Statistical Thermodynamics

Contains reports on two research projectsU. S. Air Force (Office of Scientific Research, Air Research and Development Command) under Contract AF49(638)-9

Statistical Thermodynamics

Contains a report on a research project.United States Air Force, Office of Scientific Research, Air Research and Development Command (Contract AF49(638)-95

Upwelling rates for the equatorial Pacific Ocean derived from the bomb 14C distribution

A north-south cross section of bomb-produced radiocarbon (14C) in the upper 1000 m of the central equatorial Pacific Ocean (CEP) was measured in April, 1979 during Leg 3 of the NORPAX shuttle experiment. The 14C shows an equatorial mixed layer depletion of ∼40‰ compared to subtropical surface waters. Upwelling of deeper, 14C depleted water maintains this minimum. Two subsurface tongues of high 14C water, found north and south of the equator, are associated with high salinity water and probably result from exchange with subtropical surface water. The continued increase in mixed layer 14C levels in the CEP (up to 1979) indicates the importance of 14C input from these subsurface 14C maxima. Equatorward meridional advection resulting from geostrophic flow is the predominant supply of water upwelling at the equator and controls the 14C distribution in the CEP. The results of multi-layer mixing model calculations indicate an upwelling transport rate of 47 Sverdrups (5S–4N) and a maximum depth of upwelling of 225 m (σ0 = 26.5). These equatorial circulation characteristics explain the 14C, ΣCO2, oxygen, salinity and tritium distributions measured during Leg 3. The time history of mixed layer bomb 14C concentrations in the CEP indicate an exchange time of 4–6 years between the subtropical and equatorial surface oceans

Persistence of intense, climate-driven runoff late in Mars history

Mars is dry today, but numerous precipitation-fed paleo-rivers are found across the planet’s surface. These rivers’ existence is a challenge to models of planetary climate evolution. We report results indicating that, for a given catchment area, rivers on Mars were wider than rivers on Earth today. We use the scale (width and wavelength) of Mars paleo-rivers as a proxy for past runoff production. Using multiple methods, we infer that intense runoff production of >(3–20) kg/m 2 per day persisted until 1 Ga. Our improved history of Mars’ river runoff places new constraints on the unknown mechanism that caused wet climates on Mars

Skills, strategies, sport and social responsibility : reconnecting physical education

Physical education is one of the more difficult subjects in the curriculum for generalist classroom teachers in primary schools to incorporate confidently into their teaching. In many primary schools, the generalist classroom teacher defers to a physical education specialist. This situation has both positive and negative features. In this context, this study brings together several prominent models of physical education teaching in an approach that enables the curriculum to be encountered through the interests of the children. This approach offers a generalist teacher, through appropriate professional development, a means for delivering a high-quality physical education programme, and also complements the repertoire of the specialist physical education teacher at both primary and secondary school levels.<br /

Nanoelectromechanical coupling in fullerene peapods probed via resonant electrical transport experiments

Fullerene peapods, that is carbon nanotubes encapsulating fullerene molecules, can offer enhanced functionality with respect to empty nanotubes. However, the present incomplete understanding of how a nanotube is affected by entrapped fullerenes is an obstacle for peapods to reach their full potential in nanoscale electronic applications. Here, we investigate the effect of C60 fullerenes on electron transport via peapod quantum dots. Compared to empty nanotubes, we find an abnormal temperature dependence of Coulomb blockade oscillations, indicating the presence of a nanoelectromechanical coupling between electronic states of the nanotube and mechanical vibrations of the fullerenes. This provides a method to detect the C60 presence and to probe the interplay between electrical and mechanical excitations in peapods, which thus emerge as a new class of nanoelectromechanical systems.Comment: 7 pages, 3 figures. Published in Nature Communications. Free online access to the published version until Sept 30th, 2010, see http://www.nature.com/ncomms/journal/v1/n4/abs/ncomms1034.htm

Revealing the electronic structure of a carbon nanotube carrying a supercurrent

Carbon nanotubes (CNTs) are not intrinsically superconducting but they can carry a supercurrent when connected to superconducting electrodes. This supercurrent is mainly transmitted by discrete entangled electron-hole states confined to the nanotube, called Andreev Bound States (ABS). These states are a key concept in mesoscopic superconductivity as they provide a universal description of Josephson-like effects in quantum-coherent nanostructures (e.g. molecules, nanowires, magnetic or normal metallic layers) connected to superconducting leads. We report here the first tunneling spectroscopy of individually resolved ABS, in a nanotube-superconductor device. Analyzing the evolution of the ABS spectrum with a gate voltage, we show that the ABS arise from the discrete electronic levels of the molecule and that they reveal detailed information about the energies of these levels, their relative spin orientation and the coupling to the leads. Such measurements hence constitute a powerful new spectroscopic technique capable of elucidating the electronic structure of CNT-based devices, including those with well-coupled leads. This is relevant for conventional applications (e.g. superconducting or normal transistors, SQUIDs) and quantum information processing (e.g. entangled electron pairs generation, ABS-based qubits). Finally, our device is a new type of dc-measurable SQUID

Strong tuning of Rashba spin orbit interaction in single InAs nanowires

A key concept in the emerging field of spintronics is the gate voltage or electric field control of spin precession via the effective magnetic field generated by the Rashba spin orbit interaction. Here, we demonstrate the generation and tuning of electric field induced Rashba spin orbit interaction in InAs nanowires where a strong electric field is created either by a double gate or a solid electrolyte surrounding gate. In particular, the electrolyte gating enables six-fold tuning of Rashba coefficient and nearly three orders of magnitude tuning of spin relaxation time within only 1 V of gate bias. Such a dramatic tuning of spin orbit interaction in nanowires may have implications in nanowire based spintronic devices.Comment: Nano Letters, in pres