1,200 research outputs found

    Enrollment in the 2003/2004 MILC Program: Does Timing Matter?

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    Agricultural and Food Policy, Marketing,

    Quantum Continuum Mechanics Made Simple

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    In this paper we further explore and develop the quantum continuum mechanics (CM) of [Tao \emph{et al}, PRL{\bf 103},086401] with the aim of making it simpler to use in practice. Our simplifications relate to the non-interacting part of the CM equations, and primarily refer to practical implementations in which the groundstate stress tensor is approximated by its Kohn-Sham version. We use the simplified approach to directly prove the exactness of CM for one-electron systems via an orthonormal formulation. This proof sheds light on certain physical considerations contained in the CM theory and their implication on CM-based approximations. The one-electron proof then motivates an approximation to the CM (exact under certain conditions) expanded on the wavefunctions of the Kohn-Sham (KS) equations. Particular attention is paid to the relationships between transitions from occupied to unoccupied KS orbitals and their approximations under the CM. We also demonstrate the simplified CM semi-analytically on an example system

    Pen portraits of presidents – Prof. Henry Charnock, CBE, FRS

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    This paper reviews the life of Prof. Henry Charnock. He was a President of the Royal Meteorological Society (1982–1984) whose expertise spanned both the atmosphere and ocean. He started as a meteorological forecaster with the Royal Air Force during WWII and went on to study air–sea interaction and the structure of the upper ocean. He later exerted considerable influence on the shape of both United Kingdom and international marine science

    HMS Challenger and SMS Gazelle – their 19th century voyages compared

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    This paper analyses the pioneering global voyages of HMS Challenger and SMS Gazelle in the 1870s – a time of rapid scientific advances and technological innovation. The voyage of Challenger has become well known as marking the start of the global-scale science of oceanography. The voyage of the Gazelle is much less well known despite the two voyages ending in the same year, 1876, and having similar geographical and scientific scope. Rather than focussing on the scientific achievements, the paper concentrates on how the expeditions were planned and executed, the lives and characters of the personnel involved, and the underlying motivation behind the voyages. The paper presents the author's translations of key elements of the Gazelle reports as a means of introducing the Gazelle expedition to an English-speaking readership

    The SCOR Working Group 21 intercomparison of recording current meters on R/V "AKADEMIK KURCHATOV" – 50 years later

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    This paper describes the activities of SCOR WG21 that carried out intercomparisons of moored, recording current meters in the late 1960s and early 1970s. The paper focusses particularly on the WG’s involvement in the 7th voyage of the R/V “Akademik Kurchatov” and its participation in the ground-breaking Polygon–70 programme

    Global-scale patterns of observed sea surface salinity intensified since the 1870s

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    Sea surface salinity patterns have intensified between the mid-20th century and present day, with saline areas becoming saltier and fresher areas fresher. This change has been linked to a human-induced strengthening of the global hydrological cycle as global mean surface temperatures rose. Here we analyse salinity observations from the round-the-world voyages of HMS Challenger and SMS Gazelle in the 1870s, early in the industrial era, to reconstruct surface salinity changes since that decade. We find that the amplification of the salinity change pattern between the 1870s and the 1950s was at a rate that was 54 ± 10% lower than the post-1950s rate. The acceleration in salinity pattern amplification over almost 150 years implies that the hydrological cycle would have similarly accelerated over this period

    Gauge Singlet Scalars as Cold Dark Matter

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    In light of recent interest in minimal extensions of the Standard Model and gauge singlet scalar cold dark matter, we provide an arXiv preprint of the paper, published as Phys.Rev. D50 (1994) 3637, which presented the first detailed analysis of gauge singlet scalar cold dark matter.Comment: 37 pages, 11 figures, LaTe

    Retired A Stars and Their Companions VI. A Pair of Interacting Exoplanet Pairs Around the Subgiants 24 Sextanis and HD200964

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    We report radial velocity measurements of the G-type subgiants 24 Sextanis (=HD90043) and HD200964. Both are massive, evolved stars that exhibit periodic variations due to the presence of a pair of Jovian planets. Photometric monitoring with the T12 0.80m APT at Fairborn Observatory demonstrates both stars to be constant in brightness to <= 0.002 mag, thus strengthening the planetary interpretation of the radial velocity variations. 24 Sex b,c have orbital periods of 453.8 days and 883~days, corresponding to semimajor axes 1.333 AU and 2.08 AU, and minimum masses (Msini) 1.99 Mjup and 0.86 Mjup, assuming a stellar mass 1.54 Msun. HD200964 b,c have orbital periods of 613.8 days and 825 days, corresponding to semimajor axes 1.601 AU and 1.95 AU, and minimum masses 1.85 Mjup and 0.90 Mjup, assuming M* = 1.44 Msun. We also carry out dynamical simulations to properly account for gravitational interactions between the planets. Most, if not all, of the dynamically stable solutions include crossing orbits, suggesting that each system is locked in a mean motion resonance that prevents close encounters and provides long-term stability. The planets in the 24 Sex system likely have a period ratio near 2:1, while the HD200964 system is even more tightly packed with a period ratio close to 4:3. However, we caution that further radial velocity observations and more detailed dynamical modelling will be required to provide definitive and unique orbital solutions for both cases, and to determine whether the two systems are truly resonant.Comment: AJ accepte
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