Significant Increase In Velocity Research Articles

Viscoelectric effect analysis in an electroosmotic flow with microchannel wall slip

In the present work, we developed a numerical analysis for an electroosmotic flow circulating in a rectangular microchannel considering electrolyte viscosity as a function of the induced electric field; which is also reflected in the slip condition imposed on the system walls, since the slip length is a function of the fluid viscosity. It should be clarified this is an entirely hydrodynamic problem, and for this reason there are no induced pressure gradients, because we are in the presence of a purely electroosmotic flow, where the fluid motion is due only to electrokinetic forces. Based on these comments, the problem is centered on high induced potentials, enabling viscoelectric effect analysis in the electroosmotic flow, which leads to significant increases in velocity and volumetric flow profiles compared to the case where the viscosity is a constant and there is no slip condition. Due to analytical analysis limitations, we implemented a dimensionless equation scheme defined by the continuity equation, the momentum equations in the x and y direction, the Poisson-Boltzmann equation, and the charge conservation equation to obtain the velocity and volumetric flow rate profiles mentioned above. This model is described in its variational form in order to implement the finite element technique using free software, FreeFem++. The results obtained show how the viscoelectric effect is relevant when working with high induced potentials; that is, for values of , when the dimensionless viscoelectric parameter increases, there is a significant decrease in the velocity profiles u, a situation that is not observed when , where there are low induced potentials, and for this reason, as the dimensionless parameter increases, the velocity profiles remain constant. This condition is preserved for different values of the slip length .

Systematic evaluation of the effects of the length, depth, and amount of incorporated maize straw on rill flow velocity

Flow velocity is an important indicator when evaluating rill erosion flow dynamics. In recent decades, incorporating straw in farmland fields has become an effective method of utilizing maize straw resources. However, the effect of straw incorporation on the rill flow velocity of sloping farmland is unclear. In this study, experimental treatments with three gradients of maize straw length (6, 9, and 12 cm), incorporation depth (9, 12, and 15 cm), and straw amount (1000, 4500, and 8000 kg ha−1) were set up. Flow velocity was measured via an electrolyte tracer measurement system, and the comprehensive effect of straw incorporation on the rill erosion flow velocity of sloping farmland was clarified using structural equation modeling. The results showed that the mean flow velocity of straw-incorporated sloping land was 0.120–0.189 m s−1, which was 13.25–44.92% lower than that of bare land. The flow path became convoluted owing to the residual straw on the soil surface, which increased the flow resistance thereby reducing the flow velocity. Straw length had the greatest effect on flow velocity (with a contribution rate of 46.67%), and significant increases in velocity were observed with increases in straw length owing to the water-collecting function of the exposed straw on the soil surface. In addition, the flow velocity increased with an increase in runoff and decreased with an increase in infiltration but had no evident response to sediment yield. Increasing the straw amount had a negative impact on soil bulk density and infiltration, resulting in an increase in rill flow velocity. The incorporation depth had a very small effect on flow velocity. The results are helpful for understanding the changes in rill flow velocity and interpreting the soil erosion process on sloping farmland with straw incorporation.

Botulinum toxin type A treatment of four cases of Wilson disease with lower limb dystonia: A prospective study

Botulinum toxin type A (BoNT-A) has been recommended in various neurological disorders as a useful tool for alleviating dystonia. In Wilson disease (WD) patients with dystonia, BoNT-A injection can be used as a treatment modality when conventional treatment is ineffective for alleviating symptoms. The purpose of this study was to thoroughly evaluate the efficacy of BoNT-A injection in treating WD complicated by lower extremity dystonia. The efficacy of these injections was assessed by clinical scales, surface electromyography (EMG), and gait analysis. A comparative analysis of all gait parameters, EMG parameters, and clinical scales revealed a significant increase in velocity, decrease in integrated EMG (iEMG), and improvement in modified Ashworth scale (MAS), Burke Fahn Marsden (BFM), and activities of daily living (ADL) scores (all P < 0.05). Overall, our findings indicated that BoNT-A injection led to marked relief of symptoms in patients with WD with lower extremity dystonia.

Toward off-design loads: Investigations on combustion and emissions characteristics of a micro gas turbine combustor by external combustion-air adjustments

A novel external combustion-air adjustment method (ECAM) is proposed to control the reaction zone fuel-air ratio under off-design loads. The combustion-air is redistributed by reducing the reaction zone airflow via ECAM. Investigations are carried out to characterize the combustion dynamics and emission properties of a micro gas turbine (MGT) combustor when ECAM is used. The results show that ECAM is beneficial to control the huge increase of CO emission under off-design loads, but also present the risk of the NOx increase. The detailed analyses reveal that ECAM has a slight effect on the overall internal flow field, but leads to significant velocity increase close to the jet shear layers, and thus results in a longer reaction zone residence time, especially for the burned gas generated by the pilot flame. It directly causes the increase of NOx emissions by 29.6% with the decrease of load from 100% to 50%. Furthermore, a small-scale adjustment (from 9.0% to 8.2%) of pilot fuel proportion shows a good reduction of NOx emissions about 2.7 ppmv and 2.6 ppmv by shortening residence time about 6.72 ms and 3.68 ms of burned gas in the rection zone under 75% and 50% load, respectively.

Does Macrophage Stimulation by CCL5 Alter Melanoma Migratory Behavior?

BackgroundCCL5 (RANTES, regulated upon activation, normal T‐cell expressed and secreted) is secreted not only by T‐cells, but also by melanoma cells into the tumor microenvironment. The current project is part of a bigger effort by our laboratory to determine how the stimuli present in the tumor microenvironment may contribute to the progression of melanoma. Here, we explore CCL5 receptor expression on monocytes, macrophages, and melanoma cells, and whether endogenous or exogenous CCL5 stimulation of THP‐1 macrophages produce phenotypical changes that affect melanoma migratory behavior.MethodsWe used WM278 and LM‐Mel‐45 melanoma cells and THP‐1 monocytes before and after conversion to macrophages by 2 days exposure to 50 ng/ml PMA. To examine expression of the 3 key CCL5 receptors, we compared median fluorescence intensity (MFI) of antibody‐exposed cells to MFI of unlabeled cells using antibodies for CCR1, CCR3, and CCR5. We gated out debris and multiples, corrected for spillover, and analyzed the samples on a Bio‐Rad S3e cell sorter. We used recombinant CCL5 (100 ng/ml), the CCR1 &amp; CCR3 receptor antagonist, UCB35625 (100 nM) and the CCR5 antagonist, maraviroc (100 ng/ml). Melanoma migration rate was measured by a 16 h wound‐closure assay. Treatments included: Control, CCL5 only, maraviroc only, UCB35625 only, maraviroc and UCB35625 together, and CCL5 plus both blockers. Wound closure of LM‐Mel‐45 melanoma alone, a 1:4 mixture of macrophages to melanoma, or LM‐Mel‐45 melanoma treated with macrophage‐conditioned medium were compared in each treatment condition.ResultsCCL5 receptor expression was not found on WM278 melanoma cells. LM‐Mel‐45 melanoma express CCR1 but not CCR3 or CCR5. CCR1 and CCR5, but not CCR3, are expressed by both THP‐1 monocytes and THP‐1 macrophages. Melanoma cells alone or when co‐cultured with previously treated macrophages migrated at 14.3 ± 0.4 μm/h, but neither CCL5 stimulation nor receptor blockade changed migration significantly. When LM‐Mel‐45 melanoma cells were treated with conditioned macrophage medium, velocity increased to 16.8 ± 0.7 μm/h.ConclusionsThis work suggests that CCL5 does not directly impact melanoma migration either by endogenous expression or by exogenous addition. Even in the presence of CCL5 or antagonist‐exposed macrophages, we found no phenotypical changes that altered the physical interactions of macrophages on melanoma migratory rate. There is a small but significant increase in velocity of melanoma cells when treated with conditioned macrophage medium.

Role of biomechanical assessment in rotator cuff tear repair: Arthroscopic vs mini-open approach.

BACKGROUNDRotator cuff (RC) tears are one of the most frequent pathologies within the shoulder girdle. Hand dominance and older age are associated with RC tears. Two different surgical procedures, the mini-open (MO) and all-arthroscopic (AA) approach, represented the standard of treatment.AIMTo compare the clinical and biomechanical outcomes of two surgical techniques (AA vs MO procedure) performed to address the painful shoulder syndrome with partial or total supraspinatus tendon tear.METHODSEighty-eight participants, 50 following RC repair with AA and 38 with MO approach, were recruited in the present cross-sectional case-control study (ORTHO-SHOULDER, Prot. 0054602). All patients underwent postoperative clinical evaluation for pain (Visual analogic scale), impairment, and disability (disability of the arm, shoulder, and hand) and limitation in daily activity (Constant-Murley score). Patients’ shoulder mobility was also assessed in our Laboratory of Functional Movement through a wearable inertial sensor and surface electromyography to monitor kinematics and muscle activity during the movement on the frontal (abduction/adduction) and sagittal (flexion-extension) planes.RESULTSNo statistically significant differences between the two procedures were observed in either main clinical score or range of motion. A significant increase in velocity during the movement execution and a higher contribution of upper trapezius muscles were found in the AA group compared with MO patients.CONCLUSIONIn terms of clinical scores, our findings were in line with previous results. However, the use of technology-based assessment of shoulder mobility has revealed significant differences between the two techniques in terms of mean velocity and pattern of muscle activation.

Full-field flicker evoked changes in parafoveal retinal blood flow

When retinal activity is increased by exposure to dynamic visual stimuli, blood vessels dilate and the flow of blood within vessels increases to meet the oxygen and glucose demands of the neurons. This relationship is termed ‘neurovascular coupling’ and it is critical for regulating control of the human retinal vasculature. In this study, we used a recently developed technique based on a dual-beam adaptive optics scanning laser ophthalmoscope to measure changes in red blood cell velocities, vessel diameter, and flow in interconnected small parafoveal retinal vessels (< 50 µm) of nine healthy participants. A full-field flicker stimulus was presented onto the retina to induce a vascular response to neural activity. Flicker stimulation increased blood velocity, vessel diameter, and therefore flow in arterioles, capillaries, and venules in all nine subjects. ANOVA and post hoc t-test showed significant increases in velocity and flow in arterioles and venules. These measurements indicate that the mechanism of neurovascular coupling systematically affects the vascular response in small retinal vessels in order to maintain hemodynamic regulation in the retina when exposed to visual stimulation, in our case flicker. Our findings may provide insight into future investigations on the impairments of neurovascular coupling from vascular diseases such as diabetic mellitus.

Role of movement of the walls with time-dependent velocity on flow and mixed convection in vertical cylindrical annulus with suction / injection

The unsteady, viscous flow and mixed convection heat transfer of an incompressible fluid within a vertical concentric cylindrical annulus with time-dependent moving walls are investigated. Fluid is suctioned/injected through the cylinders' walls. Role of movement of the walls on flow and heat transfer inside the vertical annulus is sought. An exact solution of the Navier-Stokes and energy equations is obtained in this problem, for the first time. Here, the transfer of heat is from the hot cylinder walls with constant temperature to the cooler moving fluid. It is interesting to note that the results indicate that the time-dependency of the cylinder walls movement has no effect on the temperature profile. The results also indicate that, compared to other time functions, usage of inverse of time for velocity movement causes significant increase in velocity, stress tensor, and Nusselt number in the vicinity of the moving wall. Also, increasing the mixed convection and suction/injection parameters would increase the Nusselt number and decrease the stress tensor on the inner and outer cylinders no matter what the velocity function is chosen. Therefore, the flow and heat transfer is controllable using the velocity function of the wall movement and change of the other non-dimensional parameters.

Effects of high-frequency repetitive transcranial magnetic stimulation on reach-to-grasp performance in individuals with Parkinson's disease: a preliminary study.

Individuals with Parkinson's disease (PD) have deficits in reach-to-grasp (RTG) execution and visuospatial processing which may be a result of dopamine deficiency in two brain regions: primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC). We hypothesized that improvement following M1 stimulation would be the result of a direct impact on motor execution; whereas, DLPFC stimulation would improve the role of DLPFC in visuospatial processing. The aim of pilot study was to investigate the effects of HF-rTMS on RTG performance by stimulating either M1 or DLPFC. Thirty individuals with PD participated (H&Y stages I-III). All of them were more affected on the right side. Participants were allocated into three groups. The DLPFC group received HF-rTMS over left DLPFC; while, the M1 group received HF-rTMS over left M1 of extensor digitorum communis representational area. The control group received HF-rTMS over the vertex. Before and immediately post HF-rTMS, right-hand RTG performance was measured under no barrier and barrier conditions. Additionally, TMS measures including motor-evoked-potential (MEP) amplitude and cortical silent period (CSP) were determined to verify the effects of HF-rTMS. For the results, there were no significant differences among the three groups. However, only the M1 group showed a significant decrease in movement time immediately after HF-rTMS for a barrier condition. Moreover, the M1 group showed a near-significant increase in hand opening and transport velocity. As for the DLPFC group, there was a near-significant increase in temporal transport-grasp coordination and a significant increase in velocity. Increased MEP amplitudes and a significantly longer CSP in the M1 and DLPFC groups confirmed the effects of HF-rTMS. Regarding non-significant results among the three groups, it is still inconclusive whether there were different effects of the rTMS on the two stimulation areas. This is a preliminary study demonstrating that HF-rTMS to M1 may improve RTG execution; whereas, HF-rTMS to DLPFC may improve visuospatial processing demands of RTG.

Seismic detectability of carbonates in the deep Earth: A nuclear inelastic scattering study

AbstractCarbonates play an important role in the transport and storage of carbon in the Earth’s mantle. However, the abundance of carbon and carbonates in subduction zones is still an unknown quantity. To determine the most abundant accessory phases and how they influence the dynamical processes that operate within the Earth, investigations on the vibrational, elastic, and thermodynamic properties of these phases are crucial for interpreting seismological observations. Recently, the nuclear inelastic scattering (NIS) method has proved to be a useful tool to access information on the lattice dynamics, as well as to determine Debye sound velocities of Fe-bearing materials. Here we derive the acoustic velocities from two carbonate compositions in the FeCO3-MgCO3 binary system up to ~70 GPa using the NIS method. We conclude that more Mg-rich samples, in this case (Fe0.26Mg0.74)CO3, have ~19% higher sound velocities than the pure end-member Fe composition. In addition, we observed a significant velocity increase after the Fe2+ spin transition was complete. After laser heating of FeCO3 at lower mantle conditions, we observed a dramatic velocity drop, which is probably associated with thermal decomposition to another phase. Parallel to our NIS experiments, we conducted a single-crystal X-ray diffraction (SCXRD) study to derive the equation of states of FeCO3 and (Fe0.26Mg0.74)CO3. The combined information from NIS (i.e., Debye velocities) and SCXRD (i.e., densities and bulk moduli) experiments enabled us to derive the primary and shear wave velocities of our samples. Our results are consistent with results obtained by other methods in previous studies, including Brillouin spectroscopy, inelastic X-ray scattering, and DFT calculations, supporting NIS as a reliable alternative method for studying the elastic properties of Fe-bearing systems at high pressures and temperatures. Finally, we discuss the seismic detectability of carbonates. We determine that nearly 22 wt% CO2 must be present in the subduction slab to detect a 1% shear wave velocity decrease compared to non-carbonated lithologies at the transition zone to lower mantle boundary depths.

Effect of foam roller, kinesiotaping and dynamic stretching on gait parameters with induced ankle muscle fatigue

Objective: The purpose of this study was to investigate the effects of foam roller (FR) stretching, kinesiotaping (KT), and dynamic stretching (DS) on gait parameters after inducing muscle fatigue in the ankle joint. Design: Cross-sectional study. Methods: The subjects were thirty healthy young adults between the ages of 20 and 31 years at Baekseok University who voluntarily participated in this study. The participants were randomly assigned to either the FR group, KT group, or the DS group after inducing muscle fatigue of the ankle joint. Fatigue induction of the ankle joint muscles was performed by alternating a heel up and down exercise with the standing posture on the ground. The speed was maintained at 40 beats/minute using a metronome. Subsequently, the respective intervention was applied to each group. Gait parameters were measured before and after ankle muscle fatigue induction, and after intervention using the GAITRite system. One-way ANOVA was used to compare gait parameters among groups, while repeated measures ANOVA was used to compare gait parameters within each intervention group. Results: The FR group increased significantly in velocity, step length, and stride length except for cadence after intervention compared to after ankle muscle fatigue induction (p<0.01). Furthermore, the KT group showed significant increases in velocity, cadence, step length, and stride length after intervention, especially in cadence group (p<0.05). All intervention groups showed significant increases in stride length after intervention, especially the DS group (p<0.05). Conclusions: Therefore, we suggest that KT, FR, and DS can be an effective intervention on gait parameters when the ankle joint is unstable and injured.

Hemodynamics of tonic immobility in the American alligator (Alligator mississippiensis) identified through Doppler ultrasonography.

American alligators (Alligator mississippiensis) held inverted exhibit tonic immobility, combining unresponsiveness with flaccid paralysis. We hypothesize that inverting the alligator causes a gravitationally promoted increase in right aortic blood flowing through the foramen of Panizza, with a concurrent decrease in blood flow through the primary carotid, and thereby of cerebral perfusion. Inverting the alligator results in displacement of the liver, post-pulmonary septum, and the heart. EKG analysis revealed a significant decrease in heart rate following inversion; this decrease was maintained for approximately 45s after inversion which is ingeneral agreement with the total duration of tonic immobility in alligators (49s). Doppler ultrasonography revealed that following inversion of the alligator, there was a reversal in direction of blood flow through the foramen of Panizza, and this blood flow had a significant increase in velocity (compared to the foraminal flow in the prone alligator). There was an associated significant decrease in the velocity of blood flow through the primary carotid artery once the alligator was held in the supine position. Tonic immobility in the alligator appears to be a form of vasovagal syncope which arises, in part, from the unique features of the crocodilian heart.

Effect of Energy Drink Consumption on Power and Velocity of Selected Sport Performance Activities.

Jacobson, BH, Hester, GM, Palmer, TB, Williams, K, Pope, ZK, Sellers, JH, Conchola, EC, Woolsey, C, and Estrada, C. Effect of energy drink consumption on power and velocity of selected sport performance activities. J Strength Cond Res 32(6): 1613-1618, 2018-Energy drinks (ED) comprise a multibillion dollar market focused on younger, active, and competitive individuals. Marketing includes claims of improved alertness and performance. The purpose of this study was to assess power (W) and velocity (m·s) of a simulated, isolated forehand stroke (FHS), and a countermovement vertical jump (CVJ) before and after ingestion of a commercially available energy shot (ES) or a placebo (PL). Healthy college-aged men and women (N = 36) volunteers were randomly placed in the ES or PL. Before and 30 minutes after ingesting either the ES or PL, participants performed 3 FHSs and CVJs. Power and velocity of each performance was measured using a linear velocity transducer and the highest value for each measure was used for subsequent analysis. The ES group demonstrated a significant (p = 0.05) increase in velocity and W for the FHS, but not for the CVJ. All measures remained unchanged in the PL group for both, the FHS and CVJ. Females demonstrated a significant increase in velocity over males in FHS, but not in CVJ. It was concluded that while the dose of stimulants in the ES was adequate to improve performance of smaller muscle groups, it may not have been sufficient to affect the larger muscle groups of the lower legs which contribute to the CVJ. While the ES used in the present study contained a caffeine dosage within the NCAA limit and did improve performance for the upper body, it must be noted that there are health risks associated with ED consumption.

End-expiratory occlusion maneuver to predict fluid responsiveness in the intensive care unit: an echocardiographic study

BackgroundIn mechanically ventilated patients, an increase in cardiac index during an end-expiratory-occlusion test predicts fluid responsiveness. To identify this rapid increase in cardiac index, continuous and instantaneous cardiac index monitoring is necessary, decreasing its feasibility at the bedside. Our study was designed to investigate whether changes in velocity time integral and in peak velocity obtained using transthoracic echocardiography during an end-expiratory-occlusion maneuver could predict fluid responsiveness.MethodsThis single-center, prospective study included 50 mechanically ventilated critically ill patients. Velocity time integral and peak velocity were assessed using transthoracic echocardiography before and at the end of a 12-sec end-expiratory-occlusion maneuver. A third set of measurements was performed after volume expansion (500 mL of saline 0.9% given over 15 minutes). Patients were considered as responders if cardiac output increased by 15% or more after volume expansion.ResultsTwenty-eight patients were responders. At baseline, heart rate, mean arterial pressure, cardiac output, velocity time integral and peak velocity were similar between responders and non-responders. End-expiratory-occlusion maneuver induced a significant increase in velocity time integral both in responders and non-responders, and a significant increase in peak velocity only in responders. A 9% increase in velocity time integral induced by the end-expiratory-occlusion maneuver predicted fluid responsiveness with sensitivity of 89% (95% CI 72% to 98%) and specificity of 95% (95% CI 77% to 100%). An 8.5% increase in peak velocity induced by the end-expiratory-occlusion maneuver predicted fluid responsiveness with sensitivity of 64% (95% CI 44% to 81%) and specificity of 77% (95% CI 55% to 92%). The area under the receiver operating curve generated for changes in velocity time integral was significantly higher than the one generated for changes in peak velocity (0.96 ± 0.03 versus 0.70 ± 0.07, respectively, P = 0.0004 for both). The gray zone ranged between 6 and 10% (20% of the patients) for changes in velocity time integral and between 1 and 13% (62% of the patients) for changes in peak velocity.ConclusionsIn mechanically ventilated and sedated patients in the neuro Intensive Care Unit, changes in velocity time integral during a 12-sec end-expiratory-occlusion maneuver were able to predict fluid responsiveness and perform better than changes in peak velocity.

The Influence of the Spatio-Temporal Terzi Treatment on the Kinematics of Cursive Writing of Dysgraphic Subjects

Many different treatment approaches have been applied for handwriting remediation in school-aged children. The effects of these treatments are usually evaluated by using ad-hoc checklists as well as some standard test protocols like Movement ABC tests, Visual-Motor Integration (V.M.I.) tests, etc. Recently, digitizing tablets have allowed the study of kinematic characteristics of handwriting and a series of parameters were estimated on cursive writing of Italian children. In this paper, the influence of a new rehabilitation protocol (Terzi's method) on kinematics of cursive writing was evaluated. The analysis was carried out on 22 nonproficient handwriting children, attending primary or secondary school, which undertook a series of three exercises, with and without linguistic concerns. A set of kinematic parameters was calculated before and after the rehabilitation process. The results showed that Terzi's rehabilitation program is capable of producing a significant velocity increase in the test without linguistic involvement, whereas a significant slowdown in the stroke realization was present in the other tasks. The effectiveness of Terzi's rehabilitation program was proved by significant improvements in the V.M.I. test, in the Movement ABC test as well as in writing legibility (evaluated by checklist).

Wind or water turbine power augmentation using the system of guiding surfaces

As fluid flows through a conventional wind or hydro turbine, it slows from losing energy to extraction from a turbine and spreads out to a wider area. This results in a loss of turbine efficiency. In order to exploit wind or water flow power more effectively, it was suggested to place the turbine inside a system of specially designed airfoils (‘a flow booster’). One part of the booster (‘a nozzle’) improves the turbine performance by speeding up the flow acting on the turbine blades. The other part of the accelerating system (‘a diffuser’) creates a field of low pressure behind the turbine which helps to draw more mass flow to the turbine and avoid the loss of efficiency due to flow deceleration. The flow booster accumulates the kinetic energy of the flow (e.g. river flow or wind) in a small volume where the smaller turbine can be installed. Another possible application of the booster could be the improvement of wind turbine efficiency during low wind period. The present paper also discusses the possibility of kinetic energy accumulation by the use of several accelerating systems of different sizes—the smaller one can be installed inside the bigger one. It helps to accumulate even more kinetic energy on the turbine blades. We call this method the kinetic energy cumulation. Lab and field experiments and CFD simulations of shrouded turbine demonstrate significant increase in velocity in comparison of those for conventional (bare) turbines.

Immediate effects of rhythmic auditory stimulation on gait in stroke patients in relation to the lesion site.

[Purpose] Rhythmic auditory stimulation has been used in gait training for stroke patients. However, few studies have investigated its effects in relation to lesion sites. Therefore, this study examined the immediate effects of rhythmic auditory stimulation on gait in stroke patients with lesions in different regions. [Subjects and Methods] One hundred and five patients were recruited and divided into five groups according to the lesion site: cerebellum, pons and medulla, thalamus, putamen, and corona radiata. During training, participants walked to an auditory, continuous rhythmic beat, which was set to each individual’s cadence. [Results] Pre- versus post-test measures revealed significant increases in velocity and stride length in the cerebellum, pons and medulla, and thalamus groups. Although the putamen and corona radiata groups demonstrated increases in velocity and stride length, the increases were not significant. [Conclusion] Rhythmic auditory stimulation was effective in facilitating the prediction of motor timing and gait rhythm in stroke patients with lesions in the cerebellum, pons and medulla, and thalamus, which are associated with impairment of the timing mechanism.

Hand Grip Strength Vs. Sprint Effectiveness in Amputee Soccer Players.

Amputee soccer is one of the types of soccer designed for the disabled, especially those who have undergone amputations, as well as those with extremity dysfunction. The objective of the study was to find the relationship between hand grip strength and sprint time in amputee soccer players. Thirteen field amputee soccer players participated in the study. A SAEHAN hydraulic hand dynamometer manufactured by Jamar was used for hand grip strength measurements. The sprint running test was conducted over a distance of 30 m. The Fusion Smart Speed System was employed for running time measurements. No statistically significant relationships were found between hand grip strength of the left or right hand, and sprint times over 1, 5, 10, 15, 20, 25 and 30 m. Analysis of the running velocity curve of the subjects showed an interesting profile characterized by a 15 meter-long acceleration phase and a significant velocity increase over a distance of 20 – 25 m. The study suggests that there is no relationship between hand grip strength and sprint effectiveness in amputee soccer players. The specificity of locomotion with the use of elbow crutches among elite Polish amputee soccer players probably accounts for the profile of the sprint velocity curve. Extension of the acceleration phase in the sprint run and a velocity increase in the subsequent part of the run were observed.

Effects Of Dual-tasking On Stability During Walking In Children With Cerebral Palsy

Background: Many children with Cerebral Palsy (CP) have impaired walking abilities associated with poor maintenance of balance. Such impairments unseen in typically developing children include reduced walking speed, reduced step length, and wider step width. Further, dual-tasking has been associated with reductions in walking speed, stride length, step width and toe clearance compared to normal walking in children with CP but not in typically developing children. However, little is known about the effects of dual-tasking on other balance characteristics during walking in this population. PURPOSE: To examine the effects of dual-tasking on stability (dynamic balance) during walking in children with CP. METHODS: Five assenting children with CP (four boys, one girl; 7.0 ± 0.9 yrs, 125.7 ± 6.5 cm, 26.0 ± 4.5 kg) participated in the experiment and walked four times across a 3.4 m GAITRite® instrumented walkway system (CIR Systems Inc., GAITRite, Sparta, NJ; 120 Hz) at their self-selected speed. Next, participants completed the same walking protocol while simultaneously carrying a tray, similar to what they might do in a school lunchroom. Foot pressure data were extracted and analyzed by footfall (minimum 12 strides per participant) to compare velocity, unilateral step width, stride width, and base of support width for each condition. Data were evaluated using a single-subject procedure (Model Statistic, α = 0.05). RESULTS: Walking velocity decreased significantly when dual tasking for two children (44.0 cm/sec and 40.7 cm/sec, respectively; p < 0.05) while two other children elicited a significant velocity increase (9.4 cm/sec and 12.5 cm/sec, respectively; p < 0.05). Three children reduced base of support when dual-tasking (2.9 ± 2.8 cm, 5.1 ± 4.2 cm, 7.6 ± 7.5 cm, respectively; p < 0.05). Stride width was reduced in two children as a result of the dual-tasking condition (3.7 ± 1.8 cm and 2.3 ± 3.2 cm, respectively; p < 0.05), and one of five children showed reduced step width (9.7 ± 5.1 cm; p < 0.05). CONCLUSION: This dual-tasking condition significantly altered dynamic balance characteristics in children with CP, most notably velocity, base of support, and stride width. Whether this was a function of the observed change in self-selected walking velocity or a characteristic of the population warrants further investigation.

Retinal blood flow and vascular reactivity in chronic smokers.

The aim of this study was to investigate the impact of cigarette smoking in otherwise healthy young individuals on retinal blood flow (RBF) and vascular reactivity (RVR). An automated gas flow controller (RespirAct) was used to achieve normoxic hypercapnia in 10 nonsmokers (mean age 28.9; SD 4.6 years) and nine smokers (mean age 27.55; SD 4.7 years). Retinal blood flow measurements were obtained using a prototype Doppler spectral-domain optical coherence tomographer (SD-OCT) and bidirectional laser Doppler velocimetry and simultaneous vessel densitometry during baseline, normoxic hypercapnia, and recovery. Group mean PETCO2 (end-tidal partial pressure of CO2) was increased by 15.9% in the nonsmoking group and by 15.7% in the smoking group, with a concomitant increase in PETO2 (end-tidal partial pressure of O2) by approximately 1.5% to 2% in both groups. In nonsmokers, retinal arteriolar diameter (P < 0.0001), centerline velocity (P = 0.0004), and blood flow (P < 0.0001) significantly increased during normoxic hypercapnia. Similarly, the venous area (P = 0.0418), venous velocity (P = 0.0068), and total venous RBF (P < 0.0001), as measured by the prototype Doppler SD-OCT, significantly increased. In smokers, normoxic hypercapnia resulted in a significant increase in velocity (P = 0.0019), flow (P = 0.0029), and total venous RBF (P = 0.002). Comparing smokers and nonsmokers, the percentage change in arteriolar diameter (P = 0.0379) and blood flow (P = 0.0101) was significantly lower in the smoking group. There was no significant difference in baseline PETCO2 level between smokers and nonsmokers. Retinal vascular reactivity in response to normoxic hypercapnia is significantly reduced in young, healthy smokers compared with nonsmokers.