21,394 research outputs found
Dynamical matrix for arbitrary quadratic fermionic bath Hamiltonians and non-Markovian dynamics of one and two qubits in an Ising model environment
We obtain the analytical expression for the Kraus decomposition of the
quantum map of an environment modeled by an arbitrary quadratic fermionic
Hamiltonian acting on one or two qubits, and derive simple functions to check
the non-positivity of the intermediate map. These functions correspond to two
different sufficient criteria for non-Markovianity. In the particular case of
an environment represented by the Ising Hamiltonian, we discuss the two sources
of non-Markovianity in the model, one due to the finite size of the lattice,
and another due to the kind of interactions.Comment: 11 pages, 10 figure
Aptidão da cultura do mamoeiro para o Estado da Bahia.
O Brasil produziu aproximadamente 1,79 milhão de toneladas de frutos de mamão no ano de 2009. A Bahia, maior estado produtor do País, respondeu por aproximadamente 49,7% desse total, seguido do Espírito Santo (30,6%) e Ceará (5,85%). O cultivo do mamoeiro na Bahia é desenvolvido predominantemente em condições de sequeiro, sendo o estresse por deficiência hídrica o principal fator limitante para expansão da área de plantio e o principal critério utilizado nos trabalhos de zoneamento climático no Nordeste brasileiro.PDF. n. 101_11
Impacto do aquecimento global na aptidão da laranjeira no Estado da Bahia.
O Brasil produziu aproximadamente 18,5 milhões de toneladas de frutos de laranjeira no ano de 2008, sendo que a Bahia contribuiu como segundo maior produtor brasileiro (6%), seguido pelos Estados de Sergipe (4%) e Minas Gerais (3%) e atrás apenas de São Paulo (78%) (IBGE, 2008). As produtividades médias obtidas na Bahia (17 t/ha) inferiores às alcançadas em São Paulo (24 t/ha) refletem tanto a aptidão das regiões onde estão situados os pomares no Estado, apresentando transição acentuada do clima úmido para o subúmido seco, bem como as deficiências nas práticas agrícolas e manejo agronômico da cultura (plantio de mudas de qualidade, espaçamentos adequados, diversificação de porta-enxertos, adubação, monitoramento e manejo fitossanitário, irrigação, dentre outros).O cultivo da laranjeira na Bahia é caracterizado por ser desenvolvimento predominantemente em condições de sequeiro, e o estresse por deficiência de água no solo é o maior limitador da expansão, sendo este o principal critério utilizadonos trabalhos de zoneamentos climático no Nordeste brasileiro. A distribuição irregular das chuvas interfere na qualidade e produtividade de frutos e esses riscos podem ser aumentados com as previsões futuras de ocorrência de eventos extremos (seca e enchentes) e maior restrição hídrica no solo, devido ao aumento da evapotranspiração das culturas, relacionadas ao aquecimento global (Assad & Pinho, 2008; Semenov, 2009).O presente trabalho teve o objetivo de avaliar os impactos do aquecimento global (aumento de temperatura) na aptidão da cultura da laranja no Estado da Bahia.pdf 236
Synthesis of new, single-isomer quaternary ammonium derivatives of beta-cyclodextrin for electrophoretic enantiomer separations
The isolation of individual enantiomers of drugs is an important subject of
interest in the pharmaceutical and medical fields, because stereochemistry can have a
significant effect on the biological activity of the drug. Therefore, it is important to
develop enantiomeric separation methods for the determination of the optical purity of
drugs, since the undesired enantiomer is regarded as one of the impurities.
The available single isomer anionic cyclodextrins (CD) can resolve the
enantiomers of only a few weakly acidic analytes. To rectify this problem, the chloride
salts of heptakis(6-deoxy-6-morpholinio)-cyclomaltoheptaose (HMBCD), and mono(6-
deoxy-6-N,N,N r,N r,N r-pentamethylethylenediammonio)-cyclomaltoheptaose
(PEMEDA-BCD), the first members of the permanently charged, single-isomer cationic
cyclodextrin family, have been synthesized. The purity of process intermediates and
final products was determined by HPLC-ELSD and indirect UV-detection capillary
electrophoresis. Structural identity was verified by 1D and 2D NMR and massBoth cationic CD derivatives have been used for the separation of the
enantiomers of strong acid, weak acid, weak base, ampholytic, and neutral analytes by
capillary electrophoresis. Because the charge state of these cationic chiral resolving
agents is independent of the pH of the buffer, separation could be performed in both low
and high pH buffers without compromising the charge density of the resolving agent.
Contrary to expectation, the multiply charged HMBCD showed poor complexation with
the newly synthesized strong electrolyte test analytes. The weak binding between the
analytes and HMBCD resulted in separation of enantiomers of only three strong
electrolyte analytes. Strong complexation was observed between PEMEDA-BCD and
the anionic and nonionic analytes in both low and high pH buffers, though complexation
was stronger in the high pH buffer. Due to strong complexation between the anions and
PEMEDA-BCD, only low concentrations of the resolving agent were required to effect
good enantiomer resolutions.
spectrometry
The Levi-Civita spacetime
We consider two exact solutions of Einstein's field equations corresponding
to a cylinder of dust with net zero angular momentum. In one of the cases, the
dust distribution is homogeneous, whereas in the other, the angular velocity of
dust particles is constant [1]. For both solutions we studied the junction
conditions to the exterior static vacuum Levi-Civita spacetime. From this study
we find an upper limit for the energy density per unit length of the
source equal for the first case and for the second
one. Thus the homogeneous cluster provides another example [2] where the range
of is extended beyond the limit value previously found in
the literature [3,4]. Using the Cartan Scalars technics we show that the
Levi-Civita spacetime gets an extra symmetry for or
. We also find that the cluster of homogeneous dust has a superior
limit for its radius, depending on the constant volumetric energy density
Angular Power Spectrum Estimation of Cosmic Ray Anisotropies with Full or Partial Sky Coverage
We study the angular power spectrum estimate in order to search for large
scale anisotropies in the arrival directions distribution of the highest-energy
cosmic rays. We show that this estimate can be performed even in the case of
partial sky coverage and validated over the full sky under the assumption that
the observed fluctuations are statistically spatial stationary. If this
hypothesis - which can be tested directly on the data - is not satisfied, it
would prove, of course, that the cosmic ray sky is non isotropic but also that
the power spectrum is not an appropriate tool to represent its anisotropies,
whatever the sky coverage available. We apply the method to simulations of the
Pierre Auger Observatory, reconstructing an input power spectrum with the
Southern site only and with both Northern and Southern ones. Finally, we show
the improvement that a full-sky observatory brings to test an isotropic
distribution, and we discuss the sensitivity of the Pierre Auger Observatory to
large scale anisotropies.Comment: 16 pages, 6 figures, version accepted for publication by JCA
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