125 research outputs found
A reactive assimilation model for regional-scale cordierite-bearing granitoids: geochemical evidence from the Late Variscan granites of the Central Iberian Zone, Spain
Regional scale biotite and cordierite-bearing granites (s.l.) in the Variscan of the Central Iberian Zone (CIZ) are spatially closely associated with cordierite-rich nebulites and cordierite-bearing two-mica granites, and with cordierite-rich high grade hornfelses and cordieritites (>60% cordierite) that are relatively common in the aureoles of these granites. Building on published field evidence, petrological data are presented which, combined with new chemical and isotopic (Sr-Nd) modelling, indicate that the cordierite-bearing granites cannot be derived by simple anatexis of regional sedimenatry protoliths; but the data are consistent with a process of reactive assimilation that involves the interaction of biotite granite magma with high-grade host rocks ranging from cordierite nebulites to andalusite-bearing cordieritites. The contribution of the postulated cordierite-rich contaminants to the diversity of cordierite granite compositions is modelled using the compositions of regional Lower Cambrian-Upper Neoproterozoic metasedimentary rocks that are generally chemically mature (CaO very rarely exceeds 1.4%). These rocks include specific horizons in which extreme chemical alteration is attributable to sediment reworking during eustatic falls in sea level. Such compositions may account for the presence of the high concentrations in Al that later produced cordieritites. Fractional crystallisation is also important, particularly in generating the more evolved cordierite granite and cordierite biotite muscovite granite compositions. Although assimilation in situ is normally regarded as a minor contributor volumetrically to evolving plutons, in this instance the emplacement of large volumes of granite magma into a high-T-low-P environment significantly increased the potential for reactive assimilation
Electrical resistivity at large temperatures: Saturation and lack thereof
Many transition metal compounds show saturation of the resistivity at high
temperatures, T, while the alkali-doped fullerenes and the high-Tc cuprates are
usually considered to show no saturation. We present a model of transition
metal compounds, showing saturation, and a model of alkali-doped fullerenes,
showing no saturation. To analyze the results we use the f-sum rule, which
leads to an approximate upper limit for the resistivity at large T. For some
systems and at low T, the resistivity increases so rapidly that this upper
limit is approached for experimental T. The resistivity then saturates. For a
model of transition metal compounds with weakly interacting electrons, the
upper limit corresponds to a mean free path consistent with the Ioffe-Regel
condition. For a model of the high Tc cuprates with strongly interacting
electrons, however, the upper limit is much larger than the Ioffe-Regel
condition suggests. Since this limit is not exceeded by experimental data, the
data are consistent with saturation also for the cuprates. After "saturation"
the resistivity usually grows slowly. For the alkali-doped fullerenes,
"saturation" can be considered to have happened already for T=0, due to
orientational disorder. For these systems, however, the resistivity grows so
rapidly after "saturation" that this concept is meaningless. This is due to the
small band width and to the coupling to the level energies of the important
phonons.Comment: 22 pages, RevTeX, 19 eps figures, additional material available at
http://www.mpi-stuttgart.mpg.de/andersen/fullerene
Video-based Simulations: Considerations for Teaching Students with Developmental Disabilities
The use of video-based multimedia simulations for teaching functional skills to persons with developmental disabilities remains an unexplored application of technology for this group. This article examines the historical literature in this area, and discusses future considerations, design issues, and implications of using multimedia simulations. Implementation issues are presented, and suggestions regarding design, development, and application of multimedia simulations are offered. Considerations address the importance of appropriate role modeling and the combination of video-based simulation and in vivo training to foster generalization and maintenance in the context of transition to the real world.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
Nonequilibrium Evolution of Correlation Functions: A Canonical Approach
We study nonequilibrium evolution in a self-interacting quantum field theory
invariant under space translation only by using a canonical approach based on
the recently developed Liouville-von Neumann formalism. The method is first
used to obtain the correlation functions both in and beyond the Hartree
approximation, for the quantum mechanical analog of the model. The
technique involves representing the Hamiltonian in a Fock basis of annihilation
and creation operators. By separating it into a solvable Gaussian part
involving quadratic terms and a perturbation of quartic terms, it is possible
to find the improved vacuum state to any desired order. The correlation
functions for the field theory are then investigated in the Hartree
approximation and those beyond the Hartree approximation are obtained by
finding the improved vacuum state corrected up to . These
correlation functions take into account next-to-leading and
next-to-next-to-leading order effects in the coupling constant. We also use the
Heisenberg formalism to obtain the time evolution equations for the equal-time,
connected correlation functions beyond the leading order. These equations are
derived by including the connected 4-point functions in the hierarchy. The
resulting coupled set of equations form a part of infinite hierarchy of coupled
equations relating the various connected n-point functions. The connection with
other approaches based on the path integral formalism is established and the
physical implications of the set of equations are discussed with particular
emphasis on thermalization.Comment: Revtex, 32 pages; substantial new material dealing with
non-equilibrium evolution beyond Hartree approx. based on the LvN formalism,
has been adde
Hadron Energy Reconstruction for the ATLAS Calorimetry in the Framework of the Non-parametrical Method
This paper discusses hadron energy reconstruction for the ATLAS barrel
prototype combined calorimeter (consisting of a lead-liquid argon
electromagnetic part and an iron-scintillator hadronic part) in the framework
of the non-parametrical method. The non-parametrical method utilizes only the
known ratios and the electron calibration constants and does not require
the determination of any parameters by a minimization technique. Thus, this
technique lends itself to an easy use in a first level trigger. The
reconstructed mean values of the hadron energies are within of the
true values and the fractional energy resolution is . The value of the ratio
obtained for the electromagnetic compartment of the combined calorimeter is
and agrees with the prediction that for this
electromagnetic calorimeter. Results of a study of the longitudinal hadronic
shower development are also presented. The data have been taken in the H8 beam
line of the CERN SPS using pions of energies from 10 to 300 GeV.Comment: 33 pages, 13 figures, Will be published in NIM
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