Heat and groundwater transport between the Antarctic Ice Sheet and subglacial sedimentary basins from electromagnetic geophysical measurements

Numerical models of contemporary as well as paleo-ice sheets suggest that groundwater and heat exchanges between subglacial sedimentary basins and the ice sheet above, can be substantial and influence the flow of ice above. So far, an approach for the measurement and assessment of such heat fluxes has not been available. Here, we summarise existing evidence for groundwater and heat exchanges between contemporary and paleo ice sheets and the substrate below. We then explain the utility of electromagnetic geophysical measurements in elucidating such exchanges, and present magnetotelluric synthetic models of the deep sedimentary basin beneath the Institute Ice Stream in West Antarctica by way of illustration. Finally, we propose a simple empirical model by which heat exchanges between subglacial sedimentary basins and the overlying ice sheet can be estimated to first-order from electromagnetic data

Pre- and In-Season Strength and Conditioning Training Changes in Leg Peak Power Performance in Collegiate Division II Women’s Basketball Team: A Case Study

Basketball is a team sport that places emphasis on explosive movements. Leg peak power (PP) performance provides an advantage for successful basketball participation. Pre-season (PS) strength and conditioning training (SCT) sets the foundation for in-season (IS) success. However, determining the optimal duration, of PS and IS SCT to develop improvements in PP is still under investigation. PURPOSE: To describe the changes over time in PP during a 4 weeks of PS and 6 weeks of IS SCT in a collegiate Division II women’s basketball team. METHODS: Besides PS in-court sessions (4.5 hrs/wk), 14 female players completed 3 hrs/wk of SCT. During the IS, the in-court sessions increased (10 hrs/wk), while the SCT reduced to 2 hrs/wk, focusing on strength (weeks 5-8), then on strength and power (weeks 9 and 10). All SCT sessions were supervised by SCT coach. PP was assessed 1 d/wk for 10 weeks by the counter-movement jump (CMJ) test performed on the Just Jump© mat. PP was calculated based on Sayers formula. PP data were normalized for body size using allometric scaling, from recorded PP scores and body mass (M) (PPn=PP/M0.67). PP scores were analyzed using one-way repeated measures ANOVA. Missing values were replaced with series mean. Statistical significance was set at p ≤ 0.05. All statistical analyses were performed using SPSS© (vs.25). RESULTS: Mauchly’s test indicated that assumption of sphericity has been violated, x2 (44) = 96.58, p = 0.000, therefore Greehouse-Geisser corrected tests are reported (ε = 0.41). PP scores were significantly different between the 10 weeks of SCT, F (3.65, 47.40) = 4.80, p = 0.003, η2 = 0.270. Post hoc test using the Bonferroni correction revealed that SCT increased PP scores at week-3 compared to week-1 and week-2, but that increase was not significant (225.03 ± 16.50 W · kg-0.67 vs 212.90 ± 17.01 W · kg-0.67, p = 0.69 and 214.01 ± 19.13 W · kg-0.67, p = 0.41). PP scores for week-7 (209.19 ± 13.5 W · kg-0.67) were significantly different than week-3 and week-4, and week-5 (225.03 ± 16.50 W · kg-0.67, p = 0.01; 219.69 ± 13.33 W · kg-0.67,p = 0.02; 218.12 ± 12.98 W · kg-0.67, p = 0.01). Following week-7, PP scores increased but not significantly at week-8 and week-9 (211.46 ± 12.30 W · kg-0.67, p = 1.00; 214.24 ± 15.18 W · kg-0.67, p = 0.67) and then at week-10 (212.36 ± 10.78 W · kg-0.67, p = 1.00) PP scores non-significantly decreased below to week-1 scores. CONCLUSION: SCT on PP performance in women’s collegiate DII basketball athletes during PS and IS are subjected to the time devoted on SCT itself. Three hrs/wk for 3 weeks seems to be adequate stimulus to elicit an increase PP. Continuing a SCT program for more than 3 weeks with less than 3 hrs/wk is not enough to maintain the already achieved adaptations. More than 7 weeks and up to 10 weeks of SCT with 2 hrs/wk has no influence on improving PP above baseline week one values. Time constraint is at expense of SCT. For SCT and basketball coaches, this study may be a useful tool when developing a periodized SCT program focusing on strength and power adaptations

Quantum Logic for Trapped Atoms via Molecular Hyperfine Interactions

We study the deterministic entanglement of a pair of neutral atoms trapped in an optical lattice by coupling to excited-state molecular hyperfine potentials. Information can be encoded in the ground-state hyperfine levels and processed by bringing atoms together pair-wise to perform quantum logical operations through induced electric dipole-dipole interactions. The possibility of executing both diagonal and exchange type entangling gates is demonstrated for two three-level atoms and a figure of merit is derived for the fidelity of entanglement. The fidelity for executing a CPHASE gate is calculated for two 87Rb atoms, including hyperfine structure and finite atomic localization. The main source of decoherence is spontaneous emission, which can be minimized for interaction times fast compared to the scattering rate and for sufficiently separated atomic wavepackets. Additionally, coherent couplings to states outside the logical basis can be constrained by the state dependent trapping potential.Comment: Submitted to Physical Review

Interference of a Tonks-Girardeau Gas on a Ring

We study the quantum dynamics of a one-dimensional gas of impenetrable bosons on a ring, and investigate the interference that results when an initially trapped gas localized on one side of the ring is released, split via an optical-dipole grating, and recombined on the other side of the ring. Large visibility interference fringes arise when the wavevector of the optical dipole grating is larger than the effective Fermi wavevector of the initial gas.Comment: 7 pages, 3 figure

A Storage Ring for Neutral Atoms

We have demonstrated a storage ring for ultra-cold neutral atoms. Atoms with mean velocities of 1 m/s corresponding to kinetic energies of ~100 neV are confined to a 2 cm diameter ring by magnetic forces produced by two current-carrying wires. Up to 10^6 atoms are loaded at a time in the ring, and 7 revolutions are clearly observed. Additionally, we have demonstrated multiple loading of the ring and deterministic manipulation of the longitudinal velocity distribution of the atoms using applied laser pulses. Applications of this ring include large area atom interferometers and cw monochromatic atomic beam generation.Comment: 4 pages, 5 figure

Biometric variables predict stone tool functional performance more effectively than tool‐form attributes: a case study in handaxe loading capabilities

Both the form of a stone tool and the anatomy of the individual using it have potential to influence its cutting performance. To date, however, the selective pressures acting on stone‐tool form and hominin biometric/biomechanical attributes have been investigated in isolation and their relative influence on performance have never been compared directly. This paper examines the influence of both tool‐form attributes and biometric variation on the functional performance of Acheulean handaxes. Specifically, it investigates the impact of 13 tool attributes and eight biometric traits on the working forces applied through the edge of 457 replica tools. The relative contribution of tool‐form and biometric attributes to handaxe loading levels were examined statistically. Results identify that both tool‐form attributes and biometric traits are significantly related to loading; however, tool–user biometric variation has a substantially greater impact relative to tool‐form attributes. This difference was demonstrated by up to a factor of 10. These results bear directly on the co‐evolutionary relationships of stone tools and hominin anatomy, and the comparative strength of selective pressure acting on each. They also underline why handaxe forms may have been free to vary in form across time and space without necessarily incurring critical impacts on their functional capabilities

Optical dipole traps and atomic waveguides based on Bessel light beams

We theoretically investigate the use of Bessel light beams generated using axicons for creating optical dipole traps for cold atoms and atomic waveguiding. Zeroth-order Bessel beams can be used to produce highly elongated dipole traps allowing for the study of one-dimensional trapped gases and realization of a Tonks gas of impentrable bosons. First-order Bessel beams are shown to be able to produce tight confined atomic waveguides over centimeter distances.Comment: 20 pages, 5 figures, to appear in Phys. Rev.

Propagation of Bose-Einstein condensates in a magnetic waveguide

Gaseous Bose-Einstein condensates of 2-3 million atoms were loaded into a microfabricated magnetic trap using optical tweezers. Subsequently, the condensates were released into a magnetic waveguide and propagated 12 mm. Single-mode propagation was observed along homogeneous segments of the waveguide. Inhomogeneities in the guiding potential arose from geometric deformations of the microfabricated wires and caused strong transverse excitations. Such deformations may restrict the waveguide physics that can be explored with propagating condensates.Comment: 5 pages, 4 figure