124 research outputs found
Nonenzymatic Exogenous and Endogenous Antioxidants
Nonenzymatic exogenous and endogenous antioxidants play an important role in human health and act as preservatives for cosmetics, pharmaceuticals, and food products. This chapter will discuss the chemical structure and mechanism of action of the most important nonenzymatic small exogenous and endogenous organic molecules that act as antioxidants. The chapter will focus on the structural features, functional groups, properties, biosynthetic origin, and mechanism of action of such antioxidants. It also covers damages that free radicals create and the mechanisms by which they are neutralized by the various antioxidants. The scope of this chapter will be limited to nonenzymatic exogenous and endogenous antioxidants since enzymatic antioxidants have been discussed extensively in several reviews
Relaxation- and Decoherence-free subspaces in networks of weakly and strongly coupled resonators
We consider a network of interacting resonators and analyze the physical
ingredients that enable the emergence of relaxation-free and decoherence-free
subspaces. We investigate two different situations: i) when the whole network
interacts with a common reservoir and ii) when each resonator, strongly coupled
to each other, interacts with its own reservoir. Our main result is that both
subspaces are generated when all the resonators couple with the same group of
reservoir modes, thus building up a correlation (among these modes), which has
the potential to shield particular network states against relaxation and/or
decoherence.Comment: 5 page
The controlled teleportation of an arbitrary two-atom entangled state in driven cavity QED
In this paper, we propose a scheme for the controlled teleportation of an
arbitrary two-atom entangled state
in driven cavity QED.
An arbitrary two-atom entangled state can be teleported perfectly with the help
of the cooperation of the third side by constructing a three-atom GHZ entangled
state as the controlled channel. This scheme does not involve apparent (or
direct) Bell-state measurement and is insensitive to the cavity decay and the
thermal field. The probability of the success in our scheme is 1.0.Comment: 10 page
The double Caldeira-Leggett model: Derivation and solutions of the master equations, reservoir-induced interactions and decoherence
In this paper we analyze the double Caldeira-Leggett model: the path integral
approach to two interacting dissipative harmonic oscillators. Assuming a
general form of the interaction between the oscillators, we consider two
different situations: i) when each oscillator is coupled to its own reservoir,
and ii) when both oscillators are coupled to a common reservoir. After deriving
and solving the master equation for each case, we analyze the decoherence
process of particular entanglements in the positional space of both
oscillators. To analyze the decoherence mechanism we have derived a general
decay function for the off-diagonal peaks of the density matrix, which applies
both to a common and separate reservoirs. We have also identified the expected
interaction between the two dissipative oscillators induced by their common
reservoir. Such reservoir-induced interaction, which gives rise to interesting
collective damping effects, such as the emergence of relaxation- and
decoherence-free subspaces, is shown to be blurred by the high-temperature
regime considered in this study. However, we find that different interactions
between the dissipative oscillators, described by rotating or counter-rotating
terms, result in different decay rates for the interference terms of the
density matrix.Comment: 42 pages, 7 figures, new discussion added, typos adde
Number of particle creation and decoherence in the nonideal dynamical Casimir effect at finite temperature
In this work we investigate the dynamical Casimir effect in a nonideal cavity
by deriving an effective Hamiltonian. We first compute a general expression for
the average number of particle creation, applicable for any law of motion of
the cavity boundary. We also compute a general expression for the linear
entropy of an arbitrary state prepared in a selected mode, also applicable for
any law of motion of the cavity boundary. As an application of our results we
have analyzed both the average number of particle creation and linear entropy
within a particular oscillatory motion of the cavity boundary. On the basis of
these expressions we develop a comprehensive analysis of the resonances in the
number of particle creation in the nonideal dynamical Casimir effect. We also
demonstrate the occurrence of resonances in the loss of purity of the initial
state and estimate the decoherence times associated with these resonances.Comment: comments are welcom
Spin stiffness and quantum fluctuations in C-type and A-type antiferromagnets
We present a systematic study of quantum fluctuations in the C-type and
A-type antiferromagnetic (AF) phases in cubic lattices and in bilayer systems.
Using the linear spin-wave theory, we show that the spin stiffness and the
quantum corrections to the order parameter and energy obtained for C-AF and
A-AF phases decrease with the increasing number of ferromagnetic bonds.
Therefore, the quantum spin effects in LaMnO_3 and in LaVO_3 are rather small,
suggesting the magnetic moments of 3.91 and 1.89 Bohr's magneton, respectively.
They cannot explain the strong reduction of the magnetic order parameter
observed in cubic vanadates.Comment: 6 pages, 4 figure
Measurement of the Bottom-Strange Meson Mixing Phase in the Full CDF Data Set
We report a measurement of the bottom-strange meson mixing phase \beta_s
using the time evolution of B0_s -> J/\psi (->\mu+\mu-) \phi (-> K+ K-) decays
in which the quark-flavor content of the bottom-strange meson is identified at
production. This measurement uses the full data set of proton-antiproton
collisions at sqrt(s)= 1.96 TeV collected by the Collider Detector experiment
at the Fermilab Tevatron, corresponding to 9.6 fb-1 of integrated luminosity.
We report confidence regions in the two-dimensional space of \beta_s and the
B0_s decay-width difference \Delta\Gamma_s, and measure \beta_s in [-\pi/2,
-1.51] U [-0.06, 0.30] U [1.26, \pi/2] at the 68% confidence level, in
agreement with the standard model expectation. Assuming the standard model
value of \beta_s, we also determine \Delta\Gamma_s = 0.068 +- 0.026 (stat) +-
0.009 (syst) ps-1 and the mean B0_s lifetime, \tau_s = 1.528 +- 0.019 (stat) +-
0.009 (syst) ps, which are consistent and competitive with determinations by
other experiments.Comment: 8 pages, 2 figures, Phys. Rev. Lett 109, 171802 (2012
Cadmium tolerance of Typha domingensis Pers. (Typhaceae) as related to growth and leaf morphophysiology
Agroforesterie et services écosystémiques en zone tropicale
Respectueux de l’environnement et garantissant une sécurité alimentaire soutenue par la diversification des productions et des revenus qu’ils procurent, les systèmes agroforestiers apparaissent comme un modèle prometteur d’agriculture durable dans les pays du Sud les plus vulnérables aux changements globaux. Cependant, ces systèmes agroforestiers ne peuvent être optimisés qu’à condition de mieux comprendre et de mieux maîtriser les facteurs de leurs productions. L’ouvrage présente un ensemble de connaissances récentes sur les mécanismes biophysiques et socio-économiques qui sous-tendent le fonctionnement et la dynamique des systèmes agroforestiers. Il concerne, d’une part les systèmes agroforestiers à base de cultures pérennes, telles que cacaoyers et caféiers, de régions tropicales humides en Amérique du Sud, en Afrique de l’Est et du Centre, d’autre part les parcs arborés et arbustifs à base de cultures vivrières, principalement de céréales, de la région semi-aride subsaharienne d’Afrique de l’Ouest. Il synthétise les dernières avancées acquises grâce à plusieurs projets associant le Cirad, l’IRD et leurs partenaires du Sud qui ont été conduits entre 2012 et 2016 dans ces régions. L’ensemble de ces projets s’articulent autour des dynamiques des systèmes agroforestiers et des compromis entre les services de production et les autres services socio-écosystémiques que ces systèmes fournissent
- …