Perpendicular Force Research Articles

Parathyroid hormone (1–34) increases attachment of PMMA cement to bone

The attachment of an implant material to bone is related to the surface of the implanted material and the ability of the bone to form around the implant. Intermittent parathyroid (PTH) administration increases bone formation by stimulating osteoblastic activity. Little is known about the effect of PTH administration on orthopedic implant incorporation. The present study determined how PTH (1–34) administration influenced bone bonding, i.e., the bone-cement interfacial tensile strength, of vacuum-mixed polymethylmethacrylate (PMMA) bone cement (surface roughness; Ra, 4.8μm). Bone bonding was evaluated by a detachment test. We used unloaded cement surfaces, which could be detached from the bone. Titanium plates were developed such that a cement fill was contained within a plate that was contained within a titanium holder. Thus, a flat cement surface came into contact with traumatized bone only, and the rest of the plate had no contact with tissue. After implantation of the plate in the left tibia, 20 adult male rats were injected daily with human PTH (1–34) at 60μg/kg per injection (n=10) or vehicle (n=10); the animals were killed after 4 weeks. The plates were detached from the bone by a perpendicular force. PTH treatment increased the median pull-away strength (0.21MPa), compared with that in the vehicle-treated rats, (0.04MPa) (P=0.02). The results suggest that PTH treatment may have the potential to enhance the incorporation of cemented orthopedic implants.

Simultaneous laser-magnetic field treatment of SrFe 12O 19 thin films grown by pulsed laser deposition

Strontium hexaferrite (SrFe 12O 19) thin films were grown by pulsed laser deposition on (0 0 0 1) single crystal sapphire substrates at substrate temperatures of 600 and 800 °C. Post-deposition Nd:YAG laser annealing with external magnetic field was applied. The films deposited at the higher substrate temperature were c-axis textured. Very high squareness (≈1) of the hysteresis loops was obtained for the films deposited at the lower temperature. The laser modification of the ferrite thin films produced a smooth film surface and higher coercive forces, particularly in the direction of applying the external magnetic field. The annealed films showed significant improvement of the perpendicular coercive force. The higher magnetization of the films is a result of the c-axis crystal orientation and formation of grain chains in the films.

An instrumented object for evaluation of lateral hand grasp during functional tasks

We developed an instrumented object for quantitative evaluation of functional tasks performed with lateral hand grasp. The device was instrumented with three force transducers based on metal foil strain gauges. The transducers allowed simultaneous monitoring of the grasp force, the perpendicular force at the tip, and the force in the long axis of the instrumented object. The device was used for evaluation of a simulated eating task performed by able-bodied subjects and a tetraplegic subject instrumented with an FES hand grasp system. Use of the instrumented object will allow us to gain a more thorough understanding of the application of forces on a tool during important functional tasks of daily living. This knowledge will be used to improve the control of a closed-loop FES hand grasp system incorporating natural sensory feedback.

3204 力覚ディスプレイによる触覚テクスチャレンダリングに関する研究

This paper describes a method for rendering of tactile texture by a haptic display. The height variation of a surface is substituted by the fluctuated coefficient of friction on a planar surface to alleviate to alleviate the amount the amount of calculation introduced by complicated geometry. The coefficient of friction is calculated from a local gradient of a surface height map. For adding a sensation of perpendicular force variation, a surface normal force is augmented by the amount of height at the contact point. We set three parameters which are needed to control the behavior of the calculate model. The parameter of frictional component decreased as cylinder diameter increased, and the parameter for height value about with the diameter of a cylinder. Then evaluation of this method by using the geometrical model of textures is discussed.

Force regulates smooth muscle actin in cardiac fibroblasts.

Chronic ventricular pressure overload can regulate expression of alpha-smooth muscle actin (SMA) in cardiac fibroblasts, but it is unclear if force alone or the concomitant activity of angiotensin II is the principal regulatory factor. To test if SMA mRNA and protein in rat cardiac fibroblasts are regulated directly by force, we first induced SMA expression in cultured cells and then applied magnetically generated perpendicular forces through focal adhesions using collagen-coated magnetite beads. Continuous static forces (0.65 pN/micrometer(2)) selectively reduced SMA but not beta-actin mRNA and protein content within 4 h (to 55 +/- 9% of controls); SMA returned to baseline by 8 h. There was no change in SMA content after force application with either plasma or the cellular fibronectin IIIA domain, BSA, or poly-L-lysine beads. The early loss of SMA was apparently due to selective leakage into the cell culture medium. Treatment with angiotensin II (10 nM) abrogated the force-induced reduction of SMA and increased the levels of this protein. The stress kinase p38 was phosphorylated by force, whereas extracellular signal-regulated kinase 1/2 and c-Jun NH(2)-terminal kinase were unaffected. The p38 kinase inhibitor SB-203580 relieved the force-induced SMA reduction. We conclude that force-induced inhibition of SMA is mediated through the p38 kinase pathway, and this pathway antagonizes angiotensin II regulation of SMA.

Transverse threshold for sliding conduction in a magnetically induced Wigner solid

The Hall voltage–current relationship in the sliding conduction régime of the magnetically induced quantum Wigner solid at a low disorder GaAs/GaAlAs heterojunction shows a non-linearity which would be expected if motion perpendicular to established sliding conduction channels were inhibited up to a threshold perpendicular force. This force is roughly a tenth of that required to establish the initial sliding.

The biaxial tension of an elastoplastic space with a prismatic inclusion

The problem on the elastoplastic state of a thick isotropic plate (the case of plane deformation) is solved. A larger prismatic inclusion is made a close fit in a polygonal hole in the plate. The plate is stretched at infinity by constant mutually perpendicular forces. The problem is solved by the small-parameter method and by the theory of ideal plasticity. The axisymmetric state of the plane with a circular hole stiffened by a round ring with a constant force applied to its inner contour is considered as a zero approximation. Some specific shapes of the hole and reinforcing elastic rigid ring are considered.

Imaging mechanisms of force detected FMR microscopy

We demonstrate spatial resolution of ferromagnetic resonance in a microscopic sample of YIG using ferromagnetic resonance force microscopy (FMRFM). Measurements were performed on a small single crystal YIG film grown on a GGG substrate, roughly rectangular in shape 20 μm×∼150 μm and 3 μm thick. The perpendicular and parallel force geometries of FMRFM, in conjunction with an external bias field both parallel and perpendicular to the film, were used to scan the sample. This enabled the detection of strong signals, even at atmospheric pressure and room temperature. The fundamental and higher-order magnetostatic modes were observed to have 26–29 Gauss separation. The intensity of these modes exhibited spatial variation as the magnetic tip was scanned over the sample, and this behavior is qualitatively explained by DE theory. An improved fabrication method for magnet on cantilever was employed, which yielded a spatial resolution of 15 μm. These results demonstrate the potential of FMRFM for investigating the spatial dependence of ferromagnetic resonance, and for studying the anisotropy fields and exchange coupling effects within multilayer films and small magnetic systems.

Influence of substrates on magnetic property and crystalline orientation of CoCrTa/TiCr perpendicular magnetic recording medium

The influence of substrates on magnetic property and crystalline orientation of CoCrTa/TiCr perpendicular magnetic recording medium was investigated using a glass plate and a Si(1 0 0) single crystal. Magnetic measurements revealed that the film sputtered on a Si(1 0 0) substrate possessed a higher perpendicular coercive force than that on glass, where the pretreatment of the Si(1 0 0) substrate by aqueous HF solution effectively improved the magnetic properties. X-ray diffraction analysis of the films indicated that the crystallinity of the TiCr layer formed on the Si(1 0 0) substrate with the HF pretreatment was higher than that on the glass substrate. It was also found that CoCrTa and TiCr layers on the Si(1 0 0) substrate with the HF pretreatment had a narrower distribution of their c-axis orientation than those on glass substrate. The results of X-ray diffraction analysis were consistent with those of the TEM observation for cross-section bright- and dark-field images and the corresponding THEED patterns. These results suggest that the crystalline surface of the Si(1 0 0) substrate with HF pretreatment has the effect of inducing preferred orientation in the TiCr underlayer, which leads to a decrease in distribution of the c-axis orientation of Co grains in the CoCrTa layer, resulting in an increase in the perpendicular coercive force.

3403 力覚ディスプレイによる触覚テクスチャの提示

This paper describes a method to present a force feedback from a manipulated rigid object colliding on a textured surface. The height variation of a surface is substituted by the fluctuated coefficient of friction on a planar surface to alleviate the amount of calculation introduced by complicated geometry. The coefficient of friction is calculated from a local gradient of a surface height map. For adding a sensation of perpendicular force variation, a surface normal force is augmented by the amount of height at the contact point. We evaluated this method by conducting a pair test which presented texture samples in a real space and a virtual space (with a haptic display). The result indicated a very high correct answer ratio regarding ten texture pairs.

A unified description of tearing modes in plasmas

A unified description of tearing modes in an electron–ion plasma is presented. For this purpose, by employing the two-fluid model, which is valid beyond the magnetohydrodynamic model, new coupled mode equations for tearing modes are derived by retaining magnetic shear, the parallel electron inertia, the electron resistivity, the electron/ion neutral drag, as well as the ion Lorentz and the perpendicular ion inertial forces on the same footing. A general dispersion relation for tearing instabilities is obtained by invoking constant ψ-approximation. The newly found dispersion relation admits a rapidly growing collisional tearing instability whose growth rate is much larger (smaller) than the ion gyrofrequency (electron collision frequency). The relevance of our investigation to reconnection of magnetic field lines in laboratory and space plasmas has been discussed.

Chronic recordings of hypoglossal nerve activity in a dog model of upper airway obstruction.

The activity of the hypoglossal nerve was recorded during pharyngeal loading in sleeping dogs with chronically implanted cuff electrodes. Three self-coiling spiral-cuff electrodes were implanted in two beagles for durations of 17, 7, and 6 mo. During quiet wakefulness and sleep, phasic hypoglossal activity was either very small or not observable above the baseline noise. Applying a perpendicular force on the submental region by using a mechanical device to narrow the pharyngeal airway passage increased the phasic hypoglossal activity, the phasic esophageal pressure, and the inspiratory time in the next breath during non-rapid-eye-movement sleep. The phasic hypoglossal activity sustained at the elevated level while the force was present and increased with increasing amounts of loading. The hypoglossal nerve was very active in rapid-eye-movement sleep, especially when the submental force was present. The data demonstrate the feasibility of chronic recordings of the hypoglossal nerve with cuff electrodes and show that hypoglossal activity has a fast and sustained response to the internal loading of the pharynx induced by applying a submental force during non-rapid-eye-movement sleep.

Specific inhibition of skeletal α-actin gene transcription by applied mechanical forces through integrins and actin

Skeletal α-actin (skA), a prominent fetal actin isoform that is re-expressed by adult cardiac myocytes after chronic overload in vivo, provides a model for studying cytoskeletal gene regulation by mechanical forces in vitro. We have determined the mechanisms by which perpendicular applied forces acting through integrins and the actin cytoskeleton regulate the expression of skA. Rat-2 fibroblasts were transiently transfected with plasmids containing 5′-regulatory regions of the skA gene fused to luciferase coding sequences. A constant, perpendicular force (0.2 pN/μm2) was applied by using a collagen-magnetic bead model; a 25% deformation was obtained on the dorsal cell surface. In this system, force is applied through focal adhesion integrins and strongly induces actin assembly [Glogauer, Arora, Yao, Sokholov, Ferrier and McCulloch (1997) J. Cell Sci. 110, 11-21]. skA promoter activity was inhibited by 68% in cells subjected to 4 h of applied force, whereas Rous sarcoma virus promoter activity was unaffected. In cells transiently transfected with a skA expression vector there was also a parallel 40% decrease in skA protein levels by force, as shown by Western blotting. In L8 cells, constitutive skA expression was decreased by more than 50%. Analyses of specific motifs in the skA promoter revealed that transcriptional enhancer factor 1 and Yin and Yang 1 sites, but not serum response factor and Sp1 sites, mediated inhibitory responses to force. In cells treated with cycloheximide the force-induced inhibition was abrogated, indicating a dependence on new protein synthesis. Inhibition of actin filament assembly with either cytochalasin D or Ca2+-depleted medium blocked the inhibitory effect induced by the applied force, suggesting that actin filaments are required for the regulation of skA promoter activity. Western blot analysis showed that p38 kinase, but not Jun N-terminal kinase or extracellular signal-regulated protein kinase 1/2, was activated by force; indeed, the p38 kinase inhibitor SB203580 relieved the force-induced inhibition of skA. We conclude that the force-induced inhibition of skA promoter activity requires an intact actin cytoskeleton and can be mapped to two different response elements. This inhibition might be mediated through the p38 kinase.

Specific inhibition of skeletal α-actin gene transcription by applied mechanical forces through integrins and actin

Skeletal alpha-actin (skA), a prominent fetal actin isoform that is re-expressed by adult cardiac myocytes after chronic overload in vivo, provides a model for studying cytoskeletal gene regulation by mechanical forces in vitro. We have determined the mechanisms by which perpendicular applied forces acting through integrins and the actin cytoskeleton regulate the expression of skA. Rat-2 fibroblasts were transiently transfected with plasmids containing 5'-regulatory regions of the skA gene fused to luciferase coding sequences. A constant, perpendicular force (0.2 pN/micrometer(2)) was applied by using a collagen-magnetic bead model; a 25% deformation was obtained on the dorsal cell surface. In this system, force is applied through focal adhesion integrins and strongly induces actin assembly [Glogauer, Arora, Yao, Sokholov, Ferrier and McCulloch (1997) J. Cell Sci. 110, 11-21]. skA promoter activity was inhibited by 68% in cells subjected to 4 h of applied force, whereas Rous sarcoma virus promoter activity was unaffected. In cells transiently transfected with a skA expression vector there was also a parallel 40% decrease in skA protein levels by force, as shown by Western blotting. In L8 cells, constitutive skA expression was decreased by more than 50%. Analyses of specific motifs in the skA promoter revealed that transcriptional enhancer factor 1 and Yin and Yang 1 sites, but not serum response factor and Sp1 sites, mediated inhibitory responses to force. In cells treated with cycloheximide the force-induced inhibition was abrogated, indicating a dependence on new protein synthesis. Inhibition of actin filament assembly with either cytochalasin D or Ca(2+)-depleted medium blocked the inhibitory effect induced by the applied force, suggesting that actin filaments are required for the regulation of skA promoter activity. Western blot analysis showed that p38 kinase, but not Jun N-terminal kinase or extracellular signal-regulated protein kinase 1/2, was activated by force; indeed, the p38 kinase inhibitor SB203580 relieved the force-induced inhibition of skA. We conclude that the force-induced inhibition of skA promoter activity requires an intact actin cytoskeleton and can be mapped to two different response elements. This inhibition might be mediated through the p38 kinase.

Note Impact of the surface slipperiness of grasped objects on their subsequent acceleration

Seven subjects were asked to reach and grasp an object between the thumb and index finger, lift it about 30 cm high and 25 cm forward from one table to another, at their preferred speed. The perpendicular grip force and the tangential load force applied to the contact surface were digitized at 500 Hz and stored on a laboratory computer. The trajectory of the wrist and of the object was recorded using four infrared cameras tracking the movement of reflective markers attached to the distal styloid process of the radius and on the top of the object. The aim of this study was to demonstrate the influence of low friction (i.e. surface slipperiness) on the acceleration of the wrist. Friction was reduced by coating the smooth brass grasping surface with talc. The seven subjects had skin to surface coefficients of friction which ranged from 0.52-1.18 for dry brass and 0.24 0.34 for talc-coated brass. Two weights (418 and 1070 g) were used with each surface. The results indicated that with the slippery surface the necessary higher grip force/load force ratio was produced by an increase in the grip force and by a decrease in the wrist acceleration and a consequent reduction in the load force. This strategy was observed for both weights over a range of grip strengths between 21-98% of the individual's maximum voluntary contraction (MVC). This implies that even with adequate grip force reserves the reduction in acceleration is an acceptable and probable alternative solution to the force control problem. Our results also suggested that the loading rate and the object acceleration were planned and controlled together which emphasizes the role played by a predictive mechanism in organizing the kinematics of movements involving hand-held objects. This study shows that friction of the grasping surface not only affects the prehensile force dynamics, but it also influences the kinematics of the entire upper limb.

Texture of Nd–Fe–B thin films prepared by magnetron sputtering

We have investigated the texture and magnetic properties of Nd12Fe88−xBx sputtered films with various boron contents, x. The c-axis orientation of Nd2Fe14B phase in the films was higher and the perpendicular coercive force became greater with increment of x. With more increment of x than 15, however, the coercive force decreased owing to formation of a large amount of amorphous soft magnetic phase. The transmission electron microscope observations revealed that highly c-axis oriented Nd12Fe71B17 film has a unique microstructure; oriented Nd2Fe14B phase and amorphous phase with widths of about 200 and 50 Å, respectively, are alternately developed. This two-phase structure has realized an exchange coupled nanostructured magnet composed of aligned hard magnetic phase and soft magnetic phase. The maximum energy product of Nd12Fe71B17 film was estimated at 270 kJ/m3 with micromagnetic analysis assuming that the film was composed of complete regular structure.

Attachment of PMMA cement to bone: force measurements in rats

The attachment of an implant material to bone relates to surface roughness and surface chemistry. There is a relatively low chemical bonding strength of so-called bioactive surfaces. Hydroxyapatite interfaces typically have an interfacial tensile strength of 0.15–1.5 MPa. An attachment force similar to that of bioactive surfaces might also be reached through mechanical interlock with ordinary bone cement. This study measured bone–cement interfacial tensile strength for polished ( R a 0.5 μm) and regular ( R a 4.8 μm) vacuum mixed PMMA bone cement. Bone bonding was evaluated by a detachment test. We used unloaded cement surfaces, which could be detached from the bone. Titanium plates were developed such that a cement fill was contained within a plate, which was contained within a titanium holder. The cement surface came into contact with traumatized bone only, and the rest of the plate had no contact with tissue. The cement surface was either polished or left untreated after conventional preparation. Four weeks later, the plates were detached from the bone by a perpendicular force. The detaching load of the polished cement surface never exceeded 0.07 MPa, whereas for unpolished cement there was a load up to 0.9 MPa. The results suggest that surface irregularities and microinterlock enable an attachment that can resist tension between bone and a cement surface.

Lateral and perpendicular interaction forces involved in mobile and immobile adhesion of microorganisms on model solid surfaces.

Gliding and near-surface swimming of microorganisms are described as a mobile form of microbial adhesion that need not necessarily be reversible. It is argued that the reversibility of microbial adhesion depends on the depth of the secondary interaction minimum, calculated from the forces between an organism and a substratum acting in a direction perpendicular to the substratum surface. The mobility of adhering microorganisms depends on lateral interactions between the organisms. On ideally homogeneous and smooth model surfaces, only mobile adhesion occurs because the multibody, lateral interactions are weak compared with the thermal or Brownian motion energy of the organisms. Minor chemical or structural heterogeneities, which exist on all real-life surfaces, yield a lateral interaction on adhering microorganisms. This causes their immobilization, which helps to explain the physicochemical nature of microbial gliding or near-surface swimming. Moreover, these lateral interaction energies are one order of magnitude smaller than the Lifshitz-Van der Waals, electrostatic, and acid-base forces acting perpendicular to substratum surfaces that are responsible for adhesion.

Lymphocyte fractionation using immunomagnetic colloid and a dipole magnet flow cell sorter

The relationship between cell function and surface marker expression is a subject of active investigation in biology and medicine. These investigations require separating cells of a homogeneous subset into multiple fractions of varying marker expression. We have developed a novel cell sorter, the dipole magnet flow sorter (DMFS), which separates selected T lymphocyte subpopulations, targeted by immunomagnetic colloid, into multiple fractions according to cell surface marker expression, as determined by flow cytometry. A narrow stream of cells is introduced into a sheath of carrier fluid in a rectangular channel while subjected to a perpendicular magnetic force. The special design of the pole pieces ensures a constant magnetic force acting on the magnetically labeled cells in the separation area. Cells are spread across the flow in relation to their magnetophoretic mobility. Separation is achieved by control of the positions of the effluent stream boundaries, which separate fluid volumes with cells of different magnetophoretic mobility. CD4 and CD8 T lymphocytes labeled with primary antibody–fluorescein isothiocyanate (FITC) conjugate and anti-FITC–magnetic colloid are the chosen cell systems. Flow cytometry analysis shows that, for CD4 cells, a three-fold increase in total marker number per cell is observed when comparing the highest to the lowest fluorescence fractions. Similarly, a four-fold increase in total marker number is observed for CD8 cells. We also observed the separation of two dissimilar cell types that differed in expression of the CD4 marker, monocytes and T helper lymphocytes. We believe that this type of separation is applicable to any cells in suspension for which a suitable antibody exists and, due to the comparatively gentle nature of the process, is particularly suitable for the sorting of fragile cells.

Plasticity, fracture and friction in steady-state plate cutting

A closed form solution to the problem of steady-state wedge cutting through a ductile metal plate is presented. The considered problem is an idealization of a ship bottom raking process, i.e. a continuous cutting damage of a ship bottom by a hard knife-like rock in a grounding event A new kinematic model is proposed for the strain and displacement fields and it is demonstrated that the analysis is greatly simplified if the strain field is assumed to be dominated by plastic shear strains and moving hinge lines. Also, it is shown that the present shear model offers the basis for a convenient extension of the presented plate model to include more structural members as for example the stiffeners attached to a ship bottom plating. The fracture process is discussed and the model is formulated partly on the basis of the material fracture toughness. The effect of friction and the reaction force perpendicular to the direction of motion is derived theoretically in a consistent manner. The perpendicular reaction force is of paramount importance for predicting the structural damage of a ship hull because it governs the vertical ship motion and rock penetration which is strongly coupled with the horizontal resistance and thus with the damaged length. The derived expressions are discussed and compared with previously published experimental results and formulas.