Touch Down Research Articles

Step width modification to change rearfoot eversion and medial longitudinal arch angle during walking and running in individuals with pronated feet

BackgroundIndividuals with pronated feet often experience altered foot biomechanics, leading to increased risk of lower limb injuries. Step width modification has been proposed as a potential intervention to improve foot alignment during gait. Research questionDoes modifying step width influence rearfoot eversion and medial longitudinal arch angle (MLAA) in individuals with pronated feet during walking and running? MethodsTwenty individuals with pronated feet underwent analysis during walking and running on treadmill, maintaining increased or decreased step width using real-time visual feedback. Three-dimensional motion analysis measured rearfoot eversion and MLAA during the stance phase of gait. ResultsWide step width significantly reduced peak rearfoot eversion during waking (mean difference — with normal step width — (MD) = 3.6°, p < 0.001) and running (MD = 4.4°, p < 0.001), time to peak rearfoot eversion during walking (MD = 16.6 p < 0.001) and running (MD = 13.8°, p = 0.014), rearfoot eversion at touch down (TD) during walking (MD = 1.3°, p = 0.004), rearfoot eversion excursion during running (MD = 4.3°, p < 0.001), and peak MLAA during walking (MD = 2.9°, p = 0.006) and MLAA excursion during running (MD = 4.8°, p = 0.004).By contrast, during running, narrow condition significantly increased peak rearfoot eversion (MD = 3.4°, p < 0.001). During walking, time to peak rearfoot eversion (MD = 16.1, p < 0.001), rearfoot eversion at TD (MD = 1.4°, p = 0.008), rearfoot eversion excursion (MD = 5.9°, p < 0.001), and peak MLAA (MD = 3.4°, p < 0.001) were significantly increased. SignificanceThis study highlights the potential of step width modification as a simple yet effective intervention to improve foot biomechanics in pronated feet individuals during walking and running. Further research could lead to the development of personalized strategies for pronated feet individuals.

Novel and Sensitive Touchdown Polymerase Chain Reaction Assays for the Detection of Goat and Sheep Milk Adulteration with Cow Milk.

Milk is the most consumed liquid food in the world due to its high nutritional value and relatively low cost, characteristics that make it vulnerable to adulteration. One of the most common types of milk adulteration involves the undeclared addition of cow's milk to milk from other mammalian species, such as goats, sheep, buffalo or donkeys. The incidence of such adulteration not only causes a crisis in terms of commercial market and consumer uncertainty but also poses a risk to public health, as allergies can be triggered by proteins in undeclared cow's milk. In this study, a specific qualitative touchdown (TD) PCR method was developed to detect the undeclared addition of cow's milk in goat and sheep milk based on the discrimination of the peak areas of the melting curves after the modification of bovine-specific primers. The developed methodology has high specificity for the DNA templates of other species, such as buffalos and donkeys, and is able to identify the presence of cow's milk down to 1%. Repeatability was tested at low bovine concentrations of 5% and 1% and resulted in %RSD values of 1.53-2.04 for the goat-cow assay and 2.49-7.16 for the sheep-cow assay, respectively. The application of this method to commercial goat milk samples indicated a high percentage of noncompliance in terms of labeling (50%), while a comparison of the results to rapid immunochromatographic and ELISA kits validated the excellent sensitivity and applicability of the proposed PCR methodology that was able to trace more adulterated samples. The developed assays offer the advantage of multiple detection in a single run, resulting in a cost- and time-efficient method. Future studies will focus on the applicability of these assays in dairy products such as cheese and yogurt.

DATA ANALYSIS OF COMMERCIAL AIRCRAFT LANDING ON THE RUNWAY AIRPORTS IN INDONESIA

A runway excursion is a runway safety issue in which an aircraft exits the runway improperly. Therefore, we believe it is necessary to conduct a data investigation of commercial airplanes landing at the airport in order to provide criticism, learning, and social control to airlines and air service policymakers in Indonesia so that they can become involved in protecting public transportation users, particularly those using air transportation. This study focuses on the procedural safety of commercial airplanes landing on the runway at airports in Indonesia. The data utilized for landing analysis is historical ADS-B data collected and acquired from the Flightradar24 website in 2019. The approach utilized in this study is exploratory data analysis (EDA), in which we explored the dataset to find trusted data (128 tier-1 data points). The results of this study showed that the aircraft that was the object of research was unlikely to land at the Touch Down Zone (TDZ), while the rest showed that its landing was highly likely outside the TDZ.

Adaptive locomotion: Foot strike pattern and limb mechanical stiffness while running over an obstacle

Previous studies of level running suggest runners adjust foot strike to control leg stiffness. This study aimed to determine how runners adjusted mechanical stiffness and foot strike prior to, during, and after a drop in surface height. Ten healthy subjects (5 male, 5 female; 24.32 ± 5.0 years) were video recorded as they ran on an outdoor path with a single drop in surface height (12.5 cm). Foot strike was recorded, while subject velocity, duty factor (DF), normalized maximum ground reaction force (GRFbw), vertical hip displacement (Δy), leg compression (ΔL), vertical (Kvert) and leg stiffness (Kleg), touchdown (TD) and takeoff angle (TO), and flight (Tf) and contact time (Tc) were calculated. Compared to the step before the drop, Tf, GRFbw, Kvert, Kleg, and TO increased, while Tc, DF, Δy, ΔL, and TD decreased in the step after the drop. Across trials, runners had either consistent or variable foot strike patterns. Runners using a consistent pattern most often shifted from rear to fore-foot strike in the steps before and after the drop, while those with a variable pattern showed less dramatic shifts. All parameters, except TD, were significantly different (p < 0.04) based on foot strike pattern, and comparisons between steps before and after the drop (except TD) were significantly different (p < 0.004). Runners with a variable foot strike pattern experienced smaller shifts within mechanical parameters when traveling over the drop, suggesting these runners may be able to stabilize limb mechanics on interrupted surfaces.

The Association Between Hip-Shoulder Separation Angles and Technique Characteristics in World-Class High Jumpers.

Hip-shoulder separation (H-Ssep) has been widely researched in many sporting activities (e.g., golf) to provide information on the contribution of torso rotation to performance and injury. Although it is necessary for high jumpers to generate significant long-axis rotation to successfully clear the bar, limited information exists on H-Ssep for high jump athletes. As such, this study aimed to (a) characterize the H-Ssep of world-class high jump athletes during competition, (b) determine if differences exist between male and female athletes and (c) to examine the relationship between H-Ssep and the biomechanical parameters used to describe high jump technique. Twenty-nine world-class high jumpers (17 males, 12 females) were video recorded (frame rate: 120–200 Hz) during the 2017 and 2018 World Athletics Championship finals. H-Ssep was quantified at touchdown (TD) and take-off (TO) following manual digitizing (SIMI motion) and a number of other common biomechanical parameters were computed. The observed levels of H-Ssep at TD (−46±12°) and TO (16 ±11°) were in line with those reported previously for other sports. The magnitude of H-Ssep varied between individuals and showed significant associations with other approach and take-off characteristics. Significant differences in H-Ssep were not evident between male and female athletes despite significant differences in other performance- and technique-related parameters. These findings highlight the divergent take-off characteristics of world-class performers and their reliance on hip-shoulder interactions when generating long axis rotation. Coaches should be mindful of the mechanical and physical consequences of H-Ssep when developing technical models, conditioning interventions and coaching strategies.

The ability to increase the base of support and recover stability is limited in its generalisation for different balance perturbation tasks

BackgroundThe assessment of stability recovery performance following perturbations contributes to the determination of fall resisting skills. This study investigated the association between stability recovery performances in two perturbation tasks (lean-and-release versus tripping).MethodsHealthy adults (12 young: 24 ± 3 years; 21 middle-aged: 53 ± 5 years; 11 old: 72 ± 5 years) were suddenly released from a forward-inclined position attempting to recover stability with a single step. In a second task, all participants experienced a mechanically induced trip during treadmill walking. To assess dynamic stability performance, the antero-posterior margin of stability (MoS), the base of support (BoS), and the rate of increase in BoS were determined at each foot touchdown (TD) for both tasks.ResultsOnly weak to moderate correlations in dynamic stability performance parameters were found between the two tasks (0.568 > r > 0.305, 0.001 < p < 0.04). A separation of participants according to the number of steps required to regain stability in the lean-and-release task revealed that multiple- (more than one step) compared to single-steppers showed a significantly lower MoS at TD (p = 0.003; g = 1.151), lower BoS at TD (p = 0.019; g = 0.888) and lower rate of increase in BoS until TD (p = 0.002; g = 1.212) after release. Despite these profound subgroup differences in the lean-and-release task, no differences between multiple- and single-steppers were observed in the stability recovery performance during tripping.ConclusionThe results provide evidence that the ability to effectively control dynamic stability following a sudden balance disturbance in adults across a wide age range is limited in its generalisation for different perturbation tasks.

Three-dimensional motion of the patella in French bulldogs with and without medial patellar luxation

BackgroundFrench bulldogs exhibit significantly larger femoral external rotation and abduction than other breeds. We were curious as to whether this peculiar leg kinematic affects patellar motion and/or might induce medial patellar subluxation (MPSL) or medial patellar permanent luxation (MPPL). We hypothesized that the more abducted leg posture during stance causes an unusual medial pull direction of the rectus femoris muscle during stance, and that this may facilitate the occurrence of MPSL or even MPPL during locomotion. To test our hypothesis, we analyzed existing stifle-joint X-ray-sequences collected during the treadmill walk and trot of seven adult female French bulldogs. We estimated 3D-patellar kinematics using Scientific Rotoscoping.ResultsThe three-dimensional motion of the patella comprises rotations and translations. From the seven dogs analyzed, three exhibited MPSL and one MPPL during the gait cycle. Medial patellar luxation (MPL) occurred mostly around toe-off in both gaits studied.Patellar position was generally not gait-related at the analyzed timepoints. In dogs with MPL, the patella was placed significantly more distally (p = 0.037) at touch-down (TD) and at midswing (p = 0.024), and significantly more medial at midswing (p = 0.045) compared to dogs without MPL.ConclusionsMedial patellar luxation seems to be the consequence of the far from parasagittal position of the stifle joint during stance due to a broad trunk, and a wide pelvis. This peculiar leg orientation leads to a medial sideway pull caused by the rectus femoris muscle and the quadriceps femoris and may initiate plastic deformation of the growing femur and tibia. Thus, a way to avoid MPL could be to control breeding by selecting dogs with lean bodies and narrow pelvis. Actual breeding control programs based on the orthopedic examination are susceptible to errors. Systematic errors arise from the fact that the grading system is highly dependent on the dog’s condition and the veterinarians’ ability to perform the palpation on the stifle. Based on our results, the position of the patella at TD, or even perhaps during stand might offer a possibility of an objective radioscopic diagnostic of the MPL.

Detection of Mycobacterium bovis in goat milk samples by loop-mediated isothermal amplification

Aims &amp;Objective: Mycobacterium bovis is the causative agent of bovine tuberculosis. It is also a pathogen for other animals such as goats and humans. Molecular methods are applied to detect members of the M. tuberculosis complex in different clinical samples as milk. The Loop-Mediated Isothermal Amplification (LAMP) proceeds at a constant temperature using a strand displacement reaction. LAMP does not require a thermal cycler. It is characterized by its efficiency, rapidity, high yield of final product, robustness, sensitivity and specificity. The primers are specifically designed to recognize 6 distinct regions on the target gene. The amplified product can be detected by naked eye as a white precipitate or a color change of the reaction solution.: To detect species of the Mycobacterium tuberculosis complex in goat milk samples by IS6110-LAMP Methods: Twenty goat milk samples from animals reacting to the tuberculin test were studied by IS6110-LAMP, Touch-Down (TD) IS6110 and Rv2807 PCR. These goats had been slaughtered, their organs and milk cultured. The isolates obtained were typed by spoligotyping. DNA extraction was performed using 500uL of milk sample. It was incubated with sodium dodecyl sulfate / proteinase K and treated twice with phenol:chloroform:isoamylic alcohol and once with chloroform:isoamylic alcohol. Then NaCl was added and DNA was precipitated with isopropanol and washed with ethanol. The remaining ethanol was evaporated and the pellet resuspended in water. IS6110-LAMP reaction was performed in a 25uL volume containing Bst DNA polymerase, betaine, magnesium sulfate, dNTPs, and primers (F3, B3, FIP, BIP, LF, LR). SYBR Gold solution was added inside of the cup of the tubes that were incubated at 63°C during one hour. After that the tubes were shacked and a yellowish color indicated a positive reaction. Results: While 17/20 goats were confirmed by bacteriology, no isolates were obtained from milk culture. The 17 isolates were further confirmed as M. bovis by spoligotyping. Neither NTM nor Nocordia sp. templates amplified by IS6110-LAMP. The 40 % (8/20) of the samples were IS6110-LAMP positive. There was only one discordant result between IS6110-LAMP, TD-Rv2807 and TD-IS6110. Conclusion: IS6110-LAMP is a useful tool to detect species of the M. tuberculosis complex in goat milk samples that could be implemented in laboratories with low technological complexity.

Kinematics of assisted and unassisted plyometric training of vertical jumping and rebounding in youth male football players – A six-week training study

The purpose of this study was to compare the kinematics of assisted and unassisted plyometric training of vertical jumping and rebounding activities following a six-week training intervention. 13 youth males from a professional football academy completed six weeks of either unassisted (n = 6) or band-assisted (n = 7) plyometric training sessions twice a week during their competitive season. Pre- and post-assessments of counter-movement jump (CMJ) height, 50 cm drop-jump (DJ50) ground contact time (GCT), jump height and reactive strength index (RSI), and submaximal-hopping (SMH) GCT, jump height and RSI were compared. Pre- and post-assessment ankle angle at touch-down (TD), peak flexion (PF) and mid-flight (MF) were also analysed for the submaximal-hop test only. Following training, significant main effects of time were observed for CMJ height, DJ50 GCT and MF ankle angle (p &lt; 0.05) and a significant effect of group was observed for DJ50 RSI (p &lt; 0.05). These results suggest that both unassisted and assisted plyometric training may be useful for enhancing the kinematics and technical performance of plyometric activities in a youth male football population.

Numerical Simulation of Thermal Fly-Height Control Slider Touchdown Test for Achieving Ideal Subnanometer Clearance Head Slider Touchdown Behaviors

Understanding the dynamics and instability of a thermal fly-height control (TFC) head slider close to and at touchdown (TD) on a magnetic recording disk is essential for developing a head slider with a clearance of ~ 0.5 nm to enhance the recording density of hard disk drives. This paper presents a theoretical simulation of a practical TD test, performed by continuously increasing the head protrusion according to the TFC power, and demonstrates ideal TD behaviors to be established in design guidelines for an effective head slider–suspension–disk system. The effects of the air-bearing stiffness and magnitude of disk waviness (DW) on the TD behaviors and their repeatability were extensively investigated. Comparison with the experimental TD behaviors of effective head sliders demonstrated that the different TD behaviors at different radial disk positions could be explained by the numerical TD simulation of the DW-excited response of a single-degree-of-freedom slider model. Possible reasons for the discrepancies between the experimental and simulation results in the light contact state were analyzed in detail, and a method of designing the head–disk interface conditions to achieve a head spacing of ~ 0.5 nm was developed. In addition, the deviation from the ideal TD behavior according to the DW magnitude was examined. The TD behavior of a head slider on a disk with a perfectly bonded lubricant was theoretically clarified, and the potential for realizing a head slider with reduced clearance was assessed.

Slip-induced fall-risk assessment based on regular gait pattern in older adults

Aging-associated fall-risk assessment is crucial for fall prevention. Thus, this study aimed to develop a prognostic model to predict fall-risk following an unexpected over-ground slip perturbation based on normal gait pattern in healthy older adults. 112 healthy older adults who experienced a novel slip in a safe laboratory environment were included. Their slip trial and natural walking trial immediately prior to it were analyzed. To identify the best fall-risk predictive model, gait related variables including step length, segment angles, center of mass state, and ground reaction force (GRF) were determined and inputted into a stepwise logistic regression. The optimal slip-induced fall prediction model was based on the right thigh angle at slipping foot touchdown (TD), the maximum GRF of the slipping limb after TD, and the momentum change from TD to recovery foot liftoff (LO), with an overall prediction accuracy of 75.9%, predicting 74.5% of falls (sensitivity) and 77.2% of recoveries (specificity). Conversely, a model based on clinical and demographic measures predicted 78.2% of falls and 47.4% of recoveries, resulting in a much lower overall accuracy of 62.5%. The fall-risk model based on normal gait pattern which was developed for slip-induced perturbations in healthy older adults was able to provide a high predictive accuracy. This information could provide insight about the ideal normal gait measures which could be used to contribute towards development of therapeutic strategies related to dynamic balance and fall prevention to enhance preventive interventions in populations with high-risk for slip-induced falls.

Acute exposure to a glyphosate-containing herbicide formulation inhibits Complex II and increases hydrogen peroxide in the model organism Caenorhabditis elegans

Glyphosate-based herbicides, such as Touchdown (TD) and Roundup, are among the most heavily-used herbicides in the world. While the active ingredient is generally considered non-toxic, the toxicity resulting from exposure to commercially-sold formulations is less clear. In many cases, cell cultures or various model organisms exposed to glyphosate formulations show toxicity and, in some cases, lethality. Using Caenorhabditis elegans, we assessed potential toxic mechanisms through which a highly-concentrated commercial formulation of TD promotes neurodegeneration. Following a 30-min treatment, we assayed mitochondrial electron transport chain function and reactive oxygen species (ROS) production. Initial oxygen consumption studies indicated general mitochondrial inhibition compared to controls (*p < 0.05). When Complex II activity was further assessed, inhibition was observed in all TD-treated groups (*p < 0.05). Complex IV activity, however, was not adversely affected by TD. This electron transport chain inhibition also resulted in reduced ATP levels (*p < 0.05). Furthermore, hydrogen peroxide levels, but not other ROS, were increased (*p < 0.05). Taken together, these data indicate that commercially-available formulations of TD may exert neurotoxicity through Complex II (succinate dehydrogenase) inhibition, decreased ATP levels, and increased hydrogen peroxide production.

Taping Benefits Ankle Joint Landing Kinematics in Subjects With Chronic Ankle Instability.

Although taping has been proven effective in reducing ankle sprain events in individuals with chronic ankle instability, insight into the precise working mechanism remains limited. To evaluate whether the use of taping changes ankle joint kinematics during a sagittal and frontal plane landing task in subjects with chronic ankle instability. Repeated measure design. Laboratory setting. A total of 28 participants with chronic ankle instability performed a forward and side jump landing task in a nontaped and taped condition. The taping procedure consisted of a double "figure of 6" and a medial heel lock. 3D ankle joint kinematics was registered. Statistical parametric mapping was used to assess taping effect on mean ankle joint angles and angular velocity over the landing phase. For both the forward and side jump, a less plantar flexed and a less inverted position of the ankle joint were found in the preparatory phase till around touchdown (TD) in the taped condition (P < .05). In addition, for both jump landing protocols, a decreased dorsiflexion angular velocity was found after TD (P < .05). During the side jump protocol, a brief period of increased inversion angular velocity was registered after TD (P < .05). Taping is capable of altering ankle joint kinematics prior to TD, placing the ankle joint in a less vulnerable position at TD.

Chronic exposure to a glyphosate-containing pesticide leads to mitochondrial dysfunction and increased reactive oxygen species production in Caenorhabditis elegans

Glyphosate-containing herbicides are among the most widely-used in the world. Although glyphosate itself is relatively non-toxic, growing evidence suggests that commercial herbicide formulations may lead to increased oxidative stress and mitochondrial inhibition. In order to assess these mechanisms in vivo, we chronically (24h) exposed Caenorhabditis elegans to various concentrations of the glyphosate-containing herbicide TouchDown (TD). Following TD exposure, we evaluated the function of specific mitochondrial electron transport chain complexes. Initial oxygen consumption studies demonstrated inhibition in mid- and high-TD concentration treatment groups compared to controls. Results from tetramethylrhodamine ethyl ester and ATP assays indicated reductions in the proton gradient and ATP levels, respectively. Additional studies were designed to determine whether TD exposure resulted in increased reactive oxygen species (ROS) production. Data from hydrogen peroxide, but not superoxide or hydroxyl radical, assays showed statistically significant increases in this specific ROS. Taken together, these data indicate that exposure of Caenorhabditis elegans to TD leads to mitochondrial inhibition and hydrogen peroxide production.

Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider in Proximity and Asperity Contact Regimes

The vibration characteristics of a thermal fly-height control (TFC) head slider in the proximity and asperity contact regimes attract much attention, because the head–disk spacing (HDS) must be less than 1 nm in order to increase the recording density in hard disk drives. This paper presents a numerical analysis of the microwaviness (MW)-excited vibrations in the flying head slider during the touchdown (TD) process. We first formulate the total force applied to the TFC head slider as a function of the HDS, based on rough-surface adhesion contact models and an air-bearing force model. Then, the MW-excited vibrations of a single-degree-of-freedom (DOF) slider model at TD are simulated by the Runge–Kutta method. It is found that, when the MW amplitude is less than the spacing range of static instability in the total force, the slider jumps to a contact state from a near-contact or mobile-lubricant-contact state. It then jumps to a flying state even when the head surface is protruded further by increasing the TFC power. When the MW amplitude is relatively large, a drastically large spacing variation that contains a wide range of frequency components below 100 kHz appears in the static unstable region. These calculated results can clarify the mechanisms behind a few peculiar experimental phenomena reported in the past.

Exposure of C. elegans eggs to a glyphosate-containing herbicide leads to abnormal neuronal morphology

Recent data demonstrate that chronic exposure of Caenorhabditis elegans (C. elegans) to a high-use glyphosate-containing herbicide, Touchdown (TD), potentially damages the adult nervous system. It is unknown, however, whether unhatched worms exposed to TD during the egg stage show abnormal neurodevelopment post-hatching. Therefore, we investigated whether early treatment with TD leads to aberrant neuronal or neurite development in C. elegans. Studies were completed in three different worm strains with green fluorescent protein (GFP)-tagged neurons to facilitate visual neuronal assessment. Initially, eggs from C. elegans with all neurons tagged with GFP were chronically exposed to TD. Visual inspection suggested decreased neurite projections associated with ventral nerve cord neurons. Data analysis showed a statistically significant decrease in overall green pixel numbers at the fourth larval (L4) stage (*p<0.05). We further investigated whether specific neuronal populations were preferentially vulnerable to TD by treating eggs from worms that had all dopaminergic (DAergic) or γ-aminobutyric acid (GABAergic) neurons tagged with GFP. As before, green pixel number associated with these discrete neuronal populations was analyzed at multiple larval stages. Data analysis indicated statistically significant decreases in pixel number associated with DAergic, but not GABAergic, neurons (***p<0.001) at all larval stages. Finally, statistically significant decreases (at the first larval stage, L1) or increases (at the fourth larval stage, L4) in superoxide levels, a developmental signaling molecule, were detected (*p<0.05). These data suggest that early exposure to TD may impair neuronal development, perhaps through superoxide perturbation. Since toxic insults during development may late render individuals more vulnerable to neurodegenerative diseases in adulthood, these studies provide some of the first evidence in this model organism that early exposure to TD may adversely affect the developing nervous system.

A Piecewise-Linear Approximation of the Canonical Spring-Loaded Inverted Pendulum Model of Legged Locomotion

Here, we introduce and analyze a novel approximation of the well-established and widely used spring-loaded inverted pendulum (SLIP) model of legged locomotion, which has made several validated predictions of the center-of-mass (CoM) or point-mass motions of animal and robot running. Due to nonlinear stance equations in the existing SLIP model, many linear-based systems theories, analytical tools, and corresponding control strategies cannot be readily applied. In order to provide a significant simplification in the use and analysis of the SLIP model of locomotion, here we develop a novel piecewise-linear, time-invariant approximation. We show that a piecewise-linear system, with the only nonlinearity due to the switching event between stance and flight phases, can predict all the bifurcation features of the established nonlinear SLIP model over the entire three-dimensional model parameter space. Rather than precisely fitting only one particular solution, this approximation is made to quantitatively approximate the entire solution space of the SLIP model and capture all key aspects of solution bifurcation behavior and parametric sensitivity of the original SLIP model. Further, we provide an entirely closed-form solution for the stance trajectory as well as the system states at the end of stance, in terms of common functions that are easy to code and compute. Overall, the closed-form solution is found to be significantly faster than numerical integration when implemented using both matlab and c++. We also provide a closed-form analytical stride map, which is a Poincaré return section from touchdown (TD) to next TD event. This is the simplest closed-form approximate stride mapping yet developed for the SLIP model, enabling ease of analysis and numerical coding, and reducing computational time. The approximate piecewise-linear SLIP model presented here is a significant simplification over previous SLIP-based models and could enable more rapid development of legged locomotion theory, numerical simulations, and controllers.

Study of Head-Disk Interface Characterization Using Touchdown Sensor and Electromagnetic Signal in Hard Disk Drives

With the introduction of thermal fly-height control sliders, the local head-disk clearance can be reduced to a range from $\sim10$ nm to contact. This actively controlled touchdown (TD) has been used as a way to study the head–disk interface (HDI), the characteristics of which greatly affect the areal density and reliability of drives. In this paper, a high spatial resolution TD study is performed at the drive level using TD sensor signals and head-media spacing signals. Different flying stages, including passive flying, TD transition, and over push modulation, are identified from the experimental results. A correlation between the aforementioned signals at the passive flying stage is found to represent the disk surface property. The passive flying stage and over push modulation stage of TD are further analyzed in both the time and frequency domains. By establishing a correlation between the fly height and the temperature response, we can provide insight into the heat transfer model for the HDI.

Modulation of reactive response to slip-like perturbations: effect of explicit cues on paretic versus non-paretic side stepping and fall-risk.

This study aimed to examine the effect of explicit cuing on reactive stepping with the paretic limb during slip-like perturbations in stroke survivors and to identify differences in postural stability and fall-risk while stepping with either limb. Eleven chronic hemiparetic stroke survivors received slip-like stance perturbations in no-cue (implicit, no instructions) and cued (explicit, instructions to step with paretic limb) conditions. Frequency of stepping with the paretic limb was recorded. Differences between non-paretic and paretic steps for falls, number of compensatory steps, relative center-of-mass position (X COM/BOS), and velocity (Ẋ(COM/BOS)), and vertical limb support (hip descent-Z hip) were analyzed. Stepping with the paretic limb increased from 6% in no-cue condition to 42% in cued condition with no significant difference in number of falls and steps regardless of stepping limb. At liftoff of the compensatory step, stability was greater (anterior X COM/BOS) with paretic than non-paretic limb stepping whereas, at touchdown (TD) of the step, stability with paretic limb reduced (posterior X COM/BOS and Ẋ(COM/BOS)) due to a smaller compensatory step taken with the paretic versus non-paretic limb. There was no significant difference in peak Z hip regardless of stepping limb; however, the timing of peak Z hip differed (occuring prior to TD during non-paretic stepping and post-TD during paretic stepping). Thus, fall onset was earlier with non-paretic versus paretic stepping. The results support that explicit cueing can facilitate initiation of reactive step from the paretic limb as compared with the no-cue condition. Stepping with the paretic limb in the cued condition however altered time of fall onset. Regardless of the stepping side, individuals demonstrated a fall risk suggesting the need for interventions focusing on reactive step training with both the limbs.

Dynamic behaviors of conventional SCR and lazy-wave SCR for FPSOs in deepwater

The general and detailed structural/dynamic performances of steel catenary risers (SCRs) and lazy-wave steel catenary risers (LWSCRs) are directly compared under the same storm and floater (deepwater turret-moored FPSO) conditions. Their global performances are simulated by using the hull/mooring/riser fully-coupled dynamic analysis program developed by authors. This study proves that conventional SCRs connected to the FPSO hull exhibit significant dynamic responses and negative tensions, which may induce large structural stress amplification, local dynamic buckling, and serious fatigue damage at the members nearby TD (touch-down) region. The generation, propagation, and decay of the elastic waves generated by the temporal dynamic buckling are investigated in detail. On the other hand, LWSCRs can eliminate the local dynamic buckling for the same floater/storm condition and significantly reduce the stress level and fatigue damage near TDZ (touch-down zone) due to the motion isolation effect. It is because the modified shape with intermediate sag and arch portions can effectively isolate and absorb the downward riser motion. Therefore, LWSCRs can effectively be used for FPSO under very harsh environmental conditions. Despite the big advantage in dynamic characteristics, LWSCR is generally more expensive, more difficult to design, and may have slugging problem for internal flows.