Lessons from dynamic cadaver and invasive bone pin studies: do we know how the foot really moves during gait?

Background: This paper provides a summary of a Keynote lecture delivered at the 2009 Australasian Podiatry Conference. The aim of the paper is to review recent research that has adopted dynamic cadaver and invasive kinematics research approaches to better understand foot and ankle kinematics during gait. It is not intended to systematically cover all literature related to foot and ankle kinematics (such as research using surface mounted markers). Since the paper is based on a keynote presentation its focuses on the authors own experiences and work in the main, drawing on the work of others where appropriate Methods: Two approaches to the problem of accessing and measuring the kinematics of individual anatomical structures in the foot have been taken, (i) static and dynamic cadaver models, and (ii) invasive in-vivo research. Cadaver models offer the advantage that there is complete access to all the tissues of the foot, but the cadaver must be manipulated and loaded in a manner which replicates how the foot would have performed when in-vivo. The key value of invasive in-vivo foot kinematics research is the validity of the description of foot kinematics, but the key difficulty is how generalisable this data is to the wider population. Results: Through these techniques a great deal has been learnt. We better understand the valuable contribution mid and forefoot joints make to foot biomechanics, and how the ankle and subtalar joints can have almost comparable roles. Variation between people in foot kinematics is high and normal. This includes variation in how specific joints move and how combinations of joints move. The foot continues to demonstrate its flexibility in enabling us to get from A to B via a large number of different kinematic solutions. Conclusion: Rather than continue to apply a poorly founded model of foot type whose basis is to make all feet meet criteria for the mechanical 'ideal' or 'normal' foot, we should embrace variation between feet and identify it as an opportunity to develop patient-specific clinical models of foot function

Multipayload interferometric wave vector determination of auroral hiss

We extend traditional, single payload, interferometric techniques to a multiple payload sounding rocket mission, and apply these techniques to measure the parallel and perpendicular wavelength of auroral VLF hiss from 8 kHz–20 kHz. We model the wavelength distribution of auroral hiss as a cone at a fixed angle with respect to the magnetic field that is isotropically distributed in the perpendicular plane. We apply this model to calculate the interferometric observables, coherency and phase, for a sounding rocket mission whose wave electric field receivers are on payloads that are separated 2–3 km along the magnetic field and 55–200 m across the magnetic field. Using an interferometer formed by comparing the collinear sphere-to-skin electric field antennas on a single payload, we estimate a lower limit on the perpendicular wavelength of VLF hiss of ∼60 m. Analysis of coherency and phase due to this conical wave vector distribution for a multipayload interferometer reveals the existence of a spin dependent coherency pattern. From this coherency pattern we generate an upper limit perpendicular wavelength estimate for VLF hiss of ∼350 m. The inter-payload phase gives an accurate estimate of the parallel wavelength of ∼6000–8000 m. This parallel wavelength is combined with the lower (upper) limit perpendicular wavelength estimates to generate upper (lower) limits on wave-normal angle. These limits are each within one degree of the predicted electrostatic whistler wave resonance cone angle verifying that VLF hiss propagates on this resonance cone

Hyperfine-structure study in the P sequence of 23 Na using quantum-beam spectroscopy

Describes use of the quantum-beat method to study hyperfine structure in the 5 2 P 3/2 and 6 2 P 3/2 states of 23 Na. A pulsed dye laser, frequency-doubled into the UV region, was used to excite sodium atoms abruptly in a beam. The fluorescent light was recorded with a fast transient digitiser, interfaced to a micro-computer. Theoretical calculations using many-body perturbation theory were performed for the entire P sequence measured so far, taking polarisation and correlation effects into account separately. Very good agreement between experimental and theoretical values was obtained

Laplacian Growth, Elliptic Growth, and Singularities of the Schwarz Potential

The Schwarz function has played an elegant role in understanding and in generating new examples of exact solutions to the Laplacian growth (or "Hele- Shaw") problem in the plane. The guiding principle in this connection is the fact that "non-physical" singularities in the "oil domain" of the Schwarz function are stationary, and the "physical" singularities obey simple dynamics. We give an elementary proof that the same holds in any number of dimensions for the Schwarz potential, introduced by D. Khavinson and H. S. Shapiro [17] (1989). A generalization is also given for the so-called "elliptic growth" problem by defining a generalized Schwarz potential. New exact solutions are constructed, and we solve inverse problems of describing the driving singularities of a given flow. We demonstrate, by example, how \mathbb{C}^n - techniques can be used to locate the singularity set of the Schwarz potential. One of our methods is to prolong available local extension theorems by constructing "globalizing families". We make three conjectures in potential theory relating to our investigation

Experimental and theoretical lifetimes and transition probabilities in Sb I

We present experimental atomic lifetimes for 12 levels in Sb I, out of which seven are reported for the first time. The levels belong to the 5p$^2$($^3$P)6s $^{2}$P, $^{4}$P and 5p$^2$($^3$P)5d $^{4}$P, $^{4}$F and $^{2}$F terms. The lifetimes were measured using time-resolved laser-induced fluorescence. In addition, we report new calculations of transition probabilities in Sb I using a Multiconfigurational Dirac-Hartree-Fock method. The physical model being tested through comparisons between theoretical and experimental lifetimes for 5d and 6s levels. The lifetimes of the 5d $^4$F$_{3/2, 5/2, 7/2}$ levels (19.5, 7.8 and 54 ns, respectively) depend strongly on the $J$-value. This is explained by different degrees of level mixing for the different levels in the $^4$F term.Comment: 10 page

Multi-payload measurement of transverse velocity shears in the topside ionosphere

Using a multi-payload sounding rocket mission, we present the first direct measurement of velocity shear in the topside auroral ionosphere. In regions of large, ∼200 mV/m, transient electric fields we directly measure differences in the plasma drift velocity. From these differences, shear frequencies reaching ±6Hz are measured. These directly measured shears are compared with the shear inferred from single payload measurements. It is shown this traditional measurement of shear overestimates the shear frequency by a factor of two for this event, highlighting the importance of the temporal component of near-DC electric field structures. Coincident with these strong fields and shears are enhanced emissions of broadband, extremely low frequency (BB-ELF) plasma waves, and a narrowband wave emission near the H+-O+bi-ion resonant frequency

The moisture effect on 223Ra and 224Ra measurements using Mn-cartridges

Important processes in the ocean can be evaluated with radioactive nuclides, including radium isotopes. An approach for quantifying radium isotopes in seawater with in-situ pumps has been developed in advance of the GEOTRACES program [1]. Precise measurements of 223Ra and 224Ra by means of the delayed coincidence counting system (RaDeCC) [2] are dependent on the moisture content of the medium [3]. In order to verify the optimum moisture content for this new approach, a set of measurements of the Mn-cartridge standards under different moisture conditions was conducted, as this was done previously for acrylic fiber. At a time, an amount of water equivalent to 5% of the cartridges weight was added, and the activities were determined. The variation of 224Ra activity occurs mainly between 0 to 15% of humidity. Under moisture conditions higher than 15%, the emanation efficiency reaches an optimum plateau until 100% of moisture. This result differs slightly from those found for 224Ra measurements using the acrylic fiber (plateau from 30 to 100 %) [3]. The 223Ra Mn-cartridge standard reaches the plateau under 5% of humidity, and above 50% moisture the activity seems to decrease. Considering the counting error (7%), it is hard to state that the effect of the moisture is critical. However, this decrease can be related to the shorter half-life of the 219Rn compared to the time needed to its diffusion through the water film, which could be a reason for the frequently observed lower efficiency of the 223Ra channel of the RaDeCC system [4]. [1] Henderson et al. (2013) J. Radioanal. Nucl. Chem. 296, 357–362. [2] Moore and Arnold (1996) J. Geophys. Res. 101, 321–1329. [3] Sun and Torgersen (1998) Mar. Chem. 61, 163–171. [4] Charette et al. (2012) Limnol. Oceanogr. 10, 451–463