25,326 research outputs found
Size-dependence of Strong-Coupling Between Nanomagnets and Photonic Cavities
The coherent dynamics of a coupled photonic cavity and a nanomagnet is
explored as a function of nanomagnet size. For sufficiently strong coupling
eigenstates involving highly entangled photon and spin states are found, which
can be combined to create coherent states. As the size of the nanomagnet
increases its coupling to the photonic mode also monotonically increases, as
well as the number of photon and spin states involved in the system's
eigenstates. For small nanomagnets the crystalline anisotropy of the magnet
strongly localized the eigenstates in photon and spin number, quenching the
potential for coherent states. For a sufficiently large nanomagnet the
macrospin approximation breaks down and different domains of the nanomagnet may
couple separately to the photonic mode. Thus the optimal nanomagnet size is
just below the threshold for failure of the macrospin approximation.Comment: 10 pages, 7 figure
An Exact Optimal Solution to a Threshold Inventory Rationing Model for Two Priority Demand Classes
An Exact Optimal Solution to a Threshold Inventory Rationing Model for Two Priority Demand Classe
Meeting Their Fullest Potential: The Beliefs and Teaching of a Culturally Relevant Science Teacher
As elementary and middle school children of color continue to score poorly on science standardized tests, culturally relevant teaching has been shown to be an effective approach to addressing the social and academic needs of students from diverse backgrounds. This article illustrates how the theory of culturally relevant pedagogy is embraced in the teaching beliefs of a sixth grade science teacher in a rural, low socioeconomic, predominantly African American school. The findings from a qualitative case study reveal beliefs and teaching practices consistent with three major tenets of culturally relevant pedagogy: conceptions of self and students; social relations; and perceptions of knowledge (Ladson-Billings, 2009). This study builds upon the culturally relevant pedagogy knowledge base by illustrating the tenets of this theory in the beliefs and teaching practices of a sixth grade science teacher
SAFT-γ force field for the simulation of molecular fluids: 8. hetero-group coarse-grained models of perfluoroalkylalkanes assessed with new vapour-liquid interfacial tension data
The air-liquid interfacial behaviour of linear perfluoroalkylalkanes (PFAAs) is reported through a combined experimental and computer simulation study. The surface tensions of seven liquid PFAAs (perfluorobutylethane, F4H2; perfluorobutylpentane, F4H5; perfluorobutylhexane, F4H6, perfluorobutyloctane, F4H8; perfluorohexylethane, F6H2; perfluorohexylhexane, F6H6; and perfluorohexyloctane, F6H8) are experimentally determined over a wide temperature range (276 to 350 K). The corresponding surface thermodynamic properties and the critical temperatures of the studied compounds are estimated from the temperature dependence of the surface tension. Experimental density and vapour pressure data are employed to parameterize a generic heteronuclear coarse-grained intermolecular potential of the SAFT- γ family for PFAAs. The resulting force field is used in direct molecular dynamics simulations to predict with quantitative agreement the experimental tensions and to explore the conformations of the molecules in the interfacial region revealing a preferential alignment of the PFAA molecules towards the interface and an enrichment of the perfluoro-groups at the outer interface region
Strongly coupled plasma with electric and magnetic charges
A number of theoretical and lattice results lead us to believe that
Quark-Gluon Plasma not too far from contains not only electrically
charged quasiparticles -- quarks and gluons -- but magnetically charged ones --
monopoles and dyons -- as well. Although binary systems like charge-monopole
and charge-dyon were considered in details before in both classical and quantum
settings, it is the first study of coexisting electric and magnetic particles
in many-body context. We perform Molecular Dynamics study of strongly coupled
plasmas with particles and different fraction of magnetic charges.
Correlation functions and Kubo formulae lead to such transport properties as
diffusion constant, shear viscosity and electric conductivity: we compare the
first two with empirical data from RHIC experiments as well as results from
AdS/CFT correspondence. We also study a number of collective excitations in
these systems.Comment: 2nd version, 22 pages, 32 figures: two important new figures have
been included to compare our results with RHIC experiments and AdS/CFT
results; a few new references and comments are added as wel
Systematic study of Pt-Ru/C catalysts prepared by chemical deposition for direct methanol fuel cells
In this research, the activity and stability for methanol electro-oxidation on Pt-Ru/C catalysts was increased by optimising the catalyst preparation method. The Pt-Ru/C catalysts were synthesised using Pt(acac)2 and Ru(acac)3 precursors for chemical deposition of the metals. Performance of the catalyst was examined by cyclic voltammetry and chronoamperometry in a methanol-containing electrolyte. TEM, EDS, X-ray photoelectron spectroscopy and XRD were used to physically characterise the catalysts. The parameters investigated were precursor decomposition phase, synthesis temperature and Pt/Ru ratio. Precursor deposition from the liquid phase was more active for methanol electro-oxidation, predominantly due to particle size and degree of alloying achieved during this precursor decomposition phase. Synthesis temperature affected the particle size, active surface area, ruthenium oxidation state and degree of alloying which in turn affected catalyst stability and activity for methanol electro-oxidation. The Pt/Ru ratio greatly affects the performance of the catalyst. The catalyst with the highest activity for methanol electro-oxidation was the catalyst synthesised at 350 °C with a Pt/Ru ratio of 50:50
Quadrupole collective modes in trapped finite-temperature Bose-Einstein condensates
Finite temperature simulations are used to study quadrupole excitations of a
trapped Bose-Einstein condensate. We focus specifically on the m=0 mode, where
a long-standing theoretical problem has been to account for an anomalous
variation of the mode frequency with temperature. We explain this behavior in
terms of the excitation of two separate modes, corresponding to coupled motion
of the condensate and thermal cloud. The relative amplitudes of the modes
depends sensitively on the temperature and on the frequency of the harmonic
drive used to excite them. Good agreement with experiment is found for
appropriate drive frequencies.Comment: 4 pages, 3 figure
Managing Change: Reflections on Innovation in the Public Sector
In January 1983, when Governor Michael S. Dukakis appointed Ira Jackson as commissioner of revenue, the Commonwealth of Massachusetts was facing an estimated 86 million has been completed. Since Jackson\u27s appointment, annual revenue collections overall have risen 60 percent, without any broad-based tax increases. This article tells the story of change at the Department of Revenue and suggests generic principles that may be inferred from the experience
Analytical investigation of magnetic field distributions around superconducting strips on ferromagnetic substrates
The complex-field approach is developed to derive analytical expressions of
the magnetic field distributions around superconducting strips on ferromagnetic
substrates (SC/FM strips). We consider the ferromagnetic substrates as ideal
soft magnets with an infinite magnetic permeability, neglecting the
ferromagnetic hysteresis. On the basis of the critical state model for a
superconducting strip, the ac susceptibility of a SC/FM
strip exposed to a perpendicular ac magnetic field is theoretically
investigated, and the results are compared with those for superconducting
strips on nonmagnetic substrates (SC/NM strips). The real part for
(where is the amplitude of the ac magnetic field,
is the critical current density, and is the thickness of the
superconducting strip) of a SC/FM strip is 3/4 of that of a SC/NM strip. The
imaginary part (or ac loss ) for of a SC/FM
strip is larger than that of a SC/NM strip, even when the ferromagnetic
hysteresis is neglected, and this enhancement of (or ) is due to
the edge effect of the ferromagnetic substrate.Comment: 8 pages, 6 figures, submitted to Phys. Rev.
Power-law weighted networks from local attachments
This letter introduces a mechanism for constructing, through a process of
distributed decision-making, substrates for the study of collective dynamics on
extended power-law weighted networks with both a desired scaling exponent and a
fixed clustering coefficient. The analytical results show that the connectivity
distribution converges to the scaling behavior often found in social and
engineering systems. To illustrate the approach of the proposed framework we
generate network substrates that resemble steady state properties of the
empirical citation distributions of (i) publications indexed by the Institute
for Scientific Information from 1981 to 1997; (ii) patents granted by the U.S.
Patent and Trademark Office from 1975 to 1999; and (iii) opinions written by
the Supreme Court and the cases they cite from 1754 to 2002.Comment: 18 pages, 3 figures; Proceedings of the IEEE Conference on Decision
and Control and the European Control Conference, Orlando, FL, Dec. 2011;
Added references; We modified the model in order to take into account
extended power-law distributions which better fit to the citations data sets;
Added proofs of theorems; Shorten version; Updated plo
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