5,211 research outputs found
Electric and magnetic fields effects on the excitonic properties of elliptic core-multishell quantum wires
The effect of eccentricity distortions of core-multishell quantum wires on
their electron, hole and exciton states is theoretically investigated. Within
the effective mass approximation, the Schrodinger equation is numerically
solved for electrons and holes in systems with single and double radial
heterostructures, and the exciton binding energy is calculated by means of a
variational approach. We show that the energy spectrum of a core-multishell
heterostructure with eccentricity distortions, as well as its magnetic field
dependence, are very sensitive to the direction of an externally applied
electric field, an effect that can be used to identify the eccentricity of the
system. For a double heterostructure, the eccentricities of the inner and outer
shells play an important role on the excitonic binding energy, specially in the
presence of external magnetic fields, and lead to drastic modifications in the
oscillator strength.Comment: 17 pages, 10 figure
Gravitational wave recoil in Robinson-Trautman spacetimes
We consider the gravitational recoil due to non-reflection-symmetric
gravitational wave emission in the context of axisymmetric Robinson-Trautman
spacetimes. We show that regular initial data evolve generically into a final
configuration corresponding to a Schwarzschild black-hole moving with constant
speed. For the case of (reflection-)symmetric initial configurations, the mass
of the remnant black-hole and the total energy radiated away are completely
determined by the initial data, allowing us to obtain analytical expressions
for some recent numerical results that have been appeared in the literature.
Moreover, by using the Galerkin spectral method to analyze the non-linear
regime of the Robinson-Trautman equations, we show that the recoil velocity can
be estimated with good accuracy from some asymmetry measures (namely the first
odd moments) of the initial data. The extension for the non-axisymmetric case
and the implications of our results for realistic situations involving head-on
collision of two black holes are also discussed.Comment: 9 pages, 6 figures, final version to appear in PR
The electrum analyzer: Model checking relational first-order temporal specifications
This paper presents the Electrum Analyzer, a free-software tool to validate and perform model checking of Electrum specifications. Electrum is an extension of Alloy that enriches its relational logic with LTL operators, thus simplifying the specification of dynamic systems. The Analyzer supports both automatic bounded model checking, with an encoding into SAT, and unbounded model checking, with an encoding into SMV. Instance, or counter-example, traces are presented back to the user in a unified visualizer. Features to speed up model checking are offered, including a decomposed parallel solving strategy and the extraction of symbolic bounds. Source code: https://github.com/haslab/ElectrumVideo: https://youtu.be/FbjlpvjgMDA.European Regional Development Fund (ERDF)
through the Operational Programme for Competitiveness and Internationalisation (COMPETE2020) and by National Funds through
the Portuguese funding agency, Fundação para a Ciência e a Tecnologia (FCT) within project POCI-01-0145-FEDER-016826, and the
French Research Agency project FORMEDICIS ANR-16-CE25-000
The effect of electric field on important food-processing enzymes : comparison of inactivation kinetics under conventional and ohmic heating
This work deals with the determination of the inactivation kinetics of several enzymes, most of them
used as time-temperature integrators in the food industry. The tested enzymes were polyphenoloxidase,
lipoxygenase, pectinase, alkaline phosphatase, and β-galactosidase, and the inactivation assays were performed
under conventional and ohmic heating conditions. The thermal history of the samples (conventional and
ohmically processed) was made equal to determine if there was an additional inactivation caused by the presence
of an electric field, thus eliminating temperature as a variable. All the enzymes followed 1st-order inactivation
kinetics for both conventional and ohmic heating treatments. The presence of an electric field does not cause
an enhanced inactivation to alkaline phosphatase, pectinase, and β-galactosidase. However, lipoxygenase and
polyphenoloxidase kinetics were significantly affected by the electric field, reducing the time needed for inactivation.
The results of the present work can be used industrially to determine processing effectiveness when ohmic
heating technology is applied
Black-hole horizons as probes of black-hole dynamics II: geometrical insights
In a companion paper [1], we have presented a cross-correlation approach to
near-horizon physics in which bulk dynamics is probed through the correlation
of quantities defined at inner and outer spacetime hypersurfaces acting as test
screens. More specifically, dynamical horizons provide appropriate inner
screens in a 3+1 setting and, in this context, we have shown that an
effective-curvature vector measured at the common horizon produced in a head-on
collision merger can be correlated with the flux of linear Bondi-momentum at
null infinity. In this paper we provide a more sound geometric basis to this
picture. First, we show that a rigidity property of dynamical horizons, namely
foliation uniqueness, leads to a preferred class of null tetrads and Weyl
scalars on these hypersurfaces. Second, we identify a heuristic horizon
news-like function, depending only on the geometry of spatial sections of the
horizon. Fluxes constructed from this function offer refined geometric
quantities to be correlated with Bondi fluxes at infinity, as well as a contact
with the discussion of quasi-local 4-momentum on dynamical horizons. Third, we
highlight the importance of tracking the internal horizon dual to the apparent
horizon in spatial 3-slices when integrating fluxes along the horizon. Finally,
we discuss the link between the dissipation of the non-stationary part of the
horizon's geometry with the viscous-fluid analogy for black holes, introducing
a geometric prescription for a "slowness parameter" in black-hole recoil
dynamics.Comment: Final version published on PR
Mercapturate Pathway in the Tubulocentric Perspective of Diabetic Kidney Disease
BACKGROUND: The recent growing evidence that the proximal tubule underlies the
early pathogenesis of diabetic kidney disease (DKD) is unveiling novel and
promising perspectives. This pathophysiological concept links tubulointerstitial
oxidative stress, inflammation, hypoxia, and fibrosis with the progression of
DKD. In this new angle for DKD, the prevailing molecular mechanisms on proximal
tubular cells emerge as an innovative opportunity for prevention and management
of DKD as well as to improve diabetic dysmetabolism.
SUMMARY: The mercapturate pathway (MAP) is a classical metabolic detoxification
route for xenobiotics that is emerging as an integrative circuitry detrimental to
resolve tubular inflammation caused by endogenous electrophilic species. Herein
we review why and how it might underlie DKD. Key Messages: MAP is a hallmark of
proximal tubular cell function, and cysteine-S-conjugates might represent targets
for early intervention in DKD. Moreover, the biomonitoring of urinary
mercapturates from metabolic inflammation products might be relevant for the
implementation of preventive/management strategies in DKD.info:eu-repo/semantics/publishedVersio
A new modified Wilson equation for the calculation of vapor–liquid equilibrium of aqueous polymer solutions
A local composition model based on the lattice theory and two-fluid theory, considering the excess heat capacity,
which is a modified Wilson equation, is developed for the excess Gibbs energy of aqueous polymer solutions. The
model represents a synergistic combination of the excess entropy for mixing molecules of different sizes and the
temperature dependent residual contribution, which combines the attractive interactions between solvent molecules
and the segments with the contribution of the excess heat capacity. The results of the extrapolation with respect
to molecular weight of phase equilibrium in aqueous polymer solutions with this model are very satisfactory, with
only two adjustable parameters.Fundação para a Ciência e a Tecnologia (FCT) – postdoctoral fellowship, Programa Operacional “Ciência, Tecnologia, Inovação” POCTI/1999/EQU/33185
Wine production with immobilized yeasts on grape pomace
The alcoholic fermentation is one of the most important stages in the winemaking process
and contributes decisively for the quality of the final product, particularly aromatic
characteristics. The immobilization of yeast cells in fermentation processes presents several
technological and economic advantages when compared with free cells systems, such as
increased productivity and greater tolerance of the cells to inhibitory substances.
In this context, the objective of this work consisted in using immobilized yeasts for driving
and controlling the alcoholic fermentation process in winemaking. The immobilization of
Saccharomyces cerevisiae took place on grape pomace by natural adsorption. The evolution
of the alcoholic fermentation was followed daily by measuring must density until a value
lower than 1000 kg/m3
was reached. Physical-chemical and sensorial characterization of the
wines, produced with free and immobilized cells, were carried out.
The immobilized yeasts were able to effectively conduct the alcoholic fermentation and
therefore, to produce wine. Sensory analysis demonstrated the existence of perceptible
olfactory differences in wines produced by free cells and immobilized cells. Moreover, the
produced wines presented significant differences respecting color attributes.A fermentação alcoólica é uma das etapas mais importantes no processo de produção de
vinho e contribui decisivamente para a qualidade final do produto, particularmente o aroma.
A imobilização de células de levedura em processos fermentativos apresenta diversas
vantagens tecnológicas e económicas quando comparada com sistemas de células livres, tais
como incremento da produtividade e maior tolerância das células a substâncias inibitórias.
Neste contexto, o objectivo do trabalho consistiu na utilização de leveduras imobilizadas para
para a condução e controlo do processo de fermentação alcoólica em vinificação. A
imobilização de Saccharomyces cerevisiae foi realizada por adsorção natural num suporte
natural constituído por bagaço de uva. A evolução da fermentação foi seguida diariamente
pela medição da massa volúmica, sendo dada por terminada para valores inferiores a 1000
kg/m3
. Os vinhos produzidos, quer com células livres quer com células imobilizadas, foram
avaliados por caracterização físico-química e por análise sensorial.
As leveduras imobilizadas foram capazes de conduzir eficazmente as fermentações alcoólicas
e, por conseguinte, de produzir vinho. A análise sensorial dos vinhos demonstrou a
existência de diferenças olfactivas perceptíveis nos vinhos produzidos a partir de células livres e de células imobilizadas. Além disso, as análises de cor demonstraram que os vinhos
produzidos apresentaram diferenças significativas
Cation effect on the (PEG 8000 + sodium sulfate) and (PEG 8000 + magnesium sulfate) aqueous two-phase system: Relative hydrophobicity of the equilibrium phases
The partitioning of four dinitrophenylated (DNP-) amino acids in aqueous two-phase systems of polyethylene glycol (PEG)-8000sodium sulfate and polyethylene glycol (PEG)-8000magnesium sulfate in five different tie-lines was experimentally determined at 298.15 K. The Gibbs free energy of transfer of a methylene group between the two phases was calculated from the measured partition coefficients. This characterizes the relative hydrophobicity of the equilibrium phases. Values of G(CH2) were in range from (-0.674 to -1.012) kJ·mol-1. A comparison of both systems was carried out. The results show that the cation type has a strong influence on the amino acids partitioning process. The largest relative hydrophobicity was noted for the ATPS system formed by sodium sulfate. This showed to be a better system for the separation.FCT/MEC and FEDER under Programe PT2020 (Project UID/EQU/50020/2013), and co-financed by QREN, ON2 and FEDER (Projects NORTE-07-0162-FEDER-000050 and NORTE-07-0124-FEDER-0000011
Laccase partition in ATPS: finding some molecular descriptors
Aqueous Two-Phase Systems (ATPS) are known since 1896, when Beijerinck reported
the formation of a biphasic system after mixing aqueous solutions of gelatine and agar
or gelatine and starch. However, only in the 50’s, Albertsson showed the potential of
these systems in the separation and purification of several biological constituents.1 In
general, ATPS are obtained by mixing two aqueous solutions of different constituents
that become immiscible above certain critical conditions, like temperature,
concentration, etc. Both phases are composed mainly by water (>80%) and each one is
enriched in a different component. ATPS formed by two polymers or a polymer and a
salt represent the traditional systems. Nevertheless, other alternative biphasic systems
can be obtained using surfactants, micellar compounds or ionic liquids
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