Field calibration of time domain reflectrometry in an Amazonian rainforest soil with variable bulk density: sources of error and influence of land-use.

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Spatial variation in small scale of soil wetness evaluated by different methods.

Evaluations of dielectric constants E and samplings for the determination of ø and bulk density þm were carried out in four profiles of a Xanthic Ferralsol with high clay content (Latossolo Amarelao - Brazil Classification) at the Experimental Statation of Embrapa Amazonia Ocidental (Manaus, AM, Brazil). The sample were taken near the soil surface. Three undisturbed core samples and three disturbed auger samples were collected at each depth. The E was determined in advance at six points with the probe inserted vertically and three points horizontally in each depth. Results and discussion on: a) volume evaluated and probe orientation; b) topsoil and subsoil measurements; c) soil characteristics; and d) accuracy of empirical equations for the determination of soil wetness are presented.bitstream/item/181061/1/ID-2600-2-69-76.pd

Distribution of Traditional Irrigation Canals and Their Discharge Dynamics at the Southern Slopes of Mount Kilimanjaro

On the southern slopes of Mt.Kilimanjaro like in many other regions in East Africa, agriculture strongly depends on irrigation. Water is supplied to farms by an extensive network of open unlined canals, most of them built centuries ago. However, information about the distribution of these irrigation canals and the dynamics of their discharge is rare thus hampering the implementation of sustainable solutions for agricultural water management. We suppose that several factors like topography, soil properties, shifts of cropping patterns, and weak institutions affect availability and management of agricultural water. Therefore, in this study we determined (i) the distribution of irrigation canals, (ii) their discharge patterns, and (iii) constraints to their sustainable management. Mixed–method approach consisting of both quantitative and qualitative methodologies was used. The discharge of canals was measured at 11 locations along an altitudinal gradient and selected canals were mapped to understanding their distribution, physical characteristics, and potential risks that limits their optimal discharge. Terrain attributes were derived from the Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Model (DEM) and soil physical and hydraulic conductivity were measured to understand permeability and stability of the soil. Additionally, we conducted focus group discussions with participants from 15 villages and 10 key informants interviews. We found that during the dry season the discharge of canals was higher than in the short rainy season. The discharge of canals increased with decreasing elevation. The median daily discharges equaled 12.6, 9.5, and 7.0 l/s in the lower, mid and upper areas, respectively. Landscape in the central part of the study area was the steepest (slope > 60%) and the roughest (Topographic Ruggedness Index > 80 m).We attribute this to terrain heterogeneity across the landscape, thus community decisions about distribution and maintenance of canals could differ across different villages. Furthermore, current shifts of cropping patterns increased irrigation water demands. Both formal and informal water institutions were constrained with several challenges that affected overall management of canals and their sources. Findings of this study could contribute to various efforts dedicated to improve management of water resources around Mt. Kilimanjaro

Calibração da técnica de Time Domain Reflectometry (TRD) para avaliação da umidade do solo, em um Latossolo Amarelo, textura muito argilosa, com diferentes valores de densidade aparente do solo - avaliação no campo.

Avaliação de umidade volumetrica do solo pela técnica de time Domain Reflectometry (TDR) para Latossolo Amarelo (Xanthic ferralsol - FAO) textura muito argilosa, com diferentes valores de p. Foram determinados os coeficientes de determinacao ajustada (R2) e o erro padrao da media. Realizou-se um ajuste por regressao multipla para P e E, selecionando-se as variaveis que contribuiam significativamente para o modelo por procedimentos de selecao stepwise. Como a variacao dos valores de p esta diretamente relacionada ao uso do solo (especie presente e o manejo praticado), foram observadas importantes diferencas entre as P das areas cultivadas e as da floresta primaria. Os valores reduzidos de P proxima as plantas de pupunha (Bactris gasipaes H.B.K.) em relacao as outras especies cultivadas (cupuaçu, Theobroma grandiflorum Schum) e Kudzu (Pueraria phaseoloides), e devido a uma elaborada trama de elevada massa de suas raizes na superficie do solo, nao permitindo haver espacos porosos. É importante o conhecimento das diferentes propriedadesdo solo que podem interferir na avaliacao de TDR, atraves dos quais e' possivel evitar ou controlar essas interferencias atraves da calibracao do campo.bitstream/item/180989/1/ID-3384-53-71.pdfAnnual Report 1996

Slow dynamics near glass transitions in thin polymer films

The $\alpha$-process (segmental motion) of thin polystyrene films supported on glass substrate has been investigated in a wider frequency range from 10$^{-3}$ Hz to 10$^4$ Hz using dielectric relaxation spectroscopy and thermal expansion spectroscopy. The relaxation rate of the $\alpha$-process increases with decreasing film thickness at a given temperature above the glass transition. This increase in the relaxation rate with decreasing film thickness is much more enhanced near the glass transition temperature. The glass transition temperature determined as the temperature at which the relaxation time of the $\alpha$-process becomes a macroscopic time scale shows a distinct molecular weight dependence. It is also found that the Vogel temperature has the thickness dependence, i.e., the Vogel temperature decreases with decreasing film thickness. The expansion coefficient of the free volume $\alpha_f$ is extracted from the temperature dependence of the relaxation time within the free volume theory. The fragility index $m$ is also evaluated as a function of thickness. Both $\alpha_f$ and $m$ are found to decrease with decreasing film thickness.Comment: 9 pages, 7 figures, and 2 table

Using the SWAT model to improve process descriptions and define hydrologic partitioning in South Korea

Watershed-scale modeling can be a valuable tool to aid in quantification of water quality and yield; however, several challenges remain. In many watersheds, it is difficult to adequately quantify hydrologic partitioning. Data scarcity is prevalent, accuracy of spatially distributed meteorology is difficult to quantify, forest encroachment and land use issues are common, and surface water and groundwater abstractions substantially modify watershed-based processes. Our objective is to assess the capability of the Soil and Water Assessment Tool (SWAT) model to capture event-based and long-term monsoonal rainfall–runoff processes in complex mountainous terrain. To accomplish this, we developed a unique quality-control, gap-filling algorithm for interpolation of high-frequency meteorological data. We used a novel multi-location, multi-optimization calibration technique to improve estimations of catchment-wide hydrologic partitioning. The interdisciplinary model was calibrated to a unique combination of statistical, hydrologic, and plant growth metrics. Our results indicate scale-dependent sensitivity of hydrologic partitioning and substantial influence of engineered features. The addition of hydrologic and plant growth objective functions identified the importance of culverts in catchment-wide flow distribution. While this study shows the challenges of applying the SWAT model to complex terrain and extreme environments; by incorporating anthropogenic features into modeling scenarios, we can enhance our understanding of the hydroecological impact

Spatial and genetic clustering of Plasmodium falciparum and Plasmodium vivax infections in a low-transmission area of Ethiopia.

The distribution of malaria infections is heterogeneous in space and time, especially in low transmission settings. Understanding this clustering may allow identification and targeting of pockets of transmission. In Adama district, Ethiopia, Plasmodium falciparum and P. vivax malaria patients and controls were examined, together with household members and immediate neighbors. Rapid diagnostic test and quantitative PCR (qPCR) were used for the detection of infections that were genetically characterized by a panel of microsatellite loci for P. falciparum (26) and P. vivax (11), respectively. Individuals living in households of clinical P. falciparum patients were more likely to have qPCR detected P. falciparum infections (22.0%, 9/41) compared to individuals in control households (8.7%, 37/426; odds ratio, 2.9; 95% confidence interval, 1.3-6.4; P = .007). Genetically related P. falciparum, but not P. vivax infections showed strong clustering within households. Genotyping revealed a marked temporal cluster of P. falciparum infections, almost exclusively comprised of clinical cases. These findings uncover previously unappreciated transmission dynamics and support a rational approach to reactive case detection strategies for P. falciparum in Ethiopia

Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS

BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports—among others—the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit

Placental transfer of the polybrominated diphenyl ethers BDE-47, BDE-99 and BDE-209 in a human placenta perfusion system: an experimental study

<p>Abstract</p> <p>Background</p> <p>Polybrominated diphenyl ethers (PBDEs) have been widely used as flame retardants in consumer products. PBDEs may affect thyroid hormone homeostasis, which can result in irreversible damage of cognitive performance, motor skills and altered behaviour. Thus, in utero exposure is of very high concern due to critical windows in fetal development.</p> <p>Methods</p> <p>A human ex vivo placenta perfusion system was used to study the kinetics and extent of the placental transfer of BDE-47, BDE-99 and BDE-209 during four-hour perfusions. The PBDEs were added to the maternal circulation and monitored in the maternal and fetal compartments. In addition, the perfused cotyledon, the surrounding placental tissue as well as pre-perfusion placental tissue and umbilical cord plasma were also analysed. The PBDE analysis included Soxhlet extraction, clean-up by adsorption chromatography and GC-MS analysis.</p> <p>Results and Discussion</p> <p>Placental transfer of BDE-47 was faster and more extensive than for BDE-99. The fetal-maternal ratios (FM-ratio) after four hours of perfusion were 0.47 and 0.25 for BDE-47 and BDE-99, respectively, while the indicative permeability coefficient (IPC) measured after 60 minutes of perfusion was 0.26 h^-1and 0.10 h^-1, respectively. The transport of BDE-209 seemed to be limited. These differences between the congeners may be related to the degree of bromination. Significant accumulation was observed for all congeners in the perfused cotyledon as well as in the surrounding placental tissue.</p> <p>Conclusion</p> <p>The transport of BDE-47 and BDE-99 indicates in utero exposure to these congeners. Although the transport of BDE-209 was limited, however, possible metabolic debromination may lead to products which are both more toxic and transportable. Our study demonstrates fetal exposure to PBDEs, which should be included in risk assessment of PBDE exposure of women of child-bearing age.</p