Sled-push load-velocity profiling and implications for sprint training prescription in young athletes

Resisted sled pushing is a popular method of sprint-specific training; however, little evidence exists to support the prescription of resistive loads in young athletes. The purpose of this study was to determine the reliability and linearity of the force-velocity relationship during sled pushing, as well as the amount of between-athlete variation in the load required to cause a decrement in maximal velocity (Vdec) of 25, 50 and 75%. Ninety (n=90) high school, male athletes (age 16.9 ± 0.9 years) were recruited for the study. All participants performed one un-resisted and three sled-push sprints with increasing resistance. Maximal velocity was measured with a radar gun during each sprint and the load-velocity relationship established for each participant. A subset of 16 participants examined the reliability of sled pushing on three separate occasions. For all individual participants, the load-velocity relationship was highly linear (r > 0.96). The slope of the load-velocity relationship was found to be reliable (CV = 3.1%), with the loads that cause a decrement in velocity of 25, 50 and 75% also found to be reliable (CVs = <5%). However, there was large between-participant variation (95%CI) in the load that caused a given Vdec, with loads of 23-42% body mass (%BM) causing a Vdec of 25%, 45-85%BM causing a Vdec of 50% and 69-131%BM causing a Vdec of 75%. The Vdec method can be reliably used to prescribe sled-push loads in young athletes, but practitioners should be aware that the load required to cause a given Vdec is highly individualized

Overview of ImageCLEFcoral 2021: Coral reef image annotation of a 3D environment

This paper presents an overview of the ImageCLEFcoral 2021 task that was organised as part of the Conference and Labs of the Evaluation Forum - CLEF Labs 2021. The task addresses the problem of automatically segmenting and labelling a collection of underwater images that can be used in combination to create 3D models for the monitoring of coral reefs. The training dataset contained 882 images from 6 subsets from 4 locations. 1 subset was complete (containing all the images to build the 3D model) and 5 subsets containing a partial collection. The test data (491 images) contained the images required to complete 4 of the partial image sets from each of the 4 locations (the final partial subset is not used for testing, only training). 8 teams registered to the ImageCLEFcoral task, of which 3 teams submitted 8 runs. Participants' entries showed that although automatic annotation of benthic substrates was possible, developing a generic algorithm to work across multiple geographical locations will be difficult due to the variation of characteristics within and between classification types

Dual quantum confinement and anisotropic spin splitting in the multi-valley semimetal PtSe2

The authors gratefully acknowledge support from the Leverhulme Trust (Grant No. RL-2016-006), the Royal Society, the European Research Council (Grant No. ERC-714193QUESTDO) CREST, JST (No. JPMJCR16F1), and the International Max-Planck Partnership for Measurement and Observation at the Quantum Limit. OJC, VS, and LB acknowledge EPSRC for PhD studentship support through grant Nos. EP/K503162/1, EP/L015110/1 and EP/G03673X/1. IM acknowledges PhD studentship support from the IMPRS for the Chemistry and Physics of Quantum Materials.We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multivalley semimetal 1T−PtSe2. Using angle-resolved photoemission and first-principles-based surface space-charge calculations, we show how the induced quantum well sub-band states form multiple Fermi surfaces, which exhibit highly anisotropic Rashba-like spin splittings. We further show how the presence of both electronlike and holelike bulk carriers causes the near-surface band bending potential to develop an unusual nonmonotonic form, with spatially segregated electron accumulation and hole accumulation regions, which in turn amplifies the induced spin splitting. Our results thus demonstrate the novel environment that semimetals provide for tailoring electrostatically induced potential profiles and their corresponding quantum sub-band states.PostprintPeer reviewe

Orbital- and kz-selective hybridisation of Se 4p and Ti 3d states in the charge density wave phase of TiSe2

We revisit the enduring problem of the 2 × 2 × 2 charge density wave (CDW) order in TiSe2, utilising photon energy-dependent angle-resolved photoemission spectroscopy to probe the full three-dimensional high- and low- temperature electronic structure. Our measurements demonstrate how a mismatch of dimensionality between the 3D conduction bands and the quasi-2D valence bands in this system leads to a hybridisation that is strongly kz-dependent. While such a momentum-selective coupling can provide the energy gain required to form the CDW, we show how additional “passenger” states remain, which couple only weakly to the CDW and thus dominate the low-energy physics in the ordered phase of TiSe2.PostprintPeer reviewe

Spin-orbit coupled spin-polarised hole gas at the CrSe2-terminated surface of AgCrSe2

Funding: We gratefully acknowledge support from the European Research Council (through the QUESTDO project, 714193), the Engineering and Physical Sciences Research Council (Grant No. EP/T02108X/1), and the Leverhulme Trust (Grant No. RL-2016-006). S.-J.K., E.A.M., A.Z., and I.M. gratefully acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.In half-metallic systems, electronic conduction is mediated by a single spin species, offering enormous potential for spintronic devices. Here, using microscopic-area angle-resolved photoemission, we show that a spin-polarised two-dimensional hole gas is naturally realised in the polar magnetic semiconductor AgCrSe2 by an intrinsic self-doping at its CrSe2-terminated surface. Through comparison with first-principles calculations, we unveil a striking role of spin-orbit coupling for the surface hole gas, unlocked by both bulk and surface inversion symmetry breaking, suggesting routes for stabilising complex magnetic textures in the surface layer of AgCrSe2.Publisher PDFPeer reviewe

Theatre des Femmes

We study the electronic structure of the Pd-terminated surface of the non-magnetic delafossite oxide metal PdCoO$_2$. Combining angle-resolved photoemission spectroscopy and density-functional theory, we show how an electronic reconstruction driven by surface polarity mediates a Stoner-like magnetic instability towards itinerant surface ferromagnetism. Our results reveal how this leads to a rich multi-band surface electronic structure, and provide spectroscopic evidence for an intriguing sample-dependent coupling of the surface electrons to a bosonic mode which we attribute to electron-magnon interactions. Moreover, we find similar surface state dispersions in PdCrO$_2$, suggesting surface ferromagnetism persists in this sister compound despite its bulk antiferromagnetic order.Comment: 6 pages, 5 figure

Weyl-like points from band inversions of spin-polarised surface states in NbGeSb

Funding: Leverhulme Trust (Grant No. PLP-2015-144), The Royal Society, and the Engineering and Physical Sciences Research Council, UK (Grant No. EP/R031924/1); CALIPSOplus project under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020; International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM) (I.M.); EPSRC for studentship support through grant nos. EP/K503162/1 and EP/L505079/1, and EP/L015110/1 (O.J.C., J.M.R., and K.U.).Band inversions are key to stabilising a variety of novel electronic states in solids, from topological surface states to the formation of symmetry-protected three-dimensional Dirac and Weyl points and nodal-line semimetals. Here, we create a band inversion not of bulk states, but rather between manifolds of surface states. We realise this by aliovalent substitution of Nb for Zr and Sb for S in the ZrSiS family of nonsymmorphic semimetals. Using angle-resolved photoemission and density-functional theory, we show how two pairs of surface states, known from ZrSiS, are driven to intersect each other near the Fermi level in NbGeSb, and to develop pronounced spin splittings. We demonstrate how mirror symmetry leads to protected crossing points in the resulting spin-orbital entangled surface band structure, thereby stabilising surface state analogues of three-dimensional Weyl points. More generally, our observations suggest new opportunities for engineering topologically and symmetry-protected states via band inversions of surface states.Publisher PDFPeer reviewe

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter