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

Explaining Machine Learning Classifiers through Diverse Counterfactual Explanations

Post-hoc explanations of machine learning models are crucial for people to understand and act on algorithmic predictions. An intriguing class of explanations is through counterfactuals, hypothetical examples that show people how to obtain a different prediction. We posit that effective counterfactual explanations should satisfy two properties: feasibility of the counterfactual actions given user context and constraints, and diversity among the counterfactuals presented. To this end, we propose a framework for generating and evaluating a diverse set of counterfactual explanations based on determinantal point processes. To evaluate the actionability of counterfactuals, we provide metrics that enable comparison of counterfactual-based methods to other local explanation methods. We further address necessary tradeoffs and point to causal implications in optimizing for counterfactuals. Our experiments on four real-world datasets show that our framework can generate a set of counterfactuals that are diverse and well approximate local decision boundaries, outperforming prior approaches to generating diverse counterfactuals. We provide an implementation of the framework at https://github.com/microsoft/DiCE.Comment: 13 page

Single Spin Asymmetry at Large x_F and k_T

The large single spin asymmetries observed at high momentum fractions x_F and transverse momenta k_T in p^\uparrow p -> \pi(x_F,k_T)+X as well as in pp -> \Lambda^\uparrow(x_F,k_T)+X suggest that soft helicity flip processes are coherent with hard scattering. Such coherence can be maintained if x_F -> 1 as k_T -> \infty, while k_T^2(1-x_F) \sim \Lambda_QCD^2 stays fixed. The entire hadron wave function, rather than a single quark, then contributes to the scattering process. Analogous coherence effects have been seen experimentally in the Drell-Yan process at high x_F. We find that the p^\uparrow p -> \pi(x_F,k_T)+X production amplitudes have large dynamic phases and that helicity flip contributions are unsuppressed in this limit, giving rise to potentially large single spin asymmetries.Comment: 11 pages, 2 figures. v2: References and a preprint number added. Calculation of section 4 modified. v3: Minor changes in text. Version to be published in JHE

Transition Probabilities Of Astrophysical Interest In The Niobium Ions Nb+ And Nb2+

Aims. We attempt to derive accurate transition probabilities for astrophysically interesting spectral lines of Nb II and Nb III and determine the niobium abundance in the Sun and metal-poor stars rich in neutron-capture elements. Methods. We used the time-resolved laser-induced fluorescence technique to measure radiative lifetimes in Nb II. Branching fractions were measured from spectra recorded using Fourier transform spectroscopy. The radiative lifetimes and the branching fractions were combined yielding transition probabilities. In addition, we calculated lifetimes and transition probablities in Nb II and Nb III using a relativistic Hartree-Fock method that includes core polarization. Abundances of the sun and five metal-poor stars were derived using synthetic spectra calculated with the MOOG code, including hyperfine broadening of the lines. Results. We present laboratory measurements of 17 radiative lifetimes in Nb II. By combining these lifetimes with branching fractions for lines depopulating the levels, we derive the transition probabilities of 107 Nb II lines from 4d(3)5p configuration in the wavelength region 2240-4700 angstrom. For the first time, we present theoretical transition probabilities of 76 Nb III transitions with wavelengths in the range 1430-3140 angstrom. The derived solar photospheric niobium abundance log epsilon(circle dot) = 1.44 +/- 0.06 is in agreement with the meteoritic value. The stellar Nb/Eu abundance ratio determined for five metal-poor stars confirms that the r-process is a dominant production method for the n-capture elements in these stars.Integrated Initiative of Infrastructure RII3-CT-2003-506350Swedish Research CouncilKnut and Alice Wallenberg FoundationBelgian FRS-FNRSFRIAUS National Science Foundation AST-0607708, AST-0908978Astronom

Structures of Loyalty: A Comparative Study of Jewish and Palestinian Evangelicals\u27 Acquiescence to Fundamentalist and Authoritarian Values

This is a qualitative comparative study of two evangelical movements in Israel and in the West Bank: the Israeli Messianic (IM) movement and the Palestinian Evangelical (PE) movement. Through interviews on how informants understand the Middle Eastern conflict, our aim is (1) to compare the prevalence of fundamentalist/authoritarian (F/A) values in the IM and PE movements and (2) to understand how a particular socio-political context —Israel and the West Bank—might affect the acquiescence to a F/A mindset amongst the two movements. To accomplish this, we created a F/A construct that measures five values: literalism, social withdrawal, authoritarian aggression, authoritarian submission, and conventionalism. We found that the IM scores higher on all five F/A values. To explain the difference, we point out the importance of structures of loyalty: the difference in how IMs and PEs connect to key societal groups affects the way they acquiesce to fundamentalist and authoritarian values

Reversible plasticity in amorphous materials

A fundamental assumption in our understanding of material rheology is that when microscopic deformations are reversible, the material responds elastically to external loads. Plasticity, i.e. dissipative and irreversible macroscopic changes in a material, is assumed to be the consequence of irreversible microscopic events. Here we show direct evidence for reversible plastic events at the microscopic scale in both experiments and simulations of two-dimensional foam. In the simulations, we demonstrate a link between reversible plastic rearrangement events and pathways in the potential energy landscape of the system. These findings represent a fundamental change in our understanding of materials--microscopic reversibility does not necessarily imply elasticity.Comment: Revised pape

Is sunlight good for our heart?

Humans evolved being exposed for about half of the day to the light of the sun. Nowadays, exposure to sunlight is actively discouraged for fear of skin cancer, and contemporary lifestyles are associated with long hours spent under artificial light indoors. Besides an increasing appreciation for the adverse effects of these life-style-related behavioural changes on our chronobiology, the balance between the beneficial and harmful effects of sunlight on human health is the subject of considerable debate, in both the scientific and popular press, and the latter is of major public health significance. While there is incontrovertible evidence that ultraviolet radiation (UVR) in the form of sunlight is a significant predisposing factor for non-melanoma and melanoma skin cancers in pale skinned people,1 a growing body of data suggest general health benefits brought about by sunlight.2 These are believed to be mediated either by melatonin or vitamin D. Melatonin is produced from serotonin by the pineal gland located in the centre of the brain during periods of darkness, and its release is suppressed as a function of the visible light intensity sensed through ocular photoreceptors. Vitamin D is formed by ultraviolet B (UVB)-mediated photolysis of 7-dehydrocholesterol in the skin. Both melatonin and vitamin D are pleiotropic hormones that exert a multitude of cellular effects by interacting with membrane and nuclear receptors, and receptor-independent actions. People with more heavily pigmented skin require higher doses of UVB to produce adequate amounts of vitamin D, and this may have been an evolutionary driver to the variation of human skin colour with latitude and intensity of solar irradiation. Our degree of exposure to sunlight is easily modified by behavioural factors such as the use of clothing, sunglasses, and sun-blocking creams, and time spent outdoors. Balancing the carcinogenic risks with the requirement for vitamin D has led to advice on moderating sun exposure, while supplementing food with vitamin D. Guidance on such behaviour is part of the public health campaigns in most countries with Caucasian populations. Following these suggestions, we may, however, be missing out on other health benefits provided by natural sunlight that are less obvious and unrelated to the above classical mediators