In-line Load Research Articles

Effect of Mechanical Compression on Ionic Conductivity of PEO-LiTFSI Solid Polymer Electrolytes

In the field of energy storage materials, the development of robust solid polymer electrolytes for lithium-ion batteries necessitates an understanding of ionic conductivity when subjected to mechanical stress. Accurate determination of ionic conductivity requires knowing the electrolyte thickness, which is subject to volumetric changes during charging and discharging of solid-state batteries. However, compressive stress reduces the thickness of the electrolyte by an indeterminate amount.This work presents experimental measurements of ionic conductivity as a function of compressive stress, using poly(ethylene oxide) and with bis(trifluoromethane) sulfonimide (PEO-LiTFSI). In this study, we not only measure the stress-strain response of the electrolytes directly, but also monitor the extent of compression during electrochemical impedance spectroscopy (EIS). Compression was applied up to 50% strain for three consecutive cycles, and the typical thickness for the fabricated electrolytes was ~50 µm. EIS testing was performed by using an impedance analyzer, with the electrolyte placed between stainless steel blocking electrodes. Bulk resistance was determined by equivalent circuit modeling of impedance between 100 Hz and 2 MHz. Ionic conductivity κ was calculated from bulk resistance Rb , electrolyte thickness h, and cross-sectional area A, according to the equation κ = h/(Rb·A).In order to measure both stress and deformation simultaneously, a custom positioning stage was engineered to apply prescribed compression. The apparatus has an in-line load cell for force measurements and a laser triangulation sensor for position tracking with submicron resolution. We found that the bulk resistance at room temperature decreases exponentially, with magnitude reduced by approximately five-fold when subjected to compressive stress up to 10 MPa. Beyond ~7 MPa, bulk resistance values were no longer dependent on the amount of applied compression.In addition to mechanical measurements, changes in crystalline and amorphous regions were correlated to the magnitude of compressive stress and the measured ionic conductivity of the electrolyte. For optical imaging with simultaneous EIS measurements, glass slides coated with an indium tin oxide (ITO) film were used instead of stainless steel disks. The extent of crystallinity was visualized by optical microscopy of spherulites through a viewing window when compressed between rigid plates.Figure 1. Apparatus (left) and representative ionic conductivity vs. compressive stress (right) data for a PEO-LiTFSI polymer electrolyte. Figure 1

Effects of Coating and Lubrication on Friction and Wear for Metal-to Metal Application

Friction and wear between sliding surfaces can lead to various issues in industrial applications, such as increased costs, reduced machine lifespan, loss of functionality, energy loss, and decreased system efficiency. To mitigate these problems, lubricants and coatings are commonly employed. This study aims to investigate the impact of coatings and lubrication on friction coefficient, wear volume loss, and lubricant temperature using the block-on-ring wear test. The effectiveness of different coatings (uncoated, DLC, CrN, and TiALN) and lubricants (anti-friction graphene oxide additive oil and strong nano engine oil additive) in reducing friction and wear is evaluated. The block-on-ring tests are conducted under varying loads (6-60 N), speeds (1450 rpm), lubricant volumes (40 ml), and durations (2-20 min). The coefficient of friction is measured using an inline load cell, wear volume loss is determined by weighing the blocks before and after the experiment, and lubricant temperature is monitored using thermocouples. The results indicate that the coefficient of friction decreases with increasing load, while the lubricant temperature rises. Coated blocks exhibit lower wear volume loss compared to uncoated blocks. Overall, the combination of CrN-coated blocks and anti-friction graphene oxide additive oil demonstrates the best tribological performance.

Modular Bioreactor Design for Directed Tendon/Ligament Tissue Engineering.

Functional tissue-engineered tendons and ligaments remain to be prepared in a reproducible and scalable manner. This study evaluates an acellular 3D extracellular matrix (ECM) scaffold for tendon/ligament tissue engineering and their ability to support strain-induced gene regulation associated with the tenogenesis of cultured mesenchymal stromal cells. Preliminary data demonstrate unique gene regulation patterns compared to other scaffold forms, in particular in Wnt signaling. However, the need for a robust bioreactor system that minimizes process variation was also evident. A design control process was used to design and verify the functionality of a novel bioreactor. The system accommodates 3D scaffolds with clinically-relevant sizes, is capable of long-term culture with customizable mechanical strain regimens, incorporates in-line load measurement for continuous monitoring and feedback control, and allows a variety of scaffold configurations through a unique modular grip system. All critical functional specifications were met, including verification of physiological strain levels from 1–10%, frequency levels from 0.2–0.5 Hz, and accurate load measurement up to 50 N, which can be expanded on the basis of load cell capability. The design process serves as a model for establishing statistical functionality and reliability of investigative systems. This work sets the stage for detailed analyses of ECM scaffolds to identify critical differentiation signaling responses and essential matrix composition and cell–matrix interactions.

The Effect of Flexor Digitorum Profundus Repair Position Relative to Camper Chiasm on Tendon Biomechanics

The purpose of this study was to investigate the impact of repairing a zone II flexor digitorum profundus (FDP) laceration anatomically versus extra-anatomically on tendon loads and work of flexion (WOF). Twenty digits from 5 cadaveric specimens were tested using an invitro active finger motion simulator under 2 FDP tendon repair conditions: anatomic and extra-anatomic. Tensile loads in FDP and flexor digitorum superficialis (FDS), WOF, and total active finger range of motion (ROM) were measured using in-line load cells and electromagnetic tracking, respectively. The anatomic repairs had no effect on tendon loads or WOF for either FDP or FDS. The extra-anatomic repairs increased FDP loads by 32% and decreased FDS loads by 9% compared with those in the intact condition. This pattern was similar for WOF following extra-anatomic repairs, which increased FDP WOF by 31% and decreased FDS WOF by 18%. Comparing the 2 repairs, FDP loads and WOF were 25% and 22% greater, respectively, with extra-anatomic repairs compared with anatomic repairs, with no significant change in FDS. Total active ROM was not affected by either repair. In this invitro cadaveric model, extra-anatomic repairs of FDP increased tendon loads and WOF compared with anatomic repairs. On the basis of this study, reconstitution of the anatomic relationship of FDP and FDS at the Camper chiasm during the repair of zone II flexor tendon lacerations is recommended.

Comparison of Different Magnitudes of Applied Syndesmotic Clamp Force: A Cadaveric Study

Overcompression of the ankle syndesmosis was once thought to be improbable. Recent studies using computerized tomography (CT) however, have demonstarted otherwise; raising pertinent questions regarding the factors associated with and consequences of syndesmotic overcompression. The purpose of the present study was to directly compare different magnitudes of applied clamp force on the coronal reduction of ankle syndesmosis. Eight through-the-knee cadaveric specimens were obtained. Fiducial cannulated screws were placed in the tibia and fibula to standardize placement of the reduction clamp's tines. CT scans were obtained as baseline controls, followed by destabilization of the syndesmosis. Reductions were then performed using a clamp equipped with an inline load cell, and objective forces (60, 80, 100, 120, 140, and 160 N) applied sequentially to each of the specimens. The syndesmosis was fixed with a single quadricortical screw, and CT were scans repeated. Applied clamp forces of 60 and 80 N resulted in lateral fibular displacement and undercompression (42.9% and 57.1%, respectively), whereas forces of 140 and 160 N resulted in medial fibular displacement (p = .011 and p = .001) and overcompression (100%). The smallest mediolateral displacements were observed with 100 and 120 N, respectively. Malreduction assessment with CT was superior to traditional radiographs [r(54) = 0.22; 95% confidence interval –0.04 to 0.45; p = .101]. In our cadaveric model, an applied clamp force of 100 N most effectively mitigated iatrogenic coronal syndesmotic malreduction from under- or overcompression. Although additional research is warranted, based on the data, inherent variabilities in the applied clamp force by surgeons appear to contribute to the unacceptably high coronal syndesmotic malreduction rate.

Femtosecond laser–assisted capsulotomy with capsular marks for toric IOL alignment: Comparison of tensile strength with standard femtosecond laser capsulotomy

To compare the capsulotomy rim strength with capsular marks (CMs) to the rim strength without CMs in porcine eyes, and to demonstrate the practicality of CMs for intraoperative toric intraocular lens (IOL) alignment. LENSAR facility, Orlando, Florida, USA. Laboratory study. The biomechanical strength of the capsulotomy with CMs was tested under two different load orientations (orthogonal to or in-line with CMs). Thirty-six porcine eyes were randomly assigned to three treatment cohorts: (1) standard capsulotomy with no CMs, (2) capsulotomy with CMs for in-line tensile testing and (3) capsulotomy with CMs for orthogonal tensile testing. Study parameters were capsulotomy break force and maximum extensibility. The ease of using CMs for toric IOL alignment was also evaluated. There was no significant difference between the mean break force for standard capsulotomy (180.57mN±22 [SD]), capsulotomy with CMs with orthogonal load (178.04±20mN, P=1.000), and with in-line load (181.05±15mN, P=1.000). Likewise, the mean extensibility at the break point for standard capsulotomy (6.47±0.33mm) was equivalent to the mean extensibility with CMs with orthogonal load (6.49±0.45mm, P=1.000) and with in-line load (6.3±0.47mm, P=.960). In the implanted eyes, toric IOLs were found to be easily aligned with the CMs. The femtosecond laser capsulotomies with CMs were equivalent in tensile strength and extensibility to standard femtosecond laser capsulotomies and showed high potential for effective alignment of toric IOLs.

Prediction of Combined Inline and Crossflow Vortex-Induced Vibrations Response of Deepwater Risers

Deepwater risers are susceptible to vortex-induced vibrations (VIV) when subjected to currents. When responding at high modes, fatigue damage in the inline (IL) direction may become equally important as the crossflow (CF) components. Accurate calculation of both IL and CF responses is therefore needed. Empirical VIV prediction programs, such as VIVANA “Passano et al. (2016, “VIVANA—Theory Manual Version 4.8,” Trondheim, Norway),” SHEAR7 “(Vandiver, J. K., and Li, L., 2007, “Shear7 v4.5 Program Theoretical Manual,” Department of Ocean Engineering, Massachusetts Institute of Technology, Cambridge, MA),” and VIVA “Triantafyllou et al. (1999, “Pragmatic Riser VIV Analysis,” Offshore Technology Conference, Houston, TX, May 3–6, Paper No. OTC-10931-MS.)” are the most common tools used by the offshore industry. Progress has been seen in the prediction of CF responses. Efforts have also been made to include an IL load model in VIVANA. A set of excitation coefficient parameters were obtained from rigid cylinder test and adjusted using measured responses of one of the flexible cylinder VIV tests. This set of excitation coefficient parameters is still considered preliminary and further validation is required. Without an accurate IL response prediction, a conservative approach in VIV analysis has to be followed, i.e., all current profiles have to be assumed to be unidirectional or acting in the same direction. The purpose of this paper is to provide a reliable combined IL and CF load model for the empirical VIV prediction programs. VIV prediction using the existing combined IL and CF load model in VIVANA is validated against selected flexible cylinder test data. A case study of a deepwater top tension riser (TTR) has been carried out. The results indicate that VIV fatigue damage using two-dimensional directional current profiles is less conservative compared to the traditional way of using unidirectional current profiles.

A Six Degrees of Freedom Dynamic Wire-Driven Traverse

A novel support mechanism for a wind tunnel model is designed, built, and demonstrated on an aerodynamic platform undergoing dynamic maneuvers, tested with periodic motions up to 20 Hz. The platform is supported by a 6-DOF (six degrees of freedom) traverse that utilizes eight thin wires, each mounted to a servo motor with an in-line load cell to accurately monitor or control the platform motion and force responses. The system is designed such that simultaneous control of the servo motors effects motion within ±50 mm translations, ±15° pitch, ±9° yaw, and ±8° roll at lower frequencies. The traverse tracks a desired trajectory and resolves the induced forces on the platform at 1 kHz. The effected motion of the platform is measured at 0.6 kHz with a motion capture system, which utilizes six near-infrared (NIR) cameras for full spatial and temporal resolution of the platform motion, which is used for feedback control. The traverse allows different platform model geometries to be tested, and the present work demonstrates its capabilities on an axisymmetric bluff body. Programmable timed outputs are synchronized relative to the model motion and can be used for triggering external systems and processes. In the present study, particle image velocimetry (PIV) is used to characterize the realized wakes of the platform undergoing canonical motions that are effected by this new wind tunnel traverse.

SPIRET: An Innovative Technique for Random Vibration Testing Of Large Spacecraft

Abstract System Point Input Random Excitation Testing (SPIRET) was developed as an alternative to both system level acoustics and base-shake random vibration testing of large spacecraft. The goal of SPIRET was to obtain an enhanced workmanship test of the spacecraft, prior to launch, by inducing a higher, more uniform dynamic acceleration response throughout the integrated system. The underlying SPIRET concept is to utilize the spacecraft modal characteristics to amplify the shaker input force and produce a high acceleration response throughout the flexible structure. SPIRET utilized commercial off-the-shelf vibration equipment coupled with satellite specific Mechanical Aerospace Ground Equipment (MAGE). Random vibration control was achieved using inline load cells and a Force Spectral Density (FSD) input spectrum which effectively provided both feedback control of the shaker and force limiting during the vibration test. SPIRET effectiveness was verified using a hi-fidelity spacecraft simulator which was previously used for structural and acoustic testing. This enabled direct comparison of SPIRET response accelerations to acoustic response accelerations at common spacecraft locations. In general, SPIRET produced higher dynamic loading throughout the spacecraft than did acoustic testing at Protoqual (PQ) levels over the tested frequency range of 5Hz to 500 Hz. This resulted in a more thorough workmanship screen of the spacecraft prior to launch. The benefits of SPIRET extend beyond the technical goal of achieving an enhanced system workmanship test. Significant schedule and cost savings were realized since the test was conducted within the spacecraft final assembly facility which enabled parallel vehicle processing activities and shared personnel resources. SPIRET has been successfully used as the final integrated spacecraft level dynamic test at Lockheed Martin Denver since 2001.

Assessment of Pedicle Bone Strength in the Lumbar Spine Using a “Smart” Ball Tip Probe

Preoperative assessment of bone mineral density (BMD) via dual X-ray absorptiometry (DEXA) has been shown to help determine the need for screw augmentation, particularly in the pedicle. However, patients frequently present without preoperative DEXA scans, especially in trauma situations. We developed a “smart” probe for intra-operative assessment of local bone strength in the pedicle. A standard ball tip probe was instrumented with an in-line load cell and was used to test the bone strength of fresh-frozen human cadaveric lumbar spine. Local bone crush strength was assessed using the probe at five locations within the centrum and the pedicle. The contralateral pedicle was outfitted with a standard pedicle screw and insertion torque and pull-out force of the screw were measured. Correlation was found between PS-centrum (probe strength-centrum) and screw pull-out strength (adj. R2 = 0.42). A stepwise linear regression revealed that when considering BMD, insertion torque, and PS-centrum, pull-out strength could be predicted based on PS-centrum and insertion torque (adj. R2 = 0.51, p < 0.01, Fisher test). The results suggest that use of the new probe may be a more quantitative measurement of screw purchase when DEXA is unavailable, such as in spinal trauma cases. Furthermore, when used in conjunction with DEXA, the “smart” ball tip probe may improve assessment of the strength of pedicle screw purchase.

1551 ENDOSCOPIC FORCEPS FOR URETEROSCOPY: A COMPARATIVE IN VITRO ANALYSIS

You have accessJournal of UrologyStone Disease: New Technology1 Apr 20131551 ENDOSCOPIC FORCEPS FOR URETEROSCOPY: A COMPARATIVE IN VITRO ANALYSIS Carl Sarkissian, Giovanni Marchini, Shubha De, and Manoj Monga Carl SarkissianCarl Sarkissian Cleveland, OH More articles by this author , Giovanni MarchiniGiovanni Marchini Cleveland, OH More articles by this author , Shubha DeShubha De Cleveland, OH More articles by this author , and Manoj MongaManoj Monga Cleveland, OH More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2013.02.3061AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The objective of this study was to compare different grasper devices in terms of opening dynamics, grasping effectiveness, safety, and influence on flexible ureteroscope deflection. METHODS The Captura (2.8F, Cook Medical), Platinum (3.0F, Bard Urological), TriClaw (2.4F, UroGyn), Graspit (2.6F, Boston Scientific), and Boston Scientific Tricep (2.4F, 3.0F; 3.0F non-retracting) graspers opening dynamics were evaluated using high-resolution images; grip strength by measuring maximum tensional force applied while grasping stone models attached to an in-line load cell (Fig. 1A,B); safety profile by the maximum force required to perforate aluminum foil (Fig. 2A); impact on deflection by measurement of maximum deflection and bending radius after insertion of the grasper through a flexible ureteroscope. Grip strength and perforation forces were compared with Tukey's test assuming unequal variance. RESULTS The TriClaw and Graspit had greater grip strengths than all other devices (Fig. 1C). Captura (1.92 N) and Tricep 2.4F (1.72 N) required the greatest forces to perforate aluminum foil (Fig. 2B). The Triceps and Captura required the least distance to attain a grasping width of 5 mm (Fig. 3). Ureteroscope deflection was least impacted by the Tricep 2.4F (213∥; 1.35 cm radius), Graspit (207∥; 1.35 cm radius) and TriClaw (206∥; 1.3 cm)(Fig. 4). CONCLUSIONS There are significant differences in opening dynamics, grip strength, perforation forces, and ureteroscope deflection among ureteroscopic graspers that may predict clinical performance capabilities. © 2013 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 189Issue 4SApril 2013Page: e635-e637 Advertisement Copyright & Permissions© 2013 by American Urological Association Education and Research, Inc.MetricsAuthor Information Carl Sarkissian Cleveland, OH More articles by this author Giovanni Marchini Cleveland, OH More articles by this author Shubha De Cleveland, OH More articles by this author Manoj Monga Cleveland, OH More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Analysis of a Knotless Flexor Tendon Repair Using a Multifilament Stainless Steel Cable-Crimp System

To compare the biomechanical and technical properties of flexor tendon repairs using a 4-strand cruciate FiberWire (FW) repair and a 2-strand multifilament stainless steel (MFSS) single cross-lock cable-crimp system. Eight tests were conducted for each type of repair using cadaver hand flexor digitorum profundus tendons. We measured the required surgical exposure, repair time, and force of flexion (friction) with a custom motor system with an inline load cell and measured ultimate tensile strength (UTS) and 2-mm gap force on a servo-hydraulic testing machine. Repair time averaged less than 7 minutes for the 2-strand MFSS cable crimp repairs and 12 minutes for the FW repairs. The FW repair was performed with 2 cm of exposure and removal of the C-1 and A-3 pulleys. The C-1 and A-3 pulleys were retained in each of the MFSS cable crimp repairs with less than 1 cm of exposure. Following the FW repair, the average increase in friction was 89% compared with an average of 53% for the MFSS repairs. Six of the 8 MFSS specimens achieved the UTS before any gap had occurred, whereas all of the FW repairs had more than 2 mm of gap before the UTS, indicating that the MFSS was a stiffer repair. The average UTS appeared similar for both groups. We describe a 2-strand multifilament stainless steel single cross-lock cable crimp flexor repair system. In our studies of this cable crimp system, we found that surgical exposure, average repair times, and friction were reduced compared to the traditional 4-strand cruciate FW repair. While demonstrating these benefits, the crimp repair also produced a stiff construct and high UTS and 2-mm gap force. A cable crimp flexor tendon repair may offer an attractive alternative to current repair methods. The benefits may be important especially for flexor tendon repair in zone 2 or for the repair of multiple tendons.

Endoscopic Forceps for Ureteroscopy: A Comparative In Vitro Analysis

To evaluate the functional characteristics of different ureteroscopic graspers. The Captura (2.8F, Cook Medical, Bloomington, IN), Platinum (3.0F, Bard Urological, Covington, GA), TriClaw (2.4F, UroGyn Medical, Inc., Valapraiso, IN), Graspit (2.6F, Boston Scientific, Natick, MA), and Boston Scientific Tricep (2.4F, 3.0F, and 3.0F non-retracting) graspers were tested. Opening dynamics were evaluated using high-resolution images. Grip strength was determined by measuring the maximum tensional force applied while grasping stone models attached to an inline load cell. Safety profile was evaluated by the maximum force required to perforate aluminum foil. Impact on ureteroscope deflection was assessed by measurement of maximum deflection (baseline = 247°) and bending radius after advancing each grasper through a flexible ureteroscope working channel. The Tukey test for inequality assuming unequal variance with Bonferroni adjustment was used to compare grip strength and perforation forces. The Tricep (2.4F, 3.0F NR, and 3.0F) and Captura graspers required the least distance (7.9-8.1 mm) to attain a grasping width of 5 mm. When compared across all stone models, the TriClaw and Graspit had greater grip strengths than all other devices. The Captura (1.92 ± 0.43 N) and Tricep 2.4F (1.72 ± 0.88 N) required the greatest forces to perforate aluminum foil. Ureteroscope deflection was least impacted by the Tricep 2.4F (213°, 1.35 cm radius), Graspit (207°, 1.35 cm radius), TriClaw (206°, 1.3 cm radius), and all graspers could be deployed and operated at maximum deflection. There are significant differences in opening dynamics, grip strength, perforation forces, and ureteroscope deflection among ureteroscopic graspers that may predict clinical performance capabilities.

Torsion tests on spun-cast prestressed concrete poles

This paper focuses on the effect of the transverse reinforcement—its amount, spacing, and direction—on torsional strength in an effort to simplify the governing codes and provide general information on the behavior of spun-cast prestressed concrete poles under pure tor- sion. The rationale behind the typical code values for spacing and direction of the transverse reinforcement is not apparent. A total of 14 specimens were produced as part of a testing program. The testing program consisted of two groups of seven specimens with two different tip diameters: 6.5 in. (165 mm) and 8.3 in. (210 mm). Within each group the spacing and direc- tion of the wound helical transverse reinforcement was varied. Each specimen was clamped at the butt end, and a counterclockwise torque load was applied at 2 ft (0.6 m) from the tip end. Applied torque and rotation of the tip were recorded using an inline load cell and electronic clinometers. The test concluded when the rotation reached approximately 13° to 15° or failure occurred. Experimental cracking torque values were compared with code-calculated theoretical values using current codes. Precracking and postcrack- ing torque-twist responses were analyzed with elastic torsion and torsional compression field theory mod- els. It was concluded that the primary function of the transverse reinforcement is to minimize the longitu- dinal precracking due to prestressing transfer forces. The prestressed concrete pole failure mode in torsion is brittle and sudden, and the transverse reinforcement provides no postcracking ductility.

Girth tensions and their variability while standing and during exercise

The tension applied to the girth is usually based on an individual's experience rather than by scientific measurement or procedure. The equine thorax is a dynamic structure, and therefore the actual readings of girth tensions at rest and during exercise (actual tension) are likely to vary from the tension to which the girth was intended to be tightened at rest while standing (intended tension). This study was undertaken to determine the variability of girth tensions at rest and during exercise. A total of 19 Hanoverian horses were lunged on a 20 m circle in walk, trot and canter on both reins. In a randomized design, each horse was exposed to intended tensions 6, 10, 14 and 18 kg (saddle and girth at appropriate intended tensions). Girth tension was measured and recorded continuously using an in-line load cell. Intended girth tensions were not significantly different with mean actual girth tensions while standing. Actual girth tensions increased significantly (P < 0.001) between walk, trot and canter at all tensions except rest to trot at tension 6 kg, where the significance level was P < 0.01. Actual girth tension was significantly higher (P < 0.001) on the left rein at tension 14 kg in walk and trot, and at tensions 6, 10 and 14 kg during canter, and there was an overall trend for higher actual girth tensions on the left rein for the other tensions. As the thorax is a dynamic structure, girth tension variation could be due to multiple factors such as respiration, breath holding, muscular contraction, back flexion and extension, speed, gait and vertical acceleration of the saddle. Girth tension is a relatively new area of research, and as there are many opportunities for further research, a better understanding of the impact the girth has on the horse could help to improve performance and welfare.

Comparison of girth materials, girth tensions and their effects on performance in racehorses

To compare the effect of girth materials and commonly used girth tensions on athletic performance of race-horses and to test the length tension properties of commercially available girths. Seven horses were exercised at speeds to produce 95% of maximal heart rates on 15 occasions using a randomised block design, and girthed with 5 different girths at 3 nominal tensions of 6, 12 or 18 kg. The girths used were a standard elastic race girth, an 'American' elastic race girth, an elastic race girth twice the normal width, a standard canvas race girth and a canvas race girth at twice the normal width. Tension in the girth was recorded continuously using an in-line load cell connected to a physiograph. Horses ran to fatigue on a treadmill inclined at 10% slope. Tensions were measured at peak inhalation (T/inh) and exhalation (T/exh), recorded at rest (rest) and during exercise (ex). An analysis of variance was used to compare the mean run to fatigue times (RTFT) between girth types and tensions, multiple pair-wise comparisons were then carried out using Tukey's test where significant differences were found. The length-tension relationships of five commercially available girths for training and racing of Thoroughbred racehorses were studied by the application of standardized weights in series to multiple samples of each type of girth. Measurements were taken in a controlled environment and analysis of variance was used to compare the means for length-tension of each girth type. The elastic and the 'American' elastic girths produced significantly longer RTFT when compared to the standard canvas girth (P = 0.01 and P = 0.001 respectively). Also girths tensioned at Texhrest 6 kg and Texhrest 12 kg produced significantly longer RTFT than when girthed at Texhrest 18 kg (P = 0.03 and P = 0.08 respectively). There were significant differences between the commercially available girth types at each tension (P < 0.05), but differences were not significant between girths of the same type. Girths with an elastic component reached their peak for maximum extension at 14.5 kg and thereafter their extension declined. The type of girth and the tension at which it is applied affects athletic performance. Lower girth tensions and the use of elastic materials in the girth would appear to optimise performance. However according to this study and our previous study, none of the commercially available girths studied would adequately protect against the potentially detrimental effects of overtightening on athletic performance.

A medical needle drive for the study of interstitial implant mechanics

We describe the construction and test performance of a computer-controlled medical needle drive. The drive represents one facet of a larger project whose aim is to investigate experimentally the mechanics of needle introduction in radioactive ‘seed’ prostate implants, with a view to identifying ways of making incremental improvements in needle placement accuracy. It is capable of mimicking a range of motions imparted to a needle by a clinical practitioner, and of monitoring the compressive force at the needle tip in real time via an in-line load cell. Tests involving driving needles into porcine gelatin samples using a variety of velocity profiles confirm intended operation. The drive will permit us to introduce needles in a controlled and reproducible manner into a realistic prostate phantom currently being designed.

Tensions used on girths on thoroughbred racehorses.

To determine commonly used girth tensions in Thoroughbred racehorses in the Melbourne metropolitan area. A prospective industry survey. Strappers were instructed to tension girths, using the same saddle, under-saddle packing and girth, sufficiently to hold the saddle for racing. These tensions were continuously recorded by an in-line load cell in the girth. Seventeen strappers from five stables participated in the study, which was conducted on 91 horses. Resting girth tensions varied considerably. The mean tension on inhalation was 13 +/- 0.4 kg. Male strappers recorded higher tensions than females for all indices measured. Age and girth size of the horse did not significantly influence results. This study confirms that there is no standard for application of a girth and saddle in the Thoroughbred racing industry and the range of tensions applied was large. Strappers were unable to reliably apply the same tensions between horses. Values recorded at the extremes of the range seem inappropriate for racing conditions as low values would result in slippage of the saddle and higher values may result in girth galls and possible reduction in athletic performance. Further work is necessary to determine the point at which girth tension affects performance.

Influence of girth strap tensions on athletic performance of racehorses.

Eight horses were exercised at speeds to produce 80% of maximal heart rates, on 4 occasions using a randomised block design, and girthed at tensions of approximately 5, 10, 15 or 20 kg using a standard canvas girth attached to a racing saddle. Tension was recorded continuously using an in-line load cell connected to a physiograph. Horses ran until fatigued on a treadmill inclined at 10% slope. Tensions were measured at peak inhalation (T/inh) and exhalation (T/exh), recorded at rest (rest) and during exercise (ex). Data were analysed by ANOVA and, in addition, least squares linear regression was performed to determine the relationship between distance travelled, time to fatigue and the recorded maximum tensions at inhalation and minimum tensions at exhalation. For T/inhrest, every increase in girth tension by 1 kg was associated with a reduction in distance to fatigue by 98.3 +/- 28.6 m and a corresponding reduction in run times of 0.24 +/- 0.07 min (P = 0.01). Results for T/exhrest were similar, with a reduction of mean +/- s.e. 81.3 +/- 26.9 m and 0.20 +/- 0.07 min per 1 kg increase in tension (P = 0.02). The mean distances to fatigue for the T/exhrest of 5, 10, 15 and 20 kg were 6624, 5812, 5268 and 5405 m respectively. These data indicate that distances to fatigue are similar once T/exhrest equals or exceeds 10 kg. Based on this study, resting girth tensions less than 10 kg are optimal for performance, but from our survey data, tensions exceeding this tension are typical for Thoroughbred racing in Victoria.

Mechanical Forces as Predictors of Healing During Tibia1 Lengthening by Distraction Osteogenesis

Direct axial loads were measured weekly during a 15% left tibial lengthening in 21 skeletally mature dogs using three in-line load cells mounted between the rings of an Ilizarov external fixator. The loads increased linearly over time to a maximum at the end of distraction (Week 4). The metaphyseal lengthening sites (mean, 155 N) generated significantly higher loads than diaphyseal sites (mean, 111 N). Stress was calculated by dividing measured load by the computed tomographic-measured cross-sectional area of each distraction osteogenesis site; the metaphyseal and diaphyseal groups demonstrated equal stress at each time point with a maximum of 47 N/cm2 at the end of distraction. Six premature consolidations occurred that demonstrated loads significantly greater than 200 N by Week 2 of distraction. Three nonunions occurred that had significantly lower loads measured by Week 3 of distraction (mean, 60 N or 26 N/cm2).