Decreased Contact Time Research Articles

Droplet Impact on the Superhydrophobic Surface with Singularities.

Reducing the contact time of an impacting droplet is highly desirable in various industrial fields including anti-icing. With the straightforward upscaling advantage, singularities on superhydrophobic surfaces can induce an annular rebound with a limited reduction in contact time. To break this limitation and further reduce contact time, this study focuses on optimizing the singularity number and arrangement. The effects of the singularity number and dimensionless spacing (l* scaled by the droplet diameter) on the dynamic and contact time characteristics of a droplet impacting the superhydrophobic surface are experimentally studied under varying Weber numbers (We). The experimental results indicate that in comparison to the single singularity, two singularities with l* < 1.0 can generate two liquid rings with four lateral liquid subunits due to the impalement at the high We region. Owing to the reduced equivalent diameter of the subunit, increasing We results in a gradually decreased contact time and accordingly breaks the limitation. However, the liquid film cannot be pierced at l* > 1.0 with a limited reduction. Considering the further reducing potential at l* < 1.0, four singularities are explored without a further reduced contact time due to the formed central liquid film. Using an additional central singularity, the central liquid film is pierced promoting its annular rebound. In consequence, five singularities significantly break the limitation in contact time, particularly a 61.7% reduction to the superhydrophobic flat surface at l* < 1.0.

Transference of outdoor gait-training to treadmill running biomechanics and strength measures: A randomized controlled trial

Outdoor gait-training has been successful in improving pain and reducing contact time during outdoor running for runners with exercise-related lower leg pain (ERLLP). However, it is unclear if these adaptations translate to gold standard treadmill running and clinical strength assessments. The study purpose was to assess the influence of a 4-week outdoor gait-training intervention with home exercises (FBHE) on treadmill running biomechanics and lower extremity strength compared to home exercises alone (HE) among runners with ERLLP. Seventeen runners with ERLLP were randomly allocated to FBHE and HE groups (FBHE: 3 M, 6F, 23 ± 4 years, 22.0 ± 4.6 kg/m2; HE: 3 M, 5F, 25 ± 5 years, 24.0 ± 4.0 kg/m2). Both groups completed eight sessions of home exercises over 4 weeks. The FBHE group received gait-training through wearable sensors to reduce contact time. Treadmill running gait and clinical strength assessments were conducted at baseline and 4-weeks. Multivariate repeated measures analyses of variance were used to assess the influence of group and timepoint for all outcomes. The FBHE group demonstrated significantly decreased contact time at 4-weeks compared to baseline and the HE group (Mean Difference [MD] range: −42 ms – −39 ms; p-range: <0.001–0.02). The FBHE group had significantly increased cadence (MD: +21 steps/min; p = 0.003) and decreased loading impulse (MD: −51, p < 0.001) during treadmill running at 4-weeks compared to the HE group. Strength did not significantly differ adjusting for multiple comparisons (p > 0.007). The outdoor FBHE intervention transferred to favorable changes in treadmill running biomechanics. Clinicians treating runners with ERLLP patients should implement data-driven outdoor gait-training to maximize patient benefits across running locations.

Unveiling the Biomechanical Insights: Motor Control Shifts Induced by Shoe Friction Adjustments and Their Impact on Defensive Slide, Crossover Dribbling, and Full Approach Jump in Basketball

This study endeavors to explore the intricate interplay between the fundamental skills of basketball—defensive slide, crossover dribbling, and full approach jump—and the shoe outsole friction coefficient, with the overarching goal of advancing our comprehension regarding the pivotal role of footwear in athlete performance. Employing a comprehensive methodology that integrates 3D motion capture, force platform dynamometry, and biomechanical modeling, the study seeks to quantify the inherent motor control intricacies associated with these fundamental skills. Data collection involved 12 varsity players, and the research systematically assesses the influence of the shoe friction coefficient on both skill quality and injury risk, utilizing a set of 13 parameters for evaluation. The findings unveil that, with an increased friction coefficient, the following changes occur: for the defensive slide, we observed decreased contact time (p &lt; 0.05), boosted medio–lateral impulse (p &lt; 0.05), and lowered ankle torque (p &lt; 0.01); for crossover dribbling, we observed increased anterior–posterior impulse (p &lt; 0.05) and ankle torque (p &lt; 0.05); for the full approach jump, we observed decreased contact time (p &lt; 0.05) and increased jump height (p &lt; 0.05). Generally, the equal increment in the shoe outsole friction coefficient did not result in equal changes in the selected parameters of motor skill control, indicating a non-linear relationship between the performance quality of essential basketball skills and the shoe friction coefficient. The results suggest the potential existence of an optimal value for skill execution. Notably, the study identifies that, while an augmentation in the friction coefficient enhances specific skill aspects, there is a discernible saturation point, signifying diminishing returns. This investigation makes a substantial contribution to our understanding of the precise impacts of shoe friction coefficients on basketball skills, thereby prompting considerations for the judicious selection of optimal friction coefficients and advocating for possible personalized footwear recommendations based on individual biomechanical profiles.

Bisphenol analogues induced social defects and neural impairment in zebrafish

There is evidence in humans that endocrine disrupting chemicals exposure, such as bisphenol A (BPA), is tied to social behavior impacts when evaluated in early life stage. However, the potential social impact of BPA alternatives and its association with central nervous system (CNS) is poorly understood. Here, we performed behavioral test for zebrafish that are continuously exposed to environmental relevant concentrations (5 and 500 ng/L) of BPA, BPF, and BPAF since embryonic stage. Surprisingly, significant social behavior defects, including increased social distance and decreased contact time, were identified in zebrafish treated by 500 ng/L BPAF and BPA. These behavioral changes were accompanied by apparent histological injury, microglia activation, enhanced apoptosis and neuron loss in brain. The gut-brain transcriptional profile showed that genes involved in neuronal development pathways were up-regulated in all bisphenol analogs treatments, indicating a protective phenotype of CNS; however, these pathways were inhibited in gut. Besides, a variety of key regulators in the gut-brain regulation were identified based on protein interaction prediction, such as rac1-limk1, insrb1 and fosab. These findings implicated that the existence of bisphenol analogues in water would influence the social life of fish, and revealed a potential role of gut-brain transcriptional alteration in mediating this effect.

The effect of upper panel stiffness on biomechanical performance in athletic footwear

Athletic footwear can improve performance through targeted design features to improve biomechanical mechanisms of performance. The alteration of athletic shoe uppers can impact athletic performance and biomechanics in both males and females; moreover, the impact may differ between males and females due to anatomical differences between sexes. Therefore, assessment of sex-specific impacts of footwear modification on athletic performance is essential when determining how to modify footwear. The purpose of this research was to determine the impact of upper panel stiffness on biomechanical performance during agility tasks and determine if the optimal upper stiffness depends on the sex of the athlete. It was hypothesized that stiffening the upper panel, quantified through uniaxial tension testing, would result in decreased contact time and increased force production during jumping and change of direction tasks. Forty participants (20 males, 20 females) were recruited and completed eight lateral skater jumps, eight counter movement jumps, three triangle drop step drills and six anterior-posterior drills in three footwear conditions that varied in upper panel stiffness. 3D motion capture and embedded force plates were used to measure biomechanical outcomes that were compared between stiffness conditions using a linear mixed effect model. Upper panel stiffness significantly affected contact time during the lateral skater jump with the stiffest shoe resulting in the shortest contact time compared to the two other conditions (p = .02–.046, η2 = 0.18). No sex-related interactions were found for any outcome variable. Taken together, upper panel stiffness is important to consider when developing both male and female footwear.

Novel Short Process for p-Xylene Production Based on the Selectivity Intensification of Toluene Methylation with Methanol.

Toluene methylation using methanol offers a high potential molecular engineering process to produce p-xylene (PX) based on shape-selective catalysts. To further improve the process economics, a novel short process was proposed by reducing the high-energy consumption separation of xylene isomers in existing processes since the PX selectivity of the xylene isomers can be enhanced more than the industrial product quality of 99.7%. The PX selectivity intensification was achieved as a result of decreased contact time by considering factors such as the feed ratio, diluents, temperature, and pressure in a toluene methylation reactor. This proposed short process indicated that the reactor effluent could be purified only through the two conventional distillation towers by removing the methanol recovery and separation of xylene isomers. The raw material utilization, energy consumption, and economic data were also analyzed for the six contrastive cases. The short process using catalyst Si–Mg–P–La/ZSM-5 exhibited the highest effective utilization rates of 96.27 and 95.50% for toluene and methanol, respectively. The short process also showed a good economic value in terms of capital investment and operating costs due to the multistage reactor without benzene byproducts. Thus, the obtained total annual cost (TAC) value of 13 848.1 k$·year–1 was 68.9 and 87.9% of the two existing processes.

Synthesis of Bio-Adsorbent for Removal of Fluoride from Groundwater – A column study

High fluoride levels in groundwater used for drinking have caused health concerns for millions of people across the world. Pakistan is one of the countries that have been contaminated by these toxins. However, a little amount of fluoride is required for tooth and bone strength. In any event, the presence of too much of it in drinking water can cause diseases in both people and animals. This study is focused on the synthesis of bio-adsorbent bone char to adsorbent for the removal of fluoride from groundwater obtained from Islamkot district Tharparkar. The bone char was synthesized by pyrolysis of used cow bones at a temperature of 550 degrees C. The fluoride removal efficiency of bone char was optimized. The impacts of different operating parameters such as flow rates (5mL/min, 10mL/min, and 15mL/min), bed height of adsorbent (2cm, 4cm, and 6cm), initial fluoride concentration 7.85 mg/L, and contact time (30min, 60min, and 90min) were studied. The removal efficiency was enhanced by increasing the adsorbent bed height and decreasing contact time and flow rate. With an initial concentration of fluoride 7.85mg/L, the maximum removal efficiency of 90.2% was obtained when the adsorbent bed height, flow rate, and contact time were optimized to 6 cm, 5 mL/min, and 30min, respectively. The finding showed that bone char can be used as an eco-friendly, inexpensive, and efficient adsorbent for removing fluoride from groundwater.

Guar gum fortified white breads for prospective postprandial glycaemic control – Effects on bread quality and galactomannan molecular weight

Guar galactomannans effectively reduce post-prandial glycaemic responses and can be used to improve the health impact of white bread. Here we compare the impact of four guars containing galactomannans with varying weight-average molecular weight (Mw) at three different wheat flour substitution levels (5, 10 and 15%) on bread quality. The negative impact of galactomannan incorporation on bread quality becomes more pronounced at higher substitution levels and with higher Mw. However, Mw is likely to be an important parameter for the efficacy of such breads. But we observed a degradation of galactomannan during baking, which was likely caused by enzymatic activity in the dough. A decreased contact time between wheat flour and guar gum, along with pre-hydration of the guar, improved sensory attributes such as texture, markedly decreased the presence of large air holes in the crumb and reduced the degree of depolymerisation of galactomannan during baking. The results from this study give an important starting point for future work of optimizing the baking procedure of guar fortified breads keeping in mind not only bread quality but also a retained Mw of the active ingredient.

Impact of a pressurised membrane: Contact time

Pressurised membranes are used in various situations involving humans (protections, sports, etc). In this context, impacts mechanics of membranes is critical since under or over inflated membranes may create injuries. The effect of inflation pressure on contact time is investigated on a model experiment using a spherical membrane. Both gas pressure and impact speed decrease contact time. Direct measurements of gas pressure and temperature variations indicate an adiabatic compression in strong interaction with the membrane. The contact time of an inflated membrane is described by three dimensionless numbers, (i) the relative inflation P˜, (ii) the presso-elactic number PE that considers the gas-membrane interaction and (iii) the presso-inertial number IP that scales membrane inertia to pressure forces. A model of pressurised membrane impact is provided and compared with experiments. It shows that contact time depends mainly on IP with corrections on PE and P˜.

National Survey on Canadian Undergraduate Medical Programs: The Decline of the Anatomical Sciences in Canadian Medical Education.

The anatomical sciences have always been regarded as an essential component of medical education. In Canada, the methodology and time dedicated to anatomy teaching are currently unknown. Two surveys were administered to course directors and discipline leaders to gain a comprehensive view of anatomical education in Canadian medical schools. Participants were queried about contact hours (classroom and laboratory), content delivery and assessment methods for gross anatomy, histology, and embryology. Twelve schools responded to both surveys, for an overall response rate of 64%. Overall, Canadian medical students spend 92.8 (± 45.4) hours (mean±SD) studying gross anatomy, 25.2 (± 21.0) hours for histology, and 7.4 (± 4.3) hours for embryology. Gross anatomy contact hours statistically significantly exceeded those for histology and embryology. Results show that most content is delivered in the first year of medical school, as anatomy is a foundational building block for upper-year courses. Laboratory contact time for gross anatomy was 56.8 (± 30.7) hours, histology was 11.4 (± 16.2) hours, and embryology was 0.25 (± 0.6) hours. Additionally, 42% of programs predominantly used instructor/technician-made prosections, another 33% used a mix of dissection and prosections and 25% have their students complete cadaveric dissections. Teaching is either completely or partially integrated into all Canadian medical curricula. This integration trend in Canada parallels those of other medical schools around the world where programs have begun to decrease contact time in anatomy and increase integration of the anatomical sciences into other courses. Compared to published American data, Canadian schools offer less contact time. The reason for this gap is unknown. Further investigation is required to determine if the amount of anatomical science education within medical school affects students' performance in clerkship, residency and beyond.

Impact of capillary drops of complex fluids on a solid surface

The drop impact on a solid surface is studied in the context of complex fluids that exhibit viscoplastic, viscoelastic, and thixotropic behavior. The effects of rheology and surface tension are investigated for a range of corresponding dimensionless numbers associated with each phenomenon. Two usual quantities are employed to understand the drop dynamics, namely, the maximum spreading diameter and the time the drop remains in contact with the solid. Another result is the drop shape evolution, captured by displaying selected instants. The first part of the work is dedicated to examine the influence of capillary effects for more real fluids, in the present case, solutions of Carbopol, kaolin, and bentonite whose mechanical properties are taken from experimental measurements reported in the literature. In the second part, we conduct parametric studies varying the dimensionless numbers that govern the problem. We have shown that the influence of surface tension in yield stress materials is less significant and can be negligible when real parameters are input in the model. On the other hand, Newtonian and viscoelastic fluids are more susceptible to surface tension effects. This quantity tends to decrease maximum spreading diameter and decrease contact time due to its resistance in the spreading stage. While inertia, elasticity, and plastic effects favor the drop to spread and to increase its contact time with the solid substrate, a more thixotropic behavior leads to the opposite trend.

The vascular bone marrow niche influences outcome in chronic myeloid leukemia via the E-selectin - SCL/TAL1 - CD44 axis.

The endosteal bone marrow niche and vascular endothelial cells provide sanctuaries for leukemic cells. In murine chronic myeloid leukemia (CML) CD44 on leukemia cells and E-selectin on bone marrow endothelium are essential mediators for the engraftment of leukemic stem cells. We hypothesized that non-adhesion of CML-initiating cells to E-selectin on the bone marrow endothelium may lead to superior eradication of leukemic stem cells in CML after treatment with imatinib than imatinib alone. Indeed, here we show that treatment with the E-selectin inhibitor GMI-1271 in combination with imatinib prolongs survival of mice with CML via decreased contact time of leukemia cells with bone marrow endothelium. Non-adhesion of BCR-ABL1+ cells leads to an increase of cell cycle progression and an increase of expression of the hematopoietic transcription factor and proto-oncogene Scl/Tal1 in leukemia-initiating cells. We implicate SCL/TAL1 as an indirect phosphorylation target of BCR-ABL1 and as a negative transcriptional regulator of CD44 expression. We show that increased SCL/TAL1 expression is associated with improved outcome in human CML. These data demonstrate the BCR-ABL1-specific, cell-intrinsic pathways leading to altered interactions with the vascular niche via the modulation of adhesion molecules – which could be exploited therapeutically in the future.

Leg Trajectory Planning for Quadruped Robots with High-Speed Trot Gait

In this paper, a single leg platform for quadruped robots is designed based on the motivation of high-speed locomotion. The leg is designed for lightweight and low inertia with a structure of three joints by imitating quadruped animals. Because high acceleration and extensive loadings will be involved on the legs during the high-speed locomotion, the trade-off between the leg mass and strength is specifically designed and evaluated with the finite element analysis. Moreover, quadruped animals usually increase stride frequency and decrease contact time as the locomotion speed increases, while maintaining the swing duration during trot gait. Inspired by this phenomenon, the foot-end trajectory for quadruped robots with a high-speed trot gait is proposed. The gait trajectory is planned for swing and stance phase; thus the robot can keep its stability with adjustable trajectories while following a specific gait pattern. Especially for the swing phase, the proposed trajectory can minimize the maximum acceleration of legs and ensure the continuity of position, speed, and acceleration. Then, based on the kinematics analysis, the proposed trajectory is compared with the trajectory of Bézier curve for the power consumption. Finally, a simulation with Webots software is carried out for verifying the motion stability with two trajectory planning schemes respectively. Moreover, a motion capture device is used for evaluating the tracking accuracy of two schemes for obtaining an optimal gait trajectory suitable for high-speed trot gait.

Assessment of Weekly Study Guide Use and Utility in a Condensed Medical Gross Anatomy and Embryology Course

Implementation of a condensed preclinical curriculum is becoming a trend among US medical schools. Condensing basic science courses to fit into an 18‐month curricular model involves careful and intentional planning in order to decrease contact hours without sacrificing foundational content. While a decrease in contact hours may allow for an increase in self‐guided study time, it diminishes important faculty‐student face‐to‐face interaction that many students need for higher‐order learning. In an attempt to augment learning in the face of decreased contact time, twelve weekly study guides were developed for first‐year medical (n=85) and graduate (n=4) students in a condensed medical gross anatomy and embryology course. Each study guide contained multiple open‐answer gross and clinical anatomy questions pertaining to selective content covered over the course of the week in lecture and laboratory sessions. Study guides were made available to all students through Blackboard. Study guide answers were not posted, though students were free to seek faculty assistance when needed. The purpose of this study is to assess student use and perception of the study guides as a focused learning resource. A post‐course, voluntary survey was sent to all students to assess frequency of study guide use, strengths, weaknesses, and perception of study guide utility in terms of learning and quiz/exam preparation. Eighty‐eight (98.8% response rate) students completed the survey. Survey results revealed that use of the 12 study guides varied among students. Thirty students (34.1%) used 1–4, 17 students (19.3%) used 5–10, 7 students (8%) used 8–11,13 students (14.8%) used all 12, and 21 students (23.8%) did not use the study guides. Using a 5‐point Likert scale (1=strongly disagree; 5=strongly agree), students rated study guide content applicability, organization, and utility for learning and quiz/exam preparation. Only responses from students who used the study guides in some capacity (n=67) were included in these analyses. Fifty‐eight (86.6%) and 47 (70.1%) students agreed/strongly agreed that study guide content was applicable to and helped in preparation for answering quiz/exam questions, respectively. Moderately strong, positive correlations were found between student study guide use frequency and perceived exam preparation (r=0.55) and perceived effect on quiz/exam performance (r=0.60). Additionally, moderate positive correlations were found between student study guide use frequency and reported understanding of gross (r=.55) and clinical (r=.46) anatomy content, respectively. Quartile rank of final course grade was not strongly correlated with survey responses, suggesting that study guide use was not limited to a specific student quartile. Overall, weekly study guides were well‐used in varying degrees among students in a condensed gross anatomy and embryology course. Students who used the study guides consistently reported positive perceived effects on learning and assessment performance. Correlative results suggest that students who completed more study guides felt better prepared for assessments and perceived the study guides as useful learning tools for gross and clinical anatomy topics. Future directions include analysis of student performance on quiz/exam questions mapped to study guide content.Support or Funding Informationn/aThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Short- and long-term effects of altered point of ground reaction force application on human running energetics.

The current study investigates the effect of altering the point of force application (PFA) from the rearfoot towards the fore of the foot on the metabolic energy consumption and the influence of transitioning to this technique over a short or a longer timeframe. The participants were randomly assigned into two experimental and one control group: a short-term intervention group (STI, N=17; two training sessions), a long-term intervention group (LTI, N=10; 14-week gradual transition) and a control group (CG, N=11). Data were collected at two running velocities (2.5 and 3.0 m s-1). The cost coefficient (i.e. energy required per unit of vertical ground reaction force; JN-1) decreased (P<0.001) after both interventions due to a more anterior PFA during running (STI: 12%, LTI: 11%), but led to a higher (P<0.001) rate of force generation (STI: 17%, LTI: 15.2%). Dynamic stability of running showed a significant (P<0.001) decrease in the STI (2.1%), but no differences (P=0.673) in the LTI. The rate of metabolic energy consumption increased in the STI (P=0.038), but remained unchanged in the LTI (P=0.660). The CG had no changes. These results demonstrate that the cost coefficient was successfully decreased following an alteration in the running technique towards a more anterior PFA. However, the energy consumption remained unchanged because of a simultaneous increase in rate of force generation due to a decreased contact time per step. The increased instability found during the short-term intervention and its neutralization after the long-term intervention indicates a role of motor control errors in the economy of running after acute alterations in habitual running execution.

Effects of altered sagittal trunk orientation on kinetic pattern in able-bodied walking on uneven ground.

ABSTRACTStudies of disturbed human locomotion often focus on the dynamics of the gait when either posture, movement or surface is perturbed. Yet, the interaction effects of variation of trunk posture and ground level on kinetic behaviour of able-bodied gait have not been explored. For 12 participants we investigated the kinetic behaviour, as well as velocity and contact time, across four steps including an unperturbed step on level ground, pre-perturbation, perturbation (10-cm drop) and post-perturbation steps while walking with normal speed with four postures: regular erect, with 30°, 50° and maximal sagittal trunk flexion (70°). Two-way repeated measures ANOVAs detected significant interactions of posture×step for the second peak of the vertical ground reaction force (GRF), propulsive impulse, contact time and velocity. An increased trunk flexion was associated with a systematic decrease of the second GRF peak during all steps and with a decreased contact time and an increased velocity across steps, except for the perturbation step. Pre-adaptations were more pronounced in the approach step to the drop in regular erect gait. With increased trunk flexion, walking on uneven ground exhibited reduced changes in GRF kinetic parameters relative to upright walking. It seems that in trunk-flexed gaits the trunk is used in a compensatory way during the step-down to accommodate changes in ground level by adjusting its angle leading to lower variations in centre of mass height. Exploitation of this mechanism resembles the ability of small birds in adjusting their zig-zag-like configured legs to cope with changes in ground level.

Effect of Ankle Joint Contact Angle and Ground Contact Time on Depth Jump Performance

Athletes often need to both jump high and get off the ground quickly, but getting off the ground quickly can decrease the vertical ground reaction force (VGRF) impulse, impeding jump height. Energy stored in the muscle-tendon complex during the stretch-shortening cycle (SSC) may mitigate the effects of short ground contact times (GCTs). To take advantage of the SSC, several coaches recommend "attacking" the ground with the foot in a dorsiflexed (DF) position at contact. However, the efficacy of this technique has not been tested. This investigation tested the hypotheses that shorter GCTs would lead to smaller vertical depth jump heights (VDJH), and that this difference could be mitigated by instructing the athletes to land in a DF as opposed to a plantar flexed (PF) foot position. Eighteen healthy junior college athletes performed depth jumps from a 45-cm box onto force platforms under instruction to achieve one of the 2 objectives (maximum jump height [hmax] or minimal GCT [tmin]), with one of the 2 foot conditions (DF or PF). These variations created 4 distinct jump conditions: DF-hmax, DF-tmin, PF-hmax, and PF-tmin. For all variables examined, there were no significant interactions. For all 4 conditions, the ankle was PF during landing, but the DF condition was 28.87% less PF than the PF condition. The tmin conditions had a 23.48% shorter GCT than hmax. There were no significant main effects for jump height. The peak impact force for tmin was 22.14% greater than hmax and 19.11% greater for DF compared with PF conditions. A shorter GCT did not necessitate a smaller jump height, and a less PF foot did not lead to improvements in jump height or contact time during a depth jump from a 45-cm box. The same jump height was attained in less PF and shorter GCT conditions by larger impact forces. To decrease contact time while maintaining jump height, athletes should be instructed to "get off the ground as fast as possible." This cue seems to be more important than foot position. However, it should be acknowledged that this technique leads to larger impact forces, which should be considered when prescribing the number of foot contacts in a plyometrics program. The ability of athletes to truly land in a DF position during depth jumps is questioned and needs further investigation.

Kinetic modelling of methanol conversion to light olefins process over silicoaluminophosphate (SAPO-34) catalyst

The MTO process over SAPO_34 catalyst was modelled with the consideration of functionality against coke deposition for products distribution, consisting of 11 reactions involving 13 reaction species and used in the assessment of experimental data acquired in a fixed bed reactor in a temperature range from 400 to 460°C using weight hour space velocity (WHSV) of 1, 2 and 4gMeOHgcatalyst−1h−1 and at atmospheric pressure. The results showed that olefins carbon selectivity increases with space velocity, suggesting that the secondary reactions which take part in the MTO reaction for the paraffinic components production are reduced by decreasing contact time. Calculation of the kinetic model parameters of best fit was performed by particle swarm optimization algorithm through solving the mass conservation equations of the reaction products of the kinetic scheme. Pre-exponential factors and apparent activation energies were then calculated based on the Arrhenius equation using the optimized rate constants. The kinetic model gave a good representation of MTO experimental data at conditions close to industrial practice.

Effects of Assisted and Traditional Drop Jumps on Jumping Performance

The purpose of the present study was to evaluate the effects of assisted and traditional drop jumps on fast stretch-shortening cycle exercises in collegiate athletes. Participants were selected into one of three groups: 1) the assisted drop jump ( n=11); the traditional drop jump ( n=11); and 3) the control ( n=11). The assisted drop jump training involved drop jumps (DJs) with assistance of tubing, whereas the traditional DJ training was performed without any assistance. Prior to and at the completion of 5-week training programs, DJs from heights of both 30 (DJ30) and 60 cm (DJ60) were conducted to determine jump height, drop jump reactivity coefficient, contact time and peak ground reaction force. Both the assisted DJ and traditional DJ training programs resulted in significant ( p&lt; 0.05) improvement in jump height, DJ reactivity coefficient and decreased contact time for DJ30. Although both the assisted DJ and traditional DJ modes also increased jump height and DJ reactivity coefficient for DJ60, an enhancement of the assisted DJ training in DJ reactivity coefficient was significantly greater compared to the traditional DJ training. In addition, the assisted DJ mode allowed for a significant reduction of ground reaction force, while the traditional DJ did not change the ground reaction force. The results of this study support the inclusion of assisted DJ training into jumping sports like basketball, volleyball, and track and field jumps. Our results further suggest that incorporating assisted DJ training may be appropriate for highly trained adult athletes due to jumping performance improvement and impact landing forces reduction simultaneously.

Footstep Manipulation during Uphill Running

The present study investigated the effects of step frequency manipulation during training on slopes (2%) on biomechanical parameters at Iso-Efficiency Speed (without increasing the metabolic demand). 24 male marathon runners were randomly allocated to one of 2 training groups for 3 weeks: step frequency manipulation group (SFM, n=12) and free step frequency group (SFF, n=12). Lower limb kinematic parameters were measured before and after the 3 weeks training. The SFM group increased step length 4.30% (p<0.001), flight time 29.48% (p<0.001) and decreased contact time 14% (p<0.01). These findings coincide with characteristics of better running performances. The SFF group did not elicit such results. The results from the study could help coaches to devise training methods which could improve an athlete's performance through increasing step length. The method provided may aid faster race times for athletes.