5,344 research outputs found
Confined colloidal crystals in and out of equilibrium
Recent studies on confined crystals of charged colloidal particles are
reviewed, both in equilibrium and out of equilibrium. We focus in particular on
direct comparisons of experiments (light scattering and microscopy) with
lattice sum calculations and computer simulations. In equilibrium we address
buckling and crystalline multilayering of charged systems in hard and soft slit
confinement. We discuss also recent crystalline structures obtained for charged
mixtures. Moreover, we put forward possibilities to apply external
perturbations, in order to drive the system out of equilibrium. These include
electrolyte gradients as well as the application of shear and electric fields.Comment: Review article, 18 pages, 5 figure
Asymptotic Entanglement Dynamics and Geometry of Quantum States
A given dynamics for a composite quantum system can exhibit several distinct
properties for the asymptotic entanglement behavior, like entanglement sudden
death, asymptotic death of entanglement, sudden birth of entanglement, etc. A
classification of the possible situations was given in [M. O. Terra Cunha,
{\emph{New J. Phys}} {\bf{9}}, 237 (2007)] but for some classes there were no
known examples. In this work we give a better classification for the possibile
relaxing dynamics at the light of the geometry of their set of asymptotic
states and give explicit examples for all the classes. Although the
classification is completely general, in the search of examples it is
sufficient to use two qubits with dynamics given by differential equations in
Lindblad form (some of them non-autonomous). We also investigate, in each case,
the probabilities to find each possible behavior for random initial states.Comment: 9 pages, 2 figures; revised version accepted for publication in J.
Phys. A: Math. Theo
Probing Low Energy Neutrino Backgrounds with Neutrino Capture on Beta Decaying Nuclei
We study the interaction of low energy neutrinos on nuclei that spontaneously
undergo beta decay showing that the product of the cross section times neutrino
velocity takes values as high as 10^{-42} cm^2 c for some specific nuclei that
decay via allowed transitions. The absence of energy threshold and the value of
the cross section single out these processes as a promising though very
demanding approach for future experiments aimed at a direct detection of low
energy neutrino backgrounds such as the cosmological relic neutrinos.Comment: Includes a discussion of local relic neutrino density effect on
neutrino capture rate. Accepted for publication in JCA
Cavity losses for the dissipative Jaynes-Cummings Hamiltonian beyond Rotating Wave Approximation
A microscopic derivation of the master equation for the
Jaynes-Cummings model with cavity losses is given, taking into account the
terms in the dissipator which vary with frequencies of the order of the vacuum
Rabi frequency. Our approach allows to single out physical contexts wherein the
usual phenomenological dissipator turns out to be fully justified and
constitutes an extension of our previous analysis [Scala M. {\em et al.} 2007
Phys. Rev. A {\bf 75}, 013811], where a microscopic derivation was given in the
framework of the Rotating Wave Approximation.Comment: 12 pages, 1 figur
The Scattering Approach to the Casimir Force
We present the scattering approach which is nowadays the best tool for
describing the Casimir force in realistic experimental configurations. After
reminders on the simple geometries of 1d space and specular scatterers in 3d
space, we discuss the case of stationary arbitrarily shaped mirrors in
electromagnetic vacuum. We then review specific calculations based on the
scattering approach, dealing for example with the forces or torques between
nanostructured surfaces and with the force between a plane and a sphere. In
these various cases, we account for the material dependence of the forces, and
show that the geometry dependence goes beyond the trivial {\it Proximity Force
Approximation} often used for discussing experiments.Comment: Proceedings of the QFEXT'09 conference (Oklahoma, 2009
Marginal bone changes around platform-switched conical connection implants placed 1 or 2 mm subcrestally: A multicenter crossover randomized controlled trial
AbstractIntroduction:This study analyzes early marginal bone modifications occurring aroundplatform-switched implants with conical connection placed 1 or 2 mm subcrestally.Methods:This crossover randomized controlled trial enrolled partially edentulouspatients needing two implants in either the posterior maxilla or mandible. Eachpatient received two platform-switched implants with conical connection inserted2 mm (Test) and 1 mm (Control) subcrestally. Definitive abutments were immediatelyconnected and, after 4 months of unsubmerged healing, screwed metal-ceramiccrowns were delivered. Radiographs were taken at implant placement (T0), prosthesisdelivery (T1), and after 1 year of prosthetic loading (T2).Results:Fifty-one patients (25 males and 26 females; mean age 61.2 ± 12.1 years)totaling 102 implants were included in the final analysis. Mean peri-implant bonelevel (PBL) reduction from T0 to T2 was not significantly different around Test (0.49± 0.32 mm) and Control implants (0.46 ± 0.35 mm;p=0.66). Multivariate linearregression models highlighted a significant positive correlation between history ofperiodontitis and PBL reduction. At T2, no Test group implant and 6 Control groupimplants exhibited PBL below the implant platform (11.8% of Control groupimplants).Conclusion:No significant differences in peri-implant marginal bone changes weredemonstrated after 1 year of prosthetic loading between platform-switched implantswith conical connection inserted either 1 or 2 mm subcrestally. However, 2 mm sub-crestal placement resulted in deeper implant positioning at T2, with no exposure oftreated implant surface and potential preventive effect against subsequent peri-implant pathology
Curcumin as prospective anti-aging natural compound: Focus on brain
The nutrients and their potential benefits are a new field of study in modern medicine for their positive impact on health. Curcumin, the yellow polyphenolic compound extracted from Curcuma longa species, is widely used in traditional Ayurvedic medicine to prevent and contrast many diseases, considering its antioxidant, immunomodulatory, anti-inflammatory, anti-microbial, cardio-protective, nephron-protective, hepato-protective, anti-neoplastic, and anti-rheumatic proprieties. In recent years, the investigations of curcumin have been focused on its application to aging and age-associated diseases. Aging is a physiological process in which there is a decreasing of cellular function due to internal or external stimuli. Oxidative stress is one of the most important causes of aging and age-related diseases. Moreover, many age-related disorders such as cancer, neuroinflammation, and infections are due to a low-grade chronic systemic inflammation. Curcumin acting on different proteins is able to contrast both oxidative stress than inflammation. In the brain, curcumin is able to modulate inflammation induced by microglia. Finally in brain tumors curcumin is able to reduce tumor growth by inhibition of telomerase activity. This review emphasizes the anti-aging role of curcumin focusing on its mechanism to counteract aging in the brain. Moreover, new formulations to increase the bioavailability of curcumin are discussed
Non-equilibrium Casimir forces: Spheres and sphere-plate
We discuss non-equilibrium extensions of the Casimir force (due to
electromagnetic fluctuations), where the objects as well as the environment are
held at different temperatures. While the formalism we develop is quite
general, we focus on a sphere in front of a plate, as well as two spheres, when
the radius is small compared to separation and thermal wavelengths. In this
limit the forces can be expressed analytically in terms of the lowest order
multipoles, and corroborated with results obtained by diluting parallel plates
of vanishing thickness. Non-equilibrium forces are generally stronger than
their equilibrium counterpart, and may oscillate with separation (at a scale
set by material resonances). For both geometries we obtain stable points of
zero net force, while two spheres may have equal forces in magnitude and
direction resulting in a self-propelling state.Comment: 6 pages, 6 figure
HMM based scenario generation for an investment optimisation problem
This is the post-print version of the article. The official published version can be accessed from the link below - Copyright @ 2012 Springer-Verlag.The Geometric Brownian motion (GBM) is a standard method for modelling financial time series. An important criticism of this method is that the parameters of the GBM are assumed to be constants; due to this fact, important features of the time series, like extreme behaviour or volatility clustering cannot be captured. We propose an approach by which the parameters of the GBM are able to switch between regimes, more precisely they are governed by a hidden Markov chain. Thus, we model the financial time series via a hidden Markov model (HMM) with a GBM in each state. Using this approach, we generate scenarios for a financial portfolio optimisation problem in which the portfolio CVaR is minimised. Numerical results are presented.This study was funded by NET ACE at OptiRisk Systems
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