Role of the phase in the identification of delay time in semiconductor lasers with optical feedback

We consider a semiconductor laser with external optical feedback operating at a regime for which the delay time signature is extremely difficult to identify from the analysis of the intensity time series, using standard techniques. We show that such delay signature can be successfully retrieved by computing the same quantifiers from the phase, the real or the imaginary part of the field, even in presence of noise. Therefore the choice of the observable is determinant for parameter identification.Financial support from the Ministerio de Ciencia e Innovacion (MICINN), Spain, and the Fondo Europeo de Desarrollo Regional under projects FIS2007-60327 [Física Interdisciplinar de Sistemas Complejos (FISICOS)] and TEC2009-14101 [Delay-Coupled Diode Lasers for Photonic Applications (DeCoDicA)] and by the European Commission (EC) Project PHOCUS (FP7-ICT-2009-C- 240763) is acknowledged. R. M. Nguimdo also acknowledges fellowship BES-2007-14627 under the FPI program of MICINN.Peer reviewe

Profiling of aminoxyTMT-labeled bovine milk oligosaccharides reveals substantial variation in oligosaccharide abundance between dairy cattle breeds.

Free milk oligosaccharides are bioactive molecules that function as prebiotics and prevent infections that commonly afflict developing infants. To date, few publications have examined the factors affecting bovine milk oligosaccharide production among cattle in the dairy industry. Here we have applied a high-throughput isobaric labeling technique to measure oligosaccharide abundances in milk collected from Danish Holstein-Friesian and Jersey dairy cattle by liquid chromatography-mass spectrometry. With a total of 634 milk samples, this collection represents the largest sample set used for milk oligosaccharide profiling in the current literature. This study is also the first to use isobaric labeling for the purpose of measuring free oligosaccharides in a real sample set. We have identified 13 oligosaccharides that vary significantly by breed, with most structures being more abundant in the milk of Jersey cattle. The abundances of several oligosaccharides were increased in second-parity cows, and correlations between the abundances of oligosaccharide pairs were identified, potentially indicating similarities in their synthetic pathways. Fucosylated oligosaccharide structures were widely identified among both breeds. Improving our understanding of oligosaccharide production will aid in developing strategies to recover these compounds from processing streams and may enable their use as a functional ingredient in foods for infants and adults

Frequency and phase locking of laser cavity solitons

Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyse experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators

Non-universal results induced by diversity distribution in coupled excitable systems

We consider a system of globally coupled active rotators near the excitable regime. The system displays a transition to a state of collective firing induced by disorder. We show that this transition is found generically for any diversity distribution with well defined moments. Singularly, for the Lorentzian distribution (widely used in Kuramoto-like systems) the transition is not present. This warns about the use of Lorentzian distributions to understand the generic properties of coupled oscillators

Chaos-Based Optical Communications: Encryption Versus Nonlinear Filtering

7 pages, 8 figures.Several chaos encoding schemes codify the message in such a way that the mean value of the transmitted signal (carrier with the message) is different for bits “0” and “1”. We present a nonlinear filtering method that is able to detect very small changes in the mean value of a signal and therefore recover this kind of messages if its amplitude is larger than the chaotic fluctuations in the mean over the length of a bit.We also introduce a new codification method in which the mean value of the transmitted signal, over the length of each bit, is preserved and we show how it is able to beat the decryption scheme.This work was supported by MEC (Spain) and Feder under Projects TEC2006-1009/MIC (PhoDECC), TEC-2006-28105-E, and FIS2007-60327 (FISICOS); from EC Project PICASSO Grant IST-2005- 34551. The work of M. C. Soriano was supported by the MEC under a “Juan de la Cierva” contract.Peer reviewe

Dynamical properties induced by state-dependent delays in photonic systems

© 2015 Macmillan Publishers Limited. All rights reserved. In many dynamical systems and complex networks time delays appear naturally in feedback loops or coupling connections of individual elements. Moreover, in a whole class of systems, these delay times can depend on the state of the system. Nevertheless, so far the understanding of the impact of such state-dependent delays remains poor with a particular lack of systematic experimental studies. Here we fill this gap by introducing a conceptually simple photonic system that exhibits dynamics of self-organised switching between two loops with two different delay times, depending on the state of the system. On the basis of experiments and modelling on semiconductor lasers with frequency-selective feedback mirrors, we characterize the switching between the states defined by the individual delays. Our approach opens new perspectives for the study of this class of dynamical systems and enables applications in which the self-organized switching can be exploited.This work was supported by MINECO (Spain) under Project TEC2012-36335 (TRIPHOP) and FIS2012-30634 (INTENSE@COSYP), Govern de les Illes Balears via the program Grups Competitius and Formació de Personal Investigador and the European Commission via FEDER and European Social Fund.Peer Reviewe

Phase Synchronization and Polarization Ordering of Globally-Coupled Oscillators

We introduce a prototype model for globally-coupled oscillators in which each element is given an oscillation frequency and a preferential oscillation direction (polarization), both randomly distributed. We found two collective transitions: to phase synchronization and to polarization ordering. Introducing a global-phase and a polarization order parameters, we show that the transition to global-phase synchrony is found when the coupling overcomes a critical value and that polarization order enhancement can not take place before global-phase synchrony. We develop a self-consistent theory to determine both order parameters in good agreement with numerical results

Iron Sucrose: A Wealth of Experience in Treating Iron Deficiency

Iron deficiency and iron-deficiency anemia are associated with increased morbidity and mortality in a wide range of conditions. In many patient populations, this can be treated effectively with oral iron supplementation; but in patients who are unable to take or who do not respond to oral iron therapy, intravenous iron administration is recommended. Furthermore, in certain conditions, such as end-stage kidney disease, chronic heart failure, and inflammatory bowel disease, intravenous iron administration has become first-line treatment. One of the first available intravenous iron preparations is iron sucrose (Venofer®), a nanomedicine that has been used clinically since 1949. Treatment with iron sucrose is particularly beneficial owing to its ability to rapidly increase hemoglobin, ferritin, and transferrin saturation levels, with an acceptable safety profile. Recently, important new data relating to the use of iron sucrose, including the findings from the landmark PIVOTAL trial in patients with end-stage kidney disease, have been reported. Several years ago, a number of iron sucrose similars became available, although there have been concerns about the clinical appropriateness of substituting the original iron sucrose with an iron sucrose similar because of differences in efficacy and safety. This is a result of the complex and unique physicochemical properties of nanomedicines such as iron sucrose, which make copying the molecule difficult and problematic. In this review, we summarize the evidence accumulated during 70 years of clinical experience with iron sucrose in terms of efficacy, safety, and cost-effectiveness

Control design of Modular Multilevel Converters in normal and AC fault conditions for HVDC grids

This paper describes a control design strategy of Modular Multilevel Converters (MMC) for High Voltage Direct Current (HVDC) applications to operate during normal and AC fault conditions. First, a steady state analysis of the converter is performed to identify the uses of the current components within the control strategy. Based on the initial stationary study, a complete converter control structure is proposed, which enables full control of the MMC internal energy during normal and AC fault conditions. A detailed design procedure is included for the current and energy regulators, in order to be able to ensure a dynamic response under any grid condition. Finally, theoretical developments are validated through simulation results by means of a detailed model in normal operation and during an AC voltage sag