Controlled Unidirectional Reflection in Atomic Lattices of Parity-Time Anti-Symmetry

Artificial optical materials have attracted great attentions in the past few decades for achieving various properties and functionalities not available in the natural media. Photonic crystals and left-handed materials are two prominent meta-materials promising the possibility of stretching usual rules and dis- playing new paradigms of light propagation and interaction. They have been exploited to design and realize various all-optical, optoelectronic, and opto-mechanical devices, though cannot be directly used to implement unidirectional light transport, a more difficult task than others. Only in recent years significant progresses have been made by considering moving photonic crystals of cold atoms and solid materials with parity-time (PT) symmetry. As compared to traditional photonic crystals, PT-symmetric materials are periodically modulated not only in terms of real parts but also imaginary parts of refractive indices, ex- hibiting a delicate balance of gain and loss alternately along the modulation direction with n(z) =n∗(−z). Very recently, PT-anti- symmetric materials are also considered, which require a more involved balance of positive and negative real refractive indices with n(z) = −n∗(−z) instead. Here we assume that cold 87Rb atoms trapped in 1D optical lattices – whose density modulation is dominated by a COSINE term - are driven into the four-level N configuration with a far-detuned dressing field applied to induce the dynamic shift of one ground level. We find that a probe field may experience the PT-anti-symmetric susceptibility with χ(z) = −χ∗(−z) when this dressing field has a traveling-wave (TW) and a standing-wave (SW) component so that the dynamic frequency shift is modulated as a SINE function along the lattice direction

Recovery of Interdependent Networks

Recent network research has focused on the cascading failures in a system of interdependent networks and the necessary preconditions for system collapse. An important question that has not been addressed is how to repair a failing system before it suffers total breakdown. Here we introduce a recovery strategy of nodes and develop an analytic and numerical framework for studying the concurrent failure and recovery of a system of interdependent networks based on an efficient and practically reasonable strategy. Our strategy consists of repairing a fraction of failed nodes, with probability of recovery $\gamma$, that are neighbors of the largest connected component of each constituent network. We find that, for a given initial failure of a fraction $1-p$ of nodes, there is a critical probability of recovery above which the cascade is halted and the system fully restores to its initial state and below which the system abruptly collapses. As a consequence we find in the plane $\gamma-p$ of the phase diagram three distinct phases. A phase in which the system never collapses without being restored, another phase in which the recovery strategy avoids the breakdown, and a phase in which even the repairing process cannot avoid the system collapse

Perfect absorption and no reflection in disordered photonic crystals

Understanding the effects of disorder on the light propagation in photonic devices is of major importance from both fundamental and applied points of view. Unidirectional reflectionless and coherent perfect absorption of optical signals are unusual yet fascinating phenomena that have recently sparked an extensive research effort in photonics. These two phenomena, which arise from topological deformations of the scattering matrix S parameters space, behave differently in the presence of different types of disorder, as we show here for a lossy photonic crystal prototype with a parity-time antisymmetric susceptibility or a more general non-Hermitian one

Fractional quantum transport and staggered topological transition in a lossy trimerized lattice

Transport in a non-Hermitian trimerized lattice with one lossy site per unit cell exhibits a quantized mean displacement before decay characterized by a two-step phase transition from zero to unity through a fractional value. Such a peculiar behavior, sensitive to both the lattice parameters and the initial state, is shown to be closely related to the presence of two nondegenerate dark states decoupled from the lossy sites and correspond to two staggered band closing points. We further check that distinct topological phases can also be characterized by the total Zak phase and by the number of midgap edge states. Moreover, we demonstrate that the edge states are topologically protected and their localization can be controlled via the couplings imbalance. Our results are expected to be relevant for implementations of topological photonics such as those based on arrays of evanescently coupled waveguides

Individual dosage of digoxin in patients with heart failure

Backgroud: After the publication of DIG trial, the therapeutic target of serum digoxin concentration (SDC) for the treatment of heart failure (HF) has been lowered (0.40-1.00 ng/ml). However, the majority of equations to calculate digoxin dosages were developed for higher SDCs. Recently, a new equation was validated in Asian population for low SDCs by Konishi et al., but results in Caucasians are unknown. Aim: This study was aimed to test the Konishi equation in Caucasians specifically targeting low SDCs. Furthermore, the Konishi equation was compared with other frequently used equations. Design: This was a prospective, multicenter study. Methods: Clinically indicated digoxin was given in 40 HF patients. The dosage was calculated with the Konishi equation. The SDC was measured at 1 and 6 months after starting digoxin. Adherence to digoxin was monitored with a specific questionnaire. Results: After exclusion of patients admitting poor adherence, we found a reasonable correlation between predicted and measured SDC (r = 0.48; P < 0.01) by the Konishi equation. Excluding patients with poor adherence and relevant worsening of renal function, the measured SDC (n = 54 measurements) was within the pre-defined therapeutic range in 95% of the cases. The mean, maximal and minimal measured SDC were 0.69 ± 0.19, 1.00 and 0.32 ng/ml, respectively. The correlation was weaker for the Jelliffe, the Koup and Jusko, and the Bauman equations. Conclusions: This study supports the clinical validity of the Konishi equation for calculating individual digoxin dosage in Caucasians, targeting SDCs according to current HF guideline

Lopsided diffractions of distinct symmetries in two-dimensional non-Hermitian optical gratings

Fraunhofer light diffraction across a thin two-dimensional lattice of cold atoms subject to transverse hybrid modulations of two standing-wave crossed pump fields is seen to yield lopsided patterns of various degrees of symmetry. We show that one can fully restrain the diffraction of a weak incident probe to two diagonal or adjacent quadrants or even just to a single quadrant, depending on the phases of two standing-wave pumps and on the probe detuning. Different diffraction symmetries with respect to the axes or diagonals of the diffraction plane quadrants are interpreted here in terms of different out-of-phase interplay of absorption and dispersion periodic distributions, resulting from different combinations of Hermitian, PT-symmetric, and non-Hermitian modulations

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer has been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, whilst ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Numerical investigations of convective phenomena of oil impingement on end-windings

A novel experimental rig for analysing intensive liquid cooling of highly power-dense electrical machine components has been developed. Coupled fluid flow and heat transfer have been modelled, using computational fluid dynamics (CFD), to inform the design of a purpose-built enclosure for optimising the design of submerged oil jet cooling approaches for electrical machine stators. The detailed modelling methodology presented in this work demonstrates the value in utilising CFD as a design tool for oil-cooled electrical machines. The predicted performance of the final test enclosure design is presented, as well as examples of the sensitivity studies which helped to develop the design. The sensitivity of jet flow on resulting heat transfer coefficients has been calculated, while ensuring parasitic pressure losses are minimised. The CFD modelling will be retrospectively validated using experimental measurements from the test enclosure

Prognostic impact of systemic inflammatory diseases in elderly patients with congestive heart failure

Background and aims: Inflammation is part of the pathophysiology of congestive heart failure (CHF). However, little is known about the impact of the presence of systemic inflammatory disease (SID), defined as inflammatory syndrome with constitutional symptoms and involvement of at least two organs as co-morbidity on the clinical course and prognosis of patients with CHF. Methods and results: This is an analysis of all 622 patients included in TIME-CHF. After an 18 months follow-up, outcomes of patients with and without SID were compared. Primary endpoint was all-cause hospitalization free survival. Secondary endpoints were overall survival and CHF hospitalization free survival. At baseline, 38 patients had history of SID (6.1%). These patients had higher N-terminal pro brain natriuretic peptide and worse renal function than patients without SID. SID was a risk factor for adverse outcome [primary endpoint: hazard ratio (HR) = 1.73 (95% confidence interval: 1.18-2.55, P = 0.005); survival: HR = 2.60 (1.49-4.55, P = 0.001); CHF hospitalization free survival: HR = 2.3 (1.45-3.65, P < 0.001)]. In multivariate models, SID remained the strongest independent risk factor for survival and CHF hospitalization free survival. Conclusions: In elderly patients with CHF, SID is independently accompanied with adverse outcome. Given the increasing prevalence of SID in the elderly population, these findings are clinically important for both risk stratification and patient managemen

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