Photoheliograph study for the Apollo telescope mount

Photoheliograph study for Apollo telescope moun

Assessment of joint kinetics in elite sprint cyclists

Sprint cycling requires the production of explosive muscle power outputs up to very high pedalling rates. The ability to assess muscular function through the course of the sprint would aid training practices for high-level performers. Inverse dynamics provides a non-invasive means of estimating the net muscle actions acting across any joint contributing to movement. However, analysis of joint kinetics requires motion-capture techniques that present some unique challenges for cycling. This thesis presents three studies investigating the application of a custom-designed force pedal system to examine the joint kinetics of elite trained track sprint cyclists. To provide the basis for selecting appropriate testing procedures, study one evaluated differences between two- and three- dimensional techniques while assessing joint kinetics of seated and standing sprint cycling at optimal cadence (the cadence where peak power is delivered). Study two examined the impact of cadence and seating position on joint kinetics, while determining testing reliability using the three-dimensional process. Coefficients of variation were established for between- and within- days repetitions of sprint performance at optimal cadence, and cadences 30% lower and 30% higher, in both seated and standing positions. Study three compared joint kinetics of sprint cycling performance with commonly-applied resistance-training exercises in an elite cycling cohort, in order to better understand training specificity. Joint-specific torque-angular velocity relationships were established from seated and standing sprinting at three cadences and the clean exercise at three loads, with other strength-based exercises examined at maximal load only. Study one determined that flattened projections of the 3D motion into 2D resulted in significant differences in joint powers calculated in the sagittal-plane. When using 2D methods, knee joint power was significantly lower and hip transfer power significantly greater, while hip range of motion was lower and the angle where hip peak power occurred later in the crank cycle. These results indicate that 3D processes should be used where evaluation of absolute values are important, although 2D processes may still be acceptable where relative differences are being assessed. It was observed in Study two that, while crank and total muscle power upheld a quadratic power-cadence relationship, joint-specific powers were uniquely related to cadence and riding position. Crank and joint-specific optimal cadences for power production were distinctly different. The hip displayed a linear maximum power-cadence relationship in seated but quadratic in standing position, with the reverse observed at the knee. Ankle and hip transfer powers both linearly declined with cadence irrespective riding position. In such a case, joint-specific power contribution, hence distribution of muscular effort, cannot be directly inferred from power assessed at the crank. Reliability was highest for crank and total muscle power, particularly at the riders’ optimal cadence. Reliability of joint powers were somewhat lower and uniquely dependent on joint, joint action and trial condition. Results indicate that external power output at the crank is relatively stable across sprints, despite variation in the underlying muscular contributions. Results of study three showed equivalence in the torque-angular velocity relationships at the hip in sprint cycling and different phases of the clean. No such relationship was evident at the knee or ankle. In contrast to the negative linear relationships observed in all other conditions, ankle mechanics in sprinting showed a positive linear relationship highlighting a distinct functional role of this joint. Highest maximal torques at the hip and knee were observed during unilateral single rack pull and step-up exercises, respectively, supporting their efficacy for improving the maximum strength characteristics at these joints. The results of this thesis indicate that joint kinetics are an effective means of assessing muscular performance in highly-trained track sprint cyclists and provide information on the underlying strategies that could not be assessed through conventional testing of power at the crank. The use of 3D processes is recommended where accuracy of assessment and absolute values are important. Flexibility of 2D processes may be advantageous in field-based settings and may be acceptable where only relative change is of interest. High reliability of 3D testing supports its use in monitoring of athletes, with the reliability data presented in this thesis providing an indication of the smallest meaningful changes in various trial conditions. Low coefficients of variation observed in crank and muscle power terms, despite greater variation in joint powers, suggest motor control strategies dynamically respond to task conditions while maintaining a consistent external power. Resistance exercises are seen to display jointspecific profiles that characterise relative hip- or knee- dominance. The comparison of these profiles with those of sprint cycling can help inform exercise selection for strength development of elite riders. The ability to monitor changes and target training intervention at joint level provides a unique approach to athlete development. Outcomes of this thesis support the practical application of joint kinetic assessment in aiding training practices to the highest levels of competition in track sprint cycling. Indeed, the equipment, methods and knowledge obtained from this research is currently applied in the preparation of Australia’s best sprint cyclists

Cassini atmospheric chemistry mapper. Volume 1. Investigation and technical plan

The Cassini Atmospheric Chemistry Mapper (ACM) enables a broad range of atmospheric science investigations for Saturn and Titan by providing high spectral and spatial resolution mapping and occultation capabilities at 3 and 5 microns. ACM can directly address the major atmospheric science objectives for Saturn and for Titan, as defined by the Announcement of Opportunity, with pivotal diagnostic measurements not accessible to any other proposed Cassini instrument. ACM determines mixing ratios for atmospheric molecules from spectral line profiles for an important and extensive volume of the atmosphere of Saturn (and Jupiter). Spatial and vertical profiles of disequilibrium species abundances define Saturn's deep atmosphere, its chemistry, and its vertical transport phenomena. ACM spectral maps provide a unique means to interpret atmospheric conditions in the deep (approximately 1000 bar) atmosphere of Saturn. Deep chemistry and vertical transport is inferred from the vertical and horizontal distribution of a series of disequilibrium species. Solar occultations provide a method to bridge the altitude range in Saturn's (and Titan's) atmosphere that is not accessible to radio science, thermal infrared, and UV spectroscopy with temperature measurements to plus or minus 2K from the analysis of molecular line ratios and to attain an high sensitivity for low-abundance chemical species in the very large column densities that may be achieved during occultations for Saturn. For Titan, ACM solar occultations yield very well resolved (1/6 scale height) vertical mixing ratios column abundances for atmospheric molecular constituents. Occultations also provide for detecting abundant species very high in the upper atmosphere, while at greater depths, detecting the isotopes of C and O, constraining the production mechanisms, and/or sources for the above species. ACM measures the vertical and horizontal distribution of aerosols via their opacity at 3 microns and, particularly, at 5 microns. ACM recovers spatially-resolved atmospheric temperatures in Titan's troposphere via 3- and 5-microns spectral transitions. Together, the mixing ratio profiles and the aerosol distributions are utilized to investigate the photochemistry of the stratosphere and consequent formation processes for aerosols. Finally, ring opacities, observed during solar occultations and in reflected sunlight, provide a measurement of the particle size and distribution of ring material. ACM will be the first high spectral resolution mapping spectrometer on an outer planet mission for atmospheric studies while retaining a high resolution spatial mapping capability. ACM, thus, opens an entirely new range of orbital scientific studies of the origin, physio-chemical evolution and structure of the Saturn and Titan atmospheres. ACM provides high angular resolution spectral maps, viewing nadir and near-limb thermal radiation and reflected sunlight; sounds planetary limbs, spatially resolving vertical profiles to several atmospheric scale heights; and measures solar occultations, mapping both atmospheres and rings. ACM's high spectral and spatial resolution mapping capability is achieved with a simplified Fourier Transform spectrometer with a no-moving parts, physically compact design. ACM's simplicity guarantees an inherent stability essential for reliable performance throughout the lengthy Cassini Orbiter mission

Effects of Lateral Shoe Wedges and Toe-in Foot Progression Angles on the Biomechanics of Knee Osteoarthritis during Stationary Cycling

Exercise is important for individuals with knee osteoarthritis (OA) but certain activities can be painful and discourage participation. Cycling is commonly prescribed for OA but practically no previous literature exists. Due to their altered knee kinematics, OA patients may be at greater risk of OA progression or other knee injuries during cycling. The purpose of Study One was to investigate the effects of lateral wedges on knee joint biomechanics and pain in patients with medial compartment knee OA. The purpose of Study Two was to investigate the effects of toe-in foot progression angles on the same variables. Thirteen OA subjects and 11 healthy subjects participated. A motion analysis system and custom instrumented pedal was used to collect 5 pedal cycles of kinematics and kinetics during 2 minutes of cycling in one neutral and two lateral wedge conditions (5° and 10°) for Study One and 2 toe-in conditions (5° and 10°) for Study Two. Subjects pedaled at 60 RPM and 80 watts and rated their knee pain on a visual analog scale. Study One: There was a 22% decrease in the knee abduction moment with the 10° wedge. This finding was not accompanied by a decrease in knee adduction angle or pain. Additionally, there was an increase in vertical and horizontal PRF which may negate the advantages of the decreased KAM. Study Two: For the OA subjects, there was a 61% (2.7°) and a 73% (3.2°) decrease in peak knee adduction angle compared to neutral. This finding was not accompanied by a decrease in pain or KAM because of high inter-subject variability. A simple linear regression showed a positive correlation between Kelgren-Lawrence (K/L) score and both peak knee adduction angle and KAM. For OA patients, cycling with a 10° lateral wedge or a decreased foot progression angle may be beneficial in slowing the progression of OA or minimizing other knee injuries. Patients with a higher K/L score may have greater risk of injury. More research is needed to investigate the joint contact forces as well as long term effects of riding with wedges or toe-in foot angles

Efficacy of a Cycling Intervention with Pedal Reaction Force Augmented Feedback on Reducing Inter-Limb Asymmetries in Patients with Unilateral Total Knee Arthroplasty

Fifteen patients with unilateral total knee arthroplasty (TKA) performed cycling at two workates (80 W and 100 W) and two walking conditions (preferred and fast speeds). Ten of these patients of TKA also participated in a short-term cycling intervention paired with visual augmented feedback of vertical pedal reaction forces for six sessions over two-three weeks. These ten patients of TKA participated in a 2nd post-training testing session. Study One compared the knee joint biomechanics for all fifteen participants during stationary cycling to ascertain if any biomechanical asymmetries may be present. The replaced limbs displayed significantly lower peak knee extension moment (KEM) and vertical pedal reaction (PRF) compared to non-replaced limbs during stationary cycling. Study Two examined the effect of the short-term cycling intervention on the knee joint biomechanics and biomechanical asymmetries during stationary cycling for the selected ten patients of TKA. The short-term cycling intervention had no significant effect for peak KEM or vertical PRF asymmetries during stationary cycling. Peak KEM asymmetries did decrease by 10% and 9.9% at 80 W and 100 W, respectively. Study Three examined the effect of the short-term cycling intervention on the knee joint biomechanics and biomechanical asymmetries during gait. Similarly, the short-term cycling intervention had no effect on peak KEM asymmetries and vertical ground reaction force (GRF) asymmetries during both walking condition. Study Four compared the estimated tibiofemoral joint forces during stationary cycling between the replaced and non-replaced limbs of the fifteen patients of TKA. The replaced limbs also had lower medical tibiofemoral contact force (MCF) compared to the non-replaced limbs during stationary cycling at 80 W. The non-replaced limb had greater peak MCF compared to the lateral tibiofemoral contact force (LCF). Unilateral TKA patients cycling with similar reductions of KEM in their replaced limbs. During cycling, there was no difference between MCF and LCF for the replaced limbs, potentially indicating a successful operation to restore knee joint alignment. In summary, the use of a short-term cycling intervention with augmented feedback for six sessions were not significantly beneficial for addressing KEM asymmetries in both cycling and gait. However, the 10% reductions of peak KEM asymmetries may indicate some clinical benefits of this intervention. Future studies should examine similar interventions with an increased number of training sessions