Extreme Events in Resonant Radiation from Three-dimensional Light Bullets

We report measurements that show extreme events in the statistics of resonant radiation emitted from spatiotemporal light bullets. We trace the origin of these extreme events back to instabilities leading to steep gradients in the temporal profile of the intense light bullet that occur during the initial collapse dynamics. Numerical simulations reproduce the extreme valued statistics of the resonant radiation which are found to be intrinsically linked to the simultaneous occurrence of both temporal and spatial self-focusing dynamics. Small fluctuations in both the input energy and in the spatial phase curvature explain the observed extreme behaviour.Comment: 5 pages, 5 figures, submitte

Filamentation and Pulse Self-compression in the Anomalous Dispersion Region of Glasses

International audienceThe propagation of near-infrared ultra-short laser pulses in the regime of anomalous dispersion of transparent solids is associated with a host of self-induced effects including a significant spectral broadening extending from the ultraviolet into the infrared region, pulse self-compression down to few-cycle pulse durations, free and driven third harmonic generation, conical emission and the formation of stable filaments over several cm showing the emergence of conical light bullets. We review measurements performed in different experimental conditions and results of numerical simulations of unidirectional propagation models showing that the interpretation of all these phenomena proceed from the formation of non-spreading conical light bullets during filamentation

Molecular basis for the DNA damage induction and anticancer activity of asymmetrically substituted anthrapyridazone PDZ-7

Anthrapyridazones, imino analogues of anthraquinone, constitute a family of compounds with remarkable anti-cancer activity. To date, over 20 derivatives were studied, of which most displayed nanomolar cytotoxicity towards broad spectrum of cancer cells, including breast, prostate and leukemic ones. BS-154, the most potent derivative, had IC50values close to 1 nM, however, it was toxic in animal studies. Here, we characterize another anthrapyridazone, PDZ-7, which retains high cytotoxicity while being well tolerated in mice. PDZ-7 is also active in vivo against anthracyclineresistant tumor in a mouse xenograft model and induces DNA damage in proliferating cells, preferentially targeting cells in S and G2phases of the cell cycle. Activation of Mre11-Rad50-Nbs1 (MRN) complex and phosphorylation of H2AX suggest doublestranded DNA breaks as a major consequence of PDZ-7 treatment. Consistent with this, PDZ-7 treatment blocked DNA synthesis and resulted in cell cycle arrest in late S and G2phases. Analysis of topoisomerase II\uce\ub1 activity and isolation of the stabilized covalent topoisomerase II\uce\ub1 - DNA complex in the presence of PDZ-7 suggests that this compound is a topoisomerase II\uce\ub1 poison. Moreover, PDZ-7 interfered with actin polymerization, thereby implying its action as a dual inhibitor of processes critical for dividing cells. Using nuclear magnetic resonance (NMR) spectroscopy we show that PDZ-7 interacts with DNA double helix and quadruplex DNA structure. Taken together, our results suggest that PDZ-7 is a unique compound targeting actin cytoskeleton and DNA

Practitioner's guide to laser pulse propagation models and simulation

The purpose of this article is to provide practical introduction into numerical modeling of ultrashort optical pulses in extreme nonlinear regimes. The theoretic background section covers derivation of modern pulse propagation models starting from Maxwell's equations, and includes both envelope-based models and carrier-resolving propagation equations. We then continue with a detailed description of implementation in software of Nonlinear Envelope Equations as an example of a mixed approach which combines finite-difference and spectral techniques. Fully spectral numerical solution methods for the Unidirectional Pulse Propagation Equation are discussed next. The modeling part of this guide concludes with a brief introduction into efficient implementations of nonlinear medium responses. Finally, we include several worked-out simulation examples. These are mini-projects designed to highlight numerical and modeling issues, and to teach numerical-experiment practices. They are also meant to illustrate, first and foremost for a non-specialist, how tools discussed in this guide can be applied in practical numerical modeling. \ua9 2011 EDP Sciences and Springer

Spatio-temporal characterization of self-formed hollow light pulses in the pump depletion regime of second harmonic generation

Depletion of the pump pulse in second harmonic generation (SHG) and its back-regeneration from the second harmonic pulse is a well known process in nonlinear optics. Nevertheless how the pump pulse reshapes as a three-dimensional object in space and time has never been investigated. In this work we apply a three-dimensional mapping technique to record this transformation and we experimentally show the formation of a hollow as well as more complex layered spatiotemporal structures of the fundamental pump pulse in different regimes. The results are compared with numerical simulations

Optimizing imaging and reducing radiation exposure during complex aortic endovascular procedures

Improvements in endovascular technologies and development of custom-made fenestrated and branched endografts currently allow clinicians to treat complex aortic lesions such as thoraco-abdominal and aortic arch aneurysms once treatable with open repair only. These advances are leading to an increase in the complexity of endovascular procedures which can cause long operation times and high levels of radiation exposure. This in turn places pressure on the vascular surgery community to display more superior interventional skills and radiological practices. Advanced imaging technology in this context represents a strong pillar in the treatment toolbox for delivering the best care at the lowest risk level. Delivering the best patient care while managing the radiation and iodine contrast media risks, especially in frail and renal impaired populations, is the challenge aortic surgeons are facing. Modern hybrid rooms are equipped with a wide range of new imaging applications such as fusion imaging and cone-beam computed tomography (CBCT). If these technologies contribute to reducing radiation, they can be complex and intimidating to master. The aim of this review is to discuss the fundamentals of good radiological practices and to describe the various imaging tools available to the aortic surgeon, both those available today and those we anticipate will be available in the near future, from equipment to software, to perform safe and efficient complex endovascular procedures

Resonant radiation from collapsing light pulses and spatiotemporal light bullets

Resonant excitation of dispersive waves from spatiotemporal light bullets exhibits unique features such as rogue statistics. Resonant radiation may also be stimulated on a co-propagating THz pulse, bridging a 6 octave spectral gap