Examining agreement between clinicians when assessing sick children.

BACKGROUND: Case management guidelines use a limited set of clinical features to guide assessment and treatment for common childhood diseases in poor countries. Using video records of clinical signs we assessed agreement among experts and assessed whether Kenyan health workers could identify signs defined by expert consensus. METHODOLOGY: 104 videos representing 11 clinical sign categories were presented to experts using a web questionnaire. Proportionate agreement and agreement beyond chance were calculated using kappa and the AC1 statistic. 31 videos were selected and presented to local health workers, 20 for which experts had demonstrated clear agreement and 11 for which experts could not demonstrate agreement. PRINCIPAL FINDINGS: Experts reached very high level of chance adjusted agreement for some videos while for a few videos no agreement beyond chance was found. Where experts agreed Kenyan hospital staff of all cadres recognised signs with high mean sensitivity and specificity (sensitivity: 0.897-0.975, specificity: 0.813-0.894); years of experience, gender and hospital had no influence on mean sensitivity or specificity. Local health workers did not agree on videos where experts had low or no agreement. Results of different agreement statistics for multiple observers, the AC1 and Fleiss' kappa, differ across the range of proportionate agreement. CONCLUSION: Videos provide a useful means to test agreement amongst geographically diverse groups of health workers. Kenyan health workers are in agreement with experts where clinical signs are clear-cut supporting the potential value of assessment and management guidelines. However, clinical signs are not always clear-cut. Video recordings offer one means to help standardise interpretation of clinical signs

Phytotoxic effect of selected crude plant extracts on soil-borne fungi of common bean

Common bean (Phaseolus vulgaris L.) is an important food and cash crop particularly in Eastern, Southern and Great lake region. The efficacy of water based crude plant extracts of Neem (Azadirachta indica), Mexican marigold (Tagetes minuta), Tobacco (Nicotiana tobacum) and Peri-winkle (Vinca rosea) in controlling soil-borne fungi (Fusarium oxysporum Schl. f. sp. phaseoli) of common bean (Phaseolus vulgaris L.) was studied in the western province of Kenya. Thirty farms were used in the study carried out in August-September 2005 and March-June 2006. Broth microdilution method was used to determine minimum inhibitory concentration (MIC). All crude plant extracts controlled Fusarium yellows with varying efficacy. Neem extract was the most effective, while peri-winkle was the least. Wilt incidence was not affected by dosage regime. Neem is inhibitory to Fusarium growth at lower dosage than tobacco, Mexican marigold and peri-winkle with MIC ranging between 2.5 and 10.0 mg ml-

Fungitoxic properties of four crude plant extacts on fusarium oxysporum schl. F. sp phaseoli.

Fusarium yellows is a disease of common beans (Phaseolus vulgaris, L.) caused by Fusarium oxysporum Schl. F. sp. phaseoli, it has been found to be important in Busia district of Western province, Kenya. The study on fungitoxic properties of four locally available crude plant extracts was aimed at evaluating their efficacy in controlling Fusarium yellows infestation under the field conditions. Crude plant extracts from Azadirachta indica, Tagetes minuta, Nicotiana tobacum and Vinca rosea were tested against Fusarium oxysporum Schl. F. sp. phaseoli. Participatory On-Farm Trials (POFT) in six (6) divisions were carried out in August-September 2005 and March- June 2006; a total of thirty (30) farms were randomly surveyed. Minimum Inhibitory Concentration (MIC) of crude plant extracts against Fusarium was determined by broth microdilution method. Analysis of variance (ANOVA) was performed on the data, using Genstat 8th edition statistical program (Release 8.11, Lawes Agricultural Trust, Rothamsted Experimental Station, Harpenden, UK). Means were separated using LSD. Crude plant extracts exhibited fungitoxic activity against Fusarium oxysporum Schl. F. sp. phaseoli, with varying degree of efficacy. Nicotiana tobacum and Vinca rosea were not effective, Azadirachta indica and Tagetes minuta exhibited significant control over Fusarium. Azadirachta indica performed better amongst all the plant extracts. Common bean treatment with Benomyl 1 significantly reduced (P≤0.05) wilt incidence and increased growth in comparison to negative (–ve) control. Azadirachta indica formulation gave a significant reduction in wilt incidence compared to the other three crude plant extracts formulations. It reduced the wilt incidence by 17.24% in comparison to Tagetes minuta, Nicotiana tobacum and Vinca rosea whose wilt incidence reduction ranged from 5.84-9.8%. Azadirachta indica inhibited Fusarium growth at lower dosage than Tagetes minuta, Nicotiana tobacum and Vinca rosea. Extracts from Azadirachta indica and Tagetes minuta are effective, cheap and ecofriendly promising methods for protecting common bean against Fusarium oxysporum Schl. F. sp. phaseoli

Carpet characteristics of eichhornia crassipes [mart.] solms (water hyacinth) in the Winam gulf (lake victoria, Kenya)

The occurrence and spread of the water hyacinth (Eichhornia crassipes [Mart.] Solms), in the Winam gulf has created numerous attributes to the human population that live around the lake, thereby making its control a priority. Navigation within the lake is a major economic activity that has been greatly affected. Before this study, little was known about the characteristics of these weed carpets, and specifically the weight that a healthy inter-connected or entangled carpet can support before it was able to sink or even get submerged. Can a light herbivore or human stranded in the lake walk on a healthy carpet to safety?. In order to better understand these unknown, a study was initiated at five locations (i.e; Dunga beach, Kisumu pier, Kusa, Kobala and Kendu bay) within the lake that appeared to contain healthy dense carpets. Carpet connectivity, mat buoyancy, distribution of mass, biomass density, rhizome length and population density were calculated. Carpet connectivity was determined as the difference in pressure when weights were added on a mesh wire measuring 0.434m2 until the carpet submerged and the pressure on the same carpet that was required to submerge it after a complete disconnection. Standing population density was determined by counting the number of plants found within quadrants measuring 1 m2; while biomass density was determined when oven dried plant materials collected from quadrants measuring 1 m2 was weighed. Plant mass and rhizome length measurements were correlated, while population density was correlated to biomass density. These observations show that water hyacinth distribution in the Winam gulf is seasonal and adopts residence in secluded bays, carpets measuring 0,434m2 in size that have a connectivity of 288.4 Pa (pascals) are able to support a weight of only 12.6 kg, with any additional weight causing them to submerge. Distribution of mass was normal except in locations that are subjected to external factors

Distinctive Roles of Two Aggregate Binding Agents in Allophanic Andisols: Young Carbon and Poorly-Crystalline Metal Phases with Old Carbon

Interaction of organic matter (OM) with soil mineral components plays a critical role in biophysical organization (aggregate structure) as well as in biogeochemical cycling of major elements. Of the mineral components, poorly-crystalline phases rich in iron (Fe) and aluminum (Al) are highly reactive and thus contribute to both OM stabilization and aggregation. However, the functional relationship among the reactive metal phases, C stability, and aggregation remains elusive. We hypothesized that relatively young C acts as a binding agent to form the aggregates of weak physical stability, whereas the reactive metal phases and older C bound to them contribute to stronger aggregation. Using four surface horizons of Andisols having a gradient of soil C concentration due to decadal OM management, we conducted sequential density fractionation to isolate six fractions (from 2.5 g cm−3) with mechanical shaking, followed by selective dissolution and radiocarbon analysis. After 28 years of no-till with litter compost addition, not only C and N but inorganic materials including the reactive metal phases (pyrophosphate-, oxalate-, and dithionite-extractable metals) showed clear shifts in their concentrations towards lower-density fractions (especially <2.0 g cm−3) on a ground-area basis. This result was explained by the binding of compost-derived OM with soil particles. Major portions of the reactive metal phases in bulk samples were distributed in mid-density fractions (2.0–2.5 g cm−3) largely as sonication-resistant aggregates. Theoretical density calculations, together with depletion in radiocarbon (Δ14C: −82 to −170‰) and lower C:N ratio, implied that the sorptive capacity of the reactive metal phases in these fractions were roughly saturated with pre-existing OM. However, the influx of the compost-derived, modern C into the mid-density fractions detected by the paired-plot comparison suggests decadal C sink in association with the reactive metal phase. Our results supported the concept of aggregate hierarchy and further provided the following new insights. At the high hierarchy level where shaking-resistant aggregates form, soil organo-mineral particles appeared to be under a dynamic equilibrium and the changes in OM input regime controlled (dis)aggregation behavior due to the binding effect of relatively young C. At a lower hierarchy level, the reactive metal phases were bound to N-rich, 14C-depleted OM and together functioned as persistent binding agent. Our study suggests that the recognition of binding agents and aggregate hierarchy level would help to untangle the complex organo-mineral interactions and to better understand soil C stability

Estimating specific surface area of fine stream bed sediments from geochemistry

Specific surface area (SSA) of headwater stream bed sediments is a fundamental property which determines the nature of sediment surface reactions and influences ecosystem-level, biological processes. Measurements of SSA – commonly undertaken by BET nitrogen adsorption – are relatively costly in terms of instrumentation and operator time. A novel approach is presented for estimating fine (2.5 mg kg−1), four elements were identified as significant predictors of SSA (ordered by decreasing predictive power): V > Ca > Al > Rb. The optimum model from these four elements accounted for 73% of the variation in bed sediment SSA (range 6–46 m2 g−1) with a root mean squared error of prediction – based on leave-one-out cross-validation – of 6.3 m2 g−1. It is believed that V is the most significant predictor because its concentration is strongly correlated both with the quantity of Fe-oxides and clay minerals in the stream bed sediments, which dominate sediment SSA. Sample heterogeneity in SSA – based on triplicate measurements of sub-samples – was a substantial source of variation (standard error = 2.2 m2 g−1) which cannot be accounted for in the regression model. The model was used to estimate bed sediment SSA at the other 1792 sites and at 30 duplicate sites where an extra sediment sample had been collected, 25 m from the original site. By delineating sub-catchments for the headwater sediment sites only those sub-catchments were selected with a dominant (>50% of the sub-catchment area) bedrock formation and land use type; the bedrock and land use classes accounted for 39% and 7% of the variation in bed sediment SSA, respectively. Variation in estimated, fine bed sediment SSA from the paired, duplicate sediment sites was small (2.7 m2 g−1), showing that local variation in SSA at stream sites is modest when compared to that between catchments. How the approach might be applied in other environments and its potential limitations are discussed

Response of a First-Order Stream in Maine to Short-Term In-Stream Acidification

An experimental short-term acidification with HCl at a first-order stream in central Maine, USA was used to study processes controlling the changes in stream chemistry and to assess the ability of stream substrate to buffer pH. The streambed exerted a strong buffering capacity against pH change by ion exchange during the 6-hour acidification. Streambed substrates had substantial cation and anion exchange capacity in the pH range of 4.1 to 6.5. The ion exchange for cations and SO42- were rapid and reversible. The speed of release of cations from stream substrates was Na1+\u3e Ca2+ \u3e Mg2+ \u3e Aln+ \u3e Be2+, perhaps relating to charge density of these cations. Ca2+ desorption dominated neutralisation of excess H+ for the first 2 hr. As the reservoir of exchangeable Ca diminished, desorption (and possibly dissolution) of Al3+ became the dominant neutralising mechanism. The exchangeable (and possibly soluble) reservoir of Al was not depleted during the 6-hour acidification. Sulphate adsorption during the acidification reduced the concentration of SO42- in stream water by as much as 20 μeq L-1 (from 70 μeq L-1). Desorption of SO42- and adsorption of base cations after the artificial acidification resulted in a prolongation of the pH depression. The streambed had the capacity to buffer stream water chemistry significantly during an acidifying event affecting the entire upstream catchment

In Search of a Binding Agent: Nano-Scale Evidence of Preferential Carbon Associations with Poorly-Crystalline Mineral Phases in Physically-Stable, Clay-Sized Aggregates

Mechanisms of protecting soil carbon (C) are still poorly understood despite growing needs to predict and manage the changes in soil C or organic matter (OM) under anticipated climate change. A fundamental question is how the submicron-scale interaction between OM and soil minerals, especially poorly-crystalline phases, affects soil physical aggregation and C stabilization. Nano-sized composites rich in OM and poorly-crystalline mineral phases were presumed to account for high aggregate stability in the Andisol we previously studied. Here we searched for these nanocomposites within a sonication-resistant aggregate using scanning transmission X-ray microscopy (STXM) and near-edge X-ray absorption fine structure (NEXAFS) as well as electron microscopy (SEM, TEM). Specifically, we hypothesized that nanometer-scale spatial distribution of OM is controlled by poorly-crystalline minerals as both co-exist as physically-stable nanocomposites. After maximum dispersion of the cultivated Andisol A-horizon sample in water, one aggregate (a few p.m in diameter) was isolated from 0.2-2 mu m size fraction which accounted for 44-47% of total C and N and 50% of poorly-crystalline minerals in bulk soil. This fraction as well as 2 mu m size fractions, implying high abundance of the nanocomposites in the smaller fractions. The isolated aggregate showed a mosaic of two distinctive regions. Smooth surface regions showed low adsorption intensity of carbon K-edge photon energy (284-290 eV) with well-crystalline mineralogy, whereas rough surface regions had features indicative of the nanocomposites: aggregated nanostructure, high C intensity, X-ray amorphous mineral phase, and the dominance of Si, O, Al, and Fe based on SEM/EDX and TEM/EDX. Carbon functional group chemistry assessed by NEXAFS showed the dominance of amide and carboxyl C over aromatic and aliphatic C with some variation among the four rough surface regions. Together with C and N isotopic patterns among the size fractions (relatively low C:N ratio, high N-15 natural abundance, and more positive Delta C-14 of the <2 mu m fractions), our results provided the direct evidence of preferential binding of microbially-altered, potentially-labile C with poorly-crystalline mineral phases at submicron scale. The role of the nanocomposite inferred from this study may help to bridge the knowledge gap between physical aggregation process and biogeochemical reactions taking place within the soil physical structure

Development and Performance of Kyoto's X-ray Astronomical SOI pixel (SOIPIX) sensor

We have been developing monolithic active pixel sensors, known as Kyoto's X-ray SOIPIXs, based on the CMOS SOI (silicon-on-insulator) technology for next-generation X-ray astronomy satellites. The event trigger output function implemented in each pixel offers microsecond time resolution and enables reduction of the non-X-ray background that dominates the high X-ray energy band above 5--10 keV. A fully depleted SOI with a thick depletion layer and back illumination offers wide band coverage of 0.3--40 keV. Here, we report recent progress in the X-ray SOIPIX development. In this study, we achieved an energy resolution of 300~eV (FWHM) at 6~keV and a read-out noise of 33~e- (rms) in the frame readout mode, which allows us to clearly resolve Mn-K$\alpha$ and K$\beta$. Moreover, we produced a fully depleted layer with a thickness of $500~{\rm \mu m}$. The event-driven readout mode has already been successfully demonstrated.Comment: 7pages, 12figures, SPIE Astronomical Telescopes and Instrumentation 2014, Montreal, Quebec, Canada. appears as Proc. SPIE 9147, Space Telescopes and Instrumentation 2014: Ultraviolet to Gamma Ra