Random lasing consists of a sequence of narrow, coherent spectral lines formed when stimulated emission in a disordered gain medium is excited above threshold excitation intensity, Ith. We studied ...the Ith distribution function in pi -conjugated polymer films, and its dependence on the excitation area size and polymer mixture with TiO sub(2) nanoparticles; optical pictures of the excited film area support the statistical measurements. At Ith we found that a single dominant random lasing resonator appears in the picture, with good agreement between its diameter and the cavity size extracted from the power Fourier transform analysis of the emission spectrum. This was directly confirmed by a new technique of space/spectrum cross-correlation of the laser emission lines from the excited area with 1010 mu m super(2) spatial resolution. The statistical results coupled with the imaging data provide strong evidence for the model of random resonators in the gain medium for explaining random lasing in pi -conjugated polymerfilms.
Random lasing consists of a sequence of narrow, coherent spectral lines formed when stimulated emission in a disordered gain medium is excited above threshold excitation intensity, Ith. We studied ...the Ith distribution function in π-conjugated polymer films, and its dependence on the excitation area size and polymer mixture with TiO 2 nanoparticles; optical pictures of the excited film area support the statistical measurements. At Ith we found that a single dominant random lasing resonator appears in the picture, with good agreement between its diameter and the cavity size extracted from the power Fourier transform analysis of the emission spectrum. This was directly confirmed by a new technique of space/spectrum cross-correlation of the laser emission lines from the excited area with 10×10 μm 2 spatial resolution. The statistical results coupled with the imaging data provide strong evidence for the model of random resonators in the gain medium for explaining random lasing in π-conjugated polymer films. PUBLICATION ABSTRACT
Although antenatal iron supplementation is beneficial to mothers, its impact on the neurodevelopment of offspring is controversial. A systematic review and meta-analysis was undertaken to assess ...whether routine maternal antenatal iron supplementation confers later neurodevelopmental benefit to offspring.
Electronic databases were searched using MESH terms or key words and identified papers were reviewed by two independent reviewers. The study quality was assessed using the Cochrane risk of bias assessment tool. The review was registered in the PROSPERO CRD data base.
Seven publications were identified, based on four randomised trials published between 2006 and 2016. Three of the trials were in the Asian sub-continent. A range of tools were used to evaluate neurodevelopment. Meta-analysis of outcomes from the three RCTs meeting our inclusion criteria showed minimal effect of antenatal iron supplementation on the neurodevelopment of offspring, which was not statistically significant: weighted mean difference of 0.54 (95% CI: -0.67 to 1.75); test for overall effect Z = 0.87; p = 0.38; and heterogeneity 48%. Meta-analysis of outcomes of these RCTs at later stages of development produced similar results.
The benefit of routine antenatal iron supplementation on neurodevelopment in offspring was not statistically significant in this relatively limited set of trials, and some benefit cannot be excluded in areas with a high prevalence of maternal anaemia. A large randomized controlled trial showing significant benefit would be required to modify our conclusions.
Helicobacter pylori infection is the major cause of peptic ulceration and gastric adenocarcinoma. To address the hypothesis that the human acquired immune response to H. pylori influences ...pathogenesis, we characterised the gastric T helper (Th) and regulatory T cell (Treg) response of infected patients.
The human gastric CD4(+) T cell response of 28 donors who were infected with H. pylori and 44 who were not infected was analysed using flow cytometry. The T cell associated mucosal cytokine response was analysed by real-time polymerase chain reaction assay of samples from 38 infected and 22 uninfected donors. Recombinant interleukin 10 (IL10) was added to co-cultures of H. pylori and AGS cells and its suppressive effects upon inflammatory responses were measured.
We found that the H. pylori-specific response consists of both T helper 1 and 2 subsets with high levels of IL10-secreting Tregs. People with peptic ulcer disease had a 2.4-fold reduced CD4(+)CD25(hi)IL10(+) Treg response (p = 0.05) but increased Th1 and Th2 responses (Th1: 3.2-fold, p = 0.038; Th2: 6.1-fold, p = 0.029) compared to those without ulcers. In vitro studies showed that IL10 inhibited IL8 expression and activation of nuclear factor kappa B induced by H. pylori in gastric epithelial cells, and enhanced H. pylori growth in a bacterial-cell co-culture model.
Together our data suggest that H. pylori induces a regulatory T cell response, possibly contributing to its peaceful coexistence with the human host, and that ulcers occur when this regulatory response is inadequate.
Random lasing emission spectra have been collected from both healthy and cancerous tissues. The two types of tissue with optical gain have different light scattering properties as obtained from an ...average power Fourier transform of their random lasing emission spectra. The difference in the power Fourier transform leads to a contrast between cancerous and benign tissues, which is utilized for tissue mapping of healthy and cancerous regions of patients.
The properties of random lasers in π‐conjugated polymer films and solutions infiltrated into opal photonic crystals are reviewed. We show that random lasing is a generic phenomenon that occurs in ...disordered gain media at an excitation intensity regime higher than that giving rise to amplified spontaneous emission. The emission radiation is coherent as demonstrated by photon statistics methods, and its spectrum contains many laser modes from which a typical cavity length can be obtained using Fourier transform spectroscopy. Since the random cavities are independent from each other, we show that laser emission in several colors is possible when mixing different dyes in the same random cavities. In addition, it is demonstrated that random lasing is formed in many disordered media with various scattering properties ranging from a regime of light prelocalization to that of weak scattering.
Random lasing is a generic phenomenon that occurs in disordered gain media at an excitation intensity regime higher than that giving rise to amplified spontaneous emission, as explained by these authors. The Figure shows a laser emission in several colors and the article unravels some of the main properties of random lasers in π‐conjugated polymers and laser dyes.
Universal properties of random lasers Polson, R.C.; Raikh, M.E.; Vardeny, Z.V.
IEEE journal of selected topics in quantum electronics,
2003-Jan-Feb, 2003-01-00, 20030101, Letnik:
9, Številka:
1
Journal Article
Recenzirano
The design and fabrication of laser resonators is often difficult. However, random lasers occur in gain media with numerous scatterers and produce coherent laser emission without any predesigned ...cavity. The generation of coherent emission from multiple scattering is quite general and its basic principles are shown here using two model systems, namely /spl pi/-conjugated polymer films and rhodamine-TiO/sub 2/ suspensions. Above a threshold excitation intensity, both systems show narrow emission lines (<0.5 nm), coherence that is determined by photon statistics, and a fundamental cavity length in the disordered material that is revealed by averaging multiple power Fourier transform spectra.
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