8,450 research outputs found
Comparação entre protocolos de extração de DNA de algodão para emprego em ensaios com marcadores moleculares.
bitstream/item/109012/1/CNPACIRTEC74.pd
Generalized local interactions in 1D: solutions of quantum many-body systems describing distinguishable particles
As is well-known, there exists a four parameter family of local interactions
in 1D. We interpret these parameters as coupling constants of delta-type
interactions which include different kinds of momentum dependent terms, and we
determine all cases leading to many-body systems of distinguishable particles
which are exactly solvable by the coordinate Bethe Ansatz. We find two such
families of systems, one with two independent coupling constants deforming the
well-known delta interaction model to non-identical particles, and the other
with a particular one-parameter combination of the delta- and (so-called)
delta-prime interaction. We also find that the model of non-identical particles
gives rise to a somewhat unusual solution of the Yang-Baxter relations. For the
other model we write down explicit formulas for all eigenfunctions.Comment: 23 pages v2: references adde
Mixtures of polymers and cholinium-based ionic liquids to tailor the phase diagrams and extraction efficiency of aqueous biphasic systems
Aqueous biphasic systems (ABS) are outstanding alternatives over conventional liquid-liquid extraction processes
since it is avoided the use of volatile and hazardous organic solvents (VOCs). ABS are more biocompatible
systems formed by two aqueous-rich phases that can be designed by combining different pairs of solutes
(polymer-polymer, polymer-salt or salt-salt) above specific concentrations. In the past years, ABS have been
studied as powerful techniques for purification, separation and extraction purposes.
Ionic liquids (ILs) have been described as interesting fluids towards the development of more sustainable
processes. Due to the ILs unique properties, their introduction in ABS led to systems with higher selectivity and
extraction performance for a wide plethora of compounds. In fact, it was already shown that ILs allow to
overcome the low hydrophilic-hydrophobic range of ABS composed of two polymers or one polymer and one
inorganic salt. IL-based ABS formed with polyethylene glycol (PEG) polymers were recently introduced and a
successful control of the phase polarities, through the manipulation of the IL chemical structure, was
demonstrated. Lately, it was also demonstrated that a new class of natural-derived cholinium-based ILs are
capable of undergoing two phase separation by the addition of PEGs with different molecular weights. In the
present work, mixtures of PEGs with different molecular weights (400 and 2000 g/mol) were used to ascertain on
the formation ability of ABS composed of water and cholinium-based ILs or salts. The results obtained indicate
that the formation ability of these ABS increase with the content of PEG2000 over PEG400 (and follow a
continuous increase), meaning that a close-fitting control on their phases polarity can be attained. These
systems were then evaluated on their performance for extracting a series of alkaloids with different polarities,
namely caffeine, theophylline, theobromine and nicotine. In general, the alkaloids partition extent to the most
hydrophobic phase (PEG-rich) follows their polarity/hydrophobicity. In summary, it is here demonstrated that
mixtures of polymers as phase-forming components of ABS allow to tailor the partition coefficients of different
alkaloids and their use in the purification of added-value compounds from biomass extracts is straightforwardly
foreseen.publishe
Controlling a resonant transmission across the -potential: the inverse problem
Recently, the non-zero transmission of a quantum particle through the
one-dimensional singular potential given in the form of the derivative of
Dirac's delta function, , with , being a
potential strength constant, has been discussed by several authors. The
transmission occurs at certain discrete values of forming a resonance
set . For
this potential has been shown to be a perfectly reflecting wall. However, this
resonant transmission takes place only in the case when the regularization of
the distribution is constructed in a specific way. Otherwise, the
-potential is fully non-transparent. Moreover, when the transmission
is non-zero, the structure of a resonant set depends on a regularizing sequence
that tends to in the sense of
distributions as . Therefore, from a practical point of
view, it would be interesting to have an inverse solution, i.e. for a given
to construct such a regularizing sequence
that the -potential at this value is
transparent. If such a procedure is possible, then this value
has to belong to a corresponding resonance set. The present paper is devoted to
solving this problem and, as a result, the family of regularizing sequences is
constructed by tuning adjustable parameters in the equations that provide a
resonance transmission across the -potential.Comment: 21 pages, 4 figures. Corrections to the published version added;
http://iopscience.iop.org/1751-8121/44/37/37530
Ab initio study of CsI and its surface
Prova tipográfica (In Press)Cesium iodide properties, both in the bulk and on (110) and (100) surfaces, are studied using
Density Functional Theory. The bulk lattice constant, bulk modulus and elastic constants are in
good agreement with the experimental values. The electronic band structure is also calculated,
as well as the density of states. On the surfaces, relaxation of the atoms was performed, and the
atomic geometry and electronic structure have been studied.Fundação para a Ciência e a Tecnologia
(FCT) - Project nr. POCI/FP/63442/2005, Ref. BSAB/466/2004.Fundação Calouste Gulbenkian
The quantum non-linear Schrodinger model with point-like defect
We establish a family of point-like impurities which preserve the quantum
integrability of the non-linear Schrodinger model in 1+1 space-time dimensions.
We briefly describe the construction of the exact second quantized solution of
this model in terms of an appropriate reflection-transmission algebra. The
basic physical properties of the solution, including the space-time symmetry of
the bulk scattering matrix, are also discussed.Comment: Comments on the integrability and the impurity free limit adde
Comparação entre protocolos de extração de DNA para algodão.
bitstream/CNPA/16799/1/COMTEC187.PD
Implantação das normas BPL e NBR ISO/IEC 17.025 na Embrapa Recursos Genéticos e Biotecnologia.
bitstream/CENARGEN/29546/1/ct052.pd
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