Modulation instability, Akhmediev Breathers and continuous wave supercontinuum generation

Numerical simulations of the onset phase of continuous wave supercontinuum generation from modulation instability show that the structure of the field as it develops can be interpreted in terms of the properties of Akhmediev Breathers. Numerical and analytical results are compared with experimental measurements of spectral broadening in photonic crystal fiber using nanosecond pulsesComment: 22 pages, 6 figure

Observation of Kuznetsov-Ma soliton dynamics in optical fibre

The nonlinear Schrödinger equation (NLSE) is a central model of nonlinear science, applying to hydrodynamics, plasma physics, molecular biology and optics. The NLSE admits only few elementary analytic solutions, but one in particular describing a localized soliton on a finite background is of intense current interest in the context of understanding the physics of extreme waves. However, although the first solution of this type was the Kuznetzov-Ma (KM) soliton derived in 1977, there have in fact been no quantitative experiments confirming its validity. We report here novel experiments in optical fibre that confirm the KM soliton theory, completing an important series of experiments that have now observed a complete family of soliton on background solutions to the NLSE. Our results also show that KM dynamics appear more universally than for the specific conditions originally considered, and can be interpreted as an analytic description of Fermi-Pasta-Ulam recurrence in NLSE propagation

Numerical instability of the Akhmediev breather and a finite-gap model of it

In this paper we study the numerical instabilities of the NLS Akhmediev breather, the simplest space periodic, one-mode perturbation of the unstable background, limiting our considerations to the simplest case of one unstable mode. In agreement with recent theoretical findings of the authors, in the situation in which the round-off errors are negligible with respect to the perturbations due to the discrete scheme used in the numerical experiments, the split-step Fourier method (SSFM), the numerical output is well-described by a suitable genus 2 finite-gap solution of NLS. This solution can be written in terms of different elementary functions in different time regions and, ultimately, it shows an exact recurrence of rogue waves described, at each appearance, by the Akhmediev breather. We discover a remarkable empirical formula connecting the recurrence time with the number of time steps used in the SSFM and, via our recent theoretical findings, we establish that the SSFM opens up a vertical unstable gap whose length can be computed with high accuracy, and is proportional to the inverse of the square of the number of time steps used in the SSFM. This neat picture essentially changes when the round-off error is sufficiently large. Indeed experiments in standard double precision show serious instabilities in both the periods and phases of the recurrence. In contrast with it, as predicted by the theory, replacing the exact Akhmediev Cauchy datum by its first harmonic approximation, we only slightly modify the numerical output. Let us also remark, that the first rogue wave appearance is completely stable in all experiments and is in perfect agreement with the Akhmediev formula and with the theoretical prediction in terms of the Cauchy data.Comment: 27 pages, 8 figures, Formula (30) at page 11 was corrected, arXiv admin note: text overlap with arXiv:1707.0565

Metabolomic, proteomic and preclinical imaging of patient-derived tumor xenografts for improving treatment of liver metastases patients

peer reviewe

Assessment of 18F-FDG uptake in idiopathic pulmonary fibrosis: influence of lung density changes

Abstract Background Idiopathic Pulmonary Fibrosis (IPF) is a progressive and irreversible disease leading to terminal respiratory insufficiency. Fluorodeoxyglucose ([18F]-FDG) PET/CT has been proposed to track the activity of the disease. However, IPF is characterized by regional changes in lung density that affects the FDG uptake, a factor generally not taken into account in previous studies. In this work, we studied the relationship between severity of IPF and lung uptake of [18F]-FDG, evaluated by mean and maximum standardized uptake value (SUV), corrected (SUVmean-corr; SUVmax-corr) and uncorrected for lung density (SUVmean-uncorr; SUVmax-uncorr). Methods [18F]-FDG PET/CT was performed in 31 IPF patients between 2013 and 2017. Lung density was determined on CT. SUV values were correlated with lung function tests, carbon monoxide diffusion (DLCO) and 6-min walking test (6MWT) at baseline and at 1 year. Correlation with the GAP index, a well-validated prognostic score in IPF, was also determined. Results At baseline, SUVmean-uncorr was highly correlated with lung density (r = 0.755; p <  0.001). SUVmean-uncorr and lung density were correlated with lung function tests (vital capacity (VC): p = 0.013 and p = 0.003; forced vital capacity (FVC): p = 0.004 and p = 0.001; total lung capacity (TLC): p = 0.001 and p = 0.001, respectively), while SUVmean-corr was not (VC: p = 0.733; FVC: p = 0.667; TLC: p = 0.382). Interestingly, SUVmean-corr was significantly higher in patients with a GAP index of 3 (p = 0.005), and negatively correlated with DLCO (r = − 0.398; p = 0.026) and desaturation during the 6MWT (r = − 0.401; p = 0.024). But no correlation was found with changes in lung function tests, walk distance and DLCO at 1 year. Conclusion To evaluate the role of ([18F]-FDG) PET/CT in IPF, correction for lung density appears necessary. As suggested by the correlation with DLCO, density-corrected SUV seems related to the intrinsic disease activity and particularly to the integrity of the alveolar-capillary barrier. However, ([18F]-FDG) PET/CT has probably a limited prognostic value as no correlation was found between SUVmean-corr and the clinical evolution at 1 year. Further studies with a longer follow-up are warranted

Observation of resonance soliton trapping due to a photo-induced gap in wavenumber

We investigate the nonlinear propagation of two forward propagating modes coupled by a resonant traveling-wave grating, which is photoinduced by illuminating an optical fiber with a beat signal. This interaction, representative of systems whose dispersion relation K=K(Ω) exhibits a gap in momentum K, shows evidence of localization mediated by resonance solitons. The signature of a still (in the grating frame) soliton is grating-induced cancellation of modal group-velocity mismatch

Shining light on an old problem

The evolution of modulational instability sidebands in an optical fibre are shown to provide new insights into Fermi–Pasta–Ulam–Tsingou recurrences

Clinical experience with 18F-JK-PSMA-7 when using a digital PET/CT

Background Digital PET/CT systems make use of a new technology with higher sensitivity and other better technological features than the analog ones. They require adaptation of the trade-off between performance, tracer dose and acquisition time. The aim of the study was to explore the performance of F-18-JK-PSMA-7 imaging when performed on a digital PET/CT with an adapted protocol, in a population of patients with prostate cancer patients (PCa). Influence of previous therapy on PET/CT performance is generally disregarded in PSMA-based imaging, despite potential influence of hormono-chemotherapy on the target expression. This potential influence was also tested in this work. Methods A total of 54 PCa patients experiencing biochemical recurrence were included in the study, in which we analysed the diagnostic performance of digital F-18-JK-PSMA-7 PET/CT. Compared to our protocol applied for acquisition on an analog system, administered dose and acquisition time were reduced by 20% and 50% respectively. We specifically took into consideration the influence of previous treatments on recurrence detection. Results We detected overall F-18-JK-PSMA-7-positive lesions in 38/54 patients (70.3%). There was no statistically significant difference regarding the detection rate between the groups of patients who had hormono-chemotherapy any time after initial diagnosis and those who never got any hormonal or chemotherapeutic treatment. Regarding the SUV max values, there was not significant difference between the two groups of patients neither in pelvic ganglions nor in other metastatic sites or the prostate region. Conclusion (18F)-JK-PSMA7 PET/CT with administered dose and acquisition time adapted to the digital technology provides valuable information in PCa patients with biochemical recurrence