Merged infrared catalogue

A compilation of equatorial coordinates, spectral types, magnitudes, and fluxes from five catalogues of infrared observations is presented. This first edition of the Merged Infrared Catalogue contains 11,201 oservations from the Two-Micron Sky Survey, Observations of Infrared Radiation from Cool Stars, the Air Force Geophysics Laboratory four Color Infrared Sky Survey and its Supplemental Catalog, and from Catalog of 10 micron Celestial Objects (HALL). This compilation is a by-product of a computerized infrared data base under development at Goddard Space Flight Center; the objective is to maintain a complete and current record of all infrared observations from 1 micron m to 1000 micron m of nonsolar system objects. These observations are being placed into a standardized system

A comparison of direct measurements and G.E.K. observations in the Florida Current off Miami

Electrical measurements represent an indirect measure of the velocity structure of an ocean current. An interpretation of such measurements requires consideration of many influences, including the distribution of the vertically averaged velocity, of the bottom topography, and of the electrical-conductivity structure of the ocean and the sea bed...

An exactly solvable toy model that mimics the mode coupling theory of supercooled liquid and glass transition

A toy model is proposed which incorporates the reversible mode coupling mechanism responsible for ergodic-nonergodic transition with trivial Hamiltonian in the mode coupling theory (MCT) of structural glass transition. The model can be analyzed without relying on uncontrolled approximations inevitable in the current MCT. The strength of hopping processes can be easily tuned and the ideal glass transition is reproduced only in a certain range of the strength. On the basis of the analyses of our model we discuss about a sharp ergodic-nonergodic transition and its smearing out by "hopping".Comment: 5 pages, 2 ps-figures, inappropriate terms replace

Mott-Hubbard exciton in the optical conductivity of YTiO3 and SmTiO3

In the Mott-Hubbard insulators YTiO3 and SmTiO3 we study optical excitations from the lower to the upper Hubbard band, d^1d^1 -> d^0d^2. The multi-peak structure observed in the optical conductivity reflects the multiplet structure of the upper Hubbard band in a multi-orbital system. Absorption bands at 2.55 and 4.15 eV in the ferromagnet YTiO3 correspond to final states with a triplet d^2 configuration, whereas a peak at 3.7 eV in the antiferromagnet SmTiO3 is attributed to a singlet d^2 final state. A strongly temperature-dependent peak at 1.95 eV in YTiO3 and 1.8 eV in SmTiO3 is interpreted in terms of a Hubbard exciton, i.e., a charge-neutral (quasi-)bound state of a hole in the lower Hubbard band and a double occupancy in the upper one. The binding to such a Hubbard exciton may arise both due to Coulomb attraction between nearest-neighbor sites and due to a lowering of the kinetic energy in a system with magnetic and/or orbital correlations. Furthermore, we observe anomalies of the spectral weight in the vicinity of the magnetic ordering transitions, both in YTiO3 and SmTiO3. In the G-type antiferromagnet SmTiO3, the sign of the change of the spectral weight at T_N depends on the polarization. This demonstrates that the temperature dependence of the spectral weight is not dominated by the spin-spin correlations, but rather reflects small changes of the orbital occupation.Comment: Strongly extended version; new data of SmTiO3 included; detailed discussion of temperature dependence include

A Non-Disordered Glassy Model with a Tunable Interaction Range

We introduce a non-disordered lattice spin model, based on the principle of minimizing spin-spin correlations up to a (tunable) distance R. The model can be defined in any spatial dimension D, but already for D=1 and small values of R (e.g. R=5) the model shows the properties of a glassy system: deep and well separated energy minima, very slow relaxation dynamics, aging and non-trivial fluctuation-dissipation ratio.Comment: 4 pages, 5 figure

Numerical electrokinetics

A new lattice method is presented in order to efficiently solve the electrokinetic equations, which describe the structure and dynamics of the charge cloud and the flow field surrounding a single charged colloidal sphere, or a fixed array of such objects. We focus on calculating the electrophoretic mobility in the limit of small driving field, and systematically linearise the equations with respect to the latter. This gives rise to several subproblems, each of which is solved by a specialised numerical algorithm. For the total problem we combine these solvers in an iterative procedure. Applying this method, we study the effect of the screening mechanism (salt screening vs. counterion screening) on the electrophoretic mobility, and find a weak non-trivial dependence, as expected from scaling theory. Furthermore, we find that the orientation of the charge cloud (i. e. its dipole moment) depends on the value of the colloid charge, as a result of a competition between electrostatic and hydrodynamic effects.Comment: accepted for publication in Journal of Physics Condensed Matter (proceedings of the 2012 CODEF conference

Development of the post-injection propulsion system for the Mariner C spacecraft

Monopropellant hydrazine-fueled rocket used as post injection propulsion system for Mariner C spacecraf

Crystal structure of Mycobacterium tuberculosis ClpP1P2 suggests a model for peptidase activation by AAA+ partner binding and substrate delivery

Caseinolytic peptidase P (ClpP), a double-ring peptidase with 14 subunits, collaborates with ATPases associated with diverse activities (AAA+) partners to execute ATP-dependent protein degradation. Although many ClpP enzymes self-assemble into catalytically active homo-tetradecamers able to cleave small peptides, the Mycobacterium tuberculosis enzyme consists of discrete ClpP1 and ClpP2 heptamers that require a AAA+ partner and protein–substrate delivery or a peptide agonist to stabilize assembly of the active tetradecamer. Here, we show that cyclic acyldepsipeptides (ADEPs) and agonist peptides synergistically activate ClpP1P2 by mimicking AAA + partners and substrates, respectively, and determine the structure of the activated complex. Our studies establish the basis of heteromeric ClpP1P2 assembly and function, reveal tight coupling between the conformations of each ring, show that ADEPs bind only to one ring but appear to open the axial pores of both rings, provide a foundation for rational drug development, and suggest strategies for studying the roles of individual ClpP1 and ClpP2 rings in Clp-family proteolysisNational Institutes of Health (U.S.) (NIH Grant GM-101988)Brown UniversityNational Science Foundation (U.S.) (CAREER award)National Institute of General Medical Sciences (U.S.) (Grant P41 GM103403)United States. Dept. of Energy (Contract DE-AC02-06CH11357

Complexity Bounds for Ordinal-Based Termination

`What more than its truth do we know if we have a proof of a theorem in a given formal system?' We examine Kreisel's question in the particular context of program termination proofs, with an eye to deriving complexity bounds on program running times. Our main tool for this are length function theorems, which provide complexity bounds on the use of well quasi orders. We illustrate how to prove such theorems in the simple yet until now untreated case of ordinals. We show how to apply this new theorem to derive complexity bounds on programs when they are proven to terminate thanks to a ranking function into some ordinal.Comment: Invited talk at the 8th International Workshop on Reachability Problems (RP 2014, 22-24 September 2014, Oxford