2,109 research outputs found
Improved source of infrared radiation for spectroscopy
Radiation from a crimped V-groove in the electrically heated metallic element of a high-resolution infrared spectrometer is more intense than that from plane areas adjacent to the element. Radiation from the vee and the flat was compared by alternately focusing on the entrance slit of a spectrograph
Soft Black Hole Absorption Rates as Conservation Laws
The absorption rate of low-energy, or soft, electromagnetic radiation by
spherically symmetric black holes in arbitrary dimensions is shown to be fixed
by conservation of energy and large gauge transformations. We interpret this
result as the explicit realization of the Hawking-Perry-Strominger Ward
identity for large gauge transformations in the background of a non-evaporating
black hole. Along the way we rederive and extend previous analytic results
regarding the absorption rate for the minimal scalar and the photon.Comment: 20 Pages, 1 figur
Simulation of a Single Polymer Chain in Solution by Combining Lattice Boltzmann and Molecular Dynamics
In this paper we establish a new efficient method for simulating
polymer-solvent systems which combines a lattice Boltzmann approach for the
fluid with a continuum molecular dynamics (MD) model for the polymer chain. The
two parts are coupled by a simple dissipative force while the system is driven
by stochastic forces added to both the fluid and the polymer. Extensive tests
of the new method for the case of a single polymer chain in a solvent are
performed. The dynamic and static scaling properties predicted by analytical
theory are validated. In this context, the influence of the finite size of the
simulation box is discussed. While usually the finite size corrections scale as
L^{-1} (L denoting the linear dimension of the box), the decay rate of the
Rouse modes is only subject to an L^{-3} finite size effect. Furthermore, the
mapping to an existing MD simulation of the same system is done so that all
physical input values for the new method can be derived from pure MD
simulation. Both methods can thus be compared quantitatively, showing that the
new method allows for much larger time steps. Comparison of the results for
both methods indicates systematic deviations due to non-perfect match of the
static chain conformations.Comment: 17 pages, 12 figures, submitted to J. Chem. Phy
[2.2](4,7)Isobenzofuranophanes - Synthesis, Characterisation and Reactivity
The isomeric Diels-Alder adducts 3, obtained by cycloaddition of tetraphenylcyclopentadienone to the 4,5:12,13-bis-(oxanorbornadieno)[2.2]paracyclophanes syn,syn- and anti,-syn-2[Note ][The stereochemical descriptors syn and anti refer to the orientation of the oxygen bridge in the oxabicyclo[2.2.1]heptadiene subunits with respect to the [2.2]paracyclophaneskeleton.], yield the unstable isobenzofuranophane 4 by consecutive extrusion of carbon monoxide and tetraphenylbenzene when heated to 180°C. The molecular ion of 4 was observed in the EI mass spectrum. The stable tetraphenyl-substituted analogue 10 was synthesized independently from the previously unknown 4,5,12,13-tetrabenzoyl[2.2]paracyclophane (9). UV/Vis as well as fluorescence spectra and an X-ray crystal structure analysis of 9 are reported
Study of interfacial conductivity Final report
Statistical theory of interfacial thermal conductivity and crystal growth under weightlessnes
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