772 research outputs found
Extended Kelvin theorem in relativistic magnetohydrodynamics
We prove the existence of a generalization of Kelvin's circulation theorem in
general relativity which is applicable to perfect isentropic
magnetohydrodynamic flow. The argument is based on a new version of the
Lagrangian for perfect magnetohydrodynamics. We illustrate the new conserved
circulation with the example of a relativistic magnetohydrodynamic flow
possessing three symmetries.Comment: Invited talk at IARD 2000, the Second International Conference on
Relativistic Dynamics, Bar-Ilan University, Israel, 26-28 June, 2000. To
appear in the proceedings in a special issue of Foundations of Physic
Fluorescence antibunching microscopy
Breaking the diffraction limit in microscopy by utilizing quantum properties
of light has been the goal of intense research in the recent years. We propose
a quantum superresolution technique based on non-classical emission statistics
of fluorescent markers, routinely used as contrast labels for bio-imaging. The
technique can be readily implemented using standard fluorescence microscopy
equipment
Minimizing total completion time on a single machine with step improving jobs
Production systems often experience a shock or a technological change, resulting in performance improvement. In such settings, job processing times become shorter if jobs start processing at, or after, a common critical date. This paper considers a single machine scheduling problem with step-improving processing times, where the effects are job-dependent. The objective is to minimize the total completion time.
We show that the problem is NP-hard in general and discuss several special cases which can be solved in polynomial time. We formulate a Mixed Integer Programming (MIP) model and develop an LP-based heuristic for the general problem. Finally, computational experiments show that the proposed heuristic yields very effective and efficient solutions
Theory of selective excitation in Stimulated Raman Scattering
A semiclassical model is used to investigate the possibility of selectively
exciting one of two closely spaced, uncoupled Raman transitions. The duration
of the intense pump pulse that creates the Raman coherence is shorter than the
vibrational period of a molecule (impulsive regime of interaction). Pulse
shapes are found that provide either enhancement or suppression of particular
vibrational excitations.Comment: RevTeX4,10 pages, 5 figures, submitted to Phys.Rev.
A Large Blue Shift of the Biexciton State in Tellurium Doped CdSe Colloidal Quantum Dots
The exciton-exciton interaction energy of Tellurium doped CdSe colloidal
quantum dots is experimentally investigated. The dots exhibit a strong Coulomb
repulsion between the two excitons, which results in a huge measured biexciton
blue shift of up to 300 meV. Such a strong Coulomb repulsion implies a very
narrow hole wave function localized around the defect, which is manifested by a
large Stokes shift. Moreover, we show that the biexciton blue shift increases
linearly with the Stokes shift. This result is highly relevant for the use of
colloidal QDs as optical gain media, where a large biexciton blue shift is
required to obtain gain in the single exciton regime.Comment: 9 pages, 4 figure
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