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The two-dimensional materials with direct band gap are attractive for optoelectronics operated in the visible and near infrared spectral range. The number of new van der Waals crystals increases systematically but the doping and the modification of their optoelectronic properties remain challenging. Here we present the tuning of the fundamental properties of different 2D mono- and dichalcogenides using millisecond range flash lamp annealing (FLA) in the controlled atmosphere. Those investigated 2D flakes are made by mechanical exfoliation onto the SiN/Si substrates. The change of internal properties of 2D chalcogenides is monitored by micro-Raman, photoluminescence and photoreflectance spectroscopies as well as conductive atomic force microscope (c-AFM). Using ms-range FLA in N2 ambient the transition metal dichalcogenides are stable up to the annealing at 1200 oC, while upon high temperature annealing the group IV-dichalcogenides can be reduced to monochalcogenides which opens new route for the fabrication of heterostructures. The formation of SnSe/SnSe2 heterostructures is proven by micro-Raman spectroscopy and current-voltage characteristic obtained by c-AFM measurements.

Stroke is a major global health problem. It is the third leading cause of death and the leading cause of adult disability. INTERHEART, a global case-control study of acute myocardial infarction in 52 countries (29,972 participants), identified nine modifiable risk factors that accounted for >90% of population-attributable risk. However, traditional risk factors (e.g. hypertension, cholesterol) appear to exert contrasting risks for stroke compared with coronary heart disease, and the etiology of stroke is far more heterogeneous. In addition, our knowledge of risk factors for stroke in low-income countries is inadequate, where a very large burden of stroke occurs. Accordingly, a similar epidemiological study is required for stroke, to inform effective population-based strategies to reduce the risk of stroke. Methods: INTERSTROKE is an international, multicenter case-control study. Cases are patients with a first stroke within 72 h of hospital presentation in whom CT or MRI is performed. Proxy respondents are used for cases unable to communicate. Etiological and topographical stroke subtype is documented for all cases. Controls are hospital- and community-based, matched for gender, ethnicity and age (+/-5 years). A questionnaire (cases and controls) is used to acquire information on known and proposed risk factors for stroke. Cardiovascular (e.g. blood pressure) and anthropometric (e.g. waist-to-hip ratio) measurements are obtained at the time of interview. Nonfasting blood samples and random urine samples are obtained from cases and controls. Study Significance: An effective global strategy to reduce the risk of stroke mandates systematic measurement of the contribution of the major vascular risk factors within defined ethnic groups and geographical locations.

Because of the dynamic equilibrium between Kerr self-focussing and plasma induced defocusing and the inexistence of collisional ionization the critical intensity during femtosecond laser filamentation in air is independent of pressure. An analytical analysis is given which is justified by a direct experimental verification. PACS: 42.65.Jx, 52.38.Hb, 52.70.Kz

We present experimental and theoretical results on white-light generation in the filamentation of a high-power femtosecond laser pulse in water and atmospheric air. We have shown that the high spatio-temporal localization of the light field in the filament, which enables the supercontinuum generation is sustained due to the dynamic transformation of the light field on the whole transverse scale of the beam, including its edges. We found that the sources of the supercontinuum blue wing are in the rings, surrounding the filament, as well as at the back of the pulse, where shock-wave formation enhanced by self-steepening takes place. We report on the first observation and demonstration of the interference of the supercontinuum spectral components arising in the course of multiple filamentation in a terawatt laser pulse. We demonstrate that the conversion efficiency of an initially narrow laser pulse spectrum into the supercontinuum depends on the length of the filament with high intensity gradients and can be increased by introducing an initial chirp., Published in the Journal of Applied Physics B: Lasers and Optics, v77 p149-165, 2003.

The continuum generation by intense femtosecond IR laser pulses focused in air including the effect of third-harmonic generation is investigated. We have used a theoretical model that includes the full spatio-temporal dynamics of both the fundamental and the third-harmonic pulses. Results of our numerical calculations show that a two-color filamentation effect occurs, in which the third-harmonic conversion efficiency remains almost constant over the whole filament length. It is found that this effect is rather independent of the wavelength of the input beam and the focal geometry. During the filamentation process the third-harmonic pulse itself generates a broad continuum, which can even overlap with the continuum of the fundamental pulse for the longer pump wavelengths. In consequence the continuum generation generated by intense IR laser pulses is further extended into the UV., Published in the Journal of Appl. Phys. B, v77 p177-183, 2003.