Significant Increase In Force Research Articles

Force profile assessment of direct-printed aligners versus thermoformed aligners and the effects of non-engaged surface patterns

BackgroundThe purpose of the study was to measure the forces delivered by direct-printed aligners (DPA) in the vertical dimension and compare the force profile with traditional thermoformed aligners (TFA) and to investigate the impact of non-engaged surface patterns to the properties of DPA and TFA.MethodsA force-measuring appliance was fabricated capable of displacing the aligner in 0.10 mm increments and measuring the resultant force. Polyethylene terephthalate glycol (ATMOS 0.030″ American Orthodontics) and TC-85DAC resin (Graphy Inc) were used to create TFA and DPA, respectively. Aligners were temperature-controlled prior to and during testing to simulate the oral environment. The resultant forces from displacements ranging from 0.10 to 0.30 mm were measured.ResultsAt intraoral temperatures, DPA demonstrated significantly less force than TFA. TFA demonstrated a substantial statistically significant increase in force with each 0.10 mm increase in vertical displacement. DPA demonstrated a much more consistent force profile across the range of displacements. The effects of surface patterns in both DPA and TFA were generally a decrease in force. Statistical significance of surface patterns was detected for TFA at displacements of 0.30 mm and greater and significant for DPA only at a displacement of 0.10 mm. Surface patterns in both DPA and the TFA did not show any statistical difference when assessing force proprieties.ConclusionsForces delivered by aligners in the vertical dimension by DPA are more consistent and of lower magnitude than those of TFA aligners. Surface patterns were not capable of altering the force properties of both DPA and TFA.

The Effects of a Real-Time Visual Kinetic Feedback Intervention on Shock Attenuation of the Equestrian Rider's Trunk: A Pilot Study.

Augmented feedback (provided by an external source) has been commonly used by practitioners who are introducing or re-educating movement patterns as a valuable tool of instruction. This study aimed to evaluate the effects of real-time visual kinetic feedback on a horse-riding coaching session. Sixteen riders volunteered to take part in this study. They performed a pre-intervention trial, a 20-min coaching intervention, and a post-intervention trial. The participants randomly received a coaching + feedback intervention or a coaching-only intervention. Forces at the bit and stirrups were recorded at trot and canter. Thirteen inertial measuring units were fitted to the horse's forelimbs and poll, to the stirrups, cantle of the saddle, distal part of the bridles, 1st sacrum vertebrae of the rider (S1), 7th cervical vertebrae of the rider (C7), wrists of the rider, and helmet. The shock attenuation (SA) between helmet:saddle and between C7:S1 and absolute force output were calculated. Changes in SA and force output were compared between groups by two-way repeated measures ANOVA (group*time) both at trot and canter. Statistical significance was set at p < 0.05. SA was significantly lower in both groups and conditions after the intervention. C7:S1 SA was significantly lower in the feedback + coaching group at canter and trot, and helmet:saddle SA was significantly lower in the feedback + coaching group at trot than in the coaching group. A significant increase in force was observed in all the groups on the stirrups at trot and canter, but no significant changes were observed on rein forces. Implementing sports wearables that provide such type of information might be of remarkable benefit for the rider's development and performance.

Experimental and numerical investigation on the impact response of CFRP under 3-point-bending

The strain rate-dependent material characteristic of carbon fiber reinforced plastics (CFRP) is widely known and has been investigated in detail at coupon level. In this study, for the first time the strain rate dependent characteristic of a three-dimensional CFRP structure was investigated. The evolution of the determined strain rate dependency was correlated with the results at coupon level. For this purpose two special 3-point-bending fixtures were developed to obtain the flexural impact response of the investigated T700S DT120 prepreg system at coupon and component (hat profile) level. The rectangular coupon specimens were loaded with quasi-static to intermediate impact velocities from 3.3×10−5 to 10m s−1, while the structural sub components were tested using impact velocities from 3.3×10−5 to 1m s−1. With increasing impact velocities, the experimental tests showed a significant increase in force at first failure and maximum deflection at coupon level. The increases in force were of 52% and 120%, respectively. However, the increase for structural hat profile components was just 12.4% due to a different failure mode. The observed initial failure modes were compressive failure provoked by fiber kinking for the coupon and interlaminar shear failure for the structural component. Regardless of the different failure modes this work proves the necessity of considering the strain rate dependency of a composite material to accurately predict the maximum load capacity of a CFRP structure during a dynamic load event. Additionally, the comparison of the experimental results restults to numerical results revealed weaknesses in the prediction accuracy of the currently used models.

Evaluating Solid-Electrolyte Interphases for Lithium and Lithium-free Anodes from Nanoindentation Features

Summary The morphology and mechanical property of SEIs for lithium anodes crucially affect the electrochemical cycling performance of Li-metal batteries such as Li-S and Li-O2 batteries. Herein, we establish the standards for rapidly assessing SEIs for Li and Li-free type of anodes by AFM nanoindentation features toward prediction of corresponding electrochemical performances. A series of single-layered and multi-layered SEIs with known composition and structures are purposely constructed. A set of unique nanoindentation features representative of mechanical properties of the basic SEIs are formed, serving as the standards for rapidly assessing the mechanical properties and electrochemical performances of unknown SEIs together with their Young’s modulus, smoothness, and thickness. To validate the applicability of the method, SEIs formed by electrochemical aging and formed on Cu substrates are further evaluated. Our work not only contributes to understanding the influence of SEIs on cycling performances but also provides a rapid way for screening SEIs.

Biceps tenodesis versus tenotomy in isolated LHB lesions: a prospective randomized clinical trial.

Currently there exists no clear evidence concerning the surgical treatment of LHB lesions with either tenotomy or tenodesis. The aim of the study is therefore to evaluate elbow flexion and forearm supination force as well as the biceps muscle distalization according to both techniques in isolated LHB lesions. Consecutive patients aged 40-70years with shoulder arthroscopies for isolated SLAP or biceps pulley lesions were prospectively randomized to arthroscopic suprapectoral intraosseous LHB tenodesis or tenotomy. Pre-, 6 and 12months postoperatively, the SST, ASES, Constant-Murley and LHB scores were recorded. The elbow flexion force was measured in 10°/90° flexion, the supination force in neutral/pronation position. In addition, the maximum upper-arm circumference and its position relative to the radial epicondyle of the humerus were evaluated preoperatively and in follow-up. 20/22 patients (mean age 52.0 ± 8.5; range 36-63 years, 11 male) completed the follow-up. 9/20 were treated with LHB tenodesis (mean age 51.5 ± 9.5; range 37-63 years, 7 male) and 11/20 with tenotomy (mean age 52.8 ± 8.0; range 36-62 years, 4 male). The force measurements and scores showed no significant difference after 12months. Tenodesis achieved a significant increase in force 6months postoperatively compared to preoperatively. One tenodesis patient and three tenotomy patients showed a postoperative popeye-sign deformity. This prospective randomized study comparing LHB tenodesis and tenotomy in isolated LHB lesions has shown no significant difference in elbow flexion and forearm supination force and clinical scores after 12months. After LHB tenotomy, there was a non-significant trend for a higher rate of popeye-sign deformities of the upper arm and biceps muscle cramps.

The Stabilising Effect of the Anterior Oblique Ligament to Prevent Directional Subluxation at the Trapeziometacarpal Joint of the Thumb: A Biomechanical Cadaveric Study.

The trapeziometacarpal joint (TMCJ) is inherently unstable, relying on ligament restraint to prevent subluxation. Subluxation of the thumb in a dorsoradial direction is often observed in clinical practice, either after acute ligament injury or more commonly with osteoarthritis (OA). This subluxation follows loss of function of trapeziometacarpal ligaments that stabilise this joint, resisting the deforming force of abductor pollicis longus (APL). The exact ligaments that stabilise and prevent the thumb from the pull of APL causing dorsoradial subluxation remain unknown, although the anterior oblique ligament (AOL) has been implicated. The aim of this study was to measure the direction of subluxation resisted by the AOL. In this study we used cadaveric limbs and custom made biomechanical testing to measure the influence AOL has in stabilising the thumb against subluxation in three planes: radial, dorsal and dorsoradial. Three fresh frozen hands were dissected to expose the TMCJ, leaving all ligaments, capsule and APL attachment in place. The force required to create a displacement of 5mm between the first metacarpal and the trapezium in these three planes was measured before and after AOL division. The average force to displace in the dorsoradial plane prior to division was 6.68N, and a statistically significant reduction to 1.15N (P<0.001) was found after division of the AOL. A statistically significant increase in force (P<0.001) from 2.89N to 4.04N was seen in the radial plane, while no change was seen dorsally (P=0.98), with average forces of 2.74N and 2.62N found pre and post division. There is clinical significance in reporting quantifiable data in this field, as subluxation of the thumb is often seen with OA. The results of our study provide support for surgical reconstruction of the AOL as the primary surgical stabilizer against dorsoradial subluxation of the thumb.Level of evidence: III.

Monosodium glutamate impairs the contraction of uterine visceral smooth muscle ex vivo of rat through augmentation of acetylcholine and nitric oxide signaling pathways

The aim of the study was to examine the toxic effects of Monosodium glutamate (MSG), an extensively used food additive, on the contraction of uterine visceral smooth muscle (UVSM) in rat and to elucidate the probable neurocrine mechanism involved in it. MSG produced significant potentiation of the force and inhibition of frequency of uterus recorded ex vivo in chronic MSG exposure and in single dose acute experiments. MSG also produced significant potentiation of force of acetylcholine induced contraction and no alterations in atropine induced contraction of uterus. Further, MSG produced significant increase in force and frequency of contraction of neostigmine incubated uterus. We have found significant potentiation of the post pause force of contraction of uterus when MSG was applied in adrenaline incubated uterus. MSG also produced significant decrease in frequency of contraction of sodium nitroprusside incubated uterus; increase in frequency of N-ω-Nitro-l-Arginine Methyl Ester incubated uterus and no significant changes in frequency of contraction of methylene blue incubated uterus. These results indicate that MSG potentiates the force of contraction of UVSM predominantly by augmenting the activity of cholinergic intrinsic efferents and inhibits the frequency of contraction probably by augmenting the activity of nitrergic efferents. In conclusion, MSG potentiates the force and inhibits the frequency of contraction of UVSM, and the MSG induced effect is probably mediated through the augmentation of acetylcholine and nitric oxide signaling pathways.

Early stage blunting causes rapid reductions in stone tool performance

Palaeolithic stone technologies have never been investigated in terms of how sharpness influences their ability to cut. In turn, there is little understanding of how quickly stone cutting edges blunt, how past populations responded to any consequent changes in performance, or how these factors influenced the Palaeolithic archaeological record. Presented here is experimental data quantitatively detailing how variation in edge sharpness influences stone tool cutting performance. Significant increases in force (N) and material displacement (mm) requirements occur rapidly within early stages of blunting, with a single abrasive cutting stroke causing, on average, a 38% increase in the force needed to initiate a cut. In energetic terms, this equates to a 70% increase in work (J). Subsequent to early stages of blunting we identify a substantial drop in the impact of additional edge abrasion. We also demonstrate how edge (included) angle significantly influences cutting force and energy requirements and how it co-varies with sharpness. Amongst other conclusions, we suggest that rapid reductions in performance due to blunting may account for the abundance of lithic artefacts at some archaeological sites, the speed that resharpening behaviours altered tool forms, and the lack of microscopic wear traces on many lithic implements.

Abstract 226: Elucidating the Mechanism of Reduced Length-dependent Activation Due to a Dilated Cardiomyopathy-associated Mutation in Tropomyosin

At the subcellular level, the Frank-Starling law of the heart is described by an increase in calcium sensitivity and force with increased sarcomere length (SL). We examine how this relationship is affected by a dilated cardiomyopathy-associated mutation in tropomyosin (D230N, denoted Tm D230N ) by measuring contractility of intact and permeabilized cardiac muscle preparations at short (2.0 μm) and long (2.3 μm) SL. Transgenic mouse hearts containing the Tm D230N mutation have significantly dilated hearts and reduced cardiac output by ~6 months of age. Intact trabeculae were electrically stimulated and paced at 1 Hz with oxygenated solution (30°C) circulating through the experimental chamber, and permeabilized preparations were bathed in solutions (15°C) of progressively increased [Ca 2+ ] for measures of steady-state force. For intact muscle we found that the Tm D230N mutation results in significantly reduced twitch forces at SL 2.0 and 2.3 μm relative to wild-type (WT). Also, WT trabeculae displayed a significant increase in twitch force upon increase in SL (as expected) but Tm D230N trabeculae did not, demonstrating a loss of SL dependence of contraction. In permeabilized preparations, maximal activation (pCa 4.5) of both WT and Tm D230N preparations exhibited significant SL-dependent increases in force. However, at submaximal Ca 2+ (pCa 5.8), where the heart operates, WT preparations had significant increases in force with increasing length (comparing SL 2.0 to 2.3 μm), while this length-dependence of force augmentation in Tm D230N was absent. The increase in pCa 50 (pCa that produces half-maximal force) going from SL 2.0 to 2.3 μm was significantly less for Tm D230N preparations compared to WT, owing to a significantly smaller increase in pCa 50 at SL 2.3 μm (the pCa 50 at SL 2.0 μm was not significantly different between WT and Tm D230N ). These results suggest that the Tm D230N mutation limits an increase in the Ca 2+ sensitivity of contraction as the muscle lengthens by damping thin filament activation. To further examine length-dependent effects of the Tm D230N mutation, future experiments will test conditions that augment cross-bridge binding/inhibition, and other models of dilated cardiomyopathy that inhibit thin filament activation. Funding: HL111197

Changes in the Force-Velocity Mechanical Profile After Short Resistance Training Programs Differing in Set Configurations.

The main aim of this study was to analyze the effect of resistance training programs differing in set configuration on mechanical force-velocity profiles. Thirteen participants performed 10 unilateral knee extension training sessions over 5 weeks. Each limb was randomized to one of the following set configurations: traditional (4 sets of 8 repetitions at maximum intended velocity, 10RM load, 3-min pause between sets) or interrepetition rest (32 maximum intended velocity repetitions, 10RM load, 17.4 s of rest between each repetition). Velocity of each repetition was recorded throughout the program. Before and after training, individual linear force velocities were calculated, and the following parameters were obtained: force and velocity axis intercept, slope, and estimated maximum power. Mean velocity was higher throughout the program for interrepetition rest configuration (0.54 ± 0.01 vs. 0.48 ± 0.01 m∙s-1 for interrepetition rest, and traditional configuration respectively; main effect of set configuration: P < .001). There was a significant increase in force and velocity intercepts, but a steeper negative slope after both training protocols (main effect of time: P < .001 for every variable). Differences in resistance training velocity did not affect the adaptations. Our results suggest that, in a short-term program, maximum intended rather than actual velocity is a key factor to modulate strength adaptations.

The Influence of Axial Grooves on Dislodgment Resistance of Prosthetic Metal Crowns in Canine Teeth of Dogs.

The reported failure rate for full veneer crowns of canine teeth of dogs is suboptimal, particularly in teeth with naturally poor retentive features, such as those with low height/diameter (H/D) ratios or high convergence angles (CAs). The objective of the present study was to evaluate the application of axial grooves in an effort to develop a crown preparation design that enhances the retention of full veneer crowns in dogs. Crown dislodgment testing was performed on cast alloy dies of canine teeth with unfavorable retention features (low H/D and high CA) prepared with (n = 14) and without axial grooves (n = 15) to evaluate the force required to dislodge a cemented full veneer crown. The crown/die units were secured within a universal testing machine and a load was applied at the 45° oblique direction from distal to mesial to replicate the vector encountered during biting-pulling action. The maximum force required to cause crown dislodgment was recorded for each crown. Statistical analysis revealed a significant increase in force required for crown dislodgment when axial grooves were included in the crown preparation design ( P < .001). Crown retention is improved in canine teeth with otherwise poor retention features when axial grooves are made in the labial and palatal/lingual walls during crown preparation.

Effects of plasma rich in growth factors (PRGF) on biomechanical properties of Achilles tendon repair.

To assess the biomechanical effects of intra-tendinous injections of PRGF on the healing Achilles tendon after repair in a sheep model. Thirty sheep were randomly assigned into one of the six groups depending on the type of treatment received (PRGF or placebo) and survival time (2, 4 and 8weeks). The Achilles tendon injury was repaired by suturing the tendinous edges employing a three-loop pulley pattern. A trans-articular external fixation system was then used for immobilization. The PRGF or placebo was administered on a weekly basis completing a maximum of three infiltrations. The force, section and tension values were compared between the operated and healthy Achilles tendons across all groups. The PRGF-treated tendons had higher force at 8weeks compared with the placebo group (p=0.007). Between 2 and 4weeks, a significant increase in force in both the PRGF-treated tendon (p=0.0027) and placebo group (p=0.0095) occurred. No significant differences were found for section ratio between PRGF-treated tendons and the placebo group for any of the time periods evaluated. At 2weeks, PRGF-treated tendons had higher tension ratio compared with placebo group tendons (p=0.0143). Both PRGF and placebo treatments significantly improved the force (p<0.001 and p=0.0095, respectively) and tension (p=0.009 and p=0.0039, respectively) ratios at 8weeks compared with 2weeks. The application of PRGF increases Achilles tendon repair strength at 8weeks compared with the use of placebo. The use of PRGF does not modify section and tension ratios compared with placebo at 8weeks. The tension ratio progressively increases between 2 and 8weeks compared with the placebo.

The Effect of Traction Force and Hip Abduction Angle on Pudendal Nerve Compression in Hip Arthroscopy: A Cadaveric Model

To investigate the site of pudendal nerve compression and the relation between traction force and abduction angle regarding pressure levels at setup for hip arthroscopy. A total of 17 hips from 9 fresh-frozen cadavers (6 male and 3 female cadavers) were used. The pudendal nerves were dissected, and 3 FlexiForce force sensors (Tekscan, Boston, MA) were implanted on the pudendal nerve where the inferior rectal nerve, perineal nerve, and dorsal nerve of the clitoris/penis emerge. A custom-made traction table in a supine position was used with a padded perineal post of 9cm. Recordings were made at 0, 10, 20, 30, and 40kg of traction at varying hip abduction angles of 0°, 15°, 30°, and 45°. The tuber ischiadicum (perineal nerve) and genital region (dorsal nerve of penis/clitoris) had statistically higher pressure values when compared with the pudendal canal (inferior rectal nerve) (P < .05). There was a significant increase in forces acting on the pudendal nerve with increasing application of 0 to 40kg of traction in steps of 10kg, with the exception of the pudendal canal sensor and reading of the perineal nerve sensor at 45° of hip abduction (P < .004 with Bonferroni correction for significant values). On the contrary, hip abduction angle had no statistically significant effect on pudendal nerve compression. (All specific P values with Bonferroni correction were greater than .003.) To avoid nerve palsy completely, the etiopathogenesis of compressive neuropathy should be identified. The location for compression and relation between different traction positions and forces are clarified in this study. This information can be used for further research and prevention. This study adds objective data on the etiopathogenesis of pudendal nerve compression, which potentially contributes to prevention of pudendal nerve palsy as a common complication of hip arthroscopy.

Time course of bone screw fixation following a local delivery of Zoledronate in a rat femoral model – A micro-finite element analysis

A good fixation of osteosynthesis implants is crucial for a successful bone healing but often difficult to achieve in osteoporotic patients. One possible solution to this issue is the local delivery of bisphosphonates in direct proximity to the implants, A critical aspect of this method, that has not yet been well investigated, is the time course of the implant fixation following the drug release. Usual destructive mechanical tests require large numbers of animals to produce meaningful results. Therefore, a micro-finite element (microFE) approach was chosen to analyze implant fixation. In vivo micro computed tomography (microCT) scans were obtained, first weekly and later bi-weekly, after implantation of polymeric screws in the femoral condyles of ovariectomized rats. In one half of the animals, Zoledronate was released from a hydrogel matrix directly in the peri-implant bone stock, the other animals were implanted only with screws as control. The time course of the implant fixation was investigated with linear elastic microFE models that were created based on in vivo microCT scans. The numerical models were validated against experimental pullout-tests measurements in an additional cadaver study. The microFE analysis revealed a significant increase in force at yield of the Zoledronate treated group compared to the control group. The force of the treated group was 28% higher after 17 days of screw implantation, 42% higher after 31 days. The significant difference persisted until the end of the in vivo study at day 58 (p<0.01). The early onset and prolonged duration of the implant anchorage improvement that was found in this study indicates the great potential of Zoledronate-loaded hydrogel for an enhancement of osteosynthesis implant fixation in impaired bone.

Changes in maximal punching forces and reaction time in boxers during training season

Buśko Krzysztof, Szulc Adam. Changes in maximal punching forces and reaction time in boxers during training season. Journal of Health Sciences. 2014;4(13):207-212. ISSN 1429-9623 / 2300-665X. http://journal.rsw.edu.pl/index.php/JHS/article/view/2014%3B4%2813%29%3A207-212 http://ojs.ukw.edu.pl/index.php/johs/article/view/2014%3B4%2813%29%3A207-212 https://pbn.nauka.gov.pl/works/521513 DOI: 10.5281/zenodo.13878 http://dx.doi.org/10.5281/zenodo.13878 The former journal has had 5 points in Ministry of Science and Higher Education of Poland parametric evaluation. Part B item 1107. (17.12.2013). © The Author (s) 2014; This article is published with open access at Licensee Open Journal Systems of Radom University in Radom, Poland Open Access. This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. This is an open access article licensed under the terms of the Creative Commons Attribution Non Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non commercial use, distribution and reproduction in any medium, provided the work is properly cited. Conflict of interest: None declared. Received: 10.09.2014. Revised 15.09.2014. Accepted: 04.11.2014. Changes in maximal punching forces and reaction time in boxers during training season Krzysztof Buśko 1 , Adam Szulc 2 1 Department of Biomechanics, Institute of Sport, Warsaw, Poland 2 Institute of Physical Culture, Kazimierz Wielki University, Bydgoszcz, Poland Buśko Krzysztof, dr hab. prof. nadzw. Zaklad Biomechaniki, Instytut Sportu, Warszawa, Trylogii 2/16, 01-982 Warszawa Tel. 22 8340812 w. 247 krzysztof.busko@insp.waw.pl Abstract The aim of this study was to determine the changes in maximal punching force and reaction time in boxers during training season. The studies involved three boxers: age 18.1±0.4 years, body height 186.7±6.1 cm, weight 81.3±0.6 kg (Measurement I), 80.9±3.3 kg (Measurement II), 80.7±5.6 kg (Measurement III), training experience 3.5±1.8 years. Body weight did not change significantly during training season. Measurements of maximal punching force and reaction time was carried out on a boxing dynamometer. Each participants performed five punches of rear and lead hand (hook and straight punches) from a typical for himself boxing position and test of simulated boxing fight lasts 60 seconds. Three measurements were carried out: Measurement I – before first starting period, Measurement II – after first starting period, Measurement III – before second preparation period. The maximal straight punching forces were 1634.7±674.0 N for lead hand, and 2899.7±457.9 N for rear hand. The maximal hook punching forces were 2645.0±1122.4 N for lead hand, and 2820.7±766.5 N for rear hand. Significant differences were observed between lead and rear hands for straight (all measurements) and hook (Measurement III during the simulated boxing fight) punches. Force of the blow inflicted on the rear limb changed significantly between the first and third and the second and third measurement in the training season. In conclusion, in the analyzed training period occurred insignificant prolongation of reaction time, accompanied by a significant increase in force of the blow hit the rear limb during the test of simulated 60-seconds of the fight.

The influence of nerve conduits diameter in motor nerve recovery after segmental nerve repair.

Many conduits have demonstrated potential to substitute nerve autografts; however, the influence of conduit inner diameter (ID) has never been studied as a separate parameter. This experimental study compared motor recovery after segmental nerve repair with two different ID collagen conduits: 1.5 and 2.0 mm. In addition, the conduits were analyzed in vitro to determine the variations of ID before and after hydration. Thirty rats were divided into three groups: 2.0 mm ID, 1.5 mm ID, and a control group autograft. After 12 weeks, the 1.5 mm ID group demonstrated significant increase in force (P < 0.0001) and weight (P < 0.0001) of the tibialis anterior muscle and better histomorphometry results of the peroneal nerve (P < 0.05) compared to 2.0 mm ID group; nevertheless, autograft results outperformed both conduits (P < 0.0001). Conduits ID were somewhat smaller than advertised, measuring 1.59 ± 0.03 mm and 1.25 ± 0.0 mm. Only the larger conduit showed a 6% increase in ID after hydration, changing to 1.69 ± 0.02 mm. Although autografts perform best, an improvement in motor recovery can be achieved with collagen conduits when a better size match conduit is being used. Minimal changes in collagen conduits ID can be expected after implantation.

Instant effects of peppermint essential oil on the physiological parameters and exercise performance.

Effect of peppermint on exercise performance was previously investigated but equivocal findings exist. This study aimed to investigate the effects of peppermint ingestion on the physiological parameters and exercise performance after 5 min and 1 h. Thirty healthy male university students were randomly divided into experimental (n=15) and control (n=15) groups. Maximum isometric grip force, vertical and long jumps, spirometric parameters, visual and audio reaction times, blood pressure, heart rate, and breath rate were recorded three times: before, five minutes, and one hour after single dose oral administration of peppermint essential oil (50 µl). Data were analyzed using repeated measures ANOVA. Our results revealed significant improvement in all of the variables after oral administration of peppermint essential oil. Experimental group compared with control group showed an incremental and a significant increase in the grip force (36.1%), standing vertical jump (7.0%), and standing long jump (6.4%). Data obtained from the experimental group after five minutes exhibited a significant increase in the forced vital capacity in first second (FVC1)(35.1%), peak inspiratory flow rate (PIF) (66.4%), and peak expiratory flow rate (PEF) (65.1%), whereas after one hour, only PIF shown a significant increase as compare with the baseline and control group. At both times, visual and audio reaction times were significantly decreased. Physiological parameters were also significantly improved after five minutes. A considerable enhancement in the grip force, spiromery, and other parameters were the important findings of this study. Conclusion : An improvement in the spirometric measurements (FVC1, PEF, and PIF) might be due to the peppermint effects on the bronchial smooth muscle tonicity with or without affecting the lung surfactant. Yet, no scientific evidence exists regarding isometric force enhancement in this novel study.

Inotropic and chronotropic effects of methanol extract of &lt;i&gt;Aquilaria agallocha&lt;/i&gt; on rabbit heart

Aquilaria agallocha Roxb. (Thymelaeceae) heartwood is used in cardiac failure; however, its cardiotonic properties are poorly understood at a pharmacological level. This study investigated methanol extract of A. agallochafor presence of glycosides and its effects on force of contraction, heart rate and coronary flow on rabbit isolated heart. Furthermore, contribution of β1-adrenoceptors and/or L-type Ca2+ channels in A. agallocha-induced cardiac effects was explored. A. agallocha extract, digoxin, verapamil and metoprolol were administered in a retrograde manner. Force of contraction and heart rate were recorded with a force transducer attached to the heart. Coronary flow was measured from collected effluent. The extract induced a significant increase in force of contraction (p&lt;0.001), decrease in heart rate (p&lt;0.05) and coronary flow (p&lt;0.001). Metoprolol (p&lt;0.01) and verapamil (p&lt;0.01) significantly inhibited the plant extract-induced effects. Thus, A. agallocha exhibited cardiotonic effects, most likely via cardiac glycosides, involving ?1-adrenoceptors and L-type Ca2+ channels.

Force and torque modelling of drilling simulation for orthopaedic surgery

The advent of haptic simulation systems for orthopaedic surgery procedures has provided surgeons with an excellent tool for training and preoperative planning purposes. This is especially true for procedures involving the drilling of bone, which require a great amount of adroitness and experience due to difficulties arising from vibration and drill bit breakage. One of the potential difficulties with the drilling of bone is the lack of consistent material evacuation from the drill's flutes as the material tends to clog. This clogging leads to significant increases in force and torque experienced by the surgeon. Clogging was observed for feed rates greater than 0.5 mm/s and spindle speeds less than 2500 rpm. The drilling simulation systems that have been created to date do not address the issue of drill flute clogging. This paper presents force and torque prediction models that account for this phenomenon. The two coefficients of friction required by these models were determined via a set of calibration experiments. The accuracy of both models was evaluated by an additional set of validation experiments resulting in average R2 regression correlation values of 0.9546 and 0.9209 for the force and torque prediction models, respectively. The resulting models can be adopted by haptic simulation systems to provide a more realistic tactile output.

Regulatory Light Chain Phosphorylation Mimic S15D Causes Partial Rescue of Isometric Force Production in FHC Causing Mutation D166V

Familial hypertrophic cardiomyopathy (FHC) is characterized by a pathological thickening of the muscle surrounding the heart and is the leading cause for sudden cardiac death in young people. There are numerous mutations in sarcomeric proteins that have been implicated in causing FHC. Myosin, the molecular motor that powers cardiac muscle contraction, consists of a globular domain and an elongated α-helical neck region, which is thought to undergo large conformational changes during muscle contraction. The myosin regulatory light chain (RLC) functions to support the neck region, therefore it is not surprising that several single amino acid substitutions in the RLC have been implicated in FHC.Here we studied D166V, an RLC point mutation that is associated with increased left ventricular wall thickness, abnormal electrocardiogram, and decreased isometric force and ATPase in skinned fibers from transgenic mouse hearts. We have expressed porcine cardiac β myosin (the same isoform found in humans) and replaced the endogenous RLC with a human RLC. The exchanged RLC contained either wild type (WT), D166V, S15A, or a double mutant D166V/S15A, or D166V/S15D. The S15D mutation served as a phosphorylation mimic. We performed frictional loading assays using a modified in vitro motility assay and determined the average force produced by a bed of monomeric myosin. While maximal unloaded velocity was unchanged for all of the mutants studied, the force of D166V and D166V/S15A was significantly reduced compared to WT, with an additive decrease in the double mutant. D166V/S15D resulted in a significant increase in force compared to D166V/S15A and was restored to near WT levels. These results suggest that D166V causes a reduction in myosin isometric force production and phosphorylation may act to recover it.