Dehn surgery, homology and hyperbolic volume

If a closed, orientable hyperbolic 3--manifold M has volume at most 1.22 then H_1(M;Z_p) has dimension at most 2 for every prime p not 2 or 7, and H_1(M;Z_2) and H_1(M;Z_7) have dimension at most 3. The proof combines several deep results about hyperbolic 3--manifolds. The strategy is to compare the volume of a tube about a shortest closed geodesic C in M with the volumes of tubes about short closed geodesics in a sequence of hyperbolic manifolds obtained from M by Dehn surgeries on C.Comment: This is the version published by Algebraic & Geometric Topology on 8 December 200

A METHOD TO QUANITIFY MOVEMENT VARIABILITY OF HIGHLY SKILLED GOLFERS PERFORMING DRIVER SWINGS

Variability has been described as inherent in the golf swing (Bradshaw et al., 2009), yet its impact on outcome is not understood. It is necessary to quantify the levels of movement variability before this relationship can be examined effectively. Thus, the aim of this study was to develop a method to quantify movement variability of golfers performing driver swings. 16 highly skilled golfers each performed 10 swings wearing retro reflective markers which were tracked by a 3D motion analysis system operating at 400Hz. Movement variability was calculated for each marker using scalene ellipsoid volume methods; a score representative of the 3D variability over 10 trials was then calculated. The variability levels calculated using this method showed increasing variability from the closed end of the chain (malleoli) to the open end of the chain (wrists)

THE CREATION AND VALIDATION OF A LARGE-SCALE COMPUTER MODEL OF THE GOLF SWING

The aim of this study was to create and validate a full-body musculoskeletal model of a golfer performing a swing with their driver club. An elite female participant performed ten shots with her driver while wearing retro-reflective markers. An optical 3-D 6-camera system captured the kinematics of the markers at 400 Hz on the participant for each trial. A launch monitor device recorded the ball and club head conditions at impact. The kinematic data from one representative trial was selected to drive inverse and forward dynamics simulations of the created model. The validation results showed a very high level of agreement between experimental and simulated trajectories for selected markers (mean r = 0.966

THE EFFECT OF THE APPLICATION OF DIFFERENT LEVELS OF MOVEMENT VARIABILITY ON MOVEMENT OUTCOME

The aim of this study was to assess the effect of the application of a previously validated golfer computer model on different levels of movement variability relative to a shot outcome measure: club head velocity. Movement variability was applied to the computer model on six measures sequentially throughout the body of the computer model. Four different levels of variability, 25%, 50%, 75% and 100% variability, were applied to x, y and z positional data of the aforementioned measures. Simulations were then performed with ADAMS/LifeMOD software for each level of movement variability applied to the measures in question. Club head velocity was measured during the simulation. The results suggest that movement variability application at these landmarks does not have an effect on outcome. These results potentially have implications for the coaching of the participant

Interaction between two invasive organisms on the European chestnut: does the chestnut blight fungus benefit from the presence of the gall wasp?

The impact of invasive fungal pathogens and pests on trees is often studied individually, thereby omitting possible interactions. In this study the ecological interaction between the chestnut blight fungus Cryphonectria parasitica and the chestnut gall wasp Dryocosmus kuriphilus was investigated. We determined if abandoned galls could be colonized by C. parasitica and thereby act as an entry point and a source of pathogen inoculum. Moreover we assessed the identity and diversity of other gall-colonizing fungal species. A total of 1973 galls were randomly sampled from 200 chestnut trees in eight Swiss stands. In a stand C. parasitica was isolated from 0.4-19.2% of the galls. The incidence of C. parasitica on the galls and the fungal diversity significantly increased with the residence time of D. kuriphilus in a stand. All but one C. parasitica cultures were virulent. The predominant fungus isolated from galls was Gnomoniopsis castanea whose abundance influenced negatively that of C. parasitica. This study shows that D. kuriphilus galls can be colonized by virulent strains of the chestnut blight fungus C. parasitica. This can have effects on the chestnut blight incidence even in chestnut stands where the disease is successfully controlled by hypovirulence. The gall wasp presence influences also the fungal species composition on chestnut tree

Rank 2 distributions of Monge equations: Symmetries, equivalences, ex-tensions

By developing the Tanaka theory for rank 2 distributions, we completely classify classical Monge equations having maximal finite-dimensional symmetry algebras with fixed (albeit arbitrary) pair of its orders. Investigation of the corresponding Tanaka algebras leads to a new Lie-Backlund theorem. We prove that all flat Monge equations are successive integrable extensions of the Hilbert-Cartan equation. Many new examples are provided

Generation of correlated photons in controlled spatial modes by down-conversion in nonlinear waveguides

We report the observation of correlated photon pairs generated by spontaneous parametric down-conversion in a quasi-phase matched KTiOPO4 nonlinear waveguide. The highest ratio of coincidence to single photon count rates observed in the 830 nm wavelength region exceeds 18%. This makes nonlinear waveguides a promising source of correlated photons for metrology and quantum information processing applications. We also discuss possibilities of controlling the spatial characteristics of the down-converted photons produced in multimode waveguide structures.Comment: 4 pages, REVTe

Mass and p-factor of the type II Cepheid OGLE-LMC-T2CEP-098 in a binary system

We present the results of a study of the type II Cepheid ($P_{puls} = 4.974 d$) in the eclipsing binary system OGLE-LMC-T2CEP-098 ($P_{orb} = 397.2 d$). The Cepheid belongs to the peculiar W Vir group, for which the evolutionary status is virtually unknown. It is the first single-lined system with a pulsating component analyzed using the method developed by Pilecki et al. (2013). We show that the presence of a pulsator makes it possible to derive accurate physical parameters of the stars even if radial velocities can be measured for only one of the components. We have used four different methods to limit and estimate the physical parameters, eventually obtaining precise results by combining pulsation theory with the spectroscopic and photometric solutions. The Cepheid radius, mass and temperature are $25.3 \pm 0.2 R_\odot$, $1.51 \pm 0.09 M_\odot$ and $5300 \pm 100 K$, respectively, while its companion has similar size ($26.3 R_\odot$), but is more massive ($6.8 M_\odot$) and hotter ($9500 K$). Our best estimate for the p-factor of the Cepheid is $1.30 \pm 0.03$. The mass, position on the period-luminosity diagram, and pulsation amplitude indicate that the pulsating component is very similar to the Anomalous Cepheids, although it has a much longer period and is redder in color. The very unusual combination of the components suggest that the system has passed through a mass transfer phase in its evolution. More complicated internal structure would then explain its peculiarity.Comment: 23 pages, 17 figures, accepted for publication in Ap