2,213 research outputs found
Production of optical phase space vortices with non-locally distributed mode converters
Optical vortices have been observed in a wide variety of optical systems.
They can be observed directly in the wavefront of optical beams, or in the
correlations between pairs of entangled photons. We present a novel optical
vortex which appears in a non-local plane of the two-photon phase space,
composed of a single degree of freedom of each photon of an entangled pair. The
preparation of this vortex can be viewed as a "non-local" or distributed mode
converter. We show how these novel optical vortices of arbitrary order can be
prepared in the spatial degrees of freedom of entangled photons.Comment: To appear in upcoming special issue "Orbital Angular Momentum" of the
Journal of Optic
EFFETS DES TRAITEMENTS THERMIQUES SUR LES PROPRIETES ELECTRIQUES DES CELLULES SOLAIRES A BASE DE SILICIUM POLYCRISTALLIN
On a étudié l'effet de recuits à haute température sur les caractéristiques électriques à l'obscurité et sous éclairement de cellules solaires à base de silicium polycristallin dont la jonction était préparée à froid par incrustation ionique et recuit par laser pulsé. Dans certains cas des dégradations notables sont observées pour des recuits à 900°C
New Roles of Government in the Governance of Business Conduct: Implications for Management and Organizational Research
Bell inequalities for three systems and arbitrarily many measurement outcomes
We present a family of Bell inequalities for three parties and arbitrarily
many outcomes, which can be seen as a natural generalization of the Mermin Bell
inequality. For a small number of outcomes, we verify that our inequalities
define facets of the polytope of local correlations. We investigate the quantum
violations of these inequalities, in particular with respect to the Hilbert
space dimension. We provide strong evidence that the maximal quantum violation
can only be reached using systems with local Hilbert space dimension exceeding
the number of measurement outcomes. This suggests that our inequalities can be
used as multipartite dimension witnesses.Comment: v1 6 pages, 4 tables; v2 Published version with minor typos correcte
Flavonoids and other compounds from Ouratea ferruginea (Ochnaceae) as anticancer and chemopreventive agents.
The chemical study of the extracts from leaves and stems of Ouratea ferruginea allowed the identification of a new isoflavone, 5-hydroxy-7,3′4′5′-tetramethoxyisoflavone, and twenty two known compounds, including friedelin, 3β-friedelinol, lupeone, a mixture of sitosterol, stigmasterol and campesterol, sitosteryl- and stigmasteryl-3-O-b-D-glucopyranosides, 5,4′-dihydroxy-7,5′,3′-trimethoxyisoflavone, 5,4′-dihydroxy-7,3′-di-methoxyisoflavone (7,3′-di-O-methylorobol), 5,7,4′-trihydroxy-3′,5′-dimethoxyisoflavone (piscigenin), 2R,3R-epicatechin, syringic acid, 2,6-dimethoxybenzoquinone, 2,6-dimethoxyhydroquinone, syringic and ferulic aldehyde, a mixture of vanillic acid, 1-hydroxy-2-methoxy-4-(1E-3-hydroxy-1-propenyl)-benzene and 3,5-dimethoxy-4-hydroxy-dihydrocinamaldehyde, besides amenthoflavone and 7-O-methylamenthoflavone (sequoiaflavone) which are considered as chemotaxonomic markers of Ouratea. The structures were identified by IR, 1H- and 13C-NMR and GC-MS, HPLC-MS, besides comparison with literature data. The inhibitory effects of 5,4′-dihydroxy-7,5′,3′-trimethoxyisoflavone, 7,3′-di-O-methylorobol, piscigenin and 7-O-methylamenthoflavone on cytochrome P450-dependent 7-ethoxycoumarin O-deethylase (ECOD) and glutathione S-transferase (GST) were evaluated in vitro. The 5,4′-dihydroxy-7,5′,3′-trimethoxy-isoflavone was the best inhibitor, inhibiting almost 75% of GST activity. Sequoiaflavone was the most potent inhibitor, inhibiting ECOD assay in 75%. These activities allow us to consider both these flavonoids as potential anticancer and chemopreventive agents
Influence of the anisotropic behavior on equibiaxial paths
Marciniak and Nakajima tests are commonly used in building FLD's, since they allow covering all regions from uniaxial to almost equibiaxial strain paths. In this work, the deviation from equibiaxial strain paths is analyzed as function of the material anisotropic behavior. The numerical results show that material with r0 = r90 present equibiaxial stress and strain paths, while for the ones with r0 ≠ r90 the paths are neither equibiaxial in stress nor strain. Moreover, it is shown that despite the similarities between the two tests, they present different sensitivity to the control of the blank holder force and to the friction coefficient. Namely, the stress and strain paths in the Marciniak specimen center are more sensitive to the control of the blank holder force. On the other hand, the stress and strain paths in the Nakajima specimen center are more sensitive to the friction coefficient. The deviation from the equibiaxial strain path indicates that the stress ratio is also not necessarily 1.0, meaning that the stress triaxiality and the Lode parameter also present some deviation from the reference values for an equibiaxial stress state. This should be taken into account when analyzing forming limit results.The authors gratefully acknowledge the financial support of the projects POCI-01-0145-FEDER030592 (PTDC/EME-EME/30592/2017) and UIDB/00285/2020 financed by the Operational Program for Competitiveness and Internationalization, in its FEDER/FNR component, and the Portuguese Foundation of Science and Technology (FCT), in its State Budget component (OE)
Caracterização da flora herbácea associada ao banco de germoplasma in situ de butiá no bioma pampa.
Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environment
We report on an experimental investigation of the dynamics of entanglement
between a single qubit and its environment, as well as for pairs of qubits
interacting independently with individual environments, using photons obtained
from parametric down-conversion. The qubits are encoded in the polarizations of
single photons, while the interaction with the environment is implemented by
coupling the polarization of each photon with its momentum. A convenient Sagnac
interferometer allows for the implementation of several decoherence channels
and for the continuous monitoring of the environment. For an
initially-entangled photon pair, one observes the vanishing of entanglement
before coherence disappears. For a single qubit interacting with an
environment, the dynamics of complementarity relations connecting single-qubit
properties and its entanglement with the environment is experimentally
determined. The evolution of a single qubit under continuous monitoring of the
environment is investigated, demonstrating that a qubit may decay even when the
environment is found in the unexcited state. This implies that entanglement can
be increased by local continuous monitoring, which is equivalent to
entanglement distillation. We also present a detailed analysis of the transfer
of entanglement from the two-qubit system to the two corresponding
environments, between which entanglement may suddenly appear, and show
instances for which no entanglement is created between dephasing environments,
nor between each of them and the corresponding qubit: the initial two-qubit
entanglement gets transformed into legitimate multiqubit entanglement of the
Greenberger-Horne-Zeilinger (GHZ) type.Comment: 15 pages, 14 figures; only .ps was working, now .pdf is also
availabl
Einstein-Podolsky-Rosen entanglement and steering in two-well BEC ground states
We consider how to generate and detect Einstein-Podolsky-Rosen (EPR)
entanglement and the steering paradox between groups of atoms in two separated
potential wells in a Bose-Einstein condensate (BEC). We present experimental
criteria for this form of entanglement, and propose experimental strategies for
detecting entanglement using two or four mode ground states. These approaches
use spatial and/or internal modes. We also present higher order criteria that
act as signatures to detect the multiparticle entanglement present in this
system. We point out the difference between spatial entanglement using
separated detectors, and other types of entanglement that do n}ot require
spatial separation. The four-mode approach with two spatial and two internal
modes results in an entanglement signature with spatially separated detectors,
conceptually similar to the original EPR paradox.Comment: 15 pages, changes mad
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