Cavity soliton inhibition of extreme events in lasers with injection.

Vortex mediated turbulence can be the key element in the generation of extreme events in spatially extended lasers with optical injection. Here, we study the interplay of vortex mediated turbulence and cavity solitons on the onset of extreme events in semiconductor lasers with injection. We first analyze and characterize these two features separately, spatiotemporal chaotic optical vortices for low values of the injection intensity and cavity solitons above the locking regime. In regimes where vortex mediated turbulence and cavity solitons coexist, localized peaks of light inhibit instead of enhancing the generation of rogue waves by locally regularizing the otherwise chaotic phase of the optical field. Cavity solitons can then be used to manipulate and control extreme events in systems displaying vortex mediated turbulence.

Excimer laser technology in percutaneous coronary interventions: Cardiovascular laser society's position paper.

Excimer Laser Coronary Atherectomy (ELCA) is a well-established therapy that emerged for the treatment of peripheral vascular atherosclerosis in the late 1980s, at a time when catheters and materials were rudimentary and associated with the most serious complications. Refinements in catheter technology and the introduction of improved laser techniques have led to their effective use for the treatment of a wide spectrum of complex coronary lesions, such as thrombotic lesions, severe calcific lesions, non-crossable or non-expandable lesions, chronic occlusions, and stent under-expansion. The gradual introduction of high-energy strategies combined with the contrast infusion technique has enabled us to treat an increasing number of complex cases with a low rate of periprocedural complications. Currently, the use of the ELCA has also been demonstrated to be effective in acute coronary syndrome (ACS), especially in the context of large thrombotic lesions.

Unifying Frequency Combs in Active and Passive Cavities: Temporal Solitons in Externally Driven Ring Lasers.

Frequency combs have become a prominent research area in optics. Of particular interest as integrated comb technology are chip-scale sources, such as semiconductor lasers and microresonators, which consist of resonators embedding a nonlinear medium either with or without population inversion. Such active and passive cavities were so far treated distinctly. Here we propose a formal unification by introducing a general equation that describes both types of cavities. The equation also captures the physics of a hybrid device-a semiconductor ring laser with an external optical drive-in which we show the existence of temporal solitons, previously identified only in microresonators, thanks to symmetry breaking and self-localization phenomena typical of spatially extended dissipative systems.

From the Lugiato-Lefever equation to microresonator-based soliton Kerr frequency combs.

The model, that is usually called the Lugiato-Lefever equation (LLE), was introduced in 1987 with the aim of providing a paradigm for dissipative structure and pattern formation in nonlinear optics. This model, describing a driven, detuned and damped nonlinear Schroedinger equation, gives rise to dissipative spatial and temporal solitons. Recently, the rather idealized conditions, assumed in the LLE, have materialized in the form of continuous wave driven optical microresonators, with the discovery of temporal dissipative Kerr solitons (DKS). These experiments have revealed that the LLE is a perfect and exact description of Kerr frequency combs-first observed in 2007, i.e. 20 years after the original formulation of the LLE-and in particular describe soliton states. Observed to spontaneously form in Kerr frequency combs in crystalline microresonators in 2013, such DKS are preferred state of operation, offering coherent and broadband optical frequency combs, whose bandwidth can be extended exploiting soliton-induced broadening phenomena. Combined with the ability to miniaturize and integrate on-chip, microresonator-based soliton Kerr frequency combs have already found applications in self-referenced frequency combs, dual-comb spectroscopy, frequency synthesis, low noise microwave generation, laser frequency ranging, and astrophysical spectrometer calibration, and have the potential to make comb technology ubiquitous. As such, pattern formation in driven, dissipative nonlinear optical systems is becoming the central Physics of soliton micro-comb technology.This article is part of the theme issue 'Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 2)'.

Publisher's Note: Refractory period of an excitable semiconductor laser with optical injection [Phys. Rev. E 95, 012214 (2017)].

This corrects the article DOI: 10.1103/PhysRevE.95.012214.

Characterization of antibody response in neuroinvasive infection caused by Toscana virus.

OBJECTIVES: Among sandfly-borne pathogens, Toscana virus (TOSV) is a prominent cause of summer meningitis in Mediterranean Europe. Here, we assessed the kinetics of anti-TOSV antibodies over time in 41 patients diagnosed with TOSV meningitis or meningoencephalitis in northeastern Italy. METHODS: Acute and follow-up serum samples were collected up to 20 months after diagnosis of TOSV infection and tested for the presence of specific antibody using immunoenzymatic and indirect immunofluorescence assays. In addition, maturation of anti-TOSV IgG over time was evaluated as well as production of neutralizing antibodies. RESULTS: Specific IgM and IgG response was present at diagnosis in 100% of patients; TOSV-specific IgM and IgG were detected in patients' sera up to 6 and 20 months after diagnosis, respectively. The avidity index (AI) increased over the first month after infection in 100% of patients and most cases exceeded 60% by Day 30 post infection. The AI subsequently plateaued then declined at 20 months after diagnosis. Finally, neutralization assay to TOSV was performed in 217 sera collected from 41 patients; 69.6% of tested samples resulted in reactive and moderate levels of neutralizing antibodies observed during all phases of infection despite high titres of total anti-TOSV IgG. CONCLUSIONS: Specific antibody response develops rapidly and is long-lasting for neuroinvasive TOSV infection. Serodiagnosis of neuroinvasive TOSV requires simultaneous detection of specific IgM and IgG. Moderate levels of neutralizing antibodies were maintained over the study period, while the protective role of antibodies lacking neutralizing activity is unclear and requires further evaluation.

Refractory period of an excitable semiconductor laser with optical injection.

Injection-locked semiconductor lasers can be brought to a neuronlike excitable regime when parameters are set close to the unlocking transition. Here we study experimentally the response of this system to repeated optical perturbations and observe the existence of a refractory period during which perturbations are not able to elicit an excitable response. The results are analyzed via simulations of a set of dynamical equations which reproduced adequately the experimental results.

Dissipative Phase Solitons in Semiconductor Lasers.

We experimentally demonstrate the existence of nondispersive solitary waves associated with a 2π phase rotation in a strongly multimode ring semiconductor laser with coherent forcing. Similarly to Bloch domain walls, such structures host a chiral charge. The numerical simulations based on a set of effective Maxwell-Bloch equations support the experimental evidence that only one sign of chiral charge is stable, which strongly affects the motion of the phase solitons. Furthermore, the reduction of the model to a modified Ginzburg-Landau equation with forcing demonstrates the generality of these phenomena and exposes the impact of the lack of parity symmetry in propagative optical systems.

Periodic and chaotic solitons in a semiconductor laser with saturable absorber.

In a semiconductor laser with saturable absorber, solitons may spontaneously drift and/or oscillate. We study three different regimes characterized by strong intensity oscillations, both periodic and chaotic. We show that (i) soliton dynamics may be similar to that of passively Q-switched lasers, (ii) solitons may drift and oscillate simultaneously, and (iii) chaotic solitons may coexist with stationary ones and with the laser off solution.

A concomitant and complete set of nonvolatile all-optical logic gates based on hybrid spatial solitons.

We theoretically demonstrate the realization of a complete canonical set of all-optical logic gates (AND, OR, NOT), with a persistent (stored) output, by combining propagative spatial solitons in a photorefractive crystal and dissipative cavity solitons in a downstream broad-area vertical cavity surface emitting laser (VCSEL). The system uses same-color, optical-axis aligned input and output channels with fixed readout locations, while switching from one gate to another is achieved by simply varying the potential applied to the photorefractive crystal. The inputs are Gaussian beams launched in the photorefractive crystal and the output is a bistable, persistent soliton in the VCSEL with a 'robust' eye diagram and large signal-to-noise ratio (SNR). Fast switching and intrinsic parallelism suggest that high bit flow rates can be obtained.

Observation of electro-activated localized structures in broad area VCSELs.

We demonstrate experimentally the electro-activation of a localized optical structure in a coherently driven broad-area vertical-cavity surface-emitting laser (VCSEL) operated below threshold. Control is achieved by electro-optically steering a writing beam through a pre-programmable switch based on a photorefractive funnel waveguide.

3D reconstruction of coronary arteries using frequency domain optical coherence tomography images and biplane angiography.

The aim of this study is to describe a new method for three-dimensional (3D) reconstruction of coronary arteries using Frequency Domain Optical Coherence Tomography (FD-OCT) images. The rationale is to fuse the information about the curvature of the artery, derived from biplane angiographies, with the information regarding the lumen wall, which is produced from the FD-OCT examination. The method is based on a three step approach. In the first step the lumen borders in FD-OCT images are detected. In the second step a 3D curve is produced using the center line of the vessel from the two biplane projections. Finally in the third step the detected lumen borders are placed perpendicularly onto the path based on the centroid of each lumen border. The result is a 3D reconstructed artery produced by all the lumen borders of the FD-OCT pullback representing the 3D arterial geometry of the vessel.

Intracoronary optical coherence tomography, basic theory and image acquisition techniques.

Optical coherence tomography (OCT) imaging is showing great potential as an alternative or complementary tool to intravascular ultrasound (IVUS) for aiding in stent procedures and future diagnosis/treatment of atherosclerosis. Here, we describe the basic theory behind OCT imaging and explain important parameters such as axial resolution, lateral resolution and sensitivity. Also, we describe several image acquisition techniques that have been adopted for OCT imaging.

Atherosclerotic plaque characterization in Optical Coherence Tomography images.

Optical Coherence Tomography (OCT) is a fiber--optic imaging modality which produces high resolution tomographic images of the coronary lumen and outer vessel wall. While OCT images present morphological information in highly resolved detail, the characterization of the various plaque components relies on trained readers. The aim of this study is to extract a set of features in grayscale OCT images and to use them in order to classify the atherosclerotic plaque. Intensity and texture based features we used in order to classify the plaque in four plaque types: Calcium (C), Lipid Pool (LP), Fibrous Tissue (FT) and Mixed Plaque (MP). 50 OCT annotated images from 3 patients were used to train and test the proposed plaque characterization method. Using a Random Forests classifier overall classification accuracy 80.41% is reported.

Difference differential equations for a resonator with a very thin nonlinear medium.

We derive from the classic Maxwell-Bloch equations a set of difference-differential equations valid, in general, when the length of the nonlinear medium in the optical cavity is much smaller than a wavelength. Such equations provide an elegant and simple framework in which the case of Fabry-Perot and ring cavity can be discussed in a unified way. We outline a complete scenario for the multimode laser instability in the Fabry-Perot case, illustrating the results for parameter values appropriate to quantum cascade lasers. Our approach can have a relevant impact also on the study of dynamical instabilities in external cavity semiconductor lasers, including multiple quantum well or quantum-dot structures.

Quality and in vitro fertilizing ability of cryopreserved cat spermatozoa obtained by urethral catheterization after medetomidine administration.

Quality and in vitro fertilizing ability of frozen-thawed cat semen collected by urethral catheterization (CT) or electroejaculation (EE) after medetomidine administration were compared. Sperm collection was performed by an urinary tomcat catheter and, 4 days apart, by electroejaculation from each of eight tomcats. Results showed that semen collected by CT was characterized by lower volume (10.5+/-5.3 microL, P<0.05), higher sperm concentration (1868.4+/-999.8 x 10(6)/mL, P<0.05) and lower pH (7.0+/-0.4, P<0.05) than that collected by EE (67.1+/-25.9 microL, 542.9+/-577.9 x 10(6)/mL, and 7.9+/-0.4, respectively). Spermatozoa characteristics after thawing at 0, 3 and 6h did not differ between the two methods of collection. Also cleavage rate and embryo production from oocytes fertilized with frozen-thawed spermatozoa collected by CT or EE showed no significant differences (P>0.05). In conclusion, the results obtained in the present study indicate that good quality freezable semen can be collected from cats by urethral catheterization after medetomidine administration. This new method of semen collection appears very useful in practice and, compared with the electroejaculation protocol, permits to obtain semen samples characterized by a higher concentration of spermatozoa, lower total volume and lower pH.

Does optical coherence tomography identify arterial healing after stenting? An in vivo comparison with histology, in a rabbit carotid model.

OBJECTIVE: To verify whether optical coherence tomography (OCT) can accurately monitor the occurrence of arterial healing after stenting. SETTING: Delayed stent endothelialisation may predispose to stent thrombosis. OCT is a high-resolution intravascular imaging technique that accurately identifies stent struts and arterial tissues. DESIGN AND INTERVENTIONS: Eight New Zealand white rabbits underwent the implantation of single bare metal stents (diameter 2-2.5 mm, length 8-13 mm) in the right common carotid artery through the external carotid artery. After a median of 11 days (range 2-28), the stented arteries were visualised by OCT, with images acquired at a pull-back speed of 0.5 mm/sec. The rabbits were then euthanised, vessels were formalin-fixed and finally processed for histopathology. RESULTS: We analysed 32 cross-sections from eight stented carotid arteries, for a total of 384 stent struts. OCT detected all of the stent struts in 30 of 32 cross-sections (93.7%), and correctly identified the presence/absence of tissue for every strut. Histological and OCT measurements of mean neointima thickness (0.135 (SD 0.079) mm and 0.145 (SD 0.085) mm, respectively, p = NS) were similar and closely related (r = 0.85, p<0.001). Neointima area progressively increased with longer time intervals from stent deployment to sacrifice; histological and OCT measurements were similar for each time interval. The intra-observer and interobserver reproducibility of OCT neointima measurements were excellent (R2 = 0.90 and 0.88, respectively). CONCLUSIONS: OCT is a promising means for monitoring stent strut coverage and vessel wall healing in vivo, the relevance of which will become even more significant with the increasing use of drug-eluting stents.

Gram-positive bloodstream infections in liver transplant recipients: incidence, risk factors, and impact on survival.

The objective of the study was to assess the incidence, risk factors, and survival of gram-positive bloodstream infections (GP-BSI(s)) among liver transplant recipients during the first year after transplantation. Between October 2000 and September 2006, 42 episodes of GP-BSI(s) occurred in 205 patients with an overall incidence of 0.20 episodes/patient. Coagulase-negative staphylococci were detected in 45.2% of cases, Enterococcus species in 42.9% (E faecalis, eight; E faecium, seven; E avium, two; E gallinarum, one) and Staphylococcus aureus in 11.9%. Retransplantation was the only independent risk factor for GP-BSI (odds ratio [OR], 0.253; 95% confidence interval (CI), 0.089 to 0.715; P = .009). Thirty-day mortality rate was 28.5% and S aureus infections were related to a poorer outcome. It is noteworthy that all the isolates of S aureus were methicillin-resistant. Ampicillin was inactive against all the strains of E faecium and 50% of E avium isolates, but active against all E faecalis and E gallinarum strains. All the isolates were glycopeptide-susceptible. No significant differences in mortality rate were observed in relation to sex, etiologies of end-stage liver disease, cytomegalovirus infection/reinfection, type of donor, rejection, or retransplantation. GP-BSI, the only independent risk factor for death (OR, 0.262; 95% CI, 0.106 to 0.643; P = .003), reduced the survival rate by 26% in the first year posttransplant. In conclusion, GP-BSI(s) impact significantly on morbidity and mortality posttransplant, particularly among retransplantations. Control measures are required to reduce the incidence of GP-BSI(s) in liver transplant recipients. These findings must be considered when empirical antimicrobial therapy is indicated while awaiting blood-culture results.

Effects of ketamine or medetomidine administration on quality of electroejaculated sperm and on sperm flow in the domestic cat.

The effects of two commonly used drugs for anaesthesia in the domestic cat, ketamine and medetomidine, on features of electroejaculated semen and on sperm flow in this species were evaluated performing three experiments. This is the first study about these topics in the domestic cat. In Experiment 1, ketamine or medetomidine effects on cat sperm quality after collection by electroejaculation (E.E.) have been assessed in nine animals. Results showed that mean sperm concentration was significantly higher (p<0.01) after medetomidine than after ketamine administration. In Experiment 2, ketamine or medetomidine effects on sperm flow in 12 electroejaculated cats were studied. Mean sperm concentration and mean total number of spermatozoa resulted significantly higher (p<0.01) in medetomidine than in ketamine treated animals. The number of spermatozoa displaced in urethra was significantly higher (p<0.01) using medetomidine. No significant differences were observed in percentages of retrograde flow. In Experiment 3, ketamine or medetomidine effects on urethral sperm flow, without any stimulation for sperm collection, were evaluated. Data obtained showed a significantly higher (p<0.05) number of spermatozoa displaced in urethra after medetomidine than after ketamine injection. In conclusion, E.E. in the cat after medetomidine administration determined a higher number of spermatozoa per ejaculate than after ketamine administration, with a good pharmacological restriction and without increasing sperm retrograde flow.