Investigation on nonradiative decay of the (Er3+I13/2)-I-4 -> I-4(15/2) transition in different tellurite glass matrix

Three kinds of Er3+-doped tellurite glasses with different hydroxyl groups are prepared by the conventional melt-quenching method. Infrared spectra are measured to estimate the exact content of OH- groups in samples. The maximum phonon energy in glasses are obtained by measuring the Raman scattering spectra. The strength parameters Omega(t) (t = 2, 4, 6) for all the samples are calculated and compared. The nonradiative decay rate of the Er3+ I-4(13/2) -> I-4(15/2) transition are calculated for the glass samples with different phonon energy and OH- group contents. Finally, the effect of OH- groups on fluorescence decay rate of Er3+ is analysed, the constant KOH-Er Of TWN, TZPL and TZL glasses are calculated to be 9.2 x 10(-19) cm(4)s(-1), 5.9 x 10(-19) cm(4)s(-1), and 3.5 x 10(-19) cm(4)s(-1), respectively.

Effect of hydroxyl groups on nonradiative decay of Er3+: I-4(13/2)-> I-4(15/2) transition in zinc tellurite glasses

A series of zinc tellurite glasses of 75TeO(2)-20ZnO-(5-x)La2O3-xEr(2)O(3) (x=0.02, 0.05, and 0.1 mol%) with the different hydroxl groups were prepared by the conventional melt-quenching method. Infrared spectra were measured in order to estimate the exact content of OH- groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH- content concentration as evidenced by IR transmission spectra. Various nonradiative decay rates from I-4(13/2) of Er3+ with. the change of OH content were determined from the fluorescence lifetime and radiative decay rates were calculated on the basis of Judd-Ofelt theory. (c) 2005 Elsevier B.V. All rights reserved.

Spectroscopic and fluorescence decay behaviors of Yb3+ -doped SiO2-PbO-Na2O-K2O glass

The spectroscopic and fluorescent decay behaviors of Yb3+-doped SiO2-PbO-Na2O-K2O glass is reported in this work. Yb2O3 contents of 1, 1.5 and 2mol% are added into the glass. Through the measurement of absorption and fluorescence spectra, and fluorescent decay rate at room temperature and at low temperature (18 K), it is found that the nonradiative decay rate of Yb3+ ions is mainly determined by the interaction between residual hydroxyl groups and Yb3+ ions. Concentration quenching effect can be omitted in this glass up to the Yb3+ ion concentration of 8.98 x 10(20)/cm(3). Multiphonon decay rate is also very small because of the large energy gap between F-2(5/2) and F-2(7/2) levels of Yb3+ ions. (c) 2004 Elsevier B.V. All rights reserved.

Adenylate Cyclase Toxin promotes bacterial internalisation into non phagocytic cells

Bordetella pertussis causes whooping cough, a respiratory infectious disease that is the fifth largest cause of vaccine-preventable death in infants. Though historically considered an extracellular pathogen, this bacterium has been detected both in vitro and in vivo inside phagocytic and non-phagocytic cells. However the precise mechanism used by B. pertussis for cell entry, or the putative bacterial factors involved, are not fully elucidated. Here we find that adenylate cyclase toxin (ACT), one of the important toxins of B. pertussis, is sufficient to promote bacterial internalisation into non-phagocytic cells. After characterization of the entry route we show that uptake of "toxin-coated bacteria" proceeds via a clathrin-independent, caveolae-dependent entry pathway, allowing the internalised bacteria to survive within the cells. Intracellular bacteria were found inside non-acidic endosomes with high sphingomyelin and cholesterol content, or "free" in the cytosol of the invaded cells, suggesting that the ACT-induced bacterial uptake may not proceed through formation of late endolysosomes. Activation of Tyr kinases and toxin-induced Ca2+-influx are essential for the entry process. We hypothesize that B. pertussis might use ACT to activate the endocytic machinery of non-phagocytic cells and gain entry into these cells, in this way evading the host immune system.

Surveying bacterial human pathogens in shrimp culture in Thailand

Any presence of bacterial human pathogen in shrimp products may be of public health concern. This note concludes that Salmonella do not appear to constitute a part of the microbial flora where shrimp culture is practiced in Thailand. Vibrio cholerae 01, the cause of cholera are rarely recovered from the environment with no isolates containing genes encoding cholera toxin. Further studies are needed to describe the prevalence of bacterial human pathogens in shrimp culture, especially determination of possible postharvest cross-contamnation with these pathogens

Long-range interactions in turbulence and the energy decay problem.

We discuss the long-range interactions that arise in homogeneous turbulence as a consequence of the Biot-Savart law. We note that, somewhat surprisingly, these long-range correlations are very weak in decaying, isotropic turbulence, and we argue that this should also be true for magnetohydrodynamic, rotating and stratified turbulence. If this is indeed the case, it is possible to make explicit predictions for the rate of decay of energy in these anisotropic systems, and it turns out that these predictions are consistent with the available numerical and experimental evidence.

Using wildlife activity and antibiotic resistance analysis to model bacterial water quality in coastal ponds

Models that help predict fecal coliform bacteria (FCB) levels in environmental waters can be important tools for resource managers. In this study, we used animal activity along with antibiotic resistance analysis (ARA), land cover, and other variables to build models that predict bacteria levels in coastal ponds that discharge into an estuary. Photographic wildlife monitoring was used to estimate terrestrial and aquatic wildlife activity prior to sampling. Increased duck activity was an important predictor of increased FCB in coastal ponds. Terrestrial animals like deer and raccoon, although abundant, were not significant in our model. Various land cover types, rainfall, tide, solar irradiation, air temperature, and season parameters, in combination with duck activity, were significant predictors of increased FCB. It appears that tidal ponds allow for settling of bacteria under most conditions. We propose that these models can be used to test different development styles and wildlife management techniques to reduce bacterial loading into downstream shellfish harvesting and contact recreation areas.