11,488 research outputs found
A Variational Estimate of the Binding Energy of Charge-Transfer Excitons in the Cuprate Superconductors.
We present a variational estimate for the binding energy of a Frenkel exciton
in the insulating cuprate superconductors. Starting from the three band Hubbard
model we perform a canonical transformation to O(), where is the bare
nearest neighbour copper-oxygen hopping integral. An effective Hamiltonian is
then derived to describe the hopping of the exciton through the copper oxide
plane. The critical parameter in the model is the nearest neighbour
copper-oxygen coulomb repulsion, . It is found that a critical value of
is needed to observe bound Frenkel excitons, and that these excitons have the
same symmetry as the parent copper orbital, . We determine the
critical value of using a variational approach, and attempt to fit the
parameters of the model to known experimental results.Comment: Latex document. Figures on request
Review of AIDS development
The operation and implementation of the aircraft integrated data system AIDS are described. The system is described as an engineering tool with strong emphasis on analysis of recorded information. The AIDS is primarily directed to the monitoring of parameters related to: the safety of the flight; the performance of the aircraft; the performance of the flight guidance system; and the performance and condition of the engines. The system provide short term trend analysis on a trend chart that is updated by the flight engineer on every flight that lasts more than 4 flight hours. Engine data prints are automatically presented during take-off and in the case of limit excedance, e.g., the print shows an automatically reported impending hotstarts on engine nr. 1. Other significant features are reported
Environment of compact extragalactic radio sources
We have studied the interrelation of young AGN with their hosts. The objects
of study are the young and powerful GPS and CSS radio sources. Due to their
small size, GPS and CSS sources are excellent probes of this relation.
Furhthermore, their young age allows us to compare them to the larger, old
radio sources and establish a time-line evolution of this relation. Combining
imaging and spectroscopy at UV, optical and radio wavelengths we find evidence
of strong interaction between the host and the radio source. The presence and
expansion of the radio source clearly affects the properties and evolution of
the host. Furthermore, the radio source and host significantly affect each
other's evolution. We describe our results and how these interactions take
place.Comment: 6 pages. To appear in "Highlights of Spanisg astrophysics IV.
Proceedings of the VII scientific meeting of the Spanish Astronomical
Society". Editors: F. Figueras, J.M. Girart, M.Hernanz, C. Jordi. Springe
Cross sections of proton-induced reactions on 152Gd, 155Gd and 159Tb with emphasis on the production of selected Tb radionuclides
Cross sections are presented for various Dy, Tb and Gd radionuclides produced in the proton bombardment
of 159Tb as well as for the reactions 152Gd(p,4n)149Tb and 155Gd(p,4n)152Tb up to 66 MeV. The
experimental excitation functions are compared with theoretical predictions by means of the geometrydependent
hybrid (GDH) model as implemented in the code ALICE/ASH, as well as with values from the
TENDL-2012 library and previous literature experimental data, where available. Physical yields have been
derived for the production of some of the medically important radioterbiums, namely 149Tb (radionuclide
therapy), 152Tb (PET) and 155Tb (SPECT). The indirect production of high-purity 155Tb via the decay of
its precursor 155Dy is reported. The possibility of a large-scale production facility based on a commercial
70 MeV cyclotron is also discussed
Winning in the long run: a quantified approach to the drivers of sustainable financial value on real estate: Working Paper 2
This working paper describes the first empirical study measuring the impact of sustainability characteristics on the financial performance of European office and retail properties. The authors present the project, the issue and the approach of their ongoing search for a �Green Alpha�. In a joint effort, university experts at Danube University Krems are in cooperation with Kingston University London tackling a robust analysis on hard data from real properties of institutional investment portfolios in the United Kingdom, France, the Netherlands, Germany, Switzerland and Austria. Their first
results are expected by the end of 2010
Bi-Directional Relativistic Jets of the Radio Galaxy 1946+708: Constraints on the Hubble Constant
We present measurements of bi-directional motions in the jets of the radio
galaxy 1946+708 at z=0.101. This is a Compact Symmetric Object with striking
S-symmetry. Sensitive 15 GHz observations reveal a compact component at the
center of symmetry with a strongly inverted spectrum, that we identify as the
core. From five 4.9 GHz observations spread over 4 years we have determined the
velocities of four compact jet components. If simple kinematic models can be
applied then the inclination of the source and the bulk jet velocity can be
directly determined for any assumed value of the Hubble constant. Conversely,
the measurements already place constraints on the Hubble constant, and we show
how further observations of 1946+708 can yield an increasingly accurate
determination of H_0.Comment: in press at ApJ Letters, 12 page LaTex document includes 5 postscript
figure
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