33,552 research outputs found
Turbulence and turbulent mixing in natural fluids
Turbulence and turbulent mixing in natural fluids begins with big bang
turbulence powered by spinning combustible combinations of Planck particles and
Planck antiparticles. Particle prograde accretions on a spinning pair releases
42% of the particle rest mass energy to produce more fuel for turbulent
combustion. Negative viscous stresses and negative turbulence stresses work
against gravity, extracting mass-energy and space-time from the vacuum.
Turbulence mixes cooling temperatures until strong-force viscous stresses
freeze out turbulent mixing patterns as the first fossil turbulence. Cosmic
microwave background temperature anisotropies show big bang turbulence fossils
along with fossils of weak plasma turbulence triggered as plasma photon-viscous
forces permit gravitational fragmentation on supercluster to galaxy mass
scales. Turbulent morphologies and viscous-turbulent lengths appear as linear
gas-proto-galaxy-clusters in the Hubble ultra-deep-field at z~7. Proto-galaxies
fragment into Jeans-mass-clumps of primordial-gas-planets at decoupling: the
dark matter of galaxies. Shortly after the plasma to gas transition,
planet-mergers produce stars that explode on overfeeding to fertilize and
distribute the first life.Comment: 23 pages 12 figures, Turbulent Mixing and Beyond 2009 International
Center for Theoretical Physics conference, Trieste, Italy. Revision according
to Referee comments. Accepted for Physica Scripta Topical Issue to be
published in 201
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How Useful are High-Precision Delta ?17O Data in Defining the Asteroidal Sources of Meteorites?: Evidence from Main-Group Pallasites, Primitive and Differentiated Achondrites
High-precision oxygen isotope analysis is capable of revealing important information about the relationship between different meteorite groups. New data confirm that the main-group pallasites are from a distinct source to either the HEDs or mesosiderites
The pragmatic maxim as learning analytics research method
It is arguable that the chief aim of Learning Analytics is to use analytics for meaningful purposes in learning and teaching contexts, and that research in the field should advance this cause. However the field does not present a single clear understanding of what constitutes quality in Learning Analytics research. In this paper we present the Pragmatic Inquiry for Learning Analytics Research (PILAR) method as one approach to conducting Learning Analytics research. Rather than creating a new method, we reintroduce an old method to a new field, drawing on the Pragmatic Maxim, proposed by Charles Sanders Peirce as a principle for making ideas clear. Our instantiation of the Pragmatic Maxim requires the researcher to situate Learning Analytics research within a clearly defined learning context and to consider the analytics in terms of the practical effects on learning. We propose three essential elements and a five step process for addressing them in research. After presenting PILAR we address two potential limitations of the approach, and conclude with some implications for its future use in Learning Analytics research
Gravitational hydrodynamics of large scale structure formation
The gravitational hydrodynamics of the primordial plasma with neutrino hot
dark matter is considered as a challenge to the bottom-up cold dark matter
paradigm. Viscosity and turbulence induce a top-down fragmentation scenario
before and at decoupling. The first step is the creation of voids in the
plasma, which expand to 37 Mpc on the average now. The remaining matter clumps
turn into galaxy clusters. Turbulence produced at expanding void boundaries
causes a linear morphology of 3 kpc fragmenting protogalaxies along vortex
lines. At decoupling galaxies and proto-globular star clusters arise; the
latter constitute the galactic dark matter halos and consist themselves of
earth-mass H-He planets. Frozen planets are observed in microlensing and
white-dwarf-heated ones in planetary nebulae. The approach also explains the
Tully-Fisher and Faber-Jackson relations, and cosmic microwave temperature
fluctuations of micro-Kelvins.Comment: 6 pages, no figure
Modification of chiral dimethyl tartrate through transesterification : immobilisation on POSS and enantioselectivity reversion in Sharpless asymmetric epoxidation
Modification of dimethyl tartrate has been investigated through transesterification with aminoalcohols to provide reactive functionalities for the covalent bonding of chiral tartrate to polyhedral oligomeric silsesquioxanes. The transesterification of dimethyl tartrate has been widely studied by means of using different catalytic systems and reaction conditions. Through the proper selection of both, the catalytic system and the reaction conditions, it is possible to achieve the mono- or the bis-substituted tartrate derivative as sole products. All the intermediate chiral tartrate-derived ligands were successfully used in the homogeneous enantioselective epoxidation of allylic alcohols providing moderate enantiomeric excess over the products. Attached amine groups have been used to support the modified tartrate ligands onto a haloaryl-functionalized silsesquioxane moiety. This final chiral tartrate ligand displays enantioselectivity reversion in the asymmetric epoxidation of allylic alcohols with regards to the starting dimethyl tartrate ligand, having both molecules them the same chiral sign. However, the POSS-containing ligand can be easily recovered in almost quantitative yield and reused in asymmetric epoxidation reactions. In addition, recovered silsesquioxane-pendant ligand, though displaying decreasing catalytic activity in recycling epoxidation tests, showed very stable enantioselective behavior
CHANDRA observations of the NGC 1550 galaxy group -- implication for the temperature and entropy profiles of 1 keV galaxy groups
We present a detailed \chandra study of the galaxy group NGC 1550. For its
temperature (1.370.01 keV) and velocity dispersion ( 300 km
s), the NGC 1550 group is one of the most luminous known galaxy groups
(L = 1.65 erg s within 200 kpc, or 0.2 \rv).
We find that within kpc, where the gas cooling time is less than a
Hubble time, the gas temperature decreases continuously toward the center,
implying the existence of a cooling core. The temperature also declines beyond
100 kpc (or 0.1 \rv). There is a remarkable similarity of the
temperature profile of NGC 1550 with those of two other 1 keV groups with
accurate temperature determination. The temperature begins to decline at 0.07 -
0.1 \rv, while in hot clusters the decline begins at or beyond 0.2 \rv. Thus,
there are at least some 1 keV groups that have significantly different
temperature profiles from those of hot clusters, which may reflect the role of
non-gravitational processes in ICM/IGM evolution. NGC 1550 has no isentropic
core in its entropy profile, in contrast to the predictions of `entropy-floor'
simulations. We compare the scaled entropy profiles of three 1 keV groups
(including NGC 1550) and three 2 - 3 keV groups. The scaled entropy profiles of
1 keV groups show much larger scatter than those of hotter systems, which
implies varied pre-heating levels. We also discuss the mass content of the NGC
1550 group and the abundance profile of heavy elements.Comment: emulateapj5.sty, 18 pages, 11 figures (including 4 color), to appear
in ApJ, v598, n1, 20 Nov 200
Shuttle STS-2 mission communication systems RF coverage and performance predictions. Volume 1: Ascent
The RF communications capabilities and nominally expected performance for the ascent phase of the second orbital flight of the shuttle are provided. Predicted performance is given mainly in the form of plots of signal strength versus elapsed mission time for the STDN (downlink) and shuttle orbiter (uplink) receivers for the S-band PM and FM, and UHF systems. Performance of the NAV and landing RF systems is treated for RTLS abort, since in this case the spacecraft will loop around and return to the launch site. NAV and landing RF systems include TACAN, MSBLS, and C-band altimeter. Signal strength plots were produced by a computer program which combines the spacecraft trajectory, antenna patterns, transmit and receive performance characteristics, and system mathematical models. When available, measured spacecraft parameters were used in the predictions; otherwise, specified values were used. Specified ground station parameter values were also used. Thresholds and other criteria on the graphs are explained
Structural and Electronic Properties of Amorphous and Polycrystalline In2Se3 Films
Structural and electronic properties of amorphous and single-phase
polycrystalline films of gamma- and kappa-In2Se3 have been measured. The stable
gamma phase nucleates homogeneously in the film bulk and has a high
resistivity, while the metastable kappa phase nucleates at the film surface and
has a moderate resistivity. The microstructures of hot-deposited and
post-annealed cold-deposited gamma films are quite different but the electronic
properties are similar. The increase in the resistivity of amorphous In2Se3
films upon annealing is interpreted in terms of the replacement of In-In bonds
with In-Se bonds during crystallization. Great care must be taken in the
preparation of In2Se3 films for electrical measurements as the presence of
excess chalcogen or surface oxidation may greatly affect the film properties.Comment: 23 pages and 12 figure
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