322 research outputs found
A CONCEPÇÃO DE DIREITOS HUMANOS E FUNDAMENTAIS NA TEORIA DA JUSTIÇA COMO EQUIDADE
O presente artigo visa, em um primeiro momento, a analisar a concepção de direitos humanos feita por Rawls, para verificar se a concepção minimalista e não-metafísica apresentada pelo autor é apta a oferecer, nos dias atuais, um ideal moral que sirva de base para uma sociedade internacional democrática e justa
Recognition-mediated hydrogel swelling controlled by interaction with a negative thermoresponsive LCST polymer
Most polymeric thermoresponsive hydrogels contract upon heating beyond the lower critical solution temperature (LCST) of the polymers used. Herein, we report a supramolecular hydrogel system that shows the opposite temperature dependence. When the non-thermosesponsive hydrogel NaphtGel, containing dialkoxynaphthalene guest molecules, becomes complexed with the tetra cationic macrocyclic host CBPQT4+, swelling occurred as a result of host–guest complex formation leading to charge repulsion between the host units, as well as an osmotic contribution of chloride counter-ions embedded in the network. The immersion of NaphtGel in a solution of poly(N-isopropylacrylamide) with tetrathiafulvalene (TTF) end groups complexed with CBPQT4+ induced positive thermoresponsive behaviour. The LCST-induced dethreading of the polymer-based pseudorotaxane upon heating led to transfer of the CBPQT4+ host and a concomitant swelling of NaphtGel. Subsequent cooling led to reformation of the TTF-based host–guest complexes in solution and contraction of the hydrogel
Simultaneous Surface Plasmon Resonance and X-ray Absorption Spectroscopy
We present here an experimental set-up to perform simultaneously measurements
of surface plasmon resonance (SPR) and X-ray absorption spectroscopy (XAS) in a
synchrotron beamline. The system allows measuring in situ and in real time the
effect of X-ray irradiation on the SPR curves to explore the interaction of
X-rays with matter. It is also possible to record XAS spectra while exciting
SPR in order to detect the changes in the electronic configuration of thin
films induced by the excitation of surface plasmons. Combined experiments
recording simultaneously SPR and XAS curves while scanning different parameters
can be carried out. The relative variations in the SPR and XAS spectra that can
be detected with this set-up ranges from 10-3 to 10-5, depending on the
particular experiment
Standard and Generalized Newtonian Gravities as ``Gauge'' Theories of the Extended Galilei Group - I: The Standard Theory
Newton's standard theory of gravitation is reformulated as a {\it gauge}
theory of the {\it extended} Galilei Group. The Action principle is obtained by
matching the {\it gauge} technique and a suitable limiting procedure from the
ADM-De Witt action of general relativity coupled to a relativistic mass-point.Comment: 51 pages , compress, uuencode LaTex fil
Vacuum structure for scalar cosmological perturbations in Modified Gravity Models
We have found for the general class of Modified Gravity Models f(R,G) a new
instability which can arise in vacuum for the scalar modes of the cosmological
perturbations if the background is not de Sitter. In particular, the
short-wavelength modes, if stable, in general have a group velocity which
depends linearly in k, the wave number. Therefore these modes will be in
general superluminal. We have also discussed the condition for which in general
these scalar modes will be ghost-like. There is a subclass of these models,
defined out of properties of the function f(R,G) and to which the f(R) and f(G)
models belong, which however does not have this feature.Comment: 17 pages, 1 figure, uses RevTeX, references adde
Polymeric Core–Shell Assemblies Mediated by Host–Guest Interactions: Versatile Nanocarriers for Drug Delivery
No AbstractPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/61526/1/982_ftp.pd
A Unified Approach to Variational Derivatives of Modified Gravitational Actions
Our main aim in this paper is to promote the coframe variational method as a
unified approach to derive field equations for any given gravitational action
containing the algebraic functions of the scalars constructed from the Riemann
curvature tensor and its contractions. We are able to derive a master equation
which expresses the variational derivatives of the generalized gravitational
actions in terms of the variational derivatives of its constituent curvature
scalars. Using the Lagrange multiplier method relative to an orthonormal
coframe, we investigate the variational procedures for modified gravitational
Lagrangian densities in spacetime dimensions . We study
well-known gravitational actions such as those involving the Gauss-Bonnet and
Ricci-squared, Kretchmann scalar, Weyl-squared terms and their algebraic
generalizations similar to generic theories and the algebraic
generalization of sixth order gravitational Lagrangians. We put forth a new
model involving the gravitational Chern-Simons term and also give three
dimensional New massive gravity equations in a new form in terms of the Cotton
2-form
f(R) theories
Over the past decade, f(R) theories have been extensively studied as one of
the simplest modifications to General Relativity. In this article we review
various applications of f(R) theories to cosmology and gravity - such as
inflation, dark energy, local gravity constraints, cosmological perturbations,
and spherically symmetric solutions in weak and strong gravitational
backgrounds. We present a number of ways to distinguish those theories from
General Relativity observationally and experimentally. We also discuss the
extension to other modified gravity theories such as Brans-Dicke theory and
Gauss-Bonnet gravity, and address models that can satisfy both cosmological and
local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in
Relativity, Published version, Comments are welcom
Avoided Crossing Patterns and Spectral Gaps of Surface Plasmon Modes in Gold Nano-Structures
The transmission of ultrashort (7 fs) broadband laser pulses through periodic
gold nano-structures is studied. The distribution of the transmitted light
intensity over wavelength and angle shows an efficient coupling of the incident
p-polarized light to two counter-propagating surface plasmon (SP) modes. As a
result of the mode interaction, the avoided crossing patterns exhibit energy
and momentum gaps, which depend on the configuration of the nano-structure and
the wavelength. Variations of the widths of the SP resonances and an abrupt
change of the mode interaction in the vicinity of the avoided crossing region
are observed. These features are explained by the model of two coupled modes
and a coupling change due to switching from the high frequency dark mode to the
low frequency bright mode for increasing wavelength of the excitation light.
PACS numbers: 73.20.Mf, 42.70.Qs, 42.25.-p,Comment: 17 pages, 4 figure
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