2,247 research outputs found
In vivo evaluation of ankle kinematics and tibiotalar joint contact strains using digital volume correlation and 3Â T clinical MRI
BACKGROUND: In vivo evaluation of ankle joint biomechanics is key to investigating the effect of injuries on the mechanics of the joint and evaluating the effectiveness of treatments. The objectives of this study were to 1) investigate the kinematics and contact strains of the ankle joint and 2) to investigate the correlation between the tibiotalar joint contact strains and the prevalence of osteochondral lesions of the talus distribution. METHODS: Eight healthy human ankle joints were subjected to compressive load and 3 T MRIs were obtained before and after applying load. The MR images in combination with digital volume correlation enabled non-invasive measurement of ankle joint kinematics and tibiotalar joint contact strains in three dimensions. FINDINGS: The total translation of the calcaneus was smaller (0.48 ± 0.15 mm, p < 0.05) than the distal tibia (0.93 ± 0.16 mm) and the talus (1.03 ± 0.26 mm). These movements can produce compressive and shear joint contact strains (approaching 9%), which can cause development of lesions on joints. 87.5% of peak tensile, compressive, and shear strains in the tibiotalar joint took place in the medial and lateral zones. INTERPRETATION: The findings suggested that ankle bones translate independently from each other, and in some cases in opposite directions. These findings help explain the distribution of osteochondral lesions of the talus which have previously been observed to be in medial and lateral regions of the talar dome in 90% of cases. They also provide a reason for the central region of talar dome being less susceptible to developing osteochondral lesions
Spin and orbital dynamics through the metal-to-insulator transition in CdOsO probed with high-resolution RIXS
High-resolution resonant inelastic x-ray scattering (RIXS) measurements
(E = 46 meV) have been performed on CdOsO through the
metal-to-insulator transition (MIT). A magnetic excitation at 125 meV evolves
continuously through the MIT, in agreement with recent Raman scattering
results, and provides further confirmation for an all-in, all-out magnetic
ground state. Asymmetry of this feature is likely a result of coupling between
the electronic and magnetic degrees of freedom. We also observe a broad
continuum of interband excitations centered at 0.3 eV energy loss. This is
indicative of significant hybridization between Os 5 and O 2 states, and
concurrent itinerant nature of the system. In turn, this suggests a possible
break down of the free-ion model for CdOsO.Comment: Accepted in Physical Review B (10 pages
Flame Evolution During Type Ia Supernovae and the Deflagration Phase in the Gravitationally Confined Detonation Scenario
We develop an improved method for tracking the nuclear flame during the
deflagration phase of a Type Ia supernova, and apply it to study the variation
in outcomes expected from the gravitationally confined detonation (GCD)
paradigm. A simplified 3-stage burning model and a non-static ash state are
integrated with an artificially thickened advection-diffusion-reaction (ADR)
flame front in order to provide an accurate but highly efficient representation
of the energy release and electron capture in and after the unresolvable flame.
We demonstrate that both our ADR and energy release methods do not generate
significant acoustic noise, as has been a problem with previous ADR-based
schemes. We proceed to model aspects of the deflagration, particularly the role
of buoyancy of the hot ash, and find that our methods are reasonably
well-behaved with respect to numerical resolution. We show that if a detonation
occurs in material swept up by the material ejected by the first rising bubble
but gravitationally confined to the white dwarf (WD) surface (the GCD
paradigm), the density structure of the WD at detonation is systematically
correlated with the distance of the deflagration ignition point from the center
of the star. Coupled to a suitably stochastic ignition process, this
correlation may provide a plausible explanation for the variety of nickel
masses seen in Type Ia Supernovae.Comment: 14 pages, 10 figures, accepted to the Astrophysical Journa
A dedicated vascular access clinic for children on haemodialysis: Two years' experience
BACKGROUND: Arteriovenous fistula (AVF) formation for long-term haemodialysis in children is a niche discipline with little data for guidance. We developed a dedicated Vascular Access Clinic that is run jointly by a transplant surgeon, paediatric nephrologist, dialysis nurse and a clinical vascular scientist specialised in vascular sonography for the assessment and surveillance of AVFs. We report the experience and 2-year outcomes of this clinic. METHODS: Twelve new AVFs were formed and 11 existing AVFs were followed up for 2Â years. All children were assessed by clinical and ultrasound examination. RESULTS: During the study period 12 brachiocephalic, nine basilic vein transpositions and two radiocephalic AVFs were followed up. The median age (interquartile range) and weight of those children undergoing new AVF creation were 9.4 (interquartile 3-17) years and 26.9 (14-67) kg, respectively. Pre-operative ultrasound vascular mapping showed maximum median vein and artery diameters of 3.0 (2-5) and 2.7 (2.0-5.3) mm, respectively. Maturation scans 6 weeks after AVF formation showed a median flow of 1277 (432-2880) ml/min. Primary maturation rate was 83Â % (10/12). Assisted maturation was 100Â %, with two patients requiring a single angioplasty. For the 11 children with an existing AVF the maximum median vein diameter was 14.0 (8.0-26.0) mm, and the median flow rate was 1781 (800-2971) ml/min at a median of 153Â weeks after AVF formation. Twenty-two AVFs were used successfully for dialysis, a median kt/V of 1.97 (1.8-2.9), and urea reduction ratio of 80.7 % (79.3-86 %) was observed. One child was transplanted before the AVF was used. CONCLUSIONS: A multidisciplinary vascular clinic incorporating ultrasound assessment is key to maintaining young children on chronic haemodialysis via an AVF
First report of generalized face processing difficulties in möbius sequence.
Reverse simulation models of facial expression recognition suggest that we recognize the emotions of others by running implicit motor programmes responsible for the production of that expression. Previous work has tested this theory by examining facial expression recognition in participants with Möbius sequence, a condition characterized by congenital bilateral facial paralysis. However, a mixed pattern of findings has emerged, and it has not yet been tested whether these individuals can imagine facial expressions, a process also hypothesized to be underpinned by proprioceptive feedback from the face. We investigated this issue by examining expression recognition and imagery in six participants with Möbius sequence, and also carried out tests assessing facial identity and object recognition, as well as basic visual processing. While five of the six participants presented with expression recognition impairments, only one was impaired at the imagery of facial expressions. Further, five participants presented with other difficulties in the recognition of facial identity or objects, or in lower-level visual processing. We discuss the implications of our findings for the reverse simulation model, and suggest that facial identity recognition impairments may be more severe in the condition than has previously been noted
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