69,678 research outputs found

    Added value of bleach sedimentation microscopy for diagnosis of tuberculosis: a cost-effectiveness study.

    Get PDF
    SETTING: Bleach sedimentation is a method used to increase the diagnostic yield of sputum microscopy for countries with a high prevalence of human immunodeficiency virus (HIV) infection and limited resources. OBJECTIVES: To compare the relative cost-effectiveness of different microscopy approaches in diagnosing tuberculosis (TB) in Kenya. METHODS: An analytical decision tree model including cost and effectiveness measures of 10 combinations of direct (D) and overnight bleach (B) sedimentation microscopy was constructed. Data were drawn from the evaluation of the bleach sedimentation method on two specimens (first on the spot [1] and second morning [2]) from 644 TB suspects in a peripheral health clinic. Incremental cost per smear-positive detected case was measured. Costs included human resources and materials using a micro-costing evaluation. RESULTS: All bleach-based microscopy approaches detected significantly more cases (between 23.3% for B1 and 25.9% for B1+B2) than the conventional D1+D2 approach (21.0%). Cost per tested case ranged between respectively euro 2.7 and euro 4.5 for B1 and B1+D2+B2. B1 and B1+B2 were the most cost-effective approaches. D1+B2 and D1+B1 were good alternatives to avoid using approaches exclusively based on bleach sedimentation microscopy. CONCLUSIONS: Among several effective microscopy approaches used, including sodium hypochlorite sedimentation, only some resulted in a limited increase in the laboratory workload and would be most suitable for programmatic implementation

    Analysis of Diffusion of Ras2 in Saccharomyces cerevisiae Using Fluorescence Recovery after Photobleaching

    Full text link
    Binding, lateral diffusion and exchange are fundamental dynamic processes involved in protein association with cellular membranes. In this study, we developed numerical simulations of lateral diffusion and exchange of fluorophores in membranes with arbitrary bleach geometry and exchange of the membrane localized fluorophore with the cytosol during Fluorescence Recovery after Photobleaching (FRAP) experiments. The model simulations were used to design FRAP experiments with varying bleach region sizes on plasma-membrane localized wild type GFP-Ras2 with a dual lipid anchor and mutant GFP-Ras2C318S with a single lipid anchor in live yeast cells to investigate diffusional mobility and the presence of any exchange processes operating in the time scale of our experiments. Model parameters estimated using data from FRAP experiments with a 1 micron x 1 micron bleach region-of-interest (ROI) and a 0.5 micron x 0.5 micron bleach ROI showed that GFP-Ras2, single or dual lipid modified, diffuses as single species with no evidence of exchange with a cytoplasmic pool. This is the first report of Ras2 mobility in yeast plasma membrane. The methods developed in this study are generally applicable for studying diffusion and exchange of membrane associated fluorophores using FRAP on commercial confocal laser scanning microscopes.Comment: Accepted for publication in Physical Biology (2010). 28 pages, 7 figures, 3 table

    The adsorption of adsorbable organic halide onto biological solids : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Technology in Environmental Engineering

    Get PDF
    Chlorinated organic molecules may be removed from wastewaters by adsorption onto the biomass present in biological treatment systems. This study assessed the adsorption onto biological solids of Adsorbable Organic Halide (AOX) from two New Zealand kraft pulp and paper mill bleach plant wastewaters. Batch adsorption studies were carried out to determine the characteristics of this adsorption process, with activated sludge as an adsorbent. Different molecular weight AOX fractions from two bleach plants' wastewaters were studied. The first wastewater was a combined C and E stage effluent from the CEH bleach sequence previously used at the Tasman Pulp and Paper Co. Ltd, Kawerau. The second was a combined D and E o stage effluent from the OODEoD bleach sequence used at New Zealand Forest Products Kinleith Mill, Tokoroa. For each mill's wastewater, the adsorption isotherms were characterised for four different molecular weight fractions, and the unfractionated wastewater. Adsorption isotherm models used to fit the data for each of the fractions were the Freundlich, Langmuir and Irreversible isotherms. No single model was able to successfully describe the adsorption characteristics for all of the fractions analysed, indicating significant differences in the adsorption processes occurring in the various fractions. Analysis of the adsorption of the different molecular weight fractions demonstrated that the adsorption affinity of the AOX increased with increasing molecular weight. It appeared that molecules with higher chlorination levels were more effectively adsorbed onto the biomass. Competition for adsorption sites on the biomass by the different molecular weight fractions was a significant factor in the adsorption of the unfractionated wastewater. Analysis of the adsorption of AOX from the wastewaters at concentrations typical of those expected in different biological treatment systems showed that: • treatment systems with low biomass concentrations, such as aerated lagoons, would not be expected to remove significant amounts of AOX by adsorption. • treatment systems utilising higher biomass levels have the potential to remove significant amounts of AOX by adsorption. Conventional activated sludge systems could remove 15-20%, and oxygen activated sludge systems 25-50% of the AOX entering these systems. The impact of the modernisation of bleach sequences on the adsorption of AOX, by the introduction of oxygen delignification and chlorine dioxide substitution, was assessed. This was carried out by comparison of the adsorption characteristics of the two mills' wastewaters. The Tasman mill's bleach sequence was used as an example of older, conventional bleaching, and the Kinleith mill's sequence an example of modernised bleaching. Significant differences were found in the adsorptive behaviour of the molecular weight fractions, and that of the unfractionated wastewaters, between the two. From the analysis, adsorption onto biomass in a biological treatment system is predicted to alter the molecular weight distribution of the AOX in wastewaters. The conventional sequence's wastewater should show a decrease in the proportion of high molecular weight AOX due to this adsorptive removal, an effect not as significant in the adsorption of AOX from a modern bleach plant wastewater. Modern bleach sequence wastewaters are expected to reveal a decrease in the proportion of the low molecular weight material, an effect not as notable for the conventional sequence's AOX. Modernisation was found to decrease the adsorptive affinity of the wastewater, suggested to be due to the lower chlorination levels and average molecular weights of the molecules in the wastewater. It was concluded that the modernisation of bleach sequences has reduced the significance of adsorption onto biological solids as an AOX removal mechanis

    Don't bleach chaotic data

    Full text link
    A common first step in time series signal analysis involves digitally filtering the data to remove linear correlations. The residual data is spectrally white (it is ``bleached''), but in principle retains the nonlinear structure of the original time series. It is well known that simple linear autocorrelation can give rise to spurious results in algorithms for estimating nonlinear invariants, such as fractal dimension and Lyapunov exponents. In theory, bleached data avoids these pitfalls. But in practice, bleaching obscures the underlying deterministic structure of a low-dimensional chaotic process. This appears to be a property of the chaos itself, since nonchaotic data are not similarly affected. The adverse effects of bleaching are demonstrated in a series of numerical experiments on known chaotic data. Some theoretical aspects are also discussed.Comment: 12 dense pages (82K) of ordinary LaTeX; uses macro psfig.tex for inclusion of figures in text; figures are uufile'd into a single file of size 306K; the final dvips'd postscript file is about 1.3mb Replaced 9/30/93 to incorporate final changes in the proofs and to make the LaTeX more portable; the paper will appear in CHAOS 4 (Dec, 1993

    Ultrafast supercontinuum spectroscopy of carrier multiplication and biexcitonic effects in excited states of PbS quantum dots

    Full text link
    We examine the multiple exciton population dynamics in PbS quantum dots by ultrafast spectrally-resolved supercontinuum transient absorption (SC-TA). We simultaneously probe the first three excitonic transitions over a broad spectral range. Transient spectra show the presence of first order bleach of absorption for the 1S_h-1S_e transition and second order bleach along with photoinduced absorption band for 1P_h-1P_e transition. We also report evidence of the one-photon forbidden 1S_{h,e}-1P_{h,e} transition. We examine signatures of carrier multiplication (multiexcitons for the single absorbed photon) from analysis of the first and second order bleaches, in the limit of low absorbed photon numbers (~ 10^-2), at pump energies from two to four times the semiconductor band gap. The multiexciton generation efficiency is discussed both in terms of a broadband global fit and the ratio between early- to long-time transient absorption signals.. Analysis of population dynamics shows that the bleach peak due to the biexciton population is red-shifted respect the single exciton one, indicating a positive binding energy.Comment: 16 pages, 5 figure

    Disabling myth or writing for the world: the secondary schools language project in the Eastern Province, South Africa

    Get PDF
    The majority of learners in South African schools are black, and they learn through English as a second language (L2). This contrasts with white students who learn through their first language (L1), English or Afrikaans. Most black students in South Africa are multilingual, and new developments in the curriculum promise to value this achievement. Even now, young black students display considerable competence in their written English when they use electronic links to communicate with fellow students and adults worldwide. Computers motivate students as writers and language learners. One of the many disabling myths that threatens to impede progress towards equity in educational outcomes in South Africa is the myth that teachers of writing in historically black schools will wait a very long time for the technologies of word processing and e-mail to be available to them. In the Eastern Province many schools have no telephones or electricity. The ANC Government is struggling to meet basic needs quickly and computers could then be used to promote equity among learners. In this study, students had only limited access to keyboard and e-mail facilities, yet the enthusiasm and concentration computers generated meant that they could leapfrog many hours of classroom instruction

    Phylloplane Sterilization With Bleach Does Not Reduce Btk Toxicity for \u3ci\u3ePapilio Glaucus\u3c/i\u3e Larvae (Lepidoptera: Papilionidae)

    Get PDF
    Neonate tiger swallowtail larvae (Papilio glaucus) were used to bioassay the effects of Btk (Bacillus thuringiensis var. kurstaki) at 4 doses (0.268, 0.034, 0.008, and 0.004 BIU per cm leaf surface) with an untreated control. Larvae, obtained from females captured in Georgia and North Carolina, were fed leaves of either tulip tree (Liriodendron tulipfera) or black cherry (Prunus serotina) in experiments that either included a pre-treatment dip and rinse in 5% chlorox bleach or not, before the application of Btk (dipping leaves in serially diluted solutions of Foray 48B). The results show no difference between North Carolina and Georgia P. glaucus larval dosage sensitivities, but do illustrate a clear dosage effect for all 4 treatments (cherry with and without bleach pre-treatment; tulip tree with and without bleach pre-treatment). The larvae on the bleached leaves do not do better (for cherry or tulip tree host plant) as would be expected if microbial symbionts on the phylloplane synergize the Btk toxicity. These results show that Btk (at doses several thousand-fold less than aerial sprays across forests for gypsy moth control) will kill P. glaucus, with or without microbial synergism on leaf phylloplanes

    Caution: Do Not Bleach!

    Get PDF
    In this lesson, students will investigate the importance of coral reefs to the Earth as a whole and learn some possible explanations for the phenomenon known as "coral bleaching". They should be able to identify ways that coral reefs benefit human beings, identify major threats to reefs and discuss how they might be reduced or eliminated, describe the Coral Reef Early Warning System, and discuss why corals might expel their zooxanthellae (symbiotic algae) when under stress. Educational levels: High school, Middle school, Undergraduate lower division

    BLEACH

    Get PDF
    The work in this exhibition investigates the unique potential for drawing to articulate the ideas and attitudes of architecture and objects. Accepting drawing as operating in conceptual space, I explore experimental loops within the visual logic of that territory. The work asserts the material fact of drawing and its connection to forms of fabrication in other materials like wood, paint, metal, and plastic. Like painting and sculpting, the drawings occupy an intangible state between objects and ideas. I embrace this irresolution. Please see Download button in top right corner for the full statement

    Efficacy of common laboratory disinfectants and heat on killing trypanosomatid parasites

    Get PDF
    The disinfectants TriGene, bleach, ethanol and liquid hand soap, and water and temperature were tested for their ability to kill bloodstream forms of Trypanosoma brucei, epimastigotes of Trypanosoma rangeli and promastigotes of Leishmania major. A 5-min exposure to 0.2% TriGene, 0.1% liquid hand soap and 0.05% bleach (0.05% NaOCl) killed all three trypanosomatids. Ethanol and water destroyed the parasites within 5 min at concentrations of 15-17.5% and 80-90%, respectively. All three organisms were also killed when treated for 5 min at 50 degrees C. The results indicate that the disinfectants, water and temperature treatment (i.e. autoclaving) are suitable laboratory hygiene measures against trypanosomatid parasites
    • …
    corecore