41 research outputs found

    Modeling of multiple filamentation of terawatt laser pulses on a hundred-meter air path

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    The results of numerical simulation of multiple filamentation of terawatt femtosecond pulse Ti:Sapphire laser performed on the experimental data obtained in the airway of a length of 106 m when changing the initial spatial focusing and laser power

    Filamentation of focused and collimated laser beams in liquids

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    Experimental results of investigations into the transformation of the spectral and spatial characteristics of femtosecond collimated and focused Ti:Sapphire-laser beams with wavelengths of 800 and 400 nm upon filamentation in continuous liquid media are presented. It is shown that broadening of the laser pulse spectrum due to phase self-modulation in the medium with a cubic nonlinearity depends on the pulse power and beam diameter. Dependences of the number of filaments, width of laser radiation spectrum, nonlinear focusing distance, and diameter of the filamentation region on the laser pulse power are measured. The existence of a relative power interval in which the explosive growth of the number of filaments occurs, is established. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

    Preventive medicine of von Hippel-Lindau disease-associated pancreatic neuroendocrine tumors

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    Pancreatic neuroendocrine tumors (PanNETs) are rare in von Hippel-Lindau disease (VHL) but cause serious morbidity and mortality. Management guidelines for VHL-PanNETs continue to be based on limited evidence, and survival data to guide surgical management are lacking. We established the European-American-Asian-VHL-PanNET-Registry to assess data for risks for metastases, survival and long-term outcomes to provide best management recommendations. Of 2330 VHL patients, 273 had a total of 484 PanNETs. Median age at diagnosis of PanNET was 35 years (range 10-75). Fifty-five (20%) patients had metastatic PanNETs. Metastatic PanNETs were significantly larger (median size 5 vs 2\u2009cm; P\u20091.5\u2009cm in diameter were operated. Ten-year survival was significantly longer in operated vs non-operated patients, in particular for PanNETs <2.8\u2009cm vs 652.8\u2009cm (94% vs 85% by 10 years; P\u2009=\u20090.020; 80% vs 50% at 10 years; P\u2009=\u20090.030). This study demonstrates that patients with PanNET approaching the cut-off diameter of 2.8\u2009cm should be operated. Mutations in exon 3, especially of codons 161/167 are at enhanced risk for metastatic PanNETs. Survival is significantly longer in operated non-metastatic VHL-PanNETs

    Treatment of Vasovagal Syncope Associated with Asystole: Literature Review and Case Report of Long-term Follow-up

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    Vasovagal syncope (VVS) can occur in every third of human population. Clinical symptoms of VVS areas a result of arterial hypotension with critical global cerebral hypoperfusion due to vasodilatation and bradicardia. Bradicardia is manifested as sinus node dysfunction and atrioventricular conduction disturbances due to activation of nervus vagus. Asystole can take place in some cases. Lack of efficacy of permanent pacemaker founds in patients to prevent of VVS. The results of double blind placebo controlled studies, European and American expert's opinions, probable causes of lack of efficacy of pacemakers in such category of patients and way of solution of this problem are discussed in the review. Syncope recurrences in spite of pacemaker implantation, risk of surgery complications and good life prognosis are arguments for therapeutic approach, now suitable for the most of patients with VVS. Case report (VVS with asystole but without of pacemaker implantation) with successful follow-up is analyzed in the article
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