85 research outputs found
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
Dissipation and Decoherence in Nanodevices: a Generalized Fermi's Golden Rule
We shall revisit the conventional adiabatic or Markov approximation, which
--contrary to the semiclassical case-- does not preserve the positive-definite
character of the corresponding density matrix, thus leading to highly
non-physical results. To overcome this serious limitation, originally pointed
out and partially solved by Davies and co-workers almost three decades ago, we
shall propose an alternative more general adiabatic procedure, which (i) is
physically justified under the same validity restrictions of the conventional
Markov approach, (ii) in the semiclassical limit reduces to the standard
Fermi's golden rule, and (iii) describes a genuine Lindblad evolution, thus
providing a reliable/robust treatment of energy-dissipation and dephasing
processes in electronic quantum devices. Unlike standard master-equation
formulations, the dependence of our approximation on the specific choice of the
subsystem (that include the common partial trace reduction) does not threaten
positivity, and quantum scattering rates are well defined even in case the
subsystem is infinitely extended/has continuous spectrum.Comment: 6 pages, 0 figure
The diversity of odonata and their endophytic ovipositions from the upper oligocene fossillagerstÀtte of rott (Rhineland, Germany)
A commented list of fossil Odonata from the Oligocene outcrop of Rott is given, together with descriptions of new traces of oviposition in plant tissues, very similar to ichnotaxa already known from the early Eocene Laguna del Hunco floras of Patagonia. The joint presences of odonatan larvae and traces of oviposition demonstrate the autochthony of these insects in the palaeolake of Rott, confirming the existence of a diverse and abundant aquatic entomofauna, a situation strikingly different to that in the contemporaneous Oligocene palaeolake of CĂ©reste (France).Fil: Petrulevicius, Julian Fernando. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. DivisiĂłn PaleozoologĂa Invertebrados; ArgentinaFil: Wappler, Torsten. Universitat Bonn; AlemaniaFil: Nel, AndrĂ©. MusĂ©um National d'Histoire Naturelle; FranciaFil: Rust, Jes. Universitat Bonn; Alemani
Explosive detection using a novel dielectric barrier discharge ionisation source for mass spectrometry
The detection of explosives is of great importance, as is the need for sensitive, reliable techniques that require little or no sample preparation and short run times for high throughput analysis. In this work, a novel ionisation source is presented based on a dielectric barrier discharge (DBD). This not only affects desorption and ionisation but also forms an ionic wind, providing mass transportation of ions towards the mass spectrometer. Furthermore, the design incorporates 2 asymmetric alumina sheets, each containing 3 DBDs, so that a large surface area can be analysed. The DBD operates in ambient air, overcoming the limitation of other plasmaâbased techniques which typically analyse smaller surface areas and require solvents or gases. A range of explosives across 4 different functional groups was analysed using the DBD with low limits of detection for cyclotrimethylene trinitramine (RDX) (100 pg), pentaerythritol trinitrate (PETN) (100 pg), hexamethylene triperoxide diamide (HMTD) (1 ng), and trinitrotoluene (TNT) (5 ng). Detection was achieved without any sample preparation or the addition of reagents to facilitate adduct formation
ADDITIONAL NOTES ON SPURILLA-ALBA (RISBEC, 1928) (MOLLUSCA OPISTHOBRANCHIA)
Volume: 21Start Page: 305End Page: 30
NOTES ON THE MITRIDAE OF THE EASTERN PACIFIC II THE GENUS THALA WITH THE DESCRIPTION OF A NEW SPECIES
Volume: 12Start Page: 84End Page: 8
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