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1

Force treadmill for measuring vertical and horizontal ground reaction forces.  

UK PubMed Central (United Kingdom)

We constructed a force treadmill to measure the vertical, horizontal and lateral components of the ground-reaction forces (Fz, Fy, Fx, respectively) and the ground-reaction force moments (Mz, My, Mx), respectively exerted by walking and running humans. The chassis of a custom-built, lightweight (90 kg), mechanically stiff treadmill was supported along its length by a large commercial force platform. The natural frequencies of vibration were >178 Hz for Fz and >87 Hz for Fy, i.e., well above the signal content of these ground-reaction forces. Mechanical tests and comparisons with data obtained from a force platform runway indicated that the force treadmill recorded Fz, Fy, Mx and My ground-reaction forces and moments accurately. Although the lowest natural frequency of vibration was 88 Hz for Fx, the signal-to-noise ratios for Fx and Mz were unacceptable. This device greatly decreases the time and laboratory space required for locomotion experiments and clinical evaluations. The modular design allows for independent use of both treadmill and force platform.

Kram R; Griffin TM; Donelan JM; Chang YH

1998-08-01

2

A pilot study of the front foot ground reaction forces in elite female fast bowlers.  

UK PubMed Central (United Kingdom)

This pilot study aimed to determine the magnitude of ground reaction forces experienced by female cricket fast bowlers at front foot contact in the delivery stride of the bowling action. The peak vertical force, peak horizontal braking force and vertical loading rate were assessed in 15 elite Australian female fast bowlers. A sequential averaging procedure indicated that a mean of twelve trials (+/-2.8) were required to achieve performance stability across these ground reaction force variables and this demonstrated the importance of analyzing a sufficient number of trials to obtain representative data. The mean peak vertical ground reaction force was 3.49kN (+/-0.81) and the mean peak horizontal braking force was 2.13kN (+/-0.52). Statistical analyses revealed that differences in body mass explained only 2.3% of the variance in peak vertical force and 2.0% of the variance in peak horizontal braking force so normalization using body mass a covariate is not recommended when reporting front foot ground reaction forces in elite female fast bowlers. The mean time to the peak vertical force was 0.033s (+/-0.009) and the vertical loading rate was 121.31kNs(-1) (+/-73.78). Further work is required to determine the best ways to minimise and attenuate front foot ground reaction forces.

Stuelcken MC; Sinclair PJ

2009-03-01

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The influence of cricket fast bowlers' front leg technique on peak ground reaction forces.  

UK PubMed Central (United Kingdom)

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.

Worthington P; King M; Ranson C

2013-01-01

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BILATERAL GROUND REACTION FORCES AND JOINT MOMENTS FOR LATERAL SIDESTEPPING AND CROSSOVER STEPPING TASKS  

Directory of Open Access Journals (Sweden)

Full Text Available Racquet sports have high levels of joint injuries suggesting the joint loads during play may be excessive. Sports such as badminton employ lateral sidestepping (SS) and crossover stepping (XS) movements which so far have not been described in terms of biomechanics. This study examined bilateral ground reaction forces and three dimensional joint kinetics for both these gaits in order to determine the demands of the movements on the leading and trailing limb and predict the contribution of these movements to the occurrence of overuse injury of the lower limbs. A force platform and motion-analysis system were used to record ground reaction forces and track marker trajectories of 9 experienced male badminton players performing lateral SS, XS and forward running tasks at a controlled speed of 3 m·s-1 using their normal technique. Ground reaction force and kinetic data for the hip, knee and ankle were analyzed, averaged across the group and the biomechanical variables compared. In all cases the ground reaction forces and joint moments were less than those experienced during moderate running suggesting that in normal play SS and XS gaits do not lead to high forces that could contribute to increased injury risk. Ground reaction forces during SS and XS do not appear to contribute to the development of overuse injury. The distinct roles of the leading and trailing limb, acting as a generator of vertical force and shock absorber respectively, during the SS and XS may however contribute to the development of muscular imbalances which may ultimately contribute to the development of overuse injury. However it is still possible that faulty use of these gaits might lead to high loads and this should be the subject of future work

Gregor Kuntze; William I. Sellers; Neil J. Mansfield

2009-01-01

5

Analysis of kinematic data and determination of ground reaction force of foot in slow squat  

Science.gov (United States)

In the present paper, the ground reaction force (GRF) acting on foot in slow squat was determined through a force measuring system, and at the same time, the kinematic data of human squat were obtained by analyzing the photographed image sequences. According to the height and body weight, six healthy volunteers were selected, three men in one group and the other three women in another group, and the fundamental parameters of subjects were recorded, including body weight, height and age, etc. Based on the anatomy characteristics, some markers were placed on the right side of joints. While the subject squatted at slow speed on the force platform, the ground reaction forces on the forefoot and heel for each foot were obtained through calibrated force platform. The analysis results show that the reaction force on heel is greater than that on forefoot, and double feet have nearly constant force. Moreover, from processing and analyzing the synchronously photographed image sequences in squat, the kinematic data of human squat were acquired, including mainly the curves of angle, angular velocity and angular acceleration varied with time for knee, hip and ankle joints in a sagittal plane. The obtained results can offer instructive reference for photographing and analyzing the movements of human bodies, diagnosing some diseases, and establishing in the future appropriate mathematical models for the human motion.

Zhang, Xu-Shu; Guo, Yuan; An, Mei-Wen; Chen, Wei-Yi

2013-02-01

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Prediction of ground reaction forces during gait based on kinematics and a neural network model.  

UK PubMed Central (United Kingdom)

Kinetic information during human gait can be estimated with inverse dynamics, which is based on anthropometric, kinematic, and ground reaction data. While collecting ground reaction data with a force plate is useful, it is costly and requires regulated space. The goal of this study was to propose a new, accurate methodology for predicting ground reaction forces (GRFs) during level walking without the help of a force plate. To predict GRFs without a force plate, the traditional method of Newtonian mechanics was used for the single support phase. In addition, an artificial neural network (ANN) model was applied for the double support phase to solve statically indeterminate structure problems. The input variables of the ANN model, which were selected to have both dependency and independency, were limited to the trajectory, velocity, and acceleration of the whole segment's mass centre to minimise errors. The predicted GRFs were validated with actual GRFs through a ten-fold cross-validation method, and the correlation coefficients (R) for the ground forces were 0.918 in the medial-lateral axis, 0.985 in the anterior-posterior axis, and 0.991 in the vertical axis during gait. The ground moments were 0.987 in the sagittal plane, 0.841 in the frontal plane, and 0.868 in the transverse plane during gait. The high correlation coefficients(R) are due to the improvement of the prediction rate in the double support phase. This study also proved the possibility of calculating joint forces and moments based on the GRFs predicted with the proposed new hybrid method. Data generated with the proposed method may thus be used instead of raw GRF data in gait analysis and in calculating joint dynamic data using inverse dynamics.

Oh SE; Choi A; Mun JH

2013-09-01

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Isokinetic analysis of ankle and ground reaction forces in runners and triathletes  

Directory of Open Access Journals (Sweden)

Full Text Available OBJECTIVE: To analyze and compare the vertical component of ground reaction forces and isokinetic muscle parameters for plantar flexion and dorsiflexion of the ankle between long-distance runners, triathletes, and nonathletes. METHODS: Seventy-five males with a mean age of 30.26 (±6.5) years were divided into three groups: a triathlete group (n=26), a long-distance runner group (n = 23), and a non-athlete control group. The kinetic parameters were measured during running using a force platform, and the isokinetic parameters were measured using an isokinetic dynamometer. RESULTS: The non-athlete control group and the triathlete group exhibited smaller vertical forces, a greater ground contact time, and a greater application of force during maximum vertical acceleration than the long-distance runner group. The total work (180º/s) was greater in eccentric dorsiflexion and concentric plantar flexion for the non-athlete control group and the triathlete group than the long-distance runner group. The peak torque (60º/s) was greater in eccentric plantar flexion and concentric dorsiflexion for the control group than the athlete groups. CONCLUSIONS: The athlete groups exhibited less muscle strength and resistance than the control group, and the triathletes exhibited less impact and better endurance performance than the runners.

Natália Mariana Silva Luna; Angelica Castilho Alonso; Guilherme Carlos Brech; Luis Mochizuki; Eduardo Yoshio Nakano; Júlia Maria D'Andrea Greve

2012-01-01

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Isokinetic analysis of ankle and ground reaction forces in runners and triathletes  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english OBJECTIVE: To analyze and compare the vertical component of ground reaction forces and isokinetic muscle parameters for plantar flexion and dorsiflexion of the ankle between long-distance runners, triathletes, and nonathletes. METHODS: Seventy-five males with a mean age of 30.26 (±6.5) years were divided into three groups: a triathlete group (n=26), a long-distance runner group (n = 23), and a non-athlete control group. The kinetic parameters were measured during running (more) using a force platform, and the isokinetic parameters were measured using an isokinetic dynamometer. RESULTS: The non-athlete control group and the triathlete group exhibited smaller vertical forces, a greater ground contact time, and a greater application of force during maximum vertical acceleration than the long-distance runner group. The total work (180º/s) was greater in eccentric dorsiflexion and concentric plantar flexion for the non-athlete control group and the triathlete group than the long-distance runner group. The peak torque (60º/s) was greater in eccentric plantar flexion and concentric dorsiflexion for the control group than the athlete groups. CONCLUSIONS: The athlete groups exhibited less muscle strength and resistance than the control group, and the triathletes exhibited less impact and better endurance performance than the runners.

Luna, Natália Mariana Silva; Alonso, Angelica Castilho; Brech, Guilherme Carlos; Mochizuki, Luis; Nakano, Eduardo Yoshio; Greve, Júlia Maria D'Andrea

2012-09-01

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Isokinetic analysis of ankle and ground reaction forces in runners and triathletes.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To analyze and compare the vertical component of ground reaction forces and isokinetic muscle parameters for plantar flexion and dorsiflexion of the ankle between long-distance runners, triathletes, and nonathletes. METHODS: Seventy-five males with a mean age of 30.26 (±6.5) years were divided into three groups: a triathlete group (n=26), a long-distance runner group (n = 23), and a non-athlete control group. The kinetic parameters were measured during running using a force platform, and the isokinetic parameters were measured using an isokinetic dynamometer. RESULTS: The non-athlete control group and the triathlete group exhibited smaller vertical forces, a greater ground contact time, and a greater application of force during maximum vertical acceleration than the long-distance runner group. The total work (180º/s) was greater in eccentric dorsiflexion and concentric plantar flexion for the non-athlete control group and the triathlete group than the long-distance runner group. The peak torque (60º/s) was greater in eccentric plantar flexion and concentric dorsiflexion for the control group than the athlete groups. CONCLUSIONS: The athlete groups exhibited less muscle strength and resistance than the control group, and the triathletes exhibited less impact and better endurance performance than the runners.

Luna NM; Alonso AC; Brech GC; Mochizuki L; Nakano EY; Greve JM

2012-09-01

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GROUND REACTION FORCE DIFFERENCES BETWEEN RUNNING SHOES, RACING FLATS, AND DISTANCE SPIKES IN RUNNERS  

Directory of Open Access Journals (Sweden)

Full Text Available Various shoes are worn by distance runners throughout a training season. This study measured the differences in ground reaction forces between running shoes, racing flats, and distance spikes in order to provide information about the potential effects of footwear on injury risk in highly competitive runners. Ten male and ten female intercollegiate distance runners ran across a force plate at 6.7 m·s-1 (for males) and 5.7 m·s-1 (for females) in each of the three types of shoes. To control for differences in foot strike, only subjects who exhibited a heel strike were included in the data analysis. Two repeated-measures ANOVAs with Tukey's post-hoc tests (p < 0.05) were used to detect differences in shoe types among males and females. For the males, loading rate, peak vertical impact force and peak braking forces were significantly greater in flats and spikes compared to running shoes. Vertical stiffness in spikes was also significantly greater than in running shoes. Females had significantly shorter stance times and greater maximum propulsion forces in racing flats compared to running shoes. Changing footwear between the shoes used in this study alters the loads placed on the body. Care should be taken as athletes enter different phases of training where different footwear is required. Injury risk may be increased since the body may not be accustomed to the differences in force, stance time, and vertical stiffness

Suzanna Logan; Ian Hunter; J. Ty Hopkins; J.T., J. Brent Feland; Allen C. Parcell

2010-01-01

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Vertical Ground Reaction Force during Water Exercises Performed at Different Intensities.  

UK PubMed Central (United Kingdom)

The aim of the present study was to compare the peak vertical ground reaction force (V-GRFpeak) and impulse of women performing water aerobic exercises at different intensities in aquatic and dry land environments. 15 young women performed 1 session in each environment consisting of 3 water aerobic exercises (stationary running, frontal kick and cross country skiing) performed at 3 cadences (first ventilatory threshold, second ventilatory threshold and maximum effort, as determined during exercise in water) in a randomized order. 2-way and 3-way repeated measures ANOVA were used to analyze the impulse and V-GRFpeak, respectively. Significantly lower values of V-GRFpeak and impulse (p<0.001) were observed for the aquatic environment. Significant differences were observed among all cadences for V-GRFpeak and impulse (p<0.001) in both environments except for the V-GRFpeak between the cadences corresponding to the second ventilatory threshold and maximum effort in the aquatic environment. In addition, significantly lower V-GRFpeak values in the aquatic environment were found for cross country skiing compared to the other exercises (p<0.001). Thus, water exercises are safe for people that need to minimize vertical ground reaction force; however, an important issue to be considered during water aerobics training is the exercise and intensity to be prescribed.

Alberton CL; Tartaruga MP; Pinto SS; Cadore EL; Antunes AH; Finatto P; Kruel LF

2013-10-01

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Assessment of changes in gait parameters and vertical ground reaction forces after total hip arthroplasty  

Directory of Open Access Journals (Sweden)

Full Text Available The principal objectives of arthroplasty are relief of pain and enhancement of range of motion. Currently, postoperative pain and functional capacity are assessed largely on the basis of subjective evaluation scores. Because of the lack of control inherent in this method it is often difficult to interpret data presented by different observers in the critical evaluation of surgical method, new components and modes of rehabilitation. Gait analysis is a rapid, simple and reliable method to assess functional outcome. This study was undertaken in an effort to evaluate the gait characteristics of patients who underwent arthroplasty, using an Ultraflex gait analyzer. Materials and Methods: The study was based on the assessment of gait and weight-bearing pattern of both hips in patients who underwent total hip replacement and its comparison with an age and sex-matched control group. Twenty subjects of total arthroplasty group having unilateral involvement, operated by posterior approach at our institution with a minimum six-month postoperative period were selected. Control group was age and sex-matched, randomly selected from the general population. Gait analysis was done using Ultraflex gait analyzer. Gait parameters and vertical ground reaction forces assessment was done by measuring the gait cycle properties, step time parameters and VGRF variables. Data of affected limb was compared with unaffected limb as well as control group to assess the weight-bearing pattern. Statistical analysis was done by?t? test. Results: Frequency is reduced and gait cycle duration increased in total arthroplasty group as compared with control. Step time parameters including Step time, Stance time and Single support time are significantly reduced ( P value < .05) while Double support time and Single swing time are significantly increased ( P value < .05) in the THR group. Forces over each sensor are increased more on the unaffected limb of the THR group as compared to the control group. Vertical ground reaction force variables are also altered. Conclusion: Significant changes ( P value < .05) in gait parameters and vertical ground reaction forces show that gait pattern is not normalized after THR and weight-bearing is not equally shared by both hips. Patient walks with residual antalgic gait even after surgery, which results in abnormal loading around hip joints and the integrity of the prosthesis fixation could be compromised.

Bhargava P; Shrivastava P; Nagariya S

2007-01-01

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Cypriot and greek army military boot cushioning: ground reaction forces and subjective responses.  

UK PubMed Central (United Kingdom)

Lower limb injuries are a continual and serious issue for military personnel. Such injuries have been associated with the requirement to train in military boots (MBs) and might be offset with commercial insoles. In this study, ground reaction forces were measured in seven male participants wearing running shoes (RS), MBs commonly used by Cypriot and Greek Army personnel, and the MBs with two types of shock-absorbing insole. The participants performed 4-min trials at walking pace (5 km·h-1) and running pace (10 km·h-1) at a 5% gradient on a treadmill under all four shod conditions. The treadmill incorporated two force plates under its belt, which provided measurements of key kinetic variables. During walking, RS showed significantly lower values for impact peak force (p < 0.01), maximum force (p < 0.05), and push-off rate (p < 0.05) compared with other conditions, although no significant differences were found during running. Although the RS were rated significantly more comfortable than any other condition, neither insole made the MBs more comfortable to wear. With little evidence to support wholesale adoption of insoles in MBs, their use by military personnel can only be recommended on a case-by-case basis.

Paisis P; Hanley B; Havenetidis K; Bissas A

2013-04-01

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Characterization of human gait by means of body center of mass oscillations derived from ground reaction forces.  

UK PubMed Central (United Kingdom)

Ground reaction forces from two force plates are used to determine the cyclic oscillations of the body center of mass while walking at preferred speed. Good approximations to the oscillations may be obtained from formulae containing just the first- and second-order Fourier coefficients of the combined left-right ground reaction forces taken over a complete walking cycle. The symmetric components of the oscillations have consistent mutual phase relations for normal subjects, so that the amplitudes alone can be used as sufficient parameters to characterize the body center of mass oscillations. The analytical technique enables detection of small but consistent gait asymmetries.

Crowe A; Schiereck P; de Boer RW; Keessen W

1995-03-01

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Gender Differences among Sagittal Plane Knee Kinematic and Ground Reaction Force Characteristics during a Rapid Sprint and Cut Maneuver  

Science.gov (United States)

Women are more prone to anterior cruciate ligament (ACL) injury during cutting sports than men. The purpose of this study was to examine knee kinematic and ground reaction forces (GRF) differences between genders during cutting. Male and female athletes performed cutting trials while force platform and video data were recorded (180 Hz).…

James, C. Roger; Sizer, Phillip S.; Starch, David W.; Lockhart, Thurmon E.; Slauterbeck, James

2004-01-01

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Relationships of body weight, body size, subject velocity, and vertical ground reaction forces in trotting dogs.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To evaluate the relationship of body weight (BW) and size, dog velocity, and vertical ground reaction forces (GRF) from a large number of dogs of various sizes. STUDY DESIGN: Clinical research. ANIMALS: Orthopedically healthy dogs (n=129) METHODS: BW and dog size, represented as height at the withers (WH), were obtained. Stance times (ST), vertical impulses (VI), and peak vertical forces (PVF) of thoracic and pelvic limbs were measured on a force plate at controlled trotting speed. They were evaluated against BW and WH using linear regression analysis in absolute (nonnormalized) values, and when normalized to BW and/or body size according to the theory of dynamic similarity. Relative velocities were calculated for each dog. RESULTS: Absolute ST, VI, and PVF showed strong positive correlations with BW and/or body size. When GRFs were normalized to BW, correlations with body size were markedly reduced, but remained positive for VI, and turned negative for PVF. Normalizing the time-dependent variables (ST and VI) also to WH eliminated most size influence. A small dependency of fully normalized GRF on body size remained that was because of differences in relative velocity between dogs of different sizes. Reference values for the fully normalized data are given. CONCLUSIONS: The inherent relationship between BW, body size, dog velocity, and vertical GRF was demonstrated. CLINICAL RELEVANCE: BW, body size, and relative dog velocity must be accounted for when wanting to obtain GRF variables that are comparable between different dogs.

Voss K; Galeandro L; Wiestner T; Haessig M; Montavon PM

2010-10-01

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Comparison of Ground Reaction Force Asymmetry in One- and Two-legged Countermovement Jumps.  

UK PubMed Central (United Kingdom)

Benjanuvatra, N, Lay, BS, Alderson, JA, and Blanksby, BA. Comparison of ground reaction force asymmetry in one- and two-legged countermovement jumps. J Strength Cond Res 27(10): 2700-2707, 2013-This study examined whether ground reaction force (GRF) asymmetry of 2-legged countermovement jumps (CMJ) is related to 1-legged CMJ asymmetry. The GRF asymmetry of a 2-legged CMJ has been suggested as a preferred test to the 1-legged CMJ for functional strength and power deficit assessment. Twenty-eight men and 30 women performed 5 trials each of a 1-legged CMJ with the right limband the left limb, and a 2-legged CMJ. Vertical GRFs were collected from each lower limb using 2 force platforms. Although several GRF variables were calculated, vertical impulse correlated most strongly with jump height in all conditions (p < 0.05), and they were used in subsequent analyses. A moderate correlation was found for impulse asymmetry between the 1- and 2-legged CMJs for women (r = 0.45, p < 0.05), but not for men (r = 0.06, p = 0.76). In contrast, cross-tabulation analyses of subjects presented with the same dominant characteristics in the 1- and 2-legged CMJs revealed poor associations for both men (Freeman-Halton exact p = 0.61) and women (Freeman-Halton exact p = 0.19). Only 11 women recorded the same dominant limb for both 1- and 2-legged CMJs. This suggests that impulse asymmetries found in the 1- and 2-legged CMJ were unrelated. As the 1-legged CMJ relies on the extension forces generated entirely from 1 limb, variations in jump heights and GRF impulses by left and right limbs separately were more indicative of functional strength differences between sides. Hence, it is recommended that the 1-legged CMJ is used when examining functional strength asymmetry in the lower limbs. In contrast, factors causing asymmetry in GRF impulses during 2-legged CMJs are more complicated and require further investigation.

Benjanuvatra N; Lay BS; Alderson JA; Blanksby BA

2013-10-01

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A rolling constraint reproduces ground reaction forces and moments in dynamic simulations of walking, running, and crouch gait.  

UK PubMed Central (United Kingdom)

Recent advances in computational technology have dramatically increased the use of muscle-driven simulation to study accelerations produced by muscles during gait. Accelerations computed from muscle-driven simulations are sensitive to the model used to represent contact between the foot and ground. A foot-ground contact model must be able to calculate ground reaction forces and moments that are consistent with experimentally measured ground reaction forces and moments. We show here that a rolling constraint can model foot-ground contact and reproduce measured ground reaction forces and moments in an induced acceleration analysis of muscle-driven simulations of walking, running, and crouch gait. We also illustrate that a point constraint and a weld constraint used to model foot-ground contact in previous studies produce inaccurate reaction moments and lead to contradictory interpretations of muscle function. To enable others to use and test these different constraint types (i.e., rolling, point, and weld constraints) we have included them as part of an induced acceleration analysis in OpenSim, a freely-available biomechanics simulation package.

Hamner SR; Seth A; Steele KM; Delp SL

2013-06-01

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Ground reaction force in basketball cutting maneuvers with and without ankle bracing and taping.  

UK PubMed Central (United Kingdom)

CONTEXT AND OBJECTIVE: In basketball, the most common injuries are ankle sprains. For this reason, players frequently use external ankle devices or taping as prophylactic and rehabilitation measures. The purpose of this study was to evaluate ground reaction force (GRF) responses in basketball players while performing typical cutting maneuvers with and without ankle bracing and ankle taping. DESIGN AND SETTING: Comparative study with experimental design of single-group repeated measurements, at Medical Rehabilitation Division, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo. METHODS: Vertical (Fy) and medial-lateral (Fz) GRF measurements were made under three conditions (taping, Aircast-type orthosis and basketball shoes alone), with analysis of peak forces at foot contact (Fymax1, Fzmax1, Fymax2 and Fzmax2), growth gradient (peak/time) (GG Fymax1, GG Fzmax1, GG Fymax2 and GG Fzmax2) and impulse after foot contact. RESULTS: Bracing significantly reduced Fymax2 and GG Fymax2. GG Fzmax1 was significantly higher for the sport shoe condition than for the taping condition. Taping increased Fy in relation to the sport shoe at foot contact, but over a longer time interval, without increasing excessive ankle loading. Fz reached a peak in less time, which might generate greater inversion/eversion loading on a player's foot. The Aircast exerted better shock-absorbing effect than did the other two conditions, since it generated less vertical force over longer time intervals and smaller medial-lateral forces in relation to taping. CONCLUSIONS: Ankle bracing and ankle taping action mechanisms are still unclear and therefore should be carefully prescribed. More studies are needed to clarify taping and bracing effects on sporting activities.

Sacco Ide C; Takahasi HY; Suda EY; Battistella LR; Kavamoto CA; Lopes JA; Vasconcelos JC

2006-09-01

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Ground reaction forces associated with an effective elementary school based jumping intervention  

Science.gov (United States)

Background: Mechanical loading during childhood plays a critical role in normal growth and development of the skeleton. Ground reaction forces (GRFs) may provide a surrogate measure for the strain experienced by bone on landing and at take off. However, there appear to be no paediatric studies that assess GRFs across a variety of loading activities. Objectives: To measure biomechanical variables in commonly performed childhood activities used in an elementary physical education intervention study which augmented bone health in boys and girls. Methods: Maximal GFR, maximal rates of force, and time to maximum force were measured for 12 different jumping activities on a force platform. The jumps measured were drop jumps from 10, 30, and 50 cm, all followed by a plyometric jump, submaximal and maximal jumping jacks, alternating feet jump, counter movement jumps, and side to side jumps over 10 and 20 cm foam barriers. The subjects were 70 children (36 boys and 34 girls), 8.3–11.7 years old. Results: Subjects ranged in height from 128.4 to 172.6 cm and had a mass of 25.0–57.0 kg. Mean (SD) for vertical jump was 24.2 (5.5) cm and 135.2 (16.6) cm for standing long jump. The children engaged in loaded physical activity 5.7 (5.3) hours a week, on average. The highest mean maximal GRFs, normalised for body weight (BW), were generated from the plyometric portion of the drop jumps and the counter movement jump (about 5 times BW) compared with 3.5 times BW for jumping jacks. Similarly, the highest rates of change in force were 514 times BW/s for the drop jump from 10 cm and 493 times BW/s for the counter movement jump. Conclusions: Simple jumps requiring minimal equipment produce GRFs of 3.5–5 times BW and rates of force of around 500 times BW/s. As children appear to attenuate higher impact forces when jumping from increased heights, it cannot be assumed that merely increasing the height of the jump will necessarily "progress" the exercise intervention.

McKay, H; Tsang, G; Heinonen, A; MacKelvie, K; Sanderson, D; Khan, K

2005-01-01

 
 
 
 
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Effects of slip-induced changes in ankle movement on muscle activity and ground reaction forces during running acceleration  

DEFF Research Database (Denmark)

Ground contact in running is always linked to a minimum amount of slipping, e.g., during the early contact phase when horizontal forces are high compared to vertical forces. Studies have shown altered muscular activation when expecting slips [2-4]. It is not known what the mechanical effect of such slip episodes are on joint loading or performance. The aim of the present study was to examine the effect of changes in ankle movement on ankle joint loading, muscle activity, and ground reaction forces during linear acceleration.

Ketabi, Shahin; Kersting, Uwe G.

2013-01-01

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Ground reaction force and electromyographic activity of transfemoral amputee gait: a case series  

Directory of Open Access Journals (Sweden)

Full Text Available Ground reaction forces (GRF) and electromyographic activity form a part of the descriptive data that characterise the biomechanics of gait. The research of these parameters is important in establishing gait training and understanding the impact of amputation and prosthetic components on movement during the act of walking. Therefore, this case series describes the GRF and electromyographic activity in the gait of transfemoral amputees. A force plate was used to measure GRF, and an electromyographic system monitored the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius lateralis muscles of the non-amputated leg. The average vertical and anteroposterior GRF time-curves, average electromyographic activity, and descriptor variables were then analysed. We observed decreases in vertical and anteroposterior GRF magnitudes as well as in anteroposterior GRF descriptor variables during the propulsive phase in the amputated leg. There were increases in phasic muscle activity and co-activation in the non-amputated leg. We concluded that, during walking, the unilateral transfemoral amputees (who were analysed in this case series) developed lower GRF in the amputated limb and a longer period of electromyographic activity in the non-amputated limb.

Alex Sandra Oliveira de Cerqueira; Edward Yuji Yamaguti; Luis Mochizuki; Alberto Carlos Amadio; Júlio Cerca Serrão

2013-01-01

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Estimating Youth Locomotion Ground Reaction Forces Using an Accelerometer-Based Activity Monitor  

Science.gov (United States)

To address a variety of questions pertaining to the interactions between physical activity, musculoskeletal loading and musculoskeletal health/injury/adaptation, simple methods are needed to quantify, outside a laboratory setting, the forces acting on the human body during daily activities. The purpose of this study was to develop a statistically based model to estimate peak vertical ground reaction force (pVGRF) during youth gait. 20 girls (10.9±0.9 years) and 15 boys (12.5±0.6 years) wore a Biotrainer AM over their right hip. Six walking and six running trials were completed after a standard warm-up. Average AM intensity (g) and pVGRF (N) during stance were determined. Repeated measures mixed effects regression models to estimate pVGRF from Biotrainer activity monitor acceleration in youth (girls 10–12, boys 12–14 years) while walking and running were developed. Log transformed pVGRF had a statistically significant relationship with activity monitor acceleration, centered mass, sex (girl), type of locomotion (run), and locomotion type-acceleration interaction controlling for subject as a random effect. A generalized regression model without subject specific random effects was also developed. The average absolute differences between the actual and predicted pVGRF were 5.2% (1.6% standard deviation) and 9% (4.2% standard deviation) using the mixed and generalized models, respectively. The results of this study support the use of estimating pVGRF from hip acceleration using a mixed model regression equation.

Neugebauer, Jennifer M.; Hawkins, David A.; Beckett, Laurel

2012-01-01

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The Effects of Opposition and Gender on Knee Kinematics and Ground Reaction Force during Landing from Volleyball Block Jumps  

Science.gov (United States)

The aim of this study was to examine the effect of opposition and gender on knee kinematics and ground reaction force during landing from a volleyball block jump. Six female and six male university volleyball players performed two landing tasks: (a) an unopposed and (b) an opposed volleyball block jump and landing. A 12-camera motion analysis…

Hughes, Gerwyn; Watkins, James; Owen, Nick

2010-01-01

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A Comparison of Accelerometers for Predicting Energy Expenditure and Vertical Ground Reaction Force in School-Age Children  

Science.gov (United States)

In this pilot study of 16 children, we evaluated the reliability and validity of three accelerometers (Mini-Motionlogger [MML], Computer Science Applications, Inc. Actigraph [CSA], and BioTrainer) as indicators of energy expenditure and vertical ground reaction force. The children wore 2 of each type of monitor while they walked, ran, and…

Garcia, Anne W.; Langenthal, Carla R.; Angulo-Barroso, Rosa M.; Gross, M. Melissa

2004-01-01

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Effect of plantar flexion and eversion on mediolateral ground reaction force in subjects with functional ankle instability  

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Full Text Available Abstract   Background and Aim: The common mechanism for lateral ankle sprain is inversion, plantar flexion, or the combination of both, if untreated successfully can lead to chronic ankle instability. It seems that the foot position, while touching the ground, has an effective role to cause ankle sprain. Thus it is possible to prevent ankle sprain through limiting foot position. Therefore the aim of this research is to study the effect of plantar flexion and eversion on mediolateral ground reaction force while landing in individuals who suffering from functional ankle instability.    Materials and Methods: In this case-control research study 32 subjects (17 subjects with unilateral functional ankle instability (FAI) and 15 control subjects), aged from 18 to 35 years, were tested. All subjects in instability group were selected by the orthopedic physician, then the anterior drawer and talar tilt tests were  performed for diagnosis of functional ankle instability and other physical examinations. Control group were matched with instability group by age, weight, height, gender and body mass index. The subjects standing with single leg on a 40 cm high platform in 25 cm front of a force-plate while the test leg relaxed and non-weight bearing. The subject landed on the test leg on the center of the force-plate. The subjects landed according to four types of position: A: neutral position of ankle and lateral foot wedge, B: neutral position of ankle, C: positive heel and lateral foot wedge and D: positive heel.   Results: Among control group, medial ground reaction force increased in the "C" position relative to "B" position (p=0.007) and "C" position relative to "D" position (p=0.018). In FAI group, lateral ground reaction force increased in "C" position relative to "B" position (p=0.001) and "C" position relative to "A" position (p=0.002). Also in FAI group medial ground reaction force decreased in "D" position relative to "A" position (p=0.014).   Conclusion: According to the findings, applying lateral foot wedge, while the ankle is in plantar flexion, increases the mediolateral ground reaction forces. Based on the results, position of plantar flexion is more possibly effective than inversion in ankle sprain. According to the study, the lateral foot wedge in ankle plantar flexion position may be more effective than in neutral one to change mediolateral ground reaction forces.   Key words: Functional ankle instability, Position of foot, Landing, Lateral foot wedge  

Nesar Yousefi; Ali Amiri; Ali Ashraf Jamshidi; Mojtaba Kamyab

2012-01-01

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Using ground reaction force to predict knee kinetic asymmetry following anterior cruciate ligament reconstruction.  

UK PubMed Central (United Kingdom)

Asymmetries in sagittal plane knee kinetics have been identified as a risk factor for anterior cruciate ligament (ACL) re-injury. Clinical tools are needed to identify the asymmetries. This study examined the relationships between knee kinetic asymmetries and ground reaction force (GRF) asymmetries during athletic tasks in adolescent patients following ACL reconstruction (ACL-R). Kinematic and GRF data were collected during a stop-jump task and a side-cutting task for 23 patients. Asymmetry indices between the surgical and non-surgical limbs were calculated for GRF and knee kinetic variables. For the stop-jump task, knee kinetics asymmetry indices were correlated with all GRF asymmetry indices (P?

Dai B; Butler RJ; Garrett WE; Queen RM

2013-09-01

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Ground Reaction Force Calcaneal Offset: A new measurement of hindfoot alignment.  

UK PubMed Central (United Kingdom)

BACKGROUND: The tibio-calcaneal angle (TCA) does not measure individual forefoot contributions to the overall foot balance. Using standard radiographs we calculated the ideal hindfoot alignment based on ground reaction force (GRF), independently from the tibial axis. METHODS: Thirty-six patients (40ft.) were included. Mean age was 56. Weight bearing radiographs were taken. Calcaneal offsets were measured using tibio-calcaneal angles and GRF algorithms. Measurements were compared using the Bland-Altman method. FINDINGS: Both methods agreed (p>0.05) but individual discrepancies were found. Mean measured offsets were -11.5mm (SD: 10.2) using TCA and -8mm (SD: 9.3) using GRF. Mean bias between the methods was -0.88mm. INTERPRETATION: The GRF algorithm successfully measured hindfoot alignment. The absence of a previous gold standard and radiographic variability are a limit. The TCA underestimated calcaneal offset. Discrepancies showed that forefoot position data provided increased accuracy. This could be of particular relevance for surgical planning.

Lintz F; Barton T; Millet M; Harries WJ; Hepple S; Winson IG

2012-03-01

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Estimation of ground reaction force and zero moment point on a powered ankle-foot prosthesis.  

UK PubMed Central (United Kingdom)

The ground reaction force (GRF) and the zero moment point (ZMP) are important parameters for the advancement of biomimetic control of robotic lower-limb prosthetic devices. In this document a method to estimate GRF and ZMP on a motorized ankle-foot prosthesis (MIT Powered Ankle-Foot Prosthesis) is presented. The method proposed is based on the analysis of data collected from a sensory system embedded in the prosthetic device using a custom designed wearable computing unit. In order to evaluate the performance of the estimation methods described, standing and walking clinical studies were conducted on a transtibial amputee. The results were statistically compared to standard analysis methodologies employed in a gait laboratory. The average RMS error and correlation factor were calculated for all experimental sessions. By using a static analysis procedure, the estimation of the vertical component of GRF had an averaged correlation coefficient higher than 0.94. The estimated ZMP location had a distance error of less than 1 cm, equal to 4% of the anterior-posterior foot length or 12% of the medio-lateral foot width.

Martinez-Villalpando EC; Herr H; Farrell M

2007-01-01

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A COMPARISON OF GOLF SHOE DESIGNS HIGHLIGHTS GREATER GROUND REACTION FORCES WITH SHORTER IRONS  

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Full Text Available In an effort to reduce golf turf damage the traditional metal spike golf shoe has been redesigned, but shoe-ground biomechanical evaluations have utilised artificial grass surfaces. Twenty-four golfers wore three different golf shoe traction designs (traditional metal spikes, alternative spikes, and a flat-soled shoe with no additional traction) when performing shots with a driver, 3 iron and 7 iron. Ground action forces were measured beneath the feet by two natural grass covered force platforms. The maximum vertical force recorded at the back foot with the 3 iron and 7 iron was 0.82 BW (body weight) and at the front foot 1.1 BW approximately in both the metal spike and alternative spike golf shoe designs. When using the driver these maximal vertical values were 0.49 BW at the back foot and 0.84 BW at the front foot. Furthermore, as performance of the backswing and then downswing necessitates a change in movement direction the range of force generated during the complete swing was calculated. In the metal spike shoe the vertical force generated at the back foot with both irons was 0.67 BW and at the front foot 0.96 BW with the 3 iron and 0.92 BW with the 7 iron. The back foot vertical force generated with the driver was 0.33 BW and at the front foot 0.83 BW wearing the metal spike shoe. Results indicated the greater force generation with the irons. When using the driver the more horizontal swing plane associated with the longer club reduced vertical forces at the back and front foot. However, the mediolateral force generated across each foot in the metal and alternative spike shoes when using the driver was greater than when the irons were used. The coefficient of friction was 0. 62 at the back and front foot whichever shoe was worn or club used

Paul Worsfold; Neal A. Smith; Rosemary J. Dyson

2007-01-01

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Functional knee brace use effect on peak vertical ground reaction forces during drop jump landing.  

UK PubMed Central (United Kingdom)

PURPOSE: The aim of the study was to investigate the landing strategies used by non-injured athletes while wearing functional knee braces (FKB, BR condition) during a drop jump task compared with non-injured, non-braced (NBR condition) subjects and also to ascertain whether accommodation to a FKB was possible by non-injured BR subjects. METHODS: Twenty-three healthy male provincial and national basketball and field hockey athletes (age, 19.4 ± 3.0 years) were tested. Each subject was provided with a custom-fitted FKB. Five NBR testing sessions were performed over 3 days followed by five BR testing sessions also over 3 days, for a total of 17.5 h of testing per condition. Each subject performed eight trials of the drop jump task during each testing session per condition. Single-leg peak vertical ground reaction forces (PVGRF) and the time to PVGRF were recorded for each NBR and BR trail. RESULTS: The BR group mean PVGRF at landing was significantly lower (1,628 ± 405 N, 2.1 ± 0.5 BW versus 1,715 ± 403 N, 2.2 ± 0.5 BW, F (1,22) = 6.83, P = 0.01) compared with NBR subjects, respectively. The group mean time to PVGRF was not statistically longer during the BR condition (F (1,22) = 0.967, P = 0.3). Further, an accommodation trend was noted as percent performance difference decreased with continued FKB use. CONCLUSIONS: The significantly lower group mean PVGRF while using a FKB could keep traumatic forces from reaching the ACL until the active neuromuscular restraints are activated to provide protection to the knee joint ligaments. Also, accommodation to FKB is possible after approximately 14.0 h of brace use. The results of this paper will assist clinicians in providing information to their patients regarding a FKB ability to offer protection to an ACL-deficient knee or to address concerns about early muscle fatigue, energy expenditure, heart rate, and decrease in performance level. LEVEL OF EVIDENCE: Prospective study, Level I.

Rishiraj N; Taunton JE; Lloyd-Smith R; Regan W; Niven B; Woollard R

2012-02-01

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Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces  

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Full Text Available Abstract Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS-) model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT-) and magnetic resonance imaging- (MRI-) data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s) on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction) calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in silico development and testing of hip prostheses.

Helms Gabriele; Behrens Bernd-Arno; Stolorz Martin; Wefstaedt Patrick; Nolte Ingo

2009-01-01

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Withdrawal reflexes examined during human gait by ground reaction forces: site and gait phase dependency.  

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The objective of this study was to investigate the modulation of the nociceptive withdrawal reflex during gait measured using Force Sensitive Resistors (FSR). Electrical stimulation was delivered to four locations on the sole of the foot at three different time points between heel-off and toe-off. Peak force changes were measured by FSRs attached to the big toe, distal to the first and fourth metatarsophalangeal joints, and the medial process of the calcaneus on both feet. Force changes were assessed in five gait sub-phases. The painful stimulation led to increased ipsilateral unloading (10 +/- 1 N) and contralateral loading (12 +/- 1 N), which were dependent on stimulation site and phase. In contrast, the hallux of the ipsilateral foot plantar flexed, thus facilitating the push-off. The highest degree of plantar flexion (23 +/- 10 N; range, 8-44 N) was seen in the second double support phase following the stimulation. Site and phase modulation of the reflex were detected in the force signals from all selected anatomical landmarks. In the kinematic responses, both site and phase modulation were observed. For stimulations near toe-off, withdrawal was primarily accomplished by ankle dorsiflexion, while the strategy for stimulations at heel-off was flexion of the knee and hip joints. PMID:18830656

Emborg, Jonas; Spaich, Erika G; Andersen, Ole K

2008-10-01

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Withdrawal reflexes examined during human gait by ground reaction forces: site and gait phase dependency.  

UK PubMed Central (United Kingdom)

The objective of this study was to investigate the modulation of the nociceptive withdrawal reflex during gait measured using Force Sensitive Resistors (FSR). Electrical stimulation was delivered to four locations on the sole of the foot at three different time points between heel-off and toe-off. Peak force changes were measured by FSRs attached to the big toe, distal to the first and fourth metatarsophalangeal joints, and the medial process of the calcaneus on both feet. Force changes were assessed in five gait sub-phases. The painful stimulation led to increased ipsilateral unloading (10 +/- 1 N) and contralateral loading (12 +/- 1 N), which were dependent on stimulation site and phase. In contrast, the hallux of the ipsilateral foot plantar flexed, thus facilitating the push-off. The highest degree of plantar flexion (23 +/- 10 N; range, 8-44 N) was seen in the second double support phase following the stimulation. Site and phase modulation of the reflex were detected in the force signals from all selected anatomical landmarks. In the kinematic responses, both site and phase modulation were observed. For stimulations near toe-off, withdrawal was primarily accomplished by ankle dorsiflexion, while the strategy for stimulations at heel-off was flexion of the knee and hip joints.

Emborg J; Spaich EG; Andersen OK

2009-01-01

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Gait Phases Recognition from Accelerations and Ground Reaction Forces: Application of Neural Networks  

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Full Text Available The goal of this study was to test the applicability of accelerometer as the sensor for assessment of the walking. We present here the comparison of gait phases detected from the data recorded by force sensing resistors mounted in the shoe insoles, non-processed acceleration and processed acceleration perpendicular to the direction of the foot. The gait phases in all three cases were detected by means of a neural network. The output from the neural network was the gait phase, while the inputs were data from the sensors. The results show that the errors were in the ranges: 30 ms (2.7%) – force sensors; 150 ms (13.6%) – nonprocessed acceleration, and 120 ms (11%) – processed acceleration data. This result suggests that it is possible to use the accelerometer as the gait phase detector, however, with the knowledge that the gait phases are time shifted for about 100 ms with respect the neural network predicted times.

N. Mijailovi?; M. Gavrilovi?; S. Rafajlovi?

2009-01-01

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The influence of heel height on vertical ground reaction force during landing tasks in recreationally active and athletic collegiate females.  

UK PubMed Central (United Kingdom)

PURPOSE: To determine if heel height alters vertical ground reaction forces (vGRF) when landing from a forward hop or drop landing. BACKGROUND: Increased vGRF during landing are theorized to increase ACL injury risk in female athletes. METHODS: Fifty collegiate females performed two single-limb landing tasks while wearing heel lifts of three different sizes (0, 12 & 24 mm) attached to the bottom of a athletic shoe. Using a force plate, peak vGRF at landing was examined. Repeated measures ANOVAs were used to determine the influence of heel height on the dependent measures. RESULTS: Forward hop task- Peak vGRF (normalized for body mass) with 0 mm, 12 mm, and 24 mm lifts were 2.613±0.498, 2.616±0.497 and 2.495±0.518% BW, respectively. Significant differences were noted between 0 and 24 mm lift (p<.001) and 12 and 24 mm lifts (p=.004), but not between the 0 and 12 mm conditions (p=.927). Jump-landing task- No significant differences were found in peak vGRF (p=.192) between any of the heel lift conditions. CONCLUSIONS: The addition of a 24 mm heel lift to the bottom of a sneaker significantly alters peak vGRF upon landing from a unilateral forward hop but not from a jumping maneuver.

Lindenberg KM; Carcia CR

2013-02-01

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A neural network model to predict knee adduction moment during walking based on ground reaction force and anthropometric measurements.  

UK PubMed Central (United Kingdom)

The external knee adduction moment (KAM) is a major variable for the evaluation of knee loading during walking, specifically in patients with knee osteoarthritis. However, assessment of the KAM is limited to locations where full motion laboratories are available. The purpose of this study was to develop and test a simple method to predict the KAM using only force plate and anthropometric measurements. Three groups of 28 knees (asymptomatic, mild osteoarthritis, and severe osteoarthritis) were studied. Walking trials were collected at different speeds using a motion capture system and a force plate. The reference KAM was calculated by inverse dynamics. For the prediction, inter-subject artificial neural networks were designed using 11 inputs coming from the ground reaction force and the mechanical axis alignment. The predicted KAM curves were similar to the reference curves with median mean absolute deviation (MAD) of 0.36%BW*Ht and median correlation coefficient of 0.966 over 756 individual trials. When comparing mean group curves, the median MAD was 0.09%BW*Ht and the median correlation coefficient 0.998. The peak values and the angular impulses extracted from the predicted and reference curves were significantly correlated, and the same significant differences were obtained among the three groups when the predicted or when the reference curves were used for 95% of the comparisons. In conclusion, this study demonstrated that a simple method using a generic artificial neural network can predict the KAM curve during walking with a high level of significance and provides a practical option for a broader evaluation of the KAM.

Favre J; Hayoz M; Erhart-Hledik JC; Andriacchi TP

2012-02-01

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A neural network model to predict knee adduction moment during walking based on ground reaction force and anthropometric measurements.  

Science.gov (United States)

The external knee adduction moment (KAM) is a major variable for the evaluation of knee loading during walking, specifically in patients with knee osteoarthritis. However, assessment of the KAM is limited to locations where full motion laboratories are available. The purpose of this study was to develop and test a simple method to predict the KAM using only force plate and anthropometric measurements. Three groups of 28 knees (asymptomatic, mild osteoarthritis, and severe osteoarthritis) were studied. Walking trials were collected at different speeds using a motion capture system and a force plate. The reference KAM was calculated by inverse dynamics. For the prediction, inter-subject artificial neural networks were designed using 11 inputs coming from the ground reaction force and the mechanical axis alignment. The predicted KAM curves were similar to the reference curves with median mean absolute deviation (MAD) of 0.36%BW*Ht and median correlation coefficient of 0.966 over 756 individual trials. When comparing mean group curves, the median MAD was 0.09%BW*Ht and the median correlation coefficient 0.998. The peak values and the angular impulses extracted from the predicted and reference curves were significantly correlated, and the same significant differences were obtained among the three groups when the predicted or when the reference curves were used for 95% of the comparisons. In conclusion, this study demonstrated that a simple method using a generic artificial neural network can predict the KAM curve during walking with a high level of significance and provides a practical option for a broader evaluation of the KAM. PMID:22257888

Favre, Julien; Hayoz, Matthieu; Erhart-Hledik, Jennifer C; Andriacchi, Thomas P

2012-01-16

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Ground reaction forces and center of mass mechanics of bipedal capuchin monkeys: implications for the evolution of human bipedalism.  

Science.gov (United States)

Tufted capuchin monkeys are known to use both quadrupedalism and bipedalism in their natural environments. Although previous studies have investigated limb kinematics and metabolic costs, their ground reaction forces (GRFs) and center of mass (CoM) mechanics during two and four-legged locomotion are unknown. Here, we determine the hind limb GRFs and CoM energy, work, and power during bipedalism and quadrupedalism over a range of speeds and gaits to investigate the effect of differential limb number on locomotor performance. Our results indicate that capuchin monkeys use a "grounded run" during bipedalism (0.83-1.43 ms(-1)) and primarily ambling and galloping gaits during quadrupedalism (0.91-6.0 ms(-1)). CoM energy recoveries are quite low during bipedalism (2-17%), and in general higher during quadrupedalism (4-72%). Consistent with this, hind limb vertical GRFs as well as CoM work, power, and collisional losses are higher in bipedalism than quadrupedalism. The positive CoM work is 2.04 ± 0.40 Jkg(-1) m(-1) (bipedalism) and 0.70 ± 0.29 Jkg(-1) m(-1) (quadrupedalism), which is within the range of published values for two and four-legged terrestrial animals. The results of this study confirm that facultative bipedalism in capuchins and other nonhuman primates need not be restricted to a pendulum-like walking gait, but rather can include running, albeit without an aerial phase. Based on these results and similar studies of other facultative bipeds, we suggest that important transitions in the evolution of hominin locomotor performance were the emergences of an obligate, pendulum-like walking gait and a bouncy running gait that included a whole-body aerial phase. PMID:23124531

Demes, Brigitte; O'Neill, Matthew C

2012-11-02

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Ground reaction forces and center of mass mechanics of bipedal capuchin monkeys: implications for the evolution of human bipedalism.  

UK PubMed Central (United Kingdom)

Tufted capuchin monkeys are known to use both quadrupedalism and bipedalism in their natural environments. Although previous studies have investigated limb kinematics and metabolic costs, their ground reaction forces (GRFs) and center of mass (CoM) mechanics during two and four-legged locomotion are unknown. Here, we determine the hind limb GRFs and CoM energy, work, and power during bipedalism and quadrupedalism over a range of speeds and gaits to investigate the effect of differential limb number on locomotor performance. Our results indicate that capuchin monkeys use a "grounded run" during bipedalism (0.83-1.43 ms(-1)) and primarily ambling and galloping gaits during quadrupedalism (0.91-6.0 ms(-1)). CoM energy recoveries are quite low during bipedalism (2-17%), and in general higher during quadrupedalism (4-72%). Consistent with this, hind limb vertical GRFs as well as CoM work, power, and collisional losses are higher in bipedalism than quadrupedalism. The positive CoM work is 2.04 ± 0.40 Jkg(-1) m(-1) (bipedalism) and 0.70 ± 0.29 Jkg(-1) m(-1) (quadrupedalism), which is within the range of published values for two and four-legged terrestrial animals. The results of this study confirm that facultative bipedalism in capuchins and other nonhuman primates need not be restricted to a pendulum-like walking gait, but rather can include running, albeit without an aerial phase. Based on these results and similar studies of other facultative bipeds, we suggest that important transitions in the evolution of hominin locomotor performance were the emergences of an obligate, pendulum-like walking gait and a bouncy running gait that included a whole-body aerial phase.

Demes B; O'Neill MC

2013-01-01

 
 
 
 
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A Wearable Ground Reaction Force Sensor System and Its Application to the Measurement of Extrinsic Gait Variability  

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Full Text Available Wearable sensors for gait analysis are attracting wide interest. In this paper, a wearable ground reaction force (GRF) sensor system and its application to measure extrinsic gait variability are presented. To validate the GRF and centre of pressure (CoP) measurements of the sensor system and examine the effectiveness of the proposed method for gait analysis, we conducted an experimental study on seven volunteer subjects. Based on the assessment of the influence of the sensor system on natural gait, we found that no significant differences were found for almost all measured gait parameters (p-values < 0.05). As for measurement accuracy, the root mean square (RMS) differences for the two transverse components and the vertical component of the GRF were 7.2% ± 0.8% and 9.0% ± 1% of the maximum of each transverse component and 1.5% ± 0.9% of the maximum vertical component of GRF, respectively. The RMS distance between both CoP measurements was 1.4% ± 0.2% of the length of the shoe. The area of CoP distribution on the foot-plate and the average coefficient of variation of the triaxial GRF, are the introduced parameters for analysing extrinsic gait variability. Based on a statistical analysis of the results of the tests with subjects wearing the sensor system, we found that the proposed parameters changed according to walking speed and turning (p-values < 0.05).

Tao Liu; Yoshio Inoue; Kyoko Shibata

2010-01-01

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Does wearing a prophylactic ankle brace during drop landings affect lower extremity kinematics and ground reaction forces?  

UK PubMed Central (United Kingdom)

The objective of the study was to determine if prophylactic ankle bracing worn by females during landings produces abnormal lower extremity mechanics. Angular kinematic and ground reaction force (GRF) data were obtained for 16 athletically experienced females who performed brace and no-brace drop landings. The brace condition displayed reduced in/external rotation and flexion displacements about the ankle and knee joints and increased vertical and mediolateral GRF peak magnitudes and rate of vertical GRF application (paired t test, P < .05). The ankle and knee joints landed in a less plantar flexed and more flexed position, respectively. No significant ab/adduction outcomes may have occurred due to interparticipant variability and/or a lack of brace restriction. Conclusion: During typical landings, this lace-up brace increases vertical GRF, decreases ankle and knee joint displacements of flexion and int/external rotation, but minimally affects ab/adduction displacements.

Simpson KJ; Yom JP; Fu YC; Arnett SW; O'Rourke S; Brown CN

2013-04-01

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Ground reaction force and kinematic analysis of limb loading on two different beach sand tracks in harness trotters.  

UK PubMed Central (United Kingdom)

REASONS FOR PERFORMING STUDY: Although beach training is commonly used in horses, limb loading on beach sand has never been investigated. A dynamometric horseshoe (DHS) is well adapted for this purpose. OBJECTIVES: To compare ground reaction force (GRF) and fetlock kinematics measured in harness trotters on 2 tracks of beach sand with different water content. METHODS: Two linear sand tracks were compared: firm wet sand (FWS, 19% moisture) vs. deep wet sand (DWS, 13.5% moisture). Four French trotters (550 ± 22 kg) were used. Their right forelimb was equipped with a DHS and skin markers. Each track was tested 3 times at 7 m/s. Each trial was filmed by a high-speed camera (600 Hz); DHS and speed data acquisition was performed at 10 kHz on 10 consecutive strides. All recordings were synchronised. The components Fx (parallel to the hoof solar surface) and Fz (perpendicular) of the GRF were considered. For 3 horses the fetlock angle and forelimb axis-track angle at landing were measured. Statistical differences were tested using the GLM procedure (SAS; P < 0.05). RESULTS: Stance duration was increased on DWS compared to FWS. Fzmax and Fxmax (oriented, respectively, downwards and forwards relatively to the solar surface) and the corresponding loading rates, were decreased on DWS and these force peaks occurred later. Fxmin (backwards) was not significantly different between both surfaces; the propulsive phase (Fx negative) was longer and the corresponding impulse higher, on DWS compared to FWS. The forelimb was more oblique to the track at landing and maximal fetlock extension was less and delayed on DWS. CONCLUSIONS: This study confirms that trotting on deep sand overall reduces maximal GRF and induces a more progressive limb loading. However, it increases the propulsive effort and likely superficial digital flexor tendon tension at the end of stance, which should be taken into account in beach training.

Crevier-Denoix N; Robin D; Pourcelot P; Falala S; Holden L; Estoup P; Desquilbet L; Denoix JM; Chateau H

2010-11-01

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NUMBER OF SUCCESSIVE CYCLES NECESSARY TO ACHIEVE STABILITY OF SELECTED GROUND REACTION FORCE VARIABLES DURING CONTINUOUS JUMPING  

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Full Text Available Because of inherent variability in all human cyclical movements, such as walking, running and jumping, data collected across a single cycle might be atypical and potentially unable to represent an individual's generalized performance. The study described here was designed to determine the number of successive cycles due to continuous, repetitive countermovement jumping which a test subject should perform in a single experimental session to achieve stability of the mean of the corresponding continuously measured ground reaction force (GRF) variables. Seven vertical GRF variables (period of jumping cycle, duration of contact phase, peak force amplitude and its timing, average rate of force development, average rate of force relaxation and impulse) were extracted on the cycle-by-cycle basis from vertical jumping force time histories generated by twelve participants who were jumping in response to regular electronic metronome beats in the range 2-2.8 Hz. Stability of the selected GRF variables across successive jumping cycles was examined for three jumping rates (2, 2.4 and 2.8 Hz) using two statistical methods: intra-class correlation (ICC) analysis and segmental averaging technique (SAT). Results of the ICC analysis indicated that an average of four successive cycles (mean 4.5 ± 2.7 for 2 Hz; 3.9 ± 2.6 for 2.4 Hz; 3.3 ± 2.7 for 2.8 Hz) were necessary to achieve maximum ICC values. Except for jumping period, maximum ICC values took values from 0.592 to 0.991 and all were significantly (p < 0.05) different from zero. Results of the SAT revealed that an average of ten successive cycles (mean 10.5 ± 3.5 for 2 Hz; 9.2 ± 3.8 for 2.4 Hz; 9.0 ± 3.9 for 2.8 Hz) were necessary to achieve stability of the selected parameters using criteria previously reported in the literature. Using 10 reference trials, the SAT required standard deviation criterion values of 0.49, 0.41 and 0.55 for 2 Hz, 2.4 Hz and 2.8 Hz jumping rates, respectively, in order to approximate the ICC results. The results of the study suggest that the ICC might be a less conservative but more objective method to evaluate stability of the data. Based on these considerations, it can be recommended that a force time history due to continuous, repetitive countermovement jumping should include minimum of four (the average from the ICC analysis) and possibly as many as nine successive jumping cycles (the upper limit of the ICC analysis) to establish stable mean values of the selected GRF data. This information is important for both experimental measurements and analytical studies of GRF signals due to continuous, repetitive countermovement jumping

Vitamor Racic; Aleksandar Pavic; Jasmes M.W. Brownjohn

2009-01-01

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The Effect of pPoron Layered Insole on Ground Reaction Force in Comparison with Common Insole on Subjects with Flexible Flat foot  

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Full Text Available Background: Flexible flat foot is a congenital common deformity in lower extremity associated with ligamentus laxity. This deformity may cause hammer toe, heel spur, inflammation of achille tendon, early muscle fatigue during sport, foot imbalance and pain in leg, knee and hip. The use of insole with medial arch support considered as one of the common treatments for patients. The purpose of this study was to determine the effect of a composite insole, Ethyl Vinyl Acetate (EVA) with Poron layer on ground reaction force on subjects with flexible flat foot in comparison with common EVA insole. Materials and Methods: Fifty two subjects (14 Male and 38 female) between 18-40 years of age with flexible flat foot participated in this study. Twenty six subjects received Poron insole (EVA with Poron layer) and 26 subjects received common EVA insole. After assessment each subject asked to walk with normal speed across two force plate in two conditions, walking with insole and shoe and walking without insole. Then each subject asked to use insole for forty hours during two weeks. Vertical ground reaction force in the first session and after two weeks was assessed.Results: Impact force and first peak of vertical ground reaction force (F1) with Poron insole in comparison with shoe significantly increased in second session (P<0.05). The second peak (F3) with common insole in comparison with shoe significantly increased in second session (P<0.05). Significant reduction was noted in first peak (F1) with common insole in second session in comparison with first session (P<0.05). There was no observable significant difference in two groups before and after intervention.Conclusion: The results of this preliminary study show that both insoles change vertical ground reaction force in comparison with shoe alone. But using a composite Poron Layer on EVA insole has not demonstrated a significant difference with common arch support insoles. Therefore appli

F Khanmohammad; MS Ghasemi; H Jafari; B Hajiaghaie; MA Sanjari

2012-01-01

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Contribution of the six major gait determinants on the vertical center of mass trajectory and the vertical ground reaction force.  

Science.gov (United States)

Saunders et al. (1953) stated that the introduction of six gait determinants (pelvic rotation, pelvic obliquity, stance knee flexion, foot and ankle mechanisms, and tibiofemoral angle) to a compass gait model (two rigid legs hinged at the hips) provides an accurate simulation of the actual trajectory of the whole body center of mass (CoM). Their respective actions could also explain the shape of the vertical ground reaction force (GRF) pattern. Saunders' approach is considered as a kinematic description of some features of gait and is subject to debate. The purpose of this study is to realize a rigorous mechanical evaluation of the gait determinants theory using an appropriated mathematical model in which specific experimental data of gait trials are introduced. We first simulate a compass-like CoM trajectory using the proposed 3D mathematical model. Then, factorizing the model to introduce successively the kinematic data related to each gait determinant, we assess their respective contribution to both the CoM trajectory and the pattern of vertical GRF at different gait speeds. The results show that the stance knee flexion significatively decreases the estimated position of the CoM during midstance. Stance knee extension and pelvic obliquity contribute to the appearance of the pattern of vertical GRF during stance. The stance ankle dorsiflexion significatively contributes to CoM vertical excursion and the ankle plantarflexion contributes to the vertical GRF during terminal stance. The largest contribution towards the minimization of the CoM vertical amplitude during the complete gait step appears when considering the foot mechanisms and the pelvic obliquity in the proposed model. PMID:23725827

Hayot, C; Sakka, S; Lacouture, P

2013-05-15

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Relationships among performance of lateral cutting maneuver from lateral sliding and hip extension and abduction motions, ground reaction force, and body center of mass height.  

Science.gov (United States)

Basketball players have to move laterally and quickly change their movement directions, especially during defensive moves. This study aimed to investigate how frontal and sagittal plane hip movements relate to fastness and quickness of lateral cutting maneuvers from sliding. Three-dimensional biomechanical data were obtained for 28 female college basketball players while they performed lateral cutting maneuvers using their left leg after 2 lateral sliding steps. The lateral cutting index (LCIndex) expressing fastness and quickness of lateral cutting maneuvers, peak hip abduction and extension velocities immediately before foot contact, hip abduction and extension velocities at foot contact, peak horizontal ground reaction force, frontal plane ground reaction force angle, and sacrum center of mass position were calculated. Simple and stepwise regression analyses were conducted to predict LCIndex. The former showed that greater maximum hip extension velocity (p = 0.03) and lesser hip abduction velocity (p = 0.04) as well as smaller ground reaction force angle (p = 0.001) and lower sacrum center of mass position (p = 0.001) at foot contact led to better LCIndex. The latter showed that sacrum center of mass position at foot contact and hip extension velocity explained 35.3% (p body center of mass are crucial for better lateral deceleration-acceleration motions. PMID:23085969

Shimokochi, Yohei; Ide, Daishi; Kokubu, Masahiro; Nakaoji, Tetsu

2013-07-01

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EFFECTS OF FATIGUE ON FRONTAL PLANE KNEE MOTION, MUSCLE ACTIVITY, AND GROUND REACTION FORCES IN MEN AND WOMEN DURING LANDING  

Directory of Open Access Journals (Sweden)

Full Text Available Women tear their Anterior Cruciate Ligament (ACL) 2-8 times more frequently than men. Frontal plane knee motion can produce a pathological load in the ACL. During a state of fatigue the muscles surrounding the knee joint may lose the ability to protect the joint during sudden deceleration while landing. The purpose of this study was to investigate the effects of fatigue and gender on frontal plane knee motion, EMG amplitudes, and GRF magnitudes during drop- jump landing. Pretest-posttest comparison group design was used. Twenty-six volunteers (14 women; 12 Men; Mean ± standard deviation age = 24.5 ± 2.7 yrs; height = 1.73 ± 0.09 m; mass = 74.3 ± 11.8 kg) participated in the study. Knee frontal plane ranges of motion and positions, ground reaction force peak magnitudes, and surface EMG RMS amplitudes from five lower extremity muscles (vastus medialis, vastus lateralis, medial hamstring, lateral hamstring, and lateral gastrocnemius) were obtained during the landing phase of a drop-jump. MANOVA and ANOVA indicated that peak GRF significantly (p < 0.05; 2.50 ± 0.75 BW vs. 2.06 ± 0.93 BW) decreased during fatigued landings. No other variables exhibited a fatigue main effect, although there was a significant (p < 0.05) fatigue by gender interaction for the frontal plane range of motion from initial contact to max knee flexion variable. Follow-up analyses failed to reveal significant gender differences at the different levels of fatigue for this variable. Additionally, no variables exhibited a significant gender main effect. Single subject analysis indicated that fatigue significantly altered frontal plane knee motion, peak GRF, and EMG in some subjects and the direction of differences varied by individual. Fatigue altered some aspects of landing performance in both men and women, but there were no gender differences. Additionally, both group and single subject analyses provided valuable but different information about factors representing neuromuscular control during drop-jump landing

Michael P. Smith; Phillip S. Sizer; C. Roger James

2009-01-01

49

Predição da força de reação do solo durante a corrida na água Prediction of ground reaction force during water immersion running  

Directory of Open Access Journals (Sweden)

Full Text Available Este estudo visou desenvolver um modelo para a predição da força de reação do solo na corrida subaquática. Participaram 20 sujeitos (9 homens e 11 mulheres), que realizaram corrida subaquática em dois níveis de imersão e três velocidades. Para cada sujeito foram coletadas seis passagens válidas em cada condição, com a utilização de uma plataforma subaquática de força. O modelo para predição da força foi construído por regressão linear múltipla. Foram consideradas variáveis dependentes a componente vertical e a componente ântero-posterior da força de reação do solo. As variáveis imersão, sexo, velocidade, massa corporal, densidade corporal e percentual de gordura foram consideradas independentes. Permaneceu no modelo final de regressão para a componente vertical a velocidade (pThis study aimed at developing a model to predict ground reaction force during deep-water running. A total of 20 subjects ((9 men, 11 women) ran in water at two immersion levels and three different speeds. Each subject performed six valid trials in each condition, data being captured by an underwater force plate. The force prediction model was build by multiple linear regression. Dependent variables were the vertical and anteroposterior components of the ground reaction force; independent variables were runners' immersion, sex, speed, body mass, body density, and percentage of fat. At the final regression model for the vertical component, only speed remained (p<0.001), while for the anteroposterior component, speed, immersion, and body mass were maintained (all at p<0.001). The obtained model for the anteroposterior component of ground reaction force may be found satisfactory, as adjusted determination coefficient was 0.79. However, the prediction model for the vertical component cannot be recommended for prediction during deep-water running, since that coefficient was 0.18. It must be noted that the proposed prediction model applies to subjects provided that they have similar characteristics to those who took part in this study.

Alessandro Haupenthal; Heiliane de Brito Fontana; Caroline Ruschel; Helio Roesler; Adriano Ferreti Borgatto

2010-01-01

50

A comparison of lower limb EMG and ground reaction forces between barefoot and shod gait in participants with diabetic neuropathic and healthy controls  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background It is known that when barefoot, gait biomechanics of diabetic neuropathic patients differ from non-diabetic individuals. However, it is still unknown whether these biomechanical changes are also present during shod gait which is clinically advised for these patients. This study investigated the effect of the participants own shoes on gait biomechanics in diabetic neuropathic individuals compared to barefoot gait patterns and healthy controls. Methods Ground reaction forces and lower limb EMG activities were analyzed in 21 non-diabetic adults (50.9 ± 7.3 yr, 24.3 ± 2.6 kg/m2) and 24 diabetic neuropathic participants (55.2 ± 7.9 yr, 27.0 ± 4.4 kg/m2). EMG patterns of vastus lateralis, lateral gastrocnemius and tibialis anterior, along with the vertical and antero-posterior ground reaction forces were studied during shod and barefoot gait. Results Regardless of the disease, walking with shoes promoted an increase in the first peak vertical force and the peak horizontal propulsive force. Diabetic individuals had a delay in the lateral gastrocnemius EMG activity with no delay in the vastus lateralis. They also demonstrated a higher peak horizontal braking force walking with shoes compared to barefoot. Diabetic participants also had a smaller second peak vertical force in shod gait and a delay in the vastus lateralis EMG activity in barefoot gait compared to controls. Conclusions The change in plantar sensory information that occurs when wearing shoes revealed a different motor strategy in diabetic individuals. Walking with shoes did not attenuate vertical forces in either group. Though changes in motor strategy were apparent, the biomechanical did not support the argument that the use of shoes contributes to altered motor responses during gait.

Sacco Isabel CN; Akashi Paula MH; Hennig Ewald M

2010-01-01

51

Bilateral symmetry of ground reaction force with a motor-controlled resistance exercise system using a mechanical advantage barbell for spaceflight.  

UK PubMed Central (United Kingdom)

The reduced gravity experienced during spaceflight leads to muscle and bone atrophy, and resistance exercise has proven to be an effective countermeasure. Thus, a compact computer-controlled electric-motor resistance exercise system is being developed for NASA. In order to save power, space, and weight, the torque specifications of the motor were reduced by half because of a unique barbell design that employs a two-to-one mechanical advantage. Since the force-generating motor is on one side of the barbell, there is the potential for asymmetric barbell loading. Therefore, the purpose of this preliminary study is to compare the unilateral ground reaction forces (GRF) of the new barbell of the motor and ground sides. Multiple repetitions of fixed tempo deadlift exercise were performed with motor-controlled resistance using the new barbell. Unilateral GRF data was measured with a force plate under each foot, and the readings from each force plate are compared to each other. Results indicate the mechanical advantage barbell exercises have bilaterally asymmetric GRF compared to a theoretical 50-50 split, and the astronauts would need to alternate the left-right orientation to compensate for the asymmetry.

Paulus DC; Settlage DM

2012-01-01

52

Zapateado technique as an injury risk in Mexican folkloric and Spanish dance: an analysis of execution, ground reaction force, and muscle strength.  

UK PubMed Central (United Kingdom)

Zapateado is a repetitive percussive footwork in dance. This percussive movement, and the differences in technique, may be risk factors for injury. A survey on zapateado dance students found a rate of 1.5 injuries/1,000 exposures. Knee injuries are more frequent than in Spanish dancers than folkloric dancers. The aim of this research was to study the relationship between technique and ground reaction force between zapateado on Spanish and Mexican folkloric dancers. Ten female dance students (age 22.4 ± 4 yrs), six Spanish dancers and four Mexican folkloric dancers, were considered. Each student performed zapateado with a flat foot, wearing high-heeled shoes during 5 seconds on a force platform. Videotapes were taken on a lateral plane, and knee and hip angles in each movement phase were measured with Dartfish software. Additionally, knee and ankle flexor and extensor strength was measured with a dynamometer. Ground reaction forces were lower for Spanish dancers than Mexican folkloric dancers. Spanish dancers had less knee flexion when the foot contacted to the ground than did Mexican folkloric dancers. On Spanish dancers, the working leg had more motion in relation to hip and knee angles than was seen in folkloric dancers. The ankle extensors were stronger on folkloric dancers, and there were no differences for the other muscle groups. Knee flexion at foot contact and muscle strength imbalance could be risk factors for injuries. It is suggested that the technique in Spanish dance in Mexico be reviewed, although more studies are required to define more risk factors.

Echegoyen S; Aoyama T; Rodríguez C

2013-06-01

53

Zapateado technique as an injury risk in Mexican folkloric and Spanish dance: an analysis of execution, ground reaction force, and muscle strength.  

Science.gov (United States)

Zapateado is a repetitive percussive footwork in dance. This percussive movement, and the differences in technique, may be risk factors for injury. A survey on zapateado dance students found a rate of 1.5 injuries/1,000 exposures. Knee injuries are more frequent than in Spanish dancers than folkloric dancers. The aim of this research was to study the relationship between technique and ground reaction force between zapateado on Spanish and Mexican folkloric dancers. Ten female dance students (age 22.4 ± 4 yrs), six Spanish dancers and four Mexican folkloric dancers, were considered. Each student performed zapateado with a flat foot, wearing high-heeled shoes during 5 seconds on a force platform. Videotapes were taken on a lateral plane, and knee and hip angles in each movement phase were measured with Dartfish software. Additionally, knee and ankle flexor and extensor strength was measured with a dynamometer. Ground reaction forces were lower for Spanish dancers than Mexican folkloric dancers. Spanish dancers had less knee flexion when the foot contacted to the ground than did Mexican folkloric dancers. On Spanish dancers, the working leg had more motion in relation to hip and knee angles than was seen in folkloric dancers. The ankle extensors were stronger on folkloric dancers, and there were no differences for the other muscle groups. Knee flexion at foot contact and muscle strength imbalance could be risk factors for injuries. It is suggested that the technique in Spanish dance in Mexico be reviewed, although more studies are required to define more risk factors. PMID:23752281

Echegoyen, Soledad; Aoyama, Takeshi; Rodríguez, Cristina

2013-06-01

54

Leg Dominance May Not be a Predictor of Asymmetry in Peak Joint Moments and Ground Reaction Forces During Sit to Stand Movements.  

UK PubMed Central (United Kingdom)

Sit-to-stand transfer is a common prerequisite for many daily tasks. Literature, often assumes symmetric behavior across the left and right side. Although this assumption of bilateral symmetry is prominent, few studies have validated this supposition. This pilot study uniquely quantifies peak joint moments and ground reaction forces (GRFs), using a Euclidian Norm approach, to evaluate bilateral symmetry and its relation to lower limb motor-dominance during sit to stand in ten (10) healthy males. Peak joint moments and GRFs were determined using a motion capture system, and inverse dynamics. This analysis included joint moment contributions from all three body planes (sagittal, coronal, and axial) as well as vertical and shearing GRFs. A paired, one-tailed t-test was utilized, suggesting asymmetrical joint moment development in all three lower extremity joints as well as ground reaction forces (P<.05). Furthermore, using an unpaired two-tailed t-test, asymmetry developed during these movements does not appear to be predictable by participants' lower limb motor-dominance (P<.025). Consequently, when evaluating sit-to-stand it is suggested the effects of asymmetry be considered in the interpretation of data. The absence of a relationship between dominance and asymmetry prevents the suggestion that one side can be tested to infer behavior of the contralateral.

Schofield J; Parent E; Lewicke J; Carey JP; El-Rich M; Adeeb S

2013-07-01

55

Effect of plantar flexion and eversion on mediolateral ground reaction force in subjects with functional ankle instability  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract   Background and Aim: The common mechanism for lateral ankle sprain is inversion, plantar flexion, or the combination of both, if untreated successfully can lead to chronic ankle instability. It seems that the foot position, while touching the ground, has an effective role to cause ank...

Nesar Yousefi; Ali Amiri; Ali Ashraf Jamshidi; Mojtaba Kamyab

56

Força de reação do solo como subsídio para prescrição de exercícios aquáticos: estudo de caso/ Ground reaction force as a subsidy for prescribing aquatic exercises: case study  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: Comparar a componente vertical da força de reação do solo nos exercícios de caminhada, corrida com deslocamento, corrida estacionária e salto vertical, realizados em ambiente aquático em diferentes níveis de imersão. MÉTODO: Participou deste estudo de caso um sujeito do sexo masculino (27 anos, 1,80 m e 84,3 kg). Utilizou-se para a coleta de dados uma plataforma subaquática de força posicionada no fundo de uma piscina térmica. O sujeito realizou 30 t (more) entativas válidas de cada exercício, imerso nos níveis do processo xifoide e do quadril. Os dados foram analisados com a utilização da estatística descritiva, teste "t" de Student para amostras pareadas e ANOVA, para medidas repetidas (p Abstract in english OBJECTIVE: To compare the vertical component of the ground reaction force in the exercises of walking, running, stationary running and vertical jump in the water, performed in different levels of immersion. METHODS: This case study was conducted with one subject (male, 27 years, 1,80 m and 84,3 kg). An underwater force plate was used for data collection, placed at the bottom of a thermal swimming pool. The subject performed 30 valid passages for each exercise in two immer (more) sion levels: xiphoid process and hip. Data were analyzed through descriptive statistics, Student's "t" test for paired samples and ANOVA for repeated measures (p

Haupenthal, Alessandro; Ruschel, Caroline; Hubert, Marcel; Fontana, Heiliane de Brito; Roesler, Helio

2010-06-01

57

ANALYSIS OF THE VERTICAL GROUND REACTION FORCES AND TEMPORAL FACTORS IN THE LANDING PHASE OF A COUNTERMOVEMENT JUMP  

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Full Text Available In most common bilateral landings of vertical jumps, there are two peak forces (F1 and F2) in the force-time curve. The combination of these peak forces and the high frequency of jumps during sports produce a large amount of stress in the joints of the lower limbs which can be determinant of injury. The aim of this study was to find possible relationships between the jump height and F1 and F2, between F1 and F2 themselves, and between F1, F2, the time they appear (T1 and T2, respectively) and the length of the impact absorption phase (T). Thirty semi-professional football players made five countermovement jumps and the highest jump of each player was analyzed. They were instructed to perform the jumps with maximum effort and to land first with the balls of their feet and then with their heels. All the data were collected using a Kistler Quattro Jump force plate with a sample rate of 500 Hz. Quattro Jump Software, v.1.0.9.0., was used. There was neither significant correlation between T1 and F1 nor between T1 and F2. There was a significant positive correlation between flight height (FH) and F1 (r = 0.584, p = 0.01) but no significant correlation between FH and F2. A significant positive correlation between F1 and T2 (r = 0.418, p < 0.05) and a significant negative correlation between F2 and T2 (r = -0.406, p < 0.05) were also found. There is a significant negative correlation between T2 and T (r = -0. 443, p < 0.05). T1 has a little effect in the impact absorption process. F1 increases with increasing T2 but F2 decreases with increasing T2. Besides, increasing T2, with the objective of decreasing F2, makes the whole impact absorption shorter and the jump landing faster.

Daniel Rojano Ortega; Elisabeth C. Rodríguez Bíes; Francisco J. Berral de la Rosa

2010-01-01

58

Effect of a rocker non-heeled shoe on EMG and ground reaction forces during gait without previous training.  

UK PubMed Central (United Kingdom)

Unstable shoes have been designed to promote "natural instability" and during walking they should simulate barefoot gait, enhancing muscle activity and, thus, attributing an advantage over regular tennis shoes. Recent studies showed that, after special training on the appropriate walking pattern, the use of the Masai Barefoot Technology (MBT) shoe increases muscle activation during walking. Our study presents a comparison of muscle activity as well as horizontal and vertical forces during gait with the MBT, a standard tennis shoe and barefoot walking of healthy individuals without previous training. These variables were compared in 25 female subjects and gait conditions were compared using ANOVA repeated measures (effect size:0.25). Walking with the MBT shoe in this non-instructed condition produced higher vertical forces (first vertical peak and weight acceptance rate) than walking with a standard shoe or walking barefoot, which suggests an increase in the loads received by the musculoskeletal system, especially at heel strike. Walking with the MBT shoe did not increase muscle activity when compared to walking with the standard shoe. The barefoot condition was more effective than the MBT shoe at enhancing muscle activation. Therefore, in healthy individuals, no advantage was found in using the MBT over a standard tennis shoe without a special training period. Further studies using the MBT without any instruction over a longer period are needed to evaluate if the higher loads observed in the present study would return to their baseline values after a period of adaptation, and if the muscle activity would increase over time.

Sacco IC; Sartor CD; Cacciari LP; Onodera AN; Dinato RC; Pantaleão E Jr; Matias AB; Cezário FG; Tonicelli LM; Martins MC; Yokota M; Marques PE; Costa PH

2012-06-01

59

Simultaneous measurement of back and front foot ground reaction forces during the same delivery stride of the fast-medium bowler.  

UK PubMed Central (United Kingdom)

Six male cricket bowlers (mean +/- s(mean): age 23.5 +/- 1.3 years; height 1.83 +/- 0.04 m; body weight 826 +/- 20 N) performed their typical bowling action at a set of stumps positioned at standard pitch length (20.1 m). A specially designed force platform rig allowed the correct positioning of two force platforms to be achieved beneath an outdoor polyflex runway (0.017 m depth) for each player's delivery stride pattern. For the back foot, the peak vertical ground reaction force was 1.95 +/- 0.08 kN (2.37 +/- 0.14 BW) and the braking force was 0.77 +/- 0.12 kN (0.94 +/- 0.16 BW). For the front foot, the peak vertical force was 4.80 +/- 0.92 kN (5.75 +/- 0.98 BW) and the braking force was 2.93 +/- 0.56 kN (3.54 +/- 0.67 BW). The mean peak vertical loading rate for front foot contact was 205 +/- 52.8 kN x s(-1) (249 +/- 64 BW x s(-1)) with mean values ranging from 81 to 446 kN x s(-1) (98 to 540 BW x s(-1)). The range for back foot contact was much smaller, 25-70 kN x s(-1) (30-85 BW x s(-1)), with a mean of 41.7 +/- 7.10 kN x s(-1) (50.6 +/- 8.6 BW x s(-1)). Mean peak impact occurred 24 ms after touchdown for the back foot and 16 ms after touchdown for the front foot. At impact, mean peak loading rates were greater for the front foot at 246 kN x s(-1) (298 BW x s(-1)), with a range of 80-483 kN x s(-1) (98-534 BW x s(-1)), than for the back foot at 65 kN x s(-1) (79 BW x s(-1)), with a range of 40-84 kN x s(-1) (49-110 BW x s(-1)).

Hurrion PD; Dyson R; Hale T

2000-12-01

60

Filtering Ground Reaction Force Data Affects the Calculation and Interpretation of Joint Kinetics and Energetics During Drop Landings.  

Science.gov (United States)

An inverse dynamic analysis and subsequent calculation of joint kinetic and energetic measures is widely used to study the mechanics of the lower extremity. Filtering the kinematic and kinetic data input to the inverse dynamics equations affects the calculated joint moment of force (JMF). Our purpose was to compare selected integral values of sagittal plane ankle, knee, and hip joint kinetics and energetics when filtered and unfiltered GRF data are input to inverse dynamics calculations. Six healthy, active, injury-free university student (5 female, 1 male) volunteers performed 10 two-legged landings. JMFs were calculated after two methods of data filtering: Unfiltered: marker data were filtered at 10 Hz, GRF data unfiltered; Filtered: both GRF and marker data filtered at 10 Hz. The filtering of the GRF data affected the shape of the knee and hip joint moment-time curves, and the ankle, knee and hip joint mechanical power-time curves. We concluded that while the contributions of individual joints to the support moment and to total energy absorption were not affected, the attenuation of high frequency oscillations in both JMF and JMP time curves will influence interpretation of CNS strategies during landing. PMID:23434732

McCaw, Steven T; Gardner, Jacob K; Stafford, Lindsay N; Torry, Michael R

2013-02-20

 
 
 
 
61

Filtering Ground Reaction Force Data Affects the Calculation and Interpretation of Joint Kinetics and Energetics During Drop Landings.  

UK PubMed Central (United Kingdom)

An inverse dynamic analysis and subsequent calculation of joint kinetic and energetic measures is widely used to study the mechanics of the lower extremity. Filtering the kinematic and kinetic data input to the inverse dynamics equations affects the calculated joint moment of force (JMF). Our purpose was to compare selected integral values of sagittal plane ankle, knee, and hip joint kinetics and energetics when filtered and unfiltered GRF data are input to inverse dynamics calculations. Six healthy, active, injury-free university student (5 female, 1 male) volunteers performed 10 two-legged landings. JMFs were calculated after two methods of data filtering: Unfiltered: marker data were filtered at 10 Hz, GRF data unfiltered; Filtered: both GRF and marker data filtered at 10 Hz. The filtering of the GRF data affected the shape of the knee and hip joint moment-time curves, and the ankle, knee and hip joint mechanical power-time curves. We concluded that while the contributions of individual joints to the support moment and to total energy absorption were not affected, the attenuation of high frequency oscillations in both JMF and JMP time curves will influence interpretation of CNS strategies during landing.

McCaw ST; Gardner JK; Stafford LN; Torry MR

2013-02-01

62

Computerized identification and classification of stance phases as made by front og hind feet of walking cows based on 3-dimensional ground reaction forces  

DEFF Research Database (Denmark)

Lameness is a frequent disorder in dairy cows and in large dairy herds manual lameness detection is a time-consuming task. This study describes a method for automatic identification of stance phases in walking cows, and their classification as made by a front or a hind foot based on ground reaction force information. Features were derived from measurements made using two parallel 3-dimensional force plates. The approach presented is based on clustering of Centre of Pressure (COP) trace points over space and time, combined with logical sequencing of stance phases based on the dynamics of quadrupedal walking. The clusters were identified as full or truncated (incomplete) stance phases furthermore the stance phases were classified as originating from a front or hind foot. Data from 370 walking trials made by 9 cows on 5 experiment days were used to test the method. Four cows were moderately lame at experimental onset. On average 5.1 stance phases per cow per trial were obtained of which 3.2 were classified as full stance phases and therefore appropriate for further gait analysis (the latter not being the scope of this study). Of the 2617 identified clusters 1844 were classified as stance phases, of these 1146 (62%) were automatically identified as full stance phases and classified as made by a front or hind foot. As intended, the procedures did not favour identification of stance phases of healthy cows over lame cows. In addition, a human observer evaluated the stance phases by visual inspection, revealing a very low discrepancy (3.5%) between manual and automated approaches. Further, a sensitivity test indicated large robustness in the automatic procedures. In conclusion, the experimental setup combined with the computerized procedures described in the present study resulted in a high number of stance phases obtained per trial. It is thus a combination which has the potential to enable unsupervised gait analysis based on data collected automatically on-farm

SkjØth, F; Thorup, Vivi MØrkØre

2013-01-01

63

The effect of tibial plateau angle on ground reaction forces 4-17 months after tibial plateau leveling osteotomy in Labrador Retrievers.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To assess the relationship between postoperative tibial plateau angle (TPA) and ground reaction forces (GRFs) in Labrador Retrievers at least 4-months after tibial plateau leveling osteotomy (TPLO) surgery. STUDY DESIGN: A retrospective longitudinal study. ANIMALS: Thirty-two Labrador Retrievers with unilateral cranial cruciate ligament disease that had TPLO and concurrent meniscal surgery. METHODS: TPA and GRFs were measured pre- and > or = 4 months postoperatively. Preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA and degree of rotation were each compared with postoperative GRFs using correlation analysis. Dogs were also grouped by postoperative TPA and compared using 1-way analysis of variance (ANOVA). Postoperative function was compared with meniscal release/meniscectomy, patient age, sex, body weight and follow-up time using ANOVA. RESULTS: No significant relationship was found between preoperative GRFs, preoperative TPA, duration of injury, postoperative TPA, degree of rotation, or meniscal release/meniscectomy and postoperative function. Mean preoperative GRFs for all dogs were 28.8 +/- 9.5 for peak vertical force (PVF) and 9.3 +/- 3.1 for peak vertical impulse (VI). Mean postoperative GRFs for all dogs were 40.4 +/- 5.0 for PVF and 14.1 +/- 1.9 for VI. CONCLUSIONS: No statistically significant relationship was found between postoperative TPA and GRFs after TPLO > or = 4 months after surgery, where the postoperative angle was between 0 and 14 degrees. No significant relationship was found between the preoperative TPA and postoperative function. CLINICAL RELEVANCE: Limb function in Labrador Retrievers was not affected by postoperative TPA and re-operation for cases with a postoperative TPA between 0 and 14 degrees is not recommended.

Robinson DA; Mason DR; Evans R; Conzemius MG

2006-04-01

64

Comparison among probabilistic neural network, support vector machine and logistic regression for evaluating the effect of subthalamic stimulation in Parkinson disease on ground reaction force during gait.  

UK PubMed Central (United Kingdom)

Deep brain stimulation of the subthalamic nucleus (DBS-STN) is an approved treatment for advanced Parkinson disease (PD) patients; however, there is a need to further evaluate its effect on gait. This study compares logistic regression (LR), probabilistic neural network (PNN) and support vector machine (SVM) classifiers for discriminating between normal and PD subjects in assessing the effects of DBS-STN on ground reaction force (GRF) with and without medication. Gait analysis of 45 subjects (30 normal and 15 PD subjects who underwent bilateral DBS-STN) was performed. PD subjects were assessed under four test conditions: without treatment (mof-sof), with stimulation alone (mof-son), with medication alone (mon-sof), and with medication and stimulation (mon-son). Principal component (PC) analysis was applied to the three components of GRF separately, where six PC scores from vertical, one from anterior-posterior and one from medial-lateral were chosen by the broken stick test. Stepwise LR analysis employed the first two and fifth vertical PC scores as input variables. Using the bootstrap approach to compare model performances for classifying GRF patterns from normal and untreated PD subjects, the first three and the fifth vertical PCs were attained as SVM input variables, while the same ones plus the first anterior-posterior were selected as PNN input variables. PNN performed better than LR and SVM according to area under the receiver operating characteristic curve and the negative likelihood ratio. When evaluating treatment effects, the classifiers indicated that DBS-STN alone was more effective than medication alone, but the greatest improvements occurred with both treatments together.

Muniz AM; Liu H; Lyons KE; Pahwa R; Liu W; Nobre FF; Nadal J

2010-03-01

65

Comparison among probabilistic neural network, support vector machine and logistic regression for evaluating the effect of subthalamic stimulation in Parkinson disease on ground reaction force during gait.  

Science.gov (United States)

Deep brain stimulation of the subthalamic nucleus (DBS-STN) is an approved treatment for advanced Parkinson disease (PD) patients; however, there is a need to further evaluate its effect on gait. This study compares logistic regression (LR), probabilistic neural network (PNN) and support vector machine (SVM) classifiers for discriminating between normal and PD subjects in assessing the effects of DBS-STN on ground reaction force (GRF) with and without medication. Gait analysis of 45 subjects (30 normal and 15 PD subjects who underwent bilateral DBS-STN) was performed. PD subjects were assessed under four test conditions: without treatment (mof-sof), with stimulation alone (mof-son), with medication alone (mon-sof), and with medication and stimulation (mon-son). Principal component (PC) analysis was applied to the three components of GRF separately, where six PC scores from vertical, one from anterior-posterior and one from medial-lateral were chosen by the broken stick test. Stepwise LR analysis employed the first two and fifth vertical PC scores as input variables. Using the bootstrap approach to compare model performances for classifying GRF patterns from normal and untreated PD subjects, the first three and the fifth vertical PCs were attained as SVM input variables, while the same ones plus the first anterior-posterior were selected as PNN input variables. PNN performed better than LR and SVM according to area under the receiver operating characteristic curve and the negative likelihood ratio. When evaluating treatment effects, the classifiers indicated that DBS-STN alone was more effective than medication alone, but the greatest improvements occurred with both treatments together. PMID:19914622

Muniz, A M S; Liu, H; Lyons, K E; Pahwa, R; Liu, W; Nobre, F F; Nadal, J

2009-11-14

66

Hip joint reaction force - review  

Directory of Open Access Journals (Sweden)

Full Text Available This paper provides a review of various methods used to determine reaction force in the human hip: from simple statical models through dynamical inverse dynamics model to experimental measurements. Special attention is taken to inverse dynamics modeling.

Matej Daniel

2007-01-01

67

Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boots REPRODUCIBILIDAD DE LAS VARIABLES ESPACIO-TEMPORALES Y DE LAS COMPONENTES DE LA FUERZA DE REACCIÓN DEL SUELO EN LA MARCHA CON BOTAS DE BOMBERO [Reproducibility of the spatio-temporal variables and the ground reaction forces walking with fire fighting boo  

Directory of Open Access Journals (Sweden)

Full Text Available AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF) when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV) in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V), condition I = 2.01%; condition II = 1.81%), of the vertical (i.e. contact force (FZA) of the left foot, condition I = 2.54%; condition II = 2.73%) and of the antero-posterior GRF (i.e. maximum force (FXMAX) of the left foot, condition I = 4.47%; condition II = 4.59%) was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions. Key words: biomechanics, footwear, variability.ResumenEl objetivo del presente trabajo es analizar la reproducibilidad de las variables espacio-temporales y de la fuerza de reacción del suelo (FRS) durante la marcha con botas de bombero y compararla con la mostrada durante la marcha con calzado de cuero sin caña. Se registraron las variables espacio-temporales de 39 personas así como las variables que definen las tres componentes de la FRS con dos tipos de calzado diferente. Se utilizó la prueba T para contrastar la hipótesis referida a la diferencia del coeficiente de variación (CV) entre los dos tipos de calzado. El CV de las variables espacio-temporales (p. ej. velocidad (V), condición I = 2,01%; condición II = 1,81%), así como de las que definen la componente vertical (p. ej. fuerza de apoyo (FZA) del pie izquierdo, condición I = 2,54%; condición II = 2,73%) y antero-posterior (p. ej. fuerza máxima (FXMAX) del pie izquierdo, condición I = 4,47%; condición II = 4,59%) de la FRS fue inferior a 12,5%, sugiriendo que estas variables pueden ser utilizadas para analizar la influencia de las botas de bombero sobre la marcha. La baja reproducibilidad mostrada por las variables que definen la componente medio-lateral desaconseja la utilización de las mismas para evaluar el efecto de las botas de bombero sobre la marcha. A excepción del tiempo de apoyo bipodal, el resto de variables durante la marcha con botas de bombero no mostró una variabilidad diferente a la obtenida durante la marcha con calzado de cuero sin caña.Palabras clave: biomecánica, calzado, variabilidad. AbstractThe aim of this study is to analyze the reproducibility of the spatio-temporal variables and the ground reaction forces (GRF) when walking with fire fighting boots in comparison to walking with low calf shoes. Spatio-temporal parameters and the variables related to the three components of the GRF of 39 people were recorded under two different walking conditions. A T-test to contrast the difference between the coefficients of variation (CV) in both conditions was used. The CV of the spatio-temporal variables (i.e velocity (V), condition I = 2.01%; condition II = 1.81%), of the vertical (i.e. contact force (FZA) of the left foot, condition I = 2.54%; condition II = 2.73%) and of the antero-posterior GRF (i.e. maximum force (FXMAX) of the left foot, condition I = 4.47%; condition II = 4.59%) was lower than 12.5%, suggesting that these variables could be used to analyze the influence of fire fighting boots on the gait. However, the low reproducibility showed by medium-lateral parameters does not allow to use them. Apart from the bipodal phase no differences were found between the two walking conditions.Key words: biomechanics, footwear, variability.

Jesús Cámara Tobalina; Raúl Martínez de Santos; Begoña Gavilanes

2010-01-01

68

Estudo da variabilidade das forças de reação do solo na aquisição do andar independente em bebês/ A study of ground reaction forces variability during acquisition of independent gait in toddlers  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Este estudo avaliou o comportamento das forças de reação do solo (FRS) nos primeiros meses do andar independente, a fim de identificar mudanças na capacidade infantil de propulsionar e equilibrar o corpo em condição dinâmica. Foram avaliadas no período de três meses dez crianças com idade de 13 meses na primeira avaliação. As crianças caminharam em uma passarela de cinco metros de comprimento com duas plataformas de força embutidas. Foram estudadas magnitude (more) s máximas e mínimas das FRS e as respectivas variabilidades. As avaliações foram comparadas através do teste não-paramétrico ANOVA de Friedman (p Abstract in english This study aimed to describe ground reaction forces' profiles during toddler's gait at the first months of the acquisition phase of independent walking, in order to identify whether there are changes in the ability to propel and balance the body in this dynamic condition. Ten thirteen-month old toddlers volunteered to the study and were evaluated three times in a three-month interval. The toddlers walked over a 5 m long walkway with two force plates fixed at ground level. (more) Vertical and horizontal peak reaction forces and variability coefficients were selected for analysis. To compare the results of the three evaluations ANOVA Friedman's tests were used at 5% level of significance. The walking experience achieved by the toddlers month after month was not sufficient to significantly change the biomechanical selected variables and statistically significant differences were not found for the selected variables along three months. However, a reduction in the variability coefficient for the vertical reaction forces suggests development towards an increasingly mature gait pattern.

Levada, Giovana; Costa, Paula Hentschel Lobo da

2012-06-01

69

Rapid acceleration in dogs: ground forces and body posture dynamics.  

UK PubMed Central (United Kingdom)

Because the ability to accelerate rapidly is crucial to the survival and reproductive fitness of most terrestrial animals, it is important to understand how the biomechanics of rapid acceleration differs from that of steady-state locomotion. Here we compare rapid acceleration with high-speed galloping in dogs to investigate the ways in which body and limb posture and ground forces are altered to produce effective acceleration. Seven dogs were videotaped at 250 Hz as they performed ;maximum effort' accelerations, starting in a standing position on a force plate and one and two strides before it. These dogs began accelerations by rapidly flexing their ankles and knees as they dropped into a crouch. The crouched posture was maintained in the first accelerating stride such that the ankle and knee were significantly more flexed than during steady high-speed galloping. The hindlimb was also significantly more retracted over the first stance period than during high-speed galloping. Ground forces differed from steady-state locomotion in that rapidly accelerating dogs supported only 43% of their body weight with the forelimbs, compared with 56-64% in steady-state locomotion. The hindlimbs applied greater peak accelerating forces than the forelimbs, but the forelimbs contributed significantly to the dogs' acceleration by producing 43% of the total propulsive impulse. Kinematically, rapid acceleration differs from steady-state galloping in that the limbs are more flexed and more retracted, while the back undergoes greater pitching movement. Ground reaction forces also differ significantly from steady-state galloping in that almost no decelerating forces are applied while propulsive force impulses are three to six times greater.

Walter RM; Carrier DR

2009-06-01

70

Effects of ground and joint reaction force exercise on lumbar spine and femoral neck bone mineral density in postmenopausal women: a meta-analysis of randomized controlled trials  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Low bone mineral density (BMD) and subsequent fractures are a major public health problem in postmenopausal women. The purpose of this study was to use the aggregate data meta-analytic approach to examine the effects of ground (for example, walking) and/or joint reaction (for example, strength training) exercise on femoral neck (FN) and lumbar spine (LS) BMD in postmenopausal women. Methods The a priori inclusion criteria were: (1) randomized controlled trials, (2) exercise intervention???24?weeks, (3) comparative control group, (4) postmenopausal women, (5) participants not regularly active, i.e., less than 150?minutes of moderate intensity (3.0 to 5.9 metabolic equivalents) weight bearing endurance activity per week, less than 75?minutes of vigorous intensity (> 6.0 metabolic equivalents) weight bearing endurance activity per week, resistance training g) was calculated for each FN and LS BMD result and pooled using random-effects models. Z-score alpha values, 95%confidence intervals (CI) and number-needed-to-treat (NNT) were calculated for pooled results. Heterogeneity was examined using Q and I2. Mixed-effects ANOVA and simple meta-regression were used to examine changes in FN and LS BMD according to selected categorical and continuous variables. Statistical significance was set at an alpha value ?0.05 and a trend at >0.05 to???0.10. Results Small, statistically significant exercise minus control group improvements were found for both FN (28?g’s, 1632 participants, g?=?0.288, 95% CI?=?0.102, 0.474, p?=?0.002, Q?=?90.5, p?I2?=?70.1%, NNT?=?6) and LS (28?g’s, 1504 participants, g?=?0.179, 95% CI?=??0.003, 0.361, p?=?0.05, Q?=?77.7, p?I2?=?65.3%, NNT?=?6) BMD. Clinically, it was estimated that the overall changes in FN and LS would reduce the 20-year relative risk of osteoporotic fracture at any site by approximately 11% and 10%, respectively. None of the mixed-effects ANOVA analyses were statistically significant. Statistically significant, or a trend for statistically significant, associations were observed for changes in FN and LS BMD and 20 different predictors. Conclusions The overall findings suggest that exercise may result in clinically relevant benefits to FN and LS BMD in postmenopausal women. Several of the observed associations appear worthy of further investigation in well-designed randomized controlled trials.

Kelley George A; Kelley Kristi S; Kohrt Wendy M

2012-01-01

71

Relação entre a mobilidade do tornozelo e pé e a magnitude da força vertical de reação do solo Relationship between ankle and foot mobility and the magnitude of the vertical ground reaction force  

Directory of Open Access Journals (Sweden)

Full Text Available OBJETIVO: Verificar a relação entre a mobilidade do tornozelo e do pé, e o pico da força vertical de reação do solo, considerada como porcentagem do peso corporal, gerada durante a fase de apoio da marcha. MÉTODOS: foram estudados pés normais do lado direito e esquerdo de 15 homens com 22,1±2,7 anos (19-28) e 15 mulheres 24,20±5,24 anos (19-34). Os parâmetros de exclusão foram: deformidades nos pés, doenças ou traumas, que pudessem acometer o sistema musculoesquelético e a marcha. A mobilidade do tornozelo e dos pés foi obtida através da goniometria da flexão plantar, dorsiflexão, extensão do hálux e extensão dos dedos, o pico da força vertical de reação do solo FRS, foi obtido pela baropodometria computadorizada do sistema FSCAN R. A correlação entre ambas foi feita pelo teste estatístico de Spearman. RESULTADOS: os indivíduos do grupo masculino apresentaram menores valores de mobilidade, e maiores valores do pico da força vertical de reação do solo, quando comparados com o grupo feminino. Não houve diferença entre os pés direito e esquerdo. No sexo feminino foi encontrada correlação negativa estatisticamente significante entre os valores da flexão plantar e a força vertical, e entre os valores da extensão dos dedos e a foça vertical. No sexo masculino, houve correlação negativa estatisticamente significante entre os valores da dorsiflexão e a força vertical. Entre os demais valores não foi encontrada correlação significante. CONCLUSÃO: Há relação entre a mobilidade e a força vertical gerada durante a marcha.OBJECTIVE: To investigate the relationship between ankle and foot mobility and the peak of the vertical ground reaction force, as a percentage of body weight, generated during the gait stance phase. METHOD: Fifteen men with mean age of 22.1 ± 2.7 years (range: 19-28) and fifteen women with mean age of 24.20 ± 5.24 years (range: 19-34) with normal feet were studied. The exclusion criteria were foot deformities or a history of trauma or diseases that might have harmed both the musculoskeletal system and gait pattern. The ankle and foot mobility was obtained by means of goniometry on the plantar flexion, dorsiflexion, hallux extension and toe extension. The peak of the vertical ground reaction force was obtained by baropodometry using the FSCAN TM system. The Spearman statistical test was used to identify correlations. RESULTS: Males presented lower mobility values and higher peak values for the vertical ground reaction force, in comparison with females. There was no difference between the right and left foot. For females, there were statistically significant negative correlations between the values for plantar flexion and vertical force, and between the values for toe extension and vertical force. For males, there were statistically significant negative correlations between the values for dorsiflexion and vertical force. Among the remaining values, no significant correlation was found. CONCLUSION: There was a relationship between mobility and the vertical force generated during gait.

DL Vianna; JMD Greve

2006-01-01

72

The influence of running shoes cumulative usage on the ground reaction forces and plantar pressure responses/ A influência do uso acumulado de calçados de corrida sobre a força de reação do solo e as respostas de pressão plantar  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Acredita-se que a eficiência do calçado seja afetada pelo uso prolongado, mas as alterações biomecânicas ainda não estão bem compreendidas. O objetivo deste estudo é analisar a influência do uso de calçados de corrida na força de reação do solo e os parâmetros de pressão plantar. Três corredores do sexo masculino receberam quatro calçados de corrida para usarem em suas sessões de treinamento. O Sistema Gaitway e o Sistema de F-scan foram usados para regi (more) strar a força de reação do solo e parâmetros pressão plantar em diferentes regiões do pé. As coletas ocorreram em quatro momentos: novo e 100, 200 e 300 km de uso. O primeiro pico diminuiu da condição novo para os 300 km de uso (p Abstract in english The prolonged use of a running shoe is thought to affect the efficiency of its impact attenuation properties. However, its effect over biomechanical variables has yet not been well understood. The aim of this study was to examine the influence of running shoe usage on ground reaction force and plantar pressure parameters. Three male runners received four running shoes each to use at their training sessions. The Gaitway System was used to register the vertical component of (more) the ground reaction force, whereas the contact area and peak plantar pressure at different regions of the foot were assessed via the the F-scan System. Data collection occurred at baseline (when the shoes were new - New) and after 100, 200 and 300km of use. The first peak decreased significantly from New to 300km (p

Bianco, Roberto; Azevedo, Ana Paula da Silva; Fraga, Carina Helena Wasem; Acquesta, Fernanda Michelone; Mochizuki, Luis; Amadio, Alberto Carlos; Serrão, Júlio Cerca

2011-12-01

73

Radiation Reaction Force on a Particle  

CERN Multimedia

The Abrahamn Lorentz radiation reaction force term, with da/dt, derived in text books is shown to be incomplete. We show that, with the addition of a term, the classical radiation reaction force can be generalized to the relativistic force expression. This addition is the Poynting Robertson term, seen mostly in astrophysics and usually missing from texts in electromagnetism. With this term added, it takes into account the rate of change of mass dm/dt of the particle and makes the generalization to the relativisitic formula for force very straight forward.

Fearn, H

2012-01-01

74

Grounding-Induced Sectional Forces and Residual Strength of Grounded Ship Hulls  

DEFF Research Database (Denmark)

The aim of the present study is to determine the sectional forces induced by ship grounding and also to assess the residual strength of groundedship hulls. An analytical approach is used to estimate the grounding-induced sectional forces of ships. The extent and location of structural damage due to grounding is defined based on the ABS Safe Hull guide. The residual strength of damaged hulls is calculated by using a simple analytical formula. The method is applied to residual strength assessment of a damaged double hull tanker of 38,400 dwt due to grounding.

Paik, Jeom Kee; Pedersen, Preben Terndrup

1996-01-01

75

Ground reaction force and electromyographic activity of transfemoral amputee gait: a case series/ Força de Reação do Solo e atividade eletromiográfica da marcha de amputados transfemorais: uma série de casos  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese O comportamento da Força de Reação do Solo (FRS) e a atividade eletromiográfica formam uma parte dos dados que caracterizam a biomecânica da marcha. O estudo destes parâmetros é importante para a recuperação da locomoção e para compreensão do impacto da amputação e dos componentes protéticos nos movimentos desenvolvidos no andar. Portanto, esta série de casos tem como objetivo descrever a atividade eletromiográfica e a FRS de amputados transfemorais. Para (more) mensurar a FRS, foi utilizada uma plataforma de força e um sistema de eletromiografia monitorou os músculos vasto lateral, bíceps femoral, tibial anterior e gastrocnêmio lateral da perna não-amputada. As médias das componentes vertical e ânteroposterior da FRS, a atividade eletromiográfica e variáveis descritivas foram analisadas. Foi observado uma diminuição da magnitude da FRS vertical e ânteroposterior e das variáveis descritivas da componente ânteroposterior da FRS durante a fase de propulsão na perna amputada. Houve aumento na atividade fásica muscular e co-ativação na perna não-amputada. Pode-se concluir que os amputados transfemorais unilaterais analisados nesta série de casos desenvolveram menor FRS na perna amputada e longos períodos de atividade eletromiográfica na perna não amputada durante a marcha. Abstract in english Ground reaction forces (GRF) and electromyographic activity form a part of the descriptive data that characterise the biomechanics of gait. The research of these parameters is important in establishing gait training and understanding the impact of amputation and prosthetic components on movement during the act of walking. Therefore, this case series describes the GRF and electromyographic activity in the gait of transfemoral amputees. A force plate was used to measure GRF (more) , and an electromyographic system monitored the vastus lateralis, biceps femoris, tibialis anterior, and gastrocnemius lateralis muscles of the non-amputated leg. The average vertical and anteroposterior GRF time-curves, average electromyographic activity, and descriptor variables were then analysed. We observed decreases in vertical and anteroposterior GRF magnitudes as well as in anteroposterior GRF descriptor variables during the propulsive phase in the amputated leg. There were increases in phasic muscle activity and co-activation in the non-amputated leg. We concluded that, during walking, the unilateral transfemoral amputees (who were analysed in this case series) developed lower GRF in the amputated limb and a longer period of electromyographic activity in the non-amputated limb.

Cerqueira, Alex Sandra Oliveira de; Yamaguti, Edward Yuji; Mochizuki, Luis; Amadio, Alberto Carlos; Serrão, Júlio Cerca

2013-02-01

76

Ground reaction force in basketball cutting maneuvers with and without ankle bracing and taping/ Análise da força de reação do solo durante o cutting no basquetebol com e sem o uso de implementos no tornozelo  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese CONTEXTO E OBJETIVO: A lesão mais comum no basquetebol é a entorse de tornozelo. Assim, os atletas freqüentemente utilizam suportes externos como medidas profiláticas. O objetivo deste estudo é avaliar as respostas da força de reação do solo (FRS) durante a execução do movimento de cutting do basquetebol com e sem acessórios de tornozelo. TIPO DE ESTUDO E LOCAL: Estudo comparativo. Delineamento experimental de grupo único com medidas repetidas; Divisão de Med (more) icina de Reabilitação, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, Brasil. MÉTODOS: Foram colhidas as forças vertical (Fy) e médio-lateral (Fz) em três condições (bandagem, Aircast e calçado esportivo) e analisados os picos de força e de propulsão no contato com o solo (Fymax1, Fzmax1, Fymax2 e Fzmax2), o gradiente de crescimento (pico/tempo) (GC Fymax1, GC Fzmax1, GC Fymax2 e GC Fzmax2) e o impulso após o contato. RESULTADOS: Os acessórios reduziram significativamente Fymax2 e GC Fymax2. GC FZmax1 foi maior na situação com tênis quando comparado com bandagem. No momento do impacto, a bandagem aumentou a Fy em relação ao calçado, mas em um intervalo de tempo maior, não aumentando a carga articular. Fz atingiu um pico em menor tempo, podendo gerar maior carga eversora/inversora. O Aircast exerceu um melhor efeito de absorção de impacto, pois gera menor Fy em um maior intervalo de tempo. CONCLUSÕES: Apesar do uso freqüente deste tipo de recurso pelos atletas, seu mecanismo de ação ainda é confuso. Mais estudos são necessários para esclarecer seus efeitos nas atividades esportivas a longo prazo. Abstract in english CONTEXT AND OBJECTIVE: In basketball, the most common injuries are ankle sprains. For this reason, players frequently use external ankle devices or taping as prophylactic and rehabilitation measures. The purpose of this study was to evaluate ground reaction force (GRF) responses in basketball players while performing typical cutting maneuvers with and without ankle bracing and ankle taping. DESIGN AND SETTING: Comparative study with experimental design of single-group rep (more) eated measurements, at Medical Rehabilitation Division, Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo. METHODS: Vertical (Fy) and medial-lateral (Fz) GRF measurements were made under three conditions (taping, Aircast-type orthosis and basketball shoes alone), with analysis of peak forces at foot contact (Fymax1, Fzmax1, Fymax2 and Fzmax2), growth gradient (peak/time) (GG Fymax1, GG Fzmax1, GG Fymax2 and GG Fzmax2) and impulse after foot contact. RESULTS: Bracing significantly reduced Fymax2 and GG Fymax2. GG Fzmax1 was significantly higher for the sport shoe condition than for the taping condition. Taping increased Fy in relation to the sport shoe at foot contact, but over a longer time interval, without increasing excessive ankle loading. Fz reached a peak in less time, which might generate greater inversion/eversion loading on a player's foot. The Aircast exerted better shock-absorbing effect than did the other two conditions, since it generated less vertical force over longer time intervals and smaller medial-lateral forces in relation to taping. CONCLUSIONS: Ankle bracing and ankle taping action mechanisms are still unclear and therefore should be carefully prescribed. More studies are needed to clarify taping and bracing effects on sporting activities.

Sacco, Isabel de Camargo Neves; Takahasi, Henrique Yuji; Suda, Eneida Yuri; Battistella, Linamara Rizzo; Kavamoto, Cristianne Akie; Lopes, José Augusto Fernandes; Vasconcelos, Jeane Cintra Peixoto de

2006-01-01

77

Perspectives on the reaction force constant.  

UK PubMed Central (United Kingdom)

A synchronous, concerted chemical process is rigorously divided by the reaction force F(R), the negative gradient of V(R), into "reactant" and "product" regions which are dominated by structural changes and an intervening "transition" region which is electronically intensive. The reaction force constant ?(R), the second derivative of V(R), is negative throughout the transition region, not just at the nominal transition state, at which ?(R) has a minimum. This is consistent with experimental evidence that there is a transition region, not simply a specific point. We show graphically that significant nonsynchronicity in the process is associated with the development of a maximum of ?(R) in the transition region, which increases as the process becomes more nonsynchronous. (We speculate that for a nonconcerted process this maximum is actually positive.) Thus, ?(R) can serve as an indicator of the level of nonsynchronicity.

Politzer P; Murray JS; Jaque P

2013-10-01

78

Perspectives on the reaction force constant.  

Science.gov (United States)

A synchronous, concerted chemical process is rigorously divided by the reaction force F(R), the negative gradient of V(R), into "reactant" and "product" regions which are dominated by structural changes and an intervening "transition" region which is electronically intensive. The reaction force constant ?(R), the second derivative of V(R), is negative throughout the transition region, not just at the nominal transition state, at which ?(R) has a minimum. This is consistent with experimental evidence that there is a transition region, not simply a specific point. We show graphically that significant nonsynchronicity in the process is associated with the development of a maximum of ?(R) in the transition region, which increases as the process becomes more nonsynchronous. (We speculate that for a nonconcerted process this maximum is actually positive.) Thus, ?(R) can serve as an indicator of the level of nonsynchronicity. PMID:23288094

Politzer, Peter; Murray, Jane S; Jaque, Pablo

2013-01-05

79

Hypohydration reduces vertical ground reaction impulse but not jump height.  

UK PubMed Central (United Kingdom)

This study examined vertical jump performance using a force platform and weighted vest to determine why hypohydration (approximately 4% body mass) does not improve jump height. Measures of functional performance from a force platform were determined for 15 healthy and active males when euhydrated (EUH), hypohydrated (HYP) and hypohydrated while wearing a weighted vest (HYP(v)) adjusted to precisely match water mass losses. HYP produced a significant loss of body mass [-3.2 +/- 0.5 kg (-3.8 +/- 0.6%); P < 0.05], but body mass in HYP(v) was not different from EUH. There were no differences in absolute or relative peak force or power among trials. Jump height was not different between EUH (0.380 +/- 0.048 m) and HYP (0.384 +/- 0.050 m), but was 4% lower (P < 0.05) in HYP(v) (0.365 +/- 0.52 m) than EUH due to a lower jump velocity between HYP(v) and EUH only (P < 0.05). However, vertical ground reaction impulse (VGRI) was reduced in both HYP and HYP(v) (2-3%) compared with EUH (P < 0.05). In conclusion, this study demonstrates the failure to improve jump height when HYP can be explained by offsetting reductions in both VGRI and body mass.

Cheuvront SN; Kenefick RW; Ely BR; Harman EA; Castellani JW; Frykman PN; Nindl BC; Sawka MN

2010-08-01

80

Relationships between ground reaction impulse and sprint acceleration performance in team sport athletes.  

UK PubMed Central (United Kingdom)

Large horizontal acceleration in short sprints is a critical performance parameter for many team sport athletes. It is often stated that producing large horizontal impulse at each ground contact is essential for high short sprint performance, but the optimal pattern of horizontal and vertical impulses is not well understood, especially when the sprints are initiated from a standing start. This study was an investigation of the relationships between ground reaction impulses and sprint acceleration performance from a standing start in team sport athletes. Thirty physically active young men with team sport background performed 10-m sprint from a standing start, whereas sprint time and ground reaction forces were recorded during the first ground contact and at 8 m from the start. Associations between sprint time and ground reaction impulses (normalized to body mass) were determined by a Pearson's correlation coefficient (r) analysis. The 10-m sprint time was significantly (p < 0.01) correlated with net horizontal impulse (r = -0.52) and propulsive impulse (r = -0.66) measured at 8 m from the start. No significant correlations were found between sprint time and impulses recorded during the first ground contact after the start. These results suggest that applying ground reaction impulse in a more horizontal direction is important for sprint acceleration from a standing start. This is consistent with the hypothesis of training to increase net horizontal impulse production using sled towing or using elastic resistance devices, which needs to be validated by future longitudinal training studies.

Kawamori N; Nosaka K; Newton RU

2013-03-01

 
 
 
 
81

Ground reaction curve based upon block theory  

International Nuclear Information System (INIS)

Discontinuities in a rock mass can intersect an excavation surface to form discrete blocks (keyblocks) which can be unstable. Once a potentially unstable block is identified, the forces affecting it can be calculated to assess its stability. The normal and shear stresses on each block face before displacement are calculated using elastic theory and are modified in a nonlinear way by discontinuity deformations as the keyblock displaces. The stresses are summed into resultant forces to evaluate block stability. Since the resultant forces change with displacement, successive increments of block movement are examined to see whether the block ultimately becomes stable or fails. Two-dimensional (2D) and three-dimensional (3D) analytic models for the stability of simple pyramidal keyblocks were evaluated. Calculated stability is greater for 3D analyses than for 2D analyses. Calculated keyblock stability increases with larger in situ stress magnitudes, larger lateral stress ratios, and larger shear strengths. Discontinuity stiffness controls blocks displacement more strongly than it does stability itself. Large keyblocks are less stable than small ones, and stability increases as blocks become more slender

1985-01-01

82

Regulation of reaction forces during the golf swing.  

Science.gov (United States)

During the golf swing, the reaction forces applied at the feet control translation and rotation of the body-club system. In this study, we hypothesized that skilled players using a 6-iron would regulate shot distance by scaling the magnitude of the resultant horizontal reaction force applied to the each foot with minimal modifications in force direction. Skilled players (n = 12) hit golf balls using a 6-iron. Shot distance was varied by hitting the ball as they would normally and when reducing shot distance using the same club. During each swing, reaction forces were measured using dual force plates (1200 Hz) and three-dimensional kinematics were simultaneously captured (110 Hz). The results indicate that, on average, the peak resultant horizontal reaction forces of the target leg were significantly less than normal (5%, p < 0.05) when reducing shot distance. No significant differences in the orientation of the peak resultant horizontal reaction forces were observed. Resultant horizontal reaction force-angle relationships within leg and temporal relationships between target and rear legs during the swing were consistent within player across shot conditions. Regulation of force magnitude with minimal modification in force direction is expected to provide advantages from muscle activation, coordination, and performance points of view. PMID:23898685

McNitt-Gray, J L; Munaretto, J; Zaferiou, A; Requejo, P S; Flashner, H

2013-06-01

83

(Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)  

Energy Technology Data Exchange (ETDEWEB)

This report contains information related to the sampling and chemical analysis of ground water at the Wright-Patterson Air Force Base. It is part of a field investigation of ground water contamination.

1992-03-01

84

Force-activated reactivity switch in a bimolecular chemical reaction at the single molecule level  

Science.gov (United States)

Mechanical force can deform the reacting molecules along a well-defined direction of the reaction coordinate. However, the effect of mechanical force on the free-energy surface that governs a chemical reaction is still largely unknown. The combination of protein engineering with single-molecule AFM force-clamp spectroscopy allows us to study the influence of mechanical force on the rate at which a protein disulfide bond is reduced by some reducing agents in a bimolecular substitution reaction (so-called SN2). We found that cleavage of a protein disulfide bond by hydroxide anions exhibits an abrupt reactivity ``switch'' at 500 pN, after which the accelerating effect of force on the rate of an SN2 chemical reaction greatly diminishes. We propose that an abrupt force-induced conformational change of the protein disulfide bond shifts its ground state, drastically changing its reactivity in SN2 chemical reactions. Our experiments directly demonstrate the action of a force-activated switch in the chemical reactivity of a single molecule. References: Sergi Garcia-Manyes, Jian Liang, Robert Szoszkiewicz, Tzu-Ling Kuo and Julio M. Fernandez, Nature Chemistry, 1, 236-242, 2009.

Szoszkiewicz, Robert; Garcia-Manyes, Sergi; Liang, Jian; Kuo, Tzu-Ling; Fernandez, Julio M.

2010-03-01

85

Japan's Dispatch of the Ground Self Defense Force to Iraq: Lessons Learned.  

Science.gov (United States)

The Iraq deployment was a new experience for Japan's Ground Self Defense Force (GSDF) in that all previous missions for humanitarian aid and reconstruction had been carried out under a UN peacekeeping operations framework. The mission therefore provided t...

D. Fouse

2007-01-01

86

Ground-state photoneutron reactions in /sup 14/C  

Energy Technology Data Exchange (ETDEWEB)

Photoneutron time-of-flight spectra from the /sup 14/C(..gamma..,n/sub 0/)/sup 13/C reaction were measured as functions of laboratory angle over the excitation energy region from 10 to 28 MeV. Angular distribution coefficients and differential cross sections were extracted as functions of excitation energy between 10 and 23 MeV. The angle-integrated ground-state cross section indicates that ground state transitions dominate the T/sub less-than/ giant dipole resonance region below 13 MeV, but only contribute about 50% of the strength in the neutron channel in the rest of the giant dipole resonance region. The results support a mechanism of dominant E1 absorption in the energy region from 13 to 23 MeV where an average value of a/sub 2/ = -0.5 indicates p/sub 1/2/..-->..d/sub 3/2/ single-particle neutron transitions. Angular distribution information suggests that much of a prominent resonance at 11.3 MeV (with an integrated cross section of about 1.03 MeV mb) is due to an M1 transition from the ground state of /sup 14/C. If this is the case, there is little fragmentation of the M1 strength i

Kuo, P.C.; McNeill, K.G.; Sherman, N.K.; Landsberger, S.; Davidson, W.F.; Jury, J.W.; Lafontaine, J.R.C.

1985-02-01

87

Radiation reaction force and unification of electromagnetic and gravitational fields  

International Nuclear Information System (INIS)

[en] A unified theory of electromagnetic and gravitational fields should modify classical electrodynamics such that the radiation reaction force is accounted for. The analysis leads to a five-dimensional unified theory of five variables. The theory is supported by showing that, for the case of a charged particle moving in a constant magnetic field, the radiation reaction force is indeed included. Moreover, this example shows explicitly that physical changes are associated with the fifth variable. Thus, the notion of a physical five-dimensional space should be seriously taken into consideration

1981-01-01

88

Calculating Ring Pucker Free Energy Surfaces From Reaction Coordinate Forces  

Science.gov (United States)

We implemented the free energy from adaptive reaction coordinate forces (FEARCF) method and applied it to the conformational investigation of carbohydrate ring puckering. The method allows for significantly enhanced sampling of reaction coordinate space. The free energies associated with the ring pucker motion of ?-D-ribose (a furanose) and ?-D-glucose (a pyranose) were calculated. These can be used to interpret catalytic mechanisms of glycosylases.

Barnett, Christopher B.; Naidoo, Kevin J.

2009-03-01

89

A thermodynamic force generated by chemical gradient and adsorption reaction  

CERN Multimedia

Biological units such as macromolecules, organelles, and cells are directed to a proper location under gradients of relevant chemicals. By considering a macroscopic element that has binding sites for a chemical adsorption reaction to occur on its surface, we show the existence of a thermodynamic force that is generated by the gradient and exerted on the element. By assuming local equilibrium and adopting the grand potential from thermodynamics, we derive a formula for such a thermodynamic force, which depends on the chemical potential gradient and Langmuir isotherm. The conditions under which the formula can be applied are demonstrated to hold in intracellular reactions. The role of the force in the partitioning of bacterial chromosome/plasmid during cell division is discussed.

Sugawara, Takeshi

2009-01-01

90

Ground-state photoneutron reactions in 14C  

International Nuclear Information System (INIS)

Photoneutron time-of-flight spectra from the 14C(?,n0)13C reaction were measured as functions of laboratory angle over the excitation energy region from 10 to 28 MeV. Angular distribution coefficients and differential cross sections were extracted as functions of excitation energy between 10 and 23 MeV. The angle-integrated ground-state cross section indicates that ground state transitions dominate the T/sub less-than/ giant dipole resonance region below 13 MeV, but only contribute about 50% of the strength in the neutron channel in the rest of the giant dipole resonance region. The results support a mechanism of dominant E1 absorption in the energy region from 13 to 23 MeV where an average value of a2 = -0.5 indicates p/sub 1/2/?d/sub 3/2/ single-particle neutron transitions. Angular distribution information suggests that much of a prominent resonance at 11.3 MeV (with an integrated cross section of about 1.03 MeV mb) is due to an M1 transition from the ground state of 14C. If this is the case, there is little fragmentation of the M1 strength in 12C brought about by the presence of valence neutrons. When combined with the observation of the lack of a pygmy E1 resonance below the giant dipole resonance region, these results suggest that a model of 14C as a 12C ''core'' with two valence, weakly coupled, neutrons is inappropriate. Below an excitation energy of about 19 MeV, there is reasonably good quantitative and qualitative agreement between the present data and the results of a recent shell model calculation

1985-01-01

91

Fore-Aft Ground Force Adaptations to Induced Forelimb Lameness in Walking and Trotting Dogs  

Science.gov (United States)

Animals alter their locomotor mechanics to adapt to a loss of limb function. To better understand their compensatory mechanisms, this study evaluated the changes in the fore-aft ground forces to forelimb lameness and tested the hypothesis that dogs unload the affected limb by producing a nose-up pitching moment via the exertion of a net-propulsive force when the lame limb is on the ground. Seven healthy Beagles walked and trotted at steady speed on an instrumented treadmill while horizontal force data were collected before and after a moderate lameness was induced. Peak, mean and summed braking and propulsive forces as well as the duration each force was exerted and the time to reach maximum force were evaluated for both the sound and the lame condition. Compared with the sound condition, a net-propulsive force was produced by the lame diagonal limbs due to a reduced braking force in the affected forelimb and an increased propulsive force in the contralateral hindlimb when the dogs walked and trotted. To regain pitch stability and ensure steady speed for a given locomotor cycle, the dogs produced a net-braking force when the sound diagonal limbs were on the ground by exerting greater braking forces in both limbs during walking and additionally reducing the propulsive force in the hindlimb during trotting. Consistent with the proposed mechanism, dogs maximize their double support phases when walking. Likely associated with the fore-aft force adaptations to lameness are changes in muscle recruitment that potentially result in short- and long-term effects on the limb and trunk muscles.

Abdelhadi, Jalal; Wefstaedt, Patrick; Nolte, Ingo; Schilling, Nadja

2012-01-01

92

Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators.  

Science.gov (United States)

Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for discussing these subcellular force generators, I first review the application of reaction coordinate diagrams to the mechanisms of simple chemical and enzyme-catalyzed reactions. My description of reaction coordinate diagrams of motors and polymer ratchets is simplified relative to the rigorous biophysical treatment found in many of the references that I use and cite, but I hope that the essay provides a valuable qualitative representation of the physical chemical parameters that underlie the generation of force and motility at molecular scales. In any case, I have found that this approach represents a useful interdisciplinary framework for understanding, researching, and teaching the basic molecular mechanisms by which motors contribute to fundamental cell biological processes. PMID:23408787

Scholey, Jonathan M

2013-02-01

93

Compare and contrast the reaction coordinate diagrams for chemical reactions and cytoskeletal force generators.  

UK PubMed Central (United Kingdom)

Reaction coordinate diagrams are used to relate the free energy changes that occur during the progress of chemical processes to the rate and equilibrium constants of the process. Here I briefly review the application of these diagrams to the thermodynamics and kinetics of the generation of force and motion by cytoskeletal motors and polymer ratchets as they mediate intracellular transport, organelle dynamics, cell locomotion, and cell division. To provide a familiar biochemical context for discussing these subcellular force generators, I first review the application of reaction coordinate diagrams to the mechanisms of simple chemical and enzyme-catalyzed reactions. My description of reaction coordinate diagrams of motors and polymer ratchets is simplified relative to the rigorous biophysical treatment found in many of the references that I use and cite, but I hope that the essay provides a valuable qualitative representation of the physical chemical parameters that underlie the generation of force and motility at molecular scales. In any case, I have found that this approach represents a useful interdisciplinary framework for understanding, researching, and teaching the basic molecular mechanisms by which motors contribute to fundamental cell biological processes.

Scholey JM

2013-02-01

94

(Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)  

Energy Technology Data Exchange (ETDEWEB)

In April 1990 Wright-Patterson Air Force Base (WPAFB) initiated an investigation to evaluate a potential CERCLA removal action to prevent, to the extent practicable, the migration of ground-water contamination in the Mad River Valley Aquifer within and across WPAFB boundaries. The action will be based on a Focused Feasibility Study with an Action Memorandum serving as a decision document that is subject to approval by the Ohio Environmental Protection Agency. The first phase (Phase 1) of this effort involves an investigation of ground-water contamination migrating across the southwest boundary of Area C and across Springfield Pike adjacent to Area B. Task 4 of Phase 1 is a field investigation to collect sufficient additional information to evaluate removal alternatives. The field investigation will provide information in the following specific areas of study: water-level data which will be used to permit calibration of the ground-water flow model to a unique time in history; and ground-water quality data which will be used to characterize the current chemical conditions of ground water.

1991-10-01

95

[Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio  

International Nuclear Information System (INIS)

The Phase I, Task 5, Focused Feasibility Study (FFS) has been prepared as part of the Environmental Investigation of Ground Water Contamination Project being conducted by Wright-Patterson Air Force Base (WPAFB). The primary objective of this FFS was to select a cost-effective method of preventing migration of contaminated ground water across the southwestern boundary of Area C of the Base. The FFS presented in this document is a portion of a much larger effort being conducted at WPAFB. The detailed analysis of alternatives for the extraction, treatment, and discharge of contaminated ground water migrating across the southwest boundary of Area C at WPAFB led to the selection of a preferred removal action alternative. Specifically, this alternative is that ground water be extracted utilizing a three well array pumping at a total of 400 to 800 gpm, removed water be treated via air stripping to achieve appropriate effluent concentrations, and treated water be discharged to the Mad River in accordance with a National Pollution Discharge Elimination System (NPDES) permit and other relevant permits.

1992-01-01

96

(Environmental investigation of ground water contamination at Wright- Patterson Air Force Base, Ohio)  

Energy Technology Data Exchange (ETDEWEB)

This Health and Safety Plan (HSP) was developed for the Environmental Investigation of Ground-water Contamination Investigation at Wright-Patterson Air Force Base near Dayton, Ohio, based on the projected scope of work for the Phase 1, Task 4 Field Investigation. The HSP describes hazards that may be encountered during the investigation, assesses the hazards, and indicates what type of personal protective equipment is to be used for each task performed. The HSP also addresses the medical monitoring program, decontamination procedures, air monitoring, training, site control, accident prevention, and emergency response.

1991-10-01

97

The study of vertical ground reaction during walk of Czech women  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to find whether it is possible to explain different plantar loading during absorption and propulsive stages of stance in the observed persons by means of basic body indicators or time characteristics of gait. Fifty-one healthy women participated in the study; their age range was between 30 and 60 years of age. The women were divided into two groups according to whether they reached higher values of vertical ground reaction during absorption (group A, 8 women, 16 %) or propulsive (group B, 43 women, 84 %) stage of stance. Capacitive pressure insoles in the shoe were used (PedarX, Novel Munich). During laboratory survey each woman performed monitored natural walk. Three stances of each leg were assessed, always from between the third and eighth steps. Five parameters had been chosen for monitoring, three recording force characteristics of gait and two time parameters. Group A reached relative value of 121 % of BW during the first stage and 110 % of BW during the second one. Group B reached 105 % in the initial stage, and 117 % of BW in the other stage. A significant difference was found for F1 parameter between groups A and B, not for the second part of stage. Group A manifested shorter duration of both stages of stance (not significantly different from group B). The level of relationship between stance duration as well as its stages and force manifestations in both groups of women was very low (from r= 0.010 to 0.015). Only in group A, the weight of the women correlated with relative values of both F1 and F2 (r = - 0.795, r = - 0.625 resp.).

Pavel Korvas; Radek Musil; Jan Došla; Kate?ina Kolá?ová; Jind?ich Pavlík; Jan Šenký?

2013-01-01

98

Forcing factors of cloud-to-ground lightning over Iberia: regional-scale assessments  

Science.gov (United States)

Cloud-to-ground lightning in a sector covering the Iberian Peninsula, the Balearic Islands and nearby seas (36-44° N, 10° W-5° E) is analysed in the period from 2003 to 2009 (7 yr). Two Iberian lightning detection networks, composed of 18 sensors over Portugal and Spain, are combined for the first time in the present study. The selected characteristics are cloud-to-ground flashes (CGFs), first stroke peak current, polarity and multiplicity (number of strokes in a given flash). This study examines the temporal (on hourly, monthly and seasonal timescales) and spatial variability of CGFs. The influence of five forcing factors on lightning (elevation, lifted index, convective available potential energy and daily minimum and maximum near-surface air temperatures) over the Iberian sector is also assessed. For regional-scale assessments, six subsectors with different climatic conditions were analysed separately. Despite important regional differences, the strongest lightning activity occurs from late spring to early autumn, and mostly in the afternoon. Furthermore, CGFs are mainly located over high-elevation areas in late spring to summer, while they tend to occur over the sea in autumn. The results suggest that (1) orographically forced thunderstorms over mountainous areas, mostly from May to September, (2) tropospheric buoyancy forcing over western-central and northern regions in summer and over the Mediterranean regions in autumn, and (3) near-surface thermal contrasts from October to February largely control the location of lightning in Iberia. There is no evidence of different forcings by polarity. A clear correspondence between summertime precipitation patterns and CGFs is also found.

Santos, J. A.; Reis, M. A.; De Pablo, F.; Rivas-Soriano, L.; Leite, S. M.

2013-07-01

99

Japan's Dispatch of the Ground Self Defense Force to Iraq: Lessons Learned  

Canada Institute for Scientific and Technical Information (Canada)

The Iraq deployment was a new experience for Japan's Ground Self Defense Force (GSDF) in that all previous missions for humanitarian aid and reconstruction had been carried out under a UN peacekeeping operations framework. The mission therefore provided the GSDF with an array of new challenges and learning opportunities. One of the major innovations for the Iraq deployment was the use of legal and political advisors from the Japan Defense Agency (JDA; recently renamed the Ministry of Defense) on the ground in Iraq with the GSDF. These advisors not only helped to improve coordination between the GSDF and other coalition forces, but also aided interagency coordination between the Ministry of Foreign Affairs (MOFA), the JDA and the GSDF officers in Iraq. Interagency coordination between MOFA and the JDA was not always smooth, but most Japanese officials agree that the "two wheels of the cart" approach that they developed through daily consultations, whereby the GSDF represented the humanitarian face of Japan's support and MOFA represented the financial aspect through its dispersion of Official Development Assistance (ODA), was successful in carrying out the overall mission. The GSDF had to overcome a number of issues in their interactions with Iraqi citizens, including high expectations regarding Japan's reconstruction efforts, poor communication, a lack of local intelligence and sometimes working around Japanese government-imposed restrictions to accomplish their mission.

2007-01-01

100

(Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)  

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB), initiated an investigation to evaluate a potential Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) removal action to prevent, to the extent practicable, the offsite migration of contaminated ground water from WPAFB. WPAFB retained the services of the Environmental Management Operations (EMO) and its principle subcontractor, International Technology Corporation (IT) to complete Phase 1 of the environmental investigation of ground-water contamination at WPAFB. Phase 1 of the investigation involves the short-term evaluation and potential design for a program to remove ground-water contamination that appears to be migrating across the western boundary of Area C, and across the northern boundary of Area B along Springfield Pike. Primarily, Task 4 of Phase 1 focuses on collection of information at the Area C and Springfield Pike boundaries of WPAFB. This Sampling and Analysis Plan (SAP) has been prepared to assist in completion of the Task 4 field investigation and is comprised of the Quality Assurance Project Plan (QAPP) and the Field Sampling Plan (FSP).

1991-10-01

 
 
 
 
101

Aerodynamic forces and flow structures of the leading edge vortex on a flapping wing considering ground effect.  

Science.gov (United States)

The aim of this work is to provide an insight into the aerodynamic performance of the beetle during takeoff, which has been estimated in previous investigations. We employed a scaled-up electromechanical model flapping wing to measure the aerodynamic forces and the three-dimensional flow structures on the flapping wing. The ground effect on the unsteady forces and flow structures were also characterized. The dynamically scaled wing model could replicate the general stroke pattern of the beetle's hind wing kinematics during takeoff flight. Two wing kinematic models have been studied to examine the influences of wing kinematics on unsteady aerodynamic forces. In the first model, the angle of attack is asymmetric and varies during the translational motion, which is the flapping motion of the beetle's hind wing. In the second model, the angle of attack is constant during the translational motion. The instantaneous aerodynamic forces were measured for four strokes during the beetle's takeoff by the force sensor attached at the wing base. Flow visualization provided a general picture of the evolution of the three-dimensional leading edge vortex (LEV) on the beetle hind wing model. The LEV is stable during each stroke, and increases radically from the root to the tip, forming a leading-edge spiral vortex. The force measurement results show that the vertical force generated by the hind wing is large enough to lift the beetle. For the beetle hind wing kinematics, the total vertical force production increases 18.4% and 8.6% for the first and second strokes, respectively, due to the ground effect. However, for the model with a constant angle of attack during translation, the vertical force is reduced during the first stroke. During the third and fourth strokes, the ground effect is negligible for both wing kinematic patterns. This finding suggests that the beetle's flapping mechanism induces a ground effect that can efficiently lift its body from the ground during takeoff. PMID:23851351

Van Truong, Tien; Byun, Doyoung; Kim, Min Jun; Yoon, Kwang Joon; Park, Hoon Cheol

2013-07-15

102

Reactions of ground-state and electronically excited sodium atoms with methyl bromide and molecular chlorine  

Energy Technology Data Exchange (ETDEWEB)

The reactions of ground- and excited-state Na atoms with methyl bromide (CH{sub 3}Br) and chlorine (Cl{sub 2}) have been studied by using the crossed molecular beams method. For both reactions, the cross sections increase with increasing electronic energy. The product recoil energies change little with increasing Na electronic energy, implying that the product internal energies increase substantially. For Na + CH{sub 3}Br, the steric angle of acceptance opens with increasing electronic energy.

Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Covinsky, M.H.; Lee, Y.T. (Lawrence Berkeley Lab., CA (United States))

1991-04-18

103

Reactions of ground-state and electronically excited sodium atoms with methyl bromide and molecular chlorine  

International Nuclear Information System (INIS)

The reactions of ground- and excited-state Na atoms with methyl bromide (CH3Br) and chlorine (Cl2) have been studied by using the crossed molecular beams method. For both reactions, the cross sections increase with increasing electronic energy. The product recoil energies change little with increasing Na electronic energy, implying that the product internal energies increase substantially. For Na + CH3Br, the steric angle of acceptance opens with increasing electronic energy.

1991-01-01

104

Coupled natural convection and atmospheric wind forced advection in above ground reacting heaps  

Energy Technology Data Exchange (ETDEWEB)

A CFD code CFX-4.1 has been employed to simulate a flow and pressure field around an above ground heap. Due to porosity of the heap material a wind driven forced gas advection field within the heap will result. If the heap material contains oxidizable material as in mine wastes and coal stockpiles, then natural-convection induced by heat of oxidation will also occur. The CFD wind flow model is coupled with a model which simulates the heat and mass transfer within heaps containing oxidizable material. This study shows that even under relatively moderate wind flows the traditional assumption that the heaps are immersed in a static atmosphere becomes questionable. 4 refs., 5 figs.

Anne, R.D.; Pantelis, G. [Australian Nuclear Science and Technology Organization, Menai, NSW (Australia)

1997-07-01

105

(Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio)  

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB) initiated an effort for the evaluation of potential removal of ground water contamination at the Base. This report presents a current assessment of the nature and extent of the contamination believed to be migrating across the southwestern boundary of Area C and the northern boundary of Area B based upon analysis of existing environmental data obtained from several sources. The existing data base indicates widespread, low-level contamination moving across Base boundaries at levels that pose no immediate threat to the Mad River Valley well fields. An investigation by the City of Dayton in May and June 1990, however, implies that a more identifiable plume of PCE and TCE may be crossing the southwestern boundary of Area C immediately downgradient of Landfill 5. More data is needed to delineate ground water contamination and to design and implement a suitable control system. This report concludes that although an extensive study of the boundaries in question would be the preferred approach, a limited, focused investigation and subsequent feasibility study can be accomplished with a reasonable certainty of achieving the desired outcome of this project.

1991-10-01

106

Violation of the action-reaction principle and self-forces induced by nonequilibrium fluctuations.  

Science.gov (United States)

We show that the extension of Casimir-like forces to fluctuating fluids driven out of equilibrium can exhibit two interrelated phenomena forbidden at equilibrium: self-forces can be induced on single asymmetric objects and the action-reaction principle between two objects can be violated. These effects originate in asymmetric restrictions imposed by the objects' boundaries on the fluid's fluctuations. They are not ruled out by the second law of thermodynamics since the fluid is in a nonequilibrium state. Considering a simple reaction-diffusion model for the fluid, we explicitly calculate the self-force induced on a deformed circle. We also show that the action-reaction principle does not apply for the internal Casimir forces between a circle and a plate. Their sum, instead of vanishing, provides the self-force on the circle-plate assembly. PMID:18850772

Buenzli, Pascal R; Soto, Rodrigo

2008-08-25

107

Resonance tongues and patterns in periodically forced reaction-diffusion systems  

CERN Multimedia

Various resonant and near-resonant patterns form in a light-sensitive Belousov-Zhabotinsky (BZ) reaction in response to a spatially-homogeneous time-periodic perturbation with light. The regions (tongues) in the forcing frequency and forcing amplitude parameter plane where resonant patterns form are identified through analysis of the temporal response of the patterns. Resonant and near-resonant responses are distinguished. The unforced BZ reaction shows both spatially-uniform oscillations and rotating spiral waves, while the forced system shows patterns such as standing-wave labyrinths and rotating spiral waves. The patterns depend on the amplitude and frequency of the perturbation, and also on whether the system responds to the forcing near the uniform oscillation frequency or the spiral wave frequency. Numerical simulations of a forced FitzHugh-Nagumo reaction-diffusion model show both resonant and near-resonant patterns similar to the BZ chemical system.

Lin, A L; Meron, E; Swinney, H L; Lin, Anna L.; Hagberg, Aric; Meron, Ehud; Swinney, Harry L.

2004-01-01

108

[Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 5, Appendix A, Part 2, Field Investigation report  

Energy Technology Data Exchange (ETDEWEB)

This report contains information related to the sampling and chemical analysis of ground water at the Wright-Patterson Air Force Base. It is part of a field investigation of ground water contamination.

1992-03-01

109

Turing patterns in the chlorine dioxide-iodine-malonic acid reaction with square spatial periodic forcing.  

UK PubMed Central (United Kingdom)

We use the photosensitive chlorine dioxide-iodine-malonic acid reaction-diffusion system to study wavenumber locking of Turing patterns to two-dimensional "square" spatial forcing, implemented as orthogonal sets of bright bands projected onto the reaction medium. Various resonant structures emerge in a broad range of forcing wavelengths and amplitudes, including square lattices and superlattices, one-dimensional stripe patterns and oblique rectangular patterns. Numerical simulations using a model that incorporates additive two-dimensional spatially periodic forcing reproduce well the experimental observations.

Feldman D; Nagao R; Bánsági T Jr; Epstein IR; Dolnik M

2012-05-01

110

(p, n) reaction and the nucleon-nucleon force  

Energy Technology Data Exchange (ETDEWEB)

The (p, n) charge exchange reaction is a powerful tool of nuclear structure physics, with spectroscopic characteristics that are closely related to the free interaction between nucleons. At proton energies in the range of 150-500 MeV, the interaction probes the spin dynamics in the charge exchange process and is particularly sensitive to nuclear pionic fields. At low energies, say less than 50 MeV bombarding energy, the reaction also probes the isovector density. An outstanding success of the reaction as a structural probe is the elucidation of the Gamow-Teller strength function in the nuclear excitation spectrum. However, the total strength found falls short of sum rule predictions by about 40%. Explanations of this quenching have been advanced along two lines, based on subnuclear degrees of freedom or on configuration mixing into high continuum states. Detailed theoretical arguments support the importance of configuration mixing. The subnuclear degrees of freedom may be comparable, but a decisive test is lacking.

Bertsch, G.F.; Esbensen, H.

1987-06-01

111

Measurement of muscle actions and foot reaction forces from crew members during entire working days on the International Space Station (ISS)  

International Nuclear Information System (INIS)

We present pilot work in preparation for ISS Experiment 318, which will investigate changes in lower limb daily mechanical loading and muscular activity profiles that have been implicated in bone mineral loss and muscle atrophy during spaceflight. Prototype equipment for the musculo-skeletal rack of the Human Research Facility (HRF) was used in conjunction with the Ambulatory Data Acquisition System to record and store data. Right foot ground reaction force profiles, right leg EMG activity profiles from the tibialis anterior and vastus medialis, and joint angular excursion profiles from the right knee and ankle were collected during five minutes each of forward and backward running in 1g as well as over a twelve hour period of activities during daily living. Ground reaction force profiles were analyzed to provide an estimate of 1g daily mechanical load stimulus, while EMG and joint angle profiles characterized the role of individual muscles in generating and absorbing energy

2000-01-19

112

Radiated power and radiation-reaction force: A derivation based on Fourier transforms  

Energy Technology Data Exchange (ETDEWEB)

On making use of the Fourier transforms, general formulas for the time-averaged radiated power and radiation-reaction force are obtained in terms of either the spectral distribution of the source current density or the source charge and current density at the retarded time. The former expressions are particularly suited for the derivation of the Lienard formula for the radiated power as well as the Abraham-Becker form of the radiation-reaction force for a pointlike charge. The procedure of getting instantaneous radiation quantities from the corresponding time-averaged ones is discussed critically and the Abraham-Lorentz force, obtained on the basis of the Heaviside-Feynman fields, is identified as the instantaneous radiation-reaction force.

Bellotti, U.; Bornatici, M. [Pavia Univ. (Italy). Dip. di Fisica `A. Volta`, Istituto Nazionale di Fisica Molecolare

1998-09-01

113

Radiated power and radiation-reaction force: A derivation based on Fourier transforms  

International Nuclear Information System (INIS)

On making use of the Fourier transforms, general formulas for the time-averaged radiated power and radiation-reaction force are obtained in terms of either the spectral distribution of the source current density or the source charge and current density at the retarded time. The former expressions are particularly suited for the derivation of the Lienard formula for the radiated power as well as the Abraham-Becker form of the radiation-reaction force for a pointlike charge. The procedure of getting instantaneous radiation quantities from the corresponding time-averaged ones is discussed critically and the Abraham-Lorentz force, obtained on the basis of the Heaviside-Feynman fields, is identified as the instantaneous radiation-reaction force.

1998-01-01

114

Shortwave radiative forcing efficiency of urban aerosols--a case study using ground based measurements.  

Science.gov (United States)

Aerosols reduce the surface reaching solar flux by scattering the incoming solar radiation out to space. Various model studies on climate change suggest that surface cooling induced by aerosol scattering is the largest source of uncertainty in predicting the future climate. In the present study measurements of aerosol optical depth (AOD) and its direct radiative forcing efficiency has been presented over a typical tropical urban environment namely Hyderabad during December, 2003. Measurements of AOD have been carried out using MICROTOPS-II sunphotometer, black carbon aerosol mass concentration using Aethalometer, total aerosol mass concentration using channel Quartz Crystal Microbalance (QCM) Impactor Particle analyser and direct normal solar irradiance using Multifilter Rotating Shadow Band Radiometer (MFRSR). Diurnal variation of AOD showed high values during afternoon hours. The fraction of BC estimated to be approximately 9% in the total aerosol mass concentration over the study area. Results of the study suggest -62.5 Wm(-2) reduction in the ground reaching shortwave flux for every 0.1 increase in aerosol optical depth. The results have been discussed in the paper. PMID:15571753

Latha, K Madhavi; Badarinath, K V S

2005-01-01

115

Shortwave radiative forcing efficiency of urban aerosols--a case study using ground based measurements.  

UK PubMed Central (United Kingdom)

Aerosols reduce the surface reaching solar flux by scattering the incoming solar radiation out to space. Various model studies on climate change suggest that surface cooling induced by aerosol scattering is the largest source of uncertainty in predicting the future climate. In the present study measurements of aerosol optical depth (AOD) and its direct radiative forcing efficiency has been presented over a typical tropical urban environment namely Hyderabad during December, 2003. Measurements of AOD have been carried out using MICROTOPS-II sunphotometer, black carbon aerosol mass concentration using Aethalometer, total aerosol mass concentration using channel Quartz Crystal Microbalance (QCM) Impactor Particle analyser and direct normal solar irradiance using Multifilter Rotating Shadow Band Radiometer (MFRSR). Diurnal variation of AOD showed high values during afternoon hours. The fraction of BC estimated to be approximately 9% in the total aerosol mass concentration over the study area. Results of the study suggest -62.5 Wm(-2) reduction in the ground reaching shortwave flux for every 0.1 increase in aerosol optical depth. The results have been discussed in the paper.

Latha KM; Badarinath KV

2005-01-01

116

RAPID DETECTION OF LISTERIA MONOCYTOGENES IN GROUND TURKEY BY IMMUNOMAGNETIC SEPARATION AND POLYMERASE CHAIN REACTION  

UK PubMed Central (United Kingdom)

The aim of this study was to determine the prevalence of Listeria monocytogenes in packaged fresh ground turkey in Turkey using immunomagnetic separation (IMS) as a selective enrichment step in method and polymerase chain reaction (PCR). A total of 180 ground turkey samples were collected during a 1-year period. Thirty-two (17.7%) of the samples contained L. monocytogenes, 24 (13.3%) contained Listeria innocua, 7 (3.8%) had Listeria ivanovii and 5 (2.7%) had Listeria seeligeri by means of IMS-based cultivation method. A PCR assay was performed, based on hlyA gene-specific primers. In all L. monocytogenes isolates, hlyA gene was confirmed, indicating that the correlation between IMS-based cultivation and PCR methods was 100%. The results suggest that the prevalence of L. monocytogenes in ground turkey is relatively high in Turkey and that ground turkey should be produced under appropriate hygienic and technological conditions for the prevention of public health hazards. Using fast and reliable methods to detect and identify foodborne pathogenic bacteria, including Listeria monocytogenes, is important to detect the risk of contaminated product and protect public health. In some ways it is time-consuming to isolate and identify the pathogenic microorganisms from food products using conventional techniques. Different methods or techniques can be used both for redounding the isolation chance and to gain time for this purpose. Immunomagnetic separation (IMS) and polymerase chain reaction (PCR) techniques are effective and rapid methods for separation, detection and confirmation of Listeria spp. from foods. In this study rapid, specific and sensitive IMS method was used to determine the prevalence of L. monocytogenes in fresh ground turkey and PCR technique was used for the verification of the L. monocytogenes isolates.

AYAZ ND; EROL I

2009-06-01

117

Analysis of diatomic bond dissociation and formation in terms of the reaction force and the position-dependent reaction force constant.  

UK PubMed Central (United Kingdom)

Bond dissociation and formation in diatomic molecules are analyzed in terms of the reaction force F(R) and the reaction force constant kappa(R). These were determined for a group of 13 molecules from their extended-Rydberg potential energy functions V(R), which are of near-experimental quality. From F(R) and kappa(R) comes a two-stage description of dissociation/formation. In dissociation, the first stage involves stretching of the bond, which is opposed by an increasingly negative retarding force F(R). This reaches a minimum and then begins to weaken in the second stage, which is the transition from stretched molecule to free atoms. Bond formation begins with the reverse transition, driven by a positive F(R) which reaches a maximum for the stretched molecule and then becomes a decreasing restoring force. In the stages in which the system is a stretched molecule, kappa(R) is positive with its maximum at the equilibrium bond length; it is zero at the minimum or maximum of F(R), and negative throughout the transition stages, going through a minimum. kappa(R) <0 has been found to characterize the transition portion of a reaction. This description of dissociation/formation is reinforced by computed B3LYP and Hartree-Fock force constants at different atom separations for the singlet molecules. Hartree-Fock wave function stability assessments suggest that, for the single-bonded singlet molecules, the onset of electron unpairing in dissociation comes in the neighborhood of the F(R) minimum.

Murray JS; Toro-Labbé A; Clark T; Politzer P

2009-06-01

118

Malaria and mefloquine prophylaxis use among Japan Ground Self-Defense Force personnel deployed in East Timor.  

UK PubMed Central (United Kingdom)

BACKGROUND: Malaria poses a significant threat to military personnel stationed in endemic areas; therefore, it is important to examine the risks of military operations, particularly in areas where malaria-related data are scarce. The recent deployment of Japan Ground Self-Defense Force (JGSDF) for a peacekeeping operation in East Timor provided an opportunity to investigate these risks. The results of these studies may be translated into chemoprophylactic strategies for travelers. METHODS: A total of 1,876 members were deployed between April 2002 and September 2003. They consisted of three battalions; each remained for 6 months and was put on mefloquine prophylaxis. Malaria infection was investigated, including exposure to Plasmodium falciparum sporozoites, assessed by seroconversion for anticircumsporozoite (anti-CS) protein antibodies. Adherence to and adverse events (AEs) of mefloquine were studied via questionnaires. RESULTS: Four members were evacuated: one each with optic neuritis, lung cancer with brain metastasis, IgA nephropathy, and psychotic reactions that may have been precipitated by mefloquine. Six clinical episodes of Plasmodium vivax occurred, including one relapse, but there were no clinical cases of P falciparum, yielding a crude malaria attack rate of 0.32% for the 6-month period. Overall, 3.1% of the study population seroconverted for the anti-CS protein antibodies, with some regional differences noted. About 24% of questionnaire respondents, reported AEs; however, none of the AEs was severe. The AEs tended to emerge during the initial doses of chemoprophylaxis. CONCLUSIONS: The implementation of mefloquine prophylaxis among JGSDF personnel in East Timor, where P falciparum constitutes a moderate risk, appears to have been a success. Mefloquine prophylaxis was generally safe for Japanese unless predisposed to neuropsychiatric illness. However, given that mefloquine is the only chemoprophylactic agent available, a risk-benefit analysis tailored to the traveler is required for visits to countries such as East Timor.

Fujii T; Kaku K; Jelinek T; Kimura M

2007-07-01

119

Relative Rates of Reaction of Olefins with the Ground and the First Excited Electronic States of Methylene.  

Science.gov (United States)

Relative rates of reaction of a number of olefins with the ground state triplet and the first excited electronic state (the lowest singlet) of methylene were determined at room temperature. The rates depend relatively little on olefin structure. Triplet m...

S. Krzyzanowski R. J. Cvetanovic

1966-01-01

120

Classical Wigner method with an effective quantum force: application to reaction rates.  

UK PubMed Central (United Kingdom)

We construct an effective "quantum force" to be used in the classical molecular dynamics part of the classical Wigner method when determining correlation functions. The quantum force is obtained by estimating the most important short time separation of the Feynman paths that enter into the expression for the correlation function. The evaluation of the force is then as easy as classical potential energy evaluations. The ideas are tested on three reaction rate problems. The resulting transmission coefficients are in much better agreement with accurate results than transmission coefficients from the ordinary classical Wigner method.

Poulsen JA; Li H; Nyman G

2009-07-01

 
 
 
 
121

Ground state proton capture reactions from 20 to 100 MeV  

Energy Technology Data Exchange (ETDEWEB)

Proton capture reactions on targets of /sup 11/B, /sup 12/C, /sup 15/N, /sup 16/O, and /sup 27/Al were measured from E/sub p/ = 20 to 100 MeV. The energy dependence of the theta/sub ..gamma../ = 60/sup 0/ differential cross sections are presented for captures populating the ground states of /sup 12/C, /sup 13/N, /sup 16/O, /sup 17/F, and /sup 28/Si. Differential-cross-section and analyzing-power angular distributions are presented at bombarding energies of E/sub p/ = 20.8, 28.35, 49.2, and 49.69 MeV. Calculations from two capture-reaction models are compared to the data.

Hausman, H.J.; Blatt, S.L.; Donoghue, T.R.; Kalen, J.; Kim, W.; Marchlenski, D.G.; Rackers, T.W.; Schmalbrock, P.; Kovash, M.A.; Bacher, A.D.; and others

1988-02-01

122

Contribution of the magnetic moment to the reaction force to the radiation in relativistic form  

International Nuclear Information System (INIS)

Starting with the magnetic Smirnov reaction force, a relativistic equation which describe the motion of a charged particle with constant magnetic moment of spin ??, is obtained. A Landau-Lifshitz-like equation is deduced with magnetic moment. A fundamental difference between the classical and relativistic radiation rate of energy is found. (Author)

2007-01-01

123

Calculations of three-nucleon reactions with N3LO chiral forces: achievements and challenges  

CERN Document Server

We discuss the application of the chiral N3LO forces to three-nucleon reactions and point to the challenges which will have to be addressed. Present approaches to solve three-nucleon Faddeev equations are based on a partial-wave decomposition. A rapid increase of the number of terms contributing to the chiral three-nucleon force when increasing the order of the chiral expansion from N2LO to N3LO forced us to develop a fast and effective method of automatized partial wave decomposition. At low energies of the incoming nucleon below about 20MeV, where only a limited number of partial waves is required, this method allowed us to perform calculations of reactions in the three-nucleon continuum using N3LO two- and three-nucleon forces. It turns out that inclusion of consistent chiral interactions, with relativistic 1/m corrections and short-range 2pi-contact term omitted in the N3LO three-nucleon force, does not explain the long standing low energy Ay-puzzle. We discuss problems arising when chiral forces are appl...

Witala, Henryk; Skibinski, Roman; Topolnicki, Kacper

2013-01-01

124

A simple model for estimating the active reactions of embryonic tissues to a deforming mechanical force.  

UK PubMed Central (United Kingdom)

Active reactions of embryonic tissues to mechanical forces play an important role in morphogenesis. To study these reactions, experimental models that enable to evaluate the applied forces and the deformations of the tissues are required. A model based upon the active intrusion of a living early gastrula Xenopus embryo into a tube half the embryo in diameter is described. The intrusion is initially triggered by a suction force of several dozen Pa but then continues in the absence of external driving force, stopping immediately after the entire embryo has penetrated into the tube. The process can be stopped by cytoskeletal drugs or by the damage of the part of the embryo still non-aspirated and is associated with the transversal contraction and meridional elongation of the non-aspirated part of the embryo surface and quasi-periodic longitudinal contractions/extensions of the cells within the part already aspirated. We suggest that this reaction is an active response to the embryo deformation and discuss its morphogenetic role. The problem of estimating the elastic modules of embryonic tissues is also discussed.

Mansurov AN; Stein AA; Beloussov LV

2012-11-01

125

Effect of acute static stretching on force, balance, reaction time, and movement time.  

UK PubMed Central (United Kingdom)

PURPOSE: The purpose of the study was to investigate the effect of an acute bout of lower limb static stretching on balance, proprioception, reaction, and movement time. METHODS: Sixteen subjects were tested before and after both a static stretching of the quadriceps, hamstrings, and plantar flexors or a similar duration control condition. The stretching protocol involved a 5-min cycle warm-up followed by three stretches to the point of discomfort of 45 s each with 15-s rest periods for each muscle group. Measurements included maximal voluntary isometric contraction (MVC) force of the leg extensors, static balance using a computerized wobble board, reaction and movement time of the dominant lower limb, and the ability to match 30% and 50% MVC forces with and without visual feedback. RESULTS: There were no significant differences in the decrease in MVC between the stretch and control conditions or in the ability to match submaximal forces. However, there was a significant (P < 0.009) decrease in balance scores with the stretch (decreasing 9.2%) compared with the control (increasing 17.3%) condition. Similarly, decreases in reaction (5.8%) and movement (5.7%) time with the control condition differed significantly (P < 0.01) from the stretch-induced increases of 4.0% and 1.9%, respectively. CONCLUSION: In conclusion, it appears that an acute bout of stretching impaired the warm-up effect achieved under control conditions with balance and reaction/movement time.

Behm DG; Bambury A; Cahill F; Power K

2004-08-01

126

Finding the Middle Ground: The U.S. Air Force, Space Weaponization, and Arms Control.  

Science.gov (United States)

This paper discusses problems associated with the current US approach to developing and deploying space weapons. Recommendations center around an alternative strategy for realizing US space control and space force application capabilities based on deploya...

B. C. Ruhm

2003-01-01

127

Negative parity states and ground state properties of the. cap alpha. -. cap alpha. -n system calculated by different forces  

Energy Technology Data Exchange (ETDEWEB)

In recent years predictions on the off-shell behavior of composite particles interactions have been made by some theoretical models. The goal of this paper is to test them by using /sup 9/Be nucleus. The bound state problem of /sup 9/Be considered as a ..cap alpha..-..cap alpha..-n three-cluster system is solved in configuration space. Several on-shell equivalent local and nonlocal forces for the ..cap alpha..-..cap alpha.. and n-..cap alpha.. interactions are used for calculation of the low lying negative parity spectrum of /sup 9/Be, and also of the charge density, quadrupole moment, and the correlation density of /sup 9/Be ground state. The contributions to the calculated quantities of different partial waves of the two-body forces are examined and discussed.

Orlowski, M.C.L.; Cheng-guang, B.; Liu-yuen

1982-04-01

128

Effects of brain polarization on reaction times and pinch force in chronic stroke  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Previous studies showed that anodal transcranial DC stimulation (tDCS) applied to the primary motor cortex of the affected hemisphere (M1affected hemisphere) after subcortical stroke transiently improves performance of complex tasks that mimic activities of daily living (ADL). It is not known if relatively simpler motor tasks are similarly affected. Here we tested the effects of tDCS on pinch force (PF) and simple reaction time (RT) tasks in patients with chronic stroke in a double-blind cross-over Sham-controlled experimental design. Results Anodal tDCS shortened reaction times and improved pinch force in the paretic hand relative to Sham stimulation, an effect present in patients with higher impairment. Conclusion tDCS of M1affected hemisphere can modulate performance of motor tasks simpler than those previously studied, a finding that could potentially benefit patients with relatively higher impairment levels.

Hummel Friedhelm C; Voller Bernhard; Celnik Pablo; Floel Agnes; Giraux Pascal; Gerloff Christian; Cohen Leonardo G

2006-01-01

129

Reaction force of percussive corer, rotary-friction corer, and rotary-percussive corer  

Science.gov (United States)

Future NASA exploration missions will increasingly require sampling, in-situ analysis and possibly the return of material to Earth for laboratory analysis. To address these objectives, effective and optimized drilling techniques are needed. This requires developing comprehensive tools to be able to determine analytically what takes place during the operation and what are the control parameters that can be enhanced. In this study, three types of coring techniques were studied and were identified as potential candidates for operation from a possible future Mars Sample Return (MSR) mission rover. These techniques include percussive, rotary-friction, and rotary-percussive coring. Theoretical models were developed to predict the dynamic reaction forces transmitted from these three types of corers to the robotic arms that hold them. The predicted reaction forces will then be used in a dynamic simulation environment to simulate a representative corer tool to obtain a best estimate of a tool that can be operated from a small rover. The predicted dynamic reaction forces will be presented in this paper.

Chang, Zensheu; Sherrit, Stewart; Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph; Backes, Paul

2006-04-01

130

Assessment of changes in gait parameters and vertical ground reaction forces after total hip arthroplasty  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The principal objectives of arthroplasty are relief of pain and enhancement of range of motion. Currently, postoperative pain and functional capacity are assessed largely on the basis of subjective evaluation scores. Because of the lack of control inherent in this method it is often difficult to int...

Bhargava P; Shrivastava P; Nagariya S

131

Extraction of ground reaction forces for real-time synthesis of walking sounds  

DEFF Research Database (Denmark)

A shoe-independent system to synthesize real-time footstep sounds on different materials has been developed. A footstep sound is considered as the result of an interaction between an exciter (the shoe) and a resonator (the floor). To achieve our goal, we propose two different solutions. The first solution is based on contact microphones attached on the exterior part of each shoe, which capture the sound of a footstep. The second approach consists on using microphones placed on the floor. In both situations, the captured sound is analysed and used to control a sound synthesis engine. We discuss advantages and disadvantages of the two approaches.

Serafin, Stefania; Turchet, Luca

2009-01-01

132

Chinese Attitudinal Reactions to Forced Compliance: A Cross-Cultural Experiment in the Theory of Cognitive Dissonance.  

Science.gov (United States)

The paper represents an attempt to provide empirical answers to the questions posed by two mutually contradictory theories pertinent to Chinese reactions in a forced compliance situation, viz. the Theory of Cognitive Dissonance and a Characterological The...

P. Hiniker

1965-01-01

133

Does foot pitch at ground contact affect parachute landing technique?  

UK PubMed Central (United Kingdom)

The Australian Defence Force Parachute Training School instructs trainees to make initial ground contact using a flat foot whereas United States paratroopers are taught to contact the ground with the ball of the foot first. This study aimed to determine whether differences in foot pitch affected parachute landing technique. Kinematic, ground reaction force and electromyographic data were analyzed for 28 parachutists who performed parachute landings (vertical descent velocity = 3.4 m x s(-1)) from a monorail apparatus. Independent t-tests were used to determine significant (p < 0.05) differences between variables characterizing foot pitch. Subjects who landed flat-footed displayed less knee and ankle flexion, sustained higher peak ground reaction forces, and took less time to reach peak force than those who landed on the balls of their feet. Although forefoot landings lowered ground reaction forces compared to landing flat-footed, further research is required to confirm whether this is a safer parachute landing strategy.

Whitting JW; Steele JR; Jaffrey M; Munro BJ

2009-08-01

134

Optimizing the third-and-a-half post-Newtonian gravitational radiation-reaction force for numerical simulations  

CERN Multimedia

The gravitational radiation-reaction force acting on perfect fluids at 3.5 post-Newtonian order is cast into a form which is directly applicable to numerical simulations. Extensive use is made of metric-coefficient changes induced by functional coordinate transformations, of the continuity equation, as well as of the equations of motion. We also present an expression appropriate for numerical simulations of the radiation field causing the worked out reaction force.

Faye, G

2003-01-01

135

Sudden drop in ground support produces force-related unload response in human overground walking  

DEFF Research Database (Denmark)

Humans maneuver easily over uneven terrain. To maintain smooth and efficient gait the motor system needs to adapt the locomotor output to the walking environment. In the present study we investigate the role of sensory feedback in adjusting the soleus muscle activity during overground walking in 19 healthy volunteers. Subjects walked unrestrained over a hydraulically actuated platform. On random trials the platform was accelerated downward at 0.8 g, unloading the plantar flexor muscles in midstance or late stance. The drop of the platform resulted in a significant depression of the soleus muscle activity of -17.9% (SD 2) and -21.4% (SD 2), with an onset latency of 49 ms (SD 1) and 45 ms (SD 1) in midstance and late stance, respectively. Input to the vestibular apparatus (i.e., the head acceleration) occurred at a latency 10.0 ms (SD 2.4) following the drop and ankle dorsiflexion velocity was decreased starting 22 ms (SD 15) after the drop. To investigate the role of length- and velocity-sensitive afferents onthe depression in soleus muscle activity, the ankle rotation was arrested by using an ankle foot orthotic as the platform was dropped. Preventing the ankle movement did not significantly change the soleus depression in late stance [-18.2% (SD 15)], whereas the depression in midstance was removed [+4.9% (SD 13)]. It is concluded that force feedback from ankle extensors increases the locomotor output through positive feedback in late stance. In midstance the effect of force feedback was not observed, suggesting that spindle afferents may have a more significant effect on the output during this phase of the step cycle.

Af Klint, Richard; Nielsen, Jens Bo

2009-01-01

136

[Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 1, Site assessment report  

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB) initiated an effort for the evaluation of potential removal of ground water contamination at the Base. This report presents a current assessment of the nature and extent of the contamination believed to be migrating across the southwestern boundary of Area C and the northern boundary of Area B based upon analysis of existing environmental data obtained from several sources. The existing data base indicates widespread, low-level contamination moving across Base boundaries at levels that pose no immediate threat to the Mad River Valley well fields. An investigation by the City of Dayton in May and June 1990, however, implies that a more identifiable plume of PCE and TCE may be crossing the southwestern boundary of Area C immediately downgradient of Landfill 5. More data is needed to delineate ground water contamination and to design and implement a suitable control system. This report concludes that although an extensive study of the boundaries in question would be the preferred approach, a limited, focused investigation and subsequent feasibility study can be accomplished with a reasonable certainty of achieving the desired outcome of this project.

1991-10-01

137

A comparison of vertical reaction forces during propulsion of three different one-arm drive wheelchairs by hemiplegic users.  

UK PubMed Central (United Kingdom)

Abstract Purpose: The aim of this pilot study was to compare the vertical reaction forces (N) generated in three different Action 3 manual one-arm drive wheelchairs: dual handrim, a lever drive and a Neater Uni-wheelchair (NUW). A CONFORmat® Pressure measurement mat, placed on top of the users' prescribed cushion, measured vertical force at the buttock/seat interface on both hemiplegic and non-hemiplegic sides in each wheelchair. Methods: Fifteen hemiplegic users were randomly assigned each wheelchair to drive around an indoor obstacle course. During propulsion of a multiple sensor, continuous measurement of force was recorded. Time taken to complete the circuit was recorded. Mean force and confidence intervals for each buttock were calculated per user per wheelchair. Results: The dual handrim produced the highest vertical force during propulsion under the right buttock ([Formula: see text]?=?484.43; SD?=?55.4; p?force ([Formula: see text]?=?368.05; SD?=?53.55; p?force during propulsion. Since increases in this seat vertical reaction force may be related to the propulsive force. Further investigation is indicated as this may be a significant factor for clinicians when prescribing one-arm drive wheelchairs. Implications for Rehabilitation Review of clinical reasoning in prescribing wheelchairs. Addition of the Neater Uni-wheelchair to wheelchair services prescribing lists.

Mandy A; Redhead L; McCudden C; Michaelis J

2013-03-01

138

EMMI Rapid Reaction Task Force on "Thermalization in Non-abelian Plasmas"  

CERN Document Server

Recently, different proposals have been put forward on how thermalization proceeds in heavy-ion collisions in the idealized limit of very large nuclei at sufficiently high energy. Important aspects of the parametric estimates at weak coupling may be tested using well-established classical-statistical lattice simulations of the far-from-equilibrium gluon dynamics. This has to be confronted with strong coupling scenarios in related theories based on gauge-string dualities. Furthermore, closely related questions about far-from-equilibrium dynamics arise in early-universe cosmology and in non-relativistic systems of ultracold atoms. These were central topics of the EMMI Rapid Reaction Task Force meeting held on December 12-14, 2011, at the University of Heidelberg, which we report on.

Berges, Juergen; Gelis, Francois

2012-01-01

139

Ground Cloud Dispersion Measurements During The Titan IV Mission number K15 (5 December 1995) at Vandenberg Air Force Base. Volume 1. Test Overview and Data Summary.  

Science.gov (United States)

Launch plume imagery, airborne and ground-level HCl measurement results, and meteorological data measured during the launch of a Titan IV vehicle at Vandenberg Air Force Base on 5 December 1995 (mission K-15) are presented. These data is used to determine...

1997-01-01

140

Forced choice reaction time paradigm in children with separation anxiety disorder, social phobia, and nonanxious controls.  

UK PubMed Central (United Kingdom)

Cognitive distortions refer to cognitive processes that are biased and therefore yield dysfunctional and maladaptive products (e.g., interpretation bias). Automatic aspects of information processing need to be considered and investigating these aspects requires forms of assessment other than self-report. Studies focussing on the specificity of cognitive biases across different types of anxiety disorders in childhood are rare. Thus, a forced choice reaction time paradigm with picture stimuli was used to assess the interpretation bias in anxious children online. The study investigated disorder-specific interpretation bias in 71 children with separation anxiety disorder (SAD), 31 children with social phobia, and 42 children without mental disorders, aged 5-13 years. Results indicated that children with SAD rated ambiguous separation pictures as significantly more unpleasant and more arousing than nonanxious children. However, no support was found that children with SAD and social phobia interpret ambiguous separation or social pictures in a more negative way than nonanxious children. Furthermore, no group differences were found in reaction times to all picture categories.

In-Albon T; Dubi K; Rapee RM; Schneider S

2009-12-01

 
 
 
 
141

The mechanism of methanol decomposition by CuO. A theoretical study based on the reaction force and reaction electronic flux analysis.  

UK PubMed Central (United Kingdom)

A theoretical study of methanol decomposition using a model representing the initial step of the reaction CH?OH + CuO ? CH?O + H?O + Cu is presented. Theoretical calculations using B3LYP/6-31 G along with Lanl2DZ pseudopotentials on metallic centers were performed and the results discussed within the framework of the reaction force analysis. It has been found that the reaction takes place following a stepwise mechanism: first, copper reduction (Cu?² ? Cu?) accompanies the oxygen transposition and then a second reduction takes place (Cu? ? Cu?) together with a proton transfer that produce formaldehyde and release a water molecule.

Cerón ML; Herrera B; Araya P; Gracia F; Toro-Labbé A

2011-07-01

142

Radiation-Reaction-Force-Induced Nonlinear Mixing of Raman Sidebands of an Ultraintense Laser Pulse in a Plasma  

Science.gov (United States)

Stimulated Raman scattering of an ultraintense laser pulse in plasmas is studied by perturbatively including the leading order term of the Landau-Lifshitz radiation reaction force in the equation of motion for plasma electrons. In this approximation, the radiation reaction force causes a phase shift in nonlinear current densities that drive the two Raman sidebands (anti-Stokes and Stokes waves), manifesting itself into the nonlinear mixing of two sidebands. This mixing results in a strong enhancement in the growth of the forward Raman scattering instability.

Kumar, Naveen; Hatsagortsyan, Karen Z.; Keitel, Christoph H.

2013-09-01

143

3D FEM Numerical Simulation of Seismic Pile-supported Bridge Structure Reaction in Liquefying Ground  

Directory of Open Access Journals (Sweden)

Full Text Available This study examines the establishment of liquefied ground pile-soil-bridge seismic interaction analysis of three-dimensional finite element analysis method for the simulation of liquefied ground shaking table test of pile-soil seismic interaction analysis, undertake OpenSees finite element based numerical simulation platform, for the shaking table test based on two-phase saturated porous media, Comparative numerical and experimental results, detailed test pile dynamic response of bridge structure and dynamic properties, especially liquefaction pore pressure, liquefaction of pile foundation and the dynamic response of the free field. Finite element method can reasonably predict the site of pore pressure, dynamic response; despite the conventional beam element simulation of pile, pile dynamic response can still accurately simulated.

Baydaa Hussain Maula; Ling XianZhang, Tang Liang and Xu Pengju

2011-01-01

144

Barrier modification in sub-barrier fusion reactions using Wong formula with Skyrme forces in semiclassical formalism  

CERN Multimedia

We obtain the nuclear proximity potential by using semiclassical extended Thomas Fermi (ETF) approach in Skyrme energy density formalism (SEDF), and use it in the extended $\\ell$-summed Wong formula under frozen density approximation. This method has the advantage of allowing the use of different Skyrme forces, giving different barriers. Thus, for a given reaction, we could choose a Skyrme force with proper barrier characteristics, not-requiring extra ``barrier lowering" or ``barrier narrowing" for a best fit to data. For the $^{64}$Ni+$^{100}$Mo reaction, the $\\ell$-summed Wong formula, with effects of deformations and orientations of nuclei included, fits the fusion-evaporation cross section data exactly for the force GSkI, requiring additional barrier modifications for forces SIII and SV. However, the same for other similar reactions, like $^{58,64}$Ni+$^{58,64}$Ni, fits the data best for SIII force. Hence, the barrier modification effects in $\\ell$-summed Wong expression depends on the choice of Skyrme fo...

Kumar, Raj

2010-01-01

145

Collisional and photoinitiated reaction dynamics in the ground electronic state of Ca-HCl  

International Nuclear Information System (INIS)

[en] Ca+HCl(?,j) reactive collisions were studied for different rovibrational states of the HCl reactant using wave-packet calculations in reactant Jacobi coordinates. A recently proposed potential-energy surface was used with a barrier of ?0.4 eV followed by a deep well. The possibility of an insertion mechanism due to this last well has been analyzed and it was found that once the wave packet passes over the barrier most of it goes directly to CaCl+H products, which shows that the reaction dynamics is essentially direct. It was also found that there is no significant change in the reaction efficiency as a function of the initial HCl rovibrational state, because CaHCl at the barrier has an only little elongated HCl bond. Near the threshold for reaction with HCl(?=0), however, the reaction shows significant steric effects for j>0. In a complementary study, the infrared excitation from the Ca-HCl van der Waals well was simulated. The spectrum thus obtained shows several series of resonances which correspond to quasibound states correlating to excited HCl(?) vibrations. The Ca-HCl binding energies of these quasibound states increase dramatically with ?, from 75 to 650 cm-1, because the wave function spreads increasingly over larger HCl bond lengths. Thus it explores the region of the barrier saddle point and the deep insertion well. Although also the charge-transfer contribution increases with ?, the reaction probability for resonances of the ?=2 manifold, which are well above the reaction threshold, is still negligible. This explains the relatively long lifetimes of these ?=2 resonances. The reaction probability becomes significant at ?=3. Our simulations have shown that an experimental study of this type will allow a gradual spectroscopic probing of the barrier for the reaction

2005-08-08

146

Reaction force/torque sensing in a master-slave robot system without mechanical sensors.  

UK PubMed Central (United Kingdom)

In human-robot cooperative control systems, force feedback is often necessary in order to achieve high precision and high stability. Usually, traditional robot assistant systems implement force feedback using force/torque sensors. However, it is difficult to directly mount a mechanical force sensor on some working terminals, such as in applications of minimally invasive robotic surgery, micromanipulation, or in working environments exposed to radiation or high temperature. We propose a novel force sensing mechanism for implementing force feedback in a master-slave robot system with no mechanical sensors. The system consists of two identical electro-motors with the master motor powering the slave motor to interact with the environment. A bimanual coordinated training platform using the new force sensing mechanism was developed and the system was verified in experiments. Results confirm that the proposed mechanism is capable of achieving bilateral force sensing and mirror-image movements of two terminals in two reverse control directions.

Liu T; Li C; Inoue Y; Shibata K

2010-01-01

147

Proton occupancies in the even Se ground states via the (d,3He) reaction  

International Nuclear Information System (INIS)

[en] The spectroscopic factors for the levels of 73As, 75As, 77As, 79As, 81As have been measured in the Se(d,3He)As reactions at 25.2 MeV. The proton occupation numbers deduced for the even Se isotopes show that the striking change in proton configuration, observed for the Ge isotope between N = 42, does persist for the Se isotopes. This change is not reproduced, either by a model calculation using spectral distribution methods or by proton wave functions recently suggested for the Se isotopes to explain the results of the Se(d,6Li)Ge reactions

1982-01-01

148

[Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 2, Work plan: Phase 1, Task 4, Field Investigation: Draft  

Energy Technology Data Exchange (ETDEWEB)

In April 1990 Wright-Patterson Air Force Base (WPAFB) initiated an investigation to evaluate a potential CERCLA removal action to prevent, to the extent practicable, the migration of ground-water contamination in the Mad River Valley Aquifer within and across WPAFB boundaries. The action will be based on a Focused Feasibility Study with an Action Memorandum serving as a decision document that is subject to approval by the Ohio Environmental Protection Agency. The first phase (Phase 1) of this effort involves an investigation of ground-water contamination migrating across the southwest boundary of Area C and across Springfield Pike adjacent to Area B. Task 4 of Phase 1 is a field investigation to collect sufficient additional information to evaluate removal alternatives. The field investigation will provide information in the following specific areas of study: water-level data which will be used to permit calibration of the ground-water flow model to a unique time in history; and ground-water quality data which will be used to characterize the current chemical conditions of ground water.

1991-10-01

149

Measurement of the rates of reaction of the ground and metastable excited states of 02+, N0+ and 0+ with atmospheric gases at thermal energy  

International Nuclear Information System (INIS)

Thermal-energy reaction rate coefficients and product ion distributions have been measured for reactions of both the ground state and metastable electronic states of 02+, N0+ and 0+ with several neutral species, using a selected-ion flow tube. In general the excited-ion reaction rates are fast, frequently approaching the Langevin limit. Collisional quenching occurs for the reactions of N0+sup(star) with N2,02 and H2 and the quenching rates have been determined. The ion source also provided a substantial yield of doubly charged 02 permitting some measurements of reaction rates of 022+. (author)

1978-10-14

150

The ground state mass of 147Gd from single-neutron transfer reactions  

International Nuclear Information System (INIS)

[en] We used thin targets of radioactive 148Gd to determine a precise value for the mass of 147Gd. The (p,d), (d,t) and (3He,?) reactions were used with high-resolution charged particle spectrometry to determine Q-values for the 148Gd target relative to several calibration targets having known Q-values. By combining the measured Q-value with the 1977 148Gd mass we get the mass excess, M(147Gd)= -75356 +- 6 keV, which differs by proportional 150 keV from both the 1977 and 1983 mass tabulations but in opposite directions. (orig.)

1984-01-01

151

The ground state mass of 147Gd from single-neutron transfer reactions  

International Nuclear Information System (INIS)

[en] Thin targets of radioactive 148Gd were used to determine a precise value for the mass of 147Gd. The (p,d), (d,t), and 3He,?) reactions were used with high-resolution charged-particle spectrometry to determine Q-values for the 148Gd target relative to several calibration targets having known Q-values. By combining the measured Q-value with the 148Gd mass, the mass defect, ?M(147Gd) = 75356 +- 6 keV, 149 keV less than the value in the 1977 mass tabulation was obtained. 7 refs., 1 fig., 1 tab

1984-01-01

152

The classical Wigner method with an effective quantum force: application to the collinear H + H2 reaction.  

UK PubMed Central (United Kingdom)

To improve the classical Wigner (CW) model, we recently proposed the classical Wigner model with an effective quantum force (CWEQF). The results of the CWEQF model are more accurate than those of the CW model. Still the simplicity of the CW model is retained. The quantum force was obtained by defining a characteristic distance ?(0) between two Feynman paths that enter the expression for the flux-flux correlation function. ?(0) was considered independent of the position along the reaction path. The CWEQF leads to a lowering of the effective potential barrier. Here we develop the method to use position dependent ?(0) values. The method is also generalized to two dimensions. Applications are carried out on one-dimensional model problems and the two-dimensional H + H(2) collinear reaction.

Li H; Poulsen JA; Nyman G

2011-06-01

153

Pullback attractors for reaction-diffusion delay equations on unbounded domains with non-autonomous deterministic and stochastic forcing terms  

Science.gov (United States)

The existence of a pullback attractor in a space of higher regularity is established for the non-autonomous non-compact dynamical system associated with the reaction-diffusion delay equation with both non-autonomous deterministic and stochastic forcing terms defined on all n-dimensional space. The asymptotical compactness of the solutions is demonstrated by using the uniform estimates for far-field values of solutions and a new method.

Wang, Jingyu; Wang, Yejuan

2013-08-01

154

Theoretical study of the reaction of ethane with oxygen molecules in the ground triplet and singlet delta states.  

UK PubMed Central (United Kingdom)

Quantum chemical calculations are carried out to study the reaction of ethane with molecular oxygen in the ground triplet and singlet delta states. Transition states, intermediates, and possible products of the reaction on the triplet and singlet potential energy surfaces are identified on the basis of the coupled-cluster method. The basis set dependence of coupled-cluster energy values is estimated by the second-order perturbation theory. The values of energy barriers are also refined by using the compound CBS-Q and G3 techniques. It was found that the C(2)H(6) + O(2)(X(3)?(g)(-)) reaction leads to the formation of C(2)H(5) and HO(2) products, whereas the C(2)H(6) + O(2)(a(1)?(g)) process produces C(2)H(4) and H(2)O(2) molecules. The appropriate rate constants of these reaction paths are estimated on the basis of variational and nonvariational transition-state theories assuming tunneling and possible nonadiabatic transitions in the temperature range 500-4000 K. The calculations showed that the rate constant of the C(2)H(6) + O(2)(a(1)?(g)) reaction path is much greater than that of the C(2)H(6) + O(2)(X(3)?(g)(-)) one. At the same time, the singlet and triplet potential surface intersection is detected that leads to the appearance of the nonadiabatic quenching channel O(2)(a(1)?(g)) + C(2)H(6) ? O(2)(X (3)?(g)(-)) + C(2)H(6). The rate constant of this process is estimated with the use of the Landau-Zener model. It is demonstrated that, in the case of the existence of thermal equilibrium in the distribution of molecules over the electronic states, at low temperatures (T < 1200 K) the main products of the reaction of C(2)H(6) with O(2) are C(2)H(4) and H(2)O(2), rather than C(2)H(5) and HO(2). At higher temperature (T > 1200 K) the situation is inverted.

Sharipov AS; Starik AM

2012-08-01

155

[Environmental investigation of ground water contamination at Wright- Patterson Air Force Base, Ohio]. Volume 4, Health and Safety Plan (HSP); Phase 1, Task 4 Field Investigation report: Draft  

Energy Technology Data Exchange (ETDEWEB)

This Health and Safety Plan (HSP) was developed for the Environmental Investigation of Ground-water Contamination Investigation at Wright-Patterson Air Force Base near Dayton, Ohio, based on the projected scope of work for the Phase 1, Task 4 Field Investigation. The HSP describes hazards that may be encountered during the investigation, assesses the hazards, and indicates what type of personal protective equipment is to be used for each task performed. The HSP also addresses the medical monitoring program, decontamination procedures, air monitoring, training, site control, accident prevention, and emergency response.

1991-10-01

156

From the self-force problem to the Radiation reaction formula  

CERN Multimedia

We review a recent theoretical progress in the so-called self-force problem of a general relativistic two-body system. Although a two-body system in Newtonian gravity is a very simple problem, some fundamental issues are involved in relativistic gravity. Besides, because of recent projects for gravitational wave detection, it comes to be possible to see those phenomena directly via gravitational waves, and the self-force problem becomes one of urgent and highly-motivated problems in general relativity. Roughly speaking, there are two approaches to investigate this problem; the so-called post-Newtonian approximation, and a black hole perturbation. In this paper, we review a theoretical progress in the self-force problem using a black hole perturbation. Although the self-force problem seems to be just a problem to calculate a self-force, we discuss that the real problem is to define a gauge invariant concept of a motion in a gauge dependent metric perturbation.

Mino, Y

2005-01-01

157

Simulation of ground-water flow and application to the design of a contaminant removal system, Loring Air Force Base, Maine  

Science.gov (United States)

The fractured-bedrock aquifer underlying the former Fire Training Area at Loring Air Force Base, Maine, has been contaminated with petroleum products as a result of fire training activities. A numerical model of the ground-water-flow system near the Fire Training Area was developed to provide information for the design and operation of a contaminant removal system. The goals of the simulation modeling were to (1) determine the maximum pumping rate that could be sustained, giventhe constraint that water levels not rise above a specified altitude, and (2) determine the effect of seasonal variation in recharge on the ability of a transient pumping scenario to capture contaminants. A steady-state simulation model of ground-water flow was used to determine the optimal pumping rate at the site. The optimal pumping rate was 8,570 ft3/d (44 gal/min). Monthly recharge rates wereestimated for use in a transient simulation model. During a typical year, most recharge probably occurs during two periods-one during snowmelt in early spring and another, possibly less significant period, during the late fall. The transient response of the water table to 8.5 inches of recharge in April, 2 inches of recharge in October, and 0.25 inches of recharge per month for each remaining month wassimulated. Fluctuations in ground-water levels caused by simulated seasonal variation of recharge would have minimal effect on the operation of thecontaminant removal system because the system is not pumped when recharge is lowest, ground-water velocities are lowest, and ground-water flow past the trench is minimal.

Starn, J. J.

1997-01-01

158

Kinetic analysis of forced aeration composting - I. Reaction rates and temperature  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The kinetics of the forced aeration composting process operated under different aeration modes was studied using two specifically designed heat insulated closed pilot-scale reactors. Five pilot-scale composting tests using fresh mixture of organic solid waste were performed. The modes of aeration ap...

Bari, QH; Koenig, A; Tao, G

159

Study of the ground-state wave function of {sup 6}He via the {sup 6}He(p, t){alpha} transfer reaction  

Energy Technology Data Exchange (ETDEWEB)

We have measured the {sup 6}He(p,t){alpha} transfer reaction in inverse kinematics at 25 MeV/nucleon. The data were compared to DWBA calculations in order to extract the spectroscopic amplitudes for {alpha}+2n and t+t configurations in the ground state of {sup 6}He. (orig.)

Giot, L.; Roussel-Chomaz, P.; Demonchy, Ch.E.; Mittig, W.; Pita, S.; Savajols, H. [GANIL (DSM/CEA, IN2P3/CNRS), B.P. 5027, Caen Cedex 5 (France); Alamanos, N.; Auger, F.; Gillibert, A.; Jouanne, C.; Lapoux, V.; Nalpas, L.; Pollacco, E.C.; Sida, J.L.; Skaza, F. [Saclay, CEA/DSM/DAPNIA/SPhN, Gif-sur-Yvette Cedex (France); Cortina-Gil, M.-D.; Fernandez, J. [Universidad Santiago de Compostela, Departamento de Fisica de Particulas, Santiago de Compostela (Spain); Mackintosh, R.S. [The Open University, Department of Physics and Astronomy, Milton Keynes (United Kingdom); Pakou, A. [The University of Ioannina, Department of Physics, Ioannina (Greece); Rodin, A.; Stepantsov, S.; Ter-Akopian, G. [Dubna, FLNR, JINR, P.O. Box 79, Moscow (Russian Federation); Rusek, K. [The Andrzej Soltan Institute for Nuclear Studies, Hoza 69, Department of Nuclear Reactions, Warsaw (Poland); Thompson, I. [University of Surrey, Department of Physics, Guildford (United Kingdom)

2005-09-01

160

[Environmental investigation of ground water contamination at Wright-Patterson Air Force Base, Ohio]. Volume 3, Sampling and analysis plan (SAP): Phase 1, Task 4, Field Investigation: Draft  

Energy Technology Data Exchange (ETDEWEB)

In April 1990, Wright-Patterson Air Force Base (WPAFB), initiated an investigation to evaluate a potential Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) removal action to prevent, to the extent practicable, the offsite migration of contaminated ground water from WPAFB. WPAFB retained the services of the Environmental Management Operations (EMO) and its principle subcontractor, International Technology Corporation (IT) to complete Phase 1 of the environmental investigation of ground-water contamination at WPAFB. Phase 1 of the investigation involves the short-term evaluation and potential design for a program to remove ground-water contamination that appears to be migrating across the western boundary of Area C, and across the northern boundary of Area B along Springfield Pike. Primarily, Task 4 of Phase 1 focuses on collection of information at the Area C and Springfield Pike boundaries of WPAFB. This Sampling and Analysis Plan (SAP) has been prepared to assist in completion of the Task 4 field investigation and is comprised of the Quality Assurance Project Plan (QAPP) and the Field Sampling Plan (FSP).

1991-10-01

 
 
 
 
161

Role of tensor forces in the 4He(d-arrow-right,3He)3H reaction  

International Nuclear Information System (INIS)

Recent experimental polarization data on the 4He(d-arrow-right,3He)3H reaction are analyzed. We performed a microscopic multichannel resonating group calculation and found sensitivity to the tensor force only for the tensor analyzing powers. In addition we fitted the experimental data by S-matrix elements and found good agreement between calculation and fit for the most important tensor-independent matrix elements and only fair agreement for the strongly tensor-dependent ones. Arguments for this finding are given

1988-01-01

162

The generalized spin-boson model for electron-transfer reactions involving two harmonic potentials with a different force constant  

Energy Technology Data Exchange (ETDEWEB)

The generalized spin-model is employed to analyze the electron-transfer reactions involving two harmonic potentials with a different force constant. An analytical expression for the nonadiabatic rate constant is derived with fill consideration of the effects of quantum modes. For a single dominant solvent mode at low frequency, the result of the high temperature regime is reduced to the formula derived earlier based on the stochastic Liouville theory. For multiple soft solvent modes, the rate constant is a convoluted integral of a rate function for each individual single mode.

Tang, J.

1994-01-01

163

Contribution of seat and foot reaction forces to anticipatory postural adjustments (APAs) in sitting isometric ramp pushes.  

UK PubMed Central (United Kingdom)

The aim of this paper was to examine the role of the upper and lower body on the dynamic phenomena, which precede the voluntary movement (anticipatory postural adjustments: APAs), and the way in which they contribute to postural control. In this view, sitting subjects were asked to perform horizontal two-handed ramp pushes as quickly as possible. A dynamometric bar was used to provide the push force (F(x)). Local reaction forces along the antero-posterior and vertical axes, at the seat and foot-rests (R(Sx), R(Sz), and R(fx), R(fz), respectively), as well as global ones (R(x) and R(z)), were measured. Two postural conditions were considered: full (100 BP) and one-third ischio-femoral contact (30 BP). Anticipatory postural adjustments durations (dAPAs) were measured between the onset of global or local (that is, at the seat and foot level) reaction forces, and the onset of push force increase. Firstly, the dAPAs were longer at the foot than at the seat level, that is, the APA sequence starts at the foot level: it is suggested that a "posturo-focal" sequence is followed, whose progression order is precisely dependent on the postural conditions. Moreover, the APA peak amplitudes (pAPA), measured at the seat contact were significantly greater than the corresponding ones measured at the foot contact: the upper body dynamics are larger than the lower body dynamics. Secondly, a greater peak push force (pF(x)) entailed significant dAPA increases, in preference to pAPA increases. As APAs are dynamic phenomena, they can perturb balance, suggesting that, in order to avoid unnecessary perturbation, APAs are increased in terms of duration rather than amplitude. Lastly, the impulses corresponding to the push force increase ("BPI(x)") and to the APA periods ("ACPI(x)") were calculated. As ACPI(x) was very low as compared to BPI(x), it was suggested that the APA action was limited to the period of the voluntary movement onset.

Le Bozec S; Bouisset S

2009-10-01

164

Control of chemical reaction pathways by femtosecond ponderomotive forces: Time-resolved multiphoton ionization spectroscopic study of OCIO photodissociation  

International Nuclear Information System (INIS)

[en] Femtosecond time-resolved multiphoton ionization spectroscopy is applied to the study of the photodissociation of OClO. The observed ratio of O2+/ClO+ signal increases 12-fold with a 3-fold increase of the pump laser intensity. They are attributed to the change in the branching ratio between the two independent reaction channels leading to Cl+O2 and ClO+O, respectively. We believe this is the first experimental demonstration of laser controlled chemical reactions by femtosecond ponderomotive forces. At low pump power, the photodissociation dynamics at 386 nm is shown to be a two-step process, with the OClO slowly approaching (time constant 4.6 ps) a transition state that falls apart rapidly (time constant 250 fs). copyright 1997 American Institute of Physics

1997-01-01

165

State-to-state quantum dynamics of the F + HCl (vi = 0, ji = 0) ? HF(vf, jf) + Cl reaction on the ground state potential energy surface.  

UK PubMed Central (United Kingdom)

The state-to-state reaction dynamics of the title reaction is investigated on the ground electronic state potential energy surface using two quantum dynamical methods. The results obtained using the Chebyshev real wave packet method are in excellent agreement with those obtained using the time-independent method, except at low translational energies. It is shown that this exothermic hydrogen abstraction reaction is direct, resulting in a strong back-scattered bias in the product angular distribution. The HF product is highly excited internally. Agreement with available experimental data is only qualitative. We discuss several possible causes of disagreement with experiment.

Li A; Guo H; Sun Z; K?os J; Alexander MH

2013-10-01

166

State-to-state quantum dynamics of the F + HCl (vi = 0, ji = 0) ? HF(vf, jf) + Cl reaction on the ground state potential energy surface.  

Science.gov (United States)

The state-to-state reaction dynamics of the title reaction is investigated on the ground electronic state potential energy surface using two quantum dynamical methods. The results obtained using the Chebyshev real wave packet method are in excellent agreement with those obtained using the time-independent method, except at low translational energies. It is shown that this exothermic hydrogen abstraction reaction is direct, resulting in a strong back-scattered bias in the product angular distribution. The HF product is highly excited internally. Agreement with available experimental data is only qualitative. We discuss several possible causes of disagreement with experiment. PMID:23928838

Li, Anyang; Guo, Hua; Sun, Zhigang; K?os, Jacek; Alexander, Millard H

2013-10-01

167

Oxytocin decreases handgrip force in reaction to infant crying in females without harsh parenting experiences.  

UK PubMed Central (United Kingdom)

Infant crying can elicit sensitive caregiving as well as hostility and harsh parenting responses. In the current study (N = 42 females) with a double-blind experimental design, we tested the effect of intranasal oxytocin administration on the use of excessive force using a hand-grip dynamometer during listening to infant cry sounds. Participants' experiences with harsh parental discipline during childhood were found to moderate the effect of oxytocin administration on the use of excessive force. Participants' whose parents did not discipline them harshly used less excessive force in the oxytocin condition, but for participants who were disciplined harshly there was no difference between the oxytocin and placebo condition. Such effects were not found during listening to infant laughter. We conclude that early caregiving experiences constitute an important moderator of the prosocial and/or stress-reducing effects of oxytocin. Oxytocin administration may increase trust and cooperation in individuals with supportive backgrounds, but not generate this effect in individuals who as a consequence of unfavorable early caregiving experiences may have a bias toward negative interpretation of social cues.

Bakermans-Kranenburg MJ; van Ijzendoorn MH; Riem MM; Tops M; Alink LR

2012-11-01

168

Oxytocin decreases handgrip force in reaction to infant crying in females without harsh parenting experiences.  

Science.gov (United States)

Infant crying can elicit sensitive caregiving as well as hostility and harsh parenting responses. In the current study (N = 42 females) with a double-blind experimental design, we tested the effect of intranasal oxytocin administration on the use of excessive force using a hand-grip dynamometer during listening to infant cry sounds. Participants' experiences with harsh parental discipline during childhood were found to moderate the effect of oxytocin administration on the use of excessive force. Participants' whose parents did not discipline them harshly used less excessive force in the oxytocin condition, but for participants who were disciplined harshly there was no difference between the oxytocin and placebo condition. Such effects were not found during listening to infant laughter. We conclude that early caregiving experiences constitute an important moderator of the prosocial and/or stress-reducing effects of oxytocin. Oxytocin administration may increase trust and cooperation in individuals with supportive backgrounds, but not generate this effect in individuals who as a consequence of unfavorable early caregiving experiences may have a bias toward negative interpretation of social cues. PMID:22037689

Bakermans-Kranenburg, Marian J; van Ijzendoorn, Marinus H; Riem, Madelon M E; Tops, Mattie; Alink, Lenneke R A

2011-10-27

169

Joint torques and joint reaction forces during squatting with a forward or backward inclined Smith machine.  

UK PubMed Central (United Kingdom)

We developed a biomechanical model to determine the joint torques and loadings during squatting with a backward/forward-inclined Smith machine. The Smith squat allows a large variety of body positioning (trunk tilt, foot placement, combinations of joint angles) and easy control of weight distribution between forefoot and heel. These distinctive aspects of the exercise can be managed concurrently with the equipment inclination selected to unload specific joint structures while activating specific muscle groups. A backward (forward) equipment inclination decreases (increases) knee torque, and compressive tibiofemoral and patellofemoral forces, while enhances (depresses) hip and lumbosacral torques. For small knee flexion angles, the strain-force on the posterior cruciate ligament increases (decreases) with a backward (forward) equipment inclination, whereas for large knee flexion angles, this behavior is reversed. In the 0 to 60 degree range of knee flexion angles, loads on both cruciate ligaments may be simultaneously suppressed by a 30 degree backward equipment inclination and selecting, for each value of the knee angle, specific pairs of ankle and hip angles. The anterior cruciate ligament is safely maintained unloaded by squatting with backward equipment inclination and uniform/forward foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are clearly explained.

Biscarini A; Botti FM; Pettorossi VE

2013-02-01

170

Changes in Mean Concentration, Phase Shifts, and Dissipation in a Forced Oscillatory Reaction  

Science.gov (United States)

Experiments are presented that confirm earlier predictions that the mode of supply of reactants to a nonlinear (bio)chemical reaction determines or controls concentrations at steady states far from equilibrium. The oxidation of nicotinamide adenine dinucleotide (NADH) catalyzed by the enzyme horseradish peroxidase with continuous input of oxygen was studied; NAD^+ is continuously recycled to NADH through a glucose-6-phosphate dehydrogenase system. A comparison of steady-state concentrations is made with an oscillatory oxygen input and a constant input at the same average oxygen input for both modes. By varying the frequency and amplitude of the perturbation (O_2 influx), the following may be changed: the average concentration of NADH; the Gibbs free energy difference ? G of the reactants and products at steady state; the average rate of the reaction; the phase relation between the oscillatory rate and ? G; and the dissipation. These results confirm the possibility of an "alternating current chemistry," of control and optimization of thermodynamic efficiency and dissipation by means of external variation of constraints in classes of nonlinear reactions and biological pumps, and of improvements of the yield in such reactions (heterogeneous catalysis, for example).

Lazar, James G.; Ross, John

1990-01-01

171

Method for the determination of the reaction forces and structural damage arising in ship collisions  

Energy Technology Data Exchange (ETDEWEB)

Recognizing that the risk of collision between a ship and an offshore structure is high, most codes and regulatory documents require designers to assess the consequent effects on the structure. Existing requirements, which demand that all the ship's kinetic energy before impact be absorbed by the structure, are very conservative. The method outlined considers the construction and mass of both the ship and structure and assesses the variation of contact force with time, using a multidegree-of-freedom lumped-mass approach. 8 refs.

Davies, I.L.

1981-10-01

172

Study of the Reactions Controlling the Mobility of Uranium in Ground and Surface Water Systems in Contact with Apatite  

Energy Technology Data Exchange (ETDEWEB)

The objective of this project was to define the mechanisms, equilibria, kinetics, and extent of sorption of aqueous uranium onto hydroxyapatite (Ca{sub 5}(PO{sub 4}){sub 3}(OH)) for a range of pH, ionic strength, aqueous uranium concentration, dissolved carbon/air CO{sub 2}, and mineral surface area. We conducted chemical modeling, batch and flow-through experiments, chemical analysis, x-ray absorption and diffraction measurement, and electron microscopy. Our motivation was the need to immobilize U in water and soil to prevent it's entry into water supplies and ultimately, biological systems. Applying hydroxyapatite to in-situ treatment of uranium-bearing ground water could be an effective, low cost technology. We found that hydroxyapatite quickly, effectively, and reversibly sorbed uranium at a high capacity by inner-sphere complexation over a wide range of conditions. Our results indicate that at aqueous uranium concentrations below 10-20 ppb: (1) equilibrium sorption of uranium to hydroxyapatite occurs in hours, regardless of pH; (2) in ambient and CO{sub 2}-free atmospheres, over 98% of initial uranium is sorbed to hydroxyapatite, (3) in waters in equilibrium with higher air CO{sub 2} concentrations, sorption removed over 97% of aqueous uranium, except above pH 9, where aqueous uranium concentrations were reduced by less than 40%, and (4) at near-neutral pH, bicarbonate alkalinities in excess of 500 slightly retarded sorption of uranium to hydroxyapatite, relative to lower alkalinities. Uranium sorption and precipitation are reversible and are not appreciably affected by ionic strength. The reversibility of these reactions requires that in situ treatment be carefully monitored to avoid breakthrough and de-sorption of uranium unto ground water. At typical surface conditions, sorption is the only mode of uranium sequestration below 20-50 ppb U - above this range, precipitation of uranium phosphate minerals begins to dominate sequestration processes. We verified that one m{sup 2} of hydroxyapatite can sorb over 7.53 X 10{sup -6} moles or 1.8 mg of uranium in agreement with calculations based on phosphate and calcium oxide sites on the unit cell. Our work is significant because small masses of hydroxyapatite can sorb appreciable masses of uranium quickly over a wide range of chemistries. Preliminary work with ground water containing 260 ppb of uranium and cow bone char indicates that its sorptive capacity is appreciable less than pure hydroxyapatite. Pure crystalline hydroxyapatite sequestered 2.9 mg of uranium per m{sup 2} as opposed to 0.083 mg of uranium sequestered per m{sup 2} of cow bone char, or 27% versus 3.5% by surface area, respectively. Extended x-ray adsorption fine structure (EXAFS) spectroscopy defined mono- and bidentate sorption of uranium to phosphate and calcium oxide groups on the hydroxyapatite surface. The EXAFS data indicate that up to several thousand parts U per million parts hydroxyapatite, surface complexation, and not precipitation, is the predominant process. Above this uranium: hydroxyapatite mass ratio, precipitation of meta-autunite (H{sub 2}(UO{sub 2})2(PO{sub 4}){sub 2} x 10H{sub 2}0) dominates the sequestration process.

Taffet, M

2004-04-22

173

Effect of residual forces on the widths of charge distributions of multinucleon transfer reaction products  

International Nuclear Information System (INIS)

The influence of the residual nucleon-nucleon interaction in nuclei on the width of the charge distributions of the multinUcleon transfer reaction products ?sub(Z)sup(2) is investigated. It is shown that the residual interaction increases the calculated results for ?sub(Z)sup(2) in two-three times in comparison with the independent-particle model. The calculations are carried out for the 208Pb+208Pb, 132Xe+196Au, 132Xe+209Bi and 132Xe+120Sn.

1984-01-01

174

Radiative forcing of Mediterranean atmospheric aerosols derived from ground-based and satellite observations: dependence on the aerosol type and single scattering albedo  

Science.gov (United States)

The Mediterranean region is characterized by a high variability in aerosol origin, composition, optical properties, and radiative effects. Ground-based measurements of aerosol optical properties and surface shortwave irradiance carried out at the island of Lampedusa (35.5° N, 12.6° E, central Mediterranean) during 2004-2007 are combined with co-located simultaneous observations of the outgoing shortwave flux at the top of atmosphere (TOA) derived from Clouds and the Earth's Radiant Energy System (CERES) to derive estimates of the aerosol radiative forcing (RF). The shortwave aerosol RF efficiency, i.e. the forcing produced by aerosols with unit optical depth at 500 nm, ?, at the surface (FES), at TOA (FETOA), and in the atmosphere (FEATM) are derived by applying the direct method, i.e., by calculating the slope of the linear regression between the net flux and ? over the available large dataset from Lampedusa. Three different particle classes are discriminated on the basis of their optical properties: desert dust (DD), urban/industrial-biomass burning aerosols (UI-BB), and mixed aerosols (MA). The average value of ? is 0.31 for DD, 0.21 for UI-BB, and 0.14 for MA. The single scattering albedo, ? at 415.6 and 868.7 nm is estimated by combining measurements of radiation fluxes and radiative transfer calculations. Average values of ? at 415.6/868.7 nm are 0.76/0.89 for DD, 0.91/0.81 for UI-BB, and 0.80/0.82 for MA. The daily mean aerosol forcing efficiency (FEd) at the equinox at the surface/TOA/atmosphere is -68.9/-45.5/+23.4 Wm-2 for DD, -59.0/-19.2/+39.8 Wm-2 for UI-BB, and -94.9/-36.2/+58.7 Wm-2 for MA. These results indicate that the atmospheric forcing is ~30-50% of the surface forcing for DD, ~70% for UI-BB, and ~60% for MA. The daily mean aerosol radiative forcing, RFd, is obtained by multiplying FEd by the mean ? for each aerosol class. At the equinox RFd at the surface and TOA is -21 and -14 Wm-2 for DD, -12 and -4 Wm-2 for UI-BB, and -13 and -5 Wm-2 for MA. The forcings at TOA and at the surface are largest for DD due to the high values of both forcing efficiency and ?. The atmospheric RFd at the equinox is +7 Wm-2 for DD, and +8 Wm-2 for both UI-BB and MA, suggesting that the mean atmospheric forcing is approximately independent of the aerosol type in the Mediterranean. Estimates of the maximum atmospheric RF are derived by multiplying the atmospheric FEd at the summer solstice by the largest aerosol optical depth for each aerosol class. The peak atmospheric RF is +35 Wm-2 for DD, +23 Wm-2 for UI-BB, and +34 Wm-2 for MA, indicating the largest role of desert dust and MA, and a large influence on the atmospheric radiative budget. Cases of MA in the solar zenith angle interval 25° ? ? ?35° are grouped in three classes of single scattering albedo (0.7? ?

di Biagio, Claudia; di Sarra, Alcide; Meloni, Daniela; Monteleone, Francesco; Piacentino, Salvatore; Sferlazzo, Damiano

2010-05-01

175

Quantum radiation reaction force on a one-dimensional cavity with two relativistic moving mirrors  

International Nuclear Information System (INIS)

We consider a real massless scalar field inside a cavity with two moving mirrors in a two-dimensional spacetime, satisfying the Dirichlet boundary condition at the instantaneous position of the boundaries, for arbitrary and relativistic laws of motion. Considering vacuum as the initial field state, we obtain formulas for the exact value of the energy density of the field and the quantum force acting on the boundaries, which extend results found in previous papers [D. T. Alves, E. R. Granhen, H. O. Silva, and M. G. Lima, Phys. Rev. D 81, 025016 (2010); L. Li and B.-Z. Li, Phys. Lett. A 300, 27 (2002); L. Li and B.-Z. Li, Chin. Phys. Lett. 19, 1061 (2002); L. Li and B.-Z. Li, Acta Phys. Sin. 52, 2762 (2003); C. K. Cole and W. C. Schieve, Phys. Rev. A 64, 023813 (2001)]. For the particular cases of a cavity with just one moving boundary, nonrelativistic velocities, or in the limit of infinity length of the cavity (a single mirror), our results coincide with those found in the literature.

2010-08-15

176

Depletion kinetics of the ground state CrO generated from the reaction of unsaturated Cr(CO)x with O2 and N2O  

International Nuclear Information System (INIS)

Unsaturated Cr(CO)x(1?x?5) molecules were generated in the gas phase from photolysis of Cr(CO)6 vapor in He using an unfocussed weak UV laser pulse and their reactions with O2 and N2O have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF)intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between O2/N2O and photo- fragments of Cr(CO)6 by one photon absorption. The depletion rate constants for the ground state CrO by O2 and N2O are 5.4±0.2x10-11 and 6.5±0.4x10-12 cm3 molecule-1s-1, respectively

2002-01-01

177

Important role of three-body repulsive force effect in nuclear reactions  

Directory of Open Access Journals (Sweden)

Full Text Available The e?ect of three-body force (TBF) is studied in nucleus-nucleus elastic scattering on the basis of Brueckner theory for nucleon-nucleon (NN) e?ective interaction (complex G matrix) in the nuclear matter. A new G matrix called CEG07 proposed recently by the present authors includes the TBF e?ect and reproduces a realistic saturation curve in the nuclear matter, and is shown to well reproduce proton-nucleus elastic scattering. The microscopic optical potential for nucleus-nucleus system is obtained by folding the G matrix with nucleon density distributions in colliding nuclei. We ?rst analyze the 16O + 16O elastic scattering at E/A = 70 MeV in detail. The observed cross sections are nicely reproduced up to the most backward scattering angles only when the TBF e?ect is included. The e?ects of the three-body attraction (TBA) and three-body repulsion (TBR) are also analyzed. The TBR contribution has an important role in nucleus-nucleus elastic scattering. The CEG07 G matrix is also tested in the elastic scattering of 16O by the 12C, 28Si and 40Ca targets at E/A = 93.9 MeV, and in the elastic scattering of 12C by the 12C target at E/A = 135 MeV with a great success. The decisive e?ect of the TBF is clearly seen also in those systems.

Furumoto T.; Sakuragi Y.; Yamamoto Y.

2010-01-01

178

[Use of parallel factor and two dimensional fluorescence spectroscopy correlation technique for measurement of reaction between MDA and cooked ground meat].  

UK PubMed Central (United Kingdom)

The fluorescence characteristics of oxidation reaction between MDA and cooked ground meat were analyzed by front face three dimensional synchronous fluorescence spectroscopy, parallel factor and two dimensional correlation technique. The results showed that the reaction system has two synchronous fluorescence peaks, one is Ex 292 nm and deltalambda 50 nm, assigned to the fluorescence characteristics of tryptophan residues in proteins; the other is Ex 400 nm, delta 70 nm, corresponding with the fluorescence characteristics of MDA-protein adducts formed during oxidation; The synchronous fluorescence landscape was analyzed using PARAFAC. The loading profiles of 1st and 2nd components had an optimal lambda 50 and 70 nm, respectively. During oxidation reaction, the synchronous fluorescence intensity of tryptophan gradually decreased, while the synchronous fluorescence intensity of MDA-protein adducts gradually increased. Two dimensional correlation synchronous fluorescence spectroscopy technique showed that the variation ratio of fluorescence intensity of tryptophan preceded that of MDA-protein adducts.

Sun YH; Jia XL; Meng JX; Peng ML

2013-04-01

179

Does leg predomination affect the measurement of patellofemoral joint reaction force (PFJRF) during single leg squatting?: a reliability study.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Although measuring patellofemoral joint reaction forces (PFJRF) may provide reliable evidence for conservative treatments to correct probable malalignment in subjects with patellofemoral pain syndrome (PFPS), it may be necessary to determine whether the inherent properties of the dominant leg influences the reliability of measuring PFJRF. The aim of the present study was to examine the effect of leg predomination on reliability testing of the PFJRF measurement during single leg squatting in healthy subjects. METHODS: Using a motion analysis system and one force plate, PFJRF of 10 healthy subjects with a right dominant leg was assessed during single leg squatting. Data was collected from superficial markers taped to selected landmarks. This procedure was performed on the both right and left legs, during three separate single leg squats from a neutral position to a depth of approximately 30° of knee flexion. Subjects were then asked to repeat the test procedure after a minimum of a week's interval. The PFJRF was calculated using a biomechanical model of the patellofemoral joint. RESULTS: There was significant difference between the PFJRF mean values of paired test of right (mean, SD of 1887.7, 325.1 N) and left knees (mean, SD of 2022.6, 270.5 N) (p < 0.05). The CV (coefficient of variation) values during within and between session tests, revealed the high repeatability and reproducibility of PFJRF measurements on both knees. The ICC (intra class correlation coefficient) values during within and between sessions tests showed the high reliability of these measurements on both knees. CONCLUSION: The high reliability of PFJRF measurements on both dominant and non-dominant legs of healthy subjects suggests that the PFJRF measurement would not be influenced by the leg predomination during single leg squatting.

Mostamand J; Bader DL; Hudson Z

2012-07-01

180

Comparison of culture, polymerase chain reaction (PCR), TaqMan Salmonella, and Transia Card Salmonella assays for detection of Salmonella spp. in naturally-contaminated ground chicken, ground turkey, and ground beef.  

Science.gov (United States)

Four types of assays were evaluated for the detection of Salmonella spp. in retail ground chicken (86 packages), ground turkey (104 packages), and ground beef (54 packages). Two 25 g samples from each package were separately subjected to pre-enrichment in buffered peptone water for 20 h at 37 degrees C followed by enrichment in Rappaport Vassiliadis (RV) broth for 20 h at 42 degrees C. The RV enrichments were plated onto Rambach agar, Rainbow Agar Salmonella, and XLT4 agar, and were also tested by a PCR assay targeting the Salmonella invA gene, as well as by the TaqMan Salmonella PCR assay. Additionally, the RV enrichments were tested using the Transia Card Salmonella immunoassay. Results showed that 16.8, 24.0, 28.8, and 26.4% of turkey samples were positive for Salmonella spp. by culture, PCR, TaqMan PCR, and Transia Card Salmonella assays, respectively. Eighteen, 28.5, 35.5, and 34.9% of chicken samples were positive by culture, PCR, TaqMan PCR, and Transia Card Salmonella assays, respectively, and 6.5, 6.5, 6.5, and 18.5% of ground beef samples were positive by the four assays, respectively. Analysis of the data using the kappa statistic showed that there was substantial to excellent agreement between the PCR and TaqMan PCR assays and between the PCR and culture assays (kappa coefficients ranging from 0.67 to 0.87), while there was poor to fair agreement between the results of the Transia Card Salmonella assay and the other methods (kappa coefficients ranging from 0.28 to 0.32). Overall, results showed that the PCR-based assays were more sensitive than the culture method, and the culture and PCR-based assays were more specific than the immunoassay for detection of Salmonella in ground chicken, turkey, and beef due to the occurrence of false positive results using the immunoassay. PMID:14580395

Fratamico, Pina M

2003-10-01

 
 
 
 
181

Influence of Coulomb and nuclear forces on the pattern of the double differential cross section d2sigma/d theta dE for deep inelastic reactions  

International Nuclear Information System (INIS)

The tremendous change in the pattern of the Wilczynski curves for deep inelastic reactions with the product Z1Z2 is interpreted within a model including both dissipation and statistical fluctuations. The competition between Coulomb and nuclear forces seems to account for this effect

1977-01-01

182

The Ground Axiom  

CERN Multimedia

A new axiom is proposed, the Ground Axiom, asserting that the universe is not a nontrivial set-forcing extension of any inner model. The Ground Axiom is first-order expressible, and any model of ZFC has a class-forcing extension which satisfies it. The Ground Axiom is independent of many well-known set-theoretic assertions including the Generalized Continuum Hypothesis, the assertion V=HOD that every set is ordinal definable, and the existence of measurable and supercompact cardinals. The related Bedrock Axiom, asserting that the universe is a set-forcing extension of a model satisfying the Ground Axiom, is also first-order expressible, and its negation is consistent. As many of these results rely on forcing with proper classes, an appendix is provided giving an exposition of the underlying theory of proper class forcing.

Reitz, J

2006-01-01

183

Total body centre of mass displacement estimated using ground reactions during transitory motor tasks: application to step ascent.  

Science.gov (United States)

A double integration technique is presented that estimates whole body centre of mass (CoM) displacement from signals of a single force platform, compensating for the drift and low frequency noise inherent in the signals. The technique is composed of two different integration techniques, which may also be used separately, and is applied to transitory motor tasks with known initial and final conditions such as step ascent and descent, single step, etc. First, the lowest frequencies within the force platform signals and considered not to be associated with actual movement are filtered out. Second, a regular and a time-reversed double integration are performed and weighted against each other. The technique's accuracy was assessed using computer generated force platform signals that were artificially perturbed. Experimental data were used to compare the estimated CoM displacement to that obtained from a regular double integration and from segmental analysis performed on stereophotogrammetric data. It was shown that the proposed technique's CoM displacement estimates were more repeatable and up to 50% more accurate than those of a regular double integration. Moreover, the CoM displacement estimated using a single force platform and the proposed technique was found to be not statistically different from that obtained with more demanding measurement and processing techniques such as stereophotogrammetry and segmental analysis. PMID:15564116

Zok, Mounir; Mazzà, Claudia; Della Croce, Ugo

2004-11-01

184

Total body centre of mass displacement estimated using ground reactions during transitory motor tasks: application to step ascent.  

UK PubMed Central (United Kingdom)

A double integration technique is presented that estimates whole body centre of mass (CoM) displacement from signals of a single force platform, compensating for the drift and low frequency noise inherent in the signals. The technique is composed of two different integration techniques, which may also be used separately, and is applied to transitory motor tasks with known initial and final conditions such as step ascent and descent, single step, etc. First, the lowest frequencies within the force platform signals and considered not to be associated with actual movement are filtered out. Second, a regular and a time-reversed double integration are performed and weighted against each other. The technique's accuracy was assessed using computer generated force platform signals that were artificially perturbed. Experimental data were used to compare the estimated CoM displacement to that obtained from a regular double integration and from segmental analysis performed on stereophotogrammetric data. It was shown that the proposed technique's CoM displacement estimates were more repeatable and up to 50% more accurate than those of a regular double integration. Moreover, the CoM displacement estimated using a single force platform and the proposed technique was found to be not statistically different from that obtained with more demanding measurement and processing techniques such as stereophotogrammetry and segmental analysis.

Zok M; Mazzà C; Della Croce U

2004-11-01

185

Effects of a plyometric program on vertical landing force and jumping performance in college women.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To examine the effects of a plyometric program on peak vertical ground reaction force as well as kinetic jumping characteristics in recreationally athletic college women. DESIGN: Six week prospective exercise intervention. SETTING: Division I university campus. PARTICIPANTS: Twenty college females who competed recreationally in basketball were randomly assigned to a training (n=10) or control (n=10) group. MAIN OUTCOME MEASURES: The absolute change values for vertical ground reaction force, countermovement jump height, peak and average jump power, and peak jump velocity. Comparisons were made using Mann-Whitney U tests. RESULTS: Vertical ground reaction force decreased in the intervention group (-222.8+/-610.9N), but was not statistically different (p=0.122) compared to the change observed in the control group (54.6+/-257.6N). There was no difference in the absolute change values between groups for countermovement jump height (1.0+/-2.8cm vs. -0.2+/-1.5cm, p=0.696) or any of the associated kinetic variables following the 6-week intervention. CONCLUSIONS: Although not statistically significant, the mean absolute reduction in vertical ground reaction force in the training group is clinically meaningful. Eight of the 10 women in the training group reduced vertical ground reaction force by 17-18%; however, improvements in jumping performance were not observed. This indicates that programs aimed at enhancing performance must be designed differently from those aimed at reducing landing forces in recreationally athletic women.

Vescovi JD; Canavan PK; Hasson S

2008-11-01

186

Simple method for estimating steady-state reaction force working a floating offshore structures; Futaishiki kaiyo kozobutsu ni sayosuru teijo koryoku no kan`i suisanho ni tsuite  

Energy Technology Data Exchange (ETDEWEB)

Simple method for estimating steady-state reaction working on different types of floating offshore structures in a steady-state flow has been developed, and its reasonability was verified. Estimating the tension working on mooring design and towing ropes requires clarifying reaction force caused by a steady-state flow. Models of floating offshore structures tested in an experiment included a semi-submersible model consisted of columns with lower hulls and bracing and a model supported with 12 columns with footings (a scale model of the POSEIDON). A towing experiment of the POSEIDON was also conducted. The method for estimating reaction force of the whole offshore structure estimates two-dimensional reaction force coefficient by dividing the constituting element members by each shape according to the existing reports, and is expanded to structures with more complex shapes by considering three-dimensional effect and inter-element interference. This simple estimation method produced good agreement with the result of a model experiment. However, it showed an agreement not very well with the result of the full-scale structure towing experiment. Reasons for this would be because three-dimensional effect and interference effect in high Reynolds regions are not made clear, and because of waves during the towing and increase in resistance caused by wind. 9 refs., 10 figs., 1 tab.

Hoshino, K. [Ship Research Inst., Tokyo (Japan); Koterayama, W. [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics

1997-04-10

187

Development of walking analysis system consisting of mobile force plate and motion sensor.  

UK PubMed Central (United Kingdom)

In walking analysis, which is one useful method for efficient physical rehabilitation, the ground reaction force, the center of pressure, and the body orientation data are measured during walking. In the past, these data were measured by a 3D motion analysis system consisting of high-speed cameras and force plates, which must be installed in the floor. However, a conventional 3D motion analysis system can measure the ground reaction force and the center of pressure just on force plates during a few steps. In addition, the subjects' stride lengths are limited because they have to walk on the center of the force plate. These problems can be resolved by converting conventional devices into wearable devices. We used a measuring device consisting of portable force plates and motion sensors. We developed a walking analysis system that calculates the ground reaction force, the center of pressure, and the body orientations and measured a walking subject to estimate this system. We simultaneously used a conventional 3D motion analysis system to compare with our development system and showed its validity for measurements of ground reaction force and the center of pressure.

Adachi W; Tsujiuchi N; Koizumi T; Aikawa M; Shiojima K; Tsuchiya Y; Inoue Y

2011-01-01

188

Development of walking analysis system consisting of mobile force plate and motion sensor.  

Science.gov (United States)

In walking analysis, which is one useful method for efficient physical rehabilitation, the ground reaction force, the center of pressure, and the body orientation data are measured during walking. In the past, these data were measured by a 3D motion analysis system consisting of high-speed cameras and force plates, which must be installed in the floor. However, a conventional 3D motion analysis system can measure the ground reaction force and the center of pressure just on force plates during a few steps. In addition, the subjects' stride lengths are limited because they have to walk on the center of the force plate. These problems can be resolved by converting conventional devices into wearable devices. We used a measuring device consisting of portable force plates and motion sensors. We developed a walking analysis system that calculates the ground reaction force, the center of pressure, and the body orientations and measured a walking subject to estimate this system. We simultaneously used a conventional 3D motion analysis system to compare with our development system and showed its validity for measurements of ground reaction force and the center of pressure. PMID:22255222

Adachi, Wataru; Tsujiuchi, Nobutaka; Koizumi, Takayuki; Aikawa, Masataka; Shiojima, Kouzou; Tsuchiya, Youtaro; Inoue, Yoshio

2011-01-01

189

Ground- and excited-state electron-transfer reactions: photoinduced redox reactions of poly(pyridine)ruthenium(II) complexes and cobalt(III) cage compounds  

Energy Technology Data Exchange (ETDEWEB)

Rate constants for the quenching of poly(pyridine)ruthenium(II) (RuL/sub 3//sup 2 +/) excited states by caged cobalt(III) amine complexes (Co(cage)/sup 3 +/) range from 2 x 10/sup 8/ to 1 x 10/sup 9/ M/sup -1/ s/sup -1/ at 25/sup 0/C. The quenching process involves parallel energy transfer (k/sub en/ approx. 1 x 10/sup 8/ M/sup -1/ s/sup -1/) and electron transfer (k/sub el/ = (0.1-1) x 10/sup 9/ M/sup -1/ s/sup -1/) from RuL/sub 3//sup 2 +/ to Co(cage)/sup 3 +/. The rate constants for electron-transfer quenching are consistent with expectations based on an adiabatic semiclassical model. The yields of electron-transfer products range from 0.3 to 1.0, increasing as the rate constants for the back-reaction of RuL/sub 3//sup 3 +/ with Co(cage)/sup 2 +/ diminish. The relatively low magnitudes of the back-reaction rate constants, (0.08-8) x 10/sup 8/ M/sup -1/ s/sup -1/, are consistent with the high yields of electron-transfer products and derive from poor coupling of the RuL/sub 3//sup 3 +/ and Co(cage)/sup 2 +/ orbitals. 30 references, 3 figures, 4 tables.

Mok, C.Y.; Zanella, A.W.; Creutz, C.; Sutin, N.

1984-08-29

190

Ground-state correlations in 12C and the mechanism of the (e,e'p) reaction  

International Nuclear Information System (INIS)

In this thesis the results of an investigation into two aspects of the mechanism of the quasi-elastic (e,e'p) reaction: the interaction between the incident electron and the bound proton and the residual nucleus (final-state interaction (FSI)), are presented and used in the extraction of nuclear-structure information from (e,e'p) measurements on 12C. The experiments were carried out at NIKHEF-K with a high-resolution spectrometer. Two kinds of experiments have been performed on 12C. The first was aimed at obtaining accurate momentum distributions for various final states in 11B. Some special measurements were carried out in order to vary the parameters influencing the FSI. The role of coupled-channels effects in the 12C(e,e'p)11Be reaction is discussed. It is discussed whether some of the weak transitions observed in this reaction, can be associated with knockout from normally unoccupied shell-model orbitals. The second experiment on 12C was devoted to the e-p coupling. These measurements were supplemented with data taken on 6Li. The latter measurement allowed for measuring simultaneously knockout from the relatively dense 4He core and the relatively dilute deuteron. In this way the density dependence of the e-p coupling in the nucleus could be studied. The results of these experiments have been compared to various models that take into account the effect of the nuclear medium upon the e-p coupling. The possible role of charge-exchange and meson-exchange currents in the interpretation of these experiments is also considered. A brief survey of the formalism of the quasi-elastic (e,e'p) reaction is also presented. (author). 196 refs.; 53 figs.; 21 tabs

1987-01-01

191

How does Pin1 catalyze the cis-trans prolyl peptide bond isomerization? A QM/MM and mean reaction force study.  

Science.gov (United States)

Pin1 represents an enzyme that specifically catalyzes the isomerization of peptide bonds between phosphorylated threonine or serine residues and proline. Despite its relevance as molecular timer in a number of biological processes related to cancer and Alzheimer disease, a detailed understanding of the factors contributing to the catalysis is still missing. In this study, we employ extensive QM/MM molecular dynamics simulations in combination with the mean reaction force (MRF) to discern the influence of the enzyme on the reaction mechanism and the origin of the catalysis. As a recently introduced method, the MRF separates the activation free energy barrier to reach the transition state into structural and electronic contributions providing a more detailed description of the enzyme's function. As a reference, we first study the isomerization starting from the cis form in solution and obtain a free energy barrier and a reaction free energy, which are in agreement with previous studies and experiment. With the new mean reaction force method, intramolecular hydrogen bonds in the peptide were identified that stabilize the transition state and reduce the electronic contribution to the free energy barrier. To elucidate the mechanism of catalysis of Pin1, the reaction in solution and in the catalytic cavity of the enzyme were compared. Both yield the same free energy barrier for the isomerization of the cis form, but with different decomposition in structural and electronic contributions by the mean reaction force. The enzyme reduces the energy required for structural rearrangements to reach the transition state, pointing to a destabilization of the reactant, but increases the electronic contribution to the barrier through specific enzyme-peptide hydrogen bonds. In the reverse reaction, the isomerization of the trans form, the enzyme alters the energetics and the mechanism of the reaction considerably. Unfavorable enzyme-peptide interactions in the catalytic cavity during the isomerization change the reaction coordinate, resulting in two minima with small energy differences to the transition state. These small free energy barriers should in principle make the reaction feasible at room temperature once the conformer is bound in the right conformation. PMID:23030417

Vöhringer-Martinez, Esteban; Duarte, Fernanda; Toro-Labbé, Alejandro

2012-10-18

192

How does Pin1 catalyze the cis-trans prolyl peptide bond isomerization? A QM/MM and mean reaction force study.  

UK PubMed Central (United Kingdom)

Pin1 represents an enzyme that specifically catalyzes the isomerization of peptide bonds between phosphorylated threonine or serine residues and proline. Despite its relevance as molecular timer in a number of biological processes related to cancer and Alzheimer disease, a detailed understanding of the factors contributing to the catalysis is still missing. In this study, we employ extensive QM/MM molecular dynamics simulations in combination with the mean reaction force (MRF) to discern the influence of the enzyme on the reaction mechanism and the origin of the catalysis. As a recently introduced method, the MRF separates the activation free energy barrier to reach the transition state into structural and electronic contributions providing a more detailed description of the enzyme's function. As a reference, we first study the isomerization starting from the cis form in solution and obtain a free energy barrier and a reaction free energy, which are in agreement with previous studies and experiment. With the new mean reaction force method, intramolecular hydrogen bonds in the peptide were identified that stabilize the transition state and reduce the electronic contribution to the free energy barrier. To elucidate the mechanism of catalysis of Pin1, the reaction in solution and in the catalytic cavity of the enzyme were compared. Both yield the same free energy barrier for the isomerization of the cis form, but with different decomposition in structural and electronic contributions by the mean reaction force. The enzyme reduces the energy required for structural rearrangements to reach the transition state, pointing to a destabilization of the reactant, but increases the electronic contribution to the barrier through specific enzyme-peptide hydrogen bonds. In the reverse reaction, the isomerization of the trans form, the enzyme alters the energetics and the mechanism of the reaction considerably. Unfavorable enzyme-peptide interactions in the catalytic cavity during the isomerization change the reaction coordinate, resulting in two minima with small energy differences to the transition state. These small free energy barriers should in principle make the reaction feasible at room temperature once the conformer is bound in the right conformation.

Vöhringer-Martinez E; Duarte F; Toro-Labbé A

2012-11-01

193

Low forced expiratory volume is associated with blunted cardiac reactions to acute psychological stress in a community sample of middle-aged men and women.  

UK PubMed Central (United Kingdom)

It has been argued recently that blunted cardiovascular reactions to acute psychological stress have adverse behavioural and health corollaries that reflect dysregulation of the neural systems that support motivation. We examined the association between cardiovascular reactions to a standard stress task, the paced auditory serial arithmetic rest, and forced expiratory volume in one second, an effort, hence motivation, dependent assessment of lung function measured by spirometry. Low forced expiratory volume, expressed as a ratio to height squared was associated with blunted heart rate, but not blood pressure, stress reactivity, r=.17, p<.001. The association survived adjustment for smoking, a range of anthropometric and sociodemographic covariates, resting heart rate and stress task performance, ?=.11, p=.005. As such, our results provide support for the hypothesis that blunted stress reactivity may be a peripheral marker of a dysfunction in the brain systems that support motivated behaviour.

Carroll D; Phillips AC; Der G; Hunt K; Bibbey A; Benzeval M; Ginty AT

2012-10-01

194

Multireference configuration interaction calculations for the F(2P)+HCl?HF+Cl(2P) reaction: A correlation scaled ground state (1 2A') potential energy surface  

International Nuclear Information System (INIS)

[en] This paper presents a new ground state (1 2A') electronic potential energy surface for the F(2P)+HCl?HF+Cl(2P) reaction. The ab initio calculations are done at the multireference configuration interaction+Davidson correction (MRCI+Q) level of theory by complete basis set extrapolation of the aug-cc-pVnZ (n=2,3,4) energies. Due to low-lying charge transfer states in the transition state region, the molecular orbitals are obtained by six-state dynamically weighted multichannel self-consistent field methods. Additional perturbative refinement of the energies is achieved by implementing simple one-parameter correlation energy scaling to reproduce the experimental exothermicity (?E=-33.06 kcal/mol) for the reaction. Ab initio points are fitted to an analytical function based on sum of two- and three-body contributions, yielding a rms deviation of ?v linear configuration that become avoided in Cs bent configurations of both the reactant and product, and should be a hallmark of all X-H-Y atom transfer reaction dynamics between (2P) halogen atoms

2006-06-14

195

Exact and truncated Coriolis coupling calculations for the S(1D)+HD reaction employing the ground adiabatic electronic state.  

UK PubMed Central (United Kingdom)

We present exact quantum differential cross sections and exact and estimated integral cross sections and branching ratios for the title reaction. We employ a time-dependent wavepacket method as implemented in the DIFFREALWAVE code including all Coriolis couplings and also an adapted DIFFREALWAVE code where the helicity quantum number and with this the Coriolis couplings have been truncated. Our exact differential cross sections at 0.453 eV total energy, one of the experimental energies, show good agreement with the experimental results for one of the product channels. While the truncated calculation present a significant reduction in the computational effort needed they overestimate the exact integral cross sections.

Yang H; Han K; Schatz GC; Smith SC; Hankel M

2010-10-01

196

Gap Forcing  

CERN Multimedia

Many of the most common reverse Easton iterations found in the large cardinal context, such as the Laver preparation, admit a gap at some small delta in the sense that they factor as P*Q, where P has size less than delta and Q is forced to be delta-strategically closed. In this paper, generalizing the Levy-Solovay theorem, I show that after such forcing, every embedding j:V[G]-->M[j(G)] in the extension which satisfies a mild closure condition is the lift of an embedding j:V-->M in the ground model. In particular, every ultrapower embedding in the extension lifts an embedding from the ground model and every measure in the extension which concentrates on a set in the ground model extends a measure in the ground model. It follows that gap forcing cannot create new weakly compact cardinals, measurable cardinals, strong cardinals, Woodin cardinals, strongly compact cardinals, supercompact cardinals, almost huge cardinals, huge cardinals, and so on.

Hamkins, J D

1998-01-01

197

Development of the ReaxFF reactive force field for describing transition metal catalyzed reactions, with application to the initial stages of the catalytic formation of carbon nanotubes.  

Science.gov (United States)

With the aim of developing a computationally inexpensive method for modeling the high-temperature reaction dynamics of transition metal catalyzed reactions we have developed a ReaxFF reactive force field in which the parameters are fitted to a substantial quantum mechanics (QM) training set, containing full reaction pathways for relevant reactions. In this paper we apply this approach to reactions involving carbon materials plus Co, Ni, and Cu atoms. We find that ReaxFF reproduces the QM reaction data with good accuracy while also reproducing the binding characteristics of Co, Ni, and Cu atoms to hydrocarbon fragments. To demonstrate the applicability of ReaxFF we performed high-temperature (1500 K) molecular dynamics simulations on a nonbranched all-carbon feedstock in the presence and absence of Co, Ni, and Cu atoms. We find that the presence of Co and Ni leads to substantial amounts of branched carbon atoms, leading eventually to the formation of carbon-nanotube-like species. In contrast, we find that under the same simulation conditions Cu leads to very little branching and leads to products with no nanotube character. In the absence of metals no branching is observed at all. These results suggest that Ni and Co catalyze the production of nanotube-like species whereas Cu does not. This is in excellent agreement with experimental observations, demonstrating that ReaxFF can provide a useful and computational tractable tool for studying the dynamics of transition metal catalytic chemistry. PMID:16833370

Nielson, Kevin D; van Duin, Adri C T; Oxgaard, Jonas; Deng, Wei-Qiao; Goddard, William A

2005-01-27

198

Development of the ReaxFF reactive force field for describing transition metal catalyzed reactions, with application to the initial stages of the catalytic formation of carbon nanotubes.  

UK PubMed Central (United Kingdom)

With the aim of developing a computationally inexpensive method for modeling the high-temperature reaction dynamics of transition metal catalyzed reactions we have developed a ReaxFF reactive force field in which the parameters are fitted to a substantial quantum mechanics (QM) training set, containing full reaction pathways for relevant reactions. In this paper we apply this approach to reactions involving carbon materials plus Co, Ni, and Cu atoms. We find that ReaxFF reproduces the QM reaction data with good accuracy while also reproducing the binding characteristics of Co, Ni, and Cu atoms to hydrocarbon fragments. To demonstrate the applicability of ReaxFF we performed high-temperature (1500 K) molecular dynamics simulations on a nonbranched all-carbon feedstock in the presence and absence of Co, Ni, and Cu atoms. We find that the presence of Co and Ni leads to substantial amounts of branched carbon atoms, leading eventually to the formation of carbon-nanotube-like species. In contrast, we find that under the same simulation conditions Cu leads to very little branching and leads to products with no nanotube character. In the absence of metals no branching is observed at all. These results suggest that Ni and Co catalyze the production of nanotube-like species whereas Cu does not. This is in excellent agreement with experimental observations, demonstrating that ReaxFF can provide a useful and computational tractable tool for studying the dynamics of transition metal catalytic chemistry.

Nielson KD; van Duin AC; Oxgaard J; Deng WQ; Goddard WA 3rd

2005-01-01

199

Reaction Studies in Nuclear Astrophysics  

International Nuclear Information System (INIS)

[en] Recent astronomical observations from ground and space-based telescopes covering all wavelengths have led to renewed interest in nuclear reactions that power stars and produce the chemical elements in the universe. In our attempt to understand the astronomical observations considerable progress has been made in reaction studies at very low energies, which are typical of the conditions in quiescent nuclear burning. In addition explosive astrophysical scenarios, which occur in novae, supernovae and X-ray bursts are one of the driving forces behind the reaction studies with radioactive beams. Some recent results from experiments with stable and unstable beams will be discussed

2006-08-14

200

Reaction studies in nuclear astrophysics.  

Energy Technology Data Exchange (ETDEWEB)

Recent astronomical observations from ground and space-based telescopes covering all wavelengths have led to renewed interest in nuclear reactions that power stars and produce the chemical elements in the universe. In our attempt to understand the astronomical observations considerable progress has been made in reaction studies at very low energies, which are typical of the conditions in quiescent nuclear burning. In addition explosive astrophysical scenarios, which occur in novae, supernovae and X-ray bursts are one of the driving forces behind the reaction studies with radioactive beams. Some recent results from experiments with stable and unstable beams will be discussed.

Rehm, K. E.; Physics

2006-01-01

 
 
 
 
201

The HNO3 forming branch of the HO2 + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings  

Directory of Open Access Journals (Sweden)

Full Text Available Recent laboratory measurements have shown the existence of a HNO3 forming branch of the HO2 + NO reaction. This reaction is the main source of tropospheric O3, through the subsequent photolysis of NO2, as well as being a major source of OH. The branching of the reaction to HNO3 reduces the formation of these species significantly, affecting O3 abundances, radiative forcing and the oxidation capacity of the troposphere. The Oslo CTM2, a three-dimensional chemistry transport model, is used to calculate atmospheric composition and trends with and without the new reaction branch. Results for the present day atmosphere, when both temperature and pressure effects on the branching ratio are accounted for, show an 11 % reduction in the calculated tropospheric burden of O3, with the main contribution from the tropics. An increase of the global, annual mean methane lifetime by 10.9 %, resulting from a 14.1 % reduction in the global, annual mean OH concentration is also found. Comparisons with measurements show that including the new branch improves the modelled O3 in the Oslo CTM2, but that it is not possible to conclude whether the NOy distribution improves. We model an approximately 11 % reduction in the tropical tropospheric O3 increase since pre-industrial times, and a 4 % reduction of the increase in total tropospheric burden. Also, an 8 % decrease in the trend of OH concentrations is calculated, when the new branch is accounted for. The radiative forcing due to changes in O3 over the industrial era was calculated as 0.33 W m?2, reducing to 0.26 W m?2 with the new reaction branch. These results are significant, and it is important that this reaction branching is confirmed by other laboratory groups.

O. A. Søvde; C. R. Hoyle; G. Myhre; I. S. A. Isaksen

2011-01-01

202

Quadriceps force generation in patients with osteoarthritis of the knee and asymptomatic participants during patellar tendon reflex reactions: an exploratory cross-sectional study  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background It has been postulated that muscle contraction is slower in patients with osteoarthritis of the knee than asymptomatic individuals, a factor that could theoretically impair joint protection mechanisms. This study investigated whether patients with osteoarthritis of the knee took longer than asymptomatic participants to generate force during reflex quadriceps muscle contraction. This was an exploratory study to inform sample size for future studies. Methods An exploratory observational cross sectional study was carried out. Two subject groups were tested, asymptomatic participants (n = 17), mean (SD) 56.7 (8.6) years, and patients with osteoarthritis of the knee, diagnosed by an orthopaedic surgeon, (n = 16), age 65.9 (7.8) years. Patellar tendon reflex responses were elicited from participants and measured with a load cell. Force latency, contraction time, and force of the reflex response were determined from digitally stored data. The Mann-Whitney U test was used for the between group comparisons in these variables. Bland and Altman within-subject standard deviation values were calculated to evaluate the measurement error or precision of force latency and contraction time. Results No significant differences were found between the groups for force latency (p = 0.47), contraction time (p = 0.91), or force (p = 0.72). The two standard deviation measurement error values for force latency were 27.9 ms for asymptomatic participants and 16.4 ms for OA knee patients. For contraction time, these values were 29.3 ms for asymptomatic participants and 28.1 ms for OA knee patients. Post hoc calculations revealed that the study was adequately powered (80%) to detect a difference between the groups of 30 ms in force latency. However it was inadequately powered (59%) to detect this same difference in contraction time, and 28 participants would be required in each group to reach 80% power. Conclusion Patients with osteoarthritis of the knee do not appear to have compromised temporal parameters or magnitude of force generation during patellar tendon reflex reactions when compared to a group of asymptomatic participants. However, these results suggest that larger studies are carried out to investigate this area further.

Dixon John; Howe Tracey E

2005-01-01

203

NRC Task Force report on review of the Federal/State program for regulation of commercial low-level radioactive waste burial grounds. Analysis of public comments  

International Nuclear Information System (INIS)

Correspondence after publication of NUREG-0217 in the Federal Register is listed by docket. A summary of the comments is given. Comments on the task force conclusions on federal/state roles, comprehensive regulator program, and need to study alternatives, provide adequate capacity, and avoid proliferation are analyzed. A breakdown of the comments of states, industry, and others on the task force conclusions and recommendations is tabulated

1977-01-01

204

Evidence for Substrate Pre-organization in the Peptidylglycine ?-Amidating Monooxygenase (PAM) Reaction Describing the Contribution of Ground State Structure to Hydrogen Tunneling  

Science.gov (United States)

Peptidylglycine ?-amidating monooxygenase (PAM) is a bifunctional enzyme which catalyzes the post-translational modification of inactive C-terminal glycine-extended peptide precursors to the corresponding bioactive ?-amidated peptide hormone. This conversion involves two sequential reactions both of which are catalyzed by the separate catalytic domains of PAM. The first step, the copper-, ascorbate-, and O2-dependent stereospecific hydroxylation at the ?-carbon of the C-terminal glycine, is catalyzed by peptidylglycine ?-hydroxylating monooxygenase (PHM). The second step, the zinc-dependent dealkylation of the carbinolamide intermediate, is catalyzed by peptidylglycine amidoglycolate lyase. Quantum mechanical tunneling dominates PHM–dependant C?-H bond activation. This study probes the substrate structure dependence of this chemistry using a set of N-acylglycine substrates of varying hydrophobicity. Primary deuterium kinetic isotope effects (KIEs), molecular mechanical docking, alchemical free energy perturbation, and equilibrium molecular dynamics were used to study the role played by ground-state substrate structure on PHM catalysis. Our data show that all N-acylglycines bind sequentially to PHM in an equilibrium-ordered fashion. The primary deuterium KIE displays a linear decrease with respect acyl chain length for straight-chain N-acylglycine substrates. Docking orientation of these substrates displayed increased dissociation energy proportional to hydrophobic pocket interaction. The decrease in KIE with hydrophobicity was attributed to a pre-organization event which decreased reorganization energy by decreasing the conformational sampling associated with ground state substrate binding. This is the first example of pre-organization in the family of non-coupled copper monooxygenases.

McIntyre, Neil R.; Lowe, Edward W.; Belof, Jonathan L.; Ivkovic, Milena; Shafer, Jacob; Space, Brian; Merkler, David J.

2010-01-01

205

Electron-transfer reactions involving two harmonic potentials with a different force constant: The Zusman approach versus the spin-boson model  

International Nuclear Information System (INIS)

Two approaches: (a generalized spin-boson model with a nonlinear spin-boson coupling and the Zusman's stochastic Liouville formalism) are employed to analyze the electron-transfer reactions involving two harmonic potentials with a different force constant. An analytical rate formula, expressed as a convoluted integral of the individual rate kernel for each mode, is derived with full consideration of quantum tunneling effects. For a dominant solvent mode at low frequency, the formula can be reduced to the results of the Zusman's theory, showing asymmetry of the Marcus rate plot between the normal and the inverted regions.

1994-01-01

206

Dynamics Study of the Reaction S + O2 ? SO + O and Its Reverse on a Single-Valued Double Many-Body Expansion Potential Energy Surface for Ground-State SO2  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Quasiclassical trajectory calculations have been carried out for the reaction S + O2 ? SO + O and its reverse using an accurate single-valued double many-body expansion (DMBE) potential energy surface previously reported for the ground electronic state of the sulfur dioxide molecule. A new scheme is...

Rodrigues, S. P. J.; Varandas, A. J. C.

207

The HNO3 forming branch of the HO2 + NO reaction: pre-industrial-to-present trends in atmospheric species and radiative forcings  

Directory of Open Access Journals (Sweden)

Full Text Available Recent laboratory measurements have shown the existence of a HNO3 forming branch of the HO2 + NO reaction. This reaction is the main source of atmospheric O3, through the subsequent photolysis of NO2, as well as being a major source of OH. The branching of the reaction to HNO3 reduces the formation of these species significantly, affecting O3 abundances, climate and the oxidation capacity of the troposphere. The Oslo CTM2, a three-dimensional chemistry transport model, is used to calculate atmospheric composition and trends with and without the new reaction branch. Results for the present day atmosphere, when both temperature and pressure effects on the branching ratio are accounted for, show an increase of the global, annual mean methane lifetime by 10.9 %, resulting from a 14.1 % reduction in the global, annual mean OH concentration. Comparisons with measurements show that including the new branch improves the modelled O3, but that it is not possible to conclude whether the NOy distribution improves. We model an approximately 11 % reduction in the tropical tropospheric O3 increase since pre-industrial times, as well as an 8 % decrease in the trend of OH concentration, when the new branch is accounted for. The radiative forcing due to changes in O3 over the industrial era was calculated as 0.33 W m?2, reducing to 0.26 W m?2 with the new reaction branch. These results are significant, and it is important that this reaction branching is confirmed by other laboratory groups.

O. A. Søvde; C. R. Hoyle; G. Myhre; I. S. A. Isaksen

2011-01-01

208

Running on uneven ground: leg adjustments to altered ground level.  

UK PubMed Central (United Kingdom)

In locomotion, humans have to deal with changes in ground level like pavement or stairs. When they encounter uneven ground with changes in terrain height, they reduce their angle of attack and leg stiffness on a step. This strategy was found for the single step upward movement. However, are these adjustments the result of a general strategy? In our study we focused on leg adjustments while running up and down, implying permanent adaptation to a new track level. To investigate this, we measured ten healthy participants as they ran along a runway with 10 cm increased and 10 cm lowered steps. We found that ground reaction force, leg length, leg stiffness, and angle of attack were adjusted to the direction of the vertical disturbance (up or down) but also to its length. When running upwards, leg stiffness decreased by about 20.4% on the single step and by about 9.3% on the permanently elevated track step. In addition to that - when running downwards - leg stiffness decreased in preparation for the downward step by about 18.8%. We also observed that the angle of attack diminished on elevated contact from 61 degrees to 59 degrees, and increased on lowered contact from 61 degrees to 65 degrees. The adjustment of leg stiffness seemed to be actively achieved, whereas the angle of attack appeared to be passively adjusted, consistent with a running model that includes leg retraction in late swing phase.

Müller R; Blickhan R

2010-08-01

209

Running on uneven ground: leg adjustments to altered ground level.  

Science.gov (United States)

In locomotion, humans have to deal with changes in ground level like pavement or stairs. When they encounter uneven ground with changes in terrain height, they reduce their angle of attack and leg stiffness on a step. This strategy was found for the single step upward movement. However, are these adjustments the result of a general strategy? In our study we focused on leg adjustments while running up and down, implying permanent adaptation to a new track level. To investigate this, we measured ten healthy participants as they ran along a runway with 10 cm increased and 10 cm lowered steps. We found that ground reaction force, leg length, leg stiffness, and angle of attack were adjusted to the direction of the vertical disturbance (up or down) but also to its length. When running upwards, leg stiffness decreased by about 20.4% on the single step and by about 9.3% on the permanently elevated track step. In addition to that - when running downwards - leg stiffness decreased in preparation for the downward step by about 18.8%. We also observed that the angle of attack diminished on elevated contact from 61 degrees to 59 degrees, and increased on lowered contact from 61 degrees to 65 degrees. The adjustment of leg stiffness seemed to be actively achieved, whereas the angle of attack appeared to be passively adjusted, consistent with a running model that includes leg retraction in late swing phase. PMID:20591519

Müller, Roy; Blickhan, Reinhard

2010-06-29

210

Hybrid Quantum Mechanical and Molecular Mechanics Study of the SN2 Reaction of CCl4 + OH? in Aqueous Solution: The Potential of Mean Force, Reaction Energetics, and Rate Constants  

Energy Technology Data Exchange (ETDEWEB)

The bimolecular nucleophilic substitution reaction of CCl{sub 4} and OH{sup -} in aqueous solution was investigated on the basis of a combined quantum mechanical and molecular mechanics method. A multilayered representation approach is employed to achieve high accuracy results at the CCSD(T) level of theory. The potential of mean force calculations at the DFT level and CCSD(T) level of theory yield reaction barrier heights of 22.7 and 27.9 kcal/mol, respectively. Both the solvation effects and the solvent-induced polarization effect have significant contributions to the reaction energetics, for example, the solvation effect raises the saddle point by 10.6 kcal/mol. The calculated rate constant coefficient is 8.6 x 10{sup -28} cm{sup 3} molecule{sup -1} s{sup -1} at the standard state condition, which is about 17 orders magnitude smaller than that in the gas phase. Among the four chloromethanes (CH{sub 3}Cl, CH{sub 2}Cl{sub 2}, CHCl{sub 3}, and CCl{sub 4}), CCl{sub 4} has the lowest free energy activation barrier for the reaction with OH{sup -1} in aqueous solution, confirming the trend that substitution of Cl by H in chloromethanes diminishes the reactivity.

Wang, Ting; Yin, Hongyun; Wang, Dunyou; Valiev, Marat

2012-02-16

211

Large atmospheric shortwave radiative forcing by Mediterranean aerosols derived from simultaneous ground-based and spaceborne observations and dependence on the aerosol type and single scattering albedo  

Science.gov (United States)

Aerosol optical properties and shortwave irradiance measurements at the island of Lampedusa (central Mediterranean) during 2004-2007 are combined with Clouds and the Earth's Radiant Energy System observations of the outgoing shortwave flux at the top of the atmosphere (TOA). The measurements are used to estimate the surface (FES), the top of the atmosphere (FETOA), and the atmospheric (FEATM) shortwave aerosol forcing efficiencies for solar zenith angle (?) between 15° and 55° for desert dust (DD), urban/industrial-biomass burning aerosols (UI-BB), and mixed aerosols (MA). The forcing efficiency at the different atmospheric levels is derived by applying the direct method, that is, as the derivative of the shortwave net flux versus the aerosol optical depth at fixed ?. The diurnal average forcing efficiency at the surface/TOA at the equinox is (-68.9 ± 4.0)/(-45.5 ± 5.4) W m-2 for DD, (-59.0 ± 4.3)/(-19.2 ± 3.3) W m-2 for UI-BB, and (-94.9 ± 5.1)/(-36.2 ± 1.7) W m-2 for MA. The diurnal average atmospheric radiative forcing at the equinox is (+7.3 ± 2.5) W m-2 for DD, (+8.4 ± 1.9) W m-2 for UI-BB, and (+8.2 ± 1.9) W m-2 for MA, suggesting that the mean atmospheric forcing is almost independent of the aerosol type. The largest values of the atmospheric forcing may reach +35 W m-2 for DD, +23 W m-2 for UI-BB, and +34 W m-2 for MA. FETOA is calculated for MA and 25° ? ? ? 35° for three classes of single scattering albedo (0.7 ? ? < 0.8, 0.8 ? ? < 0.9, and 0.9 ? ? ? 1) at 415.6 and 868.7 nm: FETOA increases, in absolute value, for increasing ?. A 0.1 increment in ? determines an increase in FETOA by 10-20 W m-2.

di Biagio, Claudia; di Sarra, Alcide; Meloni, Daniela

2010-05-01

212

Testing the cosmic censorship conjecture with point particles: The effect of radiation reaction and the self-force  

Science.gov (United States)

A classical thought-experiment to destroy black holes was envisaged by Wald in 1974: it consists of throwing particles with large angular momentum into an extremal black hole, checking whether their capture can overspin the black hole past the extremal limit and create a naked singularity. Wald showed that in the test-particle limit, particles that would be otherwise capable of producing naked singularities are simply scattered. Recently, Jacobson and Sotiriou showed that if one considers instead a black hole that is almost, but not exactly extremal, then in the absence of backreaction effects particle capture could indeed overspin the spacetime above the Kerr limit. Here we analyze backreaction effects and show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.

Barausse, Enrico; Cardoso, Vitor; Khanna, Gaurav

2011-11-01

213

Testing the Cosmic Censorship Conjecture with point particles: the effect of radiation reaction and the self-force  

CERN Multimedia

A classical thought-experiment to destroy black holes was envisaged by Wald in 1974: it consists of throwing particles with large angular momentum into an extremal black hole, checking whether their capture can over-spin the black hole past the extremal limit and create a naked singularity. Wald showed that in the test-particle limit, particles capable of producing naked singularities are simply scattered. Recently Jacobson and Sotiriou showed that if one considers instead a black hole that is almost, but not exactly extremal, naked singularities can be formed by particle capture, thus violating the Cosmic Censorship Conjecture in four-dimensional, asymptotically flat spacetimes. However, Jacobson and Sotiriou followed Wald in adopting the test-particle approximation, which neglects radiative and self-force effects. Here we analyze these effects and show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-for...

Barausse, Enrico; Khanna, Gaurav

2011-01-01

214

Testing the cosmic censorship conjecture with point particles: The effect of radiation reaction and the self-force  

International Nuclear Information System (INIS)

[en] A classical thought-experiment to destroy black holes was envisaged by Wald in 1974: it consists of throwing particles with large angular momentum into an extremal black hole, checking whether their capture can overspin the black hole past the extremal limit and create a naked singularity. Wald showed that in the test-particle limit, particles that would be otherwise capable of producing naked singularities are simply scattered. Recently, Jacobson and Sotiriou showed that if one considers instead a black hole that is almost, but not exactly extremal, then in the absence of backreaction effects particle capture could indeed overspin the spacetime above the Kerr limit. Here we analyze backreaction effects and show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.

2011-11-15

215

Dynamical response of the Galileo Galilei on the ground rotor to test the equivalence principle: Theory, simulation, and experiment. II. The rejection of common mode forces  

International Nuclear Information System (INIS)

[en] 'Galileo Galilei on the ground' (GGG) is a fast rotating differential accelerometer designed to test the equivalence principle (EP). Its sensitivity to differential effects, such as the effect of an EP violation, depends crucially on the capability of the accelerometer to reject all effects acting in common mode. By applying the theoretical and simulation methods reported in Part I of this work, and tested therein against experimental data, we predict the occurrence of an enhanced common mode rejection of the GGG accelerometer. We demonstrate that the best rejection of common mode disturbances can be tuned in a controlled way by varying the spin frequency of the GGG rotor

2006-01-01

216

Intermolecular Forces (Netorials)  

Science.gov (United States)

Intermolecular Forces: this is a resource in the collection "Netorials". In this resource there is a review of Lewis structures, molecular geometry, electronegativity, or molecular polarity. After that, you can learn about the forces of attraction that exist between molecules. This module explores London forces and dipole-dipole forces (including hydrogen bonds). The Netorials cover selected topics in first-year chemistry including: Chemical Reactions, Stoichiometry, Thermodynamics, Intermolecular Forces, Acids & Bases, Biomolecules, and Electrochemistry.

217

Forcing of Turing Patterns in the Chlorine Dioxide-Iodine-Malonic Acid Reaction With Strong Visible Light.  

UK PubMed Central (United Kingdom)

We investigate the sensitivity of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction to illumination by strong white light. Intense illumination results in an increase of [I-], in contrast to previous studies, which found only decreased [I-] for weak and intermediate intensities of illumination. We propose an expanded mechanism to explain the experimental observations. Both experimental and numerical results suggest that [ClO2] is the key parameter that determines whether the high iodide state is obtained under strong illumination. When strong illumination is applied through a spatially periodic mask with black and white stripes, a dark state with high [I-] is produced in the illuminated domain and a light state with low [I-] forms in the non-illuminated domain. Depending on the black:white ratio of the mask and its wavelength, Turing patterns can coexist with the light and dark state in the non-illuminated domain.

Nagao R; Epstein IR; Dolnik M

2013-08-01

218

Forcing of turing patterns in the chlorine dioxide-iodine-malonic Acid reaction with strong visible light.  

Science.gov (United States)

We investigate the sensitivity of Turing patterns in the chlorine dioxide-iodine-malonic acid reaction to illumination by strong white light. Intense illumination results in an increase of [I(-)], in contrast to previous studies, which found only decreased [I(-)] for weak and intermediate intensities of illumination. We propose an expanded mechanism to explain the experimental observations. Both experimental and numerical results suggest that [ClO2] is the key parameter that determines whether the high iodide state is obtained under strong illumination. When strong illumination is applied through a spatially periodic mask with black and white stripes, a dark state with high [I(-)] is produced in the illuminated domain and a light state with low [I(-)] forms in the nonilluminated domain. Depending on the black:white ratio of the mask and its wavelength, Turing patterns can coexist with either the light or the dark state in the nonilluminated domain. PMID:23991763

Nagao, Raphael; Epstein, Irving R; Dolnik, Milos

2013-09-13

219

Electron-transfer reactions of excited states  

Energy Technology Data Exchange (ETDEWEB)

Powerful models exist for the prediction and analysis of excited state outer-sphere electron transfer reactivity. Important parameters in these models are the driving force for the electron transfer and the electron exchange rate of the excited state couple. The driving force for excited state electron transfer is determined by the reduction potentials of the excited state and of its reaction partner, and the reduction potential of the excited state can be estimated from its excitation energy and the corresponding ground state reduction potential or from the free energy dependence of its reactions with characterized couples. The electron exchange rate of the excited state couple can be estimated from analogies with ground state exchanges or from the rates of its reactions with characterized reaction partners. The free energy dependences of quenching and back reactions are determined by the competition of elementary electron transfer steps and diffusional processes. Detailed analyses of these dependences can provide nearly unique information about the individual electron transfer steps - information that is crucial to the understanding of the factors determining quenching rates in particular systems and to the manipulation of photochemical yields. The relations between ground state and excited state electron transfer reactions of transition metal complexes, particularly of the polypyridine complexes, are discussed.

Sutin, N.; Creutz, C.

1983-10-01

220

The biological limits to running speed are imposed from the ground up.  

UK PubMed Central (United Kingdom)

Running speed is limited by a mechanical interaction between the stance and swing phases of the stride. Here, we tested whether stance phase limitations are imposed by ground force maximums or foot-ground contact time minimums. We selected one-legged hopping and backward running as experimental contrasts to forward running and had seven athletic subjects complete progressive discontinuous treadmill tests to failure to determine their top speeds in each of the three gaits. Vertical ground reaction forces [in body weights (W(b))] and periods of ground force application (T(c); s) were measured using a custom, high-speed force treadmill. At top speed, we found that both the stance-averaged (F(avg)) and peak (F(peak)) vertical forces applied to the treadmill surface during one-legged hopping exceeded those applied during forward running by more than one-half of the body's weight (F(avg) = 2.71 +/- 0.15 vs. 2.08 +/- 0.07 W(b); F(peak) = 4.20 +/- 0.24 vs. 3.62 +/- 0.24 W(b); means +/- SE) and that hopping periods of force application were significantly longer (T(c) = 0.160 +/- 0.006 vs. 0.108 +/- 0.004 s). Next, we found that the periods of ground force application at top backward and forward running speeds were nearly identical, agreeing to within an average of 0.006 s (T(c) = 0.116 +/- 0.004 vs. 0.110 +/- 0.005 s). We conclude that the stance phase limit to running speed is imposed not by the maximum forces that the limbs can apply to the ground but rather by the minimum time needed to apply the large, mass-specific forces necessary.

Weyand PG; Sandell RF; Prime DN; Bundle MW

2010-04-01

 
 
 
 
221

Depletion kinetics of the ground state CrO generated from the reaction of unsaturated Cr(CO){sub x} with O{sub 2} and N{sub 2}O  

Energy Technology Data Exchange (ETDEWEB)

Unsaturated Cr(CO){sub x}(1{<=}x{<=}5) molecules were generated in the gas phase from photolysis of Cr(CO){sub 6} vapor in He using an unfocussed weak UV laser pulse and their reactions with O{sub 2} and N{sub 2}O have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF)intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between O{sub 2}/N{sub 2}O and photo- fragments of Cr(CO){sub 6} by one photon absorption. The depletion rate constants for the ground state CrO by O{sub 2} and N{sub 2}O are 5.4{+-}0.2x10{sup -11} and 6.5{+-}0.4x10{sup -12} cm{sup 3} molecule{sup -1}s{sup -1}, respectively.

Son, H. S.; Ku, J. K. [POSTECH, Pohang (Korea, Republic of)

2002-02-01

222

"Emergence" vs. "Forcing"? Ein grundlegendes Problem der Methodologie der "Grounded Theory" – neu überdacht "Emergence" vs. "Forcing" of Empirical Data? A Crucial Problem of "Grounded Theory" Reconsidered ¿La "emergencia" vs. el "forzar" los datos empíricos? Un problema crucial de la reconsiderada "Teoría Fundamentada  

Directory of Open Access Journals (Sweden)

Full Text Available Seit den späten 1960er Jahren haben Barney GLASER und Anselm STRAUSS, die Begründer der Methodologie der "Grounded Theory", eine Reihe von Versuchen unternommen, grundlegende Konzepte und Annahmen dieses Ansatzes zu explizieren und zu rekonzeptualisieren. Hieraus sind unterschiedliche und zum Teil einander widersprechende Konzeptionen hervorgegangen, die schließlich sogar einen Bruch zwischen GLASER und STRAUSS mit sich brachten. Wichtige Aspekte der Überarbeitung und Weiterentwicklung der "Grounded Theory" beziehen sich auf das Verhältnis zwischen empirischen Daten und theoretischen Konzepten und auf die Bedeutung theoretischen Vorwissens. Die Monographie, die die Popularität der methodologischen Ideen von GLASER und STRAUSS ursprünglich begründete, "The Discovery of Grounded Theory", enthält dabei zwei divergierende Konzepte des Empirie-Theorieverhältnisses: das Konzept des "Emergierens" theoretischer Konzepte einerseits und andererseits das Konzept der "theoretischen Sensibilität". Die späteren Entwicklungen der Grounded Theory lassen sich als Versuche verstehen diese ursprünglich konfligierenden Konzepte miteinander zu vereinbaren, wobei GLASER empfiehlt, bei der empirisch begründeten Theoriebildung auf eine große Zahl sog. "Kodierfamilien" zurückzugreifen, wohingegen STRAUSS die Verwendung einer allgemeinen Handlungstheorie als "Achse" der Konstruktion der entstehenden Theorie empfiehlt. Der Beitrag fasst zuerst die wichtigsten Entwicklungen der "Grounded Theory", die das Verhältnis zwischen Theorie und Daten betreffen, zusammen. Dabei werden die zentralen Unterschiede zwischen GLASERs und STRAUSS' Konzepten behandelt und ausführlich auf GLASERs Kritik eingegangen, wonach die von STRAUSS und CORBIN beschriebenen Begriffe des "Kodierparadigmas" und der "axialen Kodierung" dazu führen, dass den Daten theoretische Konzepte "aufgezwungen" werden, anstatt aus ihnen zu "emergieren". Es wird gezeigt, das GLASERs Kritik tatsächlich bestehende Schwächen des STRAUSS'schen und CORBIN'schen Ansatzes thematisiert, die hierin liegenden Risiken aber in ihrer Bedeutung weit überschätzt. Ein zentrales Argument dieses Beitrags lautet, dass grundlegende Probleme empirisch begründeter Theoriebildung wesentlich effektiver behandelt werden können, wenn man explizit Bezug nimmt auf zeitgenössische wissenschaftsphilosophische Debatten und auf dort entwickelte, heute allgemein akzeptierte Konzepte. Dies betrifft insbesondere die Kritik des Naiven Realismus und Empirismus, die Konzepte des hypothetischen und abduktiven Schließens und das Konzept des empirischen Gehalts bzw. der Falsifizierbarkeit von Aussagen. URN: urn:nbn:de:0114-fqs0502275Since the late 1960s Barney GLASER and Anselm STRAUSS, developers of the methodology of "Grounded Theory" have made several attempts to explicate, clarify and reconceptualise some of the basic tenets of their methodological approach. Diverging concepts and understandings of Grounded Theory have arisen from these attempts which have led to a split between its founders. Much of the explication and reworking of Grounded Theory surrounds the relation between data and theory and the role of previous theoretical assumptions. The book which initially established the popularity of GLASER's and STRAUSS' methodological ideas, "The Discovery of Grounded Theory", contains two conflicting understandings of the relation between data and theory—the concept of "emergence" on the one hand and the concept of "theoretical sensitivity" on the other hand. Much of the later developments of Grounded Theory can be seen as attempts to reconcile these prima facie diverging concepts. Thereby GLASER recommends to draw on a variety of "coding families" while STRAUSS proposes the use of a general theory of action to build an axis for an emerging theory. This paper first summarises the most important developments within "Grounded Theory" concerning the understanding of the relation between empirical data and theoretical statements. Thereby special emphasis will be laid on

Udo Kelle

2005-01-01

223

Reliability testing of the patellofemoral joint reaction force (PFJRF) measurement during double-legged squatting in healthy subjects: a pilot study.  

UK PubMed Central (United Kingdom)

INTRODUCTION: Anterior knee pain or patellofemoral pain syndrome (PFPS) is supposed to be related to patellofemoral joint reaction forces (PFJRF). Measuring these forces may therefore provide reliable evidence for conservative treatments to correct probable malalignment in subjects with PFPS. The aim of the present study was to examine the reliability of PFJRF measurements during double-legged squatting in healthy subjects. METHODS: Using a motion analysis system and one forceplate, PFJRF of 10 healthy subjects were assessed during double-legged squatting. Data were collected from superficial markers taped to selected landmarks. This procedure was performed on the right knees, at three different knee flexion angles of 30, 45 and 60° during three separate double-legged squats. Subjects were then requested to repeat this test procedure on two separate test sessions at different occasions. The PFJRF was calculated using a biomechanical model of the patellofemoral joint. RESULTS: The data reveal an increase in PFJRF values (from mean, SD of 425.2, 35.5N to 1075.4, 70.1N)with an increase in the tibiofemoral joint angle during double-legged squatting. The CV (coefficient of variation) values during within and between session tests, revealed the high repeatability and reproducibility of PFJRF measurements, while the ICC (intra class correlation coefficient) values showed the low reliability of these measurements. CONCLUSION: The low reliability of PFJRF measurements suggests that the PFJRF measurement during double-legged squatting should be performed with caution with improving the method of kinetic measurement of the patellofemoral joint in healthy subjects.

Mostamand J; Bader DL; Hudson Z

2012-04-01

224

A quasiclassical trajectory study for the N(4S)+O2(X3?g-)->NO(X2?)+O(3P) atmospheric reaction based on a new ground potential energy surface  

International Nuclear Information System (INIS)

A quasiclassical trajectory study with the fourth-order explicit symplectic algorithm for the N(4S)+O2(X3?g-)->NO(X2?)+O(3P) atmospheric reaction has been performed by employing a new analytical fit of ab initio electronic structure calculations for the ground potential energy surface reported by Sayos et al. The effect of the relative translational energy, the vibrational energy and rotational energy of O2 molecule on the reaction probability and the reaction cross-section has been analyzed in details. The microscopic rate constant and the thermal rate constant have also been evaluated at the low translational temperature, and results have been compared with the experimental data and previous theoretical values. It is concluded that the thermal rate constants at the low temperature considered in this work agree well with the recommended experimental data and are very close to the variational transition state theory values carried out by Sayos et al.

1300-01-00

225

Light induced electron transfer reactions of metal complexes  

International Nuclear Information System (INIS)

[en] Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light decomposition of water into hydrogen and oxygen is reviewed

1980-07-19

226

Light induced electron transfer reactions of metal complexes  

Energy Technology Data Exchange (ETDEWEB)

Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light induced decomposition of water into hydrogen and oxygen is reviewed.

Sutin, N.; Creutz, C.

1980-01-01

227

Light induced electron transfer reactions of metal complexes  

Energy Technology Data Exchange (ETDEWEB)

Properties of the excited states of tris(2,2'-bipyridine) and tris(1,10-phenanthroline) complexes of chromium(III), iron(II), ruthenium(II), osmium(II), rhodium(III), and iridium(III) are described. The electron transfer reactions of the ground and excited states are discussed and interpreted in terms of the driving force for the reaction and the distortions of the excited states relative to the corresponding ground states. General considerations relevant to the conversion of light into chemical energy are presented and progress in the use of polypyridine complexes to effect the light decomposition of water into hydrogen and oxygen is reviewed.

Sutin, N; Creutz, C

1980-01-01

228

Transmission of force in the lumbosacral spine during backward falls.  

UK PubMed Central (United Kingdom)

STUDY DESIGN: Mathematical model, combined with and verified using human subject data. OBJECTIVE: (1) To develop and verify a lumped-parameter mathematical model for prediction of spine forces during backward falls; (2) to use this model to evaluate the effect of floor stiffness on spine forces during falls; and (3) to compare predicted impact forces with forces previously measured to fracture the spine. SUMMARY OF BACKGROUND DATA: Vertebral fractures are the most common osteoporotic fractures and commonly result from falls from standing height. Compliant flooring reduces the force at the ground during a backward fall from standing; however, the effect on spine forces is unknown. METHODS: A 6-df model of the body was developed and verified using data from 10 human subjects falling from standing onto 3 types of compliant floors (soft: 59 kN/m, medium: 67 kN/m, and firm: 95 kN/m). The simulated ground forces were compared with those measured experimentally. The model was also used to assess the effect of floor stiffness on spine forces at various intervertebral levels. RESULTS: There was less than 14% difference between model predictions and experimentally measured peak ground reaction forces, when averaged over all floor conditions. When compared with the rigid floor, average peak spine force attenuations of 46%, 43%, and 41% were achieved with the soft, medium, and firm floors, respectively (3.7, 3.9, 4.1 kN vs. 6.9 kN at L4/L5). Spine forces were lower than those at the ground and decreased cranially (4.9, 3.9, 3.7, 3.5 kN at the ground, L5/S1, L4/L5, and L3/L4, respectively, for the soft floor). CONCLUSION: Lowering the floor stiffness (from 400 to 59 kN/m) can attenuate peak lumbosacral spine forces in a backward fall onto the buttocks from standing by 46% (average peak from 6.9 to 3.7 kN at L4/L5) to values closer to the average tolerance of the spine to fracture (3.4 kN).

Van Toen C; Sran MM; Robinovitch SN; Cripton PA

2012-04-01

229

Force platform analysis in clinically healthy Rottweilers: comparison with Labrador Retrievers.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To (1) report ground reaction forces for healthy Rottweilers at a trot and (2) compare force platform data with values obtained for healthy Labradors. STUDY DESIGN: Prospective, clinical study. ANIMALS: Adult Rottweilers (n=9) and Labrador Retrievers (12) without orthopedic abnormalities. METHODS: Dogs were trotted over a force platform at controlled speed and acceleration. Peak vertical and craniocaudal forces, associated impulses, stance time, rising, and falling slopes were analyzed and forces, impulses, and slopes were expressed as percentages of body weight. The effects of weight and anatomic measurements on force platform values were re-evaluated with analysis of covariance (ANCOVA). RESULTS: In Rottweilers, peak vertical forces in thoracic limbs were significantly lower and vertical impulses in thoracic and pelvic limbs were significantly higher than in Labradors. Rising and falling slopes in thoracic and pelvic limbs were significantly smaller in Rottweilers. Body weight and anatomic measurements were significantly larger in Rottweilers. After removing the effect of relative velocity, functional limb length, and body weight by using ANCOVA, there were no significant differences between breeds. CONCLUSIONS: Ground reaction forces were significantly different between Rottweilers and Labradors when using standard methods of normalization. Based on ANCOVA differences were attributable to difference in conformation and body weight between breeds. CLINICAL RELEVANCE: Conformation and body weight have a significant influence on force platform values and this may cause bias when study results are compared.

Mölsä SH; Hielm-Björkman AK; Laitinen-Vapaavuori OM

2010-08-01

230

Design and Operation of a Borehole Straddle Packer for Ground-Water Sampling and Hydraulic Testing of Discrete Intervals at U.S. Air Force Plant 6, Marietta, Georgia  

Science.gov (United States)

A borehole straddle packer was developed and tested by the U.S. Geological Survey to characterize the vertical distribution of contaminants, head, and hydraulic properties in open-borehole wells as part of an ongoing investigation of ground-water contamination at U.S. Air Force Plant 6 (AFP6) in Marietta, Georgia. To better understand contaminant fate and transport in a crystalline bedrock setting and to support remedial activities at AFP6, numerous wells have been constructed that include long open-hole intervals in the crystalline bedrock. These wells can include several discontinuities that produce water, which may contain contaminants. Because of the complexity of ground-water flow and contaminant movement in the crystalline bedrock, it is important to characterize the hydraulic and water-quality characteristics of discrete intervals in these wells. The straddle packer facilitates ground-water sampling and hydraulic testing of discrete intervals, and delivery of fluids including tracer suites and remedial agents into these discontinuities. The straddle packer consists of two inflatable packers, a dual-pump system, a pressure-sensing system, and an aqueous injection system. Tests were conducted to assess the accuracy of the pressure-sensing systems, and water samples were collected for analysis of volatile organic compound (VOCs) concentrations. Pressure-transducer readings matched computed water-column height, with a coefficient of determination of greater than 0.99. The straddle packer incorporates both an air-driven piston pump and a variable-frequency, electronic, submersible pump. Only slight differences were observed between VOC concentrations in samples collected using the two different types of sampling pumps during two sampling events in July and August 2005. A test conducted to assess the effect of stagnation on VOC concentrations in water trapped in the system's pump-tubing reel showed that concentrations were not affected. A comparison was conducted to assess differences between three water-sampling methods - collecting samples from the well by pumping a packer-isolated zone using a submersible pump, by using a grab sampler, and by using a passive diffusion sampler. Concentrations of tetrachloroethylene, trichloroethylene and 1,2-dichloropropane were greatest for samples collected using the submersible pump in the packed-isolated interval, suggesting that the straddle packer yielded the least dilute sample.

Holloway, Owen G.; Waddell, Jonathan P.

2008-01-01

231

Abnormal ? particles obtained in the 28 Si + 181 Ta reaction. Evidence for transitions from shape isomeric states to shape isomeric states and to the ground states of various nuclei  

International Nuclear Information System (INIS)

The reaction 28 Si + 181 Ta has been studied at a bombarding energy of 125 MeV using C catcher foils. Long-lived coincidence events between 8.0 - 9.1 MeV ? particles events fit with theoretical predictions for transitions from the second minima of the potential energy surfaces to the second minima of the daughter nuclei, and to the ground states of various nuclei. The data are interpreted in terms of production of long-lived isomeric states in the second well of the potential. The consequences of the results regarding the discovery of long-lived superheavy elements, are discussed. (author)

1997-01-01

232

Mathematical models to assess foot-ground interaction: an overview.  

UK PubMed Central (United Kingdom)

The mechanical properties of the interface between the human body and the ground play an important role in attenuating the foot strike impact during locomotion. Understanding the properties of such an impact-attenuating system and the mathematical models governing its behavior has major implications in determining the load on the musculoskeletal system during locomotion. This interface consists of the plantar soft tissue and the sole complex of the shoe that together act like a sophisticated suspension system with generic viscoelastic properties. The interface has generally been modeled as a system of spring and damper, in which the reaction force deformation is expressed by a mathematical equation that represents the reaction force as a nonlinear function of the deformation and deformation rate of the interface. This overview intends to provide an insight into the different mathematical models that have been used to describe such relationship and into further understanding the role of the reaction model parameters in determining the behavior of the interface under compression. Various models included within this review ranged from the models representing the plantar soft tissue behavior during barefoot walking to those that consider the sole complex force-deformation behavior during shod foot running. The barefoot models are categorized under in vitro/in situ and in vivo, whereas the models representing the sole complex behavior are investigated before discussing the shod foot models. The mathematical models varied from those in which the reaction force was a nonlinear function of interface deformation to those that considered the deformation rate of the interface as a contributing factor to the interface reaction force. Ultimately, the implication of the reaction models in determining the load on the musculoskeletal system is discussed.

Naemi R; Chockalingam N

2013-08-01

233

Exact integral constraint requiring only the ground-state electron density as input on the exchange-correlation force - partial differential(V)(xc)(r)/partial differential(r) for spherical atoms.  

Science.gov (United States)

Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell. PMID:19026052

March, N H; Nagy, A

2008-11-21

234

Exact integral constraint requiring only the ground-state electron density as input on the exchange-correlation force - partial differential(V)(xc)(r)/partial differential(r) for spherical atoms.  

UK PubMed Central (United Kingdom)

Following some studies of integral(n)(r)inverted DeltaV(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller-Sucher-Feinberg [Phys. Rev. A 18, 2399 (1978)] identity to show that the scalar quantity paralleling the above vector integral, namely, integral(n)(r) partial differential(V)(r)/partial differential(r)dr, is determined solely by the electron density n(0) at the nucleus for the s-like atoms He and Be. The force - partial differential(V)/ partial differential(r) is then related to the derivative of the exchange-correlation potential V(xc)(r) by terms involving only the external potential in addition to n(r). The resulting integral constraint should allow some test of the quality of currently used forms of V(xc)(r). The article concludes with results from the differential virial theorem and the Hiller-Sucher-Feinberg identity for the exact many-electron theory of spherical atoms, as well as for the DFT for atoms such as Ne with a closed p shell.

March NH; Nagy A

2008-11-01

235

Speciation of mineralized deep-level ground water in non-saline solid rock. Examination of interaction and reactions with wastes at sealed underground disposal sites  

International Nuclear Information System (INIS)

The report contains results of analysis and specification of ground waters in Germany and subsequent investigations into specific interaction mechanisms between selected waste types and relevant water samples. The activities reported are intended to enhance scientific knowledge of the processes involved and to yield data indicating suitability or non-suitability of wastes for ecologically safe underground disposal in non-saline rock. (orig./CB)

1997-01-01

236

Equilibrium constants in aqueous lanthanide and actinide chemistry from time-resolved fluorescence spectroscopy: The role of ground and excited state reactions  

Energy Technology Data Exchange (ETDEWEB)

Equilibrium constants for aqueous reactions between lanthanide or actinide ions and (in-) organic ligands contain important information for various radiochemical problems, such as nuclear reprocessing or the migration of radioelements in the geosphere. We study the conditions required to determine equilibrium constants by time-resolved fluorescence spectroscopy measurements. Based on a simulation study it is shown that the possibility to determine equilibrium constants depends upon the reaction rates in the photoexcited states of the lanthanide or actinide ions. (orig.)

Billard, I.; Luetzenkirchen, K. [Inst. de Recherches Subatomiques, Chimie Nucleaire, CNRS/IN2P3 and Univ. Louis Pasteur, Strasbourg (France)

2003-07-01

237

Fall arrest strategy affects peak hand impact force in a forward fall.  

UK PubMed Central (United Kingdom)

We measured the peak hand impact force involved in bimanually arresting a forward fall to the ground from a 1-m shoulder height in five healthy young males. The effects of three different subject instruction sets: "arrest the fall naturally"; "keep the head as far from the ground as possible"; and "minimize the peak hand forces" were studied by measuring body segment kinematics, ground reaction forces, and upper-extremity myoelectric activity. The hypotheses were tested that the (a) arrest strategy did not influence peak impact force, (b) arm configuration, impact velocity and upper-extremity electromyography (EMG) levels correlate to the peak impact force (c) and impacting the ground with one hand leading the other does not increase the impact force over that obtained with simultaneous hand use. The results show that these subjects were able to volitionally decrease the peak impact force at the wrist by an average of 27% compared with a "natural landing" (p=0.014) and 40% compared with a "stiff-arm landing" (p<0.0005). The magnitude of the peak unilateral wrist force varied from 0.65 to 1.7 body weight for these moderate falls onto a padded surface. Peak force correlated with the elbow angle at impact, wrist velocity at impact and with pre-EMG triceps activity. The force was not significantly higher for non-simultaneous hand impacts. We conclude that fall arrest strategy can substantially alter the peak impact forces applied to the distal forearm during a fall arrest. Therefore, the fall arrest strategy likely influences wrist injury risk independent of bone strength.

DeGoede KM; Ashton-Miller JA

2002-06-01

238

Análise da força articular resultante entre diferentes movimentos do ombro com e sem carga: estudo preliminar/ Analysis of the joint reaction forces during different shoulder movements with and without external load: a preliminary study  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Os modelos de segmentos rígidos são extremamente úteis para auxiliar a compreensão do tipo de sobrecarga que as articulações estão expostas. O objetivo deste trabalho foi analisar a força articular resultante e momento proximal durante atividades sem e com carga externa, em um estudo preliminar. Um indivíduo realizou flexão, extensão, abdução de ombro e flexão de cotovelo (sem e com carga). Dados cinemáticos foram obtidos por videogrametria (freqüência de (more) amostragem de 50 campos/s). Um modelo de segmentos rígidos foi utilizado para obtenção dos dados cinéticos. O modelo é regido pelas equações de movimento de Newton-Euler. Os resultados encontrados evidenciaram aumentos não proporcionais na força e momento resultante. A força resultante longitudinal foi a única que apresentou aumento proporcional frente à carga externa. As componentes da força de cisalhamento e momento proximal apresentaram aumentos aleatórios. O aumento da carga externa promoveu aumentos da força e momento proximal, porém não de forma proporcional. As componentes de força e momento resultante sofrem influência da carga externa de maneira independente. Isto evidencia a necessidade de um controle rígido sobre os exercícios prescritos para diferentes disfunções do membro superior. Abstract in english Link segment models are extremely useful for increasing the comprehension of joint overload. The aim of the present study was to analyze proximal joint reaction forces and moments during different movements performed with and without external load. One subject performed shoulder flexion, extension and abduction, and elbow flexion movements (with and without external load) Kinematic data were obtained by videogrammetry (frequency sample 50 fields/s). One link segment model (more) was used to obtain kinetic data. The model is governed by Newton/Euler movement equations. The results suggested a not proportional increasing of proximal joint reaction forces and moments. The proximal joint reaction force longitudinal component was the only one that increased proportionally to the external load. Proximal joint reaction force shearing components and proximal moments presented increasing values of different magnitudes. The use of external load promoted increased magnitudes of proximal joint reaction force and moment, although it was not proportional. Proximal joint reaction force and moment are influenced in different ways by the external load. This suggests the need of a strict control of the prescribed exercises for different shoulder dysfunctions.

Ribeiro, Daniel Cury; Loss, Jefferson Fagundes; Toledo, Joelly Mahnic de; Castro, Marcelo Peduzzi de; Krumholz, Fábia Milman; Marques, Felipe de Osório

2010-01-01

239

Determination of coefficient for subgrade reactions of an earth-retaining structure with consideration of effects of hard ground below the excavated bottom; Kaho ni sonzaisuru katai jiban no eikyo wo koryoshita kussaku dodomeko no suihei jiban hanryoku keisu no settei hoho no kenkyu  

Energy Technology Data Exchange (ETDEWEB)

With clayey ground as the object, the previous paper proposed a new method to establish soil pressure on backside, equilibrium pressure on excavation side, passive pressure on the excavation side, and subgrade reaction coefficient for the excavation side. These factors are used in the elasto-plasticity method which is used in designing excavation earth retaining structures. This paper discusses extension of the subgrade reaction coefficient setting method proposed in the previous and present papers, so that effects of hard ground existing below the excavation bottom can be considered. This paper also shows the results of discussions on applicability of the soil pressures and subgrade reaction coefficient proposed in the previous and present papers. As a result, a new proposal is made on a rational and practical setting method for soil pressures and subgrade reaction coefficient as input items of the elasto-plasticity method used in designing ordinary excavation earth retaining structures in clayey ground. In contrast to the conventional method, the proposed method includes shear resistance in surface of an earth retaining wall, excavation width, thickness of the subject ground, depth from the ground surface, distance from the hard ground below the excavation bottom, and the Poission ratio of the ground. 10 refs., 18 figs., 12 tabs.

Nakamura, H. [Pacific Consultants K.K., Tokyo (Japan); Hirashima, K. [Yamanashi University, Yamanashi (Japan). Faculty of Engineering

1998-06-20

240

Ground improvement  

CERN Multimedia

This strongly practical and established guide to ground improvement, written by acknowledged experts, has been brought right up to date. It covers the major ground improvement techniques currently used worldwide and reflects recent improvements in productivity and control. An overview chapter sets the scene for the student or novice, and adds notes on blasting and ground freezing and on the emerging issue of the impact of improvement techniques on carbon emissions. The book remains strongly international in scope and with application across the field. It provides sound solutions to problems in

Kirsch, Klaus

2012-01-01

 
 
 
 
241

Coupling between the bacteriorhodopsin photocycle and the protonmotive force in Halobacterium halobium cell envelope vesicles. II. Quantitation and preliminary modeling of the M----bR reactions.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The cell membrane of Halobacterium halobium (H. halobium) contains the proton-pump bacteriorhodopsin, which generates a light-driven transmembrane protonmotive force. The interaction of the bacteriorhodopsin photocycle with the electric potential component of the protonmotive force has been investig...

Groma, G I; Helgerson, S L; Wolber, P K; Beece, D; Dancsházy, Z; Keszthelyi, L; Stoeckenius, W

242

Methods for Addressing Uncertainty and Variability to Characterize Potential Health Risk From Trichloroethylene-Contaminated Ground Water Beale Air Force Base in California: Integration of Uncertainty and Variability in Pharmacokinetics and Dose-Response  

Energy Technology Data Exchange (ETDEWEB)

Traditional estimates of health risk are typically inflated, particularly if cancer is the dominant endpoint and there is fundamental uncertainty as to mechanism(s) of action. Risk is more realistically characterized if it accounts for joint uncertainty and interindividual variability after applying a unified probabilistic approach to the distributed parameters of all (linear as well as nonlinear) risk-extrapolation models involved. Such an approach was applied to characterize risks to potential future residents posed by trichloroethylene (TCE) in ground water at an inactive landfill site on Beale Air Force Base in California. Variability and uncertainty were addressed in exposure-route-specific estimates of applied dose, in pharmacokinetically based estimates of route-specific metabolized fractions of absorbed TCE, and in corresponding biologically effective doses estimated under a genotoxic/linear (MA{sub g}) vs. a cytotoxic/nonlinear (MA{sub c}) mechanistic assumption for TCE-induced cancer. Increased risk conditional on effective dose was estimated under MA{sub G} based on seven rodent-bioassay data sets, and under MA, based on mouse hepatotoxicity data. Mean and upper-bound estimates of combined risk calculated by the unified approach were <10{sup -6} and <10{sup -4}, respectively, while corresponding estimates based on traditional deterministic methods were >10{sup -5} and >10{sup -4}, respectively. It was estimated that no TCE-related harm is likely occur due any plausible residential exposure scenario involving the site. The unified approach illustrated is particularly suited to characterizing risks that involve uncertain and/or diverse mechanisms of action.

Bogen, K.T.

1999-09-29

243

Methods for Addressing Uncertainty and Variability to Characterize Potential Health Risk from Trichloroethylene-Contaminated Ground Water at Beale Air Force Base in California:Integration of Uncertainty and Variability in Pharmacokinetics and Dose-Response  

Energy Technology Data Exchange (ETDEWEB)

Traditional estimates of health risk are typically inflated, particularly if cancer is the dominant endpoint and there is fundamental uncertainty as to mechanism(s) of action. Risk is more realistically characterized if it accounts for joint uncertainty and interindividual variability within a systematic probabilistic framework to integrate the joint effects on risk of distributed parameters of all (linear as well as nonlinear) risk-extrapolation models involved. Such a framework was used to characterize risks to potential future residents posed by trichloroethylene (TCE) in ground water at an inactive landfill site on Beale Air Force Base in California. Variability and uncertainty were addressed in exposure-route-specific estimates of applied dose, in pharmacokinetically based estimates of route-specific metabolized fractions of absorbed TCE, and in corresponding biologically effective doses estimated under a genotoxic/linear (MA{sub G}) vs. a cytotoxic/nonlinear (MA{sub c}) mechanistic assumption for TCE-induced cancer. Increased risk conditional on effective dose was estimated under MA{sub G} based on seven rodent-bioassay data sets, and under MA{sub c} based on mouse hepatotoxicity data. Mean and upper-bound estimates of combined risk calculated by the unified approach were <10{sup -6} and 10{sup -4}, respectively, while corresponding estimates based on traditional deterministic methods were >10{sup -5} and 10{sup -4}, respectively. It was estimated that no TCE-related harm is likely to occur due to any plausible residential exposure scenario involving the site. The systematic probabilistic framework illustrated is particularly suited to characterizing risks that involve uncertain and/or diverse mechanisms of action.

Bogen, K T

2001-05-24

244

Energy-conserving reactions in phosphorylating electron-transport particles from Nitrobacter winogradskyi. Activation of nitrite oxidation by the electrical component of the protonmotive force.  

UK PubMed Central (United Kingdom)

1. In electron-transport particles (ET particles) prepared from Nitrobacter winogradskyi, the uncoupling agent carbonyl cyanide phenylhydrazone increased the rate of NADH oxidation but decreased the rate of oxidation of NO2-. Its effectiveness in stimulating NADH oxidation closely paralleled its effectiveness in inhibiting NO2- oxidation. 2. In the presence of ADP and phosphate the oxidation of NADH was stimulated, whereas the oxidation of NO2- was inhibited. In the presence of excess of Pi the concentration dependence with respect to ADP was the same for acceleration of NADH oxidation and inhibition of NO2- oxidation. 3. Oligomycin inhibited NADH oxidation and stimulated the oxidation of NO2-. The concentration of oligomycin required to produce half-maximal effect in both systems was the same. 4. The apparent Km for NO2- was not affected by ADP together with Pi, by uncoupling agent or by oligomycin. 5. With NADH as substrate, classical respiratory control was observed. With NO2- as substrate the respiratory-control ratio was less than unity. 6. A reversible uptake of H+ accompanied the oxidation of NO2- by ET particles. 7. In the presence of NH4Cl or cyclohexylamine hydrochloride, H+ uptake was abolished and increased rates of NO2- oxidation were observed. When valinomycin was present in the reaction medium, low concentrations of NH4Cl inhibited NO2- oxidation. 8. Pretreatment of ET particles with oligomycin enhanced the stimulation of NO2- oxidation induced by NH4Cl or by cyclohexylamine hydrochloride. Pretreatment with the uncoupler carbonyl cyanide phenylhydrazone prevented these stimulations. 9. In the presence of dianemycin together with K+, the uptake of H+ was abolished and the rate of NO2- oxidation was increased. In contrast, in the presence of valinomycin together with K+, the uptake of H+ was increased, and the rate of NO2- oxidation decreased. 10. Sodium tetraphenylboron was found to be an inhibitor of NO2- oxidation, but caused a stimulation of NADH oxidation which was dependent on the presence of NH4Cl or cyclohexylamine hydrochloride. 11. It is concluded that the enhanced rate of NO2- oxidation observed in the absence of energy-dissipating processes clearly relates to some state before the involvement of adenine nucleotides, and it is suggested that the oxidation of NO2- generates a protonmotive force, the electrical component of which controls the rate of NO2- oxidation.

Cobley JG

1976-06-01

245

Global Many-body Potential Energy Surface of Ground State H2O+  

UK PubMed Central (United Kingdom)

Ground state H_(2)O~(+) is an important intermediate in atmospheric and interstellar chemistry. An accurate global ab initio potential energy surface is presented for the ground state H_(2)O~(+) molecular ion. The calculations were based on the externally contracted multi-reference configuration interaction method with all single and double excitations(EC-MRCISD) with cc-pVTZ basis. The surface was fitted as many-body function form suggested by Aguado and Paniagua and well indicates the behavior of the ground state H_(2)O~(+). The calculated results of energy changes in the dissociation reaction and the active energy of geometry-inverse reaction are coincident with experimental results. Besides, the data points were fitted to a polynomial force field, and analysis of normal vibration modes was performed.

Zhai Gaohong; Wang Yubin; Shi Ting; Wen Zhenyi

2003-01-01

246

Time-dependent quantum wave packet study of the Ar+H2+?ArH(+)+H reaction on a new ab initio potential energy surface for the ground electronic state (1(2)A').  

UK PubMed Central (United Kingdom)

A new global potential energy surface for the ground electronic state (1(2)A') of the Ar+H2(+)?ArH(+)+H reaction has been constructed by multi-reference configuration interaction method with Davidson correction and a basis set of aug-cc-pVQZ. Using 6080 ab initio single-point energies of all the regions for the dynamics, a many-body expansion function form has been used to fit these points. The quantum reactive scattering dynamics calculations taking into account the Coriolis coupling (CC) were carried out on the new potential energy surface over a range of collision energies (0.03-1.0 eV). The reaction probabilities and integral cross sections for the title reaction were calculated. The significance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The calculated cross section is in agreement with the experimental result at collision energy 1.0 eV.

Hu M; Xu W; Liu X; Tan R; Li H

2013-05-01

247

Time-dependent quantum wave packet study of the Ar+H2+?ArH(+)+H reaction on a new ab initio potential energy surface for the ground electronic state (1(2)A').  

Science.gov (United States)

A new global potential energy surface for the ground electronic state (1(2)A') of the Ar+H2(+)?ArH(+)+H reaction has been constructed by multi-reference configuration interaction method with Davidson correction and a basis set of aug-cc-pVQZ. Using 6080 ab initio single-point energies of all the regions for the dynamics, a many-body expansion function form has been used to fit these points. The quantum reactive scattering dynamics calculations taking into account the Coriolis coupling (CC) were carried out on the new potential energy surface over a range of collision energies (0.03-1.0 eV). The reaction probabilities and integral cross sections for the title reaction were calculated. The significance of including the CC quantum scattering calculation has been revealed by the comparison between the CC and the centrifugal sudden approximation calculation. The calculated cross section is in agreement with the experimental result at collision energy 1.0 eV. PMID:23656132

Hu, Mei; Xu, Wenwu; Liu, Xinguo; Tan, Ruishan; Li, Hongzheng

2013-05-01

248

Presence of Shiga Toxin-Producing Escherichia coli O-Groups in Small and Very-Small Beef-Processing Plants and Resulting Ground Beef Detected by a Multiplex Polymerase Chain Reaction Assay.  

UK PubMed Central (United Kingdom)

Abstract Shiga toxin-producing Escherichia coli (STEC) are associated with foodborne illnesses, including hemolytic uremic syndrome in humans. Cattle and consequently, beef products are considered a major source of STEC. E. coli O157:H7 has been regulated as an adulterant in ground beef since 1996. The United States Department of Agriculture Food Safety and Inspection Service began regulating six additional STEC (O145, O121, O111, O103, O45, and O26) as adulterants in beef trim and raw ground beef in June 2012. Little is known about the presence of STEC in small and very-small beef-processing plants. Therefore, we propose to determine whether small and very-small beef-processing plants are a potential source of non-O157:H7 STEC. Environmental swabs, carcass swabs, hide swabs, and ground beef from eight small and very-small beef-processing plants were obtained from October 2010 to December 2011. A multiplex polymerase chain reaction assay was used to determine the presence of STEC O-groups: O157, O145, O121, O113, O111, O103, O45, and O26 in the samples. Results demonstrated that 56.6% (154/272) of the environmental samples, 35.0% (71/203) of the carcass samples, 85.2% (23/27) of the hide samples, and 17.0% (20/118) of the ground beef samples tested positive for one or more of the serogroups. However, only 7.4% (20/272) of the environmental samples, 4.4% (9/203) of the carcass samples, and 0% (0/118) ground beef samples tested positive for both the serogroup and Shiga toxin genes. Based on this survey, small and very-small beef processors may be a source of non-O157:H7 STEC. The information from this study may be of interest to regulatory officials, researchers, public health personnel, and the beef industry that are interested in the presence of these pathogens in the beef supply.

Svoboda AL; Dudley EG; Debroy C; Mills EW; Cutter CN

2013-09-01

249

Presence of Shiga Toxin-Producing Escherichia coli O-Groups in Small and Very-Small Beef-Processing Plants and Resulting Ground Beef Detected by a Multiplex Polymerase Chain Reaction Assay.  

Science.gov (United States)

Abstract Shiga toxin-producing Escherichia coli (STEC) are associated with foodborne illnesses, including hemolytic uremic syndrome in humans. Cattle and consequently, beef products are considered a major source of STEC. E. coli O157:H7 has been regulated as an adulterant in ground beef since 1996. The United States Department of Agriculture Food Safety and Inspection Service began regulating six additional STEC (O145, O121, O111, O103, O45, and O26) as adulterants in beef trim and raw ground beef in June 2012. Little is known about the presence of STEC in small and very-small beef-processing plants. Therefore, we propose to determine whether small and very-small beef-processing plants are a potential source of non-O157:H7 STEC. Environmental swabs, carcass swabs, hide swabs, and ground beef from eight small and very-small beef-processing plants were obtained from October 2010 to December 2011. A multiplex polymerase chain reaction assay was used to determine the presence of STEC O-groups: O157, O145, O121, O113, O111, O103, O45, and O26 in the samples. Results demonstrated that 56.6% (154/272) of the environmental samples, 35.0% (71/203) of the carcass samples, 85.2% (23/27) of the hide samples, and 17.0% (20/118) of the ground beef samples tested positive for one or more of the serogroups. However, only 7.4% (20/272) of the environmental samples, 4.4% (9/203) of the carcass samples, and 0% (0/118) ground beef samples tested positive for both the serogroup and Shiga toxin genes. Based on this survey, small and very-small beef processors may be a source of non-O157:H7 STEC. The information from this study may be of interest to regulatory officials, researchers, public health personnel, and the beef industry that are interested in the presence of these pathogens in the beef supply. PMID:23742295

Svoboda, Amanda L; Dudley, Edward G; Debroy, Chitrita; Mills, Edward W; Cutter, Catherine N

2013-06-06

250

Forelimb and hindlimb forces in walking and galloping primates.  

UK PubMed Central (United Kingdom)

One trait that distinguishes the walking gaits of most primates from those of most mammalian nonprimates is the distribution of weight between the forelimbs and hindlimbs. Nonprimate mammals generally experience higher vertical peak substrate reaction forces on the forelimb than on the hindlimb. Primates, in contrast, generally experience higher vertical peak substrate reaction forces on the hindlimb than on the forelimb. It is currently unclear whether this unusual pattern of force distribution characterizes other primate gaits as well. The available kinetic data for galloping primates are limited and present an ambiguous picture about peak-force distribution among the limbs. The present study investigates whether the pattern of forelimb-to-hindlimb force distribution seen during walking in primates is also displayed during galloping. Six species of primates were video-recorded during walking and galloping across a runway or horizontal pole instrumented with a force-plate. The results show that while the force differences between forelimb and hindlimb are not significantly different from zero during galloping, the pattern of force distribution is generally the same during walking and galloping for most primate species. These patterns and statistical results are similar to data collected during walking on the ground. The pattern of limb differentiation exhibited by primates during walking and galloping stands in contrast to the pattern seen in most nonprimate mammals, in which forelimb forces are significantly higher. The data reported here and by Demes et al. ([1994] J. Hum. Evol. 26:353-374) suggest that a relative reduction of forelimb vertical peak forces is part of an overall difference in locomotor mechanics between most primates and most nonprimate mammals during both walking and galloping.

Hanna JB; Polk JD; Schmitt D

2006-08-01

251

Abnormal {alpha} particles obtained in the {sup 28} Si + {sup 181} Ta reaction. Evidence for transitions from shape isomeric states to shape isomeric states and to the ground states of various nuclei  

Energy Technology Data Exchange (ETDEWEB)

The reaction {sup 28} Si + {sup 181} Ta has been studied at a bombarding energy of 125 MeV using C catcher foils. Long-lived coincidence events between 8.0 - 9.1 MeV {alpha} particles events fit with theoretical predictions for transitions from the second minima of the potential energy surfaces to the second minima of the daughter nuclei, and to the ground states of various nuclei. The data are interpreted in terms of production of long-lived isomeric states in the second well of the potential. The consequences of the results regarding the discovery of long-lived superheavy elements, are discussed. (author) 20 refs., 7 figs., 1 tab.

Marinov, A.; Gelberg, S. [Hebrew Univ., Jerusalem (Israel). Racah Inst. of Physics; Kolb, D. [Kassel Univ. (Gesamthochschule) (Germany). Fachbereich 18 -Physik

1997-12-31

252

G-factors of the ground-state rotational bands of {sup 158,160,162}Dy derived from perturbed {gamma}-{gamma} directional correlations following ({alpha}, 2n)-reactions  

Energy Technology Data Exchange (ETDEWEB)

The ground-state rotational bands of {sup 158,160,162}Dy were excited simultaneously by ({alpha},2n)-reactions with a natural gadolinium target. A gadolinium single crystal was used with the {alpha}-axis oriented in beam directions. It was cooled by liquid helium and magnetized by an external magnetic field of {+-}4.5T parallel to the beam axis. The rotations of {gamma}-{gamma} directional correlations in the static magnetic hyperfine field were measured by use of ring 12 large Ge-detectors. The g-factors of the 4{sup 4}{sub 1},6{sup +}{sub 1} and 8{sup +}{sub 1} states were derived. The results exhibit a significant variation of g(I). A different behavior of the g-factos of {sup 162}Dy and those of the two other even dysprosium isotopes is observed which is interpreted as the consequence of differnt strengths of the interaction matrix elements between the ground-state bands and the Stockholm (S)-bands. (orig.)

Alfter, I. [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik; Bodenstedt, E. [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik; Knichel, W. [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik; Schueth, J. [Bonn Univ. (Germany). Inst. fuer Strahlen- und Kernphysik

1997-02-01

253

Magnus force and Hellmann-Feynman force: path integral approach  

International Nuclear Information System (INIS)

This paper considers the derivation of the Magnus force from a model system consisting of a single vortex imbedded in a uniform positive background coupled with a mutual interaction charged boson. By eliminating the charged boson degree of freedom, the effective action of a single vortex is obtained and can be used to derive the Hellmann-Feynman force. From the ground state contribution a Magnus force is obtained. (author)

2001-12-21

254

Detection by multiplex real-time polymerase chain reaction assays and isolation of Shiga toxin-producing Escherichia coli serogroups O26, O45, O103, O111, O121, and O145 in ground beef.  

UK PubMed Central (United Kingdom)

Six Shiga toxin-producing Escherichia coli (STEC) serogroups, which include O26, O45, O103, O111, O121, and O145, are responsible for the majority of non-O157 STEC infections in the United States, representing a growing public health concern. Cattle and other ruminants are reservoirs for these pathogens; thus, food of bovine origin may be a vehicle for infection with non-O157 STEC. Methods for detection of these pathogens in animal reservoirs and in food are needed to determine their prevalence and to develop intervention strategies. This study describes a method for detection of non-O157 STEC in ground beef, consisting of enrichment in modified tryptic soy broth at 42°C, followed by real-time multiplex polymerase chain reaction (PCR) assays targeting stx(1), stx(2), and genes in the O-antigen gene clusters of the six serogroups, [corrected] and then immunomagnetic separation (IMS) followed by plating onto Rainbow® Agar O157 and PCR assays for confirmation of isolates. All ground beef samples artificially inoculated with 1-2 and 10-20 CFU/25?g of ground beef consistently gave positive results for all of the target genes, including the internal amplification control using the multiplex real-time PCR assays after enrichment in modified tryptic soy broth for a total of 24?h (6?h at 37°C and 18?h at 42°C). The detection limit of the real-time multiplex PCR assays was ?50 CFU per PCR. IMS for O26, O103, O111, and O145 was performed with commercially available magnetic beads, and the IMS beads for O45 and O121 were prepared using polyclonal antiserum against these serogroups. A large percentage of the presumptive colonies of each serogroup picked from Rainbow Agar O157 were confirmed as the respective serogroups; however, the percent recovery of STEC O111 was somewhat lower than that of the other serogroups. This work provides a method for detection and isolation in ground beef and potentially other foods of non-O157 STEC of major public health concern.

Fratamico PM; Bagi LK; Cray WC Jr; Narang N; Yan X; Medina M; Liu Y

2011-05-01

255

A hub dynamometer for measurement of wheel forces in off-road bicycling.  

UK PubMed Central (United Kingdom)

A dynamometric hubset that measures the two ground contact force components acting on a bicycle wheel in the plane of the bicycle during off-road riding while either coasting or braking was designed, constructed, and evaluated. To maintain compatibility with standard mountain bike construction, the hubs use commercially available shells with modified, strain gage-equipped axles. The axle strain gages are sensitive to forces acting in the radial and tangential directions, while minimizing sensitivity to transverse forces, steering moments, and variations in the lateral location of the center of pressure. Static calibration and a subsequent accuracy check that computed differences between applied and apparent loads developed during coasting revealed root mean squared errors of 1 percent full-scale or less (full-scale load = 4500 N). The natural frequency of the rear hub with the wheel attached exceeded 350 Hz. These performance capabilities make the dynamometer useful for its intended purpose during coasting. To demonstrate this usefulness, sample ground contact forces are presented for a subject who coasted downhill over rough terrain. The dynamometric hubset can also be used to determine ground contact forces during braking providing that the brake reaction force components are known. However, compliance of the fork can lead to high cross-sensitivity and corresponding large (> 5 percent FS) measurement errors at the front wheel.

De Lorenzo DS; Hull ML

1999-02-01

256

Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System  

Science.gov (United States)

In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS). The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD) were ?26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and ?6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force) allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions.

Gilgien, Matthias; Sporri, Jorg; Chardonnens, Julien; Kroll, Josef; Muller, Erich

2013-01-01

257

Determination of external forces in alpine skiing using a differential global navigation satellite system.  

UK PubMed Central (United Kingdom)

In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS). The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD) were -26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and -6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force) allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions.

Gilgien M; Spörri J; Chardonnens J; Kröll J; Müller E

2013-01-01

258

Determination of External Forces in Alpine Skiing Using a Differential Global Navigation Satellite System  

Directory of Open Access Journals (Sweden)

Full Text Available In alpine ski racing the relationships between skier kinetics and kinematics and their effect on performance and injury-related aspects are not well understood. There is currently no validated system to determine all external forces simultaneously acting on skiers, particularly under race conditions and throughout entire races. To address the problem, this study proposes and assesses a method for determining skier kinetics with a single lightweight differential global navigation satellite system (dGNSS). The dGNSS kinetic method was compared to a reference system for six skiers and two turns each. The pattern differences obtained between the measurement systems (offset ± SD) were ?26 ± 152 N for the ground reaction force, 1 ± 96 N for ski friction and ?6 ± 6 N for the air drag force. The differences between turn means were small. The error pattern within the dGNSS kinetic method was highly repeatable and precision was therefore good (SD within system: 63 N ground reaction force, 42 N friction force and 7 N air drag force) allowing instantaneous relative comparisons and identification of discriminative meaningful changes. The method is therefore highly valid in assessing relative differences between skiers in the same turn, as well as turn means between different turns. The system is suitable to measure large capture volumes under race conditions.

Matthias Gilgien; Jörg Spörri; Julien Chardonnens; Josef Kröll; Erich Müller

2013-01-01

259

Motion synthesis and force distribution analysis for a biped robot.  

UK PubMed Central (United Kingdom)

In this paper, the method of generating biped robot motion using recorded human gait is presented. The recorded data were modified taking into account the velocity available for robot drives. Data includes only selected joint angles, therefore the missing values were obtained considering the dynamic postural stability of the robot, which means obtaining an adequate motion trajectory of the so-called Zero Moment Point (ZMT). Also, the method of determining the ground reaction forces' distribution during the biped robot's dynamic stable walk is described. The method was developed by the authors. Following the description of equations characterizing the dynamics of robot's motion, the values of the components of ground reaction forces were symbolically determined as well as the coordinates of the points of robot's feet contact with the ground. The theoretical considerations have been supported by computer simulation and animation of the robot's motion. This was done using Matlab/Simulink package and Simulink 3D Animation Toolbox, and it has proved the proposed method.

Trojnacki MT; Zieli?ska T

2011-01-01

260

Development of a method for quantifying the midsole reaction model parameters.  

UK PubMed Central (United Kingdom)

Midsole force-deformation pattern has important implications in determining the kinematics and kinetics of foot during locomotion. Furthermore, the midsole stiffness and viscosity determine the midsole's force-deformation behaviour. Despite the importance of stiffness and damping components of the midsole reaction, which determines the shoe-specific ground reaction forces during locomotion, there is still a lack of methodology to quantify them separately. The purpose of this study was to develop a method of extracting the shoe-specific midsole stiffness and damping components during uniaxial compression testing. For this purpose, the force-deformation behaviour of the sole was modelled as a system consisting of a nonlinear spring and a nonlinear damper. Based on the fact that the stiffness and damping component of the midsole reaction force acts in favour during loading, and work against each other during unloading, the stiffness and damping components were separated. Utilising a curve-fitting technique, a parametric curve represented by the stiffness and damping components of the midsole reaction force model was fitted to each components of force-deformation data to extract the parameters. Statistical tests indicated that the proposed method is reliable for extracting the midsole reaction model parameters with the stiffness and damping components producing favorable results (R (2) 0.998 ± 0.000 and 0.984 ± 0.018/root mean squared error of 5.550 ± 0.954 and 3.286 ± 2.504, respectively).

Naemi R; Chockalingam N

2012-04-01

 
 
 
 
261

Coaxial Atomic Force Microscope Tweezers  

CERN Document Server

We demonstrate coaxial atomic force microscope (AFM) tweezers that can trap and place small objects using dielectrophoresis (DEP). An attractive force is generated at the tip of a coaxial AFM probe by applying a radio frequency voltage between the center conductor and a grounded shield; the origin of the force is found to be DEP by measuring the pull-off force vs. applied voltage. We show that the coaxial AFM tweezers (CAT) can perform three dimensional assembly by picking up a specified silica microsphere, imaging with the microsphere at the end of the tip, and placing it at a target destination.

Brown, K A; Westervelt, R M

2010-01-01

262

Dynamic measuring of physical properties for developing a sophisticated preoperative surgical simulator: how much reaction force should a surgical simulator represent to the surgeon?  

UK PubMed Central (United Kingdom)

The acquisition of physical quantities for a living body in surgery is an important and necessary step toward developing a sophisticated preoperative surgical simulator and its validation and navigation. We have developed a multimodal measuring device that minimizes interference with the movements of the surgeon. We conducted nephrectomy surgery using a laboratory animal and successfully acquired physical quantities. From this experiment, we have acquired the following preliminary result. The surgeon feels a gripping force from -3.5 to 4.4N at the handle of the forceps for dissection. We assume that this data is not far from that of a human.

Ogata M; Makiyama K; Yamada T; Nagasaka M; Yamanaka H; Kubota Y

2013-01-01

263

A theoretical study for the reaction of vinyl cyanide C2H3CN(X 1A') with the ground state carbon atom C(3P) in cold molecular clouds  

Science.gov (United States)

The reaction of the ground state atomic carbon, C(3P), with simple unsaturated nitrile, C2H3CN(X 1A') (vinyl cyanide), is investigated theoretically to explore the probable routes for the formation of carbon-nitrogen-bearing species in extraterrestrial environments particularly of ultralow temperature. Five collision complexes without entrance barrier as a result of the carbon atom addition to the ? systems of C2H3CN are characterized. The B3YLP/6-311G(d,p) level of theory is utilized in obtaining the optimized geometries, harmonic frequencies, and energies of the intermediates, transition states, and products along the isomerization and dissociation pathways of each collision complex. Subsequently, with the facilitation of computed RRKM rate constants at collision energy of 0-10 kcal/mol, the most probable paths for each collision complexes are determined, of which the CCSD(T)/6-311G(d,p) energies are calculated. The major products predicted are exclusively due to the hydrogen atom dissociations, while the products of H2, CN, and CH2 decompositions are found negligible. Among many possible H-elimination products, cyano propargyl (p4) and 3-cyano propargyl (p5) are the most probable, in which p5 can be formed via two intermediates, cyano allene (i8) and cyano vinylmethylene (i6), while p4 is yielded from i8. The study suggests this class of reaction is an important route to the synthesis of unsaturated nitriles at the temperature as low as 10 K, and the results are valuable for future chemical models of interstellar clouds.

Su, Hsiu-Fen; Kaiser, R. I.; Chang, A. H. H.

2005-02-01

264

A theoretical study for the reaction of vinyl cyanide C2H3CN(X1A') with the ground state carbon atom C(3P) in cold molecular clouds.  

UK PubMed Central (United Kingdom)

The reaction of the ground state atomic carbon, C(3P), with simple unsaturated nitrile, C2H3CN(X1A' (vinyl cyanide), is investigated theoretically to explore the probable routes for the formation of carbon-nitrogen-bearing species in extraterrestrial environments particularly of ultralow temperature. Five collision complexes without entrance barrier as a result of the carbon atom addition to the pi systems of C2H3CN are characterized. The B3YLP/6-311G(d,p) level of theory is utilized in obtaining the optimized geometries, harmonic frequencies, and energies of the intermediates, transition states, and products along the isomerization and dissociation pathways of each collision complex. Subsequently, with the facilitation of computed RRKM rate constants at collision energy of 0-10 kcal/mol, the most probable paths for each collision complexes are determined, of which the CCSD(T)/6-311G(d,p) energies are calculated. The major products predicted are exclusively due to the hydrogen atom dissociations, while the products of H2, CN, and CH2 decompositions are found negligible. Among many possible H-elimination products, cyano propargyl (p4) and 3-cyano propargyl (p5) are the most probable, in which p5 can be formed via two intermediates, cyano allene (i8) and cyano vinylmethylene (i6), while p4 is yielded from i8. The study suggests this class of reaction is an important route to the synthesis of unsaturated nitriles at the temperature as low as 10 K, and the results are valuable for future chemical models of interstellar clouds.

Su HF; Kaiser RI; Chang AH

2005-02-01

265

The human foot and heel-sole-toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?  

Science.gov (United States)

Mechanically, the most economical gait for slow bipedal locomotion requires walking as an 'inverted pendulum', with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic 'M'-shaped vertical ground reaction forces of walking in humans reflect this impulse-vault-impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the 'M'-shaped walking ground reaction force profile does not require the plantigrade human foot or heel-sole-toe stance; it is maintained in tip-toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure--with ground-contacting heel behind ankle and toes in front--enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel-sole-toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all--largely avoiding the 'cost of muscle force'--during the passive vaulting phase. PMID:22572024

Usherwood, J R; Channon, A J; Myatt, J P; Rankin, J W; Hubel, T Y

2012-05-09

266

The human foot and heel-sole-toe walking strategy: a mechanism enabling an inverted pendular gait with low isometric muscle force?  

UK PubMed Central (United Kingdom)

Mechanically, the most economical gait for slow bipedal locomotion requires walking as an 'inverted pendulum', with: I, an impulsive, energy-dissipating leg compression at the beginning of stance; II, a stiff-limbed vault; and III, an impulsive, powering push-off at the end of stance. The characteristic 'M'-shaped vertical ground reaction forces of walking in humans reflect this impulse-vault-impulse strategy. Humans achieve this gait by dissipating energy during the heel-to-sole transition in early stance, approximately stiff-limbed, flat-footed vaulting over midstance and ankle plantarflexion (powering the toes down) in late stance. Here, we show that the 'M'-shaped walking ground reaction force profile does not require the plantigrade human foot or heel-sole-toe stance; it is maintained in tip-toe and high-heel walking as well as in ostriches. However, the unusual, stiff, human foot structure--with ground-contacting heel behind ankle and toes in front--enables both mechanically economical inverted pendular walking and physiologically economical muscle loading, by producing extreme changes in mechanical advantage between muscles and ground reaction forces. With a human foot, and heel-sole-toe strategy during stance, the shin muscles that dissipate energy, or calf muscles that power the push-off, need not be loaded at all--largely avoiding the 'cost of muscle force'--during the passive vaulting phase.

Usherwood JR; Channon AJ; Myatt JP; Rankin JW; Hubel TY

2012-10-01

267

Labor Force  

Science.gov (United States)

The labor force is the number of people ages 16 or older who are either working or looking for work. It does not include active-duty military personnel or the institutionalized population, such as prison inmates. Determining the size of the labor force is a way of determining how big the economy can get. The size of the labor force depends on two…

Occupational Outlook Quarterly, 2012

2012-01-01

268

Force or pressure feedback control for seismic vibrators  

Energy Technology Data Exchange (ETDEWEB)

A seismic vibrator source having an hydraulic vibrator coupled to vibrate a ground pad is provided with one or more force transducers such as, for example, load cells, strain gauges, or piezoelectric elements for measuring the force applied to the earth. Signals indicative of the pressure force are applied to a controller for the hydraulic vibrator to adjust control signals to prevent decoupling of the ground pad from the earth during ground seismic operations.

Bedenbender, J.W.; Kelly, G.H.

1985-05-21

269

Precision measurements of the pp??+pn and pp??+d reactions: Importance of long-range and tensor force effects  

Science.gov (United States)

Inclusive measurements of pion production in proton-proton collisions in the forward direction were undertaken at 400 and 600 MeV at the cooler synchrotron (COSY) at Forschungszentrum Julich using the Big Karl spectrograph. The high resolution in the ?+ momentum ensured that there was an unambiguous separation of the pp??+d/?+pn channels. Using these and earlier data, the ratio of the production cross sections could be followed through the ? region and compared with the predictions of final state interaction theory. Deviations are strongly influenced by long-range terms in the production operator and the tensor force in the final pn system. These have been investigated in a realistic pp??+d/?+pn calculation that includes S?D channel coupling between the final nucleons. A semiquantitative understanding of the observed effects is achieved.

Budzanowski, A.; Chatterjee, A.; Hawranek, P.; Hinterberger, F.; Jahn, R.; Jha, V.; Kilian, K.; Kirillov, Da.; Kirillov, Di.; Kliczewski, S.; Kolev, D.; Kravcikova, M.; Lesiak, M.; Lieb, J.; Machner, H.; Magiera, A.; Maier, R.; Martinska, G.; Nedev, S.; Niskanen, J. A.; Piskunov, N.; Proti?, D.; Ritman, J.; Rossen, P. Von; Roy, B. J.; Sitnik, I.; Siudak, R.; Stein, H. J.; Tsenov, R.; Urban, J.; Vankova, G.; Wilkin, C.

2009-06-01

270

Comment on "Reactive force fields for surface chemical reactions: a case study with hydrogen dissociation on Pd surfaces" [J. Chem. Phys. 132, 014704 (2010)].  

Science.gov (United States)

In a recent paper [Y. Xiao, W. Dong, and H. F. Busnengo, J. Chem. Phys. 132, 014704 (2010)], two of us (Y.X. and W.D.) and H. F. Busnengo reported the parameterization of some reactive force fields (RFF) for describing the dissociative adsorption of H2 on Pd surfaces. They obtained a sufficiently accurate RFF by using the reactive bond order (REBO) formalism of Brenner and showed that the simpler RFF based on the second moment approximation (SMA) failed in giving reliable results. It was concluded that the failure is due to the oversimplified expressions of RFF based on SMA and hence the lack of necessary flexibility. The results of our more recent investigation show that this conclusion needs to be corrected. A more suitable choice of the parameterization conditions allows, in fact, for obtaining a reliable RFF from SMA also. PMID:22047270

Shen, X J; Dong, W; Xiao, Y; Yan, X H

2011-10-28

271

Comment on "Reactive force fields for surface chemical reactions: a case study with hydrogen dissociation on Pd surfaces" [J. Chem. Phys. 132, 014704 (2010)].  

UK PubMed Central (United Kingdom)

In a recent paper [Y. Xiao, W. Dong, and H. F. Busnengo, J. Chem. Phys. 132, 014704 (2010)], two of us (Y.X. and W.D.) and H. F. Busnengo reported the parameterization of some reactive force fields (RFF) for describing the dissociative adsorption of H2 on Pd surfaces. They obtained a sufficiently accurate RFF by using the reactive bond order (REBO) formalism of Brenner and showed that the simpler RFF based on the second moment approximation (SMA) failed in giving reliable results. It was concluded that the failure is due to the oversimplified expressions of RFF based on SMA and hence the lack of necessary flexibility. The results of our more recent investigation show that this conclusion needs to be corrected. A more suitable choice of the parameterization conditions allows, in fact, for obtaining a reliable RFF from SMA also.

Shen XJ; Dong W; Xiao Y; Yan XH

2011-10-01

272

Analysing gait using a force-measuring walkway: intrasession repeatability in healthy children and adolescents.  

UK PubMed Central (United Kingdom)

The goal of this study was to determine the repeatability of gait parameters measured by a force plate gait analysis system (Leonardo Mechanograph(®) GW) in healthy children. Nineteen healthy children and adolescents (age range: 7-17 years) walked at a self-selected speed on an 11-m-long walkway. Vertical ground reaction forces were measured in the central 6 m of the walkway. Each participant performed three blocks of three trials while walking barefoot and three blocks of three trials while wearing shoes. There were no differences between trials within each condition. All force and spatiotemporal parameters had intraclass correlation coefficients above 0.87 and coefficients of variation in the order of 1-6%. In this group of healthy children and adolescents, gait analysis with a force plate system produced repeatable intra-day results.

Veilleux LN; Ballaz L; Robert M; Lemay M; Rauch F

2013-01-01

273

Energy cost and pole forces during Nordic walking under different surface conditions.  

UK PubMed Central (United Kingdom)

INTRODUCTION: 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). METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Schiffer T; Knicker A; Dannöhl R; Strüder HK

2009-03-01

274

Some applications of the virial theorem to molecular force fields: the zero virial reaction coordinate and diatomic potentials from the normalized kinetic field functions  

International Nuclear Information System (INIS)

For a fixed-angle potential energy surface (PES), W(Q), following the zero virial path (ZVP), on which ?/sub ?//sup N/Q/sub ?/ . del /sub ?/W(Q) = 0, provides an efficient way for locating the transition state and generating a good approximation to the minimum-energy reaction path; vector Q = (Q1, ..., Q/sub N/ stands for nuclear coordinates. An algorithm which employs the ZVP following is proposed for exploring PESs when starting from the reactant (or product) region. It seems that this approach allows one to avoid some discontinuities in the reaction coordinate, which often result from the bottom-following procedures. The implications of the integral forms of the virial theorem are examined and a new way of constructing potential energy functions W(R) for diatomic molecules is proposed. It starts with the normalization of the kinetic component T(R) of the potential: integral0/sup infinity/[T(R) - T(infinity)]dR = Z/sub A/Z/sub B/, where Z/sub A/ and Z/sub B/ are the nuclear charges and R is the internuclear distance. The modified potentials are derived for four different analytical representations of T(R), T/sub X(R)(X = M, R, RM, and HH) by the Morse, Rydberg, Rosen--Morse, and Hulbert--Hirschfelder functions, respectively. The three-parameter modified potentials (X = M, R, and RM) are tested against known spectroscopic data for H2+ and H2.The modified potentials require one less experimental constant to fit the potential parameters than do their original analogs. It follows that the Morse and Rydberg functions constitute satisfactory representations of the kinetic component T(R), and that enforcing its normalization improves predictions of spectroscopic constants and relations between them. 46 references.

1978-03-18

275

Strong Force  

CERN Multimedia

Without the strong force, there could be no life. The carbon in living matter is synthesised in stars via the strong force. Lighter atomic nuclei become bound together in a process called nuclear fusion. A minor change in this interaction would make life impossible. As its name suggests, the strong force is the most powerful of the 4 forces, yet its sphere of influence is limited to within the atomic nucleus. Indeed it is the strong force that holds together the quarks inside the positively charged protons. Without this glue, the quarks would fly apart repulsed by electromagnetism. In fact, it is impossible to separate 2 quarks : so much energy is needed, that a second pair of quarks is produced. Text for the interactive: Can you pull apart the quarks inside a proton?

276

On Grounding of Fast Ships  

DEFF Research Database (Denmark)

The paper deals with analysis of grounding of high-speed crafts. It is the purpose to present a comprehensive mathematical model for calculation of the overall dynamic ship response during grounding. This procedure is applied to derive the motions, the time varying sectional forces and the local loads during grounding on plane, sloping, sandy bottoms for six different designs of fast monohull ships made from steel, aluminium or GRP sandwich materials. The results show that the effect of the hull flexibility is to reduce the overall dynamic sectional loads on the hull girder. The considered numerical examples also indicate that, even with impact speeds of 40 knots against a 1:10 sloping bottom, the global strength of the hull girder is not exceeded by the grounding induced loads.For the local deformation of high-speed ship hulls at the point of contact withthe ground, the paper presents experimental results from crushing tests of aluminium hull girder components with realistic full-scale scantlings. A comparison with existing simplified calculation procedures for ductile metallic structures show that these procedures cannot be used to predict the crushing behaviour of the fore body of high speed ships.

Simonsen, Bo Cerup; Pedersen, Preben Terndrup

1997-01-01

277

Rural ground water contamination  

Energy Technology Data Exchange (ETDEWEB)

The contents of this book are: Remedial Actions; Analysis and Control of Rural Ground Wate; Ground Water Contamination Sources; Research Theory, and Practice; and Regulations Pertaining to Rural Ground Water.

D' Itri, F.M.

1987-01-01

278

Design Optimization of Ground Clearance of Domestic Cars  

Directory of Open Access Journals (Sweden)

Full Text Available Drag and lift forces plays a vital role in the performance and stability of vehicles. Less drag means less fuel consumption and hence less vehicular pollution. Also, lower lift force means higher chance of adhesion of the car body with the ground causing less overturning of the vehicle, which improves the vehicle performance. Both drag and lift forces can be manipulated by varying the ground clearance of the cars. The present study concentrates on studying the effect of ground clearance on these aerodynamic forces experimentally. Wind tunnel studies with a notch-back car model revealed increase in drag and decrease in lift with increase in ground clearance. Therefore, optimization is required for designing the best ground clearance and a preferable value of the same is thus obtained.

Debojyoti Mitra

2010-01-01

279

Ground water '89  

International Nuclear Information System (INIS)

The proceedings of the 5th biennial symposium of the Ground Water Division of the Geological Society of South Africa are presented. The theme of the symposium was ground water and mining. Papers were presented on the following topics: ground water resources; ground water contamination; chemical analyses of ground water and mining and its influece on ground water. Separate abstracts were prepared for 5 of the papers presented. The remaining papers were considered outside the subject scope of INIS.

1989-08-04

280

Does vibration counteract the static stretch-induced deficit on muscle force development?  

UK PubMed Central (United Kingdom)

OBJECTIVES: To determine the residual acute vibration-stretching effect on preactivation levels, short-latency stretch reflex, and performance during execution of drop jumps. DESIGN: Repeated measures. METHODS: Eleven male recreational athletes performed a set of three 45cm drop jumps before and immediately after a 30s static stretching exercise with and without simultaneously imposed muscle vibration (45Hz, 5mm). Drop jump height, ground reaction forces and electromyographic data including Vastus Lateralis onset/levels of preactivation and short-latency stretch reflex were recorded. RESULTS: No changes were induced on drop jump height. However, stretching-induced decrements on ground reaction force peak and time to peak as well as an increment in contact time followed a delay in short-latency stretch reflex onset and a reduced preactivation level of Vastus Lateralis. Otherwise, when vibration was simultaneously imposed, there was no evidence of changes in high-speed force production variables or electromyographic recordings. CONCLUSIONS: Mechanical vibration, when applied simultaneously to static-stretching routines, appeared to be effective to counteract decreased musculotendinous unit stiffness-induced high-speed force production deficit during jumping performance.

Fernandes IA; Kawchuk G; Bhambhani Y; Gomes PS

2013-09-01

 
 
 
 
281

Gait in children with juvenile chronic arthritis. Timing and force parameters.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To examine gait in children with juvenile chronic arthritis (JCA) with reference to velocity, ground reaction forces and temporal parameters. METHODS: Fifteen children with JCA were assigned into two groups (uni- and bilateral involvement and classified as pauci- or polyarticular arthritis). Fourteen healthy children participated in the control group. Light-beams were used to determine walking velocity and the children with JCA rated their pain on a visual analogue scale. Two force plates registered the ground reaction forces and foot-switches were used to obtain temporal parameters. RESULTS: The mean velocity for the children with JCA was significantly less than for the healthy controls. Velocity normalized to height showed a tendency for the children with JCA to walk slower than controls. Differences between JCA children and healthy controls were observed for peak vertical forces during heel contact and push-off. No temporal differences were observed between the groups. CONCLUSIONS: Such kinetic and temporal information may provide the clinician with a sensitive tool for pre- and post assessment of intra-articular steroid injections and/or physical therapy.

Broström E; Haglund-Akerlind Y; Hagelberg S; Cresswell AG

2002-01-01

282

Force sensor  

Energy Technology Data Exchange (ETDEWEB)

A force sensor and related method for determining force components. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

Grahn, Allen R. (Salt Lake City, UT)

1993-01-01

283

Force sensor  

Energy Technology Data Exchange (ETDEWEB)

A force sensor and related method for determining force components is described. The force sensor includes a deformable medium having a contact surface against which a force can be applied, a signal generator for generating signals that travel through the deformable medium to the contact surface, a signal receptor for receiving the signal reflected from the contact surface, a generation controller, a reception controller, and a force determination apparatus. The signal generator has one or more signal generation regions for generating the signals. The generation controller selects and activates the signal generation regions. The signal receptor has one or more signal reception regions for receiving signals and for generating detections signals in response thereto. The reception controller selects signal reception regions and detects the detection signals. The force determination apparatus measures signal transit time by timing activation and detection and, optionally, determines force components for selected cross-field intersections. The timer which times by activation and detection can be any means for measuring signal transit time. A cross-field intersection is defined by the overlap of a signal generation region and a signal reception region.

Grahn, A.R.

1993-05-11

284

Axial forces in piping systems  

Energy Technology Data Exchange (ETDEWEB)

This paper reviews the various pipe Code requirements related to control of axial forces in above ground piping systems. With the exception of ASME Section III (for seismic anchor motions) the Codes do not have specific limits for stresses induced by axial forces (F/A). These new limits will require changes to existing piping analysis computer programs. The present Code explicit limits on stresses due to bending moments result in implicit limits on axial stresses and associated axial forces. It is shown that the limitations of stresses in piping components due to bending moments result in corresponding conservative limits in stresses due to axial forces. Hence limits on axial forces are not required.

Wais, E.A. [Wais and Associates, Inc., Norcross, GA (United States)

1996-12-31

285

Superconducting magnet for high speed ground transportation  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the design of a superconducting magnet intended to propel, levitate and guide a magnetically levitated vehicle by means of combined ground propelling circuits. It also describes the on-board cryostat with an indirect immersion cooling system which enables both longitudinal sides of the vertical superconducting magnet to create an electrodynamic force. During coil testing a magnetomotive force of 450 kA was achieved with the maximum induction of 3.5 T at the winding surface. (author).

Klimenko, E.Yu; Novikov, S.I. (Gosudarstvennyj Komitet po Ispol' zovaniyu Atomnoj Ehnergii SSSR, Moscow (USSR). Inst. Atomnoj Ehnergii); Omelyanenko, V.I.; Sergeev, S.A. (Khar' kovskij Politekhnicheskij Inst., Kharkov (Ukrainian SSR))

1990-01-01

286

``Force,'' ontology, and language  

Science.gov (United States)

We introduce a linguistic framework through which one can interpret systematically students’ understanding of and reasoning about force and motion. Some researchers have suggested that students have robust misconceptions or alternative frameworks grounded in everyday experience. Others have pointed out the inconsistency of students’ responses and presented a phenomenological explanation for what is observed, namely, knowledge in pieces. We wish to present a view that builds on and unifies aspects of this prior research. Our argument is that many students’ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term “force” as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

Brookes, David T.; Etkina, Eugenia

2009-06-01

287

Seismic Analysis of Elevated Water Storage Tanks Subjected to Six Correlated Ground Motion Components  

Directory of Open Access Journals (Sweden)

Full Text Available In this work, rotational components of ground motion acceleration were defined according toimproved method from the corresponding available translational components based on transversely isotropicelastic wave propagation in the soil. With such improvement, it becomes possible to consider frequencydependent wave velocities on rotational components of ground motion. For this purpose, three translationalcomponents of El Centro earthquake (24 January 1951) were adopted to generate their relative rotationalcomponents based on SV and SH wave incidence by Fast Fourier transform with 4096 discrete frequencies.The translational and computed rotational motions were then applied to the concrete elevated water storagetanks with different structural characteristics and water elevations. The finite element method is used for thenonlinear analysis of water storage tanks considering the fluid-structure interaction using Lagrangian-Lagrangian approach and the concrete material nonlinearities have been taken into account through William-Warnke model. The nonlinear response of these structures considering the six components of ground motionshowed that the rotational components of ground motion can increase or decrease the maximum displacementand reaction force of the structure. These variations are depending on the frequency of structure andpredominant frequencies of translational and rotational components of ground motion.

L. Kalani Sarokolayi; B. Navayi Neya; J. Vaseghi Amiri; H. R. Tavakoli

2013-01-01

288

Modelo 3D para quantificação das forças articulares e momentos proximais resultantes para o membro superior/ 3D model for analysis of resultant proximal reaction forces and moments for the upper limb  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese Objetivos: Este estudo teve como objetivo implementar um modelo biomecânico, de segmentos articulados, associado à dinâmica inversa que permita a análise em três dimensões das forças de reação proximais e momentos proximais resultantes para diferentes gestos do membro superior. Método: Os gestos avaliados foram: flexão, extensão e abdução de ombro e flexão de cotovelo, os quais foram realizados por um indivíduo do sexo masculino. O modelo implementado é c (more) omposto por cinco segmentos rígidos (mão, antebraço, braço, escápula e tronco) conectados. As equações de movimento de Newton-Euler foram utilizadas para quantificação das forças e momentos proximais resultantes. Para registro cinemático foram utilizadas cinco câmeras digitais, com freqüência de amostragem de 50 campos/seg. A precisão estimada do sistema de videogrametria foi, em média, de 1,7 mm. Foi monitorada a atividade eletromiográfica dos músculos deltóide (anterior, médio e posterior), bíceps braquial, tríceps braquial e peitoral maior. O modelo foi avaliado através da comparação qualitativa dos resultados de momento proximal resultante, com a atividade eletromiográfica. Resultados: Os resultados sugerem que o modelo apresenta resultados coerentes. O sinal eletromiográfico e o momento proximal apresentam sincronismo temporal. Conclusão: O modelo foi capaz de estimar as forças de reacção e momentos proximais resultantes nos diferentes gestos. Abstract in english Objectives: The aim of this study was to implement a biomechanical model, with linked segments associated with inverse dynamics, to analyze proximal net forces and moments during different upper limbs? activities. Methods: one male subject performed flexion, extension and abduction of the shoulder and flexion of the elbow. The model is composed of five connected rigid segments (hand, forearm, arm, scapula and trunk). The Newton-Euler motion equations were used to quantif (more) y proximal net reaction forces and moments. For kinematics recording, five cameras with a frequency sample of 50 fps were used. Videogrammetry accuracy was, on average, 1,7mm. The following muscles had their activities monitored: deltoid (anterior, medial, posterior), biceps brachialis, triceps brachialis, pectoralis major. The model was evaluated by qualitative comparison of proximal net moments with electromyographic signal of agonist muscles. Results: The results showed a temporal synchronism between the proximal net moments and agonist EMG activity. Conclusions: The model was able to estimate proximal net forces and moments during different upper limbs? activities.

Ribeiro, Daniel Cury; Loss, Jefferson Fagundes

2010-01-01

289

Rapid Reaction Linux :  

UK PubMed Central (United Kingdom)

Rapid Reaction Linux has been created at the Universityof German Federal Armed Forces in order to enhancerealtime capabilities of the standard Linux kernel.Rapid Reaction Linux combines two well known patchesto achieve this goal on the Intel x86 architecture usingprocessors like Intel Pentium or any newer descendant.

Arnd C. Heursch; Helmut Rzehak

290

TARDEC's Intelligent Ground Systems overview  

Science.gov (United States)

The mission of the Intelligent Ground Systems (IGS) Area at the Tank Automotive Research, Development and Engineering Center (TARDEC) is to conduct technology maturation and integration to increase Soldier robot control/interface intuitiveness and robotic ground system robustness, functionality and overall system effectiveness for the Future Combat System Brigade Combat Team, Robotics Systems Joint Project Office and game changing capabilities to be fielded beyond the current force. This is accomplished through technology component development focused on increasing unmanned ground vehicle autonomy, optimizing crew interfaces and mission planners that capture commanders' intent, integrating payloads that provide 360 degree local situational awareness and expanding current UGV tactical behavior, learning and adaptation capabilities. The integration of these technology components into ground vehicle demonstrators permits engineering evaluation, User assessment and performance characterization in increasingly complex, dynamic and relevant environments to include high speed on road or cross country operations, all weather/visibility conditions and military operations in urban terrain (MOUT). Focused testing and experimentation is directed at reducing PM risk areas (safe operations, autonomous maneuver, manned-unmanned collaboration) and transitioning technology in the form of hardware, software algorithms, test and performance data, as well as User feedback and lessons learned.

Jaster, Jeffrey F.

2009-05-01

291

Subject-specific knee joint geometry improves predictions of medial tibiofemoral contact forces.  

UK PubMed Central (United Kingdom)

Estimating tibiofemoral joint contact forces is important for understanding the initiation and progression of knee osteoarthritis. However, tibiofemoral contact force predictions are influenced by many factors including muscle forces and anatomical representations of the knee joint. This study aimed to investigate the influence of subject-specific geometry and knee joint kinematics on the prediction of tibiofemoral contact forces using a calibrated EMG-driven neuromusculoskeletal model of the knee. One participant fitted with an instrumented total knee replacement walked at a self-selected speed while medial and lateral tibiofemoral contact forces, ground reaction forces, whole-body kinematics, and lower-limb muscle activity were simultaneously measured. The combination of generic and subject-specific knee joint geometry and kinematics resulted in four different OpenSim models used to estimate muscle-tendon lengths and moment arms. The subject-specific geometric model was created from CT scans and the subject-specific knee joint kinematics representing the translation of the tibia relative to the femur was obtained from fluoroscopy. The EMG-driven model was calibrated using one walking trial, but with three different cost functions that tracked the knee flexion/extension moments with and without constraint over the estimated joint contact forces. The calibrated models then predicted the medial and lateral tibiofemoral contact forces for five other different walking trials. The use of subject-specific models with minimization of the peak tibiofemoral contact forces improved the accuracy of medial contact forces by 47% and lateral contact forces by 7%, respectively compared with the use of generic musculoskeletal model.

Gerus P; Sartori M; Besier TF; Fregly BJ; Delp SL; Banks SA; Pandy MG; D'Lima DD; Lloyd DG

2013-09-01

292

Patellofemoral joint compression forces in backward and forward running.  

UK PubMed Central (United Kingdom)

Patellofemoral pain (PFP) is a common injury and increased patellofemoral joint compression forces (PFJCF) may aggravate symptoms. Backward running (BR) has been suggested for exercise with reduced PFJCF. The aims of this study were to (1) investigate if BR had reduced peak PFJCF compared to forward running (FR) at the same speed, and (2) if PFJCF was reduced in BR, to investigate which biomechanical parameters explained this. It was hypothesized that (1) PFJCF would be lower in BR, and (2) that this would coincide with a reduced peak knee moment caused by altered ground reaction forces (GRFs). Twenty healthy subjects ran in forward and backward directions at consistent speed. Kinematic and ground reaction force data were collected; inverse dynamic and PFJCF analyses were performed. PFJCF were higher in FR than BR (4.5±1.5; 3.4±1.4BW; p<0.01). The majority of this difference (93.1%) was predicted by increased knee moments in FR compared to BR (157±54; 124±51 Nm; p<0.01). 54.8% of differences in knee moments could be predicted by the magnitude of the GRF (2.3±0.3; 2.4±0.2BW), knee flexion angle (44±6; 41±7) and center of pressure location on the foot (25±11; 12±6%) at time of peak knee moment. Results were not consistent in all subjects. It was concluded that BR had reduced PFJCF compared to FR. This was caused by an increased knee moment, due to differences in magnitude and location of the GRF vector relative to the knee. BR can therefore be used to exercise with decreased PFJCF.

Roos PE; Barton N; van Deursen RW

2012-06-01

293

48 CFR 252.228-7001 - Ground and flight risk.  

Science.gov (United States)

...instruction entitled âContractor's Flight and Ground Operationsâ (Air Force Instruction 10-220, Army Regulation 95-20, NAVAIR Instruction 3710.1 (Series), Coast Guard Instruction M13020.3, and Defense Contract Management Agency Instruction...

2010-10-01

294

Measurement of 241Am Ground State Radiative Neutron Capture Cross Section with Cold Neutron Beam. Progress Report on Research Contract HUN14318 for the CRP on Minor Actinide Neutron Reaction Data (MANREAD)  

International Nuclear Information System (INIS)

[en] The ground state cross section of 242Am has been measured with beams of cold neutrons at the Budapest Research Reactor using the X-ray emission of the decay product of 242Pu. This methodology avoids the uncertainty caused by resonance neutrons in the pile activations. The target was characterized with gamma and X-ray spectrometry. The obtained ground state cross section is 540 ± 32 b, which is at the low end of the most recent literature values, but agrees with most of them within their uncertainty. (author)

2012-01-01

295

Screen charge transfer by grounded tip on ferroelectric surfaces.  

Energy Technology Data Exchange (ETDEWEB)

We have investigated polarization reversal and charge transfer effects by a grounded tip on 50 nm thick ferroelectric thin films using piezoelectric force microscopy and Kelvin force microscopy. We observed the polarization reversal in the center of written domains, and also identified another mechanism, which is the transfer of screen charges toward the grounded tip. In order to overcome these phenomena, we successfully applied a modified read/write scheme featuring a bias voltage.

Kim, Y.; Kim, J.; Buhlmann, S.; Hong, S.; Kim, Y. K.; Kim, S.-H.; No, K.; Materials Science Division; Korea Advanced Inst. of Science and Technology; Samsung Advanced Inst. of Technology; Inostek Inc.

2008-03-01

296

"Force," ontology, and language  

Science.gov (United States)

We introduce a linguistic framework through which one can interpret systematically studentsâ understanding of and reasoning about force and motion. Some researchers have suggested that students have robust misconceptions or alternative frameworks grounded in everyday experience. Others have pointed out the inconsistency of studentsâ responses and presented a phenomenological explanation for what is observed, namely, knowledge in pieces. We wish to present a view that builds on and unifies aspects of this prior research. Our argument is that many studentsâ difficulties with force and motion are primarily due to a combination of linguistic and ontological difficulties. It is possible that students are primarily engaged in trying to define and categorize the meaning of the term âforceâ as spoken about by physicists. We found that this process of negotiation of meaning is remarkably similar to that engaged in by physicists in history. In this paper we will describe a study of the historical record that reveals an analogous process of meaning negotiation, spanning multiple centuries. Using methods from cognitive linguistics and systemic functional grammar, we will present an analysis of the force and motion literature, focusing on prior studies with interview data. We will then discuss the implications of our findings for physics instruction.

Brookes, David T.; Etkina, Eugenia

2010-06-30

297

Force direction pattern stabilizes sagittal plane mechanics of human walking.  

UK PubMed Central (United Kingdom)

The neural control and mechanics of human bipedalism are inadequately understood. The variable at the interface of neural control and body mechanics that is key to upright posture during human walking is the force of the ground on the foot (ground reaction force, F). We present a model that predicts sagittal plane F direction as passing through a divergent point (DP) fixed in a reference frame attached to the person. Four reference frames were tested to identify which provided the simplest and most accurate description of F direction. For all reference frames, the DP model predicted nearly all the observed variation in F direction and whole body angular momentum during single leg stance. The reference frame with vertical orientation and with origin on the pelvis provided the best combination of accuracy and simplicity. The DP was located higher than the CM and the predicted F produced a pattern of torque about the CM that caused body pitch oscillations that disrupted upright posture. Despite those oscillations, that torque was evidence of a stability mechanism that may be a critical component enabling humans to remain upright while walking and performing other tasks.

Gruben KG; Boehm WL

2012-06-01

298

Force direction pattern stabilizes sagittal plane mechanics of human walking.  

Science.gov (United States)

The neural control and mechanics of human bipedalism are inadequately understood. The variable at the interface of neural control and body mechanics that is key to upright posture during human walking is the force of the ground on the foot (ground reaction force, F). We present a model that predicts sagittal plane F direction as passing through a divergent point (DP) fixed in a reference frame attached to the person. Four reference frames were tested to identify which provided the simplest and most accurate description of F direction. For all reference frames, the DP model predicted nearly all the observed variation in F direction and whole body angular momentum during single leg stance. The reference frame with vertical orientation and with origin on the pelvis provided the best combination of accuracy and simplicity. The DP was located higher than the CM and the predicted F produced a pattern of torque about the CM that caused body pitch oscillations that disrupted upright posture. Despite those oscillations, that torque was evidence of a stability mechanism that may be a critical component enabling humans to remain upright while walking and performing other tasks. PMID:21871681

Gruben, Kreg G; Boehm, Wendy L

2011-08-25

299

Potential Energy Surface for Ground-State H2S via Scaling of the External Correlation, Comparison with Extrapolation to Complete Basis Set Limit, and Use in Reaction Dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A global double many-body expansion potential energy surface is reported for the electronic ground state of H2S by fitting accurate ab initio energies calculated at the multireference configuration interaction level with the aug-cc-pVQZ basis set, after slightly correcting semiempirically the dynami...

Song, Y. Z.; Caridade, P. J. S. B.; Varandas, A. J. C.

300

Teleoperation of a Force Controlled Robot Manipulator Without Force Feedback to a Human Operator.  

Science.gov (United States)

A teleoperation scheme of a manipulator in orbit is presented. The schemes uses no force reflection to a human operator on the ground. Instead, the manipulator is hybrid controlled: forces or velocities of the end-effector are selectively controlled. The ...

M. Uchiyama K. Kitagaki

1989-01-01

 
 
 
 
301

The ground based plan  

International Nuclear Information System (INIS)

The paper presents a report of ''The Ground Based Plan'' of the United Kingdom Science and Engineering Research Council. The ground based plan is a plan for research in astronomy and planetary science by ground based techniques. The contents of the report contains a description of:- the scientific objectives and technical requirements (the basis for the Plan), the present organisation and funding for the ground based programme, the Plan, the main scientific features and the further objectives of the Plan. (U.K.)

1989-01-01

302

Influence of model complexity and problem formulation on the forces in the knee calculated using optimization methods.  

UK PubMed Central (United Kingdom)

BACKGROUND: Predictions of the forces transmitted by the redundant force-bearing structures in the knee are often performed using optimization methods considering only moment equipollence as a result of simplified knee modeling without ligament contributions. The current study aimed to investigate the influence of model complexity (with or without ligaments), problem formulation (moment equipollence with or without force equipollence) and optimization criteria on the prediction of the forces transmitted by the force-bearing structures in the knee. METHODS: Ten healthy young male adults walked in a gait laboratory while their kinematic and ground reaction forces were measured simultaneously. A validated 3D musculoskeletal model of the locomotor system with a knee model that included muscles, ligaments and articular surfaces was used to calculate the joint resultant forces and moments, and subsequently the forces transmitted in the considered force-bearing structures via optimization methods. Three problem formulations with eight optimization criteria were evaluated. RESULTS: Among the three problem formulations, simultaneous consideration of moment and force equipollence for the knee model with ligaments and articular contacts predicted contact forces (first peak: 3.3-3.5 BW; second peak: 3.2-4.2 BW; swing: 0.3 BW) that were closest to previously reported theoretical values (2.0-4.0 BW) and in vivo data telemetered from older adults with total knee replacements (about 2.8 BW during stance; 0.5 BW during swing). Simultaneous consideration of moment and force equipollence also predicted more physiological ligament forces (< 1.0 BW), which appeared to be independent of the objective functions used. Without considering force equipollence, the calculated contact forces varied from 1.0 to 4.5 BW and were as large as 2.5 BW during swing phase; the calculated ACL forces ranged from 1 BW to 3.7 BW, and those of the PCL from 3 BW to 7 BW. CONCLUSIONS: Model complexity and problem formulation affect the prediction of the forces transmitted by the force-bearing structures at the knee during normal level walking. Inclusion of the ligaments in a knee model enables the simultaneous consideration of equations of force and moment equipollence, which is required for accurately estimating the contact and ligament forces, and is more critical than the adopted optimization criteria.

Hu CC; Lu TW; Chen SC

2013-01-01

303

Friction Force  

Science.gov (United States)

Students use LEGO® MINDSTORMS® robotics to help conceptualize and understand the force of friction. Specifically, they observe how different surfaces in contact result in different frictional forces. A LEGO robot is constructed to pull a two-wheeled trailer made of LEGO parts. The robot is programmed to pull the trailer 10 feet and trial runs are conducted on smooth and textured surfaces. The speed and motor power of the robot is kept constant in all trials so students observe the effect of friction between various combinations of surfaces and trailer wheels. To apply what they learn, students act as engineers and create the most effective car by designing the most optimal tires for given surface conditions.

Applying Mechatronics to Promote Science (AMPS) Program GK-12,

304

Constructivist Grounded Theory?  

Directory of Open Access Journals (Sweden)

Full Text Available AbstractI refer to and use as scholarly inspiration Charmaz’s excellent article on constructivist grounded theory as a tool of getting to the fundamental issues on why grounded theory is not constructivist. I show that constructivist data, if it exists at all, is a very, very small part of the data that grounded theory uses.

Barney G. Glaser, PhD, Hon. PhD

2012-01-01

305

Feed forward and feedback control for over-ground locomotion in anaesthetized cats.  

Science.gov (United States)

The biological central pattern generator (CPG) integrates open and closed loop control to produce over-ground walking. The goal of this study was to develop a physiologically based algorithm capable of mimicking the biological system to control multiple joints in the lower extremities for producing over-ground walking. The algorithm used state-based models of the step cycle each of which produced different stimulation patterns. Two configurations were implemented to restore over-ground walking in five adult anaesthetized cats using intramuscular stimulation (IMS) of the main hip, knee and ankle flexor and extensor muscles in the hind limbs. An open loop controller relied only on intrinsic timing while a hybrid-CPG controller added sensory feedback from force plates (representing limb loading), and accelerometers and gyroscopes (representing limb position). Stimulation applied to hind limb muscles caused extension or flexion in the hips, knees and ankles. A total of 113 walking trials were obtained across all experiments. Of these, 74 were successful in which the cats traversed 75% of the 3.5 m over-ground walkway. In these trials, the average peak step length decreased from 24.9 ± 8.4 to 21.8 ± 7.5 (normalized units) and the median number of steps per trial increased from 7 (Q1 = 6, Q3 = 9) to 9 (8, 11) with the hybrid-CPG controller. Moreover, within these trials, the hybrid-CPG controller produced more successful steps (step length ? 20 cm; ground reaction force ? 12.5% body weight) than the open loop controller: 372 of 544 steps (68%) versus 65 of 134 steps (49%), respectively. This supports our previous preliminary findings, and affirms that physiologically based hybrid-CPG approaches produce more successful stepping than open loop controllers. The algorithm provides the foundation for a neural prosthetic controller and a framework to implement more detailed control of locomotion in the future. PMID:22328615

Mazurek, K A; Holinski, B J; Everaert, D G; Stein, R B; Etienne-Cummings, R; Mushahwar, V K

2012-02-13

306

Forcing isomorphism  

CERN Multimedia

A forcing extension may create new isomorphisms between two models of a first order theory. Certain model theoretic constraints on the theory and other constraints on the forcing can prevent this pathology. A countable first order theory is classifiable if it is superstable and does not have either the dimensional order property or the omitting types order property. Shelah [Sh:c] showed that if a theory T is classifiable then each model of cardinality lambda is described by a sentence of L_{infty, lambda}. In fact this sentence can be chosen in the L^*_{lambda}. (L^*_{lambda} is the result of enriching the language L_{infty, beth^+} by adding for each mu < lambda a quantifier saying the dimension of a dependence structure is greater than mu .) The truth of such sentences will be preserved by any forcing that does not collapse cardinals <= lambda and that adds no new countable subsets of lambda. Hence, if two models of a classifiable theory of power lambda are non-isomorphic, they are non-isomorphic afte...

Baldwin, J T; Shelah, S; Baldwin, John T.; Laskowski, Michael C.; Shelah, Saharon

1993-01-01

307

Kinetic and dynamic studies of the Cl(2Pu) + H2O(X?1A1) ? HCl(X?1?+) + OH(X?2?) reaction on an ab initio based full-dimensional global potential energy surface of the ground electronic state of ClH2O.  

Science.gov (United States)

Extensive high-level ab initio calculations were performed on the ground electronic state of ClH2O. The barrier region for the title reaction was found to have significant multi-reference character, thus favoring the multi-reference configuration interaction (MRCI) method over single-reference methods such as coupled-cluster. A full-dimensional global potential energy surface was developed by fitting about 25?000 MRCI points using the permutation invariant polynomial method. The reaction path features a "late" barrier flanked by deep pre- and post-barrier wells. Calculated rate constants for the forward reaction are in reasonable agreement with experiment, suggesting a good representation of the forward barrier. The dynamics of the forward reaction was also investigated using a quasi-classical trajectory method at energies just above the barrier. While the OH bond is found to be a spectator, the HCl product has significant rotational excitation. The reaction proceeds via both direct rebound and stripping mechanisms, leading to backward and sideways scattering. PMID:23968087

Li, Jun; Dawes, Richard; Guo, Hua

2013-08-21

308

Kinetic and dynamic studies of the Cl(2Pu) + H2O(X~1A1) --> HCl(X~1?+) + OH(X~2?) reaction on an ab initio based full-dimensional global potential energy surface of the ground electronic state of ClH2O  

Science.gov (United States)

Extensive high-level ab initio calculations were performed on the ground electronic state of ClH2O. The barrier region for the title reaction was found to have significant multi-reference character, thus favoring the multi-reference configuration interaction (MRCI) method over single-reference methods such as coupled-cluster. A full-dimensional global potential energy surface was developed by fitting about 25 000 MRCI points using the permutation invariant polynomial method. The reaction path features a ``late'' barrier flanked by deep pre- and post-barrier wells. Calculated rate constants for the forward reaction are in reasonable agreement with experiment, suggesting a good representation of the forward barrier. The dynamics of the forward reaction was also investigated using a quasi-classical trajectory method at energies just above the barrier. While the OH bond is found to be a spectator, the HCl product has significant rotational excitation. The reaction proceeds via both direct rebound and stripping mechanisms, leading to backward and sideways scattering.

Li, Jun; Dawes, Richard; Guo, Hua

2013-08-01

309

Kinetic and dynamic studies of the Cl((2)Pu) + H2O(X(1)A1) ? HCl(X(1)?(+)) + OH(X(2)?) reaction on an ab initio based full-dimensional global potential energy surface of the ground electronic state of ClH2O.  

UK PubMed Central (United Kingdom)

Extensive high-level ab initio calculations were performed on the ground electronic state of ClH2O. The barrier region for the title reaction was found to have significant multi-reference character, thus favoring the multi-reference configuration interaction (MRCI) method over single-reference methods such as coupled-cluster. A full-dimensional global potential energy surface was developed by fitting about 25?000 MRCI points using the permutation invariant polynomial method. The reaction path features a "late" barrier flanked by deep pre- and post-barrier wells. Calculated rate constants for the forward reaction are in reasonable agreement with experiment, suggesting a good representation of the forward barrier. The dynamics of the forward reaction was also investigated using a quasi-classical trajectory method at energies just above the barrier. While the OH bond is found to be a spectator, the HCl product has significant rotational excitation. The reaction proceeds via both direct rebound and stripping mechanisms, leading to backward and sideways scattering.

Li J; Dawes R; Guo H

2013-08-01

310

Ground water contamination: Transport and remediation  

Energy Technology Data Exchange (ETDEWEB)

This book devotes the first three chapters to a concise review of basic concepts of groundwater hydrology. The transition to contaminate transport is made through a broadly based discussion of cources of contamination and data collection - hydrology to transport to reactions to microbiological reactions. Chapters on reactive transport and bioremediation follow and the final chapter is a practical discussion of the legal aspects of ground water contamination.

Bedient, P.B.; Rifai, H.S.; Newell, C.J.

1994-12-31

311

Hydride transfer reactions  

International Nuclear Information System (INIS)

The purpose of this research was to examine the structure of the transition states of intermolecular hydride transfer reactions, i.e., whether they are linear or trigonal, by using as a probe hydrogen-deuterium kinetic isotope effects. Three sets of reactions were examined. The first set involved reactions of triarylmethyl cations with triarylmethanes and their deuterated (at central carbon) analogs. These reactions, which are considered to be one-step hydride transfer reactions, gave kH/kD isotope effects in the range 7-9. In view of the fact that the transition states are quite symmetrical with similar force constants f1 and f2, the large kinetic isotope effects exhibited by these reactions support a linear transition state. The data were not accurate enough to determine activation energy parameters and assess the extent of any mechanical tunneling. The second set of reactions involved the less sterically hindered xanthene system by reacting substituted xanthenes with the 9-xanthyl cation and xanthene with the diarylmethyl and triarylmethyl cations. The obtained kH/kD kinetic isotope effects, 3.5-7.5, are consistent with transition states where the angle between donor-hydrogen-acceptor is 120-150 degree on the assumption that the force constants on either side of the hydrogen are the same; it is also possible that the transition states are linear with somewhat unequal force constants on either side of the hydrogen. The third set involved the reactions of triphenylsilane with triarylmethyl cations. No assessment of the structure of the transition states of these reactions could be made because the kinetic isotope effects (1.6-2.2), which are in the range assigned by O'Ferral to cases where the angle between donor-hydrogen-acceptor is about 90 degree, may be due to the expected large differences in the force constants f1 and f2.

1989-01-01

312

Current status on design ground motion for buildings in Japan  

International Nuclear Information System (INIS)

This paper firstly describes the design seismic force and design ground motion currently used in Japan. In the past, the static force representing the effect of earthquake motion on the structures was used directly for design. When computer technology advanced, and a precise analytical modelling became possible, analysis using time-dependent ground motion data became more common for seismic design analysis. The design static force is given considering some uncertainties due to variations of the ground motion properties, whereas the ground motion time history is regarded as a sample data picked up from the whole data set representing the average properties of design ground motions. In general, the design seismic force should be evaluated based on the ground motions corresponding to the site conditions and the specified occurrence rate of motion. However, the consideration of such characteristics has not been possible until recently, since the earthquake data was not sufficient and the simulation technique was not fully established either. These were made possible with many experiences of structural damage, accumulation of strong motion records with the recent advances in computing technology. Here, current evaluation practice of design ground motion is introduced and some problems to be solved in near future will be added. (author)

2007-01-01

313

Military aviators, special operations forces, and causal malaria prophylaxis.  

UK PubMed Central (United Kingdom)

U.S. military aviators are currently restricted to the use of chloroquine or doxycycline for malaria prophylaxis. Ground forces are allowed the additional option of taking mefloquine. These medications are begun before deployment, must be taken for 4 weeks after leaving the malarious area, and primaquine must be added to the regimen the last 2 of those 4 weeks. Compliance with this regimen is often poor, especially in populations who travel abroad frequently for short periods of time. Causal malaria prophylaxis offers potential benefits of decreased length of postdeployment regimens and obviates the need for a second medication for terminal prophylaxis. Potential obstacles include adverse drug reactions, cost, and rapid development of resistance to new medications by Plasmodium species, which should be weighed against the risks to health and mission success in each deployment.

Chambers JA

2003-12-01

314

Modelling of substation grounding grids  

Energy Technology Data Exchange (ETDEWEB)

Describes a study on models of various grounding grids with and without ground rods to determine their effective resistance to ground and the surface potential distribution during ground faults. Results are presented.

El-Morshedy, A.; Zeitoun, A.G.; Ghourab, M.M.

1986-07-01

315

Naval Flanking in Ground Warfare  

Directory of Open Access Journals (Sweden)

Full Text Available The Mediterranean Sea, Israel’s only open border, also borders Israel’s enemies to the north and the Gaza Strip to the south, thereby linking it to enemy states. Thus, Israel’s control of this naval arena would enable it to project military strength from the sea, and afford it the capability to embark on landing operations of various types. “The shores of the State of Israel, the naval interface with each of our enemies, require us to expand our naval strength to the point of being able to land forces from the sea. David Ben-Gurion even said that we are bound to view the sea as Israel’s extended western territory.” The naval arena is the Achilles’ heel of Israel’s enemies and therefore also an opportunity for the IDF.However, even if Israel enjoys superiority in the naval arena, it is clear that the battle cannot be decided at sea. In fact, the IDF has aerial and naval superiority, two essential components for the existence of a naval ?anking option. In constructing a larger amphibious force, the IDF would be able to translate its naval superiority into a signi?cant contribution for attaining decisions in ground battles. The essay below examines the components of the landing process and offers some recommendations on construction of this type of force.

Gideon Raz

2011-01-01

316

Effects of a powered ankle-foot prosthesis on kinetic loading of the unaffected leg during level-ground walking.  

UK PubMed Central (United Kingdom)

BACKGROUND: People with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. METHODS: We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. RESULTS: Use of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. CONCLUSIONS: Use of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

Grabowski AM; D'Andrea S

2013-01-01

317

Effects of a powered ankle-foot prosthesis on kinetic loading of the unaffected leg during level-ground walking  

Science.gov (United States)

Background People with a lower-extremity amputation that use conventional passive-elastic ankle-foot prostheses encounter a series of stress-related challenges during walking such as greater forces on their unaffected leg, and may thus be predisposed to secondary musculoskeletal injuries such as chronic joint disorders. Specifically, people with a unilateral transtibial amputation have an increased susceptibility to knee osteoarthritis, especially in their unaffected leg. Previous studies have hypothesized that the development of this disorder is linked to the abnormally high peak knee external adduction moments encountered during walking. An ankle-foot prosthesis that supplies biomimetic power could potentially mitigate the forces and knee adduction moments applied to the unaffected leg of a person with a transtibial amputation, which could, in turn, reduce the risk of knee osteoarthritis. We hypothesized that compared to using a passive-elastic prosthesis, people with a transtibial amputation using a powered ankle-foot prosthesis would have lower peak resultant ground reaction forces, peak external knee adduction moments, and corresponding loading rates applied to their unaffected leg during walking over a wide range of speeds. Methods We analyzed ground reaction forces and knee joint kinetics of the unaffected leg of seven participants with a unilateral transtibial amputation and seven age-, height- and weight-matched non-amputees during level-ground walking at 0.75, 1.00, 1.25, 1.50, and 1.75 m/s. Subjects with an amputation walked while using their own passive-elastic prosthesis and a powered ankle-foot prosthesis capable of providing net positive mechanical work and powered ankle plantar flexion during late stance. Results Use of the powered prosthesis significantly decreased unaffected leg peak resultant forces by 2-11% at 0.75-1.50 m/s, and first peak knee external adduction moments by 21 and 12% at 1.50 and 1.75 m/s, respectively. Loading rates were not significantly different between prosthetic feet. Conclusions Use of a biomimetic powered ankle-foot prosthesis decreased peak resultant force at slow and moderate speeds and knee external adduction moment at moderate and fast speeds on the unaffected leg of people with a transtibial amputation during level-ground walking. Thus, use of an ankle-foot prosthesis that provides net positive mechanical work could reduce the risk of comorbidities such as knee osteoarthritis.

2013-01-01

318

Performance and Stability of a Winged Vehicle in Ground Effect  

CERN Multimedia

Present work deals with the dynamics of vehicles which intentionally operate in the ground proximity. The dynamics in ground effect is influenced by the vehicle orientation with respect to the ground, since the aerodynamic force and moment coefficients, which in turn depend on height and angle of attack, also vary with the Euler angles. This feature, usually neglected in the applications, can be responsible for sizable variations of the aircraft performance and stability. A further effect, caused by the sink rate, determines unsteadiness that modifies the aerodynamic coefficients. In this work, an analytical formulation is proposed for the force and moment calculation in the presence of the ground and taking the aircraft attitude and sink rate into account. The aerodynamic coefficients are firstly calculated for a representative vehicle and its characteristics in ground effect are investigated. Performance and stability characteristics are then discussed with reference to significant equilibrium conditions, w...

de Divitiis, Nicola

2009-01-01

319

Electrical grounding prong socket  

Energy Technology Data Exchange (ETDEWEB)

The invention is a socket for a grounding prong used in a three prong electrical plug and a receptacle for the three prong plug. The socket being sufficiently spacious to prevent the socket from significantly stretching when a larger, U-shaped grounding prong is inserted into the socket, and having a ridge to allow a snug fit when a smaller tubular shape grounding prong is inserted into the socket.

Leong, Robert (Dublin, CA)

1991-01-01

320

The Grounded Theory Bookshelf  

Directory of Open Access Journals (Sweden)

Full Text Available Bookshelf will provide critical reviews and perspectives on books on theory and methodology of interest to grounded theory. This issue includes a review of Heaton’s Reworking Qualitative Data, of special interest for some of its references to grounded theory as a secondary analysis tool; and Goulding’s Grounded Theory: A practical guide for management, business, and market researchers, a book that attempts to explicate the method and presents a grounded theory study that falls a little short of the mark of a fully elaborated theory.Reworking Qualitative Data, Janet Heaton (Sage, 2004). Paperback, 176 pages, $29.95. Hardcover also available.

Vivian B. Martin, Ph.D.

2005-01-01

 
 
 
 
321

Attractive Optical Forces from Blackbody Radiation  

Science.gov (United States)

Blackbody radiation around hot objects induces ac Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object. We explicitly calculate the resulting attractive blackbody optical dipole force for ground state hydrogen atoms. Surprisingly, this force can surpass the repulsive radiation pressure and actually pull the atoms against the radiation energy flow towards the surface with a force stronger than gravity. We exemplify the dominance of the “blackbody force” over gravity for hydrogen in a cloud of hot dust particles. This overlooked force appears relevant in various astrophysical scenarios, in particular, since analogous results hold for a wide class of other broadband radiation sources.

Sonnleitner, M.; Ritsch-Marte, M.; Ritsch, H.

2013-07-01

322

An ergonomic modular foot platform for isometric force/torque measurements in poststroke functional assessment: A pilot study  

Directory of Open Access Journals (Sweden)

Full Text Available The main goal of this article is to present the design, technical development, and preliminary validation of an innovative mechatronic device for force/torque measurements taken from the human foot using pilot data. The device, formed by a mobile platform equipped with two six-axis force/torque sensors, was used to perform accurate quantitative measurements during isometric exercises, aimed at performing functional assessment tests in poststroke patients undergoing a rehabilitation treatment. Results from pilot data provide a validation of the device. A large clinical trial has been planned to test whether the platform can be used in the clinical practice. We suggest that measurements of ground reaction forces taken from the foot of poststroke patients during the initiation of activities of daily living tasks can provide information about their motor recovery and enlighten possible areas of application, ranging from isometric motor exercise in neurorehabilitation to foot-based human-machine interface.

Stefano Mazzoleni, PhD; Jo Van Vaerenbergh, PhD; Emma Stokes, PhD; Gábor Fazekas, MD, PhD; Paolo Dario, PhD; Eugenio Guglielmelli, PhD

2012-01-01

323

Relational grounding facilitates development of scientifically useful multiscale models  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract We review grounding issues that influence the scientific usefulness of any biomedical multiscale model (MSM). Groundings are the collection of units, dimensions, and/or objects to which a variable or model constituent refers. To date, models that primarily use continuous mathematics rely heavily on absolute grounding, whereas those that primarily use discrete software paradigms (e.g., object-oriented, agent-based, actor) typically employ relational grounding. We review grounding issues and identify strategies to address them. We maintain that grounding issues should be addressed at the start of any MSM project and should be reevaluated throughout the model development process. We make the following points. Grounding decisions influence model flexibility, adaptability, and thus reusability. Grounding choices should be influenced by measures, uncertainty, system information, and the nature of available validation data. Absolute grounding complicates the process of combining models to form larger models unless all are grounded absolutely. Relational grounding facilitates referent knowledge embodiment within computational mechanisms but requires separate model-to-referent mappings. Absolute grounding can simplify integration by forcing common units and, hence, a common integration target, but context change may require model reengineering. Relational grounding enables synthesis of large, composite (multi-module) models that can be robust to context changes. Because biological components have varying degrees of autonomy, corresponding components in MSMs need to do the same. Relational grounding facilitates achieving such autonomy. Biomimetic analogues designed to facilitate translational research and development must have long lifecycles. Exploring mechanisms of normal-to-disease transition requires model components that are grounded relationally. Multi-paradigm modeling requires both hyperspatial and relational grounding.

Hunt C Anthony; Ropella Glen EP; Lam Tai; Gewitz Andrew D

2011-01-01

324

Simple Assessment of Post-Grounding Loads and Strength of Ships  

DEFF Research Database (Denmark)

The aim of the present study is to determine the sectional forces induced by the ship grounding and also to assess the residual strength of grounded ship hulls. An analytical approach is used to estimate the grounding- induced sectional forces of ships. The extent and location of structural damage due to grounding is defined based on the ABS Safe Hull guide. The residual strength of damaged hulls is calculated by using a simple analytical formula. The method is applied to the residual strength assessment of a double-hull tanker of 38.400 dwt damaged due to grounding.

Paik, Jeom Kee; Pedersen, Preben Terndrup

1997-01-01

325

Radiation Reaction at Extreme Intensity  

Directory of Open Access Journals (Sweden)

Full Text Available The radiation reaction force is examined for an idealized short pulse ofelectromagnetic radiation and for a plane wave. Exact solutions (without radiation reaction)are discussed, the total radiated power is calculated. A new and simpler approach to theapproximate form of the equation of motion is presented that automatically removes the runawaysolutions. Finally, analytical solutions are presented for the equations of motion that includethe radiation reaction forces in the very high intensity regime. A classical scattering angle isde¯ned and it shows that the electron is scattered in a small cone in the forward direction. Theradiation reaction corrections to this angle are also considered.

Richard T. Hammond

2008-01-01

326

Travelling-stripe forcing generates hexagonal patterns  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the response of Turing stripe patterns to a simple spatiotemporal forcing. This forcing has the form of a traveling wave and is spatially resonant with the characteristic Turing wavelength. Experiments conducted with the photosensitive chlorine dioxide-iodine-malonic acid reaction reveal a ...

Míguez, D. G.; Nicola, E. M.; Muñuzuri, A. P.; Casademunt i Viader, Jaume; Sagués i Mestre, Francesc; Kramer, L.

327

Redefinition of the four fundamental forces  

Energy Technology Data Exchange (ETDEWEB)

Unification of the fundamental forces has been one of the great theoretical problems in physics in the twentieth century. Beginning in 1918 with Weyl and continuing through the last thirty-five years of Einstein's life, many different attempts were made to unify the electromagnetic and the gravitational forces. Moreover, since the four fundamental forces were first defined in the early forties, extensive efforts by numerous investigators have gone into measuring and attempting to unify two or more of these forces. This paper defines the four forces and discusses some of the difficulties in unifying the forces. A new approach to unification will be presented with a discussion of the consequences and predictions of this approach. The four fundamental forces are defined. These four forces are all that are necessary to characterize all phenomena. From an Army perspective, the strong force is only of interest in the basic structure of matter and in nuclear weapons effects. The electromagnetic force is involved in the structure of matter, all electronic devices, all chemical reactions, explosives, and propellants. The weak force occurs in nuclear weapons effects. The gravitational force becomes involved in every load carrying device and in the motion of aircraft, projectiles and missiles. Frequently, such as in a fuse, more than one force is involved.

Heaston, R.J.

1980-06-01

328

Teaching Visual Grounded Theory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The paper is based on personal 20-years experience of teaching methodology of grounded theory and qualitative methods. In the following paper I would like to show the usefulness of visual analysis in teaching methodology of grounded theory. A very important tool is to use pictures and a sequenc...

Konecki, Krzysztof Tomasz

329

gamma-decay of resonance-like structure observed in sup 3 sup 0 Si(p,gamma) sup 3 sup 1 P reaction  

CERN Document Server

gamma-Decay of a resonance-like structure observed in the reaction sup 3 sup 0 Si (p, gamma) sup 3 sup 1 P in the energy region E sub p = 1.4 - 2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of sup 3 sup 1 P is identified. The position of the M1 resonance is explained taking into account pairing forces.

Kachan, A S; Korda, L P; Mishchenko, V M; Korda, V Y

2002-01-01

330

Nuclear reactions  

International Nuclear Information System (INIS)

This chapter of the textbook overviews nuclear reactions discussing the reaction mechanisms and the types of nuclear reactions, e.g. those induced by neutrons, by protons, by alpha particles and gamma photons, and finally, deuteron and thermonuclear reactions.

1987-01-01

331

The reliability of linear position transducer and force plate measurement of explosive force-time variables during a loaded jump squat in elite athletes.  

UK PubMed Central (United Kingdom)

The best method of assessing muscular force qualities during isoinertial stretch shorten cycle lower body movements remains a subject of much debate. This study had 2 purposes: Firstly, to calculate the interday reliability of peak force (PF) measurement and a variety of force-time measures, and, secondly, to compare the reliability of the 2 most common technologies for measuring force during loaded jump squats, the linear position transducer (PT), and the force plate (FP). Twenty-five male elite level rugby union players performed 3 rebound jump squats with a 40-kg external load on 2 occasions 1 week apart. Vertical ground reaction forces (GRFs) were directly measured via an FP, and force was differentiated from position data collected using a PT. From these data, a number of force-time variables were calculated for both the FP and PT. Intraclass correlation coefficient (ICC), coefficient of variation (CV), and percent change in the mean were used as measures of between-session reliability. Additionally, Pearson's product moment correlation coefficients were used to investigate intercorrelations between variables and technologies. Both FP and PT were found to be a reliable means of measuring PF (ICC = 0.88-0.96, CV = 2.3-4.8%), and the relationship between the 2 technologies was very high and high for days 1 and 2, respectively (r = 0.67-0.88). Force-time variables calculated from FP data tended to have greater relative and absolute consistency (ICC = 0.70-0.96, CV = 5.1-51.8%) than those calculated from differentiated PT data (ICC = 0.18-0.95, CV = 7.7-93.6%). Intercorrelations between variables ranged from trivial to practically perfect (r = 0.00-1.00). It was concluded that PF can be measured reliably with both FP and PT technologies, and these measurements are related. A number of force-time values can also be reliably calculated via the use of GRF data. Although some of these force-time variables can be reliably calculated using position data, variation of measurement is generally greater when using position data to calculate force.

Hansen KT; Cronin JB; Newton MJ

2011-05-01

332

The Grounded Theory Bookshelf  

Directory of Open Access Journals (Sweden)

Full Text Available The Grounded Theory Perspective III: Theoretical Coding, Barney G. Glaser (Sociology Press, 2005). Not intended for a beginner, this book further defi nes, describes, and explicates the classic grounded theory (GT) method. Perspective III lays out various facets of theoretical coding as Glaser meticulously distinguishes classic GT from other subsequent methods. Developed many years after Glaser’s classic GT, these methods, particularly as described by Strauss and Corbin, adopt the grounded theory name and engender ongoing confusion about the very premises of grounded theory. Glaser distinguishes between classic GT and the adscititious methods in his writings, referring to remodeled grounded theory and its offshoots as Qualitative Data Analysis (QDA) models.

Dr. Alvita Nathaniel, DSN, APRN, BC

2005-01-01

333

Ground energy coupling  

Science.gov (United States)

The feasibility of ground coupling for various heat pump systems was investigated. Analytical heat flow models were developed to approximate design ground coupling devices for use in solar heat pump space conditioning systems. A digital computer program called GROCS (GRound Coupled Systems) was written to model 3-dimensional underground heat flow in order to simulate the behavior of ground coupling experiments and to provide performance predictions which have been compared to experimental results. GROCS also has been integrated with TRNSYS. Soil thermal property and ground coupling device experiments are described. Buried tanks, serpentine earth coils in various configurations, lengths and depths, and sealed vertical wells are being investigated. An earth coil used to heat a house without use of resistance heating is described.

Metz, P. D.

334

Airport Ground Staff Scheduling  

DEFF Research Database (Denmark)

Modern airports are centers of transportation that service a large number of aircraft and passengers every day. To facilitate this large volume of transportation, airports are subject to many logistical and decision problems that must continuously be solved to make sure each flight and passenger travels safely and efficiently through the airport. When an aircraft lands, a significant number of tasks must be performed by different groups of ground crew, such as fueling, baggage handling and cleaning. These tasks must be complete before the aircraft is able to depart, as well as check-in and security services. These tasks are collectively known as ground handling, and are the major source of activity with airports. The business environments of modern airports are becoming increasingly competitive, as both airports themselves and their ground handling operations are changing to private ownership. As airports are in competition to attract airline routes, efficient and reliable ground handling operations are imperative for the viability and continued growth of both airports and airlines. The increasing liberalization of the ground handling market prompts ground handling operators to increase cost effectiveness and deliver fast and reliable service. This thesis presents models and algorithms for general optimization and decision problems arising within ground handling. The thesis contains an introductory part which provide an overview of the ground handling environment and reviews a series of optimization problems from the specific perspective of airport ground handling. In addition, the thesis contains five scientific papers, which consider specific optimization problems within ground handling in detail. The considered problems range from generalized approaches to workforce planning, to highly detailed scheduling problems arising in the highly dynamic environment of airports.

Clausen, Tommy

2010-01-01

335

Force-plate based computation of ankle and hip strategies from double-inverted pendulum model.  

UK PubMed Central (United Kingdom)

BACKGROUND: Using statistical characteristics of the centre of pressure displacement or of the ground reaction forces, it is difficult to have quantitative evaluation of the equilibrium strategy employed (ankle or hip). The purpose of this study is to validate a new force-plate based approach that allows to evaluate postural strategies employed through a method based on a double-inverted pendulum model. METHODS: This method allows to compute ankle and hip joint motion only from force plate data and relies on inverse kinematics with the centre of mass considered as the end effector. Furthermore, an index, depending on the covariance between hip and ankle angles, is proposed to quantify the strategy used. To validate the method and the strategy index, we compare the results of our computation to an optical stereophotogrammetry measurement of the angles considered as reference value. FINDINGS: The experiments demonstrate that our method provides acceptable results. The root mean square error between computed and measured hip and ankle angles stands between 4.5 x 10(-3)degrees for ankle angle in static condition and 1.1 x 10(-1) degrees for hip angle in hip forced condition. INTERPRETATION: The main interest of our method for clinicians is that it allows to retrieve the ankle and hip angles only using a simple and widespread device, the force-plate. Moreover, it proposes a new postural index that can be also be computed without videographic systems.

Colobert B; Crétual A; Allard P; Delamarche P

2006-05-01

336

Mechanical interface having multiple grounded actuators  

Energy Technology Data Exchange (ETDEWEB)

An apparatus and method for interfacing the motion of a user-manipulable object with a computer system includes a user object physically contacted or grasped by a user. A 3-D spatial mechanism is coupled to the user object, such as a stylus or a medical instrument, and provides three degrees of freedom to the user object. Three grounded actuators provide forces in the three degrees of freedom. Two of the degrees of freedom are a planar workspace provided by a closed-loop linkage of members, and the third degree of freedom is rotation of the planar workspace provided by a rotatable carriage. Capstan drive mechanisms transmit forces between actuators and the user object and include drums coupled to the carriage, pulleys coupled to grounded actuators, and flexible cables transmitting force between the pulleys and the drums. The flexibility of the cable allows the drums to rotate with the carriage while the pulleys and actuators remain fixed to ground. The interface also may include a floating gimbal mechanism coupling the linkage to the user object. The floating gimbal mechanism includes rotatably coupled gimbal members that provide three degrees of freedom to the user object and capstan mechanisms coupled between sensors and the gimbal members for providing enhanced sensor resolution.

Martin, Kenneth M. (Palo Alto, CA); Levin, Mike D. (Sunnyvale, CA); Rosenberg, Louis B. (Pleasanton, CA)

1998-01-01

337

Hyperspherical calculations with Skyrme-like forces  

International Nuclear Information System (INIS)

The first approximation of the hyperspherical harmonic method is used to describe in a unified way the ground state and the breathing mode of several doubly-magic nuclei with Skyrme-like forces. A comparison is made with other methods

1975-01-01

338

Spin of the 219Ra ground state  

International Nuclear Information System (INIS)

The 208Pb(18O,3n)223Th reaction at 83 MeV bombarding energy was used to populate the alpha-radioactive nucleus 223Th. Out-of-beam alpha-gamma coincidences were recorded at correlation angles of 90 degree and 180 degree. The a2 angular correlation coefficient was extracted for an alpha-gamma cascade to the 215Rn ground state via the 0.316 MeV excited state. This limited the assignment of the ground-state spin of 219Ra to ((7/2, 11) / 2 )+. .AE.

1989-01-01

339

Grounding of SNS Accelerator Structure  

CERN Multimedia

Description of site general grounding network. RF grounding network enhancement underneath the klystron gallery building. Grounding network of the Ring Systems with ground breaks in the Ring Tunnel. Grounding and Bonding of R&D accelerator equipment. SNS Building lightning protection.

Holik, Paul S

2005-01-01

340

Reducing stray ground currents  

Energy Technology Data Exchange (ETDEWEB)

Utility customers of Clark County, Washington reported that electric shocks from stray ground currents were interfering with cattle, businesses, and equipment. The Public Utility District (PUD) investigated each claim and explored several ways to lower shocks below 10 volts. Ground rods were installed as a low-cost option. The rods reduced ground voltages by 33 percent and motor starting peaks by 50 percent. Variations in earth composition, people, and animals require individualized solutions. A major part of the solution is based on cost and line location. (DCK)

Harlow, H.W.

1980-09-01

 
 
 
 
341

Osteochondrosis dissecans of the tarsus in Labrador Retrievers: clinical signs, radiological data and force plate gait evaluation after surgical treatment.  

UK PubMed Central (United Kingdom)

OBJECTIVES: To report the outcome of unilateral surgery, by a plantaromedial approach, in 15 Labrador Retrievers with osteochondrosis dissecans (OCD) of the medial trochlear ridge of the talus. To evaluate the influence on outcome of age at surgery, bilateral involvement, periarticular soft tissue increase (PSI), osteophyte size (OS), decrease of range of joint motion and follow-up. To assess the extent of tarsal hyperextension in the standing dog. METHODS: A retrospective clinical and radiographic study was conducted and the post-treatment gait was analysed using a force plate. Ground reaction force (GRF) data were compared with data derived from 24 healthy Labrador Retrievers (control group). RESULTS: Six dogs had an excellent or good clinical result. Significant differences were found between the patients and the control group for many GRF data. Propulsive and vertical forces significantly decreased in the operated limb and increased in the contralateral pelvic and ipsilateral or both thoracic limbs. The lameness was significantly correlated to the OS postoperatively, the range-of-motion, the PSI, the length of the follow-up period, and the vertical ground force. No hyperextension in stance was recorded. CLINICAL SIGNIFICANCE: Although most dogs improved, the prognosis remains guarded. This seems to be independent of age, bilateral involvement, or preoperative OS in these dogs. No relation between medial talar OCD and tarsal hyperextension in stance was found in these dogs.

van der Peijl GJ; Schaeffer IG; Theyse LF; Dijkshoorn NA; Schwencke M; Hazewinkel HA

2012-01-01

342

Frozen ground engineering  

Energy Technology Data Exchange (ETDEWEB)

This book presents the state of the art in frozen ground engineering for study at the graduate level and for those specializing in Arctic engineering or cold regions engineering. Included also are discussions of problems in permafrost areas.

Phukan, A.

1985-01-01

343

Ground State Spin Logic  

CERN Multimedia

Designing and optimizing cost functions and energy landscapes is a problem encountered in many fields of science and engineering. These landscapes and cost functions can be embedded and annealed in experimentally controllable spin Hamiltonians. Using an approach based on group theory and symmetries, we examine the embedding of Boolean logic gates into the ground state subspace of such spin systems. We describe parameterized families of diagonal Hamiltonians and symmetry operations which preserve the ground state subspace encoding the truth tables of Boolean formulas. The ground state embeddings of adder circuits are used to illustrate how gates are combined and simplified using symmetry. Our work is relevant for experimental demonstrations of ground state embeddings found in both classical optimization as well as adiabatic quantum optimization.

Whitfield, J D; Biamonte, J D

2012-01-01

344

Ground Beef and Food Safety  

Science.gov (United States)

... Content Viewer (JSR 286) Actions ${title} Loading... Ground Beef and Food Safety Questions about "ground meat" or " ... frequently asked questions and information about why ground beef requires careful handling. What's the difference between "hamburger" ...

345

Evaluation of a pressure walkway system for measurement of vertical limb forces in clinically normal dogs.  

UK PubMed Central (United Kingdom)

OBJECTIVE: To compare ground reaction forces (GRFs) measured by use of a pressure-sensitive walk-way (PSW) and a force plate (FP) and evaluate weekly variation in the GRFs and static vertical forces in dogs. ANIMALS: 34 clinically normal dogs and 5 research dogs with lameness. PROCEDURE: GRF data were collected from 5 lame and 14 clinically normal dogs by use of an FP and a PSW. Peak vertical force (PVF), vertical impulse (VI), and velocity measurements (determined by use of photocells and PSW data) were compared between groups. Peak vertical force, VI, stride length, ground phase time (ie, contact time), and static body weight distribution data were collected on 2 occasions, 1 week apart, in 20 different clinically normal dogs by use of a PSW; week-to-week variation in values was evaluated. RESULTS: Measurements of velocity derived by use of the photocells were not different from those derived by use of the PSW. For any 1 limb, values derived by use of the PSW were significantly lower than values derived with the FP. For values obtained by use of either technique, there were no differences between left and right limbs except for values of PVF measured via PSW in forelimbs. Values of PVF, VI, contact time, stride length, and static weight distribution generated by the PSW did not vary from week to week. CONCLUSIONS AND CLINICAL RELEVANCE: Values for GRFs varied between the FP and PSW. However, data derived by use of PSW were consistent and could be used to evaluate kinetic variables over time in the same dog.

Lascelles BD; Roe SC; Smith E; Reynolds L; Markham J; Marcellin-Little D; Bergh MS; Budsberg SC

2006-02-01

346

Electronic transitions and intermolecular forces  

International Nuclear Information System (INIS)

[en] This thesis describes two different subjects - electronic transitions and intermolecular forces - that are related mainly by the following observation: The wavenumber at which an electronic transition in an atom or molecule occurs, depends on the environment of that atom or molecule. This implies, for instance, that when a molecule becomes solvated its absorption spectrum may be shifted either to the blue or to the red side of the original gasphase spectrum. In part I attention is paid to the experimental aspects of VUV spectroscopy, both in the gasphase and in the condensed phase. In part II a series of papers are presented, dealing with the calculation of intermolecular forces (and some related topics) both for the ground state and for the excited state interactions, using different non-empirical methods. The calculations provide, among other results, a semiquantitative interpretation of the spectral blue shifts encountered in our experiments. (Auth.)

1981-01-01

347

Forces in 1 Dimension  

Science.gov (United States)

This is a virtual manipulative which demonstrates the principles of force. Students can click on a man and push different objects of varying masses across the screen. The resulting forces (frictional and total force) are shown. Graphs show forces, position and acceleration as a function of time. Free body diagrams of all the forces can also be viewed.

Colorado, Phet A.

2010-07-28

348

A numerical investigation on the ground effect of a flapping-flying bird  

Science.gov (United States)

The flight of a small bird under the influence of the ground effect is numerically investigated with a complete three-dimensional model including the bird's body and wings. The flight mode is not the conventional steady gliding flight but an unsteady flight consisting of flapping, twisting, and folding motions. As the bird approaches the ground, the average lift force gradually increases while the average drag force decreases. At a particular distance, the average lift force increases by approximately 47%, whereas the average drag force decreases by nearly 20%, relative to the absence of the ground effect. Because of the ground, the improved aerodynamic performance in flapping flight is much more significant than in steady flight, in which the modification of the lift-drag ratio is typically less than 10%. On the basis of the flow field, regardless of the presence or absence of the ground, there exists no evidence for an obstruction of a wing-tip vortex, which is a remarkable phenomenon and accounts for the improved performance in steady flight. The extent of the region of high pressure beneath the wing in the near-ground case seems to surpass that in the far-ground case, accounting for the greater lift and thrust forces in the near-ground case. This air cushion beneath the wing, known as the cram effect, is the dominant factor of the ground effect on a flapping bird.

Su, Jian-Yuan; Tang, Jhen-Han; Wang, Ching-Hua; Yang, Jing-Tang

2013-09-01

349

The (3He,?) reaction mechanism  

International Nuclear Information System (INIS)

The ?-rays emitted after the 163Dy(3He,?xn) reactions at E(3He)=45 MeV have been measured. The transferred angular momentum in the reaction is deduced from the side-feeding ?-intensities of the ground bands in the residual 162-xDy isotopes. With decreasing ?-energy the average spin transfer increases from ?5? to ?11?. The (3He,?) reaction at these energies is dominated by direct processes. Even at the highest spin transfer the contribution from the compound reaction channel is negligible. 12 refs., 5 figs., 2 tabs

1993-01-01

350

Rapid bottom melting widespread near Antarctic Ice Sheet grounding lines.  

UK PubMed Central (United Kingdom)

As continental ice from Antarctica reaches the grounding line and begins to float, its underside melts into the ocean. Results obtained with satellite radar interferometry reveal that bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed. The melting rate is positively correlated with thermal forcing, increasing by 1 meter per year for each 0.1 degrees C rise in ocean temperature. Where deep water has direct access to grounding lines, glaciers and ice shelves are vulnerable to ongoing increases in ocean temperature.

Rignot E; Jacobs SS

2002-06-01

351

Ground Source Heat Pumps  

Directory of Open Access Journals (Sweden)

Full Text Available A heat pump is a device that is able to transfer heat from one fluid at a lower temperature to another at a higher temperature. Ground source heat pumps are generally classified by the type of ground loop. The coefficient of performance (COP) is used to define the heating performance of heat pumps. Both the COP and EER values are valid only at the specific test conditions used in the rating. A ground source pump could reach 450%, compared with an efficient gas boiler of 90% obviously this is a big difference. The cost of equipment, material and installation can be expensive, depending on the type of heat pump installation planned.

Lale Valizade

2013-01-01

352

Ground motion predictions  

International Nuclear Information System (INIS)

Nuclear generated ground motion is defined and then related to the physical parameters that cause it. Techniques employed for prediction of ground motion peak amplitude, frequency spectra and response spectra are explored, with initial emphasis on the analysis of data collected at the Nevada Test Site (NTS). NTS postshot measurements are compared with pre-shot predictions. Applicability of these techniques to new areas, for example, Plowshare sites, must be questioned. Fortunately, the Atomic Energy Commission is sponsoring complementary studies to improve prediction capabilities primarily in new locations outside the NTS region. Some of these are discussed in the light of anomalous seismic behavior, and comparisons are given showing theoretical versus experimental results. In conclusion, current ground motion prediction techniques are applied to events off the NTS. Predictions are compared with measurements for the event Faultless and for the Plowshare events, Gasbuggy, Cabriolet, and Buggy I. (author)

1969-01-01

353

Force Control in Monopod Hopping Robot While Landing  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the issue of control of impact forces generated during the interaction between the hopping ro-bot toe and the ground while landing has been considered. The force thus generated can damage the robot altogether. With the objective to control these impact forces, impedance control strategy has been applied to the hopping robot system. The dynamics pertaining to the impact between robot toe and ground has been modeled as in case of a ball bouncing on the ground. Bond Graph theory has been used for the modeling of the hopping robot system. Simulation results show that impact forces generated during the landing has been controlled to a specified limiting value. This model and the corresponding analysis can be further extended for understanding the dynamics involved in continuous hopping of robot with constant height and velocity control.

Vaidyabhushan Leela Krishnan; Pushparaj Mani Pathak; Satish Chandra Jain

2010-01-01

354

The Mines (Control of Ground Movement) Regulations 1999  

Energy Technology Data Exchange (ETDEWEB)

The Regulations apply to all mines in the United Kingdom. They outline the duty of the mine manager to ensure that such ground control measures are taken as may be necessary for keeping secure every place in the mine where people work or pass. They include details of assessment of ground conditions, documentation, implementation of ground control measures, notification of significant ground control measures in coal mines, implementation of the rules and installation of support materials by officials, assessment of adequacy of ground control measures, and supply and installation of support material. Standards for dimensions for placing of support systems for face workings and for roadways are included in a schedule. The regulations come under the Health and Safety at Work etc. Act and come into force on 1st December 1999.

NONE

1999-09-01

355

The Fifth Force, the Sixth Force and the Spring Force  

Directory of Open Access Journals (Sweden)

Full Text Available Upon  revisiting the famous Pound-Rebka-Snider experiments on the gravitational red-shift , the fifth and even the sixth force in nature are in fact the stretching and compression force of the spring , where the spring term is the cosmological constant in Einstein’s field equations.

Ling Man Tsang

2012-01-01

356

Investigating Forces and Motion  

CERN Document Server

Forces can't be seen, but without them, nothing around us would happen! A force is a push or pull that usually causes movement. Friction is a force that opposes motion and slows things down or stops them. Famous scientist and mathematician Sir Isaac Newton wrote the rules about forces and motion.

Weir, Jane

2007-01-01

357

Deployable Ground Plane Antenna.  

Science.gov (United States)

A deployable ground plane antenna for use aboard a satellite or the like, with the antenna and erection mechanism being compactly stowable within the confines of a launch vehicle prior to and during launch thereof is described. After ejection of the satel...

L. Schwerdtfeger

1977-01-01

358

Shadow of ground zero  

Energy Technology Data Exchange (ETDEWEB)

The history of the development of nuclear weapons starting with the detonation of the A-bombs on Japan is reviewed. An overview of nuclear weapon effects is presented. The effects of electromagnetic pulse (EMP), initial nuclear radiation, thermal radiation and blast are discussed with reference to how people outside can survive when ground zero is only a few miles away. 8 references. (ACR)

Haaland, C.M.

1984-01-01

359

Technology at Ground Zero.  

Science.gov (United States)

Describes the robots used to aid in rescue and recovery at Ground Zero after the September 11, 2001 attack on the World Trade Center. The robots were developed as a result of national Science Foundation Quick Response Research Awards. Describes several awards that were made following the attack. (JOW)

Techniques: Connecting Education and Careers, 2002

2002-01-01

360

A Study of Winglet and Aerodynamic Interferences in 3-D Viscous Flow around a Flying-Boat in Ground Effect  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, the flow field about a complete flying-boat in ground effect is resolved. The influences of using winglet in ground and out of ground effects are compared and it is shown that ground affects this influence to a large extent. It is also shown that with careful shaping of the body and using a step underneath the body a propulsive force can be produced in vicinity of the ground. However, this causes an increase in drag force in free flight.

H. Afshar; M.M. Alishahi

2009-01-01

 
 
 
 
361

Ground-state energy of nuclear matter  

Energy Technology Data Exchange (ETDEWEB)

The low-density expansion of the ground-state energy for spin-dependent forces is given, through order k/sub F//sup 6/ for the ladder approximation and through order k/sub F//sup 6/lnk/sub F/ for the complete energy, in terms of derivatives with respect to the strength of the attractive part of the interaction defined by the Baker-Hind-Kahane potential. The ladder approximation is also computed by the numerical solution of the K-matrix equation. The resulting series gives a satisfactory representation of the energy at interesting densities. Using Pade extrapolation techniques, both in the density and in the attractive part of the interaction, we obtain the ground-state energy of nuclear matter.

Baker G.A. Jr.; Benofy, L.P.; Fortes, M.

1988-07-01

362

Abundance of Ground States with Positive Parity  

International Nuclear Information System (INIS)

We investigate analytically and numerically a random-matrix model for m fermions occupying (ell)1 single-particle states with positive parity and (ell)2 single-particle states with negative parity and interacting through random two-body forces that conserve parity. The single-particle states are completely degenerate and carry no further quantum numbers. We compare spectra of many-body states with positive and with negative parity. We show that in the dilute limit defined by m, (ell)1,2 ? ? and ml (ell)1,2 ? 0, ground states with positive and negative parity occur with equal probability. Differences in the ground-state probabilities are, thus, a finite-size effect and are mainly due to different dimensions of the Hilbert spaces of either parity.

2008-11-01

363

Ground-state correlations beyond RPA  

Energy Technology Data Exchange (ETDEWEB)

An approach is proposed which includes ground-state correlations beyond RPA. This is achieved by using a renormalized quasiboson approximation with reference to the correlated ground state of the system, rather than to the uncorrelated Hartree-Fock one, and by expressing the particle-particle and hole-hole pair operators in terms of the particle-hole ones. The set of the so-obtained nonlinear equations for the one-phonon energy and amplitudes are first solved within the Lipkin-Meshkov-Glick model and the results are compared with those of previous approaches as well as with the exact ones. Applications to realistic nuclei, starting from fully self-consistent HF + RPA calculations with a Skyrme force are also presented. ((orig.))

Catara, F. (Dipartimento di Fisica, Universita di Catania, Catania (Italy) Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy)); Dinh Dang, N. (Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy)); Sambataro, M. (Istituto Nazionale di Fisica Nucleare, Sezione di Catania, Corso Italia 57, I-95129 Catania (Italy))

1994-10-17

364

Ground-state correlations beyond RPA  

International Nuclear Information System (INIS)

[en] An approach is proposed which includes ground-state correlations beyond RPA. This is achieved by using a renormalized quasiboson approximation with reference to the correlated ground state of the system, rather than to the uncorrelated Hartree-Fock one, and by expressing the particle-particle and hole-hole pair operators in terms of the particle-hole ones. The set of the so-obtained nonlinear equations for the one-phonon energy and amplitudes are first solved within the Lipkin-Meshkov-Glick model and the results are compared with those of previous approaches as well as with the exact ones. Applications to realistic nuclei, starting from fully self-consistent HF + RPA calculations with a Skyrme force are also presented. ((orig.))

1994-10-17

365

Macroscopic QED in linearly responding media and a Lorentz-Force approach to dispersion forces  

International Nuclear Information System (INIS)

In this thesis, a very general quantization scheme for the macroscopic electromagnetic field in arbitrary linearly responding media is presented. It offers a unified approach to QED in such media. Applying the quantization scheme, a theory of the dispersion forces on the basis of the Lorentz force is developed. By regarding the dispersion force as the (ground-state or thermal-state) expectation value of the Lorentz force that acts on appropriately defined charge and current densities, Casimir, Casimir-Polder, and van der Waals forces are united in a very natural way that makes transparent their common physical basis. Application of the theory to planar structures yields generalizations of well-known Lifschitz and Casimir-type formulas. (orig.)

2008-01-01

366

Macroscopic QED in linearly responding media and a Lorentz-Force approach to dispersion forces  

Energy Technology Data Exchange (ETDEWEB)

In this thesis, a very general quantization scheme for the macroscopic electromagnetic field in arbitrary linearly responding media is presented. It offers a unified approach to QED in such media. Applying the quantization scheme, a theory of the dispersion forces on the basis of the Lorentz force is developed. By regarding the dispersion force as the (ground-state or thermal-state) expectation value of the Lorentz force that acts on appropriately defined charge and current densities, Casimir, Casimir-Polder, and van der Waals forces are united in a very natural way that makes transparent their common physical basis. Application of the theory to planar structures yields generalizations of well-known Lifschitz and Casimir-type formulas. (orig.)

Raabe, Christian

2008-07-08

367

Force Adaptation in Human Walking With Symmetrically Applied Downward Forces on the Pelvis.  

UK PubMed Central (United Kingdom)

The application of external constraints and/or applied forces during movement can lead to reactive as well as adaptive changes in human motion. Previous research has shown adaptation in walking kinematics when external forces were applied to a leg. This work aims to study adaptation in human walking when externally applied forces were present on the pelvis during the swing and stance phases of both legs. A novel tethered pelvic assist device (TPAD) was used to passively apply symmetric downward forces on the human pelvis while walking. During the experiment, eight healthy subjects walked on a treadmill at a constant speed while their kinematics and foot pressure data were recorded. Data analysis revealed that the healthy subjects exhibited both reactive as well as adaptive changes in their gait parameters. The immediate response of the subjects was to increase their hip flexion to clear their foot off the ground as they were unable to lift their pelvis to their usual height in the presence of downward forces. Seven out of eight subjects resisted the downward forces to move their pelvis up. Eventually, they reached a level of downward force that they could sustain over the training session. This adaptation to the downward force was reflected in the heel peak pressure values during the cycles of the gait. On removing the tethers, aftereffects in heel peak pressure values were observed as a result of higher magnitude of pelvic acceleration in vertical direction. In summary, symmetrically applied external forces on the pelvis of healthy subjects, resulted in reactive changes in the gait kinematics and adaptive changes in the gait kinetics and the foot interaction forces with the ground.

Vashista V; Agrawal N; Shaharudin S; Reisman D; Agrawal S

2013-03-01

368

Contribution to the models for calculation and analysis of grounding grids and grounding systems  

International Nuclear Information System (INIS)

The aim of this dissertation is improving the existing models and finding new for calculating the conditions in the complex grounding systems and analyzing their performances. For that purpose, firstly, a model network of the grounding system is created, and the ways of modelling the separate elements are studied and elaborated also. Some methods for solving groundings with arbitrary complexity and dimensions are studied and worked out too. Afterwards the TL in models are worked out, with or without protective rope. Appropriate models are detail worked out and formed for the energetic cables, both for isolated and distributive outer shield - type PP, XHP, XHE, IPO, and IPZO. At the same time, the eventual presence of additional groundings like steel tapes and cooper ropes placed into the cable trench together with the cable is considered. Particular attention is dedicated on the cables with steel reinforcement, whose parameters of the 'unit length depends of the current in the shield and in the reinforcement, because they are sources of nonlinearity and also of the problems connected with its modelling and solving. Therefore an approach is made to the modelling of the mutual conductive couplings between the elements of the grounding system (ex. between two and more cables, the parts of one cable, the groundings of one substation and the cables in theirs immediate nearness and so on.). The electromagnetic couplings existing between the phases conductors, under the influence of the fault, like, (protective rope (TL), the metal shields, and the cables with electric protection, are included too. The mutual couplings are estimated over introducing inducted electro motor forces (EMF) in the transversal and/or longitudinal branches of the elements of the grounding system. (depending on what kind of coupling we are talking-conductive or inductive). These inductive EMF later are transformed into equivalent current generators and in that way the system will be harnessed. The number of the current generators that appear in the cycle with the procedure 'replacing of the current generators' are transferred easily into the node of the network where the fault is made previously. Further on, some modem numerical methods and procedures for calculating the grounding system, convenient for the use of the personal computers are studied. Some modem numerical procedures are adopted and worked out for calculating networks (cycles) with radial structure and/or with small number of loops. They are used for solving the condition in the network part of the grounding system, which means that up to now the researches are pointing to the adequacy of the use of the methods for summarizing admittances and summarizing current (MSAC). The next step, after the distribution of the whole system is defined, is passing to the estimation of the safety conditions from high touch and step voltages in the environment of the different groundings. For that purpose, the characteristics of the biggest number of typical groundings of the MV/LV substations, the characteristics of some kind's network groundings of the HV/N4V substation are studied. The tower TL groundings (ring shaped, square shaped, ray shaped) are analyzed in details. At the same time, a data multitude is calculated, necessary for the further analysis, and consisting theirs resistances to ground.(for a given value of a specific resistance of the soil), the maximum and the average values of touch and step potentials, as well as the frequencies of their appearances,. (frequent histograms FH) of the touch and step potential differences) and so on. All these quantities are depending on the geometry of the grounding. The calculating FH of different kinds of groundings is performed with a computer simulation-'simulation Monte Carlo'. In order to obtain them, an appropriate software is produced, which by making the number of experiments (simulations), defines the needed performances of the grounding statistically, and at the same time, accidentally generates the position of the human in the electro energetic

2003-01-01

369

Limit cycle walking on a regularized ground  

CERN Document Server

The singular nature of contact problems, such as walking, makes them difficult to analyze mathematically. In this paper we will "regularize" the contact problem of walking by approximating the ground with a smooth repulsive potential energy and a smooth dissipative friction force. Using this model we are able to prove the existence of a limit cycle for a periodically perturbed system which consists of three masses connected by springs. In particular, this limit cycle exists in a symmetry reduced phase. In the unreduced phase space, the motion of the masses resembles walking.

Jacobs, Henry O

2012-01-01

370

75 FR 32642 - Defense Federal Acquisition Regulation Supplement; Ground and Flight Risk Clause (DFARS Case 2007...  

Science.gov (United States)

...instruction entitled ``Contractor's Flight and Ground Operations'' (Air Force Instruction 10-220, Army Regulation 95-20, NAVAIR Instruction 3710.1 (Series), Coast Guard Instruction M13020.3, and Defense Contract Management Agency Instruction...

2010-06-08

371

Transition from leg to wing forces during take-off in birds.  

Science.gov (United States)

Take-off mechanics are fundamental to the ecology and evolution of flying animals. Recent research has revealed that initial take-off velocity in birds is driven mostly by hindlimb forces. However, the contribution of the wings during the transition to air is unknown. To investigate this transition, we integrated measurements of both leg and wing forces during take-off and the first three wingbeats in zebra finch (Taeniopygia guttata, body mass 15 g, N=7) and diamond dove (Geopelia cuneata, body mass 50 g, N=3). We measured ground reaction forces produced by the hindlimbs using a perch mounted on a force plate, whole-body and wing kinematics using high-speed video, and aerodynamic forces using particle image velocimetry (PIV). Take-off performance was generally similar between species. When birds were perched, an acceleration peak produced by the legs contributed to 85±1% of the whole-body resultant acceleration in finch and 77±6% in dove. At lift-off, coincident with the start of the first downstroke, the percentage of hindlimb contribution to initial flight velocity was 93.6±0.6% in finch and 95.2±0.4% in dove. In finch, the first wingbeat produced 57.9±3.4% of the lift created during subsequent wingbeats compared with 62.5±2.2% in dove. Advance ratios were <0.5 in both species, even when taking self-convection of shed vortices into account, so it was likely that wing-wake interactions dominated aerodynamics during wingbeats 2 and 3. These results underscore the relatively low contribution of the wings to initial take-off, and reveal a novel transitional role for the first wingbeat in terms of force production. PMID:22972887

Provini, Pauline; Tobalske, Bret W; Crandell, Kristen E; Abourachid, Anick

2012-09-12

372

Transition from leg to wing forces during take-off in birds.  

UK PubMed Central (United Kingdom)

Take-off mechanics are fundamental to the ecology and evolution of flying animals. Recent research has revealed that initial take-off velocity in birds is driven mostly by hindlimb forces. However, the contribution of the wings during the transition to air is unknown. To investigate this transition, we integrated measurements of both leg and wing forces during take-off and the first three wingbeats in zebra finch (Taeniopygia guttata, body mass 15 g, N=7) and diamond dove (Geopelia cuneata, body mass 50 g, N=3). We measured ground reaction forces produced by the hindlimbs using a perch mounted on a force plate, whole-body and wing kinematics using high-speed video, and aerodynamic forces using particle image velocimetry (PIV). Take-off performance was generally similar between species. When birds were perched, an acceleration peak produced by the legs contributed to 85±1% of the whole-body resultant acceleration in finch and 77±6% in dove. At lift-off, coincident with the start of the first downstroke, the percentage of hindlimb contribution to initial flight velocity was 93.6±0.6% in finch and 95.2±0.4% in dove. In finch, the first wingbeat produced 57.9±3.4% of the lift created during subsequent wingbeats compared with 62.5±2.2% in dove. Advance ratios were <0.5 in both species, even when taking self-convection of shed vortices into account, so it was likely that wing-wake interactions dominated aerodynamics during wingbeats 2 and 3. These results underscore the relatively low contribution of the wings to initial take-off, and reveal a novel transitional role for the first wingbeat in terms of force production.

Provini P; Tobalske BW; Crandell KE; Abourachid A

2012-12-01

373

Electroweak reactions with light nuclei  

Directory of Open Access Journals (Sweden)

Full Text Available The investigation of light nuclei with ab-initio methods provides an optimal setting to probe our knowledge on nuclear forces, because the few-nucleon problem can be solved accurately. Nucleons interact not only in pairs but also via many-body forces. Theoretical e?orts need to be taken towards the identi?cation of nuclear observables sensitive to the less known many-nucleon forces. Electromagnetic reactions can potentially provide useful information on this. We present results on photo-absorption and electron scattering o? light nuclei, emphasizing the role of three-body forces and the comparison with experimental data. On the other hand, reactions induced by weak probes, like neutrino interactions with nucleonic matter, are relevant to astrophysics and can be calculated with few-body techniques. In this case, since often no experiment is possible, ab-initio predictions provide valuable input for astrophysical simulations.

Bacca S.

2010-01-01

374

The Symbol Grounding Problem  

CERN Multimedia

How can the semantic interpretation of a formal symbol system be made intrinsic to the system, rather than just parasitic on the meanings in our heads? How can the meanings of the meaningless symbol tokens, manipulated solely on the basis of their (arbitrary) shapes, be grounded in anything but other meaningless symbols? The problem is analogous to trying to learn Chinese from a Chinese/Chinese dictionary alone. A candidate solution is sketched: Symbolic representations must be grounded bottom-up in nonsymbolic representations of two kinds: (1) "iconic representations," which are analogs of the proximal sensory projections of distal objects and events, and (2) "categorical representations," which are learned and innate feature-detectors that pick out the invariant features of object and event categories from their sensory projections. Elementary symbols are the names of these object and event categories, assigned on the basis of their (nonsymbolic) categorical representations. Higher-order (3) "symbolic repre...

Harnad, S

1999-01-01

375

Ground motion effects  

International Nuclear Information System (INIS)

Ground motion caused by natural earthquakes or by nuclear explosion causes buildings and other structures to respond in such manner as possibly to have high unit stresses and to be subje