12,452 research outputs found
New DNLS Equations for Anharmonic Vibrational Impurities
We examine some new DNLS-like equations that arise when considering
strongly-coupled electron-vibration systems, where the local oscillator
potential is anharmonic. In particular, we focus on a single, rather general
nonlinear vibrational impurity and determine its bound state(s) and its
dynamical selftrapping properties.Comment: 16 pages, 5 figure
Power Switching in Hybrid Coherent Couplers
We report on a theoretical and numerical investigation of the switching of
power in new hybrid models of nonlinear coherent couplers consisting of optical
slab waveguides with various orders of nonlinearity. The first model consists
of two guides with second-order instead of the usual third-order
susceptibilities as typified by the Jensen coupler. This second-order system is
shown to have a power self-trapping transition at a critical power greater than
the third-order susceptibility coupler. Next, we consider a mixed coupler
composed of a second-order guide coupled to a third-order guide and show that,
although it does not display a rigorous self-trapping transition, for a
particular choice of parameters it does show a fairly abrupt trapping of power
at a lower power than in the third-order coupler. By coupling this mixed
nonlinear pair to a third, purely linear guide, the power trapping can be
brought to even lower levels and in this way a satisfactory switching profile
can be achieved at less than one sixth the input power needed in the Jensen
coupler.Comment: Latex source,17 pages, 5 figure
From Disordered Crystal to Glass: Exact Theory
We calculate thermodynamic properties of a disordered model insulator,
starting from the ideal simple-cubic lattice () and increasing the
disorder parameter to . As in earlier Einstein- and Debye-
approximations, there is a phase transition at . For the
low-T heat-capacity whereas for , . The van
Hove singularities disappear at {\em any finite }. For we discover
novel {\em fixed points} in the self-energy and spectral density of this model
glass.Comment: Submitted to Phys. Rev. Lett., 8 pages, 4 figure
Contested States, Hybrid Diplomatic Practices and the Everyday Quest for Recognition
This is the author accepted manuscript. The final version is available from OUP via the DOI in this record.This article examines contested state diplomatic practices with the aim to challenge
structural legal-institutional accounts of these actors’ international engagement, which
are unsatisfactory in explaining change and acknowledging their agency. Considering
contested states as liminal international actors, their diplomatic practices stand out for
their hybridity in transcending the state vs. non-state diplomacy dichotomy as well as
their structure-generating properties in enabling social forms of international recognition
– absent legal recognition. The concept is empirically applied to examine the everyday
interaction between the representatives of Palestine and Western Sahara and the EU
institutions in Brussels. It is argued that there has been a renewal and expansion of the
Palestinian and Sahrawi repertoires of diplomatic practices vis-à-vis the EU, which has
entailed growing hybridisation. Innovation originated in more “transformative”
diplomatic practices capitalising on the contested states’ own political inbetweenness,
which established relations that contributed to constituting and endogenously
empowering them in the Brussels milieu. The way was thus paved for more
“reproductive” diplomatic practices that mimic traditional state diplomacy to gain
prominence. The impact achieved on “high politics” demonstrates how bottom-up
practice-led change may allow contested states to compensate for their meagre material
capabilities and punch above their structural weight in international politics
Bulk and surface magnetoinductive breathers in binary metamaterials
We study theoretically the existence of bulk and surface discrete breathers
in a one-dimensional magnetic metamaterial comprised of a periodic binary array
of split-ring resonators. The two types of resonators differ in the size of
their slits and this leads to different resonant frequencies. In the framework
of the rotating-wave approximation (RWA) we construct several types of breather
excitations for both the energy-conserved and the dissipative-driven systems by
continuation of trivial breather solutions from the anticontinuous limit to
finite couplings. Numerically-exact computations that integrate the full model
equations confirm the quality of the RWA results. Moreover, it is demonstrated
that discrete breathers can spontaneously appear in the dissipative-driven
system as a results of a fundamental instability.Comment: 10 pages, 16 figure
Embedding method for the scattering phase in strongly correlated quantum dots
The embedding method for the calculation of the conductance through
interacting systems connected to single channel leads is generalized to obtain
the full complex transmission amplitude that completely characterizes the
effective scattering matrix of the system at the Fermi energy. We calculate the
transmission amplitude as a function of the gate potential for simple
diamond-shaped lattice models of quantum dots with nearest neighbor
interactions. In our simple models we do not generally observe an interaction
dependent change in the number of zeroes or phase lapses that depend only on
the symmetry properties of the underlying lattice. Strong correlations separate
and reduce the widths of the resonant peaks while preserving the qualitative
properites of the scattering phase.Comment: 11 pages, 3 figures. Proceedings of the Workshop on Advanced
Many-Body and Statistical Methods in Mesoscopic Systems, Constanta, Romania,
June 27th - July 2nd 2011. To appear in Journal of Physics: Conference Serie
Betalains and phenolic compounds of leaves and stems of Alternanthera brasiliana and Alternanthera tenella
Betacyanins and phenolic compounds from acetonitrile:acidified water extracts of Alternanthera brasiliana and Alternanthera tenella were characterized and quantified using a high-performance liquid chromatography system coupled with diode array and electrospray mass spectrometry detection. Four betacyanins (amaranthine, isoamaranthine, betanin and isobetanin) were tentatively identified and quantified. Twenty eight phenolic compounds of four different families (hydroxybenzoic and hydroxycinnamic acids, flavones and flavonols) were separated and characterized on the basis of their accurate MS and MS/MS information out of which ten compounds were confirmed by authentic standards. These plant species could be considered as an especially rich source of natural bioactive compounds and potential food colorants. A. brasiliana showed the highest betacyanin and polyphenols content (89 μg/g and 35,243 μg/g, respectively). Among polyphenols, flavonols were the more abundant (kaempferol-glucoside, kaempferol-rutinoside and kaempferol-rhamnosyl-rhamnosyl-glycoside). Meanwhile, A. tenella showed a different polyphenols profile with flavones as major compounds (glucopyranosil-vitexin and vitexin). As a novelty, pentosyl-vitexin and pentosyl-isovitexin were detected for the first time in Alternanthera plants. Both A. brasiliana and A. tenella leaves showed high total polyphenol content and in vitro antioxidant activity (FRAP). These results provide an analytical base concerning the phenolic and betalains composition and the antioxidant properties of two members of the promising Alternanthera gender, for subsequent applications, such as functional food ingredients.Fil: Deladino, Lorena. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; ArgentinaFil: Alvarez, I.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: De Ancos, B.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Sánchez Moreno, C.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Molina García, A. D.. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; EspañaFil: Schneider Teixeira, Aline. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigación y Desarrollo en Criotecnología de Alimentos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de Investigación y Desarrollo en Criotecnología de Alimentos; Argentina. Consejo Superior de Investigaciones Científicas. Instituto de Ciencia y Tecnologia de Alimentos y Nutrición; Españ
The \rho\rho interaction in the hidden gauge formalism and the f_0(1370) and f_2(1270) resonances
We have studied the interaction of vectors mesons within the hidden gauge
formalism and applied it to the particular case of the interaction.
We find a strong attraction in the isospin, spin channels I,S=0,0 and 0,2,
which is enough to bind the system. We also find that the
attraction in the I,S=0,2 channel is much stronger than in the 0,0 case. The
states develop a width when the mass distribution is considered, and
particularly when the decay channel is turned on. Using a
regularization scheme with cut offs of natural size, we obtain results in fair
agreement with the mass and the width of the and meson
states, providing a natural explanation of why the tensor state is more bound
than the scalar and offering a new picture for these states, which would be
dynamically generated from the interaction or, in simpler words,
molecular states.Comment: Version accepted for publicatio
Excitons in coupled InAs/InP self-assembled quantum wires
Optical transitions in coupled InAs/InP self-assembled quantum wires are
studied within the single-band effective mass approximation including effects
due to strain. Both vertically and horizontally coupled quantum wires are
investigated and the ground state, excited states and the photoluminescence
peak energies are calculated. Where possible we compare with available
photo-luminescence data from which it was possible to determine the height of
the quantum wires. An anti-crossing of the energy of excited states is found
for vertically coupled wires signaling a change of symmetry of the exciton
wavefunction. This crossing is the signature of two different coupling regimes.Comment: 8 pages, 8 figures. To appear in Physical Review
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