709 research outputs found
The influence of the mechanical properties of trans-tibial prostheses on amputee performance
Achieving the required functionality of a trans-tibial prosthesis during the stance phase ofgait (e.g., shock absorption, close to normal roll-over characteristics, and smooth transitioninto swing) depends on the "Amputee Independent Prosthesis Properties" (AIPP), definedhere as the mechanical properties of the prosthetic components distal to the socket thatdirectly influence the performance of the amputee. Accordingly, if research studies are toinform the design of better prostheses, AIPP must be a primary consideration. Therefore, theobjectives of this PhD study were: 1) develop a standardised method of AIPPcharacterisation, and 2) investigate the effects of AIPP on amputee performance throughhuman performance testing.For the first objective, a modified version of the roll-over shape model, referred to as theSalford AIPP model, was developed in order to characterise the mechanical properties of atrans-tibial prosthesis (i.e., foot and pylon). A custom-built test-rig was built in order tomeasure the parameters of this model.For the second objective, a series of human performance studies were conducted whichmeasured the biomechanical, physiological, and subjective performance of five amputeesduring four walking conditions: self-selected walking speed (SSWS) on the level, fast walkingspeed on the level, SSWS on a 5% grade incline, and SSWS on a 5% grade decline. A custombuiltfoot-ankle mechanism allowed for independent modulation of the prosthetic plantarand dorsiflexion stiffness. Four combinations of plantar and dorsiflexion stiffness weretested during each of the four walking conditions.Results indicated that dorsiflexion stiffness is a dominant factor in trans-tibial amputee gaitperformance and decreased stiffness improved performance (e.g., increased gait symmetryand reduced metabolic energy expenditure). However, future work on identifying effectiveAIPP for improved gait performance must involve amputee gait simulation, in which resultsfrom this study may serve as a means of validation
The effects of transverse rotation angle on compression and effective lever arm of prosthetic feet during simulated stance
Background and Aim: Unlike sagittal plane prosthesis alignment, few studies have observed the effects of transverse plane alignment on gait and prosthesis behaviour. Changes in transverse plane rotation angle will rotate the points of loading on the prosthesis during stance and may alter its mechanical behaviour. This study observed the effects of increasing the external transverse plane rotation angle, or toe-out, on foot compression and effective lever arm of three commonly prescribed prosthetic feet.
Technique: The roll-over shape of a SACH, Flex, and single-axis foot was measured at four external rotation angle conditions (0°, 5°, 7°, and 12° relative to neutral). Differences in foot compression between conditions were measured as average distance between roll-over shapes.
Discussion: Increasing the transverse plane rotation angle did not affect foot compression. However, it did affect the effective lever arm, which was maximised with the 5° condition, although differences between conditions were small
Stance phase mechanical characterization of transtibial prostheses distal to the socket : a review
Achieving the required functionality of a trans-tibial prosthesis during the stance phase
of gait (e.g., shock absorption, close to normal roll-over characteristics, and smooth
transition into swing) depends on the âAmputee Independent Prosthesis Propertiesâ
(AIPPs), defined here as the mechanical properties of the prosthesis that directly
influence the performance of the amputee. Accordingly, if research studies are to
advance the design of prostheses to achieve improved user performance, AIPPs must
be a primary consideration. However, the majority of reported studies can be
categorized as either human performance testing of commercial prosthetic components
or AIPP characterization; and only in a few notable cases have authors reported
studies in which these two approaches are combined. Moreover, very little consistency
exists in the current methods used for AIPP characterization, thus making comparisons
between the results of such studies very difficult. This paper introduces a framework for
studying prosthesis design, which includes AIPP characterization, human performance
and/or gait simulation studies, and detailed design. This framework provides a structure
for reviewing previous approaches to AIPP characterization, discussing both their
merits and shortcomings, and their use in previous experimental and simulation
studies. For the purposes of this review, stance phase AIPP models have been
categorized as either lumped parameter or roll-over shape based
Ultrasensitive force and displacement detection using trapped ions
The ability to detect extremely small forces is vital for a variety of
disciplines including precision spin-resonance imaging, microscopy, and tests
of fundamental physical phenomena. Current force-detection sensitivity limits
have surpassed 1 (atto ) through coupling of micro or
nanofabricated mechanical resonators to a variety of physical systems including
single-electron transistors, superconducting microwave cavities, and individual
spins. These experiments have allowed for probing studies of a variety of
phenomena, but sensitivity requirements are ever-increasing as new regimes of
physical interactions are considered. Here we show that trapped atomic ions are
exquisitely sensitive force detectors, with a measured sensitivity more than
three orders of magnitude better than existing reports. We demonstrate
detection of forces as small as 174 (yocto ), with a
sensitivity 390 using crystals of Be
ions in a Penning trap. Our technique is based on the excitation of normal
motional modes in an ion trap by externally applied electric fields, detection
via and phase-coherent Doppler velocimetry, which allows for the discrimination
of ion motion with amplitudes on the scale of nanometers. These experimental
results and extracted force-detection sensitivities in the single-ion limit
validate proposals suggesting that trapped atomic ions are capable of detecting
of forces with sensitivity approaching 1 . We anticipate that
this demonstration will be strongly motivational for the development of a new
class of deployable trapped-ion-based sensors, and will permit scientists to
access new regimes in materials science.Comment: Expanded introduction and analysis. Methods section added. Subject to
press embarg
Impacts of urbanisation on the native avifauna of Perth, Western Australia
Urban development either eliminates, or severely fragments, native vegetation, and therefore alters the distribution and abundance of species that depend on it for habitat. We assessed the impact of urban development on bird communities at 121 sites in and around Perth, Western Australia. Based on data from community surveys, at least 83 % of 65 landbirds were found to be dependent, in some way, on the presence of native vegetation. For three groups of species defined by specific patterns of habitat use (bushland birds), there were sufficient data to show that species occurrences declined as the landscape changed from variegated to fragmented to relictual, according to the percentage of vegetation cover remaining. For three other groups (urban birds) species occurrences were either unrelated to the amount of vegetation cover, or increased as vegetation cover declined. In order to maximise the chances of retaining avian diversity when planning for broad-scale changes in land-use (i.e. clearing native vegetation for housing or industrial development), land planners should aim for a mosaic of variegated urban landscapes (\u3e60 % vegetation retention) set amongst the fragmented and relictual urban landscapes (% vegetation retention) that are characteristic of most cities and their suburbs. Management actions for conserving remnant biota within fragmented urban landscapes should concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building awareness among the general public of the conservation value of remnant native vegetation
Upper limb activity in myoelectric prosthesis users is biased towards the intact limb and appears unrelated to goal-directed task performance
Studies of the effectiveness of prosthetic hands involve assessing user performance on functional tasks in the lab/clinic, sometimes combined with self-report of real-world use. In this paper we compare real-world upper limb activity between a group of 20 myoelectric prosthesis users and 20 anatomically intact adults. Activity was measured from wrist-worn accelerometers over a 7-day period. The temporal patterns in upper limb activity are presented and the balance of activity between the two limbs quantified. We also evaluated the prosthesis usersâ performance on a goal-directed task, characterised using measures including task success rate, completion time, gaze behaviour patterns, and kinematics (e.g. variability and patterns in hand aperture). Prosthesis users were heavily reliant on their intact limb during everyday life, in contrast to anatomically intact adults who demonstrated similar reliance on both upper limbs. There was no significant correlation between the amount of time a prosthesis was worn and reliance on the intact limb, and there was no significant correlation between either of these measures and any of the assessed kinematic and gaze-related measures of performance. We found participants who had been prescribed a prosthesis for longer to demonstrate more symmetry in their overall upper limb activity, although this was not reflected in the symmetry of unilateral limb use. With the exception of previously published case studies, this is the first report of real world upper limb activity in myoelectric prosthesis users and confirms the widely held belief that users are heavily reliant on their intact limb
Multi-Phase Sputtered TiO2-Induced CurrentâVoltage Distortion in Sb2Se3 Solar Cells
Despite the recent success of CdS/Sb2Se3 heterojunction devices, cadmium toxicity, parasitic absorption from the relatively narrow CdS band gap (2.4 eV) and multiple reports of inter-diffusion at the interface forming Cd(S,Se) and Sb2(S,Se)3 phases, present significant limitations to this device architecture. Among the options for alternative partner layers in antimony chalcogenide solar cells, the wide band gap, non-toxic titanium dioxide (TiO2) has demonstrated the most promise. It is generally accepted that the anatase phase of the polymorphic TiO2 is preferred, although there is currently an absence of analysis with regard to phase influence on device performance. This work reports approaches to distinguish between TiO2 phases using both surface and bulk characterization methods. A device fabricated with a radio frequency (RF) magnetron sputtered rutile-TiO2 window layer (FTO/TiO2/Sb2Se3/P3HT/Au) achieved an efficiency of 6.88% and near-record shortâcircuit current density (Jsc) of 32.44 mA cmâ2, which is comparable to established solution based TiO2 fabrication methods that produced a highly anatase-TiO2 partner layer and a 6.91% efficiency device. The sputtered method introduces reproducibility challenges via the enhancement of interfacial charge barriers in multi-phase TiO2 films with a rutile surface and anatase bulk. This is shown to introduce severe S-shaped currentâvoltage (JâV) distortion and a drastic fillâfactor (FF reduction in these devices
Impact of Lack of Breast Feeding during Neonatal Age on the Development of Clinical Signs of Pneumonia and Hypoxemia in Young Infants with Diarrhea
Hypoxemia is a grave sequel of pneumonia, and an important predictor of a fatal outcome. Pneumonia in the neonatal period is often associated with lack of breast feeding. However, there is no published report on the impact of the cessation of breast feeding in the neonatal period on the development of pneumonia and hypoxemia. The purpose of our study was to assess the impact of non-breast feeding or stopping breast feeding during the neonatal period (henceforth to be referred to as non-breast fed) on clinical features of pneumonia and hypoxemia in 0-6-month-old infants with diarrhea admitted to an urban hospital in Bangladesh.We prospectively enrolled all infants (nâ=â107) aged 0 to 6 months who were admitted to the Special Care Ward (SCW) of the Dhaka Hospital of the International Centre for Diarrhoeal Disease Research Bangladesh (ICDDR,B) with diarrhea and pneumonia from September 2007 through December 2007.We compared the clinical features of pneumonia and hypoxemia of breast fed infants (nâ=â34) with those who were non-breast fed (nâ=â73).The median (inter-quartile range) duration of hypoxemia (hours) in non-breast-feds was longer than breast-fed infants [0.0 (0.0, 12.0) vs. 12.0 (0.0, 21.75); pâ=â0.021]. After adjusting for potential confounders such as inability to drink, fever, head nodding, cyanosis, grunting respiration, and lower chest wall in drawing, the non-breast-fed infants with pneumonia along with diarrhea had a higher probability of cough (OR 9.09; CI 1.34-61.71; pâ=â0.024), hypoxemia (OR 3.32; CI 1.23-8.93; pâ=â0.017), and severe undernutrition (OR 3.42; CI 1.29-9.12; pâ=â0.014).Non-breast feeding or cessation of breast feeding during the neonatal period may substantially increase the incidence of severe malnutrition, incidence of cough, and both the incidence and duration of hypoxemia in young infants presenting with pneumonia and diarrhea. The findings emphasize the paramount importance of the continuation of breast feeding in the neonatal period and early infancy
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