197,444 research outputs found
Non-orientable surface-plus-one-relation groups
No full textRecently Dicks–Linnell determined the L2-Betti numbers of the orientable surface-plus-one-relation groups, and their arguments involved some results that were obtained topologically by Hempel and Howie. Using algebraic arguments, we now extend all these results of Hempel and Howie to a larger class of two-relator groups, and we then apply the extended results to determine the L2-Betti numbers of the non-orientable surface-plus-one-relation group
On the local-indicability cohen–lyndon theorem
No full textFor a group H and a subset X of H, we let HX denote the set {hxh?1 | h ? H, x ? X}, and when X is a free-generating set of H, we say that the set HX is a Whitehead subset of H. For a group F and an element r of F, we say that r is Cohen–Lyndon aspherical in F if F{r} is a Whitehead subset of the subgroup of F that is generated by F{r}. In 1963, Cohen and Lyndon (D. E. Cohen and R. C. Lyndon, Free bases for normal subgroups of free groups, Trans. Amer. Math. Soc. 108 (1963), 526–537) independently showed that in each free group each non-trivial element is Cohen–Lyndon aspherical. Their proof used the celebrated induction method devised by Magnus in 1930 to study one-relator groups. In 1987, Edjvet and Howie (M. Edjvet and J. Howie, A Cohen–Lyndon theorem for free products of locally indicable groups, J. Pure Appl. Algebra 45 (1987), 41–44) showed that if A and B are locally indicable groups, then each cyclically reduced element of A*B that does not lie in A ? B is Cohen–Lyndon aspherical in A*B. Their proof used the original Cohen–Lyndon theorem. Using Bass–Serre theory, the original Cohen–Lyndon theorem and the Edjvet–Howie theorem, one can deduce the local-indicability Cohen–Lyndon theorem: if F is a locally indicable group and T is an F-tree with trivial edge stabilisers, then each element of F that fixes no vertex of T is Cohen–Lyndon aspherical in F. Conversely, by Bass–Serre theory, the original Cohen–Lyndon theorem and the Edjvet–Howie theorem are immediate consequences of the local-indicability Cohen–Lyndon theorem. In this paper we give a detailed review of a Bass–Serre theoretical form of Howie induction and arrange the arguments of Edjvet and Howie into a Howie-inductive proof of the local-indicability Cohen–Lyndon theorem that uses neither Magnus induction nor the original Cohen–Lyndon theorem. We conclude with a review of some standard applications of Cohen–Lyndon asphericit
The spatiotemporal control of expert tennis players when returning first serves: a perception-action perspective
No full textThis work was supported by the ITF Development Department under Grant ITF RG 2006/08 awarded to the last author. We thankfully acknowledge the support provided by the ITF, Spanish Tennis Federation (Coaching Area), Madrid Tennis Federation and Catalan Tennis Federation. In coordination among them, the federations facilitated the access to professional tennis players and provided the facilities to carry out the data collection.
We thankfully acknowledge the support provided by the ITF, Spanish Tennis Federation (Coaching Area), Madrid Tennis Federation and Catalan Tennis Federation. In coordination among them, the federations facilitated the access to professional tennis players and provided the facilities to carry out the data collection.
© 2021 Informa UK Limited, trading as Taylor & Francis Group
Pages 16-23 | Accepted 31 Aug 2021, Published online: 17 Sep 2021
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• Vernon, G., Farrow, D., & Reid, M. (2018). Returning serve in tennis: A qualitative examination of the interaction of anticipatory information sources used by professional tennis players. Frontiers in Psychology, 9(895), 895. https://doi.org/10.3389/fpsyg.2018.00895
• Williams, A. M., & Jackson, R. C. (2019). Anticipation in sport: Fifty years on, what have we learned and what research still needs to be undertaken? Psychology of Sport and Exercise, 42(May), 16–24. https://doi.org/10.1016/j.psychsport.2018.11.014The aim of the current experiment was to examine the spatiotemporal control of expert tennis players while executing first service returns within a representative experimental setting. We recruited and tested 12 male expert tennis players in hard courts. A comprehensive analysis of the timing (eleven temporal variables analysed at 300 Hz) and performance success of the return actions were carried out, while simultaneously considering task constraints such as the accuracy and the speed of the serves. Temporal organisation of return actions were scaled relative to the server’s racket-ball contact (5 ms), an adaptation of fly-time of the split-step, which resulted in consistent landings (133 ms), and initiation of lateral movements towards the ball–with no response errors–after the server’s stroke (around 177 ms). Poorer returns occurred when responding to accurate serves accompanied by late trunk movements towards the ball. Returners scaled the timing of the response to the unfolding action of the serve in order to support both spatial and temporal accuracy. These novel findings highlight the significance of the study of fast-ball sports in representative settings and offer further detail on the spatiotemporal control of skilful perception-action.ITF Development DepartmentMadrid Tennis Federation and Catalan Tennis Federation (Spain)Spanish Tennis FederationInnovation and Technology Fund Hong Kong SAR (China)Depto. de Didáctica de las Lenguas, Artes y Educación FísicaFac. de EducaciónTRUEpu
Identification of lactic acid bacteria isolated from South African brandy based wines
No full textH.W. du Plessis, L.M.T. Dicks, I.S. Pretorius, M.G. Lambrechts, M. du Toi
Presentations for subgroups of Artin groups
No full textRecently, M. Bestvina and N. Brady have exhibited groups that are of type FP but not finitely presented. We give explicit presentations for groups of the type considered by Bestvina-Brady. This leads to algebraic proofs of some of their results
Equalisers of sections
No full textLet G and M be groups, and a, b: G → G * M group-theoretic sections of the natural projection G * M → G. We use the Almost Stability Theorem, pro-trees, and new folding sequence techniques to show that if G is finitely generated, then the equalizer of a and b is a free factor of G, which answers a question of G. M. Bergman
Senator Henry M. Jackson and Washington Congressmen Norm D. Dicks and Don Bonker meeting in front of a 1931 Ford with Olympia resident Hal Wolfe who is demonstrating for "Lower Interest Rates", Washington, D.C., October 1981
No full textNote filed with photograph: Hal Wolfe of Olympia, Washington, meets with Senator Henry M. Jackson, Congressmen Don Bonker and Norm Dicks after driving his 1931 Ford truck from Seattle to Washington, D.C. to dramatize how the Reagan Administration's policy of high interest rates are hurting the economy. Jackson, who met Wolfe on the steps of the U.S. Capitol, has taken a leadership role in fighting high interest rates. "The Administration and the Federal Reserve Board have effectively cut off credit both to business and consumers," Jackson said. "I commend Mr. Wolfe for helping us in this battle.
Fantasmatique de l'agression. Fantasmatique de la mort en psychanalyse post-Freudienne : M. Mannoni, B. Bettelheim, H.V. Dicks et l'école de Sussex
No full textVan Canneghem Denise. Fantasmatique de l'agression. Fantasmatique de la mort en psychanalyse post-Freudienne : M. Mannoni, B. Bettelheim, H.V. Dicks et l'école de Sussex. In: Bulletin de psychologie, tome 29 n°323, 1976. pp. 682-703
Land Use Implications of Expanding Biofuel Demand
No full textThe Renewable Fuel Standard mandates in the Energy Independence and Security Act of 2007 will require 36 billion gallons of ethanol to be produced in 2022. The mandates require that 16 of the 36 billion gallons must be produced from cellulosic feedstocks. The potential land use implications resulting from these mandates were examined using two methods, the POLYSYS model and a general equilibrium model. Results of the POLYSYS analysis indicated that 72.1 million tons of corn stover, 23.5 million tons of wheat straw, and 24.7 million acres would be used to produce 109 million tons of switchgrass in 2025 to meet the mandate. Results of the CGE analysis indicated that 10.9 billion bushels of corn grain, 71 million tons of corn stover, and 56,200 tons of switchgrass is needed to meet the mandate.cellulosic ethanol, corn stover, grain ethanol, renewable fuel standard, switchgrass, Crop Production/Industries, Demand and Price Analysis, Environmental Economics and Policy, Land Economics/Use, Resource /Energy Economics and Policy, Q15, Q42,
Faust : a romance / by George W. M. Reynolds. With eleven ill. by Sir John Gilbert and Henry Anelay
No full textFAUST : A ROMANCE / BY GEORGE W. M. REYNOLDS. WITH ELEVEN ILL. BY SIR JOHN GILBERT AND HENRY ANELAY
Faust : a romance / by George W. M. Reynolds. With eleven ill. by Sir John Gilbert and Henry Anelay (1)
Cover (1)
Titelseite (3)
Prologue (5)
Chapter I. - XV. (8)
Chapter XVI. - XXV. (35)
Chapter XXVI. - XL. (55)
Chapter XLI. - L. (78)
Chapter LI. - LXX. (99)
Chapter LXXI. - LXXX. (135)
Chapter LXXXI. - XCV. (153)
Epilogue (175
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