    2014-03-01

    Volume overload is a predictor of mortality in dialysis patients. However, the fluid status of patients with chronic kidney disease (CKD) but not yet on dialysis has not been accurately characterized. We used the Body Composition Monitor, a multifrequency bioimpedance device, to measure the level of overhydration in CKD patients, focusing on the association between overhydration and cardiovascular disease risk factors. Overhydration was the difference between the amount of extracellular water measured by the Body Composition Monitor and the amount of water predicted under healthy euvolemic conditions. Volume overload was defined as an overhydration value at and above the 90th percentile for the normal population. Of the 338 patients with stages 3-5 CKD, only 48% were euvolemic. Patients with volume overload were found to use significantly more antihypertensive medications and diuretics but had higher systolic blood pressures and an increased arterial stiffness than patients without volume overload. In a multivariate analysis, male sex, diabetes, pre-existing cardiovascular disease, systolic blood pressure, serum albumin, TNF-α, and proteinuria were independently all associated with overhydration. Thus, volume overload is strongly associated with both traditional and novel risk factors for cardiovascular disease. Bioimpedance devices may aid in clinical assessment by helping to identify a high-risk group with volume overload among stages 3-5 CKD patients. PMID:24025647

  1. Correlations between surrogate measures of insulin resistance and cardiovascular risk factors in obese and overweight patients.

    PubMed

    Lerman, Israel; Villa, Antonio R; Ríos Torres, Juan Manuel; Tamez, Laura Elena; Gómez Pérez, Francisco; del Villar Velasco, Sonia Luna; Rull Rodrigo, Juan Antonio

    2003-01-01

    There are different equations to estimate insulin sensitivity by using OGTT with a reasonable approximation to whole body sensitivity obtained with the glucose clamp. Further work is needed to address their role in clinical practice as markers of the metabolic syndrome and predictors for cardiovascular disease. In the present study, we determined plasma glucose and insulin values during an OGTT test in 144 overweight and obese individuals. We assessed insulin resistance by the use of different equations and established their relationship with cardiovascular risk factors associated to the insulin resistance syndrome. Distributed the patients by quintiles of body mass index (BMI), the different surrogate measures clearly demonstrated that the more obese individuals were the most insulin resistant, a similar but not significant trend was observed related to the other cardiovascular risk factors. Efforts to use both fasting and post-load glucose and insulin concentrations to create indexes for routine use in clinical practice do not seem to be particularly useful in overweight or obese patients, as most of these patients will be insulin-resistant and insulin resistance is closely linked but not equal to the metabolic syndrome. PMID:12614971

  2. Relative expression and correlation of tumor necrosis factor-α, interferon-γ, and interleukin-17 in the rheumatoid synovium.

    PubMed

    Nakajima, Arata; Aoki, Yasuchika; Sonobe, Masato; Watanabe, Fusako; Takahashi, Hiroshi; Saito, Masahiko; Nakagawa, Koichi

    2016-07-01

    Although tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and interleukin-17 (IL-17) play important roles in RA, their relative expression and possible correlation in synovial tissues are not well understood. In this study, mRNA expression levels of IFN-γ, IL-17, and TNF-α were investigated in individual patients with RA and the correlations between pairs of these three pro-inflammatory cytokines were analyzed. Synovial tissues were obtained during arthroplasties from 24 joints of 24 RA patients. After harvesting synovial tissues, total RNA was isolated then quantitative real-time polymerase chain reaction (qRT-PCR) for IFN-γ, IL-17, and TNF-α was performed. Correlation of expression levels between them was also analyzed. Expression levels of TNF-α, IFN-γ, and IL-17 in patients receiving TNF inhibitors (TNFi) and those treated with conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) alone were also compared between groups. Based on relative expression levels of the three pro-inflammatory cytokines, patients were classified into three major types; an IFN-γ plus TNF-α-dominant type, an IL-17-dominant type, and the other type. TNF-α expression levels were correlated with IFN-γ. In addition, there was a negative correlation between TNF-α and IL-17, and IFN-γ and IL-17. Median relative expression levels of TNF-α have no significant difference between the TNFi and the csDMARDs groups. In the rheumatoid synovial tissues, expression levels of TNF-α were modulated in parallel with IFN-γ, and TNF-α and IL-17, or IFN-γ and IL-17 did not co-express at high levels. This characteristic expression pattern of the three pro-inflammatory cytokines may be clinically useful information in the current cytokine-targeted treatment with biological DMARDs for RA. PMID:27038187

  3. Insulin-like growth factor-1 content and pattern of expression correlates with histopathologic grade in diffusely infiltrating astrocytomas.

    PubMed Central

    Hirano, H.; Lopes, M. B.; Laws, E. R.; Asakura, T.; Goto, M.; Carpenter, J. E.; Karns, L. R.; VandenBerg, S. R.

    1999-01-01

    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. PMID:11550306

  4. 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.

  5. 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

  6. Contrasting correlation patterns between environmental factors and chlorophyll levels in the global ocean

    NASA Astrophysics Data System (ADS)

    Feng, Jianfeng; Durant, Joël. Marcel; Stige, Leif Chr.; Hessen, Dag Olav; Hjermann, Dag Øystein; Zhu, Lin; Llope, Marcos; Stenseth, Nils Chr.

    2015-12-01

    In this study we analyze large-scale satellite-derived data using generalized additive models to characterize the global correlation patterns between environmental forcing and marine phytoplankton biomass. We found systematic differences in the relationships between key environmental drivers (temperature, light, and wind) and ocean chlorophyll in the subtropical/tropical and temperate oceans. For the subtropical/tropical and equatorial oceans, the chlorophyll generally declined with increasing temperature and light, while in temperate oceans, chlorophyll was best explained by bell-shaped or positive functions of temperature and light. The relationship between chlorophyll and wind speed is generally positive in low-latitude oceans and bell shaped in temperate oceans. Our analyses also demonstrated strong and geographically consistent positive autoregressive effects of chlorophyll from 1 month to the next and negative autoregressive effects for measurements 2 months apart. These findings imply possibly different regional phytoplankton responses to environmental forcing, suggesting that future environmental change could affect the tropical and temperate upper ocean chlorophyll levels differently.

  7. 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

  8. 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

  9. 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. PMID:23259237

  10. Altered Hypoxia-inducible factor-1 alpha expression levels correlate with coronary vessel anomalies

    PubMed Central

    Wikenheiser, Jamie; Wolfram, Julie A.; Gargesha, Madhusudhana; Yang, Ke; Karunamuni, Ganga; Wilson, David L.; Semenza, Gregg L.; Agani, Faton; Fisher, Steven A.; Ward, Nicole; Watanabe, Michiko

    2009-01-01

    The outflow tract myocardium and other regions corresponding to the location of the major coronary vessels of the developing chicken heart, display a high level of hypoxia as assessed by the hypoxia indicator EF5. The EF5 positive tissues were also specifically positive for nuclear-localized hypoxia inducible factor-1 alpha (HIF-1α), the oxygen-sensitive component of the hypoxia inducible factor-1 (HIF-1) heterodimer. This led to our hypothesis that there is a “template” of hypoxic tissue that determines the stereotyped pattern of the major coronary vessels. In this study we disturbed this template by altering ambient oxygen levels (hypoxia 15%; hyperoxia 75-40%) during the early phases of avian coronary vessel development, in order to alter tissue hypoxia, HIF-1α protein expression and its downstream target genes without high mortality. We also altered HIF-1α gene expression in the embryonic outflow tract cardiomyocytes by injecting an adenovirus containing a constitutively active form of HIF-1α (AdCA5). We assayed for coronary anomalies using anti-alpha-smooth muscle actin immunohistology. When incubated under abnormal oxygen levels or injected with a low titer of the AdCA5, coronary arteries displayed deviations from their normal proximal connections to the aorta. These deviations were similar to known clinical anomalies of coronary arteries. These findings indicated that developing coronary vessels may be subject to a level of regulation that is dependent on differential oxygen levels within cardiac tissues and subsequent HIF-1 regulation of gene expression. PMID:19777592

  11. Prevalence of dysmenorrhea and its correlating lifestyle factors in Japanese female junior high school students.

    PubMed

    Kazama, Mie; Maruyama, Keiko; Nakamura, Kazutoshi

    2015-01-01

    Dysmenorrhea is a common menstrual disorder experienced by adolescents, and its major symptoms, including pain, adversely affect daily life and school performance. However, little epidemiologic evidence on dysmenorrhea in Japanese adolescents exists. This cross-sectional study aimed to determine the prevalence of and identify factors associated with dysmenorrhea in Japanese female junior high school students. Among 1,167 girls aged between 12 and 15 years, 1,018 participants completed a questionnaire that solicited information on age at menarche, menstruation, and lifestyle, as well as demographic characteristics. Dysmenorrhea was defined based on menstrual pain using a Visual Analog Scale (VAS), with moderate or severe (moderate-severe) dysmenorrhea, which adversely affects daily life, defined as VAS ≥ 4, and severe dysmenorrhea defined as VAS ≥ 7. The prevalence of moderate-severe dysmenorrhea was 476/1,018 (46.8%), and that of severe dysmenorrhea was 180/1,018 (17.7%). Higher chronological and gynecological ages (years after menarche) were significantly associated with a higher prevalence of dysmenorrhea regardless of severity (P for trend < 0.001). In addition, short sleeping hours (< 6/day) were associated with moderate-severe dysmenorrhea (OR = 3.05, 95%CI: 1.06-8.77), and sports activity levels were associated with severe dysmenorrhea (P for trend = 0.045). Our findings suggest that dysmenorrhea that adversely affects daily activities is highly prevalent, and may be associated with certain lifestyle factors in junior high school students. Health education teachers should be made aware of these facts, and appropriately care for those suffering from dysmenorrhea symptoms, absentees, and those experiencing difficulties in school life due to dysmenorrhea symptoms. PMID:26027596

  12. Correlation between virulence factors and in vitro biofilm formation by Escherichia coli strains.

    PubMed

    Naves, Plínio; del Prado, Gema; Huelves, Lorena; Gracia, Matilde; Ruiz, Vicente; Blanco, Jorge; Dahbi, Ghizlane; Blanco, Miguel; Ponte, María del Carmen; Soriano, Francisco

    2008-08-01

    The ability of 15 Escherichia coli strains to form biofilms on polystirene plates was studied. The strains were serotyped, and their phenotypic expression of surface virulence factors (VFs), and antibiotic susceptibility was also determined. Moreover, 30 VFs-associated genes were analysed, including 15 adhesins (papC, papG and its three alleles, sfa/focDE, sfaS, focG, afa/draBC, iha, bmaE, gafD, nfaE, fimH, fimAvMT78, agn43, F9 fimbriae and type 3 fimbriae-encoding gene clusters), four toxins (hlyA, cnf1, sat and tsh), four siderophore (iron, fyuA, iutA and iucD), five proctetins/invasion-encoding genes (kpsM II, kpsMT III, K1 kps variant- neuC, traT and ibeA), and the pathogenicity island malX and cvaC. Morphological appearance and thickness of biofilms of two strong and three weak biofilm producers were also studied by confocal laser scanning microscopy (CLSM). Seven strains were classified as strong biofilm producers and the remaining eight strains were regarded as weak biofilm producers. Mannose-resistant haemagglutination was the only phenotypically expressed surface virulence factor more frequently found in the strong biofilm group. Five virulence-associated genes were more common (p<0.05) in strong biofilm producers: papC and papG alleles, sfa/focDE, focG, hlyA and cnf1. CLSM images showed irregular biofilms with projections at the top mainly in strong biofilm. PMID:18486439

  13. 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

  14. 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. PMID:26612376

  15. In vivo friction properties of human skin.

    PubMed

    Zhang, M; Mak, A F

    1999-08-01

    In vivo frictional properties of human skin and five materials, namely aluminium, nylon, silicone, cotton sock, Pelite, were investigated. Normal and untreated skin over six anatomic regions of ten normal subjects were measured under a controlled environment. The average coefficient of friction for all measurements is 0.46+/-0.15 (p<0.05). Among all measured sites, the palm of the hand has the highest coefficient of friction (0.62+/-0.22). For all the materials tested, silicone has the highest coefficient of friction (0.61+/-0.21), while nylon has the lowest friction (0.37+/-0.09). PMID:10493141

  16. Plasma brain-derived neurotrophic factor levels are increased in patients with tinnitus and correlated with therapeutic effects.

    PubMed

    Xiong, Hao; Yang, Haidi; Liang, Maojin; Ou, Yongkang; Huang, Xiayin; Cai, Yuexin; Lai, Lan; Pang, Jiaqi; Zheng, Yiqing

    2016-05-27

    Tinnitus is the perception of sound without an external source and is known to be associated with altered neuronal excitability in the auditory system. Tinnitus severity can be assessed by various psychometric instruments and there is no objective measures developed to evaluate tinnitus severity and therapeutic effects so far. Brain-derived nerve growth factor (BDNF) is believed in playing a key role in regulating neuronal excitability in the brain. To determine whether BDNF correlates with tinnitus induction and severity, we described plasma BDNF levels in patients with tinnitus and healthy controls and evaluated the correlation between plasma BDNF levels and tinnitus severity measured by Tinnitus Handicap Inventory (THI) and Visual Analog Scale (VAS). Moreover, alteration of plasma BDNF levels before and after tinnitus retraining therapy (TRT) in patients with severe tinnitus was also analyzed. We found plasma BDNF levels were elevated in patients with tinnitus compared with healthy controls. In addition, plasma BDNF levels in patients with severe tinnitus were decreased significantly after effective TRT. However, plasma BDNF levels were not correlated with tinnitus loudness and tinnitus severity measured by THI and VAS. These findings support plasma BDNF as a marker for activity changes in the auditory system and could possibly evaluate therapeutic effects in patients with tinnitus. PMID:27095590

  17. Correlation energy, structure factor, radial distribution function, and momentum distribution of the spin-polarized uniform electron gas

    NASA Astrophysics Data System (ADS)

    Ortiz, G.; Ballone, P.

    1994-07-01

    The properties of the three-dimensional uniform electron gas in the Fermi liquid regime are analyzed using variational Monte Carlo (VMC) and fixed-node diffusion Monte Carlo methods. Our study extends those of Ceperley [Phys. Rev. B 18, 3126 (1978)] and Ceperley and Alder [Phys. Rev. Lett. 45, 566 (1980)] to larger system sizes with improved statistics and, more importantly, to partial spin polarization. The density range 0.8<=rs<=10, which is the most relevant for density functional computations, is studied in detail. We analyze the size dependence of the simulation results and present an extended set of correlation energies extrapolated to the thermodynamic limit. Using the VMC method we analyze the spin dependence of the correlation energy, and we compare our results to several interpolation formulas used in density functional calculations. We summarize our results by a simple interpolation formula. In addition, we present results for the radial distribution function, the structure factor, the momentum distribution, and triplet correlation functions, and we discuss the comparison with many-body semianalytic theories.

  18. Lung Cancer Lymph Node Micrometastasis Detection Using RT-PCR – Correlation with Vascular Endothelial Growth Factor (VEGF) expression

    PubMed Central

    Nwogu, Chukwumere E.; Yendamuri, Sai; Tan, Wei; Kannisto, Eric; Bogner, Paul; Morrison, Carl; Cheney, Richard; Dexter, Elisabeth; Picone, Anthony; Hennon, Mark; Hutson, Alan; Reid, Mary; Adjei, Alex; Demmy, Todd L.

    2013-01-01

    Objectives Lymph node (LN) staging provides critical information in non-small cell lung cancer (NSCLC) patients. Lymphangiogenesis may be an important contributor to the pathophysiology of lymphatic metastases. We hypothesized that the presence of lymph node micrometastases positively correlates with VEGF-A/C/D and VEGF-receptor-3 (lymphangiogenic factors) expression in lymph nodes. Methods Forty NSCLC patients had pre-operative PET-CT and mediastinoscopy. RT-PCR assays for mRNA expression of epithelial markers (CK-7, CEACAM-5 and PLUNC) were performed in selected fluorodeoxyglucose (FDG)-avid lymph nodes. VEGF-A/C/D and VEGF-receptor-3 expression levels were measured in primary tumors and lymph nodes. Wilcoxon rank sum test was run for the association between the RT-PCR epithelial marker levels and VEGF expression levels in the LNs. Results RT-PCR for CK-7, CEACAM5 or PLUNC indicated lymph node micrometastatic disease in 19 of 35 patients (54%). There was a high correlation between detection of micrometastases and VEGF-A/C/D or VEGF-receptor-3 expression levels in lymph nodes. Median follow-up was 12.6 months. Conclusions RT-PCR analysis of FDG-avid lymph nodes results in up-staging of patients. Micrometastases correlate with the expression of VEGF in lymph nodes in NSCLC patients. This may reflect the role of lymphangiogenesis in promoting metastases. PMID:23414988

  19. 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

  20. 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

  1. Influenza-like illness in a Vietnamese province: epidemiology in correlation with weather factors and determinants from the surveillance system

    PubMed Central

    Minh An, Dao Thi; Bich Ngoc, Nguyen Thi; Nilsson, Maria

    2014-01-01

    Background Seasonal influenza affects from 5 to 15% of the world's population annually and causes an estimated 250,000–500,000 deaths worldwide. The World Health Organization (WHO) recommends ‘sentinel surveillance’ for influenza-like illness (ILI) because it is simple and calls for standardized methods at a relatively low cost that can be implemented throughout the world. In Vietnam, ILI is a key priority for public health also because of its annually recurring temporal pattern. Two major factors, on which the spread of influenza depends, are the strain of the virus and its rate of mutation, since flu strains constantly mutate as they compete with host immune systems. In the context of global climate change, the role of climatic factors has been discussed, as they may significantly contribute to the cause of large outbreaks of ILI. Objectives 1) To describe the epidemiology of ILI in Ha Nam province, Vietnam; 2) to seek scientific evidence on the association of ILI occurrence with weather factors in Ha Nam province; and 3) to analyze factors from the Ha Nam ILI surveillance system that contribute to explaining the correlation between the ILI and the weather factors. Design A data set of 89,270 monthly reported ILI cases from 2008 to 2012 in Ha Nam was used to describe ILI epidemiological characteristics. Spearman correlation analyses between ILI cases and weather factors were conducted to identify which preceding period of months and weather patterns influenced the occurrence of ILI cases. Ten in-depth interviews with health workers in charge of recording and reporting ILI cases at different levels of the ILI surveillance system were conducted to gain a deeper understanding of factors contributing to explaining the relation between the ILI and the weather factors. Results The results indicated that the ILI occurred annually in all districts of the Ha Nam province in the five studied years. An epidemic occurred in 2009 with the number of cases three times

  2. 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

  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. Application of a new theoretical procedure for calculating Kirkwood correlation factors in alkanol + hexane and alkanol + pentane mixtures.

    PubMed

    Vasiltsova, Tatiana; Heintz, Andreas

    2007-12-21

    A recently developed statistical mechanical model for calculating Kirkwood correlation factors gK in self associating liquids and liquid mixtures has been applied for the simultaneous description of gK, the molar enthalpy of mixing HEM and the infrared absorption of monomer alcoholic species as function of the composition in alkanol + hexane and alkanol + pentane mixtures (alkanol: butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, sec-butanol, tert-butanol). The majority of parameters involved into the theory are obtained by independent quantum mechanical ab initio calculations of molecular clusters consisting of up to four alcohol molecules. As a consequence only two parameters have to be adjusted freely to each binary system, a third parameter responsible for the non specific intermolecular dispersion interaction has been adjusted within a limited range of possible values given by physical arguments. Excellent agreement between theory and experimental data of gK, HEM and IR absorbance is obtained covering the whole range of concentration including the temperature dependence of these properties without adjusting further parameters. The Kirkwood correlation factor gK turns out to be a sensitive response to peculiarities of the molecular structure of hydrogen bonded systems in the condensed liquid state. The successful application of the theoretical model opens a new way of a deeper and more reliable understanding of such liquid structures. PMID:18046469

  6. Bmi-1 expression predicts prognosis in salivary adenoid cystic carcinoma and correlates with epithelial-mesenchymal transition-related factors.

    PubMed

    Yi, Chun; Li, Bin-Bin; Zhou, Chuan-Xiang

    2016-06-01

    Salivary adenoid cystic carcinoma (AdCC) is known for its high propensity to invade and metastasize. Bmi-1 acts as an oncogene by controlling cell cycle and self-renewal of adult stem cells, and its overexpression correlates with metastasis and poor prognosis in several cancers. Epithelial-mesenchymal transition (EMT) plays a central role in cancer metastasis. A key step in EMT is the down-regulation of E-cadherin that can be repressed by the transcriptional factors, such as Snail and Slug. In the present study, we investigated Bmi-1, Snail, Slug, and E-cadherin expression by immunohistochemistry in 102 patients with AdCC and analyzed statistically whether their expression correlated with clinicopathologic factors and prognosis. Reverse transcription-polymerase chain reaction was also performed in 22 tumor tissues and the adjacent noncancerous tissues to confirm Bmi-1 status in AdCCs. Our data demonstrated significant associations between the tumor metastasis and the expression of Bmi-1, Snail, Slug, and E-cadherin. Furthermore, a high level of Bmi-1 was not only correlated with the overexpression of Snail and Slug but also indicated an unfavorable metastasis-free survival and served as a high-risk marker for AdCC. In addition, Bmi-1 messenger RNA level was found much higher in AdCC tissues than in the adjacent noncancerous salivary gland tissues. Our results suggest that Bmi-1 may play a crucial role in AdCC progression by interaction with EMT-related markers and predict poor survival. PMID:27180058

  7. The correlation between Ki-67 with other prognostic factors in breast cancer: A study in Iranian patients

    PubMed Central

    Madani, Seyed-Hamid; Payandeh, Mehrdad; Sadeghi, Masoud; Motamed, Hajar; Sadeghi, Edris

    2016-01-01

    Context: Despite the fact that breast cancer (BC) is a major health issue, very few studies describe its characteristics in the Middle East. Aim: The aim of this study was to evaluate the use and value of Ki-67 as a prognostic marker in BC and associations between Ki-67, clinical, and histopathological parameters were evaluated. Subjects and Methods: In a retrospective study, 260 BC women and invasive ductal carcinoma were included to our study in Kermanshah city, Iran. Age, tumor size, lymph node involvement, histological grade, nuclear grade, and vascular invasion were other factors that determined in a lot of patients. Results: The mean age at diagnosis was 47.6 years (range, 24-84 years) with 100% female. Of 243 patients that tumor size was determined for them, 207 patients (85.2%) had tumor size ≥2 cm, and 36 patients (14.8%) had size <2 cm and also of 237 patients, 47 patients (19.8%), 140 (59.1%), and 50 (21.1%) had histological grades I, II, and III, respectively. There is significant correlation between Ki-67 with nuclear grade, human epidermal growth factor receptor 2 (HER2), and p53 (P < 0.05). Based on this result, more patients with Ki-67 ≥20% have higher nuclear grade, p53-positive, and HER2-positive. There was correlation between Ki-67 with type of tumor (P = 0.009). Conclusions: The higher Ki-67 has a direct significant correlation with higher nuclear grade, p53-positive, and HER2-positive. Furthermore, triple negative patients have higher Ki-67 compared to other subtypes. PMID:27168707

  8. Leisure time physical activity in the Framingham Offspring Study. Description, seasonal variation, and risk factor correlates.

    PubMed

    Dannenberg, A L; Keller, J B; Wilson, P W; Castelli, W P

    1989-01-01

    Self-reported leisure time physical activity was analyzed for 1,598 men and 1,762 women aged 20-69 years in the Framingham Offspring Cycle 2 exam in 1979-1983. Walking for pleasure was generally the most common physical activity for both sexes throughout the year. Substantial seasonal variation was noted for the most common activities: gardening, carpentry, lawn mowing, golf, and running for men; and gardening, swimming, health club exercise, dancing, and bicycling for women. Both sexes expended more kilocalories in physical activities in summer than in winter (p less than 0.001). Frequency of participation in activities sufficient to induce perspiration was associated with frequency of participation in at least one hour of conditioning (greater than or equal to 7.5 kilocal/minute) activities per week (p less than 0.001). Based on age-adjusted mean levels, higher high density lipoprotein cholesterol, lower heart rate, lower body mass index and fewer cigarettes smoked per day were consistently observed across four quartiles of increasing physical activity levels (p less than 0.01). Men who participated in at least one hour of conditioning activities per week had significantly different mean levels for these four risk factors than men who reported less than one hour of such activities per week (p less than 0.001). Results substantiate previous reports of an inverse relation between physical activity levels and cardiovascular risk, and suggest seasonal variation in activity levels should be considered in future studies which explore the relation between physical activity and cardiovascular disease. PMID:2910074

  9. Some microstructural characterisations in a friction stir welded oxide dispersion strengthened ferritic steel alloy

    NASA Astrophysics Data System (ADS)

    Legendre, F.; Poissonnet, S.; Bonnaillie, P.; Boulanger, L.; Forest, L.

    2009-04-01

    The goal of this study is to characterize microstructure of a friction stir welded oxide dispersion strengthened alloy. The welded material is constituted by two sheets of an yttria-dispersion-strengthened PM 2000 ferritic steel. Different areas of the friction stir welded product were analyzed using field emission gun secondary electron microscopy (FEG-SEM) and electron microprobe whereas nanoindentation was used to evaluate mechanical properties. The observed microstructural evolution, including distribution of the yttria dispersoids, after friction stir welding process is discussed and a correlation between the microstructure and the results of nanoindentation tests is established.

  10. Significant Correlation between Retinal Venous Tortuosity and Aqueous Vascular Endothelial Growth Factor Concentration in Eyes with Central Retinal Vein Occlusion

    PubMed Central

    Yasuda, Shunsuke; Kachi, Shu; Kondo, Mineo; Ueno, Shinji; Kaneko, Hiroki; Terasaki, Hiroko

    2015-01-01

    Purpose To determine whether the degree of venous tortuosity is significantly correlated with the aqueous vascular endothelial growth factor (VEGF) concentration in eyes with a central retinal vein occlusion (CRVO). Methods We reviewed the medical records of 32 eyes of 32 patients who had macular edema due to a CRVO. All of the patients were examined at the Nagoya University Hospital and were scheduled to receive an intravitreal injection of bevacizumab (IVB) or ranibizumab (IVR) within 12 weeks of the onset of the CRVO to treat the macular edema. Aqueous humor was collected just before the IVB or IVR, and the VEGF concentration was determined by enzyme-linked immunosorbent assay (ELISA). The venous tortuosity index was calculated by dividing the length of the retinal veins by the chord length of the same segment. The correlation between the mean tortuosity index of the inferotemporal and supratemporal branches of the retinal vein and the aqueous VEGF concentration was determined. Results The mean aqueous VEGF concentration was 384 ± 312 pg/ml with a range of 90 to 1077 pg/ml. The degree of venous tortuosity was significantly correlated with the VEGF concentration in the aqueous. (r = 0.49, P = 0.004), with the foveal thickness (r = 0.40, P = 0.02), and with the best-corrected visual acuity (r = 0.38, P = 0.03). Conclusions The significant correlation between the aqueous VEGF concentration and the venous tortuosity indicates that the degree of retinal venous tortuosity can be used to identify eyes that are at a high risk of developing neovascularization. PMID:26214803

  11. 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. PMID:27334115

  12. 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

  13. High temperature skin friction measurement

    NASA Technical Reports Server (NTRS)

    Tcheng, Ping; Holmes, Harlan K.; Supplee, Frank H., Jr.

    1989-01-01

    Skin friction measurement in the NASA Langley hypersonic propulsion facility is described. The sensor configuration utilized an existing balance, modified to provide thermal isolation and an increased standoff distance. For test run times of about 20 sec and ambient-air cooling of the test section and balance, the modified balance performed satisfactorily, even when it was subjected to acoustic and structural vibration. The balance is an inertially balanced closed-loop servo system where the current to a moving-coil motor needed to restore or null the output from the position sensor is a measure of the force or skin friction tending to displace the moving element. The accuracy of the sensor is directly affected by the position sensor in the feedback loop, in this case a linear-variable differential transformer which has proven to be influenced by temperature gradients.

  14. Evidence for a strong correlation between the amount of surface carbon and the tribological behaviour of ion-treated steels

    NASA Astrophysics Data System (ADS)

    Faussemagne, A.; Benyagoub, A.

    1998-02-01

    Samples of 100Cr6-bearing steel were treated by different ion beams in order to study the evolution of their tribological properties. Complementary physico-chemical characterisation techniques give evidence for a strong correlation between the amount of surface carbon, whatever its origin (contamination, direct C implantation or ion beam mixing of a deposited carbon layer), and the reduction of the friction coefficient as well as the increase of the wear resistance. It is found that the friction coefficient is improved by a factor 5 and the wear volume by two orders of magnitude when the amount of surface carbon exceeds 1017 C cm-2.

  15. 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.

  16. 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

  17. 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

  18. 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.

  19. What information can frictional properties of polymer brushes tell us?

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu; Moxey, Mark; Morse, Andrew; Armes, Steven; Lewis, Andrew; Geoghegan, Mark; Leggett, Graham

    2013-03-01

    We have used friction force microscopy (FFM) to quantitatively examine surface grown zwitterionic polymer brushes: poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), and to establish the correlation between its frictional behaviour to other intrinsic properties. In a good solvent, it was found that the coefficient of friction (μ) decreased with increasing film thickness. We conclude that the amount of bound solvent increases as the brush length increases, causing the osmotic pressure to increase and yielding a reduced tendency for the brush layer to deform under applied load. When measured in a series of alcohol/water mixtures, a significant increase in μ was observed for ethanol/water mixtures at a volume fraction of 90%. This is attributed to brush collapse due to co-nonsolvency, leading to loss of hydration of the brush chains and hence substantially reduced lubrication. We show that single asperity contact mechanics is strongly dependent on solvent quality. Friction-load relationship was found linear in methanol (good solvent), but sub-linear in water and ethanol (moderate solvent).

  20. 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.

  1. Contact and friction of nanoasperities: effects of adsorbed monolayers.

    PubMed

    Cheng, Shengfeng; Luan, Binquan; Robbins, Mark O

    2010-01-01

    Molecular dynamics simulations are used to study contact between a rigid, nonadhesive, and spherical tip with radius of order 30 nm and a flat elastic substrate covered with a fluid monolayer of adsorbed chain molecules. Previous studies of bare surfaces showed that the atomic scale deviations from a sphere that are present on any tip constructed from discrete atoms lead to significant deviations from continuum theory and dramatic variability in friction forces. Introducing an adsorbed monolayer leads to larger deviations from continuum theory but decreases the variations between tips with different atomic structure. Although the film is fluid, it remains in the contact and behaves qualitatively like a thin elastic coating except for certain tips at high loads. Measures of the contact area based on the moments or outer limits of the pressure distribution and on counting contacting atoms are compared. The number of tip atoms making contact during a time interval Deltat grows as a power of Deltat when the film is present and as the logarithm of Deltat for bare surfaces. Friction is measured by displacing the tip at a constant velocity or pulling the tip with a spring. Both static and kinetic friction rise linearly with load at small loads. Transitions in the state of the film lead to nonlinear behavior at large loads. The friction is less clearly correlated with contact area than load. PMID:20365427

  2. Friction and wear properties of smooth diamond films grown in fullerene-argon plasmas

    SciTech Connect

    Erdemir, A.; Fenske, G.R.; Bindal, C.; Zuiker, C.; Krauss, A.R.; Gruen, D.M.

    1995-08-01

    In this study, we describe the growth mechanism and the ultralow friction and wear properties of smooth (20-50 nm rms) diamond films grown in a microwave plasma consisting of Ar and fullerene (the carbon source). The sliding friction coefficients of these films against Si{sub 3}N{sub 4} balls are 0.04 and 0.1 in dry N{sub 2} and air, which are comparable to that of natural diamond sliding against the same pin material, but is lower by factors of 5 to 10 than that afforded by rough diamond films grown in conventional H{sub 2}-CH{sub 4} plasmas. Furthermore, the smooth diamond films produced in this work afforded wear rates to Si{sub 3}N{sub 4} balls that were two to three orders of magnitude lower than those of H{sub 2}-CH{sub 4} grown films. Mechanistically, the ultralow friction and wear properties of the fullerene-derived diamond films correlate well with their initially smooth surface finish and their ability to polish even further during sliding. The wear tracks reach an ultrasmooth (3-6 nm rms) surface finish that results in very little abrasion and ploughing. The nanocrystalline microstructure and exceptionally pure sp{sup 3} bonding in these smooth diamond films were verified by numerous surface and structure analytical methods, including x-ray diffraction, high-resolution AF-S, EELS, NEXAFS, SEM, and TEM. An AFM instrument was used to characterize the topography of the films and rubbing surfaces.

  3. 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.

  4. 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.

  5. Landslide Basal Friction as Measured by Seismic Waves

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Gordeev, E.

    2004-12-01

    Dynamical predictions of landslide runout require measurements of the basal friction. We present the first seismically determined bounds on the frictional coefficients for three large volcanic landslides. A landslide generates seismic waves by both shearing and loading the surface as the mass moves from a steep to a shallow slope. The effective force system is a horizontal single force. The amplitude of the seismic waves is proportional to the force drop during the landslide, just as during an earthquake the seismic wave amplitude is proportional to the seismic moment, i.e., the force drop multiplied by the source dimension. For landslides we know an additional variable that is unknown for the earthquake case. We know the gravitational driving force of the landslide while the magnitude of the tectonic forces that drive earthquakes are generally unknown. Therefore, we can find the absolute value of the frictional force for landslides whereas we are unable to perform this calculation for earthquakes. We studied three landslides (Bezymianny, Russia 1956, Sheveluch, Russia 1964 and Mount St. Helens, USA 1980) that were all followed immediately by eruptions. The landslide masses vary by a factor of 5. We test the data against the hypothesis of a constant value of apparent friction. The apparent friction μ app is defined as the ratio of the amplitude of the horizontal single force to the weight of the landslide. Since the Mount St. Helens seismic source is very well-constrained, we use the amplitude of this landslide force drop as a starting point. We calculated the value of μ app for Mount St. Helens using previous seismic results and the geological data. We then test whether or not the other two landslides are consistent with the same value of μ app. We use teleseismic and regional seismic data to show that all three landslides are consistent with an apparent coefficient of friction of 0.2 which corresponds to an actual areally-averaged frictional coefficient of 0

  6. Dissimilar friction stir welding of aluminum alloys reinforced with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Pantelis, D. I.; Karakizis, P. N.; Dragatogiannis, D. A.; Charitidis, C. A.

    2016-01-01

    This chapter is devoted to studying the possibility of incorporating carbon nanotubes (CNTs) as reinforcing fillers in dissimilar metal matrices joints produced by friction stir welding (FSW), as well as the impact of this incorporation on the microstructural and mechanical properties of these joints. Carbon nanotubes are extensively used as a reinforcing material in nanocomposites, due to their high stiffness and strength. FSW is a solid-state welding process of joining aluminum and other metallic alloys and has been employed in the aerospace, rail, automotive, and marine industries. Recently, friction stir processing (FSP), a derivative method of FSW, has been employed as an alternative for the production of metal matrix composites (MMCs). In this work, the process parameters were optimized in order to achieve nondefective welds, with and without the addition of CNTs. Two main cases were studied: (1) FSP was optimized by changing the tool rotational and travel speed as well as the number and direction of FSW passes, and (2) a Taguchi design scheme was adopted to further investigate the FSP in relevance to three factors (number, direction of passes, and tool rotational speed). Mechanical behavior was studied, and the local mechanical properties of the produced MMCs were compared with their bulk counterparts and parent materials. More specifically, the measured mechanical properties in the micro- and nanoscale (namely hardness and elastic modulus) are correlated with the microstructure and the presence of fillers.

  7. 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

  8. No evidence that social desirability response set explains the general factor of personality and its affective correlates.

    PubMed

    Rushton, J Philippe; Erdle, Stephen

    2010-04-01

    In two studies, the General Factor of Personality (GFP) remained intact after controlling for the Lie scale from the Eysenck Personality Questionnaire, despite the Lie Scale showing significant correlations with the GFP defining traits. In Study 1, a re-analysis of 29 self-ratings from 322 pairs of twins (644 individuals) yielded a GFP both before and after controlling for social desirability. In Study 2, four measures of affect in 133 university students loaded on a GFP both before and after controlling for social desirability such that those high on the GFP were high in self-esteem and positive affect and low in depression and negative affect. These results join those from other studies failing to find evidence that the GFP is merely an artifact of evaluative bias. PMID:20397743

  9. First measurements of hyperon time-like form factors at large Q2 and evidence of diquark correlations

    NASA Astrophysics Data System (ADS)

    Dobbs, Sean; Tomaradze, A.; Xiao, T.; Seth, Kamal K.

    2016-05-01

    Using e+e- annihilation data taken with the CLEO-c detector at √{s } = 3770 MeV and 4170 MeV, we report the first measurements of the electromagnetic form factors of the Λ0, Σ0, Σ+, Ξ0, Ξ-, and Ω- hyperons for the large timelike momentum transfers of |Q2| = 14.2 GeV2 and 17.4 GeV2, respectively. The enhancement in Λ0 production over that of Σ0, both of which have the same uds quark content, gives evidence for significant diquark correlations in these hyperons. Improved measurements of the branching fractions of ψ(2S) to hyperon-antihyperon pairs are also reported.

  10. 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.

  11. Positive correlations of age and parity with plasma concentration of macrophage migration inhibitory factor in Japanese black cows.

    PubMed

    Koizumi, Motoya; Nahar, Asrafun; Yamabe, Ryusei; Kadokawa, Hiroya

    2016-06-17

    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

  12. 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

  13. 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

  14. Correlation between Peripheral Levels of Brain-Derived Neurotrophic Factor and Hippocampal Volume in Children and Adolescents with Bipolar Disorder.

    PubMed

    Lauxen Peruzzolo, Tatiana; Anes, Mauricio; Kohmann, Andre de Moura; Souza, Ana Claudia Mércio Loredo; Rodrigues, Ramiro Borges; Brun, Juliana Basso; Peters, Roberta; de Aguiar, Bianca Wollenhaupt; Kapczinski, Flavio; Tramontina, Silzá; Rohde, Luis Augusto Paim; Zeni, Cristian Patrick

    2015-01-01

    Pediatric bipolar disorder (PBD) is a serious mental disorder that affects the development and emotional growth of affected patients. The brain derived neurotrophic factor (BDNF) is recognized as one of the possible markers of the framework and its evolution. Abnormalities in BDNF signaling in the hippocampus could explain the cognitive decline seen in patients with TB. Our aim with this study was to evaluate possible changes in hippocampal volume in children and adolescents with BD and associate them to serum BDNF. Subjects included 30 patients aged seven to seventeen years from the ProCAB (Program for Children and Adolescents with Bipolar Disorder). We observed mean right and left hippocampal volumes of 41910.55 and 41747.96 mm(3), respectively. No statistically significant correlations between peripheral BDNF levels and hippocampal volumes were found. We believe that the lack of correlation observed in this study is due to the short time of evolution of BD in children and adolescents. Besides studies with larger sample sizes to confirm the present findings and longitudinal assessments, addressing brain development versus a control group and including drug-naive patients in different mood states may help clarify the role of BDNF in the brain changes consequent upon BD. PMID:26075097

  15. Unraveling transcription factor interactions with heterochromatin protein 1 using fluorescence lifetime imaging microscopy and fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Siegel, Amanda P.; Hays, Nicole M.; Day, Richard N.

    2013-02-01

    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.

  16. 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

  17. 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

    2015-06-01

    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

  18. 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.

  19. Phenotypic Assays to Determine Virulence Factors of Uropathogenic Escherichia coli (UPEC) Isolates and their Correlation with Antibiotic Resistance Pattern

    PubMed Central

    Tabasi, Mohsen; Asadi Karam, Mohammad Reza; Habibi, Mehri; Yekaninejad, Mir Saeed; Bouzari, Saeid

    2015-01-01

    Objectives Urinary tract infection caused by uropathogenic Escherichia coli (UPEC) strains is one of the most important infections in the world. UPEC encode widespread virulence factors closely related with pathogenesis of the bacteria. The purpose of this study was to evaluate the presence of different phenotypic virulence markers in UPEC isolates and determine their correlation with antibiotic resistance pattern. Methods UPEC isolates from patients with different clinical symptoms of UTI were collected and screened for biofilm and hemolysin production, mannose resistant, and mannose sensitive hemagglutination (MRHA and MSHA, respectively). In addition, antimicrobial resistance pattern and ESBL-producing isolates were recorded. Results Of the 156 UPEC isolates, biofilm and hemolysin formation was seen in 133 (85.3%) and 53 (34%) isolates, respectively. Moreover, 98 (62.8%) and 58 (37.2%) isolates showed the presence of Types 1 fimbriae (MSHA) and P fimbriae (MRHA), respectively. Our results also showed a relationship between biofilm formation in UPEC isolated from acute cystitis patients and recurrent UTI cases. Occurrence of UTI was dramatically correlated with the patients' profiles. We observed that the difference in antimicrobial susceptibilities of the biofilm and nonbiofilm former isolates was statistically significant. The UPEC isolates showed the highest resistance to ampicillin, tetracycline, amoxicillin, and cotrimoxazole. Moreover, 26.9% of isolates were ESBL producers. Conclusion This study indicated that there is a relationship between the phenotypic virulence traits of the UPEC isolates, patients' profiles, and antibiotic resistance. Detection of the phenotypic virulence factors could help to improve understanding of pathogenesis of UPEC isolates and better medical intervention. PMID:26473094

  20. 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

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Fundamental mechanisms of interfacial friction. 2. Stick-slip friction of spherical and chain molecules

    SciTech Connect

    Yoshizawa, Hisae; Israelachvili, J. )

    1993-10-28

    The friction and rheological properties of molecularly thin films of hexadecane between two shearing mica surfaces were measured under different conditions of load or applied pressure, film thickness, sliding velocity, temperature, and time or previous history. The aim was to investigate the tribological and rheological properties of ultrathin liquid films composed of chain molecules and to compare these properties with those of spherical molecules. The differences were found to be more quantitative than qualitative, and the results therefore provide insights into the general properties of liquids in thin films. The results show that during steady-state sliding between two solid crystalline surfaces, a liquid film may be considered to be in a one-phase or two-phase dynamic regime. In the two-phase regime, the film undergoes periodic [open quotes]stick-slip[close quotes] transitions between a solidlike and a liquidlike state. However, especially in the case of chain molecules such as hexadecane, the liquidlike state is very different from the bulk liquid. The frequency of transitions between the two dynamic states determines the static and dynamic friction forces and other dynamic properties of a shearing film. The effects produced by changing the load, temperature, sliding velocity, stopping time, etc., were found to be highly correlated. 49 refs., 21 figs., 3 tabs.

  6. 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

  7. Factors Correlated to Protective and Risk Dietary Patterns in Immigrant Latino Mothers in Non-metropolitan Rural Communities.

    PubMed

    Torres-Aguilar, Pablo; Teran-Garcia, Margarita; Wiley, Angela; Raffaelli, Marcela; Morales, Melissa

    2016-06-01

    Immigrant Latinos face conditions which over time negatively impact their nutritional behaviors and health outcomes. Our objective was to evaluate associations between environmental and lifestyle factors and both protective dietary patterns (e.g., intake of fruits and vegetables) and harmful dietary patterns (e.g., consumption of salty snacks and fast food). Surveys were individually and orally administered to 105 foreign-born Latina mothers living in rural locations in a Midwestern state. Principal component analysis created composite variables for each construct and Spearman correlations were conducted to determine associations. Protective dietary patterns were positively associated with access to food and information (ρs = 0.21) and language acculturation (ρs = 0.24), and negatively associated with family challenges (ρs = -0.31). Food insecurity was negatively associated with harmful dietary patterns (ρs = -0.24). Findings suggest that rural Latino dietary interventions should be complemented with comprehensive strategies addressing environmental and lifestyle factors across ecological domains. PMID:25990256

  8. On the modelling of Coulomb friction

    NASA Astrophysics Data System (ADS)

    Cull, S. J.; Tucker, R. W.

    1999-03-01

    This paper analyses two different representations of Coulomb friction in the context of a dynamic simulation of the torsional vibrations of a driven drill-string. A simple model is used to compare the relative merits of a piecewise analytic approach using a discontinuous friction profile to a numerical integration using a smooth nonlinear representation of the Coulomb friction. In both cases the effects of viscous damping on the excitation of torsional relaxation oscillations are exhibited.

  9. 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.

  10. 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.

  11. 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.

  12. Friction compensation strategies in large telescopes

    NASA Astrophysics Data System (ADS)

    Smith, David R.; Souccar, Kamal

    2010-07-01

    For large telescopes, management of axis friction presents a significant challenge. In some cases, this is avoided or minimized in the design stage by employing hydrostatic bearings. However, the main axis servo systems of many large telescopes must cope with bearing or wheel friction. This friction affects or limits servo control performance in several ways. The most obvious is the stick-slip limit cycle that is characteristic of trying to hold position with an integrating control system in the presence of friction. If it is not taken into account, friction also introduces effects into the state estimation in model-based controllers. There are several standard approaches to friction compensation. These include dithering (introducing a noise signal to the drive motors), direct Coulomb friction compensation (sending an additional torque based on the rate command), and adaptive techniques based on monitoring of the final drive velocities. In this work, we experimentally compare different friction compensation approaches on the static positioning performance of the Large Millimeter Telescope/Gran Telescopio Milimetrico (LMT). Single and double integrator systems are investigated, as well as direct Coulomb friction compensation.

  13. 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.

  14. 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. PMID:23594080

  15. Surgical Intervention for Symptomatic Benign Prostatic Hyperplasia is Correlated With Expression of the AP-1 Transcription Factor Network

    PubMed Central

    Lin-Tsai, Opal; Clark, Peter E.; Miller, Nicole L.; Fowke, Jay H.; Hameed, Omar; Hayward, Simon W.; Strand, Douglas W.

    2014-01-01

    BACKGROUND Approximately one-third of patients fail medical treatment for benign prostatic hyperplasia and associated lower urinary tract symptoms (BPH/LUTS) requiring surgical intervention. Our purpose was to establish a molecular characterization for patients undergoing surgical intervention for LUTS to address therapeutic deficiencies. METHODS Clinical, molecular, and histopathological profiles were analyzed in 26 patients undergoing surgery for severe LUTS. Incidental transitional zone nodules were isolated from 37 patients with mild symptoms undergoing radical prostatectomy. Clinical parameters including age, prostate volume, medication, prostate specific antigen, symptom score, body mass index, and incidence of diabetes were collected. Multivariate logistic regression analysis with adjustments for potential confounding variables was used to examine associations between patient clinical characteristics and molecular targets identified through molecular profiling. RESULTS Compared to incidental BPH, progressive symptomatic BPH was associated with increased expression of the activating protein-1 transcription factor/chemokine network. As expected, inverse correlations were drawn between androgen receptor levels and age, as well as between 5α-reductase inhibitor (5ARI) treatment and tissue prostate specific antigen levels; however, a novel association was also drawn between 5ARI treatment and increased c-FOS expression. CONCLUSIONS This study provides molecular evidence that a network of pro-inflammatory activating protein-1 transcription factors and associated chemokines are highly enriched in symptomatic prostate disease, a profile that molecularly categorizes with many other chronic autoimmune diseases. Because 5ARI treatment was associated with increased c-FOS expression, future studies should explore whether increased activating protein-1 proteins are causal factors in the development of symptomatic prostate disease, inflammation or resistance to

  16. Correlation between serum levels of vascular endothelial growth factor-C and sentinel lymph node status in early breast cancer.

    PubMed

    Pérez, Diego; Rohde, Alexander; Callejón, Gonzalo; Pérez-Ruiz, Elisabeth; Rodrigo, Isabel; Rivas-Ruiz, Francisco; Ramos, Belen; Medina, Francisco; Villatoro, Rosa; Redondo, Maximino; Zarcos, Irene; Maañón, Claudio; Rueda, Antonio

    2015-12-01

    Axillary lymph nodes status is the most important prognosis factor in early breast cancer. This status is known by a selective sentinel lymph node biopsy (SLNB) and/or lymphadenectomy. Immunohistochemical studies of breast cancer tumour tissue have reported a relation between the increased expression of vascular endothelial growth factor-C (VEGF-C) and the risk of lymph node metastasis. We researched whether serum levels of VEGF-C could be a predictor factor of sentinel lymph node status in these patients. A prospective analysis was performed on serum from 174 patients with early breast cancer who underwent SLNB. The level of VEGF-C was determined by enzyme-linked immunosorbent assay. Clinical-pathologic variables were collected. Univariate analysis and multivariate logistic regression were conducted, taking SLNB positivity as the segmentation variable. The predictive value of VEGF-C was assessed using ROC curves. Of the sample group of 167 patients, 64 (38.3 %) had affected lymph node. Eighteen patients (28.1 %) presented micrometastasis; there were isolated tumour cells in 11 cases (17.2 %) and macrometastasis in 35 (54.6 %). The median value of VEGF-C was 6561.5 pg/ml. These values did not correlate with any clinical variables, and there was no association between the level of VEGF-C and SLNB status (p = 0.626). In the multivariate analysis, tumour size (p = 0.009) and the presence of vascular invasion (p < 0.001) were independently associated with sentinel lymph node affected. Serum levels of VEGF-C do not appear to predict sentinel lymph node status in patients with early breast cancer who undergo SLNB. PMID:26104766

  17. 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.

  18. 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

  19. Hydrodynamic skin-friction reduction

    NASA Astrophysics Data System (ADS)

    Reed, Jason C.; Bushnell, Dennis M.; Weinstein, Leonard M.

    1989-10-01

    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; 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; water, with the surface of the body; and the hull of the marine vehicle.

  20. 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.