High repetition rate fiber lasers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 117-121).This thesis reports work in high repetition rate femtosecond fiber lasers. Driven by the applications including optical arbitrary waveform generation, high speed optical sampling, frequency metrology, and timing and frequency distribution via fiber links, low noise fiber laser sources operating at multi-gigahertz repetition rates are developed systematically. A 200 MHz fundamentally mode-locked soliton laser and a 200 MHz fundamentally mode-locked similariton laser are first developed. Intra-cavity soliton formation is recognized as the optimum route towards achieving high fundamental repetition rates compact lasers, under the limitation of realistically available pump power. A 3 GHz fundamentally mode-locked femtosecond fiber laser is developed and verifies the soliton formation theory. Techniques in external cavity repetition rate multiplications are also discussed. A theoretical model that relates the repetition rate of the soliton laser and its other physical measurable parameters is developed to guide further high repetition rate laser development.by Jian Chen.Ph.D

Antibiotics induce polarization of pleural macrophages to M2-like phenotype in patients with tuberculous pleuritis

Pleural macrophages play critical roles in pathogenesis of tuberculous pleuritis, but very little is known about their response to anti-tuberculosis antibiotics treatment. Here, we examined whether and how pleural macrophages change in phenotype, transcription and function following antibiotics treatment in patients with tuberculous pleuritis. Results show pro-inflammatory cytokines were down-regulated significantly post antibiotic treatment in the pleural effusions and pleural macrophages up-regulated markers characteristic of M2 macrophages such as CD163 and CD206. Differential expression analysis of transcriptomes from four paired samples before and after treatment identified 230 treatment-specific responsive genes in pleural macrophages. Functional analysis identified interferon-related pathway to be the most responsive genes and further confirmed macrophage polarization to M2-like phenotype. We further demonstrate that expression of a significant fraction of responsive genes was modulated directly by antibiotics in pleural macrophages in vitro. Our results conclude that pleural macrophages polarize from M1-like to M2-like phenotype within a mean of 3.5 days post antibiotics treatment, which is dependent on both pleural cytokine environment and direct modulatory effects of antibiotics. The treatment-specific genes could be used to study the roles of pleural macrophages in the pathogenesis of tuberculous pleuritis and to monitor the response to antibiotics treatment