Biomechanics of coaching maximal instep soccer kick for practitioners

Kicking in soccer has been the subject of scientific research for more than 40 years yet review articles summarizing the biomechanical fundamentals of kick optimization as a guide to coaching are scarcely to be found. The current review article aims to bridge the gap between scientific research into the maximal instep kick (including studies employing 3D motion capture and full-body biomechanical modelling) and the application of such research in coaching. It does so by supplying a scientifically founded, coaching-friendly article explaining identifiable characteristics and motor control sequencing that define this skill. Relevant biomechanical factors are identified in a way that should help coaches better develop training programmes and, at the same time, foster better understanding of the skill among athletes. Such information will contribute to both accelerated skill acquisition and, by concomitant gains in skill efficiency, the development of programmes that minimize risk of injury to athletes during training.     

Experimental study of aqueous fluid infiltration into quartzite: implications for the kinetics of fluid redistribution and grain growth driven by interfacial energy reduction

To investigate the kinetics of interfacial energy‐driven fluid infiltration, experiments were carried out in a quartzite–water system at 621–925°C and 0.8 GPa. Infiltration couples were made by juxtaposing presynthesized dry quartzite cylinders and fluid reservoirs. The infiltration process was confirmed by the presence of pores at the quartzite grain edges. As predicted from theoretical considerations and previous experiments, wetting fluids such as pure water and NaCl aqueous solution infiltrated into quartzite, whereas nonwetting CO₂‐rich fluids did not. Newly precipitated quartz layers at the surfaces of the infiltrated sample proved that infiltration took place by a dissolution–precipitation mechanism. The enhancement of grain growth by fluid infiltration was observed over the entire range of experimental temperatures. The fluid fraction, gauged by the porosity of the run products, increases at the infiltration front and then decreases towards the fluid reservoir to form a high‐porosity zone with a maximum porosity of 2.3–2.9%. As infiltration proceeds, the high‐porosity zone advances like a travelling wave. This porosity wave is probably caused by a grain curvature gradient resulting from preferential grain growth in the infiltrated part of the quartzite, perhaps combined with other factors. The infiltration kinetics were modelled with a steady‐state diffusion model over the high‐porosity zone. The solubility difference between dissolving and precipitating grains was deduced to be 2 × 10^?2?3 × 10^?1 wt %. The experimentally obtained infiltration rate of aqueous fluid in the steady‐state diffusion regime (2 ± 0.5 × 10^?8 m sec^?1 at 823°C) is much faster than the estimated metamorphic fluid flux rates, so that interfacial energy‐driven fluid redistribution in quartz‐rich layers could significantly contribute to the fluid flux in high‐grade metamorphism, at least over a short distance. Cathodoluminescence observations of the run products revealed that the grain growth of quartzite in the presence of fluid proceeds extensively, which would promote the chemical equilibration between fluid and rock more effectively than would volume diffusion in quartz crystals.     

Pore‐scale analysis of trapped immiscible fluid structures and fluid interfacial areas in oil‐wet and water‐wet bead packs

The objective of this study is to obtain quantitative evidence of pore‐scale immiscible fluid distribution in oil‐wet and water‐wet porous media using X‐ray computed microtomography. Temporal and spatial saturation profiles, as well as surface and interfacial areas, are thoroughly analyzed through cycles of drainage and imbibition using samples with different wetting characteristics but similar pore structures. The population of individual immiscible fluid structures (‘blobs’) was also evaluated. The specific nonwetting phase surface areas of both porous media are found to be in close correlation with the specific solid surface area. On the other hand, the differing wetting strengths of the two porous media affect the curvature of the fluid–fluid interface and thus the specific meniscus interfacial area of the two porous media. Although the magnitude of the specific meniscus interfacial areas is different, they both trend toward a maximum at wetting phase saturations of 0.35–0.55. The differences in wetting characteristics are also apparent in the blob populations. The number of blobs in the oil‐wet porous media is three times greater than that of the water‐wet porous media at similar saturations; the increase in population is a result of the increase in the amount of smaller blobs inhabiting the smaller pore spaces. The surface areas of individual blobs as a function of the individual blob volumes are found to closely agree with the specific surface area of a sphere at blob volumes below the minimum individual grain volume and with the specific pore space surface area above this volume. These results show how wettability and saturation history influence the distribution of immiscible fluids within the pore space.     

Die Kunst des Anschlags. Elisabeth Caland und die Physio‐Ästhetik des Klavierspiels

The Art of Touch. Elisabeth Caland and the Physio‐Aesthetics of Piano Playing The issue of how it is possible to play the piano without striking it was raised by Chopin: one must ‘caresser’ and not ‘frapper’ the piano. In her teachings on the art of piano playing, Elisabeth Caland (1862–1929) attempts to articulate a scientifically grounded solution to this complex (kin‐)aesthetic problem. The solution turns on her intuitively discovered ‘lowering of the shoulderblades’ which was documented in 1904, through X‐rays, by the Berlin physiologist René du Bois‐Reymond, and recorded as a way of coordinating movement which had been unknown to physiology up to that time. Caland's physio‐aesthetic of piano playing, which she worked out on the basis of du Bois‐Reymond's observations, turns on the ideal of ‘floating sound’ put forward by her teacher Ludwig Deppe, and on Ferruccio Busoni's technique of piano playing. Her method makes essential use of what Feldenkrais would later call the ‘sixth sense’ (i.e. proprioceptive perception); in fact, it represents the first modern kinaesthetically based conception of piano playing. Caland's doctrine of touch was ahead of its time and it virtually disappeared from discussions of piano technique after 1930. But it has become accessible again through reprints of her most important writings: Deppe's doctrine of piano playing (1897), Sources of power in piano playing (1904), and Artistic piano playing (1910).     

Population Trends in a Contested Pseudo-State: The Case of Nagorno-Karabakh

A U.S. population geographer specializing in the former Soviet Union surveys the results of an October 2005 census conducted in a contested pseudo-state known as the Nagorno-Karabakh Republic (NKR). Data from the enumeration provide the first credible information about recent population characteristics, including nationality composition and migration from the war-torn republic. The data make it possible to ascertain the crude magnitudes of population losses in the republic's constituent rayons as well as changes resulting from deaths and expulsion of ethnic Armenians and/or Azerbaijanis. Changes documented since the last (1989) Soviet census in the region indicate that the current republic's population differs quite dramatically from that of the former Nagorno-Karabakh Autonomous Oblast of Azerbaijan, complicating efforts to broker a lasting peace agreement between the pseudostate's two neighbors. Journal of Economic Literature, Classification Numbers: J11, O18, R23, 1 figure, 1 table, 36 references.     

Gas breakthrough experiments on pelitic rocks: comparative study with N2, CO2 and CH4

The capillary‐sealing efficiency of intermediate‐ to low‐permeable sedimentary rocks has been investigated by N₂, CO₂ and CH₄ breakthrough experiments on initially fully water‐saturated rocks of different lithological compositions. Differential gas pressures up to 20 MPa were imposed across samples of 10–20 mm thickness, and the decline of the differential pressures was monitored over time. Absolute (single‐phase) permeability coefficients (k_abs), determined by steady‐state fluid flow tests, ranged between 10^?22 and 10^?15 m². Maximum effective permeabilities to the gas phase k_eff(max), measured after gas breakthrough at maximum gas saturation, extended from 10^?26 to 10^?18 m². Because of re‐imbibition of water into the interconnected gas‐conducting pore system, the effective permeability to the gas phase decreases with decreasing differential (capillary) pressure. At the end of the breakthrough experiments, a residual pressure difference persists, indicating the shut‐off of the gas‐conducting pore system. These pressures, referred to as the ‘minimum capillary displacement pressures’ (P_d), ranged from 0.1 up to 6.7 MPa. Correlations were established between (i) absolute and effective permeability coefficients and (ii) effective or absolute permeability and capillary displacement pressure. Results indicate systematic differences in gas breakthrough behaviour of N₂, CO₂ and CH₄, reflecting differences in wettability and interfacial tension. Additionally, a simple dynamic model for gas leakage through a capillary seal is presented, taking into account the variation of effective permeability as a function of buoyancy pressure exerted by a gas column underneath the seal.