Decoherence of Einstein-Podolsky-Rosen steering

We consider two systems A and B that share Einstein-Podolsky-Rosen (EPR) steering correlations and study how these correlations will decay, when each of the systems are independently coupled to a reservoir. EPR steering is a directional form of entanglement, and the measure of steering can change depending on whether the system A is steered by B, or vice versa. First, we examine the decay of the steering correlations of the two-mode squeezed state. We find that if the system B is coupled to a reservoir, then the decoherence of the steering of A by B is particularly marked, to the extent that there is a sudden death of steering after a finite time. We find a different directional effect, if the reservoirs are thermally excited. Second, we study the decoherence of the steering of a Schr\"odinger cat state, modeled as the entangled state of a spin and harmonic oscillator, when the macroscopic system (the cat) is coupled to a reservoir

Nearly Zero-Energy Buildings of the Lombardy Region (Italy), a Case Study of High-Energy Performance Buildings

The topic of nearly zero-energy buildings (n-ZEB), introduced by the Directive 2010/31/EU will direct the building market toward ever greater energy efficiency of new buildings. In some contexts, however, the building market for high-efficiency buildings has evolved, in recent years, on the basis of national and regional laws that have contributed to the acceleration of the process. This paper analyses the case study of the Lombardy Region (Italy), which transposed and assimilated the Directive 91/2002 (Energy Performance Building Directive), as of 2006, with regional legislation for energy efficiency of buildings. Within a few years the market for high energy-performance of buildings in the Lombardy Region had grown substantially: to date nearly 7500 energy performance certificates for buildings of Class A and Class A+ have been issued. The paper therefore analyses a success story in what is a field of great current interest, namely n-ZEB buildings. In the first part of the work, the evolution in terms of energy efficiency of the housing market in the Lombardy Region has been analyzed, with particular reference to the high energy-performance of buildings. The second part focuses on a sample of 20 n-ZEB buildings in order to highlight the design choices applied to them

Observation of the algebraic localization-delocalization transition in a 1D disordered potential with a bias force

In a one-dimensional (1D) disordered potential, quantum interferences leading to Anderson lo-calization are ubiquitous, such that all wave-functions are exponentially localized. Moreover, no phase transition toward delocalization is expected in 1D. This behavior is strongly modified in the presence of a bias force. We experimentally study this case, launching a non-interacting 39 K Bose-Einstein condensate in a 1D disordered potential induced by a far-off-resonance laser speckle, while controlling a bias force. In agreement with theoretical predictions, we observe a transition between algebraic localization and delocalization as a function of our control parameter that is the relative strength of the disorder against the bias force. We also demonstrate that the initial velocity of the wave-packet only plays a role through an effective disorder strength due to the correlation of the disorder. Adding a bias force is a quite natural way to probe the transport properties of quantum systems, a subject of broad interest that can be in particular addressed with atomic quantum gases thanks to their high degree of control and versatility [1]. For example, Bloch oscillations has been measured through the addition of a constant force to atoms in periodic potential induced by an optical lattice [2]. A force applied to a harmonic trap is equivalent to a trap displacement. The response to such a displacement permits to reveal the fluid or insulating behavior of atomic systems. In 1D interacting Bose gases, the pinning transition by an optical lattice [3] or the insulating transition in quasi-disordered optical lattice [4, 5] have been studied in this manner. More recently, transport in quantum gases is also studied in junction-type setup more analogous to condensed-matter systems: two reservoirs with different chemical potentials are connected through a constriction. For example, in a gas of fermions, the quantization of conductance through a quantum point contact [6] and the superfluid to normal transition in a disordered thin film have been observed [7]. In our work, we focus on the transport of non-interacting particles in disordered media. Without a bias force, quantum interferences between multiple paths lead to Anderson localization [8] whose signature is an exponential decay in space of single particle wave-function [9]. This phenomenon is ubiquitous in wave/quantum physics and it has been observed in many physical contexts [10] including condensed-matter [11] and ultra-cold atoms [12-14]. One-dimensional truly disordered systems are always localized [15], contrary to the 3D case where a phase transition between localized and extended single particle wave-functions takes place as a function of the disorder strength [16-18]. The localization properties of 1D disordered systems are modified in the presence of a bias force. Theoretical studies predict a transition from algebraic localization to delocalization as a function of a single control non-dimensional parameter α which is the ratio of the force to the disorder strength [19, 20]. Physically, α is the relative energy gain ∆E/E of a particle of energy E when moving over a localization length. Interestingly, in a 1D white noise disorder, this quantity is independent of E as the localization length is proportional to E. If α is small, the force does not considerably change the localization behavior of the particle while for large α its dynamics is severely affected leading to delocalization. This localization-delocalization transition is predicted in the infinite time limit for white noise disorder [20]. In a correlated disorder, as the one produced from a far-off-resonance laser speckle [21], the situation is more complicated. Speckles have no Fourier component beyond a spatial frequency 2k c. As a consequence, back-scattering and localization are not expected in the framework of Born approximation for atoms with wavevectors k > k c [12, 22]. Since localized wave-functions always have a small fraction at long distance corresponding to large energies and momenta in the presence of a bias force, we thus expect correlation-induced delocalization at infinite time. However, signatures of the algebraic localization-delocalization transition are predicted to be observable at transient times [20]. In this paper, we report on the observation of the algebraic localization-delocalization transition with cold-atoms propagating in a one dimensional disordered potential in the presence of a controlled bias force. We experimentally show that the non-dimensional parameter α is the only relevant parameter to describe the transition. We notice that the initial velocity of the quantum wave packet only plays a role through the correlation of the disordered potential, showing that the transition is in-trinsically energy independent. In the localized regime, we demonstrate an algebraic decay of the density and measure the corresponding decay exponent as a function of α. At large disorder strength, a saturation of the exp

Antioxidant activity relationship of phenolic compounds in Hypericum perforatum L.

<p>Abstract</p> <p>Background</p> <p>The St John's Wort (<it>Hypericum perforatum</it>; Clusiaceae) has been used in traditional and modern medicine for a long time due to its high content of biologically active phenolics. The purpose of this work was to develop a method for their fractionation and identification, and to determine the most active antioxidant compounds in plant extract.</p> <p>Results</p> <p>An LC-MS method which enables fast qualitative and semiquantitative analysis was developed. The composition determined is in agreement with the previous results, where 6 flavonoids, 4 naphthodianthrones and 4 phloroglucinols have been identified. Significant antioxidant activity was determined for most of the fractions by DPPH assay (the lowest IC₅₀of 0.52 μg/ml), NO scavenging (6.11 μg/ml), superoxide scavenging (1.86 μg/ml), lipid peroxidation (0.0079 μg/ml) and FRAP (the highest reduction capacity of 104 mg Fe equivalents/g) assays.</p> <p>Conclusion</p> <p>LC-MS technique has been successfully applied for a quick separation and identification of the major components of <it>H. perforatum </it>fractions. Majority of the fractions analyzed have expressed a very high antioxidative activity when compared to synthetic antioxidants. The antioxidant activity could be attributed to flavonoids and phenolic acids, while phloroglucinols and naphthodianthrones showed no significant activity. It is demonstrated that it is possible to obtain, by fractionation, <it>H. perforatum </it>preparations with significantly increased phloroglucinols-to-naphthodianthrones ratio (up to 95:5).</p