11,543 research outputs found
Asymptotic Entanglement Dynamics and Geometry of Quantum States
A given dynamics for a composite quantum system can exhibit several distinct
properties for the asymptotic entanglement behavior, like entanglement sudden
death, asymptotic death of entanglement, sudden birth of entanglement, etc. A
classification of the possible situations was given in [M. O. Terra Cunha,
{\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no
known examples. In this work we give a better classification for the possibile
relaxing dynamics at the light of the geometry of their set of asymptotic
states and give explicit examples for all the classes. Although the
classification is completely general, in the search of examples it is
sufficient to use two qubits with dynamics given by differential equations in
Lindblad form (some of them non-autonomous). We also investigate, in each case,
the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J.
Phys. A: Math. Theo
Spin-polarized transport in ferromagnetic multilayered semiconductor nanostructures
The occurrence of inhomogeneous spin-density distribution in multilayered
ferromagnetic diluted magnetic semiconductor nanostructures leads to strong
dependence of the spin-polarized transport properties on these systems. The
spin-dependent mobility, conductivity and resistivity in
(Ga,Mn)As/GaAs,(Ga,Mn)N/GaN, and (Si,Mn)/Si multilayers are calculated as a
function of temperature, scaled by the average magnetization of the diluted
magnetic semiconductor layers. An increase of the resistivity near the
transition temperature is obtained. We observed that the spin-polarized
transport properties changes strongly among the three materials.Comment: 3 pages, 4 figure
On the nature of the spin-polarized hole states in a quasi-two-dimensional GaMnAs ferromagnetic layer
A self-consistent calculation of the density of states and the spectral
density function is performed in a two-dimensional spin-polarized hole system
based on a multiple-scattering approximation. Using parameters corresponding to
GaMnAs thin layers, a wide range of Mn concentrations and hole densities have
been explored to understand the nature, localized or extended, of the
spin-polarized holes at the Fermi level for several values of the average
magnetization of the Mn ystem. We show that, for a certain interval of Mn and
hole densities, an increase on the magnetic order of the Mn ions come together
with a change of the nature of the states at the Fermi level. This fact
provides a delocalization of spin-polarized extended states anti-aligned to the
average Mn magnetization, and a higher spin-polarization of the hole gas. These
results are consistent with the occurrence of ferromagnetism with relatively
high transition temperatures observed in some thin film samples and
multilayered structures of this material.Comment: 3 page
Electron transfer driven decomposition of adenine and selected analogs as probed by experimental and theoretical methods
We report on a combined experimental and theoretical study of electron transfer induced decomposition of adenine and a selection of analogue molecules in collisions with potassium atoms (K). Time-of-flight negative ion mass spectra have been obtained in a wide collision energy range (6–68 eV in the centre-of-mass frame), providing a comprehensive investigation of the fragmentation patterns of purine, adenine, 9-methyl adenine, 6-dimethyl adenine and 2-D adenine. Following our recent communication about selective hydrogen loss from the transient negative ions (TNI) produced in these collisions [T. Dunha et al. J. Chem. Phys. 148, 021101 (2018)], this work focuses on the production of smaller fragment anions. In the low-energy part of the present range, several dissociation channels that are accessible in free electron attachment experiments are absent from the present mass spectra, notably NH2 loss from adenine and 9-methyl adenine. This can be understood in terms of a relatively long transit time of the K+ cation in the vicinity of the TNI tending to enhance the likelihood of intramolecular electron transfer. In this case, the excess energy can be redistributed through the available degrees of freedom inhibiting fragmentation pathways. Ab initio theoretical calculations were performed for 9-methyl adenine (9-mAd) and adenine (Ad) in the presence of a potassium atom and provided a strong basis for the assignment the lowest unoccupied molecular orbitals accessed in the collision process
Sensibilidade a fungicidas de isolados de corynespora cassiicola provenientes do Estado de Goiás.
O fungo Corynespora cassiicola, agente causal da mancha-alvo em soja, pode, sob condições de alta temperatura e alta umidade, causar sérios danos à cultura. No Brasil, não se tem condições suficientes para um manejo adequado dessa doença, principalmente pela escassez de fungicidas foliares registrados e cultivares resistentes. Este trabalho foi realizado visando avaliar a sensibilidade in vitro de seis isolados de C. cassiicola oriundos do Estado de Goiás, aos fungicidas boscalida, carbendazim, ciproconazol, fluopyram, fluxapiroxade, protioconazol e tiofanato-metílico, utilizados nas concentrações de 0; 0,01; 0,1; 1; 10 e 100 ug mL-1 de ingrediente ativo (i.a.). Os fungicidas fluxapiroxade e fluopyram proporcionaram as maiores inibições de crescimento micelial (ICM) do patógeno in vitro, apresentando as menores doses efetivas capaz de inibir o crescimento micelial em 50% (DE50). O fungicida tiofanato-metílico foi incapaz de inibir o crescimento micelial do fungo nas concentrações avaliadas
Theory of Stellar Oscillations
In recent years, astronomers have witnessed major progresses in the field of
stellar physics. This was made possible thanks to the combination of a solid
theoretical understanding of the phenomena of stellar pulsations and the
availability of a tremendous amount of exquisite space-based asteroseismic
data. In this context, this chapter reviews the basic theory of stellar
pulsations, considering small, adiabatic perturbations to a static, spherically
symmetric equilibrium. It starts with a brief discussion of the solar
oscillation spectrum, followed by the setting of the theoretical problem,
including the presentation of the equations of hydrodynamics, their
perturbation, and a discussion of the functional form of the solutions.
Emphasis is put on the physical properties of the different types of modes, in
particular acoustic (p-) and gravity (g-) modes and their propagation cavities.
The surface (f-) mode solutions are also discussed. While not attempting to be
comprehensive, it is hoped that the summary presented in this chapter addresses
the most important theoretical aspects that are required for a solid start in
stellar pulsations research.Comment: Lecture presented at the IVth Azores International Advanced School in
Space Sciences on "Asteroseismology and Exoplanets: Listening to the Stars
and Searching for New Worlds" (arXiv:1709.00645), which took place in Horta,
Azores Islands, Portugal in July 201
Carregando dados na arquitetura data warehousing - armazém de dados de frutas.
Data warehouse / Data Mart. Arquiteturas. O processo ETT (Extração, Transformação e carga de dados).bitstream/CNPTIA/9176/1/COMNICADOTEC3_0.pdfAcesso em: 29 maio 2008
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