Tactility as a function of grasp force: Effects of glove, orientation, pressure, load, and handle

NASA Technical Reports Server (NTRS)

Bishu, Ram R.; Bronkema, Lisa A.; Garcia, Dishayne; Klute, Glenn; Rajulu, Sudhakar

1994-01-01

One of the reasons for reduction in performance when gloves are donned is the lack of tactile sensitivity. It was argued that grasping force for a weight to be grasped will be a function of the weight to be lifted and the hand conditions. It was further reasoned that the differences in grasping force for various hand conditions will be a correlate of the tactile sensitivity of the corresponding hand conditions. The objective of this experiment, therefore, was to determine the effects of glove type, pressure, and weight of load on the initial grasping force and stable grasping force. It was hypothesized that when a person grasps an object, he/she grasps very firmly initially and then releases the grasp slightly after realizing what force is needed to maintain a steady grasp. This would seem to be particularly true when a person is wearing a glove and has lost some tactile sensitivity and force feedback during the grasp. Therefore, the ratio of initial force and stable force and the stable force itself would represent the amount of tactile adjustment that is made when picking up an object, and this adjustment should vary with the use of gloves. A dynamometer was fabricated to measure the grasping force; the tests were performed inside a glove box. Four female and four male subjects participated in the study, which measured the effects of four variables: load effect, gender effect, glove type, and pressure variance. The only significant effects on the peak and stable force were caused by gender and the weight of the load lifted. Neither gloves nor pressure altered these forces when compared to a bare-handed condition, as was suspected before the test. It is possible that gloves facilitate in holding due to coefficient of friction while they deter in peak grasp strength.

Effects of a New Cooling Technology on Physical Performance in US Air Force Military Personnel.

PubMed

O'Hara, Reginald; Vojta, Christopher; Henry, Amy; Caldwell, Lydia; Wade, Molly; Swanton, Stacie; Linderman, Jon K; Ordway, Jason

2016-01-01

Heat-related illness is a critical factor for military personnel operating in hyperthermic environments. Heat illness can alter cognitive and physical performance during sustained operations missions. Therefore, the primary purpose of this investigation was to determine the effects of a novel cooling shirt on core body temperature in highly trained US Air Force personnel. Twelve trained (at least 80th percentile for aerobic fitness according to the American College of Sports Medicine, at least 90% on the US Air Force fitness test), male Air Force participants (mean values: age, 25 ± 2.8 years; height, 178 ± 7.9cm; body weight 78 ± 9.6kg; maximal oxygen uptake, 57 ± 1.9mL/kg/ min; and body fat, 10% ± 0.03%) completed this study. Subjects performed a 70-minute weighted treadmill walking test and 10-minute, 22.7kg sandbag shuttle test under two conditions: (1) "loaded" (shirt with cooling inserts) and (2) "unloaded" (shirt with no cooling inserts). Core body temperature, exercise heart rate, capillary blood lactate, and ratings of perceived exertion were recorded. Core body temperature was lower (ρ = .001) during the 70-minute treadmill walking test in the loaded condition. Peak core temperature during the 70-minute walking test was also significantly lower (ρ = .038) in the loaded condition. This lightweight (471g), passive cooling technology offers multiple hours of sustained cooling and reduced core and peak body temperature during a 70-minute, 22.7kg weighted-vest walking test. 2016.

Compliance Testing of Eielson Air Force Base Central Heating and Power Plant, Coal Fired Boiler Number 3, Eielson Air Force Base, Alaska

DTIC Science & Technology

1988-12-01

a flue gas grab sample for orsat analysis (measures oxygen, and carbon dioxide for stack gas molecular weight determination and emissions correction... molecular weight, was obtained during particulate sampling. Testing was initially started on boiler 2 at the maximum rated steam output of 120,000 lbs/hr...I, r*~td AN[D l FL B( R\\ ViQ( lPjN L!II(,t 1 (d) Open burning of put.rcible iear- i\\ % ~i~ emisions , ec.dirig c dn jc p. c ,f1 pre- cri :rig pair

Age-related differences in postural adjustments in connection with different tasks involving weight transfer while standing.

PubMed

Jonsson, Erika; Henriksson, Marketta; Hirschfeld, Helga

2007-10-01

Weight transfer designed to change the area of the supportive base during the performance of three different motor tasks (one-leg stance, tandem stance and gait initiation) was examined both in healthy, physically active elderly people and younger adults. The former two tasks are balance tests used clinically. Our hypothesis was that the elderly subjects would demonstrate age-related changes in their postural adjustments that could be detected by analysis of the ground reaction forces. While 24 healthy elderly adults (65-77 years of age) and 26 younger adults (24-40 years of age) performed these three tasks, the ground reaction forces were recorded from two force plates. Prior to the onset of all three tasks, the elderly placed significantly more weight on the leg that was to provide support (the stance leg), than did the younger individuals. The analyses revealed two distinct phases of weight transfer, i.e., an initial thrust and a subsequent unloading phase. The elderly individuals exhibited a significantly longer unloading phase, as well as a higher frequency of peaks of vertical and lateral forces during this phase. Moreover, the maximal force rate during this phase was achieved at an earlier time point by the elderly. However, both groups generated forces of similar magnitudes and force rates. In conclusion, our findings indicate the presence of age-related differences in the temporal phasing of the ground reaction forces in all three of these tasks involving weight transfer, whereas the magnitude and rates of change of these forces are independent of age.

New devices for measuring forces on the kayak foot bar and on the seat during flat-water kayak paddling: a technical report.

PubMed

Nilsson, Johnny E; Rosdahl, Hans G

2014-03-01

The purpose was to develop and validate portable force-measurement devices for recording push and pull forces applied by each foot to the foot bar of a kayak and the horizontal force at the seat. A foot plate on a single-point force transducer mounted on the kayak foot bar underneath each foot allowed the push and pull forces to be recorded. Two metal frames interconnected with 4 linear ball bearings, and a force transducer allowed recording of horizontal seat force. The foot-bar-force device was calibrated by loading each foot plate with weights in the push-pull direction perpendicular to the foot plate surface, while the seat-force device was calibrated to horizontal forces with and without weights on the seat. A strong linearity (r2 = .99-1.0) was found between transducer output signal and load force in the push and pull directions for both foot-bar transducers perpendicular to the foot plate and the seat-force-measuring device. Reliability of both devices was tested by means of a test-retest design. The coefficient of variation (CV) for foot-bar push and pull forces ranged from 0.1% to 1.1%, and the CV for the seat forces varied from 0.6% to 2.2%. The current study opens up a field for new investigations of the forces generated in the kayak and ways to optimize kayak-paddling performance.

Fertility of male adult rats submitted to forced swimming stress.

PubMed

Mingoti, G Z; Pereira, R N; Monteiro, C M R

2003-05-01

We investigated whether stress interferes with fertility during adulthood. Male Wistar rats (weighing 220 g in the beginning of the experiment) were forced to swim for 3 min in water at 32 degrees C daily for 15 days. Stress was assessed by the hot-plate test after the last stressing session. To assess fertility, control and stressed males (N = 15 per group) were mated with sexually mature normal females. Males were sacrificed after copulation. Stress caused by forced swimming was demonstrated by a significant increase in the latency of the pain response in the hot-plate test (14.6 +/- 1.25 s for control males vs 26.0 +/- 1.53 s for stressed males, P = 0.0004). No changes were observed in body weight, testicular weight, seminal vesicle weight, ventral prostate weight or gross histological features of the testes of stressed males. Similarly, no changes were observed in fertility rate, measured by counting live fetuses in the uterus of normal females mated with control and stressed males; no dead or incompletely developed fetuses were observed in the uterus of either group. In contrast, there was a statistically significant decrease in spermatid production demonstrated by histometric evaluation (154.96 +/- 5.41 vs 127.02 +/- 3.95 spermatids per tubular section for control and stressed rats, respectively, P = 0.001). These data demonstrate that 15 days of forced swimming stress applied to adult male rats did not impair fertility, but significantly decreased spermatid production. This suggests that the effect of stress on fertility should not be assessed before at least the time required for one cycle of spermatogenesis.

Atmospheric Corrosivity at Australian and Overseas Airbases and Airports

DTIC Science & Technology

2014-07-01

climatic conditions, the correlation between the GCIA and weight loss data from aluminium alloy coupons exposed in the open at 38 sites in the US...corrosivity. The test consists of an aluminium wire wrapped around a copper bolt exposed in the atmosphere for three months; the weight loss of the wire...Abbreviations/Acronyms AAC Army Aviation Centre AB Air Base ADF Australian Defence Force AFB Air Force Base Al aluminium ANGB Air National Guard Base

Chest circumference and birth weight are good predictors of lung function in preschool children from an e-waste recycling area.

PubMed

Zeng, Xiang; Xu, Xijin; Zhang, Yuling; Li, Weiqiu; Huo, Xia

2017-10-01

The purpose of this study was to investigate the associations between birth weight, chest circumference, and lung function in preschool children from e-waste exposure area. A total of 206 preschool children from Guiyu (an e-waste recycling area) and Haojiang and Xiashan (the reference areas) in China were recruited and required to undergo physical examination, blood tests, and lung function tests during the study period. Birth outcome such as birth weight and birth height were obtained by questionnaire. Children living in the e-waste-exposed area have a lower birth weight, chest circumference, height, and lung function when compare to their peers from the reference areas (all p value <0.05). Both Spearman and partial correlation analyses showed that birth weight and chest circumference were positively correlated with lung function levels including forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV 1 ). After adjustment for the potential confounders in further linear regression analyses, birth weight, and chest circumference were positively associated with lung function levels, respectively. Taken together, birth weight and chest circumference may be good predictors for lung function levels in preschool children.

Prediction of force and acceleration control spectra for Space Shuttle orbiter sidewall-mounted payloads

NASA Technical Reports Server (NTRS)

Hipol, Philip J.

1990-01-01

The development of force and acceleration control spectra for vibration testing of Space Shuttle (STS) orbiter sidewall-mounted payloads requiresreliable estimates of the sidewall apparent weight and free (i.e. unloaded) vibration during lift-off. The feasibility of analytically predicting these quantities has been investigated through the development and analysis of a finite element model of the STS cargo bay. Analytical predictions of the sidewall apparent weight were compared with apparent weight measurements made on OV-101, and analytical predictions of the sidewall free vibration response during lift-off were compared with flight measurements obtained from STS-3 and STS-4. These analysis suggest that the cargo bay finite element model has potential application for the estimation of force and acceleration control spectra for STS sidewall-mounted payloads.

[A comparative study on behaviors of two depression models in rats induced by chronic forced swimming stress].

PubMed

Han, Ming-Fei; Gao, Dong; Sun, Xue-Li

2010-01-01

To compare the behaviors of rats with depressions induced by chronic forced swimming stress under two different conditions. Eighteen male rats were randomly divided into 3 groups, with 6 rats in each group. The rats in the control group (C group) were not forced into swimming, while the rats in the stress groups (S1 and S2) were forced to swim for 14 consecutive days. The rats in S1 group and S2 group swam for five minutes every morning, in water with (23 +/- 1) degree C, and (10 +/- 0.5) degree C in temperature, respectively. The weight gain, food intake, open-field test and saccharin solution test were observed on the seventh day and fourteenth day. On the seventh day following chronic swim stress, the rats in the S2 group had significant lower ratio in weight gain and food intake than the controls (P < 0.05). On the fourteenth day, the rats in the S2 group had significant lower ratio in weight gain (12.26 +/- 4.04)%, food intake (9.49 +/- 0.96)%, sucrose intake (28.63 +/- 3.51) g, and preference for saccharin solution (76.25 +/- 2.51)%, and less number of crossing (12.17 +/- 9.00) and times of rearing (3.17 +/- 3.60) than the controls (P < 0.05). The rats in the S1 group had significant lower ratio in weight gain and food intake than the controls on the seventh day following forced swimming. On the fourteenth day, the rats in the S1 group still had lower ratio in weight gain, but had higher ratio in food intake and preference for saccharin solution, and greater number of crossing than the controls. Chronic forced swimming at a lower temperature could induce depression better than at a higher temperature.

[Testing and analyzing the lung functions in the normal population in Hebei province].

PubMed

Chen, Li; Zhao, Ming; Han, Shao-mei; Li, Zhong-ming; Zhu, Guang-jin

2004-08-01

To investigate the lung function of the normal subjects living in Hebei province and its correlative factors such as living circumstance, age, height, and body weight. The lung volumes and breath capacities of 1,587 normal subjects were tested by portable spirometers (Scope Rotry) from August to October in 2002. The influences of living circumstance, age, gender, height, and body weight on lung functions were observed and analyzed. No significant difference was found between urban and rural areas in all indexes (P > 0.05); however, significant difference existed between male and female subjects (P = 0.000). The change trends of lung function in male and female subjects were similar. Growth spurt appeared at the age of 12-16 years in male subjects and 12-14 years in female subjects. Vital capacity (VC), forced vital capacity (FVC), and forced expiratory volume in one second (FEV1) reached their peaks at the age of 26-34 years and then decreased with age. Peak expiratory flow (PEF), 25% forced expiratory flow (FEF50%), and 75% forced expiratory flow (FEF75%) appeared at the age of 18 and then went down with age. Both height and weight had a correlation with all the indexes of lung functions, although the influence of height is stronger than weight. All the indexes of lung function have correlations with age, height, and weight. Lung function changes with aging, therefore different expected values shall be available for the adolescence, young adults, and middle-aged and old people. This study provides reference values of lung function for normal population.

Non-weight bearing-induced muscle weakness: the role of myosin quantity and quality in MHC type II fibers.

PubMed

Kim, Jong-Hee; Thompson, LaDora V

2014-07-15

We tested the hypothesis that non-weight bearing-induced muscle weakness (i.e., specific force) results from decreases in myosin protein quantity (i.e., myosin content per half-sarcomere and the ratio of myosin to actin) and quality (i.e., force per half-sarcomere and population of myosin heads in the strong-binding state during muscle contraction) in single myosin heavy chain (MHC) type II fibers. Fisher-344 rats were assigned to weight-bearing control (Con) or non-weight bearing (NWB). The NWB rats were hindlimb unloaded for 2 wk. Diameter, force, and MHC content were determined in permeabilized single fibers from the semimembranosus muscle. MHC isoform and the ratio of MHC to actin in each fiber were determined by gel electrophoresis and silver staining techniques. The structural distribution of myosin from spin-labeled fiber bundles during maximal isometric contraction was evaluated using electron paramagnetic resonance spectroscopy. Specific force (peak force per cross-sectional area) in MHC type IIB and IIXB fibers from NWB was significantly reduced by 38% and 18%, respectively. MHC content per half-sarcomere was significantly reduced by 21%. Two weeks of hindlimb unloading resulted in a reduced force per half-sarcomere of 52% and fraction of myosin strong-binding during contraction of 34%. The results suggest that reduced myosin and actin content (quantity) and myosin quality concomitantly contribute to non-weight bearing-related muscle weakness. Copyright © 2014 the American Physiological Society.

An Investigation of the Performance of Various Reaction Control Devices

NASA Technical Reports Server (NTRS)

Hunter, Paul A.

1959-01-01

An investigation of a small-scale reaction control devices in still air with both subsonic and supersonic internal flows has shown that lateral forces approaching 70 percent of the resultant force of the undeflected jet can be obtained. These results were obtained with a tilted extension at a deflection of 40 deg. The tests of tilted extensions indicated an optimum length-to-diameter ratio of approximately 0.75 to 1.00, dependent upon the deflection angle. For the two geometric types of spoiler tabs tested, blockage-area ratio appears to be the only variable affecting the lateral force developed. Usable values of lateral force were developed by the full-eyelid type of device with reasonably small losses in the thrust and weight flow. Somewhat larger values of lateral force were developed by injecting a secondary flow normal to the primary jet, but for conditions of these tests the losses in thrust and weight flow were large. Relatively good agreement with other investigations was obtained for several of the devices. The agreement of the present results with those of an investigation made with larger-scale equipment indicates that Reynolds number may not be critical for these tests. In as much as the effects of external flow could influence the performance and other factors affecting the choice of a reaction control for a specific use, it would appear desirable to make further tests of the devices described in this report in the presence of external flow.

Gastrodia elata Bl. Attenuated learning deficits induced by forced-swimming stress in the inhibitory avoidance task and Morris water maze.

PubMed

Chen, Pei-Ju; Liang, Keng-Chen; Lin, Hui-Chen; Hsieh, Ching-Liang; Su, Kuan-Pin; Hung, Mei-Chu; Sheen, Lee-Yan

2011-06-01

This study adopted the forced-swimming paradigm to induce depressive symptoms in rats and evaluated the effects on learning and memory processing. Furthermore, the effects of the water extract of Gastrodia elata Bl., a well-known Chinese traditional medicine, on amnesia in rats subjected to the forced-swimming procedure were studied. Rats were subjected to the forced-swimming procedure, and the inhibitory avoidance task and Morris water maze were used to assess learning and memory performance. The acquisition of the two tasks was mostly impaired after the 15-minute forced-swimming procedure. Administration of the water extract of G. elata Bl. for 21 consecutive days at a dosage of 0.5 or 1.0 g/kg of body weight significantly improved retention in the inhibitory avoidance test, and the lower dose showed a better effect than the higher one and the antidepressant fluoxetine (18 mg/kg of body weight). In the Morris water maze, the lower dose of the water extract of G. elata Bl. significantly improved retention by shortening escape latency in the first test session and increasing the time in searching the target zone during the probe test. These findings suggest that water extracts of G. elata Bl. ameliorate the learning and memory deficits induced by forced swimming.

Ground reaction force characteristics of Tai Chi push hand.

PubMed

Chang, Yao-Ting; Chang, Jia-Hao; Huang, Chen-Fu

2014-01-01

Push Hand is an advanced training technique for the Yang-style old frame 108 forms Tai Chi Chuan. It is performed by two practitioners. To clarify how people use forces during Push Hand training, it is important to review the ground reaction force (GRF). Here, we quantify the characteristics of the GRF during Push Hand training. Kinematic data and GRF data from 10 Tai Chi Chuan practitioners (29.9 ± 7.87 years) were synchronously recorded using a three-dimensional motion analysis system (200 frames · s(-1)) and three-dimensional force plates (1000 Hz). The resultant GRF for both feet for the 0%, 50% and 100% phases of attack and defence were compared to body weight using a paired-samples t-test. The differences in the resultant GRF between the 0%, 50% and 100% phases of attack and defence were tested by one-way repeated-measures ANOVA. The significance level was set to 0.05. The total resultant GRF was almost equal to the participant's body weight in push hand. This result was consistent throughout the entire push hand process. Our results revealed that the GRF was comparable to the body weight, implying that practitioners do not push or resist their opponents during the push hand process.

Finger Flexor Force Influences Performance in Senior Male Air Pistol Olympic Shooting

PubMed Central

Mon, Daniel; Zakynthinaki, María S.; Cordente, Carlos A.; Antón, Antonio J. Monroy; Rodríguez, Bárbara Rodríguez; Jiménez, David López

2015-01-01

The ability to stabilize the gun is crucial for performance in Olympic pistol shooting and is thought to be related to the shooters muscular strength. The present study examines the relation between performance and finger flexor force as well as shoulder abduction isometric force in senior male air pistol shooting. 46 Spanish national level shooters served as test subjects of the study. Two maximal force tests were carried out recording handgrip and deltoid force data under competition conditions, during the official training time at national Spanish championships. Performance was measured as the total score of 60 shots at competition. Linear regressions were calculated to examine the relations between performance and peak and average finger flexor forces, peak and average finger flexor forces relative to the BMI, peak and average shoulder abduction isometric forces, peak shoulder abduction isometric force relative to the BMI. The connection between performance and other variables such as age, weight, height, BMI, experience in years and training hours per week was also analyzed. Significant correlations were found between performance at competition and average and peak finger flexor forces. For the rest of the force variables no significant correlations were found. Significant correlations were also found between performance at competition and experience as well as training hours. No significant correlations were found between performance and age, weight, height or BMI. The study concludes that hand grip strength training programs are necessary for performance in air pistol shooting. PMID:26121145

Finger Flexor Force Influences Performance in Senior Male Air Pistol Olympic Shooting.

PubMed

Mon, Daniel; Zakynthinaki, María S; Cordente, Carlos A; Antón, Antonio J Monroy; Rodríguez, Bárbara Rodríguez; Jiménez, David López

2015-01-01

The ability to stabilize the gun is crucial for performance in Olympic pistol shooting and is thought to be related to the shooters muscular strength. The present study examines the relation between performance and finger flexor force as well as shoulder abduction isometric force in senior male air pistol shooting. 46 Spanish national level shooters served as test subjects of the study. Two maximal force tests were carried out recording handgrip and deltoid force data under competition conditions, during the official training time at national Spanish championships. Performance was measured as the total score of 60 shots at competition. Linear regressions were calculated to examine the relations between performance and peak and average finger flexor forces, peak and average finger flexor forces relative to the BMI, peak and average shoulder abduction isometric forces, peak shoulder abduction isometric force relative to the BMI. The connection between performance and other variables such as age, weight, height, BMI, experience in years and training hours per week was also analyzed. Significant correlations were found between performance at competition and average and peak finger flexor forces. For the rest of the force variables no significant correlations were found. Significant correlations were also found between performance at competition and experience as well as training hours. No significant correlations were found between performance and age, weight, height or BMI. The study concludes that hand grip strength training programs are necessary for performance in air pistol shooting.

Department of the Air Force Supporting Data For Fiscal Year 1984 Budget Estimates Submitted to Congress, January 31, 1983. Descriptive Summaries, Research, Development, Test and Evaluation

DTIC Science & Technology

1983-01-01

formulated to achieve weight savings, successfully completed a 100 hour pump test with no loss of fluid viscosity. Initial synthetic approaches to...acquisition cost savings in one concept and 51 percent weight savings in another. (9) (U) Advanced 3D Materials: Demonstrated the feasibility of using...in the gas phase. This research will provide the basis for future laser weapons that are more efficient, powerful, and lighter weight than infrared

49 CFR 178.606 - Stacking test.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Testing of Non-bulk Packagings and Packages § 178.606 Stacking test. (a) General. All packaging design... subjected to a force applied to the top surface of the test sample equivalent to the total weight of... non-hazardous liquids with specific gravities different from that of the liquid to be transported, the...

Does the sensorimotor system minimize prediction error or select the most likely prediction during object lifting?

PubMed Central

McGregor, Heather R.; Pun, Henry C. H.; Buckingham, Gavin; Gribble, Paul L.

2016-01-01

The human sensorimotor system is routinely capable of making accurate predictions about an object's weight, which allows for energetically efficient lifts and prevents objects from being dropped. Often, however, poor predictions arise when the weight of an object can vary and sensory cues about object weight are sparse (e.g., picking up an opaque water bottle). The question arises, what strategies does the sensorimotor system use to make weight predictions when one is dealing with an object whose weight may vary? For example, does the sensorimotor system use a strategy that minimizes prediction error (minimal squared error) or one that selects the weight that is most likely to be correct (maximum a posteriori)? In this study we dissociated the predictions of these two strategies by having participants lift an object whose weight varied according to a skewed probability distribution. We found, using a small range of weight uncertainty, that four indexes of sensorimotor prediction (grip force rate, grip force, load force rate, and load force) were consistent with a feedforward strategy that minimizes the square of prediction errors. These findings match research in the visuomotor system, suggesting parallels in underlying processes. We interpret our findings within a Bayesian framework and discuss the potential benefits of using a minimal squared error strategy. NEW & NOTEWORTHY Using a novel experimental model of object lifting, we tested whether the sensorimotor system models the weight of objects by minimizing lifting errors or by selecting the statistically most likely weight. We found that the sensorimotor system minimizes the square of prediction errors for object lifting. This parallels the results of studies that investigated visually guided reaching, suggesting an overlap in the underlying mechanisms between tasks that involve different sensory systems. PMID:27760821

Biomechanical Analysis of the Closed Kinetic Chain Upper-Extremity Stability Test.

PubMed

Tucci, Helga T; Felicio, Lilian R; McQuade, Kevin J; Bevilaqua-Grossi, Debora; Camarini, Paula Maria Ferreira; Oliveira, Anamaria S

2017-01-01

The closed kinetic chain upper-extremity stability (CKCUES) test is a functional test for the upper extremity performed in the push-up position, where individuals support their body weight on 1 hand placed on the ground and swing the opposite hand until touching the hand on the ground, then switch hands and repeat the process as fast as possible for 15 s. To study scapular kinematic and kinetic measures during the CKCUES test for 3 different distances between hands. Experimental. Laboratory. 30 healthy individuals (15 male, 15 female). Participants performed 3 repetitions of the test at 3 distance conditions: original (36 in), interacromial, and 150% interacromial distance between hands. Participants completed a questionnaire on pain intensity and perceived exertion before and after the procedures. Scapular internal/external rotation, upward/downward rotation, and posterior/anterior tilting kinematics and kinetic data on maximum force and time to maximum force were measured bilaterally in all participants. Percentage of body weight on upper extremities was calculated. Data analyses were based on the total numbers of hand touches performed for each distance condition, and scapular kinematics and kinetic values were averaged over the 3 trials. Scapular kinematics, maximum force, and time to maximum force were compared for the 3 distance conditions within each gender. Significance level was set at α = .05. Scapular internal rotation, posterior tilting, and upward rotation were significantly greater in the dominant side for both genders. Scapular upward rotation was significantly greater in original distance than interacromial distance in swing phase. Time to maximum force in women was significantly greater in the dominant side. CKCUES test kinematic and kinetic measures were not different among 3 conditions based on distance between hands. However, the test might not be suitable for initial or mild-level rehabilitation due to its challenging requirements.

Construction of a dual axis force reflection stick and test station

NASA Astrophysics Data System (ADS)

Repperger, Daniel E.; Scarborough, Eric L.; Chelette, Tamara L.

1991-11-01

This report describes the construction of a dual axis force reflecting stick controller and test station which was constructed through the use of basic research funds (ILIR monies). The prototype described in this report is powered only by electric motors and used the latest technology in computers. This was an advancement over a previous prototype which involved pneumatic devices and was very large, bulky, and awkward to use. An experiment was conducted with 5 subjects as described herein to test the overall system for its use in experimental design. The motivation for developing such a small test station for the use of force reflection in stick controllers is because with this new compact and portable system, many new applications now appear for this technology. The system described herein minimizes both weight and electric power requirements to produce the same force reflection. By upgrading the technology in the components used in this test station, wider use of force reflection is now available for a host of new applications.

Functional Evaluation of the Reusable JuniorSTAR® Half-Unit Insulin Pen.

PubMed

Klonoff, David; Nayberg, Irina; Rabbone, Ivana; Domenger, Catherine; Stauder, Udo; Oualali, Hamid; Danne, Thomas

2015-05-01

The functional performance of the JuniorSTAR(®) (Sanofi, Paris, France) half-unit insulin pen was evaluated through a series of specific objective tests to assess the dose accuracy, pen weight, injection force, and dialing torque. Pens (n = 60) were tested under standard atmospheric conditions with 3 different types of insulins manufactured by Sanofi (insulin glargine, insulin glulisine, and biphasic insulin isophane). The dose accuracy was tested according to the ISO 11608-1:2012 standards. Injection doses of 0.010, 0.155, and 0.300 ml were evaluated. For mean weight evaluation, the pens without the cartridge were weighed on precision balances. The injection force was measured using a texture analyzer and the dialing torque was measured using a torque meter. JuniorSTAR met the ISO 11608-1:2012 criteria for dose accuracy as all the delivered doses were within the predefined limits for all types of insulin tested. The mean weight of the JuniorSTAR pen was 33.4 g (SD = 0.075). The mean injection force was 6.0 N (SD = 0.8), 4.3 N (SD = 0.4), and 5.1 N (SD = 0.6) for insulin glargine, insulin glulisine, and biphasic insulin isophane, respectively. The mean dialing torque was 5.09 Ncm (SD = 0.29) and 5.88 Ncm (SD = 0.53) for setting and correcting a dose, respectively. Together with results from a previously reported usability survey, these results show that the JuniorSTAR reusable, half-unit pen is a lightweight and accurate device for insulin delivery with a dialing torque and injection force suitable for young people with type 1 diabetes. © 2015 Diabetes Technology Society.

Functional Evaluation of the Reusable JuniorSTAR® Half-Unit Insulin Pen

PubMed Central

Klonoff, David; Nayberg, Irina; Rabbone, Ivana; Domenger, Catherine; Stauder, Udo; Oualali, Hamid; Danne, Thomas

2015-01-01

Background: The functional performance of the JuniorSTAR® (Sanofi, Paris, France) half-unit insulin pen was evaluated through a series of specific objective tests to assess the dose accuracy, pen weight, injection force, and dialing torque. Method: Pens (n = 60) were tested under standard atmospheric conditions with 3 different types of insulins manufactured by Sanofi (insulin glargine, insulin glulisine, and biphasic insulin isophane). The dose accuracy was tested according to the ISO 11608-1:2012 standards. Injection doses of 0.010, 0.155, and 0.300 ml were evaluated. For mean weight evaluation, the pens without the cartridge were weighed on precision balances. The injection force was measured using a texture analyzer and the dialing torque was measured using a torque meter. Results: JuniorSTAR met the ISO 11608-1:2012 criteria for dose accuracy as all the delivered doses were within the predefined limits for all types of insulin tested. The mean weight of the JuniorSTAR pen was 33.4 g (SD = 0.075). The mean injection force was 6.0 N (SD = 0.8), 4.3 N (SD = 0.4), and 5.1 N (SD = 0.6) for insulin glargine, insulin glulisine, and biphasic insulin isophane, respectively. The mean dialing torque was 5.09 Ncm (SD = 0.29) and 5.88 Ncm (SD = 0.53) for setting and correcting a dose, respectively. Conclusions: Together with results from a previously reported usability survey, these results show that the JuniorSTAR reusable, half-unit pen is a lightweight and accurate device for insulin delivery with a dialing torque and injection force suitable for young people with type 1 diabetes. PMID:25633967

Moderate peripheral neuropathy impairs weight transfer and unipedal balance in the elderly.

PubMed

Richardson, J K; Ashton-Miller, J A; Lee, S G; Jacobs, K

1996-11-01

To quantitatively assess the performance of elderly with and without moderate, electrodiagnostically confirmed peripheral neuropathy (PN) on tasks of weight shifting and maintenance of unipedal balance. A case control study with PN subjects selected from a computerized data bank of all patients who had undergone electrodiagnostic studies at a university-based referral center. Control subjects of similar age and same gender were selected from the same source. Clinical examination included neurological and gross motor components. Quantitative evaluation included testing while the subjects stood with a force plate under each foot. Center of reaction (CR) excursions and ground reaction forces were quantified in: (1) six trials as subjects transferred their weight from bipedal stance to unipedal stance, on command, and attempted to maintain it for at least 3 seconds; and (2) in two additional trials in which subjects held unipedal stance for as long as possible. No subjects in either group had difficulty with level gait, a 180-degree turn, or required examiner assistance during an eyes-closed Romberg test. Biomechanical testing revealed that although the PN group used the same time to transfer their weight onto one foot as the C group, they achieved a significantly (1) lower rate of success in reliably maintaining 3 seconds of unipedal stance (.12 vs .58, p = .021), and (2) shorter mean maximum unipedal stance time (3.8 vs 32.3sec, p < .001). Furthermore, the PN group experienced greater difficulty in maintaining unipedal stance, as evidenced by significantly greater fluctuations in their ground reaction forces. The demonstrated impairment in reliability of unipedal stance in elderly with PN likely contributes to their known high rate of falls. Furthermore, unipedal stance testing serves to sharpen the physical examination by verifying the functional significance of impaired distal sensation-a common finding in the elderly.

Effects of elastic bands on force and power characteristics during the back squat exercise.

PubMed

Wallace, Brian J; Winchester, Jason B; McGuigan, Michael R

2006-05-01

Athletes commonly use elastic bands as a training method to increase strength and performance. The purpose of this study was to investigate the effect of elastic bands on peak force (PF), peak power (PP), and peak rate of force development (RFD) during the back-squat exercise (BSE). Ten recreationally resistance-trained subjects (4 women, 6 men, mean age 21.3 +/- 1.5 years) were tested for their 1 repetition maximum (1RM) in the BSE (mean 117.6 +/- 48.2 kg) on a Smith machine. Testing was performed on 2 separate days, with 2 sets of 3 repetitions being performed for each condition. Testing was conducted at 60% and 85% of 1RM with and without using elastic bands. In addition, 2 elastic band loading conditions were tested (B1 and B2) at each of the 2 resistances. No bands (NB) represents where all of the resistance was acquired from free-weights. B1 represents where approximately 80% of the resistance was provided by free-weights, and approximately 20% was provided by bands. B2 represents where approximately 65% of the resistance was provided by free-weights, and approximately 35% was provided from bands. The subjects completed the BSE under each condition, whereas PF, PP, and RFD was recorded using a force platform. There was a significant (p < 0.05) increase in PF between NB-85 and B2-85 of 16%. Between B1-85 and B2-85, PF was increased significantly by 5% (p < 0.05). There was a significant (p < 0.05) increase in PP between NB-85 and B2-85 of 24%. No significant differences were observed in RFD during the 85% conditions or for any of the measured variables during the 60% conditions (p < 0.05). The results suggest that the use of elastic bands in conjunction with free weights can significantly increase PF and PP during the BSE over free-weight resistance alone under certain loading conditions. The greatest differences are observed during the higher loading conditions, with the B1-85 condition appearing to be optimal for athletic performance of the ones we tested. The strength training professional could use variable resistance training (VRT) to increase PF and PP more than the traditional BSE can. VRT could also be used to train these 2 performance characteristics together, which might be especially useful in season, when weight-room training volume can sometimes be limited.

A Maximum-Likelihood Approach to Force-Field Calibration.

PubMed

Zaborowski, Bartłomiej; Jagieła, Dawid; Czaplewski, Cezary; Hałabis, Anna; Lewandowska, Agnieszka; Żmudzińska, Wioletta; Ołdziej, Stanisław; Karczyńska, Agnieszka; Omieczynski, Christian; Wirecki, Tomasz; Liwo, Adam

2015-09-28

A new approach to the calibration of the force fields is proposed, in which the force-field parameters are obtained by maximum-likelihood fitting of the calculated conformational ensembles to the experimental ensembles of training system(s). The maximum-likelihood function is composed of logarithms of the Boltzmann probabilities of the experimental conformations, calculated with the current energy function. Because the theoretical distribution is given in the form of the simulated conformations only, the contributions from all of the simulated conformations, with Gaussian weights in the distances from a given experimental conformation, are added to give the contribution to the target function from this conformation. In contrast to earlier methods for force-field calibration, the approach does not suffer from the arbitrariness of dividing the decoy set into native-like and non-native structures; however, if such a division is made instead of using Gaussian weights, application of the maximum-likelihood method results in the well-known energy-gap maximization. The computational procedure consists of cycles of decoy generation and maximum-likelihood-function optimization, which are iterated until convergence is reached. The method was tested with Gaussian distributions and then applied to the physics-based coarse-grained UNRES force field for proteins. The NMR structures of the tryptophan cage, a small α-helical protein, determined at three temperatures (T = 280, 305, and 313 K) by Hałabis et al. ( J. Phys. Chem. B 2012 , 116 , 6898 - 6907 ), were used. Multiplexed replica-exchange molecular dynamics was used to generate the decoys. The iterative procedure exhibited steady convergence. Three variants of optimization were tried: optimization of the energy-term weights alone and use of the experimental ensemble of the folded protein only at T = 280 K (run 1); optimization of the energy-term weights and use of experimental ensembles at all three temperatures (run 2); and optimization of the energy-term weights and the coefficients of the torsional and multibody energy terms and use of experimental ensembles at all three temperatures (run 3). The force fields were subsequently tested with a set of 14 α-helical and two α + β proteins. Optimization run 1 resulted in better agreement with the experimental ensemble at T = 280 K compared with optimization run 2 and in comparable performance on the test set but poorer agreement of the calculated folding temperature with the experimental folding temperature. Optimization run 3 resulted in the best fit of the calculated ensembles to the experimental ones for the tryptophan cage but in much poorer performance on the training set, suggesting that use of a small α-helical protein for extensive force-field calibration resulted in overfitting of the data for this protein at the expense of transferability. The optimized force field resulting from run 2 was found to fold 13 of the 14 tested α-helical proteins and one small α + β protein with the correct topologies; the average structures of 10 of them were predicted with accuracies of about 5 Å C(α) root-mean-square deviation or better. Test simulations with an additional set of 12 α-helical proteins demonstrated that this force field performed better on α-helical proteins than the previous parametrizations of UNRES. The proposed approach is applicable to any problem of maximum-likelihood parameter estimation when the contributions to the maximum-likelihood function cannot be evaluated at the experimental points and the dimension of the configurational space is too high to construct histograms of the experimental distributions.

The Air Force Fitness Program and the Challenge of Creating a More Fit Force

DTIC Science & Technology

2012-06-08

their fitness habits. In the early 1990s the Air Force transitioned to the bike test. The Weight Management Program continued with little change. The...member reported that he had lost ten pounds and was walking every day. I along with my Chief Master Sergeant continued to monitor the progress of the... continually high standard. The study 12 will show that the current Air Force fitness program does provide a basic view of fitness, but it does

Measurement of the Forces Acting on Gliders in Towed Flight

NASA Technical Reports Server (NTRS)

Klenperer, W B

1940-01-01

The magnitude, the direction, and the fluctuations of tow forces exerted upon gliders by towing them aloft behind an automobile were measured under a variety of conditions covering a range from gentle to severe types of operation. For these tests, the glider towing force did not exceed 1.6 of the gross weight of the glider. V-G records obtained during the towed-flight period as well as during the subsequent return glide to earth showed accelerations in the range from 3 to -1 g. The results of preliminary airplane tow tests are also presented.

Biennial Guidance Test Symposium (14th) held in Holloman Air Force Base, New Mexico on 3-5 October 1989. Volume 1

DTIC Science & Technology

1989-10-30

assembled pair is tumble lapped. Tumble lapping is a process in which Mechanically, the 1.5-inch diameter rotors a a weighted lapping element and slurry of...parameter met AGTF requirements at that site. Weighting factors were than assigned to each parameter as an indication of importance of the parameter to...AGTF. The weighted score was determined by multiplying the score by the weighting factor. The weighted scores were then totaled for each site to

Literature Review of Shear Performance of Light-weight Steel Framing Wall Panels

NASA Astrophysics Data System (ADS)

Zhang, Zhuangnan; Liu, Shen; Liu, Hong

2018-03-01

In this paper, a comprehensive review of light-weight steel framing wall panels was carried out. The structure and force characteristics of light-weight steel framing wall panels were introduced. The testing and theoretical research results on the shear behaviour of light-weight steel framing wall panels were summarized in the domestic and foreign. And combined with the existing standards in China, the author's views and ideas are put forward to the problems in the research field of this kind of structural system.

Metrics for Emitter Selection for Multistatic Synthetic Aperture Radar

DTIC Science & Technology

2013-09-01

the Faculty Department of Electrical and Computer Engineering Graduate School of Engineering and Management Air Force Insitute of Technology Air...130 5.2 Test Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 5.2.1 Weighting of Criteria...Ratio Test . . . . . . . . . . . . . . . . . . . . 20 CNR Clutter to Noise Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 QNR

Shock-absorbing effect of shoe insert materials commonly used in management of lower extremity disorders.

PubMed

Shiba, N; Kitaoka, H B; Cahalan, T D; Chao, E Y

1995-01-01

The efficacy of 3 shock-absorbing materials was compared by determining impact characteristics with a drop test method and also by testing the effect of each material when used as a shoe insert in 16 asymptomatic subjects. Peak vertical ground reaction force (F1, F2, F3) and temporal force factors (T1, T2, T3) were obtained with a force plate at a high-frequency sampling rate. Impact force, impact time, impact slope, and impact energy were determined. A standard weight was dropped from 3 heights on each material covering the force plate while reduction of peak force was compared. Impact force was attenuated most effectively by Insert 3 (polymeric foam rubber) and averaged 11% less than that in shoes without inserts. Impact time was increased for all 3 inserts. Impact slope and impact energy were reduced significantly in Insert 3. There was a significant difference in peak vertical force F1 for all 3 inserts, in vertical force F2 for Insert 2 (viscoelastic polymeric material), and in vertical force F3 for Insert 2. Drop-test studies showed that at all ball heights, the highest mean peak force was observed consistently in Insert 2.

Young-Adult Male Rats' Vulnerability to Chronic Mild Stress Is Reflected by Anxious-Like instead of Depressive-Like Behaviors.

PubMed

José Jaime, Herrera-Pérez; Venus, Benítez-Coronel; Graciela, Jiménez-Rubio; Tania, Hernández-Hernández Olivia; Lucía, Martínez-Mota

2016-01-01

In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain. These contrasting results encouraged us to explore other indicators of animal's vulnerability to stress such as anxious-like behaviors, since stress is an etiologic factor also for anxiety. Thus, in this study, we evaluated the vulnerability of these animals to CMS using behavioral tests of depression or anxiety and measuring serum corticosterone. Male Wistar rats were exposed to four weeks of CMS; the animals' body weight and sucrose preference (indicator of anhedonia) were assessed after three weeks, and, after the fourth week, some animals were evaluated in a behavioral battery (elevated plus maze, defensive burying behavior, and forced swimming tests); meanwhile, others were used to measure serum corticosterone. We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior. These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors.

Young-Adult Male Rats' Vulnerability to Chronic Mild Stress Is Reflected by Anxious-Like instead of Depressive-Like Behaviors

PubMed Central

José Jaime, Herrera-Pérez; Venus, Benítez-Coronel; Graciela, Jiménez-Rubio; Tania, Hernández-Hernández Olivia

2016-01-01

In a previous study, we found that chronic mild stress (CMS) paradigm did not induce anhedonia in young-adult male rats but it reduced their body weight gain. These contrasting results encouraged us to explore other indicators of animal's vulnerability to stress such as anxious-like behaviors, since stress is an etiologic factor also for anxiety. Thus, in this study, we evaluated the vulnerability of these animals to CMS using behavioral tests of depression or anxiety and measuring serum corticosterone. Male Wistar rats were exposed to four weeks of CMS; the animals' body weight and sucrose preference (indicator of anhedonia) were assessed after three weeks, and, after the fourth week, some animals were evaluated in a behavioral battery (elevated plus maze, defensive burying behavior, and forced swimming tests); meanwhile, others were used to measure serum corticosterone. We found that CMS (1) did not affect sucrose preference, immobility behavior in the forced swimming test, or serum corticosterone; (2) decreased body weight gain; and (3) increased the rat's entries into closed arms of the plus maze and the cumulative burying behavior. These data indicate that young male rats' vulnerability to CMS is reflected as poor body weight gain and anxious-like instead of depressive-like behaviors. PMID:27433469

Analysis of sitting forces on stationary chairs for daily activities.

PubMed

Hu, Lingling; Tackett, Bob; Tor, Onder; Zhang, Jilei

2016-04-01

No literature related to the study of sitting forces on chairs sat on by people who weighed over 136 kg was found. The Business Institutional Furniture Manufactures Association needs force data for development of performance test standards to test chairs for users who weigh up to 181 kg. 20 participants who weighed from 136 to 186 kg completed 6 tasks on an instrumented chair in the sequence of sitting down, remaining seated and rising. Effects of sitting motion, armrest use and seat cushion thickness on vertical sitting forces and centre-of-force were investigated. Results indicated hard sitting down yielded the highest sitting force of 213% in terms of participants' body weights. Armrest use affected sitting forces of normal sitting down, but not of rising and hard sitting down. Cushion thickness affected sitting forces of normal and hard sitting down and shifting, but not of rising, static seating or stretching backward situations. Practitioner Summary: Results of the sitting force and centre-of-force data obtained for this research can help furniture manufacturers develop new product performance test standards for creating reliable engineering design and manufacturing quality and durable products to meet a niche market need.

A comparison of impact force reduction by polymer materials used for mouthguard fabrication.

PubMed

Gawlak, Dominika; Mańka-Malara, Katarzyna; Mierzwińska-Nastalska, Elżbieta; Gieleta, Roman; Kamiński, Tomasz; Łuniewska, Magdalena

2017-01-01

The essential function of mouthguards is protection against the effects of injuries sustained during sports activities. This purpose will be successfully achieved if appropriate materials ensuring sufficient reduction of the injury force are used for mouthguard fabrication. The objective of the study was to investigate the force reduction capability of selected materials as well as to identify which material reduces the impact force to the highest degree. The material for the study were samples of polymers (6 samples in total), obtained during the process of deep pressing (2 samples), flasking (3 samples) and thermal injection (1 sample), which were tested for impact force damping using an impact device - Charpy impact hammer. The control group comprised of the ceramic material samples subjected to the hammer impact. The statistical analysis applied in this study were one-way Welch ANOVA with post-hoc Games-Howell pairwise comparisons. The test materials reduced the impact force of the impact hammer to varying degrees. The greatest damping capability was demonstrated for the following materials: Impak with 1:1 powder-to-liquid weight ratio polymerized with the conventional flasking technique, and Corflex Orthodontic used in the thermal injection technique of mouthguard fabrication. Impak with 1:1 weight ratio and Corflex Orthodontic should be recommended for the fabrication of mouthguards since they demonstrated the most advantageous damping properties.

Reductions in knee joint forces with weight loss are attenuated by gait adaptations in class III obesity.

PubMed

DeVita, Paul; Rider, Patrick; Hortobágyi, Tibor

2016-03-01

A consensus exists that high knee joint forces are a precursor to knee osteoarthritis and weight loss reduces these forces. Because large weight loss also leads to increased step length and walking velocity, knee contact forces may be reduced less than predicted by the magnitude of weight loss. The purpose was to determine the effects of weight loss on knee muscle and joint loads during walking in Class III obese adults. We determined through motion capture, force platform measures and biomechanical modeling the effects of weight loss produced by gastric bypass surgery over one year on knee muscle and joint loads during walking at a standard, controlled velocity and at self-selected walking velocities. Weight loss equaling 412 N or 34% of initial body weight reduced maximum knee compressive force by 824 N or 67% of initial body weight when walking at the controlled velocity. These changes represent a 2:1 reduction in knee force relative to weight loss when walking velocity is constrained to the baseline value. However, behavioral adaptations including increased stride length and walking velocity in the self-selected velocity condition attenuated this effect by ∼50% leading to a 392 N or 32% initial body weight reduction in compressive force in the knee joint. Thus, unconstrained walking elicited approximately 1:1 ratio of reduction in knee force relative to weight loss and is more indicative of walking behavior than the standard velocity condition. In conclusion, massive weight loss produces dramatic reductions in knee forces during walking but when patients stride out and walk faster, these favorable reductions become substantially attenuated. Copyright © 2016 Elsevier B.V. All rights reserved.

Effects of shoe cushioning upon ground reaction forces in running.

PubMed

Clarke, T E; Frederick, E C; Cooper, L B

1983-11-01

To determine the effects of widely varying amounts of cushioning upon vertical force (VF) parameters, ten male subjects, (mean weight = 68.0 kg) ran at a speed of 4.5 m . s-1 (6 min/mile pace) and contacted a Kistler force platform. Two shoes were tested: a hard one and a softer shoe that had 50% more cushioning as measured by an instrumented impact tester. Five right footfalls were collected for each shoe on each subject during which the ground reaction forces were sampled at 500 HZ using a PDP 11/34 minicomputer. Eight parameters from the VF data obtained for each trial were selected for analysis and compared statistically using a paired difference t test. It was found [force magnitudes expressed in multiples of body weight (BW)] that the time to the vertical force impact peak (VFIP) was significantly longer (hard = 22.5 ms, soft = 26.6 ms) in the soft shoe; however, no differences were seen in the magnitudes (hard = 2.30 BW, soft = 2.34 BW). The minimum after the VFIP was also significantly delayed in the soft shoe (hard = 33.8 ms, soft = 37.9 ms) and was significantly greater in the soft shoe (hard = 1.46 BW, soft = 1.90 BW). The peak VF propulsive force occurred statistically at the same time in both shoes (hard = 85.7 ms, soft = 84.0 ms), but was significantly greater in the soft shoe (hard = 2.73 BW, soft = 2.83 BW).(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of rockfalls on protection measures: an experimental approach

NASA Astrophysics Data System (ADS)

Yuan, J.; Li, Y.; Huang, R.; Pei, X.

2015-01-01

The determination of rockfall impact force is crucial in designing the protection measures. In the present study, laboratory tests are carried out by taking the weight and shape of the falling rock fragments, drop height, incident angle, platform on the slideway and cushion layer on the protection measures as factors to investigate their influences on the impact force. The test results indicate that the impact force is positively exponential to the weight of rockfall and the instantaneous impact velocity of the rockfall approaching the protection measures. The impact velocity is found to be dominated not only by the drop height but also by the shape of rockfall as well as the length of the platform on the slideway. A great drop height and/or a short platform produce a fast impact velocity. Spherical rockfalls experience a reater impact velocity than cubic and cylindrical ones. A layer of cushion on the protection measures may reduce the impact force to a greater extent. The reduction effects are dominated by the cushion material and the thickness of the cushion layer. The thicker the cushion layer, the greater the reduction effect and the less the impact force. The stiffer the buffer material, the less the buffering effect and the greater the impact force. The present study indicates that the current standard in China for designing protection measures may overestimate the impact force by taking no consideration for the rockfall shape, platform and cushion layer.

The Effect of Temporal Perception on Weight Perception

PubMed Central

Kambara, Hiroyuki; Shin, Duk; Kawase, Toshihiro; Yoshimura, Natsue; Akahane, Katsuhito; Sato, Makoto; Koike, Yasuharu

2013-01-01

A successful catch of a falling ball requires an accurate estimation of the timing for when the ball hits the hand. In a previous experiment in which participants performed ball-catching task in virtual reality environment, we accidentally found that the weight of a falling ball was perceived differently when the timing of ball load force to the hand was shifted from the timing expected from visual information. Although it is well known that spatial information of an object, such as size, can easily deceive our perception of its heaviness, the relationship between temporal information and perceived heaviness is still not clear. In this study, we investigated the effect of temporal factors on weight perception. We conducted ball-catching experiments in a virtual environment where the timing of load force exertion was shifted away from the visual contact timing (i.e., time when the ball hit the hand in the display). We found that the ball was perceived heavier when force was applied earlier than visual contact and lighter when force was applied after visual contact. We also conducted additional experiments in which participants were conditioned to one of two constant time offsets prior to testing weight perception. After performing ball-catching trials with 60 ms advanced or delayed load force exertion, participants’ subjective judgment on the simultaneity of visual contact and force exertion changed, reflecting a shift in perception of time offset. In addition, timing of catching motion initiation relative to visual contact changed, reflecting a shift in estimation of force timing. We also found that participants began to perceive the ball as lighter after conditioning to 60 ms advanced offset and heavier after the 60 ms delayed offset. These results suggest that perceived heaviness depends not on the actual time offset between force exertion and visual contact but on the subjectively perceived time offset between them and/or estimation error in force timing. PMID:23450805

Improved self-contained breathing apparatus concept. Final report Oct 80-Jun 82

DOE Office of Scientific and Technical Information (OSTI.GOV)

White, L.; Walker, J.

1982-08-01

Past operational experiences of USAF fire fighting and rescue teams have indicated the need for an improved self-contained breathing apparatus (SCBA). In October 1980, a contract was awarded to Electronic Data Systems, Panama City, Florida, to design and develop a prototype SCBA that would meet Air Force technical requirements. A prototype was designed, developed, and tested through a subcontract with Reimers Consultants, Falls Church, Virginia. This report describes the technical requirements, a detailed technical description of the unit, and the unmanned test procedures and results. The unmanned testing demonstrate that the prototype SCBA meets all performance requirements, except for weight.more » The fully charged prototype weights 34 pounds, the maximum acceptable weight is 30 pounds. With the other performance requirements either met or exceeded, manned testing of the SCBA can proceed.« less

Implementation and control of a 3 degree-of-freedom, force-reflecting manual controller

NASA Astrophysics Data System (ADS)

Kim, Whee-Kuk; Bevill, Pat; Tesar, Delbert

1991-02-01

Most available manual controllers which are used in bilateral or force-reflecting teleoperator systems can be characterized by their bulky size heavy weight high cost low magnitude of reflecting-force lack of smoothness insufficient transparency and simplified architectures. A compact smooth lightweight portable universal manual controller could provide a markedly improved level of transparency and be able to drive a broad spectrum of slave manipulators. This implies that a single stand-off position could be used for a diverse population of remote systems and that a standard environment for training of operators would result in reduced costs and higher reliability. In the implementation presented in this paper a parallel 3 degree-of-freedom (DOF) spherical structure (for compactness and reduced weight) is combined with high gear-ratio reducers using a force control algorithm to produce a " power steering" effect for enhanced smoothness and transparency. The force control algorithm has the further benefit of minimizing the effect of the system friction and non-linear inertia forces. The fundamental analytical description for the spherical force-reflecting manual controller such as forward position analysis reflecting-force transformation and applied force control algorithm are presented. Also a brief description of the system integration its actual implementation and preliminary test results are presented in the paper.

Change in knee contact force with simulated change in body weight.

PubMed

Knarr, Brian A; Higginson, Jill S; Zeni, Joseph A

2016-02-01

The relationship between obesity, weight gain and progression of knee osteoarthritis is well supported, suggesting that excessive joint loading may be a mechanism responsible for cartilage deterioration. Examining the influence of weight gain on joint compressive forces is difficult, as both muscles and ground reaction forces can have a significant impact on the forces experienced during gait. While previous studies have examined the relationship between body weight and knee forces, these studies have used models that were not validated using experimental data. Therefore, the objective of this study was to evaluate the relationship between changes in body weight and changes in knee joint contact forces for an individual's gait pattern using musculoskeletal modeling that is validated against known internal compressive forces. Optimal weighting constants were determined for three subjects to generate valid predictions of knee contact forces (KCFs) using in vivo data collection with instrumented total knee arthroplasty. A total of five simulations per walking trial were generated for each subject, from 80% to 120% body weight in 10% increments, resulting in 50 total simulations. The change in peak KCF with respect to body weight was found to be constant and subject-specific, predominantly determined by the peak force during the baseline condition at 100% body weight. This relationship may be further altered by any change in kinematics or body mass distribution that may occur as a result of a change in body weight or exercise program.

Classification image analysis: estimation and statistical inference for two-alternative forced-choice experiments

NASA Technical Reports Server (NTRS)

Abbey, Craig K.; Eckstein, Miguel P.

2002-01-01

We consider estimation and statistical hypothesis testing on classification images obtained from the two-alternative forced-choice experimental paradigm. We begin with a probabilistic model of task performance for simple forced-choice detection and discrimination tasks. Particular attention is paid to general linear filter models because these models lead to a direct interpretation of the classification image as an estimate of the filter weights. We then describe an estimation procedure for obtaining classification images from observer data. A number of statistical tests are presented for testing various hypotheses from classification images based on some more compact set of features derived from them. As an example of how the methods we describe can be used, we present a case study investigating detection of a Gaussian bump profile.

Design and performance testing of an ultrasonic linear motor with dual piezoelectric actuators.

PubMed

Smithmaitrie, Pruittikorn; Suybangdum, Panumas; Laoratanakul, Pitak; Muensit, Nantakan

2012-05-01

In this work, design and performance testing of an ultrasonic linear motor with dual piezoelectric actuator patches are studied. The motor system consists of a linear stator, a pre-load weight, and two piezoelectric actuator patches. The piezoelectric actuators are bonded with the linear elastic stator at specific locations. The stator generates propagating waves when the piezoelectric actuators are subjected to harmonic excitations. Vibration characteristics of the linear stator are analyzed and compared with finite element and experimental results. The analytical, finite element, and experimental results show agreement. In the experiments, performance of the ultrasonic linear motor is tested. Relationships between velocity and pre-load weight, velocity and applied voltage, driving force and applied voltage, and velocity and driving force are reported. The design of the dual piezoelectric actuators yields a simpler structure with a smaller number of actuators and lower stator stiffness compared with a conventional design of an ultrasonic linear motor with fully laminated piezoelectric actuators.

Biennial Guidance Test Symposium (13th) Held in Holloman Air Force Base, New Mexico on 6-8 October 1987. Volume 1

DTIC Science & Technology

1987-10-15

Guardiani, R. Strane, J. Profeta, Contraves Goerz Corporation, 610 Epsilon Dr., Pittsburg PA S04A "The Global Positioning System as an Aid to the Testing...errors. The weights defining the current error state as a linear combination of the gravity errors at the previous vehicle locations are maintained and...updated at each time step. These weights can also be used to compute the cross-correlation of the system errors with measured gravity quantities for use

Test Area C-72 and Line of Sight, Eglin Air Force Base, Florida Final Range Environmental Assessment (REA), Revision 1

DTIC Science & Technology

2011-07-28

missions. It was recognized that a failure to remove the trees could result in valuable data loss on Eglin test missions. Four different methods have...4-57 to 4-59) The munitions used on TA C-72 would cause noise levels ofless than 115 P- weighted (impulse sound) decibels, and receptors would not...approximate calculation is: 600 x the cube root of the net explosive weight (NEW) = distance to the reservation boundary (infeet) . No detonation can

Obese Women Have Lower Monosodium Glutamate Taste Sensitivity and Prefer Higher Concentrations Than Do Normal-weight Women

PubMed Central

Pepino, M. Yanina; Finkbeiner, Susana; Beauchamp, Gary K.; Mennella, Julie A.

2010-01-01

The goal of this study was to determine whether obese women exhibit altered umami and sweet taste perception compared to normal-weight women. A total of 57 subjects (23 obese and 34 normal weight) participated in a 2-day study separated by 1 week. Half of the women in each group were evaluated using monosodium glutamate (MSG; prototypical umami stimulus) on the first test day and sucrose on the second test day; the order was reversed for the remaining women. We used two-alternative forced-choice staircase procedures to measure taste detection thresholds, forced-choice tracking technique to measure preferences, the general Labeled Magnitude Scale (gLMS) to measure perceived intensity of suprathreshold concentrations, and a triangle test to measure discrimination between 29 mmol/l MSG and 29 mmol/l NaCl. Obese women required higher MSG concentrations to detect a taste and preferred significantly higher MSG concentrations in a soup-like vehicle. However, their perception of MSG at suprathreshold concentrations, their ability to discriminate MSG from salt, and their preference for sucrose were similar to that observed in normal-weight women. Regardless of their body weight category, 28% of the women did not discriminate 29 mmol/l MSG from 29 mmol/l NaCl (nondiscriminators). Surprisingly, we found that, relative to discriminators, nondiscriminators perceived less savoriness when tasting suprathreshold MSG concentrations and less sweetness from suprathreshold sucrose concentrations but had similar MSG and sucrose detection thresholds. Taken together, these data suggest that body weight is related to some components of umami taste and that different mechanisms are involved in the perception of threshold and suprathreshold MSG concentrations. PMID:20075854

Muscle anatomy and dynamic muscle function in osteogenesis imperfecta type I.

PubMed

Veilleux, Louis-Nicolas; Lemay, Martin; Pouliot-Laforte, Annie; Cheung, Moira S; Glorieux, Francis H; Rauch, Frank

2014-02-01

Results of previous studies suggested that children and adolescents with osteogenesis imperfecta (OI) type I have a muscle force deficit. However, muscle function has only been assessed by static isometric force tests and not in more natural conditions such as dynamic force and power tests. The purpose of this study was to assess lower extremity dynamic muscle function and muscle anatomy in OI type I. The study was performed in the outpatient department of a pediatric orthopedic hospital. A total of 54 individuals with OI type I (6-21 years; 20 male) and 54 age- and sex-matched controls took part in this study. Calf muscle cross-sectional area and density were measured by peripheral quantitative computed tomography. Lower extremity muscle function (peak force per body weight and peak power per body mass) was measured by jumping mechanography through 5 tests: multiple two-legged hopping, multiple one-legged hopping, single two-legged jump, chair-rise test, and heel-rise test. Compared with age- and sex-matched controls, patients with OI type I had smaller muscle size (P = .04) but normal muscle density (P = .21). They also had lower average peak force and lower specific force (peak force/muscle cross-sectional area; all P < .008). Average peak power was lower in patients with OI type I but not significantly so (all P > .054). Children and adolescents with OI type I have, on average, a significant force deficit in the lower limb as measured by dynamic force tests. Nonetheless, these data also show that OI type I is compatible with normal muscle performance in some individuals.

Effects of plyometric exercise training with external weights on punching ability of experienced amateur boxers.

PubMed

Bruzas, Vidas; Kamandulis, Sigitas; Venckunas, Tomas; Snieckus, Audrius; Mockus, Pranas

2018-03-01

During competition, a boxer must continue to deliver high-impact punches despite increasing fatigue. It is unclear whether the effects of plyometric training using external weights are transferred to sport-specific movements such as punching. The aim of the study was to investigate the effects of a 4-week cycle of plyometric training with external weights on punching ability. The study involved eight male amateur boxers aged 22.3±2.5 years with at least 7 years of competitive experience. They performed 12 plyometric training sessions, each comprising eight exercises of various muscle groups performed at maximum movement velocity. Six drills were performed with external weights, and two drills were performed using the body weight as resistance. All exercises required coordination. The punching ability was tested at baseline and after the 4 weeks of training using the Kiktest-100 boxing bag. The force of single punches and the frequency of punches within a series did not change from before to after the 4 weeks, except for increased power in the rear-hand low punch (P<0.05). However, there was an increase in summative force and energy output within 3 s and 8 s, and in a series of eight 8-s tests (P<0.05). Four weeks of plyometric training with external weights did not change the maximum punching power or movement frequency significantly, but had a beneficial effect on punching power endurance in boxers.

Size-weight illusion and anticipatory grip force scaling following unilateral cortical brain lesion.

PubMed

Li, Yong; Randerath, Jennifer; Goldenberg, Georg; Hermsdörfer, Joachim

2011-04-01

The prediction of object weight from its size is an important prerequisite of skillful object manipulation. Grip and load forces anticipate object size during early phases of lifting an object. A mismatch between predicted and actual weight when two different sized objects have the same weight results in the size-weight illusion (SWI), the small object feeling heavier. This study explores whether lateralized brain lesions in patients with or without apraxia alter the size-weight illusion and impair anticipatory finger force scaling. Twenty patients with left brain damage (LBD, 10 with apraxia, 10 without apraxia), ten patients with right brain damage (RBD), and matched control subjects lifted two different-sized boxes in alternation. All subjects experienced a similar size-weight illusion. The anticipatory force scaling of all groups was in correspondence with the size cue: higher forces and force rates were applied to the big box and lower forces and force rates to the small box during the first lifts. Within few lifts, forces were scaled to actual object weight. Despite the lack of significant differences at group level, 5 out of 20 LBD patients showed abnormal predictive scaling of grip forces. They differed from the LBD patients with normal predictive scaling by a greater incidence of posterior occipito-parietal lesions but not by a greater incidence of apraxia. The findings do not support a more general role for the motor-dominant left hemisphere, or an influence of apraxia per se, in the scaling of finger force according to object properties. However, damage in the vicinity of the parietal-occipital junction may be critical for deriving predictions of weight from size. Copyright © 2011 Elsevier Ltd. All rights reserved.

Velocity associated characteristics of force production in college weight lifters.

PubMed

Kanehisa, H; Fukunaga, T

1999-04-01

To determine velocity specific isokinetic forces and cross sectional areas of reciprocal muscle groups in Olympic weight lifters. The cross sectional area of the flexor or extensor muscles of the elbow or knee joint was determined by a B-mode ultrasonic apparatus in 34 college weight lifters and 31 untrained male subjects matched for age. Maximum voluntary force produced in the flexion and extension of the elbow and knee joints was measured on an isokinetic dynamometer at 60, 180, and 300 degrees/s. The average cross sectional area was 31-65% higher, and the force was 19-62% higher in weight lifters than in the untrained subjects. The ratio of force to cross sectional area was the same in both groups. The weight lifters showed a lower velocity associated decline in force than untrained subjects in the elbow and knee flexors but not in the extensors. These results indicate that for muscle contractions with velocities between 60 degrees/s and 300 degrees/s the difference in isokinetic force between weight lifters and untrained subjects can be primarily attributed to the difference in the muscle cross sectional area. However, the lower velocity associated decline in force implies that weight lifters may have a higher force per cross sectional area than untrained subjects at velocities above 300 degrees/s.

Differential Rearing Alters Forced Swim Test Behavior, Fluoxetine Efficacy, and Post-Test Weight Gain in Male Rats.

PubMed

Arndt, David L; Peterson, Christy J; Cain, Mary E

2015-01-01

Environmental factors play a key role in the etiology of depression. The rodent forced swim test (FST) is commonly used as a preclinical model of depression, with increases in escape-directed behavior reflecting antidepressant effects, and increases in immobility reflecting behavioral despair. Environmental enrichment leads to serotonergic alterations in rats, but it is unknown whether these alterations may influence the efficacy of common antidepressants. Male Sprague-Dawley rats were reared in enriched (EC), standard (SC), or isolated (IC) conditions. Following the rearing period, fluoxetine (10 or 20 mg/kg, i.p.) was administered 23.5 hrs, 5 hrs, and 1 hr before locomotor and FST measures. Following locomotor testing and FST exposure, rats were weighed to assess fluoxetine-, FST-, and environmental condition-induced moderations in weight gain. Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation. Regardless of significant fluoxetine effects on locomotor activity, fluoxetine generally decreased swimming and increased immobility in all three environmental conditions, with IC-fluoxetine (10 mg/kg) rats and EC-fluoxetine (20 mg/kg) rats swimming less than vehicle counterparts. Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress. These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being. Moreover, 20 mg/kg fluoxetine, administered subchronically, may lead to atypical effects of those commonly observed in the FST, highlighting the importance and impact of both environmental condition and dosing regimen in common animal models of depression.

Differential Rearing Alters Forced Swim Test Behavior, Fluoxetine Efficacy, and Post-Test Weight Gain in Male Rats

PubMed Central

Arndt, David L.; Peterson, Christy J.; Cain, Mary E.

2015-01-01

Environmental factors play a key role in the etiology of depression. The rodent forced swim test (FST) is commonly used as a preclinical model of depression, with increases in escape-directed behavior reflecting antidepressant effects, and increases in immobility reflecting behavioral despair. Environmental enrichment leads to serotonergic alterations in rats, but it is unknown whether these alterations may influence the efficacy of common antidepressants. Male Sprague-Dawley rats were reared in enriched (EC), standard (SC), or isolated (IC) conditions. Following the rearing period, fluoxetine (10 or 20 mg/kg, i.p.) was administered 23.5 hrs, 5 hrs, and 1 hr before locomotor and FST measures. Following locomotor testing and FST exposure, rats were weighed to assess fluoxetine-, FST-, and environmental condition-induced moderations in weight gain. Results revealed an antidepressant effect of environmental enrichment and a depressant effect of isolation. Regardless of significant fluoxetine effects on locomotor activity, fluoxetine generally decreased swimming and increased immobility in all three environmental conditions, with IC-fluoxetine (10 mg/kg) rats and EC-fluoxetine (20 mg/kg) rats swimming less than vehicle counterparts. Subchronic 20 mg/kg fluoxetine also induced significant weight loss, and differential rearing appeared to moderate weight gain following FST stress. These results suggest that differential rearing has the ability to alter FST behaviors, fluoxetine efficacy, and post-stressor well-being. Moreover, 20 mg/kg fluoxetine, administered subchronically, may lead to atypical effects of those commonly observed in the FST, highlighting the importance and impact of both environmental condition and dosing regimen in common animal models of depression. PMID:26154768

Impact-induced solidlike behavior and elasticity in concentrated colloidal suspensions

NASA Astrophysics Data System (ADS)

Chu, Baojin; Salem, David R.

2017-10-01

Modified drop weight impact tests were performed on Si O2 -ethylene glycol concentrated suspensions. Counterintuitive impact-induced solidlike behavior and elasticity, causing significant deceleration and rebound of the impactor, were observed. We provide evidence that the observed large deceleration force on the impactor mainly originates from the hydrodynamic force, and that the elasticity arises from the short-range repulsive force of a solvation layer on the particle surface. This study presents key experimental results to help understand the mechanisms underlying various stress-induced solidification phenomena.

NAPLaN Test Data, ESL Bandscales and the Validity of EAL/D Teacher Judgement of Student Performance

ERIC Educational Resources Information Center

Creagh, Sue

2014-01-01

Teachers are now experiencing the age of quantitative test-driven assessment, in which there is little weight accorded to teacher-based judgement about student progress. In the Australian context, the NAPLaN test has become a driving force in school and teacher accountability. The language of NAPLaN is one of bands and numerical scores and…

Do force-time and power-time measures in a loaded jump squat differentiate between speed performance and playing level in elite and elite junior rugby union players?

PubMed

Hansen, Keir T; Cronin, John B; Pickering, Stuart L; Douglas, Lee

2011-09-01

The purpose of this study was to investigate the discriminative ability of rebound jump squat force-time and power-time measures in differentiating speed performance and competition level in elite and elite junior rugby union players. Forty professional rugby union players performed 3 rebound jump squats with an external load of 40 kg from which a number of force-time and power-time variables were acquired and analyzed. Additionally, players performed 3 sprints over 30 m with timing gates at 5, 10, and 30 m. Significant differences (p < 0.05) between the fastest 20 and slowest 20 athletes, and elite (n = 25) and elite junior (n = 15) players in speed and force-time and power-time variables were determined using independent sample t-tests. The fastest and slowest sprinters over 10 m differed in peak power (PP) expressed relative to body weight. Over 30 m, there were significant differences in peak velocity and relative PP and rate of power development. There was no significant difference in speed over any distance between elite and elite junior rugby union players; however, a number of force and power variables including peak force, PP, force at 100 milliseconds from minimum force, and force and impulse 200 milliseconds from minimum force were significantly (p < 0.05) different between playing levels. Although only power values expressed relative to body weight were able to differentiate speed performance, both absolute and relative force and power values differentiated playing levels in professional rugby union players. For speed development in rugby union players, training strategies should aim to optimize the athlete's power to weight ratio, and lower body resistance training should focus on movement velocity. For player development to transition elite junior players to elite status, adding lean mass is likely to be most beneficial.

Re-evaluation of the interrelationships among the behavioral tests in rats exposed to chronic unpredictable mild stress

PubMed Central

Hu, Congli; Luo, Ying; Wang, Hong; Kuang, Shengnan; Liang, Guojuan; Yang, Yang; Mai, Shaoshan; Yang, Junqing

2017-01-01

The chronic unpredictable mild stress model of depression has been widely used as an experimental tool to investigate human psychopathology. Our objective was to provide an update on the validity and reliability of the chronic unpredictable mild stress model, by analyzing the interrelationships among the indexes using stepwise discriminant analysis and Pearson correlation coefficient to examine the possible combinations. We evaluated the depressive rats in both the presence and the absence of chronic unpredictable mild stress, using weight change, percentage of sucrose preference, coat state, splash test, open-field test, elevated plus-maze test, forced swimming test, and Morris water maze test. The results showed that 6-week-long chronic unpredictable mild stress produces significant depression and anxiety-like behavior. The combination of body weight change, percentage of sucrose preference, coat state score, open-field score, grooming latency of splash test, immobility time in force swimming test, and platform crossing in the Morris water maze test can effectively discriminate between normal and chronic unpredictable mild stress rats. Strong interrelationships were noted among these indexes in both open-field test and elevated plus-maze test. In conclusion, there might be certain criteria for the combination of behavioral endpoints, which is advantageous to more effectively and reliably assess the chronic unpredictable mild stress induced depression model. PMID:28931086

Titanium microgram weight low to 50 mg and measurement based on exchange weighing method

NASA Astrophysics Data System (ADS)

Ren, Xiaoping; Dong, Lei; Wang, Jian; Wang, Xiaolei

2017-03-01

The microgram weights have wide applications in the mechanical testing of nano- and bio-material sensors. They are increasing the requirement of small force and mass below 1 mg among the researchers, industry and bio-pharmaceutical manufacturing. In this paper, the current research status is presented, both from the measurement method and manufacture of microgram weights. The commonly used material for micro-weights is stainless steel and aluminum. Now NIM has developed another kind of microgram weights with titanium alloy. For the reason that it has smaller size than normal material like aluminum, special designed exchange weighing pan was used in measurement, which solved the problems that the weighing hooks cannot carry up and down the wire shape microgram weight. Then this kind of microgram weights was tested in subdivision measurement on an automatic mass comparator. It showed good performance in the experiment, which extends the choice for the industrial and metrological user. The uncertainty evaluation of micro-weight values range from 0.05 mg to 0.5 mg with standard uncertainty between 0.2 g and 0.1 μg.

Study on the Effect of Steel Wheel and Ground on Single Steel Vibratory Roller

NASA Astrophysics Data System (ADS)

Li, Jiabo; You, Guanghui; Qiao, Jiabin; Ye, Min; Guo, Jin; Zhang, Hongyang

2018-03-01

In the compacting operation of single drum vibratory roller, the forces acting on the foundation of drum include the weight of the drum, the weight of the frame, the exciting force and so on. Based on the theoretical study of ground mechanics, this paper analyzes and calculates the forces acting on the steel wheel and the ground, and obtains the distribution of the laminar stress in the ground when the working plane vibrates. Derive the formula of dynamic compressive stress and static compressive stress in the foundation during vibration compaction. Through the compaction test of the soil trough of 20T single drum roller, the compressive stress data of the soil hydraulic field are obtained. The data of the dynamic compressive stress and the static compressive stress of each layer during the third compaction are obtained, and the theoretical research is verified.

Relationship of Source Selection Methods to Contract Outcomes: an Analysis of Air Force Source Selection

DTIC Science & Technology

2015-12-01

of squares more difficult. There are, however, solutions to these issues. A weighted mean can be used in place of the grand mean1 and the STATA ...multivariate test of means provided in STATA 12.1. This test checks whether or not population variances and covariances of both DVs (PALT and CPARS

Relationship of Source Selection Methods to Contract Outcomes: An Analysis of Air Force Source Selection

DTIC Science & Technology

2015-12-01

however, solutions to these issues. A weighted mean can be used in place of the grand mean1 and the STATA software automatically handles the assignment of...covariance matrices between groups (i.e., sphericity) using the multivariate test of means provided in STATA 12.1. This test checks whether or not

Factors affecting minimum push and pull forces of manual carts.

PubMed

Al-Eisawi, K W; Kerk, C J; Congleton, J J; Amendola, A A; Jenkins, O C; Gaines, W

1999-06-01

The minimum forces needed to manually push or pull a 4-wheel cart of differing weights with similar wheel sizes from a stationary state were measured on four floor materials under different conditions of wheel width, diameter, and orientation. Cart load was increased from 0 to 181.4 kg in increments of 36.3 kg. The floor materials were smooth concrete, tile, asphalt, and industrial carpet. Two wheel widths were tested: 25 and 38 mm. Wheel diameters were 51, 102, and 153 mm. Wheel orientation was tested at four levels: F0R0 (all four wheels aligned in the forward direction), F0R90 (the two front wheels, the wheels furthest from the cart handle, aligned in the forward direction and the two rear wheels, the wheels closest to the cart handle, aligned at 90 degrees to the forward direction), F90R0 (the two front wheels aligned at 90 degrees to the forward direction and the two rear wheels aligned in the forward direction), and F90R90 (all four wheels aligned at 90 degrees to the forward direction). Wheel width did not have a significant effect on the minimum push/pull forces. The minimum push/pull forces were linearly proportional to cart weight, and inversely proportional to wheel diameter. The coefficients of rolling friction were estimated as 2.2, 2.4, 3.3, and 4.5 mm for hard rubber wheels rolling on smooth concrete, tile, asphalt, and industrial carpet floors, respectively. The effect of wheel orientation was not consistent over the tested conditions, but, in general, the smallest minimum push/pull forces were measured with all four wheels aligned in the forward direction, whereas the largest minimum push/pull forces were measured when all four wheels were aligned at 90 degrees to the forward direction. There was no significant difference between the push and pull forces when all four wheels were aligned in the forward direction.

Shoulder joint abduction motion test bench: a new shoulder test bench for in vitro experiments with active muscle force simulation.

PubMed

Onder, Ursula; Blauth, Michael; Kralinger, Franz; Schmoelz, Werner

2012-05-30

In our society the average age is increasing, as are the number of proximal humeral head fractures. For fixation of these fractures, an increasing number of implants are available. New fixation devices should be compared biomechanically with established methods in a standardized fashion. The test bench that was designed was intended to simulate abduction motion of the humerus actively induced by muscle forces. We used three pneumatic muscles to apply forces to the tendons of the musculus supraspinatus and the bifid musculus deltoideus. Thus, it was possible to create an active abduction in the scapular plane. Two different fracture models (with and without medial support) were stabilised with an angular stable plate in sawbone models to reproduce a known clinical outcome with the newly designed test setup. The resultant force acting on the proximal humerus reached approximately 47% BW (per cent body weight), which amounted to 329.0 N (SD: 21.76). The supraspinatus reached maximum forces of 254.7 N (SD: 20.1) and the deltoid muscle 258.9 N (SD: 16.5). Fracture gap instrumentation with medial support resulted in a significantly reduced per-cycle fracture gap motion. The performance evaluation showed that the simulator produced predicable, reproducible movements with physiological muscle force magnitudes.

Velocity associated characteristics of force production in college weight lifters

PubMed Central

Kanehisa, H.; Fukunaga, T.

1999-01-01

OBJECTIVE: To determine velocity specific isokinetic forces and cross sectional areas of reciprocal muscle groups in Olympic weight lifters. METHODS: The cross sectional area of the flexor or extensor muscles of the elbow or knee joint was determined by a B-mode ultrasonic apparatus in 34 college weight lifters and 31 untrained male subjects matched for age. Maximum voluntary force produced in the flexion and extension of the elbow and knee joints was measured on an isokinetic dynamometer at 60, 180, and 300 degrees/s. RESULTS: The average cross sectional area was 31-65% higher, and the force was 19-62% higher in weight lifters than in the untrained subjects. The ratio of force to cross sectional area was the same in both groups. The weight lifters showed a lower velocity associated decline in force than untrained subjects in the elbow and knee flexors but not in the extensors. CONCLUSIONS: These results indicate that for muscle contractions with velocities between 60 degrees/s and 300 degrees/s the difference in isokinetic force between weight lifters and untrained subjects can be primarily attributed to the difference in the muscle cross sectional area. However, the lower velocity associated decline in force implies that weight lifters may have a higher force per cross sectional area than untrained subjects at velocities above 300 degrees/s. 




 PMID:10205693

Creating "Intelligent" Ensemble Averages Using a Process-Based Framework

NASA Astrophysics Data System (ADS)

Baker, Noel; Taylor, Patrick

2014-05-01

The CMIP5 archive contains future climate projections from over 50 models provided by dozens of modeling centers from around the world. Individual model projections, however, are subject to biases created by structural model uncertainties. As a result, ensemble averaging of multiple models is used to add value to individual model projections and construct a consensus projection. Previous reports for the IPCC establish climate change projections based on an equal-weighted average of all model projections. However, individual models reproduce certain climate processes better than other models. Should models be weighted based on performance? Unequal ensemble averages have previously been constructed using a variety of mean state metrics. What metrics are most relevant for constraining future climate projections? This project develops a framework for systematically testing metrics in models to identify optimal metrics for unequal weighting multi-model ensembles. The intention is to produce improved ("intelligent") unequal-weight ensemble averages. A unique aspect of this project is the construction and testing of climate process-based model evaluation metrics. A climate process-based metric is defined as a metric based on the relationship between two physically related climate variables—e.g., outgoing longwave radiation and surface temperature. Several climate process metrics are constructed using high-quality Earth radiation budget data from NASA's Clouds and Earth's Radiant Energy System (CERES) instrument in combination with surface temperature data sets. It is found that regional values of tested quantities can vary significantly when comparing the equal-weighted ensemble average and an ensemble weighted using the process-based metric. Additionally, this study investigates the dependence of the metric weighting scheme on the climate state using a combination of model simulations including a non-forced preindustrial control experiment, historical simulations, and several radiative forcing Representative Concentration Pathway (RCP) scenarios. Ultimately, the goal of the framework is to advise better methods for ensemble averaging models and create better climate predictions.

Melatonin improve the sperm quality in forced swimming test induced oxidative stress in nandrolone treated Wistar rats.

PubMed

Minaii, Bagher; Moayeri, Ardeshir; Shokri, Saeed; Habibi Roudkenar, Mehryar; Golmohammadi, Taghi; Malek, Fatemeh; Barbarestani, Mohammad

2014-01-01

This study investigates the effects of melatonin on the sperm quality and testis weight after the combination of swimming exercise and nandrolone decanoate (DECA). Two groups of male Wistar rats were treated for eight weeks as follows; group A consist of CO (control), Sham, N (DECA), S (swimming) and NS (DECA plus swimming); and group B: Sham M (sham melatonin), M (melatonin), MN (melatonin plus DECA), MS (melatonin plus swimming), MNS (melatonin, DECA plus swimming). The motility of sperm was significantly improved in melatonin groups in comparison to N, S and NS groups (P≤0.05).  The left testes weight was decreased in N, NS and MNS groups, and the right testes weight was decreased in N,S,NS, MS and MNS groups in compare with the control group. This study concluded that melatonin probably could improve the sperm motility and sex organs weight after the combination of DECA and exercise.

Dynamic parameters of three-point crutch gait in female patients after total hip arthroplasty.

PubMed

Murawa, Michał; Dworak, Lechosław B; Kabaciński, Jarosław; Syczewska, Małgorzata; Rzepnicka, Agata

2016-01-01

Patient recovery after a surgical procedure depends, among other factors, on the amount of the body weight with which patient loads lower limb. Research studies report different results of the degree of body weight with which lower limb is loaded during three-point crutch gait. The aim of this study was to evaluate the level of the ground reaction forces (GRF) during crutch gait used by patients after total hip arthroplasty (THA) in the first week after discharge from the orthopaedic units. Ten female patients diagnosed with primary unilateral coxarthrosis participated in a single measurement session. In order to record kinematic and dynamic variables of this gait pattern motion analysis system was used together with two force plates. The static test of body weight distribution between lower limbs was performed on a dual-top stabilometric plate. The average peak values of loading on the operated (O) limb during mid stance and terminal stance of three-point crutch gait were 64.6% and 64.3% of body weight (BW), respectively, whereas in the case of the nonoperated (NO) limb 103.5%BW and 108.8%BW, respectively. The maximum loads on the crutches were significantly higher (by 9%BW) on the NO side as compared to the O side ( p < 0.05). During the static test, average values of body weight distribution on the O and NO limb were 36%BW and 64%BW, respectively. The patients showed surprisingly similar level of loading on the O limb. The weight bearing on the O limb was lower during static trial than during three-point crutch gait.

Consideration of Wear Rates at High Velocity

DTIC Science & Technology

2010-03-01

specimen retracted back into the test slipper. The amount of wear was analyzed by comparing the pretest and posttest specimen thicknesses and weights...and Design System (DADS) Model . . . . . . . . . . . . . . . . . . . . . . . 62 3.1.2 January 2008 Test Mission Raw DADS Data . . 64 3.1.3 DADS...The experimental high-speed test track at Holloman Air Force Base (AFB) has undergone many design innovations over a span of fifty years. One of the

The Association Between Maternal Early Life Forced Sexual Intercourse and Offspring Birth Weight: The Role of Socioeconomic Status.

PubMed

Gavin, Amelia R; Morris, Julia

2017-05-01

This study utilizes a life-course framework to investigate whether maternal early life forced sexual intercourse operates in conjunction with health behaviors during adolescence, young adulthood, and the prenatal period to influence offspring birth weight. Using data from the 1994-2009 National Longitudinal Study of Adolescent Health (Add Health), we examined whether early life forced sexual intercourse predicted offspring birth weight through a mediated pathway, including depressive symptoms, substance use, and prenatal cigarette smoking. We stratify our analysis by socioeconomic status (SES) to determine whether the proposed pathways operate similarly, or differently, according to SES. Our findings suggest that the pathways through which forced sexual intercourse affects offspring birth weight differ by SES. Among middle-to-high SES women, we found a mediated pathway linking forced sexual intercourse to offspring birth weight with prenatal cigarette smoking predicting lower offspring birth weight. Among low SES women, however, we did not find a mediated pathway linking forced sexual intercourse to birth weight. Findings suggest that prenatal cigarette smoking was not a mechanism of influence in the pathway between maternal early life forced sexual intercourse and offspring birth weight for low SES women. Our findings suggest that forced sexual intercourse may influence infant birth weight in the next generation. Infants born with a low birth weight are at increased risk for a myriad of adverse outcomes across the life-course. Study results suggest the importance of interventions designed to reduce behavioral risks and to support health promoting behaviors among survivors in the short term, in an effort to prevent long-term consequences among later-born offspring.

Neuromuscular fatigue and tibiofemoral joint biomechanics when transitioning from non-weight bearing to weight bearing.

PubMed

Schmitz, Randy J; Kim, Hyunsoo; Shultz, Sandra J

2015-01-01

Fatigue is suggested to be a risk factor for anterior cruciate ligament injury. Fatiguing exercise can affect neuromuscular control and laxity of the knee joint, which may render the knee less able to resist externally applied loads. Few authors have examined the effects of fatiguing exercise on knee biomechanics during the in vivo transition of the knee from non-weight bearing to weight bearing, the time when anterior cruciate ligament injury likely occurs. To investigate the effect of fatiguing exercise on tibiofemoral joint biomechanics during the transition from non-weight bearing to early weight bearing. Cross-sectional study. Research laboratory. Ten participants (5 men and 5 women; age = 25.3 ± 4.0 years) with no previous history of knee-ligament injury to the dominant leg. Participants were tested before (preexercise) and after (postexercise) a protocol consisting of repeated leg presses (15 repetitions from 10°-40° of knee flexion, 10 seconds' rest) against a 60% body-weight load until they were unable to complete a full bout of repetitions. Electromagnetic sensors measured anterior tibial translation and knee-flexion excursion during the application of a 40% body-weight axial compressive load to the bottom of the foot, simulating weight acceptance. A force transducer recorded axial compressive force. The axial compressive force (351.8 ± 44.3 N versus 374.0 ± 47.9 N; P = .018), knee-flexion excursion (8.0° ± 4.0° versus 10.2° ± 3.7°; P = .046), and anterior tibial translation (6.7 ± 1.7 mm versus 8.2 ± 1.9 mm; P < .001) increased from preexercise to postexercise. No significant correlations were noted. Neuromuscular fatigue may impair initial knee-joint stabilization during weight acceptance, leading to greater accessory motion at the knee and the potential for greater anterior cruciate ligament loading.

Efficacy of manual versus free-weight training to improve maximal strength and performance for microgravity conditions.

PubMed

Behringer, Michael; Schüren, Thomas; McCourt, Molly; Mester, Joachim

2016-01-01

We tested a simple and compact device designed for manual resistance training in conditions of microgravity (Self-Powered Rope Trainer Duo (SPoRT Duo)) to increase muscle performance. Twenty-four participants (20.8 ± 2.1 years) were randomly assigned to a manual resistance group (n = 12) and a free-weight group (n = 12). Participants performed eight exercises (three sets; 8-12 efforts) either with free weights or the SPoRT Duo twice a week for 6 weeks. Maximal isometric force of trunk flexion, back extension and chest press increased (P at least 0.01, d at least 0.52) both in the manual resistance group (18.4% ± 15.0%; 32.7% ± 22.7%; 15.3% ± 9.7%) and free-weight group (18.0% ± 13.9%; 26.6% ± 28.9%; 13.3% ± 7.6%). The change in maximal isometric force of wide grip row in both groups (d at best 0.38) did not reach statistical significance (P at best 0.08). The squat one-repetition-maximum increased in the manual resistance group (29.8% ± 22.1%) and the free-weight group (32.4% ± 26.6%). Jump height, determined by a jump-and-reach test, increased in the free-weight group (9.8% ± 13.2%) but not in the manual resistance group (2.0% ± 8.5%). Manual resistance training was equally effective in increasing strength as traditional resistance training with free weights. This apparatus is a useful addition to current in-flight exercise systems.

Analysis of Source Selection Methods and Performance Outcomes: Lowest Price Technically Acceptable vs. Tradeoff in Air Force Acquisitions

DTIC Science & Technology

2015-12-01

issues. A weighted mean can be used in place of the grand mean3 and the STATA software automatically handles the assignment of the sums of squares. Thus...between groups (i.e., sphericity) using the multivariate test of means provided in STATA 12.1. This test checks whether or not population variances and

Integration of sensory force feedback is disturbed in CRPS-related dystonia.

PubMed

Mugge, Winfred; van der Helm, Frans C T; Schouten, Alfred C

2013-01-01

Complex regional pain syndrome (CRPS) is characterized by pain and disturbed blood flow, temperature regulation and motor control. Approximately 25% of cases develop fixed dystonia. The origin of this movement disorder is poorly understood, although recent insights suggest involvement of disturbed force feedback. Assessment of sensorimotor integration may provide insight into the pathophysiology of fixed dystonia. Sensory weighting is the process of integrating and weighting sensory feedback channels in the central nervous system to improve the state estimate. It was hypothesized that patients with CRPS-related dystonia bias sensory weighting of force and position toward position due to the unreliability of force feedback. The current study provides experimental evidence for dysfunctional sensory integration in fixed dystonia, showing that CRPS-patients with fixed dystonia weight force and position feedback differently than controls do. The study shows reduced force feedback weights in CRPS-patients with fixed dystonia, making it the first to demonstrate disturbed integration of force feedback in fixed dystonia, an important step towards understanding the pathophysiology of fixed dystonia.

Effects of body-weight supported treadmill training on kinetic symmetry in persons with chronic stroke.

PubMed

Combs, Stephanie A; Dugan, Eric L; Ozimek, Elicia N; Curtis, Amy B

2012-11-01

The purpose was to examine changes in kinetic symmetry in persons with chronic stroke immediately and 6-months after body-weight supported treadmill training. Fifteen participants at least six-months post stroke and able to ambulate between 0.4 and 0.8m/s and 20 participants without neurological conditions completed all phases of the study and were included in the analysis. The non-disabled group served as a comparison for describing changes in kinetic symmetry. The stroke group completed 24 sessions of body-weight supported treadmill training over 8-weeks with 20 minutes of total walking per session. Bilateral 3-dimensional motion analysis and gait speed were assessed 1-week before training (pre-test), 1-week after training (post-test) and 6-months after training (retention) in a repeated measures design. Relative propulsion of the paretic leg and relative positive work of the hip, knee and ankle joints of both legs were calculated to evaluate symmetry of kinetic forces. Statistically significant differences in relative propulsion and positive joint work within the paretic and non-paretic legs were not found over time. The stroke group significantly improved gait speed from pre- to post-test (p=.001) and pre-test to retention (p=.008). In comparison to the non-disabled group, forces produced by the stroke group were asymmetrical demonstrating compensatory adaptation. Although the participants with chronic stroke walked faster after body-weight supported treadmill training, the relative percentages of propulsion and positive work remained unchanged. These findings suggest that the increase in speed was likely due to strengthening existing compensatory strategies rather than through recovery of normal kinetic symmetry. Copyright © 2012 Elsevier Ltd. All rights reserved.

Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants

PubMed Central

Kutzner, Ines; Dymke, Jörn; Damm, Philipp; Duda, Georg N.; Günzl, Reiner; Bergmann, Georg

2017-01-01

Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36–55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the course of rehabilitation or preventive therapies. PMID:28319145

Does aquatic exercise reduce hip and knee joint loading? In vivo load measurements with instrumented implants.

PubMed

Kutzner, Ines; Richter, Anja; Gordt, Katharina; Dymke, Jörn; Damm, Philipp; Duda, Georg N; Günzl, Reiner; Bergmann, Georg

2017-01-01

Aquatic exercises are widely used for rehabilitation or preventive therapies in order to enable mobilization and muscle strengthening while minimizing joint loading of the lower limb. The load reducing effect of water due to buoyancy is a main advantage compared to exercises on land. However, also drag forces have to be considered that act opposite to the relative motion of the body segments and require higher muscle activity. Due to these opposing effects on joint loading, the load-reducing effect during aquatic exercises remains unknown. The aim of this study was to quantify the joint loads during various aquatic exercises and to determine the load reducing effect of water. Instrumented knee and hip implants with telemetric data transfer were used to measure the resultant joint contact forces in 12 elderly subjects (6x hip, 6x knee) in vivo. Different dynamic, weight-bearing and non-weight-bearing activities were performed by the subjects on land and in chest-high water. Non-weight-bearing hip and knee flexion/extension was performed at different velocities and with additional Aquafins. Joint forces during aquatic exercises ranged between 32 and 396% body weight (BW). Highest forces occurred during dynamic activities, followed by weight-bearing and slow non-weight-bearing activities. Compared to the same activities on land, joint forces were reduced by 36-55% in water with absolute reductions being greater than 100%BW during weight-bearing and dynamic activities. During non-weight-bearing activities, high movement velocities and additional Aquafins increased the joint forces by up to 59% and resulted in joint forces of up to 301%BW. This study confirms the load reducing effect of water during weight-bearing and dynamic exercises. Nevertheless, high drag forces result in increased joint contact forces and indicate greater muscle activity. By the choice of activity, movement velocity and additional resistive devices joint forces can be modulated individually in the course of rehabilitation or preventive therapies.

Anticipatory scaling of grip forces when lifting objects of everyday life.

PubMed

Hermsdörfer, Joachim; Li, Yong; Randerath, Jennifer; Goldenberg, Georg; Eidenmüller, Sandra

2011-07-01

The ability to predict and anticipate the mechanical demands of the environment promotes smooth and skillful motor actions. Thus, the finger forces produced to grasp and lift an object are scaled to the physical properties such as weight. While grip force scaling is well established for neutral objects, only few studies analyzed objects known from daily routine and none studied grip forces. In the present study, eleven healthy subjects each lifted twelve objects of everyday life that encompassed a wide range of weights. The finger pads were covered with force sensors that enabled the measurement of grip force. A scale registered load forces. In a control experiment, the objects were wrapped into paper to prevent recognition by the subjects. Data from the first lift of each object confirmed that object weight was anticipated by adequately scaled forces. The maximum grip force rate during the force increase phase emerged as the most reliable measure to verify that weight was actually predicted and to characterize the precision of this prediction, while other force measures were scaled to object weight also when object identity was not known. Variability and linearity of the grip force-weight relationship improved for time points reached after liftoff, suggesting that sensory information refined the force adjustment. The same mechanism seemed to be involved with unrecognizable objects, though a lower precision was reached. Repeated lifting of the same object within a second and third presentation block did not improve the precision of the grip force scaling. Either practice was too variable or the motor system does not prioritize the optimization of the internal representation when objects are highly familiar.

Aging and the discrimination of object weight.

PubMed

Norman, J Farley; Norman, Hideko F; Swindle, Jessica M; Jennings, L RaShae; Bartholomew, Ashley N

2009-01-01

A single experiment was carried out to evaluate the ability of younger and older observers to discriminate object weights. A 2-alternative forced-choice variant of the method of constant stimuli was used to obtain difference thresholds for lifted weight for twelve younger (mean age = 21.5 years) and twelve older (mean age = 71.3 years) adults. The standard weight was 100 g, whereas the test weights ranged from 85 to 115 g. The difference thresholds of the older observers were 57.6% higher than those of the younger observers: the average difference thresholds were 10.4% and 6.6% of the standard for the older and younger observers, respectively. The current findings of an age-related deterioration in the ability to discriminate lifted weight extend and disambiguate the results of earlier research.

Pulmonary outcome in former preterm, very low birth weight children with bronchopulmonary dysplasia: a case-control follow-up at school age.

PubMed

Vom Hove, Maike; Prenzel, Freerk; Uhlig, Holm H; Robel-Tillig, Eva

2014-01-01

To assess and compare long-term pulmonary outcomes in former preterm-born, very low birth weight (VLBW) children with and without bronchopulmonary dysplasia (BPD) born in the surfactant era. Pulmonary function tests (ie, spirometry, body plethysmography, and gas transfer testing) were performed in children with a history of VLBW and BPD (n = 28) and compared with a matched preterm-born VLBW control group (n = 28). Medical history was evaluated by questionnaire. At time of follow-up (mean age, 9.5 years), respiratory symptoms (36% vs 8%) and receipt of asthma medication (21% vs 0%) were significantly more frequent in the preterm-born children with previous BPD than in those with no history of BPD. The children with a history of BPD had significantly lower values for forced expiratory volume in 1 second (z-score -1.27 vs -0.4; P = .008), forced vital capacity (z-score -1.39 vs -0.71 z-score; P = .022), and forced expiratory flow rate at 50% of forced vital capacity (z-score -2.21 vs -1.04; P = .048) compared with the preterm control group. Preterm-born children with a history of BPD are significantly more likely to have lung function abnormalities, such as airway obstruction and respiratory symptoms, at school age compared with preterm-born children without BPD. Copyright © 2014 Mosby, Inc. All rights reserved.

A randomized comparison of intraoperative PerfecTemp and forced-air warming during open abdominal surgery.

PubMed

Egan, Cameron; Bernstein, Ethan; Reddy, Desigen; Ali, Madi; Paul, James; Yang, Dongsheng; Sessler, Daniel I

2011-11-01

The PerfecTemp is an underbody resistive warming system that combines servocontrolled underbody warming with viscoelastic foam pressure relief. Clinical efficacy of the system has yet to be formally evaluated. We therefore tested the hypothesis that intraoperative distal esophageal (core) temperatures with the PerfecTemp (underbody resistive) warming system are noninferior to upper-body forced-air warming in patients undergoing major open abdominal surgery under general anesthesia. Adults scheduled for elective major open abdominal surgery (liver, pancreas, gynecological, and colorectal surgery) under general anesthesia were enrolled at 2 centers. Patients were randomly assigned to underbody resistive or forced-air warming. Resistive heating started when patients were transferred to the operating room table; forced-air warming started after patients were draped. The primary outcome was noninferiority of intraoperative time-weighted average core temperature, adjusted for baseline characteristics and using a buffer of 0.5°C. Thirty-six patients were randomly assigned to underbody resistive heating and 34 to forced-air warming. Baseline and surgical characteristics were generally similar. We had sufficient evidence (P=0.018) to conclude that underbody resistive warming is not worse than (i.e., noninferior to) upper-body forced-air warming in the time-weighted average intraoperative temperature, with a mean difference of -0.12°C [95% confidence interval (CI) -0.37 to 0.14]. Core temperatures at the end of surgery averaged 36.3°C [95% CI 36 to 36.5] in the resistive warming patients and 36.6°C [95% CI 36.4 to 36.8] in those assigned to forced-air warming for a mean difference of -0.34°C [95% CI -0.69 to 0.01]. Mean intraoperative time-weighted average core temperatures were no different, and significantly noninferior, with underbody resistive heating in comparison with upper-body forced-air warming. Underbody resistive heating may be an alternative to forced-air warming.

[Assessment of external breathing parameters and cardiovascular function in patients with constitutive exogenous obesity and reduced body weight].

PubMed

Merzlikina, N L; Romantsova, T I; Roik, O V; Lobanova, N A; Drapkina, O M; Ivashkin, V T

2009-01-01

The study was designed to evaluate external respiratory function (ERF) and cardiovascular function based on AP measurements, results of 24 hour AP monitoring, treadmill test, and ECG during weight loss therapy in patients with excess body mass. A total of 93 patients with grade 2-3 obesity were examined including 41 (39.8%) with type 2 diabetes mellitus (DM). Group 1 consisted of patients with constitutive exogenous obesity, group 2 of patients with constitutive exogenous obesity and DM, group 3 was used as control. Follow-up studies were conducted after 6 and 12 months. Patients of groups 1 and 2 showed positive dynamics of hemodynamic characteristics related to the loss of weight including significant reduction of heart rate, systolic and diastolic indices of hypertonic loading, specific peripheral vascular resistance, and left ventricular mass. Simultaneously, cardiac index and ERF increased while vital lung capacity, forced vital capacity, and forced respiratory volume in the first second returned to normal values. It is concluded that reduction of body weight has positive effect on ERF dynamics and hemodynamic characteristics in patients with constitutive exogenous obesity.

Large General Purpose Frame for Studying Force Vectors

ERIC Educational Resources Information Center

Heid, Christy; Rampolla, Donald

2011-01-01

Many illustrations and problems on the vector nature of forces have weights and forces in a vertical plane. One of the common devices for studying the vector nature of forces is a horizontal "force table," in which forces are produced by weights hanging vertically and transmitted to cords in a horizontal plane. Because some students have…

Correction of electronic record for weighing bucket precipitation gauge measurements

USDA-ARS?s Scientific Manuscript database

Electronic sensors generate valuable streams of forcing and validation data for hydrologic models, but are often subject to noise, which must be removed as part of model input and testing database development. We developed Automated Precipitation Correction Program (APCP) for weighting bucket preci...

Low velocity instrumented impact testing of four new damage tolerant carbon/epoxy composite systems

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1990-01-01

Low velocity drop weight instrumented impact testing was utilized to examine the damage resistance of four recently developed carbon fiber/epoxy resin systems. A fifth material, T300/934, for which a large data base exists, was also tested for comparison purposes. A 16-ply quasi-isotropic lay-up configuration was used for all the specimens. Force/absorbed energy-time plots were generated for each impact test. The specimens were cross-sectionally analyzed to record the damage corresponding to each impact energy level. Maximum force of impact versus impact energy plots were constructed to compare the various systems for impact damage resistance. Results show that the four new damage tolerant fiber/resin systems far outclassed the T300/934 material. The most damage tolerant material tested was the IM7/1962 fiber/resin system.

Force and displacement measurements of the distal fibula during simulated ankle loading tests for high ankle sprains.

PubMed

Markolf, Keith L; Jackson, Steven; McAllister, David R

2012-09-01

Syndesmosis (high ankle) sprains produce disruption of the distal tibiofibular ligaments. Forces on the distal fibula that produce these injuries are unknown. Twenty-seven fresh-frozen lower extremities were used for this study. A load cell recorded forces acting on the distal fibula from forced ankle dorsiflexion and applied external foot torque; medial-lateral and anterior-posterior displacements of the distal fibula were recorded. Fibular forces and axial displacements were also recorded with applied axial force. During forced ankle dorsiflexion and external foot torque tests, the distal fibula always displaced posteriorly with respect to the tibia with no measurable medial-lateral displacement. With 10 Nm dorsiflexion moment, cutting the tibiofibular ligaments approximately doubled fibular force and displacement values. Cutting the tibiofibular ligaments significantly increased fibular displacement from applied external foot torque. Fibular forces and axial displacements from applied axial weight-bearing force were highest with the foot dorsiflexed. The highest mean fibular force in the study (271.9 N) occurred with 10 Nm external foot torque applied to a dorsiflexed foot under 1000 N axial force. Two important modes of loading that could produce high ankle sprains were identified: forced ankle dorsiflexion and external foot torque applied to a dorsiflexed ankle loaded with axial force. The distal tibiofibular ligaments restrained fibular displacement during these tests. Residual mortise widening observed at surgery may be the result of tibiofibular ligament injuries caused by posterior displacement of the fibula. Therefore, a syndesmosis screw used to fix the fibula would be subjected to posterior bending forces from these loading modes. Ankle bracing to prevent extreme ankle dorsiflexion during rehabilitation may be advisable to prevent excessive fibular motions that could affect syndesmosis healing.

Effects of Angle Variations in Suspension Push-up Exercise.

PubMed

Gulmez, Irfan

2017-04-01

Gulmez, I. Effects of angle variations in suspension push-up exercise. J Strength Cond Res 31(4): 1017-1023, 2017-This study aimed to determine and compare the amount of loads on the TRX Suspension Trainer (TRX) straps and ground reaction forces at 4 different angles during TRX push-ups. Twenty-eight male (mean age, 24.1 ± 2.9 years; height, 179.4 ± 8.0 m; weight, 78.8 ± 9.8 kg) physical education and sports university students participated in this study. The subjects were tested at TRX angles (0, 15, 30, 45°) during the TRX push-ups. Force data were recorded by a force platform and load cells integrated into the TRX straps. The results show that as the TRX angle was reduced, the load applied to the TRX straps increased and simultaneously the load measured by the force platform decreased. This was true for both the elbow joint changing from flexion to extension and vice versa. When the TRX angle was set at 0° and subjects' elbows were at extension during TRX push-up, 50.4% of the subjects' body weight, and when the elbows were at flexion, 75.3% of the body weight was registered by the sensors on the TRX straps. The results of this study can be used in the calculation of the training load and volume (resistance training programming) during TRX push-up exercises at varying angles.

Soil runway friction evaluation in support of USAF C-17 transport aircraft operations

NASA Technical Reports Server (NTRS)

Yager, Thomas J.

1995-01-01

A series of NASA Diagonal-Braked Vehicle (DBV) test runs were performed on the soil runway 7/25 at Holland landing zone, Fort Bragg, North Carolina, near Pope Air Force Base in March 1995 at the request of the Air Force C-17 System Program Office. These ground vehicle test results indicated that the dry runway friction level was suitable for planned C-17 transport aircraft landing and take-off operations at various gross weights. These aircraft operations were successfully carried out. On-board aircraft deceleration measurements were comparable to NASA DBV measurements. Additional tests conducted with an Army High Mobility Multi-Purpose Wheeled Vehicle equipped with a portable decelerometer, showed good agreement with NASA DBV data.

Aerobic and Anaerobic Swimming Force Evaluation in One Single Test Session for Young Swimmers.

PubMed

de Barros Sousa, Filipe Antônio; Rodrigues, Natalia Almeida; Messias, Leonardo Henrique Dalcheco; Queiroz, Jair Borges; Manchado-Gobatto, Fulvia Barros; Gobatto, Claudio Alexandre

2017-05-01

This study aims to propose and validate the tethered swimming lactate minimum test (TSLacmin) estimating aerobic and anaerobic capacity in one single test session, using force as measurement parameter. 6 male and 6 female young swimmers (age=15.7±1.1 years; height=173.3±9.5 cm; weight=66.1±9.5 kg) performed 4 sessions comprising i) an all-out 30 s test and incremental test (TSLacmin); ii) 30 min of tethered swimming at constant intensity (2 sessions); iii) free-swimming time trials used to calculate critical velocity. Tethered swimming sessions used an acquisition system enabling maximum (Fmax) and mean (Fmean) force measurement and intensity variation. The tethered all-out test lasting 30 s resulted in hyperlactatemia of 7.9±2.0 mmol·l -1 . TSLacmin presented a 100% success applicability rate, which is equivalent to aerobic capacity in 75% of cases. TSLacmin intensity was 37.7±7.3 N, while maximum force in the all-out test was 105±27 N. Aerobic and anaerobic TSLacmin parameters were significantly related to free-swimming performance (r=-0.67 for 100 m and r=-0.80 for 200 m) and critical velocity (r=0.80). TSLacmin estimates aerobic capacity in most cases, and both aerobic and anaerobic force parameters are well related to critical velocity and free swimming performance. © Georg Thieme Verlag KG Stuttgart · New York.

Development, validity and reliability of a new pressure air biofeedback device (PAB) for measuring isometric extension strength of the lumbar spine.

PubMed

Pienaar, Andries W; Barnard, Justhinus G

2017-04-01

This study describes the development of a new portable muscle testing device, using air pressure as a biofeedback and strength testing tool. For this purpose, a pressure air biofeedback device (PAB ® ) was developed to measure and record the isometric extension strength of the lumbar multifidus muscle in asymptomatic and low back pain (LBP) persons. A total of 42 subjects (age 47.58 years, ±18.58) participated in this study. The validity of PAB ® was assessed by comparing a selected measure, air pressure force in millibar (mb), to a standard criterion; calibrated weights in kilograms (kg) during day-to-day tests. Furthermore, clinical trial-to-trial and day-to-day tests of maximum voluntary isometric contraction (MVIC) of L5 lumbar multifidus were done to compare air pressure force (mb) to electromyography (EMG) in microvolt (μV) and to measure the reliability of PAB ® . A highly significant relationship were found between air pressure output (mb) and calibrated weights (kg). In addition, Pearson correlation calculations showed a significant relationship between PAB ® force (mb) and EMG activity (μV) for all subjects (n = 42) examined, as well as for the asymptomatic group (n = 24). No relationship was detected for the LBP group (n = 18). In terms of lumbar extension strength, we found that asymptomatic subjects were significantly stronger than LBP subjects. The results of the PAB ® test differentiated between LBP and asymptomatic subject's lumbar isometric extension strength without any risk to the subjects and also indicate that the lumbar isometric extension test with the new PAB ® device is reliable and valid.

Restless behavior increases over time, but not with compressibility of the flooring surface, during forced standing at the feed bunk.

PubMed

Krebs, N; Berry, S L; Tucker, C B

2011-01-01

Interest in the use of rubber flooring in freestall barns has increased, but little is known about which design features of these surfaces are important for cattle. In 2 experiments, we evaluated how the type and compressibility of the flooring surface in front of the feed bunk influenced the behavioral response to 4 h of forced standing after morning milking. Two flooring types were compared: rubber and concrete. Rubber was tested at 3 levels of compressibility: 2, 4, and 35 times as compressible as concrete. Four hours of forced standing was evaluated because it mimicked conditions that can occur on dairies, particularly when waiting for artificial insemination or veterinary treatment. The effects of cow weight and hoof surface area, gait score, and hoof health on the response to treatment were evaluated. Restless behavior, as measured by number of steps, almost doubled over the 4h of forced standing, regardless of flooring material. Cows lay down, on average, within 5 min after access to the lying area was provided. These results indicate that the 4 h of forced standing was uncomfortable. No differences in restless behavior were observed in association with the type or compressibility of the flooring surface in front of the feed bunk. Cow size, hoof health, or gait score did not consistently explain the response to the flooring treatments or stepping rate, although these populations of animals were generally healthy. It is unclear if comfort did not differ between the flooring options tested during 4 h of forced standing or if alterative methodology, such as measuring more subtle shifts in weight, is required to assess design features of rubber flooring. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

New weight factor for Brownian force exerted on micro/nano-particles in air flow

NASA Astrophysics Data System (ADS)

Zhang, Peijie; Lin, Jianzhong; Ku, Xiaoke

2018-05-01

In order to effectively describe the effect of Brownian force exerted on the micro/nano-particles in air flow, a new weight factor, which is defined as the ratio of the characteristic velocity of the Brownian motion to the macroscopic velocity, is proposed and applied to the particle settlement under gravity. Results show that the weight factor can quantitatively evaluate the effect of Brownian force on the particle motion. Moreover, the value of the weight factor can also be used to judge the particle motion pattern and determine whether the Brownian force should be taken into account.

Relationship between body composition and vertical ground reaction forces in obese children when walking.

PubMed

Villarrasa-Sapiña, Israel; Serra-Añó, Pilar; Pardo-Ibáñez, Alberto; Gonzalez, Luis-Millán; García-Massó, Xavier

2017-01-01

Obesity is now a serious worldwide challenge, especially in children. This condition can cause a number of different health problems, including musculoskeletal disorders, some of which are due to mechanical stress caused by excess body weight. The aim of this study was to determine the association between body composition and the vertical ground reaction force produced during walking in obese children. Sixteen children participated in the study, six females and ten males [11.5 (1.2) years old, 69.8 (15.5) kg, 1.56 (0.09) m, and 28.36 (3.74) kg/m 2 of body mass index (BMI)]. Total weight, lean mass and fat mass were measured by dual-energy X-ray absorptiometry and vertical forces while walking were obtained by a force platform. The vertical force variables analysed were impact and propulsive forces, and the rate of development of both. Multiple regression models for each vertical force parameter were calculated using the body composition variables as input. The impact force regression model was found to be positively related to the weight of obese children and negatively related to lean mass. The regression model showed lean mass was positively related to the propulsive rate. Finally, regression models for impact and propulsive force showed a direct relationship with body weight. Impact force is positively related to the weight of obese children, but lean mass helps to reduce the impact force in this population. Exercise could help obese persons to reduce their total body weight and increase their lean mass, thus reducing impact forces during sports and other activities. Copyright © 2016 Elsevier Ltd. All rights reserved.

Coordination strategies for limb forces during weight-bearing locomotion in normal rats, and in rats spinalized as neonates

PubMed Central

Giszter, Simon F; Davies, Michelle R; Graziani, Virginia

2010-01-01

Some rats spinally transected as neonates (ST rats) achieve weight-supporting independent locomotion. The mechanisms of coordinated hindlimb weight support in such rats are not well understood. To examine these in such ST rats and normal rats, rats with better than 60% of weight supported steps on a treadmill as adults were trained to cross an instrumented runway. Ground reaction forces, coordination of hindlimb and forelimb forces and the motions of the center of pressure were assessed. Normal rats crossed the runway with a diagonal trot. On average hindlimbs bore about 80% of the vertical load carried by forelimbs, although this varied. Forelimbs and hindlimb acted synergistically to generate decelerative and propulsive rostrocaudal forces, which averaged 15% of body weight with maximums of 50% . Lateral forces were very small (<8% of body weight). Center of pressure progressed in jumps along a straight line with mean lateral deviations <1 cm. ST rats hindlimbs bore about 60% of the vertical load of forelimbs, significantly less compared to intact (p<0.05). ST rats showed similar mean rostrocaudal forces, but with significantly larger maximum fluctuations of up to 80% of body weight (p<0.05). Joint force-plate recordings showed forelimbs and hindlimb rostrocaudal forces in ST rats were opposing and significantly different from intact rats (p<0.05). Lateral forces were ~20% of body weight and significantly larger than in normal rats (p<0.05). Center of pressure zig-zagged, with mean lateral deviations of ~ 2cm and a significantly larger range (p<0.05). The haunches were also observed to roll more than normal rats. The locomotor strategy of injured rats using limbs in opposition was presumably less efficient but their complex gait was statically stable. Because forelimbs and hindlimbs acted in opposition, the trunk was held compressed. Force coordination was likely managed largely by the voluntary control in forelimbs and trunk. PMID:18612631

40 CFR 1066.270 - Unloaded coastdown verification.

Code of Federal Regulations, 2013 CFR

2013-07-01

... manufacturer. (2) With the dynamometer in coastdown mode, set the dynamometer inertia for the smallest vehicle... with the dynamometer inertia set for the largest vehicle weight that you expect to test. (4) Determine the average coastdown force, F, for each speed and inertia setting using the following equation...

40 CFR 1066.270 - Unloaded coastdown verification.

Code of Federal Regulations, 2012 CFR

2012-07-01

... manufacturer. (2) With the dynamometer in coastdown mode, set the dynamometer inertia for the smallest vehicle... with the dynamometer inertia set for the largest vehicle weight that you expect to test. (4) Determine the average coastdown force, F, for each speed and inertia setting using the following equation...

Impact of Surface Type, Wheelchair Weight, and Axle Position on Wheelchair Propulsion by Novice Older Adults

PubMed Central

Cowan, Rachel E.; Nash, Mark S.; Collinger, Jennifer L.; Koontz, Alicia M.; Boninger, Michael L.

2009-01-01

Objective To examine the impact of surface type, wheelchair weight, and rear axle position on older adult propulsion biomechanics. Design Crossover trial. Setting Biomechanics laboratory. Participants Convenience sample of 53 ambulatory older adults with minimal wheelchair experience (65−87y); men = 20, women = 33. Intervention Participants propelled 4 different wheelchair configurations over 4 surfaces; tile, low carpet, high carpet, and an 8% grade ramp (surface, chair order randomized). Chair configurations included: (1) unweighted chair with an anterior axle position, (2) 9.05kg weighted chair with an anterior axle position, (3) unweighted chair with a posterior axle position (Δ0.08m), and (4) 9.05kg weighted chair with a posterior axle position (Δ0.08m). Weight was added to a titanium folding chair, simulating the weight difference between very light and depot wheelchairs. Instrumented wheels measured propulsion kinetics. Main Outcome Measures Average self-selected velocity, push-frequency, stroke length, peak resultant and tangential force. Results Velocity decreased as surface rolling resistance or chair weight increased. Peak resultant and tangential forces increased as chair weight increased, surface resistance increased, and with a posterior axle position. The effect of a posterior axle position was greater on high carpet and the ramp. The effect of weight was constant, but more easily observed on high carpet and ramp. The effects of axle position and weight were independent of one another. Conclusion Increased surface resistance decreases self-selected velocity and increases peak forces. Increased weight decreases self-selected velocity and increases forces. Anterior axle positions decrease forces, more so on high carpet. Effects of weight and axle position are independent. Greatest reductions in peak forces occur in lighter chairs with anterior axle positions. PMID:19577019

KSC-2009-5373

NASA Image and Video Library

2009-09-25

VANDENBERG AIR FORCE BASE, Calif. -- At the Astrotech processing facility on Vandenberg Air Force Base in California, a crane prepares to lift NASA's Wide-field Infrared Survey Explorer, or WISE, from its test stand to determine its exact weight. The satellite will survey the entire sky at infrared wavelengths, creating a cosmic clearinghouse of hundreds of millions of objects which will be catalogued and provide a vast storehouse of knowledge about the solar system, the Milky Way, and the universe. Launch is scheduled for Dec. 7. Photo credit: NASA/Doug Kolkow

KSC-2009-5372

NASA Image and Video Library

2009-09-25

VANDENBERG AIR FORCE BASE, Calif. -- At the Astrotech processing facility on Vandenberg Air Force Base in California, workers prepare NASA's Wide-field Infrared Survey Explorer, or WISE, to be lifted from its test stand to determine its exact weight. The satellite will survey the entire sky at infrared wavelengths, creating a cosmic clearinghouse of hundreds of millions of objects which will be catalogued and provide a vast storehouse of knowledge about the solar system, the Milky Way, and the universe. Launch is scheduled for Dec. 7. Photo credit: NASA/Doug Kolkow

The F-15B Propulsion Flight Test Fixture: A New Flight Facility For Propulsion Research

NASA Technical Reports Server (NTRS)

Corda, Stephen; Vachon, M. Jake; Palumbo, Nathan; Diebler, Corey; Tseng, Ting; Ginn, Anthony; Richwine, David

2001-01-01

The design and development of the F-15B Propulsion Flight Test Fixture (PFTF), a new facility for propulsion flight research, is described. Mounted underneath an F-15B fuselage, the PFTF provides volume for experiment systems and attachment points for propulsion devices. A unique feature of the PFTF is the incorporation of a six-degree-of-freedom force balance. Three-axis forces and moments can be measured in flight for experiments mounted to the force balance. The NASA F-15B airplane is described, including its performance and capabilities as a research test bed aircraft. The detailed description of the PFTF includes the geometry, internal layout and volume, force-balance operation, available instrumentation, and allowable experiment size and weight. The aerodynamic, stability and control, and structural designs of the PFTF are discussed, including results from aerodynamic computational fluid dynamic calculations and structural analyses. Details of current and future propulsion flight experiments are discussed. Information about the integration of propulsion flight experiments is provided for the potential PFTF user.

The weight of mass or the mess of weight

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gat, U.

1987-06-24

This paper explores the cause of confusion associated with the words mass and weight, and offers suggestions to correct the problem. It is recommended that in technical and scientific use, weight shall be restricted to mean force of gravity. Technical standards, ASTM and others, and terminology shall clearly reflect and define weight to be force of gravity. Weight should be avoided in technical context because of its imprecision. Legal, formal, and official language shall use weight to mean force only. Under no circumstances should the SI units of mass, the kilogram, or its derivatives, be associated with weight. The termmore » weight should be avoided in any language and wording that intends to convey a precise or important meaning. ASTM should revise all standards and terminology accordingly.« less

Characterization and validation of a split belt treadmill for measuring hindlimb ground-reaction forces in able-bodied and spinalized felines

PubMed Central

Dimiskovski, Marko; Scheinfield, Richard; Higgin, Dwight; Krupka, Alexander; Lemay, Michel A.

2017-01-01

BACKGROUND The measurement of ground reaction forces (GRFs) in animals trained to locomote on a treadmill after spinal cord injury (SCI) could prove valuable for evaluating training outcomes; however, quantitative measures of the GRFs in spinal felines are limited. NEW METHOD A split belt treadmill was designed and constructed to measure the GRFs of feline hindlimbs during stepping. The treadmill consists of two independent treadmill assemblies, each mounted on a force plate. The design allows measurements of the vertical (Fz), fore-aft (Fy) and mediolateral (Fx) ground-reaction forces for both hindlimbs while the forelimbs are resting on a platform. RESULTS Static and dynamic noise tests revealed little to no noise at frequencies below 6 Hz. Validation of the force plate measurements with a hand-held force sensor force showed good agreement between the two force readings. Peak normalized (to body mass) vertical GRFs for intact cats were 4.89±0.85N/Kg for the left hindlimb and 4.79±0.97N/Kg for the right. In comparison, trained spinalized cats peak normalized vertical GRFs were 2.20±0.94N/Kg for the left hindlimb and 2.85±0.99N/Kg for the right. COMPARISON WITH OTHER EXISTING METHODS Previous methods of measuring GRFs used stationary single force plates or treadmill mounted to single force plate. Using independent treadmills for each hindlimb allows measurement of the individual hindlimb’s GRFs in spinalized cats following body-weight supported treadmill training. CONCLUSIONS The split belt force treadmill enables the simultaneous recording of ground-reaction forces for both hindlimbs in cats prior to spinalization, and following spinalization and body-weight-supported treadmill training (BWST). PMID:28069392

An evaluation of benthic macroinvertebrate biomass methodology : Part 1. Laboratory analytical methods.

PubMed

Mason, W T; Lewis, P A; Weber, C I

1983-03-01

Evaluation of analytical methods employed for wet weight (live or preserved samples) of benthic macroinvertebrates reveals that centrifugation at 140 x gravity for one minute yields constant biomass estimates. Less relative centrifugal force increases chance of incomplete removal of body moisture and results in weighing error, while greater force may rupture fragile macroinvertebrates, such as mayflies. Duration of specimen exposure in ethanol, formalin, and formol (formaling-ethanol combinations) causes significant body weight loss with within 48 hr formalin and formol cause less body weight loss than ethanol. However, as all preservatives tested cause body weight loss, preservation time of samples collected for comparative purposes should be treated uniformly. Dry weight estimates of macroinvertebrates are not significantly affected by kind of preservative or duration of exposure. Constant dry weights are attained by oven drying at 103 °C at a minimum of four hours or vacuum oven drying (15 inches of mercury pressure) at 103 °C for a minimum of one hour. Although requiring more time in preparation than oven drying and inalterably changing specimen body shape, freeze drying (10 microns pressure, -55 °C, 24 hr) provides constant dry weights and is advantageous for long term sample storage by minimizing curatorial attention. Constant ash-free dry weights of macroinvertebrate samples are attained by igniting samples at 500-550 °C for a minimum of one hour with slow cooling to room temperature in desiccators before weighing.

Kinematic and ground reaction force accommodation during weighted walking.

PubMed

James, C Roger; Atkins, Lee T; Yang, Hyung Suk; Dufek, Janet S; Bates, Barry T

2015-12-01

Weighted walking is a functional activity common in daily life and can influence risks for musculoskeletal loading, injury and falling. Much information exists about weighted walking during military, occupational and recreational tasks, but less is known about strategies used to accommodate to weight carriage typical in daily life. The purposes of the study were to examine the effects of weight carriage on kinematics and peak ground reaction force (GRF) during walking, and explore relationships between these variables. Twenty subjects walked on a treadmill while carrying 0, 44.5 and 89 N weights in front of the body. Peak GRF, sagittal plane joint/segment angular kinematics, stride length and center of mass (COM) vertical displacement were measured. Changes in peak GRF and displacement variables between weight conditions represented accommodation. Effects of weight carriage were tested using analysis of variance. Relationships between peak GRF and kinematic accommodation variables were examined using correlation and regression. Subjects were classified into sub-groups based on peak GRF responses and the correlation analysis was repeated. Weight carriage increased peak GRF by an amount greater than the weight carried, decreased stride length, increased vertical COM displacement, and resulted in a more extended and upright posture, with less hip and trunk displacement during weight acceptance. A GRF increase was associated with decreases in hip extension (|r|=.53, p=.020) and thigh anterior rotation (|r|=.57, p=.009) displacements, and an increase in foot anterior rotation displacement (|r|=.58, p=.008). Sub-group analysis revealed that greater GRF increases were associated with changes at multiple sites, while lesser GRF increases were associated with changes in foot and trunk displacement. Weight carriage affected walking kinematics and revealed different accommodation strategies that could have implications for loading and stability. Copyright © 2015 Elsevier B.V. All rights reserved.

How honey bees carry pollen

NASA Astrophysics Data System (ADS)

Matherne, Marguerite E.; Anyanwu, Gabriel; Leavey, Jennifer K.; Hu, David L.

2017-11-01

Honey bees are the tanker of the skies, carrying thirty percent of their weight in pollen per foraging trip using specialized orifices on their body. How do they manage to hang onto those pesky pollen grains? In this experimental study, we investigate the adhesion force of pollen to the honeybee. To affix pollen to themselves, honey bees form a suspension of pollen in nectar, creating a putty-like pollen basket that is skewered by leg hairs. We use tensile tests to show that the viscous force of the pollen basket is more than ten times the honeybee's flight force. This work may provide inspiration for the design of robotic flying pollinators.

Quantifying feedforward control: a linear scaling model for fingertip forces and object weight.

PubMed

Lu, Ying; Bilaloglu, Seda; Aluru, Viswanath; Raghavan, Preeti

2015-07-01

The ability to predict the optimal fingertip forces according to object properties before the object is lifted is known as feedforward control, and it is thought to occur due to the formation of internal representations of the object's properties. The control of fingertip forces to objects of different weights has been studied extensively by using a custom-made grip device instrumented with force sensors. Feedforward control is measured by the rate of change of the vertical (load) force before the object is lifted. However, the precise relationship between the rate of change of load force and object weight and how it varies across healthy individuals in a population is not clearly understood. Using sets of 10 different weights, we have shown that there is a log-linear relationship between the fingertip load force rates and weight among neurologically intact individuals. We found that after one practice lift, as the weight increased, the peak load force rate (PLFR) increased by a fixed percentage, and this proportionality was common among the healthy subjects. However, at any given weight, the level of PLFR varied across individuals and was related to the efficiency of the muscles involved in lifting the object, in this case the wrist and finger extensor muscles. These results quantify feedforward control during grasp and lift among healthy individuals and provide new benchmarks to interpret data from neurologically impaired populations as well as a means to assess the effect of interventions on restoration of feedforward control and its relationship to muscular control. Copyright © 2015 the American Physiological Society.

USAF shale oil program status

NASA Technical Reports Server (NTRS)

Delaney, C. L.

1984-01-01

The test and evaluation program on shale derived fuel being conducted by the Air Force is intended to accomplish the minimum amount of testing necessary to assure both the safe use of shale oil derived turbine fuels in operational USAF aircraft and its compatibility with USAF handling systems. This program, which was designed to take advantage of existing R&D testing programs, began in 1981. However, due to a problem in acquiring the necessary fuel, the testing program was suspended until July 1983 when an additional sample of shale derived fuel was received. Tentatively, the Air Force is planning to make three relatively minor revisions to the procurement specifications requirements for the production shale derived fuel. These are: (1) Aromatic Contest (min) - 9% (by volume); (2) Nitrogen (max - 20 ppm by weight); and (3) Antioxidants - 9.1 g/100 gal (U.S.)

Wheelchair pushrim kinetics measurement: A method to cancel inaccuracies due to pushrim weight and wheel camber.

PubMed

Chénier, Félix; Aissaoui, Rachid; Gauthier, Cindy; Gagnon, Dany H

2017-02-01

The commercially available SmartWheel TM is largely used in research and increasingly used in clinical practice to measure the forces and moments applied on the wheelchair pushrims by the user. However, in some situations (i.e. cambered wheels or increased pushrim weight), the recorded kinetics may include dynamic offsets that affect the accuracy of the measurements. In this work, an automatic method to identify and cancel these offsets is proposed and tested. First, the method was tested on an experimental bench with different cambers and pushrim weights. Then, the method was generalized to wheelchair propulsion. Nine experienced wheelchair users propelled their own wheelchairs instrumented with two SmartWheels with anti-slip pushrim covers. The dynamic offsets were correctly identified using the propulsion acquisition, without needing a separate baseline acquisition. A kinetic analysis was performed with and without dynamic offset cancellation using the proposed method. The most altered kinetic variables during propulsion were the vertical and total forces, with errors of up to 9N (p<0.001, large effect size of 5). This method is simple to implement, fully automatic and requires no further acquisitions. Therefore, we advise to use it systematically to enhance the accuracy of existing and future kinetic measurements. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

Variable Acceleration Force Calibration System (VACS)

NASA Technical Reports Server (NTRS)

Rhew, Ray D.; Parker, Peter A.; Johnson, Thomas H.; Landman, Drew

2014-01-01

Conventionally, force balances have been calibrated manually, using a complex system of free hanging precision weights, bell cranks, and/or other mechanical components. Conventional methods may provide sufficient accuracy in some instances, but are often quite complex and labor-intensive, requiring three to four man-weeks to complete each full calibration. To ensure accuracy, gravity-based loading is typically utilized. However, this often causes difficulty when applying loads in three simultaneous, orthogonal axes. A complex system of levers, cranks, and cables must be used, introducing increased sources of systematic error, and significantly increasing the time and labor intensity required to complete the calibration. One aspect of the VACS is a method wherein the mass utilized for calibration is held constant, and the acceleration is changed to thereby generate relatively large forces with relatively small test masses. Multiple forces can be applied to a force balance without changing the test mass, and dynamic forces can be applied by rotation or oscillating acceleration. If rotational motion is utilized, a mass is rigidly attached to a force balance, and the mass is exposed to a rotational field. A large force can be applied by utilizing a large rotational velocity. A centrifuge or rotating table can be used to create the rotational field, and fixtures can be utilized to position the force balance. The acceleration may also be linear. For example, a table that moves linearly and accelerates in a sinusoidal manner may also be utilized. The test mass does not have to move in a path that is parallel to the ground, and no re-leveling is therefore required. Balance deflection corrections may be applied passively by monitoring the orientation of the force balance with a three-axis accelerometer package. Deflections are measured during each test run, and adjustments with respect to the true applied load can be made during the post-processing stage. This paper will present the development and testing of the VASC concept.

Statistically generated weighted curve fit of residual functions for modal analysis of structures

NASA Technical Reports Server (NTRS)

Bookout, P. S.

1995-01-01

A statistically generated weighting function for a second-order polynomial curve fit of residual functions has been developed. The residual flexibility test method, from which a residual function is generated, is a procedure for modal testing large structures in an external constraint-free environment to measure the effects of higher order modes and interface stiffness. This test method is applicable to structures with distinct degree-of-freedom interfaces to other system components. A theoretical residual function in the displacement/force domain has the characteristics of a relatively flat line in the lower frequencies and a slight upward curvature in the higher frequency range. In the test residual function, the above-mentioned characteristics can be seen in the data, but due to the present limitations in the modal parameter evaluation (natural frequencies and mode shapes) of test data, the residual function has regions of ragged data. A second order polynomial curve fit is required to obtain the residual flexibility term. A weighting function of the data is generated by examining the variances between neighboring data points. From a weighted second-order polynomial curve fit, an accurate residual flexibility value can be obtained. The residual flexibility value and free-free modes from testing are used to improve a mathematical model of the structure. The residual flexibility modal test method is applied to a straight beam with a trunnion appendage and a space shuttle payload pallet simulator.

Adhesion force of staphylococcus aureus on various biomaterial surfaces.

PubMed

Alam, Fahad; Balani, Kantesh

2017-01-01

Staphylococcus comprises of more than half of all pathogens in orthopedic implant infections and they can cause major bone infection which can result in destruction of joint and bone. In the current study, adhesion force of bacteria on the surface of various biomaterial surfaces is measured using atomic force microscope (AFM). Staphylococcus aureus was immobilized on an AFM tipless cantilever as a force probe to measure the adhesion force between bacteria and biomaterials (viz. ultra-high molecular weight poly ethylene (UHMWPE), stainless steel (SS), Ti-6Al-4V alloy, hydroxyapatite (HA)). At the contact time of 10s, UHMWPE shows weak adhesion force (~4nN) whereas SS showed strong adhesion force (~15nN) due to their surface energy and surface roughness. Bacterial retention and viability experiment (3M™ petrifilm test, agar plate) dictates that hydroxyapatite shows the lowest vaibility of bacteria, whereas lowest bacterial retention is observed on UHMWPE surface. Similar results were obtained from live/dead staining test, where HA shows 65% viability, whereas on UHMWPE, SS and Ti-6Al-4V, the bacterial viability is 78%, 94% and 97%, respectively. Lower adhesion forces, constrained pull-off distance (of bacterial) and high antibacterial resistance of bioactive-HA makes it a potential biomaterial for bone-replacement arthroplasty. Copyright © 2016 Elsevier Ltd. All rights reserved.

In-Space technology experiments program. A high efficiency thermal interface (using condensation heat transfer) between a 2-phase fluid loop and heatpipe radiator: Experiment definition phase

NASA Technical Reports Server (NTRS)

Pohner, John A.; Dempsey, Brian P.; Herold, Leroy M.

1990-01-01

Space Station elements and advanced military spacecraft will require rejection of tens of kilowatts of waste heat. Large space radiators and two-phase heat transport loops will be required. To minimize radiator size and weight, it is critical to minimize the temperature drop between the heat source and sink. Under an Air Force contract, a unique, high-performance heat exchanger is developed for coupling the radiator to the transport loop. Since fluid flow through the heat exchanger is driven by capillary forces which are easily dominated by gravity forces in ground testing, it is necessary to perform microgravity thermal testing to verify the design. This contract consists of an experiment definition phase leading to a preliminary design and cost estimate for a shuttle-based flight experiment of this heat exchanger design. This program will utilize modified hardware from a ground test program for the heat exchanger.

Resolution and contrast in Kelvin probe force microscopy

NASA Astrophysics Data System (ADS)

Jacobs, H. O.; Leuchtmann, P.; Homan, O. J.; Stemmer, A.

1998-08-01

The combination of atomic force microscopy and Kelvin probe technology is a powerful tool to obtain high-resolution maps of the surface potential distribution on conducting and nonconducting samples. However, resolution and contrast transfer of this method have not been fully understood, so far. To obtain a better quantitative understanding, we introduce a model which correlates the measured potential with the actual surface potential distribution, and we compare numerical simulations of the three-dimensional tip-specimen model with experimental data from test structures. The observed potential is a locally weighted average over all potentials present on the sample surface. The model allows us to calculate these weighting factors and, furthermore, leads to the conclusion that good resolution in potential maps is obtained by long and slender but slightly blunt tips on cantilevers of minimal width and surface area.

Systemic Sclerosis Classification Criteria: Developing methods for multi-criteria decision analysis with 1000Minds

PubMed Central

Johnson, Sindhu R.; Naden, Raymond P.; Fransen, Jaap; van den Hoogen, Frank; Pope, Janet E.; Baron, Murray; Tyndall, Alan; Matucci-Cerinic, Marco; Denton, Christopher P.; Distler, Oliver; Gabrielli, Armando; van Laar, Jacob M.; Mayes, Maureen; Steen, Virginia; Seibold, James R.; Clements, Phillip; Medsger, Thomas A.; Carreira, Patricia E.; Riemekasten, Gabriela; Chung, Lorinda; Fessler, Barri J.; Merkel, Peter A.; Silver, Richard; Varga, John; Allanore, Yannick; Mueller-Ladner, Ulf; Vonk, Madelon C.; Walker, Ulrich A.; Cappelli, Susanna; Khanna, Dinesh

2014-01-01

Objective Classification criteria for systemic sclerosis (SSc) are being developed. The objectives were to: develop an instrument for collating case-data and evaluate its sensibility; use forced-choice methods to reduce and weight criteria; and explore agreement between experts on the probability that cases were classified as SSc. Study Design and Setting A standardized instrument was tested for sensibility. The instrument was applied to 20 cases covering a range of probabilities that each had SSc. Experts rank-ordered cases from highest to lowest probability; reduced and weighted the criteria using forced-choice methods; and re-ranked the cases. Consistency in rankings was evaluated using intraclass correlation coefficients (ICC). Results Experts endorsed clarity (83%), comprehensibility (100%), face and content validity (100%). Criteria were weighted (points): finger skin thickening (14–22), finger-tip lesions (9–21), friction rubs (21), finger flexion contractures (16), pulmonary fibrosis (14), SSc-related antibodies (15), Raynaud’s phenomenon (13), calcinosis (12), pulmonary hypertension (11), renal crisis (11), telangiectasia (10), abnormal nailfold capillaries (10), esophageal dilation (7) and puffy fingers (5). The ICC across experts was 0.73 (95%CI 0.58,0.86) and improved to 0.80 (95%CI 0.68,0.90). Conclusions Using a sensible instrument and forced-choice methods, the number of criteria were reduced by 39% (23 to 14) and weighted. Our methods reflect the rigors of measurement science, and serves as a template for developing classification criteria. PMID:24721558

Analyses of balance and flexibility of obese patients undergoing bariatric surgery

PubMed Central

Benetti, Fernanda Antico; Bacha, Ivan Leo; Junior, Arthur Belarmino Garrido; Greve, Júlia Maria D'Andréa

2016-01-01

OBJECTIVE: To assess the postural control and flexibility of obese subjects before and both six and 12 months after bariatric surgery. To verify whether postural control is related to flexibility following weight reductions resulting from bariatric surgery. METHODS: The sample consisted of 16 subjects who had undergone bariatric surgery. All assessments were performed before and six and 12 months after bariatric surgery. Postural balance was assessed using an Accusuway® portable force platform, and flexibility was assessed using a standard chair sit and reach test (Wells' chair). RESULTS: With the force platform, no differences were observed in the displacement area or velocity from the center of pressure in the mediolateral and anteroposterior directions. The displacement speed from the center of pressure was decreased at the six month after the surgery; however, unchanged from baseline at 12 months post-surgery. Flexibility increased over time according to the three measurements tested. CONCLUSIONS: Static postural balance did not change. The velocity of postural adjustment responses were increased at six months after surgery. Therefore, weight loss promotes increased flexibility. Yet, improvements in flexibility are not related to improvements in balance. PMID:26934236

External Hand Forces Exerted by Long-Term Care Staff to Push Floor-Based Lifts: Effects of Flooring System and Resident Weight.

PubMed

Lachance, Chantelle C; Korall, Alexandra M B; Russell, Colin M; Feldman, Fabio; Robinovitch, Stephen N; Mackey, Dawn C

2016-09-01

The aim of this study was to investigate the effects of flooring type and resident weight on external hand forces required to push floor-based lifts in long-term care (LTC). Novel compliant flooring is designed to reduce fall-related injuries among LTC residents but may increase forces required for staff to perform pushing tasks. A motorized lift may offset the effect of flooring on push forces. Fourteen female LTC staff performed straight-line pushes with two floor-based lifts (conventional, motor driven) loaded with passengers of average and 90th-percentile resident weights over four flooring systems (concrete+vinyl, compliant+vinyl, concrete+carpet, compliant+carpet). Initial and sustained push forces were measured by a handlebar-mounted triaxial load cell and compared to participant-specific tolerance limits. Participants rated pushing difficulty. Novel compliant flooring increased initial and sustained push forces and subjective ratings compared to concrete flooring. Compared to the conventional lift, the motor-driven lift substantially reduced initial and sustained push forces and perceived difficulty of pushing for all four floors and both resident weights. Participants exerted forces above published tolerance limits only when using the conventional lift on the carpet conditions (concrete+carpet, compliant+carpet). With the motor-driven lift only, resident weight did not affect push forces. Novel compliant flooring increased linear push forces generated by LTC staff using floor-based lifts, but forces did not exceed tolerance limits when pushing over compliant+vinyl. The motor-driven lift substantially reduced push forces compared to the conventional lift. Results may help to address risk of work-related musculoskeletal injury, especially in locations with novel compliant flooring. © 2016, Human Factors and Ergonomics Society.

KSC-2009-5377

NASA Image and Video Library

2009-09-25

VANDENBERG AIR FORCE BASE, Calif. -- At the Astrotech processing facility on Vandenberg Air Force Base in California, NASA's Wide-field Infrared Survey Explorer, or WISE, is secured to the crane that will lift it from its test stand to determine its exact weight. The satellite will survey the entire sky at infrared wavelengths, creating a cosmic clearinghouse of hundreds of millions of objects which will be catalogued and provide a vast storehouse of knowledge about the solar system, the Milky Way, and the universe. Launch is scheduled for Dec. 7. Photo credit: NASA/Doug Kolkow

Control of Precision Grip Force in Lifting and Holding of Low-Mass Objects

PubMed Central

Kimura, Daisuke; Kadota, Koji; Ito, Taro

2015-01-01

Few studies have investigated the control of grip force when manipulating an object with an extremely small mass using a precision grip, although some related information has been provided by studies conducted in an unusual microgravity environment. Grip-load force coordination was examined while healthy adults (N = 17) held a moveable instrumented apparatus with its mass changed between 6 g and 200 g in 14 steps, with its grip surface set as either sandpaper or rayon. Additional measurements of grip-force-dependent finger-surface contact area and finger skin indentation, as well as a test of weight discrimination, were also performed. For each surface condition, the static grip force was modulated in parallel with load force while holding the object of a mass above 30 g. For objects with mass smaller than 30 g, on the other hand, the parallel relationship was changed, resulting in a progressive increase in grip-to-load force (GF/LF) ratio. The rayon had a higher GF/LF force ratio across all mass levels. The proportion of safety margin in the static grip force and normalized moment-to-moment variability of the static grip force were also elevated towards the lower end of the object mass for both surfaces. These findings indicate that the strategy of grip force control for holding objects with an extremely small mass differs from that with a mass above 30 g. The data for the contact area, skin indentation, and weight discrimination suggest that a decreased level of cutaneous feedback signals from the finger pads could have played some role in a cost function in efficient grip force control with low-mass objects. The elevated grip force variability associated with signal-dependent and internal noises, and anticipated inertial force on the held object due to acceleration of the arm and hand, could also have contributed to the cost function. PMID:26376484

KSC-99pc0142

NASA Image and Video Library

1999-01-28

The KSC-developed X-33 weight simulator (top), known as the "iron bird," is lifted to a vertical position at the X-33 launch site as part of launch equipment testing on Edwards Air Force Base, CA. The simulator matches the 75,000-pound weight and 63-foot height of the X-33 vehicle that will be using the launch equipment. KSC's Vehicle Positioning System (VPS) placed the simulator on the rotating launch platform prior to the rotation. The new VPS will dramatically reduce the amount of manual labor required to position a reusable launch vehicle for liftoff

KSC-99pc0145

NASA Image and Video Library

1999-01-28

The KSC-developed X-33 weight simulator (top, right), known as the "iron bird," is lifted to a vertical position at the X-33 launch site as part of launch equipment testing on Edwards Air Force Base, CA. The simulator matches the 75,000-pound weight and 63-foot height of the X-33 vehicle that will be using the launch equipment. KSC's Vehicle Positioning System (VPS) placed the simulator on the rotating launch platform prior to the rotation. The new VPS will dramatically reduce the amount of manual labor required to position a reusable launch vehicle for liftoff

KSC-99pc0144

NASA Image and Video Library

1999-01-28

The KSC-developed X-33 weight simulator (left), known as the "iron bird," is fully raised to a vertical position at the X-33 launch site as part of launch equipment testing on Edwards Air Force Base, CA. The simulator matches the 75,000-pound weight and 63-foot height of the X-33 vehicle that will be using the launch equipment. KSC's Vehicle Positioning System (VPS) placed the simulator on the rotating launch platform prior to the rotation. The new VPS will dramatically reduce the amount of manual labor required to position a reusable launch vehicle for liftoff

Biennial Guidance Test Symposium (15th) Held in Holloman Air Force Base, New Mexico on 24-26 September 1991. Volume 1

DTIC Science & Technology

1991-09-01

for loss , damage, or injury resulting from manufacture or use for any purpose of any product, article, system, or material involving reliance upon any...technologies but fit within an envelope of 10 pounds total weight , 20 watus of power, 100 cubic inches of volume, and a DARPA initiated the GPS Guidance...smaller volume and9 M I " 9•r @ •) 100 9 70• too lower weight constraints should also expand the _________- -number of future vehicles for GOP use. The

Effects of a cementing technique in addition to luting agent on the uniaxial retention force of a single-tooth implant-supported restoration: an in vitro study.

PubMed

Santosa, Robert E; Martin, William; Morton, Dean

2010-01-01

Excess residual cement around the implant margin has been shown to be detrimental to the peri-implant tissue. This in vitro study examines the retentive strengths of two different cementing techniques and two different luting agents on a machined titanium abutment and solid screw implants. The amount of reduction of excess cement weight between the two cementation techniques was assessed. Forty gold castings were fabricated for 4.1 mm in diameter and 10 mm in length solid-screw dental implants paired with 5.5-mm machined titanium abutments. Twenty implants received a provisional cement, and 20 implants received a definitive cement. Each group was further divided into two groups. In the control group, cement was applied and the castings seated over the implant-abutment assembly. The excess cement was then removed. In the study group, a "practice abutment" was used to express excess cement prior to cementation. The weight of the implant-casting assembly was measured and the residual weight of cement was calculated. The samples were then stored for 24 hours at 100% humidity prior to tensile strength testing. Statistical analysis revealed significant differences in tensile strength across the groups. Further Tukey tests showed no significant difference in tensile strength between the practice abutment technique and the conventional technique for both definitive and provisional cements. There was a significant reduction in residual cement weight, irrespective of the type of cement, when the practice abutment was used prior to cementation. Cementation of implant restorations on a machined abutment using the practice abutment technique and definitive cement may provide similar uniaxial retention force and significantly reduced residual cement weight compared to the conventional technique of cement removal.

Using Maximal Isometric Force to Determine the Optimal Load for Measuring Dynamic Muscle Power

NASA Technical Reports Server (NTRS)

Spiering, Barry A.; Lee, Stuart M. C.; Mulavara, Ajitkumar P.; Bentley, Jason R.; Nash, Roxanne E.; Sinka, Joseph; Bloomberg, Jacob J.

2009-01-01

Maximal power output occurs when subjects perform ballistic exercises using loads of 30-50% of one-repetition maximum (1-RM). However, performing 1-RM testing prior to power measurement requires considerable time, especially when testing involves multiple exercises. Maximal isometric force (MIF), which requires substantially less time to measure than 1-RM, might be an acceptable alternative for determining the optimal load for power testing. PURPOSE: To determine the optimal load based on MIF for maximizing dynamic power output during leg press and bench press exercises. METHODS: Twenty healthy volunteers (12 men and 8 women; mean +/- SD age: 31+/-6 y; body mass: 72 +/- 15 kg) performed isometric leg press and bench press movements, during which MIF was measured using force plates. Subsequently, subjects performed ballistic leg press and bench press exercises using loads corresponding to 20%, 30%, 40%, 50%, and 60% of MIF presented in randomized order. Maximal instantaneous power was calculated during the ballistic exercise tests using force plates and position transducers. Repeated-measures ANOVA and Fisher LSD post hoc tests were used to determine the load(s) that elicited maximal power output. RESULTS: For the leg press power test, six subjects were unable to be tested at 20% and 30% MIF because these loads were less than the lightest possible load (i.e., the weight of the unloaded leg press sled assembly [31.4 kg]). For the bench press power test, five subjects were unable to be tested at 20% MIF because these loads were less than the weight of the unloaded aluminum bar (i.e., 11.4 kg). Therefore, these loads were excluded from analysis. A trend (p = 0.07) for a main effect of load existed for the leg press exercise, indicating that the 40% MIF load tended to elicit greater power output than the 60% MIF load (effect size = 0.38). A significant (p . 0.05) main effect of load existed for the bench press exercise; post hoc analysis indicated that the effect of load on power output was: 30% > 40% > 50% = 60%. CONCLUSION: Loads of 40% and 30% of MIF elicit maximal power output during dynamic leg presses and bench presses, respectively. These findings are similar to those obtained when loading is based on 1-RM.

Predictive and Reactive Grip Force Responses to Rapid Load Increases in People With Multiple Sclerosis.

PubMed

Allgöwer, Kathrin; Kern, Claudia; Hermsdörfer, Joachim

2017-03-01

To determine the effects of multiple sclerosis (MS) on predictive and reactive grip force control in a catching task and on clinical tests of hand function. Case-control study with matched-pairs control group. University prevention and rehabilitation center. Participants (N=30) consisted of people with multiple sclerosis (PwMS) (n=15) and healthy controls (n=15), matched for sex, age, and hand dominance. Not applicable. Performance on the Expanded Disability Status Scale (EDSS), Nine-Hole Peg Test (9-HPT), Jebsen-Taylor Hand Function Test (JTHFT), and 2-point discrimination (2PD) was evaluated. To analyze grip force control, blindfolded subjects held a receptacle equipped with grip force and acceleration sensors in their hand. In a catching task, a weight was dropped from (1) the experimenter's hand unexpectedly into the receptacle (reactive force control); and (2) from the subject's opposite hand (predictive force control). Grip forces and time lags were analyzed. PwMS (mean EDSS ± SD, 4.2±1.86) had impairments in the 9-HPT and JTHFT (P<.001). The 2PD did not differ significantly between PwMS and controls. During reactive force control (catching task 1), PwMS showed significantly higher grip forces immediately after impact (P<.05), and a significant prolongation of the time from grip force increase until reaching the peak of grip force (P<.001). PwMS and controls did not differ during predictive force control (catching task 2; P>.1). Exaggerated grip force responses and alterations of timing after an unpredictable perturbation, combined with preserved grip force control during predictable conditions, is a characteristic pattern of fine motor control deficits in MS. Measures of reactive grip force responses may be used to complement neurologic assessments. Further studies exploring the usefulness of these measures should be performed in a broader community of PwMS. Copyright © 2016 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

A device for testing the dynamic performance of in situ force plates.

PubMed

East, Rebecca H; Noble, Jonathan J; Arscott, Richard A; Shortland, Adam P

2017-09-01

Force plates are often incorporated into motion capture systems for the calculation of joint kinetic variables and other data. This project aimed to create a system that could be used to check the dynamic performance of force plate in situ. The proposed solution involved the design and development of an eccentrically loaded wheel mounted on a weighted frame. The frame was designed to hold a wheel mounted in two orthogonal positions. The wheel was placed on the force plate and spun. A VICON™ motion analysis system captured the positional data of the markers placed around the rim of the wheel which was used to create a simulated force profile, and the force profile was dependent on spin speed. The root mean square error between the simulated force profile and the force plate measurement was calculated. For nine trials conducted, the root mean square error between the two simultaneous measures of force was calculated. The difference between the force profiles in the x- and y-directions is approximately 2%. The difference in the z-direction was under 0.5%. The eccentrically loaded wheel produced a predictable centripetal force in the plane of the wheel which varied in direction as the wheel was spun and magnitude dependent on the spin speed. There are three important advantages to the eccentrically loaded wheel: (1) it does not rely on force measurements made from other devices, (2) the tests require only 15 min to complete per force plate and (3) the forces exerted on the plate are similar to those of paediatric gait.

Instrumented Static and Dynamic Balance Assessment after Stroke Using Wii Balance Boards: Reliability and Association with Clinical Tests

PubMed Central

Bower, Kelly J.; McGinley, Jennifer L.; Miller, Kimberly J.; Clark, Ross A.

2014-01-01

Background and Objectives The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Methods Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. Results All WBB-based outcomes were found to be highly reliable between testing occasions (ICC  = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. Conclusions The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness. PMID:25541939

Instrumented static and dynamic balance assessment after stroke using Wii Balance Boards: reliability and association with clinical tests.

PubMed

Bower, Kelly J; McGinley, Jennifer L; Miller, Kimberly J; Clark, Ross A

2014-01-01

The Wii Balance Board (WBB) is a globally accessible device that shows promise as a clinically useful balance assessment tool. Although the WBB has been found to be comparable to a laboratory-grade force platform for obtaining centre of pressure data, it has not been comprehensively studied in clinical populations. The aim of this study was to investigate the measurement properties of tests utilising the WBB in people after stroke. Thirty individuals who were more than three months post-stroke and able to stand unsupported were recruited from a single outpatient rehabilitation facility. Participants performed standardised assessments incorporating the WBB and customised software (static stance with eyes open and closed, static weight-bearing asymmetry, dynamic mediolateral weight shifting and dynamic sit-to-stand) in addition to commonly employed clinical tests (10 Metre Walk Test, Timed Up and Go, Step Test and Functional Reach) on two testing occasions one week apart. Test-retest reliability and construct validity of the WBB tests were investigated. All WBB-based outcomes were found to be highly reliable between testing occasions (ICC  = 0.82 to 0.98). Correlations were poor to moderate between WBB variables and clinical tests, with the strongest associations observed between task-related activities, such as WBB mediolateral weight shifting and the Step Test. The WBB, used with customised software, is a reliable and potentially useful tool for the assessment of balance and weight-bearing asymmetry following stroke. Future research is recommended to further investigate validity and responsiveness.

Applying a pelvic corrective force induces forced use of the paretic leg and improves paretic leg EMG activities of individuals post-stroke during treadmill walking.

PubMed

Hsu, Chao-Jung; Kim, Janis; Tang, Rongnian; Roth, Elliot J; Rymer, William Z; Wu, Ming

2017-10-01

To determine whether applying a mediolateral corrective force to the pelvis during treadmill walking would enhance muscle activity of the paretic leg and improve gait symmetry in individuals with post-stroke hemiparesis. Fifteen subjects with post-stroke hemiparesis participated in this study. A customized cable-driven robotic system based over a treadmill generated a mediolateral corrective force to the pelvis toward the paretic side during early stance phase. Three different amounts of corrective force were applied. Electromyographic (EMG) activity of the paretic leg, spatiotemporal gait parameters and pelvis lateral displacement were collected. Significant increases in integrated EMG of hip abductor, medial hamstrings, soleus, rectus femoris, vastus medialis and tibialis anterior were observed when pelvic corrective force was applied, with pelvic corrective force at 9% of body weight inducing greater muscle activity than 3% or 6% of body weight. Pelvis lateral displacement was more symmetric with pelvic corrective force at 9% of body weight. Applying a mediolateral pelvic corrective force toward the paretic side may enhance muscle activity of the paretic leg and improve pelvis displacement symmetry in individuals post-stroke. Forceful weight shift to the paretic side could potentially force additional use of the paretic leg and improve the walking pattern. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Weight, the Normal Force and Newton's Third Law: Dislodging a Deeply Embedded Misconception

ERIC Educational Resources Information Center

Low, David; Wilson, Kate

2017-01-01

On entry to university, high-achieving physics students from all across Australia struggle to identify Newton's third law force pairs. In particular, less than one in ten can correctly identify the Newton's third law reaction pair to the weight of (gravitational force acting on) an object. Most students incorrectly identify the normal force on the…

Terms vs. Concepts - The Case of Weight

NASA Astrophysics Data System (ADS)

Taibu, Rex

2017-01-01

Terminological and conceptual issues surrounding the definition of scientific terms have bothered teachers and students for many years. Some terms such as energy are not even usually defined, although they appear in different contexts of scientific communication, and others such as weight have debatable definitions, and for this reason the term weight is a great example to demonstrate general issues regarding terms and concepts. The term weight is defined in different ways, e.g., as the gravitational force or operationally as the force exerted by the body on its support. In an inertial situation, the magnitude of the gravitational force is equal to that of the support force. However, the two meanings are distinct when the object is in an accelerating situation (e.g., an accelerating elevator or on the surface of a rotating planet). Apart from these dichotomous definitions of weight, there are further language problems associated with each gravitational and operational definition of weight. This paper demonstrates these issues and asserts that arguing for which definition of weight is correct is not a viable approach to solve the language issue. The paper proposes an alternative route to deal with language issues facing weight and other related terms.

Ensemble average theory of gravity

NASA Astrophysics Data System (ADS)

Khosravi, Nima

2016-12-01

We put forward the idea that all the theoretically consistent models of gravity have contributions to the observed gravity interaction. In this formulation, each model comes with its own Euclidean path-integral weight where general relativity (GR) has automatically the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of the f (R ,G ) model. This specific f (R ,G ) satisfies the stability conditions and possesses self-accelerating solutions. Our model is consistent with the local tests of gravity since its behavior is the same as in GR for the high-curvature regime. In the low-curvature regime the gravitational force is weaker than in GR, which can be interpreted as the existence of a repulsive fifth force for very large scales. Interestingly, there is an intermediate-curvature regime where the gravitational force is stronger in our model compared to GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes makes it observationally distinguishable from Λ CDM .

A proposed method for determining peak power in the jump squat exercise.

PubMed

Li, Li; Olson, Michael W; Winchester, Jason B

2008-03-01

In recent years a great deal of research has been published using peak power (PP) in the jump squat (JS) exercise as a measure of athletic performance. However, no standardized method for the determination of PP exists at this time to accurately evaluate this variable. Our proposed method (PM) for determining PP (PPPM) in the JS uses the product of vertical ground reaction forces and velocity of the center of mass of both the subject and the external resistance of a loaded Olympic bar. Fifteen male subjects with a mean age of 27 +/- 3 years, weight of 78 +/- 17 kg, and height of 175 +/- 10 cm participated in this study. PP was measured in the JS at five different testing loads (30%, 35%, 40%, 45%, and 50% body weight) based on methods commonly discussed in the literature to compare PP results of previous methods to those obtained using the PM. Paired t-tests at different load levels were used for statistical analysis with an overall alpha = 0.05. The average PP among five testing loads, measured by the PM, was 3782 +/- 906 W. PP derived from the product of force and velocity of the bar alone was 72% lower than PPPM at 1057 +/- 243 W (P < 0.0001). The PP estimated by the product of bar velocity and vertical ground reaction forces of the bar plus the subject was 8% higher than PPPM at 4100 +/- 844 W (P = 0.0001). Our results indicate that using the methods traditionally reported in the literature may cause an overestimation of PP during athletic performance. Using the PM in future research will facilitate test validity and enable the generalization of results outside the scope of specific research projects.

[Walking with canes and forearm-crutches (author's transl)].

PubMed

Bergmann, G; Kölbel, R; Rauschenbach, N; Rohlmann, A

1978-02-01

Partial weight bearing is frequently prescribed but cannot be controlled adequately. In a previous paper the change of forces at the hip joint as effected by a one sided cane was determined by instrumentation of the cane and a mechanical analysis of gait on a walkway. In the present study we looked at the conditions for control of partial weightbearing when two forearm crutches are used. Instrumented crutches and a forceplate were used. In walking with two forearm crutches the total of the ground reaction forces and the force pattern differ from those in free walking. The total of two crutch forces plus the force at the leg with partial weightbearing exceeds that caused by body weight alone. This is due to mass accelerations in a changed gait pattern. When the maximal leg force is reduced from 100% body weight to zero, the additional dynamic forces exceed those caused by body weight alone by 4%-19%. Only 2% of the additional dynamic forces act on the controlateral crutch while the rest is transmitted through the ipsilateral crutch. The crutch force pattern on the ipsilateral side depends more on individual gait characteristics than does that on the controlateral side. Load reduction is more pronounced in the late stages of the stand phase than in the early ones.

Rehabilitation Tool

NASA Technical Reports Server (NTRS)

1993-01-01

Biotran, or Fastex as named by Cybex, the company that manufactures it, is a force sensing system that helps physicians and physical therapists treat people with movement deficiencies. Based on NASA sensor technology, it also has applications in sports training and evaluation. Biotran provides a means of testing weight-bearing capabilities that may have been compromised by injury or disease. It also assists in the rehabilitation process by putting patients through a course of computer-directed exercises designed to improve strength and balance reaction time. The system tests and documents progress until maximum medical improvement is achieved. Lewis Research Center also assisted the company in the selection of the material used in the Biotran force sensing platforms. Biotran is currently manufactured by Cybex under the name Fastex.

Validity and reliability of a controlled pneumatic resistance exercise device.

PubMed

Paulus, David C; Reynolds, Michael C; Schilling, Brian K

2008-01-01

During the concentric portion of the free-weight squat exercise, accelerating the mass from rest results in a fluctuation in ground reaction force. It is characterized by an initial period of force greater than the load while accelerating from rest followed by a period of force lower than the external load during negative acceleration. During the deceleration phase, less force is exerted and muscles are loaded sub-optimally. Thus, using a reduced inertia form of resistance such as pneumatics has the capability to minimize these inertial effects as well as control the force in real time to maximize the force exerted over the exercise cycle. To improve the system response of a preliminary design, a squat device was designed with a reduced mass barbell and two smaller pneumatic cylinders. The resistance was controlled by regulating cylinder pressure such that it is capable of adjusting force within a repetition to maximize force exerted during the lift. The resistance force production of the machine was statically validated with the input voltage and output force R2 =0.9997 for at four increments of the range of motion, and the intraclass correlation coefficient (ICC) between trials at the different heights equaled 0.999. The slew rate at three forces was 749.3 N/s +/- 252.3. Dynamic human subject testing showed the desired input force correlated with average and peak ground reaction force with R2 = 0.9981 and R2 = 0.9315, respectively. The ICC between desired force and average and peak ground reaction force was 0.963. Thus, the system is able to deliver constant levels of static and dynamic force with validity and reliability. Future work will be required to develop the control strategy required for real-time control, and performance testing is required to determine its efficacy.

Elegant Shadow Making Tiny Force Visible for Water-Walking Arthropods and Updated Archimedes' Principle.

PubMed

Zheng, Yelong; Lu, Hongyu; Yin, Wei; Tao, Dashuai; Shi, Lichun; Tian, Yu

2016-10-07

Forces acted on legs of water-walking arthropods with weights in dynes are of great interest for entomologist, physicists, and engineers. While their floating mechanism has been recognized, the in vivo leg forces stationary have not yet been simultaneously achieved. In this study, their elegant bright-edged leg shadows are used to make the tiny forces visible and measurable based on the updated Archimedes' principle. The force was approximately proportional to the shadow area with a resolution from nanonewton to piconewton/pixel. The sum of leg forces agreed well with the body weight measured with an accurate electronic balance, which verified updated Archimedes' principle at the arthropod level. The slight changes of vertical body weight focus position and the body pitch angle have also been revealed for the first time. The visualization of tiny force by shadow is cost-effective and very sensitive and could be used in many other applications.

Factors predicting weight-bearing asymmetry 1month after unilateral total knee arthroplasty: a cross-sectional study.

PubMed

Christiansen, Cory L; Bade, Michael J; Weitzenkamp, David A; Stevens-Lapsley, Jennifer E

2013-03-01

Factors predicting weight-bearing asymmetry (WBA) after unilateral total knee arthroplasty (TKA) are not known. However, identifying modifiable and non-modifiable predictors of WBA is needed to optimize rehabilitation, especially since WBA is negatively correlated to poor functional performance. The purpose of this study was to identify factors predictive of WBA during sit-stand transitions for people 1month following unilateral TKA. Fifty-nine people were tested preoperatively and 1month following unilateral TKA for WBA using average vertical ground reaction force under each foot during the Five Times Sit-to-Stand Test. Candidate variables tested in the regression analysis represented physical impairments (strength, muscle activation, pain, and motion), demographics, anthropometrics, and movement compensations. WBA, measured as the ratio of surgical/non-surgical limb vertical ground reaction force, was 0.69 (0.18) (mean (SD)) 1month after TKA. Regression analysis identified preoperative WBA (β=0.40), quadriceps strength ratio (β=0.31), and hamstrings strength ratio (β=0.19) as factors predictive of WBA 1month after TKA (R(2)=0.30). Greater amounts of WBA 1month after TKA are predicted by modifiable factors including habitual movement pattern and asymmetry in quadriceps and hamstrings strength. Copyright © 2012 Elsevier B.V. All rights reserved.

Teaching weight to explicitly address language ambiguities and conceptual difficulties

NASA Astrophysics Data System (ADS)

Taibu, Rex; Schuster, David; Rudge, David

2017-06-01

Language ambiguities in concept meanings can exacerbate student learning difficulties and conceptual understanding of physics concepts. This is especially true for the concept of "weight," which has multiple meanings in both scientific and everyday usage. The term weight has been defined in several different ways, with nuances, but in textbooks and teaching the term is almost always defined in one of two ways: operationally either as the contact force between an object and a measuring scale or as the gravitational force on an object due to some other body such as Earth. The use of the same name for different concepts leads to much confusion, especially in accelerating situations, and to conflicting notions of "weightlessness" in free fall situations. In the present paper, we share an innovative approach that initially avoids the term weight entirely while teaching the physics of each situation, and then teaches the language ambiguities explicitly. We developed an instructional module with this approach and implemented it over two terms in three sections of an introductory physics course for preservice elementary teachers. Learning gains for content understanding were assessed using pretests and post-tests. Participants achieved remarkably high gains for both static and accelerating situations. Surveys pre- and postinstruction showed substantially improved appreciation of language issues and ambiguities associated with weight, weightlessness, and free fall. Interviews with instructors teaching the module provided additional insight into the advantages and teaching demands of the new approach.

Balance and postural skills in normal-weight and overweight prepubertal boys.

PubMed

Deforche, Benedicte I; Hills, Andrew P; Worringham, Charles J; Davies, Peter S W; Murphy, Alexia J; Bouckaert, Jacques J; De Bourdeaudhuij, Ilse M

2009-01-01

This study investigated differences in balance and postural skills in normal-weight versus overweight prepubertal boys. Fifty-seven 8-10-year-old boys were categorized overweight (N = 25) or normal-weight (N = 32) according to the International Obesity Task Force cut-off points for overweight in children. The Balance Master, a computerized pressure plate system, was used to objectively measure six balance skills: sit-to-stand, walk, step up/over, tandem walk (walking on a line), unilateral stance and limits of stability. In addition, three standardized field tests were employed: standing on one leg on a balance beam, walking heel-to-toe along the beam and the multiple sit-to-stand test. Overweight boys showed poorer performances on several items assessed on the Balance Master. Overweight boys had slower weight transfer (p < 0.05), lower rising index (p < 0.05) and greater sway velocity (p < 0.001) in the sit-to-stand test, greater step width while walking (p < 0.05) and lower speed when walking on a line (p < 0.01) compared with normal-weight counterparts. Performance on the step up/over test, the unilateral stance and the limits of stability were comparable between both groups. On the balance beam, overweight boys could not hold their balance on one leg as long (p < 0.001) and had fewer correct steps in the heel-to-toe test (p < 0.001) than normal-weight boys. Finally, overweight boys were slower in standing up and sitting down five times in the multiple sit-to-stand task (p < 0.01). This study demonstrates that when categorised by body mass index (BMI) level, overweight prepubertal boys displayed lower capacity on several static and dynamic balance and postural skills.

Comparison of two different rehabilitation programmes for thrust plate prosthesis: a randomized controlled study.

PubMed

Unver, Bayram; Karatosun, Vasfi; Gunal, Izge; Angin, Salih

2004-02-01

Weight bearing after total hip arthroplasty is postponed in order to prevent early loosening, but this negatively affects the rehabilitation programme. For the force transfer characteristics of thrust plate prosthesis (TPP), a new type of hip prosthesis used without cement is similar to the normal hip. We evaluated the possibilities of early weight bearing after TPP by comparing early partial with early full weight bearing. Randomized controlled study. Department of orthopaedics and traumatology in a university hospital. Sixty hips of 51 patients who underwent total hip arthroplasty with TPP were randomly assigned into two groups. Both groups received accelerated rehabilitation programmes: group 1 with early partial weight bearing and group 2 with early full weight bearing. Patients were evaluated by a blind observer preoperatively, at three months after surgery by clinical (measurement of range of hip motion (universal goniometry), muscle strength (Manual Muscle Test), functional test (6-minute walk test), hip function (Harris Hip Scoring System)) and radiographical parameters and one year after surgery by clinical (Harris Hip Scoring System) and radiographical parameters. Group 2 performed transfer activities earlier, had more walking distance at the time of discharge and shorter hospital stay than group 1. At three months, Harris Hip Score, muscle strength, 6-minute walk test, and duration of crutch use were significantly (p < 0.05) in favour of group 2. None of the patients in either group showed signs of loosening one year after the operation. These results suggest that patients with TPP can tolerate an accelerated rehabilitation programme with early weight bearing and will gain the goals of rehabilitation earlier.

Buckling analysis and test correlation of hat stiffened panels for hypersonic vehicles

NASA Technical Reports Server (NTRS)

Percy, Wendy C.; Fields, Roger A.

1990-01-01

The paper discusses the design, analysis, and test of hat stiffened panels subjected to a variety of thermal and mechanical load conditions. The panels were designed using data from structural optimization computer codes and finite element analysis. Test methods included the grid shadow moire method and a single gage force stiffness method. The agreement between the test data and analysis provides confidence in the methods that are currently being used to design structures for hypersonic vehicles. The agreement also indicates that post buckled strength may potentially be used to reduce the vehicle weight.

Strength Performance Assessment in a Simulated Men’s Gymnastics Still Rings Cross

PubMed Central

Dunlavy, Jennifer K.; Sands, William A.; McNeal, Jeni R.; Stone, Michael H.; Smith, Sarah L.; Jemni, Monem; Haff, G. Gregory

2007-01-01

Athletes in sports such as the gymnastics who perform the still rings cross position are disadvantaged due to a lack of objective and convenient measurement methods. The gymnastics “cross ”is a held isometric strength position considered fundamental to all still rings athletes. The purpose of this investigation was to determine if two small force platforms (FPs) placed on supports to simulate a cross position could demonstrate the fidelity necessary to differentiate between athletes who could perform a cross from those who could not. Ten gymnasts (5 USA Gymnastics, Senior National Team, and 5 Age Group Level Gymnasts) agreed to participate. The five Senior National Team athletes were grouped as cross Performers; the Age Group Gymnasts could not successfully perform the cross position and were grouped as cross Non- Performers. The two small FPs were first tested for reliability and validity and were then used to obtain a force-time record of a simulated cross position. The simulated cross test consisted of standing between two small force platforms placed on top of large solid gymnastics spotting blocks. The gymnasts attempted to perform a cross position by placing their hands at the center of the FPs and pressing downward with sufficient force that they could remove the support of their feet from the floor. Force-time curves (100 Hz) were obtained and analyzed for the sum of peak and mean arm ground reaction forces. The summed arm forces, mean and peak, were compared to body weight to determine how close the gymnasts came to achieving forces equal to body weight and thus the ability to perform the cross. The mean and peak summed arm forces were able to statistically differentiate between athletes who could perform the cross from those who could not (p < 0.05). The force-time curves and small FPs showed sufficient fidelity to differentiate between Performer and Non- Performer groups. This experiment showed that small and inexpensive force platforms may serve as useful adjuncts to athlete performance measurement such as the gymnastics still rings cross. Key pointsStrength-related skills are difficult to assess in some sports and thus require special means.Small force platforms have sufficient fidelity to assess the differences between gymnasts who can perform a still rings cross from those who cannot.Strength assessment via small force platforms may serve as a means of assessing skill readiness, strength symmetry, and progress in learning a still rings cross. PMID:24149230

Toxicological analysis and antihyperalgesic, antidepressant, and anti-inflammatory effects of Campomanesia adamantium fruit barks.

PubMed

de Souza, Juliane C; Piccinelli, Ana Cláudia; Aquino, Diana F S; de Souza, Vanessa V; Schmitz, Wanderlei O; Traesel, Giseli K; Cardoso, Claudia A L; Kassuya, Candida A L; Arena, Arielle C

2017-01-01

This study evaluates the anti-inflammatory, antihyperalgesic, and antidepressive potential of the hydroalcoholic extract of Campomanesia adamantium fruit barks (CAE) on rodents and determines the safety of this plant. The acute toxicity of CAE was evaluated by oral administration to female rats as single doses of 0, 500, 1000, or 2000 mg/kg body weight. General behavior and toxic symptoms were observed for 14 days. In the subacute toxicity test, male and female rats received 125 or 250 mg/kg body weight of CAE for 28 days. The oral anti-inflammatory activity of CAE was evaluated in carrageenan-induced pleurisy in male mice. The effect of treatment with CAE (100 mg/kg) for 15 days was evaluated in mechanical hyperalgesia (electronic von Frey), depressive behavior (forced swimming test), and cold hypersensitivity in spared nerve injury (SNI) model in rats. No clinical signs of toxicity were observed in animals from the experimental groups during acute and subacute exposure to CAE. At pleurisy test, the oral administration of CAE significantly inhibited leukocyte migration and protein leakage at all doses tested when compared to control. Oral administration of CAE for 3-15 days significantly inhibited SNI-induced mechanical hyperalgesia and increased immobility in the forced swim test. Finally, on the 15th day, oral treatment with CAE prevented the increase in sensitivity to a cold stimulus induced by SNI. The present study shows that C. adamantium extract has anti-inflammatory, antihyperalgesic, and antidepressive properties in rodents without causing toxicity.

Force Rendering and its Evaluation of a Friction-Based Walking Sensation Display for a Seated User.

PubMed

Kato, Ginga; Kuroda, Yoshihiro; Kiyokawa, Kiyoshi; Takemura, Haruo

2018-04-01

Most existing locomotion devices that represent the sensation of walking target a user who is actually performing a walking motion. Here, we attempted to represent the walking sensation, especially a kinesthetic sensation and advancing feeling (the sense of moving forward) while the user remains seated. To represent the walking sensation using a relatively simple device, we focused on the force rendering and its evaluation of the longitudinal friction force applied on the sole during walking. Based on the measurement of the friction force applied on the sole during actual walking, we developed a novel friction force display that can present the friction force without the influence of body weight. Using performance evaluation testing, we found that the proposed method can stably and rapidly display friction force. Also, we developed a virtual reality (VR) walk-through system that is able to present the friction force through the proposed device according to the avatar's walking motion in a virtual world. By evaluating the realism, we found that the proposed device can represent a more realistic advancing feeling than vibration feedback.

Effects of bedding systems selected by manual muscle testing on sleep and sleep-related respiratory disturbances.

PubMed

Tsai, Ling-Ling; Liu, Hau-Min

2008-03-01

In this study, we investigated the feasibility of applying manual muscle testing (MMT) for bedding selection and examined the bedding effect on sleep. Four lay testers with limited training in MMT performed muscle tests for the selection of the bedding systems from five different mattresses and eight different pillows for 14 participants with mild sleep-related respiratory disturbances. For each participant individually, two bedding systems-one inducing stronger muscle forces and the other inducing weaker forces-were selected. The tester-participant pairs showed 85% and 100% agreement, respectively, for the selection of mattresses and pillows that induced the strongest muscle forces. The firmness of the mattress and the height of the pillow were significantly correlated with the body weight and body mass index of the participants for the selected strong bedding system but not for the weak bedding system. Finally, differences were observed between the strong and the weak bedding systems with regard to sleep-related respiratory disturbances and the percentage of slow-wave sleep. It was concluded that MMT can be performed by inexperienced testers for the selection of bedding systems.

Textbook Presentations of Weight: Conceptual Difficulties and Language Ambiguities

ERIC Educational Resources Information Center

Taibu, Rex; Rudge, David; Schuster, David

2015-01-01

The term "weight" has multiple related meanings in both scientific and everyday usage. Even among experts and in textbooks, weight is ambiguously defined as either the gravitational force on an object or operationally as the magnitude of the force an object exerts on a measuring scale. This poses both conceptual and language difficulties…

Weight simulator

NASA Technical Reports Server (NTRS)

Howard, W. H.; Young, D. R.

1972-01-01

Device applies compressive force to bone to minimize loss of bone calcium during weightlessness or bedrest. Force is applied through weights, or hydraulic, pneumatic or electrically actuated devices. Device is lightweight and easy to maintain and operate.

Validity of a jump training apparatus using Wii Balance Board.

PubMed

Yamamoto, Keizo; Matsuzawa, Mamoru

2013-05-01

The dynamic quantification of jump ability is useful for sports performance evaluation. We developed a force measurement system using the Wii Balance Board (WBB). This study was conducted to validate the system in comparison with a laboratory-grade force plate (FP). For a static validation, weights of 10-180kg were put progressively on the WBB put on the FP. The vertical component of the ground reaction force (vGRF) was measured using both devices and compared. For the dynamic validation, 10 subjects without lower limb pathology participated in the study and performed vertical jumping twice on the WBB on the FP. The range of analysis was set from the landing after the first jump to taking off of the second jump. The peak values during the landing phase and jumping phase were obtained and the force-time integral (force impulse) was measured. The relations of the values measured using each device were compared using Pearson's correlation coefficient test and Bland-Altman plots (BAP). Significant correlation (P<.01, r=.99) was found between the values of both devices in the static and the dynamic test. Examination of the BAP revealed a proportion error in the landing phase and showed no relation in the jumping phase between the difference and the mean in the dynamic test. The WBB detects the vGRF in the jumping phase with high precision. Copyright © 2012 Elsevier B.V. All rights reserved.

The effectiveness of body weight-supported gait training and floor walking in patients with chronic stroke.

PubMed

Peurala, Sinikka H; Tarkka, Ina M; Pitkänen, Kauko; Sivenius, Juhani

2005-08-01

To compare body weight-supported exercise on a gait trainer with walking exercise overground. Randomized controlled trial. Rehabilitation hospital. Forty-five ambulatory patients with chronic stroke. Patients were randomized to 3 groups: (1) gait trainer exercise with functional electric stimulation (GTstim), (2) gait trainer exercise without stimulation (GT), and (3) walking overground (WALK). All patients practiced gait for 15 sessions during 3 weeks (each session, 20 min), and they received additional physiotherapy 55 minutes daily. Ten-meter walk test (10MWT), six-minute walk test (6MWT), lower-limb spasticity and muscle force, postural sway tests, Modified Motor Assessment Scale (MMAS), and FIM instrument scores were recorded before, during, and after the rehabilitation and at 6 months follow-up. The mean walking distance using the gait trainer was 6900+/-1200 m in the GTstim group and 6500+/-1700 m in GT group. In the WALK group, the distance was 4800+/-2800 m, which was less than the walking distance obtained in the GTstim group (P=.027). The body-weight support was individually reduced from 30% to 9% of the body weight over the course of the program. In the pooled 45 patients, the 10MWT (P<.001), 6MWT (P<.001), MMAS (P<.001), dynamic balance test time (P<.001), and test trip (P=.005) scores improved; however, no differences were found between the groups. Both the body weight-supported training and walking exercise training programs resulted in faster gait after the intensive rehabilitation program. Patients' motor performance remained improved at the follow-up.

Vacuum-Assisted, Constant-Force Exercise Device

NASA Technical Reports Server (NTRS)

Hansen, Christopher P.; Jensen, Scott

2006-01-01

The vacuum-assisted, constant-force exercise device (VAC-FED) has been proposed to fill a need for a safe, reliable exercise machine that would provide constant loads that could range from 20 to 250 lb (0.09 to 1.12 kN) with strokes that could range from 6 to 36 in. (0.15 to 0.91 m). The VAC-FED was originally intended to enable astronauts in microgravity to simulate the lifting of free weights, but it could just as well be used on Earth for simulated weight lifting and other constant-force exercises. Because the VAC-FED would utilize atmospheric/vacuum differential pressure instead of weights to generate force, it could weigh considerably less than either a set of free weights or a typical conventional exercise machine based on weights. Also, the use of atmospheric/ vacuum differential pressure to generate force would render the VAC-FED inherently safer, relative to free weights and to conventional exercise machines that utilize springs to generate forces. The overall function of the VAC-FED would be to generate a constant tensile force in an output cable, which would be attached to a bar, handle, or other exercise interface. The primary force generator in the VAC-FED would be a piston in a cylinder. The piston would separate a volume vented to atmosphere at one end of the cylinder from an evacuated volume at the other end of the cylinder (see figure). Hence, neglecting friction at the piston seals, the force generated would be nearly constant equal to the area of the piston multiplied by the atmospheric/vacuum differential pressure. In the vented volume in the cylinder, a direct-force cable would be looped around a pulley on the piston, doubling the stroke and halving the tension. One end of the direct-force cable would be anchored to a cylinder cap; the other end of the direct-force cable would be wrapped around a variable-ratio pulley that would couple tension to the output cable. As its name suggests, the variable-ratio pulley would contain a mechanism that could be used to vary the ratio between the tension in the direct-force cable and the tension in the output cable. This mechanism could contain gears, pulleys, and/or levers, for example.

Gastroesophageal Reflux: Regurgitation in the Infant Population.

PubMed

Ferguson, Teresa D

2018-03-01

Gastroesophageal reflux (GER) is common in infancy and mainly treated through nonpharmacological interventions. Knowing the early warning signs of GER is important for nursing assessment. Untreated GER can become acute when an infant fails to gain weight and has recurrent, forceful vomiting. Further investigation of gastroesophageal reflux disease (GERD) is indicated when failure to gain weight, irritability, swallowing difficulties, regurgitation, and respiratory complications occur and should trigger referral to pediatric specialists. This article will share information about uncomplicated GER, GERD, and symptoms of these diagnoses, common screening tests, and treatment options. Copyright © 2017 Elsevier Inc. All rights reserved.

KSC-99pc0143

NASA Image and Video Library

1999-01-28

As part of X-33 launch equipment testing at Edwards Air Force Base, CA, the KSC-developed X-33 weight simulator (top), known as the "iron bird," is lifted to a vertical position at the X-33 launch site. The simulator matches the 75,000-pound weight and 63-foot height of the X-33 vehicle that will be using the launch equipment. KSC's Vehicle Positioning System (VPS) placed the simulator on the rotating launch platform prior to the rotation. The new VPS will dramatically reduce the amount of manual labor required to position a reusable launch vehicle for liftoff

Experimental research on anchoring force in intestine for the motion of capsule robot.

PubMed

Chen, Wenwen; Ke, Quan; He, Shu; Luo, Weijie; Ji, Xing Chun; Yan, Guozheng

2013-07-01

Multiple research groups are currently attempting to develop less-invasive robotic capsule endoscopes (RCEs) with better outcomes for enteroscopic procedures. Understanding the biomechanical response of the bowel to RCE is crucial for optimizing the design of these devices. For this reason, this study aims to develop an analytical model to predict the anchoring force of the model when travelling through the intestine. Previous work has developed, characterized and tested the frictional characteristics of the intestine with microgroove structures that had different surface contours. This work tested basic anchoring force characteristics with custom-built testers and clamping mechanism dummies to analyse the robot clamping movement (which is vital to improving movement efficiency). Balloon-shaped and leg-based clamping mechanisms were developed, which were found to have variable anchoring forces from 0.01 N to 1.2 N. After analysing the experimental results it was found that: (a) robot weight does not play a major role in anchoring force; (b) an increase in anchoring force corresponded to an increase in diameter of the clamping mechanism; and (c) textured contact surfaces effectively increased friction. These results could be explained by the biomechanical response of the intestine, friction and mucoadhesion characteristics of the small intestine material. With these factors considered, a model was developed for determining anchoring force in the small intestine.

An examination of the damage tolerance enhancement of carbon/epoxy using an outer lamina of spectra (R)

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1991-01-01

Low velocity instrumented impact testing was utilized to examine the effects of an outer lamina of ultra-high molecular weight polyethylene (Spectra) on the damage tolerance of carbon epoxy composites. Four types of 16-ply quasi-isotropic panels (0, +45, 90, -45) were tested. Some panels contained no Spectra, while others had a lamina of Spectra bonded to the top (impacted side), bottom, or both sides of the composite plates. The specimens were impacted with energies up to 8.5 J. Force time plots and maximum force versus impact energy graphs were generated for comparison purposes. Specimens were also subjected to cross-sectional analysis and compression after impact tests. The results show that while the Spectra improved the maximum load that the panels could withstand before fiber breakage, the Spectra seemingly reduced the residual strength of the composites.

Primary lithium-thionyl chloride cell evaluation

NASA Astrophysics Data System (ADS)

Zolla, A. E.; Waterhouse, R.; Debiccari, D.; Griffin, G. L.

1980-08-01

A test program was conducted to evaluate the Altus 1350AH cell performance against the Minuteman Survival Ground Power requirements. Twelve cells of the 17 inch diameter, 1-3/8 inch heights were fabricated and tested during this study. Under discharge rates varying from C/100 to C/400 at ambient temperature, the volumetric and gravimetric energy density performance requirements of 15 watt hours per cubic inch and 150 watt hours per pound were exceeded in all cases. All other performance requirements of voltage, current, configuration, capacity volume, weight, electrolyte leakage (none), and maintainability (none required), were met or exceeded. The abuse testing demonstrated the Altus Cell's ability to safely withstand short circuit by external shorting, short circuit by penetration with a conductive object, forced discharge, and forced charging of a cell. Disposal of discharged cells by incineration is an environmentally safe and efficient method of disposal.

OH-13H Gross Weight Increase/XM-1 Armament Kit Performance Test

DTIC Science & Technology

1963-06-01

in hovering performance beyond thai obtained in the Air Force Performance lest of the 0H-I3H, de - scribed in MFFTC-TR...The airspeed schedule used during the climbs was the same as that developed during the OH-!3H performance test de - sci iüed in AFrrC-TR-57-12...siight de - crease in control response was indicated by a small amount of feedback through the unboosted collective stick. Level Flight

Fine motor skills predict performance in the Jebsen Taylor Hand Function Test after stroke.

PubMed

Allgöwer, Kathrin; Hermsdörfer, Joachim

2017-10-01

To determine factors characterizing the differences in fine motor performance between stroke patients and controls. To confirm the relevance of the factors by analyzing their predictive power with regard to the Jebsen Taylor Hand Function Test (JTHFT), a common clinical test of fine motor control. Twenty-two people with slight paresis in an early chronic phase following stroke and twenty-two healthy controls were examined. Performance on the JTHFT, Nine-Hole Peg Test and 2-point discrimination was evaluated. To analyze object manipulation skills, grip forces and temporal measures were examined during (1) lifting actions with variations of weight and surface (2) cyclic movements (3) predictive/reactive catching tasks. Three other aspects of force control included (4) visuomotor tracking (5) fast force changes and (6) grip strength. Based on 9 parameters which significantly distinguished fine motor performance in the two groups, we identified three principal components (factors): grip force scaling, motor coordination and speed of movement. The three factors are shown to predict JTHFT scores via linear regression (R 2 =0.687, p<0.001). We revealed a factor structure behind fine motor impairments following stroke and showed that it explains JTHFT results to a large extend. This result can serve as a basis for improving diagnostics and enabling more targeted therapy. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Do Things Weigh More or Less in the Mountains?

ERIC Educational Resources Information Center

Besson, Ugo

2006-01-01

The notion of weight can be associated with three distinct physical quantities: the force of gravity due to the Earth; the resultant of this gravitational force and the centrifugal force arising from the Earth's rotation; and the "apparent weight in air", i.e., what is measured by a scale located in the Earth's atmosphere. Starting from…

Methods and instruments for materials testing

NASA Technical Reports Server (NTRS)

Hansma, Paul (Inventor); Drake, Barney (Inventor); Rehn, Douglas (Inventor); Adams, Jonathan (Inventor); Lulejian, Jason (Inventor)

2011-01-01

Methods and instruments for characterizing a material, such as the properties of bone in a living human subject, using a test probe constructed for insertion into the material and a reference probe aligned with the test probe in a housing. The housing is hand held or placed so that the reference probe contacts the surface of the material under pressure applied either by hand or by the weight of the housing. The test probe is inserted into the material to indent the material while maintaining the reference probe substantially under the hand pressure or weight of the housing allowing evaluation of a property of the material related to indentation of the material by the probe. Force can be generated by a voice coil in a magnet structure to the end of which the test probe is connected and supported in the magnet structure by a flexure, opposing flexures, a linear translation stage, or a linear bearing. Optionally, a measurement unit containing the test probe and reference probe is connected to a base unit with a wireless connection, allowing in the field material testing.

Compressive and shear hip joint contact forces are affected by pediatric obesity during walking

PubMed Central

Lerner, Zachary F.; Browning, Raymond C.

2016-01-01

Obese children exhibit altered gait mechanics compared to healthy-weight children and have an increased prevalence of hip pain and pathology. This study sought to determine the relationships between body mass and compressive and shear hip joint contact forces during walking. Kinematic and kinetic data were collected during treadmill walking at 1 m•s−1 in 10 obese and 10 healthy-weight 8–12 year-olds. We estimated body composition, segment masses, lower-extremity alignment, and femoral neck angle via radiographic images, created personalized musculoskeletal models in OpenSim, and computed muscle forces and hip joint contact forces. Hip extension at mid-stance was 9° less, on average, in the obese children (p<0.001). Hip abduction, knee flexion, and body-weight normalized peak hip moments were similar between groups. Normalized to body-weight, peak contact forces were similar at the first peak and slightly lower at the second peak between the obese and healthy-weight participants. Total body mass explained a greater proportion of contact force variance compared to lean body mass in the compressive (r2=0.89) and vertical shear (perpendicular to the physis acting superior-to-inferior) (r2=0.84) directions; lean body mass explained a greater proportion in the posterior shear direction (r2=0.54). Stance-average contact forces in the compressive and vertical shear directions increased by 41 N and 48 N, respectively, for every kilogram of body mass. Age explained less than 27% of the hip loading variance. No effect of sex was found. The proportionality between hip loads and body-weight may be implicated in an obese child’s increased risk of hip pain and pathology. PMID:27040390

Compressive and shear hip joint contact forces are affected by pediatric obesity during walking.

PubMed

Lerner, Zachary F; Browning, Raymond C

2016-06-14

Obese children exhibit altered gait mechanics compared to healthy-weight children and have an increased prevalence of hip pain and pathology. This study sought to determine the relationships between body mass and compressive and shear hip joint contact forces during walking. Kinematic and kinetic data were collected during treadmill walking at 1ms(-1) in 10 obese and 10 healthy-weight 8-12 year-olds. We estimated body composition, segment masses, lower-extremity alignment, and femoral neck angle via radiographic images, created personalized musculoskeletal models in OpenSim, and computed muscle forces and hip joint contact forces. Hip extension at mid-stance was 9° less, on average, in the obese children (p<0.001). Hip abduction, knee flexion, and body-weight normalized peak hip moments were similar between groups. Normalized to body-weight, peak contact forces were similar at the first peak and slightly lower at the second peak between the obese and healthy-weight participants. Total body mass explained a greater proportion of contact force variance compared to lean body mass in the compressive (r(2)=0.89) and vertical shear (perpendicular to the physis acting superior-to-inferior) (r(2)=0.84) directions; lean body mass explained a greater proportion in the posterior shear direction (r(2)=0.54). Stance-average contact forces in the compressive and vertical shear directions increased by 41N and 48N, respectively, for every kilogram of body mass. Age explained less than 27% of the hip loading variance. No effect of sex was found. The proportionality between hip loads and body-weight may be implicated in an obese child׳s increased risk of hip pain and pathology. Published by Elsevier Ltd.

The Effect of Increasing Inertia upon Vertical Ground Reaction Forces during Locomotion

NASA Technical Reports Server (NTRS)

DeWitt, John K.; Hagan, R. Donald; Cromwell, Ronita L.

2007-01-01

The addition of inertia to exercising astronauts could increase ground reaction forces and potentially provide a greater health benefit. However, conflicting results have been reported regarding the adaptations to additional mass (inertia) without additional net weight (gravitational force) during locomotion. We examined the effect of increasing inertia while maintaining net gravitational force on vertical ground reaction forces and kinematics during walking and running. Vertical ground reaction force was measured for ten healthy adults (5 male/5 female) during walking (1.34 m/s) and running (3.13 m/s) using a force-measuring treadmill. Subjects completed locomotion at normal weight and mass, and at 10, 20, 30, and 40% of added inertial force. The added gravitational force was relieved with overhead suspension, so that the net force between the subject and treadmill at rest remained equal to 100% body weight. Peak vertical impact forces and loading rates increased with increased inertia during walking, and decreased during running. As inertia increased, peak vertical propulsive forces decreased during walking and did not change during running. Stride time increased during walking and running, and contact time increased during running. Vertical ground reaction force production and adaptations in gait kinematics were different between walking and running. The increased inertial forces were utilized independently from gravitational forces by the motor control system when determining coordination strategies.

Investigation into the Effects of Textural Properties on Cuttability Performance of a Chisel Tool

NASA Astrophysics Data System (ADS)

Tumac, Deniz; Copur, Hanifi; Balci, Cemal; Er, Selman; Avunduk, Emre

2018-04-01

The main objective of this study is to investigate the effect of textural properties of stones on cutting performance of a standard chisel tool. Therewithal, the relationships between textural properties and cutting performance parameters and physical and mechanical properties were statistically analyzed. For this purpose, physical and mechanical property tests and mineralogical and petrographic analyses were carried out on eighteen natural stone samples, which can be grouped into three fundamentally different geological origins, i.e., metamorphic, igneous, and sedimentary. Then, texture coefficient analyses were performed on the samples. To determine the cuttability of the stones; the samples were cut with a portable linear cutting machine using a standard chisel tool at different depths of cut in unrelieved (non-interactive) cutting mode. The average and maximum forces (normal and cutting) and specific energy were measured, and the obtained values were correlated with texture coefficient, packing weighting, and grain size. With reference to the relation between depth of cut and cutting performance of the chisel tool for three types of natural stone groups, specific energy decreases with increasing depth of cut, and cutting forces increase in proportion to the depth of cut. The same is observed for the relationship between packing weighting and both of specific energy and cutter forces. On the other hand, specific energy and the forces decrease while grain size increases. Based on the findings of the present study, texture coefficient has strong correlation with specific energy. Generally, the lower depth of cut values in cutting tests shows higher and more reliable correlations with texture coefficient than the increased depth of cut. The results of cutting tests show also that, at a lower depth of cut (less than 1.5 mm), even stronger correlations can be observed between texture coefficient and cutting performance. Experimental studies indicate that cutting performance of chisel tools can be predicted based on texture coefficients of the natural stones.

Testing the hindlimb-strength hypothesis: non-aerial locomotion by Chiroptera is not constrained by the dimensions of the femur or tibia.

PubMed

Riskin, Daniel K; Bertram, John E A; Hermanson, John W

2005-04-01

In the evolution of flight bats appear to have suffered a trade-off; they have become poor crawlers relative to terrestrial mammals. Capable walking does occur in a few disparate taxa, including the vampire bats, but the vast majority of bats are able only to shuffle awkwardly along the ground, and the morphological bases of differences in crawling ability are not currently understood. One widely cited hypothesis suggests that the femora of most bats are too weak to withstand the compressive forces that occur during terrestrial locomotion, and that the vampire bats can walk because they possess more robust hindlimb skeletons. We tested a prediction of the hindlimb-strength hypothesis: that during locomotion, the forces produced by the hindlimbs of vampire bats should be larger than those produced by the legs of poorly crawling bats. Using force plates we compared the hindlimb forces produced by two species of vampire bats that walk well, Desmodus rotundus (N=8) and Diaemus youngi (N=2), to the hindlimb forces produced during over-ground shuffling by a similarly sized bat that is a poor walker (Pteronotus parnellii; N=6). Peak hindlimb forces produced by P. parnellii were larger (ANOVA; P<0.05; N=65) and more variable (93.5+/-36.6% body weight, mean +/- s.d.) than those of D. rotundus (69.3+/-8.1%) or D. youngi (75.0+/-6.2%). Interestingly, the vertical components of peak force were equivalent among species (P>0.6), indicating similar roles for support of body weight by the hindlimbs in the three species. We also used a simple engineering model of bending stress to evaluate the support capabilities of the hindlimb skeleton from the dimensions of 113 museum specimens in 50 species. We found that the hindlimb bones of vampires are not built to withstand larger forces than those of species that crawl poorly. Our results show that the legs of poorly crawling bats should be able to withstand the forces produced during coordinated crawling of the type used by the agile vampires, and this indicates that some mechanism other than hindlimb bone thickness, such as myology of the pectoral girdle, limits the ability of most bats to crawl.

Defining the impaction frequency and threshold force required for femoral impaction grafting in revision hip arthroplasty

PubMed Central

2011-01-01

Background and purpose The two most common complications of femoral impaction bone grafting are femoral fracture and massive implant subsidence. We investigated fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting. The study consisted of two arms, the first examining the force at which femoral fracture occurs in the embalmed human femur, and the second examining whether significant graft implant/subsidence occurs following impaction at a set force at two different impaction frequencies. Methods Using a standardized impaction grafting technique with modifications, an initial group of 17 femurs underwent complete destructive impaction testing, allowing sequentially increased, controlled impaction forces to be applied until femoral fracture occurred. A second group of 8 femurs underwent impaction bone grafting at constant force, at an impaction frequency of 1 Hz or 10 Hz. An Exeter stem was cemented into the neomedullary canals. These constructs underwent subsidence testing simulating the first 2 months of postoperative weight bearing. Results No femurs fractured below an impaction force of 0.5 kN. 15/17 of the femurs fractured at or above 1.6 kN of applied force. In the second group of 8 femurs, all of which underwent femoral impaction grafting at 1.6 kN, there was no correlation between implant subsidence and frequency of impaction. Average subsidence was 3.2 (1–9) mm. Interpretation It is possible to calculate a force below which no fracture occurs in the embalmed human femur undergoing impaction grafting. Higher impaction frequency at constant force did not reduce rates of implant subsidence in this experiment. PMID:21689068

Flexural Behavior of Aluminum Honeycomb Core Sandwich Structure

NASA Astrophysics Data System (ADS)

Matta, Vidyasagar; Kumar, J. Suresh; Venkataraviteja, Duddu; Reddy, Guggulla Bharath Kumar

2017-05-01

This project is concerned with the fabrication and flexural testing of aluminium honey comb sandwich structure which is a special case of composite materials that is fabricated by attaching two thin but stiff skins to a light weight but thick core. The core material is normally low density material but its high thickness provide the sandwich composite with high bonding stiffness. Honeycomb core are classified into two types based on the materials and structures. Hexagonal shape has a unique properties i.e has more bonding strength and less formation time based on the cell size and sheet thickness. Sandwich structure exhibit different properties such as high load bearing capacity at low weight and has excellent thermal insulation. By considering the above properties it has tendency to minimize the structural problem. So honey comb sandwich structure is choosed. The core structure has a different applications such as aircraft, ship interiors, construction industries. As there is no proper research on strength characteristics of sandwich structure. So, we use light weight material to desire the strength. There are different parameters involved in this structure i.e cell size, sheet thickness and core height. In this project we considered 3 level of comparison among the 3 different parameters cell size of 4, 6 and 8 mm, sheet thickness of 0.3, 0.5 and 0.7 mm, and core height of 20,25 and 30 mm. In order to reduce the number of experiment we use taguchi design of experiment, and we select the L8 orthogonal array is the best array for this type of situation, which clearly identifies the parameters by independent of material weight to support this we add the minitab software, to identify the main effective plots and regression equation which involves the individual response and corresponding parameters. Aluminium material is used for the fabrication of Honeycomb sandwich structure among the various grades of aluminium we consider the AL6061 which is light weight material and has more strength. By the power press used as forming method we fabricate the honey comb core and stacking the sheets with adhesive as epoxy resin or laser beam welding and sandwich structure will form with two face sheets. Then the specimen is taken to be tested to know the flexural behaviour by the flexural test as 3 point and 4 pont bend test. After testing of two different tests then we get the force vs displacement curve by this we can know the maximum force and by loading configurations and its displacement or deflection then we can calculate flexural stiffness and core shear modulus by the variation of three parameters. Our ultimate aim is to achieve maximum strength by minimum weight.

Physical fitness of overweight and underweight preschool children from southern Poland.

PubMed

Kryst, Łukasz; Woronkowicz, Agnieszka; Jankowicz-Szymańska, Agnieszka; Pociecha, Mariusz; Kowal, Małgorzata; Sobiecki, Jan; Brudecki, Janusz; Żarów, Ryszard

The main aim of this study was to assess differences in the level of physical fitness between children of preschool age with different BMI, as overweight and obesity are an increasing problem even in this age group. The study group consisted of 3,945 children aged 4 to 6 years living in southern Poland. Analysis included the results of body height and weight measurements (from which BMI was calculated) and motor skills tests: sit-and-reach test, standing broad jump and handgrip strength. Children were grouped according to the Obesity Task Force categories. Significant differences in body height were visible (i) between overweight and normal children and (ii) between overweight and underweight children. In terms of body weight and BMI, significant differences existed between all groups. With regard to fitness tests, the greatest differences were observed for handgrip strength and standing broad jump. The sit-and-reach test did not reveal any differences between the groups. The results showed that overall physical fitness was negatively correlated with relative weight; general fitness in overweight children was lower than in normal or underweight children. As it is obvious that physical activity is indispensable even for preschool children, any increase in physical activity could at least partially alleviate the problem of excessive weight and improve the general fitness of children. In the future this would reduce the incidence of diseases related to obesity and a lack of exercise.

Effect of the Addition of 3% Co in NiTi Alloy on Loading/Unloading Force

NASA Astrophysics Data System (ADS)

Phukaoluan, A.; Dechkunakorn, S.; Anuwongnukroh, N.; Khantachawana, A.; Kaewtathip, P.; Kajornchaiyakul, J.; Wichai, W.

2017-11-01

The study evaluated the loading-unloading force in the load-deflection curve of the fabricated NiTiCo and NiTi wires. Wire alloys with Nickel, Titanium, and Cobalt (purity-99.95%) with atomic weight ratio 47Ni:50Ti:3Co and 50.6Ni:49.4Ti were prepared, sliced, and cold-rolled at 30% reduction, followed by heat treatment in a furnace at 400oC for 1 hour. The specimens of wire size of 0.016 x 0.022 inch2 were cut and subjected to three-point bending test to investigate the load-deflection curve at deflection point 0.25, 0.5, 0.75, 1.0, 1.25, and 1.5 mm. Descriptive statistic was used to evaluate each variables and independent t-test was used to compare between the groups. The results presented a load-deflection curve that resembled a typical superelastic wire. However, significant differences were seen in the loading-unloading forces between the two with an average loading force of 412.53g and 304.98g and unloading force of 292.40g and 208.08g for NiTiCo and NiTi wire, respectively. The force at each deflection point of NiTiCo in loading-unloading force was higher than NiTi wire. This study concluded that the addition of 3%Co in NiTi alloy can increase the loading-unloading force of NiTi wire but were within the range for orthodontic tooth movement.

Development and calibration of an air-floating six-axis force measurement platform using self-calibration

NASA Astrophysics Data System (ADS)

Huang, Bin; Wang, Xiaomeng; Li, Chengwei; Yi, Jiajing; Lu, Rongsheng; Tao, Jiayue

2016-09-01

This paper describes the design, working principle, as well as calibration of an air-floating six-axis force measurement platform, where the floating plate and nozzles were connected without contact, preventing inter-dimensional coupling and increasing precision significantly. The measurement repeatability error of the force size in the platform is less than 0.2% full scale (FS), which is significantly better than the precision of 1% FS in the six-axis force sensors on the current market. We overcame the difficulties of weight loading device in high-precision calibration by proposing a self-calibration method based on the floating plate gravity and met the calibration precision requirement of 0.02% FS. This study has general implications for the development and calibration of high-precision multi-axis force sensors. In particular, the air-floating six-axis force measurement platform could be applied to the calibration of some special sensors such as flexible tactile sensors and may be used as a micro-nano mechanical assembly platform for real-time assembly force testing.

Effects of velocity and weight support on ground reaction forces and metabolic power during running.

PubMed

Grabowski, Alena M; Kram, Rodger

2008-08-01

The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.

Weight, gravitation, inertia, and tides

NASA Astrophysics Data System (ADS)

Pujol, Olivier; Lagoute, Christophe; Pérez, José-Philippe

2015-11-01

This paper deals with the factors that influence the weight of an object near the Earth's surface. They are: (1) the Earth's gravitational force, (2) the centrifugal force due to the Earth's diurnal rotation, and (3) tidal forces due to the gravitational field of the Moon and Sun, and other solar system bodies to a lesser extent. Each of these three contributions is discussed and expressions are derived. The relationship between weight and gravitation is thus established in a direct and pedagogical manner readily understandable by undergraduate students. The analysis applies to the Newtonian limit of gravitation. The derivation is based on an experimental (or operational) definition of weight, and it is shown that it coincides with the Earth’s gravitational force modified by diurnal rotation around a polar axis and non-uniformity of external gravitational bodies (tidal term). Two examples illustrate and quantify these modifications, respectively the Eötvös effect and the oceanic tides; tidal forces due to differential gravitation on a spacecraft and an asteroid are also proposed as examples. Considerations about inertia are also given and some comments are made about a widespread, yet confusing, explanation of tides based on a centrifugal force. Finally, the expression of the potential energy of the tide-generating force is established rigorously in the appendix.

Reproducibilty of partial weight bearing.

PubMed

Malviya, A; Richards, J; Jones, Richard K; Udwadia, A; Doyle, J

2005-04-01

To find out whether partial weight bearing can be reproduced and retained. In vivo experiment in normal subjects. Training for partial weight bearing (25% of body weight) using bathroom scales. Reproducibility on force platform immediately after training and after 60 min. Twelve subjects were asked to reproduce 25% of their body weight through either the dominant or non-dominant limb on force platform after three practice attempts on bathroom scales with concurrent visual feedback. No feedback was provided after the measurements on force plate. The process was repeated after 1h without any practice sessions in the interim period to find out if the weight practised could be retained. The mean 0-min reading was found to be 25.9% of body weight while the mean 60-min reading was found to be 24.4%. The p-value for the difference between the two means was found to be 0.3841. This study indicates that partial weight bearing instructions can be quantified and graded. Simple bathroom scales are sufficient to educate the patients and this can be practised at home after an initial period of supervision.

Inaccuracy of a physical strain trainer for the monitoring of partial weight bearing.

PubMed

Pauser, Johannes; Jendrissek, Andreas; Swoboda, Bernd; Gelse, Kolja; Carl, Hans-Dieter

2011-11-01

To investigate the use of a physical strain trainer for the monitoring of partial weight bearing. Case series with healthy volunteers. Orthopedic clinic. Healthy volunteers (N=10) with no history of foot complaints. Volunteers were taught to limit weight bearing to 10% body weight (BW) and 50% BW, monitored by a physical strain trainer. The parameters peak pressure, maximum force, force-time integral, and pressure-time integral were assessed by dynamic pedobarography when volunteers walked with full BW (condition 1), 50% BW (condition 2), and 10% BW (condition 3). With 10% BW (condition 3), forces with normative gait (condition 1) were statistically significantly reduced under the hindfoot where the physical strain trainer is placed. All pedobarographic parameters were, however, exceeded when the total foot was measured. A limitation to 10% BW with the physical strain trainer (condition 3) was equal to a bisection of peak pressure and maximum force for the total foot with normative gait (condition 1). Halved BW (condition 2) left a remaining mean 82% of peak pressure and mean 59% of maximum force from full BW (condition 1). The concept of controlling partial weight bearing with the hindfoot-addressing device does not represent complete foot loading. Such devices may be preferably applied in cases when the hindfoot in particular must be off-loaded. Other training devices (eg, biofeedback soles) that monitor forces of the total foot have to be used to control partial weight bearing of the lower limb accurately. Copyright © 2011 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Investigation of the Forces Acting on Gliders in Automobile-pulley-winch and Airplane Towed Flight

NASA Technical Reports Server (NTRS)

Klemperer, W B

1942-01-01

The magnitude, the direction, and the fluctuation of towing forces exerted upon gliders by towing them aloft behind an automobile, by means of a winch, and by airplane were measured under a variety of conditions covering a range from gentle to severe types of operation. For these tests the towing forces did not exceed 92 percent of the gross weight of the glider. The results indicate that in pulley and winch towing the towing forces are of about the same magnitude as in automobile towing. Speed increases in the accelerated phases of the towing jerks encountered in airplane towing can readily become critical as speeds in excess of placard speeds can be attained. Passage through the slipstream of the towing airplane can be equivalent to a severe gust that, at high speed, may impose high wing loads and require large control moments.

ESTIMATION OF THE SPACE SHUTTLE ROLLOUT FORCING FUNCTION

NASA Technical Reports Server (NTRS)

James, George H., III; Carne, Thomas; Elliott, Kenny; Wilson, Bruce

2005-01-01

The Space Shuttle Vehicle is assembled in the Vertical Assembly Building (VAB) at Kennedy Space Flight Center in Florida. The Vehicle is stacked on a Mobile Launch Platform (MLP) that weighs eight million pounds. A Crawler Transporter (CT) then carries the MLP and the stacked vehicle (12 million pounds total weight) to the launch complex located 5 miles away. This operation is performed at 0.9 mph resulting in a 4.5-hour transport. A recent test was performed to monitor the dynamic environment that was produced during rollout. It was found that the rollout is a harmonic-rich dynamic environment that was previously not understood. This paper will describe work that has been performed to estimate the forcing function that is produced in the transportation process. The rollout analysis team has determined that there are two families of harmonics of the drive train, which excite the system as a function of CT speed. There are also excitation sources, which are random or narrow-band in frequency and are not a function of CT speed. This presentation will discuss the application of the Sum of Weighted Accelerations Technique (SWAT) to further refine this understanding by estimating the forces and moments at the center-of-mass.

SOFIA 2 model telescope wind tunnel test report

NASA Technical Reports Server (NTRS)

Keas, Paul

1995-01-01

This document outlines the tests performed to make aerodynamic force and torque measurements on the SOFIA wind tunnel model telescope. These tests were performed during the SOFIA 2 wind tunnel test in the 14 ft wind tunnel during the months of June through August 1994. The test was designed to measure the dynamic cross elevation moment acting on the SOFIA model telescope due to aerodynamic loading. The measurements were taken with the telescope mounted in an open cavity in the tail section of the SOFIA model 747. The purpose of the test was to obtain an estimate of the full scale aerodynamic disturbance spectrum, by scaling up the wind tunnel results (taking into account differences in sail area, air density, cavity dimension, etc.). An estimate of the full scale cross elevation moment spectrum was needed to help determine the impact this disturbance would have on the telescope positioning system requirements. A model of the telescope structure, made of a light weight composite material, was mounted in the open cavity of the SOFIA wind tunnel model. This model was mounted via a force balance to the cavity bulkhead. Despite efforts to use a 'stiff' balance, and a lightweight model, the balance/telescope system had a very low resonant frequency (37 Hz) compared to the desired measurement bandwidth (1000 Hz). Due to this mechanical resonance of the balance/telescope system, the balance alone could not provide an accurate measure of applied aerodynamic force at the high frequencies desired. A method of measurement was developed that incorporated accelerometers in addition to the balance signal, to calculate the aerodynamic force.

Changes in Maximal Strength, Velocity, and Power After 8 Weeks of Training With Pneumatic or Free Weight Resistance.

PubMed

Frost, David M; Bronson, Stefanie; Cronin, John B; Newton, Robert U

2016-04-01

Because free weight (FW) and pneumatic (PN) resistance are characterized by different inertial properties, training with either resistance could afford unique strength, velocity, and power adaptations. Eighteen resistance-trained men completed baseline tests to determine their FW and PN bench press 1 repetition maximum (1RM). During the FW session, 4 explosive repetitions were performed at loads of 15, 30, 45, 60, 75, and 90% 1RM to assess force, velocity, and power. Participants were then assigned to a FW or PN training group, which involved three 90-minute sessions per week for 8 weeks. Both intervention groups completed identical periodized programs with the exception of the resistance used to perform all bench press movements. Free weight participants significantly increased their FW and PN 1RM (10.4 and 9.4%), and maximum (any load) force (9.8%), velocity (11.6%), and power (22.5%). Pneumatic-trained participants also exhibited increases in FW and PN 1RM (11.6 and 17.5%), and maximum force (8.4%), velocity (13.6%), and power (33.4%). Both interventions improved peak barbell velocity at loads of 15 and 30% 1RM; however, only the PN-trained individuals displayed improvements in peak force and power at these same loads. Training with PN resistance may offer advantages if attempting to improve power at lighter relative loads by affording an opportunity to consistently achieve higher accelerations and velocities (F = ma), in comparison with FW. Exploiting the inertial properties of the resistance, whether mass, elastic or PN, could afford an opportunity to develop mixed-method training strategies and/or elicit unique neuromuscular adaptations to suit the specific needs of athletes from sports characterized by varying demands.

Muscle function in Turner syndrome: normal force but decreased power.

PubMed

Soucek, Ondrej; Lebl, Jan; Matyskova, Jana; Snajderova, Marta; Kolouskova, Stanislava; Pruhova, Stepanka; Hlavka, Zdenek; Sumnik, Zdenek

2015-02-01

Although hypogonadism and SHOX gene haploinsufficiency likely cause the decreased bone mineral density and increased fracture rate associated with Turner syndrome (TS), the exact mechanism remains unclear. We tested the hypothesis that muscle dysfunction in patients with TS contributes to increased fracture risk. The secondary aim was to determine whether menarche, hormone therapy duration, positive fracture history and genotype influence muscle function parameters in patients with TS. A cross-sectional study was conducted in a single university hospital referral centre between March 2012 and October 2013. Sixty patients with TS (mean age of 13·7 ± 4·5 years) were compared to the control group of 432 healthy girls. A Leonardo Mechanograph(®) Ground Reaction Force Platform was used to assess muscle force (Fmax ) by the multiple one-legged hopping test and muscle power (Pmax ) by the single two-legged jump test. While the Fmax was normal (mean weight-specific Z-score of 0·11 ± 0·77, P = 0·27), the Pmax was decreased in patients with TS (Z-score of -0·93 ± 1·5, P < 0·001) compared with healthy controls. The muscle function parameters were not significantly influenced by menarcheal stage, hormone therapy duration, fracture history or genotype (linear regression adjusted for age, weight and height; P > 0·05 for all). Fmax , a principal determinant of bone strength, is normal in patients with TS. Previously described changes in bone quality and structure in TS are thus not likely related to inadequate mechanical loading but rather represent a primary bone deficit. A decreased Pmax indicates impaired muscle coordination in patients with TS. © 2014 John Wiley & Sons Ltd.

Early Life Stress Increases Metabolic Risk, HPA Axis Reactivity, and Depressive-Like Behavior When Combined with Postweaning Social Isolation in Rats.

PubMed

Vargas, Javier; Junco, Mariana; Gomez, Carlos; Lajud, Naima

2016-01-01

Early-life stress is associated with depression and metabolic abnormalities that increase the risk of cardiovascular disease and diabetes. Such associations could be due to increased glucocorticoid levels. Periodic maternal separation in the neonate and rearing in social isolation are potent stressors that increase hypothalamus-pituitary-adrenal axis activity. Moreover, social isolation promotes feed intake and body weight gain in rats subjected to periodic maternal separation; however, its effects on metabolic risks have not been described. In the present study, we evaluated whether periodic maternal separation, social isolation rearing, and a combination of these two stressors (periodic maternal separation + social isolation rearing) impair glucose homeostasis and its relation to the hypothalamus-pituitary-adrenal axis and depressive-like behavior. Periodic maternal separation increased basal corticosterone levels, induced a passive coping strategy in the forced swimming test, and was associated with a mild (24%) increase in fasting glucose, insulin resistance, and dyslipidemia. Rearing in social isolation increased stress reactivity in comparison to both controls and in combination with periodic maternal separation, without affecting the coping strategy associated with the forced swimming test. However, social isolation also increased body weight gain, fasting glucose (120%), and insulin levels in rats subjected to periodic maternal separation. Correlation analyses showed that stress-induced effects on coping strategy on the forced swimming test (but not on metabolic risk markers) are associated with basal corticosterone levels. These findings suggest that maternal separation and postweaning social isolation affect stress and metabolic vulnerability differentially and that early-life stress-related effects on metabolism are not directly dependent on glucocorticoid levels. In conclusion, our study supports the cumulative stress hypothesis, which suggests that metabolic risk markers arise when vulnerable individuals are exposed to social challenges later in life.

Common-pull, multiple-push, vacuum-activated telescope mirror cell.

PubMed

Ruiz, Elfego; Sohn, Erika; Salas, Luis; Luna, Esteban; Araiza-Durán, José A

2014-11-20

A new concept for push-pull active optics is presented, where the push-force is provided by means of individual airbag type actuators and a common force in the form of a vacuum is applied to the entire back of the mirror. The vacuum provides the pull-component of the system, in addition to gravity. Vacuum is controlled as a function of the zenithal angle, providing correction for the axial component of the mirror's weight. In this way, the push actuators are only responsible for correcting mirror deformations, as well as for supporting the axial mirror weight at the zenith, allowing for a uniform, full dynamic-range behavior of the system along the telescope's pointing range. This can result in the ability to perform corrections of up to a few microns for low-order aberrations. This mirror support concept was simulated using a finite element model and was tested experimentally at the 2.12 m San Pedro Mártir telescope. Advantages such as stress-free attachments, lighter weight, large actuator area, lower system complexity, and lower required mirror-cell stiffness could make this a method to consider for future large telescopes.

Biomechanical Comparison of Robotically Applied Pure Moment, Ideal Follower Load, and Novel Trunk Weight Loading Protocols on L4-L5 Cadaveric Segments during Flexion-Extension.

PubMed

Bennett, Charles R; DiAngelo, Denis J; Kelly, Brian P

2015-01-01

Extremely few in-vitro biomechanical studies have incorporated shear loads leaving a gap for investigation, especially when applied in combination with compression and bending under dynamic conditions. The objective of this study was to biomechanically compare sagittal plane application of two standard protocols, pure moment (PM) and follower load (FL), with a novel trunk weight (TW) loading protocol designed to induce shear in combination with compression and dynamic bending in a neutrally potted human cadaveric L4-L5 motion segment unit (MSU) model. A secondary objective and novelty of the current study was the application of all three protocols within the same testing system serving to reduce artifacts due to testing system variability. Six L4-L5 segments were tested in a Cartesian load controlled system in flexion-extension to 8Nm under PM, simulated ideal 400N FL, and vertically oriented 400N TW loading protocols. Comparison metrics used were rotational range of motion (RROM), flexibility, neutral zone (NZ) range of motion, and L4 vertebral body displacements. Significant differences in vertebral body translations were observed with different initial force applications but not with subsequent bending moment application. Significant reductions were observed in combined flexion-extension RROM, in flexibility during extension, and in NZ region flexibility with the TW loading protocol as compared to PM loading. Neutral zone ranges of motion were not different between all protocols. The combined compression and shear forces applied across the spinal joint in the trunk weight protocol may have a small but significantly increased stabilizing effect on segment flexibility and kinematics during sagittal plane flexion and extension.

Biomechanical Comparison of Robotically Applied Pure Moment, Ideal Follower Load, and Novel Trunk Weight Loading Protocols on L4-L5 Cadaveric Segments during Flexion-Extension

PubMed Central

Bennett, Charles R.; DiAngelo, Denis J.

2015-01-01

Background Extremely few in-vitro biomechanical studies have incorporated shear loads leaving a gap for investigation, especially when applied in combination with compression and bending under dynamic conditions. The objective of this study was to biomechanically compare sagittal plane application of two standard protocols, pure moment (PM) and follower load (FL), with a novel trunk weight (TW) loading protocol designed to induce shear in combination with compression and dynamic bending in a neutrally potted human cadaveric L4-L5 motion segment unit (MSU) model. A secondary objective and novelty of the current study was the application of all three protocols within the same testing system serving to reduce artifacts due to testing system variability. Methods Six L4-L5 segments were tested in a Cartesian load controlled system in flexion-extension to 8Nm under PM, simulated ideal 400N FL, and vertically oriented 400N TW loading protocols. Comparison metrics used were rotational range of motion (RROM), flexibility, neutral zone (NZ) range of motion, and L4 vertebral body displacements. Results Significant differences in vertebral body translations were observed with different initial force applications but not with subsequent bending moment application. Significant reductions were observed in combined flexion-extension RROM, in flexibility during extension, and in NZ region flexibility with the TW loading protocol as compared to PM loading. Neutral zone ranges of motion were not different between all protocols. Conclusions The combined compression and shear forces applied across the spinal joint in the trunk weight protocol may have a small but significantly increased stabilizing effect on segment flexibility and kinematics during sagittal plane flexion and extension. PMID:26273551

Acute toxicity evaluation of JP-8 jet fuel and JP-8 jet fuel containing additives. Final report, November 1995-February 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wolfe, R.E.; Kinead, E.R.; Feldmann, M.L.

1996-11-01

To reduce fuel fouling in current U.S Navy and Air Force aircraft systems and to provide additional heat sink and thermal stability for future systems, the Air Force is developing an improved JP-8 jet fuel (JP-8 + 100). Two companies (Betz and Mobil) have developed additive packages that are currently being tested in aircraft systems. To determine if the additive packages will produce health effects for flightline personnel, acute testing was performed on JP-8 and the two JP-8 + 100 jet fuels. A single oral dose at 5 mg jet fuel/kg body weight to five male and five female F-344more » rats, and a single dermal application of 2 g jet fuel/kg body weight applied to five male and five female NZW rabbits resulted in no deaths. No signs of toxic stress were observed, and all animals gained weight over the 14-day observation periods. Single treatment of 0.5 mL neat jet fuel to rabbit skin produced negative results for skin irritation. Guinea pigs tailed to elicit a sensitization response following repeated applications of the jet fuels. Inhalation vapor exposure to JP-8, JP-8 + 100 (Betz), and JP-8 (Mobil) were determined to be >3.43, >3.52, and >3.57 mg/L, respectively. LD% values for aerosol exposure to JP-8, JP-8 + 100 (Betz), and JP-8 + 100 (Mobil) were >4.44, >4.39, and >4.54 mg/L, respectively. Under the conditions of these tests, the additive packages did not potentiate the acute effects normally associated with JP-8 jet fuel exposures.« less

Anti-neuropeptide Y plasma immunoglobulins in relation to mood and appetite in depressive disorder.

PubMed

Garcia, Frederico D; Coquerel, Quentin; do Rego, Jean-Claude; Cravezic, Aurore; Bole-Feysot, Christine; Kiive, Evelyn; Déchelotte, Pierre; Harro, Jaanus; Fetissov, Sergueï O

2012-09-01

Depression and eating disorders are frequently associated, but the molecular pathways responsible for co-occurrence of altered mood, appetite and body weight are not yet fully understood. Neuropeptide Y (NPY) has potent antidepressant and orexigenic properties and low central NPY levels have been reported in major depression. In the present study, we hypothesized that in patients with major depression alteration of mood, appetite and body weight may be related to NPY-reactive autoantibodies (autoAbs). To test this hypothesis, we compared plasma levels and affinities of NPY-reactive autoAbs between patients with major depression and healthy controls. Then, to evaluate if changes of NPY autoAb properties can be causally related to altered mood and appetite, we developed central and peripheral passive transfer models of human autoAbs in mice and studied depressive-like behavior in forced-swim test and food intake. We found that plasma levels of NPY IgG autoAbs were lower in patients with moderate but not with mild depression correlating negatively with the Montgomery-Åsberg Depression Rating Scale scores and with immobility time of the forced-swim test in mice after peripheral injection of autoAbs. No significant differences in NPY IgG autoAb affinities between patients with depression and controls were found, but higher affinity of IgG autoAbs for NPY was associated with lower body mass index and prevented NPY-induced orexigenic response in mice after their central injection. These data suggest that changes of plasma levels of anti-NPY autoAbs are relevant to altered mood, while changes of their affinity may participate in altered appetite and body weight in patients with depressive disorder. Copyright © 2012 Elsevier Ltd. All rights reserved.

Instrumented impact and residual tensile strength testing of eight-ply carbon eopoxy specimens

NASA Technical Reports Server (NTRS)

Nettles, A. T.

1990-01-01

Instrumented drop weight impact testing was utilized to examine a puncture-type impact on thin carbon-epoxy coupons. Four different material systems with various eight-ply lay-up configurations were tested. Specimens were placed over a 10.3-mm diameter hole and impacted with a smaller tup (4.2-mm diameter) than those used in previous studies. Force-time plots as well as data on absorbed energy and residual tensile strength were gathered and examined. It was found that a critical impact energy level existed for each material tested, at which point tensile strength began to rapidly decrease with increasing impact energy.

The 'Arm Force Field' method to predict manual arm strength based on only hand location and force direction.

PubMed

La Delfa, Nicholas J; Potvin, Jim R

2017-03-01

This paper describes the development of a novel method (termed the 'Arm Force Field' or 'AFF') to predict manual arm strength (MAS) for a wide range of body orientations, hand locations and any force direction. This method used an artificial neural network (ANN) to predict the effects of hand location and force direction on MAS, and included a method to estimate the contribution of the arm's weight to the predicted strength. The AFF method predicted the MAS values very well (r 2  = 0.97, RMSD = 5.2 N, n = 456) and maintained good generalizability with external test data (r 2  = 0.842, RMSD = 13.1 N, n = 80). The AFF can be readily integrated within any DHM ergonomics software, and appears to be a more robust, reliable and valid method of estimating the strength capabilities of the arm, when compared to current approaches. Copyright © 2016 Elsevier Ltd. All rights reserved.

Age-related differences in the rhythmic structure of the golf swing.

PubMed

Kim, Tae Hoon; Jagacinski, Richard J; Lavender, Steven A

2011-01-01

Participants were 20 younger golfers (M age=19.8 years, SD=1.84 years) and 20 older golfers (M age=63.0 years, SD=2.55 years) who attempted 40- and 80-yard eight-iron shots requiring an adjustment of their force and timing. No age-related differences were found in the tempo or speed of the shot; however, there were differences in the rhythmic relationship between the clubhead force and the weight shift. Whereas younger golfers primarily exhibited a 3 versus 2 polyrhythmic pattern between the peak forces of the clubhead and weight shift, older golfers primarily exhibited a simpler 3 versus 3 rhythmic force pattern by adding a forward weight shift at the beginning of the shot. Additionally, older golfers exhibited less independence between the timing of the clubhead force and weight shift, which indicated greater use of a single integrated coordinative unit rather than 2 units. These findings are interpreted as compensations for age-related slowing and increased temporal variability that help to preserve tempo at a speed comparable to younger adults.

Body Weight and Body Mass Index in Patients with End-Stage Cystic Fibrosis Stabilize After the Start of Enteral Tube Feeding.

PubMed

Hollander, Francis M; de Roos, Nicole M; Belle van Meerkerk, Gerdien; Teding van Berkhout, Ferdinand; Heijerman, Harry G M; van de Graaf, Ed A

2017-11-01

Enteral tube feeding (ETF) is widely used in patients with cystic fibrosis (CF) and end-stage lung disease, but previous studies have been limited to investigating whether ETF improves outcomes in patients with moderately or mildly impaired pulmonary function. This study investigated body weight, body mass index (BMI; calculated as kg/m 2 ), pulmonary function, and the presence of CF-related diabetes before and after the start of ETF. This was a retrospective observational study. Data from 26 adult patients in an outpatient setting who had end-stage CF (19 women) and had been using ETF for at least 6 months between 2000 and 2014 were analyzed. Body weight, BMI, pulmonary function (forced expiratory volume in 1 second as percent of predicted) and incidence of CF-related diabetes from 6 months before to 6 months after starting ETF. Time effects were tested with one-way analysis of variance for data that were normally distributed and the Friedman test for non-parametric data. Correlations were tested with Pearson's r or Spearman's ρ, depending on the distribution of the data. Mean body weight increased by 3.5 kg (95% CI 2.2 to 4.8 kg) after patients started ETF. In women, mean BMI decreased by 0.7 in the 6 months before the start of ETF (P<0.05) and increased by 1.4 in the 6 months thereafter (P<0.05). In men, BMI changes were similar (-0.8 and +1.1), but not statistically significant. Forced expiratory volume in 1 second as percent of predicted significantly decreased in time from a median of 28% to 26% at the start of ETF to 25% after 6 months (P=0.0013), with similar trends in women and men. There was no correlation between changes in weight and lung function. CF-related diabetes was already present in 12 patients and developed in 1 more patient after the start of ETF. ETF improved body weight and BMI but not pulmonary function in 26 patients with end-stage CF. Clinical outcomes were similar in women and men, but the sample size of men was too small to determine statistical significance. Copyright © 2017 Academy of Nutrition and Dietetics. Published by Elsevier Inc. All rights reserved.

Performance characteristics of the Kin-Com dynamometer.

PubMed

Mayhew, T P; Rothstein, J M; Finucane, S D; Lamb, R L

1994-11-01

The purpose of this study was to assess the performance characteristics of a Kin-Com dynamometer (model #500-11) under controlled conditions. Comparisons were made between measurements of force, angle, and velocity obtained from the Kin-Com and measurements acquired from an external recording system of known weights, angles, and user-set velocities. The strength of the linear relationships between measurements obtained with the different recording systems was analyzed using a coefficient of determination (r2). An intraclass correlation coefficient (ICC[2,1]) was used to examine the reliability of the force, angle, and velocity measurements obtained with each recording system on 2 different days. In all conditions, the coefficient of determination for the force, angle, and velocity comparisons was above .99. The ICC for between-day comparisons for all force, angle, and velocity measurements was above .99. Our results indicate that the static measurements of force and angle that are necessary for use in the gravity-correction procedure and isometric testing are accurate and replicable between days. The Kin-Com dynamometer's control system regulating lever arm velocity is also accurate and replicable under a no-load condition. It was ascertained during the velocity testing that the use of any acceleration and deceleration mode other than "high" resulted in a loss of excursion of the lever arm.

Practical approach to subject-specific estimation of knee joint contact force.

PubMed

Knarr, Brian A; Higginson, Jill S

2015-08-20

Compressive forces experienced at the knee can significantly contribute to cartilage degeneration. Musculoskeletal models enable predictions of the internal forces experienced at the knee, but validation is often not possible, as experimental data detailing loading at the knee joint is limited. Recently available data reporting compressive knee force through direct measurement using instrumented total knee replacements offer a unique opportunity to evaluate the accuracy of models. Previous studies have highlighted the importance of subject-specificity in increasing the accuracy of model predictions; however, these techniques may be unrealistic outside of a research setting. Therefore, the goal of our work was to identify a practical approach for accurate prediction of tibiofemoral knee contact force (KCF). Four methods for prediction of knee contact force were compared: (1) standard static optimization, (2) uniform muscle coordination weighting, (3) subject-specific muscle coordination weighting and (4) subject-specific strength adjustments. Walking trials for three subjects with instrumented knee replacements were used to evaluate the accuracy of model predictions. Predictions utilizing subject-specific muscle coordination weighting yielded the best agreement with experimental data; however this method required in vivo data for weighting factor calibration. Including subject-specific strength adjustments improved models' predictions compared to standard static optimization, with errors in peak KCF less than 0.5 body weight for all subjects. Overall, combining clinical assessments of muscle strength with standard tools available in the OpenSim software package, such as inverse kinematics and static optimization, appears to be a practical method for predicting joint contact force that can be implemented for many applications. Copyright © 2015 Elsevier Ltd. All rights reserved.

Practical approach to subject-specific estimation of knee joint contact force

PubMed Central

Knarr, Brian A.; Higginson, Jill S.

2015-01-01

Compressive forces experienced at the knee can significantly contribute to cartilage degeneration. Musculoskeletal models enable predictions of the internal forces experienced at the knee, but validation is often not possible, as experimental data detailing loading at the knee joint is limited. Recently available data reporting compressive knee force through direct measurement using instrumented total knee replacements offer a unique opportunity to evaluate the accuracy of models. Previous studies have highlighted the importance of subject-specificity in increasing the accuracy of model predictions; however, these techniques may be unrealistic outside of a research setting. Therefore, the goal of our work was to identify a practical approach for accurate prediction of tibiofemoral knee contact force (KCF). Four methods for prediction of knee contact force were compared: (1) standard static optimization, (2) uniform muscle coordination weighting, (3) subject-specific muscle coordination weighting and (4) subject-specific strength adjustments. Walking trials for three subjects with instrumented knee replacements were used to evaluate the accuracy of model predictions. Predictions utilizing subject-specific muscle coordination weighting yielded the best agreement with experimental data, however this method required in vivo data for weighting factor calibration. Including subject-specific strength adjustments improved models’ predictions compared to standard static optimization, with errors in peak KCF less than 0.5 body weight for all subjects. Overall, combining clinical assessments of muscle strength with standard tools available in the OpenSim software package, such as inverse kinematics and static optimization, appears to be a practical method for predicting joint contact force that can be implemented for many applications. PMID:25952546

The analysis of three-dimensional ground reaction forces during gait in children with autism spectrum disorders.

PubMed

Hasan, Che Zawiyah Che; Jailani, Rozita; Md Tahir, Nooritawati; Ilias, Suryani

2017-07-01

Minimal information is known about the three-dimensional (3D) ground reaction forces (GRF) on the gait patterns of individuals with autism spectrum disorders (ASD). The purpose of this study was to investigate whether the 3D GRF components differ significantly between children with ASD and the peer controls. 15 children with ASD and 25 typically developing (TD) children had participated in the study. Two force plates were used to measure the 3D GRF data during walking. Time-series parameterization techniques were employed to extract 17 discrete features from the 3D GRF waveforms. By using independent t-test and Mann-Whitney U test, significant differences (p<0.05) between the ASD and TD groups were found for four GRF features. Children with ASD demonstrated higher maximum braking force, lower relative time to maximum braking force, and lower relative time to zero force during mid-stance. Children with ASD were also found to have reduced the second peak of vertical GRF in the terminal stance. These major findings suggest that children with ASD experience significant difficulties in supporting their body weight and endure gait instability during the stance phase. The findings of this research are useful to both clinicians and parents who wish to provide these children with appropriate treatments and rehabilitation programs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Body mass index and motor coordination: Non-linear relationships in children 6-10 years.

PubMed

Lopes, V P; Malina, R M; Maia, J A R; Rodrigues, L P

2018-05-01

Given the concern for health-related consequences of an elevated body mass index (BMI; obesity), the potential consequences of a low BMI in children are often overlooked. The purpose was to evaluate the relationship between the BMI across its entire spectrum and motor coordination (MC) in children 6-10 years. Height, weight, and MC (Körperkoordinationstest für Kinder, KTK test battery) were measured in 1,912 boys and 1,826 girls of 6-10 years of age. BMI (kg/m 2 ) was calculated. KTK scores for each of the four tests were also converted to a motor quotient (MQ). One-way ANOVA was used to test differences in the BMI, individual test items, and MQ among boys and girls within age groups. Sex-specific quadratic regressions of individual KTK items and the MQ on the BMI were calculated. Girls and boys were also classified into four weight status groups using International Obesity Task Force criteria: thin, normal, overweight, and obese. Differences in specific test items and MQ between weight status groups were evaluated by age group in each sex. Thirty-one percent of the sample was overweight or obese, whereas 5% was thin. On average, normal weight children had the highest MQ in both sexes across the age range with few exceptions. Overweight/obese children had a lower MQ than normal weight and thin children. The quadratic regression lines generally presented an inverted parabolic relationship between the BMI and MC and suggested a decrease in MC with an increase in the BMI. In general, BMI shows a curvilinear, inverted parabolic relationship with MC in children 6-10 years. © 2018 John Wiley & Sons Ltd.

Modeling and validating the grabbing forces of hydraulic log grapples used in forest operations

Treesearch

Jingxin Wang; Chris B. LeDoux; Lihai Wang

2003-01-01

The grabbing forces of log grapples were modeled and analyzed mathematically under operating conditions when grabbing logs from compact log piles and from bunch-like log piles. The grabbing forces are closely related to the structural parameters of the grapple, the weight of the grapple, and the weight of the log grabbed. An operational model grapple was designed and...

Comprehensive Group Therapy of Obesity and Its Impact on Selected Anthropometric and Postural Parameters.

PubMed

Horák, Stanislav; Sovová, Eliška; Pastucha, Dalibor; Konečný, Petr; Radová, Lenka; Calabová, Naděžda; Janoutová, Jana; Janout, Vladimír

2017-12-01

Obesity is a multifactorial disease. This non-infectious epidemic has reached pandemic proportions in the 21 century. Posture is a dynamic process referring to an active maintenance of body movement segments against the action of external forces. The aim of the study was to investigate the effect of comprehensive group therapy for obese persons on selected anthropometric and postural parameters. The study comprised 53 females with a mean age of 44.5 years (range 29–65 years, standard deviation 9.42 years, median 44 years), who completed a controlled weight loss programme. At the beginning and at the end of the programme, anthropometric parameters (Body Mass Index (BMI), weight and waist circumference) were measured and the posturography tests Limits of Stability (LOS) and Motor Control Test (MCT) were performed using the NeuroCom's SMART EquiTest system. The data were statistically analyzed using R software at a level of significance of 0.05. There were positive changes after the controlled weight loss programme in anthropometric parameters (BMI reduction, with p<0.001; waist circumference reduction, with p<0.001; and weight loss, with p<0.001), postural stability with statistically significant (p<0.05) improvements in both postural activity (LOS test parameters) and reactions (MCT parameters). The study showed a statistically significant effect of comprehensive group therapy for obesity in terms of reductions in waist circumference, body weight and BMI, and thus the overall reduction of both cardiovascular and metabolic risks, as well as improved postural skills (activity and reactions). Copyright© by the National Institute of Public Health, Prague 2017

Evaluation of a pneumatic Martian soil sampler concept

NASA Technical Reports Server (NTRS)

Schaefer, John L.; Neathery, James K.; Stencel, John M.

1994-01-01

The pneumatic soil sampler concept was successfully demonstrated by penetrating a Martian simulant soil to a depth of 2 meters. Working gas pressure, composition, and pulsing were evaluated with the objective of minimizing gas usage. Also, the probe penetration force was investigated with the objective of minimizing probe weight. Gas and probe penetration force, while not yet optimized, are within the range which make the soil sampler concept feasible. While the tests described in this report did not answer all the questions and address all the variables associated with pneumatic soil sampling, valuable data experience and knowledge were gained which can be used to further develop the concept.

Use of force sensors to detect and analyse lameness in dairy cows.

PubMed

Kujala, M; Pastell, M; Soveri, T

2008-03-22

Force sensors were used to detect lameness in dairy cows in two trials. In the first trial, leg weights were recorded during approximately 12,000 milkings with balances built into the floor of the milking robot. Cows that put less weight on one leg or kicked frequently during milking were checked first with a locomotion scoring system and then with a clinical inspection. A locomotion score of more than 2 was considered lame, and these cows' hooves were examined at hoof trimming to determine the cause and to identify any hoof lesions. In the second trial 315 locomotion scores were recorded and compared with force sensor data. The force sensors proved to be a good method for recognising lameness. Computer curves drawn from force sensor data helped to find differences between leg weights, thus indicating lameness and its duration. Sole ulcers and white line disease were identified more quickly by force sensors than by locomotion scoring, but joint problems were more easily detected by locomotion scoring.

Abdominal muscle response to a simulated weight-bearing task by elite Australian Rules football players.

PubMed

Hyde, Jodie; Stanton, Warren R; Hides, Julie A

2012-02-01

The aim of this study was to examine the automatic recruitment of the deep abdominal muscles during a unilateral simulated weight-bearing task by elite Australian Rules football (AFL) players with and without low back pain (LBP). An observational cross-sectional study was conducted using ultrasound imaging to measure the thickness of the internal oblique (IO) and transversus abdominis (TrA) muscles. Thirty-seven elite male AFL players participated. Repeated measures factors included 'force level' (rest, 25% and 45% of body weight), 'leg' (dominant or non-dominant kicking leg) and 'side' (ultrasound side ipsilateral or contralateral to the leg used for the weight-bearing task). The dependent variables were thickness of the IO and TrA muscles. The results of this study showed that thickness of the IO (p<.0001) and TrA (p<.0001) muscles increased in response to 'force level'. During the task, the thickness of the IO muscle on the contralateral side of the trunk relative to the leg being tested, increased more in participants with current LBP (p=.034). This pattern was more distinct on the non-dominant kicking leg. Altered abdominal muscle recruitment in elite athletes with low back pain may be an attempt by the central nervous system (CNS) to compensate for inadequate lumbo-pelvic stability. Copyright © 2011 Elsevier B.V. All rights reserved.

Locomotor Adaptation to an Asymmetric Force on the Human Pelvis Directed Along the Right Leg.

PubMed

Vashista, Vineet; Martelli, Dario; Agrawal, Sunil

2015-09-11

In this work, we study locomotor adaptation in healthy adults when an asymmetric force vector is applied to the pelvis directed along the right leg. A cable-driven Active Tethered Pelvic Assist Device (A-TPAD) is used to apply an external force on the pelvis, specific to a subject's gait pattern. The force vector is intended to provide external weight bearing during walking and modify the durations of limb supports. The motivation is to use this paradigm to improve weight bearing and stance phase symmetry in individuals with hemiparesis. An experiment with nine healthy subjects was conducted. The results show significant changes in the gait kinematics and kinetics while the healthy subjects developed temporal and spatial asymmetry in gait pattern in response to the applied force vector. This was followed by aftereffects once the applied force vector was removed. The adaptation to the applied force resulted in asymmetry in stance phase timing and lower limb muscle activity. We believe this paradigm, when extended to individuals with hemiparesis, can show improvements in weight bearing capability with positive effects on gait symmetry and walking speed.

Weight-controlled capillary viscometer

NASA Astrophysics Data System (ADS)

Digilov, Rafael M.; Reiner, M.

2005-11-01

The draining of a water column through a vertical discharge capillary tube is examined with the aid of a force sensor. The change of the mass of the liquid in the column with time is found to be not purely exponential as implied by Poiseuille's law. Using observed residuals associated with a kinetic energy correction, an approximate formula for the mass as a function of time is derived and excellent agreement with experimental data is attained. These results are verified by a viscosity test of distilled water at room temperature. A simple and inexpensive weight-controlled capillary viscometer is proposed that is especially suitable for undergraduate physics and chemistry laboratories.

Maximal bite force, facial morphology and sucking habits in young children with functional posterior crossbite.

PubMed

Castelo, Paula Midori; Gavião, Maria Beatriz Duarte; Pereira, Luciano José; Bonjardim, Leonardo Rigoldi

2010-01-01

The maintenance of normal conditions of the masticatory function is determinant for the correct growth and development of its structures. Thus, the aims of this study were to evaluate the influence of sucking habits on the presence of crossbite and its relationship with maximal bite force, facial morphology and body variables in 67 children of both genders (3.5-7 years) with primary or early mixed dentition. The children were divided in four groups: primary-normocclusion (PN, n=19), primary-crossbite (PC, n=19), mixed-normocclusion (MN, n=13), and mixed-crossbite (MC, n=16). Bite force was measured with a pressurized tube, and facial morphology was determined by standardized frontal photographs: AFH (anterior face height) and BFW (bizygomatic facial width). It was observed that MC group showed lower bite force than MN, and AFH/BFW was significantly smaller in PN than PC (t-test). Weight and height were only significantly correlated with bite force in PC group (Pearson's correlation test). In the primary dentition, AFH/BFW and breast-feeding (at least six months) were positive and negatively associated with crossbite, respectively (multiple logistic regression). In the mixed dentition, breast-feeding and bite force showed negative associations with crossbite (univariate regression), while nonnutritive sucking (up to 3 years) associated significantly with crossbite in all groups (multiple logistic regression). In the studied sample, sucking habits played an important role in the etiology of crossbite, which was associated with lower bite force and long-face tendency.

The effects of baseball bat mass properties on swing mechanics, ground reaction forces, and swing timing.

PubMed

Laughlin, Walter A; Fleisig, Glenn S; Aune, Kyle T; Diffendaffer, Alek Z

2016-01-01

Swing trajectory and ground reaction forces (GRF) of 30 collegiate baseball batters hitting a pitched ball were compared between a standard bat, a bat with extra weight about its barrel, and a bat with extra weight in its handle. It was hypothesised that when compared to a standard bat, only a handle-weighted bat would produce equivalent bat kinematics. It was also hypothesised that hitters would not produce equivalent GRFs for each weighted bat, but would maintain equivalent timing when compared to a standard bat. Data were collected utilising a 500 Hz motion capture system and 1,000 Hz force plate system. Data between bats were considered equivalent when the 95% confidence interval of the difference was contained entirely within ±5% of the standard bat mean value. The handle-weighted bat had equivalent kinematics, whereas the barrel-weighted bat did not. Both weighted bats had equivalent peak GRF variables. Neither weighted bat maintained equivalence in the timing of bat kinematics and some peak GRFs. The ability to maintain swing kinematics with a handle-weighted bat may have implications for swing training and warm-up. However, altered timings of kinematics and kinetics require further research to understand the implications on returning to a conventionally weighted bat.

Patellar tendon load in different types of eccentric squats.

PubMed

Frohm, A; Halvorsen, K; Thorstensson, A

2007-07-01

Differences in mechanical loading of the patellar tendon have been suggested as a reason for varying effects in rehabilitation of patellar tendinopathy using different eccentric squat exercises and devices. The aim was to characterize the magnitude and pattern of mechanical load at the knee and on the patellar tendon during four types of eccentric squat. Subjects performed squats with a submaximal free weight and with maximal effort in a device for eccentric overloading (Bromsman), on a decline board and horizontal surface. Kinematics was recorded with a motion-capture system, reaction forces with force plates, and electromyography from three leg muscles with surface electrodes. Inverse dynamics was used to calculate knee joint kinetics. Eccentric work, mean and peak patellar tendon force, and angle at peak force were greater (25-30%) for squats on decline board compared to horizontal surface with free weight, but not in Bromsman. Higher knee load forces (60-80%), but not work, were observed with Bromsman than free weight. Angular excursions at the knee and ankle were larger with decline board, particularly with free weight, and smaller in Bromsman than with free weight. Mean electromyography was greater on a decline board for gastrocnemius (13%) and vastus medialis (6%) with free weight, but in Bromsman only for gastrocnemius (7%). The results demonstrated clear differences in the biomechanical loading on the knee during different squat exercises. Quantification of such differences provides information that could be used to explain differences in rehabilitation effects as well as in designing more optimal rehabilitation exercises for patellar tendinopathy.

Ground reaction forces during level ground walking with body weight unloading

PubMed Central

Barela, Ana M. F.; de Freitas, Paulo B.; Celestino, Melissa L.; Camargo, Marcela R.; Barela, José A.

2014-01-01

Background: Partial body weight support (BWS) systems have been broadly used with treadmills as a strategy for gait training of individuals with gait impairments. Considering that we usually walk on level ground and that BWS is achieved by altering the load on the plantar surface of the foot, it would be important to investigate some ground reaction force (GRF) parameters in healthy individuals walking on level ground with BWS to better implement rehabilitation protocols for individuals with gait impairments. Objective: To describe the effects of body weight unloading on GRF parameters as healthy young adults walked with BWS on level ground. Method: Eighteen healthy young adults (27±4 years old) walked on a walkway, with two force plates embedded in the middle of it, wearing a harness connected to a BWS system, with 0%, 15%, and 30% BWS. Vertical and horizontal peaks and vertical valley of GRF, weight acceptance and push-off rates, and impulse were calculated and compared across the three experimental conditions. Results: Overall, participants walked more slowly with the BWS system on level ground compared to their normal walking speed. As body weight unloading increased, the magnitude of the GRF forces decreased. Conversely, weight acceptance rate was similar among conditions. Conclusions: Different amounts of body weight unloading promote different outputs of GRF parameters, even with the same mean walk speed. The only parameter that was similar among the three experimental conditions was the weight acceptance rate. PMID:25590450

Effects of tongue force training on bulbar motor function in the female SOD1-G93A rat model of Amyotrophic Lateral Sclerosis

PubMed Central

Ma, Delin; Shuler, Jeffrey M.; Kumar, Aishwarya; Stanford, Quincy R.; Tungtur, Sudheer; Nishimune, Hiroshi; Stanford, John A.

2016-01-01

Background The use of exercise in Amyotrophic Lateral Sclerosis (ALS) is controversial. Although moderate exercise appears to be beneficial for limb muscles in ALS, the effects of exercise on bulbar muscles such as the tongue have not been studied. Objective The aim of this study was to determine the effects of tongue force training on bulbar motor function in the SOD1-G93A rat model of ALS. Methods We compared the effects of tongue force training on bulbar motor function and neuromuscular junction (NMJ) innervation in female SOD1-G93A rats and age-matched female wild-type controls. Half of each group underwent afternoon tongue force training sessions, while all rats were tested under minimal force conditions in the mornings. Results Tongue force did not differ between the SOD1-G93A rats and healthy controls during the morning testing sessions, nor was it affected by training. Surprisingly, decreases in tongue motility, the number of licks per session, and body weight were greater in the tongue force-trained SOD1-G93A rats. Forelimb grip force, survival, and denervation of the genioglossus muscle did not differ between the trained and untrained SOD1-G93A rats. Genioglossus innervation was correlated with changes in tongue force but not tongue motility in SOD1-G93A rats at end stage. Conclusions The results indicate a potential deleterious effect of tongue force training on tongue motility in female SOD1-G93A rats. The lack of relationship between genioglossus innervation and tongue motility suggest that factors other than lower motor neuron integrity likely accounted for this effect. PMID:27573800

Calculation of Resistive Loads for Elastic Resistive Exercises.

PubMed

Picha, Kelsey; Uhl, Tim

2018-03-14

What is the correct resistive load to start resistive training with elastic resistance to gain strength? This question is typically answered by the clinician's best estimate and patient's level of discomfort without objective evidence. To determine the average level of resistance to initiate a strengthening routine with elastic resistance following isometric strength testing. Cohort. Clinical. 34 subjects (31 ± 13 y, 73 ± 17 kg, 170 ± 12 cm). The force produced was measured in Newtons (N) with an isometric dynamometer. The force distance was the distance from center of joint to location of force applied was measured in meters to calculate torque that was called "Test Torque" for the purposes of this report. This torque data was converted to "Exercise Load" in pounds based on the location where the resistance was applied, specifically the distance away from the center of rotation of the exercising limb. The average amount of exercise load as percentage of initial Test Torque for each individual for each exercise was recorded to determine what the average level of resistance that could be used for elastic resistance strengthening program. The percentage of initial test torque calculated for the exercise was recorded for each exercise and torque produced was normalized to body weight. The average percentage of maximal isometric force that was used to initiate exercises was 30 ± 7% of test torque. This provides clinicians with an objective target load to start elastic resistance training. Individual variations will occur but utilization of a load cell during elastic resistance provides objective documentation of exercise progression.

Kinematic Patterns Associated with the Vertical Force Produced during the Eggbeater Kick.

PubMed

Oliveira, Nuno; Chiu, Chuang-Yuan; Sanders, Ross H

2015-01-01

The purpose of this study was to determine the kinematic patterns that maximized the vertical force produced during the water polo eggbeater kick. Twelve water polo players were tested executing the eggbeater kick with the trunk aligned vertically and with the upper limbs above water while trying to maintain as high a position as possible out of the water for nine eggbeater kick cycles. Lower limb joint angular kinematics, pitch angles and speed of the feet were calculated. The vertical force produced during the eggbeater kick cycle was calculated using inverse dynamics for the independent lower body segments and combined upper body segments, and a participant-specific second-degree regression equation for the weight and buoyancy contributions. Vertical force normalized to body weight was associated with hip flexion (average, r = 0.691; maximum, r = 0.791; range of motion, r = 0.710), hip abduction (maximum, r = 0.654), knee flexion (average, r = 0.716; minimum, r = 0.653) and knee flexion-extension angular velocity (r = 0.758). Effective orientation of the hips resulted in fast horizontal motion of the feet with positive pitch angles. Vertical motion of the feet was negatively associated with vertical force. A multiple regression model comprising the non-collinear variables of maximum hip abduction, hip flexion range of motion and knee flexion angular velocity accounted for 81% of the variance in normalized vertical force. For high performance in the water polo, eggbeater kick players should execute fast horizontal motion with the feet by having large abduction and flexion of the hips, and fast extension and flexion of the knees.

Effect of armor and carrying load on body balance and leg muscle function.

PubMed

Park, Huiju; Branson, Donna; Kim, Seonyoung; Warren, Aric; Jacobson, Bert; Petrova, Adriana; Peksoz, Semra; Kamenidis, Panagiotis

2014-01-01

This study investigated the impact of weight and weight distribution of body armor and load carriage on static body balance and leg muscle function. A series of human performance tests were conducted with seven male, healthy, right-handed military students in seven garment conditions with varying weight and weight distributions. Static body balance was assessed by analyzing the trajectory of center of plantar pressure and symmetry of weight bearing in the feet. Leg muscle functions were assessed by analyzing the peak electromyography amplitude of four selected leg muscles during walking. Results of this study showed that uneven weight distribution of garment and load beyond an additional 9 kg impaired static body balance as evidenced by increased sway of center of plantar pressure and asymmetry of weight bearing in the feet. Added weight on non-dominant side of the body created greater impediment to static balance. Increased garment weight also elevated peak EMG amplitude in the rectus femoris to maintain body balance and in the medial gastrocnemius to increase propulsive force. Negative impacts on balance and leg muscle function with increased carrying loads, particularly with an uneven weight distribution, should be stressed to soldiers, designers, and sports enthusiasts. Copyright © 2013 Elsevier B.V. All rights reserved.

Saturn Apollo Program

NASA Image and Video Library

1966-01-01

Engineers and technicians at the Marshall Space Flight Center placed a Saturn V ground test booster (S-IC-D) into the dynamic test stand. The stand was constructed to test the integrity of the vehicle. Forces were applied to the tail of the vehicle to simulate the engines thrusting, and various other flight factors were fed to the vehicle to test reactions. The Saturn V launch vehicle, with the Apollo spacecraft, was subjected to more than 450 hours of shaking. The photograph shows the 300,000 pound S-IC stage being lifted from its transporter into place inside the 360-foot tall test stand. This dynamic test booster has one dummy F-1 engine and weight simulators are used at the other four engine positions.

Effects of independently altering body weight and body mass on the metabolic cost of running.

PubMed

Teunissen, Lennart P J; Grabowski, Alena; Kram, Rodger

2007-12-01

The metabolic cost of running is substantial, despite the savings from elastic energy storage and return. Previous studies suggest that generating vertical force to support body weight and horizontal forces to brake and propel body mass are the major determinants of the metabolic cost of running. In the present study, we investigated how independently altering body weight and body mass affects the metabolic cost of running. Based on previous studies, we hypothesized that reducing body weight would decrease metabolic rate proportionally, and adding mass and weight would increase metabolic rate proportionally. Further, because previous studies show that adding mass alone does not affect the forces generated on the ground, we hypothesized that adding mass alone would have no substantial effect on metabolic rate. We manipulated the body weight and body mass of 10 recreational human runners and measured their metabolic rates while they ran at 3 m s(-1). We reduced weight using a harness system, increased mass and weight using lead worn about the waist, and increased mass alone using a combination of weight support and added load. We found that net metabolic rate decreased in less than direct proportion to reduced body weight, increased in slightly more than direct proportion to added load (added mass and weight), and was not substantially different from normal running with added mass alone. Adding mass alone was not an effective method for determining the metabolic cost attributable to braking/propelling body mass. Runners loaded with mass alone did not generate greater vertical or horizontal impulses and their metabolic costs did not substantially differ from those of normal running. Our results show that generating force to support body weight is the primary determinant of the metabolic cost of running. Extrapolating our reduced weight data to zero weight suggests that supporting body weight comprises at most 74% of the net cost of running. However, 74% is probably an overestimate of the metabolic demand of body weight to support itself because in reduced gravity conditions decrements in horizontal impulse accompanied decrements in vertical impulse.

Assessment of Advanced Logistics Delivery System (ALDS) Launch Systems Concepts

DTIC Science & Technology

2004-10-01

highest force vs. rotor weight required, allows much higher magnetic field generation than the linear induction or linear permanent magnet motors , and...provides the highest force vs. rotor weight required, allows much higher magnetic generation than the linear induction or linear permanent magnet motors , and

Testing of Candidate Rigid Heatshield Materials at LHMEL for the Entry, Descent, and Landing Technology Development Project

NASA Technical Reports Server (NTRS)

Sepka, Steven; Gasch, Matthew; Beck, Robin A.; White, Susan

2012-01-01

The material testing results described in this paper were part of a material development program of vendor-supplied, proposed heat shield materials. The goal of this program was to develop low density, rigid material systems with an appreciable weight savings over phenolic-impregnated carbon ablator (PICA) while improving material response performance. New technologies, such as PICA-like materials in honeycomb or materials with variable density through-the-thickness were tested. The material testing took place at the Wright-Patterson Air Force Base Laser Hardened Materials Laboratory (LHMEL) using a 10.6 micron CO2 laser operating with the test articles immersed in a nitrogen-gas environment at 1 atmosphere pressure. Test measurements included thermocouple readings of in-depth temperatures, pyrometer readings of surface temperatures, weight scale readings of mass loss, and sectioned-sample readings of char depth. Two laser exposures were applied. The first exposure was at an irradiance of 450 W/cm2 for 50 or 60 seconds to simulate an aerocapture maneuver. The second laser exposure was at an irradiance of 115 W/cm2 for 100 seconds to simulate a planetary entry. Results from Rounds 1 and 2 of these screening tests are summarized.

Effects of chronic forced circadian desynchronization on body weight and metabolism in male mice.

PubMed

Casiraghi, Leandro P; Alzamendi, Ana; Giovambattista, Andrés; Chiesa, Juan J; Golombek, Diego A

2016-04-01

Metabolic functions are synchronized by the circadian clock setting daily patterns of food intake, nutrient delivery, and behavioral activity. Here, we study the impact of chronic jet-lag (CJL) on metabolism, and test manipulations aimed to overcome potential alterations. We recorded weight gain in C57Bl/6 mice under chronic 6 h advances or delays of the light-dark cycle every 2 days (ChrA and ChrD, respectively). We have previously reported ChrA, but not ChrD, to induce forced desynchronization of locomotor activity rhythms in mice (Casiraghi et al. 2012). Body weight was rapidly increased under ChrA, with animals tripling the mean weight gain observed in controls by day 10, and doubling it by day 30 (6% vs. 2%, and 15% vs. 7%, respectively). Significant increases in retroperitoneal and epidydimal adipose tissue masses (172% and 61%, respectively), adipocytes size (28%), and circulating triglycerides (39%) were also detected. Daily patterns of food and water intake were abolished under ChrA In contrast, ChrD had no effect on body weight. Wheel-running, housing of animals in groups, and restriction of food availability to hours of darkness prevented abnormal increase in body weight under ChrA Our findings suggest that the observed alterations under ChrA may arise either from a direct effect of circadian disruption on metabolism, from desynchronization between feeding and metabolic rhythms, or both. Direction of shifts, timing of feeding episodes, and other reinforcing signals deeply affect the outcome of metabolic function under CJL Such features should be taken into account in further studies of shift working schedules in humans. © 2016 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Sensorimotor memory of object weight distribution during multidigit grasp.

PubMed

Albert, Frederic; Santello, Marco; Gordon, Andrew M

2009-10-09

We studied the ability to transfer three-digit force sharing patterns learned through consecutive lifts of an object with an asymmetric center of mass (CM). After several object lifts, we asked subjects to rotate and translate the object to the contralateral hand and perform one additional lift. This task was performed under two weight conditions (550 and 950 g) to determine the extent to which subjects would be able to transfer weight and CM information. Learning transfer was quantified by measuring the extent to which force sharing patterns and peak object roll on the first post-translation trial resembled those measured on the pre-translation trial with the same CM. We found that the overall gain of fingertip forces was transferred following object rotation, but that the scaling of individual digit forces was specific to the learned digit-object configuration, and thus was not transferred following rotation. As a result, on the first post-translation trial there was a significantly larger object roll following object lift-off than on the pre-translation trial. This suggests that sensorimotor memories for weight, requiring scaling of fingertip force gain, may differ from memories for mass distribution.

Numerical Simulation of Unsteady Turbulent Flow Induced by Two-Dimensional Elevator Car and Counter Weight System

NASA Astrophysics Data System (ADS)

Shi, Li-qun; Liu, Ying-zheng; Jin, Si-yu; Cao, Zhao-min

2007-12-01

A two-dimensional model of unsteady turbulent flow induced by high-speed elevator system was established in the present study. The research was focused on the instantaneous variation of the aerodynamic force on the car structure during traversing motion of the counter weight in the hoistway. A dynamic meshing method was employed to treat the multi-body motion system to avoid poor distortion of meshes. A comprehensive understanding of this significant aspect was obtained by varying the horizontal gap (Δ = 0.1m, 0.2m, and 0.3m) between the elevator car and the counter weight, and the moving speed ( U 0 = 2m/s, 6m/s, and 10m/s) of the elevator system. A pulsed intensification of the aerodynamic force on the elevator car and subsequent appearance of large valley with negative aerodynamic force were clearly observed in the numerical results. In parameters studied (Δ = 0.1m, U 0 = 2m/s, 6m/s, 10m/s), the peaked horizontal and vertical forces are respectively 7-11 and 4.3-5.65 times of that when the counter weight is far from the car. These results demonstrated the prominent influence of the traversing counter weight on aerodynamic force on the elevator car, which is of great significance to designers of high-speed elevator system.

90-Day Inhalation Toxicity Study of Bio-Derived Gevo Alcohol-to-Jet (ATJ) Synthetic Paraffinic Kerosene (SPK) in Rats with Neurotoxicity Testing and Genotoxicity Assay

DTIC Science & Technology

2015-05-31

body weights, food consumption , and reproductive indices (vaginal cytology, sperm cell parameters). Neurobehavioral effects , evaluated by motor...Human Performance Wing Human Effectiveness Directorate Bioeffects Division Molecular Bioeffects Branch Wright-Patterson AFB OH 45433-5707...IV, DAF Chief, Bioeffects Division Human Effectiveness Directorate 711 th Human Perfmmance Wing Air Force Research Laboratmy This repmi is

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance

PubMed Central

Wirth, Klaus; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-01-01

Abstract The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance. PMID:28149424

Effect of 8 weeks of free-weight and machine-based strength training on strength and power performance.

PubMed

Wirth, Klaus; Keiner, Michael; Hartmann, Hagen; Sander, Andre; Mickel, Christoph

2016-12-01

The aim of this study was to evaluate the effectiveness of free-weight and machine-based exercises to increase different strength and speed-strength variables. One hundred twenty male participants (age: 23.8 ± 2.5 years; body height: 181.0 ± 6.8 cm; body mass: 80.2 ± 8.9 kg) joined the study. The 2 experimental groups completed an 8 week periodized strength training program that included 2 training sessions per week. The exercises that were used in the strength training programs were the parallel barbell squat and the leg press. Before and after the training period, the 1-repetition-maximum in the barbell squat and the leg press, the squat jump, the countermovement jump and unilateral isometric force (maximal isometric force and the rate of force development) were evaluated. To compare each group pre vs. post-intervention, analysis of variance with repeated measures and Scheffé post-hoc tests were used. The leg press group increased their 1-repetition-maximum significantly (p < 0.001), while in the squat group such variables as 1-repetition-maximum, the squat jump and the countermovement jump increased significantly (p < 0.001). The maximal isometric force showed no statistically significant result for the repeated measures factor, while the rate of force development of the squat group even showed a statistically significant decrease. Differences between the 2 experimental groups were detected for the squat jump and the countermovement jump. In comparison with the leg press, the squat might be a better strength training exercise for the development of jump performance.

Anthropometry of Law Enforcement Officers

DTIC Science & Technology

1975-09-10

were obtained in a sur- vey of Air Force women with regard to height, although they tended to underestimate their weight (table 8). Although the...ESTIMATED BODY DIMENSIONS. Measured Height (in) Estimated Difference Law Enforcement Officers Army Men* Air Force Women** 70.04 68.71 63.82 71.07...69.81 64.80 1.03 0.90 0.98 Measured Weight (lb) Estimated Difference Law Enforcement Officers Army Men* Air Force Women** 189.60 159.10

Sizing Analysis for Aircraft Utilizing Hybrid-Electric Propulsion Systems

DTIC Science & Technology

2011-03-18

of the Air Force, Robert Gates, reports that since 5 the beginning of the war “the Air Force has significantly expanded its ISR capability” and...aircraft. A popular source for aircraft designers has been Daniel P. Raymer’s book Aircraft Design: A Conceptual Approach [17]. Raymer has presented a...more thought was needed to estimate takeoff weight. Using the fuel weight that burns during mission segments, Raymer defined fuel weight fractions

Robot-Applied Resistance Augments the Effects of Body Weight-Supported Treadmill Training on Stepping and Synaptic Plasticity in a Rodent Model of Spinal Cord Injury.

PubMed

Hinahon, Erika; Estrada, Christina; Tong, Lin; Won, Deborah S; de Leon, Ray D

2017-08-01

The application of resistive forces has been used during body weight-supported treadmill training (BWSTT) to improve walking function after spinal cord injury (SCI). Whether this form of training actually augments the effects of BWSTT is not yet known. To determine if robotic-applied resistance augments the effects of BWSTT using a controlled experimental design in a rodent model of SCI. Spinally contused rats were treadmill trained using robotic resistance against horizontal (n = 9) or vertical (n = 8) hind limb movements. Hind limb stepping was tested before and after 6 weeks of training. Two control groups, one receiving standard training (ie, without resistance; n = 9) and one untrained (n = 8), were also tested. At the terminal experiment, the spinal cords were prepared for immunohistochemical analysis of synaptophysin. Six weeks of training with horizontal resistance increased step length, whereas training with vertical resistance enhanced step height and movement velocity. None of these changes occurred in the group that received standard (ie, no resistance) training or in the untrained group. Only standard training increased the number of step cycles and shortened cycle period toward normal values. Synaptophysin expression in the ventral horn was highest in rats trained with horizontal resistance and in untrained rats and was positively correlated with step length. Adding robotic-applied resistance to BWSTT produced gains in locomotor function over BWSTT alone. The impact of resistive forces on spinal connections may depend on the nature of the resistive forces and the synaptic milieu that is present after SCI.

Design of elevator control surface actuated by LIPCA for small unmanned air vehicle

NASA Astrophysics Data System (ADS)

Yoon, K. J.; Setiawan, Hery; Goo, N. S.

2006-03-01

There have been persistent interests in high performance actuators suitable for the actuation of control surfaces of small aircraft and helicopter blades and for active vibration control of aerospace and submarine structures that need high specific force and displacement. What is really needed for active actuation is a large-displacement actuator with a compact source, i.e., much higher strain. A lot of effort has been made to develop compact actuators with large displacement at a high force. One of the representative actuator is LIPCA actuator that was introduced by Yoon et al. The LIPCA design offers the advantages to be applied as actuator for the small aerial vehicle comparing with any other actuators. The weight is one of the main concerns for aerospace field, and since LIPCA has lighter weight than any other piezo-actuator thus it is suitable as actuator for small aircraft control surface. In this paper, a conceptual design of LIPCA-actuated control surface is introduced. A finite element model was constructed and analyzed to predict the deflection angle of the control surface. The hinge moment that produced by the aerodynamic forces was calculated to determine the optimum position of the hinge point, which could produce the deflection as high as possible with reasonable hinge moment. To verify the prediction, a prototype of SUAV (small unmanned air vehicle) control surface was manufactured and tested both in static condition and in the wind tunnel. The prediction and test results showed a good agreement on the control surface deflection angle.

Selective Effects of Training Against Weight and Inertia on Muscle Mechanical Properties.

PubMed

Djuric, Sasa; Cuk, Ivan; Sreckovic, Sreten; Mirkov, Dragan; Nedeljkovic, Aleksandar; Jaric, Slobodan

2016-10-01

To explore the effects of training against mechanically different types of loads on muscle force (F), velocity (V), and power (P) outputs. Subjects practiced maximum bench throws over 8 wk against a bar predominantly loaded by approximately constant external force (weight), weight plates (weight plus inertia), or weight plates whose weight was compensated by a constant external force pulling upward (inertia). Instead of a typically applied single trial performed against a selected load, the pretest and posttest consisted of the same task performed against 8 different loads ranging from 30% to 79% of the subject's maximum strength applied by adding weight plates to the bar. That provided a range of F and V data for subsequent modeling by linear F-V regression revealing the maximum F (F-intercept), V (V-intercept), and P (P = FV/4). Although all 3 training conditions resulted in increased P, the inertia type of the training load could be somewhat more effective than weight. An even more important finding was that the P increase could be almost exclusively based on a gain in F, V, or both when weight, inertia, or weight-plus-inertia training load were applied, respectively. The inertia training load is more effective than weight in increasing P and weight and inertia may be applied for selective gains in F and V, respectively, whereas the linear F-V model obtained from loaded trials could be used for discerning among muscle F, V, and P.

High-Force Versus Low-Force Lumbar Traction in Acute Lumbar Sciatica Due to Disc Herniation: A Preliminary Randomized Trial.

PubMed

Isner-Horobeti, Marie-Eve; Dufour, Stéphane Pascal; Schaeffer, Michael; Sauleau, Erik; Vautravers, Philippe; Lecocq, Jehan; Dupeyron, Arnaud

This study compared the effects of high-force versus low-force lumbar traction in the treatment of acute lumbar sciatica secondary to disc herniation. A randomized double blind trial was performed, and 17 subjects with acute lumbar sciatica secondary to disc herniation were assigned to high-force traction at 50% body weight (BW; LT50, n = 8) or low force traction at 10% BW (LT10, n = 9) for 10 sessions in 2 weeks. Radicular pain (visual analogue scale [VAS]), lumbo-pelvic-hip complex motion (finger-to-toe test), lumbar-spine mobility (Schöber-Macrae test), nerve root compression (straight-leg-raising test), disability (EIFEL score), drug consumption, and overall evaluation of each patient were measured at days 0, 7, 1, 4, and 28. Significant (P < .05) improvements were observed in the LT50 and LT10 groups, respectively, between day 0 and day 14 (end of treatment) for VAS (-44% and -36%), EIFEL score (-43% and -28%) and overall patient evaluation (+3.1 and +2.0 points). At that time, LT50 specifically improved in the finger-to-toe test (-42%), the straight-leg-raising test (+58), and drug consumption (-50%). No significant interaction effect (group-by-time) was revealed, and the effect of traction treatment was independent of the level of medication. During the 2-week follow-up at day 28, only the LT10 group improved (P < .05) in VAS (-52%) and EIFEL scores (-46%). During this period, no interaction effect (group-by-time) was identified, and the observed responses were independent of the level of medication. For this preliminary study, patients with acute lumbar sciatica secondary to disc herniation who received 2 weeks of lumbar traction reported reduced radicular pain and functional impairment and improved well-being regardless of the traction force group to which they were assigned. The effects of the traction treatment were independent of the initial level of medication and appeared to be maintained at the 2-week follow-up. Copyright © 2016. Published by Elsevier Inc.

Hip and knee joint loading during vertical jumping and push jerking

PubMed Central

Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony MJ

2014-01-01

Background The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. Methods In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. Findings The knee experienced mean peak loadings of 2.4-4.6 × body weight at the patellofemoral joint, 6.9-9.0 × body weight at the tibiofemoral joint, 0.3-1.4 × body weight anterior tibial shear and 1.0-3.1 × body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4 × body weight and the ankle 8.9-10.0 × body weight. Interpretation The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations. PMID:23146164

Hip and knee joint loading during vertical jumping and push jerking.

PubMed

Cleather, Daniel J; Goodwin, Jon E; Bull, Anthony M J

2013-01-01

The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading. In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee. The knee experienced mean peak loadings of 2.4-4.6×body weight at the patellofemoral joint, 6.9-9.0×body weight at the tibiofemoral joint, 0.3-1.4×body weight anterior tibial shear and 1.0-3.1×body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4×body weight and the ankle 8.9-10.0×body weight. The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations. Copyright © 2012 Elsevier Ltd. All rights reserved.

A response-time approach to comparing generalized rational and take-the-best models of decision making.

PubMed

Bergert, F Bryan; Nosofsky, Robert M

2007-01-01

The authors develop and test generalized versions of take-the-best (TTB) and rational (RAT) models of multiattribute paired-comparison inference. The generalized models make allowances for subjective attribute weighting, probabilistic orders of attribute inspection, and noisy decision making. A key new test involves a response-time (RT) approach. TTB predicts that RT is determined solely by the expected time required to locate the 1st discriminating attribute, whereas RAT predicts that RT is determined by the difference in summed evidence between the 2 alternatives. Critical test pairs are used that partially decouple these 2 factors. Under conditions in which ideal observer TTB and RAT strategies yield equivalent decisions, both the RT results and the estimated attribute weights suggest that the vast majority of subjects adopted the generalized TTB strategy. The RT approach is also validated in an experimental condition in which use of a RAT strategy is essentially forced upon subjects. (c) 2007 APA, all rights reserved.

One Dimensional Turing-Like Handshake Test for Motor Intelligence

PubMed Central

Karniel, Amir; Avraham, Guy; Peles, Bat-Chen; Levy-Tzedek, Shelly; Nisky, Ilana

2010-01-01

In the Turing test, a computer model is deemed to "think intelligently" if it can generate answers that are not distinguishable from those of a human. However, this test is limited to the linguistic aspects of machine intelligence. A salient function of the brain is the control of movement, and the movement of the human hand is a sophisticated demonstration of this function. Therefore, we propose a Turing-like handshake test, for machine motor intelligence. We administer the test through a telerobotic system in which the interrogator is engaged in a task of holding a robotic stylus and interacting with another party (human or artificial). Instead of asking the interrogator whether the other party is a person or a computer program, we employ a two-alternative forced choice method and ask which of two systems is more human-like. We extract a quantitative grade for each model according to its resemblance to the human handshake motion and name it "Model Human-Likeness Grade" (MHLG). We present three methods to estimate the MHLG. (i) By calculating the proportion of subjects' answers that the model is more human-like than the human; (ii) By comparing two weighted sums of human and model handshakes we fit a psychometric curve and extract the point of subjective equality (PSE); (iii) By comparing a given model with a weighted sum of human and random signal, we fit a psychometric curve to the answers of the interrogator and extract the PSE for the weight of the human in the weighted sum. Altogether, we provide a protocol to test computational models of the human handshake. We believe that building a model is a necessary step in understanding any phenomenon and, in this case, in understanding the neural mechanisms responsible for the generation of the human handshake. PMID:21206462

Chronic unpredictable mild stress-induced depressive-like behavior and dysregulation of brain levels of biogenic amines in Drosophila melanogaster.

PubMed

Araujo, Stífani Machado; Poetini, Marcia Rósula; Bortolotto, Vandreza Cardoso; de Freitas Couto, Shanda; Pinheiro, Franciane Cabral; Meichtry, Luana Barreto; de Almeida, Francielli Polet; Santos Musachio, Elize Aparecida; de Paula, Mariane Trindade; Prigol, Marina

2018-05-24

The etiopathogenesis of depression may involve repeated exposure to several unpredictable stressors. This study was conducted to investigate changes induced by chronic unpredictable mild stress (CUMS) and to assess behavioral and neurochemical changes that predict depressive-like behavior in Drosophila melanogaster. Male Drosophila melanogaster flies were exposed to CUMS with several stressors (cold, heat, starvation, and sleep deprivation) in an unpredictable and chronic manner for ten days. At the end of treatment, in vivo behavioral tests (open field, aggression, forced swimming, mating, light/dark box, male fertility evaluation, sucrose preference, weight evaluation) and ex vivo analyses (dopamine and serotonin levels) were performed. Using this CUMS model, we obtained results that contribute to the construction of a depressive model in Drosophila, where we reproduce some behavioral phenotypes corresponding to depressive symptoms, such as immobility in the forced swimming test, less exploration in the light/dark test, changes in mating behavior, changes in the aggressiveness test, reduced sucrose preference, and weight-loss, in addition to a significant reduction in the levels of serotonin and dopamine when compared to the control group. Fluoxetine was used in our study as a positive control to demonstrate that CUMS-induced depressive-like behaviors in flies can be reversed by antidepressants. In conclusion, male Drosophila melanogaster exposed to CUMS display a depressive-like phenotype, and, while this poses some limitations as an animal model for depression, it meets some of the criteria required to be a valid model, such as good face and construct validity. Copyright © 2018. Published by Elsevier B.V.

Modeling and experimental validation of sawing based lander anchoring and sampling methods for asteroid exploration

NASA Astrophysics Data System (ADS)

Zhang, Jun; Dong, Chengcheng; Zhang, Hui; Li, Song; Song, Aiguo

2018-05-01

This paper presents a novel lander anchoring system based on sawing method for asteroid exploration. The system is composed of three robotic arms, three cutting discs, and a control system. The discs mounted at the end of the arms are able to penetrate into the rock surface of asteroids. After the discs cut into the rock surface, the self-locking function of the arms provides forces to fix the lander on the surface. Modeling, trajectory planning, simulations, mechanism design, and prototype fabrication of the anchoring system are discussed, respectively. The performances of the system are tested on different kinds of rocks, at different sawing angles, locations, and speeds. Results show that the system can cut 15 mm deep into granite rock in 180 s at sawing angle of 60°, with the average power of 58.41 W, and the "weight on bit" (WOB) of 8.637 N. The 7.8 kg anchoring system is capable of providing omni-directional anchoring forces, at least 225 N normal and 157 N tangent to the surface of the rock. The system has the advantages of low-weight, low energy consumption and balance forces, high anchoring efficiency and reliability, and could enable the lander to move and sample or assist astronauts and robots in walking and sampling on asteroids.

Propelling Extended Objects

NASA Astrophysics Data System (ADS)

Humbert, Richard

2010-03-01

A force acting on just part of an extended object (either a solid or a volume of a liquid) can cause all of it to move. That motion is due to the transmission of the force through the object by its material. This paper discusses how the force is distributed to all of the object by a gradient of stress or pressure in it, which creates the local force that directly propels each part of the object. Those gradients resemble the ones created in objects by their weights. An example of the latter is the compressive stress in a column of a building increasing steadily toward its lower end. That gradient occurs because each horizontal section through the column supports all of the weight above it, including the load force pushing down on the column's upper end. The gradient resembles the pressure in a container of liquid increasing with depth in it. Likewise, the weight of a vertically hanging cable causes its tension and tensile stress to increase toward its upper end.

Improved Peptide and Protein Torsional Energetics with the OPLSAA Force Field.

PubMed

Robertson, Michael J; Tirado-Rives, Julian; Jorgensen, William L

2015-07-14

The development and validation of new peptide dihedral parameters are reported for the OPLS-AA force field. High accuracy quantum chemical methods were used to scan φ, ψ, χ1, and χ2 potential energy surfaces for blocked dipeptides. New Fourier coefficients for the dihedral angle terms of the OPLS-AA force field were fit to these surfaces, utilizing a Boltzmann-weighted error function and systematically examining the effects of weighting temperature. To prevent overfitting to the available data, a minimal number of new residue-specific and peptide-specific torsion terms were developed. Extensive experimental solution-phase and quantum chemical gas-phase benchmarks were used to assess the quality of the new parameters, named OPLS-AA/M, demonstrating significant improvement over previous OPLS-AA force fields. A Boltzmann weighting temperature of 2000 K was determined to be optimal for fitting the new Fourier coefficients for dihedral angle parameters. Conclusions are drawn from the results for best practices for developing new torsion parameters for protein force fields.

Reduced effectiveness of escitalopram in the forced swimming test is associated with increased serotonin clearance rate in food restricted rats

PubMed Central

France, CP; Li, J-X; Owens, WA; Koek, W; Toney, GM; Daws, LC

2012-01-01

Efficacy of antidepressant drugs is often limited. One of the limiting factors may be diet. This study shows that the effect of escitalopram in the forced swimming test is diminished in rats by food restriction that decreased body weight by 8%. The primary target for escitalopram is the serotonin (5-HT) transporter. Using high-speed chronoamperometry to measure 5-HT clearance in vivo in rats fed the same food restricted diet, the rate of 5-HT clearance from extracellular fluid in brain was dramatically increased. Increased 5-HT transporter function under conditions of dietary restriction might contribute to the decreased effect of escitalopram. These results suggest that diet plays an integral role in determining efficacy of antidepressant drugs, and might well generalize to other psychoactive drugs that impinge upon the 5-HT transporter. PMID:19419596

Fiber-Reinforced Reactive Nano-Epoxy Composites

NASA Technical Reports Server (NTRS)

Zhong, Wei-Hong

2011-01-01

An ultra-high-molecular-weight polyethylene/ matrix interface based on the fabrication of a reactive nano-epoxy matrix with lower surface energy has been improved. Enhanced mechanical properties versus pure epoxy on a three-point bend test include: strength (25 percent), modulus (20 percent), and toughness (30 percent). Increased thermal properties include higher Tg (glass transition temperature) and stable CTE (coefficient of thermal expansion). Improved processability for manufacturing composites includes faster wetting rates on macro-fiber surfaces, lower viscosity, better resin infusion rates, and improved rheological properties. Improved interfacial adhesion properties with Spectra fibers by pullout tests include initial debonding force of 35 percent, a maximum pullout force of 25 percent, and energy to debond at 65 percent. Improved mechanical properties of Spectra fiber composites (tensile) aging resistance properties include hygrothermal effects. With this innovation, high-performance composites have been created, including carbon fibers/nano-epoxy, glass fibers/nano-epoxy, aramid fibers/ nano-epoxy, and ultra-high-molecularweight polyethylene fiber (UHMWPE).

Effect of bacoside extract from Bacopa monniera on physical fatigue induced by forced swimming.

PubMed

Anand, T; Phani Kumar, G; Pandareesh, M D; Swamy, M S L; Khanum, Farhath; Bawa, A S

2012-04-01

The antifatigue effect of bacoside extract (BME) from Bacopa monniera (L.) Wettst. was investigated. Rats were subjected to weight-loaded forced swim test (WFST) every alternate day for 3 weeks. The BME at a dosage of 10 mg/kg body weight was administered orally to rats for 2 weeks in order to evaluate the following biomarkers of physical fatigue: swimming time, change in body weight, lipid peroxidation, lactic acid (LA), glycogen, antioxidant enzyme activities such as superoxide dismutase (SOD) and catalase (CAT) and blood parameters, namely blood urea nitrogen (BUN) and creatine kinase (CK). The exhaustive swimming time was increased by 3-fold in the BME supplemented group compared with that of the control group on day 13. The BME treatment lowered malondialdehyde (MDA) levels in brain, liver and muscle tissues by 11.2%, 16.2% and 37.7%, respectively, compared with the control exercised group (p < 0.05). The BME also reduced the LA, serum BUN and CK activities significantly compared with that of the control. Administration of BME significantly protected the depletion of SOD and CAT activities. The HSP-70 expression studies by western blot also confirmed the antifatigue property of BME. The present study thus indicates that BME ameliorates the various impairments associated with physical fatigue. Copyright © 2011 John Wiley & Sons, Ltd.

Biofeedback in Partial Weight Bearing: Validity of 3 Different Devices.

PubMed

van Lieshout, Remko; Stukstette, Mirelle J; de Bie, Rob A; Vanwanseele, Benedicte; Pisters, Martijn F

2016-11-01

Study Design Controlled laboratory study to assess criterion-related validity, with a cross-sectional within-subject design. Background Patients with orthopaedic conditions have difficulties complying with partial weight-bearing instructions. Technological advances have resulted in biofeedback devices that offer real-time feedback. However, the accuracy of these devices is mostly unknown. Inaccurate feedback can result in incorrect lower-limb loading and may lead to delayed healing. Objectives To investigate validity of peak force measurements obtained using 3 different biofeedback devices under varying levels of partial weight-bearing categories. Methods Validity of 3 biofeedback devices (OpenGo science, SmartStep, and SensiStep) was assessed. Healthy participants were instructed to walk at a self-selected speed with crutches under 3 different weight-bearing conditions, categorized as a percentage range of body weight: 1% to 20%, greater than 20% to 50%, and greater than 50% to 75%. Peak force data from the biofeedback devices were compared with the peak vertical ground reaction force measured with a force plate. Criterion validity was estimated using simple and regression-based Bland-Altman 95% limits of agreement and weighted kappas. Results Fifty-five healthy adults (58% male) participated. Agreement with the gold standard was substantial for the SmartStep, moderate for OpenGo science, and slight for SensiStep (weighted ± = 0.76, 0.58, and 0.19, respectively). For the 1% to 20% and greater than 20% to 50% weight-bearing categories, both the OpenGo science and SmartStep had acceptable limits of agreement. For the weight-bearing category greater than 50% to 75%, none of the devices had acceptable agreement. Conclusion The OpenGo science and SmartStep provided valid feedback in the lower weight-bearing categories, and the SensiStep showed poor validity of feedback in all weight-bearing categories. J Orthop Sports Phys Ther 2016;46(11):-1. Epub 12 Oct 2016. doi:10.2519/jospt.2016.6625.

Exploring the parameter space of the coarse-grained UNRES force field by random search: selecting a transferable medium-resolution force field.

PubMed

He, Yi; Xiao, Yi; Liwo, Adam; Scheraga, Harold A

2009-10-01

We explored the energy-parameter space of our coarse-grained UNRES force field for large-scale ab initio simulations of protein folding, to obtain good initial approximations for hierarchical optimization of the force field with new virtual-bond-angle bending and side-chain-rotamer potentials which we recently introduced to replace the statistical potentials. 100 sets of energy-term weights were generated randomly, and good sets were selected by carrying out replica-exchange molecular dynamics simulations of two peptides with a minimal alpha-helical and a minimal beta-hairpin fold, respectively: the tryptophan cage (PDB code: 1L2Y) and tryptophan zipper (PDB code: 1LE1). Eight sets of parameters produced native-like structures of these two peptides. These eight sets were tested on two larger proteins: the engrailed homeodomain (PDB code: 1ENH) and FBP WW domain (PDB code: 1E0L); two sets were found to produce native-like conformations of these proteins. These two sets were tested further on a larger set of nine proteins with alpha or alpha + beta structure and found to locate native-like structures of most of them. These results demonstrate that, in addition to finding reasonable initial starting points for optimization, an extensive search of parameter space is a powerful method to produce a transferable force field. Copyright 2009 Wiley Periodicals, Inc.

Validity of the Myotest® in measuring force and power production in the squat and bench press.

PubMed

Comstock, Brett A; Solomon-Hill, Glenn; Flanagan, Shawn D; Earp, Jacob E; Luk, Hui-Ying; Dobbins, Kathryn A; Dunn-Lewis, Courtenay; Fragala, Maren S; Ho, Jen-Yu; Hatfield, Disa L; Vingren, Jakob L; Denegar, Craig R; Volek, Jeff S; Kupchak, Brian R; Maresh, Carl M; Kraemer, William J

2011-08-01

The purpose of this study was to verify the concurrent validity of a bar-mounted Myotest® instrument in measuring the force and power production in the squat and bench press exercises when compared to the gold standard of a computerized linear transducer and force platform system. Fifty-four men (bench press: 39-171 kg; squat: 75-221 kg) and 43 women (bench press: 18-80 kg; squat: 30-115 kg) (age range 18-30 years) performed a 1 repetition maximum (1RM) strength test in bench press and squat exercises. Power testing consisted of the jump squat and the bench throw at 30% of each subject's 1RM. During each measurement, both the Myotest® instrument and the Celesco linear transducer of the directly interfaced BMS system (Ballistic Measurement System [BMS] Innervations Inc, Fitness Technology force plate, Skye, South Australia, Australia) were mounted to the weight bar. A strong, positive correlation (r) between the Myotest and BMS systems and a high correlation of determination (R2) was demonstrated for bench throw force (r = 0.95, p < 0.05) (R2 = 0.92); bench throw power (r = 0.96, p < 0.05) (R2 = 0.93); squat jump force (r = 0.98, p < 0.05) (R2 = 0.97); and squat jump power (r = 0.91, p < 0.05) (R2 = 0.82). In conclusion, when fixed on the bar in the vertical axis, the Myotest is a valid field instrument for measuring force and power in commonly used exercise movements.

A stab in the dark: Design and construction of a novel device for conducting incised knife trauma investigations and its initial test.

PubMed

Humphrey, Caitlin; Kumaratilake, Jaliya; Henneberg, Maciej

2016-05-01

Knife attacks are commonly seen in Australia and other countries. During forensic investigations the force with which a wound was inflicted is often questioned. The ability to examine resultant trauma and particular weapons at different forces with an experimental device may lead to better interpretations of knife wounds. The objective of this study is to design, construct and test a device to analyse the characteristics and forces involved in knife attacks, particularly incised wounds. The mechanical variables (e.g. force, angle, knife geometry) involved in knife attacks have been considered to design and construct a suitable device which allows these variables to be systematically controlled and varied. A device was designed and constructed from mild steel. This included a pivoting arm and instrumented knife holder. The arm has adjustable angle and weight so that knives can be operated at different calculated forces. A device was successfully constructed and the repeatability of incised knife trauma and its characteristics in skeletal tissues were investigated. A device which allows reproducible and controlled experiments with knife wounds will be advantageous to forensic investigations. In particular, in determining forces and types of weapons associated with particular wounds, identifying or eliminating suspected weapons and more accurately answering the common question: How much force would be required to cause that particular wound. This could help to characterise the perpetrator. The device can be altered to be used in the future to investigate trauma caused by other weapons. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Maximal bite force, facial morphology and sucking habits in young children with functional posterior crossbite

PubMed Central

CASTELO, Paula Midori; GAVIÃO, Maria Beatriz Duarte; PEREIRA, Luciano José; BONJARDIM, Leonardo Rigoldi

2010-01-01

Objective The maintenance of normal conditions of the masticatory function is determinant for the correct growth and development of its structures. Thus, the aims of this study were to evaluate the influence of sucking habits on the presence of crossbite and its relationship with maximal bite force, facial morphology and body variables in 67 children of both genders (3.5-7 years) with primary or early mixed dentition. Material and methods The children were divided in four groups: primary-normocclusion (PN, n=19), primary-crossbite (PC, n=19), mixed-normocclusion (MN, n=13), and mixed-crossbite (MC, n=16). Bite force was measured with a pressurized tube, and facial morphology was determined by standardized frontal photographs: AFH (anterior face height) and BFW (bizygomatic facial width). Results It was observed that MC group showed lower bite force than MN, and AFH/ BFW was significantly smaller in PN than PC (t-test). Weight and height were only significantly correlated with bite force in PC group (Pearson’s correlation test). In the primary dentition, AFH/BFW and breast-feeding (at least six months) were positive and negatively associated with crossbite, respectively (multiple logistic regression). In the mixed dentition, breastfeeding and bite force showed negative associations with crossbite (univariate regression), while nonnutritive sucking (up to 3 years) associated significantly with crossbite in all groups (multiple logistic regression). Conclusions In the studied sample, sucking habits played an important role in the etiology of crossbite, which was associated with lower bite force and long-face tendency. PMID:20485925

Effect of olympic weight category on performance in the roundhouse kick to the head in taekwondo.

PubMed

Estevan, Isaac; Falco, Coral; Alvarez, Octavio; Molina-García, Javier

2012-03-01

In taekwondo, kick performance is generally measured using impact force and time. This study aimed to analyse performance in the roundhouse kick to the head according to execution distance between and within Olympic weight categories. The participants were 36 male athletes divided into three categories: featherweight (n = 10), welterweight (n = 15) and heavyweight (n = 11). Our results show that taekwondo athletes in all weight categories generate a similar relative impact force. However, the results indicate that weight has a large impact on kick performance, particularly in relation to total response time.

Effect of Olympic Weight Category on Performance in the Roundhouse Kick to the Head in Taekwondo

PubMed Central

Estevan, Isaac; Falco, Coral; Álvarez, Octavio; Molina-García, Javier

2012-01-01

In taekwondo, kick performance is generally measured using impact force and time. This study aimed to analyse performance in the roundhouse kick to the head according to execution distance between and within Olympic weight categories. The participants were 36 male athletes divided into three categories: featherweight (n = 10), welterweight (n = 15) and heavyweight (n = 11). Our results show that taekwondo athletes in all weight categories generate a similar relative impact force. However, the results indicate that weight has a large impact on kick performance, particularly in relation to total response time. PMID:23486074

Joint contact forces can be reduced by improving joint moment symmetry in below-knee amputee gait simulations.

PubMed

Koelewijn, Anne D; van den Bogert, Antonie J

2016-09-01

Despite having a fully functional knee and hip in both legs, asymmetries in joint moments of the knee and hip are often seen in gait of persons with a unilateral transtibial amputation (TTA), possibly resulting in excessive joint loading. We hypothesize that persons with a TTA can walk with more symmetric joint moments at the cost of increased effort or abnormal kinematics. The hypothesis was tested using predictive simulations of gait. Open loop controls of one gait cycle were found by solving an optimization problem that minimizes a combination of walking effort and tracking error in joint angles, ground reaction force and gait cycle duration. A second objective was added to penalize joint moment asymmetry, creating a multi-objective optimization problem. A Pareto front was constructed by changing the weights of the objectives and three solutions were analyzed to study the effect of increasing joint moment symmetry. When the optimization placed more weight on moment symmetry, walking effort increased and kinematics became less normal, confirming the hypothesis. TTA gait improved with a moderate increase in joint moment symmetry. At a small cost of effort and abnormal kinematics, the peak hip extension moment in the intact leg was decreased significantly, and so was the joint contact force in the knee and hip. Additional symmetry required a significant increase in walking effort and the joint contact forces in both hips became significantly higher than in able-bodied gait. Copyright © 2016 Elsevier B.V. All rights reserved.

Role of optimization criterion in static asymmetric analysis of lumbar spine load.

PubMed

Daniel, Matej

2011-10-01

A common method for load estimation in biomechanics is the inverse dynamics optimization, where the muscle activation pattern is found by minimizing or maximizing the optimization criterion. It has been shown that various optimization criteria predict remarkably similar muscle activation pattern and intra-articular contact forces during leg motion. The aim of this paper is to study the effect of the choice of optimization criterion on L4/L5 loading during static asymmetric loading. Upright standing with weight in one stretched arm was taken as a representative position. Musculoskeletal model of lumbar spine model was created from CT images of Visible Human Project. Several criteria were tested based on the minimization of muscle forces, muscle stresses, and spinal load. All criteria provide the same level of lumbar spine loading (difference is below 25%), except the criterion of minimum lumbar shear force which predicts unrealistically high spinal load and should not be considered further. Estimated spinal load and predicted muscle force activation pattern are in accordance with the intradiscal pressure measurements and EMG measurements. The L4/L5 spine loads 1312 N, 1674 N, and 1993 N were predicted for mass of weight in hand 2, 5, and 8 kg, respectively using criterion of mininum muscle stress cubed. As the optimization criteria do not considerably affect the spinal load, their choice is not critical in further clinical or ergonomic studies and computationally simpler criterion can be used.

Assessment of hindlimb locomotor strength in spinal cord transected rats through animal-robot contact force.

PubMed

Nessler, Jeff A; Moustafa-Bayoumi, Moustafa; Soto, Dalziel; Duhon, Jessica; Schmitt, Ryan

2011-12-01

Robotic locomotor training devices have gained popularity in recent years, yet little has been reported regarding contact forces experienced by the subject performing automated locomotor training, particularly in animal models of neurological injury. The purpose of this study was to develop a means for acquiring contact forces between a robotic device and a rodent model of spinal cord injury through instrumentation of a robotic gait training device (the rat stepper) with miniature force/torque sensors. Sensors were placed at each interface between the robot arm and animal's hindlimb and underneath the stepping surface of both hindpaws (four sensors total). Twenty four female, Sprague-Dawley rats received mid-thoracic spinal cord transections as neonates and were included in the study. Of these 24 animals, training began for 18 animals at 21 days of age and continued for four weeks at five min/day, five days/week. The remaining six animals were untrained. Animal-robot contact forces were acquired for trained animals weekly and untrained animals every two weeks while stepping in the robotic device with both 60 and 90% of their body weight supported (BWS). Animals that received training significantly increased the number of weight supported steps over the four week training period. Analysis of raw contact forces revealed significant increases in forward swing and ground reaction forces during this time, and multiple aspects of animal-robot contact forces were significantly correlated with weight bearing stepping. However, when contact forces were normalized to animal body weight, these increasing trends were no longer present. Comparison of trained and untrained animals revealed significant differences in normalized ground reaction forces (both horizontal and vertical) and normalized forward swing force. Finally, both forward swing and ground reaction forces were significantly reduced at 90% BWS when compared to the 60% condition. These results suggest that measurement of animal-robot contact forces using the instrumented rat stepper can provide a sensitive and reliable measure of hindlimb locomotor strength and control of flexor and extensor muscle activity in neurologically impaired animals. Additionally, these measures may be useful as a means to quantify training intensity or dose-related functional outcomes of automated training.

Regional income inequality model based on theil index decomposition and weighted variance coeficient

NASA Astrophysics Data System (ADS)

Sitepu, H. R.; Darnius, O.; Tambunan, W. N.

2018-03-01

Regional income inequality is an important issue in the study on economic development of a certain region. Rapid economic development may not in accordance with people’s per capita income. The method of measuring the regional income inequality has been suggested by many experts. This research used Theil index and weighted variance coefficient in order to measure the regional income inequality. Regional income decomposition which becomes the productivity of work force and their participation in regional income inequality, based on Theil index, can be presented in linear relation. When the economic assumption in j sector, sectoral income value, and the rate of work force are used, the work force productivity imbalance can be decomposed to become the component in sectors and in intra-sectors. Next, weighted variation coefficient is defined in the revenue and productivity of the work force. From the quadrate of the weighted variation coefficient result, it was found that decomposition of regional revenue imbalance could be analyzed by finding out how far each component contribute to regional imbalance which, in this research, was analyzed in nine sectors of economic business.

Ontogenetic scaling of burrowing forces in the earthworm Lumbricus terrestris.

PubMed

Quillin, K J

2000-09-01

In hydrostatic skeletons, it is the internal fluid under pressure surrounded by a body wall in tension (rather than a rigid lever) that enables the stiffening of the organism, the antagonism of muscles and the transmission of force from the muscles to the environment. This study examined the ontogenetic effects of body size on force production by an organism supported with a hydrostatic skeleton. The earthworm Lumbricus terrestris burrows by forcefully enlarging crevices in the soil. I built a force-measuring apparatus that measured the radial forces as earthworms of different sizes crawled through and enlarged pre-formed soil burrows. I also built an apparatus that measured the radial and axial forces as earthworms of different sizes attempted to elongate a dead-end burrow. Earthworms ranging in body mass m(b) from hatchlings (0.012 g) to adults (8.9 g) exerted maximum forces (F, in N) during active radial expansion of their burrows (F=0.32 m(b)(0.43)) and comparable forces during axial elongation of the burrow (F=0.26 m(b)(0.47)). Both these forces were almost an order of magnitude greater than the radial anchoring forces during normal peristalsis within burrows (F=0.04 m(b)(0.45)). All radial and axial forces scaled as body mass raised to the 2/5 power rather than to the 2/3 power expected by geometric similarity, indicating that large worms exert greater forces than small worms on an absolute scale, but the difference was less than predicted by scaling considerations. When forces were normalized by body weight, hatchlings could push 500 times their own body weight, while large adults could push only 10 times their own body weight.

Required coefficient of friction in the anteroposterior and mediolateral direction during turning at different walking speeds

PubMed Central

Yamaguchi, Takeshi; Suzuki, Akito; Hokkirigawa, Kazuo

2017-01-01

This study investigated the required coefficient of friction (RCOF) and the tangent of center of mass (COM)–center of pressure (COP) angle in the mediolateral (ML) and anteroposterior (AP) directions during turning at different walking speeds. Sixteen healthy young adults (8 males and 8 females) participated in this study. The participants were instructed to conduct trials of straight walking and 90° step and spin turns to the right at each of three self-selected speeds (slow, normal, and fast). The ML and AP directions during turning gait were defined using the orientation of the pelvis to construct a body-fixed reference frame. The RCOF values and COM–COP angle tangent in the ML direction during turning at weight acceptance phase were higher than those during straight walking, and those values increased with increasing walking speed. The ML component of the RCOF and COM–COP tangent values during weight acceptance for step turns were higher than those for spin turns. The mean centripetal force during turning tended to increase with an increase in walking speed and had a strong positive correlation with the RCOF values in the ML direction (R = 0.97 during the weight acceptance phase; R = 0.95 during the push-off phase). Therefore, turning, particularly step turn, is likely to cause lateral slip at weight acceptance because of the increased centripetal force compared with straight walking. Future work should test at-risk population and compare with the present results. PMID:28640853

Required coefficient of friction in the anteroposterior and mediolateral direction during turning at different walking speeds.

PubMed

Yamaguchi, Takeshi; Suzuki, Akito; Hokkirigawa, Kazuo

2017-01-01

This study investigated the required coefficient of friction (RCOF) and the tangent of center of mass (COM)-center of pressure (COP) angle in the mediolateral (ML) and anteroposterior (AP) directions during turning at different walking speeds. Sixteen healthy young adults (8 males and 8 females) participated in this study. The participants were instructed to conduct trials of straight walking and 90° step and spin turns to the right at each of three self-selected speeds (slow, normal, and fast). The ML and AP directions during turning gait were defined using the orientation of the pelvis to construct a body-fixed reference frame. The RCOF values and COM-COP angle tangent in the ML direction during turning at weight acceptance phase were higher than those during straight walking, and those values increased with increasing walking speed. The ML component of the RCOF and COM-COP tangent values during weight acceptance for step turns were higher than those for spin turns. The mean centripetal force during turning tended to increase with an increase in walking speed and had a strong positive correlation with the RCOF values in the ML direction (R = 0.97 during the weight acceptance phase; R = 0.95 during the push-off phase). Therefore, turning, particularly step turn, is likely to cause lateral slip at weight acceptance because of the increased centripetal force compared with straight walking. Future work should test at-risk population and compare with the present results.

The effect of weight loss by ketogenic diet on the body composition, performance-related physical fitness factors and cytokines of Taekwondo athletes.

PubMed

Rhyu, Hyun-Seung; Cho, Su-Youn

2014-10-01

The purpose of this study was to investigate the effects of the weight loss through 3 weeks of ketogenic diet on performance-related physical fitness and inflammatory cytokines in Taekwondo athletes. The subjects selected for this research were 20 Taekwondo athletes of the high schools who participated in a summer camp training program. The subjects were randomly assigned to 2 groups, 10 subjects to each group: the ketogenic diet (KD) group and the non-ketogenic diet (NKD) group. Body composition, performance-related physical fitness factors (2,000 m sprint, Wingate test, grip force, back muscle strength, sit-up, 100 m sprint, standing broad jump, single leg standing) and cytokines (Iinterleukin-6, Interferon-γ, tumor necrosis factor-α) were analyzed before and after 3weeks of ketogenic diet. No difference between the KD and NKD groups in weight, %body fat, BMI and fat free mass. However, the KD group, compared to the NKD group, finished 2,000 m sprint in less time after weight loss, and also felt less fatigue as measured by the Wingate test and showed less increase in tumor necrosis factor-α. This result suggests that KD diet can be helpful for weight category athletes, such as Taekwondo athletes, by improving aerobic capacity and fatigue resistance capacity, and also by exerting positive effect on inflammatory response.

Effect of fish oil and coconut fat supplementation on depressive-type behavior and corticosterone levels of prenatally stressed male rats.

PubMed

Borsonelo, Elizabethe Cristina; Suchecki, Deborah; Galduróz, José Carlos Fernandes

2011-04-18

Prenatal stress (PNS) during critical periods of brain development has been associated with numerous behavioral and/or mood disorders in later life. These outcomes may result from changes in the hypothalamic-pituitary-adrenal (HPA) axis activity, which, in turn, can be modulated by environmental factors, such as nutritional status. In this study, the adult male offspring of dams exposed to restraint stress during the last semester of pregnancy and fed different diets were evaluated for depressive-like behavior in the forced swimming test and for the corticosterone response to the test. Female Wistar rats were allocated to one of three groups: regular diet, diet supplemented with coconut fat or with fish oil, offered during pregnancy and lactation. When pregnancy was confirmed, they were distributed into control or stress groups. Stress consisted of restraint and bright light for 45 min, three times per day, in the last week of pregnancy. The body weight of the adult offspring submitted to PNS was lower than that of controls. In the forced swimming test, time of immobility was reduced and swimming was increased in PNS rats fed fish oil and plasma corticosterone levels immediately after the forced swimming test were lower in PNS rats fed regular diet than their control counterparts; this response was reduced in control rats whose mothers were fed fish oil and coconut fat. The present results indicate that coconut fat and fish oil influenced behavioral and hormonal responses to the forced swimming test in both control and PNS adult male rats. Copyright © 2011 Elsevier B.V. All rights reserved.

Validity Of The Nintendo Wii Balance Board To Assess Weight Bearing Asymmetry During Sit-To-Stand And Return-To-Sit Task

PubMed Central

Abujaber, Sumayeh; Gillispie, Gregory; Marmon, Adam; Zeni, Joseph

2015-01-01

Weight bearing asymmetry is common in patients with unilateral lower limb musculoskeletal pathologies. The Nintendo Wii Balance Board (WBB) has been suggested as a low-cost and widely-available tool to measure weight bearing asymmetry in a clinical environment; however no study has evaluated the validity of this tool during dynamic tasks. Therefore, the purpose of this study was to determine the concurrent validity of force measurements acquired from the WBB as compared to laboratory force plates. Thirty-five individuals before, or within 1 year of total joint arthroplasty performed a sit-to-stand and return-to-sit task in two conditions. First, subjects performed the task with both feet placed on a single WBB. Second, the task was repeated with each foot placed on an individual laboratory force plate. Peak vertical ground reaction force (VGRF) under each foot and the inter-limb symmetry ratio were calculated. Validity was examined using Intraclass Correlation Coefficients (ICC), regression analysis, 95% limits of agreement and Bland-Altman plots. Force plates and the WBB exhibited excellent agreement for all outcome measurements (ICC =0.83–0.99). Bland-Altman plots showed no obvious relationship between the difference and the mean for the peak VGRF, but there was a consistent trend in which VGRF on the unaffected side was lower and VGRF on the affected side was higher when using the WBB. However, these consistent biases can be adjusted for by utilizing regression equations that estimate the force plate values based on the WBB force. The WBB may serve as a valid, suitable, and low-cost alternative to expensive, laboratory force plates for measuring weight bearing asymmetry in clinical settings. PMID:25715680

Validity of the Nintendo Wii Balance Board to assess weight bearing asymmetry during sit-to-stand and return-to-sit task.

PubMed

Abujaber, Sumayeh; Gillispie, Gregory; Marmon, Adam; Zeni, Joseph

2015-02-01

Weight bearing asymmetry is common in patients with unilateral lower limb musculoskeletal pathologies. The Nintendo Wii Balance Board (WBB) has been suggested as a low-cost and widely-available tool to measure weight bearing asymmetry in a clinical environment; however no study has evaluated the validity of this tool during dynamic tasks. Therefore, the purpose of this study was to determine the concurrent validity of force measurements acquired from the WBB as compared to laboratory force plates. Thirty-five individuals before, or within 1 year of total joint arthroplasty performed a sit-to-stand and return-to-sit task in two conditions. First, subjects performed the task with both feet placed on a single WBB. Second, the task was repeated with each foot placed on an individual laboratory force plate. Peak vertical ground reaction force (VGRF) under each foot and the inter-limb symmetry ratio were calculated. Validity was examined using Intraclass Correlation Coefficients (ICC), regression analysis, 95% limits of agreement and Bland-Altman plots. Force plates and the WBB exhibited excellent agreement for all outcome measurements (ICC=0.83-0.99). Bland-Altman plots showed no obvious relationship between the difference and the mean for the peak VGRF, but there was a consistent trend in which VGRF on the unaffected side was lower and VGRF on the affected side was higher when using the WBB. However, these consistent biases can be adjusted for by utilizing regression equations that estimate the force plate values based on the WBB force. The WBB may serve as a valid, suitable, and low-cost alternative to expensive, laboratory force plates for measuring weight bearing asymmetry in clinical settings. Copyright © 2015 Elsevier B.V. All rights reserved.

Ankle joint pressure changes in high tibial and distal femoral osteotomies: a cadaver study.

PubMed

Krause, F; Barandun, A; Klammer, G; Zderic, I; Gueorguiev, B; Schmid, T

2017-01-01

To assess the effect of high tibial and distal femoral osteotomies (HTO and DFO) on the pressure characteristics of the ankle joint. Varus and valgus malalignment of the knee was simulated in human cadaver full-length legs. Testing included four measurements: baseline malalignment, 5° and 10° re-aligning osteotomy, and control baseline malalignment. For HTO, testing was rerun with the subtalar joint fixed. In order to represent half body weight, a 300 N force was applied onto the femoral head. Intra-articular sensors captured ankle pressure. In the absence of restriction of subtalar movement, insignificant migration of the centre of force and changes of maximal pressure were seen at the ankle joint. With restricted subtalar motion, more significant lateralisation of the centre of force were seen with the subtalar joint in varus than in valgus position. Changes in maximum pressure were again not significant. The re-alignment of coronal plane knee deformities by HTO and DFO altered ankle pressure characteristics. When the subtalar joint was fixed in the varus position, migration of centre of force after HTO was more significant than when the subtalar joint was fixed in valgus. Cite this article: Bone Joint J 2017;99-B:59-65. ©2017 The British Editorial Society of Bone & Joint Surgery.

Body weight perceptions and eating-related weight control behaviors of on-reserve First Nations youth from Ontario, Canada.

PubMed

Gates, Allison; Hanning, Rhona M; Martin, Ian D; Gates, Michelle; Tsuji, Leonard J S

2014-01-01

Research investigating the body weight perceptions and eating-related weight control behaviors of First Nations (FN) youth living on reserve in Canada has been scarce. Knowledge of body weight perceptions may help to improve the relevance of initiatives promoting healthy weights. The purpose of this study was to examine the body weight perceptions and eating-related weight control behaviors of grade 6-8 on-reserve FN youth from seven Ontario communities. Data were collected from December 2003 to June 2010 from a convenience sample of FN youth (aged 10-14 years) using the Waterloo Web-based Eating Behaviour Questionnaire (WEB-Q). Participants were categorized into body mass index (BMI) categories based on International Obesity Task Force (IOTF) cut points. Frequency statistics were computed in the comparison of measured BMI and weight perceptions and weight control behaviors. Differences by BMI category were tested using Pearson Χ2 tests. A total of 267 youth from seven Ontario FN communities participated in the study (48.6% male). Overall, 36.3% of youth were overweight and 21.3% were obese (combined total of 57.6%). Similar to non-Aboriginal youth, a greater proportion of FN girls who were at a normal weight were concerned that their weight was too high compared to boys. However, one-third of normal weight boys were currently trying to lose weight. A greater proportion of obese girls were trying to lose weight compared to boys. Overall, a large proportion of both overweight boys and girls were attempting to gain weight. The present study provides a unique investigation into the weight perceptions and weight control behaviors of on-reserve FN youth living in isolated communities in Ontario, Canada. Many of the perceptions elucidated in this study are similar to those observed in non-Aboriginal youth, while others differed. The knowledge of these perceptions and further research to investigate what factors influences them will help to customize health promoting initiatives that are relevant to the youth in the participating communities.

Disuse bone loss in hindquarter suspended rats: partial weightbearing, exercise and ibandronate treatment as countermeasures

NASA Technical Reports Server (NTRS)

Schultheis, L.; Ruff, C. B.; Rastogi, S.; Bloomfield, S.; Hogan, H. A.; Fedarko, N.; Thierry-Palmer, M.; Ruiz, J.; Bauss, F.; Shapiro, J. R.

2000-01-01

The purpose of this study was to evaluate potential countermeasures for bone loss during long-term space missions in the hindquarter suspended rat, including partial weight bearing (surrogate for artificial gravity) episodic full weight bearing (2 hour/day full weight bearing) and treatment with the third generation bisphosphonate ibandronate (Roche). Graded mechanical loading was studied by housing the animals on a novel servo controlled force plate system which permitted the titration of mechanical force at varying frequency and amplitude and different levels of weight bearing. The force plate, which forms the cage floor, is a glass platform supported by an 18" diameter speaker cone filled with expanding polyurethane foam. An infrared optical sensor attached to the speaker cone yields a voltage linearly related to vertical displacement of the glass platform. The dynamic force on the paw was computed as a product of the apparent mass of the animal on the platform at rest and the acceleration of the platform determined from the second derivative of the optical sensor output. The mass of the animal on the platform was varied by adjusting tension on the tether suspending the animal. Mechanical impact loading was titrated with the force plate resonating at different frequencies, including 3 Hz and 16 Hz.

Linking actions and objects: Context-specific learning of novel weight priors.

PubMed

Trewartha, Kevin M; Flanagan, J Randall

2017-06-01

Distinct explicit and implicit memory processes support weight predictions used when lifting objects and making perceptual judgments about weight, respectively. The first time that an object is encountered weight is predicted on the basis of learned associations, or priors, linking size and material to weight. A fundamental question is whether the brain maintains a single, global representation of priors, or multiple representations that can be updated in a context specific way. A second key question is whether the updating of priors, or the ability to scale lifting forces when repeatedly lifting unusually weighted objects requires focused attention. To investigate these questions we compared the adaptability of weight predictions used when lifting objects and judging their weights in different groups of participants who experienced size-weight inverted objects passively (with the objects placed on the hands) or actively (where participants lift the objects) under full or divided attention. To assess weight judgments we measured the size-weight illusion after every 20 trials of experience with the inverted objects both passively and actively. The attenuation of the illusion that arises when lifting inverted object was found to be context-specific such that the attenuation was larger when the mode of interaction with the inverted objects matched the method of assessment of the illusion. Dividing attention during interaction with the inverted objects had no effect on attenuation of the illusion, but did slow the rate at which lifting forces were scaled to the weight inverted objects. These findings suggest that the brain stores multiple representations of priors that are context specific, and that focused attention is important for scaling lifting forces, but not for updating weight predictions used when judging object weight. Copyright © 2017 Elsevier B.V. All rights reserved.

Space Launch Initiative (SLI) Engine Test

NASA Technical Reports Server (NTRS)

2002-01-01

NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, has begun a series of engine tests on the Reaction Control Engine developed by TRW Space and Electronics for NASA's Space Launch Initiative (SLI). SLI is a technology development effort aimed at improving the safety, reliability, and cost effectiveness of space travel for reusable launch vehicles. The engine in this photo, the first engine tested at MSFC that includes SLI technology, was tested for two seconds at a chamber pressure of 185 pounds per square inch absolute (psia). Propellants used were liquid oxygen as an oxidizer and liquid hydrogen as fuel. Designed to maneuver vehicles in orbit, the engine is used as an auxiliary propulsion system for docking, reentry, fine-pointing, and orbit transfer while the vehicle is in orbit. The Reaction Control Engine has two unique features. It uses nontoxic chemicals as propellants, which creates a safer environment with less maintenance and quicker turnaround time between missions, and it operates in dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The force of low level thrust allows the vehicle to fine-point maneuver and dock, while the force of the high level thrust is used for reentry, orbital transfer, and course positioning.

Sutural loosening and skeletal flexibility during growth: determination of drop-like shapes in sea urchins.

PubMed

Johnson, Amy S; Ellers, Olaf; Lemire, Jim; Minor, Melissa; Leddy, Holly A

2002-02-07

The shape of sea urchins may be determined mechanically by patterns of force analogous to those that determine the shape of a water droplet. This mechanical analogy implies skeletal flexibility at the time of growth. Although comprised of many rigid calcite plates, sutural collagenous ligaments could confer such flexibility if the sutures between plates loosened and acted as joints at the time of growth. We present experimental evidence of such flexibility associated with weight gain and growth. Over 13-, 4-, and 2-week periods, fed urchins (Strongylocentrotus droebachiensis) gained weight and developed looser sutures than unfed urchins that maintained or lost weight. Further, skeletons of fed urchins force-relaxed more than did those of unfed urchins and urchins with loose sutures force-relaxed more than those with tight sutures. Urchins (Strongylocentrotus franciscanus) fed for two and a half weeks, gained weight, also had looser skeletons and deposited calcite at sutural margins, whereas unfed ones did not. In field populations of S. droebachiensis the percentage having loose sutures varied with urchin diameter and reflected their size-specific growth rate. The association between feeding, weight gain, calcite deposition, force relaxation and sutural looseness supports the hypothesis that urchins deform flexibly while growing, thus determining their drop-like shapes.

Propulsion Flight-Test Fixture

NASA Technical Reports Server (NTRS)

Palumbo, Nate; Vachon, M. Jake; Richwine, Dave; Moes, Tim; Creech, Gray

2003-01-01

NASA Dryden Flight Research Center s new Propulsion Flight Test Fixture (PFTF), designed in house, is an airborne engine-testing facility that enables engineers to gather flight data on small experimental engines. Without the PFTF, it would be necessary to obtain such data from traditional wind tunnels, ground test stands, or laboratory test rigs. Traditionally, flight testing is reserved for the last phase of engine development. Generally, engines that embody new propulsion concepts are not put into flight environments until their designs are mature: in such cases, either vehicles are designed around the engines or else the engines are mounted in or on missiles. However, a captive carry capability of the PFTF makes it possible to test engines that feature air-breathing designs (for example, designs based on the rocket-based combined cycle) economically in subscale experiments. The discovery of unknowns made evident through flight tests provides valuable information to engine designers early in development, before key design decisions are made, thereby potentially affording large benefits in the long term. This is especially true in the transonic region of flight (from mach 0.9 to around 1.2), where it can be difficult to obtain data from wind tunnels and computational fluid dynamics. In January 2002, flight-envelope expansion to verify the design and capabilities of the PFTF was completed. The PFTF was flown on a specially equipped supersonic F-15B research testbed airplane, mounted on the airplane at a center-line attachment fixture, as shown in Figure 1. NASA s F-15B testbed has been used for several years as a flight-research platform. Equipped with extensive research air-data, video, and other instrumentation systems, the airplane carries externally mounted test articles. Traditionally, the majority of test articles flown have been mounted at the centerline tank-attachment fixture, which is a hard-point (essentially, a standardized weapon-mounting fixture). This hard-point has large weight margins, and, because it is located near the center of gravity of the airplane, the weight of equipment mounted there exerts a minimal effect on the stability and controllability of the airplane. The PFTF (see Figure 2) includes a one-piece aluminum structure that contains space for instrumentation, propellant tanks, and feed-system components. The PFTF also houses a force balance, on which is mounted the subscale engine or other experimental apparatus that is to be the subject of a flight test. The force balance measures a combination of inertial and aerodynamic forces and moments acting on the experimental apparatus.

Skeletal Muscle, but not Cardiovascular Function, Is Altered in a Mouse Model of Autosomal Recessive Hypophosphatemic Rickets.

PubMed

Wacker, Michael J; Touchberry, Chad D; Silswal, Neerupma; Brotto, Leticia; Elmore, Chris J; Bonewald, Lynda F; Andresen, Jon; Brotto, Marco

2016-01-01

Autosomal recessive hypophosphatemic rickets (ARHR) is a heritable disorder characterized by hypophosphatemia, osteomalacia, and poor bone development. ARHR results from inactivating mutations in the DMP1 gene with the human phenotype being recapitulated in the Dmp1 null mouse model which displays elevated plasma fibroblast growth factor 23. While the bone phenotype has been well-characterized, it is not known what effects ARHR may also have on skeletal, cardiac, or vascular smooth muscle function, which is critical to understand in order to treat patients suffering from this condition. In this study, the extensor digitorum longus (EDL-fast-twitch muscle), soleus (SOL-slow-twitch muscle), heart, and aorta were removed from Dmp1 null mice and ex-vivo functional tests were simultaneously performed in collaboration by three different laboratories. Dmp1 null EDL and SOL muscles produced less force than wildtype muscles after normalization for physiological cross sectional area of the muscles. Both EDL and SOL muscles from Dmp1 null mice also produced less force after the addition of caffeine (which releases calcium from the sarcoplasmic reticulum) which may indicate problems in excitation contraction coupling in these mice. While the body weights of the Dmp1 null were smaller than wildtype, the heart weight to body weight ratio was higher. However, there were no differences in pathological hypertrophic gene expression compared to wildtype and maximal force of contraction was not different indicating that there may not be cardiac pathology under the tested conditions. We did observe a decrease in the rate of force development generated by cardiac muscle in the Dmp1 null which may be related to some of the deficits observed in skeletal muscle. There were no differences observed in aortic contractions induced by PGF2α or 5-HT or in endothelium-mediated acetylcholine-induced relaxations or endothelium-independent sodium nitroprusside-induced relaxations. In summary, these results indicate that there are deficiencies in both fast twitch and slow twitch muscle fiber type contractions in this model of ARHR, while there was less of a phenotype observed in cardiac muscle, and no differences observed in aortic function. These results may help explain skeletal muscle weakness reported by some patients with osteomalacia and need to be further investigated.

Skeletal Muscle, but not Cardiovascular Function, Is Altered in a Mouse Model of Autosomal Recessive Hypophosphatemic Rickets

PubMed Central

Wacker, Michael J.; Touchberry, Chad D.; Silswal, Neerupma; Brotto, Leticia; Elmore, Chris J.; Bonewald, Lynda F.; Andresen, Jon; Brotto, Marco

2016-01-01

Autosomal recessive hypophosphatemic rickets (ARHR) is a heritable disorder characterized by hypophosphatemia, osteomalacia, and poor bone development. ARHR results from inactivating mutations in the DMP1 gene with the human phenotype being recapitulated in the Dmp1 null mouse model which displays elevated plasma fibroblast growth factor 23. While the bone phenotype has been well-characterized, it is not known what effects ARHR may also have on skeletal, cardiac, or vascular smooth muscle function, which is critical to understand in order to treat patients suffering from this condition. In this study, the extensor digitorum longus (EDL-fast-twitch muscle), soleus (SOL–slow-twitch muscle), heart, and aorta were removed from Dmp1 null mice and ex-vivo functional tests were simultaneously performed in collaboration by three different laboratories. Dmp1 null EDL and SOL muscles produced less force than wildtype muscles after normalization for physiological cross sectional area of the muscles. Both EDL and SOL muscles from Dmp1 null mice also produced less force after the addition of caffeine (which releases calcium from the sarcoplasmic reticulum) which may indicate problems in excitation contraction coupling in these mice. While the body weights of the Dmp1 null were smaller than wildtype, the heart weight to body weight ratio was higher. However, there were no differences in pathological hypertrophic gene expression compared to wildtype and maximal force of contraction was not different indicating that there may not be cardiac pathology under the tested conditions. We did observe a decrease in the rate of force development generated by cardiac muscle in the Dmp1 null which may be related to some of the deficits observed in skeletal muscle. There were no differences observed in aortic contractions induced by PGF2α or 5-HT or in endothelium-mediated acetylcholine-induced relaxations or endothelium-independent sodium nitroprusside-induced relaxations. In summary, these results indicate that there are deficiencies in both fast twitch and slow twitch muscle fiber type contractions in this model of ARHR, while there was less of a phenotype observed in cardiac muscle, and no differences observed in aortic function. These results may help explain skeletal muscle weakness reported by some patients with osteomalacia and need to be further investigated. PMID:27242547

Object properties and cognitive load in the formation of associative memory during precision lifting.

PubMed

Li, Yong; Randerath, Jennifer; Bauer, Hans; Marquardt, Christian; Goldenberg, Georg; Hermsdörfer, Joachim

2009-01-03

When we manipulate familiar objects in our daily life, our grip force anticipates the physical demands right from the moment of contact with the object, indicating the existence of a memory for relevant object properties. This study explores the formation and consolidation of the memory processes that associate either familiar (size) or arbitrary object features (color) with object weight. In the general task, participants repetitively lifted two differently weighted objects (580 and 280 g) in a pseudo-random order. Forty young healthy adults participated in this study and were randomly distributed into four groups: Color Cue Single task (CCS, blue and red, 9.8(3)cm(3)), Color Cue Dual task (CCD), No Cue (NC) and Size Cue (SC, 9.8(3) and 6(3)cm(3)) group. All groups performed a repetitive precision grasp-lift task and were retested with the same protocol after a 5-min pause. The CCD group was also required to simultaneously perform a memory task during each lift of differently weighted objects coded by color. The results show that groups lifting objects with arbitrary or familiar features successfully formed the association between object weight and manipulated object features and incorporated this into grip force programming, as observed in the different scaling of grip force and grip force rate for different object weights. An arbitrary feature, i.e., color, can be sufficiently associated with object weight, however with less strength than the familiar feature of size. The simultaneous memory task impaired anticipatory force scaling during repetitive object lifting but did not jeopardize the learning process and the consolidation of the associative memory.

Comparison of cervical spine kinematics using a fluoroscopic model for adjacent segment degeneration. Invited submission from the Joint Section on Disorders of the Spine and Peripheral Nerves, March 2007.

PubMed

Cheng, Joseph S; Liu, Fei; Komistek, Richard D; Mahfouz, Mohamed R; Sharma, Adrija; Glaser, Diana

2007-11-01

In this cervical spine kinematics study the authors evaluate the motions and forces in the normal, degenerative, and fused states to assess how alteration in the cervical motion segment affects adjacent segment degeneration and spondylosis. Fluoroscopic images obtained in 30 individuals (10 in each group with disease at C5-6) undergoing flexion/extension motions were collected. Kinematic data were obtained from the fluoroscopic images and analyzed with an inverse dynamic mathematical model of the cervical spine that was developed for this analysis. During 20 degrees flexion to 15 degrees extension, average relative angles at the adjacent levels of C6-7 and C4-5 in the fused patients were 13.4 degrees and 8.8 degrees versus 3.7 degrees and 4.8 degrees in the healthy individuals. Differences at C3-4 averaged only about 1 degrees. Maximum transverse forces in the fused spines were two times the skull weight at C6-7 and one times the skull weight at C4-5, compared with 0.2 times the skull weight and 0.3 times the skull weight in the healthy individuals. Vertical forces ranged from 1.6 to 2.6 times the skull weight at C6-7 and from 1.2 to 2.5 times the skull weight at C4-5 in the patients who had undergone fusion, and from 1.4 to 3.1 times the skull weight and from 0.9 to 3.3 times the skull weight, respectively, in the volunteers. Adjacent-segment degeneration may occur in patients with fusion due to increased motions and forces at both adjacent levels when compared with healthy individuals in a comparable flexion and extension range.

Integrated Suit Test 1 - A Study to Evaluate Effects of Suit Weight, Pressure, and Kinematics on Human Performance during Lunar Ambulation

NASA Technical Reports Server (NTRS)

Gernhardt, Michael L.; Norcross, Jason; Vos, Jessica R.

2008-01-01

In an effort to design the next generation Lunar suit, NASA has initiated a series of tests aimed at understanding the human physiological and biomechanical affects of space suits under a variety of conditions. The first of these tests was the EVA Walkback Test (ICES 2007-01-3133). NASA-JSC assembled a multi-disciplinary team to conduct the second test of the series, titled Integrated Suit Test 1 (IST-1), from March 6 through July 24, 2007. Similar to the Walkback Test, this study was performed with the Mark III (MKIII) EVA Technology Demonstrator suit, a treadmill, and the Partial Gravity Simulator in the Space Vehicle Mock-Up Facility at Johnson Space Center. The data collected for IST-1 included metabolic rates, ground reaction forces, biomechanics, and subjective workload and controllability feedback on both suited and unsuited (shirt-sleeve) astronaut subjects. For IST-1 the center of gravity was controlled to a nearly perfect position while the weight, pressure and biomechanics (waist locked vs. unlocked) were varied individually to evaluate the effects of each on the ability to perform level (0 degree incline) ambulation in simulated Lunar gravity. The detailed test methodology and preliminary key findings of IST-1 are summarized in this report.

Research Technology

NASA Image and Video Library

2002-03-13

NASA's Marshall Space Flight Center (MSFC) in Huntsville, Alabama, has begun a series of engine tests on the Reaction Control Engine developed by TRW Space and Electronics for NASA's Space Launch Initiative (SLI). SLI is a technology development effort aimed at improving the safety, reliability, and cost effectiveness of space travel for reusable launch vehicles. The engine in this photo, the first engine tested at MSFC that includes SLI technology, was tested for two seconds at a chamber pressure of 185 pounds per square inch absolute (psia). Propellants used were liquid oxygen as an oxidizer and liquid hydrogen as fuel. Designed to maneuver vehicles in orbit, the engine is used as an auxiliary propulsion system for docking, reentry, fine-pointing, and orbit transfer while the vehicle is in orbit. The Reaction Control Engine has two unique features. It uses nontoxic chemicals as propellants, which creates a safer environment with less maintenance and quicker turnaround time between missions, and it operates in dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The force of low level thrust allows the vehicle to fine-point maneuver and dock, while the force of the high level thrust is used for reentry, orbital transfer, and course positioning.

Preserved and impaired aspects of feed-forward grip force control after chronic somatosensory deafferentation.

PubMed

Hermsdörfer, J; Elias, Z; Cole, J D; Quaney, B M; Nowak, D A

2008-01-01

Although feed-forward mechanisms of grip force control are a prerequisite for skilled object manipulation, somatosensory feedback is essential to acquire, maintain, and adapt these mechanisms. Individuals with complete peripheral deafferentation provide the unique opportunity to study the function of the motor system deprived of somatosensory feedback. Two individuals (GL and IW) with complete chronic deafferentation of the trunk and limbs were tested during cyclic vertical movements of a hand-held object. Such movements induce oscillating loads that are typically anticipated by parallel modulations of the grip force. Load magnitude was altered by varying either the movement frequency or object weight. GL and IW employed excessive grip forces probably reflecting a compensatory mechanism. Despite this overall force increase, both deafferented participants adjusted their grip force level according to the load magnitude, indicating preserved scaling of the background grip force to physical demands. The dynamic modulation of the grip force with the load force was largely absent in GL, whereas in IW only slower movements were clearly affected. The authors hypothesize that the deafferented patients may have utilized visual and vestibular cues and/or an efferent copy of the motor command of the arm movement to scale the grip force level. Severely impaired grip force-load coupling in GL suggests that sensory information is important for maintaining a precise internal model of dynamic grip force control. However, comparably better performance in IW argues for the possibility that alternative cues can be used to trigger a residual internal model.

Effect of epidural anaesthesia on clinician-applied force during vaginal delivery.

PubMed

Poggi, Sarah H; Allen, Robert H; Patel, Chirag; Deering, Shad H; Pezzullo, John C; Shin, Young; Spong, Catherine Y

2004-09-01

Epidural anesthesia (EA) is used in 80% of vaginal deliveries and is linked to neonatal and maternal trauma. Our objectives were to determine (1) whether EA affected clinician-applied force on the fetus and (2) whether this force influenced perineal trauma. After informed consent, multiparas with term, cephalic, singletons were delivered by 1 physician wearing a sensor-equipped glove to record force exerted on the fetal head. Those with EA were compared with those without for delivery force parameters. Regression analysis was used to identify predictors of vaginal laceration. The force required for delivery was greater in patients with EA (n = 27) than without (n = 5) (P < .01). Clinical parameters, including birth weight (P = .31) were similar between the groups. Clinician force was similar in those with no versus first- versus second-degree laceration (P = .5). Only birth weight was predictive of laceration (P = .02). Epidural use resulted in greater clinician force required for vaginal delivery of the fetus in multiparas, but this force was not associated with perineal trauma.

Supervisory control of drilling of composite materials

NASA Astrophysics Data System (ADS)

Ozaki, Motoyoshi

Composite materials have attractive features, such as high ratios of strength-to-weight and stiffness-to-weight. However, they are easily damaged when they are machined. A typical damage is delamination, which can occur when fiber reinforced composite laminates are drilled. The objective of this research is to study the drilling processes of carbon fiber reinforced laminates, and to develop and test a supervisory control strategy for their delamination-free drilling. Characterization of thrust force and torque is achieved through constant feedrate drilling experiments. The average values of thrust force and torque during the full engagement of the drill are utilized to obtain the Shaw's equations' parameters. The thrust force profile just before exit is given special attention. The Hocheng-Dharan equations, which give conservative values of delamination at the entrance and at the exit, are modified to express the influence of one lamina thickness explicitly. They are utilized not only for the characterization of thrust force but also for the determination of the thrust force reference for force control. In the design of the controllers of thrust force and torque, both thrust force and torque are assumed to be proportional to FPHR (Feed Per Half Revolution). A discrete-time dynamic model is established for the case when the time interval for a half revolution of the drill is divided by the sampling time, and the model is extended to the case of general spindle speeds. PI controllers are designed for the dynamic models of thrust force and torque. Root-locus techniques are used in the analysis. The phases of the drilling process are introduced and the control strategy at each phase is explained. The supervisory controller chooses not only the best control strategy for each phase, but also the reference value and the controller gain that are suitable at each drill position. Drilling experiments are conducted to show the usefulness of the concepts introduced in this dissertation, and to give an example of installing the control parameters, which were derived from data obtained in this research, on the supervisory controller. Efficient Delamination-free drilling is given special emphasis in the experiments.

Effects of Eleutherococcus senticosus Cortex on Recovery from the Forced Swimming Test and Fatty Acid β-Oxidation in the Liver and Skeletal Muscle of mice.

PubMed

Sumiyoshi, Maho; Kimura, Yoshiyuki

2016-03-01

The root and stem barks of Eleutherococcus senticosus have been used to treat emotional and physical fatigue in China, Russia, Korea, and Japan. The effects of E. senticosus on recovery from physical fatigue and the expenditure of energy currently remain unclear. We herein examined the effects of E. senticosus extract on recovery from physical fatigue after the forced swimming test as well as fatty acid β-oxidation in the liver and skeletal muscle of mice. 1) Physical fatigue; E. senticosus extract (500 and 1000 mg/kg, twice daily) was administered orally to ICR male mice for 7 consecutive days. After swimming had been performed for 15 min, each mouse was placed on the cover of a 100-mm culture plate, and the time for each mouse to move away from the cover was measured. 2) Fatty acid β-oxidation in the liver and skeletal muscle; E. senticosus extract (500 and 1000 mg/kg) was administered orally twice daily to C57BL/6J male mice for 21 consecutive days. The initial and final body and liver weight were measured, and then fatty acid β-oxidation activity in the liver and skeletal muscle was measured by methods using [1- 14 C] palmitic acid. Recovery times after forced swimming were shorter in E. senticosus extract (500 and 1000 mg/kg)-treated mice than in vehicle-treated mice. The body and liver weight had no effect by the oral administration of E. senticosus extract, vitamin mixture and L-carnitine. Fatty acid β-oxidation activity in skeletal muscle was increased by E. senticosus extract (500 and 1000 mg/kg). E. senticosus may enhance recovery from physical fatigue induced by forced swimming by accelerating energy changes through fatty acid β-oxidation in skeletal muscle.

Testing the efficacy of existing force-endurance models to account for the prevalence of obesity in the workforce.

PubMed

Pajoutan, Mojdeh; Cavuoto, Lora A; Mehta, Ranjana K

2017-10-01

This study evaluates whether the existing force-endurance relationship models are predictive of endurance time for overweight and obese individuals, and if not, provide revised models that can be applied for ergonomics practice. Data was collected from 141 participants (49 normal weight, 50 overweight, 42 obese) who each performed isometric endurance tasks of hand grip, shoulder flexion, and trunk extension at four levels of relative workload. Subject-specific fatigue rates and a general model of the force-endurance relationship were determined and compared to two fatigue models from the literature. There was a lack of fit between previous models and the current data for the grip (ICC = 0.8), with a shift toward lower endurance times for the new data. Application of the revised models can facilitate improved workplace design and job evaluation to accommodate the capacities of the current workforce.

Improvement of neurological disorders in postmenopausal model rats by administration of royal jelly.

PubMed

Minami, A; Matsushita, H; Ieno, D; Matsuda, Y; Horii, Y; Ishii, A; Takahashi, T; Kanazawa, H; Wakatsuki, A; Suzuki, T

2016-12-01

Royal jelly (RJ) from honeybees (Apis mellifera) has estrogenic activity. Estrogen deficiency after menopause leads to a high risk of memory impairment and depression as well as metabolic syndrome and osteoporosis. We here investigated the effect of RJ on memory impairment and depression-like behaviors in ovariectomized (OVX) rats. OVX rats were administered with RJ for 82 days. Hippocampus-dependent spatial memory and depression-like behaviors were assessed by the Morris water maze test and the forced swimming test, respectively. The weights of body, brain and uterus and the contents of protein and myelin galactolipids including galactosylceramide and sulfatide were measured. Memory impairment and depression-like behaviors in OVX rats were recovered to the levels of sham-operated rats by RJ administration. Increased body weight and decreased uterine weight in OVX rats were recovered to the levels of sham-operated rats by 17β-estradiol (E2) administration but not by RJ administration. In contrast, brain weight was slightly increased by RJ administration but not by E2 administration. The contents of protein and myelin galactolipids were higher in the brains of RJ-administered OVX rats than in the brains of E2-administered OVX rats. The results suggest that RJ has a beneficial effect on neurological symptoms of a menopausal disorder.

Chewing in adolescents with overweight and obesity: An exploratory study with behavioral approach.

PubMed

Pedroni-Pereira, Aline; Araujo, Darlle Santos; Scudine, Kelly Guedes de Oliveira; Prado, Daniela Galvão de Almeida; Lima, Débora Alves Nunes Leite; Castelo, Paula Midori

2016-12-01

Physiological and behavioral aspects of masticatory function may have an impact on nutritional status, which has been little studied. The aim was to perform a comprehensive evaluation of objective, subjective and behavioral aspects of masticatory function in 231 adolescents, aged 14-17 years and compare these parameters between normal-weight (n = 115) and adolescents with overweight/obesity (n = 116). Objective aspects were examined by the Oro-facial Myofunctional Evaluation-expanded protocol (OMES-e), determining the masticatory type, chewing time/frequency, abnormal movements, and other; masticatory performance (color changeable chewing gum) and bite force were also explored. The subjective and behavioral evaluations were assessed using the Quality of Mastication Function Questionnaire, which explores the masticatory behavior and frequency/intensity of difficulty in chewing different types of foods. Results were submitted to normality tests, Chi-square, unpaired t-test and Mann-Whitney. A multiple linear regression model was used to evaluate which of the variables under study contributed to the variation in Percent Body Fat (α = 0.05). The results showed that OMES-e total score differed significantly between groups, that is, individuals with overweight showed more changes in oro-facial myofunctional aspects than normal-weight ones. Unilateral mastication was more frequent among females with overweight/obesity. They also showed greater difficulty on Habits and Fruit domains, reporting the need of adding sauce to the meal to facilitate swallowing and peeling and cutting fruit (apples) in small pieces in order to better chew them. OMES-e total score also showed a significant relationship with Percent Body Fat. Masticatory performance evaluated by chewing gum and bite force did not differ between groups. This study showed that adolescents with excess weight presented changes in masticatory behavior and greater difficulty in performing the masticatory function comparing to normal-weight ones. Copyright © 2016 Elsevier Ltd. All rights reserved.

In vivo measurement of aerodynamic weight support in freely flying birds

NASA Astrophysics Data System (ADS)

Lentink, David; Haselsteiner, Andreas; Ingersoll, Rivers

2014-11-01

Birds dynamically change the shape of their wing during the stroke to support their body weight aerodynamically. The wing is partially folded during the upstroke, which suggests that the upstroke of birds might not actively contribute to aerodynamic force production. This hypothesis is supported by the significant mass difference between the large pectoralis muscle that powers the down-stroke and the much smaller supracoracoideus that drives the upstroke. Previous works used indirect or incomplete techniques to measure the total force generated by bird wings ranging from muscle force, airflow, wing surface pressure, to detailed kinematics measurements coupled with bird mass-distribution models to derive net force through second derivatives. We have validated a new method that measures aerodynamic force in vivo time-resolved directly in freely flying birds which can resolve this question. The validation of the method, using independent force measurements on a quadcopter with pulsating thrust, show the aerodynamic force and impulse are measured within 2% accuracy and time-resolved. We demonstrate results for quad-copters and birds of similar weight and size. The method is scalable and can be applied to both engineered and natural flyers across taxa. The first author invented the method, the second and third authors validated the method and present results for quadcopters and birds.

Resistance to densification, tensile strength and capsule-filling performance of some pharmaceutical diluents.

PubMed

Nikolakakis, I; Aragon, O B; Malamataris, S

1998-07-01

The purpose of this study was to compare some indicators of capsule-filling performance, as measured by tapped density under different conditions, and elucidate possible quantitative relationships between variation of capsule fill-weight (%CV) and gravitational and inter-particle forces (attractive or frictional) derived from measurements of particle size, true density, low compression and tensile strength. Five common pharmaceutical diluents (lactose, maize starch, talc, Emcocel and Avicel) were investigated and two capsule-filling methods (pouring powder and dosator nozzle) were employed. It was found that for the pouring-type method the appropriateness of Hausner's ratio (HR), Carr's compressibility index (CC%) and Kawakita's constant (alpha) as indicators of capsule fill-weight variation decreases in the order alpha > CC% > HR; the appropriateness of these indicators also decreases with increasing cylinder size and with impact velocity during tapping. For the dosator-type method the appropriateness of the indicators decreases in the order HR > CC% > alpha, the opposite of that for the pouring-type method; the appropriateness of the indicators increases with decreasing cylinder size and impact velocity. The relationship between %CV and the ratio of inter-particle attractive to gravitational forces calculated from measurements of particle size and true density (Fvdw/Wp) was more significant for the pouring-type capsule-filling method. For the dosator-type method a significant relationship (1% level) was found between %CV and the product of Fvdw/Wp and a function expressing the increase, with packing density (p(f)), in the ratio of frictional to attractive inter-particle forces derived from compression (P) and tensile-strength (T) testing, d(log(P/T))/d(p(f)). The value of tapped density in predictions of capsule-filling performance is affected by the testing conditions in a manner depending on the filling method applied. For the pouring-type method predictions can be based on the ratio of attractive (inter-particle) to gravitational forces, whereas for the dosator-type method the contribution of frictional and attractive forces should, because of packing density change, also be taken into account.

A novel mouse running wheel that senses individual limb forces: biomechanical validation and in vivo testing

PubMed Central

Roach, Grahm C.; Edke, Mangesh

2012-01-01

Biomechanical data provide fundamental information about changes in musculoskeletal function during development, adaptation, and disease. To facilitate the study of mouse locomotor biomechanics, we modified a standard mouse running wheel to include a force-sensitive rung capable of measuring the normal and tangential forces applied by individual paws. Force data were collected throughout the night using an automated threshold trigger algorithm that synchronized force data with wheel-angle data and a high-speed infrared video file. During the first night of wheel running, mice reached consistent running speeds within the first 40 force events, indicating a rapid habituation to wheel running, given that mice generated >2,000 force-event files/night. Average running speeds and peak normal and tangential forces were consistent throughout the first four nights of running, indicating that one night of running is sufficient to characterize the locomotor biomechanics of healthy mice. Twelve weeks of wheel running significantly increased spontaneous wheel-running speeds (16 vs. 37 m/min), lowered duty factors (ratio of foot-ground contact time to stride time; 0.71 vs. 0.58), and raised hindlimb peak normal forces (93 vs. 115% body wt) compared with inexperienced mice. Peak normal hindlimb-force magnitudes were the primary force component, which were nearly tenfold greater than peak tangential forces. Peak normal hindlimb forces exceed the vertical forces generated during overground running (50-60% body wt), suggesting that wheel running shifts weight support toward the hindlimbs. This force-instrumented running-wheel system provides a comprehensive, noninvasive screening method for monitoring gait biomechanics in mice during spontaneous locomotion. PMID:22723628

On displacement-based plastic design of parallel chord vierendeel girders

NASA Astrophysics Data System (ADS)

Grigorian, Mark

2014-09-01

The paper introduces the principles of displacement-based plastic design (DBPD) and its applications to the efficient design of parallel chord steel vierendeel girders under normal nodal forces. A simplifying assumption has been made that the mathematical model is composed of imaginary, pin connected modules that fit within the bays of the prototype. The use of this modeling concept in conjunction with the applications of the uniform strength theory leads to the development of an algorithm that is ideally suited for manual, minimum weight design of steel vierendeel girders under any distribution of vertical nodal forces. The resulting solutions are exact and unique and lend themselves well to DBPD and minimum weight treatment. In DBPD which is akin to performance control, member strengths and stiffnesses are assigned rather than tested. Several generic examples have been provided to illustrate the applications of the proposed design procedures. The numerical results of these examples have been verified through long hand and computer methods of analysis. An extensive proof of the proposed method of approach has been provided in the "Appendix".

Clinical effects of leg length discrepancy through ground and joint reaction force responses: A review

NASA Astrophysics Data System (ADS)

Zabri, S. W. K. Ali; Basaruddin, K. S.; Salleh, A. F.; Rusli, W. M. R.; Daud, R.

2017-09-01

Leg length discrepancy (LLD) is caused either due to functional disorder or shortening of bone structure. This disorder could contribute to the significant effects on body weight distribution and lumbar scoliosis at the certain extend. Ground reaction force and joint reaction force are the parameters that can be used to analyze the responses in weight distribution and kinetics changes on the body joints, respectively. Hence, the purpose of this paper is to review the studies that focus on the clinical effects of LLD to the lower limb and spine through ground and joint reaction force responses that could lead to the orthopedics disorder.

Divergent selection on 63-day body weight in the rabbit: response on growth, carcass and muscle traits

PubMed Central

Larzul, Catherine; Gondret, Florence; Combes, Sylvie; de Rochambeau, Hubert

2005-01-01

The effects of selection for growth rate on weights and qualitative carcass and muscle traits were assessed by comparing two lines selected for live body weight at 63 days of age and a cryopreserved control population raised contemporaneously with generation 5 selected rabbits. The animals were divergently selected for five generations for either a high (H line) or a low (L line) body weight, based on their BLUP breeding value. Heritability (h2) was 0.22 for 63-d body weight (N = 4754). Growth performance and quantitative carcass traits in the C group were intermediate between the H and L lines (N = 390). Perirenal fat proportion (h2 = 0.64) and dressing out percentage (h2 = 0.55) ranked in the order L < H = C (from high to low). The weight and cross-sectional area of the Semitendinosus muscle, and the mean diameter of the constitutive myofibres were reduced in the L line only (N = 140). In the Longissimus muscle (N = 180), the ultimate pH (h2 = 0.16) and the maximum shear force reached in the Warner-Braztler test (h2 = 0.57) were slightly modified by selection. PMID:15588570

Real-Time Dynamic Brake Assessment Proof of Concept Final Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lascurain, Mary Beth; Franzese, Oscar; Capps, Gary J

This proof-of-concept research was performed to explore the feasibility of using real-world braking data from commercial motor vehicles to make a diagnosis of brake condition similar to that of the performance-based brake tester (PBBT). This was done by determining the relationship between pressure and brake force (P-BF), compensating for the gross vehicle weight (GVW). The nature of this P-BF relationship (e.g., low braking force for a given brake application pressure) may indicate brake system problems. In order to determine the relationship between brake force and brake application pressure, a few key parameters of duty cycle information were collected. Because brakingmore » events are often brief, spanning only a few seconds, a sample rate of 10 Hz was needed. The algorithm under development required brake application pressure and speed (from which deceleration was calculated). Accurate weight estimation was also needed to properly derive the braking force from the deceleration. In order to ensure that braking force was the predominant factor in deceleration for the segments of data used in analysis, the data was screened for grade as well. Also, the analysis needed to be based on pressures above the crack pressure. The crack pressure is the pressure below which the individual brakes are not applied due the nature of the mechanical system. This value, which may vary somewhat from one wheel end to another, is approximately 10 psi. Therefore, only pressures 15 psi and above were used in the analysis. The Department of Energy s Medium Truck Duty Cycle research has indicated that under the real-world circumstances of the test vehicle brake pressures of up to approximately 30 psi can be expected. Several different types of data were collected during the testing task of this project. Constant-pressure stopping tests were conducted at several combinations of brake application pressure (15, 20, 25, and 30 psi), load conditions (moderately and fully laden), and speeds (20 and 30 mph). Data was collected at 10 Hz. Standard and stepped-pressure performance-based brake tests with brake pressure transducers were performed for each loading condition. The stepped-pressure test included the constant-pressure intervals of brake application at 15, 20, 25, and 30 psi. The PBBT data files included 10 Hz streaming data collected during the testing of each axle. Two weeks of real-world duty cycle (driving and braking) data was also collected at 10 Hz. Initial analysis of the data revealed that the data collected in the field (i.e., day-to-day operations) provided the same information as that obtained from the controlled tests. Analysis of the data collected revealed a strong linear relationship between brake application pressure and deceleration for given GVWs. As anticipated, initial speed was not found to be a significant factor in the deceleration-pressure relationship, unlike GVW. The positive results obtained from this proof of concept test point to the need for further research to expand this concept. A second phase should include testing over a wider range of speeds and include medium brake application pressures in addition to the low pressures tested in this research. Testing on multiple vehicles would also be of value. This future phase should involve testing to determine how degradation of braking performance affects the pressure-deceleration relationship.« less

A novel tool for continuous fracture aftercare - Clinical feasibility and first results of a new telemetric gait analysis insole.

PubMed

Braun, Benedikt J; Bushuven, Eva; Hell, Rebecca; Veith, Nils T; Buschbaum, Jan; Holstein, Joerg H; Pohlemann, Tim

2016-02-01

Weight bearing after lower extremity fractures still remains a highly controversial issue. Even in ankle fractures, the most common lower extremity injury no standard aftercare protocol has been established. Average non weight bearing times range from 0 to 7 weeks, with standardised, radiological healing controls at fixed time intervals. Recent literature calls for patient-adapted aftercare protocols based on individual fracture and load scenarios. We show the clinical feasibility and first results of a new, insole embedded gait analysis tool for continuous monitoring of gait, load and activity. Ten patients were monitored with a new, independent gait analysis insole for up to 3 months postoperatively. Strict 20 kg partial weight bearing was ordered for 6 weeks. Overall activity, load spectrum, ground reaction forces, clinical scoring and general health data were recorded and correlated. Statistical analysis with power analysis, t-test and Spearman correlation was performed. Only one patient completely adhered to the set weight bearing limit. Average time in minutes over the limit was 374 min. Based on the parameters load, activity, gait time over 20 kg weight bearing and maximum ground reaction force high and low performers were defined after 3 weeks. Significant difference in time to painless full weight bearing between high and low performers was shown. Correlation analysis revealed a significant correlation between weight bearing and clinical scoring as well as pain (American Orthopaedic Foot and Ankle Society (AOFAS) Score rs=0.74; Olerud-Molander Score rs=0.93; VAS pain rs=-0.95). Early, continuous gait analysis is able to define aftercare performers with significant differences in time to full painless weight bearing where clinical or radiographic controls could not. Patient compliance to standardised weight bearing limits and protocols is low. Highly individual rehabilitation patterns were seen in all patients. Aftercare protocols should be adjusted to real-time patient conditions, rather than fixed intervals and limits. With a real-time measuring device high performers could be identified and influenced towards optimal healing conditions early, while low performers are recognised and missing healing influences could be corrected according to patient condition. Copyright © 2015 Elsevier Ltd. All rights reserved.

A partition function-based weighting scheme in force field parameter development using ab initio calculation results in global configurational space.

PubMed

Wu, Yao; Dai, Xiaodong; Huang, Niu; Zhao, Lifeng

2013-06-05

In force field parameter development using ab initio potential energy surfaces (PES) as target data, an important but often neglected matter is the lack of a weighting scheme with optimal discrimination power to fit the target data. Here, we developed a novel partition function-based weighting scheme, which not only fits the target potential energies exponentially like the general Boltzmann weighting method, but also reduces the effect of fitting errors leading to overfitting. The van der Waals (vdW) parameters of benzene and propane were reparameterized by using the new weighting scheme to fit the high-level ab initio PESs probed by a water molecule in global configurational space. The molecular simulation results indicate that the newly derived parameters are capable of reproducing experimental properties in a broader range of temperatures, which supports the partition function-based weighting scheme. Our simulation results also suggest that structural properties are more sensitive to vdW parameters than partial atomic charge parameters in these systems although the electrostatic interactions are still important in energetic properties. As no prerequisite conditions are required, the partition function-based weighting method may be applied in developing any types of force field parameters. Copyright © 2013 Wiley Periodicals, Inc.

Hologram interferometry in automotive component vibration testing

NASA Astrophysics Data System (ADS)

Brown, Gordon M.; Forbes, Jamie W.; Marchi, Mitchell M.; Wales, Raymond R.

1993-02-01

An ever increasing variety of automotive component vibration testing is being pursued at Ford Motor Company, U.S.A. The driving force for use of hologram interferometry in these tests is the continuing need to design component structures to meet more stringent functional performance criteria. Parameters such as noise and vibration, sound quality, and reliability must be optimized for the lightest weight component possible. Continually increasing customer expectations and regulatory pressures on fuel economy and safety mandate that vehicles be built from highly optimized components. This paper includes applications of holographic interferometry for powertrain support structure tuning, body panel noise reduction, wiper system noise and vibration path analysis, and other vehicle component studies.

Characterization and application of shape-changing panels with embedded rubber muscle actuators

NASA Astrophysics Data System (ADS)

Peel, Larry D.; Molina, Enrique, Jr.; Baur, Jeffery W.; Justice, Ryan S.

2013-09-01

Cylindrical soft actuators efficiently convert fluid pressure into mechanical energy and thus offer excellent force-to-weight ratios while behaving similar to biological muscle. McKibben-like rubber muscle actuators (RMAs) were embedded into neat elastomer and act as shape-changing panels. The effect of actuator spacing and modeling methods on the performance of these panels was investigated. Simulations from nonlinear finite element models were compared with results from test panels containing four RMAs that were spaced 0, 1/2, 1, and 1.3 RMA diameters apart. Nonlinear ‘laminated plate’ and ‘rod & plate’ finite element (FE) models of individual (non-embedded) RMAs and panels with embedded RMAs were developed. Due to model complexity and resource limitations, several simplified 2D and 3D FE model types, including a 3D ‘Unit Cell’ were created. After subtracting the ‘activation pressure’ needed to initiate contraction, all the models for the individual actuators produced forces consistent with experimental values, but only the more resource-intensive rod & plate models replicated fiber/braid re-orientation and produced more realistic values for actuator contraction. For panel models, the Full 3D rod & plate model appeared to be the most accurate for panel contraction and force, but was not completed for all configurations due to resource limitations. Most embedded panel FE models produced maximum panel actuator force and maximum contraction when the embedded actuators are spaced between 1/2 and 1 diameter apart. Seven panels with embedded RMAs were experimentally fabricated and tested. Panel tests confirmed that maximum or optimal performance occurs when the RMAs are spaced between 1/2 and 1 diameter apart. The tested actuator force was fairly constant in this range, suggesting that minor design or manufacturing differences may not significantly affect panel performance. However, the amount of axial force and contraction decreases significantly at greater than optimal spacing. This multi-faceted work provides useful design, simulation fabrication, and test characteristics for shape-adaptive panels. Bending panels were demonstrated but not modeled. Developers of future shape-adaptive air vehicles have been provided with additional simulation and design tools.

Limited independent flexion of the thumb and fingers in human subjects.

PubMed Central

Kilbreath, S L; Gandevia, S C

1994-01-01

1. We investigated whether human subjects can activate selectively flexor pollicis longus (FPL) and digital portions of flexor digitorum profundus (FDP). These muscles were selected because they are the only flexors of the distal phalanges. 2. Electromyographic activity (EMG) was recorded with intramuscular electrodes from one digital component of the deep flexors ('test') while subjects lifted weights by flexing the distal interphalangeal joint of the other digits in turn ('lifting' digits). Only recording sites at which single motor units were recruited selectively at low forces were used. The weights lifted represented 2.5-50% of the maximal voluntary contraction (MVC). We measured the lowest weight lifted which produced phasic and tonic coactivation in the 'test' muscle. 3. The extent of coactivation varied with the 'distance' between the test and lifting digits although no significant difference occurred in the pattern of coactivation thresholds among the digital flexors. The extent of coactivation increased when angular displacement or velocity at the distal interphalangeal joint of the lifting digit increased but was not critically dependent on restraint of the hand. 4. Because mechanical 'connections' could interfere with the ability to move a distal phalanx independently, the arms of nine cadavers were studied. The separation of tendons between the thumb (FPL) and the index portion of FDP, and between the index and middle portions of FDP, usually extended more proximally in the forearm than separation between the tendons to the middle and ring fingers and between the ring and little fingers. Direct intertendinous links were also noted. 5. It is not possible to direct a sufficiently focal motor command to flex selectively the distal joint of the fingers and thumb when forces exceeding 2.5% MVC are generated. For the middle, ring and little fingers in particular, movement of adjacent digits may also involve 'in-series' mechanical links between adjacent components of FDP. Images Figure 6 PMID:7837104

Morphologic Characteristics Help Explain the Gender Difference in Peak Anterior Cruciate Ligament Strain During a Simulated Pivot Landing

PubMed Central

Lipps, David B.; Oh, Youkeun K.; Ashton-Miller, James A.; Wojtys, Edward M.

2015-01-01

Background Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading. Hypothesis Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs. Study Design Controlled laboratory study. Methods Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle tensile stiffness. Peak relative strain in the anteromedial bundle of the ACL (AM-ACL) was measured using a differential variable reluctance transducer, while ACL cross-sectional area and lateral tibial slope were measured using magnetic resonance imaging. A repeated-measures Mann-Whitney signed-rank test was used to test the hypothesis. Results Female knees exhibited 95% greater peak AM-ACL relative strain than male knees (6.37% [22.53%] vs 3.26% [11.89%]; P = .004). Anterior cruciate ligament cross-sectional area and lateral tibial slope were significant predictors of peak AM-ACL relative strain (R2 = .59; P = .001). Conclusion Peak AM-ACL relative strain was significantly greater in female than male knees from donors of the same height and weight. This gender difference is attributed to a smaller female ACL cross-sectional area and a greater lateral tibial slope. Clinical Relevance Since female ACLs are systematically exposed to greater strain than their male counterparts, training and injury prevention programs should take this fact into consideration. PMID:21917612

A Study on the Mechanical Properties and Impact-Induced Initiation Characteristics of Brittle PTFE/Al/W Reactive Materials.

PubMed

Ge, Chao; Maimaitituersun, Wubuliaisan; Dong, Yongxiang; Tian, Chao

2017-04-26

Polytetrafluoroethylene/aluminum/tungsten (PTFE/Al/W) reactive materials of three different component mass ratios (73.5/26.5/0, 68.8/24.2/7 and 63.6/22.4/14) were studied in this research. Different from the PTFE/Al/W composites published elsewhere, the materials in our research were fabricated under a much lower sintering temperature and for a much shorter duration to achieve a brittle property, which aims to provide more sufficient energy release upon impact. Quasi-static compression tests, dynamic compression tests at room and elevated temperatures, and drop weight tests were conducted to evaluate the mechanical and impact-induced initiation characteristics of the materials. The materials before and after compression tests were observed by a scanning electron microscope to relate the mesoscale structural characteristics to their macro properties. All the three types of materials fail at very low strains during both quasi-static and dynamic compression. The stress-strain curves for quasi-static tests show obvious deviations while that for the dynamic tests consist of only linear-elastic and failure stages typically. The materials were also found to exhibit thermal softening at elevated temperatures and were strain-rate sensitive during dynamic tests, which were compared using dynamic increase factors (DIFs). Drop-weight test results show that the impact-initiation sensitivity increases with the increase of W content due to the brittle mechanical property. The high-speed video sequences and recovered sample residues of the drop-weight tests show that the reaction is initiated at two opposite positions near the edges of the samples, where the shear force concentrates the most intensively, indicating a shear-induced initiation mechanism.

A Study on the Mechanical Properties and Impact-Induced Initiation Characteristics of Brittle PTFE/Al/W Reactive Materials

PubMed Central

Ge, Chao; Maimaitituersun, Wubuliaisan; Dong, Yongxiang; Tian, Chao

2017-01-01

Polytetrafluoroethylene/aluminum/tungsten (PTFE/Al/W) reactive materials of three different component mass ratios (73.5/26.5/0, 68.8/24.2/7 and 63.6/22.4/14) were studied in this research. Different from the PTFE/Al/W composites published elsewhere, the materials in our research were fabricated under a much lower sintering temperature and for a much shorter duration to achieve a brittle property, which aims to provide more sufficient energy release upon impact. Quasi-static compression tests, dynamic compression tests at room and elevated temperatures, and drop weight tests were conducted to evaluate the mechanical and impact-induced initiation characteristics of the materials. The materials before and after compression tests were observed by a scanning electron microscope to relate the mesoscale structural characteristics to their macro properties. All the three types of materials fail at very low strains during both quasi-static and dynamic compression. The stress-strain curves for quasi-static tests show obvious deviations while that for the dynamic tests consist of only linear-elastic and failure stages typically. The materials were also found to exhibit thermal softening at elevated temperatures and were strain-rate sensitive during dynamic tests, which were compared using dynamic increase factors (DIFs). Drop-weight test results show that the impact-initiation sensitivity increases with the increase of W content due to the brittle mechanical property. The high-speed video sequences and recovered sample residues of the drop-weight tests show that the reaction is initiated at two opposite positions near the edges of the samples, where the shear force concentrates the most intensively, indicating a shear-induced initiation mechanism. PMID:28772812

Anti-gravity treadmills are effective in reducing knee forces.

PubMed

Patil, Shantanu; Steklov, Nikolai; Bugbee, William D; Goldberg, Timothy; Colwell, Clifford W; D'Lima, Darryl D

2013-05-01

Lower body positive pressure (LBPP) treadmills permit significant unweighting of patients and have the potential to enhance recovery following lower limb surgery. We determined the efficacy of an LBPP treadmill in reducing knee forces in vivo. Subjects, implanted with custom electronic tibial prostheses to measure forces in the knee, were tested on a treadmill housed within a LBPP chamber. Tibiofemoral forces were monitored at treadmill speeds from 1.5 mph (0.67 m/s) to 4.5 mph (2.01 m/s), treadmill incline from -10° to +10°, and four treadmill chamber pressure settings adjusted to decrease net treadmill reaction force from 100% to 25% of the subject's body weight (BW). The peak axial tibiofemoral force ranged from 5.1 times BW at a treadmill speed of 4.5 mph (2.01 m/s) and a pressure setting of 100% BW to 0.8 times BW at 1.5 mph (0.67 m/s) and a pressure setting of 25% BW. Peak knee forces were significantly correlated with walking speed and treadmill reaction force (R(2)  = 0.77, p = 0.04). The LBPP treadmill might be an effective tool in the rehabilitation of patients following lower-extremity surgery. The strong correlation between tibiofemoral force and walking speed and treadmill reaction forces allows for more precisely achieving the target knee forces desired during early rehabilitation. Copyright © 2012 Orthopaedic Research Society.

Using robot-applied resistance to augment body-weight-supported treadmill training in an individual with incomplete spinal cord injury.

PubMed

Lam, Tania; Pauhl, Katherine; Krassioukov, Andrei; Eng, Janice J

2011-01-01

The efficacy of task-specific gait training for people with spinal cord injury (SCI) is premised on evidence that the provision of gait-related afferent feedback is key for the recovery of stepping movements. Recent findings have shown that sensory feedback from flexor muscle afferents can facilitate flexor muscle activity during the swing phase of walking. This case report was undertaken to determine the feasibility of using robot-applied forces to resist leg movements during body-weight-supported treadmill training (BWSTT) and to measure its effect on gait and other health-related outcomes. The patient described in this case report was a 43-year-old man with a T11 incomplete chronic SCI. He underwent 36 sessions of BWSTT using a robotic gait orthosis to provide forces that resist hip and knee flexion. Tolerance to the training program was monitored using the Borg CR10 scale and heart rate and blood pressure changes during each training session. Outcome measures (ie, 10-Meter Walk Test, Six-Minute Walk Test, modified Emory Functional Ambulation Profile [mEFAP], Activities-specific Balance Confidence Scale, and Canadian Occupational Performance Measure) were completed and kinematic parameters of gait, lower-extremity muscle strength (force-generating capacity), lower-limb girth, and tolerance to orthostatic stress were measured before and after the training program. The patient could tolerate the training. Overground walking speed, endurance, and performance on all subtasks of the mEFAP improved and were accompanied by increased lower-limb joint flexion and toe clearance during gait. The patient's ambulatory self-confidence and self-perceived performance in walking also improved. These findings suggest that this new approach to BWSTT is a feasible and potentially effective therapy for improving skilled overground walking performance.

Research on mechanical and sensoric set-up for high strain rate testing of high performance fibers

NASA Astrophysics Data System (ADS)

Unger, R.; Schegner, P.; Nocke, A.; Cherif, C.

2017-10-01

Within this research project, the tensile behavior of high performance fibers, such as carbon fibers, is investigated under high velocity loads. This contribution (paper) focuses on the clamp set-up of two testing machines. Based on a kinematic model, weight optimized clamps are designed and evaluated. By analyzing the complex dynamic behavior of conventional high velocity testing machines, it has been shown that the impact typically exhibits an elastic characteristic. This leads to barely predictable breaking speeds and will not work at higher speeds when acceleration force exceeds material specifications. Therefore, a plastic impact behavior has to be achieved, even at lower testing speeds. This type of impact behavior at lower speeds can be realized by means of some minor test set-up adaptions.

Textbook presentations of weight: Conceptual difficulties and language ambiguities

NASA Astrophysics Data System (ADS)

Taibu, Rex; Rudge, David; Schuster, David

2015-06-01

The term "weight" has multiple related meanings in both scientific and everyday usage. Even among experts and in textbooks, weight is ambiguously defined as either the gravitational force on an object or operationally as the magnitude of the force an object exerts on a measuring scale. This poses both conceptual and language difficulties for learners, especially for accelerating objects where the scale reading is different from the gravitational force. But while the underlying physical constructs behind the two referents for the term weight (and their relation to each other) are well understood scientifically, it is unclear how the concept of weight should be introduced to students and how the language ambiguities should be dealt with. We investigated treatments of weight in a sample of twenty introductory college physics textbooks, analyzing and coding their content based on the definition adopted, how the distinct constructs were dealt with in various situations, terminologies used, and whether and how language issues were handled. Results indicate that language-related issues, such as different, inconsistent, or ambiguous uses of the terms weight, "apparent weight," and "weightlessness," were prevalent both across and within textbooks. The physics of the related constructs was not always clearly presented, particularly for accelerating bodies such as astronauts in spaceships, and the language issue was rarely addressed. Our analysis of both literature and textbooks leads us to an instructional position which focuses on the physics constructs before introducing the term weight, and which explicitly discusses the associated language issues.

Department of the Air Force Supporting Data for FY 1991 Budget Estimates Submitted to Congress January 1990. Descriptive Summaries, Research, Development, Test and Evaluation

DTIC Science & Technology

1990-05-16

Redondo Beach. CA. Civilian subcontractors are ITEK (cameras). Lexington. MA; Contraves Georz (telescopes), Pittsburgh. PA; and Kentron (operations and...Improvements include a higher maximum takeoff weight , improved air-to-air gun sight algorithms, digital flight controls, and improved pilot interface...ambient propagation loss , significant penetration of sea water, and good performance in a nuclear environment. C. (U) JUSTIFICATION FOR PROJECTS LESS

Foot forces induced through Tai Chi push-hand exercises.

PubMed

Wong, Shiu Hong; Ji, Tianjian; Hong, Youlian; Fok, Siu Lun; Wang, Lin

2013-08-01

The low impact forces of Tai Chi push-hand exercises may be particularly suited for older people and for those with arthritis; however, the biomechanics of push-hand exercises have not previously been reported. This paper examines the ground reaction forces (GRFs) and plantar force distributions during Tai Chi push-hand exercises in a stationary stance with and without an opponent. Ten male Tai Chi practitioners participated in the study. The GRFs of each foot were measured in three perpendicular directions using two force plates (Kistler). The plantar force distribution of each foot was measured concurrently using an insole sensor system (Novel). The results showed that the average maximum vertical GRF of each foot was not more than 88% ± 6.1% of the body weight and the sum of the vertical forces (103% ± 1.4%) generated by the two feet approximately equals the body weight at any one time. The horizontal GRFs generated by the two feet were in the opposite directions and the measured mean peak values were not more than 12% ± 2.8% and 17% ± 4.3% of the body weight in the medio-lateral and antero-posterior directions respectively. Among the nine plantar areas, the toes sustained the greatest plantar force. This study indicates that push-hand exercises generate lower vertical forces than those induced by walking, bouncing, jumping and Tai Chi gait, and that the greatest plantar force is located in the toe area, which may have an important application in balance training particularly for older adults.

Obesity-induced decreases in muscle performance are not reversed by weight loss.

PubMed

Seebacher, F; Tallis, J; McShea, K; James, R S

2017-08-01

Obesity can affect muscle phenotypes, and may thereby constrain movement and energy expenditure. Weight loss is a common and intuitive intervention for obesity, but it is not known whether the effects of obesity on muscle function are reversible by weight loss. Here we tested whether obesity-induced changes in muscle metabolic and contractile phenotypes are reversible by weight loss. We used zebrafish (Danio rerio) in a factorial design to compare energy metabolism, locomotor capacity, muscle isometric force and work-loop power output, and myosin heavy chain (MHC) composition between lean fish, diet-induced obese fish, and fish that were obese and then returned to lean body mass following diet restriction. Obesity increased resting metabolic rates (P<0.001) and decreased maximal metabolic rates (P=0.030), but these changes were reversible by weight loss, and were not associated with changes in muscle citrate synthase activity. In contrast, obesity-induced decreases in locomotor performance (P=0.0034), and isolated muscle isometric stress (P=0.01), work-loop power output (P<0.001) and relaxation rates (P=0.012) were not reversed by weight loss. Similarly, obesity-induced decreases in concentrations of fast and slow MHCs, and a shift toward fast MHCs were not reversed by weight loss. Obesity-induced changes in locomotor performance and muscle contractile function were not reversible by weight loss. These results show that weight loss alone may not be a sufficient intervention.

Assessment of leg muscles mechanical capacities: Which jump, loading, and variable type provide the most reliable outcomes?

PubMed

García-Ramos, Amador; Feriche, Belén; Pérez-Castilla, Alejandro; Padial, Paulino; Jaric, Slobodan

2017-07-01

This study aimed to explore the strength of the force-velocity (F-V) relationship of lower limb muscles and the reliability of its parameters (maximum force [F 0 ], slope [a], maximum velocity [V 0 ], and maximum power [P 0 ]). Twenty-three men were tested in two different jump types (squat and countermovement jump: SJ and CMJ), performed under two different loading conditions (free weight and Smith machine: Free and Smith) with 0, 17, 30, 45, 60, and 75 kg loads. The maximum and averaged values of F and V were obtained for the F-V relationship modelling. All F-V relationships were strong and linear independently whether observed from the averaged across the participants (r ≥ 0.98) or individual data (r = 0.94-0.98), while their parameters were generally highly reliable (F 0 [CV: 4.85%, ICC: 0.87], V 0 [CV: 6.10%, ICC: 0.82], a [CV: 10.5%, ICC: 0.81], and P 0 [CV: 3.5%, ICC: 0.93]). Both the strength of the F-V relationships and the reliability of their parameters were significantly higher for (1) the CMJ over the SJ, (2) the Free over the Smith loading type, and (3) the maximum over the averaged F and V variables. In conclusion, although the F-V relationships obtained from all the jumps tested were linear and generally highly reliable, the less appropriate choice for testing the F-V relationship could be through the averaged F and V data obtained from the SJ performed either in a Free weight or in a Smith machine. Insubstantial differences exist among the other combinations tested.

The effect of moderate altitude on some respiratory parameters of physical education and sports' students.

PubMed

Orhan, O; Bilgin, U; Cetin, E; Oz, E; Dolek, B Ertas

2010-08-01

Analysis of the effects of moderate altitude on some respiratory functions of students enrolled in School of Physical Education and Sports. The study group comprised of 9 female and 10 male volunteers who were attending a 5-day skiing training camp. All participants were enrolled in School of Physical Education and Sports at Gazi University. The male students had an age range of 22.2 +/- 1.7 years, height of 175.0 +/- 4.3 cm, and body weight of 71.0 +/- 10.4 kg; the female students had an age range of 21.2 +/- 1.7 years, height of 167.1 +/- 4.9 cm, and body weight of 53.7 +/- 4.8 kg. Respiratory tests were performed on the 1st and 5th days (the first and second measurements) at an altitude of 1880 m (in Ilgaz Mountain); 10 days after being exposed to high altitude, further tests were performed at an altitude of 856 m (in Ankara) (the third measurement). Data were analyzed using SPSS software (version 10.0). Intragroup differences were analyzed using repeated measures analysis of variance (ANOVA). According to the results of normality test results, an independent-sample t test was used in comparisons between the groups. A significance level of p < .05 was used in analysis. Statistical analysis indicated that there was no significant difference between the intragroup comparisons of female and male students. Intergroup comparisons showed significant differences in forced vital capacity (FVC), forced expiratory volume (FEV), peak expiratory flow (PEF), maximal voluntary ventilation (MVV), and VC parameters (p < .05). The authors conclude that moderate altitude does not have any effect on some respiratory parameters after 5 days of skiing camp.

Optimizing pneumatic conveying of biomass materials

NASA Astrophysics Data System (ADS)

DiCianni, Matthew Edward Michael

2011-12-01

Biomass is a readily available but underutilized energy resource. One of the main challenges is the inability of biomass feed stocks like corn stover or wood chips to flow freely without intermittent jamming. This research integrated an automated pneumatic conveying system to efficiently transport biomass into a biomass reactor. Material was held in a storage container until an end effector attached to a 3-axis controller engaged the material to flow through pneumatic vacuum in the carrier fluid of air. The material was disengaged from the carrier fluid through centripetal forces induced by a cyclone separator. As the air was pulled out of the cyclone, the biomass drops out the bottom due to gravitational forces and fell into a secondary storage hopper. The second storage container was for testing purposes only, where the actual apparatus would use a vertically oriented lock hopper to feed material into the biomass reactor. In the experimental test apparatus, sensors measured the storage hopper weight (mass-flow rate), pressure drop from the blower, and input power consumption of the motor. Parameters that were adjusted during testing include pipe diameter, material type, and motor speed. Testing indicated that decreasing the motor speed below its maximum still allows for conveyance of the material without blockage forming in the piping. The data shows that the power consumption of the system can be reduced based on the size and weight of the material introduced to the conveying pipe. Also, conveying certain materials proved to be problematic with particular duct diameters. Ultimately, an optimal duct diameter that can perform efficiently for a broad range of materials was chosen for the given system. Through these improvements, the energy return on investment will be improved for biomass feed stocks, which is taking a step in the right direction to secure the nation's energy independence.

A Comparison between Bench Press Throw and Ballistic Push-Up tests to assess upper-body power in trained individuals.

PubMed

Bartolomei, Sandro; Nigro, Federico; Ruggeri, Sandro; Lanzoni, Ivan Malagoli; Ciacci, Simone; Merni, Franco; Sadres, Eliahu; Hoffman, Jay R; Semprini, Gabriele

2018-03-06

The purpose of the present study was to validate the ballistic push-up test performed with hands on a force plate (BPU) as a method to measure upper-body power. Twenty-eight experienced resistance trained men (age = 25.4 ± 5.2 y; body mass = 78.5 ± 9.0 kg; body height = 179.6 ± 7.8 cm) performed, two days apart, a bench press 1RM test and upper-body power tests. Mean power and peak power were assessed using the bench press throw test (BT) and the BPU test performed in randomized order. The area under the force/power curve (AUC) obtained at BT was also calculated. Power expressed at BPU was estimated using a time-based prediction equation. Mean force and the participant's body weight were used to predict the bench press 1RM. Pearson product moment correlations were used to examine relationships between the power assessment methods and between the predicted 1RM bench and the actual value. Large correlations (0.79; p < 0.001) were found between AUC and mean power expressed at BPU. Large correlations were also detected between mean power and peak power expressed at BT and BPU (0.75; p < 0.001 and 0.74; p < 0.001, respectively). Very large correlations (0.87; p < 0.001) were found between the 1RM bench and the 1RM predicted by the BPU. Results of the present study indicate that BPU represents a valid and reliable method to estimate the upper-body power in resistance-trained individuals.

Modeling the macrodynamics of international migration: determinants of emigration from Cyprus, 1946-85.

PubMed

Diamantides, N D; Constantinou, S T

1989-07-01

"A model is presented of international migration that is based on the concept of a pool of potential emigrants at the origin created by push-pull forces and by the establishment of information feedback between origin and destination. The forces can be economic, political, or both, and are analytically expressed by the 'mediating factor'. The model is macrodynamic in nature and provides both for the main secular component of the migratory flow and for transient components caused by extraordinary events. The model is expressed in a Bernoulli-type differential equation through which quantitative weights can be derived for each of the operating causes. Out-migration from the Republic of Cyprus is used to test the tenets of the model." excerpt

Use of an Arduino to Study Buoyancy Force

ERIC Educational Resources Information Center

Espindola, P. R.; Cena, C. R.; Alves, D. C. B.; Bozano, D. F.; Goncalves, A. M. B.

2018-01-01

The study of buoyancy becomes very interesting when we measure the apparent weight of the body and the liquid vessel weight. In this paper, we propose an experimental apparatus that measures both the forces mentioned before as a function of the depth that a cylinder is sunk into the water. It is done using two load cells connected to an Arduino.…

Simulation of in vivo dynamics during robot assisted joint movement.

PubMed

Bobrowitsch, Evgenij; Lorenz, Andrea; Wülker, Nikolaus; Walter, Christian

2014-12-16

Robots are very useful tools in orthopedic research. They can provide force/torque controlled specimen motion with high repeatability and precision. A method to analyze dissipative energy outcome in an entire joint was developed in our group. In a previous study, a sheep knee was flexed while axial load remained constant during the measurement of dissipated energy. We intend to apply this method for the investigation of osteoarthritis. Additionally, the method should be improved by simulation of in vivo knee dynamics. Thus, a new biomechanical testing tool will be developed for analyzing in vitro joint properties after different treatments. Discretization of passive knee flexion was used to construct a complex flexion movement by a robot and simulate altering axial load similar to in vivo sheep knee dynamics described in a previous experimental study. The robot applied an in vivo like axial force profile with high reproducibility during the corresponding knee flexion (total standard deviation of 0.025 body weight (BW)). A total residual error between the in vivo and simulated axial force was 0.16 BW. Posterior-anterior and medio-lateral forces were detected by the robot as a backlash of joint structures. Their curve forms were similar to curve forms of corresponding in vivo measured forces, but in contrast to the axial force, they showed higher total standard deviation of 0.118 and 0.203 BW and higher total residual error of 0.79 and 0.21 BW for posterior-anterior and medio-lateral forces respectively. We developed and evaluated an algorithm for the robotic simulation of complex in vivo joint dynamics using a joint specimen. This should be a new biomechanical testing tool for analyzing joint properties after different treatments.

Ground reaction forces on stairs. Part II: knee implant patients versus normals.

PubMed

Stacoff, Alex; Kramers-de Quervain, Inès A; Luder, Gerhard; List, Renate; Stüssi, Edgar

2007-06-01

The goal of this study was to compare selected parameters of vertical ground reaction forces (GRF) of good outcome patients with different prosthesis designs with a matched control group during level walking, stair ascent and descent. Forty subjects, 29 with three main implant designs (including four subjects with a passive knee flexion restriction), and 11 healthy controls were measured with 8-10 repetitions. Vertical ground reaction forces were measured during two consecutive steps with force plates embedded in the walkway and the staircase. Defined parameters of the force signals were used to compare the results of the test groups. The results show, that, postoperatively, good outcome patients produce gait patterns of the vertical ground reaction force which are comparable to normal healthy subjects with the exception of a few distinct differences: a significant reduction (p<0.05) in the vertical loading on the operated side during level walking at take-off, at weight acceptance and take-off during stair ascent of the normal stair. During stair descent, the patients did not reduce load on the operated side, but increased load variation and side-to-side asymmetry; thus, the mechanical loads on the implants were high, which may be important information with respect to loading protocols of knee implant simulators. No systematic differences in any of the test parameters were found between posterior cruciate-retaining (LCS MB and Innex CR) versus non-retaining (LCS RP and Innex UCOR) implant designs. The restricted group showed significant reductions (p<0.05) of several loading parameters as well as an increased side-to-side asymmetry. About one third of the force parameters of the good outcome patients showed a side-to-side asymmetry between two consecutive steps, which was over a proposed level of acceptance.

Decoding tactile afferent activity to obtain an estimate of instantaneous force and torque applied to the fingerpad

PubMed Central

Birznieks, Ingvars; Redmond, Stephen J.

2015-01-01

Dexterous manipulation is not possible without sensory information about object properties and manipulative forces. Fundamental neuroscience has been unable to demonstrate how information about multiple stimulus parameters may be continuously extracted, concurrently, from a population of tactile afferents. This is the first study to demonstrate this, using spike trains recorded from tactile afferents innervating the monkey fingerpad. A multiple-regression model, requiring no a priori knowledge of stimulus-onset times or stimulus combination, was developed to obtain continuous estimates of instantaneous force and torque. The stimuli consisted of a normal-force ramp (to a plateau of 1.8, 2.2, or 2.5 N), on top of which −3.5, −2.0, 0, +2.0, or +3.5 mNm torque was applied about the normal to the skin surface. The model inputs were sliding windows of binned spike counts recorded from each afferent. Models were trained and tested by 15-fold cross-validation to estimate instantaneous normal force and torque over the entire stimulation period. With the use of the spike trains from 58 slow-adapting type I and 25 fast-adapting type I afferents, the instantaneous normal force and torque could be estimated with small error. This study demonstrated that instantaneous force and torque parameters could be reliably extracted from a small number of tactile afferent responses in a real-time fashion with stimulus combinations that the model had not been exposed to during training. Analysis of the model weights may reveal how interactions between stimulus parameters could be disentangled for complex population responses and could be used to test neurophysiologically relevant hypotheses about encoding mechanisms. PMID:25948866

Biomechanical analysis of the knee during the power clean.

PubMed

Souza, Aaron L; Shimada, Sean D

2002-05-01

To our knowledge, no scientific literature has examined the 3-dimensional forces acting at the knee joint during a power clean. Ten male weightlifting subjects (25.9 years, SD 3.54) performed 1 set of the power clean at 60 and 70% of their maximal collegiate level for 5 repetitions. The subjects displayed a large compressive, moderate anterior, and a small degree of lateral and medial force at the knee during both percentage lifts. The majority of these forces occurred during the second pull phase or the catching phase of the lift. Lifters with decreased weight/system weight percentages displayed a more efficient lift that placed less stress on the knees. This analysis may provide invaluable information in the assessment of weight percentages used for Olympic weightlifters throughout the training year. the power clean.

Experimental studies on the tensile properties of human umbilical cords.

PubMed

Tantius, Britta; Rothschild, Markus A; Valter, Markus; Michael, Joern; Banaschak, Sibylle

2014-03-01

When tried in court, mothers accused of neonaticide may claim that the umbilical cord just broke during birth and the newborn child bled to death accordingly. To evaluate the possibility of a breakage of the umbilical cord is the goal of this work. Therefore 25 umbilical cords from neonates of both sexes born at term were stretched using an electrically operated material testing machine and the energy necessary to break them was measured. This experimental set-up equals a static strain, not a dynamic one. The maximum force endured (F max) ranged from 37.24 N to 150.04 N. The average force endured was 79.87 N with a standard deviation of 27.39. The elongation at break varied from 13.24% to a maximum of 119.93%. We found no relationship between the force endured and any of the following parameters: birth weight, pH of the venous umbilical blood, diameter of cord, free length under testing, duration of pregnancy or the mother's age. We performed a literature research and tried to define the circumstances in which a break is more likely to occur, these being malformations, entanglement or disease, e.g. inflammation. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Impact kinetics associated with four common bilateral plyometric exercises.

PubMed

Stewart, Ethan; Kernozek, Thomas; Peng, Hsien-Te; Wallace, Brian

2018-04-20

This study quantified the peak vertical ground reaction force (VGRF), impulse, and average and instantaneous loading rates developed during bilateral plyometric exercises. Fourteen collegiate male athletes performed four different bilateral plyometric exercises within a single testing session. Depth jumps from thirty, sixty and ninety centimeter heights (DJ30, DJ60, and DJ90, respectively), and a two consecutive jump exercise (2CJ), were randomly performed. The subjects landed on and propelled themselves off two force platforms embedded into the floor. The stance phase of each plyometric movement was analyzed for vertical force characteristics. The dependent variables were normalized to body weight. One-way repeated-measures ANOVA revealed significant differences between exercises (p ≤ 0.05). For VGRF, only the DJ60 and 2CJ exercises were not different from each other. The impulses between DJ60 and DJ90, and DJ30 and 2CJ, were not different. All exercises were different from each other in regards to average and instantaneous loading rate except for DJ30 vs. DJ60, and DJ90 vs. 2CJ. The DJ90 condition reported the highest peak VGRF by approaching five times body weight. The 2CJ condition had similar impulse and loading rates as the DJ90 condition. A proper progression and detailed program planning should be utilized when implementing plyometric exercises due to their different impact kinetics and how they might influence the body upon ground contact.

Ground-based testing of the dynamics of flexible space structures using band mechanisms

NASA Technical Reports Server (NTRS)

Yang, L. F.; Chew, Meng-Sang

1991-01-01

A suspension system based on a band mechanism is studied to provide the free-free conditions for ground based validation testing of flexible space structures. The band mechanism consists of a noncircular disk with a convex profile, preloaded by torsional springs at its center of rotation so that static equilibrium of the test structure is maintained at any vertical location; the gravitational force will be directly counteracted during dynamic testing of the space structure. This noncircular disk within the suspension system can be configured to remain unchanged for test articles with the different weights as long as the torsional spring is replaced to maintain the originally designed frequency ratio of W/k sub s. Simulations of test articles which are modeled as lumped parameter as well as continuous parameter systems, are also presented.

Low Force Penetration of Icy Regolith

NASA Technical Reports Server (NTRS)

Mantovani, J. G.; Galloway, G. M.; Zacny, K.

2016-01-01

A percussive cone penetrometer measures the strength of granular material by using percussion to deliver mechanical energy into the material. A percussive cone penetrometer was used in this study to penetrate a regolith ice mixture by breaking up ice and decompacting the regolith. As compared to a static cone penetrometer, percussion allows low reaction forces to push a penetrometer probe tip more easily into dry regolith in a low gravity environment from a planetary surface rover or a landed spacecraft. A percussive cone penetrates icy regolith at ice concentrations that a static cone cannot penetrate. In this study, the percussive penetrator was able to penetrate material under 65 N of down-force which could not be penetrated using a static cone under full body weight. This paper discusses using a percussive cone penetrometer to discern changes in the concentration of water-ice in a mixture of lunar regolith simulant and ice to a depth of one meter. The rate of penetration was found to be a function of the ice content and was not significantly affected by the down-force. The test results demonstrate that this method may be ideal for a small platform in a reduced gravity environment. However, there are some cases where the system may not be able to penetrate the icy regolith, and there is some risk of the probe tip becoming stuck so that it cannot be retracted. It is also shown that a percussive cone penetrometer could be used to prospect for water ice in regolith at concentrations as high as 8 by weight.

The evolution of vertical climbing in primates: evidence from reaction forces.

PubMed

Hanna, Jandy B; Granatosky, Michael C; Rana, Pooja; Schmitt, Daniel

2017-09-01

Vertical climbing is an essential behavior for arboreal animals, yet limb mechanics during climbing are poorly understood and rarely compared with those observed during horizontal walking. Primates commonly engage in both arboreal walking and vertical climbing, and this makes them an ideal taxa in which to compare these locomotor forms. Additionally, primates exhibit unusual limb mechanics compared with most other quadrupeds, with weight distribution biased towards the hindlimbs, a pattern that is argued to have evolved in response to the challenges of arboreal walking. Here we test an alternative hypothesis that functional differentiation between the limbs evolved initially as a response to climbing. Eight primate species were recorded locomoting on instrumented vertical and horizontal simulated arboreal runways. Forces along the axis of, and normal to, the support were recorded. During walking, all primates displayed forelimbs that were net braking, and hindlimbs that were net propulsive. In contrast, both limbs served a propulsive role during climbing. In all species, except the lorisids, the hindlimbs produced greater propulsive forces than the forelimbs during climbing. During climbing, the hindlimbs tends to support compressive loads, while the forelimb forces tend to be primarily tensile. This functional disparity appears to be body-size dependent. The tensile loading of the forelimbs versus the compressive loading of the hindlimbs observed during climbing may have important evolutionary implications for primates, and it may be the case that hindlimb-biased weight support exhibited during quadrupedal walking in primates may be derived from their basal condition of climbing thin branches. © 2017. Published by The Company of Biologists Ltd.

Social defeat stress induces a depression-like phenotype in adolescent male c57BL/6 mice.

PubMed

Iñiguez, Sergio D; Riggs, Lace M; Nieto, Steven J; Dayrit, Genesis; Zamora, Norma N; Shawhan, Kristi L; Cruz, Bryan; Warren, Brandon L

2014-05-01

Abstract Exposure to stress is highly correlated with the emergence of mood-related illnesses. Because major depressive disorder often emerges in adolescence, we assessed the effects of social defeat stress on responses to depressive-like behaviors in juvenile mice. To do this, postnatal day (PD) 35 male c57BL/6 mice were exposed to 10 days of social defeat stress (PD35-44), while control mice were handled daily. Twenty-four hours after the last episode of defeat (PD45), separate groups of mice were tested in the social interaction, forced swimming, sucrose preference, and elevated plus-maze behavioral assays (n = 7-12 per group). Also, we examined body weight gain across days of social defeat and levels of blood serum corticosterone 40 min after the last episode of defeat stress. Our data indicates that defeated mice exhibited a depressive-like phenotype as inferred from increased social avoidance, increased immobility in the forced swim test, and reduced sucrose preference (a measure of anhedonia), when compared to non-defeated controls. Defeated mice also displayed an anxiogenic-like phenotype when tested on the elevated plus-maze. Lastly, stressed mice displayed lower body weight gain, along with increased blood serum corticosterone levels, when compared to non-stressed controls. Overall, we show that in adolescent male c57BL/6 mice, social defeat stress induces a depression- and anxiety-like phenotype 24 h after the last episode of stress. These data suggest that the social defeat paradigm may be used to examine the etiology of stress-induced mood-related disorders during adolescence.

Social defeat stress induces a depression-like phenotype in adolescent male c57BL/6 mice

PubMed Central

Iñiguez, Sergio D.; Riggs, Lace M.; Nieto, Steven J.; Dayrit, Genesis; Zamora, Norma N.; Shawhan, Kristi L.; Cruz, Bryan; Warren, Brandon L.

2016-01-01

Exposure to stress is highly correlated with the emergence of mood-related illnesses. Because major depressive disorder often emerges in adolescence, we assessed the effects of social defeat stress on responses to depressive-like behaviors in juvenile mice. To do this, postnatal day (PD) 35 male c57BL/6 mice were exposed to 10 days of social defeat stress (PD35–44), while control mice were handled daily. Twenty-four hours after the last episode of defeat (PD45), separate groups of mice were tested in the social interaction, forced swimming, sucrose preference, and elevated plus-maze behavioral assays (n = 7–12 per group). Also, we examined body weight gain across days of social defeat and levels of blood serum corticosterone 40 min after the last episode of defeat stress. Our data indicates that defeated mice exhibited a depressive-like phenotype as inferred from increased social avoidance, increased immobility in the forced swim test, and reduced sucrose preference (a measure of anhedonia), when compared to non-defeated controls. Defeated mice also displayed an anxiogenic-like phenotype when tested on the elevated plus-maze. Lastly, stressed mice displayed lower body weight gain, along with increased blood serum corticosterone levels, when compared to non-stressed controls. Overall, we show that in adolescent male c57BL/6 mice, social defeat stress induces a depression- and anxiety-like phenotype 24 h after the last episode of stress. These data suggest that the social defeat paradigm may be used to examine the etiology of stress-induced mood-related disorders during adolescence. PMID:24689732

Effect of Heavy Consumption of Alcoholic Beverages on the Perception of Sweet and Salty Taste.

PubMed

Silva, Camile S; Dias, Vaneria R; Almeida, Juliane A Regis; Brazil, Jamile M; Santos, Ramon A; Milagres, Maria P

2016-05-01

To determine the threshold index of sweet and salty tastes in alcoholics undergoing treatment. Taste threshold was assessed using type 3-Alternative Forced Choice in a control group (92 non-alcoholic volunteers) and a test group (92 alcoholics in therapy). The test group completed a structured questionnaire on lifestyle and habits. Significant difference were found between the threshold rates found in the test (3.78) and control groups (1.39). In the salty stimulus, no significant difference was noted in the threshold detection between the control (0.17) and test groups (0.30). A significant correlation was observed between the index Pearson's threshold to sweet taste in the test group and their reported alcohol consumption. The test group reported characteristics such as loss of appetite (93%), weight loss during consumption (62%) and weight gain after quitting drinking (72%). That the alcoholic group reported less sensitivity to sweet taste suggests that drinking habits may influence choice of foods, with a greater preference for foods with higher sucrose concentration. This contribute to poor health, because excess consumption of sugar raises risk for several diseases. No conclusive results were found for the salty stimulus. © The Author 2015. Medical Council on Alcohol and Oxford University Press. All rights reserved.

A lunar/Martian anchor emplacement system

NASA Astrophysics Data System (ADS)

Clinton, Dustin; Holt, Andrew; Jantz, Erik; Kaufman, Teresa; Martin, James; Weber, Reed

On the Moon or Mars, it is necessary to have an anchor, or a stable, fixed point able to support the forces necessary to rescue a stuck vehicle, act as a stake for a tent in a Martian gale, act as a fulcrum in the erection of general construction poles, or support tent-like regolith shields. The anchor emplacement system must be highly autonomous. It must supply the energy and stability for anchor deployment. The goal of the anchor emplacement system project is to design and build a prototype anchor and to design a conceptual anchor emplacement system. Various anchors were tested in a 1.3 cubic meter test bed containing decomposed granite. A simulated lunar soil was created by adjusting the moisture and compaction characteristics of the soil. We conducted tests on emplacement torque, amount of force the anchor could withstand before failure, anchor pull out force at various angles, and soil disturbances caused by placing the anchor. A single helix auger anchor performed best in this test bed based on energy to emplace, and the ultimate holding capacity. The anchor was optimized for ultimate holding capacity, minimum emplacement torque, and minimum soil disturbance in sandy soils yielding the following dimensions: helix diameter (4.45 cm), pitch (1.27 cm), blade thickness (0.15 cm), total length (35.56 cm), shaft diameter (0.78 cm), and a weight of 212.62 g. The experimental results showed that smaller diameter, single-helix augers held more force than larger diameter augers for a given depth. The emplacement system consists of a flywheel and a motor for power, sealed in a protective box supported by four legs. The flywheel system was chosen over a gear system based on its increased reliability in the lunar environment.

The Impact of Nitinol Staples on the Compressive Forces, Contact Area, and Mechanical Properties in Comparison to a Claw Plate and Crossed Screws for the First Tarsometatarsal Arthrodesis.

PubMed

Aiyer, Amiethab; Russell, Nicholas A; Pelletier, Matthew H; Myerson, Mark; Walsh, William R

2016-06-01

Background The optimal fixation method for the first tarsometatarsal arthrodesis remains controversial. This study aimed to develop a reproducible first tarsometatarsal testing model to evaluate the biomechanical performance of different reconstruction techniques. Methods Crossed screws or a claw plate were compared with a single or double shape memory alloy staple configuration in 20 Sawbones models. Constructs were mechanically tested in 4-point bending to 1, 2, and 3 mm of plantar displacement. The joint contact force and area were measured at time zero, and following 1 and 2 mm of bending. Peak load, stiffness, and plantar gapping were determined. Results Both staple configurations induced a significantly greater contact force and area across the arthrodesis than the crossed screw and claw plate constructs at all measurements. The staple constructs completely recovered their plantar gapping following each test. The claw plate generated the least contact force and area at the joint interface and had significantly greater plantar gapping than all other constructs. The crossed screw constructs were significantly stiffer and had significantly less plantar gapping than the other constructs, but this gapping was not recoverable. Conclusions Crossed screw fixation provides a rigid arthrodesis with limited compression and contact footprint across the joint. Shape memory alloy staples afford dynamic fixation with sustained compression across the arthrodesis. A rigid polyurethane foam model provides an anatomically relevant comparison for evaluating the interface between different fixation techniques. Clinical Relevance The dynamic nature of shape memory alloy staples offers the potential to permit early weight bearing and could be a useful adjunctive device to impart compression across an arthrodesis of the first tarsometatarsal joint. Therapeutic, Level V: Bench testing. © 2015 The Author(s).

A lunar/Martian anchor emplacement system

NASA Technical Reports Server (NTRS)

Clinton, Dustin; Holt, Andrew; Jantz, Erik; Kaufman, Teresa; Martin, James; Weber, Reed

1993-01-01

On the Moon or Mars, it is necessary to have an anchor, or a stable, fixed point able to support the forces necessary to rescue a stuck vehicle, act as a stake for a tent in a Martian gale, act as a fulcrum in the erection of general construction poles, or support tent-like regolith shields. The anchor emplacement system must be highly autonomous. It must supply the energy and stability for anchor deployment. The goal of the anchor emplacement system project is to design and build a prototype anchor and to design a conceptual anchor emplacement system. Various anchors were tested in a 1.3 cubic meter test bed containing decomposed granite. A simulated lunar soil was created by adjusting the moisture and compaction characteristics of the soil. We conducted tests on emplacement torque, amount of force the anchor could withstand before failure, anchor pull out force at various angles, and soil disturbances caused by placing the anchor. A single helix auger anchor performed best in this test bed based on energy to emplace, and the ultimate holding capacity. The anchor was optimized for ultimate holding capacity, minimum emplacement torque, and minimum soil disturbance in sandy soils yielding the following dimensions: helix diameter (4.45 cm), pitch (1.27 cm), blade thickness (0.15 cm), total length (35.56 cm), shaft diameter (0.78 cm), and a weight of 212.62 g. The experimental results showed that smaller diameter, single-helix augers held more force than larger diameter augers for a given depth. The emplacement system consists of a flywheel and a motor for power, sealed in a protective box supported by four legs. The flywheel system was chosen over a gear system based on its increased reliability in the lunar environment.

Forced Marriage and Birth Outcomes.

PubMed

Becker, Charles M; Mirkasimov, Bakhrom; Steiner, Susan

2017-08-01

We study the impact of marriages resulting from bride kidnapping on infant birth weight. Bride kidnapping-a form of forced marriage-implies that women are abducted by men and have little choice other than to marry their kidnappers. Given this lack of choice over the spouse, we expect adverse consequences for women in such marriages. Remarkable survey data from the Central Asian nation of Kyrgyzstan enable exploration of differential birth outcomes for women in kidnap-based and other types of marriage using both OLS and IV estimation. We find that children born to mothers in kidnap-based marriages have lower birth weight compared with children born to other mothers. The largest difference is between kidnap-based and arranged marriages: the magnitude of the birth weight loss is in the range of 2 % to 6 % of average birth weight. Our finding is one of the first statistically sound estimates of the impact of forced marriage and implies not only adverse consequences for the women involved but potentially also for their children.

New Tool to Control and Monitor Weighted Vest Training Load for Sprinting and Jumping in Soccer.

PubMed

Carlos-Vivas, Jorge; Freitas, Tomás T; Cuesta, Miguel; Perez-Gomez, Jorge; De Hoyo, Moisés; Alcaraz, Pedro E

2018-04-26

Carlos-Vivas, J, Freitas, TT, Cuesta, M, Perez-Gomez, J, De Hoyo, M, and Alcaraz, PE. New tool to control and monitor weighted vest training load for sprinting and jumping in soccer. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this study was to develop 2 regression equations that accurately describe the relationship between weighted vest loads and performance indicators in sprinting (i.e., maximum velocity, Vmax) and jumping (i.e., maximum height, Hmax). Also, this study aimed to investigate the effects of increasing the load on spatio-temporal variables and power development in soccer players and to determine the "optimal load" for sprinting and jumping. Twenty-five semiprofessional soccer players performed the sprint test, whereas a total of 46 completed the vertical jump test. Two different regression equations were developed for calculating the load for each exercise. The following equations were obtained: % body mass (BM) = -2.0762·%Vmax + 207.99 for the sprint and % BM = -0.7156·%Hmax + 71.588 for the vertical jump. For both sprinting and jumping, when the load increased, Vmax and Hmax decreased. The "optimal load" for resisted training using weighted vest was unclear for sprinting and close to BM for vertical jump. This study presents a new tool to individualize the training load for resisted sprinting and jumping using weighted vest in soccer players and to develop the whole force-velocity spectrum according to the objectives of the different periods of the season.

Improvement of hemolysis in a centrifugal blood pump with hydrodynamic bearings and semi-open impeller.

PubMed

Kosaka, Ryo; Yamane, Takashi; Maruyama, Osamu; Nishida, Masahiro; Yada, Toru; Saito, Sakae; Hirai, Shusaku

2007-01-01

We have developed a centrifugal blood pump with hydrodynamic bearings and semi-open impeller, and evaluated the levitation performance test and the hemolysis test. This pump is operated without any complicated control circuit and displacement-sensing module. The casing diameter is 74 mm and the height is 38 mm including flanges for volts. The weight is 251 g and the volume is 159 cm3. By changing the stator relative position against the rotor, the levitation characteristics of the impeller can be adjusted. The diameter of impeller is 36 mm and the height is 25 mm. The impeller is levitated by the thrust bearing of spiral groove type and a radial bearing of herringbone type. The pump performance was evaluated through the levitation performance test and the hemolysis test. As a result, the normalized index of hemolysis (NIH) was reduced from 0.72 g/100 L to 0.024 g/100 L corresponding to the changes of the groove direction of the hydrodynamic bearing and the expansion of the bearing gap. During these studies, we confirmed that the hemolytic property was improved by balancing the fluid dynamic force and the magnetic force.

Chronic fluoxetine treatment partly attenuates the long-term anxiety and depressive symptoms induced by MDMA ('Ecstasy') in rats.

PubMed

Thompson, Murray R; Li, Kong M; Clemens, Kelly J; Gurtman, Clint G; Hunt, Glenn E; Cornish, Jennifer L; McGregor, Iain S

2004-04-01

Use of the drug 3,4-methylenedioxymethamphetamine (MDMA, 'Ecstasy') can have long-term adverse effects on emotion in both humans and laboratory animals. The present study examined whether chronic treatment with the antidepressant drug fluoxetine could reverse such effects. Male Wistar rats were briefly exposed to MDMA (4 x 5 mg/kg over 4 h) or vehicle on 2 consecutive days. Approximately 9-12 weeks later, half of the rats received a dose of approximately 6 mg/kg/day fluoxetine in their drinking water for a 5-week period. Fluoxetine administration reduced fluid intake and body weight in MDMA and vehicle pretreated rats. After several weeks of fluoxetine treatment, rats were assessed on the social interaction test, the emergence test of anxiety and the forced swim model of depression. MDMA pretreated rats showed reduced social interaction, increased anxiety on the emergence test, and increased immobility and decreased active responses in the forced swim test. Fluoxetine treatment reversed MDMA-induced anxiety in the emergence test and depressive-like effects in the forced swim test, yet exhibited no effects on the social interaction test. MDMA pretreated rats had decreased 5-HT and 5-HIAA levels in limbic and cortical regions, and decreased density of serotonin transporter sites in the cortex. Fluoxetine treatment did not greatly affect 5-HT levels in MDMA pretreated rats, but significantly decreased 5-HIAA levels in all brain sites examined. Postmortem blood serum levels of fluoxetine and norfluoxetine did not differ in MDMA and vehicle pretreated rats. These results indicate that fluoxetine may provide a treatment option for some of the deleterious long-term effects resulting from MDMA exposure.

Moving force identification based on redundant concatenated dictionary and weighted l1-norm regularization

NASA Astrophysics Data System (ADS)

Pan, Chu-Dong; Yu, Ling; Liu, Huan-Lin; Chen, Ze-Peng; Luo, Wen-Feng

2018-01-01

Moving force identification (MFI) is an important inverse problem in the field of bridge structural health monitoring (SHM). Reasonable signal structures of moving forces are rarely considered in the existing MFI methods. Interaction forces are complex because they contain both slowly-varying harmonic and impact signals due to bridge vibration and bumps on a bridge deck, respectively. Therefore, the interaction forces are usually hard to be expressed completely and sparsely by using a single basis function set. Based on the redundant concatenated dictionary and weighted l1-norm regularization method, a hybrid method is proposed for MFI in this study. The redundant dictionary consists of both trigonometric functions and rectangular functions used for matching the harmonic and impact signal features of unknown moving forces. The weighted l1-norm regularization method is introduced for formulation of MFI equation, so that the signal features of moving forces can be accurately extracted. The fast iterative shrinkage-thresholding algorithm (FISTA) is used for solving the MFI problem. The optimal regularization parameter is appropriately chosen by the Bayesian information criterion (BIC) method. In order to assess the accuracy and the feasibility of the proposed method, a simply-supported beam bridge subjected to a moving force is taken as an example for numerical simulations. Finally, a series of experimental studies on MFI of a steel beam are performed in laboratory. Both numerical and experimental results show that the proposed method can accurately identify the moving forces with a strong robustness, and it has a better performance than the Tikhonov regularization method. Some related issues are discussed as well.

Maximizing coupling strength of magnetically anchored surgical instruments: how thick can we go?

PubMed

Best, Sara L; Bergs, Richard; Gedeon, Makram; Paramo, Juan; Fernandez, Raul; Cadeddu, Jeffrey A; Scott, Daniel J

2011-01-01

The Magnetic Anchoring and Guidance System (MAGS) includes an external magnet that controls intra-abdominal surgical instruments via magnetic attraction forces. We have performed NOTES (Natural Orifice Transluminal Endoscopic Surgery) and LESS (Laparoendoscopic Single Site) procedures using MAGS instruments in porcine models with up to 2.5-cm-thick abdominal walls, but this distance may not be sufficient in some humans. The purpose of this study was to determine the maximal abdominal wall thickness for which the current MAGS platform is suitable. Successive iterations of prototype instruments were developed; those evaluated in this study include external (134-583 g, 38-61 mm diameter) and internal (8-39 g, 10-22 mm diameter) components using various grades, diameters, thicknesses, and stacking/shielding/focusing configurations of permanent Neodymium-iron-boron (NdFeB) magnets. Nine configurations were tested for coupling strength across distances of 0.1-10 cm. The force-distance tests across an air medium were conducted at 0.5-mm increments using a robotic arm fitted with a force sensor. A minimum theoretical instrument drop-off (decoupling) threshold was defined as the separation distance at which force decreased below the weight of the heaviest internal component (39 g). Magnetic attraction forces decreased exponentially over distance. For the nine configurations tested, the average forces were 3,334 ± 1,239 gf at 0.1 cm, 158 ± 98 gf at 2.5 cm, and 8.7 ± 12 gf at 5 cm; the drop-off threshold was 3.64 ± 0.8 cm. The larger stacking configurations and magnets yielded up to a 592% increase in attraction force at 2.5 cm and extended the drop-off threshold distance by up to 107% over single-stack anchors. For the strongest configuration, coupling force ranged from 5,337 gf at 0.1 cm to 0 gf at 6.95 cm and yielded a drop-off threshold distance of 4.78 cm. This study suggests that the strongest configuration of currently available MAGS instruments is suitable for clinically relevant abdominal wall thicknesses. Further platform development and optimization are warranted.

Effect of low-speed impact damage on the buckling properties of E-glass/epoxy laminates

NASA Astrophysics Data System (ADS)

Yapici, A.; Metin, M.

2009-11-01

The postimpact buck ling loads of E-glass/epoxy laminates have been measured. Composite samples with the stacking sequence [+45/-45/90/0]2s were subjected to low-speed impact loadings at various energy levels. The tests were conducted on a specially developed vertical drop-weight testing machine. The main impact parameters, such as the peak load, absorbed energy, deflection at the peak load, and damage area, were evaluated and com pared. The damaged specimens were subjected to compressive axial forces, and their buckling loads were determined. The relation between the level of impact energy and buck ling loads is investigated.

Defense Small Business Innovation Research Program (SBIR). Volume 3. Air Force Abstracts of Phase 1 Awards from FY 1988 SBIR Solicitation

DTIC Science & Technology

1989-05-01

THE TARGET DOPPLER FREQUENCIES. ADAPTIVE SENSORS INC 216 PICO BLVD - STE 8 SANTA MONICA, CA 90405 CONTRACT NUMBER: JOHN S BAILEY TITLE: SPATIALLY...APPLIED RESEARCH ASSOCS INC 4300 SAN MATEO BLVD NE - STE A220 ALBUQUERQUE, NM 87110 CONTRACT NUMBER: FRANK A MAESTAS TITLE: PARAMETRIC ANALYSIS OF EXPLOSIVE...VERIFIED THROUGH SUBSCALE FABRICATION AND TEST. AV DYNAMICS INC 825 MYRTLE AVE MONROVIA, CA 91016 CONTRACT NUMBER: DR P B S LISSAMAN TITLE: LIGHT WEIGHT

Displacement of Tethered Hydro-Acoustic Modems by Uniform Horizontal Currents

DTIC Science & Technology

2009-12-01

smooth and plane surfaces (in incompressible flow ) in air and in water (From [4]) ..............22  Figure 13.  Drag of streamline bodies, tested in...from a stationary sea- surface buoy or Unmanned Surface Vehicle (USV) weighted by a dense object at the free end (Figure 2). The equations of static...forces on the free end are caused by an attached ballast or float. The moored cable has a free -moving sub- surface buoy positioned at a water depth

Signal and power roll ring testing update

NASA Technical Reports Server (NTRS)

Smith, Dennis W.

1989-01-01

The development of the roll ring as a long-life, low-torque alternative to the slip ring is discussed. A roll ring consists of one or more circular flexures captured by their own spring force in the annular space between two concentric conductors or contact rings. The advantages of roll rings over other types of electrical transfer devices are: extremely low drag torque, high transfer efficiencies in high-power configurations, extremely low wear debris generation, long life, and low weight for high-power applications.

Optimizing Muscle Parameters in Musculoskeletal Modeling Using Monte Carlo Simulations

NASA Technical Reports Server (NTRS)

Hanson, Andrea; Reed, Erik; Cavanagh, Peter

2011-01-01

Astronauts assigned to long-duration missions experience bone and muscle atrophy in the lower limbs. The use of musculoskeletal simulation software has become a useful tool for modeling joint and muscle forces during human activity in reduced gravity as access to direct experimentation is limited. Knowledge of muscle and joint loads can better inform the design of exercise protocols and exercise countermeasure equipment. In this study, the LifeModeler(TM) (San Clemente, CA) biomechanics simulation software was used to model a squat exercise. The initial model using default parameters yielded physiologically reasonable hip-joint forces. However, no activation was predicted in some large muscles such as rectus femoris, which have been shown to be active in 1-g performance of the activity. Parametric testing was conducted using Monte Carlo methods and combinatorial reduction to find a muscle parameter set that more closely matched physiologically observed activation patterns during the squat exercise. Peak hip joint force using the default parameters was 2.96 times body weight (BW) and increased to 3.21 BW in an optimized, feature-selected test case. The rectus femoris was predicted to peak at 60.1% activation following muscle recruitment optimization, compared to 19.2% activation with default parameters. These results indicate the critical role that muscle parameters play in joint force estimation and the need for exploration of the solution space to achieve physiologically realistic muscle activation.

Evaluation of wheelchair resistive forces during straight and turning trajectories across different wheelchair configurations using free-wheeling coast-down test.

PubMed

Lin, Jui-Te; Huang, Morris; Sprigle, Stephen

2015-01-01

The purpose of this study was to develop a simple approach to evaluate resistive frictional forces acting on manual wheelchairs (MWCs) during straight and turning maneuvers. Using a dummy-occupied MWC, decelerations were measured via axle-mounted encoders during a coast-down protocol that included straight trajectories and fixed-wheel turns. Eight coast-down trials were conducted to test repeatability and repeated on separate days to evaluate reliability. Without changing the inertia of the MWC system, three tire inflations were chosen to evaluate the sensitivity in discerning deceleration differences using effect sizes. The technique was also deployed to investigate the effect of different MWC masses and weight distributions on resistive forces. Results showed that the proposed coast-down technique had good repeatability and reliability in measuring decelerations and had good sensitivity in discerning differences in tire inflation, especially during turning. The results also indicated that increased loading on drive wheels reduced resistive losses in straight trajectories while increasing resistive losses during turning. During turning trajectories, the presence of tire scrub contributes significantly to the amount of resistive force. Overall, this new coast-down technique demonstrates satisfactory repeatability and sensitivity for detecting deceleration changes during straight and turning trajectories, indicating that it can be used to evaluate resistive loss of different MWC configurations and maneuvers.

Excessive eccentric exercise leads to transitory hypothalamic inflammation, which may contribute to the low body weight gain and food intake in overtrained mice.

PubMed

Pereira, B C; da Rocha, A L; Pauli, J R; Ropelle, E R; de Souza, C T; Cintra, D E; Sant'Ana, M R; da Silva, A S R

2015-12-17

Low body weight gain and food intake are related to exhaustive training and overtraining; however, the molecular mechanisms responsible for these alterations remain unknown. The main aim of this study was to evaluate the effects of running overtraining (OT) protocols performed downhill, uphill and without inclination on the inflammatory pathway in the mouse hypothalamus. The rodents were randomized into the control (C), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up) and overtrained by running without inclination (OTR) groups. The body weights and food intake were recorded daily. The incremental load, exhaustive, rotarod and grip force tests were used to measure performance. At 36 h after the grip force test was performed at the end of OT protocols (i.e., week eight) and/or after a 2-week total recovery period (i.e., week 10), the hypothalamus and gastrocnemius were extracted for immunoblotting analysis. In addition, the serum was used to determine cytokine and leptin concentrations. From week 0 to week 8, the OTR/down group exhibited decreased body weight and food intake, and the OTR/up group increased their food intake. At week 10, the OTR/down group exhibited increased body weight, while the OTR group decreased their food intake. The OTR/down group exhibited increased IL-1beta, IL-6, TNF-alpha, pSAPK/JNK and SOCS3 levels at week eight. The OTR/down, OTR/up and OTR groups exhibited increased IL-10 levels at week 10. The OTR/up group displayed increased pJAK2 levels at week eight. While the OTR/down group exhibited increased IL-1beta levels, the OTR/down and OTR/up groups exhibited increased IL-6 and TNF-alpha levels, but decreased IL-10 levels in the gastrocnemius at week eight. The three OT protocols increased the IL-1beta and IL-6 levels, but only the OTR/down and OTR/up groups had increased TNF-alpha levels in serum at week eight. The serum leptin levels were lower for the OTR group compared with the CT group at week eight. In conclusion, the OTR/down protocol induced transitory hypothalamic inflammation with concomitant reductions in the body weight and food intake. After the 2-week total recovery period, the OTR/down group had reversed the hypothalamic inflammation, with the concomitant normalization of the body weight and food intake. Copyright © 2015 IBRO. Published by Elsevier Ltd. All rights reserved.

Difference in peak weight transfer and timing based on golf handicap.

PubMed

Queen, Robin M; Butler, Robert J; Dai, Boyi; Barnes, C Lowry

2013-09-01

Weight shift during the golf swing has been a topic of discussion among golf professionals; however, it is still unclear how weight shift varies in golfers of different performance levels. The main purpose of this study was to examine the following: (a) the changes in the peak ground reaction forces (GRF) and the timing of these events between high (HHCP) and low handicap (LHCP) golfers and (b) the differences between the leading and trailing legs. Twenty-eight male golfers were recruited and divided based on having an LHCP < 9 or HHCP > 9. Three-dimensional GRF peaks and the timing of the peaks were recorded bilaterally during a golf swing. The golf swing was divided into different phases: (a) address to the top of the backswing, (b) top of the backswing to ball contact, and (c) ball contact to the end of follow through. Repeated measures analyses of variance (α = 0.05) were completed for each study variable: the magnitude and the timing of peak vertical GRF, peak lateral GRF, and peak medial GRF (α = 0.05). The LHCP group had a greater transfer of vertical force from the trailing foot to the leading foot in phase 2 than the HHCP group. The LHCP group also demonstrated earlier timing of peak vertical force throughout the golf swing than the HHCP group. The LHCP and HHCP groups demonstrated different magnitudes of peak lateral force. The LHCP group had an earlier timing of peak lateral GRF in phase 2 and earlier timing of peak medial GRF in phases 1 and 2 than the HHCP group. In general, LHCP golfers demonstrated greater and earlier force generation than HHCP golfers. It may be relevant to consider both the magnitude of the forces and the timing of these events during golf-specific training to improve performance. These data reveal weight shifting differences that can be addressed by teaching professionals to help their students better understand weight transfer during the golf swing to optimize performance.

Fast force actuators for LSST primary/tertiary mirror

NASA Astrophysics Data System (ADS)

Hileman, Edward; Warner, Michael; Wiecha, Oliver

2010-07-01

The very short slew times and resulting high inertial loads imposed upon the Large Synoptic Survey Telescope (LSST) create new challenges to the primary mirror support actuators. Traditionally large borosilicate mirrors are supported by pneumatic systems, which is also the case for the LSST. These force based actuators bear the weight of the mirror and provide active figure correction, but do not define the mirror position. A set of six locating actuators (hardpoints) arranged in a hexapod fashion serve to locate the mirror. The stringent dynamic requirements demand that the force actuators must be able to counteract in real time for dynamic forces on the hardpoints during slewing to prevent excessive hardpoint loads. The support actuators must also maintain the prescribed forces accurately during tracking to maintain acceptable mirror figure. To meet these requirements, candidate pneumatic cylinders incorporating force feedback control and high speed servo valves are being tested using custom instrumentation with automatic data recording. Comparative charts are produced showing details of friction, hysteresis cycles, operating bandwidth, and temperature dependency. Extremely low power actuator controllers are being developed to avoid heat dissipation in critical portions of the mirror and also to allow for increased control capabilities at the actuator level, thus improving safety, performance, and the flexibility of the support system.

Skeletal muscle strength and endurance are maintained during moderate dehydration.

PubMed

Périard, J D; Tammam, A H; Thompson, M W

2012-08-01

This study investigated the effects of moderate dehydration (~2.5% body weight) on muscle strength and endurance using percutaneous electrical stimulation to quantify central and peripheral fatigue, and isolate the combined effects of exercise-heat stress and dehydration, vs. the effect of dehydration alone. Force production and voluntary activation were calculated in 10 males during 1 brief and 15 repeated maximal voluntary isometric contractions performed prior to (control) walking in the heat (35°C), immediately following exercise, and the next morning (dehydration). The protocol was also performed in a euhydrated state. During the brief contractions, force production and voluntary activation were maintained in all trials. In contrast, force production decreased throughout the repeated contractions, regardless of hydration status (P<0.001). The decline in force was greater immediately following exercise-heat stress dehydration compared with control and euhydration (P<0.001). When dehydration was isolated from acute post-exercise dehydration, force production was maintained similarly to control and euhydration. Despite the progressive decline in force production and the increased fatigability observed during the repeated contractions, voluntary activation remained elevated throughout each muscle function test. Therefore, moderate dehydration, isolated from acute exercise-heat stress, does not appear to influence strength during a single contraction or enhance fatigability. © Georg Thieme Verlag KG Stuttgart · New York.

High shear rate flow in a linear stroke magnetorheological energy absorber

NASA Astrophysics Data System (ADS)

Hu, W.; Wereley, N. M.; Hiemenz, G. J.; Ngatu, G. T.

2014-05-01

To provide adaptive stroking load in the crew seats of ground vehicles to protect crew from blast or impact loads, a magnetorheological energy absorber (MREA) or shock absorber was developed. The MREA provides appropriate levels of controllable stroking load for different occupant weights and peak acceleration because the viscous stroking load generated by the MREA force increases with velocity squared, thereby reducing its controllable range at high piston velocity. Therefore, MREA behavior at high piston velocity is analyzed and validated experimentally in order to investigate the effects of velocity and magnetic field on MREA performance. The analysis used to predict the MREA force as a function of piston velocity squared and applied field is presented. A conical fairing is mounted to the piston head of the MREA in order reduce predicted inlet flow loss by 9% at nominal velocity of 8 m/s, which resulted in a viscous force reduction of nominally 4%. The MREA behavior is experimentally measured using a high speed servo-hydraulic testing system for speeds up to 8 m/s. The measured MREA force is used to validate the analysis, which captures the transient force quite accurately, although the peak force is under-predicted at the peak speed of 8 m/s.

Role of the site of synaptic competition and the balance of learning forces for Hebbian encoding of probabilistic Markov sequences

PubMed Central

Bouchard, Kristofer E.; Ganguli, Surya; Brainard, Michael S.

2015-01-01

The majority of distinct sensory and motor events occur as temporally ordered sequences with rich probabilistic structure. Sequences can be characterized by the probability of transitioning from the current state to upcoming states (forward probability), as well as the probability of having transitioned to the current state from previous states (backward probability). Despite the prevalence of probabilistic sequencing of both sensory and motor events, the Hebbian mechanisms that mold synapses to reflect the statistics of experienced probabilistic sequences are not well understood. Here, we show through analytic calculations and numerical simulations that Hebbian plasticity (correlation, covariance, and STDP) with pre-synaptic competition can develop synaptic weights equal to the conditional forward transition probabilities present in the input sequence. In contrast, post-synaptic competition can develop synaptic weights proportional to the conditional backward probabilities of the same input sequence. We demonstrate that to stably reflect the conditional probability of a neuron's inputs and outputs, local Hebbian plasticity requires balance between competitive learning forces that promote synaptic differentiation and homogenizing learning forces that promote synaptic stabilization. The balance between these forces dictates a prior over the distribution of learned synaptic weights, strongly influencing both the rate at which structure emerges and the entropy of the final distribution of synaptic weights. Together, these results demonstrate a simple correspondence between the biophysical organization of neurons, the site of synaptic competition, and the temporal flow of information encoded in synaptic weights by Hebbian plasticity while highlighting the utility of balancing learning forces to accurately encode probability distributions, and prior expectations over such probability distributions. PMID:26257637

Improving the Response of a Load Cell by Using Optimal Filtering

PubMed Central

Hernandez, Wilmar

2006-01-01

Load cells are transducers used to measure force or weight. Despite the fact that there is a wide variety of load cells, most of these transducers that are used in the weighing industry are based on strain gauges. In this paper, an s-beam load cell based on strain gauges was suitably assembled to the mechanical structure of several seats of a bus under performance tests and used to measure the resistance of their mechanical structure to tension forces applied horizontally to the seats being tested. The load cell was buried in a broad-band noise background where the unwanted information and the relevant signal sometimes share a very similar frequency spectrum and its performance was improved by using a recursive least-squares (RLS) lattice algorithm. The experimental results are satisfactory and a significant improvement in the signal-to-noise ratio at the system output of 27 dB was achieved, which is a good performance factor for judging the quality of the system.

Delivery of cardiopulmonary resuscitation in the microgravity environment

NASA Technical Reports Server (NTRS)

Barratt, M. R.; Billica, R. D.

1992-01-01

The microgravity environment presents several challenges for delivering effective cardiopulmonary resuscitation (CPR). Chest compressions must be driven by muscular force rather than by the weight of the rescuer's upper torso. Airway stabilization is influenced by the neutral body posture. Rescuers will consist of crew members of varying sizes and degrees of physical deconditioning from space flight. Several methods of CPR designed to accommodate these factors were tested in the one G environment, in parabolic flight, and on a recent shuttle flight. Methods: Utilizing study participants of varying sizes, different techniques of CPR delivery were evaluated using a recording CPR manikin to assess adequacy of compressive force and frequency. Under conditions of parabolic flight, methods tested included conventional positioning of rescuer and victim, free floating 'Heimlich type' compressions, straddling the patient with active and passive restraints, and utilizing a mechanical cardiac compression assist device (CCAD). Multiple restrain systems and ventilation methods were also assessed. Results: Delivery of effective CPR was possible in all configurations tested. Reliance on muscular force alone was quickly fatiguing to the rescuer. Effectiveness of CPR was dependent on technique, adequate restraint of the rescuer and patient, and rescuer size and preference. Free floating CPR was adequate but rapidly fatiguing. The CCAD was able to provide adequate compressive force but positioning was problematic. Conclusions: Delivery of effective CPR in microgravity will be dependent on adequate resuer and patient restraint, technique, and rescuer size and preference. Free floating CPR may be employed as a stop gap method until patient restraint is available. Development of an adequate CCAD would be desirable to compensate for the effects of deconditioning.

Fabrication and investigation on field-dependent properties of natural rubber based magneto-rheological elastomer isolator

NASA Astrophysics Data System (ADS)

Ain Abd Wahab, Nurul; Amri Mazlan, Saiful; Ubaidillah; Kamaruddin, Shamsul; Intan Nik Ismail, Nik; Choi, Seung-Bok; Haziq Rostam Sharif, Amirul

2016-10-01

This study presents a laminated magnetorheological elastomer (MRE) isolator which applies to vibration control in practice. The proposed isolator is fabricated with multilayer MRE sheets associated with the natural rubber (NR) as a matrix, and steel plates. The fabricated MRE isolator is then magnetically analysed to achieve high magnetic field intensity which can produce high damping force required for effective vibration control. Subsequently, the NR-based MRE specimen is tested to identify the field-dependent rheological properties such as storage modulus with 60 weight percentage of carbonyl iron particles. It is shown from this test that the MR effect of MRE specimen is quantified to reach up to 120% at 0.8 T. Following the design stage, the electromagnetic simulation using the finite element method magnetic (FEMM) software is carried out for analysing the magnetic flux distribution in the laminated MRE isolator. The laminated MRE isolator is then examined to a series of compression for static and dynamic test under various applied currents using the dynamic fatigue machine and biaxial dynamic testing machine. It is shown that the static compression force is increased by 14.5% under strong magnetic field compared to its off-state. Meanwhile, the dynamic compression test results show that the force increase of the laminated MRE isolator is up to 16% and 7% for low and high frequency respectively. From the results presented in this work, it is demonstrated that the full-scale concept of the MRE isolator can be one of the potential candidates for vibration control applications by tunability of the dynamic stiffness.

Mechanical evidence that flamingos can support their body on one leg with little active muscular force.

PubMed

Chang, Young-Hui; Ting, Lena H

2017-05-01

Flamingos (Phoenicopteridae) often stand and sleep on one leg for long periods, but it is unknown how much active muscle contractile force they use for the mechanical demands of standing on one leg: body weight support and maintaining balance. First, we demonstrated that flamingo cadavers could passively support body weight on one leg without any muscle activity while adopting a stable, unchanging, joint posture resembling that seen in live flamingos. By contrast, the cadaveric flamingo could not be stably held in a two-legged pose, suggesting a greater necessity for active muscle force to stabilize two-legged versus one-legged postures. Our results suggest that flamingos engage a passively engaged gravitational stay apparatus (proximally located) for weight support during one-legged standing. Second, we discovered that live flamingos standing on one leg have markedly reduced body sway during quiescent versus alert behaviours, with the point of force application directly under the distal joint, reducing the need for muscular joint torque. Taken together, our results highlight the possibility that flamingos stand for long durations on one leg without exacting high muscular forces and, thus, with little energetic expenditure. © 2017 The Author(s).

Calculation of muscle loading and joint contact forces during the rock step in Irish dance.

PubMed

Shippen, James M; May, Barbara

2010-01-01

A biomechanical model for the analysis of dancers and their movements is described. The model consisted of 31 segments, 35 joints, and 539 muscles, and was animated using movement data obtained from a three-dimensional optical tracking system that recorded the motion of dancers. The model was used to calculate forces within the muscles and contact forces at the joints of the dancers in this study. Ground reaction forces were measured using force plates mounted in a sprung floor. The analysis procedure is generic and can be applied to any dance form. As an exemplar of the application process an Irish dance step, the rock, was analyzed. The maximum ground reaction force found was 4.5 times the dancer's body weight. The muscles connected to the Achilles tendon experienced a maximum force comparable to their maximal isometric strength. The contact force at the ankle joint was 14 times body weight, of which the majority of the force was due to muscle contraction. It is suggested that as the rock step produces high forces, and therefore the potential to cause injury, its use should be carefully monitored.

Research Technology

NASA Image and Video Library

2002-03-11

Engineers at the Marshall Space Flight Center (MSFC) have begun a series of engine tests on a new breed of space propulsion: a Reaction Control Engine developed for the Space Launch Initiative (SLI). The engine, developed by TRW Space and Electronics of Redondo Beach, California, is an auxiliary propulsion engine designed to maneuver vehicles in orbit. It is used for docking, reentry, attitude control, and fine-pointing while the vehicle is in orbit. The engine uses nontoxic chemicals as propellants, a feature that creates a safer environment for ground operators, lowers cost, and increases efficiency with less maintenance and quicker turnaround time between missions. Testing includes 30 hot-firings. This photograph shows the first engine test performed at MSFC that includes SLI technology. Another unique feature of the Reaction Control Engine is that it operates at dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The low-level thrust of 25 pounds of force allows the vehicle to fine-point maneuver and dock while the high-level thrust of 1,000 pounds of force is used for reentry, orbit transfer, and coarse positioning. SLI is a NASA-wide research and development program, managed by the MSFC, designed to improve safety, reliability, and cost effectiveness of space travel for second generation reusable launch vehicles.

Reaction Control Engine for Space Launch Initiative

NASA Technical Reports Server (NTRS)

2002-01-01

Engineers at the Marshall Space Flight Center (MSFC) have begun a series of engine tests on a new breed of space propulsion: a Reaction Control Engine developed for the Space Launch Initiative (SLI). The engine, developed by TRW Space and Electronics of Redondo Beach, California, is an auxiliary propulsion engine designed to maneuver vehicles in orbit. It is used for docking, reentry, attitude control, and fine-pointing while the vehicle is in orbit. The engine uses nontoxic chemicals as propellants, a feature that creates a safer environment for ground operators, lowers cost, and increases efficiency with less maintenance and quicker turnaround time between missions. Testing includes 30 hot-firings. This photograph shows the first engine test performed at MSFC that includes SLI technology. Another unique feature of the Reaction Control Engine is that it operates at dual thrust modes, combining two engine functions into one engine. The engine operates at both 25 and 1,000 pounds of force, reducing overall propulsion weight and allowing vehicles to easily maneuver in space. The low-level thrust of 25 pounds of force allows the vehicle to fine-point maneuver and dock while the high-level thrust of 1,000 pounds of force is used for reentry, orbit transfer, and coarse positioning. SLI is a NASA-wide research and development program, managed by the MSFC, designed to improve safety, reliability, and cost effectiveness of space travel for second generation reusable launch vehicles.

Deficits of anticipatory grip force control after damage to peripheral and central sensorimotor systems.

PubMed

Hermsdörfer, Joachim; Hagl, Elke; Nowak, Dennis A

2004-11-01

Healthy subjects adjust their grip force economically to the weight of a hand-held object. In addition, inertial loads, which arise from arm movements with the grasped object, are anticipated by parallel grip force modulations. Internal forward models have been proposed to predict the consequences of voluntary movements. Anesthesia of the fingers impairs grip force economy but the feedforward character of the grip force/load coupling is preserved. To further analyze the role of sensory input for internal forward models and to characterize the consequences of central nervous system damage for anticipatory grip force control, we measured grip force behavior in neurological patients. We tested a group of stroke patients with varying degrees of impaired fine motor control and sensory loss, a single patient with complete and permanent differentation from all tactile and proprioceptive input, and a group of patients with amyotrophic lateral sclerosis (ALS) that exclusively impairs the motor system without affecting sensory modalities. Increased grip forces were a common finding in all patients. Sensory deficits were a strong but not the only predictor of impaired grip force economy. The feedforward mode of grip force control was typically preserved in the stroke patients despite their central sensory deficits, but was severely disturbed in the patient with peripheral sensory deafferentation and in a minority of stroke patients. Moderate deficits of feedforward control were also obvious in ALS patients. Thus, the function of the internal forward model and the precision of grip force production may depend on a complex anatomical and functional network of sensory and motor structures and their interaction in time and space.

Pyro shock simulation: Experience with the MIPS simulator

NASA Technical Reports Server (NTRS)

Dwyer, Thomas J.; Moul, David S.

1988-01-01

The Mechanical Impulse Pyro Shock (MIPS) Simulator at GE Astro Space Division is one version of a design that is in limited use throughout the aerospace industry, and is typically used for component shock testing at levels up to 10,000 response g's. Modifications to the force imput, table and component boundary conditions have allowed a range of test conditions to be achieved. Twelve different designs of components with weights up to 23 Kg are in the process or have completed qualification testing in the Dynamic Simulation Lab at GE in Valley Forge, Pa. A summary of the experience gained through the use of this simulator is presented as well as examples of shock experiments that can be readily simulated at the GE Astro MIPS facility.

Rotor blade assembly having internal loading features

DOE Office of Scientific and Technical Information (OSTI.GOV)

Soloway, Daniel David

Rotor blade assemblies and wind turbines are provided. A rotor blade assembly includes a rotor blade having exterior surfaces defining a pressure side, a suction side, a leading edge and a trailing edge each extending between a tip and a root, the rotor blade defining a span and a chord, the exterior surfaces defining an interior of the rotor blade. The rotor blade assembly further includes a loading assembly, the loading assembly including a weight disposed within the interior and movable generally along the span of the rotor blade, the weight connected to a rotor blade component such that movementmore » of the weight towards the tip causes application of a force to the rotor blade component by the weight. Centrifugal force due to rotation of the rotor blade biases the weight towards the tip.« less

In-shoe foot force sensor to assess hoof balance determined by radiographic method in ponies trotting on a treadmill.

PubMed

Caudron, I; Grulke, S; Farnir, F; Vanschepdael, P; Serteyn, D

1998-10-01

Adaptation of an in-foot shoe force sensor and the gait analysis system 'Fscan' makes it possible to monitor the distribution of the vertical forces under the equine foot in motion. The aim of this study is to investigate the effects of two different trimmings on forces under the foot during the trot. The first one increased the height of the lateral hoof wall and the second one restored the mediolateral balance of the foot. These two trimmings were examined by using a radiographical method that quantifies the interphalangeal articular asymmetries due to asymmetrical bearing. The location of the centre of force of the weight-bearing foot and the distribution of the forces applied to the lateral and medial solar surfaces during a stride were analyzed. After optimal trimming, the centre of force of the weight-bearing foot tended to approach the centre of the palmar figure, perpendicular to the distal interphalangeal joint centre. The sum of the forces recorded under the lateral and medial parts respectively of the foot during one stride tended to balance out after corrective trimming.

Gender differences in tibio-femoral kinematics and quadriceps muscle force during weight-bearing knee flexion in vitro.

PubMed

Wünschel, Markus; Wülker, Nikolaus; Müller, Otto

2013-11-01

Females have a higher risk in terms of anterior cruciate ligament injuries during sports than males. Reasons for this fact may be different anatomy and muscle recruitment patterns leading to less protection for the cruciate- and collateral-ligaments. This in vitro study aims to evaluate gender differences in knee joint kinematics and muscle force during weight-bearing knee flexions. Thirty-four human knee specimens (17 females/17 males) were mounted on a dynamic knee simulator. Weight-bearing single-leg knee flexions were performed with different amounts of simulated body weight (BW). Gender-specific kinematics was measured with an ultrasonic motion capture system and different loading conditions were examined. Knee joint kinematics did not show significant differences regarding anteroposterior and medial-lateral movement as well as tibial varus-valgus and internal-external rotation. This applied to all simulated amounts of BW. Simulating 100 N BW in contrast to AF50 led to a significant higher quadriceps overall force in female knees from 45° to 85° of flexion in contrast to BW 50 N. In these female specimens, the quadriceps overall force was about 20 % higher than in male knees being constant in higher flexion angles. It is indicated by our results that in a squatting movement females compared with males produce higher muscle forces, suggesting an increased demand for muscular stabilization, whereas tibio-femoral kinematics was similar for both genders.

Can Science Education Research Give an Answer to Questions Posed by History of Science and Technology? The Case of Steam Engine's Measurement

ERIC Educational Resources Information Center

Kanderakis, Nikos E.

2009-01-01

According to the principle of virtual velocities, if on a simple machine in equilibrium we suppose a slight virtual movement, then the ratio of weights or forces equals the inverse ratio of velocities or displacements. The product of the weight raised or force applied multiplied by the height or displacement plays a central role there. British…

Comparison of Body Composition Metrics for United States Air Force Airmen.

PubMed

Griffith, J R; White, Edward D; Fass, R David; Lucas, Brandon M

2018-03-01

The United States Air Force currently uses AFI 36-2905 for cardiovascular fitness standards and evaluation. Regarding its fitness test, the Air Force considers waist circumference (WC) twice as important as push-ups or sit-ups. Because of this weighting, one assumes that the Air Force considers WC relatively correlated with overall fitness or at least cardiovascular fitness. To our knowledge, the Air Force has not considered on a large scale how body mass index (BMI), height-to-weight ratio (H-W), or waist-to-height ratio (WHtR) compares with WC with respect to its fitness test. Using a 5.38 million record database from the Air Force Fitness Management System, we evaluated how WC, BMI, WHtR, and H-W correlate with fitness as assessed by the 1.5-mile run in addition to total fitness, which incorporates the 1.5-mile run time, number of push-ups and sit-ups. As this previously collected data were anonymous to us, this study fell under the definition of exempt status and approved by the institutional review board overseeing Joint Base San Antonio. For each waist metric, we performed a simple ordinary least squares regression to ascertain the correlation between that particular metric and either run time or total fitness; when incorporating more than one explanatory variable or covariate (to control for age and/or sex), we performed multiple ordinary least squares regressions. Due to the large database size and to mitigate against a type I error, we used an alpha of 0.001 for all statistical hypothesis tests. Approximately 18% of the 5.38 million records belonged to women. With respect to sex differences, males appeared noticeably faster and performed more push-ups on average than females. The number of sit-ups completed was more comparable, with males having a slight advantage. Males also appeared to have larger WC, BMI, H-W, and WHtR measurements. We compared the ordinary least squares results between WC, H-W, WHtR, and BMI and ranked them by R2. Models varied in R2 from 1% to 46% depending on the covariates in the model, with sex having a greater effect than age. Whether individually or adjusting for age and sex, WHtR performed better than the other body composition variables with an average rank score of 1.1 and a median improvement of approximately 4% to the current Air Force metric of WC. From our findings, we present a 20-point WHtR scoring system for the Air Force to use in lieu of its traditional usage of WC. We used this assessment chart to score all Airmen in our database and compared the results to their current scores on the abdominal circumference portion of the test with respect to predicting run time, after accounting for sex, age, and number of push-ups and sit-ups. The R2 value improved from 40.3 to 43.6, a relative improvement of approximately 8%, a fairly significant effect given the database consisted of over 5 million records. Future studies should investigate the longitudinal effect of varying waist metrics over time on run time or total fitness performance. Published by Oxford University Press on behalf of the Association of Military Surgeons of the United States 2018. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Research of the BWS system for lower extremity rehabilitation robot.

PubMed

Zhang, Xiao; Li, Weida; Li, Juan; Cai, Xiaowei

2017-07-01

Body weight support (BWS) system is increasingly used in conjunction with treadmills to assist the patients with neurological impairments. Owing to lower limbs of the patients unable to bear the whole weight during the rehabilitation training, some weight can be removed to help the patients recover the basic walking ability gradually. Therefore, considering the man-machine relationship and the effects of the rehabilitation, a wire-driven BWS system is designed. The main unit of the system is an active closed-loop controlled drive to generate the exact desired force. The force acted on the body is through the adjustment of the length of the rope which is connected to the harness worn by the patient. The structure designed in the research is easy to operate to realize the goal of the rehabilitation. To verify the effectiveness and practicability of the BWS system, some experiments have been curried out. From the results, not only the constant unloading force can be realized, but also the response time is limited in a small range which can bring a positive effect on correcting gait, improving balance and reducing muscle spasms. Also, compared to the traditional body weight support system, such as static system or passive elastic system, it has the advantages of the fast response, small errors and constant unloading force.

The Use of Session RPE to Monitor the Intensity of Weight Training in Older Women: Acute Responses to Eccentric, Concentric, and Dynamic Exercises

PubMed Central

Ferreira, Sandro S.; Krinski, Kleverton; Alves, Ragami C.; Benites, Mariana L.; Redkva, Paulo E.; Elsangedy, Hassan M.; Buzzachera, Cosme F.; Souza-Junior, Tácito P.; da Silva, Sergio G.

2014-01-01

The rating of perceived exertion (RPE) is ability to detect and interpret organic sensations while performing exercises. This method has been used to measure the level of effort that is felt during weight-training at a given intensity. The purpose of this investigation was to compare session RPE values with those of traditional RPE measurements for different weight-training muscle actions, performed together or separately. Fourteen women with no former weight-training experience were recruited for the investigation. All participants completed five sessions of exercise: familiarization, maximum force, concentric-only (CONC-only), eccentric-only (ECC-only), and dynamic (DYN = CONC + ECC). The traditional RPE method was measured after each series of exercises, and the session RPE was measured 30 min after the end of the training session. The statistical analyses used were the paired t-test, one-way analysis of variance, and repeated measures analysis of variance. Significant differences between traditional RPE and session RPE for DYN, CONC, and ECC exercises were not found. This investigation demonstrated that session RPE is similar to traditional RPE in terms of weight-training involving concentric, eccentric, or dynamic muscle exercises, and that it can be used to prescribe and monitor weight-training sessions in older subjects. PMID:24834354

Inferring Admixture Histories of Human Populations Using Linkage Disequilibrium

PubMed Central

Loh, Po-Ru; Lipson, Mark; Patterson, Nick; Moorjani, Priya; Pickrell, Joseph K.; Reich, David; Berger, Bonnie

2013-01-01

Long-range migrations and the resulting admixtures between populations have been important forces shaping human genetic diversity. Most existing methods for detecting and reconstructing historical admixture events are based on allele frequency divergences or patterns of ancestry segments in chromosomes of admixed individuals. An emerging new approach harnesses the exponential decay of admixture-induced linkage disequilibrium (LD) as a function of genetic distance. Here, we comprehensively develop LD-based inference into a versatile tool for investigating admixture. We present a new weighted LD statistic that can be used to infer mixture proportions as well as dates with fewer constraints on reference populations than previous methods. We define an LD-based three-population test for admixture and identify scenarios in which it can detect admixture events that previous formal tests cannot. We further show that we can uncover phylogenetic relationships among populations by comparing weighted LD curves obtained using a suite of references. Finally, we describe several improvements to the computation and fitting of weighted LD curves that greatly increase the robustness and speed of the calculations. We implement all of these advances in a software package, ALDER, which we validate in simulations and apply to test for admixture among all populations from the Human Genome Diversity Project (HGDP), highlighting insights into the admixture history of Central African Pygmies, Sardinians, and Japanese. PMID:23410830

Structural Benchmark Tests of Composite Combustion Chamber Support Completed

NASA Technical Reports Server (NTRS)

Krause, David L.; Thesken, John C.; Shin, E. Eugene; Sutter, James K.

2005-01-01

A series of mechanical load tests was completed on several novel design concepts for extremely lightweight combustion chamber support structures at the NASA Glenn Research Center (http://www.nasa.gov/glenn/). The tests included compliance evaluation, preliminary proof loadings, high-strain cyclic testing, and finally residual strength testing of each design (see the photograph on the left). Loads were applied with single rollers (see the photograph on the right) or pressure plates (not shown) located midspan on each side to minimize the influence of contact stresses on corner deformation measurements. Where rollers alone were used, a more severe structural loading was produced than the corresponding equal-force pressure loading: the maximum transverse shear force existed over the entire length of each side, and the corner bending moments were greater than for a distributed (pressure) loading. Failure modes initiating at the corner only provided a qualitative indication of the performance limitations since the stress state was not identical to internal pressure. Configurations were tested at both room and elevated temperatures. Experimental results were used to evaluate analytical prediction tools and finite-element methodologies for future work, and they were essential to provide insight into the deformation at the corners. The tests also were used to assess fabrication and bonding details for the complicated structures. They will be used to further optimize the design of the support structures for weight performance and the efficacy of corner reinforcement.

Attenuation of cryocooler induced vibration using multimodal tuned dynamic absorber

NASA Astrophysics Data System (ADS)

Veprik, A.; Babitsky, V.; Tuito, A.

2017-12-01

Modern infrared imagers often rely on low Size, Weight and Power split Stirling linear cryocoolers comprised of side-by-side packed compressor and expander units fixedly mounted upon a common frame and interconnected by the configurable transfer line. Imbalanced reciprocation of moving assemblies generates vibration export in the form of tonal force couple producing angular and translational dynamic responses. Resulting line of sight jitter and dynamic defocusing may affect the image quality. The authors explore the concept of multimodal tuned dynamic absorber, the translational and tilting modal frequencies of which are essentially matched to the driving frequency. Dynamic analysis and full-scale testing show that the dynamic reactions (forces and moments) produced by such a device may effectively attenuate both translational and angular components of cryocooler-induced vibration.

Reproducibility and validity of the Nintendo Wii Balance Board for measuring shoulder sensorimotor control in prone lying.

PubMed

Eshoj, H; Juul-Kristensen, Birgit; Jørgensen, Rene Gam Bender; Søgaard, Karen

2017-02-01

For the lower limbs, the Nintendo Wii Balance Board (NWBB) has been widely used to measure postural control. However, this has not been performed for upper limb measurements. Further, the NWBB has shown to produce more background noise with decreasing loads, which may be of concern when used for upper limb testing. The aim was to investigate reproducibility and validity of the NWBB. A test-retest design was performed with 68 subjects completing three different prone lying, upper limb weight-bearing balance tasks on a NWBB: two-arms, eyes closed (1) one-arm, non-dominant/non-injured (2) and one-arm, dominant/injured (3). Each task was repeated three times over the course of two test sessions with a 30-min break in between. Further, the level of background noise from a NWBB was compared with a force platform through systematic loading of both boards with increasing deadweights ranging from 5 to 90kg. Test-retest reproducibility was high with ICCs ranging from 0.95 to 0.97 (95% CI 0.92 to 0.98). However, systematic bias and tendencies for funnel effects in the Bland Altman plots for both one-armed tests were present. The concurrent validity of the NWBB was low (CCC 0.17 (95% CI 0.12-0.22)) due to large differences between the NWBB and force platform in noise sensitivity at low deadweights (especially below 50kg). The NWBB prone lying, shoulder sensorimotor control test was highly reproducible. Though, concurrent validity of the NWBB was poor compared to a force platform. Further investigation of the impact of the background noise, especially at low loads, is needed. Copyright © 2016 Elsevier B.V. All rights reserved.

Shoulder muscle forces during driving: Sudden steering can load the rotator cuff beyond its repair limit

PubMed Central

Pandis, Petros; Prinold, Joe A.I.; Bull, Anthony M.J.

2015-01-01

Background Driving is one of the most common everyday tasks and the rotator cuff muscles are the primary shoulder stabilisers. Muscle forces during driving are not currently known, yet knowledge of these would influence important clinical advice such as return to activities after surgery. The aim of this study is to quantify shoulder and rotator cuff muscle forces during driving in different postures. Methods A musculoskeletal modelling approach is taken, using a modified driving simulator in combination with an upper limb musculoskeletal model (UK National Shoulder Model). Motion data and external force vectors were model inputs and upper limb muscle and joint forces were the outputs. Findings Comparisons of the predicted glenohumeral joint forces were compared to in vivo literature values, with good agreement demonstrated (61 SD 8% body weight mean peak compared to 60 SD 1% body weight mean peak). High muscle activation was predicted in the rotator cuff muscles; particularly supraspinatus (mean 55% of the maximum and up to 164 SD 27 N). This level of loading is up to 72% of mean failure strength for supraspinatus repairs, and could therefore be dangerous for some cases. Statistically significant and large differences are shown to exist in the joint and muscle forces for different driving positions as well as steering with one or both hands (up to 46% body weight glenohumeral joint force). Interpretation These conclusions should be a key consideration in rehabilitating the shoulder after surgery, preventing specific upper limb injuries and predicting return to driving recommendations. PMID:26139549

The Effects of Walking Speed on Tibiofemoral Loading Estimated Via Musculoskeletal Modeling

PubMed Central

Lerner, Zachary F.; Haight, Derek J.; DeMers, Matthew S.; Board, Wayne J.; Browning, Raymond C.

2015-01-01

Net muscle moments (NMMs) have been used as proxy measures of joint loading, but musculoskeletal models can estimate contact forces within joints. The purpose of this study was to use a musculoskeletal model to estimate tibiofemoral forces and to examine the relationship between NMMs and tibiofemoral forces across walking speeds. We collected kinematic, kinetic, and electromyographic data as ten adult participants walked on a dual-belt force-measuring treadmill at 0.75, 1.25, and 1.50 m/s. We scaled a musculoskeletal model to each participant and used OpenSim to calculate the NMMs and muscle forces through inverse dynamics and weighted static optimization, respectively. We determined tibiofemoral forces from the vector sum of intersegmental and muscle forces crossing the knee. Estimated tibiofemoral forces increased with walking speed. Peak early-stance compressive tibiofemoral forces increased 52% as walking speed increased from 0.75 to 1.50 m/s, whereas peak knee extension NMMs increased by 168%. During late stance, peak compressive tibiofemoral forces increased by 18% as speed increased. Although compressive loads at the knee did not increase in direct proportion to NMMs, faster walking resulted in greater compressive forces during weight acceptance and increased compressive and anterior/posterior tibiofemoral loading rates in addition to a greater abduction NMM. PMID:23878264

Creating "Intelligent" Climate Model Ensemble Averages Using a Process-Based Framework

NASA Astrophysics Data System (ADS)

Baker, N. C.; Taylor, P. C.

2014-12-01

The CMIP5 archive contains future climate projections from over 50 models provided by dozens of modeling centers from around the world. Individual model projections, however, are subject to biases created by structural model uncertainties. As a result, ensemble averaging of multiple models is often used to add value to model projections: consensus projections have been shown to consistently outperform individual models. Previous reports for the IPCC establish climate change projections based on an equal-weighted average of all model projections. However, certain models reproduce climate processes better than other models. Should models be weighted based on performance? Unequal ensemble averages have previously been constructed using a variety of mean state metrics. What metrics are most relevant for constraining future climate projections? This project develops a framework for systematically testing metrics in models to identify optimal metrics for unequal weighting multi-model ensembles. A unique aspect of this project is the construction and testing of climate process-based model evaluation metrics. A climate process-based metric is defined as a metric based on the relationship between two physically related climate variables—e.g., outgoing longwave radiation and surface temperature. Metrics are constructed using high-quality Earth radiation budget data from NASA's Clouds and Earth's Radiant Energy System (CERES) instrument and surface temperature data sets. It is found that regional values of tested quantities can vary significantly when comparing weighted and unweighted model ensembles. For example, one tested metric weights the ensemble by how well models reproduce the time-series probability distribution of the cloud forcing component of reflected shortwave radiation. The weighted ensemble for this metric indicates lower simulated precipitation (up to .7 mm/day) in tropical regions than the unweighted ensemble: since CMIP5 models have been shown to overproduce precipitation, this result could indicate that the metric is effective in identifying models which simulate more realistic precipitation. Ultimately, the goal of the framework is to identify performance metrics for advising better methods for ensemble averaging models and create better climate predictions.

Development of a thermal-hydraulics experimental system for high Tc superconductors cooled by liquid hydrogen

NASA Astrophysics Data System (ADS)

Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Hata, K.; Kobayashi, H.; Naruo, Y.; Inatani, Y.; Kato, T.; Futakawa, M.; Kinoshita, K.

2010-06-01

A thermal-hydraulics experimental system of liquid hydrogen was developed in order to investigate the forced flow heat transfer characteristics in the various cooling channels for wide ranges of subcoolings, flow velocities, and pressures up to supercritical. A main tank is connected to a sub tank through a hydrogen transfer line with a control valve. A channel heater is located at one end of the transfer line in the main tank. Forced flow through the channel is produced by adjusting the pressure difference between the tanks and the valve opening. The mass flow rate is measured from the weight change of the main tank. For the explosion protection, electrical equipments are covered with a nitrogen gas blanket layer and a remote control system was established. The first cryogenic performance tests confirmed that the experimental system had satisfied with the required performances. The forced convection heat transfer characteristics was successfully measured at the pressure of 0.7 MPa for various flow velocities.

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1991-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches; the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(sup eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(sup eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

Modeling of crack bridging in a unidirectional metal matrix composite

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1992-01-01

The effective fatigue crack driving force and crack opening profiles were determined analytically for fatigue tested unidirectional composite specimens exhibiting fiber bridging. The crack closure pressure due to bridging was modeled using two approaches: the fiber pressure model and the shear lag model. For both closure models, the Bueckner weight function method and the finite element method were used to calculate crack opening displacements and the crack driving force. The predicted near crack tip opening profile agreed well with the experimentally measured profiles for single edge notch SCS-6/Ti-15-3 metal matrix composite specimens. The numerically determined effective crack driving force, Delta K(eff), was calculated using both models to correlate the measure crack growth rate in the composite. The calculated Delta K(eff) from both models accounted for the crack bridging by showing a good agreement between the measured fatigue crack growth rates of the bridged composite and that of unreinforced, unbridged titanium matrix alloy specimens.

Evaluation of T-111 forced-convection loop tested with lithium at 1370 C. [free convection

NASA Technical Reports Server (NTRS)

Devan, J. H.; Long, E. L., Jr.

1975-01-01

A T-111 alloy (Ta-8% W-2% Hf) forced-convection loop containing molten lithium was operated 3000 hr at a maximum temperature of 1370 C. Flow velocities up to 6.3 m/sec were used, and the results of this forced-convection loop are very similar to those observed in lower velocity thermal-convection loops of T-111 containing lithium. Weight changes were determined at 93 positions around the loop. The maximum dissolution rate occurred at the maximum wall temperature of the loop and was less than 1.3 microns/year. Mass transfer of hafnium, nitrogen, and, to a lesser extent, carbon occurred from the hotter to cooler regions. Exposed surfaces in the highest temperature region were found to be depleted in hafnium to a depth of 60 microns with no detectable change in tungsten content. There was some loss in room-temperature tensile strength for specimens exposed to lithium at 1370 C, attributable to depletion of hafnium and nitrogen and to attendant grain growth.

Lightweight Low Force Rotary Percussive Coring Tool for Planetary Applications

NASA Technical Reports Server (NTRS)

Hironaka, Ross; Stanley, Scott

2010-01-01

A prototype low-force rotary-percussive rock coring tool for use in acquiring samples for geological surveys in future planetary missions was developed. The coring tool could eventually enable a lightweight robotic system to operate from a relatively small (less than 200 kg) mobile or fixed platform to acquire and cache Mars or other planetary rock samples for eventual return to Earth for analysis. To gain insight needed to design an integrated coring tool, the coring ability of commercially available coring bits was evaluated for effectiveness of varying key parameters: weight-on-bit, rotation speed, percussive rate and force. Trade studies were performed for different methods of breaking a core at its base and for retaining the core in a sleeve to facilitate sample transfer. This led to a custom coring tool design which incorporated coring, core breakage, core retention, and core extraction functions. The coring tool was tested on several types of rock and demonstrated the overall feasibility of this approach for robotic rock sample acquisition.

Instrument Package Manipulation Through the Generation and Use of an Attenuated-Fluent Gas Fold

NASA Technical Reports Server (NTRS)

Breen, Daniel P.

2012-01-01

This document discusses a technique that provides a means for suspending large, awkward loads, instrument packages, components, and machinery in a stable, controlled, and precise manner. In the baseplate of the test machine, a pattern of grooves and ports is installed that when pressurized generates an attenuated- fluent gas fold providing a low-cost, near-zero-coefficient-of-friction lubrication boundary layer that supports the object evenly, and in a predictable manner. Package movement control requires minimal force. Aids to repeatable travel and positional accuracy can be added via the addition of simple guide bars and stops to the floor or object being moved. This allows easily regulated three-axis motions. Loads of extreme weight and size can be moved and guided by a single person, or by automated means, using minimal force. Upon removal of the attenuated fluent gas fold, the object returns to a stable resting position without impact forces affecting the object.

Ground reaction force comparison of bilateral symmetry with pneumatic resistance squat device and free weights - biomed 2009.

PubMed

Paulus, David C; Schilling, Brian K

2009-01-01

The unloading of spaceflight leads to bone and muscle atrophy, and a pneumatic resistance squat exercise countermeasure has the potential to provide optimized controllable resistance in a lightweight and compact configuration. However each end of the barbell in the proposed device is connected to a separate resistance cylinder which could lead to bilaterally asymmetric loading. Therefore, the purpose of the study is to compare the unilateral ground reaction forces (GRF) of the new squat device compared to free weights. Four previously trained men (mean +/- SD; age = 20+/-2 years, body mass = 99+/-18 kg) performed three sets of three repetitions of maximal exertion squat exercises with pneumatically controlled constant resistance and free weights each with a resistance level set to half of the body weight of each subject. Unilateral GRF data for each lifting modality at the negative to positive transition of the squat exercise was measured with a force plate under each foot. The pneumatic resistance GRF (N; mean +/- SD) was 749+/-114 on the left leg and 786+/-123 on the right leg and the free weight GRF was 786+/-114 left and 861+/-111 right resulting in a 5% difference between left and right GRF with pneumatics and 9% difference with free weights. The correlation coefficient between left and right GRF was 0.92 with pneumatics and 0.80 with free weights. Because the pneumatic device elicited more bilaterally symmetric GRF than traditional free weights, the separate resistance cylinders are an acceptable design configuration.

Motor adaptation to lateral pelvis assistance force during treadmill walking in individuals post-stroke

PubMed Central

Wu, Ming; Hsu, Chao-Jung; Kim, Janis

2018-01-01

The goal of this study was to determine how individuals post-stroke response to the lateral assistance force applied to the pelvis during treadmill walking. Ten individuals post chronic (> 6 months) stroke were recruited to participate in this study. A controlled assistance force (~10% of body weight) was applied to the pelvis in the lateral direction toward the paretic side during stance of the paretic leg. Kinematics of the pelvis and legs were recorded. Applying pelvis assistance force facilitated weight shifting toward the paretic side, resulting in a more symmetrical gait pattern but also inducing an enlarged range of motion of the pelvis during early adaptation period. The neural system of individuals post stroke adapted to the pelvis assistance force and showed an aftereffect consists of reduced range of motion of the pelvis following load release during post adaptation period. PMID:28813835

Motor adaptation to lateral pelvis assistance force during treadmill walking in individuals post-stroke.

PubMed

Wu, Ming; Hsu, Chao-Jung; Kim, Janis

2017-07-01

The goal of this study was to determine how individuals post-stroke response to the lateral assistance force applied to the pelvis during treadmill walking. Ten individuals post chronic (> 6 months) stroke were recruited to participate in this study. A controlled assistance force (∼10% of body weight) was applied to the pelvis in the lateral direction toward the paretic side during stance of the paretic leg. Kinematics of the pelvis and legs were recorded. Applying pelvis assistance force facilitated weight shifting toward the paretic side, resulting in a more symmetrical gait pattern but also inducing an enlarged range of motion of the pelvis during early adaptation period. The neural system of individuals post stroke adapted to the pelvis assistance force and showed an aftereffect consists of reduced range of motion of the pelvis following load release during post adaptation period.

Do Bilateral Vertical Jumps With Reactive Jump Landings Achieve Osteogenic Thresholds With and Without Instruction in Premenopausal Women?

PubMed

Clissold, Tracey L; Winwood, Paul W; Cronin, John B; De Souza, Mary Jane

2018-04-01

Jumps have been investigated as a stimulus for bone development; however, effects of instruction, jump type, and jump-landing techniques need investigation. This study sought to identify whether ground reaction forces (GRFs) for bilateral vertical jumps (countermovement jumps and drop jumps) with reactive jump-landings (ie, jumping immediately after initial jump-landing), with instruction and with instruction withdrawn, achieve magnitudes and rates of strain previously shown to improve bone mass among premenopausal women. Twenty-one women (Mean ± SD: 43.3 ± 5.9 y; 69.4 ± 9.6 kg; 167 ± 5.5 cm; 27.5 ± 8.7% body fat) performed a testing session 'with instruction' followed by a testing session performed 1 week later with 'instruction withdrawn.' The magnitudes (4.59 to 5.49 body weight [BW]) and rates of strain (263 to 359 BW·s -1 ) for the jump-landings, performed on an AMTI force plate, exceeded previously determined thresholds (>3 BWs and >43 BW·s -1 ). Interestingly, significantly larger peak resultant forces, (↑10%; P = .002) and peak rates of force development (↑20%; P < .001) values (in relation to BW and BW·s -1 , respectively) were observed for the second jump-landing (postreactive jump). Small increases (ES = 0.22-0.42) in all landing forces were observed in the second jump-landing with 'instruction withdrawn.' These jumps represent a unique training stimulus for premenopausal women and achieve osteogenic thresholds thought prerequisite for bone growth.

A grouping method based on grid density and relationship for crowd evacuation simulation

NASA Astrophysics Data System (ADS)

Li, Yan; Liu, Hong; Liu, Guang-peng; Li, Liang; Moore, Philip; Hu, Bin

2017-05-01

Psychological factors affect the movement of people in the competitive or panic mode of evacuation, in which the density of pedestrians is relatively large and the distance among them is small. In this paper, a crowd is divided into groups according to their social relations to simulate the actual movement of crowd evacuation more realistically and increase the attractiveness of the group based on social force model. The force of group attraction is the synthesis of two forces; one is the attraction of the individuals generated by their social relations to gather, and the other is that of the group leader to the individuals within the group to ensure that the individuals follow the leader. The synthetic force determines the trajectory of individuals. The evacuation process is demonstrated using the improved social force model. In the improved social force model, the individuals with close social relations gradually present a closer and coordinated action while following the leader. In this paper, a grouping algorithm is proposed based on grid density and relationship via computer simulation to illustrate the features of the improved social force model. The definition of the parameters involved in the algorithm is given, and the effect of relational value on the grouping is tested. Reasonable numbers of grids and weights are selected. The effectiveness of the algorithm is shown through simulation experiments. A simulation platform is also established using the proposed grouping algorithm and the improved social force model for crowd evacuation simulation.

Improved Automatically Locking/Unlocking Orthotic Knee Joint

NASA Technical Reports Server (NTRS)

Weddendorf, Bruce

1995-01-01

Proposed orthotic knee joint improved version of one described in "Automatically Locking/Unlocking Orthotic Knee Joint" (MFS-28633). Locks automatically upon initial application of radial force (wearer's weight) and unlocks automatically, but only when all loads (radial force and bending) relieved. Joints lock whenever wearer applies weight to knee at any joint angle between full extension and 45 degree bend. Both devices offer increased safety and convenience relative to conventional orthotic knee joints.

Weight-bearing recommendations after operative fracture treatment-fact or fiction? Gait results with and feasibility of a dynamic, continuous pedobarography insole.

PubMed

Braun, Benedikt J; Veith, Nils T; Rollmann, Mika; Orth, Marcel; Fritz, Tobias; Herath, Steven C; Holstein, Jörg H; Pohlemann, Tim

2017-08-01

Rehabilitation after lower-extremity fractures is based on the physicians' recommendation for non-, partial-, or full weight-bearing. Clinical studies rely on this assumption, but continuous compliance or objective loading rates are unknown. The purpose of this study was to determine the compliance to weight-bearing recommendations by introducing a novel, pedobarography system continuously registering postoperative ground forces into ankle, tibial shaft and proximal femur fracture aftercare and test its feasibility for this purpose. In this prospective, observational study, a continuously measuring pedobarography insole was placed in the patients shoe during the immediate post-operative aftercare after ankle, tibial shaft and intertrochanteric femur fractures. Weight-bearing was ordered as per the institutional standard and controlled by physical therapy. The insole was retrieved after a maximum of six weeks (28 days [range 5-42 days]). Non-compliance was defined as a failure to maintain, or reach the ordered weight-bearing within 30%. Overall 30 patients were included in the study. Fourteen (47%) of the patients were compliant to the weight-bearing recommendations. Within two weeks after surgery patients deviated from the recommendation by over 50%. Sex, age and weight did not influence the performance (p > 0.05). Ankle fracture patients (partial weight-bearing) showed a significantly increased deviation from the recommendation (p = 0.01). Our study results show that, despite physical therapy training, weight-bearing compliance to recommended limits was low. Adherence to the partial weight-bearing task was further decreased over time. Uncontrolled weight-bearing recommendations should thus be viewed with caution and carefully considered as fiction. The presented insole is feasible to determine weight bearing continuously, could immediately help define real-time patient behaviour and establish realistic, individual weight-bearing recommendations.

Electrostatic demonstration of free-fall weightlessness

NASA Astrophysics Data System (ADS)

Balukovic, Jasmina; Slisko, Josip; Corona Cruz, Adrian

2015-05-01

The phenomena of free-fall weightlessness have been demonstrated to students for many years in a number of different ways. The essential basis of all these demonstrations is the fact that in free-falling, gravitationally accelerated systems, the weight force and weight-related forces (for example, friction and hydrostatic forces) disappear. In this article, an original electrostatic demonstration of weightlessness is presented. A charged balloon fixed at the opening of a plastic container cannot lift a light styrofoam sphere sitting on the bottom when the container is at rest. However, while the system is in free-fall, the sphere becomes weightless and the charged balloon is able to lift it electrostatically.

The relationship between obesity and forced vital capacity among university students.

PubMed

Sun, Xugui; Chen, Xiaohong

2015-05-01

We sought to explore the relationship between vital capacity and obesity among university students in China. A cross-sectional study was designed to collect the routine health screening data for university students in 2013. The height, weight and force vital capacity of students were measured, and BMI was calculated with height and weight, so as to estimate the relationship between force vital capacity and obesity. Based on Working Group on Obesity references in China, obesity has a higher force vital capacity in both male and female university students. No correlation was found between vital capacity and BMI. obesity may have effect on pulmonary function among university students, which is a reference for further epidemic study. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

Features calibration of the dynamic force transducers

NASA Astrophysics Data System (ADS)

Sc., M. Yu Prilepko D.; Lysenko, V. G.

2018-04-01

The article discusses calibration methods of dynamic forces measuring instruments. The relevance of work is dictated by need to valid definition of the dynamic forces transducers metrological characteristics taking into account their intended application. The aim of this work is choice justification of calibration method, which provides the definition dynamic forces transducers metrological characteristics under simulation operating conditions for determining suitability for using in accordance with its purpose. The following tasks are solved: the mathematical model and the main measurements equation of calibration dynamic forces transducers by load weight, the main budget uncertainty components of calibration are defined. The new method of dynamic forces transducers calibration with use the reference converter “force-deformation” based on the calibrated elastic element and measurement of his deformation by a laser interferometer is offered. The mathematical model and the main measurements equation of the offered method is constructed. It is shown that use of calibration method based on measurements by the laser interferometer of calibrated elastic element deformations allows to exclude or to considerably reduce the uncertainty budget components inherent to method of load weight.

Changes in stature following plyometric drop-jump and pendulum exercises.

PubMed

Fowler, N E; Lees, A; Reilly, T

1997-12-01

The aim of this study was to compare the changes in stature following the performance of plyometric exercises using drop-jumps and a pendulum swing. Eight male participants aged 21.7 +/- 1.8 years with experience of plyometric training gave their informed consent to act as participants. Participants undertook two exercise regimens and a 15-min standing test in a random order. The exercises entailed the performance of 50 drop-jumps from a height of 0.28 m or 50 pendulum rebounds. Participants were instructed to perform maximal jumps or rebounds using a 'bounce' style. Measurements of stature were performed after a 20-min period of standing (pre-exercise), 2-min after exercise (post-exercise) and after a 20-min standing recovery (recovery). Back pain and muscle soreness were assessed using an analogue-visual scale, at each of the above times and also 24 and 36 h after the test. Peak torque during isokinetic knee extension at 1.04 rads-1 was measured immediately before and after the exercise bouts, to assess the degree of muscular fatigue. Ground/wall reaction force data were recorded using a Kistler force platform mounted in the floor for drop-jumps and vertically on the rebound wall for pendulum exercises. Drop-jumps resulted in the greatest (p < 0.05) change in stature (-2.71 +/- 0.8 mm), compared to pendulum exercises (-1.77 +/- 0.7 mm) and standing (-0.39 +/- 0.2 mm). Both exercise regimens resulted in a significant (p < 0.01) decrease in stature when compared to the standing condition. Drop-jumps resulted in significantly greater peak impact forces (p < 0.05) than pendulum exercises (drop-jumps = 3.2 +/- 0.5 x body weight, pendulum = 2.6 +/- 0.5 x body weight). The two exercise conditions both invoked a small degree of muscle soreness but there were no significant differences between conditions. Both exercise regimens resulted in a non-significant decrease in peak torque indicating a similar degree of muscular fatigue. Based on the lower shrinkage resulted and lower peak forces, it can be concluded that pendulum exercises pose a lower injury potential to the lower back than drop-jumps performed from a height of 28 cm.

Deflection-Compensating Beam for use inside a Cylinder

NASA Technical Reports Server (NTRS)

Goodman, Dwight; Myers, Neill; Herren, Kenneth

2008-01-01

A design concept for a beam for a specific application permits variations and options for satisfying competing requirements to minimize certain deflections under load and to minimize the weight of the beam. In the specific application, the beam is required to serve as a motion-controlled structure for supporting a mirror for optical testing in the lower third portion of a horizontal, cylindrical vacuum chamber. The cylindrical shape of the chamber is fortuitous in that it can be (and is) utilized as an essential element of the deflection-minimizing design concept. The beam is, more precisely, a table-like structure comprising a nominally flat, horizontal portion with vertical legs at its ends. The weights of the beam and whatever components it supports are reacted by the contact forces between the lower ends of the legs and the inner cylindrical chamber wall. Whereas the bending moments arising from the weights contribute to a beam deflection that is concave with its lowest point at midlength, the bending moments generated by the contact forces acting on the legs contribute to a beam deflection that is convex with its highest point at midlength. In addition, the bending of the legs in response to the weights causes the lower ends of the legs to slide downward on the cylindrical wall. By taking the standard beam-deflection equations, combining them with the geometric relationships among the legs and the horizontal portion of the beam, and treating the sliding as a component of deflection, it is possible to write an equation for the net vertical deflection as a function of the load and of position along the beam. A summary of major conclusions drawn from the equation characterization is included.

The influence of cricket fast bowlers' front leg technique on peak ground reaction forces.

PubMed

Worthington, Peter; King, Mark; Ranson, Craig

2013-01-01

High ground reaction forces during the front foot contact phase of the bowling action are believed to be a major contributor to the high prevalence of lumbar stress fractures in fast bowlers. This study aimed to investigate the influence of front leg technique on peak ground reaction forces during the delivery stride. Three-dimensional kinematic data and ground reaction forces during the front foot contact phase were captured for 20 elite male fast bowlers. Eight kinematic parameters were determined for each performance, describing run-up speed and front leg technique, in addition to peak force and time to peak force in the vertical and horizontal directions. There were substantial variations between bowlers in both peak forces (vertical 6.7 ± 1.4 body weights; horizontal (braking) 4.5 ± 0.8 body weights) and times to peak force (vertical 0.03 ± 0.01 s; horizontal 0.03 ± 0.01 s). These differences were found to be linked to the orientation of the front leg at the instant of front foot contact. In particular, a larger plant angle and a heel strike technique were associated with lower peak forces and longer times to peak force during the front foot contact phase, which may help reduce the likelihood of lower back injuries.

A power autonomous monopedal robot

NASA Astrophysics Data System (ADS)

Krupp, Benjamin T.; Pratt, Jerry E.

2006-05-01

We present the design and initial results of a power-autonomous planar monopedal robot. The robot is a gasoline powered, two degree of freedom robot that runs in a circle, constrained by a boom. The robot uses hydraulic Series Elastic Actuators, force-controllable actuators which provide high force fidelity, moderate bandwidth, and low impedance. The actuators are mounted in the body of the robot, with cable drives transmitting power to the hip and knee joints of the leg. A two-stroke, gasoline engine drives a constant displacement pump which pressurizes an accumulator. Absolute position and spring deflection of each of the Series Elastic Actuators are measured using linear encoders. The spring deflection is translated into force output and compared to desired force in a closed loop force-control algorithm implemented in software. The output signal of each force controller drives high performance servo valves which control flow to each of the pistons of the actuators. In designing the robot, we used a simulation-based iterative design approach. Preliminary estimates of the robot's physical parameters were based on past experience and used to create a physically realistic simulation model of the robot. Next, a control algorithm was implemented in simulation to produce planar hopping. Using the joint power requirements and range of motions from simulation, we worked backward specifying pulley diameter, piston diameter and stroke, hydraulic pressure and flow, servo valve flow and bandwidth, gear pump flow, and engine power requirements. Components that meet or exceed these specifications were chosen and integrated into the robot design. Using CAD software, we calculated the physical parameters of the robot design, replaced the original estimates with the CAD estimates, and produced new joint power requirements. We iterated on this process, resulting in a design which was prototyped and tested. The Monopod currently runs at approximately 1.2 m/s with the weight of all the power generating components, but powered from an off-board pump. On a test stand, the eventual on-board power system generates enough pressure and flow to meet the requirements of these runs and we are currently integrating the power system into the real robot. When operated from an off-board system without carrying the weight of the power generating components, the robot currently runs at approximately 2.25 m/s. Ongoing work is focused on integrating the power system into the robot, improving the control algorithm, and investigating methods for improving efficiency.

Mechanics of Granular Materials (MGM)

NASA Technical Reports Server (NTRS)

Alshibli, Khalid A.; Costes, Nicholas C.; Porter, Ronald F.

1996-01-01

The constitutive behavior of uncemented granular materials such as strength, stiffness, and localization of deformations are to a large extend derived from interparticle friction transmitted between solid particles and particle groups. Interparticle forces are highly dependent on gravitational body forces. At very low effective confining pressures, the true nature of the Mohr envelope, which defines the Mohr-Coulomb failure criterion for soils, as well as the relative contribution of each of non-frictional components to soil's shear strength cannot be evaluated in terrestrial laboratories. Because of the impossibility of eliminating gravitational body forces on earth, the weight of soil grains develops interparticle compressive stresses which mask true soil constitutive behavior even in the smallest samples of models. Therefore the microgravity environment induced by near-earth orbits of spacecraft provides unique experimental opportunities for testing theories related to the mechanical behavior of terrestrial granular materials. Such materials may include cohesionless soils, industrial powders, crushed coal, etc. This paper will describe the microgravity experiment, 'Mechanics of Granular Materials (MGM)', scheduled to be flown on Space Shuttle-MIR missions. The paper will describe the experiment's hardware, instrumentation, specimen preparation procedures, testing procedures in flight, as well as a brief summary of the post-mission analysis. It is expected that the experimental results will significantly improve the understanding of the behavior of granular materials under very low effective stress levels.

Test-Anchored Vibration Response Predictions for an Acoustically Energized Curved Orthogrid Panel with Mounted Components

NASA Technical Reports Server (NTRS)

Frady, Gregory P.; Duvall, Lowery D.; Fulcher, Clay W. G.; Laverde, Bruce T.; Hunt, Ronald A.

2011-01-01

A rich body of vibroacoustic test data was recently generated at Marshall Space Flight Center for a curved orthogrid panel typical of launch vehicle skin structures. Several test article configurations were produced by adding component equipment of differing weights to the flight-like vehicle panel. The test data were used to anchor computational predictions of a variety of spatially distributed responses including acceleration, strain and component interface force. Transfer functions relating the responses to the input pressure field were generated from finite element based modal solutions and test-derived damping estimates. A diffuse acoustic field model was employed to describe the assumed correlation of phased input sound pressures across the energized panel. This application demonstrates the ability to quickly and accurately predict a variety of responses to acoustically energized skin panels with mounted components. Favorable comparisons between the measured and predicted responses were established. The validated models were used to examine vibration response sensitivities to relevant modeling parameters such as pressure patch density, mesh density, weight of the mounted component and model form. Convergence metrics include spectral densities and cumulative root-mean squared (RMS) functions for acceleration, velocity, displacement, strain and interface force. Minimum frequencies for response convergence were established as well as recommendations for modeling techniques, particularly in the early stages of a component design when accurate structural vibration requirements are needed relatively quickly. The results were compared with long-established guidelines for modeling accuracy of component-loaded panels. A theoretical basis for the Response/Pressure Transfer Function (RPTF) approach provides insight into trends observed in the response predictions and confirmed in the test data. The software modules developed for the RPTF method can be easily adapted for quick replacement of the diffuse acoustic field with other pressure field models; for example a turbulent boundary layer (TBL) model suitable for vehicle ascent. Wind tunnel tests have been proposed to anchor the predictions and provide new insight into modeling approaches for this type of environment. Finally, component vibration environments for design were developed from the measured and predicted responses and compared with those derived from traditional techniques such as Barrett scaling methods for unloaded and component-loaded panels.

Comparison of Mechanical Axis and Dynamic Range Assessed with Weight Bearing Radiographs and Navigation System in Closed Wedge High Tibial Osteotomy

PubMed Central

Bae, Dae Kyung; Lee, Jong Whan; Cho, Seong Jin; Song, Sang Jun

2017-01-01

Purpose To compare navigation and weight bearing radiographic measurements of mechanical axis (MA) before and after closed wedge high tibial osteotomy (HTO) and to evaluate post-osteotomy changes in MA assessed during application of external varus or valgus force. Materials and Methods Data from 30 consecutive patients (30 knees) who underwent computer-assisted closed-wedge HTO were prospectively analyzed. Pre- and postoperative weight bearing radiographic evaluation of MA was performed. Under navigation guidance, pre- and post-osteotomy MA values were measured in an unloaded position. Any change in the post-osteotomy MA in response to external varus or valgus force, which was named as dynamic range, was evaluated with the navigation system. The navigation and weight bearing radiographic measurements were compared. Results Although there was a positive correlation between navigation and radiographic measurements, the reliability of navigation measurements of coronal alignment was reduced after osteotomy and wedge closing. The mean post-osteotomy MA value measured with the navigation was 3.5°±0.8° valgus in an unloaded position. It was 1.3°±0.8° valgus under varus force and 5.8°±1.1° valgus under valgus force. The average dynamic range was >±2°. Conclusions Potential differences between the postoperative MAs assessed by weight bearing radiographs and the navigation system in unloaded position should be considered during computer-assisted closed wedge HTO. Care should be taken to keep the dynamic range within the permissible range of alignment goal in HTO. PMID:28854769

A randomized controlled trial of a commercially available weight loss program

USDA-ARS?s Scientific Manuscript database

The U.S. Preventive Services Task Force (USPSTF) recommends that clinicians refer obese adults for intensive, multi-component behavioral counseling, yet most obese Americans choose a self-help approach to lose weight. The current study examined weight loss between a community-based, intensive behavi...

Loading forces in shallow water running in two levels of immersion.

PubMed

Haupenthal, Alessandro; Ruschel, Caroline; Hubert, Marcel; de Brito Fontana, Heiliane; Roesler, Helio

2010-07-01

To analyse the vertical and anteroposterior components of the ground reaction force during shallow water running at 2 levels of immersion. Twenty-two healthy adults with no gait disorders, who were familiar with aquatic exercises. Subjects performed 6 trials of water running at a self-selected speed in chest and hip immersion. Force data were collected through an underwater force plate and running speed was measured with a photocell timing light system. Analysis of covariance was used for data analysis. Vertical forces corresponded to 0.80 and 0.98 times the subject's body weight at the chest and hip level, respectively. Anteroposterior forces corresponded to 0.26 and 0.31 times the subject's body weight at the chest and hip level, respectively. As the water level decreased the subjects ran faster. No significant differences were found for the force values between the immersions, probably due to variability in speed, which was self-selected. When thinking about load values in water running professionals should consider not only the immersion level, but also the speed, as it can affect the force components, mainly the anteroposterior one. Quantitative data on this subject could help professionals to conduct safer aqua-tic rehabilitation and physical conditioning protocols.

The effect of hardhats on head and neck response to vertical impacts from large construction objects.

PubMed

Suderman, Bethany L; Hoover, Ryan W; Ching, Randal P; Scher, Irving S

2014-12-01

We evaluated the effectiveness of hardhats in attenuating head acceleration and neck force in vertical impacts from large construction objects. Two weight-matched objects (lead shot bag and concrete block) weighing 9.1 kg were dropped from three heights (0.91 m, 1.83 m and 2.74 m) onto the head of a 50th percentile male Hybrid III anthropomorphic test device (ATD). Two headgear conditions were tested: no head protection and an ANSI Type-I, Class-E hardhat. A third headgear condition (snow sport helmet) was tested at 1.83 m for comparison with the hardhat. Hardhats significantly reduced the resultant linear acceleration for the concrete block impacts by 70-95% when compared to the unprotected head condition. Upper neck compression was also significantly reduced by 26-60% with the use of a hardhat when compared to the unprotected head condition for the 0.91 and 1.83 m drop heights for both lead shot and concrete block drop objects. In this study we found that hardhats can be effective in reducing both head accelerations and compressive neck forces for large construction objects in vertical impacts. Copyright © 2014 Elsevier Ltd. All rights reserved.

Energy cost and pole forces during Nordic walking under different surface conditions.

PubMed

Schiffer, Thorsten; Knicker, Axel; Dannöhl, Regine; Strüder, Heiko K

2009-03-01

The purpose of the study was to identify the effect of three different surfaces on energy consumption and the forces acting on the walking poles during ground contact in Nordic walking (NW). Thirteen female NW instructors (age = 26 +/- 4 yr, weight = 58.5 +/- 4.2 kg, height = 168.1 +/- 4.6 cm) volunteered in the study. The subjects walked a distance of 1200 m at a controlled, constant speed of 2.2 m x s(-1) on each of a concrete surface (C), an artificial athletics track (A), and a naturally grown soccer lawn (G). They used NW poles with inbuilt strain gauge force transducers to measure ground reaction forces acting along the long axes of the poles. Oxygen uptake, capillary blood lactate (La), HR, and RPE were measured before and after the tests. Impact forces, maximum forces, force rates during ground contact identified from the registered force time histories, displayed significant differences related to the surface conditions. However, force time integrals did not show surface-related differences. Relative oxygen consumption showed significant differences between NW on C and on G whereas no surface-related differences could be identified between the surface conditions for the parameters La, HR, and RPE. Our data indicate that the impulse that is generated by the poles on the subjects is identical between the varying surfaces. Because there are differences for the oxygen uptake between C and G, the main regulator for the propulsion must be the musculature of the lower extremities. The work of the upper extremities seems to be a luxury effort for Nordic walkers with a proper technique.

Measurement of the elastic modulus of spider mite silk fibers using atomic force microscopy

NASA Astrophysics Data System (ADS)

Hudson, Stephen D.; Zhurov, Vladimir; Grbić, Vojislava; Grbić, Miodrag; Hutter, Jeffrey L.

2013-04-01

Bio-nanomaterials are one of the fastest developing sectors of industry and technology. Spider silk, a highly attractive light-weight biomaterial, has high tensile strength and elasticity and is compatible with human tissues, allowing for many areas of application. In comparison to spider silk fibers with diameters of several micrometers, spider mite silk fibers have much smaller diameters of tens of nanometers, making conventional tensile testing methods impractical. To determine the mechanical properties of adult and larval Tetranychus urticae silk fibers, we have performed three-point bending tests with an atomic force microscope. We found that because of the small diameters of these fibers, axial tension—due to both the applied force and a pre-existing strain—has a significant effect on the fiber response, even in the small-deformation limit. As a result, the typical Euler-Bernoulli-Timoshenko theory cannot be applied. We therefore follow the approach of Heidelberg et al. to develop a mechanical model of the fiber response that accounts for bending, an initial tension in the fibers, and a tension due to elongation during testing. This model provides self-consistent results, allowing us to determine that adult and larval fibers have Young's moduli of 24±3 GPa and 15±3 GPa, respectively. Both adult and larval fibers have an estimated ultimate strength of 200-300 MPa and a toughness of order 9 MJ/m3. We note that with increasing interest in the mechanical properties of very high aspect ratio nanomaterials, the influence of pre-existing tension must be considered in any measurements involving a bending test.

Significance of heel pad confinement for the shock absorption at heel strike.

PubMed

Jørgensen, U; Ekstrand, J

1988-12-01

Shock absorption (SA) is a simple way to reduce the body load and can be used in the prevention and treatment of injuries. The heel pad is the most important shock absorber in the shoe heel complex. The purpose of this study was to investigate whether the SA at heel strike can be increased by heel support in people and shoes with high or low SA. The impact forces at heel strike were measured on an AMTI (R) force platform. Fourteen legs were tested in seven persons (nine with normal and five with low heel pad SA) in gait analysis and in human drop tests. The tests were performed barefooted, and in a soccer and a running shoe (selected by shoe drop test), with and without the distal 2 cm of the heel counter. The heel pad confinement produced by the heel counter (the heel counter effect) increased the SA in both shoe types significantly in both impact situations. The mean increase in SA was 8.8% (range 5.8%-15.5%). The heel counter effect was in all situations significantly higher in persons with low heel pad shock absorbency (LHPSA) than in those with normal heel pads. The barefoot impact peak force per kg body weight was significantly higher (6% mean) on the side with LHPSA. The running shoe provided the significantly greatest SA compared with the soccer shoe. It is concluded that the shock absorbency at heel strike can be increased significantly by heel support, with highest effect in persons with LHPSA, both in shoes with high and low SA.(ABSTRACT TRUNCATED AT 250 WORDS)

Soleus Fiber Force and Maximal Shortening Velocity After Non-Weight Bearing with Intermittent Activity

NASA Technical Reports Server (NTRS)

Widrick, Jeffrey J.; Bangart, Jill J.; Karhanek, Miloslav; Fitts, Robert H.

1996-01-01

This study examined the effectiveness of intermittent weight bearing (IWB) as a countermeasure to non-weight-bearing (NWB)-induced alterations in soleus type 1 fiber force (in mN), tension (P(sub o); force per fiber cross-sectional area in kN/sq m), and maximal unloaded shortening velocity (V(sub o), in fiber lengths/s). Adult rats were assigned to one of the following groups: normal weight bearing (WB), 14 days of hindlimb NWB (NWB group), and 14 days of hindlimb NWB with IWB treatments (IWB group). The IWB treatment consisted of four 10-min periods of standing WB each day. Single, chemically permeabilized soleus fiber segments were mounted between a force transducer and position motor and were studied at maximal Ca(2+) activation, after which type 1 fiber myosin heavy-chain composition was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. NWB resulted in a loss in relative soleus mass (-45%), with type 1 fibers displaying reductions in diameter (-28%) and peak isometric force (-55%) and an increase in V(sub o) (+33%). In addition, NWB induced a 16% reduction in type 1 fiber P., a 41% reduction in type 1 fiber peak elastic modulus [E(sub o), defined as ((delta)force/(delta)length x (fiber length/fiber cross-sectional area] and a significant increase in the P(sub o)/E(sub o) ratio. In contrast to NWB, IWB reduced the loss of relative soleus mass (by 22%) and attenuated alterations in type 1 fiber diameter (by 36%), peak force (by 29%), and V(sub o)(by 48%) but had no significant effect on P(sub o), E(sub o) or P(sub o)/E(sub o). These results indicate that a modest restoration of WB activity during 14 days of NWB is sufficient to attenuate type 1 fiber atrophy and to partially restore type 1 peak isometric force and V(sub o) to WB levels. However, the NWB-induced reductions in P(sub o) and E(sub o) which we hypothesize to be due to a decline in the number and stiffness of cross bridges, respectively, are considerably less responsive to this countermeasure treatment.

Carbon nano fibers reinforced composites origami inspired mechanical metamaterials with passive and active properties

NASA Astrophysics Data System (ADS)

Kshad, Mohamed Ali E.; D'Hondt, Clement; Naguib, Hani E.

2017-10-01

Core panels used for compression or impact damping are designed to dissipate energy and to reduce the transferred force and energy. They are designed to have high strain and deformation with low density. The geometrical configuration of such cores plays a significant role in redistributing the applied forces to dampen the compression and impact energy. Origami structures are renowned for affording large macroscopic deformation which can be employed for force redistribution and energy damping. The material selection for the fabrication of origami structures affects the core capacity to withstand compression and impact loads. Polymers are characterized by their high compression and impact resistance; the drawback of polymers is the low stiffness and elastic moduli compared with metallic materials. This work is focused on the study of the effect of Carbon Nano Fibers (CNF) on the global mechanical properties of the origami panel cores made of polymeric blends. The base matrix materials used were Polylactic Acid (PLA) and Thermoplastic Polyurethane (TPU) blends, and the percentages of the PLA/TPU were 100/0, 20/80, 65/35, 50/50, 20/80, and 0/100 as a percentage of weight. The weight percentages of CNF added to the polymeric blends were 1%, 3%, and 5%. This paper deals with the fabrication process of the polymeric reinforced blends and the origami cores, in order to predict the best fabrication conditions. The dynamic scanning calorimetry and the dynamic mechanical analyzer were used to test the reinforced blended base material for thermomechanical and viscoelastic properties. The origami core samples were fabricated using per-molded geometrical features and then tested for compression and impact properties. The results of the study were compared with previous published results which showed that there is considerable enhancement in the mechanical properties of the origami cores compared with the pure blended polymeric origami cores. The active properties of the origami unit cell made of composite polymers containing a low percentage of CNF were also investigated in this study, in which the shape memory effect test conducted on the origami unit cell.

Relationship between the properties of raw and cooked spaghetti - new indices for pasta quality evaluation

NASA Astrophysics Data System (ADS)

Biernacka, Beata; Dziki, Dariusz; Różyło, Renata; Wójcik, Monika; Miś, Antoni; Romankiewicz, Daria; Krzysiak, Zbigniew

2018-04-01

The quality of pasta can be evaluated by measuring the characteristics which encompass the most important quality parameters, such as colour, cooking properties and texture. The aim of the study was to suggest new indices which can be used to evaluate the quality of pasta. For the tests, 15 samples of spaghetti (produced from either semolina or common wheat flour) were used. The bending test was performed for the determination of the strength properties of raw pasta, while the pasta colour parameters were evaluated via the Commission Internationale de l'Eclairage system. The pasta cooking test included the evaluation of optimum cooking time, weight increase index and cooking loss. The samples of cooked spaghetti were cut, and the parameters describing pasta texture were determined. Statistical analysis showed significant correlations (α = 0.05) between colour parameters (lightness and redness) and pasta ash content (R = -0.90 and 0.84, respectively). The mechanical properties of raw pasta correlated positively with pasta density. The strongest correlation was found between pasta density and flexural strength. The destruction force for raw spaghetti during the bending test correlated significantly and positively with the cutting force of the cooked pasta. The obtained correlations can be helpful in pasta quality evaluation.

Scramjet analysis, testing

NASA Technical Reports Server (NTRS)

Leingang, J. L.; Stull, F. D.

1992-01-01

A survey of supersonic combustion ramjet (scramjet) engine development in the US covers development of this unique engine cycle from its inception in the early 1960's through the various programs currently being pursued and, in some instances, describing the future direction of the programs. These include developmental efforts supported by the US Navy, NASA, and US Air Force. Results of inlet, combustor, and nozzle component tests, free-jet engine tests, analytical techniques developed to analyze and predict component and engine performance, and flight-weight hardware development are presented. These results show that efficient scramjet propulsion is attainable in a variety of flight configurations with a variety of fuels. Since the scramjet is the most efficient engine cycle for hypersonic flight within the atmosphere, it should be given serious consideration in future propulsion schemes.

Are grain packing and flow turbulence the keys to predicting bedload transport in steep streams? (Invited)

NASA Astrophysics Data System (ADS)

Yager, E.; Monsalve Sepulveda, A.; Smith, H. J.; Badoux, A.

2013-12-01

Bedload transport rates in steep mountain channels are often over-predicted by orders of magnitude, which has been attributed to a range of processes from grain jamming, roughness drag, changes in fluid turbulence and a limited upstream sediment supply. We hypothesize that such poor predictions occur in part because the grain-scale mechanics (turbulence, particle arrangements) of sediment transport are not well understood or incorporated into simplified reach-averaged calculations. To better quantify how turbulence impacts sediment movement, we measured detailed flow velocities and forces at the onset of motion of a single test grain with a fixed pocket geometry in laboratory flume experiments. Of all measured parameters (e.g. flow velocity, shear stress), the local fluid drag force had the highest statistical correlation with grain motion. Use of flow velocity or shear stress to estimate sediment transport may therefore result in erroneous predictions given their relatively low correlation to the onset of sediment motion. To further understand the role of grain arrangement on bedload transport, we measured in situ grain resisting forces to motion (using a force sensor) for a range of grain sizes and patch classes in the Erlenbach torrent, Switzerland (10% gradient). Such forces varied by over two orders of magnitude for a given grain weight and were statistically greater than those calculated using empirical equations for the friction angle. In addition, when normalized by the grain weight, the resisting forces declined with higher grain protrusion above the surrounding bed sediment. Therefore, resisting forces from grain packing and interlocking are substantial and depend on the amount of grain burial. The onset of motion may be considerably under-estimated when calculated solely from measured grain sizes and friction angles. These packing forces may partly explain why critical Shields stresses are higher in steep channels. Such flow and grain parameters also spatially vary in steep streams because of boulder steps and patches of different grain size distributions. To determine if this spatial variation is important for bedload transport, we incorporated probability density functions of flow turbulence and patch grain size distributions into a simple bedload transport equation. Predicted bedload fluxes were significantly improved when distributions of these parameters, rather than single reach-averaged values, were used.

The reliability of isoinertial force-velocity-power profiling and maximal strength assessment in youth.

PubMed

Meylan, César M P; Cronin, John B; Oliver, Jon L; Hughes, Michael M G; Jidovtseff, Boris; Pinder, Shane

2015-03-01

The purpose of this study was to quantify the inter-session reliability of force-velocity-power profiling and estimated maximal strength in youth. Thirty-six males (11-15 years old) performed a ballistic supine leg press test at five randomized loads (80%, 100%, 120%, 140%, and 160% body mass) on three separate occasions. Peak and mean force, power, velocity, and peak displacement were collected with a linear position transducer attached to the weight stack. Mean values at each load were used to calculate different regression lines and estimate maximal strength, force, velocity, and power. All variables were found reliable (change in the mean [CIM] = - 1 to 14%; coefficient of variation [CV] = 3-18%; intraclass correlation coefficient [ICC] = 0.74-0.99), but were likely to benefit from a familiarization, apart from the unreliable maximal force/velocity ratio (CIM = 0-3%; CV = 23-25%; ICC = 0.35-0.54) and load at maximal power (CIM = - 1 to 2%; CV = 10-13%; ICC = 0.26-0.61). Isoinertial force-velocity-power profiling and maximal strength in youth can be assessed after a familiarization session. Such profiling may provide valuable insight into neuromuscular capabilities during growth and maturation and may be used to monitor specific training adaptations.

Feasibility and acceptability of using jumping mechanography to detect early components of sarcopenia in community-dwelling older women

PubMed Central

Hannam, K.; Hartley, A.; Clark, E.M.; Sayer, A. Aihie; Tobias, J.H.; Gregson, C.L.

2017-01-01

Objective: To determine the feasibility and acceptability of using peak power and force, measured by jumping mechanography (JM), to detect early age-related features of sarcopenia in older women. Methods: Community-dwelling women aged 71-87 years were recruited into this cross-sectional study. Physical function tests comprised the short physical performance battery (SPPB), grip strength and, if SPPB score≥6, JM. JM measured peak weight-adjusted power and force from two-footed jumps and one-legged hops respectively. Questionnaires assessed acceptability. Results: 463 women were recruited; 37(8%) with SPPB<6 were ineligible for JM. Of 426 remaining, 359(84%) were able to perform ≥1 valid two-footed jump, 300(70%) completed ≥1 valid one-legged hop. No adverse events occurred. Only 14% reported discomfort. Discomfort related to JM performance, with inverse associations with both power and force (p<0.01). Peak power and force respectively explained 8% and 10% of variance in SPPB score (13% combined); only peak power explained additional variance in grip strength (17%). Conclusions: Peak power and force explained a significant, but limited, proportion of variance in SPPB and grip strength. JM represents a safe and acceptable clinical tool for evaluating lower-limb muscle power and force in older women, detecting distinct components of muscle function, and possibly sarcopenia, compared to those evaluated by more established measures. PMID:28860427

Parrotfish grazing ability: interspecific differences in relation to jaw-lever mechanics and relative weight of adductor mandibulae on an Okinawan coral reef

PubMed Central

2016-01-01

Parrotfishes (family Labridae: Scarini) are regarded to have important roles for maintaining the ecosystem balance in coral reefs due to their removal of organic matter and calcic substrates by grazing. The purpose of the present study was to clarify the interspecific differences in grazing ability of five parrotfish species (Chlorurus sordidus, C. bowersi, Scarus rivulatus, S. niger and S. forsteni) in relation to interspecific differences in jaw-lever mechanics and the relative weight of the adductor mandibulae (muscles operating jaw closing). The grazing ability was calculated by using stomach contents (CaCO3 weight/organic matter weight) defined as the grazing ability index (GAI). There were significant interspecific differences in GAI (C. sordidus = C. bowersi > S. rivulatus > S. niger = S. forsteni). Teeth of C. sordidus and C. bowersi were protrusive-shape whereas teeth of S. rivulatus, S. niger and S. forsteni were flat-shape. C. sordidus and C. bowersihave jaw-lever mechanics producing a greater biting force and have a larger weight of adductor mandibulae. S. rivulatus has jaw-lever mechanics producing a greater biting force but a smaller weight of adductor mandibulae that produce an intermediate biting force. In contrast, S. niger and S. forsteni have jaw-lever mechanics producing a lesser biting force and have a smaller weight of adductor mandibulae. Feeding rates and foray size of S. rivulatus, S. niger and S. forsteni were greater than C. sordidus and C. bowersi. The degree in bioerosion (GAI × feeding rate) was the largest for S. rivulatusand the smallest for S. forsteni. The degree in bioerosion for C. sordidus was larger than S. niger whereas relatively equal between C. bowersi and S. niger. These results suggest that interspecific difference in GAI was explained by interspecific differences in teeth shape, jaw-lever mechanics and relative weight of adductor mandibulae. The interspecific difference in the degree of bioerosion suggests the importance of various size of parrotfishes with diverse feeding modes to maintain healthy coral reef ecosystems. PMID:27635364

Parrotfish grazing ability: interspecific differences in relation to jaw-lever mechanics and relative weight of adductor mandibulae on an Okinawan coral reef.

PubMed

Nanami, Atsushi

2016-01-01

Parrotfishes (family Labridae: Scarini) are regarded to have important roles for maintaining the ecosystem balance in coral reefs due to their removal of organic matter and calcic substrates by grazing. The purpose of the present study was to clarify the interspecific differences in grazing ability of five parrotfish species (Chlorurus sordidus, C. bowersi, Scarus rivulatus, S. niger and S. forsteni) in relation to interspecific differences in jaw-lever mechanics and the relative weight of the adductor mandibulae (muscles operating jaw closing). The grazing ability was calculated by using stomach contents (CaCO3 weight/organic matter weight) defined as the grazing ability index (GAI). There were significant interspecific differences in GAI (C. sordidus = C. bowersi > S. rivulatus > S. niger = S. forsteni). Teeth of C. sordidus and C. bowersi were protrusive-shape whereas teeth of S. rivulatus, S. niger and S. forsteni were flat-shape. C. sordidus and C. bowersihave jaw-lever mechanics producing a greater biting force and have a larger weight of adductor mandibulae. S. rivulatus has jaw-lever mechanics producing a greater biting force but a smaller weight of adductor mandibulae that produce an intermediate biting force. In contrast, S. niger and S. forsteni have jaw-lever mechanics producing a lesser biting force and have a smaller weight of adductor mandibulae. Feeding rates and foray size of S. rivulatus, S. niger and S. forsteni were greater than C. sordidus and C. bowersi. The degree in bioerosion (GAI × feeding rate) was the largest for S. rivulatusand the smallest for S. forsteni. The degree in bioerosion for C. sordidus was larger than S. niger whereas relatively equal between C. bowersi and S. niger. These results suggest that interspecific difference in GAI was explained by interspecific differences in teeth shape, jaw-lever mechanics and relative weight of adductor mandibulae. The interspecific difference in the degree of bioerosion suggests the importance of various size of parrotfishes with diverse feeding modes to maintain healthy coral reef ecosystems.

Comparison Virtual Landing Gear Drop Test for Commuter Aircraft Utilize MSC ADAMS And Solidworks Motion Analysis

NASA Astrophysics Data System (ADS)

Hidayat, Dony; Istiyanto, Jos; Agus Sumarsono, Danardono

2018-04-01

Loads at main landing gear while touchdown impact is function of aircraft weight and ground reaction load factor. In regulation states ground reaction load factor at Vsink = 3.05 m/s is below 3. Contact/impact force from simulation using MSC ADAMS is 94680 N, while using Solidworks Motion Analysis is 97691 N. The difference between MSC ADAMS and Solidworks Motion Analysis is 3.08%. The ground reaction load factor in MSC ADAMS is 2.78 while in Solidworks Motion Analysis is 2.87.

Approach for Structurally Clearing an Adaptive Compliant Trailing Edge Flap for Flight

NASA Technical Reports Server (NTRS)

Miller, Eric J.; Lokos, William A.; Cruz, Josue; Crampton, Glen; Stephens, Craig A.; Kota, Sridhar; Ervin, Gregory; Flick, Pete

2015-01-01

The Adaptive Compliant Trailing Edge (ACTE) flap was flown on the NASA Gulfstream GIII test bed at the NASA Armstrong Flight Research Center. This smoothly curving flap replaced the existing Fowler flaps creating a seamless control surface. This compliant structure, developed by FlexSys Inc. in partnership with Air Force Research Laboratory, supported NASA objectives for airframe structural noise reduction, aerodynamic efficiency, and wing weight reduction through gust load alleviation. A thorough structures airworthiness approach was developed to move this project safely to flight.

Proceedings of the Tenth Biennial Guidance Test Symposium Held at Holloman Air Force Base, New Mexico, 7-9 October, 1981. Volume I,

DTIC Science & Technology

1981-10-01

SOLDER FILLET. SOLD R FILET.S CURRENT TORQUE INPUT [] SCALE FACTOR SELECT RESISTOR 5NP BETWEEN PINS 10 & 11. 6 SIGNAL OUTPUT 1.UNIT WEIGHT : 200 ± 10...The engineers at Contraves Goerz Corporation have recently applied a high range IADS as a high pass compensation element in a rate table control...frequency, since at that frequency the low pass signal phase is -900 and the high pass signal phase is +90". Contraves Goerz has solved that system

Increased medial longitudinal arch mobility, lower extremity kinematics, and ground reaction forces in high-arched runners.

PubMed

Williams, D S Blaise; Tierney, Robin N; Butler, Robert J

2014-01-01

Runners with high medial longitudinal arch structure demonstrate unique kinematics and kinetics that may lead to running injuries. The mobility of the midfoot as measured by the change in arch height is also suspected to play a role in lower extremity function during running. The effect of arch mobility in high-arched runners is an important factor in prescribing footwear, training, and rehabilitating the running athlete after injury. To examine the effect of medial longitudinal arch mobility on running kinematics, ground reaction forces, and loading rates in high-arched runners. Cross-sectional study. Human movement research laboratory. A total of 104 runners were screened for arch height. Runners were then identified as having high arches if the arch height index was greater than 0.5 SD above the mean. Of the runners with high arches, 11 rigid runners with the lowest arch mobility (R) were compared with 8 mobile runners with the highest arch mobility (M). Arch mobility was determined by calculating the left arch height index in all runners. Three-dimensional motion analysis of running over ground. Rearfoot and tibial angular excursions, eversion-to-tibial internal-rotation ratio, vertical ground reaction forces, and the associated loading rates. Runners with mobile arches exhibited decreased tibial internal-rotation excursion (mobile: 5.6° ± 2.3° versus rigid: 8.0° ± 3.0°), greater eversion-to-tibial internal-rotation ratio (mobile: 2.1 ± 0.8 versus rigid: 1.5 ± 0.5), decreased second peak vertical ground reaction force values (mobile: 2.3 ± 0.2 × body weight versus rigid: 2.4 ± 0.1 × body weight), and decreased vertical loading rate values (mobile: 55.7 ± 14.1 × body weight/s versus rigid: 65.9 ± 11.4 × body weight/s). Based on the results of this study, it appears that runners with high arch structure but differing arch mobility exhibited differences in select lower extremity movement patterns and forces. Future authors should investigate the impact of arch mobility on running-related injuries.

Impact behaviour of Napier/polyester composites under different energy levels

NASA Astrophysics Data System (ADS)

Fahmi, I.; Majid, M. S. Abdul; Afendi, M.; Haslan, M.; Helmi E., A.; M. Haameem J., A.

2016-07-01

The effects of different energy levels on the impact behaviour of Napier fibre/polyester reinforced composites were investigated. Napier fibre was extracted using traditional water retting process to be utilized as reinforcing materials in polyester composite laminates. 25% fibre loading composite laminates were prepared and impacted at three different energy levels; 2.5,5 and 7.5 J using an instrumented drop weight impact testing machine (IMATEK IM10). The outcomes show that peak force and contact time increase with increased impact load. The energy absorption was then calculated from the force displacement curve. The results indicated that the energy absorption decreases with increasing energy levels of the impact. Impacted specimens were observed visually for fragmentation fracture using an optical camera to identify the failure mechanisms. Fracture fragmentation pattern from permanent dent to perforation with radial and circumferential was observed.

Systematic model researches on the stability limits of the DVL series of float designs

NASA Technical Reports Server (NTRS)

Sottorf, W.

1949-01-01

To determine the trim range in which a seaplane can take off without porpoising, stability tests were made of a Plexiglas model, composed of float, wing, and tailplane, which corresponded to a full-size research airplane. The model and full-size stability limits are in good agreement. After all structural parts pertaining to the air frame were removed gradually, the aerodynamic forces replaced by weight forces, and the moment of inertia and position of the center of gravity changed, no marked change of limits of the stable zone was noticeable. The latter, therefore, is for practical purposes affected only by hydrodynamic phenomena. The stability limits of the DVL family of floats were determined by a systematic investigation independent of any particular sea-plane design, thus a seaplane may be designed to give a run free from porpoising.

Low body weight/thinness, overweight and obesity of children and adolescents from a Brazilian region of low economic status.

PubMed

Guedes, Dartagnan Pinto; Almeida, Francisléia Nascimento; Neto, Jaime Tolentino M; Maia, Maria de Fátima de M; Tolentino, Thatiana Maia

2013-12-01

To assess the prevalence of low body weight/thinness, overweight and obesity in a representative sample of children and adolescents from a Brazilian region with low economic development. A total of 982 girls and 986 boys, aged seven to 17 years old and assisted by Segundo Tempo Program, from Montes Claros, Minas Gerais, Brazil, were included in the study. Low body weight/thinness, overweight and obesity were defined based on body mass cut-off indexes recommended by the International Obesity Task Force. The prevalence of the nutritional status according to sex and age was compared by chi-square test. In girls, the frequency of low body weight/thinness, overweight and obesity was 4.1, 18.4 and 3.8%, respectively; in boys, these percentages were 6.3, 13.2 and 2.9%, respectively. The low body weight/thinness for girls raised from 2.7% (7-10 years old) to 5.5% (15-17 years old); the body weight excess (overweight and obesity) decreased from 30.1 to 16.2% for the same age groups. In boys, the corresponding trends were from 3.2 to 9.4% for low body weight/thinness, and from 23.4 to 9.2%, for body weight excess. The data indicate that, even in a region with low economic status, the body weight excess was the main problem associated with nutritional health. The high overweight and obesity prevalence rates indicate the need of public policies for promoting healthy feeding behaviors and physical activity.

Low body weight/thinness, overweight and obesity of children and adolescents from a Brazilian region of low economic status

PubMed Central

Guedes, Dartagnan Pinto; Almeida, Francisléia Nascimento; M., Jaime Tolentino; Maia, Maria de Fátima de M.; Tolentino, Thatiana Maia

2013-01-01

OBJECTIVE: To assess the prevalence of low body weight/thinness, overweight and obesity in a representative sample of children and adolescents from a Brazilian region with low economic development. METHODS: A total of 982 girls and 986 boys, aged seven to 17 years old and assisted by Segundo Tempo Program, from Montes Claros, Minas Gerais, Brazil, were included in the study. Low body weight/thinness, overweight and obesity were defined based on body mass cut-off indexes recommended by the International Obesity Task Force. The prevalence of the nutritional status according to sex and age was compared by chi-square test. RESULTS: In girls, the frequency of low body weight/thinness, overweight and obesity was 4.1, 18.4 and 3.8%, respectively; in boys, these percentages were 6.3, 13.2 and 2.9%, respectively. The low body weight/thinness for girls raised from 2.7% (7-10 years old) to 5.5% (15-17 years old); the body weight excess (overweight and obesity) decreased from 30.1 to 16.2% for the same age groups. In boys, the corresponding trends were from 3.2 to 9.4% for low body weight/thinness, and from 23.4 to 9.2%, for body weight excess. CONCLUSIONS: The data indicate that, even in a region with low economic status, the body weight excess was the main problem associated with nutritional health. The high overweight and obesity prevalence rates indicate the need of public policies for promoting healthy feeding behaviors and physical activity. PMID:24473947

Wind Tunnel Strain-Gage Balance Calibration Data Analysis Using a Weighted Least Squares Approach

NASA Technical Reports Server (NTRS)

Ulbrich, N.; Volden, T.

2017-01-01

A new approach is presented that uses a weighted least squares fit to analyze wind tunnel strain-gage balance calibration data. The weighted least squares fit is specifically designed to increase the influence of single-component loadings during the regression analysis. The weighted least squares fit also reduces the impact of calibration load schedule asymmetries on the predicted primary sensitivities of the balance gages. A weighting factor between zero and one is assigned to each calibration data point that depends on a simple count of its intentionally loaded load components or gages. The greater the number of a data point's intentionally loaded load components or gages is, the smaller its weighting factor becomes. The proposed approach is applicable to both the Iterative and Non-Iterative Methods that are used for the analysis of strain-gage balance calibration data in the aerospace testing community. The Iterative Method uses a reasonable estimate of the tare corrected load set as input for the determination of the weighting factors. The Non-Iterative Method, on the other hand, uses gage output differences relative to the natural zeros as input for the determination of the weighting factors. Machine calibration data of a six-component force balance is used to illustrate benefits of the proposed weighted least squares fit. In addition, a detailed derivation of the PRESS residuals associated with a weighted least squares fit is given in the appendices of the paper as this information could not be found in the literature. These PRESS residuals may be needed to evaluate the predictive capabilities of the final regression models that result from a weighted least squares fit of the balance calibration data.

A RLS-SVM Aided Fusion Methodology for INS during GPS Outages

PubMed Central

Yao, Yiqing; Xu, Xiaosu

2017-01-01

In order to maintain a relatively high accuracy of navigation performance during global positioning system (GPS) outages, a novel robust least squares support vector machine (LS-SVM)-aided fusion methodology is explored to provide the pseudo-GPS position information for the inertial navigation system (INS). The relationship between the yaw, specific force, velocity, and the position increment is modeled. Rather than share the same weight in the traditional LS-SVM, the proposed algorithm allocates various weights for different data, which makes the system immune to the outliers. Field test data was collected to evaluate the proposed algorithm. The comparison results indicate that the proposed algorithm can effectively provide position corrections for standalone INS during the 300 s GPS outage, which outperforms the traditional LS-SVM method. Historical information is also involved to better represent the vehicle dynamics. PMID:28245549

Experimental study on nonlinear vibrating of aluminum foam using electronic speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Yang, Fujun; Ma, Yinhang; Tao, Nan; He, Xiaoyuan

2017-06-01

Due to its multi properties, including excellent stiffness-to-weight and strength-to-weight ratios, closed-cell aluminum and its alloy foams become candidate materials for use in many high-technology industries, such as the automotive and aerospace industries. For the efficient use of closed-cell foams in structural applications, it is necessary and important to detailly understand their mechanical characteristics. In this paper, the nonlinear vibration responses of the cantilever beams of closed-cell aluminum foams were investigated by use of electronic speckle pattern interferometry (ESPI). The nonlinear resonant mode shapes of testing specimens under harmonic excitation were measured. It is first time to obtain from the experimental results that there exist super-harmonic responses when the cantilever beams of closed-cell aluminum foam were forced to vibrate, which was caused by its specific cellular structures.

A RLS-SVM Aided Fusion Methodology for INS during GPS Outages.

PubMed

Yao, Yiqing; Xu, Xiaosu

2017-02-24

In order to maintain a relatively high accuracy of navigation performance during global positioning system (GPS) outages, a novel robust least squares support vector machine (LS-SVM)-aided fusion methodology is explored to provide the pseudo-GPS position information for the inertial navigation system (INS). The relationship between the yaw, specific force, velocity, and the position increment is modeled. Rather than share the same weight in the traditional LS-SVM, the proposed algorithm allocates various weights for different data, which makes the system immune to the outliers. Field test data was collected to evaluate the proposed algorithm. The comparison results indicate that the proposed algorithm can effectively provide position corrections for standalone INS during the 300 s GPS outage, which outperforms the traditional LS-SVM method. Historical information is also involved to better represent the vehicle dynamics.

Preventing fall-related vertebral fractures: effect of floor stiffness on peak impact forces during backward falls.

PubMed

Sran, Meena M; Robinovitch, Stephen N

2008-08-01

In vivo biomechanical study of 11 male volunteers. To measure the peak forces applied to the buttocks in a backward fall from standing, and to determine whether this force is lowered by reductions in floor stiffness. Fall-related vertebral fractures are common and backward falls result in impact to the buttocks. Compliant flooring may reduce impact force and risk for vertebral fracture during a fall. However, we have little knowledge of the peak forces applied to the body during a backward fall, or how floor stiffness affects this force. Eleven males, mean age 25 +/- 5 (SD) years, were suddenly released from a backward lean of 15 degrees , falling backward onto the ground which was covered with 4.5, 7.5, or 10.5 cm of ethylene vinyl acetate foam rubber. We measured 3-dimensional impact forces applied to the buttocks at 960 Hz with a force plate. We used repeated measures analysis of variance and post hoc t tests to compare peak forces between conditions. We also modeled peak vertical force for falls onto a bare floor. RESULTS.: There was a significant difference in peak vertical force between falls onto the 10.5 cm foam condition compared with the 7.5 cm (P = 0.002) and 4.5 cm (P < 0.001) conditions. Peak vertical force (N) was (mean +/- SD) 5099 +/- 868, 4788 +/- 702, and 4544 +/- 672 for the 4.5, 7.5, and 10.5 cm foam conditions, respectively, and estimated at 6027 +/- 988 for the rigid (bare floor) condition. Compared with the bare floor, these foam floors provided, on average, 24, 20, and 15% force attenuation respectively. In a backward fall onto the buttocks, peak impact forces are 6.4 to 9.0 times body weight in a fall onto a bare floor. Reducing floor stiffness using even a thin (4.5 cm) layer of foam may provide 15% vertical force attenuation during a fall onto the buttocks.

Weight Loss Behaviors Used by Active Duty Air Force Personnel to Maintain Compliance with Weight Control Standards

DTIC Science & Technology

1997-05-01

lose weight. The methods of weight loss reported were exercising , skipping meals, using diet pills, and self- induced vomiting. In each case, females...Restrictive Diet Popular Diet Self- induced Vomifing Laxatives Diuretics Diet Pills Exercise Other Note- N = frequency of resf were allowed to...Rate 69 Demographic Data 69 Exercise 70 Weight Loss Beliefs and Practices 71 Additional Data Collected 76 Implications for Military Health Care

Low motor performance scores among overweight children: poor coordination or morphological constraints?

PubMed

Chivers, Paola; Larkin, Dawne; Rose, Elizabeth; Beilin, Lawrence; Hands, Beth

2013-10-01

This study examined whether lower motor performance scores can be full attributed to poor coordination, or whether weight related morphological constraints may also affect motor performance. Data for 666 children and adolescents from the longitudinal Western Australian Pregnancy Cohort (Raine) Study were grouped into normal weight, overweight and obese categories based on the International Obesity Task Force cut points. Participants completed the 10-item McCarron Assessment of Neuromuscular Development (MAND) at the 10 and 14 year follow-up. The prevalence of overweight and obese participants classified with mild or moderate motor difficulties was not different from the normal weight group at 10 years (χ2 = 5.8 p = .215), but higher at 14 years (χ2 = 11.3 p = .023). There were no significant differences in overall motor performance scores between weight status groups at 10 years, but at 14 years, the normal weight group achieved better scores than the obese group (p<.05). For specific items, the normal weight group consistently scored higher than the overweight and obese groups on the jump task at 10 (p<.001) and 14 (p<.01)years but lower on the hand strength task at both ages (p<.01). Our findings raise the question as to whether some test items commonly used for assessing motor competence are appropriate for an increasingly overweight and obese population. Copyright © 2013 Elsevier B.V. All rights reserved.

Effect of gamma irradiation on phenol content, antioxidant activity and biological activity of black maca and red maca extracts (Lepidium meyenii walp).

PubMed

Zevallos-Concha, A; Nuñez, D; Gasco, M; Vasquez, C; Quispe, M; Gonzales, G F

2016-01-01

This study was performed to determine the effects of gamma irradiation on UV spectrum on maca, total content of polyphenols, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities and in vivo biological activities of red and black maca extracts (Lepidium meyenii). Adult mice of the strain Swiss aged 3 months and weighing 30-35 g in average were used to determine biological activities. Daily sperm production, effect on testosterone-induced prostate hyperplasia and forced swimming test were used to determine the effect of irradiation on biological activities of maca extracts. Irradiation did not show differences in UV spectrum but improves the amount of total polyphenols in red maca as well as in black maca extracts. In both cases, black maca extract has more content of polyphenols than red maca extract (p < 0.01). Gamma irradiation significantly increased the antioxidant capacity (p < 0.05). No difference was observed in daily sperm production when irradiated and nonirradiated maca extract were administered to mice (p > 0.05). Black maca extract but not red maca extract has more swimming endurance capacity in the forced swimming test. Irradiation of black maca extract increased the swimming time to exhaustion (p < 0.05). This is not observed with red maca extract (p > 0.05). Testosterone enanthate (TE) increased significantly the ventral prostate weight. Administration of red maca extract in animals treated with TE prevented the increase in prostate weight. Irradiation did not modify effect of red maca extract on prostate weight (p > 0.05). In conclusion, irradiation does not alter the biological activities of both black maca and red maca extracts. It prevents the presence of microorganisms in the extracts of black or red maca, but the biological activities were maintained.

[INFLUENCE OF IONIZING RADIATION ON THE LOCOMOTOR ACTIVITY AND BODY WEIGHT OF RATS].

PubMed

Saimova, A; Chaizhunusоva, N; Kairkhanova, Y; Uzbеkоv, D; Hоshi, М

2017-02-01

The aim of our study was to study influence of ionizing radiation on the locomotor activity and body weight of rats, for this animals was irradiated by via inhalation. Beta- emitter 56Mn was obtained by neutron activation of powdered MnО2 by using nuclear reactor IVG.1M (experimental facility «Baikal-1», Kurchatov, Kazakhstan). Exposure of rats to radioactive powder had two way, the first experiment was contained only air filter for animal's breathing and the second with the system of forced ventilation. Also we developed the method for observation of the locomotor activity of rats, based on quantitative data. The experiment was conducted on 8 «Wistar» breed white laboratory rats. Statistical analysis was performed using descriptive statistics and non-parametric test. Based on our data, we can say that our method has the advantage over the others is that there is no need to move about the animal out of the box in the test field. So we reduce animal stress factor, as the transfer of an animal from one to second place creates additional stress for him. The initial activity of the pulverized powder in both experiments were 2,74х108Bq, but in the second experiment when we used the system of forced ventilation, internal radiation doses were 0.041±0.0075 Gy, this didn't have effect on locomotor activity of rats (Z= -0,841, р=0,4). In the first experiment where we used only air filter for animal's breathing internal radiation doses were 0.15±0.025 Gr, that showed a decrease in locomotor activity in rats (Z=-6,653, р=0,001). After exposure to ionizing radiation changes in the mammals' weight were not found. Thus, based on our data we have made conclusion, that even after a single irradiation at low dose 0.15±0.025 Gr changes occur in the nervous system.

Maximal Oxygen Consumption, Respiratory Volume and Some Related Factors in Fire-fighting Personnel.

PubMed

Khazraee, Touraj; Fararouei, Mohammad; Daneshmandi, Hadi; Mobasheri, Farzane; Zamanian, Zahra

2017-01-01

Firefighters for difficult activities and rescue of damaged people must be in appropriate physical ability. Maximal oxygen capacity is an indicator for diagnosis of physical ability of workers. This study aimed to assess the cardiorespiratory system and its related factors in firefighters. This study was conducted on 110 firefighters from various stations. An self-administered questionnaire (respiratory disorders questionnaire, Tuxworth-Shahnavaz step test, and pulmonary function test) was used to collection of required data. Average of humidity and temperature was 52% and 17°C, respectively. Background average noise levels were between 55 and 65 dB. Data were analyzed using SPSS software (version 19). The mean age of the study participants was 32 ± 6.2 years. The means of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and FEV1/FVC were 92% ±9.4%, 87% ±9.2%, and 80% ±6.1%, respectively. The participants' mean VO 2 -max was 2.79 ± 0.29 L/min or 37.34 ± 4.27 ml/kg body weight per minute. The results revealed that weight has a direct association with vital capacity (VC), FVC, and peak expiratory flow. In addition, height was directly associated with VC, FVC, and VO 2 -max ( P < 0.05). However, there was an inverse and significant association between height and FEV1/FVC ( r = -0.23, P < 0.05). Height, weight, body mass index, and waist circumference were directly associated with VO 2 -max. The findings of this study showed that the amount of maximum oxygen consumption is close with the proposed range of this parameter among firefighters in other studies. Furthermore, the results of the study revealed that individuals had normal amounts of lung volume index. This issue can be attributed to the appropriate usage of respiratory masks.

Development and modeling of multi-phase polymeric origami inspired architecture by using pre-molded geometrical features

NASA Astrophysics Data System (ADS)

Kshad, Mohamed Ali E.; Naguib, Hani E.

2017-02-01

Using Origami folded cores in sandwich structures for lightweight applications has attracted attention in different engineering applications, especially in the applications where the stiffness to weight ratio is a critical design parameter. Recently, common sandwich cores such as honey-comb and foamed cores have been replaced with origami core panels due to their way of force redistribution and energy absorption; these unique characteristics give origami cores high stiffness to weight ratio and high bending and twisting resistance. This paper presents the results of experimental investigations of the effect of base material on the mechanical properties and the impact resistance of Miura-Origami sandwich cores; then, the experimental results are compared with FEA simulation results. The materials used in the study for the origami cores were polymer blends composed of polylactic acid (PLA) and thermoplastic polyurethane (TPU). PLA/TPU blend compositions are (100/0, 80/20, 65/35, 50/50, 20/80, and 0/100) as a weight percentage. The geometrical parameters of the unit cell, base material thickness, and the panel thickness were considered to be constants in this study. The study shows the behavior of the origami cores under impact test and the energy absorbed by the origami folded cores. It was found that 20/80 PLA/TPU blend demonstrated the highest specific energy absorption efficiency both in quasi-static compression and impact tests. Fractured Origami structures were observed to fail at folded edges (creases lines), while the facets exhibit rigid body rotations. The FEM simulation showed a consistency in the impact behavior of the origami cores, and the directional deformational of origami core units which explain the ability of the structure to redistribute the applied force and absorb energy. In this work the origami folded core features were molded directly from the blended material.

Processing of probabilistic information in weight perception and motor prediction.

PubMed

Trampenau, Leif; van Eimeren, Thilo; Kuhtz-Buschbeck, Johann

2017-02-01

We studied the effects of probabilistic cues, i.e., of information of limited certainty, in the context of an action task (GL: grip-lift) and of a perceptual task (WP: weight perception). Normal subjects (n = 22) saw four different probabilistic visual cues, each of which announced the likely weight of an object. In the GL task, the object was grasped and lifted with a pinch grip, and the peak force rates indicated that the grip and load forces were scaled predictively according to the probabilistic information. The WP task provided the expected heaviness related to each probabilistic cue; the participants gradually adjusted the object's weight until its heaviness matched the expected weight for a given cue. Subjects were randomly assigned to two groups: one started with the GL task and the other one with the WP task. The four different probabilistic cues influenced weight adjustments in the WP task and peak force rates in the GL task in a similar manner. The interpretation and utilization of the probabilistic information was critically influenced by the initial task. Participants who started with the WP task classified the four probabilistic cues into four distinct categories and applied these categories to the subsequent GL task. On the other side, participants who started with the GL task applied three distinct categories to the four cues and retained this classification in the following WP task. The initial strategy, once established, determined the way how the probabilistic information was interpreted and implemented.

Hamstrings Stiffness and Landing Biomechanics Linked to Anterior Cruciate Ligament Loading

PubMed Central

Blackburn, J. Troy; Norcross, Marc F.; Cannon, Lindsey N.; Zinder, Steven M.

2013-01-01

Context: Greater hamstrings stiffness is associated with less anterior tibial translation during controlled perturbations. However, it is unclear how hamstrings stiffness influences anterior cruciate ligament (ACL) loading mechanisms during dynamic tasks. Objective: To evaluate the influence of hamstrings stiffness on landing biomechanics related to ACL injury. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: A total of 36 healthy, physically active volunteers (18 men, 18 women; age = 23 ± 3 years, height = 1.8 ± 0.1 m, mass = 73.1 ± 16.6 kg). Intervention(s): Hamstrings stiffness was quantified via the damped oscillatory technique. Three-dimensional lower extremity kinematics and kinetics were captured during a double-legged jump-landing task via a 3-dimensional motion-capture system interfaced with a force plate. Landing biomechanics were compared between groups displaying high and low hamstrings stiffness via independent-samples t tests. Main Outcome Measure(s): Hamstrings stiffness was normalized to body mass (N/m·kg−1). Peak knee-flexion and -valgus angles, vertical and posterior ground reaction forces, anterior tibial shear force, internal knee-extension and -varus moments, and knee-flexion angles at the instants of each peak kinetic variable were identified during the landing task. Forces were normalized to body weight, whereas moments were normalized to the product of weight and height. Results: Internal knee-varus moment was 3.6 times smaller in the high-stiffness group (t22 = 2.221, P = .02). A trend in the data also indicated that peak anterior tibial shear force was 1.1 times smaller in the high-stiffness group (t22 = 1.537, P = .07). The high-stiffness group also demonstrated greater knee flexion at the instants of peak anterior tibial shear force and internal knee-extension and -varus moments (t22 range = 1.729–2.224, P < .05). Conclusions: Greater hamstrings stiffness was associated with landing biomechanics consistent with less ACL loading and injury risk. Musculotendinous stiffness is a modifiable characteristic; thus exercises that enhance hamstrings stiffness may be important additions to ACL injury-prevention programs. PMID:24303987

A Standardized Rat Model of Volumetric Muscle Loss Injury for the Development of Tissue Engineering Therapies

DTIC Science & Technology

2012-12-01

isometric tetanic force (Po) of 28.4% and 32.5% at 2 and 4 months. Importantly, Po corrected for differences in body weight and muscle wet weights were...development, we removed progres- sively larger amounts of muscle tissue followed by a mea- surement of maximal isometric force (Po). The final model, and...indicated by increased collagen deposition (Fig. 2). The scarred area and the area immediately adjacent to it contained disorganized muscle fibers

Agmatine attenuates chronic unpredictable mild stress induced behavioral alteration in mice.

PubMed

Taksande, Brijesh G; Faldu, Dharmesh S; Dixit, Madhura P; Sakaria, Jay N; Aglawe, Manish M; Umekar, Milind J; Kotagale, Nandkishor R

2013-11-15

Chronic stress exposure and resulting dysregulation of the hypothalamic pituitary adrenal axis develops susceptibility to variety of neurological and psychiatric disorders. Agmatine, a putative neurotransmitter has been reported to be released in response to various stressful stimuli to maintain the homeostasis. Present study investigated the role of agmatine on chronic unpredictable mild stress (CUMS) induced behavioral and biochemical alteration in mice. Exposure of mice to CUMS protocol for 28 days resulted in diminished performance in sucrose preference test, splash test, forced swim test and marked elevation in plasma corticosterone levels. Chronic agmatine (5 and 10 mg/kg, ip, once daily) treatment started on day-15 and continued till the end of the CUMS protocol significantly increased sucrose preference, improved self-care and motivational behavior in the splash test and decreased duration of immobility in the forced swim test. Agmatine treatment also normalized the elevated corticosterone levels and prevented the body weight changes in chronically stressed animals. The pharmacological effect of agmatine was comparable to selective serotonin reuptake inhibitor, fluoxetine (10mg/kg, ip). Results of present study clearly demonstrated the anti-depressant like effect of agmatine in chronic unpredictable mild stress induced depression in mice. Thus the development of drugs based on brain agmatinergic modulation may represent a new potential approach for the treatment of stress related mood disorders like depression. © 2013 Published by Elsevier B.V.

The preparatory state of ground reaction forces in defending against a dribbler in a basketball 1-on-1 dribble subphase.

PubMed

Fujii, Keisuke; Yoshioka, Shinsuke; Isaka, Tadao; Kouzaki, Motoki

2015-03-01

We previously demonstrated the relationship between sidestepping performance and the preparatory state of ground reaction forces (GRFs). The present study investigated the effect of the preparatory state of GRFs on defensive performance in 1-on-1 subphase of basketball. Ten basketball players participated in 1-on-1 dribble game of basketball. The outcomes (penetrating and guarding) and the preparatory state of GRFs (non-weighted and weighted states, i.e. vertical GRFs below and above 120% of body weight, respectively) were assessed by separating the phases. In the non-weighted state and the weighted state to determine the outcome, the probability of successful guarding was 78.8% and 29.6%, respectively. The non-weighted state prevented delay of the defensive step in the determination phase. Both the non-weighted and weighted states, immediately before the determination phase, were likely to change to the weighted state in the determination phase; during this time, the defender's preparatory state would be destabilised, presumably by the dribbler's movement. These results revealed that the preparatory GRFs before the defensive step help to explain the outcome of the 1-on-1 subphase, and suggest a better way to prevent delaying initiation of the defensive step and thereby to guard more effectively against a dribbler.

Load-bearing ability of the mosquito tarsus on water surfaces arising from its flexibility

NASA Astrophysics Data System (ADS)

Kong, X. Q.; Liu, J. L.; Zhang, W. J.; Qu, Y. D.

2015-03-01

Mosquitoes possess a remarkable ability to stand effortlessly and walk freely on water surfaces because their six legs provide a large force to support the body weight. This study is focused on the role of the tarsus (the distal segment of the mosquito leg) because it was observed that normally only the tarsi make contact with water. The maximum value of the supporting force of the tarsus (6 mm long) in contact with water is estimated as 492 ± 5 μN, nearly 20 times the body weight of the mosquito, whereas the value for the whole leg (11 mm) is about 23 times the body weight. We demonstrate that the huge force provided by the tarsus originates from its flexibility, which ensures that the leg does not easily pierce the water. Adjustment of the initial stepping angle of the tarsus assists the mosquito to control the supporting force. These findings help to illustrate how mosquitoes stand or walk on water with only their tarsi in nearly horizontal contact with the water surface. Besides enhancing our understanding of mechanisms underlying "walking on water" by semi-aquatic insects, these investigations could provide inspiration for the biomimetic design of miniature robotics.

Use of a Force Sensor in Archimedes' Principle Experiment, Determination of Buoyant Force and Acceleration Due To Gravity

NASA Astrophysics Data System (ADS)

Aurora, Tarlok

2013-04-01

In introductory physics, students verify Archimedes' principle by immersing an object in water in a container, with a side-spout to collect the displaced water, resulting in a large uncertainty, due to surface tension. A modified procedure was introduced, in which a plastic bucket is suspended from a force sensor, and an object hangs underneath the bucket. The object is immersed in water in a glass beaker (without any side spout), and the weight loss is measured with a computer-controlled force sensor. Instead of collecting the water displaced by the object, tap water was added to the bucket to compensate for the weight loss, and the Archimedes' principle was verified within less than a percent. With this apparatus, buoyant force was easily studied as a function of volume of displaced water; as well as a function of density of saline solution. By graphing buoyant force as a function of volume (or density of liquid), value of g was obtained from slope. Apparatus and sources of error will be discussed.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis.

PubMed

Augustsson, J; Thomeé, R; Lindén, C; Folkesson, M; Tranberg, R; Karlsson, J

2006-04-01

A fatiguing exercise protocol was combined with single-leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test-retest experiment, 11 healthy male subjects performed two trials of single-leg hops under three different test conditions: non-fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower-extremity joint kinematics and kinetics during single-leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground-reaction forces were recorded with a six-camera, motion-capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take-off for the single-leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground-reaction forces decreased for the fatigued hop conditions compared with the non-fatigued condition (P<0.05). Compared with landing during the non-fatigued condition, hip moments and ground-reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post-exercise. It is concluded that the fatiguing exercise protocol combined with single-leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take-off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single-leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Microprocessor controlled force actuator

NASA Technical Reports Server (NTRS)

Zimmerman, D. C.; Inman, D. J.; Horner, G. C.

1986-01-01

The mechanical and electrical design of a prototype force actuator for vibration control of large space structures (LSS) is described. The force actuator is an electromagnetic system that produces a force by reacting against a proof-mass. The actuator has two colocated sensors, a digital microcontroller, and a power amplifier. The total weight of actuator is .998 kg. The actuator has a steady state force output of approximately 2.75 N from approximately 2 Hz to well beyond 1000 Hz.

Biomechanics of Atlanto-Occipital and Atlanto-Axial Joint Injuries,

DTIC Science & Technology

1982-11-12

conditions, after physiological lordosis is taken into account, the main acting forces are: the weight of the head--force P21 the force of the muscles...position, the force Pv’ because of physiological lordosis , is directed away from the cen- tral axis of the vertebral shafts and can be considered using two...and the equivalent tension force in the transverse ligament of the atlas--R. We found out that under intermediate degree of physiological lordosis

Instrumented socket inserts for sensing interaction at the limb-socket interface.

PubMed

Swanson, Eric C; McLean, Jake B; Allyn, Katheryn J; Redd, Christian B; Sanders, Joan E

2018-01-01

The objective of this research was to investigate a strategy for designing and fabricating computer-manufactured socket inserts that were embedded with sensors for field monitoring of limb-socket interactions of prosthetic users. An instrumented insert was fabricated for a single trans-tibial prosthesis user that contained three sensor types (proximity sensor, force sensing resistor, and inductive sensor), and the system was evaluated through a sequence of laboratory clinical tests and two days of field use. During in-lab tests 3 proximity sensors accurately distinguish between don and doff states; 3 of 4 force sensing resistors measured gradual pressure increases as weight-bearing increased; and the inductive sensor indicated that as prosthetic socks were added the limb moved farther out of the socket and pistoning amplitude decreased. Multiple sensor types were necessary in analysis of field collected data to interpret how sock changes affected limb-socket interactions. Instrumented socket inserts, with sensors selected to match clinical questions of interest, have the potential to provide important insights to improve patient care. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

Development of superconducting magnetic bearing using superconducting coil and bulk superconductor

NASA Astrophysics Data System (ADS)

Seino, H.; Nagashima, K.; Arai, Y.

2008-02-01

The authors conducted a study on superconducting magnetic bearing, which consists of superconducting rotor and stator to apply the flywheel energy-storage system for railways. In this study, high temperature bulk superconductor (HTS bulk) was combined with superconducting coils to increase the load capacity of the bearing. In the first step of the study, the thrust rolling bearing was selected for application by using liquid nitrogen cooled HTS bulk. 60mm-diameter HTS bulks and superconducting coil which generated a high gradient of magnetic field by cusp field were adopted as a rotor and a stator for superconducting magnetic bearing, respectively. The results of the static load test and the rotation test, creep of the electromagnetic forces caused by static flux penetration and AC loss due to eccentric rotation were decreased to the level without any problems in substantial use by using two HTS bulks. In the result of verification of static load capacity, levitation force (thrust load) of 8900N or more was supportable, and stable static load capacity was obtainable when weight of 460kg was levitated.

Practice guidelines for evaluating new fever in critically ill adult patients. Task Force of the Society of Critical Care Medicine and the Infectious Diseases Society of America.

PubMed

O'Grady, N P; Barie, P S; Bartlett, J G; Bleck, T; Garvey, G; Jacobi, J; Linden, P; Maki, D G; Nam, M; Pasculle, W; Pasquale, M D; Tribett, D L; Masur, H

1998-05-01

The development of practice guidelines for evaluating adult patients who develop new fever in the intensive care unit (ICU) for the purpose of guiding clinical practice. A task force of 13 experts in disciplines related to critical care medicine, infectious diseases, and surgery was convened from the membership of the Society of Critical Care Medicine and the Infectious Disease Society of America. The task force members provided personal experience and determined the published literature (articles retrieved with use of MEDLINE or textbooks) from which consensus would be sought. The published literature was reviewed and classified into one of four categories, according to study design and scientific value. The task force met several times in person and twice monthly by teleconference over a 1-year period to identify the pertinent literature and arrive at consensus recommendations. Consideration was given to the relationship between the weight of scientific evidence and the experts' opinions. Draft documents were composed and debated by the task force until consensus was reached by nominal group process. The panel concluded that because fever can have many infectious and noninfectious etiologies, a new fever in an adult patient in the ICU should trigger a careful clinical assessment rather than automatic orders for laboratory and radiological tests. A cost-conscious approach to obtaining diagnostic studies should be undertaken if they are indicated after a clinical evaluation. The goal of such an approach is to determine, in a directed manner, whether infection is present so that additional testing can be avoided and therapeutic options can be identified.

A rapid prototyping model for biomechanical evaluation of pelvic osteotomies.

PubMed

Pressel, Thomas; Max, Stefan; Pfeifer, Roman; Ostermeier, Sven; Windhagen, Henning; Hurschler, Christof

2008-04-01

The biomechanical consequences of Salter pelvic osteotomy are difficult to assess due to the complex three-dimensional anatomy of the pelvis. Therefore, models of the dysplastic pelvis are required to allow realistic biomechanical simulation of possible outcomes. A polyamide reversed-engineering model of the left hemipelvis and proximal femur was produced from a computed tomography dataset of an 8-year-old child with severe dysplasia of both hips using selective laser sintering. Hip joint forces before and after Salter osteotomy of the hip were measured using an experimental setup in which an industrial robot was exerting hip joint forces and moments representing one-legged stance. Hip extensor and abductor actuator forces were measured which counterbalanced the joint moments. The preoperative hip joint resultant force was 583 N (270% body weight), while after the operation a mean force of 266 N (120% body weight) was measured. The resulting bony model was geometrically accurate, while apparent joint incongruencies were due to the neglected cartilaginous structures in the model. The preoperative joint resultant force was within the limits reported in the literature. The results suggest that Salter innominate osteotomy not only increases joint contact area but also reduces the hip joint force.

Instrumented figure skating blade for measuring on-ice skating forces

NASA Astrophysics Data System (ADS)

Acuña, S. A.; Smith, D. M.; Robinson, J. M.; Hawks, J. C.; Starbuck, P.; King, D. L.; Ridge, S. T.; Charles, S. K.

2014-12-01

Competitive figure skaters experience substantial, repeated impact loading during jumps and landings. Although these loads, which are thought to be as high as six times body weight, can lead to overuse injuries, it is not currently possible to measure these forces on-ice. Consequently, efforts to improve safety for skaters are significantly limited. Here we present the development of an instrumented figure skating blade for measuring forces on-ice. The measurement system consists of strain gauges attached to the blade, Wheatstone bridge circuit boards, and a data acquisition device. The system is capable of measuring forces in the vertical and horizontal directions (inferior-superior and anterior-posterior directions, respectively) in each stanchion with a sampling rate of at least 1000 Hz and a resolution of approximately one-tenth of body weight. The entire system weighs 142 g and fits in the space under the boot. Calibration between applied and measured force showed excellent agreement (R > 0.99), and a preliminary validation against a force plate showed good predictive ability overall (R ≥ 0.81 in vertical direction). The system overestimated the magnitude of the first and second impact peaks but detected their timing with high accuracy compared to the force plate.

The influence of gravity and wind on land plant evolution.

PubMed

Niklas, K J

1998-07-01

Aspects of the engineering theory treating the elastic stability of vertical stems and cantilevered leaves supporting their own weight and additional wind-induced forces (drag) are reviewed in light of biomechanical studies of living and fossil terrestrial plant species. The maximum height to which arborescent species can grow before their stems elastically buckle under their own weight is estimated by means of the Euler-Greenhill formula which states that the critical buckling height scales as the 1/3 power of plant tissue-stiffness normalized with respect to tissue bulk density and as the 2/3 power of stem diameter. Data drawn from living plants indicate that progressively taller plant species employ stiffer and lighter-weight plant tissues as the principal stiffening agent in their vertical stems. The elastic stability of plants subjected to high lateral wind-loadings is governed by the drag torque (the product of the drag force and the height above ground at which this force is applied), which cannot exceed the gravitational bending moment (the product of the weight of aerial organs and the lever arm measured at the base of the plant). Data from living plants indicate that the largest arborescent plant species rely on massive trunks and broad, horizontally expansive root crowns to resist drag torques. The drag on the canopies of these plants is also reduced by highly flexible stems and leaves composed of tissues that twist and bend more easily than tissues used to stiffen older, more proximal stems. A brief review of the fossil record suggests that modifications in stem, leaf, and root morphology and anatomy capable of simultaneously coping with self-weight and wind-induced drag forces evolved by Devonian times, suggesting that natural selection acting on the elastic stability of sporophytes occurred early in the history of terrestrial plants.

Exercise support for therapy

NASA Technical Reports Server (NTRS)

Long, M. J.; Irick, S. C.

1976-01-01

Constant-value weight-relieving apparatus, which moves on rollers on overhead track, supports weight of walking, stooping, squatting, or standing patient with combination of multiple pulleys and spring clusters. Individually preselected support force is constant for all movements.

Investigation of Corrosion Protection in Oil Mineral Reservoirs by Nanocomposites Used as Coating Layers

NASA Astrophysics Data System (ADS)

Al-Sarraf, Abdulhameed R.; Al-Saaidi, Samer A.

2018-05-01

In this study, a number of nanocomposites were prepared by adding magnesium oxide (MgO) with weight percentages (1, 2 & 3)% to cellulose nitrate and sodium silicate as an intermediate layer and other nanocomposites by adding MgO, coal coke and hybrid (MgO & coal coke with ratio 1:1) with weight percentages (1, 2 & 3)% to epoxy resin as final layer. The identity of the used metal is determined by spectrometer OE thermo. The nature and topography of the surface layers were examined by optical microscope and atomic force microscope (AFM). Mechanical properties are indicated by hardness, wear rate, impact strength and adhesion strength. The efficiency of the layers prepared to inhibit corrosion in the oil mineral reservoirs of the oil products distribution company was studied by electrochemical corrosion test in addition to the chemical corrosion test. The used metal is (St-37) according to (ASTM). It was found that the best intermediate layer (cellulose nitrate+3%MgO) and the final layer is the epoxy resin reinforced by 2% hybrid.

Antistress and antioxidant effects of virgin coconut oil in vivo.

PubMed

Yeap, Swee Keong; Beh, Boon Kee; Ali, Norlaily Mohd; Yusof, Hamidah Mohd; Ho, Wan Yong; Koh, Soo Peng; Alitheen, Noorjahan Banu; Long, Kamariah

2015-01-01

Virgin coconut oil (VCO) has been consumed worldwide for various health-related reasons and some of its benefits have been scientifically evaluated. Medium-chain fatty acids were found to be a potential antidepressant functional food; however, this effect had not been evaluated in VCO, which is rich in polyphenols and medium-chain fatty acids. The aim of this study was to evaluate the antistress and antioxidant effects of VCO in vivo , using mice with stress-induced injury. The antistress effect of VCO (administered per os , at a dose of 10 ml/kg body weight) was evaluated using the forced swim test and chronic cold restraint stress models. VCO was able to reduce immobility time and restore oxidative stress in mice post-swim test. Furthermore, mice treated with VCO were found to exhibit higher levels of brain antioxidants, lower levels of brain 5-hydroxytryptamine and reduced weight of the adrenal glands. Consequently, the serum cholesterol, triglyceride, glucose and corticosterone levels were also lower in VCO-treated mice. These results suggest the potential value of VCO as an antistress functional oil.

Antistress and antioxidant effects of virgin coconut oil in vivo

PubMed Central

YEAP, SWEE KEONG; BEH, BOON KEE; ALI, NORLAILY MOHD; YUSOF, HAMIDAH MOHD; HO, WAN YONG; KOH, SOO PENG; ALITHEEN, NOORJAHAN BANU; LONG, KAMARIAH

2015-01-01

Virgin coconut oil (VCO) has been consumed worldwide for various health-related reasons and some of its benefits have been scientifically evaluated. Medium-chain fatty acids were found to be a potential antidepressant functional food; however, this effect had not been evaluated in VCO, which is rich in polyphenols and medium-chain fatty acids. The aim of this study was to evaluate the antistress and antioxidant effects of VCO in vivo, using mice with stress-induced injury. The antistress effect of VCO (administered per os, at a dose of 10 ml/kg body weight) was evaluated using the forced swim test and chronic cold restraint stress models. VCO was able to reduce immobility time and restore oxidative stress in mice post-swim test. Furthermore, mice treated with VCO were found to exhibit higher levels of brain antioxidants, lower levels of brain 5-hydroxytryptamine and reduced weight of the adrenal glands. Consequently, the serum cholesterol, triglyceride, glucose and corticosterone levels were also lower in VCO-treated mice. These results suggest the potential value of VCO as an antistress functional oil. PMID:25452773

Comparison of impact strength of acrylic resin reinforced with kevlar and polyethylene fibres.

PubMed

Kamath, G; Bhargava, K

2002-01-01

The present study was done to evaluate the impact strengths of heat-activated acrylic resins reinforced with Kevlar fibres, polyethylene fibres and unreinforced heat activated acrylic resin. Each of three groups had 25 specimens. Brass rods of uniform length of 40 mm and diameter of 8 mm were used to prepare the moulds. A combination of long fibres (40 mm length) and short fibres (6 mm length) were used. The total amount of fibres incorporated was limited to 2% by weight of the resin matrix. Short and long fibres of equal weight were incorporated. The short fibres were mixed with polymer and monomer and packed into the mould, while, the long axis of the specimen, perpendicular to the applied force. The specimens were then processed. Impact strength testing was done on Hounsfield's impact testing machine. Kevlar fibre reinforced heat activated acrylic resin specimens recorded higher mean impact strength of 0.8464 Joules, while polyethylene fibres reinforced heat activated acrylic resin recorded mean impact strength of 0.7596 joules. The unreinforced heat activated acrylic resin recorded mean impact strength of 0.3440 Joules.

Effects of genotype and slaughter weight on the meat quality of Criollo Cordobes and Anglonubian kids produced under extensive feeding conditions.

PubMed

Peña, F; Bonvillani, A; Freire, B; Juárez, M; Perea, J; Gómez, G

2009-11-01

Physicochemical and organoleptic characteristics of meat (longissimus muscle) from Criollo Cordobes (CC) and Anglonubian (AN) suckling kids were analysed to determine the effects of genotype and slaughter weight. Forty suckling entire male kids, 20 CC and 20 AN were assigned to two age/slaughter weight groups (I: 60+2days old and ⩽11kg, and II: 90+2days old and >11kg). Colour, shear force and cholesterol levels of meat were affected by breed. Tenderness decreased and cholesterol increased with age/slaughter weight. Fatty acid profiles were affected primarily by genotype. The sensory attributes were perceived as medium-high intensity, and meat from CC and AN goat kids was valued as tender. However, initial tenderness and connective tissue varied with genotype. The main effect due to the increase in age/slaughter weight was a decrease in tenderness (initial and overall), as observed for instrumental shear force.

The pull in olympic weightlifting.

PubMed

Enoka, R M

1979-01-01

Data from five experienced weightlifters on the vertical forces applied to the barbell and system (barbell and lifter) during the pull were in excellent agreement with earlier displacement-time descriptions of the double knee bend as consisting of two stages of extension interrupted by a period of realignment (second knee bend). The vertical component of the ground reaction force (Rz) consisted of three phases: Weighting I, Unweighting, and Weighting II. The relative magnitude of the Rz impulse with respect to the system weight impulse (as an indicant of the proportion of the Rz impulse contributing to system acceleration) ranged from 118--141% for Weighting I, 74--89% for Unweighting, and 122--135% for Weighting II. In agreement with published theoretical calculations the most experienced and successful lifter produced the larger phase of positive acceleration first. The rebending of the knees was associated with the Unweighting phase. Although this latter interval corresponded to a phase of barbell deceleration, it appeared that the concomitant enhancement of the back, hip, and knee extensor activity outweighed any adverse effects.

Experimental formability analysis of bondal sandwich sheet

NASA Astrophysics Data System (ADS)

Kami, Abdolvahed; Banabic, Dorel

2018-05-01

Metal/polymer/metal sandwich sheets have recently attracted the interests of industries like automotive industry. These sandwich sheets have superior properties over single-layer metallic sheets including good sound and vibration damping and light weight. However, the formability of these sandwich sheets should be enhanced which requires more research. In this paper, the formability of Bondal sheet (DC06/viscoelastic polymer/DC06 sandwich sheet) was studied through different types of experiments. The mechanical properties of Bondal were determined by uniaxial tensile tests. Hemispherical punch stretching and hydraulic bulge tests were carried out to determine the forming limit diagram (FLD) of Bondal. Furthermore, cylindrical and square cup drawing tests were performed in dry and oil lubricated conditions. These tests were conducted at different blank holding forces (BHFs). An interesting observation about Bondal sheet deep drawing was obtaining of higher drawing depths at dry condition in comparison with oil-lubricated condition.

Haptic interfaces using dielectric electroactive polymers

NASA Astrophysics Data System (ADS)

Ozsecen, Muzaffer Y.; Sivak, Mark; Mavroidis, Constantinos

2010-04-01

Quality, amplitude and frequency of the interaction forces between a human and an actuator are essential traits for haptic applications. A variety of Electro-Active Polymer (EAP) based actuators can provide these characteristics simultaneously with quiet operation, low weight, high power density and fast response. This paper demonstrates a rolled Dielectric Elastomer Actuator (DEA) being used as a telepresence device in a heart beat measurement application. In the this testing, heart signals were acquired from a remote location using a wireless heart rate sensor, sent through a network and DEA was used to haptically reproduce the heart beats at the medical expert's location. A series of preliminary human subject tests were conducted that demonstrated that a) DE based haptic feeling can be used in heart beat measurement tests and b) through subjective testing the stiffness and actuator properties of the EAP can be tuned for a variety of applications.

Quantitative motor assessment of muscular weakness in myasthenia gravis: a pilot study.

PubMed

Hoffmann, Sarah; Siedler, Jana; Brandt, Alexander U; Piper, Sophie K; Kohler, Siegfried; Sass, Christian; Paul, Friedemann; Reilmann, Ralf; Meisel, Andreas

2015-12-23

Muscular weakness in myasthenia gravis (MG) is commonly assessed using Quantitative Myasthenia Gravis Score (QMG). More objective and quantitative measures may complement the use of clinical scales and might detect subclinical affection of muscles. We hypothesized that muscular weakness in patients with MG can be quantified with the non-invasive Quantitative Motor (Q-Motor) test for Grip Force Assessment (QGFA) and Involuntary Movement Assessment (QIMA) and that pathological findings correlate with disease severity as measured by QMG. This was a cross-sectional pilot study investigating patients with confirmed diagnosis of MG. Data was compared to healthy controls (HC). Subjects were asked to lift a device (250 and 500 g) equipped with electromagnetic sensors that measured grip force (GF) and three-dimensional changes in position and orientation. These were used to calculate the position index (PI) and orientation index (OI) as measures for involuntary movements due to muscular weakness. Overall, 40 MG patients and 23 HC were included. PI and OI were significantly higher in MG patients for both weights in the dominant and non-dominant hand. Subgroup analysis revealed that patients with clinically ocular myasthenia gravis (OMG) also showed significantly higher values for PI and OI in both hands and for both weights. Disease severity correlates with QIMA performance in the non-dominant hand. Q-Motor tests and particularly QIMA may be useful objective tools for measuring motor impairment in MG and seem to detect subclinical generalized motor signs in patients with OMG. Q-Motor parameters might serve as sensitive endpoints for clinical trials in MG.

Conceptual Problems in the Foundations of Mechanics

NASA Astrophysics Data System (ADS)

Coelho, Ricardo Lopes

2012-09-01

There has been much research on principles and fundamental concepts of mechanics. Problems concerning the law of inertia, the concepts of force, fictitious force, weight, mass and the distinction between inertial and gravitational mass are addressed in the first part of the present paper. It is argued in the second that the law of inertia is the source of these problems. Consequences drawn from the law explain the metaphysical concept of force, the problematic concept of fictitious force, the nominal definition of weight and the difficulty with defining mass operationally. The core of this connection between the law and these consequences lies in the fact that acceleration is a sufficient condition for force. The experimental basis of the law in the course of its history shows, however, that the law presupposes acceleration necessarily whereas acceleration does not presuppose the law. Therefore, there is no inconvenience in taking acceleration independently of the law. This is enough to bypass those problems. Taking into account how force is measured by force meters and how mass is basically determined, by comparison with the standard mass, a minimal meaning for both concepts of force and mass is established. All this converges with several solutions proposed in the course of history and increases the communicability of mechanics, as outlined in the final part of this paper.

Discrepancies in anthropometric parameters between different models affect intervertebral rotations when loading finite element models with muscle forces from inverse static analyses.

PubMed

Zhu, Rui; Rohlmann, Antonius

2014-06-01

In only a few published finite element (FE) simulations have muscle forces been applied to the spine. Recently, muscle forces determined using an inverse static (IS) model of the spine were transferred to a spinal FE model, and the effect of methodical parameters was investigated. However, the sensitivity of anthropometric differences between FE and IS models, such as body height and spinal orientation, was not considered. The aim of this sensitivity study was to determine the influence of those differences on the intervertebral rotations (IVRs) following the transfer of muscle forces from an IS model to a FE model. Muscle forces were estimated for 20° flexion and 10° extension of the upper body using an inverse static musculoskeletal model. These forces were subsequently transferred to a nonlinear FE model of the spino-pelvic complex, which includes 243 muscle fascicles. Deviations of body height (±10 cm), spinal orientation in the sagittal plane (±10°), and body weight (±10 kg) between both models were intentionally generated, and their influences on IVRs were determined. The changes in each factor relative to their corresponding reference value of the IS model were calculated. Deviations in body height, spinal orientation, and body weight resulted in maximum changes in the IVR of 19.2%, 26% and 4.2%, respectively, relative to T12-S1 IVR. When transferring muscle forces from an IS to a FE model, it is crucial that both models have the same spinal orientation and height. Additionally, the body weight should be equal in both models.

The influence of officer equipment and protection on short sprinting performance.

PubMed

Lewinski, William J; Dysterheft, Jennifer L; Dicks, Nathan D; Pettitt, Robert W

2015-03-01

As advances in protective equipment are made, it has been observed that the weight law enforcement officers must carry every day is greatly increasing. Many investigations have noted the health risks of these increases, yet none have looked at its effects on officer mobility. The primary purpose of this study was to examine the influence of both the weight of officer safety equipment, as well as a lateral focal point (FP), on the stride length, stride velocity, and acceleration of the first six strides of a short sprint. Twenty male law enforcement students performed two maximal effort sprint trials, in the participating college's gymnasium, from each of four starting positions: forwards (control position), backwards, 90° left, and 90° right. Subjects placed in the FP group (n = 9) were required to maintain focus on lateral FP during the 90° left and 90° right trials, and a forwards FP during the backwards trials. On a second testing date, subjects repeated the sprint tests while wearing a 9.07 kg weight belt, simulating officer equipment and protective gear. The belt averaged 11.47 ± 1.64% of subject body mass. A significant main effect of weight belt trials was found (F = 20.494, p < 0.01), in which significant decreases were found for velocity and acceleration. No other significant effects were found as a result of starting position or focal point and no significant interactions were found between independent variables. Conclusively, the results of this study show the increasing weights of duty gear and protective equipment have detrimental effects on officer velocity and acceleration, impeding their mobility, which may be dangerous in use of force or threatening situations. Copyright © 2014 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Application of the maximum entropy principle to determine ensembles of intrinsically disordered proteins from residual dipolar couplings.

PubMed

Sanchez-Martinez, M; Crehuet, R

2014-12-21

We present a method based on the maximum entropy principle that can re-weight an ensemble of protein structures based on data from residual dipolar couplings (RDCs). The RDCs of intrinsically disordered proteins (IDPs) provide information on the secondary structure elements present in an ensemble; however even two sets of RDCs are not enough to fully determine the distribution of conformations, and the force field used to generate the structures has a pervasive influence on the refined ensemble. Two physics-based coarse-grained force fields, Profasi and Campari, are able to predict the secondary structure elements present in an IDP, but even after including the RDC data, the re-weighted ensembles differ between both force fields. Thus the spread of IDP ensembles highlights the need for better force fields. We distribute our algorithm in an open-source Python code.

Introductory Physics Experiments Using the Wii Balance Board

NASA Astrophysics Data System (ADS)

Starr, Julian; Sobczak, Robert; Iqbal, Zohaib; Ochoa, Romulo

2010-02-01

The Wii, a video game console by Nintendo, utilizes several different controllers, such as the Wii remote (Wiimote) and the balance board, for game-playing. The balance board was introduced in early 2008. It contains four strain gauges and has Bluetooth connectivity at a relatively low price. Thanks to available open source code, such as GlovePie, any PC with Bluetooth capability can detect the information sent out by the balance board. Based on the ease with which the forces measured by each strain gauge can be obtained, we have designed several experiments for introductory physics courses that make use of this device. We present experiments to measure the forces generated when students lift their arms with and without added weights, distribution of forces on an extended object when weights are repositioned, and other normal forces cases. The results of our experiments are compared with those predicted by Newtonian mechanics. )

Effect of load, cadence, and fatigue on tibio-femoral joint force during a half squat.

PubMed

Hattin, H C; Pierrynowski, M R; Ball, K A

1989-10-01

Ten male university student volunteers were selected to investigate the 3D articular force at the tibio-femoral joint during a half squat exercise, as affected by cadence, different barbell loads, and fatigue. Each subject was required to perform a half squat exercise with a barbell weight centered across the shoulders at two different cadences (1 and 2 s intervals) and three different loads (15, 22 and 30% of the one repetition maximum). Fifty repetitions at each experimental condition were recorded with an active optoelectronic kinematic data capture system (WATSMART) and a force plate (Kistler). Processing the data involved a photogrammetric technique to obtain subject tailored anthropometric data. The findings of this study were: 1) the maximal antero-posterior shear and compressive force consistently occurred at the lowest position of the weight, and the forces were very symmetrically disposed on either side of this halfway point; 2) the medio-lateral shear forces were small over the squat cycle with few peaks and troughs; 3) cadence increased the antero-posterior shear (50%) and the compressive forces (28%); 4) as a subject fatigues, load had a significant effect on the antero-posterior shear force; 5) fatigue increased all articular force components but it did not manifest itself until about halfway through the 50 repetitions of the exercise; 6) the antero-posterior shear force was most affected by fatigue; 7) cadence had a significant effect on fatigue for the medio-lateral shear and compressive forces.

Supersonic stability and control characteristics of a 0.015 scale model 69-0 of the space shuttle orbiter with forebody RSI modifications in the NASA/LaRC 4-foot UPWT (legs 1 and 2) (LA71A/B)

NASA Technical Reports Server (NTRS)

1977-01-01

Investigations are reported for the determination of aerodynamic effects of reducing the thickness of the reusable surface insulation located along the sides of the shuttle orbiter in order to allow weight reduction in the nose region. Six-component aerodynamic force and moment data were obtained at Mach numbers from 1.5 to 4.6 over an angle of attack range from about -1 deg to 28 deg. Additional tests were made over an angle of sideslip range from -6 deg to 6 deg at selected angles of attack. Test results are presented in graph and tables.

Pharmacological activities of a new glycosaminoglycan, acharan sulfate isolated from the giant African snail Achatina fulica.

PubMed

Shim, Jin Young; Lee, Yeon Sil; Jung, Sang Hoon; Choi, Hyung Seok; Shin, Kuk Hyun; Kim, Yeong Shik

2002-12-01

Acharan sulfate (AS) is a glycosaminoglycan (GAG) prepared from the giant African snail, Achatina fulica. In this study, some biological activities of AS were evaluated on the basis of structural similarities to heparin/heparan sulfate and the biological functions of GAGs. We demonstrated that it exhibited strong immunostimulating activities as measured by carbon clearance test in mice and in vivo phagocytosis. It also exhibited a significant hypoglycemic activity in epinephrine (EP)-induced hyperglycemia as well as antifatigue effects by weight-loaded forced swimming test. And it showed hypolipidemic activities in cholesterol-rich mixture induced hyperlipidemia in rats. The above results indicate that AS has diverse biological activities and suggest therapeutically important target molecules.

Calculation of Dynamic Loads Due to Random Vibration Environments in Rocket Engine Systems

NASA Technical Reports Server (NTRS)

Christensen, Eric R.; Brown, Andrew M.; Frady, Greg P.

2007-01-01

An important part of rocket engine design is the calculation of random dynamic loads resulting from internal engine "self-induced" sources. These loads are random in nature and can greatly influence the weight of many engine components. Several methodologies for calculating random loads are discussed and then compared to test results using a dynamic testbed consisting of a 60K thrust engine. The engine was tested in a free-free condition with known random force inputs from shakers attached to three locations near the main noise sources on the engine. Accelerations and strains were measured at several critical locations on the engines and then compared to the analytical results using two different random response methodologies.

The Addition of Graphene to Polymer Coatings for Improved Weathering

DOE PAGES

Nuraje, Nurxat; Khan, Shifath I.; Misak, Heath; ...

2013-01-01

Graphene nanoflakes in different weight percentages were added to polyurethane top coatings, and the coatings were evaluated relative to exposure to two different experimental conditions: one a QUV accelerated weathering cabinet, while the other a corrosion test carried out in a salt spray chamber. After the exposure tests, the surface morphology and chemical structure of the coatings were investigated via atomic force microscopy (AFM) and Fourier transform infrared (FTIR) imaging. Our results show that the addition of graphene does in fact improve the resistance of the coatings against ultraviolet (UV) degradation and corrosion. It is believed that this process willmore » improve the properties of the polyurethane top coating used in many industries against environmental factors.« less

Physically weighted approximations of unsteady aerodynamic forces using the minimum-state method

NASA Technical Reports Server (NTRS)

Karpel, Mordechay; Hoadley, Sherwood Tiffany

1991-01-01

The Minimum-State Method for rational approximation of unsteady aerodynamic force coefficient matrices, modified to allow physical weighting of the tabulated aerodynamic data, is presented. The approximation formula and the associated time-domain, state-space, open-loop equations of motion are given, and the numerical procedure for calculating the approximation matrices, with weighted data and with various equality constraints are described. Two data weighting options are presented. The first weighting is for normalizing the aerodynamic data to maximum unit value of each aerodynamic coefficient. The second weighting is one in which each tabulated coefficient, at each reduced frequency value, is weighted according to the effect of an incremental error of this coefficient on aeroelastic characteristics of the system. This weighting yields a better fit of the more important terms, at the expense of less important ones. The resulting approximate yields a relatively low number of aerodynamic lag states in the subsequent state-space model. The formulation forms the basis of the MIST computer program which is written in FORTRAN for use on the MicroVAX computer and interfaces with NASA's Interaction of Structures, Aerodynamics and Controls (ISAC) computer program. The program structure, capabilities and interfaces are outlined in the appendices, and a numerical example which utilizes Rockwell's Active Flexible Wing (AFW) model is given and discussed.

Gravity-Off-loading System for Large-Displacement Ground Testing of Spacecraft Mechanisms

NASA Technical Reports Server (NTRS)

Han, Olyvia; Kienholz, David; Janzen, Paul; Kidney, Scott

2010-01-01

Gravity-off-loading of deployable spacecraft mechanisms during ground testing is a long-standing problem. Deployable structures which are usually too weak to support their own weight under gravity require a means of gravity-off-loading as they unfurl. Conventional solutions to this problem have been helium-filled balloons or mechanical pulley/counterweight systems. These approaches, however, suffer from the deleterious effects of added inertia or friction forces. The changing form factor of the deployable structure itself and the need to track the trajectory of the center of gravity also pose a challenge to these conventional technologies. This paper presents a novel testing apparatus for high-fidelity zero-gravity simulation for special application to deployable space structures such as solar arrays, magnetometer booms, and robotic arms in class 100,000 clean room environments

Disruption in the relationship between blood pressure and salty taste thresholds among overweight and obese children

PubMed Central

Bobowski, Nuala K.

2015-01-01

Background Prevalence of high blood pressure (BP) among American children has increased over the past two decades, due in part to increasing rates of obesity and excessive dietary salt intake. Objective We tested the hypotheses that the relationships among BP, salty taste sensitivity, and salt intake differ between normal-weight and overweight/obese children. Design In an observational study, sodium chloride (NaCl) and monosodium glutamate (MSG) taste detection thresholds were measured using the Monell two-alternative, forced-choice, paired-comparison tracking method. Weight and BP were measured, and salt intake was determined by 24-hour dietary recall. Participants/Setting Eight- to 14-year-olds (N=97; 52% overweight or obese) from the Philadelphia area completed anthropometrics and BP measurements; 97% completed one or both thresholds. Seventy-six percent provided valid dietary recall data. Testing was completed between December 2011 and August 2012. Main outcome measures NaCl and MSG detection thresholds, BP, and dietary salt intake. Statistical analyses Outcome measures were compared between normal-weight and overweight/obese children with t-tests. Relationships among outcome measures within groups were examined with Pearson correlations, and multiple regression analysis was used to examine the relationship between BP and thresholds, controlling for age, BMI-Z score, and dietary salt intake. Results Salt and MSG thresholds were positively correlated (r(71)=0.30, p=0.01) and did not differ between body-weight groups (p>0.20). Controlling for age, BMI-Z score, and salt intake, systolic BP was associated with NaCl thresholds among normal-weight children (p=0.01), but not among overweight/obese children. All children consumed excess salt (>8 g/day). Grain and meat products were the primary source of dietary sodium. Conclusions The apparent disruption in the relationship between salty taste response and BP among overweight/obese children suggests the relationship may be influenced by body weight. Further research is warranted to explore this relationship as a potential measure to prevent development of hypertension. PMID:25843808

How tight are beetle hugs? Attachment in mating leaf beetles

NASA Astrophysics Data System (ADS)

Voigt, Dagmar; Tsipenyuk, Alexey; Varenberg, Michael

2017-09-01

Similar to other leaf beetles, rosemary beetles Chrysolina americana exhibit a distinct sexual dimorphism in tarsal attachment setae. Setal discoid terminals occur only in males, and they have been previously associated with a long-term attachment to the female's back (elytra) during copulation and mate guarding. For the first time, we studied living males and females holding to female's elytra. Pull-off force measurements with a custom-made tribometer featuring a self-aligning sample holder confirmed stronger attachment to female elytra compared with glass in both males and females; corresponding to 45 and 30 times the body weight, respectively. In line with previous studies, males generated significantly higher forces than females on convex elytra and flat glass, 1.2 times and 6.8 times, respectively. Convex substrates like elytra seem to improve the attachment ability of rosemary beetles, because they can hold more strongly due to favourable shear angles of legs, tarsi and adhesive setae. A self-aligning sample holder is found to be suitable for running force measurement tests with living biological samples.

How tight are beetle hugs? Attachment in mating leaf beetles.

PubMed

Voigt, Dagmar; Tsipenyuk, Alexey; Varenberg, Michael

2017-09-01

Similar to other leaf beetles, rosemary beetles Chrysolina americana exhibit a distinct sexual dimorphism in tarsal attachment setae. Setal discoid terminals occur only in males, and they have been previously associated with a long-term attachment to the female's back (elytra) during copulation and mate guarding. For the first time, we studied living males and females holding to female's elytra. Pull-off force measurements with a custom-made tribometer featuring a self-aligning sample holder confirmed stronger attachment to female elytra compared with glass in both males and females; corresponding to 45 and 30 times the body weight, respectively. In line with previous studies, males generated significantly higher forces than females on convex elytra and flat glass, 1.2 times and 6.8 times, respectively. Convex substrates like elytra seem to improve the attachment ability of rosemary beetles, because they can hold more strongly due to favourable shear angles of legs, tarsi and adhesive setae. A self-aligning sample holder is found to be suitable for running force measurement tests with living biological samples.

In vivo recording of aerodynamic force with an aerodynamic force platform: from drones to birds.

PubMed

Lentink, David; Haselsteiner, Andreas F; Ingersoll, Rivers

2015-03-06

Flapping wings enable flying animals and biomimetic robots to generate elevated aerodynamic forces. Measurements that demonstrate this capability are based on experiments with tethered robots and animals, and indirect force calculations based on measured kinematics or airflow during free flight. Remarkably, there exists no method to measure these forces directly during free flight. Such in vivo recordings in freely behaving animals are essential to better understand the precise aerodynamic function of their flapping wings, in particular during the downstroke versus upstroke. Here, we demonstrate a new aerodynamic force platform (AFP) for non-intrusive aerodynamic force measurement in freely flying animals and robots. The platform encloses the animal or object that generates fluid force with a physical control surface, which mechanically integrates the net aerodynamic force that is transferred to the earth. Using a straightforward analytical solution of the Navier-Stokes equation, we verified that the method is accurate. We subsequently validated the method with a quadcopter that is suspended in the AFP and generates unsteady thrust profiles. These independent measurements confirm that the AFP is indeed accurate. We demonstrate the effectiveness of the AFP by studying aerodynamic weight support of a freely flying bird in vivo. These measurements confirm earlier findings based on kinematics and flow measurements, which suggest that the avian downstroke, not the upstroke, is primarily responsible for body weight support during take-off and landing.

Impact behaviour of Napier/polyester composites under different energy levels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fahmi, I., E-mail: fahmi-unimap@yahoo.com; Majid, M. S. Abdul, E-mail: shukry@unimap.edu.my; Afendi, M., E-mail: afendirojan@unimap.edu.my

2016-07-19

The effects of different energy levels on the impact behaviour of Napier fibre/polyester reinforced composites were investigated. Napier fibre was extracted using traditional water retting process to be utilized as reinforcing materials in polyester composite laminates. 25% fibre loading composite laminates were prepared and impacted at three different energy levels; 2.5,5 and 7.5 J using an instrumented drop weight impact testing machine (IMATEK IM10). The outcomes show that peak force and contact time increase with increased impact load. The energy absorption was then calculated from the force displacement curve. The results indicated that the energy absorption decreases with increasing energymore » levels of the impact. Impacted specimens were observed visually for fragmentation fracture using an optical camera to identify the failure mechanisms. Fracture fragmentation pattern from permanent dent to perforation with radial and circumferential was observed.« less

Application of microwave irradiation for the removal of polychlorinated biphenyls from siloxane transformer and hydrocarbon engine oils.

PubMed

Antonetti, Claudia; Licursi, Domenico; Raspolli Galletti, Anna Maria; Martinelli, Marco; Tellini, Filippo; Valentini, Giorgio; Gambineri, Francesca

2016-09-01

The removal of polychlorinated biphenyls (PCBs) both from siloxane transformer oil and hydrocarbon engine oil was investigated through the application of microwave (MW) irradiation and a reaction system based on polyethyleneglycol (PEG) and potassium hydroxide. The influence of the main reaction parameters (MW irradiation time, molecular weight of PEG, amount of added reactants and temperature) on the dechlorination behavior was studied. Promising performances were reached, allowing about 50% of dechlorination under the best experimental conditions, together time and energy saving compared to conventional heating systems. Moreover, an interesting dechlorination degree (up to 32%) was achieved for siloxane transformer oil when MW irradiation was employed as the unique driving force. To the best of our knowledge, this is the first time in which MW irradiation is tested as the single driving force for the dechlorination of these two types of PCB-contaminated oils. Copyright © 2016 Elsevier Ltd. All rights reserved.

40 CFR 1066.805 - Road-load power, test weight, and inertia weight class determination.

Code of Federal Regulations, 2014 CFR

2014-07-01

.... (a) Simulate a vehicle's test weight on the dynamometer using the appropriate equivalent test weight shown in Table 1 of this section. Equivalent test weights are established according to each vehicle's... weight class corresponding to each equivalent test weight; the inertia weight class allows for grouping...

Development and Validation of High Performance Unshrouded Centrifugal Impeller

NASA Technical Reports Server (NTRS)

Chen, Wei-Chung; Williams, M.; Paris, John K.; Prueger, G. H.; Williams, Robert; Turner, James E. (Technical Monitor)

2001-01-01

The feasibility of using a two-stage unshrouded impeller turbopump to replace the current three-stage reusable launch vehicle engine shrouded impeller hydrogen pump has been evaluated from the standpoint of turbopump weight reduction and overall payload improvement. These advantages are a by-product of the higher tip speeds that an unshrouded impeller can sustain. The issues associated with the effect of unshrouded impeller tip clearance on pump efficiency and head have been evaluated with one-dimensional tools and full three-dimensional rotordynamic fluid reaction forces and coefficients have been established through time dependent computational fluid dynamics (CFD) simulation of the whole 360 degree impeller with different rotor eccentricities and whirling ratios. Unlike the shrouded impeller, the unshrouded impeller forces are evaluated as the sum of the pressure forces on the blade and the pressure forces on the hub using the CFD results. The turbopump axial thrust control has been optimized by adjusting the first stage impeller backend wear ring seal diameter and diverting the second stage backend balance piston flow to the proper location. The structural integrity associated with the high tip speed has been checked by analyzing a 3D-Finite Element Model at maximum design conditions (6% higher than the design speed). This impeller was fabricated and tested in the NASA Marshall Space Flight Center water-test rig. The experimental data will be compared with the analytical predictions and presented in another paper. The experimental data provides validation data for the numerical design and analysis methodology. The validated numerical methodology can be used to help design different unshrouded impeller configurations.

MEMS in Space Systems

NASA Technical Reports Server (NTRS)

Lyke, J. C.; Michalicek, M. A.; Singaraju, B. K.

1995-01-01

Micro-electro-mechanical systems (MEMS) provide an emerging technology that has the potential for revolutionizing the way space systems are designed, assembled, and tested. The high launch costs of current space systems are a major determining factor in the amount of functionality that can be integrated in a typical space system. MEMS devices have the ability to increase the functionality of selected satellite subsystems while simultaneously decreasing spacecraft weight. The Air Force Phillips Laboratory (PL) is supporting the development of a variety of MEMS related technologies as one of several methods to reduce the weight of space systems and increase their performance. MEMS research is a natural extension of PL research objectives in micro-electronics and advanced packaging. Examples of applications that are under research include on-chip micro-coolers, micro-gyroscopes, vibration sensors, and three-dimensional packaging technologies to integrate electronics with MEMS devices. The first on-orbit space flight demonstration of these and other technologies is scheduled for next year.

Comparison Between Elite and Subelite Swimmers on Dry Land and Tumble Turn Leg Extensor Force-Time Characteristics.

PubMed

Jones, Julian V; Pyne, David B; Haff, G Greg; Newton, Robert U

2018-06-01

Jones, JV, Pyne, DB, Haff, GG, and Newton, RU. Comparison between elite and subelite swimmers on dry land and tumble turn leg extensor force-time characteristics. J Strength Cond Res 32(6): 1762-1769, 2018-Elite swimmers demonstrate faster swimming turn times that are potentially a result of having better strength-power characteristics than subelite swimmers. We quantified differences between dry-land and swimming turn force-time characteristics in elite swimmers and subelite swimmers. Subelite (11 males: 17.4 ± 0.6 years; 10 females: 17.1 ± 0.6 years) and elite swimmers (15 male: 23.2 ± 2.3 years; 7 female: 21.6 ± 2.5 years) were tested in a cross-sectional design. All swimmers performed a body weight and loaded (20 kg females, 30 kg males) squat jump (SJ) on a portable force platform. On the same day, all swimmers completed swimming turn analyses using a force platform fixed within the pool wall. The magnitude of difference between groups was estimated using a standardized mean difference (effect size statistic). Elite male and female swimmers had superior swimming turn and dry-land force-time characteristics to subelite swimmers in all tests. The standardized mean differences between groups ranged from small to very large. The largest differences were SJ peak velocity unloaded (3.07 ± 1.0 m·s males, 3.49 ± 2.29 m·s females; standardized mean difference ± 90% confidence limits) and SJ peak power unloaded (2.59 ± 0.79 w male, 2.80 ± 1.64 w female) with elite male and female swimmers having a ∼25-50% higher performance than the subelites in both characteristics. Elite swimmers exhibit superior strength and power characteristics for the swimming turn compared with younger and less experienced swimmers. A well-planned and executed strength and conditioning program is needed for emerging swimmers to develop these qualities, as they transition to senior levels.

Experimental investigation on the dissipative and elastic characteristics of a yaw colloidal damper destined to carbody suspension of a bullet train

NASA Astrophysics Data System (ADS)

Suciu, B.; Tomioka, T.

2016-09-01

Yaw damper represents a major source of excitation for flexural vibration of the railway carbody. In order to reduce transmissibility of such undesired excitation, yaw damper should allow for large force transmission at low working frequencies, but should behave as vibration isolator at high working frequencies. Unfortunately, the yaw oil damper (OD), which is nowadays in service, has poor intrinsic elastic capabilities and provides damping forces varying as a power function versus the piston speed. Since colloidal damper (CD) has intrinsic elastic capabilities and larger damping forces at lower excitation frequencies, it occurs as an attractive alternative solution to traditional yaw dampers. In this work, a yaw CD destined to carbody suspension of a bullet train was designed and manufactured; then, its dynamic characteristics, produced by both the frictional and colloidal effects, were evaluated from the experimental results, obtained during horizontal vibration tests, performed on a ball-screw shaker. Compared to the corresponding classical yaw OD, the trial yaw CD allowed for: weight reduction of 31.6%; large damping force, dissipated energy and spring constant at long piston stroke under low excitation frequency; low damping force, dissipated energy and spring constant at short piston stroke under high excitation frequency. Elastic properties were justified by introducing a model for the spring constant that included the effect of pore size distribution.

On the design of a miniature haptic ring for cutaneous force feedback using shape memory alloy actuators

NASA Astrophysics Data System (ADS)

Hwang, Donghyun; Lee, Jaemin; Kim, Keehoon

2017-10-01

This paper proposes a miniature haptic ring that can display touch/pressure and shearing force to the user’s fingerpad. For practical use and wider application of the device, it is developed with the aim of achieving high wearability and mobility/portability as well as cutaneous force feedback functionality. A main body of the device is designed as a ring-shaped lightweight structure with a simple driving mechanism, and thin shape memory alloy (SMA) wires having high energy density are applied as actuating elements. Also, based on a band-type wireless control unit including a wireless data communication module, the whole device could be realized as a wearable mobile haptic device system. These features enable the device to take diverse advantages on functional performances and to provide users with significant usability. In this work, the proposed miniature haptic ring is systematically designed, and its working performances are experimentally evaluated with a fabricated functional prototype. The experimental results obviously demonstrate that the proposed device exhibits higher force-to-weight ratio than conventional finger-wearable haptic devices for cutaneous force feedback. Also, it is investigated that operational performances of the device are strongly influenced by electro-thermomechanical behaviors of the SMA actuator. In addition to the experiments for performance evaluation, we conduct a preliminary user test to assess practical feasibility and usability based on user’s qualitative feedback.

The influence of patellofemoral joint contact geometry on the modeling of three dimensional patellofemoral joint forces.

PubMed

Powers, Christopher M; Chen, Yu-Jen; Scher, Irving; Lee, Thay Q

2006-01-01

The purpose of this study was to determine the influence of patellofemoral joint contact geometry on the modeling of three-dimensional patellofemoral joint forces. To achieve this goal, patellofemoral joint reaction forces (PFJRFs) that were measured from an in-vitro cadaveric set-up were compared to PFJRFs estimated from a computer model that did not consider patellofemoral joint contact geometry. Ten cadaver knees were used in this study. Each was mounted on a custom jig that was fixed to an Instron frame. Quadriceps muscle loads were accomplished using a pulley system and weights. The force in the patellar ligament was obtained using a buckle transducer. To quantify the magnitude and direction of the PFJRF, a six-axis load cell was incorporated into the femoral fixation system so that a rigid body assumption could be made. PFJRF data were obtained at 0 degrees , 20 degrees , 40 degrees and 60 degrees of knee flexion. Following in vitro testing, SIMM modeling software was used to develop computational models based on the three-dimensional coordinates (Microscribe digitizer) of individual muscle and patellar ligament force vectors obtained from the cadaver knees. The overall magnitude of the PFJRF estimated from the computer generated models closely matched the direct measurements from the in vitro set-up (Pearson's correlation coefficient, R(2)=0.91, p<0.001). Although the computational model accurately estimated the posteriorly directed forces acting on the joint, some discrepancies were noted in the forces acting in the superior and lateral directions. These differences however, were relatively small when expressed as a total of the overall PFJRF magnitude.

Estimation of AFEES (Armed Forces Entrance Examination Stations) Survey Weights.

DTIC Science & Technology

1984-01-01

DISTRIBUTION OF POPULATION CHARACTERISTICS IN SPRING WAVE % Unweighted % Weighted % Population Characteristic Survey Survey Eligible Education Level HS...4’ - 22 - Table 10 EFFECT OF WEIGHTING ON ESTIMATED DISTRIBUTION OF POPULATION CHARACTERISTICS IN FALL WAVE % Unweighted % Weighted % Population ... Characteristic Survey Survey Eligible Education Level HS grad or beyond 64.6 59.9 54.4 Cert of gen educ develop 7.4 6.4 4.9 Not HS grad 27.9 33.6 40.5

A Flying Ejection Seat

NASA Technical Reports Server (NTRS)

Hollrock, R. H.; Barzda, J. J.

1972-01-01

To increase aircrewmen's chances for safe rescue in combat zones, the armed forces are investigating advanced escape and rescue concepts that will provide independent flight after ejection and thus reduce the risk of capture. One of the candidate concepts is discussed; namely, a stowable autogyro that serves as the crewman's seat during normal operations and automatically converts to a flight vehicle after ejection. Discussed are (1) the mechanism subsystems that the concept embodies to meet the weight and cockpit-packaging constraints and (2) tests that demonstrated the technical feasibility of the stowage, deployment, and flight operation of the rotor lift system.

Normative Data for the BTrackS Balance Test of Postural Sway: Results from 16,357 Community-Dwelling Individuals Who Were 5 to 100 Years Old.

PubMed

Goble, Daniel J; Baweja, Harsimran S

2018-05-17

Postural sway is routinely assessed because increased postural sway is associated with poorer performance of activities of daily living, higher rates of residential care, and increased risk of falling. Force plate technology is one of the most sensitive and objective means of assessing postural sway in the clinic. The aim of this study was to provide the first set of normative data for the BTrackS Balance Test (BBT) of postural sway. The design was descriptive and population based. BBT results from 16,357 community-dwelling individuals who were 5 to 100 years old were accumulated and assessed for effects of age, sex, height, and weight. Percentile rankings were calculated for significant groupings. BBT results were dependent on age and sex but not height or weight. Therefore, percentile rankings were determined for male and female individuals in each age category, with no consideration of participant height or weight. Data were collected by third-party practitioners with various backgrounds in more than 50 locations across the United States and Canada. There was an imbalance in the sample sizes for age and sex groupings. The findings of this study represent the largest normative dataset ever published for postural sway results. Normative data on the BBT can assist in determining abnormalities in postural sway, which have been linked to negative clinical outcomes.

Pathfinder

NASA Image and Video Library

2001-07-01

This photograph shows two Marshall Space Flight Center (MSFC) engineers, Mark Vaccaro (left) and Ken Welzyn, testing electrodynamic tethers in the MSFC Tether Winding and Spark Testing Facility. For 4 years, MSFC and industry partners have been developing the Propulsive Small Expendable Deployer System experiment, called ProSEDS. ProSEDS will test electrodynamic tether propulsion technology. Electrodynamic tethers are long, thin wires that collect electrical current when passing through a magnetic field. The tether works as a thruster as a magnetic field exerts a force on a current-carrying wire. Since electrodynamic tethers require no propellant, they could substantially reduce the weight of the spacecraft and provide a cost-effective method of reboosting spacecraft. The initial flight of ProSEDS is scheduled to fly aboard an Air Force Delta II rocket in the summer of 2002. In orbit, ProSEDS will deploy from a Delta II second stage. It will be a 3.1-mile (5 kilometer) long, ultrathin base-wire tether cornected with a 6.2-mile (10 kilometer) long non-conducting tether. This photograph shows Less Johnson, a scientist at MSFC, inspecting the nonconducting part of a tether as it exits a deployer similar to the one to be used in the ProSEDS experiment. The ProSEDS experiment is managed by the Space Transportation Directorate at MSFC.

Paternal environmental enrichment transgenerationally alters affective behavioral and neuroendocrine phenotypes.

PubMed

Yeshurun, Shlomo; Short, Annabel K; Bredy, Timothy W; Pang, Terence Y; Hannan, Anthony J

2017-03-01

Recent studies have demonstrated that paternal stress in rodents can result in modification of offspring behavior. Environmental enrichment, which enhances cognitive stimulation and physical activity, modifies various behaviors and reduces stress responses in adult rodents. We investigated the transgenerational influence of paternal environmental enrichment on offspring behavior and physiological stress response. Adult C57BL/6J male mice (F0) were exposed to either environmental enrichment or standard housing for four weeks and then pair-mated with naïve females. The F2 generation was generated using F1 male offspring. Male and female F1 and F2 offspring were tested for anxiety using the elevated-plus maze and large open field at 8 weeks of age. Depression-related behavior was assessed using the forced-swim test. Hypothalamic-pituitary-adrenal (HPA) axis function was determined by quantification of serum corticosterone and adrenocorticotropic hormone (ACTH) levels at baseline and after forced-swim stress. Paternal environmental enrichment was associated with increased body weights of male F1 and F2 offspring. There was no significant effect on F1 offspring anxiety and depression-related behaviors. There were no changes in anxiety-related behaviors in the F2 offspring, however these mice displayed a reduced latency to immobility in the forced-swim test. Furthermore, F2 females had significantly higher serum corticosterone levels post-stress, but not ACTH. These results show that paternal environmental enrichment exerts a sex-specific transgenerational impact on the behavioral and physiological response to stress. Our findings have implications for the modelling of psychiatric disorders in rodents. Copyright © 2017 Elsevier Ltd. All rights reserved.

Object discrimination using electrotactile feedback.

PubMed

Arakeri, Tapas J; Hasse, Brady A; Fuglevand, Andrew J

2018-04-09

A variety of bioengineering systems are being developed to restore tactile sensations in individuals who have lost somatosensory feedback because of spinal cord injury, stroke, or amputation. These systems typically detect tactile force with sensors placed on an insensate hand (or prosthetic hand in the case of amputees) and deliver touch information by electrically or mechanically stimulating sensate skin above the site of injury. Successful object manipulation, however, also requires proprioceptive feedback representing the configuration and movements of the hand and digits. Therefore, we developed a simple system that simultaneously provides information about tactile grip force and hand aperture using current amplitude-modulated electrotactile feedback. We evaluated the utility of this system by testing the ability of eight healthy human subjects to distinguish among 27 objects of varying sizes, weights, and compliances based entirely on electrotactile feedback. The feedback was modulated by grip-force and hand-aperture sensors placed on the hand of an experimenter (not visible to the subject) grasping and lifting the test objects. We were also interested to determine the degree to which subjects could learn to use such feedback when tested over five consecutive sessions. The average percentage correct identifications on day 1 (28.5%  ±  8.2% correct) was well above chance (3.7%) and increased significantly with training to 49.2%  ±  10.6% on day 5. Furthermore, this training transferred reasonably well to a set of novel objects. These results suggest that simple, non-invasive methods can provide useful multisensory feedback that might prove beneficial in improving the control over prosthetic limbs.

Dynamic weight bearing analysis is effective for evaluation of tendinopathy using a customized corridor with multi-directional force sensors in a rat model.

PubMed

Wu, Po-Ting; Hsu, Chieh-Hsiang; Su, Fong-Chin; Jou, I-Ming; Chen, Shih-Yao; Wu, Chao-Liang; Su, Wei-Ren; Kuo, Li-Chieh

2017-08-18

Few studies discuss kinetic changes in tendinopathy models. We propose a customized corridor to evaluate dynamic weight bearing (DWB) and shearing forces. Sixty rats were randomly given ultrasound-assisted collagenase injections (Collagenase rats) or needle punctures (Control rats) in their left Achilles tendons, and then evaluated 1, 4, and 8 weeks later. The Collagenase rats always had significantly (p < 0.001) higher histopathological and ultrasound feature scores than did the Controls, significantly lower DWB values in the injured than in the right hindlimbs, and compensatorily higher (p < 0.05) DWB values in the contralateral than in the left forelimbs. The injured hindlimbs had lower outward shearing force 1 and 4 weeks later, and higher (p < 0.05) push-off shearing force 8 weeks later, than did the contralateral hindlimbs. Injured Control rat hindlimbs had lower DWB values than did the contralateral only at week 1. The Collagenase rats had only lower static weight bearing ratios (SWBRs) values than did the Controls at week 1 (p < 0.05). Our customized corridor showed changes in DWB compatible with histopathological and ultrasound feature changes in the rat tendinopathy model. The hindlimb SWBRs did not correspond with any tendinopathic changes.

Model of the hydrodynamic loads applied on a rotating halfbridge belonging to a circular settling tank

NASA Astrophysics Data System (ADS)

Dascalescu, A. E.; Lazaroiu, G.; Scupi, A. A.; Oanta, E.

2016-08-01

The rotating half-bridge of a settling tank is employed to sweep the sludge from the wastewater and to vacuum and sent it to the central collector. It has a complex geometry but the main beam may be considered a slender bar loaded by the following category of forces: concentrated forces produced by the weight of the scrapping system of blades, suction pipes, local sludge collecting chamber, plus the sludge in the horizontal sludge transporting pipes; forces produced by the access bridge; buoyant forces produced by the floating barrels according to Archimedes’ principle; distributed forces produced by the weight of the main bridge; hydrodynamic forces. In order to evaluate the hydrodynamic loads we have conceived a numerical model based on the finite volume method, using the ANSYS-Fluent software. To model the flow we used the equations of Reynolds Averaged Navier-Stokes (RANS) for liquids together with Volume of Fluid model (VOF) for multiphase flows. For turbulent model k-epsilon we used the equation for turbulent kinetic energy k and dissipation epsilon. These results will be used to increase the accuracy of the loads’ sub-model in the theoretical models, e. the finite element model and the analytical model.

Relationship between asymmetry of quiet standing balance control and walking post-stroke.

PubMed

Hendrickson, Janna; Patterson, Kara K; Inness, Elizabeth L; McIlroy, William E; Mansfield, Avril

2014-01-01

Spatial and temporal gait asymmetry is common after stroke. Such asymmetric gait is inefficient, can contribute to instability and may lead to musculoskeletal injury. However, understanding of the determinants of such gait asymmetry remains incomplete. The current study is focused on revealing if there is a link between asymmetry during the control of standing balance and asymmetry during walking. This study involved review of data from 94 individuals with stroke referred to a gait and balance clinic. Participants completed three tests: (1) walking at their usual pace; (2) quiet standing; and (3) standing with maximal loading of the paretic side. A pressure sensitive mat recorded placement and timing of each footfall during walking. Standing tests were completed on two force plates to evaluate symmetry of weight bearing and contribution of each limb to balance control. Multiple regression was conducted to determine the relationships between symmetry during standing and swing time, stance time, and step length symmetry during walking. Symmetry of antero-posterior balance control and weight bearing were related to swing time and step length symmetry during walking. Weight-bearing symmetry, weight-bearing capacity, and symmetry of antero-posterior balance control were related to stance time symmetry. These associations were independent of underlying lower limb impairment. The results support the hypothesis that impaired ability of the paretic limb to control balance may contribute to gait asymmetry post-stroke. Such work suggests that rehabilitation strategies that increase the contribution of the paretic limb to standing balance control may increase symmetry of walking post-stroke. Copyright © 2013 Elsevier B.V. All rights reserved.

Trabecular trajectory in the articular processes of the human fourth cervical vertebra

PubMed Central

HERRERA, M.; PANCHÓN, A.; PEREZ-BACETE, M.

2001-01-01

The articular processes (AP) of the neural arch have been implicated in weight transmission through the cervical spine. To analyse the mechanism of weight transmission in the AP, we studied the direction of forces within it, in particular, the pattern of trabecular trajectories. Twenty-two AP from C4 vertebrae were studied in anatomical sections, and corresponding photoelastic models from selected sections were constructed and analysed. Anatomical and photoelastic findings show the subarticular spongiosa of the superior articular process (SAP) to be orthogonally arranged with vertical and oblique trabeculae in the direction of compressive forces and additional trabeculae always oriented perpendicular to the former. Vertical and oblique trabeculae are divided into rostral, middle and posterior groups. Rostral and middle trabeculae end in the anterior wall of the SAP and the transitional zone with the pedicle. Posterior trabeculae end in the subarticular spongiosa of the inferior articular process (IAP). The findings relating to trabecular trajectories in the SAP differ from previous descriptions and instead suggest that a part of the weight forces distributed within the AP transmit to the subchondral zone of the IAP. Knowledge of the trajectorial architecture of the AP may contribute to refining finite element analytical models for investigating its weight-bearing function. PMID:11554512

Tail autotomy and subsequent regeneration alter the mechanics of locomotion in lizards.

PubMed

Jagnandan, Kevin; Russell, Anthony P; Higham, Timothy E

2014-11-01

Animals can undergo significant weight change for a variety of reasons. Autotomy, the voluntary shedding of an appendage in response to a predator stimulus, provides an effective model for measuring the effects of rapid weight change on locomotor behavior and the responses to more gradual weight gain, particularly in lizards capable of both autotomizing and regenerating their tail. Although the general effects of autotomy on locomotor performance are commonly explored, we investigated changes in locomotor mechanics associated with tail loss and long-term regeneration for the first time by measuring morphology, 3D kinematics and ground reaction forces (GRFs) in the leopard gecko Eublepharis macularius. Tail autotomy resulted in a 13% anterior shift in the center of mass (CoM), which only partially recovered after full regeneration of the tail. Although no changes in body or forelimb kinematics were evident, decreases in hindlimb joint angles signify a more sprawled posture following autotomy. Changes in hindlimb GRFs resulted in an increase in weight-specific propulsive force, without a corresponding change in locomotor speed. Hindlimb kinematics and GRFs following autotomy recovered to pre-autotomy values as the tail regenerated. These results suggest an active locomotor response to tail loss that demonstrates the causal relationships between variations in morphology, kinematics and force. © 2014. Published by The Company of Biologists Ltd.

Glide performance and aerodynamics of non-equilibrium glides in northern flying squirrels (Glaucomys sabrinus)

PubMed Central

Bahlman, Joseph W.; Swartz, Sharon M.; Riskin, Daniel K.; Breuer, Kenneth S.

2013-01-01

Gliding is an efficient form of travel found in every major group of terrestrial vertebrates. Gliding is often modelled in equilibrium, where aerodynamic forces exactly balance body weight resulting in constant velocity. Although the equilibrium model is relevant for long-distance gliding, such as soaring by birds, it may not be realistic for shorter distances between trees. To understand the aerodynamics of inter-tree gliding, we used direct observation and mathematical modelling. We used videography (60–125 fps) to track and reconstruct the three-dimensional trajectories of northern flying squirrels (Glaucomys sabrinus) in nature. From their trajectories, we calculated velocities, aerodynamic forces and force coefficients. We determined that flying squirrels do not glide at equilibrium, and instead demonstrate continuously changing velocities, forces and force coefficients, and generate more lift than needed to balance body weight. We compared observed glide performance with mathematical simulations that use constant force coefficients, a characteristic of equilibrium glides. Simulations with varying force coefficients, such as those of live squirrels, demonstrated better whole-glide performance compared with the theoretical equilibrium state. Using results from both the observed glides and the simulation, we describe the mechanics and execution of inter-tree glides, and then discuss how gliding behaviour may relate to the evolution of flapping flight. PMID:23256188

Glide performance and aerodynamics of non-equilibrium glides in northern flying squirrels (Glaucomys sabrinus).

PubMed

Bahlman, Joseph W; Swartz, Sharon M; Riskin, Daniel K; Breuer, Kenneth S

2013-03-06

Gliding is an efficient form of travel found in every major group of terrestrial vertebrates. Gliding is often modelled in equilibrium, where aerodynamic forces exactly balance body weight resulting in constant velocity. Although the equilibrium model is relevant for long-distance gliding, such as soaring by birds, it may not be realistic for shorter distances between trees. To understand the aerodynamics of inter-tree gliding, we used direct observation and mathematical modelling. We used videography (60-125 fps) to track and reconstruct the three-dimensional trajectories of northern flying squirrels (Glaucomys sabrinus) in nature. From their trajectories, we calculated velocities, aerodynamic forces and force coefficients. We determined that flying squirrels do not glide at equilibrium, and instead demonstrate continuously changing velocities, forces and force coefficients, and generate more lift than needed to balance body weight. We compared observed glide performance with mathematical simulations that use constant force coefficients, a characteristic of equilibrium glides. Simulations with varying force coefficients, such as those of live squirrels, demonstrated better whole-glide performance compared with the theoretical equilibrium state. Using results from both the observed glides and the simulation, we describe the mechanics and execution of inter-tree glides, and then discuss how gliding behaviour may relate to the evolution of flapping flight.